# Patent

## Title
Methods of reducing polystyrene foams using dibasic esters with extruders

## Abstract

The present invention is directed to novel polystyrene foam reduction recycling compositions and methods that solve the volume problem of recycling polystyrene foam materials while simultaneously allowing the easy and inexpensive shipment of the foamed materials after reduction in volume by use of one or more dibasic ester compositions in combination with one or more low heat based mechanical extruders. The methods of the present invention are applicable to all types of expanded or foamed polystyrene materials known to those of skill in the art.

## Background
FIELD OF THE INVENTION
This invention provides novel methods employing chemical agents with extruders to reduce polystyrene foam plastics to a compact form using a dibasic ester-based chemical agent in liquid form which reduces the polystyrene foam to a sludge-like material that is safe to ship and greatly reduces its volume of waste.
BACKGROUND OF THE INVENTION
Polystyrene foam has been used for some time as packing material, insulation material, structural materials and other various uses. Polystyrene foams exhibit many useful qualities in a wide variety of fields. The foams usefulness is based partly on its cost effectiveness, its inherent insulating qualities and the ease with which it may be formed into a great variety of shapes. For instance, the food handling industry has found polystyrene foam packaging to be of great use in the packaging of food products for its consumers. In addition, the building industry has found a large variety of uses for the foam. The chief concern for the various uses of the foam has been the amount of waste that is generated by the use of polystyrene foam products.
Generally speaking, polystyrene foam has primarily caused great concern because of its lack of biodegradability. The foam by its very nature takes up a great deal of volume per weight, which has caused many individuals to question its overall commercial usefulness when compared to the overall possible detrimental environmental impact. The environmental impact includes the accelerated rate that landfill space is being used up at because the foam, in its useful form, takes a large amount of space per weight of waste. Moreover, the transportation of the foam waste is very inefficient due to the volume weight ratio. Typically, the waste material is transported from a restaurant facility to a waste area. This transportation usually involves motor vehicle transport. The vehicles can transport a much greater weight of refuse than can be placed in the vehicle due to the large volume the polystyrene foam takes up. Therefore, the transportation of polystyrene foam products in general is very inefficient because the full capacity of the shipping means is not utilized.
Also, in the industry it has been very difficult to find an effective method of recycling the polystyrene foam products. This is due in part to the shipping cost described above and the cost of the process of the actual recycling. There is a therefore a continued need for a polystyrene foam volume reduction method to allow use of more conventional plastic recycling and processing equipment. At the present, very expensive and specialized processing equipment and extra polystyrene foam compaction steps are required to recycle polystyrene foam products.
One approach to the recycling of polystyrene foam is to use chemicals to reduce the foam. The basic problem in the industry, however, is that the chemicals that are often considered the most obvious to use are very toxic to the environment with the result that they are often banned by environmental legislation or regulations. One chemical series, pinene and terpenes such as d-limonene can reduce the foam volume. This approach is interesting but unfortunately it fails to be an effective method in some cases. Specifically, the cost of d-limonene is directly related to the crop levels of citrus products. Accordingly, when there is a problem with the production of citrus-based products due to bad growing conditions, it directly effects the price to recycle foam products to the point where it may no longer be cost effective.
Moreover, prior approaches evidence an inconsistent activity in collapsing polystyrene foams that has not previously been addressed in the industry. For example, while heat activation of the terpenes has removed this problem (U.S. Pat. No. 5,223,543, the entire contents of which are incorporated herein by reference), it adds to the overall cost of recycling and it involves a volatile environmentally compromising chemical. The chemicals used in the '543 patent were problematic for shipping due to their flash point. They are highly volatile and therefore extra precautions have to be taken when shipping such products that ultimately make use of such chemicals cost-ineffective. Moreover, the process used in the '543 patent was basically vapor phase, providing for possible emissions of vapors which were a Clean Air Act Problem. Thus there continues to be a major need for a polystyrene foam reduction process that uses low volatility agents.
Also, the use of volatile chemicals presents another problem for the recycling efforts of polystyrene foam products. The chemicals used heretofore suffer great loss in the recycling process due to evaporation. This makes the recycling materials vary hard to recover to be used again in the recycling process. As such, it greatly increases the cost to the recycling efforts. The evaporated chemicals would also potentially increase the danger of an accident during the recycling process due to unacceptable flash points of the chemicals. This is especially true were the best performance of the chemicals is aided by the application of heat to the recycling process. Ultimately, the volatile chemicals and heat required lead to conditions during the recycling process that are potentially very dangerous.
An ideal process would have little need for the heat activation step of U.S. Pat. No. 5,223,543 and would further allow viscous and higher boiling point materials to be employed. Ideally, these materials would not require longer residence times prior to recycling. A long time would delay the sequence of breaking down the polystyrene foam products and shipping of same. This increase in residence times adds to the overall cost of the recycling process. Also, the need to decrease residence time must be balanced with reduced heat activation in combination with higher boiling point materials whose combination would result in a heretofore unobtainable efficient and safe chemical reactant. In addition, it would be most desirable to have the product or sludge of the polystyrene foam collapsing reactions safely shippable. It would also be advantageous to identify effective compounds that insulate the polystyrene foam reducer market from the wide price variation of the orange crop related d-limonene market.
Also, it would be desirable to have a compound that is environmentally friendly. Part of the major problem with the past use of foam products is that they now occupy a great deal of space in our landfills. Therefore, there is a significant need for an agent that can be used at these landfills on foam, which has already been deposited into landfills. The only way to accomplish this is by the application of a foam reducing agent that has no detrimental side effects on the environment.
In a prior effort to address some of these needs, Katz et al. were recently issued U.S. Pat. No. 6,743,828 which is directed to a polystyrene foam reduction agent consisting of dibasic esters and a process using a liquid contact with polystyrene foam wherein the higher boiling temperature of the dibasic esters and contact with the liquid provides a volume reduction process and less evaporation loss as well as safer transportation of the chemicals and the polystyrene in its reduced state. The foam reduction agent consisting of dibasic esters and the process employed results in a reduced sludge that is also recyclable to superior quality raw polystyrene foam beads and the reduction agents are recoverable for future use.
In addition to the use of the dibasic esters to reduce the volume of polystyrene foam or expanded polystyrene foam (EPS), traditional methods used in the normal course of reducing and/or recycling polystyrene foam or expanded polystyrene foam (EPS) typically involve the use of significant ancillary equipment including, but not limited to, thin film evaporators (TFEs), and/or machines commonly referred to in the art as “fluffers”. Even if the temperature is considered low in the art, the TFE and/or fluffer time factors come into play and in the normal course of processing this results in a burning of the polystyrene foam or expanded polystyrene foam. It would therefore be beneficial in the processing stage for the polystyrene foam or expanded polystyrene foam to have a short residence time so as to shorten the thermal history of the polystyrene. The beaded polystyrene end product of such a process would be of higher quality and would be less likely to degrade.
Notwithstanding the usefulness of the prior polystyrene foam reduction recycling systems using dibasic or dialkyl esters, there is a continuing need in the art to develop other more versatile polystyrene foam reduction recycling systems to enhance the efficiency and full range of recycling possibilities. This invention solves these and other long felt needs by providing compositions and methods utilizing dibasic esters, low vapor pressure dibasic esters or functional derivatives thereof in combination with one or more extruders in a polystyrene foam reduction recycling system.
SUMMARY OF THE INVENTION
In general, the present invention is directed to novel polystyrene foam reduction recycling compositions and methods that solve the volume problem of recycling polystyrene foam materials while simultaneously allowing the easy and inexpensive shipment of the foamed materials after reduction in volume by use of one or more dibasic ester compositions in combination with one or more low heat based mechanical extruders. The methods of the present invention are applicable to all types of expanded or foamed polystyrene materials known to those of skill in the art.
In one aspect, a method of reducing/recycling polystyrene foam is provided comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: one or more standard dibasic ester (DBE) compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300° C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300° C.; and (e) recapturing the dibasic esters; wherein said recaptured dibasic esters are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.
In yet another aspect, a method of reducing/recycling polystyrene foam is provided comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: one or more low vapor pressure dibasic ester (LVP-DBE) compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300° C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300° C.; and (e) recapturing the low vapor pressure dibasic esters; and wherein said recaptured low vapor pressure dibasic esters are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.
In another aspect, a method of reducing/recycling polystyrene foam is provided comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: (i) one or more terpenes or isopernoids or any combination thereof and (ii) one or more surfactants; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300° C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300° C.; and (e) recapturing the terpenes or isopernoids; and wherein said recaptured terpenes or isopernoids are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.
In each of the aforementioned aspects and embodiments, the method of reducing a volume of polystyrene foam may further comprise one or more vegetable oils.
In yet another aspect, the invention relates, in part, to a novel polystyrene low heat treatment extruder recycling system comprising the steps of (a) exposing polystyrene foam in a container to a solution of specific esters comprising dimethyl glutrate [CAS # 1119-40-0] and dimethyl adipate [CAS# 627-93-0], wherein the esters specifically exclude dimethyl succinate in weight percentage amounts greater than 1%; (b) optionally covering said container; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300° C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300° C.; (e) optionally supplementing polystyrene foam until maximum reduction is achieved and (f) recapturing the dibasic esters; and wherein said recaptured dibasic esters are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.
In another aspect, a method of reducing/recycling polystyrene foam is provided comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: (i) one or more low vapor pressure dibasic ester compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate; (ii) one or more dibasic ester compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate or (iii) (a) one or more terpenes or isopernoids or any combination thereof and (b) one or more surfactants; or any combination thereof of (i)-(iii); (c) subjecting the polygel to a low source of heat over a temperature range not to exceed 200-300° C.; (d) subjecting the polygel to one or more extruders over a temperature range not to exceed 200-300° C.; and (e) recapturing the dibasic esters, the low vapor pressure dibasic esters and/or the terpenes or isopernoids; and wherein said recaptured dibasic esters, low vapor pressure dibasic esters and/or the terpenes or isopernoids are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.
In yet another aspect, the present invention provides a novel polystyrene low heat treatment extruder recycling system comprising a LVP-DBE composition that exhibits one or more of the following characteristics: (a) a significantly lower vapor pressure than standard DBE, (b) the distillation range of the solvent is narrower, (c) chemically more stable than standard DBE, (d) that is incompatible or can react with, inter alia, strong oxidizers, acids, alkalies, etc., (e) that will not undergo polymerization, (f) that reduces foamed polystyrene at a rate of action that equals or exceeds that of standard DBE, (g) that exhibits a greater holding capacity than standard DBE, (h) that exhibits a higher flash point than standard DBE, (i) that is not regulated as a hazardous material by DOT, IMO, or IATA, and (j) for which none of the components present in the LVP-DBE composition are listed by IARC, NTP, OSHA or ACGIH as a carcinogen.
In yet another aspect, the invention relates, in part, to a novel polystyrene low heat treatment extruder recycling system comprising exposing said foams to liquid sprays of specific esters exhibiting one or more of the aforementioned characteristics.
In yet another aspect, the invention relates, in part, to a novel polystyrene low heat treatment extruder recycling system comprising exposing said foams to liquid sprays of specific esters comprising dimethyl glutarate [CAS # 1119-40-0] and dimethyl adipate [CAS# 627-93-0], wherein the ester specifically excludes dimethyl succinate in weight percentage amounts greater than 1%, and wherein said esters exhibit one or more of the aforementioned characteristics.
In yet another aspect, the invention relates, in part, to a novel polystyrene low heat treatment extruder recycling system comprising exposing said foams to liquid sprays of specific esters, wherein the ester is selected from the group consisting of dimethyl glutarate [CAS # 1119-40-0] and dimethyl adipate [CAS# 627-93-0], wherein the esters specifically exclude dimethyl succinate in weight percentage amounts greater than 1%, and wherein said esters exhibit one or more of the aforementioned characteristics.
In yet another aspect, the present invention provides a novel polystyrene low heat treatment extruder recycling system in which the recaptured standard dibasic ester, LVP-DBE and/or terpene or isopernoid composition is useful for rendering organic polymeric coatings and finishes such as paints, varnishes, lacquers, shellacs, gums, natural and synthetic resins removable from a wide range of coatings and surfaces such as, for example, and not by way of limitation, wood, metal, and plastic. An important feature of the recaptured standard dibasic ester, LVP-DBE and/or terpene or isopernoid composition is that it provides excellent results without the need of evaporation retardants or film-forming compounds. Thus, there is no need to include in the formulation such evaporation retardants as paraffin wax or the like, which have the disadvantage that they need to be removed in subsequent processing steps. Another feature of the recaptured standard dibasic ester, LVP-DBE and/or terpene or isopernoid composition produced by the novel polystyrene low heat treatment extruder recycling system of the present invention is that it has a shelf life in excess of about one year to about 10 years.
In one embodiment, the polystyrene foam may be shredded or grinded prior to exposure to the aforementioned specific ester combination using one or more extruders of the present invention in combination with any other mechanical apparatus known to those of skill in the art for shredding or grinding polystyrene foam. By converting the polystyrene foam into smaller fragments, a greater surface area for exposure to the specific ester combination is provided thereby affording faster polystyrene foam reduction. Also contemplated for use with the extruders used in the methods of the present invention are certain hot air machines and/or dryers known to those of skill in the art for partially or fully drying the polystyrene foam prior to use with the extruder.
In one embodiment, in each of the aforementioned aspects, step (b) of adding the solution comprising the dibasic esters, the low vapor pressure dibasic esters, and/or the terpenes or isopernoids or any combination thereof may be carried out without prior treatment of the polystyrene foam with one or more thin film evaporators or one or more fluffers, and/or one or more dryers.
In each of the aforementioned aspects and embodiments of the low heat extruder polystyrene recycling methods disclosed herein the ratio of DBE, low vapor pressure DBE and/or the terpene and/or isoprenoid is approximately one third (wt %) to approximately two thirds (wt %) polystyrene foam or EPS. Any ratio higher than approximately 50% of solvent to polystyrene foam or EPS in the low heat extruder polystyrene recycling methods disclosed herein is not as effective as the extruder is unable to strip or remove the solvent fast enough.
In yet another embodiment, in each of the aforementioned aspects, after the step of recapturing the dibasic esters, the low vapor pressure dibasic esters and/or the terpenes or isopernoids, the resultant polystyrene polygel may optionally be subjected to one or more thin film evaporators (TFEs) for a time period of approximately 1-2 minutes, but not to exceed approximately 10 minutes.
In each of the aforementioned aspects and embodiments, the resultant high quality beaded polystyrene product so produced has a series of desired properties including, but not limited to, a heat index of less than about 9, a final concentration of less than about 1-1000 ppm of the standard DBE composition, LVP-DBE composition, or terpene and/or isoprenoid in the high quality beaded polystyrene product, no evidence of spleaning, crazing and/or burnt discoloration, and a relatively low melt viscosity and molecular weight, or any combination thereof.
Other preferred embodiments of the invention will be apparent to one of ordinary skill in the art in light of what is known in the art, in light of the following drawings and description of the invention, and in light of the claims.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a process schematic for a 30 mm devolatilization extruder.
FIG. 2 depicts a 30 mm devolatilizer screw and barrel arrangement 961841—1.
FIG. 3 depicts a rear vent yield versus feed superheat, calculated for sample conditions from adiabatic flash model of polystyrene and dimethyl succinate.
FIG. 4 depicts a specific energy consumption versus specific rate.
FIG. 5 depicts a melt temperature versus specific rate for samples 5 to 14.



DETAILED DESCRIPTION OF THE INVENTION
This invention reveals a method to provide rapid destruction of the cells of polystyrene foams by use of a combination of specific chemicals of the class of aliphatic dibasic esters, either alone or with other foam reduction agents and surfactants that are active and which readily attack, with no or little heat activation, polystyrene foam and allows easy recycling. The easy recycling is due to reduced bulk and ease of storage of the collapsed polystyrene foam in sludge foam, ease of processing, and economical transportation prior to recycling. The collapsed polystyrene foam may be easily and safely transported.
The inventors have unexpectedly found that by using one or more extruders, operating in the presence of low heat, the DBE and/or LVP DBE, taken either alone or in combination with one or more terpenes and/or isopernoids, may be efficiently recovered or recycled so that the final concentration of the DBE, the LVP DBE, the terpenes and/or isopernoids in the reduced polystyrene foam and/or EPS is less than approximately 1 ppm. Such low final concentrations of DBE and/or LVP DBE have heretofore not been previously obtainable in the polystyrene foam recycling industry.
The inventors have also unexpectedly found that by use of one or more extruders in the presence of low heat the DBE and/or LVP DBE, either alone or in combination with one or more terpenes and/or isoprenoids, the recovered or recycled reagents react faster when used to reduce the polystyrene as the amount of water is vented away from the DBE and/or LVP DBE. Thus, the less water in the faster the reaction time with expanded polystyrene foam or the polystyrene foam. The venting process is accomplished by use of one or more extruders in the presence of low heat.
Standard Dibasic Ester Compositions
Specifically included within the scope of the polystyrene foam reduction low heat treatment extruder recycling system of the present invention is the use of standard dibasic esters including, for example, and not by way of limitation, as disclosed in the inventors' U.S. Pat. No. 6,743,828.
Also specifically included within the scope of the polystyrene foam reduction low heat treatment extruder recycling system of the present invention is the use of DBE, DBE-4, and DBE-9 as specifically set forth in Table 1, infra.
Low Vapor Pressure Dibasic Ester (LVP-DBE) Compositions
In those embodiments of low heat treatment extruder methods of reducing polystyrene foam that use low vapor pressure dibasic esters, the low vapor pressure dibasic esters of the present invention comprise a composition of LVP-DBE comprising dimethyl glutarate [CAS # 1119-40-0] and dimethyl adipate [CAS# 627-93-0]. In one embodiment, the novel polystyrene foam reduction recycling system of the present invention further comprises a composition of LVP-DBE comprising dimethyl glutarate [CAS # 1119-40-0], dimethyl adipate [CAS# 627-93-0] and dimethyl succinate (CAS# 106-65-0), wherein the weight percentage of dimethyl succinate is 1% and less. For example, and not by way of limitation, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, and any numerical values there between are specifically permitted for use in the polystyrene foam reduction recycling system of the present invention. Other LVP-DBE-based compositions that may be used in the novel polystyrene foam reduction low heat treatment extruder recycling system of the present invention include LVP-DBE-2, LVP-DBE-3, LVP-DBE-5, LVP-DBE-6, and LVP-DBE-1B as specifically set forth in Table 1, infra.
In those embodiments of the low heat treatment extruder methods of reducing polystyrene foam that use low vapor pressure dibasic esters, specifically excluded within the scope of those embodiments is the use of non-low vapor pressure DBE. Also specifically excluded within the scope of the polystyrene foam reduction low heat treatment extruder recycling system of the present invention is the use of DBE, DBE-4, and DBE-9 as specifically set forth in Table 1, infra. Also specifically excluded within the scope of the polystyrene foam reduction low heat treatment extruder recycling system of the present invention is the use of dimethyl succinate (CAS# 106-65-0) in weight percentage amounts greater than 1%.
In one embodiment of the polystyrene foam reduction low heat treatment extruder recycling system of the present invention, the percentage of dimethyl glutarate in the LVP-DBE composition of the present invention is in the range of between about 5% and about 98% weight percent. In one embodiment, the percentage of dimethyl adipate in the LVP-DBE composition of the present invention is in the range of between about 20% and about 98.5% weight percent. In one embodiment, the percentage weight of total diesters in the LVP-DBE composition of the present invention is at least 98.5% weight percent, with an average weight percentage of approximately 99.4-99.7%. It is intended herein that the ranges recited also include all those specific percentage amounts between the recited range. For example, the range of about 20 to 98.5% also encompasses 21 to 97.5% weight percent, 22 to 98.5% weight percent, 21 to 96.5% weight percent, etc., without actually reciting each specific range therewith. In another embodiment of the polystyrene foam reduction low heat treatment extruder recycling system of the present invention, the percentage of dimethyl glutarate in the LVP-DBE composition of the present invention is in the range of between about 2% and about 40% weight percent and the percentage of dimethyl adipate in the LVP-DBE composition of the present invention is in the range of between about 10% and about 50% weight percent.
In yet another aspect, the present invention provides a polystyrene foam reduction low heat treatment extruder recycling system comprising a composition of LVP-DBE that exhibits a significantly lower vapor pressure than standard DBE. In one embodiment, the lower vapor pressure exhibited by the LVP-DBE composition of the present invention is in the range of between about 0.01 to about 0.001 mm Hg @ 20° C. (68° F.), compared to the vapor pressure of standard DBE which is in the range of between about 0.10 to about 0.02 mm Hg @ 20° C. (68° F.). Such lower vapor pressure is important because it translates into a healthier work environment and a lower inhalation risk for potential users and recyclers. The lower vapor pressure also minimizes any apparent odor in the work area for users and recyclers.
In yet another aspect, the present invention provides a polystyrene foam reduction low heat treatment extruder recycling system comprises a composition of LVP-DBE that exhibits a significantly lower vapor pressure than standard DBE, which LVP-DBE meets the low vapor pressure criteria established by the California Air Resources Board for volatile organic compounds in consumer products per California Code of Regulations, Title 17, Division 3, Chapter 1, Subchapter 8.5, Article 2, Section 94508(a) 80(A), the entire contents of which are incorporated herein by reference.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a composition of LVP-DBE that exhibits a significantly lower vapor pressure than standard DBE, which LVP-DBE meets the exemption criteria for consumer products per EPA 40 C.F.R. Section 59.203(f)1, the entire contents of which are incorporated herein by reference.
In one embodiment, the novel polystyrene foam heat treatment extruder recycling system of the present invention further comprises a two component composition of LVP-DBE (for example, dimethyl adipate and dimethyl glutarate) that provides simplified distillation or other recycling methods.
In yet another embodiment, the novel polystyrene low heat treatment extruder recycling system of the present invention comprises a three component composition of LVP-DBE in which the distillation range of the solvent used to reduce the polystyrene or EPS is unexpectedly narrower than that found in U.S. Pat. No. 6,743,828. Such narrower distillation ranges result in lower equipment costs, better control and lower production and use costs. In one embodiment, the distillation range of the solvent of the LVP-DBE composition of the present invention is in the range of between about 210 to about 225° C. (about 410 to about 437° F.), compared to the distillation range of the solvent of standard DBE which is in the range of between about 196 to about 225° C. (about 385 to about 437° F.). The unexpectedly narrower distillation range of the solvent of the LVP-DBE composition serves to narrow down the boiling range by over 9%. Thus, the range can now be narrowed to reflect the closer boiling point which will result in a better polystyrene bead. By use of a higher heat ratio in the LVP-DBE polygel, breakdown of the LVP-DBE will not occur as easily.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that is chemically more stable than standard DBE. Since the vapor pressure of the LVP-DBE is lower, the polystyrene product is more stable and has certain properties that make LVP-DBE a better choice to use in a given work place. For example, in one embodiment, the LVP-DBE composition will not remove paint or adhesives as quickly as standard DBE.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that is incompatible or can react with, inter alia, strong oxidizers, acids, alkalies, etc.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that will not undergo polymerization.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that reduces foamed polystyrene at a rate of action that equals or exceeds that of standard DBE. Thus, in one embodiment, in outdoor conditions when the temperature is warm, the lower vapor pressure DBE will not evaporate as quickly and therefore will be more effective in reducing expanded polystyrene foam (EPS).
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that exhibits a greater holding capacity than standard DBE. In one embodiment, such greater holding capacity at ambient temperature approaches approximately 55%-approximately 75% of polystyrene with the remainder being solvent (LVP-DBE), whereas the holding capacity for a polystyrene low heat treatment extruder recycling system using standard DBE approaches approximately 0-50%. Such greater holding capacity is demonstrated by virtue of the lower viscosity of the solution at equal concentrations. This lower viscosity leads to a more cost effective use of the solvent as a more concentrated polygel can be produced which makes recycling of polystyrene foam more effective.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that exhibits a higher flash point than standard DBE. In one embodiment, the flash point of the LVP-DBE composition of the present invention is in the range of between about 102 to about 104° C. (about 216 to about 219° F.), compared to the flash point of standard DBE which is about 100° C. (about 212° F.). Such higher flash points leads to increased safety for the user and recycling process and will minimize transportation restrictions.
In yet another aspect, the present invention provides a novel polystyrene foam low heat treatment extruder recycling system comprising a LVP-DBE composition that is not regulated as a hazardous material by Department of Transportation (DOT), International Maritime Organization (IMO), or International Air Transport Association (IATA).
In yet another aspect, the present invention provides a novel polystyrene low heat treatment extruder recycling system comprising a LVP-DBE composition for which none of the components present in the LVP-DBE composition are listed by International Agency for Research on Cancer (IARC), National Transportation Program (NTP), Occupational Health and Safety Organization (OSHA) or American Conference of Industrial Hygienists (ACGIH) as a carcinogen.
In yet another aspect, the present invention provides a novel polystyrene low heat treatment extruder recycling system comprising a LVP-DBE composition that exhibits biodegradability as measured by the 28-day closed bottle test. The LVP-DBE composition was tested for biodegradability using the 28-day closed bottle test. A minimum of 60% biodegradation must be reached in a 14 day window after exceeding the 10% level in order to pass this test and be rated as readily biodegradable. All of the components of the low heat treatment extruder recycling system of the present invention pass this test and, therefore, DBE-LVP is considered readily biodegradable. In one embodiment, the biodegradability of the dimethyl glutrate in the LVP-DBE composition of the present invention is in the range of between about 70% at day 7 and about 84% at day 14%. In one embodiment, the biodegradability of the percentage of dimethyl adipate in the LVP-DBE composition of the present invention is in the range of between about 58% at day 7 and about 84% at day 14. In one embodiment, the biodegradability of the dimethyl succinate in the LVP-DBE composition of the present invention is in the range of between about 80% at day 7 and about 90% at day 22.
The method of the present invention involves the exposure of said foams to liquid sprays of specific esters comprising LVP-DBEs that exhibit one or more of the following characteristics: (a) a significantly lower vapor pressure than standard DBE, (b) the distillation range of the solvent is narrower, (c) chemically more stable than standard DBE, (d) that is incompatible or can react with, inter alia, strong oxidizers, acids, alkalies, etc., (e) that will not undergo polymerization, (f) that reduces foamed polystyrene at a rate of action that equals or exceeds that of standard DBE, (g) that exhibits a greater holding capacity than standard DBE, (h) that exhibits a higher flash point than standard DBE, (i) that is not regulated as a hazardous material by DOT, IMO, or IATA, and (j) for which none of the components present in the LVP-DBE composition are listed by IARC, NTP, OSHA or ACGIH as a carcinogen. Examples of DBE dibasic esters are known to those of skill in the art and include for example, and not by way of limitation, those listed in Table 1 infra.
In addition to the aforementioned list of properties for the LVP-DBE composition for use in the polystyrene low heat treatment extruder recycling system of the present invention, the specific properties of each of the LVP-DBE-2, LVP-DBE-3, LVP-DBE-5, LVP-DBE-6, and LVP-DBE-1B DBE Dibasic Ester compositions as specifically set forth in Table 1 infra are also included as if specifically set forth herein, including for example, and not by way of limitation, ester content (wt. %, min.), water content (wt. %, max.), acid number, mg KOH/g, max., color, APHA, max., turbidity, max., methanol, wt %, isobutanol, wt %, molecular weight, specific gravity at 20/20° C., density at 20° C. (lb/gal), distillation range, ° C., vapor pressure at 20° C. (mm Hg), solubility in water, wt % at 20° C., water solubility in DBE, wt % at 20° C., freezing point, ° C., flashpoint, Tag closed cup, ° C., auto ignition temperature, ° C., latent heat of vaporization, cal/g, viscosity at 25° C., cst, and properties of the solvent including, for example, and not by way of limitation, non-polar, polar, hydrogen bonding, surface tension at 20° C., dynes/cm, and electrical resistance at 24° C., Meg Ohms, or any combination thereof.
The above-listed characteristics, as well as any other characteristics provided in Table 1 infra, confer superior and unexpected results, properties, and advantages to the LVP-DBE composition for its use in the polystyrene low heat treatment extruder recycling system of the present invention compared to the standard DBE composition as used in U.S. Pat. No. 6,743,828. The aforementioned features and benefits of using the LVP-DBE composition of the present invention translate into a stronger commitment for more responsible stewardship of the environment and provide an excellent example of the concept of closed-loop recycling.







TABLE 1







DBE Dibasic Esters
















DBE
DBE-2
DBE-3
DBE-4
DBE-5
DBE-6
DBE-9
DBE-IB



















Specification










Ester content,
99.0 
99.0 
99.0 
98.5 
99.0 
99.0 
99.0 
98.5 


wt. %, min.


Water content,
 0.10
 0.10
 0.20
 0.04
 0.10
 0.05
 0.10
0.1


wt. %, max.


Acid number, mg
 0.30
 1.00
 1.00
 0.50
 0.50
 1.00
 0.50
 1.00


KOH/g, max.


Dimethyl
10-25
20-28
85-95
0.1 max.
0.2 max.
98.5 min.
0.3 max.
10-20f


adipate, wt %


Dimethyl
55-65
72-78
 5-15
0.4 max.
98.0 max. 
 1.0 max.
65-69
55-70f


glutarate, wt %


Dimethyl
15-25
1.0 max.
1.0 max. 
98.0 max. 
1.0 max.
0.15 max.
31-35
20-30f


succinate, wt %


Color, APHA, max
15 max.
15 max.
15 max.
 15 max.
 15 max.
  15 max.
 15 max.
15 max.


Turbidity, max.
 5 max.
 5 max.
 5 max.
  5 max.
  5 max.
  5 max.
  5 max.
 5 max.


Typical


Composition


Ester content,
99.5 
99.5 
99.5 
99.5 
99.5 
99.0 
99.0 
99.5 


wt. %, min.


Dimethyl
21  
24  
89  
—
0.1
99  
0.2
21f 


adipate, wt %


Dimethyl
59  
75  
10  
0.3
99  
<0.5  
66  
59f 


glutarate, wt %


Dimethyl
20  
0.3
0.2
98  
0.4
<0.1  
33  
20f 


succinate, wt %


Methanol, wt %
 0.20
<0.1  
<0.1  
<0.1  
<0.1  
<0.1  
<0.1  
N/A


Isobutanol, wt %
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.2


Water, wt %
 0.05
 0.02
 0.04
 0.02
 0.03
 0.03
 0.04
 0.05


Physical


Properties


(typical values)


Molecular Weight
159a  
163a  
173a  
146   
160   
174   
156a  
242   


Specific gravity at
  1.092c
  1.081c
  1.068c
 1.121
 1.091
 1.064
  1.099c
0.958-0.960  


20/20°


Density at 20° C.
  9.09c
  9.00c
  8.89c
 9.33
 9.08
 8.86
  9.18c
  7.97c


(lb/gal)


Distillation
196-225
210-225
215-225
196   
210-215
227-230
196-215
275-295  


Range, ° C.


Vapor Pressure at
  0.20c
  0.04c
  0.02c
 0.13
 0.05
 0.01
  0.07c
 <0.01c


20° C. (mm Hg)


Solubility in water,
5.3
4.2
2.5
7.5
4.3
2.1
ca. 5  
<0.1  


wt % at 20° C.


Water Solubility in
3.1
2.9
2.5
3.8
3.2
2.4
ca. 3.5
0.6


DBE, wt % at


20° C.


Freezing Point, ° C.
−20c  
−13c  
8c 
19  
−37   
10  
−10c  
−55   


Flashpoint, Tag
100   
104   
102   
94  
107   
113   
94  
133   


closed cup ° C.


Physical


Properties


(typical values)


Auto ignition
370   
375   
360   
365   
365   
360   
365   
>370   


temp., ° C.


Latent heat of
81  
80  
79  
85  
81  
79  
82  
N/A


vaporization, cal/g


Viscosity at 25° C.,
2.4
2.5
2.5
2.5
2.5
2.5
2.4
18.8 


cst


Solvent Properties


non-polard
8.3
8.3
8.3
8.3
8.3
8.3
8.3
7.9


polard
2.3
2.2
2.1
2.5
2.3
2.1
2.3
1.3


hydrogen bondingd
4.8
4.7
4.5
5.0
4.8
4.5
4.8
3.6


Surface tension
 3.56
N/A
N/A
N/A
N/A
N/A
N/A
27.2


at 20° C., dynes/cm


Electrical
0.5
N/A
N/A
N/A
N/A
N/A
N/A
N/A


Resistancee at


24° C., Meg Ohms





aAverage for mixture


bÄsp. Gr./ÄT = −0.0007 per ° C. over the range 20-50° C.


cApproximate, based on composition


dHansen Solubility Theory


eRansberg Paint Resistance Tester Model 219CB


fDi-Isobutylester






Terpene and Isoprenoid Compositions
In yet another aspect, the invention relates, in part, to the novel use of either standard DBE or LVP-DBE in a polystyrene low heat treatment extruder recycling system that can be more effective if mixed with terpenes or isopernoids such as, for example, and not by way of limitation, d-limonene. In certain other embodiments, the polystyrene low heat treatment extruder recycling system of the present invention can be utilized solely with one or more terpenes or one or more isopernoids or any combination thereof.
In one embodiment, terpenes, isopernoids can be added and the addition of any from the family of non-ionic surfactants will serve to raise the flash point. A representative example of a non-ionic surfactant would be NP 9 or the terpenes such as d-limonene, etc. Other foam reducing agents such as esters from celery, or other vegetables such as soybean, etc., or for example, olive oil, will work but prove to be inefficient on their own. In another embodiment, some of the above esters do not have a low flash point or have higher vapor pressure working in combination with LVP-DBE but will work in combination just as fast and in some case even at faster rates of reduction. In short, the addition of surfactants serves to help raise the boiling point of other solvents. All of the other compositions in the terpenes and isoprenoids family have lower boiling points compared to both standard DBE and or LVP-DBE.
The term “surfactant” is used following the nomenclature system of the International Cosmetic Ingredient Dictionary, 5.sup.th ed., J. A. Wenninger et al. eds., The Cosmetic, Toiletry, and Fragrance Association, Washington, D.C. (1993), usually followed by a chemical name and a trademark name of a particular product. Other non-limiting examples of surfactants useful in the compositions and methods of the present invention are isotridecyl alcohol tri-ethoxylate (SurfonicTM TDA-3B, Huntsman Corp.), C.sub.9-C.sub.11 pareth-6 [polyethylene glycol ether of mixed synthetic C.sub.9-C.sub.11 fatty alcohols having an average of 6 moles of ethoxalate; NeodolTM 91.6], C.sub.11-C.sub.15 pareth-59 [polyethylene glycol ether of mixed synthetic C.sub.11-C.sub.15 fatty alcohols having an average of 59 moles of ethoxalate; TergitolTM 15-S-59], nonoxynol-6 [polyethylene glycol (6) nonylphenyl ether; TergitolTM NP-6], nonoxynol-9 [polyethylene glycol (9) nonylphenyl ether; TergitolTM NP-9], and a modified alkanolamide alkanolamine [MonamineTM 1255], as well as other surfactants known to those of skill in the art.
Extruders and Thin Film Evaporators
In each of the aforementioned aspects and embodiments of the low heat treatment extruder methods of reducing polystyrene foam of the present invention, any form of extruder known to those of skill in the art may be used, in combination with low heat, to reduce the volume of polystyrene foam. Non-limiting representative examples of extruders that may be used in the methods of the present invention include, inter alia, U.S. Pat. Nos. 5,490,725, 5,141,426, 5,125,824, 5,096,638, 5,089,193, 5,064,587, 4,892,691, 4,615,664, 4,431,311, 4,201,480, 4,160,638, the entire contents of each of which are incorporated by reference in their entirety.
The preferred extruders for use in the methods of the present invention include those extruders for example as manufactured by Berstorff Corporation (Florence, Kentucky) and/or Hermann Berstorff Maschinenbau GmbH (Hannover, Del.). A non limiting representative example of a Berstorff Corporation extruder for use in the methods of the present invention is Model Number Twin Screw Extruder ZE-25.
Such extruders include, for example, and not by way of limitation, single extruders with varying bore sizes, twin extruders with varying bore sizes, devolatilization extruder, devolatilizer screw and barrel arrangement, rear vent extruder, feed superheat extruder, and/or any combination thereof. The varying bore sizes of the extruders used in the methods of the present invention are preferably on the order of approximately 25 mm to 128 mm. In certain embodiments, The bore size of one or more large bore size extruders that may optionally be used in the methods of the present invention is the order of approximately 756 mm.
One example of a twin screw extruder that may be used in the low heat treatment extruder methods of the present invention is that described in Example 1, infra. Yet another of a twin screw extruder that may be used in the low heat treatment extruder methods of the present invention is that depicted in Example 2, infra.
In each of the aforementioned aspects and embodiments of the low heat treatment extruder methods of reducing polystyrene foam of the present invention, any form of thin film evaporator known to those of skill in the art may optionally be used, in combination with low heat extruders, to reduce the volume of polystyrene foam. Such thin film evaporators include, for example, and not by way of limitation, the thin film evaporator depicted in Example 1, infra.
In another embodiment, the polystyrene foam may be shredded or grinded prior to exposure to the specific esters combination using one or more extruders of the present invention in combination with any other mechanical apparatus known to those of skill in the art for shredding or grinding polystyrene foam and the aforementioned specific ester combination is then applied using a solvent spraying unit physically connected to the mechanical apparatus. In this embodiment, a container may be placed under the apparatus to collect the reduced sprayed polystyrene foam.
In yet another embodiment, the polystyrene foam may be shredded or grinded prior to exposure to the specific esters combination using any mechanical apparatus and the specific ester combination is then applied using a hand held solvent spraying unit.
Properties of the Recaptured Low Vapor Pressure Dibasic Ester (LVP-DBE) Composition
In each of the aforementioned aspects and embodiments, the resultant high quality beaded polystyrene product so produced has a heat index of less than about 9. It is intended herein that the range implied within a heat index of less than 9 also includes all those specific recitations, including 9, 8, 7, etc., and any fraction thereof without actually reciting each specific range therewith.
In each of the aforementioned aspects and embodiments, the resultant high quality beaded polystyrene product so produced contains the dibasic esters, the low vapor pressure dibasic esters and/or the terpenes or isopernoids in a concentration of less than about 1-1000 ppm. It is intended herein that the range concentration of less than about 1-1000 ppm also includes all those specific recitations, including 1, 2, 3- to about 998, 999, 1000, etc., without actually reciting each specific range therewith.
In each of the aforementioned aspects and embodiments, the resultant high quality beaded polystyrene product so produced contains no evidence of spleaning, crazing or burnt discoloration. As used herein, the phrase no evidence of spleaning or crazing is commonly known to those of skill in the art of polystyrene that the beaded polystyrene end product will contain no evidence of hairline fractures and/or cloudiness in the end product. As used herein, the phrase no evidence of burnt discoloration is commonly known to those of skill in the art of polystyrene that the beaded polystyrene will contain no golden brownish or reddish color.
In each of the aforementioned aspects and embodiments, the resultant high quality beaded polystyrene product so produced has relatively low melt viscosity. As used herein, relatively low melt viscosity means under a load temperature of 450 degrees Farenheit.
Uses of the Recaptured Standard Dibasic Ester and/or Low Vapor Pressure Dibasic Ester (LVP-DBE) Compositions
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a paint stripper.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a graffiti remover.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a water proofing agent that may be applied via spray means or brush on means.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention for removing paints, inks, grease, and the like from skin.
In yet another aspect, the invention relates, in part, to the novel use of the Standard Dibasic Ester and/or LVP-DBE composition of the present invention as an extender of the life of concrete by mixing in a minimum of 1.5% of the composition (the reduced polystyrene) but not to exceed 27.5% of the composition.
In yet another aspect, the invention relates, in part, to the use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as an adhesive remover.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a tar remover.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a stain remover.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured Standard Dibasic Ester and/or LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a scuff mark remover.
In yet another aspect, the invention relates, in part, to the novel use of the recaptured LVP-DBE composition of the polystyrene low heat treatment extruder recycling system of the present invention as a general degreaser.
In each of the aforementioned aspects and embodiments, the resultant high quality beaded polystyrene product so produced by the novel polystyrene low heat treatment extruder recycling system may be separated from said solution so that the gel-like substance may be applied externally to said object or mixed with said materials to increase said object's or said material's waterproofing agent's characteristics, paint stripper's characteristics, graffiti remover's characteristics, extender of the life of concrete's characteristics, adhesive remover's, stain remover's characteristics, scuff mark remover's characteristics, and/or general degreaser's characteristics, or any combination thereof, or increase the recycleability of the gel-like substance into polystyrene foam.
Methods of Reducing Polystyrene Foam Using the Low Heat Treatment Extruder Recycling System
This invention solves the volume problem of polystyrene foam materials and allows the easy and inexpensive shipment of the foam materials after cost effective reduction in volume by use of certain liquid aliphatic dibasic esters. The materials used in the LVP-DBE composition comprise dimethyl glutarate, dimethyl adipate and dimethyl succinate (with the proviso that the dimethyl succinate is in weight percentage amounts of 1% and less), which are effective foam reduction agents. While they have activity individually, as mixtures of dimethyl glutarate and dimethyl adipate with dimethyl succinate in weight percentage amounts of 1% and less, the action is especially favorable. Moreover, with the addition of small amounts of heat to the process, the overall effectiveness of the LVP-DBE composition is increased while having little effect on the cost of recycling. In particular, when heat is added to the process the speed of reduction of the polystyrene foam or expanded polystyrene (EPS) is increased. The heat can be introduced by several methods, for example, and not by way of limitation, heating the mixture by use of a drum heater or an inline heating element delivering the LVP-DBE or LVP-DBE mixture will dramatically the increase rate of reduction by up to three (3) to five (5)-fold but not to exceed twenty fold. Also, because of the lower boiling points of the individual reactants, very little reactant is lost in the heating process. The lower boiling points and benign nature of the reactants makes the reactant process safer than previously known and commercially used chemical reactants with higher boiling points.
The use of the aforementioned active LVP-DBEs in the polystyrene low heat treatment extruder recycling system of the present invention assist in making the expanded or foamed polystyrene materials easier to reduce, collapse and/or reprocess. The polystyrene foam bead or pumpable polygel product of this process is solvatable. The polystyrene foam bead product can also be made pumpable and can then be filtered and reprocessed or injected into furnaces where the high fuel value of the material offers considerable energy savings for users and/or recyclers. If filtered and recycled, high quality polystyrene raw material bead product can be made. In particular, both the standard DBE and LVP-DBE produce high quality beads. This is a function of the Styro Solve recycling system previously implemented by Katz et al., the contents of which are specifically incorporated by reference in their entirety. By using the LVP-DBE of the present invention, the polygel so produced and transported to the plant has proven to be more consistent than that produced using standard DBE. Since the LVP-DBE used in the methods of the present invention has a lower vapor pressure, it is noted that less evaporation occurs on route to the processing plant and hence one receives a more constant polygel product. This also translates into less solvent being used in the polystyrene reprocessing center. Moreover, by using less solvent to produce the correct viscosity for recycling, one also reduces the time and energy required in the process. This results in a more cost effective and cost efficient polystyrene foam recycling process.
Heretofore, it has been impossible to cost effectively recycle polystyrene high quality raw post consumer material. High quality recycling is important in polystyrene recycling where the recycled product is desirable to be used in the food packing industry. The food packing industry has strict requirements for parts per million of contaminants in the polystyrene used, the contents of which are specifically incorporated by reference in their entirety. The process disclosed herein is the only known recycling process that is both cost effective and yields recycled material that meets the requirements of the food packing industry while still satisfying the low vapor pressure criteria established by the California Air Resources Board for volatile organic compounds in consumer products per California Code of Regulations, Title 17, Division 3, Chapter 1, Subchapter 8.5, Article 2, Section 94508(a) 80(A) and meets the exemption criteria for consumer products per EPA 40CFR59.203(f)1, the entire contents of which are incorporated herein by reference. The polystyrene low heat treatment extruder recycling system of the present invention achieves these and other benefits as set forth herein.
Furthermore, the process of volume reduction of polystyrene foam has been previously hampered by high loss due to evaporation. The use of the novel composition of the present invention helps cure this problem by employing polystyrene foam reduction agents comprising LVP-DBEs that exhibit one or more of the following characteristics: (a) a significantly lower vapor pressure than standard DBE, (b) the distillation range of the solvent is narrower, (c) chemically more stable than standard DBE, (d) that is incompatible or can react with, inter alia, strong oxidizers, acids, alkalies, etc., (e) that will not undergo polymerization, (f) that reduces foamed or expanded polystyrene at a rate of action that equals or exceeds that of standard DBE, (g) that exhibits a greater holding capacity than standard DBE, (h) that exhibits a higher flash point than standard DBE, (i) that has a relatively low odor compared to standard DBE; (j) that is not regulated as a hazardous material by DOT, IMO, or IATA, and (k) for which none of the components present in the LVP-DBE composition are listed by IARC, NTP, OSHA or ACGIH as a carcinogen.
The materials used in this method of polystyrene foam volume reduction are also recoverable by removal in the recycling process and the majority of compounds used can be easily separated from moisture and volatile organics by a combination of decanting, mutual solubility with other organic compounds and thermal stripping. The materials are further environmentally non-toxic.
The development of this invention began with identification of the unexpected affinity of the vapors of certain solvents found in perfumes. Identification of the active agent in the process became the key to the initial polystyrene foam volume reduction process. This material identified was d-limonene. D-limonene vapors acted upon the polystyrene foam and rapidly reduced the volume. The sorption process, when there was sufficient vapor present, was one that continued until the polystyrene foam was reduced to a viscous liquid. This aggressive mutual solubility was relatively fast as long as there is a presence of the needed vapors.
This invention furthers the concept of foam reduction by the further discovery of a set of chemicals which are as effective as the vapor process noted with d-limonene but which work in a liquid state and thus avoids the need for a vapor saturated atmosphere around the collapsing foam. The inventor's prior work focused on the combined use of non-low vapor pressure dimethyl glutarate and dimethyl adipate, and dimethyl succinate (CAS# 119-40-0; CAS# 627-93-0; CAS# 106-65-0, respectively) which are effective polystyrene foam reduction agents. The present invention furthers this prior discovery in that one or more extruders are used to grind the polystyrene foam in the presence of low heat.
The present invention also furthers this prior discovery in that one or more mechanical extruders are used to grind the polystyrene foam in the presence of low heat and one or more LVP-DBEs are employed as effective polystyrene foam reduction agents. In certain embodiments, the use of dimethyl succinate (CAS# 106-65-0) in weight percentage amounts greater than 1% is specifically excluded from the scope of the claims of the polystyrene low heat treatment extruder recycling system.
This invention discloses the new combination of chemicals in conjunction with low heat extruder processing of polystyrene foam and/or EPS that have not previously been considered for this purpose since they are not easy to use in the vapor phase. This new low vapor pressure dibasic ester combination of dimethyl glutarate and dimethyl adipate with dimethyl succinate present in weight percentage amounts of 1% and less eliminates much of the loss of the LVP-DBE reagents and further improves fire safety of the recycling or foam reduction process. The extra factor is the removal of the vapor requirement with discovery of liquid phase foam reduction agents. Importantly, by lowering the vapor pressure and lowering the loss of the LVP-DBE, the final stage of the reprocessing (recycling) is completed in a much more efficient manner. More importantly, this new method of recycling polystyrene foam using LVP-DBE now falls under the new California Code of Regulations, Title 17, Division 3, Chapter 1, Subchapter 8.5, Article 2, Section 94508 (a) 80(A) vapor-pressure EPA standards, the entire contents of which are incorporated herein by reference, thereby allowing the product to be used whereas the current standard DBE can not. Also, as noted supra, use of the LVP-DBE allows the polygel to be more safely transported to the recycling plant since there is less vapor pressure and thus, less evaporation of the LVP-DBE.
The formulas used for this invention consist of esters, specifically dibasic esters. These esters, especially the aliphatic dibasic esters such as dimethyl glutarate and dimethyl adipate (CAS# 119-40-0 and CAS# 627-93-0, respectively) have rapid reaction with polystyrene foams (both foamed and expanded), again acting as a stress cracking agent to destroy the cell wall webs which are highly stressed, then destroying the intercellular structure that remains. In addition, through experimentation that is the subject of the invention disclosed herein it was learned that the esters themselves were effective reactants when small amounts of heat were added to the process. Esters have been disclosed in a U.S. patent to Shiino et al. U.S. Pat. No. 5,629,352. However, that disclosure does not teach nor contemplate heating. The addition of small amounts of heat to the LVP DBE ester composition of the present invention prior to its use as a reactant greatly increases is reactant characteristics. The presence of esters without heat will reduce foam but in a time period that is not efficient for recycling purposes.
The dibasic or dialkyl esters disclosed herein for use in the polystyrene low heat treatment extruder recycling system of the present invention are not like the vapor processes used previously for foam reduction, which attack polystyrene foam by dissolving the polystyrene foam in the vapors of natural organic compounds. The present dibasic ester chemicals act as liquids. The dibasic esters have boiling points of 196 to 225° C., with a vapor pressure of only 0.2 mm Hg at 20° C. while the vapor pressure for LVP-DBE is only 0.02 Hg@ 20° C. They have an evaporation rate one tenth that of butyl acetate (Vapor pressure: 8 mm Hg at 20° C.), a common reference. Should the evaporation read from one fortieth for standard DBE (vapor pressure of 0.2 mm Hg @20° C.) and one four hundredth for LVP-DBE (vapor pressure of 0.02-0.04 mm Hg @ 20° C.). The specific gravity is slightly greater that water and mutual solubility is limited, allowing easy separation from water mixes. The dibasic esters also have low solubility in water and very high solubility in many alcohols so that separation schemes for recovery of the dibasic mix is feasible. The use of the dibasic esters, especially as a mixture, eliminates the large loss due to evaporation of the d-limonene used as the reducing agent in previous polystyrene foam reduction and recovery methods. The evaporation of active agents had previously made the process partly ineffective in many applications because of cost. The present invention is cost effective since this loss is very low.
The active agents also have several key property requirements or needs. Since the active agents will ultimately be placed into trash and garbage dumps, they must be environmentally safe and sound. Ideally, the active agents should not be within a range of boiling points and vapor pressures that will either immediately flash off or will over time evaporate to form a vapor layer within a landfill. With respect to solvents, which attack polystyrene foams, nearly all solvents are environmental problem chemicals. One class of chemicals broadly noted as isoprenoid and terpene compounds contain mostly environmentally safe naturally derived compounds, but most of these compounds are relatively volatile and would at least form a vapor layer in a landfill dump situation. The dibasic esters of this invention are of sufficiently low volatility that they do not form an indump/landfill vapor layer. This removes future problems of large vapor escape if the dump/landfill top impermeable layers are destroyed or damaged by man made or natural phenomena such as, inter alia, earthquakes.
In the prior patents on activation (for example, U.S. Pat. No. 5,223,543) the emphasis was on d-limonene. This reduction agent was selected for cost and volatility reasons since prior uses in the field relied on rapid action due to application in exposed areas as activated liquid. The use of a variety of liquid volatilities as long as vapor is generated over an extended time ranging from several hours to several days is also contemplated herein. The present use of esters with small amounts of heat, dibasic esters, and d-limonene in combination with esters and dibasic esters, as foam reduction agents is also effective and is specifically contemplated herein. The present invention is vastly superior compared to the use of standard DBE in creating a vast reduction in the vapor loss, in preventing vapor layers within garbage or landfill disposal dumps, in reduction of loss in reprocessing operations, which are typically at temperatures of over 270° C. Also, the present invention limits reliance on d-limonene, which can experience unstable pricing and is not easily reclaimed after recycling.
Finally, all of the contemplated reactants described herein may be optionally aided in their reactant effectiveness by including in the reactant process a pretreatment shredding or grinding of the polystyrene. The shredding can be effectively accomplished through the use of a hopper that shreds the polystyrene in the first stage of the process. The second stage of the process would have the shredded polystyrene being treaded with one of the disclosed reactants in a holding compartment of the hopper. The resultant foam sludge could then be pumped from the hopper to containers for transportation to waste or recycling locations.
In one embodiment, a mixture of a dibasic esters comprising dimethyl glutarate, dimethyl adipate, and dimethyl succinate with the dimethyl succinate being present in weight percentage amounts of 1% and less; and a surfactant, are sprayed onto pre-shredded polystyrene foam waste. In another embodiment, a mixture of a dibasic esters comprising dimethyl glutarate, dimethyl adipate, and dimethyl succinate with the dimethyl succinate being present in weight percentage amounts of 1% and less, are sprayed onto pre-shredded polystyrene foam waste in the absence of a surfactant.
Types of Polystyrene Foam and/or Expanded Polystyrene Foam that May be Reduced Using the Low Heat Extruder Methods
Examples of foam waste that can be reduced using the compositions and methods of the present invention can be from a variety of sources that include, for example, and not by way of limitation, foam serving plates and containers in a fast food restaurant, the residues of packing for food or industrial objects (representative non-limiting examples of foamed or expanded polystyrene that can be reduced using the methods of the present invention include, inter alia, computer end caps, packaging expanded polystyrene (EPS) peanuts, insulation board, Styrofoam®, construction forms, coffee cups, egg cartons, drink cups, meat trays, vegetable trays, protective packaging, furniture, lamps, lamp shades, paintings, appliances such as refrigerators, stove dish washers, microwave ovens, cameras, VCRs, TVs, telephones, vacuums, radios, chemical packaging military applications for pollution prevention items such as: munitions packaging, target drones, weapons, food service, agriculture; seedling trays, various industries such as tobacco growers, greenhouses (for their seeding trays) plant growers for their planting, fruit and vegetable growers for their shipping containers; foam coolers, fish containers, among others. The foam waste would be shredded in a hopper. The shreds of polystyrene foam would be contained in a compartment of the hopper. The reactant would be sprayed onto the shredded foam waste. The spray and shredded foam combination will rapidly decrease in volume as the foam collapses and would result in the forming of foam sludge and volume of reducing agent. The sludge and reducing agent would be pumped from the hopper compartment into drum type containers and sent to dumps where it occupies a greatly reduced volume or sent to a reprocessor to recover the active agent dibasic esters and the polystyrene polymer. Preferably the reducing agent is ninety percent dibasic ester and not to exceed 10 percent surfactant.
The process is preferably the same as described above with alternate reactant compositions. However, the embodiments contemplated herein are not limited to the pre shredding of the foam waste, the use of a hopper, the pumping of the foam sludge and reactant or the use of drum-like containers for transporting the foam sludge and reactant. Indeed, the embodiments contemplated herein may be used in conjunction with other processing methods of polystyrene foam waste known to those of skill in the art.
In a second embodiment, the reactant is at least one of the three named dibasic esters which is combined with d-limonene; and a surfactant, whereby the reactant in a liquid state contacts polystyrene foam causing the collapse of the polystyrene cell to form a compact polystyrene gel material that is easily shippable. Preferably the reactant, or foam reduction agent, is eighty eight weight percent of the dibasic ester, ten percent d-limonene and two percent of the surfactant. In addition, it is preferred that the surfactant is at least one of an industry standard surfactant known as NP5 and NP9. Other non-ionic surfactants know to those of skill in the art can be used in conjunction with the DBE and LVP-DBE compositions of the present invention.
In a third embodiment, the reactant is a dibasic esters that is at least one of the group of dimethyl glutarate, dimethyl adipate, and dimethyl succinate, with the dimethyl succinate being present in weight percentage amounts of 1% and less; d-limonene; and, a vegetable oil are used as the reducing agent whereby the reactant in a liquid state contacts the polystyrene foam causing the collapse of the polystyrene cell to form a compact polystyrene gel material that is shippable. Preferably, the reactant, or foam reduction agent, is fifty five percent vegetable oil, thirty percent dibasic ester and fifteen percent d-limonene. It is also preferred that the vegetable oil is soy oil. Other examples of preferred oils include, for example, and not by way of limitation, oils from celery and olives.
All of the embodiments described above are sprayed onto polystyrene foam. The preferred process is to have the polystyrene foam placed into a hopper wherein the foam is converted to small pieces that can be combined with the reducing agent. The resulting material, sludge and reducing agent are pumped from the hopper to drums for transportation.
EXAMPLES
It will be understood by one of ordinary skill in the relevant arts that other suitable modifications and adaptations to the methods and applications described herein are readily apparent from the description of the invention contained herein in view of information known to the ordinarily skilled artisan, and may be made without departing from the scope of the invention or any embodiment thereof. Having now described the present invention in detail, the same will be more clearly understood by reference to the following examples, which are included herewith for purposes of illustration only and are not intended to be limiting of the invention.
The embodiments described herein are not a limitation to invention disclosed by this application but are shown to illustrate the best methods and uses of the invention. Further uses would be obvious to those skilled in the art by a complete review of the disclosure made herein.
Example 1
Abstract
The objective of this experiment was to demonstrate the capacity of a counter rotating, non-intermeshing, twin screw extruder for devolatilization of recovered polystyrene from dimethyl succinate solvent. The feed to the devolatilizing extruder consisted of a syrup prepared by dissolving polystyrene foam in dimethyl succinate to 50% solids solutions. The devolatilization goal was less than 1,000 ppm dimethyl succinate residuals; with minimal degradation of the polystyrene.
Introduction
Devolatilization is the thermodynamically driven removal of a solvent from a polymer solution. When the amount of solvent to be removed is a significant fraction of the solution, the devolatilization is most efficiently performed in a staged separator. A staged, non-intermeshing, twin screw extruder has many characteristics which attract it to the devolatilization process.
The non-intermeshing geometry has inherently more volume in the screw channels than intermeshing designs of the same screw diameter. By rotating the screws counter currently, the vent opening can extend above and beyond the center line of both screws. The downward motion of both screws in the apex conveys material away from the vent opening and forward to the next melt seal. The vent opening can be as long as 8 screw diameters, which results in a generous area for vapor flow, with correspondingly low vapor velocity and particle entrainment.
The rate of devolatilization for a concentrated polymer solution is largely controlled by molecular diffusion of the solvent through the polymer. The diffusion rate is determined by residence time and the concentration gradient in the melt, which is in turn determined by the surface area renewal rate and vapor pressure above the melt. The rate of surface area renewal is enhanced in counter rotating, non-intermeshing twin screw extruders by the exchange of material from one screw to the other, resulting in good distributive mixing. It is also possible to increase the surface area in the melt by injection of a stripping agent under pressure, which foams the melt on contact. An additional benefit of injecting a stripping agent is the reduction of solvent vapor pressure above the melt, which increases the driving force for devolatilization.
Materials and Methods
Equipment and Feed Materials
Extruder:
The 30 mm devolatilizing extruder arrangement featured a Welding Engineers model HTR-30 mm-22-1 V2-2-3-13-E1 twin screw extruder. The total length of the extruder consisted of 54:1 L/D twin screw plus a 6:1 L/D single screw discharge. A process schematic for the extruder configuration is shown in FIG. 1.
Extruder Heating:
The 30 mm devolatilizing extruder was heated with hot oil circulated through the barrels, which were cored or jacketed. One zone of hot oil was used for all of the barrels.
Feed Equipment:
The feed system for the devolatilizing extruder consisted of a Zenith 11 cc/rev gear pump downstream of a pressurized, 50 gallon Pfaudler jacketed kettle, feeding into the second barrel on the extruder. Nitrogen was used to pressurize the kettle. A Koch SMR heat exchanger with 6 ft2 of area was used to preheat the feed, and was positioned upstream of a solution feed valve installed on the second barrel. The feed kettle, heat exchanger, and pipe heat tracing were heated with hot oil to allow control of the feed temperature.
Solvent Recovery System:
Vapors from the rear vent were condensed in a 21 ft2 shell and tube heat exchanger mounted upstream of a 30 gallon kettle.
A Nash model AHF120 liquid ring pump with 100 SCFM capacity was used for the rear vent and first downstream vent of the 30 mm extruder. Initially pure water, then collected dimethyl succinate, was used as the seal fluid in the pump. A 16 ft2 shell and tube heat exchanger was used as a condenser between the vent stack and the Nash pump, with plant cooling water on the shell side.
Two Stokes Microvac model 148-10 oil-sealed pumps with 50 SCFM capacity were used on the two final downstream vents. 1 ft2 shell and tube heat exchangers were used as condensers between the second and third downstream vent stacks and the corresponding collectors, with plant cooling water on the shell side.
The vacuum level in all vents was measured by dial gauges.
Materials:
The following feed materials were used, and are designated by their respective letter codes in the experimental run summary in Section VII, and the operator log sheets in Section IX.
A. Recovered polystyrene in dimethyl succinate, approximately 50% solids.
Experimental Procedure
For each days run of the devolatilization extruder, the 50 gallon feed kettle was filled with syrup supplied in a 55 gallon drum. The syrup had to be filtered to remove undissolved polymer by pouring it through a screen into 5 gallon buckets, which were then poured into the kettle.
The extruder screw and barrel arrangement 961841—1, shown in FIG. 2, used a rear vent and three downstream vents to remove the solvent. The rear vent was operated with slight vacuum drawn off the Nash pump. The maximum vacuum that the pumps could develop was used in the downstream vents. The product was collected by extruding through a two hole strand die into a water bath, and then pelletized. A day by day description of the trial now follows.
Day 1
On the first run day of the trial, a lot of time was spent filtering the syrup to charge the 50 gallon kettle. There was a lot of undissolved polymer in the syrup that looked like pieces of plastic bags. When the kettle became mostly full of syrup, the extruder was started up to check the operation of the feed and vacuum systems.
When the extruder was first started, the vacuum pump for vent 3 spewed oil because it was dead headed and not primed. The system was shut down to check operation of the vacuum pump, then restarted at a relatively low rate. The extruder was run for about 20 minutes with the vents clear and the temperatures stabilized, then sample 1 was collected at 19.4 lb/hr product rate and 244 rpm screw speed. The screw speed was increased to 400 rpm for sample 2, then the rate was increased to 32.2 lb/hr for sample 3. The rate was increased further to 40.1 lb/hr for sample 4, before shutting down the process to fix some problems experienced with the vacuum system.
During the run the vacuum level in vent 3 was always worse than expected, and no solvent was collected off the rear vent, because the feed temperature was too low. The vent 3 vacuum pump oil was changed, and it was discovered that a large amount of solvent was collected off vent 4. These factors combined indicate that samples 1 through 4 should have high residuals, because of poor utilization of the upstream vents.
Day 2
On the second day of the trial, the extruder was started up with higher feed and barrel temperatures, which resulted in solvent being recovered off the rear vent. After start up, poor vacuum was again seen in the third vent. Further investigation revealed the vent 3 condenser was clogged with polymer, which when replaced with a clear condenser allowed for strong vacuum in the third vent.
The extruder was started up at a low rate of 12 lb/hr at 215 rpm, to allow time for the feed temperature to gradually increased above 200° C., at which temperature the rear vent started to work. This was also done to conserve material, since the second drum of syrup shipped for the trial was too dirty to screen effectively. All of the samples in this trial were taken from the initial drum of feed that was supplied.
Sample 5 was taken at the low rate condition, then the rate was increased to 18.7 lb/hr and the screw speed increased to 300 rpm for sample 6. The screw speed was increased to 400 rpm for sample 7, then the rate was increased to 27.6 lb/hr for sample 8. The next three samples were collected at 31.9 lb/hr, 37 lb/hr, and 41.3 lb/hr; all at a screw speed of 400 rpm. For sample 12 the screw speed was increased to 500 rpm, then the rate was increased to 55 lb/hr, before increasing to the maximum rate of 83.2 lb/hr for sample 14.
At the maximum rate of 83.2 lb/hr at 500 rpm, the screw channels in the downstream vents were seen to be full of melt. Increasing the rate further would have caused melt to flood one or more vent stacks. Shortly after sample 14 was taken, the feed kettle was depleted, and the extruder was shutdown, thus ending the experimental part of the trial.
Results and Discussion
A summary of the run conditions for the samples collected is given in Section VII. A copy of the operator log sheets is given in Section IX. This trial was successful in identifying rate and product performance specifications for devolatilization of recycled polystyrene foam from dimethyl succinate. Sufficient data was collected to design commercial scale extruders for this process.
The devolatilization performance can be evaluated in terms of rear vent performance, screw design and specific rate, residual solvent levels, melt temperatures, and melt flow index.
Rear Vent Performance
Rear vent flow rates were not measured in this test, because the rear vent collector was operated under slight vacuum. During the first run day, little if any solvent was taken off the rear vent, because the feed temperature was too low. During the last run day, the higher feed temperatures used resulted in some solvent entering the rear vent collector.
Typically, dilute solution ( ̃50% solids feed) devol extruders reach maximum capacity at rear vent yields around 60%. However, since dimethyl succinate has a high boiling point, the feed temperature must be quite high to achieve high rear vent yields. This is because the rear vent is an adiabatic flash separation stage, and the yield off the rear vent is a function of both the feed superheat and extruder pumping capacity. FIG. 3 is a plot of rear vent yield as a function of feed superheat, calculated from an adiabatic flash, where the feed superheat was defined as the difference between the partial pressure of dimethyl succinate in the feed, and the rear vent pressure. Flory-Huggins thermodynamics was used to calculate the partial pressure of dimethyl succinate at the measured temperature and concentration of the feed.
The adiabatic flash calculation shown in FIG. 3 indicates that rear vent yields were half or less the desired value of 60%. This was because the feed temperature was low, even at 215° C. Note that there were some sample conditions with calculated negative feed superheats. These correspond to the samples run the first day, were the feed temperature was below the equilibrium boiling point of the dimethyl succinate, resulting in no solvent off the rear vent. Although the points in FIG. 3 are calculated from a model, the scatter in the results is because the measured feed superheats are relatively low, which caused the computer code to perform a lot of iterations to find the proper solution.
The maximum amount of solvent that can be removed from the rear vent will set a volumetric rate limitation for the extruder. Typically for a 30 mm extruder at specific feed rates of 0.2 lb/hr/rpm and above, the rear vent yield will drop off because the rear vent becomes volumetrically limited. Normally when this occurs, foam will fill either the rear vent or first downstream vent stack, as more solvent is passed downstream. Samples 4, 11, and 13 had specific feed rates around 0.2 lb/hr/rpm; and sample 14 had a specific feed rate of 0.33 lb/hr/rpm. However, both the rear vent and first downstream vent appeared well behaved for those samples. It is not desirable to operate a devolatilization extruder at low rear vent yields, because a lot of solvent is passed to the downstream vents and vacuum system, and the product residuals will be high.
Effects of Screw Design and Specific Rate
Only one screw design was tested in this trial. The screw design (see FIG. 2) featured scaled conveying elements in the rear vent, and melt seal cylinder sizes, that have proved successful in 6′′ devolatilization extruders processing styrenic copolymers at product rates up to 3 ton/hr.
The specific energy as a function of specific rate is plotted in FIG. 4. Specific energy decreases with increasing specific rate, because the extruder becomes a more efficient pump as it becomes more full. This curve can be scaled up and used to determine the power consumption and motor size of commercial size extruders, as discussed in Section E of Example 1. The specific energies measured in this trial are low relative to what Welding Engineers' typically measure for devolatilization extruders. This indicates the recycled polystyrene processed had relatively low melt viscosity and molecular weight, two desirable properties of the methods employed herein.
Residual solvent levels usually correlate to specific rate, with lower residuals corresponding to lower specific rate. In this trial, the samples that were analyzed for residual solvent level had all less than 1 ppm dimethyl succinate. No trend could be seen in the data because the values were so low. This result was unexpected, however the samples were analyzed by the customer using GC and FTIR methods, and are believed to be accurate.
Effects of Melt Temperatures
Since extruder devolatilization is mostly mass transfer limited, there is usually an influence of melt temperature on the residuals. Lower residuals are the result of higher melt temperatures. The melt temperature profile is determined by screw design, screw speed, and rate. The influence of barrel temperature is significant at 30 mm scale, but becomes less so as extruder size increases.
In this trial, the variable that most determined the melt temperatures was the specific rate, as shown in FIG. 5. The scatter was due to the independent affects of screw speed and rate on melt temperature, because samples were taken over a range of screw speeds from 215 to 500 RPM. In general, higher rates at a constant screw speed result in lower melt temperatures, because the screw channels are more full and the melt experiences less overall shear. With high viscosity polymers, screw speed becomes the dominant variable that determines the melt temperature profile.
For polymers which can degrade or depolymerize, there exists a maximum melt temperature that the material can withstand in an extruder. Styrene monomer will depolymerize from styrenic polymers at temperatures near 300° C. The screw design can be adjusted to maintain the maximum permissible melt temperature by changing the diameter of the cylindrical melt seal elements.
Product Degradation and Melt Flow Index
Product degradation was quantified in this trial by measuring the melt flow index. It is expected that higher temperatures and shear would contribute to more degradation, and therefore higher melt flow index values. However, no significant degradation was measured by the customer for any of the samples collected in this trial.
Scale Up Considerations for Devolatilization
The rate and residuals achievable on a production size extruder can be estimated from scaling up the results of this trial. As extruder size increases, the volume and conveying capacity goes up with the cube of diameter, while the area for heat and mass transfer goes up with the square of diameter. Vent pressure and feed temperature are used to control rear vent yield and/or vapor velocity on commercial scale extruders.
As seen in FIG. 3, the rear vent yield depended on the feed superheat, as long as the rear vent was not volumetrically limited. Ideally, the extruder should reach maximum capacity at about 60% yield in the rear vent, and 30 to 40% yield in the first downstream vent. This typically requires a feed superheat of about 200 psi, which is achieved by preheating the feed. In this trial, the highest feed superheats were about 40 psi, which is why the rear vent was under utilized. The feed temperature needed for 200 psi superheat depends on the concentration and vapor pressure of solvent in the feed.
The data in Section VII show that to achieve less than 1 ppm residuals on a 30 mm extruder, specific rates about 0.1 lb/hr/RPM are sufficient. From FIG. 4, the specific energy consumption at 0.1 lb/hr/RPM is 0.08 Hp-hr/lb, which is less than the typical value for existing commercial styrenic polymer devol extruders. Based on a 2.5 scaling exponent for screw diameter ratio, the following table of maximum capacity at <1 ppm residuals, and power consumption at 500 rpm, versus extruder size, can be constructed:












Extruder Size (inch)
Rate (lb/hr) at 1 ppm
Power Consumption (Hp)







2.0
187
18


2.8
433
46









It is expected that higher feed superheat will allow for higher capacity than projected above, because of improved utilization of the rear vent.
Conclusions
This trial demonstrated the capacity of a non-intermeshing, twin screw extruder to devolatilize dimethyl succinate from recycled foam polystyrene. All the samples analyzed by the customer to date had less than 1 ppm dimethyl succinate residuals, which was well below the customer's goal of less than 1,000 ppm. The results show that a 2.8′′ extruder will be required to devolatilize to less than 1 ppm, at a production rate of over 400 lb/hr solids. It is expected that higher feed temperatures than tested in this trial will allow for higher capacity.
Melt temperatures were determined by barrel temperatures, specific rate, and screw speed. It is possible to optimize the melt temperature profile in a commercial devol extruder through screw design changes.
Product degradation, as determined by melt flow index, was found to be insignificant for the samples collected. Further testing of the samples will be required to quantify the effects that shear rate and temperature had on any degradation of the recovered polystyrene.
Experimental Run Summary










Recycled Polystrene Devor

















Vent Performance Data:





























Specific



Vent 2
Vent 3
Vent 4






Product
Feed
Screw
Drive
Rate
Specific
Solvent
Rear Vent
Press.
Press.
Press





% PS in
Rate
Rate
Speed
Current
(lb/hr/
Energy
Residuals
Press
(mm
(mm
(mm


Date
Time
Sample
FEED
(lb/hr)
((lb/hr)
(RPM)
(Amps)
RPM)
(HP-hr/lb)
(ppm)
(mm Hg)
Hg)
Hg)
Hg)





Day 1
15:38
1
50
19.4
38.8
244
5.0
0.080
0.081
—
519
76
152
13



15:49
2
50
19.2
38.4
400
5.0
0.048
0.134
<1
545
89
177
13



16:00
3
50
32.2
64.4
400
4.0
0.081
0.064
—
583
101
177
13



16:11
4
50
40.1
80.2
400
3.0
0.100
0.039
<1
583
165
253
13


Day 2
11:26
5
50
12
24.0
215
5.0
0.056
0.116
—
659
76
<13
13



11:51
6
50
18.7
37.4
300
6.0
0.062
0.124
<1
659
63
<13
13



12.05
7
50
18.4
36.8
400
6.0
0.046
0.168
—
659
76
<13
13



12:19
8
50
27.6
55.2
400
6.0
0.069
0.112
<1
671
76
<13
13



12:27
9
50
31.9
63.8
400
6.0
0.080
0.097
—
671
76
<13
13



12:39
10
50
37
74.0
400
6.0
0.093
0.084
<1
671
76
<13
13



12:48
11
50
41.3
82.6
400
6.0
0.103
0.075
—
684
76
<13
13



13:00
12
50
40.6
81.2
500
6.0
0.081
0.095
<1
671
76
<13
13



13:09
13
50
55
110.0
500
6.0
0.110
0.070
—
684
76
<13
13



13:22
14
50
83.2
166.4
500
5.5
0.166
0.043
—
684
76
<13
13












Process Temperatures and Pressures:
























HX Inlet
HX Out
Feed
Rear Vent
Barrel 3
Vent 2
Barrel 5
Barrel 7

Die
Hot Oil
Setpoints





Temp.
Temp.
Temp.
Temp.
Temp.
Temp.
Temp.
Temp.
Die Temp.
Press.
Koch Hx
Extruder


Day
Time
Sample
(° C.)
(° C.)
(° C.)
(° C.)
(° C.)
(° C.)
(° C.)
(° C.)
(° C.)
(psig)
(° C.)
(° C.)





Day 1
15:38
1
61.7
192.4
180.6
194.1
186.3
163.3
186.1
191.8
163.3
52
221
221



15:49
2
59.8
192.6
181.2
194.7
185.9
164.6
188.9
198.3
165.3
53
221
221



16:00
3
58.8
190.5
186.9
195.5
186.5
167.1
183.3
186.2
170.0
39
221
221



16:11
4
58.5
188.9
186.4
195.7
186.9
167.2
182.7
183.6
168.1
24
221
221


Day 2
11:26
5
76.6
217.7
185.3
228.3
218.3
205.0
229.7
233.3
199.0
27
260
260



11:51
6
63.6
223.1
209.4
228.9
217.8
191.4
228.6
241.2
203.1
29
260
260



12.05
7
65.5
223.7
210.8
229.2
218.4
194.0
231.5
247.4
204.5
29
260
260



12:19
8
68.0
223.6
216.8
229.3
218.2
183.8
225.5
244.9
205.7
31
260
260



12:27
9
69.4
222.3
217.7
229.3
218.1
180.8
221.4
242.0
205.8
32
260
260



12:39
10
71.3
219.7
216.7
228.4
218.0
177.5
216.5
237.0
203.9
35
260
260



12:48
11
73.7
218.0
216.3
228.5
217.8
175.0
213.4
233.5
203.9
36
260
260



13:00
12
77.1
217.5
215.9
228.7
217.5
175.5
215.8
239.7
205.3
33
260
260



13:09
13
80.2
211.7
213.4
228.4
217.7
170.5
207.5
227.9
205.4
42
260
260



13:22
14
85.0
204.0
205.9
227.5
216.3
167.3
197.4
204.5
201.7
38
260
260






















Adiabatic









Feed
Flash
Specific
Koch Heat
Log





SuperHeat
Rear Vent
Feed Rate
Transferred
Mean
Koch Uo


Day
Time
Sample
(PSI)
Yield (%)
(lb/hr/RPM)
(BTU/hr)
DT (° F.)
(BTU/hr/ft2)





Day 1
15:38
1
−3.0
0
0.159
4475
137
5.4



15:49
2
−4.2
0
0.096
4497
138
5.4



16:00
3
−0.8
0
0.161
7482
142
8.8



16:11
4
−1.3
0
0.201
9224
145
10.6


Day 2
11:26
5
−7.7
0
0.112
2989
173
2.9



11:51
6
27.5
13
0.125
5261
172
5.1



12.05
7
30.2
19
0.092
5135
170
5.0



12:19
8
42.0
26
0.138
7576
169
7.5



12:27
9
44.1
27
0.160
8600
170
8.4



12:39
10
41.7
20
0.185
9684
173
9.3



12:48
11
40.1
24
0.207
10513
174
10.1



13:00
12
39.9
23
0.162
10059
173
9.7



13:09
13
33.8
16
0.220
12765
180
11.8



13:22
14
19.4
9
0.333
17470
188
15.5

























TABLE 3









SCREW

VACUUM
PRODUCT



HOT OIL



SPEED

INCHES
RATE

DIE
PROD.
FOOD




















TIME
FEED
SCREWS
R.P.M.
AMPERES
1
2
3
#/HR.
SAMPLE
DIE
PSIO
TEMP.
ZONE 1 ° C.












2:37
Start-up - turn on feed pump - low speed
2.30


3:00
Shut down - states pump on vent 3 flooded; Rear vent has material in it


3:20
Start-up again - vacuum on rear vent


3:25
at 2.0 feed pump, 244 adjust rpm


















3:38
A
1
244
5

19.4
1
A


2.30








3:40
Raise screw speed to 357 rpm


















3:49
A
1
400
5

19.2
2
A


2.30








3:51
Raise rate, gear pump to 3.0, Poor vacuum vent 7


















4:00
A
1
400
4

32.2
3
A


2.30








4:05
Rate at 3.5 set point; Near limit of vent flow in vent 3; Melt forms in vent 4, Temperatures too low.


















4:11
A
1
400
3

40.1
4
A


2.30








4:17
Shut down - turn off gear pump, empty extender, cool, close extender and leave.















FEATURED
ZENITH
VACUUM LEVELS


















ZONE 2
PUMP 3
Vent 1
Vent 2
Vent 3
Vent 4




TIME
° C.
Set-up
4 mmHg
5 mmHg
6 mmHg
7 mmHg
8







2:37
2.30










3:00
Shut down - states pump on vent 3 flooded; Rear vent has material in it












3:20
Start-up again -
1.1





vacuum on rear vent










3:25
at 2.0 feed pump, 244 adjust rpm
















3:38
2.30
2.0
9.5
27  
24
29.5
1










3:40
Raise screw speed to 357 rpm
















3:49
2.30
2.0
8.5
26.5
23
29.5











3:51
Raise rate, gear pump to 3.0, Poor vacuum vent 7
















4:00
2.30
3.0
7.0
26.0
23
29.5
2










4:05
Rate at 3.5 set point; Near limit of vent flow in vent 3; Melt forms in vent 4,




Temperatures too low.
















4:11
2.30
3.5
7.0
23.5
20
29.5
3










4:17
























TABLE 4









SCREW

VACUUM
PRODUCT





SPEED

INCHES
RATE

DIE


















TIME
FEED
SCREWS
R.P.M.
AMPERES
1
2
3
#/HR.
SAMPLE
DIE
PSIO












11:00
Start-up higher temperatures









11:15
At 1.0 gear pump setting, 187 rpm; replacing vent 3 condense -



original one way was plugged, causing poor vacuum before
















11:26
A
1
215
5

12  
 5
A









11:27
Raise screw speed to 300, rate to 2.00 setting
















11:51
A
1
300
6

18.7
 6
A









11:52
Raise screw speed to 400 rpm
















12:05
A
1
400
6

18.4
 7
A









12:06
Raise rate to 3.0
















12:17
A
1
400
6

27.6
 8
A









12:19
Raise rate to 3.5
















12:27
A
1
400
6

31.9
 9
A









12:29
Raise rate to 4.0 - venting o.k.
















12:39
A
1
400
6

37.0
10
A









12:39
Raise rate to 4.5
















12:48
A
1
400
6

41.3
11
A









12:50
Raise screw speed to 500 rpm
















 1:00
A
1
500
6

40.6
12
A









 1:01
Raise rate to 6.0
















 1:09
A
1
500
6

55.0
15
A









 1:09
Push rate, final limit - 8.5 set point = 81.6 16/11(12     rate)
















 1:22
A
1
500
5-6

83.2
14
A










 1:26
Shut down
















HOT OIL







FOOD
FEATURED
ZENITH
VACUUM LEVELS

















PROD.
ZONE 1
ZONE 2
PUMP 3
Vent 1
Vent 2
Vent 3
Vent 4



TIME
TEMP.
° C.
° C.
Set-up
4 mmHg
5 mmHg
6 mmHg
7 mmHg
8














11:00

/260
/260










11:15
At 1.0 gear pump setting, 187 rpm; replacing vent 3




condense - original one way was plugged, causing poor



vacuum before
















11:26

2.60
2.60
1.5
4
27
30
29.5










11:27
Raise screw speed




to 300, rate to



2.00 setting
















11:51

2.60
2.60
2.0
4
27
30
29.5










11:52
Raise screw speed




to 400 rpm
















12:05

2.60
2.60
2.0
4
27
30
29.5









12:06
Raise rate to 3.0
















12:17

2.60
2.60
3.0
3.5
27
30
29.5









12:19
Raise rate to 3.5
















12:27

2.60
2.60
3.5
3.5
27
30
29.5









12:29
Raise rate to 4.0 - venting o.k.
















12:39

2.60
2.60
4.0
3.5
27
30
29.5









12:39
Raise rate to 4.5
















12:48

2.60
2.60
4.5
3.0
27
30
29.5









12:50
Raise screw speed to 500 rpm
















 1:00

2.60
2.60
4.5
3.5
27
30
29.5









 1:01
Raise rate to 6.0
















 1:09

2.60
2.60
6.0
3.0
27
30
29.5









 1:09
Push rate, final limit - 8.5 set point = 81.6 16/11(12     rate)
















 1:22

2.60
2.62
8.5
3.0
27
30
29.5









 1:26





1 Five Minute rate check


2 Solvent collecting in wash


3 Poor vacuum, low temperatures = high pp






Example 2
Determination of the Exposure Limits of the Recaptured LVP-DBE Composition of the Polystyrene Low Heat Treatment Extruder Recycling System
Exposure Limits
DBE-LVP
PEL (OSHA): None Established
TLV (ACGIH): None Established
AEL*: 1.5 ppm, 10 mg/m3, 8 Hr. TWA
* AEL is DuPont Chemical Inc.'s Acceptable Exposure Limit. Where governmentally imposed occupational exposure limits which are lower than the AEL are in effect, such limits shall take precedence.
Example 3
Determination of the Physical and Chemical Properties of the Recaptured LVP-DBE Composition of the Polystyrene Low Heat Treatment Extruder Recycling System
Physical and Chemical Properties
Odor: Sweet
Form: Liquid
Specific Gravity: 1.1 @ 20 C (68)
Boiling Point: 210-225 C (410-437 F)
Vapor Pressure: 0.02-0.04 mm Hg @ 20 C (68 F)
Melting Point: −13 to 8 C (9-46 F)
% Volatiles: 100 WT % @ 20 C (68 F)
Evaporation Rate: <0.1 (Butyl Acetate=1.0)
Solubility in Water: 2.5-4.2 WT % @ 20 C (68 F)
Example 4
Determination of the Exposure Guidelines of the Recaptured LVP-DBE Composition of the Polystyrene Low Heat Treatment Extruder Recycling System
Exposure Guidelines
Exposure Limits
DBE-LVP
PEL (OSHA): None Established
TLV (ACGIH): None Established
AEL *: 1.5 ppm, 10 mg/m3, 8 Hr. TWA
This limit is for DBE.
* AEL is DuPont's Acceptable Exposure Limit. Where governmentally imposed occupational exposure limits which are lower than the AEL are in effect, such limits shall take precedence.
Example 5
Determination of the Hazardous Chemical Indicators of the Recaptured LVP-DBE Composition of the Polystyrene Low Heat Treatment Extruder Recycling System
Hazardous Chemical Lists
SARA Extremely Hazardous Substance: No
CERCLA Hazardous Substance: No
SARA Toxic Chemical: No
DBE-LVP is considered 100% VOC (1080 g/l) per EPA 40 C.F.R. Section 51.100(s)1.
DBE-LVP meets the VOC exemption criteria for consumer products per EPA 40 C.F.R. Section 59.203(f)1.
DBE-LVP meets the low vapor pressure (LVP) criteria established by the California Air Resources Board for volatile organic compounds in consumer products per California Code of Regulations, Title 17, Division 3, Chapter 1, Subchapter 8.5, Article 2, Section 94508(a)80(A).
Canadian Regulations
CLASS D Division 2 Subdivision B—Toxic Material. Skin or Eye Irritant.
Equivalents
The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising,” “consisting essentially of,” and “consisting of” may be replaced with either of the other two terms. The terms and expressions that have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed herein, optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.
The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein. Other aspects of the invention are within the following claims.
All publications, patents and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains, and are herein incorporated by reference to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference.

## Claims

1. A method of reducing/recycling polystyrene foam comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: one or more standard dibasic ester (DBE) compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300.degree. C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300.degree. C.; and (e) recapturing the dibasic esters; wherein said recaptured dibasic esters are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.

2. A method of reducing/recycling polystyrene foam comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: one or more low vapor pressure dibasic ester (LVP-DBE) compositions selected from the group consisting of dimethyl glutarate, and dimethyl adipate, (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300.degree. C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300.degree. C.; and (e) recapturing the low vapor pressure dibasic esters; and wherein said recaptured low vapor pressure dibasic esters are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.

3. A method of reducing/recycling polystyrene foam comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: (i) one or more terpenes or isoprenoids or any combination thereof and (ii) one or more surfactants; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300.degree. C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300.degree. C.; and (e) recapturing the terpenes or isoprenoids; and wherein said recaptured terpenes or isoprenoids are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.

4. A polystyrene low heat treatment extruder recycling method comprising the steps of (a) exposing polystyrene foam in a container to a solution of specific esters comprising dimethyl glutarate [CAS#1119-40-0] and dimethyl adipate [CAS#627-93-0], wherein the esters specifically exclude dimethyl succinate in weight percentage amounts greater than 1%; (b) optionally covering said container; (c) subjecting the resultant polygel to a low source of heat over a temperature range not to exceed 200-300.degree. C.; (d) subjecting the resultant polygel to one or more extruders over a temperature range not to exceed 200-300.degree. C.; (e) optionally supplementing polystyrene foam until maximum reduction is achieved and (f) recapturing the dibasic esters; and wherein said recaptured dibasic esters are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.

5. A method of reducing/recycling polystyrene foam comprising the steps of (a) providing polystyrene foam; (b) applying to said polystyrene foam a solution comprising: (i) one or more low vapor pressure dibasic ester compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate; (ii) one or more dibasic ester compositions selected from the group consisting of dimethyl glutarate, dimethyl adipate, and dimethyl succinate or (iii) (a) one or more terpenes or isoprenoids or any combination thereof and (b) one or more surfactants; or any combination thereof of (i)-(iii); (c) subjecting the polygel to a low source of heat over a temperature range not to exceed 200-300.degree. C.; (d) subjecting the polygel to one or more extruders over a temperature range not to exceed 200-300.degree. C.; and (e) recapturing the dibasic esters, the low vapor pressure dibasic esters and/or the terpenes or isoprenoids; and wherein said recaptured dibasic esters, low vapor pressure dibasic esters and/or the terpenes or isoprenoids are reused or recycled and the resultant polystyrene foam polygel may be recycled into high quality beaded polystyrene foam.

6. A polystyrene low heat treatment extruder recycling system method including an LVP-DBE composition that exhibits one or more of the following characteristics: (a) a significantly lower vapor pressure than standard DBE, (b) the distillation range of the solvent is narrower, (c) chemically more stable than standard DBE, (d) that is incompatible or can react with, inter alia, strong oxidizers, acids, alkalies, etc., (e) that will not undergo polymerization, (I) that reduces polystyrene foam at a rate of action that equals or exceeds that of standard DBE, (g) that exhibits a greater holding capacity than standard DBE, (h) that exhibits a higher flash point than standard DBE, (i) that is not regulated as a hazardous material by DOT, IMO, or IATA, and (j) for which none of the components present in the LVP-DBE composition are listed by IARC, NTP, OSHA or ACGIH as a carcinogen.

7. The polystyrene low heat treatment extruder recycling method of claim 6 further comprising exposing said foams to liquid sprays of specific esters exhibiting one or more of the aforementioned characteristics.

8. The polystyrene low heat treatment extruder recycling method of claim 6 further comprising exposing said foams to liquid sprays of specific esters comprising dimethyl glutarate [CAS#1119-40-0] and dimethyl adipate [CAS#627-93-0], wherein the ester specifically excludes dimethyl succinate in weight percentage amounts greater than 1%, and wherein said esters exhibit one or more of the aforementioned characteristics.

9. The polystyrene low heat treatment extruder recycling method of claim 6 further comprising exposing said foams to liquid sprays of specific esters, wherein the ester is selected from the group consisting of dimethyl glutarate [CAS#1119-40-0] and dimethyl adipate [CAS#627-93-0], wherein the esters specifically exclude dimethyl succinate in weight percentage amounts greater than 1%, and wherein said esters exhibit one or more of the aforementioned characteristics.

10. The method of claims 1-9, wherein step (b) of adding the solution comprising the dibasic esters, the low vapor pressure dibasic esters, and/or the terpenes or isoprenoids or any combination thereof is carried out without prior treatment of the polystyrene foam with one or more thin film evaporators or one or more fluffers, and/or one or more dryers.

11. The method of claims 1-9, wherein after the step of recapturing the dibasic esters, the low vapor pressure dibasic esters and/or the terpenes or isoprenoids, the resultant polystyrene polygel is optionally be subjected to one or more thin film evaporators (TFEs) for a time period of approximately 1-2 minutes, but not to exceed approximately 10 minutes.

12. The method of claims 1-9, wherein the resultant high quality beaded polystyrene product exhibits a series of properties comprising a heat index of less than about 9, concentration of dibasic esters, low vapor pressure dibasic esters and/or terpenes or isoprenoids of less than about 1-1000 ppm, and/or no evidence of spleaning, crazing or burnt discoloration, low melt viscosity or molecular weight, or any combination thereof.

13. The method of claims 1-9, wherein the polystyrene foam products are subject to the vapor of low vapor pressure dibasic esters in an enclosed area for a period of time until they are reduced to a gelatinous state or close to a viscous state.

14. The method of claim 13, wherein said polystyrene foams are reduced in volume by the effect of sprayed liquids containing low vapor pressure dibasic esters in addition to said vapors.

15. The method of claim 13, wherein said enclosed area is a plastic bag, drum, or any other closed container.

16. A recycling method to reduce the volume of polystyrene foams wherein said polystyrene foams are exposed to vapors of low vapor pressure dibasic esters over an extended period in a container which prevents escape of said vapors, liquid or a combination thereof.

17. The recycling method of claim 16, wherein said vapors are contained in a tank or vessel which has ports for addition of polystyrene foams, for addition of low vapor pressure dibasic esters, and for withdrawal of dissolved polystyrene or polygel.

18. The recycling method of claim 17, wherein said vapors arise from a combination of a spray of the liquid low vapor pressure dibasic esters and vapors transported from a second tank, and the polystyrene foam in its reduced state is withdrawn by flow to said second tank.