Patent Description:
The present disclosure relates to low density polyester foam. More specifically, the present disclosure is directed toward low density polyester foam utilizing low Intrinsic Viscosity (I. ) polyester feedstock, methods for production thereof, and articles made thereof.

Foam is a substance formed by trapping pockets of gas in a liquid or solid. Solid foams can be closed-cell or open-cell. In closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In open-cell foam, gas pockets connect to each other. A bath sponge is an example of an open-cell foam, where water easily flows through the entire structure, displacing the air. A camping mat is an example of a closed-cell foam, where gas pockets are sealed from each other so the mat cannot soak up water. Foam can refer to many different variations of foam material, such as quantum foam, polyurethane foam (foam rubber), XPS foam, polystyrene, phenolic, or many other manufactured types of foam. As used herein, foam may refer to polyester foam, namely, low density polyester foam.

Low density polyester foam may have significant advantages over many other materials due to the low weight of articles achieved by foaming, large thermal window of performance, and inherent toughness of the material. However, the high specific gravity of the material results in a part weight increase which, along with resin cost has placed this material at a cost disadvantage to other materials. As a result, low density polyester foam has remained largely unused commercially. For example, while an excellent alternative to polystyrene foam containers, the cost has remained too high to be competitive.

The disclosure recognizes that by using lower cost polyester resin of lower intrinsic viscosity (I. ), as measured by ASTM method D-<NUM>, specifically post-consumer resins, the cost disadvantage of polyester foams may be abated, thereby, making these polyester foams a viable commercial product. But, prior to the disclosure, polyester resin of low intrinsic viscosity is unsuited for producing PET foam.

During the <NUM>'s, a concerted effort was made to commercialize low density polyester foam. (Low density here is defined as having a specific gravity of less than <NUM>/cc. ) <CIT>), produced a foam grade polyester resin. He determined that a linear polyester required an I. of approximately <NUM> dl/g to produce the melt strength needed to foam polyester to low density. <CIT>,), simultaneously developed a foam grade of PET with an I. of <NUM> dl/g, but their resin was highly branched. Eastman produced a foaming system wherein a standard virgin PET of I. of <NUM> dl/g would be used and reactively the I. would be increased in the extrusion process via a cross linking additive. This additive was patented by <CIT>), <CIT> and <CIT>) and others.

Once these resins became available, additional research by Shell Chemical, <CIT>) produced a functional nucleator. Work at <CIT>), developed and patented functional blowing agent systems. With additional process development, Genpak commercialized low density PET foam.

While a technical success, the product that Genpak commercialized was a commercial failure. The target market was ovenable trays, an alternative to solid, crystallized PET trays (CPET). While functional, the insulative properties of the foam slowed both heating and cooling times offsetting the financial incentive of a lower cost product. The product was discontinued not long after entering the market and no significant effort has since been made to commercialize low density PET foam in food packaging.

To successfully compete in the market on other applications than the one listed above, the cost of the product must be reduced. Because of the high specific gravity of the resin itself and the inability to reach extremely low specific gravity (less than <NUM>/cc) such as is possible with polystyrene, there is an inherent weight increase and therefore financial penalty in using PET foam.

Previous attempts to produce foam required the use of a high I. resin that sold at a premium or a virgin resin with I. above <NUM> dl/g along with a crosslinking additive to produce said foam. A need exists for a lower cost raw material alternative in manufacturing low density PET foam.

<CIT> discloses the manufacturing of polyester based expanded materials made of pre-cleaned and compound post-consumer polymer by increasing the intrinsic viscosity (IV) during an extrusion process, the manufacturing of such materials and the use of products made thereof. In preferred embodiments D1 discloses the use of reactive additives (RA) in order arrive at an intrinsic viscosity of the exciting foam of higher than <NUM>/g, wherein the authors possibly meant an intrinsic viscosity of higher than <NUM> dl/g.

The disclosure is designed to address at least certain aspects of the problems or needs discussed above by providing a method for production of low density polyester foam and article made thereof utilizing low I. polyester feedstock.

Preferred features of the invention are set out in the dependent claims. Accordingly, in one aspect, the present disclosure embraces a method of producing low density polyester foam utilizing low I. polyester feedstock. The method of producing low density polyester foam utilizing low I. polyester feedstock includes providing a low intrinsic viscosity raw material. The low intrinsic viscosity raw material includes between <NUM>% to <NUM>% of a post consumer polyester. The low intrinsic viscosity raw material is provided with an intrinsic viscosity of less than <NUM> dl/g. The intrinsic viscosity of the low intrinsic viscosity raw material is increased via a de-condensation reaction configured to support foaming. The intrinsic viscosity of the low intrinsic viscosity raw material is increased to <NUM> dl/g or greater. A starting formulation is created including the low intrinsic viscosity raw material with the increased intrinsic viscosity. The starting formulation is foamed to create the polyester foam. Wherein, the polyester foam produced has a specific gravity of less than <NUM>/cc.

In select embodiments, the method for producing polyester foam may further include crystallizing the low intrinsic viscosity raw material in a crystallizer. In an alternative embodiment, the method for producing polyester foam may further include pelletizing the low intrinsic viscosity raw material. The crystallizing or the pelletizing may be configured to prevent the low intrinsic viscosity raw material from melting during the de-condensation reaction.

In other select embodiments of the method for producing polyester foam, the low intrinsic viscosity raw material may include virgin polyester, the post consumer polyester may be a polyester feedstock that consists of post- industrial waste resin, and process regrind. In select embodiments, the post-industrial waste resin of the low intrinsic viscosity raw material may consist of post-consumer scrap bottle flake.

In select embodiments of the method for producing polyester foam, increasing the viscosity of the low intrinsic viscosity raw material via a de-condensation reaction to support foaming may include increasing the molecular weight of the low intrinsic viscosity raw material. In select embodiments, the molecular weight of the low intrinsic viscosity raw material may be increased by feeding the low intrinsic viscosity raw material into a solid-state reactor. In other select embodiments, the molecular weight of the low intrinsic viscosity raw material may be increased by a melt-phase de-condensation reaction with vacuum using a melt phase reactor.

In select embodiments of the method for producing polyester foam, creating of the starting formulation may include adding a viscosity enhancing agent and/or a nucleating agent. The viscosity enhancing agent may be configured to fine tune the viscosity of the low intrinsic viscosity raw material. The nucleating agent may be configured for aiding in nucleating the low intrinsic viscosity raw material. In select embodiments, the viscosity enhancing agent may be a cross-linking agent. In other select embodiments, the nucleating agent may consist of a poly-flouro-ethylene particle.

In select embodiments of the method for producing polyester foam, foaming of the starting formulation to create the polyester foam may include tandem extrusion of the starting formulation to create the polyester foam. The tandem extrusion of the starting formulation to create the polyester foam may include a primary twin screw extruder and a secondary cooling extruder. The primary twin screw extruder may include an injection system and a blowing agent storage system configured to introduce a blowing agent into the starting formulation once the starting formulation is melted and mixed via the primary twin screw extruder. A homogenous mixture of the starting formulation with the blowing agent injected therein may exit the primary twin screw extruder. The secondary cooling extruder may be configured to cool the homogenous mixture that exits the primary twin screw extruder for giving the necessary rheology needed to the homogenous solution for successful foaming. The secondary cooling extruder may be configured to give heat exchange with minimal shear heat generation. The secondary cooling extruder may include a screw configured to act as a heat exchanger for removing heat from the homogenous mixture and increasing viscosity. In select embodiments, a screen changer between the primary twin screw extruder and the secondary cooling extruder may be included. The screen changer may be configured to screen for solid impurities. In select embodiments, a gear pump may be between the primary twin screw extruder and the secondary cooling extruder. The gear pump may be configured to pressurize the homogenous mixture exiting the primary twin screw extruder and to impart minimal additional shear heat while wiping and renewing a surface contact of the homogenous mixture. In select embodiments, the blowing agent may consist of a hydrocarbon. The hydrocarbon of the blowing agent may be, but is clearly not limited thereto, C5 hydrocarbons, C6 hydrocarbons, the like, etc..

In select embodiment, the method for producing polyester foam may further include using a die to form the polyester foam. The die may be any desired type, size or shape of die, including, but not limited to, a board die or a sheet die. The die may be configured with associated finishing equipment. As an example, and clearly not limited thereto, the associated finishing equipment for the die may include a sizing drum, a pull unit, and a winder to produce a roll. The pull unit may be configured to pull a bubble of the polyester foam over the sizing drum and slit the bubble to open a flat sheet. In select embodiments, the polyester foam may be produced as the flat sheet in a roll stock form to a thickness of at least <NUM> inches (<NUM>) and of up to <NUM> inches (<NUM>) thick. In other select embodiments, the polyester foam may be produced with the thicknesses greater than <NUM> inches (<NUM>) and widths of greater than <NUM> inches. As examples, and clearly not limited thereto, the flat sheet may be used as a thermal barrier, the polyester foam may be utilized as a wood or equivalent substitute, or combinations thereof.

In other select embodiments, the flat sheet may be thermoformed into useful articles. The useful articles may include, but are clearly not limited thereto, clamshells, meat trays, plates, bowls etc. In select embodiments, the flat sheet may be thermoformed into useful articles via: unwinding the roll of flat sheet of the polyester foam; heating the unwinded roll of flat sheet in an oven, where temperatures of the oven are controlled to soften but not melt the flat sheet of polyester foam; forming the heated flat sheet of polyester foam in a forming station, where the heated flat sheet of polyester foam is amorphous or crystallized when formed; cutting the formed flat sheet of polyester foam in a trim press, where skeletal waste or regrind is stored to be reused; and packaging the useful articles for sale.

In another aspect, the disclosure embraces a useful article made of polyester foam. The useful article disclosed herein is made by any of the embodiments of the method of producing polyester foam as shown and/or described herein. As a result, the useful article includes a low intrinsic viscosity raw material. The low intrinsic viscosity raw material includes between <NUM>% to <NUM>% of a post consumer polyester. The low intrinsic viscosity raw material provided has an intrinsic viscosity of less than <NUM> dl/g. The intrinsic viscosity of the low intrinsic viscosity raw material is increased to <NUM> dl/g or greater to support foaming. The low intrinsic viscosity raw material may include virgin polyester, the post consumer polyester is a polyester feedstock that consists of post- industrial waste resin, and/or process regrind. The post-industrial waste resin of the low intrinsic viscosity raw material consists of post-consumer scrap bottle flake. With this low intrinsic viscosity raw material of the useful article made of polyester foam, a starting material includes with the low intrinsic viscosity raw material with the increased intrinsic viscosity, a viscosity enhancing agent configured to fine tune the viscosity of the low intrinsic viscosity raw material, and a nucleating agent configured for aiding in nucleating the low intrinsic viscosity raw material. Wherein, the polyester foam of the useful article has a specific gravity of less than <NUM>/cc.

In select embodiments of the useful article made of polyester foam, the polyester foam may be produced with the thicknesses greater than <NUM> inches (<NUM>) and widths of greater than <NUM> inches (<NUM>).

In other select embodiments of the useful article made of polyester foam, the polyester foam may be produced as the flat sheet in a roll stock form to a thickness of at least <NUM> inches (<NUM>) and of up to <NUM> inches (<NUM>) thick.

In other select embodiments of the useful article made of polyester foam, the flat sheet may be used as a thermal barrier.

In other select embodiments of the useful article made of polyester foam, the flat sheet may be utilized as a wood or equivalent substitute.

In other select embodiments of the useful article made of polyester foam, the flat sheet may be thermoformed into the useful articles. Examples of such thermoformed useful articles may include, but are clearly not limited thereto, clamshells, meat trays, plates, bowls, the like, etc..

The foregoing illustrative summary, as well as other exemplary objectives and/or advantages of the disclosure, and the manner in which the same are accomplished, are further explained within the following detailed description and its accompanying drawings.

The present disclosure will be better understood by reading the Detailed Description with reference to the accompanying drawings, which are not necessarily drawn to scale, and in which like reference numerals denote similar structure and refer to like elements throughout, and in which:.

It is to be noted that the drawings presented are intended solely for the purpose of illustration and that they are, therefore, neither desired nor intended to limit the disclosure to any or all of the exact details of construction shown, except insofar as they may be deemed essential to the claimed disclosure.

Referring now to <FIG>, in describing the exemplary embodiments of the present disclosure, specific terminology is employed for the sake of clarity. The present disclosure, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish similar functions. Embodiments of the claims may, however, be embodied in many different forms and should not be construed to be limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples and are merely examples among other possible examples.

Referring now to <FIG>, in a possibly preferred embodiment, the present disclosure overcomes the above-mentioned disadvantages and meets the recognized need for such an apparatus or method by providing of method <NUM> of producing low density polyester foam utilizing low I. polyester feedstock <NUM>. Method <NUM> of producing low density polyester foam utilizing low I. polyester feedstock <NUM> may generally include step <NUM> of providing low intrinsic viscosity raw material <NUM>. Low intrinsic viscosity raw material <NUM> may include between <NUM>% to <NUM>% of post consumer polyester <NUM>. Low intrinsic viscosity raw material <NUM> provided may have an intrinsic viscosity of less than <NUM> dl/g. The intrinsic viscosity of the low intrinsic viscosity raw material <NUM> may be increased in step <NUM> via a de-condensation reaction configured to support foaming step <NUM>. The intrinsic viscosity of the low intrinsic viscosity raw material may be increased to <NUM> dl/g or greater in step <NUM>. Starting formulation <NUM> may be created in step <NUM>. Step <NUM> of creating starting formulation <NUM> may include low intrinsic viscosity raw material <NUM> with the increased intrinsic viscosity. Starting formulation <NUM> may be foamed to create the polyester foam in step <NUM>. Wherein, the polyester foam produced via method <NUM> may have a specific gravity of less than <NUM>/cc.

The low intrinsic viscosity raw material <NUM> may include any types of polyester materials. In select, possibly preferred embodiments, low intrinsic viscosity raw material may include virgin polyester <NUM>, post consumer polyester <NUM>, and process regrind <NUM>. Post consumer polyester <NUM> may be any types of recycled or reusable polyester materials. In select possibly preferred embodiments, post consumer polyester <NUM> may be polyester feedstock that consists of post- industrial waste resin. In select possibly most preferred embodiments, the post-industrial waste resin of the low intrinsic viscosity raw material <NUM> may consist of post-consumer scrap bottle flake. Flake, as used herein, may refer to a particle having a length, width and thickness, wherein the thickness is less than <NUM>% of the smaller dimension of length or width. As such, a flake as used herein may be a particle with significant surface area to volume ratio.

Crystallizing the low intrinsic viscosity raw material <NUM> in crystallizer <NUM> may be included in select embodiments of method <NUM> for producing polyester foam in step <NUM>. In an alternative embodiment, method <NUM> may include pelletizing the low intrinsic viscosity raw material in step <NUM>. The crystallizing or the pelletizing steps <NUM> or <NUM>, respectively, may be configured to prevent the low intrinsic viscosity raw material <NUM> from melting during the de-condensation reaction in step <NUM>.

Step <NUM> of increasing the viscosity of low intrinsic viscosity raw material <NUM> may be included in method <NUM>. Step <NUM> of increasing the viscosity of low intrinsic viscosity raw material <NUM> via the de-condensation reaction to support foaming may include increasing the molecular weight of the low intrinsic viscosity raw material <NUM>. Step <NUM> of increasing the viscosity of the low intrinsic viscosity raw material <NUM> via the de-condensation reaction may include any various processes or apparatuses for increasing the viscosity of low intrinsic viscosity raw material <NUM> by increasing the molecular weight, including any processes or apparatuses currently known and/or discovered in the future. In select embodiments, the molecular weight of low intrinsic viscosity raw material <NUM> may be increased in step <NUM> by feeding the low intrinsic viscosity raw material into solid-state reactor <NUM>. In other select embodiments, the molecular weight of the low intrinsic viscosity raw material may be increased in step <NUM> by a melt-phase de-condensation reaction with vacuum using melt phase reactor <NUM>.

Step <NUM> of creating starting formulation <NUM> may be included in method <NUM>. Step <NUM> of creating starting formulation <NUM> may include any processes or apparatuses for creating starting formulation <NUM>, including any processes or apparatuses currently known and/or discovered in the future. In select embodiments, step <NUM> of creating of starting formulation <NUM> in method <NUM> may include adding viscosity enhancing agent <NUM> and/or nucleating agent <NUM>. Viscosity enhancing agent <NUM> may be configured to fine tune the viscosity of the low intrinsic viscosity raw material <NUM>. In select embodiments, viscosity enhancing agent <NUM> may be a cross-linking agent. Nucleating agent <NUM> may be configured for aiding in nucleating low intrinsic viscosity raw material <NUM>. In select embodiments, the nucleating agent <NUM> may be configured to control bubble or cell size. In other select embodiments, nucleating agent <NUM> may consist of a poly-flouro-ethylene particle.

Step <NUM> of foaming of starting formulation <NUM> may be included in in method <NUM>. Step <NUM> of foaming may be to create the polyester foam. Step <NUM> may include any processes or apparatuses for creating the polyester foam including any processes or apparatuses currently known and/or discovered in the future. In select embodiments, step <NUM> of foaming of starting formulation <NUM> may include tandem extrusion <NUM> of starting formulation <NUM> to create the polyester foam. Step <NUM> of tandem extrusion of starting formulation <NUM> may be to create the polyester foam and may include the use of primary twin screw extruder <NUM> and secondary cooling extruder <NUM>. Primary twin screw extruder <NUM> may include injection system <NUM> and blowing agent storage system <NUM> configured to introduce blowing agent <NUM> into starting formulation <NUM> once starting formulation <NUM> is melted and mixed via primary twin screw extruder <NUM>. In select embodiments, blowing agent <NUM> may consist of a hydrocarbon. The hydrocarbon of the blowing agent may be, but is clearly not limited thereto, C5 hydrocarbons, C6 hydrocarbons etc. Whereby, a homogenous mixture may exit primary twin screw extruder <NUM>. Secondary cooling extruder <NUM> may be configured to cool the homogenous mixture that exits primary twin screw extruder <NUM> for giving the necessary rheology needed to the homogenous solution for successful foaming. Secondary cooling extruder <NUM> may be configured to give heat exchange with minimal shear heat generation. As such, in select embodiments, secondary cooling extruder <NUM> may include a screw configured to act as a heat exchanger for removing heat from the homogenous mixture and increasing viscosity. In select embodiments, screen changer <NUM> may be included between primary twin screw extruder <NUM> and secondary cooling extruder <NUM>. Screen changer <NUM> may be configured for step <NUM> of screening for solid impurities. In select embodiments, gear pump <NUM> may be between primary twin screw extruder <NUM> and secondary cooling extruder <NUM>. Gear pump <NUM> may be configured for step <NUM> of pressurizing the homogenous mixture exiting primary twin screw extruder <NUM> and to impart minimal additional shear heat while pressurizing.

Step <NUM> of forming the polyester foam may be included with method <NUM>. Step <NUM> of forming the polyester foam may include any processes or apparatuses for forming the polyester foam including any currently known processes or apparatuses and/or any processes or apparatuses discovered in the future. In select embodiment, step <NUM> of forming the polyester foam in method <NUM> may include using die <NUM> to form the polyester foam. Die <NUM> may be any desired type, size or shape of die, including, but not limited to, a board die or a sheet die. Die <NUM> may be configured with associated finishing equipment <NUM>. As an example and clearly not limited thereto, associated finishing equipment <NUM> for die <NUM> may include sizing drum <NUM>, pull unit <NUM>, winder <NUM>, to produce roll <NUM>. Pull unit <NUM> may be configured to pull a bubble of the polyester foam over sizing drum <NUM> and slit the bubble to open a flat sheet. In select embodiments, the polyester foam may be produced as the flat sheet in a roll stock form to a thickness of at least <NUM> inches (<NUM>) and of up to <NUM> inches (<NUM>) thick. In other select embodiments, the polyester foam may be produced with the thicknesses greater than <NUM> inches (<NUM>) and widths of greater than <NUM> inches. As examples, and clearly not limited thereto, the flat sheet may be used as a thermal barrier, the polyester foam may be utilized as a wood or equivalent substitute, the like, or combinations thereof.

Referring now to <FIG>, in other select embodiments of method <NUM> of producing low density polyester foam utilizing low I. polyester feedstock <NUM>, the flat sheet may be thermoformed into useful articles <NUM>. Useful articles <NUM> may include, but are clearly not limited thereto, clamshells, meat trays, plates, bowls etc. In select embodiments, the flat sheet may be thermoformed into useful articles via: step <NUM> of unwinding roll <NUM> of flat sheet of the polyester foam; step <NUM> of heating the unwinded roll of flat sheet in oven <NUM>, where temperatures of the oven may be controlled to soften but not melt the flat sheet of polyester foam; step <NUM> of forming the heated flat sheet of polyester foam in forming station <NUM>, where the heated flat sheet of polyester foam may be amorphous or crystallized when formed; step <NUM> of cutting the formed flat sheet of polyester foam in trim press <NUM>, where skeletal waste or regrind is stored to be reused; and step <NUM> of packaging the useful articles <NUM> for sale.

In another aspect, the disclosure embraces useful article or articles <NUM> made of polyester foam. The useful article <NUM> disclosed herein may generally be made by any of the various embodiments of method <NUM> of producing polyester foam as shown and/or described herein. As a result, useful article <NUM> may include low intrinsic viscosity raw material <NUM>. The low intrinsic viscosity raw material may include between <NUM>% to <NUM>% of post consumer polyester <NUM>. Low intrinsic viscosity raw material <NUM> provided may have an intrinsic viscosity of less than <NUM> dl/g. The intrinsic viscosity of low intrinsic viscosity raw material <NUM> may be increased to <NUM> dl/g or greater to support foaming. Low intrinsic viscosity raw material <NUM> may include virgin polyester <NUM>, post consumer polyester <NUM> that may be a polyester feedstock that consists of post- industrial waste resin, and process regrind <NUM>. In select embodiments, the post-industrial waste resin of low intrinsic viscosity raw material <NUM> may consist of post-consumer scrap bottle flake, as disclosed and defined herein. With this low intrinsic viscosity raw material <NUM> of useful article <NUM> made of polyester foam, starting material <NUM> may be included with low intrinsic viscosity raw material <NUM> with the increased intrinsic viscosity, viscosity enhancing agent <NUM> may be included to fine tune the viscosity of low intrinsic viscosity raw material <NUM>, and nucleating agent <NUM> may be included for aiding in nucleating low intrinsic viscosity raw material <NUM>. Wherein, the polyester foam of useful article <NUM> may have a specific gravity of less than <NUM>/cc.

In select embodiments of useful article <NUM> made of polyester foam, the polyester foam may be produced with the thicknesses greater than <NUM> inches (<NUM>) and widths of greater than <NUM> inches (<NUM>).

In other select embodiments of useful article <NUM> made of polyester foam, the polyester foam may be produced as the flat sheet in a roll stock form to a thickness of at least <NUM> inches (<NUM>) and of up to <NUM> inches (<NUM>) thick.

In other select embodiments of useful article <NUM> made of polyester foam, the flat sheet may be used as a thermal barrier.

In other select embodiments of useful article <NUM> made of polyester foam, the flat sheet may be utilized as a wood or equivalent substitute.

In other select embodiments of useful article <NUM> made of polyester foam, the flat sheet may be thermoformed into the useful articles, as shown in <FIG>. Examples of such thermoformed useful articles <NUM> may include, but are clearly not limited thereto, clamshells, meat trays, plates, bowls, the like, etc..

In sum, the disclosure may be directed toward increasing the melt strength of lower viscosity PET raw materials <NUM> to produce a low-density polyester foam. This method involves utilizing PET resins <NUM> with an I. of less than <NUM> dl/g and using solid state de-condensation to produce a foamable PET resin. Combined with prior developments in both nucleation and blowing agents, low density PET foam may be successfully produced, which may be utilized as extruded material, or be formed into useful articles <NUM> in a secondary operation. Specifically, method <NUM> may utilize a low I. polyester feedstock <NUM>. This feedstock can be pelletized or used as flake. The feedstock I. may be increased to greater than <NUM> dl/g via solid state reactor <NUM>. The material, now with an improved I. , may be processed using tandem extrusion <NUM> to produce foam. enhancer may be used to achieve optimal density reduction. Various die configurations may be used to make roll, boards, or other geometry useful for commercial applications.

As a starting material, the disclosure may utilize a lower I. virgin resin for low IV raw material <NUM>, with post consumer polyester <NUM>, which may be post-industrial or post-consumer PET resin available through recycling of bottles and other PET articles in recycle systems widely used across the country. Such materials are widely available and at considerably lower cost than the resins previously used for PET foam development. To produce a foam grade material, this material undergoes a de-condensation reaction with vacuum to increase the molecular weight either via solid-state reactor <NUM> such as is offered by Starlinger of Austria or by a melt phase de-condensation reaction with vacuum using melt phase reactor such as is offered by NGR of Austria.

Muschiatti (see <CIT>) disclosed use of post -consumer polyester as well, but this was never reduced to practice. Muschiatti used a chain extender to make foamable resin, but I. is not linear and large amounts of enhancer are needed to achieve an I. of <NUM> dl/g. This can result in uneven reactions yielding a lumpy extrudate unable to be uniformly formed. By first increasing the I. by solid state de-condensation, foam can be made with little or no enhancer. This results in a uniform and stable extrudate.

Depending on other needs, this material is combined with <NUM>% to <NUM>% virgin PET polyester resin <NUM> and extruded to produce low density foam. The foaming technology of choice may be tandem extrusion <NUM> which is well known in the industry with the primary extruder <NUM> preferably consisting of a twin rather than single screw extruder. This is advantageous for mixing and reducing loss of I. due to shear. The secondary extruder <NUM> may typically be a single screw extruder configured to give heat exchange with minimal shear heat generation but any type of polymer heat exchanger can be used. Typical blowing agents <NUM> may consist of hydrocarbons as well as hydro-chloro-flouro-carbons. Poly-flouro-ethylene particles have been found to be effective nucleators for cell size control.

In addition, a cross-linking agent can be used to fine tune the viscosity as viscosity enhancing agent <NUM>. Polyester foam will collapse if the viscosity is too low, but becomes non-uniform (lumpy) and unusable if the viscosity becomes too high or is uneven. As such, control is best maintained by using the de-condensation reaction with vacuum to attain an I. of greater than <NUM> dl/g and then add a cross linking agent to fine tune the formulation to optional performance. Such agents are commercially available from companies such as Sukano S606-HP.

A board or sheet die <NUM> can be used with the correct associated finishing equipment <NUM>. Utilizing such a system, PET foam can be produced at less than <NUM>/cc, a reduction in density of at least <NUM>% from the base resin. This foam may be used for large cross-section applications, such as marine board, or can be made into roll-stock for the production of thermoformed articles <NUM>, as shown and described in <FIG>.

Referring now specifically back to <FIG>, virgin Polyester <NUM>, post consumer polyester <NUM>, and process regrind <NUM> in any proportions may be first crystallized to prevent material from melting during solid state de-condensation. This blend may then be fed into solid-state de-condensation reactor <NUM> where the I. may be increased to greater than a <NUM> dl/g intrinsic viscosity. Alternately, this blend may first be pelletized before the solid-state de-condensation reaction.

The polyester resin, now of high I. may be conveyed to a feed system where it is combined in proper proportions with viscosity enhancing additive <NUM> and nucleating agent <NUM>. This mixture may be fed into primary extruder <NUM>.

In a separate operation, blowing agent <NUM> may feed a metering system that is injected into primary extruder <NUM>.

Primary extruder <NUM> may first melt and mix the solid components. Once melted, blowing agent <NUM> may be injected and mixed such that a homogenous mixture exits primary extruder <NUM>. The melt is subsequently screened for solid impurities that can get caught in die <NUM>, pressurized utilizes gear pump <NUM>, and then cooled in secondary cooling extruder <NUM>. This secondary cooling extruder <NUM> may be designed with a screw to act as a heat exchanger removing heat from the melt and increasing the viscosity for optimal foam expansion out of die <NUM>.

To produce thermoformed articles <NUM>, roll stock may be made by pulling a bubble over sizing drum <NUM> and slitting the bubble to open a flat sheet. Pull unit <NUM> may ensure uniform gauge with the resulting material wound into roll form on winder <NUM>. Rolls <NUM> can then be used as is or further processed by thermoforming.

Referring now specifically back to <FIG> depicts a thermoforming operation wherein roll <NUM>, such as produced via the process of <FIG>, may be placed on unwind <NUM> that feeds the material into oven <NUM>. The oven temperatures are carefully controlled to soften but not melt the polyester foam material. This softened material is then formed. The material may be amorphous or crystallized when formed. The formed items may be cut out in trim press <NUM>. The skeletal waste or regrind may be stored to be reused in method <NUM> of <FIG>. Useful articles <NUM> may then be packaged for sale.

In a possibly preferred embodiment, as an example, and clearly not limited thereto, polyester foam can be created utilizing method <NUM> disclosed herein using post-consumer polyester bottle flake. The post-consumer polyester bottle flake be washed and cleaned, and may have a nominal intrinsic viscosity of <NUM> dl/g. The post-consumer polyester bottle flake may be first crystallized using a Starlinger crystallizer. This material can then be processed using a Starlinger ViscoSTAR solid state Polycondensation Plant to an intrinsic viscosity of <NUM> dl/g or more.

A mixture of <NUM>% virgin polyester having an intrinsic viscosity of <NUM>. 8dl/g and <NUM>% of the improved bottle flake may be gravimetrically fed into a twin screw extruder. A chain extender additive, such as pyromellitic-di-anhydride, may also be added at a ½% level to build the desired final viscosity. This additional level may vary based on the temperature of the melt as well as the blowing agent composition. Typically, experience indicates the amount needed based on the motor amps of the secondary extruder, which may serve as a defacto viscometer.

After the melt is plasticated, a melt seal may be provided in the screw design. After this seal, under high pressure, the blowing agent may be injected. Cyclo-pentane may be added at about <NUM>%, for optimal foaming. The level added can, however, vary based on the requirements of the product. The remainder of the twin screw extruder may be designed to mix and homogenize the composition.

The homogenous melt may exit the twin screw extruder and flow through a screen changer which may filter out any unwanted particles. The melt, typically at a temperature of <NUM>°F and a pressure of <NUM>,<NUM> psi, (<NUM> Kpa) may enter the gear pump which may increase the pressure to <NUM>,<NUM> psi (<NUM> kPa). The gear pump may be sized to impart minimal additional shear heat.

On exiting the gear pump, the melt may enter the secondary or cooling extruder <NUM>. The screw may be designed to impart minimal shear heat while wiping and renewing the surface contact of the melt with the barrel. The barrel may be oil cooled to avoid the thermal shock that can accompany heat of vaporization. The purpose of the secondary extruder may be to reduce the melt temperature from <NUM>°F (<NUM>) to between <NUM>°F (<NUM>) and <NUM>°F, (<NUM>), which may give the necessary rheology needed for successful foaming.

The tempered melt may exit the extrusion line through an annular die and may pass over a cooling drum which may freeze the foam in place. A pull unit and winder may collect the product in the form of rolls.

The rolls can be used directly or formed in a secondary operation into useful articles. For example, but clearly not limited thereto, one such article may be a meat tray. Using a thermoformer, such as an Irwin Model <NUM>, and the appropriate tooling, such articles can be produced. Typical conditions for the former may include an oven temperature of about <NUM>°F with a cycle speed of <NUM> cycles per minute. The formed shape may be trimmed in a punch and die trim station and the part may then be packaged for sale.

While this may be the preferred embodiment of the invention, it is understood that other processes that reasonably meet the criteria of equivalence are also included within the scope of this invention as are products made from the resulting foam produced.

With this first example, polyester foam was created utilizing method <NUM> disclosed herein according to select possibly preferred embodiments. Primatop GP-<NUM> virgin polyester resin with a measured I. of <NUM> di/gram was loaded into a Starlinger SSP solid state reactor. Approximately <NUM>,<NUM> pounds of material were loaded into the reactor.

The reactor was set at a temperature of <NUM> with a purge of <NUM>, <NUM> liters per hour of nitrogen. The material was held in the reactor for a period of <NUM> hours. After this time, the material was unloaded and allowed to cool. The resulting material was measured for intrinsic viscosity. The results ranged from <NUM> di/gram to <NUM> di/gram. Prior art has shown this level of intrinsic viscosity may be suitable for low density foaming applications, as shown and described herein.

With this second example, polyester foam was created utilizing method <NUM> disclosed herein according to select possibly preferred embodiments. Post-consumer bottle flake was loaded into a Starlinger SSP reactor. Approximately <NUM>,<NUM> pounds of material was loaded. This material was characterized as having <NUM> ppm of wood, <NUM> ppm of polyvinyl chloride, and <NUM> ppm of G-Pet as contamination. In addition, the material contained <NUM> ppm of colored flake and <NUM>,<NUM> ppm of yellow discolored flake. The beginning intrinsic viscosity of this material was measured to have a range of <NUM> di/gram to <NUM> di/gram.

The reactor was heated and maintained at a temperature of <NUM> and under a nitrogen purge of <NUM>,<NUM> liters per hour per a period of <NUM> hours. The material was then unloaded and allowed to cool. The resultant material was measured for final intrinsic viscosity.

Values ranged from <NUM> to <NUM> di/gram. Prior art has shown this level of intrinsic viscosity may be suitable for low density foaming applications, as shown and described herein.

With this third example, polyester foam was created utilizing method <NUM> disclosed herein according to select possibly preferred embodiments. Post-Consumer polyester resin in the form of Bottle Flake with a measure I. of <NUM> dl/gram after the de-condensation reaction (produced in Example <NUM>) was mixed with <NUM>% Equicell nucleating agent and then fed into a <NUM> Listritz twin screw extruder. The Extruder had an L/D of <NUM>:<NUM> consisting of ten barrel sections and a three-hole strand die.

The polyester/nucleator mixture was fed into primary twin screw extruder <NUM> using a Brabender gravimetric feeder. Input rate to the extruder was <NUM> lb/hr. This rate may be low for an extruder of this size but was done so deliberately to allow residence time in the latter barrel sections to achieve needed cooling of the melt phase so that optimal viscosity for foaming could be achieved.

Using gear pump <NUM> with variable speed drive, blowing agent <NUM> was injected in the ninth barrel section. Blowing agent <NUM> consisted of a mixture of hexane and heptane isomers and was added to the melt at a rate of <NUM>% by weight.

Primary twin screw extruder <NUM> was used to melt, mix, and cool the polymer mixture with the resultant foam exiting the three-hole strand die. Process conditions for this sample were:.

Due to the difficulty in taking samples, both due to shape and small size, the density of the extruded polyester foam was determined by water displacement. The foam density was estimated to be <NUM> grams/cubic centimeter +/- <NUM> grams/cubic centimeter.

This example showed the feasibility of producing low density polyester foam using <NUM>% post-consumer bottle flake.

In the specification and/or figures, typical embodiments of the disclosure have been disclosed. The present disclosure is not limited to such exemplary embodiments. The use of the term "and/or" includes any and all combinations of one or more of the associated listed items. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.

Claim 1:
A method for producing a polyester foam comprising:
providing a low intrinsic viscosity raw material, the low intrinsic viscosity raw material includes between <NUM>% to <NUM>% of a post consumer polyester, and the post consumer polyester has an intrinsic viscosity of less than <NUM> dl/g as measured by ASTM method D-<NUM>;
increasing the intrinsic viscosity of the low intrinsic viscosity raw material via a de-condensation reaction configured to support foaming, including increasing a molecular weight of the low intrinsic viscosity raw material by feeding the low intrinsic viscosity raw material into a solid-state reactor or by a melt-phase de-condensation reaction with vacuum using a melt-phase reactor,
wherein the intrinsic viscosity of the low intrinsic viscosity raw material is increased to <NUM> dl/g or greater;
creating a starting formulation including the low intrinsic viscosity raw material with the increased intrinsic viscosity;
foaming the starting formulation to create the polyester foam;
wherein, the polyester foam produced has a density of less than <NUM>/cc.