Abstract:
The invention relates to a composition and a process for inhibiting the movement of free flowing particles. The process comprises adding a mixture of (a) an aqueous alkaline solution of a phenolic resole resin, and (b) a liquid organic ester to the free flowing particles, which are to be immobilized.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a utility application based upon provisional application 60/539,934 filed on Jan. 29, 2004.  
       CLAIM TO PRIORITY  
       [0002]     Applicants claim the priority date of provisional application Ser. No. 60/539,934 filed on Jan. 29, 2004, which is hereby incorporated by reference. 
     
    
     Field of the Invention  
       [0003]     The invention relates to a composition and a process for inhibiting the movement of free flowing particles. The process comprises adding a mixture of (a) an aqueous alkaline solution of a phenolic resole resin, and (b) a liquid organic ester to the free flowing particles which are to be immobilized.  
       BACKGROUND OF THE INVENTION  
       [0004]     Experience during military and civilian operations in deserts has shown that there is a need to immobilize the particles of sand on the surface of the desert, which are blown due to natural causes, such as wind, or man-made causes, such as a helicopter or an airplane. If the sand is not immobilized, it can be blown into the eyes of personnel on the ground, which could damage the eyes, or into operation equipment, e.g. aircraft engines, helicopter blades, etc., which results in foreign object damage (FOD) and/or damage to the equipment due to erosion. Operations are often interrupted when these circumstances occur. If the sand were immobilized, these hazards could be prevented and operations could proceed without interruption.  
         [0005]     It is known that sand can be shaped into molds and cores used in the casting of metals, by the no-bake process using an aqueous alkaline solution of a phenolic resole resin and a liquid ester curing catalyst. The components must be kept separately before they are applied to sand, otherwise, they will prematurely act, which will prevent the sand from being used effectively to make cores and/or molds. The components are separately applied to the foundry aggregate (typically sand), which is used to make the cores and/or molds. After the components of the binder and the sand are mixed, the mixture is shaped and allowed to cure. It is not practical to immobilize porous particles covering a vast surface area while they are in place by this method.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention relates to a composition and a process for inhibiting the movement of free flowing particles. The process comprises adding a mixture of (a) an aqueous alkaline solution of a phenolic resole resin, and (b) a liquid organic ester to the free flowing particles, which are to be immobilized, wherein the weight ratio of (a) to (b) is from 90:10 to 70:30, preferably from 85:15 to 75:25. The mixture of (a) and (b) acts as flow inhibitor.  
         [0007]     “Free flowing particles” are particles that are actually free flowing or particles that have the potential to be free flowing when subjected to wind, rain, or other forces, whether they are man-made or natural.  
         [0008]     The use of such flow inhibitors is particularly useful in inhibiting the flow of desert sand, which enables military and civilian operations in deserts to proceed without distraction and interruption. The flow inhibitors fill the spaces between the sand particles, and when the flow inhibitor cures, the sand is immobilized. The desert sand is immobilized from movement due to natural causes, such as wind, or man-made causes, such as a helicopter or an airplane. When the sand is immobilized, visibility problems for people on the ground or in aircraft are minimized, and the disruption of operations is minimized.  
         [0009]     The flow inhibitors are applied to the free flowing particles in a manner, which will partially, but preferably totally immobilize the movement of the particles. For example, the particles can be impregnated or sprayed with the flow inhibitor. The flow inhibitors do not need to be mixed with the particles with mixing equipment in order for them to be effective in immobilizing the sand. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     The detailed description and examples will illustrate specific embodiments of the invention will enable one skilled in the art to practice the invention, including the best mode. It is contemplated that many equivalent embodiments of the invention will be operable besides these specifically disclosed.  
         [0011]     The aqueous alkaline solutions of phenolic resole resins used in the subject binder compositions are prepared by methods well known in the foundry art. The general procedure involves reacting an excess of aldehyde with a phenolic compound in the presence of a basic catalyst at temperatures of about 50° C. to 120° C. to prepare a phenolic resole resin. Generally the reaction will also be carried out in the presence of water. The resulting phenolic resole resin is diluted with a base and/or water so that an aqueous alkaline solution of the phenolic resole resin results having the following characteristics: 
    1. a viscosity of less than about 250 centipoise, preferably less than about 100 centipoise at 25° C. as measured with a Brookfield viscometer, spindle number 3 at number 12 setting;     2. a solids content of 35 percent by weight to 75 percent by weight, preferably 50 percent by weight to 60 percent by weight, based upon the total weight of the aqueous alkaline solution, as measured by a weight loss method by diluting 0.5 gram of aqueous resole solution with one milliliter of toluene and then heating on a hotplate at 150° C. for 15 minutes; and     3. an equivalent ratio of base to phenol of from 0.2:1.0 to 1.1:1.0, preferably from 0.3:1.0 to 0.95:1.0.    
 
         [0015]     As an alternative to the procedure outlined, it is be possible to prepare the aqueous alkaline solutions by dissolving all of the base in phenol and then reacting with formaldehyde until the desired properties are achieved.  
         [0016]     It has been found that aqueous alkaline solutions having viscosities outside the cited range are difficult to use as flow inhibitors. Aqueous alkaline solution with a solids content below the cited range will not be sufficiently flowable. The equivalent ratio specified for the base relates to the need for having solutions, which have adequate shelf stability.  
         [0017]     The phenolic compounds used to prepare the phenolic resole resins can be represented by the following structural formula:  
                         
 
 where B is a hydrogen atom, or hydroxyl radicals, or hydrocarbon radicals or oxyhydrocarbon radicals, or halogen atoms, or combinations of these. Multiple ring phenols such as bisphenol A may be used. 
 
         [0018]     The aldehyde used in preparing the phenolic resole resin may also vary widely. Suitable aldehydes include aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde, and benzaldehyde. In general, the aldehydes used have the formula RCHO, where R is a hydrogen or a hydrocarbon radical of 1 to 8 carbon atoms. The most preferred aldehyde is formaldehyde.  
         [0019]     The alkaline catalysts used in preparing the phenolic resole resin include basic catalysts such as alkali or alkaline earth hydroxides, and organic amines. The amount of catalyst used will vary depending upon the specific purposes. Those skilled in the art are familiar with the levels needed.  
         [0020]     It is possible to add compounds such as lignin and urea when preparing the phenol-formaldehyde resole resins as long as the amount is such that it will not detract from achieving the desired properties of the aqueous alkaline solutions. Urea is added as a scavenger to react with unreacted formaldehyde and remove the odor caused by it.  
         [0021]     The phenolic resole resins used in the practice of this invention are generally made from phenol and formaldehyde at a mole ratio of formaldehyde to phenol in the range of from about 1.1:1.0 to about 3.0:1.0. The most preferred mole ratio of formaldehyde to phenol is a mole ratio in the range of from about 1.4:1.0 to about 2.2:1.0.  
         [0022]     As was mentioned previously, the phenolic resole resin is either formed in the aqueous alkaline solution, or it is diluted with an aqueous alkaline solution. The base used in the aqueous alkaline solution is usually an alkali or alkaline earth metal hydroxide such as potassium hydroxide, sodium hydroxide, calcium hydroxide, or barium hydroxide, preferably potassium hydroxide.  
         [0023]     The organic ester can be any liquid organic ester, including cyclic organic esters, which hydrolyze in the presence of water. The liquid esters used are well known in the art. Those, which are preferred, include lactones, organic carbonates, carboxylic acid esters, and mixtures thereof.  
         [0024]     Generally, low molecular weight lactones are suitable, such as gamma-butyrolactone, valerolactone, caprolactone, beta-propiolactone, beta-butyrolactone, isopentylactone and delta-pentylactone. Specific carboxylic acid esters include, but are not limited to, n-butyl acetate, ethylene glycol diacetate, diacetin (glycerol diacetate), triacetin (glycerol triacetate), dimethyl succinate, dimethyl glutarate, and dimethyl adipate. Specific organic carbonates include, but are not limited to, propylene carbonate.  
         [0025]     Although the flow inhibitor can be used to immobilize any particulate solid, it is particularly useful for immobilizing sand particles, e.g. zircon, olivine, aluminosilicate, chromite sand, and the like. It is also useful for immobilizing mixtures that contain sand and clay.  
         [0026]     The resin and the organic ester are mixed together and then applied to the sand to be immobilized. The amount of flow inhibitor used is an amount sufficient to substantially or completely immobilize the surface of the sand for a time sufficient to carry out the operations without disruption. Generally, the amount of flow inhibitor required will be 0.5 to 5.0 pounds per square foot, preferably 1 to 3 pounds per square foot, or 2.5 to 25 kilograms per square meter, preferably 5 to 15 kilograms per square meter.  
         [0027]     The amount of sand immobilized by the flow inhibitor is greatest when all of the flow inhibitor penetrates into the spaces between the sand particles before curing occurs. If curing occurs before penetration is completed, a layer of cured resin will form on top of the sand, and less sand will be immobilized.  
         [0028]     To avoid this, the viscosity and the curing time of the flow inhibitor need to be correctly adjusted. The examples illustrate several ways this can be achieved. For example, if curing occurs before all of the flow inhibitor has a chance to penetrate spaces between the sand particles, additional water can be added to lower the viscosity of the flow inhibitor, thereby enabling the flow inhibitor to penetrate between the spaces of the sand particles more quickly. The ability to balance viscosity and cure speed will depend upon the particular system and solid particulate to be immobilized, but the approaches described above will be appreciated by those skilled in the art.  
         [0029]     Although the viscosity of the flow inhibitor can vary over wide ranges, typically a good balance of penetration and cure speed can be achieved with a representative sand when the flow inhibitor has a viscosity less than 250 centipoise at 25° C., preferably less than 100 centipoise, and most preferably less than 50 centipoise.  
         [0000]     Abbreviations and/or Definitions  
         [0030]     The following abbreviations and/or definitions are used in the examples: 
    NOVASET® HP an alkaline aqueous solution of a phenolic resole resin sold by Ashland Specialty Chemical Company, a division of Ashland Inc., having a viscosity of about 30 to 60 centipoise at 25 C.     CRE-A an organic ester co-reactant, which is a mixture of gamma-butyrolactone, triacetin and resorcinol.     CRE-B an organic ester co-reactant, which consists of pure triacetin.     CRE-C an organic ester, which is a mixture of triacetin, dibasic ester (DBE) and resorcinol.    
 
       EXAMPLES  
       [0035]     While the invention has been described with reference to a preferred embodiment, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In this application, all units are in the metric system and all amounts and percentages are by weight, unless otherwise expressly indicated.  
         [0036]     In the examples, the sand used was lake sand (Manley 1L5W).  
       Example 1  
       [0037]     Flow Inhibitor Using a Fast Co-Reactant  
         [0038]     Sixteen grams of NOVASET HP and 4 grams of CRE-A were mixed for one minute. Then 15 grams of the mixture were added by pipette to 100 gm of sand in a 3 ounce cup. Curing of the resin occurred after 4 minutes, but all of the resin did not have a chance to penetrate into the sand.  
         [0039]     The surface and subsurface of the sand became noticeably harder with time, because the spaces between the sand particles had been filled and the flow inhibitor had cured. The sample was allowed to cure overnight, and the immobilized sand was recovered. The weight of immobilized sand was determined as follows: 
 
Weight of immobilized sand=(weight of cured sand+resin)−(weight of resin added to sand) 
 
         [0040]     In this case, the amount of immobilized sand was 39 grams.  
         [0041]     The resin-immobilized sand had good very structural integrity, which indicates that the sand particles were immobilized.  
       Example 2  
       [0042]     Impregnation with a Slower Acting Ester-Cured Phenolic Thermosetting Composition  
         [0043]     This example uses a slower-acting ester catalyst than that used in Example 1. NOVASET HP and CRE-B were combined to form the flow inhibitor. CRE-B hydrolyzes more slowly when mixed with the resin than CRE-A.  
         [0044]     Sixteen grams of NOVASET HP and 4 grams of CRE-B were mixed for one minute. Fifteen grams of the mixture were added to 100 gm of sand in a 3 ounce cup. Almost all of the resin penetrated into the sand before curing, but there was still a thin layer of cured resin on top of the sand.  
         [0045]     After 15 minutes, the surface and subsurface of the sand had become noticeably harder, because the spaces between the sand particles had been filled and the flow inhibitor had cured. This trend continued with time. The sample was allowed to cure overnight, and the immobilized sand was recovered.  
         [0046]     In this case, the amount of immobilized sand was 51 grams.  
       Example 3  
       [0047]     Impregnation with an Even Slower Acting Ester-Cured Phenolic Thermosetting Composition  
         [0048]     This example uses a slower-acting ester catalyst than that used in Example 2.  
         [0049]     NOVASET HP and NOVASET CRE-C were combined to form the flow inhibitor.  
         [0050]     Sixteen grams of NOVASET HP and 4 grams of CRE-C were mixed for one minute. Fifteen grams of the mixture were added to 100 gm of sand in a 3 ounce cup. In this case, all of the flow inhibitor penetrated into the sand before curing occurred.  
         [0051]     After 37 minutes, the surface and subsurface of the sand had become noticeably harder, because the spaces between the sand particles had been filled and the flow inhibitor had cured. This trend continued with time. The sample was allowed to cure overnight, and the immobilized sand was recovered.  
         [0052]     In this case, the amount of immobilized sand was 61 grams.  
         [0053]     This example shows that the judicious selection of a catalyst with the appropriate curing time enables all of the flow inhibitor to penetrate into the sand and increases the amount of resin-immobilized sand.  
       Example 4  
       [0054]     Impregnation with a Lower Viscosity Ester-Cured Phenolic Thermosetting Composition  
         [0055]     In this case the same components, as used in Example 2, were used to prepare the flow inhibitor. However, the NOVASET® HP was first diluted with additional water before mixing it with the CRE-B.  
         [0056]     Seventeen grams of NOVASET HP was mixed with 3 grams of water. Then five grams of CRE-B were added, and the mixture was stirred for 1 minute. The viscosity of this mixture was 28 centipoise, as compared to 53 centipoise for the mixture used in Example 2.  
         [0057]     Fifteen grams of this mixture were added to 100 gm of sand in a 3 ounce cup. All of the resin penetrated into the sand before curing occurred.  
         [0058]     After 6 minutes, the surface and subsurface of the sand had become noticeably harder, because the spaces between the sand particles had been filled and the flow inhibitor had cured. This trend continued with time. The sample was allowed to cure overnight, and the immobilized sand was recovered.  
         [0059]     In this case, the amount of immobilized sand was 58 grams.  
         [0060]     These examples show that a mixture of an aqueous alkaline solution of a phenolic resole resin and a liquid organic ester is effective as a flow inhibitor. They also show that the effectiveness depends upon the reactivity of the organic ester and the viscosity of the aqueous alkaline solution of a phenolic resole resin.  
         [0061]     The results of the Examples are summarized in Table I.  
                                                   TABLE I                           Summary of ester-cured phenolic flow inhibitors                    Weight of           Exam-       Immobilized   Appearance/       ple   Flow Inhibitor   sand (grams)   properties                    1   NOVASET HP/CRE-A   39   Layer of cured resin                   on top of sand.       2   NOVASET HP/CRE-B   51   Small amount of                   cured resin on top.       3   NOVASET HP/CRE-C   61   No resin layer                   on top.       4   (85% NOVASET HP/15%   58   No resin layer           H 2 O)/CRE-B       on top.