MXPA01008516A - Method for degassification of high internal phase emulsion components - Google Patents

Abstract

This application relates to flexible, microporous, open-celled polymeric foam materials with physical characteristics that make them suitble for a variety of uses. This application particularly relates to degassing the components of the high internal phase emulsions which are subsequently cured to form such foams.

Description

METHOD FOR DEGASIFICATION OF INTERNAL HIGH-PHASE EMULSION COMPONENTS FIELD OF THE INVENTION This application relates to open cell, microporous, flexible polymer foam materials with physical characteristics that make them suitable for a variety of uses. This application is particularly related to methods for degassing the components of high internal phase emulsions which are subsequently cured to form said foams.

BACKGROUND OF THE INVENTION The development of microporous foams is the subject of substantial commercial interest. Said foams have found utility in various applications such as thermal, acoustic, electrical and mechanical insulators (for example, for cushioning or packaging), absorbent materials, filters, membranes, floor mats, toys, carriers for inks, dyes, lubricants, and lotions, and the like. References describing such uses and properties of the foam include Oertel, G., Polvurethane Handbook, Hanser Publishers, Muchich, 1985, and Gibson, L.J .; Ashby, M.F., Cellular Solids.

Structure and Properties, Pergamon Press, Oxford, 1988. Other uses for foams are generally obvious to one skilled in the art. Open cell foams prepared from high internal phase emulsions (hereinafter referred to as "HIPE") are particularly useful in a variety of applications including disposable absorbent articles (patents of the United States Nos. 5,331, 015 (DesMarais et al.) Issued on July 19, 1994, 5,260,345 (DesMarais et al.) Issued on November 9, 1993, 5,268,224 (DesMarais et al.) Issued on December 7, 1993, 5,632,737 ( Stone et al.) Issued on May 27, 1997, 5,387,207 (Dyer et al.) Issued on February 7, 1995, 5,786,395 (Stone et al.) Of July 28, 1998, 5,795,921 (Dyer et al.) Issued August 18. 1998), insulation (thermal, acoustic, mechanical) (patents of the United States Nos. 5,770,634 (Dyer et al.) Issued June 23, 1998, 5,753,359 (Dyer et al.) Issued May 19, 1998, and 5,633,291 (Dyer et al.) Issued May 27, 1997), filtering ( Bhumgara, Z. Filtration &Separation 1995, March, 245-251; Walsh et al. J. Aerosol Sci. 1996, 27, 5629-5630, published PCT application WO / 97/37745, published on October 16, 1997, name of Shell Oil Co.), and other diverse uses. The patents and references cited above are incorporated herein by reference. The HIPE process provides easy control over density, cell and pore size and distribution, ratio of cell struts to windows, and porosity in these foams. The physical properties of the HIPE foam are governed by: (1) the properties of the polymer from which the foam is comprised, (2) the density of the foam, (3) the structure of the foam (ie, the thickness, shape and aspect ratio of the polymer struts, cell size, pore size, pore size distribution, etc.), and (4) the surface properties of the foam (for example, if the surface of the foam is hydrophilic or hydrophobic). Once these parameters have been defined and obtained for a particular application, an economically attractive process for preparing the material is desired. A key aspect of this process is the rate of polymerization and crosslinking, together referred to as curing, of the oil phase of a HIPE to form a reticulated network of the polymer. Previously, this curing step requires that the emulsion be maintained at an elevated temperature (40 ° C-82 ° C) for a relatively long period of time (typically from 2 hours to 18 hours or more). Such long curing times require relatively low rates of expenditure, as well as high capital and production costs. Previous efforts to devise commercially successful schemes for producing HIPE foams have involved, for example, emptying the HIPE into a large holding container which is placed in a heated area for curing (see for example U.S. Pat. 5,250,576 (DesMarais) issued October 5, 1993). U.S. Patent Nos. 5,189,070 (Brownscombe et al.), Issued February 23, 1993; 5,290,820 (Brownscombe et al.) Issued on 1 st. March 1994; and 5,252,619 (Brownscombe et al.) issued October 12, 1993 reports the curing of the HIPE in multiple stages. The first stage is conducted at a temperature of less than about 65 ° C until the foam reaches a state of partial cure. Then the temperature is increased between 70 ° C and 175 ° C to effect the final curing quickly. The total process takes approximately 3 hours. Another scheme for producing HIPE foams involves placing the emulsion on a layer of impermeable film which would then be cooled and placed in a curing chamber (U.S. Patent No. 5,670,101 (Nathoo, et al.) Issued September 23. of 1997). The cooled film / emulsion sandwich can then be cured using the sequential temperature sequence disclosed in the Brownscombe patents and others discussed above. The patent of the United States No. ,849,805 (Dyer et al.) Issued December 15, 1998 discloses the formation of the HIPE at a temperature of 82 ° C (pouring temperature in example 2) and curing the HIPE at 82 ° C for 2 hours. However, none of these approaches offers the combination of very rapid conversion (eg, in minutes or seconds) of the HIPE to the polymeric foam that would provide a relatively simple, low capital process to produce HIPE foams both economically and economically. with the series of desired properties. The technique also discloses using pressure to control the volatility of the monomers, which would otherwise be removed by boiling at a suitable polymerization / curing temperature. For example, the commonly assigned patent of the United States No. 5,767,168, issued to Dyer et al. On June 16, 1998, discloses the suitability of pressurization to control the volatility of relatively volatile conjugated diene monomers. However, the cure time for the foams disclosed there is still greater than two hours such that there is still a substantial opportunity for a substantial improvement in curing speed that would improve the economic attractiveness of the HIPE foams. The deoxygenation of the components (for example, monomers and dispersion phases) used in the processes such suspension polymerization is well known. Said components are deoxygenated in order to reduce the efficiency of the polymerization inhibitors typically used to prevent premature polymer formation because typical inhibitors adhere to dissolved oxygen. An illustrative method of this type is described in Japanese Patent Application Serial No. 06-172406, published on June 21, 1994. Described therein is a method for suspension polymerization of the vinyl chloride monomer where the monomer is dispersed in a phase of degassed water (deoxygenated to less than 2 ppm of O2) at a temperature lower than a polymerization temperature. The dispersed monomer is then raised to a polymerization temperature and an initiator is charged into the aqueous medium. This method is said to reduce the amount of scale that is deposited on the polymerization apparatus during the polymerization. While these processes may use a phase of degassed water, the attempt at such degassing is deoxygenation (other processes use spraying to replace dissolved oxygen with nitrogen for the same purpose). Therefore, there is no recognition in the art of the desirability of degassing the phases (as opposed to deoxygenation) that are formed in a HIPE and subsequently cured in a HIPE foam for the purpose of minimizing defects ( example, gaps) in the foam. Accordingly, it would be desirable to develop a rapid and efficient process for preparing open cell polymeric HIPE foam materials with the desired properties. It would further be desirable for such processes to provide HIPE foams substantially free of defects. It would be more desirable that said processes comprise simple unit operations.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a process for obtaining open cell foams by polymerizing a high internal phase emulsion, or, HIPE, which has a relatively small amount of a continuous phase of oil and a relatively greater amount of an aqueous discontinuous phase. The present invention relates particularly to relatively high temperature processes for curing the oil phase, wherein one or both of the oil and water phases is / are degassed. Among other benefits said degassing allows the HIPE to be heated allowing more than the foam to be prepared in a much shorter interval than has been previously possible with a reduction in the level of internal defects. This allows the practical processes of continuous production of HIPE foams which have up to this point been done through batch processes. The process of the present invention generally comprises the steps of: 1) forming a water-in-oil emulsion (HIPE) wherein the oil phase comprises polymerizable monomers; 2) polymerizing and crosslinking the monomers at a temperature greater than 90 ° C to form a HIPE foam. Specifically, the oil phase comprises: 1) from about 85 to 99% by weight of a monomer component capable of forming a crosslinked copolymer having a Tg of about 90 ° C or less, wherein the monomorphic component comprises a monomer mixture monofunctionals, crosslinking agents, and comonomers capable of modifying the properties of the foam; and 2) from about 1 to about 20% of an emulsifier component capable of forming a stable HIPE. The aqueous phase comprises from about 0.2 to about 40% by weight of a water soluble electrolyte and an effective amount of a polymerization initiator. The volume to weight ratio of the aqueous phase to the oil phase is between about 8: 1 and about 140: 1. After polymerization, the aqueous fraction of the HIPE foam can be removed by a variety of techniques to produce the low density, microporous, open cell product. The curing of the HIPE in a relatively short period of time at high temperatures allows for increased production and improved economy in relation to the previously described methods. Any of the processes can be used by batch or continuous. In any case, due to the vapor pressure of both phases in the emulsion increases as the temperature increases, some containment and / or pressurized system may be required to avoid the volatilization of the components of the HIPE. Said high pressures may also serve to reduce the separation of the dissolved gases during the high temperature curing and / or the emulsification steps. Volatilization to form gas or vapor bubbles can create defects (eg, voids) that degrade the fine structure, particularly the cell size distribution, of the HIPE and the resulting HIPE foam, and is usually what is going to be avoided. This can be achieved by vacuum degassing one or both of the oil and water phases, applying pressure from an external source such as a pump or cylinder with pressurized gas, heating the emulsion in a closed vessel with relatively large head volume small, heating a portion of the composition below the surface of the emulsion in an open container so that the "hydrostatic" pressure prevents the volatilization of liquid comprising the emulsion, or by any other method or device generally known to those skilled in the art. The technique. The elements of these approaches can be combined to develop an appropriate process for the rapid curing of HIPE foams.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an electronic photomicrograph at an amplification 500 times of a control HIPE foam in its expanded state wherein the emulsion was formed at 47 ° C and cured at 65 ° C under ambient pressure according to the prior art. Figure 2 is an electronic photomicrograph at a 500-fold amplification of a representative polymer foam in its expanded state according to the present invention described as described in example 1. Figure 3 is an electron photomicrograph at a magnification of 1000 times of a control foam in its expanded state wherein the emulsion was formed at 47 ° C and cured at 65 ° C under ambient pressure according to the prior art. Figure 4 is an electronic photomicrograph at a 1000-fold amplification of a representative polymer foam in its expanded state according to the present invention prepared as described in the example.

Figure 5 is an electronic photomicrograph at a 2500-fold amplification of a HIPE control foam in its expanded state where the emulsion was formed at 47 ° C and cured at 65 ° C under ambient pressure according to the prior art . Figure 6 is an electronic photomicrograph at a 2500 fold amplification of a representative polymer foam in its expanded state according to the present invention prepared as described in the example. Figure 7 is a schematic diagram of the curing chamber used to prepare the foams illustrated in Figures 1 and 2. Figure 8 is a schematic diagram of a continuous process for preparing HIPE foams.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions The following definitions are offered in relation to the present invention. "Curing" is the process of converting a HIPE into a HIPE foam. The curing involves the polymerization of the monomers in polymers. One more step included in the curing process is the reticulate. A cured HIPE foam is one that has the physical properties, e.g., mechanical integrity, that are maintained in the later stages of processing (which may include post curing treatment to confer desired final properties). Generally, curing is carried out by the application of heat. An indication of the cure limit is the mechanical strength of the foam, as measured by the yield point stress described in the Test Methods section below.

"Polymerization" is the part of the curing process by which the monomers of the oil phase are converted to a relatively high molecular weight polymer. "Crosslinking" is the part of the curing process by which monomers having more than one functional group with respect to free radical polymerization are copolymerized in more than one chain of the growing polymer. "Hydrostatic" is related to the pressure conferred by a column of liquid in a gravitational field, sometimes referred to as "hydrostatic height". The liquid is not necessarily water, but it can be a solution, emulsion, aqueous suspension or other liquid. "Defects" are irregular pores within the polymeric foam. Typically, a defect has an effective diameter much greater than the desired pore size distribution for the foam and can be considered to be a gap in the foam. "Deoxygenation" of a liquid is the partial or complete removal of dissolved oxygen, usually effected by the replacement of dissolved oxygen by replacement with an inert gas (for example N2 or Ar). The bubbling of a liquid with the N2 gas is a well-known deoxygenation method. "Disappearing" or "degassing" a liquid is the removal of a substantial portion of the dissolved gases of all types.

I. Polymeric foam derived from an emulsion of high internal phase A. General characteristics of the foam 1. Components of the oil phase The continuous oil phase of the HIPE comprises monomers that are polymerized to form a solid foam structure and the emulsifier necessary to stabilize the emulsion. In general, the monomers will include from about 20 to about 95% by weight of at least one monofunctional substantially water-insoluble monomer capable of forming an atactic amorphous polymer having a glass transition temperature (Tg) of about 35 ° C or less . This comonomer is added to the lowest total Tg of the resulting HIPE foam. Exemplary monomers of this type include C4-C4 alkyl acrylates and C6-Ci6 methacrylates such as 2-ethylhexyl acrylate, n-butyl acrylate, hexyl acrylate, n-octyl acrylate, nonyl acrylate, acrylate. decyl, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl acrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, and tetradecyl methacrylate; substituted acrylamides, such as N-octadecyl acrylamide; dienes such as isoprene, butadiene, chloroprene, piperylene, 1, 3,7-octatriene, ß-myrcene and amyl butadiene; C4-C 2 -substituted styrenics such as p-n-octyl styrene; and combinations of said monomers. Monofunctional monomers that reduce Tg will generally comprise from 20% to about 95%, more preferably from 45% to about 65%, by weight of the monomer component. The oil phase will also comprise from about 5 to about 80% by weight of at least one polyfunctional crosslinking agent, substantially insoluble in water. This comonomer is added to confer resistance to the resulting HIPE foam. Exemplary crosslinking monomers of this type encompass a wide variety of monomers containing two or more activated vinyl groups, such as the divinyl benzenes and analogs thereof. These analogs include m.p-divinyl benzene (including commercially available mixtures of said divinyl benzenes with ethyl styrene), divinyl naphthalene, trivinyl benzene, divinyl alkyl benzenes, divinyl biphenyls, divinyl phenyl ethers, divinyl ferrocenes, divinyl furans, and the like.

Other useful crosslinking agents may be selected from a group derived from the reaction of acrylic acid or methacrylic acid with polyfunctional alcohols and amines. Non-limiting examples of this group include 1,6-hexanedioldiacrylate, 1,4-butanediolmethacrylate, trimethylolpropane triacrylate, hexamethylene bisacrylamide, and the like. Other examples of crosslinking monomers include divinyl sulfide, divinyl sulfone, and trivinyl phosphine. Other crosslinkers useful in this regard are well known to those skilled in the art. It should be distinguished that the weight fraction of the crosslinking component is calculated on the basis of the pure crosslinker in cases where the crosslinking monomer is commonly used as a mixture (for example, divinyl benzene is often a pure mixture at 55% with the balance that is ethyl styrene). Any third comonomer substantially insoluble to the water can be added to the oil phase in percentages by weight from about 0% to about 70%, preferably from about 15% to about 40%, to modify the properties in another way. In certain cases, the "hardening" monomers may be desired which impart toughness to the resulting HIPE foam equivalent to that provided by the styrene. These include styrenics such as styrene and ethyl styrene and methyl methacrylate. Also included are styrenics and other compounds that may also help reduce Tg or improve the strength of the resulting HIPE foam such as p-n-octyl styrene.

The monomers may be added to confer flame retardancy as disclosed in the commonly assigned, co-pending, United States of America patent application Serial No. 09/1 18,613 (Dyer) filed July 17, 1998. monomers can be added to confer color, fluorescent properties, radiation resistance, radiation opacity (for example, lead tetraacrylate), to disperse the charge, to reflect incident infrared light, to absorb radio waves, to form a wet surface on the foam struts of HIPE, or for any other purpose. 2. Components of the aqueous phase The discontinuous internal phase of the HIPE is generally an aqueous solution containing one or more dissolved components. An essential dissolved component of the water phase is a water soluble electrolyte. The dissolved electrolyte minimizes the tendency of the monomers, comonomers and crosslinkers that are mainly soluble in oil to also dissolve in the water phase. Another component of the aqueous phase is a water-soluble free radical initiator as may be known in the art. The initiator may be present in up to about 20 mol percent based on the total moles of the polymerizable monomers present in the oil phase. More preferably, the initiator is present in an amount of about 0.001 to about 10 mol percent based on the total moles of the polymerizable monomers in the oil phase. Suitable initiators include ammonium persulfate, potassium persulfate, hydrogen peroxide, and peroxyacetic acid. 3. Emulsifier The emulsifier is necessary to form and stabilize the HIPE. The emulsifier is generally included in the oil phase and tends to be relatively hydrophobic in character. (See, for example, Williams, J.M., Lanqmuir 1991, 7, 1370-1377, incorporated herein by reference). An example of an emulsifier that works very well is diglycerol monooleate. Other emulsifiers of this general type also include diglycerol monomiristate, diglycerol monoisostearate, diglycerol monoesters of coconut fatty acids, sorbitan monooleate, sorbitan monomiristate, sorbitan monoesters of coconut fatty acids, sorbitan isostearate, and similar compounds and mixtures thereof. U.S. Patent No. 5,786,395 (Stone et al.) Issued July 28, 1998 offers more examples of these emulsifiers and is incorporated herein by reference. Said emulsifiers are advantageously added to the oil phase in such a way that it comprises from about 1% to about 15% thereof. Obviously, emulsifiers that are particularly capable of stabilizing HIPE at elevated temperature are preferred. The diglycerol monooleate is illustrative in this respect. Coemulsifiers can also be used to provide additional control of cell size, cell size distribution, and emulsion stability. Co-emulsifiers include phosphatidyl cholines and compositions containing phosphatidyl choline, aliphatic, long-chain dialiphatic beta-C22 betaines, short-chain dialiphatic dialiphatic ammonium salts of d-C4, long chain dialcoyl (alkenoyl) -2-hydroxyethyl of C12-C22, short-chain dialiphatic quaternary ammonium salts of C? -C4, long chain dialiphatic imidazolinium quaternary ammonium salts of C12-C22, short chain dialiphatic benzyl quaternary ammonium salts of C? -C4, long chain monoaliphatics of C12-C22, dialkoyl (alkenoyl) -2-aminoethyl long-chain of C12-C22, short-chain monoaliphatics of CrC4, short-chain monohydroxyaliphatics d-C4. Particularly preferred is dimodimethyl ammonium methyl sulfate. Said coemulsifiers and additional examples are described in greater detail in U.S. Patent No. 5,650,222 (DesMarais et al.) Issued July 22, 1997, the disclosure of which is incorporated herein by reference. 4. Optional Ingredients Various optional ingredients can also be included in any of the water or oil phase for various reasons. Examples include antioxidants (e.g., hindered phenolic light stabilizers, hindered amine stabilizers, ultraviolet ray absorbers), plasticizers (e.g., dioctyl phthalate, dinonyl sebacate), flame retardants (e.g., halogenated hydrocarbons, phosphates, borates, inorganic salts such as antimony trioxide or ammonium phosphate or magnesium hydroxide), dyes and pigments, fluorescing agents, filler particles (eg, starch, carbon dioxide, carbon black, or calcium carbonate), fibers, chain transfer agents, odor absorbers, such as activated carbon particles, dissolved polymers and oligomers, and such other agents as are commonly added to polymers for a variety of reasons. Such additives can be added to confer color, fluorescent properties, radiation resistance, radiation opacity (eg, lead compounds), to disperse the charge, to reflect incident infrared light, to absorb radio waves, to form a wet surface on the foam struts of HIPE, or for any other purpose.

B. Processing conditions to obtain the HIPE foams The foam preparation typically involves the steps of: 1) forming a stable high internal phase emulsion (HIPE); 2) curing this stable emulsion under suitable conditions to form a cellular polymer structure; 3) optionally squeezing and washing the cellular polymeric structure to remove or remove the original residual water phase from the polymeric foam structure and, if necessary, treat the polymeric foam structure, with a hydrophilizing surfactant and / or a hydratable salt for depositing any hydrophilizing surfactant / hydratable salt ed, and 4) subsequently dehydrating this polymeric foam structure. 1. Formation of the HIPE The HIPE is formed by combining the components of the water and oil phase in a ratio between approximately 8: 1 and 140: 1. Preferably, the ratio is between about 10: 1 and about 75: 1, more typically between about 13: 1 and about 65: 1. As discussed above, the oil phase will typically contain the required monomers, comonomers, crosslinkers, and emulsifiers, as well as the optional components. The water phase will typically contain the electrolyte or electrolytes and initiators or initiators of the polymerization. The HIPE can be formed from the combined water and oil phases by subjecting these combined phases to shear agitation. The shear agitation is generally applied to the point and for a period of time necessary to form a stable emulsion. Said process may be conducted either batchwise or continuously and is generally carried out under suitable conditions to form an emulsion where the droplets of the water phase are dispersed to such an extent that the resulting polymeric foam will have the required structural characteristics. Emulsification of the combination of the oil and water phases will often involve the use of a mixing or stirring device such as a stirrer. A preferred method for forming the HIPE involves a continuous process that combines and emulsifies the required phases of water and oil. In said process, a liquid stream comprising the oil phase is formed. Concurrently, a separate liquid stream comprising the water phase is also formed. The two separate streams are provided to a suitable mixing chamber at a suitable emulsification pressure and combined there so that the specified pre-specified water-to-oil weight ratios are obtained. In the mixing chamber or area, the combined streams are generally subjected to shear agitation provided, for example, by a stirrer of suitable configuration and dimensions, or by any other means for imparting shear or turbulent mixing generally known to those skilled in the art. The shear stress will typically be applied to the combined oil / water phase stream at an appropriate rate and grade. Once formed, the stable liquid HIPE can then be removed or pumped from the chamber or mixing zone. This preferred method for forming HIPE by means of a continuous process is described in greater detail in U.S. Patent No. 5,149,720 (DesMarais et al.), Issued September 22, 1992, which is incorporated by reference. Also see commonly assigned U.S. Patent No. 5,827,909 (DesMarais) issued October 27, 1998 (incorporated herein by reference), which describes an improved continuous process having a recirculation cycle for the HIPE. The process also allows the formation of two or more different types of HIPE in the same container as disclosed in U.S. Patent No. 5,817,704 (Shiveley et al.) Issued October 6, 1998, incorporated herein by reference. In this example, two or more pairs of oil and water streams can be mixed separately and then mixed as required. Alternatively, the techniques of in-line mixing as described in the United States provisional patent application Serial No. 60 / 158,620, filed in the name of Catalfamo, and others on October 8, 1999 may be used. Degassing one or both of the oil and water phases is particularly important when the required shear stress is provided by an agitator such as the pin mixer described in the aforementioned US Patents Nos. 5,149,720 and 5,827,909. The separation of the dissolved gases due to the relatively lower pressure in the wake of the agitator can cause cavitation with the resulting loss of mixing efficiency in addition to being a source of defects in the foam if one or both of the streams are not degassed. 2. Polymerization / curing of the oil phase of the HIPE The present invention relates to the polymerization / curing of the oil phase of the emulsion at high cure temperatures in a batch process, or in a continuous process. One measure of the cure degree of the polymer is the foam resistance, as measured by the yield point stress described in the Methods section of Test below. Another measure of the degree of cure of the polymer is the degree to which it swells in a good solvent such as toluene (being crosslinked, the HIPE foam does not dissolve without being chemically altered). Without being bound by theory, it is believed that curing comprises two overlapping but distinct processes. The first involves the polymerization of the monomers. The second is the formation of the lattices between the active sites in the main chains of adjacent polymers. Crosslinking is essential for the formation of HIPE foams with strength and integrity essential for handling and further use. The step of controlling the speed of this crosslinking reaction is believed to be related to the diffusion rate of the active sites attached to the polymer chains. It has been surprisingly discovered that an increase in the production rate of free radicals in HIPE does not accelerate curing in a useful manner. However, increasing the diffusion rate of the active sites by increasing the temperature of the system in a conventional curing process is limited by the volatility of the components of the emulsion. In one embodiment, the present invention provides for the curing of the emulsion under high pressure in order to allow the high temperatures and fast cure times that are obtained without excessive volatilization of the emulsion components. In another embodiment, the present invention requires only degassing one or both of the phases that are used to form the HIPE prior to the formation of HIPE. It should be noted that the oil phase and the aqueous phase of the emulsion may contain dissolved gases. At elevated temperatures, the solubility of these gases in the liquid phase is reduced, and the gas can be released to form bubbles in the emulsion. These bubbles can disrupt the structure of the HIPE and cause undesirable defects in the finished structure of the foam. The formation of such defects can be reduced or eliminated by: 1) degassing the aqueous and / or oil phases of the emulsion before heating, 2) using sufficient pressure to reduce or eliminate the formation of bubbles at the cure temperature, or combinations of these approaches. Because the amount of the aqueous phase is typically much greater than the amount of the oil phase in the HIPE, most of the gas dissolved in the system can be removed by degassing only the aqueous phase. The degassing can be obtained by heating the liquid, or by applying a vacuum, with or without a nucleating agent (for example, boiling media, available from Aldrich Chemical Co., Milwaukee, Wl), or by another technique known to those skilled in the art. The technique. The liquid can be degassed in a batch process, or preferably in a continuous process immediately prior to the formation of the HIPE. Said degassing is useful at cure temperatures as low as 40 ° C. As is known, the solubility of the gas goes down as the temperature increases so that this aspect of the present invention becomes more useful as the temperature increases. of healing. Typically, the curing temperature will vary from about 40 ° C to about 250 ° C. The preferred cure temperatures are greater than about 65 ° C, the most preferred cure temperatures are greater than about 75 ° C. The even more preferred curing temperatures are greater than about 85 ° C. Particularly preferred are continuous or semi-continuous processes for degassing. For example, a stream of liquid to be degassed can be pumped through an evacuated chamber where the reduced pressure provides the driving force to reduce the amount of gas dissolved in the liquid. If desired, said chamber may be provided with a packing means to increase the surface area of the liquid as it is exposed to vacuum. Illustrative packaging means include glass drops, crenellated glass strips, formed glass or polymer pieces (eg bearings, Raschig rings, etc.), cooking stones and other solid materials that can serve to increase the surface area of the glass. fluid that is exposed to vacuum. Suitable packaging materials can be obtained from a wide variety of commercial sources, for example, from Aldrich Chemicals of Milwaukee, Wl. A continuous process for degassing the aqueous phase used to form the HIPE according to the present invention is described in Example 2. It has been found that the structural separation of the HIPE is reduced to a minimum if one or both of the phases used to form HIPE is degassed so that the level of a tracer gas (the level of a tracer gas, such as oxygen, is more easily measured and indicated as another gas, such as nitrogen, can be dissolved in the phase.) reduced to at least half of its value initiate after the step of degassing and before the formation of the HIPE. Preferably, the tracer gas level is reduced to 25% of its initial value by the degassing step.

More preferably, the tracer gas level is reduced to less than about 15% of its initial value (the amount of tracer gas in a phase that is measured when the phase is at room temperature (~ 25 ° C) and at a pressure of 1 atmosphere). Exposure to a vacuum of at least about 30 centimeters of mercury at a residence time where the level of a tracer gas is reduced to at least half of its initial value is adequate. Preferably, the vacuum is at least about 61 centimeters of mercury. In particular, the exposure of the liquid to be degassed to a vacuum of approximately 61 centimeters of mercury with a residence time of at least about 20 seconds has been found to reduce the dissolved gas to an adequate level within a reasonable time. Preferably, the residence time under a vacuum of at least about 61 centimeters of mercury is at least about 60 seconds. More preferably, the residence time is greater than about two minutes. A person skilled in the art will recognize that variables such as the amount of liquid to be degassed, the level of the vacuum, the liquid temperature, the surface area of the exposed liquid, and other similar variables They all interact to determine the amount of time under vacuum that is required to reduce the initial level of dissolved gas to an acceptable level. Such a determination is easily made by those who are knowledgeable in chemical engineering techniques. The illustrative non-limiting embodiments of the invention are described below. In the first mode, the HIPE is formed in a batch process, as described in example 1 below. The formed HIPE is transferred to a suitable reaction vessel 200, such as that shown in Figure 7, capable of withstanding pressures (typically from about 2 to about 40 atmospheres) necessary to allow curing at the desired temperature (typically about 90). ° up to approximately 250 ° C). As will be recognized, such pressure is necessary to avoid the volatilization or evaporation of one or more of the components of the HIPE. The temperature at which the HIPE is provided to the container can be significantly lower than the polymerization / curing temperature. Figure 7 is an illustrative reaction vessel 200 which is suitable for the batch curing of the HIPE according to the present invention. The recipient 200 comprises a container body 210 having sufficient volume to cure the desired amount of HIPE. The container body can have any desired shape including cylindrical, cubic, rectangular solid, or other irregular shape as may be desired. The container must be constructed so that the polymerized / cured solid foam material can be easily removed for further processing after the polymerization / curing has been carried out to the desired degree. For certain purposes where the cured HIPE is further processed in a web of material by cutting it as described in U.S. Patent Application Serial No. 08/939, 172 (Sabatelli et al.) Filed on September 29, 1997, a cylindrical shape has been found to be useful. The closure of the container 220 has a shape that is complementary to the shape of the container body 210 to provide a closure thereto. The seal 230 is interposed between the closure 220 and the body 210 to provide resistance to leakage of the materials enclosed within the reaction vessel 200 during the curing process. The container 200 should be constructed of materials that are capable of withstanding the pressures necessary to cure the HIPE at the desired temperature as discussed above. The closure means (not shown) capable of resisting said pressure are also necessary in order to keep the container 200 in a sealed condition during the curing process. The container 200 may further be lined with a material compatible with the HIPE such that it does not cause the HIPE to degrade on the interior surfaces of the container that are in contact with the HIPE. Illustrative surfaces in this regard include: stainless steel, titanium, glass, polyethylene, polypropylene, and polytetrafluoroethylene. One skilled in the art will recognize that the choice of materials will depend on the environmental factors that the material will experience. For example, curing temperatures greater than the softening point of a polymer surface will render the polymeric liner inadequate. For curing conditions that will require the surface to be exposed to the high concentration of the chlorine ion (of the aqueous phase of the HIPE) and the combination of high pressure and temperature that provide the accelerated cure described herein, a titanium surface is suitable. The container 200 is filled with the HIPE to minimize the top space volume before it is sealed. By minimizing the volume of the upper space, the degree to which the volatilization of the emulsion components can occur is limited. The container 200 can be pressurized simply by heating the container and its contents, for example in an oven. In such a case, the pressure inside the container is determined by the partial vapor pressures of the components of the emulsion. Alternatively, pressure can be introduced through an appropriate valve from an external source of pressure such as a pump which can provide an incompatible fluid to raise the pressure or use a cylinder with pressurized gas. The suitable curing conditions will vary depending on the composition of the oil and aqueous phases of the emulsion (especially the emulsifying systems used), the type and the amounts of the polymerization initiators used. As noted above, the cure temperature will typically vary from about 40 ° C to about 250 ° C. Frequently, however, it will be desirable to maintain the HIPE at elevated temperatures above about 90 ° C, more preferably above about 100 ° C, most preferably between about 125 ° C and 165 ° C (from 2.5 to 7 atmospheres) , for a period of time ranging from about 20 seconds to about 1 hour, more preferably from about 40 seconds to about 20 minutes, most preferably from about 1 minute to about 10 minutes. Figures 1 to 6 are photomicrographs comparing illustrative foams produced according to the prior art and according to the present invention as described in example 1 in various amplifications. Specifically, the foam of Figures 1, 3 and 5 was produced according to condition 2 of Example 1 and the foam of Figures 2, 4 and 6 was produced according to condition 7 of Example 1. As can be seen comparing the process conditions given in table 1, the only substantial difference in curing is the curing temperature, with the resulting reduction in curing time. As is clearly evident from the properties data in Table 1 below and comparing the various pairs of figures, the rapid curing process of the present invention provides foams having essentially the same properties as the foams produced in accordance with the prior art using curing processes that required substantially longer cure times. In the alternative embodiments of batch processes, a plurality of reaction vessels 200 may be attached, for example, to a continuous web that moves the containers from a HIPE filling station through the heating zone to a section that it expels the cured HIPE foam into a processing line and carries the containers back to the filling zone (after any washing process that may be needed to re-establish the containers to the usable condition).

In a second embodiment, the HIPE is formed in a continuous process, as schematically shown in Figure 8 and described in example 2 below. Figure 8 describes a method and apparatus 300 suitable for continuously forming the HIPE foams according to the present invention. A HIPE is made using the methods generally described in the patents of the United States of America.

United Nos. 5,149,720 and 5,827,909 mentioned above. That is, the oil phase (the desired monomer mixture and emulsifier) is prepared and stored in a supply container of oil phase 305. Similarly, the desired aqueous phase (mixture of water, electrolyte and initiator) is prepared and stored in a supply container of the aqueous phase 310. The oil phase and the aqueous phase are supplied in the desired proportions towards the mixing head 330 by means of a pump supplying the oil phase 315 and a supply pump of the aqueous phase 325. The mixing head 330 supplies the mechanical energy (shear) necessary to form the HIPE. If desired, a HIPE 335 recirculation pump can be used. The formed HIPE is pumped into an elongate curing chamber 340 with specific cross-sectional shape and dimensions as desired for the foam product. The oil phase supply pump 315 and the water phase supply pump can be used to pump the HIPE from the mixing head 330 to the curing chamber 340. In this case, the emulsification will occur at substantially the pressure of curing. One skilled in the art will recognize that the emulsification pressure must be a little greater than the curing pressure to allow the flow to occur. Alternatively, an optional lift pump 345 can be used to pump the HIPE from the mixing head 330 to the curing chamber 340. In this case, the emulsification will occur at a pressure and / or temperature lower than the curing step.

In an alternative embodiment of the present invention (not shown), multiple systems, similar to those described above, can be used to make multiple HIPEs having different combinations of properties (eg, pore dimensions, mechanical properties, etc.). Multiple can be introduced into the curing chamber 340 to provide a cured foam having regions of variable properties as may be desired for a particular end use. The chamber 340 may also be lined with a material compatible with the HIPE in such a way that it does not cause the degradation of the structure of the HIPE on the interior surfaces that are with the HIPE, and is not degraded by the components of the phase of oil or water at the attempted elevated temperatures. Optionally, a slip layer can be provided between the cured HIPE and the walls of the chamber to minimize non-uniform flow patterns as the HIPE progresses through the chamber 340. As with the liner discussed above, the slip layer it must be compatible with the components of the oil and water phase of the HIPE and have sufficient mechanical stability at the curing temperature to be effective. Said slip layer has particular utility when used with curing chamber designs that incorporate the "hydrostatic head" as discussed below. At least a portion of the chamber 340 is heated in order to drive the HIPE to the curing temperature attempted as it passes through this section or zone. Any manner of heating this zone or section can be employed in order to achieve and maintain the desired temperature in a controlled manner. Examples include heating by electrical resistance elements, steam, hot oil or other fluids, hot air or other gases, or any other heating method known to those skilled in the art. Optionally, a static mixer / heat exchanger and another heat exchanger can be used by forced convection in the heated section to improve heat transfer to the HIPE. Once the HIPE begins to gel, the composition can no longer be mixed because of the risk of damaging or even destroying the structure of the foam. The chamber 340 should be designed so that the pressure required to pump the emulsion and / or cured foam through the chamber under stable condition conditions is sufficient to prevent volatilization of the emulsion components at the cure temperature. The chamber 340 may be in a horizontal, inclined or vertical position. The inclined and vertical orientations can be used to provide the additional "hydrostatic" back pressure to help avoid the volatilization of the HIPE components, thus allowing a shorter curing chamber to be employed. The length of the optional heated section, the temperature of the optional heated section and the speed at which the emulsion is pumped through the tube are selected to allow sufficient residence time within the chamber 340 for adequate thermal transfer to the center of the 340 camera in order to achieve the complete cure. If optional heating is done within the chambers 340, then the chambers 340 are preferred with relatively thin cross-sectional dimensions in order to facilitate rapid heat transfer. The HIPE is substantially cured in a HIPE foam at the time it leaves the curing chamber 340. Optionally, a raised extension 350 may be located above and downstream of the curing chamber 340 to provide a hydrostatic head. The curing chamber 340 may have any desired cross section that is consistent with the flow requirements of the cured HIPE pump. For example, the cross section may be rectangular, circular, triangular, annular, oval, hourglass, dog bone, asymmetrical, etc., as may be desired for a particular use of the cured HIPE. Preferably, the cross-sectional dimensions of the chamber 340 are such that the polymerized HIPE foam is produced in the sheet-like shape with the desired cross-sectional dimensions. Alternatively, the cross-sectional shape may be designed to facilitate the manufacture of the desired product in subsequent processes. For example, a cross-section in the form of an hourglass (or co-joined hourglass sections) of the appropriate size can facilitate the manufacture of disposable absorbent products such as diapers by cutting relatively thin slices or sheets of the formed HIPE foam. Other sizes and shapes can be prepared to make feminine hygiene pads, surgical towels, facial masks, and the like. Regardless of the cross-sectional dimensions of the curing chamber 340, the resulting HIPE foam can be cut or sliced into a sheet-like shape of suitable thickness for the intended application. The cross section of the healing chamber 340 may be varied along the length of the chamber in order to increase or decrease the pressure required to pump the HIPE through the chamber. For example, the cross-sectional area of a vertical healing chamber can be increased above the point at which the HIPE foam is cured, in order to reduce the flow resistance caused by friction between the walls of the chamber and the foam. healed Alternatively, the cross-sectional area of a healing chamber 340 can be decreased past the point at which the HIPE foam is cured, in order to increase the pressure required to pump the HIPE through the chamber thus allowing a chamber of shortest healing to be used. An initiator solution can optionally be injected into the HIPE at a point between the mixing head 330 and the curing chamber 340 (not shown). If the injection of the optional initiator is chosen, the aqueous phase, as provided from the aqueous phase supply container, is substantially free of initiator. Additional mixing means, such as a continuous mixer (not shown) may also be desirably downstream of the injection point and upstream of the curing chamber 340 to ensure that the initiator solution is distributed throughout the HIPE. Said arrangement has the advantage of substantially reducing the risk of undesirable curing in the mixing head 330 in the event of an unanticipated stoppage of the equipment. An open cell HIPE foam, filled with water, porous, is the product obtained after curing in the reaction chamber. As noted above, the cross-sectional dimensions of the chamber 340 are preferably such that the polymerized HIPE foam is produced in the shape resembling a sheet or sheet with the desired cross-sectional dimensions. Alternative cross-sectional dimensions may be employed, but without considering the shape of the curing chamber 340, the resulting HIPE foam may be cut or sliced into a shape similar to a sheet or sheet of the desired thickness suitable for the intended application. The sheets of the HIPE cured foam are easier to process during the subsequent treatment / washing and dehydration stages, as well as to prepare the HIPE foam for use in the intended applications. Alternatively, the product of the HIPE foam can be cut, milled or otherwise crushed into desired particles, cubes, rods, spheres, plates, filaments, fibers, or other shapes. The remaining aqueous phase with the HIPE is typically removed by compressing the foam and / or exposing the foam to a vacuum source. The residual moisture can be removed as desired by conventional evaporative drying techniques.

As noted above, in the continuous curing process, the emulsification step can be carried out at a relatively low pressure and the preformed emulsion pumped into the curing chamber under relatively high pressure using the lift pump 345. An alternative process links the pump the oil phase and the aqueous phase into the mixing chamber under relatively high pressure using the oil phase supply pump 315 and the supply pump of the aqueous phase 325. In this case, the emulsification step occurs under pressure relatively high, and the emulsion leaves the mixing chamber directly into the curing chamber under the required pressure. This eliminates the need to actively pump the preformed emulsion into the healing chamber. The HIPE may comprise at least one monomer with a boiling point less than about 60 ° C. Exemplary monomers include chloroprene, isoprene, and butadiene. These volatile monomers are not easily handled with the HIPE curing processes disclosed to date. When these are employed in the present invention, the process pressure must be sufficient to prevent undue volatilization of these monomers even with the heating necessary to effect rapid cure. The foams that use these monomers in an appropriate manner can be biodegradable as disclosed in the aforementioned U.S. Patent No. 5,767,168, in which the HIPE foams made with isoprene are prepared at a pressure of about 2 atmospheres and a temperature from 50 ° C for 48 hours or more. The process according to the present invention allows the curing time to be shortened significantly by applying higher temperatures and pressures. The chloroprene-based foams may be flame retardants, as disclosed in the aforementioned copending United States patent application No. 09 / 118,613. As taught in each of these references, the inclusion of antioxidants may be especially preferred for HIPE foams made with 1,3-dienes. lll. Test Methods Test methodologies for measuring Tg, yield point stress, expansion factors, and stability in the compressed state are disclosed in U.S. Patent No. 5,753,359. Methodologies for measuring resistance to compression deflection (RTCD), and free absorbent capacity (FAC) are disclosed in U.S. Patent No. 5,849,805. 1. Swelling ratio: The swelling ratio can be used as a relative measurement of the degree of crosslinking of the polymer comprising the HIPE foam. The degree of crosslinking is the critical part of curing as defined herein above. The swelling ratio is determined by cutting a cylindrical sample of foam 2 to 6 mm thick, 2.5 cm in diameter. The foam sample is vigorously washed with water and 2-propanol to remove any residual salts and / or emulsifiers. This will be achieved by placing the sample on a piece of filter paper in a Büchner funnel attached to a filter flask. A vacuum is applied to the filter flask by means of a laboratory aspirator and the sample is vigorously washed with distilled water and then with 2-propanol so that water and 2-propanol are entrained through the porous foam by vacuum . The washed foam sample is then dried in an oven at 65 ° C for three hours, the oven removed, and allowed to cool to room temperature before measuring the swelling ratio. The sample is weighed within ± 1 mg, to obtain the dry weight of the sample, Wd. The sample is then placed in a vacuum flask containing enough methanol to completely immerse the foam sample. The remnants of the air bubbles in the foam structure are removed by gently reducing the pressure inside the flask by means of a laboratory aspirator. Soft vacuum is applied and released several times until no more bubbles are seen coming out of the foam sample when the vacuum is applied, and the foam sample settles when the vacuum is released. The fully saturated foam sample is gently removed from the flask and weighed within ± 1 mg, taking care not to squeeze the methanol from the sample during the weighing process. After the weight of the sample saturated with methanol is recorded, (Wm), the sample is dried again by gently squeezing most of the methanol followed by drying in the oven at 65 ° C for 1 hour. The dry sample is then placed in a vacuum flask containing enough toluene to completely immerse the foam sample. The residual air trapped within the pores of the foam is removed by gentle application and vacuum release, as described above. The weight saturated with toluene in the sample, Wt, is also obtained as described above. The swelling ratio can be calculated from the needs of methanol and toluene, and the weights recorded in the above procedure as follows: Swelling ratio = [(Wt - Wd) / (Wm-Wd)] x 0.912 where 0.912 is the ratio of methanol and toluene densities. 2. Effort to the transfer point: The effort to the transfer point is the most practical measurement of the degree of cure and related to the compressive strength of the HIPE foam. The effort to the yield point is the effort at which a marked change in the inclination of the stress-strain curve occurs. This is practically determined by the intersection of the extrapolated regions of the stress-strain curve above and below the elastic point, as described in more detail below. The general test method for measuring the transfer point effort is disclosed in U.S. Patent No. 5,753,359. Specifically, for the purposes of this application, the following method is used: Apparatus: Rheometrics RSA-2 DMA, as available from Rheometrics Inc., of Piscataw, NJ. Arrangements: Tension rate of 0.1% per second for 600 seconds (up to 60% tension) using parallel plates of 2.5 cm in diameter in compression mode; Temperature of the oven at 31 ° C maintained for 10 minutes before starting the test, and throughout the test. Sample: HIPE foam samples cut into cylinders from 2 to 6 mm thick and 2.5 cm in diameter. The resulting stress-strain curve can be analyzed by adjusting the line of the initial elastic and linear portions of the graph using a linear regression method. The intersection of the two lines thus obtained gives the effort to the transfer point (and tension to the transfer point). 3. Density: The density of the foam can be measured in dry, expanded foams, using any reasonable method. The method used herein is disclosed in the aforementioned U.S. Patent No. 5,387,2087. 4. Determination of the curing speed: The HIPE are prepared at specific temperatures and placed in suitable containers for specific times at the cure temperatures. The HIPE foams produced in this way are submerged in an ice bath to cool the healing process. The cooled foams are removed and processed for analysis, usually comprising removing the water by using pressure, washing in water and / or organic solvent, and drying followed by slicing and / or cutting to the desired dimensions.

IV. Specific examples These non-limiting examples illustrate the specific preparation of the HIPE foams according to the present invention.

Example 1: Preparation of the foam from a HIPE A) Preparation of the HIPE Anhydrous calcium chloride (22.73 kg) and a potassium persulfate are dissolved (35.5 g) in 454 liters of water. This provides the current of the water phase to be used in a continuous process for the formation of a HIPE emulsion. This is degassed continuously as in Example 2 before feeding the rest of the process. To a monomeric combination comprising distilled divinylbenzene (42.4% divinylbenzene and 57.6% ethyl styrene) (2640 g), 2-ethylhexyl acrylate (4400), and hexanedioldiacrylate (960 g) was added an emulsifier of diglecerol monooleate (480 g), dimethyl ammonium methyl diphosphate sulfate (80 g), and tinuvin 765 (20 g). The diglycerol monooleate emulsifier (Grindsted Products, Brabrand, Denmark) comprises approximately 81% of diglycerol monooleate, 1% of other diglycerol monoesters, 3% polyols, and 15% of other polyglycerol esters, imparts a minimum value of interfacial oil / water tension of approximately 2.7 dyne / cm and has a critical oil / water aggregation concentration of approximately 2.8% by weight. After mixing, this combination of materials is allowed to settle during the night. No visible residues are formed and all of the mixture is removed and used as the oil phase in a process continuous for the formation of a HIPE emulsion. Separate currents are fed from the oil phase (25 ° C) and the degassed water phase (85 ° -87 ° C) to a dynamic mixing apparatus. By mixing the combined streams in the dynamic mixing apparatus it is achieved by means of a pin driver or stirrer. The pin agitator comprises a cylindrical arrow of approximately 36.5 cm in length with a diameter of approximately 2.9 cm. The arrow retains 6 rows of pins, 3 rows having 58 pins and 3 rows having 57 pins, each of the three pins in each level arranged at an angle of 120 ° from each other, with the next level down arranged at 60 ° from its neighbor level with each level separated by 0.03 mm, each having a diameter of 0.3 cm extending downward from the central axis of the arrow to a length of 2.3 cm. The pin agitator is mounted on a cylindrical sleeve which forms the dynamic mixing apparatus and the pins have a space of 1.5 mm from the walls of the cylindrical sleeve. A smaller portion of the effluent leaving the dynamic mixing apparatus is removed and enters a recirculation zone, as in Example 1 of U.S. Patent No. 5,827,909. The Waukesha pump in the recirculation zone returns to the lower portion at the point of entry of the flow currents of the oil and water phase in the dynamic mixing zone. A static spiral mixer is mounted downstream of the dynamic mixing apparatus to provide counter pressure in the dynamic mixing apparatus and to provide improved incorporation of the components in the HIPE that is eventually formed. The static mixer (TAH Industries model 100-812) is a static tube mixer with 12 elements with a diameter of 2.5 cm. A hose is mounted downstream from the static mixer to facilitate delivery of the emulsion to the device for curing. Optionally, an additional static mixer is used to provide counter pressure to keep the hose full. The optional static mixer can be a 2.5 cm, 12-element pipe mixer (McMaster-Carr model 3529K53). The installation of the combined mixing and recirculation apparatus is filled with the oil phase and the water phase at a ratio of 4 parts of water to 1 part of oil. The dynamic mixing apparatus is ventilated to allow air to escape while filling the apparatus completely. The flow rates during filling are 7.5 g / sec of the oil phase and 30.3 cm3 / sec of the water phase. Once the installation of the apparatus is filled, stirring is started in the dynamic mixer, with the impeller spinning at 1750 RPM and the recirculation started at a speed of approximately 30 cm3 / sec. The flow rate of the water phase is then increased steadily at a rate of 151.3 cnWsec for a period of time of about 1 minute, and the flow rate of the oil phase is reduced to 3.36 g / sec for a period of time. Time period of approximately 3 minutes. The recirculation rate is constantly increased to approximately 150 cm3 / sec during the last period of time. The counter pressure created by the dynamic zone and the static mixers at this point is approximately 19.9 PSI (137 kPa), which represents the total pressure drop of the system. The speed of the Waukesha pump (Model 30) is steadily decreased until it produces a recirculation velocity of approximately 75 cm3 / sec. B) Polymerization of the HIPE The HIPE that flows from the static mixer at this point is collected in a round tub of preheated polyethylene (at approximately 80 ° C), with a diameter of 102 cm and height of 31.8 cm, with removable sides, very similar to a saucepan used to bake cakes. A polyethylene insert similar to a 31.8 cm diameter pipe at its base is firmly fixed to the center of the base and is 31.8 cm high. The tubs containing the HIPE are kept in a room kept at 80 ° C for 2 hours to effect the polymerization and form the foam. C) Foam washing and dehydration Cured HIPE foam is removed from the curing vats. The foam at this point has a residual water phase (containing dissolved emulsifiers, electrolyte, residues of the initiator, and initiator) of approximately 43 to 47 times (43-47X) the weight of the polymerized monomers. The foam is sliced with a sharp closing blade of reciprocal movement in sheets that are 4.7 mm thick. These sheets are then subjected to compression in a series of 2 porous pressure rollers equipped with vacuum that gradually reduces the content of the residual water phase of the foam to approximately 6 times (6X) the weight of the polymerized material. At this point, the sheets are then re-saturated with a 2% solution of CaCl2 at 60 ° C, they are squeezed in a series of 3 porous pressure rollers equipped with vacuum to a water phase content of about 4X. The CaCl2 content of the foam is between 8 and 10%. The foam remains compressed after the final pressure to a thickness of approximately 0.071 cm. The foam is then air dried for approximately 16 hours. Said drying reduces the moisture content to about 9 to 17% by weight of the polymerized material. At this point, the sheets of the foam have a high draping capacity. Example 2: Degassing the components of the HIPE This example is intended to show the continuous degassing of the water phase of a HIPE.

Column apparatus: a closed tube, catalog 80 CPVC, which has a diameter of 20 cm which is 4 meters long and provided with an inlet for the water phase and a vacuum hole in the upper part, an outlet for the phase of degassed water in the bottom, and a packing support plate (Norton polypropylene model 818 with a standard punch pattern) of approximately 76 cm from the bottom is suitable. Packaging: The column is partially filled (0.05 m3) with Norton # 1 SUPER INTALOX polypropylene bearings. Piping: Piping should be used as necessary from the supply of the water phase to the storage of the degassed water phase. Rotameters: The Brooks model R-10M-75-3, 0-0.3 liters / second is suitable. Vacuum source: A Thomas multi-stage vacuum pump, model H50A-60 is suitably operated to provide a vacuum of at least about 61 centimeters of mercury. Operation The column suction is used to supply the water phase from a supply and is capable of supplying a flow rate of between approximately 1.8 to 13.6 kilograms per minute adjusted as desired using the rotameter and a manual valve. The water phase enters the upper part of the packing bed where it flows on the package is degassed. The degassed water is collected in a 25 liter tank inside the column. In continuous operation at 44 kg / minute approximately 6 liters are contained in the vacuum chamber at a given time. Degassed water is removed as needed from the tank to be used or to an intermediate storage container. Disclosures of all patents, patent applications (and any patents issued thereon, as well as any corresponding published foreign patent applications) and publications mentioned throughout this description are hereby incorporated by reference herein. . However, it is not expressly admitted that any of the documents incorporated by reference herein teach or disclose the present invention. Although the particular embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art that other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, attempts are made to protect all these changes and modifications within the scope of this invention in the appended claims.

Claims (8)

1. A process for the preparation of a polymeric foam material having a substantial reduction in defects therein, the process comprising the steps of: A) forming a water-in-oil emulsion from: 1) an oil phase that comprises: a) from about 85 to about 99% by weight of a monomer component capable of forming a copolymer having a Tg value below about 90 ° C or less, the monomeric component comprising: i) from about 5 to about 80% by weight of a monofunctional monomer substantially insoluble in water capable of forming a polymer having a Tg of about 35 ° C or less; ii) from about 0 to about 70% by weight of a monofunctional comonomer substantially insoluble in water capable of imparting other desired properties to the foam; iii) from about 5 to about 80% by weight of at least one polyfunctional crosslinking agent, substantially insoluble in water; and b) from about 1 to about 20% by weight of an emulsifier component that is soluble in the oil phase and which is suitable to form a stable water-in-oil emulsion; and 2) a water phase comprising an aqueous solution containing: (a) from about 0.2 to about 40% by weight of a water-soluble electrolyte; and (b) an effective amount of a polymerization initiator; wherein the emulsion has a volume to weight ratio of the water phase to the oil phase in the range of about 8: 1 to about 140: 1; B) characterized in that means are provided for reducing the level of dissolved gases in at least one of said oil phase and said water phase from an initial level of a dissolved tracer gas to a level that is less than half of said initial level of said tracer gas; and C) curing the monomer component in the oil phase of the water-in-oil emulsion using a polymerization reaction that is conducted at a cure temperature, the cure temperature being between about 40 ° C and about 250 ° C to form a polymeric foam material.

2. A method according to claim 1, wherein said means for reducing the level of the dissolved gases comprises exposing at least one of said oil phase and said water phase to a vacuum of at least about 61. cm of mercury at a residence time, preferably at least 20 seconds, sufficient to reduce the level of dissolved gases in at least one of said oil phase and said water phase from an initial level of a dissolved tracer gas to a level that is less than half the initial level of tracer gas.

3. A method according to claim 1 or 2, wherein said means for reducing the level of the dissolved gases comprises heating at least one of said oil phase and said water phase.

4. A method according to any of the preceding claims, wherein said means for reducing the level of dissolved gases is a batch process.

5. A method according to claims 1, 2 or 3, wherein the means for reducing the level of dissolved gases is a continuous process.

6. A method according to claim 5, wherein said means for reducing the level of dissolved gases comprises exposing at least one of said oil phase and said water phase to a vacuum in a selected packing medium. from the group consisting of glass beads, crenellated glass strips, formed glass or polymer pieces, frames, Raschig rings, cooking stones or other solid materials that can serve to increase the surface area of the fluid that is exposed to said emptiness.

7. A method according to any of the preceding claims, wherein the level of dissolved gases in at least one said oil phase and said water phase is reduced from an initial level of a dissolved tracer gas to a level that is less than 25% of said initial level of tracer gas . A method according to claim 7, wherein the level of gases dissolved in at least one said oil phase and said water phase is reduced from an initial level of a dissolved tracer gas to a level that is lower of 15% of said initial level of tracer gas.