MXPA97004407A - Acrylic emulsions prepared in the presence of alcohol of poly (vinyl) completely hydrolized - Google Patents

Abstract

The present invention relates to a process for the polymerization of an emulsion of a monomer mixture consisting essentially of ethylenically unsaturated, insoluble monomers in water having an acrylic unsaturation to produce the polyacrylic polymer particles wherein a monomeric polymerizable system consisting of essentially of at least one acrylic monomer, is polymerized in the presence of water and of a stabilizer to produce a polyacrylic polymer, the improvement to produce an acrylic emulsion having a solids content greater than 45% by weight without microfluidization comprising: a ) carrying out the polymerization in a polymerization zone employing a stabilizer consisting essentially of a poly (vinyl alcohol) selected from the group consisting of a poly (vinyl) alcohol having a hydrolysis value greater than 96.5% and an alcohol of poly (vinyl) having a hydrolysis value of at least 86% where the molecular pso is within an approximate range of 5,000 to 13,000 and in the substantial absence of surfactants and solvents, said poly (vinyl) alcohol is present in an amount of 2 to 15% by weight of the monomers going to be polymerized, and b) carry out the polymerization in the presence of a cation transfer agent.

Description

ACRYLIC EMULSIONS PREPARED IN THE PRESENCE OF COMPLETELY HYDROLYZED POLY (VINYL) POLYMER DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of stable polyacrylate emulsions in the presence of a poly (vinyl alcohol) and the resulting emulsion . Polyvinyl alcohol is a stabilizer widely used for the polymerization of emulsions of many vinyl ester monomers. The use of a polyvinyl alcohol as a stabilizer allows control of particle size, rheology and interlacing characteristics, which are valuable for applications such as adhesives, sealants, coatings and binders. One limitation has been the inability to prepare stable acrylic emulsions at relatively low levels of polyvinyl alcohol stabilizer, for example, less than 12% by weight of the acrylic monomer to be polymerized. Another limitation of polyvinyl alcohol has been the inability of the industry to expand the use of this as a stabilizer for acrylic emulsions having a high solids content, eg, greater than 45% by weight. Many attempts have been made to overcome this limitation, and in doing so, everything has generally depended on the process or changes in composition. The following comments of the patents and references relato the use of the poly (vinyl) alcohol as a stabilizing system for the polymerization of the emulsion of a monomer mixture consisting of monomers having an acrylic unsaturation. Patent GB 1348449 and in Farmer, D.B. in "Polyvinyl alcohol-Developments", C.A. Finch De. John Wiley & Sons, New York, NY, (p 459.1992) discloses the preparation of acrylic emulsions employing nonionic or anionic surface active agents. It is assumed that the same polyvinyl alcohol is inadequate to produce a stable emulsion. The U.S. Patent 5,326,809 discloses the use of a co-vinyl amine of poly (vinyl alcohol) as a stabilizer for the emulsion polymerization of a wide range of ethylenically unsaturamonomers. A co-vinyl amine stabilizer of poly (vinyl alcohol) containing from 50 to 99% moles of the poly (vinyl) alcohol and from 0.1 to 50% of the poly (vinyl) amine. All examples where the acrylic monomers were exclusively used showed the addition of the surfactant to improve the stability of the emulsion. Some improvement in stability is achieved by the functionality of the amine. Also, the acrylic monomer was methyl acrylate which by itself is easier to stabilize with PVOH due to its greater water solubility. The U.S. Patent 5,354,803 discloses the preparation of formaldehyde-free poly (vinyl alcohol) graft copolymer without surfactant comprising from 12 to 35 of a fully hydrolyzed low molecular weight poly (vinyl) alcohol. In this work, a high concentration (12 to 35% by weight) of the poly (vinyl) alcohol was used to promote the chemical grafting of the acrylic monomer with the poly (vinyl) alcohol. In addition, the solids contents of the prepared emulsions were consistently less than 40% by weight. The U.S. Patent 5,364,904 discloses the preparation of a polymeric emulsion for use as a sizing agent for glass fibers. The emulsion is formed by a microfluidization technique of an emulsion containing an alkyl acrylic (acrylic) acrylate monomer and stabilized with a polyvinyl alcohol. The polyvinyl alcohol preferably has a degree of hydrolysis of at least 70% although the hydrolysis of the polyvinyl alcohol is not indica Examples show the addition of the surfactant which undouby promotes the stability of the emulsion. GB Patent 1,438,449 discloses the use of a polyvinyl alcohol containing acid or mercaptan groups as a means to stabilize all acrylic emulsion compositions. further, this reference also indicates the lack of utility to employ a conventional polyvinyl alcohol as the stabilizer for all acrylic emulsion compositions. The patent of the U.S.A. discloses the use of low molecular weight amino alcohol as part of a stabilization system for the polymerization of the emulsion of the met (acrylic) monomers in the presence of protective colloids and surfactants. Preparing acrylic systems without vinyl acetate present in an amount at least 50% results in unstable systems when prepared in the presence of poly (vinyl) alcohol. The U.S. Patent 2,318,429 discloses a process for producing an aqueous dispersion of polymerized alkyl methacrylates, ie, methyl methacrylates and isobutyl acrylate, which employs a partially saponified polyvinyl acetate as a dispersing agent. The beneficiary of the patent disclosed that aqueous dispersions of polyacrylates have been obtained with anionic surface active agents but these emulsions have limited their usefulness for textile finishes because they are rapidly coagulated by cationic surface active agents, by means of polyvalent metal ions. and by positively charged emulsions and dispersions.

The patent beneficiary reported that colloidal systems can be prepared by the polymerization of alkyl acrylates in the presence of a partially saponified polyvinyl acetate having a saponification number of 40-130 and an approximate viscosity of 20 centipoise (one solution 4% aqueous at 20 ° C. Table 1 discloses the preparation of polymethyl methacrylate and the presence of a partially hydrolyzed and partially saponified polyvinyl acetate.The patent beneficiary disclosed that the emulsions prepared with polyvinyl acetate completely Saponified were unstable US Patent 2,407,107 discloses a process for producing stable dispersions of alkyl acrylate polymers by an emulsion polymerization process wherein the alkyl acrylate monomers are emulsified in an aqueous solution and polymerized. A partially hydrolyzed saponified polyvinyl acetate Water-soluble is used as the emulsifying agent and is accompanied with a small amount of a petroleum hydrocarbon such as mineral oil or wax. The hydrocarbon is used in an amount between about 0.5 to 5% based on the weight of an alkyl acrylate monomer and was used to improve the stability of the emulsion, which typically contains 10 to 40% by weight of an acrylate. of polymerized alkyl. The U.S. Patent 2,773,050 discloses a process for polymerizing an acrylic ester while mixing with a polymer containing hydroxyl radicals, for example a polyvinyl alcohol which can be cured by a treatment with an entanglement agent. The polymerization is advantageously carried out by preparing a dispersion of an acrylic ester in an aqueous solution of a vinyl polymer having hydroxyl radicals, for example a polyvinyl alcohol and optionally, an emulsifying agent, for example, alkali metal salts of a sulfated fatty alcohol. The ratio by weight of the acrylic resin in relation to the poly (vinyl) alcohol and the range of the emulsion approximated from 80:20 to 50:50, although the preferable one is from 80:20 to 65:35. This invention relates to improved acrylic emulsion compositions and to an improved process for preparing an acrylic emulsion. The improvement for the polymerization of the water-insoluble acrylic monomer systems resides in carrying out the polymerization of the acrylic monomers in the presence of a stabilizing system consisting essentially of a polyvinyl alcohol having specified levels of hydrolysis and in the presence of a chain transfer agent. This medium allows the preparation of emulsions with useful and suitable properties for use in applications such as adhesives, coatings, binders and cement additives. It has been found that it is possible to substantially polymerize the entire acrylic monomer system, insoluble to water, wherein at least a majority of the acrylic monomer has a higher carbon content than the methyl acrylate and stabilizes the entire acrylic emulsion system with high solids content greater than 45% by weight at concentrations less than 12% of the poly (vinyl alcohol selected from the group consisting substantially of a fully hydrolyzed poly (vinyl) alcohol and a poly (vinyl) alcohol having a value of hydrolysis of at least 86% and an approximate molecular weight of 5,000 to 13,000.The lower hydrolysis levels of about 96.5% can be used in poly (vinyl) alcohols with a low molecular weight, considering that the poly (vinyl) alcohols with A higher molecular weight leads to instability.There are several advantages associated with the invention and these include: • an ability to produce essentially acrylic emulsions with high solids content using a protective colloid of poly (vinyl alcohol) as the stabilizer; • an ability to produce acrylic emulsions having relatively low levels of the poly (vinyl) alcohol, for example from 2 to 125 and generally within a range between 3 to 5% by weight of the monomers; • a capacity to produce stable acrylic emulsions without the use of conventional surfactants or hydrocarbon solubilization or microfluidization techniques; • an ability to produce acrylic emulsions that have excellent adhesion to a variety of substrates, such as wood and that have excellent moisture resistance and water resistance; • a capacity to form excellent films and coatings; • an ability to produce redispersible acrylic polymers with poly (vinyl) alcohol; and • a capacity to produce acrylic emulsions having low viscosities. In the practice of this invention, all substantially acrylic emulsions can be produced by an emulsion polymerization process employing a stabilizer system consisting of a polyvinyl alcohol as the stabilizer. Acrylic monomers, particularly those acrylic monomers have a water insolubility lower than those of methyl acrylate, it has been essentially impossible to polymerize an emulsion system employing polyvinyl alcohol as the stabilizer. A wide range of acrylic monomers can be used in the polymerization process described herein and can be used alone or in combination with other acrylic monomers. These polymerizable ethylenically unsaturated C? -C8 alkyl esters of acrylic and methacrylic acid include methylacrylate, ethylacrylate, butylacrylate, 2-ethylhexyl acrylate and the corresponding methacrylates. Preferred lower alkyl acrylates are these methyl methacrylates and butyl acrylates used in the polymerization process to produce a variety of polymer systems suitable for adhesives, coatings, binders and cementitious applications. Other ethylenically unsaturated monomers can be copolymerized with the acrylic esters. The composition of the resulting copolymer depends greatly on the application. Typical monomers include vinyl acetate, acrylamide, methacrylamide, acrylic and methacrylic acid, fumaric and maleic anhydride and so on. Slightly more water soluble acrylates including hydroxy acrylates, for example ethylhydroxy acrylate and glycidyl acrylates may also be copolymerized with acrylic esters. Monomers other than acrylic esters will be kept to a minimum so that the emulsion is considered an acrylic emulsion, for example, below about 10% and preferably below 5% by weight of the monomers used to produce the polymer. The more hydrophilic monomers, ie, monomers that are more hydrophilic than the acrylic monomers to be polymerized, will be avoided to maintain the water resistance properties. One of the keys to producing an acrylic emulsion with high solids content, for example, greater than 45% by weight of the entire acrylic emulsion, without the use of surfactants, solubilizers and microfluidization techniques, resides in the use of poly ( vinyl) selected from the group consisting of a fully hydrolyzed poly (vinyl) alcohol and a partially hydrolyzed poly (vinyl) alcohol, > 86% as the stabilizing agent where the molecular weight varies from approximately 5,000 to 13,000. The low molecular weight alcohols, ie below 13,000 can be used upwards from 86% hydrolyzed to fully hydrolyzed. The level of the polyvinyl alcohol used as a stabilizer is about 2 to 12%, preferably about 3 to 7% based on the weight of the polymerized total monomers. One type of poly (vinyl) alcohol has a hydrolysis value of at least 96.5%, ie 96.5% of the acetate groups in the poly (vinyl acetate) are converted to hydroxyl groups. When less than 96.5% of the acetate groups are converted to hydroxyl groups, ie the polyvinyl acetate is less than the hydrolyzate completely, and the molecular weight is above 13,000, there is a tendency for an acrylic emulsion formulation with high Solids content will become sandy. When the degree of hydrolysis is substantially reduced below 96.5%, latex can become unstable. A second type of polyvinyl alcohol is a polyvinyl alcohol having a hydrolysis value of at least 86% to be fully hydrolyzed and a molecular weight within a range of 5,000 to 13,000. Poly (vinyl) alcohols having lower hydrolysis values and high molecular weights may be acceptable for producing low solids acrylic emulsions as observed in the prior art but are unable to produce emulsions with high solids content at low levels of the poly (vinyl) alcohol stabilizer. The molecular weight of the poly (vinyl) alcohol is an important factor in stabilizing the acrylic emulsion. A fully hydrolyzed poly (vinyl) alcohol having an average number of molecular weight within an approximate range of 5,000 to 45,000 will be used with a preferred range of about 15,000 to 30,000. Poly (vinyl) alcohols with a low hydrolysis value can be used, provided that the molecular weight does not exceed about 13,000. Fully hydrolyzed polyvinyl alcohol blends can be used with favorable results. One type of mixture consists of 20 to 80%, preferably 50 to 75% of a poly (vinyl) alcohol with a low molecular weight of (5,000 to 13,000), which includes between 86 to 90% of hydrolyzed alcohol, among 20 at 80% of a higher molecular weight and preferably between 50 to 75% of a higher molecular weight of a poly (vinyl) alcohol with a molecular weight between 25,000 to 45,000. Another mixture may consist of a fully hydrolyzed poly (vinyl) alcohol and a partially hydrolyzed alcohol which by itself will be unacceptable to stabilize the solution. In other words, not all of the poly (vinyl) stabilizing alcohol is needed to be completely hydrolyzed but may contain a part of the hydrolyzed material, for example, a hydrolysis value between 85 to 90% at a molecular weight greater than 15,000. In case part of the most reduced hydrolysis material is used, the level will be closely monitored until the emulsion becomes less stable. A hydrolysis between 0 to 25% of such reduced hydrolysis alcohol of poly (vinyl) can be used but the rest of the poly (vinyl alcohol) will have a hydrolysis value of at least 98% as the stabilizing component. Other keys to producing an emulsion containing stable lower alkyl acrylate are supported by the use of a chain tran agent. These chain tran agents are incorporated in an amount of about 0.2 to 3% and preferably 0.5 to 1.5% by weight of the monomers to be polymerized. Representative chain tran agents include the conventional mercaptans, such as n-dodecyl mercaptan and water soluble chain tran agents. Typically, these chain tran agents will have a chain tran coefficient of at least 0.6 based on methyl methacrylate. The emulsion polymerization of the lower alkyl esters of an acrylic or methacrylic acid in the presence of the poly (vinyl alcohol) and a chain tran agent can be carried out using conventional post-addition addition polymerization techniques or by a method of conventional lots. In the delay procedure, which is preferredapproximately 10 to 30% of the monomers to be polymerized are added to the polymerization reactor containing a stabilizer and the balance of the monomers added over a period of time. The time for the addition may vary but the conventional procedure will add to the monomers for a period of time of 2 to 4 hours. An additional description is set forth in the U.S. Patent. 5,326,809 and is incorporated by reference. When in the conventional emulsion polymerization process, the catalyst used is a free radical-forming catalyst, such as a peroxide, for example, t-butyl hydroperoxide, persulfate such as potassium persulfate, ammonium persulfate and the like so as also azo compounds, for example 2, 2'-azo bis amidino propane hydrochloride and reduction systems such as sodium formaldehyde sulfoxylate and sodium erythrobate. The oxidizing agent is generally employed in an amount of 0.01 to 1%, preferably 0.05 to 0.5% based on the weight of the monomers introduced into the polymerization system. The reducing agent is added as an aqueous system and the necessary equivalent or stoichiometric amount. The particle size of the copolymers and acrylic polymers in the emulsion is in the range of 0.3 to 2 microns. This range of particle size has advantages over the extremely fine particle size emulsions obtained through microfluidization. These advantages include high shear stability, wet stickiness, setting rates, salt stability and a wide range of formulations that offer an array of formulators. One of the significant advantages of the lower alkyl acrylate emulsions described herein is that they are stabilized with a stabilization system consisting essentially of a fully hydrolyzed poly (vinyl) alcohol and / or partially polyvinyl alcohol. Hydrolyzed, as described, does not contain the levels of nonionic and anionic surfactants that can adversely affect the properties of the resulting polymer in many applications. The characteristic advantages associated with the polymer in the presence of a fully hydrolyzed poly (vinyl) alcohol include those mentioned, and the desirable emulsion viscosity. Emulsions of the prior art having high levels of polyvinyl alcohol tend to have high levels of grafting which contributes to processing disadvantages associated with undesirable viscosity, poor film formation and water resistance. Emulsions stabilized with lower levels of the poly (vinyl) alcohol provide an improvement in these properties. The following examples are provided to illustrate various embodiments of the invention and are not intended to limit the scope thereof. All quantities are in equal parts by weight unless otherwise specified.

EXAMPLE 1 Hydrolysis of Poly (vinyl Acetate) The following method was used to determine the degree of hydrolysis of the poly (vinyl alcohol) samples used in the examples. A weight of the polyvinyl alcohol sample was placed in a flask and dissolved in 75/25 volume / volume mixture of water and methanol. An aliquot of the sodium hydroxide solution of a known concentration was then added in an amount sufficient to completely hydrolyse all remaining acetate groups. Subsequently, the solutions were refluxed for one hour to ensure complete reaction. Finally, the degree of hydrolysis was determined by a re-titration of the excess sodium hydroxide with a standardized acid solution. The amount of sodium hydroxide consumed to complete hydrolysis of the polyvinyl alcohol was then used to determine the degree of hydrolysis of the polyvinyl alcohol. EXAMPLE 2 Preparation of Butyl Acrylate / Methylmethacrylate Emulsions in the Presence of a Poly (vinyl) Alcohol General Synthesis Procedure: As the polymerization vessel was used a covered 2 liter glass reactor equipped with a mixer, a condenser, a nitrogen purge and the feed materials for the addition of the solution. An aqueous system consisting of an initial charge consisting of water, the stabilizing agent, the oxidizing agent a small level (10 to 30%) of the monomer and the promoter. The mixture was heated to the reaction temperature and allowed to equilibrate to the desired temperature. The reaction is then initiated by the addition of a small amount of the reducing agent. When the reaction begins to generate heat, the addition of the feeding materials (delayed addition) begins. The desired reaction temperature is maintained by heating or cooling the jacket or shell of the reactor and by controlling the rate of addition of the delayed components. After all of the monomer and initiator solutions are added, the products are maintained at the reaction temperature for 30 to 90 minutes to ensure complete coinversion of the monomer. The products are then cooled to room temperature and removed. The emulsions from A to F, based on butyl acrylate and methyl methacrylate were prepared using the above general description and in accordance therewith. Examples A to F differ fundamentally from the use of various poly (vinyl alcohol) polymers as the stabilizer, such as the poly (vinyl alcohol) polymers which are designated as A-F, to be corresponding with the different emulsions. The poly (vinyl) alcohols from A to F are described in the following table. Alcohol of Poly (vinyl) Polyvinyl alcohol emulsion A This example illustrates the preparation of an emulsion of butyl acrylate / methylmethacrylate copolymer prepared in the presence of a poly (vinyl) alcohol A as the sole stabilizer. Initial charge to reactor Deionized water 230 grams Aqueous solution at 10% Poly (vinyl) alcohol At 340 grams Monomer mixture (the same percentage as below) 357 grams Butyl hydroperoxide tere. (70% aqueous solution) 1.0 grams ferrous ammonium sulfate 5 grams Acetic acid 3.9 grams. POST-GRADED FOOD MATERIALS Solutions Quantity 1) Deionized water 323.4 grams Sodium formaldehyde sulfoxylate 6.6 grams Total 330 grams 2) Deionized water 169.5 grams Butyl hydroperoxide tere, (70% aqueous solution) 10.65 grams Foamaster VF * 1.5 Total 181.65 grams 3) Acrylate n-butyl 383 grams methylmethacrylate 467 grams n-dodecyl mercaptan 7 grams Total 857 grams * Foamaster VF is a commercial defoaming agent The reaction was carried out at 70 ° C. Initially the delayed solution 1 was added at a speed of 0.2 gm / min during a period of 2 hours. The postponed solution 2 was initially added at a rate of 0.1 gm / min then increased to 0.5 gm / min after 15 minutes. The delayed monomer solution 3 was added at a rate of 3.3 gm / min. The reaction was complete in 4 hours. The product had the following properties. Unreacted monomeric butyl acrylate 39 ppm methylmethacrylate 133 ppm % solids 49.5% Accelerated sedimentation 4.% pH 3.2 Tg 12.1 ° C Viscosity 60 RPM 225 cps Viscosity 12 RPM 420 cps sandstone, mesh 100 2500 ppm The viscosity was measured in a 4% emulsion, with a Brookfield instrument. The emulsion was stable, thus showing that butyl acrylate / methyl methacrylate emulsions with a high solids content can be prepared using a polyvinyl alcohol as the sole stabilizer. The sandstone levels were modest. Polyvinyl alcohol emulsion B This example illustrates the preparation of an emulsion of the butyl acrylate / methylmethacrylate copolymer prepared in the presence of a poly (vinyl) alcohol B having a hydrolysis value of 98% to 98.8%.

Initial charge to the Reactor Deionized water 230 grams Aqueous solution to 10% of Alcohol of poly (vinyl) B 340 grams Mixture of monomers (the same percentage as below) 357 grams Butylhydroperoxide tere, (aqueous solution to 70%) 1.0 grams Sulfate of Ferrous ammonium 5 grams Acetic acid 6.2 grams. POSTPONED FEED MATERIALS Solutions Quantity 1) Deionized water 323.4 grams Sodium formaldehyde sulfoxylate 6.6 grams Total 330 grams 2) Deionized water 169.5 grams Butylhydroperoxide tere. (water content at 70%) 10.65 grams Foamaster VF * 1.5 Total 181.65 grams 3) n-Butyl acrylate 383 grams methylmethacrylate 467 grams n-dodecyl mercaptan 7 grams Total 857 grams The reaction was carried out at 70 ° C. Initially, the delayed solution 1 was added at a speed of 0.5 gm / min followed by an increase to 1.3 gm / min during a period of 1.5 hours. The postponed solution 2 was initially added at a rate of 0.3 gm / min then increased to 0.7 gm / min after 15 minutes. The delayed monomer solution 3 was added at a speed of 3.7 gm / min. The reaction was complete in 4 hours. The product had the following properties. Unreacted monomeric butyl acrylate 80 ppm methylmethacrylate 140 ppm % solids 49% pH 3.1 Tg 20.9 ° C Viscosity 12 RPM ND Viscosity 60 RPM 265 cps sandstone mesh 100 100 ppm Accelerated Sedimentation 3.0% The emulsion was stable and had little sandstone content, thus showing the effectiveness of poly (vinyl) B alcohol as a stabilizer. It is considered that the poly (vinyl) alcohol with a higher molecular weight, ie, from 7,000 to 13,000, compared to that of the poly (vinyl) alcohol A is the main cause for reducing the level of sandstone. This result is considered to be due to higher stabilization forces in alcohol with higher molecular weight. Emulsion of polyvinyl alcohol C This example demonstrates that the preparation of an emulsion of butyl acrylate / methylmethacrylate copolymer in the presence of a poly (vinyl) C alcohol (hydrolysis between 96.5% to 97.5%) as the sole stabilizer. Initial charge to the Reactor Deionized water 230 grams Aqueous solution at 10% Poly (vinyl) alcohol C 340 grams Monomer mixture (the same percentage as below) 357 grams Butyl hydroperoxide tere. (70% aqueous solution) 1.0 grams Ferrous ammonium sulfate 5 grams Acetic acid 3.1 grams. POSTPONED FOOD MATERIALS Solutions Quantity 1) Deionized water 323.4 grams Sodium formaldehyde sulfoxylate 6.6 grams Total 330 grams 2) Deionized water 169.5 grams Butyl hydroperoxide tere. (70% aqueous solution) 10.65 grams Foamaster VF * 1.5 Total 181.65 grams 3) N-butyl acrylate 383 grams methylmethacrylate 467 grams n-dodecyl mercaptan 7 grams Total 857 grams The reaction was carried out at 70 ° C. Initially the delayed solution 1 was added at a speed of 0.2 gm / min followed by an increase to 1.2 gm / min during a period of 2 hours. The postponed solution 2 was initially added at a rate of 0.1 gm / min then increased to 0.7 gm / min after 30 minutes. The monomeric delayed solution 3 was added at a rate of 3.6 gm / min. The reaction was complete in 4 hours. The product had the following properties. Unreacted monomeric butyl acrylate 49 ppm methyl methacrylate ND% solids 50.3% pH 4.0 Tg 22 ° C Viscosity 12 RPM 19,000 cps Viscosity 60 RPM 7,980 cps Accelerated sedimentation 7.0% Sandstone, 100 100 ppm mesh The results show that polyvinyl alcohol was effective in stabilizing the acrylic monomer system. However, in comparison with the poly (vinyl) B alcohol there was a higher viscosity and the formation of sandstones is probably due to the lower hydrolysis values of the poly (vinyl) alcohol. Polyvinyl alcohol emulsion D This example illustrates the preparation of an emulsion of the butyl acrylate / methylmethacrylate copolymer prepared in the presence of a poly (vinyl) D alcohol having a hydrolysis of 96.7% as the sole stabilizer. Initial charge to the reactor Deionized water 230 grams Aqueous solution at 10% Poly (vinyl) alcohol D 340 grams Monomer mixture (the same percentage as below) 357 grams Butyl hydroperoxide tere. (70% aqueous solution) 1.0 grams Ferrous ammonium sulfate (1% aqueous solution) 5 grams Acetic acid 4.8 grams. POSTPONED FOOD MATERIALS Solutions Quantity 1) Deionized water 323.4 grams Sodium formaldehyde sulfoxylate 6.6 grams Total 330 grams 2) Deionized water 169.5 grams Butyl hydroperoxide tere. (70% aqueous solution) 10.65 grams Foamaster VF * 1.5 Total 181.65 grams 3) N-butyl acrylate 383 grams methylmethacrylate 467 grams n-dodecyl mercaptan 7 grams Total 857 grams The reaction was carried out at 70 ° C. Initially the delayed solution 1 was added at a speed of 0.2 gm / min followed by an increase to 1.9 gm / min over a period of 2 hours. The postponed solution 2 was initially added at a rate of 0.1 gm / min then increased to 0.6 gm / min after 15 minutes. The delayed monomer solution 3 was added at a rate of 3.3 gm / min. Large amounts of clots were observed immediately at the start of the reaction. This instability persisted through the reaction. The reaction was complete in 4 hours. The product had the following properties. Unreacted monomeric butyl acrylate 24 ppm methylmethacrylate 63 ppm% solids ND Accelerated sedimentation ND pH ND Tg ND Viscosity 12 RPM ND Viscosity 60 RPM ND Sandstone, mesh 100 ND ND- Not determined due to product instability As noted in In the description, the polymer coagulated almost immediately and the lower hydrolysis value of the polyvinyl alcohol is considered to be the basis for the ineffectiveness of the polyvinyl alcohol as a stabilizer. The presence of the chain transfer agent did not help. It is considered that the results obtained here are somehow false because the data can not be reconciled with the work. Please refer to Example 5 in relation to the summary of the Tests. However, the poly (vinyl) alcohol employed is at the limit of acceptable stabilizers and one can expect unexpected results. Emulsion of polyvinyl alcohol E This example illustrates the preparation of an emulsion of butyl acrylate / methylmethacrylate copolymer prepared in the presence of a poly (vinyl) alcohol E as the sole stabilizer.

Initial charge to the reactor Deionized water 230 grams Aqueous solution at 10% Poly (vinyl) alcohol E 340 grams Monomer mixture (the same percentage as below) 357 grams Butyl hydroperoxide tere. (70% aqueous solution) 1.0 grams Ferrous ammonium sulphate (1% aqueous solution) 5 grams Acetic acid 3.3 grams. POSTPONED FOOD MATERIALS Solutions Quantity 1) Deionized water 323 .4 grams Sodium formaldehyde sulfoxylate 6.6 grams 2) Deionized water 169.5 grams Butyl hydroperoxide tere. (70% aqueous solution) 10. (55 grams Foamaster VF * 1.5 3) n-Butyl acrylate 383 grams methylmethacrylate 467 grams n-dodecyl mercaptan 7 grams The reaction was carried out at 70 ° C. Initially the delayed solution 1 was added to a speed of 0.2 gm / min followed by an increase to 1.9 gm / min over a period of 2 hours. The postponed solution 2 was initially added at a rate of 0.1 gm / min then increased to 0.6 gm / min after 15 minutes. The delayed monomer solution 3 was added at a rate of 3.3 gm / min. Large amounts of clots were observed immediately at the start of the reaction. This instability persisted through the reaction. The reaction stopped after 2 hours. The product had the following properties. Unreacted monomeric butyl acrylate 43 ppm methyl methacrylate 238 ppm % of solids 34% Sedimentation Accelerated ND pH 2.7 Tg ND Viscosity 12 RPM ND Viscosity 60 RPM ND Sandstone, mesh 100 49,000 ppm ND- Not determined due to product instability The ineffectiveness of polyvinyl alcohol with low hydrolysis and high molecular weight as the stabilizer confirms the results of previous researchers regarding the ability of poly (vinyl) alcohol to stabilize the monomers acrylics more soluble in water in the absence of other hydrophilic monomers and / or stabilizers. Polyvinyl alcohol emulsion F This example illustrates the preparation of an emulsion of the butyl acrylate / methylmethacrylate copolymer prepared in the presence of a poly (vinyl) alcohol F as the sole stabilizer. Initial charge to the Reactor Deionized water 245 grams Aqueous solution at 10% Poly (vinyl) alcohol F 218 grams Mixture of monomers (the same percentage as below) 40 grams Butyl hydroperoxide tere. (70% aqueous solution) 0.5 grams Ferrous ammonium sulfate 5 grams Acetic acid 2.3 grams, POST-GARDEN FOOD MATERIALS Solutions Quantity 1) Deionized water 237. 5 grams Sodium formaldehyde sulfoxylate 12.5 grams Total 250 grams 2) Deionized water 200 grams Butylhdiroperoxide tere. (water content 70%) 8.0 grams Total 208 grams 3) N-butyl acrylate 289 grams methyl methacrylate 193 grams n-dodecyl mercaptan 1.5 grams Total 483 5 grams The reaction was carried out at 70 ° C. Initially, the delayed solution 1 was added at a speed of 0.2 gm / min followed by an increase to 0.3 gm / min during a period of 2 hours. The postponed solution 2 was initially added at a rate of 0.1 gm / min then increased to 0.4 gm / min after 15 minutes. The delayed monomer solution was added at a rate of 1.4 gm / min. Large amounts of clots were observed immediately at the start of the reaction. This instability persisted through the reaction. The reaction was complete in 6 hours. The product had the following properties. Unreacted monomeric butyl acrylate 172 ppm methyl methacrylate *% solids 39.5% Accelerated Sedimentation ND pH 2.3 Tg -7 ° C Viscosity 12 RPM ND Viscosity 60 RPM ND Sandstone, 100 ND mesh ND- Not determined due to product instability The product was unstable, thus reducing the importance of using the polyvinyl alcohol having a hydrolysis value of at least 96.5%, even though the molecular weight of the polyvinyl alcohol is within a desirable range. EXAMPLE 3 Batch Process for Producing a Butyl Acrylate / Methylmethacrylate Emulsion This example demonstrates that the preparation of an emulsion of butyl acrylate / methylmethacrylate copolymer prepared in the presence of a poly (vinyl) B alcohol as the sole stabilizer employing a batch process as a way of distinguishing the delayed process used in Example 2. Initial charge to the Reactor Deionized water 140 grams Aqueous solution at 10% Alcohol of poly (vinyl) B 160 grams Methylmethacrylate 158 grams Butyl acrylate 141 grams n- dodecyl mercaptan 0.9 grams Butyl hydroperoxide tere. (70% aqueous solution) 2.3 grams Ferrous ammonium sulphate (1% aqueous solution) 5 grams Foamaster VF 2.3 grams POSTPONED FOOD MATERIALS Solutions Quantity 1) Deionized water 237.5 grams sodium formaldehyde sulfoxylate 12.5 grams Total 250 grams The reaction is started at 40 ° C and increased in the cover at 70 ° C for 1 hour. The delayed solution 1 was added at a speed of 0.3 gm / min. The reaction temperature was controlled by the variation of the addition rate of the delayed solution 1. The reaction was completed in 2 hours. The product showed good stability throughout the entire process. The product had the following properties. Unreacted monomeric butyl acrylate 31 ppm methyl methacrylate % solids 45.8% Sedimentation Accelerated 4.0% pH Viscosity 60 RPM Tg 1 -3.3 ° C Viscosity 12 RPM Sand mesh 100 * Not detected EXAMPLE 4 Preparation of Butyl Acrylate / Methylmethacrylate Emulsions In the presence of a mixture of poly alcohols (vinyl) This example demonstrates the preparation of an emulsion of the butyl acrylate / methylmethacrylate copolymer prepared in the presence of a mixture of the poly (vinyl) C alcohol with the poly (vinyl) G alcohol as the stabilizer. Initial Charge to Reactor Deionized Water 403 grams Aqueous solution at 10% Poly (vinyl) Alcohol C 619 grams Aqueous solution at 10% Poly (vinyl) Alcohol G 185 grams Monomeric Mixture (same ratio as below) 434 grams Butyl hydroperoxide tere. (70% aqueous solution) 2.2 grams Ferrous ammonium sulfate (1% aqueous solution) 5 grams Acetic acid 5.8 grams POSTPONED FOOD MATERIALS Solutions Quantity 1) Deionized water 393.9 grams Sodium formaldehyde sulfoxylate 10.1 grams Total 404 grams 2) Water deionized 387 grams Butylhdiroperoxide tere. (70% aqueous solution) 15.4 grams Total 402.4 grams 3) N-butyl acrylate 935 grams methylmethacrylate 935 grams n-dodecyl mercaptan 13.2 grams Total 1883.2 grams The reaction was carried out at 70 ° C. Initially, delayed solutions 1 and 2 were added at a speed of 0.3 gm / min followed by an increase to 1.7 gm / min over a period of 2 hours. The delayed monomer solution was added at a rate of 16.1 gm / min. The reaction was complete at 2.5 hours. Of the total amounts of the delayed solutions 1 and 2 shown above, the actual quantities were for the delayed solution 1, 105.1 grams and for the delayed solution 2, 156.9 grams. Additional water was added to adjust the final solids content ~ 50%. The product had the following properties. Unreacted monomeric butyl acrylate 235 ppm methyl methacrylate% solids 50.4% Sedimentation Accelerated 3.0% pH 3.9 Viscosity 60 RPM 2,400 cps Tg 1 0.7 ° C Viscosity 12 RPM 5,400 CPS Sand mesh 100 50 ppm * Not detected This example indicates the good properties that can be achieved through the use of poly (vinyl alcohol) polymer combinations with different molecular weights and hydrolysis levels. The sandstone formation was lower with any of the types of polyvinyl alcohol used separately. Example 5 Test Summary A series of tests were carried out to determine the effectiveness of a wide variety of commercial poly (vinyl) alcohols. The general procedure of Example 1 was followed. The poly (vinyl) alcohols are described in the following table.

PVOH% H-Viscosity / No. Prompt Stabilization Tested drolysis Effective Molecular Weight in Acrylate A - 502 87--89 3.0-3.7 / 7,000-13,000 Si, high viscosity A - 203 87--89 3-0-4.5 / 7, 000-15, 000 Yes A - 205 87--89 5.2-6.2 / 15,000-27,000 No, sandstone and high sedimentation A - 523 87 -89 23-27 / 44,000-65,000 No, sandstone and high sedimentation WS-42 96.5-97. 5 14-17 / 27,000-44,000 Yes A - 425 95 .5-96. 5 27-31 / 44,000-65,000 No, sandstone and high sedimentation and viscosity A - 103 98--98 .8 3.5-4.5 / 7,000-15,000 Yes A - 107 98--98 .8 5.5-6.6 / 15,000- 27,000 Yes A- 321 98--98 .8 16.5-20.5 / 27,000-44,000 Yes A- 125 99 .3+ 28-32 / 44,000-65,000 If Ope. 1 97 .6 2.6 / 6,000 If Ope. 2 97 .2 2.4 / 5,000 If A in the above table is an abbreviation for the Airvol brand, which is owned by Air Products and Chemicals, Inc. for its polyvinyl alcohol line. The number that follows in the designation of the degree. Seds is an abbreviation for sedimentation.

As can be seen from the table, the best results are obtained with poly (vinyl) alcohols with a medium weight and a high hydrolysis > 98%. The results also show that a poly (vinyl) alcohol with low hydrolysis at a low molecular weight was more effective in stabilizing the acrylic emulsion and is in contrast to the poly (vinyl) D alcohol, supra. Comparative Example In this specific example a copolymer emulsion of butyl acrylate / methyl methacrylate was prepared according to the procedure of the Example employing a poly (vinyl) alcohol B as the sole stabilizer, the difference being the omission of the mercaptan transfer agent of dodecyl The polymerization was terminated after a few hours due to the excess formation of sandstone and the instability of the emulsion.

Claims (18)

1. NOVELTY OF THE INVENTION Having described the invention as above, we consider what is contained in the following: CLAIMS 1. In a process for the polymerization of an emulsion of a monomer mixture consisting essentially of ethylenically unsaturated, water-insoluble monomers having an unsaturation to the acrylic to produce the polyacrylic polymer particles wherein the monomeric polymerizable system consists essentially of at least one acrylic monomer that is polymerized in the presence of water and a stabilizer to produce a polyacrylic polymer, the improvement to produce an acrylic emulsion that has a solids content greater than 4 %% by weight without the microfluidization technique comprising: a) carrying out the polymerization in a polymerization zone employing a stabilizer consisting essentially of a poly (vinyl alcohol) selected from the group consisting of e a spirit of pol i (vinyl) having a hydrolysis value greater than 96.5% and a polyvinyl alcohol having a hydrolysis value of at least 86% where the molecular weight is within a range of approximately 5,000 to 13,000 and in the substantial absence of surfactants and solvents, said polyvinyl alcohol is present in an amount of 2 to 15% by weight of the monomers to be polymerized; and b) carrying out the polymerization in the presence of a chain transfer agent.
2. 2. The process of claim 1, wherein the poly (vinyl alcohol) is incorporated in the emulsion in an amount of about 3 to 7% by weight of the polymerized monomers.
3. 3. The process of claim 2, wherein the chain transfer agent is incorporated in an amount of 0.2 to 3% by weight of the monomers to be polymerized.
4. 4. The process of claim 3, wherein the polymerization is effected by a delayed addition of the acrylic monomer to the polymerization zone.
5. The process of claim 4, wherein the delayed addition is effected by charging from 10 to 30% of the acrylic monomer to be polymerized as an initial charge in the polymerization zone and then adding the monomer over a period of time 6.
6. The process of claim 3, wherein the acrylic monomers are C? _8 alkyl esters of an acrylic and methacrylic acid.
7. The process of claim 6, wherein the acrylic monomers are selected from the group consisting of methyl methacrylate, ethylacrylate, ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate.
8. The process of claim 6, wherein the poly (vinyl) alcohol has a hydrolysis percentage of at least 98%.
9. The process of claim 7, wherein the poly (vinyl alcohol) stabilizer is present as a mixture comprising from 20 to 80% of a low molecular weight poly (vinyl) alcohol (5,000 to 13,000) and 20 to 80% of a poly (vinyl) alcohol with a higher molecular weight of 25,000 to 45,000.
10. The process of claim 9, wherein the poly (vinyl alcohol) stabilizer is present in an amount of 50 to 75% of a poly (vinyl) alcohol with a low molecular weight (5,000 to 13,000) and a approximate hydrolysis value between 86% to 90% and 25% to 50% of a poly (vinyl) alcohol with a molecular weight greater than 25,000 to 45,000.
11. 11. In an aqueous emulsion consisting essentially of polymerized ethylenically unsaturated monomers having an unsaturation to the acrylic to produce polyacrylic polymer particles, said improvement comprises: said emulsion stabilized with a stabilizer consisting essentially of a poly (vinyl alcohol) selected from the group consisting of a poly (vinyl) alcohol having a hydrolysis value greater than 96.5% and a poly (vinyl) alcohol of at least 86% where the molecular weight is within a range of about 5, 000 to 13,000, and said emulsion is substantially free of surfactants and solvents, said emulsion has a solids content of at least 45% by weight of the emulsion and the poly (vinyl alcohol) is incorporated in an amount of 2 to 12% by weight of polyacrylic polymers.
12. The process of claim 11, wherein the poly (vinyl alcohol) is incorporated in the emulsion in an amount of 3 to 7% by weight of the polymerized monomers.
13. The process of claim 12, wherein the chain transfer agent is incorporated in an amount of 0.2 to 35 by weight of the monomers to be polymerized.
14. The process of claim 13, wherein the acrylic monomers are C este _ alquilo alkyl esters of an acrylic and methacrylic acid and the chain transfer agent is a mercaptan.
15. 15. The process of claim 14, wherein the acrylic monomers are selected from the group consisting of methyl methacrylate, ethylacrylate, ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate.
16. 16. The process of claim 15, wherein the poly (vinyl) alcohol has a hydrolysis percentage of at least 98%. The process of claim 15, wherein the poly (vinyl alcohol) stabilizer is present in an amount of 20 to 80% of a poly (vinyl) alcohol with a low molecular weight (5,000 to 13,000) and to 80% of a polyvinyl alcohol with a higher molecular weight of 35,000 to 45,000. The process of claim 16, wherein the poly (vinyl alcohol) stabilizer is present in an amount of 50 to 75% of a poly (vinyl) alcohol with a low molecular weight (5,000 to 15,000) and to 50% of a polyvinyl alcohol with a higher molecular weight of 35,000 to 45,000.