GB1595249A - Terpolymer emulsions comprising alpha betaunsaturated acids and their lower alkyl esters and methods for their production - Google Patents

Description

(54) TERPOLYMER EMULSIONS COMPRISING ALPHA. BETA UNSATURATED ACIDS AND THEIR LOWER ALKYL ESTERS AND METHODS FOR THEIR PRODUCTION (71) We, GAF CORPORATION, a corporation organized and existing under the laws of the State of Delaware, United States of America. having its main office at 140 West 51st Street, New York, New York 10020, United Siates of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to terpolymer compositions comprising an a,(3-unsaturated acid and an alkyl ester of an (x,ss-unsaturated acid. More particularly, the invention relates to stable aqueous emulsions or latices of said terpolymers, to an emulsion process for their preparation, and to their use in altering the rheological properties of polymer latices such as acrylic polymer and butadiene-styrene systems.

The terpolymer latices of this invention are prepared from monomers comprising (1) from 30 to 85 wt. % of an a, ss -unsaturated acid of the formula

wherein R is methyl or ethyl, (2) from 5 to 50 wt.% of an alkyl ester of an α,ss-unsaturated acid of the formula

wherein R1 is alkyl of from 1 to 8 carbon atoms and R2 is hydrogen, methyl or ethyl, and (3) from 0.5 to 20 wt.% of an ethylenically unsaturated orgnic monomer which is different from and copolymerizable with monomers (1) and (II) above to form a stable latex and which is further characterized in that the probability of acid-acid linkages of the terpolymer formed by the polymerization of said monomer with monomers (I) and (II) above is less than 81%.

In accordance with this invention the terpolymer latices or emulsions are prepared by inducing in a reactor emulsion polymerization of the above monomers, all the ingredients necessary for the polymerization being present in the reactor upon initiation of the polymerization.

The termonomer (3), which is critical in obtaining terpolymer emulsions of the proper characteristics for this invention is preferably represented by the formula:

wherein R3 is hydrogen, methyl, ethyl or halogen such as chlorine, bromine, iodine or fluorine, X is hydrogen or CI-C,, alkoxycarbonyl, and X2 is aryl, aminocarbonyl cyano, C1-C4 alkoxy, carboxyl, CI-Clx alkoxycarbonyl, halo, acyl, acyloxy, aldehyde, a keto- containing group, isocyanato. C3-C9 heterocyclic, C2-C4 alkenyl, C1-C4 alkyl, halomethyl, acetomethyl, a sulfo-containing group, tri(C1-C4 alkoxy)-silyl or hydrogen.

Stable aqueous emulsions containing these terpolymers are prepared according to ah emulsion polymerization technique, described hereinafter.

Latices containing these terpolymers are useful for altering the rheological properties of, polymer latex systems. In particular, they are useful as thickening agents for acrylic' polymer and butadiene-styrene latices.

The terpolymer emulsions prepared according to the process of this invention preferably have the following repeating units:

and preferably wherein R, RX, R2, R3, X and X, are as defined hereinabove.

The inclusion of the described monoethylenically unsaturated termonomer, preferably of formula (1it) as defined hereinabove, and the polymerization method are the most important features of this invention. The excellent performance and unique behaviour of the polymers of the invention are due to the presence of the termonomers in the polymer chain, the inclusion of all of the ingredients for the polymerization reaction in the reactor at the initiation of the polymerization, and the resultant molecular unit spacing such that the probability of acid-acid linkages in the polymer chain is less than 81%.

It has now been found that the changes in rheological properties brought about by the introduction of a termonomer into the system according to this invention can be many times more than would be expected from the amount of the termonomer. By utilizing this unexpected effect. tailor-made thickeners. suitable for a variety of applications can be made.

To illustrate the effect of the termonomers, methacrylic acid-ethyl acrylate-termonomer systems were emulsion polymerized employing a constant monomer ratio of the ingredients of 66/28/6, respectively, and the reactions were run under the same conditions. The results are given in Table I below.

TABLE I VISCOSITY OF BUTADIENE-STYRENE LATEX AS AFFECTED BY METHACRYLIC ACID-ETHYL ACRYLATE-THERMONOMER SYSTEMS Probability of Brookfield Acid-Acid Linkages Viscosity Termonomer Q-Value e-Value -% cps Styrene 1.0 -0.8 70.4 18,600 Acrylamide 1.12 1.19 74.6 14,000 Acrylonitrile 0.6 1.2 76.0 11,750 n-Butylvinyl Ether 0.087 -1.2 78.8 9.900 isobutyl Vinyl Ether 0.023 -1.77 79.6 8,200 Vinyl Pyrrolidone 0.14 -1.14 78.2 6,950 Diethyl Maleate 0.059 1.49 80.1 6,800 Mono-Ethylhexyl Maleate 0.05 1.5 80.2 5,800 Triethoxy Vinyl Silane 0.023 0.04 80.0 3,600 Vinyl Acetate 0.028 -1.13 79.6 3,430 Details of the testing procedure are given in Example I below. The results show that the properties of the thickened polymer system can be changed over a wide range, by simply changing the chemical nature of the termonomer employed in the terpolymer.

The salient point here is that the amount of carboxyl groups remained the same in all of the experiments, and that the hydrophylic-hydrophobic ratio, set by the respective amounts of the methacrylic acid and ethyl acrylate, was also kept constant. Therefore, the common prior art contention that the amount of the carboxylic acid units and the hydrophylichydrophobic ratio are the only important factors in, the development of viscosity, is not accurate.

There is also no correlation between the observed changes in properties and the hydrophilicity of the termonomer. The termonomer units can produce a large variation in the character of the polymer radicals, thus influencing their reactivity towards the more abundant acid molecules. Therefore, the conclusion is that the termonomer affects the sequencing, and through that, the effective interaction distance, of the carboxy substituted monomers during the polymerization.

The correlation between the effective interaction distance and the rheological behavior of the terpolymers was unambiguously supported by computer simulations. In these computer simulated experiments, the probability of acid-acid linkages was calculated based on the Qand e- values of the respective termonomers. Q and e are constant characteristic for each particular monomer. The value of Q described the general monomer reactivity and is related to possibilities for stabilization in a radical addict. The value of e takes account of polar factors influencing copolymerization. Further details regarding these constants are in Alfrey & Price, "Relative Reactivities in Vinyl Copolymerization", J. Polymer Sci. 2, 101 (1947), pertinent portions of which are incorporated herein by reference. The calculations of acid-acid linkage probabilities were performed according to the method described in Maxim, Kuist & Meyer, "The Ultraviolet Degradation of Terpolymer Scissioning Systems", Macromolecules 1, 86 (1968), pertinent portions of which are incorporated herein by reference. The calculations were carried to an integrated 20% conversion, which can be considered typical and free of disturbing effects, e.g. chain transfer, Trommsdorff effect, etc. Table I lists the respective Q and e values, as well as the calculated probability for acid-acid linkages and measured viscosity values of carboxylated butadiene-styrene latices thickened with 1% of the respective terpolymers.

The higher the probability for acid-acid linkages, the lower is the effective interaction distance. As a consequence, the lower this parameter, the lower is the viscosity of the thickened latex.

The finding that the rheological behavior of the polymer lates can be changed by simply varying the termonomer in the process of this invention even though it is present in only a few percent. shows that the inclusion of the termonomer results not in slightly modified polymers, but, on a molecular level, in profoundly different products.

In the practice of the present invention, the latex is required to contain conomer units of at least three different kinds: (1) From 30 percent to 85 percent, preferably from 50 percent to 70 percent, by weight, of an (x,ss-monoethylenically unsaturated carboxylic acid of Formula 1. i.e. methacryclic acid, ethacrylic acid or mixtures thereof. Other unsaturated carboxylic acids such as acrylic acid can be employed in admixture therewith in amounts up to 50% or more by weight of such mixtures depending upon the concentration and hydrophobic nature of the carboxylic acid ester units (2) in the resulting polymer. As the concentration and/or hydrophobic nature of the ester (2) increases, increasing amounts of such other unsaturated carboxylic acids, e.g., acrylic acid, can be employed to the extent that a stable latex can still be obtained.

(2) From 5 percent to 50 percent, preferably from 2() percent to 30 percent, by weight, of at least one alkyl ester of an a,p -unsaturated carboxylic acid of Formula 11, preferably at least a predominant portion of said ester having from I to 4 carbon atoms in the alkyl moiety. Preferably the Precursor acid is acrylic or methacrylic acid.

(3) From 0.5 percent to 20 percent, preferably from 3 percent to 8 percent, by weight, of an ethylenically unsaturated organic termohomer different from and copolymerizable with monomers (1) and (2), preferably represented by Formula III. Illustrative of such termonomers are styrene, vinyltoluene, chlorostyrene, acrylamide, methacrylamide.

N-isopropyl acrylamide, acrylonitrile, methacrylonitrile, methylvinyl ether, ethylvinylether, butyl vinyl ether, halfacid ethylmaleate, halfacid 2-ethylhexyl maleate, halfteid ethylfumarate, halfacid ethylitaconate, diethylmaleate, dibutyl maleate, diethyl fumarate. vinylchloride, vinylidene chloride, vinylbromide, vinylidene fluoride, vinylacetate, vinylpropionate, vinylchloracetate, vinylbenzoate, vinylthioacetate, acrolein, methacrolein. methylvinyl ketone, ethylvinylketone, isopropenyl methyl ketone, vinyl isocytnate, isopropenyl isocyanate, vinyl isothiocyanate. N-vinyl-2-pyrrolidone, N-vinyl-,- oxazolidinone, vinylfurane, indene, 2.3-dihydrofurane, vinyl succinimide, bitadiene, isoprene, chloroprene, allyl chloride, allyl acetate, allyllaurate, methallylchloride, vinyl sulfonic acid, sodium vinyl sulfonate, vinyltriethoxysilane, vinyl triisopropoxysilane, ethylene and propylene.

Small amounts of some bifunctional, ethylenically unsaturated crosslinking monomers can also be added to the mixture. This monomer has to be capable of polymerizing under free radical conditions to bond covalently different chains of the polymer. Polyfunctional monomers, such as divinyl benzene, polyethylenglycol-dimethacrylate, methylenebisacrylamide may serve as examples. Other monomers, which can render the polymer curable through heat-treatment, or otherwise crosslinkable, such as methylolacrylamide, glycidylmethacrylate, epoxybutadiene may also be used as comonomers.

It is to be understood, that percentages are based on the total terpolymer weight and they have to be 100% together.

Chain transfer agents may be used to regulate the average molecular weight of the polymer. Preferred agents are mercaptans such as t-dodecylmercaptan.

The preparation of the terpolymers of this invention is carried out in an emulsion system.

The term "emulsion" as used herein, is intended to mean a true colloidal dispersion of the terpolymers in water.

Polymerization is effected in the presence of a catalyst or initiator, preferably one which serves as a thermally activated source of free radicals. Such catalysts include peracetic acid, hydrogen peroxide, persulfates, perphosphates, perborates and percarbonates. The preferred catalyst is ammonium persulfate, which provides efficient reaction rates and contains a fugitive cation. The amount of initiator used is normally 0.03 to 3.0 percent, by weight based on the weight of the total monomers and preferably from 0.25 to 0.5 percent.

Preferably, the initiator is a redox combination of the water soluble perfulfate as the oxidizing component and a hydrosulfite, e.g. sodium hydrosulfite as the reducing component of the redox combination. Water soluble bisulfites, metabisulfites, or thiosulfates, reducing sugars, formaldehyde sulfoxylate may be used in lieu of the hydrosulfites. Other typical redox combinations, such as sodium azide and ceric ammonium sulfate, titanium trichloride and hydroxylamine may also be used. Generally useful proportions of the indicated persulfate-hydrosulfite system are 0.01 percent to 1.0 percent for the oxidizing component and 0.015 to 1.05 percent for the reducing component based on the amount of monomers.

The redox combination can be further activated by the presence of polyvalent metal ions at the lower oxidation state, e.g. ferrous sulfate and cuprous sulfate. The preferred amount of these metal salts may be between 5 PPM and 100 PPm by weight based on the total amount of the monomers.

The aqueous medium for polymerization contains some emulsifiers to help to disperse the monomers in the aqueous medium and to protect the particles formed. Anionic surfactants such as the salts of the higher molecular weight sulfonic acids, e.g. alkyl aryl sodium sulfonates, are eminently suitable for the purpose, though other anionic surfactants can also be used with good results. The amount of surfactant employed can be varied considerably, but ordinarily ranges from 0.1 percent to 10 percent and more preferably. ranges from 0.2 percent to 1.0 percent, by weight, based on the total weight of the comonomers employed.

The reaction mixture can also contain a small amount of a lower aliphatic alcohol which is believed to act as a solubilizer for the water insoluble monomers. Methanol, ethanol and n-butanol may serve as examples.

The emulsion can also contain a small amount of a protective colloid, such as water soluble cellulose derivatives, poly(vinylpyrrolidone), alkali metal polyacrylates and water soluble alginates. The amount of such a colloid used can range, for example from 0.1 percent to 2 percent and more particularly from 0.5 percent to 1 percent.

The emulsions of the invention typically have from 15 percent and preferably from 20 percent to 50 percent solids content. The average particle size of the latex may be from sooAngstroms or smaller to 3000 Angstroms or greater.

The reaction temperature applied depends. in the first place, on the polymerization catalyst and the monomers used. In general, the polymerization is carried out at a temperature in the range of from 5"C. to 12ü C. When the catalyst is a redox system. the recommended initial temperature range is 5"C. to 80"C., advantageously 15"C. to 60"C.

It is advisable to operate with the exclusion of oxygen, for example under a neutral gas such as nitrogen or argon. Sometimes. it may also be advantageous to run the reaction under elevated or reduced pressure.

The polymerization is run by a single stage procedure, when all the ingredients are present in the reactor at the initiation of reaction. Since the polymerization reaction is exothermic, the initiation thereof can be evidenced by the increasing temperature. When the polymerization has proceeded to the extent that the consumption of the monomers is practically complete, the terminal point is indicated by the cessation in the. rise of the temperature, followed by temperature drop. The time period necessary for aforedescribed operation can range from about 10 minutes to about 2 hours.

The terpolymer emulsions of the invention are excellent thickening agents and can influence the viscosity of a variety of latex systems in an effective and unique way. Not only can they form viscous systems with water based dispersions of materials insoluble intht medium, but also, they can thicken dilute solutions of organic materials soluble in water; as well as liquid organic materials per se which are miscible with water.

These terpolymer emulsions of the invention are eminently useful to change the rheological behavior of butadiene-styrene base synthetic elastomers. However, they also can be used for the thickening of dispersions of water insoluble and water soluble polymers of all types. Examples of water soluble dispersions may include natural rubber latex, emulsion polymers of acrylic and vinyl types, as well as their copolymers. .Poly(vinyl- pyrrolidone), poly (acrylamide) and poly(vinyl methyl ether) are examples of the thickenable water soluble species. Importantly, moreover, they can thicken water itself, at pH 7.0 and higher, a unique property which may be attributed to the high molecular weight of the terpolymers. Another property which may contribute to this phenomenon. is the uniquely high acid content of the terpolymers. The viscosity of a solution at pH 7.0 which contains as little as 0.5% (total solids basis) of the terpolymer emulsions of the invention can be as high as 2000 cps or more as compared to the few hundred centipoiSe viscosities obtained by thickeners made under different circumstances.

Only a relatively small amount of the terpolymer latices of the present invention is required to produce significant thickening of the materials with which such terpolymers are blended. Such blends can contain from 0.1 to 5% of the terpolymer latex on a total solids basis and preferably from 0.5 to of the terpolymer latex on a total solids basis.

The important feature of this invention is that the terpolymers are prepared as low viscosity emulsions. Therefore, they act as "in situ" thickening agents. By 'the term "in situ?' --as it is used herein-- is meant that a system of high viscosity is prepared by adding a low viscosity acid latex to a low viscosity alkaline solution or dispersion, and blending the two ingredients into a uniform system. Of course, the latter ingredient.can also be neutral or -even slightly acidic, in which case, the high viscosity may be åchieved by simply adjristing the pH of the blend above the neutral point. This is a distinct advantage -òver the -use of known thickening agents which are generally stored and -used as high viscosity solutions. As a contrast, the latices of this invention are of very low viscosity (usually less than !50 cups).

Therefore, they can be stored and handled with ease. While water solúble polymers and insoluble dispersions to be thickened by the terpolymer latices of the invention, are most conveniently used for the backing of upholstery and carpet fabrics, they may also be used for coating, impregnating, cementing, laminating textiles and for dressing,-sizing alid finishing of paper, leather, felts and the like. The aqueous solutions and dispersions to be thickened may contain other substances suitable to enhance the properties of the thickened system, such as fillers, pigments, stabilizers, curing agents, binders. foaming agents, dyes and other such additives. They are applicable also in the thickening of cosmetic preparations such as creams, lotions and hair grooming aids. They may be used as thickening agents also of paints, printing inks, detergents and cleaning compositions.

The terpolymers employed herein can be made more water soluble through the addition of a base such as sodium hydroxide or ammonium hydroxide. The anionic polyelectrolytes prepared by this fashion are useful as thickeners, dye leveling agents, anti-migrants, flocculants, sewage treatment aids, protective colloid agents, drilling mud stabilizers and in other fields of application.

The following examples are provided to illustrate the principles and practice of the invention. All amounts and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.

Example 1. (Method of Testing for Thickening Carboxylated Butadiene-Styrene Latices).

A 400 ml beaker was tared on an electric top-loading balance. and 200 gms carboxylated butadiene-styrene latex (GAF-14()0 available from GAF. Corporation, Chattanooga, Tennessee; "GAF" is a Registered Trade Mark) was weighed in it with 0.05 gram accuracy.

(The solid content of the latex was 50%). After that, the sample to be tested was weighed in a 100 ml beaker, under similar conditions. (The solid content of the sample has been -determined previously). The amount of the sample was made to give exactly 1.0 gra polymer solids. To this sample, distilled water was added to make the- total weight of the sample 80.0 grams. The 400 ml. beaker holding the butadiene-styrene latex was placed under an electric stirring apparatus equipped with a Teflon-lined. three-blade stirrer of 1/4 inch diameter. ("Teflon" is a Registered Trade Mark). The beaker rested on a lab jack in such a way that the tip of stirrer was 1 inch above the bottom of the beaker. Agitation was started with 800 RPM, and the diluted sample was added to the latex in 15 seconds. The agitation continued for exactly three minutes while moving the beaker slowly up and down to insure uniform mixing. After that, the beaker was removed and- the viscosity of the thickened latex was determined immediately with an LVF Brookfield viscosimeter using Spindle #4 at 12 RPM.

This method was found to give a reproducibility of + 100 centipoise or better.

Example 11. 66/28/6 Methacrylic Acid-Ethylacrylate-Styrene Terpolymer Apparatus: 3 liter resin kettle, equipped with mechanical stirrer, reflux condenser, thermometer and gas inlet tube.

Procedure: Under a blanket of nitrogen, the ingredients of the reaction were charged with agitation, in the following order: 1626.6 g. distilled water, 9.9 g. Siporiate DS-10, 25% (dodecyl ben zene sodium sulfonate of Alcolac Co.,).

7.4 g. n-butanol.

325.7 g. methacrylic acid, 138.1 g. ethylacrylate, 29.6 g. styrene 0.016 g. divinylbenzene (6üC/c) 1.97 g. of a 10% ammonium persulfate solution and 3.29g. of a 0.1% ferrous sulfate solution.

At this point, the agitation was stopped and 2.46 g. of a 10% solution of concentrated sodium hydrosulfite (Lykopon available from Rohm & Haas Co.) was introduced. Five minutes later, slow agitation was started. as slight temperature rise (from 25 C. to 25.5 C.) signaled that the reaction had already begun. Five minutes later, at 260C., the speed of the agitation was adjusted to 150 RPM. After that, the temperature rose steadily and it peaked at 63 C. Finally, the system was allowed to cool to room temperature, and the product, a free flowing milky latex was discharged through a 100 mesh screen, U.S. Standard Sieve Scale.

Examples 111- Xl Apparatus and Procedure for testing and preparation as described in Examples I and II.

Ratio of Methacrylic Acid-Ethylacrylate-Termonomer: 66/28/6. Details of termonomer, reaction time and results of Examples II-XI are Summarized in Table II Attention is drawn to our co-pending applications 1118/78 [Serial No. 1595248] and 520/78 [Serial No. 1595605].

TABLE II Reaction Turbid- Surface Intrinsic Viscosity cps.

Time itv Tension Viscosity* GAF 1400*** Example Termonomer Mins. * dyn/cm II Styrene 20 3.091 56.6 12.7 18.600 III Acrylamide 30 2.550 56.5 13.9 14,000 IV Acrylonitrile 45 2,515 54.5 13.4 11,750 V n-Butyl Vinyl 12 2,750 52.5 11.9 9,900 Ether VI iso Butyl Vinyl 18 2,923 52.3 12.0 8,200 Ether VII Vinyl Pyrroli- 360 2.357 53.8 12.0 6,950 done VIII Diethyl Maleate 33 2.762 50.7 14.7 6,800 IX Ethylhexyl Acid 20 2,678 42.3 14.0 5,800 Maleate X Triethoxy Vinyl 40 2,923 52.3 5.0 3,600 Silane XI Vinyl Acetate 27 2,780 57.3 9.2 3,430 Higher numbers indicate smaller particle size.

Determined in 0.2 molar NaCl solution at 25 C.

Carboxylated Butadiene-Styrene Latex. Viscosity determined as described in Example 1.

Claims (6)

WHAT WE CLAIM IS:

1. A stable aqueous emulsion of a terpolymer prepared by inducing in a reactor emulsion polymerization of monomers comprising (1) from 30 to 85 wt.% of an -unsaturated acid of the formula:

wherein R is methyl or ethyl (2) from 5 to 50 wt. % of an alkyl ester of an a,p -unsaturated acid of the formula:

wherein Kl is alkyl of ftom 1 to K carbon atoms and K2 is hydrogen, methyl or ethyl. and (3) from 0.5 to 20 wt. % of an ethylenically unsaturated organic termonomer which is different from and copolymerizable with monomers (1) and (2) to form a stable latex and which is further characterized in that the probability of acid-acid linkages of the terpolymer formed bv the polymerization of said termonomer with monomers (1) and (2) is less than 81%, wherein all the ingredients necessary for the polymerization are present in the reactor upon initiation of the polymerization.

2. A terpolymer emulsion according to claim 1 in which monomer (1) is methacrylic acid, monomer (2) is a C1 to C4 alkyl ester of acrylic acid or methacrylic acid, and termonomer (3) is a compound of the formula:

wherein R3 is hydrogen, methyl, ethyl or halogen, XX is hydrogen or C1-C18 alkoxycarbonyl and X2 is aryl, aminocarnonyl, cyano, CI-C4 alkoxy, carboxyl, C1-C18 alkoxycarbonyl, halo, acyl, acyloxy, aldehyde, a keto-containing group, isocyanato, C.7-C9 heterocyclic, C2-C4 alkenyl, Cl-C4 alkyl, halomethyl, acetomethyl, a sulfo-containing group, tri(C1-C4 alkoxy)silyl or hydrogen.

3. A terpolymer emulsion according to claim 1 in which monomer (1) is methacrylic acid, monomer (2) is ethyl acrylate, and termonomer (3) is styrene, acrylamide, acrylonitrile, C1-C4 alkyl vinyl ether, vinyl pyrrolidone, dialkyl (CI-C18) maleate, mono-alkyl (C1-C18) maleate, trialkoxy (C,-C4) vinyl silane or vinyl acetate.

4. A terpolymer emulsion according to any of claims 1 - 3 in which monomer (1) is present in an amount ranging from 50 wt. % to 70 wt. %, monomer (2) is present in an amount ranging from 20 wt. % to 30 wt. %, and termonomer (3) is present in an amount ranging from 3 wt. % to 8 wt. %.

5. A terpolymer emulsion according to any of claims l - 4 which is prepared by a redox-initiated polymerization reaction.

6. A terpolymer emulsion substantially as described in any one of Examples II to Xl herein.