[1]3 @ 4 2 6 @ 0 0 4 Utlited States Patent Office Patented Feb. 4, 1969 3,426,004 CROSSLINKED ACRYLIC ACID INTERPOLYMERS Frank A. Wagner, Avon Lake, Ohio, assignor to The B. F. Goodrich Company, New York, N.Y., a corporation of New York 5 No Drawing. Filed Jan. 13, 1965, Ser. No. 425,32@8 U.S.,Cl. 260-80.3 13 Claims Int. Cl. C08f 3144,3146,- C09j 3114 lo ABSTRACT OF THE DISCLOSURE Interpolymers prepared by the interpolymerization of acrylic or metbacrylic acid with a polyallyl phosphate or polyallyl phosphite have been found to be improved thickening or suspending agents useful for mucilaginous 15 applications having superior sbear resistance. These polymers are insoluble but swellable in water and the maximum thickening is achieved by treating the aqueous suspension of the polymer with a neutralizing agent. 20 This invention relates to new, crosslinked, water-insoluble, acrylic acid interpolymers derived from a monomeric mixture cornprising acrylic acid and a polyunsat- 25 urated organic phosphate compound, and to methods for the preparation of the interpolymers. More particularly, this invention corcerns crosslinked interpolymers comprised of at least 10% by weight of acrylic or methacrylic acid or mixtures thereof, a minor amount of a polyallyl 30 phosphate or phosphite ester, and optionally one or more monoolefinically unsaturated compounds co polymerizable therewith. Various types of synthetic resins are known which are crosslinked interpolymers of acrylic or methaerylic acid 35 or mixtures of said acids with a minor amount of a polyunsaturated compound having a plurality of terminally unsaturated polymerizable groups, e.g., about 0.5 to about 2.5% by weight of the polyunsaturated crosslinking monomer based on total interpolymer weight. For exarn- 40 ple, U.S. Patent No. 2,798,053 describes crosslinked copolymers of acrylic or metbacrylic acid with said minor amounts of vinyl, allyl and methallyl ethers of polyhydric alcohol,S having at least four carbon atoms and at least three alcoholic hydroxy groups, wherein the preferred 45 polyalkenyl polyether monomers are polyallyl sucrose and pplyallyl pentaerythritol, desirably containing an average of at least about 3 allyl groups for each - molecule of suc 4 rose or pentaerytbritol, the allyl groups attached ro thereto by means of ether linkages. U.S. Patent NO. 2,8581?81 describes acrylic acid copolymers containing crosslinking monomers which are the polymeric, - benzenesoluble products resulting f rorn Na or K polymerization of diolefins, preferably conjugated dienes. These - polymers 55 have a very large proportion of 1,2 structures in the chain and consequently have a plurality of CHi= side groups which can be copolymerized with the acrylic acids. U.S. Patent No. 2,958,679 discloses crosslinked copolymers of acrylic acid and polyallyl or polymethallyl trimethyl- 60 ene trisulfones. U.S. Patent No. 2,985,631 discloses copoly,mers of acrylic acid and the polyvinyl, polyallyl or polymethallyl silanes or the corresponding tin compounds, tetrallyl or tetravinyl silane or tin being preferred. The aforedescribed interpolymers, other similarly con- 65 stituted crosslinked carboxylic interpolymers, and the interpolymers embodied in the present invention, and their salts (i.e., sodium, ammonium, and amine salts) are characterized by being insoluble in water but capable of swelling rapidly to a high degree therein; they are capable 70 of thickening water at extremely low concentrations of the interpolymers to form a heavy mucila@ge or gel. These 2 interpolymers and their salts also are in.soluble in aliphatic and aromatic hydrocarbons but they are solvent-sensitive and can thicken non-polar solvents under certain conditions although with comparatively less effectiveness than in the thickening of water. These crosslinked carboxyliccontaining interpolymers are useful for preparing printing pastes, auto polishes and cleaners, household polishes and cleaners, cosmetic preparations such as hair creams and pastes, gelled hand cleaners, carrying agents, sand suspensions in oil and water well treatment, and thickening of flood water for secondary crude oil recovery. The advantage of the interpolymers of this invention is the capability of the interpolymers and their salts to thicken water to form i,-encrally heavier mucilages and gels than the previously known crosslinked carboxylic interpolymers, at low and comparative concentrations of polymer. Moreover, the mucilages prepared with the interpolymers of this invention, in general, have greater clarity, i.e., are more transparent, and the mucilages exhibit more stability upon aging, at times even shown a viscosity increase with a.-e. The crosslinked interpolymers of this invention are composed of (A) At least 10% by weight of polymerized units of acrylic acid or methacrylic acid or mixtures thereof; (B) From O' I to 2% by weight of polymerized units of a polyallyl phosphate or polyallyl phosphite ester crosslinking monomer, or mixture thereof, conforn-iin@g to the formulae: R 0 Ri CTT2@c CH2--O-@-O-OH2-C=@H2 I L) I U2 and R RI I R2 wherein R and RI are independently selected from the group consisting of a hydrogen atom and a methyl radical, and R2 is selected from the group consisting of a hydrogen atom, an allyl radical, a methallyl radical, an alkyl radical, an aralkyl radical, an aryl radical and an alkaryl radical; and (C) From 0 to 89.9% by weight of polymerized units of one or more other monoolefinically unsaturated monomers copolymerizable with the acrylic or methacrylic acid and the polyallyl phosphate ester crosslinking monomer. (It is, of course, understood that the total of components (A), (B) and (C) equals 100%.) Representative examples of suitable crosslinking monomers include triallyl phosphate, diallyl monohydrogen phosphate, dimethallyl monohydrogen phosphate, diallyl monomethyl phosphate, diallyl monophenyl phosphate, diallyl mono(4- ethylphenyl)phosphate, diallyl monobenzyl phosphate, etc. and the corresponding phosphites. The allyl phosphates(ites) can be prepared by classical methods that are known in the art and certain of these compounds are commercially available. Triallyl phosphate and triallyl phosphite are preferred crosslinking agents. Typical examples of other monoolefinically unsaturated monomers copolymerizable with the acrylic acids and the crosslinking monomers are other polymerizable alpha, beta-unsaturated carboxylic acids such as ethacrylic acid, chloroacrylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, glutaconic acid and the like. Other representative olefinically unsaturated copolymerizable monomers are acrylamide, methacrylamide, N-methyl
[2]3,426,004 3 acrylamide, N-ethyl acrylamide, N-t-butyl acrylamide, styrene, ethylene, isobutylene, acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, the propyl acrylates, butyl acrylates, amyl acrylates, hexyl acrylates, heptyl acrylates, octyl acrylates, methyl methacrylate, methyl ethacrylate, vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, isopropenyl propionate, isopropenyl butyrate, vinyl benzoate, isopropenyl benzoate, vinyl pyridines, vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene bromide, methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, methyl vinyl ketone, ethyl vinyl ketone, methyl isopropenyl ketone, dimethyl maleate, diethyl maleate, dimethyl fumarate, diethyl fumarate, and others. The preferred carboxylic interpolymers of this invention contain at least 50% by weight of acrylic or methacrylic acid or mixtures thereof, from 0 to 49.9% of one or more of the other monoolefinically unsaturated monomers and 0.1 to 2% of the polyallyl monomer. At least 90% of acrylic acid and 0 to 9.9% of the other olefinically unsaturated compounds are more preferred. The range of the polyallyl phosphate(ite) in the interpolymer for producin- a resin havin@ the best water-thickening properties is from about 0.75 to about 1.25% by weight. Thiis, the most preferred interpolymers consist of 98 tO 99-9% of acrylic acid and 0.1 to 2% of triallyl phosphate, and even more desirable are those of 98.75% to 99.25% of acrylic acid and 0.75 to 1.25% of triall3il phosphate. The preferred method of preparation of the interpolymers of this invention is the polymerization of the mixture of tieir constituent monomers in an inert organic diluent having some solubilizing action on one or more of the monomeric ingredients but siibstantially none on the resultant interpolymer. Polymerization in mass may be employed, but is not preferred because of the difficulty in working up the solid polymeric masses obtained. Polymerization in an aqueous medium containin- a w-,itersoluble free-radical catalyst is an operative method but is less desirable than polymerization in the organic inert diluent. In aqueous polymerizations, the product is recovered either as a granular precipitate or as a hi,-hly swollen gel, either of which may be used directly or further subdivided and dried. As above-mentioned, polymerization in an organic liquid diluent which may be a solvent for the monomers but is a non-solvent for the interpolymer, or in a mixture of such solvents, in the presence of a solvent-soluble freeradical catalyst such as benzoyl peroxide and azobisisobutyronitrile is most preferred because the product is usually obtained as a very fine friable and often fluffy precipitate which, after solvent removal, seldom requires grinding or other furlber treatment before use. Suitable diluents include benzene, toluene, xylene, ethyl benzene, tetralin, hexane, heptane, octane, carbon tetrachloride, methyl chloride, ethyl chloride, ethylene dichloride, bromotrichloro methane, chlorobenzene, acetone, methyl ethyl ketone, and others, and mixtures of these and other solvents. The polymerization in the diluent medium may be carried out in the presence of a freeradical catalyst in a closed vessel containing an inertatmosphere and under autogenous pressure or artifically-induced pressure, or in an open vessel under reflux at atmospheric pressure. The temperature of the polymerization may be varied from O' C. or lower, depending on the freezing point of the diluent, to 100' C. or higher, more preferably from 20' to 90 C., the temperature depending to a large degree upon the activity of the monomers and catalyst used and the mofecular weight desired in the polymeric product. The molecular weights of the product interpolymers are greater for those made in the lower temperature range than for those made in the higher temperature range. Polymerization at 50' to 90' C. under atmospheric pressure using a free-radical catalyst generally gives a polymer yield of 90 to about 100% of theory in IQ55 than 20 hours, usually 4 in less than 6 hours. Suitable free-radical catalysts include peroxides such as sodium, potassium and ammonium persulfates, caprylyl peroxide, benzoyl peroxide, and pelargonyl peroxide, hydrogen peroxide, ctimene hydroperoxides, tertiary butyl 4LIiperphthalate, tertiary butyl perbenzoate, sodium peracetate, sodium percarbonate and the like as well as azobisi sobutyronitrile and others. Other useful catalysts are the so-called "redox" type of catalyst and the heavymetal activated catalyst systems. General10 ly, from about 0.1 to 2.5% by weight or more of catalyst based on monomers wei,- ht is sufficient in the process of the present invention. Polymerization may also be induced by radicals formed in the polymerization system by nuclear rad;ation, Xrays and ultra-violet radiation. '@olymers of this invention are high molecular 15 The inter weight resins but the actual molecular weights thereof are difficult to measure. It is believed that the molecular weights of the linear carbon chain structural portions of the interpolymers are in the range of about 100,000 to 20 about 300,000, however, the crosslinking monomer units therein are believed to bring the molecular weigbts of the interpolymers into the range of about 2,000,000 to 3,000;000 or higher. As previously stated, the interpolymers of this inven25 tion are especially useful in soft, mucilaginous aqtieous compositions containing a small amount of the interpolymer, e.g., in the ra,-ige ol. about 0.05% to about 2%, preferably about 1 %, by weight of the gel. The swollen interpolymers generally do not attain their maximum volume 30 in water until a portion of the free carboxyl groups in said interpolymers are converted to an alkali, ammonium or amine salt. It therefore is advantageous to neutralize the interpolymer while it is being dispersed in the aqueous coniposition to a pH in the ran,-e of 3 to 35 12, desirably to a pH of about 7. The neutralizing agent may be a monovalent alkali such as sodium, potassium, lithium or ammonium hydroxide or the carbonates and bicarbonates thereof, or mixtures of the same, or an amine base having not more than one primary or sec40 ondary amine group per molecule. Typical amine neutralizing agents are monoethanol amine, triethanol amine, diisopropanol amine, triethyl amine, the octyl, dodecyl, tetradecyl, hexadecyl, octadecyl, arachic, lauroleic, myristoleic, palmitoleic, oleic, erucic, linoleic, eleostearic, linolenic, didodecyl, ditetradecyl, diocatadecyl, dicoco, di45 (octadecenyl-octadecadienyl) trioctyl, tridodecyl, and tricoco amines, and the like and mixtures thereof. The examples next set forth are presented to illustrate and clarify the invention. The proportions of ingredients are given in parts by weight or weight percents unless 50 otherwise specified. EXAMPLE I A series of four acrylic acid/triallyl phosphate copolymers were prepared in benzene diluent using a con55 ventional bottle-polymerization unit. The followin.- recipe was employed. Ingredient: Parts Acrylic acid ----------------------- 98 to 99.5 Triallyl phosphate ------------------ 0.5 to 2 60 Caprylyl peroxide ------------------ 0.25 Benzene --------------------------- 900 In the above recipe the total amount of monomers was always equal to 100 parts. The polymerizations were 65 carried out at 7G' C. under a nitrogen atmosphere for about 20 hours to obtain a conversion of monomer to polymer of 95 %. The reaction product was in the form of a thick slurry from which the copolytner was recovered by filtration. The filter cake was washed with fresh ben70 zene and dried at about 50' C. in an air circulating oven. The dried cake was a white, friable inass which was readily converted into a fine -white powder. Clear aqueous mucilages (gels) were prepared by dispersing a small a@mount of the powder in a major pro75 portion of water and neutralizing the copolymer mix.
[3]3)426)004 5 ture with a sufficient amount of 28% iammonium hydroxide solution to give a pH of approximately 7 to the final mucilage. The viscosities of the aqueous mucilages were obtained with a Brookfield rotational viscometer operated at 20 r.p.m. The viscosities are expressed here- .5 inbelow in centipoises. In the tabulation of the data a symbol indicates the measurement was not made. Viscosities of mucilages at belowPercent triallyl stated concentration of copolymer Copolyinpr pliosphate in in water 10 co_polyiner - - 0.2% cone. 0.5% cone. A ---------------- 0.5 2,100 4,400 B ---------------- 1.0 12,500 70i 000 c ---------------- l' 6 --------- -------- 30,000 D ---------------- 2. 0 ------------------ 18,000 15 EYAMPLE H In. this series of experiments the gelation efficacy of an acrylic acid/triallyl phosphate copoly@mer (Copolymer 2 0 B for Example 1) was compared to that of two commercially @available crosslinked acrylic acid copolymers, more specifically, a copolyrner of acrylic acid and 1% by weight of a polyallyl ether of sucrose having an average of about 5.8 allyl groups per each sucrose molecule. 25 hereinafter referred to as Copolymer X, @and a copolyxner of acrylic acid ard 1% by weiaht of the polyallyl ether of pentaerythritol, i.e., tetraallyl pentaerythritol, hereinafter referred to as Copolymer Y. Aqueous mucilages, which -were preparred as in Example 1, had the 30 following viscosities at the stated concentration of pcilymer in water. Viscosities Copolymer 0.250/@ conc. 0.57@ cone. 1 35 x ---------------- 3,200 34,000 64, (@00 * ---------------- 21,000 56,000 68,000 * ---------------- 16,000 54,000 128,000 Portions of the foregoing mucilages were left stand- 40 ing exposed to the norrnal light in a laboratory for one week and the viscosities were j--neasured with the following results. Viscosities Copolymer 0.25% cone. 0.5% cone. 1% cone. 45 x ---------------- 3,400 32,000 Bo, 000 Y ---------------- 22,000 50,000 64, 000 B ---------------- 27,000 56,000 82,000 - Other portions of the mucila.-es were stored in the 50 dark for one month and the viscosities were then measured with these results. Viscosities Copolymer 5 5 0.25% cone. 0.5% cone. 1% Colic. x ---------------- 3,500 34,000 60,000 Y ---------------- 20,000 42,000 64,000 B ---------------- 26,000 66,000 98,000 The above data illustrate that the crosslinked carboxylic 60 polymers of this invention iii general have superior thickening properties and aqueous gels produced therewith have outstanding age-stability. The shear resistances of the mucilages at 0.5% con- 65 centration were also determined by subjecting them to the shearing action of an I 1,000 r.p.m. "Waring Blendor" for three minutes, cooling the gels to room temperature and measuring viscosity. The results, set forth beli:)W, show that the trialtyl phosphate-crosslinked acrylic acid 70 copolymer has superior shear resistance. Copolymer: viscosity after shearing x ----------------------------------- 16,000 Y ----------------------------------- 2@2,000 B ----------------------------------- 48,000 75 6 EXAMPLE III A series of seven acrylic acid/triallyl phosphate copolymers were prepared according to the procedures set forth in Example I using the folowing recipe. Ingredient: Parts Acrylic acid ---------------------- 98.7 to 99.3 Triallyl phosphate ------------------ 0.7 to 1.3 Caprylyl peroxide ------------------------ 0.25 Benzene -------------------------------- 900 Clear aqueous mucilages prepared from the ammonium salts of the cop6lymers by the procedure described in Example I had the following viscosities. Viscosities of Mueflages at Percent Triallyl Below-stated Concentratioii Copolymer Phosphate in of Copolymer iri Water Copolymer - 0.2% cone. 0.5% cone. F ----------------- 0.7 32,000 58,000 F ----------------- 0.8 36,000 80,000 G ---------------- 09 28,000 68,000 H ---------------- 1.0 30,000 68,000 JF ----------------- 1.1 14, 000 70,000 K -- ------------- 1.2 14,000 54,000 L ----------------- 1.3 ------------------ 14,000 EXAMPLES IV In this example mucilages were prepared in the manner set forth in Example I using two copolymers produced in the preceding example in accordance with this invention. These gels were compared to mucilages prepared with theaforementioned comrnercial thickeners (Copolymer X and Copolymer Y) and a copc)lymer of acrylic acid and 2.2% by weight of tetravinyl silane, hereinafter referred to as Copolymer Z. The clarit3@ of the mucilages is reported as the "percent transmission@" of light through the mucilage at a wave length of 4250 A. using a Fisher Electrophotometer. The data are presented below. Viscosities of inucilages Copolyraer 0.06% cone. 0.1% cone. 0.25% cone. 0.5% cone. x -------------- 10 35 5@ 000 30,000 Y -------------- 17.5 1,600 24i 000 62,000 Z --- 22.6 330 11,500 44,000 G -------------- 440 6,200 42,,000 64,000 i --------------- 120 4,000 24,000 42,000 Percent light transmission through the above-described Copolymer mucilages 0.05% cone. 0.1% cone. 0.25% cone. 0.5% cone. x --------------- 80 68 48 49 Y --------------- 94 85 61 88 Z --------------- 74 53 29 10 G --------------- 99 98 '74 66 ---------------- 01 81 77 40 The above results shov@ that in the majority of cases the gels prepared with the interpolymers of this invention are unexpectedly thicker iand clearer than gels produced with similar carboxylic-containing interpolymers containing other cros@linking monomers.. EXAMPLE V An interpoly@mer of acrylic acid and 1% of triallyl phosphite was prepared according to the procedure set forth in Example I from the following recipe. Parts Acrylic acid -------------------------------- 99.0 Triallyl phosphite ---------------------------- 1.0 Benzene ------------------------------------ 900 Caprylyl peroxide ---------------------------- 0.5 Ammopium hydroxide-neutralized :aqueous mucilages prepared with the copoiymer had these properties measured on the Broc>kfiel,d Viscometer at 20 r.p.m. Viscosities of mucilages, cps.: 0.2% conc - --------------------------- 14,000 0.5% cone - --------------- ------------ 20,000
