GB2127836A - Polymeric thickener - Google Patents

Abstract

Copolymers useful as paint thickeners comprise: (I) 5-45 percent of a monomer of the formula ROCACOG where G is -(OCH2CH2)pOC6H4(CnH2n+1); p is an integer from 10 to 70; n is an integer from 4 to 20; R is hydroxy, C2-C8 alkoxy, or G; and A is C2-C8 alkenylene; (II) 20-50 percent of at least one monomer which is either of the formula CH2=CR<1>R<2> wherein R<1> is C2-C9 alkoxycarbonyl, C2-C3 hydroxyalkylamido or cyano, and R<2> is hydrogen or methyl, or is an unsaturated C4-C10 dibasic acid di- esterified with C1-C5 aliphatic alcohols, (III) 30-70 percent of a monomer which is either of the formula CH2=C(R<3>)COOH wherein R<3> is hydrogen or methyl, or is a C4-C10 unsaturated dibasic acid or such dibasic acid being mono-esterified with C1-C8 aliphatic alcohol; the total percentages of (I), (II), and (III) being 100, all by weight. A typical copolymer is formed from (I) nonylphenyl polyethylene oxide maleate, (II) butyl acrylate and (III) methacrylic acid.

Description

SPECIFICATION Polymeric thickener 1. FIELD OF INVENTION This invention relates to a polymer composition useful as thickener for latex based paints.

2. BACKGROUND OF THE INVENTION In recent years, latex paints, i.e., paints based on aqueous dispersions of synthetic organic polymers, have come into widespread use because they can be easily applied, easily cleaned from brushes and rollers, and because they are generally free of objectionable odor.

Materiais known as thickeners are commonly used in latex paints, as well as a variety of other coating compositions, to provide thickening effects. An effective thickener should be used in a minimum amount and should not affect the basic properties of the aqueous coating composition in which it is used.

There are many types of thickeners now used in paints and other coating compositions. Watersoluble materials employed as thickeners include naturai gums and resins, such as starch, gum, arabic, modified starch products, dextrins, sodium alginates, gums such as tragacanths and other such compounds. Synthetic materials employed as thickeners include carboxymethyl cellulose, poly(vinyl alcohol), polyacrylamide, poly(acrylic acids) and salts thereof, methylcellulose and other cellulose derivatives, such as carboxymethyl cellulose and hydroxyethyl cellulose, poly(vinylpyrrolidone), poly(vinyl methyl ether), poly(ethylene oxide) and vinyl methylether-maleic anhydride copolymers.

Thickeners of the polyelectrolyte type include synthetic polymeric water-soluble thickeners, such as the sodium polyacrylates as well as the copolymers of various acrylates, such acrylic thickeners being described more particularly in U.S. Patent Nos. 2,883,381,2,956,046, 3,054,004 and 3,436,378.

Water soluble polyelectrolyte copolymers employed as thickeners include those esters prepared by the esterification reaction between the acid anhydride groups of a copolymer of an alkyl vinyl ether and maleic anhydride with the terminal hydroxyl groups of an alkylphenoxy(polyethoxy)ethanol (APEE).

The resulting water-soluble polymer is a partial ester which contains free acid groups suitable for subsequent neutralization with a basic material, such as an amine or a metal oxide or hydroxide. The water-soluble polymeric esterification materials are employed as emulsion stabilizers, thickeners and film formers. Interpolymers prepared by the reaction of maleic anhydride with vinyl monomers, which interpolymers are useful as thickeners, are described in U.S. Patent No. 3,499,876.

Water-soluble, polymeric surfactant thickeners comprising a copolymer of an ester of an alkylarylpolyether alcohol with an unsaturated carboxylic acid compound are described in U.S. Patent No. 3,708,445. The specification describes these copolymers as containing 70 to 95% of the ester and 5 to 30% of the acid.

In U.S. Patent No. 4,138,381 a polymeric thickener is disclosed which uses an acrylate or a methacrylate of APEE. The other monomers of the copolymers include at least one unsaturated carboxylic acid of three to six carbon atoms and an alkyl acrylate or alkyl methacrylate wherein the alkyl group is from one to 30 carbon atoms.

In United Kingdom Patent No.1,276,271 a polymeric thickener is disclosed in which less than 65% of the monomers are methacrylic acid and an ester of ethylenically unsaturated carboxylic acid anhydride and APEE. This reference teaches that the resultant product contains at least 35% by weight of styrene and/or butadiene.

U.S. Patent No. 3,794,608 teaches the use of vinyl benzyl ether derivatives of a nonionic surfactant as a monomer.

U.S. Patent No. 3,301,829 teaches the preparation of a maleic anhydride copolymer with a vinyl monomer and then reacting such copolymer with APEE. The resultant polymer spine is different and distinct from the copolymer of the instant invention.

United Kingdom Patent 1,523,408 discloses a copolymer of acrylamide, APEE acrylic or maleic acid ester and acrylic acid. No acrylamide is employed in this invention.

SUMMARY OF THE INVENTION According to the present invention there is provided an improved copolymer containing (1) 5-45 percent of a monomer of the formula ROOCACO(OCH2CH2)pOC6H4(CnH2n+1), wherein A is C2-C8 alkenylene, R is hydrogen or C2-C8 alkyl, n is an integer from 4 to 20, and p is an integer from 10 to 70, (Il) 20-50 percent of at least one monomer of the formula CH2=CR1R2 wherein R1 is C2-C9 alkoxycarbonyl, C2-C3 hydroxyalkylamido or cyano and R2 is hydrogen or methyl, or (II) is an unsaturated C4-C10 dibasic acid di-esterified with C1-C8 aliphatic alcohols; (III) 30-70 percent of a monomer of the formula CH2=C(R3)COOH wherein R3 is hydrogen or methyl or (III) is a C4-C10 unsaturated dibasic acid or such dibasic acid mono-esterified with C1-C8 aliphatic alcohol; the total percentages of monomers (I), (II) and (III) being 100, all by weight.

DETAILED DESCRIPTION OF THE INVENTION This invention provides polymeric thickeners which, when added to coating compositions such as latex paints, will provide improved flow, leveling (after shear) sag resistance and resistance to oxidative degradation. The invention provides especially improved leveling at high paint viscosity along with resistance to sag without affecting other desirable properties such as gloss.

The polymeric thickening agent consists essentially of (1) 5-45 (preferably 1 0-40) percent of at least one monomer of the formula ROCACOG wherein G is -(OCH2CH2)OC8H4(CH2+1); p is an integer from 10 to 70; n is an integer from 4 to 20; R is hydroxy, C2-C8 alkoxy or G, and A is C2-C8 alkenylene; (Il) 20-50 (preferably 24-36) percent of at least one monomer of the formula CH2=CR1R2.

wherein R1 is C2-C9 alkoxycarbonyl, C2-C3 hydroxyalkylamido or cyano, and R2 is hydrogen or methyl, or (II) is an unsaturated C4-C10 dibasic acid di-esterified with C1-C8 aliphatic alcohols; (III) 30-70 (preferably 36-54) percent of a monomer of the formula CH2=C(R3)COOH wherein R3 is hydrogen or methyl or (III) is a C4-C10 unsaturated dibasic acid or such dibasic acid being monoesterified with C1-C8 aliphatic alcohol; the total percentages of monomers (I), (II) and (III) being 100, all percentages being by weight.

Useful type (III) monomers are acrylic acid, methacrylic acid, ethylacrylic acid, crotonic acid, and dibasic acids such as maleic, fumaric, or itaconic acid or their partial esters where the alcohol derived portion of the ester is C, through C8 hydrocarbons. Methacrylic acid and acrylic acid are especially preferred.

Useful monomers of type (II) are butyl acrylate, methyl acrylate, methyl methacrylate, methacrylonitrile, methylolacrylamide, hydroxymethyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, esters of unsaturated dibasic acids such as maleic, fumaric, or itaconic acid where the alcohol derived portion of the ester is a C, through C8 hydrocarbon. Butyl acrylate is preferred.

The type (I) monomer described above wherein R is hydroxy is preferred, based on maleic acid, fumaric acid or itaconic acid.

The polymeric thickeners of the invention have a number of advantages. They are stable and compatibie thickeners for latex systems. Thickener properties can be controlled through compositional variation providing the latex systems with the desirable balance of properties. For example, the high shear rate viscosity (control of film build and brush drag), the medium shear rate viscosity (control of brush load and dripping) and low shear rate viscosity (control of flow and leveling and sag resistance) can be adjusted to the desirable range depending on the type of latex, e.g., paint, prepared, i.e., wall paint, house paint, trim paint, etc. A high shear rate is greater than 5,000 sec1, a medium shear rate is in the range of 50-300 sec-1 and a low shear rate is lower than 10 sec-1.

All the polymeric thickeners disclosed in the examples were prepared by conventional latex polymerization techniques using the following recipe: Water 900 Mixed Monomers 250 Dioctyl ester of sodium sulfosuccinate* 3.9 ml of 75% aqueous solution n-Butyl Alcohol 4.3 ml Potassium Persulfate (2% solution) 40 ml initially 60 ml continuously * Aerosol [trademark] OT.

The water is charged to a N2 flushed, resin kettle equipped with thermometer, addition funnels, stirrer, and reflux condenser, and the water was heated to 780C. The initial charge of persulfate is added when the reactor temperature is above 650C. The monomers are mixed with the Aerosol OT and butyl alcohol. This mixture and the remaining persulfate are added from separate dropping funnels over two hours. After the addition is complete the reaction is stirred for an additional 2 hour at about 780C. Ten drops of formaldehyde is added as a biocide. The resulting latex is then cooled and filtered through a double layer of cheese cloth.

In a few cases, especially at high type (I) monomer levels, the latex is not completely stable. In these cases the thickener was diluted and neutralized with NH4OH to a pH 7 before evaluation in paint.

Alternatively, the latex may be stabilized with additional surfactant, if necessary.

The type (I) monomer may be made as follows: APEE is reacted with an equal molar amount of maleic anhydride in refluxing toluene. Water is removed as an azeotrope using a Dean-Stark tube. The reaction is allowed to continue for one day until the maleic anhydride infrared adsorptions at 1 790 and 1 850 cm-1 are replaced by the maleic ester band at 1 740 cm-'. The toluene is removed by vacuum distillation.

The thickeners were compounded into paint and evaluated in an acrylic paint formula as follows: A masterbatch was prepared on a Cowles [trademark] Model 1-VG mixing machine by adding the TiO2 to propylene glycol and dispersant. The TiO2 was dispersed for 10 minutes at 3900 RPM until the particle size (as determined by ASTM D-1 210-64) was 7.5 N.S. The remaining ingredients were then added with stirring at reduced speed.

MASTERBATCH Propylene Glycol 65 Dispersant* 8 Gloss Grade TiO2 275 Water 25 CMP Acetate (Mercurial biocide) 1 Carbitol Acetate 15 Defoamer 2 Acrylic Latex (Rohm s Haas) 550 941 * Bisulfite terminated acrylonitrile-acrylic acid co oligomer; Polywet [trademark] ND-2.

The Masterbatch was used to prepare the following paint formulations: Control* Test Paint Masterbatch 941 941 Hydroxyethyl cellulose (3% aqueous solution) 125 Water plus experimental thickener latex - 125 (NH4OH (28%) to adjust pH to 8.0) * Example 8 in Table II.

EXAMPLES Table I shows the compositions of several thickeners prepared from an acrylic ester and methacrylic acid with APEE-maleates wherein the phenyl group carries various alkyl substituents.

Examples 1 and 3 are outside this invention. Example 1 contains less than 30% acid and Example 1 and 3 contain more than 45% APEE-maleate.

These thickeners were used to prepare paints described previously, and the paint properties are shown in Table II along with a hydroxyethyl cellulose (HEC) control. A significant improvement in leveling is observed using the compositions of this invention in comparison to the HEC control.

In general there is a correlation between paint viscosity and leveling. More viscous paints level more poorly than less viscous paints. Thus the paints with a higher viscosity than the control which also show greatly improved leveling are truly remarkable. (Such as Examples 10, 12 and 14-1 7.) The viscosity of the paint may be controlled by the amount of the thickener used.

TABLE I Composition of Composition of THICKENER APEE MALEATE by wt. % Example Alkyl* Moles Ethylene APEE Butyl Methacrylic No. Group Oxide Maleate Acrylate Acid 1 OCTYL 40 50 30 20 2 OCTYL 40 20 48 32 3 OCTYL 70 50 20 30 4 NONYL 40 10 36 54 5 NONYL 40 20 32 48 6 NONYL 40 40 24 36 7 NONYL 40 20 32** 48 * Substituent on phenyl moiety.

** Ethyl acrylate.

TABLE II Viscosity Use Overnight Overnight Example Level Wt Unsheared Sheared* Level- Gloss Thickener (dry)/qt pH KU KU ing** Sag* (600) 8(1) HEC 3.75 8.6 90 83 2 10 69 9 1 8.6 77 70 4 10 55 10 2 11.8 9.5 100 90 8 10 66 11 3 17 8.6 85 76 3 10 66 12 4 19 8.6 110 104 6 10 62 13 6 4.5 9.4 72 68 8 10 48 14 7 19 8.5 120 116 5 10 71 15 5 22 8.7 138 124 6 10 72 16 5 15 8.5 110 103 8 10 70 17 5 12 8.5 106 100 8 10 67 18 5 8 8.5 94 87 8 9 66 KU = Krebs Units.

* Sheared - Stirred 5 minutes prior to evaluation.

** According to Leneta method.

(1) Control (outside invention).

As a further comparison of the compositions of this invention with the compositions described in U.S. Patent No. 4,238,383 (Example 20) and U.K. Patent No. 1276271 (Example 21) the following experiments were conducted essentially according to the above procedure: TABLE Ill Example 19 20 21 Alkyl Group* nonyl nonyl nonyl Moles of Ethylene Oxide 40 40 40 Polymerizable functional group maleate acrylate maleate % APEE Monomer 20 20 20 Methacrylic Acid 48 48 48 Butyl acrylate 32 32 Styrene - - 32 I * Substituent on phenyl moiety of type (I) monomer.

The acrylic ester of APEE was prepared by the following method: 100 g of a nonylphenol-40 mole ethylene oxide adduct, 2 g of phenolthiazine, 0.5 g nitrobenzene, and 300 ml of ethyl acrylate were charged to a round bottom flask equipped with a 10 inch (25.4 cm) Vigerou column and a distilling head. Approximately 20 ml of distilate were collected and discarded with the vapor temperature reaching 940C to remove ethanol and water. The reaction mixture was cooled, and 2.5 ml of catalyst TYZOR [trademark] TPT (tetraisopropyl titanate)) was added. The reaction mixture was distilled for 2 hours at vapor temperature of 81 94o C. The reaction product was flocced in hexane, dissolved in acetone, and reflocced in hexane. The flocculated material was then washed with 300 ml hexane saturated with monomethyl ether of hydroquinone [less than 1 9/300 ml] and dried. The presence of the acrylic double bond in the product was confirmed by nuclear magnetic resonance analysis.

These compositions were evaluated in a latex paint by the method previously described. The paints were all made to essentially the same viscosity, and results are shown in Table IV.

TABLE IV Thickener from Example 19 20 21 Paint Viscosity Unsheared KU 93 93 102 Sheared KU 88 87 90 Leneta Leveling 8 2 4 Leneta Sag 10 10 10 60 Gloss 65 37 59 The data demonstrate the superior results obtained with the compositions of this invention over those taught by the above two references especially with regard to leveling and gloss.

Claims (6)

1. A polymer composition comprising (i) 5-45 percent of a monomer of the formula ROCACOG where G is -(0CH2CH2)pOC6Ha(CnH2n+1); p is an integer from 10 to 70; n is an integer from 4 to 20; R is hydroxy, C2-C8 alkoxy, or G; and A is C2-C8 alkenylene; (ii) 20-50 percent of at least one monomer of the formula CH2=CR1R2 wherein R' is C2-C8 alkoxycarbonyl, C2-C3 hydroxyalkylamido or cyano, and R2 is hydrogen or methyl, or (ii) is an unsaturated C4-C10 dibasic acid di-esterified with C1-C8 aliphatic alcohols; (iii) 30-70 percent of a monomer of the formula CH2=C(R3)COOH wherein R3 is hydrogen or methyl or (iii) is a C4-C10 unsaturated dibasic acid or such dibasic acid being monoesterified with C1-C8 aliphatic alcohol; the total percentages of (i), (ii) and (iii) being 100, all by weight.

2. A polymer composition according to claim 1 wherein (i) is 1 0-40 percent by weight, (ii) is 24-36 percent by weight and (iii) is 36-54 percent by weight.

3. A polymer composition according to claim 1 or claim 2 wherein (iii) is selected from acrylic acid, methacrylic acid, ethylacrylic acid and crotonic acid and dibasic acids.

4. A polymer composition according to any of the preceding claims wherein (ii) is selected from butyl acrylate, methyl acrylate, methyl methacrylate, methacrylonitrile, methylol acrylamide, hydroxymethyl methacrylate, esters of unsaturated dibasic acids such as maleic, fumaric, or itaconic acid where the alcohol derived portion of the ester is a C1 through C8 hydrocarbon.

5. A polymer according to any of the preceding claims wherein R of monomer (i) is hydroxy and A is C2-C3 alkenylene.

6. A method for thickening a latex paint comprising adding the composition of any of the preceding claims to a latex based paint.