Use of acrylic acid/ethyl acrylate copolymers for enhanced clay soil removal in liquid laundry detergents

Abstract: Acrylic acid/ethyl acrylate copolymers, when incorporated into liquid laundry detergents in an amount of from about 0.5 to about 5 weight percent of the liquid detergent formulation provide enhanced clay soil removal performance. Particularly useful are copolymers containing, as polymerized units, from 70 to 98 percent by weight acrylic acid and 2 to 30 percent by weight ethyl acrylate.

Description: This invention is concerned with laundry detergent compositions; more specifically to the use of certain water soluble acrylic acid/ethyl acrylate copolymers in liquid laundry detergent compositions to provide enhanced clay soil removal. Certain water soluble polymers and copolymers have been known to impart favourable performance and processing properties when incorporated into detergent formulations. These properties range from encrustation inhibition to lowering crutcher viscosity. Although the benefits of certain polymers in detergent formulations has been appreciated by those skilled in the art, polymers have previously found very little utility in liquid laundry detergents. The most important reason polymers and copolymers are added to detergent formulations is to improve the performance of the detergent with regard to stain removal. Stains can generally be classified as belonging to one of the following groups: particulates (e.g. clay soil), oily particulates (e.g. sebum), oxidizable (e.g. tea stains), and enzyme sensitive (e.g. grass). We have now found that the addition of certain copolymers to liquid laundry detergents imparts enhanced performance of the clay-soil removal properties of the liquid laundry detergent. Certain polymeric additives for liquid laundry detergents are disclosed in EP-A-368,214 which discloses improved primary and secondary washing action of liquid laundry detergents which include copolymers of (a) monoethylenically unsaturated mono- and di-carboxylic acids and esters thereof, and (b) amides of monoethylenically unsaturated C 3 -C 8 carboxylic acids. Similar polymeric additives are disclosed in US-A-4,702,858 which discloses amine-neutralized polymers including homopolymers of acrylic acid, homopolymers of methacrylic acid, copolymers of acrylic acid/methacrylic acid, and copolymers of (C 4 -C 6 ) ethylenically unsaturated dicarboxylic acids with acrylic acid, methacrylic acid or (C 2 -C 6 )-alkyl esters of ethylenically unsaturated (C 3 -C 6 ) carboxylic acid. US-A-3,328,309 discloses the use of certain polymeric additives to heavy duty liquid detergent formulations as stabilizers. These polymeric additives comprise as copolymerized units (a) ethylenically unsaturated anhydrides, and (b) monomers containing the group C=CH 2 including acrylic acid and derivatives of acrylic acid such as methyl acrylate and ethyl acrylate. US-A-4,664,848 addresses the problem of clay soil removal and anti-redeposition in powdered and liquid laundry detergents and discloses the addition of ethoxylated cationic monoamines, ethoxylated cationic diamines, ethoxylated cationic polyamines, ethoxylated cationic polymers and mixtures thereof to liquid and granular detergent formulations. Japanese Patent Application 58065795 discloses the use of low molecular weight polymers and copolymers in liquid detergent compositions comprising (a) 1-15 percent by weight of nonionic or anionic surfactant, (b) 1-15 percent by weight of a homopolymer of acrylic acid and (c) 1-15 percent by weight of a hydrotropic agent, for example ethanolamine salts of p-toluenesulphonic acid. It is further disclosed that the polymers may contain up to 5 mole percent of a comonomer and that the liquid detergents have improved storage stability and detergency for mud stains. US-A-4,814,102 discloses polymeric detergent additives comprising monoethylenically unsaturated (C 3 -C 6 ) carboxylic acids reacted with ethylene oxide, propylene oxide, n-butylene oxide or isobutylene oxide for use as a builder and for providing dispersing power for pigment dirt in powdered detergents. US-A- 4,698,174 discloses various copolymers of acrylic acid and maleic acid as additives for pulverulent detergents and cleaning agents. US-A-3,922,230 discloses biodegradable oligomeric polyacrylates terminated with hydroxy groups and/or sulphur groups for use as detergent builders. US-A-4,490,271 to discloses a mixture of acrylic homopolymers or copolymers and polyethylene glycol as additives to a surfactant-based phosphate-free powdered detergent formulation. It is disclosed that these detergents enhance clay soil removal. The copolymers may contain up to 20 percent by weight of methacrylic acid, hydroxyacrylic acid, vinyl chloride, vinyl alcohol, furan, acrylonitrile, methacrylonitrile, vinyl acetate, methyl acrylate, methyl methacrylate, styrene, alpha methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, acrylamide, ethylene, propylene and 3-butenoic acid. It is an object of this invention to enhance the clay soil removal properties of liquid detergent formulations. This objective is achieved by incorporating into the formulations a copolymer, containing as polymerized units, acrylic acid and ethyl acrylate units in an amount effective to provide enhanced clay soil removal. By the term "acrylic acid" we mean to include not only acrylic acid itself, but also salts of acrylic acid such as the alkali metal, ammonium and amine salts of acrylic acid, and combinations thereof, unless a clearly different meaning is indicated. In one embodiment, we have found effective enhancement of the clay soil removal properties by using from 0.5 to about 5 percent by weight of copolymer having a weight average molecular weight of from 1000 to 30000 (as measured by aqueous gel permeation chromatography) and containing as polymerized units (a) from about 70 to about 98 percent by weight acrylic acid (or salts thereof), and (b) from about 2 to about 30 percent by weight ethyl acrylate. Methods of making the copolymers for use in this invention are well known to persons skilled in the art of copolymerization and may be learned from US-A-4,314,004 which is directed to one suitable synthesis and to which reference may be made. This method requires a specific concentration range of a copolymerization initiator and a specific molar ratio range of the initiator concentration and the concentration of certain metal salts to obtain the desired low molecular weight copolymers useful in the present invention. Another suitable method for preparing these low molecular weight copolymers is described in US-A-4,301,266, to which reference is also directed. In this process isopropanol is used as the molecular weight regulator as well as the reaction solvent. The reaction solvent may also be an aqueous mixture of isopropanol containing at least 40 percent by weight isopropanol. The process used to prepare the copolymers may be water based or solvent based, it may be run as a batch process, a semi-continuous process or continuous process, the reaction may be thermally initiated, redox initiated or free-radical initiated. The copolymers may be isolated from solution by any of the conventional means or it may be used as a dilute solution. Preferably, the process used for the production of the copolymers is an aqueous based, free-radical initiated process and the copolymer is used as a dilute aqueous solution. The acrylic acid portion of the copolymer may be present in the acid form, or as water-soluble salt of acrylic acid. Such salts include alkali metal salts, ammonium salts, or amine salts. Preferably, the copolymers contain acrylic acid (or salt thereof) at a level of from about 80 to about 95 percent by weight of the copolymer. Preferably, the copolymers contain ethyl acrylate units at a level of from about 5 to about 20 percent by weight of the copolymer. The weight average molecular weight (M w ) of the copolymers is from about 1,000 to about 30,000, preferably from about 1,500 to about 10,000 and most preferably from about 2,000 to about 7,000 as measured by aqueous gel permeation chromatography (GPC). The copolymers are incorporated into the liquid detergent formulation at levels where they provide the intended benefit, which is generally from about 0.5 to about 5 percent by weight of polymer solids based on the total liquid detergent formulation. Preferably, the copolymers are present at levels of from about 1 to about 4 percent and most preferably at about 3 percent by weight of polymer solids based on the total liquid detergent formulation. At copolymer levels below 0.5 percent by weight, the desired effects on clay soil removal are not observed. At levels above 5 percent, the copolymers are generally incompatible with liquid laundry detergent formulations. We evaluated homopolymers of acrylic acid and found them to be not compatible with the liquid laundry detergent formulations. The copolymers may be, with advantage, added to any of the liquid detergent formulations typically available. These formulations generally contain surfactants, builders, buffering agents, bleaches, enzymes, stabilizers, perfumes, whiteners, softeners, preservatives, opacifiers, and water. Although anionic, cationic, nonionic and zwitterionic surfactants may each be used in liquid detergent formulations, such formulations usually contain anionic and nonionic surfactants. Suitable anionic surfactants include, for example, C 8 to C 12 alkylbenzenesulfonates, from C 12 to C 16 alkanesulfonates, C 12 to C 16 alkylsulfates, C 12 to C 16 alkylsulfosuccinates and C 12 to C 16 sulfated ethoxylated alkanols. Suitable nonionic surfactants include, for example, C 6 to C 12 alkylphenol ethoxylates, from C 12 to C 20 alkanol alkoxylates, and block copolymers of ethylene oxide and propylene oxide. Optionally, the end groups of polyalkylene oxides can be blocked, whereby the free OH groups of the polyalkylene oxides can be etherified, esterified, acetalized and/or aminated. The surfactants usable in detergents can also have an amphoteric character and they can be soaps. In general, the surfactants constitute from 2 to 50, preferably 5 to 45 percent by weight of the detergent formulation. Examples of builders typically present in liquid formulations include phosphates, specifically, orthophosphates, pyrophosphates and especially sodium tripolyphosphate. Further examples are the zeolites, sodium carbonate, low molecular weight polycarboxylic acids, nitrilotriacetic acid, citric acid, tartaric acid, the salts of the aforesaid acids and the monomeric, oligomeric or polymeric phosphonates. Builders are generally present in the liquid detergent formulations at levels of from about 0.5 to about 30 percent by weight and preferably from about 5 to about 20 percent by weight of the formulation. Other common additives to detergent and cleaning agent formulations are bleaching agents, used in an amount of up to 30 percent by weight of the formulation; corrosion inhibitors, such as silicates, used in an amount of up to 25 percent by weight of the formulation; and greying inhibitors used in an amount of up to 5%. Suitable bleaching agents are for example, perborates, percarbonates or chlorine-generating substances, such as chloroisocyanurates. Suitable silicates used as corrosion inhibitors are, for example, sodium silicate, sodium disilicate and sodium metasilicate and examples of greying inhibitors are carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose and graft copolymers of vinyl acetate and polyalkylene oxides having a molecular weight of 1000 to 15,000. Other common detergent additives optionally used are optical brighteners, enzymes and perfumes. In addition, liquid detergents may contain up to 80 wt % of water. Liquid Detergent Formulation and Performance Evaluation The efficacy of the polymers of this invention in a liquid detergent formulation was evaluated by washing soiled cotton fabrics in a commercially available, heavy duty liquid composition utilizing Sears Kenmore Ultra Fabric Care brand washing machines (model Heavy Duty 80 Series) set to typical U.S. laundering parameters. Washing conditions are detailed in Table I below, and the liquid detergent formulation base used for evaluating the copolymers of the invention was, for example, that shown in EP-A-0348183 and depicted in Table II. Table III shows other suitable formulations for liquid detergents which are possible but not limiting for use with the copolymers of the invention. Cotton cloth #405 was purchased from Test Fabrics, Inc. (Middlesex, NJ) and cut to a specified size 8.9 cm x 11.43 cm (3 1 / 2 " x 4 1 / 2 "). The cloths were then soiled by applying from 0.7 to 0.8 grams of a 25% clay slurry (in water) using a China bristle brush (#10). The soil was "painted" onto the cloth inside a 5.1 cm (2") diameter circle and allowed to air dry overnight prior to laundering. The clays used to soil the cloths were of two types: (a) a reddish brown particulate clay, and (b) a deep-orange clay. In addition, cloths pre-soiled with clay were purchased from Scientific Services (Oakland, N.J.). The clay used by Scientific Services was a brown clay. Reflectance of each of the cloths was measured using a Pacific Scientific Colorimeter (Colorgard System 1000) and the data recorded using the X,Y,Z colour scale. The reflectance (Y) of the soiled cloths was measured before laundering so that only cloths of the same reflectance were used in a test. Reflectance was then measured after laundering to evaluate the efficacy of the detergent. The ΔY values reported in Table IV are the change in reflectance relative to the control cloths laundered in detergent not containing polymer. Each of the three clay soils was evaluated with four replicates. The data appearing in Table IV are composite averages of the reflectance values obtained from all of the clay soils laundered with the polymer listed. WASH CONDITIONS APPARATUS SEARS KENMORE BRAND WASHING MACHINE TEMPERATURE WARM (35°C) WATER HARDNESS MODERATE (120 PPM) AGITATION HIGH WASH CYCLE MEDIUM (10 MIN.) WATER CAPACITY 63.2 LITRES (16.7 GALLONS)/LOAD DETERGENT DOSAGE (RECOMMENDED LEVEL) 130 GRAMS POLYMER CONCENTRATION 3% SOLIDS (NEUTRALIZED, pH 7) BASE LIQUID DETERGENT FORMULATION Component % by weight Surfactants Linear Dodecylbenzene Sulfonate 17.00 Alcohol Ethoxylate (Nonionic) 7.00 Builder Sodium Citrate 10.00 Hydrotrope/Solubilizing Agent Monoethanolamine 2.00 Misc. and Water up to 100% LIQUID COMPOSITIONS Unbuilt Citrate Citrate/Fatty Acid Soap Phosphate Non-Phosphate LAS 3.5 5 8 7 19 Alc. Ether Sulfate --- --- 16 --- --- Citrate --- 10 6 --- --- Fatty Acid Soap --- -- 0 --- --- Nonionic Surfactant 16 .5 6 3 15 Propylene Glycol --- --- 8 --- 4 Ethanol 5 --- 4 --- 8.5 Na Xylene Sulfonate --- 5.5 --- --- --- Opt. Brightener 0.2 0.2 0.15 0.1 0.25 Enzyme 0.7 --- 0.5 0.5 0.75 Water Q.S. Q.S. Q.S. Q.S. Q.S. Borax --- --- --- 3 --- Tripolyphosphate --- --- --- 23 --- Glycerin --- --- --- 6 --- LAS means "Linear Alkylbenzene Sulfonate" Polymer Composition M w Reflectance (Y) Net Change (ΔY) none 63.3 -- Example 1 95 AA/ 5 EA 2500 65.6 2.3 Example 2 90 AA/10 EA 3400 64.7 1.4 Example 3 95 AA/ 5 EA 2100 64.2 0.9 Example 4 81 AA/19 EA 2120 63.3 0.0 Example 5 70 AA/10 EA/20 MAL 4590 62.2 -1.1 Example 6 40 AA/30 EA/30 NIS 4760 63.0 -0.3 none 63.1 -- Example 7 100 AA 1000 63.2 0.1 Example 8 100 AA 2000 64.3 1.2 Example 9 100 AA 4500 64.5 1.4 Example 10 100 AA 10000 63.9 0.8 Example 11 100 AA 40000 63.2 0.1 Example 12 100 AA 60000 62.7 -0.4 none 64.8 -- Example 13 80 AA/20 EA 6470 65.7 0.9 Example 14 80 AA/20 HPA 6530 65.5 0.7 Example 15 80 AA/20 ØAA 2850 64.7 -0.1 Example 16 80 AA/20 AM 3290 65.5 0.7 Example 17 80 AA/20 IA 3810 64.9 0.1 Example 18 80 AA/20 IA 58700 64.7 -0.1 none 63.4 -- Example 19 70 AA/30 MAA 3500 62.7 -0.7 Example 20 80 AA/20 MAA 4000 61.5 -1.9 Example 21 100 MAA 4000 61.4 -2.0 Example 22 80 MAA/20 NIS 2080 63.7 0.3 none 62.5 -- Example 23 80 AA/20 MAL 4080 62.3 -0.2 Example 24 80 AA/20 MAL 15200 62.1 -0.4 Example 25 65 AA/35 MAL 11900 62.3 -0.2 Example 26 65 AA/35 MAL 30000 61.7 -0.8 Example 27 40 AA/60 MAL 4300 62.9 0.4 Example 28 40 AA/60 MAL 11700 61.8 -0.7 KEY: AA Percent by weight Acrylic Acid EA Percent by weight Ethyl Acrylate MAL Percent by weight Maleic Acid NIS Nonionic Surfactant HPA Percent by weight Hydroxypropyl Acrylate ØAA Percent by weight Phenylacrylic Acid AM Percent by weight Acrylamide IA Percent by weight Itaconic Acid MAA Percent by weight Methacrylic Acid Examples 5 to 12 and 14 to 28 are comparative. These results demonstrate that acrylic acid/ethyl acrylate copolymers are particularly effective for the removal of clay soils. Acrylic acid/ethyl acrylate copolymers show superior results compared to homopolymers, copolymers containing comonomers other than ethyl acrylate, and terpolymers. Sears Kenmore is a trademark which may be registered in some countries.

Claims: The use in a liquid detergent composition of from 0.5 to 5 percent by weight (based on the composition weight) of copolymer having a weight average molecular weight of from 1000 to 30000 (as measured by aqueous gel permeation chromatography) and containing as polymerized units (a) from 70 to 98 percent by weight units of acrylic acid or salt thereof, and (b) from 2 to 30 percent by weight ethyl acrylate units, in order to enhance the clay soil removal properties thereof. A liquid laundry detergent composition containing at least one anionic surfactant and from 0.5 to 5 percent by weight (based on the composition weight) of copolymer containing, as polymerized units (a) from 70 to 98 percent by weight units of acrylic acid or salt thereof and (b) from 2 to 30 percent by weight units of ethyl acrylate, and having a weight average molecular weight of from 1000 to 30000 (as measured by aqueous gel permeation chromatography). Use as claimed in claim 1 or composition as claimed in claim 2, wherein the copolymer contains as polymerized units (a) about 80 percent by weight acrylic acid and (b) about 20 percent by weight ethyl acrylate. Use as claimed in claim 1 or composition as claimed in claim 2, wherein the copolymer contains as polymerized units (a) about 90 percent by weight acrylic acid and (b) about 10 percent by weight ethyl acrylate. Use as claimed in claim 1 or composition as claimed in claim 2, wherein the copolymer contains as polymerized units (a) about 95 percent by weight acrylic acid and (b) about 5 percent by weight ethyl acrylate. Use or composition as claimed in any preceding claim wherein the copolymer has a weight average molecular weight of from 1500 to 10000. Use or composition as claimed in any preceding claim wherein the copolymer has a weight average molecular weight of from 2000 to 7000. Use or composition as claimed in any preceding claim wherein the copolymer is present at from 1 to 4 percent (by weight of the detergent composition). Use or composition as claimed in any preceding claim wherein the copolymer is present at about 3 percent (by weight of the detergent composition). Use or composition as claimed in any preceding claim wherein said composition is free of phosphate.

Inventors: JONES CHARLES ELWOOD, SHULMAN JAN EDWARD, JONES, CHARLES ELWOOD, SHULMAN, JAN EDWARD
Applicants: ROHM & HAAS, ROHM AND HAAS COMPANY
Application year: 1992
Main classification: C11D3
IPC codes: C11D3