Thus use of a post detergent step for removing aqueous residue from ware combined with a subsequent step using a potable rinse or a dilute solution of an aqueous food grade rinse aid to rinse alkaline washed ware provides significant advantages. The two step rinse method insures complete and sanitary cleaning of ware while permitting the use of different formulations in the post detergent step and the subsequent rinse step. Such process conditions permit the use of differing times and temperatures in the post detergent step and in the rinse step and permits the use of different formulations in the post detergent step and in the rinse step.

The invention relates to cleaning and rinsing ware in institutional or industrial automatic warewashing machines. More particularly, the invention involves post detergent treatments and rinsing steps for ware that is first cleaned using alkaline detergents leaving clean ware with an alkaline detergent residue on the ware surface. The clean ware is then processed in a procedure involving a post detergent step and a rinse step. The post detergent step involves the use of an aqueous solution of surfactant or chemical rinse additive or agent that can remove a substantial proportion of previously formed detergent residue. This step can leave some amount, typically a small but measurable proportion of rinse aid, food, surfactant, detergent or a combination residue. A subsequent rinse step uses an aqueous potable rinse or an aqueous dilute solution of food grade surfactant to complete the cleaning method and substantially remove such remaining residue.
The use of automatic warewashing machines to clean and rinse ware has been known for many years. Fernholz et al., U.S. Reissue Pat. Nos. 32,818 and 32,763 disclose the use of solid block alkaline cleaning compositions and subsequently rinsing alkaline residues from clean ware. Commonly, after ware is cleaned using alkaline detergents, the ware is often rinsed using a dilute aqueous solution of a typically synthetic polymeric composition comprising at least a block of ethylene oxide in combination with other moieties in the composition to result in an aqueous composition that can cause the rapid sheeting of the rinse water from ware for the intended purpose of leaving a bright, clean, unspotted product. These polymeric materials are typically called rinse aid agents. When dissolved in water a rinse agent forms a rinse solution or composition that, because of the surface energy of the ware and the relationship between the rinse aid and the surface energy, causes sheeting. Warewashing and rinsing processes have been embodied in a variety of institutional and industrial automatic warewashing machines that have automatic control mechanisms that expose ware to a variety of prescraping, scraping, prerinse, alkaline wash, acid wash, rinse, sanitize, post-sanitize, etc. steps. Particularly in large, high volume, multistep warewashing machines, the sequence of steps can be programmed to achieve a desired result.
A variety of cleaning and rinsing processes are known, including Avram, U.S. Pat. No. 5,879,469, which teaches a warewashing system using a basic aqueous wash followed by an acidic aqueous wash. Howland et al., U.S. Pat. No. 5,448,115, shows that aqueous rinse cycles can be effectively controlled to modify dispensing and timing of cleaning chemicals. Young, Jr. et al., U.S. Pat. No. 5,429,679, shows further control systems and in particular directing rinse water recycle into other washing cycle steps. Steindorf, U.S. Pat. No. 5,447,648, and Baum, U.S. Pat. No. 5,589,099, disclose solid food grade rinse aid compositions and improved synthetic ethylene oxide propylene oxide block copolymer based rinse aids. Groult et al., U.S. Pat. No. 4,501,681, show at Column 8, lines 35-55 and elsewhere, the use of multiple rinse steps. Groult et al. appear to show a process involving a first and second rinse step using rinse water followed by a third rinse step using acid or neutral rinsing agents. Jones et al., U.S. Pat. No. 5,232,622, show two sequential rinse steps (Column 6, lines 49-64). Jones et al. disclose nothing regarding the compositions used in the rinse cycles, however, the cycles likely contain conventional synthetic alkaline oxide based rinse agents.
Haslop et al., U.S. Pat. No. 4,618,446, discloses ingredients for use in spherical liquid detergent compositions. Haslop et al., U.S. Pat. No. 4,793,943, teaches a variety of ingredients useful for making liquid detergent compositions. Akred et al., U.S. Pat. No. 4,871,467, teaches a variety of compositions and materials used to form non sedimenting liquid detergent compositions. Aronson et al., U.S. Pat. No. 5,045,225, teaches a combination of hydrocarbon oils and silicone compositions as antifoam materials. Gentle et al., U.S. Pat. No. 5,073,298, teaches silicone silicate based defoaming compositions. Chun et al., U.S. Pat. No. 5,133,892, teaches machine dishwashing detergent tablets having timed release of enzyme and chlorine bleach and a variety of other ingredients used in making the detergent composition.
Tsukada, Japanese Patent Application Publication Kokai 49-126,703, teaches carbohydrate aliphatic ester rinse agents. Miura et al., Japanese Patent Application Publication Kokai 50-62,211, teaches polyhydric alcohol containing rinse agents. Miura et al., Japanese Patent Application Publication Kokai 51-68,608, teaches polyol aliphatic ester containing rinse agent compositions. Suzuki et al., Japanese Patent Application No. 86-131,272, teaches a rinse agent comprising a polyethoxylated sorbitan fatty acid ester glycerol and a sugar alcohol. Suzuki et al., Japanese Patent Application No. 86-161,193, teaches a similar material. Nantaku, Japanese Patent Application No. 59-187,096, teaches a polyglycerine ester of a C6-8 fatty acid containing rinse agent. Wilson et al., xe2x80x9cRinse Additives for Machine Dishwashingxe2x80x9d, Soap and Chemical Specialties. pp. 48 et seq. (February 1958), discusses the basic technology regarding rinse agent formulation. The use of a rinse composition often remove substantial amounts of alkaline residue but can leave some proportion of food residue and some amount of rinse agent residue.
The use of a food grade rinse aid has attracted increasing attention over recent years. Such surfactants are attractive to people requesting more natural chemical materials in warewashing processes. These food grade rinse aids commonly comprise sucrose fatty acid esters, sorbitan fatty acid esters, glycerol fatty acid esters and other similar materials comprising a natural polyol or polymerized polyol derivatized with one or more fatty acid or other natural hydrophobic moiety. Depending on the nature of the ware, the type and content of soil, the hardness of service water, the temperature of washing, and other variables, a food grade rinse aid often provide a level of rinsing which does not meet or exceed the level of rinsing obtained from synthetic polyalkylene oxide type rinse agents.
While the level of activity of the food grade rinse agent is typically acceptable to most operators, a synthetic polyalkylene oxide rinse aid provide a level of sheeting at an effective concentration that is superior to food grade rinse aids. Further, in many kitchens, a strong desire to use food grade rinse aids in a final stage is evident while the use of a synthetic polyalkylene oxide based rinse aid are not desirable in a final step.
Accordingly, a substantial need exists for warewashing methods that can obtain the advantages of conventional rinsing cycles with desired performance while also obtaining the advantages of food grade rinse aid compositions. Such benefits include clean, well rinsed ware with no residue, spotting or streaking.
We have found improved warewashing methods involving cleaning ware with an alkaline detergent producing clean ware, leaving aqueous alkaline residue, followed by a post detergent regimen. In the post detergent regimen, the clean ware is then contacted with a first aqueous post detergent step using an aqueous composition. The aqueous composition comprises a rinse composition having a rinse agent with a polyalkylene oxide moiety to remove the alkaline residue producing treated ware. The treated ware is then contacted in a rinse step with a rinse composition comprising either a food grade rinse agent or an aqueous or potable water rinse, said aqueous or potable water rinse is substantially free of a synthetic rinse agent, for at least three seconds. To ensure complete sanitization of the ware, a sanitation step is used prior to the post detergent regimen. Such a step can include any technique that reduces the numbers of pathogens to a sanitizing level. Preferably, the method uses a biocide or an elevated aqueous rinse temperature to achieve sanitized ware or both.
Accordingly, the invention is found in a method of cleaning ware involving a first cleaning step using an aqueous alkaline cleaning composition, resulting in cleaned ware having an alkaline residue. The cleaned ware is then contacted with an aqueous composition in post detergent step, the aqueous composition comprising about 10 to 500 ppm, of a synthetic nonionic sheeting agent comprising a polyalkylene oxide moiety, to form treated ware. The method further comprises contacting the treated ware with an aqueous rinse composition; wherein the cleaning method also includes a post detergent sanitizing step.
The invention is also found in a method of cleaning ware involving a first cleaning step using an aqueous alkaline cleaning composition, resulting in cleaned ware having an alkaline residue. The cleaned ware is then contacted with an aqueous composition in a post detergent step, the aqueous composition comprising about 10 to 500 ppm, of a synthetic nonionic sheeting agent comprising a polyalkylene oxide moiety, to form treated ware. The method further comprises contacting the treated ware with an aqueous rinse composition comprising about 1 to 800 ppm of a combination of a food grade sheeting agent and a solubility agent; wherein the cleaning method also includes a post detergent sanitizing step.
The warewashing process of the invention includes an alkaline washing step, a first post detergent step and a rinse step. In the alkaline warewashing step, the ware is contacted with an alkaline aqueous cleaning solution that removes food soils from the ware surface. The alkaline step, which leaves minor alkaline residue on the surface of the ware, is followed by a post detergent step in which the ware is contacted with an aqueous solution of a rinse agent in a rinse composition that is designed to substantially remove the alkaline residue, preferably leaving clean unspotted ware. However, such steps can leave some small food and rinse agent residue on the ware surface. The ware, after the post detergent step, is contacted with an aqueous rinse. Such a rinse can comprise a composition as simple as a potable water rinse or can comprise a rinse composition containing a food grade rinse agent at an effective concentration.
The post detergent step can contain rinse agents that are conventional rinse agents containing a polyalkylene, preferably a polyethylene oxide moiety, while the rinse step can contain a food grade rinse agent, typically comprising a soya phospholipid, a sugar fatty acid ester such as a glucose or sucrose fatty acid ester, a sorbitan fatty acid ester, a C2-C4 polyol fatty acid ester or a soya phospholipid or mixtures thereof. An effective post detergent rinse composition or other rinse composition commonly is tested for sheeting and low foaming properties. Sheeting is typically tested using substantially subjective visual testing determining whether the ware completely sheets or leaves some type of residue. Rinse agent foaming is tested using a foaming apparatus and method set forth in Steindorf, U.S. Pat. No. 5,447,648 at Column 9, line 1 through Column 11, line 3.
There are two general types of detergent/rinse cycles in commercial warewashing machines. A first type, a sanitizing cycle, uses sanitizing water at least about 180xc2x0 F. (about 82xc2x0 C. or higher) for at least 3 seconds. A second type in non-sanitizing machines use lower temperature non-sanitizing rinse water. Typically, the temperature of the service water available, from the water heaters installed at the use location, is about 125xc2x0 F. (about 52xc2x0 C.), 140xc2x0 F. (about 60xc2x0 C.), 160xc2x0 F. (about 71xc2x0 C.), etc. A surfactant useful in any of these use locations is an aqueous rinse can have a cloud point greater than the available hot service water. For the purpose of this invention, the term xe2x80x9crinse agentxe2x80x9d includes concentrate materials that are diluted with an aqueous stream to produce an aqueous rinse.
Accordingly, an aqueous rinse agent is an aqueous material that is contacted with ware in a rinse cycle. A sheeting agent is the polymeric material used to promote the even drainage of the aqueous rinse. Sheeting is defined as forming a continuous, evenly draining film, leaving virtually no spots or film upon the evaporation of water. For the purpose of this invention, the term xe2x80x9cdishxe2x80x9d or the term xe2x80x9cwarexe2x80x9d is used in the broadest sense of the term to refer to various types of articles used in the preparation, serving, consumption, and disposal of foodstuff""s including pots, pans, trays, pitchers, bowls, plates, saucers, cups, glasses, forks, knives, spoons, spatulas, and other glass, metal, ceramic, plastic composite articles commonly available in the institutional or household kitchen or dining room.
Biocides
Biocides can be used in a sanitizing step. Biocides are antimicrobial agents or chemical compositions that can prevent microbiological contamination or deterioration caused by microorganisms. Most useful antimicrobial agents comprise phenolics, halogen compounds, quaternary ammonium compounds, amines, alkanol amines, nitro compounds and a variety of miscellaneous types of antimicrobial agents. Antimicrobial agents operate by either interfering with a cellular mechanism or a cellular component of the microbe resulting in the substantial reduction of microbial populations or simply prevent proliferation in numbers of microorganisms that would prevent the accumulation of harmful numbers of microorganisms. Antimicrobial agents are often effective against one or more of typical microbial classifications such as gram positive, gram negative, fungi, molds and yeasts.
The preferred antimicrobial agent used to kill or reduce microbial populations requires physical and chemical compatibility with the system, stability and resistance to be inactivated by other components or ingredients in this system, stability under use and storage conditions of pH temperature and light exposure while being safe and essentially non-toxic to humans in handling formulation and use. Typical antimicrobial agents are used in aqueous solution at a concentration of about 0.1 to 1000 ppm, preferably about 1 to 200 ppm and are simply contacted with the ware in a separate step or as a component of the post detergent rinse or the final aqueous rinse step of the invention. Preferred antimicrobial agents for use in the invention for sanitizing the surface of ware include the following classes of compounds Biocides are antimicrobial agents or chemical compositions that can prevent microbiological contamination or deterioration caused by microorganisms. Most useful antimicrobial agents comprise phenolics, halogen compounds, quaternary ammonium compounds, amines, alkanol amines, nitro compounds and a variety of miscellaneous types of antimicrobial agents. Antimicrobial agents operate by either interfering with a cellular mechanism or a cellular component of the microbe resulting in the substantial reduction of microbial populations or simply prevent proliferation in numbers of microorganisms that would prevent the accumulation of harmful numbers of microorganisms. Antimicrobial agents are often effective against one or more of typical microbial classifications such as gram positive, gram negative, fungi, molds and yeasts.
The preferred antimicrobial agent used to kill or reduce microbial populations requires physical and chemical compatibility with the system, stability and resistance to be inactivated by other components or ingredients in this system, stability under use and storage conditions of pH temperature and light exposure while being safe and essentially non-toxic to humans in handling formulation and use. Typical antimicrobial agents are used in aqueous solution at a concentration of about 0.1 to 1000 ppm, preferably about 1 to 200 ppm and are simply contacted with the ware in a separate step or as a component of the post detergent rinse or the final aqueous rinse step of the invention.
Post Detergent Rinse
The use of nonionic surface active agents for rinse agents and rinse compositions include typically synthetic organic molecules including at least a polyoxyethylene group. Preferred agents for use in this invention include polyoxyethylene/polyoxypropylene/polyoxyethylene block copolymers, polyoxypropylene/polyoxyethylene/polyoxypropylene block copolymers and alkalethoxylate polymeric materials. Such materials have the following formulae:
(EO)x(PO)y(EO)z
(PO)x(EO)y(PO)z
ROxe2x80x94(EO)xH
wherein R is a C6-C24 alkyl or a C6-C24 alkyl substituted phenol moiety, EO comprises ethylene oxide, PO comprises propylene oxide and x, y and z reflect the average molecular proportion of each alkylene oxide moiety in the overall polymer composition. In this, x typically ranges from about 10 to about 130, y typically ranges from about 10 to about 70, while z typically ranges from about 10 to about 130, and x plus y is typically greater than about 60. The total polyoxyethylene moiety of each polymeric material constitutes typically at least about 40 mole %, commonly at least 75 mole %. These polymeric rinse agent materials preferably have a molecular weight greater than about 5000, more preferably greater than about 10,000. In a preferred embodiment, the post detergent rinse step comprises about 10 to 500 ppm of a synthetic nonionic sheeting agent comprising a polyalkylene oxide moiety.
Food Grade Rinse
The second rinse step can comprise potable water, either with or without inclusion of a suitable food grade rinse agent. Preferred food grade rinse agents include sucrose fatty acid ester, a sorbitan fatty acid ester, a glycerol fatty acid ester, a propylene glycol fatty acid ester, a soya phospholipid, or mixtures thereof. The second rinse step may also include such components as a solubility agent and an acidity source. If so, the solubility agent is preferably present at a concentration of about 1 to 400 ppm and the acid is preferably present at a concentration of about 0.01 to 25 ppm.
In a preferred embodiment, the aqueous rinse composition comprises a surfactant composition comprising 1 to 250 ppm of a sucrose fatty acid ester, about 1 to 320 ppm of a solubility agent. In one embodiment, the solubility agent comprises ethanol, propylene glycol, glycerol or mixtures thereof. Preferably, the aqueous rinse has a pH of less than 7. In another preferred embodiment, the food grade sheeting agent comprises a sucrose fatty acid ester, a sorbitan fatty acid ester, a glycerol fatty acid ester, a propylene glycol fatty acid ester, a soya phospholipid, or mixtures thereof. Preferably, the food grade sheeting agent is used at a concentration of about 20 to 300 ppm, more preferably about 25 to 150 ppm.
To meet the requirements of particular Asian markets, the post detergent step is preferably conducted for at least three seconds. Likewise, the rinse step involving potable water alone or in combination with a food grade sheeting agent is carried out for about 3 to 7 seconds, preferably about 4 to 6 seconds. Preferably, the aqueous rinse composition consists essentially of potable water.
Sorbitan Aliphatic Esters
Sorbitan aliphatic esters suitable for use in the rinse aid composition include any sorbitan aliphatic ester capable of providing effective foam control and cooperating with the other components for producing a solid nose aid composition. One group of particularly suitable sorbitan aliphatic esters are the sorbitan fatty acid esters. Sorbitan fatty acid esters can provide effective sheeting action and rinsing performance. Sorbitan fatty acid esters suitable for the use in the rinse aid composition include mono-, di-, tri- and tetra-esters and mixtures thereof. Sorbitan fatty acid esters may be derived by esterification of sorbitol with such fatty acids as lauric, myristic, palmitic, stearic, oleic, linolic, and similar saturated and unsaturated, branched and straight chain fatty acids. Preferably, the fatty acids are C6-24 straight chain fatty acids having less than 3 unsaturated carbon bonds.
Based upon cost, availability and ability to provide excellent sheeting action and rinsing performance, the preferred useful sorbitan fatty acid esters include monoesters such as sorbitan monocaprylate acid, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan monolinoleate, sorbitan mono eleostearate, sorbitan monopentadecanoic acid ester, sorbitan monoheptadecanoate; diesters such as sorbitan sesquistearate and sorbitan sesquioleate; tri esters such as sorbitan tristearate and sorbitan trioleate. Because of the difficulty encountered in attempting to purify sorbitan fatty acid esters from the reaction mixture, the sorbitan fatty acid ester will typically contain various amounts of sorbitol fatty acid ester(s), sorbide fatty acid ester(s) and trace quantities of sorbitan, sorbitol, sorbide and fatty acid(s). Sorbitan fatty acid esters containing such xe2x80x9ccontaminantsxe2x80x9d may be effectively employed in the rinse aid composition without significant adverse effect.
Sucrose Aliphatic Esters
Sucrose aliphatic esters suitable for use in the rinse aid composition include any sucrose aliphatic ester capable of contributing to the sheeting action and rinsing performance of the composition and cooperating with the other components for producing a solid rinse aid composition. Sucrose has a total of eight reactive hydroxyl groups which are subject to substitution. One group of particularly suitable sucrose aliphatic esters are the sucrose fatty acid esters which are generally solid at room temperature and can also assist in solidifying the composition. The sucrose fatty acid esters suitable for the use in the rinse aid composition include mono to octa-fatty acid esters and mixtures thereof. Sucrose fatty acid esters may be derived by esterification of sucrose with such saturated fatty acids as acetic, propionic, butyric, valeric, caproic, enanthic, caprylic, pelargonic, capric, lauric, myristic, palmitic, and stearic; unsaturated fatty acids such as palmitoleic, oleic, vaccenic, linoleic, sorbic, linolenic, and arachidonic and similar saturated and unsaturated, branched and unbranched fatty acids. Sucrose fatty acid esters are readily available from a number of sources including Mitsubishi-Kasei Foods Corporation of Tokyo, Japan under the designation Ryoto Sugar Esters, and Dai-ichi Kogyo Seiyaku Company Ltd. of Tokyo, Japan.
The preferred sucrose fatty acid ester for use in the rinse aid composition is a mixture of about 2 to about 12 wt % sucrose laurate and about 25 to about 85 wt % sucrose palmitate. Such a materials provides effective sheeting action and rinsing performance while contributing to the formation of a solid product with beneficial dispensing characteristics. The sucrose laurate and sucrose palmitate may be provided as monoesters, diesters, triesters, tetraesters, pentaesters, hexaesters, heptaesters, octaesters and mixtures thereof. However, the shelf life and performance of the of the rinse aid composition is enhanced when at least about 70% of the sucrose palmitate is a monoester and at least about 80% of the sucrose laurate is a monoester.
Polyglycerol Aliphatic Esters
Polyglycerol aliphatic esters suitable for use in the rinse aid composition include any polyglycerol aliphatic ester capable of contributing to the sheeting action and rinsing performance of the composition and cooperating with the other components for producing a solid rinse aid composition. One group of particularly suitable polyglycerol aliphatic esters are the polyglycerol fatty acid esters. Suitable polyglycerol fatty acid esters include specifically, but not exclusively, those derived by esterification of a polyglycerol with such saturated fatty acids as acetic, propionic, butyric, valeric, caproic, enanthic, caprylic, pelargonic, capric, lauric, myristic, palmitic, and stearic; unsaturated fatty acids such as palmitoleic, oleic, vaccenic, linoleic, sorbic, linolenic, and arachidonic; and similar saturated and unsaturated, branched and unbranched fatty acids. Polyglycerol fatty acid esters are readily available from a number of sources including Nikko Chemicals Company, Ltd of Tokyo, Japan, and Toho Chemical Industry Company, Ltd. of Tokyo, Japan. Because of the relatively low cost, ready availability, sheeting performance, and ability to provide a rinse aid composition with beneficial dispensing characteristics, the preferred polyglycerol fatty acid ester for use in the rinse aid composition is decaglycerol monolaurate available from Nikko Chemicals Company, Ltd of Tokyo, Japan. The polyglycerol aliphatic ester may be effectively used within the rinse aid composition at a concentration of about 2 to about 20 wt %.
Optional Polyol Fatty Acid Esters
The food grade rinse aids of the invention may also contain one or more additional food grade fatty acid esters of other polyols such as glycerol, glycerol, diglycerol, triglycerol, glyceraldehyde, erythrose, threose, ribose, arabinose, xylose, glucose, mannose, galactose, ribulose, xylose, fructose, lactose, maltose, cellobiose, and the like. Such polyol fatty acid esters are useful for contributing to the sheeting action and rinsing performance of the composition and cooperating with the other components for producing a useful rinse aid composition.
Defoaming Agents
Defoaming agents (defoamers) include a variety of different materials adapted for defoaming a variety of compositions. Defoamers can comprise an anionic or nonionic material such as polyethylene glycol, polypropylene glycol, fatty acids and fatty acid derivatives, fatty acid sulfates, phosphate esters, sulfonated materials, silicone based compositions, and others.
Preferred defoamers are food additive defoamers including silicones and other types of active anti-foam agents. For the purposes of this application, the term xe2x80x9cfood additivexe2x80x9d means materials listed in the U.S. Code of Federal Regulations 21 Part 172xe2x80x94Food Additives Permitted for Direct Addition to Food for Human Consumption, 21 Part 182xe2x80x94Substance Generally Recognized as Safe and 21 Part 184xe2x80x94Direct Food Substances A:ffired as Generally Recognized as Safe, and 21 Part 173xe2x80x94Secondary Direct Food Additives Permitted in Food for human Consumption, Section 173.310.
Silicone foam suppressers include polydialkylsiloxane preferably polydimethylsiloxane. Such silicone based foam suppressers can be combined with silica. Such silica materials can include silica, fumed silica, derivatized silica, silanated silica, etc. Commonly available anti-foaming agents combines a polydimetbylsiloxane and silica gel. Another food additive defoaming agent comprises a fatty acid defoamer. Such defoamer compositions can comprise simple alkali metal or alkaline earth metal salts of a fatty acid or fatty acid derivatives. Examples of such derivatives include mono, di- and tri-fatty acid esters of polyhydroxy compounds such as ethylene glycol, glycerol, propylene glycol, hexylene glycol, etc. Preferably such defoaming agents comprise a fatty acid monoester of glycerol. Fatty acids useful in such defoaming compositions can include any C6-24 saturated or unsaturated, branched or unbranched mono or polymeric fatty acid and salts thereof, including for example myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, palmitoleic acid, oleic acid, linoleic acid, arachidonic acid, and others commonly available. Other food additive anti-foam agents available include water insoluble waxes, preferably microcrystalline wax, petroleum wax, synthetic petroleum wax, rice base wax, beeswax having a melting point in the range from about 35xc2x0 to 125xc2x0 C. with a low saponification value, white oils, etc. Such materials are used in the rinse agents of the invention at a sufficient concentration to prevent the accumulation of any measurable stable foam within the dish machine during rinse cycle.
Food Grade Fillers
The food grade rinse aid composition of the invention can contain one or more solid water soluble food grade fillers for the purpose of facilitating processing, product stability, or dispensing of the composition or contributing to other performance characteristics. Many different types of fillers may be utilized in the rinse agent composition, including specifically but not limited to such compounds as a sugar such glucose, fructose, sucrose; an alkali metal salt such as sodium chloride, potassium chloride, sodium carbonates, sodium bicarbonate, sodium sulfate, potassium sulfate, sodium acetate, sodium lactate, water soluble amino acids such as alanine, arginine, glycine, lysine, proline; phosphates such as tetrasodium pyrophosphate, sodium phosphate and others.
Chelating Agents
The rinse agents of the invention can contain a complexing or chelating agent that aids in reducing the harmful effects of hardness components in service water. Typically calcium, magnesium, iron, manganese, and other polyvalent metal cations present in service water, can interfere with the action of either washing compositions or rinsing compositions. A chelating agent can effectively complex with and prevent such ions from the service water interfering with the action of an active component increasing rinse agent performance. Both organic and inorganic chelating agents are common. Inorganic chelating agents include such compounds as sodium pyrophosphate, and sodium tripolyphosphate while organic chelating agents include both polymeric and small molecule chelating agents. Polymeric chelating agents commonly comprise ionomer compositions such as polyacrylic acids compounds. Small molecule organic chelating agents include salts of ethylenediaminetetracetic acid (EDTA) and hydroxyethylene-diaminetetracetic acid, nitrilotriacetic acid, ethylenediaminetetrapropionates, triethylene-tetraminehexacetates, and the respective alkali metal ammonium and substituted ammonium salts thereof. Amino phosphates are also suitable for use as chelating agents in the composition of the invention and include ethylenediamine tetra(methylene-phosphonate), nitrilotrismethylenephosphonate, diethylenetriaminepenta(methylene phosphonates). These amino phosphonates commonly contain alkyl or alkylene groups with less than 8 carbon atoms. Preferred chelating agents for this invention include approved food additive chelating agents such as the disodium salt of ethylenediamine-tetracetic acid.
Solubility Agents
Solubility aids or agents can be used to enhance the water solubility of the food grade sheeting agents used in the invention. Preferred solubility agents include ethanol, propylene glycol, glycerine and mixtures thereof.
Liquid Carriers
The liquid rinse agents of the invention can have a liquid base component which functions as a carrier and cooperates with aqueous diluents to form the aqueous rinse. Liquid bases are preferably water or a solvent compatible with water to obtain compatible mixtures thereof. Exemplary nonlimiting solvents in addition to water include a low molecular weight C1-6 primary and secondary mono, di- and tri-hydroxy alcohol such as methanol, ethanol, isopropanol, and polyols containing from two to six carbon atoms and from two to six hydroxyl groups such as propylene glycol, ethylene glycol, glycerine, propane diol, propylene glycol, etc.
Other Components
The organic nature of the rinse agents of the invention can be subject to microbial and chemical decomposition. Organic materials are commonly useful in stabilizing the mixtures. Preferred preservatives or stabilizers for the invention include food grade stabilizers, food grade antioxidants, etc. Most preferred materials for use in stabilizing the compositions of the invention include C1-10 mono, di- and tricarboxylic acid compounds. Preferred examples of such acids include acetic acid, citric acid, benzoic, sorbic, lactic, maleic, tartaric and fumaric. Optional ingredients which can be included in the rinse agents of the invention in conventional levels for use include solvents, hydrotropes, processing aids, corrosion inhibitors, dyes, fillers, optical brighteners, germicides, pH adjusting agents (monoethanolamine, sodium carbonate, sodium hydroxide, hydrochloric acid, phosphoric acid, et cetera), bleaches, bleach activators, perfumes and the like.
The compositions of the invention can be formulated using conventional formulating equipment and techniques. The compositions of the invention typically can comprise proportions as set forth in Table 1. In the manufacture of the liquid rinse agent of the invention, typically the materials are manufactured in commonly available mixing equipment by charging to a mixing chamber the liquid diluent or a substantial proportion of a liquid diluent. Into a liquid diluent is added preservatives or other stabilizers. Care must be taken in agitating the rinse agent as the formulation is completed to avoid degradation of polymer molecular weight or exposure of the composition to elevated temperatures. The materials are typically agitated until uniform and then packaged in commonly available packaging and sent to distribution center before shipment to the consumer.
The liquid materials of the invention can be adapted to a cast solid format by incorporating into the composition a casting agent. Typically organic and inorganic solidifying materials can be used to render the composition solid. Preferably organic materials are used because inorganic compositions tend to promote spotting in a rinse cycle. The most preferred casting agents are polyethylene glycol and an inclusion complex comprising urea and a nonionic polyethylene or polypropylene oxide polymer. Polyethylene glycols (PEG) are used in melt type solidification processing by uniformly blending the sheeting agent and other components with PEG at a temperature above the melting point of the PEG and cooling the uniform mixture. An inclusion complex solidifying scheme is set forth in Morganson et al., U.S. Pat. No. 4,647,258.
The solid compositions of the invention are set forth in Table 2 as follows:
Liquid rinse agents are dispensed by incorporating compatible packaging containing the liquid material into a dispenser adapted to diluting the liquid with water to a final use concentration wherein the active material is present in the aqueous rinse at a concentration of 20 to 500 parts of the active block copolymer per million parts of the aqueous rinse. More preferably the material is present in the aqueous rinse at a concentration of about 30 to 300 parts of the block copolymer per million parts of the aqueous rinse most preferably the material is present at a concentration of about 40 to 200 parts of the block copolymer per million parts of the aqueous rinse. Examples of dispensers for the rinse of the invention are DRYMASTER-P sold by Ecolab Inc. Cast solid may be conveniently dispensed by inserting a cast solid material in a container or with no enclosure into a spray-type dispenser such as the volume SOL-ET controlled Rinse Injection Cylinder system manufactured by Inc., St. Paul, Minn. Such a dispenser cooperates with a warewashing machine in the rinse cycle. When demanded by the machine, the dispenser directs a spray of water onto the cast solid block of rinse agent which effectively dissolves a portion of the block creating a concentrated aqueous rinse solution which is then fed directly into the rinse water forming the aqueous rinse. The aqueous rinse is then contacted with the dishes to affect a complete rinse. This dispenser and other similar are capable of controlling the effective concentration of the active block copolymer in the aqueous rinse by measuring the volume of material dispensed, the actual concentration of the material in the rinse water (an electrolyte measured with an electrode) or by measuring the time of the spray on the cast block.
The following examples and data further illustrate the practice of the invention, should not be taken as invention and contains the best mode. The following examples and data show the effectiveness of the invention in promoting adequate rinsing.

Multi-step post detergent treatment method


Compositions described herein are aqueous detergent compositions, preferably hard surface cleaning compositions, which contain a flexible lamellar sheet phase dispersed in the aqueous phase. The compositions are viscous, provide excellent soap scum and hard water properties and are easy to rinse. Such compositions are formulated by using an alkylaryl detergent composition in combination with an alcohol and/or cationic surfactant, together with a hydrotropic solvent, in an acidic system further optionally comprising a peroxide.

This invention relates to liquid detergent compositions for use in cleaning hard surfaces, particularly bathroom surfaces. Such compositions typically contain detergent surfactants, solvents, builders, etc.
The use of solvents and organic water-soluble synthetic detergent surfactants for cleaning hard surfaces is well established. Known liquid detergent compositions comprise organic cleaning solvents, detergent surfactants, and optional detergent builders and/or abrasives.
Liquid cleaning compositions have the great advantage that they can be applied to hard surfaces in neat or concentrated form so that a relatively high level of, e.g., surfactant material and/or organic solvent is delivered directly to the soil. Therefore, liquid cleaning compositions have the potential to provide superior soap scum, grease, and oily soil removal as compared to dilute wash solutions, e.g., those prepared from powdered cleaning compositions.
It is often desirable to raise the viscosity of liquid hard surface cleaners. Higher viscosity can allow for more specific dispensing of the product during use. Also, higher viscosity can promote better action of the product on non-horizontal surfaces, such as toilets, bath tubs, shower and the like. Enhanced surface cling and coverage allows for improved cleaning action of the surfactant/solvent system. A product with shear-thinning viscosity is particularly preferred because it can be packaged and sold either as a spray or liquid product, is easy to use, and can deliver good cling and coverage on surfaces. These are important product attributes that limit the amount of product wasted, during use, through dripping. Additionally, a viscous, shear-thinning liquid product can be less irritating in-use and can be perceived as milder. Viscosity and shear-thinning properties can be obtained via methods known in the art, such as the use of shear-thinning gums or polymers. However, thickeners, such as gums or polymers have drawbacks in that they raise formula cost, yet provide only one benefit, thickening. They do not participate in the actual cleaning of the surface and therefore represent xe2x80x9cinertxe2x80x9d materials. In many cases, these polymers leave streaks and films on surfaces, and are often not shear-thinning enough to be useful in spray bottle applications.
Preferably, viscosity is built by a xe2x80x9cself-thickeningxe2x80x9d system wherein the surfactant/solvent actives in the composition are used to provide viscosity. Such an approach has several advantages versus polymeric thickeners. First, surfactant/solvent systems are often more economical than polymers. Second, the surfactants/solvents can provide a dual benefit by providing both viscosity and cleaning. Thickening polymers tend to compete for surface sites and can inhibit the action of the cleaning system. Third, judicious selection of surfactants/solvents allows for improved compatibility at acidic pH and/or with optional additives, such as peroxide. Many polymeric thickeners are either ineffective at a pH below 4, or are not compatible with optional actives such as peroxide. Finally, the residues of surfactants tend to be more easily rinsed away.
It is known in the art how to formulate self thickened compositions where the thickening is achieved without the use of polymeric thickeners, see for instance, EP 518 401 and EP 21 581, incorporated herein by reference. However, for many purposes these particular non-polymer thickened approaches are not desirable, since the viscosity is obtained at the expense of producing compositions that display very stable foams, leading to rinsing difficulties. This was addressed by WO95/33024, incorporated herein by reference, via the use of a combination of amine oxide and secondary or primary mono-branched alkyl sulfate or sulfonate surfactants in acidic media. Limitations of this approach are that it requires a specific choice of surfactant, and desirable viscosities are not achieved unless the product has a pH greater than 3, thus limiting the scope of hard water removal efficacy. Additionally, it has been discovered that the compositions of the present invention can incorporate higher levels of hydrotropic solvent, leading to improved soap scum removal, while still preserving the desired viscosity profiles. Compositions that are chemically similar to those of the present invention but do not predominantly exhibit a flexible lamellar phase structure do not provide the same level of cleaning. While not wishing to be limited by theory, it is believed that the lamellar structure provides a better coverage and/or more surfactant contact with the soil.
The present invention provides viscous acidic hard surface cleaning compositions suitable for removal of soils commonly encountered in the bathroom, said compositions being made viscous by means of a self thickening system, but which are nevertheless easy to rinse. These acidic hard surface cleaning compositions remove soap scum and hard water marks. The invention can provide viscous acidic hard surface cleaning compositions with shear-thinning properties suitable for dispensing out of either spray or liquid packages and which are non-irritating in use. The compositions can have disinfectant properties achieved through the choice of actives, including citric acid and cationic surfactants, and can be used with or without additives such as hydrogen peroxide for additional mold/mildew prevention benefits.
The hard surface detergent cleaning compositions herein are predominantly in the form of flexible lamellar sheets dispersed in an aqueous phase. Such compositions provide excellent soap scum cleaning; good hard-water-soil removal properties; low levels of suds; and excellent rinsing characteristics. The product viscosity is provided by shear-thinning rheology achieved through phase chemistry, specifically the formation of lamellar surfactant sheets dispersed in the aqueous phase. The invention relates more particularly to aqueous detergent compositions that comprise:
a. from about 1% to about 5% alkyl aryl sulfonate detergent surfactant;
b. from about 0.3% to about 2% nonionic alcohol and/or cationic surfactant;
c. from about 1% to about 8% of one, or more, hydrotropic solvents;
d. optionally, an effective amount, up to about 5% hydrogen peroxide; and
e. the balance an aqueous solvent system, and
wherein the cleaning compositions predominantly comprise flexible lamellar sheets dispersed in an aqueous phase and have a pH from about 0.5 to about 6.
The flexible lamellar sheets comprising surfactant provide viscosity and improved cleaning. It is believed that the improved cleaning is a direct result of the lamellar sheets, since the lamellar structure allows for more surfactant contact with the soil.
The compositions of the invention are especially useful for cleaning soils that are commonly encountered in the bathroom. These include dust particles, hard water stains, fatty acids, triglycerides, lipids, insoluble fatty acid soaps, and the like. The detergent compositions can be used on many different surface types, such as ceramic, Fiberglas, polyurethane, and plastic surfaces.
Alkyl aryl sulfonates are an essential component of the invention. Suitable alkyl aryl sulfonates can be neutralized with any alkali metal such as lithium, sodium, potassium and the like, or can alternatively be neutralized with an ammonium or C1-C9 ammonium salt derivative such as mono-ethanol amine, diethylamine, tri-isopropanol amine and the like. They can be produced via any suitable process, leading to the formation of either xe2x80x9clow 2-phenylxe2x80x9d or xe2x80x9chigh 2-phenylxe2x80x9d derivatives, though the xe2x80x9clow 2-phenylxe2x80x9d derivatives are generally preferred. Such surfactants are commercially available from several suppliers globally, including Witco Corporation (One American Lane, Greenwich, Connecticut 06831), Stepan Company (Edens and Witnetka Rd, Northfield, Ill. 60093) and BASF Aktiengesellschaft (ESA/1550, D-67056 Ludwigshafen, Germany).
The detergent compositions according to the present invention are prepared with relatively low levels of active. Typically, compositions will comprise sufficient surfactant and solvent, as discussed hereinafter, to be effective as hard surface cleaners yet remain economical; accordingly they typically contain from about 0.5% to about 5% alkyl aryl sulfonate surfactant, more preferably from about 1% to about 4.5% alkyl aryl sulfonate surfactant, and even more preferably from about 1.2% to about 4% alkyl aryl sulfonate surfactant.
The alkyl aryl sulfonates of the invention have a chain length average of from about 8 carbon atoms to about 14 carbon atoms, more preferably from about 9 carbon atoms to about 13 carbon atoms, most preferably from about 9 carbon atoms to about 13 carbon atoms. The chain length distribution can vary from about 8 carbon atoms to about 16 carbons. Mixtures of linear and/or branched alkyl aryl benzene sulfonates are suitable.
Ammonium and sodium salts of C11 to C12 linear alkyl benzene sulfonates are most preferred in the context of the present invention. Examples of particularly preferred, commercially available sodium alkyl benzene sulfonates include Polystep A-13(copyright) available from Stepan, Calsoft L40(copyright) A slurry available from Pilot Chemical Company (11756 Burke Street, Santa Fe Springs, Calif.). and Witconate P1059(copyright) available from Witco Corporation (Greenwich, Conn.). Alternatively, the desired alkyl aryl sulfonate surfactant can be produced in-situ by neutralization of the corresponding alkyl aryl sulfonic acid. Examples of suitable alkyl aryl sulfonic acids include Biosoft100(copyright) available from Stepan Company, Calsoft LAS-99(copyright) available from Pilot Chemical, and Lutensit A-LABS(copyright) available from BASF AG in Germany.
The detergent compositions of the present invention also preferably comprise one, or more nonionic alcohols, and/or cationic surfactants. The combination of the alkylaryl detergent surfactant with the alcohol and/or cationic surfactant is essential to the invention. Cleaning compositions comprising both nonionic alcohol and cationic surfactant can be employed. As used herein, xe2x80x9cnonionic alcoholxe2x80x9d means a linear or mono-branched nonionic alcohol comprising an average of from about 8 carbon atoms to about 16 carbon atoms, more preferably from about 9 carbon atoms to about 14 carbon atoms, most preferably from about 10 carbon atoms to about 13 carbon atoms. Examples of suitable nonionic alcohols include 2-butyl-1-octanol, 2-methyl-1-undecanol and dodecanol. Linear C10-13 nonionic alcohols are most preferred. Examples of preferred, commercially available nonionic alcohols include Neodol 1(copyright) and Neodol 23(copyright) available from Shell Chemical (1 Shell Plaza, Houston, Tex. 77252). It is believed that best results are achieved when the chain length of the nonionic alcohol most closely matches that of the alkyl aryl sulfonate surfactant. For this reason, nonionic alcohols comprising less than 8 carbon atoms or longer than 16 carbon atoms are not preferred in this invention. If present, the nonionic alcohol is present in effective concentrations not exceeding about 2%, more preferably in concentrations of 1.5% or less, most preferably in concentrations of 1.25% or less by weight of the composition.
Detergent compositions herein that do not contain a nonionic alcohol will normally contain one, or more, cationic surfactants. As used herein, cationic surfactants are those which at acidic pH behave substantially as cationic materials. The cationic surfactant is to creates viscosity via ion pairing with the alkyl aryl sulfonate surfactant disclosed hereinbefore. Cationic surfactants can also provide disinfectancy properties and can be selected so as to enhance such benefits. Preferred cationic materials have hydrophobic chain lengths of from about 8 carbon atoms to about 16 carbon atoms, more preferably from about 10 carbon atoms to about 16 carbon atoms, most preferably from about 12 carbon atoms to about 14 carbon atoms. Suitable cationic surfactants include quaternary alkyl and alkyl benzyl ammonium salts (e.g., Bardac(copyright) 208M from Lonza Incorporated, 1717 Route 208, Fairlawn, N.J. 07410), ethoxylated quaternary ammonium salts (e.g., Ethoquad(copyright) surfactants available from Akzo Nobel Chemicals, 300 South Riverside Plaza, Chicago, Ill.), ethoxylated amines (e.g., Ethomeen(copyright) surfactants available from Akzo Nobel Chemical), alkyl dimethyl betaines (e.g., Rewoteric AM DML-35(copyright) from Witco Corporation) or amido propyl betaines (e.g., Rewoteric AMB 15U(copyright) from Witco Corporation) and amine oxides (e.g., Barlox 10S(copyright) from Lonza Incorporated). Incorporation of quaternary ammonium surfactants is particularly preferred for compositions intended to deliver antibacterial, fungistatic and fungicidal properties. Quaternary ammonium surfactants are known in the art and include C10-16 alkyl trimethyl ammonium, C8-14 dialkyl dimethyl ammonium and C10-16 alkyl dimethylbenzyl ammonium derivatives and mixtures thereof Suitable and commercially available C10-16 alkyl trimethyl ammonium and C8-C 14 dialkyl dimethyl ammonium quaternaries are available from Witco corporation under the tradename Adogen(copyright); suitable C10-16 alkyl dimethylbenzyl ammonium surfactants may be purchased from Lonza incorporated under the tradename Bardac(copyright).
The level of cationic surfactant in the compositions of the present invention is preferably no greater than about 2%, more preferably no greater than about 1.5%, most preferably no greater than about 1.25% by weight of the composition. Cationic surfactants can be used alone or in combination with nonionic alcohols for viscosity. The level of cationic surfactant plus nonionic alcohol comprises at least about 0.3%, more preferably at least 0.4%, most preferably at least about 0.5%, and still more preferably from about 0.5% to about 2.0%, by weight of the composition.
The compositions can also contain one or more hydrotropic solvents at effective levels, typically no less than about 2%, preferably from about 2% to about 8%, more preferably from about 2% to about to about 6%, most preferably from about 3% to about 6% by weight of the composition.
It is experimentally found that viscosity building requires the use of hydrotropic solvent. By hydrotropic solvent, it is meant an agent which helps solubilize the hydrophobic ingredients in the compositions. The hydrotropic solvent participates in the building of the viscosity and increases the stability of the composition. Such solvents typically have a terminal C3-C6 hydrocarbon attached to from one to three ethylene glycol or propylene glycol moieties. Examples of commercially available hydrotropic solvents based on ethylene glycol chemistry include ethylene glycol mono butyl ether (Butyl Cellosolve(copyright) available from Union Carbide, 39 Old Ridgebury road, Danbury, Conn.), diethylene glycol mono-butyl ether (Butyl Carbitol(copyright) available from Union Carbide), and mono-ethylene glycol n-hexyl ether (Hexyl Cellosolve(copyright) available from Union Carbide). Examples of commercially suitable commercially available hydrotropic solvents based on propylene glycol chemistry include the mono-, di-, and tri-propylene glycol derivatives of propyl and butyl alcohol, which are available from Arco Chemical, 3801 West Chester Pike, Newtown Square, Pa. 19073) and Dow Chemical (1691 N. Sweede Road, Midland, Mich.) under the trade names Arcosolv(copyright) and Dowanol(copyright). The most preferred hydrotropic solvent is dipropylene glycol n-butyl ether, sold under the trade names Arcosolv DPNB(copyright) and Dowanol DPNB(copyright). The amount of hydrotropic solvent can vary depending on the amount of other ingredients present in the composition, but should be present in concentrations of from about 2% to about 8%, more preferably from about preferably 2% to about 6%, most preferably from about 3% to about 5% by weight of the total composition.
In the absence of hydrotropic solvent, the compositions of the present invention often appear as milky, low viscosity mixtures which are often indefinitely stable at room temperature conditions. Addition of hydrotropic solvent serves to increase product viscosity to yield more translucent solutions. It is believed that the solvent dilutes the initially obtained phase and transforms it into predominantly flexible lamellar sheets dispersed in the aqueous solvent system. Cryogenic tunneling electron microscopy (hereinafter Cryo-TEM) measurements indicate that the phase chemistry consists of small concentric vesicles which become increasing flexible and more open ended lamellar sheets upon the addition of hydrotropic solvent.
For purposes of hard water stain removal, the compositions are acidic with a pH of from about 0.5 to about 6, more preferably from about 1.5 to about 5, still more preferably from about 2.0 to about 4. For removal of hard water stains, the pH is typically about 3 or less. Acidity is preferably accomplished through the use of one or more organic acids that have a pKa of less than about 6, preferably less than about 4. Such organic acids assist in phase formation as well as provide hard water stain removal properties. It is found that organic acids are very efficient in promoting good hard water removal properties within the framework of the compositions of the present invention. Lower pH and use of one or more suitable acids is also found to be advantageous for disinfectancy benefits. Examples of suitable organic acids include citric acid, benzoic acid, lactic acid, tartaric acid, glycolic acid, succinic acid, glutaric acid, adipic acid, gluconic acid and mixtures thereof. Such acids are readily available in the trade. Examples of more preferred acids include citric acid (available from Aldrich Corporation, 1001 West Saint Paul Avenue, Milwaukee, Wis.), benzoic acid (available from Aldrich Chemical) and a mixture of succinic, glutaric and adipic acids available from DuPont (Wilmington, Del.) sold as xe2x80x9crefined AGS di-basic acidsxe2x80x9d. Citric acid is most preferred. The amount of organic acid in the compositions herein can be from about 1% to about 10%, more preferably from about 2% to about 8%, most preferably from about 3% to about 6% by weight of the composition.
The compositions of the invention can contain peroxide such as hydrogen peroxide, or a source of hydrogen peroxide, for further disinfectancy, fungistatic and fungicidal benefits. Peroxide is believed to enhance the longevity of the benefit because of its well known residuality and slow decomposition to produce radical species. The components of the present composition are substantially compatible with the use of peroxides. Preferred peroxides include benzoyl peroxide and hydrogen peroxide. These can optionally be present in the compositions herein in levels of from about 0.05% to about 5%, more preferably from about 0.1% to about 3%, most preferably from about 0.2% to about 1.5%.
When peroxide is present, it is desirable to provide a stabilizing system. Suitable stabilizing systems are known. A preferred stabilizing system consists of radical scavengers and/or metal chelants present at levels of from about 0.01% to about 0.5%, more preferably from about 0.01% to about 0.25%, most preferably from about 0.01% to about 0.10%, by weight of the composition. Examples of radical scavengers include anti-oxidants such as propyl gallate, butylated hydroxy toluene (BHT), butylated hydroxy anisole (BHA) and the like. Examples of suitable metal chelants include diethylene triamine penta-acetate, diethylene triamine penta-methylene phosphonate, hydroxyethyl diphosphonate and the like.
Optional Surfactants and Solvents
In addition to alkyl aryl sulfonates and the hydrotropic solvents, the compositions of the present invention preferably comprise other additional anionic surfactants. Such surfactants typically comprise a hydrophobic chain containing from about 8 carbon atoms to about 18, preferably from about 10 to about 16, carbon atoms, and include a sulfate, sulfonate or carboxylate hydrophilic head group. Examples of suitable anionic surfactants include linear or branched alkyl sulfate detergent surfactant (e.g., Stepanol AM(copyright) from Stepan), paraffin sulfonates (Hostapur SAS(copyright) from Hoechst, Aktiengesellschaft, D-6230 Frankfurt, Germany), alkyl ethoxy carboxylates detergent surfactant (Neodex(copyright) from Shell Chemical Corporation), and the like. It is found that alkyl sulfate surfactants, in particular, are preferred as they offer improved soap scum cleaning benefits. In general, the level of optional anionic surfactants in the compositions herein is from about 0.5% to about 2%, preferably from about 0.6% to about 1%, by weight of the composition.
Nonionic detergent surfactants can also be present. Suitable nonionic detergent surfactants for use herein are alkoxylated alcohols generally comprising from about 6 to about 16 carbon atoms in the hydrophobic alkyl chain of the alcohol. Typical alkoxylation groups are ethoxy and/or propoxy groups. Such compounds are commercially available under the series Neodol(copyright) from Shell, or Lutensol(copyright) from BASF AG with a wide variety of chain length and alkoxylation degrees. Preferred nonionic detergent surfactants for use herein are according to the formula R(X)nH, were R is an alkyl chain having from about 6 to about 16 carbon atoms, preferably from about 6 to about 10, X is an alkoxy group, preferably ethoxy, or a mixture of ethoxy and propoxy groups, n is an integer of from about 4 to about 30 preferably about 5 to about 8. Other non-ionic surfactants that can be used include those derived from natural sources such as sugars and include alkyl polyglucosides (e.g., Simusol(copyright) surfactants from Seppic Corporation, 75 Quai d""Orsay, 75321 Paris, Cedex 7, France) and N-alkyl glucose amide surfactants. If present, the concentration of nonionic surfactant is from about 0.1% to about 3%, more preferably from about 0. 1% to about 2%, by weight of the composition.
The compositions of the present invention can also include zwitterionic surfactants such as sulfobetaines and hydroxy sulfobetaines in effective concentrations preferably not exceeding about 2% by weight of the composition.
Other commercial sources of such surfactants can be found in McCutcheon""s EMULSIFIERS AND DETERGENTS, North American Edition, 1997, McCutcheon Division, MC Publishing Company, also incorporated herein by reference.
The Aqueous Solvent System and Other Solvents
The compositions are in aqueous form, comprising at least about 60% aqueous solvent by weight of the composition, more preferably from about 60% to about 90% by weight of the composition. The aqueous solvent system can comprise low molecular weight solvents typically found in detergent compositions like ethanol, isopropanol, etc.
The compositions of the present invention can also include other solvents, and in particular paraffins, which have been found to substantially reduce the suds created by the composition.
Optional components, such as perfumes and other conventional adjuvants can also be present.
Optional Perfume and Additional Adjuvants
An optional, but highly preferred ingredient, is a perfume, usually a mixture of perfume ingredients. Indeed, perfume ingredients, which are typically hydrophobic materials, have been found to provide a contribution to building viscosity, perhaps through supporting the phase structure of the product, as well as improving the overall stability of the product. As used herein, perfume includes constituents of a perfume which are added primarily for their olfactory contribution.
Most hard surface cleaner products contain some perfume to provide an olfactory aesthetic benefit and to cover any xe2x80x9cchemicalxe2x80x9d odor that the product may have. The main function of a small fraction of the highly volatile, low boiling (having low boiling points), perfume components in these perfumes is to improve the fragrance odor of the product itself, rather than impacting on the subsequent odor of the surface being cleaned. However, some of the less volatile, high boiling perfume ingredients can provide a fresh and clean impression to the surfaces, and it is sometimes desirable that these ingredients be deposited and present on the dry surface. The perfumes are preferably those that are more water-soluble and/or volatile to minimize spotting and filming. The perfumes useful herein are described in more detail in U.S. Pat. No. 5,108,660, Michael, issued Apr. 28, 1992, at col. 8 lines 48 to 68, and col. 9 lines 1 to 68, and col. 10 lines 1 to 24, said patent, and especially said specific portion, being incorporated by reference.
Perfume components can be natural products such as essential oils, absolutes, resinoids, resins, concretes, etc., and/or synthetic perfume components such as hydrocarbons, alcohols, aldehydes, ketones, ethers, acids, acetals, ketals, nitriles, etc., including saturated and unsaturated compounds, aliphatic, carbocyclic and heterocyclic compounds. Examples of such perfume components are: geraniol, geranyl acetate, linalool, linalyl acetate, tetrahydrolinalool, citronellol, citronellyl acetate, dihydromyrcenol, dihydromyrcenyl acetate, terpineol, terpinyl acetate, acetate, 2-phenylethanol, 2-phenylethyl acetate, benzyl alcohol, benzyl acetate, benzyl salicylate, benzyl benzoate, styrallyl acetate, amyl salicylate, dimenthylbenzylcarbinol, trichloromethylphenycarbinyl acetate, p-tert.butyl-cyclohexyl acetate, isononyl acetate, alpha-n-amnylcinammic aldehyde, alpha-hexyl-cinammic aldehyde, 2-methyl-3-(p-ter.butylphenyl)-propanal, 2-methyl-3(p-isopropylphenyl)propanal, 3-(p-tert.butylphenyl)propanal, tricyclodecenyl acetate, tricyclodecenyl propionate, 4-(4-hydroxy-4-methylpentyl)-3-cyclohexenecarbaldehyde, 4-(4-methyl-3-pentenyl)-3cyclohexenecarbaldehyde, 4-acetoxy-3-pentyl-tetrahhydropyran, methyl dihydrojasmonate, 2-n-heptyl-cyclopentanone, 3-methyl-2-pentyl-cyclopentanone, n-decanal, n-dodecanal, 9-decenol-1, phenoxyethyl isobutyrate, phenylacetaldehyde dimenthyl acetal, phenylacetaldehyde dicetyll acetal, geranonitrile, citronellonitrile, cedryl acetate, 3-isocamphyl-cyclohexanol, cedryl ether, isolongifolanone, aubepine nitrile, aubepine, heliotropine, coumarin, eugenol, vanillin, diphenyl oxide, hydroxycitronellal, ionones, methyl ionones, isomethyl ionones, irones, cis-3-hexenol and esters thereof, indane musks, tetralin musks, isochroman musks, macrocyclic ketones, macrolactone musks, ethylene brassylate, aromatic nitromusk. Compositions herein typically comprise from 0.1% to 2% by weight of the total composition of a perfume ingredient, or mixtures thereof, preferably from 0.1% to 1.0%. In the case of the preferred embodiment containing peroxide, the perfumes must be chosen so as to be compatible with the oxidant. In a preferred execution, the perfume ingredients are hydrophobic and highly volatile, e.g., ingredients having a boiling point of less than about 260xc2x0 C., preferably less than about 255xc2x0 C.; and more preferably less than about 250xc2x0 C., and a ClogP of at least about 3, preferably more than about 3.1, and even more preferably more than about 3.2.
The logP of many ingredients has been reported; for example, the Pomona92 database, available from Daylight Chemical Information Systems, Inc. (Daylight CIS), Irvine, Calif., contains many, along with citations to the original literature. However, the logP values are most conveniently calculated by the xe2x80x9cCLOGPxe2x80x9d program, also available from Daylight CIS. This program also lists experimental logP values when they are available in the Pomona92 database. The xe2x80x9ccalculated logPxe2x80x9d (ClogP) is determined by the fragment approach of Hansch and Leo (cf., A. Leo, in Comprehensive Medicinal Chemistry, Vol. 4, C. Hansch, P. G. Sammens, J. B. Taylor and C. A. Ramsden, Eds., p. 295, Pergamon Press, 1990, incorporated herein by reference). The fragment approach is based on the chemical structure of each ingredient, and takes into account the numbers and types of atoms, the atom connectivity, and chemical bonding. The ClogP values, which are the most reliable and widely used estimates for this physicochemical property, are preferably used instead of the experimental logP values in the selection of the principal solvent ingredients which are useful in the present invention. Other methods that can be used to compute ClogP include, e.g., Crippen""s fragmentation method as disclosed in J. Chem. Inf. Comput. Sci., 27, 21 (1987); Viswanadhan""s fragmentation method as disclose in J. Chem. Inf. Comput. Sci., 29, 163 (1989); and Broto""s method as disclosed in Eur. J. Med. Chem.xe2x80x94Chim. Theor., 19, 71 (1984).
The compositions herein can comprise a variety of other optional ingredients, including further actives and detergent builder, as well as mere aesthetical ingredients. In particular the rheology of the compositions herein would be suitable for suspending particles in the composition, e.g., particles of abrasives.
Detergent builders that are efficient for hard surface cleaners and have reduced filming/streaking characteristics at the critical levels are another optional ingredient. Preferred detergent builders are the carboxylic acid detergent builders described hereinbefore as part of the carboxylic acid disclosure, including citric and tartaric acids. Tartaric acid improves cleaning and can minimize the problem of filming/streaking that usually occurs when detergent builders are added to hard surface cleaners.
The detergent builder is present at levels that provide detergent building, and, if not part of the acid pH adjustment described hereinbefore, are typically present at a level of from about 0.1% to about 0.3%. more preferably from about 0.2% to about 2%, and most preferably from about 0.5 to about 1.0%.
Typically the improvement with regard to acceptable filming/streaking results occurs most when the builder is combined with amphoteric and/or zwitterionic detergent surfactant compositions although an improvement is also seen with the less preferred anionic or anionic/nonionic detergent surfactant compositions.
The compositions herein can also contain other various adjuncts which are known to the art for detergent compositions. Preferably they are not used at levels that cause unacceptable filming/streaking.
Non-limiting examples of other adjuncts are: enzymes such as proteases; hydrotropes such as sodium toluene sulfonate, sodium cumene sulfonate and potassium xylene sulfonate; thickeners such as xanthan gums, e.g., Keltrol, or Keltrol RD, typically at a level of from about 0.01% to about 2%, preferably from about 0.05% to about 0.5%; and aesthetic-enhancing ingredients such as colorants, providing they do not adversely impact on filming/streaking.
Antibacterial agents can be present, but preferably only at low levels to avoid filming/streaking problems. More hydrophobic antibacterial/germicidal agents, like orthobenzyl-para-chlorophenol, are avoided. If present, such materials should be kept at levels below about 0.1%.
Composition Making
The compositions herein can be made by mixing together all ingredients. In general, a preferred order of addition is to first incorporate water, alkyl aryl sulfonate surfactant and organic acid, followed by optional anionic, non-ionic and/or zwitterionic surfactants. The mixture is initially cloudy and becomes less opaque as hydrotropic solvent is added; the addition of hydrotropic solvent also results in a substantial increase in product viscosity resulting from the formation of more flexible and more open-ended vesicles and/or lamellar sheets. In most cases, addition of hydrotropic solvent causes the solution to become translucent or transparent. Once the solvent is added, pH is adjusted to optimum as desired by the formulator. Optional peroxide, perfume and dye can then be added. The compositions herein eventually reach a viscosity of from 50 cP to 200 cP, measured using a Brookfield viscometer at a 60 RPM shear rate with spindle #2.
As used herein, all numerical values are approximations based upon normal variations, all parts, percentages, and ratios are by weight unless otherwise specified, and all patents and other publications are incorporated herein by reference.
Experimental
Phase Chemistry by Cryo-TEM
Samples are prepared in a controlled environment vitrification system (CEVS) which is described in J. Electron Microsc. Tech., 1988, 10, 87-111, said article being incorporated herein by reference. A 5 xcexcl drop of the sample solution is placed on a carbon-coated polymer support film with holes in the film, said film being mounted on the surface of a standard 300-mesh TEM grid (Ted Pella, Inc., Catalog # 01883). The drop is blotted with filter paper until it is reduced to a thin film (10-200 nm) of the sample spanning the holes (2-8 xcexcm) of the support film. The sample is then vitrified by rapidly plunging it through a synchronous shutter at the bottom of the CEVS into liquid ethane at its freezing point. The vitreous specimen is transferred under liquid nitrogen into a Philips CM12 microscope or a CM120 microscope with integrated bio-filter for imaging. The temperature of the sample is kept under xe2x88x92170xc2x0 C. throughout the examination. Images are recorded either on Kodak SO-163 film or by a Gatan slow-scan CCD camera with Digital Micrograph software.
Soap Scum Cleaning
Standard soiled plates that are used to provide a reproducible, standard soiled surface are treated with each product and the surface is then wiped with a sponge using a Gardner Straight line Washability Machine. The number of strokes required for complete cleaning is measured and recorded. The soap scum cleaning index is calculated using the following equation: (# strokes for control product/# strokes for experimental product) * 100, where the control product is Mastro Lindo (Italy) and the experimental prototypes are compositions 1-8 disclosed herein. Indices greater than 100 are suggestive of products with superior soap scum removal properties.
Hard Water Cleaning
Four marble chips for each product tested of approximate dimensions xc2xexe2x80x3xc3x97xc2xexe2x80x3xc3x97xc2xcxe2x80x3 are weighed to four decimal places using an analytical balance. The chips are then placed in 100 ml beakers containing 20 grams of product for a total of 10 minutes. The marble chips are then removed, rinsed and allowed to dry. They are then re-weighed and the weight lost is computed. Using averages of four trials for each product, the hard water removal index is computed as follows: (average weight loss of the marble chips immersed in the control product/average weight loss of the marble chips immersed in the experimental compositions) * 100.

Aqueous cleaning compositions in dispersed lamellar phase


Novel polymer compositions are disclosed, along with their use as well service fluids, for example as completion fluids, work-over fluids or drilling fluids, comprising water soluble copolymers having sulfonate groups and carboxylate groups, along with alkali metal salts of carboxylic acid. Exemplary copolymer has 5 to 95 wt. % structural units derived from 2-acrylamido-2-methylpropanesulfonic acid or salt thereof, and 5 to 95 wt. % structural units derived from acrylic acid or salt thereof. A salt of the polymer may be used, such as the sodium, potassium, ammonium and calcium salts. Exemplary alkali metal salts of the polymer composition include sodium, potassium and cesium salts of formic acid and/or acetic acid in amounts suitable to develop high temperature viscosity suitable for such well servicing fluids. The polymer composition is hydrateble/soluble in a brine of sodium and/or potassium and/or cesium salts of formic and/or acetic acid.

This invention relates to certain polymer compositions, their preparation and their use as viscosifiers in alkali metal salt solutions which are particularly useful in viscosifying well-drilling fluids for oil field operations at temperatures above 350xc2x0 F.
It is known to use aqueous polysaccharide compositions in well-drilling operations, e.g. in oil and gas wells. Examples of polysaccharides include cellulose derivatives, such as carboxyethylcellulose, carboxymethylcellulose, carboxyrnethylhydroxyethylcellulose, alkylhydroxyalkylcelluloses, alkylcelluloses, alkylcarboxyalkylcelluloses and hydroxyalkylcelluloses (particularly hydroxyethylcellulose); and microbial polysaccharides such as Succinoglycan polysaccharides, Scleroglucan polysaccharides and Xanthan polysaccharides.
In order to achieve suitable density for use in well-drilling operations, it is conventional for the known aqueous polysaccharide compositions to include water soluble salts, e.g. as described in UK Patent No. 1,549,734. These salts are typically halide salts (e.g. chlorides and bromides) of mono- or divalent cations, such as sodium, potassium, calcium and zinc, e.g. sodium chloride, potassium chloride, calcium bromide or zinc bromide.
One problem faced in drilling operations relates to thermal stability of well service fluids such as completion fluids, work-over fluids and drilling fluids. Temperatures in subsurface formations generally rise approximately 1 degree C. per hundred feet (30 meters) depth. Any aqueous polysaccharide composition has its own characteristic temperature above which it undergoes severe chemical degradation with undesirable reduction of viscosity, thus imposing limitations upon its use in drilling operations below a corresponding depth.
Additives, for example blends of polymeric alkaline materials such as that sold by International Drilling Fluids (UK) Ltd., under the trade mark xe2x80x9cPTS 200,xe2x80x9d have been used to improve thermal stability of aqueous polysaccharide compositions.
Polymer compositions have now been found that have excellent thermal stability and excellent performance characteristics for use in well service fluid applications. Novel polymer/alkali metal carboxylate compositions disclosed here are suitable for use in aqueous well servicing fluids and incorporate high molecular weight copolymer soluble in brine. Adding salt to a solution of polymer in water is a known method of removing the polymer from solution. The highest molecular weights will come out of solution first and, as more and more salt is added, lower and lower molecular weight polymers come out of solution. In contrast, in the novel aqueous polymer compositions disclosed here, the high molecular weight copolymer, further described below, is sufficiently soluble in brine comprising alkali metal carboxylate to develop suitable high temperature viscosity, that is, viscosity at the elevated temperatures encountered by well drilling fluids. Moreover, in accordance with at least certain preferred embodiments, the polymer compositions have xe2x80x9cdurablexe2x80x9d viscosity, that is, advantageous density and excellent high temperature viscosity is maintained even after prolonged working of the well service fluid. The polymer compositions disclosed here comprise water soluble copolymer having functionality which includes at least sulfonate groups and carboxylate groups. The copolymer is sufficiently soluble in saturated and other high concentration brines of alkali and metal salt(s) of carboxylic acid(s), for example, cesium formate brine, to provide polymer compositions having good density and excellent high temperature viscosity for well servicing fluids.
According to one aspect of the present invention, there is provided aqueous polymer compositions comprising the aforesaid copolymer having at least sulfonate group and carboxylate group functionality, dissolved in brine for use as well service fluids, such as completion fluids, work-over fluids and drilling fluids. Preferably, such soluble copolymer is the polymerization reaction product of acrylamidomethylpropanesulfonic acid or salt thereof with acrylic acid and/or alkali metal salts or ammonium salts of carboxylic acid or other suitable unsaturated carbonyl compounds.
In accordance with another aspect, an aqueous polymer composition comprises water soluble copolymer having functionality including at least sulfonate groups and carboxylate groups, and alkali metal salt of carboxylic acid.
It will be apparent to those skilled in the art that incidental quantities of other salts, such as sulfates, nitrates and bicarbonates, may also be present in compositions of the invention, and inevitably will be present in compositions where sea water or other naturally occurring brine is used in preparing the composition. If desired the composition may also contain an antioxidant, e.g. 2-mercaptobenzothiazole and/or other suitable additives. When 2-mercaptobenzothiazole is used it may conveniently be incorporated in the same proportion, w/v, as the water soluble copolymer. Those skilled in the art will appreciate that 1% w/v corresponds to a concentration of 10 kgm.sup.xe2x88x923 (10 g/l) of composition. It is advantageous for the pH of the composition to be preferably greater than 8.0, but not higher than 11.5, preferably at least 9.0 and less than 10.5, for reasons of stability and reduced corrosiveness of the composition. The pH may be controlled by addition of suitable reagents, e.g. sodium hydroxide. The presence of a monovalent salt, e.g., a carbonate salt, e.g. potassium carbonate or cesium carbonate , in the composition can enable a suitable buffering effect to be achieved.
The invention also provides a process of preparing an aqueous polymer composition of the invention. In accordance with one aspect, the alkali metal salt of carboxylic acid is added to an aqueous composition, optionally a brine composition, in which the water soluble copolymer is already dissolved and hydrated. In accordance with one preferred embodiment, the alkali metal salt of formic, acetic and/or other suitable carboxylic acid is added to an aqueous composition containing the water soluble copolymer with, when present, other salts and/or other ingredients, etc. In accordance with an alternative embodiment, the polymer composition described above comprising the water soluble copolymer and the alkali metal salt of carboxylate acid, optionally with other dry ingredients, intended for use in a well service fluid, is provided as a dry powder to which water or brine solution is added to hydrate the polymer and dissolve the alkali metal salt of carboxylic acid. In accordance with another alternative embodiment, the water soluble copolymer is added to a brine comprising the alkali metal salt.
In accordance with certain preferred embodiments, the brine employed in an aqueous polymer composition of this invention contains primarily sodium or potassium salt of carboxylic acid, although as mentioned above, other salts may be present in trace or minor amounts. Typically, such brines are substantially saturated solutions of the sodium or potassium salt. In other preferred embodiments, the cesium salt of carboxylic acid is used with only trace or minor amounts of other salts. Such cesium brines provide aqueous polymer compositions of higher density than corresponding compositions employing sodium or potassium brines. More specifically, for example, aqueous polymer compositions of the invention employing cesium brines above about 40% to 43% w/w (i.e., 4 parts by weight of cesium salt to 10 parts by weight of water used in the polymer composition) have density equal to or greater than corresponding compositions employing substantially saturated potassium brine. Thus, in accordance with certain especially preferred embodiments, aqueous polymer compositions of the invention employ the water soluble copolymer in a cesium formate brine or other suitable brine of cesium carboxylate, with at most only trace or minor amounts of other salts (i.e., such as might be contributed by sea water), and the cesium salt is used in an amount from about 40% to fully saturated.
In accordance with another aspect, there is provided the use of a polymer composition of the invention as a well service fluid, especially as a completion fluid, a work-over fluid or drilling fluid in a well-drilling operation. Preferably, the water soluble copolymer has a weight average molecular weight of at least about 1,000,000, preferably from 1,000,000 to 5,000,000, more preferably 1,500,000 to 3,000,000. In that regard, it is a significant advantage of the present invention, that at least preferred embodiments of the aqueous polymer compositions disclosed here provide well servicing fluids which develop high viscosity, i.e., have an improved and retained viscosity at temperatures up to at least 425xc2x0 F. Moreover, it is a notable advantage of the present invention that such preferred embodiments retain their excellent viscosity characteristics at elevated temperature even after extended use as a completion or drilling fluid. In certain preferred embodiments, the copolymer is soluble in a saturated alkali metal carboxylate brine solution, e.g., is a substantially saturated cesium formate solution, in an amount of at least about 4 lbs/bbl, more preferably at least 6 lbs/bbl. Certain such preferred embodiments have retained viscosity at temperatures up to at least about 425xc2x0 F. after 700 hours of extended use as a well service fluid, as tested and defined by xe2x80x9cRecommended Practice Standard Procedure for Field Testing Water-Based Drilling Fluidsxe2x80x9d API Recommended Practice 13B-1 (RP 13B-1) First Edition, Jun. 1, 1990 (American National Standard, ANSI/API RP 13B-1-90 Approved: Jul. 12, 1993) . Certain such preferred embodiments employing the high molecular weight, water soluble copolymer described above in an amount of 0.05 to 5 wt. % (based on the total weight of all solids components of the polymer composition) and the alkali metal carboxylate in an amount of 95 to 99.95 wt. % (also based on the weight of all solids components) to produce a substantially saturated or other concentration brine, to provide a well-servicing fluid which develops an apparent viscosity greater than or equal to 20 cPs., a plastic viscosity of greater than or equal to 15 cPs, and a yield point of greater or equal to 5 lb./100 ft2 when dissolved in alkali metal formate brine at a concentration of 2 pounds per barrel and measured at 120 degrees F. In accordance with certain highly preferred embodiments, the well-servicing fluid retains at least 50% of its apparent viscosity after roller aging for 30 days at 375 degrees F. and measured at 120 degrees F. Suitable water soluble copolymers can be prepared in accordance with the teachings of published European patent application No. EP 0068189, the entire disclosure of which is hereby incorporated by reference.
The alkali metal salt of carboxylic acid preferably is selected from the sodium, potassium and cesium salts of suitable carboxylic acids, preferably C1 to C3 carboxylic acid, most preferably the sodium, potassium and/or cesium salts of formic acid, acetic acid or mixtures thereof that are blended to obtain the desired density of the drilling, completion, workover or packer fluid. In accordance with certain preferred embodiments, substantially saturated brine of sodium formate, sodium acetate, potassium formate and/or potassium acetate is used. In accordance with other preferred embodiments, the brine is a 40% w/w or high solution of cesium formate and/or cesium acetate. In accordance with certain highly preferred embodiments, at least about 5 wt. % of the alkali metal salt of carboxylic acid is the cesium salt. Such embodiments are found to provide well service fluids having high density and unexpectedly advantageous density and durable viscosity. In that regard, the cesium brines at about 43% of saturation are found to provide densities equal to the density of substantially saturated potassium brines. At concentrations higher than 43%, the cesium brines advantageously provide even high densities, such as 2.18 to 2.3. As noted above, it is a significant and unexpected advantage of the polymer compositions disclosed here, that they are sufficiently water soluble to yield durable, high temperature viscosities suitable for well servicing fluids, in saturated brines of alkali metal carboxylates or in brines having salt concentrations less than saturation but sufficiently high to provide necessary density levels. It is significant and quite unexpected, for example, that the water soluble copolymers disclosed above, having a weight average molecular weight of 1,000,000 to 5,000,000 are soluble at least to levels of 0.05 to 5.0 wt. % (based on the weight of all solids contents of the polymer composition) in an 80% brine or higher of alkali metal carboxylate, yielding an apparent viscosity greater than or equal to 20 cPs., a plastic viscosity of greater than or equal to 15 cPs, and a yield point of greater or equal to 5 lb./100 ft2 when dissolved in alkali metal formate brine at a concentration of 2 pounds per barrel and measured at 120 degrees F. Moreover, this advantageous viscosity is durable, in that the aqueous polymeric compositions retain at least 50% of its apparent viscosity after roller aging for 30 days at 375 degrees F. and measured at 120 degrees F. As discussed elsewhere herein, it should be understood that reference to a cesium brine means a brine in which cesium carboxylate is the only or the primary salt. Brines in which cesium carboxylate is the primary salt have only trace or minor amounts of other salts, such as would be introduced through the use of seawater in the polymer composition. Corresponding meanings apply for potassium brine, sodium brine, etc.
Preferably the water soluble copolymer is an AMPS copolymer prepared as the reaction product of 2-acrylamido-2-methylpropanesulfonic acid or salt thereof, most preferably 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid or salt thereof, with acrylamide, vinylpyrrolidone, acrylic acid or salt thereof. Optionally, a crosslinker reactant also is employed to achieve a higher molecular weight copolymer reaction product. Alternatively, reaction conditions may be controlled or other techniques employed to achieve a desired molecular weight without the use of a cross-linking agent. When used, the cross-linking agent should be at least bifunctional, such as N,Nxe2x80x2-methylenebis[2-propenamide]. The water soluble copolymer preferably has about 5 to 95 wt. %, more preferably about 40 to 80 wt. % structural units derived from the 2-acrylamido-2-methylpropanesulfonic acid or salt thereof, or like reactant, and about 5 to 95 wt. %, more preferably about 20 to 60 wt. % structural units derived from the acrylic acid or its salt or like reactant, and about 0 to 5 wt. %, more preferably about 0 to 0.1 wt. % structural units derived from the cross-linking agent. Preferred salts of the copolymer include, for example, alkali metal salts, ammonium salts and the like.
An aqueous polymer composition suitable for use as a well service fluid, comprises the polymer composition described above together with water or brine solution in an amount preferably sufficient to substantially fully hydrate the water soluble copolymer and to dissolve the alkali metal salt of carboxylic acid.
In accordance with preferred embodiments, the water soluble copolymer is present in an amount of about 0.05 to 5.0 wt. %, based on the combined weight of all of the dry ingredients of the polymer composition period reference here to the dry ingredients means the undissolved salt(s), non-hydrated copolymer, and any other solids of the polymer composition in the absence of water. Typically, therefore, the dry ingredients will include the copolymer, alkali metal salt of carboxylic acid, the solids content of any additives, etc. The alkali metal salt in such preferred embodiments is present in an amount of about 95 to 99.95 wt. %, again based on the combined weight of the dry ingredients. These amounts are stated for the dry ingredients, not including the water content of any polymer compositions disclosed here which are aqueous polymer compositions.
The polymer compositions may further comprise other suitable ingredients, including, for example, alkali metal salts of at least 1 halide. Thus, for example, the polymer compositions may incorporate the sodium, potassium and/or cesium salts of chloride, bromide or mixtures thereof. In addition, minor amounts of suitable additive may be present in the polymer -compositions, including for example, any of the additives currently known for use in well servicing fluids of this general type.
The water soluble copolymer can be prepared in accordance with known polymerization techniques. Preferably, 2-acrylamido-2-methylpropanesulfonic acid or like AMPS reactant is polymerized together with acrylic acid or other suitable carboxylic acid, after which the resulting water soluble copolymer is optionally neutralized to the salt by addition of suitable ammonium, sodium or calcium compound or the like. It should be understood that the term water swellable and water soluble is used herein to include both the dry and the hydrated form of the copolymer, unless otherwise clearly indicated by context. As such, it will be recognized that the term water-soluble refers to the hydrophilic nature of the copolymer whether or not the polymer is in the hydrated form. It should also be recognized that the term acrylic acid is used here interchangeably with propanoic acid.

Compositions comprising water soluble copolymer and cesium salt of a carboxylic acid