DE69130137T2

DE69130137T2 - Method of preventing tissue incrustation

Info

Publication number: DE69130137T2
Application number: DE69130137T
Authority: DE
Inventors: Stephen B. Alameda California 94501 Kong
Original assignee: Clorox Co
Current assignee: Clorox Co
Priority date: 1990-06-22
Filing date: 1991-06-20
Publication date: 1999-01-28
Anticipated expiration: 2011-06-21
Also published as: ES2121770T3; ATE170910T1; EP0463802A1; CA2044947A1; JPH05132697A; DE69130137D1; EP0463802B1

Abstract

Cleaning composition and method comprising in a first embodiment an alkali metal carbonate builder and a fabric encrustation prevention system comprising a sub-stoichiometric level of an organic dicarboxylic acid, water-soluble salts or anhydrides thereof which acts to inhibit and prevent the deposition of insoluble precipitates containing water hardness ions on fabrics; in a second embodiment the cleaning composition includes a detersive surfactant for laundry applications, in either embodiment the following adjuncts may be included: co-builders, alkali metal silicates, bleaching species, enzymes, fragrances, dyes, brighteners and others.

Description

The invention relates to methods for preventing crust formation on fabrics by reducing or suppressing the formation of crusting residues when detergent applications and formulations are used during "hard water" washing of fabrics. The invention particularly relates to the use of certain organic dicarboxylic acids to prevent the growth or deposition of insoluble compounds on fabric surfaces during washing operations. The invention primarily relates to inhibiting the formation and deposition of insoluble compounds on the fabric.

The growth of insoluble compounds on fabric surfaces (fabric encrustation) due to repeated washing with phosphate-free detergents in "hard water" is a negative effect that affects the appearance and feel of the fabric. The fabric takes on a rough feel and dyed garments show a faded appearance.

The insoluble compounds are primarily calcium and magnesium carbonate precipitates caused by builders such as sodium carbonate typically used in phosphate-free detergents. Prevention of scaling or deposition of insoluble compounds formed during the "hard water" wash process is therefore highly desirable. Phosphonates and polyacrylates have been shown to be effective in preventing scaling in detergent applications. Phosphonates can act as crystal growth inhibitors, preventing the growth of insoluble calcium and magnesium compounds at substoichiometric concentrations. Polyacrylates can act as sequestering and dispersing agents, as well as crystal growth inhibitors. Some disadvantages associated with phosphonates and polyacrylates are that phosphonates can contribute to eutrophication and that polyacrylates are not biodegradable.

High performance laundry detergents typically contain two main ingredients, namely surfactant and builder, as well as a number of other ingredients that are essential to an acceptable product. Although of minor importance to detergency, these additional ingredients can impart desirable functions to the overall formulated detergent. These various ingredients include anti-corrosion agents, anti-redeposition agents of contaminants, fluorescent whitening agents, bleaches, enzymes, odorants, etc. The two main ingredients most important for the washing power are the surfactant and the builder.

The surfactant provides the detergent with a detergency effect based on its fundamental property of adsorbing or concentrating at the contaminant/fiber/water interface. The detergent builder acts primarily to prevent interference with the surfactant effect by calcium and magnesium ions resulting from water hardness. The builder can also provide alkalinity, thereby improving fatty acid saponification and buffering capacity, preventing flocculation, maintaining ionic strength, extracting metals from contaminants, and removing alkaline earth metal ions from wash solutions. Phosphates are extremely effective builders, but are disadvantageous in lakes and rivers because of their eutrophication effect. Many states in the United States have passed laws limiting phosphate levels. This legislation to reduce phosphate levels has resulted in a variety of non-phosphate builders being proposed and/or used. Examples include silicates, zeolites, carbonates and polycarboxylates, citrates, EDTA and sodium nitrilotriacetate (NTA). These alternatives themselves also have various limitations. Silicates are not preferred because they are not completely water soluble and can therefore precipitate on the fabrics. They can also form precipitates with the ions resulting from hardness. Zeolites are generally effective co-builders, but not necessarily as the only builder. Polycarboxylate builders are expensive.

High levels of alkali metal carbonates have been found to be effective phosphate-free builders, particularly in applications where a high pH is required, for example for the removal of oily soils. A disadvantage associated with such high carbonate levels is that the calcium and magnesium ions present in the wash water readily form precipitates with the carbonates and that these precipitates deposit and/or form on the fabrics. These precipitates leave the fabrics with a rough feel and a worn appearance. Various approaches have been made in the prior art to combat the formation of calcium or magnesium precipitates, including Addition of seed crystals, crystal growth inhibitors and non-precipitating sequestrants. Non-precipitating sequestrants and complexing agents tend to be expensive due to the stoichiometric levels required and therefore contribute significantly to the overall cost of the preparation.

US Patent 3,896,056 relates to detergent builders which contain as essential ingredients an organic surfactant, a precipitating builder and a precipitation modifier. This patent describes a functional test to test the ability of compounds to prevent the formation of precipitates as an indication of their effectiveness as crystal growth inhibitors. A detergent matrix consisting of an inorganic precipitating builder is used. A number of polycarboxylic acid compounds are described as precipitation modifiers.

US-PS 4 097 016 relates to a solid washing, cleaning and bleaching agent which contains at least one basic compound, a solid polylactone as a sequestering agent and which may also contain activators for persalts, such as anhydrides of organic acids, succinic acid, phthalic acid and the like.

US-PS 4,814,102 describes copolymers consisting of acrylic, maleic, fumaric, itaconic or hydroxyalkyl esters of these acids as builders, inhibitors for incrustations or dispersants in detergents.

Phosphate-free detergent formulations are described in numerous patents. EP 130 640 describes a laundry detergent comprising a surfactant, 5 to 80% of a phosphate-free detergent builder, which may be a carbonate, and about 0.3 to 5% of a polyacrylate polymer. EP 137 669 describes a detergent composition containing 5 to 60% surfactant, 7 to 80% polycarboxylate/zeolite builder and a bleaching system.

EP 82 564 describes machine dishwashing and rinsing agents containing non-ionic detergent surfactants, a water-soluble calcium sequestrant, a special polymeric material and an alkaline detergent material to produce a composition having improved non-film forming, non-staining or non-streaking properties. It is stated that the calcium sequestrants comprise an organic builder salt such as water-soluble citrates, a water-soluble salt of nitrilotriacetic acid (NTA), a water-soluble salt of carboxymethoxysuccinic acid or other builders such as zeolites or organic chelating agents.

EP 82 564 shows an example of a calcium sequestrant. It is described that dipicolinic acid does not cause film formation on dishes. Similarly, according to US 3 850 852, sodium carbonate is combined with a polyacrylate, a phosphonate and a calcium sequestrant.

EP 233 730 describes the use of 2,6-pyridinedicarboxylic acid as a chelating stabilizer for potassium sulfoperoxybenzoate in detergent compositions. This is necessary in cases where inorganic or organic peroxyacids are unstable in the presence of non-ionic surfactants. It was not possible to consider the storage of liquid compositions containing both components without the use of a chelating peroxidic stabilizer such as dipicolinic acid.

EP 266 904 relates to dishwasher detergents containing few or zero phosphates using dipicolinic acid derivatives as builders. Enzymes are also provided to improve performance.

Also mentioned are DE-A-2 240 309 (GB 1 398 263) which is said to be based on the discovery that a detergent composition containing an alkali metal carbonate detergent builder is improved when a calcium sequestrant and a calcium carbonate anti-deposit agent are incorporated therein; EP-A-0 094 723 which relates to a method of washing fabrics in hard water and phosphate-free detergent compositions for use therein; and FR-A-2 396 076 (GB 2 000 177) which relates to a detergent composition in which the acid component and the alkaline component are present separately.

The prior art describes polymers of aliphatic polycarboxylic acids as builders in detergent preparations. However, it has not yet been recognized that substoichiometric concentrations of the monomeric forms of some of these compounds alter the kinetics or crystal morphology of calcium carbonate and can therefore be used in industry to prevent scale formation and to reduce crust formation in fabrics in phosphate-free detergent preparations. In view of the cited prior art, there remains a need for means and methods for effectively preventing scale formation. crust formation in textile fabrics or fabrics in detergent applications and preparations. The present invention is primarily effective in preventing crust formation in fabrics in phosphorus-free detergents with a high carbonate content. The present invention therefore provides an alternative to phosphonates and polyacrylates for preventing crust formation.

The invention relates to a method for using certain organic dicarboxylic acids and water-soluble derivatives thereof as effective inhibitors of the formation of crusts in fabrics when using detergents and preparations. The prior art relates only to the use of certain organic dicarboxylic acids to reduce water hardness or as stabilizing agents against the degradation of peroxy bleaches. It will be appreciated that the addition of certain organic dicarboxylic acids and their water-soluble salts and anhydrides to detergents or compositions to reduce and/or suppress the formation of crusting residues in fabrics due to minerals contained in hard water, which is attributable to the presence of a sodium carbonate builder in the detergent preparation, is not considered in the prior art.

A leading inorganic substitute for phosphate builders is sodium carbonate. However, high carbonate non-phosphate builders bring with them the problem of "hard water" precipitation from the calcium and magnesium ions contained in the "hard water". The growth or deposition of precipitates on fabrics during washing processes makes carbonate-based detergents otherwise not preferred.

The object of the invention is therefore to provide a cleaning process in which no phosphate builders are used.

Another object of the invention is to provide a high carbonate cleaning process that leads to reduced deposits of calcium and magnesium salts on fabrics.

Another object of the invention is to provide the use of a biodegradable, completely phosphorus-free compound which prevents carbonate salt precipitation and/or controls or combats crust formation.

Another object of the invention is to provide a cleaning method which results in the removal of stains and soiling.

A further object of the invention is to provide a cleaning method for reducing crust formation in tissues, which does not contribute to eutrophication and which agent is biodegradable.

The invention relates to a method for washing a textile fabric or fabric with water so that crust formation is prevented, which is characterized in that it comprises the use of a phosphate-free fabric cleaning composition which gives a washing pH range of between 8.0 and 13.00 and contains the following:

(a) at least 20% by weight of an alkali metal carbonate detergent builder,

(b) an anti-crusting amount of not more than 20% by weight of an anti-crusting organic dicarboxylic acid, water-soluble salt, anhydride or mixtures thereof having the formula

wherein

R is 2,3-pyridenyl, 2,4-pyridenyl, 2,6-pyridenyl, 1,2-phenylene, 1,3-phenylene or

where R' and R" independently represent H, -OH or C₁-C₆-alkyl or R' and R" together represent oxygen, n is 0 or an integer from 1 to 3, m is 0, 1 or 2, and M₁ and M₂ independently represent hydrogen, sodium, potassium, lithium and ammonium, and

(c) 0.1 to 20% by weight of a surfactant, wherein (b) is present in a substoichiometric amount, based on the hardness ions, in the wash water.

It has now been found that by applying the process according to the invention, encrustations on textile fabrics or woven fabrics can be reduced or eliminated when phosphate-free detergents with a high carbonate content are used with water containing calcium and/or magnesium ions. The process is characterized in that certain water-soluble organic dicarboxylic acids, anhydrides, salts and derivatives thereof are used. The invention more preferably relates to the use of certain organic dicarboxylic acids, water-soluble salts and anhydrides thereof, in particular ketomalonic acid, hydroxymalonic acid and 2,6-pyridinedicarboxylic acid.

In particular, the invention relates to the use of detergent compositions containing ketomalonic acid and 2,6-pyridinedicarboxylic acid or a water-soluble salt thereof with monovalent cations in a concentration of 1 to 20% by weight, preferably 2 to 12% by weight.

Alkali metal salts, in particular sodium salts, potassium salts or ammonium salts, can be used as water-soluble salts of the organic dicarboxylic acids according to the invention with monovalent cations. Ammonium ions can also be considered as monovalent cations for the purposes of the present invention. It is pointed out that for the purposes of the present invention the acid or anhydride forms of the organic dicarboxylic acids are equivalent to the salt forms, except when the acid has a limited solubility. It is pointed out that the anhydride can be hydrolyzed in situ to form the diacid. It is also noted that, except where expressly stated or implied herein, the acid and salt forms are used interchangeably. It is further noted that when the organic dicarboxylic acid derivative is added as a water-soluble salt, the required range expressed as a weight percent is higher than in the case of the acid due to the presence of the counter ion.

Alkali metal carbonate. The alkali metal carbonate used in the present invention is the primary builder material and may be the only builder material of the composition of the present invention. The primary builder is defined herein as that builder which in the total amount has a higher capacity for the hardness ions (e.g. calcium (+2) and magnesium (+2)). The term "co-builder" refers to any residual builder which has a lower capacity (typically less than 30%) for such ions. Alkali metal carbonates, sesquicarbonates and bicarbonates are suitable primary builders. However, the preferred builders are sodium and/or potassium carbonates. An effective amount of carbonate as a builder is included in the compositions used in the present invention. This is defined as the amount of alkali metal carbonates as primary builders which would precipitate in the presence of hardness ions in solution during a wash period of 50°C and at a hardness of 250 ppm. Such precipitation is determined by an increase in the turbidity of the solution as indicated by an abrupt change in percent transmittance over time (as additionally defined below). Generally, assuming 68 liters of wash water and about 100 grams of the composition, at least about 30% by weight, preferably 40% by weight, more preferably 50% by weight, of carbonate is used. As used herein, unless otherwise indicated, all percentages are by weight of the actives of the total composition. Higher levels of carbonate are effective, however, at levels greater than about 80%, and there is not enough room for the other ingredients that contribute to the overall effectiveness of using the composition. The carbonate acts as a builder to remove divalent metal ions such as calcium, and it also provides alkalinity and contributes to soil removal. At the high levels described herein, the alkali metal carbonate provides good cleaning performance. In situations requiring a high pH, such as oily contaminants, the carbonate builder can be superior to other builders.

The anti-crust system based on organic dicarboxylic acids

The inhibiting system contains substoichiometric amounts of an organic dicarboxylic acid, a water-soluble salt or anhydride thereof, and these materials inhibit crust formation in tissues. For purposes of the invention, substoichiometric levels of the particular organic dicarboxylic acids are defined as average levels that are incapable of preventing the precipitation of calcium and magnesium carbonate by sequestering the water hardness ions. For example, such levels generally comprise less than about 30%, more preferably less than about 20% of the total builder capacity.

Herein, the term "organic dicarboxylic acid" is to be understood as an organic compound having at least two carboxyl groups. The specific and particular organic dicarboxylic acid compounds used in the invention have the following general formulas

wherein

R is selected from the group consisting of 2,3-pyridenyl, 2,4-pyridenyl, 2,6-pyridenyl, 1,2-phenylene, 1,3-phenylene and

wherein R' and R" independently represent H, -OH or lower alkyl having 1 to 4 carbon atoms inclusive or R' and R" taken together represent oxygen,

n is 0 or an integer from 1 to 3 inclusive,

m is 0, 1 or 2, and

M₁ and M₂ are independently selected from the group consisting of hydrogen, sodium, potassium, lithium and ammonium.

Representative compounds used in the invention are given below:

Connection 1

Phthalic acid

Connection 2

Isophthalic acid

Connection 3

2,4-pyridinedicarboxylic acid

Connection 4

2,6-pyridinedicarboxylic acid

Connection 5

2,3-pyridinedicarboxylic acid

Connection 6

Oxalic acid

Connection 7

Malonic acid

Connection 8

Hydroxymalonic acid

Connection 9

Ketomalonic acid

Connection 10

Methylmalonic acid

Connection 11

Succinic acid

Connection 12

Adipic acid

Connection 13

Hydroxysuccinic acid

Connection 14

Tartaric acid

Components (a) and (b) are as described above. Component (c) is further described below.

Surfactant

A myriad of surfactants are known to be useful for detersive purposes, including anionic, cationic, nonionic and amphoteric surfactants. Preferred surfactants are anionic, nonionic and mixtures thereof and are present in an amount effective for cleaning when added. Preferred anionic agents are selected from surfactants such as alkali metal alkyl sulfates, primary and secondary alkane sulfonates, linear alkyl benzene sulfonates, alkyl ether sulfates and mixtures thereof. These anionic surfactants preferably have alkyl chain groups averaging about 8 to 18 carbon atoms. The preferred anionic surfactant is a LAS compound having an alkyl group averaging about 8 to 18 carbon atoms. Commercial sources for such surfactants are Stephan Chemical Company (Northfield, IL) and Vista Chemical Company (Houston, TX). A further preferred anionic surfactant, primarily with regard to its detergency, is a secondary alkane sulfonate. An example of a particularly preferred secondary alkane sulfonate is HOSTAPUR SAS, a trademarked product manufactured by Farbwerke Hoechst AG (Frankfurt, West Germany).

It is most preferred to add to the anionic surfactant at least one nonionic, especially a C₁₋₄ alkoxylated aliphatic alcohol and a C₁₋₄ alkoxylated alkylphenol. Particularly preferred are ethoxylated/propoxylated C₈₋₁₄ alcohols. There should be at least about three alkoxy groups per alcohol, preferably at least about nine. Examples of preferred ethoxylated/propoxylated aliphatic alcohols are products of BASF Corporation (Parsippany, NJ) under the trademarks INDUSTROL and PLURAFAC. Certain C1-4 alkylene oxide copolymers, such as ethylene oxide/propylene oxide copolymers, are also preferred as wetting agents. Examples of these are the products of BASF under the trademark PLURONIC series. Other suitable nonionic wetting agents are polyethoxylated alcohols manufactured and sold by Shell Chemical Company (Houston, TX) under the trademark NEODOL. Examples of preferred NEODOL products are NEODOL 25-7, which is a mixture of alcohols having a chain length of 12 to 15 carbon atoms with about 7 ethylene oxide groups per molecule, NEODOL 23-65, which is a C12-13 mixture containing about 6.5 moles of ethylene oxide, and NEODOL 25-9, a C12-15 mixture containing about 9 moles of ethylene oxide. Also suitable are trimethylnonyl polyethylene glycol ether, manufactured and sold by Union Carbide Corporation under the trademark TERGITOL TMN-6, and an octylphenoxypolyethoxyethanol, sold by Rohm and Haas (Philadelphia, PA) under the trademark TRITON X-114. The total surfactant content is preferably from 0.1% to about 20%, more preferably from about 2% to 15%.

Elements (a), (b) and (c) are as described above.

Elements (d) to (g) are further described below.

Bleach

Preferred peroxygen bleaches are available in solid form. Examples are sodium percarbonate, sodium perborate, sodium phosphate peroxyhydrate, potassium permonosulfates and metal peroxides. Bleach activators, also known as peracid precursors, may be added along with the peroxygen compounds. Examples of activators are tetraacetylethylenediamine (TAED), nonanoyloxybenzenesulfonate (NOBS) and nonanoylglycolate phenolsulfonate (NOGPS). NOBS and TAED are described, for example, in U.S. Patent No. 4,417,934 and NOGPS is described, for example, in U.S. Patent No. 4,778,168. The disclosures are incorporated by reference. Peracid bleaches (including monoperacids and diperacids) may be beneficial in terms of bleaching performance. Suitable peracid bleaches are C8-12 alkyl peracids, particularly perazelaic and diperazelaic acid, diperoxydodecanedioic acid (DPDDA) and alkylmonoperoxysuccinic acid. Peracid bleaches and processes for their preparation are described in US Patent 4,337,213, the disclosure of which is incorporated by reference. The bleach is present in an amount sufficient to provide effective bleaching, for example in an active weight amount of about 0% to 10%, more preferably in an active weight of 0.05% to 5%, depending on the bleaching agent chosen.

Also suitable are chlorine bleaches, which may be pre-formed and suspended on a substrate, attenuated or formed in situ.

Alkali metal silicate

An alkali metal silicate may be added to provide alkalinity and corrosion resistance. Preferably one having the formula:

M₂O(SiO₂)n

wherein M is an alkali metal and n is between about 1 and 4. Preferred alkali metal silicates are sodium, potassium and lithium silicates, with sodium silicate being most preferred. A preferred value of n is 2.0 to 2.4. A most preferred maximum value for n is about 3.2 to minimize insoluble silicates during storage. It is further preferred that at least about 10% of the total silicates have a value of n greater than about 1.6 to impart suitable anti-corrosion properties. Examples of other suitable silicates are sodium or potassium orthosilicates and metasilicates. The term "silicate" as used herein is intended to encompass any of these alkali metal silicates either individually or in combination.

Mixtures of any of the foregoing alkali metal silicates are also suitable. The alkali metal silicate is present in an amount of from about 0% to 10%, preferably from about 2% to 5%. A minimum of about 1% silicate is preferred to provide adequate corrosion resistance. A commercial sodium silicate is sold by Philadelphia Quartz Corporation (Valley Forge, PA) under the trademarks RU (as a 47% solution) and D (as a 44.1% solution). In addition to their anti-corrosion effects, the silicates provide alkalinity and act as processing aids to increase the particle size of the agglomerates. Sodium silicates also aid in cleaning, particularly oily and greasy stains.

filler

The filler is preferably a salt such as sodium chloride, nitrate or sulfate and is used to adjust the density of the composition to obtain desired physical properties such as grain size and flowability. Depending on the filler used and the process, the filler may also contain a surface area for loading of the actives. The filler material also contributes to solubility under cold water wash conditions. Because of its low cost and availability, sodium chloride is preferred. However, other materials such as buffered borax, bentonite clays, and inorganic salts such as sodium or potassium sulfate, chloride, bromide, nitrate, and borate, as well as organic materials such as sugar, may also be suitable. Some water may be intentionally added as a filler. Generally, about 0 to 30% filler is present, preferably about 5 to 25%.

Co-Builder

Optionally, any non-phosphate builder material known in the art to be compatible with the high carbonate composition contemplated herein may be added as a co-builder selected from the group consisting of silicates, citrates, polymeric polycarboxylic acids such as polyacrylates and malonic anhydride-based copolymers, zeolites, salts of ethylenediaminotetraacetic acid and sodium nitrilotriacetate. Silicates in amounts greater than about 10% and citrates may be added as co-builders. When added, the amount of co-builder should not be more than about 30% of the total weight of the composition and preferably not more than about 20%. Zeolites are preferred as optional co-builders because they work well when used in an amount that promotes non-scaling. A non-scaling promoting amount is that amount which, when present in the detergent preparation and in the presence of water hardness ions, does not contribute to or encourage the formation of scaling.

For example, zeolite A is available from PQ Corp., Valley Forge, PA, under the trademark VALFOR 100. Zeolite A typically contains about 21% moisture.

Adjuncts

While the alkali metal carbonate is generally sufficient to keep the wash pH range within the desired limits, it may be appropriate to adjust the pH of the wash water by adding an electrolyte/buffer. Generally these are salts of inorganic acids, hydroxides or oxides of alkali metals. It may also be appropriate to use such materials as aluminates and organic materials such as gluconates, citrates, succinates, maleates and their alkali metal salts. The wash pH range must be between 8.0 and 13.0, especially preferably 9.0 to 12.0. If an electrolyte/buffer is required, sodium hydroxide is preferred as it does not react adversely with the other ingredients and is very cost effective. The amount of electrolyte/buffer added purely for buffering purposes can vary from 0% to 10%.

Minor additives may be present in the standard composition used in accordance with the invention. These include dyes such as monastral blue and anthraquinone dyes (as described, for example, in U.S. Patents 4,661,293 and 4,746,461). Pigments which are also suitable colorants may be selected without limitation from titanium dioxide, ultramarine blue (see also U.S. Patent 4,708,816) and colored aluminosilicates. Fluorescent whitening agents are other suitable adjuncts. These include stilbene, styrene and styrene and naphthalene derivatives which release or fluoresce light at a visible wavelength upon exposure to ultraviolet light. These fluorescent whitening agents or brighteners are useful for improving the appearance of fabrics which have become unsightly from repeated soiling and washing. Preferred fluorescent whitening agents are TINOPTAL 5BM-GX and TINOPAL AMS, both from Ciba Geigy AG (Tom River, NJ) and PHORWITE RKH from Mobay Chemicals (Union, NJ).

Enzymes, particularly hydrolases such as lipases, proteases and amylases, are suitable additives in the compositions used in the present invention. Suitable technical sources include ESPERASE and SAVINASE, both of which are trademarks of Novo Industries (Danbury, CT). Generally, very low levels of enzymes are required, i.e., about 0.1 to 1.0 weight percent. Flavors are also desirable adjuncts in these compositions. The total composition of the minor ingredients ranges from 0% to about 5%. Anti-redeposition agents such as carboxymethylcellulose are potentially useful. Foam boosters such as suitable anionic surfactants may also be suitable for inclusion herein. Furthermore, in the event of excess foaming resulting from the use of certain surfactants, antifoaming agents such as alkylated polysiloxanes, e.g., dimethylpolysiloxane, may be useful. Water may be present as free water or as water of hydration of inorganic salts such as sodium carbonate. The detergent composition used is prepared by a process which produces a dry free-flowing granular mixture, for example by agglomeration or spray drying. However, the compositions used in the invention are not limited to such forms and they may also be formulated in other dry forms such as tablets or beads, or they may be formulated as pastes, gels or liquids. An exemplary preparation is given below as Example A. Example A

Experimental

To determine the effectiveness of the compositions used herein to reduce the deposition of scaling, their scaling reduction efficiencies were tested in beaker tests. The compounds used and the results obtained are summarized in the following table.

Procedure

The measurement of turbidity involves measuring the percent transmittance using a dip probe and a colorimeter. The probe is placed in deionized water and the percent transmittance (%T) is set to 100%. The detergent is dissolved in 50 ml of water beforehand and then added to 950 ml of water containing hardness ions such as [Ca²⁺]/[Mg²⁺] = 3/L molar ratio. The hardness of the final solution was 300 ppm. The percent transmittance is plotted continuously and measured against time. The results are presented as time before the onset of calcium precipitation (tm) determined by an abrupt change in the slope of a curve of %T against time. longer tm, the more effective the crystal growth inhibitor. Ideally, for crystal growth inhibitor compounds, the tm should be longer than the wash cycle, ie, about 12 to 15 min in the case of US wash conditions. In practice, a tm greater than about 10 min, preferably 12 min, will give commercially acceptable results since calcium precipitation will still be inhibited to a level sufficient to avoid consumer complaints.

Simultaneously with the measurement of %T, a 100% cotton rag trimmed to 1.0 g, measuring 3.5 x 4 inches, is immersed in each detergent sample container. Slits approximately 7.6 cm (approximately 3 inches) long were made at approximately 0.6 an (approximately 0.25 inches) intervals to facilitate circulation in the test container. After washing for 10 minutes, the rag is rinsed twice with 2 L of deionized water and placed in a flask containing 25 mL of water and 10 mL of 1.2 M HCl to dissolve the CaCO3. 15 mL of a standard NH4OH hardness buffer and a Caimagite indicator are then added and the solution is titrated with standardized EDTA. Results are reported as mg CaCO3 per g of tissue (rag). Preferably, this value should be below about 4 mg/g, most preferably below about 2 mg/g.

The preferred level of calcium carbonate deposits per gram of fabric can be achieved without necessarily increasing the value of tm. While the invention is not intended to be limited to any theory, it is believed that precipitation modifiers have little or no effect or actually shorten the value of tm and still result in low levels of scaling of the fabric. Crystal growth inhibitors, on the other hand, increase the value of tm. The presence of any of these types of compounds in a high carbonate phosphate-free builder detergent results in lower levels of scaling on the surface of the fabric. Table I

(a) An agglomerated phosphate-free detergent base containing 1.16 g/l Na₂CO₃ was used. Unless otherwise stated, all acids were evaluated at 1.0 x 10⁻³ M.

(b) Compounds evaluated at 1.27 · 10⊃min;³ M.

Multiple cycle wash studies

To demonstrate the effectiveness of the composition used in the present invention in reducing the deposition of encrustations, 100% terry cloth washcloths were washed for multiple cycles at the specified washing conditions. A base wash composition consisting of 61% Na₂CO₃, 11.0% surfactant, 5.0% sodium silicate and 5.0% sodium perborate was used. The organic dicarboxylic acid compound was added to the base composition in the amounts exemplified in Table II. For each wash load, about 3/4 cup (125 g/application) of detergent and about 68 liters of wash water were used.

Table II Multiple cycle wash studies B. Multiple cycle awake examinations weight & ash/5 cycles/cotton washcloth

(a) The multiple cycle wash tests were carried out with an agglomerated detergent containing 61 g/application of Na₂CO₃. All tests were carried out at a water hardness with a molar concentration of 3/1 Ca/mg. The concentrations are given on an "active ingredient" basis.

(b) Ash is defined as the residue remaining after pyrolysis at 950ºC in oxygen. The values are given as wt.%.

Table II shows that the use of substoichiometric levels of the anti-scaling system of the present invention using an organic dicarboxylic acid in accordance with the present invention resulted in less calcium residue (as ash) than the base detergent composition at two different treatment levels. Given the observed results for inhibition of calcium carbonate deposition, an organic dicarboxylic acid used in accordance with the present invention could be a direct replacement for polyacrylate, which is known to have an antiprecipitation nature. Furthermore, the organic dicarboxylic acid and the water-soluble salts and anhydrides thereof should be more readily biodegradable than polyacrylates.

Claims

1, A method for washing a textile fabric or fabric with water so that crust formation is prevented, characterized in that it comprises the use of a phosphate-free fabric cleaning composition which gives a washing pH range of between 8.0 and 13.00 and contains the following:

(a) at least 20% by weight of an alkali metal carbonate detergent builder,

(b) a tissue anti-crusting amount of not more than 20% by weight of an anti-crusting organic dicarboxylic acid, water-soluble salt, anhydride or mixtures thereof having the formula

wherein

where R' and R" independently of one another represent H, -OH or C₁-C₆-alkyl, or R' and R" together represent oxygen, n is 0 or an integer from 1 to 3, m is 0, 1 or 2, and M₁ and M₂ independently of one another represent hydrogen, sodium, potassium, lithium and ammonium, and

(c) 0.1 to 20% by weight of a surfactant, wherein (b) is present in a substoichiometric amount based on the hardness ions in the wash water.

2. Process according to claim 1, characterized in that the composition further contains:

(d) 1 to 10% by weight of a sodium silicate having a SiO₂/M₂O ratio of 1:1 to 4:1, where M is an alkali metal,

(e) a bleaching effective amount of a bleaching agent,

and that the surfactant (c) in the composition is selected from anionic, nonionic, cationic, amphoteric surfactants and mixtures thereof.

3. Process according to claim 1 or 2, characterized in that the amount of alkali metal carbonate builder

(a) in the composition is 20 to 80 wt.%, preferably 30 to 70 wt.%.

4. Process according to one of claims 1 to 3, characterized in that the amount of organic dicarboxylic acid, water-soluble salt or anhydride thereof

(b) in the composition is 1 to 20 wt.%.

5. Process according to one of claims 1 to 4, characterized in that the surfactant (c) in the composition is selected from alkyl sulfates, primary and secondary alkyl sulfonates, linear alkylaryl sulfonates, alkyl ether sulfates, alkoxylated aliphatic alcohols, alkoxylated alkylphenols, copolymers of C₁-C₄ alkylene oxides and mixtures thereof.

6. Process according to one of claims 1 to 5, characterized in that the composition further contains a non-crust-forming promoting amount of a cobuilder, selected from silicates, citrates, polymeric polycarboxylic acids, salts or ethylenediaminetetraacetic acid and sodium nitrilotriacetate, and preferably zeolites.

7. Process according to one of claims 1 to 6, characterized in that the alkali metal carbonate is sodium carbonate and that the organic dicarboxylic acid or the water-soluble salt is selected from phthalic acid, isophthalic acid, 2,4-pyridinedicarboxylic acid, 2,6-pyridinedicarboxylic acid, 2,3-pyridinedicarboxylic acid, malonic acid, hydroxymalonic acid, ketomalonic acid, methylmalonic acid, succinic acid, adipic acid, hydroxysuccinic acid and tartaric acid, preferably 2,6-pyridinedicarboxylic acid, ketomalonic acid and hydroxymalonic acid.