NO172751B - STABLE MATERIAL SUITABLE AS OR IN ACID RINSE OIL. - Google Patents

Description

The present invention relates to a stable material which is suitable as or in acidic rinse agents, in particular acidic rinse agents for dishwashers. But the material can also be suitable as or in glass cleaners, e.g. window cleaners, metal cleaners, in textile manufacturing, in washing-up agents and in water treatment agents, e.g. in cooling systems.

Rinse aid is always used in dishwashers for professional and institutional use and often in household dishwashers. A final rinse serves to remove previous rinse water and its content of surfactants and food residues. In large commercial machines, the final rinse water is usually added at a temperature of 80°C or more. The high temperature is used for hygienic reasons and to promote rapid drying of the surfaces of glassware, glassware or plastic goods (hereafter referred to as "items") when they come out of the machine. In some "low-energy" commercial dishwashers, rinse water can be used in the final rinse with a temperature below approx. 60°C, and it can contain approx. 50 parts per million (ppm) of a conventional chlorine-releasing agent to achieve hygienic conditions. Hygienic conditions are achieved in household dishwashers by effective batch cleaning with many wash and rinse cycles using fresh water.

Rinse aids for dishwashers are usually aqueous solutions containing a low-foaming, nonionic surfactant and which can be added to the final fresh water rinse in a concentration of 50-100 ppm. The surfactant in the rinse water lowers the rinse water's surface tension and improves the wetting effect of the rinse water on slightly hydrophobic surfaces on objects. Better wetting reduces the tendency of the rinse water to form droplets containing dissolved solids on the object's surface, which can cause stains when drying. Accordingly, the functions of the surfactant in the rinse aid are to effectively lower the surface tension during runoff and to be low-foaming to avoid leaving traces of foam on the object, which can result in a residue upon evaporation.

In commercial dishwashers, the final rinse water after being used for rinsing the objects will be mixed with circulated, previously used rinse water. The rinse water can also be led back to the wash water and used directly as wash water for the next cycle. When formulating a rinse aid, the surfactant and other additives should therefore be selected based on their effect in the wash bath and in the rinse water. A further important feature of a rinse aid is therefore its ability to skim off food residues in the alkaline water bath. Protein-containing food residues are particularly prone to foaming in stirred, alkaline water baths. Foam, or more precisely trapped air, in washing jets, will reduce the jet's mechanical effect and weaken the maximum removal of dirt. Many low-foaming surfactants are effective dirt defoamers. But other additives can affect the anti-dirt foam.

Although low-foaming surfactants improve the wetting of rinsing water on objects, they have not completely eliminated the problems of spotting and streaking. It is known that the addition of polycarboxylated polymers, such as polyacrylic acid, to rinse water can further reduce spot and film or streak formation. It is assumed that these water-soluble polymers can be adsorbed on slightly soiled substrates and make the surface more hydrophilic. A more hydrophilic surface can be wetted more easily in winter with the rinse water containing the surfactant. Polycarboxylated polymers are particularly useful because they do not contribute to foam formation and do not interfere with the dirt-defoaming effect of the low-foaming surfactants. Such polycarboxylated polymers also have the advantage that, when used in hard water, they help to prevent precipitation of hardness ion salts.

There is, however, a serious obstacle to the use of polycarboxylated polymers in fabric softeners. This obstacle is due to the incompatibility of these polymers in aqueous fabric softeners containing low-foaming surfactants. Combining such polymers with surfactants in water results in phase separation. When stored for a short period of time, the water containing these polymers and surfactants will form two or more layers with different compositions. It is clear that this phase separation is unsatisfactory as uneven addition of the desired components will occur when the agent is introduced into the machine. For example the agent may contain too little surfactant to effect satisfactory wetting, or too much, which leads to too much foam.

Hydrotopes such as sodium xylene sulfonate, cumene sulfonate, and short chain alkyl sulfates have been used to enable the preparation of low-foaming, nonionic surfactants in stable, aqueous concentrates (see, e.g., US Patents 3,563,901 and 4,443,270). However, these hydrotopes have little effect when it comes to improving the compatibility of low-foaming surfactants with polycarboxylated polymers in aqueous concentrates. Even in cases where the hydrotopes provide limited compatibility, however, they suffer from the major disadvantage that they affect the food residue antifoam action of the surfactants. Water-miscible solvents, such as isopropanol and propylene glycol, and hydrogen bond-cleaving compounds, such as urea, have also been proposed for use in formulating rinse agents containing low-foaming, nonionic surfactants. However, they have been found to have little or no effect in increasing the compatibility of polycarboxylated polymers with low foaming surfactants. Combinations of a hydrotope and such solvents provide some improvement over the use of one of these compounds alone, but the combinations still result in rinse agents which have limited compatibility and which adversely affect food residue foaming activity.

Low-molecular polyelectrolytes have been combined with low-foaming surfactants in powdered synthetic detergents. US patent 4,203,858 describes a low-foaming, phosphate-free agent for dishwashers, which comprises an alkali metal or ammonium carbonate, such as sodium carbonate, a water-soluble salt of a polyelectrolyte with a molecular weight of 500-4,000, and optionally up to 10% by weight of a antifoam, nonionic surfactant. The weight ratio between polyelectrolyte and carbonate is from 5:95 to 20:80. Typically, the polyelectrolytes are acrylic, methacrylic, maleic and itaconic acid polymers. Homopolymers and copolymers of acrylic and methacrylic acid with a molecular weight in the range from 504 to 1,291 are preferred. In the above-mentioned US patent document 4,203,858, it is described that the main differences between this agent and previously known agents for dishwashers are the low concentration of polyelectrolyte, and that these polyelectrolytes have a poor ability to form complexes with metal ions. Other publications where (meth)acrylic acid polymers and their salts in synthetic detergents and for use in cleaning are described, among others, in US patents 3,671,550, 3,853,981. 3,950,260, 3,933,663, 3,922,230 and 4,521,332. However, none of these publications indicate the use of or solutions for polyelectrolytes with low-foaming surfactants in fabric softener concentrates.

The desired properties of a rinse aid depend on the hardness of the water used in the dishwasher. In the case of soft water that has a low degree of hardness, e.g. under approx. 10 French degrees of hardness, the rinse aid preferably has a pH of 7 or more (here referred to as alkaline rinse aid), and for hard water that has a hardness of e.g. above 30 French degrees of hardness, the fabric softener preferably has a pH of less than 7 (referred to here as acidic fabric softener). In the case of alkaline fabric softeners, the problem of compatibility between low-foaming nonionic surfactants and polycarboxylated polymers has been overcome, and alkaline fabric softeners have been prepared using, as compatibilizers or stabilizers, high molecular weight copolymers made from monomers comprising methacrylic acid and one or more C^-Cg -alkyl (meth)acrylates, where at least 50% of the acid groups in the copolymer are neutralized with alkali (see EP-A-02345987). However, such high molecular weight copolymers are unsuitable when it comes to making low-foaming nonionic surfactants compatible with polycarboxylated polymer in an acidic fabric softener, as phase separation has been shown to occur.

In connection with the present invention, it has surprisingly been shown that a low-foaming nonionic surfactant can be made compatible with polycarboxylated polymer, and a stable, acidic fabric softener is produced, by using a further, nonionic surfactant as compatibilizer or stabilizer.

The material according to the invention is characterized by the fact that it contains

(a) 1-60 parts by weight low foaming nonionic surfactant, with a flash point below 70°C and comprising one or more of cg~c22 fatty alcohol/ethylene oxide condensates, polyoxypropylene-polyoxyethylene condensates, alkylpolyoxypropylene-polyoxyethylene condensates, alkylpolyoxyethylene-polyoxypropylene condensates, polyoxyalkylene glycols, benzyl ethers of polyoxyethylene condensates of alkylphenols, and butylene oxide-alcohol condensates, (b) 0.5-20 parts by weight of polymer having a weight average molecular weight of 1,000-2,50,000 and which is a homopolymer of acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid or acrylamide, or which is a copolymer comprising units derived from two or more of acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, hydroxyacrylic acid, C^-C^-alkyl-(meth)acrylates or amides, 2-acrylamido-2-methylpropanesulfonic acid , styrene, acrylamide, isobutadiene, dimethylaminoethyl methacrylate and tert-butylacrylamide, c) 0.1-10 parts by weight of other nonionic surface active substance with a flash point of at least 70°C and comprising alkylaryl polyether alcohols with an average of at least 10 ethylene oxide units per molecule, and alkyl polyether alcohols with an average of at least 10 ethylene oxide units per molecule, d) water, where the parts by weight are calculated from 100 parts by weight of the sum of a) plus b) plus c) plus d), and

that the material has a pH of less than 7.

For the stabilization of an aqueous material comprising a mixture of low-foaming, nonionic surfactant (which, because it must be low-foaming, will have a flash point below 70°C) and polymer that has a weight average molecular weight of 1,000-250,000 and which is a homopolymer of acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid or acrylamide, or which is a copolymer formed by two or more of acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, hydroxyacrylic acid, C-^-C^-alkyl (met) acrylates or

-amides, e.g. ethyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), styrene, acrylamide, isobutadiene, dimethylaminoethylmeth-

acrylate (DMAEMA) and tert-butylacrylamide (t-BEM). To the material is added the nonionic surfactant which has a flash point of 70°C or above, e.g. 80°C or above.

Unless otherwise specifically stated, in the description all amounts are expressed as parts by weight of the low-foaming nonionic surfactant, polymer and additional nonionic surfactant per 100 parts by weight of low-foaming nonionic surfactant, polymer, additional nonionic surfactant plus water.

The low-foaming nonionic surfactant can e.g. be any known low-foaming nonionic surfactant useful in dishwashing machines or fabric softeners. Suitable low-foaming nonionic surfactants include: C^-C--fatty alcohol/ethylene oxide condensates, polyoxypropylene-polyoxyethylene condensates, alkylpolyoxypropylene-polyoxyethylene condensates, alkylpolyoxyethylene-polyoxypropylene condensates, polyoxyalkylene glycols, benzyl ethers of polyoxyethylene condensates of alkylphenols, as well as butylene oxide-alcohol condensates such as e.g. has the formula:

where R is a C 8 -C 8 alkyl group, y has an average value of 3.5-10 and x has an average value of 0.5-1.5. Typical commercially available low-foaming nonionic surfactants include: "Triton CF-10" (an alkylaryl polyether), "Triton DF-15" (a modified polyoxyalkylated alcohol), "Pluronic L-62"

(a polyoxyethylene-polyoxypropylene block copolymer), "Lutensol LF 403" and "Lutensol LF 404", as well as "Antarox BL-330" (a modified, unbranched, aliphatic polyethoxylated alcohol with chlorinated end groups).

The material according to the invention can contain at least 1 part by weight, preferably at least 5 parts by weight and preferably at least 10 parts by weight

of the low foaming nonionic surfactant. Up to 60 parts by weight, preferably up to 50 parts by weight and most preferably up to 40 parts by weight of the low-foaming, nonionic surfactant can e.g. present in the material.

According to one embodiment of the invention, the polymer is a homopolymer of acrylic acid, methacrylic acid or maleic acid, or a copolymer made from two or more of acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, hydroxyacrylic acid, C2~C4-alkyl(meth)acrylates or -amides and 2-acrylamido-2-methylpropane sulfonic acid.

The polymer used in the material according to the invention can be a polycarboxylated polymer.

The weight average molecular weight of the polymer is at least 1,000 and is preferably up to 100,000, more preferably up to 70,000. The polymer can be used in free acid form or in partially neutralized or completely neutralized form, e.g. as an alkali metal or ammonium salt when producing the material according to the invention, but is preferably used in the partially neutralized form as it may then be unnecessary to carry out a pH regulation to achieve the desired acidic pH.

Suitable commercially available polymers include "Acrysol LMW 45" (an acrylic acid homopolymer which is 20% neutralized and has a weight average molecular weight of 4,500) and "Acrysol LMW 45N" (an acrylic acid homopolymer which is fully neutralized and has a weight average molecular weight of 4,500).

The material according to the invention contains at least 0.5 parts by weight, preferably at least one part by weight of the polymer. Up to 20 parts by weight, preferably up to 10 parts by weight and most preferably up to 5 parts by weight of the polymer can be present in the material.

Suitable nonionic surfactants include alkyl-aryl polyether alcohols having an average of at least 10 ethylene oxide units per molecule, and alkyl polyether alcohols having an average of at least 10 ethylene oxide units per molecule. Preferably, the cosurfactant is a reaction product between ethylene oxide and an octyl or nonylphenol, such as a compound with

the formulas:

or

where x has an average value of at least 10.

Suitable commercially available materials having formula (I) include: "Triton X-165" (average value for x = 16), "Triton X-305" (average value for x = 30), "Triton X-405" ( average value for x = 40), as well as "Triton X-705" - 70% (average value for x = 70). Suitable commercially available materials having formula (II) include "Triton N-150" (average value for x = 15), "Triton N-302"

(average value for x = 30), "Triton N-401" (average value for x = 40), "Triton N-998" - 70% (average value for x = 100), as well as "Triton N-998" - 100% (average value for x = 100).

The material according to the invention can contain at least 0.1 part by weight, preferably at least 0.5 part by weight of the nonionic cosurfactant. Up to 10 parts by weight, preferably up to 5 parts by weight, of the nonionic cosurfactant can e.g. present in the material.

It should be understood that the material according to the invention can contain one or more of each low-foaming nonionic surfactant, polymer and nonionic cosurfactant. In one embodiment of the invention, the total amount of low-foaming nonionic surfactant, polymer, nonionic co-surfactant and water is 100% by weight of the material.

The material according to the invention may contain other additives, e.g. one or more complexing substances, such as nitrile triacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), phosphonates, citric acid or sodium nitrate, as well as water-miscible solvents such as isopropanol or propylene glycol. Examples of suitable phosphonates are 1-hydroxy-ethylene-bis-phosphonic acid, nitrile-tris(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and hexamethylenediaminetetra(methylenephosphonic acid). Suitable commercially available phosphonates include "Dequest-2006", -2016, -2046, -2056 and -2066, and "Mykon-P060", -P110, -P200, -P310 and P-400. Based on the total weight of the material, EDTA can e.g. present in an amount of up to 2% by weight, NTA may be present in an amount of up to 4% by weight, citric acid may be present in an amount of up to 10% by weight or phosphonates may be present in an amount of up to 2% by weight. If more than one complexing additive is used, the amounts of these additives will require adjustment. The above-mentioned acidic materials that may be added can be used in acid form or in partially or completely neutralized form.

In table 1 below, examples are given of a number of formulations according to the invention, where the indicated numbers for each component are percentages by weight calculated from the total weight of the material, and the rest is water.

It has been shown that it is possible to produce materials according to the invention which remain stable for several weeks at 40°C, for at least 90 days at room temperature and which withstand five freeze/thaw cycles. Although one does not wish to be bound by any theory, it is believed that this stability is due to the formation of a microemulsion upon the addition of the nonionic cosurfactant. Observations support the formation of a microemulsion. First, the material without the nonionic cosurfactant is cloudy and rapidly separates into two or more phases, but when the nonionic cosurfactant is added, the material becomes transparent. This transparency is believed to be due to the formation of a microemulsion where the particle sizes are too small to result in scattering of the light. Secondly, when the nonionic cosurfactant is added, a stable dispersion is spontaneously formed, i.e. it is formed without the input of mechanical energy, e.g. without stirring. In oil/surfactant/water systems where no homogeneous phase is formed, it is known that the addition of a cosurfactant can produce spontaneous formation of a stable dispersion due to the formation of a microemulsion, and a similar situation is believed to occur in connection with the material according to the present invention.

When used as or in a rinse agent, e.g. a rinse aid for automatic dishwashers, the material according to the invention can promote wetting of a substrate and reduce the formation of stains on the substrate when it is dried. These properties of the material can also make it suitable for other applications, e.g. as or in means for cleaning glass (eg windows) or metal.

The invention will be explained in more detail below with reference to the accompanying drawing.

Example 1

This example illustrates the need to use a nonionic cosurfactant to stabilize an aqueous material comprising a low foaming nonionic surfactant and polymer. A number of materials were prepared using low foaming nonionic surfactant, polymer, water, and some materials also nonionic cosurfactant. The stability of these materials against phase separation at 40°C for 24 hours (or more) was measured, and the results obtained are set out in Table 2 below.

Table 2 shows that the materials according to the invention (i.e. materials 2, 4, 6 and 8) were stable, while the comparison materials (i.e. materials 1, 3, 5 and 7), which did not contain nonionic cosurfactants, were not stable.

As indicated above, the presence of polymers, e.g. polycarboxylated polymers, in acidic fabric softeners advantageously since such polymers inhibit the precipitation of hardness ion salts from the water in which the fabric softener is used. However, known fabric softeners have the disadvantage that no or very little polymer can be used, otherwise phase separation of the low-foaming nonionic surfactant and polymer takes place in the fabric softener.

The presence of the cosurfactant used according to the invention enables greater concentrations of polymer in the rinse aid, which results in increased efficiency in inhibiting precipitation of hardness ion salts from water in which the rinse aid is used, without resulting in phase separation of the polymer and the low-foaming nonionic surfactant. This means that the cosurfactant enables the production of stable materials that contain low-foaming nonionic surfactants of polymer, where higher concentrations of polymer can be present than those that can be used in known materials.

The ability of the nonionic cosurfactants to enable the production of stable aqueous materials containing low-foaming nonionic surfactant and polymer, e.g. polycarboxylated polymer, was investigated by comparing the light transmission of materials 4 and 8 in Table 2 (ie materials according to the invention) with a known material that does not contain a nonionic cosurfactant, where the known material is an aqueous material of 30% by weight low foaming nonionic surfactant fabric, 10% by weight isopropanol and 60% by weight water. The light transmission can be used as an indication of whether precipitation of hardness ion salts is taking place or not in the materials, since any such precipitation will reduce the light transmission.

The light transmission of each of the three materials when added to soft water, medium hard water and hard water was determined. The results are shown in the accompanying drawing, which is in the form of a diagram where the x-axis indicates the hardness of the water, with A representing soft water, B representing medium-hard water and X representing hard water, and the y-axis being the percentage of light transmission. (i) is the line obtained for material 8 in Table 2, (ii) is the line obtained for material 4 in Table 2 and (iii) is the line obtained for the known material.

It is clear from the diagram that the materials according to the invention (represented by lines (i) and (ii)) have a significantly higher light transmission, i.e. greater inhibition of precipitation of hardness ion salts, than the known material (represented by line (iii)) in medium hard and hard water.

The stronger inhibition of precipitation of hardness ion salts by means of the materials according to the invention compared to the known material contributes to the ability to form stable materials which have a higher concentration of polymer than that which can be used in the known material.

Lines (i) and (ii) in the accompanying diagram also show that the higher the concentration of polymer in the rinse aid, the greater the inhibition of hardness ion salt precipitation, especially in medium hard and hard water, and consequently the light transmission is higher. Line (i) represents the material containing 10 parts by weight polymer, and (ii) represents the material containing 2 parts by weight polymer.

Example 2

This example shows two methods for producing the material according to the invention.

Procedure A:

To water was added polymer, then the low foaming nonionic surfactant, and finally the nonionic cosurfactant was added.

Method B;

To water, the low foaming nonionic surfactant was added, then the polymer was added, and finally the cosurfactant was added.

A number of materials according to the invention were prepared by the methods described above, and the stability of the materials at 40°C for 24 hours (or longer) was determined. The results are shown in table 3.

The total weight of each material was 100 parts by weight. Table 3 shows that with "Triton DF-16" as a low-foaming nonionic surfactant, both methods A and B can be used for the production of stable materials according to the invention. Table 3 also indicates that stable materials are also produced when the polycarboxylated polymer is varied.

But in some cases, e.g. when alkoxypolyethoxypolypropoxybenzyl ether is used as the low-foaming nonionic surfactant, the order of addition of the components in the material is important. Table 4 below shows the stability of materials according to the invention produced by the above described methods A and B and two further methods C and D. Method C is the addition of polymer to water followed by the addition of nonionic cosurfactant and finally the addition of low foaming nonionic surfactant , and method D is addition of nonionic cosurfactant to water, followed by addition of low foaming nonionic surfactant and finally polymer. In each of these materials, the low foaming surfactant was an alkoxypolyethoxypolypropoxy benzyl ether.

This example shows that the manufacturing method for the material according to the invention can vary depending on the chemical structure of the low-foaming nonionic surfactant.

Claims (9)

1. Stable material suitable as or in acid rinse agents, characterized in that it contains (a) 1-60 parts by weight of low-foaming nonionic surfactant, with a flash point below 70°C and comprising one or more of cg~C22 fatty alcohol/ethylene oxide condensates, polyoxypropylene- polyoxyethylene condensates, alkylpolyoxypropylene-polyoxyethylene condensates, alkylpolyoxyethylene-polyoxypropylene condensates, polyoxyalkylene glycols, benzyl ethers of polyoxyethylene condensates of alkylphenols, and butylene oxide-alcohol condensates, (b) 0.5-20 parts by weight of polymer having a weight average molecular weight of 1,000-250,000 and which is a homopolymer of acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid or acrylamide, or which is a copolymer comprising units derived from two or more of acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, hydroxyacrylic acid, C^-C^-alkyl-(met )acrylates or amides, 2-acrylamido-2-methylpropanesulfonic acid, styrene, acrylamide, isobutadiene, d imethylaminoethyl methacrylate and tert-butylacrylamide, c) 0.1-10 parts by weight of other nonionic surfactant with a flash point of at least 70°C and comprising alkylaryl polyether alcohols with an average of at least 10 ethylene oxide units per molecule, and alkyl polyether alcohols with an average of at least 10 ethylene oxide units per molecule, d) water, where the parts by weight are calculated from 100 parts by weight of the sum of a) plus b) plus c) plus d), and that the material has a pH of less than 7. 2. Material in accordance with claim 1, characterized in that the low-foaming nonionic surfactant (a) is present in an amount of 5-50 parts by weight per 100 parts by weight of the components (a), (b), (c) and (d). 3. Material in accordance with claim 1 or 2, characterized in that the low-foaming nonionic surfactant (a) is present in an amount of 10-40 parts by weight, per 100 parts by weight of the components (a), (b), (c), ( d). 4. Material in accordance with one of the preceding claims, characterized in that the polymer (b) has a weight average molecular weight of up to 100,000, preferably up to 70,000. 5. Material in accordance with one of the preceding claims, characterized in that the polymer (b) is partially neutralized. 6. Material in accordance with one of the preceding claims, characterized in that the polymer (b) is present in an amount of 1-10, preferably 1-5 parts by weight, per 100 parts by weight of the components (a), (b), (c) and D). 7. Material in accordance with claim 1, characterized in that the alkylaryl polyether alcohols are compounds with the formula: or where x has an average value of at least 10. 8. Material in accordance with one of the preceding claims, characterized in that the second nonionic surfactant (c) is present in an amount of 0.5-5 parts by weight per 100 parts by weight of the components (a), (b), (c) and D). 9. Use of nonionic surfactant which has a flash point of at least 70°C, for stabilizing an aqueous material comprising low-foaming nonionic surfactant and polymer, where the polymer is as stated in claim 1.