NO124783B - - Google Patents

Description

Liquid synthetic detergent mixture.

The invention relates to liquid synthetic detergent mixtures. The detergent mixtures are suitable for use in cleaning hard surfaces, e.g. by manual or machine washing of plates, silverware or cookware.

The invention relates to liquid synthetic detergent mixtures comprising an ammonium salt of an alkylbenzenesulfonic acid,

wherein the alkyl group contains 8 to 16 carbon atoms, and a water-soluble nonionic synthetic detergent which is liquid at ambient temperature. Until now, these products have made use of an ammonium salt made by neutralizing the alkylbenzene sulfonic acid with a solution of ammonium hydroxide. This neutralization product has a high water content and a high content of inorganic contamination

(ie ammonium sulphate), which together make up at least 25% by weight of the product. When these paste-like products are used in liquid synthetic agent mixtures, they raise problems with regard to phase stability under normal storage conditions for the products (which may be at temperatures down to -20°C), and also with the varying viscosity demanded by the consumer, which may vary from country to country, but fall in the range of 50 to 1500 centistokes. These phase stability problems are solved by incorporating a hydrotrope, but this is an expensive agent that contributes little or nothing to the product's washing properties. A liquid synthetic detergent mixture with a maximum content of active detergent and minimal impurities is certainly advantageous from a sales point of view and with regard to packaging economy, which is a product which is phase stable and which has a viscosity acceptable to the consumer.

It has now been found that an ammonium salt of an alkylbenzenesulfonic acid with a high active detergent content (ie a high % by weight of pure surfactant) can be used as an anionic surfactant component in conjunction with a liquid nonionic surfactant with a high active detergent content to obtain of a liquid synthetic detergent mixture possessing the aforementioned advantages. Such products not only possess a significantly higher active content than has so far been shown to be possible using the above-mentioned ammonium alkylbenzene sulphonate paste, but surprisingly do not raise any phase stability problems in a wide range of products. It is also surprising that this ammonium salt, which is in gel form, can easily be incorporated into a liquid, non-ionic detergent with a high active content to obtain a product in clear, phase-stable, liquid form.

The detergent mixtures according to the invention are a clear, homogeneous product with an active content of at least 80%, which possesses satisfactory properties with regard to washing capacity for dirty plates and with regard to foaming ability.

The detergent mixture according to the invention is characterized

in that the sulphonate and the non-ionic synthetic detergent together make up 80-100% by weight of the mixture. It may also possibly contain 0-15% by weight of sodium C11_1,--alkyl ether sulfate. 3E0.

A preferred composition of the detergent mixture according to the invention contains the sulphonate and the non-ionic detergent in the weight ratio from 4:1 to 2:3.

The detergent mixture according to the invention preferably has at least 90% active detergent content. In the products that have 80% active detergent content, the remaining 20% is essentially water, usually no more than 7%, which originates either from the ammonium salt or the non-ionic detergent or both, and from a viscosity-reducing agent such as e.g. an aliphatic alcohol,

which is present in no more than 15%.

An ammonium alkylbenzenesulfonate with an active content of at least 80% can conveniently be prepared by neutralizing a liquid alkylbenzenesulfonic acid with gaseous anhydrous ammonia. The neutralization takes place at atmospheric pressure and at temperatures between 10 and 90°C, preferably 15-30°C, and is allowed to continue until the reaction mixture's pH value exceeds 7. Excess ammonia can be removed from the product by blowing nitrogen gas through the reaction mixture - the duct. The product is a gel that contains at least 80% active detergent and is practically free of water and ionic by-products such as ammonium sulphate. Practically 100% conversion of the sulphonic acid can be achieved. A further reduction in the already low concentration of the by-product pollutant, ammonium sulphate, can be carried out by blowing an inert purge gas, e.g. nitrogen gas, through the alkylarylsulfonic acid prior to neutralization.

Suitable sulfonic acids for neutralization with gaseous, anhydrous ammonia are decyltoluene, dodecylxylene, octylbenzene, nonylbenzene, decylbenzene, undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, pentadecylbenzene and hexadecylbenzene. The preferred acid is dodecylbenzenesulfonic acid.

Suitable non-ionic synthetic detergents are ethylene oxide condensates of alkylphenol, e.g. a condensate of octyl or nonyl phenol with 3 to 15 moles of ethylene oxide; a condensate of cn_^3~ or C, . or C,,.r-secondary alcohol with 3 to 12 moles of ethylene oxide,

14-15 11-15

a condensate of oleyl alcohol with 3 to 15 moles of ethylene oxide or an ethoxylated ethanolamide.

The detergent mixture according to the invention can be prepared from commercially available alkylbenzene sulphonic acids. When these acids are very dark in color, the resulting ammonium salt may be too dark for incorporation into liquid synthetic detergent compositions. Color improvement is preferably carried out by bleaching the commercial acid with hydrogen peroxide solution before the preparation of the salt, as this bleaching process requires the least water and also because it introduces smaller amounts of inorganic contaminants. An optimal concentration of aqueous hydrogen peroxide at which no significant foam production occurs during the neutralization is approx. 5-7% aqueous hydrogen peroxide of a strength of 50 parts by volume and enables the production of a bleached ammonium alkylbenzene sulphonate containing only 4-6% water. When this sulfonate is used as the main ingredient in a liquid synthetic detergent, it contributes only 2 to 3%

water in the total composition.

In compositions comprising a nonionic synthetic detergent which is inert to ammonia, it is convenient to carry out the ammonia neutralization of the alkylbenzenesulfonic acid in the presence of the water-soluble nonionic agent to be used in the detergent composition. The nonionic detergent is not affected by the ammonia and performs the useful function of keeping the viscosity of the reacting liquid at a reasonably low level, ie 100 to 500 centistokes. If the liquid detergent mixture consisting of the ammonium alkylbenzene sulfonate and the nonionic synthetic detergent is too viscous, then a viscosity-reducing agent may be added upon neutralization of the sulfonic acid, provided that the agent is inert to the anhydrous ammonia, and that it is present in amounts that do not exceed the concentration tolerated by the system. Suitable substances are methyl, ethyl or isopropyl alcohol. If the neutralization is carried out in the presence of an aromatic solvent, e.g. benzene, this must be removed before the final preparation of the liquid detergent mixture.

In the past, liquid synthetic detergent mixtures have

high total active content, i.e. 80-95%, have relied on water-soluble, non-ionic surfactants, which are commercially available as 100% active, as the main ingredient (i.e. used in conjunction with inorganic builders such as sodium tripolyphosphate) or as only component. However, these water-soluble, non-ionic surfactants are unsuitable for liquid detergent compositions when used alone, or as a main component, due to their relatively poor foaming properties in the presence of grease/flour/protein soils. This is an anti-foam dirt, well known from the prior art.

When the detergent composition according to the invention, i.e. a highly active ammonium alkylbenzene sulphonate in combination with a water-soluble, non-ionic agent, is used, the foam volume developed under standardized conditions (as described in test method 1 below) and their stability to grease/flour/protein soiling are claimed advantageously in practically the same concentration with regard to active content, in relation to the foam volume and stability of recognized conventional, low-active detergent mixtures, i.e. a mixture of sodium dodecylbenzene sulphonate and tert-octylphenol-11,5-ethylene oxide condensate.

(Such a mixture is unstable at high concentrations of active material). Table 1 shows the improved foam figure in the non-ionic/anionic systems specified in the table, at a concentration of 0.1% active detergent in relation to each agent alone, as well as the improvement in soil removal index (test method 3) shown by the combination compared to non-ionic detergent alone. A is ammonium dodecylbenzene sulphonate with 95% active detergent content. B is tert-octylphenol-11.5 ethylene oxide condensate (11.5 is the average ethoxylate chain) with 100% active detergent content:

The preferred ternary mixtures for detergent mixtures according to the invention are those where the ammonium alkylbenzene sulphonate constitutes 40-65%, preferably 45-55%, the alkyl ether sulphate 1.8-15%, preferably 3-12%, and the water-soluble non-ionic detergent is 20-60 %, preferably 25-40%, of the product (all expressed as 100% active). These ranges represent a compromise between the ranges found to be preferable for the various foam, dishwashing capacity and viscosity properties discussed below. Alcohol additives as solvents can amount to up to 10%, the ratio between alkylbenzene sulphonate and alkyl ether sulphate and non-ionic agent being kept within the above-mentioned limits.

When selecting within these wide areas, one must always keep in mind the desirable properties with regard to producing a good foam - which is known to be influenced in a harmful way by a high content of non-ionic agents - and good dispersibility - which is known to be influenced to a harmful degree by the content of anionic agents that raise the viscosity. The addition of the alkyl ether sulfate modifies the foam, i.e. produces a dense foam and stabilizes the foam against dirt, even when incorporated as a minor component. The foam figures for the following composition: (a) highly active ammonium dodecylbenzene sulfonate, (b) tert-octylphenol-11,5 ethylene oxide condensate, (c) sodium C11-C15<-a>alkyl ether sulfate (3 ethylene oxide) exhibit synergistic foaming properties. The sodium C₁-C₂ alkyl ether sulfate (3 ethylene oxide) used here contained only 60% active detergent. At the present time, this concentration of active content is the highest commercially available. The remaining 40% consists of 25% alcohol and 75% water.

Particularly useful products in this (a) + (b) + (c) system are

those having 45-70% (a), 20-40% (b) and 1-25% (c) by weight of the total composition, expressed as 100% active, 100% active and 60% active respectively. The use of sulphates with a low content of water is desirable, i.e. the use of amine salt which can be prepared by neutralizing the alkyl ether sulfuric acid with an organic base, e.g. morpholine, tri-ethanolamine or isopropylamine, instead of the sodium salt.

The foaming ability of this (a) + (b) + (c) system in the presence of dirt

was further examined using a plate washing test which is described below as test method 2. Products with 40-90% (a), 1-60% (b) and 1-30% (c) exhibit synergistic properties, and products with respectively 50 -65%, 25-40% and 3-18% will be preferred if foaming ability is desired in the liquid detergent.

In order for it to be used in an aqueous environment, a liquid synthetic detergent must have good water dispersibility, a property that is directly related to the product's viscosity. The viscosities of products within the aforementioned preferred ternary system, determined using an Ostwald-type viscometer tube at 25°C, show that an optimum range when considering low viscosity, i.e. 80-500 centistokes, covers products with 20 -55% (a), 20-60% (b) and 5-30% (c).

Products prepared within the ranges indicated above for the preferred (a) + (b) + (c) system have been found to be phase stable and to require no addition of hydrotrope other than viscosity-reducing alcohol.

Although the carefully studied ternary system used the specified non-ionic, tert-octylphenol-11,5 ethylene oxide, other non-ionic agents can also be used. The effect of the foam figure property by replacing (b), the tert-octylphenol-11,5-ethylene oxide, with another ethylene oxide adduct in a product of the following composition: 45% ammonium dodecylbenzenesulfonate, 30% (b) and 15% sodium C12 ~alkyl ether-

The products according to the invention may comprise more than one non-ionic surfactant. The soil removal ability can be improved without loss of phase stability by replacing part of the water-soluble non-ionic agent with a less water-soluble non-ionic agent, e.g. a fatty acid mono- or -di-ethanolamide or

a fatty acid amine, e.g. lauric acid isopropylamine. In cleaning agents for hard surfaces, it is common to add perfume, a bacteriostatic agent, i.e. formalin, and possibly a dye. These additions can also be made to the aforementioned ternary system for the usual application purposes. However, the addition of a bacteriostatic agent is not essential for stable products when no water is present in the product. The amount of active synthetic detergent in a hard surface cleaner is usually in the range of 0.05-0.25% active detergent in aqueous solution.

The invention will now be illustrated by means of examples. Example 1 describes a highly active detergent where the active agent is ammonium dodecylbenzenesulfonate and an ethoxylated octylphenol, produced by neutralization of sulfonic acid using anhydrous, gaseous ammonia in the presence of the ethoxylated octylphenol.

EXAMPLE 1.

300 g of dodecylbenzenesulfonic acid was filled into a 500 ml reaction vessel, 21 g of 50% by volume hydrogen peroxide solution was added and the mixture stirred for 10 minutes at room temperature. 40 ml of tert.-octylphenol-11.5 ethylene oxide was added when the viscosity fell to approx. 1000 cS, the mixture was stirred and anhydrous. ammonia gas was bubbled through at 20-30°c, until the mixture's pH value had risen above 7. Excess ammonia was removed by bubbling through with nitrogen for approx. 15 minutes. The product was a golden yellow, light-flowing liquid with a total active synthetic detergent content of 94% (83% with respect to the sulphonate component). This product can be used in any of the mixtures in Examples 2-5 by adjusting the non-ionic content by a simple addition.

Examples 2-5 describe liquid dishwashing detergent mixtures according to the invention.

(The ammonium dodecylbenzene sulphonate had an active content of

95%).

EXAMPLE 2.

EXAMPLES 3-5.

In Examples 2-5, the alcohol content can be freely adjusted to produce any desired viscosity without any noticeable effect on the appearance of the products, provided the ratio of the other components is kept constant.

Test method 1: Cylinder foam test.

100 ml of a solution containing 0.1% synthetic detergent was transferred to a graduated 250 ml measuring cylinder and kept in a thermostatic water bath at 45°C. The cylinder was sealed again and turned upside down 10 times, whereby the height of the foam was determined visually. A series of additions of 0.1 g dirt were made (fat/flour/protein dirt), while after each addition the cylinder was turned upside down 5 times and the foam height measured until all foam was destroyed. All read foam heights were summed and expressed as foam numbers.

Test method 2: Plate washing

5 liters of washing-up solution were made in a 36 cm plastic bowl

in diameter, at 45°C, the solution having a reproducible foam volume, by means of a standardized procedure which involved adding 4.5 1 of hot water to 0.5 1 of water containing the total amount of detergent, by empty it in a reproducible manner from a height of 2.07 m. 25.4 cm diameter dinner plates each soiled with 2.4 g of a grease/flour/olein mess were then washed individually in the bowl of liquid until the foam layer above the liquid surface was broken. The number of plates needed to break the foam cover at two concentrations of active detergent was noted <p>g the average calculated. The products according to the invention were used in concentrations of 0.02 and 0.04% (active detergent). Plate washing grades are expressed as a percentage of the number of plates washed using the conventional washing-up liquid referred to in the description.

Test method 3; Dirt removal index

The dirt removal ability of detergents is expressed as "dirt removal index". This index is determined by comparing the degree of removal of thin layers of dried egg yolk from glass surfaces using a 0.1% active solution of the detergent in demineralized water with the degree of removal caused by a 0.1% active solution of octylphenol -11.5 E.O., both degrees being determined at 45°c and a solution pH of 7. The ratio is multiplied by a factor of 10 in order to obtain comparable figures. Conventional anionic/non-ionic washing-up liquids show soil removal indices of 22.

The liquid dishwashing detergents according to the invention are clear, homogeneous, synthetic detergents with low viscosity and good phase stability that contain very little water, have a high active detergent content and do not require the addition of hydrotropes, apart from a viscosity-adjusting, water-miscible solvent. A further advantage of the small amount of water present in these products is that the agents can be added either in solution, suspension or encapsulated, so that they can react with water when the product is in use, to achieve useful effects such as e.g. bleaching, sanding or foaming.

Claims (3)

1. Liquid detergent mixture consisting essentially of ammonium alkylbenzene sulphonate, where the alkyl group has from 8-16 carbon atoms, and a water-soluble, non-ionic synthetic detergent which is liquid at ambient temperature, characterized in that the sulphonate and the non-ionic detergent together amount to 80-100 % by weight of the mixture, and that it possibly contains 0-15% by weight of sodium C-j^_^-alkyl ether sulfate. 3E0. 2. Detergent mixture as stated in claim 1, characterized in that the weight ratio between sulphonate and non-ionic detergent is from 4:1 to 2:3. 3. Detergent mixture as stated in claim 1, characterized in that the sulfonate is present in an amount of 40-65% and the non-ionic detergent in an amount of 20-60%, both by weight of the entire mixture.