WAESSERIGE WASCHMITTELHALTIGE FLEET FOR WASHING TEXTTILIEN

{21) Application No. 40209/76 (22) Filed 28 Sept. 1976

(31) Convention Application No. 2 544 949 (32) Filed 8 Oct. 1975 in

(33) Fed. Rep. of Germany (DE)

(44) Complete Specification published 19 July 1978

(51) INT CL^{1 2} C11D 3/12, 3/065, 3/075 (52) Index at acceptance

C5D 6A5C 6A5D1 6A5D2 6Α5Ε 6Α8Β 6Α9 6Β10Α 6Β12Ε

6B12G2A 6Β12Ν1 6Β1 6Β2 (72) Inventors KLAUS HENNING and JOACHIM KANDLER

(54) PROCESS FOR WASHING TEXTILES

(71) We, HOECHST AKTIENGESELL-SCHAFT, a body corporate organised under the laws of the Federal Republic of Germany, of D6230 Frankfurt am Main 80, Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to the washing of textiles (as herein defined) with an aqueous detergent-containing bath whose detergent comprises at least one organic anionic, ηοηionic, ampholytic, or zwitterionic surfactant, an alkali metal tripolyphosphate (which may be a technical grade) as water-soluble builder, and a finely divided alkali metal aluminium silicate as water-insoluble builder, with or without one or more additional detergent adjuvants. The word “textiles” is employed herein in a broad sense; thus it includes knitted fabrics and non-woven fabrics, and also textile fibres, filaments, rovings and yarns, in addition to woven fabrics.

It is known that the washing and cleaning power of soaps and synthetic surfactants can be increased by the addition of certain substances known as builders.

The mechanism and precise nature of the action of these builders have not yet been completely elucidated, so that a prediction based on theoretical principles as to which types of compound could be suitable for this purpose is not yet possible.

Having regard to the multiplicity of individual effects which can cooperate in increasing the washing power of surfactants, we consider that the requirements which must be imposed on a builder in the light of present knowledge are that the builder should be capable of:

1. forming water-soluble complexes w_ith hardness-producing salts present in the water being used, e.g. with calcium and magnesium ions;

2. dispersing, in the washing bath, pigmentary soil particles representing a principal component of the soil carried by the textiles being washed;

3. stabilising detached soil in the washing bath in order to prevent soil particles from being redeposited upon by the textiles being washed;

4. inactivating any mineral constituents present in the washing bath;

5. reducing the adsorption of surfactants on the textiles being washed.

In order to obtain information regarding the efficiency and suitability of particular products as builders, it is appropriate to determine their behaviour and efficiency in the washing process itself. It is thereby ensured that all factors affecting the builder action are taken into account, qualitatively and quantitatively.

Known builders include water-soluble alkali metal salts of mineral acids, e.g. alkali metal carbonates, borates, phosphates, polyphosphates, bicarbonates, and silicates. Among known builders a preferential position is occupied by the alkali metal polyphosphates, since these fulfil all the requirements indicated above, and exhibit, during washing, synergistic effects in combination with surface-active substances. Consequently they constitute at the present time the most important builders in lightduty, heavy-duty, and coloured-wash detergents. For this purpose pentasodium triphosphate is mainly used. The content of this builder in detergents is commonly 25 to 65%, and in certain preparations this content is up to 90% by weight.

Because of the recent considerable increase in the consumption of phosphatecontaining detergents and cleaning agents, both in the household field and in industry, the proportion of these phosphates present in natural waters has correspondingly increased. In discussions of the causes of the increasing eutrophication of waters, the water-soluble nitrate and phosphate salts have recently been said to possess the property of promoting the growth of certain species of algae under certain conditions and thus contributing towards the eutrophication of waters, whereby their oxygen balance is disturbed. Although at the present time it is not yet possible to make a definitive assessment of the part played by phosphate-containing washing and cleansing agents in the eutrophication of waters, nevertheless it appears to be desirable to make available substitutes, containing no nitrogen or phosphates, for the builders used hitherto in detergent formulations; or alternatively, by blending alkali metal polyphosphates with certain other detergent components, to effect a reduction in the phosphorous contents of detergent formulations.

In this connection various organic compounds have already been proposed as builders, for example nitriloacetic acid, ethylene-diaminetetraacetic acid, citric acid, oxydiacetic acid, oxydisuccinic acid, cyclocarboxylic acids, and polymeric carboxylic acids, e.g. polymers of maleic acid and acrylic acid, and their copolymers with other unsaturated carboxylic acids, olefins, or short-chain unsaturated aliphatic ethers or alcohols.

The substances mentioned above have not proved to be satisfactory builders in every respect, however, inasmuch as they (1) have a strong tendency to form complexes with heavy metals and transition metals, so that increased contents of these metals are found in surface waters (whether as the result of direct sequestration or subsequent remobilisation of flow sediment) and may pass into drinking water;

or (2) do not to an adequate extent possess the previously mentioned properties of a builder, so that they do not give satisfactory washing results; or (3) are not sufficiently biodegradable.

It has recently been recognised that, by virtue of their ion exchange capacity, the water-insoluble alkali metal aluminium silicates are also suitable for replacing part of the sodium tripolyphosphate in detergent formulations, and thus reducing the total phosphate content of the detergent. On completion of the washing process, these water-insoluble builders can readily be separated from the washing bath, but even if they are discharged in the waste water they do not give rise to any biologically undersirable loading of surface-waters, unlike the known organic builders.

A method of washing (e.g.) textiles in the presence of water-insoluble alkali metal aluminium silicates, these being employed in conjuction with commonly used detergent components, has been described in German Published Specification (“Offenlegungsschrift”) No. 2,412,837. The proportion of metaphosphates and polyphosphates in these detergent formulations is so regulated that the maximum phosphate content in the washing bath amounts to 0.6 gram of phosphorus per litre of washing bath. According to the examples given in this German Specification, 2.5 to 29.2 parts be weight of pentasodium triphosphate and 45 to 11.3 parts by weight of sodium aluminium silicate having a calcium sequestering power of 150 mg of CaO per gram of silicate would be employed per 100 parts by weight of detergent.

The advantages attributed in the above-mentioned German Specification to the use of a blend of sodium tripolyphosphate and sodium aluminium silicate or sodium borosilicate in detergent formulations apply only to what is called the primary washing action; this represents only a measure of the brightening effect achieved for an artificially soiled test fabric. In practice, however, it has been found that what is called the secondary washing action of the detergent formulation, this being defined by the degree to which the fabric is loaded or “encrusted”, is unsatisfactory. Nevertheless, in judging a washing process, the secondary washing action is of importance as well as the primary washing action. Heavily loaded or “encrusted” laundry loses some of its usefulness inasmuch as its absorptivity is reduced, it wears more rapidly, and it becomes less attractive because of its hard rough feel. Another disadvantage of this prior detergent formulation results from the encrustation occurring during the washing process on the heating elements in the washing machine used. Encrusted heating elements increase the energy cost of the washing process, and tend to necessitate unduly early servicing or replacement of the washing machine.

We have now found, to our surprise, that the disadvantages of the detergent compositions of the above-mentioned German Specification can be overcome if one ensures that the proportion of alkali metal mono- and/or diphosphate(s) in the washing bath is not more than 0.1 gram per litre. The presence of this alkali metal mono- or diphosphate in the washing bath results from the method of production of the alkali metal tripolyphosphate or of the detergent composition as a whole. If the proportion just mentioned is duly kept to 0.1 gram per litre or less, contents of 0.5 to 2 grams of alkali metal tripolyphosphate and 0.5 to 4 grams of alkali metal aluminium silicate per litre of washing bath are sufficient to obtain satisfactory primary and secondary washing actions.

In ordinary commercially available technical grade alkali metal tripolyphosphates, the proportion of'alkali metal mono- and/or diphosphate(s) present may be as much as 20% by weight, according to which production process is employed. Moreover, if the detergent composition is produced by the hot spray drying process, which is very commonly employed, the content of alkali metal mono- and/or diphosphate(s) is additionally increased, in some cases to a considerable extent, by hydrolysis occurring during the preparation of the slurry, and by pyrolysis of the tripolyphosphate during the hot spray drying;

thus the final product may contain considerable proportions of mono- and/or diphosphate(s). Alkali metal mono- and diphosphates form insoluble precipitates with calcium and magnesium ions present in the washing water, unless these hardness-producing ions are rendered ineffective by suitable measures. Ordinary detergent compositions which are produced with the use of ordinary commercial sodium tripolyphosphate by the methods of the prior art do give satisfactory washing results, despite their contents of alkali metal monoand/or diphosphate(s), because the content of the ordinary commercial sodium tripolyphosphate in the detergent composition is sufficiently high to ensure that, after the complexing of the calcium and magnesium ions has taken place, an excess of sodium tripolyphosphate is still available in the washing process, so that the precipitation of alkali metal mono- and/or diphosphate(s) is avoided even at washing temperatures up to 90°C. When detergent compositions according to the above-mentioned German Specification having a reduced alkali metal tripolyphosphate content are used, however, the precipitation of salts having an encrusting action naturally cannot be prevented.

According to the present invention, therefore, we provide a process for washing textiles (as herein defined), at a temperature of 20 to 95°C, with an aqueous detergent-containing bath whose detergent comprises at least one organic anionic, non-ionic, ampholytic, or zwitterionic surfactant, an alkali metal tripolyphosphate associated with alkali metal mono- and/or diphosphate(s) as water-soluble builder, and a finely divided alkali metal aluminium silicate having a calcium sequestering power of at least 5 grams of Ca⁺⁺ per 100 grams of dehyrated silicate as water-insoluble builder, with or without one or more additional detergent adjuvants, wherein, the alkali metal tripolyphosphate being present in a proportion of 0.5 to 2 grams per litre of the said bath, and the alkali metal aluminium silicate being present in a proportion of 0.5 to 4 grams per litre of the said bath, the said bath contains not more than 0.1 gram of alkali metal mono- and/or diphosphate(s) per litre.

In a preferred form of the process of the invention the washing bath may contain 0.3 to 1 gram of the said organic surfactant(s) per litre.

In addition it has been found advantageous to use as water-insoluble builder an alkali metal aluminium silicate having a particle size which is not more than 40 microns; it is also advantageous that the silicate should have a calcium sequestering power of 10 to 14 grams of Ca⁺⁺ per 100 grams of dehydrated silicate. The alkali metal aluminium silicate may for example be represented by a crystalline zeolite which in its unactivated form substantially contains 18.2% Na_zO, 30.8% A1₂0₃, 34.1% Si0₂ and 16.7% H₂0, the balance being impurities.

The washing bath employed in the process of the invention may additionally contain one or more of the following detergent adjuvants: sodium silicate;

magnesium silicate; carboxymethylcellulose; sodium perborate tetrahydrate;

ethylenediaminetetraacetic acid; sodium sulphate.

The surfactants which may be employed in the process of the invention broadly comprise anionic, zwitterionic, ampholytic, and non-ionic surfactants.

The “anionic” surfactants are to be understood to include water-soluble salts of higher fatty acids or resin acids, e.g. sodium or potassium soaps of hardened or unhardened coconut palm oil or rapeseed oil and also tallow and mixtures thereof. Also these anion-active substances which may be employed in the process of the invention are to be understood to include salts of higher-alkyl-substituted mononuclear aromatic sulphonates, e.g. alkylbenzene sulphonates having 9 to 14 carbon atoms in the alkyl radical, alkyl naphthalene sulphonates, alkyl toluene sulphonates, alkyl xylene sulphonates, or alkyphenol sulphonates, and also salts of sulphated aliphatic alcohols or alcohol ethers, e.g. sodium or aluminium lauryl or hexadecyl sulphate, triethanolamine lauryl sulphate, sodium or potassium oleyl sulphate, and also sodium or potassium salts of lauryl sulphate ethoxylated with (e.g.) 2 to 6 moles of ethylene oxide. Other suitable anionic surfactants are secondary linear alkane sulphonates and also alpha-olefin sulphonates having a chain length of 12 to 20 carbon atoms.

The non-ionic or non-ionogenic surfactants which may be employed in the present process are to be understood to include non-ionogenic compounds which contain an organic hydrophobic group and also a hydrophilic radical. Examples of non-ionogenic surfactants are: condensation products of alkyl phenols with ethylene oxide, or of higher fatty alcohols with ethylene oxide; condensation products of polypropylene glycol with ethylene oxide or propylene oxide; condensation products of ethylene oxide with a product of a reaction between ethylene-diamine and propylene oxide; long-chain tertiary amine oxides.

The ampholytic or zwitterionic surfactants which may be employed in the process of the invention include: derivatives of aliphatic secondary and tertiary amines or quaternary ammonium compounds containing 8 to 18 carbon atoms and having a hydrophilic group in the aliphatic radical, e.g. sodium-3-dodecylaminopropionate, sodium-3-dodecylaminopropane sulphonate, 3-(N,N-dimethyl-N-hexadecyl-amino)propane-l-sulphonate; fatty acid amino alkyl-N,N-dimethylacetobetaines, the fatty acid containing 8 to 18 carbon ' atoms and the alkyl radical containing 3 carbon atoms.

Detergent adjuvants (additives) which may be employed in the process of the invention include the following, for example: alkali metal or ammonium salts of sulphuric acid, silicic acid, carbonic acid, boric acid, or an alkylene-hydroxyalkylene- or amino alkylene phosphonic acid; bleaching agents; stabilisers for peroxide compounds; water-soluble organic complexing agents.

. More specifically, use may be made of:

sodium perborate mono- or tetrahydrate;

alkali metal salts of peroxymono- or disulphuric acid; alkali metals salts of perpyrophosphoric acid; precipitated water-insoluble magnesium silicate; alkali metal salts of iminodiacetic acid, nitrilotriacetic acid, ethylene diaminetetraacetic acid, methylene diphosphonic acid, hydroxyethane diphosphonic acid, or nitrilotrismethylene phosphonic acid.

Use may also be made of: substances which increase the soil-suspending power of washing baths, e.g. carboxymethylcellulose polyvinyl alcohol or polyvinylpyrrolidone;

foam regulators, e.g. mono- or dialkyl phosphoric esters containing 16 to 20 carbon atoms in the alkyl radical; optical whitening agents; disinfectants; proteolytic enzymes. Detergent adjuvants (additives) which when employed with the other constituents of the washing bath contribute towards an improvement of the detergent effect include in particular: magnesium silicate;

sodium silicate; sodium perborate tetrahydrate; sodium sulphate; carboxymethylcellulose.

The detergent compositions having a low alkali metal mono- and/or diphosphate content which are suitable for use in preparing the washing bath employed in the process of the invention can for example be produced by the use of sodium tripolyphosphate which either has been purified by recrystallisation or has been produced from thermal phosphoric acid by a single-stage hot spray method, and which has an active pentasodium triphosphate content of at least 95%, this tripolyphosphate being utilised in a hot spray drying process for the production of a detergent composition; it is also possible to use at least 90% sodium tripolyphosphate in the production of the detergent composition by a dry mixing method. In this latter case there are no losses of sodium tripolyphosphate through hydrolysis and pyrolysis in the production of the detergent composition.

The invention is illustrated by the following example; however, it is not restricted thereto.

In order to determine the influence of tetrasodium diphosphate on the secondary washing action of blends of sodium tripolyphosphate and sodium aluminium silicate, washing tests were carried out in a domestic washing machine of the Miele 416 S type, using natural industrial water of 18°dH. The detergent components used were:

a) constant amounts of a basic detergent preparation, together with

b) variable amount of sodium tripolyphosphate, tetrasodium diphosphate, and sodium aluminium silicate.

The basic detergent preparation had the following composition:

7% by weight of dodecylbenzene sulphonate;

3% by weight of tallow fatty alcohol ethoxylate containing 11 moles of ethylene oxide per mole of tallow fatty alcohol;

3% by weight of hardened tallow soap;

4% by weight of magnesium silicate;

3% by weight of sodium silicate;

1% by weight of carboxymethyl cellulose;

25% by weight of sodium perborate tetrahydrate;

0.2% by weight of ethylenediaminetetraacetic acid;

8% by weight of water; and

sodium sulphate to make 100% by weight. The sodium tripolyphosphate used in the washing tests was obtained by recrystallisation of technical sodium tripolyphosphate, the purity of which amounted to 94.2%, in accordance with the information given by O. Τ. Quimby in J. Phys. Chem. 58 (1954) page 603. The purified sodium tripolyphosphate still contained 0.1% by weight of disodium hydrogen phosphate and 0.2% by weight of tetrasodium diphosphate.

The tetrasodium diphosphate used in the washing tests was a commercial product and still contained 1% by weight of disodium hydrogen phosphate and also 0.5% by weight of sodium tripolyphosphate.

The sodium aluminium silicate used was a finely divided crystalline zeolite of the “molecular sieve A” type. The exchange capacity of this product for Ca⁺⁺ ions at 90°C was 14 g of Ca'¹"*' per 100 g of substance. Molecular sieve A had the following composition:

18.2% by weight of NajO, 30.8% by weight of A1₂0₃, 34.1% by weight of Si0₂, and 16.7% by weight of H₂0. The mole ratio amounted to 0.97 Na2O.Al2O3.L9 Si0₂. 3.1 H₂0. The maximum particle size of the molecular sieve A was 40 μ.

The dosage of the basic detergent preparation in the washing bath amounted to 5 grams per litre of washing bath for each washing test. The amount of the other components of the detergent varied, as can be seen from the Table below. The washing tests were carried out in accordance with the washing programme for a boiling wash with prewash and clear wash. The maximum temperature in the prewash stage was 40°C and in the clear wash stage about 85 to 90°C. Following the clear wash the material washed was rinsed five times and subjected to a new washing cycle without intermediate drying, since in preliminary tests no difference was found in the washing results when the goods washed were previously dried in the clothes dryer.

Based on the procedure proposed by Schweizerische Gesellschaft fiir analytische und angewandte Chemie in “Seifen und Waschmittel”, Berne, 1955, page 116, unsoiled “Renforce” cotton fabric of Eidgenossische Materialpriifungsanstalt (Federal Material Testing Institute) of St. Gallen, Switzerland, was used as test fabric and ballast, in stitched strips of 40 χ 80 cm. The weight of the fabric amounted to 1.2 kg, so that there was a bath ratio of 1:12.5. After 50 washing cycles, the fabric was 55 ashed at 900°C and the encrustation of the fabric was ascertained as percentage of ignition residue. After 50 washing cycles, the heating bar elements were also examined for encrustation, for which 60 purpose they were removed from the washing machine. The results obtained in the individual series of tests, each comprising 50 washing cycles, are shown in the Table. 65 TABLE

Theheadings in the Table should

beas follows:

ColumnAmount of basic detergent

preparation in grams per litre

of washing bath.

ColumnAmount of sodium aluminium

silicate (molecular sieve A) in

grams per litre of washing

bath.

Amount of sodium

tripolyphosphate in grams per

litre of washing bath.

ColumnAmount of tetrasodium

diphosphate in grams per litre

of washing bath.

Column V: Loading of fabric after 50

washing cycles in (%).

Column VI: Encrustation of heating bars after 50 washing cycles in (%). 20

The series of experiments 2-4, 7, 8, 10, 11, and 14 correspond to the process of the invention, while the other series of experiments serve for comparison. From the Table it can be seen that the washing tests 25 carried out under the washing conditions of the invention result in substantially less loading of the fabrics washed and substantially less encrustation of the heating bar elements of the washing machine than 30 in the comparison tests. The process of the invention can thus be said to be a technical improvement in relation to the process of DT OS 2,412,837.