The present invention relates to a particulate alka- line detergent containing an alkaline agent and an alkali perborate hydrate and/or an alkali carbonate peroxohydrate as bleaching agent. As a result of coating at least the alkaline agent or the bleaching agent with an alkyl glycoside or an alkyl glycamide, the detergent has a low tendency to caking and excellent cleaning capacity.

When stored, particulate detergents, such as machine dishwashing detergents, easily cake, probably because weakly bound water migrates from one component to another, thereby forming so-called salt bridges. It is known that small amounts of chlorine isocyanurates, which are used as bleaching agents, can prevent caking. Patent Specification DE 3,818,660 Al, for instance, discloses such machine dishwashing detergents. It has, however, been found that chlorine isocyanurates in alkaline aqueous solutions gene- rate organic chlorine compounds, such as tetrachlorine dibenzo paradioxine, which are toxic as well as not readi¬ ly biodegradable- Thus, there is every reason to avoid using chlorine isocyanurates as bleaching agents and an i- caking agents. Chlorine-free and comparatively environment-friendly bleaching agents include alkali perborate hydrates, such as sodium perborate monohydrate and sodium perborate tetrahydrate, and alkali carbonate peroxohydrates, such as sodium carbonate peroxo-1,5-hydrate. Such agents do, however, exhibit a marked tendency towards caking, which usually is intensified if the bleaching agents are used together with silicate as the alkaline agent. Attempts to use surface-active agents as anti-caking agents have only met with limited success, since it has not been possible to combine satisfactory anti-caking capacity with satis¬ factory cleaning capacity with regard to fat, starch, protein and tea.

One object of this invention is to replace chlorine isocyanurates with more environment-friendly bleaching agents in freeflowing alkaline detergents, such as parti¬ culate alkaline dishwashing detergents. Another object of the invention is to select the components of the deter¬ gent in such manner that it does not contain any special anti-caking agents and is given excellent cleaning capa¬ city.

It has been found that these- objects are achieved by using alkyl glycosides or glycamides as a combined sur¬ face-active agent and anti-caking agent. More specifical¬ ly, the invention relates to a particulate alkaline deter¬ gent containing a conventional complexing agent, charac¬ terised in that it further contains a) 0.05-10% by weight, preferably 0.05-4% by weight, and most preferably 0.2-2.5% by weight of a C _fi -C _1Q -alkyl glycoside having a degree of polymerisation of 1-4, a gly¬ camide of formula

0 R _n II I ¹

R ₂ C N C H ₂ (CH0H) ₄ CH ₂ 0H (I)

wherein R. is hydrogen or an alkyl group having 1-4 carbon atoms, and R~ is an alkyl group having 6-10 carbon atoms, or a mixture thereof, b) 10-80% by weight, preferably 20-70% by weight of a water-soluble inorganic alkaline agent, and c) 1-80% by weight, preferably 1-20% by weight, and most preferably 3-15% by weight of an alkali perborate hydrate and/or an alkali carbonate peroxohydrate, at least one of components b) and c), and, optionally, other components of the detergent, being coated with com¬ ponent a). In a preferred embodiment, both the alkaline agent b) and the bleaching chemicals c) are surface-coated with component a), suitably together with other compo¬ nents, such as the complexing agent. A suitable coating

is obtained by dissolving the alkyl glycoside or the glycamide in a solvent, e.g. water and/or ethanol, and is sprayed onto a powder of the components to be coated, whereupon the thus-sprayed powder is dried in a manner known per se. Also other conventional processes of coating may be employed.

If only one of components b) and c) is coated with alkyl glycoside or glycamide, the content thereof may become so low that another surface-active agent should be added to the detergent to give the desired cleaning capacity. Apart from adding more alkyl glycoside or glyc¬ amide, other surface-active agents can be added, such as amphoteric compounds, non-ionic compounds or mixtures thereof, or a mixture of non-ionic and anionic compounds. If the detergent is a dishwashing detergent, low-foaming surface-active agents or mixtures of such agents should be used. Supplementary surface-active agents may also be added to adapt, and thereby optimise, the detergent to different applications. Patent Specification US 4,675,127 discloses the use of alkyl glycosides in particulate detergent compositions. In this case, the alkyl glycoside is to contribute to reducing the viscosity and increasing the homogeneity of the aqueous slurry to be spray-dried. Further, DE-A1- 3,925,858 discloses the coating with an alkyl glycoside of a chemically and physiologically inert carrier which in water is neutral or weakly alkaline. However, these patent specifications do not provide any guidance on how to avoid caking in a particulate alkaline composition according to the invention.

The specific alkyl glycosides used in the invention have an alkyl group with 6-10 carbon atoms and a degree of polymerisation of 1-4. Conveniently, the length of the alkyl chain and the degree of polymerisation are so chosen that the alkyl glycoside obtains a HLB value of 16-21. Preferably, the alkyl group has 7-9 carbon atoms and the degree of polymerisation is 1.0-2.0. In detergent

compositions according to the invention, such alkyl gly¬ cosides have been found to give excellent cleaning capa¬ city, suitable foaming, and a low tendency towards cak¬ ing. Suitable alkyl groups include n-heptyl, 2-ethyl hexyl, n-octyl, isononyl, n-nonyl and n-decyl.

In the glucamide, R~ conveniently is n-heptyl, 2-ethyl hexyl, isononyl, n-nonyl and n-decyl, and R., conveniently is methyl or ethyl.

As water-soluble alkaline agents, use is primari- ly made of sodium silicates, sodium carbonates, sodium borates and sodium hydroxide or mixtures thereof. Prefer¬ ably, use is made of sodium silicate, optionally combined with sodium carbonate. In strongly alkaline dishwashing detergents, i.e. detergents that give a pH exceeding 11, preferably exceeding 11.5, in a 1% aqueous solution, use is conveniently made of an alkaline agent of which at least 50% by weight is a sodium eta-silicate with or without hygroscopic water. For weakly alkaline dishwash¬ ing detergents, i.e. dishwashing detergents that have a pH below 11, preferably 9-11, in a 1% aqueous solution, use is preferably made of an alkaline agent of which at least 10% by weight is a sodium silicate in which the molar ratio of SiO_ to Na ₂ 0,is 1.0-3.5, preferably 2.0-2.4. Advantageously, these silicates are combined with alkaline buffers, e.g. sodium hydrogen carbonate. The cleaning capacity of weakly alkaline detergents may further be enhanced by an addition of enzymes, since the stability of the enzymes is not affected by the bleaching agents used in the invention or by the moderately alkaline pH. Suitable enzymes are amylases and proteases.

Usually, the alkali perborate hydrate and the alkali carbonate peroxohydrate are sodium compounds, such as sodium perborate monohydrate, sodium perborate tetrahy- drate and sodium carbonate peroxo-1,5-hydrate. If desired, the two bleaching agents can be mixed with one another, but sodium perborate monohydrate is usually preferred as

bleaching agent owing to its excellent stability and cost effectiveness.

Suitably, component c) is coated with at least some of component a) in a separate step, it being possible to apply comparatively large amounts of component a) on the bleaching agents making up component c). This results in a satisfactory anti-caking effect, since the bleaching agents making up component c) belong to those components of the detergent that form salt bridges. Thus, the present invention also concerns a particulate bleaching agent con¬ sisting of an alkali perborate hydrate and/or an alkali carbonate peroxohydrate and coated with 0.5-20% by weight, preferably 0.5-10% by weight, and most preferably 1-5% by weight of a C _fi -C _lf .-alkyl glycoside having a degreee of polymerisation of 1-4 and/or a glycamide of formula (I).

Also the particulate alkaline agent may advantageous¬ ly be coated with component a), since this agent markedly contributes to the formation of salt bridges. Thus, the present invention also concerns a particulate, water- soluble and inorganic alkaline agent coated with 0.2-10% by weight, preferably 0.2-5% by weight, and most prefer¬ ably 0.5-2.5% by weight of a C _fi -C, ₀ -alkyl glycoside having a degree of polymerisation of 1-4 and/or a glycamide of formula (I). Preferably, at least 10% by weight of the alkaline agent is a sodium silicate.

The complexing agent may be inorganic as well as organic. Suitable complexing agents include polymeric inorganic phosphates, such as tripolyphosphates and pyro- phosphates; organic compounds, such as nitrilo triace- tates, ethylene diamine tetraacetates and phosphonates; and multi-functional carboxylic acids, such as citrates. Other complexing agents are zeolites and carboxylate- group-containing polymers, such as polyacrylates. Poly¬ phosphates are the most common complexing agents, but the use of polyphosphates is being questioned owing to their fertilising effect on watercourses. By using a perborate as bleaching agent, it is possible to considerably reduce

the polyphosphate content without impairing the cleaning capacity of the detergent. Usually, the complexing agent makes up 10-40% of the particulate detergent.

Apart from the components indicated above, the detergent according to the invention may contain a num¬ ber of other common additives, such as colouring agents, defoamers, solubilising agents, perfume, anti-redeposi- tion agents, such as cellulose derivatives and water- soluble fillers. The content of these additives may vary within wide limits, but usually is 0-20% by weight of the detergent.

Strongly alkaline particulate dishwashing detergents according to the invention suitably have the following composition:

Component % by weight

Complexing agent, preferably sodium tripolyphosphate 10-35 Co-alkyl glycoside (degree of polymerisation of 1.0-2.0) or C _R -alkyl glycamide 0.5-2.5 Alkaline agents of which at least

50% by weight is sodium meta- silicate 35-80 Sodium perborate monohydrate and/or sodium carbonate peroxo-1,5-hydrate 3-15 Other components 0-15

Weakly alkaline particulate dishwashing detergents according to the invention suitably have the following compos tion:

Component % by weight

Complexing agent, preferably sodium tripolyphosphate, polycarboxylate, sodium citrate 20-50, preferably 20-40

Cg-alkyl glycoside (degree of polymerisation of 1.0-2.0) or C _Q -alkyl glycamide 0.5-8, preferably 0.5-2.5

Alkaline agent of which at least 10% by weight is a sodium sili¬ cate having a Si0 ₂ _Na ₂ 0 ratio of 2.0-2.4 5-70, preferably 10-60

Sodium perborate monohydrate and/ or sodium carbonate peroxo-1,5- 3-40, preferably hydrate 3-15

Other components 2-30, preferably

5-20

The invention will now be illustrated in more detail with the aid of the following Examples. Examples 1-5

A particulate composition consisting of 27 parts by weight of sodium tripolyphosphate, 67 parts by weight of sodium metasilicate, 4 parts by weight of sodium carbonate and 10 parts of sodium perborate monohydrate was coated with 2 parts by weight of one of the alkyl glycosides below or with octyl-N-methyl glucamide. The resulting dishwashing detergent compositions and the basic formula¬ tion were tested as to caking after storing for 24 hours at 40°C and 60% RH. The degree of caking was assessed by visual inspection on a scale from 1 to 5, in which 1 = freeflowing, 2 = freeflowing with lumps (about 25%), 3 = about 50% caked, 4 = about 75% caked, and 5 = completely caked. The following results were obtained.

AG-8-1.1 = octyl glucoside having a degree of polyme¬ risation of 1.1.

AG-8 -1.1 = 2-ethyl hexyl glucoside having a degree of polymerisation of 1.1.

AG-8 -1.5 = 2-ethyl hexyl glucoside having a degree of polymerisation of 1.5.

AG-8-2.0 = octyl glucoside having a degree of polyme¬ risation of 2.0.

As appears from the results, the detergent composi¬ tion of the invention is freeflowing, whereas the pulve¬ rulent composition without alkyl glycoside or alkyl glycamide exhibits tendencies towards caking. Examples 6 and 7

To a particulate composition consisting of 27 parts by weight of sodium tripolyphosphate, 67 parts by weight of sodium metasilicate and 4 parts by weight of sodium carbonate was added 10 parts by weight of sodium perborate monohydrate which had been treated with 2 parts by weight of an alkyl glycoside. Then, caking tests as in Examples 1-5 were performed, yielding the following results.

Example Alkyl glycoside Caking

Control 2 ^a) - 2

Control 3 ^b) - 3

Example 6 AG-8-1.1

E Exx<ample 7 AG-8 -1.1 a) in the absence of sodium perborate monohydrate ' in the presence of untreated sodium perborate monohydrate.

It is evident from the results that a freeflowing dish¬ washing detergent is obtained also when only the sodium perborate monohydrate is treated with alkyl glycoside.

Examples 8 and 9 A pulverulent composition consisting of 27 parts by weight of sodium tripolyphosphate, 67 parts by weight of sodium meta-silicate and 4 parts by weight of sodium car¬ bonate was coated with 2 parts by weight of an alkyl gly¬ coside, whereupon 10 parts by weight of sodium perborate monohydrate was added. The tendencies towards caking were established as in Examples 1-5, giving the following results.

a) without bleaching agent

It is clear from these results that a freeflowing dishwashing detergent is obtainable also when the basic composition, including alkaline agents, has been coated with alkyl glycoside, while the bleaching agent remains uncoated.

Examples 10 and 11

A particulate composition consisting of 27 parts by weight of ^" sodium tripolyphosphate, 67 parts by weight of sodium metasilicate, 4 parts by weight of sodium carbonate and 10 parts by weight of sodium perborate monohydrate was coated with 2 parts by weight of alkyl glycoside, where¬ upon caking tests were performed at 20°C and 60% RH, as in Examples 1-5. For comparison, the particulate composition was tested also in the absence of alkyl glycoside, and further tested after having been coated with a conven¬ tional non-ionic alkylene oxide adduct, Plurafac LF 403. The following results were obtained.

Example Surface-active agent Caking Control 6 - 4.5

Control 7 Plurafac LF 403 5.0

Example 10 AG-8-1.1 3.0

Example 11 AG-8 -1.1 1.5

It is evident from these results that the presence of alkyl glycoside according to the invention considerably reduces tendencies towards caking, whereas the presence of a conventional non-ionic alkylene oxide adduct common in dishwashing detergent compositions instead intensifies tendencies towards caking. Examples 12 and 13

A particulate composition consisting of 27 parts by weight of sodium tripolyphosphate, 67 parts by weight of sodium metasilicate, 4 parts by weight of sodium carbo- nate and 10 parts by weight of sodium perborate mono¬ hydrate was coated with 2 parts by weight of an alkyl glycoside. The cleaning capacity of the resulting dish¬ washing detergent was then tested in a household dish¬ washer at 55°C with regard to starch, protein and fat. For comparative purposes, tests were also performed on the particulate composition without alkyl glycoside. The cleaning effect was measured by means of a spectrophoto-

meter after the remaining soil had been coloured with iodine. The cleaning effect was assessed on a scale from 1 to 10, in which 1 represents washing up with clean water, and 10 represents a completely clean plate. The following results were obtained.

As is apparent, the presence of alkyl glycoside con¬ siderably improved the cleaning capacity. Examples 14 and 15 A particulate composition consisting of 35 parts by weight of sodium citrate, 29 parts by weight of sodium disilicate, 10 parts by weight of sodium carbonate, 13 parts by weight of sodium sulphate, 1 part by weight of magnesium sulphate, and 10 parts by weight of sodium per- borate monohydrate was coated with 2 parts by weight of alkyl glycoside. The resulting low-alkaline dishwashing detergent was tested as to caking at 20°C and 60% RH as in Examples 1-5. The results were as follows.

Example Alkyl glycoside Caking Control 9 - 2

Example 14 AG-8-1.1 1

Example 15 AG-8 ¹ -!.! 1

It is obvious that the low-alkaline dishwashing detergent according to the invention give freeflowing compositions, whereas the corresponding composition without alkyl glycoside exhibits tendencies towards caking.

Examples 16 and 17 A particulate composition consisting of 27 parts by weight of sodium tripolyphosphate, 67 parts by weight of sodium metasilicate, 4 parts by weight of sodium carbonate

and 10 parts by weight of sodium carbonate peroxo-1,5- hydrate was coated with 2 parts by weight of an alkyl gly¬ coside in accordance with the Table below. The resulting dishwashing detergent compositions as well as, for compa¬ rative purposes, the basic formulation proper and the basic formulation coated with a non-ionic surface-active agent (Plurafac LF 403) were tested as to caking after storage for 24 hours at 40°C and 60% RH, as in Examples 1-5. The following results were obtained.

It is clear that the dishwashing detergents formu¬ lated according to the invention have much better free- flowing properties than the compositions included for comparative purposes.