WO1996027650A1

WO1996027650A1 - Granular bleach/builder product

Info

Publication number: WO1996027650A1
Application number: PCT/GB1996/000504
Authority: WO
Inventors: Malcolm John Thorpe; Philip George Hughes
Original assignee: Brunner Mond & Company Limited
Priority date: 1995-03-06
Filing date: 1996-03-06
Publication date: 1996-09-12
Also published as: AU4886196A; GB9504442D0

Abstract

Co-granules comprise an alkali metal silicate, and a hydrogen peroxide addition compound of a builder salt which, when the co-granule is dissolved in water, is capable of providing active oxygen for bleaching and being converted to said builder salt. The co-granules are useful for their combined builder and bleaching properties and may be used in detergent compositions for laundry or dishwashing purposes.

Description

GRANULAR BLEACH/BUILDER PRODUCT

The present invention relates to a granular product intended for use particularly, but not exclusively, as a builder and/or oxygen bleach carrier in a powdered or granular detergent formulation for use in laundry and dishwash applications.

It is well known for powdered and granular detergent products (hereinafter referred to generically as granular detergent products) to incorporate a builder to sequester or precipitate divalent metal ions (e.g. Ca²⁺ and Mg²⁺) so that they do not interfere with the properties of other ingredients in the formulation e.g. surfactants.

It is also well known that the builder may be provided in the form of co-granules (i.e. a product in which the individual granules comprise two or more components) produced by agglomeration of a solution of an alkali metal silicate (typically sodium silicate) and at least one builder salt (e.g. sodium carbonate, sodium bicarbonate etc.).

Examples of such co-granules are disclosed in U.K. Patent No. 1.396.215 (Diamond Shamrock) and their use as builders is described in European Patent Specification No. 0 488.868 (Rhone Poulenc). An example of a sodium silicate/sodium carbonate co-granule made using this prior process typically contains 27% sodium silicate expressed as disilicate. 54% sodium carbonate of which about ½ is present as monohydrate and about 19% total water. (Unless otherwise stated all percentages referred to herein are by weight).

A further example of a co-granule with an increased silicate content is disclosed in WO-A-9521237 (Brunner Mond et al) which describes a co-granule comprised of sodium silicate, sodium carbonate and sodium bicarbonate. Co-granules prepared in accordance with WO-A-9521237 may contain higher amounts of silicate than those produced by the procedures mentioned in the preceding paragraph. For example, a granule produced in accordance with WO-A-9521237 may contain 32.5% sodium silicate expressed as disilicate. 42% sodium carbonate of which nearly all is thought to be present as monohydrate, 4% sodium bicarbonate, and about 21.5% total water.

Co-granular builder salts may also be produced by the combination of alkali metal silicates with alkali metal phosphates (which term includes primary, secondary and tertiary phosphates and pyrophosphates). One example of such a phosphate is sodium tripolyphosphate.

Co-granules as disclosed above are perfectly acceptable as builders and may be used in detergent products incorporating a separate bleaching system. It would however be more convenient if the granule itself also provided the bleaching properties (thus avoiding the need to incorporate a separate bleaching agent in the formulation).

It is therefore an object of the present invention to provide granules, and methods for their production, having builder and bleaching properties.

According to the present invention there are provided co-granules comprising an alkali metal silicate, and a hydrogen peroxide addition compound of a builder salt which, when the co-granule is dissolved in water is capable of providing active oxygen for bleaching and being converted to said builder salt.

Co-granules in accordance with this invention possess builder properties by virtue of the presence, in the co-granule, of the alkali metal silicate. Bleaching properties for the granules are provided by the presence of the hydrogen peroxide addition product of the builder salt which under the aqueous conditions in which the co-granules will be used will release active oxygen for bleaching purposes and regenerate the builder salt which adds to the builder effect provided by the alkali metal silicate.

The co-granules may contain the precursor builder salt as well as its hydrogen peroxide addition compound and the alkali metal silicate.

The hydrogen peroxide addition product content of granules in accordance with the invention is preferably such that there is no substantial precipitation of silica or silicate when the granule is dissolved as a 1% solution in distilled water. The 1% level represents the industry standard. It is however more preferred that the amount of percarbonate in the granules is such that there will be no substantial precipitation of silica or silicate at a concentration (of the granule) of 2% in distilled water. More preferably there should be no substantial precipitation at the 10% level, and even more preferably no precipitation up to the solubility limit of the granule.

The builder salt is. for preference, sodium carbonate for which the hydrogen peroxide addition product is sodium percarbonate (generally designated as Na₂CO₃. 1 ½ H₂O₂). Other builder salts which may be used include alkali metal phosphates (which term is used herein to include primary (ortho) phosphates, secondary and tertiary phosphates, and pyrophosphates) since phosphates are also capable of producing hydrogen peroxide addition compounds (phosphate peroxyhydrates) having bleaching properties. It is also possible for the granules of the invention to comprise hydrogen peroxide addition products of sodium carbonate and an alkali metal phosphate as well (optionally) as the original builder salt.

A further possibility is for the granule to comprise at least one builder salt other than the precursor builder salt of the hydrogen peroxide addition compound (e.g. other carbonates, a bicarbonate, or borate).

The alkali metal silicate is preferably sodium silicate although other silicates, e.g. potassium silicate, could be used.

Co-granules in accordance with the invention preferably have a mean particle size of 0.2-2.5 mm, more preferably 0.5-1.4 mm. The granules preferably have a pouring density of 0.6-1.3 g/cm³, more preferably 0.75-1 g/cm³.

According to a first preferred embodiment of the invention the hydrogen peroxide addition compound is formed in situ during production of the granule by reaction of the builder salt and hydrogen peroxide.

Co-granules in accordance with the first preferred embodiment of the invention will typically comprise:

For preference, the hydrogen peroxide addition product in the above formulation is sodium percarbonate.

Granules in accordance with the first preferred embodiment of the invention may be produced by a method (the co-granule treatment method) which involves treating co- granules comprised of an alkali metal silicate and a builder salt capable of forming a hydrogen peroxide addition compound with hydrogen peroxide so as to convert at least a portion of the builder salt to its hydrogen peroxide addition compound.

An important feature of the co-granule treatment method is that the hydrogen peroxide addition compound (which provides an oxygen bleach carrier) is formed in situ in the co-granule from the builder salt. This provides the ability to control the ratios of builder salt to its hydrogen peroxide addition product to alkali metal silicate and to provide all of these components into a single robust particle. The exact formulation of the co-granules may therefore be tailored to meet the needs of formulations of detergent products with regard to the bleaching/builder properties of the co-granule.

Typically, the hydrogen peroxide for treating the co-granules is used as 30 to 70% wt/vol, more preferably 60 to 70%. As an example. 1kg of "starting granules" including sodium carbonate requires 40 ml of 60% w/v hydrogen peroxide per 1% rise in active oxygen content in the finished granule. The reaction may be carried out at ambient temperature using any suitable mixing apparatus. The hydrogen peroxide reacts with the builder in the co-granule to form the addition compound. It is also possible that trace amounts of persilicate may be produced. The conversion efficiency of the hydrogen peroxide is about 80-100%. Excess water is driven off by the heat of reaction although the granular product may optionally be subjected to additional drying depending on reaction conditions to avoid "stickiness" of the product. The co-granule used as a starting material for this process may comprise sodium carbonate and/or an alkali metal phosphate as the builder salt. The starting granule may also comprise at least one further builder salt which does not form a hydrogen peroxide addition product.

The co-granules used as the "starting material" for the co-granule treatment method may be of the type disclosed in UK-A-1 396 215. EP-0 488 868. or WO-A- 9521237, the disclosures of which are incorporated herein by reference.

A preferred starting co-granule will typically comprise:

The alkali metal silicate preferably has a SiO₂:M₂O ratio (where M is an alkali metal) of 1.6-3.5 (more preferably 1.6-2.5) although conventionally amounts of silicate present in compositions are exposed as disilicate.

Alternatively, granules in accordance with the first preferred embodiment of the invention may be produced by admixture of hydrogen peroxide, alkali metal silicate solution and a builder salt (capable of being converted to a hydrogen peroxide addition product). At least one further builder salt may optionally also be admixed. The mixing procedure is preferably effected by adding the hydrogen peroxide and alkali metal silicate solution separately to the (solid) builder salt(s) such that substantially all of the hydrogen peroxide is added before the mix begins to agglomerate to any significant degree. Mixing is then continued to produce an agglomerated product comprised of co- granules of the desired composition.

The hydrogen peroxide used in this method preferably has a concentration of 30 to 70% wt/vol. more preferably 60 to 70%. The alkali metal silicate preferably has a solids content of 28-55% (more preferably 45-55%) and a SiO₂:M₂O ratio (where M is an alkali metal) of 1.6-3.5 (more preferably 1.6-2.5). Preferably the silicate is sodium silicate. The builder salt may typically be "light ash" (sodium carbonate) as available from Brunner Mond.

In accordance with a second preferred embodiment of the present invention the co-granules comprise the hydrogen peroxide addition compound of a builder salt compacted with the alkali metal silicate powder.

Co-granules as defined in the preceding paragraph may be produced by dry mixing a hydrogen peroxide addition compound with an alkali metal silicate powder and compacting the product to a granular form.

The hydrogen peroxide addition compound for use in this second embodiment of the invention is preferably a percarbonate. The percarbonate is preferably an alkali metal percarbonate. more preferably sodium percarbonate. Alternatively the hydrogen peroxide addition product may be any other such product as used in accordance with the first embodiment of the invention. Thus, for example, a hydrogen peroxide addition compound of a phosphate may be used.

The alkali metal silicate, for use in the second embodiment of the invention, is preferably in the form of a disilicate powder, more preferably sodium disilicate powder.

It is also possible that co-granules in accordance with the second embodiment of the invention to incorporate additional builder salts including, for example, bicarbonates. carbonates, phosphates (including poly phosphate) and borate.

Co-granules in accordance with the second embodiment of the invention typically comprise:

Granules in accordance with the invention may be formulated with at least one surface active agent into powdered or granular detergent formulations for use in laundry and dishwash applications. Such formulations may, of course, include other conventional components, e.g. a bleach accelerator such as TAED. The invention is illustrated by the following non-limiting examples.

Example 1

Samples were prepared in accordance with the formulations given in Table 1 by adding 60% w/v hydrogen peroxide to sodium silicate/sodium carbonate co-granules over a period of 10 mins whilst mixing at a low speed in a Kenwood mixer at ambient temperature. The sodium silicate/sodium carbonate co-granule used had a composition of 27.64% Na₂O.2SiO₂ and 55.32% Na₂CO₃ and a particle size of less than 1.4 mm. The granules produced were slightly sticky with a tendency to adhere to each other. A free flowing product was obtained by air drying at ambient temperature.

Example 2

1 Kg of sodium silicate/sodium carbonate co-granules (comprised of 31.4% sodium silicate (expressed as disilicate). 56.2% sodium carbonate and 12.4% water) were mixed at low speed in a Kenwood mixer at ambient temperature whilst 243 mls of 60% w/v hydrogen peroxide were added dropwise at a constant rate via a peristaltic dosing pump. The volume of hydrogen peroxide to be added was calculated to approach, but not exceed, that required fully to peroxidate the sodium carbonate present in the granules. The temperature was monitored during addition to ensure that the temperature of the mix did not rise more than 5°C above ambient temperature. Mixing was continued for 10 minutes after completion of addition of hydrogen peroxide.

The co-granules produced were dried in a fluid bed drier for 10 minutes at an air temperature up to 60°C without loss of active oxygen. The resulting granules had similar physical characteristics to those of the original co-granules and were of the following chemical composition

Example 3

Sodium carbonate (550 g) (light ash available from Brunner Mond) was mixed at low speed in a Kenwood mixer at ambient temperature. 60% w/v hydrogen peroxide (243 mls) and 586 g sodium disilicate solution (SiO₂:Na₂O. ratio 2:1. solids content:53.5% w/w disilicate) were added dropwise, simultaneously but separately, to the sodium carbonate via peristaltic dosing pumps. This technique avoids direct contact between concentrated silicate and peroxide solutions which may tend to cause the silicate to gel.

The volume of hydrogen peroxide to be added was calculated to approach, but not exceed, that required completely to peroxidate the sodium carbonate. The rate of addition was controlled so that the temperature of the mix did not rise more than 5°C above ambient temperature and also so that full addition of the peroxide occurred before the mix began to agglomerate to my significant degree. After agglomeration, mixing was continued for 10 minutes.

The co-granules produced were dried in a fluid bed drier for 10 minutes at an air temperature up to 60°C without loss of active oxygen.

Claims

1. Co-granules comprising an alkali metal silicate, and a hydrogen peroxide addition compound of a builder salt which, when the co-granule is dissolved in water, is capable of providing active oxygen for bleaching and being converted to said builder salt.

2. Co-granules as claimed in claim 1 wherein the hydrogen peroxide addition product is sodium percarbonate.

3. Co-granules as claimed in claim 1 or 2 wherein the hydrogen peroxide addition product thereof is a phosphate peroxyhydrate.

4. Co-granules as claimed in any one of claims 1 to 3 comprising at least one builder salt.

5. Co-granules as claimed in claim 4 wherein said at least one builder salt is or includes the precursor salt of the hydrogen peroxide addition product.

6. Co-granules as claimed in any one of claims 1 to 5 wherein the alkali metal silicate is present in an amount of 15-35% by weight.

7. Co-granules as claimed in claim 6 wherein the alkali metal silicate is present in an amount of 20-35% by weight.

8. Co-granules as claimed in any one of claims 1 to 7 containing a total of 30-75% by weight of at least one hydrogen peroxide addition compound of a builder salt, optionally with the precursor builder salt and with optional further builder salts.

9. Co-granules as claimed in claim 8 containing a total of 30-65% by weight alkali metal, alkali metal percarbonate, optional alkali metal carbonate, and optional further builder salts.

10. Co-granules as claimed in any one of claims 1 to 9 containing 10 to 30% water.

11. Co-granules as claimed in claim 10 containing 13-28% water.

12. Co-granules as claimed in any one of claims 1 to 11 capable of providing 0.1-10%) of active oxygen.

13. Co-granules as claimed in claim 12 capable of providing 0.5-6% active oxygen.

14. Co-granules as claimed in any one of claims 1 to 13 wherein the alkali metal silicate is sodium silicate.

15. Co-granules as claimed in any one of claims 1 to 13 having a mean particle size of0.2 to 2.5 mm.

16. Co-granules as claimed in any one of claims 1 to 14 having a pouring density of 0.6 to 1.3 g/cm³.

17. Co-granules comprising an alkali metal silicate, a builder salt capable of being converted to a hydrogen peroxide addition compound, and said hydrogen peroxide addition compound formed in situ from the builder salt.

18. A method of producing co-granules as claimed in claim 17. the method comprising treating co-granules comprised of an alkali metal silicate and the builder salt with hydrogen peroxide to convert at least a proportion of the builder salt to the corresponding hydrogen peroxide addition compound.

19. A method as claimed in claim 18 wherein the builder salt comprises sodium carbonate.

20. A method as claimed in claim 19 wherein the co-granule to be treated with hydrogen peroxide comprises 24-35% alkali metal silicate, 40-69% sodium carbonate and optional other builder salts, and 5-28% water.

21. A method as claimed in claim 18 or 19 wherein the builder salt comprises a phosphate.

22. A method of producing co-granules as claimed in claim 17 comprising treating an admixture of builder salt capable of forming a hydrogen peroxide addition compound and an alkali metal silicate solution with hydrogen peroxide and effecting agglomeration of the admixture to produce co-granules.

23. Co-granules as claimed in claim 1 comprising a hydrogen peroxide addition compound compacted with an alkali metal silicate powder.

24. Co-granules as claimed in claim 23 wherein the hydrogen peroxide addition compound is a percarbonate.

25. Co-granules as claimed in claim 24 wherein the percarbonate is an alkali metal percarbonate.

26. Co-granules as claimed in claim 25 wherein the alkali metal percarbonate is sodium percarbonate.

27. Co-granules as claimed in claim 23 wherein said addition compound is a hydrogen peroxide addition compound of a phosphate.

28. Co-granules as claimed in any one of claims 23 to 27 containing 0.1 to 40% alkali metal silicate.

29. Co-granules as claimed in any one of claims 23 to 28 containing 30 to 95% of the addition compound.

30. Co-granules as claimed in any one of claims 24 to 29 containing a total of up to 20% of the precursor builder salt and/or another builder salt.

31. Co-granules as claimed in any one of claims 23 to 30 containing up to 5% compaction agents.

32. Co-granules as claimed in any one of claims 23 to 31 wherein the alkali metal silicate is provided in the form of a disilicate powder.

33. Co-granules as claimed in claim 32 wherein the disilicate is sodium disilicate.

34. Co-granules as claimed in any one of claims 23 to 33 having a particle size of 0.2 to 2.5 mm.

35. Co-granules as claimed in any one of claims 23 to 34 having a pouring density of 0.6 to 1.3 g/cm³.

36. A method of producing a co-granule as defined in claim 23 comprising dry mixing a hydrogen peroxide addition compound with an alkali metal silicate powder and compacting the product to a granular form.

37. The use of co-granules as claimed in any one of claims 1 to 17 or 23 to 35 as a builder/bleach product.

38. A detergent formulation comprising at least one surface active agent and co-granules as claimed in any one of claims 1 to 17 or 23 to 35.

39. A formulation as claimed in claim 38 which incorporates a bleach initiator.