GB2274105A

GB2274105A - Bleaching process.

Info

Publication number: GB2274105A
Application number: GB9300867A
Authority: GB
Inventors: Vinodkumar Ramniranjan Dhanuka; Niraj Dhansukhlal Mistry
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1992-11-27
Filing date: 1993-01-18
Publication date: 1994-07-13
Also published as: IN176964B; GB9300867D0

Abstract

A process for bleaching an organic compound comprises treating the organic compound with a bleaching agent in the presence of a complexing agent. A detergent composition containing a bleached organic compound so obtained is also disclosed.

Description

AN IMPROVED flLHACNZ PROVES8 The present invention relates to an improved process for the bleaching of organic compounds such as sulphonic acids, fatty acids, oils and mixtures thereof in the production of detergents. More specifically the invention relates to the use of both a bleaching agent and a complexing agent to maximize the whiteness and storage life of a detergent prepared using such organic compounds.

The whiteness of a detergent formulation prepared using bleached organic compounds is important from the point of view of consumer perception as well as cleaning performance. Processes for improving the colour of such compounds are known, h2O2 bleaching in the presence of sulphuric acid is one example.

The whiteness of a detergent is largely dependent on the colour of the starting compound, e.g. sulphonic acid which is a precursor for the active component. Additives such as whiteners have been used to improve the whiteness but this has not resulted in a major improvement in the whiteness of detergents.

The present inventors initially suggested bleaching of the compounds to improve the colour of the starting compound, e.g., by treating sulphonic acid with hydrogen peroxide.

However, this did not give the desired results. In fact deterioration of the colour resulted. Thereafter sulphonic acid was added together with the bleaching agent but there was not improvement in the colour.

Surprisingly, after further investigations, the inventors discovered that the colour of the compounds and consequently that of the final product can be significantly improved by incorporating certain complexing agents before, during or after addition of a bleaching agent to the compounds. It has also been found that the whiteness of the compounds as well as the product containing the compounds is stable on storage.

Thus, in broad terms the present invention relates to a process for bleaching an organic compound comprising treating the organic compound with a bleaching agent and a complexing agent.

The organic compound can be treated with the complexing agent before, during, or after the organic compound has been treated with the bleaching agent. Preferably the organic compound is treated with the complexing agent prior to treatment with the bleaching agent.

Preferably the complexing agent is used in an amount that is at least sufficient so that the whiteness of the treated organic compound is superior to that that would be achieved if the organic compound were treated with the bleaching agent alone.

The term "organic compound" is intended to refer to organic compounds such as sulphonic acids, fatty acids, oils and the oils and the like including mixtures thereof. Preferred "organic compounds include linear alkyl benzene sulphonate (LAS), fatty acid ester sulphonate (FAES), fatty acids ex vegetable origin, fatty acids, alpho-olefin sulphonate sodium salt, secondary alkane sulphonate sodium salt, lauryl ester sulphate sodium salt, and the like.

However, LAS, DAES and rice bran oil are particularly preferred.

The term "bleaching agent" is intended to refer to oxygen based bleaching agents such as peroxides, perborates, percarbonates, persulphates and organic peracids and the like including mixtures thereof. Preferred bleaching agents include hydrogen peroxide, Na peroxides, Na perborates, sodium percarbonate, K monopersulphate, Oxone and phthaloylamide percaproic acid. However, hydrogen peroxide is particularly preferred for the purpose of the present invention.

The term Ucomplexing agents for the purpose of the process of the present invention is intended to include compounds that form complexes with polyvalent ions. Such compounds include those chosen form the following class of compounds and any mixtures thereof: - Hydroxyphosphonates e.g EHDP - Aininopolycarboxylate, e.g. EDTA, NTA, HEDTA etc.

- Hydroxycarboxylic acids, e.g. citric acid, tartaric acid, gluconic acid, salicylic acid - Polycarboxylic acids, e.g. oxalic acid - Phosphonic acid and other phosphates, e.g. pyro and tripoly - DEG (dihydroxyethyl glycine) - Pyridine carboxylic acid - Pyridine dicarboxylic acid.

For the purpose of the invention, the preferred complexing agents are selected from EHDP and EDTA.

It is thought that the complexing agent binds free iron which, if not removed, can cause detergent formulations to be decolorised.

The amount of the complexing agent will depend upon the quality (colour) of the organic compound treated but generally the amount will vary between 0.0018 to 10t by wt. of the organic compound, preferably from 0.01-3% by wt. and most preferably from 0.1% to 1.0% by wt.

When H202 is selected as the bleaching agent, it is used in amounts of 0.18-10% and preferably O.3%-3% (calculated at 100% H202 basis) The step of bleaching is effected at a temperature of up to 600C while it is preferred to effect bleaching in the range of from 250C-450C. The bleaching time will generally be at least 5 minutes while a preferred time is between 10 min. to 24 hours and most preferably between 30 mins to 3 hours. The bleaching time is affected when iron impurities are present hence the need to remove same by the use of the complexing agent.

The compounds thus obtained are significantly whiter in comparison to their original colour. Apart from the consumer appeal due to improved whiteness of the product, it has a further advantage in that the fabric treated with the product does not lose its whiteness and the HUE of the colour of the fabric is not altered even after prolonged washing.

The invention will now be described with reference to the following examples. These examples are intended to illustrate the process of the present invention and not limit the scope of the invention as claimed.

Example I Bleaching of Linear Alkyl BenzeneSulhonate (LAS) with H,Q and colour measurement Bleaching of LAS was carried out using 3% HiOa (as 30% solution) and the colour of bleached LAS was monitored by measuring transmittance of a 508 solution of LAS in methanol at 420 nm. The stability of bleached LAS was examined by monitoring the transmittance over a period of 1 week.

The results reported in Table 1 show that the bleaching efficiency improves significantly when EHDP was added to LAS. In fact, when no EHDP was added, the colour of the LAS deteriorated after bleaching.

The product made using the various LAS was examined by monitoring the whiteness index and R460 of a composition comprising 28 & detergent active, 25% sodium tripolyphosphate and 20% sodium carbonate in a transparent sachet. The results (Table 2) show that the product colour improves significantly when bleached LAS is used.

When LAS bleached without EHDP was used the colour of the product deteriorated distinctly showing reddish brown tint. The product made using bleached LAS (with EHDP) showed good stability on storage.

Table 1 Effect of various parameters on bleaching efficiency S.No. Sample iZansmi;tance at 420 no LAS A1 1. LAS as such 33 2. LAS bleached without EHDP 16 3. LAS bleached with EHDP 51 Table 2 Colour measurement of product LAS Used R4601 Whiteness Index LAS as such 65.24 45.6 LAS bleached with EHDP 79.13 76.2 LAS bleached without EHDP 53.88 33.9 Measured in Elrepho reflectance spectrophotometer.

2 Measured in a colour scan reflectance spectrophotometer.

Further modifications will be apparent to one skilled in the art and so those are intended to be incorporated within the scope of the invention.

Claims

1. A process for bleaching an organic compound comprising treating the organic compound with a bleaching agent and a complexing agent.

2. A process according to claim 1 wherein the organic compound is treated with the complexing agent before, during, or after the organic compound has been treated with the bleaching agent.

3. A process according to claim 1 or 2 wherein the organic compound is treated with the complexing agent before the organic compound has been treated with the bleaching agent.

4. A process according to any preceding claim wherein the amount of complexing agent used in that which is at least sufficient for the whiteness of the treated organic compound to be superior to that that would be achieved if the organic compound has been treated with the bleaching agent alone.

5. A process according to any preceding claim wherein the organic compound is selected from sulphonic acids and fatty acids, their respective salts, oils and mixtures thereof.

6. A process according to claim 5 wherein the organic compound is a linear alkyl benzene sulphonate (LAS), fatty acid ester sulphonate (FAES), fatty acid ex vegetable origin, fatty acid, alpho-olefin sulphonate sodium salt, secondary alkane sulphonate sodium salt, lauryl ester sulphate sodium salt, or a mixture thereof.

7. A process according to claim 6 wherein the organic compound is a linear benzene sulphonate, a fatty acid ester sulphonate or rice bran oil.

8. A process according to any preceding claim wherein the bleaching agent is oxygen based.

9. A process according to claim 8 wherein the bleaching agent is a peroxide, perborate, percarbonate, persulphate or an organic peracid, or n mixture thereof.

10. A process according to claim 9 wherein the bleaching agent is hydrogen peroxide, sodium peroxide, sodium perborate, sodium percarbonate, potassium monopersulphate, oxone, phthaloylamide percaproic acid or a mixture thereof.

11. A process according to claim 10 wherein the bleaching agent is hydrogen peroxide.

12. A process according to any preceding claim wherein the complexing agent is a compound that forms complexes with polyvalent ions.

13. A process according to claim 12 wherein the complexing agent is selected from hydroxyphosphonates, aminopolycarboxylates, hydroxycarboxylic acids, polycarboxylic acids, phosphonic acid and other phosphates, dihydroxyethyl glycine, pyridine carboxylic acid and pyridine dicarboxylic acid.

14. A process according to claim 13 wherein the complexing agent is EHDP or EDTA.

15. A process according to claim 11 wherein the bleaching agent is used in an amount of 0.1-10% calculated at 100% H202 basis.

16. A process according to claim 15 wherein the bleaching agent is used in an amount of 0.3-3% calculated at 100% H2Oa basis.

17. A process according to wherein the complexing agent is used in an amount of 0.001-10% by weight of the organic compound.

18. A process according to claim 17 wherein 0.01-3% by weight of the organic compound is used.

19. A process according to claim 18 wherein 0.1-1.0% by weight of the organic compound is used.

20. A process according to any preceding claim wherein the organic compound is bleached at a temperature of up to 600C.

21. A process according to claim 20 wherein the organic compound is bleached at a temperature in the range of 25-450C.

22. A process according to any preceding claim wherein the bleaching time is at least 5 minutes.

23. A process according to claim 22 wherein the bleaching time is between 10 minutes and 24 hours.

24. A process according to claim 23 wherein the bleaching time is between 30 minutes and 3 hours.

25. A process for bleaching an organic compound comprising treating the organic compound with a bleaching agent in the presence of a complexing agent substantially as herein defined with reference to the examples.

26. A bleached organic compound when prepared by the process of any preceding claim.

27. A detergent formulation containing a bleached organic compound prepared by the process of any one of claims 1 to 25.