Bleach products

Abstract: A bleach product for use in the washing machine as an adjunct to a normal detergent powder or liquid comprises a closed bag containing a particulate bleach composition, the bag being formed of sheet material having pores large enough to render it water-permeable but small enough to confine the bleach composition within the bag. The bleach composition comprises sodium perborate with an activator such as tetraacetyl ethylenebiamine or sodium octanoyloxy­ benzene sulphonate. Preferably at least 25 mole per cent of the perborate is in monohydrate form: this gives reduced malodour development on short storage.

Description: The present invention relates to an improved wash adjunct product in the form of a small closed bag, containing a powdered bleaching. composition. The bag can be used to improve the bleaching of fabrics washed in a domestic or industrial washing machine. The product of the invention contains a bleaching powder including sodium perborate in combination with a so-called bleach activator, that is to say, an organic compound which can react at a relatively low temperature, for example 20 to 60°C, with the perborate to form an organic peracid. GB-A-1 459 973 (Procter & Gamble) discloses an article in bag form for bleaching fabrics in the tumble-dryer. The article consists of a powdered bleaching composition within a closed flexible receptacle of material, such as foam, polyester or cotton cloth, having relatively large open pores. The bleaching composition may contain alkali metal perborates of any degree of hydration, used in combination with an activator, for example, tetraacetyl ethylene diamine (TAED) or 1,3,4,6-tetraacetyl glycouranil (TAGU). The pore size of the receptacle is larger than the particle size of the bleaching composition, so that during tumble-drying the powdered bleaching composition will be delivered through the pores of the receptacle onto the fabric load. It is thus difficult to prevent premature escape (dusting-out) of the bleaching composition during transport and storage, and expensive profile packaging may be required. EP 18 678A (Unilever) describes a wash adjunct bleach product in bag form. A powdered bleach composition comprising a percompound, for example, an alkali metal perborate, and a bleach activator such as TAED, is contained within a closed water-insoluble but water-permeable bag of fibrous material provided with a protective water-impermeable coating which is removable in water at a temperature of 30 to 75°C, preferably 35 to 65°C. This bag is thus intended to release its contents only when the wash temperature exceeds this value, in order that catalase present on the soiled wash load should be destroyed, by heat, before the bleach composition enters the wash liquor; this is stated to be necessary in order to prevent deactivation of the perborate by the catalase. The bag material used should have a pore size such that, before the coating is applied, there is no appreciable dusting out of the bleach composition in the dry state; the coating, however, completely closes the pores of the bag material. The particular hydrate of sodium perborate used in the Examples of EP 18 678A (Unilever) is not stated, except in Examples I and II wherein the tetrahydrate was used. Detergent compositions containing sodium perborate monohydrate have been disclosed in GB-A-1 573 406 (Unilever), EP 98 108A (Unilever) and GB-A-1 321 627 (Henkel). GB-A-1 573 406 discloses detergent compositions containing a bleach system consisting of sodium perborate monohydrate and the activator tetraacetyl ethylenediamine (TAED) in granular form, together with detergent-active compounds, detergency builders, enzymes, fluorescers and other usual constituents. As compared with similar compositions containing sodium perborate tetrahydrate, these compositions exhibit superior storage stability over a four-week period, as illustrated by reduced TAED loss, reduced perborate loss, reduced fluorescer loss and improved enzyme stability. The present invention provides a wash adjunct product comprising a particulate bleach composition consisting essentially of sodium perborate and an activator therefor, which activator on reaction with the perborate generates a percarboxylic acid of which the corresponding carboxulic acid is malodorous, the composition being contained within a closed bag of sheet material which is porous to air and has pores large enough to render it water-permeable but small enough to confine the particulate bleach composition within the bag, wherein at least 25 mole per cent of the sodium perborate in the particulate bleach composition is in monohydrate form. In the bag of the invention, the particle size of the bleach composition and the pore size of the bag are matched so that the bleach composition cannot escape from the bag but yet can be efficiently leached out, in use, by the wash liquor. The average particle size of the composition is preferably at least 30 µm, more preferably at least 50 µm, and advantageously does not exceed 2000 µm. A range of 100 to 900 µm is especially preferred. The bags used to form the products of the invention are preferably of the type which remains closed during the washing and bleaching process in the washing machine. They are preferably formed from water-insoluble sheet material which may for example, be in the form of paper or of woven, nonwoven or knitted fabric which should, of course have sufficient wet strength to survive the washing process without disintegrating. The pore size and porosity of the bag material are very important. The pores must be large enough to allow rapid entry of water into the bag to leach out the contents, but also sufficiently small that there is no appreciable leakage of the bleach composition out of the bag in the dry state. The porosity to air of the bag material is preferably at least 5000 litres/m 2 /s, more preferably from 7000 to 10000 litres/m 2 /s. Also of major importance is the porosity of the bag material to the powder contained in the bag. As stated previously, the bag porosity should be matched to the powder particle size such that the powder is substantially wholly confined within the bag. A simple method was used to estimate the porosity to powder of various bag materials. This involved determining the percentage loss of a standard particulate material after shaking for 5 minutes or 30 minutes. The standard particulate material chosen consisted of spherical glass ballotini (ex Potters) of sieve fraction 90-106 µm, chosen to be reasonably representative of detergent powder fines (particles smaller than 150 µm) yet to show no attrition under the conditions of the test. The bag materials under test were formed into sachets of internal dimensions 4 cm x 4 cm, filled with 5 g of the ballotini, and closed by heat-sealing or with double-sided tape. Four sachets at a time were placed on a 20 cm diameter sieve grid of a large mesh size (2.8 mm) that would not impede the passage of any ballotini released during the test, the sieve grid being fitted over a base pan. The sieve was then covered and placed on a Russell Laboratory Finex (Registered Trade Mark) Model 8552 sieving machine, and an intermediate continuous shaking setting (5 on the scale) was selected. The sachet weights were monitored over a total period of 30 minutes. Some results of this test are shown in Table 1, which (*) denotes a Registered Trade Mark, duplicate results being shown where these were carried out. Two materials of well-defined pore size (nylon meshes having 118 µm square and 100 µm square apertures) were included in an attempt to relate porosity to pore size: these are samples (n) and (p). For the purpose of the present invention, bag materials can be classified on the basis of this test as follows: % weight loss after 5 min 30 min Highly acceptable <1 <5 Acceptable from 1 to 10 from 5 to 20 Unacceptable >10 >20 Thus of the materials listed in Table 1, samples (a), (b), (I) and (m) are highly acceptable; samples (c), (g) and (i) are acceptable; and samples (d), (e), (f), (h), (j) and (k) are unacceptable. It must also be remembered that the porosity should be sufficient to allow adequate water permeability, otherwise the bag will not deliver its contents sufficiently quickly. Thus materials of very low porosity, such as samples (I) and (m), may in practice be less preferred than ones of slightly higher porosity, such as samples (a), (b) or (i). As may be inferred from these various considerations, suitable bag materials include water-permeable paper or nonwoven fabrics of high wet strength. The fibres used for the sheet materials may be of natural or synthetic origin and may be used alone or in admixture, for example, polyamide, polyester, polyacrylic, cellulose acetate, polyethylene, polyvinyl chloride, polypropylene or cellulosic fibres. It is preferred to include at least a proportion of thermoplastic fibres, in order to increase the resistance to chemical attack by the bleaching agent, and also to enable the bags to be closed by heat-sealing. The bag materials may be treated with a binding agent provided that this does not close its pore structure to an extent that it is rendered impermeable to water. In this case, the discussion of porosity above will relate to the material plus the binding agent. Especially preferred bag materials are single-layer or multilayer nonwoven fabrics and wet-strength papers having base weights in the range of from 15 to 250 g/m 2 , especially from 20 to 150 g/m 2 . The bag materials may advantageously consist of a mixture of polyester and cellulosic fibres. The bags are conveniently square or rectangular in shape, although any shape may be used. The size of the bag will of course depend on the dosage of bleach composition it contains. A rectangular bag intended for a single domestic washload of typical size, and containing perhaps from 10 to 40 g of bleach composition, may conveniently have dimensions of 60-150 mm x 60-150 mm, especially 80-120 mm x 80-120 mm. According to the invention, at least 25 mole per cent of the sodium perborate contained in the bag of the present invention is in monohydrate form. Advantageously substantially all of the sodium perborate may be in monohydrate form. Sodium perborate in monohydrate form has the additional advantages of greater water-solubility, especially at low temperatures, and of lower molecular weight which allows a smaller dose to be used to deliver the same level of available oxygen, so that a smaller and lighter bag product can be produced. As previously explained, an unexpected benefit was found to accrue from the use of sodium perborate at least partially in monohydrate form, when used in conjunction with an activator which on reaction with the perborate generates a percarboxylic acid of which the corresponding carboxylic acid is malodorous. This benefit, of reduced development of malodour on short storage, was first observed with activators that generate peracetic acid; with bags containing tetraacetyl ethylenediamine (TAED) and sodium perborate tetrahydrate, for example, it was found that because the bag contents were open to the atmosphere through the porous bag walls an unpleasant odour could develop even after periods of storage, for example, one week, that were so short that no measurable decomposition of either TAED or perborate could be detected. This problem does not occur when fully formulated detergent compositions containing TAED and sodium perborate tetrahydrate are packed in sachets, but is apparently peculiar to sachets intended for use as wash adjunct products and containing only minor proportions of ingredients other than the bleaching agents. Surprisingly, it was found that this problem could be solved by replacing sodium perborate tetrahydrate, at least in part, by the monohydrate. Further experiments indicated that the benefit of reduced malodour on short storage could be observed with other bleach activators whose ultimate decomposition products were malodorous carboxylic acids. The activator used in the bag of the present invention is a material that reacts with the perborate, in the environment of the wash liquor, to yield a percarboxylic acid. This is the active bleaching species and is decomposed by the bleaching reaction to give the corresponding carboxylic acid which is a malodorous material. In a preferred embodiment of the invention the peracid generated is peracetic acid, the decomposition product of which (acetic acid) has an unpleasant vinegary smell. Examples of bleach activators that react with sodium perborate to yield peracetic acid include the following: (a) sugar esters, for example, glucose pentaacetate and xylose tetraacetate; (b) esters of phenols, for example, sodium acetoxybenzene sulphonate; (c) N-acylated amines and amides, for example, tetraacetyl ethylenediamine, tetraacetyl methylenediamine and tetraacetyl glycouranil; (d) acetyl oximes, for example, dimethylglyoxime acetate. An example of a bleach activator that does not generate peracetic acid yet can still give malodour problems on short storage when used with sodium perborate tetrahydrate in a bag product is sodium octanoyloxybenzene sulphonate. The preferred bleach activator for use in the bag of the present invention is tetraacetyl ethylenediamine (TAED). Preferably the weight ratio of sodium perborate to activator is within the range of from 35:1 to 1:5, more preferably from 20:1 to 1:5 and advantageously within the range of from 3:1 to 0.8:1. In detergent powders it is normal to include a large excess of per-compound to allow for mechanical loss and deactivation by catalase, but that has been found not to be essential with the bag of the present invention: the elimination of mechanical losses by the use of a bag product is to be expected, but the lack of deactivation by catalase is more surprising. Use of an excess of activator may be useful if the bag is to supplement a detergent powder containing perborate but no activator. The activator, for example, TAED, may conveniently be used in the form of granules obtaining by granulating a suitable inorganic or organic carrier material, for example, inorganic phosphate, nonionic surfactant, fatty acid, hardened tallow, paraffin wax or sodium carboxymethyl cellulose, with activator particles. The particle size of the composite granules may conveniently lie within the 200 to 2000 µm range, the particle size of the activator within the granules being advantageously less than 150 µm and preferably less than 100 µm. The bag of the invention conveniently contains an amount of sodium perborate suitable for an averagesized single wash operation, together with an appropriate amount of activator. Alternatively, smaller bags can each contain an appropriate amount for 1 kilogram of soiled fabrics, and can be used in multiples as required. In a bag intended for a single domestic washload, the amount of perborate is suitably within the range of from 0.5 to 30 g, preferably from 1 to 15 g. For use in a commercial or industrial laundry, larger doses will in general be appropriate. The preferred quantities of activator can readily be inferred from the preferred perborate to activator ratios given above. If desired, there may be included in the bag of the invention a stabiliser for the bleach system, for example, ethylene diamine tetramethylene phosphonate or diethylene triamine pentamethylene phosphonate. The stabiliser can be used in acid or salt form, preferably in calcium, magnesium, zinc or aluminium complex form, as described in GB-A-2 048 930 (Unilever). The stabiliser may advantageously be present in an amount of from 0.5 to 5% by weight, more preferably from 1.5 to 2.5% by weight, based on the total weight of sodium perborate, activator and stabiliser. Use of a stabiliser is not, however, essential. The bag of the present invention does not contain all the ingredients of a fully formulated detergent composition. It is intended not as a replacement for a conventional detergent composition but for use as a bleach adjunct together with a conventional bleaching or non-bleaching detergent composition. The essential components of the bag contents are sodium perborate and an activator: this combination of ingredients represents a complete bleaching system, effective at low or high wash temperatures, and the bag can then be used as an adjunct or supplement when washing with powders containing no bleach system or containing one ineffective at low temperatures, or when extra bleach efficiency is required, for example, when dealing with an especially heavily stained fabric load. The bag may, however, contain minor amounts of perfume, bleach stabiliser or other suitable additives. If desired, too, minor amounts of other adjunct materials, or particular ingredients used in detergent compositions, may be included to give specific benefits. Furthermore, as previously indicated, the bleach activator may of course be in the form of granules which contain quite substantial amounts of carrier material or binding agent. The invention will now be illustrated by the following non-limiting Examples. EXAMPLE 1 A bag product in accordance with the invention was prepared from a porous nonwoven fabric, of average pore size 70µm, consisting of 40% polyester fibres and 60% viscose fibres. The fabric was coated on one side (the inside of the bag) with a polyamide heat-seal finish. The bag was rectangular, had dimensions of 100 x 110 mm, and was closed by heat-sealing. Its contents were as follows: Sodium perborate monohydrate (ex Degussa, particle size substantially 100-700 µm) 10.66 g TAED granules (300-2000 µm) (65.3% TAED, 32% phosphates, 2.7% water) 15.32 g EXAMPLE 2 A bag product of the invention, similar to that of Example 1 but also containing a bleach stabiliser, was prepared from a multilayer nonwoven fabric having a base weight of about 100 g/m 2 and consisting of 40% by weight of acrylic fibres and 60% by weight of mixed polyester/cellulosic fibres (80% polyester, 20% cellulose). The bag was rectangular, had dimensions of approximately 100 x 80 mm, and was closed by heat-sealing. The bag contained the following ingredients: Sodium perborate monohydrate (particle size 50-600 µm ex Air Liquide) 13 g TAED granules (300-2000 µm) (65% TAED, 35% inorganic phosphate) 12 g Ethylene diamine tetramethylene phosphonate 0.5 g EXAMPLE 3 The bleach performance of the bag product of Example 2 was compared with that of a coated bag in accordance with the aforementioned EP 18 678A (Unilever). The comparison bag was coated with a paraffin wax having a melting point of 40-42 °C, but was otherwise identical to the bag described above. Comparative washing tests were carried out in the presence of catalase using fabric loads consisting of test cloths stained with tea or with wine. Bleaching efficiency was compared by means of reflectance measurements. Each wash was carried out using a Vedette (Registered trade Mark) 494 washing machine set to the 45°C wash cycle. In each test a detergent powder, in the recommended dosage of 197 g, was added to the washing machine in the normal manner; the powder contained the usual detergent ingredients, fillers, enzymes, but no bleach ingredients. The bleach bags were placed with the fabric loads at the beginning of the wash cycle. The results were as follows: Reflectance Coated bag Uncoated bag Tea-stained cloth 43 51 Wine-stained cloth 61 61 It will be seen that although the results on the wine-stained cloth were identical, the uncoated bag gave a much better result (8 reflectance units) on the tea-stained cloth. EXAMPLE 4 The procedure of Example 3 was repeated using the higher wash temperature of 60°C. This time the comparison bag was coated with a paraffin wax having a melting point of 55°C. The results were as follows: Reflectance Coated bag Uncoated bag Tea-stained cloth 60.5 63 Wine-stained cloth 70 72 It will be seen that at this temperature the uncoated bag gave better results on both types of stain. EXAMPLE 5 In this Example the low-temperature bleaching performance of a bag according to the invention, used in conjunction with a base powder containing no bleach ingredients, was compared with that of a base powder additionally containing the same levels of perborate and TAED. The tests were carried out in the Vedette 494 washing machine using the 30°C wash cycle, in the presence of catalase, using tea-stained or wine-stained test cloths. In each test 203.5 g of base powder (with filler) was used. In the comparative test the powder also contained 18 g of sodium perborate monohydrate and 12 g of TAED granules (65% TAED, 35% inorganic phosphate) and 0.5 g of the stabiliser used in Example 2. In the test according to the invention the powder contained none of these ingredients, and a bag similar to that of Example 2, but containing 18 g of perborate monohydrate instead of 13 g, was placed with the fabrics before the start of the wash cycle. The results were as follows: Without bag (bleach in powder) Bleach in bag Tea-stained cloth 42.7 50.6 Wine-stained cloth 59.2 63.9 On both types of stain the bleaching was substantially more efficient at this temperature when the bleach ingredients were contained in a bag according to the invention. EXAMPLE 6 A bag similar to that of Example 5 was prepared containing sodium perborate tetrahydrate instead of sodium perborate monohydrate. To give the same available oxygen level a dosage of 27 g, as compared with 18 g of monohydrate, was required. The bleaching performance of this bag was compared with that of the bag of Example 5 using the procedure of that Example. The results were as follows: Tetrahydrate Monohydrate Tea-stained cloth 49.6 50.6 Wine-stained cloth 62.8 63.9 The tetrahydrate gave marginally worse results than the monohydrate but comparison with the results of Example 5 shows that both bags were better than the bleach-containing powder. EXAMPLE 7 Using a Brandt (Registered Trade Mark) washing machine set to a 60°C cycle, the bag of Example 2, used with a bleach-free base powder, was compared with a typical commercial product containing perborate tetrahydrate (28 g), TAED granules (4.7 g) and the stabiliser used in Example 2 (0.5 g). 200.8 g of base powder (non-bleach) was used in each case. The comparison was carried out in the presence of catalase. The results were as follows: Tetrahydrate in powder Monohydrate in bag Tea-stained cloth 49.7 54.0 Wine-stained cloth 63.2 67.5 EXAMPLE 8 A first set of bags as described in Example 1 was prepared. A second set of bags was also prepared in which each contained 16.42 g of sodium perborate tetrahydrate (ex Degussa, particle size substantially 100-700 µm) instead of the monohydrate, but were otherwise identical: the larger amount of tetrahydrate was required to give the same level of available oxygen. The development of malodour by the two types of bag after 1, 2 and 4 weeks' storage under three different sets of conditions was compared by means of a "triad test" involving the sensory perception of smell by the members of a panel. The samples (bags) were grouped in threes or "triads" in which two were the same and the other different, i.e. either one contained monohydrate and two contained tetrahydrate, or vice versa. Each triad was presented to a panellist who was required to attempt to indentify the "odd" sample that was different from the other two. The panellist was next asked: (i) whether he preferred the smell of the "odd" sample of that of the other two; (ii) whether he found the smell of the "odd" sample stronger or weaker than that of the other two, and (iii) whether he found the smell of the "odd" sample pleasant, unpleasant or neutral. Only the answers of those panellists who had correctly identified the "odd" sample were analysed further. The order of presentation of the samples comprising the triads to the panellists was randomised, each triad being assessed by ten panellists. The triad test is described in the Manual on Sensory Testing Methods, ASTM STP 434. Using the "chisquare" statistical test it can be shown that when ten panellists are used, seven out of ten correct indentifications are required for significance at the 95% confidence level. Each bag was stored in a closed 900 g glass bottle at one of three different temperatures. The results are set out in the following Tables, in which "X" denotes the first set of bags and "Y" the second set. Table 2 shows the number of correct identifications out of 10 for each triad after 1-week, 2-week and 4-week storage periods. Triad Temperature (°C) Number of correct identifications out of 10 after 1 week 2 weeks 4 weeks A (XXY) 37 10 10 10 B (XYY) 37 7 10 (3) C (XXY) 28 7 10 9 D (XYY) 28 9 7 9 E (XXY) 20 8 10 9 F (XYY) 20 7 8 10 The bracketed result was too low for significance. It will be seen that the panellists were readily able to distinguish the two types of bag on a smell basis, ever after a week. Further analysis of the significant results is given in Tables 3 to 8, which show the responses to the three questions above by those panellists who had correctly identified the "odd" sample. It will be seen that an overwhelming majority of panellists considered the Y bags to be more strongly smelling than the X bags, after all three storage periods. The high percentage of panellists who found the smell of the Y bags unpleasant but the smell of the X bags neutral will also be noted. Table 9 is a summary of these results over all temperatures and storage times. Triad A (37°C, XXY) 1 week 2 weeks 4 weeks Number of correct identifications out of 10 10 10 10 % of these who preferred "odd" one - - - % of these who preferred other two 100 100 100 % of these who found "odd" one stronger 100 100 100 % of these who found "odd" one weaker - - - % of these who found "odd" one pleasant - - - % of these who found "odd" one unpleasant 100 100 70 % of these who found "odd" one neutral - - 30 Triad B (37°C, XYY) 1 week 2 weeks Number of correct identifications out of 10 7 10 % of these who preferred "odd" one 71 100 % of these who preferred other two 29 - % of these who found "odd" one stronger - - % of these who found "odd" one weaker 100 100 % of these who found "odd" one pleasant - - % of these who found "odd" one unpleasant 29 20 % of these who found "odd" one neutral 71 80 Triad C (28°C, XXY) 1 week 2 weeks 4 weeks Number of correct identifications out of 10 7 10 9 % of these who preferred "odd" one - - - % of these who preferred other two 100 100 100 % of these who found "odd" one stronger 71 100 100 % of these who found "odd" one weaker 29 - - % of these who found "odd" one pleasant - - - % of these who found "odd" one unpleasant 86 100 70 % of these who found "odd" one neutral 17 - - Triad D (28°C, XYY) 1 week 2 weeks 4 weeks Number of correct identifications out of 10 9 7 9 % of these who preferred "odd" one 100 86 89 % of these who preferred other two - 14 11 % of these who found "odd" one stronger 11 14 - % of these who found "odd" one weaker 89 86 100 % of these who found "odd" one pleasant 11 - - % of these who found "odd" one unpleasant 11 43 11 % of these who found "odd" one neutral 78 57 89 Triad E (20°C, XXY) 1 week 2 weeks 4 weeks Number of correct identification out of 10 8 10 9 % of these who preferred "odd" one - - 11 % of these who preferred other two 100 100 89 % of these who found "odd" one stronger 100 100 89 % of these who found "odd" one weaker - - 11 % of these who found "odd" one pleasant - - - % of these who found "odd" one unpleasant 100 80 89 % of these who found "odd" one neutral - 20 11 Triad F (20°C, XYY) 1 week 2 weeks 4 weeks Number of correct identification out of 10 7 8 10 % of these who preferred "odd" one 100 100 90 % of these who preferred other two - - 10 % of these who found "odd" one stronger - - - % of these who found "odd" one weaker 100 100 100 % of these who found "odd" one pleasant 14 12 10 % of these who found "odd" one unpleasant 14 12 30 % of these who found "odd" one neutral 72 76 60 Odd sample in triad Y X % who detect "odd" sample 83 out of 90 = 92% 70 out of 90 = 78% % of those who prefer X 82 out of 83 = 99% 65 out of 70 = 93% % of those who find the "odd" sample unpleasant 76 out of 83 = 92% - % of those who find the "odd" sample neutral - 51 out of 70 = 73% % of those who find Y stronger than X 80 out of 83 = 96% - % of those who find X weaker than Y - 68 out of 70 = 97% The contents of the bags were analysed after 1, 2 and 4 weeks for TAED decomposition and perborate decomposition. The results on TAED loss are shown in Table 10. (i) Bags (X) (monohydrate) Temperature (°C) TAED (g) remaining after 1 week 2 weeks 4 weeks 37 10.4 9.6 9.4 28 10.1 9.8 10.3 20 10.8 10.1 10.1 (ii) Bags (Y) (tetrahydrate) Temperature (°C) TAED (g) remaining after 1 week 2 weeks 4 weeks 37 10.3 9.5 10.7 28 9.1 10.0 10.2 20 11.2 10.8 9.9 These results show that there was no significant TAED loss, and no significant difference between the bags containing perborate monohydrate and the bags containing perborate tetrahydrate. The results on perborate loss were as shown in Table 11: for ease of comparison between monohydrate and tetrahydrate these are shown as percentages. (i) Bags (X) (monohydrate) Temperature (°C) % perborate remaining after 1 week 2 weeks 4 weeks 37 98 105 98 28 95 98 100 20 100 98 100 (ii) Bags (Y) (tetrahydrate) Temperature (°C) % perborate remaining after 1 week 2 weeks 4 weeks 37 100 104 96 28 101 100 96 20 96 98 96 Although in general slight losses of perborate occurred, there was no significant difference between the two sets of bags. Thus the reduced malodour development in the bags containing the monohydrate cannot simply be attributed to reduced decomposition of TAED and perborate as described in GB-A-1 573 406 (Unilever). The TAED granules used in Example 1 contained phosphate binders. Rapid screening of bags containing TAED granules containing other binding agents (tallow alcohol ethoxylate, hardened tallow fatty acid, hardened tallow, paraffin wax) indicated a similar difference between perborate monohydrate and tetrahydrate. EXAMPLE 9 In Example 8 bags (X) containing sodium perborate of which 100% was in monohydrate form were compared with bags (Y) containing sodium perborate of which 100% was in tetrahydrate form. In the following experiment triad test methodology was used to compare bags containing various mixtures of monohydrate and tetrahydrate with bags containing only tetrahydrate. The bags used in the test were of the same material and dimensions as that of Example 1, and each contained 15.32 g of the TAED granules used in Example 1. The sodium perborate contents of the bags, chosen to give an identical available oxygen level for every bag, were as shown in Table 12. Bags Monohydrate (g) Tetrahydrate (g) Mole % of monohydrate G 2.67 12.32 25 H 5.33 8.21 50 J 8.00 4.11 75 The results of the triad test after 1 week's storage at 37° C are shown in Table 13. It will be seen that 25 mole per cent of monohydrate was sufficient to give a significant reduction in malodour development after 1 week's storage at 37° C. Triad GGH HHY JJY Number of correct identifications out of 10 8 10 10 % of these who preferred Y 0 10 0 % of these who preferred other two 100 90 100 % of these who found Y stronger 100 100 100 % of these who found Y weaker 0 0 0 % of these who found Y pleasant 0 0 0 % of these who found Y unpleasant 80 90 100 % of these who found Y neutral 20 10 0 COMPARATIVE EXAMPLE The bags tested in Examples 8 and 9 were intended for use as wash adjunct products, and contained only TAED and perborate. The following comparative experiment was carried out in order to determine whether a similar difference between perborate monohydrate and perborate tetrahydrate could be detected in fully formulated detergent powders packed in sachets. A detergent base powder was prepared containing 16.5% active detergent 45.2% builder 38.3% other components A first set of bags (P), of size and material as described in Example 1, each contained 30 g of a powder composed as follows: Base powder 25.3 g Sodium perborate monohydrate 2.4 g TAED granules (as in Example 1) 1.0 g Anhydrous sodium sulphate 1.3 g A second set of bags (Q) each contained 30 g of a powder composed as follows: Base powder 25.3 g Sodium perborate tetrahydrate 3.7 g TAED granules 1.0 g After 1 week's storage, the bags of the two sets were grouped in threes and subjected to the triad test as described in Example 8. The results were as shown in Table 14. Triad Temperature (°C) Number of correct identifications out of 10 after 1 week K (PPQ) 37 4 L (PQQ) 37 4 M (PPQ) 28 3 N (PQQ) 28 1 It will be seen that in all cases the number of correct identifications was below the 7 out of 10 level required for significance. Thus after 1 week's storage there was no significant difference in smell between the two sets of bags; the reduced development of malodour according to the invention is observed only in the adjunct type of product. EXAMPLE 10 A further sensory test was carried out on bags as described in Example 1 to determine the relative humidity conditions under which malodour development was most pronounced. After 1 week's storage at 28°C under various conditions of relative humidity, the bags were assessed by two trained panellists under "double blind" conditions, that is, neither the presenter nor the panellists knew which sample was which. The panellists were asked to say: (i) whether the X or Y bag had the stronger smell, and (ii) whether the smell of the bag having the stronger smell was strong or weak. The replies to question (i) are summarised in Table 15, from which it may be seen that the monohydrate-containing bags X were never found to be stronger-smelling. Relative humidity (%) Stronger smelling bag after storage for 1 week 2 weeks 3 weeks 12 Y Y Y 32 Y Y Y 52 Y Y Y 75 no difference no difference Y 85 no difference no difference Y 96 no difference no difference Y Table 16 shows the answers to question (ii) on the bags Y. Relative humidity (%) Intensity of malodour after storage for 1 week 2 weeks 3 weeks 12 Strong Strong Strong 32 Strong Strong Strong 52 Strong Strong Strong 75 - - Weak 85 - - Weak 96 - - Weak These results show that, surprisingly, the development of malodour is most marked under conditions of low relative humidity. EXAMPLE 11 A further triad test was carried out using bags containing sodium perborate (monohydrate or tetrahydrate) with a different activator, sodium octanoyloxybenzene sulphonate. In each triad the "odd" sample contained the tetrahydrate. The results are shown in Table 17. Number out of 10 detecting "odd" sample correctly 7 % of these preferring mono 100 % of these finding smell of "odd" sample (tetra) unpleasant 86 % of these finding smell of "odd" sample (tetra) stronger than that of mono 100 These results show that the malodour reduction benefit obtained by using sodium perborate monohydrate is not restricted to activators that generate peracetic acid.

Claims: A wash adjunct product comprising a particulate bleach composition consisting essentially of sodium perborate and an activator therefor, which activator on reaction with the perborate generates a percarboxylic acid of which the corresponding carboxylic acid is malodorous, the composition being contained within a closed bag of sheet material which is porous to air and has pores large enough to render it water-permeable but small enough to confine the particulate bleaching composition within the bag, characterised in that at least 25 mole per cent of the sodium perborate in the particulate bleach composition is in monohydrate form. A product as claimed in claim 1 in which substantially all the sodium perborate is in monohydrate form. A product as claimed in claim 1 or claim 2, characterised in that the activator for the perbcrate is a material which on reaction therewith generates peracetic acid. A product as claimed in claim 1 or claim 2, characterised in that the activator for the perborate is tetraacetyl ethylenediamine. A product as claimed in claim 1 or claim 2, characterised in that the activator for the perborate is sodium octanoyloxybenzene sulphonate. A product as claimed in anyone of claims 1 to 5, characterised in that the bleaching composition has an average particle size of at least 30 µm. A product as claimed in claim 6, characterised in that the bleaching composition has an average particle size within the range of from 50 to 2000 µm. A product as claimed in claim 7, characterised in that the bleaching composition has an average particle size within the range of from 100 to 900 µm. A product as claimed in any one of claims 1 to 8, characterised in that the porosity of the bag material is such that the weight percentage loss of 90-106 µm particulate material after 5 minutes shaking is less than 10, and after 30 minutes shaking is less than 20. A product as claimed in claim 9, characterised in that the porosity of the bag material is such that the weight percentage loss of 90-106 µm particulate material after 5 minutes, shaking is less than 1, and after 30 minutes' shaking is less than 5. A product as claimed in any one of claims 1 to 10, characterised in that the porosity of the bag material to air is at least 5000 litres/m 2 /s. A product as claimed in claim 11, characterised in that the porosity of the bag material to air is from 7000 to 10,000 litres/m 2 /s. A product as claimed in any one of claims 1 to 12, characterised in that the bag is formed of a paper or nonwoven fabric having a base weight within the range of from 15 to 250 g/m 2 . A product as claimed in claim 13 characterised in that the bag is formed of a paper or nonwoven fabric having a base weight within the range of from 20 to 150 g/m 2 . A product as claimed in any one of claims 1 to 14, characterised in that the bleaching composition contains sodium perborate and activator in a weight ratio within the range of from 20:1 to 1:5. A product as claimed in claim 15, characterised in that the bleaching composition contains sodium perborate and activator in a weight ratio within the range of from 3:1 to 0.8:1. A product as claimed in any one of claims 1 to 16, characterised in that the bag contains from 0.5 to 30 g of sodium perborate. A bleach product as claimed in claim 17, characterised in that the bag contains from 1 to 15 g of sodium perborate. A product as claimed in any preceding claim, characterised in that the bag contains from 10 to 40 g of total composition.

Inventors: TAI HO TAN, TAI, HO TAN
Applicants: UNILEVER NV, UNILEVER N.V.
Application year: 1985
Main classification: C11D3
IPC codes: C11D17, C11D3, C11D7