GB2320253A

GB2320253A - Detergent composition

Info

Publication number: GB2320253A
Application number: GB9625798A
Authority: GB
Inventors: Vinodkumar Ramniranjan Dhanuka; Fakhruddin Esmail Pacha
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1996-12-12
Filing date: 1996-12-12
Publication date: 1998-06-17
Also published as: GB9625798D0

Abstract

In order to improve the activity of soda ash as a builder in a detergent composition, the release of a sequestering builder such as sodium tripolyphosphate, tetrasodium orthophosphate, trisodium polyphosphate or zeolite is delayed for about 30 seconds. There is provided a detergent composition comprising a water-dispersible precipitating builder component and a water-soluble sequestering builder component, at least part of the precipitating builder component being present in non granular form and substantially all of the water soluble sequestering agent being present in granules coated with a coating material whereby, when the composition is mixed with sufficient water to disperse the composition, less than 1% by weight of the sequestering builder is released into solution within 30 seconds of mixing and the rest of the sequestering builder is released into solution thereafter.

Description

DETERGENT COMPOSITIONS This invention relates to detergent compositions having enhanced detergency particularly under hand washing conditions.

BACKGROUND AND PRIOR ART Detergent manufacturers have long recognised the need to handle water hardness to ensure adequate cleaning by detergent. Detergent builders play a very important role in maintaining the water hardness and ensuring efficient cleaning by detergents. Various types of builders are used for the purpose. These builders can be classified under two general headings: sequestering builders and precipitating builders. A typical precipitating builder is soda ash, but soda ash built detergent powder do not give detergency comparable to that of powders based on sequestering builders such as sodium tripolyphosphate.

Control of Calcium ion concentration in the wash liquor during the washing process affects the detergency properties. It is known that precipitating builders, such as alkali metal carbonates lower the calcium ions in solution through precipitation of calcium carbonates. Precipitation of calcium carbonate may be assisted by the incorporation in a composition of seed crystals of calcium carbonate, such as high surface area calcite. The subsequent growth of these calcium carbonate crystals is strongly influenced by the poisoning effect of various ions including phosphate which may be introduced as a sequestering builder. Attempts have been made to overcome the poisoning effect of phosphates in carbonate built formulations.

GB 1437950 describes detergent compositions containing alkali metal carbonate and 15% of a high surface area calcium carbonate as a precipitating builder. This can lead to increased inorganic deposition on the fabric. Moreover, high surface area calcium carbonate is an expensive material.

US 4040988 (1977) teaches detergent compositions containing two specific types of granules. The first contains sodium carbonate, a precipitating builder, and calcite. The second contains a sequestering builder, such as sodium tripolyphosphate, sodium silicate and detergent active material.

Due to the presence of sodium silicate, the second type of granule dissolves more slowly in the wash liquor than the first. This delays the dissolution of the sequestering builder, and reduces its poisoning effect on the growth of calcium carbonate crystals.

GB 2104912 disclosed that where precipitating builder is used, sequestering builder should be added to the wash liquor after the system has reached a particular state described as a critical state, i.e., when the free calcium ion concentration in the wash liquor is reduced to about 10-5 molar. If a sequestering builder is added prior to the system reaching the critical state this reduction in free calcium ion concentration is not achieved at all or is not achieved within a reasonable time. In GB 2104912 the sequestering builder is added within at least 60 minutes preferably within about 30 minutes from the addition of the alkali metal carbonate. GB 2104912 describes experiments in which the sequestering builder is added at various times between 1 minute and 30 minutes from the addition of alkali metal carbonate liquor. GB 2104912 specifically discloses that where the sequestering builder material is a calcium carbonate crystal growth poison, less that 1 part in 100 of the sequestering builder material should have dissolved in 1 minute. Various methods for the delayed release of the sequestering builder have been outlined in GB 2104912. These include sequential dosing of the second builder, the use of large crystals of the sequestering builder, and coating of the sequestering builder such that the builder is released as the temperature of the wash liquor rises in a machine wash by coating or by encapsulating the sequestering builder with a water dispersible and water insoluble material or with a water soluble material. The examples of coating material include Fatty Acids such as C16 C20 saturated Fatty acids, alkanolamides Fatty Acids, glycerol esters of Fatty acids, long chain hydrocarbon aliphatic alcohols, paraffin waxes, mineral oil, proteins such as gelatin, sugar, non-ionic surface active agents, polyvinyl alcohol and sodium carboxymethyl cellulose as described in US 3847830 and GB 124247. Coating to sequestering builder ratios between about 0.5:1 and 2:1 by wt. may be suitable.

GB 2104912 teaches that if there is a partial release of the sequestering builder at a very early stage viz. between 0-60 seconds it does not effect the precipitation of calcium carbonate from the wash liquor. Contrary to the teachings of prior art we have found that under hand washing conditions for carbonate built formulations even a trace ( < 1 ppm) of the sequestering builder released between 0-30 seconds of the dissolution process can strongly influence the growth of the calcium carbonate crystals. We have also found that essentially the major part of the sequestering builder should be released between 30-60 seconds. This appears to be essential for an efficient hand-washing as opposed to a solely machine-washing powder where time to complete dispersal of the components can be longer.

DEFINITION OF THE INVENTION We have determined by ensuring that essentially no release of the sequestering builder viz., sodium tri polyphosphate (STPP), tetrasodium orthophosphate (TSOP), trisodium polyphosphate (TSPP), zeolite etc, within 0-30 seconds of the dissolution of the detergent composition and essentially complete release after 30 seconds will substantially improve the activity of soda ash used as primary builder in the detergent composition and the detergency benefit of the composition will increase significantly. We have determined that sequential release of the sequestering builder in the wash liquor after 30 seconds can be achieved by a granular composition in which the sequestering builder is treated with a coating material and/or a binding agent.

Based on these findings we have prepared a novel detergent composition particularly suitable for hand washing condition using a novel process.

Accordingly, the present invention provides a detergent composition comprising a water-dispersible precipitating builder component and a water-soluble sequestering builder component, at least a part of said precipitating builder component being present in non granular form, and substantially all of said water-soluble sequestering agent being present in granules coated with a coating material and wherein, when the composition is mixed with sufficient water to disperse the composition, less than It of the sequestering builder is released into solution within 30 seconds of mixing and rest of the sequestering builder is released into solution thereafter.

A further aspect of the present invention provides a washing process comprising the step of mixing a detergent composition with water wherein said detergent composition comprising a water-dispersible precipitating builder component, at least a part of said precipitating builder component being present in non granular form, and a water-soluble sequestering builder component, said water-soluble sequestering agent being substantially all present in granules coated with a coating material and wherein, when the composition is mixed with sufficient water to disperse the composition, less than It of the sequestering builder is released into solution within 30 seconds of the onset of mixing and rest of the sequestering builder is released into solution thereafter.

A yet further aspect of the present invention comprises a process for the preparation of a detergent composition which comprises the steps of: a) granulating a sequestering builder to form granules, b) coating the granules provided in step (a) with a coating material to form coated particles enrobed in 2-10 layers of coating material, said coated granules being such that when mixed with sufficient water to disperse them, less than It of the sequestering builder is released into solution within 30 seconds of the onset of mixing and rest of the sequestering builder is released into solution thereafter, and c) combining said coated particles with a detergent base comprising both precipitating builder and a non-soap detergent active material, said detergent base being free of sequestering builder and at least a part of said precipitating builder being present in non-granular form.

Preferably, the granulation step is performed in a high speed mixer.

More preferably, the coated particles obtained from step (b) are screened with a sieve having a 12-22 mesh screen prior to step (c). It is believed that removal of any fast dissolving fines and slow dissolving large particles from the granular material containing the sequestering builder ensures that the sequestering builder dissolves in the desired time window.

The fractions which are removed can be recycled.

In preferred embodiments the coated granules further comprise a binder. This binder can be itself a precipitating builder or a material which is chemically inert under the conditions of use.

In a preferred embodiment of the invention, less than 0.1%wt of the sequestering builder is released into solution within 30 seconds of the onset of mixing and rest of the sequestering builder is released into solution thereafter.

NON-SOAP DETERGENT ACTIVE MATERIAL The non-soap detergent active material is selected from anionic, nonionic, cationic, zwitterionic, amphoteric or mixtures thereof, as well known to those skilled in the art and generally described in the literature, for example in Surface Active Agents and Detergents, Volume II by Schnartz, Perry and Berch (Interscience Publishers, N.Y. 1958) and the preferred being anionic actives and the detergent active is present in an amount of between 5 to 40% by wt. and preferably between 15 to 30% by wt.

PRECIPITATING BUILDER The precipitating builder is preferably Sodium carbonate.

Preferably sodium carbonate is present in an amount of between 5 to 70% by wt. more preferably between 20 to 30% by wt.

SEOUESTERING BUILDER Preferably, the sequestering builder is selected from Sodium tripolyphosphate, Tetrasodium orthophosphate, Trisodium polyphosphate, zeolites and mixtures thereof. Sodium tripoly phosphate is a particularly preferred sequestering builder.

The builder is preferably present in an amount of between 0.5 to 10% by wt. more preferably between 2 to 5% by wt.

COATING MATERIAL The coating material is selected from polymers which include poly vinyl acetate, gelatin, silicates, polyethylene glycol, poly vinyl alcohol, poly vinyl pyrollidone, fatty acids, alkanolamides fatty acids, silicone oils, cellulose esters, cellulose ethers and acrylate derivatives like hydroxy ethyl cellulose, hydroxy methyl cellulose, hydroxy propyl methyl cellulose, hydroxy propyl ethyl cellulose, methyl cellulose and their combinations. The coating material being in an amount of between 0.1 to 20% by wt. and preferably between 3 to 10% by wt. Preferably the coating is not dependent on an increase in temperature for its removal, i.e., the coating will be shed without the necessity of heating the wash-liquor.

BINDING MATERIAL The binding materials may be selected from water insoluble inorganic binding materials include calcite, silica, talc, kaolin, china clay, and water soluble inorganic materials include soda ash, sodium sulphate, sodium chloride and their combinations. The binder being in an amount of between 0.1 to 20% by wt. and preferably between 3 to 10% by wt.

The invention will now be illustrated by non-limiting examples: Example I: 70 kg of STPP in a plough share mixer is heated to 700C.

30 kg of water is sprayed over a period to granulate STPP and discharge. The mass is then sieved to remove < 30 mesh and > 60 mesh particles which are recycled. 60 Kgs of the STPP granules is taken in a ploughshare mixer and mixed with precipitated calcite. 6 Kgs of precipitated calcite and 6 Kgs of polyvinyl alcohol (PVA) solution is sprayed on to it five times. The step of addition calcite and spraying of PVA is repeated 5 times to complete the layering process. The granules are sieved again to eliminate < 12 and > 22 mesh particles. Oversize and fines are recycled again.

ExamDle II: Effect of release of sequestering builder within 30 seconds: The detergency benefit was measured using granules produced as per the invention where no sequestering builder is released upto 30 seconds and compared with release of sequestering builder after 5-10 seconds.

The data presented in table 1 shows that release of any sequestering builder within 30 seconds brings down the detergency significantly.

Table 1

Sample % Detergency No release of sequestering 59.6 builder upto 30 seconds.

Release of sequestering builder 51.2 within 30 seconds.

Example III 1. STPP and zeolite coated with PVA/calcite: Comparative detergency benefits for the formulations that contain 20% active detergent(AD), the primary builder is 35% soda ash, the sequestering builder is 5% coated or uncoated STPP or zeolite. The control contained only STPP at 22% level or only soda ash at 35% level, were determined.

Sample A: Sequestering builder namely coated STTP (delayed release granule) Sample B: Ion exchange builder namely coated zeolite (delayed release granule) Sample C: Soda ash and uncoated STPP physically mixed Sample D: Soda ash and uncoated zeolite physically mixed Sample E: STPP as the sole builder Sample F: Soda ash as the sole builder DETERGENCY MEASUREMENT The standard soiled test cloth pieces were washed in 24 French hard water at 1:8 cloth:liquor ratio for 15 minutes at 30 C. The reflectance (R) of the unsoiled sample, soiled sample before wash and after wash was measured in at 460 nm. in colour scan spectrophotometer. The % detergency is calculated using the following formula.

(100-RW) (100-Rs) 200 Rw 200 Rs x 100 = %Detergency flOO-Rc)2 flOO-Rsl2 (100-Rc) (100-Rs) 200 Rc 200 Rs Rc =R460 clean cloth R, = R460 washed cloth Rs = R,60 soiled cloth The summary of results is presented in Table 2.

Table 2

Formulation % Detergency Sample A 49.4 Sample B 48.0 Sample C 44.5 Sample D 38.2 Sample E 50.1 Sample F 41.3 * Statistically significant over physically mixed formulations.

The effect of delayed release granules was also clearly demonstrated by higher detergency compared to physical mix of uncoated builders. It is significant to note that both STPP and zeolite coated delayed release granules showed detergency comparable to a control formulation where phosphate was the sole builder.

2. Polymer coated STPP: The results of detergency test is given in fig 1. It can be seen that the polymer coated STPP gives detergency benefits over commercially available carbonate built spray dried powder (Sunlight Detergent powder). Thermophos (granular STPP), which is a slow dissolving STPP gives lower detergency than polymer coated STPP, because of significant release of STPP within 30 seconds which is known to poison precipitation of calcium carbonate. Thus results in higher free calcium ions in the wash liquor. It is clear that by incorporating low level of polymer coated STPP, significant benefit in detergency can be obtained.

Example IV: Delayed release of Sequestering builder in wash liquor: Kinetic measurements were carried out in wash liquor using STPP coated detergent formulation of the invention to ascertain the release rate. The Coated STPP granules were measured by Standard phosphorous analysis. The free Ca level level in the wash liquor by using the delayed release granules as compared to simultaneous addition of the two builders was measured by standard calcium - sensitive electrode.

The results presented in Fig. 2 show that no STPP is released at all up to 30 seconds. The data in Fig. 3 shows that with simultaneous addition of the sequestering builder the Ca level is brought to 10 FH and the level is maintained constant over the period of time. However with the coated granules the Ca level is significantly brought down and is below 0.10 FH.

From the above discussions it is clear that our invention was instrumental in i. effective utilisation of precipitating builder, soda ash used in the composition; ii. low levels of use of the expensive sequestering builder; iii. production of improved detergency for carbonate built powders; and iv. cost saving for phosphate built powders.

Claims

1. A detergent composition comprising a water-dispersible precipitating builder component and a water-soluble sequestering builder component, at least a part of said precipitating builder component being present in non granular form, and substantially all of said water-soluble sequestering agent being present in granules coated with a coating material and wherein, when the composition is mixed with sufficient water to disperse the composition, less than 1% by weight of the sequestering builder is released into solution within 30 seconds of mixing and the rest of the sequestering builder is released into solution thereafter.

2. A process for the preparation of a detergent composition which comprises the steps of: a) granulating a sequestering builder to form granules, b) coating the granules provided in step (a) with a coating material to form coated particles coated with 2-10 layers of coating material, said coated granules being such that when mixed with sufficient water to disperse them, less than 1% by weight of the sequestering builder is released into solution within 30 seconds of the onset of mixing and the rest of the sequestering builder is released into solution thereafter, and c) combining said coated particles with a detergent base comprising both precipitating builder and a non soap detergent active material, said detergent base being free of sequestering builder and at least a part of precipitating builder being present in non-granular form.