Title of Invention | A PROCESS FOR DRYING OF A SURFACTANT PASTE |
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Abstract | A process for the drying of a surfactant to form a granule having from 50 to 90 wt% non soap anionic surfactant and 5 to 25 % hydrated inorganic hydratable salts, the process comprising the steps of: (i) mixing an aqueous surfactant blend (I) containing from 20 to 50 wt% water and one or more inorganic hydratable salts (II) to form mixture having a maximum viscosity of 100 pa. s, at a shear rate of 20 s-1 and a temperature of 80° C, where the ratio of I:II is greater than 1:1 and less than 10:1, (II) drying the mixture by applying heat to produce an intermediate material with a total water content of 4 to 15 wt% (III) processing this intermediate to form a free flowing granular detergent component. Use of the inorganic hydratable salt reduces the heat needed for the drying step. |
Full Text | C4438/C FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) DRYING SURFACTANT PASTE HINDUSTAN LEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India The following specification particularly describes the invention and the manner in which it is to be performed. C4438 (C) COM - 1 - DRYING SURFACTANT PASTE TECHNICAL FIELD 5 This invention relates to a process for drying surfactant paste, particularly to a process for drying a hygroscopic surfactant such as an alpha olefin sulphonate. BACKGROUND AND PRIOR ART 10 15 Surfactants, like alpha olefin sulphonate (AOS), are manufactured as an aqueous paste with about 40% active surfactant. For some detergent applications, it is desirable to drive off the water to form a solid material. This solid material may then be milled or otherwise granulated to enable it to be dry mixed with other detergent ingredients. This problem is only present for non-soap detergents. When making soap detergents active levels of nearly 90% can be achieved without there being any problem in achieving the necessary drying. There are two problems associated with the production of such dried material. The first problem is that the energy used to dry the surfactant sufficiently for it to be 25 miliable is considerable. This is because as the paste loses water it takes proportionately more and more energy to drive off the remaining water. This problem becomes worse if the process is being operated in a very humid climate where the drying air is already at a high humidity and 30 requires additional heating to get it sufficiently dry to be able to pick up the water. This could be overcome by use of C4438 (C) COM - 2 - vacuum drying and/or by reducing the throughput of the drying equipment. These are costly solutions that may not be acceptable. 5 The second problem that remains even if the above alternative drying techniques are employed is that the solid produced has a tendency to re-absorb moisture vapour from the air, leaving it sticky and difficult to mill, especially if it cannot be processes immediately. Many processes 10 cannot be fed with hot surfactant so if the drying process has been modified to use high temperature this is particularly disadvantageous. Sodium pyrophosphate and similar salts have been used as 15 ingredients in detergent formations. EP 0 349 199 teaches that the reversion of tripolyphosphate to pyrophosphate and orthophosphate is to be avoided so far as possible, thus reducing the levels of orthophosphate and pyrophosphate to less than 3%. 20 US 4 186 114 discloses a granular detergent composition comprising 18 wt% AOS and 15 wt% sodium pyrophosphate. The composition is spray dried and contains other ingredients than these two. 25 US 5 366 652 discloses a process in which surfactant paste is added to a mixture containing Magnesium sulphate. The inorganic salt helps to remove moisture from the paste. No drying stage is mentioned. C4438 (C) COM - 3 - WO2005/040325 is concerned with a process for manufacturing a detergent granule comprising blending a paste of anionic surfactant with a dehydrating agent. This process must not dry the materials by more than 5 wt%. As such, it should 5 not be regarded as a drying process. GB 2308128 describes a detergent composition in paste form comprising an anionic surfactant in an amount of 5 to 40% by weight of the composition and a hydratable builder salt in 10 an amount of more than 5% by weight of the composition wherein the level of the builder salt exceeds that of the anionic surfactant and the paste has a viscosity of 7 to 700Pa.s at a shear rate of Is . Suitably any hydratable salt may be employed although it is preferred if the 15 hydratable builder salt is selected from builders such as polyphosphates orthophosphates, 2 tripolyphosphates, phosphates, tetraphosphates, pyrophosphates, carbonates and bicarbonates and the alkaline metal and ammonium salts of any of the foregoing. In a particularly preferred 20 embodiment, the hydratable salt comprises sodium tripolyphosphate and optionally sodium carbonate. Any conventional anionic surfactant may be employed. Suitably the level of hydratable builder salt exceeds the level of surfactant in the composition but is preferably less than 25 5:1, more preferably 1.1 to 2.5:1 builder salt to surfactant on a weight basis. SUMMARY OF THE INVENTION 30 According to the present invention there is provided a process for the drying of a surfactant to form a granule C4438 (C) COM having from 50 to 90 wt% non soap anionic surfactant and 5 to 2 5% hydrated inorganic hydratable salts, the process comprising the steps of: 5 (i) mixing an aqueous surfactant blend (I) containing from 20 to 50 wt% water and one or more inorganic hydratable salts (II) to form a mixture having a maximum viscosity of 100 Pa.s, at a shear rate of 2 0 s"1 and a temperature of 8 0°C, where the ratio 10 of I:II is greater than 2:1 and less than 20:1, (ii) drying the mixture by applying heat to produce an intermediate material with a total water content of 5 to 15 wt%, (iii) processing this intermediate material to form a 15 granular detergent component. Advantageously the hydratable salts are able to form inorganic hydrates which are stable at greater than 45°C and 2 0 where the total water content of the hydrated hydratable salt at 45°C, is at least 25 wt% of the weight of the unhydrated salt. Most advantageously the initial water content of the mixture is 10 to 30%. Desirably step (i) is carried out at a temperature in excess of 75°C, preferably 25 85 to 90°C, and the degree of hydration of the inorganic hydratable salt is initially less than 5% of its maximum degree of hydration. The surfactants suitable for use in the process may comprise 3 0 a major part of anionic surfactant, preferably AOS, PAS, LAS, SLES, or mixtures of these, with nonionic, cationic C4438 (C) COM - 5 - and/or amphoteric surfactants; excluding soaps. The paste may contain 15 to 30 wt% water. A process wherein step (iii) is carried out by cooling, 5 milling and granulating with an appropriate liquid binder; such as water, aqueous polymer solutions, or PEG, cooling is preferred. In this case, the most suitable hydratable salt is sodium pyrophosphate. 10 The level of component I used in the process is preferably 60-90 wt%, most preferably 70-90 wt% of the product of step (iii). If present, soap may be present in the feedstock at a level of less than 25 wt%, preferably less than 2 0 wt% and most preferably less than 10 wt% based on the total weight 15 of the feedstock. The soap may provide the advantage of structuring of the component or composition. Incorporation of a hydratable salt at a temperature above its hydration temperature produces a pumpable paste, which 20 can be fed into a drier and allows for the evaporative load on the dryer to be reduced. For the purposes of this invention, a pumpable paste is one having a viscosity of at most 100 Pa.s. The salt hydrates on cooling after the dryer giving chemical dehydration and salt crystal structuring to 25 the product. This reduces the drying load at lower relative humidity (RH) or moisture content. I.e. the moisture that is most difficult or costly to remove. This process allows the dryer to operate more efficiently 30 and gives a product that is suitable for milling or subsequent post processing at higher total moisture contents than could be achieved without the use of inclusion of the C4438 (C) COM - 6 - inorganic hydratable salt. The level of moisture in the final granules lies in the range 2-30 wt%. The Inorganic Hydratable Salt 5 The inorganic hydratable salt can absorb water such that, when fully hydrated, at least 25% of its weight is water and it has an equilibrium relative humidity at 25°C of less than 60%. In this way, it can absorb significant amounts of 10 moisture but keeps the moisture 'locked away' so that it does not readily evaporate and create powder flow problems. It is also preferable that it is stable with respect to moisture loss up to 50°C. This means that the water bound 15 in the hydrated salt remains in a stable state up to 50°C. Sodium carbonate decahydrate heated up to 40°C dissolves in its own water of crystallisation and results in sodium carbonate solution, this then is not stable with respect to moisture loss. 20 Suitable hydratable salts are few in number. It has been found that magnesium sulphate; sodium pyrophosphate, sodium acetate and mixtures thereof have suitable characteristics to function as dehydrating agents in the context of the 25 present invention. Of these, sodium pyrophosphate is preferred due to its high efficacy and compatibility with built detergent systems (magnesium salts being regarded as undesirable components of normal detergent systems), especially compositions containing a phosphate builder 30 system. Swelling cellulosics absorb water only at an unacceptably high RH. Therefore, they are not suitable. (C) COM - 7 - Table 1 gives a list of hydratable salts and other water absorbing agents or common detergent ingredients and demonstrates why they are suitable (pass) or unsuitable (fail) as hydratable salts for use in the present invention. Table 1 Material Hydrate level % Waterin hydrate DehydrationTemp.(°C) MinimumRH of hydrate Passor Fail Magnesium Sulphate 7H20 51 >100 43 Pass Sodium Acetate 3 H20 40 55 32 Pass Sodium Pyrophosphate 10 H20 40 76 52 Pass Sodium Carbonate H20 10 H20 14 63 34 93 Fail Fail Sodium Sulphate 10 H20 56 32 93 Fail Sodium Orthophosphate 12 H20 57 75 88 Fail Disodium Hydrogen Orthophosphate 12 H20 2 H20 60 20 35 - Fail Fail Sodium Tripolyphosphate 6 H20 23 >100 52 Fail Tri-sodium Citrate 2 H20 12 - 52 Fail The invention will now be further described with reference to the following non-limiting examples: C4438 (C) COM - 8 - Example 1 90 parts of AOS paste, (80% surfactant, ca 20% water) was mixed with 10 parts of anhydrous Sodium Pyrophosphate at 5 80°C. The viscosity of the mixture at this temperature was measured to be 4 3 Pa.s @ 20 s The mixture was then oven dried at 12 0°C to a target total water content of 8.0 wt%. The actual measured moisture 10 content was 7.6% and the measured hardness value was 3.08 N/mm . This intermediate material was then cooled to ambient temperature and milled to form a powder. Finally, the powder was granulated, using a 90/10 ratio of 15 powder to water, in a high shear granulator. Finished formulation: AOS (surfactant) =81 20 Sodium pyrophosphate = 11 Total water content = 8 Comparative Example 2 25 This comparative example used Sodium Sulphate as the electrolyte. This hydratable salt falls outside the scope of claim 1 because it loses its water on heating to 45°C (see table 1). C4438 (C) COM - 9 - 90 parts of AOS paste (80% surfactant, ca 20% water) was mixed with 10 parts of anhydrous Sodium Sulphate at 80°C. This mixture was oven dried at 12 0°C to a target total water 5 content of 8.0 wt%. The actual measured moisture content was 6.7%. Hardness value 2.48 N/mm . The intermediate material obtained was then cooled to ambient temperature. An attempt was made to mill the cooled 10 material, but it was too soft to mill. AOS (surfactant) = 81 Sodium sulphate = 11 Total water content = 8 15 Comparative Example 3 100 parts of AOS paste, (80% surfactant, ca 20% water) was oven dried at 120°C to a target total water content of 20 8.0 wt%. The actual measured total water content was 7.6%. The Hardness value was measured to be 2.3 6 N/mm . This intermediate material was then cooled to ambient temperature and an attempt made to mill to form a powder. 25 The product was too soft to mill. AOS (surfactant) = 92 Total water content = 8 C4438 (C) COM - 10 - Example 4 95 parts of AOS paste, (80% surfactant, ca 20% water) was mixed with 5 parts of anhydrous sodium pyrophosphate at 5 80°C. The mixture was dried at 130°C to a range of total water contents of between 3 and 10 wt% (measured using an infrared balance at 160°C). The material was then rapidly cooled 10 to ambient temperature. Hardness values and milling tests were carried out to assess these parameters as a function of moisture content. The results are given in Table 2 (tests 4.1 to 4.7). 15 The samples that could be milled were granulated using a 90/10 ratio of powder to water in a high shear granulator. Finished formulation: 20 AOS (surfactant) = 88-90% Sodium pyrophosphate = 6 Total water content = 4-6% Comparative Example 5 25 100 parts of AOS paste, (80% surfactant, ca 20% water) was used for this example The mixture was dried at 13 0°C to a range of total water 3 0 contents of between 1 and 5 wt% (measured using an infra-red balance at 160°C). The material was then rapidly cooled to C4438 (C) COM - 11 - ambient temperature. Hardness values and milling tests were assessed as a function of moisture content. The results are given in Table 2 (tests 5.1 to 5.4). 5 This intermediate material was cooled to ambient temperature and an attempt was made to mill it to form a powder. This product was too soft to mill at moisture contents above 2.5 wt%, measured using this technique. AOS (surfactant) = 97.5 - 100% Total water content = 0 - 2.5% Table 2 Test Water Wt% (IR) hardness N/mm2 4.1 3.95 32.54 4.2 4.14 45.60 4.3 5.13 24.87 4.4 5.23 20.03 4.5 5.3 17.89 4.6 7.97 9.20 4.7 10.16 7.71 5.1 0.97 51.18 5.2 1.38 52.67 5.3 1.76 40.04 5.4 2.47 15.26 C4438 (C) COM - 12 CLAIMS 1. A process for the drying of a surfactant to form a 5 granule having from 50 to 90 wt% non soap anionic surfactant and 5 to 2 5% hydrated inorganic hydratable salts, the process comprising the steps of: (i) mixing an aqueous surfactant blend (I) 10 containing from 20 to 50 wt% water and one or more inorganic hydratable salts (II) to form a mixture having a maximum viscosity of 100 Pa.s, at a shear rate of 2 0 s"1 and a temperature of 8 0°C, where the ratio of I:II 15 is greater than 1:1 and less than 10:1, (ii) drying the mixture by applying heat to produce an intermediate material with a total water content of 4 to 15 wt%. (iii) processing this intermediate material to form 20 a free flowing granular detergent component. 2. A process according to claim 1 in which the hydratable salts are able to form inorganic hydrates which are stable at greater than 45°C and where the total water 25 content of the hydrated hydratable salt at 45°C, is at least 25 wt% of the weight of the unhydrated salt. 3. A process according to any preceding claim in which the initial water content of the mixture is 10 to 30%. 30 A process according to any preceding claim in which the surfactants comprise a major part of anionic C) COM 13 surfactant, preferably AOS, PAS, LAS, SLES, or mixtures of these, with nonionic, cationic and/or amphoteric surfactants; excluding soaps. 5. A process according to any preceding claim in which step (iii) is carried out by cooling, milling and granulating with an appropriate liquid binder; such as water, aqueous polymer solutions, or PEG. 6. A process according to claim 2 in which the hydratable salt is sodium pyrophosphate. 7. A process according to and preceding claim in which the level of surfactant blend I is 60-90 wt%, preferably 70-90 wt% of the product of step (iii). 8. A process according to any preceding claim in which soap is present in the feedstock at a level of less than 25 wt% of the total surfactant(s). Dated this 4th day of April 2006 HINDUSTAN LEVER LIMITED (S. Venkatramani) Sr Patents Manager (C) COM 14 ABSTRACT A process for the drying of a surfactant to form a granule having from 50 to 90 wt% non soap anionic surfactant and 5 to 25% hydrated inorganic hydratable salts, the process comprising the steps of: (i) mixing an aqueous surfactant blend (I) containing from 2 0 to 50 wt% water and one or more inorganic hydratable salts (II) to form a mixture having a maximum viscosity of 100 Pa.s, at a shear rate of 20 s"1 and a temperature of 80°C, where the ratio of I:II is greater than 1:1 and less than 10:1, (ii) drying the mixture by applying heat to produce an intermediate material with a total water content of 4 to 15 wt%. (iii) processing this intermediate material to form a free flowing granular detergent component. Use of the inorganic hydratable salt reduces the heat needed for the drying step. |
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515-MUM-2006-ABSTRACT(13-8-2009).pdf
515-mum-2006-abstract(granted)-(7-4-2010).pdf
515-MUM-2006-CANCELLED PAGES(13-8-2009).pdf
515-mum-2006-cancelled pages(27-1-2010).pdf
515-MUM-2006-CLAIMS(13-8-2009).pdf
515-MUM-2006-CLAIMS(AMENDED)-(27-1-2010).pdf
515-mum-2006-claims(granted)-(7-4-2010).pdf
515-mum-2006-correspondance-received.pdf
515-mum-2006-correspondence 1(21-2-2008).pdf
515-mum-2006-correspondence 2(24-9-2007).pdf
515-MUM-2006-CORRESPONDENCE(22-5-2009).pdf
515-MUM-2006-CORRESPONDENCE(4-11-2009).pdf
515-MUM-2006-CORRESPONDENCE(7-12-2009).pdf
515-MUM-2006-CORRESPONDENCE(8-2-2012).pdf
515-mum-2006-correspondence(ipo)-(8-4-2010).pdf
515-mum-2006-description (complete).pdf
515-MUM-2006-DESCRIPTION(COMPLETE)-(13-8-2009).pdf
515-mum-2006-description(granted)-(7-4-2010).pdf
515-MUM-2006-FORM 1(13-8-2009).pdf
515-mum-2006-form 13(3-10-2007).pdf
515-mum-2006-form 18(21-2-2008).pdf
515-mum-2006-form 2(13-8-2009).pdf
515-mum-2006-form 2(granted)-(7-4-2010).pdf
515-MUM-2006-FORM 2(TITLE PAGE)-(13-8-2009).pdf
515-mum-2006-form 2(title page)-(granted)-(7-4-2010).pdf
515-MUM-2006-FORM 3(24-2-2010).pdf
515-MUM-2006-OTHER DOCUMENT(22-5-2009).pdf
515-MUM-2006-POWER OF ATTORNEY(27-1-2010).pdf
515-MUM-2006-REPLY TO EXAMINATION REPORT(13-8-2009).pdf
515-MUM-2006-REPLY TO HEARING(27-1-2010).pdf
515-mum-2006-specification(amanded)-(13-8-2009).pdf
Patent Number | 239901 | |||||||||||||||
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Indian Patent Application Number | 515/MUM/2006 | |||||||||||||||
PG Journal Number | 15/2010 | |||||||||||||||
Publication Date | 09-Apr-2010 | |||||||||||||||
Grant Date | 07-Apr-2010 | |||||||||||||||
Date of Filing | 04-Apr-2006 | |||||||||||||||
Name of Patentee | HINDUSTAN UNILEVER LIMITED | |||||||||||||||
Applicant Address | HIDUSTAN LEVER HOUSE,165-166 BACKBAY RECLAMATION ,MUMBAI 400 020, | |||||||||||||||
Inventors:
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PCT International Classification Number | C11D11/00 | |||||||||||||||
PCT International Application Number | N/A | |||||||||||||||
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PCT Conventions:
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