Title of Invention

PROCESS FOR THE PREPARATION OF SILICA PRECIPITATED HYDROHOBI CALLY MODIFIED POLYSACCHARIDE

Abstract

A process for the preparation of silica precipitated hydrophobically modified polysaccharide is disclosed. The process comprises the steps of subjecting a polysaccharide to etherification and/or etherification by treating the polysaccharide with etherifying agents; treating the modified polysaccharide with a silicate compound to obtain a silica precipitated modified polysaccharide; and recovering the silica precipitated hydrophobically modified polymer from the reaction mixture. The polysaccharide is preferably selected from starch, guar, gum, tamarind gum, locust bean gum, xanthan gum and the like.

Full Text

FORM-2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See Section 10) IMPROVED SIZING COMPOSITION PROCESS FOR THE PREPARATION OF SILICA PRECIPITATED MODIFIRD POLY SACCNARIDE 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 nature of the invention and the manner in which it is to be performed. 19-09-2001 Technical Field: The present invention relates to a proocess for the preparation of silica precipitated ^ hydrophobically modified polysaccharides that are useful as paper surface sizing/coating agents in the paper industry. The invention also relates to a process for paper manufacture comprising paper surface sizing/coating using the aforesaid modified polysaccharides and also to paper thereby produced. Background: Surface sizing of paper is an operation often followed by paper manufacturers in the case of writing and printing grades of paper. In surface sizing a thin film of a polymer (often a starch derivative) is coated onto the surface of the paper. Generally enzyme modified, acid degraded or oxidised starches are used for sizing. The film produced on the surface of the paper improves the surface properties of paper, and thereby reduces the catch on the pen when the paper is written on and prevents pick if the paper is printed with tacky inks. Surface sizing also leads to improvement in oil resistance, porosity, stiffness and smoothness. The principal sjizing agents commonly used in the paper industry are starch, animal glue, carboxymethyl cellulpse, methyl cellulose, polyvinyl alcohol, and wax emulsions. Certain synthetic resins are also used for surface sizing of paper. It is felt that the surface properties need to be improved further to provide paper having better printability, smoothness, IN179117 and INI 82583 refer to subjecting the polysaccharide to graft coplymerisation with at least one vinyl monomer and treating the polysaccharide graft copolymer with poly ethylene glycol or silicate compounds and recovering the PEG or sihca precipitated polymers which have been used as improved surface sizing agents in paper industry. It has now been found that silica precipitated hydrophobically modified polysaccharides give a significantly superior benefit when used as paper sizing agents. The prior art refers to grafted polymers which involve complex grafting reactions as compared to the compounds of the present invention which are simple hydrophobically modified polysaccharides. OBJECTS It is an object of the present invention to provide silica precipitated hydrophobically modified polysaccharides which may be used as surface sizing agents to significantly improve the surface properties of paper, such as smoothness, porosity, burst strength and stiffness of the paper. It is another object of the present invention to provide paper having reduced porosity and improved burst strength together with improvements like stiffness and smoothness. Invention: The present invention relates to a process for the preparation of sihca precipitated hydrophobically modified polysaccharide comprising the steps of: subjecting polysaccharide to esterification and/or etherification, followed by treating the modified polysaccharide with a silicate compound to obtain a silica precipitated modified polysaccharide and recovering the silica precipitated hydrophobically modified polymer. The polysaccharides used in the present invention are preferably chosen from starch, guar gum, tamarind gum, locust bean gum, xanthan gum and the Uke. These materials may be of any origin and either used as such or in a physically or chemically modified form. More preferably starch is used in the process of the invention and it may be a native starch, degraded starch or any other chemically or physically modified starch. The polysaccharide is treated with esterifying/etherifying agents such that the polysaccharide is modified to a degree of substitution from about 0.005 to 0.4 with either: a) an ether group R-0-, where R is an hydroxyalkyl or alkyl of 1 to 4 carbon atoms or alkenyl of 2 to 4 carbon atoms; or b) an ester group (O-CO-R) where R is an alkyl of 1 to 4 carbon atoms or alkenyl of 2 to 4 carbon atoms. The modification of the polysaccharide with an ether group involves formation of an etherified polysaccharide compound having the formula: Po - O - R where Po represents the polysaccharide base material and R is an hydroxyalkyl or alkyl of 1 to 4 carbons, or an alkenyl of 2 to 4 carbons. Preferably the R group is an hydroxyalkyl of 2 to 3 carbon atoms. These polysaccharide ethers may be prepared by reaction with alkylene oxides and its precursor halohydrins, alkyl halides, and alkenyl halides. Etherification with alkylene oxides are preferred. Ethylene oxide, propylene oxide and butylene oxide are compounds useful in etherifying the polysaccharide materials. Other compounds such as modified alkylene oxides, e.g., allyl glycidyl ether, may be used to prepare useful polysaccharide ethers. Aryl compounds such as benzyl halide may also be used in the modification but are less preferable. Varying amounts of such compounds may be used depending on the final degree of substitution desired. The ester modification involves formation of an esterified polysaccharide compound having the formula Po-O-COR : where Po represents the polysaccharide base material and R is an alkyl of 1 to 4 carbon atoms or alkenyl group of 2 to 4 carbon atoms and preferably alkyl of 1 to 2 carbon atoms. Polysaccharide esters of this type include polysaccharide acetate, polysaccharide propionate and polysaccharide butyrate. The polysaccharide esters are typically prepared by reacting polysaccharide with organic acid anhydrides such as acetic anhydride, succinic anhydride, octenyl succinic anhydride, etc. The weight ratio of the polysaccharide to the esterifying/etherifying agent is in the range 1:0.005 to 1:1, It is preferable that the polysaccharides used in the present invention have a viscosity from 2 to 500 cps and more preferably from 30 to 200 cps. The viscosity is measured using a Brdok^eld viscometer Model LVT at 30 RPM at 50°C for a 10% aqueous solution. Silica precipitation on polymer The esterified/etherified starch polymer is made into a slurry with water. The solution of a silicate compound is added to the polymer and the pH is adjusted to a pH range 3-6.8 by adding an acid, e.g., hydrochloric acid, sulphuric acid, etc. The reaction mixture is thereafter stirred, filtered, washed and dried. The weight ratio of the hydrophobically modified polysaccharide to sodium silicate is in the range of 1: 0.005 to 1:0.5 and more preferably between 1:0.05 to 1:0.2. It is particularly preferred to have the particle size of silica in the range from 1 to 30 Q and more preferably 10 to 20 D • Surface sizing of paper A further aspect of the invention is a process for surface sizing of paper using the silica precipitated polymer according to the invention,for .this,, purpose any conventional surface sizing process and any conventional equipment for surface sizing can be used. Simply the conventional surface sizing agent used in such process is substituted by the silica precipitated polymer according to the invention. In the process of surface sizing of paper the paper is treated with 0.5 to 5% by weight of the silica precipitated hydrophobically modified polymer prepared according to the invention, basedjstf"dry paper. The present invention also relates to paper prepared by the process aforesaid. The invention will now be illustrated with a few typical non-limiting working examples. EXAMPLES Example I Preparation of the silica precipitated hydrophobically modified starch: Oxidation of starch: 1 kg tapioca starch was slurried in 1.3 kg water and added into a 5L three-necked round bottomed flask fitted with a mechanical stirrer. The pH of the slurry was adjusted to 8.5 and the temperature was maintained at 40°C. Sodium hypochlorite solution (200g with 10% available chlorine) was added slowly, while constantly maintaining the pH between 8 to 9. The mixture was stirred for 2 hours. Esterification reaction: The oxidised starch prepared as described above was reacted with either octenyl succinic anhydride or acetic anhydride as described below. a. Acetic anhydride (20 g) was added slowly while constantly maintaining the pH between 7.5 to 8.5. b. Octenyl succinic anhydride (20 g) was added slowly while constantly maintaining the pH between 8 to 9. The reaction was continued for 2 hours under constant stirring at 40 °C. Silica precipitation: To the above prepared octenyl succinic anhydride or acetic anhydride modified starch neutral sodium silicate solution (llOg, 27%) solution was added and the pH was adjusted to 5.8 with hydrochloric acid. The silica precipitated hydrophobically modified starch was recovered by filtration and it was dried first in air at room temperature and finally in an air oven at 50°C till the moisture content became less than 15%. The modified polymers according to the invention were evaluated and the results of such study are set out herein below. EXAMPLE II; Characteristics of the silica precipitated hydrophobically modified starches: a. Viscosity: The moisture content of silica precipitated hydrophobically modified starches were determined by heating the samples in an air oven at 130°C for 3 hrs. 10 g of dry sample was dispersed in 90 g water in a 150 ml beaker and cooked in a boiling water bath for 20 minutes. The hot dispersion was screened through a 500 micron sieve and the viscosity was determined at 50°C using a Brookfield viscomdter Model LVT at 30 RPM. J) / b. Determination of acetyl content: 5 grams of the modified polymer prepared (Example I (a)) was taken in a 500 ml conical flask, 100 ml water was added to that and a few drops of phenolphthalein solution was added. Dilute sodium hydroxide solution was added to the above to get a pink colour. 20 ml of sodium hydroxide (0.1 N) was added to it and heated to boihng over a hot plate for 20 minutes. It was cooled to about 25°C and titrated against 0.1 N hydrochloric acid solution. A blank was carried out with oxidised starch % acetyl content was calculated as follows: % acetyl content = (V1-V2)X Nl X 4.3 W1 VI = Titer value for blank; V2 - Titer value for sample Nl = Normality of HC1; W1= Dry weight of the sample c. Determination of Octenyl succinic anhydride content (OSA): 20 grams of the modified polymer prepared (Example I (b)) was taken in a 500 ml conical flask and 100 ml of 0.1 N hydrochloric acid was added and stirred for 1 hour. The modified polymer was recovered by filtration and hydrochloric acid was removed by repeated washing with water. The sample was dried. 2 gram of the dried sample was slurried in 100 ml water taken in a 500 ml conical flask and heated in a boiling water bath for 20 minutes. The cooked starch solution was cooled to ~ 25°C. 20 ml of 0.1 N sodium hydroxide solution was added and stirred occasionally for 30 minutes. The sodium hydroxide was titrated with standard hydrochloric acid. A blank was carried out with oxidised starch and the % OSA content was calculated as follows. % OSA= (V1-V2) X Nl X 21 Wl VI = Titer value for blank; V2 = Titer value for sample Nl = Normality of HC1; Wl= Dry weight of the sample d. Determination of silica in modified polymers: The modified polymer (5 g) was taken in a silica cracible and the organic matter was burnt by a Bunsen flame. Then the crucible was heated at 900°C for 2 hrs in a Muffle furnace. The crucible was cooled in a desiccator and the ash was determined. From the ash content, the amount of silica in the sample was calculated as follows : % Sihca = % Ash in silica precipitated hydrophobically modified starch - % Ash in oxidised starch. e. Determination of the particle size of silica: The moisture content of silica precipitated hydrophobically modified starches were i determined by heating the samples in an air oven at 130°C for 3 hrs. 2 g of dry sample was dispersed in 98 g water in a 150 ml beaker and cooked in a boiling water bath for 20 minutes. The hot dispersion was screened through a 500 microns and cooled to ~ 25°C. The solution was used to determine the particle size of silica in a Zeta sizer. The data are presented in Table 1. Table 1 Sample Viscosity (cps) Sihca content (%) Particle size of silica ) Acetyl Content (%) OSA Content (%) Oxidised starch 40 ■- - - - Silica precipitated acetylated starch 46 2.9 16 1.4 - Sihca precipitated OSA starch 69 2.9 17 - 1.2 The data show the incorporation of sihca in the particle size claimed and the level of modification of the starch in the modified starches prepared according to the invention. EXAMPLE III: Evaluation of the modified polymers for surface sizing of paper: Coating of Paper: Non-surface sized cream woven paper of 76g/m with 80% bamboo and 20% hardwood furnish was used as the base paper. The paper was coated with the different materials, as described in Table II. Surface sizing was carried out by coating the surface of paper with a film of the starch derivative. The starch derivative was cooked in water and the cooked dispersion was applied on the surface of the paper by using coating rods. The coating weight was 2 g/sq.m of paper. The amount of starch derivative film formed on the surface of the paper was 2% by weight of the paper. The surface sized paper prepared as described above were evaluated for different properties and compared with suitable controls described in Table 2. a. Measurement of porosity of paper: The porosity was measured using Bendsten porosity meter. Readings were taken at ten different spots on a A4 (30 X 21 cm) paper. Three replicates were maintained. Table 2 Sizing material Porosity ml/min. Control 75 Silica 65 Oxidised Starch 50 Silica precipitated oxidised Starch 27 Octenyl succinic anhydride modified starch 23 Acetic anhydride modified starch 20 Silica precipitated Octenyl succinic anhydride modified starch 5 Silica precipitated acetic anhydride modified starch 5 The data presented in Table 2 show that although silica aids in reducing the porosity of the sized paper there is surprisingly synergistic reduction in porosity when used in combination with hydrophobically modified starch. b. Measurement of Gurley porosity, smoothness, stiffness and burst factor: \ The control and paper sized with the modified polymer prepared according to the invention were evaluated to determine the effect on sizing properties such as Gurley porosity, smoothness, stiffness and burst factor and the data are presented in Table 3. Table 3 Sizing material Gurley * Porosity (Sec/100 ml) Smoothness** PPS (u) Stiffness* (Taber) Burst factor* Control 11 15 3.9 16 Oxidised Starch - 16 9.3 4.4 22 Silica precipitated acetic Anhydride modified starch 23 7.0 4.7 25 * Higher the value better is the quality of paper. ** Lower the value better is the quality of paper. The data presented show that the silica precipitated polymer prepared according to the invention improves different properties of the sized paper. WE CLAIM: 1. A process for the preparation of silica precipitated hydrophobically modified polysaccharide comprising"V" a) subjecting a polysaccharide to esterification and/or etherification by treating the polysaccharide with esterifying and/or etherifying agents ; b) treating the modified polysaccharide thus formed with a silicate compound to obtain a silica precipitated modified polysaccharide ; and c) recovering the silica precipitated hydrophobically modified polymer from the reaction mixture. 2. A process as claimed in claim 1, wherein the polysaccharide is selected from starch, guar gum, tamarind gum, locust bean gum, xanthan gum and the like. 3. A process as claimed in claim 2, wherein the polysaccharide is starch, 4. A process as claimed in claim 3, wherein the starch is selected from native starch, degraded starch or any other chemically or physically modified starch. 5. A process as claimed in any one of the preceding claims, wherein the etherification of polysaccharide is effected using an ether group R-0-, where R is an hydroxyalkyl or alkyl of 1 to 4 carbon atoms or alkenyl of 2 to 4 carbon atoms such that the polysaccharide is modified to a degree of substitution of from about 0.005 to 0.4. 6. A process as claimed in claim 5, wherein the step of etherification results in the formation of an etherified polysaccharide compound having the formula: Po - O - R where Po represents the polysaccharide base material and R is an hydroxyalkyl or alkyl of 1 to 4 carbons, or an alkenyl of 2 to 4 carbons. 7. A process as claimed in claim 6, wherein R is an hydroxyalkyl of 2 to 3 carbon atoms. 8. A process as claimed in any one of claims 5 to 7, wherein etherification is effected by reaction with alkylene oxides and its precursor halohydrins, alkyl halides, and alkenyl halides. 9. A process as claimed in claim 8, wherein etherification is effected by reaction with alkylene oxides. 10. A process as claimed in claim 9, wherein the alkylene oxide is selected from ethylene oxide, propylene oxide and butylene oxide. 11. A process as claimed in one of the preceding claims 1 to 4, wherein the esterification of polysaccharide is effected using an ester group O-CO-R, where R is an alkyl of 1 to 4 carbon atoms or alkenyl of 2 to 4 carbon atoms such that the polysaccharide is modified to a degree of substitution of from about 0.005 to 0.4. 12. A process as claimed in claim 11, wherein the step of esterification results in the formation of esterified polysaccharide compound having the formula : Po-O-COR where Po represents the polysaccharide base material and R is an alkyl of 1 to 4 carbon atoms or alkenyl group of 2 to 4 carbon atoms and preferably alkyl of 1 to 2 carbon atoms. 13. A process as claimed in claim 12, wherein the polysaccharide compound produced is polysacchaade..acetate polysaccharide propionate or polysaccharide butyrate. 14. A process as claimed in claim 11, wherein the polysaccharide esterification is effected by reacting polysaccharide with organic acid anhydrides. 15. A process as claimed in claim 14, wherein the organic acid anhydride is selected from acetic anhydride, succinic anhydride, octenyl succinic anhydride. 16. A process as claimed in claim 11, wherein the ratio of the polysaccharide to the esterifying is in the range 1:0.005 to 1:0.4. 17. A process as claimed in any one of the preceding claims, wherein the polysaccharide has a viscosity from 2 to 500 cps and preferably from 30 to 200 cps, the viscosity being measured using a Brookfield viscometer Model LVT at 30 RPM at 50°C for a 10% aqueous solution. 18. A process as claimed in any one of the preceding claims, wherein solution of a silicate compound is added to the polymer and the pH is adjusted to a pH range 3-6.8 by adding an acid. 19. A process as claimed in any one of the preceding claims, wherem weight ratio of the hydrophobically modified polysaccharide to sodium silicate is in the range of 1: 0.005 to 1:0.5 and preferably between 1:0.05 to 1:0.2. 20. A process as claimed in any one of the preceding claims, wherein the particle size of silica is in the range from 1 to 30 and preferably 10 to 20 u. 21. A process for surface sizing of paper using the silica precipitated polymer prepared by the process according to any one of claims 1 to 20. 22. A process as claimed in claim 21, wherein the paper is treated with 0.5 to 5% by weight of the silica precipitated hydrophobically modified polymer based on dry paper prepared by the process according to claims 1 to 21. Dated this 19th day of September 2001, HINDUSTAN LEVER LIMITED

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863-mum-2000-abstract(19-09-2001).doc

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863-mum-2000-cancelled page(19-09-2001).pdf

863-mum-2000-claims(granted)-(19-09-2001).doc

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863-mum-2000-correspondence(ipo)-(08-11-2004).pdf

863-mum-2000-correspondence-1-(27-04-2005).pdf

863-mum-2000-correspondence-2-(19-09-2001).pdf

863-mum-2000-form 1(20-09-2000).pdf

863-mum-2000-form 19(23-06-2003).pdf

863-mum-2000-form 2(granted)-(19-09-2001).doc

863-mum-2000-form 2(granted)-(19-09-2001).pdf

863-mum-2000-form 3(19-09-2001).pdf

863-mum-2000-form 5(19-09-2001).pdf

863-mum-2000-genral power of attorney(10-08-2004).pdf