WATER-SOLUBLE SACCHARIDE POLYMERS

Abstract: Water-soluble vinyl saccharide copolymers derived from a water-soluble vinyl saccharide monomer and a water-soluble cationic monomer and preparation thereof via a free-radical initiated copolymerization of monomers at 0 to 95 °C.

Description: The present invention relates to water-soluble saccharide copolymers, more in particular to certain water-soluble monovinyl saccharide copolymers, and to their preparation and use. Water-soluble polymers such as polysaccharides are being used in a wide range of applications, such as in water treatment, in enhanced oil recovery, and as additives, e.g. in the paper industry. Such polysaccharides are normally microbiologically prepared using certain polysaccharide producing microorganisms like Xanthomonas Campestris. It has now been found that very useful water-soluble saccharide polymers can be prepared synthetically, in particular certain vinyl saccharide copolymers carrying cationic groups, derived from a water-soluble monovinyl saccharide monomer and a water-soluble cationic monomer. These copolymers are believed to be novel. Accordingly the invention provides water-soluble vinyl saccharide copolymers derived from a water-soluble monovinyl saccharide monomer and a water-soluble cationic monomer. The term monovinyl saccharide monomer in this application refers to mono- or disaccharide compounds containing one polymerizable vinyl group. The term cationic monomer refers to a compound having an olefinically unsaturated polymerizable group and a cationic group. The water-soluble monovinyl saccharide monomers, from which the copolymers of the present invention may be derived include those wherein the polymerizable vinyl group is a vinyloxy or a vinylcarbonyloxy group. Suitably such vinyloxy group-containing monosaccharide compounds include: 3-0-vinyl-­ D-glucose, 6-vinyl-D-galactose and 1-0-vinyl-L-sorbose. The group of polymerizable monosaccharide compounds bearing a vinylcarbonyloxy group include compounds such as 3-0-acryloyl-D-glucose, 3-0-methacryloyl-D-glucose, 6-0-acryloyl-D-galactose, 6-0-methacryloyl-D-galactose, 1-0-acryloyl-L-sorbose, 1-0-methacryloyl-L-sorbose 1-0-acryloyl-mannose and 1-0-methacryloyl-mannose. Methods for the preparation of the polymerizable water-soluble vinyloxy group-containing monosaccharides have been disclosed by e.g. Reppe et al, in Annalen, 1956, 601, 81 and Watanabe and Colon in J. Amer Chem. Soc. 1957, 79, 2828. A method for the preparation of the polymerizable water-soluble vinylcarbonyloxy group containing monosaccharides has been disclosed by Black et al, Makromol. Chem. 117 (1968), 210. The preferred monovinyl saccharide monomer is a vinyl­ carbonyloxy group-containing saccharide monomer, because it is known that it is more difficult to prepare high molecular weight polymers employing a vinyloxy group-containing saccharide monomer. Within the group of water-soluble vinylcarbonyloxy group-containing saccharide monomers there is a preferance for a monomethacryloyl group-containing saccharide monomer as it is thought that they will result in water-soluble polymers which generally are hydrolytically more stable than the corresponding acrylic acid based products. Particularly preferred is 3-0-methacryloyl-D-glucose. The polymerizable olefinically unsaturated group in the water-soluble cationic monomer is preferably a vinyl, a vinyloxy, a vinylcarbonyl or a vinylcarbonyloxy group. The cationic group in said cationic monomer is suitably a quaternary ammonium group or a salt of an amino group. The nature of said amino group is not critical and includes primary, secondary and tertiary alkyl and/or aryl amino groups as well as heterocyclic amino groups. Suitably such vinyl group-containing cationic monomers include monovinylpyridines such as 2-vinylpyridine, 3-vinyl­ pyridine, 4-vinylpyridine and substituted monovinylpyridines such as 2-methyl-5-vinylpyridine. Vinylcarbonyl group-containing cationic monomers include compounds such as methacryloylamidopropyl trimethyl ammonium chloride and acryloylamidopropyltrimethylammonium chloride. Preferred vinylcarbonyloxy group-containing cationic monomers are 2-(methacryloyloxy)ethyltrimethylammonium chloride, 2-(acryloyloxy)-ethyltrimethylammonium chloride, 2-(methacryloyloxy)ethyl-trimethylammonium methyl sulfate, 2-(acryloyloxy)ethyl-trimethylammonium methyl sulfate, 2-(methacryloyloxy)ethyl-dimethylammonium hydrochloride, 3-(acryloyloxy)propyl-dimethylammonium hydroacetate, 2-­ (acryloyloxy)ethyl-dimethylcetyl ammonium chloride and 2-(methacryloyloxy)ethyl-diphenylammonium chloride. Vinyl­ carbonyl and vinylcarbonyloxy group-containing cationic monomers are preferred. Another species of water-soluble cationic monomer, from which the polymer of the present invention may be derived, is diallyldimethylammonium chloride. The composition of the polymers of the present invention may vary over a wide range and will primarily be determined by the performance requirements of the ultimate polymer end-use. Hence the polymers may include those which are predominantly polyvinylsaccharide polymers, i.e. polymers having a relatively low cationic group content, as well as polymers having a relatively low number of saccharide groups. The invention further provides a composition comprising water and at least a copolymer as hereinbefore described. Such a composition is for example a water-in-oil emulsion comprising at least a copolymer as hereinbefore described. Other water-soluble polymers such as the biologically prepared polysaccharide may be present in such composition together with a copolymer as hereinbefore described. The invention also provides a process for the preparation of these novel water-soluble cationic vinyl saccharide polymers, wherein at least one water-soluble monovinyl saccharide monomer and at least one water-soluble cationic monomer are copolymerized at a temperature in the range of from 0°C to 95°C in the presence of a free-radical initiator. The free-radicals to be used in the process of the present invention may originate from compounds which are capable of generating free-radicals via a reduction-oxidation reaction, so called redox initiators, as well as from compounds which are capable of generating free-radicals by decomposition, e.g. upon heating thereof. Redox initiator systems have been described e.g. in Prog. Polym. Sci. Vol. 8, pp 61-131(1982). Preferred redox initiator systems are a peroxide, a persulphate, a peroxydiphosphate or a permanganate type of oxidant, and a reducing agent. Preferred reducing agents are based on a reducing acid of sulphur. Compounds which are capable of generating free-radicals via a decomposition reaction, have been described e.g. in J. Macromol. Sci. Rev. Macromol. Chem., C 20(1), 149-205(1981) and include azo and diazo compounds, organic peroxides, hydroperoxide, peroxydicarbonate and persulphate type of free-radical initiators, and hydrogen peroxide. Should the performance requirements of the ultimate polymer end-use be such, that they require the polymer of the present invention to have a high molecular weight, it may be advantageous to use in the process of the present invention a free-radical initiator of limited solubility in water, e.g. a solubility in water of less than 2500 µmol/kg at 20°C; 2,2′-azobisisobutyronitrile is a preferred free-radical initiator. The amount of free-radical or redox initiator to be used in the preparation of the polymers of the present invention may vary over wide ranges. In the preparation of high molecular weight polymers however there should be a limit to the amount of free-radical or redox initiator used, e.g. the molar ratio of water-soluble monomer - i.e. monovinyl saccharide monomer and cationic monomer - to free-radical initiator or the oxidant compound of a redox initiator system is preferably at least 100:1 and more preferably at least 500:1. When employing a free-radical initiator of low-solubility it is advantageous to add said initiator as a solution in a water-miscible solvent such as acetone. The aqueous polymer solution may become quite viscous due to the viscosifying power of the copolymer produced. Therefore the monovinyl saccharide monomer is suitably present in water in a concentration which is not higher than 150 kg/m³, and preferably not higher than 120 kg/m³. The copolymers according to the present invention may be employed as water thickeners, e.g. in floading water which is applied in the enhanced oil recovery. Another important outlet for these polymers is in water treatment, e.g. as coagulant and/or flocculant. They may also be applied e.g. as additive in the paper industry and as paint thickener. The invention will be further illustrated by the following Examples for which the following information is provided. b Preparation of MG 4 g of 1,2:5,6-di-0-isopropylidene-3-0-methyacryloyl-D-glucose (DIMG), 25 mg of p-methoxyphenol and 30 ml of 0.5 N hydrochloric acid were introduced into a 100 ml glass reactor equipped with a glass stirrer, a thermometer and a reflux condensor, and subsequently the reactor was placed in a thermostated oil-bath. The reactor contents were heated to 70°C with continuous stirring, and maintained at this temperature until the contents had become homogeneous (1-2 h). After cooling to room temperature the reactor contents were transferred to a separatory funnel. To remove the p-methoxyphenol, the 3-0-methacryloyl-D-glucose solution was treated with 50 ml diethyl ether and after phase separation had occurred the organic phase was removed. This extraction procedure was repeated four times. Subsequently the aqueous solution was transferred to the above-mentioned 100 ml glass reactor and a pressure slightly below atmospheric was applied to remove the last traces of diethyl ether. Finally the solution was neutralized to a pH of 7 with 1.0 N NaOH, which procedure was carefully monitored by pH measurement. A solids determination indicated that the MG content of the aqueous solution was 8 %w (=0.32 mol/1). c Removing the inhibitor from the cationic monomer The polymerization inhibitor present in the aqueous cationic monomer solutions were removed by extraction with diethyl ether according to the procedure as described in section b. d Measuring the viscosity of the aqueous polymer solutions The viscosity of the aqueous polymer solutions was measured at 25°C using a Contraves low Shear viscometer at a shear rate γ which was varied over a range of from 0.0746-­ 7.46 s⁻¹. e Determining the flocculation/coagulation efficiency of the polymer prepared e-1 Preparation of colloidal suspensions A colloidal SiO₂ suspension (Synton - W30, mean particle size 0.125 µm, ex Monsanto) and a colloidal Bentonite suspension (mean particle size 1-2 m, ex Magocel) were diluted with commercial buffer solutions of pH 4 and/or 7 and also with demineralized (demi) water, to arrive at suspensions containing 4.32 g/l of SiO₂ or bentonite. The pH values of the demi water based suspensions were 8.9 and 9.6 for SiO₂ and bentonite respectively. A colloidal Al₂O₃ suspension (Martoxin GL-1, mean particle size 0.5 m, ex Martins Werk was diluted with only demi water to arrive at a suspension containing 4.23 g Al₂O₃/l and having a pH of 9.6. e-2 Sample preparation for flocculation testing The flocculation tests were carried out in a 100 ml calibrated glass tube (internal diameter: 30 mm) having a cone-shaped closed end (volume: 25 ml, i.e. 25 %w of total volume). 50 ml of the SiO₂, bentonite or Al₂O₃ suspensions prepared as in section e-1 were introduced into the tubes together with so much of a 0.1 %w aqueous polymer solution to arrive at polymer/SiO₂, bentonite or Al₂O₃ weight ratio's as indicated in Tables 4-6 hereinafter. After homogenizing the tube contents (on a roller table) they were stored in a vertical position at ambient temperature. e-3 Measuring the flocculation/coagulation efficiency The flocculation efficiency was determined by measuring the clarity of the liquid phase of said suspensions relative to that of water in a spectrophotometer at regular intervals. Simultaneously for a number of systems the sediment volume (ml) in the hereinbefore mentioned tubes was also measured. Examples I-IV MG/DMAEM·HCl 8/2 and MG/MAPTAC 8/2, 6/4 and 4/6 copolymers. 1. Copolymer preparation An aqueous monomer solution (50 ml) containing 8 %w of a monomer mixture comprising MG and DMAEM·HCl or MAPTAC in a molar ratio as indicated in Table 1 hereinafter, and AIBN in a monomer/AIBN molar ratio also as indicated in Table 1, were introduced into a 100 ml glass reactor. With mild stirring and a N₂ purge the reactor contents were heated at 40°C for 48 hours. Subsequently the reactor contents were cooled and poured out under continuous stirring in approximately 150 ml ethyl alcohol, whereupon a white precipitate was obtained. After removing the liquid phase, the residue was dried under reduced pressure at 50°C to constant weight. The ultimate products were white, water-soluble powders. 2. Viscosifying properties of polymers prepared The viscosifying properties of the polymers were determined by measuring the viscosity of the aqueous polymer solutions following the procedures as hereinbefore described in section d. The resulting viscosity data are given in Tables 2 and 3. 3. Flocculation/coagulation efficiency of polymers prepared The flocculation and coagulation efficiency of the polymers, was determined by the procedures as hereinbefore described in section e. The resulting data is given in Tables 4-6. From the Examples it will be clear that the copolymers according to the present invention appear to possess a considerable viscosifying power and ability to act as flocculants and coagulants.

Claims: 1. Water-soluble vinyl saccharide copolymers derived from a water-soluble monovinyl saccharide monomer and a water-soluble cationic monomer. 2. Copolymers as claimed in claim 1, in which the water-soluble monovinyl saccharide monomer is a vinylcarbonyloxy group-containing saccharide monomer. 3. Copolymers as claimed in claim 2, in which the vinylcarbonyloxy group-containing saccharide monomer is a monomethacryloyl or a monoacryloyl group-containing saccharide monomer. 4. Copolymers as claimed in claim 3, in which the monomethacryloyl group-containing saccharide monomer is 3-0-methyacryloyl-D-glucose. 5. Copolymers as claimed in any one of the preceding claims, in which the water-soluble cationic monomer is a vinyl, vinyloxy, vinylcarbonyl or vinylcarbonyloxy group-con­ taining cationic monomer. 6. Copolymers as claimed in claim 5, in which the vinylcarbonyloxy group-containing cationic monomer is 2-(methacryloyloxy)-ethyltrimethylammonium chloride, 2-­ (acryloyloxy)ethyltrimethylammonium chloride, 2-­ (methacryloyloxy)ethyltrimethylammonium methyl sulfate, 2-(acryloyloxy)ethyltrimethylammonium methyl sulfate, 2-(methacryloyloxy)ethyldimethylammonium hydrochloride, 3-(acryloyloxy)propyldimethylammonium hydroacetate, 2-­ (acryloyloxy)ethyldimethylcetylammonium chloride or 2-­ (methacryloyloxy)ethyldiphenylammonium chloride. 7. Copolymers as claimed in any one of claims 1-4, in which the cationic monomer is diallyldimethylammonium chloride. 8. A composition comprising water and at least a copolymer as claimed in any one of the preceding claims. 9. A process for the preparation of copolymers as claimed in any one of the claims 1-7, in which at least one water-soluble monovinyl saccharide monomer and at least one water-soluble cationic monomer are copolymerized at a temperature in the range of from 0°C to 95°C in the presence of a free-radical initiator as hereinbefore defined. 10. A process as claimed in claim 9, in which the concentration of water-soluble monovinyl saccharide monomer is not higher than 120 kg/m³ water. 11. The process as claimed in claim 9 or 10, in which the water-soluble monovinyl saccharide monomer is a vinylcarbonyloxy group-containing monomer. 12. A process as claimed in claim 11, in which the vinylcarbonyloxy group-containing saccharide monomer is a monomethacryloyl or a monoacryloyl group-containing saccharide monomer. 13. A process as claimed in claim 12, in which the methacryloyl group-containing saccharide monomer is 3-0-­ methacryloyl-D-glucose. 14. A process as claimed in any one of claims 9 to 13, in which the water-soluble cationic monomer is a vinyl, vinyloxy, vinylcarbonyl or vinylcarbonyloxy group-containing cationic monomer. 15. A process as claimed in claim 14, in which the vinylcarbonyloxy group-containing cationic monomer is 2-(methacryloyloxy)-ethyltrimethylammonium chloride, 2-­ (acryloyloxy)ethyltrimethylammonium chloride, 2-­ (methacryloyloxy)ethyltrimethylammonium methyl sulfate, 2-(acryloyloxy)ethyltrimethylammonium methyl sulphate, 2-(methacryloyloxy)ethyldimethylammonium hydrochloride, 3-(acryloyloxy)propyldimethylammonium hydroacetate, 2-­ (acryloyloxy)ethyldimethylcetylammonium chloride or 2-­ (methacryloyloxy)ethyldiphenylammonium chloride. 16. A process as claimed in any one of claims 9 to 13, in which the water-soluble cationic monomer is diallyldimethyl­ ammonium chloride.

Inventors: GRAAFLAND, TEUNIS
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1987
Main classification: C08F220
IPC codes: C08F220, C08F20