GB800481A - Compositions for use in coating compositions - Google Patents

Abstract

A composition for use in a lacquer comprises a blend of a benzyl ether of a dextran and an ester of a dextran with one or more fatty acids containing 8 to 18 carbon atoms, said ester containing an average of between 2 and 3 fatty acid radicals per anhydroglycopyranosidic unit. The composition may be dissolved in chloroform, carbon tetrachloride, chlorofluoromethanes, benzene, toluene or xylene and dyes, pigments and other effect substances for example zinc dust may be added. The esters may be made by reacting one or more caprylic, pelargonic, cupric, undecyclic, lauric, tridecyclic, myristic, pentadecyclic palmitic or stearic acids or their chlorides with dextran in the presence of an acid acceptor such as quinoline, pyridine or N-methyl morpholine and a swelling agent for the product such as xylene, toluene or dioxane. The product is then washed and to the aqueous layer is added a non-solvent for the ester such as methanol, ethanol or isopropanol. The ester may also be prepared by reacting the dextran with a fatty acid in the presence of chloracetic acid anhydride and magnesium perchlorate, dissolving out the ester from the reaction mass and pouring this solution into a non-solvent for the ester which retains chloroacetic acid in solution. The benzyl ethers of the dextran are made by heating a dextran with benzyl chloride and sodium hydroxide. The dextrans may be made by the action of strains of Leuconostoc mesenteroides, Leuconostoc dextranicum, Betabacterium vermiforme or Streptobacterium dextranicum on sucrose solutions or by the action on sucrose solutions of an enzyme isolated from a culture of a suitable organism, e.g. Leuconostoc mesenterides or by bacterial conversion of 1 : 4 linkages of dextrin to 1 : 6 linkages of dextran. In examples the compositions are applied to metal bases; they may be applied e.g. by brushing, roller-coating or spraying.ALSO:An ester of a dextran with a fatty acid containing 8-18 carbon atoms, the ester containing an average of between 2 and 3 fatty acid radicals per anhydroglycopyranosidic unit (see Group III) may be made by reacting a dextran with an esterifying derivative of the higher fatty acid, e.g. a chloride, in the presence of an acid acceptor such as quinoline, pyridine or N-methyl morpholine and also in the presence of a solvating agent for the product such as xylene, toluene or dioxane. The reaction is carried out at between 100 DEG and 155 DEG C. for times of between half an hour to three hours and the product is recovered from the crude mix by washing with water, dissolving the ester from the aqueous layer in a solvent and precipitating it by adding methanol, ethanol or isopropanol. The ester may also be made by reacting the dextran with the selected acid in the presence of a condensing agent such as chloroacetic acid anhydride and an esterification catalyst such as magnesium perchlorate at temperatures at which the reaction mixture remains in the liquid state, i.e. between 50 and 100 DEG C. and for times of half-anhour to two hours. The mass is cooled, dissolved in a solvent and precipitated into a nonsolvent in which the chloroacetic acid formed is soluble. Caprylic, pelargonic, capric, undecylic, lauric, tridecylic, myristic, penta-decylic, palmitic, margaric and stearic acids or mixtures of two or more of these or, for example, technical or commercial stearic acid may be used. The esters are soluble in organic solvents, e.g. of the non-polar type such as chloroform, carbon tetrachloride, the chloro-fluoro methanes, benzene, toluene and xylene. The dextrans may be produced by inoculating a nutrient medium of pH 6.5 to 7.5 containing sucrose, corn steep liquor, and inorganic salts with micro-organisms such as Leuconostoc mesenteroides (U.S.A. Northern Regional Research Laboratories B-512 classification) or L. dextranicum, and incubating. Calcium chloride is added to bring the pH to between 7.0 and 8.0 and the dextran is precipitated with, for example, methyl, ethyl or isopropyl alcohol or acetone. Water-soluble dextrans may be obtained by using L. mesenteroides B-119, B-1146, B-1190 and water-insoluble dextrans by using L. mesenteroides B-742, B-1191, B-1196, B-1208, B-1216, B-1120, B-1144 or B-523, Streptobacterium dextranicum B-1254 or Betabacterium vermiforme B-1139. The dextran may be produced in the absence of bacteria by cultivating L.mesenteroides B-512, isolating the dextran-producing enzyme and introducing this into a sucrose medium. Alternatively the 1 : 4 linkages of dextrin may be converted to the 1 : 6 linkages of dextran by inoculating a medium such as described but made up with dextrin instead of sucrose with dextran producing bacteria.