Patent GB-729302-A (GB)
Title: Polymerized starch esters and ethers
IPC: C08B31/00
Filed: 1951-03-13
Abstract: Textile fabrics are stiffened by treatment with an aqueous dispersion of an unsaturated starch derivative obtained by reacting a starch in an aqueous alkaline medium with an organic anhydride, a chloroformate, an organic halide etherifying agent or an epoxy compound, each containing the polymerizable group -C(R) : CH2, where R is hydrogen or an alkyl group, so as to produce a water-dispersible starch ether or ester containing not substantially more than one such polymerizable group per 15 anhydroglucose units (see Group IV (b)). The fabric is then treated with a water-soluble vinyl polymerization type catalyst, whereby the starch derivative is insolubilized by polymerization in situ (see Group IV (a)).  In an example, unsized cotton sheeting is saturated with an aqueous dispersion of a starch ester derived from acid-converted corn starch and methacrylic anhydride, ironed dry and then passed through aqueous sodium bisulphite and again ironed dry; the material so treated retains its stiffness after washing.ALSO:Polymerized starch esters and ethers are prepared by reacting a water-dispersible starch in an aqueous alkaline medium with an amount of an aqueous alkaline medium with an amount of an organic anhydride, a chloroformate, an organic halide etherifying agent or an epoxy compound each containing the polymerizable olefinic group <FORM:0729302/IV (a)/1> where R is hydrogen or an alkyl group such as to produce a water-dispersible starch ester or ether containing not substantially more than one said polymerizable group per 15 anhydroglucose units (see Group IV (b)) and contacting the water-dispersible ester or ether with a water-soluble free radical producing vinyl polymerization catalyst thereby reducing the solubility in water of the starch derivative. The solubility may be so reduced that the product does not form a dispersion even after boiling in water for several hours.  Suitable starches include corn, waxy maize, potato, sweet potato, sago, wheat, rice and tapioca starches; they may be in ungelatinized form or may be gelatinized or converted by heat and/or acids or oxidizing agents into thin boiling starches, dextrine or British gum.  Reactants used for producing the esters or ethers include the anhydrides of acrylic and methacrylic acids, allyl chloroformate, allyl bromide and butadiene monoxide.  The after-treatment of the water-dispersible starch derivatives may be effected by mixing an aqueous dispersion or suspension of the starch derivative with the catalyst, e.g. a persulphate, a bisulphite, hydrogen peroxide and ceric sulphate. Catalyst activators may also be present, e.g. ferrous and ferric sulphates, silver nitrate, hydroxylamine hydrochloride and the reductant activators.  The process may be utilized in the treatment of textiles and paper, wherein the fabric and paper are sized or coated with an aqueous dispersion of the water-dispersible starch derivative and then contacted with the catalyst, e.g. an aqueous solution of sodium bisulphite whereby the material is given water-resistance and the paper has increased wet strength (see Groups IV (c) and VIII).  The products may also be used in adhesives.  In examples: (1) a water-dispersible starch ester obtained from corn starch and methacrylic anhydride is treated in aqueous suspension with ammonium persulphate and ferrous sulphate, sodium meta bisulphite or ceric sulphate giving a non-gelatinizable product; (2) an ether obtained from gelatinized waxy maize starch and butadiene-monoxide is treated in aqueous dispersion with sodium metabisulphite yielding a rubbery gel; (3) a starch derivative obtained from potato starch and allyl chloroformate is treated with hydrogen peroxide and various catalyst activators yielding non-gelatinizable insoluble products.ALSO:Water-dispersible starch esters or ethers are prepared by reacting a water-dispersible starch in an aqueous alkaline medium with an amount of an organic anhydride, a chloroformate, an organic halide etherifying agent or an epoxy compound each containing the polymerizable group <FORM:0729302/IV (b)/1> where R is hydrogen or an alkyl group, such as to produce a water-dispersible starch ether or ester containing not substantially more than one said polymerizable olefinic group per 15 anhydro-glucose units.  Suitable starches include corn, waxy maize, potato, sago, wheat, rice, sweet potato and tapioca starches; these may be in their ungelatinized state or they may be gelatinized or converted by heat and/or acids or oxidizing agents to thin boiling starch, dextrine or British gum.  If desired, the gelatinization of the starch molecule may be effected during or after the formation of the dispersible ester or ether.  The dispersibility of the products may be reduced up to complete indispersibility in water by contacting them with a water-soluble free radical producing vinyl polymerization catalyst (see Group IV (a)) yielding products having application in the manufacture of high wet strength papers (see Group VIII) water-resistent sizes and coatings for textiles (see Group IV (c)) and adhesives.  In examples: (1) corn starch is suspended in aqueous caustic soda solution and methacrylic anhydride added slowly, a pH of 8-9 being maintained by addition of caustic soda and the resulting ester is still dispersible after cooking in water; (2) allyl bromide is added to a suspension of tapioca in aqueous caustic soda containing sodium sulphate to prevent gelatinization; (3) allyl chloroformate is added to a suspension of potato starch in aqueous sodium carbonate; (4) butadiene monoxide is added to a mixture of acid-converted waxy maize starch in aqueous caustic soda.  Acrylic acid anhydride is also mentioned.