Improvements in or relating to the sizing, coating and laminating of paper and paper-board

Primary amino-alkyl starch ethers and esters obtained by reacting starch, e.g. gelatinized, thin-boiling or oxidized starch, with b -chloroethylamine or its hydrochloride, b -aminoethyl sulphate, ethylene imine or a lactam such as b -propiolactam are used, e.g. together with oxidized starch, in sizes and adhesives in the manufacture of water-resistant paper, paperboard and laminates thereof (see Divisions D1 and D2). The sizes and adhesives contain water-soluble aldehydes e.g. formaldehyde, glyoxal, glutaraldehyde and a -hydroxyadipaldehyde, which may undergo condensation with the amino-alkyl starch derivative. According to the Provisional Specification, a secondary amino-alkyl may, alternatively, be used.ALSO:An aqueous adhesive composition for use in the manufacture of water-resistant paper &c. (see Divisions D1 and D2) comprises a primary amino-alkyl starch ether or ester and a hardening, water-soluble aldehyde and, if desired, sodium hexa-meta-phosphate and a pigment such as kaolin. Suitable ethers and esters are obtained by reacting starch, e.g. gelatinized, thin-boiling or oxidized starch, with b -chloroethylamine or its hydrochloride, b -aminoethyl sulphate, ethylene imine or a lactam such as b -propiolactam. Suitable aldehydes are : formaldehyde, glyoxal, glutaraldehyde and a -hydroxyadipaldehyde. Part of the ether or ester may be replaced by oxidized starch. The composition may have a pH value between 6 and 10. According to the Provisional Specification, a secondary amino-alkyl starch ether or ester may, alternatively, be used in the composition. Glyoxal may be present as polyglyoxal. A hardening agent containing at least two keto groups per molecule may be used instead of an aldehyde.ALSO:In making water-resistant paper, paper-board or a laminate thereof, an aqueous sizing or adhesive composition comprising an aqueous dispersion of a primary amino-alkyl starch ether or ester and an insolubilising, water-soluble aldehyde and, if desired, sodium hexa-meta-phosphate and a pigment such as kaolin, is applied to the paper or paper-board or to at least one of the adjacent surfaces of the laminae, and the paper, paper-board or laminate is then dried. Suitable ethers and esters may be obtained by reacting starch, e.g. gelatinised, thin-boiling or oxidised starch, with b -chloroethylamine or its hydrochloride, b -amino-ethyl sulphate, ethylene imine or a lactam such as b -propiolactam. Suitable aldehydes are:- formaldehyde, glyoxal, glutaraldehyde and a -h