SINGLE- OR MULTI-LAYER FILM CONTAINING RELATED POLYVINYL ALCOHOL Russian patent published in 2017 - IPC A22C13/00 

FIELD: chemistry.

SUBSTANCE: single- or multi-layer film made on the basis of a mixture of (co) polyamide and polyvinyl alcohol (PVA) soluble in, at least, one solvent A containing more than 50% of water, wherein the film comprises polyvinyl alcohol-PVA_S, soluble in the same solvent A, and bound polyvinyl alcohol-PVA_B, which (i) is practically insoluble in the same solvent A at a temperature of 18°C to the initial boiling point at normal pressure, (ii) is soluble in, at least, one of the solvents that dissolve (co) polyamide, (iii) gives a colour reaction with iodine typical for PVA, and (iv) reacts with, at least, one primary amine to form a water-soluble PVA. The ratio A_b/A_s, where C_b - a content of PVA_B in a film becoming water-soluble after its treatment with primary amine, C_s - a content of PVA_S in the film, is not less than 0.05. The technology for the production of this film includes the steps of preparing the polymer raw materials, including thermal and, if necessary, thermo-oxidative treatment of PVA used as a polymeric raw material and (co) extruding the film from the melt, wherein directly for the film (co) extrusion, a granular raw material is used, containing, at least, one of the two components, including PVA_B in the proportion of the soluble PVA corresponding to the above-mentioned condition, in the composition of the granulated mixture containing (co) polyamide and PVA, and carbonyl modified PVA, the product of thermo-oxidative and/or thermal degradation of PVA, a 4% predominantly aqueous solution of which in excess of 1,4-dinitrophenylhydrazine has an optical density of not less than 0.1 at a wavelength of 490 nm, in the composition of any PVA-containing granular raw material. The proposed single- or multi-layer film can be used, in particular, as a sausage casing.

EFFECT: stability of the manufacturing process and the mechanical strength of the film are improved.

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