Societa' Italiana Resine S.i.r. S.p.a.

Pierpaolo Buzio

Lucio Edefonti

Vito Galli

Gianluigi Argela'

Riccardo Balloni

Heat-sealable films are described which are constituted by a polyolefin film, particularly polypropylene, having on one surface thereof a layer of primer, applied in aqueous or aqueous-alcoholic solution, and chosen from: polyethylenimines, products of the condensation of urea or melamine with formaldehyde, particularly the etherified compounds; alkoxyalkyl melamine polyhydroxylates; or mixtures of the said compounds; and, on the other surface thereof, a layer of the said primer or one similar to the first, followed by a layer of vinyl, vinylidene or acrylic polymer or copolymer. The process for the production of these films includes the surface treatment of the polyolefin film by means of an electric discharge, flame or chemical agents, followed by the application of both surfaces, by means of an aqueous or aqueous-alcoholic solution, of a layer of primer chosen from: polyethylenimines, products of the condensation of urea or melamine with formaldehyde, particularly the etherified compounds; alkoxyalkyl melamine polyhydroxylates; or mixtures of the said compounds; and finally followed by the application, to one of the surfaces thus treated, of a layer of vinyl, vinylidene or acrylic polymer or copolymer. The heat-sealable films thus obtained have improved characteristics, particularly with regard to their printability, dimensional stability and residual solvent content both in the film per se, and when printed, and are particularly suitable for use in flow packing.

Heat-sealable polyolefin films and processes for their preparation

Flexible double-layer polypropylene laminate consisting essentially of a biaxially oriented film of isotactic polypropylene with an atactic polypropylene content of less than 6% by weight and an intrinsic viscosity of from 1.5 to 3 dl/g, adhesively bonded to a non-oriented film of isotactic polypropylene with an atactic polypropylene content of from 15 to 30% by weight, said polypropylene in said non-oriented film deriving directly from the polymerization of propylene and having an intrinsic viscosity of from 2 to 8 dl/g.

Flexible double-layer polypropylene laminates

A flexible double-layer polypropylene laminate consisting of a bioriented film consisting essentially of isotactic polypropylene with an atactic polypropylene content of less than 6% by weight and an intrinsic viscosity (standard ASTM D 1601) of from 1.5 to 3.0 dl/g, adhesively bonded with a non-oriented film consisting essentially of a mixture of isotactic polypropylene and atactic polypropylene, the latter in an amount of from 15 to 30% by weight of the total weight of the said mixture, the isotactic polypropylene of said mixture having an intrinsic viscosity (standard ASTM D 1601) of from 1.0 to 1.5 dl/g and the atactic polypropylene of said mixture having a density (standard ASTM D 1505) of from 0.855 to 0.865 g/cm.sup.3 and a viscosity at 160.degree. C. of from 3,000 to 10,000 cps.

Flexible double-layer polypropylene laminates for the packaging of food

A surface-activated polyolefin is coated by applying a solution in an organic solvent of a vinylidene copolymer material containing from 35 to 60 wt.% of vinylidene chloride, from 30 to 50 wt.% of alkyl ester of acrylic or methacrylic acid, from 1 to 10 wt.% of acrylic and/or methacrylic acids and from 1 to 10 wt.% of hydroxyalkyl ester of acrylic or methacrylic acid, a ratio of from 0.5:1 to 5:1 being maintained in the material between the number of carboxyl groups and the number of hydroxyl groups and said solution containing a latent catalyst for the cross-linking of said material, and heat-treating at 70.degree.-130.degree. C. said coated film to provoke said cross-linking. The coating shows an excellent adhesion to the film and improves the thermal weldability, impermeability and flexibility of the latter.

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Rho, Italy

Pierpaolo Buzio