Dupont Canada Inc.

Peter Y Kelly

John R Boocock

Trevor C Arthurs

Wayne F Bryce

David John Mitchell

Brian L Hetherington

A silicone-containing resin, film and film on a subweb are described. The resin and film are formed from (i) polyolefin, (ii) dimethyl polysiloxane having functional end-groups, (iii) vinyl silane compound, and (iv) ultra-high molecular weight silicone polymer optionally using (v) an organo-peroxide agent and (vi) an organo-metallic moisture curing agent. Resins consisting essentially of (a) functionalized polyolefins; (b) dimethyl polysiloxanes having functional end-groups to react with said functionalized polyolefins; (c) ultra-high molecular weight silicone and optional organo-metallic moisture curing agent and films or multilayer structures made therefrom are also described. The film is suitable for use in release films and in liquid-absorbing products.

Silicone-containing polyolefin film

A method for the grafting of a monomer onto a polyolefin in the presence of an organic peroxide is disclosed. The polyolefin is a polyolefin that, when molten, undergoes cross-linking in the presence of the organic peroxide. The method comprises: (a) admixing the polyolefin in an extruder with 25 to 6000 ppm, based on the weight of the polyolefin, of an organic peroxide coated onto a carrier polymer and up to 5%, by weight of the polyolefin, of a grafting monomer capable of being grafted onto the polyolefin in the presence of the organic peroxide. The admixture is heated to a temperature above the melting point of both the polyolefin and the carrier polymer under admixing conditions to effect grafting of said grafting monomer onto the polyolefin, said carrier polymer undergoing chain scission in preference to cross-linking in the presence of the organic peroxide at said temperature. Grafted polyolefin is extruded from the extruder. The method may be used to produce grafted polyolefins with lower levels of gels and specks, especially for use in films and adhesives.

Grafting of monomers onto polyolefins in presence of organic peroxides

An adhesive composition formed by admixing under melt conditions (a) 50-95% by weight of a moisture cross-linkable silane-grafted polyolefin having a melt viscosity of less than 100,000 cps, and (b) 5-50% by weight of a polyolefin grafted with at least one ethylenically-unsaturated carboxylic acid or anhydride, and derivatives thereof. The grafted polyolefin has a melt viscosity of less than 100,000 cps, and contains a catalyst for moisture cross-linking of the silane-grafted polyolefin of (a). The adhesive may be used to bond a variety of substrates.

Cross-linkable adhesive polymers

An adhesive composition formed by admixing under melt conditions (a) 50-95% by weight of a moisture cross-linkable silane-grafted polyolefin having a melt viscosity of less than 100 000 cps, and (b) 5-50% by weight of a polyolefin grafted with at least one ethylenically-unsaturated carboxylic acid or anhydride, and derivatives thereof. The grafted polyolefin has a melt viscosity of less than 100 000 cps, and contains a catalyst for moisture cross-linking of the silane-grafted polyolefin of (a). The adhesive may be used to bond a variety of substrates.

Polyolefin coatings and films having release characteristics, also known as release sheets, are disclosed. The release sheets are formed by treating a sheet formed from polyolefin and dimethyl polysiloxane having functional end groups with a corona discharge. In a preferred embodiment, the release sheet is formed from polyolefin, the dimethyl polysiloxane, vinyl silane, an agent to graft the vinyl silane onto the polyolefin and a moisture curing agent by extrusion in the form of sheet, treating the sheet with a corona discharge and then subjecting the sheet to moisture. The release sheets may be used, for instance, as the backing sheet for labels.

Corona-discharge treated release films

A method for the manufacture of a physical blend of pigment and a polymer powder whereby polymer powder having a particle size in the range of 250 to 750 microns is fed to a high intensity mixer and then powdered pigment is fed to the mixer at a rate of not more than 0.5 parts of pigment per 100 parts of polymer per minute. The pigment has a particle size that is substantially smaller than that of the polymer powder. The resultant admixture is mixed for a further period of time and then discharged from the mixer. The method is particularly applicable to powdered polyethylene intended for use in a rotational moulding process e.g. for the manufacture of containers and other hollow articles.

Preparation of physical blends of polymers and pigments

The present invention relates to an improvement in a method for thermoforming of containers from thermoplastic materials in which method the rim of the container is formed as an integral part of the pre-form from which the container is thermoformed. The pre-form is obtained by introducing thermoplastic material into a closed space and then mechanically compressing the material. The improvement of the present invention relates to improved uniformity of flow of the thermoplastic material into the closed space, the use of a closed space defined by surfaces having a surface roughness in the range of 50-125 .mu.m rms and to a modified sequence of steps for forming the pre-form in which the compression of the thermoplastic material is commenced prior to the completion of the introduction of the material into the closed space. The process may be used in the manufacture of containers, e.g., for the packaging of margarine, from polyethylene or polypropylene.

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Kingston, Canada

Peter Y Kelly