Laminates of polyolefin-based film and metal and processes for p

Details Laminates of polyolefin-based film and metal and processes for p Laminates of polyolefin-based film and metal and processes for p

1989-06-09

1990-12-25

Seidleck, James

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

156321, 156327, 428 364, 428331, 428461, 4284758, 428516, B32B 1508, B32B 3126, B32B 516

Patent

active

049802100

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND

This invention relates to laminated materials comprising a polyolefin-based film bonded to a surface of a metal sheet.
Polyolefin coated metal strip has been used for various purposes and has a number of useful properties, but the previously available material has significant limitations as a material for making cans and can ends. In particular, coatings of polypropylene and polyethylene are relatively soft as compared with the lacquers conventionally used for coating can ends. As a result, polyolefin coatings tend to fibrillate during the conventional double seaming of a can end to a can body. The result is unsightly and renders the coating ineffective for protecting the metal of the can end.


OBJECT AND SUMMARY OF PREFERRED FORMS OF INVENTION

An object of the present invention is to provide a laminated material comprising a polyolefin-based film bonded to a metal sheet which will not be subject to this disadvantage, while retaining the known useful properties of such materials.
According to the present invention, in a laminated material comprising a polyolefin-based film bonded to one major surface of a metal sheet, the polyolefin-based film (B) is a multi-layer co-extruded film comprising an inner layer (B1) of a bonding resin which is an acid-modified polyolefin resin containing carboxyl or anhydride groups and an outer layer (B2) of a polyolefin or a polyamide containing 0.15% to 0.5% by weight of a finely divided non-reactive low-opacity synthetic silica having an average particle size in the range of 0.5 to 5 microns. The term "non-reactive" is used herein to indicate that the silica does not react with the other materials of the laminate, i.e. the polyolefin or polyamide and the metal.
It has been surprisingly found that the addition of such small quantities of synthetic silica, with an average particle size of 0.5 to 5 microns, produces a marked improvement in the performance of the material, when formed into can ends and double seamed to a can body, without affecting the appearance of the coating or its adhesion to the metal. It is of course known to incorporate inorganic pigments into polyolefin coatings, but these pigments are used in much greater amounts and are not found to have any effect in improving the performance of the coatings during double seaming. Addition of small quantities of inorganic materials such as silica to polypropylene films is also well known for the purpose of reducing blocking, but these films have not been employed in forming laminates with metal strip, and it is surprising that such additions can enhance the performance of the coating in double seaming since it has been found that comparable organic slip agents have no such beneficial effect.
Preferably the outer layer (B2), if of a polyolefin, is polypropylene or an ethylene-propylene copolymer, or if of a polyamide, is nylon 6.
The bonding resin layer (B1) is an acid-modified polyolefin resin containing carboxyl or anhydride groups. Typical acids for use in preparing such acid-modified polymers are ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, and itaconic acid. Typical anhydrides used for the same purpose are ethylenically unsaturated carboxylic anhydrides such as maleic anhydride.
The acid groups can be present as copolymers of ethylene, for example ethylene/acrylic acid (EAA) or ethylene/methacrylic acid (EMAA). Typically the acid concentration is 5 to 15%.
The acid modification of the acid modified polymers can be obtained, for example, by grafting maleic anhydride to a polyolefin such as polypropylene, polyethylene, ethylenepropylene or ethylene-vinylacetate copolymer. The graft can be introduced by techniques such as reacting maleic anhydride with polyolefin in solution in an organic solvent and using a free radical catalyst such as dibenzoyl peroxide or dicumyl peroxide. Alternatively, an active centre can be introduced into the polymer by using high energy radiation such as gamma rays or X-rays and then reacting the

REFERENCES:
patent: 4358493 (1982-11-01), Ohtsuki et al.
patent: 4451506 (1984-05-01), Kobayashi et al.
patent: 4695492 (1987-09-01), Godar

Affiliated with

Also associated with

Rating

Laminates of polyolefin-based film and metal and processes for p does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Laminates of polyolefin-based film and metal and processes for p, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laminates of polyolefin-based film and metal and processes for p will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1161831