Silicone containing laminate adhesive

Details Silicone containing laminate adhesive Silicone containing laminate adhesive

1999-07-15

2003-02-04

Gallagher, John J. (Department: 1733)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C156S273700, C156S329000, C528S026000, C528S392000

Reexamination Certificate

active

06514584

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to silicone containing laminates having barrier properties which are useful in packaging applications.
BACKGROUND OF THE INVENTION
It is well known that coatings containing silane compounds and itaconic acid improve the gas, oil, and flavor barrier performance of organic polymer film substrates. Moreover, the adhesion of the coating to the film surface, as well as the improved barrier characteristics provided by the silane coating, are greatly enhanced by exposing the coated film to electron beam radiation.
A particularly useful barrier composition is described in U.S. Pat. No. 5,215,822, which teaches a methanol solution of a vinyl benzyl amine silane (Dow Corning Corp. Z-6032), itaconic acid, and water; coating this solution on a corona treated low density polyethylene film, drying, and then subjecting the coated film to electron beam radiation to graft the coating to the film surface and further improve the barrier properties of the silane coating. However, while this coating gives excellent gas barrier properties at low to moderate relative humidity values, the gas permeability increases drastically at very high relative humidity values. The present inventors have surprisingly discovered that the combination of an aminofunctional silane, a multifunctional acrylate and an ethylenically unsaturated acid gives excellent gas barrier properties at low to moderate relative humidity values, as well as excellent gas barrier properties at very high relative humidity values.
While other patents teach the combination of a mono or multifunctional acrylate with an aminofunctional silane, none teaches the addition of the ethylenically unsaturated acid with an acrylate. For example, U.S. Pat. No. 5,368,941 teaches a deformable, abrasion-resistant coating formulated from at least one multi-functional acrylate monomer, at least one aminofunctional silane, colloidal silica and at least one acrylate-terminated polyalkylene oxide, but does not teach the addition of an ethylenically unsaturated acid. The acrylate-terminated polyalkylene oxide helps prevent gelling of the coating composition during stripping and also imparts the composition with deformability, without sacrificing abrasion resistance. Also, U.S. Pat. No. 5,434,007 teaches a silane resin coated on a plastic film, where the silane resin is composed of a monofunctional acrylate and an aminofunctional silane. The composition does not utilize a free radical cure, nor does it incorporate the ethylenically unsaturated acid.
U.S. Pat. Nos. 5,260,350 and 5,374,483 relate to a silicone coating composition which, when cured on a solid substrate either by ultraviolet or electron beam radiation, provides a transparent abrasion resistant coating firmly adhered thereon. The silicone coating is prepared by reacting at least one multifunctional acrylate monomer with an amino-organofunctional silane, mixing the modified silane with at least one acrylic monomer and thereafter adding colloidal silica. Again however, neither of these compositions teach the addition of an ethylenically unsaturated acid to achieve barrier properties.
JP (Kokai) publication 7-18221 published on Jan. 20, 1995 teaches a surface treatment composition for gas barrier comprising an aminosilane and a compound having an aromatic ring or hydrogenated ring. The present invention is distinguishable, however, because it does not require the addition of cyclic compounds having an aromatic ring.
The present invention is distinguishable from the prior art because none teach the addition of a polymerizable additive to achieve gas barrier properties, nor do they teach a composition having both barrier and adhesive characteristics.
SUMMARY OF THE INVENTION
The invention comprises a laminate structure made by the following method:
coating at least one side of a substrate with a laminating adhesive,
bringing a coated side of said substrate into contact with a second substrate to form a multi-layer film,
and curing said multi-layer film by initiating a free-radical reaction after the second substrate is contacted with the first substrate, wherein said laminating adhesive is the reaction product of a multifunctional acrylate, an amninofunctional silane, and an ethylenically unsaturated acid,
optionally dissolved in a solvent, wherein the multifunctional acrylate has a molecular weight of from 100 to 3000, and the aminofunctional silane has at least one molecule of the formula
wherein
0≦a≦4
R
1
is independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, acryl, methacryl, alkylaryl, R
2
—SiR
m
(OR)
3−m
, or an alkylene linking group having 2 to 12 carbon atoms connected to one or two nitrogen atoms, with the proviso that at least one R
1
is a hydrogen atom and at least one R
1
is an R
2
—SiR
m
(OR)
3−m
group, where m is 0, 1 or 2, and R is independently a hydrogen or an all group having from 1 to 6 carbon atoms;
R
2
is independently selected from the group consisting of:
linear or branched alkylene groups having from 1 to 12 carbon atoms;
arylene groups having from 6 to 12 carbon atoms; and
linear or branched hydrocarbon groups having from 1 to 16 carbon atoms and at least one alcohol, alcohol ether, ester, amide, urea, thiourea or polyether group.
The invention is a laminate, which can be made from a variety of substrates. The laminate can then be used alone or with other substrates to give structural or barrier properties to packaging containers. The laminate adhesive can be further cured by drying in the presence of water prior to exposure to electron beam irradiation.
A composition according to the present invention may be employed to provide a barrier layer which improves resistance of the material to transmission of gases and aromas therethrough. For example, a 30 &mgr;m uncoated biaxilly oriented, corona treated polypropylene film is generally found to have a permeability to oxygen of 1500 ml/m
2
/day as measured at ASTM D3985-81 measured at 80% relative humidity. With the present coatings, the oxygen transmission rate of the same film can be reduced to less than 250 ml/m
2
/day as measured at 80% relative humidity. As used herein, the terminology “improved barrier” refers to a coating which can reduce oxygen transmission rate of the aforementioned uncoated polypropylene film from 1500 ml/m
2
/day to 250 ml/m
2
/day as measured at ASTM D3985-81 measured at 80% relative humidity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
While the invention is susceptible of embodiment in many different forms there is described herein in detail preferred and alternate embodiments of the invention.
Aminofunctional Silanes
The aminofunctional silanes are described generally by the formula:
wherein
0≦a≦4
R
1
is independently hydrogen, alkyl substituted alkyl, aryl, substituted aryl, arylalkyl, acryl, methacryl, alkylaryl, R
2
—SiR
m
(OR)
3−m
, or an alkylene linking group having 2 to 12 carbon atoms connected to one or two nitrogen atoms, with the proviso that at least one R
1
is a hydrogen atom and at least one R
1
is an R
2
—SiR
m
(OR)
3−m
group, where m is 0, 1 or 2, and R is independently a hydrogen or an alkyl group having from 1 to 6 carbon atoms;
R
2
is independently selected from the group consisting of:
linear or branched alkylene groups having from 1 to 12 carbon atoms;
arylene groups having from 6 to 12 carbon atoms; and
linear or branched hydrocarbon groups having from 1 to 16 carbon atoms and at least one alcohol, alcohol ether, ester, amide, urea, thiourea or polyether group.
The most preferred aminofunctional silanes useful for the present invention are N-(2-aminoethyl)-3-aminopropyltrimethoxy silane. and aminopropyltriethoxysilane, and blends thereof.
For the purpose of the present invention, the above mentioned amine functional silane has the general formula
In the above formula, R
1
is a monovalent radical independently selected from the group consisting of hydrogen; acryl, methacryl, alkyl groups having 1 to 18 carbon atoms, such as methyl, ethyl, propyl, isobutyl,

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