Stock material or miscellaneous articles – Composite – Including interfacial reaction product of adjacent layers
Reexamination Certificate
2000-04-14
2001-01-30
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Including interfacial reaction product of adjacent layers
C428S424400, C428S342000, C428S351000, C428S3550RA, C428S3550AC, C428S511000, C524S832000, C524S833000
Reexamination Certificate
active
06180242
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to laminating adhesive compositions and, more particularly, to aqueous laminating adhesive compositions based on vinyl ester/acrylic copolymers for wet lamination of substrates.
BACKGROUND
There is a constant effort in the adhesives art to develop aqueous laminating adhesive compositions for wet lamination of substrates, for example packaging materials such as cardboard, that provide improved adhesion without requiring the addition of volatile organic solvents.
SUMMARY OF THE INVENTION
An aqueous adhesive composition is disclosed. The adhesive composition includes from about 30 weight percent to about 65 weight percent solids dispersed in an aqueous medium, wherein the solids comprise a polymer having repeating units derived from a vinyl ester monomer and having a glass transition temperature of about −15° C. to about +15° C. and from about 0.1 parts by weight to about 40 parts by weight of a plasticizer compound per 100 parts by weight of the polymer.
A laminated article is disclosed. The laminated article includes a first substrate layer, a second substrate layer and an adhesive layer interposed between the first and second substrate layers and bonding the first and second substrate layers together, wherein the adhesive layer comprises the solids portion of the above disclosed aqueous adhesive composition.
A method for making a laminated article wherein two substrate layers are bonded together by a dried layer of adhesive composition is disclosed. The method includes applying a wet layer of the above-described aqueous adhesive composition to a first substrate layer, covering the wet layer of adhesive composition with a second substrate layer and drying the layer of adhesive composition to form the laminated article.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive composition of the present invention includes a polymer having a glass transition temperature (T
g
) of about −15° C. to about +15° C.
In a preferred embodiment, the polymer has a T
g
of about −15° C. to about 0° C.
In a highly preferred embodiment, the polymer has a T
g
of about −15° C. to about −5° C.
The polymer is made by polymerizing a monomer or a mixture of monomers to provide a polymer having repeating units derived from the monomer or the respective monomers of the mixture. The identity and relative amounts of the monomers of the mixture are selected, according to methods known in the art, so that the polymer produced by polymerizing the monomer mixture exhibits a T
g
in the desired range.
The T
g
of a polymer of a proposed composition may be estimated by methods known in the art such as, for example, by calculating the weighted average of the T
g
values for homopolymers derived from the respective monomers M
1
, M
2
, . . . M
n
, of the reaction mixture, according to equation (1):
T
g
(
copolymer
)
=
∑
i
=
1
n
w
i
T
gi
(
1
)
wherein:
T
g
(copolymer) is the glass transition temperature calculated for the copolymer
w
i
is the weight fraction of monomer M
1
in the copolymer
T
gi
is the glass transition temperature of the homopolymer of M
i
.
The glass transition temperature of homopolymers may be found, for example, in “Polymer Handbook”, edited by J. Brandrup and E. H. Immergut, Interscience Publishers.
The polymer includes repeating units derived from a vinyl ester monomer. Suitable vinyl ester monomers include, for example, vinyl acetate, vinyl propionate, vinyl neononanoate, vinyl neodecanoate, vinyl 2-ethylhexanoate, vinyl pivalate, vinyl versatate and mixtures thereof.
In one embodiment, the polymer is a vinyl ester homopolymer, that is, a polymer wherein all the repeating units are identical to each other, having repeating units derived from a vinyl ester monomer.
In an alternative embodiment, the polymer is a vinyl ester copolymer, that is, a polymer wherein the repeating units are not identical to each other, having repeating units derived from a mixture of vinyl ester monomers.
In a third embodiment, the polymer is a vinyl ester/acrylic copolymer and includes first repeating units derived from a vinyl ester monomer and second repeating units derived from a (C
1
-C
12
)alkyl (meth)acrylate monomer. As used herein the terminology “(C
1
-C
12
)alkyl” denotes an alkyl substituent group having from 1 to 12 carbon atoms per group and the terminology “(meth)acrylate monomer” refers collectively to acrylate monomers and methacrylate monomers. Suitable (C
1
-C
12
)alkyl (meth)acrylate monomers include, for example, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate and mixtures thereof. Preferably, the alkyl (meth)acrylate monomer is butyl acrylate or
2
-ethylhexyl acrylate.
In a preferred embodiment, the polymer is a vinyl ester/acrylic copolymer that includes about 40 weight percent (wt %) to about 70 wt %, more preferably, about 40 wt % to about 60 wt %, repeating units each derived from a vinyl ester monomer and about 30 wt % to about 60 wt %, more preferably, about 40 wt % to about 60 wt %, repeating units each derived from a (C
1
-C
12
)alkyl (meth)acrylate monomer.
In a highly preferred embodiment, the polymer is a vinyl ester/acrylic copolymer includes up to about 10 wt%, more preferably up to about 5 wt %, third repeating units derived from a monoethylenically unsaturated polar monomer, provided that the vinyl ester/acrylic copolymer includes no more than 3 wt %, more preferably no more than 2 wt %, repeating units derived from a monoethylenically unsaturated carboxylic acid monomer. The terminology “monoethylenically unsaturated” means having a single site of ethylenic unsaturation per molecule. Suitable monoethylenically unsaturated polar monomers include, for example, (C
1
-C
8
)hydroxyalkyl (meth)acrylate monomers, wherein the terminology “(C
1
-C
8
) hydroxyalkyl” denotes a hydroxyalkyl substituent group having from 1 to 8 carbon atoms per group, and monoethylenically unsaturated carboxylic acid monomers. Suitable hydroxyalkyl (meth)acrylate monomers include, for example, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate and mixtures thereof. Suitable monoethylenically unsaturated carboxylic acid monomers include, for example, acrylic acid, methacrylic acid, itaconic acid, crotonoic acid, fumaric acid and mixtures thereof.
In a preferred embodiment, the polymer vinyl ester/acrylic copolymer that includes from about 0.1 wt % to about 10 wt % third repeating units derived from a monoethylenically unsaturated polar monomer. More preferably, the vinyl ester/acrylic copolymer includes from about 0.5 wt % to about 2 wt % third repeating units derived from a monoethylenically unsaturated carboxylic acid monomer.
The vinyl ester/acrylic copolymer may, optionally, be pre-crosslinked, that is crosslinked during synthesis of the copolymer, by including a small amount, for example, about 0.01 wt % to about 5 wt %, of a polyethylenically unsaturated monomer in the monomer mixture, wherein the terminology “polyethylenically unsaturated” means having two or more sites of ethylenic unsaturation per molecule. Suitable polyethylenically unsaturated monomers include, for example, allyl (meth)acrylate, diallyl phthalate, 1,4-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, divinyl ketone, N, N′-methylenediacrylimide, the polyallyl and polyvinyl ethers of pentaerythritol and mixtures thereof.
The polymer is made, for example, by free radical-initiated emulsion polymerization of a monomer or monomer mixture.
In a preferred embodiment, the polymer is made by an aqueous emulsion polymerization wherein a discontinuous monomer phase is dispersed in a continuous aqueous phase and polymerized in the presence of a colloidal stabilizer, for example, hydroxyethyl cellulose, carboxymethyl cellulose, poly(vinyl alcohol), partially hydrolyzed poly(vinyl alcohol), fully
Eisenhart Eric Karl
Graziano Louis Christopher
Jacobs Bradley Anson
Asinovsky Olga
Falk Stephen T.
Rohm and Haas Company
Seidleck James J.
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