Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1999-02-03
2002-07-30
Reddick, Judy M. (Department: 1713)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C156S060000, C156S278000, C156S280000, C156S306300, C156S327000, C427S207100, C427S316000, C427S393500
Reexamination Certificate
active
06426151
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improved aqueous based pressure sensitive adhesive emulsions, the improvement residing in the incorporation of polymerized units of a vinyl ester of a neo-acid into the copolymer present in these emulsions.
Pressure sensitive adhesives are widely used for fabricating paper labels, laminating polymeric films such as laminating poly(vinyl chloride), polyester, etc., for forming decals and other related products. Most of the pressure sensitive adhesives have been solvent based but in recent year government regulations have forced the industry to develop environmentally friendly aqueous based pressure sensitive adhesives.
Aqueous based pressure sensitive adhesives comprised of polymerized monomer units of vinyl acetate, ethylene, and/or acrylic esters, etc. have been inferior to the solvent based pressure sensitive adhesives in that they do not have sufficient adhesive power to low surface energy substrates nor do they have good water resistance and so forth.
The following patents describe a variety of emulsion polymers incorporating vinyl esters and/or emulsion based pressure sensitive adhesives:
U.S. Pat. No. 5,461,103 discloses aqueous based pressure sensitive adhesive emulsions having an ability to coat low energy surfaces without retracting or cratering. The emulsion polymers are prepared by a two stage emulsion polymerization process, the first stage resulting in the formation of an alkali insoluble polymeric system incorporating acid functional groups and polymerized hydrophobic monomer units, e.g., C
4-12
alkyl acrylates and the second stage incorporating monomer units suited for the manufacture of pressure sensitive adhesives, e.g., acrylic and methacrylic esters, vinyl esters of C
2-5
carboxylic acids, e.g., vinyl acetate and vinyl propionate and the like.
U.S. Pat. No. 4,923,919 discloses pressure sensitive adhesive emulsions based on acrylic polymers that contain at least 40% by weight of an alkyl acrylate and a support resin that is alkali soluble. The support resin contains polymerizable carboxylic acid anhydride groups with the polymeric resin having a umber average molecular weight of from 1000-15,000. Typically the support resins are based on vinyl monomers such as acrylic and methacrylic acid esters, styrene and combinations thereof.
U.S. Pat. No. 4,322,516 discloses aqueous based pressure sensitive adhesives formed from ethylene units, acrylic ester units, vinyl acetate units, acrylamide units and other olefinically unsaturated monomers. Tackifying agents are incorporated into the ethylene based pressure sensitive adhesives.
U.S. Pat. No. 4,939,190 discloses emulsion type pressure sensitive adhesives wherein the emulsions are prepared in a staged procedure, the first stage comprising polymerizing an ethylenically unsaturated monomer such as styrene, acrylonitrile and/or (meth)acrylates in the presence of a tackifier resin and a second stage comprising polymerizing alkyl acrylates having at least 4 carbon atoms in the presence of the first stage polymer.
U.S. Pat. No. 5,276,084 discloses aqueous based pressure sensitive adhesives based on polymers comprising vinyl acetate, ethylene, alkyl acrylates dialkyl maleate and fumarates, hydroxyalkyl acrylates, acrylamides and unsaturated carboxylic acids such as acrylic acid.
U.S. Pat. No. 3,697,618 discloses acrylic pressure sensitive adhesives incorporating a vinyl ester of a carboxylic acid, e.g., vinyl acetate, a lower alkyl acrylate and a copolymerizable alpha, beta-ethylenically unsaturated dicarboxylic acid or anhydride.
U.S. Pat. No. 3,562,229 discloses solvent polymerized copolymers of ethylene and vinyl esters where the vinyl esters are derived from long chain carboxylic acids, e.g., versatic acid which are mixtures of C
9-11
carboxylic acids. Isotridecanoic and isononanoic are representative acids. The solvent based polymers incorporating vinyl esters of versatic acid were alleged to be superior to polymers incorporating vinyl laurate which has the same number of carbon atoms.
U.S. Pat. No. 3,294,727 discloses polymerizing vinyl esters of saturated monocarboxylic acids to form emulsions having suitability for producing freeze-thaw stable paints. The preferred saturated aliphatic monocarboxylic acids for forming vinyl esters are based upon compounds of the formula:
wherein R
1
and R
2
are alkyl radicals of normal, branched, or cyclic structure and R
3
represents a hydrogen or hydrocarbyl radical. The carboxylic acids have from about 9-19 carbon atoms. Representative copolymers are comprised of polymerized units of vinyl acetate and/or acrylic acid and the representative vinyl esters.
U.S. Pat. No. 3,669,942 discloses solvent based polymers comprising a vinyl ester of an alpha-branched, saturated aliphatic monocarboxylic acid having from 5-20 carbon atoms and an alpha, beta-ethylenically unsaturated carboxylic acid having 3-5 carbon atoms, a monovinyl aromatic compound and acrylic acid esters including hydroxyalkyl acrylate esters. The compositions are useful as water thinnable paint binders.
U.S. Pat. No. 3,654,213 discloses tacky pressure sensitive adhesives based on interpolymers of vinyl esters and alkyl acrylates, the interpolymers being dissolved at high solids content in organic solvents. Representative interpolymers are based upon vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl valerate with vinyl acetate being preferred. Other monomers which can be incorporated into the polymer include acrylic acid esters such as methyl acrylate, ethyl acrylate and so forth.
U.S. Pat. No. 4,322,516 discloses pressure sensitive adhesive emulsions whose copolymers comprise:
(a) 10-30 wt % ethylene,
(b) 29-69 wt % acrylic aciesters of alcohols,
(c) 20-55 wt % vinyl acetate,
(d) 0.2-8 wt % (meth)acrylamide, and
(e) 0-12 wt % other olefinically unsaturated comonomers.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to improved aqueous based pressure sensitive adhesive emulsion polymers. Conventional aqueous emulsion based pressure sensitive adhesives are comprised of a copolymer comprised of polymerized units of acrylic esters and ethylenically unsaturated monomers, the copolymer having a T
g
of from −15 to −70° C. The improvement in the aqueous based, emulsion polymerized pressure sensitive adhesives resides in the incorporation of a vinyl ester of a C
8-13
neo-acid into the copolymers present in the pressure sensitive adhesives. Such copolymers incorporate a vinyl ester formed from a mixture of propylene oligomers and such vinyl ester is represented by the chemical formula:
C
8-13
H
17-27
CO
2
CH═CH
2
There are significant advantages associated with the above aqueous based pressure sensitive adhesive emulsions and the process for producing these emulsions and these advantages include:
an ability to provide enhanced properties to pressure sensitive adhesives through the methyl group rich vinyl aster mixture which exhibits a lower solubility parameter compared to t he corresponding linear alkyl vinyl esters;
an ability to provide enhanced properties to pressure sensitive adhesives through the ability of the vinyl ester monomer to undergo emulsion polymerization with a variety of olefincally unsaturated comonomers;
an ability to form an excellent bond and enhanced resistance to plasticizer migration with plasticized poly(vinyl chloride);
an ability to generate a class of pressure sensitive adhesives which have an excellent balance of peel and cohesive strength;
an ability to provide enhanced thermal and hydrolytic stability to emulsion based pressure sensitive adhesives is compared to aqueous based vinyl acetate counterparts; and,
an ability to provide enhanced properties to pressure sensitive adhesives through binding to lower surface energy surfaces of lower polarity, such as polyethylene, by virtue of stronger bonding of the copolymers
DETAILED DESCRIPTION OF THE INVENTION
Emulsion polymerization of ethylenically unsaturated monomers such as lower alkyl acrylates and vinyl esters, typically represented by vinyl acet
Kem Kenneth Merle
Mao Chung-Ling
Air Products and Chemicals Inc.
Bongiorno Mary E.
Brewer Russell L.
Reddick Judy M.
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