Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-09-15
2002-08-06
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S016000, C522S037000, C522S042000, C522S044000, C522S046000, C522S050000, C522S053000, C522S093000, C522S095000, C522S096000, C522S120000, C522S121000, C522S141000, C522S142000, C526S328000, C526S328500, C526S322000
Reexamination Certificate
active
06429235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present disclosure relates to adhesives, and particularly to pressure sensitive adhesives derived from energy-curable polymer-forming compositions.
2. Background of the Related Art
Pressure sensitive adhesives are known in the art. A pressure sensitive adhesive (“PSA”) is one which in dry form is aggressively and permanently tacky at room temperature and which firmly adheres to a variety of dissimilar surfaces upon mere contact without the need of more than finger or hand pressure. PSA requires no activation by heat or solvents. It should have a sufficiently cohesive holding and elastic nature so that it can be removed from a surface without leaving a residue. PSAs are generally used in adhesive tapes and labels. An adhesive tape typically includes a substrate, i.e., a backing, to which the PSA is applied. Usually a primer is used to treat the surface of the backing to provide greater anchoring of the PSA. If the tape is stored in a rolled configuration the opposite surface of the backing is generally coated with a release coating, such as silicone, to allow unrolling of the tape.
Various types of PSAs are known. For example, PSA can be made from tackified natural or synthetic rubbers, ethylene-vinyl acetate copolymers, acrylics, vinyl acetate copolymers, silicones, and polymerized vinyl alkyl ethers.
Hot melt type PSAs are typically heated to a temperature sufficient to render the PSA sufficiently fluid so that it can be applied to a substrate.
Solution type PSA's are generally dissolved in a solvent to form a fluid which can be applied to a substrate. The solvent is thereafter evaporated to form the PSA coating.
Energy-curable formulations for making PSAs typically include unsaturated monomers or oligomers, especially acrylate type compounds. Such formulations also typically include a photoinitiator which is responsive to, for example, ultraviolet radiation (UV) for initiating polymerization. Such formulations are applied to a substrate as a fluid prepolymer, and are thereafter polymerized to form the PSA layer.
The properties of the PSA can be tailored by altering the type and/or composition percentage of the components in the formulation. However, it is not uncommon that improvement in one property of the PSA results in a detrimental change in another. For example, to increase the peel strength of the PSA a higher softening point tackifier can be used, or the content of di-or multi-functional oligomer resin can be increased. However, in each case, the PSA tack is reduced. What is needed is a method which can be used to improve the peel strength, while not incurring a corresponding detriment to the tack.
SUMMARY
An energy-curable polymer-forming composition is provided herein which includes an unsaturated oligomer resin and a compound of the general formula:
CH
2
═C(R
1
)—COO—R
2
—O—C(O)—CR
3
R
4
—CR
5
R
6
(—CR
7
R
8
)
n
—COOH
wherein R
1
is hydrogen or methyl, R
2
is a substituted or unsubstituted alkylene group having from 2 to about 6 carbon atoms, and R
3
, R
4
, R
5
, R
6
, R
7
, and R
8
are independently selected from the group consisting of hydrogen and the other of said groups R
3
and R
4
is a straight or branched chain, saturated or unsaturated aliphatic, cycloaliphatic, or polycycloaliphatic groups possessing from 1 to about 20 carbon atoms, subject to the provision that at least one of groups R
3
, R
4
, R
5
, R
6
, R
7
, and R
8
is, other than hydrogen, and n is 0 or 1.
The pressure sensitive adhesive derived from the composition described herein exhibits improved peel strength and tack.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
All quantities appearing hereafter shall be understood to be modified by the term “about” except in the Examples and where otherwise indicated.
The energy-curable PSA formulation of the present invention includes an unsaturated oligomer resin and a novel adhesion promoter discussed in detail below. The PSA formulation advantageously also includes a tackifier, chain extender and/or reactive diluent, and optionally a polymerization initiator and antioxidant. Various other optional additives can also be incorporated into the PSA formulation, such as plasticizers, fillers, colorants, fibers, glass or polymeric particles, electrically or thermally conducting particles, and other such materials known in the art.
A range of typical component percentages for energy-curable PSA formulations is given below in Table I.
TABLE I
(% by Weight)
Component
Broad Range
Preferred Range
Oligomer Resin
from 10% to 70%
from 30% to 40%
Chain Extender
from 0% to 50%
from 20% to 30%
Reactive Diluent
from 0% to 50%
from 2% to 10%
Tackifier
from 5% to 50%
from 10% to 30%
Adhesion Promoter
from 0% to 50%
from 2% to 10%
Polymerization Initiator
from 0.1% to 20%
from 3% to 10%
Antioxidant
from 0% to 5%
from 0.5% to 2%
Polymerization Stabilizer
from 0.01% to 1%
from 0.05% to 0.2%
Referring now more specifically to the individual components, the oligomers used in the energy-curable PSA formulation are liquid at room temperature without adding solvent thereto and contain at least one unsaturated double bond at terminals or side chains of the molecule.
These liquid oligomers can be synthesized by various, for example, methods such as:
(1) A condensation polymerization process by reacting a diol and a diacid or diester with a number average molecular weight of from about 500 g/mole to about 40,000 g/mole in a suitable organic solvent by a conventional solution polymerization, and then reacting the hydroxyl groups on the resulting polyester with an acrylic or methacrylic acid in the presence of a polymerization inhibitor and a catalyst to introduce olefinic unsaturated bonds into the resin;
(2) A condensation polymerization process by reacting a diamine and a diacid or diester with a number average molecular weight of from about 500 g/mole to about 40,000 g/mole, and then reacting the hydroxyl groups on the resulting polyamide with an acrylic or methacrylic acid in the presence of a polymerization inhibitor and a catalyst to introduce olefinic unsaturated bonds into the resin;
(3) A condensation polymerization process by reacting a diol and a diisocyanate with a number average molecular weight of from about 500 g/mole to about 40,000 g/mole, and then reacting the resulting compound (half urethane) with a hydroxyl terminated acrylic molecule to introduce olefinic unsaturated bonds into the resin;
(4) A condensation polymerization by reacting a polyether and a diisocyanate with excess isocyanate functionality having a number average molecular weight of from about 500 g/mole to about 40,000 g/mole, and then reacting the resulting compound (half urethane) with a hydroxyl terminated acrylic molecule in the presence of a polymerization inhibitor and a catalyst to introduce olefinic unsaturated bonds into the resin;
(5) A condensation polymerization by reacting a diol and diacid or diester with excess functionality and having a number average molecular weight of from about 500 g/mole to about 40,000 g/mole, and then reacting the resulting compound with an unsaturated monomer having an epoxy group in the presence of a polymerization inhibitor and a catalyst to introduce olefinic unsaturated bonds into the resin;
(6) A polymerization process by reacting a hydroxyl terminated polyether and a diisocyanate, diol, or dicarboxylic acid with a number average molecular weight of from about 500 g/mole to about 40,000 g/mole, and then reacting the resulting epoxy functional compound with a carboxylic acid pendent vinyl monomer in the presence of a polymerization inhibitor and a catalyst to introduce olefinic unsaturated bonds into the resin.
The polyester compounds referred to above may be produced from linear, branched, or cyclic aliphatic or aryl diols or diacids such as, for example, neopentane diol, hexamethylene diol, cyclohexane diol, phthalic acid, adipic acid, or the like. The diisocyanate compounds can be, for example, tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or t
Chen Ning
Marzuki Arifin
Narayan Ramesh
Varlemann Ulrike
Berman Susan W.
Cognis Corporation
Drach John E.
LandOfFree
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