Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1994-08-11
2001-08-14
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S098000, C525S314000, C524S485000
Reexamination Certificate
active
06274666
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to polymers for use in adhesive compositions and to adhesive compositions containing such polymers.
BACKGROUND OF THE INVENTION
Adhesives have been used for various industrial purposes. Two major application processes are sprayable and fine-line application of hot melt adhesives. Of particular interest in such application methods are the viscosity of the hot melt adhesive at coating or spraying temperatures and cohesive strength of the adhesive itself. Other important properties include tack, adhesion to substrate and aging.
As base polymers of hot-melt adhesives, various polymers have been used such as polymers such as ethylene-vinyl acetate copolymers, block copolymers of conjugated dienes and vinyl aromatic hydrocarbons, ethylene-&agr;-olefin copolymers, and polyester resins. Block copolymers are particularly preferred as adhesives because of possessing a relatively favorable balance between adhesive properties and creep resistance. Furthermore, butadiene-styrene block polymers are especially preferred as adhesives due to relatively low cost, excellent balancing of properties and good aging.
U.S. Pat. No. 4,792,584 (Shiraki et al.) discloses an adhesive composition containing a block copolymer containing at least one polymer block composed mainly of a vinyl aromatic hydrocarbon and at least one polymer block composed mainly of butadiene. The block copolymer is characterized by the fact that the vinyl aromatic hydrocarbon content [S] as measured by weight percent of the total block copolymer is 10 to 30% by weight of the block copolymer and the vinyl content [V] of the butadiene monomer contributed units in the block copolymer is 20 to 50%. To prepare an acceptable adhesive, the vinyl aromatic hydrocarbon content [S] and the vinyl content of the butadiene portion [V] must satisfy the following formula:
40≦[
S]+[V]≦
70.
According to this disclosure if the total vinyl aromatic hydrocarbon content and the vinyl content of the butadiene portion is outside the above range, the initial tack of the resultant adhesive is insufficient.
Applicants have discovered, contrary to the teachings of U.S. Pat. No. 4,792,584, that a block copolymer of high styrene and high vinyl content in the butadiene portion exhibits an excellent combination of low melt viscosity and high adhesive tensile while maintaining other adhesive properties. Block polymers containing styrene contents over 30% and a vinyl content in the butadiene portion which exceeds 35% are particularly preferred. These results are in complete opposition to the teachings of U.S. Pat. No. 4,792,584.
It is therefore an object of the present invention to provide block copolymers exhibiting excellent adhesive tensile strength and low melt viscosity while maintaining other desirable physical and adhesive properties. It is a further object of the present invention to provide adhesive compositions containing block copolymers having high adhesive tensile strength and low melt viscosity.
SUMMARY OF THE INVENTION
It has been discovered that block copolymers containing at least two polymer blocks formed from a vinyl aromatic hydrocarbon monomers and at least one polymer block compound formed from conjugated diene monomers exhibit very desirable properties when utilized in adhesive compositions. The vinyl aromatic hydrocarbon content [S] of the instant block copolymers is 25% to 60% by weight and the 1,2-vinyl content of the conjugated diene portion [V] is 30% to 70%. The block copolymers possess a vinyl aromatic hydrocarbon content [S] and a vinyl (1,2-microstructure) content of the conjugated diene portion [V] satisfying the formula:
75≦[
S]+[V]≦
100.
The “vinyl aromatic hydrocarbon content [S]” is expressed in percent by weight of the vinyl aromatic hydrocarbon contributed units per weight of the block copolymer. The “vinyl content [V]” of the conjugated diene portion is the percentage of conjugated diene monomers units polymerized having a vinyl (1,2-microstructure) structure of the total diene monomer contributed units in the block copolymer. The diene units polymerize in either the form of 1,4-microstructure or 1,2-microstructure. The vinyl or 1,2-microstructure percentage can be calculated by determining the vinyl content in the conjugated diene portion using an infrared spectrometer, NMR apparatus or the like.
The preferred vinyl aromatic hydrocarbon monomer is styrene and the preferred conjugated diene monomer is butadiene. The preferred relationship between the vinyl aromatic hydrocarbon content [S] and the vinyl content [V] of the conjugated diene portion satisfies the formula:
90≦[
S]+[V]<
100
According to the instant invention, adhesive compositions exhibiting superior adhesive tensile strength may be prepared containing about 10% to about 50% of the instant thermoplastic elastomers, about 20% to about 80% of a compatible tackifying resin; about 10% to about 40% of a plasticizing oil; about 0.2% to about 2.5% of various stabilizers and 0% to about 10% of a compatible wax.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The block copolymers prepared in accordance with this invention are prepared by the copolymerization of conjugated diene monomers and vinyl substituted aromatic hydrocarbons monomers. Polymerizable 1,3-diene monomers that can be employed in the production of the copolymers of the present invention are 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like mixtures thereof, preferably butadiene and isoprene. Exemplary vinyl substituted aromatic hydrocarbons, hereinafter vinyl aromatic hydrocarbons, include: styrene, alpha-methylstyrene; 1-vinylnaphthalene; 2-vinyl-naphthalene; 1-alpha-methylvinylnaphthalene; 2-alpha-methyl-vinylnaphthalene; and mixtures of these as well as alkyl, cycloalkyl, aryl, alkaryl and aralkyl derivatives thereof in which the total number of carbon atoms in the combined hydrocarbon is generally not greater than 12. Examples of these latter compounds include: 4-methylstyrene; vinyl toluene; 3,5-diethylstyrene; 2-ethyl-4-benzylstyrene; 4-phenylstyrene; 4-para-tolylstyrene; and 4,5-dimethyl-1-vinylnaphthalene. Occasionally, di- and tri-vinyl aromatic hydrocarbons are used in small amounts in addition with mono-vinyl aromatic hydrocarbons. The preferred vinyl aromatic hydrocarbon is styrene.
Any anionic initiator that is known in the art as useful in the copolymerization of diene monomers with vinyl aromatic hydrocarbons can be employed in the process of the instant invention. Exemplary organo-lithium catalysts include lithium compounds having the formula R(Li)
x
, wherein R represents a hydrocarbyl radical of 1 to 20 preferably 2 to 8 carbon atoms per R group and x is an integer from 1 to 4. Typical R groups include aliphatic radicals and cycloaliphatic radicals, such as alkyl, cycloalkyl, cycloalkylalkyl, alkylcycloalkyl, aryl and alkylaryl radicals. Specific examples of R groups for substitution in the above formulas include primary, secondary and tertiary groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-amyl, isoamyl, n-hexyl, n-octyl, n-decyl, cyclopentyl-methyl, cyclohexyl-ethyl, cyclopentyl-ethyl, methylcyclopentylethyl, cyclopentyl, dimethylcyclopentyl, ethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, isopropylcyclohexyl, and the like. These anionic initiators are useful in amounts ranging from 0.01 to 50 millimoles per hundred grams of monomer charge.
Specific example of other suitable lithium catalysts include: p-tolyllithium, 4-phenylbutyl-lithium, 4-butylcyclohexyllithium, 4-cyclohexylbutyl-lithium, lithium dialkyl amines, lithium dialkyl phosphines, lithium alkyl aryl phosphine, lithium diaryl phosphines and the like.
The block polymers of the instant invention must include at least two vinyl aromatic hydrocarbon blocks and at least o
Bridgestone/Firestone Inc.
Burleson David G.
Skerry Ann M.
Szekely Peter
LandOfFree
Adhesive and polymer for adhesives does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adhesive and polymer for adhesives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adhesive and polymer for adhesives will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2473716