Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-04-07
2003-08-12
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S207000, C526S237000, C526S346000, C526S283000, C526S348200, C526S348300, C526S348600, C526S348700
Reexamination Certificate
active
06605680
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to tackifier resin compositions for use in adhesives and to methods for their preparation. More particularly, this invention relates to low color, aromatic-modified C
5
hydrocarbon compositions prepared from piperylene concentrate and vinyl aromatic compounds and their use in adhesive applications.
BACKGROUND OF THE INVENTION
Tackifier resins can be used for making thermoplastic adhesives such as hot melt adhesives (HMA) and hot melt pressure sensitive adhesives (HMPSA). A hot melt adhesive is a solid, thermoplastic material that melts quickly upon heating. A hot melt adhesive then sets to a firm bond on cooling. A hot melt pressure sensitive adhesive retains its tackiness upon cooling. Most other types of adhesives set by evaporation of a solvent or free radical curing mechanisms. Hot melt adhesives offer quick bonding making them well suited for many automated operations. The hot melt adhesives are made of elastomers, block copolymers, ethylene vinyl acetate (EVA), or amorphous polyolefins along with low molecular weight oligomer tackifiers.
A tackifier must generally be compatible with the adhesive application. Tackifiers are chosen to impart substantial adhesive strength, promote substrate wetting and generally enhance adhesive performance. Tackifiers are commonly made by polymerization of unsaturated liphatic petroleum hydrocarbon feedstocks, such as feedstock from ethylene crackers in petroleum or petrochemical processing plants.
More specifically, tackifiers are often made from unsaturated C
5
hydrocarbons having two double bonds, such as C
5
dienes and C
5
cyclodienes. The C
5
resins are commonly made using AlCl
3
catalyst at a reaction temperature from about 30° to about 70° C. These resins have a softening point from 70°-120° C. for adequate wetting of a substrate, for maintaining adhesive properties and for ease of packaging. These resins often, however, have a Gardner color of about 5 to about 7 or greater, which is often too dark of a color for many adhesive applications.
Reducing the amount of C
5
cyclodienes in a C
5
resin will generally improve or lower the Gardner color, but adhesive properties of the C
5
resin may also be influenced, such as a lower softening point and reduced adhesive properties. For low color tackifiers with a reduced C
5
cyclodiene content, aromatics may be added to the C
5
resin to improve the resin's adhesive characteristics. Such low cyclodiene resins often also require the use of a terpene, an unsaturated cyclic C
10
H
16
hydrocarbon, to satisfy the adhesive requirements, such as color and softening point. See, for example, U.S. Pat. No. 4,994,516, requiring a C
5
resin obtained from C
5
piperylenes, unsaturated vinyl aromatics and terpenes to get adequate low color without loss of softening point. The use of terpenes, however, often require preparation of that feed stream, such as feed purification or hydrotreating prior to use, making the use of terpenes often more costly and complicated manufacturing process.
C
5
resins with aromatic substitution often have high color and require post resin hydrogenation or hydrotreating. See, for example, U.S. Pat. No. 4,952,639 where C
5
resins substituted with vinyl monounsaturated aromatics have dark Gardner colors from about 5 to 7 before hydrogenation and Gardner color of less than 2 after hydrogenation of the C
5
resin. See also, U.S. Pat. No. 5,817,900 where hydrotreating of an aromatic-modified C
5
hydrocarbon resin was required to lower the Gardner color of the resin from about 7 to about 2.
Low color C
5
resins have been proposed without the use of post resin hydrogenation or hydrotreating. Such resins are, however, often limited in the amount of aromatic substitution. For example, U.S. Pat. No. 5,853,874 describes a low color, aromatic-modified C
5
resin with a Gardner color of about 3, but only describes about 5 to 15 percent weight substitution of a monovinyl aromatic into the resin. Such a substitution range on monovinyl aromatic substitution limits the usefulness of these C
5
resins as a tackifier in certain hot melt applications.
Other resins have been proposed with higher levels of monovinyl aromatic substitution, but require the use of a BF
3
catalyst, which is less active than the more commonly used AlCl
3
catalyst, resulting in increased manufacturing complexity and cost. For example, U.S. Pat. No. 5,177,163 describes low color monovinyl aromatic substituted C
5
resins having at least 30 percent by weight of a monovinyl aromatic component formed with a BF
3
catalyst. The BF
3
catalyst, however, must be neutralized with chemicals, such as lime or NH
4
OH, which is more costly as compared to a water wash neutralization of the more commonly used AlCl
3
catalysts. The reaction temperature necessary for low color C
5
resins are about from 0° C. to about 10° C. with the BF
3
catalysts which is generally lower than reaction temperature requirements of the AlCl
3
catalyst, resulting in longer reaction times and more costly processing. Furthermore, increasing the reaction temperature of the BF
3
catalyst system to more economical conditions often results in undesirable molecular weights of the resulting C
5
resin.
As such there is a need for a monovinyl aromatic substituted C
5
resins with low color and good adhesive qualities without the above-mentioned disadvantages of complicated or costly resin formation processing.
SUMMARY OF THE INVENTION
The present invention relates to a random copolymer hydrocarbon composition useful as a tackifier. The inventive resins are useful in hot melt adhesives and in hot melt pressure sensitive adhesives, such as with block copolymers of styrene-isoprene-styrene (SIS), block copolymers of styrene-butadiene-styrene (SBS), multiblock (SB)
n
where n is from 100 to 1000, amorphous polyolefins, ethylene vinyl acetate (EVA) polymers and atactic polyalpha olefins (APAO).
In one aspect of the present invention, there is provided a hydrocarbon which is a reaction product of a first predominantly C
5
hydrocarbon stream containing unsaturated aliphatic monomers, such as piperylene monomers, less than about 2% weight cyclopentadiene and dicyclopentadiene monomers and less than about 1% weight isoprene, and a second hydrocarbon stream which includes a monovinyl aromatic C
8
to C
12
monomer. The weight ratio of said unsaturated aliphatic monomers to the monovinyl aromatic C
8
to C
12
monomers is from about 1.5/1 to about 6/1 to yield a unique resin having a Gardner color of less than about 4 and having a ring and ball softening point from about 85° C. to about 100° C. Desirably, the monovinyl aromatic C
8
to C
12
monomer is &agr;-methylstyrene. The inventive resin may further include from about 0 to about 15 weight percent isobutylene, isoamylene or combinations thereof. Desirably, the resin has a Mz from about 2000 to 4000 and a polydispersity of about 1.7 to about 2.0. A resin having a Mz from about 2500 to 3700 is also useful.
In another aspect of the present invention, there is provided a hydrocarbon resin which is a reaction product of a first predominantly C
5
hydrocarbon stream which includes: (i) unsaturated aliphatic monomers, such as piperylene monomers; (ii) less than about 2% weight cyclopentadiene and dicyclopentadiene monomers; and (iii) less than about 1% weight isoprene; and a second hydrocarbon stream which includes a monovinyl aromatic C
8
to C
12
monomer. The weight ratio of the unsaturated aliphatic monomers to the monovinyl aromatic C
8
to C
12
monomers is desirably from about 15/1 to about 50/1. In this aspect of the invention, this resin has a Gardner color of less than about 4 and having a ring and ball softening point from about 85° C. to about 100° C. Desirably, the monovinyl aromatic C
8
to C
12
monomer is &agr;-methylstyrene. The inventive resin may further include from about 15 to about 25 weight percent isobutylene, isoamylene or combinations thereof. Desirably, the resin has a Mz from about 2500 to 4000 and a polydispersity of about 1.7 t
Donker Chretien P. L. C.
Gielens Ester E. C.G.
Verrijzer Gerard A.
Boshears B. J.
Cheung William K.
Eastman Chemical Resins Inc.
Graves, Jr. Bernard J.
Owen Polly C.
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