Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-06-27
2003-06-10
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S274000, C524S491000, C525S098000
Reexamination Certificate
active
06576686
ABSTRACT:
FIELD
This invention relates generally to linear tetrablock copolymer compositions and their use in road marking applications. These tetrablock copolymers contain polystyrene, polyisoprene and polybutadiene components. Road marking compounds prepared from these copolymers typically further contain hydrocarbon resin, fillers and glass beads.
BACKGROUND
Block copolymers are generally known in the art and have been used in a variety of applications. There are two basic and distinct types of block copolymers, linear and radial block copolymers.
Radial block copolymers contain branches of polymer blocks radiating from a central coupling agent. Such polymers are described in, for example, U.S. Pat. No. 5,399,627. This patent describes such polymers for use in pressure sensitive adhesive compositions. These radial block copolymers are comprised of polystyrene, polyisoprene and polybutadiene block segments.
Linear block copolymers do not have radiating branches; rather, the block components are arranged sequentially. For example, U.S. Pat. No. 5,750,623 describes linear styrene-isoprene-styrene and styrene-butadiene-styrene block copolymers useful in hot-melt adhesive formulations.
Linear block copolymers are also used to prepare compositions for road or pavement marking. Such compositions typically comprise copolymer elastomer and hydrocarbon resin components as well as color and reflective additives such as pigments and glass beads.
U.S. Pat. No. 5,213,439 is directed to pavement marking and describes a dry-blended powder composition containing a linear or radial tri-block copolymer containing two poly(vinylaromatic) blocks and a conjugated diene block. This copolymer must be ground to a powder prior to being combined with hydrocarbon resin and other additives. This grinding step is intended to replace the otherwise necessary step of melt blending thermoplastic rubbers such as these block copolymers with hydrocarbon resin using expensive high-shear stirring during a prolonged melt blending procedure.
We have discovered that certain linear tetrablock copolymer compositions are readily melted and mixed with hydrocarbon resin thus obviating the need for either powder grinding or high-shear stirring. Such copolymers thus have particular potential value in road marking applications in addition to the more typical adhesive applications.
SUMMARY
The present invention relates to a copolymer composition comprising a linear S-I-S-B tetrablock copolymer wherein the S component is polystyrene, the I component is polyisoprene and the B component is polybutadiene. In particular, in this S-I-S-B block copolymer, the S component is present in the amount of about 10 parts to about 90 parts per 100 parts by weight of the block copolymer, the I component is present in the amount of about 10 parts to about 90 parts per 100 parts by weight of the block copolymer, and the B component is present in the amount of about 10 parts to about 90 parts per 100 parts by weight of the block copolymer. The overall peak weight average molecular weight of the copolymer ranges from about 10,000 to about 1,000,000; and the copolymer contains less than 10% residual S-I diblock, less than 10% residual S-I-S triblock, and less than 10% residual S-B diblock.
This invention further relates to a road marking compound comprising a linear tetrablock copolymer having four blocks independently selected from polystyrene, polyisoprene and polybutadiene, and hydrocarbon resin.
More specifically, this road marking compound comprises: (a) a linear tetrablock copolymer represented by the formula S-I-S-B, S-I-S-I, S-B-S-B or S-B-S-I wherein S is a polystyrene component, I is a polyisoprene component and B is polybutadiene component; wherein each copolymer component is present in the amount of about 10 parts to about 90 parts per 100 parts by weight of the block copolymer; the overall peak weight average molecular weight of the copolymer ranges from about 10,000 to about 1,000,000; and the copolymer contains less than 10% residual S-I diblock and less than 10% residual S-I-S triblock; and (b) a substantially non-aromatic hydrocarbon resin.
DETAILED DESCRIPTION
The linear tetrablock copolymers of this invention are particularly useful in road marking compounds due to their quick melting capability and flowability. They can be easily melt mixed with hydrocarbon resins and other additives without the need for either powdering or high shear mixing. Each block may be either polystyrene (“S”), polybutadiene (“B”) or polyisoprene (“I”). It will be recognized that since there must be four blocks, at least one of the blocks will be repeated. Preferably the tetrablock copolymer contains two S blocks, and two B blocks, two I blocks or one each of the B and I blocks combined with the two S blocks. Examples of such linear tetrablock copolymers are represented by the formulae: S-I-S-I, S-I-S-B, S-B-S-B and S-B-S-I.
Each block is present in the amount of about 10% by weight to about 90% by weight of the block copolymer based on the total weight of the block copolymer. Preferably, an S component makes up from about 5% to about 70% by weight of the tetrablock copolymer, more preferably from about 10% to about 60% by weight of the copolymer, even more preferably from about 10% to about 40% by weight of the copolymer and most preferably from about 10% to about 30% by weight of the copolymer.
The weight average molecular weight of the tetrablock copolymers of this invention varies widely depending on the exact make-up of the copolymer. Generally the overall peak weight average molecular weight ranges from about 10,000 to about 1,000,000, preferably from about 50,000 to about 500,000, more preferably from about 100,000 to about 300,000 and most preferably from about 100,000 to about 200,000.
Preferably, the linear tetrablock copolymers of this invention are “pure” in the sense that they contain no measurable residual triblock or diblock copolymer. However, the linear tetrablock copolymers of this invention may contain up to 1% by weight residual triblock and/or diblock copolymer.
For road marking application, these linear tetrablock copolymers are mixed with a hydrocarbon resin, preferably a substantially non-aromatic hydrocarbon resin, or with a rosin ester or a blend of both. Commercially available resins such as Escorez 1102RM (ExxonMobil Chemical) are suitable. Such resins preferably have a Ring and Ball softening point (ASTM D 28-96) of greater than 90, or from about 90° C. to about 110° C., preferably from about 95° C. to about 105° C., and a melt viscosity at 160° C. (ETM-E-31) in the range of 100-10,000 mPa·s, or from about 500 to about 3000 mPa·s, preferably from about 1000 to about 2500 mPa·s. Such hydrocarbon resins are well known and commercially available; for example suitable hydrocarbon resins are those available under the trademarks “Escorez”, “Hercules”, “Quintone” and suitable rosin esters are available under the trademarks “Beviline”, “Sylvatac”. These non-aromatic hydrocarbon resins typically have a wax cloud point of 190° C. or below.
The relative amounts of tetrablock copolymer and hydrocarbon resin depends on the particular components selected. Typically, the block copolymer and hydrocarbon resin are present in a weight ratio of from about 0.5:99.5 to about 20:80, preferably from about 2:98 to about 15:85.
The road marking compounds of this invention may further contain additives such as pigments, glass beads, fillers, oils and viscosity modifiers. Titanium dioxide is a particularly useful pigment and mineral aggregates are particularly useful fillers.
The individual components of the road marking composition may be combined in any number of ways, but the tetrablock copolymers of this invention are uniquely suited to simple melt mixing with the hydrocarbon resin and any desired additive. The typical melt mixing temperature ranges from about 170° C. to about 210° C., preferably from about 180° C. to about 200° C.
The linear tetrablock copolymers of this invention may be prepared by any number of polymerization processes well known in t
Delmé Roger Robert
Lechat Jacques Bernard
Martin Chantal Mathilde
ExxonMobil Chemical Patents Inc.
Runyan Charles E.
Schmidt Paige
Teskin Fred
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