Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-02-03
2001-02-06
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S339000, C526S283000, C526S308000, C526S335000, C526S339000, C526S340000, C526S347000, C526S347100, C526S348200
Reexamination Certificate
active
06184308
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to thermally polymerized copolymers of dicyclopentadiene and vinyl aromatic compounds, a method for making the copolymers, and the hydrogenated products thereof.
BACKGROUND OF THE INVENTION
Methods are known for thermally polymerizing and copolymerizing dicyclopentadiene (DCPD) feedstocks and for hydrogenating the copolymer product. For example, U.S. Pat. No. 4,650,829 discloses a hydrogenated hydrocarbon resin having a softening point lower than 90° C. and containing at least 40 weight % of monomer units derived from cyclopentadiene alone and cyclopentadiene plus a comonomer of the class consisting of alkyl-substituted cyclopentadiene, acyclic dienes, vinyl aromatics and mixtures thereof. U.S. Pat. No. 5,171,793 discloses the thermal polymerization of a vinyl aromatic component comprising a mixture of styrene and indene and alkylated derivatives thereof, and a cyclodiene at a temperature of 270° C. for two hours. The dark colored resin product is mixed with a solvent diluent and hydrogenated to produce a resin having softening points higher than 100° C. U.S. Pat. No. 3,040,009 discloses the production of light colored resins by redistilling the bottom fraction of dripolene, a normally liquid mixture of hydrocarbons obtained by high temperature pyrolysis of hydrocarbon gases. The thermally polymerized resin is hydrogenated using a catalyst consisting of metallic nickel distributed on a porous support.
In the past, the molecular weight of cyclopentadiene-based resins was controlled by including codimers of cyclopentadiene with a diene such as methylcyclopentadiene, butadiene, isoprene or piperylene, and also by adding these same linear dienes directly into the polymerization process. In these processes, insoluble waxy polymers were often obtained below a reaction temperature of 250° C. Other methods of softening point and molecular weight control involved not only temperature, but also initial monomer concentration and time in the reactor. Advantages have also been claimed in the final adhesives when indene streams and/or C-9 streams are copolymerized with DCPD streams. However, these C-9 and indene streams are known to contain sulfur, which can create problems in the subsequent hydrogenation process due to early poisoning of the catalyst.
It is known that in a given family of hydrocarbon resins, i.e., all of those based on the same feedstock, as the softening point goes up, molecular weights and polydispersity also tend to increase. It is also known that there is a trend toward higher softening points and molecular weights as reaction times and temperatures are increased during the thermal homopolymerization of dicyclopentadiene. In addition, when vinyl monomers other than alpha-methylstyrenes are used to modify DCPD feedstocks, e.g., styrene and other ring-substituted styrenes such as t-butylstyrene and vinyltoluenes, high molecular weights and polydispersities result.
It would be desirable to provide thermally polymerized resins based on low cost DCPD feedstocks, with relatively low molecular weights and relatively high softening points that do not change substantially with time in the reactor. These resins should preferably readily convert to the corresponding hydrogenated water-white and thermally stable derivatives.
SUMMARY OF THE INVENTION
The hydrocarbon resins of this invention consist essentially of a thermally polymerized copolymer made from (1) about 40% to 90% by weight based on total monomers of a cyclic diolefin component comprising at least about 50% by weight dicyclopentadiene, and (2) about 60% to 10% by weight based on total monomers of at least one vinyl aromatic component having the formula
where R
1
is H or a 1-10 carbon linear or branched chain alkyl group at the meta- or para-position and R
2
is a 1-10 carbon linear or branched chain alkyl group or a 2-methyl-2-phenylpropyl group, the resin having a Ring and Ball softening point of about 70° C. to about 150° C. Alpha-methylstyrene; para-methyl-alpha-methylstyrene; 2,4-diphenyl-4-methyl-1-pentene, or mixtures thereof are the preferred aromatic compounds. The resins are essentially free of halogen, since thermal polymerization avoids the need for Friedel-Crafts catalysts, which produce resins containing organically bound halogen.
Also according to the invention, the thermally polymerized resin can be hydrogenated to produce resins useful as tackfiers for adhesives. The preferred hydrogenated resin are water-white in color and thermally stable. In a preferred embodiment, resins that can be hydrogenated efficiently with minimal poisoning of the hydrogenation catalyst are produced from relatively sulfur-free DCPD feedstocks.
Use of the specified aromatic comonomers makes it possible to control the molecular weight and the softening point during the thermal polymerization. It is thus possible to obtain a resin with a suitably high softening point without rapid increase in molecular weight during the polymerization process.
DETAILED DESCRIPTION OF THE INVENTION
Monomers suitable for use as the cyclic diolefin component (1) in the manufacture of the hydrocarbon resins of this invention include essentially pure DCPD (at least 95% by weight pure monomer), or mixtures of dicyclopentadiene with codimers of cyclopentadiene and at least one of methylcyclopentadiene, isoprene, butadiene, and piperylene, for example, a mixture containing 50% to 95% or more dicyclopentadiene. Particularly useful DCPD feedstocks are DCPD 101 and/or DCPD 108 available from Lyondell Petrochemical Co., Houston, Tex., U.S.A., which have <1 ppm sulfur. Low sulfur DCPD feedstocks allow more efficient hydrogenation, since there is little sulfur present to poison the catalyst. However, the use of low sulfur feedstocks is not essential for the practice of this invention. Resins made from sulfur-containing DCPD feedstocks can still be hydrogenated, since there are processes that over-come the effect of catalyst poisoning from the sulfur.
The vinyl aromatic monomer comprises at least one compound having the formula
where R
1
, is H, or a 1-10 carbon linear or branched chain alkyl group at the meta- or para-position, e.g., a methyl, ethyl, isopropyl or t-butyl group, and R
2
is a 1-10 carbon linear or branched chain alkyl group or a 2-methyl-2-phenylpropyl group. Alpha-methylstyrene (AMS); para-methyl-alpha-methylstyrene; 2,4-diphenyl-4-methyl-1-pentene (an unsaturated dimer of AMS), or mixtures thereof are preferred. AMS is most preferred. Up to about 15% by weight of total monomers can be a vinyl aromatic monomer other than those specified above, e.g., styrene and styrenes that are ring-substituted with straight chain or branched aliphatic groups, e.g., vinyltoluenes and t-butylstyrene.
The resin product consists essentially of about 40% to 90% by weight based on total monomers of the cyclic diolefin component and about 60% to 10% by weight based on total monomers of the vinyl aromatic component, the total equaling 100%. For the most efficient reaction, the ratio of cyclic diolefin component (1) to vinyl aromatic component (2) is preferably 1:1 or greater. If the amount of vinyl aromatic component exceeds 50%, the yield will decrease, since there will not be enough DCPD to react with all of the vinyl aromatic component AMS and the other vinyl monomers defined by the formula given above do not homopolymerize. The softening point of the resin product is about 70° to 150° C., preferably about 80° to 140° C.
Reactions can be carried out in solution or neat. When a solvent is used, it is preferably either aliphatic or aromatic. The copolymerization can be carried out in a continuous process, or in a batch mode.
The polymerization is carried out at a temperature of about 210° to 300° C., more preferably about 215° to 280° C., and most preferably about 225° to 275° C. The reaction pressure is self-generated and is typically between 0 and about 150 psig. The reaction time is typically about 10 minutes to about 16 hours at reaction temperature.
The resins of this invention with Ring and Ball (R&B) softe
Daughenbaugh Norman Edward
Goodfellow Dane George
Riedl Deborah Ann
Hercules Incorporated
O'Brien Robert P. O'Flynn
Zitomer Fred
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