Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-12-18
2003-11-18
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S347100
Reexamination Certificate
active
06649716
ABSTRACT:
FIELD OF THE INVENTION
The current invention relates to processes for the production of polymers. More particularly, the current invention relates to processes for the production of polymers of &agr;-methylstyrene.
BACKGROUND OF THE INVENTION
Poly &agr;-methylstyrene has many applications including, as processing aids and fusion enhancer/modifiers in applications such as vinyl flooring, as a processing aid in the extrusion and injection molding of PVC piping and profile extrusions such as vinyl siding and windows.
Traditional processes for the polymerization of &agr;-methylstyrene to poly &agr;-methylstyrene have made use of boron trifluoride or other protic acid catalyst/initiators, such as tetrafluorboric acid, hexafluorophosphoric acid and pentafluoroantimonate.
Other work has focused on the use of Lewis acids as coinitiators with cationic carbon species. This work includes: Li et al, “Living Carbocationic Polymerization of &agr;-Methylstyrene Using Tin Halides as Coinitiators”,
Macromolecules,
1996, 29, 6061-6067; Cotrel et al, “Kinetic Study of the Cationic Polymerization of p-Methoxystyrene Initiated by Trityl Hexachloroantimonate”,
Macromolecules
, November-December 1976, vol. 9, No. 6, 931-936; Hotzel et al, “Studies on Cationic Copolymerization of &agr;-Methylstyrene and Indene”,
Polymer Bulletin
6, 521-527 1982; and Matsuguma et al, “The Effect of Counteranions on the Polymer Steric Structure in the Cationic Polymerization of &agr;-Methylstyrene”,
Polymer Journal
, vol. 2, No. 3, 353-358, 1971.
A drawback of most current art methods using cationic and Lewis acid initiators is that they require cold temperatures to control the polymerization and obtain polymers of the desired molecular weight and molecular weight distribution. Li et al report in “Living Carbocationic Polymerization of &agr;-Methylstyrene Using Tin Halides as Coinitiators” that a rapid and uncontrolled polymerization may lead to side reactions and a broad molecular weight distribution.
A typical industrial process that was run by Amoco utilized boron trifluoride as an initiator to produce poly &agr;-methylstyrene homopolymer. The process was run in a chlorohydrocarbon solvent at −25 to −80° C. In addition to the costs introduced by such extreme temperatures, the use of an environmentally unfavorable solvent such as chlorohydrocarbon, which is typical in similar processes, makes this an unattractive process.
Typical anionic catalyst/initiators are alkyl lithiums (U.S. Pat. Nos. 4,614,768, 4,725,654 and 4,748,222) and metal naphthalides, in “Ionic Polymerization of p-Isopropyl-&agr;-Methylstyrene”,
Journal of Macromolecular Sci.-Chem.
, A11(11), 2087-2112, 1977. Léonard et al.
A drawback of anionic initiators is that they are particularly sensitive to impurities. Unrefined &agr;-methylstyrene, such as what may be obtained directly from an &agr;-methylstyrene manufacturing facility, generally contains a number of trace oxygenated impurities, which adversely affect a number of commonly used polymerization initiators. These impurities include, but are not limited to 3-methyl-2-cyclopentanone (3-MCP), acetophenone, 2-methylbenzofuran (2-MBF) and acetone. In many cases, the presence of these trace impurities has the effect of inhibiting or killing an anionic polymerization initiator, with the result that little or no conversion of the monomer is obtained. As a result, it has been found to be necessary to pre-treat the monomer feed stream, such as with an acidic alumina or via distillation, to remove these trace impurities before proceeding to the polymerization step, adding time and costs to production. U.S. Pat. No. 4,614,768 to Lo, U.S. Pat. No. 4,725,654 to Priddy et al and U.S. Pat. No. 4,748,222 to Malanga disclose the necessity of purifying reactants in processes for polymerizing &agr;-methylstyrene using an organolithium initiator.
Lack of viable alternatives for the production of poly &agr;-methylstyrene homopolymer has led to a lapse in its production and the adoption of alternative co-polymers of &agr;-methylstyrene, such as &agr;-methylstyrene/styrene and &agr;-methylstyrene/vinyltoluene.
Hence, it would be desirable to provide a process for producing polymers of &agr;-methylstyrene that can be efficiently run and controlled at ambient temperatures, does not make use of environmentally unfavorable solvents and consistently produces a polymer of the desired molecular weight. It would further be desirable to provide a process for producing polymers of &agr;-methylstyrene that does not require expensive and time-consuming pre-treatment of the monomer prior to polymerization. The advantages of such a process would include lower costs, a more robust reproducible process, increased efficiency and more controllable process temperature exotherms.
SUMMARY OF THE INVENTION
The current invention provides a process for the polymerization of &agr;-methylstyrene that can manageably be carried out at ambient temperature. The current invention also provides a process for the polymerization of &agr;-methylstyrene, which does not require extensive purification of the monomer prior to polymerization.
The invention achieves this through the use of tin IV chloride as an initiator for the polymerization of &agr;-methylstyrene. According to one embodiment of the invention, &agr;-methylstyrene monomer is provided as a solution in an organic solvent, preferably toluene or cumene. A small amount of tin IV chloride is then added to initiate polymerization of the &agr;-methylstyrene. Preferably, the amount of tin IV chloride added is from about 0.10 to about 0.40% by weight based on the weight of &agr;-methylstyrene in solution. The process is run at a temperature greater than about 0° C., preferably greater than about 10° C., and more preferably greater than about 20° C. The initiator may be added either neat or as a solution in a suitable solvent. Preferably, the initiator is added in a suitable solvent. The process may be run as a batch process or in continuous production.
According to one embodiment, the process may be run with &agr;-methylstyrene and one or more co-monomers including, but not limited to propylene, ethylene, styrene, butadiene, acrylonitrile and methylmethacrylate to produce an &agr;-methylstyrene co-polymer.
DETAILED DESCRIPTION
The process according to the current invention uses tin IV chloride as an initiator for the polymerization of &agr;-methylstyrene to produce a poly &agr;-methylstyrene polymer. It has been discovered that the use of tin IV chloride as an initiator for the polymerization of &agr;-methylstyrene eliminates the need for tedious and expensive purification of the monomer prior to the polymerization. Additionally, it has been discovered that using tin IV chloride as an initiator, the polymerization can be initiated at ambient or higher temperatures without resulting in uncontrolled polymerization.
Examples 1 through 4 and the data in Tables I through IV demonstrate the superiority of the inventive process using tin IV chloride as a polymerization initiator.
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