Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-02-09
2002-09-17
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S173000, C526S181000, C526S269000, C526S270000
Reexamination Certificate
active
06451949
ABSTRACT:
FIELD OF INVENTION
This invention relates to a method of producing poly(trimethylene carbonate)(PTMC). More particularly, this invention relates to an improved method of producing poly(trimethylene carbonate) in which no decarboxylation is observed. In addition, the improved method results in an extremely desirable quality of poly(trimethylene carbonate), characterized in that the product is particularly clear and virtually all end groups are hydroxypropyl groups, with no measurable allyl end groups.
BACKGROUND OF THE INVENTION
In methods currently known in the art for the production of poly(trimethylene carbonate), problems with decarboxylation during the reaction are common and the products typically have an undesirably large percentage of allyl end groups. Allyl end groups are undesirable, because they reduce the hydroxyl functionality, result in dead ends, and are less effective in chemistry which requires hydroxy terminated species, such as, for example, in urethane or melamine chemistry. In addition, the transparency of poly(trimethylene carbonate) currently available in the art is typically not as clear as would be desirable, thus presenting problems in obtaining the clarity sought after in clear urethane or melamine coatings formulations.
It is known in the art that cyclic carbonates can be converted in the presence of polyhydric alcohols at higher temperatures and under increased pressures into liquid to viscous polycarbonates of relatively low molecular weight. It is also known that cyclic carbonates can be converted without the presence of alcohols.
Various groups of catalysts are known in the art for ring-opening polymerization, however previously used catalysts generally have one or more undesirable effects, such as, for example, longer reaction times, poor conversion, color formation, decarboxylation, and the formation of allyl end groups. Decarboxylation is undesirable because it yields ether links which reduce UV and thermal stability of the material and allyl end groups reduce the hydroxyl functionality.
Kricheldorf, et al, used methyl triflate or triethyloxonium fluorborate to polymerize 1,3-dioxan-2-one, as discussed in
J. Macromol. Sci., Chem
., A26(4), 631-44 (1989), however this article describes many side chemistries. In
Makromol. Chem
., 192(10), 2391-9 (1991), Kricheldorf, et al, describe numerous bulk polymerizations of trimethylene carbonate, at various temperatures, using catalysts containing butyl groups, tin, and bromide, inter alia; ether groups were not found, and all polycarbonates contain a CH
2
CH
2
CH
2
OH end-group. It does not appear these products were examined for clarity. In the present invention it was found that using catalysts of the type described by Kricheldorf, et al resulted in products with less clarity than those described herein. In
Polymer
, 36(26), 4997-503 (1995), Kricheldorf, et al, used tin halides for polymerization of cyclotrimethylene carbonate. Additional work, described in
J. Polym. Sci., Part A: Polym. Chem
., 33(13), 2193-201(1995), described the use of BuSnCl
3
—, Bu
2
SnCl
2
—, and Bu
3
SnCl initiators. In both studies using tin-containing compounds the chemistry results in dead ends and further chemistry would be required to convert the halide end groups to hydroxy groups. An article by Kricheldorf, et al, in
Macromol. Chem. Phys
., 197(3), 1043-54 (1996), discloses the spontaneous and hematin-initiated polymerizations of trimethylene carbonate and neopentylene carbonate. This method would also result in dead ends.
In an article titled, “Homopolymerization of 1,3-dioxan-2-one to high-molecular-weight poly(trimethylene carbonate)”, in
J. Macromol. Sci.—Chem
., 29(1), 43-54 (1991), Albertsson, et al, discuss the use of sodium ethoxide or stannous 2-ethylhexanoate as a transesterification catalyst. It was found that the polymer contained 2.6% ether linkages formed by decarboxylation during polymerization at high temperature. At page 51, it is stated “Immediately after the polymerization, all the polymers were transparent, but on cooling the polymers with low molecular weight became opaque due to crystallization of unreacted monomer”. In
J. Macromol. Sci.—Chem
., 29(1), 43-54 (1991), Albertsson, et al, discuss the homopolymerization of 1,3-dioxan-2-one to high molecular weight poly(trimethylene carbonate) using either EtONa or stannous 2-ethylhexanoate as the transesterification catalyst. This chemistry generated significant amounts of decarboxylation. In an article by Albertsson, et al,
J. Macromol. Sci., Pure Appl. Chem
., A29(1), 43-54 (1992), there is described the homopolymerization of 1,3-dioxan-2-one to high molecular weight poly(trimethylene carbonate). This chemistry also generated significant amounts of decarboxylation. In
J. Polym. Sci
., Part A: Polym. Chem., 32(2), 265-79 (1994), Albertsson, et al, describe a new type of copolymer synthesized from 1,3-dioxan-2-one and oxepan-2-one using either tin octoate, zinc acetate, dibutyltin oxide, or tributyltinchloride as the catalyst.
In German Patent Application EP 96-117263 there is disclosed a method of rendering polyesters such as polylactides, lactide/glycolide copolymers, and poly(trimethylene carbonates) hydrophobic by reaction of terminal OH and/or CO
2
H groups with long-chain fatty acids and/or fatty alcohols or their derivatives. This reference primarily discloses a particular product and would result in dead ends in urethane and coatings applications.
An alkyl halide-initiated cationic polymerization of cyclic carbonate is described in an article by Ariga, et al,
J. Polym. Sci., Part A: Polym. Chem
., 31(2), 581-4 (1993). It is believed this chemistry would produce one dead end for every initiator group.
A rare earth halide was used in the ring-opening polymerization of trimethylene carbonate, as well as &egr;-caprolactone, in an article by Shen, et al,
J. Polym. Sci., Part A: Polym. Chem
., 35(8), 1339-1352 (1997). Rare earths are typically pro-oxidants and, therefore, would be expected to negatively impact aging properties of poly(trimethylene carbonate).
In an article by Ariga, et al, in
Macromolecules
, 30(4), 737-744 (1997), there is disclosed the cationic ring-opening polymerization of cyclic carbonates with an alkyl halide as initiator. The methods discussed in this reference would produce dead ends, thus making the products unsuitable for urethanes and coatings.
The use of an alcohol-acid catalyst for the ring-opening polymerization of cyclic carbonates is described in an article by Matsuo, et al,
J. Polym. Sci., Part A: Polym. Chem
., 36(14), 2463-2471(1998). The product of this method would result in dead ends and would require hydrolysis to produce active end groups.
In
Polym. Prepr
. (Am. Chem. Soc., Div. Polym. Chem.), 39(2), 144-145 (1998), an article by Deng, et al, describes the ring-opening polymerization of &egr;-caprolactone and trimethylene carbonate catalyzed by lipase Novozym 435. In this case, the removal of the lipase would be problematic.
In an article by Bisht, et al, in
Macromolecules
, 30(25), 7735-7742 (1997), the use of lipase-catalyzed ring-opening polymerization was extended to cyclic carbonate monomers.
An article by Matsuo, et al, in
Macromol. Chem. Phys
., 199(1), 97-102 (1998), describes the ring-opening polymerization of a 7-membered cyclic carbonate in nitrobenzene; and of a 6-membered cyclic carbonate in dichloromethane, the latter generally accompanied by partial elimination of CO
2
. This paper supports the observation that decarboxylation occurs when polymerizing trimethylene carbonate.
There is still a technical demand for the development of a process by which poly(trimethylene carbonate) of a quality that would exhibit optimum properties for use in urethane chemistry could be obtained, and which would also be economical and uncomplicated in operation. It would be particularly desirable in the art if poly(trimethylene carbonate) could be made in one simple step, while avoiding the typical decarboxylation and formation of allyl end groups. It would constitute a great advance in the art and
Boon Wyndham Henry
Forschner Thomas Clayton
Gwyn David Eric
Smith Roy Frank
Haas Donald F.
Pezzuto Helen L.
Shell Oil Company
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