Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-07-25
2003-03-18
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06534623
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a process for the preparation of semicrystalline polycarbonate oligomer compositions from amorphous polycarbonate oligomer compositions in the presence of i) a fugitive plasticizer which acts as a temporary crystallization-rate enhancing agent and/or ii) a particulate nucleating agent. The semicrystalline compositions produced are useful as starting materials for the production of high molecular weight polycarbonate by solid state polymerization.
TECHNICAL BACKGROUND OF THE INVENTION
High molecular weight polycarbonate is a valuable engineering resin useful for producing many objects, especially clear sheeting, compact recording discs and housings for electronic equipment. There are a number of ways this resin can be produced. The most common industrial method is the interfacial polymerization method in which bisphenol-A and phosgene are reacted in a heterogeneous mixture of water and methylene chloride. Although this process produces the desired high molecular weight polymer, there are disadvantages associated with it. Phosgene is extremely toxic and hence results in safety concerns. In addition the use of methylene chloride raises environmental concerns. Finally, the polymer produced by this method contains residues of sodium chloride which are produced by neutralization of sodium hydroxide used to dissolve bisphenol-A in water. This impurity is undesirable in some applications and is difficult to remove. A second method used to produce polycarbonate is the melt polymerization of bisphenol-A and diphenyl carbonate. This process requires the removal of the condensation by-product from the viscous polymer melt. The high temperatures required to achieve low viscosity can lead to degradation of the polycarbonate polymer. A final method known for producing polycarbonate is solid state polymerization. This type of polymerization is widely practiced for the production of polyethylene terephthalate resin for containers. In this process a low or moderate molecular weight polymer is produced and isolated as a solid material such as chips, particles, granules, or powders. Particles of controlled size and shape are most desirable. The polymerization of this solid material is accomplished by heating it to a temperature below its melting temperature with a heated inert gas. The solid state polymerization is thus carried out at lower temperature, which reduces the degradation problem. Before this final step of the solid state polymerization is carried out, the starting materials must be crystallized. For polycarbonate this step is known to be very difficult because of the slow crystallization rate of polycarbonate. Although technologies for crystallization of polycarbonate have been described, all of these technologies have serious drawbacks associated with them.
European Patent No. 0 864 597 discloses a process for the solid state polymerization of polycarbonate oligomer under an atmosphere of a swelling solvent gas or under a stream of a poor solvent gas. The process is applied to either amorphous oligomer particles or powders or to semicrystalline particles or powders. The process does not include a separate crystallization step and hence does not allow one to control the conditions under which crystallization occurs. The swelling solvent gas or poor solvent gas is present throughout the process along with a second inert gas. Since this mixed gas stream will also contain condensation by-products that must be removed during the solid state polymerization, the required constant presence of swelling or poor solvent gas complicates the gas handling requirements of this process, especially if the gas is recycled. Suitable swelling solvents listed include aromatic hydrocarbons, e.g. benzene and substituted benzenes; ethers, e.g. tetrahydrofuran and dioxane; and ketones, e.g. methyl ethyl ketone. Suitable poor solvent gases listed include cyclic hydrocarbons, straight chain or branched saturated hydrocarbons, and unsaturated hydrocarbons.
U.S. Pat. No. 5,191,001 discloses a process for the production of polycarbonate by solid state polymerization of an intimate mixture of oligomeric polycarbonates. The oligomers to be used in this process have a particular endgroup composition. Although crystallization is a required step for this process, the authors do not disclose any particular crystallization technology. A number of general schemes of possible applicability to many polymers are included. The only crystallization method applied is the well-known solution procedure where a semicrystalline powder is prepared by solvent removal from a solution of the oligomers in methylene chloride.
U.S. Pat. No. 5,717,056 discloses a method for preparing a polycarbonate comprising the steps of (a) converting a precursor polycarbonate to an enhanced crystallinity precursor polycarbonate, and (b) polymerizing in the solid state. Converting the precursor polycarbonate to an enhanced crystallinity precursor polycarbonate entails contact at above 110° C. with a basic compound. Specific basic compounds listed include alkali metal hydroxides, tetraalkylammonium hydroxides, tetraalkylammonium carboxylates, tetraalkylphosphonium hydroxides, and tetraalkylphosphonium hydroxides. The preferred basic compounds are tetramethylammonium maleate and tetraethylammonium hydroxide. The procedure described to produce this enhanced crystallinity precursor polycarbonate involves contact of polycarbonate particles with a solution containing this basic compound followed by a thermal treatment.
European Patent No. 0 848 030 discloses a process for crystallizing a polycarbonate prepolymer comprising dissolving it in a solvent at elevated temperatures, then cooling the solution to effect crystallization. Preferred solvents are aromatic compounds which form solutions of a concentration of 20-90% polycarbonate. The crystalline product produced is then shaped into the form desired for solid state polymerization. This shape is then dried to volatilize the solvent. This process requires many steps to produce the desired crystallized product.
Japanese Patent Heisei 93 178979 discloses a process for the manufacture of aromatic polycarbonate by solid phase polymerizing crystalline polycarbonate prepolymer characterized in that intermediate polymer that has been solid phased is treated with a crystallization solvent and then subjected again to solid phase polymerization.
It is well known that polycarbonate can be crystallized by exposure to solvents such as acetone. U.S. Pat. No. 5,214,073 discloses a method for preparing a porous crystallized polycarbonate oligomer or prepolymer. In one process described an amorphous polycarbonate oligomer is slurried with acetone to produce the crystallized polycarbonate oligomer. The large amorphous particles that are charged to the acetone bath break up into a very fine powder during the crystallization process. A second process described consists of the melt extrusion of the prepolymer melt into a stirred volume of acetone. This also produces a very fine crystallized powder. Both powders are dried before being subjected to the solid state polymerization. A very fine powder is often not desirable in solid state polymerization because of difficulties associated with material handling.
SUMMARY OF THE INVENTION
Provided herein is an improved method for crystallization of polycarbonate or polycarbonate production by solid state polymerization.
This invention provides a process for the preparation of crystalline polycarbonate oligomer compositions from amorphous polycarbonate oligomer compositions comprising the steps of
a) preparing a mixture of the amorphous polycarbonate oligomer with:
i) a fugitive crystallization enhancing agent, and/or
ii) a high melting particulate polymeric nucleating agent
b) forming this mixture into a shape desired, and
c) crystallizing this mixture at a temperature above its glass transition temperature.
Step a) of the above process can be carried out by first producing the oligomeric polycarbonate by contacting a bisphenol with a diary
Boykin Terressa M.
E.I. du Pont de Nemours and Company
LandOfFree
Process for the preparation of crystalline polycarbonate... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of crystalline polycarbonate..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of crystalline polycarbonate... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3049784