Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
1999-09-13
2001-12-18
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S491000, C528S495000, C528S499000, C528S50200C, C528S50200C, C528S503000
Reexamination Certificate
active
06331608
ABSTRACT:
FIELD OF INVENTION
This invention relates to the field of processes for producing poly(arylene sulfide), hereinafter referred to as P(AS).
BACKGROUND OF THE INVENTION
The production of P(AS) for a variety of industrial and commercial uses has been known for some time. P(AS) is moldable into various articles including, but not limited to, parts, films, and fibers by means of, for example, injection molding and extrusion molding techniques. These articles have utility in a variety of applications where heat and chemical resistance properties are desired. For example, P(AS) can be utilized as a material for preparing electrical and electronic parts and automotive parts.
Generally, P(AS) is prepared by contacting reactants comprising at least one halogenated aromatic compound, at least one polar organic compound, hereinafter referred to as POC, at least one sulfur source, and at least one base under polymerization reaction conditions. Molecular weight modifier compounds can be added to produce high molecular weight P(AS). The most preferred modifier compound is sodium acetate due to its availability and effectiveness.
There are several problems associated with the synthesis of high molecular weight P(AS) that can cause production expenses to be high. First, in a quench recovery P(AS) process, there is a 5% to 15% reduced feedstock conversion to P(AS) product due to the loss of low molecular weight P(AS) and cyclic and linear P(AS) oligomers in a waste stream called “slime”. Typically, this waste stream often is disposed in landfills or other disposal facilities. Secondly, the modifier compound utilized to synthesize high molecular weight P(AS) often is used only once in a polymerization process and is not captured and recycled for subsequent use. This constitutes a great expense in P(AS) production due to higher feedstock and waste disposal costs. Thirdly, the POC utilized in the process can be recovered, but often at a high cost. For example, n-hexanol often is utilized to extract N-methyl-2-pyrrolidone, a common POC. Operating a hexanol extractor system can require handling as much as 30 to 40 pounds of n-hexanol per pound of P(AS) produced causing high equipment and operational costs.
This invention provides a P(AS) process which recovers low molecular weight P(AS) and cyclic and linear P(AS) oligomers for future use. In addition, this invention provides a method for recovering the modifier compound, which greatly reduces feedstock and disposal expenses compared to current P(AS) processes. This invention also provides a more efficient means to recover the POC utilized in the process. Finally, as a result of these improvements, the P(AS) produced by this invention has higher purity than that produced from current P(AS) processes.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a process to produce P(AS).
It is another object of this invention to provide a process to recover at least one modifier compound and at least one POC.
It is yet another object of this invention to provide a process that efficiently separates high molecular weight P(AS) from low molecular weight P(AS) and cyclic and linear P(AS) oligomers.
It is still another object of this invention to provide a process that produces high purity, high molecular weight P(AS) product.
In accordance with a first embodiment of the present invention, a process is provided comprising (or optionally, “consisting essentially of” or “consisting of”) the sequential steps of:
1) cooling said P(AS) reaction mixture comprising high molecular weight poly(arylene sulfide), low molecular weight poly(arylene sulfide), cyclic and linear poly(arylene sulfide) oligomers, at least one polar organic compound, at least one modifier compound, an alkali metal halide by-product, and water to a temperature sufficient to solidify said high molecular weight poly(arylene sulfide) to produce a cooled reaction mixture;
2) venting said cooled reaction mixture to remove a majority of the water from said cooled reaction mixture to produce a cooled, dehydrated reaction mixture.
In accordance with a second embodiment of this invention, a process is provided comprising (or optionally, “consisting essentially of” or “consisting of”):
1) contacting said cooled, dehydrated reaction mixture with methanol to produce a methanol-rich mixture;
2) separating said methanol-rich mixture to produce a high molecular weight poly(arylene sulfide) product, a recycle mixture, and optionally, a low molecular weight poly(arylene sulfide) stream;
wherein said recycle mixture comprises methanol, said polar organic compound, and said modifier compound;
wherein said low molecular weight poly(arylene sulfide) stream comprises low molecular weight poly(arylene sulfide) and cyclic and linear poly(arylene sulfide) oligomers.
In accordance with a third embodiment of this invention, a process is provided comprising (or optionally, “consisting essentially of” or “consisting of”):
1) contacting said cooled, dehydrated reaction mixture with said polar organic compound to produce a polar organic compound-rich mixture;
2) separating said polar organic compound-rich mixture to produce a solid stream and a liquid stream;
wherein said solid stream is in a substantially solid form and comprises high molecular weight poly(arylene sulfide), said polar organic compound, said modifier compound, and said alkali metal halide by-product;
wherein said liquid stream is in a substantially liquid form and comprises substantially all of said low molecular weight poly(arylene sulfide) and cyclic and linear poly(arylene sulfide) oligomers, said polar organic compound, and said modifier compound;
3) contacting said solid stream with methanol to produce a methanol-rich poly(arylene sulfide) product mixture; and
4) separating said methanol-rich poly(arylene sulfide) product mixture to produce a high molecular weight poly(arylene sulfide) product and a recycle mixture;
wherein said recycle mixture comprises methanol, said polar organic compound, and said modifier compound. In accordance with a fourth embodiment of this invention, a process is provided comprising (or optionally, “consisting essentially of” or “consisting of”):
1) contacting said liquid stream with methanol to produce a methanol-rich low molecular weight poly(arylene sulfide) mixture;
2) separating said methanol-rich low molecular weight poly(arylene sulfide) mixture to produce a low molecular weight poly(arylene sulfide) product and a recycle stream;
wherein said recycle stream comprises methanol, polar organic compound, and said modifier compound; and
wherein said low molecular weight poly(arylene sulfide) product comprises said low molecular weight poly(arylene sulfide) and cyclic and linear poly(arylene sulfide) oligomers;
These objects and other objects of this invention will become more apparent with reference to the following.
DETAILED DESCRIPTION OF THE INVENTION
Different embodiments of this invention provide processes for producing P(AS) and recovering at least one modifier and at least one POC. The first step of a first embodiment of this invention comprises cooling a P(AS)reaction mixture to a temperature sufficient to cause the high molecular weight P(AS) to solidify to produce a cooled reaction mixture.
At the termination of a P(AS) polymerization reaction, the P(AS) reaction mixture comprises high molecular weight P(AS), low molecular weight P(AS), cyclic and linear P(AS) oligomers, at least one POC, at least one modifier compound, an alkali metal by-product, and water. The P(AS) reaction mixture is in a substantially liquid form at reaction temperatures. Alkali metal halide by-product is present as a precipitate.
The P(AS) reaction mixture is cooled to a temperature sufficient to cause the high molecular weight P(AS) to solidify into granules. U.S. Pat. Nos. 4,414,729 and 5,128,445 describe this process, and both patents are herein incorporated by reference. Generally, the reaction mixture is cooled to below about 240° C. to solidify the high molecular weight P(AS) into granules. Preferably, said reaction mixtu
Chaffin Jay M.
Fodor Jeffrey S.
Geibel Jon F.
Kile Glenn F.
South, Jr. Aubrey
Owen Polly C.
Phillips Petroleum Company
Truong Duc
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