Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2000-05-04
2001-11-13
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S50200C
Reexamination Certificate
active
06316592
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods for isolating polymer resins from solution slurries utilizing a precipitation aid.
2. Brief Description of Related Art
A number of methods have been disclosed for separating soluble thermoplastic resins from organic solvents. A majority of these methods are energy intensive requiring the removal of the organic solvent. More energy efficient means involve the precipitation or coprecipitation of the polymer resin from solution. These precipitation techniques can be hindered by the presence of a solid phase of fine particulates within the solution. These fine particulates are not easily recovered before precipitation of the soluble polymer resin and can interfere with the recovery of the precipitate. The presence of this solid particulate phase is particularly troublesome when attempting to employ equipment which is not adapted to handle fine particles.
An example where this problem occurs is in the copolymerization of 2,6-xylenol and 2,3,6-trimethylphenol via oxidative coupling. It is reported that most of the copolymers formed from these monomers spontaneously precipitate in the reaction mixture as very fine particles. This reaction mixture turns into a three-phase slurry comprising: a solid phase of copolymer particles, a copolymer solution phase and an aqueous phase. In the preparation of polyphenylene ether homopolymers with 2,6-xylenol, the polymer reaction product remains solubilized in the toluene reaction solution. After purification of the solution, the homopolymer is typically precipitated in methanol. The polyphenylene ether homopolymer of 2,6-xylenol precipitates as large size clusters suitable for liquid-solid filtration. In contrast, the three-phase reaction mixture obtained with the preparation of polyphenylene ether copolymers of 2,6-xylenol and 2,3,6-trimethylphenol is unsuitable for the polymer purification and isolation techniques used for the polyphenylene ether homopolymers of 2,6xylenol. Separate equipment is therefore required.
It is desirable to provide an isolation technique for polymer resins within a solution slurry that contains a solid phase of the polymer resin as fine particulates which does not require special equipment to remove these particulates.
SUMMARY OF THE INVENTION
This invention provides a method for a separating soluble polymer resin from a solution slurry that contains a solid phase of said polymer resin as particulates. This method comprises adding a precipitation aid to a solution slurry which contains a soluble polymer resin and a solid phase of said polymer resin as particulates. The precipitation aid is a linear or branched polymer which absorbs onto the surface of the polymer resin particulates. This polymeric precipitation aid is also a suitable blend component for formulations of the polymer resin to be isolated.
Following the addition of the precipitation aid, the solution slurry is added to a non-solvent for the soluble polymer resin to precipitate the soluble polymer resin in the solution slurry.
Following precipitation of the soluble polymer resin, it can be recovered by conventional techniques such as by conventional filtration techniques.
The polymer resins which can be isolated from a solution slurry by the methods of this invention have a weight average molecular weight of above about 500 as determined by differential scanning calorimetry. Suitable polymer resins include most thermoplastic resins, i.e., polymers which become plastic and flowable under the action of pressure and heat. Specific examples of suitable thermoplastic resins which can be isolated by the methods of this invention are: polycarbonates, polystyrenes, high impact polystyrenes, polyphenylene ethers, polyetherimides; polyamides; polyesters including polyethylene terephthalates and polybutylene terephthalates. The polymer resins suitable for use in this invention include both homopolymers and copolymers of these thermoplastic resins. The preferred thermoplastic resins employed in the methods of this invention are temperature sensitive polymer resins such as polyphenylene ether resins.
The polyphenylene ether resins suitable for use in the methods of this invention are typically prepared in solution by the oxidative coupling of at least one monohydroxy aromatic compound in the presence of a copper, manganese, or cobalt catalyst. These polyphenylene ether polymers comprise a plurality of aryloxy repeating units preferably with at least 50 repeating units of the following Formula I:
wherein in each of said units independently, each Q
1
is independently halogen, alkyl (preferably primary or secondary lower alkyl containing up to 7 carbon atoms), aryl (preferably phenyl), halohydrocarbon groups (preferably haloalkyl) having at least two carbons between the halogen atoms and the phenyl nucleus of Formula I, aminoalkyl, hydrocarbonoxy or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms and at least two carbon atoms separate the halogen atoms and the phenyl nucleus of Formula I.
Each Q
2
is independently hydrogen, halogen, alkyl (preferably primary or secondary lower alkyl up to 7 carbon atoms), aryl (preferably phenyl), halohydrocarbon (preferably haloalkyl) having at least two carbon atoms between the halogen atoms and the phenyl nucleus of Formula I, hydrocarbonoxy groups or halohydrocarbonoxy groups wherein at least two carbon atoms separate the halogen and oxygen atoms and at least two carbon atoms separate the halogen atoms from the phenyl nucleus of Formula I. Each of Q
1
and Q
2
can suitably contain up to about 12 carbon atoms and most often, each Q
1
is an alkyl or phenyl, especially C
1
-C
4
alkyl and each Q
2
is hydrogen.
The term “polyphenylene ether resin,” as used in the specification and claims herein, includes:
unsubstituted polyphenylene ether polymers;
substituted polyphenylene ether polymers, wherein the aromatic ring is substituted;
polyphenylene ether copolymers;
polyphenylene ether graft polymers containing grafted moieties such as vinyl monomers, polystyrenes and elastomers;
polyphenylene ether coupled polymers, wherein coupling agents, e.g., polycarbonates, form high molecular weight polymers; and
end-capped polyphenylene ether polymers with functional end groups.
It will be apparent to those skilled in the art from the foregoing that the polyphenylene ether polymers contemplated for use in the methods of the present invention include all of those presently known, irrespective of the variations in structural units.
Specific polyphenylene ether polymers which can be used in the methods of the present invention include but are not limited to
poly(2,6-dimethyl-1,4-phenylene ether);
poly(2,3,6-trimethyl-1,4-phenylene) ether;
poly(2,6-diethyl-1,4-phenylene) ether;
poly(2-methyl-6-propyl-1,4phenylene) ether;
poly(2,6-dipropyl-1,4-phenylene) ether;
poly(2-ethyl-6-propyl-1,4-phenylene)ether;
poly(2,6-dilauryl-1,4-phenylene) ether;
poly(2,6-diphenyl-1,4-phenylene) ether;
poly(2,6-dimethoxy-1,4 phenylene) ether;
poly(2,6-diethoxy-1,4-phenylene) ether;
poly(2-methoxy-6-ethoxy-1,4-phenylene) ether;
poly(2-ethyl-6-stearyloxy-1,4-phenylene) ether;
poly(2,6-dichloro-1,4-phenylene) ether;
poly(2-methyl-6-phenyl-1,4-phenylene) ether;
poly(2-ethoxy-1,4-phenylene) ether;
poly(2-chloro-1,4-phenylene) ether;
poly(2,6-dibromo-1,4-phenylene) ether;
poly(3-bromo-2,6-dimethyl-1,4-phenylene) ether; mixtures thereof, and the like.
The methods of this invention provide effective results with polyphenylene ether resins which are copolymers of 2,6-dimethyl-1,4-phenylene ether units (from 2,6-xylenol) and 2,3,6-trimethyl-1,4-phenylene ether units (from 2,3,6-trimethylphenol) which typically form fine particulates in the reaction medium.
Specific examples of suitable polyphenylene ether resins and methods for preparing these polyphenylene ether resins are set forth in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,914,266 and 4,028,341 (Hay); U.S. Pat. Nos. 3,257,357 and 3,257,358 (Stamatoff); U.S. Pat. Nos. 4,935,472 and 4,806,297 (S. B.
Bates Gary Mell
Guo Hua
General Electric Company
Michl Paul R.
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