Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Patent
1987-11-13
1989-06-20
Anderson, Harold D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
528388, 528491, 528492, 528494, 528495, 528496, 528497, C08G 7502
Patent
active
048410225
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for removing impurities composed mainly of sodium chloride and other alkali metal compounds from polyphenylene sulfide (hereinafter referred to as "PPS") to obtain PPS having a high purity.
BACKGROUND ART
PPS has excellent characteristics such as a high heat resistance, high dimension stability, and low melt viscosity. However, ordinary PPS contains sodium chloride and other alkali metal compounds resulting from the preparation process as impurities, and therefore, the product does not have a reliable moisture resistance and the use thereof is considerably restricted even though the use of PPS as an encapsulant for IC or LSI is desired.
Various methods for removing impurities such as alkali metal compounds from PPS have been proposed. For example, Japanese Unexamined Patent Publication No. 57-108,135 discloses a method in which PPS is treated with a mixed solvent comprising ethylene glycol and N-methyl-2-pyrrolidone; Japanese Unexamined Patent Publication No. 57-108,136 discloses a method in which a chemical such as sodium carbonate is added to an aqueous slurry of PPS and the mixture is treated at a high temperature under a high pressure; and Japanese Unexamined Patent Publication No. 59-219,331 discloses a method in which PPS is heat-treated in an aromatic solvent such as diphenyl ether, diphenyl, 1-chloronaphthalene, p-chlorophenol or benzonitrile.
In the method where PPS is treated with a mixed solvent of ethylene glycol and N-methyl-2-pyrrolidone, a large quantity of the solvent must be used and the same operation must be repeated at least two times, preferably 3 to 5 times, for removing impurities to a required level. The effect of removing impurities is not sufficient in the method where sodium carbonate is added to an aqueous slurry of PPS and the mixture is treated. Moreover, the method in which PPS is heat-treated in an aromatic solvent such as diphenyl ether or diphenyl has a problem in that, since the melting point of the solvent is relatively high, the treatment must be carried out at a high temperature and separation of the solvent is relatively difficult.
It is an object of the present invention to provide a method for removing impurities such as alkali metal compounds from PPS with a high efficiency.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, there is provided a method for removing impurities from a polyphenylene sulfide resin, which comprises heat-mixing a powdery polyphenylene sulfide resin with a solvent selected from the group consisting of (I) at least one solvent selected from dimethylsulfoxide, sulfolane, glycerol, ethylene glycol, and diethylene glycol, (II) a mixed solvent of a solvent selected from dimethylsulfoxide, sulfolane, glycerol, ethylene glycol, and diethylene glycol with an .alpha.-halogenated naphthalene or biphenyl, (III) a mixed solvent of the mixed solvent (II) or at least one solvent selected from benzyl alcohol, sulfolane, and glycerol with N-methyl-2-pyrrolidone and (IV) a mixed solvent of the solvent (I) or N-methyl-2-pyrrolidone with water to bring the powder and the solvent in contact with each other in the partially dissolved state, cooling and filtering the mixture, and washing the filter cake with a solvent incapable of dissolving the polyphenylene sulfide resin therein.
BEST MODE FOR CARRYING OUT THE INVENTION
The PPS referred to in the present invention is a PPS having a particle size in the range of from 5 to 200 .mu.m and an average particle size of 30 to 50 .mu.m, which is prepared according to a method as disclosed in Japanese Examined Patent Publication No. 45-3,368 or Japanese Examined Patent Publication No. 52-12,240, and this PPS ordinarily contains 1,000 to 000 ppm of impurities such as alkali metal compounds. The PPS prepared through the ordinary preparation steps is in the powdery form, but in order to increase the contact area, preferably the PPS is finely divided by the dry method or the wet method.
When a mixed solvent is used as the solvent, the mi
Marukawa Kiichi
Nagaki Kazuyoshi
Nakamura Yoshiaki
Anderson Harold D.
Tohpren Co., Ltd.
LandOfFree
Method for removing impurities from polyphenylene sulfide resin does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for removing impurities from polyphenylene sulfide resin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for removing impurities from polyphenylene sulfide resin will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-526011