JPS60210631A - Removal of alkali metal salt from polyphenylene sulfide resin - Google Patents

Abstract

PURPOSE:To facilitate the removal of an alkali metal salt from a polyphenylene sulfide resin containing the alkali metal salt, by heating with agitation the resin to a specified temperature or above in an ethylene glycol solvent. CONSTITUTION:A polyphenylene sulfide resin (hereinafter abbreviated as a PPS resin) containing at least about 70mol% structural component having a recurring unit of the formula, said PPS resin containing an alkali metal salt, is fed to an ethylene glycol solvent. This solution is heated with agitation at a temperature of 200 deg.C or above for, usually, 10min or longer, and then cooled. The PPS resin is separated by filtration and, if desired, washed with hot water and dried to obtain PPS resin of a low alkali metal salt content. The obtained PPS resin has a lighter color than untreated one. When this PPS resin is used in sealing electronic parts, the resulting sealed parts can be used in a circuit without detriment to its insulation.

Description

[Detailed description of the invention] The present invention relates to a method for removing alkali metal salts from.

Generally, electronic components such as 0,) transistors, diodes, thyristors, coils, connectors, resistors, etc. Capacitors or their composite components must maintain electrical insulation. Coating or sealing with synthetic resin is widely practiced for the purpose of mechanical protection and prevention of changes in characteristics due to external atmosphere.

As this synthetic resin, thermosetting resins such as epoxy resins and silicone resins are mainly used.

However, when sealing electronic components using these thermosetting resins, the storage stability of the resins is insufficient, or
Since the resin is hardened in the mold, there are drawbacks such as a longer molding time.

In recent years, as an alternative to thermosetting resins that have these drawbacks, we have developed new technologies that have the properties of both thermoplastic resins and thermosetting resins, and
The use of polyphenylene sulfide (hereinafter abbreviated as PP8), which has excellent heat resistance, chemical resistance, and dimensional stability, is attracting attention.

PPS is currently manufactured worldwide only by Phillips Petroleum and sold under the trade name "Ryton."

Various methods for producing pps are known, but a common method is a method in which p-dichlorobenzene and sodium sulfide are reacted in a polar organic solvent.
In Publication No. 568, Sara K.

Japanese Patent Publication No. 52-122 describes a method for producing pps with a molecular weight of 100 ml by adding an alkali metal carboxylate as a polymerization aid.
It is disclosed in Publication No. 40.

However, when using this more advanced PPB manufacturing method, alkali metal salts such as common salt, unreacted sodium sulfide, and sodium ions at the terminals of polymer molecules are produced as by-products during the reaction.
Commercially available products usually contain 1,000 to 5,000 ppm of alkali metal salts.For this reason, PP8 molded products obtained using such PP8 as a raw material are used in the electrical and electronic parts fields. This poses an obstacle to its application. In other words, when PPS containing large amounts of alkali metal salts, which are ionic impurities, is used to encapsulate electronic components such as ICs, it absorbs moisture and deteriorates the insulation properties of the circuits, electrodes and leads. It is known that corrosion of the frame causes deterioration of characteristics and failure of elements such as broken wires.

As a method to improve these drawbacks,
No. 156542 discloses that extractable alkali metal salts are extracted by extracting the alkali metal salts several times with hot water (1001)2.
A method for reducing the number to below m is disclosed. However, according to the research of the present inventors, in this method, even though the extraction was repeated for an extremely long time, the alkali metal salts that adhered to the surface of the haholimer particles that were extracted,
Since the alkali metal salt was only present in the extreme surface layer, and the alkali metal salt was present in the polymer in an amount of IQ 00 ppm or more, the removal effect of the dialkali metal salt was poor.

Furthermore, Japanese Patent Application Laid-Open No. 57-108135 discloses a method for reducing alkali metal salts by bringing PPS into contact with a mixed solvent of a polar aprotic solvent and ethylene glycol. According to this method, it is possible to reduce the alkali metal salts in pps, but in order to perform sufficient desalting, a large amount of mixed solvent is required for PP8, and it is also possible to reduce the amount of alkali metal salts in pps. In this case, it is necessary to increase the contact time and the number of times of contact, which cannot be said to be industrially practical.

The present inventors have discovered the present invention through extensive research into a method for removing alkali metal salts from PP8 that is simpler and more industrially applicable.

That is, the present invention resides in a method for removing an alkali metal salt from a polyphenylene sulfide resin, which comprises heating the polyphenylene sulfide resin containing the alkali metal salt in an ethylene glycol solvent at a temperature of 200° C. or higher. Furthermore, one of the major features of the present invention is that the polymer obtained by the present invention has a pale white color compared to an untreated polymer.

PPe referred to in the present invention is a product copolymerized with other components as long as it contains 70 moles or more, preferably 90 moles or more of a structure having a repeating unit represented by the general formula); Alternatively, it may have a structure in which a portion thereof is crosslinked. Examples of other components in this case include the following.

In the present invention, ethylene glycol is the only effective solvent, and amide solvents, aromatic solvents, and the like used as polymerization solvents have poor alkali metal salt removal effects.

The amount of ethylene glycol solvent used can be changed as appropriate depending on the amount of alkali metal salt in pps, desired purity, and heating temperature, and usually an equivalent amount or more is used.

The heating temperature may be 200°C or higher, and the temperature range commonly used is 200 to 300°C, preferably 220 to 280°C. If the heating temperature is lower than 200°C, the alkali metal salt removal effect becomes extremely poor, and it becomes difficult to reduce the alkali metal salt content to several hundred ppm.

The heating time can be changed as appropriate depending on the amount of sodium salt in PPS, the amount of solvent, and the heating temperature, and is usually 10 minutes or more.
Preferably, 30 minutes or more is employed.

In the present invention, pps in ethylene glycol solvent,
Various methods can be used to heat the product to a temperature of 200° C. or higher, and conventionally known batch, semi-continuous or continuous heating devices can be used.

Recovery of pps may use conventional and common techniques. For example, the method includes distillation removal of the solvent, flushing, or filtering after cooling.

Note that when organic solvents are conventionally used to remove inorganic salts such as alkali metal salts from polymers, washing with hot water or the like is required as a post-treatment to remove the inorganic salts after recovering the polymer. However, in the present invention, such post-processing is not particularly required. For example, the amount of alkali metal salts can be significantly reduced simply by separating the heat-treated mixture in a furnace and drying it according to a conventional method. This is also one of the features of the present invention.

EXAMPLES Next, the method of the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

The residual sodium ion content used in the following Examples and Comparative Examples is approximately The liquid was adjusted to a constant volume by adding 10% of the total volume, and was then diluted by atomic absorption spectroscopy, and the color of the polymer was determined visually after drying the polymer.

Example 1 300 - Sodium ion content in autoclave is 18
00 ppm PPS powder (Rydon ppsv-1
; manufactured by Philips Vetroleum Co.) 309 and 180 g of ethylene glycol, and after replacing with nitrogen,
The mixture was heated and stirred at 40°C for 2 hours. After the autoclave was cooled, the PPS was taken from house to house, dried, and the residual sodium ion content was measured. In addition, after the PPS was distributed to each house, it was washed three times with hot water as a post-treatment, and then dried and the residual sodium ion content was measured.

The results are shown in Table 1.

Example 2 The same operation as in Example 1 was performed except that the heating temperature was 260°C. The results are shown in Table 1.

Example 3 The same operation as in Example 1 was performed except that the heating temperature was 200°C. The results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed except that the heating temperature was 180''C. The results are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was performed except that N-methylpyrrolidone was used instead of ethylene glycol. The results are shown in Table 1.

Comparative Example 5 Using deionized water instead of ethylene glycol
The same operation as in Example 1 was performed except that the extraction was heated at 0° C. for 20 hours. The results are shown in Table 1.

Table 1 Umbrella *) NMP; M-methylpyrrolidone % from Table 1
It can be seen that by heating PP8 to 200° C. or higher in an ethylene glycol solvent, sodium ions can be significantly reduced and the color of the polymer can be lightened. On the other hand, as seen in Comparative Example 1, the heating temperature was 200°C.
It can be seen that when the temperature is very low, the sodium ion removal effect is poor and the polymer has no lightening effect.

In addition, in Examples, the presence or absence of water washing as a post-treatment has little effect on the desalination effect, but Comparative Example 2V
As shown in c, when N-methylpyrrolidone was used, the desalting effect was poor unless washed with water, and even with water washing, the desalting effect was smaller than when ethylene glycol was used.

Further, as seen in Comparative Example 3, it is found that extraction with hot water alone is not effective in removing IJium ions.

Patent applicant: Toyo Soda Kogyo Co., Ltd.

Claims (1)

[Claims] A method for removing an alkali metal salt from a polyphenylene sulfide resin, which comprises heating the polyphenylene sulfide resin containing the alkali metal salt in an ethylene glycol solvent at a temperature of 200°C or higher.