JPH0429527B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyphenylene sulfide resin molded article having novel properties, particularly excellent tensile elongation at break, and a method for producing the same. Polyphenylene sulfide resin (hereinafter abbreviated as PPS) has better chemical resistance than other thermoplastic resins.
It has excellent heat resistance, high frequency characteristics, and nonflammability, and is being used widely in fields such as electrical equipment parts, automobile parts, and aircraft parts that take advantage of these properties. However, although molded products made of PPS exhibit excellent mechanical properties in an amorphous state, if they are placed in a high-temperature atmosphere above its glass transition temperature, especially above 120°C, it rapidly crystallizes and becomes mechanically unstable. It has the disadvantage that its mechanical properties, especially its elongation at break, are significantly reduced and it becomes extremely brittle. On the other hand like this
In order to improve the brittleness of PPS, it is widely used to strengthen it by adding reinforcing agents such as glass fiber to PPS. smoothness is impaired,
Not only does it have drawbacks such as increased specific gravity, but PPS, which is a matrix resin, is extremely brittle, so it is difficult to add a reinforcing agent (usually 30 to 40% by weight) to the extent that it does not inhibit molding processability such as injection molding. There was a problem that the effect of improving mechanical strength, particularly impact resistance, was not sufficient. Therefore, the inventors of the present invention have conducted intensive studies with the aim of improving the drawback that PPS becomes extremely brittle due to crystallization as described above. By heat-treating PPS under specific conditions and then molding it,
The present invention was achieved by discovering that a PPS molded product can be obtained which has excellent new properties such as a crystallization peak temperature of 160° C. or lower, which makes it difficult to crystallize, and a tensile elongation at break of 10% or more. In other words, the present invention involves processing a PPS molded product and a granular material made of PPS, which has a crystallization peak temperature of 160°C or less and a tensile elongation at break of 10% or more as measured by a differential scanning calorimeter, in the presence of oxygen. The present invention provides a method for producing a PPS molded article having the above characteristics, which is characterized in that the product is heat treated at a temperature higher than its melting point and then compression molded. The structural formula of PPS used in the method of the present invention is

A polymer containing 90 mol% or more, preferably 95 mol% or more of repeating units represented by the formula, at a temperature of 300°C and an apparent shear rate.
Melt viscosity measured under 200sec ^-1 condition is 50~
50,000 poise, especially one in the range of 100 to 20,000 poise is suitable. The PPS used contains granular fillers such as talc, fused silica, mica, and glass beads, as well as conventional additives such as lubricants, crystal nucleating agents, coloring agents, and mold release agents, as well as additives to promote the heat treatment effect of the present invention. It may contain auxiliary agents such as oxides, and it may also blend small proportions of other types of polymers within a range that does not impede the object of the present invention. In order to obtain a PPS molded article having the novel properties of the present invention, it is first necessary to subject the PPS granules, such as powder, chips, pellets, etc., to a specific heat treatment prior to molding. This heat treatment is a process in which PPS powder is exposed to an atmosphere at least once at a temperature higher than the melting point of PPS in the presence of oxygen.Setting the heat treatment temperature higher than the melting point of PPS shortens the processing time. Not only the meaning of PPS
This is an indispensable condition for imparting the desired new properties to a molded product, and even if it is heat-treated at a temperature below its melting point, it will not be possible to obtain a molded product with a crystallization peak temperature of 160°C or less. The upper limit of the heat treatment temperature is
The temperature is about 450°C, and it is not appropriate to set it higher than necessary. It is also essential that the heat treatment be performed in the presence of oxygen; if heat treatment is performed under reduced pressure or in an inert gas atmosphere such as nitrogen, the peak crystallization temperature of PPS cannot be lowered to below 160°C. , the object of the invention is not achieved. The heat treatment time varies depending on the heat treatment temperature, and the higher the treatment temperature, the shorter the time. However, the combination of treatment temperature and treatment time should be set so that the PPS crystallization peak temperature is 160°C or less, and the crystallization If the heat treatment is stopped at a stage where the peak temperature is 160° C. or higher, a molded article with sufficient improvement in tensile elongation at break cannot be obtained. In addition, in the present invention, the crystallization peak temperature of 160°C or less means that due to the progress of heat treatment,
This also includes a case where the crystallization peak temperature is substantially no longer observed. Equipment used for heat treatment includes hot air ovens, infrared heating furnaces, and combinations thereof.The specific method for heat treatment is to place PPS powder flat on a mesh or tray, and heat it to an appropriate temperature. Examples include a method in which heat treatment is carried out batchwise or continuously if the material is placed in an apparatus set to Of course, it is also possible to start the heat treatment temperature from a low temperature and increase it stepwise until it reaches the melting point or higher. Since the melt viscosity of PPS powder heat-treated under these conditions increases significantly, it is impossible to use it for melt molding such as ordinary injection molding or extrusion molding in the next molding step. If appropriate, compression molding should be used. The following method is exemplified as this compression formation. 1 The PPS powder or granules after heat treatment are reheated to above the melting point, or the PPS powder or granules immediately after heat treatment are kept above the melting point and heated to above the melting point of PPS, usually 290 to 350°C. After being supplied to the mold and compressed, the temperature is below the melting point of PPS, usually
A method of cooling at 150-200℃ and removing the molded product from the mold. 2. Either reheat the heat-treated PPS powder to a temperature above the melting point, or directly maintain the heat-treated PPS powder to a temperature above the melting point and feed it to a mold set at a temperature below the melting point of PPS. , a method of pressurizing and shaping (so-called stamping molding method and drawing method). 3 PPS powder is uniformly spread on a metal conveyor belt, heat treated by passing it continuously through a heating furnace set at a temperature higher than the melting point of PPS, and then installed immediately after the heating furnace. A method of producing plate-shaped molded products by guiding powder between a pair of metal belts and continuously heating and cooling the metal belts while applying pressure from both sides. The PPS molded products of the present invention, such as films, sheets, and three-dimensional shaped products, obtained in this way have excellent new properties such as a crystallization peak temperature of 160°C or less and a tensile elongation at break of 10% or more. Compared to conventional PPS molded products, it is extremely resistant to crystallization and has superior mechanical properties, making it expected to be used in a variety of applications. The present invention will be explained in further detail by giving examples below. Note that the crystallization peak temperature and melting point as used in the present invention and the following examples mean values measured by the following method. That is, using a differential scanning calorimeter (manufactured by PerkinElmer, Model DSC-IB), approximately 10 mg of the sample was heated at a temperature increase rate of 20°C/min in a nitrogen gas atmosphere, and when the temperature reached 360°C, it was held for 5 minutes. After that,
The apex of the endothermic peak that appears when the temperature is raised when the temperature is lowered at a cooling rate of 20°C/min is defined as the melting point, and the apex of the exothermic peak that appears when the temperature is lowered is defined as the crystallization peak temperature.
Further, the tensile elongation at break was measured according to the method of ASTM D-638. Examples 1 to 6 and Comparative Examples 1 to 5 32.6 kg of sodium sulfide (250
mol, including 40% by weight of water of crystallization), 100 g of sodium hydroxide, 36.1 Kg (250 mol) of sodium benzoate,
and N-methyl-2-pyrrolidone (hereinafter NMP)
(abbreviated as )) was charged, and the temperature was gradually raised to 205℃ while stirring, resulting in a distillate of 7.0 kg containing 6.9 kg of water.
was removed. 1,4-dichlorobenzene 37.5Kg in the residual mixture
(255 mol) and NMP20.0Kg and heated to 265℃ for 4 hours.
heated for an hour. The reaction product was washed 8 times with hot water,
Dry at 80°C for 24 hours using a vacuum dryer to obtain a powder with a melt viscosity of 2900 voids and a melting point of 277°C with a high degree of polymerization.
Obtained PPS21.2Kg. The above PPS powder was uniformly spread into a flat container with an open bottom, placed in an oven, and heat treated in the presence of oxygen under the conditions shown in Table 1. A sheet approximately 1 mm thick was prepared by heating, pressurizing, and cooling at 200°C. Table 1 shows the results of measuring the mechanical properties of the obtained sheet.

[Table] As is clear from Table 1, the PPS sheets (Examples 1 to 6) with a crystallization peak temperature of 160°C or less obtained by the method of the present invention exhibit excellent mechanical properties,
Tensile elongation at break is 10% or more. However, sheets heat-treated below the melting point (Comparative Examples 1 to 4)
The crystallization peak temperature was 160°C or higher, and the tensile elongation at break was 10% or lower. In addition, when heat treated for a very long time even below the melting point, the crystallization peak temperature is below 160℃ (Comparative Example 5)
However, when this powder was formed into a sheet in the same manner as above and its mechanical strength was measured, the tensile elongation at break was 10% or less as shown in Table 1. As described above, it can be seen that the PPS molded article obtained after processing at a temperature above the melting point as in the present invention exhibits excellent mechanical properties. Furthermore, an attempt was made to cut the PPS of Example 6 and form it into a sheet using an extrusion molding machine, but the melt viscosity was too high to form the sheet. Example 7 and Comparative Examples 6 and 7 Using the same PPS powder as in Example 1, the powder was uniformly spread in the same container as in Example 1, and the powder was heated under reduced pressure in the presence of oxygen (in the atmosphere, in an oven). Bottom (vacuum degree 50mm
Hg) and nitrogen atmosphere at 300℃ for 2 hours, and compression molded in the same manner as in Example 1 to 1mm.
The crystallization peak temperature and mechanical properties of the thick sheet were measured and the results are shown in Table 2.

[Table] As is clear from Table 2, under reduced pressure and under a nitrogen atmosphere, no effect of lowering the crystallization peak temperature or improving mechanical properties was observed at all. It was found that in the treatment in an oxygen atmosphere in the present invention, the crystallization peak temperature was significantly lowered and the mechanical strength was also significantly improved. Example 8 PPS powder heat-treated under the same conditions as Example 4 was
After heating and melting in an oven set at 320℃ for 5 minutes, this was placed in a cup-forming mold (opening diameter 100mmφ, bottom diameter 80mmφ, height 50mm,
When the cup was compression-molded at a pressure of 100 kg/cm ² (thickness: 1.0 mm), the moldability was good, and the resulting cup had extremely strong characteristics. On the other hand, when PPS powder heat-treated under the same conditions as Comparative Example 3 was subjected to compression molding in the same manner as above, the powder not only stuck when taken out of the oven and was difficult to handle, but also the resulting cup was extremely brittle. It was hot.

Claims (1)

[Scope of Claims] 1. A polyphenylene sulfide resin molded product characterized by having a crystallization peak temperature of 160° C. or less as measured by a differential scanning calorimeter, and a tensile elongation at break of 10% or more. 2. A differential scanning calorimeter, characterized in that a granular material made of polyphenylene sulfide resin is heat-treated at a temperature equal to or higher than the melting point of the polyphenylene sulfide resin in the presence of oxygen, and then compression molded. A method for producing a polyphenylene sulfide resin molded product having a crystallization peak temperature of 160°C or less and a tensile elongation at break of 10% or more.