JPH0741673A - Polyphenylene sulfide resin composition - Google Patents

Abstract

PURPOSE:To suppress change in color in melting, kneading and molding a polyphenylene sulfide resin, to reduce change in melt viscosity shown in the case of adding a conventional organic phosphorus-based or phenol-based stabilizer and to improve weld strength of a molded article. CONSTITUTION:This polyphenylene sulfide resin composition comprises 100 pts.wt. of a polyphenylene sulfide resin and 0.01-5 pts.wt. of a polytetrafluoroethylene resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyarylene sulfide resin composition, particularly a polyphenylene sulfide resin composition, in which discoloration is significantly reduced and weld strength is improved.

[0002]

2. Description of the Related Art Polyarylene sulfide resins, typically polyphenylene sulfide resins, are used in automobile equipment parts because of their excellent mechanical properties, heat resistance, chemical resistance, flame retardancy, and good processing productivity. It is used as a material for electrical / electronic parts, chemical equipment parts, etc. In recent years, advances in polymerization methods for polyarylene sulfide resins have made it possible to obtain resins with high whiteness. However, the resin is discolored by the influence of heat and oxygen during the kneading with a filler or the like and the extrusion process, and the whiteness or hue of the molded product deteriorates. In order to reduce discoloration, an organic phosphorus-based or phenol-based stabilizer is added,
The effect is not sufficient, and the use of the organic phosphorus stabilizer causes another problem that the melt viscosity of the resin is changed.

Further, generally, the melt viscosity of polyphenylene sulfide resin is low, which may cause remarkable burrs on an injection molded product, which is inconvenient. There is known a method of heating and kneading a polyphenylene sulfide resin and a silane compound in order to increase the melt viscosity (JP-A-63-251430). Alternatively, by treating the polyphenylene sulfide resin with an acid or an aqueous solution of a strong acid-weak base type salt and kneading this with a silane compound by heating, a resin having excellent weld strength and impact strength with little burr generation in the molded product It is known that a composition can be obtained (JP-A 1-146955). However, the polyphenylene sulfide resin composition obtained by these methods also has the problem of discoloration during molding.

[0004]

DISCLOSURE OF THE INVENTION The present invention is directed to melt kneading,
It is an object of the present invention to provide an excellent polyarylene sulfide resin composition by significantly suppressing the discoloration of the polyarylene sulfide resin at the time of molding and finding an additive where the weld strength is improved, but there is no change in melt viscosity. .

[0005]

The present invention is a polyarylene sulfide resin composition containing 100 parts by weight of a polyarylene sulfide resin and 0.01 to 5 parts by weight of a polytetrafluoroethylene resin.

[0006] Preferably, the polyarylene sulfide resin composition of the present invention further comprises 0.01 to 5 parts by weight of a silane coupling agent.

Polyarylene sulfide resin (hereinafter, PA
S) are well known, and examples of the arylene group include p-, m- and o-phenylene groups, their substitution products, preferably p-phenylene group, diphenylene ether group, diphenylene group and diphenylene ether group. Phenylene sulfone group,
It may contain a biphenylene group, a diphenylenecarbonyl group, a naphthalene group, or the like, and may be a polymer obtained by using a small amount of a trifunctional monomer to increase the melt viscosity. Preferably, the temperature is 300 ° C. and the shear rate is 121.
10 to 10 ⁴ poise measured at 6 sec ^-1 , especially 50 to
Polyphenylene sulfide with a viscosity of 5,000 poise is used. For example, high molecular weight polyphenylene sulfide produced by the method described in JP-B-52-122403 and JP-A-61-7332, high molecular weight polyphenylene sulfide obtained by treatment with a gas containing oxygen, etc. Used.

It is preferable to use a high molecular weight and linear polyarylene sulfide prepared by the method described in Japanese Patent Application No. 4-291908. That is, in a method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide solvent, cooling the gas phase part of the reaction vessel to remove one of the gas phase in the reaction vessel. A polyarylene sulfide made by a method characterized by condensing a part and refluxing it in a liquid phase is used.

The refluxed liquid has a high water content compared to the liquid phase bulk due to the vapor pressure difference between water and the amide solvent.
This reflux liquid having a high water content forms a layer having a high water content on the reaction solution. As a result, a large amount of residual alkali metal sulfide (for example, Na ₂ S), alkali metal halide (for example, NaCl), oligomer and the like will be contained in the layer. 230 in the conventional method
At a high temperature of ℃ or higher, when the generated PAS and the raw materials such as Na ₂ S and by-products are uniformly mixed, not only a high-molecular weight PAS cannot be obtained, but also the depolymerization of the generated PAS. Is also generated, and thiophenol by-product is observed. However, in this method, the above inconvenient phenomenon can be avoided by actively cooling the gas phase portion of the reaction vessel and returning a large amount of the water-rich reflux liquid to the upper portion of the liquid phase, so that the reaction is inhibited. It seems that these factors can be eliminated with high efficiency and high molecular weight PAS can be obtained. However, the present method is not limited only by the effect of the above phenomenon, and high-molecular weight PAS can be obtained by various influences caused by cooling the gas phase portion.

In this method, it is not necessary to add water during the reaction unlike the conventional method. However, the addition of water is not excluded at all. However, if water is added, some of the advantages of this method are lost. Therefore, preferably, the total amount of water in the polymerization reaction system is constant during the reaction.

The gas phase portion of the reactor can be cooled by external cooling or internal cooling, and can be performed by a cooling means known per se. For example, a method of flowing a cooling medium into an internal coil installed in the upper part of the reaction can, a method of flowing a cooling medium into an external coil or jacket wound around the upper part of the outside of the reaction can, and a reflux condenser installed in the upper part of the reaction can are used. The method may be such as sprinkling water or spraying gas (air, nitrogen, etc.) on the upper part of the outside of the reaction can, but any method is effective as long as it has the effect of increasing the amount of reflux in the can. May be used. If the outside air temperature is relatively low (for example, room temperature), it is also possible to perform appropriate cooling by removing the heat insulating material conventionally provided on the upper part of the reaction can. In the case of external cooling, water condensed on the reactor wall surface
The amide-based solvent mixture enters the liquid phase along the wall of the reaction vessel. Therefore, the water-rich mixture accumulates above the liquid phase,
Keep the water content there relatively high. For internal cooling,
The mixture condensed on the cooling surface likewise travels along the surface of the cooling device or the wall of the reaction vessel into the liquid phase.

On the other hand, the temperature of the liquid phase bulk is maintained at a predetermined constant temperature or controlled according to a predetermined temperature profile. 230 to 2 when the temperature is constant
It is preferable to carry out the reaction at a temperature of 75 ° C. for 0.1 to 20 hours. More preferably, at a temperature of 240 to 265 ° C, 1 to
6 hours. 2 to obtain higher molecular weight PAS
It is preferred to use a reaction temperature profile of more than one stage. The first stage is preferably performed at a temperature of 195 to 240 ° C. If the temperature is low, the reaction rate is too slow, which is not practical. If the temperature is higher than 240 ° C., the reaction rate is too fast, PAS having a sufficiently high molecular weight cannot be obtained, and the side reaction rate remarkably increases. The completion of the first stage is preferably carried out at a time when the residual ratio of the dihalo-aromatic compound in the polymerization reaction system is 1 mol% to 40 mol% and the molecular weight is 3,000 to 20,000. More preferably, the residual ratio of the dihaloaromatic compound in the polymerization reaction system is 2 mol% to 15 mol% and the molecular weight is 5,000 to 15,000. When the residual rate exceeds 40 mol%, side reactions such as depolymerization tend to occur in the second-step reaction, while when it is less than 1 mol%, it is difficult to finally obtain a high molecular weight PAS. Thereafter, the temperature is raised, and the reaction in the final stage is preferably carried out at a reaction temperature of 240 to 270 ° C. for 1 hour to 10 hours. If the temperature is low, PAS having a sufficiently high molecular weight cannot be obtained, and if the temperature is higher than 270 ° C., side reactions such as depolymerization are likely to occur, making it difficult to stably obtain a high molecular weight product.

As an actual operation, first, dehydration or water addition is carried out in an inert gas atmosphere, if necessary, so that the amount of water in the alkali metal sulfide in the amide solvent becomes a predetermined amount. The water content is preferably 0.5 to 2.5 mol (per 1 mol of alkali metal sulfide). If it is less than 0.5 mol, the reaction rate is too fast, and undesired reactions such as side reactions occur. If it exceeds 2.5 mol, the reaction rate becomes small, and further, by-products such as phenol are produced in the filtrate after the reaction. The amount of material increases and the degree of polymerization does not increase. The dihaloaromatic compound may be added to the reaction system from the beginning, or may be added after the completion of dehydration. The amount used is high molecular weight PA in the range of 0.9 to 1.1 mol with respect to 1 mol of alkali metal sulfide.
Desirable to obtain S. In the case of a one-step reaction at a constant temperature, it is desirable to cool the gas phase portion during the reaction from the start of the reaction, but it must be performed at least during the temperature increase of 250 ° C. or less. In the multi-step reaction, it is desirable to carry out the cooling from the first step reaction, but it is preferable to perform the cooling from the middle of the temperature rise after the completion of the first step reaction at the latest. Regarding the degree of cooling effect, the pressure inside the reaction vessel is usually the most suitable index. The absolute value of the pressure varies depending on the characteristics of the reaction vessel, the stirring state, the water content in the system, the molar ratio of the dihalo aromatic compound to the alkali metal sulfide, and the like. However, as compared with the case of not cooling under the same reaction conditions, if the reactor pressure decreases, the amount of reflux increases, which means that the temperature at the reaction solution gas-liquid interface decreases. It is considered that the degree of relative decrease indicates the degree of separation between the layer having a high water content and the layer having no water content. Therefore, the cooling must be performed to such an extent that the internal pressure of the reactor becomes lower than that in the case where no cooling is performed. The degree of cooling is
Those skilled in the art can appropriately set the values according to the device to be used and the operating conditions.

The polymeric PAS thus obtained is separated from by-products and dried by post-treatment methods known to those skilled in the art.

Further, preferably, Japanese Patent Application No. 4-152980.
Using a polyarylene sulfide that has been acid-treated according to the method described in the specification, that is, a polyarylene sulfide obtained by reacting a dihaloaromatic compound with an alkali metal sulfide is treated in an acid solution at 100 ° C. or lower. To separate the polyarylene sulfide from the acid solution,
Next, it is a polyarylene sulfide obtained by heating and curing in a gas phase oxidizing atmosphere.

In the present method, the temperature when treating PAS in an acid solution is 100 ° C. or lower, preferably 40 to 80 ° C.
Is important. If the temperature exceeds 100 ° C., the intrinsic viscosity (that is, the molecular weight) of the product PAS obtained after the curing treatment is low, and thus the curing treatment for a longer time is required to obtain the intrinsic viscosity equivalent to that of this method.

The PAS obtained by this method has few branches. This is evidenced by the fact that PAS according to the method is completely soluble in 1-chloronaphthalene.

Further, the PAS according to the present method has good thermal stability, and therefore, its melt viscosity does not increase or decrease significantly during the residence in the molding machine.

Polytetrafluoroethylene resin (hereinafter,
PTFE, which may be referred to as PTFE), may be a homopolymer or a copolymer with, for example, α-olefin, and has an average particle size of 0.01 to 100 μ (particularly 0.1 to 10 μ) and a specific gravity of 1.9 to 2.
A powder having a melting point of 250 to 340 ° C. (preferably 2.0 to 2.2) is preferable. You may use the paste-like thing which disperse | distributed the powder to the organic solvent. By adding PTFE to PAS, discoloration of PAS during melt-kneading and molding can be significantly suppressed and weld strength can be improved.

PTFE is used in an amount of 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of PAS. If the amount of PTFE is less than this, the effect of the present invention cannot be achieved. On the other hand, even if it is more than this, the effect of the present invention is not particularly increased.

Silane coupling agents are known, and examples thereof include vinylalkoxysilane, aminoalkoxysilane (particularly γ-aminopropyltriethoxysilane), epoxyalkoxysilane, and mercaptoalkoxysilane. JP-A-63-251430 It is described in. By adding this to PAS, the weld strength of the molded product is significantly improved. The silane coupling agent is 0.01 to 5 parts by weight with respect to 100 parts by weight of PAS, preferably
Use 0.1 to 3 parts by weight. If it is less than this range, it is not effective, while if it is more than this range, the adverse effect of thickening is great and the molding operation is difficult.

The composition of the present invention may optionally further contain an inorganic filler, for example, 400 parts by weight or less, preferably 200 parts by weight or less. The inorganic filler may be any known filler, for example, fibrous filler such as glass fiber, asbestos, carbon fiber, silica fiber, silica-alumina fiber and potassium titanate fiber, or granular filler, for example. Carbon black, silica, quartz, glass beads, silicates, metals, metal oxides, metal salts and the like can be used.

Further, the composition of the present invention may contain known phenolic stabilizers, phosphorus stabilizers and release agents. The phenolic stabilizer is preferably one having a hindered phenolic structure from the viewpoint of heat resistance, hue, etc., the phosphorus stabilizer is preferably organic bisphosphite or triallylphosphite, and the release agent is sodium stearate or polyolefin. Waxes and the like are preferable.
These can be added in an amount of 5 parts by weight or less, preferably 3 parts by weight or less.

Furthermore, other conventional agents such as other antioxidants, UV absorbers and the like can be added to the composition of the present invention.

The composition of the present invention comprises PAS, PTFE, and an optional silane coupling agent, inorganic filler, phosphorus or phenolic stabilizer, or any other conventional agent, together or in any order. It can be made by kneading.
Kneading should be done above the melting temperature of PAS, preferably 300 ℃ ~ 340
Perform at ℃.

The present invention will be described below with reference to examples.

[0027]

EXAMPLES The components used in the examples are as follows. PAS: Polyphenylene sulfide (LN-2, Topren Co., Ltd.) PTFE: Fluon L170 and 171 (Asahi Glass Co., Ltd.) Silane coupling agent: (3-glycidyl ether propyltrimethoxysilane) Inorganic filler: Surface-treated glass fiber (A404 , Asahi Fiber Glass Co., Ltd.) Organic phosphorus stabilizer: PEP36 (Asahi Denka Co., Ltd.) Phenolic stabilizer: A0330 (Asahi Denka Co., Ltd.) Each component was used in parts by weight shown in Table 1. First, PAS
, PTFE, and an organophosphorus stabilizer and a phenolic stabilizer (when used) were dry blended, then a silane coupling agent was added little by little and mixed, and finally an inorganic filler was added and dry blended. This is the screw diameter
Rotation in the same direction using a 20 mm, L / D = 28 twin screw extruder 120 rp
The mixture was kneaded and extruded at a barrel temperature of 320 ° C to prepare pellets. Next, each test piece was prepared using the pellet, and the properties were measured as described below. L value: Injection molding machine (cylinder temperature 320 ℃, mold temperature 15
A 80 × 80 × 3 mm flat plate was molded at 0 ° C.) and measured using a color difference meter. Melt viscosity: Toyo Seiki Co., Ltd. Capirograph was used for the above pellets, 320 ℃, L / D = 40, shear rate 1216
Measured at S ^-1 . Weld strength: A dumbbell having a thickness of 1 mm conforming to ASTM D638 type I dumbbell was made. The mold had side gates at both ends and had a weld part in the middle. Dumbbell
Tensile tests were performed according to ASTM D638.

[0028]

[Table 1] First, comparing Comparative Example 1 and Comparative Example 2, the hue is slightly improved by adding the phenolic stabilizer. In Comparative Examples 3 and 4 using the phosphorus-based stabilizer, the hue was improved to some extent, but the melt viscosity was decreased.

In Examples 1 to 3, since PTFE was used, the hue was remarkably improved and the weld strength was improved as compared with Comparative Example 1, but the melt viscosity was not lowered. In Examples 4 to 7, the conventional stabilizer was used in addition to PTFE, and the hue was further improved.

In Example 8, no glass fiber was used, which is significantly improved in L value and weld strength as compared with Comparative Example 5. (Because it does not contain glass fiber, both melt viscosities are small.)

[0031]

According to the present invention, discoloration of PAS resin is prevented, weld strength is improved, and melt viscosity is not lowered.

Claims (2)

[Claims] 1. A polyarylene sulfide resin composition containing 100 parts by weight of a polyarylene sulfide resin and 0.01 to 5 parts by weight of a polytetrafluoroethylene resin. 2. A silane coupling agent is added in an amount of 0.01-5.
The polyarylene sulfide resin composition according to claim 1, which comprises parts by weight.