JPH0625299B2 - Method for producing unsaturated polyester resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method for producing an unsaturated polyester resin composition having excellent wear resistance and appearance of a molded article.

[Prior art]

The unsaturated polyester resin composition has excellent electrical properties,
In particular, it is widely used in electric parts because of its arc resistance and tracking resistance. Among those applications, molded products with sliding parts such as magnet switches and switch cases require the wear resistance of the molded products, but the unsaturated polyester resin composition has good wear resistance. It can not be said.

Conventionally, as means for improving such abrasion resistance, use of asbestos as a filler, addition of tetrafluoroethylene resin (Teflon), polyethylene and the like have been performed.

However, there is a limit to the improvement of wear resistance by selecting a filler such as asbestos, and in many cases the wear resistance is deteriorated by not using inorganic fillers such as talc, mica, glass fiber, etc. that deteriorate the wear resistance. Only the so-called negative effect of preventing it is recognized, and the positive effect of further improving the abrasion resistance of the resin is not seen.

Although addition of Teflon surely reduces the surface frictional resistance, the wear resistance of Teflon itself is not so great, and in terms of wear resistance, an inevitable result cannot be obtained. Not only that, but the addition of a large amount of Teflon lowers the thermal rigidity of the molding material and adversely affects the mechanical strength.

On the other hand, the addition of polyethylene is described in JP-A Nos. 51-111890 and 56-74147.
To improve the wear resistance of the unsaturated polyester resin composition,
You can see the effect. However, since the evaluation method of wear resistance is not generally established, even if the wear resistance is good under certain conditions, it is not necessarily good under other conditions. Cases can arise. In particular, there may be cases where excellent wear resistance is exhibited under mild conditions for a relatively short period of time, but not so good under severe conditions for a longer period of time. JP-A-51-
The example of the addition of finely divided polyethylene described in Japanese Patent No. 111890 corresponds exactly to such a case.
This point will be specifically described in Examples and Comparative Examples.

Further, when considering the commercial value of the molded product, not only the function in terms of physical properties, but also the surface state of the molded product, that is, the appearance is important, depending on the type of polyethylene and the method for producing the unsaturated polyester resin composition. In some cases, the appearance is not preferable. Furthermore, it is more difficult to achieve both excellent wear resistance and excellent appearance of the molded product.

[Object of the Invention]

The present invention has conducted extensive studies as to obtain a high degree of abrasion resistance that could not be obtained by the conventional technique, and as a result, a certain type of polyethylene was added to the unsaturated polyester resin and the abrasion resistance was remarkably increased by heating and mixing. The present invention has been found out to be improved. It is an object of the invention to provide a method for producing an unsaturated polyester resin composition having excellent abrasion resistance without deteriorating the appearance of a molded product.

[Structure of Invention]

The present invention adds 50 to 600 parts by weight of fillers and other additives to 100 parts by weight of resin, and 1 to 35 parts by weight of fibrous polyethylene having a melting point of 130 to 135 ° C. and a diameter of 20 μm or less. A method for producing an unsaturated polyester resin composition, which comprises kneading by heating at a resin temperature.

As the unsaturated polyester resin used in the present invention, for example, an isophthalic acid resin, a terephthalic acid resin, or the like is used. As the cross-linking agent, for example, vinyl monomers such as styrene, diallyl phthalate, methacrylic acid methyl ester, divinylbenzene, acrylamide, vinyltoluene, monochlorostyrene and acrylonitrile, and diallyl phthalate prepolymer are used. Examples of the reaction initiator include benzoyl peroxide, lauroyl peroxide, butyl peroxybutane, di-t-butyl peroxyisophthalate, dicumyl peroxide, 2,5-dimethylhexane-2,5-dihydroperoxide, Peroxides such as t-butyl peroxyenzoate, cumene hydroperoxide and methyl ethyl ketone peroxide are used.

As the filler, it is possible to use commonly used fillers such as glass fiber, asbestos, calcium carbonate, clay, inorganic fillers such as aluminum hydroxide, wood powder, organic fillers such as pulp, and the type of these fillers. Is not limited in any way. The amount of the filler is 50 to 100 parts by weight of the resin.
It is 500 parts by weight. If it is 50 parts by weight or less, it is not preferable in terms of rigidity and strength, and if it is 500 parts by weight or more, the viscosity increases, which is not preferable in terms of molding processability.

The core of the present invention lies in the polyethylene used and the heat kneading conditions. First, the melting point of polyethylene is 130 to 135.
Must be ° C. At a melting point of 130 ° C or less, only the effect of improving the wear resistance due to the lubricating effect on the surface of the molded product can be seen, so it seems that the wear resistance is excellent at the initial stage of wear, but due to the progress of wear, After the skin layer on the surface of the product is lost, the wear rapidly increases. The higher the melting point and the higher the molecular weight of polyethylene itself, the more excellent the abrasion resistance is. Therefore, polyethylene having a melting point of 130 ° C. or higher is required to obtain such physical properties even after polymer blending.

On the other hand, since polyethylene having such a high melting point is used, it is not possible to obtain a good appearance of a molded product and excellent abrasion resistance unless polyethylene is uniformly dispersed in the resin composition. For this purpose, it is necessary to heat-knead after adding polyethylene, and the temperature is 120
A temperature of ~ 140 ° C is suitable. At 120 ° C. or lower, the melting of polyethylene is not sufficient, and at 140 ° C. or higher, the curing reaction of the unsaturated polyester resin progresses and stable kneading cannot be performed. In this way, since there is an upper limit to the kneading temperature, conversely,
The melting point of polyethylene has an upper limit, and the upper limit is about 135 ° C.

The heat kneading under the above conditions is necessary but not sufficient for obtaining a good appearance of the molded product. Since the kneading temperature is relatively high, the kneading cannot be continued for a long time. Therefore, in order to achieve uniform dispersion in a short time, polyethylene is preferably fine particles. However, polyethylene having a high melting point, such as polyethylene used in the present invention, is difficult to make into ultrafine powder by so-called chemical pulverization. The present inventors made the most effort in this respect, but finally, they found a fibrous polyethylene having a diameter of 20 μm or less, and completed the present invention. Since it is very fine, it melts and disperses very easily. In the case of particles with a diameter of more than 100 μm, which is obtained by general mechanical grinding,
It is impossible to obtain an excellent appearance of the molded product.

The amount of polyethylene added is 1 to 35 parts by weight with respect to 100 parts by weight of the polyester resin, but preferably 2
-30 parts by weight. If it is less than 1 part by weight, sufficient abrasion resistance cannot be obtained, and if it is more than 35 parts by weight, other properties are adversely affected.

Other release agents, pigments, flame retardants and the like can be used as necessary.

If necessary, kneading with a ribbon may be performed with a ribbon blender, a kneader,
After premixing with a Henschel mixer or the like, it is performed with a roll, a twin-screw kneader, a cokneader, or the like under the temperature conditions described above. After kneading in this manner, it may be granulated by crushing or extruding, or may have another shape.

〔The invention's effect〕

The unsaturated resin composition thus obtained has extremely excellent wear resistance and has a good appearance of a molded product equivalent to that of a general material. Best suited for parts.

〔Example〕

 Examples will be shown below.

The wear resistance used in the present invention was measured by using two molded products as shown in FIG. 1 and fixing one of them and rotating the other at a rotation speed of 60 rpm for 24 hours under a load of 3 kg. Then, the volume decreased due to wear is obtained from the weight difference before and after the rotation and sliding, and the total amount of wear of the two molded products is compared.

The size of the molded product is 5mm x 25mm x 10mm and 18φ
× 10 mm.

The material composition used for material evaluation in the present invention is as follows.

Terephthalic acid type unsaturated polyester resin 100 parts by weight diallyl phthalate 20 〃
Calcium carbonate 350 parts by weight Glass fiber 50 〃
Dicumyl peroxide 4〃
Zinc stearate 10 〃
The polyethylene used for evaluation in the present invention is shown in Table 1.

Table 2 shows the results of experiments conducted using these polyethylenes.
Shown in. The material was manufactured using a hot roll, and the molded product was manufactured by transfer molding at 160 ° C. and 200 kg / cm ² for 4 minutes.

As can be seen from these results, it is clear that the inventive examples are superior to the comparative examples.

Further, FIG. 2 shows changes in wear with time in Example 1 and Comparative Examples 1 and 4. As shown in this figure, the wear resistance of Example 1 is suitably good, while the wear resistance of Comparative Example 4 is
At the initial stage, the abrasion was less than that of Comparative Example 1 in which polyethylene was not added, but the abrasion gradually increased, and there was no great difference from Comparative Example 1 at 24 hours. As described above, low-melting-point polyethylene has a limited ability to impart wear resistance, and simply adding polyethylene cannot provide excellent wear resistance as in the present invention.

[Brief description of drawings]

FIG. 1 shows a molded product for measuring the amount of wear in the present invention. FIG. 2 shows the change over time in the amount of wear.

Claims (1)

[Claims] 1. A melting point of 130 to 135 ° C. with 50 to 500 parts by weight of a filler and other additives relative to 100 parts by weight of resin.
1 to 35 parts by weight of fibrous polyethylene having a diameter of 20 μm or less and heated and kneaded at a resin temperature of 120 to 140 ° C. for producing an unsaturated polyester resin composition.