JPH0674365B2 - Glass fiber reinforced resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a glass fiber reinforced polypropylene resin composition, and more particularly to a polypropylene resin composition useful as a material for wheel caps of automobiles.

[Prior Art] In recent years, resin-made wheel caps have been widely used due to demands for weight reduction and the like. Since wheel caps are required to have impact resistance and heat resistance, engineering plastic materials such as nylon and modified PPO are used as resin materials. However, these materials are expensive, and improvement in cost is desired.

Therefore, the applicant of the present application has proposed in Japanese Utility Model Laid-Open No. 1-62333 a wheel cap made of an inexpensive composition of polypropylene resin and glass fiber.

[Problems to be Solved by the Invention] Although glass fiber reinforced polypropylene is generally excellent in mechanical strength, rigidity, heat resistance, creep resistance, etc.,
On the other hand, a problem of poor appearance may occur due to the addition of glass fiber, and various measures are required when high appearance quality is required. For example, Japanese Examined Patent Publication No. 64-7618 discloses a composition in which a specific amount of glass fiber having an average diameter of 7 μm or less is blended in order to improve the above-mentioned problems of the glass fiber reinforced polypropylene resin.

In the above-mentioned JP-B-64-7618, it is supposed that the desired performance is imparted mainly by specifying the glass fiber.However, the present invention specifies the components in the resin to provide a high appearance quality as a wheel cap. Is obtained, and the mechanical strength and heat resistance are excellent.

[Means for Solving the Problems] In view of the above problems, the present inventors have investigated the performance of various polypropylene resins. As a result, they have completed the present invention by discovering that a specific low molecular weight component has a great influence on impact resistance.

That is, the glass fiber reinforced resin composition of the present invention comprises 3 to 12% by weight of an ethylene component, 0.3 to 3.5% by weight of a low molecular weight component having a weight average molecular weight of 1000 to 50,000, and a melt flow rate of 20 to 100 g / 10 min. 45-83% by weight of ethylene-propylene block copolymer and unsaturated carboxylic acid (modified polypropylene resin 2 modified with an unsaturated or derivative thereof)
.About.20 wt.% And glass fiber 15 to 35 wt.%.

The glass fiber reinforced resin composition of the present invention comprises a crystalline ethylene-propylene block copolymer, a modified polypropylene resin and glass fibers. The most important feature of the present invention lies in the crystalline ethylene-propylene block copolymer.

In the crystalline ethylene-propylene block copolymer,
The ethylene component is contained in an amount of 3 to 12% by weight. If the ethylene component is less than 3% by weight, the impact resistance is lowered, and if it exceeds 12% by weight, the rigidity and strength are lowered.

The crystalline ethylene-propylene block copolymer has a weight average molecular weight of 1,000 to 50,000 and a low molecular weight component of 0.3 to 3.5.
It is contained by weight%. 0.3% by weight of this low molecular weight component
If it does not meet the requirements, the impact resistance will be extremely reduced, and if it exceeds 3.5% by weight, the rigidity and strength will be reduced. The low molecular weight component can be quantified by chloroform extraction or the like.

The crystalline ethylene-propylene block copolymer must have a melt flow rate of 20 to 100 g / 10 minutes. If the melt flow rate is less than 20 g / 10 minutes, the molded appearance will be deteriorated, and if it exceeds 100 g / 10 minutes, the mechanical strength, especially the impact strength will be reduced.

The modified polypropylene resin is a polypropylene resin modified with an unsaturated carboxylic acid such as maleic acid or fumaric acid or an acid anhydride (derivative of unsaturated carboxylic acid) such as maleic anhydride. Can be used. The blending amount is 2 to 20% by weight.
Rigidity when the modified polypropylene resin is less than 2% by weight,
The strength and impact resistance are reduced, and the appearance is also deteriorated. 20% by weight
If it exceeds, the cost becomes high and the effect of the modified polypropylene resin is saturated.

The glass fiber reinforced resin composition of the present invention further contains 15 to 35% by weight of glass fiber. Glass fiber content
If it is less than 15% by weight, various properties such as rigidity, strength, impact resistance and heat resistance are deteriorated, and if it exceeds 40% by weight, glass fibers are exposed on the surface and the appearance is deteriorated. The fiber length of the glass fiber is not particularly limited, and various conventionally used ones can be selected and used.

[Operation and Effect of the Invention] In the glass fiber reinforced resin composition of the present invention, the crystalline ethylene-propylene block copolymer has a weight average molecular weight of
Low molecular weight components of 1000 to 50,000 are contained in 0.3 to 3.5% by weight. The presence of this low molecular weight component remarkably improves the impact resistance of a molded product molded using this resin composition. Further, when the melt flow rate is in the range of 20 to 100 g / 10 minutes, the molded product has an extremely excellent appearance regardless of the fiber length of the glass fiber.

Therefore, when the glass fiber reinforced resin composition of the present invention is used for molding, a wheel cap excellent in various properties such as appearance quality, impact resistance, rigidity, strength and heat resistance can be obtained. Therefore, without using expensive engineering plastics such as nylon and modified PPO as in the past, it is possible to manufacture at a low cost, with performance equivalent to or better than that of wheel caps made from these resins.

[Examples] Specific examples will be described below.

(Example 1) 7 wt% of ethylene component and 0.9 wt% of low molecular weight component (Soxhlet extraction with chloroform for 8 hours, room temperature) were included, and the melt flow rate (hereinafter referred to as MFR) was 30 g / 10.
65 parts of crystalline ethylene-propylene block copolymer
The glass fiber reinforced resin composition of Example 1 was prepared by mixing 30% by weight of glass fiber having a fiber length of 3 mm and 5% by weight of maleic acid-modified polypropylene resin.

A test piece was molded from this resin composition by injection molding at a cylinder temperature of 200 ° C., and the bending strength, flexural modulus and Izod impact value according to ASTM were measured and the results are shown in Table 1. Further, a flat plate of 40 × 110 × 2 (mm) was similarly molded, and the floating state (molding appearance) of the glass fiber was visually determined. Further, a 12.7 × 100 × 6.4 (mm) test piece was similarly molded, and the state of the sink mark in the central portion was visually determined. The respective results are shown in Table 1.

(Examples 2 to 5, Comparative Examples 1 to 8) As shown in Table 1, various amounts of components, MFR, glass fiber amount, modified polypropylene resin amount, etc. in the crystalline ethylene-propylene block copolymer were changed. , Each resin composition was prepared. Then, a test piece was molded in the same manner as in Example 1 and a performance test was conducted in the same manner, and the results are shown in Table 1.

(Evaluation) As shown in Table 1, the molded products molded from the resin compositions of Examples 1 to 5 are excellent in various mechanical strengths and molded appearances. On the other hand, in Comparative Example 1, since the MFR was as small as 15 g / 10 minutes, the molded appearance and sink condition were poor. In Comparative Example 2 as well, since the MFR was as small as 12 g / 10 minutes, the molding appearance and sink condition were poor, and the bending strength was also low. In Comparative Example 3, since the ethylene component and the low molecular weight component are not present, the Izod impact value is remarkably small. Has become. In Comparative Example 4, although the ethylene component and the chloroform extracted component were present, they were insufficient in quantity,
The Izod impact value is insufficient. Further, in Comparative Example 5, the ethylene component is in an appropriate range, but as compared with Example 1 and the like, the low molecular weight component is extremely small at 0.1% by weight. Therefore, the Izod impact value shows a particularly small value, indicating that the impact resistance is poor. In Comparative Example 6, the glass fiber amount is 10
Since it is as small as wt%, the flexural strength and flexural modulus are poor. Further, in Comparative Example 7, the amount of glass fiber is as large as 40% by weight, so that the molding appearance is inferior. Comparative Example 8
However, since the modified polypropylene resin amount is as small as 1% by weight, various mechanical properties and molding appearance are inferior.

(Product Test) Next, using the resin compositions of Example 1 and Comparative Examples 1 and 5, actual wheel caps were molded by injection molding, and various performances were evaluated. The results are shown in Table 2.

The wheel disc is wheeled for repeated desorption evaluation. Repeatedly attaching and detaching the le cap, we investigated the occurrence of defects such as cracks. As a result, with the wheel caps obtained from the compositions of Example 1 and Comparative Example 1, defects such as cracks did not occur even after repeated desorption of 30 times or more, but Comparative Example 5
In the wheel cap molded from the resin composition having a small amount of chloroform extracted, cracks were generated 5 times.

In the heat resistance test, the wheel cap was put in a constant temperature bath at 120 ° C, and after 24 hours, the wheel cap was taken out and the dimensional change was measured. As a result, practically no harmful changes occurred in Example 1, Comparative Example 1 and Comparative Example 5.

Although the drop ball test evaluates impact resistance, 500 g of steel balls were naturally dropped onto the designed surface of the wheel cap in an atmosphere of 23 ° C., and the surface condition was visually evaluated. as a result,
In the wheel caps of Example 1 and Comparative Example 1, the height is 50 cm.
Although no cracks and the like were generated when dropped from the above, the wheel cap of Comparative Example 5 had cracks when dropped at a height of 20 cm, and was inferior in impact resistance.

Regarding the product appearance, the sink marks on the surface due to the ribs on the back surface of the wheel cap were judged. As a result, the wheel caps of Example 1 and Comparative Example 5 were excellent in product appearance without sink marks, but the wheel caps of Comparative Example 1 were inferior in product appearance because sink marks were generated at the positions where the ribs were present on the back surface. Was there.

Claims (1)

[Claims] 1. A crystalline ethylene-propylene block copolymer having an ethylene component of 3 to 12% by weight, a low molecular weight component of 0.3 to 3.5% by weight having a weight average molecular weight of 1000 to 50,000, and a melt flow rate of 20 to 100 g / 10 min. A glass fiber reinforced resin composition comprising 45 to 83% by weight, 2 to 20% by weight of a modified polypropylene resin modified with an unsaturated carboxylic acid or a derivative thereof, and 15 to 35% by weight of glass fiber.