JP2003321555A - Long fiber-reinforced resin molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long fiber-reinforced resin molded article excellent in strength, rigidity and fatigue strength, and having almost no unopened fiber. <P>SOLUTION: This long fiber-reinforced resin molded article 1 consists of a substrate 2 consisting of a synthetic resin and fibers 3 dispersed in the substrate 2. The melt flow rate of the substrate 2 is ≤20 g/10 min, and the weight- average fiber length of the fiber 3 is 1-3 mm. It is preferable that the substrate 2 consists of a polypropylene-based resin and the fiber 3 is a glass fiber. Also, the long fiber-reinforced resin molded article is preferably a front end carrier. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a long fiber reinforced resin molded article comprising a base material made of synthetic resin and fibers dispersed in the base material.

[0002]

2. Description of the Related Art A long fiber reinforced resin molded article obtained by dispersing fibers such as glass fibers having a large fiber length in a synthetic resin which is a base material is a molded article which is made of only a synthetic resin which is a base material without containing fibers. , And impact resistance and rigidity are improved as compared with a short fiber reinforced resin molded product containing short fibers of about 0.3 mm, and the dimensional stability and heat resistance to heat are excellent. Therefore, the long fiber reinforced resin molded product is widely used for automobile parts such as front end carriers, fan shrouds and instrument panels.

Generally, the strength and rigidity of the long fiber reinforced resin molded product is improved as the fiber length of the fiber is increased. Therefore, various technical developments have been made so far in order to increase the fiber length of the fibers contained in the long-fiber-reinforced resin molded product. For example, the synthetic resin has a melt flow rate (hereinafter appropriately abbreviated as MFR) of 50 to 200 g / 10.
It is to use the one with low viscosity. By using such a low-viscosity synthetic resin, fiber breakage due to the synthetic resin during molding can be prevented. By using an injection molding machine equipped with a screw for so-called long fiber reinforced resin, in which the compression ratio is set to a low level in the deep groove, fiber breakage is prevented and a long fiber reinforced resin molded product with a large fiber length is produced. is doing.

[0004]

The conventional long-fiber-reinforced resin molded product has a MFR of 50 as a base material as described above.
It contains a low-viscosity synthetic resin of about 200 g / 10 minutes and very long fibers having a weight average fiber length of more than 8 mm. However, since the molding is performed with a low kneading in order to prevent breakage of the fibers, there is a problem that an unopened fiber bundle remains in the molded product. As a result, the appearance of the molded product deteriorates,
Depending on the degree, physical properties may vary depending on the part.

Further, the above-mentioned conventional long-fiber-reinforced resin molded product contains a low-viscosity synthetic resin. Such a long fiber reinforced resin molded product has a problem that it is impossible to secure sufficient fatigue strength. Therefore, when stress is repeatedly applied to the long-fiber-reinforced resin molded product, there is a problem that defects such as breakage easily occur.

The present invention has been made in view of the above conventional problems, and it is an object of the present invention to provide a long fiber reinforced resin molded product which has few unopened fibers in the molded product and is excellent in strength rigidity and fatigue strength. Is.

[0007]

According to a first aspect of the present invention, there is provided a long-fiber-reinforced resin molded product comprising a base material made of synthetic resin and fibers dispersed in the base material, wherein the synthetic resin has a melt flow rate of 20 g / 10. The weight-average fiber length of the fibers is 1 to 3 mm, which is a long fiber-reinforced resin molded article (claim 1).

In the present invention, the MFR is 20 g / 10.
It contains a synthetic resin with a high viscosity of less than a minute. Therefore, the long-fiber-reinforced resin molded product has excellent fatigue strength and is less likely to cause a failure such as breakage due to repeated impact or deformation. The long fiber reinforced resin molded product of the present invention contains fibers having a weight average fiber length of 1 to 3 mm. Therefore, it has excellent strength and rigidity, and there is almost no unopened fiber.
Therefore, even if the above-mentioned long fiber reinforced resin molded product is used in a product requiring strength, rigidity, fatigue strength, etc., such as a vehicle structure of an automobile, a defect such as breakage hardly occurs. As described above, according to the present invention, it is possible to provide a long-fiber-reinforced resin molded product which is excellent in strength and rigidity, fatigue strength, and has almost no unopened fibers.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the melt flow rate of the synthetic resin is 20 g / 10 minutes or less. When the melt flow rate of the synthetic resin exceeds 20 g / 10 minutes, the fatigue strength of the long fiber reinforced resin molded product decreases. The value of the melt flow rate of the synthetic resin contained in the long-fiber-reinforced resin molded product should be determined, for example, by the value of the melt-flow rate of the resin used in the production of pellets, which is the material of the long-fiber reinforced resin molded product. You can

The weight average fiber length of the above fibers is from 1 to
It is 3 mm. When the weight average fiber length is less than 1 mm, the strength and rigidity of the long fiber reinforced resin molded product is reduced. On the other hand, when it exceeds 3 mm, unopening is likely to occur.

Examples of the fibers include glass fibers, carbon fibers, graphite fibers, silicon carbide fibers, alumina fibers, boron fibers, Kevlar fibers, stainless steel fibers and the like. Examples of the synthetic resin include polypropylene,
Examples thereof include thermoplastic resins such as polyethylene, polystyrene, acrylonitrile / styrene, butadiene copolymer, polyvinyl chloride, polyamide, polycarbonate, polyethylene terephthalate and the like, or a mixture thereof, and polymer alloy.

Next, it is preferable that the base material is made of polypropylene resin and the fiber is glass fiber. In this case, a lightweight, high-strength, high-rigidity molded product can be obtained at a relatively low cost.

Next, the long fiber reinforced resin molded product is preferably a front end carrier (claim 3). The front end carrier is a kind of automobile parts, and is a part that serves as a frame for arranging a radiator, a fan and the like. Then, by applying the above long-fiber-reinforced resin molded product to a front-end carrier, it is possible to obtain the high-quality front-end carrier with excellent durability by effectively utilizing the above-mentioned characteristics of excellent strength and rigidity and fatigue strength. You can

It is preferable that the front-end carrier integrally has at least one tank for containing a liquid (claim 4). In this case, the tank can be integrally formed with the front end carrier, and the manufacturing process can be streamlined.

[0015]

EXAMPLE 1 Next, a long fiber reinforced resin molded product according to an example of the present invention will be described with reference to FIG.
The long fiber reinforced resin molded product 1 of this example is as shown in FIG.
It is composed of a base material 2 made of a synthetic resin and fibers 3 dispersed in the base material 2. The melt flow rate of the synthetic resin is 20 g / 10 minutes or less, and the weight average fiber length of the fibers 3 is 1 to 3 mm.

First, a method of manufacturing the long fiber reinforced resin molded product 1 of this example will be described. Pellets of a long fiber reinforced resin composed of polypropylene resin having an MFR of 15 g / 10 min and long glass fibers (Sumithtran manufactured by Sumitomo Chemical Co., Ltd.) were prepared. Here, the MFR value of the polypropylene resin is measured according to the method defined in JIS K 7210 under the conditions of a temperature of 230 ° C. and a test load of 21.18 N. The pellet 1 has a substantially columnar shape and contains long glass fibers arranged in parallel in the longitudinal direction of the pellet. The length of the pellet in the longitudinal direction and the glass fiber length are preferably 20 mm or less,
In this example, a 9 mm one was used.

The pellets were put into an injection molding machine equipped with a shallow groove type screw whose compression rate was set to a low value, that is, a so-called long fiber reinforced resin dedicated screw. Next, the pellets are melted and plasticized by the injection molding machine and then injection-molded to form a long-fiber-reinforced resin molded product 1 (inventive product E according to the present invention E which is a front end carrier integrally provided with a tank.
1) was produced. In this example, the injection molding machine had a gate diameter of 20 mm and a screw back pressure of 0 MPa.

Next, the weight average fiber length of the fibers contained in the long fiber reinforced resin molded article of this example is calculated as follows.
It measured based on the measuring method method disclosed by the 4th publication. The weight-average fiber length of the fibers contained in the long-fiber-reinforced resin molded product of this example was 1.9 mm, and the MFR of the polypropylene resin contained in the long-fiber-reinforced resin molded product of this example was
It was 15 g / 10 minutes as can be seen from the MFR value of the polypropylene resin contained in the pellets.

As shown in FIG. 1, the long-fiber-reinforced resin molded product 1 of this example contains a base material 2 made of a highly viscous synthetic resin having an MFR of 20 g / 10 minutes or less. Therefore, the long-fiber-reinforced resin molded product is excellent in fatigue strength and is less likely to cause defects such as breakage due to repeated impact and deformation. Further, the long fiber reinforced resin molded product 1 of this example contains the fibers 3 having a weight average fiber length of 1.9 mm. for that reason,
It has excellent strength and rigidity, and there is almost no unopened fiber. Therefore, even if the long fiber reinforced resin molded product 1 is used for a vehicle structure of an automobile or the like that requires strength, rigidity, fatigue strength, etc., problems such as breakage hardly occur. As described above, according to this example, it is possible to provide a long-fiber-reinforced resin molded product which is excellent in strength and rigidity and fatigue strength and has almost no unopened fibers.

Example 2 In this example, in order to clarify the excellent strength and rigidity of the long fiber reinforced resin molded article of Example 1,
The relationship between bending strength and weight average fiber length was investigated. First, by the same method as in Example 1, a plurality of long fiber reinforced resin molded products having different final fiber weight average fiber lengths were produced, and various long fiber reinforced resin molded products having various weight average fiber lengths were produced. Obtained. The long fiber reinforced resin molded product of this example is a front end carrier integrally provided with a tank, as in the first embodiment.

Subsequently, the bending strength of these long fiber reinforced resin molded products at 80 ° C. was measured. The bending strength was measured according to the method specified in JIS K7171. First, 15 × 60 from the 3 mm thick part in the molded product.
A strip test piece of mm was cut out and the bending strength of this test piece was measured. The relationship between the bending strength and the weight average fiber length measured in this way is shown in FIG. In FIG. 2, the weight average fiber length is plotted on the abscissa and the bending strength is plotted on the ordinate, and the bending strength measured at 80 ° C. is shown by a solid line.

As is known from FIG. 2, when the weight average fiber length is less than 2 mm, the bending strength of the long fiber reinforced resin molded product increases in proportion to the weight average fiber length, but when it reaches a certain value, it becomes steady. It becomes a state. Therefore, it is not necessary to increase the above weight average fiber length more than necessary,
It can be seen that the bending strength of the long-fiber-reinforced resin molded product is sufficiently excellent even in the range of 2 mm.

(Example 3) Next, in order to clarify the superiority regarding unopened fiber, various kneading conditions in the method for producing the long fiber reinforced resin molded product (invention product E1) of Example 1 were changed, Various long fiber reinforced resin molded articles having different final weight average fiber lengths were produced and evaluated in comparison with the present invention article E1. First, as shown in Table 1, the pellet length, screw type, and gate diameter are changed so as to change the kneading property in the molding process, and the screw back pressure is changed under the molding conditions.
Four types of long-fiber-reinforced resin molded products having different final weight-average fiber lengths were produced. Of these long-fiber-reinforced resin molded products, three types of long-fiber-reinforced resin molded products having a weight-average fiber length of 1.0 to 3.0 mm were manufactured according to the present invention products E2 to E.
4 and the remaining one not in the range of 1.0 to 3.0 mm was designated as comparative product C1. Then, with respect to the product E1 of the present invention manufactured in Example 1 and the four types of long-fiber-reinforced resin molded products (product E2-E4 of the present invention, comparative product C1) manufactured in this example, the presence or absence of unopened fiber was evaluated. did. The results are shown in Table 1.

[0024]

[Table 1]

As is known from Table 1, the unopened fibers are
Almost no generation occurs in the products E1 to E4 of the present invention, which are long fiber reinforced resin molded products having a weight average fiber length of 3 mm or less.
On the other hand, in the comparative product C1 having a weight average fiber length of 3 mm or more, many unopened fibers were confirmed. Therefore, it is necessary to reduce the weight average fiber length in order to suppress the generation of unopened fibers.

From the above results, the weight average fiber length of the fibers contained in the long fiber reinforced resin molded product is 1.0 to 3.0.
It can be seen that, in the case of mm, the above-mentioned long fiber reinforced resin molded product is excellent in strength and rigidity and has almost no unopened fibers.

Example 4 In this example, in order to clarify the excellent fatigue strength of the long fiber reinforced resin molded article of Example 1,
The relationship between the number of repetitions until breakage and the MFR of the synthetic resin was examined. First, in the same manner as in Example 1, a plurality of long fiber reinforced resin molded articles having different synthetic resin MFRs were produced,
Various long fiber reinforced resin moldings having various MFR values were obtained.

Next, a test piece having a thickness of 3 mm was prepared from these long fiber reinforced resin molded articles, and the test piece was repeatedly bent at a stress of 40 MPa, and the number of repetitions until breakage was measured. This measurement method is based on JIS K 71
It is based on the method specified in No. 19. The result is shown in FIG.

As is known from FIG. 3, the number of repetitions to break, that is, the fatigue strength is improved as the MFR value of the synthetic resin becomes smaller. Compared with the conventional product having an MFR of 50 or more, the product of the present invention having a synthetic resin MFR of 20 g / 10 minutes or less has high fatigue strength and can exhibit extremely excellent durability even after repeated use. I understand.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a cross section of a long fiber reinforced resin molded product according to a first embodiment.

FIG. 2 is an explanatory view showing the relationship between bending strength and weight average fiber length according to Example 2.

FIG. 3 is an explanatory diagram showing the relationship between the number of repetitions until breakage and the MFR of synthetic resin according to the fourth embodiment.

[Explanation of symbols]

1. ． ． Long fiber reinforced resin molded product, 2. ． ． Base material, 3. ． ． fiber,

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayoshi Moshioka             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Hisano Chino             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Isamu Inai             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Norihisa Sasano             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F term (reference) 4F072 AB09 AD04 AK15 AL07

Claims (4)

[Claims] 1. A long fiber reinforced resin molded article comprising a base material made of a synthetic resin and fibers dispersed in the base material,
A long-fiber-reinforced resin molded product, wherein the melt flow rate of the synthetic resin is 20 g / 10 minutes or less, and the weight average fiber length of the fibers is 1 to 3 mm. 2. The long-fiber-reinforced resin molded product according to claim 1, wherein the base material is made of polypropylene resin, and the fibers are glass fibers. 3. The long fiber reinforced resin molded article according to claim 1, wherein the long fiber reinforced resin molded article is a front end carrier. 4. The long fiber reinforced resin molded product according to claim 3, wherein the front end carrier integrally has at least one tank for containing a liquid.