JPH0317653B2 - - Google Patents

Description

[Detailed Description of the Invention] <<Field of Industrial Application>> The present invention relates to a method for producing a stampable sheet made of a composite of a pine-like reinforcing material made of long glass fibers and a thermoplastic resin. The present invention relates to a manufacturing method that can prevent deterioration in appearance due to the protrusion of glass fibers as a reinforcing material during processing.

<<Background of the Invention>> An aggregate of long glass fibers is needle-punched into a mat shape, which is then impregnated with a resin such as polypropylene, polyester, polyamide, etc. as a stampable sheet, which is then preheated and shaped into a desired shape. Press-molded reinforced thermoplastic resin molded products are being used as an alternative material to metals, etc., because they are lightweight, have high strength, and can reduce the number of processing steps.

There are stampable sheets with this type of structure that use polypropylene as a thermoplastic resin, but molded products of this type of sheet are widely used for automobile parts, and recently they have also been used for some of the outer panels of automobiles. It's coming.

However, when used as part of the exterior of an automobile, after the molded parts are assembled using stampable sheets, the entire assembly goes through a painting process.
In this coating process, for example, in the case of baking coating, the thermoplastic resin is exposed to temperatures near the softening point or melting point, such as baking in an atmosphere of 140 to 160° C. for about 30 minutes.

In such cases, the thermoplastic resin molded product containing long glass fibers is in a state where the long glass fibers as reinforcing fibers are matted by needle punching, so the surrounding force of the thermoplastic resin softens the resin. If the glass fibers are weakened by this, the glass fibers will rise to the surface and spoil the appearance of the molded product.

In addition, the above baking conditions of 160℃ x 30 minutes are the limit conditions when polypropylene is used as the thermoplastic resin, and if the temperature increases further or the time is extended, the surface appearance will be significantly damaged. There was also a fear that it would be lost.

Possible ways to solve this problem include, for example, increasing the softening point or melting point of the thermoplastic resin, or relaxing the punching conditions for the glass mat so that the glass fibers do not float up.

However, in the former method, polypropylene
The upper limit is around 170℃, and if you use a resin with a large molecular weight or add a filler to increase the viscosity when melting due to high temperature exposure and reduce fluidity, the mold temperature will rise during molding. This requires an increase in pressure and pressure, which poses a problem in terms of energy costs.

In addition, in the latter method of changing the glass mat, appropriate cutting and entanglement of the glass fibers are reduced, and the glass fibers are uniformly flowed and dispersed during press molding, thereby exerting a reinforcing effect. The character of the resin is lost.

In view of the above problems, the present inventors have arrived at the present invention by intensively studying a practical method that is free from economical or technical difficulties. It is an object of the present invention to provide a manufacturing method that has a simple configuration and can prevent the reinforcing fiber material from lifting up when the resin is heated above the softening point of the resin after molding.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention provides a primary process of pressurizing and shaping a composite material made of a pine-like reinforcing material of long glass fibers and a thermoplastic resin, and a process of performing this primary process. A method for producing a reinforced thermoplastic resin molded product, which is then subjected to heat treatment to apply a temperature higher than the softening point of the thermoplastic resin, the method comprising: a mold that comes into contact with the surface side of the molded product during the primary processing; The method is characterized by using a mold with a texture having a large number of concavo-convex shapes with a depth of 20 μm or more and a pitch of 10 mm or less.

The reinforced thermoplastic resin molded product that can be applied to the present invention is a composite reinforcement made by impregnating a pine-like reinforcing material made of long glass fibers with a thermoplastic resin such as polypropylene, polyester, or polyamide selected according to the application, physical properties, etc. This is a molded article that is press-molded by preheating a resin sheet, and may be exposed to temperatures above the softening point of the thermoplastic resin during subsequent steps or during use.

The shape of the uneven texture of the molding die to prevent appearance defects due to the embossment of glass fibers is not limited, but the depth of the texture should be 20 μm or more and the pitch should be small.
Must be 10mm or less.

In addition to the above-mentioned thermoplastic resins, the scope of the thermoplastic resin of the present invention includes various thermoplastic resins having appropriate melt viscosity, various modified resins, copolymers, etc. that can be melt extruded and impregnated into glass mats. are all included.

<<Operation>> According to the manufacturing method having the above configuration, since a mold having uneven textures is used as a molding die, the long glass fibers are pressed by the textures during molding, and the long glass fibers have low rigidity. Since the mold cannot be deformed to follow the uneven shape of the surface of the mold, the portion of the surface of the molded product corresponding to the height of the uneven portion is covered only with the resin.

Therefore, even if the molded product is heated after the fact and the resin softens and melts, the glass fibers will not lift up the resin-only layer on the surface of the molded product, thereby preventing damage to the appearance.

Example The present invention will be explained below with reference to Examples.

Example 1 A glass fiber cake with a single fiber diameter of 23 μm was shaped into a mat, and this was needle-punched at a punching density of 20 to 40 times/cm ² to form a glass mat with a basis weight of 900 g/m ² and a glass content of 40 impregnated with polypropylene resin. % by weight of a stampable sheet (manufactured by the applicant: product name Azdel) and heated to 210°C.
Two hot blanks heated in
A flat molded product with a thickness of 3 mm was produced using a flat mold having a length of 10 cm and a width of 14 cm and having 28 grain shapes. Note that a mirror-like lower mold was used.

After placing this molded product in an oven at 160°C for 30 minutes, we observed the appearance of the surface shape and found that as the grain height became smaller, the protrusion of glass fibers tended to become more noticeable. However, it was tolerable for practical purposes. In the case where the grain depth was 80 μm, almost no glass fibers were visible.

On the other hand, for comparison with the above-mentioned examples, the molding die in which a mirror-finished upper mold was used had a poor appearance with many glass fibers protruding.

It should be noted that if the pitch of the uneven texture of the uneven texture is about 10 mm or less, the above-mentioned effect of preventing the glass fibers from coming out can be obtained.

<<Effects of the Invention>> As explained above, the manufacturing method according to the present invention has a mold surface with a depth of 20 μm or more and a pitch of 10 μm.
This is a method that effectively prevents the appearance of molded products from deteriorating due to heating by providing uneven textures of less than mm in size, and the cost of forming the textures on the mold is within an appropriate range. Therefore, it is an extremely practical and effective method.

Claims (1)

[Claims] 1. Primary processing of pressure molding a composite material consisting of a pine-like reinforcement material made of long glass fibers and a thermoplastic resin;
A method for producing a reinforced thermoplastic resin molded product, in which after this primary processing, a heat treatment is applied to apply a temperature equal to or higher than the softening point of the thermoplastic resin, wherein the surface side of the molded product is applied during the primary processing. A method for manufacturing a reinforced thermoplastic resin molded product, characterized in that a mold with a texture having a large number of concavo-convex shapes with a depth of 20 μm or more and a pitch of 10 mm or less is used as a contacting mold.