JPH0410848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a press molding method, and more particularly to a press molding method that allows integral molding of a molded product consisting of a thin wall portion and a thick wall portion using a press.

[Prior Art and Problems] In general, thermoplastic resins impregnated with long glass fibers are widely used as materials for press molding because they have high strength, high rigidity, and excellent chemical resistance.

By the way, even when using the above-mentioned thermoplastic resin, which is relatively easy to mold, as a material, it is difficult to press a molded product with thin and thick parts, especially where the thick part is 2 to 10 times the thickness of the thin part. It was often difficult to mold them integrally. The reason for this is that when using thick-walled materials, the press pressure must be high to form thin-walled parts, and conversely, when thin-walled materials are used, it is impossible to form thick-walled parts. It is said that it becomes.

Therefore, in the past, two parts of the thin wall part and the thin wall part
In order to press a molded product consisting of a thick part that is 10 times as thick, the thin part and thick part are first press-formed separately, and both parts are then welded by ultrasonic welding or vibration welding. It was meant to be integrated into one. Therefore, this conventional method has the disadvantage that the process is complicated and the cost is high.

[Purpose of the invention]

An object of the present invention is to provide a press molding method that eliminates the above-mentioned drawbacks.

[Structure of the invention]

In a press-molding method for a thermoplastic resin molded body impregnated with long glass fibers, the molded body is composed of a thin part with a thickness of 1 to 2 mm and a thick part with a thickness of 2 to 10 times that of the thin part. , a thin sheet made of thermoplastic resin impregnated with long glass fibers forming a thin section, and a thermoplastic resin impregnated with glass fiber forming a thick section having a thickness 2 to 10 times that of the thin sheet. The preheating temperature of the thin sheet is 170~190℃, and the preheating temperature of the thick sheet is 190~220℃.
℃, then feed both sheets into a mold that has been preheated to 40 to 70℃, and then stack both sheets together under a press pressure of 40 to 60 kg/cm ^2. This is a press molding method characterized by press molding.

[Implementation and aspects of the invention]

Next, the present invention will be described with reference to embodiments shown in the drawings. FIG. 1 shows a longitudinal cross-sectional view of a thin sheet 1 and a thick sheet 2, both sheets being made of thermoplastic resin impregnated with long glass fibers, the thin sheet 1 being preheated to 170-190°C, and the thick sheet 2 being preheated to 170-190°C. Preheated to 190-220℃.

FIG. 2 is a longitudinal cross-sectional view when the thin sheet 1 and the thick sheet 2 are fed in an overlapping state between an upper die 3 and a lower die 4 of a press.

3 to 5 are perspective views of the molded body 5, 5a
5b indicates a thin portion, and 5b indicates a thick portion.

Examples of thermoplastic resins impregnated with long glass fibers include low density polyethylene, high density polyethylene, polypropylene, polyamide, polystyrene, polyethylene terephthalate, polyphenylene sulfide, polyvinyl chloride, polyacetal, polycarbonate, etc. Examples of long glass fibers include those having an average fiber length of 5 mm or more and forms such as continuous mats, chopped strand mats, and needle-punched mats, with the thick sheet portion preferably being a needle-punched mat.

Next, the thin sheet 1 is preheated to 170 to 190°C, but if the temperature is less than 170°C, it will not be sufficiently welded to the thick sheet 2, and if it exceeds 190°C, the surface of the molded product 5 will become fluffy and the appearance will be poor. Also, thick sheets are 190 to 220
℃, but if the temperature is lower than 190°C, it will not be sufficiently welded to the thin sheet 1, and if it exceeds 220°C, the surface of the molded product 5 will become fluffy and the appearance will be poor.

Further, the thick sheet 2 is supplied to the concave part or undercut part of the mold, the thin sheet 1 is supplied to the flat part of the mold, the thin sheet and the thick sheet are superimposed, and the press mold is clamped. Press pressure at this time: 40-60Kg/
cm ² and mold temperature of 40 to 70°C. Note that the thick sheet 2 can be prepared not only by itself, but also by stacking several thin sheets 1.

Examples of molded bodies completed by this method include rain gutters and melon cultivation beds.

Example 1 A polypropylene sheet impregnated with thin needle-punched long glass fibers with a thickness of 2.0 mm was preheated to 180°C, and a thick-walled sheet with a thickness of 4.5 mm was preheated to 200°C. feed into the mold shown;
The mold was clamped with a press pressure of 50 kg/cm ² . As a result, a molded article having a thin part with a thickness of 1.5 mm and a thick part with a thickness of 4.0 mm was obtained according to the mold.

Comparative Example 1 A thick sheet with a thickness of 5 mm was preheated to 210°C and fed into the mold of Example 1, and the mold was clamped with a press pressure of 160 kg/cm ² , but the finished molded product It was not possible to mold thin parts.

〔Effect of the invention〕

Therefore, according to the present invention, a molded body consisting of a thin part and a thick part can be manufactured by integral molding with a press, and the molding pressure at that time is considerably lower than that of the conventional method. It has excellent effects such as being able to.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of a thin sheet and a thick sheet.
The figure is a vertical cross-sectional view when a thin sheet and a thick sheet are fed into a mold in an overlapping state, Figure 3 is a perspective view of a molded body, Figure 4 is a perspective view of a molded body (rain gutter), and Figure 5 is a perspective view of a molded body (melon cultivation bed). 1... Thin sheet, 2... Thick sheet, 3... Upper die, 4... Lower die, 5... Molded body, 5a... Thin wall portion, 5b... Thick wall portion.

Claims (1)

[Claims] 1. Press molding method for a thermoplastic resin molded body impregnated with long glass fibers, which consists of a thin part with a thickness of 1 to 2 mm and a thick part with a thickness of 2 to 10 times that of the thin part. , a thin sheet made of thermoplastic resin impregnated with long glass fibers forming a thin section, and a thermoplastic resin impregnated with long glass fibers forming a thick section having a thickness 2 to 10 times that of the thin sheet. The preheating temperature for the thin sheet is 170~190℃, and the preheating temperature for the thick sheet is 190~190℃.
After preheating to 220℃, both sheets are fed into a mold preheated to 40 to 70℃, and then both sheets are placed one on top of the other and pressed together at a pressing pressure of 40 to 60Kg/cm ² . A press forming method characterized by press forming.