JPH03261533A - Molding method for resin molding - Google Patents

Abstract

PURPOSE:To prevent draw-down and to obtain a hollow resin molding high in rigidity of a projecting part by blow-molding a parison by the use of a forming mold equipped with a slide core having a recessed part or a projected part and thereafter retreating and moving the slide core and filling the dissimilar molding material having the quality of material different from the parison into the formed space. CONSTITUTION:A parison A extruded from an extruder is blow-molded by a forming mold 1 equipped with a first slide core 4 having a recessed part 4a. A projected part b3 correspondent to the recessed part 4a of the first slide core 4 is formed in the main body b1 of a molding. Thereafter the first slide core 4 is retreated and moved by the supply pressure of dissimilar molding material C. This dissimilar molding material C is filled into the space 5 formed by retreating motion of the first slide core 4. In such a way, only a projecting part b2 can be molded of the dissimilar molding material C. Since increase in weight of the parison A can be prevented at a time of extrusion, draw-down phenomena are prevented and also rigidity of only the projecting part b2 can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method for blow molding a hollow resin molded product in which a protrusion projecting outward is formed on the main body of the molded product.

(Prior Art) In recent years, filler pipes and the like used around the engines of vehicles such as automobiles have been manufactured by blow molding in order to reduce their weight.

The blow-molded filler vibe and the like are supported on the vehicle body by a bracket, but it is preferable if the bracket can be integrally molded with the filler vibe and the like because the number of parts to be assembled can be reduced. As a method for blow molding a hollow resin molded product in which a protrusion such as a bracket is formed so as to protrude outward from the molded product body, for example,
As disclosed in Japanese Patent No. 34433, when blow molding a parison extruded from an instant extruder, resin is replenished with an auxiliary plunger, and a protrusion is formed on the molded product body with the replenished resin. It has been known.

(Problem to be Solved by the Invention) However, since the method disclosed in the above-mentioned publication only replenishes only the same resin as the molded product body, the rigidity of the protruding portion may be too low depending on the type and use of the product. There are cases.

Therefore, it may be possible to increase the rigidity by blow molding with a resin mixed with fillers such as glass fibers. However, in this case, the rigidity of not only the protruding parts but the entire product increases, so the rigidity increases to the point where such rigidity is not originally required, and for example, the damping force against vibrations and shocks becomes weaker, which is rather inconvenient. occurs. Further, when a filler is mixed into the resin, there is a problem in that the weight of the parison extruded from the extruder becomes large, and a so-called drawdown phenomenon occurs in which the parison is torn in the middle.

The present invention has been made in view of the above points, and its purpose is to reduce drawdown by taking appropriate means to mold only the protruding portion with a different type of molding material mixed with filler, etc. The objective is to increase the rigidity of only the protruding portion without causing any problems.

(Means for solving the problems) In order to achieve the above object, the solution of the present invention provides a method for blow molding a hollow resin molded product in which a protrusion projecting outward is formed on the molded product body. A mold having a slide core having four parts or a convex part is prepared. First, the parison extruded from the extruder is blow-molded using the mold to form convex portions or concave portions corresponding to the concave portions or convex portions of the slide core in the molded product body.

Next, the slide core was moved backward, and the space formed by the backward movement of the slide core was filled with a molding material of a different material from that of the parison, thereby forming a protrusion projecting outward on the molded product body. A hollow resin molded product is obtained.

(Function) With the above configuration, in the method of the present invention, the parison extruded from the extruder is blow-molded in a mold equipped with a slide core having a recess or a convex part, and the molded product body is formed into the recess or the recess of the slide core. After a convex portion or a concave portion corresponding to the convex portion is formed, the slide core is moved backward, and the space formed by the backward movement of the slide core is filled with a different molding material made of a material different from that of the parison. A hollow resin molded product is obtained in which a protrusion projecting outward is formed on the molded product body.

In this way, since only the protruding parts are molded with a different molding material, the weight increase of the parison during extrusion is eliminated, thereby preventing the drawdown phenomenon and increasing the rigidity of only the protruding parts. .

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1(a) and FIG. 1(b) show a mold 1 to which a method for molding a resin molded product according to an embodiment of the present invention is applied,
First, before explaining the method of the present invention, the structure of the mold 1 will be explained.

The mold 1 includes two molds 2 and 3 arranged on the left and right, and the right mold 2 has a parison extrusion direction (vertical direction).
A first slide core 4 that moves forward and backward in a circular arc in the circumferential direction of the cavity orthogonal to the first slide core 4 is disposed, and a keyhole-shaped recess 4a is formed in the first slide core 4. Further, in the mold 2, a parison A and a filler material such as glass fiber, etc., are provided in a space 5 (clearly visible in FIG. 6) formed when the first slide core 4 moves backward. A resin passage 6 is formed for supplying a different type of molding material mixed with. Note that the first slide core 4 has a built-in heater (not shown). On the other hand, a second slide core 7 that moves forward and backward in the cavity radial direction perpendicular to the parison extrusion direction is arranged in the left mold 3, and as shown in FIGS. 4(b) and 5(b), When the second slide core 7 moves backward, a space 8 is formed behind the first slide core 4 in which the first slide core 4 can move backward.

Next, using the mold 1 configured as described above, the molded product body b! The procedure for blow molding the hollow resin molded product B in which the protrusion b2 protruding outward is formed will be explained.

First, as shown in FIG. 2(a) and FIG. 2(b),
The parison A is extruded from an extrusion head 9 of an extruder (not shown), and the extruded parison A is introduced into the cavity of the mold 2.3 of the mold 1. At this time, the protrusion b of the parison A! The thickness of the forming part (part corresponding to the first slide core 4) is thicker than that of other parts. Also,
The first and second slide cores 4 and 7 of the mold 23 are both in a forward moving state.

Next, as shown in FIGS. 3(a) and 3(b), the mold 1 is clamped and the parison A is inflated by applying pre-blow pressure.

Thereafter, as shown in FIGS. 4(a) and 4(b), a predetermined blowing pressure is applied to the parison A to bring it into close contact with the cavity surface of the mold 1, and the parison A is molded into a predetermined shape. to form a molded product body b1. At this time, the above parison A
The resin in the thick portion is flushed into the recess 4a of the first slide core 4, thereby forming a protrusion b3 corresponding to the recess 4a of the first slide core 4 on the molded product main body b1.

Thereafter, after cooling the molded product main body bl to an extent that it can withstand the blowing pressure and the sliding resistance of the first slide core 4, the second slide core 7 is moved backward to create a space 8 behind the first slide core 4. At the same time, the heater built in the first slide core 4 is turned on to warm the convex portion b3.

Thereafter, as shown in FIGS. 5(a) and 5(b), a different molding material C mixed with a filler such as glass fiber, which is different from the material of the parison A, is passed through the resin passage 6 and heated to a predetermined pressure. With this supply pressure, the first
The slide core 4 is moved backward into the space 8 behind it.

As a result, the space 5 formed by the backward movement of the first slide core 4 is filled with the dissimilar molding material C, and a hollow resin molded product B is formed in which the molded product main body b1 has a protrusion portion 2 that protrudes outward. can get.

In this example, the parison A extruded from the extruder is blow-molded using the mold 1 equipped with the first slide core 4 having the recess 4a, and the first slide core is attached to the molded product main body b1. After forming the convex portion b3 corresponding to the concave portion 4a of No. 4, the first slide core 4 is moved backward by the supply pressure of the dissimilar molding material C, and the first slide core 4
Since the space 5 formed by the retreating operation is filled with the dissimilar molding material C, only the protruding portions can be molded with the dissimilar molding material C, thereby eliminating the heavy Qj of the parison A when it is immediately put out. As a result, the drawdown phenomenon can be prevented and the rigidity of the protrusion can be increased.

Further, in the above embodiment, since the protruding part 1 is supported by the convex part b3 and joined to the molded product main body 2, the mounting state can be strengthened.

Furthermore, what is shown in FIGS. 7 to 9 is another embodiment, and in this embodiment, the first slide core 4 is provided only on the mold 2 side on the right side, and the first slide core 4 is provided on the mold 3 side on the left side. 2 slide core 7 was not provided. Furthermore, the first slide core 4 is disposed so as to move linearly in the tangential direction with respect to the molded product main body b1, as in the case of the above embodiment. Therefore, in this embodiment as well, the same effects as in the above embodiment can be achieved. In addition, in this embodiment, since the first slide core 4 moves linearly in the tangential direction, when the first slide core 4 moves backward, the first slide core 4 becomes separated from the parison A, and therefore , when dissimilar molding material C (j+) is fed into the space 5, it is not necessary to consider the sliding resistance of the first slide core 4, which eliminates the need to cool the molded product body b1, and shortens the molding cycle time. can do.

In the above embodiment, the first slide core 4 has a recess 4a.
and a convex portion b3 corresponding to the four portions 4a of the first slide core 4 is formed on the molded product body,
On the contrary, it is also possible to form convex portions on the first slide core 4, and to form four portions corresponding to the convex portions of the first slide core 4 on the molded product body b1.

(Effects of the Invention) As explained above, according to the method of the present invention, a parison extruded from an extruder is blow-molded using a mold equipped with a slide core having a concave portion or a convex portion, and the above-mentioned After forming convex portions or concave portions corresponding to the concave portions or convex portions of the slide core, the slide core is moved backward, and the space formed by the backward movement of the slide core is filled with a different molding material made of a material different from that of the parison. As a result, a hollow resin molded product is obtained in which a protrusion projecting outward is formed on the molded product body, so that the rigidity of only the protrusion can be increased without causing a drawdown phenomenon.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1(a) is a longitudinal sectional front view of the mold, FIG. 1(b) is a cross-sectional plan view thereof, and FIGS. 2 to 5(a) are hollow resin. A vertical sectional front view of the mold in each molding process of the molded product, (b) of FIGS. 2 to 5 are cross-sectional plan views thereof, and FIG. 6 is an explanatory diagram explaining the procedure for forming a protrusion on the molded product body be. 7, 8 and 9 are views corresponding to FIG. 4(b), FIG. 5(b) and FIG. 6 showing another embodiment. (b) (b) (Q) ((1) Figure Figure C (■ (CI) 1... Molding mold 4... First slide core 4a... Recess 5... Space A. ...Parison B...Hollow resin molded product bl...Molded product body is amazing...Protruding part b3...Convex part C...Different molding material (Q) Figure (0) 1... Molding Mold 4...First slide core 4a...Concave part 5...Space A...Parison B...Hollow resin molded product bl...Molded product body b2...Protrusion part b2...Protrusion part C...41 Molding material No. 9

Claims (1)

[Claims] (1) A method for blow molding a hollow resin molded product in which a protrusion projecting outward is formed on the molded product body, in which a mold equipped with a slide core having a concave or convex portion is prepared, and the extrusion process is first performed. Blow molding the parison extruded from the machine with the mold to form a convex part or a concave part corresponding to the concave part or convex part of the slide core in the molded product body,
Next, the slide core was moved backward, and the space formed by the backward movement of the slide core was filled with a molding material of a different material from that of the parison, thereby forming a protrusion projecting outward on the molded product body. A method for molding a resin molded product, characterized by obtaining a hollow resin molded product.