JPS60212318A - Nylon block copolymer reacting injection molding - Google Patents

Abstract

PURPOSE:To reduce the molding cycle by providing a slide core in a mold to advance it into a cavity following the shrinkage of a molding material associated with the hardening thereof in the mold. CONSTITUTION:The first material liquid A and the second material liquid B are fed to a mixing head 10 to mix, then, injected into a cavity 8 and heated to cause a hardening reaction. In such a reactive injection molding of a nylon block copolymer, a slide core 3 is provided in a mold 1 and advanced into the cavity 8 following the shrinkage of a molding material caused with the proceeding of the hardening reaction thereof. Otherwise, a clearance may be generated in the cavity 8 and cause an insufficient heating of the molding material to delay the reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a reaction injection molding method for obtaining molded articles made of polyamide copolymers.

As is well known in the art, polyamide, commonly known as nylon, is known as I! In addition to its general uses, it has come to be prized as an engineering plastic due to its excellent physical properties such as abrasion resistance and impact resistance. In addition, as a molding method for polyamide, all general molding methods for thermoplastic resins can be applied, but in the case of molding by monomer casting, two types of raw material liquids (hereinafter referred to as liquid A, 81') are used. In some cases, reaction injection molding (RIM) is used, in which the mixture is mixed and then injected into a mold.In other words, a reaction injection molding method of nylon block copolymer is used to obtain a molded article made of a polyamide copolymer. Toshiso, for example, uses a mixture of polyether polyol, a nylon polymerization catalyst, and caprolactam as liquid A, uses a mixture of caprolactam and another nylon polymerization catalyst as liquid BIL, and mixes liquid A and β liquid with a mixing head. A method is used in which the mixed liquid is injected into the cavity of a mold and heated (approximately 130°C).However, this reaction injection molding method originally has the advantage of being able to perform rapid molding. However, in the nylon block copolymer reaction injection molding described above, the molding material undergoes polymerization shrinkage as it hardens, creating gaps in the cavity1, resulting in heat input to the molding material during the reaction process. is insufficient, the reaction is delayed,
For this reason, it is necessary to lengthen the period of time when the mold is held in the mold, resulting in a problem of lengthening the molding cycle and, in turn, raising the processing cost.

Purpose of the Invention The present invention has been made in view of the above circumstances, and is directed to a nylon block copolymer reaction that can shorten the molding cycle by preventing the formation of gaps between the molding material and the cavity during the reaction process. The purpose is to provide an injection molding method.

Structure and Function of the Invention The present invention is characterized in that a slide core provided in a mold is caused to protrude into a cavity following the contraction of the molding material as the curing reaction progresses. Therefore, in the method of the present invention, the slide core protrudes into the cavity, thereby reducing the internal volume of the cavity.
As a result, the molding material is always in close contact with the inner surface of the cavity, and heat input to the molding material is maintained well.

EXAMPLES The present invention will now be described in detail based on examples. First, the outline of the apparatus for carrying out the method of the present invention will be explained with reference to FIGS. 1 and 2. An upper mold 1 is attached to the lower surface of an upper mold die base 2. A slide core 3 is fitted into the lower center part so as to be vertically movable. That is, a fluid pressure actuator 4 such as a hydraulic cylinder or an air cylinder is installed downward in the upper die 1 , and its piston rod 5 is connected to the upper end surface of the slide core 3 . Further, a lower die 6 that is paired with the upper die 1 is attached to the upper surface of the lower die base 7, and the lower die 6 is provided with a recess that forms a cavity 8 together with the upper die 1 and the slide core 3. . Further, a raw material runner 9 is formed on the upper surface of the lower mold 6 and extends from the concave portion to the outer surface, and a mixing head 10 is attached to the outer surface where the raw material runner 9 opens. The mixing head 10 mixes two types of raw material liquids and then injects the mixture, and can be of a normal plunger type in which two pairs of raw material liquid supply pipes and raw material liquid return pipes are connected. Note that reference numeral 11 in FIG. 1 is a mixing head upper block, and since the mixing head 10 is configured to inject the raw material liquid upward, the mixing head 10 is designed to guide the injected raw material liquid to the raw material runner 9. It is attached to the outer surface of the upper mold 1 so as to tightly cover it.

Further, each of the upper and lower molds 1.6 and the slide core 3 have a heater, and are configured to heat the molding material.

To perform injection molding using the above-described apparatus, first, the upper mold 1 is brought into close contact with the lower mold 6 with the slide core 3 pulled up to the upper limit by the fluid pressure actuator 4, and the upper mold 1, the slide core 3, and the lower mold are brought into close contact with each other. The three molds 6 form a cavity 8. Next, the mixing head 10 is operated to mix and inject the raw material liquids A and B. Here, liquid A is a mixture of polyether polyol (PPG), nylon polymerization number 1 (ABC), and caprolactam, and liquid B is a mixture of caprolactam and another nylon polymerization number 1 (BMC). The mixed liquid of A″a and B liquid is injected into the cavity 8 through the raw material runner 9 by being injected from the mixing head 10 (
Figure 3). Mixed liquid in cavity 8, that is, molding material 1
2 is heated to around 130° C. to cause a polymerization reaction, and gradually shrinks as a result, but since the amount of shrinkage can be known in advance, the slide core 3 is moved into a cavity by a fluid pressure actuator 4 according to the shrinkage of the molding material 12. 8 (Fig. 4). Therefore, the internal volume of cavity 8 is
Since it decreases in accordance with the shrinkage of the molding material 12, the molding material 1
2 can be maintained in close contact with the inner surface of the cavity 8,
As a result, heat transfer to the molding material 12 is improved and the curing reaction can be accelerated.

After the molding is performed as described above, the mold is opened and the molded product 13 is taken out as shown in FIG. Thereafter, in preparation for the next cycle, the slide core 3 is raised to its upper limit by the fluid pressure actuator 4 (FIG. 6).

In carrying out the method of the invention, it goes without saying that the shape of the slide core should match the shape of the molded product to be obtained, and the driving means is not limited to a fluid pressure actuator. (Furthermore, the slide core may be raised from the lower mold instead of being lowered from the upper mold.)

Effects of the Invention As is clear from the above explanation, in the nylon block copolymer reaction injection molding method of the present invention, the slide core provided in the mold is moved into the cavity following the shrinkage of the molding material as the curing reaction progresses. Because of the protrusion, the internal volume of the cavity decreases as the molding material shrinks, and as a result, the molding material is always kept in close contact with the inner surface of the cavity, allowing good heat input to be maintained, thereby promoting the curing reaction of the molding material. , the molding cycle can be shortened, and molded products made of polyamide copolymer can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is a front view schematically showing an example of an apparatus for carrying out the method of the present invention, and FIG.
The cross-sectional view taken along the line ■--■ in the figure, and FIGS. 3 to 6 are cross-sectional views similar to FIG. 2, respectively, showing the molding process. DESCRIPTION OF SYMBOLS 1... Upper mold, 3... Slide core, 6... Lower mold, 8... Cavity, 10... Mixing head, 12... Molding material, 13... Molded product. Applicant Toyota Motor Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (and 1 other person)

Claims (1)

[Claims] In the nylon block copolymer reaction injection molding method, a molded product is obtained by mixing a first raw material liquid and a second raw material liquid, and then injecting the mixed liquid into the cavity of a molding die and heating it to cause a curing reaction. A nylon block copolymer reaction injection molding method, characterized in that a slide core is provided in the mold, and the slide core is made to protrude into the cavity following shrinkage of the molding material as the curing reaction progresses.