JPH01206011A - Method for integrally forming plastic product and plastic product thereof - Google Patents

Abstract

PURPOSE:To make it possible to easily and accurately form a part with a complicated shape by a method wherein liquid resin is poured in gaps made by a core and a mold and, after the solidification of the liquid resin, a plastic product is integrally formed by removing the core and the mold. CONSTITUTION:Cores 20 and 21, which form respectively the water passage part 14 and the central part 15 of a guide casing or a part of a pump, are prepared. In addition, molds 22, 23 and 24 are arranged outside the cores 20 and 21 so as to make gaps 27 and 28. Further, a plurality of pouring ports 26 for pouring liquid resin in the gaps 27 and 28 are made in the mold 24 and in the core 21. The cores 20 and 21 and the like, which can not release from the molds without being broken, are formed out of a molding material which is produced by blending molding sand for manufacturing mold with a proper amount of binder. After that, resin sent from a resin pouring pump is poured through a resin disperser from the pouring ports 26. After liquid resin fills the gaps 27 and 28 and solidifies, the molds 22, 23 and 24 and the cores 20 and 21 are removed and a plastic guide casing 10 is completed as an integral body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for integrally molding a plastic product such as a pump part or the like having a hollow or undercut shape by a resin injection method.

[Prior art]

Advances in reinforced plastic technology have made it possible to make small-bore pumps and the like from plastics in terms of strength. In particular, by making equipment used in corrosive environments made of plastic, various effects such as maintenance-free operation can be obtained. However, most of the casings and impellers of pump parts, for example, have an internal passageway which is hollow and has an undercut shape.

Conventional methods for producing plastic products such as hollow and undercut shaped parts include the following methods.

■Method of forming parts separately and later gluing them together.

(2) A method in which a mold is formed with a low-melting alloy, a liquid resin is injected and solidified, and then the mold formed with the low-melting alloy is dissolved into the liquid to obtain a plastic product.

■A method of laminating resin using hand lay-up for medium and large molded products in small lots.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional manufacturing methods (1) to (4) each have the following problems.

Method (2) requires a process of bonding and assembling multiple molded products, and is expensive. There are also limitations on the shape of the parts and the strength of the adhesive surfaces.

Method (2) involves molding and is suitable for mass production, but the parts that can be molded are limited to small ones.

Method (2) has limitations on the shape of the parts to be molded, and it is almost impossible to mold parts with hollow or undercut shapes, and it is also impossible to obtain products with good precision. The present invention has been made in view of the above-mentioned points, and provides an integral molding method for plastic products that can integrally mold parts with complex shapes such as hollow and undercut shapes at low cost and with high precision, and the plastic product. There is a particular thing.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has a medium mold and an outer mold, and at least a mold that cannot be released without being destroyed. molding with a molding material having a polymer material, permeating and solidifying a polymer material on the surface to form an impregnated layer of a predetermined thickness from the surface, and further applying a mold release agent to the surface to form the mold release agent film,
A liquid resin such as unsaturated polyester epoxy, urethane, nylon, or olefin is injected into the void formed by the middle mold and the outer mold, and after the liquid resin has solidified, the middle mold and the outer mold are removed to create a hollow and undercut shape. It is characterized by integrally molded plastic products.

In addition, a hollow member with a large number of small through holes formed in the wall surface is inserted as a core material for reinforcing the core and stably supporting the core inside the core of the mold molded with the molding material, and the hollow member is heated to a predetermined temperature. The method is characterized by sending hot air to preheat the core, adjusting the balance between the temperature of the injected liquid resin and the core temperature, and adjusting the solidification time of the liquid resin.

Further, the present invention is characterized in that it is a hollow and undercut shaped plastic product manufactured by the above-mentioned integral molding method for plastic products.

[Effect]

By manufacturing a plastic product as described above, at least a mold that cannot be released from the mold without being destroyed is molded with a molding material having caking properties made by mixing an appropriate amount of a binding agent into fine powder particles, A polymer material is permeated and solidified on the surface to form an impregnated layer of a predetermined thickness from the surface, and a release agent is further applied to the surface to form a film of the release agent, so hollow and undercut plastic products can be manufactured. Can be easily molded with high precision at low cost. In particular, since an impregnated layer of polymeric material and a mold release agent film are formed on the surface of the mold formed with the molding material, even if a molding material made of powder and granules is mixed with a binder, the penetration of the liquid resin is prevented. There is no staining of the mold material, and the mold can be released smoothly.

〔Example〕

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

In this embodiment, an example in which the guide casing of the pump component shown in FIG. 3 is integrally molded using liquid resin will be described.

The guide casing 10 of the pump component shown in the third example has a shape in which a casing outer body part 11 and a casing inner body part 12 are integrally formed, and between the casing outer body part 11 and the casing inner body part 12, as shown in FIG. A guide vane 13 shown in FIG.

In order to manufacture the guide casing 10 having the above shape by the resin injection method, a medium mold forming the water passage part 14 of the guide casing 10, a medium mold forming the center part 15,
An outer mold is required which is placed outside these middle molds with a corresponding gap in the outer body 11 of the casing.

FIG. 1 is a diagram showing the arrangement structure of the middle mold, outer mold, etc. for integrally molding the guide casing 10 by the resin injection method. As shown in the figure, the outer mold 24 is arranged at the bottom and the guide is placed in the center. A middle mold 21 forming the center portion 15 of the casing 10 is disposed, and a gap 28 corresponding to the inner casing body 12 of the guide casing 10 is formed on the outside of the middle mold 21 to form a water passage portion 14 of the guide casing 10.
A middle mold 20 is disposed for forming a guide casing 10, and outer molds 23 and 22 are disposed outside the middle mold 20 with a gap 27 corresponding to the casing outer body 11 of the guide casing 10. Further, a plurality of injection holes 26 are formed in the outer mold 24 and the middle mold 21 for injecting liquid resin into the voids 28 and 27. FIG. 5 is a diagram showing the shape of the middle mold 20. The middle mold 20 is made of a molding material made by mixing an appropriate amount of binder with foundry sand used when manufacturing a mold, and the surface of the middle mold 20 is shown in FIG. As shown, an impregnated layer 31 having a thickness of about 1 to 10 seconds is formed by impregnating a polymer material on the surface of the molding material 30. In addition, Fig. 6 is A-A in Fig. 5.
It is a figure which shows a part of line cross section.

The middle mold 21 is also formed of the same molding material as the middle mold 20,
Thickness 1 to 1 formed by infiltrating the surface with a polymer material
An impregnated layer of about 0 nwn is formed. By forming the impregnated polymer material M31 on the surface of the molding material 30, the surface of the molding material 3o has an enhanced shielding function and prevents penetration and leakage of liquid resin during resin injection. Further, by applying a mold release agent to the surface of the impregnated layer 31 to form a mold release agent film 32, the mold can be easily peeled off.

As shown in FIG. 2, a large number of small through-holes 25a with a diameter of 5 to 10 mm are formed in the cores of the medium-sized molds 20 and 21 to prevent the mold material from collapsing on the wall surface as a core material for stable support. A vibrator 25 that is not destroyed when a mold made of metal or plastic or the like is destroyed is inserted. This small through hole 25a functions to prevent the core and the vibrator 25 from coming apart.

In this embodiment, wooden molds are used for the outer molds 22, 23, and 24 so that they can be used repeatedly, but if repeated use is ignored, these outer molds 22, 23, and 24 can also be made of the above molding material. The impregnated layer 31 and the release agent film 32 may be sequentially formed on the inner surface thereof. Note that even if the outer molds 22, 23, 24 are wooden molds, forming the mold release agent film 32 on the inner surface of the outer molds 22, 23, 24 improves mold release.

In addition, in the above embodiment, an example was explained in which foundry sand was used as the fine powder used for the mold material, but this sand can be made from naturally occurring alluvial sand, river sand, natural silica sand, or crushed rocks. Artificial silica sand may also be used. In short, any sand can be used as long as it can achieve a specified strength by adding an appropriate amount of caking agent to the sand. Further, the granular material used for the molding material is not limited to the above-mentioned sand, and wood chips, rock salt grains, etc. can also be used, for example. In addition, in the case of the above-mentioned types of sand, the caking agents include CO, sodium silicate for processing, portral cement for cement molds, furan and linocure resin for self-hardening molds, and inorganic and organic materials such as resin for shell molds. caking agent is used.

The polymeric material forming the impregnated layer 31 may be any material that can prevent the liquid resin from penetrating into the gaps between the sand grains when the liquid resin is injected, and suitable examples include paraffin wax, silicone wax, carnauba wax, vaseline, and lecithin. It is.

The release agent for forming the release agent film 32 may be one that prevents sand from seeping into the plastic product formed by solidifying the liquid resin and promotes peeling between the plastic product and the mold. Often, cellophane, polyester, polyethylene, polyvinyl alcohol, Teflon, etc. are suitable.

In the arrangement structure of the middle mold, the outer mold, etc. shown in FIG. 1, liquid resin is injected into the voids 27 and 28 from the injection hole 26. In this liquid resin injection operation, resin discharged from a resin injection pump (not shown) is injected from the injection hole 26 via a resin distributor (not shown). The void 27 and the void 28 are filled with liquid resin, and after the liquid resin has solidified, the outer mold 22, 23, 24, the middle mold 20, and the middle mold 21 are removed, thereby producing a plastic pump component having the shape shown in FIG. The guide casing 1o is completed.

To release the middle mold 20 and the middle mold 21 formed of mold material, the mold material is broken with a sand removal tool, chisel, chipping hammer, jet chisel, etc., and removed from the plastic product. In addition, if there are defects such as recesses on the outer surface of the product,
Repaired using the so-called hand-rearing method.

As the liquid resin to be injected, two-component curing resins such as unsaturated polyester resins, epoxy resins, urethane resins, nylon resins, and olefin resins are used.

In addition, the voids 27 and 28 are filled with resin-reinforced filler materials such as surf ace mats, chopped strand mats, cross tapes, and rovings such as glass lll1 fibers, carbon m fibers, silicon carbide fibers, metal #i fibers, and organic aramid Aa fibers. Filled with cloth, continuous strand mat, etc.

In the above-mentioned integral molding method for plastic products, the mold temperature decreases in winter, which delays curing of the resin, which significantly impedes productivity. One way to counter this is to keep the temperature of the workplace constant, but as a practically effective measure, blow hot air at 30°C to 50°C, which does not affect the physical properties of the resin, into the vibrator 25, and Warm air is blown into the mold material from 25a to preheat the mold material, and the solidification time can be adjusted in consideration of the balance between this preheating and the temperature of the liquid resin.

Further, according to the above embodiment, the molding of the middle mold 20 and the middle mold 21 can be performed using conventional mold molding technology as is, and the impregnated layer 31 and the mold release agent film 3 are formed on the surface of the mold made by this mold molding technology. By forming the middle molds 20 and 21, the middle molds 20 and 21 are completed.

In addition, in the above example, a method was shown in which the guide casing, which is a pump component, is integrally molded from plastic, but the molded product may have a shape that cannot be released from the mold without breaking at least a part of the mold, such as a hollow or undercut shape. It can be widely used for integrally molding plastics.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects can be obtained.

(1) A one-time mold that cannot be released without breaking is molded using a molding material with caking properties, which is made by mixing an appropriate amount of binder with fine powder particles, so this mold can be manufactured at low cost.

■Hollow and undercut plastics that cannot be released from the mold without destroying the middle mold can be easily produced. It is particularly suitable for molding medium and large plastic products.

■It has become possible to mold medium and large products that require material strength regardless of their shape using reinforced plastic.

■Using mold manufacturing technology as is, plastic products with good dimensional accuracy can be manufactured at low cost, and equipment such as pumps, which are used in environments where metal products such as castings are prone to corrosion, can be made corrosion-resistant. It will be easier to change to plastic products.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the arrangement structure of the middle mold, outer mold, etc. used in the method for integrally molding plastic products according to the present invention, Fig. 2 is a partially cutaway sectional view showing a part of a pipe, and Fig. 3 is a main A diagram showing a guide casing of a pump which is an example of a product manufactured by the integral molding method of a plastic product according to the invention, FIG. 4 shows a guide vane of the guide casing, and FIG. 5 shows the shape of the medium 20. 6 is a partial cross-sectional view taken along the line A--A in FIG. 5. In the figure, 10...Guide casing, 11...Casing outer body, 12...Casing inner body, 13
... Guide vane, 14 ... Water passage part, 15 ... Center part, 20.21 ... Medium size, 22, 23.24 ...
...outer mold, 25...vibrator, 26...liquid resin injection hole.

Claims (7)

[Claims] (1) A mold that is equipped with a middle mold and an outer mold and cannot be released from the mold without at least breaking is molded with a molding material having caking properties made by mixing an appropriate amount of binding agent into fine powder particles,
A method for integrally molding a plastic product, comprising injecting a liquid resin into the gap formed by the middle mold and the outer mold, and after the liquid resin solidifies, removing the middle mold and the outer mold to integrally mold the plastic product. . (2) The method for integrally molding a plastic product according to claim (1), characterized in that a polymeric material is permeated and solidified on the surface of the mold formed using the molding material to form an impregnated layer of a predetermined thickness from the surface. (3) The method for integrally molding a plastic product according to claim 1 or 2, wherein the liquid resin is a liquid resin such as unsaturated polyester, epoxy, urethane, nylon, or olefin. (4) Claim (1) or (2) characterized in that the release agent film is formed by applying a release agent to the surface of the impregnated layer formed on the surface of the mold formed using the molding material. or (3) the method for integrally molding a plastic product. (5) A hollow member with a large number of small through holes formed in the wall surface is inserted as a core material for reinforcing the core and supporting and stabilizing the core inside the core of the mold molded with the molding material, and the hollow member is Preheat the core by sending hot air at a predetermined temperature,
The plastic product according to claim (1) or (2) or (3) or (4), characterized in that the solidification time of the liquid resin is adjusted by adjusting the balance between the temperature of the injected liquid resin and the core temperature. Integral molding method. (6) Said claim (1) or (2) or (3) or (4)
) or (5) A plastic product manufactured by the method for integrally molding a plastic product described in (5). (7) Claim (6) characterized in that the interior of the plastic product is filled with a resin-reinforcing filler material.
Plastic products listed.