JPH07266355A - Production of resin molded product - Google Patents

Abstract

PURPOSE:To produce a resin molded product without receiving restriction from the aspect of equipment such as a special injection nozzle or the like, easily control a place where foaming is caused and enhance the transfer properties of a thick-walled molded product. CONSTITUTION:At least one foamble substance and the thermosetting resin 1 covering the same are introduced into the cavity 2a of a preheated mold 2 and, after the mold 2 is closed, the foamable substance 3 is foamed in the thermosetting resin 1 and the inner shape of the cavity 2a is transferred to the surface of the thermosetting resin 1 by the pressure generated in the mold by foaming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin molded product, and more particularly, it can be applied to a molding technique for high precision plastic mirrors and the like. The present invention relates to a method for producing a resin molded product that can prevent the occurrence of foaming, can easily control the location where foaming occurs, and can improve the transferability of a thick molded product.

[0002]

2. Description of the Related Art In the conventional method for producing a resin molded product, when a thermosetting resin is generally used to obtain a precision molded product having a thick and uneven thickness, the uneven temperature and pressure of the resin causes unevenness in the molded product. However, there is a problem in that the molding transfer accuracy is deteriorated. The conventional technique for preventing the problem that the molding transfer accuracy deteriorates in the thick part of the molded product due to the uneven distribution of the resin temperature and pressure is
For example, a method for producing a resin molded product by the sandwich molding method reported in Japanese Patent Laid-Open No. 5-104576 is known.

In this sandwich molding method, two kinds of resins are injected from a molding machine nozzle, first the molding resin is poured, and then the foamed resin is poured. As a result, the molding resin is
The skin layer is formed, and the foamed resin forms the core layer inside the molding resin. At this time, the foamed resin of the core layer causes foaming and expansion, and the skin layer made of the molding resin is pressed against the inner wall of the cavity from the inside. The generated internal pressure can prevent sink marks and form thick-walled molded articles and the like.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the conventional method for producing a resin molded article reported in Japanese Patent Publication No. 04576, since the sandwich molding method is used, sink marks can be prevented in the thick portion, but when the sandwich molding is performed, the resin flow into the molding machine. There is a problem that a dedicated molding machine (injection nozzle) having both a passage and a foaming agent passage is required, and there is a restriction on equipment. Further, when performing the sandwich molding method, since the molding resin and the foaming agent are injected into the mold through the gate of the mold, there is a problem that it is difficult to control the location where foaming occurs.

Further, in the conventional method for producing a resin molded product, when a thick product is molded with a thermosetting resin, there is a problem that the thick part is hard to be hardened and is likely to be an uncured part. Therefore, the present invention can avoid the restriction on equipment such as a special injection nozzle, can easily control the location where foaming occurs, and improve the transferability of a thick molded product. An object of the present invention is to provide a method for producing a resin molded product that can be used.

[0006]

The invention according to claim 1 is
At least one foam substance and a thermosetting resin covering the foam substance are introduced into a cavity of a preheated mold, and the mold is closed to foam the foam substance in the thermosetting resin. The internal shape of the cavity is transferred to the surface of the thermosetting resin by the generated internal pressure generated by the foaming.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the hollow material is formed by foaming the foaming substance in the thick portion of the thermosetting resin molded article. The method for producing a resin molded product according to claim 1. According to a third aspect of the present invention, in the above first and second aspects of the invention, the thermosetting resin is a resin that is solid at room temperature, and the surface of the thermosetting resin is the state in which the foamed substance is arranged inside. It is characterized by comprising a preform molded into the shape of the cavity.

A fourth aspect of the invention is characterized in that, in the first to third aspects of the invention, the thermosetting resin is smaller than the cavity volume. According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the foamed substance causes a reaction involving gas generation in a temperature range higher than room temperature and lower than the curing temperature of the thermosetting resin. It is characterized by being made of a substance.

The invention according to claim 6 is characterized in that, in the invention according to any one of claims 1 to 4, the foaming substance is a substance which is vaporized or generates a gas by irradiation with energy rays. The invention according to claim 7 is characterized in that, in the inventions according to claims 5 and 6, the foaming substance is made of a substance that generates a harmless gas.

The invention according to claim 8 is the invention according to any one of claims 1 to 7, characterized in that the foamed substance is covered with a coating layer. The invention according to claim 9 is the invention according to any one of claims 1 to 8, characterized in that the foamed substance is dispersed and covered in a carrier. The invention according to claim 10 is the invention according to claims 8 and 9, characterized in that at least one of the coating layer and the carrier is made of a material that melts at a foaming temperature of the foaming substance. Is.

The invention according to claim 11 is the above-mentioned claim 8,
In the invention described in Item 9, at least one of the coating layer and the carrier is made of a material that softens or becomes rubber-like at the foaming temperature of the foamed substance. The invention according to claim 12 is the above-mentioned claims 1 to 11.
In the invention described above, the foamed substance is installed in a state of being separated from the surface of the mold cavity.

According to a thirteenth aspect of the present invention, in the above-described eighth to twelfth aspects, the foamed substance dispersed in the carrier or the foamed substance covered with a film-forming layer is
It is characterized by having at least two or more protrusions. The invention according to claim 14 is the above-mentioned claim 1.
The invention according to any one of claims 1 to 13 is characterized in that the foamed substance is installed at an arbitrary portion in the thermosetting resin material.

A fifteenth aspect of the present invention is characterized in that, in the first to thirteenth aspects of the present invention, the foamed substance is installed in a thick portion of the thermosetting resin material.

[0014]

In the present invention, the foamed substance and the molding resin material are placed in a heated mold so that the foamed substance is placed in the mold cavity corresponding to a portion where a sink is likely to occur such as a thick portion in the molded product. To foam the foamed material inside the resin. By the pressure generation of the foaming gas, the resin in the cavity is pressed against the wall surface of the mold from the inside, so that the transferability of the thick-walled molded product can be improved.
Moreover, the conventional molding machine can be used as it is in terms of equipment. Further, even when thick parts are scattered in the molded product, by placing a foaming agent in each part, it is possible to form pores that generate pressure at any place in the molded product.
Hereinafter, the operation of the present invention will be described for each claim.

According to the first aspect of the invention, the mold is closed in a state in which the cavities of the preheated mold are filled with the foam substance and the thermosetting resin is placed so as to cover the lump of the foam substance. With this configuration, the resin can be cured from the outside by heat transfer from the mold. Also at this time,
Since the pressure inside the cavity can be increased by foaming that occurs inside the thermosetting resin, it is possible to obtain a resin molded product with good transferability without causing sink marks in the thick resin portion.

According to the second aspect of the present invention, since the foamed material is foamed in the thick portion of the thermosetting resin molded article to form the hollow portion, the thickness of the resin molded article is equalized. You can For this reason, the entire resin molded product can be cured more uniformly, so that defective molding due to uncured resin can be prevented. In the invention according to claim 3, since the thermosetting resin is composed of a resin which is solid at room temperature, and the foaming agent is arranged inside, it is composed of a preform having a cavity-shaped surface. Since the curable resin material can be handled easily and the injection molding machine can be dispensed with, the molding apparatus and equipment can be simplified.

According to the fourth aspect of the invention, since the thermosetting resin preform is configured to be smaller than the cavity volume, the preform can be easily inserted into the mold and the mold is closed. In this case, it is possible to prevent excessive pressure from being applied to the preform. In the invention according to claim 5, since the foaming substance is composed of a substance (single substance or mixture) which causes a reaction accompanied with generation of gas at a temperature higher than room temperature and lower than the curing temperature of the thermosetting resin, the resin is A gas can be efficiently generated inside the resin when it starts to solidify from the outside, and the pressure inside the resin can be increased at the thick part of the molded product where the viscosity of the resin is the lowest to improve the mold transferability.

According to the sixth aspect of the present invention, since the foamed substance is composed of a substance that is vaporized or generates a gas by irradiation with energy rays such as ultraviolet rays, electron beams, and laser light, the timing for generating the gas inside the resin is It can be set arbitrarily regardless of the temperature. In the invention according to claim 7, since the foamed substance is composed of a substance that generates a gas that is harmless to the human body or the device, such as water vapor, carbon dioxide, or nitrogen at the resin temperature, it is safe to handle and may damage the device. There can be no.

In the invention according to claim 8, since the foamed substance is constituted so as to be covered with the coating film, the foamed substance can be easily handled, and the foamed substance diffuses in the resin. It is possible to prevent air bubbles from being dispersed and reaching the surface of the molded product. In the invention according to claim 9, since the foamed substance is configured to be covered in the carrier, the foamed substance can be easily handled, and the foamed substance diffuses in the resin or bubbles are dispersed. It is possible to prevent it from reaching the surface of the molded product.

According to the tenth aspect of the present invention, at least one of the coating layer and the carrier that wraps the foamed material is made of a material that melts in the foaming temperature range of the foamed material, so that when the temperature of the molding resin rises. The generated gas can be expanded and moved toward a location having the lowest temperature and low viscosity in the molding resin that has started to cure, and the pressure of the generated gas can be transmitted to the molding resin as it is.

In the invention according to claim 11, since at least one of the coating layer and the carrier for enclosing the foamed substance is made of a rubber-like or soft material in the foaming temperature range of the foamed substance, it solidifies at a high temperature. Since the internal pressure of the gas generated in the molding resin that has begun to expand allows it to expand and expand, it is possible to transmit the gas pressure to the surrounding molding resin and prevent the generated gas from reaching the surface of the molded product. You can

According to the twelfth aspect of the invention, since the foamed substance is installed in a state of being separated from the surface of the mold cavity, it is possible to prevent the generated gas from reaching the surface of the molded product. The pressure can be effectively transmitted to the molded product (resin). In the invention according to claim 13, since the foamed substance dispersed in the carrier or the foamed substance covered with the coating layer is constituted to have at least two or more protrusions, foaming occurs even when the molding resin is in a liquid state. Since the substance can be held in a state of being separated from the surface of the mold cavity, it is possible to prevent the generated gas from reaching the surface of the molded product. Therefore, the pressure of the foaming gas can be effectively transmitted to the molded product (resin).

According to the fourteenth aspect of the present invention, since the foamed substance is arranged to be installed at an arbitrary portion in the thermosetting resin material, a hollow portion is formed at an arbitrary position in the molded article by foaming of the foamed substance. In addition to the above, depending on the shape of the molded product, it is possible to form hollow portions at a plurality of distant locations by foaming the foamed substance. According to the fifteenth aspect of the invention, since the foamed substance is arranged in the thick-walled portion of the thermosetting resin material, it is possible to improve the transferability of the thick-walled portion of the uneven-thickness molded product which is difficult to perform homogeneous molding. Therefore, a good molded product can be obtained.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, first, as shown in FIG. 1, the lump of the foamed substance 3 and the foamed substance 3 are wrapped in the cavity 2a of the mold 2 which has been heated above the curing temperature of the thermosetting resin 1 in advance. Put the thermosetting resin 1 and close the mold 2. Thus, when the mold 2 is closed, the foam substance 3 foams (or vaporizes) in the cavity 2a of the mold 2 as shown in FIG.
Then, the hollow portion 3a is formed. For this reason, when the foamed substance 3 foams and becomes the hollow portion 3a, a rapid volume expansion occurs, so that the thermosetting resin 1 that has started to cure from the outside inside the cavity 2a is transferred from the inside to the inside wall of the cavity 2a. It is pressed against.

As described above, the thermosetting resin 1 is free from sink marks when the volume of the thermosetting resin 1 shrinks due to the increase in the pressure inside the cavity 2a caused by the foaming of the foamed material 3, and a resin molded product having good transferability is obtained. You can Further, generally, when a thick product is molded with the thermosetting resin 1, the thick portion is hard to be hardened and is likely to be partially uncured. However, in the present embodiment,
Since the hollow portion 3a is formed by the foaming of the foaming substance 3 in the thick part of the molded product of the thermosetting resin 1, the thickness of the resin molded product can be made uniform. For this reason, the entire resin molded product can be cured more uniformly, so that defective molding due to uncured resin can be prevented.

Further, in this embodiment, the foam material 3 is placed in the mold 2.
Since it is configured to be installed away from the surface of the cavity 2a, it is possible to prevent the generated gas from reaching the surface of the molded product, so that the pressure of the foaming gas can be effectively transmitted to the molding resin. In the present embodiment, it is preferable that the thermosetting resin 1 is composed of a resin that is solid at room temperature, and is made of a preform whose surface is formed into a cavity shape with the foaming substance 3 arranged inside. in this case,
Since the thermosetting resin material can be handled easily and the injection molding machine can be dispensed with, the molding apparatus and equipment can be simplified. The thermosetting resin 1 composed of this preform is preferably configured so as to be smaller than the volume of the cavity 2a. In this case,
It is possible to easily insert the preform thermosetting resin 1 into the cavity 2a of the mold 2, and to prevent excessive pressure from being applied to the preform thermosetting resin 1 when the mold 2 is closed. You can

Further, in this embodiment, the foam substance 3 is made of a substance (a single substance or a mixture) which causes a reaction accompanied by the generation of gas at a temperature higher than room temperature and lower than the curing temperature of the thermosetting resin 1. In this case, since the gas can be efficiently generated inside the resin 1 when the resin 1 starts to solidify from the outside, the pressure inside the resin 1 is increased at the thick part of the molded product where the viscosity of the resin 1 is the lowest. Mold transferability can be improved. Further, the foamed substance 3 is preferably made of a substance that is vaporized or generates a gas by irradiation with energy rays such as ultraviolet rays, electron beams, and laser light. In this case, the timing of generating the gas inside the resin 1 is set to the temperature of the resin 1. It can be arbitrarily set without depending on it. The foaming substance 3 may be a single substance or a mixture, and may be a liquid or a solid at room temperature. The gas generated by the foamed substance 3 is water vapor or carbon dioxide at the temperature of the resin 1,
It is preferable to use a substance such as nitrogen that generates a gas that is harmless to the human body and the device, and in this case, handling is safe and there is no risk of damaging the device. As the foaming substance 3, inorganic compounds such as magnesium sulfate, aluminum hydroxide, sodium bicarbonate, sodium borohydride, azodicarbonamide, p, p′-oxybisbenzenesulfonyl hydrazide, etc. are desirable.

In the above embodiment, the foaming substance 3 was constructed so as to be in direct contact with the thermosetting resin 1. However, in the present invention, when the foaming substance 3 is in the form of powder, liquid, needle crystals, etc.,
As shown in FIGS. 3 and 4, the foamed substance 3 may be covered with a coating layer 11 such as resin or rubber. In this case, the foamed substance 3 can be handled easily and 3 diffuses in the resin 1 or foam is dispersed,
It is possible to prevent reaching the surface of the molded product. Further, as shown in FIGS. 5 and 6, the foamed substance 3 is made of resin, rubber, gel,
The carrier 21 such as jelly may be kneaded and dispersed. In this case, the foamed substance 3 can be easily handled, and the foamed substance 3 diffuses in the resin or bubbles. Can be prevented from reaching the surface of the molded product by being dispersed.

However, the coating layer 11 or the carrier 21 that wraps the foamed substance 3 is preferably made of a material that becomes rubber or soft in the foaming temperature range of the foamed substance 3, and in this case, when foaming occurs, this coating layer Since 11 or the carrier 21 can expand and expand the volume of the foam, it can expand and expand due to the internal pressure of the gas generated in the molding resin 1 which has begun to solidify at a high temperature. Therefore, the pressure of the gas can be transmitted to the surrounding resin 1, and the generated gas can be prevented from reaching the surface of the molded product.

Further, the coating layer 11 or the carrier 21 may be made of a material that melts in the foaming temperature range of the foamed substance 3, in which case the gas spreads in the molding resin 1 and the thick wall inside the molded product is formed. The hollow portion 3a of the generated gas can be formed near the center of the portion (the portion where the resin temperature is low and the viscosity is low because the resin heating is the slowest). For this reason, the gas generated when the temperature of the molding resin 1 rises can be expanded and moved toward the location where the temperature is lowest and the viscosity is low in the molding resin 1 that has started to cure. The pressure of the generated gas can be directly transmitted to the resin 1.

In the above embodiment, the foam material 3 is simply separated from the surface of the cavity 2a.
Although it is arranged in the central portion, in the present invention, as shown in FIG.
As shown in FIG.
It may be arranged such that the pressure distribution is likely to occur and a transfer failure is likely to occur in the thick portion. In this case, since it is possible to control the generation position of the hollow portion in the uneven molded product, it is possible to improve the transferability of the thick-walled part of the uneven thickness molded product that is difficult to perform homogeneous molding, and to obtain a good molded product. Can be obtained. However, since the generation position of the hollow portion 3a is also influenced by the resin viscosity, the foamed substance 3 may be installed at an arbitrary portion in the thermosetting resin 1, and may be formed in an arbitrary portion in the molded product. The hollow portion 3a can be formed at the location, and depending on the shape of the molded product, the hollow portion 3a can be formed at a plurality of spaced locations.

Further, in the present invention, as shown in FIGS. 8 and 9, the foamed substance 3 dispersed in the carrier 21 or the foamed substance 3 covered by the coating layer 11 has at least two or more protrusions 31. It may be configured as follows. In this case, even when the molding resin 1 is in a liquid state, the foam substance 3 can be held in a state of being separated from the surface of the cavity 2a of the mold 2, so that the generated gas can be prevented from reaching the surface of the molded product. Therefore, the pressure of the bubble gas can be effectively transmitted to the molded product (resin).

[0033]

According to the present invention, it is possible to prevent restrictions on equipment such as a special injection nozzle, and to easily control the location where foaming occurs, thus making it possible to obtain a thick-walled molded product. There is an effect that the transferability can be improved.

[Brief description of drawings]

FIG. 1 is a view showing a state in which a thermosetting resin and a foam material are contained in a mold of an embodiment according to the present invention.

FIG. 2 is a view showing a state where a foamed material is foamed in the thermosetting resin shown in FIG. 1 to form a hollow portion.

FIG. 3 is a diagram showing a state in which a foam material applicable to the present invention is covered with a coating layer.

FIG. 4 is a view showing a state in which the foam material shown in FIG. 3 foams to form a hollow portion.

FIG. 5 is a diagram showing a state in which a foaming material applicable to the present invention is dispersed in a carrier.

6 is a view showing a state in which the foamed material shown in FIG. 5 foams to form a hollow portion.

FIG. 7 is a diagram showing a state in which a foamed material applicable to the present invention is arranged in a thick portion in a cavity.

FIG. 8 is a view showing a state in which protrusions are formed on a foam material covered with a coating layer or a carrier applicable to the present invention.

FIG. 9 is a view showing a state in which a protrusion is formed on a foamed material covered with a coating layer or a carrier.

[Explanation of reference numerals] 1 thermosetting resin 2 mold 2a cavity 3 foam material 3a hollow portion 11 coating layer 21 carrier 31 protrusion

Claims (15)

[Claims] 1. At least one foam substance and a thermosetting resin covering the foam substance are introduced into a cavity of a preheated mold, the mold is closed and the thermosetting resin is sealed in the thermosetting resin. A method for producing a resin molded article, which comprises foaming a foaming material and transferring the internal shape of the cavity to the surface of the thermosetting resin by the generated internal pressure generated by the foaming. 2. The method for producing a resin molded product according to claim 1, wherein a hollow part is formed by foaming the foaming substance in a thick part of the thermosetting resin molded product. 3. The thermosetting resin is made of a resin that is solid at room temperature, and the foamed substance is placed inside the thermosetting resin.
The method for producing a resin molded product according to claim 1, wherein the surface is made of a preform molded into the shape of the cavity. 4. The method for producing a resin molded product according to claim 1, wherein the thermosetting resin is smaller than the cavity volume. 5. The foamed substance is formed of a substance which causes a reaction involving the generation of gas in a temperature range higher than room temperature and lower than the curing temperature of the thermosetting resin. Method for manufacturing resin molded products of. 6. The method for producing a resin molded product according to claim 1, wherein the foamed substance is a substance which vaporizes or generates a gas upon irradiation with energy rays. 7. The method for producing a resin molded product according to claim 5, wherein the foaming substance is made of a substance that generates a harmless gas. 8. The method for producing a resin molded article according to claim 1, wherein the foamed substance is covered with a coating layer. 9. The method for producing a resin molded article according to claim 1, wherein the foamed substance is dispersed and covered in a carrier. 10. The method for producing a resin molded product according to claim 8, wherein at least one of the coating layer and the carrier is made of a material that melts at a foaming temperature of the foamed substance. 11. The resin molded product according to claim 8, wherein at least one of the coating layer and the carrier is made of a material that softens or becomes rubber-like at a foaming temperature of the foamed substance. Production method 12. The method for producing a resin molded product according to claim 1, wherein the foamed substance is installed in a state of being separated from the surface of the mold cavity. 13. The foamed substance dispersed in the carrier or the foamed substance covered by the coating layer has at least two protrusions. Method for manufacturing resin molded products of. 14. The foamed substance is installed at an arbitrary portion in a thermosetting resin material.
3. The method for producing a resin molded article according to item 3. 15. The method for producing a resin molded product according to claim 1, wherein the foamed substance is provided in a thick portion of the thermosetting resin material.