JP2001293742A - Method for manufacturing injection-molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an injection-molded article, capable of forming a core good in moldability and deformation resistance at the time of molding of a main body, capable of recovering a part of the core and capable of reducing a production cost. SOLUTION: The method for manufacturing the injection-molded article has a process for injection-molding a water soluble resin core (10) having a shape corresponding to a hollow part from a water soluble molding material 11 prepared by dispersing almost spherical glass beads (20) in a water soluble resin 12, a process for arranging the water soluble resin core (10) in a mold after water soluble resin core (10) is formed to inject a molding material in the space between the mold and the water soluble resin core (10) to mold a molded object (30) integrated with the water soluble resin core (10) and a process for washing the integrated molded object (30) to remove the water soluble resin core (10) from the molded object (30).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an injection-molded article having a complicated inner surface shape at a low cost.

[0002]

2. Description of the Related Art Conventionally, a product having a complicated inner surface shape has a complicated uneven portion and has a reverse taper portion or the like, or in the middle of a hollow portion formed inside the product. It may have a portion that bulges outward. In such a case, that is, in the production of a hollow injection molded article having a shape that cannot be removed from the mold, it is impossible to remove a mold called a core that forms a hollow portion after molding by general injection molding.

[0003] For this reason, in a product having such a complicated inner surface shape, a plurality of parts each partially formed are bonded and integrated in a later step. Alternatively, the core was divided into complicated shapes, the divided cores were assembled, used, and disassembled to remove the mold. However, the former manufacturing method, in which a plurality of parts are bonded in a later step, requires a plurality of dies, and requires time and labor for bonding a plurality of molded products, resulting in an increase in production cost. In addition, since they are not integrally molded, the adhesive strength is low and joints are formed in molded products.

In the latter manufacturing method using the divided core, the cost of the divided core also increases, and it takes time to assemble and disassemble. Therefore, a method of using a water-soluble resin as a material of the resin core and dissolving and removing the water-soluble resin core made of the water-soluble resin has been studied (JP-A-10-2).
No. 96748). According to this production method, an injection molded article having a complicated inner surface shape can be formed by using a water-soluble resin core.

[0005]

However, the prior art described in the above-mentioned Japanese Patent Application Laid-Open No. H10-296748 discloses that the water-soluble resin used for the core inside the molded product has a higher temperature than the heat softening temperature. When the injection molded product is injection molded around a water soluble resin core made of a water soluble resin when the thermal softening temperature of the injection molded product is higher, a part of the water soluble resin core melts, There was a problem that the internal shape could not be formed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to form a core and to reduce deformation during molding of a main body. It is an object of the present invention to provide a method of manufacturing an injection molded article, which can form a good core, can further recover a part of the core, and can reduce the production cost. .

[0007] In addition, the inventions of claims 2 and 3 specifically specify the invention of claim 1 and improve the deformation resistance during molding of the main body and the moldability of the core. It is an object of the present invention to provide a method for producing an injection molded article that can be used. In addition to the above, the invention according to claim 4 will provide a method for producing an injection-molded article capable of improving the recoverability of glass beads, moldability of the core, strength of the molded article, and surface roughness of the molded article. It is assumed that.

[0008] In addition, the invention according to claim 5 aims to provide a method of manufacturing an injection-molded article that can further improve the moldability of the core.

[0009]

SUMMARY OF THE INVENTION The present invention is to achieve the above object. (Claim 1) The invention according to claim 1 is a method for producing an injection-molded article (60) having a hollow portion therein, the method comprising:
2) injection molding a water-soluble resin core (10) having a shape corresponding to a hollow portion with a water-soluble molding material (11) in which substantially spherical glass beads (20) are dispersed inside; After forming the resin core (10), the water-soluble resin core (1
(0) is disposed, and a molding material (30) integrated with the water-soluble resin core (10) by injection molding a molding material into a space between the mold and the water-soluble resin core (10). And a step of removing the water-soluble resin core (10) from the molded body (30) by washing the integrated molded body (30) with water.

(Explanation of terms) Here, the "water-soluble molding material" may be any material that can be dissolved in water, and the material is not particularly limited. Specifically, for example, it is mainly made of starch and contains a biodegradable resin having both biodegradable and water-soluble properties, a polyvinyl alcohol-based resin, a urea-based resin, and the like. Also, here, the water used, depending on the type of water-soluble resin (12), water-soluble resin (12)
A surfactant, an acid, an alkali, or the like may be added in order to easily dissolve the acid.

The term "glass beads (20)" does not refer to a small decorative ball having a threading hole used for interior decoration or handicrafts, but refers to a ball having a substantially spherical shape as a whole. In addition, it has a heat softening temperature higher than that of a water-soluble molding material (11) mainly composed of glass and made of a biodegradable resin such as starch. Specifically, for example, UNIBEADS Unibeads UB-13L, UB-34L or UB-58 for blast manufactured by Union Co., Ltd.
L and the like.

(Operation) In general, when a resin such as the water-soluble resin (12) according to the present invention is molten (in a molding temperature range, that is, in a temperature range not lower than a glass transition temperature), a so-called “structural viscosity” is obtained. ". This "structural viscosity" means that when the shear stress increases and the flow velocity increases,
The internal structure is destroyed and the fluid tends to flow, and the apparent viscosity decreases. In addition, during injection molding of a molten resin having the property of “structural viscosity”, the apparent viscosity is reduced because the shear rate applied to the molten resin is particularly large compared to other molding methods, and the water-soluble resin (12 ) Will maintain a good state of fluidity.

The water-soluble resin core according to the present invention (10)
Uses a water-soluble molding material (11) in which substantially spherical glass beads (20) are dispersed in a water-soluble resin (12). For this reason,
As described above, the water-soluble resin (1
When molding the water-soluble resin core (10) using 2), the flowability of the water-soluble resin (12) is lower than that of a fibrous material such as glass fiber, and the movement resistance is less, and And the degree of freedom is large and good. Thereby, the flow characteristics at the time of molding can be improved, and the moldability can be improved. Furthermore, approximately spherical glass beads (20)
Because of the good fluidity, the damage to the mold for forming the water-soluble resin core (10) can be suppressed.

On the other hand, after forming the water-soluble resin core (10),
A water-soluble resin core (10) is placed in a mold, and a molding material is injection-molded into a space between the mold and the water-soluble resin core (10) to form a water-soluble resin core (10). And a molded body (30) integrated with the molded body. In this step, the water-soluble resin core (10) itself is hardly subjected to shear stress and is not deformed. Therefore, even if the temperature rises, the internal structure of the water-soluble resin core (10) is not destroyed, it becomes difficult to flow, the apparent viscosity increases, and the water-soluble resin core (10) Shape can be maintained.

Further, the present invention uses, as the water-soluble resin core (10), a water-soluble molding material (11) in which glass beads (20) are dispersed in a water-soluble resin (12). For this reason, a water-soluble resin core (10) is arranged in a molding die, and a molding material is injection-molded in a space between the molding die and the water-soluble resin core (10) to form a water-soluble resin core. When forming the molded body (30) integrated with (10), if the water-soluble resin (12) alone has insufficient deformation resistance during molding of the main body, the glass beads (20 ) Can form a water-soluble resin core (10) having excellent deformation resistance during molding of the molded body (30).

When forming the molded body (30) integrated with the water-soluble resin core (10), a fibrous material such as glass fiber has a low deformation resistance per se, The glass beads (20)
Has large deformation resistance against forces from all directions, and can prevent the water-soluble resin core (10) from being out of shape.

After the injection, when the temperature of the water-soluble resin (12) decreases and solidifies, the shape of the glass beads (20) is substantially spherical. Since it is uniform, dimensional stability can be improved. Therefore, the water-soluble resin (12) using substantially spherical glass beads (20) is more fluid than the one using fibrous glass fibers when molding the water-soluble resin core (10). In addition to having good properties, when the solidified water-soluble resin core (10) is used as the core to form the main body of the molded body (30), the molded body (30) can be made hard to lose its shape.

Also, since the glass beads (20) are substantially spherical, the water-soluble resin core (10) can be easily separated and recovered by washing with a predetermined mesh sieve after washing with water. Glass beads (2
0) can be easily reused. Thereby, the production cost can be reduced. Also, the present invention
The water-soluble resin core (10) is formed from a water-soluble molding material. For this reason, after taking out the molded body (30) after cooling and solidification having the water-soluble resin core (10) inside from the mold, it is made of a water-soluble molding material by a simple treatment of immersing it in water. Dissolve the water-soluble resin core (10) in water and mold the molded product (3
0) can be easily and reliably removed from the inside. Since the water-soluble resin core (10) does not need to be drawn toward one side of the cooled and solidified injection-molded product, the shape of the water-soluble resin core (10) is
There is no restriction on the shape for taking out from the inside of (60). Thereby, even if the shape of the core hollow portion (43) of the injection molded product (60) has a reverse tapered portion, or has an undercut portion outward, An injection molded product (60) having a complicated inner surface shape can be integrally molded at one time. Therefore, multiple product molds (42)
And a single product mold (42), the number of production steps can be reduced, and production costs can be reduced. In addition, since they can be integrally molded, no seams are generated and the strength can be improved as compared with the case where they are divided and molded and then adhesively bonded. (Claim 2) The invention according to claim 2 is the above-described claim 1.
In addition to the features described, substantially spherical glass beads (20) dispersed inside the water-soluble resin (12), the content is the total of the water-soluble resin (12) and the glass beads (20) It is characterized by being in the range from 20% to 65% by weight relative to the total weight.

(Operation) The reason for limiting the numerical value of the content of the substantially spherical glass beads (20) in the method for producing an injection-molded article according to the present invention will be described. Substantially spherical glass beads (20)
Is to increase the deformation resistance of the water-soluble resin core (10) at the time of molding the main body without deteriorating the flow characteristics at the time of molding. If the content of the glass beads (20) is less than 20% by weight, the deformation resistance of the water-soluble resin core (10) during the molding of the main body is insufficient. In addition, the content of glass beads (20) is 65% by weight.
When the ratio exceeds the above range, the water-soluble resin (12) as a binder between the glass beads (20) becomes relatively short, and cracks occur in the injection molded product, resulting in a decrease in strength. On the other hand, if the content of the glass beads (20) exceeds 65% by weight, when the melted resin is injected into the mold for the water-soluble resin core (10), the flow of the molten metal becomes poor, and the flow characteristics deteriorate. And the moldability deteriorates. Therefore, the content of the glass beads (20) is from 20% by weight to 65% by weight.
% By weight. (Claim 3) The invention according to claim 3 is the above-described claim 1.
Or, in addition to the features of claim 2, the substantially spherical glass beads (20) dispersed inside the water-soluble resin (12) have a content of the water-soluble resin (12) and the glass beads (20). Is in the range of 45% by weight to 65% by weight relative to the total weight of

(Function) In the present invention, only the lower limit of the content of the glass beads (20) is changed from 20% by weight of the invention described in claim 2 to 45% by weight. It is similar to that described. That is, by setting the content of the glass beads (20) in the range of 45% by weight to 65% by weight, the deformation of the water-soluble resin core (10) during the molding of the main body is further improved as compared with the invention of claim 2. Good resistance can be obtained. Thereby, as a material of the injection molded product, a metal material having a low melting point can be used in addition to the resin. (Claim 4) The invention according to claim 4 is characterized in that, in addition to the features described in claim 1, 2, or 3, substantially spherical glass beads dispersed in the water-soluble resin (12). (2
In the particle size distribution of (0), a particle having a particle size of 38 μm to 125 μm is 80% based on the total weight of the glass beads (20).
% By weight or more.

(Operation) Next, the reason for limiting the numerical value of the particle size distribution of the substantially spherical glass beads (20) in the method for producing an injection-molded article according to the present invention will be described. Glass beads (20) having a particle size of 38 to 125 microns
In the case of less than 10% by weight, in the remaining glass beads (20), if the glass beads (20) having a particle diameter smaller than 38 microns increase, the glass beads (20) become too fine and difficult to recover by sieving. The recoverability is poor. Further, since the number of the glass beads (20) having a small particle diameter increases, the surface area of the glass beads (20) increases, the frictional resistance increases, the kneading resistance increases, and the moldability becomes slightly poor.

When the particle size of the glass beads (20) is less than 80% by weight of 38 to 125 microns, the remaining glass beads (20) have a particle size larger than 125 microns. ) Increases,
The particle size of the glass beads (20) becomes too large, so that the fluidity during molding deteriorates, and the moldability deteriorates. Further, it becomes difficult to uniformly disperse the glass beads (20) in the minute portions of the water-soluble resin core (10), and a portion of the glass beads (20) having insufficient deformation resistance at the time of molding the main body due to segregation occurs. Also, the particle size of the glass beads (20) is too large, and the water-soluble resin core (10)
The surface of the injection-molded article (60) becomes uneven, and the surface roughness of the injection-molded article (60) increases.

Accordingly, the particle size distribution of the glass beads (20) is such that the particles having a particle size of 38 to 125 microns are contained in an amount of 80% by weight or more based on the total weight of the glass beads (20). (Claim 5) The invention according to claim 5 is the above-described claim 4.
In addition to the features described, the glass beads (20) are a mixture of two types of large-diameter glass beads (21) having a large particle diameter and small-diameter glass beads (22) having a small particle diameter, and Small particle size glass beads (22) have a particle size of 38 microns to 53 microns.
Micron size is in the range of 30% to 70% by weight based on the total weight of the glass beads (20), and the large particle size glass beads (21) have a particle size of 75 microns to 125%. In the range of 30 to 70% by weight, based on the total weight of the glass beads (20), the one in the micron range is characterized.

(Operation) Next, the reason for limiting the numerical value of the particle size distribution of the large-diameter glass beads (21) and the small-diameter glass beads (22) in the method for producing an injection-molded article according to the present invention will be described. In the present invention, the glass beads (20) are a mixture of two types of large-diameter glass beads (21) having a large particle diameter and small-diameter glass beads (22) having a small particle diameter.

When the large-diameter glass beads (21) are mixed with the small-diameter glass beads (22), the large-diameter glass beads (21) play the role of a roller and improve the flow characteristics. , The increase in kneading resistance can be suppressed, and particularly excellent moldability can be obtained. When the small-diameter glass beads (22) are less than 30% by weight, the large-diameter glass beads (21) relatively exceed 70% by weight, and the large-diameter glass beads (21) having a large particle diameter are mainly used. Bridges tend to occur during kneading, and particularly good moldability cannot be obtained. 70% by weight of small glass beads (22)
Is exceeded, the relatively large-diameter glass beads (21) are less than 30% by weight, and the small-diameter glass beads (22) have a small particle diameter.
Mainly, the total surface area of the glass beads (20) increases,
As the frictional resistance increases, the kneading resistance increases. Therefore, the small particle size glass beads (22) are in the range of 30% to 70% by weight based on the total weight of the glass beads (20),
The large-diameter glass beads (21) are set in a range of 30% by weight to 70% by weight based on the total weight of the glass beads (20).

[0026]

Embodiments of the present invention will be described below in more detail with reference to the drawings. 1 to 9 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view showing a state in which a core mold is assembled in one manufacturing process of an injection molded product, and FIG. 2 is injection molding. FIG. 3 is a longitudinal sectional view showing a state in which a water-soluble molding material and glass beads are injected into a hollow portion for a core in one manufacturing process of an article. FIG. 3 shows a water-soluble resin core in one manufacturing process of an injection-molded product. FIG. 4 is a longitudinal sectional view showing a state in which a product mold is assembled in one production process of an injection molded product, and FIG. 5 is a diagram showing a product resin in a product hollow portion in one production process of an injection molded product. FIG. 6 is a longitudinal sectional view showing a state in which a molded body is taken out in one manufacturing process of an injection molded product, and FIG. 7 is a vertical sectional view showing a state in which a molded body is taken out in a manufacturing process of the injection molded product. FIG. 8 is a vertical sectional view showing a state in which the injection molding is performed in one manufacturing process. Longitudinal sectional view of the completed injection molded article, FIG. 9 shows a partial longitudinal sectional view of a water-soluble resin core, respectively.

The method of manufacturing the injection molded product 60 according to the present embodiment is intended for an injection molded product 60 having a product hollow portion 44 having a complicated inner surface shape such as an undercut portion and a large number of uneven portions inside. It is assumed that. First, as shown in FIG. 1, a core mold 41 having a core hollow portion 43 is assembled. Around the inner surface of the core hollow portion 43, an uneven portion 14 is formed on the outer surface of the water-soluble resin core 10 and has an uneven shape toward the inside. The core mold 41
, An extruder 50 is connected via a passage 51. The passage 51 is formed so that the resin and the like extruded from the extruder 50 can be injected into the hollow portion 43 for the core.

Next, although not specifically shown, a mixture of the water-soluble resin 12 and the substantially spherical glass beads 20 is put into the extruder 50. The content of the substantially spherical glass beads 20 dispersed inside the water-soluble resin 12 is based on the total weight of the water-soluble resin 12 and the glass beads 20 in total.
It is in the range of 20% to 65% by weight, more preferably in the range of 45% to 65% by weight. And this approximately spherical glass beads 20
Has a particle size of 38 μm to 125 μm in a range of 80% by weight or more based on the total weight of the glass beads 20.

More specifically, for example, UNIBEADS Unibeads UB-1 manufactured by Union Co., Ltd.
3L (38 to 53 microns), UB-34L
(53 microns to 63 microns) and UB-58L
(75 microns to 125 microns) in a weight mixing ratio of 35% by weight, 30% by weight, and 35% by weight, respectively.

Further, the glass beads 20 are composed of a large-diameter glass bead 21 having a large particle size and a small-diameter glass bead 22 having a small particle size in the above-mentioned particle size distribution in order to make the moldability particularly good. The types may be mixed. The small-diameter glass beads 22 have a particle size of 38 μm to 53 μm.
The size in the micron range is set in the range of 30% by weight to 70% by weight based on the total weight of the glass beads 20. The large-diameter glass beads 21 having a particle diameter in the range of 75 μm to 125 μm are glass beads.
It is set in the range of 30% by weight to 70% by weight with respect to the total weight of 20%.

Specifically, for example, UNIBEADS Unibeads UB-1 manufactured by Union Co., Ltd.
3L (38-53 microns) and UB-58
L (75 μm to 125 μm) and 50% by weight with respect to the total weight of the glass beads 20. Before the water-soluble resin 12 and the glass beads 20 are charged into the extruder 50,
The powder is agitated and mixed in advance by another powder mixer to form a homogeneous water-soluble molding material 11.

Here, the "powder mixer" is an apparatus for uniformly mixing resin raw materials and the like before being applied to a molding machine. Specifically, a high-speed flow-type mixer such as a Henschel mixer manufactured by Erich Co., Ltd., which rotates a rotating blade in a container at a high speed, and a device that stirs and mixes powder and granular material, a horizontal cylindrical type,
It includes a mixer or the like that rotates and mixes a V-shaped or double-cone-shaped mixing container for a certain period of time.

The water-soluble resin 12 is made of polypropylene (PP, XK3262 manufactured by Chisso Corporation) and a starch-based biodegradable and water-soluble naturally decomposed plastic (NOVON manufactured by Novon Japan KK).
RO390) at a weight ratio of 80:20. This naturally decomposed plastic is an additive, and can be dissolved in water by mixing with a resin such as polypropylene, and finally, water, carbon dioxide, biomass (microorganisms), etc. It can be decomposed into The resin to be mixed is not limited to polypropylene (PP), but may be polyethylene (PE) instead of polypropylene (PP).
A mixture of P) and polyethylene (PE) may be used.

The resin to be mixed may be a polyester resin such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) or Hytrel. In addition, an ionomer resin used for coating the surface of a golf ball or the like may be used instead of polyethylene. Further, a mixture of these polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and the like at an appropriate ratio may be used.

Next, the water-soluble molding material 11 is kneaded in a screw inside the extruder 50, extruded from the extrusion port of the extruder 50 into the passage 51, and passes through the passage 51 to form a core mold. It is injected into the core hollow portion 43 inside 41. As a result, as shown in FIG. 2, the water-soluble molding material 11 in which the substantially spherical glass beads 20 are dispersed in the water-soluble resin 12 is filled in the core hollow portion 43.

Next, as shown in FIG.
After the solidification of the core 10, the core mold 41 is divided into left and right parts, and the water-soluble resin core 10 is taken out from the inside. At this time, the water-soluble resin core 10 is embedded in the water-soluble resin 12 in a state where the substantially spherical glass beads 20 are uniformly dispersed, as shown in FIG. Next, as shown in FIG. 4, the water-soluble resin core 10 is disposed inside the product mold 42, and the space between the inner surface of the product hollow portion 44 and the outer surface of the water-soluble resin core 10 is formed. Form a space into which the molding material enters.

Next, as shown in FIG.
The molding material in a molten state is injected from the extruder 50 into the space between the inner surface of the core and the outer surface of the water-soluble resin core 10 via the passage 51. The molten molding material is cooled and solidified to form an injection-molded product 60 which finally becomes a product, and is formed around the water-soluble resin core 10 in an integrated state. Then, a molded body 30 in which the water-soluble resin core 10 and the injection molded product 60 are integrated is formed. The surface of the water-soluble resin core 10 has irregularities corresponding to the shape of the inner surface of the injection molded product 60.
Since 14 is formed, the uneven portion 14 of the water-soluble resin core 10 is formed.
The molten molding material enters between them, and a material having a corresponding shape is formed on the inner surface side of the injection molded product 60.

Here, the molding material is usually
Uses synthetic resin. Specifically, for example, a PPS resin having a molding temperature of about 290 to 350 degrees is used. However, the molding material is not limited to these synthetic resins, and may be made of a metal material having a low melting point. Specifically, for example, zinc (Z
n), white metals such as lead (Pb) and tin (Sn), bismuth (Bi), and alloys thereof. When these metal materials are used as molding materials, the deformation resistance during molding of the main body can be increased by setting the content of the glass beads 20 to the upper limit of the usable range. Specifically, the content of the glass beads 20 is 45% by weight of the total weight of the water-soluble resin 12 and the glass beads 20.
By setting the content within the range of from about 65% by weight to about 65% by weight, it is possible to form a member having a deformation resistance at the time of forming the main body that can cope with a molding material of a metal material.

Next, as shown in FIG. 6, the product mold 42 is divided into left and right parts, and the water-soluble resin core 10 and the injection molded product 60 are integrated from inside the product mold 42. The molded body 30 is taken out. At that time, the water-soluble resin core 10 and the injection molded product 60 are
Since it is strongly connected to the inside through the uneven portion 14 having a complicated inner surface shape, the water-soluble resin core
You can't get ten. Then, after the molded body 30 is taken out, it is naturally left for about 30 hours. Thereby, the dimensions of the injection molded product 60 can be stabilized.

Next, as shown in FIG.
Immersed in a water tank 65 covered with water. As a result, the water-soluble resin 12 of the water-soluble resin core 10 is dissolved in water, and the glass beads 20 are released into the water. Thereby, for example, in the case of a cylindrical water-soluble resin core 10 having a diameter of about 8 mm, about 6 hours,
It can be dissolved by immersing it in the water tank 65. At this time, water 66 may be filled in the water tank 65. However, by dissolving the water-soluble resin 12 in the water by dissolving the water-soluble resin 12 in the water tank 65 instead of water at a temperature of about 60 to 80 degrees. The required time can be reduced. Specifically, the water-soluble resin core 10 can be melted by immersing it in the columnar water-soluble resin core 10 having the above-described size and shape for about 4 hours in a water bath 65 filled with warm water at the above temperature. Further, at this time, the speed at which the water-soluble resin 12 dissolves in the warm water can be accelerated by applying ultrasonic waves to the molded body 30 in the warm water to apply vibration. Specifically, by using ultrasonic cleaning together, the columnar water-soluble resin core 10 having the above-described dimensions and shape is used.
Can be dissolved in about 1.5 hours.

Next, after the molded body 30 is washed and washed, the final washing is performed in another water tank 65 for about 20 minutes, thereby completely
The water-soluble resin 12 of the water-soluble resin core 10 is dissolved in water,
The water-soluble resin core 10 that has been fitted inside the 30 disappears. Then, as shown in FIG. 8, only the injection molded product 60 can be obtained. Since the substantially spherical glass beads 20 are floating or settling in the water 66 in the water tank 65, the glass beads 20 having a predetermined size are formed by passing the water 66 through a wire mesh of a predetermined mesh. Can be recovered. Thereby, the glass beads 20 can be collected and used over and over again.

Next, the operation and effect of the above embodiment will be described. In the present embodiment, the water-soluble resin core 10
Is formed from a water-soluble molding material. For this reason, after taking out the molded body 30 after cooling and solidification having the water-soluble resin core 10 inside from the mold, this is immersed in water. The child 10 can be dissolved in water and easily and reliably removed from the inside of the molded body 30. And this water-soluble resin core 10
Does not need to be pulled out to one side of the cooled and solidified injection molded product, so that the water-soluble resin core 10
Is not restricted by the shape for taking it out of the injection molded article 60. Thereby, even if the shape of the hollow portion 43 for the core of the injection molded product 60 has a reverse tapered portion,
In addition, even if it has an undercut portion toward the outside, the injection molded article 60 having such a complicated inner surface shape can be integrally formed at one time. Therefore, a single product mold 42 can be used without requiring a plurality of product molds 42, and the number of production steps can be reduced, and production costs can be reduced. In addition, since they can be integrally molded, no seams are generated and the strength can be improved as compared with the case where they are divided and molded and then adhesively bonded.

In general, when the resin such as the water-soluble resin 12 according to the present embodiment is molten (in a molding temperature region, that is, in a temperature region equal to or higher than the glass transition temperature),
It has a so-called "structural viscosity" property. This "structural viscosity" is a property in which the apparent viscosity decreases when the shear stress increases, and when the shear stress increases and the flow velocity increases, the internal structure is broken and the fluid tends to flow. . In addition, the injection molding is one in which the shear rate applied to the molten resin is high, in addition to the large calender molding, among all the molding methods. Therefore, at the time of injection molding of a molten resin having such “structural viscosity”, the shear rate is high, so that the apparent viscosity becomes small, and the fluidity of the water-soluble resin 12 is maintained in a good state.

The water-soluble resin core 10 according to the present embodiment uses a water-soluble molding material 11 in which substantially spherical glass beads 20 are dispersed in a water-soluble resin 12. For this reason, when molding the water-soluble resin core 10 using the water-soluble resin 12 in a state of low viscosity as described above, the fluidity of the water-soluble resin 12 is compared with that of a fibrous material such as glass fiber. Less movement resistance, no directionality, greater freedom,
Good. Thereby, the flow characteristics at the time of molding can be improved, and the moldability can be improved. Furthermore, since the fluidity is good by using the substantially spherical glass beads 20, damage to a mold for forming the water-soluble resin core 10 can be suppressed.

On the other hand, after forming the water-soluble resin core 10 as described above, the water-soluble resin core 10 is disposed in a molding die,
A molded body integrated with the water-soluble resin core 10 by injection molding a molding material into a space between the mold and the water-soluble resin core 10
Form 30. In this step, the water-soluble resin core 10 itself is hardly subjected to shear stress and is not deformed. Therefore, even if the temperature is increased, the internal structure of the water-soluble resin core 10 is not destroyed, it becomes difficult to flow, the apparent viscosity increases, and the shape of the water-soluble resin core 10 is maintained. be able to.

Further, in the present embodiment, the water-soluble resin core
As 10, a water-soluble molding material 11 in which glass beads 20 are dispersed in a water-soluble resin 12 is used. For this reason, the water-soluble resin core 10 is arranged in the molding die, and a molding material is injection-molded in a space between the molding die and the water-soluble resin core 10 to be integrated with the water-soluble resin core 10. When forming the molded body 30, when only the water-soluble resin 12 has insufficient deformation resistance at the time of molding the main body, the glass beads 20 having a high heat softening temperature are mixed, so that when the molded body 30 is molded. A water-soluble resin core 10 having excellent deformation resistance can be formed.

When the molded body 30 integrated with the water-soluble resin core 10 is formed, a fibrous material such as glass fiber has a small deformation resistance per se, and the fiber is in a transverse direction in the longitudinal direction of the fiber. Although it is easy to deform with a slight force, it is easy to lose its shape easily, but the substantially spherical glass beads 20 have a large deformation resistance to forces from all directions, and the water-soluble resin core 10 loses its shape. Can be suppressed.

After the injection, in a state where the temperature of the water-soluble resin 12 is lowered and solidified, the shape of the glass beads 20 is substantially spherical, so that there is no directionality and the shrinkage is uniform in all directions. In addition, the dimensional stability can be improved. Therefore, the water-soluble resin 12 using the substantially spherical glass beads 20, compared with the one using fibrous glass fiber, when molding the water-soluble resin core 10, on top of good fluidity, When the main body of the molded body 30 is formed using the solidified water-soluble resin core 10 as a core, it is possible to make the molded body 30 difficult to lose its shape.

Further, since the glass beads 20 have a substantially spherical shape, the water-soluble resin core 10 can be easily separated and recovered by washing with a predetermined mesh sieve after washing the water-soluble resin core 10 with water. Can be easily reused. Thereby, the production cost can be reduced. Next, a second embodiment will be described.

FIG. 10 is a longitudinal sectional view showing a second embodiment of the present invention, in which a water-soluble molding material and glass beads are injected into a hollow portion for a core in one production process of an injection molded product. The figure is shown. In the present embodiment, another core is formed inside a core, and specifically, an inner core 13 made of a normal resin or the like is formed inside a water-soluble resin core 10. Is what you are doing. Even if the inner core 13 is formed inside the water-soluble resin core 10, the injection molded article 60 can be formed in exactly the same procedure as in the first embodiment. Then, when the water-soluble resin core 10 is immersed in water 66 in the water tank 65,
When the water-soluble resin 12 is dissolved, the inner core 13 itself does not dissolve in the water 66, but since the water-soluble resin 12 around the inner core 13 dissolves in the water 66, the inner core 13 can be easily removed from the molded body 30. 13 can be separated. As a result, the amount of the water-soluble molding material 11 used can be reduced by the volume of the inner core 13, and the amount of the water-soluble resin 12 used can be reduced as compared with the case where the inner core 13 is not used. Costs can be reduced.

[0051]

Embodiment 1 Next, an embodiment according to the present invention will be described in comparison with a comparative example in which the content of the glass beads 20 is outside the scope of the claims. The injection molded article 60 obtained by the method for manufacturing the injection molded article 60 according to the present invention, and the injection molded article obtained by the manufacturing method deviating from the present invention are manufactured, and for each, the molding of the water-soluble resin core 10 Tests were conducted and evaluated for the properties, deformation resistance during molding of the main body, and occurrence of cracks. Table 1 shows the test results. Particularly good test results are indicated by the symbol ◎, and good test results are indicated by the symbol ○.
The test results with a slightly poor test result are indicated by a symbol △, and the test results with a poor test result are indicated by a symbol X.

The content of the glass beads 20 in Table 1 is a ratio (% by weight) to the total weight of the water-soluble resin 12 and the glass beads 20. The glass beads 20 are UNIBEADS Unibeads UB-13L (38 to 53 microns) and UB-34L (53 to 63 microns) for blasting manufactured by Union Corporation.
And UB-58L (75 to 125 microns)
Were used in a weight mixing ratio of 35% by weight, 30% by weight, and 35% by weight, respectively. The particle size distribution of the mixture of these glass beads 20 is as follows.
8 micron to 125 micron glass beads
It is contained in a range of 80% by weight or more with respect to the total weight of 20.

The water-soluble resin 12 is made of polypropylene (PP, XK3262 manufactured by Chisso Corporation) and a starch-based biodegradable and water-soluble naturally decomposed plastic (NOVON® manufactured by Novon Japan KK).
O390) at a weight ratio of 80:20. The water-soluble resin 12 had a softening temperature of 110 degrees as a result of the Vicat softening temperature test.

The injection molded article 60 uses a PPS resin having a deflection temperature under load (HDT) of 260 ° C. using a load of 1.82 MPa.

[0055]

[Table 1]

As is apparent from Table 1, the test results of Examples 1 to 4 for the water-soluble resin core 10 showing good moldability, deformation resistance at the time of molding the main body, and generation of cracks were all good. there were. In addition, as shown in Examples 3 and 4, when the content of the glass beads 20 was 45% by weight or 65% by weight, the deformation resistance at the time of molding the main body was particularly good.

On the other hand, in Comparative Example 1 in which no glass beads 20 were added, the water-soluble resin core 10 was formed only with the water-soluble resin 12 (normal molding temperature of about 120 to 160 ° C.). Around PPS resin (normal molding temperature is 29
When injection molding is performed at about 0 ° to 350 °), the water-soluble resin core 10 is melted, the shape of the core is lost, and the product shape as the core cannot be maintained. became. In Comparative Examples 2 and 3 in which the content of the glass beads 20 was small, a part of the water-soluble resin core 10 was melted, and the deformation resistance of the water-soluble resin core 10 at the time of molding the main body was slightly poor. It became. Comparative Examples 4 and 5 having a large content of glass beads 20 were relatively glass beads.
The amount of the water-soluble resin 12 as a binder for bonding the 20 is reduced, cracks are generated, the occurrence of the cracks becomes slightly defective or defective, and the amount of the water-soluble resin 12 is reduced, so that the amount of the water-soluble resin 12 is reduced. The flow characteristics at high temperatures were reduced, and the moldability was somewhat poor or poor.

[0058]

Embodiment 2 Next, an embodiment according to the present invention will be described in comparison with a comparative example in which the particle size range of the glass beads 20 is outside the scope of the claims. The injection molded article 60 obtained by the method of manufacturing the injection molded article 60 according to the present invention, and the injection molded article obtained from using the glass beads 20 having a particle size range deviating from the present invention, and each is manufactured. ,
Moldability of the water-soluble resin core 10, recoverability of the glass beads 20,
A test was conducted and evaluated for the surface roughness and economy of the injection molded product 60. Table 2 shows the test results. Good test results were indicated by the symbol ○, test results with slightly poor test results were indicated by the symbol 、, and test results with poor test results were indicated by the symbol ×. In addition, the glass bead content indicates the ratio of the added weight of the glass beads 20 of each particle size range to the total weight of the glass beads 20.

The glass beads 20 are made of UNIBEADS Unibeads UB manufactured by Union Corporation.
-13L (38 to 53 microns), UB-3
4L (53-63 microns) and UB-58
L (75 microns to 125 microns) in a weight mixing ratio of 35% by weight, 30% by weight and 35% by weight, respectively.
UB-01L (0-38 microns) and UB-810L (125 microns-18
0 micron) and the like were appropriately mixed and used. The same water-soluble resin 12 and injection molded product 60 as those in Example 1 were used.

[0060]

[Table 2]

As is clear from Table 2, in Examples 5 to 9, the test results of the moldability of the water-soluble resin core 10, the recoverability of the glass beads 20, and the surface roughness of the injection-molded article 60 were obtained. All were good. On the other hand, the glass beads 20 having a particle diameter of 38 to 125 microns are 70% by weight, and those having a particle diameter of less than 38 microns are 30% by weight. The recoverability of the glass beads 20 due to the sieving was poor, and the kneading resistance was high, and the moldability was slightly poor.

The glass beads 20 having a particle size of 38 μm to 125 μm are 70% by weight, and the remaining glass beads 20 are glass beads 20 having a particle size larger than 125 μm in an amount of 30% by weight. Comparative Example 7
In the case, the particle diameter of the glass beads 20 becomes too large, the flowability at the time of molding becomes poor, the moldability becomes slightly poor, and the surface of the water-soluble resin core 10 has irregularities, and the injection molded product 60 The molding surface became uneven, and the surface roughness of the injection molded product 60 became poor.

[0063]

Embodiment 3 Next, in the above-described embodiment according to the present invention, a description will be given of the particle size range of the glass beads 20 which can improve the moldability of the water-soluble resin core. The size range of the glass beads 20 is as follows: small-size glass beads 22 having a particle size in the range of 38 to 53 microns, and large-size glass beads 21 having a particle size in the range of 75 to 125 microns.
Using the glass beads 20 in which the mixing ratio of the two kinds of glass beads 20 was changed, the moldability of the water-soluble resin core, the recoverability of the glass beads, and the surface roughness of the injection molded product were tested and evaluated. Was done. Table 3 shows the test results. Particularly good test results were indicated by the symbol ◎, and good test results were indicated by the symbol ○. The glass bead content is
Small particle size glass beads 22 based on the total weight of glass beads 20
Alternatively, it indicates the ratio of the added weight of the large-diameter glass beads 21.

The glass beads 20 are manufactured by UNIBEADS Unibeads UB manufactured by Union Corporation.
-13L (38 to 53 microns) and UB-
What mixed 58L (75 micrometer-125 micrometer) so that it might become each mixing ratio was used. The same water-soluble resin 12 and injection molded product 60 as those in Example 1 were used.

[0065]

[Table 3]

As apparent from Table 3, Example 10
In Examples 16 to 16, the test results of the moldability of the water-soluble resin core 10, the recoverability of the glass beads 20, and the surface roughness of the injection molded product 60 were all good. Further, Example 12 in which the addition ratio of the small-sized glass beads 22 was 30% by weight and the addition ratio of the large-sized glass beads 21 was 70% by weight, and Example 12 in which the addition ratio of the small-sized glass beads 22 was 50% by weight. Particle size glass beads 21
Example 13 in which the addition ratio of 50% by weight was added to the glass beads, and the addition ratio of the small-size glass beads 22 was 70% by weight and the large-size glass beads
With Example 14 in which the addition ratio of 21 was 30% by weight, the water-soluble resin core 10 showed particularly good moldability.

[0067]

Since the present invention is configured as described above, it has the following effects. Claim 1
According to the described invention, a core having good moldability and deformation resistance during molding of the main body can be formed, and a part of the core can be recovered, thereby reducing production cost. It is possible to provide a method for producing an injection-molded article that can achieve the above.

According to the second and third aspects of the present invention, it is possible to provide a method of manufacturing an injection-molded article capable of improving deformation resistance during molding of a main body and moldability of a core. According to the fourth aspect of the present invention, it is possible to provide a method of manufacturing an injection molded article capable of improving the recoverability of glass beads, moldability of a core, strength of a molded article, and surface roughness of a molded article. it can.

According to the fifth aspect of the present invention, it is possible to provide a method of manufacturing an injection-molded article capable of further improving the moldability of the core.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention, showing a state in which a core mold is assembled in one manufacturing process of an injection molded product.

FIG. 2 is a longitudinal sectional view showing a state in which a water-soluble molding material and glass beads are injected into a hollow portion for a core in one manufacturing process of an injection-molded product according to the first embodiment of the present invention. is there.

FIG. 3 is a longitudinal sectional view showing a state in which a water-soluble resin core is taken out in one manufacturing process of an injection-molded product according to the first embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a state in which a product mold is assembled in one manufacturing process of an injection molded product according to the first embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of the first embodiment of the present invention, showing a state where a product resin is injected into a product hollow portion in one manufacturing process of an injection molded product.

FIG. 6 is a longitudinal sectional view showing a state in which a molded product is taken out in one manufacturing process of an injection molded product according to the first embodiment of the present invention.

FIG. 7 is a longitudinal sectional view showing a state in which a molded product is immersed in a water tank in one manufacturing process of an injection molded product according to the first embodiment of the present invention.

FIG. 8 is a longitudinal sectional view showing a completed injection molded product in one manufacturing process of the injection molded product according to the first embodiment of the present invention.

FIG. 9 is a partial longitudinal sectional view showing a water-soluble resin core according to the first embodiment of the present invention.

FIG. 10 is a longitudinal sectional view showing a state in which a water-soluble molding material and glass beads are injected into a hollow portion for a core in one manufacturing process of an injection-molded product according to a second embodiment of the present invention. is there.

[Explanation of symbols]

10 Water-soluble resin core 11 Water-soluble molding material 12 Water-soluble resin 13 Inner core 14 Irregularities 20 Glass beads 21 Large-diameter glass beads 22 Small-diameter glass beads 30 Molded body 41 Core mold 42 Product metal Mold 43 Hollow for core 44 Hollow for product 50 Extruder 51 Passage 60 Injection molded product 65 Water tank 66 Water

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AG07 AG25 AJ03 AJ07 AJ11 CA11 CB01 CD01 CK81 CM27 4F206 AG07 AG25 AJ03 AJ07 AJ11 JA05 JL02 JM16 JQ81

Claims (5)

[Claims] 1. A method for producing an injection-molded article having a hollow portion inside, comprising a water-soluble molding material in which substantially spherical glass beads are dispersed in a water-soluble resin. Injecting a resin core, and after forming the water-soluble resin core, disposing the water-soluble resin core in a mold, and a space between the mold and the water-soluble resin core. Forming a molded article integrated with a water-soluble resin core by injection molding a molding material into the molded article; and washing the integrated molded article with water to remove the water-soluble resin core from the molded article. And a process for producing an injection-molded article. 2. The content of the substantially spherical glass beads dispersed in the water-soluble resin is 20 to 65% by weight based on the total weight of the water-soluble resin and the glass beads.
The method for producing an injection-molded article according to claim 1, wherein the amount is in the range of% by weight. 3. The content of the substantially spherical glass beads dispersed in the water-soluble resin is 45 to 65% by weight based on the total weight of the water-soluble resin and the glass beads.
3. The method for producing an injection-molded article according to claim 1, wherein the amount is in the range of% by weight. 4. The particle size distribution of the substantially spherical glass beads dispersed in the water-soluble resin is such that those having a particle diameter of 38 μm to 125 μm are 80% by weight or more based on the total weight of the glass beads. The method for producing an injection-molded article according to claim 1, 2 or 3, wherein the method is included in a range. 5. The glass beads are a mixture of two types, a large-diameter glass bead having a large particle diameter and a small-diameter glass bead having a small particle diameter. The range of 38 to 53 microns is in the range of 30% to 70% by weight based on the total weight of the glass beads, and the large-diameter glass beads have a particle size of 75 to 125 microns. 5. The method for producing an injection-molded article according to claim 4, wherein the range is from 30% by weight to 70% by weight based on the total weight of the glass beads.