JP2002321249A - Insert molded product and its injection-molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a dimensional precision, productivity and a product design freedom of an insert molded product composed of a core material and a coating material without damaging the design freedom of the insert molded product itself, decreasing average molecular weight of a thermoplastic resin composition, restricting the resin composition, necessitating a complex mold structure and increasing the resin temperature and an injection velocity to higher levels more than necessary levels by facilitating the filling of the resin into a cavity of a mold. SOLUTION: An insert molded product composed of at least a core material and a coating material is obtained by filling a mixture of a thermoplastic resin composition composing the coating material and carbon dioxide pressurized to a pressure not lower than the atmospheric pressure into a cavity of a mold in which a preliminarily formed core material is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insert molded product composed of a core material and a coating material and a method of injection molding the same. More specifically, an insert molded product obtained by filling a mixture of a thermoplastic resin composition and carbon dioxide constituting a coating material into a mold cavity in which a preformed core material is installed, and an injection molding method thereof It is about.

[0002]

2. Description of the Related Art Generally, in many insert molded articles composed of a core material and a coating material, a core material formed in advance is placed in a mold cavity, and then a thermoplastic resin composition serving as a coating material is formed into a cavity. Manufactured by filling into. However, when the thickness of the coating material is small, it is difficult to fill the thermoplastic resin composition serving as the coating material into the mold cavity. In order to fill the thermoplastic resin composition without leaving unfilled portions, it is conceivable to increase the injection speed, and the resin pressure at the time of filling increases in proportion to the injection speed. For this reason, the thermoplastic resin composition filled in the mold cavity is solidified by cooling under a high-pressure environment, and a large amount of strain remains therein (hereinafter referred to as “residual strain”) in many cases.

[0003] The residual strain gradually relaxes after molding.
This is often due to shrinkage and deformation of the coating material, and if the degree is large, it causes cracking of the coating material itself and deformation of the entire insert molded product. Therefore, it can be said that the insert molded product is preferably injection-molded by a molding method and molding conditions in which residual distortion hardly remains. On the other hand, in normal injection molding including at the time of insert molding,
After filling the thermoplastic resin composition into the mold cavity, the thermoplastic resin composition is further held under pressure (hereinafter referred to as “pressure holding”).
) Is generally included. In this pressure-holding step, the thermoplastic resin composition itself filled in the mold cavity compensates for the volume shrinkage caused by the temperature drop. This pressure-holding step is a necessary step to ensure the dimensional accuracy of the molded product and the mold transferability.

However, when the holding pressure value (hereinafter referred to as "holding pressure") is inappropriate or when the pressure distribution in the molded product is significantly uneven, injection molding obtained after molding is performed. It may cause deformation of the product. In the case of an insert molded product, if this deformation force is large, it may cause deformation of the insert molded product including the core material. Therefore, in injection molding including insert molding, it can be said that it is preferable that the thermoplastic resin composition filled in the mold cavity be cooled and solidified under a uniform and not excessively high pressure environment.

[0005] However, when the thickness of the coating material is small, when the thermoplastic resin composition is filled so that the unfilled portion does not remain, a resin pressure of a certain value or more is required. A high holding pressure is required for a thermoplastic resin composition having a large volume shrinkage. Resin pressure, as a method of keeping the holding pressure low, also for the thermoplastic resin composition used,
It is possible to optimize. For example, it is to secure high fluidity by reducing the molecular weight of the thermoplastic resin composition.

However, in general, a thermoplastic resin composition having a small molecular weight inevitably suffers from a decrease in toughness. When it is used for a coating material of an insert molded product, the thermoplastic resin composition causes a contraction force of the thermoplastic resin composition itself. There is a concern about the occurrence of cracks. In addition, impact resistance is reduced, and the life of fatigue due to repeated loads is generally shortened. It is difficult to secure the product strength required for insert molded products. Is difficult to secure.

[0007] In addition, a method in which the resin pressure and the holding pressure are kept low by raising the conditions at the time of injection molding, specifically, the temperature of the thermoplastic resin composition and the mold temperature is conceivable. However, in the method of increasing the temperature of the thermoplastic resin composition, since it becomes a cause of promoting the thermal decomposition of the thermoplastic resin composition,
Degradation, generation of decomposition gas, the generated decomposition gas sticks to the mold cavity and becomes a mold deposit, and causes defects such as appearance defects called silver (silver streaks) on the molded product surface However, there is a limit to the range for increasing the temperature. In addition, when the temperature of the thermoplastic resin composition is high, the volume shrinkage generated during cooling increases, and there is a concern that defects such as sink marks may occur in the obtained molded product. For this reason, it can be said that the resin temperature during injection molding is preferably as low as possible.

[0008] In the method of increasing the mold temperature, the time required for cooling the thermoplastic resin composition filled in the mold cavity becomes longer, which may cause a problem in productivity. Also, if the gate position and score are inappropriate,
Since the resin pressure distribution tends to be uneven near the gate and at the end of the flow, the product design, the mold design, and the molding conditions are often restricted for the improvement.

On the other hand, if the pressure at the time of filling the mold cavity with the thermoplastic resin as the coating material is high, the pressure may cause deformation of the core material provided in the mold cavity. . Therefore, it is necessary that the material serving as the core material has strength, hardness, and shape that does not cause deformation when the thermoplastic resin is filled in the mold cavity.
On the other hand, J.I. Appl. Polym. Sci. , Vol.
30, 2633 (1985), it is known that when carbon dioxide is absorbed by a resin, it acts as a plasticizer for the resin and lowers the glass transition temperature. It has not been widely applied to processing.

[0010] WO 98/52734 discloses that
In injection molding of thermoplastic resin,
Shows a method of filling molten resin whose viscosity has been reduced by dissolving more than 1% by weight into a mold cavity that has been kept pressurized with a gas such as carbon dioxide at a pressure higher than the pressure at which foaming does not occur at the flow front of the molten resin. The mold surface reproducibility, glossiness, and weld lines are less noticeable.
It is described as being effective for reproducibility of sharp edges on a mold surface, reproducibility of irregularities on a fine mold surface, and the like. However, the method and the conditions for dissolving carbon dioxide in a thermoplastic resin efficiently have not been disclosed.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the average molecular weight of a thermoplastic resin composition without impairing the degree of freedom in designing an insert molded product itself composed of a core material and a coating material. It is not necessary to limit the composition, complicate the mold structure, and to increase the dimensional accuracy, productivity, and product design of the insert molded product without excessively increasing the resin temperature and injection speed during injection molding. It is an object to improve the degree of freedom. Specifically, an object of the present invention is to improve the dimensional accuracy and productivity of an insert molded product composed of a core material and a coating material because the mold cavity can be easily filled.

[0012]

Means for Solving the Problems The present inventor has restricted the average molecular weight and the resin composition of a thermoplastic resin composition without impairing the degree of freedom of design of at least the insert molded product itself composed of a core material and a coating material. Dimensional accuracy and productivity of insert molded products without increasing the temperature and injection speed of the resin during injection molding without the need to complicate the mold structure
We studied to make it possible to improve the degree of freedom in product design.

As a result, a mixture of the thermoplastic resin composition constituting the coating material and carbon dioxide pressurized to above the atmospheric pressure is introduced into the mold cavity in which the preformed core material is installed. The present inventors have found that an insert molded product characterized by being obtained by filling makes it possible to improve the productivity of the insert molded product, and have completed the present invention. That is, the present invention provides: An insert molded product composed of at least a core material and a coating material, into a mold cavity in which the preformed core material is installed, and a thermoplastic resin composition constituting the coating material at atmospheric pressure or higher. Insert molded article characterized by being obtained by filling a mixture of pressurized carbon dioxide,

2. 2. The insert molded article according to claim 1, wherein the thermoplastic resin composition is a crystalline resin composition. 3. The insert molded article according to claim 1, wherein the thermoplastic resin composition is an amorphous resin composition. 2. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin composition is a thermoplastic resin composition comprising at least an amorphous resin and / or a crystalline resin and an inorganic and / or organic filler. Insert molded products,

[0015] 5. The core material that constitutes the insert molded product is
5. The insert molded product according to claim 1, wherein the insert molded product is made of at least one metal member. The core material constituting the insert molded product has at least one core material.
The insert molded product according to any one of claims 1 to 4, wherein the insert molded product is made of two metal members and a thermoplastic resin.

[7] The core material that constitutes the insert molded product is
7. The insert molded product according to any one of claims 1 to 4, wherein the insert molded product is made of at least one metal member and a thermosetting resin. The insert molded product according to any one of claims 1 to 4, wherein the core material constituting the insert molded product is made of at least a thermoplastic resin and / or a thermosetting resin.

9. The core material that constitutes the insert molded product is
9. The insert molded product according to any one of claims 5 to 8, comprising a magnetic material and / or a conductor. 6. The insert molded product or a core material constituting the insert molded product is a storage medium.
Insert molded product according to any one of to 9;

11. The injection molding method, after mixing the thermoplastic resin composition in a molten state in the heating cylinder of the molding machine and carbon dioxide pressurized to above atmospheric pressure, a preformed core material was installed. 11. The injection molding method for an insert molded product according to claim 1, wherein an insert molded product is obtained by filling the mold cavity. The injection molding method is performed by filling a mixture of a thermoplastic resin composition and carbon dioxide into a mold cavity in which a preformed core material is installed and adjusted or held at atmospheric pressure to 15 MPa or less. An injection molding method for an insert molded article according to claim 11, which is obtained.

The present invention will be specifically described below.
The insert molded product according to the present invention is an integrally molded product composed of at least a core material and a coating material, and a thermoplastic resin serving as a coating material is filled into a mold cavity in which a preformed core material is installed. It is obtained by this. The insert molded product according to the present invention is characterized in that it is a molded product composed of at least a core material and a coating material, but the coating material of the thermoplastic resin composition covers a part or the whole of the core material. It is possible to implement even if there is more than one as needed.

In the present invention, the core material refers to a component to be embedded in an insert molded product, and is a component that is previously installed in a mold cavity and then covered with a coating material to be filled. Further, the whole core material does not need to be covered with the covering material, and a part thereof may be exposed. In the present invention, the covering material means that the core material to be embedded in the insert molded product is previously set in the mold cavity, and then the whole or a part of the core material is filled by filling the mold cavity with a thermoplastic resin in a molten state. Refers to the material to be coated.

In the present invention, the term "thermoplastic resin composition" refers to a composition containing a thermoplastic resin as a main component, which softens when heated and exhibits plasticity, and solidifies when cooled. Further, the thermoplastic resin composition can be used without distinction between a crystalline resin and an amorphous resin. In the present invention, a crystalline resin is a composition mainly composed of a thermoplastic resin having a specific melting point, in which molecular chains are regularly arranged to form a three-dimensional structure. Above the melting point, it refers to a composition mainly composed of a thermoplastic resin which loses its crystallinity and becomes a liquid state.

Specifically, polyacetal or polyoxymethylene (hereinafter abbreviated as “POM”) resin, polyamide (hereinafter abbreviated as “PA”) resin, polyethylene terephthalate (hereinafter abbreviated as “PET”) resin, polybutylene terephthalate (hereinafter abbreviated as “PET”) Hereinafter, the resin is abbreviated as “PBT”, a high-density polyethylene (hereinafter, abbreviated as “HDPE”) resin, a low-density polyethylene (hereinafter, abbreviated as “LDPE”) resin, a linear low-density polyethylene (hereinafter, abbreviated as “LLDPE”) resin. ,
A polyether ether ketone (hereinafter abbreviated as “PEEK”) resin, a polypropylene (hereinafter abbreviated as “PP”) resin, and the like are conceivable.

As the crystalline resin composition used in the present invention, a POM resin containing a POM component, PA
It can be said that a PA-based resin containing a component is preferable. Where P
OM is not distinguished from POM homopolymer and POM copolymer, and may be a POM block copolymer in which another component such as a lubricating polymer is chemically bonded to the terminal portion of the POM molecule.

PA means PA6, PA66, PA
A polymer compound having an acid amide bond, such as 610, PA11, and PA12. In the present invention, the amorphous resin refers to a resin composition containing a thermoplastic resin component which cannot take a crystalline state among thermoplastic resins or has a very low crystallinity even when crystallized. More specifically, it is also called an amorphous or amorphous polymer, and it is also called a solid state in which atoms or molecules do not form a three-dimensionally regular spatial lattice and are totally irregularly assembled in a solid state. The amorphous state includes a glass state and a rubber state. The amorphous state has a characteristic of showing a hard glass state below the glass transition point (Tg), but has a characteristic of showing a soft rubber state above the glass transition point (Tg).

Specifically, polystyrene (hereinafter “PS”)
) Resin, polyphenylene ether (hereinafter referred to as “PP”).
E "), a modified PPE obtained by blending a resin or a PPE resin with another resin or by graft polymerization.
Resin, acrylonitrile / butadiene / styrene copolymer (hereinafter abbreviated as “ABS resin”), acrylonitrile / styrene copolymer (hereinafter abbreviated as “AS resin”),
A polycarbonate (hereinafter abbreviated as “PC”) resin, a methacryl (hereinafter abbreviated as “PMMA”) resin, and the like are conceivable.

The thermoplastic resin composition of the present invention may be a polymer alloy which is a composite resin material in which two or more thermoplastic resins are physically and chemically mixed. The resin having different properties that can be used in combination with the thermoplastic resin as the main component is a resin component having the same molecular structure as the thermoplastic resin as the main component,
Resin components having different molecular weights and molecular weight distributions may be used, or other resin components having different molecular structures may be used.

There is no particular limitation on the resin component having different properties which can be used by being mixed with the thermoplastic resin as the main component as long as it is compatible with the thermoplastic resin as the main component. , PP, PA, PET, PBT, P
EEK, polyethylene, PS, ABS resin, polyvinyl chloride, PC, modified PPE, polyphenylene sulfide,
Polyimide, polyamide imide, polyether imide,
Examples thereof include polyarylate, polysulfone, polyethersulfone, liquid crystal polymer, polytetrafluoroethylene, thermoplastic elastomer, polytetrafluoroethylene, and polyvinyl alcohol.

As an example of a mixture containing a thermoplastic resin as a main component and resins having different characteristics, a polymer alloy of a PA resin and a PPE resin (hereinafter referred to as “PA / PP”)
Abbreviated as “E-based polymer alloy”), PP-based resin and PPE
Polymer alloys (hereinafter abbreviated as "PP / PPE-based polymer alloys") of PC-based resins and PC / ABS-based polymer alloys of PC-based resins and ABS-based resins. An inorganic or organic filler can be added to the thermoplastic resin composition used in the present invention for the purpose of imparting specific gravity, strength, and ensuring dimensional accuracy.

Examples of the specific gravity imparting agent include inorganic salts, oxides, such as barium sulfate, red iron oxide, and tungsten powder.
Metal powder and the like can be considered. Further, as a strength imparting agent,
Glass fiber, carbon fiber, metal fiber, aramid fiber, potassium titanate, asbestos, silicon carbide, ceramic,
Silicon nitride, barium sulfate, calcium sulfate, kaolin, clay, pyrophyllite, bentonite, sericite, zeolite, mica, mica, nepheline sinite, talc, atalpargite, wollastonite,
Slag fiber, ferrite, silicon, calcium, calcium carbonate, magnesium carbonate, dolomite, zinc oxide,
Gypsum, glass beads, glass powder, glass balloon, quartz, quartz glass, alumina and the like can be considered.

The shape of the inorganic or organic filler is not limited, and a fibrous, plate-like or spherical shape can be arbitrarily selected. In addition, two or more of the above-mentioned inorganic or organic fillers can be used in combination. Further, if necessary, it can be used after being pre-treated with a silane-based or titanium-based coupling agent. The amount of the inorganic or organic filler added to the thermoplastic resin composition of the present invention is not limited, but adjusts the specific gravity of the thermoplastic resin composition, improves rigidity,
Ensuring dimensional accuracy, suppressing deformation such as warpage,
In order to sufficiently obtain the effect of adding an additive, the amount of addition is preferably 5% by weight or more, and more preferably 10% by weight or more. When the amount is less than 5% by weight, the effect of adding the above-mentioned filler is small.

Here, the added amount of the inorganic or organic filler refers to the amount added when only one filler is added, and when two or more fillers are used, the total amount added. Point. Further, the amount of the inorganic or organic filler added indicates a ratio when the total amount of the resin component, the inorganic or organic filler, and other additives is 100% by weight.
In the thermoplastic resin composition of the present invention, commonly used additives, for example, antioxidants, flame retardants, release agents, lubricants, heat stabilizers, weather resistance stabilizers, rust inhibitors, fillers, One or more colorants, antibacterial agents, fungicides and the like can be added as necessary.

Further, as other additives, carbon fiber,
The electrical resistance value of the thermoplastic resin composition can be reduced by selecting at least one of metal fibers and graphite. This is preferable because a small powder such as dust can be prevented from being attached to the insert molded product made of the thermoplastic resin composition by static electricity. The insert molded article of the thermoplastic resin composition of the present invention is prepared by filling a mixture of the thermoplastic resin composition serving as a coating agent and carbon dioxide pressurized at or above atmospheric pressure into a mold cavity in which a core material has been previously installed. The feature is that, by mixing carbon dioxide in the thermoplastic resin composition,
Because the viscosity of the thermoplastic resin composition at the time of melting decreases, the thermoplastic resin composition does not leave an unfilled portion in the mold cavity, in a relatively low pressure range, because it is easy to fill. is there.

This is supposedly because carbon dioxide is efficiently dispersed as a plasticizer of the amorphous resin composition by mixing the molten thermoplastic resin composition with carbon dioxide. As a result, there is no need to raise the resin temperature, so there is no need to worry about thermal decomposition and deterioration of the thermoplastic resin composition, and it is not necessary to raise the mold temperature more than necessary, which is preferable. As described above, the insert molded article of the thermoplastic resin composition of the present invention fills a mold cavity with a mixture of the thermoplastic resin composition in a molten state and carbon dioxide pressurized at or above atmospheric pressure. This makes it possible to increase the flow distance without increasing the resin temperature more than necessary, so that the thermoplastic resin composition can be filled into the mold cavity with a low filling pressure. Therefore, the residual distortion is hardly left in the obtained molded product, so that the warpage or the like generated after the molding is reduced.In addition, since the unfilled portion is hardly left, the incidence of defects during continuous molding is low, and the productivity is improved. Seem.

In the present invention, the insert-molded article in which the coating material is a thermoplastic resin composition is a mixture of the thermoplastic resin composition in a molten state and carbon dioxide pressurized to an atmospheric pressure or higher. Although it is characterized by filling, if the carbon dioxide is less than atmospheric pressure, it is difficult to mix with the thermoplastic resin composition in a molten state, and it is possible to obtain an effect by mixing the thermoplastic resin composition and carbon dioxide It is not preferable because it is difficult.

The pressure of carbon dioxide efficiently mixed with the thermoplastic resin composition in the molten state is at least atmospheric pressure, preferably at least 1 MPa, more preferably at least 2 MPa. It is pressurized, and most preferably pressurized to 4 MPa or more. The insert molded article in the present invention is characterized by being obtained by filling a mold cavity with a mixture of a thermoplastic resin composition in a molten state and carbon dioxide pressurized to an atmospheric pressure or higher, The mixing method is not limited.

However, in order to efficiently mix carbon dioxide into the molten state of the thermoplastic resin, it is preferable that the thermoplastic resin composition is in a molten state, and the thermoplastic resin composition is melted in a heating cylinder of an injection molding machine. A method of mixing with a resin composition, a method of mixing with a thermoplastic resin composition in a molten state from a nozzle portion of a molding machine, a facility for supplying carbon dioxide between a mold and a nozzle of a molding machine, and a molten state. And a method in which resin pellets are granulated in a state in which carbon dioxide is mixed with a thermoplastic resin composition in a molten state in advance, and injection molding is possible.

Considering that carbon dioxide is easily and uniformly dispersed in the thermoplastic resin composition in a short time, the mixing amount is easily adjusted, and the setup before molding is not complicated, the heating cylinder of the injection molding machine is taken into consideration. Among them, by providing a facility for supplying carbon dioxide at any position between the nozzle of the molding machine and the nozzle of the molding machine and the mold, carbon dioxide is supplied to the thermoplastic resin composition in a molten state. The method of mixing is preferable. In the present invention, carbon dioxide is dissolved or absorbed in the thermoplastic resin composition by mixing the thermoplastic resin composition with carbon dioxide, but the amount of the dissolved or absorbed carbon dioxide is not limited.

The insert molded article of the thermoplastic resin composition according to the present invention preferably has a foamed portion inside, particularly at a portion which is thicker than the peripheral portion.
When the amorphous resin composition cools and solidifies in the mold cavity and causes volume shrinkage, carbon dioxide dissolved or absorbed in the thermoplastic resin composition foams appropriately in the foamed portion. It is supposed to be formed by this. Since the foamed portion is formed inside the relatively thick portion of the insert molded product, the volume shrinkage of the amorphous resin composition is supplemented from inside the insert molded product, and the surface of the insert molded product is reduced. The occurrence of defects such as sink marks after molding is suppressed. As a result, it is possible to apply the present invention to a molded product having a partially thick portion, and it is expected that the degree of freedom in product design is increased. Further, the foamed portion is different from that obtained by adding a foaming agent to the thermoplastic resin composition.

The thickness of the non-foamed layer can be adjusted by the holding pressure and the holding time. The higher the holding pressure and the longer the holding time, the thicker the non-foamed layer tends to be. However, when the holding pressure is too high or when the holding time is too long, the thermoplastic resin composition is cooled and solidified in the mold cavity, and is dissolved in the thermoplastic resin composition. Carbon dioxide hardly forms a foamed portion inside the molded article, and may cause sink marks on the surface of the molded article.

Here, the foamed portion means the foamed portion of an insert molded article made of the thermoplastic resin composition when an arbitrary cross section of the thermoplastic resin composition portion is magnified and observed 10 to 20 times by an optical microscope or the like. A void or a portion where a whitening phenomenon is confirmed is referred to, and a non-foamed layer is a portion where a void or a whitening phenomenon is not confirmed due to foaming. In the present invention, the injection molding method of a thermoplastic resin composition is a molding and processing method of a thermoplastic resin which is usually performed, and in addition to the most common ordinary injection molding method, a hollow injection molding method, a gas Assist molding method, blow molding method, injection / compression molding method and the like are included.

In the injection molding method of an insert molded article using the thermoplastic resin composition of the present invention, when a mixture of the thermoplastic resin composition and carbon dioxide is filled into a mold cavity, the amount of dissolved or absorbed carbon dioxide is reduced. If it is more than a certain value, a foam pattern may be generated on the surface of the insert molded product. In order to suppress the occurrence of a foaming pattern on the surface of the insert molded product, the inside of the mold cavity is adjusted or held by a pressurized gas at or above a pressure at which foaming does not occur at the flow front of the crystalline resin composition. Is preferred.

The pressure of the pressurized gas may be a minimum pressure at which a foaming pattern is not generated on the surface of the insert molded article made of the thermoplastic resin composition. The gas pressure is preferably low to minimize the amount of gas used during the molding cycle and to simplify the structure of the mold cavity seal and gas supply device. If the gas pressure exceeds 15 MPa, the mold may open due to the gas pressure, and problems such as difficulty in sealing the mold cavity may easily occur. Therefore, the pressure of the gas for pressurizing the mold cavity is higher than atmospheric pressure,
The pressure is preferably 5 MPa or less, more preferably from atmospheric pressure to 10 MPa.

Further, since the inside of the mold cavity is adjusted or maintained at a pressure at which foaming does not occur at the flow front of the thermoplastic resin composition by the pressurized gas, the mold cavity is formed near the gate portion. This is preferable because it also has the effect of suppressing poor appearance caused by turbulence in the flow of the thermoplastic resin composition, which is often called jetting. In the present invention, when the mold cavity is filled with the thermoplastic resin composition in which carbon dioxide is dissolved or absorbed, the mold cavity is at least atmospheric pressure and 15M.
It is preferably adjusted or maintained at Pa or less, from the start of resin filling, at least until the completion of the cooling step, preferably until the completion of the pressure-holding step, more preferably before the start of the pressure-holding step, Preferably, the pressure in the mold cavity is released.

At this time, as the gas for adjusting or maintaining the inside of the mold cavity at a constant pressure, a single or mixture of various gases inert to the thermoplastic resin composition can be used.
Carbon dioxide and hydrocarbons having high solubility in the thermoplastic resin composition, and gases in which hydrogen is partially replaced with fluorine are preferred. Considering that a high-purity gas can be easily obtained at relatively low cost, it is possible to use nitrogen gas. The usual injection molding method has a step of filling the thermoplastic resin composition into the mold cavity and then holding the thermoplastic resin composition in the cavity under pressure. This process is called the “holding process”, and the degree of the pressure is called “holding pressure”.
In the injection molding method of the thermoplastic resin composition according to the present invention, after filling the thermoplastic resin composition into the mold cavity, the thermoplastic resin in the mold cavity is subjected to a pressure corresponding to 30% or more of the filling pressure. Preferably, the composition is held under pressure.

In the present invention, the holding pressure is 30% of the filling pressure.
If it is less than 1, the thickness of the non-foamed layer formed on the surface layer of the molded article becomes thin, and the proportion of the foamed portion in an arbitrary cross section becomes large. An insert molded article obtained by filling a mold cavity with a mixture of a thermoplastic resin composition in a molten state and carbon dioxide pressurized to an atmospheric pressure or higher has a non-molded surface having a moderate thickness on its surface. In order to form a foamed layer and have an appropriate foamed portion inside, a preferable range of the holding pressure in the injection molding step is a range of 30% or more with respect to the filling pressure, and more preferably. It is in a range of 40% or more, and most preferably in a range of 50% or more.

Here, the filling pressure refers to a resin pressure generated when the molten thermoplastic resin composition is filled into a mold cavity. Specifically, the screw position in an in-line screw type injection molding machine and the plunger position in a pre-plasticity type injection molding machine refer to the maximum value of the resin pressure generated when moving from the measurement position to the VP switching position. is there. Further, the pressure holding time is not limited, but if the pressure holding time is extremely short, the carbon dioxide mixed with the thermoplastic resin composition before filling the mold cavity expands, It is not preferable because a swelling phenomenon may occur in the molded product.

The insert molded product according to the present invention is characterized in that it is a molded product composed of at least a core material and a coating material. However, the material constituting the core material is not limited. It may be configured. Further, the core material embedded in the insert molded product may be plural. However, considering that the mold cavity in which the core material is installed is filled with the thermoplastic resin in a molten state, it is preferable that the thermoplastic resin does not melt, deform, or disappear due to the temperature of the thermoplastic resin and the pressure at the time of filling. . Specifically, it is preferable that the core material is a material selected from a metal, a thermoplastic resin composition, and a thermosetting resin composition, and the core material can be implemented even if it is a composite part composed of a plurality of materials. is there. Further, the manufacturing method is not limited, and is manufactured by a known technique and method.

The shape of the core is not limited, and may be a part functioning as a single core. Specifically, a ball bearing, a bearing, a gear, a storage medium, a shaft, a coil, a motor, a ring motor, and the like can be given.
In the present invention, the thermosetting resin refers to a resin composition having a property that can be cured by heat or a catalyst, and a fusible and relatively low molecular weight substance has a three-dimensional network structure by a chemical reaction. Refers to becoming an insoluble and infusible substance.

The thermosetting resin of the present invention includes a resin composition which is cured by a combination of a material and a catalyst, and may be a resin composition which is not necessarily cured by heat. Specifically, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin,
In addition to diallyl phthalate resin, polyurethane resin, silicon resin, polyimide resin and the like, thermosetting acrylic resin and thermosetting polybutadiene can be mentioned.

It is preferable that the core material, or the whole or a part of the core material, is a magnetic material or a conductor, since the function of the insert molded product is improved. Further, it is preferable that a member necessary for the magnetic body and the conductor to exert their functions, and a member necessary for signal transmission and power transmission between other components are integrally formed. Specifically, it is a cord, a plug, an electric contact, or the like. The method for manufacturing the core material is not limited, and the core material can be implemented by a method obtained by existing technology.

The shape and application of the insert molded product according to the present invention are not limited, and may be a personal computer, a printer,
Electronic devices and their peripheral devices such as copiers, fax machines, various OA devices, storage media, etc., electric devices and their peripheral devices such as home appliances and audio devices, automobiles,
Insert-molded products used for products such as optical devices, industrial parts, building materials, batteries, and secondary batteries and peripheral devices thereof, and are insert-molded products used for interiors and exteriors constituting these products.

More specifically, in addition to components for fixing other components such as an external component such as a housing and an internal skeleton component, there are also mechanical components that emit their functions by linear motion, rotational motion, and vibration. it can. Specifically, rollers, gears, cams, sliders, motors, electrical contacts,
Switches, handles, diaphragms of speakers, and the like. On the other hand, the storage medium described above is an IC chip,
It refers to a storage medium having a function of mainly storing electronic information, such as a ROM and a RAM, and the content, storage method, and storage capacity of the electronic information are not limited. In particular, storage media that are small and thin so that they are easy to carry are preferable. These storage media are also called “memory sticks”, “smart media”, and the like. Specifically, floppy (registered trademark) disks, Besides, IC card, mobile phone, personal computer, electronic organizer, video camera,
Storage media such as a digital camera, a still camera, and various audio devices are included.

The secondary battery described above is also called a storage battery and refers to a battery that can be repeatedly used by discharging and then charging. Specifically, it is a secondary battery used for electric equipment and electronic equipment, particularly a secondary battery used for portable electric equipment and electronic equipment, and is also referred to as a “battery pack” or “battery pack”. For example,
Rechargeable batteries and batteries used in mobile phones, notebook computers, electronic organizers, video cameras, digital cameras, still cameras, various audio equipment, etc.
Battery packs and the like.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically by way of examples, but the present invention is not limited to the following. The thermoplastic resin used for the injection molding is a POM resin (“TENAC 4010” manufactured by Asahi Kasei Corporation) and a modified PPE resin (“Zylon 340” manufactured by Asahi Kasei Corporation)
V "), each of which is in the form of a pellet before molding. The molding machine is "TUPA" manufactured by Sodick Plustech Co., Ltd.
RL TR50S2 "was used.

[0055]

Examples 1 to 4 A mold was prepared which can mold a roller-type model insert-formed product having the shape shown in FIG.
The gate was a side gate, and one was provided on the parting surface. The core material has a diameter of 8 mm and a total length of 120 mm, and is made of SUS304. The thickness of the covering material is 2 mm, and the total length is 80 mm. The wall thickness of the molded article is uniform, 0.2 mm.

Using “TENAC 4010”, 1.8
Carbon dioxide adjusted to an arbitrary pressure of ~ 8.2 MPa,
The gas is supplied from a gas supply unit provided at the center of the heating cylinder of the molding machine to the molten resin in the heating cylinder to be mixed and then filled into a mold cavity.
A roller-type model / insert molded product having the shape shown in FIG. At this time, the resin temperature was adjusted to 195 ° C, and the mold temperature was adjusted to 80 ° C. After conditioning for 24 hours in a constant temperature and humidity chamber controlled at a temperature of 23 ° C. and a humidity of 50% RH for 24 hours, the coaxiality of the roller-type model / insert molded product was measured. The measurement method was as follows. With reference to two points A and C shown in FIG. 1, a swing width at a point B was measured, and this was defined as coaxiality.

After measuring the coaxiality, a heating treatment is performed for 5 days in a hot air drier adjusted to a temperature of 80 ° C., taken out of the hot air drier and stored again in a constant temperature and humidity chamber. The condition of time was adjusted, and the coaxiality was measured again. For measurement of the coaxiality, a roundness cylindrical shape measuring machine “Round Test RA-400 (manufactured by Mitutoyo Corporation)” was used. Table 1 shows the results of measuring the coaxiality of the molded product.
Shown in In addition, the measurement was performed about five molded articles, and the average value was shown.

[0058]

Comparative Example 1 In the same manner as in Examples 1 to 4, a mold capable of molding a roller-type model / insert molded article having the shape shown in FIG. 1 was prepared. By using "TENAC 4010", carbon dioxide is not supplied from the gas supply unit provided at the center of the heating cylinder of the molding machine, and by the same process as ordinary injection molding,
A roller model insert molded product was obtained. At this time, the resin temperature was adjusted to 195 ° C, and the mold temperature was adjusted to 80 ° C.

The concentricity of the roller-type model / insert molded product was adjusted for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23 ° C. and a humidity of 50% RH, and then dried with hot air adjusted to a temperature of 80 ° C. Heat treatment was performed in the machine for 5 days, and after taking out from the hot air dryer, the condition was adjusted again for 24 hours by storing again in a constant temperature / humidity chamber, and then twice.
Table 1 shows the results of measuring the coaxiality of the molded product.

[0060]

[Table 1]

[0061]

Examples 5 to 8 A mold was prepared which can mold a disk-shaped model / insert molded article having the shape shown in FIG. The gates were pin gates and were provided at three locations on the disk. The diameter of the core material is 2.4 mm, the total length is 50 mm, and the material is SUS304. . The coating material thickness is 0.8mm
And the outer diameter is 40 mm. "Zylon 340
V ", the carbon dioxide adjusted to an arbitrary pressure of 2.2 to 12.2 MPa is supplied from a gas supply unit provided at the center of the heating cylinder of the molding machine to a resin in a molten state inside the heating cylinder. After mixing by feeding, the mixture was filled into a mold cavity to obtain a disk-shaped model / insert molded product having the shape shown in FIG. The resin temperature at this time is 2
The temperature was adjusted to 90 ° C and the mold temperature to 60 ° C.

Ten molded article samples under the same conditions were prepared, and the condition was adjusted in a constant temperature and humidity chamber controlled at a temperature of 23 ° C. and a humidity of 50% RH for 24 hours after molding. Then 80 ° C
The heat treatment was carried out in a hot-air drier whose temperature was adjusted to. After the elapse of any time, remove it from the hot air dryer,
The occurrence of cracks or cracks in the coating material was visually observed. During the heat treatment, after an elapse of an arbitrary time, the number of samples in which cracks or cracks occurred was counted. Table 2 shows the results.

[0063]

Comparative Example 2 In the same manner as in Examples 5 to 8, a mold capable of molding a disk model insert molded article having the shape shown in FIG. 2 was prepared. By using “Zylon 340V”, carbon dioxide is not supplied from the gas supply unit provided in the center of the heating cylinder of the molding machine, and the shape shown in FIG. A disk-shaped model / insert molded product was obtained. At this time, the resin temperature was adjusted to 290 ° C, and the mold temperature was adjusted to 60 ° C.

Ten molded article samples were prepared under the same conditions, and the condition was adjusted for 24 hours after molding in a constant temperature and humidity chamber controlled at a temperature of 23 ° C. and a humidity of 50% RH. Then 80 ° C
The heat treatment was carried out in a hot-air drier whose temperature was adjusted to. After the elapse of any time, remove it from the hot air dryer,
The occurrence of cracks or cracks in the coating material was visually observed. During the heat treatment, after an elapse of an arbitrary time, the number of samples in which cracks or cracks occurred was counted. Table 2 shows the results.

[0065]

[Table 2]

[0066]

According to the present invention, the average molecular weight of the thermoplastic resin composition can be reduced, and the resin composition can be restricted without impairing the degree of freedom in designing the insert molded product itself composed of the core material and the coating material. The dimensional accuracy, productivity and product design flexibility of insert molded products are improved without the need for complicated mold structures, without increasing the resin temperature and injection speed more than necessary during injection molding. It is possible to make.

[Brief description of the drawings]

[Fig. 1] Roller type model / insert molded product

[Fig.2] Disc type model / insert molded product

[Explanation of symbols]

 1 core material 2 coating material

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B29L 9:00 B29L 9:00

Claims (12)

[Claims] 1. An injection-molded product formed by injection molding comprising at least a core material and a coating material, and is inserted into a mold cavity in which the preformed core material is installed.
An insert-molded article obtained by filling a mixture of a thermoplastic resin composition constituting the coating material and carbon dioxide pressurized to an atmospheric pressure or higher. 2. The insert molded article according to claim 1, wherein the thermoplastic resin composition is a crystalline resin composition. 3. The insert molded article according to claim 1, wherein the thermoplastic resin composition is an amorphous resin composition. 4. A thermoplastic resin composition comprising at least an amorphous resin and / or a crystalline resin and an inorganic and / or organic filler. Item 2. An insert molded product according to Item 1. 5. The insert molded product according to claim 1, wherein the core material constituting the insert molded product is formed of at least one metal member. 6. The insert-molded product according to claim 1, wherein a core material constituting the insert-molded product is made of at least one metal member and a thermoplastic resin. 7. The insert molded product according to claim 1, wherein the core material constituting the insert molded product is made of at least one metal member and a thermosetting resin. 8. The insert-molded product according to claim 1, wherein the core material constituting the insert-molded product is made of at least a thermoplastic resin and / or a thermosetting resin. . 9. The insert molded product according to claim 5, wherein the core material constituting the insert molded product includes a magnetic material and / or a conductor. 10. The insert molded product according to claim 5, wherein the insert molded product or a core material constituting the insert molded product is a storage medium. 11. An injection molding method comprising: mixing a thermoplastic resin composition in a molten state with carbon dioxide pressurized to an atmospheric pressure or higher in a heating cylinder of a molding machine; The injection molding method for an insert molded product according to claim 1, wherein an insert molded product is obtained by filling a mold cavity in which a mold is installed. 12. A mold obtained by filling a mixture of a thermoplastic resin composition and carbon dioxide into a mold cavity in which a preformed core material is installed and adjusted or maintained at a pressure of not less than atmospheric pressure and not more than 15 MPa. The injection molding method for an insert molded product according to claim 11, wherein: