JP2003053765A - Molded product for sealing member and injection molding method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded product for a sealing member with such advantages that the degree of designing freedom of a molded product itself constituting a sealing member made of a thermoplastic resin composition is not impaired and the reduction of an average molecular weight of the thermoplastic resin composition, the limiting of a resin composition and the complication of a mold configuration need not be required, and further, the resin temperature during injection molding and the injection speed need no be increased beyond the level of requirements and the welding strength can be enhanced by upgrading the dimensional precision, productivity and the degree of freedom of a finished product design, and an injection molding method. SOLUTION: This molded product for a sealing member is intended for constituting a sealing member of such a construction that it is shut off from an open. At least one of the molded product can be obtained by filling a mold cavity with a mixture of the thermoplastic resin composition, and a carbon dioxide pressurized at a level above an atmospheric pressure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a molded member for a seal member and an injection molding method thereof. More specifically, it relates to a molded member for a seal member obtained by filling a mold cavity with a mixture of a thermoplastic resin composition and carbon dioxide pressurized to atmospheric pressure or above, and an injection molding method thereof.

[0002]

2. Description of the Related Art A seal member generally has a desired shape by combining a plurality of molded products. Further, the molded body forming the seal member is manufactured by a manufacturing method suitable for the shape and material selected for its purpose and required characteristics. For example, a molded member for a seal member made of a thermoplastic resin composition is generally manufactured by an injection molding method.

However, in many cases, the injection molded article made of the thermoplastic resin composition has internal strain (hereinafter referred to as "residual strain") remaining during the injection molding process. High pressure is required to fill the molten thermoplastic resin composition into the mold cavity without leaving unfilled portions. Therefore, the thermoplastic resin composition filled in the mold cavity is cooled and solidified under a high pressure environment. As a result, in many cases, the resulting molded body has a residual strain due to the pressure during injection molding.

This residual strain is gradually relaxed after molding.
This is the volume shrinkage of the thermoplastic resin composition after injection molding,
This is often caused by deformation, and when the degree is large, it causes cracking of the molded body itself and deformation of the entire molded body. The plurality of molded bodies forming the seal member are assembled by a joining method mainly composed of welding to obtain a desired shape. In order to secure the strength after assembly, it is necessary that the welding strength is high, the joint surface of the molded body is smooth without sink marks, and the molded body itself is free from deformation such as warping. is important.

Therefore, it can be said that the molded product for a seal member is preferably manufactured by a molding method and molding conditions which have good mold transfer properties and hardly cause residual strain. 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 is cooled and solidified under a uniform and not too high pressure environment. However, when the thickness of the molded body is thin, when filling the thermoplastic resin composition so that the unfilled portion does not remain, a resin pressure that is a certain value or more is necessary, and volume shrinkage during cooling and solidification A high holding pressure is required for a thermoplastic resin composition having a large amount.

As a method of suppressing the resin pressure and the holding pressure to be low,
It is also possible to optimize the thermoplastic resin composition used. For example, it is to ensure high fluidity by reducing the molecular weight of the thermoplastic resin composition. However, generally, a thermoplastic resin composition having a small molecular weight is inevitably accompanied by a decrease in toughness, and when used for a thermoplastic resin composition of a molded article for a seal member, the shrinkage force of the thermoplastic resin composition itself is There is concern about the occurrence of cracks due to. In addition, the impact resistance is reduced, and in general, the life against fatigue due to repeated load tends to be shortened, and it is difficult to secure the product strength required for the molded member for the seal member. It can be said that it is difficult to secure reliability.

Further, a method of suppressing the resin pressure and the holding pressure by increasing the conditions of the injection molding, specifically, the temperature of the thermoplastic resin composition and the mold temperature can be considered. However, in the method of increasing the temperature of the thermoplastic resin composition, since it causes the thermal decomposition of the thermoplastic resin composition,
Deterioration, 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 streak) on the surface of the molded product. However, there is a limit to the range in which the temperature can be raised. In addition, when the temperature of the thermoplastic resin composition is high, the amount of volume contraction that occurs during cooling increases, and thus there is a concern that defects such as sink marks may occur in the obtained molded body. Therefore, it can be said that the resin temperature during injection molding is preferably as low as possible.

In the method of increasing the mold temperature, it takes a long time to cool the thermoplastic resin composition filled in the mold cavity, which may cause a problem in productivity. Also, if the gate position and score are inappropriate,
Since the resin pressure distribution near the gate and the flow end portion is likely to be biased, this improvement often restricts the product design, mold design, and molding conditions.

On the other hand, when the pressure for filling the thermoplastic resin composition to be the thermoplastic resin composition in the mold cavity is high, the pressure causes the core material set in the mold cavity to be deformed. There is a risk that Therefore, the material used as the core material needs to have strength, hardness, and a shape that do not deform when the thermoplastic resin composition is filled in the mold cavity. On the other hand, J. Appl. Pol
ym. Sci. , Vol. 30, 2633 (1985)
As shown in many documents, it is known that when carbon dioxide is absorbed into a resin, it acts as a plasticizer for the resin and lowers the glass transition temperature, but it is widely applied to resin molding processing. Has not reached.

Further, WO98 / 52734 discloses that
In injection molding of a thermoplastic resin composition, a molten resin in which carbon dioxide is dissolved in an amount of 0.2% by weight or more to reduce its viscosity is preliminarily mixed with a gas such as carbon dioxide at a pressure at which foaming does not occur at the flow front of the molten resin. Shows how to fill the mold cavity that is kept under pressure, reproducibility of mold surface, improvement of glossiness, inconspicuous weld line, reproducibility of sharp edge of mold surface, fine mold surface It is described that it is effective for reproducibility of unevenness. However, in the injection molding method, to disclose a method of efficiently dissolving carbon dioxide in the thermoplastic resin composition, to disclose the dissolution conditions, and to disclose a specific application in which the effect is remarkably exhibited. I haven't arrived.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a molded product capable of improving the welding strength of a molded product constituting a seal member and an injection molding method thereof. Specifically, lowering the average molecular weight of the thermoplastic resin composition and restricting the resin composition without impairing the degree of freedom in designing the molded body itself that constitutes the seal member manufactured from the thermoplastic resin composition That is, the dimensional accuracy, productivity, and product design flexibility of the seal member molded body do not need to increase the resin temperature and injection speed during injection molding more than necessary without complicating the mold structure. It is an object of the present invention to provide a molded product capable of improving the welding strength and an injection molding method thereof by improving the welding strength.

[0012]

Means for Solving the Problems The present inventor has made it possible to reduce the average molecular weight of a thermoplastic resin composition without impairing the degree of freedom in the design of the molded body itself constituting the sealing member produced from the thermoplastic resin composition. Dimensional accuracy of the molded body for the seal member without increasing the resin temperature and the injection speed during injection molding, without the need to restrict the resin composition or complicate the mold structure. The present invention has been studied in order to provide a molded article and its injection molding method capable of improving the welding strength by improving the productivity and the degree of freedom in product design.

As a result, a molded body which constitutes a seal member having a structure that is shielded from the outside air, wherein at least one of the molded bodies is a mixture of a thermoplastic resin composition and carbon dioxide pressurized above atmospheric pressure. The present invention has found that a molded product for a seal member, which is obtained by filling a mold cavity with a resin, can improve the welding strength of the molded product constituting the seal member. Has been completed.

That is, the present invention is as follows. A molded body that constitutes a seal member having a structure that is shielded from the outside air, wherein at least one of the molded bodies is filled with a mixture of a thermoplastic resin composition and carbon dioxide pressurized to atmospheric pressure or more into a mold cavity. 1. A molded product for a seal member, which is obtained by The seal member manufactured by joining a plurality of molded members for a seal member is welded in the assembly process, so that the structure in which the seal member is shielded from the outside air is maintained. A molded body for a seal member according to

3. By joining the joint of the molded body for a seal member by vibration welding in the assembly process of the seal member,
3. The molded body for a seal member according to 1 or 2 above, characterized in that the structure that is shielded from the outside air is maintained. 4. The seal member molded article according to any one of 1 to 3 above, wherein the seal member is an internal part of an automobile. Any of 1 to 4 above, wherein the molded product for a seal member is obtained by filling a mold cavity with a mixture of a crystalline resin composition and carbon dioxide pressurized at atmospheric pressure or higher. A molded body for a seal member according to

6. 6. The molded product for a seal member according to any one of 1 to 5 above, wherein the thermoplastic resin composition is a polyamide resin composition. 7. The molded product for a seal member according to any one of 1 to 5 above, wherein the thermoplastic resin composition is a polyester resin composition. Any of the above 5 to 7, wherein the thermoplastic resin composition is a thermoplastic resin composition composed of at least an amorphous resin and / or a crystalline resin and an inorganic and / or organic filler. A molded body for a seal member according to

9. By the injection molding method, in a heating cylinder of a molding machine, a thermoplastic resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or more are mixed, and then filled in a mold cavity. 10. An injection molding method for a molded member for a seal member according to 1 above, which is characterized in that a molded member for a seal member is obtained. The injection molding method is obtained by filling a mixture of a thermoplastic resin composition and carbon dioxide into a mold cavity adjusted or held at a pressure of not less than atmospheric pressure and not more than 15 MPa with a pressurized gas body. 10. An injection molding method for a molded body for a seal member according to 9 above, The injection molding method has a step of filling a mold cavity with a mixture of a thermoplastic resin composition and carbon dioxide pressurized to atmospheric pressure or higher, and then maintaining the mixture under pressure for a certain period of time. 13. A method for injection molding a molded body for a seal member according to the above or 10, wherein the molded body for a seal member is obtained.

The present invention will be specifically described below.
The seal member according to the present invention refers to a seal member having a structure that is shielded from the outside air. Specifically, the structure is such that the fluid inside the seal member does not physically leak to the outside of the seal member, or the leak amount is such a level that it penetrates the seal member, and the leak amount is a structure with no practical problem. It means a member. Here, the fluid is indistinguishable between liquid and gas, and may be, for example, a mixture of two or more kinds of liquid and / or gas. The fluid itself may be flowing or may be stationary.

The shape and use of the seal member according to the present invention are not limited, but it can be preferably used as a seal member inside an automobile in which the weight of the constituent parts has been reduced in recent years. Specifically, cylinder head covers, intake manifolds, etc. can be considered. In addition, external parts such as fans and pumps that convey fluid, cases,
In addition to piping parts such as pipes, a container having a closed structure such as a radiator and a container having a semi-closed structure in which the closed structure is maintained by connecting with other related members are considered.

Particularly for piping parts, pipes having two or more curved portions, which are difficult to manufacture by extrusion molding or ordinary injection molding, and pipes having three-dimensional bending directions, or plural pipes. It is preferably used for pipes and the like in which the channels of (1) are integrated. Further, in the seal member according to the present invention, the case portion and the pipe portion are integrated, so that the number of constituent parts is reduced, the assembly process is simplified by reducing the connecting portion, the assembly error is reduced, and the connecting portion is reduced. It is considered effective in preventing leakage.

The seal member according to the present invention is composed of a plurality of molded bodies, and by assembling these, a seal member having a desired shape is obtained. Further, the shapes and materials of these molded bodies and the assembling method are not limited. The seal member according to the present invention is characterized in that it is constituted by assembling a plurality of molded bodies manufactured in advance. Although the assembling method is not limited, it is essential that the sealing structure of the sealing member is satisfactory.

However, considering that it is easy to secure the closed structure, the assembling method is preferably such that the joint surfaces are joined by a welding method. Here, the welding method refers to a method of joining by melting the joining surface of the molded body, and the method is not limited. For example, a method of injecting a molten resin or an adhesive into the joint surface of the molded body to melt a part of the joint surface and then solidifying the joint surface, or a method of joining by vibration welding can be considered.

The above-mentioned vibration welding is also called vibration welding,
This is a welding method that utilizes frictional heat generation due to vibration. Specifically, the frictional heat generated by applying reciprocal vibration of mm order while pressing the welding surface between the members,
This is a method of joining thermoplastic resin materials. That is, after once melting the welding surface of the molded body forming the seal member,
It is a method to secure the welding strength by solidifying,
Variations in welding strength are less likely to occur. Therefore, it can be said that this is a preferable welding method as the method for forming the seal member in the present invention.

The seal member according to the present invention is composed of a plurality of molded products, and at least one of the molded products is characterized by being manufactured from the thermoplastic resin composition. This is because the thermoplastic resin composition has characteristics that it has a smaller specific gravity and can be made lighter than metal, is excellent in productivity because the main processing method is injection molding, and is easy to recycle. This is because it has many excellent points as a molded body that constitutes the seal member.

In the present invention, the thermoplastic resin composition means
It refers to a composition containing a thermoplastic resin as a main component, which is characterized by softening when heated and exhibiting plasticity, and solidifying when cooled. In addition, the thermoplastic resin composition can be used without distinction between a crystalline resin and an amorphous resin.
The above-mentioned, crystalline resin, the molecular chains are regularly arranged to form a three-dimensional structure, is a composition mainly composed of a thermoplastic resin composition having a unique melting point, below the melting point is a regular crystal A composition containing a thermoplastic resin composition as a main component, which has a structure but loses its crystallinity at a melting point or higher 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, "PBT" resin, high-density polyethylene (hereinafter "HDPE") resin, low-density polyethylene (hereinafter "LDPE") resin, linear low-density polyethylene (hereinafter "LLDPE") resin ,
Polyether ether ketone (hereinafter abbreviated as "PEEK") resin, polypropylene (hereinafter abbreviated as "PP") resin, and the like are considered.

On the other hand, the amorphous resin refers to a resin composition containing a thermoplastic resin composition component which cannot be in a crystalline state in the thermoplastic resin composition or has a very low crystallinity even when crystallized. It is a thing. More specifically, amorphous,
It is also called amorphous polymer, and it is also called amorphous, which is a solid state in which atoms or molecules do not form a three-dimensionally ordered spatial lattice but are totally disordered. The amorphous state has a glass state and a rubber state,
Below the glass transition point (Tg), it shows a hard glassy state,
It has a characteristic of showing a soft rubbery state at Tg or higher.

Specifically, polystyrene (hereinafter referred to as "PS")
Abbreviated as “) resin, polyphenylene ether (hereinafter“ PP ”
Abbreviated as "E")-based resin, PPE-based resin blended with other resins, or modified PPE modified by graft polymerization
-Based resin, acrylonitrile-butadiene-styrene copolymer (hereinafter abbreviated as "ABS-based resin"), acrylonitrile-styrene copolymer (hereinafter abbreviated as "AS-based resin"),
Polycarbonate (hereinafter abbreviated as “PC”) resin, methacrylic (hereinafter abbreviated as “PMMA”) resin, and the like are considered.

A crystalline resin composition is preferable as the molded body constituting the seal member in the present invention in view of its high heat resistant temperature. Further, considering that it is easy to obtain a molded product having excellent mechanical strength and high heat resistance, and that it is easy to add an inorganic and / or organic filler represented by glass fiber, a PA-based PA containing It can be said that a polyester resin composition containing a resin and a polyester component is preferable. Here, any PA can be used as long as it has an acid amide bond shown in Chemical Formula 1 below.

[0030]

[Chemical 1]

Generally, the PA resin is obtained by ring-opening polymerization of lactams, polycondensation of diamine and dicarboxylic acid, polycondensation of aminocarboxylic acid, etc., but is not limited thereto. P that can be preferably used in the present invention
As the A-based resin, PA6, PA6-6, PA4-6,
PA11, PA12, PA6-10, PA6-12, P
A6 / 6-6, PA6 / 6-12, PA6 / MXD (m
-Xylylenediamine), PA6-T (terephthalic acid), PA6-I (isophthalic acid), PA6 / 6-T,
PA6 / 6-I, PA6-6 / 6-T, PA6-6 / 6
-I, PA6 / 6-T / 6-I, PA6-6 / 6-T /
6-I, PA6 / 12 / 6-T, PA6-6 / 12/6
-T, PA6 / 12 / 6-I, PA6-6 / 12 / 6-
I etc. are mentioned.

PAs obtained by copolymerizing a plurality of PAs with an extruder or the like can also be used. Preferred PA resins are PA6, PA6-6, PA12 and mixtures thereof. The preferable range of the number average molecular weight of the PA preferably used in the present invention is 5,000 to 100,000, and more preferably 10,000 to 30,000. Any polyester-based resin may be used as long as it has an ester component represented by the following chemical formula 2.

[0033]

[Chemical 2]

Specifically, it refers to a crystalline resin having an ester bond in the main chain of the molecule as shown in Chemical Formula 3 below.

[0035]

[Chemical 3]

Here, n is an arbitrary natural number. More specific polyester resins include PBT, PET,
Examples thereof include polyester resin and polyarylate. In particular, the polyester-based resin containing PBT or PET as a main component has a high melting point, and thus a molded product for a seal member having a high heat resistant temperature is easily obtained, which is preferable. The thermoplastic resin composition in the present invention is a thermoplastic resin component having the same molecular structure, and may be composed of thermoplastic resin components having different molecular weights and different molecular weight distributions, or two or more thermoplastic resins. It may be a polymer alloy that is a composite resin material in which the components are physically and chemically mixed.

In the above polymer alloy, it can be obtained by physically and chemically mixing a thermoplastic resin component as a main component with another type of resin component, but other than the thermoplastic resin component as a main component. The resin component is not particularly limited as long as it is compatible with the thermoplastic resin composition as the main component. For example, POM, 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, polyether sulfone, liquid crystal polymer, polytetrafluoroethylene, thermoplastic elastomer, polytetrafluoroethylene, and polyvinyl alcohol.

As a concrete example of the polymer alloy, a polymer alloy of PA resin and PPE resin (hereinafter abbreviated as "PA / PPE polymer alloy"),
Polymer alloy of PP resin and PPE resin (hereinafter abbreviated as "PP / PPE polymer alloy"), PBT
Polymer alloys (hereinafter abbreviated as "PBT / ABS polymer alloys") made of B type resins and ABS type resins, PB
Examples thereof include polymer alloys of T-based resins and AS-based resins (hereinafter abbreviated as “PBT / AS-based polymer alloys”).

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 and strength, ensuring dimensional accuracy, and the like. Moreover, the deflection temperature under load (load deformation temperature) is increased by adding an inorganic or organic filler. Therefore, a molded product for a seal member having a higher heat resistant temperature can be obtained, and thus it can be said that the thermoplastic resin composition is preferable.

This tendency is remarkable in the crystalline resin composition. For example, when the deflection temperature under load at 1.82 MPa is compared in the measuring method according to the ASTM (D648) standard, in the crystalline resin composition to which glass fiber is added, as compared with that to which glass fiber is not added, It can be seen that a temperature range of 50 ° C. or higher can be used. Specific gravity-imparting agents include barium sulfate,
Inorganic salts, oxides, metal powders, etc. such as red iron oxide, tungsten powder, etc. can be considered.

As the strength-imparting agent, glass fiber,
Carbon fiber, metal fiber, aramid fiber, potassium titanate, asbestos, silicon carbide, ceramics, silicon nitride, barium sulfate, calcium sulfate, kaolin, clay, pyrophyllite, bentonite, sericite, zeolite, mica, mica, nephelinesh Knight, talc, atargulgite, wollastonite, slag fiber, ferrite, silicon, calcium, calcium carbonate, magnesium carbonate, dolomite, zinc oxide, gypsum,
Glass beads, glass powder, glass balloons, quartz, quartz glass, alumina, etc. are considered.

The shape of these inorganic or organic fillers is not limited, and fibrous, plate-like, spherical or the like can be arbitrarily selected. Further, two or more kinds of the above-mentioned inorganic or organic fillers can be used in combination. If necessary, a silane-based or titanium-based coupling agent may be pretreated before use. The amount of the inorganic or organic filler added to the thermoplastic resin composition of the present invention is not limited, but the specific gravity of the thermoplastic resin composition is adjusted, and the heat resistant temperature is improved. In order to sufficiently obtain the effect of adding the additive such as improving rigidity, ensuring dimensional accuracy, and suppressing deformation such as warpage, the amount added is preferably 5% by weight or more, and 10% by weight or more Is more preferable.

Here, the addition amount of the inorganic or organic filler means the addition amount of one kind of filler to be added, and the total addition amount of two kinds or more of fillers. Point to. Further, the addition amount of the inorganic or organic filler refers to a ratio when the total amount of the resin component, the inorganic or organic filler, and other additives is 100% by weight.
The thermoplastic resin composition in the present invention, the additives usually used, for example, antioxidants, flame retardants, mold release agents, lubricants, heat stabilizers, weather resistance stabilizers, rust inhibitors, fillers, One or more kinds of colorants, antibacterial agents, antifungal agents and the like can be added if necessary.

As other additives, carbon fiber,
The electrical resistance value of the thermoplastic resin composition can be reduced by selecting at least one of metal fiber and graphite. This is preferable because it is possible to prevent small powder such as dust from adhering to the molded member for the seal member made of the thermoplastic resin composition by static electricity. A molded member for a seal member using the thermoplastic resin composition of the present invention is characterized in that it is obtained by filling a mold cavity with a mixture of the thermoplastic resin composition and carbon dioxide pressurized at atmospheric pressure or higher. However, this is because the viscosity of the thermoplastic resin composition at the time of melting is reduced by mixing carbon dioxide into the thermoplastic resin composition. Therefore, when the thermoplastic resin composition is filled in the mold cavity, it is easy to fill the mold cavity without leaving any unfilled portion.

It is supposed that this is because the carbon dioxide is efficiently dispersed as a plasticizer for the thermoplastic resin composition by mixing the molten thermoplastic resin composition with the carbon dioxide. As a result, since it is not necessary to raise the resin temperature, there is no fear of thermal decomposition or deterioration of the thermoplastic resin composition, and it is not necessary to raise the mold temperature more than necessary, which is preferable in terms of production efficiency. Can be said.

As described above, the molded member for a seal member made of the thermoplastic resin composition of the present invention contains a mixture of the molten thermoplastic resin composition and carbon dioxide pressurized at atmospheric pressure or above. By filling the mold cavity, the flow distance can be increased without raising the resin temperature more than necessary, so that the mold cavity can be filled with the thermoplastic resin composition at a low filling pressure. Therefore, residual strain is unlikely to remain in the obtained molded product, so warpage that occurs after molding is reduced, and since the unfilled part is difficult to remain, the incidence of defects during continuous molding is low and productivity is improved. I think so.

In the present invention, the molded member for a seal member, in which the thermoplastic resin composition is a thermoplastic resin composition, is a mixture of the thermoplastic resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or higher. Is filled in the mold cavity, but when carbon dioxide is less than atmospheric pressure, it is difficult to mix with the thermoplastic resin composition in a molten state, and the thermoplastic resin composition and carbon dioxide are mixed. This is not preferable because it is difficult to obtain the effect.

The pressure of carbon dioxide efficiently mixed with the thermoplastic resin composition in the molten state needs to be atmospheric pressure or higher, preferably 1 MPa or higher. The pressure is preferably 2 MPa or more, and most preferably 4 MPa or more. The molded member for a seal member in the present invention is a thermoplastic resin composition in a molten state,
It is characterized in that it is obtained by filling a mold cavity with a mixture with carbon dioxide pressurized above atmospheric pressure, but the mixing method is not limited.

However, in order to efficiently mix carbon dioxide into the molten state of the thermoplastic resin composition, it is preferable that the thermoplastic resin composition is in a molten state, and the molten state in the heating cylinder of the injection molding machine is the same. Method for mixing with thermoplastic resin composition, method for mixing with thermoplastic resin composition in molten state from nozzle of molding machine, installation of equipment for supplying carbon dioxide between die and nozzle of molding machine A method of mixing with the thermoplastic resin composition in a molten state, a method of injection molding using a granulated resin pellet in a state where carbon dioxide is mixed with the thermoplastic resin composition in a molten state in advance, and the like are considered. .

Considering that carbon dioxide can be uniformly mixed in the thermoplastic resin composition in a short time, the amount of the mixture can be easily adjusted, and the preparation before molding is not complicated, the heating cylinder of the injection molding machine is considered. Inside, the nozzle portion of the molding machine, at any position between the nozzle portion of the molding machine and the mold, by providing equipment for carbon dioxide supply, carbon dioxide to the molten thermoplastic resin composition A 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 and carbon dioxide, but the dissolved amount or absorbed amount is not limited.

The molded body for a seal member made of the thermoplastic resin composition according to the present invention preferably has a foamed portion inside, particularly at a joint portion or a portion thicker than the peripheral thickness. In the foamed portion, carbon dioxide dissolved or absorbed in the thermoplastic resin composition is appropriately foamed when the amorphous resin composition is cooled and solidified in the mold cavity to cause volume contraction. It is supposed to be formed by things. Since the molded product according to the present invention has an appropriate foamed portion inside, it is unlikely to cause sink marks on the surface of the molded product. For this reason, when it is used in a molded body for a seal member, the smoothness of the joint becomes high and the welding strength is improved. Also,
By selectively forming a portion where the foamed portion has a relatively thick wall, it is possible to realize a molded body having a partially thick wall portion and a molded body having a thicker wall portion.

As a result, since the welding strength is increased, it is expected that the reliability as a seal member is improved and the degree of freedom in product design is increased. The foamed portion is different from that obtained by adding a foaming agent to the thermoplastic resin composition. Further, 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 pressure, the thicker the non-foamed layer tends to be. However, when the holding pressure is too high or the holding time is too long, when the thermoplastic resin composition is cooled and solidified in the mold cavity, the dioxide dissolved in the thermoplastic resin composition is dissolved. Carbon is unlikely to form a foamed portion inside the molded body, and there is a risk of sink marks on the surface of the molded body.

The term "foamed portion" as used herein means that when an arbitrary cross section of the thermoplastic resin composition portion of the molded product for a sealing member made of the thermoplastic resin composition is magnified 10 to 20 times with an optical microscope or the like, The voids due to foaming or the part where the whitening phenomenon is confirmed is referred to, and the non-foaming layer refers to the voids due to the foaming or the part where the whitening phenomenon is not confirmed. In the present invention, the injection molding method of a thermoplastic resin composition is a molding and processing method of a thermoplastic resin composition which is usually performed, and in addition to the most general ordinary injection molding method, a hollow injection molding method. , Gas assist molding, blow molding, injection
A compression molding method and the like are included.

In the injection molding method for molding a seal member using the thermoplastic resin composition of the present invention, when the mold cavity is filled with the mixture of the thermoplastic resin composition and carbon dioxide, the amount of carbon dioxide dissolved or absorbed. When the amount is a certain value or more, a foamed pattern may occur on the surface of the molded member for a seal member. In order to suppress the occurrence of foaming patterns on the surface of the molded product for a seal member, the pressure inside the mold cavity is adjusted or maintained at a pressure higher than that at which foaming does not occur at the flow front of the crystalline resin composition. Is preferably provided.

The pressure of the pressurized gas may be the lowest pressure at which a foaming pattern does not occur on the surface of the molded member for a seal member made of the thermoplastic resin composition. The gas pressure is preferably low in order to minimize the amount of gas used during the molding cycle and to simplify the structure of the mold cavity seal structure and the structure of the gas supply device. When the gas pressure exceeds 15 MPa,
The gas pressure may cause the mold to open, and problems such as difficulty in sealing the mold cavity are likely to occur. Therefore, the pressure of the gas that pressurizes the mold cavity is preferably not less than atmospheric pressure and not more than 15 MPa, and more preferably not less than atmospheric pressure and not more than 10 MPa.

In addition, since the pressure inside the mold cavity is adjusted or maintained by the pressurized gas to a pressure above which foaming does not occur at the flow front of the thermoplastic resin composition, it is generated in the vicinity of the gate portion. This is preferable because it often has the effect of suppressing the appearance defect due to the disturbance of the flow of the thermoplastic resin composition 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 has an atmospheric pressure of 15 M or more.
It is preferably adjusted or maintained at Pa or less, but at least after the resin filling is started, until at least the cooling step is completed, preferably until the pressure holding step is completed, and more preferably before the pressure holding step is started. It is preferable to release the pressure in the mold cavity.

At this time, as the gas for adjusting or holding the inside of the mold cavity at a constant pressure, a single substance or a mixture of various gases inert to the thermoplastic resin composition can be used.
Carbon dioxide, a hydrocarbon and a gas in which a part of hydrogen thereof is replaced with fluorine, which have high solubility in the thermoplastic resin composition, are preferable. Also, considering that it is easy to obtain a high-purity gas at a relatively low cost, it is possible to use nitrogen gas. A usual injection molding method has a step of filling the mold cavity with the thermoplastic resin composition and then holding the thermoplastic resin composition in the cavity under pressure. This process is called "pressure-holding process" and the degree of pressure is called "holding pressure".
In the method of injection molding a thermoplastic resin composition according to the present invention, after the thermoplastic resin composition is filled in a mold cavity, the thermoplastic resin in the mold cavity is subjected to a pressure corresponding to 30% or more of the filling pressure. It is preferable to hold the composition under pressure.

This is because the non-foamed layer formed on the surface layer portion of the molded body maintains an appropriate thickness because the holding pressure is a pressure value of 30% or more of the filling pressure. The occupancy rate becomes small, and the fear that the mechanical strength is lowered is reduced. A molded member for a seal member obtained by filling a mixture of a molten thermoplastic resin composition and carbon dioxide pressurized at atmospheric pressure or higher into a mold cavity has an appropriate thickness in its surface layer portion. In order to have a proper foamed portion inside while forming the non-foamed layer, the preferable range of the holding pressure in the injection molding step is 30% or more of the filling pressure. It is preferably in the range of 40% or more, and most preferably in the range of 50% or more. Here, the filling pressure refers to a resin pressure generated when the molten thermoplastic resin composition is filled in the mold cavity.
Specifically, the screw position in the in-line screw type injection molding machine and the plunger position in the pre-plastic type injection molding machine indicate the maximum value of the resin pressure generated when moving from the measuring position to the VP switching position. is there.

Although the pressure holding time is not limited, if the pressure holding time is extremely short, the carbon dioxide mixed with the thermoplastic resin composition before being filled into the mold cavity expands. As a result, the molded product may be swollen, which is not preferable.

[0060]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. The thermoplastic resin composition used for injection molding is PB
T / AS polymer alloy ("Duranex (registered trademark) 733L" manufactured by Wintec Polymer Co., Ltd.
D ”), PA6-6 type resin (“ Leona (registered trademark) 14G33 ”manufactured by Asahi Kasei Co., Ltd.). Before molding, both were in pellet form, and "DURANEX 733LD"
Is a thermoplastic resin composition containing 30% by weight of glass fiber, and "Leona 14G33" is a thermoplastic resin composition containing 33% by weight of glass fiber. The injection molding machine is “SG” manufactured by Sumitomo Heavy Industries, Ltd.
125M-HP "was used. The temperature of the heating cylinder of the injection molding machine is set to 265 ° C for PBT / AS polymer alloy molding, 285 ° C for PA6-6 resin molding, and the mold temperature is set to 80 ° C for injection molding. Was carried out.

[0061]

Examples 1 to 4 A mold capable of molding a box-shaped model molded body having the shape shown in FIG. 1 was prepared. The box-shaped model compact has a height, width, and length of 20 mm, 80 mm, and 1, respectively.
It is 60 mm. Further, the gate was a pin gate having a diameter of 1.5 mm and was provided at two places on the top surface. The basic thickness of the box-shaped model molded body is 2 mm, and the thickness of the ribs provided inside is 0.8 mm. "Duranex 733LD"
Is used to supply carbon dioxide adjusted to an arbitrary pressure of 1.8 to 8.2 MPa from a gas supply unit provided in the center of the heating cylinder of the molding machine to the molten resin inside the heating cylinder. After mixing by doing so, it was filled in a mold cavity to obtain a box-shaped model molded body having the shape shown in FIG.

24 hours after molding, temperature 23 ° C., humidity 50%
After adjusting the condition in the constant temperature and humidity room adjusted to RH,
The heat treatment was carried out for 4 hours in a hot air dryer adjusted to ° C, and the condition was again adjusted in the high temperature and humidity chamber for 20 hours after the heat treatment. After performing the second condition adjustment in the constant temperature and constant humidity chamber, the flatness of the flatness measuring surface shown in FIG. 1 was measured.
The flatness is "3D measuring machine (AE1
22) ”and the company's“ Measurement program (Geopack 4
00) "according to the multipoint flatness measuring method. Table 1 shows the results of measuring the flatness of the molded body.

[0063]

Comparative Example 1 Similar to Examples 1 to 4, a mold capable of molding a box-shaped model molded body having the shape shown in FIG. 1 was prepared. The number of gate points was two, as in Examples 1 to 4.
Using "DURANEX 733LD", carbon dioxide was not supplied from the gas supply part provided in the center of the heating cylinder of the molding machine, and a box-shaped model molded body was obtained by the same process as in ordinary injection molding. After the condition adjustment and the heat treatment after molding were performed in the same manner as in Examples 1 to 4, the flatness of the box-shaped model molded body was measured. The measurement results are shown in Table 1.

[0064]

Comparative Example 2 Similar to Examples 1 to 4, a mold capable of molding a box-shaped model molded body having the shape shown in FIG. 1 was prepared. There were three gate points. "Juranex 733
Using "LD", carbon dioxide was not supplied from the gas supply unit provided in the central portion of the heating cylinder of the molding machine, and a box-shaped model molded body was obtained by the same process as ordinary injection molding. Example 1
After adjusting the condition after molding and heat treatment in the same manner as ~ 4,
The flatness of the molded product that also had a box shape was measured. Table 1 shows the measurement results
Shown in.

[0065]

[Table 1]

[0066]

[Examples 5 to 8] A mold capable of molding a plate-shaped vibration welding sample a having a thickness, a height, and a length of 5 mm, 60 mm, and 120 mm shown in FIG. 2, and FIG. Thickness, height and length are 10mm, 60mm, 1 respectively
A mold capable of molding a plate-shaped vibration welding sample b of 20 mm was prepared. Using "Leona 14G33",
Carbon dioxide adjusted to an arbitrary pressure of 2.2 to 12.2 MPa is supplied to the molten resin inside the heating cylinder from the gas supply unit provided in the center of the heating cylinder of the molding machine to mix the carbon dioxide. After that, the mold cavity was filled to obtain the samples a and b for vibration welding shown in FIGS. The injection-molded molded body sample was conditioned for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23 ° C. and a humidity of 50% RH.

The amount of sink mark on the welded surface of the vibration welding sample b was measured using "surface roughness profile measuring machine (Surfcom 570A)" manufactured by Tokyo Seimitsu Co., Ltd. Then BRA
NSON "vibration welding machine (VIBRATION WE
LDER M2800J) "was used to perform vibration welding of samples a and b for vibration welding. The vibration welding was vibration in the longitudinal direction, and at a frequency of 240 (Hz), the welding pressure was 3.2 (MPa) as the area conversion value of the welding surface. The melting margin is 2 (mm) and the amplitude is 1.7 (mm).
The holding time was 5 (seconds). The state of the sample after welding is shown in FIG.

After vibration welding, the condition was again adjusted in the constant temperature and humidity chamber for 24 hours, and then the central portion of the sample after welding was cut to have a thickness of 5 mm, and the welding strength having the shape shown in FIG. 5 was obtained. A measurement sample was obtained. After disconnecting,
Conditioning was carried out for 24 hours in a constant temperature and humidity room. The measurement of the welding strength was carried out by measuring the tensile strength using a "universal tester (MODEL 1185)" manufactured by INSTRON JAPAN. The conditions of the tensile test were a chuck distance of 40 (mm) and a tensile speed of 5 (mm / sec).
Further, the number of times of the tensile test was set to 7, and the average value of 5 measured values excluding the highest value and the lowest value was obtained. The measurement results are shown in Table 2.

[0069]

Comparative Example 3 Similar to Examples 5 to 8, a mold capable of molding the vibration welding sample a shown in FIG. 2 and a mold capable of molding the vibration welding sample b shown in FIG. 3 were prepared. By using "Leona 14G33", by a process similar to normal injection molding in which the gas supply unit provided in the central portion of the heating cylinder of the molding machine does not supply the molten resin inside the heating cylinder, Samples a and b for vibration welding were obtained. The injection-molded molded body sample was adjusted in the same manner as in Examples 5 to 8, the amount of sink was measured, and vibration welding was performed. After the vibration welding was performed, the condition was adjusted and the cutting was performed to obtain a welding strength measurement sample having the shape shown in FIG. After cutting, the condition was adjusted again. After the condition adjustment was completed, the welding strength was measured. The measurement results are shown in Table 2.

[0070]

[Table 2]

[0071]

INDUSTRIAL APPLICABILITY The present invention reduces the average molecular weight of the thermoplastic resin composition without impairing the degree of freedom in designing the molded body itself constituting the seal member produced from the thermoplastic resin composition, and Dimensional accuracy, productivity, and products of molded products for seal members without limiting the composition, complicating the mold structure, and increasing the resin temperature and injection speed during injection molding more than necessary. By improving the degree of freedom in design, it is possible to provide a molded product and its injection molding method capable of improving the welding strength.

[Brief description of drawings]

FIG. 1 shows a box-shaped model molded body.

FIG. 2 shows a sample a for vibration welding.

FIG. 3 shows a sample b for vibration welding.

FIG. 4 shows a state in which a vibration welding sample is welded.

FIG. 5 shows a sample for measuring welding strength.

[Explanation of symbols]

1 Box type molded body 2 Flatness measurement surface 3 Vibration welding sample a 4 Welding surface 5 Sample for vibration welding b 6 Welded part 7 Welding strength measurement sample

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 31:30 B29L 31:30 F term (reference) 4F206 AA24 AA29 AB11 AB16 AB19 AH13 AH26 AR025 JA04 JA07 JF01 JF02 JF06 JF12 JF21 JL02 JM01 JM04 JM05 JN01 JN11 JN21 JN27

Claims (11)

[Claims] 1. A molded body that constitutes a seal member having a structure that is shielded from the outside air, wherein at least one of the molded bodies is a mixture of a thermoplastic resin composition and carbon dioxide pressurized to atmospheric pressure or higher. A molded product for a seal member, which is obtained by filling a mold cavity. 2. A seal member manufactured by joining a plurality of molded seal member bodies is welded in an assembling step thereof to maintain a structure in which the seal member is shielded from the outside air. The molded body for a seal member according to claim 1, characterized in that 3. The structure according to claim 1 or 2, wherein the joint portion of the seal member molded body is vibration-welded in the step of assembling the seal member to maintain a structure that is shielded from the outside air. Molded body for seal member. 4. The molded product for a seal member according to claim 1, wherein the seal member is an internal part of an automobile. 5. The molded product for a seal member is obtained by filling a mold cavity with a mixture of a crystalline resin composition and carbon dioxide pressurized at atmospheric pressure or higher. Item 5. A molded member for a seal member according to any one of items 1 to 4. 6. The molded product for a seal member according to claim 1, wherein the thermoplastic resin composition is a polyamide resin composition. 7. The molded product for a seal member according to claim 1, wherein the thermoplastic resin composition is a polyester resin composition. 8. The thermoplastic resin composition is a thermoplastic resin composition composed of at least an amorphous resin and / or a crystalline resin and an inorganic and / or organic filler. Item 10. A molded member for a seal member according to any one of items 5 to 7. 9. The injection molding method comprises mixing a thermoplastic resin composition in a molten state with carbon dioxide pressurized at atmospheric pressure or more in a heating cylinder of a molding machine, and then in a mold cavity. The injection molding method for a molded product for a seal member according to claim 1, wherein the molded product for a seal member is obtained by filling the molded product for a seal member. 10. The injection molding method comprises filling a mixture of a thermoplastic resin composition and carbon dioxide into a mold cavity adjusted or held at a pressure of not less than atmospheric pressure and not more than 15 MPa by a pressurized gas body. The injection molding method for a molded body for a seal member according to claim 9, which is obtained by 11. The injection molding method comprises the steps of filling a mold cavity with a mixture of a thermoplastic resin composition and carbon dioxide pressurized at atmospheric pressure or higher, and then maintaining the mixture under pressure for a certain period of time. The method for injection molding a molded product for a seal member according to claim 9 or 10, wherein the molded product for a seal member is obtained by having.