JP2002178355A - Thin-walled molding and its injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dimensional precision and productivity of a thin-walled molding such as the housing of a secondary battery and a storage medium due to easy packing in a mold cavity, without spoiling the degree of freedom in the design of the molding itself the minimum wall thickness of which is 0.5 mm or below, without making the restrictions of the average molecular weight and composition of a thermoplastic resin and the structure of a mold complex, and without increasing a resin temperature and an injection speed unnecessarily during injection molding. SOLUTION: The molding having a part the minimum thickness of 0.5 mm or below is formed from an amorphous resin composition and obtained by packing the mixture of the molten composition and carbon dioxide pressurized at 1 MPa or above in the mold cavity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a semiconductor device having a minimum thickness of 0.5
The present invention relates to a thin-walled molded article made of an amorphous resin composition having a portion of not more than mm and an injection molding method thereof. More specifically, the present invention relates to a case of a secondary battery, a case of a storage medium, and a method of injection molding the same using an amorphous resin composition having a portion having a minimum thickness of 0.5 mm or less.

[0002]

2. Description of the Related Art Molded articles made of many thermoplastic resins, not limited to amorphous resin compositions, are usually produced by injection molding. However, injection-molded articles having a portion having a minimum thickness of 0.5 mm or less, particularly 0.2 mm or less, such as a case of a secondary battery and a case of a storage medium, are not melted by the amorphous resin composition used. Due to the high viscosity, the viscosity of the amorphous resin composition increases due to a decrease in temperature after filling into the mold cavity, the amorphous resin composition is added to the mold cavity so as not to leave unfilled portions. Is difficult to fill.

In order to fill the amorphous resin composition into the mold cavity without leaving an unfilled portion, the temperature of the amorphous resin composition during injection molding is increased, and the mold cavity is filled. This has been addressed by adjusting molding conditions, such as increasing the injection speed and increasing the mold temperature. However, increasing the temperature of the amorphous resin composition at the time of injection molding causes a promotion of thermal decomposition of the amorphous resin composition. As a result, the amorphous resin composition deteriorates, decomposed gas is generated, the decomposed gas adheres to the mold cavity to form a mold deposit, and a defective appearance called silver (silver streak) is generated on the surface of the molded product. There is a limit to the range where the temperature is high because it may cause a problem of the above. In addition, when the temperature of the amorphous resin composition is high, the volume shrinkage generated during cooling increases, and there is a concern that defects such as sinks may occur in the obtained molded product.

A method for increasing the injection speed when filling the mold cavity requires special equipment of an injection molding machine.
High accuracy such as injection speed and filling amount is required. Further, the amorphous resin composition injected at a high speed generates shear heat, which also causes thermal decomposition. In addition, in the method of increasing the injection speed, the filling pressure into the mold cavity generally increases in proportion to the injection speed. Also,
When the amorphous resin composition is filled in the mold cavity and then has a step of further holding the filled amorphous resin composition under pressure (hereinafter referred to as “holding pressure”), a high holding pressure is applied to a thin molded article. Often needed.

[0005] A molded product injection-molded under filling conditions such as high-speed injection and high holding pressure into a mold cavity is cooled and solidified under high pressure. The amorphous resin composition cooled and solidified under high pressure results in a large amount of distortion remaining inside the molded article. The molding distortion remaining in this molded product is called "residual distortion".
It is also called. This residual strain is gradually relaxed after molding, but this is often due to deformation and shrinkage of the molded product. Therefore, it can be said that it is preferable to carry out injection molding by a molding method and molding conditions in which residual distortion hardly remains.

In the method of increasing the mold temperature, it is difficult to stabilize the temperature of the mold cavity surface uniformly and also, the time required for cooling the amorphous resin composition filled in the mold cavity is reduced. Because of the length, there is a concern that a problem may occur in productivity. On the other hand, in terms of mold design, filling the mold cavity with resin becomes easier by increasing the number of gate points. However, in the case of injection molded products such as secondary battery housings and storage media housings, the impact strength may be reduced due to the occurrence of welds, and the appearance may be impaired due to the large number of gates. Yes, it is hard to say that it is preferable.

[0007] Regarding the amorphous resin composition used,
It is possible to optimize. For example, by reducing the molecular weight of the amorphous resin composition, high fluidity is ensured, and uniform pressure is easily transmitted to the terminal end of the fluid. However, in general, amorphous resin compositions with low molecular weight tend to reduce toughness and impact resistance, and have a tendency to shorten the life of fatigue due to repeated loading, etc., so that the product strength required for the housing is secured. Difficult to do. Therefore, it can be said that it is difficult to achieve both fluidity and product strength by adjusting the molecular weight of the amorphous resin composition.

Therefore, in the method for producing a thin-walled molded product having a portion having a minimum thickness of 0.5 mm or less, the temperature, injection speed, and mold temperature of the amorphous resin composition are more than necessary at the time of injection molding. Without using a mold having the minimum necessary number of gates without using a mold, it has been awaited to establish an injection molding method in which an unfilled portion hardly occurs and a defective rate is small. On the other hand, J.I. Appl. Polym. Sci. , Vo
l. 30, 2633 (1985), 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. It has not been widely applied to processing.

[0009] 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 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.

[0010]

SUMMARY OF THE INVENTION The present invention provides a thin molded article having a minimum thickness of 0.5 mm or less without impairing the degree of freedom of design of the molded article itself. It is an object to improve the dimensional accuracy and productivity of a thin-walled molded product without complicating a mold structure and increasing a resin temperature and an injection speed more than necessary during injection molding. Specifically, the present invention is to improve the dimensional accuracy and productivity of a thin-walled molded product represented by a housing of a secondary battery, a storage medium, and the like because the mold cavity can be easily filled. .

[0011]

Means for Solving the Problems The inventor of the present invention did not impair the degree of freedom in designing a thin-walled molded product having a minimum thickness of 0.5 mm or less, and limited the average molecular weight and the resin composition of the thermoplastic resin, A study was made to improve the dimensional accuracy and productivity of thin-walled molded products without complicating the mold structure and without unnecessarily increasing the resin temperature and injection speed during injection molding. As a result, a thin molded product characterized by being obtained by filling a mold cavity with a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized to 1 MPa or more, They have found that it is possible to improve the productivity of molded articles, and have completed the present invention.

That is, the present invention provides: The thin-walled molded article is a thin-walled molded article made of an amorphous resin composition having a portion having a minimum thickness of 0.5 mm or less, and is pressurized to 1 MPa or more with the amorphous resin composition in a molten state. 1. A thin-walled molded product obtained by filling a mixture of carbon dioxide into a mold cavity. 2. The thin-walled molded product according to the above 1, wherein the molded product has a portion having a minimum thickness of 0.2 mm or less. 3. The thin molded article according to the above 1 or 2, wherein the thin molded article is a housing of a secondary battery. 3. The thin-walled molded article according to the above 1 or 2, wherein the thin-walled molded article is a housing of a storage medium.

5. 5. The thin molded article made of the thermoplastic resin according to any one of the above items 1 to 4, wherein the amorphous resin composition is a modified polyphenylene ether-based resin containing at least a polyphenylene ether component. The thin-walled molded article according to any one of the above 1 to 5, wherein the thin-walled molded article has a foamed portion inside, and has a non-foamed layer that is not substantially foamed in a surface layer portion.

7. 7. The thin molded article made of a thermoplastic resin according to any one of the above items 1 to 6, wherein the apparent specific gravity of the thin molded article is 95 to 99.5% of the specific gravity of the thermoplastic resin. The injection molding method, in the heating cylinder of the molding machine,
The thin-walled molded product is obtained by kneading the amorphous resin composition in a molten state and carbon dioxide pressurized to 1 MPa or more, and filling the mixture into a mold cavity. Injection molding method for thin molded products,

9. The thin-walled molded product is obtained by filling a mixture of the amorphous resin composition and carbon dioxide into a mold cavity adjusted or maintained at a pressure of not less than atmospheric pressure and not more than 15 MPa to obtain a thin-walled molded product. Injection molding method for thin molded products. 10. By filling the mixture of the amorphous resin composition and carbon dioxide into the mold cavity, and then holding the resin under pressure at a pressure of 30% or more of the filling pressure, it is possible to obtain a thin molded product. The present invention relates to a method for injection-molding a thin-walled molded product according to the above item 8 or 9, which is characterized in that

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The thin molded article according to the present invention is an injection molded article having at least a portion having a minimum thickness of 0.5 mm or less, particularly an injection molded article having a portion having a minimum thickness of 0.2 mm or less. is there. Specific examples of the thin molded product include a housing of a secondary battery and a housing of a storage medium.

The above secondary battery is also called a storage battery,
A battery that can be used repeatedly 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”. Examples thereof include rechargeable batteries, batteries, and battery packs used for mobile phones, notebook computers, electronic organizers, video cameras, digital cameras, still cameras, various audio devices, and the like.

Further, the storage medium is an IC chip, RO
M, RAM, etc., refer mainly to storage media having a function of storing electronic information.
The storage method and storage capacity 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, In addition to the above, storage media such as an IC card, a mobile phone, a personal computer, an electronic organizer, a video camera, a digital camera, a still camera, and various audio devices are included.

In the present invention, the housing refers to an exterior part of a product, and may be a single unit or a case and a cover.
It may be composed of a plurality of parts, and its shape is not limited. In addition, it is possible to provide ribs and the like for the purpose of improving the strength of the product and for supporting the flow of resin, and to provide a convex shape for the purpose of positioning, fixing and fixing each built-in component. It is. Also,
The outside and inside of the housing need not be hermetically sealed, and it is practical to provide a terminal window for transmitting and receiving electric energy, electronic information, and the like, which can be said to be a preferable shape.

In the present invention, the amorphous resin composition is
Among resin compositions containing a thermoplastic resin as a main component, which has the characteristic of softening when heated and showing plasticity and solidifying when cooled, thermoplastics that cannot take a crystalline state or have extremely low crystallinity even when crystallized It refers to a resin composition containing a resin component. More specifically, it is also called an amorphous or amorphous polymer, and is a solid state in which atoms or molecules do not form a three-dimensionally ordered spatial lattice but are completely irregularly assembled, also called an amorphous 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 amorphous 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. For example, PC / ABS resin
ABS polymer alloy, polyamide resin and PPE
And PA / PPE-based polymer alloys based on polypropylene-based resins and PP / PPE-based polymer alloys based on polypropylene-based resins and PPE-based resins.

When the thin molded article according to the present invention is a casing of a secondary battery, it is hardly deteriorated by an electrolytic solution used for the secondary battery, has a high heat resistance temperature, and has a non-halogen flame retardant. It is preferable that the specific gravity is small for ease of weight reduction and weight reduction. On the other hand, when the thin-walled molded product according to the present invention is a casing of a storage medium, the dimensional accuracy is high, the dimensional change due to humidity and temperature is small, the heat resistance temperature is high, and the flame retardant due to a non-halogen flame retardant is used. It is preferable that the specific gravity is small for ease of weight reduction and weight reduction.

In consideration of these required characteristics, the amorphous resin composition used for the thin molded article according to the present invention is made of PP
It can be said that E-based resins and modified PPE-based resins are preferred. An inorganic or organic filler can be added to the amorphous resin composition used in the present invention for the purpose of imparting specific gravity and strength, ensuring dimensional accuracy, and the like.

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 amorphous resin composition of the present invention is not limited, but adjusts the specific gravity of the amorphous resin composition, improves rigidity, In order to obtain sufficient effects by adding additives, such as securing dimensional accuracy and suppressing deformation such as warpage, it is necessary to use 5
The addition amount is preferably at least 10% by weight, more preferably at least 10% by weight. 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 filler refers to a ratio when the total amount of the amorphous resin composition to which the filler is added is 100% by weight, and when two or more fillers are used. Indicates the total amount of the additives. In the present invention, the amount of the inorganic or organic filler to be added refers to the amount of the inorganic filler to be added when one kind is added, and to the total amount of the addition when two or more kinds of the inorganic filler are added. In addition, the amount of the inorganic or organic filler added is a resin component, an inorganic or organic filler,
It indicates the ratio when the total amount of other additives is 100% by weight.

The amorphous resin composition of the present invention may contain additives usually used, for example, an antioxidant, a flame retardant, a mold release agent, a lubricant, a heat stabilizer, a weather resistance stabilizer, and a rust inhibitor. Fillers, coloring agents, antibacterial agents, fungicides, etc.
More than one kind can be added. Further, by selecting one or more of carbon fiber, metal fiber, and graphite as other additives, the electric resistance value of the crystalline resin can be reduced. This is preferable because it is possible to prevent small powder such as dust from attaching to a molded article made of a thermoplastic resin by static electricity.

The thin molded article made of the amorphous resin composition according to the present invention is obtained by mixing the amorphous resin composition in a molten state with 1MP.
a, characterized in that the mixture is filled into a mold cavity with carbon dioxide pressurized to at least a, by mixing carbon dioxide into the amorphous resin composition, the amorphous resin composition When filling the mold cavity, the flow distance increases. This is supposedly because carbon dioxide is efficiently dispersed as a plasticizer of the amorphous resin composition by mixing the amorphous resin composition in the molten state with carbon dioxide. As a result, since it is not necessary to raise the resin temperature, there is no need to worry about thermal decomposition and deterioration of the amorphous resin composition, and it is preferable because the mold temperature does not need to be raised more than necessary.

As described above, the thin molded article made of the amorphous resin composition of the present invention is obtained by molding a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized to 1 MPa or more in a mold. By filling the cavity, the flow distance can be increased without increasing the resin temperature more than necessary, so that the amorphous 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. Seem.

In the present invention, a thin-walled molded article made of the amorphous resin composition may be mixed with the amorphous resin composition in a molten state by 1M.
It is characterized by filling a mold cavity with a mixture of carbon dioxide pressurized to Pa or more, but when the pressure is less than 1 MPa, an effect is obtained by mixing a thermoplastic resin in a molten state and carbon dioxide. Because it is difficult
Not preferred.

The thin molded article of the present invention is obtained by filling a mold cavity with a mixture of an amorphous resin composition in a molten state and carbon dioxide pressurized to 1 MPa or more. However, as the method, a method of mixing with the crystalline resin in a molten state in a heating cylinder of an injection molding machine, a method of mixing with the crystalline resin in a molten state from a nozzle portion of the molding machine, a mold and a molding machine A method of providing equipment for supplying carbon dioxide between the nozzles and mixing the crystalline resin with the molten crystalline resin, producing resin pellets in a state where carbon dioxide is mixed with the amorphous resin composition in a molten state in advance. A method of injection molding using the granulated material is conceivable.

Considering that carbon dioxide is easily and uniformly dispersed in the amorphous resin composition in a short time, the mixing amount is easily adjusted, and the setup before molding is not complicated,
In the heating cylinder of the injection molding machine, at the nozzle portion of the molding machine, or at any position between the nozzle portion of the molding machine and the mold, a facility for supplying carbon dioxide is provided, whereby the crystalline resin in a molten state is provided. A method of mixing carbon dioxide with the composition is preferred.
In the present invention, carbon dioxide is dissolved or absorbed in the amorphous resin by mixing the amorphous resin composition and carbon dioxide, but the amount of the dissolved or absorbed carbon dioxide is not limited.

The amount of dissolution or absorption required to improve the fluidity when filling the amorphous resin composition into the mold cavity and to suppress the increase in the filling pressure is 0.2.
% By weight or more, more preferably 0.4% by weight or more. 0.2 carbon dioxide dissolved or absorbed
When the content is less than the weight%, it is difficult to obtain the fluidity improving effect by dissolving or absorbing the carbon dioxide, and it is difficult to obtain sufficient dimensional accuracy and dimensional stability, which is not preferable.

The measurement of the dissolved amount or the absorbed amount is performed by the following method. (1) Immediately after molding, the weight of the thin molded article is measured (M1). (2) The thin-walled molded product is left in a hot-air drier kept at 100 ° C. for 48 hours or more to disperse carbon dioxide, taken out of the hot-air drier, and weighed again (M2). . (3) The amount of carbon dioxide dissolved or absorbed (% by weight)
It is calculated from (M1−M2) ÷ M2 × 100.

The thin molded article made of the amorphous resin composition according to the present invention preferably has a foamed portion inside, particularly at a portion which is thicker than the peripheral thickness. When the amorphous resin composition cools and solidifies in the mold cavity and causes volume shrinkage in the mold cavity, carbon dioxide dissolved or absorbed in the amorphous resin composition foams appropriately. It is supposed to be formed by doing.

Since the foamed portion is formed inside a relatively thick portion of the thin-walled molded product, the volume shrinkage of the amorphous resin composition is compensated for from the inside of the thin-walled molded product, and The occurrence of defects such as sink marks on the surface of the product 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 amorphous 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 amorphous resin composition is cooled and solidified in the mold cavity and is dissolved in the amorphous 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 an arbitrary cross section of a thin molded article made of an amorphous resin composition by an optical microscope or the like.
When observed at a magnification of up to 20 times, a void or whitening phenomenon due to foaming is observed, and a non-foamed layer refers to a void or whitening phenomenon not observed due to foaming. In the present invention, the apparent specific gravity of the thin-walled molded article made of the amorphous resin composition is not limited, but the apparent specific gravity of the thin-walled molded article made of the amorphous resin composition is determined by the specific gravity of the crystalline resin composition. Is preferably in the range of 95 to 99.5%.

The fact that the apparent specific gravity of the thin molded article made of the amorphous resin composition is less than 95% of the specific gravity of the amorphous resin composition means that the proportion of the foamed portion in the thin molded article is too large. This is not preferable because a decrease in strength of the thin-walled molded product cannot be ignored. When the apparent specific gravity exceeds 99.5% of the specific gravity of the amorphous resin composition, it means that the foamed portion is not sufficiently formed inside the thin molded article made of the amorphous resin composition. And
It is considered that the internal foamed portion is not effectively present, such as sink marks on the surface of the thin molded article.

The apparent specific gravity of a thin molded article made of the amorphous resin composition of the present invention is in the range of 95 to 99.5% of the specific gravity of the amorphous resin composition used.
It is considered that the inside of the thin molded article has a range of apparent specific gravity in which a foamed portion is appropriately present, and more preferably ranges from 96 to 99.5%, and more preferably ranges from 98 to 99.5%. Most preferred. In the present invention, the apparent specific gravity is the specific gravity of a thin-walled molded article made of the amorphous resin composition, and the specific gravity of the entire thin-walled molded article, or the portion of the thin-walled molded article that is not substantially foamed with the foamed portion is Refers to the specific gravity of any mixed part. The specific gravity of the amorphous resin composition indicates the specific gravity of the resin pellet.

In the present invention, the injection molding method of the amorphous resin composition is a usual molding and processing method of a thermoplastic resin. In addition to the most common ordinary injection molding method, a hollow injection molding method is used. Molding method, gas assist molding method, blow molding method, injection / compression molding method and the like are included. In the injection molding method of a thin-walled molded article using the amorphous resin composition of the present invention, when filling the mixture of the amorphous resin composition and carbon dioxide into the mold cavity, the amount of dissolved or absorbed carbon dioxide is constant If the value is more than the value, a foam pattern may be generated on the surface of the thin molded article.

In order to suppress the formation of a foaming pattern on the surface of the thin molded article, the pressure inside the mold cavity is adjusted to a pressure higher than the pressure at which foaming does not occur at the flow front of the crystalline resin composition by pressurized gas. It is preferable that it is held. The pressure of the pressurized gas may be a minimum pressure that does not generate a foaming pattern on the surface of a thin molded article made of the amorphous 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 be opened 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,
MPa or less, and more preferably 1 MPa or less.
It is not less than MPa and not more than 10 MPa. In addition, 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 amorphous resin composition by the pressurized gas, the mold cavity may be generated in the vicinity of the gate portion. This is preferable because it also has an effect of suppressing appearance defects caused by disorder of the flow of the amorphous resin composition, which is called jetting.

In the present invention, when the amorphous resin composition in which carbon dioxide is dissolved or absorbed is filled into a mold cavity, the mold cavity is kept at a pressure higher than atmospheric pressure and 15 MPa.
It is preferable that the temperature is adjusted or held below, but after the resin filling starts, at least until the cooling step is completed,
Preferably, the pressure in the mold cavity is released until the pressure-holding step is completed, and more preferably, before the pressure-holding step is started. At this time, as the gas for adjusting or maintaining the inside of the mold cavity to a constant pressure, a single substance or a mixture of various gases inert to the amorphous resin composition can be used. Highly soluble carbon dioxide in the amorphous resin composition,
Hydrocarbons and gases in which hydrogen has been partially replaced by fluorine are preferred. Considering that a high-purity gas can be easily obtained at relatively low cost, it is possible to use nitrogen gas.

On the other hand, in the present invention, the filling pressure refers to a resin pressure generated when a molten amorphous resin composition is filled into a 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 refer to the maximum value of the resin pressure generated when moving from the measuring position to the VP switching position. In a usual injection molding method, after filling the amorphous resin composition into the mold cavity, the method further includes a step of holding the amorphous resin composition in the cavity under pressure. This step is referred to as a “holding step”, and the degree of the pressure is referred to as “holding pressure”. In the injection molding method of the amorphous resin composition according to the present invention,
After filling the amorphous resin composition into the mold cavity, it is preferable to hold the amorphous resin composition in the mold cavity under pressure by a pressure corresponding to 30% or more of the filling 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. A thin molded article obtained by filling a mold cavity with a mixture of an amorphous resin composition in a molten state and carbon dioxide pressurized to 1 MPa or more has a non-molded product 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.

The pressure holding time is not limited, but if the pressure holding time is extremely short, carbon dioxide mixed with the amorphous resin composition before filling into the mold cavity expands. Doing so is not preferable because a swelling phenomenon may occur in the molded product. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

The amorphous resin used for injection molding was PC /
ABS-based polymer alloy ("Pycoroy MC5400" manufactured by Nippon GE Plastics Co., Ltd.), modified PP
E-based resin (“Zylon 340V” manufactured by Asahi Kasei Corporation)
Both are pellets before molding. The molding machine is “TUPAR manufactured by Sodick Plustech Co., Ltd.
L TR50S2 ”,“ SG ”manufactured by Sumitomo Heavy Industries, Ltd.
125M-HP "was used.

[0050]

Examples 1 to 4 A mold capable of molding a secondary battery casing model molded article having the shape shown in FIG. 1 was prepared. The wall thickness of the molded article is uniform, 0.2 mm. The molding machine is "TR5
OS2 "was used. The number of gates provided on the mold is
As shown in FIG. 1, one point was provided on the side surface of the secondary battery housing model molded product. The temperature of the heating cylinder of the molding machine is 26
The mold temperature was set at 0 ° C and the mold temperature was set at 80 ° C.

Using “Psychoroy MC5400”,
By supplying carbon dioxide adjusted to an arbitrary pressure of 1.8 to 8.2 MPa from a gas supply unit provided at the center of the heating cylinder of the molding machine to a polymer alloy in a molten state inside the heating cylinder. After mixing, the mixture was filled into a mold cavity to obtain a molded secondary battery case model shown in FIG.

The filling pressure during molding was a value obtained by reading the filling pressure during injection on a monitor screen of a molding machine, and the holding pressure was a value corresponding to 70% of the filling pressure. The dwell time was 3 seconds and the cooling time was 15 seconds. The flatness of the molded article was measured according to a multipoint flatness measurement method using a three-dimensional measuring machine “AE122 manufactured by Mitutoyo Corporation” and a measurement program “Geopak 400 manufactured by the company”. The measurement location is the location shown in 3 of FIG. Table 1 shows the measurement results of the filling pressure during injection molding and the flatness of the molded product.

[0053]

COMPARATIVE EXAMPLE 1 The temperature of the heating cylinder of the injection molding machine was set to 260 ° C., the mold temperature was set to 80 ° C., and carbon dioxide adjusted to 0.4 MPa using the same mold as in Examples 1 to 4. By mixing by supplying to a polymer alloy in a molten state inside the heating cylinder from a gas supply unit provided in the center of the heating cylinder of the molding machine, the mixture is filled into a mold cavity, as shown in FIG. However, it was not possible to fill the mold cavity with resin so as not to leave unfilled portions.

[0054]

Comparative Example 2 The temperature of the heating cylinder of the injection molding machine was set to 280 ° C., the mold temperature was set to 80 ° C., and the same mold as in Examples 1 to 4 was used. Although the carbon dioxide was not supplied from the gas supply unit, the secondary battery housing model molded article shown in FIG. 1 was obtained by the same process as the normal injection molding. It was not possible to fill the mold cavity with resin so as not to leave it.

[0055]

Comparative Example 3 The temperature of the heating cylinder of the injection molding machine was set at 300 ° C., the mold temperature was set at 80 ° C., and the same mold as in Examples 1 to 4 was used. The carbon dioxide was not supplied from the gas supply unit, and the secondary battery housing model molded article shown in FIG. 1 was obtained by the same process as that of ordinary injection molding. As in Examples 1 to 4, the filling pressure and the flatness of the molded product were measured.

Table 1 shows the results.

[0057]

[Table 1]

[0058]

Examples 5 to 8 A mold was prepared for molding an IC card model molded article having the shape shown in FIG. The reference thickness of the molded product is 0.5 mm, and a thin portion having a thickness of 0.2 mm is provided as shown in 5 of FIG. The molding machine used was "SG125M-HP". The number of gates provided on the mold was one provided on the side surface of the molded IC card model as shown in FIG. The temperature of the heating cylinder of the molding machine was set at 280 ° C., and the temperature of the mold was set at 80 ° C.

Using “Zylon 340V”, 2.2
Carbon dioxide adjusted to an arbitrary pressure of ~ 12.2 MPa was mixed by being supplied from a gas supply unit provided in the center of the heating cylinder of the molding machine to a polymer alloy in a molten state inside the heating cylinder. Thereafter, the molded product was filled in a mold cavity to obtain an IC card model molded product shown in FIG. The filling amount of the mixture of the resin and carbon dioxide was a necessary minimum filling amount in which no unfilled portion remained. The injection speed was set to 200 mm / sec, and the pressure-holding step was omitted. The cooling time was 10 seconds.

After setting the molding conditions, the resin was discharged once. Thereafter, continuous molding of 2000 shots was performed. The flow end portion was visually observed, and a molded product in which an unfilled portion was confirmed was counted as a defective molded product, and a defect occurrence rate was calculated. The filling pressure during molding was a value obtained by reading the filling pressure during injection on a monitor screen of a molding machine. Table 1 shows the calculation results of the defect occurrence rate during injection molding and the measurement results of the filling pressure.

[0061]

Comparative Example 4 The temperature of the heating cylinder of the molding machine was set at 280 ° C., the mold temperature was set at 80 ° C., and the injection speed was set at 200 mm / sec.
Using the same mold as in Examples 5 to 8, carbon dioxide adjusted to 0.4 MPa was supplied from the gas supply unit provided at the center of the heating cylinder of the molding machine to the molten state inside the heating cylinder. An attempt was made to obtain the IC card model molded product shown in FIG. 2 by supplying the mixture to a certain resin and then filling the mold cavity. Could not be filled with resin.

[0062]

Comparative Examples 5 and 6 The temperature of the heating cylinder of the injection molding machine was 320.
° C, the mold temperature is set to 80 ° C, and the injection speed is 400, 6
It was set to 00 mm / sec. Using the same mold as in Examples 5 to 8, the carbon dioxide was not supplied from the gas supply unit provided at the center of the heating cylinder of the molding machine, and the same steps as those in ordinary injection molding were performed. The molded product of the IC card model shown in FIG. In the same manner as in Examples 5 to 8, the defect occurrence rate during injection molding was calculated, and the filling pressure was measured. Table 2 shows the results.

[0063]

[Table 2]

[0064]

According to the present invention, the average molecular weight of the thermoplastic resin, the restriction on the resin composition and the complexity of the mold structure are not impaired without impairing the design freedom of the thin-walled molded product having a minimum thickness of 0.5 mm or less. Dimensional accuracy of thin molded products without increasing the resin temperature and injection speed more than necessary during injection molding.
It is possible to improve productivity.

[Brief description of the drawings]

[Fig. 1] Secondary battery housing model molded product

[Fig. 2] IC card model molded product

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rechargeable battery case model molded product 2 Gate 3 Flatness measurement surface 4 IC card model molded product 5 Thin part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 71:12 C08L 71:12

Claims (10)

[Claims] The thin molded article is a thin molded article made of an amorphous resin composition having a portion having a minimum thickness of 0.5 mm or less, and wherein the amorphous resin composition is in a molten state. A thin molded product obtained by filling a mold cavity with a mixture of carbon dioxide pressurized to 1 MPa or more. 2. The thin molded article according to claim 1, wherein the molded article has a portion having a minimum thickness of 0.2 mm or less. 3. The thin molded article according to claim 1, wherein the thin molded article is a housing of a secondary battery. 4. The thin-walled molded product according to claim 1, wherein the thin-walled molded product is a housing of a storage medium. 5. The thin film made of the amorphous resin composition according to claim 1, wherein the amorphous resin composition is a modified polyphenylene ether resin containing at least a polyphenylene ether component. Molding. 6. A thin-walled molded product having a foamed portion inside,
The thin-walled molded product according to any one of claims 1 to 5, wherein the surface layer has a non-foamed layer that is not substantially foamed. 7. The amorphous material according to claim 1, wherein the apparent specific gravity of the thin-walled molded product is 95 to 99.5% of the specific gravity of the amorphous resin composition. Thin-walled molded product made of resin composition. 8. An injection molding method comprising the steps of: heating a non-crystalline resin composition in a molten state in a heating cylinder of a molding machine;
The injection molding method for a thin-walled molded product according to claim 1, wherein a thin-walled molded product is obtained by kneading carbon dioxide pressurized to a or more and filling the mixture into a mold cavity. 9. A thin-walled molded product is obtained by filling a mixture of an amorphous resin composition and carbon dioxide into a mold cavity adjusted or maintained at a pressure of not less than atmospheric pressure and not more than 15 MPa. An injection molding method for a thin-walled molded product according to claim 8. 10. A thin-wall molding comprising a step of filling a mold cavity with a mixture of an amorphous resin composition and carbon dioxide, and then holding the resin under a pressure of 30% or more of the filling pressure. The injection molding method for a thin-walled molded product according to claim 8, wherein a product is obtained.