JP2003170461A - Thin-walled molding and method for injection molding the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the dimensional accuracy and productivity of a thin-walled molding without increasing resin temperature and injection speed more than necessity at the time of injection molding without limiting a mean molecular weight and a resin composition of a thermoplastic resin and without complicating a mold structure without impairing the flexibility in designing the thin molding itself having a minimum thickness of 0.5 mm or less and to improve the productivity of the thin-walled molding represented by the housing of a secondary battery, a storage medium or the like by making it easy to inject resin into the mold cavity and reducing the deformation at the time of removing from the mold. <P>SOLUTION: The thin-walled molding contains an amorphous resin composition having at least a part including the minimum thickness of 0.5 mm or less. The method for injection molding the thin-walled molding comprises the step of filling a mixture of the amorphous resin composition in a molten state with a carbon dioxide pressurized to an atmospheric pressure or more in a mold cavity regulated to a temperature lower by 20°C or more than the thermal deforming temperature of the resin, thereby obtaining the thin-walled molding. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a minimum thickness of 0.5.
TECHNICAL FIELD The present invention relates to a thin-walled molded product made of an amorphous resin composition having a portion having a size of not more than mm and an injection molding method thereof. More specifically, the present invention relates to a case of a secondary battery made of an amorphous resin composition having a portion having a minimum thickness of 0.5 mm or less, a case of a storage medium, and an injection molding method thereof.

[0002]

2. Description of the Related Art Usually, not only an amorphous resin composition but also many molded articles made of a thermoplastic resin are manufactured by an injection molding method. However, an injection-molded article 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 or a case of a storage medium, is a melt of the amorphous resin composition used. Amorphous resin composition to the mold cavity so as not to leave an unfilled part due to high viscosity and increase in viscosity of the amorphous resin composition due to temperature decrease after filling into the mold cavity 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 dealt with by adjusting the molding conditions such as increasing the injection speed and increasing the mold temperature. However, increasing the temperature of the amorphous resin composition during injection molding promotes thermal decomposition of the amorphous resin composition. Therefore, alteration of the amorphous resin composition, generation of decomposition gas, decomposition gas sticks to the mold cavity and becomes a mold deposit, and appearance defects called silver (silver streak) occur on the surface of the molded product. Since it causes the problem of (1), there is a limit in the range where the temperature is high. Further, when the temperature of the amorphous resin composition is high, the amount of volume shrinkage that occurs during cooling increases, and thus there is a concern that defects such as sink marks may occur in the obtained molded product.

The method of increasing the injection speed when filling the mold cavity requires special equipment of the injection molding machine,
High precision such as injection speed and filling amount is required. Further, the amorphous resin composition injected at high speed causes shear heat generation, which also causes thermal decomposition. Further, in the method of increasing the injection speed, it is general that the filling pressure in the mold cavity is increased in proportion to the injection speed. Also,
When the step of holding the filled amorphous resin composition under pressure (hereinafter referred to as “holding pressure”) after filling the amorphous resin composition into the mold cavity has a high holding pressure for a thin-walled molded product. Often needed.

A molded article injection-molded under conditions such as high-speed injection and high holding pressure to fill the mold cavity is cooled and solidified under high pressure. The amorphous resin composition that is cooled and solidified under high pressure results in a large amount of strain remaining inside the molded product. The molding strain remaining in this molded product is "residual strain".
It is also called. This residual strain gradually relaxes after molding, but this is often due to deformation or shrinkage of the molded product. Therefore, it can be said that injection molding is preferably performed according to the molding method and molding conditions in which residual strain is less likely to remain.

With the method of increasing the mold temperature, it is difficult to uniformly and stably stabilize the temperature of the mold cavity surface, and the time required for cooling the amorphous resin composition filled in the mold cavity is high. Since it becomes long, there is a concern that productivity will be a problem. When ejecting a molded product from the mold cavity, the molded product is ejected (extruded) from the mold cavity by an ejector pin, but if the amorphous resin composition is not sufficiently cooled at this time, ejection deformation occurs, As a result, the molded product warps. Further, when the mold temperature is higher than the heat deformation temperature of the amorphous resin composition used, the molded product is hard to solidify. For this reason, the ejector pin may bite into the molded product at the time of protrusion, and it may be impossible to protrude.

On the other hand, in terms of mold design, by increasing the number of gates, it becomes easy to fill the resin into the mold cavity. However, in injection-molded products such as secondary battery housings and storage media housings, there is concern that the impact strength may decrease due to the occurrence of weld parts, and the appearance may be impaired due to the large number of gate parts. Yes, it is hard to say that it is preferable. It is also possible to optimize the amorphous resin composition used. For example, it is to secure high fluidity by making the molecular weight of the amorphous resin composition small so that uniform pressure can be easily transmitted to the fluid end portion.

However, in general, an amorphous resin composition having a small molecular weight has a low toughness and impact resistance, and also tends to have a short service life against fatigue due to repeated loads, so that it is required for a housing. It is difficult to secure strength. 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 wall thickness of 0.5 mm or less, the temperature, injection speed, and mold temperature of the amorphous resin composition are increased more than necessary during the injection molding. Without using the mold, which has the minimum required number of gates, it has been awaited to establish an injection molding method in which an unfilled portion is unlikely to occur and a defective rate is small.

On the other hand, J. Appl. Polym. Sc
i. , Vol. It is known that when carbon dioxide is absorbed into a resin, it acts as a plasticizer of the resin and lowers the glass transition temperature, as shown in many documents such as 30, 2633 (1985). It has not been widely applied to processing. Also, WO98 / 5273
No. 4, in injection molding of a thermoplastic resin, 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 oxidized to a pressure above which foaming does not occur at the flow front of the molten resin. A method of filling a mold cavity kept under pressure with a gas such as carbon is shown,
It is described that it is effective for reproducibility of the mold surface, improvement of glossiness, inconspicuous weld line, reproducibility of sharp edges on mold surface, reproducibility of fine mold surface irregularities, etc. . However, a method for efficiently dissolving carbon dioxide in a thermoplastic resin and dissolution conditions have not been disclosed yet.

[0010]

DISCLOSURE OF THE INVENTION The present invention does not impair the degree of freedom in designing a thin-walled molded product itself having a minimum thickness of 0.5 mm or less, and limits the average molecular weight of the thermoplastic resin, the resin composition, and An object of the present invention is to improve the dimensional accuracy and productivity of thin-walled molded products without making the mold structure complicated and without increasing the resin temperature and injection speed during injection molding more than necessary. Specifically, the present invention is intended to improve the dimensional accuracy and productivity of a thin-walled molded product typified by a case of a secondary battery, a storage medium, etc., because the mold cavity can be easily filled. .

[0011]

Means for Solving the Problems The present inventor has made a restriction on the average molecular weight and resin composition of a thermoplastic resin without impairing the degree of freedom in designing a thin-walled molded article itself having a minimum thickness of 0.5 mm or less, Studies were conducted to make it possible to improve the dimensional accuracy and productivity of thin-walled molded products without complicating the mold structure and increasing the resin temperature and injection speed during injection molding more than necessary. As a result, a thin-walled molded article, which is obtained by filling a mold cavity with a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or higher, The inventors have found that it is possible to improve the productivity of thin-walled molded products, and have completed the present invention.

That is, the present invention is as follows: The thin-walled molded article is a thin-walled molded article made of an amorphous resin composition having at least a portion having a minimum wall thickness of 0.5 mm or less, and the amorphous resin composition in a molten state and the atmospheric pressure or higher. A thin-walled molded article, which is obtained by filling a mixture of pressurized carbon dioxide into a mold cavity adjusted to a temperature lower by 20 ° C. or more than the heat distortion temperature of the amorphous resin, 2. The amorphous resin composition in a molten state and atmospheric pressure or higher,
The thin-walled molded product according to the above 1, which is obtained by filling a mold cavity with a mixture of carbon dioxide pressurized to 7 MPa or less,

3. 3. The thin-walled molded article according to 1 or 2 above, which has a portion having a minimum wall thickness of 0.2 mm or less. 4. The thin-walled molded article according to any one of the above 1 to 3, wherein the thin-walled molded article is a casing of a secondary battery. 5. The thin-walled molded article according to any one of 1 to 3 above, wherein the thin-walled molded article is a housing for a storage medium. The amorphous resin composition is a modified polyphenylene ether-based resin containing at least a polyphenylene ether component, and the thin-walled molded product of the amorphous resin composition according to any one of the above 1 to 5,

7. 7. The thin-walled molded product of the amorphous resin composition according to any one of 1 to 5 above, wherein the amorphous resin composition is a polycarbonate resin containing at least a polycarbonate component. 8. The thin-walled molded article according to any one of 1 to 7 above, wherein the thin-walled molded article has a foamed portion inside and a non-foamed layer that is not substantially foamed in the surface layer portion. 9. The thin-wall molded product according to any one of 1 to 8 above, wherein the thin-wall molded product has an apparent specific gravity of 95 to 99.5% of the specific gravity of the amorphous resin composition. Goods,

10. The injection molding method, in the heating cylinder of the molding machine, after mixing the amorphous resin composition in a molten state and carbon dioxide pressurized to atmospheric pressure or more, from the heat distortion temperature of the amorphous resin 11. The injection molding method for a thin-walled molded article as described in 1 above, wherein a thin-walled molded article is obtained by filling a mold cavity adjusted to a temperature lower by 20 ° C. or more. The injection molding method is as follows: the amorphous resin composition in a molten state and the atmospheric pressure or higher in a heating cylinder of a molding machine,
A thin-walled molded product is obtained by mixing carbon dioxide pressurized to MPa or less, and then filling the mold cavity adjusted to a temperature lower than the heat deformation temperature of the amorphous resin by 20 ° C. or more. An injection molding method for a thin-walled molded article according to 1 or 2 above,

12. 12. The thin-walled molded article is obtained by filling a mixture of an amorphous resin composition and carbon dioxide into a mold cavity adjusted or held at an atmospheric pressure or higher and 15 MPa or lower, to obtain a thin-walled molded article. 13. An injection molding method of a thin-walled molded article, By filling the mold cavity with a mixture of the amorphous resin composition and carbon dioxide, and then holding the resin under pressure with a pressure that is 30% or more of the filling pressure, it is possible to obtain a thin-walled molded product. 13. A method for injection-molding a thin-walled molded article according to any one of 10 to 12 above.

The present invention will be specifically described below.
The thin-walled molded article according to the present invention is an injection-molded article having at least a portion having a minimum wall thickness of 0.5 mm or less,
In particular, it refers to an injection-molded product having a portion having a minimum wall thickness of 0.2 mm or less. Specific examples of the thin-walled molded product include a case of a secondary battery and a case of a storage medium. The secondary battery, which is also called a storage battery, refers to a battery that can be repeatedly used by being charged after being discharged.

Specifically, it is a secondary battery used in electric equipment and electronic equipment, and more particularly, a secondary battery used in portable electric equipment and electronic equipment, such as "battery pack" and "battery pack". It is also referred to as a mobile phone, laptop, electronic notebook, video camera, digital
Examples include rechargeable batteries, batteries, and battery packs used in cameras, still cameras, and various audio equipment.

The storage medium is an IC chip or RO.
It refers to a storage medium mainly having a function of storing electronic information, such as M and RAM.
The storage method and storage capacity are not limited. In particular, a storage medium that is small and thin so that it can be easily carried is preferable, and these storage media are also referred to as "memory sticks" and "smart media".
In addition to the above, a storage medium such as an IC card, a mobile phone, a personal computer, an electronic notebook, a video camera, a digital camera, a still camera, and various audio devices can be used.

In the present invention, the term "casing" refers to an exterior part of a product, and is used as a single body or as a case portion and a lid portion.
It may be composed of a plurality of parts, and its shape is not limited. In addition, it is possible to provide ribs etc. inside for the purpose of improving the product strength, supporting the flow of resin, etc., and providing convex shapes for positioning, fixing, fixing etc. of each built-in component. Is. Also,
The outside and the inside of the housing do not have to be hermetically sealed, and it is practical and preferable to have a terminal window for transmitting and receiving electric energy, electronic information, and the like.

In the present invention, the amorphous resin composition means
Of the resin compositions whose main component is a thermoplastic resin that has the characteristics of softening when heated and showing plasticity, and solidifying when cooled, a thermoplastic resin that cannot take a crystalline state or has an extremely low crystallinity even when crystallized. It refers to a resin composition containing a resin component. More specifically, it is sometimes referred to as 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 irregularly assembled, and are also called amorphous. The amorphous state includes a glass state and a rubber state, and shows a hard glass state at a glass transition point (Tg) or lower, but T
It has a characteristic of showing a soft rubbery state when it is more than g.

Specifically, polystyrene (hereinafter "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.

The amorphous resin composition in the present invention may be a polymer alloy which is a composite resin material in which two or more kinds of thermoplastic resins are physically and chemically mixed. For example, PC / PC made of PC resin and ABS resin
ABS polymer alloy, polyamide resin and PPE
PA / PPE-based polymer alloys made of resin based on polypropylene, PP / PPE-based polymer alloys made from polypropylene resin and PPE-based resin, etc.

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

Taking these required characteristics into consideration, the amorphous resin composition used in the thin-walled molded article according to the present invention is PP
E resin, modified PPE resin, PC resin, PC / AB
It can be said that the S-based polymer alloy is preferable.
Inorganic or organic fillers 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.

Specific gravity imparting agents include inorganic salts and oxides such as barium sulfate, red iron oxide, and tungsten powder.
Metal powder etc. can be considered. Further, as the 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 Cinite, Talc, Atalpulgite, Wollastonite,
Slag fiber, ferrite, silicon, calcium, calcium carbonate, magnesium carbonate, dolomite, zinc oxide,
Gypsum, glass beads, glass powder, glass balloons, quartz, quartz glass, alumina and the like are considered.

The shape of these inorganic or organic fillers is not limited, and fibrous, plate-like or spherical shapes 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 amorphous resin composition of the present invention is not limited, but the specific gravity of the amorphous resin composition is adjusted, and the rigidity is improved. To ensure sufficient dimensional accuracy and suppress deformation such as warpage, it is necessary to add 5
The amount added is preferably not less than 10% by weight, more preferably not less than 10% by weight.

In the present invention, the addition amount of the inorganic or organic filler refers to the addition amount of one kind of inorganic filler to be added, and the total addition amount of two or more kinds of inorganic fillers. Refers 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 amorphous resin composition in the present invention, the additives usually used, for example, antioxidants, flame retardants, mold release agents, lubricants, heat resistance stabilizers, weather resistance stabilizers, rust inhibitors, fillers , Colorants, antibacterial agents, antifungal agents, etc.
More than one kind can be added.

As other additives, carbon fiber,
The electrical resistance value of the amorphous resin can be lowered by selecting at least one of metal fiber and graphite. This is preferable because small powder such as dust can be prevented from adhering to the molded product made of the thermoplastic resin by static electricity. The thin-walled molded product of the amorphous resin composition in the present invention is characterized in that a mold cavity is filled with a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or higher. However, this is because, when carbon dioxide is mixed with the amorphous resin composition, the flow distance becomes large when the amorphous resin composition is filled in the mold cavity.

It is supposed that this is because the carbon dioxide is efficiently dispersed as a plasticizer for the amorphous resin composition by mixing the amorphous resin composition in the molten state 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 amorphous resin composition, and it is preferable that the die temperature does not need to be raised more than necessary. As described above, the thin-walled molded product of the amorphous resin composition of the present invention is a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or more into the mold cavity. By filling, the flow distance can be increased without raising the resin temperature more than necessary, so that the mold cavity can be filled with the amorphous resin composition at a low filling pressure. Therefore, since residual strain is less likely to remain in the obtained molded product, warpage or the like that occurs after molding is reduced, and since the unfilled portion is less likely to remain, the occurrence rate of defects during continuous molding is low and productivity is improved. Seem.

In the present invention, the thin-walled molded article made of the amorphous resin composition is obtained by filling a mold cavity with a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or higher. However, if the atmospheric pressure is lower than the atmospheric pressure, it is difficult to obtain the effect of mixing the molten thermoplastic resin and carbon dioxide, which is not preferable. As the method, a method of mixing with a molten amorphous resin in a heating cylinder of an injection molding machine, a method of mixing with a molten amorphous resin from a nozzle of the molding machine, a mold and a molding machine A method for providing equipment for supplying carbon dioxide between the nozzles to mix with the amorphous resin in a molten state, and to prepare 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 a granulated material can be considered.

Considering that carbon dioxide can be uniformly and easily dispersed in the amorphous resin composition in a short time, the mixing amount can be easily adjusted, and the preparation before molding is not complicated,
Amorphous resin in a molten state is provided by installing equipment for supplying carbon dioxide in the heating cylinder of the injection molding machine, the nozzle part of the molding machine, or any position between the nozzle part of the molding machine and the mold. A method in which carbon dioxide is mixed with the composition is preferable. Further, carbon dioxide, when mixed with the amorphous resin composition,
It is known that there is an action of lowering the Tg and the heat distortion temperature of the amorphous resin composition depending on the amount of the mixture.

A molded product made of the amorphous resin composition must be taken out after being cooled to a temperature not higher than the heat distortion temperature in the mold cavity. At this time, if the cooling is insufficient, the molded product is easily deformed when it is ejected (extruded) from the mold cavity by an ejector pin or the like. For this reason, it is necessary to cool the inside of the mold cavity to a temperature lower than the heat distortion temperature, but an amorphous resin composition having a low heat distortion temperature requires a long time.

Therefore, it is preferable to suppress the decrease in heat distortion temperature due to the mixture of the amorphous resin composition and carbon dioxide as much as possible. Specifically, when the pressure of carbon dioxide to be mixed with the amorphous resin composition exceeds 7 MPa, the heat distortion temperature is lowered, and the effects such as insufficient cooling time during injection molding increase. Therefore, the pressure of carbon dioxide mixed with the amorphous resin composition is preferably 7 MPa or less.

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 dissolved or absorbed is not limited. . The amount of dissolution or absorption necessary for improving the fluidity when the amorphous resin composition is filled in the mold cavity and suppressing the increase of the filling pressure is 0.2% by weight or more. More preferably 0.4% by weight or more.

The amount of dissolved or absorbed carbon dioxide is 0.2
If it is less than wt%, it is difficult to obtain the effect of improving the fluidity by dissolving or absorbing carbon dioxide, and it is difficult to obtain sufficient dimensional accuracy and dimensional stability, which is not preferable. Moreover, the amount of dissolution or the amount of absorption is measured by the following method. (1) The weight of the thin-walled molded product is measured immediately after molding (denoted as M1). (2) The thin-walled molded product is left in a hot-air dryer kept at 100 ° C. for 48 hours or more to release carbon dioxide, then taken out from the hot-air dryer and weighed again (M2). . (3) The amount of carbon dioxide dissolved or absorbed (% by weight)
Calculated from (M1−M2) ÷ M2 × 100.

In the present invention, the heat distortion temperature of the amorphous resin composition means a load of 1. in accordance with ASTM standard "D648".
It refers to the deflection temperature under load at 82 MPa. In the present invention, the temperature of the mold cavity refers to the temperature of the mold temperature controller and the temperature of the medium circulating in the mold when the temperature of the mold body is adjusted. This medium is a fluid and is not limited as long as it can easily control the mold temperature, but it is common to use water or oils adjusted for controlling the mold temperature.

In the present invention, the temperature of the mold cavity is
It is characterized in that the temperature is adjusted to 20 ° C. or more lower than the heat distortion temperature of the amorphous resin composition used. Since the temperature of the mold cavity is in this range, the mixture of the amorphous resin composition filled in the mold cavity and carbon dioxide pressurized at atmospheric pressure or higher is cooled and solidified in a short time. The amount of deformation when the obtained molded product is ejected from the mold cavity by an ejector pin or the like can be suppressed.

When the temperature of the mold cavity is higher than the above range, the deformation that occurs during ejection is likely to occur. In addition, since the volume shrinkage amount in the cooling process is large, the molding shrinkage rate is increased, and there is a concern that warpage due to shrinkage may occur. It is preferable that the thin-walled molded product of the amorphous resin composition according to the present invention has a foamed portion inside, particularly in a thicker portion than the peripheral thickness. When the amorphous resin composition is cooled and solidified in the mold cavity to cause volume contraction, carbon dioxide dissolved or absorbed in the amorphous resin composition is appropriately foamed in the foamed portion. It is supposed to be formed by doing.

By forming the foamed portion inside the relatively thick portion of the thin-walled molded article, the volumetric shrinkage of the amorphous resin composition is compensated from the inside of the thin-walled molded article, and the thin-walled molded article is formed. The occurrence of defects such as sink marks on the surface of the product after molding is suppressed. As a result, it can be applied to a molded product that partially has a thick portion, and it can be expected that the degree of freedom in product design is increased. 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 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, the amorphous resin composition is dissolved in the amorphous resin composition when it is cooled and solidified in the mold cavity. Carbon dioxide is unlikely to form a foamed part inside the molded product, which may cause sink marks on the surface of the molded product.

The term "foamed portion" as used herein refers to an arbitrary cross section of a thin-walled molded product made of an amorphous resin composition, which is measured by an optical microscope.
A void or a whitening phenomenon due to foaming is observed when magnified to 20 times or more and observed, and a non-foaming layer refers to a void or a portion where the whitening phenomenon due to foaming is not confirmed. In the present invention, the apparent specific gravity of the thin-walled molded product of the amorphous resin composition is not limited, but the apparent specific gravity of the thin-walled molded product of the amorphous resin composition is the specific gravity of the crystalline resin composition. Is preferably in the range of 95 to 99.5%.

The apparent specific gravity of the thin-walled molded product of the amorphous resin composition is less than 95% of the specific gravity of the amorphous resin composition, which means that the foamed portion occupies too large a proportion in the thin-walled molded product. This means that the reduction in strength of the thin-walled molded product cannot be ignored and is not preferable. Further, 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. Then
It is considered that internal foaming portions are not effectively present such as sink marks on the surface of the thin molded product.

The apparent specific gravity of the thin-walled molded product 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-walled molded article has an apparent specific gravity in which an appropriately foamed portion exists, and it is more preferably in the range of 96 to 99.5%, further preferably in the range of 98 to 99.5%. Most preferred. In the present invention, the apparent specific gravity is the specific gravity of a thin-walled molded product made of an amorphous resin composition, and the specific gravity of the thin-walled molded product as a whole or a foamed portion of the thin-walled molded product and a portion which is not substantially foamed. Refers to the specific gravity of any part that is mixed. Moreover, the specific gravity of the amorphous resin composition refers to the specific gravity of the resin pellets.

In the present invention, the injection molding method of an amorphous resin composition is a molding method of a thermoplastic resin which is usually carried out, and in addition to the most common ordinary injection molding method, hollow injection molding A molding method, a gas assist molding method, a blow molding method, an injection / compression molding method and the like are included. In the injection molding method of a thin-walled molded product by the amorphous resin composition of the present invention, when the mixture of the amorphous resin composition and carbon dioxide is filled in the mold cavity, the dissolved amount or absorbed amount of carbon dioxide is constant. If the value is more than the value, a foamed pattern may occur on the surface of the thin molded product.

In order to prevent the foamed pattern from being generated on the surface of the thin-walled molded product, the pressure inside the mold cavity is adjusted to be higher than the pressure at which foaming does not occur at the flow front of the amorphous resin composition. It is preferably held. The pressure of the pressurized gas may be the lowest pressure at which a foamed pattern does not occur on the surface of the thin-walled molded product made of the amorphous resin composition. It is preferable that the gas pressure is low in order to minimize the amount of gas used during the molding cycle and to simplify the structure of the mold cavity and the structure of the gas supply device.

If 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 15
It is preferably equal to or lower than MPa, and more preferably equal to or higher than atmospheric pressure and equal to or lower than the pressure of carbon dioxide mixed with the amorphous resin composition. In addition, since the pressure inside the mold cavity of the mold cavity is adjusted or maintained at a pressure higher than the pressure at which foaming does not occur at the flow front of the amorphous resin composition, the mold cavity may be generated near the gate portion. It is preferable because it also has an effect of suppressing the appearance defect caused by the disordered flow of the amorphous resin composition, which is often called jetting.

In the present invention, when the mold cavity is filled with the amorphous resin composition in which carbon dioxide is dissolved or absorbed, the mold cavity has a pressure of not less than atmospheric pressure and 15 MPa.
It is preferable that the temperature is adjusted or maintained below, but at least from the start of resin filling to the completion of the cooling step,
It is preferable to release the pressure in the mold cavity preferably before the completion of the pressure holding step, and more preferably before the start of the pressure holding step. At this time, as the gas for controlling or maintaining the pressure inside the mold cavity at a constant pressure, a simple substance or a mixture of various gases inert to the amorphous resin composition can be used. Carbon dioxide, which has a high solubility in the amorphous resin composition,
A gas in which hydrocarbon and a part of hydrogen thereof are replaced with fluorine is 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.

On the other hand, the filling pressure in the present invention refers to the resin pressure generated when the molten amorphous resin composition is filled into 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. The usual injection molding method includes a step of filling the mold cavity with the amorphous resin composition and then holding the amorphous resin composition in the cavity under pressure. This step is referred to as a "pressure-holding step" and the degree of the pressure is referred to as "pressure-holding". 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 pressurize and hold the amorphous resin composition in the mold cavity with 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 the above range, the thickness of the non-foamed layer formed on the surface layer of the molded article becomes small, and the proportion of the foamed portion in an arbitrary cross section becomes large. A thin molded product obtained by filling a mold cavity with a mixture of an amorphous resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or higher has an appropriate thickness in its surface layer portion. In order to have an appropriate 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, and more preferable. Is in the range of 40% or more, and most preferably in the range of 50% or more. Further, the pressure holding time is not limited, but when the pressure holding time is extremely short, carbon dioxide mixed in the amorphous resin composition before expanding into the mold cavity may expand. However, it is not preferable because the molded product may be swollen.

[0051]

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 amorphous resin composition used for injection molding is PC /
ABS polymer alloy ("CYCOLOY MC5400" manufactured by Japan GE Plastics Co., Ltd.), polymer alloy ("MULTILON TN- manufactured by Teijin Kasei Co., Ltd."
3813BW ") and modified PPE resin (" Zylon 340V "manufactured by Asahi Kasei Co., Ltd.), both of which are in pellet form before molding. As a molding machine, "TUPARL TR50S2" manufactured by Sodick Plus Tech Co., Ltd. was used.

[0052]

Examples 1 to 5 A mold capable of molding a secondary battery housing model molded product having the shape shown in FIG. 1 was prepared. The molded product has a uniform wall thickness of 0.2 mm. As shown in FIG. 1, the number of gates provided on the mold was one point provided on the side surface of the secondary battery housing model molded product. The temperature of the heating cylinder of the molding machine is set to 260 ° C, and the medium temperature is set to 60, 6
The temperature of the mold was adjusted by setting the temperature to 5, 70 ° C.

Using "Psycholoy MC5400",
Carbon dioxide adjusted to an arbitrary pressure in the range of 4.2 to 6.8 MPa is supplied from a gas supply unit provided at the center of the heating cylinder of the molding machine to the amorphous resin composition in a molten state inside the heating cylinder. And mixed in the mold cavity to fill the mold cavity to obtain the secondary battery casing model molded product shown in FIG. The filling pressure during molding was the value obtained by reading the filling pressure during injection on the monitor screen of the molding machine, and the holding pressure was a value corresponding to 70% of this filling pressure. Packing time is 3
Seconds, and the cooling time was 10 seconds. The amount of deformation of the molded product was measured according to the multipoint flatness measuring method using a coordinate measuring machine "AE122 manufactured by Mitutoyo Co., Ltd." and a measurement program "Geopak 400 manufactured by the same company." The measurement location is the location indicated by 3 in FIG. Table 1 shows the measurement results of the filling pressure during injection molding and the amount of deformation of the molded product.

[0054]

[Comparative Examples 1 and 2] Temperature of the heating cylinder of the molding machine is 280,
The temperature of the mold was adjusted by setting it to 0 ° C. and setting the medium temperature to 95 ° C., and using the same mold as in Examples 1 to 5, it was provided in the center of the heating cylinder of the molding machine. Attempt to obtain the secondary battery housing model molded product shown in FIG. 1 by filling the mold cavity by the same process as the normal injection molding method without supplying carbon dioxide from the gas supply unit. However, it was not possible to fill the resin into the mold cavity without leaving the unfilled portion.

[0055]

[Comparative Example 3] The temperature of the heating cylinder of the molding machine was set to 260 ° C, and the temperature of the mold was adjusted by setting the medium temperature to 90 ° C, and the same mold as in Examples 1 to 5 was used. hand,
Carbon dioxide adjusted to 5.8 MPa was supplied from the gas supply unit provided in the center of the heating cylinder of the molding machine to the amorphous resin composition in the molten state inside the heating cylinder to mix them, and then gold was mixed. By filling the mold cavity, the secondary battery housing model molded product shown in FIG. 1 was obtained. Table 1 shows the measurement results of the filling pressure during injection molding and the amount of deformation of the molded product.

[0056]

Examples 6 to 8 A mold capable of molding an IC card model molded product having the shape shown in FIG. 2 was prepared. The reference thickness of the molded product is 0.85 mm, and a thin portion having a wall thickness of 0.15 mm is provided in the center of the molded product. As shown in FIG. 2, the number of gates provided on the mold was one on the side surface of the IC card model molded product. The temperature of the heating cylinder of the molding machine was set to 300 and 320 ° C., and the temperature of the mold was adjusted by setting the medium temperature to 70 and 75 ° C.

Using "Zylon 340V", 4.8
Carbon dioxide adjusted to MPa is supplied to the molten amorphous resin composition in 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, and then the mold is used. The IC card model molded product shown in FIG. 2 was obtained by filling the cavity. The target shape was obtained by filling the mixture of the amorphous resin composition and carbon dioxide so that the unfilled portion did not remain in the mold cavity, and the pressure holding step was omitted. The cooling time was 8 seconds.

The filling pressure during molding was the value obtained by reading the filling pressure during injection on the monitor screen of the molding machine. For 3 days after molding, the state was adjusted in a constant temperature / humidity chamber adjusted to a temperature of 23 ° C. and a humidity of 50% RH, and the deformation amount was measured using the deformation amount measuring jig shown in FIG. This deformation amount measuring jig is 1.40 mm every 0.90 mm to 0.05 mm
Prepare a jig with a gap up to
The minimum width of passing through this gap was measured by its own weight. The amount of deformation of the molded product was calculated by calculating the difference between the minimum width and the thickness of the molded product of 0.85 mm. Table 1 shows the measurement results of the filling pressure during injection molding and the deformation amount of the obtained molded product.

[0059]

[Embodiments 9 and 10] Similar to Embodiments 6 to 8, a mold capable of molding an IC card model molded product having the shape shown in Fig. 2 was prepared. Further, the temperature of the heating cylinder of the molding machine was set to 260 ° C., and the temperature of the mold was adjusted by setting the medium temperature to 65 and 70 ° C. "Multilon TN-381
3BW "is used to mix carbon dioxide adjusted to 6.8 MPa by supplying to the molten amorphous resin composition inside the heating cylinder from a gas supply unit provided in the center of the heating cylinder of the molding machine. After that, the mold cavity was filled to obtain the IC card model molded product shown in FIG.
The target shape was obtained by filling the mixture of the amorphous resin composition and carbon dioxide so that the unfilled portion did not remain in the mold cavity, and the pressure holding step was omitted. Also,
The cooling time was 8 seconds. In the same manner as in Examples 6 to 8, the filling pressure during molding and the amount of deformation of the molded product were measured. Table 2 shows the measurement results
Shown in.

[0060]

Comparative Example 4 Similar to Examples 6 to 8, a mold capable of molding an IC card model molded product having the shape shown in FIG. 2 was prepared. The temperature of the heating cylinder of the molding machine was 320 ° C., and the temperature of the mold was adjusted by setting the medium temperature to 85 ° C. 4.8 using "Zylon 340V"
Carbon dioxide adjusted to MPa is supplied to the molten amorphous resin composition in 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, and then the mold is used. The IC card model molded product shown in FIG. 2 was obtained by filling the cavity. The target shape was obtained by filling the mixture of the amorphous resin composition and carbon dioxide so that the unfilled portion did not remain in the mold cavity, and the pressure holding step was omitted. The cooling time was 8 seconds. In the same manner as in Examples 6 to 8, the filling pressure during molding and the amount of deformation of the molded product were measured. The measurement results are shown in Table 2.

[0061]

COMPARATIVE EXAMPLE 5 Similar to Examples 6 to 8, a mold capable of molding an IC card model molded product having the shape shown in FIG. 2 was prepared. Further, the temperature of the heating cylinder of the molding machine was set to 260 ° C, and the temperature of the mold was adjusted by setting the medium temperature to 85 ° C. Using "MULTILON TN-3813BW", the same process as the ordinary injection molding method in which carbon dioxide is not supplied from the gas supply part provided in the heating cylinder center of the molding machine is shown in FIG. An attempt was made to obtain an IC card model molded product, but it was not possible to fill the resin into the mold cavity so as not to leave an unfilled portion.

[0062]

COMPARATIVE EXAMPLE 6 Similar to Examples 6 to 8, a mold capable of molding an IC card model molded product having the shape shown in FIG. 2 was prepared. Further, the temperature of the heating cylinder of the molding machine was set to 260 ° C, and the temperature of the mold was adjusted by setting the medium temperature to 80 ° C. Carbon dioxide adjusted to 6.8 MPa using "MULTILON TN-3813BW" is supplied from a gas supply unit provided in the center of the heating cylinder of the molding machine to the amorphous resin composition in a molten state inside the heating cylinder. And mixed in the mold cavity to obtain the IC card model molded product shown in FIG. The target shape was obtained by filling the mixture of the amorphous resin composition and carbon dioxide so that the unfilled portion did not remain in the mold cavity, and the pressure holding step was omitted. The cooling time was 8 seconds. In the same manner as in Examples 6 to 8, the filling pressure during molding and the amount of deformation of the molded product were measured. The measurement results are shown in Table 2.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

INDUSTRIAL APPLICABILITY The present invention does not impair the degree of freedom in designing a thin-walled molded product itself having a minimum thickness of 0.5 mm or less, limits the average molecular weight of the thermoplastic resin, the resin composition, and complicates the mold structure. Without increasing the resin temperature and injection speed during injection molding more than necessary, the dimensional accuracy of thin-walled molded products,
It makes it possible to improve productivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a secondary battery housing model molded product.

[Figure 2] Schematic diagram of IC card model molded product

FIG. 3 is a schematic diagram of a deformation amount measuring jig.

[Explanation of symbols]

1 Secondary battery housing model molded product 2 gates 3 Deformation amount measurement surface 4 IC card model molded products 5 Thin part 6 Deformation amount measurement jig 7 gap

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 101: 00 C08L 101: 00 F term (reference) 4F074 AA13 AA70 AA77 BA32 CA26 CC04Y CC32Y CC34 CC34Y DA19 DA22 DA24 DA47 4F202 AB18 AR03 AR06 CA11 CB01 CK11 CN01 CN05 4F206 AA28 AA32 AB07 AB15 AG20 AG21 AH42 AM34 AM35 AR02 AR065 JA04 JA07 JE30 JF04 JF06 JF46 JL02 JN16 JN27 JN43 JQ81 5H011 AA00 BB03 CC02 DD03 KK00

Claims (13)

[Claims] 1. A thin-walled molded article made of an amorphous resin composition having at least a portion having a minimum wall thickness of 0.5 mm or less, and the amorphous resin composition in a molten state. And a carbon dioxide mixture pressurized at atmospheric pressure or higher to a mold cavity adjusted to a temperature lower by 20 ° C. or more than the heat deformation temperature of the amorphous resin. Thin-walled molded product. 2. It is obtained by filling a mold cavity with a mixture of the amorphous resin composition in a molten state and carbon dioxide pressurized at atmospheric pressure or more and 7 MPa or less. The thin-walled molded product according to claim 1. 3. The thin-walled molded product according to claim 1, which has a portion having a minimum wall thickness of 0.2 mm or less. 4. The thin-walled molded article according to claim 1, which is a casing of a secondary battery. 5. The thin-walled molded article according to claim 1, wherein the thin-walled molded article is a housing of a storage medium. 6. The amorphous resin composition according to any one of claims 1 to 5, wherein the amorphous resin composition is a modified polyphenylene ether resin containing at least a polyphenylene ether component. Molding. 7. The thin-walled molded product of the amorphous resin composition according to claim 1, wherein the amorphous resin composition is a polycarbonate resin containing at least a polycarbonate component. 8. A thin-walled molded article has a foamed portion inside,
The thin-walled molded product according to any one of claims 1 to 7, wherein the surface layer portion has a non-foamed layer that is not substantially foamed. 9. The amorphous according to claim 1, wherein the thin molded product has an apparent specific gravity of 95 to 99.5% of the specific gravity of the amorphous resin composition. Thin-walled molded product made of resin composition. 10. The injection molding method comprises mixing a molten amorphous resin composition with carbon dioxide pressurized at atmospheric pressure or higher in a heating cylinder of a molding machine, and then mixing the amorphous resin. The injection molding method for a thin-walled molded article according to claim 1, wherein the thin-walled molded article is obtained by filling a mold cavity adjusted to a temperature lower than the heat distortion temperature of 20 ° C. by 20 ° C. or more. 11. The method of injection molding comprises mixing a molten amorphous resin composition with carbon dioxide pressurized at a pressure of not less than atmospheric pressure and not more than 7 MPa in a heating cylinder of a molding machine. The thin-walled molded article according to claim 1 or 2, wherein a thin-walled molded article is obtained by filling a mold cavity adjusted to a temperature lower than the heat distortion temperature of the crystalline resin by 20 ° C or more. Method. 12. A thin-walled molded article is obtained by filling a mixture of an amorphous resin composition and carbon dioxide into a mold cavity adjusted or held at an atmospheric pressure or higher and 15 MPa or lower. Item 12. An injection molding method for a thin-walled molded article according to item 10 or 11. 13. A thin-walled molding comprising a step of filling a mold cavity with a mixture of an amorphous resin composition and carbon dioxide, and then pressurizing and holding the resin with a pressure that is 30% or more of the filling pressure. An injection molding method for a thin-walled molded product according to any one of claims 10 to 12, wherein a product is obtained.