JP7543966B2 - Manufacturing method of foamed molded article - Google Patents

Description

The present invention relates to a method for producing a foam molded article in which a surface layer of an insert film is formed on the foam molded part by injection foam molding a polycarbonate resin composition in a mold loaded with an insert film.

Polycarbonate resins are resins with excellent heat resistance, mechanical properties, and electrical properties, and are widely used, for example, in automobile materials, electrical and electronic equipment materials, housing materials, and materials for manufacturing parts in other industrial fields, etc. In particular, they are suitably used as parts for electrical and electronic equipment such as computers, notebook personal computers, various portable terminals, printers, copiers, and office automation and information equipment.
In recent years, these devices have been rapidly becoming smaller and lighter, and foam molding methods are being adopted to reduce the amount of resin used and make them lighter.

As the foam molding method, there are methods using chemical foaming agents and physical foaming agents, but the chemical foaming method is expensive because it uses a foaming agent, and has problems such as discoloration of the foam and odor generation due to decomposition residues of the foaming agent remaining in the foam, and contamination of the molding machine by the chemical foaming agent.
On the other hand, the gas foaming method using a physical foaming agent is a method in which a resin is melted in a molding machine, a low-boiling organic compound such as butane is fed and kneaded, and then released into a low-pressure region to foam and mold the resin. The low-boiling organic compound used in this method has an affinity for the resin, so it has excellent solubility and can produce a foam with a high expansion ratio. However, these foaming agents are expensive, and the low-boiling organic compound has dangers such as flammability.

To solve these problems, a method has been proposed in which inert gases such as nitrogen gas and carbon dioxide gas, which are clean and inexpensive among physical foaming agents, are used as the foaming agent. However, these inert gases have low affinity with resins as they are, and therefore poor solubility. The resulting foam has large, non-uniform air bubbles and a low cell density, resulting in problems with appearance and mechanical strength.

Patent Document 1 describes a technique for obtaining a foam having extremely fine cell diameters and large cell density by using a supercritical fluid as a foaming agent and impregnating the resin with the supercritical fluid. The foam molding method using a supercritical fluid as a foaming agent is a fine foam molding technique also called MuCell (registered trademark), in which a supercritical fluid is dissolved in a molten resin under high pressure, which is fed to a molding machine, and a molded product having fine foam cells is obtained by rapid decompression.
According to such supercritical foam molding, since a supercritical fluid has excellent solubility close to that of a liquid and excellent diffusivity close to that of a gas, it has high solubility in a resin and also has a high diffusion rate in the resin, so that it is possible to impregnate the foaming agent into the resin in a short period of time.

By the way, injection foam molding can cause streaky appearance defects called swirl marks. These are marks left by bubbles that form at the end of the molten resin flow and burst, stretching out on the surface of the molded product. In injection foam molding, countless bubbles are generated, causing streaks to form all over the surface of the molded product.

To address this problem, in order to smooth the surface and improve the appearance, a method has been proposed in which a decorative layer is provided on the surface by film insert molding or the like, as described in Patent Documents 2 and 3. This method produces a foamed molded article having a surface layer formed by an inserted film.
In this case, however, the non-foamed layer becomes thicker due to the presence of the film layer on the surface, and in a thin molded product or one with a large weight reduction rate of the foamed layer, the proportion of the non-foamed layer becomes large in both weight and volume, resulting in a molded product with little weight reduction effect and little heat insulation effect.
In particular, when a thick film is inserted, the proportion of the film in the entire molded article increases, and the weight reduction effect and heat insulation effect are significantly impaired.

By making the thickness of the inserted film thin, for example 150 μm or less, it is believed that the proportion of the film in the entire molded product can be reduced, making it possible to suppress a decrease in the weight reduction effect and the heat insulating effect.
However, the inventors' research revealed that when a thin film is used, even if the insert film is made of the same resin system as the foam molded portion of the main body, the adhesion between the insert film and the foam molded portion is poor, and a new problem occurs in that the surface layer of the film is easily peeled off.

U.S. Pat. No. 5,158,986 Special Publication No. 2004-523375 JP 2004-98459 A

The present invention aims to solve the problems of the conventional technology and provide a method for producing a foam molded article that can obtain a foam molded article having high adhesion between the foam molded part and the surface layer formed by the insert film when a thin insert film that has little effect on the weight reduction effect and heat insulation effect of the foam molding is used in injection foam molding of a polycarbonate resin composition using an insert film.

As a result of various investigations to solve the above problems, the inventors discovered that adhesion can be improved by setting the surface temperature of the insert film during injection foam molding to specific conditions, and thus arrived at the present invention.
That is, the present invention relates to the following.

[1] A method for producing a foam molded article in which a foam molded part and a surface layer made of the insert film are integrally molded by injection foam molding a molten polycarbonate resin composition (A) in a mold filled with an insert film, the method comprising using a film having a thickness of 50 to 150 μm and an adhesive surface made of polycarbonate resin composition (B) as the insert film, setting the injection foam molding temperature of the polycarbonate resin composition (A) to (300 + a) ° C (where a is a number from -20 to 40), and setting the surface temperature of the insert film to a predetermined temperature of (90 - a) ° C or higher and lower than the glass transition temperature (Tg) of the polycarbonate resin composition (B), and performing injection foam molding.

[2] A method for producing a foam molded article according to [1], characterized in that injection foam molding is performed using a volatile foaming agent, an inorganic foaming agent, or a decomposition type foaming agent.

[3] The method for producing the foamed molded article described in [2], characterized in that supercritical or subcritical injection foam molding is carried out using nitrogen, carbon dioxide, or a mixture thereof in a supercritical or subcritical state as the inorganic foaming agent.

[4] The method for producing a foamed molded article according to any one of [1] to [3], characterized in that the insert film is loaded so as to be in contact with the mold surface.

According to the present invention, when injection foam molding of a polycarbonate resin composition using an insert film is performed, the temperature is controlled so that the surface temperature of the insert film satisfies specific conditions relative to the injection foam molding temperature of the polycarbonate resin composition. This makes it possible to obtain a foam molded product with high adhesion between the foam molded part and the surface layer formed by the insert film, while using a thin insert film that has little effect on the weight reduction effect and heat insulation effect of the foam molding.

FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a method for producing a foamed molded article of the present invention.

The following describes in detail the embodiments of the present invention.

The method for producing a foam molded article of the present invention is a method for producing a foam molded article in which a foam molded part and a surface layer made of the insert film are integrally molded by injection foam molding a molten polycarbonate resin composition (A) in a mold filled with an insert film (B), characterized in that the insert film is a film made of polycarbonate resin composition (B) and having a thickness of 50 to 150 μm, the injection foam molding temperature of the polycarbonate resin (A) is set to (300 + a) ° C (where a is a number from -20 to 40), and the surface temperature of the insert film is set to a predetermined temperature of (90 - a) ° C or higher and lower than the glass transition temperature (Tg) of the polycarbonate resin composition (B).

Specifically, as shown in Figures 1(a) and (b), a 50-150 μm thick insert film 2 made of a polycarbonate resin composition (B) is loaded onto the mold surface of one of the molds 1A and 1B (mold 1A in Figure 1(a)), and then the molds are clamped to inject a molten resin 3 of the polycarbonate resin composition (A) into the cavity of the molds 1A and 1B by foam molding. This results in a foam molded product 10 in which a surface layer 2A made of the insert film and a foam molded portion 3A of the polycarbonate resin layer (A) are laminated together, as shown in Figure 1(b). 3a in Figure 1(b) is a skin layer (a non-foamed layer formed near the mold in injection foam molding) formed on both surface layers of the foam molded portion 3A.
The compositions of the polycarbonate resin compositions (A) and (B) used in the present invention will be described later.

In the present invention, in such injection foam molding, the injection foam molding temperature of the polycarbonate resin composition (A) is set to (300+a)°C (where a is a number between -20 and 40), and the surface temperature of the insert film is set to a predetermined temperature of (90-a)°C or higher and lower than the Tg of the polycarbonate resin composition (B).

[Injection foam molding conditions]
When the injection foam molding temperature of the polycarbonate resin composition (A) (here, the injection foam molding temperature is the temperature of the molten resin injected from the cylinder of the injection molding machine during injection foam molding) exceeds 340°C (i.e., a exceeds 40 and 300 + a exceeds 340), the resin components such as the polycarbonate resin in the polycarbonate resin composition (A) deteriorate, causing problems such as yellowing of the foam molded part that is formed, and it is not possible to obtain a high-quality foam molded product.
If the injection foam molding temperature is lower than 280°C (i.e., a is less than -20 and 300+a is less than 280), a foam molded product with excellent adhesion of the surface layer by the insert film cannot be obtained. Therefore, the injection foam molding temperature is set to (300+a)°C (where a is a number from -20 to 40), that is, 340 to 280°C, preferably 330 to 290°C.

In addition, if the surface temperature of the insert film in the mold during injection foaming is too low, it is not possible to obtain a foamed molded product with excellent adhesion of the surface layer due to the insert film, and at high temperatures exceeding Tg, the product becomes easily deformed when loaded into the mold, which may cause damage. In addition, the product also becomes above Tg, making it easy to deform and difficult to remove.
For this reason, the surface temperature of the insert film during injection foam molding is set to a predetermined temperature that is not lower than (90-a)° C. and not higher than the Tg of the polycarbonate resin composition (B).

As a method for adjusting the surface temperature of the insert film to the above-mentioned predetermined temperature,
1. A method of heating the mold during injection and dwell pressure during injection molding, and adjusting the surface temperature of the insert film by heating from the mold. 2. A method of directly heating the insert film without using a mold. Either one or both of the above methods 1 and 2 can be used.

Specifically, in the above method 1, when the mold temperature exceeds 120°C, the product is easily deformed and difficult to remove, so in order to implement this, the mold temperature is instantaneously raised during the injection and pressure-holding process and instantly returned to the cooling temperature during the cooling process. As for the heating and cooling means, there are a method of switching between a heat medium and a refrigerant, and a method of directly heating the mold where the insert film is attached.
Methods for instantly switching between heat transfer media and refrigerants include switching between pressurized hot water and cold water, steam and cold water, or heating oil and cooling oil. Methods for directly heating the mold where the insert film is attached include high-frequency induction heating the part of the mold where the insert film comes into contact, heating with a heater embedded in the mold, and providing a conductive layer on the surface of the mold and heating by passing electricity through this conductive layer.

Method 2 above includes heating the insert film with radiant heat such as infrared rays or hot air while the mold is open, or warming the insert film with a heated roller, etc.

The surface temperature of the insert film during injection foam molding can be checked using a temperature sensor inserted into the mold.

In the present invention, there are no particular limitations on the injection foam molding method, and the following methods can be used, for example:

A foaming agent is mixed or dissolved in molten resin in an injection molding machine, and the resin is foamed and filled into the mold when injection molding is performed into a mold with an insert film inserted. Methods that can be used include (1) the short shot method, in which an amount of resin smaller than the cavity capacity is injected, air bubbles are generated by the reduced pressure during injection, and the air bubbles expand to fill the cavity; and (2) the core back method, in which a mold with a variable cavity capacity is used and an amount of resin equal to the cavity capacity is injected, and the cavity volume is expanded after filling to generate and expand air bubbles, resulting in a foamed molded product.

The blowing agent used may be any of volatile blowing agents, inorganic blowing agents, and decomposition type blowing agents. Volatile blowing agents include lower aliphatic hydrocarbon compounds such as n-butane, i-butane, n-pentane, i-pentane, and hexane; alicyclic hydrocarbon compounds such as cyclobutane and cyclopentane; aromatic hydrocarbon compounds such as benzene, toluene, and xylene; lower aliphatic monohydric alcohol compounds such as methanol and ethanol; lower aliphatic ketone compounds such as acetone and methyl ethyl ketone; and low-boiling halogenated hydrocarbon compounds such as chloromethyl, chloroethyl, and 1-chloro-1,1-difluoroethane. Inorganic blowing agents include nitrogen and carbon dioxide in a gaseous, supercritical, or subcritical state; and water.

Examples of decomposition type foaming agents include azo compounds such as barium azocarboxylate and azodicarbonamide, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, hydrazine compounds such as hydrazocarbonamide, and bicarbonates such as sodium bicarbonate.

Of these, supercritical or subcritical nitrogen, carbon dioxide or a mixture thereof is preferred.
The foaming agents may be used alone or in combination of two or more kinds.
The amount of the foaming agent used can be appropriately determined depending on the type of foaming agent and the desired expansion ratio, but is preferably 0.1 to 20 parts by mass of the foaming agent per 100 parts by mass of the polycarbonate resin.

As the injection foam molding method in the present invention, supercritical injection foam molding is preferred from the viewpoint of production efficiency in particular.
The gas used for the supercritical fluid is preferably nitrogen gas or carbon dioxide gas.
The supercritical injection foam molding can be performed using the short shot method, the core back method, etc. All of these methods have in common that a supercritical fluid is injected into a cylinder when measuring the resin and dissolving it, but the foaming process is different.
The generation of bubble nuclei is achieved by reducing the pressure in the mold to a pressure equal to or lower than the critical pressure of nitrogen or carbon dioxide, thereby causing the nitrogen or carbon dioxide to become supersaturated, and a large number of cell nuclei are generated in the supersaturated molten resin composition.

Specific examples of supercritical injection foam molding are as follows:

First, pellets of the polycarbonate resin composition (A) are fed from the hopper of the injection molding machine into the molding machine, heated and melted in the conveying zone and compression zone of the molding machine screw, and then sent to the metering zone and compression zone of the molding machine screw. Then, nitrogen or carbon dioxide gas made into a supercritical fluid is injected from an inlet provided in the metering zone, and this supercritical fluid and molten resin are pressurized and made into a single phase, injected from the nozzle of the injection molding machine, and flowed through the sprue and runner while maintaining a single phase, and sent to the mold cavity in which the insert film has been previously loaded. After passing through the gate, bubble nuclei are generated, and the bubbles expand as they fill the mold, thereby performing supercritical injection foam molding. Here, the generation of bubble nuclei is achieved when the pressure in the mold drops to a pressure below the critical pressure of nitrogen or carbon dioxide, causing the nitrogen or carbon dioxide to become supersaturated, and a large number of cell nuclei are generated in the molten resin composition in the supersaturated state.

As the injection foam molding conditions, usual conditions can be adopted. For example, the injection speed of the polycarbonate resin composition (A) is usually 10 to 150 mm/sec, pressure holding during mold clamping is not required, and the mold is completely filled by the pressure caused by foaming.
The surface temperature of the film can be set to the target temperature by controlling the mold temperature. However, it may be close to the Tg of the injected resin, or may exceed the Tg if the molten resin temperature is low. Therefore, it is desirable to use a method in which the mold temperature is heated only during injection and pressure holding, and is lower than the Tg during cooling, by using heating and cooling of the mold in accordance with the molding process, or by heating only the film immediately before injection.

[Polycarbonate resin composition (A)]
The polycarbonate resin composition (A) used in the present invention is not particularly limited.
The polycarbonate resin composition (A) is not limited to a composition in which other components are blended with a polycarbonate resin, and may be a polycarbonate resin alone. The polycarbonate resin composition (A) preferably contains 80% by mass or more, particularly 85 to 100% by mass of a polycarbonate resin, since the effects of the present invention are effectively exhibited.

<Polycarbonate resin>
Examples of the polycarbonate resin contained in the polycarbonate resin composition (A) include aromatic polycarbonate resins, aliphatic polycarbonate resins, and aromatic-aliphatic polycarbonate resins. An aromatic polycarbonate resin is preferred. Specifically, a thermoplastic aromatic polycarbonate polymer or copolymer obtained by reacting an aromatic dihydroxy compound with phosgene or a diester of carbonic acid is used.

Examples of aromatic dihydroxy compounds include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), tetramethylbisphenol A, α,α'-bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, and 4,4'-dihydroxydiphenyl. In order to improve flame retardancy, a compound in which one or more tetraalkylphosphonium sulfonates are bonded to the aromatic dihydroxy compounds described above, a polymer containing phenolic OH groups at both ends and having a siloxane structure, or an oligomer thereof may also be used.

Preferred examples of polycarbonate resins include polycarbonate resins that use 2,2-bis(4-hydroxyphenyl)propane as a dihydroxy compound or 2,2-bis(4-hydroxyphenyl)propane in combination with other aromatic dihydroxy compounds.

The polycarbonate resin may be a homopolymer consisting of one type of repeating unit, or a copolymer having two or more types of repeating units. In this case, the copolymer may be of various copolymer forms, such as a random copolymer or a block copolymer.

There are no restrictions on the molecular weight of the polycarbonate resin, but the viscosity average molecular weight (Mv) calculated from the solution viscosity measured at 20°C using methylene chloride as a solvent is preferably 10,000 to 40,000, more preferably 14,000 to 32,000. If the viscosity average molecular weight is in this range, the resulting resin composition has good moldability in supercritical foam molding, and molded products with high mechanical strength are easily obtained. The most preferred molecular weight range for polycarbonate resin is 16,000 to 30,000.

In the present invention, the viscosity average molecular weight (Mv) of a polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 20° C. using an Ubbelohde viscometer, and then calculating the intrinsic viscosity from the following Schnell viscosity formula:
[η]=1.23×10 ⁻⁴ Mv ^0.83

The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resin produced by either the phosgene method (interfacial polymerization method) or the melting method (ester exchange method) can be used. Also preferred is polycarbonate resin produced by the melting method, which has been subjected to post-treatment to adjust the amount of OH groups at the terminals.

The polycarbonate resin may also contain a polycarbonate oligomer. The viscosity average molecular weight [Mv] of this polycarbonate oligomer is usually 1,500 or more, preferably 2,000 or more, and usually 9,500 or less, preferably 9,000 or less. Furthermore, it is preferable that the polycarbonate oligomer contained is 30% by mass or less of the polycarbonate resin (including the polycarbonate oligomer).

In addition, polycarbonate resin can be made not only from virgin raw materials, but also from aromatic polycarbonate resins recycled from used products, so-called material recycled aromatic polycarbonate resins. Preferred examples of used products include optical recording media such as optical disks, light guide plates, automobile window glass, automobile headlamp lenses, transparent vehicle components such as windshields, containers such as water bottles, eyeglass lenses, soundproof walls, glass windows, corrugated sheets, and other building components. In addition, crushed products obtained from non-conforming products, sprues, or runners, or pellets obtained by melting these can also be used as recycled polycarbonate resins.

<Other ingredients>
The polycarbonate resin composition (A) may contain, in addition to the polycarbonate resin, other thermoplastic resins other than the polycarbonate resin and additives.

Other thermoplastic resins include polyester resins, polyamide resins, polyolefin resins, polyphenylene ether resins, styrene resins, polysulfones, polyethersulfones, polyphenylene sulfides, polyacrylates, polyamideimides, polyetherimides, etc.

Examples of polyester resins include polybutylene terephthalate, polyethylene terephthalate, polybutylene naphthalate, and polyethylene naphthalate. Examples of polyolefin resins include polyethylene and polypropylene. Examples of polyphenylene ether resins include polyphenylene ether resins and mixed resins of polyphenylene ether and polystyrene and/or HIPS (high impact polystyrene). Examples of styrene resins include polystyrene, HIPS, AS resin, and ABS resin.

In addition, various additives, such as ultraviolet absorbers, antioxidants, stabilizers such as heat stabilizers, pigments, dyes, lubricants, flame retardants, anti-dripping agents, release agents, and sliding improvers, can be blended into the polycarbonate resin composition (A) as necessary to obtain the desired physical properties.

(Antioxidants)
The antioxidant includes hindered phenol-based antioxidants.

When an antioxidant is contained in the polycarbonate resin composition (A), the amount of the antioxidant is usually 0.001 to 1 part by mass, and preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the antioxidant is less than 0.001 part by mass, the antioxidant effect is insufficient, and if it exceeds 1 part by mass, the effect will plateau and it will be uneconomical.

(Heat stabilizer)
The heat stabilizer may be at least one selected from the group consisting of a phosphite compound in which at least one ester in the molecule is esterified with phenol and/or a phenol having at least one alkyl group having 1 to 25 carbon atoms, phosphorous acid, and tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene-di-phosphonite.

When a heat stabilizer is contained in the polycarbonate resin composition (A), the amount of the heat stabilizer is usually 0.001 to 1 part by mass, and preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the heat stabilizer is less than 0.001 part by mass, the effect as a heat stabilizer is insufficient, and if it exceeds 1 part by mass, hydrolysis resistance may deteriorate.

(Release Agent)
The releasing agent may be at least one compound selected from the group consisting of aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds having a number average molecular weight of 200 to 15,000, and polysiloxane-based silicone oils.

When a release agent is contained in the polycarbonate resin composition (A), the amount of the release agent is usually 0.001 to 2 parts by mass, and preferably 0.01 to 1 part by mass, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the release agent is less than 0.001 parts by mass, the release effect may not be sufficient, and if it exceeds 2 parts by mass, problems such as reduced hydrolysis resistance and mold contamination during injection foam molding may occur.

(Ultraviolet absorber)
Specific examples of the ultraviolet absorbing agent include inorganic ultraviolet absorbing agents such as cerium oxide and zinc oxide, as well as organic ultraviolet absorbing agents such as benzotriazole compounds, benzophenone compounds and triazine compounds.

When the polycarbonate resin composition (A) contains an ultraviolet absorber, the amount of the ultraviolet absorber is usually 0.01 to 3 parts by mass, and preferably 0.1 to 1 part by mass, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the ultraviolet absorber is less than 0.01 parts by mass, the effect of improving weather resistance may be insufficient, and if it exceeds 3 parts by mass, problems such as mold deposits may occur.

(dyes and pigments)
The dyes and pigments include inorganic pigments, organic pigments, and organic dyes.

When a dye or pigment is contained in the polycarbonate resin composition (A), the amount of the dye or pigment is usually 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 12 parts by mass or less, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the dye or pigment exceeds 20 parts by mass, the impact resistance may be insufficient.

Among inorganic pigments, carbon black also functions as an inorganic conductive substance. When carbon black is used as an inorganic conductive substance, as mentioned above, the amount of carbon black blended can be set to be greater than the amount blended as a dye pigment.

(Flame retardant)
Examples of the flame retardant include halogen-based flame retardants such as halogenated bisphenol A polycarbonate, brominated bisphenol epoxy resin, brominated bisphenol phenoxy resin, and brominated polystyrene; phosphate-based flame retardants; organometallic salt-based flame retardants such as dipotassium diphenylsulfone-3,3'-disulfonate, potassium diphenylsulfone-3-sulfonate, and potassium perfluorobutanesulfonate; and polyorganosiloxane-based flame retardants. Phosphate-based flame retardants are particularly preferred.

When a flame retardant is contained in the polycarbonate resin composition (A), the amount of the flame retardant is usually 1 to 30 parts by mass, preferably 3 to 25 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the flame retardant is less than 1 part by mass, the flame retardancy may be insufficient, and if it exceeds 30 parts by mass, the heat resistance may decrease.

(Anti-drip agent)
Examples of the anti-dripping agent include fluorinated polyolefins such as polyfluoroethylene, and polytetrafluoroethylene, which has fibril-forming ability, is particularly preferred.

When the polycarbonate resin composition (A) contains an anti-dripping agent, the amount of the anti-dripping agent is usually 0.02 to 4 parts by mass, and preferably 0.03 to 3 parts by mass, per 100 parts by mass of the polycarbonate resin in the polycarbonate resin composition (A). If the amount of the anti-dripping agent exceeds 5 parts by mass, the appearance of the molded product obtained by molding the obtained CF/PC pellets may deteriorate.

<Method for producing polycarbonate resin composition (A)>
There is no limitation on the method for producing the polycarbonate resin composition (A), and any of the known methods for producing thermoplastic resin compositions can be widely used.
A specific example includes a method in which the polycarbonate resin and other components to be blended as necessary are premixed using various mixers such as a tumbler or a Henschel mixer, and then the mixture is melt-kneaded using a mixer such as a Banbury mixer, a roll, a Brabender, a single-screw kneading extruder, a twin-screw kneading extruder, or a kneader.

In addition, for example, the thermoplastic resin composition of the present invention can be produced by not mixing the components in advance, or by mixing only some of the components in advance, feeding the mixture to an extruder using a feeder, and melt-kneading the mixture.
In addition, for example, a portion of the components may be mixed in advance, fed to an extruder, and melt-kneaded to obtain a resin composition, which may be used as a masterbatch. The masterbatch may then be mixed again with the remaining components and melt-kneaded to produce the polycarbonate resin composition (A).
In addition, for example, when mixing a component that is difficult to disperse, the dispersibility can be improved by dissolving or dispersing the component in advance in a solvent such as water or an organic solvent, and then kneading the component with the solution or dispersion.

[Polycarbonate resin composition (B)]
The polycarbonate resin composition (B) constituting the adhesive surface of the insert film used in the present invention is not particularly limited, but from the viewpoint of adhesion, it is preferable to use one having the same composition as the polycarbonate resin composition (A).

[Insert film]
In the present invention, an insert film having a thickness of 50 to 150 μm is used as the insert film made of the polycarbonate resin composition (B). If the thickness of the insert film is less than 50 μm, the mechanical strength is insufficient and there is a risk of breakage during handling. There is also a possibility of air bubbles being introduced during molding. In addition, such a thin film is not preferable as a surface layer of a foam molded product for improving surface smoothness. In the case of an insert film having a thickness of more than 150 μm on one side, adhesion can be obtained without adopting the present invention.
For this reason, in the present invention, an insert film having a thickness of 50 to 150 μm, preferably 80 to 120 μm, is used.

Such an insert film can be produced using the polycarbonate resin composition (B) by conventional methods, such as T-die molding.

The surface of the insert film opposite to the injection molding surface (the surface onto which the polycarbonate resin composition (A) is injected) may have a hard coat layer or a decorative layer formed thereon as required, or may have decorative printing or the like applied thereto.

As the hard-coating agent for forming the hard-coating layer, a known material can be appropriately used, and various hard-coating agents such as silicone-based, acrylic-based, silazane-based, and urethane-based agents can be used. In order to improve adhesion and weather resistance, a two-coat type hard-coating agent may be used in which a primer layer is provided before applying the hard-coating agent. There is no particular limitation on the coating method of the hard-coating agent, and it can be applied by any coating method such as spray coating, dip coating, flow coating, spin coating, bar coating, curtain coating, die coating, gravure coating, roll coating, blade coating, and air knife coating. The insert film may be a film whose adhesive surface side is made of a laminate of a polycarbonate resin composition and another resin, and examples of such laminates include laminates formed by co-extrusion molding of acrylic resin and different types of polycarbonate resin compositions.

The thickness of the hard coat layer is preferably 1 to 50 μm, more preferably 5 to 30 μm.

[Foam molded product]
The foam molded article produced by the foam molded article producing method of the present invention (hereinafter sometimes referred to as the "foam molded article of the present invention") has high adhesion of the surface layer formed by the insert film and is excellent in durability.
There are no particular limitations on the expansion ratio of the foam molded portion of the foam molded product of the present invention, or the shape, dimensions, color, surface decoration, etc. of the foam molded product, which may be arbitrarily set according to the application, but the foam molded product of the present invention is effective for thin-walled foam molded products in which the surface layer of the insert film has a large effect on the weight reduction and heat insulation properties of the foam molded product. Examples of such products include thin-walled foam molded products having an overall thickness of 5 mm or less, for example, about 1.5 to 3.0 mm, particularly thin-walled foam molded sheets and films.

There are no particular limitations on the uses of such foamed molded articles of the present invention, and they can be used in a variety of parts, such as electrical and electronic devices, office automation equipment, information terminal devices, machine parts, home appliances, vehicle parts, building materials, various containers, and lighting equipment.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and can be modified as desired without departing from the gist of the present invention.

In the following, the following polycarbonate resins were used for injection molding and insert films.
Polycarbonate resin for injection molding: Bisphenol A type polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation, product name: Iupilon (registered trademark) S-2000R)
Viscosity average molecular weight (Mv): 23,000
Tg = 145 ° C.
Polycarbonate resin for insert film: Bisphenol A type polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation, product name: Iupilon (registered trademark)
E-2000)
Viscosity average molecular weight (Mv): 26,000
Tg = 145 ° C.

[Example 1]
Polycarbonate resin pellets for injection molding were pre-dried at 120°C for 6 to 12 hours, and nitrogen was made into a supercritical state using a MuCell SCF device (model: T-100J) manufactured by Trexel Corporation. A predetermined amount of nitrogen was then injected into the cylinder of a J100ADS injection molding machine manufactured by Japan Steel Works, Ltd., mixed with the molten resin, and injected into a mold in which an insert film (thickness: 100 μm) had been previously loaded. Supercritical foam molding was performed by the short shot method, and a foam molded product with a wall thickness of 2 mm (including the surface layer of the insert film), length of 80 mm, and width of 80 mm was obtained.
The molding conditions were as follows: nitrogen inflow amount 0.3 mass %, weighing 53 mm, injection time 1.3 seconds, and no pressure holding step.

At this time, the molten resin temperature (cylinder temperature), i.e., the injection foam molding temperature, was 300°C, and the mold temperature was 100°C, and the surface temperature of the insert film inside the mold was 96°C.

The obtained foam molded article was cut with a cutter knife so that the surface film layer penetrated to a width of 15 mm, and the end of the surface layer was released in advance, and then the end of the surface layer was gripped with a gripping jig for tensile testing, and the gripping jig was pulled using a push-pull gauge to perform a 90° peel test between the surface layer of the insert film and the foam molded part, and the peel strength was examined. The results are shown in Table 1.
This peel strength is preferably 5 N/15 mm or more.

[Examples 2 to 3, Comparative Examples 1 and 2]
A foam molded article was obtained in the same manner as in Example 1, except that the injection foam molding temperature and mold temperature during injection foam molding were changed to the temperatures shown in Table 1, and the surface temperature of the insert film during injection foam molding was changed to the temperature shown in Table 1. A peel test was also performed in the same manner, and the results are shown in Table 1.

[Reference Examples 1 to 3]
A foam molded article was obtained in the same manner as in Example 1, except that the thickness of the insert film was 200 μm, the injection foam molding temperature and mold temperature during injection foam molding were changed to the temperatures shown in Table 1, and the surface temperature of the insert film during injection foam molding was changed to the temperature shown in Table 1. A peel test was also performed in the same manner, and the results are shown in Table 1.

The following can be seen from Table 1.
In Comparative Examples 1 and 2, which are outside the range of the present invention and in which the film surface temperature is lower than (90-a)° C., the peel strength is extremely low and no adhesion of the surface layer is obtained.
In contrast to this, in Examples 1 to 3 in which the film surface temperature was set to (90-a)° C. or higher, high adhesion was obtained.
In addition, in Reference Examples 1 to 3 in which the insert film had a thickness of 200 μm, high adhesion was obtained regardless of the film surface temperature.

Reference Signs List 1A, 1B Mold 2 Insert film 2A Surface layer 3 Molten resin 3A Foam-molded part 10 Foam-molded body

Claims (4)

A method for producing a foam-molded article in which a foam-molded part and a surface layer made of an insert film are integrally molded by injection foam-molding a molten polycarbonate resin composition (A) in a mold containing an insert film, comprising the steps of:
As the insert film, a film having a thickness of 50 to 150 μm and having an adhesive surface made of a polycarbonate resin composition (B) is used,
The method for producing a foam molded article is characterized in that the injection foam molding temperature of the polycarbonate resin composition (A) is set to (300+a)°C (wherein a is a number from -20 to 40) and the surface temperature of the insert film is set to a predetermined temperature that is not lower than (90-a)°C and not higher than the glass transition temperature (Tg) of the polycarbonate resin composition (B), and the injection foam molding is performed. The method for producing the foam molded article according to claim 1, characterized in that injection foam molding is performed using a volatile foaming agent, an inorganic foaming agent, or a decomposition type foaming agent. The method for producing a foamed molded article according to claim 2, characterized in that supercritical or subcritical injection foam molding is carried out using nitrogen, carbon dioxide or a mixture thereof in a supercritical or subcritical state as the inorganic foaming agent. 4. The method for producing a foamed molded article according to claim 1, wherein the insert film is loaded so as to be in contact with the mold surface.

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