JP5479772B2 - Foam molded body and method for producing the same - Google Patents

Description

  The present invention relates to a foamed molded article excellent in moldability, aesthetics, light weight, rigidity, and vibration damping properties, and a method for producing the same.

In recent years, plastics have been increasingly used in automobile exterior materials and interior materials. Examples include back panels, fenders, bumpers, door panels, pillars, side protectors, side moldings, various spoilers, bonnets, roof panels, and the like. The advantages of using plastic include that it can be reduced in weight, can be designed more freely, can be reduced in cost due to module assembly, and has no rigidity or deformation in light impacts. Points can be mentioned.
And the method of manufacturing a foaming molding by foaming the resin composition using polyolefin as such a molding is known.

By the way, as a plastic foaming method, it is long known that a chemical foaming agent is added to a resin to cause the resin to foam (for example, refer to Patent Document 1). Appearance is not so good compared to general injection molded products. Therefore, there is a technique for obtaining a foamed molded article having a good appearance by injecting a resin to be a skin layer and immediately injecting a foamable resin to be a core layer (see, for example, Patent Document 2). Various methods have been developed.
Recently, in order to improve the foaming ability, a supercritical foam molding method in which a resin is impregnated with carbon dioxide or nitrogen in a supercritical state to perform foam molding of the resin has been proposed (for example, see Patent Document 3). As another method, a method of producing a foam using a resin composition containing thermally expandable microcapsules has been proposed (see, for example, Patent Document 4).

Japanese Examined Patent Publication No. 39-22213 Japanese Patent Publication No. 47-26108 US Pat. No. 5,334,356 JP 2000-17103 A

Various materials and production methods have been proposed as described above, but the foamed molded product obtained is not yet satisfactory in terms of weight reduction and mechanical strength as described above.
Accordingly, an object of the present invention is to provide an excellent foamed molded article having high strength while having a high foaming ratio and a light weight, and a method for producing the same.

As a result of intensive studies in view of the above problems, the present inventors have used a foamed molded article having a sea-island structure in which a thermoplastic resin having a different melting temperature is used, a resin having bubbles becomes an island portion, and another resin forms a sea portion. The knowledge that the above requirements such as weight reduction and mechanical strength are satisfied was obtained, and the present invention was made based on this knowledge.
That is, the present invention
(1) A foamed molded article comprising a thermoplastic resin (a) and a thermoplastic resin (b) having different melting temperatures, wherein the thermoplastic resin (a) is a polyolefin resin, and the thermoplastic resin (b) is Polycarbonate resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polystyrene resin or ABS resin, a mixture of thermoplastic resin (a) and thermoplastic resin (b) impregnated with gas is melted in thermoplastic resin (a) Thermoplastic resin (a) is sea part, and thermoplastic resin (b) having air bubbles is island part, which is injection foam molded at a foaming ratio of 2 times or more below the melting temperature of thermoplastic resin (b). Foam molded product characterized by having a sea-island structure,
(2) The foamed molded article according to (1) , wherein the expansion ratio is 2.1 times or more,
( 3 ) The foamed molded article according to (1) or ( 2 ) , wherein the thermoplastic resin (a) is a polypropylene resin,
(4) the thermoplastic resin (a) is, in foamed molded, foam molded body according to any one of 25 to 80 wt% (1) to (3),
(5) the melting temperature difference of the thermoplastic resin (b) and the thermoplastic resin (a) is a 20 to 120 ° C. (1) foamed molded article according to any one of - (4),
( 6 ) The foam molded article according to any one of (1) to ( 5 ), wherein the bending strength in accordance with JIS K7171 is 40 MPa or more,
( 7 ) The foamed molded article according to any one of (1) to ( 6 ), wherein the thermoplastic resin (a) includes glass fibers having an average fiber length of 1 mm or more,
(8) the thermoplastic resin (a) is, according to any one of characterized in that it is a thermoplastic resin which comprises 5 to 70 wt% of glass fiber (1) to (7) Foam molded body,
( 9 ) A method for producing a foamed molded article in which a thermoplastic resin (a) and a thermoplastic resin (a) and a thermoplastic resin (b) having different melting temperatures are mixed and injection-molded. After the step of filling and pressing to impregnate the pellet-shaped or powder-shaped thermoplastic resin (b) with the gas and then releasing the pressure, the thermoplastic resin impregnated with the thermoplastic resin (a) and the gas (B) is supplied to the injection molding machine in a premixed state, or the thermoplastic resin (a) and the thermoplastic resin (b) impregnated with the gas so as to be mixed in the injection molding machine. Each of the steps of supplying to the injection molding machine is performed, and then injection filling is performed in the mold under molding conditions not lower than the melting temperature of the thermoplastic resin (a) and not higher than the melting temperature of the thermoplastic resin (b). Sea island structure with foamed island Method for producing a foamed molded product having,
( 10 ) The method for producing a foamed molded product according to ( 9 ) , wherein the thermoplastic resin (b) before impregnating the gas is a powder having an average particle diameter of 2 to 50 μm, and ( 11) ) impregnation of the gas into the thermoplastic resin (b) a method for producing a foamed molded article according to the gas and performing a supercritical state (9) or (10),
Is to provide.

The foamed molded article of the present invention has a sea-island structure in which the thermoplastic resin (a) is a sea part and the thermoplastic resin (b) having a large number of closed cells inside is an island part, and the expansion ratio of the thermoplastic resin (b) Can be made larger than usual, so that the foaming ratio of the entire molded body can be increased and the weight can be reduced. Despite its high foaming ratio and light weight, it has excellent strength, particularly bending strength and bending elastic modulus.
Moreover, this foaming molding has the effect | action which converts vibration energy into heat energy and absorbs vibration energy by the internal cell structure and the viscoelasticity of two different thermoplastic resins, and improves damping property. Furthermore, since these two thermoplastic resins have different glass transition points, high vibration damping properties can be obtained in a relatively wide operating temperature range.
Furthermore, by adding a reinforcing agent such as glass fiber to the thermoplastic resin (a), it is possible to obtain a foamed molded article having both vibration damping properties and high rigidity. It can be widely applied.

It is a schematic process drawing which shows the manufacturing method of this invention. It is a schematic diagram which shows the cross-sectional structure of the foaming molding of this invention.

A preferred embodiment of the foamed molded product of the present invention will be described in detail.
The thermoplastic resin (a) and the thermoplastic resin (b) constituting the foamed molded article of the present invention are particularly limited if the melting temperature of the thermoplastic resin (b) is higher than the melting temperature of the thermoplastic resin (a). For example, polyolefin resin (polyethylene resin, ethylene-vinyl acetate copolymer, polypropylene resin, etc.), polycarbonate resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfite resin, polyamideimide resin. , Polyether ether ketone resin, polyether sulfone resin, polyimide resin, polyvinyl chloride resin, polystyrene resin (polystyrene resin, syndiotactic polystyrene resin, acrylonitrile-styrene copolymer, ABS resin, etc.), polyamide resin, Riacetal resin, acrylic resin, cellulose resin (cellulose acetate, etc.), polystyrene thermoplastic elastomer, polyolefin thermoplastic elastomer, polyurethane thermoplastic elastomer, 1,2-polybutadiene thermoplastic elastomer, ethylene-vinyl acetate A thermoplastic resin appropriately selected from copolymer-based thermoplastic elastomers, fluororubber-based thermoplastic elastomers, chlorinated polyethylene-based thermoplastic elastomers, and the like can be used.

The melting temperature of the thermoplastic resin (b) is higher than the melting temperature of the thermoplastic resin (a) and is equal to or higher than the injection temperature at the time of molding the foamed molded product of the present invention.
The melting temperature means a lower limit temperature that can be normally formed when, for example, a plate-shaped molded product is formed.
The difference in melting temperature between the thermoplastic resin (b) and the thermoplastic resin (a) is not particularly limited, but is preferably 20 to 120 ° C, more preferably 40 to 100 ° C. Convenient to do.

  Examples of the thermoplastic resin (a) include polyolefin resins (polyethylene resins, ethylene-vinyl acetate copolymers, polypropylene resins, etc.), polystyrene resins (polystyrene resins, acrylonitrile-styrene copolymers, ABS resins, etc.), and polystyrene-based thermoplastics. Elastomers, polyolefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, ethylene-vinyl acetate copolymer-based thermoplastic elastomers, 1,2-polybutadiene-based thermoplastic elastomers, ethylene-vinyl acetate copolymer-based thermoplastic elastomers, fluororubber-based heat A plastic elastomer or a chlorinated polyethylene thermoplastic elastomer is preferable, and a polyolefin resin (polyethylene resin, ethylene-vinyl acetate copolymer, polypropylene resin, etc.) is particularly preferable.

  The thermoplastic resin (b) includes polycarbonate resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfite resin, polyamide imide resin, polyether ether ketone resin, polyether sulfone resin, polyimide resin, polyvinyl chloride resin. , Polystyrene resins (polystyrene, acrylonitrile-styrene copolymers, ABS resins, etc.), polyamide resins, polyacetal resins, acrylic resins, or cellulose resins (cellulose acetate, etc.) are preferred, especially polycarbonate resins, polybutylene terephthalate resins, Polyethylene terephthalate resin, polyphenylene sulfite resin, or polystyrene resin (polystyrene resin, syndiotactic polystyrene resin, acrylo Tolyl - styrene copolymer, ABS resin, etc.) is preferred.

Preferred combinations of the thermoplastic resin (a) and the thermoplastic resin (b) are: (a) polypropylene resin and (b) polycarbonate resin, (a) polypropylene resin and (b) polybutylene terephthalate resin, (a) polypropylene resin And (b) syndiotactic polystyrene resin.
The blending ratio of the thermoplastic resin (a) is preferably 25 to 80% by mass and more preferably 30 to 50% by mass in the foamed molded product. If this ratio is too high, the sea part of the molded body will increase, so the foaming ratio will be low and the purpose of weight reduction will not be achieved, and if it is less, the sea part of the molded body will decrease and the foamed part will increase so that the purpose of high strength will be achieved. This is because it disappears.

  These thermoplastic resins include cell nucleating agents, crystal nucleating agents, plasticizers, lubricants, colorants, ultraviolet absorbers, antioxidants, fillers, reinforcing agents such as glass fibers, flame retardants, antistatic agents, etc. An appropriate amount of the additive can be added as required.

The thermoplastic resin (a) is preferably a fiber reinforced thermoplastic resin to which glass fibers are added in order to obtain a foamed molded article having superior strength. When adding glass fiber, it is preferable that the average fiber length of glass fiber is 1 mm or more, More preferably, it is 2-10 mm, More preferably, it is 3-8 mm. If the glass fiber length is less than 1 mm, high rigidity may not be obtained with a foamed molded product. If the glass fiber length exceeds 10 mm, plasticization becomes insufficient even when supplied to an injection molding machine and molding becomes unstable. Sometimes.
Moreover, content of glass fiber in a thermoplastic resin (a), Preferably it is 5-70 mass%, More preferably, it is 10-40 mass%. If the blended amount of glass fibers is small, the foam molded article may not have a desired strength. If it exceeds 70% by mass, the injection molding may become unstable and the light weight effect of the foam molded article may be reduced. .

The shape of the thermoplastic resin (b) as a raw material is not particularly limited, but is preferably a pellet of 3 mm or less or powder (including fine powder), more preferably an average particle size of 2 to 50 μm, more preferably an average It is a fine powder having a particle size of 3 to 50 μm. In addition, the average particle diameter of said fine powder means the value measured with the micro track FRA laser type particle size distribution analyzer (made by Nikkiso Co., Ltd.).
As a method for foaming the pellets or powder of the thermoplastic resin (b), a method of foaming using a pressurized high-pressure gas (a foaming method in which high-pressure gas is impregnated as a foaming means and then decompressed) is used in the present invention. In chemical foaming using a foaming agent, both the thermoplastic resins (a) and (b) are foamed, and it is difficult to form a fine cell structure, and in particular, it is extremely difficult to form fine cells of 300 μm or less. It is.
The high-pressure gas is not particularly limited as long as it is inert and can be impregnated with respect to the thermoplastic resin (b), and examples thereof include air and inert gases (carbon dioxide, nitrogen, helium, etc.). These gases may be mixed and used. Among these, an inert gas is preferable from the viewpoint of a large amount of impregnation and a high impregnation rate, and carbon dioxide is particularly preferable among them.

Furthermore, from the viewpoint of increasing the impregnation speed, the high-pressure gas (particularly carbon dioxide) is preferably a fluid in a supercritical state. In the supercritical state, the solubility of the gas in the thermoplastic resin (b) increases and high concentration can be mixed. In addition, when the pressure drops suddenly after impregnation, since it is possible to impregnate at a high concentration as described above, the generation of bubble nuclei increases, and the density of bubbles formed by the growth of the bubble nuclei increases. Fine bubbles can be obtained, and the expansion ratio can be increased as compared with the conventional case.
In the present invention, the shape of the foam-formed body is not particularly limited. It may be a plate shape, a cylindrical shape, a square shape, a spherical shape, or the like, and can be further molded into an appropriate shape according to various uses and usage scenes.

Next, a preferred embodiment of a method for producing a foam molded article will be described with reference to FIG.
The raw material pellets or powdered thermoplastic resin (b) 2 is filled with gas in the pressure vessel 3 at room temperature (10 to 25 ° C.), pressurized, and preferably impregnated with supercritical gas. To be a thermoplastic resin (b) impregnated with gas.
The raw thermoplastic resin (a) 1 and the thermoplastic resin (b) impregnated with gas are stirred and mixed (dry blended) by the mixer 4 and supplied to the injection molding machine 5 in a premixed state. Alternatively, the thermoplastic resin (a) and the thermoplastic resin (b) impregnated with gas can be supplied to the injection molding machine 5 from a hopper or a side feeder, respectively, so as to be mixed in the injection molding machine.
The thermoplastic resin (a) melts and is impregnated with the thermoplastic resin (b) under molding conditions not lower than the melting temperature of the thermoplastic resin (a) and not higher than the melting temperature of the thermoplastic resin (b). Foams. The foamed molded product 6 having the sea-island structure of the present invention can be obtained by injection-filling this into a mold. In the foamed molded product 6, some bubbles generated in the thermoplastic resin (b) may be present in the thermoplastic resin (a). The molding temperature is determined by the thermoplastic resin used, but is preferably 220 to 290 ° C.

Using a colored one as the thermoplastic resin (a), the foam molded body obtained by foam injection molding is cut using a slicer or the like so that the cross-sectional structure is not destroyed, and the cross section is obtained with a scanning electron microscope. An example of the cross-sectional structure of the foamed molded product of the present invention, whose structure was observed, is shown in FIG. 2 as a schematic diagram.
The foamed molded body 6 has a sea-island structure in which the thermoplastic resin (a) constitutes the sea portion 7 and the thermoplastic resin (b) having the bubbles 9 constitutes the island portion 8. The particle size of the portion corresponding to the island portion 8 is approximately 0.05 to 0.8 mm, and the size (maximum diameter) of the bubbles is approximately 30 to 200 μm.
When the thermoplastic resin (a) is made of a material containing glass fiber, the glass fiber remains in the sea part 7 almost as it is.

Foaming at the time of injection molding is lower than the melting temperature of the thermoplastic resin (b) and occurs in the molten state of the thermoplastic resin (a), so the bubbles 9 are closed cells, and the thermoplastic resin (b) alone The foaming ratio can be made larger than that of foaming. Therefore, it is possible to increase the foaming ratio of the entire foamed molded body and to reduce the weight. In addition, since a large number of bubbles are independent, they have excellent mechanical strength, preferably 40 MPa or more, and more preferably 45 MPa or more (value according to JIS K7171). Also, the flexural modulus is excellent.
Furthermore, when this foamed molded body is subjected to vibration, vibration energy is converted into heat energy by the internal cell structure and the viscoelasticity of two different thermoplastic resins, so that vibration energy is absorbed. improves. Furthermore, since these two thermoplastic resins have different glass transition points, it is possible to obtain high vibration damping properties in a wide operating temperature range.
In addition, by adding a reinforcing agent such as glass fiber to the thermoplastic resin (a), it is possible to obtain a foamed molded article having both vibration damping properties and high rigidity. It can be widely applied.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
Production methods are described in the following examples and comparative examples, and the outline is shown in Tables 1 to 3. Further, the obtained foamed molded article was evaluated for moldability and appearance, and measured for bending strength, bending elastic modulus and expansion ratio as mechanical strength, and the results are also shown in Tables 1 to 3.
The thermoplastic resins used in each example and comparative example are listed in Table 4.

<Example 1>
As the thermoplastic resin (a), pellet-shaped polypropylene (“Novatec BC03C” manufactured by Nippon Polypro) was used, and as the thermoplastic resin (b), polycarbonate (“Iupilon S3000” manufactured by Mitsubishi Engineering Plastics) was used. The thermoplastic resin (b) was in the form of pellets, and after charging the pellets into a pressure vessel, carbon dioxide was filled at 8 MPa and 23 ° C., which brought a supercritical state.
Next, the thermoplastic resin (a) and the thermoplastic resin (b) impregnated with carbon dioxide gas are mixed at a mass ratio of 30:70 and then charged into the popper of the injection molding machine, and the melting temperature of the thermoplastic resin (a) The mold was injection-filled into the mold under the molding conditions of 260 ° C. below the melting temperature of the thermoplastic resin (b) to obtain a plate-like foamed molded body (length 150 mm, width 150 mm, thickness 4 mm).

<Examples 2 to 4>
As the thermoplastic resin (a), polypropylene (“NOVATEC BC03C” manufactured by Nippon Polypro Co., Ltd.) was used as in Example 1. As the thermoplastic resin (b), polybutylene terephthalate (“DURA” manufactured by Polyplastics Co., Ltd.) was used. Nex 2002 "), syndiotactic polystyrene (" Zarek S100 "manufactured by Idemitsu Kosan Co., Ltd.) or polyethylene terephthalate (" SA-1206 "manufactured by Unitika). The thermoplastic resin (b) has a pellet shape. The pellets were put into a pressure vessel in the same manner as in Example 1 and then filled with carbon dioxide at 8 MPa at 23 ° C.
Next, as in Example 1, the thermoplastic resin (a) and the thermoplastic resin (b) were mixed at a mass ratio of 30:70 and then charged into the popper of the injection molding machine. As shown in Table 1, the thermoplastic resin It is injection-filled into a mold under molding conditions of 220 ° C., 270 ° C. and 240 ° C., which are not lower than the melting temperature of (a) and not higher than the melting temperature of the thermoplastic resin (b), respectively, 150 mm, width 150 mm, thickness 4 mm).

<Examples 5 and 6>
As shown in Table 1, the thermoplastic resin (a) is a pellet-like long fiber glass-containing polypropylene ("Funkster LR23C" manufactured by Nippon Polypro Co., Ltd., containing about 4 mm of glass fiber length: 30% by mass) or a long fiber glass-containing polypropylene. (Nippon Polypro "Funkster LR23C", glass fiber length of about 8 mm: 30% by mass) was used, and the thermoplastic resin (b) was polycarbonate ("Iupilon S3000" manufactured by Mitsubishi Engineering Plastics). The thermoplastic resin (b) was in the form of a pellet. The pellet was put into a pressure vessel in the same manner as in Example 1 and then filled with carbon dioxide at 8 MPa at 23 ° C.
Next, after mixing the thermoplastic resin (a) and the thermoplastic resin (b) at a mass ratio of 30:70, the mixture is put into the popper of the injection molding machine, and the thermoplastic resin is at or above the melting temperature of the thermoplastic resin (a). The mold was injection-filled into a mold under molding conditions of 260 ° C. below the melting temperature of (b) to obtain a plate-like foamed molded body (length 150 mm, width 150 mm, thickness 4 mm).

<Examples 7 and 8>
The thermoplastic resin (a) is a pellet-like long fiber glass-containing polypropylene (“Funkster LR23C” manufactured by Nippon Polypro, glass fiber length of about 8 mm: 30% by mass), and the thermoplastic resin (b) is a pellet-like polycarbonate (Mitsubishi). “Iupilon S3000” manufactured by Engineering Plastics Co., Ltd. was used. This pellet-shaped thermoplastic resin (b) was charged into a pressure vessel in the same manner as in Example 1 and then filled with carbon dioxide at 8 MPa at 23 ° C. Next, after mixing the thermoplastic resin (a) and the thermoplastic resin (b) at a mass ratio of 50:50 in Example 8 and at a mass ratio of 70:30 in Example 9, respectively, the mixture was added to the popper of the injection molding machine. It is injected and filled into a mold under molding conditions of 260 ° C. which is not less than the melting temperature of the thermoplastic resin (a) and not more than the melting temperature of the thermoplastic resin (b), and is formed into a plate-like foam molded body (length 150 mm) , Width 150 mm, thickness 4 mm).

<Examples 9 to 11>
As shown in Table 2, the thermoplastic resin (a) is a pellet-shaped long fiber glass-containing polypropylene ("Funkster LR21V" manufactured by Nippon Polypro Co., Ltd., glass fiber length of about 8 mm: containing 10% by mass), containing long fiber glass Polypropylene (Nippon Polypro "Funkster LR22W", glass fiber length of about 8mm: 20% by mass) or long fiber glass-containing polypropylene (Nippon Polypro "Funkster LR24A", glass fiber length of about 8mm: 40% by mass) The thermoplastic resin (b) was polycarbonate ("Iupilon S3000" manufactured by Mitsubishi Engineering Plastics). The thermoplastic resin (b) was in the form of a pellet. The pellet was put into a pressure vessel in the same manner as in Example 1 and then filled with carbon dioxide at 8 MPa at 23 ° C.
Next, after mixing the thermoplastic resin (a) and the thermoplastic resin (b) at a mass ratio of 30:70, the mixture is put into the popper of the injection molding machine, and the thermoplastic resin is at or above the melting temperature of the thermoplastic resin (a). The mold was injection-filled into a mold under molding conditions of 260 ° C. below the melting temperature of (b) to obtain a plate-like foamed molded body (length 150 mm, width 150 mm, thickness 4 mm).

<Example 12>
For the thermoplastic resin (a), polypropylene (“Novatec BC03C” manufactured by Nippon Polypro) was used, and for the thermoplastic resin (b), acrylonitrile copolymer resin (“N230S” manufactured by Nippon Synthetic Rubber Co., Ltd.) was used. The acrylonitrile copolymer resin was in the form of a powder having an average particle size of about 30 μm, and this powder was charged into a pressure vessel and then filled with carbon dioxide at 8 MPa at 23 ° C. Next, after mixing the thermoplastic resin (a) and the thermoplastic resin (b) at a mass ratio of 30:70, the mixture is put into the popper of the injection molding machine, and the thermoplastic resin is at or above the melting temperature of the thermoplastic resin (a). The mold was injected and filled under molding conditions of 220 ° C. below the melting temperature of (b) to obtain a plate-like foamed molded body (length 150 mm, width 150 mm, thickness 4 mm).

<Comparative Example 1>
The thermoplastic resin (a) uses polypropylene (“Novatec BC03C” manufactured by Nippon Polypro), is not blended with the thermoplastic resin (b), is injection molded at 200 ° C., and is formed into a plate-like molded body (length 150 mm, width) 150 mm, thickness 4 mm).

<Comparative example 2>
The thermoplastic resin (a) is not blended, and the pellet-shaped polypropylene ("Novatec BC03C" manufactured by Nippon Polypro Co., Ltd.) is used as the thermoplastic resin (b). Filled at 23 ° C. Next, this thermoplastic resin (b) was put into a popper of an injection molding machine and injected and filled in a mold under molding conditions of 180 ° C. below the melting temperature of the thermoplastic resin (b), but could not be molded. .

<Reference Example 1>
The thermoplastic resin (a) is a long fiber glass-containing polypropylene (“Funkster” manufactured by Nippon Polypro, glass fiber length of about 12 mm: 30%), and the thermoplastic resin (b) is polycarbonate (“Iupilon S3000 manufactured by Mitsubishi Engineering Plastics). ")It was used. The thermoplastic resin (b) was in the form of pellets, and the pellets were charged into a pressure vessel and filled with carbon dioxide at 8 MPa and 23 ° C.
Next, after mixing the thermoplastic resin (a) and the thermoplastic resin (b) at a mass ratio of 70:30, the mixture is put into a popper of an injection molding machine, and the thermoplastic resin is at or above the melting temperature of the thermoplastic resin (a). Molding was carried out by injection filling into the mold under molding conditions of 260 ° C. below the melting temperature of the resin (b).

<Reference Example 2>
As the thermoplastic resin (a), polypropylene (“Novatec BC03C” manufactured by Nippon Polypro) was used, and as the thermoplastic resin (b), acrylonitrile copolymer resin (“N230S” manufactured by Nippon Synthetic Rubber Co., Ltd.) was used. The thermoplastic resin (b) was in the form of a powder having an average particle size of about 30 μm, and this powder was charged into a pressure vessel and filled with carbon dioxide at 8 MPa at 23 ° C.
Next, after mixing the thermoplastic resin (a) and the thermoplastic resin (b) at a mass ratio of 20:80, the mixture is put into a popper of an injection molding machine, and the thermoplastic resin is at or above the melting temperature of the thermoplastic resin (a). The mold was injection-filled under molding conditions of 220 ° C. below the melting temperature of the resin (b) to obtain a plate-like molded body.

Test Example The cross-sectional structure of the molded body of each example was examined with a scanning electron microscope. In either case, the thermoplastic resin (a) has a sea-island structure in which the sea part and the thermoplastic resin (b) constitutes an island part, and a large number of bubbles were observed in the island part.

The fillers and molded bodies obtained in each of the examples, comparative examples and reference examples were evaluated according to the specifications shown below. The results are shown in Tables 1-3. Table 4 shows the resins used.
a. Formability 150 × 150 × 4 mm molded body was produced, and the case where the molded product was not unfilled was defined as “good”, and the state where unmolded or unmolded or the molded state was unstable was defined as “bad”. .
b. Appearance The case where there was no sink or weld that could cause a problem in performance on the surface was judged as “good”, and when there was a large sink, unevenness or weld on the surface, it was judged as defective and the state was shown in the table.
c. Bending strength, and d. Bending elastic modulus Bending strength and bending elastic modulus were evaluated in accordance with JIS K7171 by cutting out an 80 mm × 10 mm × 4 mm sample plate from the plate-like molded body obtained in each example to obtain an evaluation sample. .
e. Foaming ratio The mass of a molded product (150 × 150 × 4 mm) “unfoamed molded product” in a state where foaming is not performed is calculated from the density of each material, and this is set to a foaming magnification of 1, and injection foam molding is performed as in Examples and Comparative Examples. Measure the mass of the molded product “foamed molded product” and define the formula below (mass of “non-foamed molded product”) / (mass of “foamed molded product”) = foaming ratio to obtain the foaming ratio. It was.

As shown in Tables 1 and 2, in Examples 1 to 12, the material was excellent in moldability and appearance, had high bending strength, bending elastic modulus, and high foaming ratio, and was a light weight and high strength material. Especially, in Examples 5-11 in which the thermoplastic resin (a) includes glass fibers, the strength was very excellent compared to Example 1 using the same PC as the resin (b).
On the other hand, as shown in Table 3, the appearance of Comparative Example 1 was good, but since it did not contain foaming gas, it was not a foam and was not reduced in weight. In Comparative Example 2, molding could not be performed. Further, in Reference Example 1, since many glass fibers having a long fiber length were contained, the moldability was poor and it was not suitable for molding. In Reference Example 2, the moldability was good, but many balloons were broken and the surface was uneven, the appearance was poor, and the bending strength and bending elastic modulus were low.

1 Thermoplastic resin (a) (raw material)
2 Thermoplastic resin (b) (raw material)
DESCRIPTION OF SYMBOLS 3 Pressure vessel 4 Mixer 5 Injection molding machine 6 Foam molding 7 Sea part 8 Island part 9 Bubble

Claims (11)

A foamed molded article comprising a thermoplastic resin (a) and a thermoplastic resin (b) having different melting temperatures, wherein the thermoplastic resin (a) is a polyolefin resin, and the thermoplastic resin (b) is a polycarbonate resin, A polybutylene terephthalate resin, a polyethylene terephthalate resin, a polystyrene resin or an ABS resin, and a mixture of the thermoplastic resin (a) and the thermoplastic resin (b) impregnated with gas at a temperature equal to or higher than the melting temperature of the thermoplastic resin (a). In addition, a sea-island structure in which the thermoplastic resin (a) is a sea part and the thermoplastic resin (b) having bubbles is an island part, which is injection-foamed and molded at a foaming ratio of 2 times or less at a melting temperature of the thermoplastic resin (b) or less. A foamed molded article characterized by having. The foamed molded product according to claim 1, wherein the expansion ratio is 2.1 times or more. The foamed molded article according to claim 1 or 2, wherein the thermoplastic resin (a) is a polypropylene resin. The thermoplastic resin (a) is, in foamed molded, foam molded body according to any one of claims 1 to 3 which is 25 to 80 mass%. The foamed molded product according to any one of claims 1 to 4 , wherein a difference in melting temperature between the thermoplastic resin (b) and the thermoplastic resin (a) is 20 to 120 ° C. The foaming molded article according to any one of claims 1 to 5 , wherein a bending strength in accordance with JIS K7171 is 40 MPa or more. The foamed molded article according to any one of claims 1 to 6 , wherein the thermoplastic resin (a) includes glass fibers having an average fiber length of 1 mm or more. The foamed molded article according to any one of claims 1 to 7 , wherein the thermoplastic resin (a) is a thermoplastic resin containing 5 to 70 mass% of glass fibers.   A method for producing a foamed molded article in which a thermoplastic resin (a) and a thermoplastic resin (a) and a thermoplastic resin (b) having different melting temperatures are mixed and injection-molded, and filled with gas in a pressure vessel After the step of pressing and impregnating the pellet-shaped or powdered thermoplastic resin (b) with the gas and then releasing the pressure, the thermoplastic resin (a) and the thermoplastic resin impregnated with the gas (b) And the step of supplying to the injection molding machine in a premixed state, or the injection molding of the thermoplastic resin (a) and the thermoplastic resin (b) impregnated with the gas so as to be mixed in the injection molding machine. Performing any one of the steps of supplying to the machine, and then injection-filling the mold under molding conditions not lower than the melting temperature of the thermoplastic resin (a) and not higher than the melting temperature of the thermoplastic resin (b). Has a sea-island structure with foamed parts Method of manufacturing a foam molded body. The method for producing a foamed molded product according to claim 9, wherein the thermoplastic resin (b) before impregnating the gas is in the form of a powder having an average particle diameter of 2 to 50 µm. The method for producing a foamed molded product according to claim 9 or 10 , wherein the impregnation of the thermoplastic resin (b) with a gas is performed in a supercritical state.

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