JP3375377B2 - Method for producing fiber-reinforced thermoplastic resin foam molded article - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fiber-reinforced thermoplastic resin foam molded article . [0002] Conventionally, as a method of molding a foam,
A method in which a bead-shaped foam material is placed in a mold and foamed by blowing heated steam into the mold, or a reaction injection molding method in which a polyol and an isocyanate, which are raw materials of a polyurethane foam, are injected and reacted in the mold to obtain a foam. Are well known.
However, with these molding methods, only foams having low strength and which cannot be recycled were obtained. Therefore, recently, recyclable thermoplastic resin foams and fiber-reinforced thermoplastic resin foams have been widely used. [0004] As a method for producing the above-mentioned thermoplastic resin foam, for example, a method of injecting a thermoplastic resin mixed with a foaming agent into a short cavity in a closed mold cavity, or a method of filling the cavity with a short shot. And foaming by increasing the cavity volume (industrial material 2
9 [3] (March 1981) Kenjiro Hashimoto 60-6
4). [0005] However, when a fiber-reinforced thermoplastic resin foam is molded by using the above-described technique,
Because the containing reinforcing fibers are randomly oriented, the number of reinforcing fibers that are reinforcing in directions other than the necessary reinforcing direction increases,
There was a problem that the reinforcing efficiency was poor for the weight. An object of the present invention is to provide a method for producing a fiber-reinforced thermoplastic resin foamed molded article having a high strength lightweight and particularly the thickness direction. SUMMARY OF THE INVENTION The present invention provides a method for producing a fiber-reinforced thermoplastic resin foam molded article having a skin layer in which reinforcing fibers are oriented substantially parallel to the surface on both surfaces of a foamed core layer. In the mold cavity, a heat-expandable fiber-reinforced thermoplastic resin containing 20 to 70% by weight of a reinforcing fiber having a length of 5 to 25 mm is heated at a temperature not lower than the melting temperature of the thermoplastic resin and not lower than the foaming temperature. While the temperature of the heat-expandable fiber-reinforced thermoplastic resin is equal to or higher than the melting temperature, the mold is opened so that the cavity volume becomes 1.5 to 10 times that at the time of the filling, and the fiber-reinforced thermoplastic resin is opened. The resin is foamed, and 20% by weight or more of the reinforcing fibers contained in the core layer are oriented almost perpendicularly to the skin layer. Examples of the reinforcing fiber include organic fibers such as glass fiber, carbon fiber, silicon / titanium / carbon fiber, boron fiber, fine metal fiber, aramid fiber, polyester fiber and polyamide fiber. The diameter of the monofilament is preferably 1 to 50 μm, particularly preferably 3 to 23 μm. The fiber length is in the range of 5 to 25 mm and is appropriately determined according to the required performance and shape of the product. Fiber length is 5mm
If it is less than 25 mm, the desired product cannot be obtained.
It becomes difficult to knead and mix with the thermoplastic resin and the foaming agent, melt, supply to a mold, and the like, and it becomes difficult for the reinforcing fibers in the core layer to be oriented almost perpendicularly to the skin layer. It is necessary to mix the reinforcing fibers so that the content thereof is in the range of 20 to 70% by weight. If the content of the reinforcing fibers is less than 20% by weight, the desired foamed molded article cannot be obtained. If the content of the reinforcing fibers exceeds 70% by weight, the thermoplastic resin penetrating between the monofilament fibers becomes insufficient, and Body stiffness is significantly reduced. As the thermoplastic resin, any resin that melts and softens when heated can be used. For example, polyethylene,
Polypropylene, polyvinyl chloride, polystyrene, polyamide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyvinylidene fluoride, polyphenylene sulfide, polyphenylene oxide, polyether sulfone, polyether ether ketone and the like are used. In addition, copolymers, graft resins and blend resins containing the above-mentioned thermoplastic resin as a main component, for example, ethylene-vinyl chloride copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-vinyl chloride copolymer, Urethane-vinyl chloride copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic acid-modified polypropylene, maleic acid-modified polyethylene and the like can also be used. And the thermoplastic resin includes a stabilizer, a lubricant, a processing aid, a plasticizer,
Additives such as coloring agents and fillers such as talc, mica and calcium carbonate may be blended. As a foaming agent to be blended with the thermoplastic resin,
Azodicarbonamide, azobisisobutyronitrile, N, N'-
Dinitrosopentamethylenetetramine, pp'-oxybisbenzenesulfonylhydrazide, barium azodicarboxylate, trihydrazinotriazine, p-toluenesulfonylhydrazide and the like. The compounding amount varies depending on the foaming agent, but in order to obtain high strength, it is preferable that the compounding is performed so that the expansion ratio becomes about 1.5 to 3.5 times. The heat-expandable fiber-reinforced thermoplastic resin can be obtained by mixing a reinforcing fiber and a foaming agent with the thermoplastic resin or kneading the thermoplastic resin at a foaming temperature or lower. At least 20% by weight of the reinforcing fibers contained in the core layer must be oriented substantially vertically. In this specification, “substantially perpendicular” refers to a state in which the reinforcing fibers are oriented at an angle of 75 ° or more with respect to one of the two skin layers. That is, it reaches one of the skin layers at an angle of 75 degrees or more, and draws an arc so that the reinforcing fibers in contact with another reinforcing fiber, thermoplastic resin, or the other skin layer are oriented substantially vertically. I do. If the orientation angle of the reinforcing fibers with respect to the skin layer is less than 75 degrees, the strength is weak against the compressive force applied perpendicularly to the skin layer, and the reinforcing fibers contained in the core layer are oriented substantially vertically. Even if the content of the fibers is less than 20% by weight, the strength is weak against the compressive force applied perpendicularly to the skin layer. It is preferable that a layer made of only a thin thermoplastic resin is formed on the exposed surface of the skin layer. [0014] reinforcing fibers of the core layer is oriented radially around the dispensing location when the heating foamable fiber-reinforced thermoplastic resin of the supplied molten state is filled into the cavity, then the fiber-reinforced thermoplastic resin Orientation in a direction substantially perpendicular to one skin layer due to foaming of the fibers and napping of the fibers themselves. As a method for filling the foamed fiber reinforced thermoplastic resin in a molten state into a mold cavity, a method for injecting the same into a cavity which is closed in advance, or a method for supplying the resin to an open mold cavity is provided. There is a method in which the mold is closed immediately and the filling is performed by a compressive force. However, in the method in which the mold is closed and filling is performed by compressive force, the skin layer becomes thicker than in the method of injection filling, so that it is desirable to open the mold earlier. The opening of the mold after filling must be performed while the thermoplastic resin is at or above the melting temperature in the mold. Depends on the temperature of the molten thermoplastic resin, but if the thermoplastic resin is kept in the cavity for a long time, the thickness of the skin layer will increase, making it difficult to foam, and the excess gas generated will also be difficult to escape. This may cause the product shape to deteriorate. The thickness of the skin layer is preferably 0.5 to 5 mm.
The foaming of the fiber-reinforced thermoplastic resin may be performed by opening the mold while the thermoplastic resin is at or above the foaming temperature of the foaming agent, or the foaming agent foams and the gas foamed in the thermoplastic resin increases the pressure. You may open the mold while holding it. If the cavity volume is less than 1.5 times that at the time of filling, more than 20% by weight of the reinforcing fibers contained in the core layer will not be oriented almost perpendicularly to the skin layer, If the volume exceeds 10 times that at the time of filling, a large cavity is likely to be formed in the core layer, and the strength of the obtained molded body may be reduced. The mold opening is preferably performed so that the cavity volume is 2 to 4 times that of the thermoplastic resin. The opening gap of the mold is usually 8 to 10
0 mm, preferably in the range of 5 to 40 mm. The larger the mold opening distance, the more easily the fibers are oriented in the direction perpendicular to the skin layer. When the mold is opened for a distance longer than the length of the fibers contained in the resin, more than half of the fibers in the core layer are removed. Orients vertically to the skin layer,
If it is too large, the cavity volume will be excessive, and the strength of the compact will be reduced. [0020] DETAILED DESCRIPTION OF THE INVENTION The present invention, in the method for producing a fiber-reinforced thermoplastic resin foamed molded reinforcing fibers with a skin layer that is oriented substantially parallel to the surface on both sides of the foam core layer, length 5 2
A heat-expandable fiber-reinforced thermoplastic resin containing 20 to 70% by weight of a 5 mm reinforcing fiber is filled in a mold cavity while being heated at a temperature higher than the melting temperature of the thermoplastic resin and higher than the foaming temperature. While the temperature of the foamable fiber-reinforced thermoplastic resin is equal to or higher than the melting temperature, the mold is opened so that the cavity volume becomes 1.5 to 10 times that of the filling, and the fiber-reinforced thermoplastic resin is foamed. Since 20% by weight or more of the reinforcing fibers contained in the layer are oriented almost perpendicularly to the skin layer, a foam molded article having high strength in the thickness direction for a light weight can be obtained. . [0021] The embodiment of EXAMPLES Hereinafter the present invention, with reference to the drawings will be described in comparison with Comparative Example. [0022] Example 1 Tabular fiber reinforced thermoset shown in FIG thermoplastic resin foamed molded
(1) A skin made of a fiber-reinforced thermoplastic resin containing 40% by weight of a reinforcing fiber having a length of 12.5 mm, and a reinforcing fiber oriented on both surfaces of a foamed core layer (2) substantially parallel to the surface. A layer (3), in which about 30% by weight of the reinforcing fibers contained in the core layer (2) are oriented almost perpendicular to the skin layer (3). Is made of glass fiber, and polypropylene is used as the thermoplastic resin. [0023] One example of a method for manufacturing the fiber-reinforced thermoplastic resin expanded molded article is as follows. Firstly, polypropylene 100 containing a diameter of 23 .mu.m, the glass fiber length 12.5 mm 40 wt%
5 parts by weight of an azodicarbonamide-based blowing agent was mixed with the parts by weight to obtain a heat-expandable fiber-reinforced thermoplastic resin. Next, the heating foamable fiber-reinforced thermoplastic resin (4), as shown in FIG. 2, approximately at the exit (not shown) 2
After heating to 15 ° C, the upper mold (6) is lowered until the cavity clearance of the compression mold (5), which has been temperature-controlled to 60 ° C, becomes 10 mm. The filling was performed in about 4 seconds through the hot runner (9) of the mold (8). 3 seconds after the completion of filling, the mold is opened so that the cavity volume is 2.5 times that at the time of filling and the opening gap is 25 mm, and the product is cooled until the temperature of the product reaches 70 ° C., and the product as shown in FIG. Was taken out. [0026] The thickness of the resulting foamed molded article (1) 35m
m, the thickness of the skin layer (3) is 2 mm on both sides, the glass fibers are oriented almost parallel to the surface, the thickness of the core layer (2) is 31 mm, and the thickness of the By weight, the fibers were oriented almost perpendicular to the skin layer (3). [0027] Another example of the manufacturing method of Example 2 fiber-reinforced thermoplastic resin expanded molded article is as follows. After the same heat-expandable fiber-reinforced thermoplastic resin (4) as in Example 1 was heated to about 215 ° C., as shown in FIG.
Insert the discharge part (10) of the extruder (not shown) between the upper die (12) and the lower die (13) of the compression molding die (11), and properly insert the two die (12) and (13). While moving, discharge from the nozzle (14) to the lower mold (13), and after retreating the discharge part (10) from between the two molds (12) (13),
Immediately, the mold was closed until the cavity clearance became 10 mm, and the cavity (15) was filled with the heat-expandable fiber-reinforced thermoplastic resin (4). After 3 seconds from the completion of filling, the mold is opened so that the cavity volume is 2.5 times that at the time of filling and the opening gap is 25 mm, and the product is cooled until the product temperature reaches 70 ° C. I took it out. [0029] The thickness of the obtained molded body 35 mm, thickness lower surface 4mm of the skin layer, the upper surface is 3 mm, and substantially oriented parallel to the both glass fiber surface, the thickness of the core layer 28mm And about 2% of the glass fibers contained in the core layer.
5% by weight of the fibers were oriented almost perpendicular to the skin layer. [0030] Example 3 fiber diameter 23 .mu.m, a polypropylene resin 100 glass fibers having a fiber length of 6.3 mm, containing 40 wt% fiber content
5 parts by weight of an azodicarbonamide-based blowing agent was mixed with the parts by weight to obtain an expandable fiber-reinforced thermoplastic resin. The foamable fiber-reinforced thermoplastic resin (4), as shown in FIG. 2,
After heating to about 215 ° C with an injection molding machine (not shown) , the hot runner (9) in the lower mold (8) is passed into the compression mold (5) cavity, which is closed until the cavity clearance becomes 10 mm. , About 2 seconds. One second after filling is complete,
The product was opened by an 8 mm mold (1.8 times), cooled as it was until the temperature of the product reached 70 ° C., and the product was taken out. [0031] The thickness of the obtained molded body 18 mm, thickness of the skin layer in 2mm on both sides, the thickness of the core layer 14m
m, about half of the glass fibers in the core layer were oriented. Comparative Example 1 In this comparative example, a fiber-reinforced thermoplastic resin foam molded article was obtained in the same manner as in Example 1 except that a glass fiber having a length of 3.0 mm was used as the heat-expandable thermoplastic resin. . [0032] Comparative Example 2 This comparative example was filled with foamable fiber-reinforced thermoplastic resin in the compression mold cavity, as 1.4 times the cavity volume is filled, the mold opening gap is 5mm A foamed fiber-reinforced thermoplastic resin molded article was obtained in the same manner as in Example 1 except that the mold was opened. With respect to the foamed molded articles obtained in each of the examples and comparative examples, the density was measured and the compression strength test was performed. Table 1 shows the results. The density measurement is based on JIS
-K7222 The compression strength test conforms to the method for measuring the density of the rigid foamed plastic according to JIS-K7220. [ Table 1] As is clear from Table 1, the fiber-reinforced thermoplastic resin foam molded article of the present invention is lightweight and has excellent compressive strength in the thickness direction. [0035] [Effect of the Invention] fiber-reinforced thermoplastic resin foamed molding of the present invention
According to the method for producing a body, it is possible to surely obtain an excellent foam molded article having high reinforcement efficiency for the weight.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an example of a flat fiber-reinforced thermoplastic resin foam molded article obtained according to the present invention . FIG. 2 is a cross-sectional view showing one example of the present invention and showing a state in which a fiber-reinforced thermoplastic resin foam molded article is being formed. FIG. 3 is a cross-sectional view showing another example of the embodiment of the present invention and showing a state in which a fiber-reinforced thermoplastic resin foam molding is being formed. [Explanation of Signs] (1): Fiber-reinforced thermoplastic resin foam molded article (2): Foam core layer (3): Skin layer

Claims (1)

(57) [Claim 1] A method for producing a fiber-reinforced thermoplastic resin foam molded article having a skin layer on both surfaces of a foamed core layer in which reinforcing fibers are oriented substantially parallel to the surface, Length 5-25m
A foamable fiber-reinforced thermoplastic resin containing 20 to 70% by weight of a reinforcing fiber of m is filled in a mold cavity while being heated at a temperature not lower than the melting temperature of the thermoplastic resin and not lower than the foaming temperature. While the temperature of the foamable fiber-reinforced thermoplastic resin is equal to or higher than the melting temperature, the mold is opened so that the cavity volume becomes 1.5 to 10 times that of the filling, and the fiber-reinforced thermoplastic resin is foamed. A method for producing a fiber-reinforced thermoplastic resin foam, characterized in that at least 20% by weight of fibers among the reinforcing fibers contained in the layer are oriented substantially perpendicular to the skin layer.