JPH10100185A - Manufacturing method and mold for fiber reinforced thermoplastic resin lightweight molded product - Google Patents

Abstract

(57) [Problem] To provide a lightweight fiber-reinforced thermoplastic resin molded article having excellent strength and rigidity without using a large amount of a foaming agent, using thermoplastic resin pellets containing fibers. In addition, the present invention provides a method for efficiently producing a final molded product having a good end face appearance and faithful to the shape of a mold, and a mold used for the production method. SOLUTION: Fiber-containing thermoplastic resin pellet (A),
Alternatively, the molding material comprising the pellet (A) and the thermoplastic resin is melt-kneaded, and is being filled in or after filling a mold cavity having a smaller volume than the final molded product, and then the mold cavity is in a state corresponding to the final molded product. In a method of manufacturing a molded article whose weight is reduced by enlarging, a part excluding an end forming portion in a final molded article is enlarged to manufacture a fiber-reinforced thermoplastic resin lightweight molded article. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lightweight molded article of a fiber-reinforced thermoplastic resin and a mold, and more particularly, it is not necessary to use a large amount of a foaming agent by injection molding using a fiber-reinforced thermoplastic resin pellet. The present invention relates to a method for faithfully manufacturing a lightweight molded article of a fiber-reinforced thermoplastic resin which is lightweight, high-strength, high-rigidity and excellent in appearance, and a mold used for producing the molded article.

[0002]

2. Description of the Related Art Glass fiber reinforced resin is used as an important material because of its excellent tensile strength, rigidity, heat resistance, etc. However, injection molding is difficult because of its easiness. Widely used. However, when the amount of the glass fiber is increased, the specific gravity of the molded article is increased, and the strength is reduced due to cutting of the glass fiber during molding. As a method for remedying these drawbacks, a method using resin pellets reinforced with glass fibers equal to a specific pellet length and arranged in parallel (for example, Japanese Patent Publication No. 63-37694, Japanese Unexamined Patent Publication No.
188131). But,
In these methods, although the strength and the like are improved, the problem that the weight increases due to the blending of the glass fiber has not been solved yet.

On the other hand, as a method for reducing the weight of the molded article, a foam injection molding method using a foaming agent is known (Japanese Patent Laid-Open No. 7-247679, etc.). It is not easy to increase the expansion ratio, and the content of glass fiber is limited. Further, a defect such as a silver mark occurred on the surface of the molded product, and the strength and rigidity of the molded product were not sufficient.

[0004] In view of these circumstances, the present inventors have previously described
In molding a similar molding raw material, the molding raw material is melt-kneaded, and the molten resin is injected into a closed mold so as to be smaller than a mold volume corresponding to a final molded product, or before completion of injection of the resin or A method of manufacturing a lightweight molded article of glass fiber reinforced thermoplastic resin, characterized in that the mold is opened to the volume of the final molded article after completion (Japanese Patent Application No. 08-028841).
issue).

However, in such a method, when the entire surface of the cavity of the molded product is expanded, when the molten resin comes into contact with the mold, the mold contact portion immediately starts to solidify. In the case of products, skin layers with good appearance are formed on both surfaces, but the solidification has begun partially on the end faces, so that even if the cavity is expanded, the expansion and flow of the molten resin are smooth. In some cases, the appearance of the end face is poor.

[0006]

SUMMARY OF THE INVENTION According to the present invention, it is possible to obtain a lightweight molded article having excellent surface properties, strength and rigidity without using a foaming agent, using thermoplastic resin pellets containing fibers. Moreover, it is an object of the present invention to provide a method for efficiently manufacturing a final molded product having a good end face faithful to the shape of a mold and a mold used in the manufacturing method.

[0007]

Means for Solving the Problems The present inventors injection-molded a lightweight molded article of a fiber-reinforced thermoplastic resin which satisfies weight reduction and strength, has good appearance including end faces, and is faithful to the mold shape. As a result of intensive studies, it has been found that the above-mentioned object is achieved by a specific molding method, and an excellent lightweight molded product is obtained. The present invention has been completed based on such findings.

That is, according to the present invention, a fiber-containing thermoplastic resin pellet (A) or a raw material comprising the pellet (A) and a thermoplastic resin is melt-kneaded, and the resulting mixture is placed in a mold cavity having a smaller volume than the final molded product. In a method of manufacturing a light-weight molded article by expanding a mold cavity to a state corresponding to a final molded article during or after filling, a portion excluding an end forming portion in the final molded article. It is intended to provide a method (1) for producing a lightweight molded article of a fiber-reinforced thermoplastic resin, characterized by enlarging the above. Further, the same molding material as used in the above (1) is melted and kneaded, and the molten resin is injected into a closed mold so that the cavity portion becomes smaller than the shape equivalent to the final molded product. Immediately before the injection is completed and the closed mold is filled with the resin, or after the resin is filled and the end of the final molded product is formed, the operating core is set so that the cavity portion is equivalent to the final molded product. And a method (2) for producing a fiber-reinforced thermoplastic resin light-weight molded product, characterized in that: Further, the same molding material as used in the above (1) or (2) is melt-kneaded, and the molten resin is injected into a closed mold so that the cavity portion is smaller than the shape equivalent to the final molded product. Before or simultaneously with the completion of the injection of the resin, the operating core is once advanced so that the resin is filled in the mold, and the end of the final molded article is simultaneously filled with the resin or filled with the resin. The method of manufacturing a lightweight fiber-reinforced thermoplastic resin molded product is characterized in that the working core is retracted so that the cavity portion becomes equivalent to the final molded product after the formation of the molded product. Moreover,
It is intended to provide a mold used in the above manufacturing method.

[0009]

Embodiments of the present invention will be described below. 1. Fiber-Containing Thermoplastic Resin Pellets (A) The method for producing the fiber-reinforced thermoplastic resin lightweight molded article of the present invention comprises:
Fiber-containing thermoplastic resin pellets (A) are used as a raw material for molding. (1) Thermoplastic resin The thermoplastic resin used here is not particularly limited. For example, polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin , Polyaromatic ether or thioether resins, polyaromatic ester resins, polysulfone resins,
Acrylate-based resins and the like can be mentioned.

The polyolefin resin includes, for example, α-olefin homopolymers such as ethylene; propylene; butene-1; 3-methylbutene-1; 3-methylpentene-1; These copolymers, or copolymers of these with other copolymerizable unsaturated monomers, and the like can be mentioned. As a representative example,
Polyethylene resins such as high-, medium-, and low-density polyethylene, linear polyethylene, ultra-high-molecular-weight polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, syndiotactic polypropylene, isotactic Polypropylene resins such as tic polypropylene, propylene-ethylene block copolymer or random copolymer, poly-4-methylpentene-1
And the like.

As the styrene resin, for example,
Homopolymers such as styrene and α-methylstyrene, copolymers thereof, and copolymers with unsaturated monomers copolymerizable therewith are exemplified. Representative examples include general-purpose polystyrene, impact-resistant polystyrene, heat-resistant polystyrene (α-methylstyrene polymer), syndiotactic polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS), and acrylonitrile-styrene copolymer ( AS), acrylonitrile-chlorinated polyethylene-styrene copolymer (ACS), acrylonitrile-ethylene-propylene rubber-styrene copolymer (A
ES), acrylic rubber-acrylonitrile-styrene copolymer (AAS), and the like.

As the polyvinyl chloride resin, for example,
Examples thereof include a vinyl chloride homopolymer and a copolymer of vinyl chloride with an unsaturated monomer copolymerizable with vinyl chloride. Examples of the copolymer include vinyl chloride-acrylate copolymer, vinyl chloride-methacrylate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, and vinyl chloride-vinyl acetate copolymer. Polymers, vinyl chloride-vinylidene chloride copolymers and the like can be mentioned. further,
Those obtained by post-chlorination of these polyvinyl chloride resins to increase the chlorine content can be used.

As the polyamide resin, for example, 6-
Ring-opening polymerization of cyclic aliphatic lactams such as nylon and 12-nylon, and condensation polymerization of aliphatic diamine and aliphatic dicarboxylic acid such as 6,6-nylon; 6,10-nylon; 6,12-nylon And polycondensation products of aromatic diamine and aliphatic dicarboxylic acid, such as polycondensation products of m-xylene diamine and adipic acid, polycondensation products of p-phenylenediamine and terephthalic acid, and m-phenylenediamine And polycondensation products of isophthalic acid and polycondensation products of aromatic diamine and aromatic dicarboxylic acid, and polycondensation products of amino acids such as 11-nylon.

Examples of the polyester-based resin include those obtained by condensation polymerization of an aromatic dicarboxylic acid and an alkylene glycol, and specific examples include polyethylene terephthalate and polybutylene terephthalate. Examples of the polyacetal-based resin include a polyoxymethylene homopolymer and a formaldehyde-ethylene oxide copolymer obtained from trioxane and ethylene oxide.

As the polycarbonate resin, 4,
A 4'-dihydroxydiarylalkane-based polycarbonate, particularly a bisphenol A-based polycarbonate obtained by a phosgene method of reacting bisphenol A with phosgene or a transesterification method of reacting bisphenol A with a diester carbonate such as diphenyl carbonate is preferably used. . Modification in which a part of bisphenol A is substituted with 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, or the like. Bisphenol A-based polycarbonate and flame-retardant bisphenol A-based polycarbonate can also be used.

The polyaromatic ether or thioether resin has an ether bond or a thioether bond in the molecular chain. Examples of such a resin include polyphenylene ether, polyphenylene ether grafted with styrene, and polyether. Examples include ether ketone and polyphenylene sulfide. Examples of the polyaromatic ester resin include polyoxybenzoyl obtained by polycondensation of p-hydroxybenzoic acid, and polyarylate obtained by polycondensation of bisphenol A with an aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid. Is mentioned.

The polysulfone resin has a sulfone group in the molecular chain. Examples of the polysulfone resin include polysulfone and phenylene groups obtained by polycondensation of bisphenol A with 4,4'-dichlorodiphenyl sulfone. Are linked to the p-position via an ether group and a sulfone group, and polyaryl sulfones having a structure in which diphenylene groups and diphenylene ether groups are alternately linked via a sulfone group. it can.

Examples of the acrylate resin include a methacrylate polymer and an acrylate polymer. These monomers include methyl, ethyl, n-propyl and isopropyl methacrylate and acrylate. Butyl ester, etc., and methyl methacrylate resin is a typical industrial molding material.

In the present invention, the above thermoplastic resins may be used alone or in combination of two or more. In addition, among the above thermoplastic resins, polypropylene, a random copolymer of propylene and another olefin, a polypropylene resin such as a block copolymer or a mixture thereof are preferable, and particularly, an unsaturated carboxylic acid or a derivative thereof. A polypropylene-based resin containing an acid-modified polyolefin-based resin modified with is preferred.

The polyolefin resin used for the acid-modified polyolefin resin includes, for example, polypropylene, polyethylene, ethylene-α-olefin copolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, Examples include an ethylene-α-olefin copolymer rubber, an ethylene-α-olefin-non-conjugated diene compound copolymer (eg, EPDM), and an ethylene-aromatic monovinyl compound-conjugated diene compound copolymer rubber. Examples of the α-olefin include propylene; butene-1; pentene-1; hexene-1; 4-methylpentene-1 and the like, and these may be used alone or in combination of two or more. You may. Among these polyolefin-based resins, a polypropylene-based resin or a polyethylene-based resin containing a copolymer is preferable, and among them, a polypropylene-based resin is most preferable.

Specific examples of the unsaturated carboxylic acids or derivatives thereof used for the modification include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, sorbic acid, mesaconic acid, and angelica. Unsaturated carboxylic acids such as acid, maleic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate,
Acid anhydrides, esters, amides, imides, such as methyl methacrylate, ethyl acrylate, butyl acrylate, monoethyl maleate, acrylamide, maleic monoamide, maleimide, N-butylmaleimide, sodium acrylate, and sodium methacrylate; Metal salts and the like can be mentioned. Among these, unsaturated dicarboxylic acids and derivatives thereof are preferred, and maleic anhydride is particularly preferred.

These unsaturated carboxylic acids and derivatives thereof may be used alone or in combination of two or more when modifying the polyolefin resin. The modification method is not particularly limited, and various conventionally known methods can be used. For example, a method of dissolving the polyolefin resin in an appropriate organic solvent, adding an unsaturated carboxylic acid or a derivative thereof and a radical generator, stirring and heating, or supplying each of the components to an extruder and performing melt kneading. A method or the like can be used. In the modified polyolefin resin, the amount of the unsaturated carboxylic acid or derivative thereof added is 0.01 to 20% by weight, preferably 0.1 to 20% by weight.
Those in the range of 1 to 10% by weight are preferred, and especially 0.1 to 1%.
0% by weight of a maleic anhydride-modified polypropylene resin is preferred. (2) Fiber The fiber used in the present invention is not particularly limited, but glass fiber; ceramic fiber such as boron fiber, silicon carbide fiber, alumina fiber, silicon nitride fiber, zirconia fiber, calcium silicate fiber, rock wool; magnesium oxide fiber,
Inorganic fibers such as magnesium oxysulfate fiber, magnesium hydroxide fiber and gypsum fiber; copper fiber, brass fiber,
Metal fibers such as steel fibers, stainless fibers, aluminum fibers, and aluminum alloy fibers; organic fibers such as polyethylene fibers, polypropylene fibers, aramid fibers, Kepler fibers, and polyarylate fibers; and carbon fibers.
Particularly, glass fiber is preferably used.

The glass fiber is preferably surface-treated with a coupling agent. As the coupling agent, any one of conventionally known silane coupling agents and titanium coupling agents can be selected and used. Specific examples of the silane coupling agent include triethoxysilane; vinyl tris (β-
Methoxyethoxy) silane; γ-methacryloxypropyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; β- (1,1-epoxycyclohexyl) ethyltrimethoxysilane; N-β- (aminoethyl) -γ- Aminopropyltrimethoxysilane; N-β
-(Aminoethyl) -γ-aminopropylmethyldimethoxysilane; γ-aminopropyltriethoxysilane;
N-phenyl-γ-aminopropyltrimethoxysilane; γ-mercaptopropyltrimethoxysilane; γ-
Chloropropyltrimethoxysilane; γ-aminopropyltrimethoxysilane; γ-aminopropyl-tris (2-methoxy-ethoxy) silane; N-methyl-γ-
Aminopropyltrimethoxysilane; N-vinylbenzyl-γ-aminopropyltriethoxysilane; triaminopropyltrimethoxysilane; 3-ureidopropyltrimethoxysilane; 3-4,5 dihydroimidazolepropyltriethoxysilane; hexamethyldisilazane N, O- (bistrimethylsilyl) amide; N, N
-Bis (trimethylsilyl) urea and the like.
Among them, γ-aminopropyltriethoxysilane; N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; β- (3,4-epoxycyclohexyl)
Aminosilanes such as ethyltrimethoxysilane and epoxysilanes are preferred. In particular, it is preferable to use the amino silane compound described above.

Specific examples of the titanium-based coupling agent include isopropyl triisostearoyl titanate; isopropyl tridodecylbenzenesulfonyl titanate; isopropyl tris (dioctyl pyrophosphate) titanate; tetraisopropyl bis (dioctyl phosphite) titanate; Bis (ditridecylphosphite) titanate; tetra (1,1-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate; bis (dioctylpyrophosphate) oxyacetate titanate; bis (dioctylpyrophosphate) ethylene titanate; Isopropyl trioctanoyl titanate;
Isopropyl dimethacryl isosteroyl titanate; isopropyl isostearoyl diacryl titanate; isopropyl tri (dioctyl phosphate) titanate; isopropyl tricumyl phenyl titanate;
Isopropyl tri (N-amidoethyl, aminoethyl)
Titanate; dicumylphenyloxyacetate titanate; diisostearoylethylene titanate;

The surface treatment of the glass fiber using such a coupling agent can be performed by a usual method, and there is no particular limitation. For example, it is desirable to carry out a sizing treatment in which an organic solvent solution or suspension of the coupling agent is applied to glass fibers as a so-called sizing agent, dry mixing, or a spray method. Further, a film-forming substance for glass can be used in combination with the above-mentioned coupling agent. The film-forming substance is not particularly limited, and examples thereof include polymers of polyester type, urethane type, epoxy type, acrylic type, vinyl acetate type and isocyanate type.

In the present invention, the glass fiber is E
Glass fibers such as glass and S-glass having an average fiber diameter of 20 μm or less are preferably used. Further, preferably 1 to 17 μm, more preferably 3 to 14 μm.
μm. If it is less than 1 μm, wetting and impregnation of the resin during pellet production becomes difficult, and if it is more than 20 μm, fiber breakage tends to occur during melt-kneading. Further, using the thermoplastic resin, particularly a polypropylene-based resin, pelletized using a pultrusion molding method or the like, 2 to 100 mm
It is preferably used as a thermoplastic resin pellet reinforced with a glass fiber having a length equal to the length of the pellet. When pelletizing, it is preferable to use a fiber bundle in which glass fibers are converged using an appropriate sizing agent, preferably in the range of 100 to 10,000 fibers, more preferably in the range of 150 to 5000 fibers.

As the sizing agent, there are, for example, urethane type, olefin type, acrylic type, butadiene type, epoxy type and the like, and all of them can be used. Among them, urethane type and olefin type are preferable. The urethane-based sizing agent is usually a polyisocyanate obtained by a polyaddition reaction between a diisocyanate compound and a polyhydric alcohol.
It is contained at a ratio of 0% by weight or more, and there are a one-part type such as an oil-modified type, a moisture-curable type and a block type, and a two-part type such as a catalyst-curable type and a polyol-curable type. be able to. As the olefin resin, a modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof can be used.

The glass fiber-containing thermoplastic resin pellets (A) can be produced by impregnating the thus bundled fiber bundle with a thermoplastic resin. The method of adhering and impregnating the glass fiber bundle with the resin is as follows. For example, a method of immersing the fiber bundle in the molten resin and passing it, a method of passing the fiber bundle through the coating die, a method of extruding the molten resin around the fiber bundle using the die, and the like can be adopted. In order to further improve the impregnation and wettability of the molten resin in the fiber bundle, an uneven portion is provided in the die, the fiber bundle (strand) to which the molten resin is adhered is pulled out under tension, and further pressed with a pressure roll. A pultrusion method incorporating the process can also be employed. The use of a sizing agent is not necessarily required as long as the impregnating property of the thermoplastic resin into the glass fibers and the productivity of the pellets are satisfied. After cooling the strand-shaped long-fiber-containing thermoplastic resin obtained in this way, by cutting into pellets of an appropriate length, the glass fibers are arranged in parallel with each other, and the glass fiber length and the pellet length are equal. The glass fiber-containing thermoplastic resin pellet (A) can be obtained.

In the present invention, it is preferable to use pellets having a length of 2 to 100 mm. Thereby, the length of the glass fiber is 2 to 10 which is equal to the pellet length.
0 mm. If the fiber length is less than 2 mm, it is difficult to reduce the weight of the molded product even if the production method of the present invention is used, the mechanical strength is not sufficient, the warpage may be large, and the fiber length may be 100 mm. If it exceeds 300, the injection molding becomes difficult, and the dispersibility of the glass fiber and the surface characteristics of the molded product may decrease. The pellet length reduces the weight of the molded product,
3 to 80 m from the viewpoint of mechanical strength, appearance characteristics and warpage
m, and more preferably 5 to 50 mm in consideration of dispersibility, appearance, and surface characteristics.

Even when fibers other than glass fibers, such as other ceramic fibers, inorganic fibers, organic fibers, metal fibers, and carbon fibers, are used, the same method as described above for glass fibers is used. Thus, fiber-containing thermoplastic resin pellets can be produced. The polypropylene resin used for producing these pellets has a melt index: M
I (230 ° C., 2.16 kgf) is 10 to 1000 g
/ 10 minutes, preferably 30 to 600 g / 10 minutes, is preferable in terms of impregnation, moldability and the like. Further, as the polypropylene-based resin, a resin whose MI is adjusted by polymerization conditions or a resin whose permeation is adjusted so that the MI is increased by adding a peroxide and melt-kneading can be used. The pellets are not limited to those obtained by cutting strands, but may be formed into sheets, tapes, and bands to have a fiber length of substantially 2 to 100 m.
m may be cut.

In the method for producing a lightweight molded article of the present invention,
The fiber-containing thermoplastic resin pellet (A) can be used alone for molding, but a mixture of (A) and the thermoplastic resin can also be used as a molding material. In this case, it is desirable that the content of the fiber in the pellet (A) is 20 to 80% by weight, preferably 30 to 70% by weight of the whole forming raw material. The thermoplastic resin used together with (A) is not particularly limited, and the shape thereof such as commercially available general-grade pellets, granules, and powders is not limited, but pellets are preferably used. In addition, talc, mica, calcium carbonate, glass fiber milled fiber, carbon fiber, magnesium sulfate fiber,
Examples include pellets containing a reinforcing agent such as potassium titanate fiber, titanium oxide fiber, and organic fiber, a filler, and a pellet containing an antioxidant, an antistatic agent, a flame retardant, a pigment, a dispersant, and the like. 2. Manufacturing method of fiber-reinforced thermoplastic resin lightweight molded article The method of manufacturing the fiber-reinforced thermoplastic resin lightweight molded article of the present invention,
The fiber-containing thermoplastic resin pellet (A) alone or a mixture of (A) and the thermoplastic resin is used as a raw material for molding, usually by injection molding under specific conditions. In this case, the fibers in the molding material are arranged parallel to each other in the pellet, the fiber length is 2 to 100 mm, preferably 3 to 80 mm, and the fiber content is 20 to 80% by weight, preferably 30 to 80% by weight. ７０70% by weight. Fiber length is 2
If the thickness is less than 100 mm, it is difficult to achieve a sufficient weight reduction.
If it exceeds 300, supply to an injection molding machine becomes difficult, and even when supplied, plasticization becomes unstable and it is difficult to produce a uniform molded product. In addition, long fibers (2-1
If the content is less than 20% by weight, it may be difficult to continuously draw the filaments in the production of long fiber pellets, and the weight may not be sufficiently reduced. On the other hand, if the content is 80% by weight or more, the fiber bundle is not sufficiently impregnated with the resin, and unfibrillated fibers may remain in the molded product. As the fiber-containing thermoplastic resin pellets (A), pellets having different fiber lengths and pellets having different fiber contents may be mixed and used as necessary. 3. Forming method As a method of melt-kneading and injection of the forming material, a forming material is put into a heating cylinder of a forming machine, heated and melted, and then fibers and the like are dispersed. Injection method, etc., into the heating cylinder, put the molding raw material, after heating and melting, send it to the screw part of the injection molding machine with a plunger, etc., disperse the fiber etc., then inject the method, deep groove Using a screw with a small compression ratio, and keeping the cylinder temperature etc. extremely high, feeding the resin to the tip of the injection molding machine while preventing fiber breakage,
There is a method of injection molding with a plunger or the like. Here, the injection molding method includes a general injection molding method and an injection compression molding method. In the present invention, the molding material is melted and kneaded, and during or after filling into a mold cavity having a smaller volume than the final molded product, the mold cavity is expanded to a state corresponding to the final molded product, thereby reducing the weight. In the method of manufacturing a molded article, a portion excluding an end forming portion in a final molded article is enlarged. The term “end” as used herein refers to a part other than the part formed by the retreat of the operating core in the final molded product. In the present invention, such an end is formed before the retreat of the operating core. Therefore, even if the operation core starts to retract, the shape of the end is already formed, and the shape of the end surface is good and faithful to the mold shape without being affected by the retraction of the operation core. The final molded product is obtained. In enlarging the part excluding the end forming part, the part to be enlarged may be all or part of the part excluding the end forming part. The edges must not be formed by enlargement.

The method is not particularly limited as long as the method satisfies such characteristics, but the embodiments of the injection molding method and the injection compression molding method will be illustratively described in detail below. Any method that satisfies the above characteristics may be used, and it is not limited to that mode. (1) Injection molding method In the case of injection molding, the production method of the present invention puts molten resin in a closed mold so that the cavity is smaller than the state equivalent to the final molded product. After the injection and injection of the resin are completed, immediately before filling the closed mold or after filling the resin, after forming the end of the final molded product first, the cavity part is equivalent to the final molded product This is performed by retracting the operation core so that

In this case, the closing state of the first mold is appropriately set based on the fiber content of the molding material, the fiber length, the porosity of the target molded product (specific gravity of the molded product), and the like. However, it is usually preferably set to be 15 to 90% of the final cavity volume. Further, the timing for retracting the operating core may be appropriately determined in consideration of the temperature of the mold, the thickness of the skin layer on the surface of the molded product, the thickness of the molded product, etc., as schematically shown in FIG. It is necessary to form the end of the final molded article first and then retract the working core. By adopting such a method, it is possible to obtain a final molded product having a good end face appearance and faithful to the mold shape. In the case of a resin that is extremely hard to solidify,
The operating core may be retracted immediately before filling the closed mold with the resin, but in this case also, the end of the final molded product needs to be formed first. Usually, it is preferable that the operating core is retracted after a certain period of time required for the resin to solidify after the resin is filled. If the method of expanding the entire surface of the cavity portion is adopted as schematically shown in FIG. 2 without employing the method of the present invention,
When the molten resin comes into contact with the mold, the mold contact part immediately begins to solidify.Therefore, when the movable mold is retracted and the cavity is expanded, the solidified layer allows the unsolidified resin to flow smoothly. As a result, there is a possibility that an unfilled portion is generated and an uneven end face is formed, so that a desired final shape with good appearance cannot be obtained.

The retreating speed of the operating core varies depending on the molding material such as resin used or the shape of the final molded product, but is usually selected in the range of 0.1 to 10 mm / sec. Further, the speed is not necessarily required to be constant, and the speed may be gradually increased from the initial stage of the retreat. Also, instead of stopping at the position corresponding to the final molded product for the purpose of retreating the operating core, the operating core is temporarily retracted to a position larger than the final molded product equivalent volume, and then the operating core is moved to the final molded product equivalent volume. May be reversed and compressed. (2) Injection compression molding method In the case of injection compression molding, the production method of the present invention melts in a closed mold so that the cavity portion becomes smaller than the state equivalent to the final molded product. Before or simultaneously with the completion of the resin injection, the operating core is once advanced so that the resin is filled in the mold, and simultaneously with or after the resin is filled. After the end of the molded article is formed, the operating core is retracted so that the cavity portion is in a state equivalent to the final molded article.

According to the present method, the resin can be injected at a low injection pressure, so that it is possible to effectively prevent fiber breakage and orientation which are likely to occur during injection filling.
In this method, the operating core is once advanced so that the resin is filled in the mold. In this case, the distance to be advanced is usually in the range of 0.1 to 50 mm. In particular, the range of 0.1 to 10 mm is preferably used from the viewpoint of preventing appearance defects such as flow marks from occurring due to air entrainment on the surface of the molded product. The forward speed is usually 0.5-30m
It is appropriately selected from the range of m / sec.

After the operation of filling the resin in the mold by compression due to the advancement of the operating core, the operating core is subsequently retracted. The state of the mold after the resin is filled and a series of operations are described above. The contents described in the molding method are applied as they are. (3) The melt-kneaded product of the resin injected into the mold is preferably in a state in which the fibers are entangled with each other, and the molten resin injected by the entanglement becomes a molten resin state having expandability in the mold.

In the production method of the present invention, a small amount of a foaming agent (gas, volatile compound, decomposition type foaming agent) may be used, if necessary. In addition, additives such as a stabilizer, an antistatic agent, a weathering agent, and a coloring agent can be added as long as the purpose is not hindered. Furthermore, in the method for manufacturing a lightweight molded product of the present invention, at least one surface of a molding die is preliminarily or fully fitted with a foam material, a fibrous material such as a nonwoven fabric, and a skin material such as a printed resin film. It can also be molded. 4. Fiber-reinforced thermoplastic resin lightweight molded product The fiber-reinforced thermoplastic resin lightweight molded product obtained by the production method of the present invention has a porosity of 10 to 80%, preferably 20 to 70%. If it is less than 10%, the effect of weight reduction is not obtained, and if it exceeds 80%, it becomes difficult to form a skin layer having no voids reliably, and the strength may be insufficient. Here, the porosity is a ratio of a volume excluding a volume occupied by a fiber, a resin, or the like in a molded product. The weight-average glass fiber length in the molded product is 1-2.
0 mm, preferably 1.5 to 15 mm, more preferably 2.0 to 12 mm. If the fiber length in the molded product is less than 1 mm, the expandability of the molten resin is low, it is difficult to secure the porosity, and the strength of the molded product is not sufficient.
Even if it exceeds mm, the influence on the strength and the like by this is small, and conversely, it is necessary to make the molding conditions mild, the molding time is long, the productivity is reduced, and it is not practical. The lightweight molded article of the present invention has a bending specific strength (bending strength / specific gravity) of 80M.
It is at least Pa, preferably at least 90 MPa, more preferably at least 100 MPa. The specific strength of such bending is
This is achieved by forming a skin layer and reinforcing a specific length of fiber.

In the production method of the present invention, various molded products can be produced, and are formed into plate-like molded products and molded products, particularly as plate-like molded products of 30 mm or less, such as automobile parts, home electric parts, Used in fields such as building components. 5. Mold The mold used in the production method of the present invention is a fixed mold,
A movable mold and an operating core arranged inside the movable mold so as to be able to advance or retreat independently in the same direction as the moving direction of the movable mold. It is formed of a movable mold and an operating core, and has a structure in which the volume of the cavity portion can be changed by moving the operating core forward or backward. The position setting and forward or backward movement of the operating core may be performed by a limit switch or the like, or may be performed by timer control. The operation core and the movable mold may be driven by any means such as hydraulic, pneumatic or electric. The drive unit may be incorporated in the mold unit or may be a separate device.

[0039]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The glass fiber-containing thermoplastic resin pellets (long fiber pellets) used in Examples and Comparative Examples were prepared by the following method. [Manufacturing Example 1] Dice: A die was attached to the tip of an extruder, and five rods were linearly arranged in the impregnated part. (Manufactured by a method using an apparatus in accordance with JP-A-3-183531, FIG. 2.) Fiber bundle: glass fiber having a fiber diameter of 13 μm, surface-treated with γ-aminopropyltriethoxysilane, was treated with a urethane-based sizing agent for 170 minutes. Pre-heating temperature: 200 ° C Thermoplastic resin: 230 ° C, 2.16 kgf melt index (hereinafter simply referred to as MI) = modified polypropylene containing maleic anhydride containing 1.0% by weight of 60 g / 10 min. Temperature: 240 ° C. Rod: 5, 6 mm (diameter) × 3 mm (length) Inclination angle: 25 ° C. Under the above conditions, the fiber bundle is fed into a die while adjusting the amount of the fiber bundle between the tension rolls, impregnated, and cooled. The glass fiber content is 41% by weight and the length is 2
A 0 mm glass fiber-containing pellet (hereinafter referred to as long fiber pellet A-1) was produced.

In the following Examples and Comparative Examples, evaluation of molded articles and tests of test pieces cut out from the molded articles were performed by the following methods. Flexural strength and flexural modulus: determined in accordance with JIS K-7203. Specific strength of bending = Flexural strength / Specific gravity Specific elastic modulus of bending = Flexural modulus / Specific gravity Weight average glass fiber length in molded product: Ashing the molded product, then magnifying the glass fiber by 10 times with a universal projector , And about 3000 pieces were measured with a digitizer, and the average value was obtained. [Example 1] The following materials, equipment, conditions, operations, etc. were used. (1) Molding raw material: long fiber pellets obtained in Production Example 1 above (2) Mold: cavity: 800 mm long x 4 wide
A test plate of a rectangular plate test type of 00 mm (variable thickness), which can move forward or backward independently in the same direction as the moving direction of the movable mold, at a position 3 mm from the inner end face of the movable mold. It is arranged. See FIG. (3) Molding machine: Injection molding machine (Mitsubishi Heavy Industries, Ltd .:
850MGW-160) Idemitsu IP to make the mold movable
M unit is mounted. (4) Molding conditions Molding temperature (cylinder temperature): 260 ° C Mold temperature: 50 ° C Injection pressure: 80 kg / cm ² G Injection speed: 60% Resin filling time: 3.2 seconds Holding pressure: 30 kg / cm ² G Hold Time: 3.0 seconds Cooling time: 120 seconds (5) Molding operation The molding operation was performed according to the following procedure.

In the injection molding machine, the movable mold was moved and the mold was closed in the same manner as in normal injection molding. Next, the operating core is advanced so that the clearance between the fixed mold and the operating core in the cavity becomes 4 mm,
Held. From the injection unit, the molten molding raw material was injected into a mold to completely fill the initial cavity and apply a pressure.

Immediately after the elapse of the dwell time, the retreat of the operating core was started. The retreat speed is set to 0.4 mm / sec, and the retreat distance is set to 4 mm, so that the thickness of the final cavity is 8 mm.
mm to complete the retreat. After the elapse of the cooling time, the movable mold was retracted, the mold was opened, and the molded product was taken out. Table 1 shows the evaluation results.

[0043]

[Table 1]

[Comparative Example 1] In Example 1, no cavity was formed only by a fixed mold and a movable mold as shown in FIG. 2 without an operating core, and the movable mold was moved. The procedure was performed in the same manner as in Example 1 except that the mold was changed so that the volume of the cavity portion could be changed. Table 1 shows the evaluation results.

[0045]

The method for producing a fiber-reinforced thermoplastic resin lightweight molded article according to the present invention does not require the use of a large amount of a foaming agent.
The obtained molded body is light in weight and has a high strength and high rigidity in combination with the reinforcement of the glass fiber because a skin layer is formed on the surface. Further, it is possible to obtain a final molded product which is faithful to the shape of the mold having a good appearance at the end face of the molded product.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically showing injection molding in an example or a comparative example.

Claims (6)

[Claims] 1. A fiber-containing thermoplastic resin pellet (A),
Alternatively, the molding material comprising the pellet (A) and the thermoplastic resin is melt-kneaded, and is being filled in or after filling a mold cavity having a smaller volume than the final molded product, and then the mold cavity is in a state corresponding to the final molded product. A method for producing a light-weight molded article by enlarging a part, wherein a portion excluding an end portion forming part in a final molded article is enlarged, wherein: . 2. A fiber-containing thermoplastic resin pellet (A),
Alternatively, the molding material comprising the pellet (A) and the thermoplastic resin is melt-kneaded, and the molten resin is injected into a closed mold so that the cavity is smaller than a shape equivalent to the final molded product, Immediately before the injection is completed and the closed mold is filled with the resin, or after the resin is filled and the end of the final molded product is formed, the operating core is set so that the cavity portion is equivalent to the final molded product. A method for producing a lightweight molded article of a fiber-reinforced thermoplastic resin, wherein 3. A fiber-containing thermoplastic resin pellet (A),
Alternatively, the molding material comprising the pellet (A) and the thermoplastic resin is melt-kneaded, and the molten resin is injected into a closed mold so that the cavity is smaller than a shape equivalent to the final molded product, Before or simultaneously with the completion of the injection, the operating core is once advanced so that the resin is filled in the mold, and simultaneously with or after the resin is filled and the end of the final molded article is formed. A method of manufacturing a lightweight fiber-reinforced thermoplastic resin molded product, comprising retreating an operating core so that a cavity portion is equivalent to a final molded product. 4. The method according to claim 1, wherein the fibers are glass fibers. 5. The fiber-containing thermoplastic resin pellet (A), wherein the fiber content is 20 to 80% by weight, the fibers are arranged in parallel with each other, and the length is 2 to 100 mm. Item 4. The method for producing a lightweight molded article of a fiber-reinforced thermoplastic resin according to any one of Items 1 to 3. 6. A mold used in the method for producing a fiber-reinforced thermoplastic resin lightweight molded product according to claim 1, wherein the fixed mold, the movable mold, and the moving direction of the movable mold. And a working core disposed inside the movable mold so as to be able to independently advance or retreat in the same direction as the above, and a cavity is formed from the fixed mold, the movable mold and the working core, An injection mold capable of changing the volume of the cavity by moving the operating core forward or backward.