JP3960660B2 - Manufacturing method of lightweight molded product of fiber reinforced thermoplastic resin - Google Patents

Description

【００３８】
〔比較例１〕
金型温度をすべて４０℃の均一とした以外は、実施例１と同様に行った。評価結果を第１表に示す。
〔比較例２〕
最初から成形品の厚み（ｔ）が３ｍｍとなるような位置に金型コアをセットし、コアバックを行わなかった以外は、実施例１と同様に行った。評価結果を第１表に示す。
〔比較例３〕
成形原料として、ガラス繊維含有量が４０重量％で、ガラス繊維の重量平均繊維長が０.4２ｍｍである短繊維ガラス繊維強化ポリプロピレンを用いた以外は、実施例１と同様にして成形品を得た。評価結果を第１表に示す。
〔実施例２〕
ポリプロピレン（出光石油化学（株）製，商品名Ｊ−６０８３Ｈ）９５重量部に無水マレイン酸含有量１重量％の無水マレイン酸変性ポリプロピレン５重量部を加え、これを実施例１と同様にしてペレットの長さが８ｍｍになるように切断した。得られたペレット中の繊維量は６０重量％であった。このペレットにポリプロピレン（出光石油化学（株）製，商品名Ｊ−６０８３Ｈ）を、ガラス繊維含有量が３０重量％になるようにドライブレンドし、さらにこのドライブレンド物１００重量部に対し、発泡剤マスターバッチペレット〔ポリスレンＥＶ−３０６Ｇ（永和化成工業株式会社製）：発泡剤含有量＝３０重量％〕を０．３重量部ブレンドした後、以下の手順にした以外は実施例１と同様に射出成形を行った。 まず、予め厚み（ｔ）が３ｍｍの成形品を得るのに必要な溶融原料量を計量しておいた。次に、成形品の厚み（ｔ）が２ｍｍとなるような位置まで可動金型を前進させセットした後、先に計量しておいた量の溶融原料の射出を開始した。射出開始とほぼ同時に、最終成形品の厚みが９ｍｍになるようにコアバックを行った。冷却後、肉厚９ｍｍの軽量成形品を得た。評価結果を第１表に示す。
〔比較例４〕
金型温度をすべて５０℃の均一とした以外は、実施例２と同様に行った。評価結果を第１表に示す。
〔比較例５〕
成形原料として、ガラス繊維含有量が３０重量％で、ガラス繊維の重量平均繊維長が０.4８ｍｍである短繊維ガラス繊維強化ポリプロピレンを用い、さらに発泡剤マスターバッチペレット〔ポリスレンＥＶ−３０６Ｇ（永和化成工業株式会社製）：発泡剤含有量＝３０重量％〕を３重量部ブレンドしたものを用いた以外は、実施例２と同様にして成形品を得た。評価結果を第１表に示す。
〔比較例６〕
成形原料として、ガラス繊維含有量が３０重量％で、ガラス繊維の重量平均繊維長が０.4８ｍｍである短繊維ガラス繊維強化ポリプロピレンを用い、さらに発泡剤を１０重量部ブレンドしたものを用いて、最初から成形品の厚み（ｔ）が３ｍｍとなるような位置に可動金型をセットし、射出開始とほぼ同時に、最終成形品の厚みが９ｍｍになるようにコアバックを行った。この際、金型温度をすべて５０℃の均一とした。また、金型はカウンタープレッシャー用にシールを施した。それ以外は実施例２と同様におこなった。冷却後、肉厚９ｍｍの軽量成形品を得た。評価結果を第１表に示す。
【００３９】
【発明の効果】
本発明による繊維強化軽量熱可塑性樹脂軽量成形品の製造法は、発泡剤を多量に用いることなく製造することができ、得られた成形体は、軽量であるとともに、表面状態等の外観に極めて優れ、しかも表面にスキン層が形成されるため、繊維の補強と相まって高強度、高剛性である。
【図面の簡単な説明】
【図１】溶融樹脂充填完了時点であり、未膨張状態における固定金型及び可動
金型の概略平面図
【図２】可動金型を後退させ、膨張完了状態における固定金型及び可動金型の
概略平面図
【図３】端部膨張率及び中央部膨張率の測定における試験用矩形板の中央部で
の概略断面図
【図４】反り量試験用矩形板の概略平面図
【符号の説明】
１： 固定金型
２： 可動金型
３： 金型における加熱された部分
４： 溶融樹脂
５： スプルー
６： 初期キャビティ部
７： 最終成形品におけるキャビティ部
８： 端部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a fiber-reinforced thermoplastic resin lightweight molded article, and in particular, by injection molding using a specific fiber-reinforced thermoplastic resin pellet, it is lightweight, has a good surface state, and has high strength and high rigidity. It is related with the method of manufacturing the fiber reinforced thermoplastic resin lightweight molded article which is.
[0002]
[Prior art]
For the purpose of improving the tensile strength, rigidity, and heat resistance, conventionally, various fibers have been widely blended with resin. However, when the amount of fibers is increased, high strength is achieved. There was a drawback that the specific gravity of the molded product was high.
On the other hand, as a method for obtaining a lightweight molded article, a foam injection molding method using a foaming agent at the time of molding is known (Japanese Patent Laid-Open No. 7-247679, etc.). A considerable amount of foaming agent must be used, and even if a large amount of foaming agent is used, it is not so easy to increase the expansion ratio, and sufficient weight reduction cannot be achieved. Furthermore, the surface appearance of the molded product is inferior due to non-uniform foaming, and a large hollow portion is formed inside, and a molded product satisfying in terms of strength and rigidity cannot be obtained.
[0003]
In addition, even when the resin is blended with fibers and injection molding is performed using a foaming agent, as described above, sufficient foaming cannot be obtained at the time of injection molding, or the molded product surface is defective such as a silver mark. At present, the phenomenon has occurred and there are many problems in terms of strength, and it has not been put into practical use.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a lightweight molded article excellent in surface appearance, strength and rigidity using a specific fiber-containing thermoplastic resin pellet having a long fiber length without using a large amount of a foaming agent. And
[0005]
[Means for Solving the Problems]
The present inventors have intensively studied to obtain a lightweight fiber-reinforced thermoplastic resin molded product that satisfies weight reduction and strength, has an excellent surface appearance, and is sufficiently expanded on all surfaces of the molded product by injection molding. As a result, for example, the molten resin is injected into a closed mold so as to be smaller than the mold volume corresponding to the final molded product, and the mold is filled up to the volume of the final molded product before or after the resin injection is completed. Although the method of taking the opening method was previously proposed (Japanese Patent Application No. 8-277920, Japanese Patent Application No. 8-298599, Japanese Patent Application No. 8-298600), a combination of these specific molding raw materials and molding methods In addition to the above, it has been found that the object can be achieved more effectively by molding under specific mold conditions. The present invention has been completed based on such findings.
[0006]
That is, this invention provides the manufacturing method of the following fiber reinforced thermoplastic resin lightweight molded articles.
(1) Fiber-containing thermoplastic resin pellet (A) having a fiber length of 2 to 100 mm in the pellet, or a mixture of the pellet (A) and the thermoplastic resin as a molding raw material, and the fiber content in the molding raw material Melting and kneading the amount of 5 to 80% by weight, and injecting the molten resin into a closed mold so as to be smaller than the mold volume equivalent to the final molded product, before or after completion of resin injection In manufacturing a lightweight fiber reinforced thermoplastic resin molded product by opening the mold to the volume of the final molded product later,The mold has a female mold and a male mold slidably fitted to the female mold, and the volume of the cavity defined by the female mold and the male mold is variable, The side part on which the male mold slides on the inner surface of the female mold is hotter than the other parts.A process for producing a lightweight molded product of fiber reinforced thermoplastic resin characterized by the above.
(2) When the same raw material as in the above (1) is melt-kneaded and the molten raw material is injected into a closed mold, the volume of the cavity portion is made smaller than the entire volume of the molten raw material to be injected. In order to produce a fiber-reinforced thermoplastic resin lightweight molded product by injecting into a closed mold, and then opening the mold to the volume of the final molded product,The mold has a female mold and a male mold slidably fitted to the female mold, and the volume of the cavity defined by the female mold and the male mold is variable, The side part on which the male mold slides on the inner surface of the female mold is hotter than the other parts.A process for producing a lightweight molded product of fiber reinforced thermoplastic resin characterized by the above.
(3) The same raw materials as in (1) above are melted and kneaded, and simultaneously with the injection of the molten resin into the cavity or after the start of injection, the movable mold is advanced and compressed once, and then the mold is finalized. In manufacturing a fiber reinforced thermoplastic resin lightweight molded product by opening up to the volume of the molded product,The mold has a female mold and a male mold slidably fitted to the female mold, and the volume of the cavity defined by the female mold and the male mold is variable, The side part on which the male mold slides on the inner surface of the female mold is hotter than the other parts.A process for producing a lightweight molded product of fiber reinforced thermoplastic resin characterized by the above.
(4) In the manufacturing method of said (1)-(3), as a material used for melt-kneading, the fiber-containing thermoplastic resin pellet (A) whose length of the fiber in a pellet is 2-100 mm, or this pellet ( A mixture of A) and a thermoplastic resin is used as a forming raw material, and 100 parts by weight of the fiber content in the forming raw material is 5 to 80% by weight, and 0.1 to 3 parts by weight of a foaming agent is blended. A method for producing a lightweight molded article of fiber-reinforced thermoplastic resin according to any one of (1) to (3), wherein the method is used.
(5) Production of fiber-reinforced thermoplastic resin lightweight molded article according to any one of (1) to (3), wherein the porosity of the lightweight molded article in (1) to (3) is 30 to 80%. Law.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
1. Fiber-containing thermoplastic resin pellet (A)
In the method for producing a fiber-reinforced thermoplastic resin lightweight molded article of the present invention, fiber-containing thermoplastic resin pellets (A) are used as a molding raw material.
(1) Thermoplastic resin
There is no particular limitation on the thermoplastic resin used here, for example, polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, polyaromatic ether or Examples include thioether resins, polyaromatic ester resins, polysulfone resins, and acrylate resins.
[0008]
Examples of the polyolefin resin include homopolymers of α-olefins such as ethylene and propylene, and copolymers of these with other copolymerizable unsaturated monomers.
Examples of the styrene resin include homopolymers such as styrene and α-methylstyrene, and copolymers with unsaturated monomers copolymerizable therewith.
[0009]
Examples of the polyvinyl chloride resin include vinyl chloride homopolymers and copolymers with unsaturated monomers copolymerizable with vinyl chloride.
Examples of the polyamide-based resin include 6-nylon, 12-nylon, 6,6-nylon, 6,10-nylon, 6,12-nylon, and 11-nylon.
[0010]
Examples of the polyester resin include polyethylene terephthalate and polybutylene terephthalate.
Examples of the polyacetal resin include a homopolymer polyoxymethylene and a formaldehyde-ethylene oxide copolymer obtained from trioxane and ethylene oxide.
[0011]
As the polycarbonate resin, 4,4'-dihydroxydiarylalkane polycarbonate, particularly bisphenol A polycarbonate is preferably used. Also, modified bisphenol A-based polycarbonates, flame retardant bisphenol A-based polycarbonates, and the like can be used.
Examples of the polyaromatic ether or thioether-based resin include polyphenylene ether, polyphenylene ether grafted with styrene, polyether ether ketone, and polyphenylene sulfide.
[0012]
Examples of the polyaromatic ester-based resin include polyarylate.
Examples of the polysulfone resin include polysulfone, polyethersulfone, and polyarylsulfone.
Examples of the acrylate resin include methacrylic acid ester polymers and acrylic acid ester polymers.
[0013]
In the present invention, the above thermoplastic resins may be used alone or in combination of two or more. Furthermore, for example, acid-modified polyolefin resins modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and fumaric acid, acid anhydrides such as maleic anhydride or derivatives thereof are also preferably used. Of these, maleic anhydride is particularly preferred.
[0014]
These unsaturated carboxylic acids and derivatives thereof may be used singly or in combination of two or more. There is no particular limitation on the modification method.
(2) Fiber
The fiber used in the present invention is not particularly limited. Glass fiber; Boron fiber, Silicon carbide fiber, Alumina fiber, Silicon nitride fiber, Zirconia fiber ceramic fiber; Copper fiber, Brass fiber, Steel fiber, Stainless steel fiber, Aluminum fiber, Aluminum alloy fiber and other metal fiber; Polyester fiber, Organic fibers such as polyamide fiber, aramid fiber and polyarylate fiber; carbon fiber and the like can be mentioned. Glass fibers are preferably used, but two or more of the above fibers may be used in combination.
[0015]
When glass fiber is used, one that has been surface treated with a coupling agent is preferred. As the coupling agent, any of silane coupling agents such as aminosilane and epoxysilane, and titanium coupling agents can be preferably used. Moreover, the film-forming substance for glass can be used together with a coupling agent. The film-forming substance is not particularly limited, and examples thereof include polyester-based, urethane-based, epoxy-based, acrylic-based, vinyl acetate-based, and isocyanate-based polymers. As the glass fibers, glass fibers such as E-glass and S-glass are preferably used.
[0016]
In the present invention, the fiber preferably has an average fiber diameter of 20 μm or less. Furthermore, it is preferably 1 to 17 μm, more preferably 3 to 14 μm. If it is smaller than 1 μm, it becomes difficult to wet and impregnate the resin during the production of pellets, and if it exceeds 20 μm, the fiber tends to be damaged during melt-kneading.
(3) Method for producing fiber-containing thermoplastic resin pellet (A)
Although it does not restrict | limit especially about preparation of a fiber containing thermoplastic resin pellet (A), The length of the fiber in the obtained pellet (A) is 2-100 mm, Preferably it is 3-80 mm, More preferably, it is 5 It must be ˜50 mm. If the fiber length is less than 2 mm, even if the manufacturing method of the present invention is adopted, sufficient expansion is not performed, so it is difficult to achieve a lightweight molded product, mechanical strength is not sufficient, and warping deformation is large. There is a case. Moreover, when it exceeds 100 mm, while injection molding becomes difficult, the dispersibility of a fiber worsens and the surface characteristic of a molded article may fall.
[0017]
For producing the pellet (A), for example, the method described below is preferably used.
(1) A method of impregnating and adhering a bundle of fibers with a thermoplastic resin
It is a method of producing pellets by bundling the fibers used, impregnating them with a thermoplastic resin, drawing out a fiber bundle (strand) to which the molten resin is adhered, and cutting it. For example, glass fibers, inorganic fibers, carbon fibers It is preferably used when using fibers that are relatively easy to break. A fiber bundle in which fibers are bundled with an appropriate sizing agent, preferably in the range of 100 to 10,000 is used.
[0018]
Examples of the sizing agent include urethane, olefin, acrylic, butadiene, and epoxy. Of these, urethane and olefin are preferable. Examples of methods for attaching and impregnating resin to the fiber bundle include, for example, a method in which the fiber bundle is immersed in the molten resin, a method in which the fiber bundle is passed through the coating die, and a molten resin is extruded around the fiber bundle using the die. The method etc. are mentioned. In addition, if the impregnation property of the thermoplastic resin to the fiber and the manufacturability of the pellet are satisfied, the use of the sizing agent is not necessarily required. The strand-like long fiber-containing thermoplastic resin thus obtained is cooled and then cut into pellets of an appropriate length so that the fibers are arranged in parallel with each other, and the fiber length and the pellet length are equal. A thermoplastic resin pellet (A) can be obtained. If a pellet obtained by cutting (A) into a length of 2 to 100 mm is used, the fiber length is 2 to 100 mm, which is equal to the pellet length.
[0019]
As the thermoplastic resin, for example, a polypropylene resin is preferably used. In that case, a resin having a melt index (230 ° C., 2.16 kgf) in the range of 10 to 1000 g / 10 min is impregnated, moldability, etc. This is preferable. The pellets are not limited to those obtained by cutting strands, but are formed into sheets, tapes, or bands and cut so that the fiber length is substantially 2 to 100 mm. There may be.
[0020]
In the case of this method, it is preferable to mix the resin and the fiber so that the fiber content in the pellet (A) is 20 to 80% by weight. If the amount is less than 20% by weight, the strands may not be continuously drawn out during pellet production. If the amount exceeds 80% by weight, the impregnation of the resin into the fiber bundle may be deteriorated.
(2) Method of kneading thermoplastic resin and fiber using a Banbury mixer or the like
In this method, a thermoplastic resin and fibers are added to a Banbury mixer and the like, and the resin is melted by heating, and then extruded from an extruder and cut into strands to produce pellets. For example, it is a method preferably employed when using fibers that are relatively difficult to break, such as organic fibers.
[0021]
What is necessary is just to select suitably the quantity of the fiber in this method so that it may become 5 to 80 weight% with respect to the whole which consists of a thermoplastic resin and a fiber.
In the case of this method, the fibers in (A) are not necessarily arranged in parallel in the pellet.
2. Manufacturing method of lightweight molded product of fiber reinforced thermoplastic resin
The method for producing a fiber-reinforced thermoplastic resin lightweight molded article according to the present invention uses the above-mentioned fiber-containing thermoplastic resin pellet (A) alone or a mixture of (A) and a thermoplastic resin as a molding raw material, and a small amount as required. A blended foaming agent is molded by injection molding under specific conditions.
(1) Molding raw material
The fiber-containing thermoplastic resin pellet (A) is as described above, but the fiber content needs to be 5 to 80% by weight, preferably 5 to 60% by weight, and more preferably 15 to 55% by weight. is there. Pellets having different fiber contents and pellets having different fiber lengths can be mixed and used as necessary. Even when pellets having different fiber contents are mixed as necessary, the fiber content is 5 to 80% by weight, preferably 5 to 60% by weight, more preferably 15 to 55% by weight based on the whole. It is necessary to be.
[0022]
In addition, when a mixture of the fiber-containing thermoplastic resin pellet (A) and the thermoplastic resin is used as a forming raw material, the thermoplastic resin is not limited in its shape such as pellet, granule, powder, etc. Is preferably used. Even in this case, the mixing of the (A) and the thermoplastic resin is not limited, and the fiber content is 5 to 80% by weight, preferably based on the entire forming raw material composed of the mixture of the (A) and the thermoplastic resin. It is necessary to be 5 to 60% by weight, more preferably 15 to 55% by weight. If it is less than 5% by weight, the product may have insufficient rigidity and impact resistance. On the other hand, if it exceeds 80% by weight, undefibrated fibers may remain in the molded product, or the appearance of the product may deteriorate. In this case, the fiber content may be 5 to 80% by weight with respect to the entire forming raw material composed of the mixture of (A) and the thermoplastic resin, and (A) the fiber content itself is 5 to 80% by weight. There is no particular limitation.
[0023]
Further, it may contain reinforcing agents such as talc, mica and calcium carbonate, fillers, antioxidants, antistatic agents, flame retardants, pigments, dispersants and the like.
Furthermore, in the manufacturing method (4) of the lightweight molded article of the present invention, 100 parts by weight of the fiber-containing thermoplastic resin pellet (A), or 100 parts by weight of a mixture comprising the fiber-containing thermoplastic resin pellet (A) and the thermoplastic resin. On the other hand, a blend containing 0.01 to 3 parts by weight of a foaming agent is used for injection molding. When the amount is less than 0.01 parts by weight, a sufficient amount of gas is not generated, and when the mold is retracted and the cavity is enlarged, the inside of the cavity is in a negative pressure state and stable expansion is not performed. There is a possibility that undulations may occur on the surface and smoothness may deteriorate. When the amount exceeds 3 parts by weight, the amount of gas in the cavity becomes excessive, and the molded product may have uneven distribution of voids, which may reduce the mechanical strength. The type of foaming agent is not particularly limited, but it is necessary that the foaming agent be decomposed by heat to generate gas. The preferred amount of foaming agent varies depending on the type of foaming agent and the type or amount of fiber contained in the raw material used for molding, but generally, when the amount of fiber is 30 to 80% by weight, it is used for molding. When the raw material is 100 to 100 parts by weight and the fiber amount is 20 to 30% by weight, it is similarly 0.05 to 1.5 parts by weight and the fiber amount is 5 to 20%. In the case of% by weight, it is similarly selected from the range of 0.1 to 3 parts by weight.
[0024]
Specific examples of blowing agents include oxalic acid derivatives, azo compounds, hydrazine derivatives, semicarbazides, azides, nitroso compounds, triazoles, urea and related compounds, nitrites, hydrides, carbonates and bicarbonates. Used.
(2) Molding method
In the production method of the present invention, a molding raw material is melted, and the molten raw material (in the production method (1), the molten resin is referred to as a molten resin in the production method (4)), The same applies hereinafter), and is selected from the following methods (1) to (3).
[0025]
(1) The molten resin is injected into a closed mold so as to be smaller than the mold volume equivalent to the final molded product, and the mold is opened to the final molded product volume before or after the resin injection is completed. How to do by.
The closing condition of the first mold in this case may be appropriately set based on the fiber content, fiber length, etc. in the forming raw material. The timing for opening the mold 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, and the like.
[0026]
Specifically, as shown in FIG. 1 and FIG. 2, a fixed mold and a movable mold are formed, and a cavity portion is formed from the fixed mold and the movable mold, and the movable mold is moved forward or backward. It is preferable to perform molding using a mold that can change the volume of the cavity. That is, the molten resin is injected into the closed mold, and immediately after the injection of the resin is completed and the resin is filled into the closed mold, the movable mold is set so that the cavity part is equivalent to the final molded product. It is desirable to perform molding by retreating. The speed at which the movable mold is retracted varies depending on the molding raw material such as the resin used or the shape of the final molded product, but is usually selected in the range of 0.1 to 10 mm / second. Furthermore, the speed does not necessarily have to be constant, and the speed may be gradually increased from the initial reverse.
[0027]
(2) A method of injecting the mold into a closed mold so that the volume of the cavity portion is smaller than the total volume of the molten raw material to be injected, and then opening the mold to the volume of the final molded product. .
This method is an improvement of the above method (1), and as a method of closing the mold before injection, the volume of the cavity portion is made smaller than the total volume of the molten raw material to be injected. It is. In this state, the core back is started simultaneously with the start of injection. The injected molten resin is pressed against the mold to improve surface transfer, and since the core back is continuously performed, there is no hesitation and good expansibility is exhibited. Thereby, a molded article having a good surface state can be obtained.
[0028]
What is necessary is just to determine suitably according to the kind of resin to be used, the quantity of the fiber to contain, etc. about how much the volume of a cavity part is closed so that it may become smaller than the total volume of the molten raw material injected. Usually, the volume of the cavity portion is preferably set in the range of 60 to 99%, preferably 80 to 95% with respect to the total volume of the molten raw material to be injected. Alternatively, when the molded product is plate-shaped, it is 60 to 99%, preferably 80 to 95% of the thickness of the molded product obtained when all the molten raw materials are filled. It is preferable to close the mold in order to make the cavity portion small.
[0029]
The molten raw material is injected into the mold thus closed, and then the operation of opening the mold to the volume of the final molded product is performed. The timing for opening the mold 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, and the like. This core back operation may be started simultaneously with the injection, or may be started immediately before the injection is completed. Usually, since the filling speed of the molten raw material is extremely high, it is not necessary to wait until the injection is completed, and it is preferable to start the core back operation simultaneously with the start of the injection. The final lightweight molded product is obtained by opening the mold until it reaches the volume of the final molded product and cooling. The speed at which the movable mold is retracted is the same as in the above (1).
[0030]
(3) A method in which the movable mold is advanced and compressed once at the same time as or after the injection of the molten resin into the cavity, and then the mold is opened to the volume of the final molded product.
This method is a method in which the mold is not opened immediately after the injection of the raw material as in the above (1) and (2), but is opened after the movable mold is once advanced to compress the raw material.
[0031]
According to this method, the volume of the first cavity may be in a state where the mold is opened, that is, the volume of the final molded product, or may be a smaller volume. From the viewpoint that it is possible to effectively prevent fiber breakage and orientation that are likely to occur during injection filling by injecting the resin at a low injection pressure, it is preferable that the mold is open. At the same time as or after the start of injection of the molten resin, the movable mold is once advanced so that the resin fills the mold. In this case, the advance distance is usually in the range of 0.1 to 50 mm. It is good to do. In particular, the range of 0.1 to 20 mm is preferable from the viewpoint of preventing appearance defects such as flow marks due to air entrainment on the surface of the molded product. The speed to advance is usually selected from the range of 0.5 to 30 mm / second.
[0032]
The timing for compressing the cavity portion may be started simultaneously with the injection of the molten resin or after the start of the injection. Usually, since the filling speed of the molten raw material is extremely high, it is not necessary to wait until just before the injection is completed, and it is preferable to start the compression simultaneously with the injection.
Subsequently, an operation of opening the mold to the volume of the final molded product is performed. The timing at which the mold starts to open and the retracting speed of the movable mold are the same as described in the above (1) and (2).
(2) Mold temperature
In the present invention, it is necessary to mold the mold to be used so that the portion where the end portion of the final molded product is formed has a higher temperature than the other portions. As shown in FIG. 1 and FIG. 2, the term “end portion” as used herein refers to a side surface portion of a final molded product including a surface formed by a fixed mold by retreating a movable mold. By making the temperature of the portion where the end portion is formed in this way higher than the other portions, the portion where the end portion of the final product is formed is cooled and solidified first by contacting the fixed mold. Insufficient expansion caused by this can be prevented. In the mold used, the temperature at which the end part is formed should be appropriately selected depending on the type of molding raw material such as resin used and the volume of the cavity part. However, specifically, it is preferably at least 10 ° C. or higher. There is no particular limitation on the method for raising the temperature of the part of the mold compared to other parts, but a method of burying a heater in the mold part or heating with infrared rays is preferably performed.
4). Fiber reinforced thermoplastic resin lightweight molded product
The fiber-reinforced thermoplastic resin lightweight molded article obtained by the production method of the present invention has a fiber content of 5 to 80% by weight, preferably 5 to 60% by weight, more preferably 15 to 55% by weight. Moreover, the porosity is 30 to 80%, preferably 40 to 75%, and more preferably 50 to 70%. The porosity is the ratio of the volume of the void, excluding the volume occupied by fibers and resins in the molded product. For example, the ratio of the specific gravity of the material and product, It can also be calculated on the basis of the foaming ratio.
[0033]
In the production method of the present invention, various lightweight molded products can be produced. The fiber-reinforced thermoplastic resin lightweight molded product obtained by the production method according to the present invention is not particularly limited in shape or size, but is preferably a plate-shaped molded product, particularly a plate-shaped molded product or mold of 30 mm or less. Includes molded articles. Specifically, it is lightweight like a helmet storage box mounted on automobile parts (for example, instrument panel cores, bumper beams, door steps, roof racks, rear quarter panels, air cleaner cases, sunshades, etc.), motorcycles, etc. Various boxes, home appliance parts, building materials (for example, concrete panels (concrete formwork), cable troughs, wall materials, floor materials, etc.) used for places where impact resistance and strength are required, flooring for unit baths And water pans.
[0034]
【Example】
EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited by this.
In the following examples and comparative examples, the molded products were evaluated by the following methods.
The following evaluation was performed on a rectangular plate for 600 mm × 300 mm × thickness tmm test.
(A) Expansion state of product end
(1) End part expansion coefficient = a / t
(2) Center part expansion coefficient = b / t
Here, as shown in FIG. 3, “a” indicates the thickness of the side surface portion formed by being in contact with the end portion forming portion of the product in the fixed die even after the core back of the movable die is finished. Further, b represents the thickness of the final molded product after expansion due to the end of the core back of the movable mold. Further, t represents the thickness of the product in a state before the movable mold is core-backed.
(B) Warpage amount: A test rectangular plate was placed on the surface plate, the distance at which the left and right ends warped from the surface plate as shown in FIG. 4 was determined, and the amount of warpage was determined by the following equation.
[0035]
Warpage amount = h₁+ H₂
(D) Expansion state: The central part of the test rectangular plate was cut, and the cut surface was visually evaluated.
[Example 1]
While 96 parts by weight of polypropylene (trade name J-6083H, manufactured by Idemitsu Petrochemical Co., Ltd.) was added 4 parts by weight of maleic anhydride-modified polypropylene having a maleic anhydride content of 1% by weight, this was extruded into a die, while γ -A glass roving in which 170 glass fibers having a fiber diameter of 13 μm surface-treated with aminopropyltriethoxysilane were bundled with urethane sizing agent was drawn into a die, the resin was impregnated into the fiber bundle, and then the fiber was drawn out and cooled. The pellet was cut to a length of 15 mm. The amount of fibers in the obtained pellets was 40% by weight.
[0036]
The pellets were injection-molded using an injection molding machine (Mitsubishi Heavy Industries, Ltd .: 850MGW, equipped with an Idemitsu compression unit) using a mold (rectangular shape with a thickness of 600 mm × 300 mm × tmm). At this time, the resin temperature was 250 ° C., the portion of the mold corresponding to the end of the molded product was 80 ° C., and other portions were 40 ° C. The molding procedure is as follows. First, the amount of molten raw material necessary to obtain a molded product having a thickness (t) of 3 mm was measured in advance. Next, after the movable mold was advanced and set to a position where the thickness (t) of the molded product was 3 mm, injection of the molten raw material in the amount weighed earlier was started. Almost simultaneously with the start of injection, the movable mold was moved backward to open the mold so that the final molded product had a thickness of 7.5 mm. After cooling, a lightweight molded product having a thickness of 7.5 mm was obtained. The evaluation results are shown in Table 1.
[0037]
[Table 1]

[0038]
[Comparative Example 1]
The same operation as in Example 1 was performed except that the mold temperature was all uniform at 40 ° C. The evaluation results are shown in Table 1.
[Comparative Example 2]
The same procedure as in Example 1 was performed except that the mold core was set at a position where the thickness (t) of the molded product was 3 mm from the beginning and the core back was not performed. The evaluation results are shown in Table 1.
[Comparative Example 3]
A molded product was obtained in the same manner as in Example 1 except that a short fiber glass fiber reinforced polypropylene having a glass fiber content of 40% by weight and a glass fiber weight average fiber length of 0.42 mm was used. It was. The evaluation results are shown in Table 1.
[Example 2]
5 parts by weight of maleic anhydride-modified polypropylene having a maleic anhydride content of 1% by weight was added to 95 parts by weight of polypropylene (trade name J-6083H, manufactured by Idemitsu Petrochemical Co., Ltd.). Was cut to a length of 8 mm. The amount of fibers in the obtained pellets was 60% by weight. Polypropylene (trade name J-6083H, manufactured by Idemitsu Petrochemical Co., Ltd.) was dry blended to the pellets such that the glass fiber content was 30% by weight, and a foaming agent was added to 100 parts by weight of the dry blend. Master batch pellets [Polyslen EV-306G (manufactured by Eiwa Kasei Kogyo Co., Ltd.): foaming agent content = 30 wt%] were blended in 0.3 parts by weight and then injected in the same manner as in Example 1 except that the following procedure was followed. Molding was performed. First, the amount of molten raw material necessary to obtain a molded product having a thickness (t) of 3 mm was measured in advance. Next, after the movable mold was advanced and set to a position where the thickness (t) of the molded product was 2 mm, injection of the molten raw material in the previously weighed amount was started. Almost simultaneously with the start of injection, the core back was performed so that the final molded product had a thickness of 9 mm. After cooling, a lightweight molded product having a thickness of 9 mm was obtained. The evaluation results are shown in Table 1.
[Comparative Example 4]
The same procedure as in Example 2 was performed except that the mold temperature was all uniform at 50 ° C. The evaluation results are shown in Table 1.
[Comparative Example 5]
As a forming raw material, a short fiber glass fiber reinforced polypropylene having a glass fiber content of 30% by weight and a glass fiber weight average fiber length of 0.48 mm is used. Further, a foaming agent master batch pellet [Polyslen EV-306G (Yewa Kasei) A molded product was obtained in the same manner as in Example 2 except that a blend of 3 parts by weight of (manufactured by Kogyo Co., Ltd.): foaming agent content = 30 wt%] was used. The evaluation results are shown in Table 1.
[Comparative Example 6]
As a forming raw material, using a short fiber glass fiber reinforced polypropylene having a glass fiber content of 30% by weight and a glass fiber weight average fiber length of 0.48 mm, and further blended with 10 parts by weight of a foaming agent, From the beginning, the movable mold was set at a position where the thickness (t) of the molded product was 3 mm, and core back was performed so that the final molded product had a thickness of 9 mm almost simultaneously with the start of injection. At this time, the mold temperatures were all made uniform at 50 ° C. The mold was sealed for counter pressure. Otherwise, the same procedure as in Example 2 was performed. After cooling, a lightweight molded product having a thickness of 9 mm was obtained. The evaluation results are shown in Table 1.
[0039]
【The invention's effect】
The manufacturing method of the fiber-reinforced lightweight thermoplastic resin lightweight molded product according to the present invention can be manufactured without using a large amount of foaming agent, and the obtained molded product is lightweight and extremely in appearance such as surface condition. Excellent, and since a skin layer is formed on the surface, it has high strength and high rigidity combined with fiber reinforcement.
[Brief description of the drawings]
FIG. 1 is a point when a molten resin filling is completed, and a fixed mold and a movable in an unexpanded state
Schematic plan view of mold
FIG. 2 shows that the movable mold is retracted and the fixed mold and the movable mold are in an expanded state.
Schematic plan view
[Fig. 3] In the central part of the test rectangular plate in the measurement of the end part expansion coefficient and the center part expansion coefficient
Schematic cross section of
FIG. 4 is a schematic plan view of a rectangular plate for warpage test.
[Explanation of symbols]
1: Fixed mold
2: Movable mold
3: Heated part in the mold
4: Molten resin
5: Sprue
6: Initial cavity
7: Cavity in the final molded product
8: Edge

Claims (5)

A fiber-containing thermoplastic resin pellet (A) having a fiber length of 2 to 100 mm in a pellet or a mixture of the pellet (A) and a thermoplastic resin is used as a forming raw material, and the fiber content in the forming raw material is 5 Melting and kneading what is -80% by weight, injecting molten resin into a closed mold so as to be smaller than the mold volume equivalent to the final molded product, and mold before or after completion of resin injection In manufacturing a lightweight molded product of fiber reinforced thermoplastic resin by opening up to the volume of the final molded product,
The mold has a female mold and a male mold slidably fitted to the female mold, and the volume of the cavity defined by the female mold and the male mold is variable,
A method for producing a lightweight molded article of fiber reinforced thermoplastic resin , wherein a side portion on which the male die slides is hotter than the other portion on the inner surface of the female die . A fiber-containing thermoplastic resin pellet (A) having a fiber length of 2 to 100 mm in a pellet or a mixture of the pellet (A) and a thermoplastic resin is used as a forming raw material, and the fiber content in the forming raw material is 5 When melted and kneaded at -80% by weight and injecting the molten raw material into a closed mold, the cavity is closed so that the volume of the cavity is smaller than the total volume of the molten raw material to be injected In order to manufacture a lightweight fiber reinforced thermoplastic resin molded product by injecting into the mold, and then opening the mold to the volume of the final molded product,
The mold has a female mold and a male mold slidably fitted to the female mold, and the volume of the cavity defined by the female mold and the male mold is variable,
A method for producing a lightweight molded article of fiber reinforced thermoplastic resin , wherein a side portion on which the male die slides is hotter than the other portion on the inner surface of the female die . A fiber-containing thermoplastic resin pellet (A) having a fiber length of 2 to 100 mm in a pellet or a mixture of the pellet (A) and a thermoplastic resin is used as a forming raw material, and the fiber content in the forming raw material is 5 -80% by weight is melt-kneaded and the molten resin is injected into the cavity at the same time or after the injection starts, the movable mold is advanced and compressed once, and then the mold is filled with the volume of the final molded product. In manufacturing a lightweight molded product of fiber reinforced thermoplastic resin by opening up to
The mold has a female mold and a male mold slidably fitted to the female mold, and the volume of the cavity defined by the female mold and the male mold is variable,
A method for producing a lightweight molded article of fiber reinforced thermoplastic resin , wherein a side portion on which the male die slides is hotter than the other portion on the inner surface of the female die .   In Claims 1-3, as a material used for melt-kneading, a fiber-containing thermoplastic resin pellet (A) having a fiber length of 2 to 100 mm in a pellet, or a mixture of the pellet (A) and a thermoplastic resin is used. The molding raw material is used by blending 0.01 to 3 parts by weight of a foaming agent with respect to 100 parts by weight of the fiber content in the molding raw material of 5 to 80% by weight. The manufacturing method of the fiber reinforced thermoplastic resin lightweight molded article in any one of -3.   The manufacturing method of the fiber reinforced thermoplastic resin lightweight molded article in any one of Claims 1-3 whose porosity of the lightweight molded article in Claims 1-3 is 30 to 80%.

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