JPH10315262A - Method for molding fiber-reinforced resin and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding fiber-reinforced resin for obtaining fiber-reinforced resin molding of a multilayer with excellent external appearance quality by improving mechanical characteristics such as strength and rigidity and weight reduction, and to provide moldings. SOLUTION: The method for molding a fiber-reinforced resin comprises the steps of first injecting resin to mold melted resin so that reinforcing fiber becomes 5 to 70 wt.% of overall raw material by using fiber-containing thermoplastic resin pellet containing reinforcing fiber having a length of a range of 2 to 100 mm, forming dense reinforcing fiber-containing resin sold layer, starting second resin injection in the state that a movable core 12 is retracted to a position T, then retracting the core 12 to a position U, and expanding the melted resin by spring back phenomenon. Thus, even if the reinforcing fiber-containing resin solid layer is ensured, the melted resin can be sufficiently expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a molded product of a fiber-reinforced resin, and more particularly, to a fiber-reinforced resin molded product having excellent rigidity and strength, which has improved surface conditions and reduced weight. And a molded article obtained by this molding method.

[0002]

BACKGROUND ART Conventionally, fiber resin molded articles reinforced with fibers such as glass fibers are excellent in mechanical properties such as tensile strength, rigidity and heat resistance, so that instrument panel cores, bumper beams, door steps, and roofs are used. -Widely used as automotive parts such as racks, rear quarter panels and air cleaner cases, as well as architectural and civil engineering members such as outer wall panels, partition wall panels and cable troughs. In producing such a fiber-reinforced resin molded product, an injection molding method of injecting a molten resin containing fibers into a mold can be used. According to this injection molding method, it is possible to mold even a complicated shape, and since a predetermined molding cycle can be continuously repeated, there is an advantage that mass production of the same shape can be achieved.

[0003] A fiber-reinforced resin molded product formed by injection molding tends to be heavy because it is necessary to contain a fiber in a predetermined ratio or more in order to secure strength and rigidity.
For this reason, there has been proposed a foam injection molding method in which a foaming agent is mixed into raw materials and molding is performed while foaming a resin forming a molded article (Japanese Patent Laid-Open No. Hei 7-247679). However, in this method, even if a considerable amount of a foaming agent is used, it is not easy to increase the expansion ratio to 2 to 5 times, and furthermore, the content of the glass fiber is limited, and sufficient mechanical properties are obtained. In some cases, it is difficult to reduce the weight while maintaining mechanical properties such as strength, rigidity and heat resistance and appearance quality. Also, by injecting gas, the internal pressure of the mold cavity is maintained at a pressure higher than the foaming pressure of the foaming agent, and the internal pressure of the cavity suppresses foaming of the foaming agent in the molten resin. After cooling the surface to form the skin layer, it is conceivable to use a counter pressure molding method for foaming the foaming agent, thereby improving the appearance quality. However, in the counter pressure molding method, since the foaming agent is foamed after the molten resin is cooled to some extent, the expansion ratio is limited, and a large hollow portion or nest is easily generated inside the molded product, and the weight is reduced. In addition, there is a problem that the strength is not always sufficient, and a gas facility for injecting a gas into the cavity, a mold having excellent airtightness, and the like are required, and there is also a problem in terms of manufacturing cost. In any case, the foam molding method is significantly inferior in appearance to the molded product as compared with the injection molding, and cannot be adopted as a method for reducing the weight of various injection molded products conventionally used. It is. On the other hand, by adopting a two-layer (two-color) molding method in which resin injection is performed twice, an injection-molded layer (solid layer) is formed on the front side and a foamed layer is formed on the back side. A layered structure is also conceivable, but this requires two injection molding machines and two types of molding materials, and also requires a volume of 2
It is difficult to obtain a foamed layer foamed so as to be up to 5 times, and no example has been actually adopted.

[0004] In order to solve the above problems, the present applicant has proposed a molding method utilizing a springback phenomenon which occurs during molding of a resin containing reinforcing fibers (Japanese Patent Application No. 8-28841). ). This method employs a resin containing a certain amount of reinforcing fibers longer than a certain amount, and injects molten resin into a cavity that is smaller than the volume of the molded product to form a skin layer on the surface of the resin. After the resin is filled, the cavity is expanded to the volume of the molded product, the resin is expanded by a springback phenomenon, and countless continuous voids are generated inside. Here, when the content of the reinforcing fiber is small and the resin does not expand sufficiently only by the springback phenomenon, the resin can be expanded sufficiently by adding a small amount of a foaming agent. According to such a method, it is possible to contain a sufficient amount of reinforcing fibers to secure the strength,
Unlike foam molding, independent air bubbles and large hollow portions are not formed inside, and countless small voids are formed. Therefore, it is possible to achieve both strength assurance and sufficient weight reduction.

[0005]

However, with the above-mentioned molding method, a light-weight molded article can be produced, but the appearance quality (smoothness) of the molded article depends on the type, content and molding conditions of the reinforcing fibers. Properties, mold transferability, hardness, etc.) may not be sufficient. Further, the conventional two-layer molding requires two injection molding machines and two types of molding materials for molding the two layers, so that there is a problem that the apparatus and the molding procedure are complicated.

An object of the present invention is to improve the mechanical properties such as strength, rigidity, heat resistance and the like and to reduce the weight, and to improve the appearance quality of a fiber reinforced one injection molding machine and one kind of molding material. It is an object of the present invention to provide a method of molding a fiber-reinforced resin and a molded article that can efficiently obtain a resin molded article.

[0007]

According to a first aspect of the present invention, there is provided a fiber-containing thermoplastic resin pellet including a reinforcing fiber having a length in a range of 2 to 100 mm, and the reinforcing fiber is used. Injecting a molten resin obtained by plasticizing the raw material into a mold having a movable die capable of moving back and forth with respect to an internal cavity, using a raw material that accounts for 5 to 70% by weight of the entire raw material. Thus, a method of molding a fiber-reinforced resin for molding a molded article, wherein the first resin injection is performed in a state where the movable mold is disposed at a first position where the cavity has a predetermined volume. After forming the reinforcing fiber-containing resin solid layer, the movable mold is retracted to the second position, and after the second resin injection is started with the cavity expanded, the cavity is With the volume according to the molded product And wherein the retracting the movable mold to a third position that. Here, as the raw material, a fiber-containing thermoplastic resin pellet including a reinforcing fiber having a length in the range of 2 to 100 mm may be used alone, or the resin pellet and another molding material may be used. May be used. In the present invention, since a raw material containing a predetermined amount or more of the reinforcing fiber having a predetermined length or more is used, when the movable mold is retracted to the third position at the time of molding, a springback phenomenon occurs reliably. Thus, the molten resin can be expanded sufficiently. Then, the solid layer containing the reinforcing fiber-containing resin is formed with the molten resin that is first injected into the cavity, and the remaining molten resin that is injected next can be sufficiently expanded. For this reason,
By the formed solid layer of reinforcing fiber-containing resin, the smoothness of the surface of the molded article is sufficiently ensured, excellent appearance quality is obtained, and the molten resin injected in the second time is sufficiently expanded. Thus, all of the mechanical properties such as the strength, rigidity and heat resistance of the molded product and the weight reduction can be ensured. Here, the reinforcing fiber-containing resin solid layer refers to a layer formed by injecting a molten resin and having a substantially dense interior and a good surface smoothness. This also includes those having voids formed therein so as not to affect the properties.

In the above, the raw material may contain a foaming agent in an amount of 3 parts by weight or less based on 100 parts by weight of the raw material. When such a small amount of the foaming agent is mixed, the content of the reinforcing fiber is small, and even if the expansion of the resin cannot be expected by the springback phenomenon alone, the expansion of the resin by the springback phenomenon causes the foaming of the foaming agent. And the resin can be sufficiently expanded. In addition, since the small amount of the foaming agent to be mixed is sufficient to supplement the expansion of the resin due to the springback phenomenon, independent bubbles and large hollow portions can be formed inside as in conventional foam molding. Absent. Furthermore, since the foaming agent hardly foams when forming the reinforcing fiber-containing resin solid layer, it does not adversely affect the surface of the molded product. Here, the type of the foaming agent is not limited as long as it decomposes by heat to generate gas. For example, azo compounds such as oxalic acid derivatives and azodicarbonamide, hydrazine derivatives, semicarbazides, azide compounds, nitroso compounds, triazoles, ureas and related compounds, nitrites, hydrides, carbonates and bicarbonates can be employed. More specifically, azodicarbonamide (ADCA), benzenesulfohydrazide, N, N-dinitropentamethylenetetramine, terephthalazide and the like can be used. In addition to the foaming agent,
Fillers such as stabilizers, antistatic agents, weathering agents, coloring agents, short fibers, and talc can be added as necessary.

The raw material has a total length of 2-1.
The fiber-containing thermoplastic resin pellets having a length of 00 mm and reinforcing fibers having a length equal to the total length are arranged in parallel with each other and contained 20 to 80% by weight of the whole. Also, a raw material in which the reinforcing fibers are 20 to 70% by weight of the whole raw material can be used. Even with such raw materials, the third
When the movable mold is retracted to the position, the spring-back phenomenon occurs reliably, and the molten resin can be sufficiently expanded. Furthermore, the amount of the molten resin injected first corresponds to the volume of the reinforcing fiber-containing resin solid layer,
It is preferable that the amount of the molten resin injected at the second time corresponds to a volume expansion of the cavity expanded when the movable mold retreats to the second position. With this configuration, when injecting the molten resin into the cavity whose volume is changed stepwise, the molten resin can be injected into the cavity at each stage without excess or shortage, and the movable mold is retracted from the second position. By expanding the molten resin, it is possible to reliably obtain a molded product having a predetermined volume.

The thermoplastic resin used as the main component of the resin pellets is not particularly limited, but examples thereof include polyolefins such as polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, and polyethylene. Resin, polystyrene resin, ABS
Resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, polyaromatic ether or thioether resin, polyaromatic ester resin, polysulfone resin, acrylate resin, etc. it can. Here, the thermoplastic resin may be used alone, or two or more kinds may be used in combination. Among such thermoplastic resins, polypropylene, a random copolymer of propylene and another olefin, a block copolymer, or a polypropylene resin such as a mixture thereof is preferable, particularly, an unsaturated carboxylic acid, or A polyolefin-based resin containing an acid-modified polyolefin-based resin modified with a derivative thereof is preferred.

Further, as the reinforcing fibers contained in the resin pellets, the following (1) to (5) can be adopted, and particularly, glass fibers are desirably employed. Ceramic fiber: boron fiber, silicon carbide fiber, alumina fiber, silicon nitride fiber, zirconia fiber, calcium silicate fiber, rock wool Inorganic fiber: glass fiber, magnesium oxide fiber, magnesium oxysulfate fiber, magnesium hydroxide fiber, gypsum fiber , Carbon fiber Metal fiber: copper fiber, brass fiber, steel fiber, stainless fiber, aluminum fiber, aluminum alloy fiber Organic fiber: polyethylene fiber, polypropylene fiber,
Aramid fiber, Kevlar (trade name) fiber, polyarylate fiber

Here, the glass fibers contained in the resin pellets are E-glass or S-glass glass fibers having an average fiber diameter of 25 μm or less, preferably 3 to 20 μm. Things can be adopted.
If the diameter of the glass fiber is less than 3 μm, the glass fiber does not adapt to the resin during the production of the pellets, making it difficult to impregnate the resin.

When pellets are produced from these thermoplastic resins and reinforcing fibers by a pultrusion method or a solution impregnation method, the fibers are surface-treated with a coupling agent, and then treated with a sizing agent. 10,000,
Preferably, it is desirable to bundle them in the range of 150 to 5000. The coupling agent can be appropriately selected from so-called silane coupling agents and titanium coupling agents that have been conventionally used. For example, γ-aminopropyltriethoxysilane, N-β
Aminosilanes and epoxysilanes such as-(aminoethyl) -γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane can be used. In particular, it is preferable to employ the amino silane compound. In performing the surface treatment of the fiber using such a coupling agent, in addition to the sizing treatment of applying an organic solvent solution or a turbid liquid obtained by mixing the above-described coupling agent to an organic solvent to the fiber as a so-called sizing agent, a dry process Mixing and spraying methods can be adopted. Also,
In performing the surface treatment, a film-forming substance for glass can be used in combination with the above-described coupling agent. As the film-forming substance, for example, polyester-based, urethane-based, epoxy-based, acrylic-based, vinyl acetate-based, and isocyanate-based polymers can be used. As the sizing agent, for example, urethane-based, olefin-based, acrylic-based, butadiene-based, and epoxy-based can be used, and among these, urethane-based and olefin-based can be used. Of these, the urethane-based sizing agent is usually an oil-modified type, a moisture-curable type, or a moisture-curable type, as long as it contains 50% by weight or more of polyisocyanate obtained by a polyaddition reaction of a diisocyanate compound and a polyhydric alcohol. Any of a one-pack type such as a block type and a two-pack type such as a catalyst-curable type and a polyol-curable type can be adopted. On the other hand, a modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof can be used as the olefin sizing agent.

By attaching and impregnating the thermoplastic resin to the fibers converged with the above-mentioned sizing agent, resin pellets containing the fibers are produced. As a method of attaching and impregnating the thermoplastic resin to the fiber, for example, a method of passing a fiber bundle through a molten resin put in a container or the like, a method of impregnating the resin with the fiber, a suspension, impregnating the fiber bundle with the resin by emulsion, After that, a method of impregnating the fiber bundle through the coating die or impregnating the fiber bundle by spreading the molten resin adhered around the fiber with the die can be adopted. Here, in order to make the fiber bundle and the resin well-fitted, that is, in order to improve the wettability, the molten resin is pulled out through the tensioned fiber bundle into the inside of the die provided with the uneven portion on the inner periphery. After impregnating with a fiber bundle, a pultrusion molding method in which a step of pressing the fiber bundle with a pressure roller is further incorporated can be adopted. In addition, if the fiber and the molten resin are compatible with each other, if the material has good wettability, the molten resin is easily impregnated into the fiber, and the production of pellets becomes easy. , May be omitted. If the long fiber bundle (strand etc.) containing the resin is cut along the longitudinal direction of the fiber by the above method, the resin pellet containing the long fiber having the same length as the entire length of the pellet is obtained. Can be obtained. At this time, as the resin pellets, the fiber bundle is formed into a strand, and the cross-sectional shape is not limited to a cut resin-containing long fiber bundle having a substantially circular shape. The resin-containing long fiber bundle in the shape of a band or a band may be cut into a predetermined length.

[0015] The second invention of the present invention is, for example, a molded article obtained by the molding method of the first invention. That is, the second invention provides a substantially dense reinforcing fiber-containing resin molding layer,
It is characterized in that the reinforcing fiber-containing resin void layer having voids is integrally molded from a resin having the same composition to reduce the weight. According to the second aspect of the invention, the molded article is reduced in weight, excellent in mechanical properties such as tensile strength, rigidity and heat resistance, and is also secured in appearance quality. It can be widely used as automobile parts such as beams, door steps, roof racks, rear quarter panels, and air cleaner cases, and as architectural and civil engineering members such as outer wall panels, partition wall panels, and cable troughs. In the above, the weight is reduced by the expansion of the molten resin, and R =
It is preferable that the weight reduction ratio R expressed by (V × ρ−W) / (V × ρ) is in the range of 0.2 to 0.8. Here, V is the volume of the molded article, ρ is the average density of the raw material, and W is the weight of the molded article. With such a weight reduction rate, all of the weight, mechanical strength, and appearance quality of the molded product are ensured in a well-balanced manner, so that the molded product is most suitable as an automobile part or a member for building civil engineering. The molded article preferably has an average fiber length of 2 mm or more, more preferably 4 mm or more, of fibers contained in the molded article. . By setting the average fiber length in the molded product to 2 mm or more, it becomes easy to expand the molten resin to a desired size at the time of molding due to a springback phenomenon, and mechanical properties such as impact resistance and rigidity are obtained. Will be improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an injection molding machine 1 according to one embodiment of the present invention. This injection molding machine 1 performs molding by injecting a molten resin into a mold 10. The mold 10 includes a fixed mold 10A and a movable mold 10B.
Is divided into Inside the movable mold 10B of the mold 10, there is provided a movable core 12 which is a movable mold capable of moving back and forth with respect to the cavity 11 of the mold 10. By moving the movable core 12, the cavity of the mold 10 is
11 has a variable volume. In addition, a passage 13 such as a sprue or a runner for introducing molten resin into the inside of the fixed mold 10A of the mold 10 is formed. This passage 13
A strip-shaped electric heating element 14 is provided around. Thus, the passage 13 forms a so-called hot runner that does not cure the molten resin flowing inside the passage 13.

The injection molding machine 1 includes a cavity 11 of a mold 10.
An injection device 1A for injecting a molten resin into a mold, a fixed die plate 3 to which a fixed mold 10A is attached, a movable die plate 4 to which a movable mold 10B is attached, and the movable die plate 4 is directed toward the fixed die plate 3. A mold clamping device 5 for moving the movable core 12 of the mold 10 to an arbitrary position within a predetermined range and stopping the movable core 12 at the position are provided. The moving die plate 4
The hydraulic cylinder device 6 for mold clamping is slidably provided along a tie bar 8 bridged between a fixed plate 7 and a fixed die plate 3 to which the fixed cylinder 7 is fixed. The mold clamping device 5 has a toggle mechanism 9 to which the piston rod 6A of the hydraulic cylinder device 6 is connected. The pressing force of the hydraulic cylinder device 6 is increased by the toggle mechanism 9 to move the movable die plate 4 forward. The movable mold 10B is brought into close contact with the fixed mold 10A to close the mold 10.

The mold moving device 20 applies a compressive force to the molten resin injected into the cavity 11 by advancing the movable core 12 with respect to the cavity 11 and retreats the movable core 12 to the cavity. 11 is extended, and is interposed between the movable die plate 4 and the movable mold 10B. In addition, the mold moving device 20 is a cavity clearance changing unit that can change the clearance between the molding surface of the movable core 12 and the molding surface of the fixed mold 10A by moving the movable core 12 forward and backward. is there. The mold moving device 20 has inclined surfaces 21A and 22A that are inclined with respect to the moving direction of the movable core 12, respectively.
21A, a pair of inclined members 21 and 22 that abut each other, 22A,
A base plate 23 having a flat surface perpendicular to the moving direction of the movable core 12, a mold mounting base 24 connecting the movable die plate 4 and the movable mold 10B,
And a compression plate 25 for connecting the inclined member 22.

The inclined member 21 is slidable along the surface of the base plate 23 attached to the movable die plate 4, and is orthogonal to the moving direction of the movable core 12 by the hydraulic cylinder device 26. To be driven in the direction of Here, the inclined surface of the inclined member 22
At both ends of 22A, rising portions 22B are provided along the moving direction of the inclined member 21. This rising part 22B
The groove 22 extending in the longitudinal direction of the rising portion 22B
C is provided. On the other hand, on the side surface of the inclined member 21 that is in contact with the inner side surface of the rising portion 22B, a ridge 21B that fits into the groove 22C of the inclined member 22 is provided. Thus, when the piston rod 26A of the hydraulic cylinder device 26 is advanced, the inclined member 21 presses the inclined member 22 and the movable core 12 advances, while when the piston rod 26A of the hydraulic cylinder device 26 is retracted, the inclined member 21 draws the inclined member 22, and the movable core 12 retreats. A hydraulic unit 30 is provided to supply hydraulic pressure to the mold moving device 20. Further, a control device 31 for controlling the hydraulic unit 30 and causing the mold moving device 20 to perform a desired operation is provided. Is provided. The control device 31 has a sequence control circuit such as a digital sequencer and the like.
It is possible to set so that arbitrary different operations can be continuously performed, for example, by gradually moving forward and backward with respect to the cavity 11, temporarily stopping at a predetermined position, and then moving backward.

Next, the molding operation (forming procedure) of the present embodiment
Will be described. First, the mold 10 and the mold moving device 20
Is mounted on a general injection molding machine 1 as shown in FIG. 1, and a predetermined raw material is put into a hopper (not shown). First, after mounting the mold 10 on the injection molding machine 1 and supplying resin pellets into the injection cylinder 11 of the injection device 1A,
The injection molding machine 1 is started, and plasticization and kneading of the resin pellets in the injection cylinder 11 are started. Here, the resin pellets, which are raw materials, are mainly made of polypropylene and have a total length of 2 to 100 mm. In this resin pellet, reinforcing glass fibers having a length equal to the entire length thereof are arranged in parallel with each other, and a total of 20 to
80% by weight. On the other hand, when a mixture of the above resin pellets and another resin pellet not containing the reinforcing glass fiber is used as a raw material, the reinforcing glass fiber is contained in an amount of 5 to 70% by weight of the entire raw material. Can be employed. In addition, if necessary, 3 parts per 100 parts by weight of the raw material may be used.
Up to parts by weight of a blowing agent can be mixed. Here, the mixing of the foaming agent is preferably performed by mixing the master batch pellets containing the foaming agent into the above-mentioned resin pellets. In addition, as a masterbatch pellet containing a foaming agent, for example, trade name: Polyslen TS-1
82 (manufactured by Eiwa Chemical Industry Co., Ltd.). In addition, in the injection cylinder 11, while suppressing the breakage of the fibers, by sufficiently plasticizing and kneading the resin pellets, the amount of molten resin necessary for molding a molded article is obtained, and the molten resin in the molten resin is obtained. Countless glass fibers are uniformly distributed and are sufficiently entangled with each other so that a springback phenomenon is likely to occur.

Then, the mold clamping device 5 is operated to move the movable die plate 4 toward the fixed die plate 3,
As shown in FIG. 1, the movable mold 10B is brought into contact with the fixed mold 10A,
The mold 10 is closed. Next, the mold moving device 20 is operated, and as shown in FIG. 2A, the movable core 12 is moved to a first position S, and the thickness of the cavity 11 is reduced.
to t1. As a result, the volume of the cavity 11 is smaller than the volume of the molded product. In this state, the first resin injection is performed to fill the cavity 11 with the molten resin. Here, the cavity formed by the movable core 12 stationary at the position S
The thickness t1 of 11 is set so that the cavity 11 having the thickness t1 has a volume corresponding to the amount of the molten resin injected at the first time. The amount of the molten resin injected at the first time is set to at least an amount sufficient to form a reinforcing fiber-containing resin solid layer on the surface side of the molded article. The molten resin filled in the cavity 11 is cooled for a predetermined time to solidify the solid layer containing the reinforcing fiber-containing resin. At this time, in order to obtain the solid layer containing the reinforcing fiber-containing resin, a method using a general injection molding method (a method of injecting and filling a cavity in a completely closed state) or a method using an injection compression molding method (improper). A method of injecting the resin into the cavity in a completely closed state, and after starting the injection, compressing the resin by advancing the movable core can be adopted. These can be appropriately selected according to the thickness of the reinforcing fiber-containing resin solid layer and the area and dimensions of the molded product.

Next, the mold moving device 20 is operated, and FIG.
As shown in (B), the movable core 12 is retracted to the position T, and the thickness dimension of the cavity 11 is set to t2. As a result, the volume of the cavity 11 becomes a volume corresponding to the amount of resin necessary for molding a molded product. In this state, a second resin injection is performed to fill the cavity 11 with all the remaining molten resin, and the cavity 11 is filled with the molten resin. Here, the thickness t2 of the cavity 11 formed by the movable core 12 that is stationary at the position T is such that the volume of the cavity 11 is a volume corresponding to the total amount of the molten resin necessary for molding a molded product. Is set to Also this cavity
The thickness t2 of 11 is larger than the thickness t1 of the cavity 11 formed by the movable core 12 at the position S. As a result, the amount of the molten resin injected in the second resin injection is equal to or greater than the amount of the molten resin injected in the first resin injection, and the molten resin injected in the first injection is reinforced. Even when the solidification of the solid layer of the fiber-containing resin is completed, the desired expansion rate can be achieved by expanding the molten resin injected in the second time. Before the completion of the second injection,
Immediately after or after a predetermined time has elapsed from the completion of injection,
The mold moving device 20 is operated again, and as shown in FIG. 2C, the movable core 12 is retracted to the position U where the cavity 11 has a volume corresponding to the molded product, and the thickness of the cavity 11 is measured. To t3. Here, the retreat speed Vr of the movable core 12
Is in the range of 0.05 to 100 mm / sec, preferably 0.1 mm / sec.
It can be set in the range of 0.5 to 50 mm / sec. When the movable core 12 is retracted, due to the springback phenomenon,
The molten resin expands due to the elastic restoring force of the glass fiber that was crushed in the molten resin, and numerous voids were generated inside the molten resin, making the volume larger and lighter than the amount of raw materials used A molded article is molded. After a predetermined time required for sufficiently cooling the molded product has elapsed, the mold clamping device 5 is operated to move the movable die plate 4 backward, and the mold 10 is opened. Then, the molded product is taken out of the mold 10 and the molding is completed. Thereafter, the above molding operation is repeated as necessary.

The molded product obtained by such a molding procedure is as follows:
The reinforcing fiber-containing resin solid layer in which the inside on the surface side is substantially dense, and the reinforcing fiber-containing resin void layer having voids are integrally formed, and the weight is reduced, and the tensile strength, Excellent mechanical properties such as stiffness and heat resistance, as well as appearance quality are ensured, so automotive parts such as instrument panel cores, bumper beams, door steps, roof racks, rear quarter panels and air cooler cases, and exterior walls Panel, partition wall panel and cable
It can be widely used as architectural and civil engineering members such as troughs. Such a molded article has a weight reduction ratio R in order to ensure all of the weight, mechanical strength and appearance quality of the molded article in a well-balanced manner and to be optimal as an automobile part or a member for building civil engineering. The range is from 0.1 to 0.8. However, the weight reduction ratio R is R = (V × ρ−
W) / (V × ρ). Here, V is the volume of the molded article, ρ is the average density of the raw material, and W is the weight of the molded article. In addition, in order to facilitate the expansion of the molten resin to a desired size at the time of molding by the springback phenomenon, and to improve mechanical properties such as impact resistance and rigidity, an average of fibers contained in the molded article is used. The fiber length is at least 2 mm, more preferably at least 5 mm.

According to the above-described embodiment, the following effects can be obtained. That is, since a raw material containing a predetermined amount or more of reinforcing fibers having a predetermined length or more is used, a spring-back phenomenon occurs reliably during molding, and the molten resin can be sufficiently expanded. And, by the molten resin injected into the cavity 11 in the first resin injection,
Since a dense reinforcing fiber-containing resin solid layer was formed practically and the remaining molten resin injected in the second resin injection was expanded, the reinforcing fiber-containing resin solid layer on the front surface side was formed. Even if is formed, the molten resin can be reliably expanded to a predetermined size, and the appearance quality excellent in surface smoothness and transferability can be imparted to the molded product, and the molded product can be reduced in weight.

When it is not possible to incorporate an amount of reinforcing fibers capable of achieving a predetermined expansion coefficient, for example, 3 parts by weight or less of a foaming agent is mixed with 100 parts by weight of the raw material, if necessary. Therefore, even if a sufficient expansion of the resin cannot be expected only by the springback phenomenon, the expansion of the resin due to the springback phenomenon is compensated by the foaming of the foaming agent, and the resin can be sufficiently expanded. In addition, since the small amount of the foaming agent to be mixed is sufficient to supplement the expansion of the resin due to the springback phenomenon, independent bubbles and large hollow portions are not formed inside unlike conventional foam molding, There is no loss of mechanical properties such as strength, rigidity and heat resistance.

The raw material fiber-containing thermoplastic resin pellets have a total length in the range of 2 to 100 mm, and reinforcing fibers having a length equal to the total length are arranged in parallel with each other. Since the fiber containing 20 to 80% by weight of the whole is employed, even if it is sufficiently plasticized by the injection device 1A, the contained fiber is hardly broken, the fiber length is secured, and the reinforcing fiber Even when mixed with other resin pellets containing no, a springback phenomenon surely occurs during molding, and the molten resin can be sufficiently expanded. Therefore, a specific one is appropriately selected from a plurality of types of fiber-containing thermoplastic resin pellets having different fiber contents, or a mixing ratio of the fiber-containing thermoplastic resin pellet and the resin pellet not containing the reinforcing fiber. By appropriately adjusting the content, the content of the reinforcing fiber can be arbitrarily adjusted within the range of 5 to 70% by weight, the required content can be easily achieved, and the desired weight reduction rate and A molded article having mechanical properties can be obtained.

Further, the injection amount of the first molten resin is
At the position S, the volume of the cavity 11 formed by the movable core 12 is set to correspond to the volume of the cavity 11 (in the case of injection molding). Since the amount of expansion is set to correspond to the volume expansion, when injecting the molten resin into the cavity 11 whose volume can be changed stepwise, the cavity 11 at each stage can be filled with the molten resin without excess or shortage. Here, the thickness t2 of the cavity 11 formed by the movable core 12 at the position T is
Since the thickness t1 of the cavity 11 formed by the movable core 12 at the position S was made larger and the amount of the second molten resin injection was set to be equal to or more than the amount of the first molten resin injection, the first time Even if the solid layer containing the reinforcing fiber-containing resin is formed with the injected molten resin, the molten resin injected in the second round will surely expand to a predetermined size, and effective weight reduction can be achieved. .

Further, since the first injection amount of the molten resin is set to an amount necessary to secure the thickness of the reinforcing fiber-containing resin solid layer formed on the surface of the molded article, the cavity at the position S The volume of 11 is significantly smaller than the volume of the molded product. For this reason, at the time of the first resin injection,
The injection pressure of the injection device 1A is applied to the entire molten resin filled in the cavity 11, and the injection pressure causes the molten resin to be pressed against the molding surface inside the cavity 11, so that the surface of the obtained molded product Excellent smoothness can be secured.

[0029]

Next, the effects of the present invention will be described based on specific examples. [Example 1] Example 1 is an experiment in which molding is performed using the above-described mold 10, the injection molding machine 1 and the molding procedure based on the above embodiment. In the first embodiment, the following raw materials, molds, injection molding machines and injection procedures are employed. a) Raw material: fiber-containing polypropylene pellets. Composition of the pellet; glass fiber, polypropylene, and maleic acid-modified polypropylene Total length of the pellet; 15 mm glass fiber length; 15 mm glass fiber content; 40% by weight content of maleic acid-modified polypropylene; 2% by weight polypropylene Rate: 58% by weight b) Die: Die having a cavity for forming a rectangular flat plate and a movable core. The dimensions (inner method) of the cavity are shown below. Width W: 600 mm Depth D: 300 mm Thickness t: Variable in size due to movement of the movable core Mold temperature during molding: 80 ° C c) Injection molding machine: Mold moving device 2 for general-purpose horizontal injection molding machine
One with 0 attached. The control device 31 incorporates a multi-stage injection sequence. Injection temperature of the molten resin; 250 ° C. (in the injection cylinder) d) Molding procedure: a procedure including the following steps (see FIG. 2) Before the molten resin is injected, the thickness t2 is 6 mm. The resin corresponding to the volume of the cavity 11 is plasticized and measured by the injection device, the mold 10 is closed, the movable core 12 of the mold 10 is advanced to the position S, and stopped at that position. here,
The position S is set so that the thickness t1 of the cavity 11 is 2 mm. In this state, the first resin injection is performed. The amount of molten resin injected in this first injection is
The thickness t1 is an amount corresponding to the volume of the cavity 11 having a thickness of 2 mm. When the formation of the reinforcing fiber-containing resin solid layer is completed in the first resin injection, the movable core 12 is retracted to the position T,
Stop at that position. Here, the position T is the cavity
The thickness t2 of 11 is set to be 6 mm. In this state, the second resin injection is performed. In the second injection, all the remaining molten resin that has been plasticized and measured is injected. Simultaneously with the completion of the second resin injection, the movable core 12 is retracted to the position U, and in this state, the molten resin is cooled and solidified. Here, the position U is set so that the thickness t3 of the cavity 11 becomes 14 mm.

[Embodiment 2] This embodiment 2 is similar to the embodiment 1 described above.
This is an experiment in which a similar molded article is molded after changing the conditions in as follows. a) Change of raw materials: Change the fiber-containing polypropylene pellets as follows. Total length of the pellet; 20 mm glass fiber length; 20 mm glass fiber content; 50 wt% content of maleic acid-modified polypropylene; 2 wt% content of polypropylene; 48 wt% b) Change of mold temperature: molding Mold temperature at time: 40 ° C. c) The thicknesses t1 to t3 of the cavities at each stage of molding are changed as follows. Thickness t1; 2.5mm thickness t2; 5mm thickness t3; 10mm

[Comparative Example 1] This Comparative Example 1 is an experiment in which the same molded article as that of the above-mentioned Example 2 is molded by single-stage resin injection. Specifically, molding is performed under the same conditions as in Example 2 except that the molding procedure in Example 2 is changed as follows. Before injecting the molten resin, a resin corresponding to the volume of the cavity 11 having a thickness t of 5 mm is plasticized and measured by an injection device, the mold 10 is closed, and the thickness t of the cavity 11 is reduced.
The movable core 12 is moved to a position where the distance becomes 5 mm, and is stopped at this position. In this state, molten resin is injected into the mold 10 in an amount corresponding to the volume of the cavity 11 having a thickness t of 5 mm. Simultaneously with the completion of the resin injection, the movable core 12 is retracted to a position where the thickness t of the cavity 11 becomes 14 mm. In this state, the molten resin is cooled and solidified.

[Comparative Example 2] The present Comparative Example 2 is the same as the embodiment 1 described above.
By replacing the resin pellets containing long fibers in the above with resin pellets containing short fibers for which no springback phenomenon can be expected, and further adding a foaming agent, it is possible to obtain the same molded article as in Example 1 above. This is an experiment. Specifically, molding is performed under the same conditions as in the first embodiment except that the raw materials in the first embodiment are changed as follows. a) Change of raw material: Fiber-containing polypropylene pellets mixed with blowing agent. Weight average fiber length of glass fiber; 0.52 mm Glass fiber content; 40% by weight Content of maleic acid-modified polypropylene; 1% by weight Content of polypropylene; 59% by weight Weight ratio of resin pellet and foaming agent; 100% by weight Department:
1.5 parts by weight In order to minimize the breakage of the glass fiber during molding, the glass fiber was side-fed when producing the above resin pellets. b) Change of injection molding machine: Change the injection device nozzle to a shut-off nozzle.

[Comparative Example 3] The present Comparative Example 3 is the same as that of Example 1 described above.
Of multi-stage injection to single-stage injection
This is an experiment in which the same molded product as that of the first embodiment is obtained by omitting the backward movement of 12. Specifically, molding is performed under the same conditions as in Example 1 except that the molding procedure in Example 1 is changed as follows. Before injecting the molten resin, a resin corresponding to the volume of the cavity 11 having a thickness t of 6 mm is plasticized and measured by an injection device, the mold 10 is closed, and the thickness t of the cavity 11 is reduced.
The movable core 12 is moved to a position where the distance becomes 14 mm and stopped. In this state, all the plasticized and measured molten resin is
To cool and solidify the molten resin.

[Experimental Results] Each product molded in each of Examples 1 and 2 and Comparative Examples 1 to 3 is evaluated by the following evaluation methods A) to D). The results are shown in Table 1. A) A weight reduction ratio R is obtained from the following equation, and how much each product (molded product) is reduced is evaluated based on the magnitude of the weight reduction ratio R. R = (V × ρ−W) / (V × ρ) where V is the volume of the molded product, ρ is the average density of the raw material, and W is the weight of the molded product. B) Cut the center of each product, visually observe the cut surface, evaluate the state of expansion inside each product, visually observe the appearance and smoothness of the surface of each product, and observe the appearance quality. To evaluate. C) Place each product on the surface plate with the top surface flat, hold down one edge of one surface, lift the other edge of the other surface, and connect the other edge of the product to the surface of the surface plate. Is measured with a height gauge, and the degree of warpage of each product is evaluated based on this distance. D) As shown in FIG. 3, a test machine 37 that bends the DUT with one moving pressing part 36 that enters between a pair of fixed pressing parts 35 is bent until each product 38 is broken and broken. The resulting load is measured, and the magnitude of the breaking strength of the product is evaluated. Here, the interval L between the pair of fixed pressing portions 35 provided in the bending tester 37 is 350 mm. Further, the reinforcing fiber-containing resin solid layer is disposed on the lower side in the figure.

[0035]

[Table 1]

According to Example 1, it can be seen that the molten resin expands sufficiently, weight reduction can be sufficiently achieved, and a flat surface can be obtained, and a product having a light and excellent surface smoothness can be obtained. Further, since no large voids are formed inside and the warpage is small, it can be seen that a product excellent in breaking strength and appearance quality can be obtained. The glass fibers in the molded article had an average fiber length of 6 mm. According to the second embodiment, as in the first embodiment, a sufficient weight reduction and smoothness can be achieved, and since no large voids are formed inside and the warpage is small, the breaking strength and the appearance quality are also reduced. It turns out that an excellent product is obtained.

According to Comparative Example 1, as in Examples 1 and 2, the weight can be sufficiently reduced and the breaking strength is excellent.
In addition, an excellent product having a small warpage can be obtained, but the surface has undulation, which indicates that the surface smoothness is slightly inferior to Examples 1 and 2. In Comparative Example 2, weight reduction can be achieved to some extent, but the weight reduction rate is inferior to those of Examples 1 and 2, and irregularities and silver marks are generated on the surface.
The molded product is warped, and sufficient appearance quality cannot be obtained. It is also found that the breaking strength is insufficient. In Comparative Example 3, since a short shot was taken, it can be seen that a product (molded product) could not be molded.

[Embodiment 3] This embodiment 3 is similar to the embodiment 1 described above.
This is an experiment in which a similar molded product is molded under the same conditions as in Example 1 except that the molding procedure in is changed as follows. Before injecting the molten resin, a resin corresponding to the volume of the cavity 11 having a thickness t2 of 6 mm is plasticized and measured by an injection device, the mold 10 is closed, and the thickness t2 of the cavity 11 is reduced.
The movable core 12 is arranged at a position where is 4 mm, and in this state,
After starting the first resin injection, move the movable core 12 to the position S
Until the molten resin in the cavity 11 is compressed.
Here, the position S is set such that the thickness t1 of the cavity 11 is 1.5 mm. In addition, the amount of the molten resin injected in the first injection is an amount corresponding to the volume of the cavity 11 having the thickness t1 of 1.5 mm. When the formation of the reinforcing fiber-containing resin solid layer is completed in the first resin injection, the movable core 12 is retracted to the position T,
Stop at that position. Here, the position T is the cavity
The thickness t2 of 11 is set to be 6 mm. In this state, the second resin injection is performed. In the second injection, all the remaining molten resin that has been plasticized and measured is injected. Simultaneously with the completion of the second resin injection, the movable core 12 is retracted to the position U, and in this state, the molten resin is cooled and solidified. Here, the position U is set so that the thickness t3 of the cavity 11 becomes 14 mm. In the third embodiment as well, as in the first embodiment, sufficient weight reduction and smoothness can be achieved, and no large voids are formed in the interior and the warpage is small. It turns out that a product excellent in quality can be obtained. From this, it is understood that the injection compression molding method is also an effective molding method for the molten resin injected in the first time.

Although the present invention has been described with reference to the preferred embodiments and examples, the present invention is not limited to these embodiments and examples, and various modifications may be made without departing from the gist of the present invention. And design changes are possible. For example, the mold is divided into a fixed mold and a movable mold, and is not limited to a mold provided with a movable core as a movable mold in the movable mold, and is divided into a fixed mold and a movable mold. Further, the movable mold itself may be a movable mold. In addition, as a solid layer containing a reinforcing fiber-containing resin for a molded product, it is preferable that the resin is densely filled and a layer having no voids, but depending on the molding method and molding conditions employed, some voids are generated. The layer may be a closed layer, and is not limited to a layer covering the entire front side of the molded product, and may be a layer formed so as to cover a part of the surface. Further, in the above embodiment, the resin injection is performed in two stages, but the number of times of resin injection is not limited to two, and may be three or more.

The thermoplastic resin used as the main component of the resin pellets is not limited to polypropylene, but may be propylene resin.
Polyethylene resin such as ethylene block copolymer, polyethylene, polystyrene resin, ABS resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, polyaromatic ether or thioether A resin, a polyaromatic ester resin, a polysulfone resin, or an acrylate resin may be used, and a specific composition can be appropriately selected as long as it is a thermoplastic resin capable of forming a fiber-reinforced molded product. Furthermore, the reinforcing fibers contained in the resin pellets are not limited to glass fibers, but may be ceramic fibers, inorganic fibers, metal fibers, organic fibers, and the like. The specific selection of the fibers may be appropriately performed upon implementation.

In the above embodiment, the raw material did not contain a foaming agent. However, the raw material may contain 3 parts by weight or less of the foaming agent with respect to 100 parts by weight of the raw material.
Thus, if the foaming agent is contained, even when the restoring force of the fiber in the springback phenomenon is insufficient,
Since the foaming force of the foaming agent complements the restoring force of the fiber, in order to cause the springback phenomenon, even if the amount of fiber is somewhat insufficient, the molten resin reaches a desired volume as the movable mold recedes. Can be reliably expanded. Here, when the content of the foaming agent exceeds 3 parts by weight, a silver mark often occurs, and there is a possibility that a defect in appearance quality may occur. And the rigidity may be significantly reduced.

[0042]

As described above, according to the present invention, multiple types of resin layers having different structures can be molded in multiple layers with one injection molding machine and one type of molding material, and the rigidity, heat resistance, etc. In addition to improving the mechanical properties and reducing the weight, a fiber-reinforced resin molded product with excellent appearance quality can be obtained.
If applied to automobile parts and building civil engineering melt members, their mechanical efficiency and work efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a side view showing an entire injection molding machine according to a first embodiment of the present invention.

FIG. 2 is a view for explaining a molding procedure of the embodiment.

FIG. 3 is a diagram for explaining an evaluation method of an example of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding machine 10 Mold 11 Cavity 12 Movable core as movable mold S 1st position T 2nd position U 3rd position

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 105: 04 105: 12

Claims (7)

[Claims] 1. A fiber-containing thermoplastic resin pellet containing reinforcing fibers having a length in the range of 2 to 100 mm is contained, and said reinforcing fibers are 5 to 7 parts of the whole raw material.
By injecting a molten resin obtained by plasticizing the raw material into a mold having a movable mold capable of moving back and forth with respect to an internal cavity by using the raw material set to 0% by weight,
A method of molding a fiber-reinforced resin for molding a molded article, wherein the first resin injection is performed in a state where the movable mold is disposed at a first position where the cavity has a predetermined volume, and reinforcement is performed. After forming the solid layer containing the fiber for resin, the movable mold is retracted to the second position, and after the second resin injection is started in a state where the cavity is expanded, the cavity is molded. Characterized in that the movable die is retracted to a third position having a volume corresponding to the shape of the fiber-reinforced resin. 2. A fiber reinforced resin molding method according to claim 1, wherein said raw material contains 3 parts by weight or less of a foaming agent with respect to 100 parts by weight of said raw material. Molding method. 3. The method of molding a fiber-reinforced resin according to claim 1, wherein the raw material has a total length of 2 to 1
The fiber-containing thermoplastic resin pellets having a length of 00 mm and reinforcing fibers having a length equal to the total length are arranged in parallel with each other and contained 20 to 80% by weight of the whole. A method of molding a fiber-reinforced resin, wherein a raw material in which the reinforcing fiber is 20 to 70% by weight of the whole raw material is used. 4. The method for molding a fiber-reinforced resin according to claim 1, wherein the amount of the molten resin injected at the first time is equal to or less than the amount of the reinforcing fiber-containing resin solid layer. The amount of the molten resin injected for the second time corresponds to the volume expansion of the cavity expanded when the movable mold is retracted to the second position. Molding method of fiber reinforced resin. 5. The method of claim 1 wherein the substantially dense reinforcing fiber-containing resin molding layer and the reinforcing fiber-containing resin void layer having voids are integrally molded from a resin having the same composition to reduce the weight. Characterized molded product of fiber reinforced resin. 6. A molded article of the fiber reinforced resin according to claim 5, wherein R = (V × ρ−W) / (V ×
A molded article of a fiber reinforced resin, wherein the weight reduction ratio R represented by ρ) is in the range of 0.1 to 0.8. Here, V is the volume of the molded article, ρ is the average density of the raw material, and W is the weight of the molded article. 7. A fiber-reinforced resin molded article according to claim 5, wherein the average fiber length of the fibers contained in the molded article is 2 mm or more. Molded products.