Injection molding method and apparatus for long fiber reinforced resin

Abstract

To provide an injection molding apparatus in which fibers in a thermoplastic resin are not cut and a fiber direction is aligned even when the resin is melted in the injection molding apparatus using long-fiber pellets.SOLUTION: An apparatus for injection molding a long-fiber reinforced resin comprises: a cylindrical housing 11 for receiving long-fiber pellets 40 fed from a pellet feeding passage 71 from a hopper into an inside; and a melting vessel 11 having openings at a top and a bottom. A top opening diameter D1 of a tapered through hole 13 of the melting vessel is made larger than a bottom opening diameter, to draw to align a direction to which long-fibers flow. When a diameter of the top opening of the tapered through hole 13 is D1, a length of the fiber pellets is L, and an outer diameter is d, L>D1>d.SELECTED DRAWING: Figure 2

Description

【Technical Field】 【0001】 The present invention relates to an injection molding method and apparatus for long fiber reinforced resins. More specifically, the present invention relates to an injection molding method and apparatus for long fiber reinforced resins, which are a molding method and a molding apparatus optimal for long fiber reinforced resins in which the fibers contained in the thermoplastic resin are long. 【Background Art】 【0002】 Today, thermoplastic resins obtained by mixing glass fibers, carbon fibers, etc. with thermoplastic resins to improve mechanical strengths such as rigidity are widely used. When it is desired to increase the mechanical strength of a thermoplastic resin containing fibers, generally long fibers are preferred as the fibers to be mixed with the thermoplastic resin. It is known that fiber orientation has a great influence on the strength of parts in a composite material. The most common orientations of fiber reinforced composites are unidirectional, random, bidirectional, and multi-directional, etc. Fiber orientation can improve the mechanical and chemical properties of injection molded parts. However, when injection molding with a thermoplastic resin containing long fibers, even if long fibers are mixed in, the effect is halved because the long fibers are cut by the melting screw or the like of the injection molding apparatus. Therefore, in the case of a screw type injection molding apparatus, proposals have been made to devise the structure of the screw to reduce the probability of fiber cutting (see, for example, Patent Documents 1 and 2). 【0003】 The applicant of the present application has proposed an injection molding apparatus that pressurizes molten resin with a ram without using this screw (see, for example, Patent Document 3). Also, in a plunger type injection molding apparatus, although the probability of fiber cutting is low, the fibers become entangled with each other and the strength of the molded product does not increase. Also, various thermoplastic resin pellets containing long fibers have been proposed (see, for example, Patent Documents 4 and 5). 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2017-105184 [Patent Document 2] Japanese Patent Publication No. 2014-46631 [Patent Document 3] WO2016 / 088874 issue [Patent Document 4] Japanese Patent Application Publication No. 5-162124 [Patent Document 5] Japanese Patent Publication No. 2008-221574 [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 As mentioned above, with conventional injection molding equipment and molding methods, even when pellets containing long fibers are used, the long fibers are cut by the screw, nozzle, etc., or the long fibers become entangled with each other, reducing the effectiveness of using long fibers by half. Based on the above background, the present invention aims to achieve the following objectives. The object of the present invention is to provide an injection molding method and apparatus for long-fiber reinforced resin in which the fibers within the thermoplastic resin are not cut and the fiber direction is aligned in a desired direction. [Means for solving the problem] 【0006】 The injection molding method for long fiber reinforced resin according to the present invention 1 is: A hopper for supplying pellets containing fibers and thermoplastic resin, A cylindrical housing that receives pellets supplied from a pellet supply passage communicating with the hopper, A melting vessel for heating and melting the pellets, having an upper opening and a lower opening, with the upper opening being larger than the lower opening, and a melting unit located at the bottom of the housing, which is a heater arranged on the outer circumference of the melting vessel for heating the pellets. A plunger is placed in the housing and pressurizes the pellets and the molten resin in which the pellets have melted, A molten resin reservoir is located at the bottom of the melting vessel and has a nozzle for injecting the molten resin from below, which collects the molten resin melted in the melting unit. In an injection molding apparatus comprising, The aforementioned pellets are made of a thermoplastic resin containing aligned long fibers, have a length-to-diameter ratio of 1 or more, and are cylindrical or prismatic long fiber pellets in cross-sectional shape. The long fibers of the long fiber pellets are supplied from the pellet supply path of the hopper so that the long fibers of the long fiber pellets are parallel to each other in the supply direction. The long fiber pellets are arranged vertically and flowed downward into the housing. The long fiber pellets are flowed from the housing in the direction of the tapered through-hole. The plunger is characterized by pressurizing the molten resin through the vertically aligned long fiber pellets and injecting it from the nozzle. 【0007】 The injection molding method for long fiber reinforced resin according to the present invention 2 is characterized in that, in the injection molding method for long fiber reinforced resin according to the present invention 1, the long fiber pellet has a circular or polygonal cross-sectional shape, the long fibers are aligned in the longitudinal direction of the long fiber pellet, and the length is L and the outer diameter is d, and when the diameter of the upper opening is D1, L>D1>d. The injection molding method for long fiber reinforced resin according to the third invention is the injection molding method for long fiber reinforced resin according to the first or second invention, characterized in that the length of the long fibers in the long fiber pellet is 3 to 30 mm and is glass fiber or carbon fiber. 【0008】 The injection molding apparatus for long fiber reinforced resin according to Invention 1 is an injection molding apparatus for long fiber reinforced resin used in the injection molding method for long fiber reinforced resin according to Invention 1, characterized in that the long fiber pellets have a circular or polygonal cross-sectional shape, are aligned in the longitudinal direction of the long fiber pellets, have a length L and an outer diameter d, and when the diameter D1 of the upper opening is given by L > D1 > d, and the length of the long fibers in the long fiber pellets is 3 to 30 mm. [Effects of the Invention] 【0009】 The injection molding method and apparatus for long-fiber reinforced resin of the present invention produce molded articles with high mechanical strength because the fibers within the thermoplastic resin are not cut and their directions are aligned. [Brief explanation of the drawing] 【0010】 [Figure 1] Figure 1 is a front view showing the external appearance of an embodiment of an injection molding apparatus for long fiber reinforced resin. [Figure 2] Figure 2 is a cross-sectional view illustrating the principle of injection molding of the long fiber reinforced resin injection molding apparatus shown in Figure 1. [Figure 3] Figure 3 shows the shape of a melting unit for heating and melting resin; Figure 3(a) is a plan view, and Figure 3(b) is a cross-sectional view of bb in Figure 3(a). [Figure 4] Figure 4 shows an external view of a long fiber pellet. [Figure 5] Figure 5 shows an example of a molded product produced by injection molding using the injection molding method and apparatus of the present invention, and is an X-ray CT image of a cross-sectional view of the surface of the molded product. [Modes for carrying out the invention] 【0011】 Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a front view showing the external appearance of an embodiment of an injection molding apparatus for long fiber reinforced resin. Figure 2 is a cross-sectional view illustrating the principle of injection molding of the injection molding apparatus for long fiber reinforced resin shown in Figure 1. The injection molding apparatus 1 includes a cylindrical injection device 2 arranged in the vertical direction. The injection device 2 melts pellets, pressurizes them with a plunger 61 (described later), and injects the molten resin from a nozzle 92; it is a so-called plunger-type injection device. Parallel to the injection device 2, on the back side (rear side in Figure 1), an air cylinder unit 3 is mounted on the machine base 5, which drives the entire injection device 2 up and down toward the injection mold 4. A plunger drive unit 6, which is driven by air pressure to drive the ram, is mounted on the upper part of the injection device 2. 【0012】 A hopper 7 for supplying pellets is fixedly arranged on a cylindrical housing 21 that constitutes the main body of the injection device 2. On the outer periphery of the lower housing 21, a radiator 8 composed of a number of plate-shaped heat dissipation fins is arranged and fixed. Further, a melting unit 10 is arranged below the radiator 8 of the housing 21. Long fiber pellets 40 (see FIG. 4) are supplied to the injection device 2 from the pellet supply path 71 of the hopper 7. The long fiber pellets 40 are aligned in the housing 21 communicating with the pellet supply path 71 and supplied by their own weight. FIG. 4 is a view showing the appearance of the long fiber pellets 40. The long fiber pellets 40 are rod-shaped with a circular cross-section, having a length of L and an outer diameter of d, and an outer shape with the relationship L>d. The long fiber pellets 40 are, in this example, long fiber reinforced thermoplastic resin pellets containing a number of reinforcing fiber filaments 41 with a length of 3 to 30 mm and aligned fiber directions in a thermoplastic resin 42. The long fibers of the long fiber pellets 40 are, for example, those wrapped in a thermoplastic resin 42 such as PEEK, PPS, RENY, PA6, PA, PA66, PA9T, etc. and arranged in parallel in large numbers. 【0013】 Preferably, the long fiber pellets 40 preferably contain 70 to 35% by weight of an amorphous thermoplastic resin and 30 to 65% by weight of reinforcing fibers such as glass fibers and carbon fibers. The length of the reinforcing fiber filaments 41 is the same as the length L of the long fiber pellets 40. The length of the reinforcing fiber filaments 41 is not limited to this, and it is preferable that fibers of different lengths are mixed according to the intended use, function, and strength of the required molded body, rather than being the same length as the long fiber pellets 40. Although the long fiber pellets 40 shown in FIG. 4 are rod-shaped with a circular cross-section, the cross-sectional shape may be polygonal. The external shape of the long fiber pellets 40 is elongated, with the relationship L>d (L: length of the pellet, d: diameter of the pellet). 【0014】 FIG. 2 is a cross-sectional view for explaining the injection molding principle of the injection molding apparatus for long fiber reinforced resin shown in FIG. 1. As shown in FIG. 2, the supply of the long fiber pellets 40 to the cylindrical supply path 71 of the hopper 7 is aligned by an aligner (not shown, such as a vibrating hopper) so that the supply direction and the center line of the long fiber pellets 40 are parallel to each other. The aligned long fiber pellets 40 flow into the housing 21 having a hollow interior from the pellet supply path 71 in an aligned state. The long fiber pellets 40 are aligned by an aligner, a gate, etc. and are in contact with and constrained by each other. Therefore, as shown in FIG. 2, most of the long fiber pellets 40 from the pellet supply path 71 to the housing 21 are aligned so that this center line is in the vertical direction and are supplied by falling due to gravity. 【0015】 A melting unit 10 having a cylindrical appearance is arranged at the lower part of the housing 21. The melting unit 10 includes a central melter 11 and an electric heating heater 12 on its outer periphery. FIG. 3 shows the shape of the melting unit for heating and melting the resin. FIG. 3(a) is a plan view, and FIG. 3(b) is a cross-sectional view taken along the line b-b of FIG. 3(a). The melter 11 has a cylindrical appearance, but a plurality of tapered through-holes 13 are formed. In this example, a total of seven through-holes are arranged in the vertical direction at the center and the outer periphery. When the upper opening 14 of the tapered through-hole 13 has a diameter D1 and the lower opening 15 has a diameter D2, the relationship is D1 > D2, that is, it is a tapered hole. Further, the above-mentioned long fiber pellets 40 have a length L, and the relationship between the diameter L of the long fiber pellets 40 and the diameter D1 of the upper part of the tapered through-hole 13 is L > D1. 【0016】 For this reason, if the long fiber pellets 40 are oriented horizontally, they will block the upper opening 14 even if supplied, and will not enter the upper opening 14 of the tapered through hole 13. For this reason, the long fiber pellets 40 need to be aligned vertically and flow into the upper opening 14. The vertically aligned long fiber pellets 40 are heated by the electric heater 12 and gradually become melted. At this time, the long fibers do not become entangled, and the fluid resistance of the flow is minimized when the fibers are aligned as they flow, so they flow along the peripheral wall of the tapered through hole 13 in the direction of the fibers. The reinforcing fiber filaments 41 in the molten resin have their fiber directions aligned and the probability of them becoming entangled with each other is low. The long fiber pellets 40 enter vertically from the top of the tapered through hole 13, gradually soften and melt, and exit from the lower opening 15 with their fiber directions aligned. 【0017】 The molten resin 91, with its fibers aligned in the same direction, flows into the molten resin reservoir 9. The molten resin reservoir 9 temporarily stores the molten resin 91. A nozzle 92 opens at the bottom of the molten resin reservoir 9, and the resin is injected from this nozzle 92 into the injection mold 4. This injection is performed under pressure by a plunger 61, as shown in Figure 2. As can be understood from the above description, in this embodiment, the injection molding apparatus 1 for long fiber reinforced resin is supplied with long fiber pellets 40 so that the long fibers are aligned parallel to each other from the moment they are supplied to the injection molding apparatus, melted, and injected, thereby obtaining mechanical strength that conforms to the shape of the initial molded product. [Examples] 【0018】 Figure 5 shows an X-ray CT image of the molded product when it is injection molded using the injection molding method and apparatus described above, and is a cross-sectional image of the area near the surface of the molded product. The observation method is as follows: (1) Molding conditions • Materials: Polyplastics Co., Ltd. (Head office: Minato-ku, Tokyo, Japan) PLASTRON LFT (Registered Trademark) LFT PP-GF-40-01 (Long fiber glass-reinforced PP resin) • Electric heater 12 setting temperature: 240℃ • Mold setting temperature: 80℃ • Plunger 61 pressing force: 6MPa ·Injection speed: 15mm / s • Holding time: 2 min (2) X-ray CT observation conditions • Observation equipment: Comscan Techno Co., Ltd. (Head office: Yokohama City, Kanagawa Prefecture, Japan) ScanXmate-D090SS270 Observation conditions: Tube voltage 50kV, Tube current 155μA (3) Findings Near the surface of the molded product, bundles of glass fibers were observed to be randomly oriented without being cut. [Explanation of symbols] 【0019】 1…Injection molding apparatus for long fiber reinforced resin 2...Injection device 3…Air cylinder unit 4…Injection mold 5…Machine base 6…Plunger drive unit 7... Hoppa 8…Radiator 9... Molten resin reservoir 10…Melting Unit 11...Melter 12...Electric heater 13... Tapered through hole 14… Upper opening 15...Lower opening 21… Housing 40…Long fiber pellets 41…Reinforcement fiber filament 61... Plunger 71...Pellet supply route 91…Molten resin 92... Nozzle

Claims

[Claim 1] A hopper for supplying pellets containing fibers and thermoplastic resin, A cylindrical housing that receives pellets supplied from a pellet supply passage communicating with the hopper, A melting vessel for heating and melting the pellets, having an upper opening and a lower opening, with the upper opening being larger than the lower opening, and a melting unit located at the bottom of the housing, which is a heater arranged on the outer circumference of the melting vessel for heating the pellets. A plunger is placed in the housing and pressurizes the pellets and the molten resin in which the pellets have melted, A molten resin reservoir is located at the bottom of the melting vessel and has a nozzle for injecting the molten resin from below, which collects the molten resin melted in the melting unit. In an injection molding apparatus comprising, The aforementioned pellets are made of a thermoplastic resin containing aligned long fibers, have a length-to-diameter ratio of 1 or more, and are cylindrical or prismatic long fiber pellets in cross-sectional shape. The long fibers of the long fiber pellets are supplied from the pellet supply path of the hopper so that the long fibers of the long fiber pellets are parallel to each other in the supply direction. The long fiber pellets are aligned vertically and flowed downward into the housing. The long fiber pellets are flowed from the housing in the direction of the tapered through-hole. The plunger pressurizes the molten resin through the vertically aligned long fiber pellets and injects it from the nozzle. A method for injection molding a long fiber reinforced resin, characterized by the above. [Claim 2] In the injection molding method for long fiber reinforced resin according to claim 1, The long fiber pellet has a circular or polygonal cross-sectional shape, and the long fibers are aligned along the length of the long fiber pellet, with a length L and outer diameter d, and the diameter of the upper opening D1 such that L > D1 > d. A method for injection molding a long fiber reinforced resin, characterized by the above. [Claim 3] In the injection molding method for long fiber reinforced resin according to claim 1 or 2, The length of the long fibers in the long fiber pellet is 3 to 30 mm, and they are glass fibers or carbon fibers. A method for injection molding a long fiber reinforced resin, characterized by the above. [Claim 4] An injection molding apparatus for a long fiber reinforced resin used in the injection molding method for a long fiber reinforced resin according to claim 1 or 2, When the diameter of the upper opening is D1, the length of the long fiber pellet is L, and the outer diameter is d, then L > D1 > d. An injection molding apparatus for long fiber reinforced resin, characterized by the following features.

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