Fiber-reinforced resin pellets

Abstract

SOLUTION: To provide a reinforcement fiber-containing resin pellet which contains 50 mass% or more and 95 mass% or less of a propylene-based polymer and 5 mass% or more and 50 mass% or less of a reinforcement fiber (total of propylene-based polymer and reinforcement fiber is 100 mass%), and has a length of 3 mm or more and 10 mm or less, where a fiber diameter of the reinforcement fiber is 5 μm or more and less than 17 μm, and a fiber length of the reinforcement fiber is shorter than a length of the pellet and 1.5 mm or longer.EFFECT: A reinforcement fiber-containing resin pellet is a fiber-reinforced resin pellet containing a reinforcement fiber having a fiber length longer than that of a reinforcement fiber in a conventional short fiber reinforcement resin, is excellent in productivity of an injection molding, and has excellent mechanical properties and appearance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to reinforced fiber-containing resin pellets, and more particularly to reinforced fiber-containing resin pellets containing short fibers that exhibit excellent productivity of injection molded products and superior mechanical properties. [Background technology]

[0002] Reinforced fiber-containing resin pellets are used in various applications such as automotive parts and office automation equipment, taking advantage of their excellent mechanical properties. A common method for manufacturing reinforced fiber-containing resin pellets involves supplying thermoplastic resin to an extruder to melt it, then supplying fibers to the molten thermoplastic resin, mixing and kneading the thermoplastic resin and glass fibers in the extruder, and finally extruding the mixed material as strands from a die nozzle, which are then cut to form pellets. In extruders, it is common to use a screw such as a kneading disc for kneading, but it is known that using a screw with numerous notches on a reverse-feed flight disc, as disclosed in Patent Document 1, has advantages such as improving kneading performance and simplifying the screw configuration of the kneading section.

[0003] It is known that higher strength molded products can be obtained from reinforced fiber-containing resin pellets if the remaining fibers in the pellets are long. However, when long reinforcing fibers are incorporated during the manufacturing of reinforced fiber-containing resin pellets, the reinforcing fibers may break during kneading or stranding in a die, resulting in shorter remaining fibers in the pellets and sometimes failing to obtain sufficient mechanical properties.

[0004] Methods for producing reinforced fiber-containing resin pellets that include residual fibers with long fiber lengths include a method for producing strands using an extrusion die having a die hole with a conical shape in part, as disclosed in Patent Document 2, and a method for using a glass fiber-reinforced thermoplastic resin pellet with a high glass fiber content as a glass masterbatch and adding other resins to it, as disclosed in Patent Document 3. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-120271 [Patent Document 2] Japanese Patent Application Publication No. 08-001662 [Patent Document 3] Japanese Patent Publication No. 2003-183411 [Overview of the project] [Problems that the invention aims to solve]

[0006] As mentioned above, superior mechanical properties are obtained when the residual fibers in the pellet are longer. However, reinforced fiber-containing resin pellets containing long residual fibers have not been obtained until now due to the problem that conventional dies cannot stably extrude and cut the strands. Even using the die described in Patent Document 2, it was not possible to improve injection moldability or appearance. Furthermore, when melt kneading was performed using the neutral element having a screw surface forming part described in Patent Document 2, the fibers broke in the extruder, resulting in a shorter residual reinforcing fiber length in the pellet.

[0007] Therefore, there was a need to develop reinforced fiber-containing resin pellets in which the remaining fibers present in the pellets had a long fiber length and could exhibit excellent mechanical properties. The present invention aims to provide reinforced fiber-containing resin pellets that exhibit excellent productivity in injection molded products, have long residual fiber lengths, and can exhibit superior mechanical properties. [Means for solving the problem]

[0008] The present invention relates, for example, to the following [1] to [4]. [1] It is a reinforced fiber-containing resin pellet containing 50% to 95% by mass of a propylene-based polymer and 5% to 50% by mass of a reinforcing fiber (the total of the propylene-based polymer and the reinforcing fiber is 100% by mass), and the reinforcing fiber has a length of 3 mm or more and 10 mm or less. The fiber diameter of the reinforcing fiber is 5 μm or more and less than 17 μm. The reinforcing fiber-containing resin pellet is characterized in that the fiber length of the reinforcing fiber is shorter than the length of the pellet and is 1.5 mm or more.

[0009] [2] The reinforcing fiber-containing resin pellet according to [1], wherein the fiber length of the reinforcing fiber is 3.0 mm or less.

[0010] [3] The reinforcing fiber-containing resin pellet according to [1] or [2], wherein the propylene-based polymer is an isotactic propylene homopolymer.

[0011] [4] The reinforcing fiber-containing resin pellet according to any one of [1] to [3], wherein the reinforcing fiber is a glass fiber or a carbon fiber. [Advantages of the Invention]

[0012] The reinforcing fiber-containing resin pellet of the present invention is a fiber-reinforced resin pellet containing a reinforcing fiber having a longer fiber length than the reinforcing fiber in a conventional short fiber-reinforced resin, is excellent in the productivity of injection-molded products, and has excellent mechanical properties and appearance. [Brief Description of the Drawings]

[0013] [Figure 1] FIG. 1 is a schematic longitudinal sectional view seen from the horizontal direction of a twin-screw extruder 1 and a die 2, which are a specific example of the twin-screw extruder and the die used in the method for producing the reinforcing fiber-containing resin pellet of the present invention. [Figure 2] FIG. 2 is an enlarged view of the die 2 shown in FIG. 1. [Figure 3] FIG. 3 is a view of the die 2 shown in FIG. 1 seen from the nozzle outlet 11 side. [Figure 4] FIG. 4 is a schematic longitudinal sectional view including a nozzle, as viewed in the horizontal direction, of a die 2A provided with a nozzle 9A having no tapered portion and only a parallel portion 9aA. [Figure 5] FIG. 5 is a schematic longitudinal sectional view including a nozzle, as viewed in the horizontal direction, of a die 2A provided with a nozzle 9B having no parallel portion and only a tapered portion 9bB. [Figure 6] FIG. 6 is an explanatory view showing the structure of the screw used in Example 1 and Example 2. [Figure 7] FIG. 7 is an explanatory view showing the structure of the screw used in Comparative Example 1 and Comparative Example 2.

MODE FOR CARRYING OUT THE INVENTION

[0014] The reinforced fiber-containing resin pellets of the present invention contain a propylene-based polymer and a reinforcing fiber. The propylene-based polymer is a propylene homopolymer or a propylene copolymer. In the case of a propylene copolymer, the content of the structural unit derived from propylene is preferably 40 mol% or more, more preferably 50 mol% or more. As the monoolefin that becomes the structural unit derived from a monomer other than propylene, preferably ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, etc. are mentioned, and more preferably ethylene and 1-butene. The polymerization mode may be random type or block type. Among these resins, a propylene homopolymer, a propylene / ethylene block copolymer, a propylene / ethylene random copolymer, a propylene / ethylene / butene random copolymer, etc. are preferable, and a propylene homopolymer is more preferable. As the propylene-based polymer, any of isotactic, syndiotactic, and atactic may be used, but isotactic propylene is preferable. That is, as the resin used in the method for producing the reinforced fiber-containing resin pellets of the present invention, an isotactic propylene homopolymer is particularly preferable. These polymers may be used alone or in combination of two or more.

[0015] The propylene polymer has a melt flow rate of 20 to 500 g / 10 min at 230°C and a 2.16 kg load, preferably 30 to 200 g / 10 min, and more preferably 30 to 150 g / min. A melt flow rate within this range of the propylene polymer is preferable because it results in a high toughness and low melt viscosity of the resin in the resulting molded article, which reduces the shearing of the reinforcing fibers in the twin-screw extruder and suppresses the breakage of the reinforcing fibers.

[0016] The reinforcing fibers are not particularly limited as long as they are commonly used to reinforce resins, and examples include glass fibers, carbon fibers, metal fibers, and organic fibers (polyamide, polyester, aramid, polyphenylene sulfide, liquid crystal polymer, acrylic, etc.). Among these, glass fibers and carbon fibers are particularly desirable. As for glass fibers, commonly used E-glass and high-strength, high-modulus T-glass are preferred.

[0017] The reinforced fiber-containing resin pellets of the present invention contain 5% by mass or more and 50% by mass or less of reinforcing fibers, preferably 15% by mass or more and 50% by mass or less, more preferably 25% by mass or more and 45% by mass or less, and 50% by mass or more and 95% by mass or less of propylene polymer, preferably 50% by mass or more and 85% by mass or less, more preferably 55% by mass or more and 75% by mass or less (the total of the reinforcing fibers and the propylene polymer is 100% by mass).

[0018] The length of the reinforced fiber-containing resin pellets of the present invention is 3 mm to 10 mm, preferably 4 mm to 8 mm, and more preferably 4 mm to 6 mm. The length of the pellet refers to the length in the extension direction of the strand (length perpendicular to the cut portion). There are no particular restrictions on the shape of the reinforced fiber-containing resin pellets of the present invention.

[0019] The fiber length of the reinforcing fibers contained in the reinforcing fiber-containing resin pellets of the present invention is shorter than the length of the pellet and is 1.5 mm or longer. Preferably, the fiber length of the reinforcing fibers is 1.5 mm or longer and 3.0 mm or shorter, and more preferably 2.0 mm or longer and 3.0 mm or shorter. Reinforcing fiber-containing resin pellets are usually manufactured by melt-kneading resin and reinforcing fibers, as described later, extruding the mixture from a die nozzle, taking it up as strands, and then pelletizing these strands. During the melt-kneading, extrusion, and taking processes, the reinforcing fibers may be cut and further stretched in the direction of extension of the strands. Therefore, the longest length of the reinforcing fibers in the reinforcing fiber-containing resin pellets is usually the length in the direction of extension of the strands of the pellet (length perpendicular to the cut portion).

[0020] While longer reinforcing fibers in pellets generally result in superior mechanical properties, longer fibers can also make injection molding difficult because they tend to protrude from the pellet and are difficult to remove from the hopper during molding. Furthermore, some fibers may not open during molding, potentially degrading the appearance of the molded product.

[0021] The reinforced fiber-containing resin pellets of the present invention contain reinforcing fibers with longer fiber lengths than those in conventional short-fiber reinforced resins, and therefore possess excellent mechanical properties. These pellets are characterized by their ability to produce molded articles with superior appearance. Furthermore, they offer excellent productivity for injection molded products and result in injection molded articles with superior appearance.

[0022] The fiber diameter of the reinforcing fiber is 5 μm or more and less than 17 μm, preferably 10 μm or more and 17 μm or less, and more preferably 10 μm or more and 13 μm or less. A fiber diameter within the above range is preferable in terms of mechanical strength.

[0023] The reinforced fiber-containing resin pellets of the present invention may be blended with known substances commonly used in thermoplastic resins to impart desired properties depending on the purpose, such as antioxidants, heat stabilizers, UV absorbers and other known stabilizers, antistatic agents, flame retardants, flame retardant aids, colorants such as dyes and their content, lubricants, plasticizers, crystallization accelerators, crystal nucleating agents, etc. It is also possible to simultaneously blend inorganic fillers such as glass flakes, glass powder, glass beads, silica, montmorillonite, quartz, talc, clay, alumina, carbon black, wollonite, mica, calcium carbonate, and metal powders.

[0024] The manufacturing method for the reinforced fiber-containing resin pellets of the present invention is not particularly limited, but the manufacturing method described below allows for efficient production of the reinforced fiber-containing resin pellets of the present invention.

[0025] This manufacturing method uses a twin-screw extruder and a die. The twin-screw extruder has a first kneading section and a second kneading section located on the outlet side of the first kneading section and equipped with a notched reverse-feed screw element. The die is located at the outlet of the twin-screw extruder and is equipped with a nozzle. Figure 1 shows a schematic cross-sectional view of a specific example of the twin-screw extruder and die used in this manufacturing method, viewed from the horizontal direction.

[0026] The twin-screw extruder 1 shown in Figure 1 has a cylinder 3 and a screw 4 housed in the inner bore of the cylinder 3. The twin-screw extruder 1 has two screws 4 in the horizontal direction. The twin-screw extruder 1 has a first kneading section 5 and a second kneading section 6 located on the outlet B side of the first kneading section 5. The second kneading section 6 is equipped with a reverse-feed screw element (not shown). Furthermore, the twin-screw extruder 1 has a resin supply section 7 located on the inlet A side of the first kneading section and a fiber supply section 8 located on the outlet B side of the first kneading section 5 and on the inlet A side of the second kneading section 6.

[0027] A die 2 is mounted at the outlet B of the twin-screw extruder 1. The die 2 is provided with a nozzle 9 that is directly connected to the inner bore of the cylinder 3. Figure 2 shows an enlarged view of the die 2 shown in Figure 1. The nozzle 9 is a circular cross-section hole that penetrates the die 2 horizontally, with a nozzle inlet 10 formed on the twin-screw extruder 1 side and a nozzle outlet 11 formed on the opposite side from the twin-screw extruder 1.

[0028] The nozzle 9 has a parallel section 9b extending horizontally with the same diameter on the nozzle inlet 10 side, and a tapered section 9a on the nozzle outlet 11 side, where the diameter decreases at a constant ratio toward the nozzle outlet 11. In Figure 2, the nozzle flow path length, which is the horizontal length of the nozzle 9, is shown as L1, and the parallel flow path length, which is the horizontal length of the parallel section 9b, is shown as L2.

[0029] Figure 3 shows the die 2 as viewed from the nozzle outlet 11 side. The die 2 has five nozzle outlets 11 arranged horizontally. In other words, the die 2 has five nozzles 9. However, there is no limit to the number of nozzles in the die used in the manufacturing method described above.

[0030] The nozzle satisfies the following requirements (1) to (4). (1) The nozzle flow path length is 60 mm or more and 150 mm or less. In the nozzle 9 shown in Figures 1-3, the nozzle flow path length is the length indicated by L1 in Figure 2. The nozzle flow path length is 60 mm to 150 mm, preferably 80 mm to 140 mm, and more preferably 100 mm to 130 mm.

[0031] If the nozzle flow path length is shorter than 60 mm, and reinforcing fibers with the fiber length described later are used, the fibers will not be oriented in the flow direction, causing them to fly out of the strand at the die exit, making it impossible to stably and continuously extrude and take up the strand. Fibers may also fly out of the manufactured pellets. As a result, when pellets are fed into the hopper of an injection molding machine, bridging may occur, preventing them from falling stably into the barrel and screw. If the nozzle flow path length is longer than 150 mm, the resin pressure may increase, which may affect productivity.

[0032] (2) The area (S1) of the nozzle inlet is 6 mm

[0035] , 2 , 2 , , 2 ,

[0034] , 2 , , , 2 , 2 , 2 , , 2 , , , or more and 80 mm 2 or less. The area (S1) of the nozzle inlet is, in the nozzle 9 shown in FIGS. 1 to 3, the area of the nozzle inlet 10 shown in FIG. 2. The area (S1) of the nozzle inlet is 6 mm 2 or more and 80 mm 2 mm or less, preferably 10 mm 2 or more and 60 mm 2 or less, more preferably 12 mm 2 or more and 50 mm 2 or less. When the area (S1) of the nozzle inlet is within the above range, it is preferable in terms of productivity and pellet shape.

[0033] (3) The area (S0) of the nozzle outlet is 3 mm 2 or more and 20 mm 2 or less. [[ID=ID=34]]The area (S0) of the nozzle outlet is, in the nozzle 9 shown in FIGS. 1 to 3, the area of the nozzle outlet 11 shown in FIGS. 2 and 3. The area (S0) of the nozzle outlet is 3 mm 2 or more and 20 mm 2 mm or less, preferably 4 mm 2 or more and 15 mm 2 or less, more preferably 5 mm 2 or more and 10 mm 2 or less. When the area (S0) of the nozzle outlet is within the above range, it is preferable in terms of pellet shape.

[0034] (4) The relationship S1 ≥ S0 holds. In the said nozzle, the area (S0) of the nozzle outlet is smaller than or the same as the area (S1) of the nozzle inlet. When the relationship S1 ≥ S0 holds, it is preferable in terms of discharge amount and pellet shape.

[0035] In the aforementioned nozzle, the cross-sectional area of ​​the nozzle is either the same from the nozzle inlet to the nozzle outlet, or decreases from the nozzle inlet to the nozzle outlet. Since the nozzle 9 shown in Figures 1-3 has a parallel section 9b and a tapered section 9a, the relationship S1 > S0 holds true.

[0036] The nozzle used in the above manufacturing method preferably has both a parallel section and a tapered section, but it is not necessary to have both. For example, as shown in Figure 4, nozzle 9A of die 2A may have no tapered section and only a parallel section 9bA, or as shown in Figure 5, nozzle 9B of die 2B may have no parallel section and only a tapered section 9aB. When the nozzle has only a parallel section, L1=L2 and S1=S0, and when the nozzle has only a tapered section, S1>S0.

[0037] The above manufacturing method includes a step (1) of supplying resin into a twin-screw extruder from the inlet side of the first kneading section and melting and kneading the resin in the first kneading section; a step (2) of supplying reinforcing fibers into a twin-screw extruder from the outlet side of the first kneading section and from the inlet side of the second kneading section and further melting and kneading the resin in the presence of the reinforcing fibers; and a step (3) of extruding the resin containing the melted and kneaded reinforcing fibers as strands of reinforcing fiber-containing resin from the nozzle outlet of the die.

[0038] The following explanation of steps 1 to 3 will use the twin-screw extruder 1 and die 2 shown in Figures 1 to 3 as an example. In step 1, resin is supplied from the resin supply unit 7 to the inner bore of the cylinder 3 of the twin-screw extruder 1. The supplied resin moves through the cylinder 3 by the action of the screw 4 and is transported to the first kneading unit 5. The structure of the screw 4 up to the first kneading unit 5 is, for example, full flight. The resin transported to the first kneading unit 5 is melted and kneaded in the first kneading unit 5.

[0039] The kneading section in a twin-screw extruder refers to the part that has the function of kneading and homogenizing materials. The kneading section includes not only the part that mixes, kneads, and homogenizes two or more materials, but also the part that mixes, kneads, and homogenizes a single material to achieve uniform physical properties. The kneading section is, for example, the part of the screw structure that has a kneading disc rather than a full flight. The resin used in the above manufacturing method is the aforementioned propylene polymer.

[0040] In step 2, the reinforcing fibers to be used as raw materials (hereinafter also referred to as raw material reinforcing fibers) are supplied from the fiber supply unit 8 to the inner bore of the cylinder 3 of the twin-screw extruder 1. The supplied raw material reinforcing fibers are mixed with the molten and kneaded resin transported from the first kneading unit 5, and then moved inside the cylinder 3 by the action of the screw 4 and transported to the second kneading unit 6. The structure of the screw 4 from the first kneading unit 5 to the second kneading unit 6 is, for example, full flight. The resin mixed with the reinforcing fibers, transported to the second kneading unit 6, is further molten and kneaded in the second kneading unit 6.

[0041] The type of raw material reinforcing fiber is the same as that of the reinforcing fiber contained in the reinforcing fiber-containing resin pellets of the present invention. The fiber length of the raw material reinforcing fiber is 2.5 mm or more and 8 mm or less, preferably 3 mm or more and 7 mm or less, and more preferably 3 mm or more and 6 mm or less.

[0042] The fiber diameter of the raw material reinforcing fiber is 5 μm or more and less than 17 μm, preferably 10 μm or more and 17 μm or less, and more preferably 10 μm or more and 13 μm or less. There are no particular restrictions on the number of reinforcing fibers to bundle; bundling 10 to 20,000 single fibers or monofilaments is desirable as it improves handling. Typically, the reinforcing fibers can also be used after surface treatment with a silane coupling agent or similar to improve interfacial adhesion with the resin.

[0043] The ratio of the supplied resin to the raw material reinforcing fiber is adjusted so as to obtain the required resin-to-reinforcing fiber ratio in the reinforcing fiber-containing resin pellet of the present invention. As described above, the second mixing section 6 is equipped with a reverse-feed screw element having a notch. When the second mixing section 6 is equipped with a reverse-feed screw element having a notch, the mixing performance and dispersion performance can be improved, energy consumption is reduced, thermal efficiency is improved, the melting temperature of the synthetic resin raw material can be kept low, and the properties of the raw material can be more easily ensured.

[0044] As a reverse feed screw element with notches, a screw element having multiple notches formed at the tip of the flight of the flight screw is preferred. The reverse feed screw element is preferably composed of one or two reverse leads (in the reverse direction). The lead of the reverse feed screw element is preferably composed of 0.15xD to 1.0xD (D: screw diameter). The notches are preferably formed 2 to 30 times between one lead of the reverse feed screw element, and may be parallel to the axial direction of the screw or twisted in either direction. The reverse feed screw element is preferably a single-start screw with L / D=1, has notches, and has a lead of 0.25D or more and 0.5D or less. Specifically, BMS manufactured by Japan Steel Works Ltd. can be cited. By using a reverse feed screw element with notches, reinforcing fibers can be dispersed uniformly in the molten resin with good fiber-opening properties without bending the fibers too much.

[0045] In step 3, the molten and kneaded resin containing the raw material reinforcing fibers is extruded from the nozzle outlet 11 of die 2 as strands of reinforcing fiber-containing resin. The structure of the screw 4 from the second kneading section 6 to die 2 is, for example, full flight. The dice used in step 3 must satisfy the following conditions (1) to (4). (1) The nozzle flow path length is 60 mm or more and 150 mm or less. (2) The cross-sectional area of ​​the nozzle inlet (S1) is 6 mm 280mm or more 2 That is the case. (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm 2 20mm or more 2 The following applies: (4) The relationship S1 ≥ S0 holds.

[0046] With conventional dies, long reinforcing fibers would protrude from the strand at the die exit, and these protruding fibers would stick to the die exit, cutting the strand and preventing the production of pellets.

[0047] By using the nozzle in step 3, even if the reinforcing fiber length in the resin is long, there is no protrusion of reinforcing fibers from the strand, enabling continuous production. Since there is no protrusion of reinforcing fibers from the resulting pellets, stable injection molding is possible without bridging in the hopper of the injection molding machine during injection molding.

[0048] The screw rotation speed of the twin-screw extruder in steps 1 to 3 is preferably between 250 rpm and 800 rpm. In steps 1 to 3, the set temperature from the first kneading section of the twin-screw extruder to the nozzle is preferably 240°C or higher and 290°C or lower.

[0049] In the above manufacturing method, the reinforced fiber-containing resin pellets of the present invention are obtained by pelletizing the strands of the reinforced fiber-containing resin obtained by steps 1 to 3 above using a known method. As for pelletizing, a method in which the strands are cooled and pelletized with a cutter, as disclosed in Japanese Patent Publication No. 41-20738, or a method in which the strands are cut to a predetermined size immediately after being extruded from a die, is preferred.

[0050] The reinforced fiber-containing resin pellets of the present invention can be molded by known molding methods such as injection molding, injection press molding, extrusion molding of tubes, pipes, sheets, etc., and blow molding. During molding, it is desirable to enlarge the nozzle and gate shape and to make the groove depth of the molding machine screw greater than or equal to the pellet size in order to suppress damage to the reinforcing fibers. [Examples]

[0051] The methods used to measure physical properties in the examples and comparative examples are shown below. (Melt Flow Rate (MFR)) The melt flow rate was measured in accordance with ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0052] (Remaining fiber length) One gram of pellet was incinerated at 600°C for 75 minutes. The incinerated sample was photographed with a micro-camera, and the length of more than 1000 fibers was measured using image processing software. The average length was defined as the remaining fiber length.

[0053] (Test specimen preparation) Using the pellets obtained in the examples and comparative examples, test specimens were prepared by injection molding under the following conditions. Injection molding machine: NEX110, manufactured by Nissei Plastic Industrial Co., Ltd. Molding temperature: 250℃ Mold temperature: 40℃ Specimen shape: ISO 1A dumbbell

[0054] (Tensile test) The tensile test was conducted in accordance with ISO 527. Using the above-mentioned test specimens, tensile tests were performed at a tensile speed of 5 mm / min at 23°C, and the tensile fracture stress and tensile fracture strain were determined.

[0055] (Bending strength, bending modulus) The bending strength and bending modulus were measured by a three-point bending test. Using a Shimadzu Autograph AG-X, the above-mentioned test specimens were cut to the specified dimensions in accordance with ISO 178, and the bending strength and bending modulus were measured at 23°C and a test speed of 2 mm / min.

[0056] (Charpy impact strength) Using the above test specimens, test specimens were prepared with notches machined in accordance with ISO 179, and a Charpy impact test was performed to determine the Charpy impact strength (kJ / m²) at 23°C.2 ) was sought.

[0057] (Temperature of deflection under load) Using the above test specimens, they were cut to the specified dimensions in accordance with ISO 75-1,2, and the temperature of deflection under load was measured at a load of 1.8 MPa.

[0058] [Example 1] A twin-screw extruder, a TEX30 manufactured by Japan Steel Works Ltd. (number of cylinder blocks: 15), was used. The cylinder blocks were designated C1, C2, C3, ..., C13, C14, and C15 from the upstream side of the extruder. The resin supply section was located in C1, and the fiber supply section was located in C11. The set temperatures were C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / C10 / C11 / C12 / C13 / C14 / C15 = water cooling / 100 / 260 / 260 / 260 / 260 / 260 / 260 / 260 / 260 / 260 / 260 / 260 / 260 / 260°C.

[0059] The screw shown in Figure 6 was loaded into the twin-screw extruder. The screw rotation speed was set to 300 rpm. A die having the shape shown in Figure 2 was mounted at the outlet of the twin-screw extruder. The die had a nozzle with a circular cross-section, which had a parallel section and a tapered section, with a nozzle flow path length (L1) of 125 mm and a parallel flow path length (L2) of 85 mm. In addition, the nozzle inlet area (S1) of the die was 20 mm². 2 The nozzle outlet area (S0) is 7 mm². 2 The die temperature was set to 280°C.

[0060] Polypropylene resin (a pre-mixed mixture of propylene homopolymer manufactured by Prime Polymer Co., Ltd., MFR: 210 g / 10 min, propylene homopolymer manufactured by Prime Polymer Co., Ltd., MFR: 30 g / 10 min, and Addivant Polybond 3200 in a 60 / 10 / 1 ratio) was supplied from the resin supply section of the twin-screw extruder at a speed of 49 kg / h using a gravimetric feeder. 4000 monofilaments of glass fiber (manufactured by Nippon Electric Glass Co., Ltd., 6T-480H, fiber diameter: 10 μm) were bundled together and cut to a length of 6 mm, and supplied from the fiber supply section at a speed of 21 kg / h. The twin-screw extruder was operated under the above conditions, and the molten mixture was extruded from the nozzle outlet as strands of reinforced fiber-containing resin.

[0061] The obtained strands were pelletized using a cutter to obtain 6 mm long reinforced fiber-containing resin pellets. The production rate of these pellets per hour was 70 kg / h, and the glass fiber content in the pellets was 30% by mass. The results of the physical property measurements of the aforementioned pellets are shown in Table 1.

[0062] [Example 2] Except for supplying bundles of 4,000 monofilaments of glass fiber (manufactured by Nippon Electric Glass Co., Ltd., 6T-480H, fiber diameter: 10 μm) cut to a length of 6 mm, the procedure was carried out in the same manner as in Example 1, except that bundles of 4,000 monofilaments of glass fiber (manufactured by Nippon Electric Glass Co., Ltd., T-480H, fiber diameter: 10 μm) cut to a length of 3 mm were supplied, and 6 mm long reinforced fiber-containing resin pellets were obtained. The production rate of the pellets per hour was 70 kg / h, and the glass fiber content in the pellets was 30% by mass. The results of the physical property measurements of the aforementioned pellets are shown in Table 1.

[0063] [Comparative Example 1] The same twin-screw extruder as in Example 1 was used. The settings for the twin-screw extruder were also the same as in Example 1. The screw shown in Figure 7 was loaded into the twin-screw extruder. The screw rotation speed was set to 300 rpm. A die having the shape shown in Figure 4 was mounted at the outlet of the twin-screw extruder. The die had a nozzle with a circular cross-section, and the nozzle had no tapered section, only a parallel section, with nozzle flow path length (L1) and parallel flow path length (L2) of 20 mm. In addition, the nozzle inlet area (S1) and nozzle outlet area (S0) of the die were 13 mm². 2 The die temperature was set to 230°C.

[0064] A polypropylene-based resin (a pre-mixed propylene homopolymer manufactured by Prime Polymer Co., Ltd., with an MFR of 30 g / 10 min and Addivant's Polybond 3200 in a 70 / 1 ratio) was supplied from the resin supply section of the twin-screw extruder at a speed of 42 kg / h using a gravimetric feeder. 4000 monofilaments of glass fiber (manufactured by Nippon Electric Glass Co., Ltd., T-480H, fiber diameter: 10 μm) were bundled together and cut to a length of 3 mm, and supplied from the fiber supply section at a speed of 18 kg / h. The twin-screw extruder was operated under the above conditions, and the molten mixture was extruded from the nozzle outlet as strands of reinforced fiber-containing resin.

[0065] The obtained strands were pelletized using a cutter to obtain 3 mm long reinforced fiber-containing resin pellets. The production rate of these pellets per hour was 60 kg / h, and the glass fiber content in the pellets was 30% by mass. The results of the physical property measurements of the aforementioned pellets are shown in Table 1.

[0066] [Comparative Example 2] The same twin-screw extruder as in Example 1 was used. The settings for the twin-screw extruder were also the same as in Example 1. The twin-screw extruder was loaded with the same screw as in Comparative Example 1. The screw settings were also the same as in Comparative Example 1. A die similar to that in Example 1 was mounted at the outlet of the twin-screw extruder. The die temperature was set to 230°C.

[0067] Polypropylene resin (a pre-mixed mixture of propylene homopolymer from Prime Polymer Co., Ltd., MFR: 210 g / 10 min, propylene homopolymer from Prime Polymer Co., Ltd., MFR: 30 g / 10 min, and Addivant Polybond 3200 in a 60 / 10 / 1 ratio) was supplied from the resin supply section of the twin-screw extruder at a speed of 21 kg / h using a gravimetric feeder. 4000 monofilaments of glass fiber (T-480H, fiber diameter: 10 μm, manufactured by Nippon Electric Glass Co., Ltd., cut to a length of 3 mm) were bundled together and supplied from the fiber supply section at a speed of 9 kg / h. The twin-screw extruder was operated under the above conditions, and the molten mixture was extruded from the nozzle outlet as strands of reinforced fiber-containing resin.

[0068] The obtained strands were pelletized using a cutter to obtain pellets with a length of 6 mm. The yield of these pellets per hour was 30 kg / h, and the glass fiber content in the pellets was 30% by mass. The results of the physical property measurements of the aforementioned pellets are shown in Table 1.

[0069] [Table 1] [Explanation of Symbols]

[0070] 1. Twin-screw extruder 2 dice 3 cylinders 4 Screws 5. First Mixing Section 6. Second Mixing Section 7. Resin supply unit 8. Fiber supply section 9 nozzles 9a Parallel part 9b Tapered section 10 Nozzle Inlet 11 Nozzle outlet

Claims

1. A reinforcing fiber-containing resin pellet containing 50% by mass or more and 95% by mass or less of a propylene-based polymer and 5% by mass or more and 50% by mass or less of reinforcing fibers (the total of the propylene-based polymer and the reinforcing fibers being 100% by mass), and having a length of 3 mm or more and 10 mm or less, The fiber diameter of the reinforcing fiber is 5 μm or more and less than 17 μm, A reinforcing fiber-containing resin pellet, characterized in that the fiber length of the reinforcing fibers is shorter than the length of the pellet and is 1.5 mm or more.

2. 2. The reinforcing fiber-containing resin pellet according to claim 1, wherein the reinforcing fibers have a fiber length of 3.0 mm or less.

3. The reinforcing fiber-containing resin pellet according to claim 1 or 2, wherein the propylene-based polymer is an isotactic propylene homopolymer.

4. The reinforcing fiber-containing resin pellet according to any one of claims 1 to 3, wherein the reinforcing fiber is glass fiber or carbon fiber.

Images