Method for producing reinforcing fiber-containing resin pellets

Abstract

To provide a method for producing a resin pellet containing reinforcing fibers, which has an excellent productivity and excellent mechanical property equivalent to a long fiber reinforced resin pellet.SOLUTION: A method for producing a resin pellet containing reinforcing fibers, uses: a twin-screw extruder 1 that includes a first kneading unit 5, and a second kneading unit 6 that is provided at a side closer to an outlet than the first kneading unit 5 and has a reverse feed screw element having a notch and / or a kneading disk including a reverse feed; and a die 2 equipped with a nozzle 9, provided at an outlet of the twin-screw extruder 1. The method comprises the steps of: melt-kneading a resin in the first kneading unit 5; supplying reinforcing fibers into the twin-screw extruder 1 from a side closer to an outlet than the first kneading unit 5 and a side closer to an inlet than the second kneading unit 6, and further melt-kneading the resin in the presence of the reinforcing fibers; and extruding a melted and kneaded resin containing the reinforcing fibers from an outlet of the nozzle 9 of the die 2 as a strand of the reinforcing fiber-containing resin, in which the nozzle 9 satisfies predetermined requirements.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing reinforcing fiber-containing resin pellets, and more particularly to a method for producing reinforcing fiber-containing resin pellets containing short fibers, which are excellent in productivity and have mechanical properties equivalent to those of long fiber reinforced resin pellets. [Background technology]

[0002] Taking advantage of their excellent mechanical properties, reinforcing fiber-containing resin pellets are used in various applications such as automobile parts and office automation equipment. A typical method for producing reinforcing fiber-containing resin pellets is to feed a thermoplastic resin to an extruder to melt the thermoplastic resin, then feed fibers to the molten thermoplastic resin, mix and knead the thermoplastic resin and glass fiber in the extruder, and finally extrude the mixed and kneaded material as a strand from a die nozzle, which is cut and pelletized. In an extruder, a screw such as a kneading disk is generally used for kneading, but it is known that using a screw with a number of notches on a reverse-feeding flight disk as disclosed in Patent Document 1 has the advantage of simplifying the screw configuration of the kneading section while improving kneading performance.

[0003] It is known that the longer the fiber length of the remaining fibers in the reinforcing fiber-containing resin pellets, the stronger the molded product will be. However, when long reinforcing fibers are blended during the production of the reinforcing fiber-containing resin pellets, the reinforcing fibers are broken during kneading or stranding in a die, and the fiber length of the remaining fibers in the pellets becomes short, making it impossible to obtain sufficient mechanical properties.

[0004] Known methods for producing reinforcing fiber-containing resin pellets containing residual fibers with long fiber length include a method for producing strands using an extrusion die having a die hole having a partial conical shape, as disclosed in Patent Document 2, and a method for making glass fiber reinforced thermoplastic resin pellets with a high glass fiber content into a glass master batch and adding other resins to this, as disclosed in Patent Document 3. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-120271 A [Patent Document 2] Japanese Patent Application Publication No. 08-001662 [Patent Document 3] JP 2003-183411 A Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, the longer the fiber length of the remaining fibers in the pellet, the better the mechanical properties are obtained. On the other hand, reinforcing fiber-containing resin pellets containing long-length remaining fibers have problems such as reduced productivity due to the inability to stably produce strands with a normal die, difficulty in injection molding because the fibers are difficult to drop from the hopper during molding, and poor appearance of the molded body because some of the fibers do not open during molding. Even when the die described in Patent Document 2 is used, it is not possible to improve the injection moldability or appearance. In addition, when melt-kneading is performed using a neutral element having a screw uneven surface forming portion described in Patent Document 2, the fibers are broken in the extruder, and the reinforcing fiber length remaining in the pellet is shortened. In addition, in order to produce long-fiber reinforced resin pellets in which the pellet length and the fiber length in the pellet are equal, an expensive dedicated manufacturing device is required.

[0007] For this reason, there has been a demand for the development of a method for producing reinforcing fiber-containing resin pellets that does not require a dedicated production device for long fiber reinforced resin pellets, that is easy to injection mold, and that exhibits excellent appearance and mechanical properties even if the remaining fibers in the pellets have a long fiber length.

[0008] The present invention aims to provide a method for producing reinforcing fiber-containing resin pellets which allows stable continuous production when producing reinforced fiber resin pellets even if the remaining fibers have a long fiber length, which easily drops from a hopper during molding, which is easy to injection mold, which produces a molded product with excellent appearance, and which can exhibit excellent mechanical properties. [Means for solving the problem]

[0009] The present invention relates to, for example, the following [1] to [6]. [1] A twin-screw extruder having a first kneading section, and a reverse feed screw element having a notch and / or a second kneading section having a kneading disk including a reverse feed, which is provided on the outlet side of the first kneading section, and a die having a nozzle provided at the outlet of the twin-screw extruder, A step of supplying a resin into the twin-screw extruder from an inlet side of the first kneading section and melt-kneading the resin in the first kneading section; A step of supplying reinforcing fibers into the twin-screw extruder from an outlet side of the first kneading section and an inlet side of the second kneading section, and further melt-kneading the resin in the presence of the reinforcing fibers; A step of extruding the melt-kneaded resin containing the reinforcing fibers from a nozzle outlet of the die as a strand of a reinforcing fiber-containing resin; A method for producing reinforcing fiber-containing resin pellets comprising: The nozzle satisfies the following requirements (1) to (4), the resin is a propylene-based polymer having a melt flow rate of 20 to 500 g / 10 min at 230° C. under a load of 2.16 kg; The fiber length of the reinforcing fiber is 2.5 mm or more and 8 mm or less, The fiber diameter of the reinforcing fiber is 5 μm or more and less than 17 μm, The method for producing reinforcing fiber-containing resin pellets is characterized in that the reinforcing fiber-containing resin pellets contain 5% by mass or more and 50% by mass or less of the reinforcing fiber and 50% by mass or more and 95% by mass or less of the resin (the total of the reinforcing fiber and the resin is 100% by mass). (1) The nozzle flow path length is 60 mm or more and 150 mm or less. (2) The area of ​​the nozzle inlet (S1) is 6 mm 2 More than 80mm 2 The following is the result. (3) The area of ​​the nozzle outlet (S0) is 3 mm 2 More than 20mm 2 The following is the result. (4) The relationship S1≧S0 holds.

[0010] [2] The method for producing reinforcing fiber-containing resin pellets according to [1], wherein the propylene-based polymer is an isotactic propylene homopolymer.

[0011] [3] The method for producing reinforcing fiber-containing resin pellets according to [1] or [2], wherein the reinforcing fibers are glass fibers or carbon fibers.

[0012] [4] The method for producing reinforcing fiber-containing resin pellets according to any one of [1] to [3], wherein the screw rotation speed of the twin-screw extruder is 250 rpm or more and 800 rpm or less.

[0013] [5] The method for producing reinforcing fiber-containing resin pellets according to any one of [1] to [4], wherein the set temperature from the first kneading section to the nozzle of the twin-screw extruder is 240°C or higher and 290°C or lower.

[0014] [6] The method for producing reinforcing fiber-containing resin pellets according to any one of [1] to [5], wherein the reverse screw element having a notch is a single-start screw, has an L / D ratio of 1, has a notch, and has a lead of 0.25D or more and 0.5D or less. Effect of the Invention

[0015] The method for producing reinforcing fiber-containing resin pellets of the present invention can produce short fiber reinforced resin pellets in which the remaining fibers are long, and can produce reinforcing fiber-containing resin pellets with excellent productivity and excellent mechanical properties equivalent to those of long fiber reinforced resin pellets. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a vertical cross section, viewed from the horizontal direction, of a twin-screw extruder 1 and a die 2 which are one specific example of a twin-screw extruder and a die used in the method for producing reinforcing fiber-containing resin pellets of the present invention. [Diagram 2] FIG. 2 is an enlarged view of the die 2 shown in FIG. [Diagram 3] FIG. 3 is a view of the die 2 shown in FIG. 1 as seen from the nozzle outlet 11 side. [Figure 4] FIG. 4 is a schematic diagram of a vertical cross section, including a nozzle, of a die 2A equipped with a nozzle 9A having only a parallel portion 9aA without a tapered portion, as viewed from the horizontal direction. [Diagram 5] FIG. 5 is a schematic diagram of a vertical cross section, including the nozzle, viewed from the horizontal direction, of a die 2A equipped with a nozzle 9B having only a tapered portion 9bB without a parallel portion. [Figure 6] FIG. 6 is an explanatory diagram showing the structure of the screw used in Examples 1 and 2. [Figure 7] FIG. 7 is an explanatory diagram showing the structure of the screw used in Comparative Example 1. [Figure 8] FIG. 8 is a diagram showing an example of a kneading disk including a reverse feed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The method for producing reinforcing fiber-containing resin pellets of the present invention uses a twin-screw extruder and a die. The twin-screw extruder has a first kneading section, and a second kneading section provided on the outlet side of the first kneading section and equipped with a reverse screw element and / or a kneading disk including a reverse feed. The die is provided at the outlet of the twin-screw extruder and equipped with a nozzle. A schematic diagram of a vertical section viewed from a horizontal direction of one specific example of the twin-screw extruder and the die used in the method for producing reinforcing fiber-containing resin pellets of the present invention is shown in FIG. 1.

[0018] The twin-screw extruder 1 shown in FIG. 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 provided on the outlet B side of the first kneading section 5. The second kneading section 6 is equipped with a reverse feed screw element and / or a kneading disk including a reverse feed (not shown). The twin-screw extruder 1 further has a resin supply section 7 provided on the inlet A side of the first kneading section, and a fiber supply section 8 provided on the outlet B side of the first kneading section 5 and on the inlet A side of the second kneading section 6.

[0019] A die 2 is attached to 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. An enlarged view of the die 2 shown in Fig. 1 is shown in Fig. 2. The nozzle 9 is a hole with a circular cross section that passes horizontally through the die 2, with a nozzle inlet 10 formed on the twin-screw extruder 1 side and a nozzle outlet 11 formed on the opposite side to the twin-screw extruder 1.

[0020] Nozzle 9 has, on the nozzle inlet 10 side, a parallel section 9b that extends horizontally with the same diameter, and, on the nozzle outlet 11 side, a tapered section 9a whose diameter decreases at a constant rate toward the nozzle outlet 11. In Fig. 2, the nozzle flow path length, which is the horizontal length of nozzle 9, is indicated as L1, and the parallel flow path length, which is the horizontal length of parallel section 9b, is indicated as L2.

[0021] 3 is a view of the die 2 as viewed from the nozzle outlet 11 side. The die 2 is provided with five nozzle outlets 11 in the horizontal direction. In other words, the die 2 is provided with five nozzles 9. However, there is no limit to the number of nozzles in the die used in the manufacturing method for reinforcing fiber-containing resin pellets of the present invention.

[0022] The nozzle used in the method for producing reinforcing fiber-containing resin pellets of the present invention satisfies the following requirements (1) to (4). (1) The nozzle flow path length is 60 mm or more and 150 mm or less. The nozzle flow path length in the nozzle 9 shown in FIGS. 1 to 3 is the length indicated by L1 in FIG. The nozzle flow path length is 60 mm or more and 150 mm or less, preferably 80 mm or more and 140 mm or less, and more preferably 100 mm or more and 130 mm or less.

[0023] If the nozzle flow length is shorter than 60 mm, when using reinforcing fibers having the fiber length of the present invention, the fibers will not be oriented in the flow direction, and the fibers will fly out of the strand at the die outlet, making it impossible to stably and continuously extrude and take out the strand. Fibers may also fly out of the produced pellets. For this reason, when the pellets are fed into the hopper of the injection molding machine, they may form bridges and not fall stably into the barrel and screw. If the nozzle flow path length is longer than 150 mm, the resin pressure will increase, which may affect productivity.

[0024] (2) The area of ​​the nozzle inlet (S1) is 6 mm 2 More than 80mm 2 The following is the result. The area (S1) of the nozzle inlet is the area of ​​the nozzle inlet 10 shown in FIG. 2 in the nozzle 9 shown in FIGS. The area of ​​the nozzle inlet (S1) is 6 mm 2 More than 80mm 2 mm or less, preferably 10 mm 2 More than 60mm 2 Less than or equal to 12 mm, preferably 2 More than 50mm2 It is preferable in terms of the pellet shape if the area (S1) of the nozzle inlet is within the above range.

[0025] (3) The area of ​​the nozzle outlet (S0) is 3 mm 2 More than 20mm 2 The following is the result. The area (S0) of the nozzle outlet is the area of ​​the nozzle outlet 11 shown in FIGS. 2 and 3 in the nozzle 9 shown in FIGS. The nozzle outlet area (S0) is 3 mm 2 More than 20mm 2 mm or less, preferably 4 mm 2 More than 15mm 2 Less than 5mm, preferably 2 More than 10mm 2 The area (S0) of the nozzle outlet is preferably within the above range in terms of pellet shape.

[0026] (4) The relationship S1≧S0 holds. In the nozzle used in the method for producing reinforcing fiber-containing resin pellets of the present invention, the area (S0) of the nozzle outlet is smaller than or equal to the area (S1) of the nozzle inlet. It is preferable in terms of the discharge amount and pellet shape if the relationship S1≧S0 is satisfied.

[0027] In the nozzle used in the method for producing reinforcing fiber-containing resin pellets of the present invention, the cross-sectional area of ​​the nozzle is the same from the nozzle inlet to the nozzle outlet, or decreases from the nozzle inlet to the nozzle outlet. Nozzle 9 shown in FIGS. 1 to 3 has parallel portion 9b and tapered portion 9a, so that the relationship S1>S0 holds.

[0028] The nozzle used in the method for producing reinforcing fiber-containing resin pellets of the present invention preferably has both a parallel portion and a tapered portion, but does not need to have both a parallel portion and a tapered portion, and may have only a parallel portion 9bA without a tapered portion, as in nozzle 9A of die 2A shown in Fig. 4, or may have only a tapered portion 9aB without a parallel portion, as in nozzle 9B of die 2B shown in Fig. 5. When the nozzle has only a parallel portion, L1=L2 and S1=S0, and when the nozzle has only a tapered portion, S1>S0.

[0029] The method for producing reinforcing fiber-containing resin pellets of the present invention includes a step of supplying a resin into a twin-screw extruder from the inlet side of a first kneading section and melt-kneading the resin in the first kneading section (step 1), a step of supplying reinforcing fibers into the twin-screw extruder from the outlet side of the first kneading section and the inlet side of the second kneading section and further melt-kneading the resin in the presence of the reinforcing fibers (step 2), and a step of extruding the melt-kneaded resin containing the reinforcing fibers from the nozzle outlet of the die as strands of reinforcing fiber-containing resin (step 3).

[0030] Hereinafter, steps 1 to 3 will be described using the twin-screw extruder 1 and the die 2 shown in Figs. 1 to 3 as examples. In step 1, resin is supplied from a resin supply section 7 to the inner bore of a cylinder 3 of a twin-screw extruder 1. The supplied resin moves inside the cylinder 3 by the action of a screw 4 and is transported to a first kneading section 5. The structure of the screw 4 up to the first kneading section 5 is, for example, a full flight. The resin transported to the first kneading section 5 is melt-kneaded in the first kneading section 5.

[0031] In the present invention, the kneading section means a section in a twin-screw extruder that has the function of kneading and homogenizing materials. The kneading section in the present invention includes not only a section that mixes, kneads, and homogenizes two or more materials, but also a section that mixes, kneads, and homogenizes a single material so that the material has uniform physical properties. The kneading section in the present invention is, for example, a section that has a kneading disk or the like as a screw structure, rather than a full flight.

[0032] The resin used in the method for producing reinforcing fiber-containing resin pellets of the present invention is a propylene-based polymer. The propylene-based polymer is a propylene homopolymer or a propylene copolymer. In the case of a propylene copolymer, the content of structural units derived from propylene is preferably 40 mol% or more, more preferably 50 mol% or more, and the monoolefins that are structural units derived from monomers other than propylene are 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., and more preferably ethylene and 1-butene. The polymerization mode may be random or block type. Among these resins, propylene homopolymers, propylene-ethylene block copolymers, propylene-ethylene random copolymers, and propylene-ethylene-butene random copolymers are preferred, and propylene homopolymers are more preferred. The propylene-based polymer may be any of isotactic, syndiotactic, and atactic, but isotactic propylene is preferred. That is, isotactic propylene homopolymer is particularly preferred as the resin used in the method for producing reinforcing fiber-containing resin pellets of the present invention. These polymers may be used alone or in combination of two or more.

[0033] The propylene polymer has a melt flow rate of 20 to 500 g / 10 min, preferably 30 to 200 g / 10 min, more preferably 30 to 150 g / min at 230° C. and a load of 2.16 kg. When the melt flow rate of the propylene polymer is within the above range, the melt viscosity of the resin is low, so that the reinforcing fibers are less susceptible to shear in the twin-screw extruder, and breakage of the reinforcing fibers is suppressed, which is preferable.

[0034] In step 2, reinforcing fibers are supplied from the fiber supply section 8 to the inner bore of the cylinder 3 of the twin-screw extruder 1. The supplied reinforcing fibers are mixed with the melt-kneaded resin conveyed from the first kneading section 5, move inside the cylinder 3 by the action of the screw 4, and are conveyed to the second kneading section 6. The structure of the screw 4 from the first kneading section 5 to the second kneading section 6 is, for example, a full flight. The resin mixed with the reinforcing fibers conveyed to the second kneading section 6 is further melt-kneaded in the second kneading section 6.

[0035] The reinforcing fibers are not particularly limited as long as they are generally used to reinforce resins, and glass fibers, carbon fibers, metal fibers, and organic fibers (polyamide, polyester, aramid, polyphenylene sulfide, liquid crystal polymer, acrylic, etc.) can be used. Among these, glass fibers and carbon fibers are particularly desirable. As glass fibers, commonly used E-glass and high-strength, high-elasticity T-glass are suitable.

[0036] The fiber length of the reinforcing fibers 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. If the fiber length of the reinforcing fibers is within the above range, it is preferable from the viewpoint of productivity.

[0037] The fiber diameter of the reinforcing fibers 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. If the fiber diameter of the reinforcing fibers is within the above range, it is preferable in terms of mechanical properties.

[0038] There is no particular limit to the number of reinforcing fibers bundled together, and it is preferable to bundle 10 to 20,000 single fibers or monofilaments, as this improves handling. Usually, the reinforcing fibers can be used after surface treatment with a silane coupling agent or the like to improve the interfacial adhesion with the resin.

[0039] The ratio of the resin and reinforcing fibers supplied is preferably 5% by mass or more and 50% by mass or less, 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, of reinforcing fibers, and 50% by mass or more and 95% by mass or less, 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 resin is 100% by mass).

[0040] As described above, the second kneading section 6 is provided with a reverse screw element having a notch and / or a kneading disk including a reverse feed. A reverse screw element having a notch is preferable because the residual fiber length is longer. When the second kneading section 6 is provided with a reverse screw element, the kneading 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, the glass fiber is less likely to break, and the characteristics of the raw material are easily secured.

[0041] The reverse screw element is preferably a screw element in which a plurality of notches are formed at the tip of the flight of the flight screw. The reverse screw element is preferably configured with one or two threads in the reverse lead (reverse direction). The lead of the reverse screw element is preferably configured to be 0.15xD to 1.0xD (D: screw diameter). The notches are preferably formed at 2 to 30 locations within one lead of the reverse screw element, and may be parallel to the axial direction of the screw or twisted in either direction. The reverse screw element is preferably a single thread, L / D=1, has a notch, and has a lead of 0.25D to 0.5D. A specific example is BMS manufactured by Japan Steel Works, Ltd. By using a reverse screw element having a notch, the reinforcing fiber in the resin can be long without breaking the reinforcing fiber too much, and can be uniformly dispersed in the molten resin with good fiber opening.

[0042] The kneading disc including the reverse feed has a structure shown in FIG. 8, for example, and a commercially available kneading disc can be used. In step 3, the melt-kneaded resin containing the reinforcing fibers is extruded as strands of reinforcing fiber-containing resin from the nozzle outlet 11 of the die 2. The structure of the screw 4 from the second kneading section 6 to the die 2 is, for example, a full flight.

[0043] The dice used in step 3 satisfy the following (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 2 More than 80mm 2 It is. (3) The cross-sectional area of ​​the nozzle outlet (S0) is 3 mm 2 More than 20mm 2 The following is the result. (4) The relationship S1≧S0 holds.

[0044] By using the nozzle in process 3, even if the reinforcing fibers in the resin are long, they do not protrude from the strands, making continuous production possible. Since the reinforcing fibers do not protrude from the resulting pellets, there is no bridging in the hopper of the injection molding machine during injection molding, making stable injection molding possible.

[0045] The screw rotation speed of the twin-screw extruder in steps 1 to 3 is preferably 250 rpm or more and 800 rpm or less. The set temperature from the first kneading section to the nozzle of the twin-screw extruder in steps 1 to 3 is preferably 230°C or more and 290°C or less, and more preferably 240°C or more and 290°C or less, from the viewpoint of increasing the remaining glass fiber length and preventing thermal deterioration of the resin.

[0046] In the method for producing reinforcing fiber-containing resin pellets of the present invention, reinforcing fiber-containing resin pellets are obtained by pelletizing the strands of reinforcing fiber-containing resin obtained by the above steps 1 to 3 using a known method. As the pelletizing method, for example, as disclosed in JP-B-41-20738, a method of cooling the strands and pelletizing them with a cutter, or a method of cutting them to a predetermined size immediately after extrusion from a die is preferred.

[0047] There is no particular restriction on the shape and size of the reinforcing fiber-containing resin pellets produced by the method for producing reinforcing fiber-containing resin pellets of the present invention. For example, the length of the reinforcing fiber-containing resin pellets in the extension direction of the strands can be 3 mm or more and 10 mm or less. If the length is less than 3 mm, the remaining fiber length in the pellets becomes short, and the specified strength may not be achieved. If the length exceeds 10 mm, the metering during injection molding becomes unstable, which may cause problems with the molding cycle.

[0048] The reinforcing fiber-containing resin pellets obtained by the method for producing reinforcing fiber-containing resin pellets of the present invention contain reinforcing fiber at 5% by mass or more and 50% by mass or less, 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 contain resin at 50% by mass or more and 95% by mass or less, 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 reinforcing fiber and resin is 100% by mass). In the method for producing reinforcing fiber-containing resin pellets of the present invention, the supply amounts of reinforcing fiber and resin are determined in the above steps 1 and 2 so that the content ratio of reinforcing fiber and resin in the reinforcing fiber-containing resin pellets is within the above range.

[0049] The fiber length of the reinforcing fiber (residual fiber) contained in the reinforcing fiber-containing resin pellet produced by the method for producing reinforcing fiber-containing resin pellets of the present invention is shorter than the pellet length, for example, 1.5 mm to 8 mm, and can also be 1.5 mm to 3.0 mm. In the method for producing reinforcing fiber-containing resin pellets of the present invention, reinforcing fiber-containing resin pellets containing short fibers can be produced in this way. The reinforcing fiber-containing resin pellets produced by the method for producing reinforcing fiber-containing resin pellets of the present invention are characterized in that they have mechanical properties equivalent to those of reinforcing fiber-containing resin pellets containing long fibers, even when they contain short fibers. The reason why the reinforcing fiber-containing resin pellets of the present invention can produce reinforcing fiber-containing resin pellets having mechanical properties equivalent to those of reinforcing fiber-containing resin pellets containing long fibers, even when they contain short fibers, is presumed to be because the remaining fibers in the pellets are long, which allows them to exhibit excellent mechanical strength.

[0050] In order to impart desired properties according to the purpose to the reinforcing fiber-containing resin pellets produced by the method for producing reinforcing fiber-containing resin pellets of the present invention, known substances generally used in thermoplastic resins, such as known stabilizers such as antioxidants, heat stabilizers, and ultraviolet absorbers, antistatic agents, flame retardants, flame retardant assistants, colorants such as dyes and content, lubricants, plasticizers, crystallization accelerators, crystal nucleating agents, etc., can also be blended at the same time with inorganic fillers such as glass flakes, glass powder, glass beads, silica, montmorillonite, quartz, talc, clay, alumina, carbon black, wollastonite, mica, calcium carbonate, and metal powder.

[0051] The reinforcing fiber-containing resin pellets produced by the method for producing reinforcing 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., blow molding, etc. During molding, in order to prevent damage to the reinforcing fibers, it is desirable to enlarge the nozzle and gate shapes and set the groove depth of the molding machine screw to be equal to or greater than the pellet size. EXAMPLES

[0052] The methods for measuring physical properties in the examples and comparative examples are shown below. (Melt Flow Rate (MFR)) The melt flow rate was measured in accordance with ISO1133 at a temperature of 230° C. and a load of 2.16 kg.

[0053] (Remaining fiber length) 1 g of pellets was incinerated at 600°C for 75 minutes. The incinerated sample was photographed with a micro camera, and the lengths of more than 1000 fibers were measured using image software. The average length was taken as the remaining fiber length.

[0054] (GF pops out at the die exit) The protrusion of glass fibers at the die outlet was visually observed and evaluated according to the following criteria. None: No protruding glass fibers were observed. Somewhat present: Glass fibers are occasionally observed protruding. Present: Glass fibers are always observed protruding.

[0055] (Continuous Productivity) The continuous productivity of the reinforcing fiber-containing resin was evaluated according to the following criteria. ○: Strands can be taken up continuously and pelletized stably. ×: The strands could not be taken up continuously, and stable pelletization was not possible.

[0056] [Example 1] The twin-screw extruder used was a TEX30 (number of cylinder blocks: 15) manufactured by Japan Steel Works, Ltd., having the structure shown in Figure 1. The cylinder blocks are named C1, C2, C3, . . ., C13, C14, and C15 from the upstream side of the extruder. The resin supply section was provided in C1, and the fiber supply section was provided 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°C.

[0057] In the second kneading section, one BMS manufactured by Japan Steel Works, Ltd. having the structure shown in FIG. 6 was installed as a reverse feed screw element having a notch. The screw rotation speed was set to 300 rpm.

[0058] A die having a shape as shown in Fig. 2 was attached to the outlet of the twin-screw extruder. The die had a nozzle with a circular cross section, which had a parallel portion and a tapered portion, a nozzle flow path length (L1) of 125 mm, and a parallel flow path length (L2) of 85 mm. The area (S1) of the nozzle inlet of the die was 20 mm 2 and the nozzle outlet area (S0) is 7 mm 2 The die temperature was 280°C.

[0059] Prime Polypro manufactured by Prime Polymer Co., Ltd., MFR: 210 g / 10 min, Prime Polypro manufactured by Prime Polymer Co., Ltd., MFR: 30 g / 10 min, and Polybond 3200 manufactured by Addivant Co., Ltd. were premixed in a mass ratio of 60 / 10 / 1 and fed from the resin feed section of the twin-screw extruder at a rate 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 and cut to a length of 6 mm and fed from the fiber feed section at a rate 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 a strand of reinforcing fiber-containing resin.

[0060] The obtained strand was pelletized by a cutter to obtain pellets of the reinforcing fiber-containing resin having a length of 6 mm. The hourly production rate of the pellets was 70 kg / h, and the glass fiber content in the pellets was 30 mass %.

[0061] [Example 2] Pellets were obtained in the same manner as in Example 1, except that the die was changed to one having a shape as shown in Figure 4. The die had a nozzle with a circular cross section, which only had a parallel portion and did not have a tapered portion, and the nozzle flow path length (L1) was 210 mm. In addition, the area (S1) of the nozzle inlet and the area (S0) of the nozzle outlet of the die were 20 mm. 2 It was.

[0062] [Example 3] Pellets were obtained in the same manner as in Example 1, except that the amount of glass fiber supplied was changed so that the glass fiber content in the obtained pellets was 35 mass %.

[0063] [Example 4] Pellets were obtained in the same manner as in Example 1, except that the die was changed to one having a shape as shown in Figure 4. The die had a nozzle with a circular cross section, which only had a parallel portion and did not have a tapered portion, and the nozzle flow path length (L1) was 65 mm. In addition, the area (S1) of the nozzle inlet and the area (S0) of the nozzle outlet of the die were 20 mm 2 It was.

[0064] [Example 5] Pellets were obtained in the same manner as in Example 1, except that the die was changed to one having a shape as shown in Figure 5. The die had a nozzle with a circular cross section, which only had a tapered portion and did not have a parallel portion, and the nozzle flow path length (L1) was 125 mm. In addition, the area (S1) of the nozzle inlet of the die was 20 mm 2 , the nozzle outlet area (S0) is 7mm 2 It was.

[0065] [Example 6] Pellets were obtained in the same manner as in Example 1, except that a reverse kneading disk having no notches and having a shape as shown in FIG. 8 was used instead of the reverse screw element having notches.

[0066] [Example 7] Pellets were obtained in the same manner as in Example 1, except that the extruder temperatures were set to C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / C10 / C11 / C12 / C13 / C14 / C15=water cooling / 100 / 230 / 230 / 230 / 230 / 230 / 230 / 230 / 230 / 230 / 230°C.

[0067] [Example 8] A polypropylene resin (manufactured by Prime Polymer Co., Ltd., MFR: 210 g / 10 min) and Admer QX100 manufactured by Mitsui Chemicals, Inc. were premixed in a mass ratio of 79 / 1 and fed at a rate of 56 kg / h from the resin feed section of the twin-screw extruder using a gravimetric feeder, and carbon fiber manufactured by Toray Industries, Inc. (TORAYCA CUT FIBER TV14-006, cut length 6 mm) was fed at a rate of 14 kg / h from the fiber feed section. Except for this, the same procedure as in Example 1 was carried out to obtain pellets.

[0068] [Comparative Example 1] The same procedure as in Example 1 was carried out, except that a progressive full flight having a shape as shown in FIG. 7 was incorporated in the second kneading section instead of the BMS, to obtain pellets.

[0069] [Comparative Example 2] Pellets were obtained in the same manner as in Example 1, except that the die was changed to one having a shape as shown in Figure 4. The die had a nozzle with a circular cross section, which only had a parallel portion and did not have a tapered portion, and the nozzle flow path length (L1) was 20 mm. In addition, the area (S1) of the nozzle inlet and the area (S0) of the nozzle outlet of the die were 13 mm. 2 It was.

[0070] [Comparative Example 3] The same procedure as in Example 1 was repeated, except that the glass fibers were prepared by bundling 4,000 monofilaments of glass fibers (manufactured by Nippon Electric Glass Co., Ltd., 9T-480, fiber diameter: 13 μm) and cutting them to a length of 9 mm. However, glass fibers were ejected from the strand at the die exit, making continuous production impossible.

[0071] [Comparative Example 4] A polypropylene resin (Prime Polymer Co., Ltd., MFR: 210 g / 10 min) and Admer QX100 manufactured by Mitsui Chemicals, Inc. were premixed in a mass ratio of 79 / 1 and fed from the resin feed section of the twin-screw extruder at a rate of 56 kg / h using a gravimetric feeder, and carbon fiber manufactured by Toray Industries, Inc., Torayca Cut Fiber TV14-006, cut length 6 mm, was fed from the fiber feed section at a rate of 14 kg / h, and the die was changed to a die having a shape as shown in FIG. 4. The same procedure was followed as in Example 1. The die had a nozzle with a circular cross section, which only had a parallel portion and did not have a tapered portion, and the nozzle flow path length (L1) was 20 mm. In addition, the area (S1) of the nozzle inlet and the area (S0) of the nozzle outlet of the die were 13 mm. 2 It was. Table 1 shows the evaluation results in the production of the reinforcing fiber-containing resin pellets.

[0072] [Table 1]

[0073] [Example 9] Using the reinforcing fiber-containing resin pellets obtained in Example 1, a molded article (test piece for measuring mechanical properties) was produced by the following injection molding method. Injection molding machine: NEX110, manufactured by Nissei Plastics Co., Ltd. Molding temperature: 250℃ Mold temperature: 40℃ Mechanical property measurement specimen shape: ISO 1A dumbbell

[0074] In addition, using the reinforcing fiber-containing resin pellets obtained in Example 1, a molded article for appearance observation was produced by the following injection molding method. Injection molding machine: EC100 manufactured by Toshiba Machine Co., Ltd. Molding temperature: 240℃ Mold temperature: 40℃ Shape of molded body for external observation: 80mm x 240mm x 2mm

[0075] The molded bodies were evaluated under the following conditions. (Tensile test) Tensile tests were performed according to ISO 527. Using the above test pieces for measuring mechanical properties, a tensile test was carried out at a tensile speed of 5 mm / min at 23° C. to determine the tensile stress at break and the tensile strain at break.

[0076] (Flexural strength, flexural modulus) The bending strength and bending modulus were measured by a three-point bending test. Using the above mechanical property measurement test pieces, the test pieces were cut to the test piece 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 using an autograph AG-X manufactured by Shimadzu Corporation.

[0077] (Charpy impact strength) Using the above mechanical property test pieces, test pieces for measuring impact strength were prepared by machining notches in accordance with ISO 179, and Charpy impact tests were performed to measure the Charpy impact strength (kJ / m) at 23°C. 2 ) was sought.

[0078] (Deflection temperature under load) The above test pieces for measuring mechanical properties were cut to test piece dimensions in accordance with ISO 75-1,2, and the deflection temperature under load was measured at a load of 1.8 MPa.

[0079] (Appearance evaluation of molded body) The appearance of the molded article for appearance observation was visually evaluated according to the following criteria. ◯: White spots caused by poor opening of glass fibers are not noticeable on the test piece. △: White spots caused by poor opening of glass fibers are slightly noticeable on the test piece. ×: White spots due to poor opening of glass fibers are clearly noticeable on the test piece.

[0080] [Example 10] A molded article was produced in the same manner as in Example 9, except that the reinforcing fiber-containing resin pellets obtained in Example 6 were used instead of the reinforcing fiber-containing resin pellets obtained in Example 1.

[0081] [Example 11] A molded article was produced in the same manner as in Example 9, except that the reinforcing fiber-containing resin pellets obtained in Example 8 were used instead of the reinforcing fiber-containing resin pellets obtained in Example 1.

[0082] [Comparative Example 5] A molded article was produced in the same manner as in Example 9, except that the reinforcing fiber-containing resin pellets obtained in Comparative Example 1 were used instead of the reinforcing fiber-containing resin pellets obtained in Example 1. The evaluation results of the obtained molded bodies are shown in Table 2.

[0083] [Table 2] [Explanation of symbols]

[0084] 1 Twin screw extruder 2 Dice 3 Cylinder 4 Screw 5. First kneading section 6. Second kneading section 7 Resin supply section 8 Fiber Supply Section 9 Nozzles 9a Parallel part 9b Tapered section 10 Nozzle inlet 11 Nozzle outlet

Claims

1. A twin-screw extruder having a first kneading section, and a reverse-feed screw element having a notch and / or a second kneading section having a kneading disk including a reverse feed, which is provided on the outlet side of the first kneading section, and a die having a nozzle provided at the outlet of the twin-screw extruder, A step of supplying a resin into the twin-screw extruder from an inlet side of the first kneading section and melt-kneading the resin in the first kneading section; A step of supplying reinforcing fibers into the twin-screw extruder from an outlet side of the first kneading section and an inlet side of the second kneading section, and further melt-kneading the resin in the presence of the reinforcing fibers; A step of extruding the melt-kneaded resin containing the reinforcing fibers from a nozzle outlet of the die as a strand of a reinforcing fiber-containing resin; A method for producing reinforcing fiber-containing resin pellets comprising: The nozzle satisfies the following requirements (1) to (4), the resin is a propylene-based polymer having a melt flow rate of 20 to 500 g / 10 min at 230° C. under a load of 2.16 kg; The fiber length of the reinforcing fiber is 2.5 mm or more and 8 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 pellets contain 5% by mass or more and 50% by mass or less of the reinforcing fiber and 50% by mass or more and 95% by mass or less of the resin (the total of the reinforcing fiber and the resin is 100% by mass). A method for producing reinforcing fiber-containing resin pellets. (1) The nozzle flow path length is 60 mm or more and 150 mm or less. (2) The cross-sectional area (S1) of the nozzle inlet is 6 mm 2 More than 80mm 2 It is. (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm 2 More than 20mm 2 The following is the result. (4) The relationship S1≧S0 holds.

2. The method for producing reinforcing fiber-containing resin pellets according to claim 1, wherein the propylene-based polymer is an isotactic propylene homopolymer.

3. The method for producing reinforcing fiber-containing resin pellets according to claim 1 or 2, wherein the reinforcing fibers are glass fibers or carbon fibers.

4. The method for producing reinforcing fiber-containing resin pellets according to any one of claims 1 to 3, wherein the screw rotation speed of the twin-screw extruder is 250 rpm or more and 800 rpm or less.

5. The method for producing reinforcing fiber-containing resin pellets according to any one of claims 1 to 4, wherein the set temperature from the first kneading section to the nozzle of the twin-screw extruder is 240 ° C. or more and 290 ° C. or less.

6. The method for producing reinforcing fiber-containing resin pellets according to any one of claims 1 to 5, wherein the reverse screw element having the notch is a single thread, L / D = 1, and the lead is 0.25D or more and 0.5D or less.

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