Method and apparatus for producing reinforcing fiber-containing resin pellet

Abstract

[Problem] To provide a method and an apparatus for producing a reinforcing fiber-containing resin pellet which, even when a die having a wide width and a long die length is used in producing pellets each containing reinforcing fibers having a long fiber length, is capable of obtaining a stable strand, exhibiting an excellent appearance of a molded body, and exhibiting excellent mechanical properties. [Solution] A method for producing a reinforcing fiber-containing resin pellet comprises: a step for supplying, to a twin-screw extruder, a resin from the inlet side relative to a first kneading part and melt-kneading the resin in the first kneading part; a step for supplying, to the twin-screw extruder, reinforcing fibers from the outlet side relative to the first kneading part and the inlet side relative to a second kneading part and further melt-kneading the resin in the presence of the reinforcing fibers; and a step for extruding, from a nozzle outlet of a die and in the form of a strand of a reinforcing fiber-containing resin, the melt-kneaded resin containing the reinforcing fibers. The combination of a base and the die having a nozzle satisfies a specific condition. An apparatus for producing a reinforcing fiber-containing resin pellet is used for said method and comprises: a twin-screw extruder having a first kneading part and a second kneading part which is provided at the outlet side relative to the first kneading part and which is equipped with a reverse-feeding screw element having a notch and / or a kneading disk featuring reverse feeding; and a die part provided at an outlet of the twin screw extruder.

Description

Manufacturing method and manufacturing device for reinforcing fiber-containing resin pellets

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

[0002] Taking advantage of their excellent mechanical properties, reinforcing fiber-containing resin pellets are used in a variety of applications, such as automotive parts and office automation equipment. A common method for producing reinforcing fiber-containing resin pellets involves feeding a thermoplastic resin into an extruder to melt the thermoplastic resin, then feeding fibers into the molten thermoplastic resin, mixing and kneading the thermoplastic resin and glass fiber in the extruder, and finally extruding the mixed and kneaded material as a strand from a die nozzle, which is then cut and pelletized. While extruders typically use a screw such as a kneading disk for kneading, using a screw with a reverse flight disk provided with multiple notches, as disclosed in Patent Document 1, is known to have advantages such as improving kneading performance while simplifying the screw configuration of the kneading section.

[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, if long reinforcing fibers are blended during the production of the reinforcing fiber-containing resin pellets, the reinforcing fibers may be broken during kneading or when stranded in a die, resulting in a shorter fiber length of the remaining fibers in the pellets, making it impossible to obtain sufficient mechanical properties.

[0004] Known methods for producing reinforcing fiber-containing resin pellets containing long residual fibers include a method of producing strands using an extrusion die having a die hole in the shape of a part of a cone, as disclosed in Patent Document 2, and a method of using glass fiber reinforced thermoplastic resin pellets with a high glass fiber content as a glass master batch to which other resins are added, as disclosed in Patent Document 3.

[0005] JP 2002-120271 A JP 08-001662 A JP 2003-183411 A JP 2022-154027 A

[0006] As mentioned above, longer residual fibers in pellets provide better mechanical properties. However, reinforcing fiber-containing resin pellets containing long residual fibers have problems such as reduced productivity due to the inability to stably produce strands using conventional dies, difficulty in injection molding due to the fibers not dropping from the hopper during molding, and poor appearance of the molded product due to some of the fibers not opening during molding. 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 the screw uneven surface forming portion described in Patent Document 2, the fibers broke in the extruder, resulting in a shorter length of the reinforcing fibers remaining in the pellets. Furthermore, producing long-fiber-reinforced resin pellets in which the pellet length is equal to the fiber length in the pellets requires expensive, dedicated manufacturing equipment.

[0007] Therefore, there has been a demand for 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 can exhibit excellent appearance and mechanical properties even if the fiber length of the remaining fibers in the pellets is long. Patent Document 4 shows a method for producing reinforcing fiber-containing resin pellets that has been developed to meet such demands.

[0008] However, as shown in Patent Document 4, the inventors have found through their investigations that even if a long die is used, when a medium- or large-scale reinforcing fiber-containing resin pellet manufacturing device with a wide die width is used, there is a problem in that the strands are not stable.

[0009] That is, in a large-scale reinforcing fiber-containing resin pellet manufacturing device, when the strand extruded from the extruder flows into the die, it is rapidly spread in width within the die holder and is supplied downstream into multiple tip nozzles.

[0010] Within the die holder, the resin is oriented along the wall surface, so the flow rate from the nozzles at both ends tends to be larger than the flow rate from the nozzles closer to the center due to the shear flow that is unique to fibrous materials.

[0011] Therefore, when a medium-scale or large-scale reinforcing fiber-containing resin pellet manufacturing device with a wide die width is used, the inventors have found through their investigations that the strands extruded from the nozzles at both ends become loose and unstable, as shown in Figure 14.

[0012] The present invention aims to provide a method and apparatus for producing reinforcing fiber-containing resin pellets that stabilize strands, produce molded products with excellent appearance, and exhibit excellent mechanical properties, even when a wide and long die is used to produce pellets containing long reinforcing fibers.

[0013] The present invention relates to, for example, the following [1] to

[12] . [1] A method for producing reinforcing fiber-containing resin pellets using a twin-screw extruder having a first kneading section and a second kneading section equipped with a reverse-feed screw element having a notch and / or a kneading disk including a reverse feed, which is provided on the outlet side of the first kneading section, and a die section provided at the outlet of the twin-screw extruder, wherein the die section comprises a nozzle die having a nozzle and a seat, and the seat has an opening with an inlet and an outlet connected to the nozzle, the method comprising: supplying a resin into the twin-screw extruder from the inlet side of the first kneading section and melt-kneading the resin in the first kneading section; 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; and extruding the melt-kneaded resin containing reinforcing fibers from the nozzle outlet of the nozzle die as strands of reinforcing fiber-containing resin, wherein the nozzle and the seat satisfy (1) to (8), A method for producing reinforcing fiber-containing resin pellets, wherein the nozzle die has a width of 94 mm or more, the number of nozzles arranged in the die is 5 to 70, and the openings are arranged in a horizontal row in the pedestal, 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 fibers is 2.5 mm or more and 8 mm or less, and the fiber diameter of the reinforcing fibers is 5 μm or more and less than 17 μm, and the reinforcing fiber-containing resin pellets contain 5% by mass or more and 50% by mass or less of the reinforcing fibers and 50% by mass or more and 95% by mass or less of the resin (the total of the reinforcing fibers 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 cross-sectional area (S1) of the smallest cross-sectional area portion of the opening of the pedestal is 6 mm. ２ Over 80mm ２ (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm ２ More than 20 mm ２or less. (4) The relationship S1 ≧ S0 is established. (5) Among the openings formed in the pedestal, the ratio of the number of end openings having non-standard hole diameters to the total number of openings is in the range of 20% or less. (6) Among the openings formed in the pedestal, the ratio of the hole diameters of the end openings to the standard hole diameter is in the range of 50% or more and 98% or less. (7) Among the openings formed in the pedestal, the ratio of the number of central openings having non-standard hole diameters to the total number of openings is in the range of 20% or less. (8) Among the openings formed in the pedestal, the ratio of the hole diameters of the central openings to the standard hole diameter is in the range of 70% or more and 100% or less. [2] The method for producing reinforcing fiber-containing resin pellets according to [1], wherein the nozzle outlets of the nozzle die are arranged in a horizontal row, or the nozzle outlets are arranged in two rows, one above the other, in a staggered pattern. [3] The method for producing reinforcing fiber-containing resin pellets according to [1], wherein the pedestal satisfying (9) is used. (9) When the number of openings having a non-standard hole diameter is multiple among the openings formed in the base, the cross-sectional area of ​​the opening located at the outermost (end) position is equal to or less than the cross-sectional area of ​​the opening not located at the outermost (end) position and having a non-standard hole diameter is less than the cross-sectional area of ​​the openings having a standard hole diameter. [4] The method for producing reinforcing fiber-containing resin pellets according to [1], wherein the propylene-based polymer is an isotactic propylene homopolymer. [5] The method for producing reinforcing fiber-containing resin pellets according to [1], wherein the reinforcing fiber is glass fiber or carbon fiber. [6] The method for producing reinforcing fiber-containing resin pellets according to [1], wherein the screw rotation speed of the twin-screw extruder is 250 rpm or more and 800 rpm or less. [7] The method for producing reinforcing fiber-containing resin pellets according to [1], 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. [8] The reverse screw element having the notch is a single-thread screw, L / D (screw length / screw diameter) = 1, and the lead is 0.25D or more and 0.5D or less. [1] The method for producing reinforcing fiber-containing resin pellets.[9] A twin-screw extruder having a first kneading section and a second kneading section equipped with a reverse screw element having a notch and / or a kneading disk including a reverse feed, the second kneading section being located closer to the outlet than the first kneading section, and a die section provided at the outlet of the twin-screw extruder, wherein the die section comprises a nozzle die having a nozzle and a base, the base having an opening with an inlet and an outlet connected to the nozzle, the nozzle and the base satisfying (1) to (8), the nozzle die has a width of 94 mm or more, the number of nozzles arranged in the nozzle die is 5 to 70, and the openings are arranged in a horizontal row in the base. (1) The nozzle flow path length is 60 mm or more and 150 mm or less, and (2) The cross-sectional area (S1) of the smallest cross-sectional area portion of the base opening is 6 mm. ２ Over 80mm ２ (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm ２ More than 20 mm ２(4) The relationship S1 ≧ S0 is established. (5) Among the openings formed in the pedestal, the ratio of the number of end openings having non-standard hole diameters to the total number of openings is within a range of 20% or less. (6) Among the openings formed in the pedestal, the ratio of the hole diameters of the end openings to the standard hole diameter is within a range of 50% or more and 98% or less. (7) Among the openings formed in the pedestal, the ratio of the number of central openings having non-standard hole diameters to the total number of openings is within a range of 20% or less. (8) Among the openings formed in the pedestal, the ratio of the hole diameters of the central openings to the standard hole diameter is within a range of 70% or more and 100% or less.

[10] The apparatus for producing reinforcing fiber-containing resin pellets according to [9], wherein the nozzle outlets of the nozzle die are arranged in a horizontal row, or the nozzle outlets are arranged in two rows, one above the other, in a staggered pattern.

[11] The apparatus for producing reinforcing fiber-containing resin pellets according to [9], having the pedestal that satisfies (9). (9) When there are a plurality of openings formed in the base that do not have a standard hole diameter, the cross-sectional area of ​​the opening located at the outermost (end) ≦ the cross-sectional area of ​​the opening that is not located at the outermost (end) and does not have a standard hole diameter < the cross-sectional area of ​​the opening with the standard hole diameter.

[12] The reverse screw element having the notch is a single-start screw, L / D = 1, and a lead of 0.25D or more and 0.5D or less. The apparatus for producing reinforcing fiber-containing resin pellets according to [9].

[0014] The manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention can produce short fiber-reinforced resin pellets in which the remaining fibers have a long fiber length, and can produce reinforcing fiber-containing resin pellets that have excellent continuous productivity with improved deflection of both end strands and excellent mechanical properties equivalent to those of long fiber-reinforced resin pellets.

[0015] FIG. 1 is a schematic diagram of a twin-screw extruder and a vertical cross section of a die section, as viewed from the horizontal direction, which are one example of a twin-screw extruder and a die section used in the method for producing reinforcing fiber-containing resin pellets of the present invention. FIG. 2 is an enlarged view of the die section shown in FIG. 1. FIG. 3 is an example of a diagram showing the outlets of multiple openings formed on the downstream side of the base of the die section shown in FIG. 2. FIG. 4 is a schematic diagram of a vertical cross section, including the nozzle, as viewed from the horizontal direction, of a die equipped with a nozzle having only a parallel portion and no tapered portion. FIG. 5 is a schematic diagram of a vertical cross section, including the nozzle, as viewed from the horizontal direction, of a die equipped with a nozzle having only a tapered portion and no parallel portion. FIG. 6 is a diagram showing an example of a kneading disk including reverse feed. FIG. 7 is an explanatory diagram showing the structure of the screw used in Example 1. FIG. 8 is a table showing the specifications and evaluation results of Examples 1 to 4 and Comparative Example 1. FIG. 9 is a diagram showing the hole diameters of the openings formed in the base used in Examples 1 to 4 and Comparative Example 1. FIG. 10 is a table showing the specifications and evaluation results of Examples 5 to 7 and Comparative Example 2. Fig. 11 is a diagram showing the hole diameter of the opening formed in the pedestal used in Examples 5 to 7 and Comparative Example 2. Fig. 12 is a schematic cross-sectional view showing a case where a pedestal with a tapered opening is placed in a die section. Fig. 13 is a diagram showing a state where the nozzle outlets of the nozzle die are staggered. Fig. 14 is a diagram showing a state where a strand is loosened when a large-scale reinforcing fiber-containing resin pellet manufacturing device with a long die is used.

[0016] The method and apparatus for producing reinforcing fiber-containing resin pellets of the present invention use a twin-screw extruder and a die. The twin-screw extruder has a first kneading section and a second kneading section provided closer to the outlet than the first kneading section, the second kneading section including a reverse-feed screw element and / or a kneading disk including a reverse feed. The die section is provided at the outlet of the twin-screw extruder and includes a nozzle die, which is a die equipped with a nozzle, and a base. Figure 1 shows a schematic diagram of a vertical cross section, viewed from the horizontal direction, of one specific example of the twin-screw extruder and die used in the method for producing reinforcing fiber-containing resin pellets of the present invention.

[0017] The twin-screw extruder 1 shown in FIG. 1 has a cylinder 3 and a screw 4 housed in the bore of the cylinder 3. The twin-screw extruder 1 has two screws 4 arranged horizontally. The twin-screw extruder 1 has a first kneading section 5 and a second kneading section 6 located closer to the outlet B than the first kneading section 5. The second kneading section 6 is equipped with a reverse-feeding screw element and / or a kneading disk including a reverse feed (not shown). The twin-screw extruder 1 further has a resin supplying section 7 located closer to the inlet A than the first kneading section, and a fiber supplying section 8 located closer to the outlet B than the first kneading section 5 and closer to the inlet A than the second kneading section 6.

[0018] A die section 2 is attached to the outlet B of the twin-screw extruder 1 for extruding a resin containing melt-kneaded reinforcing fibers as a strand of reinforcing fiber-containing resin. FIG. 2 is an enlarged view of the die section 2 shown in FIG. 1. As shown in FIG. 2, the die section 2 includes a die holder 12, a base 13, and a nozzle die 14. A space is formed within the die section 2, which is directly connected to the inner bore of the cylinder 3, penetrates the die section 2, and serves as a resin flow path. This space consists of an intra-holder space 15 within the die holder 12, an opening 16 within the base 13, and a nozzle 9 within the nozzle die 14. The space has a brush-like shape, with a single line on the upstream side and multiple branches on the downstream side.

[0019] The die holder 12 is attached to the twin-screw extruder 1 and has a resin flow path inlet 20 formed upstream thereof, which is directly connected to the inner bore of the cylinder 3 and serves as the entrance to the resin flow path. The die holder 12 is attached to the twin-screw extruder 1. The holder space 15 is formed so that its height decreases in the vertical direction and its width gradually increases in the horizontal direction as it advances downstream. The holder space 15 has one resin flow path inlet 20 on the upstream side and multiple resin flow path outlets on the downstream side, and within the holder space 15, one space branches into multiple holes from upstream to downstream.

[0020] The base 13 is a component attached to the die holder 12, and has an opening 16 formed therein to serve as a resin flow path, with a plurality of opening outlets 16B arranged in a horizontal row. Note that there is no limit to the number of nozzle inlets 10 in the die section 2 used in the method for producing reinforcing fiber-containing resin pellets of the present invention.

[0021] The nozzle die 14 is a component attached to the base 13, and multiple (14 to 40) nozzles 9 are provided inside the nozzle die 14. Each nozzle 9 is a hole with a circular cross section that penetrates the nozzle die 14 in the horizontal direction, for example, and has 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.

[0022] As shown in Fig. 2, the nozzle 9 has a parallel portion 9b extending toward the nozzle inlet 10 and a tapered portion 9a toward the nozzle outlet 11, the diameter of which decreases at a constant rate toward the nozzle outlet 11. In Fig. 2, the nozzle flow path length, which is the horizontal length of the nozzle 9, is indicated as L1, and the parallel flow path length, which is the horizontal length of the parallel portion 9b, is indicated as L2.

[0023] The nozzle die and base used in the method and apparatus for producing reinforcing fiber-containing resin pellets of the present invention satisfy the following requirements (1) to (4).

[0024] (1) The nozzle flow path length is 60 mm or more and 150 mm or less. In the nozzle 9 shown in Figures 1 to 3, the nozzle flow path length is the length indicated by L1 in Figure 2. 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.

[0025] If the nozzle flow path length is shorter than 60 mm, when using reinforcing fibers with a fiber length as in the present invention, the fibers will not be oriented in the flow direction, and the fibers will fly out of the strand at the outlet of the nozzle die 14, making it impossible to stably and continuously extrude and withdraw the strand. Fibers may also fly out of the produced pellets. Therefore, when the pellets are introduced into the hopper of the injection molding machine, bridging may occur, preventing them from steadily falling 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.

[0026] (2) The area (S1) of the smallest cross-sectional area of ​​the base opening is 6 mm ２ Over 80mm ２The area (S1) of the minimum cross-sectional area of ​​the opening 16 of the base 13, which will be described later, is 6 mm ２ Over 80mm ２ less than 10 mm, preferably ２ 60mm or more ２ Less than 12 mm, more preferably ２ More than 50 mm ２ The area (S1) of the minimum cross-sectional area portion of the opening 16 of the base 13 is preferably within the above range in terms of pellet shape. The opening 16 formed in the base 13 may have a straight shape with the same diameter from the inlet to the outlet, as shown in FIG. 2 . In this case, the hole diameter of the opening 16 may be the same as the hole diameter of the opening outlet 16B, and the hole diameter of the opening 16 from the opening inlet 16A to the opening outlet 16B is the diameter of the minimum cross-sectional area portion of the opening 16. Alternatively, the opening 16 formed in the base 13 may have a straight shape with the same diameter on the upstream side of the opening 16 and a tapered shape with the diameter gradually increasing toward the nozzle die 14 on the downstream side, as shown in FIG. 12 . In this case, the diameter of the minimum cross-sectional area portion of the opening 16 (for example, the diameter at the start of the taper) is the hole diameter of the opening 16. In the present invention, the taper is usually merely a chamfering of the corners of the opening 16. Furthermore, the distance from the start of the taper to the opening outlet 16B is usually about the distance required when the above-mentioned chamfering is performed.

[0027] (3) The area of ​​the nozzle outlet (S0) is 3 mm ２ More than 20 mm ２ The area (S0) of the nozzle outlet 11 is the area of ​​the nozzle outlet 11 shown in Figures 5 and 3 in the nozzle 9 shown in Figures 1 to 3. The area (S0) of the nozzle outlet 11 is 3 mm ２ More than 20 mm ２ less than 4 mm, preferably ２ More than 15mm ２ Less than 5 mm, more preferably ２ More than 10 mm ２ The area (S0) of the nozzle outlet 11 within the above range is preferable in terms of pellet shape.

[0028] (4) The relationship S1 ≧ S0 is established. In the nozzle die and pedestal used in the manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention, the area (S0) of the nozzle outlet 11 is smaller than the area (S1) of the minimum cross-sectional area portion of the opening 16 of the pedestal 13, or is the same as the area (S1) of the minimum cross-sectional area portion of the opening 16 of the pedestal 13. Establishing the relationship S1 ≧ S0 is preferable in terms of the discharge amount and pellet shape.

[0029] In the nozzle die 14 used in the manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention, the cross-sectional area of ​​the nozzle is the same from the nozzle inlet 10 to the nozzle outlet 11, or decreases from the nozzle inlet 10 to the nozzle outlet 11. The nozzle 9 shown in Figures 1 to 3 has a parallel portion 9b and a tapered portion 9a, so the relationship S1 > S0 holds. In addition, if the area of ​​the nozzle inlet 10 in the nozzle 9 formed in the nozzle die 14 is defined as S2, S2 is 6 mm ２ Over 80mm ２ The nozzle 9 formed in the nozzle die 14 used in the present invention is not particularly limited, but specifically, a nozzle having the same shape and dimensions as the invention described in JP-A-2022-154027 can be used. For example, Example 1 of the same publication (L1 = 125 mm, L2 = 85 mm, S2 = 20 mm) ２ , S0=7 mm ２ ), Example 2 (L1 = 125 mm, L2 = 125 mm, S2 = 20 mm ２ , S0=20 mm ２ ), Example 4 (L1 = 65 mm, L2 = 65 mm, S2 = 20 mm ２ , S0=20 mm ２ ), Example 5 (L1 = 125 mm, L2 = 0 mm, S2 = 20 mm ２ , S0=7 mm ２ ), etc. is also a preferred embodiment.

[0030] The nozzle 9 used in the manufacturing method and manufacturing apparatus for 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 the parallel portion 9b and the tapered portion 9a. It may have only a parallel portion 9bA without a tapered portion, like the nozzle 9A of the nozzle die 14A shown in Fig. 4, or it may have only a tapered portion 9aB without a parallel portion, like the nozzle 9B of the nozzle die 14B shown in Fig. 5. When the nozzle 9 has only a parallel portion, L1 = L2.

[0031] Furthermore, the nozzle used in the manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention has a nozzle die 14 with a width of 94 mm or more, with no particular upper limit. However, the width of the nozzle die 14 is preferably 94 mm to 665 mm, and more preferably 230 mm to 600 mm. Setting the width within this range provides excellent strand stability. Note that the width of the nozzle die 14 refers to the dimension in the depth direction of the paper, for example, in the nozzle die 14 shown in Figures 1 and 2. The number of nozzles 9 arranged within the nozzle die 14 is 5 to 70, and the nozzle outlets 11 are preferably arranged in a single horizontal row, or, as shown in Figure 13, the nozzle outlets 11 are preferably arranged in two upper and lower rows in a staggered arrangement. A staggered arrangement refers to a state in which the openings in the two upper and lower rows are staggered, as shown in Figure 13. Furthermore, when there are two rows of openings, the openings in the upper row do not contact the openings in the lower row. When viewed vertically, the openings in the upper row and the openings in the lower row usually do not overlap. Also, there is usually one more opening in the lower row than in the upper row. In the case of a staggered arrangement, the distance between the upper and lower rows of openings is 6 mm or more, preferably 6 to 20 mm, and more preferably 7 to 15 mm. The distance here refers to the distance between straight lines passing through the centers of the openings in each row.

[0032] That is, as a premise of the invention, as shown in Patent Document 4, even if a long die having a long die length is used as the nozzle die 14, there is a problem that the strands are unstable when a medium-scale or large-scale device for producing reinforcing fiber-containing resin pellets having a wide die width is used. For this reason, it is necessary to assume that the nozzle die 14 is a medium-scale or large-scale long die.

[0033] The relationship between the width of the nozzle die 14 and the number of openings 16 in the base 13 is such that if the width of the nozzle die 14 is 94 mm to 665 mm, the number of openings 16 is approximately 5 to 70, and if the width of the nozzle die 14 is 230 mm to 600 mm, the number of openings 16 is approximately 14 to 40.

[0034] Furthermore, the nozzle die 14 and the base 13 used in the method and apparatus for producing reinforcing fiber-containing resin pellets of the present invention further satisfy the following requirements (5) to (8), preferably (5) to (9).

[0035] (5) Among the openings formed in the base, the proportion of the number of openings at both ends that do not have a standard hole diameter is within a range of 20% or less of the total number. The standard hole diameter is the average value of the hole diameters of some of the openings formed in a row in the base 13. Specifically, the standard hole diameter refers to the average diameter of the openings formed in the base excluding the following (α) and (β): (α) Of the openings formed on both end sides of the base, the number of openings is 20% or less of the total number of openings. (β) Of the openings formed on the center side of the base, the number of openings is 20% or less of the total number of openings.

[0036] The definition of the average diameter of the openings excluding (α) and (β) is intended to average out the diameters of the openings excluding (α) and (β), since the diameters of the openings excluding (α) and (β) may vary. The cross-sectional area of ​​the openings 16 used to calculate the standard hole diameter is preferably within ±5% of the average cross-sectional area of ​​all the openings formed in the base 13. The cross-section of the openings 16 formed in the base 13 is generally circular. As described above, when the openings 16 formed in the base 13 have a straight shape as shown in FIG. 2, the diameter of the opening outlet 16B may be taken as the diameter of the opening 16. On the other hand, when the upstream side of the opening 16 has a straight shape and a portion of the downstream side has a tapered shape as shown in FIG. 12, the diameter of the opening 16 is taken as the diameter of the smallest cross-sectional area portion of the opening 16 that is closest to the nozzle die 14.

[0037] Furthermore, with regard to the exclusion condition (α) above, it is assumed that the number of openings formed on each end of the base is the same. Specifically, "20% or less of the total number of openings" refers to all of the openings 16 formed on one end of the base 13 that account for 10% or less of the total number of openings, and all of the openings 16 formed on the other end that account for 10% or less of the total number of openings.

[0038] Here, the percentage of the number of end openings with non-standard hole diameters is the percentage obtained by dividing the number of end openings with non-standard hole diameters by the total number of openings formed on the base. For example, if the total number of openings on the base is 40, as in base opening type E shown in Figure 9, and the number of openings on each end of the base is two, the percentage is 10%. By adjusting the diameter of the openings on both ends of the base in this way, the flow rate of the nozzles on both ends can be suppressed due to the influence of shear flow unique to fibrous materials, and slack in the strands on both ends can be reduced.

[0039] Furthermore, it is preferable that, among the openings formed on both end sides of the base, the proportion of the number of openings having a non-standard hole diameter at one end side is the same as the proportion of the number of openings having a non-standard hole diameter at the other end side. Furthermore, with regard to the proportion of the number of openings having a non-standard hole diameter, it is preferable that the proportion of the number of openings having a non-standard hole diameter formed at one end side of the base be 10% or less of the total number of openings, and that the proportion of the number of openings having a non-standard hole diameter formed at the other end side of the base be also 10% or less of the total number of openings.

[0040] (6) In the openings formed in the base, the ratio of the hole diameter of the non-standard end openings to the standard hole diameter is in the range of 50% to 98%. That is, from (5) and (6), it is preferable that there is always one opening with a non-standard hole diameter at each end of the base. The ratio of the hole diameter of the non-standard end openings to the standard hole diameter is the ratio obtained by dividing the hole diameter of the non-standard end opening by the standard hole diameter of the opening.

[0041] (7) Among the openings formed in the base, the ratio of the number of central openings having a non-standard hole diameter is within the range of 20% or less of the total number. This ratio is calculated by dividing the number of central openings having a non-standard hole diameter by the total number of openings formed in the base. In particular, in large-scale nozzle dies 14, the flow rate in the central portion decreases, so by making the opening hole diameter in the central portion a non-standard hole diameter and suppressing the flow rate, it is possible to reduce slack in the central strand.

[0042] (8) In the openings formed in the base, the ratio of the hole diameter of the central opening to the standard hole diameter is in the range of 70% to 100%. In other words, from (7) and (8), there may be a case where there is no opening in the central opening that is not of the standard hole diameter.

[0043] (9) When there are a plurality of openings formed in the base that do not have a standard hole diameter, the cross-sectional area of ​​the opening located at the outermost (edge) is less than or equal to the cross-sectional area of ​​the opening that is not located at the outermost (edge) and has a non-standard hole diameter < the cross-sectional area of ​​the opening with the standard hole diameter.

[0044] That is, in medium-scale and large-scale nozzle dies 14, the flow rate of the outermost nozzle is large due to the influence of shear flow specific to fibrous materials. Therefore, in order to stabilize the strand, it is preferable to reduce the cross-sectional area of ​​the opening 16 of the base 13 located at the outermost (edge) position and the cross-sectional area of ​​the opening 16 of the base 13 within the range specified in the present invention.

[0045] From the viewpoint of flow rate balance, it is preferable that the flow rate distribution between the right and left halves of the die be uniform. Specifically, it is preferable that the cross-sectional areas and flow rates of the openings that are symmetrical about the die center be equal.

[0046] 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 reinforcing fibers from the nozzle outlet of the die as strands of reinforcing fiber-containing resin (step 3).

[0047] Steps 1 to 3 will be described below using the twin-screw extruder 1 and die section 2 shown in Figures 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 the twin-screw extruder 1. The supplied resin moves within the cylinder 3 by the action of the screw 4 and is transported to the first kneading section 5. The structure of the screw 4 up to the first kneading section 5 is, for example, full flight. The resin transported to the first kneading section 5 is melt-kneaded in the first kneading section 5.

[0048] In the present invention, the kneading section refers to 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 to achieve 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.

[0049] The resin used in the method and apparatus 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. Preferred monoolefins that are structural units derived from monomers other than propylene include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene, with ethylene and 1-butene being more preferred. The polymerization mode may be random or block. Among these resins, propylene homopolymers, propylene-ethylene block copolymers, propylene-ethylene random copolymers, and propylene-ethylene-butene random copolymers are preferred, with propylene homopolymers being 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 manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention. These polymers may be used alone or in combination of two or more.

[0050] The propylene polymer has a melt flow rate of 20 to 500 g / 10 min, preferably 30 to 200 g / 10 min, and 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, which is preferable in that the reinforcing fibers are less susceptible to shear in the twin-screw extruder and breakage of the reinforcing fibers is suppressed.

[0051] 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, and are moved within the cylinder 3 by the action of the screw 4 and 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 may be, for example, 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.

[0052] The reinforcing fibers are not particularly limited as long as they are those typically used to reinforce resins, and examples thereof 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. Suitable glass fibers include commonly used E-glass and high-strength, high-elasticity T-glass.

[0053] 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. The fiber length of the reinforcing fibers within the above range is preferable in terms of productivity.

[0054] 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. When the fiber diameter of the reinforcing fibers is within the above range, it is preferable in terms of mechanical properties.

[0055] There is no particular limitation on the number of reinforcing fibers in the bundle, and it is desirable 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 interfacial adhesion with the resin.

[0056] The ratio of the resin to the 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 the 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, of the resin (the total of the reinforcing fibers and the resin is 100% by mass).

[0057] As described above, the second kneading section 6 is equipped with a reverse screw element having a notch and / or a kneading disk including a reverse feed. Reverse screw elements having a notch are preferred because they result in a longer residual fiber length. When the second kneading section 6 is equipped with a reverse screw element, the kneading performance and dispersion performance can be improved, energy consumption is reduced, thermal efficiency is improved, and the melting temperature of the synthetic resin raw material can be kept low, making the glass fiber less likely to break and making it easier to maintain the properties of the raw material.

[0058] The reverse screw element is preferably a screw element having multiple notches formed at the tip of the flight screw. The reverse screw element is preferably configured with a single or double thread 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-start screw with an L / D (screw length / screw diameter) of 1, has notches, and preferably has a lead of 0.25D to 0.5D. A specific example is BMS manufactured by The Japan Steel Works, Ltd. Using a reverse screw element with notches allows the reinforcing fibers to be long in the resin without excessive breakage, and allows the fibers to be uniformly dispersed in the molten resin with good fiber opening.

[0059] The kneading disc including the reverse feed has a structure shown in Fig. 6, for example, and a commercially available kneading disc can be used. In step 3, the resin with long reinforcing fibers obtained in step 2 is supplied from outlet B of the twin-screw extruder 1 to the resin flow path inlet 20. The supplied resin flows into the space within the holder 15, and while the flow path is narrowed within the die holder 12, it is rapidly diffused across the width and supplied to the base 13. At this time, the resin is oriented along the wall surface, so the flow rate at the openings 16 at both ends is greater than the flow rate at the openings 16 closer to the center due to the influence of shear flow specific to fibrous materials.

[0060] The resin in the base 13 is supplied to each nozzle 9 through the outlets of the multiple openings 16, i.e., the nozzle inlets 10. The melt-kneaded resin containing the reinforcing fibers is extruded as strands of reinforcing fiber-containing resin from the nozzle outlets 11 of the die section 2. The structure of the screw 4 from the second kneading section 6 to the die section 2 may be, for example, a full flight.

[0061] The base and nozzle used in step 3 satisfy the following requirements (1) to (8): (1) The nozzle flow path length is 60 mm or more and 150 mm or less. (2) The cross-sectional area (S1) of the smallest cross-sectional area portion of the opening of the base is 6 mm. ２ Over 80mm ２ (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm ２ More than 20 mm ２ (4) The relationship S1≧S0 holds.

[0062] (5) Among the openings formed in the pedestal, the ratio of the number of end openings having a non-standard hole diameter to the total number is within a range of 20% or less. (6) Among the openings formed in the pedestal, the ratio of the hole diameters of the end openings to the standard hole diameter is within a range of 50% or more and 98% or less. (7) Among the openings formed in the pedestal, the ratio of the number of central openings having a non-standard hole diameter to the total number is within a range of 20% or less. (8) Among the openings formed in the pedestal, the ratio of the hole diameters of the central openings to the standard hole diameter is within a range of 70% or more and 100% or less. Furthermore, the pedestal used in step 3 preferably satisfies the following (9). (9) When there are multiple openings having a non-standard hole diameter among the openings formed in the pedestal, the cross-sectional area of ​​the opening located at the outermost (end) is less than the cross-sectional area of ​​the opening with a non-standard hole diameter that is not located at the outermost (end) < the cross-sectional area of ​​the opening with a standard hole diameter.

[0063] By using the nozzle in step 3, even if the reinforcing fibers in the resin are long, the reinforcing fibers do not protrude from the strands, making continuous production possible.Since the reinforcing fibers do not protrude from the resulting pellets either, stable injection molding is possible without bridging in the hopper of the injection molding machine during injection molding.

[0064] 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 zone to the nozzle of the twin-screw extruder in steps 1 to 3 is preferably 230°C or more and 290°C or less, more preferably 240°C or more and 290°C or less, from the viewpoint of increasing the length of the remaining glass fibers and preventing thermal degradation of the resin.

[0065] In the method for producing reinforcing fiber-containing resin pellets of the present invention, reinforcing fiber-containing resin pellets are obtained by pelletizing, by a known method, the strand of reinforcing fiber-containing resin obtained by the above steps 1 to 3. As the pelletizing method, for example, as disclosed in Japanese Patent Publication No. 41-20738, a method in which the strand is cooled and pelletized with a cutter, or a method in which the strand is cut to a predetermined size immediately after being extruded from a die, is preferred.

[0066] The shape and size of the reinforcing fiber-containing resin pellets produced by the reinforcing fiber-containing resin pellet manufacturing method and manufacturing apparatus of the present invention are not particularly limited. For example, the length of the reinforcing fiber-containing resin pellets in the strand extension direction can be 3 mm to 10 mm. If the length is less than 3 mm, the remaining fiber length in the pellets will be short, and the desired strength may not be achieved. If the length is more than 10 mm, the metering during injection molding will become unstable, which may cause problems with the molding cycle.

[0067] The reinforcing fiber-containing resin pellets obtained by the manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention contain 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 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 fiber and the resin is 100% by mass). In the manufacturing method for reinforcing fiber-containing resin pellets of the present invention, the supply amounts of the reinforcing fiber and the resin are determined in the above steps 1 and 2 so that the content ratio of the reinforcing fiber and the resin in the reinforcing fiber-containing resin pellets is within the above range.

[0068] The fiber length of the reinforcing fibers (residual fibers) contained in the reinforcing fiber-containing resin pellets produced by the manufacturing method and manufacturing apparatus for 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. The manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention can produce reinforcing fiber-containing resin pellets containing short fibers in this manner. The reinforcing fiber-containing resin pellets produced by the manufacturing method and manufacturing apparatus for reinforcing fiber-containing resin pellets of the present invention are characterized in that even when they contain short fibers, they have mechanical properties equivalent to those of reinforcing fiber-containing resin pellets containing long fibers. The reason why the manufacturing method and manufacturing apparatus for 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 presumably because the remaining fibers in the pellets are long, resulting in excellent mechanical strength.

[0069] To impart desired properties to the reinforcing fiber-containing resin pellets produced by the method and apparatus for producing reinforcing fiber-containing resin pellets of the present invention, known substances commonly used in thermoplastic resins can be blended, such as known stabilizers such as antioxidants, heat stabilizers, and UV absorbers, antistatic agents, flame retardants, flame retardant assistants, colorants such as dyes and pigments, 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, wollastonite, mica, calcium carbonate, and metal powder.

[0070] The reinforcing fiber-containing resin pellets produced by the method and apparatus 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.

[0071] According to the present invention, it is possible to provide a manufacturing method and manufacturing apparatus for manufacturing reinforcing fiber-containing resin pellets that stabilize strands, have excellent appearance of molded products, and exhibit excellent mechanical properties, even when a wide and long die is used to manufacture pellets containing long reinforcing fibers.

[0072] 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 ISO 1133 at a temperature of 230° C. and a load of 2.16 kg.

[0073] (Residual Fiber Length) 1 g of pellets was incinerated at 600° C. for 75 minutes. The incinerated sample was photographed with a microcamera, and the lengths of 1,000 or more fibers were measured using imaging software. The average length was taken as the residual fiber length.

[0074] (Glass fiber (GF) protrusion at die outlet) Protrusion of glass fibers at the die outlet was visually observed and evaluated according to the following criteria: None: No protrusion of glass fibers observed. Slight: Protrusion of glass fibers observed occasionally. Protrusion of glass fibers observed constantly.

[0075] (Continuous productivity) The state of the strands at the center of the die and at the end of the die was visually compared and judged. Strands where looseness was observed were rated as x, and strands where no looseness was observed were rated as o.

[0076] Example 1 A twin-screw extruder, TEX65 (number of cylinder blocks: 15) manufactured by The Japan Steel Works, Ltd., having the structure shown in Figure 1, was used. The cylinder blocks are 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°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C.

[0077] In the second kneading section, one BMS manufactured by The Japan Steel Works, Ltd. having the structure shown in Fig. 7 was installed as a reverse screw element having a notch. Fig. 8 is a table showing the specifications and evaluation results of Examples 1 to 4 and Comparative Example 1.

[0078] The screw rotation speed was 330 rpm. A nozzle die and a base having the shape shown in Figure 12 were attached to the outlet of the twin-screw extruder. The nozzle 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. The nozzle outlet of the nozzle die was not arranged in a staggered manner but in a straight arrangement with the nozzles lined up in a row. There were 40 nozzles. In addition, part of the opening of the base was a tapered type with a straight shape on the upstream side of the opening and a tapered shape on the downstream side. The taper was formed by chamfering the corners of the opening. In the nozzle die, the area (S2) of the nozzle inlet was 20 mm ２ and the nozzle outlet area (S0) is 7 mm ２ The die temperature was 280°C.

[0079] As shown in Figures 9(a) and 9(b) for type B of nozzle die pedestal, the pedestal of the nozzle die has 40 openings, numbered 1 to 40, arranged in a horizontal row. The cross section of the openings is circular. In this Example 1, each opening has a width of 20 mm, except for six nozzles on both ends and six nozzles in the center, as shown below. ２ It should be noted that Fig. 9 is divided into two parts, Fig. 9(a) and Fig. 9(b), because the width of the base is long (600 mm).

[0080] The openings (No. 1 to 3, 38 to 40, 18 to 23) are tapered types with a tapered shape on the downstream side. The openings on both ends (No. 1 to 3, No. 38 to 40) are 14 mm ２ The central base opening (No. 18 to 23) has a minimum cross-sectional area of ​​18 mm. ２ has a minimum cross-sectional area of

[0081] The other openings (Nos. 4 to 17, Nos. 24 to 37) are straight openings with the same diameter from the inlet to the outlet, and are 20 mm ２ The base portion has a minimum cross-sectional area of ​​0.01 mm. The base portion is structured so that the resin flows from each opening outlet of the base to each corresponding nozzle inlet.

[0082] The hole diameters of the openings Nos. 5 to 16 and Nos. 25 to 36 were used as the openings to be used in calculating the standard hole diameter, excluding the 20% of the openings on both ends (Nos. 1 to 4, 37 to 40) and the 20% of the openings in the center (Nos. 17 to 20, 21 to 24).

[0083] The ratio of the number of end openings with a non-standard hole diameter to the total 40 openings is 15% (6 / 40), the ratio of the hole diameters at both ends to the standard hole diameter is 85%, and the ratio of the number of center openings with a non-standard hole diameter to the total 40 openings is 15% (6 / 40), and the ratio of the center hole diameter to the standard hole diameter is 95%.

[0084] Furthermore, among the nozzle outlets, the flow rate ratio for one hole at each end is 121%, the flow rate ratio for the three end holes is 94%, and the flow rate ratio for one hole in the center is 93%. Here, the flow rate ratio refers to the ratio of the production volume per hour at the target nozzle outlet to the standard production volume (described below). For example, the flow rate ratio for one hole at each end is the value obtained by dividing the production volume per hour for one end hole by the standard production volume. The flow rate ratio for one hole in the center is calculated in the same way. Furthermore, the flow rate ratio for three end holes is the value obtained by dividing the average production volume per hour for the three end holes by the standard production volume.

[0085] In addition, the production volume per hour can be calculated by actually measuring the flow rate from the nozzle outlet in question, and the standard production volume indicates the average flow rate per hole, and can be calculated by dividing the total flow rate per hour calculated from the amount of raw material supplied per hour by the total number of nozzle outlets.

[0086] Prime Polypro (MFR: 210 g / 10 min) manufactured by Prime Polymer Co., Ltd., Prime Polypro (MFR: 30 g / 10 min) manufactured by Prime Polymer Co., Ltd., and Polybond 3200 manufactured by Addivant Co., Ltd. were pre-mixed in a mass ratio of 60 / 10 / 1 and fed at a rate of 395 kg / h from the resin supply section of the twin-screw extruder using a gravimetric feeder. 4,000 monofilaments of glass fiber (manufactured by Nippon Electric Glass Co., Ltd., 3T-480H, fiber diameter: 10 μm) were bundled and cut to a length of 3 mm and fed at a rate of 165 kg / h from the fiber supply section. 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.

[0087] The resulting strand was pelletized using a cutter to obtain 3 mm long pellets of reinforcing fiber-containing resin. The hourly production rate of the pellets was 560 kg / h, and the glass fiber content of the pellets was 30 mass%. According to Example 1, the strands at both ends did not loosen, allowing for continuous withdrawal and stable pelletization.

[0088] [Example 2] In Example 1, the hole diameters of Nos. 18 to 23 in the central opening and Nos. 2, 3, 38, and 39 in the edge openings were changed to the standard hole diameter, and the minimum cross-sectional area of ​​Nos. 1 and 40 in the edge base openings was changed to 17 mm 2 Pellets were obtained in the same manner as in Example 1, except that the pedestal opening Nos. 1 and 40 were tapered openings. The other openings were straight openings.

[0089] The ratio of the number of end openings with a non-standard hole diameter to the total number of 40 openings is 5% (2 / 40), the ratio of the hole diameters of the openings at both ends to the standard hole diameter is 92%, and the ratio of the number of center openings with a non-standard hole diameter to the total number of 40 nozzles is 0% (0 / 40), and the ratio of the hole diameters of the center openings to the standard hole diameter is 100%.

[0090] Here, the flow rate ratio of the single hole at each end at the nozzle outlet was 132%, and the flow rate ratio of the three holes in the center was 109%. The flow rate ratio of the single hole at each end was 93%. According to Example 2, the strands at both ends did not loosen, allowing for continuous withdrawal and stable pelletization.

[0091] Example 3 Pellets were obtained in the same manner as in Example 2, except that the hole diameters of openings No. 1 and 40 at the end and the hole diameters of openings No. 2 and 39 were changed.

[0092] The openings on both ends (No. 1, No. 40) have non-standard hole diameters and 16 mm ２ The openings (No. 2, No. 39) have a non-standard hole diameter and a minimum cross-sectional area of ​​18 mm. ２ The other openings (No. 3 to 38) have a minimum cross-sectional area of ​​20 mm. ２ (Pedestal opening type D in FIG. 9).

[0093] The ratio of the number of end openings with non-standard hole diameters to the total number of 40 openings is 10% (4 / 40), and the ratio of the standard hole diameters at both ends is 90%. Note that pedestal openings Nos. 1, 2, 39, and 40 are tapered openings, and the other openings are straight openings.

[0094] Here, the flow rate ratio of the single hole at each end at the nozzle outlet was 107%, and the flow rate ratio of the three holes in the center was 101%. The flow rate ratio of the single hole at each end was 93%. According to Example 3, the strands at both ends did not loosen, allowing for continuous withdrawal and stable pelletization.

[0095] Example 4 Pellets were obtained in the same manner as in Example 2, except that the hole diameters of openings No. 1 and 40 at the end and the hole diameters of openings No. 2 and 39 were changed.

[0096] The openings on both ends (No. 1, No. 40) have non-standard hole diameters and 14 mm ２ The openings (No. 2, No. 39) have a non-standard hole diameter and a minimum cross-sectional area of ​​16 mm. ２The openings (No. 1, 2, 39, 40) are tapered type openings. The other openings (No. 3 to 38) are straight type openings, and have a standard hole diameter and a minimum cross-sectional area of ​​20 mm. ２ (Pedestal opening type E in FIG. 9).

[0097] The ratio of the number of openings at the end that do not have a standard hole diameter to the total number of 40 openings is 10% (4 / 40), and the ratio of the openings at both ends to the standard hole diameter is 85%.

[0098] Here, the flow rate ratio for the single hole at both ends was 118%, and the flow rate ratio for the three holes in the center was 104%. The flow rate ratio for the single hole at both ends was 93%. According to Example 4, the strands at both ends did not loosen, allowing for continuous withdrawal and stable pelletization.

[0099] Comparative Example 1 Pellets were obtained in the same manner as in Example 2, except that the hole diameters of all openings were changed to the standard hole diameter (base opening type A in Figure 9). Note that all of the base openings in this example were straight openings. Here, the flow rate ratio for the single hole at both ends was 143%, and the flow rate ratio for the three holes in the center was 112%. Furthermore, the flow rate ratio for the single hole at both ends was 93%. In Comparative Example 1, as shown in Figure 14, the strands at both ends were bent, resulting in the problem of not being able to ensure continuous productivity.

[0100] 10 is a table showing the specifications and evaluation results of Examples 5 to 7 and Comparative Example 2. The openings of the bases in these Examples and Comparative Example are all straight.

[0101] The twin-screw extruder used was a TEX44 (15 cylinder blocks) manufactured by The Japan Steel Works, Ltd., with the structure shown in Figure 1. The cylinder blocks are 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°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C / 260°C.

[0102] In the second kneading section, one BMS manufactured by Japan Steel Works, Ltd. having the structure shown in Fig. 7 was installed as a reverse feed screw element having a notch. The screw rotation speed was set to 350 rpm.

[0103] A die section having a shape as shown in Figure 2 was attached to the outlet of the twin-screw extruder. The nozzle die had a nozzle with a circular cross section, which had a parallel section and a tapered section, and the nozzle flow path length (L1) was 125 mm and the parallel flow path length (L2) was 85 mm. The area (S1) of the opening of the base was 7 to 20 mm. ２ In the nozzle die, the area of ​​the nozzle outlet (S0) is 7 mm ２ The die temperature was 280° C. The number of nozzles was 14.

[0104] As shown in Figure 11 for base opening type B, the base has 14 openings, numbered 1 to 14, arranged in a horizontal row. The openings are circular, and the base has a horizontal width of 230 mm.

[0105] The openings at both ends of the base (No. 1, No. 14) are 7 mm ２ The two central openings (No. 7 and No. 8) have a cross-sectional area of ​​12.6 mm ２ The other openings have a minimum cross-sectional area of ​​20 mm ２ has a minimum cross-sectional area of

[0106] The openings in the base that were used to calculate the standard hole diameter were those labeled Nos. 2 to 6 and 9 to 13, excluding the openings at either end (Nos. 1 and 14) and the openings in the center (Nos. 7 and 8) that were less than 20% of the total area. Nos. 1, 7, 8, and 14 have non-standard hole diameters. The base is designed so that resin flows from each opening outlet to the corresponding nozzle inlet.

[0107] The ratio of the number of end openings with a non-standard hole diameter to the total 14 openings is 14% (2 / 14), and the ratio of the hole diameters at both ends to the standard hole diameter is 60%. The ratio of the number of center openings with a non-standard hole diameter to the total 14 openings is 14% (2 / 14), and the ratio of the center openings to the standard hole diameter is 80%. All openings are straight.

[0108] Here, the flow rate ratio of one hole at both ends of the nozzle outlet is 74%, and the flow rate ratio of one hole at both ends is 93%. Prime Polypro (manufactured by Prime Polymer Co., Ltd.) with an MFR of 210 g / 10 min, Prime Polypro (manufactured by Prime Polymer Co., Ltd.) with an MFR of 30 g / 10 min, and Polybond 3200 (manufactured by Addivant) were pre-mixed in a mass ratio of 60 / 10 / 1 and fed at a rate of 140 kg / h from the resin supply section of the twin-screw extruder using a gravimetric feeder. 4,000 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 at a rate of 60 kg / h from the fiber supply section. 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. According to Example 5, the strands at both ends did not loosen, and the strands could be taken up continuously, allowing stable pelletization.

[0109] [Example 6] Pellets were obtained in the same manner as in Example 5, except that the hole diameters of the openings No. 1 and No. 14 at the ends of the base and the hole diameters of the openings No. 7 and No. 8 at the center were changed. ２ The central openings (Nos. 7 and 8) have a minimum cross-sectional area of ​​16 mm ２(Pedestal opening type C in FIG. 11).

[0110] The ratio of the number of end openings with non-standard hole diameters to the total 14 openings was 14% (2 / 14), and the ratio of the hole diameters of the end openings to the standard hole diameter was 80%. Furthermore, the ratio of the number of central openings with non-standard hole diameters to the total 14 openings was 14% (2 / 14), and the ratio of the hole diameters of the central openings to the standard hole diameter was 90%. All openings were straight. Here, the flow rate ratio at both ends in the nozzle was 87%, and the flow rate ratio at the central portion was 101%. According to Example 6, the strands at both ends did not loosen, allowing the strands to be continuously withdrawn, and stable pelletization was achieved.

[0111] [Example 7] Pellets were obtained in the same manner as in Example 5, except that the hole diameters of the openings No. 1 and 14 at the ends of the base and the hole diameters of the openings No. 7 and 8 at the center were changed. Here, the openings at both ends (No. 1 and 14) were 16 mm ２ The central openings (No. 7 and No. 8) have a cross-sectional area of ​​18 mm ２ (Pedestal opening type D in FIG. 11).

[0112] The ratio of the number of end openings with non-standard hole diameters to the total 14 openings was 14% (2 / 14), and the ratio of the hole diameters of the end openings to the standard hole diameter was 90%. Furthermore, the ratio of the number of center openings with non-standard hole diameters to the total 14 openings was 14% (2 / 14), and the ratio of the hole diameters of the center openings to the standard hole diameter was 95%. All openings were straight. Here, the flow rate ratio of the nozzle outlet at both ends was 99%, and the flow rate ratio at the center was 106%. According to Example 7, the strands at both ends did not loosen, allowing the strands to be continuously withdrawn, and stable pelletization was achieved.

[0113] Comparative Example 2 In Example 5, the hole diameters of all openings were changed to be the same as the openings used to calculate the standard hole diameter (pedestal opening type A in FIG. 11), and the screw rotation speed was set to 280 rpm.

[0114] In Comparative Example 2, as shown in FIG. 14, the strands at both ends are bent, and the problem of being unable to ensure continuous productivity arises.

[0115] REFERENCE SIGNS LIST 1 Twin-screw extruder 2 Die section 3 Cylinder 4 Screw 5 First kneading section 6 Second kneading section 7 Resin supply section 8 Fiber supply section 9, 9A, 9B Nozzle 9a, 9aB Tapered section 9b, 9bA Parallel section 10 Nozzle inlet 11 Nozzle outlet 12 Die holder 13 Base 14, 14A, 14B Nozzle die 15 Space inside holder 16 Opening 16A Opening inlet 16B Opening outlet 20 Resin flow path inlet

Claims

1. A method for producing reinforcing fiber-containing resin pellets using a twin-screw extruder having a first kneading section and a second kneading section equipped with a reverse-feed screw element having a notch and / or a kneading disk including a reverse feed, which is provided closer to the outlet than the first kneading section, and a die section provided at the outlet of the twin-screw extruder, wherein the die section comprises a nozzle die having a nozzle and a seat, and the seat has an opening with an inlet and an outlet connected to the nozzle, the method comprising the steps of: supplying a resin into the twin-screw extruder from the inlet side of the first kneading section and melt-kneading the resin in the first kneading section; 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; and extruding the melt-kneaded resin containing reinforcing fibers from the nozzle outlet of the nozzle die as strands of reinforcing fiber-containing resin, wherein the nozzle and the seat satisfy (1) to (8), A method for producing reinforcing fiber-containing resin pellets, wherein the nozzle die has a width of 94 mm or more, the number of nozzles arranged in the die is 5 to 70, and the openings are arranged in a horizontal row in the pedestal, 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 fibers is 2.5 mm or more and 8 mm or less, and the fiber diameter of the reinforcing fibers is 5 μm or more and less than 17 μm, and the reinforcing fiber-containing resin pellets contain 5% by mass or more and 50% by mass or less of the reinforcing fibers and 50% by mass or more and 95% by mass or less of the resin (the total of the reinforcing fibers 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 cross-sectional area (S1) of the smallest cross-sectional area portion of the opening of the pedestal is 6 mm. ２ Over 80mm ２ (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm ２ More than 20 mm ２ (4) The relationship S1≧S0 is established. (5) Among the openings formed in the base, the ratio of the number of end openings that do not have a standard hole diameter is within a range of 20% or less of the total number. (6) Among the openings formed in the base, the ratio of the hole diameters of the end openings to the standard hole diameter is within a range of 50% or more and 98% or less. (7) Among the openings formed in the base, the ratio of the number of central openings that do not have a standard hole diameter is within a range of 20% or less of the total number. (8) Among the openings formed in the base, the ratio of the hole diameters of the central openings to the standard hole diameter is within a range of 70% or more and 100% or less.

2. The method for producing reinforcing fiber-containing resin pellets according to claim 1, wherein the nozzle outlets of the nozzle die are arranged in a single horizontal row, or in two vertical rows and staggered.

3. The method for producing reinforcing fiber-containing resin pellets according to claim 1, using the pedestal that satisfies (9). (9) When there are a plurality of openings with a non-standard hole diameter among the openings formed in the pedestal, the cross-sectional area of ​​the opening located at the outermost (edge) ≦ the cross-sectional area of ​​the opening with a non-standard hole diameter that is not located at the outermost (edge) < the cross-sectional area of ​​the opening with a standard hole diameter.

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

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

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

7. The method for producing reinforcing fiber-containing resin pellets according to claim 1, 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.

8. A method for producing reinforcing fiber-containing resin pellets as described in claim 1, wherein the reverse screw element having the notch is a single-start screw, L / D (screw length / screw diameter) = 1, and the lead is 0.25D or more and 0.5D or less.

9. A twin-screw extruder having a first kneading section and a second kneading section equipped with a reverse feed screw element having a notch and / or a kneading disk including a reverse feed, which is provided closer to the outlet than the first kneading section, and a die section provided at the outlet of the twin-screw extruder, wherein the die section comprises a nozzle die having a nozzle and a base, the base has an opening with an inlet and an outlet connected to the nozzle, and the nozzle and the base satisfy (1) to (8), the nozzle die has a width of 94 mm or more, the number of nozzles arranged in the nozzle die is 5 to 70, and the openings are arranged in a horizontal row in the base. (1) The nozzle flow path length is 60 mm or more and 150 mm or less. (2) The cross-sectional area (S1) of the smallest cross-sectional area portion of the opening of the base is 6 mm ２ Over 80mm ２ (3) The cross-sectional area (S0) of the nozzle outlet is 3 mm ２ More than 20 mm ２ (4) The relationship S1≧S0 is established. (5) Among the openings formed in the base, the ratio of the number of end openings that do not have a standard hole diameter is within a range of 20% or less of the total number. (6) Among the openings formed in the base, the ratio of the hole diameters of the end openings to the standard hole diameter is within a range of 50% or more and 98% or less. (7) Among the openings formed in the base, the ratio of the number of central openings that do not have a standard hole diameter is within a range of 20% or less of the total number. (8) Among the openings formed in the base, the ratio of the hole diameters of the central openings to the standard hole diameter is within a range of 70% or more and 100% or less.

10. The apparatus for producing reinforcing fiber-containing resin pellets according to claim 9, wherein the nozzle outlets of the nozzle die are arranged in a single horizontal row, or in two vertical rows and staggered.

11. The apparatus for producing resin pellets containing reinforcing fiber according to claim 9, having the base that satisfies (9). (9) When there are a plurality of openings with a non-standard hole diameter among the openings formed in the base, the cross-sectional area of ​​the opening located at the outermost (end) ≦ the cross-sectional area of ​​the opening with a non-standard hole diameter that is not located at the outermost (end) < the cross-sectional area of ​​the opening with a standard hole diameter.

12. The apparatus for producing reinforcing fiber-containing resin pellets according to claim 9, wherein the reverse screw element having the notch is a single-start screw, L / D=1, and the lead is 0.25D or more and 0.5D or less.

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