Method for producing resin pellets

Abstract

The purpose of the present invention is to uniformly produce resin pellets having a low flatness ratio without variations. A method for manufacturing resin pellets, in which: when a thermoplastic resin composition is extruded from a mold at the front end of an extruder in the shape of a wire, a transverse flat mold is used as the mold; setting the temperature of the wire material from the die hole at the edge of the flat die to be 4-14 DEG C lower than the temperature of the wire material from the die hole at the center of the flat die; the distance (A-C) from the guide roller to the position C where the wire material is in contact with the initial guide roller is 7-30 cm; and the distance (B-C) from the position B where the line material enters the water surface to the position C is 10-60% of the distance A-C.

Description

Technical Field

[0001] The present invention relates to a method for producing resin pellets and a method for producing pellets having a highly round cross section, that is, a small flattening ratio, from a thermoplastic resin or a composition comprising a thermoplastic resin and a reinforcing material. Background Art

[0002] To produce resin pellets, raw materials such as resin and additives are placed in a trough or hopper, then fed into an extruder using a feeder. The raw materials in the extruder are then mixed, heated, and melted, and extruded as strands through a die nozzle at the front end of the extruder. The resulting resin strands are then directed into a cooling water tank, cooled and solidified, and then cut into specified lengths using a pelletizer to form pellets.

[0003] The pellets obtained by the granulator are then subjected to multiple post-processing, such as a pellet cooler, a screening machine, a magnetic roller separator, and a device for adding a lubricant to the pellets. The pellets need to pass through these post-processings smoothly without being retained. If the pellets have an elliptical cylindrical shape with a large flatness, their rotation in the direction of the elliptical cross section is prevented, so that they can move less smoothly than cylindrical pellets with a high roundness, so they are retained in the post-processing, causing productivity to decrease. In order for the pellets to move smoothly without being retained in the post-processing, they need to have a small flatness, which is preferably less than 0.2, more preferably less than 0.15, and even more preferably less than 0.1.

[0004] The flattening factor is a value that indicates the degree of flattening (the degree of collapse) of an elliptical cylindrical pellet's elliptical cross-section compared to a perfectly circular cross-section. The flattening factor is defined as follows: Flattening factor (f) = (ab) / a, or 1-b / a, where "a" is the major radius of the ellipse and "b" is the minor radius of the ellipse. The flattening factor of a cylindrical pellet with a perfectly circular cross-section is 0, and approaches 1 as the cross-section collapses.

[0005] For any pellet, regardless of the type of thermoplastic resin and reinforcement material, a small flatness is preferred because this makes the pellet less likely to remain in post-processing. Furthermore, in recent years, there has been a strong demand for pellets with uniform shapes because, for example, if the shape of pellets used as injection molding materials varies, they cannot be stably measured, which can impair the stable operation of the injection molding machine. Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The subject (object) of the present invention is to produce pellets having a small flatness uniformly and without variation.

[0008] Solutions for solving problems

[0009] As a result of intensive research conducted to achieve the above-mentioned problems, the present inventors have discovered that resin pellets with a low flatness can be produced uniformly and without variation by: using a horizontal flat die; setting the temperature of the strands passing through the die holes at the ends of the flat die to be 4°C to 14°C lower than the temperature of the strands passing through the die holes in the center of the flat die; setting the distance between the die holes and the position where the strands contact a first guide roller disposed below the water surface in a cooling water tank to be 7 to 30 cm; and setting the distance between the point where the strands enter the water and the position where the strands contact the first guide roller to be within a specific range, thereby preventing the strands from being flattened due to vibration and tension differences.

[0010] The present invention relates to a method for producing resin pellets as described below.

[0011] 1. A method for producing resin pellets, comprising: extruding a thermoplastic resin or a composition comprising a thermoplastic resin and a reinforcing filler from a die at the front end of an extruder in the form of a strand; guiding the strand into a water tank provided with guide rollers to cool the strand; and cutting the cooled strand into resin pellets, wherein

[0012] The die is a horizontal flat die, and the temperature of the strands passing through the die holes at the ends of the flat die is 4°C to 14°C lower than the temperature of the strands passing through the die holes in the center of the flat die, and

[0013] The distance between the center position A of the die hole in the center of the flat die and the position C where the strand contacts the first guide roller (distance between AC) is 7 to 30 cm, and the distance between the position B where the strand reaches the water surface and the position C (distance between BC) is in the range of 10% to 60% of the distance between AC.

[0014] 2. The manufacturing method according to item 1 above, wherein the water tank is provided with a second guide roller downstream of the first guide roller, so that the second guide roller is located deeper in the water tank than the first guide roller.

[0015] 3. The manufacturing method according to 1 or 2 above, wherein the distance between the position C and the position D where the strand contacts the second guide roller is 4 to 30 cm.

[0016] 4. The production method according to any one of 1 to 3 above, wherein the strand forms an angle of 130° or more and less than 180° before and after the first guide roller.

[0017] 5. The production method according to any one of 1 to 4 above, wherein the thermoplastic resin is a crystalline thermoplastic resin.

[0018] 6. Resin pellets produced by the production method according to any one of 1 to 5 above.

[0019] Effects of the Invention

[0020] According to the production method of the present invention, resin pellets with a small flatness can be produced uniformly and without variation. The obtained pellets can be accurately measured for injection molding, etc., and thus can be molded stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] [ Figure 1 ] is a conceptual diagram showing an example of the water cooling process in the present invention.

[0022] [ Figure 2 ] is a conceptual diagram showing another example of the water cooling process in the present invention.

[0023] [ Figure 3 ] is a diagram showing an example of the die portion of the extruder used in the present invention.

[0024] [ Figure 4 ] is a cross-sectional view showing an example of a transverse flat die used in the present invention.

[0025] [ Figure 5 ] is a cross-sectional view showing another example of the transverse flat die used in the present invention.

[0026] [ Figure 6 ] is a cross-sectional view showing another example of the transverse flat die used in the present invention.

[0027] [ Figure 7 ] is a conceptual diagram of the screw structure of the extruder used in the examples or comparative examples. DETAILED DESCRIPTION

[0028] Hereinafter, the present invention will be described in detail by way of embodiments and examples, but the present invention is not limited to the following embodiments and examples, and can be arbitrarily modified within the scope of the gist of the present invention.

[0029] The manufacturing method of the present invention comprises: extruding a thermoplastic resin or a composition comprising a thermoplastic resin and a reinforcing filler from a die at the front end of an extruder in the form of a strand; guiding the strand into a water tank provided with guide rollers to cool it; and cutting the cooled strand into resin pellets.

[0030] The extruder used in the present invention may be a single-screw extruder, but is preferably a twin-screw extruder, more preferably a ventilated twin-screw extruder, and even more preferably an intermeshing co-rotating ventilated twin-screw extruder, wherein two screws rotating in the same direction are arranged in a barrel and a kneading section composed of a plurality of kneading disks is arranged in the middle of the screw in an intermeshing manner.

[0031] In the present invention, the die at the front end of the extruder is a horizontal flat die, and the temperature of the strands passing through the die holes at the end of the flat die is 4 to 14° C. lower than that of the strands passing through the die holes in the center of the flat die.

[0032] Figure 3 This is a diagram showing an example of a die portion of an extruder used in the present invention, as viewed along a cross section parallel to the bottom surface of the die portion.

[0033] The molten resin composition is fed from the twin-screw extruder screw 21 into the die section. The die section consists of a perforated plate (breaker plate) 22 (or annular plate), a die base 23, a flange 24, a manifold 25, and a transverse flat die 1. Depending on the situation, the die base may be referred to as a die plate, and the flange may be referred to as a hinge plate. The combination of the flange 24 (or hinge plate) and the die base 23 (or die plate) is generally referred to as a die head.

[0034] The flange and manifold are provided with thermocouples 26 and 27 respectively, so that the temperature of the flange and the die base can be measured. In addition, the barrel, flange and die base have built-in heaters for temperature control.

[0035] The perforated plate 22 may be equipped with a screen.

[0036] The porous plate 22 includes a desired number of holes, each having a desired diameter and a desired land length. When no screen is present, a porous plate 22 in the form of a ring or annular plate is typically used. In the Examples and Comparative Examples of the present application, an annular plate is used. The porous plate or annular plate is used to prevent resin leakage.

[0037] The transverse flat die 1 has die holes 31 , 32 , 33 arranged transversely.

[0038] Figures 4 to 6 1 is a cross-sectional view showing an example of a transverse flat die 1. The transverse flat die is a die having die holes 31, 32, 33 arranged transversely, such as Figure 4 (a) is shown in a row, as shown in Figure 4 (b) as shown in zigzag, or as Figure 5 Alternatively, as long as the die holes 31, 32, 33 extending from the manifold portion 25 are arranged horizontally, the horizontal flat die can also be arranged as shown in (a) of FIG. Figure 6 (a) and Figure 6 All of these examples are preferred embodiments of the present invention.

[0039] like Figure 5As shown in (a), when the die holes are arranged horizontally in two rows, namely, upper and lower rows, the die holes 32 and 33 at the ends are generally located below the upper die hole and above the lower die hole. This arrangement allows a separator plate 34 to be provided between the upper and lower die holes of the horizontal flat die, thus dividing the resin flow path into upper and lower sections.

[0040] The temperature of the strand passing through the central orifice of a horizontal flat die (also referred to as the strand temperature at the die center) refers to the temperature of the strand immediately after being extruded through die orifice 31, which is closest to the geometric center when viewed from the front of the die. When an odd number of orifices are arranged horizontally at equal intervals, the strand temperature at the die center is the temperature of the strand immediately after being extruded through the central orifice. When an even number of orifices are arranged, the strand temperature at the die center is defined as the average temperature of the two strands immediately after being extruded through the two central orifices.

[0041] The strand temperature at the center of the mold can be measured directly using a thermocouple in contact with the strand. Alternatively, the strand temperature can be measured using an infrared thermometer. It is estimated that the strand temperature at the center of the mold is close to the resin temperature inside the mold.

[0042] The temperature of the strand passing through the die holes at the ends of the transverse flat die (this may also be referred to as the strand temperature at the die ends) refers to the temperature of the strand passing through each of the die holes 32 and 33 at both ends (left and right) of the die when viewed from the front of the die. In the case where the strand has different temperatures between the left and right ends, the strand temperature at the die ends is defined as their average temperature.

[0043] In such Figure 5 In the case of randomly arranging the die holes horizontally as shown in (b), the die holes 32 and 33 at the left and right ends of the flat die are end die holes, respectively, and the die hole 31 closest to the geometric center when viewed from the front of the die is the die hole at the center of the die. The horizontal flat die 1 has die holes arranged horizontally and is typically located at the front end of the manifold section 25, where the resin flow path extends horizontally within the die base. The die holes do not necessarily have the same diameter d and the same molding section length L, but may differ in diameter d and molding section length L.

[0044] In addition to horizontal flat dies, there are also so-called circular dies, which are circular dies with die holes arranged in a circular ring shape on their inner circumference. However, to achieve high discharge, such circular dies require a larger number of die holes, resulting in a larger diameter. Consequently, the strands extruded through the die holes in the upper circumference must travel a longer distance before reaching the sink, resulting in flattened and unstable strands that are prone to breakage. Therefore, circular dies are not suitable for quality assurance and stable production, and the use of horizontal flat dies is essential. Therefore, the present invention does not include the use of circular dies in which the die holes are arranged circumferentially rather than transversely.

[0045] The diameter d of the die hole depends on the size of the pellets to be obtained, and is generally about 2 to 5 mm, preferably 3 to 4 mm. As mentioned above, the die holes do not have to have the same diameter d and the same forming section length L, but can differ from each other in diameter d and forming section length L.

[0046] The strands extruded from the transverse flat die were introduced into a water tank provided with guide rollers to be cooled.

[0047] Figure 1 This is a conceptual diagram illustrating an example of the water cooling process in the present invention. Strand 2 extruded from the extruder's horizontal flat die 1 is cooled while moving underwater in a water tank 3. A first guide roller 4 allows strand 2 to remain submerged below the water surface 5 in the water tank 3. The guide rollers may further include a second guide roller 6 and an nth guide roller 7 positioned downstream. Finally, strand 2 emerges from the water tank 3 at position E.

[0048] The strand 2, originating from position A, the center of the die hole in the center of the flat die 1, is introduced into the water in the water tank 3 and contacts the first guide roller 4 at position C. Before reaching position C, the strand 2, in a nearly molten state, moves through the air while vibrating. This vibration is unavoidable and primarily consists of an up-and-down oscillation (a fundamental vibration with a single antinode), with nodes at either end corresponding to position A, the center of the die hole in the center of the flat die 1, and position C, where the strand contacts the first guide roller. This vibration places the strand under tension, further stretching and flattening it. Because the tension generated by this vibration is periodic, the flattening of the strand varies along the strand direction, resulting in pellets with a highly variable flattening, i.e., a flattening with a higher standard deviation. This vibration increases with the distance between A and C, resulting in an increase in tension and flattening. To avoid this, the distance between A and C (distance between A and C) should be 30 cm or less, preferably 28 cm or less, more preferably 25 cm or less, and even more preferably 20 cm or less. At the same time, if the distance between the AC rollers is too short, the strands are forced to contact the first guide roller in a high-temperature molten state, potentially resulting in a large flatness. Therefore, the distance between the AC rollers needs to be 7 cm or greater, preferably 10 cm or greater, more preferably 12 cm or greater, and even more preferably 15 cm or greater.

[0049] The distance (BC distance) between point B, where the strand 2 reaches the water surface 5 in the water tank 3, and point C, where the strand 2 contacts the first guide roller 4, needs to be between 10% and 60% of the AC distance. If the BC distance is less than 10% of the AC distance, the strand will not cool sufficiently and will bend in a semi-molten state due to the first guide roller, easily flattening it. The BC distance is preferably at least 12% of the AC distance, more preferably at least 15%, and even more preferably at least 20%. If the BC distance is longer than 60% of the AC distance, the strand will be under tension due to resistance in the water, easily flattening it. The BC distance is preferably at most 55% of the AC distance.

[0050] The following is a supplementary explanation of contact positions C and D. Since each guide roller is generally cylindrical with a diameter, the strand forms an arc when in contact with the guide roller. Therefore, contact positions C and D are each defined as the center of the arc of the strand (i.e., the position where the arc is split in half).

[0051] Except for positions A, B, and C, it is essential that the temperature of the strands passing through the die holes at the ends of the flat die is 4°C to 14°C lower than that of the strands passing through the die holes in the center of the flat die. The lower limit of the temperature difference is preferably 4.5°C or higher, more preferably 5°C or higher. The upper limit of the temperature difference is preferably 13°C or lower, more preferably 12°C or lower. If the temperature difference is greater than 14°C, the strands are subjected to different tensions at the center and ends, resulting in large variations in the flatness of the pellets and a high standard deviation. In addition, these pellets have a larger average flatness. If the temperature difference is less than 4°C, the resulting pellets tend to have a larger flatness, although the reason for this is not yet determined. It is hypothesized that when the strand temperature varies less in the transverse direction of the flat die, the strands are under the same tension and vibrate up and down at a uniform frequency in the transverse direction. This vibration propagates to the first guide roller, which in turn vibrates synchronously with the vibrating strands, causing further vibration of the entire strand.

[0052] As described above, it is essential to appropriately set the distances between AC and BC, use a horizontal flat die, and maintain the strand temperature difference between the center and ends of the die at the predetermined value by adjusting the die base and flange temperatures. As demonstrated in the examples below, this allows pellets with a low standard deviation and a small average flatness. For polyester resin compositions such as polycarbonate resin compositions, polyamide resin compositions, or polybutylene terephthalate, the die base and flange temperatures are approximately 250°C to 300°C, and for polyacetal resin compositions, approximately 180°C to 220°C.

[0053] The average flatness of the pellets needs to be 0.2 or less, preferably 0.15 or less, more preferably less than 0.10, still more preferably 0.08 or less, 0.07 or less, 0.06 or less, and particularly preferably 0.05 or less.

[0054] The standard deviation of the flatness is preferably no greater than half the average flatness. If the standard deviation is higher than half the average flatness, such pellets may have a change in mobility and be retained in downstream processes.

[0055] In order to obtain pellets with smaller flatness and smaller flatness variation, as Figure 2 As shown, the second guide roller 6 should be located downstream of the first guide roller 4. Thus, the strands are guided into the water in the water tank by both guide rollers. The second guide roller 6 is preferably located deeper in the water tank than the first guide roller 4. This configuration allows the first guide roller 4 to exert less tension on the strands 2, suppressing vertical vibrations of the strands 2 and producing pellets with a smaller flatness and less flatness variation.

[0056] The strand 2 contacts the second guide roller 6 at position D. The distance between position C, where the strand contacts the first guide roller, and position D (the CD distance) is preferably 4 to 30 cm. If the CD distance is longer than 30 cm, the strand 2 is subjected to a high tension due to the resistance of the water in the water tank 3 and the second guide roller 6. This is disadvantageous because the flatness of the strand, which depends primarily on the position of the first guide roller, increases due to the tension applied by the second guide roller 6 if the strand is not sufficiently solidified by the first guide roller. The CD distance is more preferably 20 cm or less.

[0057] Furthermore, to obtain pellets with a further reduced flatness, it is necessary for the strand 2 to form a large angle θ before and after the first guide roller 4. If the angle θ is small, the strand 2 is under strong tension and is subjected to a strong force applied by the roller in a direction that causes the strand 2 to collapse. The angle θ is preferably 130° or greater, more preferably 140° or greater, even more preferably 145° or greater, 150° or greater, or 155° or greater, particularly preferably 160° or greater, and preferably less than 180°. When the second guide roller 6 is positioned deeper than the first guide roller 4, the strand 2 can form a large angle θ.

[0058] The diameter of each guide roller is preferably at least 1 cm and no more than 10 cm. If the diameter is less than 1 cm, the strand is forced to bend and easily flattens. If the diameter is greater than 10 cm, it becomes difficult to optionally change the distance between the guide rollers. The diameter is more preferably 2 to 8 cm, and even more preferably 3 to 7 cm. The guide rollers preferably, but not necessarily, rotate along the strand and may be in the form of cylindrical rods or round bars.

[0059] For thermoplastic resins containing reinforcing fillers, the distance between position B and position E is preferably 30 cm to 2 m, more preferably 40 cm to 1.5 m. Meanwhile, for compositions without reinforcing fillers, heat is not easily transferred, and the distance is preferably 40 cm to 3 m, more preferably 50 cm to 2 m.

[0060] The strands coming out of the water tank 3 are fed to a pelletizer where they are cut into pellets. The pellets preferably have a length of 2 to 5 mm and a diameter of 2 to 5 mm.

[0061] The manufacturing method of the present invention is applicable to any thermoplastic resin without limitation, including crystalline thermoplastic resins and non-crystalline thermoplastic resins. Examples of thermoplastic resins include: polycarbonate resins; polyamide resins such as polyamide 6, polyamide 66 and polyamide MXD; polyester resins such as polybutylene terephthalate and polyethylene terephthalate; polyacetal resins; polyphenylene ether resins; polyolefin resins; polystyrene resins; vinyl chloride resins; and acrylic resins. These resins can be used alone or in combination with one or more other resins. Among these thermoplastic resins, so-called engineering plastics such as polycarbonate resins, polyamide resins, polybutylene terephthalate resins, polyacetal resins and polyphenylene ether resins are particularly effective in demonstrating the effects of the present invention because these thermoplastic resins with high melt kneading temperatures are easily flattened by being subjected to a significant temperature difference between the extruder and the cooling water tank.

[0062] The reinforcing filler that may be contained in the thermoplastic resin is an agent that improves the strength and rigidity of the thermoplastic resin, and may be in any form such as fiber, plate, granular, or amorphous.

[0063] When the reinforcing filler is fibrous, it can be inorganic or organic. Examples of fibrous reinforcing fillers include inorganic fibers such as glass fiber, carbon fiber, alumina-silicon fiber, zirconium oxide fiber, boron fiber, boron nitride fiber, potassium nitride silicon titanate fiber, metal fiber, and wollastonite; and organic fibers such as fluororesin fiber and aromatic polyamide fiber. The fibrous reinforcing filler is preferably an inorganic fiber, particularly preferably glass fiber.

[0064] When included, the content of the reinforcing filler is preferably about 5 to 50 parts by mass relative to 100 parts by mass of the thermoplastic resin.One type of reinforcing filler may be included, or two or more types of reinforcing fillers may be included in combination.

[0065] In addition to reinforcing fillers, the thermoplastic resin may also contain any number of other additives, without limitation. Examples include stabilizers, antioxidants, flame retardants, flame retardant aids, mold release agents, lubricants, UV absorbers, antistatic agents, plasticizers, dyes, and pigments. Typically, the content of such additives is preferably 0.01 to 50% by mass, and particularly preferably 0.01 to 40% by mass.

[0066] [Example]

[0067] Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples and can be arbitrarily changed within the scope of the gist of the present invention.

[0068] Table 1 below shows thermoplastic resins and reinforcing fillers used as raw materials in Examples and Comparative Examples.

[0069] [Table 1]

[0070]

[0071] In the following Examples and Comparative Examples, an intermeshing co-rotating ventilating twin-screw extruder ("TEX44αIII", manufactured by The Japan Steel Works, Ltd., barrel diameter D = 47 mm) was used.

[0072] Screw structure Figure 7 shown.

[0073] The feed barrel (feed barrel) is located at barrel position C1; the vent barrel is located at C7 and C12; the open vent is located at C7; the pressure reducing vent is located at C12; and the side feed barrel is located at C9. The first kneading section for melt-kneading the thermoplastic resin is located between positions C5 and C6, and its screw structure is RRNNL (R is a forward conveying kneading disk element; N is an orthogonal kneading disk element; and L is a reverse conveying screw), each screw is 1Ds long (1Ds=44mm) and has 5 blades. Glass fiber as a reinforcing filler is fed from the C9 side. The second kneading section for kneading the glass fiber is located between positions C10 and C11. The second kneading section includes an R having 5 blades and a length of 1Ds and 3 back-mixing screws, each of which is equally long (with a lead of 0.25Ds), such as Figure 7 shown.

[0074] The transverse flat die used in the present invention has 10 die holes arranged linearly in the transverse direction, each with a diameter of 3.8 mm, and a forming section length of 20 mm. The strand temperature was measured using a contact thermocouple (thermometer DP-350 and thermocouple JB-15, element: K, manufactured by RKC Instrument Inc.).

[0075] Example 1

[0076] 80 kg / h of polyamide resin PA1 and 60 kg / h of polyamide resin PA2 were fed into the feed barrel at position C1 of the barrel of an extruder ("TEX44αIII," manufactured by The Japan Steel Works, Ltd.), and 60 kg / h of glass fiber (GF1) was fed from a side-feed hopper into the side-feed barrel at position C9. The total feed rate of the raw materials was 200 kg / h; the screw speed was 250 rpm; and the barrel temperature was set to 260°C. The die base temperature was set to 280°C, and the flange was also set to the same temperature as the die base. In the following Examples and Comparative Examples, the flange was set to the same temperature as the die base.

[0077] The average temperature of the two strands in the center of the horizontal flat die is 321° C., and the average temperature of the two strands at the two ends is 313° C. The temperature difference between them is 8° C.

[0078] The water level in the cooling water tank and the position of the first guide roller were adjusted so that the distance between the guide rollers AC was 17 cm and the distance between the guide rollers BC was 35% of the distance between the guide rollers AC. The second guide roller was positioned at the same level as the first guide roller in the water tank (this is indicated as "same" in the table below). The distance between point C, where the strand contacts the first guide roller, and point D, where the strand contacts the second guide roller (distance CD) was 20 cm.

[0079] The third guide roller is located downstream of the second guide roller so that the wire material reaches the water surface. The distance between the position B where the wire material reaches the water surface and the position E where the wire material reaches the water surface is 1 meter. The diameter of each guide roller is 5 cm.

[0080] The strand forms an angle of 140° before and after the first guide roller.

[0081] The strands cooled in a water tank were cut into pellets using a pelletizer, each having a length of 3 mm and a diameter of 3 mm. 20 pellets were randomly selected to measure the average flatness. A good average flatness of 0.10 was obtained.

[0082] Table 2 below shows the standard deviation of the flatness, the standard deviation of the flatness / the average flatness, and the evaluation results.

[0083] The evaluation in the table is based on the following criteria:

[0084] A: The average flatness is less than 0.1;

[0085] B: Average flatness is 0.1 or more and 0.15 or less;

[0086] C: The average flatness is greater than 0.15 and less than 0.2;

[0087] D: The average flatness is greater than 0.2.

[0088] Example 2

[0089] The results are shown in Table 2.

[0090] Example 3

[0091] The results are shown in Table 2.

[0092] Example 4

[0093] Pellets were produced in the same manner as in Example 1, except that the second guide roller was located 5 cm below the first guide roller, resulting in a CD distance of 21 cm and an angle of 155° between the strands before and after the first guide roller. The results are shown in Table 2.

[0094] Example 5

[0095] Pellets were produced in the same manner as in Example 1, except that the second guide roller was located 10 cm below the first guide roller, resulting in a CD distance of 23 cm and an angle of 168° between the strands before and after the first guide roller. The results are shown in Table 2.

[0096] Example 6

[0097] The results are shown in Table 2. Pellets were produced in the same manner as in Example 1, except that the distance between AC was 12 cm and the distance between BC was 50% of the distance between AC.

[0098] Example 7

[0099] The results are shown in Table 2. Pellets were produced in the same manner as in Example 1, except that the distance between AC was 27 cm and the distance between BC was 22% of the distance between AC.

[0100] Example 8

[0101] Pellets were produced in the same manner as in Example 1, except that 160 kg / h of polybutylene terephthalate resin PBT1 was fed to the feed cylinder at C1 of the extruder ("TEX44αIII", manufactured by The Japan Steel Works, Ltd.), and 40 kg / h of glass fiber (GF2) was fed from the side feed hopper to the side feed cylinder at C9. The results are shown in Table 2.

[0102] Example 9

[0103] The pellets were produced in the same manner as in Example 1 except that 200 kg / h of polybutylene terephthalate resin PBT2 was fed to the feed cylinder at C1 of the extruder ("TEX44αIII", manufactured by The Japan Steel Works, Ltd.) and no glass fiber was fed.

[0104] Example 10

[0105] Pellets were produced in the same manner as in Example 1, except that 180 kg / h of polycarbonate resin PC was fed to the feed cylinder at C1 of the extruder ("TEX44αIII", manufactured by The Japan Steel Works, Ltd.), and 20 kg / h of glass fiber (GF2) was fed from the side feed hopper to the side feed cylinder at C9. The results are shown in Table 2.

[0106] Comparative Example 1

[0107] The pellets were produced in the same manner as in Example 1, except that the distance between BC was set to 6% of the distance between AC, which was maintained at 17 cm.

[0108] Comparative Example 2

[0109] The results are shown in Table 3.

[0110] Comparative Example 3

[0111] The results are shown in Table 3.

[0112] Comparative Example 4

[0113] The results are shown in Table 3. Pellets were produced in the same manner as in Example 1, except that the distance between AC was 32 cm and the distance between BC was 19% of the distance between AC.

[0114] Comparative Example 5

[0115] Pellets were produced in the same manner as in Example 1, except that the temperature of the die base and the flange was 310° C., which resulted in a strand temperature of 328° C. at the center of the die and 325° C. at the ends of the die, with a difference of 3° C. The results are shown in Table 3.

[0116] Comparative Example 6

[0117] Pellets were produced in the same manner as in Example 1, except that the temperature of the die base and flange was 240° C., which resulted in a strand temperature of 316° C. at the center of the die and 299° C. at the ends of the die, with a difference of 17° C. The results are shown in Table 3.

[0118] [Table 2]

[0119]

[0120] [Table 3]

[0121]

[0122] Industrial applicability

[0123] The production method of the present invention makes it possible to produce resin pellets having a small flatness uniformly and without variation, and the resin pellets thus produced can be stably formed into various products.

[0124] Description of Reference Numerals

[0125] 1 horizontal flat die

[0126] 2 wire material

[0127] 3 cooling water tank

[0128] 4 First guide roller

[0129] 5 Water surface in the sink

[0130] 6 Second guide roller

[0131] 7nth guide roller

[0132] 21 Extruder screw

[0133] 22 multiwell plates

[0134] 23 mold base

[0135] 24 flange

[0136] 25 Manifold

[0137] 26,27 Thermocouple

[0138] 31,32,33 die holes

Claims

1. A method for producing resin pellets, comprising: Extruding a thermoplastic resin or a composition comprising a thermoplastic resin and a reinforcing filler in the form of a strand from a die at the front end of an extruder; The strands are introduced into a water tank provided with guide rollers to be cooled; and the cooled strands are cut into resin pellets, wherein The die is a horizontal flat die, and the temperature of the strands passing through the die holes at the ends of the flat die is 4°C to 14°C lower than the temperature of the strands passing through the die holes in the center of the flat die, and The distance between the center position A of the die hole in the center of the flat die and the position C where the strand contacts the first guide roller (distance between AC) is 7 to 30 cm, and the distance between the position B where the strand reaches the water surface and the position C (distance between BC) is in the range of 10% to 60% of the distance between AC. 2 . The manufacturing method according to claim 1 , wherein the water tank is provided with a second guide roller downstream of the first guide roller, so that the second guide roller is located deeper in the water tank than the first guide roller. 3 . The manufacturing method according to claim 1 , wherein the distance between the position C and the position D where the strand contacts the second guide roller is 4 to 30 cm. 4 . The manufacturing method according to claim 1 , wherein the strand forms an angle of 130° or more and less than 180° before and after the first guide roller. 5 . The production method according to claim 1 , wherein the thermoplastic resin is a crystalline thermoplastic resin. 6 . Resin pellets produced by the production method according to claim 1 .

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