Wire manufacturing method

Abstract

To provide an air-cooled granulation device capable of granulating resin admixture composed of resin with at least either a flame-retardant or a filler added while suppressing mutual adhesion of pellets, a cutter blade for a granulation device used in the device, and a granulation method of resin admixture using the cutter blade for a granulation device.SOLUTION: In an aspect of the present invention, a cutter blade 34 for a granulation device comprises: a cutter blade body 340 including a granulation surface 341; and an amorphous carbon coating film 342 covering the granulation surface 341.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cutter blade for a granulator, a granulator, and a method for granulating a resin mixture. [Background technology]

[0002] Conventionally, granulation devices that granulate plastics to form pellets are known (see, for example, Patent Document 1). Granulation devices include air-cooled types that use air to cool the pellets obtained by granulation, and water-cooled types that use water. Some plastics, such as soft PVC (polyvinyl chloride), which does not easily adhere to the cutter blade of the granulation device in a molten state and is less likely to adhere to each other (sticking together) or to form multiple pellets linked together (beading), can be granulated using an air-cooled granulation device.

[0003] On the other hand, for granulating plastics such as resin mixtures in which at least one of a flame retardant and a filler is added to the resin, where pellets are prone to sticking together during granulation, water-cooled granulating equipment such as strand granulation, underwater granulation, water mist granulation, and watering granulation is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-176932 Summary of the Invention [Problem to be solved by the invention]

[0005] Compared to water-cooled granulators, air-cooled granulators are superior in that they do not require a post-process to remove water from the pellets and do not require visual inspection of the string-like plastic before pelletization. In order to granulate plastics that have traditionally been granulated using water-cooled granulators using air-cooled granulators, it is necessary to prevent adhesion to the cutter blade during granulation and to prevent the pellets from sticking to each other.

[0006] The object of the present invention is to provide an air-cooled granulation device capable of granulating a resin mixture to which at least one of a flame retardant and a filler has been added while suppressing adhesion of the pellets to each other, a cutter blade for the granulation device used in the device, and a method for granulating a resin mixture using the cutter blade for the granulation device. [Means for solving the problem]

[0007] SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a cutter blade for a granulating device, comprising a cutter blade body having a granulating surface and an amorphous carbon coating covering the granulating surface.

[0008] Furthermore, in order to solve the above-mentioned problems, the present invention provides an air-cooled granulating device that is equipped with the above-mentioned cutter blade for a granulating device.

[0009] In addition, for the purpose of solving the above-mentioned problems, the present invention provides a method for granulating a resin mixture, which includes a step of cutting and pelletizing a resin mixture, in which at least one of a flame retardant and a filler has been added to a resin extruded from a resin discharge hole of a die, using a cutter blade for the above-mentioned granulation device. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an air-cooled granulation device that can granulate a resin mixture in which at least one of a flame retardant and a filler has been added to the resin while suppressing adhesion of the pellets to each other, a cutter blade for the granulation device that is used in the device, and a method for granulating a resin mixture using the cutter blade for the granulation device. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a part of the configuration of a granulating apparatus according to an embodiment of the present invention. [Figure 2]Fig. 2(a) is a perspective view of a cutter blade included in a cutter device according to an embodiment of the present invention, and Fig. 2(b) is a cross-sectional view of the vicinity of the tip of the cutter blade along the length direction. [Figure 3] 3(a) and (b) are cross-sectional views that schematically show how a cutter blade cuts resin extruded in a string shape from a resin discharge hole of an air-cooled granulation die. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Embodiment] (Configuration of granulation equipment) 1 is a cross-sectional view showing a schematic configuration of a granulation apparatus 1 according to an embodiment of the present invention. The granulation apparatus 1 is an air-cooled granulation apparatus, and includes an extruder 10 that extrudes a molten resin mixture 50, an air-cooled granulation die 20 that has a plurality of annularly arranged resin discharge holes 21 and is installed at the outlet of a space in a cylinder 11 that is a passage for the resin mixture 50 of the extruder 10, and a cutter device 30 that cuts the resin mixture 50 extruded in a string-like shape from the resin discharge holes 21 of the air-cooled granulation die 20 into pellets.

[0013] The extruder 10 includes a cylinder 11 into which the molten resin mixture 50 is supplied, a screw 12 installed inside the cylinder 11 for extruding the molten resin mixture 50 forward, and a plate-shaped breaker plate 13 installed in front of the screw 12 inside the cylinder 11 and having a plurality of resin passage holes.

[0014] The resin mixture 50 is, for example, a resin mixture containing a base polymer to which at least one of a flame retardant such as magnesium hydroxide, a bromine-based flame retardant, or antimony trioxide and a filler such as calcined clay has been added. The base polymer is, for example, a polyolefin-based resin. Examples of polyolefin-based resins that can be used include polyethylenes such as chlorinated polyethylene (CPE), polypropylene, high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE), ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers (EVA), and ethylene-ethyl acrylate copolymers (EEA), either alone or in combination. The amount of the flame retardant or filler added is, for example, 50 to 300 parts by mass per 100 parts by mass of the base polymer.

[0015] The cutter device 30 includes a rotary drive source 31 such as an inverter motor, a shaft 32 installed to rotate by the rotary drive source 31, a cutter blade mounting base 33 attached to the shaft 32 so as to rotate around the shaft 32 as a rotation axis, a plurality of cutter blades 34 attached to the cutter blade mounting base 33, and a housing 35 that houses the shaft 32, the cutter blade mounting base 33, the cutter blades 34, etc. The cutter device 30 is installed, for example, on a movable base (not shown), so that the cutter blades 34 can be separated from the air-cooled granulation die 20 when granulation is not being performed. In the example shown in FIG. 1, two cutter blades 34 are attached to the cutter blade mounting base 33, but the number of attached cutter blades 34 is not limited to two and may be, for example, three or four.

[0016] The cutter blade 34 is fixed to the cutter blade mounting base 33 so that the distance between its tip and the air-cooled granulation die 20 is approximately 0.01 to 0.1 mm (for example, 0.02 mm). The cutter blade 34 is fixed to the cutter blade mounting base 33 using, for example, a bolt 331. Then, by rotating the cutter blade mounting base 33 using the rotary drive source 31, the cutter blade 34 rotates above the area on the surface of the air-cooled granulation die 20 where the multiple resin discharge holes 21 are arranged in an annular shape.

[0017] The molten resin mixture 50 extruded by the screw 12 inside the cylinder 11 of the extruder 10 is extruded in a string-like shape from the resin discharge holes 21 of the air-cooled granulation die 20 arranged in a ring shape surrounding the torpedo 22, and is cut by a cutter blade 34 rotating on the surface of the air-cooled granulation die 20 to form pellets.

[0018] (Cutter blade configuration) FIG. 2(a) is a perspective view of the cutter blade 34 included in the cutter device 30. FIG. 2(b) is a cross-sectional view of the tip of the cutter blade 34 along the longitudinal direction. The cutter blade 34 comprises a cutter blade body 340 and an amorphous carbon coating 342 covering a granulation surface 341 of the body 340. The granulation surface 341 of the body 340 faces away from the air-cooled granulation die 20 when the cutter blade 34 is fixed to the cutter blade mounting base 33, and is the surface that comes into contact with the resin mixture 50 cut and pelletized by the cutter blade 34. The surface 345 of the body 340 opposite the granulation surface 341 has an inclined surface 346 that forms an acute angle at the tip of the body 340 in a longitudinal cross section. The cutter blade 34 also has a recess 344 for fixing a bolt, for example, for passing a bolt 331 through it.

[0019] 3(a) and (b) are cross-sectional views schematically showing how the cutter blade 34 cuts the resin mixture 50 extruded in a string-like shape from the resin discharge holes 21 of the air-cooled granulation die 20. As shown in Fig. 3(a) and (b), the string-like portion 51 of the resin mixture 50 extruded from the resin discharge holes 21 is cut by the tip of the cutter blade 34 moving on the surface of the air-cooled granulation die 20, and pellets 52 are obtained.

[0020] Here, pellets 52 separated from string-like portions 51 of resin mixture 50 come into contact with cutter blade 34, but because granulation surface 341, which is the surface on the traveling direction side of cutter blade 34, is covered with amorphous carbon coating 342, adhesion of pellets 52 to cutter blade 34 is suppressed even if resin mixture 50 is a resin in which pellets tend to stick to each other during granulation, such as a resin mixture in which at least one of a flame retardant and a filler is added to polyethylene or polyolefin. As a result, adhesion of pellets 52 to each other and beading can be suppressed.

[0021] The body 340 of the cutter blade 34 is made of a metal such as SK steel or SKH steel. The amorphous carbon coating 342 is a film made of an amorphous material that is primarily composed of carbon and hydrogen and has an irregular bonding state, such as diamond-like carbon (DLC).

[0022] To more effectively prevent the pellets 52 from sticking together during granulation, the surface roughness Rz of the granulation surface 341 of the main body 340 is preferably 0.08 μm or more and 3.5 μm or less, and more preferably 0.1 μm or less.

[0023] 2(a), the granulation surface 341 of the main body 340, which is the base surface of the amorphous carbon coating 342, is preferably flat to prevent cracks from occurring in the amorphous carbon coating 342. In addition, to more effectively prevent the pellets 52 from adhering to the cutter blade 34, it is preferable that the entire granulation surface 341 be covered with the amorphous carbon coating 342.

[0024] The amorphous carbon coating 342 is made of amorphous carbon or carbon in which a portion of the amorphous carbon has been substituted with another element such as silicon. The amorphous carbon coating 342 is formed by, for example, a CVD method such as a plasma CVD method or a plasma ion implantation CVD method, or a PVD method such as an ionization vapor deposition method, an arc ion plating method, or an unbalanced magnetron (UBM) sputtering method. In particular, it is preferable to form the amorphous carbon coating 342 by a filtered arc ion plating method, in order to more effectively prevent fusion of the workpiece (adhesion of pellets to each other) and increase the number of times the amorphous carbon coating 342 can be reused.

[0025] By using the arc ion plating method, it is possible to form an amorphous carbon coating 342 that is substantially free of hydrogen, has high hardness, and has excellent wear resistance. However, when using the arc ion plating method, particles (graphite spheres) that are several micrometers in size, called droplets, may inevitably be mixed into the amorphous carbon coating 342. If droplets or impurities are present on the surface of the amorphous carbon coating 342, these may act as starting points for fusion of the workpiece. Therefore, by using the filtered arc ion plating method, it is possible to prevent droplets, impurities, and the like from being mixed into the amorphous carbon coating, thereby forming an amorphous carbon coating 342 that is high hardness, has excellent wear resistance, and has a smooth surface.

[0026] Specifically, by using the filtered arc ion plating method, the arithmetic mean roughness Ra (based on JIS-B-0601-2001) of the surface of the amorphous carbon coating 342 can be set to 0.03 μm or less, and the maximum height roughness Rz (based on JIS-B-0601-2001) can be set to 0.5 μm or less. If Ra and Rz are within these ranges, it can be said that the inclusion of droplets, impurities, etc. in the amorphous carbon coating 342 is suppressed to a level that prevents the formed material from fusing. Furthermore, by setting Ra to 0.02 μm or less and Rz to 0.3 μm or less, fusing of the formed material can be more effectively reduced.

[0027] Furthermore, by using the filtered arc ion plating method, the nanoindentation hardness measured from the surface of the amorphous carbon coating 342 can be set to 50 GPa or more and 100 GPa or less. By setting the nanoindentation hardness to 50 GPa or more, the wear resistance is increased, and the life of the cutter blade 34 can be extended. Furthermore, by setting the nanoindentation hardness to 100 GPa or less, the residual stress in the amorphous carbon coating 342 can be suppressed, and the adhesion to the main body 340 can be improved.

[0028] Here, nanoindentation hardness refers to the plastic hardness when a probe is pressed into a sample (amorphous carbon coating 342) to cause plastic deformation, and the hardness is calculated by determining a load-displacement curve from the indentation load and indentation depth (displacement). Specifically, using a nanoindentation device manufactured by Elionix Co., Ltd., the hardness of the coating surface was measured at 10 points under measurement conditions of an indentation load of 9.8 mN, a maximum load holding time of 1 second, and a removal rate after load application of 0.49 mN / second, and the hardness was calculated by averaging the six points, excluding the two points with the highest and two points with the lowest values.

[0029] The thickness of the amorphous carbon coating 342 is preferably 0.2 μm or more and 1 μm or less. By making the thickness of the amorphous carbon coating 342 0.2 μm or more, it is possible to more effectively prevent the pellets from sticking together during granulation, and by making the thickness 1 μm or less, it is possible to increase the number of times the amorphous carbon coating 342 can be reused. Furthermore, the amorphous carbon coating 342 is required to have heat resistance capable of withstanding the temperature during granulation (e.g., 190°C), and in order to further improve heat resistance, the thickness is preferably 0.6 μm or more.

[0030] (Effects of the embodiment) According to the above embodiment, it is possible to provide an air-cooled granulation device that can granulate a resin mixture in which at least one of a flame retardant and a filler has been added to the resin while suppressing adhesion of the pellets to each other, a cutter blade for the granulation device used in the device, and a method for granulating a resin mixture using the cutter blade for the granulation device. [Example]

[0031] A plurality of types of cutter blades with different configurations, including the cutter blade 34 according to the above embodiment, were manufactured and their performance was evaluated. The configuration of the cutter blade, the evaluation method, and the evaluation results will be described in detail below.

[0032] (Cutter blade configuration) The cutter blade body was prepared with and without buffing on the granulation surface (#300). SK5 or SKH51 was used as the body material. Three types of coatings (Coatings A to C) were used as the coatings covering the granulation surface of the cutter blade. Table 1 below shows the materials and coating methods for Coatings A to C.

[0033] [Table 1]

[0034] Coating A was obtained by forming a carbon coating to a thickness of 3.5 μm or less on the granulation surface of the cutter blade body using a plasma CVD method, using a silicon-containing hydrocarbon gas as the starting material. The "substitution rate" of Coating A in Table 1 refers to the percentage obtained by performing elemental analysis of the surface layer of the coating by X-ray spectroscopy, dividing the resulting nitrogen mass concentration by the carbon concentration when not substituted.

[0035] Coating B was obtained by applying a diamond-like carbon coating to a thickness of 1.1 μm or less on the granulated surface of the cutter blade body using a filtered arc ion plating method, using a solid graphite target as the starting material, at a temperature of 473 K or less. Coating C was obtained by applying silicone oil to the granulated surface of the cutter blade body using a brush.

[0036] The following Table 2 shows the configurations of seven types of cutter blades (referred to as samples A to G) equipped with the above-mentioned body and coating. Note that, since it is difficult to measure the thickness of the applied silicone oil, the thickness of coating C of sample F was not measured.

[0037] [Table 2]

[0038] (Evaluation method) The above-mentioned cutter blade was evaluated by granulating two different types of resin mixtures (resin mixture A and resin mixture B) using a granulating device equipped with a cutter blade.

[0039] Resin mixture A was a flame-retardant resin mixture in which 80 parts by mass of magnesium hydroxide as a flame retardant was added to 100 parts by mass of ethylene vinyl acetate copolymer (EVA) as a base polymer, and its tensile elongation value was 450%.

[0040] Granulation of resin blend A was carried out by kneading a 6L kneader manufactured by Toshin Corporation at 160°C, and feeding the kneaded mass of resin blend A into a granulating extruder TEC-7.5 manufactured by Toshin Corporation, equipped with an air-cooled granulating head. A hot-cut die with 28 resin discharge holes with a diameter of 3 mm was used as the air-cooled granulating die. Specific granulation conditions were: the cylinder temperature and die temperature of the granulator were both 160°C, the granulator rotation speed (the rotation speed of the screw 12 of the extruder 10) was 15 rpm, and the cutter blade rotation speed was 190 rpm.

[0041] Resin blend B is a flame-retardant resin blend containing 100 parts by mass of a mixture of high-density polyethylene (HDPE), ethylene-ethyl acrylate copolymer (EEA), and chlorinated polyethylene (CPE) (HDPE / EEA / CPE = 50 / 40 / 10) as the base polymer, to which 35 parts by mass of a brominated flame retardant, 35 parts by mass of antimony trioxide, and 20 parts by mass of magnesium hydroxide were added, and its tensile elongation value was 500%.

[0042] Granulation of resin blend B was carried out by kneading a 6L kneader manufactured by Toshin Corporation at 160°C, and feeding the kneaded mass of resin blend B into a TEC-7.5 granulation extruder manufactured by Toshin Corporation, equipped with an air-cooled granulation head. A hot-cut die with 28 3mm diameter resin discharge holes was used as the air-cooled granulation die. Specific granulation conditions were a granulator cylinder temperature of 165°C and a die temperature of 170°C, respectively, a granulator rotation speed of 15 rpm, and a cutter blade rotation speed of 190 rpm.

[0043] 200 g of pellets obtained by granulation of the above-mentioned resin blend A and resin blend B were each sampled, and the mass of the pellets that were stuck together or linked together was taken as A. The granulation property was evaluated based on the value of the mass-missing pellet rate X, which was calculated by X = {A / (200 + 200)} × 100 = A / 4. The evaluation of granulation property was performed 1 hour and 2 hours after the start of granulation. The granulation of resin blend A and resin blend B and the evaluation of their granulation property were repeated on different days and times, for a total of 5 times. As an index for evaluating granulation property, an X value of 10% or less can be evaluated as good, and one exceeding 10% can be evaluated as poor.

[0044] The tensile elongation values ​​of the above-mentioned resin blend A and resin blend B are the tensile elongation values ​​of the insulators of electric wires manufactured using pellets granulated from resin blend A and resin blend B, respectively, and were measured by pulling out the conductor from the manufactured electric wire, forming each insulator into a tube shape, and conducting a tensile test in accordance with JIS C3005.

[0045] (Evaluation results) Table 3 below shows the X values ​​for the granulation of resin mixture A carried out using samples A to G, and Table 4 shows the X values ​​for the granulation of resin mixture B carried out using samples A to G.

[0046] [Table 3]

[0047] [Table 4]

[0048] As shown in Tables 3 and 4, good results were obtained in granulation using samples A, B, C, and D, which had coating B as a coating, for both resin blend A and resin blend B. On the other hand, in granulation using sample E, which had no coating, and sample F, which had coating C as a coating, pellets frequently stuck together and became beaded, so the experiment was stopped after the third time. In addition, in granulation using sample G, which had coating A as a coating, the X value increased after the third time, but the X value was able to be kept below 10% until the second time.

[0049] These results show that the use of an amorphous carbon coating as the cutter blade coating results in good granulation properties, which is thought to be due to the excellent peelability of the amorphous carbon coating from the molten resin mixture under the temperature conditions during granulation.

[0050] Furthermore, it was found that forming an amorphous carbon coating for the cutter blade using the filtered arc ion plating method extended the life of the coating. This is thought to be due to the fact that hydrogen embrittlement of the coating is unlikely to occur under the temperature conditions during granulation, and deterioration is suppressed, as well as the fact that the coating is formed thinly.

[0051] From the thickness of the coatings of samples A, B, C, and D, it can be said that the thickness of the cutter blade coating is preferably 0.2 μm or more and 1 μm or less. By making the thickness 0.2 μm or more, the X value can be increased, and by making the thickness 1 μm or less, the number of times the coating can be reused can be increased.

[0052] Furthermore, when comparing the X values ​​in granulation using samples A, B, C, and D, the X values ​​for samples A and C are higher than the X values ​​for samples B and D. This is thought to be due to the fact that the granulation surface of the main body of samples A and C is buffed, which reduces the surface roughness Rz of the granulation surface. Since good granulation properties are obtained in all granulations using samples A, B, C, and D, it can be said that good granulation properties are obtained when the surface roughness Rz of the granulation surface of the main body of the cutter blade is 0.08 μm or more and 3.5 μm or less, but it can be said that better granulation properties are obtained when the surface roughness Rz of the granulation surface of the main body of samples A and C is 0.1 μm or less.

[0053] Furthermore, since good results were obtained in granulation using Samples A, B, C, and D, which have Coating B as a coating, for both Resin Blend A and Resin Blend B, it is possible to suppress the inclusion of air bubbles when molding a resin molded product using the granulated pellets as a raw material, and to obtain a resin molded product with a large tensile elongation value (for example, 400% or more). In other words, using Resin Blend A and B pelletized by granulation using Samples A, B, C, and D, it is possible to mold a resin molded product with a tensile elongation value of 400% or more.

[0054] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[0055] [1] A cutter blade (34) for a granulator, comprising: a cutter blade body (340) having a granulating surface (341); and an amorphous carbon coating (342) covering the granulating surface (341).

[0056] [2] The cutter blade (34) for a granulator according to [1] above, wherein the amorphous carbon coating (342) has a surface with an arithmetic mean roughness Ra of 0.03 μm or less and a maximum height roughness Rz of 0.5 μm or less.

[0057] [3] The cutter blade (34) for a granulator according to [1] or [2] above, wherein the surface roughness Rz of the granulation surface (341) is 0.1 μm or less.

[0058] [4] The cutter blade (34) for a granulator according to any one of the above [1] to [3], wherein the thickness of the amorphous carbon coating (342) is 0.2 μm or more and 1 μm or less.

[0059] [5] The cutter blade (34) for a granulator according to any one of the above [1] to [4], wherein the amorphous carbon coating (342) does not contain hydrogen.

[0060] [6] A granulator (1) that is an air-cooled granulator and is equipped with the cutter blade (34) for a granulator according to any one of the above [1] to [5].

[0061] [7] A method for granulating a resin mixture, comprising a step of cutting and pelletizing a resin mixture (50) obtained by adding at least one of a flame retardant and a filler to a resin extruded from a resin discharge hole (21) of a die (20) using the cutter blade (34) for a granulator according to any one of the above [1] to [5].

[0062] [8] A method for granulating a resin mixture according to the above [7], comprising a step of molding a resin molded product having a tensile elongation value of 400% or more using the pelletized resin mixture (50).

[0063] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the gist of the invention. Furthermore, the above-described embodiments and examples do not limit the invention according to the claims. Furthermore, it should be noted that not all of the combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention. [Explanation of symbols]

[0064] 1 Granulation equipment 10. Extruder 20 Air-cooled granulation die 21 Resin discharge hole 30 Cutter device 34 cutter blade 340 Main Unit 341 Granulation Surface 342 Amorphous carbon coating

Claims

[Claim 1] A method for manufacturing an electric wire having an insulator on a conductor, comprising: a step of cutting a resin mixture, in which at least one of a flame retardant and a filler has been added to a resin extruded from a resin discharge hole of a die, into pellets using a cutter blade for a granulator, the cutter blade having a granulating surface and a hydrogen-free amorphous carbon coating covering the granulating surface; forming the insulator on the conductor using the pellet; the amorphous carbon coating has a surface with an arithmetic mean roughness Ra of 0.03 μm or less and a maximum height roughness Rz of 0.5 μm or less; the surface roughness Rz of the granulation surface is 0.1 μm or less, the amorphous carbon coating has a thickness of 0.2 μm or more and 1 μm or less; The insulator has a tensile elongation value of 400% or more. Manufacturing method of electric wire.

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