Method for producing thermoplastic resin composition

Abstract

To provide a production method for a thermoplastic resin composition in which carbon black can be well dispersed.SOLUTION: A production method for a thermoplastic resin composition includes a process of melting and kneading thermoplastic resin and carbon black with a twin-screw extruder having a pair of screws equipped with kneading discs in a barrel. A maximum distance between a tip of the kneading disc and an opposite position of the tip of the kneading disc on the inner wall of the barrel is 1.0 to 5.0 mm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a thermoplastic resin composition containing carbon black. [Background technology]

[0002] Thermoplastic resins are excellent in moldability, mechanical properties, weather resistance, and other properties, and are therefore widely used in applications such as various automobile parts, electrical and electronic parts, and the like, mainly for injection molding applications. In general, in order to further improve the above-mentioned properties of thermoplastic resins or to compensate for their shortcomings, various additives are added to the thermoplastic resins and used as resin compositions. For example, carbon black is generally added to color a thermoplastic resin composition black. As an example, a mode can be given in which carbon black is blended with pellets or powder of a thermoplastic resin, melt-kneaded by an extruder, extruded into a strand shape, and then cut into pellets.

[0003] When carbon black is used to color a thermoplastic resin composition black, poor dispersion of the carbon black occurs during melt-kneading with the thermoplastic resin, resulting in problematic agglomerates. Increasing the primary particle size of the carbon black reduces the problem of poor dispersion, but causes another problem of reduced mechanical properties and jet blackness of the molded product. In addition, increasing the amount of carbon black added to suppress the decrease in jet blackness causes problems such as adverse effects on the properties of the thermoplastic resin composition and reduced insulation.

[0004] For these reasons, it is preferable to use carbon black with a small particle size in order to maintain the mechanical strength and insulating properties of the molded product. However, as described above, when carbon black with a small primary particle size is melt-kneaded, it is necessary to suppress the generation of agglomerates due to poor dispersion of the carbon black. Therefore, Patent Document 1 proposes a thermoplastic resin composition in which carbon black with a primary particle size of 70 to 200 nm is dispersed with a maximum particle size of 50 μm or less, thereby suppressing the generation of agglomerates of carbon black. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5206903 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, when dispersing carbon black, the residence time (initial residence time) of the thermoplastic resin composition between the raw material inlet position of the thermoplastic resin and carbon black and 3L / 10 relative to the total length (L) from the raw material inlet position to the discharge position of the twin-screw extruder is set to a predetermined time, and multiple kneading disks are installed in the kneading section. However, it is difficult to say that satisfactory results have been obtained for dispersing carbon black, which has a small primary particle size and is prone to aggregation. In addition, Patent Document 1 does not describe melt kneading by increasing the distance between the tip of the kneading disk and the inner wall of the barrel.

[0007] The present invention provides a method for producing a thermoplastic resin composition capable of dispersing carbon black satisfactorily. [Means for solving the problem]

[0008] One aspect of the present invention that solves the above problems is as follows. (1) A method for producing a thermoplastic resin, comprising a step of melt-kneading a thermoplastic resin and carbon black using a twin-screw extruder having a pair of screws equipped with kneading discs in a barrel, the method comprising the steps of: A method for producing a thermoplastic resin composition, wherein the maximum distance between the tip of the kneading disc and a position on the inner wall of the barrel facing the tip of the kneading disc is 1.0 to 5.0 mm.

[0009] (2) The method for producing a thermoplastic resin composition according to (1) above, wherein the thermoplastic resin is a polybutylene terephthalate resin.

[0010] (3) The method for producing a thermoplastic resin composition according to (1) or (2) above, wherein the screw rotation speed of the twin-screw extruder is 250 to 600 rpm, and the inner diameter of the barrel is 40 to 85 mm.

[0011] (4) The method for producing a thermoplastic resin composition according to any one of (1) to (3) above, wherein the carbon black has a primary particle size of 10 to 60 nm.

[0012] (5) The method further includes a step of pre-kneading the thermoplastic resin and the carbon black before the step of melt-kneading the thermoplastic resin and the carbon black, The method for producing a thermoplastic resin composition according to any one of (1) to (4), wherein in the pre-kneading step, the thermoplastic resin and the carbon black are melt-kneaded using a pair of screws having kneading discs with a thickness of 0.05D to 0.3D attached to the pair of screws so as to have a length of 0.5D to 5.0D. Effect of the Invention

[0013] According to the present invention, it is possible to provide a method for producing a thermoplastic resin composition capable of dispersing carbon black satisfactorily. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a conceptual diagram showing the configuration of a twin-screw extruder used in the method for producing a thermoplastic resin composition of the present embodiment. [Diagram 2] FIG. 2 is a partial cross-sectional view showing an example of an arrangement of kneading discs (two rows) in a barrel. [Diagram 3] FIG. 2 is a partial cross-sectional view showing an example of an arrangement of kneading discs (with three eccentric teeth) in a barrel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The method for producing a thermoplastic resin composition according to the present embodiment is a method for producing a thermoplastic resin, comprising a step of melt-kneading a thermoplastic resin and carbon black using a twin-screw extruder having a pair of screws with kneading discs attached thereto in a barrel, and is characterized in that the maximum distance between the tip of the kneading disc and the position on the inner wall of the barrel facing the tip of the kneading disc is 1.0 to 5.0 mm.

[0016] When carbon black is dispersed by feeding a thermoplastic resin and carbon black into a twin-screw extruder and melt-kneading the carbon black, the carbon black is initially agglomerated to the order of millimeters when fed into the twin-screw extruder. In order to increase the jet blackness, it is desirable to disintegrate such agglomerated carbon black into particles of the order of micrometers during dispersion. However, carbon black is more strongly agglomerated, particularly as the primary particle size becomes smaller, making it more difficult to disintegrate. When attempting to finely disintegrate carbon black when melt-kneading thermoplastic resin and carbon black using a twin-screw extruder, it is desirable to apply shear stress to the entire carbon black in order to reduce the remaining agglomerates. Therefore, in this embodiment, in the twin-screw extruder, the maximum value of the distance between the tip of the kneading disc and the opposing position of the tip of the kneading disc on the inner wall of the barrel is set to a predetermined range. That is, in this embodiment, the gap between the tip of the kneading disc and the inner wall of the barrel at the opposing position of the tip is set wider, so that the amount of the mixture of thermoplastic resin and carbon black passing through the gap during melt-kneading increases. As a result, a shear stress sufficient to disintegrate the carbon black agglomerates is applied. Therefore, the remaining agglomerates of carbon black are reduced, and disintegration to the order of micrometers is possible. In addition, it becomes possible to disperse carbon black well, and even carbon black with a small primary particle size, which is particularly difficult to disintegrate, can be dispersed well. Furthermore, the smaller the primary particle diameter of the carbon black, the less the blending amount can be made in proportion to the jet blackness. Therefore, in this embodiment, even if the blending amount of carbon black having a small primary particle diameter is reduced, sufficient jet blackness can be ensured.

[0017] In the method for producing a thermoplastic resin composition of the present embodiment, a twin-screw extruder is used to melt-knead the thermoplastic resin and carbon black. An example of a twin-screw extruder is the one shown in FIG. 1. The twin-screw extruder 10 shown in FIG. 1 includes a first feed port 14 having a hopper 12 for feeding the thermoplastic resin, a plasticization zone 16, a second feed port 18, a preliminary kneading zone 20, a kneading zone 22, and a die section 24. The granular thermoplastic resin fed into the first feed port 14 is transported as a solid to the plasticization zone 16 and melted. There is no limitation on the element configuration of the plasticization zone 16 as long as most of the thermoplastic resin is expected to melt. For example, a plasticization zone can be formed by combining two sets of 1.0D (disk thickness 0.2D x 5 pieces, offset angle 45°) forward two-thread kneading disc elements in which the distance between the tip of the kneading disc on one side and the inner wall of the barrel is 0.4 mm, and one set of 1.0D (disk thickness 0.2D x 5 pieces, offset angle 45°) reverse two-thread kneading disc elements in which the distance between the tip of the kneading disc on one side and the inner wall of the barrel is 0.4 mm. The second feed port 18 may include, for example, a side feeder screw through which carbon black may be fed into the twin screw extruder 10 . The pre-kneading zone 20 is an optional zone located upstream of the kneading zone 22, in which a composition containing a thermoplastic resin and carbon black is pre-kneaded. The pre-kneading is carried out in order to actively bring the thermoplastic resin in a molten or unmolten state into contact (wet) with the carbon black, prior to kneading of the molten resin with the carbon black in the kneading zone 22, and to inhibit the aggregation of the carbon black. The kneading zone 22 is located downstream of the pre-kneading zone 20, and is a zone in which the composition containing the thermoplastic resin and the carbon black that has been pre-kneaded is melt-kneaded. In the following, the kneading disc used in the kneading zone 22 is also called "kneading disc A", and the kneading disc used in the pre-kneading zone 20 is also called "kneading disc B".

[0018] In this embodiment, the kneading zone 22 of the twin-screw extruder 10 has a pair of screws equipped with kneading discs A in the barrel. The maximum value of the distance between the tip of the kneading disc A and the position of the inner wall of the barrel facing the tip of the kneading disc A is 1.0 to 5.0 mm. If the maximum value of the distance is less than 1.0 mm, the amount of the kneaded product of the molten resin and carbon black to which shear stress is applied is limited, and good dispersibility cannot be ensured for the entire kneaded product. If the maximum value of the distance exceeds 5.0 mm, it is not possible to apply a shear stress sufficient to disintegrate the carbon black. The maximum value of the distance is preferably 1.5 to 4.5 mm.

[0019] The kneading disc A according to this embodiment will be described with reference to FIG. 2. FIG. 2 shows the arrangement of kneading discs 34, 36 attached to a pair of screws (not shown) in a barrel 32. The barrel 32 has a shape in which two cylindrical bodies are partially overlapped, and a screw is arranged in each of the two cylindrical bodies. The pair of screws rotate in the same direction or in the opposite direction by a driving means in the barrel 32, and the axis of the rotation shaft coincides with the center of a circle when the cross section of the cylindrical body is viewed as a circle. The kneading discs 34, 36 are all of the same shape, and have an asymmetric shape with respect to the rotation shaft (the center when the inner walls 38, 40 of the barrel 32 are viewed as a circle, respectively). More specifically, in the case of the kneading disc 34 located on the left side of FIG. 2, the distance between the upper tip and the opposing position of the upper tip on the inner wall 38 of the barrel 32 is d1. The maximum value of the distance d1 is 1.0 to 5.0 mm. On the other hand, the distance between the lower end of the kneading disc 34 and the opposing position of the lower end on the inner wall of the barrel 32 is shorter than the distance d1, for example, 0.5 mm or less. In this way, the end of the kneading disc 34 is spaced from the inner wall 38 of the barrel 32 by the distance d1, so that shear stress can be applied uniformly or nearly uniformly to the entire carbon black. Conversely, the lower end is close to the inner wall 38 of the barrel 32, and the kneading disc 34 has the function of cleaning the inner wall 38 of the barrel 32 by rotating. The kneading disc 36 on the right side of FIG. 2 is similar to the kneading disc 34 on the left side. It is also possible to configure the kneading disc such that all of its ends are spaced from the opposing positions of the inner wall of the barrel.

[0020] Next, another embodiment of the kneading disc according to this embodiment will be described. The embodiment shown in FIG. 3 differs from that shown in FIG. 2 in the shape of the kneading disc. FIG. 3 shows the arrangement of kneading discs 44, 46 attached to a pair of screws (not shown) in a barrel. The kneading discs 44, 46 have a three-fold rotationally symmetrical approximately equilateral triangular shape, with the symmetry center at point b. On the other hand, the rotation axis of the screw, that is, the rotation center of the kneading discs 44, 46 is point a, which is different from the position of the symmetry center point b. That is, the kneading discs 44, 46 are attached so as to rotate eccentrically with respect to the rotation axis of the screw. Therefore, in the case of the kneading disc 44, the distance d2 between the tip and the opposing position of each tip on the inner wall 48 of the barrel is constant regardless of the rotation of the screw. The maximum value of the distance d2 is 1.0 to 5.0 mm. The kneading disc 46 on the right side of FIG. 3 is the same as the kneading disc 44 on the left side.

[0021] Although the form of the kneading disc A according to this embodiment has been described above with reference to Fig. 2 and Fig. 3, this embodiment is not limited to the form shown in Fig. 2 and Fig. 3. That is, as long as the maximum value of the distance between the tip of the kneading disc A and the inner wall of the barrel is 1.0 to 5.0 mm, there is no particular limitation. Any of a normal kneading disc, a shoulder element, an eccentric element, etc. may be used.

[0022] The thickness of the kneading disc A is preferably 0.05D to 0.5D, and more preferably 0.1D to 0.3D. When the thickness is 0.05D to 0.5D, the strength and durability are sufficient, and sufficient shear stress can be applied to the passing thermoplastic resin. In addition, the load on the screw is small. In this specification, D means the inner diameter of the barrel. For example, when the thickness of the kneading disc A is expressed as 0.05D, this means that the thickness is 0.05 times the inner diameter of the barrel.

[0023] The length of the kneading zone is preferably 0.5D to 10.0D, more preferably 1.0D to 9.0D, and even more preferably 1.5D to 8.0D. When the length of the kneading zone is 0.5D to 10.0D, the thermoplastic resin and the carbon black can be sufficiently kneaded, and the length of the screw is not excessively long, making it easy to secure other zones. Note that, as long as the total length of the zones is 0.5D to 10.0D, the kneading zone may exist alone or may be divided into a plurality of zones.

[0024] The kneading disc A may be any of a forward kneading disc, a reverse kneading disc, and an orthogonal kneading disc, but from the viewpoints of residence time and heat generation, a forward kneading disc is preferred.

[0025] A preferred specific example of the kneading disc A is shown below, but as long as the maximum value of the distance between the tip of the kneading disc and the inner wall of the barrel is within a predetermined range, a disc different from the example shown below may be used. The kneading discs below may be used alone or in combination. In the following, the distance between the tip of the kneading disc and the opposing position of the tip of the kneading disc on the inner wall of the barrel is expressed as "the distance between the tip and the inner wall of the barrel". The same expression is used in the description of the kneading disc B and other discs described below. (1) A 0.5D (disk thickness 0.1D x 5 pieces, offset angle 45°) progressive two-row kneading disk element with a distance of 3.0 mm on either side between the tip and the barrel inner wall (2) A 0.5D (disk thickness 0.2D x 5 pieces, offset angle 45°) progressive two-row kneading disk element with a distance of 3.0 mm on either side between the tip and the barrel inner wall (3) A 0.5D (disk thickness 0.2D x 5 pieces, offset angle 45°) progressive two-row kneading disc shoulder element with a tip-to-barrel inner wall distance of 0.4 mm and 4.0 mm on each side. (4) A 0.5D (disk thickness 0.2D x 5, offset angle 45°) progressive three-row eccentric element with distances between the tip and the barrel inner wall of 0.4 mm, 4.0 mm, and 4.0 mm on each side.

[0026] In this embodiment, from the viewpoint of improving the dispersibility of carbon black, the screw rotation speed is preferably 250 to 600 rpm, and more preferably 270 to 580 rpm. From the same viewpoint, the inner diameter of the barrel is preferably 40 to 85 mm, and more preferably 45 to 80 mm. In particular, when the inner diameter of the barrel is 85 mm or less, the shear rate does not increase excessively, and re-agglomeration can be prevented.

[0027] In this embodiment, it is preferable to further include a step of pre-kneading the thermoplastic resin and the carbon black before the step of melt-kneading the thermoplastic resin and the carbon black. In other words, as shown in FIG. 1, it is preferable to provide a pre-kneading zone on the upstream side of the kneading zone. In the pre-kneading step, it is preferable to melt-knead the thermoplastic resin and the carbon black using a pair of screws in which kneading disks having a thickness of 0.05D to 0.3D are attached to have a length of 0.5D to 5.0D. By including the pre-kneading step, as described above, the thermoplastic resin in a molten or unmelted state and the carbon black are actively brought into contact (wet) with each other before the kneading of the molten resin and the carbon black in the kneading zone, and the aggregation of the carbon black can be suppressed.

[0028] The thickness of the kneading disc B used in the preliminary kneading zone is preferably 0.05D to 0.3D, and more preferably 0.1D to 0.2D. When the thickness of the kneading disc B is 0.05D to 0.3D, the strength and durability are sufficient, and the thermoplastic resin in a molten or unmolten state can be actively brought into contact (wet) with the carbon black. In addition, the load on the screw is small.

[0029] The length of the preliminary kneading zone is preferably 0.5 D to 5.0 D, more preferably 1.0 D to 4.0 D. When the length of the preliminary kneading zone is 0.5 D to 5.0 D, wetting is sufficient, the length of the screw is not excessively long, and other zones can be easily secured.

[0030] The shape of the kneading disc B used in the preliminary kneading zone is not particularly limited, and may be any of a kneading disc, a shoulder cut kneading disc, and an eccentric kneading disc.

[0031] The maximum value of the distance between the tip of the kneading disc B and the position facing the tip of the kneading disc B on the inner wall of the barrel is the same as that of the kneading disc A used in the kneading zone. In other words, from the viewpoint of suppressing shear heat generation, the maximum value of the distance is preferably 0.5 to 5.0 mm. However, the distance is not particularly limited as long as it is in the range of 0.1 to 5.0 mm.

[0032] The kneading disc B may be any of a forward kneading disc, a reverse kneading disc, and an orthogonal kneading disc, but from the viewpoints of residence time and heat generation, a forward kneading disc is preferred. A preferred specific example of kneading disc B is one having a length of 3.0D, using six sets of 0.5D (0.1D x 5 discs, offset angle 45°) progressive kneading discs with a distance between the tip and the inner wall of the barrel of 0.4 mm on either side.

[0033] Hereinafter, each component used in the method for producing the thermoplastic resin composition of the present embodiment will be described.

[0034] [Thermoplastic resin] Examples of the thermoplastic resin according to this embodiment include polybutylene terephthalate resin (hereinafter, also referred to as "PBT resin"), liquid crystal resin, polyacetal resin, polyethylene terephthalate resin, polyamide resin, polycarbonate resin, polytrimethylene terephthalate resin, etc., and this embodiment is particularly useful for PBT resin. Below, the description will be given taking PBT resin as an example, but this embodiment is not limited thereto.

[0035] (Polybutylene terephthalate resin) PBT resin is a resin obtained by polycondensation of a dicarboxylic acid component containing at least terephthalic acid or its ester-forming derivative (C1-6 alkyl ester, acid halide, etc.) and a glycol component containing at least alkylene glycol having 4 carbon atoms (1,4-butanediol) or its ester-forming derivative (acetylated product, etc.). The PBT resin is not limited to polybutylene terephthalate, but may be a copolymer containing 60 mol % or more (particularly 75 mol % to 95 mol %) of butylene terephthalate units.

[0036] The amount of terminal carboxyl groups in the PBT resin is not particularly limited as long as it does not impair the effects of the thermoplastic resin according to this embodiment. The amount of terminal carboxyl groups in the PBT resin is preferably 30 meq / kg or less, and more preferably 25 meq / kg or less.

[0037] The intrinsic viscosity of the PBT resin is preferably 0.65 to 1.20 dL / g. When a PBT resin having an intrinsic viscosity in this range is used, the resulting resin composition is particularly excellent in mechanical properties and fluidity. Conversely, if the intrinsic viscosity is less than 0.65 dL / g, excellent mechanical properties cannot be obtained, and if it exceeds 1.20 dL / g, excellent fluidity may not be obtained. In addition, the intrinsic viscosity of the PBT resin having the above range can be adjusted by blending PBT resins having different intrinsic viscosities. For example, a PBT resin having an intrinsic viscosity of 0.8 dL / g can be prepared by blending a PBT resin having an intrinsic viscosity of 0.9 dL / g with a PBT resin having an intrinsic viscosity of 0.7 dL / g. The intrinsic viscosity of the PBT resin in this specification is a value measured in o-chlorophenol at a temperature of 35°C.

[0038] In the PBT resin, examples of dicarboxylic acid components (comonomer components) that can be used in combination with terephthalic acid and its ester-forming derivatives include C8-14 aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-dicarboxydiphenyl ether; C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; C5-10 cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; and ester-forming derivatives of these dicarboxylic acid components (C1-6 alkyl ester derivatives, acid halides, etc.). These dicarboxylic acid components can be used alone or in combination of two or more.

[0039] Among these dicarboxylic acid components, C8-12 aromatic dicarboxylic acids such as isophthalic acid, and C6-12 alkanedicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid are more preferred.

[0040] In the PBT resin, examples of glycol components (comonomer components) that can be used in combination with 1,4-butanediol include C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl; C2-4 alkylene oxide adducts of bisphenol A, such as 2-mol ethylene oxide adducts of bisphenol A and 3-mol propylene oxide adducts of bisphenol A; and ester-forming derivatives of these glycols (acetylated products, etc.). These glycol components can be used alone or in combination of two or more.

[0041] Among these glycol components, C2-6 alkylene glycols such as ethylene glycol and trimethylene glycol, polyoxyalkylene glycols such as diethylene glycol, and alicyclic diols such as cyclohexanedimethanol are more preferred.

[0042] Examples of comonomer components that can be used in addition to the dicarboxylic acid component and the glycol component include aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-carboxy-4'-hydroxybiphenyl, etc.; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; C3-12 lactones such as propiolactone, butyrolactone, valerolactone, caprolactone (ε-caprolactone, etc.); and ester-forming derivatives of these comonomer components (C1-6 alkyl ester derivatives, acid halides, acetylated products, etc.).

[0043] [Carbon black] The carbon black is not limited in type, raw material, or production method, and any of furnace black, channel black, acetylene black, ketjen black, etc. can be used.

[0044] Carbon black is blended to color the thermoplastic resin composition black. In general, the larger the primary particle size of carbon black, the lower the jet blackness corresponding to the blending amount, and the lower the insulation performance corresponding to the jet blackness. However, in the present embodiment, the number of carbon black agglomerates can be significantly reduced, and the carbon black can be well dispersed. Therefore, even if the blending amount of carbon black is small, the thermoplastic resin composition can be colored with sufficient jet blackness.

[0045] As described above, in this embodiment, even carbon black with a small primary particle size can be dispersed well. For example, even carbon black with a primary particle size of 10 to 60 nm can be dispersed well. Therefore, sufficient jet blackness can be obtained even with a small blending amount. In addition, since the amount of carbon black is small, adverse effects on thermoplastic resins and deterioration of insulating properties can be suppressed. In the present embodiment, the primary particle size of carbon black is an average value determined by measuring the particle sizes of 3,000 unit particles from an acquired enlarged image in accordance with the ASTM D3849 standard.

[0046] In this embodiment, the amount of carbon black to be blended with respect to 100 parts by mass of the thermoplastic resin can be appropriately set depending on the desired jet blackness, etc., but is preferably, for example, 10 to 200 parts by mass, and more preferably 5 to 40 parts by mass.

[0047] In addition, in this embodiment, the nitrogen adsorption specific surface area (NSA) of the carbon black is not particularly limited, but is preferably 50 to 600 m 2 / g. The nitrogen adsorption specific surface area of ​​carbon black is the specific surface area calculated by the S-BET equation from the nitrogen adsorption amount in JIS K6217. In general, the smaller the particle size, the larger the specific surface area. The DBP (dibutyl phthalate) absorption amount of carbon black is not particularly limited, but is preferably 45 to 200 cm 2 / 100g is preferred. The DBP absorption of carbon black is the amount of dibutyl phthalate absorbed by 100g of carbon black, and is a value measured according to the method described in JIS K6221. In general, the more developed the structure, which is the aggregated constituent of the primary particles of carbon black, the greater the DBP absorption. Furthermore, the amount of volatilization of carbon black is not particularly limited, but is preferably 7% or less. The amount of volatilization of carbon black is the amount of volatilization (weight loss) (the ratio of the mass of volatile matter to the original mass) when carbon black is heated at 950°C for 7 minutes. In general, the more surface functional groups there are, the more volatile matter there is.

[0048] [Other ingredients] In the present embodiment, one or more types of general additives for thermoplastic resins, such as a lubricant, a release agent, an antistatic agent, a surfactant, a flame retardant, an organic polymer material, or an inorganic or organic fibrous, powdery, or plate-like filler, may be added as necessary. EXAMPLES

[0049] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0050] [Examples 1 to 18, Comparative Examples 1 to 2] In each of the Examples and Comparative Examples, 100 parts by mass of polybutylene terephthalate resin and 28 parts by mass of carbon black (A or B) were melt-kneaded under the following extrusion conditions using the twin-screw extruder shown in Figure 1 to obtain a pellet-shaped composition. The polybutylene terephthalate resin was supplied from a first supply port 14, and the carbon black was supplied from a second supply port 18. Details of each component used are as follows. (1) Polybutylene terephthalate resin Polyplastics Co., Ltd., PBT resin (intrinsic viscosity (measured in o-chlorophenol at 35°C): 0.88 dL / g) (2) Carbon black Carbon black A: Mitsubishi Chemical Corporation, #750B (particle size: 22 nm) Carbon black B: Mitsubishi Chemical Corporation, #10 (particle size: 75 nm)

[0051] (Extrusion conditions) Cylinder temperature: 260℃ Barrel diameter: In each of the Examples and Comparative Examples, the following twin-screw extruders with different barrel diameters were used. 32mm Model number: TEX30αII, manufactured by Japan Steel Works, Ltd. 47mm Model number: TEX44αII, manufactured by Japan Steel Works, Ltd. 58mm Model number: TEX54αII, manufactured by Japan Steel Works, Ltd. 69mm Model number: TEX65αII, manufactured by Japan Steel Works, Ltd. 82.5mm Model number: TEX77HCT, manufactured by Japan Steel Works, Ltd. ·Kneading disc A (kneading zone) Kneading disc A1: 2-row kneading disc Shape: The distance between the tip and the barrel inner wall was equal to each other, and the maximum distance between the tip and the barrel inner wall on one side (shown as "maximum clearance" in Table 1) was as shown in Table 1. Four sets of 0.5D (0.1D x 5 pieces, offset angle 45°) progressive kneading elements were used to create a length of 2.0D. Kneading disc A2: Eccentric 3-groove kneading disc Shape: Four sets of 0.5D (disk thickness 0.2D x 5 pieces, offset angle 45°) progressive three-row eccentric elements with distances between the tip and the barrel inner wall of 0.4 mm, 4.0 mm, and 4.0 mm, respectively, were used to create a length of 4.0. · Kneading disc B (pre-kneading zone) Kneading disc B: Kneading disc Shape: Six sets of 0.5D (0.1D x 5 pieces, offset angle 45°) progressive kneading elements with a gap of 0.4 mm at the tip on one side were used to create a length of 3.0D.

[0052] [Table 1]

[0053] [Table 2]

[0054] [Table 3]

[0055] [evaluation] (1) Dispersion degree of carbon black In each of the Examples and Comparative Examples, 40 g of the obtained pellet-like composition was mixed with 2,000 g of polybutylene terephthalate resin, and extrusion was performed using a twin-screw extruder with one vent port and a barrel diameter of 30 mm equipped with a 300-mesh screen mesh at the discharge section under the conditions of L / D=35, extrusion temperature of 260°C, screw rotation speed of 160 rpm, vent vacuum degree of -700 mmHg, and discharge rate of 18 kg / hr. After completion of the extrusion operation, the screen mesh was removed and the adhering resin was removed. Next, the 300-mesh screen mesh was observed using a microscope, and it was found that the 14 cm 2 The number of aggregates in each area was counted and the aggregates were classified and evaluated according to the following criteria A to D. The evaluation results are shown in Tables 1 to 3. A: Less than 20 aggregates B: 20 ​​to less than 80 aggregates C: 80 to less than 100 aggregates D: 100 or more aggregates

[0056] (2) Jet blackness (L value) The pellet-shaped compositions obtained in Examples 14 and 16 were mixed in an amount of 10 parts by mass per 100 parts by mass of PBT resin pellets, and a flat plate-shaped test piece measuring 50 mm in length, 90 mm in width, and 2 mm in thickness was injection molded using an injection molding machine (manufactured by Japan Steel Works, Ltd., J55AD). The lightness (L value) of the molded test piece was measured using a Spectrophotometer SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd. The smaller the L value, the higher the jet blackness, which indicates good coloring when the purpose is black coloring.

[0057] From Tables 1 and 2, it can be seen that carbon black could be dispersed well in all of Examples 1 to 18. In particular, the dispersibility was extremely good in Examples 17 and 18, in which preliminary kneading was performed. Furthermore, when comparing the jet blackness of Examples 14 and 16, Example 14, which used carbon black with a smaller primary particle size, had a higher jet blackness. From these results, it can be seen that when a high jet blackness is required in proportion to the carbon black concentration, it is preferable that the primary particle size of the carbon black is smaller.

Claims

1. A method for producing a thermoplastic resin, comprising: melt-kneading a thermoplastic resin and carbon black using a twin-screw extruder having a pair of screws with kneading discs attached thereto in a barrel, The maximum distance between the tip of the kneading disc and the opposing position of the tip of the kneading disc on the inner wall of the barrel is 1.0 to 5.0 mm; The method for producing a thermoplastic resin composition, wherein the kneading disc is a progressive kneading disc.

2. The method for producing a thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is a polybutylene terephthalate resin.

3. The method for producing a thermoplastic resin composition according to claim 1 or 2, wherein the screw rotation speed of the twin-screw extruder is 250 to 600 rpm, and the inner diameter of the barrel is 40 to 85 mm.

4. The method for producing a thermoplastic resin composition according to any one of claims 1 to 3, wherein the carbon black has a primary particle size of 10 to 60 nm.

5. The method further includes a step of pre-kneading the thermoplastic resin and the carbon black before a step of melt-kneading the thermoplastic resin and the carbon black, The method for producing a thermoplastic resin composition according to any one of claims 1 to 4, wherein in the pre-kneading step, the thermoplastic resin and the carbon black are melt-kneaded using a pair of screws having kneading discs with a thickness of 0.05D to 0.3D attached to the pair of screws so as to have a length of 0.5D to 5.0D.

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