JP2018161860A - Production method of pellets of thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a pellet of a thermoplastic resin composition in which resin deterioration (brown streak) is suppressed while maintaining dispersibility of a filler component and strength thereof in a high level even at high output.SOLUTION: There is provided a method that comprises melt-kneading of a thermoplastic resin composition containing at least a thermoplastic resin using a twin-screw extruder, and when a pellet is produced, the twin-screw extruder has a die head having a mouth ring, a screw and a screw head, and the screw head has a cylindrical portion, and melt-kneading is performed so as to satisfy the following formula (1) and formula (2): Q>0.045Dformula (1); S/D<1.35 formula (2). In the formula, Q represents an amount of output (kg/h), D represents a screw outer diameter (diameter; mm), and S represents a contact area (mm) between the cylindrical portion and the resin composition.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing pellets of a thermoplastic resin composition.

  Engineering plastics with a high melting point are obtained by kneading with various additives and inorganic fillers at a high melt kneading temperature using a twin-screw extruder to prepare the thermoplastic resin composition. .

  A method for producing pellets of a thermoplastic resin composition containing an engineering plastic generally uses a twin-screw extruder having the configuration illustrated in FIG. 1, and a filler such as a thermoplastic resin, an additive, or an inorganic filler. From a hopper, kneaded and melted with a biaxial screw in a cylinder, deformed the cross-sectional shape of the flow path through which the kneaded material passes by a die head, and a plurality of thermoplastic resin composition strands from a die having a plurality of discharge holes A step of extruding, cooling and granulating.

  The optimum melt-kneading temperature differs depending on the type of thermoplastic resin, the blending ratio of the filler, etc., but if the temperature is too high, there will be insufficient kneading due to resin deterioration or viscosity reduction, and if the temperature is too low, the viscosity will increase and the resin will increase. The reduction in the reactivity of the filler, the decrease in strength due to the breakage of the fibrous filler, and the decrease in the discharge amount due to overload on the apparatus are problems, so the optimum temperature range is narrow.

  In recent years, twin screw extruders have been able to deepen the screw groove by improving the torque strength of the screw, and even smaller twin screw extruders have been able to deliver the same amount of discharge as conventional large extruders. For this reason, miniaturization of the twin screw extruder is progressing from the viewpoint of space saving and cost reduction. However, when trying to carry out a high discharge amount of melt kneading with a small twin-screw extruder, the residence time in the extruder is reduced compared to when melting and kneading with the same discharge amount with a large twin-screw extruder. For this reason, it is important to more efficiently disperse and react the filler by controlling the melt kneading temperature of the resin more precisely in order to carry out melt kneading at a high discharge rate with a small twin screw extruder. It is coming.

  When pellets of thermoplastic resin composition are produced at a high discharge rate, it is thought that thermal degradation of the molten resin occurs in the process of deforming the cross-sectional shape of the flow path through which the kneaded material passes from the die head toward the discharge hole of the die. . As a result, colored pellets (tea stripe pellets) are generated, and a decrease in yield is a problem. For this reason, it is unavoidable to deal with the processing of sorting the tea streak pellets as a defective product, or to reduce the discharge amount, and the productivity of manufacturing the thermoplastic resin composition is reduced.

  Conventionally, an extrusion technology that suppresses the deterioration of the molten resin in the flow path from the die head to the die discharge hole by changing the shape of the screw head attached to the screw tip for fixing the screw element of the twin screw extruder Proposed.

  For example, in Patent Document 1, in order to suppress resin stagnation in the die head portion, the screw head shape is elliptical, a roof shape that is inclined from the major axis to the minor axis direction is formed, and the major axes of the screw heads are perpendicular to each other. It is assembled to form.

  Further, in Patent Document 2, in order to reduce local friction inside the die head, a plurality of blades are protruded from the screw head at intervals in the circumferential direction and installed so as to be close to the inner surface of the die head.

  Furthermore, in Patent Document 3, in order to prevent stagnation deterioration and to heat a uniform resin composition, a taper portion gradually expanded from the screw diameter of the kneading portion toward the tip and a barrel inner diameter on the tip side from the taper portion. A screw head constituted by a parallel portion having a constant gap is attached.

JP-A-55-57444 Japanese Patent Laid-Open No. 9-76326 JP-A-9-85804

  However, the screw heads described in Patent Documents 1, 2, and 3 are not general shapes and have a high degree of processing difficulty. Among them, the screw heads described in Patent Documents 1 and 2 require phase alignment of a pair of screw heads for assembly, and the assembly is not easy. Further, at the time of shape change due to wear of the screw head, which becomes a problem particularly in continuous production with high discharge, there is no fear of breakage due to a decrease in mechanical strength and the intended effect of suppressing resin deterioration. The screw head described in Patent Document 3 is effective in suppressing the retention of the resin composition in the extruder, but by increasing the diameter of the screw head, more severe shearing is applied under high discharge conditions, Deterioration is accelerated.

  On the other hand, as a manufacturing condition of the pellets of the thermoplastic resin composition, it is conceivable to suppress deterioration of the molten resin by reducing the screw rotation speed and the cylinder temperature. However, when melt-kneading a high discharge amount with a small twin-screw extruder, the reduction in screw rotation speed is a problem of undispersed filler components (for example, glass fibers), and the reduction in cylinder temperature The decrease in strength due to a decrease in reactivity is a problem. For this reason, it has been very difficult to suppress resin deterioration (tea stripes) while maintaining the dispersibility and strength of the filler component at a high level at a high discharge rate.

  The purpose of the present invention is to suppress resin deterioration (tea stripes) while maintaining a high level of dispersibility and strength of the filler component even when performing high-discharge-rate melt kneading with a small twin-screw extruder. It is providing the manufacturing method of the pellet of the thermoplastic resin composition which has the outstanding quality.

The manufacturing method of the pellet of the thermoplastic resin composition of this invention which solves the said subject consists of the structure of (1)-(8) below. (1) A method of producing a pellet of a thermoplastic resin composition by melt-kneading a thermoplastic resin composition containing at least a thermoplastic resin using a twin screw extruder, wherein the twin screw extruder is a die head, A screw and a screw head attached to the tip of the screw; the die head has a base; the screw head has a cylindrical portion; and the following expressions (1) and (2) are satisfied: A method for producing pellets of a thermoplastic resin composition, which is melt-kneaded as described above.
Q> 0.045D ^2.3 (1) Formula S / D ² <1.35 (2) Formula where Q is the discharge amount (kg / h) of the thermoplastic resin composition, D Represents an outer diameter of the screw (diameter: mm), and S represents a contact area (mm ² ) between the cylindrical portion and the resin composition.
(2) The method for producing pellets of the thermoplastic resin composition according to (1), further melt-kneaded so as to satisfy the following expression (3).
S / D ² <1.10 (3) where D represents the screw outer diameter (diameter; mm), and S represents the contact area (mm ² ) between the cylindrical portion and the resin composition.
(3) The manufacturing method of the pellet of the thermoplastic resin composition as described in said (1) or (2) whose melting | fusing point of the said thermoplastic resin is 200 degreeC or more.
(4) The method for producing pellets of the thermoplastic resin composition according to any one of (1) to (3), wherein the thermoplastic resin is polyamide.
(5) The method for producing pellets of the thermoplastic resin composition according to any one of (1) to (4), wherein the thermoplastic resin composition further contains an inorganic filler.
(6) The manufacturing method of the pellet of the thermoplastic resin composition as described in said (5) whose said inorganic filler is glass fiber.
(7) The method for producing pellets of the thermoplastic resin composition according to (5) or (6), wherein the content of the inorganic filler is 80 parts by weight or more with respect to 100 parts by weight of the thermoplastic resin.
(8) The base has a plurality of discharge holes, and the difference between the temperature Tc of the thermoplastic resin composition discharged from each discharge hole and the melting point Tm of the thermoplastic resin (Tc) in all the discharge holes. -Tm) is the manufacturing method of the pellet of the thermoplastic resin composition in any one of said (1)-(7) whose are 35 degreeC or more and 55 degrees C or less.

  According to the method for producing a pellet of the thermoplastic resin composition of the present invention, by reducing the contact area between the screw head and the thermoplastic resin composition, it is melt kneaded at a high discharge rate using a small twin screw extruder. Even so, it is possible to reduce resin deterioration (the number of tea streak pellets) while maintaining the dispersibility and strength of the filler component.

It is the schematic which shows the cross section of an example of embodiment of the twin-screw extruder used for the manufacturing method of this invention. It is the (A) top view and (B) side view of the discharge part in the twin-screw extruder of FIG. It is a graph which shows the discharge temperature distribution of the thermoplastic resin composition in the manufacturing method of an Example and a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a twin-screw extruder suitably used in the method for producing pellets of the thermoplastic resin composition of the present invention. This twin-screw extruder includes a raw material supply unit (a), a melt kneading unit (b), and a discharge unit (c).

  FIG. 2 is a schematic cross-sectional view showing an example of an embodiment of the discharge section (c), where (A) is a top view and (B) is a side view.

  The raw material supply unit (a) is composed of at least one pair of feeders and hoppers, and has a function of supplying raw materials such as thermoplastic resin, inorganic filler, and other compounding agents from the upper part and / or the side part of the twin screw extruder. Have. In addition, the raw material is supplied from the main input port arranged on the most upstream side (driving machine side) of the twin-screw extruder and / or the side port arranged at an arbitrary position between the upstream and downstream of the twin-screw extruder. be able to. The form of the raw material may be either solid or liquid. The feeder may be any of a capacity type and a weight measurement type, and may be any of a single-screw type, a bi-axial screw type, a vibration type, a pump type, and a belt type.

  The melt kneading part (b) is constituted by a cylinder (d) and a screw (e), and two screws (e) are accommodated in a space inside the cylinder (d) arranged in parallel to the machine direction, Connected to the drive. The two screws (e) rotate in the same direction or different directions from each other with their respective axis centers as rotational axes. As the screw (e) rotates, the raw material charged into the raw material supply unit (a) receives heat while being conveyed toward the discharge unit (c), and the raw material resin melts, is distributed, dispersed, and kneaded. . The cylinder (d) is configured by arranging a plurality of barrels side by side, performs temperature control for each barrel, and can determine the presence or absence of a raw material inlet and a deaeration port. The screw (e) is composed of a plurality of screw elements, and arbitrary elements such as full flight, kneading disk, and mixing can be combined. Further, the twisting direction of each element may be any of the forward direction, the neutral direction, and the reverse direction with respect to the flow direction of the kneaded material. Further, the element cross section may be either a two-row shape or a three-row shape, may be either a meshing type or a non-meshing type, may be either a deep groove type or a shallow groove type, or a combination thereof. A set of screws is assembled by combining a plurality of elements on each screw shaft, fitting them in an arbitrary form, and fitting and fixing a screw head (h) to the tip of the screw shaft. In the present specification, the upstream side from the screw head (h) from the drive side end of the screw (e) is referred to as a melt kneading part (b).

  The discharge part (c) consists of a die head (f) for extruding the melt-kneaded product obtained in the melt-kneading part (b) in a predetermined shape outside the machine, and a screw head (h) inside Have. FIG. 2 shows that the melt-kneaded product obtained in the melt-kneading part (b) passes through a plurality of discharge holes arranged in a long rectangular region of the die head (f) and the base (g) at the tip thereof, The apparatus structure which extrudes as a strand is illustrated. The extruded strand is cooled by an arbitrary method and cut with a strand cutter to produce pellets. The example of FIG. 2 describes a base (g) in which a plurality of discharge holes are arranged in a long rectangular region, but the arrangement of the plurality of discharge holes in the base (g) is not limited to this, You may arrange | position on the circumference | surroundings of the top or several concentric circles. Further, immediately after the melt-kneaded product is extruded from the discharge hole, it may be cut by hot cutting, underwater cutting, etc., and cooled to a pellet shape.

  The twin-screw extruder used in the production method of the present invention has at least a die head (f), a screw (e), and a screw head (h) attached to the tip of the screw. The die head (f) has a base (g), and the screw head (h) has a cylindrical portion. The cylindrical part is not particularly limited except that the center line of the cylinder overlaps with the extension line of the axial center of the screw (e), and constitutes an arbitrary part of the screw head (h). To do. The outer diameter (diameter) of the cylindrical portion is preferably substantially the same as or different from the inscribed circle at the groove bottom of the screw (e).

  The shape of the screw head (h) in the present invention is characterized by having a cylindrical portion that does not affect the molten resin temperature even if the shape changes due to friction, and that is easy to process and easy to assemble. . The shape other than the cylindrical portion of the screw head (h) is not particularly limited. Further, the die head (f) may have a space around the screw head wider than the cylinder inner diameter in order to reduce the pressure in the die head.

  The material of the screw head (h) preferably has an HRC hardness of 50 or more in order to prevent a shape change due to wear, and may be subjected to a surface treatment such as chrome plating or titanium nitride coating.

As a result of research, the inventors of the present invention have brown stripes when the temperature of the resin discharged from the discharge holes existing on the extension line of the screw head (h) is higher than the temperature of the resin discharged from the other discharge holes. It has been found that there is a correlation that the amount of pellets increases, and that the amount of pellets having brown stripes increases when the maximum value of the resin temperature discharged from all the discharge holes is high. And in the kneading conditions of the high discharge amount satisfying the following formula (1), the melt kneading temperature is not lowered by satisfying the requirement of the following formula (2), more preferably satisfying the requirement of the formula (3). It has been found that while ensuring excellent kneading performance, the maximum value of the discharged resin temperature is reduced and the amount of pellets having tea streaks is greatly reduced.
Q> 0.045D ^2.3 (1) Formula S / D ² <1.35 (2) Formula S / D ² <1.10 (3) where Q is The discharge amount (kg / h) of the thermoplastic resin composition, D is the screw outer diameter (diameter: mm), and S is the contact area (mm ² ) between the cylindrical portion and the resin composition.

  The manufacturing method of the present invention satisfies the formula (1), and has a tea streak in which a discharge amount Q (kg / h) is manufactured at a high discharge amount with respect to the screw outer diameter D (mm). This is to solve the problem under the condition where the occurrence of the problem is likely to occur. Generally, a twin screw extruder is capable of a higher discharge amount as the screw outer diameter D (mm) of the extruder is larger. In the present invention, the pressure in the twin-screw extruder is increased by producing pellets with a high discharge amount with respect to the screw outer diameter so that the discharge amount Q (kg / h) satisfies the formula (1). As a result, a large shear is applied to the molten resin, and the molten resin temperature increases. Further, in order to extrude a large amount of molten resin, it is necessary to increase the screw rotation speed. If the screw rotation speed is increased, the shearing resin temperature further rises and the molten resin temperature further rises. Therefore, the above equation (1) is satisfied. In the production of pellets at a high discharge rate, resin degradation (tea stripes) is likely to occur. In the present invention, even when the pellets are produced at a high discharge rate, the deterioration of the resin can be prevented or greatly reduced by satisfying the formula (2).

  As a result of research, when the thermoplastic resin composition comes into contact with the cylindrical portion of the screw head (h), the resin temperature tends to increase locally, and the contact area between the cylindrical portion of the screw head (h) and the thermoplastic resin composition It was found that the larger the (S), the higher the temperature of the resin discharged from the discharge holes existing on the extension line of the screw head (h) than the temperature of the resin discharged from the other discharge holes. Furthermore, it has been found that there is a correlation between the maximum value of the resin temperature discharged from all the discharge holes and the amount of tea streaks.

The relationship between the cylindrical portion of the screw head (h) and the contact area S of the thermoplastic resin composition with respect to the screw outer diameter D requires that S / D ² is 1.35 or less, preferably 1 .10 or less. By the S / D ² to 1.35, and optimizing the temperature of the resin discharged from the discharge hole, it is possible to reduce the temperature distribution. However, in order to maintain the mechanical strength, it is preferable S / ^{D 2} is at least 0.30. The contact area S between the cylindrical portion and the thermoplastic resin composition is that the molten resin is extruded from the die by applying pressure, so the thermoplastic resin composition is densely filled from the die head to the periphery of the screw head. The area of the outer peripheral surface can be defined as the contact area S with the thermoplastic resin composition, and can be calculated by the outer peripheral length of the cylindrical portion × the cylindrical length. Normally, the characteristics of the twin screw extruder, because it is similar in shape to the square D ² of the screw outer diameter D, by normalizing the contact area S in square D ² of the screw outer diameter, a different screw outer diameter D It is applicable also to the twin-screw extruder which has.

  The production method of the present invention is preferably used for a thermoplastic resin composition containing a thermoplastic resin having a high melting point where the melting point of the thermoplastic resin is 200 ° C. or higher and tea streaks that require kneading at a high temperature are likely to occur. Can do. As the thermoplastic resin, for example, polyamide (nylon 6, nylon 66, nylon 610, nylon 9T, nylon 10T, etc.), polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyphenylene ether, polyether ether ketone, liquid crystal plastic, etc. are used. Can do. Of these, a more suitable thermoplastic resin is a polyamide that easily generates tea stripes.

  When an inorganic filler is blended in the thermoplastic resin composition, the viscosity becomes high, so that shear heat generation becomes large and resin degradation is likely to occur, but it is preferable because the mechanical strength of the thermoplastic resin composition can be improved. . When manufacturing the thermoplastic resin composition containing an inorganic filler, generation | occurrence | production of the pellet which has a tea streak can be suppressed by using the manufacturing method of this invention.

  As the inorganic filler that can be used in the present invention, those usually used as an inorganic filler of a thermoplastic resin composition can be used. Examples of inorganic fillers include glass fiber, carbon fiber, asbestos fiber, graphite fiber, metal fiber, potassium titanate whisker, aluminum borate whisker, magnesium whisker, silicon whisker, slag fiber, gypsum fiber, silica fiber, and silica alumina. Fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber and boron fiber, etc. Site, feldspar powder, talc, calcium carbonate, lithium carbonate, magnesium hydroxide, kaolin, zeolite (including synthetic zeolite), talc, mica, synthetic mica and wollastonite (including synthetic wollastonite), glass fiber Silicate minerals such as ceramics, glass beads, hydrotalcite and silica, silicate minerals and various minerals, such as plate, needle, and granular inorganic fillers that have been pulverized by processing such as grinding. Two or more inorganic fillers may be blended. Among these, glass fiber is preferable as the inorganic filler to be used. The production method of the present invention is suitable for producing pellets of a thermoplastic resin composition having a high viscosity, in which an inorganic filler is preferably blended in an amount of 80 parts by weight or more with respect to 100 parts by weight of the thermoplastic resin.

  About additives, plasticizer, mold release agent, coupling agent, crystal nucleus material, antioxidant, light stabilizer, ultraviolet absorber, epoxy resin, silane coupling agent, hydrous magnesium silicate, PEEK resin, PTFE resin, Examples thereof include graphite, raw carbon, stearates, phosphate esters, and iron oxide.

  In the present invention, the difference between the temperature Tc of the thermoplastic resin composition discharged from each discharge hole and the melting point Tm of the thermoplastic resin contained in the thermoplastic resin composition (Tc−Tm) in all the discharge holes. Is preferably 35 ° C. or higher and 55 ° C. or lower. If the difference (Tc−Tm) between the temperature Tc and the melting point Tm of the thermoplastic resin composition is less than 35 ° C., strength reduction due to a decrease in the reactivity of the filler due to a decrease in viscosity and an overload on the extruder become a problem. When (Tc−Tm) exceeds 55 ° C., poor dispersion of the filler and resin degradation become a problem.

  Next, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples.

  The thermoplastic resin composition containing the thermoplastic resin and the inorganic filler was manufactured using a twin screw extruder, and the shape of the screw head and the kneading conditions were varied to produce pellets of the thermoplastic resin composition. About the obtained pellet, the presence or absence of the pellet which has a tea streak, the dispersion state of an inorganic filler (glass fiber), and the mechanical characteristic of a molded article were evaluated.

  The composition of the thermoplastic resin composition is nylon 66 (E3001 (melting point: 265 ° C.) manufactured by Toray Industries, Inc.) as a thermoplastic resin, and glass fiber (T-253 (length: 3 mm, manufactured by Nippon Electric Glass Co., Ltd.) as an inorganic filler. Chopped strands having a fiber diameter of 13 μm)), and 82 parts by weight of the inorganic filler with respect to 100 parts by weight of the thermoplastic resin, and the discharge amount Q (kg / h) described in Table 1 In addition, the supply amount of the thermoplastic resin from the main feeder and the supply amount of the inorganic filler from the side feeder were respectively determined.

The twin screw extruder used is as follows.
Twin screw extruder: Toshiba Machine twin screw extruder TEM75-SS Screw length (L); 3000 mm
Screw outer diameter (D); 75mm
Position of main feeder; upper part of barrel of L / D = 0 to 10 Side feeder position; side of barrel of L / D = 50 to 60 When melt kneading with this twin-screw extruder, the above formula (1) The value on the right side is 0.045D ^2.3 = 924, and when the discharge amount Q is larger than 924 (kg / h), the relationship of the expression (1) is satisfied.

Moreover, the screw head which has a cylindrical part was attached to the front-end | tip of a screw, and the shape of the cylindrical part was varied as follows.
Screw head A: cylinder part length is 20.0 mm, cylinder part diameter is 48.0 mm, and the contact area between the cylinder part and the resin composition is 3016 mm ² .
Screw head B: cylinder part length is 40.0 mm, cylinder part diameter is 48.0 mm, and the contact area between the cylinder part and the resin composition is 6032 mm ² .
Screw head C: cylinder part length is 50.0 mm, cylinder part diameter is 48.0 mm, and the contact area between the cylinder part and the resin composition is 7540 mm ² .
Screw head D: cylinder part length is 73.5 mm, cylinder part diameter is 48.0 mm, and the contact area between the cylinder part and the resin composition is 11084 mm ² .

  The die head of the twin-screw extruder has a rectangular cross-sectional shape that is elongated in a substantially horizontal direction toward the die, and is extruded from the melt-kneading part (b) with a substantially elliptical cross-sectional shape. In such a manner that the fluid flows while gradually deforming its shape so as to conform to the shape of the die so that it becomes substantially the same. In the die provided in the die head, 57 discharge holes were arranged in a substantially horizontal straight line. In addition, the number of the discharge hole at the left end toward the extruder is set to 1, and numbers 2, 3,..., 57 are sequentially assigned to the right, and the temperature of the molten resin composition extruded from each discharge hole is measured. . The temperature of the molten resin composition was a portable thermography (Ti32 manufactured by Fluke).

  The above-mentioned thermoplastic resin composition is melt-kneaded under the seven types of kneading conditions described in Table 1 (Examples 1 to 3, Comparative Example 1, Reference Examples 1 to 3), and extruded from the discharge holes. The strand of the composition was water-cooled and then cut with a strand cutter to obtain a thermoplastic resin composition pellet as a product. The obtained pellets were evaluated for resin deterioration (tea stripe failure), GF undefibration failure, and Charpy impact strength of the molded product by the following methods.

Evaluation of resin degradation (number of pellets containing tea streaks)
250 g of the obtained pellets were sampled, and the number of pellets containing tea streaks (pieces / 250 g) was visually observed.

Filler dispersibility evaluation (number of GF undefibrated pellets)
250 g of the obtained pellets were sampled, and a thin sheet was formed by hot pressing. The number of pellets (glass pieces / 250 g) in which the glass fibers (GF) in this sheet were not defibrated was visually observed.

Mechanical properties (Charpy impact strength)
The obtained pellets were vacuum-dried at 80 ° C. for 12 hours, and then ISO 179-1 was used under the conditions of a cylinder temperature of 290 ° C. and a mold temperature of 80 ° C. using an injection molding machine (NS60-9A manufactured by Nissei Plastic Industrial Co., Ltd.). ISO test pieces (3 mm thick) conforming to the above were injection molded. Using the obtained ISO test piece), the Charpy impact strength with a notch was measured under the condition of 23 ° C. in accordance with ISO 179-1.

  The evaluation result of the obtained thermoplastic resin composition is shown in result table 1 and FIG.

  In the production examples of Examples 1 to 3 and Comparative Example 1, the discharge rate was 1000 kg / h, and kneading was performed under conditions of a high discharge rate satisfying the expression (1).

Regarding the formula (2), it can be seen that in the production examples of Examples 1 to 3, S / D ² is smaller than 1.35, the number of pellets containing tea streaks is greatly reduced, and S / D ² is 1.10. In the smaller production examples of Examples 1 and 2, it can be seen that pellets containing tea streaks are not generated at all. In contrast, in the production example of Comparative Example 1 S / ^{D 2} is less than 1.35, Brown streaks Enter the number of pellets becomes large as 80/250 g.

  In order to reduce the number of tea streaks, as shown in Reference Example 1, the number of GF undefined pellets increased when the screw rotation speed was reduced. Further, when the cylinder temperature was lowered, the Charpy impact strength was lowered as shown in Reference Example 2. For this reason, as shown in Reference Example 3, there is only means for reducing the discharge amount in order to prevent the dispersion of the filler under the extrusion conditions and the decrease in the strength of the thermoplastic resin composition. In the production example, the production efficiency is low and the production cost is high.

FIG. 3 shows resin temperatures discharged from the discharge holes of Examples 1, 2, and 3 and Comparative Example 1. In the manufacturing example of Comparative Example 1, the resin temperatures of the discharge holes 15 to 24 and 33 to 40 existing on the extension line of the screw head were higher than the resin temperatures of the other discharge holes. In contrast, in the production example of Example 1, 2 and 3, the resin temperature of the discharge hole 15～24,33～40 is lower than that of Preparation of Comparative Example 1, S / ^{D 2} has a smaller screw head It can be seen that the manufacturing example of Example 1 has a lower resin temperature and a smaller temperature distribution width for each discharge hole.

(A): Raw material supply part (b): Melting and kneading part (c): Discharge part (d): Cylinder (e): Screw (f): Die head (g): Die (h): Screw head

Claims (8)

A method of producing a pellet of a thermoplastic resin composition by melt-kneading a thermoplastic resin composition containing at least a thermoplastic resin using a twin screw extruder, wherein the twin screw extruder includes a die head, a screw, and It has a screw head attached to the tip of the screw, the die head has a base, the screw head has a cylindrical portion, and the following formulas (1) and (2) are satisfied: A method for producing pellets of a thermoplastic resin composition, which is melt-kneaded.
Q> 0.045D ^2.3 (1) Formula S / D ² <1.35 (2) where Q is the discharge amount (kg / h) of the thermoplastic resin composition, D Represents an outer diameter of the screw (diameter: mm), and S represents a contact area (mm ² ) between the cylindrical portion and the resin composition. Furthermore, the manufacturing method of the pellet of the thermoplastic resin composition of Claim 1 which melt-kneads so that the following (3) Formula may be satisfy | filled.
S / D ² <1.10 (3) where D represents the screw outer diameter (diameter; mm), and S represents the contact area (mm ² ) between the cylindrical portion and the resin composition.     The manufacturing method of the pellet of the thermoplastic resin composition of Claim 1 or 2 whose melting | fusing point of the said thermoplastic resin is 200 degreeC or more.     The manufacturing method of the pellet of the thermoplastic resin composition in any one of Claims 1-3 whose said thermoplastic resin is polyamide.     The manufacturing method of the pellet of the thermoplastic resin composition in any one of Claims 1-4 in which the said thermoplastic resin composition contains an inorganic filler further.     The manufacturing method of the pellet of the thermoplastic resin composition of Claim 5 whose said inorganic filler is glass fiber.     The manufacturing method of the pellet of the thermoplastic resin composition of Claim 5 or 6 whose content of the said inorganic filler is 80 weight part or more with respect to 100 weight part of said thermoplastic resins.     The base has a plurality of discharge holes, and the difference between the temperature Tc of the thermoplastic resin composition discharged from each discharge hole and the melting point Tm of the thermoplastic resin (Tc−Tm) in all the discharge holes The manufacturing method of the pellet of the thermoplastic resin composition in any one of Claims 1-7 whose is 35 to 55 degreeC.

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