WO2012137666A1

WO2012137666A1 - Process for producing pellets of glass-fiber-reinforced thermoplastic resin composition

Info

Publication number: WO2012137666A1
Application number: PCT/JP2012/058400
Authority: WO
Inventors: 邦紘平田; 石田　大; 元一平郡
Original assignee: ポリプラスチックス株式会社
Priority date: 2011-04-01
Filing date: 2012-03-29
Publication date: 2012-10-11
Also published as: TWI501859B; JP5536705B2; CN103459110A; MY163186A; JP2012213997A; TW201302430A; CN103459110B

Abstract

A process for producing pellets of a glass-fiber-reinforced thermoplastic resin composition is provided with which the productivity of pellets of a glass-fiber-reinforced thermoplastic resin composition can be rendered higher than in conventional processes and it is possible to minimize the probability that monofilament masses (unfibrillated glass-fiber bundles) remain in the produced pellets. In the process, a thermoplastic resin and glass fibers are kneaded with a screw which comprises a screw element having a specific shape, and pellets of a glass-fiber-reinforced thermoplastic resin composition are produced under specific conditions. The screw element having a specific shape is a single-thread back-feed screw element which has a flight part having circular-arc-shaped notches.

Description

Method for producing glass fiber reinforced thermoplastic resin composition pellets

The present invention relates to a method for producing glass fiber reinforced thermoplastic resin composition pellets.

As a method for producing glass fiber reinforced thermoplastic resin composition pellets by mixing and kneading glass fibers with a thermoplastic resin, first, a thermoplastic resin is supplied to an extruder and the thermoplastic resin is melted. Next, glass fibers are supplied to the molten thermoplastic resin, and the thermoplastic resin and glass fibers are mixed and kneaded in an extruder. Finally, a method of cooling and granulating the mixture is common. As the extruder, generally, a single-screw extruder and a fully meshed twin-screw extruder in the same direction (hereinafter sometimes referred to as a twin-screw extruder) are used. Compared with a single screw extruder, a twin screw extruder has higher productivity and freedom of operation, and therefore, a twin screw extruder is more preferably used for producing glass fiber reinforced thermoplastic resin pellets. .

The glass fiber used in the production of the glass fiber reinforced thermoplastic resin composition pellets is a monofilament having a diameter of 6 μm to 20 μm, which is bundled into about 300 to 3000 pieces and wound on a roving, or the roving has a length of 1 Cut to 4 mm (hereinafter sometimes referred to as chopped strands). Since chopped glass can be used more easily, in the case of producing glass fiber reinforced thermoplastic resin composition pellets industrially, the thermoplastic resin is supplied to a twin screw extruder, and after the thermoplastic resin is melted, The most common method is to supply chopped glass from the middle of a shaft extruder, mix and knead a molten thermoplastic resin and glass fiber, extrude the mixture, and cool and solidify.

The productivity of the glass fiber reinforced thermoplastic resin composition pellets using the above twin screw extruder is determined by the plasticizing and mixing and kneading ability of the twin screw extruder. The plasticizing ability of the twin screw extruder depends on the screw design, the torque generated by the screw, the groove depth of the screw (the difference between the outer diameter and the valley diameter of the screw), the rotational speed of the screw, and the like. Patent Document 1 discloses a twin screw extruder that has a high plasticizing ability and is excellent in productivity by defining a value obtained by dividing the distance between the centers of two screws by the cube of three as a torque density.

Also, the mixing and kneading ability of the twin screw extruder depends on the screw design. The residence time decreased with the improvement of the plasticizing ability of the twin screw extruder. For this reason, development of a screw design having an efficient mixing and kneading ability in a short time is required. As described above, studies on techniques for increasing the plasticizing ability and kneading ability of a twin-screw extruder have been conducted.

By the way, as the glass fiber, a monofilament bundle is used as described above. This is because, in the method of supplying glass fibers to a twin-screw extruder without forming a bundle of monofilaments, the monofilament becomes cottony, loses fluidity, and is difficult to handle. The chopped strand is mixed and kneaded in a twin-screw extruder until it is fibrillated and becomes a monofilament. At the same time, the chopped strand is broken by a screw or the like until the monofilament length reaches an average of 200 μm to 800 μm.

If mixing and kneading in the twin-screw extruder is insufficient, the monofilament will not be defibrated, and a part or all of the chopped strand that is in the state of a monofilament aggregate (undefibrated glass fiber bundle) will be resin composition It remains in the product pellet. If some or all of the chopped strands remain in the glass fiber reinforced thermoplastic resin composition pellets, in injection molding, some or all of the chopped strands may be clogged in the gate, making injection molding impossible, or injection molding. Even if it is possible, some or all of the chopped strands are present in the molded product, resulting in poor appearance or reduced function.

Particularly in recent years, with the advancement of electronics-related technology, glass fiber reinforced thermoplastic resin compositions used as parts are required to be thin and molded into complex shapes. The gate nozzle of a molding machine that performs such precision molding is often 1 mm or less. In precision molded products, the presence of undefined glass fiber bundles becomes a very serious defect.

Japanese National Patent Publication No. 11-512666

The use of the twin-screw extruder of Patent Document 1 is said to improve productivity. Particularly in the precision molded product as described above, the residence time is shortened under the condition of a high discharge amount, and the chopped strand is completely removed. It has become more difficult to defibrate monofilaments and shorten the fiber length.

The present invention has been made in order to solve the above-mentioned problems. The object of the present invention is to increase the productivity of glass fiber reinforced thermoplastic resin composition pellets as compared with the prior art, and to collect the monofilaments in the manufactured pellets. It is providing the manufacturing method of the glass fiber reinforced thermoplastic resin composition pellet which can make very low the probability that (un-defibrated glass fiber bundle) remains.

The inventors of the present invention have made extensive studies to solve the above problems.
As a result, the physical quantities obtained by numerical analysis, such as average shear stress history, average shear strain history, specific energy, shortest particle outflow time, etc., are the number N of pellets containing undefined glass fiber bundles (per unit weight). It is found that there is no clear correlation with the number of pellets containing undefined glass fiber bundles) and the smallest value among the time integral values of shear stress applied to each glass fiber bundle derived by the particle tracking method. minimum shear stress history value T _min is has been found that there is a correlation between the pellets number N containing non-fibrillated glass fiber bundles.
Further, the shear stress generated in the twin screw extruder is analyzed, and when the ratio (Q / Ns) between the discharge amount Q and the screw rotation speed Ns is constant, the minimum shear stress history value T _min is controlled. The present inventors have found that the number N of pellets per unit amount including undefined glass fibers can be controlled.
Further, even if the ratio (Q / Ns) is not constant, the number N of pellets per unit amount including undefined glass fibers can be expressed by a specific formula using the T _min and (Q / Ns). I found out.
Further, the screw for kneading the thermoplastic resin and the glass fiber has a screw element having a specific shape, and can produce the glass fiber reinforced thermoplastic resin composition pellets under specific conditions, thereby solving the above-mentioned problem. As a result, the present invention has been completed. More specifically, the present invention provides the following.

(1) A method for producing glass fiber reinforced thermoplastic resin pellets using a twin screw extruder provided with screws that rotate and mesh with each other, wherein the thermoplastic resin is supplied to the extruder and heated. A plasticizing step of kneading and plasticizing, and after the plasticizing step, supplying one or more bundles of glass fibers to the extruder, defibrating the glass fibers while disentangling the glass fiber bundles, A kneading step of kneading the plasticized thermoplastic resin with a screw, an extrusion step of extruding the glass fiber reinforced thermoplastic resin composition after the kneading step, and the extruded glass fiber reinforced thermoplastic resin composition. And in the kneading step, the screw includes one or more reverse feed screw elements each having a flight portion in which an arcuate cutout is formed. The torque density, which is a value obtained by dividing the torque of the screw in the single reverse feed screw element by the cube of the inter-center distance between the engaging screws, is 11 (Nm / cm ³ ) or more, When the screw rotation speed in the kneading step is Ns and the discharge amount of the glass fiber reinforced thermoplastic resin composition in the extruding step is Q, Q / Ns is divided by the cube of the center-to-core distance between the engaging screws. A method for producing glass fiber reinforced thermoplastic resin pellets having a Q / Ns density of 0.013 (kg / h / rpm / cm ³ ).

(2) The method for producing a glass fiber reinforced thermoplastic resin composition pellet according to (1), wherein the one reverse feed screw element satisfies the following inequalities (I) to (III).

0.05D ≦ r ≦ 0.15D (I)
7 ≦ n ≦ 20 (II)
Le ≦ 0.3D (III)

(The r in the inequality (I) is the radius of the circle forming the arc or the major axis / 2 or the minor axis / 2 of the ellipse forming the arc, and n in the inequality (II) is , The number of notches per one lead length of the one reverse feed screw element, and Le in the inequality (III) is the lead length of the one reverse feed screw element, the inequality (I), ( D) in II) is the screw diameter.)

(3) The method for producing glass fiber reinforced thermoplastic resin composition pellets according to (1) or (2), wherein the thermoplastic resin is composed of a polybutylene terephthalate resin.

(4) The method for producing a glass fiber reinforced thermoplastic resin pellet according to (1) or (2), wherein the thermoplastic resin is composed of a liquid crystalline resin.

According to the present invention, the productivity of the glass fiber reinforced thermoplastic resin composition pellets is increased more than before, and the probability that monofilament aggregates (undefined glass fiber bundles) remain in the manufactured pellets is very high. Can be lowered.

FIG. 1 is a schematic diagram illustrating an example of a screw configuration of an extruder. FIG. 2 is a diagram schematically illustrating a reverse feed single screw element having a flight portion in which an arcuate cutout is formed. FIG. 3 is a schematic diagram showing the screw configuration of the extruder used in the examples. FIG. 4 is a diagram showing a specific screw pattern used in the example. FIG. 5 is a diagram showing a specific screw shape used in the example. FIG. 6 shows the minimum shear stress history value (Pa · sec) and the number of pellets in which part or all of the glass fiber bundle is undefined (Q / Ns = 1.0 of the extruder used in the examples). It is a figure which shows the relationship with a piece / pellet 10kg). FIG. 7 shows the minimum shear stress history value (Pa · sec) under the conditions of Q / Ns = 1.0, Q / Ns = 0.8 and Q / Ns = 0.5 of the extruder used in the examples. It is a figure which shows the relationship (correlation line) with the number of pellets (one piece / pellet 10kg) in which some or all of the glass fiber bundles are undefined. FIG. 8 shows the minimum shear stress history value (Pa · sec) independent of the Q / Ns of the extruder used in the examples, and the number of pellets in which part or all of the glass fiber bundle is not defibrated (pieces / pellet 10 kg). It is a figure which shows the relationship (correlation line). FIG. 9 is a diagram showing a distribution of shear stress history values for each type of screw element. FIG. 10 is a diagram showing the relationship between the discharge rate and the number of pellets containing undefined glass fibers. FIG. 11 is a diagram showing the relationship between the discharge amount and the discharge resin temperature (the temperature of the resin composition discharged from the die). FIG. 12 is a diagram showing an operation region (maximum discharge amount) in which no undefined glass fiber bundle remains in the manufactured pellet.

Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<Method for Producing Glass Fiber Reinforced Thermoplastic Resin Composition Pellet>
The manufacturing method of the glass fiber reinforced thermoplastic resin composition pellet of the present invention includes the following steps.
A plasticizing process in which a thermoplastic resin is supplied to an extruder and heated, kneaded and plasticized.
After the plasticization step, one or more glass fiber bundles are supplied to the extruder, and the glass fiber bundles and the plasticized thermoplastic resin are screwed together with the screws while the glass fiber bundles are defibrated. A kneading step for kneading.
An extrusion step of extruding the glass fiber reinforced thermoplastic resin composition after the kneading step.
A pelletizing step of pelletizing the extruded glass fiber reinforced thermoplastic resin composition.

The production method of the present invention uses a screw having a specific screw element in the kneading step.

Hereinafter, the manufacturing method of the glass fiber reinforced thermoplastic resin composition pellets of the present invention will be described taking the case of using the twin screw extruder shown in FIG. 1 as an example. FIG. 1 shows a twin-screw extruder including a cylinder 1, a screw 2 disposed in the cylinder, and a die 3 provided at a downstream end portion of the cylinder 1. FIG. 1 also shows the screw configuration of the screw 2. Specifically, the screw 2 includes a supply unit 20, a plasticizing unit 21, a transport unit 22, and a kneading unit 23 in this order from the upstream side. A plasticizing process is performed in the supply unit 20 and the plasticizing unit 21. A kneading step is performed in the conveying unit 22 and the kneading unit 23. The extrusion process is performed after the kneading section 23. And a pelletization process is performed after the glass fiber reinforced thermoplastic resin composition is extruded from the die | dye 3 of an extruder.

The cylinder 1 in which the screw 2 is disposed includes a hopper 10 for supplying a raw material such as a thermoplastic resin to the supply unit 20 and a feed port for supplying auxiliary materials such as a glass fiber bundle to the conveyance unit 22. 11 and a vacuum vent 12 having vacuuming means such as a vacuum pump for performing vacuum deaeration at a predetermined degree of vacuum.

[Plasticization process]
In the plasticizing step, the thermoplastic resin supplied from the hopper 10 is transferred and melted to make a homogeneous melt. First, the thermoplastic resin will be described, and then the details of the plasticizing process until the thermoplastic resin supplied from the hopper becomes a homogeneous melt will be described.

(Thermoplastic resin)
The kind of thermoplastic resin is not particularly limited. Specific examples of the thermoplastic resin include polypropylene, polyacetal, liquid crystal resin, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, nylon 66, and the like. Among these thermoplastic resins, the lower the viscosity, the more likely the problem of undefining the glass fiber bundle is. This is because if the viscosity is low, shear stress hardly occurs in the molten state, and the glass fiber bundle in which the monofilaments are converged is difficult to be defibrated. Examples of the low-viscosity resin include polybutylene terephthalate, liquid crystal resin, polyethylene terephthalate, and nylon 66.

Generally, the thermoplastic tree used as a raw material is shaped into a pellet. In addition, you may use what made the thermoplastic resin composition containing other components into the pellet form.

(Details of plasticization process)
The plasticizing process is performed in the supply unit 20 and the plasticizing unit 21 of the screw 2. Examples of the screw element used in the supply unit 20 include a transport element made of a flight. Examples of the screw element used for the plasticizing portion 21 generally include a combination of screw elements such as reverse flight, seal ring, forward kneading disk, and reverse kneading disk.

Supplied part 20 transfers resin pellets. The supply unit 20 functions to transfer the resin pellets from the hopper 10 side to the die 3 direction side. In general, preheating by an external heater is performed as a melting preparation stage. Further, since the resin pellet is sandwiched between the rotating screw 2 and the cylinder 1, a frictional force is applied to the resin pellet to generate frictional heat. The resin pellets may start to melt due to the preheating or frictional heat. In some cases, the supply unit 20 needs to adjust the groove depth of the screw 2 and adjust the preheating temperature by a conventionally known method so that the transfer of the resin pellets proceeds smoothly.

The plasticizing unit 21 applies pressure to the resin pellets transferred from the supply unit 20 to melt the resin pellets. In the plasticizing part 21, as a result of applying shear stress to the resin pellets, the resin pellets are further transferred forward (in the direction from the hopper 10 to the die 3) while melting.

[Kneading process]
In the kneading step, after the plasticizing step, one or more glass fiber bundles are supplied to an extruder and the glass fiber bundle is defibrated and melted in the plasticizing step with the defibrated glass fibers. And knead. The kneading step is performed by the conveying unit 22 and the kneading unit 23 of the screw 2. As a screw element used by the conveyance part 22, the element for conveyance which consists of a forward flight is mentioned, for example. Moreover, as a screw element used in the kneading part 23, the combination of screw elements, such as a reverse flight, a seal ring, a forward kneading disk, a reverse kneading disk, is common.

In the manufacturing method of the present invention, at least a part of the kneading part 22 of the screw 2 is provided with a single reverse feed screw element having a flight part in which an arc-shaped notch is formed on the outer periphery. By providing the screw element in at least a part of the kneading part 22, almost no undefined glass fiber bundle remains in the manufactured pellet.

First, the glass fiber bundle will be briefly described. The glass fiber bundle is a chopped strand in which 300 to 3000 monofilaments are bundled. In particular, chopped strands in which 1100 pieces or 2200 pieces are bundled are preferably used. The diameter of the monofilament is not particularly limited, but is preferably in the range of 6 μm to 20 μm, and those having a diameter of 6 μm, 10 μm, and 13 μm are widely distributed in the market. A bundle of monofilaments can be continuously fed to the twin screw extruder while roving. However, the chopped strand from which roving is cut is easy to handle in transportation and supply to a twin screw extruder.

In the conveyance unit 22, the glass fiber bundle and the molten resin introduced from the feed port 11 are conveyed to the kneading unit 23. In this conveyance part 22, it is an area | region where a glass fiber bundle and molten resin are not completely filled into the groove | channel of a screw, but a shearing force is not applied to a glass fiber bundle.

In the kneading part 23, shear stress is applied to the glass fiber bundle and the molten resin. When the shear stress is applied, the glass fiber bundle is defibrated and the monofilament and the molten resin are kneaded.

[Extrusion process, pelletizing process]
There are no particular limitations on how the glass fiber reinforced thermoplastic resin composition is extruded and how it is pelletized. For example, the glass fiber reinforced thermoplastic resin composition extruded into a rod shape from the die 3 can be cut and pelletized. The cutting method is not particularly limited, and a conventionally known method can be used. The discharge amount in the extrusion process corresponds to the discharge amount Q, and the rotation speed of the screw corresponds to the rotation speed Ns.

<Screw element>
As a conventional kneading part of a screw, a combination of screw elements such as a reverse flight, a seal ring, a forward kneading disk, and a reverse kneading disk is generally used. However, in the case of high discharge under conditions where Q / Ns is large, some glass fiber bundles are not defibrated and remain undefibrated.

The present invention is a production method determined by using as an index the shear stress history value received by each glass fiber bundle in the extruder. Specifically, as an index the minimum shear stress history value T _min is the minimum value of the shear stress history value each glass fiber bundle is subjected in a twin-screw extruder. By using the minimum shear stress history value T _min as an index, it is possible to distinguish between a production method in which an undisentangled glass fiber bundle remains and a production method in which an undefined glass fiber bundle hardly remains. This invention is a manufacturing method of the glass fiber reinforced thermoplastic resin composition pellet which hardly produces the pellet with which the undisentangled glass fiber bundle remained.

First, using the minimum shear stress history value _Tmin as an index will be described. The discharge amount Q of the glass fiber reinforced thermoplastic resin composition, the screw diameter D of the screw element in the kneading section 23, the screw rotation speed Ns, the minimum shear stress history value T _min , the number N of undefined pellets per unit amount (undissolved The following formula (IV) is derived based on the number of pellets including fiber glass fiber bundles. The following formula (IV) is also useful in that the amount of pellets containing undefined glass fiber bundles can be studied with one formula even if the Q / Ns condition changes. Moreover, even if the kind of screw element which a kneading part has differs, the quantity of the pellet containing an undefined glass fiber bundle can be examined with one numerical formula (IV). However, when the size of the twin-screw extruder is changed, it is necessary to derive the formula (IV) again. Even under the same discharge amount Q and the same screw rotation speed Ns, a small twin screw extruder and a large twin screw extruder have different heat transfer amounts from the cylinders and heat energy applied to the molten resin. It is.

When the twin screw extruder to be used is determined, the screw diameter D is uniquely determined. Based on the screw diameter D, the arbitrarily determined lead length Le of the kneading part 23 of the screw, the discharge amount Q as the arbitrarily determined molding condition, and the screw rotational speed Ns, the minimum shear stress history value T _min is derived.

The minimum shear stress history value T _min can be derived using conventionally known three-dimensional flow analysis software in a twin-screw extruder. For example, it can be derived by particle tracking analysis as described in the examples. The minimum shear stress history value T _min is a time integration value obtained by performing time integration of shear stress. The integration section is a section where shear stress is applied to the molten resin and the glass fiber bundle, and the extrusion shown in FIG. In the case of a machine, it is a section of the kneading unit 23.

The method for deriving the minimum shear stress history value _Tmin is not particularly limited. A method of deriving using commercially available software, a method of deriving by experiment, and the like can be mentioned.

The number N of undefibrated pellets may be derived experimentally or using an analysis method or the like.

Then, based on these derivation results, the horizontal axis is the minimum shear stress history value T _min , the vertical axis is the number N of undefined pellets, and a graph representing the above formula (IV) is created, thereby formula (IV) To derive.

From this graph, it is possible to derive the minimum shear stress history value T _min necessary for setting the number N of undefined pellets to a desired value or less.

Next, the case of changing the size of the twin screw extruder will be described. In this case, the above relational expression needs to be derived again. However, when the above formula (IV) in the case of a predetermined twin-screw extruder has already been derived, different sizes can be easily obtained by the following method. Formulas applicable when using a twin screw extruder can be derived.

Screw diameter D of the screw element, vary from d1 to d2, the following equation (V) is established between the discharge amount Q _M in the discharge amount Q _m and a large extruder in a small extruder and, following equation (VI) is established between the screw rotation speed Ns _M at a screw rotation speed Ns _m and a large extruder a small extruder.

Δ and ε in the above formulas (V) and (VI) are determined so that the specific energies applied to the molten resin are equal. As a method for determining δ and ε, either a theoretical determination method or an experimental determination method may be used. As a theoretical determination method, in general, assuming an adiabatic state, the parameter δ is set so that the specific function, the total shear amount, the residence time, etc. of the objective function are the same between the small machine and the large machine. And ε are derived. Assuming the difference in heat transfer between the small machine and the large machine, the parameters δ and ε can be derived so that the specific energy as the objective function matches between the small machine and the large machine. As a method for experimental determination, the objective function is a specific energy, or a parameter indicating physical properties is adopted, and the parameter δ is statistically set so that the objective function matches between a small machine and a large machine. And a method of calculating ε.

By deriving the above formulas (V) and (VI) that are established between the small extruder and the large extruder, the number N of undefibrated pellets per unit amount and the minimum shearing that is established in the large extruder The following mathematical formula (VII) between the stress history value T _min can be easily derived.

Thus, the larger the value of the minimum shear stress history value T _min, there is a tendency that the value of the non-fibrillation pellets number N is reduced. Therefore, it is necessary to manufacture glass fiber reinforced thermoplastic resin composition pellets under conditions that increase the minimum shear stress history value _Tmin .

A single screw element having a flight part with a notch formed on the outer periphery is preferable because the minimum shear stress history value _Tmin tends to increase. A single screw element itself having a flight part with a notch formed on the outer periphery is known, and is described, for example, in Patent Document (DE4134026A1).

In particular, by using a single reverse feed screw element described below, the number of undefibrated pellets can be suppressed to a small value. In particular, among the screw elements having the notches, it is possible to use a reverse-feeding one having an arc-shaped notch, and the value of the minimum shear stress history value _Tmin is set to reverse flight, seal ring, forward knee. It can be larger than a combination of screw elements such as a ding disk and a reverse kneading disk, and is preferable because the glass fiber bundle can be defibrated in a shorter time than other screw elements.

The single feed reverse feed screw element used in the kneading section 23 will be described. It is preferable that this one-way reverse feed screw element has a flight part in which an arc-shaped notch satisfying the following inequalities (I) to (III) is formed on the outer periphery.

0.05D ≦ r ≦ 0.15D (I)
7 ≦ n ≦ 20 (II)
Le ≦ 0.3D (III)

(The r in the inequality (I) is the radius of the circle forming the arc or the major axis / 2 or the minor axis / 2 of the ellipse forming the arc, and n in the inequality (II) is , The number of notches per one lead length of the one reverse feed screw element, and Le in the inequality (III) is the lead length of the one reverse feed screw element, the inequality (I), ( D) in II) is the screw diameter.)

The above-mentioned reverse feed screw element will be described with reference to FIG. FIG. 2 shows a schematic diagram of the single feed reverse feed screw element, wherein (a) is a sectional view in the axial direction, and (b) is a side view.

2, the single reverse feed screw element 4 includes a flight part 40 and an arc-shaped notch 41 formed on the outer periphery of the flight part 40. The notch 41 is formed in a direction from the outer periphery of the flight part toward the axis of the screw element. 2 shows a case where the ellipse forms an arc shape, but the ellipse or the center of the circle forming the arc shape exists on the outer periphery of the flight part 40 (in FIG. 2A, the center of the ellipse is present). Indicated by O). The notch has an arc shape, and the arc shape is formed by the circle or ellipse, so that there are advantages in manufacturing and minimizing a decrease in flight strength due to the notch. In addition, the said circular arc shape should just be formed by said circle | round | yen or ellipse. Further, the present invention is not limited to one in which the entire cutout is formed by the one circle or ellipse described above. However, it is preferable that substantially the entire arc shape is formed by one circle or ellipse.

The arc shape is most preferably a circle. When the arc shape is formed as an ellipse, it is preferable that the direction in which the cutout extends and the direction in which the major axis of the ellipse extend substantially coincide.

The range of the radius r is preferably 0.05D ≦ r ≦ 0.15D. If r is within the above range, the minimum shear stress history value _Tmin tends to increase, which is preferable. A more preferable range of r is 0.06D ≦ r ≦ 0.12D.

Also, the minimum shear stress history value T _min tends to increase as the number of notches n increases. However, since the mechanical strength of the screw element decreases when the number of notches n increases excessively, it is preferable to adjust the number of notches n within the range of inequality (II). A particularly preferable range of the number of notches n is 10 ≦ n ≦ 15, and the most preferable number of notches is 11.

The lead length Le of the screw element is not more than 0.3 times the screw diameter D of the screw element (Le is not more than 0.3D). If the lead length Le is 0.3D or less, even if the discharge rate Q is very high, undisrupted glass fibers tend not to be contained in the manufactured pellets. It should be noted that the discharge amount Q is very high, for example, when the screw element is provided with an axial length of 2D and a screw diameter D is 47 mm, the screw diameter is 47 mm. This is a twin screw extruder having a diameter D of 69 mm and is 800 kg / h or more. Even in such a high discharge area, problems due to the above-described undefined glass fibers can be suppressed.

As described above, the upper limit of the lead length Le of the screw element used in the present invention is preferably 0.3D or less, but the lower limit is preferably 0.1D or more. Setting it above this lower limit is preferable because the thickness of the flight part is maintained and the strength is maintained.

The function and shape of the single screw element having the flight part in which the arc-shaped notch is formed have been described above. One of the features of the present invention is that the single line having the flight part in which the notch is formed. By using a screw element, the productivity of the glass reinforced resin composition is dramatically improved.

Even if a normal kneading disk is used, the conventional low productivity can produce a glass reinforced resin composition without generating undefibrated glass. Thus, in the part where the shear stress history value becomes small, pellets containing undefibrated glass are generated.

<Productivity of glass fiber reinforced thermoplastic resin composition pellets>
By defining the torque output by dividing the torque output by the screw by the cube of the center-to-core distance between adjacent screws, the torque density can be used to control the performance of the extruder regardless of the size of the extruder. Can be prescribed.

In the present invention, the torque density of the screw is set to 11 (Nm / cm ³ ) or more. When the torque density is 11 (Nm / cm ³ ) or more, the filling rate of the material in the extruder is increased, the energy density is reduced, and the temperature rise is low even if the rotational speed is higher than the conventional one. . Also, a preferable range of the torque density is 13 (Nm / cm ³⁾ or more 18 (Nm / cm ³⁾ or less.

Similarly, it is effective to define the extrusion conditions by the extruder using a common index regardless of the size. An important operating condition that affects whether or not unbreaked glass fibers are contained in the pellet is Q / Ns. As described above, Q is the discharge amount and Ns is the screw rotation speed. Q / Ns depends on the viscosity and specific energy of the glass fiber reinforced thermoplastic resin composition. In a specific glass fiber reinforced thermoplastic resin composition, the upper limit of Q / Ns is determined by the torque density of extrusion and the meshing rate. When the torque density is high, the filling rate can be increased, and a large Q / Ns operating region can be adopted. When Q / Ns is large, the increase in the temperature of the resin due to the increase in the number of rotations becomes slow, and a high number of rotations can be realized until reaching the limit resin temperature at which deterioration starts, and as a result, a high discharge amount can be obtained. .

Of course, Q / Ns depends on the screw diameter of the extruder. Q / Ns is scaled up according to the following relationship in a twin screw extruder having a constant meshing ratio. When the screw diameter D of the screw element becomes changed from d2 to D1, the discharge amount to Q ₁ in discharge quantity q ₂ and a large extruder a small _extruder, screw rotation speed ns ₂ on small extruder And the screw rotation speed Ns ₁ in a large extruder, the following mathematical formula (VIII) is established.

Q ₁ / Ns ₁ = (D ₁ / d ₂ ) ^α × (q ₂ / ns ₂ ) (VIII)

In the above formula (VIII), α = 3 is usually adopted in a twin-screw extruder having a constant meshing ratio. Q / Ns is an index of the filling rate, but if the meshing ratio is constant, the effective volume is proportional to the cube of the center-to-core distance between adjacent screws. It is proportional to the cube of the distance. Here, the effective volume refers to the volume of the space where the material can be filled in the twin-screw extruder.

Q / Ns depends on the size of the extruder as described above, but the value obtained by dividing the Q / Ns by the calculated value of the cube of the center-to-core distance between adjacent screws is the Q / Ns density. When defined, the Q / Ns density is a constant value even if the size of the extruder is different.

For example, in the glass fiber reinforced thermoplastic resin composition, the ratio of the outer diameter and the valley diameter of the screw is 1.54, the screw diameter is Φ40 mm, and the diameter is Φ70 mm. Assuming that Q / Ns ≧ 0.47 at Φ40 mm and Q / Ns ≧ 2.5 at Φ70 mm, the distance between the centers is the third power (Φ40 mm is 35.9 cm ³ , and Φ70 mm is 192.4 cm ³ ). When it is divided, it becomes a common value of 0.013 [kg / h / rpm / cm ³ ].

The present invention provides an element for a reverse feed flight having a flight part having a notch formed in the outer periphery of the kneading part under an operating condition where the Q / Ns density is 0.013 [kg / h / rpm / cm ³ ] or more. Is used to efficiently produce a glass-reinforced resin composition that does not contain glass undefibrated with high productivity. A preferable Q / Ns density is 0.015 [kg / h / rpm / cm ³ ] or more and 0.018 [kg / h / rpm / cm ³ ] or less.

Hereinafter, although an example and a comparative example are shown and the present invention is explained concretely, the present invention is not limited to these examples.

<Evaluation 1>
In Evaluation 1, the following materials were used.
Thermoplastic resin: Polybutylene terephthalate resin (PBT) (melt index (MI) = 70 g / 10 min)
Carbon masterbatch glass fiber bundle: 3 mm long chopped strand obtained by bundling 2200 monofilaments having a diameter of 13 μm The composition is as follows.
PBT is 67.5 mass%, carbon masterbatch is 2.5 mass%, glass fiber bundle is 30 mass%
Extrusion conditions are as follows.
Extruder: Same direction full meshing type twin screw extruder TEX44αII (manufactured by Nippon Steel) Screw diameter D of screw element is 0.047m
Extrusion conditions;

Barrel temperature; 220 ° C
Screw design;
(1) Outline The screw of the extruder can be represented as shown in FIG. 1, and the outline of the screw pattern shown in FIG. 3 is as follows.
C1: Hoppers C2 to C5: Supply sections C5 to C6: Plasticization sections C6 to C8: Transport section C9: Feed port C10: Kneading section A
C11: Kneading part B (consisting of kneading part b1 and kneading part b2)
(2) The specific screw pattern used in Evaluation 1 is as shown in FIG. A kneading disk having a 45 ° phase shift in the feeding direction is defined as FK, and an element having a notch in one reverse flight is defined as BMS. Moreover, 1.0D etc. represents the length of the kneading part b1. The short diameter / 2 of the notch on the outer periphery of the BMS is 3 mm, and the long diameter / 2 (the direction in which the notch extends) is 4.15 mm.
The screw pattern shown in FIG. 4A is FK1.0D (L / D = 1),
The screw pattern shown in FIG. 4B is FK2.0D (L / D = 2),
The screw pattern shown in FIG. 4 (c) is BMS1.0D (L / D = 1),
The screw pattern shown in FIG. 4 (d) is BMS2.0D (L / D = 2),
The screw pattern shown in FIG. 4 (e) is BMS2.5D (L / D = 2.5),
And L / D is a ratio (L / D) between the length (L) of the kneading part b1 and the screw diameter (D) of the screw element. In addition, the length L of the kneading part 23 in the description of the embodiment corresponds to the length of the kneading part b1.
(3) Screw shape The screw patterns shown in FIG. 4 differ only in the kneading part B of C11. The shape of the screw of the kneading part B of C11 is shown in FIG. The screw shape of the pattern of FIG. 4 (a) is shown in FIG. 5 (a), the screw shape of the pattern of FIG. 4 (b) is shown in FIG. 5 (b), and the screw shape of the pattern of FIG. 5 (c), the screw shape of the pattern of FIG. 4 (d) is shown in FIG. 5 (d), and the screw shape of the pattern of FIG. 4 (e) is shown in FIG. 5 (e).
The screw shown in FIG. 5 (a) has a kneading part b1 with a forward feed kneading disk having a length of 1.0D, and the kneading part b2 has a reverse feed flight with a length of 0.5D. The screw shown in FIG. A forward kneading disc having a length of 2.0D, a reverse feed flight in which the kneading part b2 has a length of 0.5D. The screw shown in FIG. 5 (c) has a single kneading part b1 having a notch having a length of 1.0D. Reverse feed kneading disc, reverse feed flight with kneading part b2 of 0.5D length The screw shown in FIG. 5 (d) is a single reverse feed kneading disc with kneading part b1 having a notch length of 2.0D. The kneading part b2 has a reverse feed flight with a length of 0.5D. The screw shown in FIG. 5 (e) has a kneading part b1 with a notch with a length of 2.5D and a kneading part b2 0.5D length reverse feed Light

Under the condition of Q / Ns = 1.0, the minimum shear stress history value (Pa · sec) as shown in FIG. 6 and the number of pellets in which part or all of the glass fiber bundle is undefined (pieces / pellet 10 kg) Sought the relationship. Specifically, it was derived by the following method.

First, necessary for derivation of the relationship, L / D, the discharge amount Q, screw rotation speed Ns, non fibrillation pellets number N, a plurality determine a set of minimum shear stress history value T _min. L / D, the discharge amount Q, by arbitrarily determining the screw rotation speed Ns, the following method, to derive the minimum shear stress history value T _min, was determined non-fibrillated pellets number N by experiments. Specifically, it was determined as follows.

First, the derivation of the minimum shear stress history value (Pa · sec) by simulation will be described.
Resin behavior in the same direction complete meshing type twin screw extruder was analyzed using a three-dimensional flow analysis software in the twin screw extruder (Screw Flow-Multi, manufactured by Earl Flow).
The governing equations used in the analysis are the continuous equation (A), the Navier-Stokes equation (B), and the temperature balance equation (C).

As an analysis assumption, the incompressible fluid was completely melted and completely filled. Moreover, Arrhenius approximation and WLF approximation were used for the viscosity approximation formula. The analysis method is a finite volume method, a SOR method, or a SIMPLE algorithm. As a calculation, a steady analysis is first performed, and an unsteady analysis is performed using this as an initial value. After unsteady analysis, tracer particles were arranged (about 5000 particles), and local information concerning the tracer particles was collected (particle tracking analysis). Minimum value T _min of the time integral value of the shear stress integrates the shear stress of local information relating to the tracer particles time, in which determining the minimum value of the total particle.

Next, derivation of the number of undefined pellets by experiment will be described.
After supplying PBT to a twin screw extruder, glass chopped strands are supplied under the above extrusion conditions, kneaded and mixed, then the resin composition is extruded from the die, and the molten resin composition is taken up from the die to form a strand. The strand was cooled and solidified in a water tank, and the strand was cut into a length of 3 mm with a cutter to produce a pellet. 10 kg of the pellets were collected, glass undefibrated (silver-colored agglomerates) in the black pellets were visually found, and the number of pellets containing glass undefibrated was counted.

An approximate curve (correlation line) representing the relationship between the number of undefined pellets and the minimum shear stress history value was obtained by the method of least squares. When Q / Ns = 1.0, the different elements shown in FIGS. 4 (a) to 4 (e) were added to the kneading part B as described above, and the experiment and simulation were performed with different Q values. An approximate curve was obtained. The approximate curve is shown in FIG.

In the above formula (III), α was 11.5042, and β was −2.200.

Even under the conditions of Q / Ns = 0.8 and Q / Ns = 0.5, as shown in FIG. 7, the minimum shear stress history value (Pa · sec) and a part of the glass fiber bundle or The relationship (correlation line) with the number of undefibrated pellets (pieces / pellet 10 kg) was obtained. FIG. 7 also shows the correlation line when Q / Ns = 1.0.

As shown in FIG. 7, the correlation line is different for each Q / Ns. Therefore, the function of the formula (IV) is approximated by the method of least squares. The approximate curve is shown in FIG. As shown in FIG. 8, it was possible to approximate with one correlation line independent of Q / Ns. Note that γ was 3.0.

As shown in FIG. 8, it was confirmed that the number of undefined pellets per unit amount was less than a predetermined value as long as it was a predetermined minimum shear stress history value or more.

As described above, even if the Q / Ns condition changes, Formula (IV) can be used to study the amount of undefined glass fiber bundles contained in the pellet, and the screw element that the kneading unit has It was confirmed that the amount of undefined glass fiber bundles contained in the pellets can be examined with a single mathematical formula (IV) even if the types of are different.

<Evaluation 2>
A kneading disk (FIG. 5 (a) and (FIG. 5 (a) and ((5))) having a composition of 70% by mass of PBT resin and 30% by mass of glass fiber (glass monofilament diameter 13 μm) and used in a kneading part of a twin screw extruder (screw diameter 47 mm). b) Evaluation of each simulation using the symbol FK) and a single reverse feed screw element (FIG. 5 (c) (d) (e) symbol BMS) having a notched flight part. The distribution of the shear stress history value obtained by performing the time integration of the shear stress of the local information applied to the tracer particles by the same method as described in FIG. The center of the notch is the outer peripheral part, the lead length Le of the reverse feed flight (symbol BMS in the figure) is L / D = 0.25, and the radius of the circle forming the arc shape of the notch is r = 3 mm. .

In kneading discs (FK), the distribution spreads over a wide range from where the shear stress history value is small. Having a small shear stress history value means that there is a high probability that glass undefibration remains. On the other hand, in a single reverse feed screw element having a flight part in which a notch is formed, since the distribution of shear stress history values is narrow, the minimum shear stress history value is large. For this reason, if the screw element which has the said notch is used, it will become difficult to remain | survive an undisentangled glass fiber bundle in a pellet.

<Evaluation 3>
Next, the shape required for the notch element will be described by flow analysis using the minimum shear stress history value as an index. In the twin-screw extruder shown in FIG. 1 (screw diameter 47 mm), a kneading part is composed of a single screw element having a flight part in which an arc-shaped notch is formed with a composition of 70% by mass of PBT resin and 30% by mass of glass fiber. The simulation when used in the No. 23 was performed. Specifically, the relationship between the minimum shear stress history value T _min obtained by the same method as in Evaluation 1 and the number of notches (groove number) n was obtained. For a single reverse feed screw element (BMS) having an arc-shaped notch as the outer peripheral portion and a flight portion in which the arc-shaped notch is formed, the lead length Le is L / D = 0.2, 0 Evaluation was performed under three conditions of .25 and 0.3. The arc shape is formed from an ellipse, and the minor axis / 2 of this ellipse is 3 mm and the major axis / 2 (the direction in which the notch extends) is 4.1 mm. The results of Evaluation 3 are shown in Table 2.

According to Table 2, the minimum shear stress history value T _min is high when the number n of notches per lead length Le is 13 to 15. As the number of notches n is larger, the minimum shear stress history value _Tmin is higher. However, since the mechanical strength of the screw element decreases as the number of notches n increases, it can be said that 13 to 15 is preferable.

<Evaluation 4>
In the twin-screw extruder (diameter 47 mm) shown in FIG. 1, a single screw element having a flight part in which an arc-shaped notch is formed with a composition of 70% by mass of PBT resin and 30% by mass of glass fiber is added to the kneading part 23. A simulation was performed when used. Specifically, the relationship between the minimum shear stress history value T _min obtained by the same method as described in Evaluation 1 and the major axis in the depth direction of the notch is shown. The center of the notch is on the outer periphery of the flight part, the shape of the notch is an ellipse, the short diameter / 2 of the notch on the outer periphery is 3 mm, and the long diameter / 2 (the direction in which the notch extends) is 3 mm, 4 mm, 4. The simulation was performed in the case of 125 mm, 4.5 mm, and 5 mm. Further, the number of notches n was 11, and the lead length Le of the screw element having the notches was L / D = 0.25. The results of Evaluation 4 are shown in Table 3.

According to Table 3, the minimum shear stress history value T _min has a maximum value when the major axis of the groove depth of the notch / 2 is 4 to 5 mm. With respect to the diameter D, the short diameter / 2 of the notch on the outer periphery is 0.064D, and the range of the long diameter / 2 in the groove depth direction is 0.085D to 0.11D.

<Evaluation 5>
Except that the size of the minor axis / 2 is changed to that shown in Table 3, it extends in the direction perpendicular to the minimum shear stress history value _Tmin and the direction in which the notch is formed, in the same manner as in the evaluation 4. The long diameter relationship was shown. The results of Evaluation 5 are shown in Table 4.

According to Evaluation 5, even when the major axis of the ellipse forming the arc shape extends in a direction perpendicular to the direction in which the notch extends, the larger value of the major axis increases the minimum shear stress history value. It was confirmed that Further, from comparison between Evaluation 4 and Evaluation 5, it is more effective that the major axis of the ellipse extends in the direction in which the cutout extends.

<Evaluation 6>
The relationship between the minimum shear stress history value _Tmin and the radius of the circle was shown in the same manner as in Evaluation 4 except that the circular arc was changed into a circle. The results of Evaluation 6 are shown in Table 5.

It was confirmed that the minimum shear stress history value increases as the radius increases even when the arc forms a circle. In addition, from the comparison of evaluations 4 to 6, it was confirmed that the minimum shear stress history value is larger when the circular arc is formed than the ellipse is formed.

<Example-1>
In the examples, the following materials were used.
Thermoplastic resin: Polybutylene terephthalate resin (PBT) (melt index (MI) = 70 g / 10 min)
Carbon masterbatch glass fiber bundle: 3 mm long chopped strand obtained by bundling 2200 monofilaments having a diameter of 13 μm The composition is as follows.
PBT is 67.5 mass%, carbon masterbatch is 2.5 mass%, glass fiber bundle is 30 mass%
Extruder: Same direction complete meshing type twin screw extruder TEX44αII (manufactured by Nippon Steel) Screw element diameter D is 0.047mm
The cylinder temperature is 220 ° C., and the extrusion conditions are listed in Table 6 below.

The specific screw pattern used in the examples is as shown in FIG. A kneading disk, in which each disk is 45 ° out of phase in the feed direction, is FK, and a screw element having a notch in one reverse flight is called BMS.

The notch radius r of the single reverse flight used here is 0.064D, and the number n of notches per round is n = 11. The center of the notch is on the flight periphery.

Next, derivation of the number of undefined pellets by experiment will be described.
After PBT was supplied to the twin screw extruder, glass chopped strands were supplied, kneaded and mixed under the extrusion conditions shown in Table 6 above, and the resin composition was extruded from the die. The extruded resin composition was taken out from the die to form a strand, the strand was cooled and solidified in a water tank, and the strand was cut to a length of 3 mm with a cutter to produce a pellet. 10 kg of the pellets were collected, glass undefibrated (silver-colored agglomerates) in the black pellets were visually found, and the number of pellets containing glass undefibrated was counted. Table 7 shows the results using the extruder shown in FIG. 5 (a), Table 8 shows the results obtained using the extruder shown in FIG. 5 (b), and Table 9 shows the results obtained using the extruder shown in FIG. 5 (c). Table 10 shows the results using the extruder shown in FIG. 5D, and Table 11 shows the results obtained using the extruder shown in FIG.

FIG. 10 is a diagram showing the relationship between the discharge rate and the number of pellets containing undefined glass fibers. FIG. 10A summarizes examples of Q / Ns = 0.8, and FIG. 10B summarizes Q / Ns = 1.0. 10 (a) and 10 (b), when FK is used in the kneading part, if Q / Ns is set to 0.8 or more, undefined bundles of glass may remain in many pellets. I can confirm. On the other hand, if a screw equipped with BMS is used, even if the discharge rate is 600 kg / hr or more in a region of Q / Ns = 0.8 or more in a twin screw extruder having a diameter of Φ = 47 mm, it is unsolved. It was confirmed that generation | occurrence | production of the pellet (non-defibrated pellet) containing fiber glass fiber can be suppressed.

Also, the relationship between the discharge amount and the discharge resin temperature (the temperature of the resin composition discharged from the die) is summarized in FIG. FIG. 11A is a diagram showing a case where Q / Ns is 0.5 and 1.0, and FIG. 11B is a diagram showing a case where Q / Ns is 0.8. Although it is considered that the PBT resin used in this example does not deteriorate up to 300-310 ° C., in FIG. 11A, when Q / Ns = 0.5, the discharge amount is 300 kg / h, and the discharge resin temperature is Since it exceeds 310 ° C., the limit of the discharge amount is 300 kg / h. However, at Q / Ns = 1.0, the discharge resin temperature is less than 310 ° C. up to 700 kg / h, and if Q / Ns is increased, the productivity of high-quality pellets is dramatically improved.

As described above, as can be confirmed from FIGS. 10 and 11, when using a screw having a single reverse feed screw element having a flight part with a notch formed on the outer periphery, under a large condition of Q and Q / Ns, It was confirmed that the generation of undefined pellets can be suppressed and the resin can be extruded at a temperature that does not deteriorate the resin. On the other hand, in a kneading disk (FK) that is normally used, the occurrence of undefined pellets cannot be suppressed unless the Q and Q / Ns are small. The condition where Q / Ns is small indicates that the discharge amount is low.

Furthermore, the embodiment described above, in the manufacture of pellets for each condition of the comparative example, the minimum shear stress history value T _min determined in the manner described above. In each case of a commonly used kneading disk (FK) and a single reverse feed screw element (BMS) having a flight part with a notch formed, undefined glass fiber bundles remain in the produced pellets. FIG. 12 shows the operation region (maximum discharge amount) that is not performed. FIG. 12 shows data when a twin screw extruder having a screw diameter D = Φ47 mm is used, FIG. 12A shows the result when Q / Ns = 1.0, and FIG. FIG. 12C shows the result when Q / Ns = 0.5.

The discharge rate at which the undefined glass fiber bundle does not remain in the pellet is the length (L / D) of the kneading disk (FK) used in the kneading part, and a single reverse feed having a flight part in which a notch is formed. Since it depends on the length (L / D) of the screw element (BMS), the relationship is shown by a straight line. On the other hand, the resin has an inherent limit temperature at which the thermal decomposition becomes significant and the processing becomes a limit as the temperature rises. When the temperature of the resin reaches that temperature during pellet production, the discharge becomes a limit. The kneading disk (FK) and the single-feed reverse screw element (BMS) having a flight part with a notch also increase the resin temperature as the length (L / D) used in the twin-screw extruder increases. . 12 (a) to 12 (c) also show the limit of the resin temperature, and the intersection of the limit of the resin temperature and the limit at which the undefined glass fiber bundle does not remain in the pellet is the productivity. It is a limit.

In FIGS. 12 (a) and 12 (b), the productivity when using a single reverse feed screw element (BMS) having a flight part with a notch used is a kneading disk (FK). It is shown that it is 2 to 4 times the case. On the other hand, FIG.12 (c) shows the result when Q / Ns is as small as 0.5 with the same material and the same extruder. Under the conditions of FIG. 12 (c), when a single reverse feed screw element (BMS) having a flight part with a notch is used, the resin temperature rises greatly, and the productivity is limited at the temperature limit. It shows that there is no significant difference in productivity compared to the ding disc (FK). This indicates that a single reverse feed screw element having a notched flight portion is effective to increase Q / Ns and increase productivity, and at the same time, Q / Ns Is small, it indicates that the use of a single reverse feed screw element having a flight part is not effective.

The Q / Ns in FIGS. 12A and 12B are 1.0 and 0.8. The above-described Q / Ns densities are 0.014 [kg / h / rpm / cm ³ ] and 0.018 [kg / h / rpm / cm ³ ], respectively. In FIG.12 (c), Q / Ns is 0.5 and the Q / Ns density at this time will be 0.009 [kg / h / rpm / cm < ³ >]. To summarize the above results, a single reverse feed screw element having a flight part in which a notch is formed has a Q / Ns density of 0.013 [kg / h / rpm / cm ³ ] or more in an operating region. Since the defibrated glass fiber bundle is difficult to remain in the pellet, high productivity can be realized.

DESCRIPTION OF SYMBOLS 1 Cylinder 10 Hopper 11 Feed port 12 Vacuum vent 2 Screw 20 Supply part 21 Plasticizing part 22 Conveying part 23 Kneading part 3 Die 4 Single feed reverse feed screw element 40 Flight part 41 Notch

Claims

A method for producing glass fiber reinforced thermoplastic resin pellets using a twin-screw extruder equipped with screws that rotate and mesh with each other,
A plasticizing step of supplying a thermoplastic resin to the extruder and heating, kneading and plasticizing;
After the plasticizing step, one or more glass fiber bundles are supplied to the extruder, and the defibrated glass fibers and the plasticized thermoplastic resin are screwed together while defibrating the glass fiber bundles. A kneading step for kneading;
After the kneading step, an extrusion step of extruding the glass fiber reinforced thermoplastic resin composition,
Pelletizing step of pelletizing the extruded glass fiber reinforced thermoplastic resin composition,
In the kneading step, the screw has one or more reverse feed screw elements having a flight part in which arc-shaped notches are formed,
The torque density, which is a value obtained by dividing the torque of the screw in the single reverse screw element by the cube of the inter-center distance between the engaging screws, is 11 (Nm / cm 3 ) or more,
When the screw rotation speed in the kneading step is Ns, and the discharge amount of the glass fiber reinforced thermoplastic resin composition in the extrusion step is Q, Q / Ns is the cube of the distance between the cores engaged with each other. The manufacturing method of the glass fiber reinforced thermoplastic resin composition pellet whose Q / Ns density which is the value which remove | divided is 0.013 (kg / h / rpm / cm < 3 >).
The method for producing glass fiber reinforced thermoplastic resin pellets according to claim 1, wherein the one reverse feed screw element satisfies the following inequalities (I) to (III).

0.05D ≦ r ≦ 0.15D (I)
7 ≦ n ≦ 20 (II)
Le ≦ 0.3D (III)

(The r in the inequality (I) is the radius of the circle forming the arc or the major axis / 2 or the minor axis / 2 of the ellipse forming the arc, and n in the inequality (II) is , The number of notches per one lead length of the one reverse feed screw element, and Le in the inequality (III) is the lead length of the one reverse feed screw element, the inequality (I), ( D) in II) is the screw diameter.)
The method for producing glass fiber reinforced thermoplastic resin pellets according to claim 1 or 2, wherein the thermoplastic resin is composed of a polybutylene terephthalate resin.
The method for producing glass fiber reinforced thermoplastic resin composition pellets according to claim 1 or 2, wherein the thermoplastic resin is composed of a liquid crystalline resin.