Method for producing glass-fiber reinforced polyester resin composition

Abstract

A method for producing a glass-fiber reinforced resin composition of (A) 10 to 60 mass% of polyester resin, (B) 40 to 70 mass% of glass fiber, and (C) 0 to 50 mass% by mass of other polymer or additive, by using a twin-screw extruder, wherein the resin composition has a shear viscosity of 400 to 2000 Pa·s at 265°C, 91 / sec, and when extruding a strand (10) from horizontal flat die (25) installed on a die holder (8) at the tip of the twin-screw extruder, a temperature of the strand (10) from die hole (31) in the center of the flat die (25) is 295°C to 340°C, and a temperature of the strand (10) from the die hole (32,33) at the end of the flat die (25) is lower by 4°C to 14°C than the temperature of the strand (10) from the die hole (31) at the center of the flat die (25).

Description

Method for producing glass fiber reinforced polyester resin composition

[0001] The present invention relates to a method for producing a glass fiber-reinforced polyester resin composition, and more particularly to a method for producing a glass fiber-reinforced polyester resin composition containing a high concentration of glass fibers using a twin-screw extruder, in the form of pellets that suppress strand breakage, enable continuous and stable production, have high productivity, and maintain a good pellet shape.

[0002] Polyester resins, such as polybutylene terephthalate resin and polyethylene terephthalate resin, are widely used, primarily for injection molding, in various electric and electronic components, machine components, and automobile components, etc. In particular, glass fiber-reinforced polyester resin compositions containing a high content of glass fiber are excellent in mechanical strength, heat resistance, chemical resistance, etc., and are used as components in the fields of automobiles and electric and electronic equipment, etc.

[0003] Patent Document 1 describes a resin composition in which 5 to 80% of glass fiber is blended with polybutylene terephthalate resin, and Patent Document 2 describes a glass fiber-reinforced polyester resin composition in which 100 parts by mass of polyester resin is blended with 10 to 150 parts by mass of glass fiber.

[0004] However, polyester resin compositions containing glass fibers at high concentrations, such as 40% by mass or more, are prone to strand breakage when extruded through a die in a twin-screw extruder. This reduces productivity, and broken strands tend to overlap when fed into a pelletizer, disrupting the strand flow and producing long pellets. Furthermore, the strands are less easily cut, resulting in dull pellet cross sections and increased chipping. This tendency becomes more pronounced as the glass fiber concentration increases. Long pellets and chippings are prone to plasticization failure during molding in an injection molding machine, resulting in longer metering times, machine shutdowns, and reduced productivity.

[0005] Japanese Patent Publication No. 51-7702 Japanese Patent Application Laid-Open No. 2006-16577

[0006] The object (object) of the present invention is to suppress breakage of strands emerging from a die when a glass fiber-reinforced polyester resin composition containing a high content of glass fiber is produced using a twin-screw extruder, thereby enabling continuous and stable production and suppressing the generation of long pellets.

[0007] The present inventors conducted extensive research to solve the above-mentioned problems. However, when a polyester resin composition containing a high glass fiber content (40 to 70% by mass) is produced using a twin-screw extruder, the viscosity of the resin composition becomes high. However, by adjusting the shear viscosity to 400 to 2000 Pa·s (91 / sec at 265°C), setting the strand temperature to a specific temperature, and lowering the temperature of the strand at the die edge by 4 to 14°C relative to the strand at the center of the die, strand breakage is suppressed, enabling continuous, stable production, and significantly reducing the generation of long pellets. The inventors also discovered that in this case, it is preferable to set the die holder temperature to a high temperature of 260 to 340°C, and that it is preferable to set the resin pressure in the die to 2 to 9 MPa or to set the die holder temperature to 240 to 340°C. The present invention relates to the following production method.

[0008] 1. A method for producing a glass fiber-reinforced polyester resin composition using a twin-screw extruder, the method comprising: (A) 10 to 60% by mass of polyester resin; (B) 40 to 70% by mass of glass fiber; and (C) 0 to 50% by mass of other polymers or additives (the total of all components being 100% by mass); wherein the glass fiber-reinforced polyester resin composition has a shear viscosity of 400 to 2000 Pa·s at 265°C and 91 / sec; and when a strand is extruded through a horizontal flat die attached to a die holder at the tip of the twin-screw extruder, the temperature of the strand from the central die hole of the flat die is 295 to 340°C, and the temperature of the strand from the end die hole of the flat die is 4 to 14°C lower than the temperature of the strand from the central die hole of the flat die. 2. A production method according to 1 above, wherein the resin is extruded so that the resin pressure inside the die when it exits the flat die is 2 to 9 MPa. 3. 2. The method according to claim 1, wherein the temperature of the die holder is 240 to 340°C.

[0009] According to the production method of the present invention, a glass fiber-reinforced polyester resin composition (pellet) containing a high content of glass fiber can be produced in a good pellet shape while suppressing strand breakage and enabling continuous and stable production.

[0010] Fig. 1 is a conceptual diagram showing an example of a process from a twin-screw extruder used in the present invention to a pelletizer. Fig. 2 is a diagram showing an example of a die section of a twin-screw extruder used in the present invention. Fig. 3 is a cross-sectional view showing an example of a transverse flat die used in the present invention. Fig. 4 is a cross-sectional view showing another example of a transverse flat die used in the present invention. Fig. 5 is a conceptual diagram of the screw configuration of an extruder used in Examples or Comparative Examples.

[0011] The present invention will be described in detail below with reference to embodiments and examples, but the present invention is not limited to the embodiments and examples shown below and can be implemented with any modifications within the scope of the gist of the present invention. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0012] In the production method of the present invention, a glass fiber-reinforced polyester resin composition comprising (A) 10 to 60% by mass of polyester resin, (B) 40 to 70% by mass of glass fiber, and (C) 0 to 50% by mass of other polymers or additives is produced using a twin-screw extruder.

[0013] The extruder used in the present invention is a vented twin-screw extruder, preferably an intermeshing co-rotating twin-screw extruder, which has two screws rotating in the same direction inside a barrel, and preferably has a kneading section composed of a plurality of kneading discs in a mutually intermeshing form provided midway along the screws.

[0014] As shown in Figure 1, the vented twin-screw extruder has a cylinder equipped with a main raw material hopper 1, an open vent 2, a side feed hopper 3, and a decompression vent 4, and a die holder 8 attached to the tip via a flange 6. The screw inside the cylinder is driven and rotated by a motor 16 via a screw connection part 14 and a gear box 15.

[0015] (A) polyester resin and (C) other polymers or additives are supplied from a main raw material hopper 1 and kneaded in a first kneading section (Step 1). (B) glass fiber is typically side-fed from a side feed hopper 3 downstream of the first kneading section and kneaded in a second kneading section (Step 2). Next, downstream of the second kneading section, a vent 4 is depressurized to remove volatiles and increase the pressure, and the mixture is extruded through a die attached to a die holder 8 (Step 3). Strands 10 emerging from the die are then water-cooled and cut in a pelletizer 11 (Step 4), yielding pellets 12 of the resin composition.

[0016] In the first step, (A) polyester resin and (C) other polymers or additives are fed into the extruder from a main raw material hopper 1 and heated, kneaded, and melted by a screw. A first kneading section composed of multiple kneading discs is formed midway through the screw. The first kneading section is a kneading section where (A) polyester resin and (C) other polymers or additives are mixed after being added, and refers to the kneading section before (B) glass fiber is added. The screw configuration is preferably a combination of two or more of R kneading discs, N kneading discs, L kneading discs, L screws, seal rings, mixing screws, or rotor screws, and the length is preferably 5.0 to 9.0 D (D is the cylinder diameter). The first kneading section is a kneading section where (A) polyester resin and (C) other polymers or additives are mixed after being added, and refers to the kneading section before (B) glass fiber is added.

[0017] This first kneading section may be a single section or may be divided into multiple sections. That is, the first kneading section may also be divided, with a feed screw inserted between the sections. Even in the case of division, it is preferable that the total length of the kneading section is in the range of 5.0 to 9.0D.

[0018] The R kneading disc (hereinafter also referred to as R) is a forward kneading disc element, which usually has two or more blades, and the blade twist angle θ is preferably 10 to 75 degrees. By installing the blades at a predetermined angle in this manner, a pseudo-screw structure is formed, which applies a strong shear force while feeding the resin in the feed direction, forming a kneading zone. The L kneading disc (hereinafter also referred to as L) is a backward kneading disc element, which usually has two or more blades, and the blade twist angle θ is preferably -10 to -75 degrees. The backward kneading disc element is an element that has the ability to block the incoming resin or to increase pressure by acting in the direction of sending the incoming resin back. By installing it downstream of the element that promotes kneading, it blocks the resin and exerts a powerful kneading effect. The N kneading disc (hereinafter sometimes referred to as N) is an orthogonal kneading disc element, which usually has two or more blades, and the twist angle θ of the blades is 75 to 105 degrees. Because the blades are installed offset by approximately 90 degrees, the resin delivery force is weak but the kneading force is strong.

[0019] The L screw is a reverse feed screw, the seal ring restricts the flow upstream by the gaps in the seal ring section, the mixing screw is a screw element with notched screw flights, and the rotor screw is a screw element with one or more grooves on its outer surface.

[0020] Among these, the R kneading disc, the N kneading disc and the L kneading disc are preferred, and a configuration in which a plurality of these are combined is preferred.

[0021] The screw configuration of the first kneading section in the first step is preferably such that an element that promotes kneading is arranged upstream and an element that has the ability to increase pressure is arranged downstream. Therefore, in the first kneading section, it is preferable to arrange two or more elements selected from R, N, and L in the order R → N → L from the upstream side, and it is also preferable to arrange multiple elements of each of R, N, and L. In particular, a configuration in which R is arranged upstream, followed by multiple N elements, and then L is arranged is preferred.

[0022] The screw length of the first kneading section is preferably in the range of 5.0 to 9.0 D, where D is the cylinder diameter, and such a screw length ensures sufficient melt plasticization of the (A) polyester resin and can also prevent decomposition of the resin composition. If the screw length of the first kneading section is shorter than 5.0 D, insufficient shearing tends to result in insufficient melt plasticization of the resin, while if it exceeds 9.0 D, excessive kneading tends to lead to localized decomposition of the resin composition, and the mechanical properties of the composition are likely to be poor.

[0023] After the polyester resin (A) has been kneaded and melted in the first step, it is preferably vented through the open vent 2. A seal ring is preferably provided downstream of the open vent 2.

[0024] In the second step, after the first step, (B) glass fiber is side-fed from a side feed hopper 3 located downstream of the first kneading section, and the (B) glass fiber and the molten (A) polyester resin are kneaded in the second kneading section. The second kneading section refers to a kneading section in which the (B) glass fiber enters, opens, and kneads it. The screw configuration of the second kneading section is preferably a combination of one or more of an R kneading disk, an N kneading disk, an L kneading disk, an L screw, a seal ring, and a mixing screw. Kneading with such a screw configuration tends to result in sufficient opening and dispersion of the (B) glass fiber. Among the above, a configuration having at least a mixing screw, particularly a forward-feed notched mixing screw or a reverse-feed notched mixing screw, is preferred.

[0025] The screw length of the second kneading section is preferably in the range of 2.5 to 5.0D. This second kneading section may be combined into one section, or may be divided into multiple sections. That is, the second kneading section may be divided and a feed screw may be inserted between the sections. In either configuration, the total length of the kneading section is preferably in the range of 2.5 to 5.0D. By setting the screw length of the second kneading section in this way, the opening and dispersion of the (B) glass fibers is improved, and the strength of the resin composition is likely to be improved.

[0026] The resin temperature (cylinder temperature) in the second step is typically operated at around 260°C, but in the method of the present invention, it is preferable to set it at a lower temperature of 150 to 220°C. This second kneading section is the process where (B) glass fiber is introduced and kneaded with (A) polyester resin and (C) other polymers or additives, and the resin temperature is likely to rise. Setting the cylinder temperature in this section to a lower temperature range of 150 to 220°C is effective in suppressing breakage of the strand 10 upon exiting the die holder 8. If the temperature is lower than 150°C, the viscosity of the resin tends to increase, which leads to poor impregnation of the (B) glass fiber, resulting in uneven kneading and increased strand breakage. On the other hand, if the temperature is higher than 220°C, the resin temperature tends to increase, which increases the generation of pyrolysis gas and increases the risk of strand breakage. The resin temperature (cylinder temperature) in the second step is more preferably 160°C or higher and 210°C or lower.

[0027] The screw rotation speed of the twin-screw extruder is preferably 250 to 800 rpm, more preferably 300 to 700 rpm. The output rate for TEX44αIII is preferably 200 to 650 kg / h, more preferably 250 to 630 kg / h. For extruders of different sizes, the output rate is proportional to the 2.5th power of the cylinder diameter ratio.

[0028] After the second step, in the third step, the pressure is reduced at the vacuum vent 4 downstream of the second kneading section to remove volatilization and increase the pressure, and the mixture is extruded through a die attached to a die holder 8. The degree of vacuum during the reduced pressure and volatilization at the vacuum vent 4 is preferably −0.097 MPa to −0.07 MPa. Here, the degree of vacuum means gauge pressure.

[0029] In the third step, pressure is increased at the tip of the screw and the resin is extruded as a strand from the die. The resin pressure in the die during extrusion is preferably 2 to 9 MPa. The resin pressure in the die (also referred to as die pressure) refers to the resin pressure at the tip of the screw. This position is the highest pressure. A resin pressure gauge 7 is usually installed at this position, allowing pressure to be measured over time. The resin pressure in the die is preferably 2 MPa or more and 9 MPa or less. The (B) glass fibers are usually in a bundled state during feeding. By setting the resin pressure in the die to 2 MPa or more and 9 MPa or less, the fibers are kneaded together with the resin. Applying an appropriate pressure facilitates impregnation of the resin into the (B) glass fiber bundles, enabling uniform kneading and reducing strand breakage. If the pressure is less than 2 MPa, the resin and (B) glass fibers are unevenly kneaded, making the strands more likely to break when they exit the die. The (B) glass fibers are usually in bundle form when fed and are kneaded together with the resin. The application of pressure facilitates impregnation of the (B) glass fiber bundles with the resin, enabling uniform kneading. A more preferred resin pressure in the die is 2.5 MPa or more, and even more preferably 3 MPa or more. On the other hand, if the resin pressure is too high, the retention area at the tip of the screw becomes longer, gas is more likely to be generated by thermal decomposition, and the strands are more likely to break due to the gas when they emerge from the die. A more preferred resin pressure is 8 MPa or less, and even more preferably 7 MPa or less.

[0030] The temperature of the die holder 8 is preferably higher than usual, and is preferably 240°C or higher and 340°C or lower. Setting the temperature in this range facilitates the prevention of strand breakage. If the die temperature is lower than 240°C, the die temperature will be lower than the resin temperature of the resin composition, and the temperature of the strands at both ends of the die will be lower than the central strand. This will result in a difference in viscosity between the strands, making them more likely to break. The temperature of the die holder 8 is more preferably 250°C or higher, particularly 260°C or higher, 270°C or higher, and even more preferably 280°C or higher. If the temperature exceeds 340°C, gas will be more likely to be generated due to heat retention inside the die, which will also make the strands more likely to break. The temperature of the die holder 8 is more preferably 330°C or lower, and even more preferably 320°C or lower.

[0031] Thermocouples 5 and die holder thermocouples 9 are inserted into the cylinder and die holder 8 of the extruder, respectively, to measure the temperatures of the cylinder and die holder. Furthermore, heaters are built into the cylinder and die holder, allowing for temperature control. The temperatures of the cylinder and die holder are measured by the inserted thermocouples.

[0032] In the method of the present invention, a horizontal flat die is provided in the die holder 8 at the tip of the twin-screw extruder, and when a strand is extruded from the die holder, the temperature of the strand extruded from the central die hole of the horizontal flat die is set to 295 to 340°C, and the temperature of the strand extruded from the end die hole of the horizontal flat die is set to be 4 to 14°C lower than the temperature of the strand extruded from the central die hole of the flat die.

[0033] FIG. 2 is a diagram showing an example of a die portion of a twin-screw extruder used in the present invention, and is a cross-sectional view of the die portion cut along a plane parallel to the bottom surface thereof.

[0034] The molten polyester resin composition is fed into the die section from the screw 21 of the twin-screw extruder 1. The die section is composed of a breaker plate 23 (or ring plate), a die holder 8, a flange 6, a manifold section 24, and a horizontal flat die 25. In some cases, the die holder is also called a die plate, and the flange is also called a hinge plate.

[0035] A screen mesh can be installed inside the breaker plate 23. Foreign matter and the like are removed by filtration. The screen mesh may be made of one or a combination of two or more types of metal mesh. The mesh size of the metal mesh is preferably #10 to #300, more preferably #20 to #200, and particularly #30 to #200. It is preferable to use a combination of two to five types selected from these, stacked together. The breaker plate 23 is provided with a desired number of holes with a desired diameter d and land length L. When a screen mesh is not used, it is common to install a ring-shaped plate 23. A ring plate was installed in the examples and comparative examples of this application. This breaker plate or ring plate can prevent resin leakage.

[0036] The horizontal flat die refers to a die having die holes arranged in the horizontal direction, such as a die having a plurality of die holes 31, 32, and 33 arranged in a single horizontal row as shown in Fig. 3(a), a die having a plurality of die holes 31, 32, and 33 arranged in a staggered horizontal row as shown in Fig. 3(b), or a die having die holes 31, 32, and 33 arranged in two horizontal rows, one above the other, as shown in Fig. 4(d).

[0037] When the die holes are arranged in two rows, one above the other, in the horizontal direction, the end die holes 32 and 33 are often arranged below the upper die hole and above the lower die hole, as shown in Figure 4(d). This arrangement occurs when a separator plate 34 is provided between the two rows in the horizontal flat die 25, dividing the resin flow path into upper and lower sections.

[0038] Alternatively, as shown in Figure 4(e), the die holes may be randomly arranged in the horizontal direction. In this case, the die holes 32 and 33 at the left and right ends of the die are the end die holes, and the die hole 31 closest to the geometric center of the die is the central die hole. A horizontal flat die 25 is generally located at the tip of a manifold portion 24 where the resin flow path expands horizontally within the die holder, and is a die with die holes arranged in the horizontal direction. The diameter d of each die hole does not need to be the same, and the land length L of the die hole does not need to be the same; the diameter d and land length L may be different for each die hole.

[0039] The shape of the extrusion die is not particularly limited, and any known die may be used. The diameter d of the die hole depends on the desired pellet size, but is usually about 2 to 5 mm, preferably about 3 to 4 mm.

[0040] When producing glass fiber-reinforced polyester-containing resin composition pellets, the use of a horizontal flat die is advantageous in terms of improving productivity. Other circular dies, such as those shown in Figure 3(c), have die holes arranged circumferentially. However, when high throughput is desired, the number of die holes is increased. This increases the diameter of the circumference, and strands emerging from the die holes on the circumference travel a longer distance to the water tank, becoming unstable and prone to breakage. Thus, horizontal flat dies are advantageous for stable production in terms of improving productivity. However, with a horizontal flat die, strands emerging from the end die holes 32 and 33 are more likely to break than strands emerging from the inner die hole 31. Strands emerging from the end die holes 32 and 33 tend to bend outward when viewed from the center of the die. This phenomenon, known as curling, causes strands emerging from the end die holes 32 and 33 to spiral outward. This curling makes strands emerging from the end die holes more likely to break. This becomes more pronounced as the concentration of glass fibers increases.

[0041] Although the cause of this curling is unclear, the end die holes 32 and 33 are susceptible to the influence of the wall surface of the die holder. It is believed that the frictional force between the resin and the wall surface of the die holder remains as residual stress, causing the outward bending (curling). In this invention, by setting the temperature of the strand from the central die hole to 295 to 340°C and creating a temperature difference of 4 to 14°C between the strands from the center and end dies, it is possible to eliminate or minimize strand breakage at the ends and suppress strand breakage in all strands.

[0042] The strand temperature at the center of the die refers to the temperature of the strand immediately after it emerges from the die hole 31 closest to the geometric center of the die. If the die has an odd number of die holes arranged at equal intervals in the horizontal direction, this refers to the average temperature of the die hole at the center of the die; if the die has an even number of die holes, this refers to the average temperature of the two strands at the center of the die. This strand temperature at the center of the die can be measured directly by contacting a thermocouple. It can also be measured using an infrared thermometer. This strand temperature at the center of the die is considered to be close to the resin temperature inside the die.

[0043] The temperature of the strand at the die end refers to the temperature of one strand at each of the left and right die ends 32, 33 as viewed from the die. If the temperatures of the left and right strands are different, their average value is used. Similarly, it refers to the temperature of the strand immediately after it leaves the die. The temperature of the strand at the die end is easily affected by the temperatures of the die holder, flange, and die. However, because the die holder, flange, and die vary from extruder to extruder, the relationship between their temperatures and the end strand temperature cannot be determined uniformly.

[0044] The temperature (ΔT) obtained by subtracting the temperature of the strands at both ends of the die from the temperature of the strand at the center of the die is set to 4°C or higher and 14°C or lower. By setting ΔT in this manner, strand breakage at the ends can be eliminated and strand breakage of all strands can be suppressed. If ΔT is lower than 4°C, the high strand temperature reduces the elastic recovery force of the strands at the ends, making them more likely to break due to curling (weak elastic recovery force from curling). On the other hand, if ΔT is higher than 14°C, the force that causes curling itself becomes stronger, leading to breakage due to curling. Adjusting ΔT to 4°C or higher and 14°C or lower can be achieved, for example, by setting the temperature of the die holder slightly lower than the resin temperature in the die. ΔT is preferably 4.5°C or higher, more preferably 5°C or higher, and preferably 12°C or lower, more preferably 10°C or lower.

[0045] The temperature of the strand from the center of the die must be 295°C or higher and 340°C or lower. By setting this temperature, the resin component of the resin composition can be impregnated well into the glass fiber bundles, and by setting the above-mentioned ΔT, strand breakage can be prevented. If the temperature is lower than 295°C, the viscosity of the resin component of the resin composition is high, impregnation into the glass fiber bundles is poor, and bundle-like fibers remain. When the strand emerges from the die, stress concentration points form in the strand, causing it to easily break. The temperature of the strand from the center of the die is preferably 300°C or higher, more preferably 310°C or higher. On the other hand, if the temperature exceeds 340°C, the polyester resin will thermally decompose, generating gas, which will easily break the strand when it emerges from the die. The temperature of the strand from the center of the die is preferably 335°C or lower, more preferably 330°C or lower.

[0046] In the fourth step, the strand 10 emerging from the die is water-cooled and cut by a pelletizer 11. The strand temperature during strand cutting is preferably 100°C or higher and 150°C or lower. By setting the temperature at such a level, it becomes easier to prevent the generation of chips and pellets with poor shapes. If the temperature is lower than 100°C, the strand is hard and chips are likely to be generated when cut by the pelletizer. This makes the plasticization unstable during molding such as injection molding. If the temperature exceeds 150°C, the flattening ratio of the cut pellets to an elliptical cylindrical shape becomes large, which may also result in poor plasticization. The strand temperature during strand cutting is more preferably 110°C or higher and 140°C or lower.

[0047] Glass fiber-reinforced polyester resin compositions containing high concentrations of glass fiber tend to break after exiting the die and before cooling and strand cutting. The low resin content weakens the viscoelastic properties, causing the strands to lose toughness and become brittle and prone to breakage. Furthermore, the high glass fiber content tends to produce fiber bundles with poor opening properties. Fiber bundles with poor opening properties are prone to breakage initiation points during strand drawing (stretching). Furthermore, if the fiber bundles are not sufficiently filled with resin, these points may become breakage initiation points (insufficient resin impregnation of the glass fiber bundles). Furthermore, the high glass fiber concentration increases the viscosity of the resin, which tends to increase the resin temperature. This generates pyrolysis gas, which causes the strands to break upon exiting the die. These factors, including reduced strand toughness, insufficient opening of the glass fiber bundles, insufficient resin impregnation of the glass fiber bundles, and gas generation, make it difficult to consistently cut the strands. When a strand breaks, it must be manually reloaded into the pelletizer. This disrupts the overall strand flow, causing the strand to enter the cutter at an angle, resulting in the generation of long pellets. Furthermore, because the glass fiber concentration is high and the strands are hard, the cut surface by the pelletizer is not sharp, becoming dull and generating chips. To suppress chip generation, it is necessary to increase the strand cutting temperature. This results in a sharper cut and reduced chips. However, if the strand cutting temperature is too high, the strands become soft and are crushed by the pelletizer's take-up roll, resulting in increased eccentricity of the elliptical cylindrical pellets. The greater the number of long pellets and chips and the higher the flatness, the more likely it is that poor plasticization will occur during injection molding using the pellets, resulting in reduced productivity. The number of long pellets (usually more than twice the length of the pellets) is preferably five or fewer per kg. The amount of chips is preferably 300 ppm by mass or less of the total mass (pellets + chips). Furthermore, the flatness ratio (major axis / uniaxial) is preferably 1.30 or less.

[0048] The strand 10 is taken up by a take-up roller and brought into contact with water to be cooled. The contact with water may be carried out by conveying the strand 10 through water stored in a cooling water tank 13, or by pouring water onto the strand 10 to bring it into contact with water, or by pulling the strand on a mesh belt conveyor and pouring water onto it using a water spraying device. The shorter the time between the strand being extruded from the die and the water cooling or immersion in water, the better. Usually, it is best for the strand to be immersed in water within one second after being extruded from the die.

[0049] The cooled strand is sent to a pelletizer by a take-up roller, where it is cut into pellets.

[0050] In the method of the present invention, the shear viscosity of the glass fiber reinforced polyester resin composition at 265°C and 91 / sec is set to 400 Pa·s or more and 2000 Pa·s or less. Setting the shear viscosity in the range of 400 to 2000 Pa·s and combining it with the above-mentioned steps suppresses strand breakage and enables continuous, stable production. If the viscosity is below 400 Pa·s, the elastic properties of the strands are weak and the strands are prone to breakage. Furthermore, if the viscosity exceeds 2000 Pa·s, shear heat generation increases, the resin temperature rises, thermal decomposition occurs, and the strands easily break. A more preferred range is 500 Pa·s or more and 1700 Pa·s or less, and an even more preferred range is 600 Pa·s or more, preferably 1400 Pa·s or less.

[0051] The shear viscosity is a value measured using a Capillograph (Capillograph 1D2 manufactured by Toyo Seiki Seisaku-sho, Ltd.) with an orifice having a capillary diameter of 1 mm and a capillary length of 3 mm at 265°C and a shear rate of 91 / sec in accordance with JIS K7199.

[0052] To adjust the shear viscosity within the above range, increasing the amount of (B) glass fiber increases the shear viscosity, while decreasing it decreases the shear viscosity. This can also be achieved by adjusting the amount and viscosity of the (C) other polymer to be blended, such as a styrene polymer or polycarbonate resin. It can also be adjusted by changing the viscosity of the polyester. Furthermore, the resin component may be thermally decomposed or hydrolyzed due to the thermal history in the extruder, resulting in a decrease in shear viscosity.

[0053] Next, the raw material components used in the present invention will be described.

[0054] (A) Polyester Resin The (A) polyester resin is a thermoplastic polyester resin, which is a polyester obtained by polycondensation of a dicarboxylic acid compound and a dihydroxy compound, polycondensation of an oxycarboxylic acid compound, or polycondensation of these compounds, and may be either a homopolyester or a copolyester.

[0055] The dicarboxylic acid compound constituting the polyester resin (A) is preferably an aromatic dicarboxylic acid or an ester-forming derivative thereof. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, diphenylisopropylidene-4,4'-dicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, anthracene-2,5-dicarboxylic acid, anthracene-2,6-dicarboxylic acid, p-terphenylene-4,4'-dicarboxylic acid, and pyridine-2,5-dicarboxylic acid, with terephthalic acid being preferred.

[0056] These aromatic dicarboxylic acids may be used in combination of two or more. As is well known, in addition to the free acids, dimethyl esters and the like can be used as ester-forming derivatives in polycondensation reactions. Small amounts of these aromatic dicarboxylic acids may be used in combination with one or more aliphatic dicarboxylic acids such as adipic acid, azelaic acid, dodecanedioic acid, and sebacic acid, or alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.

[0057] Examples of dihydroxy compounds constituting the (A) polyester resin include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, hexylene glycol, neopentyl glycol, 2-methylpropane-1,3-diol, diethylene glycol, and triethylene glycol; alicyclic diols such as cyclohexane-1,4-dimethanol; and mixtures thereof. A small amount of copolymerization may be used with one or more long-chain diols having a molecular weight of 400 to 6,000, such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol. Aromatic diols such as hydroquinone, resorcinol, naphthalenediol, dihydroxydiphenyl ether, and 2,2-bis(4-hydroxyphenyl)propane may also be used.

[0058] In addition to the above-mentioned bifunctional monomers, a small amount of a trifunctional monomer such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, or trimethylolpropane can be used in combination to introduce a branched structure, or a monofunctional compound such as a fatty acid can be used in combination to adjust the molecular weight.

[0059] The polyester resin (A) is usually a resin obtained by polycondensation of a dicarboxylic acid and a diol, i.e., a resin in which 50% by mass or more, preferably 70% by mass or more of the total resin is made up of this polycondensate. The dicarboxylic acid is preferably an aromatic dicarboxylic acid, and the diol is preferably an aliphatic diol.

[0060] Among these, polyalkylene terephthalates in which 95 mol % or more of the acid component is terephthalic acid and 95 mass % or more of the alcohol component is an aliphatic diol are preferred. Representative examples are polybutylene terephthalate resin and polyethylene terephthalate resin. These are similar to homopolyesters, that is, preferably, 95 mass % or more of the entire resin is composed of terephthalic acid components and 1,4-butanediol or ethylene glycol components.

[0061] The polyester resin (A) preferably has a main component (i.e., 50% by mass or more) of polybutylene terephthalate resin or polyethylene terephthalate resin, and particularly preferably polybutylene terephthalate resin.

[0062] The polyester resin (A) preferably has an intrinsic viscosity of 0.60 dL / g or more but less than 1.0 dL / g, more preferably 0.60 dL / g or more but less than 0.95 dL / g, and even more preferably 0.65 dL / g or more but less than 0.95 dL / g. If an intrinsic viscosity of less than 0.60 dL / g is used, the resulting resin composition is likely to have low mechanical strength, poor hydrolysis resistance, and low heat shock resistance, while if the intrinsic viscosity is 1.0 dL / g or more, it is likely to be difficult to obtain good fluidity.

[0063] The intrinsic viscosity of the polyester resin is a value measured at 30° C. in a mixed solvent of 1,1,2,2-tetrachloroethane and phenol in a 1:1 (mass ratio).

[0064] The amount of terminal carboxyl groups in the polyester resin (A) may be appropriately selected and determined, but is usually 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. If it exceeds 60 eq / ton, gas tends to be generated during melt molding of the resin composition. The lower limit of the amount of terminal carboxyl groups is not particularly specified, but is usually 10 eq / ton, taking into consideration the productivity of polyester resin production.

[0065] The amount of terminal carboxyl groups in the polyester resin is determined by dissolving 0.5 g of polyalkylene terephthalate resin in 25 mL of benzyl alcohol and titrating the solution with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventional method, such as adjusting the polymerization conditions, such as the raw material charge ratio, polymerization temperature, and pressure reduction, or by reacting a terminal blocking agent.

[0066] (B) Glass Fiber As the (B) glass fiber, any known glass fiber can be used, so long as it is one that is normally used in polyester resins, regardless of the form of the glass fiber when blended, such as A-glass, E-glass, alkali-resistant glass compositions containing a zirconia component, chopped strands, glass roving, master batches of thermoplastic resins and glass fibers, etc. Among these, alkali-free glass (E-glass) is preferred as the (B) glass fiber used in the present invention for the purpose of improving the thermal stability of the resin composition.

[0067] It is also preferable to use, as the (B) glass fiber, glass fibers having an irregularity ratio of the longitudinal cross section in the range of 2.0 to 6.0. The irregularity ratio of the longitudinal cross section is the ratio of the major axis to the minor axis when a rectangle having the smallest area circumscribing the cross section perpendicular to the longitudinal direction of the glass fiber is assumed, and the length of the long side of this rectangle is the major axis and the length of the short side is the minor axis.

[0068] (B) The cross-sectional area of ​​the glass fiber in the longitudinal direction is 90 μm ２ Super 300μm ２ With such a cross-sectional area, the polyester resin can easily become a matrix, and as a result, the heat resistance can easily be improved. ２ Super 250μm ２ Less than 90 μm, more preferably ２ Super 200μm ２ (B) The thickness of the glass fiber is not particularly limited, but it is preferable that the minor axis is about 2 to 20 μm and the major axis is about 5 to 50 μm.

[0069] The (B) glass fiber may be treated with a sizing agent or a surface treatment agent. Furthermore, during the production of the resin composition of the present invention, a sizing agent or a surface treatment agent may be added separately from the untreated glass fiber to perform surface treatment.

[0070] Examples of sizing agents include resin emulsions of vinyl acetate resin, ethylene / vinyl acetate copolymer, acrylic resin, epoxy resin, polyurethane resin, polyester resin, etc. Examples of surface treatment agents include aminosilane compounds such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, chlorosilane compounds such as vinyltrichlorosilane and methylvinyldichlorosilane, alkoxysilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, epoxysilane compounds such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane, acrylic compounds, isocyanate compounds, titanate compounds, and epoxy compounds.

[0071] Two or more of these sizing agents and surface treatment agents may be used in combination, and the amount used (adhesion amount) is usually 10% by mass or less, preferably 0.05 to 5% by mass, based on the mass of the (B) glass fiber. By setting the adhesion amount to 10% by mass or less, a necessary and sufficient effect can be obtained, and it is economical.

[0072] Two or more types of (B) glass fibers may be used in combination depending on the required properties.

[0073] The content of (B) glass fiber is set to a high content of 40 to 70 mass% relative to 100 mass% of the total of (A) polyester resin, (B) glass fiber, and (C) other polymers or additives. If the content of (B) glass fiber is less than 40 mass%, rigidity tends to be insufficient, while if it exceeds 70 mass%, impact resistance and fluidity tend to be insufficient and production tends to be difficult. The content of (B) glass fiber is more preferably 42 mass% or more, more preferably 65 mass% or less, and even more preferably 60 mass% or less.

[0074] (C) Other polymers or additives are polymers other than (A) polybutylene ester resin and / or various other additives.

[0075] Examples of other additives include various resin additives, such as (B) fillers other than glass fiber (talc, glass flakes, mica, kaolin, ceramic beads, clay, zeolite, barium sulfate, titanium oxide, silicon oxide, aluminum oxide, magnesium hydroxide, zinc sulfide, etc.), flame retardants, flame retardant aids, stabilizers, antioxidants, mold release agents, ultraviolet absorbers, weather stabilizers, lubricants, colorants such as dyes and pigments, catalyst deactivators, antistatic agents, foaming agents, plasticizers, crystal nucleating agents, and crystallization accelerators.

[0076] Examples of other polymers include various elastomers, styrene-based polymers described below, polycarbonate resins, polyolefin resins such as polyethylene resins and polypropylene resins, polyamide resins, polyimide resins, polyetherimide resins, polyphenylene ether resins, polyphenylene sulfide resins, polysulfone resins, polymethacrylate resins, etc. One type of other resin may be contained, or two or more types may be contained in any combination and ratio.

[0077] The amount of (C) other polymers or additives is 0 to 50% by mass, based on 100% by mass of the total of (A) to (C), and is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, and is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, 4% by mass or more, and particularly preferably 5% by mass or more.

[0078] Examples of styrene-based polymers include homopolymers of styrene, graft copolymers obtained by polymerizing styrene in the presence of rubber, copolymers of styrene and (meth)acrylonitrile, copolymers of styrene and (meth)acrylic acid alkyl esters, copolymers of styrene, (meth)acrylonitrile and other copolymerizable monomers, and graft copolymers obtained by graft polymerizing styrene and (meth)acrylonitrile in the presence of rubber. Specific examples of the resin include polystyrene (general-purpose polystyrene, GPPS), impact-resistant polystyrene (high impact polystyrene, HIPS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), styrene-butadiene-styrene copolymer (SBS resin), hydrogenated styrene-butadiene-styrene copolymer (hydrogenated SBS), hydrogenated styrene-isoprene-styrene copolymer (SEPS), styrene-maleic anhydride copolymer (SMA resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), methyl methacrylate-butadiene-styrene copolymer (MBS resin), methyl methacrylate-acrylonitrile-butadiene-styrene copolymer (MABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), and styrene-IPN type rubber copolymer, or mixtures thereof.

[0079] Among these, acrylonitrile-styrene copolymer (AS resin), polystyrene (GPPS), high impact polystyrene (HIPS), and acrylonitrile-butadiene-styrene copolymer (ABS resin) are preferred, and acrylonitrile-styrene copolymer (AS resin), polystyrene (GPPS), high impact polystyrene (HIPS), and acrylonitrile-butadiene-styrene copolymer (ABS resin) are particularly preferred.

[0080] As the styrene-based polymer, a styrene-based elastomer can also be used. As the styrene-based elastomer, a block copolymer consisting of a polymer block containing a vinyl aromatic compound as a polymerization component and a polymer block containing a conjugated diene as a polymerization component, and a hydrogenated product thereof are preferred.

[0081] Examples of vinyl aromatic compounds constituting the vinyl aromatic hydrocarbon polymer block include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-t-butylstyrene, 1,3-dimethylstyrene, lower alkyl-substituted styrene, vinylnaphthalene, vinylanthracene, and other styrenes or derivatives thereof. These can be used alone or in combination of two or more.

[0082] Examples of the conjugated diene constituting the conjugated diene block include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene.

[0083] The styrene polymer may be used alone or in combination of two or more. The amount of the styrene polymer is preferably 5 to 45% by mass, based on 100% by mass of the total of (A) to (C).

[0084] The polycarbonate resin is preferably an aromatic polycarbonate resin, and specifically, a thermoplastic aromatic polycarbonate polymer or copolymer obtained by reacting an aromatic dihydroxy compound with phosgene or a diester of carbonic acid is used.

[0085] Examples of aromatic dihydroxy compounds include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and tetramethylbisphenol A.

[0086] Preferred examples of polycarbonate resins include polycarbonate resins containing 2,2-bis(4-hydroxyphenyl)propane as a dihydroxy compound or a combination of 2,2-bis(4-hydroxyphenyl)propane and another aromatic dihydroxy compound.

[0087] The polycarbonate resin may be a homopolymer consisting of one type of repeating unit, or a copolymer having two or more types of repeating units, and the copolymer may be a random copolymer, a block copolymer, or any of a variety of copolymer forms.

[0088] Although there are no restrictions on the molecular weight of the polycarbonate resin, the viscosity average molecular weight (Mv) is usually about 10,000 to 100,000, and preferably about 12,000 to 35,000. By setting the viscosity average molecular weight to at least the lower limit of the above range, the mechanical strength can be further improved, making it more preferable for use in applications requiring high mechanical strength.

[0089] The viscosity average molecular weight (Mv) of the polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 25°C using an Ubbelohde viscometer, and then using the following Schnell viscosity formula: [η] = 1.23 × 10 －４ Mv ０．８３

[0090] The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by either the phosgene method (interfacial polymerization method) or the melt method (ester interchange method) can be used. Also preferred is a polycarbonate resin produced by the melt method and then subjected to post-treatment to adjust the amount of terminal OH groups.

[0091] In addition, polycarbonate resins can be made not only from virgin raw materials but also from aromatic polycarbonate resins recycled from used products, i.e., so-called material-recycled aromatic polycarbonate resins. Preferred examples of used products include optical recording media such as optical disks, light guide plates, transparent vehicle components such as automobile window glass, automobile headlamp lenses, and windshields, containers such as water bottles, eyeglass lenses, soundproof walls, glass windows, and building components such as corrugated sheets. Furthermore, crushed products obtained from non-conforming products, sprues, or runners, or pellets obtained by melting these, can also be used as recycled polycarbonate resins.

[0092] When polycarbonate resin is contained, the amount is preferably 5 to 45% by mass, based on 100% by mass of the total of (A) to (C).

[0093] The glass fiber reinforced polyester resin composition produced by the method of the present invention can be used to produce molded articles with high strength, and therefore can fully satisfy the requirements for weight reduction, thinning, and strength, and can be widely used for molded articles or parts in, for example, the fields of electrical and electronic equipment, office automation equipment such as computers, precision equipment, optical equipment, automobiles, and various other industrial fields.

[0094] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples and can be practiced with any modifications within the scope of the present invention.

[0095] The raw materials (A) polyester resin, (B) glass fiber, and (C) other polymers used in the examples and comparative examples are as shown in Table 1 below.

[0096]

[0097] In the following examples and comparative examples, a vented intermeshing co-rotating twin screw extruder ("TEX44αIII" manufactured by The Japan Steel Works, Ltd., cylinder diameter D=47 mm) was used.

[0098] The screw configuration is shown in Figure 5. C1 is a feed cylinder, C7 and C12 are vent cylinders, C7 is an open vent, C12 is a vacuum vent, and C9 is a side feed cylinder. The first kneading section, which melt-kneads (A) polyester resin and (C) other polymers, was located at C5 to C6, and its screw configuration was a 1D, five-paddle RRNNL (1D = 44 mm). (B) Glass fiber was side-fed from C9. The second kneading section, which kneads (B) glass fiber, was a 1D, five-paddle R and three 1D back-mixing screws (lead 0.25D), arranged as shown in Figure 2.

[0099] The first kneading section is the section where (A) polyester resin and (C) other polymers are added and where (B) glass fiber is fed, and the section from C1 to C9 is the first step. Next, (B) glass fiber enters the extruder, and the kneading section up to the decompression vent is the second kneading section, and the section from C10 to C11 is the second step. The third step is the section from C12 to C14, including the die holder, where the kneaded resin comes out of the die. Furthermore, the strand coming out of the die is water-cooled and cut with a pelletizer to obtain pellets, which is the fourth step.

[0100] In the following Examples 1 to 9 and Comparative Examples 1 to 4, resin compositions were produced using the raw material proportions shown in Recipe 1 in Table 1 above.

[0101] Example 1 Polybutylene terephthalate resin (PBT2) 65 kg / h, polyethylene terephthalate resin (PET) 50 kg / h, and elastomer (EL) 10 kg / h were supplied from the main raw material hopper to the C1 feed barrel of a twin-screw extruder "TEX44αIII." Furthermore, glass fiber (GF) 125 kg / h was supplied from the side feed hopper to the C9 side feed cylinder. The total feed rate of the raw materials was 250 kg / h, and the screw rotation speed was 300 rpm.

[0102] The set temperatures of cylinders C2 to C9 and cylinders C12 to C14 were 250°C. The set temperatures of cylinders C10 and C11 in the second kneading section were 170°C. The set temperature of the die holder in the third process was 300°C. The flange temperature was also 300°C. A horizontal flat die was used with a die hole diameter of 3.8 mm, a land length of 20 mm, and 10 holes. The resin pressure in the die holder at this time was 4.8 MPa. The average temperature of the two strands in the center of the die was 325°C. The average temperature of the strands at both ends of the die was 318°C. In the present examples and comparative examples, the flange temperature was the same as the die holder temperature.

[0103] The take-up speed of the pelletizer was 40 m / min. Extrusion was continued under these conditions for 1 hour. All 10 strands were stable and did not break even once. The strands at both ends of the die showed what appeared to be slight outward curling, but did not break. The strands emerging from the die were cooled in a water bath and strand-cut using a pelletizer to obtain pellets with an average length of 3 mm.

[0104] The resulting pellets were dried at 120°C for 5 hours, and the shear viscosity was measured at a shear rate of 91 / sec at 265°C using a Toyo Seiki Seisakusho "Capilograph 1D2" with an orifice having a capillary diameter of 1 mm and a capillary length of 3 mm. The shear viscosity was 910 Pa s. 1 kg of the resulting pellets was visually inspected, and the number of long pellets (pellets longer than 6 mm) was counted. The results are shown in Table 2.

[0105] The obtained pellets were dried at 120°C for 5 hours, and the shear viscosity was measured at a temperature of 265°C and a shear rate of 91 / sec using a "Capilograph 1D2" manufactured by Toyo Seiki Seisaku-sho, Ltd., with an orifice having a capillary diameter of 1 mm and a capillary length of 3 mm.

[0106] The strand breakage evaluation was judged according to the following criteria: A: Number of strand breakages: 0 times / hour B: Number of strand breakages: 1 to 2 times / hour C: Number of strand breakages: 3 to 5 times / hour D: Number of strand breakages: 6 to 9 times / hour E: Number of strand breakages: ≥ 10 times / hour The results are shown in Table 2.

[0107] Example 2 The same procedure as in Example 1 was carried out except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 10 mm.

[0108] Example 3 The same procedure as in Example 1 was carried out except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 30 mm.

[0109] Example 4 The same procedure as in Example 1 was carried out except that the temperature of the die holder was set to 270°C.

[0110] Example 5 The same procedure as in Example 1 was carried out except that the temperature of the die holder was set to 320°C.

[0111] Example 6 The same procedure as in Example 1 was carried out except that the temperature of the die holder was set to 250°C.

[0112] Example 7 The same procedure as in Example 1 was carried out except that the temperature of the die holder was set to 330°C.

[0113] Example 8 The same procedure as in Example 1 was carried out, except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 5 mm. The resin pressure inside the die was 1.7 MPa. The strands inside the die and at both ends of the die were prone to breakage, and fibrous fluff was observed on the strands. It was determined that the resin pressure was low and the fiber opening was insufficient.

[0114] Example 9 The same procedure as in Example 1 was carried out, except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 40 mm. The resin pressure inside the die was high at 9.2 MPa, and the strands inside the die and at both ends of the die were prone to breakage. The strand breakage occurred at the die exit, so it was thought that the strand breakage was caused by gas. The strand surface was smooth, and it was determined that there was no problem with the fiber spreadability.

[0115] Comparative Example 1 The same procedure as in Example 1 was carried out except that the die holder temperature was set to 230°C. The temperature difference between the center of the strand die and both ends of the strand die was 15°C. All strand breaks occurred at both ends of the die. There was severe curling, and the strands were seen to be bending outward from the die. This was thought to be due to curling breakage.

[0116] Comparative Example 2 The same procedure as in Example 1 was carried out, except that the die holder temperature was set to 350°C. The temperature difference ΔT between the center of the strand die and both ends of the strand die was only 3°C. The temperature at the center of the strand die was also high at 335°C, and the strand broke 8 times at both ends of the die and 13 times on the inside. It is thought that the small ΔT meant that there was no resistance to curling, and that the resin temperature was also high, generating gas and causing the breakage on the inside.

[0117] Comparative Example 3 The same procedure as in Example 1 was carried out except that the screw rotation was set to 200 rpm, the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 10 mm. The temperature at the center of the strand die was 292°C.

[0118] Comparative Example 4 The same procedure as in Example 1 was carried out, except that the screw rotation was set to 500 rpm. The temperature at the center of the strand die was 344°C. The strands broke equally on the inside and at both ends of the die. The strand surfaces were clean, and no poor glass fiber spreading was observed. Since the strand breakage occurred at the die exit, it was thought to be due to gas-induced breakage.

[0119] The results are shown in Table 2 below.

[0120]

[0121] In the following Examples 10 to 18 and Comparative Examples 5 to 8, resin compositions were produced using the raw material proportions shown in Recipe 2 in Table 1 above.

[0122] Example 10: 37.5 kg / h of polybutylene terephthalate resin (PBT1), 62.5 kg / h of polystyrene resin (PS), and 12.5 kg / h of polycarbonate resin (PC) were fed from the main raw material hopper to the C1 feed barrel of the twin-screw extruder "TEX44αIII." Furthermore, 137.5 kg / h of glass fiber (GF) was fed from the side feed hopper to the C9 side feed cylinder. The total feed rate of the raw materials was 250 kg / h, and the screw rotation speed was 300 rpm. The cylinder set temperatures for C2 to C8 and C12 to C14 were set to 250 ° C, and the cylinder set temperatures for C9 and C10 in the second kneading section were set to 170 ° C. The set temperature of the die holder in the third step was 300 ° C. In addition, a horizontal flat die with a die hole diameter of 3.8 mm, a land length of 20 mm, and 10 holes was used. The resin pressure of the die holder at this time was 4.7 MPa. The average temperature of the two strands in the center of the die was 322°C. The average temperature of the strands at both ends of the die was 314°C. The pelletizer take-up speed was 40 m / min. Extrusion continued under these conditions for 1 hour. All 10 strands were stable and did not break even once. The strands at both ends of the die showed what appeared to be slight outward curling, but did not break. The strands emerging from the die were cooled in a water bath and cut with a pelletizer to obtain pellets. The resulting pellets were dried at 120°C for 5 hours, and the shear viscosity was measured at a shear rate of 91 / sec at 265°C using a "Capilograph 1D2" manufactured by Toyo Seiki Seisakusho Co., Ltd., using an orifice with a capillary diameter of 1 mm and a capillary length of 3 mm. The shear viscosity was 850 Pa*sec.

[0123] Example 11 The same procedure as in Example 10 was carried out except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 10 mm.

[0124] Example 12 The same procedure as in Example 10 was carried out except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 30 mm.

[0125] Example 13 The same procedure as in Example 10 was carried out except that the temperature of the die holder was set to 270°C.

[0126] Example 14 The same procedure as in Example 10 was carried out except that the temperature of the die holder was 320°C.

[0127] Example 15 The same procedure as in Example 10 was carried out except that the temperature of the die holder was set to 250°C.

[0128] Example 16 The same procedure as in Example 10 was carried out except that the temperature of the die holder was set to 330°C.

[0129] Example 17 The same procedure as in Example 10 was carried out, except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 5 mm. The resin pressure inside the die was 1.6 MPa. The strands inside the die and at both ends of the die were prone to breakage, and fibrous fluff was observed on the strands. It was determined that the resin pressure was low and the fiber opening was insufficient.

[0130] Example 18 The same procedure as in Example 10 was carried out, except that the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 40 mm. The resin pressure inside the die was high at 9.1 MPa, and the strands inside the die and at both ends of the die were prone to breakage. The strand breakage occurred at the die exit, so it was thought that the strand breakage was caused by gas. The strand surface was smooth, and it was determined that there was no problem with the fiber spreadability.

[0131] Comparative Example 5 The same procedure as in Example 10 was carried out except that the die holder temperature was set to 230°C. The temperature difference between the center of the strand die and both ends of the strand die was 17°C. All strand breaks occurred at both ends of the die. There was severe curling, and the strands were seen to be bending outward from the die. This was thought to be due to curling breakage.

[0132] Comparative Example 6 The same procedure as in Example 10 was carried out, except that the die holder temperature was 350°C. The temperature difference ΔT between the center of the strand die and both ends of the strand die was only 2°C. The temperature at the center of the strand die was also high at 333°C, and the strand broke 10 times at both ends of the die and 16 times on the inside. It is thought that the small ΔT meant that there was no resistance to curling, and that the resin temperature was also high, generating gas and causing the breakage on the inside.

[0133] Comparative Example 7 The same procedure as in Example 10 was carried out except that the screw rotation was set to 200 rpm, the horizontal flat die had a hole diameter of 3.8 mm, the number of holes was 10, and the land length was 10 mm. The temperature at the center of the strand die was 290°C.

[0134] Comparative Example 8 The same procedure as in Example 10 was carried out except that the screw rotation was set to 500 rpm. The temperature at the center of the strand die was 342°C. The strands broke equally on the inside and at both ends of the die. The strand surfaces were clean, and no poor glass fiber spreading was observed. Since the strand breakage occurred at the die exit, it was thought to be due to gas-induced breakage.

[0135] The results are shown in Table 3 below.

[0136]

[0137] According to the production method of the present invention, it is possible to stably produce high-quality pellets of a glass fiber-reinforced polyester resin composition containing glass fibers at a high concentration.

[0138] 1: Main material hopper 3: Side feed hopper 4: Decompression vent 5: Second kneading section thermocouple 6: Flange 7: Resin pressure gauge 8: Die holder 9: Die holder thermocouple 10: Strand 11: Pelletizer 12: Pellets 13: Cooling water tank 15: Gear box 16: Motor 20: Cylinder tip 21: Screw 23: Ring plate 24: Manifold section 25: Horizontal flat die 31, 32, 33: Die holes

Claims

1. A method for producing a glass fiber-reinforced polyester resin composition using a twin-screw extruder, the method comprising: (A) 10-60% by weight of polyester resin; (B) 40-70% by weight of glass fiber; and (C) 0-50% by weight of other polymers or additives (the total of all components is 100% by weight); wherein the glass fiber-reinforced polyester resin composition has a shear viscosity of 400-2000 Pa·s at 265°C and 91 / sec; and when a strand is extruded from a horizontal flat die attached to a die holder at the tip of the twin-screw extruder, the temperature of the strand emerging from the central die hole of the flat die is 295-340°C, and the temperature of the strand emerging from the end die hole of the flat die is 4-14°C lower than the temperature of the strand emerging from the central die hole of the flat die.

2. The manufacturing method according to claim 1, wherein the resin is extruded so that the resin pressure inside the die when it emerges from the flat die is 2 to 9 MPa.

3. The manufacturing method according to claim 1, wherein the temperature of the die holder is 240 to 340°C.