Process for producing a fiber-reinforced polybutylene terephthalate resin composition

Abstract

Provided is a production method of a fiber-reinforced polybutylene terephthalate resin composition by a twin-screw extruder, the resin composition comprising (A) 40 to 90 mass% of a polybutylene terephthalate resin, (B) 10 to 60 mass% of a reinforcing fiber, and (C) 0 to 35 mass% of other polymers or additives, the method being characterized in that it includes a first step of kneading (A) and (C) with a first kneading section using polybutylene terephthalate resin pellets having an average weight of 16 to 29 mg as a raw material for (A); a second step of adding (B) at a downstream portion of the first kneading section and kneading with a second kneading section; and a third step of performing pressure reduction devolatilization on a discharge port at a downstream portion of the second kneading section, wherein the first kneading section includes a configuration having a length of 5.0 to 9.0D and including a specific screw configuration, the second kneading section includes a specific screw configuration, and the production is performed under conditions in which a screw shaft torque density is 11.5 to 19 Nm / cm 3 .

Description

Technical Field

[0001] This invention relates to a method for producing fiber-reinforced polybutylene terephthalate resin compositions, and more specifically to a method for producing fiber-reinforced polybutylene terephthalate resin compositions having higher strength than those in the prior art and produced with high productivity using a high-torque twin-screw extruder. Background Technology

[0002] Polybutylene terephthalate (PET) resins are widely used in various electrical and electronic components, mechanical parts, and automotive parts, primarily for injection molding. In particular, PET resin compositions reinforced with blended reinforcing fibers such as glass fiber and carbon fiber exhibit excellent mechanical strength, heat resistance, and chemical resistance, and are used as components in the automotive, electrical and electronic device, and other fields.

[0003] However, as components have recently become smaller, thinner, and lighter, there is a strong demand for fiber-reinforced polybutylene terephthalate resin compositions exhibiting even higher mechanical strength.

[0004] Fiber-reinforced polybutylene terephthalate (PET) resin compositions are typically produced using twin-screw extruders. Over the years, attempts have been made to improve the plasticizing and kneading capabilities of twin-screw extruders to enhance production capacity. Recently, extruders have been developed that allow shaft torque density to approach 18 Nm / cm². 3 The ultra-high torque extruder (e.g., the "TEXαIII" manufactured by Japan Steel Works, Ltd.) enables production in high torque ranges that were previously impossible, thus making higher discharge rates possible than in the past.

[0005] However, it is clear that problems can occur if this type of ultra-high torque extruder is used, such as shorter resin residence time, less likely resin temperature to rise, reduced adhesion to reinforcing fibers such as glass fibers, and reduced mechanical strength.

[0006] PTL1 discloses an invention in which a backward feeding screw element with a threaded portion having an arc-shaped notch is used to improve the productivity of glass fiber reinforced thermoplastic resin composition granules, exceeding the productivity possible in the past, and significantly reducing the possibility of monofilament assemblies (undefused glass fiber bundles) remaining in the produced granules. The conditions in this case are specified such that (i) the torque density is 11 Nm / cm². 3The torque density mentioned above is a value obtained by dividing the torque of the screw in the reverse feed screw element by the cube of the inter-core distance between the meshing screws, and (ii) the Q / Ns density is 0.013 kg / h / rpm / cm. 3 Q / Ns is a value obtained by dividing Q / Ns by the cube of the distance between the screw cores, which is the discharge volume Q divided by the screw speed Ns.

[0007] However, regarding torque density, PTL 1 (

[0063] section) only states that "if the torque density is 11 (Nm / cm) 3 At speeds above 13 Nm / cm², the material filling rate in the extruder increases, the energy density decreases, and there is almost no temperature increase even at higher speeds. Furthermore, a preferred torque density range is 13 Nm / cm². 3 ) or above and 18 (Nm / cm 3 The embodiments do not disclose the level of torque density in any way, nor how such torque density is achieved. A TEX44αII (manufactured by Japan Steel Works, Ltd.) with a screw element barrel diameter D of 0.047 m was used as the twin-screw extruder in the embodiments of PTL 1, but the permissible shaft torque density of the TEX44αII is 13 Nm / cm². 3 Furthermore, because the screw shaft or gearbox will be damaged at shaft torque densities exceeding this, the torque density is at most 10.5 Nm / cm². 3 This is because the equipment is typically operated at less than 80% of the allowable shaft torque density.

[0008] Furthermore, at the time PTL 1 was filed, ultra-high torque density twin-screw extruders (such as the extruder described above) were not yet available anywhere in the world. Therefore, PTL 1 specifically discloses the conditions of a conventional low-torque extruder and does not disclose or suggest problems that occur during ultra-high torque operation covered by this invention, nor does it provide means for solving these problems.

[0009] [List of Citations]

[0010] [Patent Literature]

[0011] [PTL 1]JP 2012-213997 A Summary of the Invention

[0012] The problem the invention aims to solve

[0013] When using an ultra-high torque extruder to produce fiber-reinforced polybutylene terephthalate (PET) resin compositions at high torque density, problems have arisen due to the short residence time. For example, the resin temperature is unlikely to rise, meaning insufficient adhesion to the reinforcing fibers and no increase in the strength of the resulting resin composition. To increase the resin temperature, reducing the discharge rate and increasing the kneading time have been considered, but there is no justification for using an ultra-high torque extruder due to the reduced production volume.

[0014] In view of the problems mentioned above, the object of the present invention is to produce fiber-reinforced polybutylene terephthalate resin (granules) with higher strength than in the past and produced with high productivity by using an ultra-high torque extruder.

[0015] Solution for solving the problem

[0016] As a result of diligent research aimed at solving the aforementioned problems, the inventors of this invention have discovered that by using polybutylene terephthalate resin granules with an average weight within a specific range as raw material, and by using a first kneading section having a specific screw structure and screw length, and a second kneading section having a specific screw structure, a screw shaft torque density of 11.5 to 19 Nm / cm² can be achieved. 3 In this case, production is carried out in a high torque region, the resin temperature can be maintained at a temperature above a certain level, the adhesion between the polybutylene terephthalate resin and the reinforcing fibers increases, the strength improvement due to the reinforcing fibers is further enhanced, the reduction in fiber length of the reinforcing fibers that inhibit defibrillation and dispersion does not occur, the resin degradation can be carried out at a high productivity, and fiber-reinforced polybutylene terephthalate resin with high strength can be produced.

[0017] Specifically, the above problem can be solved using the methods described below.

[0018] 1. A fiber-reinforced polybutylene terephthalate resin composition produced by means of a twin-screw extruder, the fiber-reinforced polybutylene terephthalate resin composition comprising (A) 40-90% by weight of polybutylene terephthalate resin, (B) 10-60% by weight of reinforcing fibers, and (C) 0-35% by weight of other polymers or additives (total of all components being 100% by weight).

[0019] The method includes:

[0020] Polybutylene terephthalate resin granules with an average weight of 16 mg or more and 29 mg or less are used as the raw material for component (A).

[0021] The first step involves kneading components (A) and (C) using a first kneading section; the second step involves adding component (B) downstream of the first kneading section and kneading it using a second kneading section; and the third step involves depressurizing and volatilizing the exhaust port of the downstream section of the second kneading section.

[0022] The first kneading section has a length of 5.0D to 9.0D (D is the diameter of the barrel), and is constructed by combining two or more of the following: R kneading disc, N kneading disc, L kneading disc, L screw, sealing ring, mixing screw, and rotor screw.

[0023] The second kneading section has a structure obtained by combining one or more of the following: R kneading disc, N kneading disc, L kneading disc, L screw, sealing ring, and mixing screw.

[0024] Between 11.5 and 19 Nm / cm 3 Production is carried out under conditions of screw shaft torque density.

[0025] 2. The production method according to 1 above, wherein component (C) comprises a styrene-based polymer in an amount of 5 to 30% by mass relative to 100% of the total amount of components (A) to (C).

[0026] 3. According to the production method described in 1 or 2 above, the temperature of the resin filament immediately after extrusion in the third step is 290-310°C.

[0027] 4. The production method according to any one of 1 to 3 above, wherein the intrinsic viscosity of the polybutylene terephthalate resin (A) is 0.72 to 0.83 dl / g.

[0028] 5. The production method according to any one of 1 to 4 above, wherein the total length of the second kneading portion is 2.5D or more and 5.0D or less.

[0029] 6. The production method according to any one of 1 to 5 above, wherein the notched Charpy impact strength of the resulting resin composition, measured according to ISO 179-1.2, is 9 kJ / m. 2 above.

[0030] 7. The production method according to any one of 1 to 6 above, wherein the tensile strength of the obtained resin composition, measured according to ISO 527, is 140 MPa or more.

[0031] 8. The production method according to any one of 1 to 7 above, wherein the screw shaft torque density is 13 to 19 Nm / cm². 3 .

[0032] The effects of the invention

[0033] The method for producing fiber-reinforced polybutylene terephthalate (PPT) resin compositions according to the present invention can increase the adhesion between PPT resin and reinforcing fibers even when production is carried out under high torque range, high discharge rate, and short residence time. The strength improvement effect achieved by the reinforcing fibers is extremely high, as higher strength is achieved without resin degradation, and fiber-reinforced PPT resin compositions can be produced with high productivity. Furthermore, high-strength resin compositions, such as those with a Charpy impact strength of 9 kJ / m, that were previously unattainable in operations performed within high torque ranges can be produced with extremely high productivity. 2 The above-mentioned polybutylene terephthalate resin composition with a tensile strength of 140 MPa or higher. Attached Figure Description

[0034] [ Figure 1 This is a conceptual diagram illustrating an example of the screw construction of the extruder used in the embodiments and comparative examples. Detailed Implementation

[0035] The present invention will now be described in detail using embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be modified arbitrarily as long as it does not depart from the spirit of the invention. Furthermore, the symbol “~” used in this specification indicates that the values ​​mentioned before and after “~” include their lower and upper limits.

[0036] The production method of the fiber-reinforced polybutylene terephthalate resin composition of the present invention is a production method using a twin-screw extruder. The fiber-reinforced polybutylene terephthalate resin composition comprises (A) 40-90% by weight of polybutylene terephthalate resin, (B) 10-60% by weight of reinforcing fibers, and (C) 0-35% by weight of other polymers or additives (the total amount of each component is 100% by weight).

[0037] The method includes:

[0038] Polybutylene terephthalate resin granules with an average weight of 16 mg or more and 29 mg or less are used as the raw material for component (A).

[0039] The first step involves kneading components (A) and (C) using a first kneading section; the second step involves adding component (B) downstream of the first kneading section and kneading it using a second kneading section; and the third step involves depressurizing and volatilizing the exhaust port of the downstream section of the second kneading section.

[0040] The first kneading section has a length of 5.0D to 9.0D (D is the diameter of the barrel) and is constructed by combining two or more of the following: R kneading disc, N kneading disc, L kneading disc, L screw, sealing ring, mixing screw, and rotor screw.

[0041] The second kneading section has a structure obtained by combining one or more of the following: R kneading disc, N kneading disc, L kneading disc, L screw, sealing ring, and mixing screw.

[0042] The screw shaft torque density is 11.5–19 Nm / cm. 3 Production is carried out under the following conditions.

[0043] The extruder used in this invention is a vented twin-screw extruder, and preferably a meshing co-rotating twin-screw extruder, which has two screws rotating in the same direction inside the barrel, wherein a kneading section composed of a plurality of kneading discs is provided so that the screws mesh with each other in the middle.

[0044] A vented twin-screw extruder comprises: a barrel having a feed inlet, a vent, and a jacket; and a die head connected to the front end of the extruder, having a feed inlet for (A) granules of polybutylene terephthalate resin and (C) other polymers or additives, a first kneading section, a feed inlet for side-feeding (B) reinforcing fibers, a second kneading section, and a venting section. The resin composition is produced using a method comprising the following steps: a first step of kneading components (A) and (C) in the first kneading section; a second step of adding component (B) downstream of the first kneading section and kneading it in the second kneading section; and a third step of depressurizing and devolatilizing the vent in the downstream section of the second kneading section.

[0045] In the first step, components (A) and (C) are fed into the extruder from the raw material feed port, melted by heating, and kneaded by the screw. A first kneading section, consisting of multiple kneading discs, is formed in the middle of the screw. The first kneading section kneads the polybutylene terephthalate resin granules and other polymers or additives after their introduction, and is located before the introduction of reinforcing fibers. The screw is constructed with a length of 5.0D to 9.0D (D is the barrel diameter) and is obtained by combining two or more of the following: R kneading discs, N kneading discs, L kneading discs, L screw, sealing ring, mixing screw, and rotor screw. The first kneading section kneads polybutylene terephthalate resin granules with an average weight of 16 to 29 mg, as well as other polymers or additives introduced thereafter, and is located before the introduction of reinforcing fibers.

[0046] The first kneading section can be assembled into a single segment or divided into multiple segments. That is, the first kneading section can be divided into multiple segments, and a forward feeding screw can be inserted between these segments. Importantly, the total length of the kneading section is 5.0D to 9.0D.

[0047] The R-kneading disc (hereinafter also referred to as R) is a feed kneading disc element and typically has two or more blades, with a torsion angle θ between the blades preferably between 10° and 75°. By offsetting the blades by a predetermined angle in this way, a pseudo-screw structure is formed, the resin is conveyed in the forward direction, strong shear force is applied, and a kneading zone is formed.

[0048] The L-shaped kneading disc (hereinafter also referred to as L) is a reverse-feed kneading disc element, and typically has two or more blades, with the torsion angle θ between the blades preferably being -10° to -75°. The reverse-feed kneading disc element has the function of blocking the conveyed resin and acting on the conveyed resin in the opposite direction to increase its pressure, and by arranging the reverse-feed kneading disc element downstream of the kneading-promoting element, the resin is blocked and exhibits a strong kneading effect.

[0049] The N-kneading disc (hereinafter also referred to as N) is an orthogonal kneading disc element and typically has two or more blades with a torsion angle θ between the blades ranging from 75° to 105°. Because the blades are set off at approximately 90°, the force for conveying resin is weaker, but the kneading force is stronger.

[0050] L-screws are reverse-feed screws. The sealing ring restricts the flow of resin in the upstream section through the gap in the sealing ring section. Mixing screws are screw elements with notches in the screw peaks (threaded sections), and rotating screws are screw elements with more than one line on their outer circumferential surface.

[0051] Among them, R kneading disc, N kneading disc and L kneading disc are preferred, and the combination of multiple kneading discs is preferred.

[0052] The screw structure of the first kneading section in the first step is formed by combining two or more of the aforementioned elements. However, it is preferable that the element promoting kneading is provided on the upstream side, and the element with the pressure-boosting function is provided on the downstream side. Therefore, in the first kneading section, it is preferable to provide two or more of R, N, and L in the order R→N→L from the upstream side, and it is also preferable to provide multiple R, N, and L. Particularly preferably, R is provided on the upstream side, followed by multiple N, and then L.

[0053] The screw length in the first kneading section is 5.0D to 9.0D, where D represents the barrel diameter. If the screw length falls within this range, the polybutylene terephthalate resin is sufficiently melted and plasticized, and the decomposition of the resin composition can be suppressed. If the screw length in the first kneading section is less than 5.0D, insufficient melting and plasticization occur due to insufficient shearing, and if the screw length exceeds 9.0D, excessive kneading tends to promote localized decomposition of the resin composition, and the mechanical properties of the composition deteriorate.

[0054] After kneading and melting the polybutylene terephthalate resin in the first step, it is preferable to vent the effluent using an vent. A sealing ring is preferably located downstream of the vent.

[0055] In the second step, following the first step described above, reinforcing fibers are fed from the supply port side located downstream of the first kneading section, and the reinforcing fibers and molten polybutylene terephthalate resin are kneaded together by the second kneading section. The second kneading section is a kneading section for introducing, opening, and kneading the reinforcing fibers. The screw configuration of the second kneading section is formed by combining one or more of an R-kneading disc, an N-kneading disc, an L-kneading disc, an L-screw, a sealing ring, and a mixing screw. If kneading is performed without these configurations, the opening and dispersion of the reinforcing fibers tend to be insufficient. Among the above components, a configuration having at least one mixing screw is preferred, particularly a forward-feed notch type mixing screw and a reverse-feed notch type mixing screw.

[0056] The screw length in the second kneading section is preferably 2.5D to 5.0D. The second kneading section can be assembled into a single segment or divided into multiple segments. That is, the second kneading section can be divided into multiple segments, and feed screws can be inserted between these segments. In any configuration, the total length of the kneading section is preferably 2.5D to 5.0D. By setting the screw length in the second kneading section within such a range, the opening and dispersion of the reinforcing fibers are good, and the strength of the resin composition tends to be improved.

[0057] Using a high-torque twin-screw extruder with a screw shaft torque density of 11.5–19 Nm / cm³ 3 The operation is carried out under the following conditions.

[0058] The screw shaft torque density is defined as the value obtained by dividing the required torque (Nm) for operating a screw by the cube of the distance between the screw shaft centers, and has Nm / cm². 3The unit is torque density. Even when extruding using extruders of different sizes, if the torque density value is the same, the torque applied to the resin per unit volume is the same. The motor driving the screw generates torque (Nm), which is transmitted to the screw shaft, which performs tasks such as conveying and melting polybutylene terephthalate resin, and conveying and opening reinforcing fibers. In this invention, the torque density represents the intensity of the torque applied to the base of the screw shaft. The value of the torque density decreases towards the front end and is almost zero at the front end of the screw.

[0059] The torque generated by the motor driving the extruder screw is displayed on the control panel as a percentage of 100% of the screw's allowable torque. For example, in the case of TEX44αIII, 100% of the torque value corresponds to 17.6 Nm / cm. 3 The torque density can be calculated based on the displayed percentage of operation. Alternatively, in the case of a standard VVVF inverter control, the value obtained by dividing the current (A) in the fixed torque region by the rated current is matched with the torque percentage.

[0060] The screw shaft torque density is 11.5~19 Nm / cm³. 3 However, 12.0 Nm / cm is preferred. 3 The above, more preferably 12.5 Nm / cm 3 The above is further optimized to 13 Nm / cm. 3 The above, and preferably 18 Nm / cm 3 Below, and more preferably 17 Nm / cm 3 The following describes how, by setting the screw shaft torque density within this range, high-strength fiber-reinforced polybutylene terephthalate (PET) resin compositions can be stably produced at high discharge rates.

[0061] To ensure that the screw shaft torque density falls within this range, the screw shaft torque density can be adjusted by controlling the feed rate of the raw material to achieve this torque range.

[0062] In this invention, under the aforementioned torque density conditions, polybutylene terephthalate (PET) resin granules with an average weight of 16–29 mg are used as the raw material. By feeding granules with this type of average weight into the extruder, the resin temperature can be easily controlled within a suitable range. If the average weight is too low, the resin temperature tends to rise to a higher temperature than required, and if the average weight is too high, it is difficult to increase the resin temperature.

[0063] The average weight is preferably 18 mg or more, more preferably 19 mg or more, even more preferably 20 mg or more, and preferably 27 mg or less, more preferably 25 mg or less, and even more preferably 24 mg or less.

[0064] The average weight of polybutylene terephthalate resin granules is the number-average weight of the granules, and more specifically, the average value (mg / granule) calculated from 100 arbitrary granules. For example, fragmented products, powders, and granules that are not in granule form, such as those generated during production, transportation, or handling, are not included.

[0065] The resin temperature in the second step is preferably 280–320°C, particularly 290–310°C. The resin temperature can be adjusted by appropriately adjusting the extruder discharge rate or screw speed, or by adjusting the screw configuration in the first step or by setting a low preset barrel temperature in the second step.

[0066] The screw speed of the twin-screw extruder is preferably 300–800 rpm, more preferably 400–700 rpm. Furthermore, in the case of TEX44αIII, the discharge rate is preferably 450–650 kg / h, and more preferably 480–630 kg / h. When the extruder has different dimensions, the discharge rate is preferably within a range proportional to the 2.5th power of the barrel diameter ratio.

[0067] Following the second step, a depressurization devolatilization process is performed in the third step using a downstream exhaust section, but the vacuum level during this process is preferably -0.097 MPa to -0.07 MPa. Here, vacuum level refers to gauge pressure.

[0068] Next, the polybutylene terephthalate resin composition is extruded from the extrusion die at the front end of the extruder in the form of a filament (extrusion step). The temperature of the extruded resin composition filament is preferably 290–310°C, particularly 295–310°C.

[0069] There are no particular restrictions on the shape of the extrusion die, and known types of dies can be used. The diameter of the die orifice depends on the desired pellet size, but is typically 2 to 5 mm, preferably about 3 to 4 mm.

[0070] The wire is then wound up by a take-up roller and cooled by contact with water.

[0071] Contact with water allows the yarn to be cooled by means of water transport maintained in a cooling water tank, or by applying water to the yarn to achieve contact with water, or by a method including stretching the yarn on a mesh belt conveyor and applying water to the yarn using a drainage device. The time interval between extruding the yarn from the die and water cooling the yarn or immersing the yarn in water is preferably short. Generally, it is preferable to immerse the yarn in water within one second of extrusion from the die.

[0072] The cooled wire is then fed to a pelletizer via a winding roller and cut to form pellets.

[0073] According to the method of the present invention, high-strength polybutylene terephthalate (PPT) resin compositions that were previously unattainable in operations performed within high torque ranges can be produced with extremely high productivity. The resulting PPT resin compositions (granules) exhibit extremely high strength. Specifically, the notched Charpy impact strength is preferably 9 kJ / m. 2 The above, more preferably 9.5 kJ / m 2 Above, and within this range, 10 kJ / m 2 Above, and especially 10.5 kJ / m 2 The above, and the tensile strength is preferably 140 MPa or more, more preferably 145 MPa or more, and within this range 150 MPa or more, and particularly 155 MPa or more.

[0074] Here, the notched Charpy impact strength is measured according to ISO 179-1.2, and the tensile strength is measured according to ISO 527. Specific details of these measurement methods are described in the Examples section.

[0075] The raw material components used in this invention will now be described.

[0076] Polybutylene terephthalate resin (A) is a polyester resin having a structure in which terephthalic acid units and 1,4-butanediol units are bonded by ester bonds, and includes, in addition to polybutylene terephthalate resin (homogene), polybutylene terephthalate copolymers containing other copolymer components in addition to terephthalic acid units and 1,4-butanediol units, as well as homopolymers and mixtures of such copolymers.

[0077] Polybutylene terephthalate resins may contain dicarboxylic acid units other than terephthalic acid, and specific examples of these other dicarboxylic acid units include aromatic dicarboxylic acids, such as isophthalic acid, phthalic 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, bis(4,4'-carboxyphenyl)methane, anthracene dicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid; alicyclic dicarboxylic acids, such as 1,4-cyclohexanedicarboxylic acid and 4,4'-dicyclohexyldicarboxylic acid; and aliphatic dicarboxylic acids, such as adipic acid, sebacic acid, azelaic acid, and dimer acids.

[0078] In cases where polybutylene terephthalate resin (A) contains diol units other than 1,4-butanediol, specific examples of these other diol units include aliphatic and alicyclic diols having 2 to 20 carbon atoms and bisphenol derivatives. Specific examples include ethylene glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, decamethyldiol, cyclohexanediol, 4,4′-dicyclohexylhydroxymethane, 4,4′-dicyclohexylhydroxypropane, and ethylene oxide addition diols of bisphenol A. In addition to the bifunctional monomers mentioned above, small amounts of trifunctional monomers, such as trimellitic acid, benzopyridinic acid, pyromellitic acid, pentaerythritol, or trimethylolpropane, can be used to introduce branched structures, or monofunctional compounds, such as fatty acids, can be used to adjust the molecular weight.

[0079] The preferred polybutylene terephthalate resin is a polybutylene terephthalate homopolymer obtained by polycondensation of terephthalic acid and 1,4-butanediol. However, it can also be a polybutylene terephthalate copolymer containing one or more dicarboxylic acids other than terephthalic acid as carboxylic acid units and / or one or more diols other than 1,4-butanediol as diol units, as long as the crystallinity of the polybutylene terephthalate resin is not impaired. In the case where the polybutylene terephthalate resin is a copolymerized polybutylene terephthalate resin, preferred examples of specific copolymers include polyester-ether resins obtained by copolymerization with polyalkylene glycols, especially polytetramethylene glycol, polybutylene terephthalate resins copolymerized with dimer acids, and polybutylene terephthalate resins copolymerized with isophthalic acid.

[0080] Furthermore, in these copolymers, the copolymerization amount is more than 1 mol% and less than 50 mol% of all segments in the polybutylene terephthalate resin. Within this range, the copolymerization amount is preferably more than 2 mol% and less than 50 mol%, more preferably 3 to 40 mol%, and particularly preferably 5 to 20 mol%. This copolymerization ratio is preferred from the perspective of improving flowability and extensibility.

[0081] The intrinsic viscosity (IV) of the polybutylene terephthalate resin is preferably 0.72 to 0.83 dl / g. It has been found that by having this type of low intrinsic viscosity, the resin temperature can be easily controlled to a temperature at which the adhesion strength to the reinforcing fibers is high and the strength reduction due to resin degradation is unlikely, such as the resin temperature of 290 to 310°C at high torque densities. If the intrinsic viscosity is less than 0.72 dl / g, the adhesion to the reinforcing fibers tends to be insufficient, and if the intrinsic viscosity exceeds 0.83 dl / g, heat generation tends to occur, resin degradation occurs, and the strength tends to decrease. The intrinsic viscosity is more preferably 0.73 dl / g or higher, and more preferably 0.82 dl / g or lower.

[0082] In this invention, the intrinsic viscosity of polybutylene terephthalate resin is measured using an Ubbelohde viscometer at a temperature of 30°C and a Huggins constant of 0.33 in a mixed solvent containing tetrachloroethane and phenol in a mass ratio of 1:1. Furthermore, it is preferable to perform the measurement after removing glass fibers by filtration.

[0083] The reinforcing fiber (B) can be an organic reinforcing fiber or an inorganic reinforcing fiber, but inorganic reinforcing fibers are preferred, such as glass fiber, carbon fiber, alumina fiber, boron fiber, or ceramic fiber, and more preferably glass fiber or carbon fiber, with glass fiber being particularly preferred.

[0084] There are no particular limitations on the type of glass fiber, examples of which include glass fibers such as E-glass, C-glass, A-glass, and S-glass. Among these, E-glass fiber is preferred from the viewpoint that it does not adversely affect the thermal stability of polybutylene terephthalate resin.

[0085] The average fiber diameter of the glass fiber is not particularly limited, but it is preferably selected in the range of 1 to 100 μm, more preferably 2 to 50 μm, further preferably 3 to 30 μm, and particularly preferably 5 to 20 μm. Glass fibers with an average fiber diameter of less than 1 μm are difficult to produce and raise concerns about increased costs, while glass fibers with an average fiber diameter of more than 100 μm raise concerns about reduced tensile strength. Furthermore, the fiber cross-section can be circular or flat.

[0086] Glass fibers can have a perfectly circular or flat fiber cross-section, but generally circular glass fibers with an ellipticity (major axis / minor axis) of 1 to 1.5 are preferred. This ellipticity is preferably 1 to 1.4, more preferably 1 to 1.2, and particularly preferably 1 to 1.1.

[0087] There is no particular limitation on the average fiber length of the raw glass fibers, but it is preferably 1 to 10 mm, more preferably 1.5 to 6 mm, and most preferably 2 to 5 mm. If the average fiber length of the raw glass fibers is less than 1 mm, there is concern that the reinforcing effect will not be sufficiently manifested, and if the average fiber length exceeds 10 mm, there is concern that the molding of the obtained resin composition may be difficult.

[0088] From the perspective of improving the adhesion of polybutylene terephthalate resin, the glass fibers used can be surface-treated with silane coupling agents such as aminosilane or epoxysilane.

[0089] Examples of coupling agents include chlorosilane compounds such as vinyltrichlorosilane and methylvinyldichlorosilane, alkoxysilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane and γ-methacryloyloxypropyltrimethoxysilane, epoxysilane compounds such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane, acrylic compounds, isocyanate compounds, titanate compounds and epoxy compounds.

[0090] Furthermore, the raw material glass fiber is generally preferred as chopped strands (chopped glass fiber), which is obtained by bundling these fibers into many bundles and then cutting them to a specified length, and in this case, it is preferable to mix the sizing agent with the glass fiber.

[0091] There are no particular limitations on the sizing agents used for glass fibers, examples of which include resin emulsions of vinyl acetate resin, ethylene-vinyl acetate copolymer, acrylic resin, epoxy resin, polyurethane resin, and polyester resin, with acrylic resin, epoxy resin, and polyurethane resin being preferred.

[0092] The amount of reinforcing fiber is 10–60% by mass relative to the total of polybutylene terephthalate resin (A), reinforcing fiber (B), and other polymers or additives (C) in 100% by mass. If this amount falls within such a range, the resin composition has high strength, and a resin composition with excellent appearance and flowability can be obtained during molding. If the content is less than 10% by mass, the reinforcing effect is insufficient, and if the content exceeds 60% by mass, the appearance and impact resistance deteriorate, and the flowability of the resin composition tends to be insufficient.

[0093] Other polymers or additives (C) are polymers other than polybutylene terephthalate resin and / or various additives.

[0094] Examples of additives include a variety of resin additives, including flame retardants, auxiliary flame retardants, stabilizers, antioxidants, mold release agents, ultraviolet radiation absorbers, weather stabilizers, lubricants, colorants such as dyes and pigments, catalyst deactivators, antistatic agents, foaming agents, plasticizers, crystal nucleating agents, and crystallization promoters.

[0095] Examples of other resins include polyethylene terephthalate resins and polyethylene terephthalate resins; 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; and polymethacrylate resins.

[0096] In addition, one of these other resins or any combination of two or more types in any proportion can be introduced.

[0097] The amount of other polymers or additives (C) added is preferably 0 to 35% by mass relative to the total of components (A) to (C) 100% by mass, and more preferably 5 to 30% by mass.

[0098] It is known that blending amorphous resins with polybutylene terephthalate (PET) resin is a means of suppressing molecular orientation caused by PET crystallization, and blending polycarbonate resins or styrene resins as amorphous resins is a common practice. However, resin compositions, especially those containing styrene-based resins, have lower viscosity than PET resins alone, and problems arise, such as difficulty in fiber opening of reinforcing fibers, susceptibility to dispersion defects, poor adhesion to reinforcing fibers due to difficulty in raising resin temperature, and a lack of strength in the resin composition.

[0099] One approach to address these problems is to reduce the discharge rate and extend the kneading time, but this results in reduced production output. Furthermore, fiber opening of the reinforcing fibers is insufficient when using methods involving increasing the resin temperature due to the low viscosity of styrene-based polymers. However, the method of the present invention is particularly effective as a means of solving these problems because it allows for the production of high-strength fiber-reinforced resin compositions with good productivity.

[0100] Styrene polymers at 250°C and 912 seconds -1 The preferred melt viscosity is 70–1000 Pa·s, particularly 70–500 Pa·s. This melt viscosity (η) can be achieved through blending. B Styrene-based polymers can be used to produce high-strength, fiber-reinforced polybutylene terephthalate (PET) resin compositions with low molding shrinkage, exhibiting high productivity and excellent production stability. The polystyrene-based polymers have the effect of reducing viscosity in high-shear regions and allow the resin to be easily impregnated into the reinforcing fiber bundles in the second kneading section (fiber opening section) of the extruder. Therefore, the adhesion strength between the fiber surface and the resin can be enhanced.

[0101] Melt viscosity can be measured using a capillary rheometer and a slit rheometer according to ISO 11443. More specifically, when a piston is pushed into a furnace with an inner diameter of 9.5 mm at a piston speed of 75 mm / min and heated to a temperature of 250 °C using a capillary with a diameter of 1 mm and a length of 30 mm, the melt viscosity can be calculated from stress.

[0102] Examples of styrene-based polymers include styrene homopolymers, graft copolymers obtained by polymerizing styrene in the presence of rubber, copolymers of styrene and (meth)acrylonitrile, copolymers of styrene and (meth)acrylate, copolymers of styrene, (meth)acrylonitrile and other copolymerizable monomers, and graft copolymers obtained by graft polymerization of styrene and (meth)acrylonitrile in the presence of rubber. Specific examples include resins such as polystyrene (general purpose polystyrene, GPPS), high impact 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 resin), 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 rubber copolymer; and mixtures thereof.

[0103] Among them, 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.

[0104] Styrene-based elastomers can be used as styrene-based polymers.

[0105] Block copolymers containing polymer blocks with vinyl aromatic compounds as polymerizing components and polymer blocks containing conjugated dienes as polymerizing components, and their hydrogenated products, are preferably styrene-based elastomers.

[0106] Examples of vinyl aromatic compounds constituting blocks of vinyl aromatic hydrocarbon polymers include styrene compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, lower alkyl-substituted styrene compounds, vinylnaphthalene, and vinylanthracene and their derivatives. One of these compounds may be used alone, or in combination of two or more types thereof.

[0107] Examples of conjugated dienes that constitute a conjugated diene block include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene.

[0108] A single styrene polymer or a mixture of two or more types thereof can be used.

[0109] The amount of the styrene polymer relative to the total mass of components (A) to (C) is preferably 5 to 30% by mass.

[0110] The polybutylene terephthalate resin composition produced using the method of the present invention can produce molded articles with extremely high strength, and thus can fully achieve the desired properties in terms of light weight, thinness and strength, and can be widely used in molded articles and parts in a variety of industrial fields, such as electrical / electronic equipment, OA equipment such as computers, precision instruments, optical equipment, motor vehicles and other fields.

[0111] Example

[0112] The invention will now be described in more detail through the use of embodiments. However, the invention is not limited to the embodiments given below, and can be modified in any way as long as it does not deviate from the spirit of the invention.

[0113] The polybutylene terephthalate resin granules, reinforcing fibers, and other resins used in the examples and comparative examples are shown in Table 1 below.

[0114] [Table 1]

[0115]

[0116] [Extruder]

[0117] The extruder used was a vented meshing co-rotating twin-screw extruder (TEXαIII manufactured by Japan Steel Works, Ltd.; barrel diameter D = 47 mm).

[0118] The screw configuration used in the embodiments and comparative examples is such that the first pinching part includes the screws 1 to 4 below, and the second pinching part includes the screws 1 to 3 below.

[0119] First kneading section

[0120] Screw 1: RNNNNL; Length 5.62D

[0121] Screw 2: RNNNNNNL; Length 7.48D

[0122] Screw 3: RNNNNNNNNL; Length 9.36D

[0123] Screw 4: RNNLL; Length 4.68D

[0124] The aforementioned kneading disc is a double-threaded disc with a length of 44mm.

[0125] Second kneading part

[0126] Screw 1: Reverse feed mixing screw, 44mm in length (four screws)

[0127] Total length: 176mm (3.74D)

[0128] Screw 2: Reverse feed mixing screw, 44mm in length (six screws)

[0129] Total length: 264mm (5.62D)

[0130] Screw 3: Reverse feed mixing screw, 44mm in length (two screws)

[0131] Total length: 88mm (1.87D)

[0132] Figure 1 This is a conceptual diagram illustrating an example of the screw construction of the extruder used in the embodiments and comparative examples.

[0133] The hopper is placed at position C1, and polybutylene terephthalate resin granules listed in Table 2 are fed and conveyed by screw R. A first kneading section is located at position C6 in the barrel and is constituted by any one of screws 1-4 listed in the table. The granules are kneaded by the first kneading section, and glass fiber is fed into the barrel from the position C8 side at a rate of 30% by mass, and kneaded by a second kneading section consisting of any one of screws 1-3 listed in the table, located at positions C9-C11. The pressure is then reduced using the vacuum vent at position C12, and the filament is extruded from the die, cooled using a water bath, and cut into granules using a granulator. Screw speed, discharge rate, and torque (percentage of 100% torque) are shown in the table, and 100% torque corresponds to an axial torque density of 17.6 Nm / cm² applied to one screw. 3 The table shows the shaft torque density at the screw shaft connection of the extruder base and the resin temperature of the filament immediately after extrusion. Furthermore, the measured torque (%) is multiplied by the permissible screw torque (17.6 Nm / cm). 3 This determines the shaft torque density applied to the screw shaft.

[0134] The obtained granules were molded into Type A test specimens (170mm × 10mm, 4mm thickness) using an injection molding machine (J85AD, manufactured by Japan Steel Works, Ltd.) according to ISO 294-1.

[0135] Using the obtained test specimen, measure the notched Charpy impact strength (unit: kJ / m²) according to ISO 179-1.2. 2 ), and measure the tensile strength (unit: MPa) according to ISO 527.

[0136] In addition, to evaluate the degree of degradation of polybutylene terephthalate resin, the intrinsic viscosity of the obtained polybutylene terephthalate resin granules was measured using the following method.

[0137] The intrinsic viscosity was measured using an Ubbelohde viscometer with a phenol / tetrachloroethane mixture in a 1:1 ratio, as described above. Alternatively, the glass fiber-containing granules were dissolved in the mixed solvent and filtered to remove only the glass fibers; the intrinsic viscosity was then measured from the filtered solution.

[0138] (Example 1-1)

[0139] Granules were produced using 35% by mass of PBT1A and 35% by mass of PBT2A (arithmetic mean intrinsic viscosity IV: 0.775 dl / g), and using screw 1 as both the first and second kneading sections, at a screw speed of 500 rpm and a discharge rate of 600 kg / h. Extrusion was stable and the filament did not break.

[0140] (Examples 1-2)

[0141] Except for the screw structure in which the screw 2 is used as the first kneading part, the same procedure as that used in Embodiment 1-1 is performed.

[0142] (Comparative Example 1-1)

[0143] Except for using screw 3 as the screw structure of the first kneading part, the same procedure as that used in Example 1-1 is performed.

[0144] (Comparative Examples 1-2)

[0145] Except for the screw structure in which the screw 4 is used as the first kneading part, the same procedure as that used in Example 1-1 is performed.

[0146] (Comparative Examples 1-3)

[0147] Except for the discharge rate of 400 kg / h, the same procedure as used in Examples 1-1 was performed.

[0148] (Comparative Examples 1-4)

[0149] Except for the discharge rate of 400 kg / h, the same procedures as those used in Examples 1-2 were performed.

[0150] (Comparative Examples 1-5)

[0151] Except for the discharge rate of 400 kg / h, the same procedure as that used in Comparative Example 1-1 was performed.

[0152] (Comparative Examples 1-6)

[0153] Except for the discharge rate of 400 kg / h, the same procedure as that used in Comparative Examples 1-2 was performed.

[0154] The results are shown in Table 2-3 below.

[0155] [Table 2]

[0156]

[0157] [Table 3]

[0158]

[0159] (Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2)

[0160] Except that the amount of PBT1A was 56% by mass, the amount of PBT2A was 14% by mass, and the arithmetic mean intrinsic viscosity was 0.82 dl / g, the same procedure as that used in Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 was performed.

[0161] The results are shown in Table 4 below.

[0162] [Table 4]

[0163]

[0164] (Examples 3-1 and 3-2 and Comparative Examples 3-1 and 3-2)

[0165] Except that the amount of PBT1A was 14% by mass, the amount of PBT2A was 56% by mass, and the arithmetic mean intrinsic viscosity was 0.73 dl / g, the same procedure as that used in Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 was performed.

[0166] The results are shown in Table 5 below.

[0167] [Table 5]

[0168]

[0169] (Examples 4-1 and 4-2 and Comparative Examples 4-1 and 4-2)

[0170] Except that the amount of PBT1A was 70% by mass and the intrinsic viscosity was 0.85 dl / g, the same procedures as those used in Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 were performed.

[0171] The results are shown in Table 6 below.

[0172] [Table 6]

[0173]

[0174] (Examples 5-1 and 5-2 and Comparative Examples 5-1 and 5-2)

[0175] Except that the amount of PBT2A was 70% by mass and the intrinsic viscosity was 0.70 dl / g, the same procedures as those used in Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 were performed.

[0176] The results are shown in Table 7 below.

[0177] [Table 7]

[0178]

[0179] (Examples 1-3)

[0180] Except for using screw 2 as the screw structure of the second kneading part, the same procedure as that used in Example 1-1 is performed.

[0181] (Examples 1-4)

[0182] Except for using screw 3 as the screw structure for the second kneading part, the same procedure as used in Examples 1-1 is performed. In this case, the wire is cut every 2 minutes, and it can be understood that a slight problem occurs in terms of productivity. The screw structure is weak, and the fiber opening of the glass fiber may be insufficient.

[0183] The results are shown in Table 8 below.

[0184] [Table 8]

[0185]

[0186] (Examples 6-1 and 6-2, Comparative Examples 6-1 and 6-2)

[0187] Except that the amount of PBT1A was 30% by mass, the amount of PBT2A was 30% by mass, the arithmetic mean intrinsic viscosity was 0.775 dl / g, and 10% by mass of AS resin was added, the same procedure as that used in Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 was performed.

[0188] The results are shown in Table 9 below.

[0189] [Table 9]

[0190]

[0191] (Comparative Example 7-1)

[0192] Except that PBT1B is used instead of PBT1A in Example 1-1 and PBT2B is used instead of PBT2A, the same procedure is performed as in Example 1-1.

[0193] (Comparative Example 7-2)

[0194] Except that PBT1C is used instead of PBT1A in Example 1-1 and PBT2C is used instead of PBT2A, the same procedure is performed as in Example 1-1.

[0195] The results are shown in Table 10 below.

[0196] [Table 10]

[0197]

[0198] (Comparative Example 8-1)

[0199] Except that PBT1B is used instead of PBT1A in Examples 1-2 and PBT2B is used instead of PBT2A, the same procedure is performed as in Examples 1-2.

[0200] (Comparative Example 8-2)

[0201] Except that PBT1C is used instead of PBT1A in Examples 1-2 and PBT2C is used instead of PBT2A, the same procedure is performed as in Examples 1-2.

[0202] The results are shown in Table 11 below.

[0203] [Table 11]

[0204]

[0205] (Comparative Example 9-1)

[0206] Except that PBT1B is used instead of PBT1A in Example 2-2 and PBT2B is used instead of PBT2A, the same procedure is performed as in Example 2-2.

[0207] (Comparative Example 9-2)

[0208] Except that PBT1C is used instead of PBT1A in Example 2-2 and PBT2C is used instead of PBT2A, the same procedure is performed as in Example 2-2.

[0209] The results are shown in Table 12 below.

[0210] [Table 12]

[0211]

[0212] (Comparative Example 10-1)

[0213] Except that PBT1B is used instead of PBT1A in Example 3-2 and PBT2B is used instead of PBT2A, the same procedure is performed as in Example 3-2.

[0214] (Comparative Example 10-2)

[0215] Except that PBT1C is used instead of PBT1A in Example 3-2 and PBT2C is used instead of PBT2A, the same procedure as in Example 3-2 is performed.

[0216] The results are shown in Table 13 below.

[0217] [Table 13]

[0218]

[0219] (Comparative Example 11-1)

[0220] Except that PBT1B is used instead of PBT1A in Example 6-2 and PBT2B is used instead of PBT2A, the same procedure is performed as in Example 6-2.

[0221] (Comparative Example 11-2)

[0222] Except that PBT1C is used instead of PBT1A in Example 6-2 and PBT2C is used instead of PBT2A, the same procedure as in Example 6-2 is performed.

[0223] The results are shown in Table 14 below.

[0224] [Table 14]

[0225]

[0226] Industrial availability

[0227] According to the production method of the present invention, fiber-reinforced polybutylene terephthalate resin compositions with excellent mechanical strength can be produced with high productivity, and molded articles containing said compositions can fully achieve the desired performance in terms of light weight, thinness and strength, and can be used in a wide range of applications, such as components of motor vehicles, electrical / electronic equipment and precision instruments.

Claims

1. A fiber-reinforced polybutylene terephthalate resin composition produced by means of a twin-screw extruder, said resin composition comprising (A) 40-90% by weight of polybutylene terephthalate resin, (B) 10-60% by weight of reinforcing fibers, and (C) 0-35% by weight of other polymers or additives, wherein the total amount of all components is 100% by weight. The method includes: Polybutylene terephthalate resin granules with an average weight of 18 mg or more and 25 mg or less were used as raw materials for component (A). The first step involves kneading components (A) and (C) using a first kneading section; the second step involves adding component (B) downstream of the first kneading section and kneading it using a second kneading section; and the third step involves depressurizing and volatilizing the exhaust port downstream of the second kneading section. The first kneading section has a length of 5.0D to 9.0D, and is constructed by providing one or more R-type kneading discs on the upstream side, followed by one or more N-type kneading discs, and then one or more L-type kneading discs, where D is the diameter of the barrel. The second kneading part has a structure obtained by combining one or more of the following: R kneading disc, N kneading disc, L kneading disc, L screw, sealing ring, and mixing screw. The screw shaft torque density is 11.5~14.1 Nm / cm. 3 Production is carried out under the following conditions: The screw shaft torque density is a value obtained by dividing the required torque Nm for operating a screw by the cube of the distance between the screw shaft centers. The temperature of the resin filament immediately after extrusion in the third step is 290~310℃.

2. The production method according to claim 1, wherein component (C) comprises a styrene-based polymer in an amount of 5 to 30% by mass relative to a total of 100% by mass of components (A) to (C).

3. The production method according to claim 1 or claim 2, wherein the intrinsic viscosity of the polybutylene terephthalate resin (A) is 0.72~0.83 dl / g.

4. The production method according to claim 1 or claim 2, wherein, The total length of the second kneading part is 2.5D or more and 5.0D or less.

5. The production method according to claim 1 or claim 2, wherein the notched Charpy impact strength of the obtained resin composition, measured according to ISO 179-1,2, is 9 kJ / m. 2 above.

6. The production method according to claim 1 or claim 2, wherein the tensile strength of the obtained resin composition, measured according to ISO 527, is 140 MPa or higher.

7. The production method according to claim 1 or claim 2, wherein the screw shaft torque density is 13~14.1 Nm / cm². 3 .

Images