Method for manufacturing repellets and repellets

Abstract

This invention provides a novel recycling method that efficiently recycles market-recovered PBT resin compositions containing fibrous fillers, and that yields recycled molded products with minimal warping. [Solution] A method for producing repellets, the method comprising kneading a molded article and / or a pulverized product thereof containing a polybutylene terephthalate resin (A) and a fibrous filler (B) to adjust the weight-average fiber length of the fibrous filler (B) in the repellet to 200 μm or less.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a pellet and a pellet.

Background Art

[0002] Polybutylene terephthalate resin (hereinafter, may also be referred to as "PBT resin") is excellent in various properties such as mechanical properties, electrical properties, heat resistance, chemical resistance, and solvent resistance. Therefore, as an engineering plastic, it is used in various applications such as automotive parts and electrical and electronic parts. In particular, by adding fibrous fillers such as glass fiber and carbon fiber to PBT resin, the mechanical properties and heat deflection temperature are improved. Therefore, a polybutylene terephthalate resin composition containing a fibrous filler (hereinafter, may also be referred to as "fibrous filler-containing PBT resin composition") is widely used.

[0003] On the other hand, in recent years, in order to realize a sustainable society, it has been required to efficiently recycle resin molded products. Engineering plastics represented by PBT resin are added with various additives such as inorganic fillers, impact modifiers, and flame retardants according to market requirements. In injection molding sites, in some cases, waste shot molded products, sprues, runners, etc. are pulverized and used on-site to reuse recycled materials with the same composition as virgin materials and produce molded products with stable quality. However, the amount of recycling is small. Therefore, when trying to obtain recycled products with stable quality such as mechanical properties, it is necessary to separate the products recovered from the market by resin type and further select and recycle them according to the blending amount of the inorganic filler. However, such a method is difficult to implement because of the high cost. In addition, recycled materials also have a problem that their physical properties are likely to deteriorate compared to virgin materials. Therefore, at present, as a recycling method for molded products (market recovered products) recovered after being put on the market, there are substantially only thermal recycling and chemical recycling.

[0004] To address these issues, Patent Document 1 describes that, for process waste polyamide containing glass fibers, adding glass fibers to match the glass fiber length distribution of virgin material and then repelling it can maintain physical properties comparable to virgin material. However, this method assumes the use of process waste with a known composition and cannot be applied to molded products of resin compositions with unknown compositions, such as those recalled from the market. Furthermore, no conventionally known recycling method exists for efficiently recycling market-recovered PBT resin compositions containing fibrous fillers. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-24516 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, molded articles of PBT resin compositions containing fibrous fillers are prone to warping due to differences in shrinkage rates caused by the orientation of the fibrous fillers. Therefore, in virgin materials, methods such as adding amorphous resin or plate-shaped or granular fillers are employed to reduce warping. Therefore, the present disclosure aims to provide a new recycling method that can efficiently recycle market-recovered PBT resin compositions containing fibrous fillers, and that can produce recycled molded products with less warping. [Means for solving the problem]

[0007] To solve the above problems, the inventors of this application conducted diligent research and found that the above problems can be solved by re-pelletizing and recycling molded articles and / or pulverized products containing polybutylene terephthalate resin and fibrous fillers, and further by kneading the molded articles and / or pulverized products in the production of the re-pellets so that the weight-average fiber length of the fibrous inorganic filler in the re-pellets is below a specific range. In other words, this disclosure includes the following aspects: [1] A method for producing repellets, The above-mentioned manufacturing method is a method for producing repellets, comprising kneading a molded article and / or a pulverized product thereof containing a polybutylene terephthalate resin (A) and a fibrous filler (B) to adjust the weight-average fiber length of the fibrous filler (B) in the repellets to 200 μm or less. [Effects of the Invention]

[0008] According to this disclosure, a new recycling method can be provided that efficiently recycles market-recovered PBT resin compositions containing fibrous fillers, and that yields recycled molded products with less warping. [Brief explanation of the drawing]

[0009] [Figure 1] This is an explanatory diagram illustrating the dimensions of the mold used for warpage measurement in the example. [Modes for carrying out the invention]

[0010] One embodiment of this disclosure will be described in detail below. This disclosure is not limited to the following embodiment and may be implemented with appropriate modifications, provided that the effects of this disclosure are not impaired. Each configuration and combination thereof in each embodiment is an example, and configurations can be added, omitted, replaced, and otherwise modified as appropriate, without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments. Each aspect disclosed herein can be combined with any other features disclosed herein. If a specific description given for one embodiment also applies to other embodiments, that description may be omitted in the other embodiments. In this disclosure, the expression "X~Y" for a numerical range means "X or greater and Y or less".

[0011] [Manufacturing method for repelletizers] A first embodiment of this disclosure relates to a method for producing repellet. In other words, the first embodiment relates to a method for producing repellets, the method comprising kneading a molded article and / or a pulverized product thereof containing a polybutylene terephthalate resin (A) and a fibrous filler (B) to adjust the weight-average fiber length of the fibrous filler (B) in the repellet to 200 μm or less. According to the production method of the first embodiment, market-recovered PBT resin compositions containing fibrous fillers can be efficiently recycled, and recycled molded articles with less warping than virgin material can be obtained.

[0012] In this disclosure, "virgin material" means a resin composition comprising PBT resin (A) and a fibrous filler (B), or pellets and / or crushed products thereof of a resin composition comprising PBT resin (A) but not comprising a fibrous filler (B), which are not on the market (including unused materials). "Recycled molded products" refer to molded products that have been remolded using recycled materials. "Market recalled products" refers to molded products and / or their crushed products that have been recovered after being used in the market. In addition, recovered products such as sprues, runners, and discard shot molded products recovered from manufacturing sites where injection molding or other processes using virgin material are performed are referred to as "process recalled products." In this disclosure, "low warping" may include not only a small absolute value of the amount of warping of the molded article (recycled molded article) of the resin material containing the repellets prepared by the manufacturing method of this embodiment, but also a relatively small amount of warping of the recycled molded article compared to the amount of warping of a molded article made of virgin material.

[0013] The manufacturing method according to the first embodiment uses molded articles and / or crushed products thereof containing PBT resin (A) and fibrous filler (B) as recycled raw materials. The manufacturing method according to the first embodiment includes kneading these recycled raw materials and repelling them. Here, "recycled raw materials" means all molded articles and / or crushed products thereof containing PBT resin (A) and fibrous filler (B) that can be repelled by the manufacturing method according to this embodiment, and includes market recovered products and process recovered products. Virgin material containing PBT resin (A) may also be included in recycled raw materials. Recycled raw materials may be used individually or in combination of two or more types. When two or more types are combined as recycled raw materials, it is sufficient that one or more types contain fibrous inorganic filler (B). For example, when using a combination of market recovered products and virgin material as recycled raw materials, a combination of market recovered products containing PBT resin (A) and fibrous filler (B) and virgin material containing PBT resin (A) may be used.

[0014] When recycled raw materials include virgin material, it is desirable to use a high-viscosity virgin material from the viewpoint of making it easier to adjust the weight-average fiber length of the fibrous filler (B) to 200 μm or less. In one embodiment, the virgin material was measured at a temperature of 260°C and a shear rate of 1000 sec. -1 A melt viscosity of 0.2 kPa·s or higher is preferred, and 0.22 kPa·s or higher is more preferred. From the viewpoint of fluidity, the upper limit of the melt viscosity is preferably 0.35 kPa·s or lower. From the viewpoint of effectively recycling market-recovered products and enhancing environmental sustainability, the proportion of virgin material in the recycled raw material is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less, relative to the total mass of the recycled raw material.

[0015] When the recycled raw material includes market-recovered products and process-recovered products, their mixing ratio is arbitrary. However, from the perspective of effectively recycling market-recovered products and enhancing environmental sustainability, it is preferably to contain 20% or more of market-recovered products, more preferably 25% or more, and even more preferably 30% or more. Also, only market-recovered products may be used as the recycled raw material.

[0016] <Molded product> As described above, the molded product containing the PBT resin (A) and the fibrous filler (B) is not particularly limited, and it may be a market-recovered product or a process-recovered product. Also, virgin materials may be included. When using market-recovered products, in order to prevent the mixing of foreign substances, metals, etc., it is preferable to remove metals, etc. or wash them using a magnetic material such as a magnet.

[0017] When using market-recovered products, it is necessary to select molded products of PBT resin from the market-recovered products. When the molded product has an imprint conforming to standards such as JIS K6899 or ISO11469, only the molded products made of PBT resin can be selected according to the description of the imprint. (Imprint example: >PBT-GF30<). For molded products without the above imprint, for example, a method of selection by spectroscopic measurement or a method of selection by density can be adopted. As a method of selection by spectroscopic measurement, for example, a method of irradiating near-infrared rays to a sample and discriminating the type of resin by the transmitted light transmitted through the sample or the reflected light reflected from the sample can be mentioned. The molded products obtained in this way may be further separated for each certain density range by using solutions with different densities to recover only the molded products containing inorganic fillers.

[0018] <Ground product> When using a crushed product as a recycled raw material, a product obtained by crushing the above molded product into an arbitrary size can be adopted. The crushed product may be one crushed in the process of market collection, or a product obtained by crushing the above molded product using a crusher. In one embodiment, from the viewpoint of stably kneading the recycled raw material, it is preferable to use the crushed product as the recycled raw material. For a molded product with a small size (for example, a molded product with a size of 1 cm or less), it may be used as a recycled raw material without being crushed.

[0019] (Crusher) The crusher for crushing the molded product is not particularly limited. For example, a compression crusher (such as a roll crusher), an impact crusher (such as an impact crusher, a hammer mill), a cutting or shearing crusher [such as a cutter mill, a reciprocating crusher, a low-speed rotary crusher (such as a two-axis shearing crusher), etc.], an impact shearing crusher (such as a shredder), and various fine crushers (such as a ball mill, a disk mill, a pin mill, a hammer mill, a turbo mill, a jet mill, etc.) can be mentioned. Using these crushers, it is preferable to crush, for example, into a crushed product having a length of about 1 to 8 mm, and more preferably into a crushed product having a length of about 2 to 5 mm.

[0020] (PBT resin (A)) PBT resin (A) is a resin obtained by polycondensing a dicarboxylic acid component containing at least terephthalic acid or its ester-forming derivative (such as a C1-6 alkyl ester or an acid halide) and a glycol component containing at least an alkylene glycol having 4 carbon atoms (such as 1,4-butanediol) or its ester-forming derivative (such as an acetylated product). The PBT resin (A) contained in the recycled raw material is not particularly limited. In market-collected products and process-recovered products, PBT resins having various performances according to market requirements are used. For example, the PBT resin (A) is not limited to a homopolybutylene terephthalate resin, and may be a copolymer containing 60 mol% or more (particularly 75 mol% or more and 95 mol% or less) of butylene terephthalate units.

[0021] The PBT resin (A) may be polymerized using fossil resource-derived raw materials, or it may be polymerized using biomass-derived raw materials. Furthermore, the recycled raw material may contain two or more types of PBT resin (A).

[0022] The amount of PBT resin (A) in the recycled material is not particularly limited. For example, the content of PBT resin (A) in the recycled material may be 10 to 70% by mass, 15 to 60% by mass, or 20 to 50% by mass, based on the total mass of the molded product and / or crushed product.

[0023] (Fibrous filler (B)) Examples of fibrous fillers (B) included in the recycled raw material include glass fibers, carbon fibers, silica fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, and the like. The manufacturing method according to this embodiment includes a method of kneading the recycled raw material using a kneader (preferably an extruder). Since polybutylene terephthalate resin is often used in insulating applications, it is preferable from the standpoint of insulation if it does not contain metal, and from the viewpoint of preventing wear on the kneader's screw, it is preferable not to use recycled raw materials that contain metal fibers. Of the fibrous fillers (B) described above, those containing glass fibers or carbon fibers are preferred from the viewpoint of being readily available as recalled products on the market.

[0024] The content of fibrous filler (B) in the recycled material is not particularly limited. For example, the content of fibrous filler (B) in the recycled material may be 5 to 50% by mass, 10 to 40% by mass, or 15 to 30% by mass, based on the total mass of the molded product and / or crushed product.

[0025] The fibrous filler (B) contained in the recycled raw material may be surface-treated as needed with a consolidator, a surface treatment agent (for example, functional compounds such as epoxy compounds, acrylic compounds, isocyanate compounds, silane compounds, titanate compounds, and carboxylic acid compounds).

[0026] The average fiber diameter of the fibrous filler (B) contained in the recycled material is not particularly limited, and fibrous filler (B) having any average fiber diameter can be included. Furthermore, if the recycled material is a process recovery product and the average fiber diameter of the fibrous filler (B) can be determined, or if it is a market recovery product and the average fiber diameter can be determined by prior sorting, it is more preferable to use molded and / or crushed products containing fibrous filler (B) with an average fiber diameter of 1 to 50 μm, preferably 3 to 20 μm. With repellets obtained from such recycled materials, nozzle clogging and gate clogging during injection molding are less likely to occur.

[0027] The fibrous filler (B) may have either a circular cross-section or a non-circular cross-section. Examples of non-circular cross-sections include oval, elliptical, and cocoon-shaped shapes.

[0028] The average fiber length (B) of the fibrous filler (B) in the recycled material is not particularly limited, and for example, a length of 0.1 to 10 mm (preferably 400 to 500 μm) can be used. The average fiber length of the fibrous filler (B) in the recycled material can be measured by the method described later.

[0029] (Other ingredients) The recycled raw materials may contain components other than PBT resin (A) and fibrous filler (B). Examples of these other components include non-fibrous fillers, phosphorus-based stabilizers, antioxidants, weather stabilizers, molecular weight modifiers, UV absorbers, antistatic agents, dyes, pigments, lubricants, crystallization accelerators, crystal nucleating agents, flame retardants, flame retardant aids, organic fillers, and colorants. The amount of these other components is also optional.

[0030] <Mixing process> The manufacturing method according to the first embodiment includes kneading the above-mentioned recycled materials (molded products and / or crushed products) to adjust the weight-average fiber length of the fibrous filler (B) in the final repellet to 200 μm or less. The kneading of the recycled materials can be carried out using a kneader.

[0031] (Mixing machine) Examples of mixing machines include roll mills, internal mixers (such as Banbury mixers), and extruders. Of these, an extruder is preferred from the viewpoint of easily adjusting the weight-average fiber length of the fibrous filler (B) contained in the recycled material to 200 μm or less, and from the viewpoint of processing efficiency of the recycled material.

[0032] [Extruder] Examples of extruders that can be used in the first embodiment include single-screw extruders, twin-screw extruders, multi-screw extruders (extruders with two or more screws), and planetary roller extruders. Of these, it is preferable to use a twin-screw extruder because the kneading shape of the screw can be adjusted relatively easily and heat generation due to shear can be relatively suppressed. Specific examples of twin-screw extruders include the ZSK series from Coperion, Inc., the TEM series from Toshiba Machine Co., Ltd., and the TEX series from Japan Steel Works Ltd.

[0033] The screw used in the extruder can be selected as appropriate. For example, single-thread, double-thread, or triple-thread screws can be used. The more threads a screw has, the more engagements occur per screw rotation, which tends to increase the shearing and kneading capacity, allowing for more effective fracture of the fibrous filler (B) in the recycled material. On the other hand, with more threads, the conveying capacity of the molten resin within the extruder tends to decrease, and the discharge rate of the raw material after kneading tends to decrease. Therefore, it is preferable to use a double-thread screw, which has a wide range of adjustment for both the conveying capacity of the molten resin and the shearing and kneading capacity.

[0034] <Screw configuration> While a screw with a directly machined screw shape may be used for the extruder's screw configuration, it is preferable to use an element or disk with a changeable screw pattern, from the viewpoint of being able to easily change the screw configuration and replace it in case of wear, damage, etc. In terms of element shape, forward flight screw elements, reverse flight screw elements, forward kneading elements, reverse kneading elements, neutral kneading elements, forward screw mixing elements, reverse screw mixing elements, seal ring elements, etc., can be used. By arbitrarily combining these, an extruder screw configuration suitable for this embodiment can be easily obtained. The following describes each extruder screw element and its operation and effect.

[0035] A "forward-direction flight screw element" is an extruder screw element having a continuous screw structure in the right-hand direction, and which has the function of moving resin components in the extrusion direction by the rotation of the screw (the rotation direction is clockwise when viewed from the extruder's discharge port).

[0036] A "reverse-direction flight screw element" is an extruder screw element having a continuous screw structure in the left-hand thread direction, and the rotation of the screw has the effect of moving the resin in the opposite direction to the extrusion direction.

[0037] A "forward kneading element" is a configuration in which multiple basically pseudo-elliptical flat plates are stacked in the thickness direction of the flat plates, offset from each other in the opposite direction to the extrusion direction, with the rotational axis of the extruder as the axis, and with a twist angle greater than 0 degrees and less than 90 degrees in the positive direction when the rotational direction of the axis is considered positive. This extruder screw element has the action of moving the resin in the extrusion direction as the rotation of the extruder screw element occurs, and at the same time, it has the action of kneading the resin. Alternatively, a kneading element that is not elliptical, such as V-kneading or BMS, may also be used.

[0038] A "reverse-direction kneading element" is a configuration in which multiple basically pseudo-elliptical flat plates are stacked in the thickness direction of the flat plates, offset from each other in the opposite direction to the extrusion direction, with the screw rotation axis as the axis of rotation. This extruder screw element has the function of moving the resin in the opposite direction to the extrusion direction as the rotation of the extruder screw element moves the resin, and at the same time, kneads the resin.

[0039] A "neutral kneading element" has a configuration in which multiple basically pseudo-elliptical flat plates are stacked in the thickness direction of the pseudo-elliptical flat plates, with the screw rotation axis as the center, while being alternately offset at a substantially 90-degree twist angle. This extruder screw element has the function of kneading the resin by the rotation of this extruder screw element.

[0040] A "forward-direction screw mixing element" is an extruder screw element that has a structure in which a notch is provided in the threads of a forward-direction flight screw. The rotation of the screw moves the resin in the extrusion direction, and at the same time moves a portion of the resin in the opposite direction to the extrusion direction through the notch, thereby mixing the resin.

[0041] A "reverse-direction screw mixing element" is an extruder screw element that has a structure in which a notch is provided in the threads of a reverse-direction flight screw. By rotating the screw, it moves the resin in the opposite direction to the extrusion direction, and at the same time moves a portion of the resin in the extrusion direction from the notch, thereby mixing the resin.

[0042] A "seal ring element" is an extruder screw element that basically consists of at least one circular flat plate and has the function of blocking the progress of the resin and increasing the resin filling rate.

[0043] In one embodiment, it is preferable to include a kneading element from the viewpoint of efficiently breaking the fibrous filler (B) in the recycled raw material and easily adjusting the weight-average fiber length of the fibrous filler (B) in the repellets to 200 μm or less.

[0044] One conventional recycling method involves repelling recovered materials from the manufacturing process. However, to prevent a decline in the mechanical properties of the recycled molded product, it is common to use a kneader (e.g., a single-screw extruder) that does not have a kneading section or has a screw with very loose kneading properties. When repelling recycled raw materials, including recovered market products, it is considered practically impossible to maintain the fiber length and amount of filler as much as possible, because the average fiber length and amount of filler in the recovered market products are not constant. The inventors of this invention have been investigating a new recycling method that can efficiently recycle recovered market products. As a result, they have considered that by actively breaking the fibrous filler contained in the recovered market products and repelling them, it may be possible to efficiently recycle recovered market products whose composition, fiber length, and amount of filler are unknown. Furthermore, the inventors of this application conducted further studies and discovered that by kneading recycled materials, the fibrous filler in the recycled materials can be effectively broken, and that, surprisingly, by kneading the recycled materials so that the weight-average fiber length of the fibrous filler is 200 μm or less, recycled molded products with less warping can be obtained.

[0045] From the viewpoint of easily adjusting the weight-average fiber length of the fibrous filler (B) in the recycled raw material to 200 μm or less, it is preferable to install two or more kneading elements on one screw, more preferably three or more kneading elements, and even more preferably four or more kneading elements. When two or more kneading elements are installed, two or more types of kneading elements may be used. In one preferred embodiment, three or more forward kneading elements may be installed.

[0046] In the manufacturing method according to this embodiment, it is preferable to knead the recycled raw material to adjust the weight-average fiber length of the fibrous filler (B) in the repellet to 180 μm or less, and more preferably to 150 μm or less. The weight-average fiber length of the fibrous filler (B) in the repellet can be measured by the following method. (Method for measuring weight-average fiber length) 5g of repellets are placed in a heating furnace such as an electric furnace and heated at 600°C for 2 hours to ash. The ashing residue is thoroughly dispersed in a 5% by mass polyethylene glycol aqueous solution, then transferred to a petri dish, and the fibrous packing material (B) is observed with a stereomicroscope. At this time, images of 1000 fibrous packing material (B) strands in the ashing residue are captured from a CCD camera to a PC, and the fiber length of the 1000 fibrous packing material (B) strands is measured using an image processing method with an image measuring instrument (for example, "LUZEX® AP" manufactured by Nireco Corporation, or "PITA-3" manufactured by Seishin Corporation, etc.) (cutoff limit: 50 μm or less), and the average value is taken as the weight-average fiber length. The weight-average fiber length is the value obtained by rounding the average value to the first decimal place.

[0047] [Repellet] A second embodiment of this disclosure relates to repellets. In other words, the second embodiment relates to a repellet comprising a polybutylene terephthalate resin (A) and a fibrous inorganic filler (B) having a weight-average fiber length of 200 μm or less. The repellet according to the second embodiment can produce a recycled molded product (molded product) with less warping.

[0048] The repellets according to the second embodiment include PBT resin (A). The PBT resin (A) is not particularly limited and may include any PBT resin (A) as described in the section on the manufacturing method according to the first embodiment. The content of PBT resin (A) in the repellets is not particularly limited and any range can be adopted. For example, it may be 10 to 70% by mass, 15 to 60% by mass, or 20 to 50% by mass, relative to the total mass of the repellets.

[0049] The type and content of the fibrous filler (B) in the repellets are not particularly limited, and any fibrous filler (B) described in the section on the manufacturing method according to the first embodiment may be included. For example, the content of the fibrous filler (B) in the repellets may be 30 to 90% by mass, 40 to 85% by mass, or 50 to 80% by mass, based on the total mass of the repellets.

[0050] In the second embodiment, the weight-average fiber length of the fibrous filler (B) in the repellet is 200 μm or less, preferably 180 μm or less, and more preferably 150 μm or less. The weight-average fiber length of the fibrous filler (B) in the repellet can be measured by the method described above.

[0051] In one embodiment, the average length of the repellets may be 2 to 8 mm or 3 to 5 mm.

[0052] In addition, the repellets according to the second embodiment may contain other components described in the section on the first embodiment.

[0053] The refelettes according to the second embodiment are preferably refelettes made from recycled materials, including market-collected products. Such refelettes can be prepared by the manufacturing method according to the first embodiment. In one embodiment, the proportion of market-recovered material in the repellets (the proportion of market-recovered material included in the raw materials for manufacturing the repellets) is preferably 20% or more, and more preferably 30% or more.

[0054] [Molded products] A third embodiment of this disclosure relates to a molded article of a repellet according to the second embodiment, or a molded article and / or a pulverized product thereof comprising a repellet according to the second embodiment and a polybutylene terephthalate resin composition that does not contain fibrous filler (B). The molded article according to the third embodiment exhibits less warping.

[0055] When the molded product according to the third embodiment is a molded product of the composite material, the ratio of the repellets according to the second embodiment to the total mass of the composite material is preferably such that the shrinkage rate is small, preferably 50 to 95%, and more preferably 60 to 90%, from the viewpoint of dimensional accuracy.

[0056] <Method for manufacturing molded products> The molded article according to the third embodiment can be manufactured by a method that includes molding the repellet according to the second embodiment, or the composite material, using conventional methods such as extrusion molding, injection molding, compression molding, blow molding, vacuum molding, rotational molding, and gas injection molding. In one embodiment, obtaining repellet by the manufacturing method according to the first embodiment may include molding the repellet (or the composite material).

[0057] A non-limiting list of exemplary embodiments of this disclosure and combinations of exemplary embodiments is provided below. [1] A method for producing repellets, The above-mentioned manufacturing method is a method for producing repellets, comprising kneading a molded article and / or a pulverized product thereof containing a polybutylene terephthalate resin (A) and a fibrous filler (B) to adjust the weight-average fiber length of the fibrous filler (B) in the repellets to 200 μm or less. [2] A repellet comprising a polybutylene terephthalate resin (A) and a fibrous filler (B) having a weight-average fiber length of 200 μm or less. A molded product of the repellets described in [3][2]. A molded article of a composite material comprising the repellets described in [4][2] and a molded article and / or a pulverized product thereof containing a polybutylene terephthalate resin composition that does not contain the fibrous filler (B). [Examples]

[0058] The embodiment will be described in more detail below with reference to examples, but this embodiment is not limited to the following examples.

[0059] The following ingredients were used for each example. • PBT resin (A): Manufactured by Polyplastics Co., Ltd., polybutylene terephthalate resin (intrinsic viscosity IV: 0.74 dL / g). • Fibrous filler (B): Glass fiber (manufactured by Nippon Electric Glass Co., Ltd., product name "ECS 03 T-127H"). • Powdered / granular filler: Glass beads (manufactured by Potters Barotini, average particle size 35 μm). Other ingredients Elastomer: Manufactured by Kaneka Corporation, product name "KaneAce (registered trademark) MP90". Lubricant: Manufactured by Sanyo Chemical Industries, Ltd., product name "Sunwax (registered trademark) 161-P".

[0060] [Preparation of molded products (Reference Examples 1-3)] Each component listed in Table 1 was melt-kneaded and extruded in the ratios (mass%) shown in Table 1 using a 30 mmφ twin-screw extruder (manufactured by Japan Steel Works Ltd., product name "TEX30") with a screw having two kneading elements, at a cylinder temperature of 260°C and a screw rotation speed of 130 rpm, to obtain pellets consisting of resin compositions I, II, and III. In the preparation of the pellets of resin composition I, glass fibers were side-fed. Of the resin compositions I to III, resin composition I corresponds to a PBT resin composition containing fibrous fillers.

[0061] After drying pellets I-III at 140°C for 3 hours, ISO 1A type test specimens (10 mm wide, 4 mm thick) conforming to ISO 3167 were created using an injection molding machine (FANUC, product name "ROBOSHOT® S-2000i 100B") at a cylinder temperature of 260°C and a mold temperature of 80°C.

[0062] (Measurement of mechanical properties) The tensile strength (MPa) and tensile fracture strain (%) of ISO test specimens obtained from pellets I to III were measured using a Shimadzu Autograph universal testing machine in accordance with ISO 527-1,2.

[0063] (Measurement of warping) Next, using the dried pellets I to III, a flat plate-shaped test specimen measuring 80 mm × 80 mm × 1.5 mm thick was fabricated using an injection molding machine (FANUC, product name "ROBOSHOT α-S100iA") at a cylinder temperature of 260°C, a mold temperature of 80°C, and a holding pressure of 70 MPa, using a mold with a side gate measuring 3 mm wide × 1.5 mm thick located in the center of one side. After molding, the specimens were left to stand at 23°C × 50% RH for more than 24 hours. Then, the dimensions of the flat plate-shaped test specimen were measured at a position 20 mm from the edge in the direction of flow and in the direction perpendicular to the direction of flow, and the shrinkage rate was calculated from the difference in the mold dimensions corresponding to that position. Furthermore, the flat plate-shaped test specimen was placed on a horizontal surface, and the height from the horizontal plane was measured at the nine locations shown in Figure 1. The flatness was measured by calculating the difference between the maximum and minimum heights.

[0064] (Measurement of weight-average fiber length) For pellets I to III, the weight-average fiber length of glass fibers in the re-pellets was measured using the following method. First, 5 g of re-pellet was placed in an electric furnace and heated at 600°C for 2 hours to ash it. The ashing residue was thoroughly dispersed in a 5% by mass polyethylene glycol aqueous solution, then transferred to a petri dish, and the glass fibers were observed with a stereomicroscope. At that time, images of 1000 glass fibers in the ashing residue were captured from a CCD camera to a PC, and the fiber length of the 1000 glass fibers was measured using an image processing method with an image measuring instrument (manufactured by Nireco Co., Ltd., product name "LUZEX AP") (cutoff limit: 50 μm or less), and the average value was defined as the "weight-average fiber length". The weight-average fiber length was obtained by rounding the average value to the first decimal place.

[0065] The evaluation results of molded products of pellets I to III are shown in Table 2 as Reference Examples 1, 3, and 5.

[0066] [Preparation of crushed products, preparation of recycled molded products from crushed products (Reference Examples 4-6)] The ISO test specimens (molded articles) obtained from pellets I to III prepared as described above were crushed to create pulverized products. The pulverized products obtained from each pellet were designated as pulverized products I', II', and III', respectively. Each pulverized product was remolded using an injection molding machine to create ISO test specimens and flat test specimens. For each test specimen, the mechanical properties and warpage were measured using the same method as described above. The evaluation results of the recycled molded articles from pulverized products I' to III' are shown in Table 2 as Reference Examples 2, 4, and 6.

[0067] [Examples 1-2 and Comparative Examples 1-2] The pulverized product I' or pulverized products I' and II' were used as recycled raw materials and fed into an extruder (manufactured by Japan Steel Works Ltd., product name "TEX30") to prepare repellets. In Example 1, four forward kneading elements were used to knead the recycled raw materials. In Example 2, pulverized products I' and II' were mixed in a 50:50 ratio. In Comparative Examples 1 and 2, recycled materials were kneaded using one to two forward kneading elements. For the repellets obtained in each example, the mechanical properties, warping, and the weight-average fiber length of the fibrous filler (B) within the pellets were measured using the same method as described above. The results are shown in Table 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] As shown in Reference Examples 1-2 of Table 2, the molded articles of the fibrous filler-containing PBT resin composition exhibited large differences in shrinkage rates in the flow direction and perpendicular to the flow direction, as well as high flatness values, indicating warping. On the other hand, the molded articles (recycled molded articles) obtained from repellets prepared by the manufacturing method according to the first embodiment showed smaller differences in shrinkage rates and significantly lower flatness values ​​compared to the molded articles of Reference Examples 1-2, confirming reduced warping. Even more surprisingly, the molded articles of Examples 1-2, despite containing a fibrous filler (B) with a specific weight-average fiber length, exhibited smaller absolute values ​​of shrinkage rates in the flow direction and perpendicular to the flow direction than the molded articles of Reference Examples 3-4 containing a granular filler, and the molded articles of Reference Examples 4-6 not containing an inorganic filler. Conversely, the molded articles of Comparative Examples 1-2, obtained from repellets with a weight-average fiber length exceeding 200 μm, exhibited warping to a similar degree as Reference Examples 1-2, and thus failed to solve the problems of this disclosure. In the above examples and comparative examples, process-recovered materials were used as recycled raw materials. However, since the above examples confirmed the advantage of adjusting the weight-average fiber length in the repellets to 200 μm or less, it is presumed that similar effects can be obtained even when using recycled raw materials including market-recovered materials. Furthermore, despite the different compositions of Example 1 and Example 2, the tensile strength was 60 MPa and the flatness was 0.2 mm. This indicates that even when repelling materials with different compositions, such as market-recovered materials, the repellet manufacturing method according to the first embodiment can produce recycled molded products of stable quality.

Claims

1. A method for producing repellets, The above-mentioned manufacturing method is a method for producing repellets, comprising kneading a molded article and / or a pulverized article containing a polybutylene terephthalate resin (A) and a fibrous filler (B) to adjust the weight-average fiber length of the fibrous filler (B) in the repellet to 200 μm or less.

2. A repellet comprising a polybutylene terephthalate resin (A) and a fibrous filler (B) with a weight-average fiber length of 200 μm or less.

3. A molded article of the repellet described in claim 2.

4. A molded article of a composite material comprising the repellets described in claim 2 and a molded article and / or a pulverized product thereof containing a polybutylene terephthalate resin composition that does not contain the fibrous filler (B).

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