JP7079699B2 - Improved weighability Polybutylene terephthalate resin pellets - Google Patents

Description

The present invention relates to polybutylene terephthalate resin pellets with improved measurable properties.

Polybutylene terephthalate resin (PBT resin) is excellent in various properties such as mechanical properties, electrical properties, and heat resistance, and is therefore widely used as engineering plastics in various applications such as automobile parts and electrical / electronic equipment parts.

Injection molding can be mentioned as a method for obtaining a molded product from a polybutylene terephthalate resin. In injection molding, as a method for increasing productivity, that is, the production quantity per unit time, there is a method of increasing the number of mold cavities to increase the number of molded products obtained per shot. On the other hand, it is also effective to increase the number of shots per unit time by shortening the molding cycle time per shot.

Here, in order to shorten the molding cycle time, there are methods of lowering the temperature of the mold to shorten the cooling time, or increasing the injection speed to shorten the injection time. However, shortening the cooling time may lead to insufficient crystallization of the molded product, which in turn may lead to deterioration of physical properties, and high-speed injection may also cause poor appearance due to jetting or gas burning. Therefore, as a step that has little influence on the characteristics of the molded product, it is preferable to shorten the "weighing time" for weighing one shot of the molten resin in the cylinder.

INDUSTRIAL APPLICABILITY According to the present invention, when a polybutylene terephthalate resin is injection-molded to obtain a molded product, it is possible to shorten the "weighing time" for weighing one shot of the molten resin in a cylinder, and the poly has improved measurable property. An object of the present invention is to provide a butylene terephthalate resin pellet.

As a result of diligent studies, the present inventors have found that in polybutylene terephthalate resin pellets containing a lubricant, the above-mentioned problems can be solved by setting the amount of the lubricant to seep out to the pellet surface within a specific range. It came to be completed. This is to increase the amount of lubricant leaching to a certain extent and cover a wide range, and without strict control of drying conditions as required when suppressing the amount of lubricant leaching to a low range. In a good point, it also solves the problem that management becomes complicated in controlling the amount of lubricant seeping out.

That is, the present invention relates to the following (1) to (5).
(1) Containing polybutylene terephthalate resin and lubricant, the lubricant-derived infrared spectrum peak intensity (2850 cm ^-1 absorption / absorption /) with respect to the polybutylene terephthalate resin-derived infrared spectrum peak intensity after pre-drying and before charging the molding machine. A polybutylene terephthalate resin pellet having an absorption of 1019 cm ^-1 ) of 0.080 or more and 0.215 or less.
(2) As the surface crystallized state before pre-drying, the infrared spectral peak intensity derived from the crystallized polybutylene terephthalate resin (absorption of 917 cm ^-1 / 1019 cm-) with respect ^to the infrared spectral peak intensity derived from the entire polybutylene terephthalate resin. ^1. The polybutylene terephthalate resin pellet according to (1), wherein the absorption) is 0.200 or more and 0.265 or less.
(3) The polybutylene terephthalate resin pellet according to (1) or (2), wherein the lubricant is a fatty acid ester.
(4) The polybutylene terephthalate resin pellet according to any one of (1) to (3), wherein the temperature of the pellet immediately after strand cutting is 150 ° C. or lower.
(5) The polybutylene terephthalate resin pellet according to any one of (1) to (4), which does not contain an inorganic filler.

According to the present invention, when a molded product is obtained by injection molding from polybutylene terephthalate resin, it is possible to shorten the "weighing time" for weighing one shot of the molten resin in the cylinder. Can provide improved polybutylene terephthalate resin pellets.

Hereinafter, one embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications as long as the effects of the present invention are not impaired.

[Polybutylene terephthalate resin pellets]
The polybutylene terephthalate resin pellet of the present invention contains a polybutylene terephthalate resin and a lubricant, and has an infrared spectrum peak intensity derived from the lubricant with respect to the infrared spectrum peak intensity derived from the polybutylene terephthalate resin after pre-drying and before loading into the molding machine. (Absorption of 2850 cm ^{-1 / Absorption of 1019 cm -1 )} is 0.080 or more and 0.215 or less.

The polybutylene terephthalate resin pellet of the present invention has an infrared spectral peak intensity derived from crystallized polybutylene terephthalate resin (917 cm) as opposed to an infrared spectral peak intensity derived from the entire polybutylene terephthalate resin as a surface crystallized state before pre-drying. ( ^-1 absorption / 1019 cm ^-1 absorption) is preferably 0.200 or more and 0.265 or less.

Further, the lubricant used in the polybutylene terephthalate resin pellet of the present invention is preferably a fatty acid ester.

Further, in the polybutylene terephthalate resin pellet of the present invention, the temperature of the pellet immediately after strand cutting is preferably 150 ° C. or lower, more preferably 130 ° C. or lower, further preferably 110 ° C. or lower, 100. The temperature is particularly preferably ℃ or less, and most preferably 90 ℃ or less. The lower limit of the pellet temperature immediately after the strand cut is not particularly limited, but when the pellet temperature is to be extremely lowered, it is necessary to take a long cooling process of the strand, which complicates the arrangement of equipment and the like. The above is preferable, the temperature is more preferably 50 ° C. or higher, and the temperature is even more preferably 60 ° C. or higher. In the present invention, the temperature of the pellets immediately after the strand cut is about 1 kg of the pellets immediately after the strand cut, and the pellets are collected in a container that can be collected in a sufficiently dense state so that the pellets do not cool down. The temperature near the center of the container filled with the pellets is measured with a contact thermometer.

Further, it is preferable that the polybutylene terephthalate resin pellet of the present invention does not contain an inorganic filler.

(Polybutylene terephthalate resin)
The polybutylene terephthalate resin (PBT resin) contains a dicarboxylic acid component containing at least terephthalic acid or an ester-forming derivative thereof (such as an alkyl ester of C _1-6 or an acid halide) and an alkylene glycol having at least 4 carbon atoms (1). , 4-Butandiol) or a polybutylene terephthalate resin obtained by polycondensing with a glycol component containing an ester-forming derivative (acetylated product, etc.). In the present embodiment, the polybutylene terephthalate resin is not limited to the homopolybutylene terephthalate resin, and may be a copolymer containing 60 mol% or more of the butylene terephthalate unit.

The amount of the terminal carboxyl group of the polybutylene terephthalate resin is not particularly limited as long as it does not impair the object of the present invention, but is preferably 30 meq / kg or less, and more preferably 25 meq / kg or less.

The intrinsic viscosity of the polybutylene terephthalate resin is not particularly limited as long as it does not impair the object of the present invention, but is preferably 0.60 dL / g or more and 1.2 dL / g or less, and 0.65 dL / g or more and 0.9 dL / g. It is more preferably g or less. When a polybutylene terephthalate resin having an intrinsic viscosity in such a range is used, the obtained polybutylene terephthalate resin composition is particularly excellent in moldability. It is also possible to adjust the intrinsic viscosity by blending polybutylene terephthalate resins having different intrinsic viscosities. For example, a polybutylene terephthalate resin having an intrinsic viscosity of 0.9 dL / g can be prepared by blending a polybutylene terephthalate resin having an intrinsic viscosity of 1.0 dL / g and a polybutylene terephthalate resin having an intrinsic viscosity of 0.7 dL / g. Can be done. The intrinsic viscosity of the polybutylene terephthalate resin can be measured, for example, in o-chlorophenol under the condition of a temperature of 35 ° C.

When an aromatic dicarboxylic acid other than terephthalic acid or an ester-forming derivative thereof is used as a comonomer component in the preparation of a polybutylene terephthalate resin, for example, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'- C _8-14 aromatic dicarboxylic acid such as dicarboxydiphenyl ether; C _4-16 alcandicarboxylic acid such as succinic acid, adipic acid, azelaic acid, sebacic acid; C _5-10 cycloalcandicarboxylic acid such as cyclohexanedicarboxylic acid. Acids; Ester-forming derivatives of these dicarboxylic acid components (C _1-6 alkyl ester derivatives, acid halides, etc.) can be used. These dicarboxylic acid components can be used alone or in combination of two or more.

Among these dicarboxylic acid components, C _8-12 aromatic dicarboxylic acids such as isophthalic acid and C _6-12 alcandicarboxylic acids such as adipic acid, azelaic acid and sebacic acid are more preferable.

When a glycol component other than 1,4-butanediol is used as the comonomer component in the preparation of the polybutylene terephthalate resin, for example, ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl C _2-10 alkylene glycols such as glycols and 1,3-octanediols; polyoxyalkylene glycols such as diethylene glycols, triethylene glycols and dipropylene glycols; alicyclic diols such as cyclohexanedimethanol and hydride bisphenol A; bisphenols Aromatic diols such as A, 4,4'-dihydroxybiphenyl; C _2-4 alkylene oxide adduct of bisphenol A such as ethylene oxide 2 mol adduct of bisphenol A and propylene oxide 3 mol adduct of bisphenol A; Alternatively, ester-forming derivatives of these glycols (acetylated products, etc.) can be used. These glycol components can be used alone or in combination of two or more.

Among these glycol components, C _2-6 alkylene glycols such as ethylene glycol and trimethylene glycol, polyoxyalkylene glycols such as diethylene glycol, and alicyclic diols such as cyclohexanedimethanol are more preferable.

Examples of the comonomer component that can be used in addition to the dicarboxylic acid component and the glycol component include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-carboxy-4'-hydroxybiphenyl and the like. Aromatic hydroxycarboxylic acids; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; C _3-12 lactones such as propiolactone, butyrolactone, valerolactone, caprolactone (ε-caprolactone etc.); esters of these comonomer components Examples thereof include formable derivatives (C _1-6 alkyl ester derivatives, acid halides, acetylates, etc.).

The content of the polybutylene terephthalate resin is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, and more preferably 30 to 70% by mass, based on the total mass of the polybutylene terephthalate resin pellets. More preferred.

(Glidant)
The polybutylene terephthalate resin pellet of the present invention contains a lubricant. Lubricants include fatty acids, fatty acid metal salts, oxy fatty acids, paraffins, low molecular weight polyolefins, fatty acid amides, aliphatic ketones, partially saponified fatty acid esters, lower fatty acid lower alcohol esters, polyhydric alcohol esters, fatty acid polyglycol esters, modified silicones, etc. Can be mentioned.

The fatty acid preferably has 6 to 40 carbon atoms, and specifically, oleic acid, stearic acid, lauric acid, hydroxystearic acid, behenic acid, arachidonic acid, linoleic acid, linolenic acid, ricinoleic acid, palmitic acid, and montan. Examples include acids and mixtures thereof. As the fatty acid metal salt, an alkali metal salt of a fatty acid having 6 to 40 carbon atoms and an alkaline earth metal salt are preferable, and specific examples thereof include calcium stearate, sodium montanate, calcium montanate and the like.

Examples of the oxy fatty acid include 1,2-oxystearic acid and the like. The paraffin preferably has 18 or more carbon atoms, and examples thereof include liquid paraffin, natural paraffin, microcrystalline wax, and petrolactam.

As the low molecular weight polyolefin, for example, one having a molecular weight of 5,000 or less is preferable, and specific examples thereof include polyethylene wax, maleic acid-modified polyethylene wax, oxidation type polyethylene wax, chlorinated polyethylene wax, polypropylene wax and the like.

The fatty acid amide preferably has 6 or more carbon atoms, and specifically, oleic acid amide, erucic acid amide, behenic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, N, N-bis (2-hydroxy). Ethyl) stearic acid amide and the like can be mentioned.

The aliphatic ketone is preferably one having 6 or more carbon atoms, and examples thereof include higher aliphatic ketones.

Examples of the fatty acid partially saponified ester include montanic acid partially saponified ester.

Examples of the fatty acid lower alcohol ester include stearic acid ester, oleic acid ester, linoleic acid ester, linolenic acid ester, adipic acid ester, behenic acid ester, arachidonic acid ester, montanic acid ester, isostearic acid ester and the like. These may be mixed esters with multiple types of fatty acids and / or lower alcohols.

Examples of fatty acid polyvalent alcohol esters include (poly) glycerin tristearate, (poly) glycerin distearate, (poly) glycerin monostearate, (poly) pentaerythritol tetrastearate, and (poly) pentaerythritol. Examples thereof include tristearate, (poly) pentaerythritol distearate, (poly) pentaerythritol monostearate, (poly) pentaerythritol adipate stearate, and sorbitambechenic acid ester. These may be mixed esters with multiple types of fatty acids and / or polyhydric alcohols.

Examples of the fatty acid polyglycol ester include polyethylene glycol fatty acid ester and polypropylene glycol fatty acid ester.

Examples of the modified silicone include polyether-modified silicone, higher fatty acid alkoxy-modified silicone, higher fatty acid-containing silicone, higher fatty acid ester-modified silicone, methacryl-modified silicone, and fluorine-modified silicone.

Preferred lubricants include, for example, fatty acid metal salts, low molecular weight polyolefins, fatty acid amides, fatty acid partially saponified esters, fatty acid lower alcohol esters, fatty acid polyvalent alcohol esters and the like. Of these, low molecular weight polyolefins, polyunsaturated fatty acid esters, and fatty acid amides are more preferable. Among them, polyethylene wax, adipic acid ester, montanic acid ester, behenic acid ester, stearic acid ester, glycerin fatty acid ester, pentaerythritol fatty acid ester, trimethylolpropane fatty acid ester, sorbitan fatty acid ester, and ethylene bisstearic acid amide are more preferable. A mixed ester of propane and montanic acid and adipic acid, a glycerin stearate ester, a glycerin behenic acid ester, and a pentaerythritol stearate ester are particularly preferable.

(filler)
A filler is used for the polybutylene terephthalate resin pellet of the present invention, if necessary. Such a filler is preferably blended in order to obtain excellent performance properties such as mechanical strength, heat resistance, dimensional stability, and electrical properties, and is particularly effective for the purpose of increasing rigidity. For this, a fibrous, powdery or plate-like filler is used depending on the purpose.

Fibrous fillers include circular cross-section glass fibers, asbestos fibers, carbon fibers, silica fibers, silica-alumina fibers, zirconia fibers, potassium titanate fibers, and metal fibers such as stainless steel, aluminum, titanium, copper, and brass. Things and the like can be mentioned. In addition, organic fibrous substances having a high melting point such as fluororesin and acrylic resin can also be used.

Examples of the powder and granular filler include glass beads, glass powder, quartz powder, kaolin, clay, diatomaceous earth, wollastonite, iron oxide, titanium oxide, alumina, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, and others, silicon carbide. , Silicon nitride, various metal powders and the like.

Examples of the plate-shaped filler include mica, glass flakes, and various metal foils.

The type of filler is not particularly limited, and one or more types of filler can be added.

The amount of the filler added is not particularly specified, but is preferably 200 parts by mass or less with respect to 100 parts by mass of the polybutylene terephthalate resin pellet. When the filler is added excessively, the moldability is poor and the toughness is lowered.

(Additive)
Further, a known substance generally added to a thermoplastic resin or the like can be added and used in combination with the polybutylene terephthalate resin pellet of the present invention, depending on the purpose. For example, antioxidants, UV absorbers, stabilizers such as light stabilizers, antistatic agents, mold release agents, colorants such as dyes and pigments, plasticizers, fluidity improvers, toughness improvers, and hydrolysis resistance improvement agents. It is possible to mix any agent, other resin, etc.

(Example)
Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. The characteristic evaluation was performed by the following method.
(1) Evaluation of the amount of lubricant (lubricant exudation amount) present on the surface of the pellet A Hyperion 3000 manufactured by Bruker was used as a measuring device, the irradiation area was set to 100 μm × 100 μm, and the examples and comparative examples obtained by the methods described below were used. Infrared spectrum measurement was performed using 10 pellets each. The peak derived from polybutylene terephthalate resin was assigned to 1019 cm ^{-1, and the peak derived from lubricant was assigned to 2850 cm -1 ,} and the peak intensity derived from lubricant (2850/1019) was determined with respect to the peak intensity derived from polybutylene terephthalate resin. The results are shown in Tables 1 to 4.
(2) Evaluation of Surface Crystallinity of Pellets Using Hyperion 3000 manufactured by Bruker Co., Ltd., the irradiation area was 100 μm × 100 μm, and 10 pellets of each Example and Comparative Example obtained by the method described later were used. Infrared spectrum measurement was performed. The peak derived from the entire polybutylene terephthalate resin is assigned to 1019 cm ^-1 , and the peak derived from the crystallized polybutylene terephthalate resin is assigned to 917 cm ^-1 , respectively. The peak intensity derived from the resin (917/1019) was determined. The results are shown in Tables 1 to 4.
(3) Evaluation of Weighability The pellets of each Example and Comparative Example obtained by the method described later were pre-dried at 140 ° C. for the drying time (hr) shown in Tables 1 to 4, and then molded by a molding machine (FANUC). Using "ROBOSHOT S-2000i 100B" manufactured by Co., Ltd., screw diameter Φ28 mm), the fluctuation of the weighing time when molding a strip-shaped test piece of 127 mm × 12.7 mm × 1.6 mm under the following molding conditions It was measured. 50 shots were performed, and the average weighing time and the standard deviation of the weighing time were calculated as variations (σ).
〔Molding condition〕
Cylinder temperature: 260 ° C
Mold temperature: 60 ° C
Injection speed: 20 mm / sec
Holding pressure: 50 MPa
Weighing stroke: 21 mm
Screw rotation speed: 80 rpm
Back pressure: 3 MPa

Regarding the evaluation of measurableness, in Examples 1 to 10 and Comparative Examples 1 to 17, those having a weighing time of 4 seconds or less were evaluated as ◯, and those having a measuring time of more than 4 seconds were evaluated as x. Further, for Examples 11 to 15 and Comparative Examples 18 to 22, which were carried out using a mold different from those of Examples 1 to 10 and Comparative Examples 1 to 17, those having a weighing time of 5 seconds or less were measured as ◯. The time exceeding 5 seconds and 6 seconds or less was marked with Δ, and the weighing time exceeding 6 seconds was marked with ×.

(4) Evaluation of handleability The pellets of each Example and Comparative Example obtained by the method described later were rubbed into a glass beaker having a bottom inner diameter of 43 mm and a capacity of 50 ml, and filled in a glass beaker at 180 ° C. for 1 hour in a constant temperature bath. It was heated. Then, the beaker was taken out from the constant temperature bath and allowed to stand indoors to cool to room temperature. After that, with a plate with a smooth horizontal surface placed on the beaker, with the opening of the beaker rotated downward, gently lift the beaker and visually check for sticking of pellets. I confirmed it in. Those with no sticking were marked with ○, those with slight sticking were marked with Δ, and those with significant sticking were marked with ×.
(5) Evaluation of Physical Properties After drying the pellets of Examples and Comparative Examples obtained by the method described later at 140 ° C. for 3 hours, the tensile test piece of ISO3167 was dried at a resin temperature of 260 ° C. and a mold temperature of 80 ° C. Type 1A (thickness: 4 mm) was formed and the tensile elongation (%) was measured according to ISO527-1 and ISO. Those having a tensile elongation of 10% or more were evaluated as ◯, and those having a tensile elongation of less than 10% were evaluated as x.

(Manufacturing of pellets)
The material dry-blended with the components and compositions (% by mass) shown in Tables 1 to 4 is supplied to the extruders shown in Tables 1 to 4, and the water immersion distance (cm) shown in Tables 1 to 4 is applied at a cylinder temperature of 250 ° C. ), Screw rotation speed (rpm), and discharge rate (kg / hr), and the obtained pellets containing the polybutylene terephthalate resin and the lubricant were used as samples for each of the above evaluations. Here, the inundation distance refers to the length of the cooling water tank before pelletizing (cutting) the strands of the melt-kneaded material extruded from the die of the extruder. The longer the inundation distance, the faster the cooling of the strands is promoted, and the pellets are pelletized in a state where the surface temperature is low. Therefore, the crystallization of the pellet surface is difficult to proceed, and the pellet has a low degree of surface crystallization. Further, the smaller the discharge amount, the lower the speed at which the strands are discharged, and even if the length of the cooling water tank is the same, the passage time becomes longer and the cooling of the strands is promoted. The degree of surface crystallinity is low. Normally, the higher the screw rotation speed, the larger the discharge amount tends to be. As the temperature of the pellets immediately after strand cutting in the present invention, in each Example and Comparative Example, 1 kg of pelletized pellets immediately after strand cutting were collected in a container in a state where the pellets were sufficiently densely packed, and the center of the container. The results of measuring the temperature in the vicinity of the section with a contact thermometer are shown in Tables 1 to 4 together as the pellet temperature (° C.). Here, the time required for collecting 1 kg of pellets varies depending on the discharge amount, but since it is about several seconds to several minutes, the temperature drop during collection can be ignored.

Details of each component shown in Tables 1 to 4 are as follows.
PBT resin: Polybutylene terephthalate resin fatty acid ester manufactured by Wintech Polymer Co., Ltd., terminal carboxyl group concentration 20 meq / kg, intrinsic viscosity 0.84 dL / g 1: Rikemar B74 manufactured by RIKEN Vitamin Co., Ltd.
Fatty acid ester 2: RIKEN Vitamin Co., Ltd. Licorub WE40
Fatty Acid Ester 3: Clariant Japan Co., Ltd. Rico Wax E
Fatty acid ester 4: Licocare RBW300TP manufactured by Clariant Japan Co., Ltd.
Fatty acid ester 5: Licocare RBW102TP manufactured by Clariant Japan Co., Ltd.
Aliphatic Amide 1: Light Amide WH-510K manufactured by Kyoeisha Chemical Co., Ltd.
Fatty acid amide 2: Kyoeisha Chemical Co., Ltd. Light Amide WH-215
Fatty acid amide 3: Light Amide WH-255 manufactured by Kyoeisha Chemical Co., Ltd.
Talc: Micron White # 5000A manufactured by Hayashi Kasei Co., Ltd.
Antioxidant: Irganox1010 manufactured by BASF Japan Ltd.
Stabilizer: ADEKA CORPORATION ADEKA STAB PEP36
Carbodiimide: Stabacol P400 manufactured by Rhein Chemie Japan Co., Ltd.
Potassium acetate: Made by Fujifilm Wako Pure Chemical Corporation Potassium acetate Carbon black: Made by Mitsubishi Chemical Corporation MA600B

Claims (5)

Melting and kneading raw materials containing polybutylene terephthalate resin and lubricant with an extruder
Cooling the strands of the melt-kneaded product extruded from the die of the extruder in a water tank,
A method for producing polybutylene terephthalate resin pellets, which comprises pelletizing the strands to obtain resin pellets.
The cooling step of the strand is to cool the strand so that the temperature of the resin pellet immediately after pelletizing becomes 150 ° C. or lower.
After the pelletizing step, the infrared spectrum of the obtained resin pellet was measured, and the ratio of the infrared spectrum peak intensity derived from the lubricant to the infrared spectrum peak intensity derived from the polybutylene terephthalate resin (spectrum peak intensity of 2850 cm ^-1 ). A polybutylene terephthalate resin, which comprises confirming (spectrum peak intensity of / 1019 cm ^-1 ) and then drying for 3 to 24 hours to obtain resin pellets having a strength ratio of 0.080 or more and 0.215 or less . How to make pellets. The strand cooling step further comprises adjusting the surface crystallization state of the polybutylene terephthalate resin pellets.
The poly in the infrared spectrum of the resin pellet before the surface crystallizing state adjusting step is dried for 3 to 24 hours by adjusting at least one condition selected from the discharge amount and the inundation distance . The infrared spectrum peak intensity derived from the crystallized polybutylene terephthalate resin (spectrum peak intensity of 917 cm ^-1 / spectrum peak intensity of 1019 cm ^-1 ) is 0.200 or more with respect to the infrared spectrum peak intensity derived from the entire butylene terephthalate resin. The method for producing a polybutylene terephthalate resin pellet according to claim 1, which comprises 0.265 or less. The method for producing a polybutylene terephthalate resin pellet according to claim 1 or 2 , wherein the strand cooling step is to cool the strand so that the temperature of the resin pellet immediately after pelletizing becomes 40 ° C. or higher and 150 ° C. or lower. The method for producing a polybutylene terephthalate resin pellet according to any one of claims 1 to 3 , wherein the lubricant contains a fatty acid ester. The method for producing a polybutylene terephthalate resin pellet according to any one of claims 1 to 4 , wherein the polybutylene terephthalate resin pellet does not contain an inorganic filler.