JP7701424B2 - Polybutylene terephthalate resin composition - Google Patents

Description

The present disclosure relates to a polybutylene terephthalate resin composition.

Components for optical devices installed in vehicles such as automobiles, such as drive recorders, backup cameras, and ADAS, and components for display devices such as head-up displays, liquid crystal meters, and car navigation systems are required to have low gloss in order to reduce glare caused by reflections, etc. Many plastic materials form a high-gloss surface when molded, so low gloss is achieved by providing a texture on the mold used for injection molding to give the molded product surface a textured finish, or by painting the molded product surface with a matte agent. Attempts to achieve low gloss using the properties of the material itself include, for example, Patent Documents 1 and 2.

Special Publication No. 2008-540803 JP 2018-144581 A

The objective of the present disclosure is to provide a polybutylene terephthalate resin composition that has excellent jet blackness and low gloss with little uneven gloss.

The present disclosure encompasses the following aspects.
[1] A composite material comprising: (A) a polybutylene terephthalate resin; (B) a polycarbonate resin; (C) glass flakes; and (D) carbon black;
(A) the polybutylene terephthalate resin comprises (a1) a modified polybutylene terephthalate resin containing 5 to 30 mol % of a comonomer unit,
(C) The average thickness of the glass flakes is 1 μm or less and the median diameter is 5 to 70 μm;
(A) per 100 parts by mass of polybutylene terephthalate resin,
(B) the content of the polycarbonate resin is 60 to 100 parts by mass,
(C) the content of glass flakes is 60 to 100 parts by mass,
(D) A polybutylene terephthalate resin composition having a carbon black content of 0.8 to 15 parts by mass.
[2] The polybutylene terephthalate resin composition according to [1], further comprising (F) a phosphorus-based compound.
[3] A molded article comprising the resin composition according to [1] or [2].

According to the present disclosure, it is possible to provide a polybutylene terephthalate resin composition that has excellent jet blackness and low gloss with little uneven gloss.

Hereinafter, one embodiment of the present disclosure will be described in detail, but the scope of the present disclosure is not limited to the embodiment described here, and various modifications can be made within the scope of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. In addition, when multiple upper and lower limit values are described for a specific parameter, any upper and lower limit values among these upper and lower limit values can be combined to form a suitable numerical range. In addition, the lower and/or upper limit values of the numerical range described in this disclosure are numerical values within the numerical range and may be replaced with numerical values shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less". When a specific description described for one embodiment is also applicable to other embodiments, the description may be omitted in other embodiments.
Each configuration and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of configurations are possible as appropriate without departing from the spirit of this disclosure.

[Polybutylene terephthalate resin composition]
The polybutylene terephthalate resin composition of the present disclosure (hereinafter also simply referred to as “resin composition”) contains (A) a polybutylene terephthalate resin, (B) a polycarbonate resin, (C) glass flakes, and (D) carbon black,
(A) the polybutylene terephthalate resin comprises (a1) a modified polybutylene terephthalate resin containing 5 to 30 mol % of a comonomer unit,
(C) The average thickness of the glass flakes is 1 μm or less and the median diameter is 5 to 70 μm;
(A) per 100 parts by mass of polybutylene terephthalate resin,
(B) the content of the polycarbonate resin is 60 to 100 parts by mass,
(C) the content of glass flakes is 60 to 100 parts by mass,
(D) The carbon black content is 0.8 to 15 parts by mass.

When light is incident on the surface of a molded article, the phenomenon of reflection, transmission, and absorption of light occurs. From the viewpoint of increasing the absorption of light and reducing the reflection of light on the surface of a molded article, it is preferable that the resin composition has excellent jet blackness. Conventionally, black coloring has been performed by blending carbon black into a resin composition, but depending on the composition of the resin composition, sufficient jet blackness may not be obtained even if carbon black is blended. In addition, since the glossiness increases when there is a lot of reflected light on the surface of the molded article, it is preferable to reduce the reflected light. It is expected that the light is taken into the inside of the molded article by increasing the light transmittance of the resin material, and the reflected light is reduced, but if the light transmittance is too high, the glossiness may increase or the jet blackness may decrease. Furthermore, if the injection speed changes when the resin composition is injection molded, the glossiness of the molded article obtained may become uneven. In particular, in molded articles having complex shapes, the filling speed of the resin varies depending on the part of the molded article even when multi-stage speed control is performed, so that the glossiness of the molded article obtained may become uneven.
The resin composition of the present disclosure has the above-described configuration, and thus can achieve both excellent jet blackness and low gloss, and can provide a molded product with little gloss unevenness.

In this disclosure, the term "polybutylene terephthalate resin composition" refers to a resin composition containing polybutylene terephthalate resin. The content of polybutylene terephthalate resin will be described later.

<(A) Polybutylene terephthalate resin>
The (A) polybutylene terephthalate resin contains (a1) a modified polybutylene terephthalate resin containing 5 to 30 mol % of a comonomer unit (hereinafter, also simply referred to as "(a1) modified polybutylene terephthalate resin"). By containing the (a1) modified polybutylene terephthalate resin, a polybutylene terephthalate resin composition having excellent jet blackness and low glossiness with little gloss unevenness can be obtained. In addition, the jet blackness can be further enhanced by blending carbon black.

The (a1) modified polybutylene terephthalate resin is a copolymer having polybutylene terephthalate as the main component obtained by polycondensation reaction of terephthalic acid or its ester-forming derivative ( _C1-6 alkyl ester, acid halide, etc.) as the dicarboxylic acid component with an alkylene glycol having 4 carbon atoms (1,4-butanediol) or its ester-forming derivative (acetylated product, etc.) as the glycol component, into which 5 to 30 mol % (preferably 7 to 25 mol %, more preferably 8 to 20 mol %, even more preferably 10 to 15 mol %, for example 10 to 13 mol %) of another comonomer component (third component) is introduced relative to 100 mol % of the total dicarboxylic acid components. The other comonomer component (third component) means a copolymerizable monomer component different from terephthalic acid or its ester-forming derivative and 1,4-butanediol or its ester-forming derivative. (a1) The content of the comonomer component (third component) in the modified polybutylene terephthalate resin can be measured, for example, by using ¹ H-NMR.

Examples of dicarboxylic acid components that can be used as other comonomer components (third component) include C8-14 aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-dicarboxydiphenyl ether; _C4-16 alkanedicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and _sebacic acid; _C5-10 cycloalkanedicarboxylic acids such as cyclohexanedicarboxylic acid; and ester-forming derivatives of these dicarboxylic acid components ( _C1-6 alkyl ester derivatives, acid halides, and the like). These dicarboxylic acid components can be used alone or in combination of two or more.

Among these dicarboxylic acid components, _C8-12 aromatic dicarboxylic acids such as isophthalic acid, and _C6-12 alkanedicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid are more preferred.

Examples of glycol components that can be used as the other comonomer component (third component) include _C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, and 1,3-octanediol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol; alicyclic diols such as cyclohexanedimethanol and hydrogenated bisphenol A; aromatic diols such as bisphenol A and 4,4'-dihydroxybiphenyl; _C2-4 alkylene oxide adducts of bisphenol A, such as 2-mol ethylene oxide adducts of bisphenol A and 3-mol propylene oxide adducts of bisphenol A; and ester-forming derivatives of these glycols (acetylated products, etc.). These glycol components can be used alone or in combination of two or more.

Among these glycol components, _C2-6 alkylene glycols such as ethylene glycol and trimethylene glycol, polyoxyalkylene glycols such as diethylene glycol, and alicyclic diols such as cyclohexanedimethanol are more preferred.

Examples of the comonomer component (third component) that can be used in addition to the dicarboxylic acid component and the glycol component include aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-carboxy-4'-hydroxybiphenyl, etc.; aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxycaproic acid; _C3-12 lactones such as propiolactone, butyrolactone, valerolactone, caprolactone (e.g., ε-caprolactone), etc.; and ester-forming derivatives of these comonomer components ( _C1-6 alkyl ester derivatives, acid halides, acetylated products, etc.).

Any of the polybutylene terephthalate copolymers produced by polycondensation of the above compounds as comonomer components can be suitably used as the (a1) modified polybutylene terephthalate resin.
In one embodiment, the (a1) modified polybutylene terephthalate resin preferably contains an isophthalic acid-modified polybutylene terephthalate copolymer and/or an alkylene (excluding 1,4-butanediol)-modified polybutylene terephthalate copolymer, and more preferably contains an isophthalic acid-modified polybutylene terephthalate copolymer. The (a1) modified polybutylene terephthalate resin can be used alone or in combination of two or more kinds.

The content of the (a1) modified polybutylene terephthalate resin in the total amount (100% by mass) of the (A) polybutylene terephthalate resin is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, even more preferably 90 to 100% by mass, and particularly preferably 95 to 100% by mass. In one embodiment, the (A) polybutylene terephthalate resin may be composed solely of the (a1) modified polybutylene terephthalate resin.

In one embodiment, the (A) polybutylene terephthalate resin may contain (a2) homopolybutylene terephthalate polymer (unmodified polybutylene terephthalate resin) in addition to (a1) modified polybutylene terephthalate resin. The content of (a2) homopolybutylene terephthalate polymer may be 0 to 20% by mass, 0 to 10% by mass, or 0 to 5% by mass in the total amount (100% by mass) of the (A) polybutylene terephthalate resin.

The intrinsic viscosity of the (A) polybutylene terephthalate resin is preferably 0.65 to 1.15 dL/g, more preferably 0.67 to 1.00 dL/g, from the viewpoint of improving moldability. The intrinsic viscosity can also be adjusted 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 with a polybutylene terephthalate resin having an intrinsic viscosity of 0.7 dL/g. The intrinsic viscosity of the (A) polybutylene terephthalate resin is a value measured in o-chlorophenol at a temperature of 35°C using an Ubbelohde viscometer.

(A) The amount of terminal carboxyl groups (CEG) of the polybutylene terephthalate resin is not particularly limited as long as it does not impede the objectives of the present disclosure, but is preferably 5 to 30 meq/kg, and more preferably 10 to 25 meq/kg. By using a polybutylene terephthalate resin with an amount of terminal carboxyl groups in this range, it is possible to suppress the decrease in strength of the resulting polybutylene terephthalate resin composition in a humid and hot environment.

The content of (A) polybutylene terephthalate resin is preferably 20 to 60 mass% of the total amount (100 mass%) of the resin composition, more preferably 25 to 50 mass%, and even more preferably 30 to 40 mass%.

As described below, the resin composition may contain thermoplastic resins other than (A) polybutylene terephthalate resin and (B) polycarbonate resin. However, from the viewpoint of easily obtaining a polybutylene terephthalate resin composition having excellent jet blackness and low gloss with little uneven gloss, the total content of (A) polybutylene terephthalate resin and (B) polycarbonate resin is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass% of the total amount (100 mass%) of the thermoplastic resins constituting the resin composition. In one embodiment, the thermoplastic resin contained in the resin composition may be composed only of (A) polybutylene terephthalate resin and (B) polycarbonate resin.

<(B) Polycarbonate resin>
The resin composition contains a polycarbonate resin (B). By containing the polycarbonate resin (B), a polybutylene terephthalate resin composition having excellent jet blackness and low gloss with little gloss unevenness can be obtained.
The polycarbonate resin (B) may be a polymer obtained by reacting a dihydroxy compound with a carbonate ester such as phosgene or diphenyl carbonate. The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by the conventionally known phosgene method (interfacial polymerization method) or melting method (ester exchange method) may be used.

Dihydroxy compounds include, for example, alicyclic compounds (e.g., alicyclic diols) and bisphenol compounds, with bisphenol compounds being preferred.

Bisphenol compounds include bis(4-hydroxyphenyl)methane, bis(4-hydroxy-3-methylphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxy-3-methylphenyl)ethane, 1,1-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)propane ("bisphenol A"), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3-ethylphenyl)propane, 2,2-bis(4-hydroxy-3-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3-ethylphenyl)propane, 2,2-bis(4-hydroxy-3-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromo ... Bis(hydroxyaryl)C such as bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 2,2-bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxyphenyl)hexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)dibenzylmethane, 1,1-bis(4-hydroxyphenyl)-1-phenylpropane, and 2,2,2',2'-tetrahydro-3,3,3',3'-tetramethyl-1,1'-spirobi-[1H-indene]-6,6'-diol. _1-10 alkanes, preferably bis(hydroxyaryl) C _1-6 alkanes; bis(hydroxyaryl) C such as 1,1-bis(4-hydroxyphenyl)cyclopentane and 1,1-bis(4-hydroxyphenyl)cyclohexane; dihydroxyaryl ethers such as _4,4' -dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether; dihydroxyaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone; dihydroxyaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; dihydroxyaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; and dihydroxyaryl ketones such as 4,4'-dihydroxydiphenyl ketone and 4,4'-dihydroxy-3,3'-dimethyldiphenyl ketone.

A preferred example of the (B) polycarbonate resin is bisphenol A polycarbonate.

The polycarbonate resin (B) may be a homopolycarbonate or a copolycarbonate. In addition, the polycarbonate resin may be used alone or in combination of two or more kinds.

From the viewpoint of fluidity, the melt viscosity of the (B) polycarbonate resin is preferably 0.40 kPa·s or less, more preferably 0.35 kPa·s or less, and even more preferably 0.30 kPa·s or less, as measured at 300°C and 1000 sec ^-1 in accordance with ISO 11443. The melt viscosity is a value measured using a Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd., using a 1 mmφ×20 mmL/flat die as a capillary, at a barrel temperature of 300°C, and a shear rate of 1000 sec ^-1 .

The content of the (B) polycarbonate resin is 60 to 100 parts by mass, preferably 65 to 95 parts by mass, more preferably 70 to 90 parts by mass, even more preferably 75 to 85 parts by mass, and particularly preferably 75 to 83 parts by mass, relative to 100 parts by mass of the (A) polybutylene terephthalate resin. By blending a predetermined amount of the (B) polycarbonate resin with the (A) polybutylene terephthalate resin, a polybutylene terephthalate resin composition with excellent jet blackness and low glossiness with little gloss unevenness can be obtained. As a non-limiting mechanism, it is believed that by blending a predetermined amount of the (B) polycarbonate resin with the (A) polybutylene terephthalate resin, transparency can be appropriately increased, and light incident on the surface of the molded article can be transmitted into the interior of the molded article without reducing the jet blackness, and the transmitted light can be absorbed by a light absorbing material such as (D) carbon black, thereby reducing the reflected light on the surface of the molded article.

In one embodiment, the content of (B) polycarbonate resin may be 77 parts by mass, 78 parts by mass, 80 parts by mass, 82 parts by mass, or 85 parts by mass relative to 100 parts by mass of (A) polybutylene terephthalate resin, or may be within the range in which these are the upper or lower limit values of the above numerical range, or may be a range that combines these.

<(C) Glass Flakes>
The resin composition contains (C) glass flakes. The glass flakes have an average thickness of 1 μm or less. The median diameter (D50) of the (C) glass flakes contained in the resin composition is 5 to 70 μm. By containing (C) glass flakes having an average thickness of 1 μm or less and a median diameter of 5 to 70 μm, a polybutylene terephthalate resin composition having excellent jet blackness and low gloss with little gloss unevenness can be obtained.

The average thickness of the (C) glass flakes is preferably 0.9 μm or less, more preferably 0.8 μm or less, and may be 0.7 μm or less. In one embodiment, the average thickness of the (C) glass flakes may be 0.01 to 1 μm, 0.05 to 1 μm (e.g., 0.05 to 0.9 μm, 0.05 to 0.8 μm, or 0.05 to 0.7 μm), or 0.1 to 1 (e.g., 0.1 to 0.9 μm, 0.1 to 0.8 μm, 0.1 to 0.7 μm, 0.7 to 1 μm, or 0.7 to 0.9 μm).
The average thickness of the (C) glass flakes may be calculated from the raw material manufacturer's value or by measurement. For example, it can be calculated by analyzing images taken with a CCD camera using a 2-propanol solvent with a dynamic image analysis method/particle (state) analyzer PITA-3 manufactured by Seishin Enterprise Co., Ltd., and calculating the weighted average. The average value may also be determined by direct observation using an electron microscope or the like. The average thickness of the (C) glass flakes in the experimental data is a value measured by the above-mentioned method for the (C) glass flakes in the resin composition.

The median diameter (D50) of the glass flakes (C) contained in the resin composition is 5 to 70 μm, preferably 10 to 60 μm, and more preferably 20 to 50 μm. In one embodiment, the median diameter of the glass flakes (C) may be 40 μm or 41 μm, or may be within the range of the upper or lower limit of the above numerical range.
In the present disclosure, the median diameter refers to the median diameter of the glass flakes (C) in the resin composition measured by a laser diffraction/scattering method (for example, LA-960 manufactured by Horiba, Ltd.) The median diameter of the glass flakes (C) in the resin composition can be measured by treating the resin composition or a molded product thereof in an electric furnace at 600° C. for 4 hours and measuring the remaining residue by the laser diffraction/scattering method.

The average aspect ratio of the (C) glass flakes is not limited within a range that does not impair the effects of the present disclosure, and is preferably 5 to 200, more preferably 20 to 150, and even more preferably 30 to 100. The average aspect ratio is used here as an index representing the anisotropy of the plate shape, and is the ratio of the median diameter to the average thickness (aspect ratio = median diameter / average thickness). The median diameter can be measured by a laser diffraction/scattering method (LA-960 manufactured by Horiba, Ltd.) or the like. Alternatively, the ratio of the particle diameter to the thickness may be calculated by direct observation using an electron microscope or the like, and the average value may be calculated. The median diameter and aspect ratio of the (C) glass flakes are values measured by the above method for the (C) glass flakes remaining as residue after treating a molded product made of a resin composition in an electric furnace at 600°C for 4 hours.

The content of the (C) glass flakes is 60 to 100 parts by mass, preferably 65 to 95 parts by mass, more preferably 70 to 90 parts by mass, even more preferably 75 to 85 parts by mass, and particularly preferably 75 to 83 parts by mass, relative to 100 parts by mass of the (A) polybutylene terephthalate resin. By blending a predetermined amount of (C) glass flakes having a predetermined thickness and a predetermined median diameter in the resin composition with the (A) polybutylene terephthalate resin, a polybutylene terephthalate resin composition with excellent jet blackness and low glossiness with little uneven gloss can be obtained. As a non-limiting mechanism, it is believed that the thin-walled (C) glass flakes having a predetermined thickness and median diameter tend to break into an amorphous shape during molding, forming a surface with no regularity, and blending them in a predetermined amount tends to roughen the surface of the molded product into a matte finish with fine irregularities, resulting in random reflection of light. When light is reflected randomly, the reflected light is repeatedly taken in and absorbed inside the molded product, and is attenuated. This is thought to result in a low gloss with little uneven gloss without reducing the jet black color.

In one embodiment, the content of (C) glass flakes may be 77 parts by mass, 78 parts by mass, 80 parts by mass, 81 parts by mass, or 85 parts by mass relative to 100 parts by mass of (A) polybutylene terephthalate resin, or may be within the range in which these are the upper or lower limit values of the above numerical range, or may be a range that combines these.

As described below, the resin composition may contain fillers other than the (C) glass flakes. However, from the viewpoint of easily obtaining a polybutylene terephthalate resin composition with excellent jet blackness and low gloss with little uneven gloss, the content of the (C) glass flakes is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass% of the total amount (100 mass%) of the inorganic fillers contained in the resin composition. In one embodiment, the inorganic fillers contained in the resin composition may be composed solely of the (C) glass flakes.

<(D) Carbon Black>
The resin composition contains (D) carbon black. Examples of (D) carbon black include furnace black, ketjen black, channel black, acetylene black, and thermal black. (D) carbon black can be used alone or in combination of two or more. (D) carbon black may be used as a pigment (or colorant).

From the viewpoint of blackness and light absorbency, the dibutyl phthalate (DBP) oil absorption of the carbon black (D) is preferably 30 to 600 cm ³ /100g, more preferably 40 to 550 cm ³ /100g, and even more preferably 50 to 500 cm ³ /100g. In one embodiment, the DBP oil absorption of the carbon black (D) may be 40 to 100 cm ³ /100g (e.g., 50 to 80 cm ³ /100g), or may be more than 100 cm ³ /100g and 500 cm ³ /100g or less (e.g., 100 to 495 ^{cm 3} /100g). The dibutyl phthalate oil absorption is a value measured in accordance with JIS K6217-4:2008.

The average particle size of the (D) carbon black is preferably 5 to 100 nm, more preferably 8 to 50 nm, and even more preferably 10 to 40 nm. In one embodiment, the average particle size of the (D) carbon black is preferably 8 to 30 nm, and more preferably 10 to 30 nm, from the viewpoint of increasing the jet blackness of the molded article and easily giving a molded article with high light absorption. In one embodiment, the average particle size of the (D) carbon black may be 13 nm, 16 nm, 22 nm, or 34 nm, or may be within the range in which these are the upper or lower limit values of the above numerical ranges, or may be within a range that combines these.
The average particle size is the arithmetic average particle size determined by observing 1,000 particles of carbon black under an electron microscope before the carbon black is blended into the resin composition.

The content of (D) carbon black is 0.8 to 15 parts by mass (e.g., 0.9 to 15 parts by mass or 1 to 15 parts by mass) relative to 100 parts by mass of (A) polybutylene terephthalate resin, and preferably 0.8 to 12 parts by mass (e.g., 0.9 to 12 parts by mass or 1 to 12 parts by mass). By including (D) carbon black in an amount of 0.8 to 15 parts by mass relative to 100 parts by mass of (A) polybutylene terephthalate resin, a polybutylene terephthalate resin composition having excellent jet blackness and low gloss with little gloss unevenness can be obtained. From the viewpoint of easily obtaining a polybutylene terephthalate resin composition having better jet blackness, less uneven glossiness, and better low glossiness, the content of (D) carbon black is more preferably 0.8 to 11 parts by mass (0.9 to 11 parts by mass, 1 to 11 parts by mass) relative to 100 parts by mass of (A) polybutylene terephthalate resin, more preferably 0.8 to 10 parts by mass, even more preferably 0.8 to 8 parts by mass, and may be 1 to 6 parts by mass. In one embodiment, the content of (D) carbon black may be 1.3 parts by mass, 2.6 parts by mass, or 5.3 parts by mass relative to 100 parts by mass of (A) polybutylene terephthalate resin, or may be in a range in which these are the upper or lower limit values of the above numerical range, or may be in a range that combines these.

<(F) Phosphorus Compound>
The resin composition may contain a phosphorus-based compound (F) as required. By containing the phosphorus-based compound (F), it is possible to improve the mold releasability during injection molding and the heat resistance of the molded product.

Examples of the phosphorus-based compound include organic phosphite-based compounds, organic phosphonite-based compounds, alkali metal phosphates, and alkaline earth metal phosphates.
Examples of the organic phosphite compound include bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,4-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, and bis(nonylphenyl)pentaerythritol diphosphite.
An example of the organic phosphonite compound is tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphonite.
Examples of alkali metal phosphates include alkali metal salts such as potassium phosphate and sodium phosphate [sodium monophosphate (sodium dihydrogen phosphate), sodium disodium phosphate (sodium hydrogen phosphate, sodium monohydrogen phosphate, disodium hydrogen phosphate, etc.)].
Examples of alkaline earth metal phosphates include alkaline earth metal salts such as calcium phosphate [monocalcium phosphate (calcium dihydrogen phosphate, calcium bis(dihydrogen phosphate) monohydrate, etc.), secondary calcium phosphate (calcium hydrogen phosphate, calcium hydrogen phosphate dihydrate, etc.)], and magnesium phosphate (magnesium hydrogen phosphate, magnesium dihydrogen phosphate, etc.). The alkali metal salt or alkaline earth metal salt may be either anhydrous or hydrated. (F) The phosphorus-based compound may be used alone or in combination of two or more kinds.

Of these phosphorus compounds, one or more selected from alkali metal phosphates, alkaline earth metal phosphates, and organic phosphites are preferred.

The content of the (F) phosphorus-based compound is preferably 0.01 to 2.0 parts by mass, and more preferably 0.05 to 1.0 parts by mass, per 100 parts by mass of the (A) polybutylene terephthalate resin.

(Other resin components)
The resin composition may contain other thermoplastic resins other than the polybutylene terephthalate resin (A) and the polycarbonate resin (B) as long as the effects of the present disclosure are not impaired. Examples of other thermoplastic resins include polyethylene terephthalate and acrylonitrile styrene resin. The content of the other thermoplastic resin is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and may be 0 to 5 parts by mass relative to 100 parts by mass of the polybutylene terephthalate resin (A).

The resin composition may contain an elastomer (e.g., ABS, core-shell elastomer, etc.) that is generally used to improve impact resistance, but since whitening is likely to occur if the refractive index difference between the elastomer and polybutylene terephthalate or polycarbonate is large, the refractive index of the elastomer is preferably about 1.55 to 1.60 in order to further enhance the jet blackness of the molded product. For example, a core-shell elastomer with a particle size of about 1 to 10 μm has the effect of reducing gloss, but since the acrylic resin used in the shell, etc. has a low refractive index and is prone to whitening, the content is preferably less than 2 mass%, more preferably less than 1 mass%, of the total amount (100 mass%) of the resin composition.

(Other fillers)
The resin composition may contain other fillers other than the glass flakes (C) as necessary. As the filler, a fibrous filler, a powdery filler (excluding carbon black), and a plate-like filler (excluding glass flakes) may be used depending on the purpose. The content of the other filler is preferably 0 to 60 parts by mass, more preferably 0 to 50 parts by mass, more preferably 0 to 30 parts by mass, and may be 0 to 20 parts by mass relative to 100 parts by mass of the polybutylene terephthalate resin (A).

Glass fibers are easily oriented in molded products produced by injection molding and are not prone to diffuse reflection, which can easily cause uneven gloss. In one embodiment, from the viewpoint of easily achieving a polybutylene terephthalate resin composition with low gloss, the content of glass fibers in the resin composition is preferably less than 20 parts by mass, more preferably less than 10 parts by mass, even more preferably less than 5 parts by mass, and particularly preferably less than 1 part by mass, relative to 100 parts by mass of the polybutylene terephthalate resin (A).

(Additives)
In addition to the above-mentioned components, the resin composition may contain known additives that are generally added to thermoplastic resins and thermosetting resins, i.e., burr inhibitors, release agents, lubricants (e.g., fatty acid esters, etc.), plasticizers, flame retardants, colorants such as dyes and pigments (excluding carbon black), crystallization accelerators, crystal nucleating agents (e.g., boron nitride, etc.), various antioxidants, heat stabilizers, weather resistance stabilizers, corrosion inhibitors, etc., within the scope of the present disclosure.

The method for preparing the resin composition is not limited, and examples of the method include a method in which each component is melt-kneaded and extruded into pellets using a melt-kneading device such as a single-screw or twin-screw extruder, or a method in which pellets (master batches) with different compositions are prepared and then mixed in a predetermined amount. The pellets may be prepared, for example, by melt-mixing the components other than the brittle component (glass flakes, etc.) and then mixing the brittle component.

The resin composition has excellent low gloss and little gloss unevenness. In one embodiment, the resin composition has a 60° gloss of 27 or less, more preferably 23 or less, according to JIS-Z-8741, for the molded product. In one embodiment, the resin composition has a 60° gloss of 27 or less, more preferably 23 or less, according to JIS-Z-8741:1997, for the molded product injection molded at an injection speed of 30 mm/s, 80 mm/s, or 120 mm/s. The gloss can be measured at an angle of 60° using a gloss meter (e.g., Handy Gloss Meter PG-II, manufactured by Nippon Denshoku Industries Co., Ltd.).

In one embodiment, the resin composition has excellent jet-black properties. In one embodiment, the resin composition has a molded product with an L* value of preferably 14 or less, more preferably 13 or less, as measured in accordance with JIS-Z-8781-4:2013. Because of its excellent jet-black properties, it is possible to absorb light and prevent reflection. In one embodiment, the resin composition has an L* value of preferably 14 or less, more preferably 13 or less, as measured in three arbitrarily selected locations on the molded product, as measured by the above method.

(Application)
The resin composition of the present disclosure has excellent jet blackness and low gloss with little uneven gloss, and therefore can be preferably used for manufacturing various optical device components and display device components. For example, it can be preferably used for manufacturing components used in drive recorders, backup cameras, ADAS, head-up displays, liquid crystal meters, car navigation systems, etc.

[Molded product]
The molded article contains the polybutylene terephthalate resin composition described above. Since the molded article contains the polybutylene terephthalate resin composition described above, the molded article has excellent jet blackness and low gloss, and has little uneven gloss depending on the part of the molded article.

In one embodiment, the molded product has a 60° gloss according to JIS-Z-8741 of preferably 27 or less, more preferably 23 or less. In one embodiment, the molded product has a 60° gloss measured by the above method at three arbitrarily selected points of preferably 27 or less, more preferably 23 or less.

In one embodiment, the molded article has an L* value according to JIS-Z-8781-4 of preferably 14 or less, more preferably 13 or less. In one embodiment, the molded article has an L* value measured by the above method at three arbitrarily selected points of preferably 14 or less, more preferably 13 or less.

The molded product may have a textured surface to further improve its low gloss properties, but as the inclusion of the resin composition provides excellent low gloss properties and little uneven gloss, the surface does not need to be textured. The molded product may have a textured surface to further improve its low gloss properties, but as the inclusion of the resin composition provides excellent low gloss properties and little uneven gloss, the surface does not need to be textured. Examples of the textured agent include acrylic, urethane, and epoxy paints.

The molding method for the molded product is not limited, and may be a conventional method such as extrusion molding, injection molding, compression molding, blow molding, vacuum molding, rotational molding, or gas injection molding, but is usually injection molding. The mold temperature during injection molding is usually 40 to 120°C, preferably 50 to 80°C, and more preferably about 60 to 80°C.

The following examples are provided to further illustrate the present disclosure, but the interpretation of the present disclosure is not limited to these examples.

<Materials>
A-1: Polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., intrinsic viscosity (IV) 0.69 dL/g, terminal carboxyl group amount (CEG) 16 meq/kg)
A-2: Isophthalic acid modified polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., isophthalic acid 12.5 mol% modified polybutylene terephthalate resin)
B: Polycarbonate resin (Teijin Limited, Panlite L-1225L), melt viscosity (300°, 1000 sec ⁻¹ ) 0.27 kPa·s
C-1: Glass flakes (manufactured by Nippon Sheet Glass Co., Ltd., Fine Flake MEG160FY-M01), average thickness 0.7 μm, average particle size 160 μm (manufacturer catalog value)
C-2: Glass flakes (REFG-108 manufactured by Nippon Sheet Glass Co., Ltd.), average thickness 5 μm, average particle size 600 μm (manufacturer catalog value)
C-3: Potassium titanate (manufactured by Otsuka Chemical Co., Ltd., TISMO N102)
C-4: Talc (Micron White Upn HS-T0.8, manufactured by Hayashi Kasei Co., Ltd.), average particle size 2.7 μm
C-5: Talc (manufactured by Matsumura Sangyo Co., Ltd., Crown Talc ID), average particle size 19 μm
D-1: Ketjen black (EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd.), average particle size 34 nm, DBP absorption 495 cm ³ /100 g
D-2: Carbon black (manufactured by Mitsubishi Chemical Corporation, carbon black #750B), average particle size 22 nm, DBP absorption 116 cm ³ /100 g
D-3: Carbon black (manufactured by Mitsubishi Chemical Corporation, carbon black #960B), average particle size 16 nm, DBP absorption 69 cm ³ /100 g
D-4: Carbon black (manufactured by Mitsubishi Chemical Corporation, carbon black #2600), average particle size 13 nm, DBP absorption 77 cm ³ /100 g
E-1: Core-shell elastomer (Kaneka Corporation, Kane Ace MP90)
E-2: Core-shell elastomer (Aica Kogyo Co., Ltd., Staphyloid PO-0935)
F: Dibasic calcium phosphate (manufactured by Taihei Chemical Industry Co., Ltd., ester exchange inhibitor)
G: Boron nitride (manufactured by Mizushima Ferroalloy Co., Ltd., nucleating agent)
H: Fatty acid ester (Riken Vitamin Co., Ltd., Rikemal B-150, lubricant)

[Examples 1 to 10, Comparative Examples 1 to 21]
The raw materials were mixed in the ratios shown in Tables 1 and 2, and melt-kneaded and extruded using a twin-screw extruder at a cylinder temperature of 260° C. and a screw rotation of 150 rpm to prepare polybutylene terephthalate resin compositions of Examples 1 to 10 and Comparative Examples 1 to 21.
Using the obtained polybutylene terephthalate resin composition, three flat plate-shaped molded products (dimensions: 70 mm x 50 mm x thickness 3 mm) were molded at a cylinder temperature of 260°C, a mold temperature of 80°C, a holding pressure of 60 MPa, and injection speeds of 30 mm/s, 80 mm/s, or 120 mm/s.

[Measurement and Evaluation]
The 60° gloss and lightness L* of each of the molded articles were measured by the following methods. The results are shown in Tables 1 and 2.

<60° Glossiness>
The gloss (%) was measured in accordance with JIS-Z-8741:1997 using a handy gloss meter PG-II (60°) manufactured by Nippon Denshoku Industries Co., Ltd. Low gloss and uneven gloss were evaluated based on the following criteria.
(Low gloss)
3: The gloss of all three molded products with different injection speeds is 23% or less (excellent low gloss and little gloss unevenness)
2: The gloss of all three molded products with different injection speeds is 27% or less (good low gloss).
1: The gloss of one or more of the three molded products with different injection speeds exceeds 27% (low gloss is poor (high gloss))
(Uneven gloss)
3: The difference between the maximum and minimum gloss values of three molded products with different injection speeds is 5 or less. 2: The difference between the maximum and minimum gloss values of three molded products with different injection speeds is more than 5 and less than 10. 1: The difference between the maximum and minimum gloss values of three molded products with different injection speeds is more than 10.

(Lightness L*)
The L* value was measured in accordance with JIS-Z-8781-4:2013 using an SM-P color computer manufactured by Suga Test Instruments Co., Ltd. The jet blackness was evaluated based on the following criteria.
3: All L* values of three molded products with different injection speeds are 13 or less (excellent jet blackness)
2: All L* values of three molded products with different injection speeds are greater than 13 and less than 14 (good jet blackness)
1: One or more of the three molded products with different injection speeds have an L* value greater than 14.

(Median diameter of glass flakes)
A molded article made of a polybutylene terephthalate resin composition (among the above molded articles, a molded article molded at an injection speed of 80 mm/s) was treated in an electric furnace at 600°C for 4 hours, and the median diameter of the glass flakes was calculated from the remaining residue using a laser diffraction/scattering type particle size distribution measuring device LA-960 manufactured by Horiba, Ltd.

As shown in Table 1, the resin compositions of Examples 1 to 10 can produce molded products with excellent jet blackness and low gloss with little uneven gloss.

INDUSTRIAL APPLICABILITY The resin composition of the present disclosure has excellent jet-black properties and low gloss with little uneven gloss, and therefore can be preferably used for producing various optical device components and display device components, and has industrial applicability.

Claims (3)

(A) polybutylene terephthalate resin, (B) polycarbonate resin, (C) glass flakes, and (D) carbon black;
(A) the polybutylene terephthalate resin comprises (a1) a modified polybutylene terephthalate resin containing 5 to 30 mol % of a comonomer unit,
(C) The average thickness of the glass flakes is 1 μm or less and the median diameter is 5 to 70 μm;
(A) per 100 parts by mass of polybutylene terephthalate resin,
(B) the content of the polycarbonate resin is 60 to 100 parts by mass,
(C) the content of glass flakes is 60 to 100 parts by mass,
(D) the carbon black content is 0.8 to 15 parts by mass;
The modified polybutylene terephthalate resin is an isophthalic acid modified polybutylene terephthalate copolymer,
The polybutylene terephthalate resin composition , wherein the (B) polycarbonate resin is a bisphenol A polycarbonate . The polybutylene terephthalate resin composition according to claim 1, further comprising (F) a phosphorus-based compound. A molded article comprising the resin composition according to claim 1 or 2.