JP7522003B2 - Laser weldable molded products, agent for suppressing variation in laser transmittance of laser weldable molded products, agent for improving alkali resistance of laser weldable molded products - Google Patents

Description

The present invention relates to a molded article for laser welding that has excellent alkali resistance, visible light transmittance, and laser transmittance and also has suppressed variation in laser transmittance, an agent for suppressing variation in laser transmittance of a molded article for laser welding, and an agent for improving the alkali resistance of a molded article for laser welding.

Polybutylene terephthalate (hereinafter referred to as "PBT") resin is used in many applications due to its excellent properties such as heat resistance, chemical resistance, electrical properties, mechanical properties, and moldability.

Specific applications include various automotive electrical components (various control units, various sensors, ignition coils, etc.), connectors, switch components, relay components, coil components, etc. To manufacture these components, multiple molded parts are joined using joining methods such as adhesives, screw fastening, snap fitting, hot plate welding, and ultrasonic welding. However, several problems have been pointed out with these joining methods. For example, when adhesives are used, there is a problem with the time lost during the process until the adhesive hardens, as well as the burden on the environment. In addition, screw fastening increases the effort and cost of fastening, and there is a concern that heat, vibration, and other factors may damage the product when using hot plate welding and ultrasonic welding.

On the other hand, laser welding does not damage the product due to heat or vibrations associated with welding, and the welding process is very simple. For this reason, laser welding has recently come into widespread use, and is attracting attention as a welding method for various plastic parts. In particular, because no wear particles are generated during welding, it is often used for precision circuit boards and housings for sensors.

In addition, because laser welding is highly productive, the development of methods for checking for welding defects is also underway. Methods under consideration include checking the welded area using ultrasound, and taking a picture of the welded area after laser welding with a CCD camera, processing the image on a personal computer, and comparing it with a reference image pattern for management (see Patent Documents 1 and 2). However, these require special equipment. Therefore, in order to meet the demand for a simpler method of visually checking the welded state, the resin in the welded area may be required to be transparent to visible light as well as transparent to laser light.

Furthermore, some circuit boards built into the housing are equipped with LED indicators for checking operation, allowing visual confirmation of operation. In order to make such indicators visible, the housing joined by laser welding may be required to be transparent to visible light, and transparent resins such as PMMA and polystyrene are sometimes used as materials for this purpose. However, resins such as PMMA and polystyrene have low heat resistance and low chemical resistance to organic solvents, limiting their uses. On the other hand, although PBT has excellent heat resistance and chemical resistance, it lacks transparency because it is a crystalline resin.

In addition, in the laser welding process, when laser irradiation processing is performed under certain conditions, if there are differences in transmittance depending on the part of the molded product, problems may occur such as insufficient welding in some places due to insufficient laser transmittance and insufficient joint strength, or excessive energy being applied to the welded parts due to high laser transmittance in other places, causing decomposition, deterioration, and carbonization of the resin. Therefore, there was a need to reduce the variation in laser light transmittance.

On the other hand, in applications such as the above-mentioned various automotive electrical components and electrical and electronic equipment components, they may be used in places where they come into contact with snow-melting agents, cleaning agents, bleaching agents, etc. These agents contain sodium hydroxide, sodium hypochlorite, sodium percarbonate, calcium chloride, etc., and therefore the resin molded product is exposed to an alkaline atmosphere. Here, molded products that have joints with other members by welding such as laser welding are prone to distortion due to the shape being restricted by the joint with the other member, and if the molded product is exposed to an alkaline atmosphere as described above for a long period of time while in this distorted state, so-called environmental stress cracking occurs due to the influence of both the distortion and the alkaline components, causing cracks in the molded product, which has been a problem. Therefore, there has been a demand for improving the alkali resistance of laser-welded molded products.

Japanese Patent Application Publication No. 8-211030 JP 2004-167840 A

The present invention aims to provide a molded article for laser welding that has excellent alkali resistance, visible light transmittance, and laser transmittance and also has reduced variation in laser transmittance, an agent for suppressing variation in laser transmittance of molded articles for laser welding, and an agent for improving the alkali resistance of molded articles for laser welding.

The present inventors have found that the above problems can be solved by a laser welded molded article having a weld thickness of 1 ^mm or more, the laser welded molded article comprising a polybutylene terephthalate resin composition containing (A) 100 parts by mass of polybutylene terephthalate resin, (B) 60 parts by mass or more and 90 parts by mass or less of a polycarbonate resin having a melt viscosity of 0.20 kPa·s or more and 0.40 kPa·s or less at 300°C and a shear rate of 1000 sec-1, (C) 1 part by mass or more and 10 parts by mass or less of an epoxy-based compound, and (D) 1 part by mass or more and 15 parts by mass or less of an aromatic polycarboxylic acid ester, an alkali resistance improver for laser welded molded articles containing an epoxy-based compound and an aromatic polycarboxylic acid ester, and an agent for suppressing variation in laser transmittance for laser welded molded articles containing an epoxy-based compound, and have completed the present invention.

That is, the present invention relates to the following (1) to (8).
(1) A laser weldable molded product comprising a polybutylene terephthalate resin composition containing (A) 100 parts by mass of a polybutylene terephthalate resin, (B) 60 parts by mass or more and 90 parts by mass or less of a polycarbonate resin having a melt viscosity of 0.20 kPa·s or more and 0.40 kPa·s or less at 300° ^C and a shear rate of 1000 sec-1, (C) 1 part by mass or more and 10 parts by mass or less of an epoxy-based compound, and (D) 1 part by mass or more and 15 parts by mass or less of an aromatic polyvalent carboxylic acid ester, and having a thickness of 1 mm or more at a welded portion.
(2) The polybutylene terephthalate resin composition has a light transmittance of 50% or more at any wavelength in the range of 400 nm to 700 nm inclusive in a molded article having a wall thickness of 1.2 mm, comprising the composition. (1) A molded article for laser welding.
(3) The molded article for laser welding according to (1) or (2), wherein the polybutylene terephthalate resin composition has a light transmittance of 60% or more at a wavelength of 980 nm in a molded article having a wall thickness of 1.2 mm and made of the composition.
(4) The molded product for laser welding according to any one of (1) to (3), wherein the polybutylene terephthalate resin composition has a light transmittance variation of 6% or less at a wavelength of 980 nm in a molded product having a wall thickness of 1.2 mm and made of the composition.
(5) (D) the aromatic polycarboxylic acid ester is represented by formula I:
φ-(COOR)n...I
(In formula I, φ represents a C _6-12 arene ring, R represents an alkyl group, a cycloalkyl group or an aralkyl group, n represents an integer of 2 or more, and R in each -COOR group may be the same or different.)
The laser weldable molded article according to any one of (1) to (4), wherein the compound is a compound represented by the formula:
(6) The laser weldable molded product according to any one of (1) to (5), wherein (D) the aromatic polycarboxylic acid ester is an alkyl ester of an aromatic tetracarboxylic acid.
(7) An agent for suppressing variation in light transmittance at a wavelength of 980 nm of a laser welding molded product made of a polybutylene terephthalate resin, a polycarbonate resin, and a polybutylene terephthalate resin composition containing an aromatic polycarboxylic acid ester, which contains an epoxy compound.
(8) An agent for improving the alkali resistance of a laser weldable molded article, comprising a polybutylene terephthalate resin composition containing a polybutylene terephthalate resin and a polycarbonate resin, the polybutylene terephthalate resin composition containing an epoxy compound and an aromatic polycarboxylic acid ester.

The present invention can provide a molded article for laser welding that has excellent alkali resistance, visible light transmittance, and laser transmittance and also has suppressed laser transmittance variation, an agent for suppressing laser transmittance variation in a molded article for laser welding, and an agent for improving the alkali resistance of a molded article for laser welding.

One embodiment of the present invention will be described in detail below. The present invention is not limited to the following embodiment, and can be implemented with appropriate modifications within the scope that does not impair the effects of the present invention. In addition, the expression "X to Y" in this specification means "X or more and Y or less."

[Polybutylene terephthalate resin composition]
((A) Polybutylene terephthalate resin)
The polybutylene terephthalate resin (A) of the present invention is a polybutylene terephthalate resin obtained by polycondensation of a dicarboxylic acid component containing at least terephthalic acid or an ester-forming derivative thereof ( _C1-6 alkyl ester, acid halide, etc.) and a glycol component containing an alkylene glycol having at least 4 carbon atoms (1,4-butanediol) or an ester-forming derivative thereof (acetylated product, etc.). In this embodiment, the polybutylene terephthalate resin (A) is not limited to a homopolybutylene terephthalate resin, and may be a copolymer containing 60 mol % or more of butylene terephthalate units.

(A) The amount of terminal carboxyl groups in the polybutylene terephthalate resin is preferably 50 meq/kg or less, but is not particularly limited as long as it does not impede the object of the present invention, and is preferably 30 meq/kg or less, and more preferably 25 meq/kg or less.

(A) The intrinsic viscosity of the polybutylene terephthalate resin is not particularly limited as long as it does not impede the object of the present invention, but is preferably 0.60 dL/g or more and 1.2 dL/g or less, and more preferably 0.65 dL/g or more and 0.9 dL/g or less. When a polybutylene terephthalate resin having an intrinsic viscosity in such a range is used, the resulting polybutylene terephthalate resin composition has particularly excellent moldability. In addition, the intrinsic viscosity can be adjusted by blending polybutylene terephthalate resins having different intrinsic viscosities. For example, 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 blended to prepare a polybutylene terephthalate resin having an intrinsic viscosity of 0.9 dL/g. The intrinsic viscosity of the polybutylene terephthalate resin can be measured, for example, in o-chlorophenol at a temperature of 35°C.

In the preparation of (A) polybutylene terephthalate resin, when an aromatic dicarboxylic acid other than terephthalic acid or an ester-forming derivative thereof is used as a comonomer component, for example, _C8-14 aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl ether, _C4-16 alkane dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, _C5-10 cycloalkane dicarboxylic acids such as cyclohexane dicarboxylic acid, and ester-forming derivatives of these dicarboxylic acid components ( _C1-6 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, _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.

In the preparation of polybutylene terephthalate resin, when a glycol component other than 1,4-butanediol is used as a comonomer component, for example, _C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butylene glycol, hexamethylene glycol, neopentyl glycol, 1,3-octanediol, etc.; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, etc.; 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 adduct of bisphenol A and 3-mol propylene oxide adduct of bisphenol A; or 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, _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 comonomer components 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, hydroxycaproic acid, etc.; _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.).

The content of (A) polybutylene terephthalate resin is preferably 20 to 80 mass% of the total mass of the resin composition, more preferably 30 to 70 mass%, and even more preferably 35 to 60 mass%.

((B) Polycarbonate resin)
The polycarbonate resin (PC resin) (B) of the present invention may be a polymer obtained by reacting a dihydroxy compound with a carbonate ester such as phosgene or diphenyl carbonate. The dihydroxy compound may be an alicyclic compound such as an alicyclic diol, but is preferably an aromatic compound, more preferably a bisphenol compound. The dihydroxy compound may be used alone or in combination of two or more kinds.

Examples of 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, and 2,2-bis(4-hydroxyphenyl)propane. 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; _4-10 cycloalkanes; 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 (B) may be used alone or in combination of two or more kinds.

The polycarbonate resin (B) used in the present invention has a melt viscosity at 300°C and a shear rate of 1000 sec ^-1 of 0.20 kPa·s or more and 0.40 kPa or less, with the lower limit being preferably 0.21 kPa·s or more, more preferably 0.22 kPa·s or more, even more preferably 0.24 kPa·s or more, and particularly preferably 0.25 kPa·s or more. The upper limit is preferably 0.38 kPa·s or less, more preferably 0.36 kPa·s or less, even more preferably 0.34 kPa·s or less, and particularly preferably 0.32 kPa·s or less.

In the present invention, the content of the (B) polycarbonate resin is preferably 60 parts by mass or more and 90 parts by mass or less, more preferably 65 parts by mass or more and 85 parts by mass or less, and even more preferably 70 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the (A) polybutylene terephthalate resin.

((C) Epoxy Compound)
Examples of the epoxy compound (C) in the present invention include aromatic epoxy compounds such as biphenyl type epoxy compounds, bisphenol A type epoxy compounds, phenol novolac type epoxy compounds, and cresol novolac type epoxy compounds. The epoxy compound (C) may be used in any combination of two or more compounds. The epoxy equivalent is preferably 600 to 1500 g/equivalent (g/eq).

In the present invention, the amount of epoxy compound (C) added is 1 to 10 parts by weight, preferably 1.5 to 5 parts by weight, and more preferably about 2 to 4 parts by weight, per 100 parts by weight of polybutylene terephthalate resin (A). If the amount added is too small, the transmittance suppression effect will not be obtained, and if the amount added is too large, the viscosity will increase during injection molding, which may cause unfilling or discoloration.

((D) Aromatic polycarboxylic acid ester)
The aromatic polyvalent carboxylate (D) in the present invention may be an aromatic compound having two or more ester groups (such as an alkoxycarboxyl group, a cycloalkyloxycarbonyl group, or an aralkyloxycarbonyl group) on an aromatic ring, and examples of such compounds include compounds represented by the following formula I.

φ-(COOR)n...I
In formula I, φ represents a C _6-12 arene ring, R represents an alkyl group, a cycloalkyl group, or an aralkyl group, n represents an integer of 2 or more, and R of each -COOR group may be the same or different. In φ, the hydrogen atoms other than the hydrogen atom substituted with -COOR may be substituted with other substituents or may not be substituted. For example, φ is - It is also possible to have a structure in which one or more of the hydrogen atoms other than the hydrogen atoms substituted with COOR are substituted with -OH and/or _-NH2 . (A) Compatibility with polybutylene terephthalate resin From this viewpoint, it is preferable that n is 3 or more (for example, 3 to 6 or 3 to 4). These aromatic polyvalent carboxylic acid esters can be used alone or in combination of two or more.

Examples of the _C6-12 arene ring include a benzene ring, a naphthalene ring, etc. Examples of the polycarboxylic acid of the aromatic polycarboxylic acid ester component include aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, and anhydrides thereof), aromatic tricarboxylic acids (trimellitic acid and anhydrides thereof), and aromatic tetracarboxylic acids (pyromellitic acid and anhydrides thereof).

Examples of the alkyl group constituting the alkyl ester (-COOR) include linear or branched C 1-20 alkyl groups such as butyl, t-butyl, pentyl, hexyl, octyl, 2-ethylhexyl, isononyl, decyl, isodecyl, and triisodecyl. Preferred alkyl groups are linear or branched C _3-16 alkyl groups, particularly linear or branched C _4-14 alkyl groups. Examples of the cycloalkyl group constituting _{the cycloalkyl ester group include C 5-10 cycloalkyl groups such as cyclohexyl. Examples of the aralkyl group constituting the aralkyl ester group include C 6-12 aryl-C 1-4 alkyl groups such} as benzyl.

Representative examples of the aromatic polyvalent carboxylate ester (D) include trimellitic acid tri C _4-20 alkyl esters (tributyl trimellitate, trioctyl trimellitate, tri(2-ethylhexyl) trimellitate, triisodecyl trimellitate, etc.), trimellitic acid tri C _5-10 cycloalkyl esters (tricyclohexyl trimellitate, etc.), trimellitic acid triaralkyls (tribenzyl trimellitate, etc.), trimellitic acid dialkyl monoaralkyls (di(2-ethylhexyl)monobenzyl trimellitate), pyromellitic acid tetra C _4-20 alkyl esters (tetrabutyl pyromellitate, tetraoctyl pyromellitate, tetra-2-ethylhexyl pyromellitate, tetraisodecyl pyromellitate, etc.), pyromellitic acid tetraaralkyls (tetrabenzyl pyromellitate, etc.), pyromellitic acid dialkyl diaralkyls (di(2-ethylhexyl)dibenzyl pyromellitate, etc.). The carboxylate may be a mixed ester having different ester groups (such as an alkoxycarboxyl group, a cycloalkyloxycarbonyl group, or an aralkyloxycarbonyl group).

The blending amount of the (D) aromatic polycarboxylic acid ester is 1 to 15 parts by mass, preferably 1.5 to 12 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the (A) polybutylene terephthalate resin. By making the blending amount of the (D) aromatic polycarboxylic acid ester 1 part by mass or more per 100 parts by mass of the (A) polybutylene terephthalate resin, the resistance to alkaline solutions can be further improved. By making the blending amount of the (D) aromatic polycarboxylic acid ester 15 parts by mass or less per 100 parts by mass of the (A) polybutylene terephthalate resin, the long-term durability against alkaline solutions can be further exhibited, and the occurrence of defects such as the (D) aromatic polycarboxylic acid ester bleeding onto the molded product surface can be suppressed. In one embodiment, the blending amount of the (D) aromatic polycarboxylic acid ester is 4 to 7 parts by mass per 100 parts by mass of the (A) polybutylene terephthalate resin.

(Silicone-based compounds)
The polybutylene terephthalate resin composition according to an embodiment of the present invention may contain a silicone compound, if necessary, for the purpose of further enhancing alkali resistance.

Preferred silicone compounds include, but are not limited to, pure silicone resins such as dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane, which are generally known as silicone oils, and modified silicones obtained by reacting pure silicone resins with modifying resins such as alkyd resins, polyester resins, acrylic resins, and epoxy resins.

It is also possible to use a cured silicone powder that has absorbed silicone oil. The silicone oil-absorbed cured silicone powder used here is obtained by blending 0.5 to 80% by weight of silicone oil into a fine powder of cured silicone, allowing it to absorb, and powdering it using any method. As the silicone that absorbs silicone oil to form the cured silicone powder, for example, conventionally known silicone rubber or silicone gel can be used.

Examples of silicone oils include those represented by the following general formula II:
R ₃ SiO[R ₂ SiO]nSiR ₃ ...II
(wherein R is a substituted or unsubstituted monovalent hydrocarbon group or a hydroxyl group, and n is an integer).
In the above formula, R is a substituted or unsubstituted monovalent hydrocarbon group or a hydroxyl group, and examples of the substituted or unsubstituted monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, and propyl groups, alkenyl groups such as vinyl and allyl groups, aralkyl groups such as cycloalkyl groups and β-phenylethyl groups, 3,3,3-trifluoropropyl groups, 3-mercaptopropyl groups, 3-aminopropyl groups, and 3-glycidoxypropyl groups. All of the R may be the same or different.

The silicone compound preferably has a kinetic viscosity of 1000 to 10000 cSt (10 to 100 cm ² /s) at 25° C., and from the viewpoint of alkali resistance, it is more preferably 2000 to 8000 cSt, and even more preferably in the range of 3000 to 6000 cSt. The kinetic viscosity is measured by placing 10 ml of the silicone compound kept at 25° C. in an Ostwald viscometer (capillary viscometer) and measuring the time t for the upper surface of the measurement liquid to travel a certain distance. When the viscosity of the reference liquid is η ₀ , the density is ρ ₀ , and the flow time is t ₀ , the kinetic viscosity is expressed as follows:
Kinematic viscosity (cSt) = (η ₀ /ρ ₀ )×(t/t ₀ )
The kinetic viscosity can be calculated using the value given in the catalogue of the silicone compound manufacturer.

The silicone-based compounds may be used alone or in combination of two or more.

The content of the silicone-based compound is preferably 1 part by mass or more and 5 parts by mass or less, and more preferably 1.5 parts by mass or more and 4 parts by mass or less, per 100 parts by mass of the polybutylene terephthalate resin composition. If the content of the silicone-based compound is 1 part by mass or more, the effect of improving alkali resistance can be obtained, and if it is 5 parts by mass or less, it is preferable because the transmittance of laser light is not impaired.

In addition, in a molded article having a thickness of 1.2 mm molded from the polybutylene terephthalate resin composition of the present invention, the transmittance of any wavelength in the range of 400 nm to 700 nm is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, particularly preferably 65% or more, and most preferably 70% or more.

In a molded article having a thickness of 1.2 mm that is molded from the laser welding polybutylene terephthalate resin composition of the present invention, the light transmittance at a wavelength of 980 nm is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, and particularly preferably 80% or more.

In addition, in a molded article having a thickness of 1.2 mm that is molded from the polybutylene terephthalate resin composition of the present invention, the variation in light transmittance at a wavelength of 980 nm is preferably 8% or less, more preferably 7% or less, even more preferably 6% or less, particularly preferably 5% or less, and most preferably 4% or less.

(Agent for suppressing variation in light transmittance of 980 nm wavelength of laser welded molded products)
Furthermore, by using the above-mentioned epoxy-based compound, it is possible to use an agent for suppressing variation in light transmittance at a wavelength of 980 nm of a laser welding molded product made of a polybutylene terephthalate resin, a polycarbonate resin, and a polybutylene terephthalate resin composition containing an aromatic polycarboxylic acid ester.

(Improves alkali resistance of laser welded molded products)
Furthermore, by using the above-mentioned epoxy compound and aromatic polyvalent carboxylic acid ester, it is possible to obtain an alkali resistance improver for a laser welding molded article made of a polybutylene terephthalate resin composition containing a polybutylene terephthalate resin and a polycarbonate resin.

(filler)
A filler is used as necessary in the laser welding polybutylene terephthalate resin composition of the present invention. It is preferable to add such a filler in order to obtain excellent properties such as mechanical strength, heat resistance, dimensional stability, and electrical properties, and it is particularly effective for the purpose of increasing rigidity. A fibrous, powdery, or plate-like filler is used according to the purpose.

Examples of fibrous fillers include glass fibers, silica fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, and boron fibers. In addition, organic fibrous materials with high melting points such as polyamides, fluororesins, and acrylic resins can also be used.

Examples of powdered and granular fillers include quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, silicates such as wollastonite (excluding talc), silicon carbide, silicon nitride, boron nitride, etc.

Furthermore, examples of plate-like inorganic fillers include mica and glass flakes.

There are no particular limitations on the type of filler, and one or more types of fillers can be added. In particular, it is preferable to use glass fiber or glass flakes.

The amount of filler to be added is not particularly specified, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the polybutylene terephthalate resin composition. If an excessive amount of filler is added, the transmittance of visible light and laser light decreases, and moldability and toughness decrease.

(Other ingredients)
In the polybutylene terephthalate resin composition of the embodiment of the present invention, in order to impart desired properties according to the purpose, it is possible to blend known substances generally added to thermoplastic resins and thermosetting resins, such as stabilizers such as antioxidants and ultraviolet absorbers, hydrolysis resistance improvers (e.g., carbodiimides, etc.), antistatic agents, flame retardants, flame retardant assistants, drip prevention agents, colorants such as dyes and pigments, crystallization promoters, crystal nucleating agents, etc., within the scope that does not impair the effects of the present invention. In particular, as a stabilizer added to the polybutylene terephthalate resin composition of the present embodiment, it is preferable to add a phosphorus-based stabilizer (such as a metal phosphate such as calcium monophosphate) in order to suppress ester exchange between (A) polybutylene terephthalate resin and (B) polycarbonate resin. In addition, since (D) aromatic polycarboxylic acid ester can also act as a plasticizer or mold release agent, it is usually not necessary to add a plasticizer or mold release agent, but this does not exclude the inclusion of other plasticizers or mold release agents in the polybutylene terephthalate resin composition of the embodiment of the present invention.

(Laser weldable molded products)
The laser welding molded article according to the embodiment of the present invention is obtained by molding the polybutylene terephthalate resin composition of the present invention. The molding method is not particularly limited, and known molding methods can be adopted. For example, (1) each component is mixed, kneaded and extruded by a single-screw or twin-screw extruder to prepare pellets, and then molding; (2) pellets (master batches) having different compositions are first prepared, and the pellets are mixed (diluted) in a predetermined amount and molded to obtain a molded article of a predetermined composition; (3) one or more of each component are directly charged in a molding machine. The pellets may be prepared, for example, by melt-mixing components other than brittle components (such as glass-based reinforcing materials) and then mixing the brittle components. The molding method of other molded articles made of thermoplastic resins is also not particularly limited, and known molding methods can be adopted.

The molded article may be produced by melt-kneading the resin composition and molding it by a conventional method such as extrusion molding, injection molding, compression molding, blow molding, vacuum molding, rotational molding, or gas injection molding, but is usually molded by injection molding. The mold temperature during injection molding is usually 40 to 100°C, preferably 50 to 90°C, and more preferably about 60 to 80°C.

The shape of the molded product is not particularly limited, but since the molded product is used by joining it to a mating material (another molded product made of thermoplastic resin) by laser welding, a shape with a contact surface such as a flat surface (e.g., plate-like) is preferable. In addition, since the molded product of the present invention has high transparency to laser light, the thickness of the welded part, i.e., the thickness of the molded product at the part through which the laser light passes (thickness in the direction through which the laser light passes) can be selected from a wide range and may be, for example, about 0.1 to 3.0 mm, preferably 0.5 to 2.5 mm, and more preferably about 1.0 to 2.0 mm. In consideration of the strength and transparency of the molded product, about 1.2 to 1.5 mm is particularly preferable.

The laser light source is not particularly limited, and examples that can be used include dye lasers, gas lasers (excimer lasers, argon lasers, krypton lasers, helium-neon lasers, etc.), solid-state lasers (YAG lasers, etc.), and semiconductor lasers. A pulsed laser is usually used as the laser light.

The molded product has excellent laser weldability, so it is usually preferable to weld it to the mating resin molded product by laser welding, but if necessary, it can also be welded to other resin molded products by other heat welding methods, such as vibration welding, ultrasonic welding, and hot plate welding.

(Composite moldings)
In the composite molded product of the present invention, a molded product (first molded product) formed of a polybutylene terephthalate resin composition and a resin molded product (second molded product, another molded product made of a thermoplastic resin) of a mating material are preferably joined and integrated by laser welding. For example, the first molded product and the second molded product are brought into contact (particularly, at least the joint portion is surface-contacted) and irradiated with laser light, thereby partially melting the interface between the first molded product and the second molded product to bring the joint surfaces into close contact, and then cooled to join and integrate the two molded products into one molded product. In such a composite molded product, when the molded product of the present invention is used, a high joint strength can be obtained by welding, and a high welding strength equivalent to that of a non-welded member that is not welded by irradiation of laser light can be maintained. Therefore, even if the laser welding is performed, the joint strength is not substantially reduced, and a firmly joined composite molded product can be obtained.

The resin constituting the resin molded product of the mating material is not particularly limited, and may be various thermoplastic resins, such as olefin-based resins, vinyl-based resins, styrene-based resins, acrylic-based resins, polyester-based resins, polyamide-based resins, and polycarbonate-based resins. Among these resins, the mating material may be made of the same type or family of resins (polyester-based resins such as PBT-based resins and PET-based resins, polycarbonate-based resins, styrene-based resins, acrylic resins, etc.) as the resin constituting the polybutylene terephthalate resin composition for laser welding, or a composition thereof. For example, the first molded body and the second molded body may each be formed from the polybutylene terephthalate resin composition for laser welding of the present invention.

The adherend may contain an absorbent or colorant for the laser beam. The colorant can be selected according to the wavelength of the laser beam, and examples of the colorant include inorganic pigments [black pigments such as carbon black (e.g., acetylene black, lamp black, thermal black, furnace black, channel black, ketjen black, etc.), red pigments such as iron oxide red, orange pigments such as molybdate orange, white pigments such as titanium oxide, etc.], and organic pigments (yellow pigments, orange pigments, red pigments, blue pigments, green pigments, etc.). These absorbents can be used alone or in combination of two or more. As the absorbent, a black pigment or dye, particularly carbon black, can usually be used. The average particle size of carbon black may usually be about 10 to 1000 nm, preferably about 10 to 100 nm. The proportion of the colorant is about 0.1 to 10% by weight, preferably about 0.3 to 5% by weight (e.g., 0.3 to 3% by weight) based on the total weight of the adherend.

The laser light is usually irradiated from the first molded body toward the second molded body, and heat is generated at the interface of the second molded body, which contains an absorbent or colorant, to weld the first molded body to the second molded body. If necessary, a lens system may be used to focus the laser light on the interface between the first molded product and the second molded product to weld the contact interface.

A preferred embodiment of the present invention also includes a composite molded article formed by joining a molded article made of the polybutylene terephthalate resin composition of the present invention to another molded article made of a thermoplastic resin by laser welding.

(Double-molded product)
Furthermore, since the polybutylene terephthalate resin composition of the present invention has excellent interfacial adhesion in double molding with a molded article made of a polycarbonate resin composition, it can also be preferably used for double molding with a polycarbonate resin composition.

The method for obtaining the double molded product is not particularly limited, and a known method can be used. For example, a molded product (polycarbonate molded product) obtained in advance by injection molding a polycarbonate resin composition can be placed in a mold cavity, and a polybutylene terephthalate resin composition can be injection molded onto the polycarbonate molded product to obtain a double molded product. Here, the polycarbonate resin composition used for the polycarbonate molded product is one in which 50% by mass or more of the resin components in the entire composition is polycarbonate resin. The proportion of polycarbonate resin in the resin components of the polycarbonate resin composition is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

Since such polycarbonate molded products have an extremely high visible light transmittance, they can be used as windows for observing the operating state of various parts housed inside the double molded product. In other words, the polybutylene terephthalate resin composition of the present invention can be used to form a double molded product with a polycarbonate molded product and then subjected to laser welding, resulting in a composite molded product with high bonding strength at both the interface of the double molded product and the interface of the laser welded part.

[Example]
The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

<Ingredients>
(A) Polybutylene terephthalate resin: PBT resin manufactured by Polyplastics Co., Ltd., inherent viscosity 0.69 dl/g
(B) Polycarbonate resin (B-1) 300°C, melt viscosity at shear rate 1000 sec ^-1 : PC resin of 0.42 kPa·s (B-2) 300°C, melt viscosity at shear rate 1000 sec ^-1 : PC resin of 0.27 kPa·s (B-3) 300°C, melt viscosity at shear rate 1000 sec ^-1 : PC resin of 0.09 kPa·s (C) Epoxy compound Mitsubishi Chemical Epoxy resin 1004K Epoxy equivalent 900 g/eq
(D) Aromatic polycarboxylic acid ester: Pyromellitic acid alkyl ester "ADEKA Cizer UL-100" manufactured by ADEKA CORPORATION
(D'-1) Aromatic monocarboxylic acid ester Polycaprolactone dibenzoate "PLACCEL BCL2" manufactured by Daicel Corporation
(D'-2) Aliphatic polycarboxylic acid ester: Pentaerythritol distearate "Unistar H476" manufactured by NOF Corporation
(E) Silicone compound Dimethylpolysiloxane with a dynamic viscosity of 5000 cSt at 25°C (filler) Glass fiber Circular cross-section glass fiber "ECS03T-127 (average fiber diameter 13 μm, average fiber length 3 mm)" manufactured by Nippon Electric Glass Co., Ltd.
・(Other ingredients) Phosphorus stabilizer: Daihei Chemical Industry Co., Ltd. Calcium phosphate

<Examples 1 to 3 and Comparative Examples 1 to 11>
After mixing the components in the ratios shown in Table 1, the mixture was melt-kneaded and extruded at a cylinder temperature of 260°C, a discharge rate of 15 kg/h, and a screw rotation speed of 130 rpm using a TEX30 manufactured by Japan Steel Works, Ltd., to obtain pellets of a polybutylene terephthalate resin composition. The obtained pellets were then used to mold test pieces under the following molding conditions and to carry out various evaluations.

<Molding conditions>
The obtained pellets of polybutylene terephthalate resin composition were dried at 140°C for 3 hours, and then test pieces of 80 mm x 80 mm x 1.2 mmt were prepared using an injection molding machine S-2000i100B manufactured by FANUC Corporation at a cylinder temperature of 260°C and a mold temperature of 60°C.

<Visible light transmittance>
A test piece of 80 mm x 80 mm x 1.2 mmt was divided into 16 pieces of 20 mm x 20 mm x 1.2 mmt, and the light transmittance (%) of each test piece was measured at wavelengths of 400 nm, 500 nm, 600 nm, and 700 nm using a spectrophotometer (V770, manufactured by JASCO Corporation) for the center part of each test piece, and the average value at 16 points was calculated. At any one or more wavelengths, the transmittance was evaluated as 70% or more, 60% or more but less than 70%, △, and less than 50% at any wavelength. The results are shown in Table 1.

<Laser light transmittance>
A test piece of 80 mm × 80 mm × 1.2 mmt was divided into 16 pieces of 20 mm × 20 mm × 1.2 mmt, and the light transmittance (%) of each test piece at a wavelength of 980 nm was measured for the center of each piece using a spectrophotometer (V770, manufactured by JASCO Corporation), and the average value for the 16 points was calculated. The results are shown in Table 1, where transmittance was evaluated as 70% or more as ◎, 60% or more but less than 70% as ○, and less than 60% as ×.
<Laser light transmittance variation>
The laser light transmittance measured as described above was calculated as the difference between the maximum and minimum values of the transmittance at 16 points within one test piece, and the laser light transmittance variation was calculated. The results are shown in Table 1, where the variation was 4% or less as ◎, more than 4% and 6% or less as ○, more than 6% and 8% as △, and more than 8% as ×.
<Alkaline resistance>
The pellets of the obtained polybutylene terephthalate resin composition were dried at 140 ° C for 3 hours, and then injection molded at a cylinder temperature of 250 ° C and a mold temperature of 70 ° C to produce a molded piece having a thickness of 1 mmt, a side of 120 mm, and a weld part. Next, this molded piece was cut into a strip shape of 10 mm wide and 100 mm long so that the weld part was located at the approximate center in the longitudinal direction. This test piece was fixed to a jig in a bent state, so that a bending strain of 1.0% was always applied to the weld part. In this state, the jig was immersed in a 10% by mass aqueous sodium hydroxide solution, and left to stand at an ambient temperature of 23 ° C., and the test piece after immersion for 60 hours was visually observed to see whether cracks occurred. For each example and comparative example, three test pieces were used for evaluation, and the results were shown in Table 1, with the following judgement: no cracks occurred in any of the three test pieces, O if cracks occurred in only one of the three test pieces, △ if cracks occurred in two of the three test pieces, and × if cracks occurred in all three test pieces.
<PC double layer molding adhesion>
As a primary molded product, the above-mentioned (B-2) PC resin was dried at 120°C for 5 hours, and then an Izod test piece (63.5 mm x 12.7 mm x 6.4 mm) in accordance with ASTM D256 was injection molded at a cylinder temperature of 280°C, a mold temperature of 100°C, and a holding pressure of 98 MPa, and allowed to stand at 23°C and 50% RH for 24 hours. This was then prepared and placed in the cavity (127 mm x 12.7 mm x 6.4 mm) of a mold for molding bending test pieces in accordance with ASTM D790 so as to be in contact with one end surface of the mold. Next, the pellets of the polybutylene terephthalate resin composition of each Example dried at 140 ° C for 3 hours were injection molded into the remaining space (63.5 mm × 12.7 mm × 6.4 mm) of the cavity of the mold for molding the bending test piece at a cylinder temperature of 270 ° C, a mold temperature of 70 ° C, and a holding pressure of 78 MPa, to obtain a double molded product of 127 mm × 12.7 mm × 6.4 mm in which one end surface of the polycarbonate molded product and one end surface of the molded product made of the polybutylene terephthalate resin composition of each Example were joined. Using the obtained double molded product, a tensile test was performed according to ISO527-1, 2, and the bonding strength was evaluated as double moldability. The results are shown in Table 1, where the bonding strength was 20 MPa or more, ◎, 15 MPa or more and less than 20 MPa, ○, 10 MPa or more and less than 15 MPa, and ×.

As shown in Table 1, the molded article made of the polybutylene terephthalate resin composition of the present invention had excellent alkali resistance, visible light transmittance, and laser light transmittance, and showed little variation in laser light transmittance.

Claims (7)

(A) a polybutylene terephthalate resin composition containing 100 parts by mass of a polybutylene terephthalate resin, (B) 60 parts by mass or more and 90 parts by mass or less of a polycarbonate resin having a melt viscosity of 0.20 kPa·s or more and 0.40 kPa·s or less at 300°C and a shear rate of 1000 sec ^- 1, (C) 1 part by mass or more and 10 parts by mass or less of an epoxy-based compound having an epoxy equivalent of 600 to 1500 g/equivalent, and (D) 1 part by mass or more and 15 parts by mass or less of an aromatic polyvalent carboxylate ester,
(D) The aromatic polycarboxylic acid ester is represented by the formula I:
φ-(COOR)n...I
(In formula I, φ represents a C _6-12 arene ring, R represents an alkyl group, n represents an integer of 3 to 6, and R in each -COOR group may be the same or different.)
and a laser weldable molded product having a weld thickness of 1 mm or more. The molded article for laser welding according to claim 1, wherein the polybutylene terephthalate resin composition has a light transmittance of 50% or more at any wavelength in the range of 400 nm to 700 nm in a molded article having a wall thickness of 1.2 mm and made of the composition. The molded article for laser welding according to claim 1 or 2, wherein the polybutylene terephthalate resin composition has a light transmittance of 60% or more at a wavelength of 980 nm in a molded article having a wall thickness of 1.2 mm and made of the composition. The molded article for laser welding according to any one of claims 1 to 3, wherein the polybutylene terephthalate resin composition has a variation in light transmittance at a wavelength of 980 nm of 6% or less in a molded article having a wall thickness of 1.2 mm and made of the composition. The laser weldable molded article according to any one of claims 1 to 4 , wherein the aromatic polycarboxylic acid ester (D) is an alkyl ester of an aromatic tetracarboxylic acid. The composition comprises a polybutylene terephthalate resin containing an epoxy compound having an epoxy equivalent of 600 to 1500 g/equivalent , a polycarbonate resin having a melt viscosity of 0.20 kPa·s or more and 0.40 kPa·s or less at 300°C and a shear rate of 1000 sec ^-1 , and a polybutylene terephthalate resin composition containing an aromatic polycarboxylic acid ester ;
The aromatic polycarboxylic acid ester has the formula I:
φ-(COOR)n...I
(In formula I, φ represents a C _6-12 arene ring, R represents an alkyl group, n represents an integer of 3 to 6, and R in each -COOR group may be the same or different.)
The compound represented by the formula (1) is an agent for suppressing variation in light transmittance at a wavelength of 980 nm of a molded product for laser welding. a polybutylene terephthalate resin composition containing 100 parts by mass of a polybutylene terephthalate resin containing an epoxy compound having an epoxy equivalent of 600 to 1500 g/equivalent and an aromatic polyvalent carboxylic acid ester, and 60 parts by mass or more and ⁹⁰ parts by mass or less of a polycarbonate resin having a melt viscosity of 0.20 kPa·s or more and 0.40 kPa·s or less at 300°C and a shear rate of 1000 sec-1 ;
(D) The aromatic polycarboxylic acid ester is represented by the formula I:
φ-(COOR)n...I
(In formula I, φ represents a C _6-12 arene ring, R represents an alkyl group, n represents an integer of 3 to 6, and R in each -COOR group may be the same or different.)
An agent for improving the alkali resistance of molded products for laser welding, the agent being a compound represented by the formula :