JP2019131667A - Resin composition for vehicle lamp cover, molded body for vehicle lamp cover, laminate for vehicle lamp cover, and vehicle lamp cover - Google Patents

Abstract

To provide a resin composition for vehicle lamp cover having high scratch resistance and transparency, and excellent in melt flowability, and a molded body for vehicle lamp cover by molding the resin composition.SOLUTION: There is provided a resin composition containing 30 to 99 pts.mass of an acrylic resin (A) containing a methyl (meth)acrylate unit of 50 mass% or more, and 1 o 70 pts.mass of colloidal silica (B) and having haze value of 5.0% or less, shear viscosity measured at 240°C and shear rate of 1000 secof 500 Pa sec or less.SELECTED DRAWING: None

Description

  The present invention relates to a resin composition for a vehicle lamp cover, a molded article for a vehicle lamp cover, a laminate for a vehicle lamp cover, and a vehicle lamp cover.

Acrylic resins and polycarbonate resins are widely used in various fields such as optical materials, vehicle parts, lighting materials, and building materials because of their excellent transparency and dimensional stability. In recent years, it is being used for a vehicle member such as a vehicle interior / exterior material, in particular, a vehicle lamp cover.
In recent years, acrylic resin used as a vehicle lamp cover is required to have high scratch resistance and transparency.
Recently, an acrylic resin excellent in melt fluidity has been demanded from the viewpoint of weight reduction while maintaining the scratch resistance and transparency of the molded product.
However, the polycarbonate resin has excellent heat resistance and impact resistance, but has a large birefringence, which is an optical distortion, and tends to cause optical anisotropy in the molded product. In addition, the weather resistance, molding processability, scratch resistance and oil resistance are remarkably inferior.
For this reason, studies are being made to improve the scratch resistance of the obtained molded article while maintaining melt fluidity and transparency for acrylic resins typified by polymethyl methacrylate. For example, Patent Document 1 discusses a technique for obtaining a colloidal silica-containing acrylic resin by freezing and thawing an aqueous dispersion of acrylic resin particles and an aqueous dispersion of colloidal silica particles after mixing.

Japanese Patent Laying-Open No. 2015-193833

However, since the acrylic resin obtained by the method of Patent Document 1 has colloidal silica aggregated in the acrylic resin, the transparency characteristic of the acrylic resin is insufficient, and the melt fluidity of the acrylic resin is low. It is insufficient. Furthermore, since the colloidal silica is not sufficiently present in the vicinity of the surface of the obtained molded product, the scratch resistance of the molded product is insufficient.
Accordingly, an object of the present invention is to provide a resin composition having high scratch resistance and transparency and excellent in melt fluidity.

The present invention has the following configuration.
The first gist of the present invention is a resin composition for a vehicle lamp cover comprising an acrylic resin (A) and colloidal silica (B),
The acrylic resin (A) contains 50% by mass or more of methyl (meth) acrylate units with respect to the total mass of the acrylic resin (A),
The resin composition for a vehicle lamp cover contains 30 to 99 parts by mass of acrylic resin (A) and 1 to 70 parts by mass of colloidal silica (B) with respect to 100 parts by mass of the total mass of the resin composition for vehicle lamp cover. In addition, the resin composition for a vehicle lamp cover has a haze value of 5.0% or less and a shear viscosity of 500 Pa · sec or less measured at a shear rate of 1000 sec ⁻¹ at 240 ° C.
The second gist of the present invention resides in a molded article for a vehicle lamp cover formed by molding the resin composition for a vehicle lamp cover.
The third gist of the present invention resides in a vehicle lamp cover formed by molding a resin composition for a vehicle lamp cover.
The fourth gist of the present invention resides in a laminated body for a vehicle lamp cover obtained by laminating the molded article for a vehicle lamp cover on the surface of a thermoplastic resin base material.
The fifth gist of the present invention resides in a vehicle lamp cover formed by laminating the molded article for vehicle lamp cover on the surface of a thermoplastic resin base material.
The sixth gist of the present invention is that the mixture containing the acrylic resin (A) and the colloidal silica (B) is kneaded so that the temperature of the resin composition at the time of kneading is in the range of 230 ° C. or higher and 250 ° C. or lower. And the said acrylic resin (A) contains 50 mass% or more of methyl (meth) acrylate units with respect to the total mass of this acrylic resin (A),
The mixture includes 30 to 99 parts by mass of the acrylic resin (A) and 1 to 70 parts by mass of the colloidal silica (B) with respect to 100 parts by mass of the total mass of the mixture.

The colloidal silica (B) is surface-treated with a surface modifier,
A resin composition for a vehicle lamp cover, comprising kneading the obtained resin composition for a vehicle lamp cover so that a shear viscosity measured at a shear rate of 1000 sec ⁻¹ at 240 ° C. is 500 Pa · sec or less. In the manufacturing method.

INDUSTRIAL APPLICABILITY According to the present invention, a vehicle lamp cover resin composition having high scratch resistance and transparency, excellent melt fluidity can be obtained, and molding for vehicle lamp cover having high scratch resistance and transparency. The body can be provided stably.
The resin composition of the present invention can be applied to injection molding, extrusion molding, pressure molding (press molding), pressure molding and vacuum molding.

In the present invention, “(meth) acrylate” means at least one selected from “acrylate” and “methacrylate”, and “(meth) acrylic acid” is selected from “acrylic acid” and “methacrylic acid”. Means at least one.
In the present invention, “monomer” means an unpolymerized compound, and “repeating unit” means a unit derived from the monomer formed by polymerization of the monomer. The repeating unit may be a unit directly formed by a polymerization reaction, or may be a unit in which a part of the unit is converted into another structure by treating a polymer.
Unless otherwise specified, “mass%” indicates the content of a predetermined component contained in the total amount of 100 mass%.
Unless otherwise specified, a numerical range expressed using “to” in the present specification means a range including numerical values described before and after “to” as a lower limit value and an upper limit value, and “A to B”. Means A or more and B or less.

<Resin composition for vehicle lamp cover>
The vehicle lamp cover resin composition of the present invention (hereinafter simply referred to as “resin composition”) is a resin composition containing an acrylic resin (A) described later and a colloidal silica (B) described later.
By including the acrylic resin (A) and colloidal silica (B), the fluidity of the thermoplastic resin composition is improved, and further, it is obtained by producing a molded body using the production method of the present invention described later. The molded article has good scratch resistance and transparency.

The resin composition of the present invention comprises 30 to 99 parts by mass of acrylic resin (A) and 1 to 70 parts by mass of colloidal silica (B) with respect to 100 parts by mass of the total mass of the resin composition. Can be included.
The lower limit of the content of the acrylic resin (A) in the resin composition is 30 with respect to 100 parts by mass of the total mass of the resin composition from the viewpoint of excellent melt fluidity, transparency, and mechanical properties of the resin composition. It is preferably at least 40 parts by mass, more preferably at least 50 parts by mass, particularly preferably at least 75 parts by mass. The upper limit of the content of the acrylic resin (A) in the resin composition is preferably 99 parts by mass or less, more preferably 95 parts by mass or less, from the viewpoint of excellent scratch resistance of a molded article obtained from the resin composition. 90 parts by mass or less is more preferable.
The lower limit of the content of the colloidal silica (B) in the resin composition is 1 with respect to 100 parts by mass of the total mass of the resin composition from the viewpoint of excellent scratch resistance of the molded body obtained from the resin composition. It is preferably at least 5 parts by mass, more preferably at least 5 parts by mass and even more preferably at least 10 parts by mass. The upper limit of the content of colloidal silica (B) in the resin composition is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, from the viewpoint of excellent melt fluidity, transparency, and mechanical properties of the resin composition. 50 parts by mass or less is more preferable, and 25 parts by mass or less is particularly preferable.
In addition, content (unit: mass part) of colloidal silica (B) in a resin composition measures the silica content rate (unit: mass%) mentioned later by making the total mass of a resin composition into 100 mass%, This silica content was defined as the content of colloidal silica (B) in the resin composition when the total mass of the resin composition was 100 parts by mass. It is calculated as the content (unit: part by mass) of colloidal silica (B) when the total mass of the resin composition is 100 parts by mass. The content (unit: part by mass) of the acrylic resin (A) in the resin composition is the content obtained by removing the colloidal silica (B) from the resin composition as the acrylic resin (A). Calculated as

<Acrylic resin (A)>
The acrylic resin (A) is one of the constituent components of the resin composition of the present invention.
In the acrylic resin (A) in the present invention, a repeating unit derived from methyl (meth) acrylate (hereinafter abbreviated as “methyl (meth) acrylate unit”) is added to a total mass of 100 mass% of the acrylic resin (A). On the other hand, it is a polymer containing 50% by mass or more.
The minimum of the content rate of the methyl (meth) acrylate unit in an acrylic resin (A) is the total mass of this acrylic resin (A) from a viewpoint which is excellent in the scratch resistance and transparency of a resin composition and the obtained molded object. Is preferably 70% by mass or more, and more preferably 90% by mass or more. On the other hand, the upper limit of the content of the methyl (meth) acrylate unit in the acrylic resin (A) is not particularly limited, and may be 100% by mass with respect to the total mass of the acrylic resin (A). It may be less than 100% by mass.

  Further, as another embodiment of the acrylic resin (A) in the present invention, it is a homopolymer of methyl methacrylate (MMA) or the content of MMA-derived repeating units (MMA units) is the acrylic polymer. The methyl methacrylate copolymer (henceforth "polymer (A1)") which is 70 mass% or more and less than 100 mass% with respect to the total mass of resin (A) can be mentioned.

<Polymer (A1)>
The polymer (A1) contains MMA unit of 70% by mass or more and less than 100% by mass, and a repeating unit derived from another monomer described later (other monomer unit) exceeding 0% by mass and 30% by mass or less. MMA copolymer.
In the polymer (A1), the lower limit of the content of the MMA unit is preferably 70% by mass or more based on the total mass of the polymer (A1) because the original performance of the (meth) acrylic resin is hardly impaired. 80 mass% or more is more preferable, and 85 mass% or more is further more preferable. The upper limit of the content of the MMA unit is preferably 99.5% by mass or less from the viewpoint that the dispersion state of the colloidal silica (B) becomes good and the resin composition and the obtained molded article are excellent in scratch resistance and transparency. 98 mass% or less is preferable, and 95 mass% or more is more preferable.

  The upper limit of the content of other monomer units in the polymer (A1) is 30 masses with respect to the total mass of the polymer (A1) from the viewpoint of hardly impairing the original performance of the (meth) acrylic resin. % Or less is more preferable, 20 mass% or less is more preferable, and 15 mass% or less is further more preferable. On the other hand, the lower limit of the content of other monomer units in the polymer (A1) is such that the dispersed state of the colloidal silica (B) becomes good, and the resin composition and the obtained molded article have scratch resistance and transparency. From the viewpoint of superiority, it is preferably 0.5% by mass or more, more preferably 2% by mass or more, and further preferably 5% by mass or more.

<Other monomers>
Other monomers are not particularly limited as long as they are copolymerizable with MMA, and examples thereof include the following a) to h).
a) As the (meth) acrylic acid ester monomer, specifically, methyl acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) acrylic Hexyl acid, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate , Undecyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, (meth) acrylic acid Cyclohexyl, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid ester compounds other than methyl methacrylate such as 2-naphthyl acid and phenoxymethyl (meth) acrylate. Among these, alkyl acrylates having 1 to 8 carbon atoms in the alkyl group portion are preferable, and methyl acrylate is more preferable.
b) Styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p-methoxystyrene, p-acetoxystyrene, α -Aromatic vinyl compounds such as vinyl naphthalene and 2-vinyl fluorene.
c) Unsaturated nitrile compounds such as acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, vinylidene cyanide.
d) Ethylenically unsaturated ether compounds such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, ethyl allyl ether.
e) Vinyl halide compounds such as vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene.
f) 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, substituted linear conjugated pentadienes, Aliphatic conjugated diene compounds such as linear and side chain conjugated hexadiene.

These other monomers may be used individually by 1 type, and may use 2 or more types together.
Among these other monomers, methyl acrylate, ethyl acrylate, and n-butyl acrylate are more preferable because they tend not to impair the original performance of the (meth) acrylic resin and tend to be excellent in the thermal decomposition resistance of the molded body. More preferred are methyl acrylate and ethyl acrylate.

The number average molecular weight of the acrylic resin (A) is preferably 5,000 or more, more preferably 10,000 or more, and still more preferably 30,000 or more. Moreover, 200,000 or less is preferable, 150,000 or less is more preferable, and 130,000 or less is still more preferable. When the number average molecular weight of the acrylic resin (A) is 5,000 or more, the mechanical properties of the resin composition are excellent. Moreover, it is excellent in the melt fluidity | liquidity of a resin composition as the number average molecular weight of an acrylic resin (A) is 200,000 or less.
In the present specification, the number average molecular weight is a value measured using gel permeation chromatography using standard polymethyl methacrylate as a standard sample.

<Method for producing acrylic resin (A)>
The acrylic resin (A) in the present invention can be obtained by polymerizing the monomer raw material (1) containing the methyl (meth) acrylate using a known polymerization method.
The lower limit of the content of methyl (meth) acrylate contained in the monomer raw material (1) is from the viewpoint of excellent scratch resistance and transparency of the resin composition and the obtained molded article. 70 mass% or more is preferable with respect to 100 mass% of total mass of (1), and it is more preferable that it is 90 mass% or more. On the other hand, the upper limit of the content of the methyl (meth) acrylate unit in the monomer raw material (1) is not particularly limited, and is 100% by mass with respect to the total mass of the monomer raw material (1). It may be less than 100% by mass.

Moreover, when the acrylic resin (A) in the present invention is the polymer (A1), MMA is 70% by mass or more and less than 100% by mass, and the other monomer is more than 0% by mass and 30% by mass or less. It can be obtained by polymerizing a monomer raw material (2) containing bismuth using a known polymerization method.
The lower limit of the content of MMA contained in the monomer raw material (2) is 70% with respect to the total mass of the monomer raw material (2) because it is difficult to impair the original performance of the (meth) acrylic resin. % By mass or more is preferable, 80% by mass or more is more preferable, and 85% by mass or more is more preferable. The upper limit of the content of MMA is preferably 99.5% by mass or less from the viewpoint of good dispersibility of the colloidal silica (B) and excellent scratch resistance and transparency of the resin composition and the obtained molded body. 98 mass% or less is preferable and 95 mass% or more is further more preferable.

The upper limit of the content of the other monomer contained in the monomer raw material (2) is the total mass of the monomer raw material (2) from the viewpoint of hardly impairing the original performance of the (meth) acrylic resin. On the other hand, 30 mass% or less is more preferable, 20 mass% or less is more preferable, and 15 mass% or less is further more preferable. On the other hand, the lower limit of the content of other monomers is 0.5 from the viewpoint that the dispersion state of the colloidal silica (B) becomes good and the resin composition and the obtained molded article are excellent in scratch resistance and transparency. More preferably, it is more preferably at least 2% by mass, and even more preferably at least 5% by mass.
The other monomer is more preferably methyl acrylate, ethyl acrylate, or n-butyl acrylate because the original performance of the (meth) acrylic resin is less likely to be impaired, and the molded product tends to have excellent thermal decomposition resistance. More preferred is ethyl acrylate.
Furthermore, the monomer raw material may contain “monomer other than methyl (meth) acrylate” described in the above-mentioned section of the acrylic resin (A) in a proportion of less than 50% by mass.
Examples of the monomer polymerization method include bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. Among these polymerization methods, suspension polymerization or emulsion polymerization is preferable from the viewpoint of facilitating complexation of the acrylic resin (A) and colloidal silica (B) described later.

  In order to adjust the number average molecular weight of the acrylic resin (A), a chain transfer agent may be used when the monomer raw material is polymerized. Examples of the chain transfer agent include known mercaptan compounds, α-methylstyrene dimers, known terpinolene compounds, and the like. These chain transfer agents may be used individually by 1 type, and may use 2 or more types together.

  The amount of the chain transfer agent used is preferably 0.05 parts by mass or more and 2 parts by mass or less, and more preferably 0.07 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of the monomer raw material. It is excellent in the melt fluidity of a resin composition as the usage-amount of a chain transfer agent is 0.05 mass part or more. Moreover, it is excellent in the mechanical strength of the resin composition and the obtained molded object as the usage-amount of a chain transfer agent is 2 mass parts or less.

  Further, when the acrylic resin (A) is polymerized, an alkoxysilyl group can be introduced into the acrylic resin (A) by using the chain transfer agent in combination with an alkoxysilane compound having a mercapto group. The dispersion state of the colloidal silica (B) in the composition becomes good, and the scratch resistance and transparency of the molded product can be further improved.

Examples of the alkoxysilane compound having a mercapto group include compounds represented by the following general formula (I).
HS (CH ₂ ) _p SiR _1n (OR ₂ ) _3-n (I)
[In formula (I), R ₁ is a hydrocarbon group having 1 to 10 carbon atoms, R ₂ is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain an ether bond, and n is 0 to 2 An integer, p represents an integer of 1-10. ]
Among the alkoxysilane compounds represented by the general formula (I), the dispersion state of the colloidal silica (B) in the resin composition is improved, and the scratch resistance and transparency of the obtained molded body are improved. From the viewpoint of possible, for example, γ-mercaptopropyltrimethoxysilane (γMPTMS) and γ-mercaptopropylmethyldimethoxysilane (γMPMDMS) are preferable.

<Colloidal silica (B)>
Colloidal silica (B) is one of the components of the thermoplastic resin composition of the present invention.
When the resin composition of the present invention contains colloidal silica (B), the scratch resistance of the molded article obtained by molding the resin composition becomes excellent.
As the colloidal silica (B) used in the present invention, colloidal silica using water as a dispersion medium can be used, and a commercially available colloidal silica aqueous dispersion can be used. Specifically, Snowtex O (trade name, manufactured by Nissan Chemical Industries, Ltd., colloidal silica average particle size 15 nm, silica content 20% by mass), Snowtex O-40 (trade name, Nissan Chemical Industries, Ltd.) ), An average particle diameter of colloidal silica of 25 nm, and a silica content of 40% by mass.
The colloidal silica preferably used in the present invention preferably has an average particle size of 50 nm or less, more preferably 30 nm or less, from the viewpoint of improving the scratch resistance and transparency of the resin composition and the molded product.

The average primary particle diameter of the colloidal silica (B) particles (hereinafter abbreviated as “silica particles” as appropriate) contained in the resin composition of the present invention and the molded product obtained by molding the resin composition is 1 nm or more. 30 nm or less is preferable. When the average primary particle diameter of the silica particles is 1 nm or more, the melt fluidity of the resin composition is excellent. When the average primary particle diameter of the silica particles is 30 nm or less, the resin composition and the obtained molded article are excellent in scratch resistance and transparency. The average primary particle diameter of the silica particles is more preferably 5 nm or more and 30 nm or less, and further preferably 10 nm or more and 30 nm or less.
In this specification, “average primary particle diameter” means about 30 arbitrary silica particles observed on an observation image of a transmission electron microscope in an arbitrary cross section of a small piece cut out from a molded body using a microtome or the like. The maximum particle diameter of the primary particle diameter of silica particles was measured and averaged. Aggregated particles refer to secondary particles formed by contacting primary particles of silica particles.
Silica particles that are not surface-treated may be used, but in the present invention, the surface of the silica particles is surface-treated with an organosilicon compound from the viewpoint of good dispersion of the silica particles in the resin composition. You may use what is done. When using a surface modifier, a known reaction catalyst can be used as necessary.
Examples of the surface modifier include organic silicon compounds such as known silylating agents and known silane coupling agents.

Specific examples of the surface modifier include the following i) or ii).
i) Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane (DMDMS), dimethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxy Silane (TMES), γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyldimethyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) Ethylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, poly having silanol group or alkoxysilyl group Methylsiloxane compound ii) Alkoxysilane compound having mercapto group such as γ-mercaptopropyltrimethoxysilane (γMPTMS), γ-mercaptopropylmethyldimethoxysilane (γMPMDMS) The surface modifier has a polydimethylsiloxane compound and a mercapto group At least one of alkoxysilane compounds can be included.

  Among the surface modifiers, an alkoxysilane compound having a mercapto group can introduce an alkoxysilyl group into the acrylic resin (A) when used in combination with the chain transfer agent when the acrylic resin (A) is polymerized. The dispersion state of the colloidal silica (B) in the resin composition can be improved, and the scratch resistance and transparency of the molded product can be further improved.

Examples of the alkoxysilane compound having a mercapto group include compounds represented by the following general formula (II).
HS (CH ₂ ) _p SiR _1n (OR ₂ ) _3-n (II)
[In the formula (II), R ₁ is a hydrocarbon group having 1 to 10 carbon atoms, R ₂ is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain an ether bond, and n is 0 to 2 An integer, p represents an integer of 1-10. ]

Among the alkoxysilane compounds having a mercapto group represented by the general formula (II), the dispersion state of the silica particles in the resin composition can be improved, and the scratch resistance and transparency of the obtained molded body are further improved. From the viewpoint of possible, γMPTMS and γMPMDMS are preferable.
Alternatively, an organic solvent dispersion of colloidal silica in which the surface of the colloidal silica is surface-treated in advance with a surface modifier such as a silylating agent or a silane coupling agent and dispersed in an organic solvent can be used. Specifically, commercially available MEK-ST-40 (trade name, manufactured by Nissan Chemical Industries, Ltd., surface organic modified colloidal silica particles having a primary particle diameter of 15 nm are dispersed in MEK, and the concentration of the silica particles is 40. Colloidal silica-dispersed MEK solution in weight%), EAc-ST (trade name, manufactured by Nissan Chemical Industries, Ltd., silica particles having a primary particle size of 20 nm are dispersed in ethyl acetate, and the concentration of the silica particles is 30 An ethyl acetate-dispersed colloidal silica-dispersed ethyl acetate solution and the like that are weight percent) can be used.

<Resin composition for vehicle lamp cover>
The vehicle lamp cover resin composition (resin composition) of the present invention will be described in more detail.
When the resin composition of the present invention is molded into a 3 mm-thick plate-shaped molded product, the total light transmittance of the molded product measured according to ISO 13468-1 is 75.0% or more. Is preferably 80.0% or more, more preferably 85.0% or more, and particularly preferably 90.0% or more. When the total light transmittance is 75.0% or more, the resin composition and the obtained molded article are excellent in transparency, and thus the resin composition is suitable for a vehicle lamp cover.
The total light transmittance can be controlled by using a method for producing a resin composition for a vehicle lamp cover, which will be described later, when producing the resin composition of the present invention.

The resin composition of the present invention has a haze value of 5.0% or less and 3.0% or less when measured on a ISO14782 when molded into a plate-shaped molded product having a thickness of 3 mm. It is preferable that it is 2.0% or less. When the haze value is 5.0% or less, the resin composition and the obtained molded article are excellent in transparency, and thus the resin composition is suitable for a vehicle lamp cover.
The haze value can be controlled by using a method for producing a resin composition for a vehicle lamp cover, which will be described later, when producing the resin composition of the present invention.

When the resin composition of the present invention is molded into a plate-shaped molded product having a thickness of 3 mm, the yellow index (YI) of the molded product measured in accordance with ISO 17223 is preferably 15 or less. Is preferably 0.0 or less, more preferably 7.0 or less, and particularly preferably 5.0 or less. When YI is 10.0 or less, the resin composition and the obtained molded article are excellent in transparency, and thus the resin composition is suitable for a vehicle lamp cover.
The YI can be controlled by using a method for producing a resin composition for a vehicle lamp cover, which will be described later, when producing the resin composition of the present invention.

The resin composition of the present invention has a haze value of 30 after the scratch treatment in which # 0000 steel wool was reciprocated 11 times on the surface of a molded body obtained by molding the resin composition under a load of 14 kPa. It is preferably 0.0% or less, more preferably 25.0% or less, still more preferably 20.0% or less, and particularly preferably 15.0% or less. When the haze value after the scratch treatment using steel wool is 30.0% or less, the obtained molded article is excellent in scratch resistance, so the resin composition is suitable for a vehicle lamp cover.
The haze value after the scratch treatment using steel wool can be controlled by using a method for producing a resin composition for a vehicle lamp cover, which will be described later, when producing the resin composition of the present invention.

  The resin composition of the present invention may contain other additives in addition to the acrylic resin (A) and colloidal silica (B). Examples of other additives include ultraviolet absorbers, antioxidants, plasticizers, light diffusing agents, matting agents, lubricants, mold release agents, antistatic agents, and coloring agents such as pigments. These other additives may be used alone or in combination of two or more.

  <Method for producing resin composition for vehicle lamp cover>

  The vehicle lamp cover resin composition (resin composition) of the present invention can be obtained by combining an acrylic resin (A) and colloidal silica (B). The method of combining the acrylic resin (A) and the colloidal silica (B) is not particularly limited. For example, an aqueous dispersion of acrylic resin (A) particles (hereinafter referred to as “aqueous dispersion of acrylic resin (A)”). Liquid colloidal silica (B) particles and an aqueous dispersion of colloidal silica (B) particles (hereinafter abbreviated as “colloidal silica (B) aqueous dispersion”). A method of freezing and thawing and mixing the acrylic resin (A) and colloidal silica (B) and then separating water to obtain particles of the resin composition can be mentioned.

<When a resin composition is obtained by an emulsion polymerization method>
When the resin composition of the present invention is obtained by emulsion polymerization, an aqueous dispersion of colloidal silica (B) that is not surface-modified is mixed with an aqueous dispersion of acrylic resin (A) to generate heteroaggregation. Thereafter, a method of separating the water and obtaining particles of the resin composition can be used. Hereinafter, the emulsion polymerization method will be described.

  As the radical polymerization initiator used in carrying out the emulsion polymerization, known radical polymerization initiators can be used. For example, organic radicals such as tert-butyl hydroperoxide, cumene hydroperoxide, and diisopropylbenzene hydroperoxide can be used. A redox initiator by a combination of an oxidizing agent and a reducing agent such as a sugar-containing iron pyrophosphate formulation, a sulfoxylate formulation, or a mixed formulation of a sugar-containing iron pyrophosphate formulation / sulfoxylate formulation; potassium persulfate, Persulfates such as ammonium sulfate; azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile, dimethyl-2,2′-azobisisobutyrate; organic peroxides such as benzoyl peroxide and lauroyl peroxide Etc., but preferably It is the initiator of the redox system. What is necessary is just to set the usage-amount of these radical polymerization initiators suitably according to a well-known technique.

As the emulsifier used in the emulsion polymerization, known emulsifiers can be used, for example, the following emulsifiers a) to c): a) polyoxyethylene alkyl ether phosphate sodium salt and polyoxyethylene alkyl phenyl ether phosphate sodium salt , Phosphate-based emulsifiers such as mono-n-dodecyloxytetraoxyethylene phosphate sodium salt b) carboxylates such as potassium oleate, sodium N-lauroyl sarcosinate, sodium N-myristoyl sarcosinate, potassium alkenyl succinate C) Nonionic emulsifiers such as polyoxyethylene alkyl esters and polyoxyethylene alkyl aryl ethers

Among the emulsifiers, phosphate emulsifiers and carboxylate emulsifiers are more preferable, and phosphate emulsifiers are more preferable. The use of a phosphate emulsifier has the advantage that colloidal silica can be most efficiently introduced into the resin composition of the present invention when colloidal silica is added to the emulsion polymerization latex of an acrylic resin.
The phosphate emulsifier contains a phosphoric acid emulsifier typified by polyoxyethylene alkyl ether phosphate and polyoxyethylene alkyl allyl ether phosphate, and a part of phosphate group of the phosphate emulsifier. In addition, a polymer having surface active ability is also included.
A sulfonate emulsifier can be used in combination with the above-mentioned emulsifier. Examples of the sulfonate emulsifier used in combination include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium diphenyl ether disulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkylphenyl ether sulfate, and the like.
What is necessary is just to set the usage-amount of an emulsifier suitably according to a well-known technique.
Moreover, various electrolytes, pH adjusters, etc. can be used together as needed.
Emulsion polymerization is performed under conditions of a polymerization temperature of 5 to 100 ° C., preferably 40 to 95 ° C., and a polymerization time of about 0.1 to 24 hours. The method for adding the monomer to the reactor may be batch, divided, or continuous, or a combination thereof.

In the present invention, it is preferable to use an aqueous dispersion of negatively charged acrylic resin (A) particles. If an aqueous dispersion of a positively charged acrylic resin (A) is mixed with an aqueous dispersion of colloidal silica (B), which will be described later, the acrylic resin (A) particles (positively charged) and colloidal silica are mixed. Since the particles (negatively charged) of (B) have opposite signs, the aggregation due to the electric attractive force is too rapid and non-uniform aggregation occurs. If so, the mixing system becomes unstable, solidifying the components in the polymerization vessel, generating aggregates (cullet), etc., which is not preferable in terms of the process. In addition, since the resin composition having a structure in which the colloidal silica (B) particles are uniformly attached around the particles of the acrylic resin (A) while maintaining the state of the primary particles is not generated, it is an object of the present invention. Scratch resistance and transparency of the molded article, which are performance obtained by dispersing the colloidal silica (B) in the resin composition in the state of primary particles, are not expressed.
The method of mixing the aqueous dispersion of the acrylic resin (A) and the aqueous dispersion of the colloidal silica (B) is performed by adding the water of the colloidal silica (B) to the aqueous dispersion of the acrylic resin (A) obtained as described above. The dispersion may be added and stirred at room temperature to 100 ° C. for an arbitrary time. By this stirring, an aqueous dispersion of the resin composition is obtained.
When mixing the aqueous dispersion of the acrylic resin (A) and the aqueous dispersion of the colloidal silica (B), the particles of the colloidal silica (B) are used from the viewpoint of improving the dispersion state of the silica particles in the resin composition. In order to surface-treat, an organic silicon compound such as a known silylating agent or a known silane coupling agent may be added as a surface modifier.
In the production method of the present invention, when emulsion polymerization is used, at least one of the following step 1 and step 2 can be included in order to add the surface modifier.
Step 1) After producing an aqueous dispersion of an acrylic resin (A) in the presence of a surface modifier, an aqueous dispersion of colloidal silica (B) is mixed.
Step 2) When mixing the aqueous dispersion of acrylic resin (A) and the aqueous dispersion of colloidal silica (B), a surface modifier is added.
By including at least one of step 1 and step 2, the dispersion state of the silica particles in the resin composition becomes good.

  As the surface modifier, the same surface modifier as described in the above-mentioned colloidal silica (B) can be used. Specifically, the surface modifier preferably contains at least one of the polydimethylsiloxane compound and the alkoxysilane compound having a mercapto group. The alkoxysilane compound having a mercapto group is preferably a compound represented by the general formula (II).

Examples of the method for separating water from the aqueous dispersion of the resin composition include a coagulation method such as a salt coagulation method and an acid coagulation method, and a spray drying method (spray drying method).
Specific examples of the coagulation method include adding an aqueous dispersion of the resulting resin composition to an aqueous solution of a salt such as calcium chloride, magnesium chloride, magnesium sulfate, aluminum sulfate, calcium acetate, or an acid such as sulfuric acid. A method of heating and coagulating according to the above is exemplified. Further, instead of using an aqueous solution of salt or acid, a solvent that is soluble in water such as methanol, ethanol, isopropyl alcohol, etc. and does not dissolve the polymer of the acrylic resin is used. Solidification is also possible by adding and heating.
The powdered product obtained by separating water from the aqueous dispersion of the resin composition is washed with water and then dried using a known means such as a steam dryer to obtain particles of the resin composition. it can.

<When obtaining a resin composition by suspension polymerization>
As a composite method of acrylic resin (A) and colloidal silica (B), when acrylic resin (A) was obtained by suspension polymerization, it was surface-treated with a surface modifier such as a silylating agent or a silane coupling agent. About the organic solvent dispersion of colloidal silica, the methyl (meth) acrylate dispersion of surface-modified colloidal silica (B) obtained by replacing the organic solvent with a methyl (meth) acrylate monomer is vigorously stirred in water. Polymerization is performed, and then water is separated using a known means to obtain particles of the resin composition.
The suspension polymerization is carried out under conditions of a polymerization temperature of 5 to 100 ° C., preferably 40 to 95 ° C., and a polymerization time of about 0.1 to 24 hours. The method for adding the monomer to the reactor may be batch, divided, or continuous, or a combination thereof.

The average particle diameter of particles of a resin composition for a vehicle lamp cover (hereinafter simply referred to as “resin composition particles”) obtained by a method such as the emulsion polymerization method or suspension polymerization method is particularly limited. It is not a thing and can be 20 nm or more and 500 nm or less. When the lower limit of the average particle diameter of the resin composition particles is 20 nm or more, the handleability of the resin composition powder is excellent. When the upper limit of the average particle diameter of the resin composition particles is 500 nm or less, the dispersion state of the primary particles of colloidal silica in the resin composition becomes good. The average particle size of the resin composition particles is more preferably 40 nm or more and 300 nm or less.
The resin composition particles obtained by the above-described method are a mixture containing 40 to 99 parts by mass of acrylic resin (A) and 1 to 60 parts by mass of colloidal silica (B).
The resin composition of the present invention is processed into a pellet by heating and kneading the mixture obtained by the above-described method or the like with an extruder or a kneader.

  In the production method of the present invention, the temperature of the resin composition measured when the mixture is melt-kneaded needs to be 230 ° C. or higher and 250 ° C. or lower. When the lower limit of the temperature of the resin composition during melt-kneading is 230 ° C. or higher, the fluidity of the resin composition during melt-kneading is improved, and the melt viscosity of the resin composition during melt-kneading can be lowered. The primary particles of (B) can be uniformly dispersed, and the obtained resin composition and the obtained molded article are excellent in scratch resistance and transparency. Further, if the upper limit of the temperature of the resin composition during melt-kneading is 250 ° C. or less, the melt viscosity of the resin composition is too low during melt-kneading, and the primary particles of colloidal silica (B) are aggregated. Since it can suppress, the obtained resin composition and the obtained molded object are excellent in scratch resistance and transparency.

In the production method of the present invention, the upper limit of the shear viscosity at a shear rate of 1000 sec ⁻¹ at 240 ° C. measured according to JIS K7199 of the resin composition obtained after melt kneading is 500 Pa · sec or less. Thus, it is preferable to melt-knead and more preferably 400 Pa · sec or less.
When the upper limit of the shear viscosity of the resin composition is 500 Pa · sec or less, in addition to excellent melt fluidity of the resin composition, the viscosity during melting and kneading of the resin composition is low. In a molded body that can be uniformly dispersed and is formed by molding the resin composition, observation is made at an arbitrary position within a range from the surface of the molded body to a depth of 1 μm within the cross section in the thickness direction of the molded body. 5 or more of colloidal silica (B) is observed in an arbitrary region of 100 nm × 100 nm on the observation image of the transmission electron microscope, so that the obtained molded product has scratch resistance and transparency. Excellent. Further, colloidal silica (B) observed on an observation image of a transmission electron microscope observed at an arbitrary position within a range from the surface of the molded body to a depth of 1 μm within the cross section in the thickness direction of the molded body. ) Is 100 nm or less, the resulting molded article is excellent in scratch resistance and transparency.
Further, the lower limit of the shear viscosity at the shear rate of 1000 sec ⁻¹ at 240 ° C. of the resin composition is not particularly limited, but is preferably 300 Pa · sec or more, and more preferably 330 Pa · sec or more. . When the lower limit of the shear viscosity is 300 Pa · sec or more, an appropriate shearing force is applied to the resin composition being melt-kneaded, so that primary particles of colloidal silica can be uniformly dispersed, and the obtained molded body Is excellent in scratch resistance and transparency.

The shear viscosity at a shear rate of 1000 sec ⁻¹ at 240 ° C. of the resin composition optimizes known production conditions such as the screw shape and screw rotation speed of the kneading apparatus used during melt-kneading, and as described above. The temperature of the resin composition measured at the time of melt-kneading can be controlled to a desired value by setting the temperature within the range of 230 ° C. to 250 ° C.

  When processing the resin composition of the present invention into a pellet, the resin composition and a known thermoplastic resin or a known polymer are blended at an arbitrary ratio according to the required performance. You can also. Moreover, when the thermosetting resin is used for the polymer, it can be used as a thermoplastic resin composition by blending with a thermoplastic polymer.

<Molded body for vehicle lamp cover>
The molded article for a vehicle lamp cover of the present invention (hereinafter abbreviated as “molded article”) is obtained by molding the resin composition of the present invention.
Examples of the molding method for obtaining the molded article of the present invention include injection molding, extrusion molding, pressure molding (press molding), pressure molding and vacuum molding.
The molding temperature is preferably 200 ° C. or higher and 250 ° C. or lower, and more preferably 210 ° C. or higher and 240 ° C. or lower. When the molding temperature is 200 ° C. or higher, the melt flowability of the resin composition is excellent, and particularly when the injection molding or extrusion molding is used as the molding method, the productivity of the molded body is excellent. Further, when the molding temperature is 250 ° C. or lower, the viscosity of the resin composition can be prevented from being lowered more than necessary, and aggregation of primary particles of colloidal silica in the resin composition can be inhibited and obtained. The molded body is excellent in scratch resistance and transparency.
Moreover, you may shape | mold the obtained molded object further using well-known forming methods, such as a pressure forming method and a vacuum forming method. What is necessary is just to set suitably molding conditions, such as molding temperature and molding pressure.

The dispersion state of the colloidal silica (B) in the resin composition and the molded body of the present invention is observed using a transmission electron microscope.
On the observation image of the transmission electron microscope, observed at an arbitrary position within the range from the surface of the molded body to a depth of 1 μm within the cross section in the thickness direction of the molded body obtained by molding the resin composition. The number of colloidal silica (B) particles observed in an arbitrary region of 100 nm × 100 nm is preferably 5 or more. When the number of particles of the colloidal silica (B) observed is 5 or more, since the colloidal silica (B) is sufficiently present on the surface of the molded body, the molded body is excellent in scratch resistance. It is more preferable that the number of colloidal silica (B) particles observed is 20 or more. In order to make five or more colloidal silica (B) observed at an arbitrary position in the range from the surface of the molded body to a depth of 1 μm, the above-described method for producing a resin composition for a vehicle lamp cover can be used. .
In addition, an observation image of a transmission electron microscope observed at an arbitrary position within a range from the surface of the molded body to a depth of 1 μm within the cross section in the thickness direction of the molded body obtained by molding the resin composition. The maximum distance between primary particles of colloidal silica (B) observed above is preferably within 100 nm. The maximum distance between the primary particles of the colloidal silica (B) is more preferably within 75 nm, and further preferably within 50 nm. The resin composition is excellent in transparency because the maximum distance between the primary particles of colloidal silica (B) dispersed is within 100 nm.
The maximum distance between primary particles of colloidal silica (B) can be controlled by using the above-described method for producing a resin composition for a vehicle lamp cover when producing the resin composition of the present invention.
In the molded product of the present invention, the silica particles are not aggregated, the silica fine particles are dispersed in the form of primary particles, and the silica fine particles are present in a sufficient concentration near the surface of the molded product. It is excellent in scratch resistance and transparency of the body, and can be used for optical materials, vehicle parts, lighting materials, building materials, and the like. In particular, in applications for vehicle lamp covers, and among them, vehicle head lamp covers among vehicle components, the resin composition is required to have high melt fluidity, and the resulting molded product has high scratch resistance and transparency. Therefore, the resin composition and the molded body of the present invention can be suitably used for the first time for the application.
Other vehicle parts include, for example, an optical member inside a rear lamp, an inner lens for a headlight (sometimes called a projector lens or a PES lens), a meter cover, a door mirror housing, a pillar cover (sash cover), License garnish, front grille, fog garnish, emblem and the like.

<Laminated body for vehicle lamp cover and vehicle lamp cover>
The laminate for vehicle lamp cover of the present invention (hereinafter abbreviated as “laminate”) and the vehicle lamp cover are obtained by laminating the resin composition of the present invention on the surface of a thermoplastic resin substrate. .
The material which comprises the said thermoplastic resin base material is not specifically limited, A well-known thermoplastic resin or a well-known copolymer can be mentioned. For example, polyethylene resin, polypropylene resin, poly-4-methyl-1-pentene resin, polymethyl methacrylate resin, polymethyl methacrylate copolymer, methyl methacrylate-styrene copolymer, polystyrene resin, styrene-acrylonitrile Copolymer, styrene-maleic anhydride copolymer, styrene-maleimide copolymer, rubber-modified styrene-maleimide copolymer, rubber-reinforced polystyrene (HIPS), acrylonitrile-butadiene-styrene resin (ABS resin), acrylonitrile -Ethylene propylene-styrene resin (AES resin), methyl methacrylate-butadiene-styrene resin (MBS resin), acrylonitrile-butadiene-methyl methacrylate, styrene resin, acrylonitrile-n-butyl Polyacrylate-styrene resin (AAS resin), polyvinyl chloride resin, polyvinylidene chloride resin, polycarbonate resin, polyethylene terephthalate resin, polyacetal resin, polyamide resin, epoxy resin, polyvinylidene fluoride resin, polysulfone Resin, ethylene-vinyl acetate copolymer, PPS resin, polyether ether ketone, PPO resin, rubber-modified PPO resin, polyamide elastomer, polyester elastomer, polybutadiene resin, butadiene-styrene copolymer, acrylonitrile-butadiene copolymer Polymer, polyisoprene, natural rubber, acrylic rubber, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, chlorinated butyl rubber, chlorinated polyethylene, styrene-butadiene Block copolymer, styrene - butadiene - styrene block copolymer, various thermoplastic polymers and blends thereof such as a hydride of these block copolymers.
Examples of the method for obtaining the laminate include a method using a two-color injection molding method and a pressure molding method (press molding method).
The lamination temperature when laminating the resin composition of the present invention on the surface of the thermoplastic resin substrate is preferably 200 ° C. or higher and 250 ° C. or lower, more preferably 210 ° C. or higher and 240 ° C. or lower. When the lamination temperature is 200 ° C. or higher, the resin composition is excellent in melt fluidity, and the productivity of the laminate is excellent. Further, when the lamination temperature is 250 ° C. or lower, the viscosity of the resin composition can be prevented from being lowered more than necessary, and aggregation of primary particles of colloidal silica in the resin composition can be inhibited and obtained. The laminate is excellent in scratch resistance and transparency.

Since the laminate of the present invention is excellent in scratch resistance and transparency, it can be used for optical materials, vehicle parts, lighting materials, building materials, and the like, particularly for vehicles such as vehicle interior and exterior materials. Suitable for members. In particular, in the use of a vehicle lamp cover such as a vehicle headlamp cover among vehicle members, the laminate is required to have high scratch resistance and transparency, and the resin composition is required to have high melt fluidity. The laminate of the present invention can be suitably used for the first time for the application.
Other vehicle members include, for example, an optical member inside a rear lamp, an inner lens for a headlight (sometimes called a projector lens or a PES lens), a meter cover, a door mirror housing, a pillar cover (sash cover), License garnish, front grille, fog garnish, emblem and the like.
The vehicle lamp cover obtained by the present invention can be obtained by molding the resin composition of the present invention or laminating the resin composition of the present invention on the surface of a thermoplastic resin substrate.
The vehicle lamp cover of the present invention is excellent in scratch resistance and transparency. In the use of a vehicle lamp cover such as a vehicle headlamp cover, the lamp cover is required to have high scratch resistance and transparency, and the resin composition is required to have high melt fluidity. Therefore, the vehicle lamp cover of the present invention is required. Can be suitably used for the first time in this application.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
<Evaluation method>
Evaluation in Examples and Comparative Examples was performed by the following method.
<Number average molecular weight>
10 mg of the acrylic resin (A) obtained in Examples and Comparative Examples was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.5 μm membrane filter to obtain a sample solution. About the obtained sample solution, the number average molecular weight was measured using the gel permeation chromatography (Model name "HLC-8320 GPC Eco SEC", Tosoh Corporation make). Two separation columns, “TSKgel SuperHZM-H” (trade name, manufactured by Tosoh Corporation, ID 4.6 mm × length 15 cm) in series, tetrahydrofuran as solvent, differential refractometer as detector, standard sample Standard polymethyl methacrylate was used under the conditions of a flow rate of 0.6 ml / min, a measurement temperature of 40 ° C., and an injection amount of 0.1 ml.

<Silica content>
The amount of ash was calculated by subjecting the resin compositions obtained in Examples and Comparative Examples to a combustion test in accordance with A method of JIS K7250, and this was defined as the silica content of the resin composition.

<Preparation of test piece>
The resin compositions obtained in Examples and Comparative Examples were supplied to an injection molding machine (model name: IS-100, manufactured by Toshiba Machine Co., Ltd.), injection molded at a molding temperature of 240 ° C., and plate-shaped molding A body (width 50 mm, length 100 mm, thickness 3 mm) was obtained. This molded body was used as a test piece for evaluation.

<Dispersed state of colloidal silica>
The dispersion state of the colloidal silica in the molded body is the average primary particle diameter of the colloidal silica and the dispersion state of the colloidal silica in the vicinity of the surface of the molded body obtained from the resin compositions obtained in Examples and Comparative Examples. And the maximum distance between primary particles of colloidal silica.
In this example, the test piece was evaluated according to the method described later.

<Average primary particle diameter of colloidal silica>
An arbitrary portion of the test piece was cut in a direction perpendicular to the surface of the test piece. Next, a thin slice was cut from the cut surface using a diamond knife, the obtained thin slice was embedded with an epoxy resin for an electron microscope, and a slice having a thickness of about 80 nm was cut using a microtome. Subsequently, an observation image at an arbitrary position was photographed with a transmission electron microscope (model name: H-7600, manufactured by Hitachi High-Technologies Corporation, acceleration voltage: 80 kV, observation magnification: 150,000 times) for the obtained section. . Arbitrary 30 colloidal silica particles observed on the observation image of the transmission electron microscope were selected, the maximum primary particle diameter of the colloidal silica particles was measured, and the average value was calculated as the average of the colloidal silica. The primary particle size was used.

<Number of particles of colloidal silica (B) near the surface of the molded body>
An arbitrary portion of the test piece was cut in a direction perpendicular to the surface of the test piece. Next, a thin slice was cut from the cut surface using a diamond knife, the obtained thin slice was embedded with an epoxy resin for an electron microscope, and a slice having a thickness of about 80 nm was cut using a microtome. Next, the obtained section was examined with a transmission electron microscope (model name: H-7600, manufactured by Hitachi High-Technologies Corporation, acceleration voltage: 80 kV, observation magnification: 150,000 times), 1 μm deep from the surface of the test piece. An observation image at an arbitrary position in the range up to was taken.
A region of 100 nm × 100 nm is observed at 10 arbitrary positions on the observation image, and the number of colloidal silica (B) particles observed in the region (hereinafter, appropriately abbreviated as “the number of silica particles”). ) Was measured. Among the observed 10 locations, the number of particles with the smallest number of measured silica particles was taken as the number of silica particles near the surface of the molded body. Moreover, it determined using the following criteria.
(Criteria)
AA: The number of silica particles is 20 or more A: The number of silica particles is 5 or more and less than 20 B: The number of silica particles is less than 5

<Maximum distance between primary particles of colloidal silica (B)>
From the observation image of the transmission electron microscope obtained by the above method, the distance (unit: nm) of the place where the distance between the primary particles of the colloidal silica (B) is the most distant is measured, and this is measured with the colloidal silica. The maximum distance between primary particles was used. Furthermore, it determined using the following references | standards.
(Criteria)
AA: Maximum distance between primary particles is 50 nm or less A: Maximum distance between primary particles exceeds 50 nm and 100 nm or less B: Maximum distance between primary particles exceeds 100 nm and is 400 nm or less C: Maximum distance between primary particles is Over 400nm

<Transparency>
The transparency of the resin composition can be evaluated from the total light transmittance, haze value, and yellow index (YI) of a plate-like molded product formed by molding the resin composition. In this example, according to the method described above, the total light transmittance, haze value, and YI were evaluated using the molded product obtained from the resin composition as a test piece for evaluation.

<Total light transmittance>
Using a haze meter (model name “NDH-2000”, manufactured by Nippon Denshoku Industries Co., Ltd.) as an index of transparency of the resin composition, the total light transmittance of the test piece is measured according to ISO 13468-1. did. Measurement was performed once for each test piece using three test pieces, and the average value was defined as the total light transmittance. Furthermore, it determined using the following references | standards.
(Criteria)
AA: Total light transmittance is 85% or more A: Total light transmittance exceeds 70% and less than 85% B: Total light transmittance is less than 70% <Haze value>
As a transparency index of the resin composition, a haze meter (model name “NDH-2000”, manufactured by Nippon Denshoku Industries Co., Ltd.) was used, and the haze value of the test piece was measured according to ISO14782. Measurement was performed once for each test piece using three test pieces, and the average value was defined as the haze value. Furthermore, it determined using the following references | standards.
(Criteria)
AA: Haze value is 3.0% or less A: Haze value exceeds 3.0% and 10% or less B: Haze value exceeds 10%

<Yellow Index (YI)>
As an index of transparency of the resin composition, an instantaneous multi-photometry system (model name “MCPD-3000”, manufactured by Otsuka Electronics Co., Ltd.) was used, and the yellow index (YI) of the test piece was measured according to ISO 17223. . Measurement was performed once for each test piece using three test pieces, and the average value was defined as a yellow index (YI). Furthermore, it determined using the following references | standards.
(Criteria)
AA: YI is 8.0% or less A: YI exceeds 8.0% and is 15% or less B: YI exceeds 15%

<Scratch resistance test>
The scratch resistance of the molded product of the present invention was evaluated according to the following method.
Set a test piece on a Bencott abrasion tester (model name: HEIDON TYPE30, manufactured by Shinto Kagaku Co., Ltd.), set a weight so that a pressure of 14 kPa is applied to 1 cm ² , and load # 0000 steel wool. In order to pass through the center of the surface of the test piece under the condition of 14 kPa / cm ² , scratching was performed by reciprocating 11 times at a sweep distance of 30 mm at a sweep speed of 3000 mm / min. Formed. The haze value was measured for the frictional wear treated part of the test piece after the abrasion treatment. Measurement was performed once for each test piece using three test pieces, and the average value was defined as the haze value after the scratch treatment. Furthermore, it determined using the following references | standards.
(Criteria)
AA: Haze value after abrasion treatment is 23% or less A: Haze value after abrasion treatment exceeds 23% and 30% or less B: Haze value after abrasion treatment exceeds 30%

<Melting fluidity>
As an index of the melt fluidity of the resin composition, the resin composition is supplied to a capillary rheometer (model name: twin capillary rheometer RH7, manufactured by ROSAND), and in accordance with JIS K7199, the shear rate is 1000 sec ⁻¹ at 240 ° C. Shear viscosity (unit: Pa · sec) was measured. The melt fluidity of the resin composition was determined using the following criteria.
(Criteria)
A: Melt fluidity is 300 Pa · sec or more and 500 Pa · sec or less B: Melt fluidity is less than 300 Pa · sec or exceeds 500 Pa · sec

<Average particle diameter of resin composition particles>
The volume average particle size of the resin composition particles obtained in Examples, Comparative Examples, and Reference Examples is measured using a laser diffraction / scattering particle size distribution analyzer (model name: LA-960, manufactured by Horiba, Ltd.). It was measured.

MEK: methyl ethyl ketone MMA: methyl methacrylate MA: methyl acrylate TMES: trimethylethoxysilane DDMMS: dimethyldimethoxysilane γMPTMS: γ-mercaptopropyltrimethoxysilane γMPMDMS: γ-mercaptopropylmethyldimethoxysilane EDTA: ethylenediaminetetraacetate sodium TBH: tert-butyl Hydroperoxide nOcSH: n-octyl mercaptan AMBN: 2,2′-azobis-2-methylbutyronitrile (trade name: V-59, manufactured by Wako Pure Chemical Industries, Ltd.)
(S-1): Colloidal silica aqueous dispersion (average particle diameter of colloidal silica 15 nm, silica content 20 mass%, manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex O)
(S-2): Colloidal silica aqueous dispersion (average particle diameter of colloidal silica 25 nm, silica content 40% by mass, manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex O-40)

[Production Example 1: Monomeric dispersion of colloidal silica (S-3)]
MEK-ST-40 (manufactured by Nissan Chemical Industries, Ltd., colloidal silica-dispersed MEK solution in which surface organically modified colloidal silica particles having a primary particle diameter of 15 nm are dispersed in MEK, and the concentration of the silica particles is 40% by weight ) Was added while distilling off MEK using an evaporator to obtain colloidal silica-dispersed MMA. Next, MMA and MA are added to the obtained colloidal silica-dispersed MMA, and the composition of the finally obtained colloidal silica monomer dispersion is MMA 89.1 parts by mass, MA 0.9 parts by mass, colloidal silica 10 It prepared so that it might become 0.0 mass part. This was designated as colloidal silica monomer dispersion (S-3).

[Production Example 2: Colloidal silica monomer dispersion (S-4)]
The composition of the finally obtained colloidal silica monomer dispersion was 79.2 parts by mass, 0.8 parts by mass of MA, and 20.0 parts by mass of colloidal silica. A colloidal silica monomer dispersion (S-4) was obtained.

[Production Example 3: Dispersant (D-1)]
Supply 900 parts by weight of deionized water, 60 parts by weight of sodium 2-sulfoethyl methacrylate, 10 parts by weight of potassium methacrylate, and 12 parts by weight of MMA to a flask equipped with a stirrer, thermometer and condenser, and discharge nitrogen. The flask was heated so that the internal temperature of the flask was 50 ° C. Thereafter, 0.08 part by mass of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was supplied, and the flask was heated so that the internal temperature of the flask became 60 ° C. Then, MMA was dripped for 75 minutes at the speed | rate of 0.24 mass part / min using the dripping pump. Then, it hold | maintained for 6 hours and obtained the dispersing agent (D-1) (10 mass% of solid content).

[Example 1]
(Step 1) 200 parts by mass of deionized water, 1.25 parts by mass of sodium mono-n-dodecyloxytetraoxyethylene phosphate (manufactured by Toho Chemical Co., Ltd., trade name: RS-610NA) as an emulsifier, EDTA 0.0003 A separable flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, 0.2 parts by mass of sodium formaldehyde sulfoxylate (hereinafter abbreviated as SFS) and 0.0001 parts by mass of ferrous sulfate. The mixture was heated to 75 ° C. with stirring. A mixture of 90 parts by mass of MMA and 10 parts by mass of MA, 0.5 parts by mass of γMPTMS as a surface modifier, and 0.125 parts by mass of TBH as a polymerization initiator was added dropwise over 3 hours. After completion of dropping, the mixture was kept at 75 ° C. for 2 hours to obtain an aqueous dispersion of acrylic resin particles (hereinafter abbreviated as “acrylic resin aqueous dispersion”). The average particle size of this acrylic resin was 94 nm. The number average molecular weight of the acrylic resin was 62,000.

  (Step 2) Next, 125 parts by mass of colloidal silica aqueous dispersion (S-1) (25 parts by mass of silica) was added to the acrylic resin aqueous dispersion in Step 1 while stirring, and held at 75 ° C. for 1 hour. An aqueous dispersion of resin composition particles was obtained. The resin composition particles thus obtained had an average particle size of 109 nm.

  (Step 3) After cooling the reaction system, the aqueous dispersion of the resin composition particles obtained in Step 2 is put into a warm aqueous solution in which 5 parts by mass of calcium acetate is dissolved in 500 parts by mass of warm water, and salted out and solidified. Thus, the powdery resin composition was separated. The obtained powdery resin composition was sufficiently washed with water, and then dried at 90 ° C. for 24 hours using a steam dryer to obtain particles of the powdery resin composition.

(Step 4) Using a biaxial kneading extruder (manufactured by Werner & Pfleiderer, 30 mmφ), the resin temperature during melting is within the range of 240 ± 5 ° C. using particles of the resin composition obtained in step 3 The mixture was melt-kneaded to fit and processed into a pellet.
The pellet-shaped resin composition had a silica content of 20.3% by mass when the total mass of the resin composition was 100 parts by mass.
Table 2 shows the evaluation results of the obtained pellet-shaped resin composition.
[Example 2]
A resin composition was obtained in the same manner as in Example 1 except that in Step 2 of Example 1, the colloidal silica aqueous dispersion (S-1) was changed to 214 parts by mass (silica content: 43 parts by mass). The evaluation results of the obtained resin composition are shown in Table 2.
[Example 3]
When mixing the acrylic resin aqueous dispersion and the colloidal silica aqueous dispersion (S-1) in Step 2 of Example 1, with the exception of adding 2.5 parts by mass of DMDMS as a surface modifier, Example 1 and Similarly, a resin composition was obtained. The evaluation results of the obtained resin composition are shown in Table 2.
[Example 4]
Example 2 except that, when mixing the acrylic resin aqueous dispersion and the colloidal silica aqueous dispersion (S-1) in Step 2 of Example 1, 2.5 parts by mass of TMES was added as a surface modifier. In the same manner as in Example 1, a resin composition was obtained. The evaluation results of the obtained resin composition are shown in Table 2.
[Example 5]
A resin composition was obtained in the same manner as in Example 1 except that γMPMDMS was used in place of γMPTMS as the surface modifier when the acrylic resin aqueous dispersion was produced in Step 1 of Example 1. The evaluation results of the obtained resin composition are shown in Table 2.
[Example 6]
When producing an acrylic resin aqueous dispersion in Step 1 of Example 1, 0.5 parts by mass of nOcSH was added without using γMPTMS, and in Step 2, an acrylic resin aqueous dispersion and a colloidal silica aqueous dispersion ( A resin composition was obtained in the same manner as in Example 1 except that 1.25 parts by mass of DMDMS was added as a surface modifier when mixing S-1). The evaluation results of the obtained resin composition are shown in Table 2.
[Example 7]
A resin composition was obtained in the same manner as in Example 6 except that the surface modifying agent DMDMS was changed to 2.5 parts by mass in Step 2. The evaluation results of the obtained resin composition are shown in Table 2.
[Example 8]
Except having used 62.5 mass parts (25 mass parts of silica contents) of colloidal silica aqueous dispersion liquid (S-2) instead of 125 mass parts of colloidal silica aqueous dispersion liquid (S-1) at the process 2 of Example 1. FIG. A resin composition was obtained in the same manner as in Example 1. The evaluation results of the obtained resin composition are shown in Table 2.
[Example 9]
A resin composition was obtained in the same manner as in Example 8, except that the colloidal silica aqueous dispersion (S-2) in Step 2 was changed to 107.5 parts by mass (silica content 43 parts by mass). The evaluation results of the obtained resin composition are shown in Table 2.
[Example 10]
A resin composition was obtained in the same manner as in Example 8 except that when the acrylic resin aqueous dispersion was produced in Step 1, the surface modifier γMPTMS was changed to 1.0 part by mass. The evaluation results of the obtained resin composition are shown in Table 2.
[Example 11]
A resin composition was obtained in the same manner as in Example 8 except that when the acrylic resin aqueous dispersion was produced in Step 1, the surface modifier γMPTMS was changed to 0.25 parts by mass. The evaluation results of the obtained resin composition are shown in Table 2.

[Example 12]
A resin composition was obtained in the same manner as in Example 8, except that 99 parts by mass of MMA and 1.0 part by mass of MA were used as monomer raw materials when the acrylic resin aqueous dispersion was produced in Step 1. The evaluation results of the obtained resin composition are shown in Table 2.

[Comparative Example 1]
200 parts by mass of deionized water and 0.42 parts by mass of sodium sulfate were supplied to a separable flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas introduction pipe, and stirred at a stirring speed of 320 rpm for 15 minutes. Thereafter, 99 parts by mass of MMA and 1 part by mass of MA as monomer raw materials, 0.28 parts by mass of AMBN as a polymerization initiator, and 0.3 parts by mass of nOcSH as a chain transfer agent were supplied to a separable flask and stirred for 5 minutes. Thereafter, 0.672 parts by mass of the dispersant (D-1) was supplied to the separable flask and stirred to disperse the monomer mixture in the separable flask in water. Thereafter, nitrogen gas was discharged for 15 minutes.
Then, it heated so that the internal temperature of a separable flask might be 75 degreeC, and the temperature was hold | maintained until the polymerization exothermic peak was observed. After the polymerization exothermic peak was observed, the separable flask was heated to an internal temperature of 90 ° C. and held for 60 minutes to complete the polymerization. Thereafter, the mixture in the separable flask was filtered, the filtrate was washed with deionized water, and dried at 90 ° C. for 24 hours using a steam dryer to obtain acrylic resin beads.
The obtained acrylic resin beads were melt-kneaded using a twin-screw kneading extruder and processed into pellets. In the melt-kneading, the temperature of the acrylic resin was adjusted to 240 ± 5 ° C. Table 2 shows the evaluation results of the obtained pellet-shaped acrylic resin.

[Comparative Example 2]
When producing an acrylic resin aqueous dispersion in Step 1 of Example 1, a resin composition was obtained in the same manner as in Example 1 except that 0.2 parts by mass of nOcSH was added without using the surface modifier γMPTMS. It was. The evaluation results of the obtained resin composition are shown in Table 2.
[Comparative Example 3]
Resin in the same manner as in Example 8 except that the resin temperature during melting was within the range of 260 ± 5 ° C. when the resin composition was melt-kneaded using a twin-screw kneading extruder in Step 4. A composition was obtained. The evaluation results of the obtained resin composition are shown in Table 2.

[Example 13]
300 parts by mass of deionized water and 0.63 parts by mass of sodium sulfate were supplied to a separable flask equipped with a stirrer, a thermometer, a cooling pipe and a nitrogen gas introduction pipe and stirred for 15 minutes at a stirring speed of 320 rpm. Thereafter, 100 parts by mass of colloidal silica monomer dispersion (S-3), 0.15 parts by mass of AMBN and 0.2 parts by mass of nOcSH were supplied to the separable flask and stirred for 5 minutes. Thereafter, 1.008 parts by mass of the dispersant (D-1) was supplied to the separable flask and stirred, and the monomer mixture in the separable flask was dispersed in water. Thereafter, nitrogen gas was discharged for 15 minutes.
Then, it heated so that the internal temperature of a separable flask might be 75 degreeC, and the temperature was hold | maintained until the polymerization exothermic peak was observed. After the polymerization exothermic peak was observed, the separable flask was heated to an internal temperature of 90 ° C. and held for 60 minutes to complete the polymerization. Thereafter, the mixture in the separable flask was filtered, the filtrate was washed with deionized water, and dried at 90 ° C. for 24 hours using a steam dryer to obtain beads of a resin composition. The silica content of the beads of the resin composition was 10.3% by mass.
The resin composition beads were melt-kneaded using a twin-screw kneading extruder so that the resin temperature during melting was within a range of 240 ± 5 ° C., and processed into pellets. Table 2 shows the evaluation results of the obtained pellet-shaped resin composition.

[Example 14]
A resin composition was obtained in the same manner as in Example 13 except that (S-4) was used as a monomer dispersion of colloidal silica. The evaluation results of the obtained resin composition are shown in Table 2.

Since the resin composition of Comparative Example 1 did not contain colloidal silica (B), the molded article had poor scratch resistance.
Since the resin composition of Comparative Example 2 did not use a surface modifier, the molded article had poor transparency.
Since the kneading temperature of the process 4 was high, the resin composition of the comparative example 3 had low melt fluidity of the resin composition. Moreover, the transparency and scratch resistance of the molded product were inferior.

The resin composition obtained in the present invention has excellent transparency and scratch resistance, and can be used for optical materials, vehicle parts, lighting materials, building materials, etc. Among them, it can be particularly suitably used for a vehicle lamp cover, and among them, a vehicle headlamp cover.
In addition, since it has a melt fluidity suitable for melt molding, it can be a molding material that can be suitably used for injection molding, extrusion molding, pressure molding (press molding), compressed air molding, vacuum molding, and the like. it can.

Claims (17)

A resin composition for a vehicle lamp cover comprising an acrylic resin (A) and colloidal silica (B),
The acrylic resin (A) contains 50% by mass or more of methyl (meth) acrylate units with respect to the total mass of the acrylic resin (A),
The resin composition for a vehicle lamp cover is 30 to 99 parts by mass of the acrylic resin (A) and 1 to 70 parts by mass of the colloidal silica (B) with respect to 100 parts by mass of the total mass of the resin composition for a vehicle lamp cover. Part, and
The haze value is 5.0% or less, and
A resin composition for a vehicle lamp cover, having a shear viscosity of 500 Pa · sec or less measured at a shear rate of 1000 sec ⁻¹ at 240 ° C. The acrylic resin (A) has a total content of the homopolymer of methyl methacrylate or a repeating unit derived from methyl methacrylate with respect to the total mass of the acrylic resin (A). The resin composition for a vehicle lamp cover according to claim 1, which is a methyl methacrylate copolymer that is 70% by mass or more and less than 100% by mass. The resin composition for a vehicle lamp cover according to claim 1 or 2, wherein the particles of the colloidal silica (B) are surface-treated with a surface modifier. The resin composition for a vehicle lamp cover according to claim 3, wherein the surface modifier contains at least one of a polydimethylsiloxane compound and an alkoxysilane compound having a mercapto group. The resin composition for a vehicle lamp cover according to any one of claims 1 to 4, wherein the colloidal silica (B) has an average primary particle diameter of 1 to 30 nm. The resin composition for vehicle lamp covers as described in any one of Claims 1-5 whose haze value after the abrasion process using steel wool is 30.0% or less. The resin composition for vehicle lamp covers as described in any one of Claims 1-6 whose yellow index measured based on ISO17223 is 15 or less. The molded article for vehicle lamp covers formed by shape | molding the resin composition for vehicle lamp covers as described in any one of Claims 1-7. In a cross section in the thickness direction of the vehicle lamp cover molded body, an arbitrary region on an observation image of a transmission electron microscope, which is observed at an arbitrary position within a range from the surface of the molded body to a depth of 1 μm × 100 nm × The molded article for a vehicle lamp cover according to claim 8, wherein five or more colloidal silica (B) are observed in a range of 100 nm. Of the colloidal silica (B) observed on the observation image of the transmission electron microscope, observed at an arbitrary position within the range from the surface of the molded body to a depth of 1 μm within the cross section in the thickness direction of the molded body. The molded article for a vehicle lamp cover according to claim 8 or 9, wherein the maximum distance between the primary particles is 100 nm or less. The vehicle lamp cover formed by shape | molding the resin composition for vehicle lamp covers as described in any one of Claims 1-7. The laminated body for vehicle lamp covers formed by laminating | stacking the molded object for vehicle lamp covers as described in any one of Claims 8-10 on the surface of a thermoplastic resin base material. The vehicle lamp cover formed by laminating | stacking the molded object for vehicle lamp covers as described in any one of Claims 8-10 on the surface of a thermoplastic resin base material. A method for producing a resin composition for a vehicle lamp cover,
Kneading a mixture containing acrylic resin (A) and colloidal silica (B) so that the temperature of the resin composition during kneading is in the range of 230 ° C. or higher and 250 ° C. or lower; and
The acrylic resin (A) contains 50% by mass or more of methyl (meth) acrylate units with respect to the total mass of the acrylic resin (A),
The mixture includes 30 to 99 parts by mass of the acrylic resin (A) and 1 to 70 parts by mass of the colloidal silica (B) with respect to 100 parts by mass of the total mass of the mixture.
The colloidal silica (B) is surface-treated with a surface modifier,
Kneading the obtained resin composition for a vehicle lamp cover so that the shear viscosity measured at a shear rate of 1000 sec ⁻¹ at 240 ° C. is 500 Pa · sec or less,
A method for producing a resin composition for a vehicle lamp cover.   The vehicle lamp according to claim 14, wherein the mixture includes 50 to 90 parts by mass of the acrylic resin (A) and 10 to 50 parts by mass of the colloidal silica (B) with respect to 100 parts by mass of the total mass of the mixture. A method for producing a resin composition for a cover. The method for producing a resin composition for a vehicle lamp cover according to claim 14 or 15, wherein the surface modifier contains at least one of a polydimethylsiloxane compound and an alkoxysilane compound having a mercapto group. The method for producing a resin composition for a vehicle lamp cover according to any one of claims 14 to 16, comprising at least one of the following step 1 and step 2 when obtaining the mixture.
Process 1) The process of mixing the aqueous dispersion of colloidal silica (B), after manufacturing the aqueous dispersion of an acrylic resin (A) in presence of a surface modifier.
Step 2) A step of adding a surface modifier when mixing the aqueous dispersion of acrylic resin (A) and the aqueous dispersion of colloidal silica (B).