JP7239436B2 - Two-color molding manufacturing method - Google Patents

Description

The present invention relates to a method for producing a two-color molding.

BACKGROUND ART Conventionally, molded articles such as hard-coated polycarbonate and ABS resin, and jet-black painted ASA and ABS resin have been used for interior and exterior parts of automobiles. However, the hard coat treatment (HC treatment) has problems such as defects due to the occurrence of coat spots and low productivity. Against the background of these problems, from the viewpoint of cost reduction, moldings that do not require HC treatment or painting have been desired, and the use of compounds to replace resins has been actively studied in recent years.

Among them, methacrylic resins are mainly considered as thermoplastic resins. The reason for this is that methacrylic resins have excellent weather resistance, belong to the class with the highest surface hardness among resins, and are excellent in appearance.

However, methacrylic resins tend to have lower mechanical strength than other resins, and are not currently used as front and side decorative parts for automotive interiors and exteriors. Therefore, a two-color molded body is known in which a methacrylic resin is used for the surface layer of the molded body and the base layer is reinforced with a different resin. Also, by using a methacrylic resin for the surface layer, it is possible to develop a glossy and high-quality appearance.

However, when two-color molding is performed, warpage may occur. When a warped part is installed in an automobile, the warp is forcibly corrected before installation in order to obtain an appropriate shape. In that case, there is a problem that defects such as cracks are likely to occur in the market.
In order to eliminate this warpage, for example, Patent Literature 1 defines a range in which warpage is small by the ratio of the linear expansion coefficient to the molding shrinkage.
Further, Patent Document 2 describes a method of molding a transparent portion after molding a frame portion.

JP 2008-94087 A JP-A-2003-320548

However, Patent Document 1 specifies only the molding shrinkage rate of the frame portion that is injection molded later, and does not consider the molding shrinkage rate of the design portion that is injection molded first. Further, in Patent Document 2, the percentage of holes in the frame portion is 50% or more, and a shape that is originally resistant to warping is adopted.

Under such circumstances, in view of the above-mentioned problems of the prior art, the present invention aims to provide a two-color molded article that does not require painting or HC, has a low environmental load, suppresses warpage, etc., and has an excellent appearance. aim.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that it is possible to solve problems related to appearance such as warpage of two-color moldings, and have completed the present invention.

That is, the present invention is as follows.
[1]
It is a two-color molded body in which the base layer is first molded using an amorphous thermoplastic resin and the surface layer is molded later using a methacrylic resin,
A method for producing a two-color molding, characterized by satisfying formula (1).
S1-S2≧0 (1)
(S2: Mold shrinkage rate of the methacrylic resin to be molded later)
(S1: molding shrinkage rate of the amorphous thermoplastic resin to be molded first)
[2]
In the two-color molding,
The method for producing a two-color molded article according to [1] , wherein the ratio of the area of the through holes provided in the underlayer to the area of the underlayer is 25% or less.
[3]
The methacrylic resin contains 70 to 99.9% by mass of methacrylic acid ester monomer units and 0.1 to 30% by mass of at least one vinyl monomer copolymerizable with the methacrylic acid ester [1] Or the method for producing a two-color molded article according to [2] .
[4]
The weight average molecular weight of the methacrylic resin measured by gel permeation chromatography (GPC) is 50000 to 300000,
The ratio of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) obtained from the GPC elution curve of the methacrylic resin is 6 to 50 with respect to the total area of the GPC elution curve of the methacrylic resin. % .
[5]
The amorphous thermoplastic resin to be molded first is polycarbonate resin, ABS resin (acrylonitrile, butadiene-styrene copolymer), AS resin (acrylonitrile, styrene copolymer), MBS resin (methyl methacrylate, butadiene/styrene copolymer), AAS resin (acrylonitrile, acrylic rubber, styrene copolymer), ASA resin (acrylonitrile, styrene, acrylic rubber copolymer), impact-resistant methacrylic resin and AES The method for producing a two-color molded article according to any one of [1] to [4] , wherein the resin is one or more selected from the group consisting of system resins (acrylonitrile, ethylene-propylene-diene, styrene).
[6]
The method for producing a two-color molded article according to any one of [1] to [5] , wherein the amorphous thermoplastic resin to be molded first has a VICAT softening temperature of 95° C. or higher.
[7]
The method for producing a two-color molded article according to any one of [1] to [6] , wherein the amorphous thermoplastic resin to be molded first is a thermoplastic resin composition containing a flame retardant and/or a colorant.
[8]
The method for producing a two-color molded article according to any one of [1] to [7] , wherein the thickness t1 of the surface layer and the thickness t2 of the underlayer satisfy formula (3).
0.2≦t1/t2≦4 (3)
[9]
The method for producing a two-color molded product according to any one of [1] to [8] , wherein the two-color molded product is a design material for automobiles.
[ 10 ]
[ 9] .
[ 11 ]
The method for producing a two-color molded product according to any one of [1] to [8] , wherein the two-color molded product is office equipment or home appliances.

According to the present invention, it is possible to provide a two-color molded article that does not require painting or HC, has a low environmental load, is suppressed in warping, and has an excellent appearance.

1 is a perspective view showing the entire two-color molding for evaluation used in Examples and Comparative Examples. FIG. FIG. 2 is a cross-sectional view of the two-color molded product for evaluation shown in FIG. 1 taken along the line AA. FIG. 4 is a perspective view showing a pin gate position when forming an underlying layer first in Examples and Comparative Examples. FIG. 10 is a perspective view showing a gate position in the case of one side gate when forming a surface layer later in Examples and Comparative Examples. FIG. 10 is a perspective view showing gate positions in the case of two side gates when forming a surface layer later in Examples and Comparative Examples. FIG. 10 is a perspective view showing the gate position of the one-point side gate when forming the surface layer first in Examples and Comparative Examples. FIG. 10 is a perspective view showing the gate position of a one-point side gate when forming an underlying layer later in Examples and Comparative Examples; FIG. 3 is a perspective view showing how two two-color molded bodies are welded together in Examples and Comparative Examples.

EMBODIMENT OF THE INVENTION Hereinafter, the form (henceforth "this embodiment") for implementing this invention is demonstrated in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be modified appropriately within the scope of its gist.
In this specification, a monomer component before polymerization is referred to as "-monomer" and may be simply referred to as "monomer". Further, a structural unit constituting a polymer is referred to as "-monomer unit", and sometimes simply written as "-unit".

<Method for producing two-color molding>
The method for producing a two-color molded body of the present embodiment satisfies formula (1).
S1-S2≧0 (1)
(S2: molding shrinkage rate of thermoplastic resin to be molded later)
(S1: molding shrinkage rate of thermoplastic resin to be molded first)

That is, in the present embodiment, the thermoplastic resin S1 to be molded first is the same as the molding shrinkage rate S2 of the thermoplastic resin to be injection-molded later, or the molding shrinkage rate S1 of the thermoplastic resin to be injection-molded later. should be greater than

Since the warp of the previously molded product is suppressed to some extent by the resin to be molded later, the warp of the final product becomes smaller as the shrinkage ratio S2 of the resin to be molded later is smaller. If S1 is smaller than S2, the warp of the molded product to be molded later becomes large.
From the viewpoint of easily obtaining the effect of the present invention, it is preferable that S1 is larger than S2 by 0.1 to 2.0%. Further, it is more preferable that S1 is greater than S2 by 0.1 to 1.5%. Furthermore, it is even more preferred that S1 is 0.1-1.0% greater than S2. Most preferably, S1 is 0.1-0.5% greater than S2.
As long as the relationship between S1 and S2 above is satisfied, the same phenomenon as described above will occur with respect to the warpage of a molded product that has been two-color molded. No restrictions. Both are preferably combinations of amorphous resins.

As long as the relationship between the above S1 and S2 is satisfied, the same phenomenon as described above will occur with respect to the warpage of the two-color molded product. There are no restrictions on combinations. Both are preferably combinations of amorphous resins.

The surface layer of the two-color molding of the present embodiment is not particularly limited, but it is preferable to use a methacrylic resin that is excellent in surface hardness and weather resistance. However, when the methacrylic resin is a single layer, it has excellent surface hardness and weather resistance, but is weak in strength, so it cannot be used for parts that require strength.
In order to improve the strength of the two-color molded product, it is preferable to use a thermoplastic resin for the base layer of the two-color molded product. In addition, in the case of a thermoplastic resin single layer, although the strength is high, the surface hardness is low, and a hard coat treatment is required. In addition, it is not preferable because it has poor weather resistance and easily discolors. Further, the thicker the base layer using the thermoplastic resin, the higher the strength. Two-color molding of methacrylic resin and thermoplastic resin enables the realization of products with high strength, hardness, and weather resistance.

In the method for producing a two-color molded body of the present embodiment, a thermoplastic resin is used as the thermoplastic resin to be molded first to form a base layer, and a thermoplastic resin to be molded later is a methacrylic resin to form a surface layer. preferably.

The two-color molded article of the present embodiment can be less warped by first molding the thermoplastic resin and then molding the methacrylic resin. Therefore, it is preferable to use a thermoplastic resin for the base layer that is molded first, and a methacrylic resin for the surface layer that is molded later.

As for the molding order of the two-color molding, it is preferable to first injection mold the thermoplastic resin and then mold the methacrylic resin. Since the methacrylic resin has a lower molding shrinkage rate than the thermoplastic resin, it is preferable to mold the methacrylic resin afterward because the warp can be reduced.

A methacrylic resin is preferably used for the surface layer of the two-color molded article of the present embodiment. It is preferable to use a methacrylic resin for the surface layer because the surface hardness and weather resistance of the product are excellent. It is preferable to use a thermoplastic resin for the underlayer. It is preferable to use a thermoplastic resin for the underlayer because the strength of the two-color molding is improved.

The molding shrinkage of the thermoplastic resin used for the two-color molding of this embodiment may be measured according to JIS K7152-4.
Specifically, it may be measured according to the following procedure.
- A flat plate mold (100 mm x 100 mm x 3 mmt, gate: central part of 100 mm side, side gate) is molded under the following molding conditions.
・Injection conditions Molding machine: EC100SX (manufactured by Toshiba Machine)
Mold temperature: VICAT softening temperature of the resin -40 ± 10 ° C (when the VICAT softening temperature of the resin is less than 120 ° C)
VICAT softening temperature of the resin -50±10°C (when the VICAT softening temperature of the resin is 120°C or higher)
Resin temperature: VICAT softening temperature of the resin + 150 ± 10 ° C
Filling speed: 50±20mm/sec
Holding pressure time: 10±3sec
Cooling time: 20±5sec
Molding cycle: 40±10sec
After taking out the molded flat plate, it is left in a desiccator at a temperature of 23±2° C. for 1 hour or more. After removing the flat plate from the desiccator, measure the dimensions of the four sides of the flat plate. The shrinkage rate (%) of each of the four sides was measured from the dimensions of the mold and the flat plate, and the average value of the molding shrinkage rate of the four sides was calculated to obtain the molding shrinkage rate (%).
More specifically, it may be measured by the method described in Examples below.

The warpage of the two-color molded article of this embodiment correlates with the difference in molding shrinkage of each thermoplastic resin. It does not correlate with the difference in linear expansion coefficient of each thermoplastic resin. It also does not correlate with the difference in VICAT softening temperature of each resin.

The two-color molded article of the present embodiment can be produced, for example, as follows, and is preferably produced by a two-color molding method.
First, it is preferable to put a thermoplastic resin composition containing a thermoplastic resin having a VICAT softening temperature of 80° C. or higher in the form of pellets into a mold cavity of an injection molding machine, if necessary. When the two-color molding is used for vehicle interiors and exteriors, it is more preferable to use a thermoplastic resin having a VICAT softening temperature of 95° C. or higher in order to prevent deformation due to heat such as direct sunlight. At this time, it is more preferable to use a mold having a mold cavity having a shape corresponding to the shape of the molded product, and having two or more gates in order to enhance the flow of the resin and reduce the molding strain. In particular, when molding a thermoplastic resin having high heat resistance and mechanical strength, molding with two or more gates is effective. Moreover, the gate type is more preferably a pin gate, a side gate, or the like.

Then, a methacrylic resin composition is injection-molded as a surface layer under predetermined conditions by the injection molding machine. In this case, it is preferable to use a mold having a mold cavity having a shape corresponding to the shape of the molded product and having a one-point gate in order to suppress the occurrence of welds on the surface.

In addition, the position of the gate in the mold is preferably a position in contact with a portion of the finally obtained molded article that is covered by another member and cannot be visually confirmed. Fan gates, tab gates, hot runner valve gates and the like are preferred. In this way, the two-color molding of this embodiment can be obtained.

The length of the two-color molded article is preferably 100 mm or more for obtaining a long molded article. It is more preferably 110 mm or more, and even more preferably 120 mm or more.

The mold temperature during injection molding of the surface layer is preferably adjusted to a range of VICAT-65°C to VICAT-5°C with respect to the VICAT softening temperature of the methacrylic resin to be molded. The mold temperature is more preferably in the range of VICAT-60°C to VICAT-10°C, more preferably in the range of VICAT-55°C to VICAT-15°C, and most preferably in the range of VICAT-50°C to It is in the range of VICAT-20°C. By adjusting the content within this range, it is possible to obtain a two-color molded article having an excellent appearance.

When a polycarbonate-based resin is used as the thermoplastic resin, the mold temperature during injection molding of the polycarbonate-based resin is adjusted to a range of VICAT-110°C to VICAT-20°C relative to the VICAT softening temperature of the polycarbonate-based resin. is preferred. The mold temperature is more preferably in the range of VICAT-100°C to VICAT-30°C, and more preferably in the range of VICAT-90°C to VICAT-40°C. By adjusting the content within this range, it is possible to obtain a two-color molded article having an excellent appearance.

When an ABS resin is used as the thermoplastic resin, the mold temperature during injection molding of the ABS resin is adjusted to a range of VICAT-75°C to VICAT-5°C relative to the VICAT softening temperature of the ABS resin. is preferred. The mold temperature is more preferably in the range of VICAT-70°C to VICAT-10°C, more preferably in the range of VICAT-65°C to VICAT-15°C, and most preferably in the range of VICAT-60°C to It is in the range of VICAT-20°C. By adjusting the content within this range, it is possible to obtain a two-color molded article having an excellent appearance.

When a polymer alloy of a polycarbonate resin and an ABS resin (PC/ABS resin) is used as the thermoplastic resin, the mold temperature during injection molding of the polymer alloy of the polycarbonate (PC) resin and the ABS resin is It is preferable to adjust the softening temperature of the PC/ABS resin to be molded within the range of VICAT-100°C to VICAT-10°C. The mold temperature is more preferably in the range of VICAT-90°C to VICAT-15°C, and more preferably in the range of VICAT-80°C to VICAT-20°C. By adjusting the content within this range, it is possible to obtain a two-color molded article having an excellent appearance.

In addition, in the manufacturing method of the present embodiment, in addition to two-color molding in which another layer is continuously molded by rotating the movable mold after molding one layer, a molded body having a separately molded layer is molded. Insert molding can also be performed in which a mold is fitted to additionally mold another layer.

<Two-color molding>
The two-color molded article of the present embodiment manufactured by the method for manufacturing a two-color molded article of the present embodiment will be described below.
The two-color molded article of the present embodiment may include a surface layer and a base layer, and may further include layers other than these layers.

Each component constituting the surface layer and the base layer of the two-color molded article of the present embodiment will be described below.

[Methacrylic resin]
Details of the methacrylic resin contained in the surface layer are described below.
The methacrylic resin, even if it is a homopolymer consisting of methacrylic acid ester monomer units (monomer units derived from "methacrylic acid ester monomer"), the methacrylic acid ester monomer unit and the It may be a copolymer containing other vinyl monomer units copolymerizable with methacrylic acid ester monomers (monomer units derived from "another vinyl monomer"). Among these, copolymers are preferred.

（一般式（Ｉ）中、Ｒ₁は炭素原子が１～１８個からなる炭化水素基であって、該炭化水素基の炭素上の水素原子は水酸基やハロゲン基によって置換されていてもよい。） (Methacrylate ester monomer)
The methacrylic acid ester monomer is not particularly limited as long as it can achieve the effects of the present invention, but preferred examples thereof include monomers represented by the following general formula (I).

(In general formula (I), R ₁ is a hydrocarbon group having 1 to 18 carbon atoms, and the hydrogen atoms on the carbon atoms of the hydrocarbon group may be substituted with a hydroxyl group or a halogen group. )

The methacrylate monomer is not particularly limited, but examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and methacryl. acid (2-ethylhexyl), methacrylic acid (t-butylcyclohexyl), benzyl methacrylate, methacrylic acid (2,2,2-trifluoroethyl) and the like. Among these, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and the like are more preferable, and methyl methacrylate is particularly preferable, from the viewpoint of ease of handling and availability. The methacrylic acid ester monomers may be used singly or in combination of two or more.

When the methacrylic resin is a copolymer, the content of the methacrylic acid ester monomer unit is preferably 70 to 99.9% by mass, more preferably 80 to 99.9% by mass, based on the total amount of the methacrylic resin. 99.5% by mass, more preferably 85 to 99% by mass. Most preferably it is 90 to 98% by mass. When the content of the methacrylic acid ester monomer unit is 70% by mass or more, the heat resistance tends to be further improved. Further, when the content of the methacrylic acid ester monomer unit is 99.9% by mass or less, the fluidity tends to be further improved.

（一般式（ＩＩ）中、Ｒ₂は炭素原子が１～１８個からなる炭化水素基であって、該炭化水素基の炭素上の水素原子が水酸基やハロゲン基によって置換されていてもよい。） (other vinyl monomers)
The other vinyl monomer is not particularly limited, but a preferable example thereof is an acrylic acid ester monomer represented by the following general formula (II).

(In general formula (II), R ₂ is a hydrocarbon group having 1 to 18 carbon atoms, and the hydrogen atoms on the carbon atoms of the hydrocarbon group may be substituted with a hydroxyl group or a halogen group. )

The acrylic ester monomer is not particularly limited, but examples include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, phenyl acrylate, acrylic acid (2-ethylhexyl), acrylic acid (t-butylcyclohexyl), benzyl acrylate, acrylic acid (2,2,2-trifluoroethyl) and the like. Among these, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, and the like are more preferred, and methyl acrylate is particularly preferred, from the viewpoint of ease of handling and availability.

In addition, the vinyl monomer other than the acrylic acid ester monomer represented by the general formula (II), which can be copolymerized with the methacrylic acid ester monomer, is not particularly limited, but examples include acrylic acid and α,β-unsaturated acids such as methacrylic acid; unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid, itaconic acid and cinnamic acid, and their alkyl esters; styrene, o-methylstyrene, m-methylstyrene , p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p -Styrenic monomers such as tert-butylstyrene and isopropenylbenzene (α-methylstyrene); 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenyltoluene, isopropenylethylbenzene, isopropenyl Aromatic vinyl compounds such as propylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; maleic anhydride, itaconic anhydride, etc. Unsaturated carboxylic anhydrides; maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, N-substituted maleimide such as N-cyclohexylmaleimide; amides such as acrylamide and methacrylamide; ethylene glycol di( meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, etc. Esterified with acrylic acid or methacrylic acid on both terminal hydroxyl groups of ethylene glycol or oligomers thereof ; Neopentyl glycol di (meth) acrylate, di (meth) acrylate, etc. esterified hydroxyl groups of two alcohols with acrylic acid or methacrylic acid; or those esterified with methacrylic acid; polyfunctional monomers such as divinylbenzene; and the like.

Other vinyl monomers such as vinyl monomers other than the acrylic acid ester monomer represented by the general formula (II) and the acrylic acid ester monomer represented by the general formula (II) , may be used alone or in combination of two or more.

The content of monomer units derived from other vinyl monomers is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, based on the total amount of the methacrylic resin. more preferably 1.0 to 15% by mass, particularly preferably 1.5 to 12% by mass. Most preferably, it is 2.0 to 10% by mass. When the content of monomer units derived from other vinyl monomers is 0.1% by mass or more, fluidity and heat resistance tend to be further improved. Moreover, when the content of monomer units derived from other vinyl monomers is 20% by mass or less, the heat resistance tends to be further improved.

In the methacrylic resin, for the purpose of improving properties such as heat resistance and workability, a vinyl monomer other than the vinyl monomers exemplified above may be appropriately added and copolymerized.

(Weight average molecular weight and molecular weight distribution of methacrylic resin)
The weight average molecular weight and molecular weight distribution of the methacrylic resin will be described.

The weight average molecular weight (Mw) of the methacrylic resin measured by gel permeation chromatography (GPC) is preferably 50,000 to 300,000. When the weight average molecular weight of the methacrylic resin is within the above range, it is possible to achieve a balance between fluidity, mechanical strength, and solvent resistance, and tends to maintain good moldability. In particular, from the viewpoint of obtaining excellent mechanical strength and solvent resistance, the weight average molecular weight (Mw) of the methacrylic resin is preferably 50,000 or more, more preferably 60,000 or more, even more preferably 70,000 or more, and even more preferably 80,000 or more. Preferably, 90,000 or more is even more preferable. Further, from the viewpoint that the methacrylic resin exhibits good fluidity, the weight average molecular weight (Mw) of the methacrylic resin is preferably 300,000 or less, more preferably 250,000 or less, even more preferably 230,000 or less, and further preferably 210,000 or less. More preferably, 180,000 or less is even more preferable.

The molecular weight distribution (Mw/Mn) of the methacrylic resin is preferably 1.6 to 6.0, more preferably 1.7 to 5.0, still more preferably 1.8 to 5.0. . When the molecular weight distribution of the methacrylic resin is within the above range, there is a tendency that the balance between molding flow and mechanical strength is more excellent. Here, Mw represents the weight average molecular weight and Mn represents the number average molecular weight.
Methods for controlling the molecular weight distribution of methacrylic resins include a method of stepwise addition of a chain transfer agent or iniferter during production of the methacrylic resin described later, and a method of separately polymerizing and melt-blending the low-molecular-weight component and the high-molecular-weight component. methods and the like.

The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the methacrylic resin can be measured by GPC, and specifically, by the method described in Examples below.
Specifically, a standard methacrylic resin that has a known monodisperse weight-average molecular weight and is available as a reagent, and an analytical gel column that first elutes high-molecular-weight components are used to create a calibration curve from the elution time and weight-average molecular weight. Subsequently, based on the calibration curve obtained, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin to be measured can be obtained. A molecular weight distribution can be calculated from the obtained weight average molecular weight (Mw) and number average molecular weight (Mn). The number average molecular weight (Mn) is the average molecular weight per simple molecule and is defined as the total weight of the system/number of molecules in the system. Weight average molecular weight (Mw) is defined as the average molecular weight by weight fraction.

(Proportion of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp))
From the viewpoint of solvent resistance and fluidity, the ratio of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) obtained from the GPC elution curve of the methacrylic resin is the total area of the GPC elution curve of the methacrylic resin. , preferably 6 to 50%, more preferably 7 to 45%, still more preferably 8 to 43%, even more preferably 9 to 40%, still more preferably 10 to 38%. When the ratio of the component having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) in the methacrylic resin is 6% or more, molding fluidity is further improved and warpage tends to be reduced. Moreover, since the proportion of the component having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) in the methacrylic resin is 50% or less, the solvent resistance tends to be further improved.
Here, "proportion (%) of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp)" is the peak top molecular weight (Mp) when the total area area of the GPC elution curve is 100% It is the ratio of the area area corresponding to the component having a molecular weight of 1/5 or less of , and can be measured by the method described in the examples below. In addition, "peak top molecular weight (Mp)" refers to the weight molecular weight showing a peak in the GPC elution curve. When there are multiple peaks in the GPC elution curve, the molecular weight at the peak indicated by the weight molecular weight with the highest abundance is defined as the peak top molecular weight (Mp).
The methacrylic resin component having a weight-average molecular weight of 500 or less is preferably as small as possible in order to prevent occurrence of a foam-like appearance defect called silver during molding.

(Moisture percentage)
The moisture content of the methacrylic resin is preferably 0.01 to 1.0% by mass with respect to 100% by mass of the methacrylic resin. Since injection molding is performed at 260° C., the initial moisture content is about 0.01 to 0.1% by mass. Also, when left in a high-temperature, high-humidity environment in summer, the moisture content of the methacrylic resin may increase to about 1.0% by mass, but this is preferable because there is little change in warpage.
Moreover, the moisture content of the methacrylic resin before molding is preferably 0.01 to 0.15% by mass. If the moisture content exceeds 0.15% by mass, silver defects (flash-like defects) tend to occur during molding, which is not preferable. More preferably, it is 0.01 to 0.1% by mass.

(spiral length)
The spiral length of the methacrylic resin is preferably 20 to 55 cm, more preferably 22 to 50 cm. More preferably, it is 24 to 45 cm. If the spiral length of the methacrylic resin is less than 20 cm, the fluidity is poor and injection molding becomes difficult, which is not preferable. If the spiral length of the methacrylic resin exceeds 55 cm, it is necessary to lower the molecular weight or lower the heat resistance in order to increase the fluidity, and the strength and heat resistance of the product cannot be maintained, which is not preferable.
Specifically, the spiral length may be measured according to the following procedure.
・Under the following molding conditions, methacrylic resin is poured into a cavity having a constant cross-sectional area and a spiral shape, and the relative fluidity is determined by the distance that the resin has flowed.
・Injection conditions Injection molding machine: Toshiba Machine EC100SX
Mold for measurement: A mold in which a groove with a depth of 2 mm and a width of 10 mm is dug in the surface of the mold in an Archimedean spiral shape from the center of the surface Resin temperature: 250 ± 5 ° C.
Mold temperature: 60±5℃
Injection pressure: 75MPa
Injection time: 10 sec
Cooling time: 20 sec
The resin is injected into the center of the mold surface under the above conditions, and after molding, the spiral molded product is taken out and the length of the spiral portion is measured.
More specifically, it may be measured by the method described in Examples below.

(Method for producing methacrylic resin)
The methacrylic resin can be produced by bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. Among these, bulk polymerization, solution polymerization and suspension polymerization are preferred, and suspension polymerization is more preferred.

The polymerization temperature may be appropriately selected depending on the polymerization method, and is preferably 50°C or higher and 100°C or lower, more preferably 60°C or higher and 90°C or lower.

A polymerization initiator may be used when producing the methacrylic resin. The polymerization initiator is not particularly limited, but when performing radical polymerization, for example, di-t-butyl peroxide, lauroyl peroxide, decanoyl peroxide, stearyl peroxide, benzoyl peroxide, t-butyl peroxide neodecanate, t-butyl peroxypivalate, dilauroyl peroxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3, Organic peroxides such as 3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane; azo bisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis(1-cyclohexanecarbonitrile), 2,2'-azobis-4-methoxy-2,4-azobisisobutyronitrile, 2,2 '-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-2-methylbutyronitrile, 2-(carbamoyl azo) isobutyronitrile and other azo general radical polymerization initiators; mentioned. These may be used singly or in combination of two or more. A combination of these radical initiators and a suitable reducing agent may be used as a redox initiator.

These radical polymerization initiators and/or redox initiators are generally used in the range of 0 to 1 part by mass with respect to 100 parts by mass of the total amount of all monomers used in the polymerization of the methacrylic resin. It can be appropriately selected in consideration of the polymerization temperature and the half-life of the polymerization initiator.

When a bulk polymerization method, a cast polymerization method, or a suspension polymerization method is selected as the polymerization method for the methacrylic resin, an organic peroxide is used as a polymerization initiator from the viewpoint of preventing coloring of the methacrylic resin. Polymerization is preferred. Examples of such organic peroxides include those mentioned above. Among these, lauroyl peroxide, decanoyl peroxide, and t-butylperoxy-2-ethylhexanoate are preferred. Oxide is more preferred.

Further, when a methacrylic resin is polymerized by a solution polymerization method at a high temperature of 90 ° C. or higher, an organic peroxide and azobis that have a 10-hour half-life temperature of 80 ° C. or higher and are soluble in the organic solvent used It is preferable to use an initiator or the like as the polymerization initiator. Examples of such organic peroxides and azobis initiators include those mentioned above. Among them, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, Oxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 1,1-azobis(1-cyclohexanecarbonitrile), 2-(carbamoylazo)isobutyronitrile and the like are preferred.

When producing a methacrylic resin, the molecular weight of the methacrylic resin may be controlled as necessary. A method for controlling the molecular weight of the methacrylic resin is not particularly limited, but examples thereof include a method of changing the polymerization method or polymerization conditions, a method of selecting a polymerization initiator, a method of adjusting the amount of a chain transfer agent, an iniferter, and the like. . As for these molecular weight control methods, only one method may be used, or two or more methods may be used in combination.

Examples of iniferters include, but are not limited to, dithiocarbamates, triphenylmethylazobenzene, tetraphenylethane derivatives and the like.

Examples of chain transfer agents include, but are not limited to, alkylmercaptans, dimethylacetamide, dimethylformamide, triethylamine, and the like. Among these, alkyl mercaptans are preferable from the viewpoint of handleability and stability. The alkyl mercaptans are not particularly limited, but examples include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan, 2-ethylhexyl thioglyco ethylene glycol dithioglycolate, trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate) and the like.

The chain transfer agent and iniferter can be appropriately added according to the molecular weight of the target methacrylic resin (A), and the molecular weight can be adjusted by adjusting the amount of the chain transfer agent and iniferter added. be. Generally, it is used in the range of 0.001 to 5 parts by weight per 100 parts by weight of the total amount of all monomers used in the polymerization of the methacrylic resin (A).

In addition, as a method for producing a methacrylic resin in which the ratio of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) obtained from the GPC elution curve is in the range of 6 to 50%, low molecular weight methacrylic Examples include a method of melt-blending a system resin and a high-molecular-weight methacrylic resin, and a method of manufacturing by a multistage polymerization method. When producing a methacrylic resin in which the proportion of the component having a molecular weight of 1/5 or less of the above Mp is 6 to 50%, the method is not particularly limited, but from the viewpoint of quality stability It is more preferable to use legal.

When using a multistage polymerization method, first, in the first stage polymerization, a methacrylic acid ester monomer and another vinyl monomer are polymerized, and a polymer having a weight average molecular weight measured by GPC of 5000 to 50000 is obtained. It is preferred to produce (i). Next, the inside of the polymerization system is held at a temperature higher than the polymerization temperature in the first stage for a certain period of time. Thereafter, a methacrylic acid ester monomer and another vinyl monomer are further polymerized in the presence of polymer (i) to produce polymer (ii) having a weight average molecular weight of 60,000 to 350,000. preferable. When the methacrylic resin is a homopolymer, homopolymerization is performed in the first and second stages of polymerization without using other vinyl monomers. Moreover, when the methacrylic resin is a mixture of a homopolymer and a copolymer, homopolymerization can be performed in the first stage polymerization, and copolymerization can be performed in the second stage polymerization.

From the viewpoint of improving the polymerization stability during production, the fluidity of the methacrylic resin, the mechanical strength of the resin molded product, and the relaxation of the molecular orientation on the surface of the molded product, the content of the polymer (i) is The content of the polymer (ii) is preferably 95 to 50% by mass based on the total amount of the methacrylic resin. Considering the balance between polymerization stability, fluidity, mechanical strength of the molded article, and relaxation of molecular orientation on the surface of the molded article, the content ratio of polymer (i)/polymer (ii) is more preferably 7 to 47. % by mass/93 to 53% by mass, more preferably 10 to 45% by mass/90 to 65% by mass, still more preferably 13 to 43% by mass/87 to 57% by mass, still more preferably 15 to 40% by mass/85 to 60% by mass.

Furthermore, the polymer (i) is preferably a polymer containing 80 to 100% by mass of methacrylic acid ester monomer units and 0 to 20% by mass of other vinyl monomer units. It is more preferably a polymer containing 90 to 100% by mass of units and 0 to 10% by mass of other vinyl monomer units, and 95 to 100% by mass of methacrylic acid ester monomer units and other vinyl monomer units. More preferably, the polymer contains 0 to 5% by mass. The ratio of the monomer units constituting the polymer (i) can be adjusted by controlling the amount of the monomers added in the polymerization step of the polymer (i) in the multistage polymerization. Polymer (i) preferably has a lower content of other vinyl monomers, and does not have to contain other vinyl monomers.

In addition, from the viewpoint of suppression of defects such as silver during molding, polymerization stability, and fluidity, the weight average molecular weight of the polymer (i) is preferably 5,000 to 50,000, more preferably 10,000 to 45,000. , more preferably 18,000 to 42,000, and particularly preferably 20,000 to 40,000. As described above, the weight average molecular weight of polymer (i) can be controlled by using a chain transfer agent or iniferter, adjusting the amounts thereof, or appropriately changing the polymerization conditions. The weight average molecular weight of polymer (i) can be measured by GPC in the same manner as described above.

Polymer (ii) is preferably a polymer containing 80 to 99.9% by mass of methacrylic acid ester monomer units and 0.1 to 20% by mass of other vinyl monomer units. More preferably, it is a polymer containing 90 to 99.9% by mass of monomer units and 0.1 to 10% by mass of other vinyl monomer units, and 92.5 to 99.8% by mass of methacrylic acid ester monomer units. More preferably, it is a polymer containing 0.2 to 7.5% by mass of other vinyl monomer units. The ratio of the monomer units constituting the polymer (ii) can be controlled by adjusting the amount of the monomers added in the polymerization step of the polymer (ii) in the multistage polymerization.

From the viewpoint of solvent resistance and fluidity, the weight average molecular weight of polymer (ii) is preferably 60,000 to 350,000, more preferably 100,000 to 320,000, and still more preferably 130,000 to 300,000. , and more preferably 150,000 to 270,000. As described above, the weight average molecular weight of polymer (ii) can be controlled by using a chain transfer agent or iniferter, adjusting the amounts thereof, or appropriately changing the polymerization conditions. The weight average molecular weight of polymer (ii) can be measured by GPC in the same manner as described above.

The multi-stage polymerization method makes it easy to control the respective compositions of the polymer (i) and the polymer (ii), suppresses temperature rise due to polymerization heat generated during polymerization, and stabilizes the viscosity in the system. In this case, the raw material composition mixture of the polymer (ii) may be partially polymerized before the polymerization of the polymer (i) is completed. (maintaining a temperature higher than the polymerization temperature) and adding the raw material composition mixture of the polymer (ii) after completing the polymerization. Curing in the first stage not only completes the polymerization, but also removes or deactivates unreacted monomers, initiators, chain transfer agents, etc., which adversely affects the second stage polymerization. no longer affect. As a result, the target weight average molecular weight can be obtained.

The polymerization temperature may be appropriately selected according to the polymerization method, and is preferably 50° C. or higher and 100° C. or lower, more preferably 60° C. or higher and 90° C. or lower. The polymerization temperatures of polymer (i) and polymer (ii) may be the same or different.
The temperature to be raised during curing is preferably 5° C. or higher, more preferably 7° C. or higher, still more preferably 10° C. or higher than the polymerization temperature of the polymer (i). Furthermore, the time for holding at the elevated temperature during curing is preferably 10 minutes or more and 180 minutes or less, more preferably 15 minutes or more and 150 minutes or less.

(Method for kneading additives and coloring agents)
As a method for obtaining a methacrylic resin composition by kneading the methacrylic resin with various additives and coloring agents described later, for example, a kneader such as an extruder, a heating roll, a kneader, a roller mixer, or a Banbury mixer is used. A method of manufacturing by kneading and the like can be mentioned. In particular, kneading by an extruder is preferable in terms of productivity. In addition, the methacrylic resin composition may be pelletized.
The kneading temperature may follow the preferred processing temperature of the methacrylic resin, and is in the range of 150 to 350°C as a guideline.
After obtaining the methacrylic resin composition, a two-color molding is obtained by performing two-color molding or the like using this. The methacrylic resin composition may be a methacrylic resin alone, or may be a mixture of a methacrylic resin, an additive, a coloring agent, and the like.

[Thermoplastic resin]

The thermoplastic resin used for the underlayer is not particularly limited, but polystyrene resin, polycarbonate resin, syndiotactic polystyrene resin, ABS resin (acrylonitrile, butadiene-styrene copolymer), AS resin (acrylonitrile , styrene copolymer), MBS resin (methyl methacrylate, butadiene-styrene copolymer), AAS resin (acrylonitrile, acrylic rubber, styrene copolymer), ASA resin (acrylonitrile, styrene, acrylic rubber copolymers), AES resins (acrylonitrile, ethylene/propylene/diene, styrene), methacrylic resins, impact-resistant methacrylic resins, biodegradable resins, modified polyphenylene ether resins, and the like. Among these, at least one selected from the group consisting of polycarbonate-based resins, ABS-based resins, AS-based resins, MBS-based resins, AAS-based resins, ASA-based resins, impact-resistant methacrylic-based resins, and AES-based resins is preferable. Polycarbonate-based resins, ABS-based resins, ASA-based resins, and AES-based resins are more preferable from the viewpoint of impact resistance. These may be used individually by 1 type, and may be used in combination of 2 or more types.
The thermoplastic resin may be a polymer alloy in which a plurality of resins are mixed, preferably a polymer alloy containing polycarbonate and ABS resin, and more preferably a polymer alloy containing only polycarbonate and ABS resin.

The VICAT softening temperature of the thermoplastic resin is preferably 80° C. or higher, more preferably 85° C. or higher, and still more preferably 90° C. or higher. When used for the interior and exterior of a vehicle, the temperature is preferably 95° C. or higher in order to prevent deformation due to heat such as direct sunlight.
The VICAT softening temperature can be measured by the method described in Examples below.

(Method for producing thermoplastic resin)
A thermoplastic resin can be produced by a conventional method in the technical field.

(Method for kneading additives and coloring agents)
Examples of methods for obtaining a thermoplastic resin composition by kneading the thermoplastic resin of the underlayer with various additives and colorants described later include kneaders such as extruders, heating rolls, kneaders, roller mixers, and Banbury mixers. A method of kneading and manufacturing using is mentioned. In particular, kneading by an extruder is preferable in terms of productivity. The thermoplastic resin composition may be pelletized.
The kneading temperature may follow the preferred processing temperature of a thermoplastic resin having a VICAT softening temperature of preferably 80°C or higher, and is in the range of 150 to 350°C as a guideline.
After obtaining a thermoplastic resin composition containing a thermoplastic resin, a two-color molded article is obtained by two-color molding using this. The thermoplastic resin composition may be a thermoplastic resin alone, or may be a mixture of a thermoplastic resin, an additive, a coloring agent, and the like.

[Other additives]
If necessary, various other additives may be added to the methacrylic resin and thermoplastic resin that constitute the two-color molded article of the present embodiment.
Examples of the additives include antistatic agents such as polyether-based, polyetherester-based, polyetheresteramide-based, alkylsulfonate, and alkylbenzenesulfonate; antioxidants, ultraviolet absorbers, heat stabilizers, Stabilizers such as light stabilizer; flame retardant; flame retardant aid; curing agent; curing accelerator; Nucleating agent; reinforcing agent; reinforcing agent; flow control agent; sensitizer; rubbery polymer; thickener; - Antifungal agents; antifouling agents; conductive polymers; and the like.

In particular, it is preferable to add a heat stabilizer, an ultraviolet absorber, a flame retardant, and the like for a wide range of indoor and outdoor uses. Also, a rubbery copolymer may be added as a stress relaxation agent or impact imparting agent.

(Heat stabilizer)
Examples of the heat stabilizer include, but are not limited to, hindered phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. The methacrylic resin of the present embodiment is suitably used in various applications such as melt extrusion, injection molding, and film molding. The heat history received during processing varies depending on the processing method, but it ranges from several tens of seconds for extruders to several tens of minutes to several hours for thick product molding and sheet molding. Various.
When subjected to a long heat history, it is necessary to increase the amount of heat stabilizer added in order to obtain the desired heat stability. From the viewpoint of suppressing the bleeding out of the heat stabilizer and preventing the film from sticking to the roll during film formation, it is preferable to use a plurality of types of heat stabilizers in combination, such as a phosphorus antioxidant and a sulfur antioxidant. It is preferable to use together at least one selected from the antioxidants and a hindered phenol-based antioxidant.
These antioxidants may be used singly or in combination of two or more.

From the viewpoint of better thermal stability in air, the heat stabilizer may be a binary system using a hindered phenol antioxidant and a sulfur antioxidant, or a hindered phenol antioxidant and a phosphorus antioxidant. A binary system using a system antioxidant is preferable, especially from the viewpoint of excellent thermal stability in the air over a short and long period of time, a hindered phenol antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. A ternary system using three kinds of is more preferable.

Examples of heat stabilizers include, but are not limited to, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylenebis[3-( 3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,3′,3″,5 ,5′,5″-hexa-tert-butyl-a,a′,a″-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl) -o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene Bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3 ,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl]-1, 3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine -2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 2-tert-acrylate Butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl and the like.
In particular pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-[1-(2-Hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate is preferred.

In addition, the hindered phenolic antioxidant as the heat stabilizer may be a commercially available phenolic antioxidant, and such commercially available phenolic antioxidants are limited to the following. However, for example, Irganox (registered trademark) 1010 (Irganox 1010: pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF), Irganox 1330 (Irganox 1330: 3,3′,3″,5,5 ',5''-hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, manufactured by BASF), Irganox 3114 (Irganox 3114: 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF ), Irganox 3125 (Irganox 3125, manufactured by BASF), ADEKA STAB (registered trademark) AO-60 (pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], ADEKA ), Adekastab AO-80 (3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2, 4,8,10-tetraoxaspiro[5.5]undecane, manufactured by ADEKA), Sumilizer (registered trademark) BHT (Sumilizer BHT, manufactured by Sumitomo Chemical), Cyanox (registered trademark) 1790 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (Sumilizer GA-80, manufactured by Sumitomo Chemical), Sumilizer GS (Sumilizer GS: 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6 acrylic acid -Di-tert-pentylphenyl, manufactured by Sumitomo Chemical), Sumilizer GM (Sumilizer GM: 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate , Sumitomo Chemical Co., Ltd.), Vitamin E (Eisai Co., Ltd.), etc. .
Among these commercially available hindered phenolic antioxidants, Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, Sumilizer GS, and the like are preferable from the viewpoint of the effect of imparting thermal stability to the resin. .
These may be used individually by 1 type, or may be used in combination of 2 or more types.

Further, the phosphorus antioxidant as the heat stabilizer is not limited to the following, but examples include tris(2,4-di-t-butylphenyl)phosphite, bis(2,4- Bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, tetrakis(2,4-di-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosph Phonite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,4 -dicumylphenyl)pentaerythritol-diphosphite, tetrakis(2,4-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, di-t-butyl-m-cresyl- Phosphonite, 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2 -methyl-6-tert-butylphenol and the like.
Furthermore, a commercially available phosphorus antioxidant may be used as the phosphorus antioxidant, and examples of such commercially available phosphorus antioxidants include, but are not limited to, Irgafos (registered Trademark) 168 (Irgafos 168: tris (2,4-di-t-butylphenyl) phosphite, manufactured by BASF), Irgafos 12 (Irgafos 12: tris [2-[[2,4,8,10-tetra-t -butyldibenzo[d,f][1,3,2]dioxaphosphefin-6-yl]oxy]ethyl]amine, manufactured by BASF), Irgafos 38 (Irgafos 38: bis(2,4-bis(1 , 1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, manufactured by BASF), ADEKA STAB 329K (ADK STAB-329K, manufactured by ADEKA), ADEKA STAB PEP-36 (ADK STAB PEP-36, manufactured by ADEKA), ADEKA STAB PEP-36A (ADK STAB PEP-36A, manufactured by ADEKA), ADEKA STAB PEP-8 (ADK STAB PEP-8, manufactured by ADEKA), ADEKA STAB HP-10 (ADK STAB HP-10, manufactured by ADEKA), ADEKA STAB 2112 (ADK STAB 2112 , ADEKA), ADEKA STAB 1178 (ADKA STAB 1178, ADEKA), ADEKA STAB 1500 (ADK STAB 1500, ADEKA), Sandstab P-EPQ (Clariant), Weston 618 (GE), Weston 619G (Weston 619G, manufactured by GE), Ultranox 626 (Ultranox 626, manufactured by GE), Sumilizer GP: 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][ 1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical), HCA (9,10-dihydro-9-oxa-10-phos Faphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.) and the like.
Among these commercially available phosphorus-based antioxidants, Irgafos 168, Adekastab PEP-36, Adekastab PEP-36A, and Adekastab HP are considered effective in imparting thermal stability to the resin and in combination with various antioxidants. -10 and Adekastab 1178 are preferred, and Adekastab PEP-36A and Adekastab PEP-36 are particularly preferred.
These phosphorus-based antioxidants may be used alone or in combination of two or more.

Further, the sulfur-based antioxidant as the heat stabilizer is not limited to the following, but for example, 2,4-bis(dodecylthiomethyl)-6-methylphenol (Irganox 1726, BASF ), 2,4- HYPERLINK "http://www.weblio.jp/content/%E3%83%93%E3%82%B9" ＼o "Meaning of bis" Bis(octylthiomethyl)-6- Methylphenol (Irganox 1520L, manufactured by BASF), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3-dodecylthio]propionate] (ADEKA STAB AO-412S , manufactured by ADEKA), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3-dodecylthio]propionate] (Cheminox PLS, manufactured by Chemipro Kasei Co., Ltd.), di(tridecyl) 3,3'-thiodipropionate (AO-503, manufactured by ADEKA) and the like.
Among these commercially available sulfur antioxidants, Adekastab AO-412S and Cheminox PLS are preferred from the viewpoints of thermal stability imparting effect in the resin, combined effect with various antioxidants, and handleability.
These sulfur-based antioxidants may be used alone or in combination of two or more.

The content of the heat stabilizer may be any amount as long as the effect of improving the heat stability can be obtained, and if the content is excessive, problems such as bleeding out during processing may occur. Based on 100 parts by mass of the system resin, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less. It is preferably 0.01 to 0.8 parts by mass, particularly preferably 0.01 to 0.5 parts by mass.
In addition, from the viewpoint of suppressing the thermal decomposition of the resin, suppressing the deterioration of the color tone of the obtained molded product, suppressing the volatilization of the heat stabilizer and suppressing the generation of silver streaks during molding, the methacrylic resin Per 100 parts by mass, 0.01 to 2 parts by mass (preferably 0.02 to 1 part by mass) of a hindered phenol antioxidant, and a total of a phosphorus antioxidant and a sulfur antioxidant It preferably contains 0.01 to 2 parts by weight (preferably 0.01 to 1 part by weight).

(Ultraviolet absorber)
Examples of ultraviolet absorbers include, but are not limited to, benzotriazole-based compounds, benzotriazine-based compounds, benzoate-based compounds, benzophenone-based compounds, oxybenzophenone-based compounds, phenol-based compounds, oxazole-based compounds, malonic acid ester-based compounds, Cyanoacrylate-based compounds, lactone-based compounds, salicylic acid ester-based compounds, benzoxazinone-based compounds, and the like are included. Among these, benzotriazole-based compounds and benzotriazine-based compounds are preferred. These may be used individually by 1 type, and may be used in combination of 2 or more types.

In addition, from the viewpoint of obtaining excellent moldability, the vapor pressure (P) of the ultraviolet absorber at 20°C is preferably 1.0 × 10 ^-4 Pa or less, more preferably 1.0 × 10 ^{-6 .} Pa or less, more preferably 1.0×10 ⁻⁸ Pa or less. Here, "excellent molding processability" means, for example, that there is little adhesion of UV absorbers, etc. to the mold surface during injection molding, and that there is little adhesion of UV absorbers, etc., to rolls during film molding. etc. If the UV absorber adheres to the roll, the UV absorber will eventually adhere to the surface of the target molded product, which may deteriorate the appearance and optical characteristics. Therefore, the molded product is used as an optical material. When it is used, it is particularly important that the moldability is excellent.

From the viewpoint of preventing bleeding out, the melting point (Tm) of the ultraviolet absorber is preferably 80° C. or higher, more preferably 100° C. or higher, still more preferably 130° C. or higher, and even more preferably 160° C. °C or higher.

Furthermore, from the viewpoint of preventing bleeding out, the mass reduction rate of the ultraviolet absorber when the temperature is increased from 23 ° C. to 260 ° C. at a rate of 20 ° C./min is preferably 50% or less, more preferably 30% or less. , more preferably 15% or less, even more preferably 10% or less, and even more preferably 5% or less.

(Flame retardants)
The flame retardant is not particularly limited. and flame retardants.

The kneading method for mixing various additives may be according to the above-described method and the like, and is not particularly limited.

[Coloring agent]
In this embodiment, a coloring agent can be preferably used.
As a coloring agent suitably used in the present embodiment, a coloring agent having a weight loss initiation temperature of 250° C. or higher when measured with a thermobalance under a nitrogen atmosphere at a heating rate of 10° C./min. is preferably selected from Here, the mass decrease start temperature when measured with a thermobalance is the mass decrease start temperature (T1) described in JIS K-7120, which is an index of the thermal stability of the colorant. . If the mass loss initiation temperature is lower than 250°C, the thermal stability of the colorant is insufficient, which is undesirable because it causes coloration of the finally obtained resin. More preferably, the mass loss initiation temperature is 300° C. or higher. Moreover, it is more preferable that the resin does not decompose under the temperature at which it is in a molten state.

In this embodiment, blue color modifiers, red colorants, purple colorants, orange colorants, and green colorants are preferably used. Here, the blue-based colorant is a color tone adjustment dye that is generally commercially available and is described as "Blue". Specifically, the maximum absorption wavelength in the visible light absorption spectrum in a solution is about 580 to 650 nm. Similarly, the violet color tone adjusting dye is a color tone adjusting dye that is commercially available and is labeled as "Violet". Specifically, the maximum absorption wavelength in the visible light absorption spectrum in a solution is Those at about 560 to 580 nm are shown. The red color tone adjusting dye is a commercially available color tone adjusting dye that is labeled as "Red", and specifically, the maximum absorption wavelength in the visible light absorption spectrum in solution is 480 to 480. It is on the order of 520 nm. The orange-based color tone adjusting dye is a commercially available color tone adjusting colorant described as "Orange".

Oil-soluble dyes are particularly preferable as these color tone adjusting dyes, and specific examples thereof include the following.
Blue color tone adjusting dyes include C.I. I. Solvent Blue 11, C.I. I. Solvent Blue 25, C.I. I. Solvent Blue 35, C.I. I. Solvent Blue 36, C.I. I. Solvent Blue 45 (Telasol Blue RLS), C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 63, C.I. I. Solvent Blue 78, C.I. I. Solvent Blue 83, C.I. I. Solvent Blue 87, C.I. I. SolventBlue 94 (diaresin blue N), C.I. I. SolventBlue 97 (Macrolex Blue RR), C.I. I. Solvent Blue 104, C.I. I. SolventBlue122 etc. are mentioned.
Examples of dyes for adjusting purple color tone include C.I. I. Solvent Violet 8, C.I. I. Solvent Violet 13 (diaresin blue G), C.I. I. Solvent Violet 14, C.I. I. Solvent Violet 21, C.I. I. Solvent Violet 27, C.I. I. Solvent Violet 28, C.I. I. SolventViolet 36 (Macrolex Violet 3R), C.I. I. Solvent Violet 37, C.I. I. Solvent Violet 49 etc. are mentioned.
Red color tone adjusting dyes include C.I. I. Solvent Red 24, C.I. I. Solvent Red 25, C.I. I. Solvent Red 27, C.I. I. Solvent Red 30, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Solvent Red 100, C.I. I. Solvent Red 109, C.I. I. Solvent Red 111, C.I. I. Solvent Red 121, C.I. I. Solvent Red 135, C.I. I. Solvent Red 149, C.I. I. Solvent Red 168, C.I. I. Solvent Red 179, C.I. I. SolventRed195 etc. are illustrated.
Orange color tone adjusting dyes include C.I. I. Solvent Orange 3, C.I. I. Solvent Orange 14, C.I. I. Solvent Orange 54, C.I. I. Solvent Orange 60, C.I. I. Solvent Orange 62, C.I. I. Solvent Orange 63, C.I. I. Solvent Orange 86, C.I. I. and Solvent Orange 107.
Examples of dyes for adjusting yellow color tone include C.I. I. Disperse Yellow 5, C.I. I. Disperse Yellow 42, C.I. I. Disperse Yellow 54, C.I. I. Disperse Yellow 64, C.I. I. Disperse Yellow 79, C.I. I. Disperse Yellow 82, C.I. I. Disperse Yellow 83, C.I. I. Disperse Yellow 93, C.I. I. Disperse Yellow 99, C.I. I. Disperse Yellow 100, C.I. I. Disperse Yellow 119, C.I. I. Disperse Yellow 122, C.I. I. Disperse Yellow 124, C.I. I. Disperse Yellow 126, C.I. I. Disperse Yellow 160, C.I. I. Disperse Yellow 184:1, C.I. I. Disperse Yellow 186, C.I. I. Disperse Yellow 198, C.I. I. Disperse Yellow 199, C.I. I. Disperse Yellow 204, C.I. I. Disperse Yellow 211, C.I. I. Disperse Yellow 224, C.I. I. DisperseYellow237 etc. are mentioned.
Green color tone adjusting dyes include C.I. I. Solvent Green 3, C.I. I. Solvent Green 5, C.I. I. Solvent Green 7, C.I. I. SolventGreen28 etc. are mentioned.

Other coloring agents that may be used include carbon black, ketjen black, lionite black, carbon nanotubes, titanium oxide, calcium carbonate, talc, kaolin, mica, wollastonite, and carbon nanotubes.
The above colorants may be used singly or in combination of two or more.

The content of the coloring agent may be any amount as long as the coloring effect is obtained, and if the content is excessive, problems such as bleeding out during processing may occur. On the other hand, it is preferably 2 parts by mass or less, more preferably 1.5 parts by mass or less, still more preferably 1 part by mass or less, even more preferably 0.9 parts by mass or less, and even more preferably 0.9 parts by mass or less. 8 parts by mass or more, particularly preferably 0.7 parts by mass or more.

When the other additives and coloring agents mentioned above are contained, S1 and S2 shall use the molding shrinkage ratios of the thermoplastic resin composition containing the other additives and coloring agents.

[Characteristics of two-color molding]
The characteristics of the two-color molding of this embodiment will be described below.

(Percentage of through-holes in underlayer)
Through-holes can be provided in the base layer of the two-color molded article manufactured by the method for manufacturing the two-color molded article of the present embodiment. Warping tends to decrease as the ratio of holes in the underlayer increases, but if the window-like holes are too large, the strength of the product decreases, which is not preferable. The two-color molded article of the present embodiment is characterized in that warping can be reduced even in a product shape that tends to warp due to a small ratio of holes in the base layer.
The ratio of the area of the through holes provided in the underlayer to the area of the underlayer is preferably 25% or less. If the underlying layer is provided with ribs, the ribs are taken into consideration in the calculation of the area of the underlying layer. The ratio is more preferably 20% or less, still more preferably 15% or less, and most preferably 10% or less. Also, if the through-hole is located near the center of the product, warping tends to be less, but this is the location where the impact of the decrease in product strength is greatest, which is not preferable.

(Relationship between the thickness of the surface layer of the compact and the thickness of the base layer)
In the two-color molded article of the present embodiment, it is preferable that the thickness t1 of the surface layer and the thickness t2 of the base layer satisfy the relationship represented by the formula (3).
0.2≦t1/t2≦4 (3)
When the molded article has the relationship represented by the above formula (3), the molded article is excellent in appearance and mechanical strength.
The above t1 means the average thickness of the surface layer, and the above t2 means the average thickness of the underlying layer.

t1/t2 is preferably 0.3 to 3.5, more preferably 0.5 to 2.5, most preferably 0.7 to 2.0. When t1/t2 is less than 1, the appearance of surface sink marks and welds tends to be improved, and when t1/t2 exceeds 1, the strength of the underlying layer tends to be maintained. Further, when t1/t2 is less than 0.2, the surface layer is too thin, and it may become difficult to flow the resin to the end of the flow. If t1/t2 exceeds 4, the underlying layer may be too thin and the strength may decrease.

The overall thickness of the two-color molding is preferably 6.0 mm or less, more preferably 5.0 mm or less, and even more preferably 4.0 mm or less. Moreover, the thickness is preferably 2.5 mm or more, more preferably 3.0 mm or more. By setting the thickness within the above range, it is possible to reduce the weight and material cost of various members made of the two-color molding.

(Surface hardness of two-color molding)
As for the surface hardness of the two-color molding of the present embodiment, it is preferable that the pencil hardness of the surface is B or higher. If the pencil hardness is less than B, the surface of the product is easily scratched, and surface treatment such as hard coating is required. It is more preferably HB or higher, and still more preferably H or higher. Most preferably it is 2H or more.
The surface hardness may be specifically determined by the method described in Examples.

(Impact strength of two-color molding)
The two-color molded article of this embodiment can greatly improve the strength of the product by using a high-strength material for the base layer. The DuPont impact strength of the two-color molding is preferably 7 kg·cm or more. If the DuPont impact strength is less than 7 kg·cm, it cannot be said that the strength of the product is greatly improved, which is not preferable. More preferably, the DuPont impact strength of the two-color molding is 10 kg·cm or more. It is more preferably 15 kg·cm or more, and most preferably 15 kg·cm or more.
Incidentally, the impact strength may be specifically determined by the method described in Examples.

(Solvent resistance of two-color molding)
The two-color molded article of this embodiment can reduce product warpage. If the warp is large, it will be distorted because it will be corrected to the correct dimensions when it is attached to the product. In that case, it is not preferable because the possibility of occurrence of defects such as cracks during use of the product increases.
The solvent resistance may be specifically determined by the method described in Examples.

[Use of two-color molding]
The two-color molded article of this embodiment can be suitably used for various applications requiring surface hardness, high appearance, and impact resistance. Such uses are not particularly limited, but examples include furniture, household goods, storage/stockpile items, building materials such as walls and roofs, toys/playground equipment, hobby uses such as pachinko machines, medical/welfare goods, and home appliances. , OA equipment, AV equipment, office equipment, battery electrical equipment, lighting equipment, ship, aircraft body parts, vehicle parts, etc. Especially vehicle applications such as body parts and vehicle parts, optical It can be suitably used for electrical and electronic applications. Examples of optical applications include various lenses, touch panels, etc., and transparent substrates used in solar cells.

In addition, in the fields of optical communication systems, optical exchange systems, and optical measurement systems, it can be used as waveguides, optical fibers, coating materials for optical fibers, LED lenses, covers for lens covers EL illumination, and the like.

Electrical and electronic applications include, for example, personal computers, game machines, televisions, car navigation systems, display devices such as electronic paper, printers, copiers, scanners, fax machines, multifunction machines, electronic notebooks and PDAs, electronic desk calculators, electronic dictionaries, Examples include cameras, video cameras, mobile phones, battery packs, recording medium drives and readers, mice, numeric keys, CD players, MD players, and portable radio/audio players. In particular, it can be suitably used for designable parts of casings of televisions, personal computers, car navigation systems, electronic paper, and the like.

In particular, it is preferably used as a design material for automobiles. Automotive design materials include, for example, automobile exterior design materials and automobile interior design materials. Examples of automotive exterior finishing materials of the present embodiment include tail lamp garnish, front lamp garnish, pillar garnish, front grill, rear grill, license garnish and license plate garnish, and these are suitable. Examples of automotive interior design materials of the present embodiment include center consoles, instrument panels, air conditioner panels, audio panels, display parts, etc., and these are suitable.

In the present embodiment, it is preferable to use a flame-retardant resin or a resin composition for the base layer, because combustion from the inside can be suppressed. Examples of such two-color molded products include home appliances, office equipment, lighting equipment, air conditioners, automobile parts, ship parts, aircraft parts, game machines, pachinko machines, game machines, toys, furniture, building materials, etc. In particular, office equipment such as copiers, printers, scanners and multi-function peripherals, audio equipment such as televisions and DVD players, and lighting equipment are suitable.

EXAMPLES Hereinafter, the present embodiment will be specifically described with reference to examples, but the present embodiment is not limited to the examples described later.

[Raw materials used in Examples and Comparative Examples]
The raw materials used for the production of the two-color molding are as follows.
(raw material for methacrylic resin)
・ Methyl methacrylate (MMA): Asahi Kasei Chemicals (2,4-dimethyl-6-t-butylphenol (2,4-di-methyl-6-tert-butylphenol) manufactured by Chugai Boeki as a polymerization inhibitor is added at 2.5 ppm what is being done)
- Methyl acrylate (MA): manufactured by Mitsubishi Chemical (with 14 ppm of 4-methoxyphenol manufactured by Kawaguchi Chemical Industry Co., Ltd. added as a polymerization inhibitor)
・Ethyl acrylate (EA): manufactured by Mitsubishi Chemical ・n-octylmercaptan: manufactured by Arkema ・2-ethylhexyl thioglycolate: manufactured by Arkema ・Lauroyl peroxide: manufactured by Japan Fats and oils Tricalcium phosphate: Nippon Kagaku Kogyo, used as a suspending agent Calcium carbonate: Shiraishi Kogyo, used as a suspending agent Sodium lauryl sulfate: Wako Jun Used as a pharmaceutical and suspension aid

(Thermoplastic resin)
・ ABS-1: Stylac ABS220, color number S133ST (black) (manufactured by Asahi Kasei), VICAT softening temperature = 98 ° C.
・PC/ABS-1: Techniace H-270, color number 901 (black) (manufactured by A&L Japan), VICAT softening temperature = 130°C
・PC-1: Iupilon S-3000UR, color number 9001 (black) (manufactured by Mitsubishi Engineering Plastics), VICAT softening temperature = 148°C
・PC-2: Iupilon S-3000, transparent (manufactured by Mitsubishi Engineering Plastics), VICAT softening temperature = 148°C
・ABS-2: Techno ABS H814, transparent (manufactured by Techno Polymer), VICAT softening temperature = 87°C
・ ABS-3: Stylac ABS VA518, black (manufactured by Asahi Kasei), flame retardant formulation: halogen, VICAT softening temperature = 90 ° C
・ ABS-4: Stylac ABS VN33H, black (manufactured by Asahi Kasei), flame retardant formulation: non-halogen, VICAT softening temperature = 87 ° C.
・ ABS-5: Stylac ABS VGB20, black (manufactured by Asahi Kasei), flame retardant formulation: non-halogen + GF, VICAT softening temperature = 100 ° C
・PC/ABS-2: Novaloy S S6700, black (Daicel polymer), flame retardant formulation: non-halogen, VICAT softening temperature = 101°C
・PC-3: Iupilon EHR3400, black (manufactured by Mitsubishi Engineering Plastics), flame retardant formulation: non-halogen, VICAT softening temperature = 148 ° C

(coloring agent)
・B-1: (Purple) SolventViolet 36, Anthraquinone system ・B-2: (Yellow) Disperse Yellow 160, Heterocyclic compound system ・B-3: (Green) SolventGreen 3, Anthraquinone system ・B -4: (Blue) SolventBlue 94, anthraquinone system C-A0: (Mitsubishi Chemical Co., Ltd.) Mitsubishi carbon black # 2600
· C-A1: C-A0 is surface-coated with zinc stearate. The ratio is a mass ratio, C-A0/surface coating agent = 40/60

[Measurement and evaluation method]
<I. Measurement of molecular weight and molecular weight distribution of methacrylic resin>
The weight average molecular weight and molecular weight distribution of the methacrylic resin were measured using the following equipment and conditions.
Measuring device: Tosoh gel permeation chromatography (HLC-8320GPC)
Columns: 1 TSKgel SuperH2500, 2 TSKgel SuperHM-M, 1 TSKguardcolumn SuperH-H, connected in series With this column, high molecular weights are eluted early, and low molecular weights are eluted slowly.
Detector: RI (differential refraction) detector Detection sensitivity: 3.0 mV/min
Column temperature: 40°C
Sample: 10 mL solution of 0.02 g of resin in tetrahydrofuran Injection volume: 10 μL
Developing solvent: tetrahydrofuran, flow rate: 0.6 mL/min
As standard samples for the calibration curve, the following 10 types of polymethyl methacrylate (Polymethyl methacrylate Calibration Kit PL2020-0101 MM-10) with known monodisperse weight peak molecular weights and different molecular weights were used.
In addition, since the polymethyl methacrylate used for the standard sample for the calibration curve has a single peak, (Mp) is indicated as the peak molecular weight, and is distinguished from the notation "peak top molecular weight" when there are multiple peaks. .
Peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 8 5,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity was measured with respect to the elution time of the thermoplastic resin.
Based on the area area in the GPC elution curve and the calibration curve of the cubic approximation formula, the weight average molecular weight (Mw) of the methacrylic resin, the molecular weight distribution (Mw / Mn), the GPC peak molecular weight (Mp) and the GPC peak top molecular weight (Mp ) was determined as the ratio (%) of the component having a molecular weight of 1/5 or less.

<II. Measurement of Mold Shrinkage>
Mold shrinkage measurement of the thermoplastic resin was performed according to JIS K7152-4.
A flat plate mold (100 mm×100 mm×3 mmt, gate: central portion of 100 mm side, side gate) was molded under the following molding conditions.
Injection conditions Molding machine: EC100SX (manufactured by Toshiba Machine)
Mold temperature: 70°C
Filling speed: 50mm/sec
Holding pressure time: 10 sec
Cooling time: 20 sec
Molding cycle: 40 sec
Molding temperature: methacrylic resin; 260°C, PC; 300°C, PC/ABS; 280°C, ABS; 250°C
After taking out the molded flat plate, it was left in a desiccator at a temperature of 23±2° C. for 1 hour or more. After removing the flat plate from the desiccator, measure the dimensions of the four sides of the flat plate. The shrinkage rate (%) of each of the four sides was measured from the dimensions of the mold and the flat plate, and the average value of the shrinkage rates of the four sides was calculated as the molding shrinkage rate (%).

<III. Measurement of coefficient of linear expansion>
The measurement was carried out according to JIS K7197 standard, and the linear expansion coefficients of the methacrylic resin and the thermoplastic resin were measured. A test piece used was a flat plate (100 mm x 100 mm x 3 mmt, gate: central part of 100 mm side, side gate) single-layer molding.

<IV. Measurement of VICAT softening temperature>
The VICAT softening temperature of the methacrylic resin and the thermoplastic resin was measured according to the JIS K7206 standard, test method B50.

<V. Measurement of spiral length>
Under the following molding conditions, a methacrylic resin was flowed through a cavity having a constant cross-sectional area and a spiral shape, and the relative fluidity was determined by the distance over which the resin flowed.
Injection molding machine: Toshiba Machine EC100SX
Mold for measurement: A mold in which a groove with a depth of 2 mm and a width of 10 mm was dug from the center of the surface in an Archimedean spiral shape on the surface of the mold Injection conditions Resin temperature: 250°C
Mold temperature: 60°C,
Injection pressure: 75 MPa,
Injection time: 10 sec
Cooling time: 20 sec
The resin was injected onto the center of the mold surface under the above conditions. After molding, the spiral molded article was taken out and the length of the spiral portion was measured.

<VI. Appearance Evaluation>
(warp)
Warpage in the longitudinal direction of the obtained two-color molded article is checked, and the molded article is placed on a plate so that the central portion is convex. A gap gauge was used to measure the maximum gap between the fixed plate and the center of the molded product caused by warpage.
Warp judgment criteria ○ (excellent): the gap in the central part is less than 0.6 mm △ (good): the gap in the central part is 0.6 mm or more and less than 1.2 mm × (poor): the gap in the central part is 1.2 mm or more

(weld)
The appearance of the obtained two-color molding was evaluated based on the length of welds (marks where resins collide with each other) generated on the flow end side. The flow terminal side here was defined as a point after 50% of the total length of the flow path.
Weld judgment criteria ○ (excellent): no weld △ (good): weld length less than 10 mm × (poor): weld length 10 mm or more

(sink marks)
Appearance evaluation of sink marks (distortion) on the flow end side of the obtained two-color molding is evaluated by the reduction rate of wall thickness. The wall thickness on the gate side and the wall thickness on the flow end side were measured, and the thickness reduction rate was calculated and evaluated. The gate side here is defined as a point before 10% of the total length of the flow path, and the flow end side here is defined as a point after 90% of the total length of the flow path.
Thickness reduction rate (%): 100 × {(gate side thickness - flow terminal side thickness) / gate side} thickness Criteria for sink marks ○ (excellent): thickness reduction rate is less than 3% △ (good): Thickness reduction rate is 3% or more and less than 6% × (poor): Thickness reduction rate is 6% or more

(Appearance Comprehensive Evaluation)
Appearance evaluation of molded bodies was carried out from the above viewpoints, and overall evaluation of appearance was carried out according to the following ⊚ to × evaluation.
◎ (Excellent): All the above appearance evaluations are ○
○ (slightly excellent): Any one of the above appearance evaluations is △
△ (Good): Any two of the above appearance evaluations are △
× (Inferior): Any one of the above appearance evaluations is ×

<VII. Evaluation of Surface Pencil Hardness>
It was measured according to the JIS K5600 standard and used as an index of the surface pencil hardness of the two-color molding.
Surface pencil hardness criteria ○ (excellent): H or more △ (good): B or more and less than H × (poor): less than B

<VIII. Measurement of Dupont impact strength>
Using a Dupont type drop impact tester (manufactured by Toyo Seiki, maximum drop height of 1000 mm, interval of 25 mm, 12.7 mm diameter shot type, 12.7 mm diameter cradle, drop weight of 100 to 1000 g), JIS K7211 -1 (2006), 50% impact breaking energy impact strength was measured in an atmosphere at a temperature of 23°C. A higher value of impact strength indicates better impact resistance. The test surface was always evaluated by giving an impact from the surface layer side.
Dupont impact strength criteria ○ (excellent): 15 kg cm or more △ (good): 7 kg cm or more and less than 15 kg cm × (poor): less than 7 kg cm

<IX. Evaluation of Solvent Resistance>
Two-color moldings of Examples and Comparative Examples were produced. After the rib portions of the two two-color moldings were brought into contact with a hot plate heated to 250° C. for 15 seconds, the two two-color moldings were welded so that the tips of the rib portions were in contact with each other (see FIG. 8). ). After hot plate welding was completed and left for one hour or longer, shampoo for vehicles and wax were applied to the surface layer of one of the two-color moldings, and left for one hour. After that, the shampoo and wax are wiped off, and the environmental test (shift from the environment of 20 ° C., 50% RH to 80 ° C., 95% RH in 1 hour, leave it for 2 hours in the environment of 80 ° C., 95% RH, 10 cycles) were carried out in which the temperature was lowered to −30° C. over a transition time of 2 hours, allowed to stand at −30° C. for an additional 2 hours, and then shifted to an environment of 20° C. and 50% RH for 1 hour. After the two-color molding was taken out after completion of the environmental test, the presence or absence of cracks on the surface was evaluated.
○: No cracks ×: Cracks present

<X. Total light transmittance>
Based on JIS K7361-1, the total light transmittance (%) of the surface layer of the two-color molding was evaluated using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. The evaluation was carried out on a single test piece of the resin constituting the surface layer of 70 mm wide×150 mm long and 1.5 mm thick, which was obtained by a method according to the manufacturing method of the two-color molded body described later.

<XI. Flammability>
The combustibility of the thermoplastic resin was evaluated based on UL94 (see the standard No. below for details). A combustion test piece was cut from a single test piece having a width of 70 mm, a length of 150 mm, and a thickness of 1.5 mm, and a test piece having a width of 13 mm, a length of 125 mm, and a thickness of 1.5 mm was used.
・UL94HB: HB (IEC60695-11-10A method, ASTM D635)
・UL94V: V-0, V-1, V-2 (IEC60695-11-10B method, ASTM D3801)

<Production Example A1 (Production of methacrylic resin (A-1))>
Ion-exchanged water: 2 kg, tribasic calcium phosphate: 65 g, calcium carbonate: 39 g, and sodium lauryl sulfate: 0.39 g were put into a container having a stirrer to obtain a mixture (a). Next, ion-exchanged water: 26 kg was put into a 60 L reactor and the temperature was raised to 80 ° C., and the mixture (a), methyl methacrylate: 21.2 kg, methyl acrylate: 0.43 kg, lauroyl peroxide: 27 g and n-octyl mercaptan: 62 g were charged.
Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80° C. After observing an exothermic peak, the temperature was raised to 92° C. at a rate of 1° C./min and aged for 60 minutes to substantially complete the polymerization reaction.
Next, in order to cool to 50° C. and dissolve the suspending agent, 20% by mass sulfuric acid was added, and then the polymerization reaction solution was passed through a 1.68 mm mesh sieve to remove aggregates, and the obtained bead-like polymer was separated. After washing, dehydration and drying, fine polymer particles were obtained.
The fine polymer particles thus obtained were melt-kneaded in a twin-screw extruder of φ30 mm set at 240° C., and the strands were cooled and cut to obtain resin pellets (methacrylic resin A-1).
The weight average molecular weight of the obtained resin pellets was 102,000, and the molecular weight distribution (Mw/Mn) was 1.85. Moreover, the structural unit was MMA/MA=98 mass %/2 mass %. The proportion of components having a molecular weight of ⅕ or less of the peak top molecular weight (Mp) was 4.6%. As a result of measuring the spiral length, it was 27 cm. Moisture content was 0.09% by mass.

<Production Example A2 (Production of methacrylic resin (A-2))>
Ion-exchanged water: 2 kg, tribasic calcium phosphate: 65 g, calcium carbonate: 39 g, and sodium lauryl sulfate: 0.39 g were put into a container having a stirrer to obtain a mixture (b).
Next, ion-exchanged water: 26 kg was added to a 60 L reactor, the temperature was raised to 80 ° C., and the mixture (b) and methyl methacrylate: 3.76 kg, methyl acrylate: 0.1 kg, lauroyl peroxide: 27 g, 2-ethylhexylthioglycolate: 62 g were charged.
Thereafter, suspension polymerization was carried out while keeping the temperature at about 80°C. An exothermic peak was observed 80 minutes after the raw materials were added. After that, the temperature was raised to 92° C. at a rate of 1° C./min, and the temperature was kept at 92° C. to 94° C. for 30 minutes. After that, the temperature was lowered to 80° C. at a rate of 1° C./min, then methyl methacrylate: 17.4 kg, ethyl acrylate: 1.35 kg, lauroyl peroxide: 23 g, n-octyl mercaptan: 35 g were added, Suspension polymerization was then carried out while maintaining the temperature at about 80°C. An exothermic peak was observed 105 minutes after the raw materials were added.
Thereafter, the temperature was raised to 92° C. at a rate of 1° C./min, followed by aging for 60 minutes to substantially complete the polymerization reaction.
Next, after cooling to 50° C. and adding 20% by mass of sulfuric acid to dissolve the suspending agent, the polymerization reaction solution is passed through a 1.68 mm mesh sieve to remove aggregates, and the obtained bead-like polymer is separated. After washing, dehydration and drying, fine polymer particles were obtained.
The resulting fine polymer particles were melt-kneaded in a twin-screw extruder of φ30 mm set at 230° C., and the strand was cooled and cut to obtain resin pellets (A-2). The obtained pellets had a weight average molecular weight of 118,000, a peak top molecular weight (Mp) of 125,000, and a molecular weight distribution (Mw/Mn) of 2.45. As a result of measuring the spiral length, it was 33 cm. Moisture content was 0.09% by mass.
Furthermore, the ratio (%) of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) was 13.5%.

<Production Example A3 (Production of methacrylic resin (A-3))>
Ion-exchanged water: 2 kg, tribasic calcium phosphate: 65 g, calcium carbonate: 39 g, and sodium lauryl sulfate: 0.39 g were put into a container having a stirrer to obtain a mixture (b).
Next, ion-exchanged water: 26 kg was added to a 60 L reactor, the temperature was raised to 80 ° C., and the mixture (b) and methyl methacrylate: 3.76 kg, methyl acrylate: 0.1 kg, lauroyl peroxide: 27 g, 2-ethylhexylthioglycolate: 62 g were charged.
Thereafter, suspension polymerization was carried out while keeping the temperature at about 80°C. An exothermic peak was observed 80 minutes after the raw materials were added. After that, the temperature was raised to 92° C. at a rate of 1° C./min, and the temperature was kept at 92° C. to 94° C. for 30 minutes. After that, the temperature was lowered to 80° C. at a rate of 1° C./min, then methyl methacrylate: 17.4 kg, ethyl acrylate: 1.35 kg, lauroyl peroxide: 23 g, n-octyl mercaptan: 35 g were added, Suspension polymerization was then carried out while maintaining the temperature at about 80°C. An exothermic peak was observed 105 minutes after the raw materials were added.
Thereafter, the temperature was raised to 92° C. at a rate of 1° C./min, followed by aging for 60 minutes to substantially complete the polymerization reaction.
Next, after cooling to 50° C. and adding 20% by mass of sulfuric acid to dissolve the suspending agent, the polymerization reaction solution is passed through a 1.68 mm mesh sieve to remove aggregates, and the obtained bead-like polymer is separated. After washing, dehydration and drying, fine polymer particles were obtained.
100 parts by mass of the obtained polymer fine particles and B-1: 0.15 parts by mass, B-2: 0.04 parts, B-3: 0.3 parts by mass, and B-4: 0.05 parts by mass as a coloring agent , C-A1: 0.125 parts by mass are blended in advance, melt-kneaded with a φ30 mm twin-screw extruder set at 240 ° C., and the strand is cooled and cut to obtain resin pellets (methacrylic resin A-3). rice field.
The obtained pellets had a weight average molecular weight of 118,000, a peak top molecular weight (Mp) of 125,000, and a molecular weight distribution (Mw/Mn) of 2.45. As a result of measuring the spiral length, it was 33 cm. Moisture content was 0.08% by mass.
Furthermore, the ratio (%) of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) was 13.5%.

<Production Example A4 (Production of methacrylic resin (A-4))>
Polymer microparticles were obtained by the same polymerization method as in Production Example A3.
100 parts by mass of the obtained polymer fine particles and 0.01 part by mass of C-A0 as a coloring agent were blended in advance, and resin pellets (methacrylic resin A-4) were obtained by the same granulation method as in Production Example A3.
The obtained pellets had a weight average molecular weight of 118,000, a peak top molecular weight (Mp) of 125,000, and a molecular weight distribution (Mw/Mn) of 2.45. As a result of measuring the spiral length, it was 33 cm. Moisture content was 0.08% by mass.
Furthermore, the ratio (%) of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) was 13.5%.

<Production Example A5 (Production of methacrylic resin (A-5))>
Polymer microparticles were obtained by the same polymerization method as in Production Example A3.
100 parts by mass of the obtained polymer fine particles and B-1: 0.0015 parts by mass, B-2: 0.0004 parts by mass, B-3: 0.003 parts by mass, and B-4: 0.0005 parts by mass as a coloring agent were blended in advance, and resin pellets (methacrylic resin A-5) were obtained by the same granulation method as in Production Example A3.
The obtained pellets had a weight average molecular weight of 118,000, a peak top molecular weight (Mp) of 125,000, and a molecular weight distribution (Mw/Mn) of 2.45. As a result of measuring the spiral length, it was 33 cm. Moisture content was 0.08% by mass.
Furthermore, the ratio (%) of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) was 13.5%.

<Production Example A6 (Production of methacrylic resin (A-6))>
Ion-exchanged water: 2 kg, tribasic calcium phosphate: 65 g, calcium carbonate: 39 g, and sodium lauryl sulfate: 0.39 g were put into a container having a stirrer to obtain a mixture (a). Next, 26 kg of ion-exchanged water was added to a 60 L reactor and the temperature was raised to 80 ° C., and the mixture (a), methyl methacrylate: 21.2 kg, ethyl acrylate: 0.43 kg, lauroyl peroxide: 27 g and n-octyl mercaptan: 62 g were charged.
Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80° C. After observing an exothermic peak, the temperature was raised to 92° C. at a rate of 1° C./min and aged for 60 minutes to substantially complete the polymerization reaction.
Next, in order to cool to 50° C. and dissolve the suspending agent, 20% by mass sulfuric acid was added, and then the polymerization reaction solution was passed through a 1.68 mm mesh sieve to remove aggregates, and the obtained bead-like polymer was separated. After washing, dehydration and drying, fine polymer particles were obtained.
100 parts by mass of the obtained polymer fine particles and B-1: 0.0015 parts by mass, B-2: 0.0004 parts by mass, B-3: 0.003 parts by mass, and B-4: 0.0005 parts by mass as a coloring agent were blended in advance, melt-kneaded with a twin-screw extruder of φ30 mm set at 240° C., and the strand was cooled and cut to obtain resin pellets (methacrylic resin A-6).
The weight average molecular weight of the obtained resin pellets was 102,000, and the molecular weight distribution (Mw/Mn) was 1.85. Moreover, the structural unit was MMA/MA=98 mass %/2 mass %. The proportion of components having a molecular weight of ⅕ or less of the peak top molecular weight (Mp) was 4.6%. As a result of measuring the spiral length, it was 27 cm. Moisture content was 0.08% by mass.

[Examples 1 to 29] [Comparative Examples 1 to 6, 10 to 14]
Detailed conditions of Examples and Comparative Examples are shown in Tables 1 to 8.

[Method for producing two-color molding]
(injection molding)
The pellets of methacrylic resin and thermoplastic resin are put into a two-color injection molding machine, and the two-color molded body (as shown in FIGS. 1 and 2, the long side of a flat plate with a width of 70 mm and a length of 150 mm 5mm ribs installed.Both the flat plate portion and the rib portion have the same thickness.The thickness of the surface layer is 0.5 to 3mm, and the thickness of the base layer is 0.5 to 3mm. There is.) and was used as a molded body for evaluation.
FIG. 1 is a perspective view showing the entire two-color molding for evaluation used in Examples and Comparative Examples. FIG. 2 is a cross-sectional view of the two-color molded product for evaluation shown in FIG. 1 taken along the line AA.
The gate used to form the underlying layer was set at a single pin gate in the center of the size of 70 mm wide×150 mm long (see FIG. 3).
FIG. 3 is a perspective view showing the pin gate position when forming the base layer first in the example and the comparative example.
The gate when forming the surface layer later is one side gate (see FIG. 4) at one end of 150 mm length and 70 mm width at the center, or) one end of 150 mm length and width Two side gates were installed at the center of 70 mm, the other end of 150 mm in length, and the center of 70 mm in width. In addition, for the gate when molding the surface layer, both the one-point gate and the two-point gate can be selected by exchanging the piece of the mold.
FIG. 4 is a perspective view showing a gate position in the case of one side gate when forming the surface layer later in Examples and Comparative Examples. FIG. 5 is a perspective view showing gate positions in the case of two side gates when forming the surface layer later in Examples and Comparative Examples.
In addition, as the order of molding, both the order of surface layer → base layer and the order of base layer → surface layer are used for molding, so molds for each combination were created and two-color molded bodies were molded. .
The gate when forming the surface layer first is one side gate (see FIG. 6) at one end of the length 150 mm and the center of the width 70 mm (see FIG. 6). The gate of (1) was one side gate (see FIG. 7) at the other end of the length of 150 mm and the center of the width of 70 mm.

The molding conditions were set as follows.
Injection molding machine: Sumitomo Heavy Industries SE-280D-CI (clamping force 280t, two-color molding)
Injection conditions Mold temperature: 70°C
Filling speed: 100mm/s
Holding pressure time: 10 sec
Cooling time: 20 sec
Molding cycle for each layer: 50 sec
Base layer + surface layer molding cycle: 100 sec
Molding temperature Methacrylic resin: 260°C
PC: 300°C
PC/ABS: 280°C
ABS: 250°C
In addition, only in Example 12, the injection molding was carried out by changing the gate of the base layer to a side two-point gate.

[Comparative Examples 7 to 9]
Table 5 shows the detailed conditions for the single-layer molded product.

[Manufacturing method of single-layer compact]
A single-layer molded article was molded using a surface layer mold. The gate was one side gate (see FIG. 6) at one end of the length of 150 mm and the center of the width of 70 mm.

Detailed results of Examples and Comparative Examples are shown in Tables 1 to 8.

Regarding the two-color molded body manufactured by the method for manufacturing a two-color molded body of the present embodiment, applications requiring low environmental load, applications requiring high appearance (low warpage, no welds, no sink marks), surface hardness, There is general industrial applicability in applications requiring impact resistance and the like. In addition, by using a flame-retardant material for the base layer, ignition from inside is suppressed, and it can also be used for applications that require flame-retardant properties (for example, office equipment such as multifunction printers, home appliances, etc.). be.

1 : Surface layer 2 : Base layer 3 : Rib 4 : Runner 5 : Pin gate 6 : Side gate 7 : Heated part, welding part t1 : Thickness of surface layer t2 : Thickness of base layer

Claims (11)

It is a two-color molded body in which the base layer is first molded using an amorphous thermoplastic resin and the surface layer is molded later using a methacrylic resin,
A method for producing a two-color molding, characterized by satisfying formula (1).
S1-S2≧0 (1)
(S2: Mold shrinkage rate of the methacrylic resin to be molded later)
(S1: molding shrinkage rate of the amorphous thermoplastic resin to be molded first) In the two-color molding,
2. The method for producing a two-color molded article according to claim 1 , wherein the ratio of the area of the through-holes provided in the underlayer to the area of the underlayer is 25% or less. Claim 1 , wherein the methacrylic resin contains 70 to 99.9% by mass of methacrylic acid ester monomer units and 0.1 to 30% by mass of at least one vinyl monomer copolymerizable with the methacrylic acid ester. 3. or the method for producing a two-color molded article according to 2 . The weight average molecular weight of the methacrylic resin measured by gel permeation chromatography (GPC) is 50000 to 300000,
The ratio of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) obtained from the GPC elution curve of the methacrylic resin is 6 to 50 with respect to the total area of the GPC elution curve of the methacrylic resin. %, the method for producing a two-color molded article according to any one of claims 1 to 3 . The amorphous thermoplastic resin to be molded first is polycarbonate resin, ABS resin (acrylonitrile, butadiene-styrene copolymer), AS resin (acrylonitrile, styrene copolymer), MBS resin (methyl methacrylate, butadiene/styrene copolymer), AAS resin (acrylonitrile, acrylic rubber, styrene copolymer), ASA resin (acrylonitrile, styrene, acrylic rubber copolymer), impact-resistant methacrylic resin and AES The method for producing a two-color molded product according to any one of claims 1 to 4 , wherein the resin is one or more selected from the group consisting of system resins (acrylonitrile, ethylene-propylene-diene, styrene). The method for producing a two-color molded product according to any one of claims 1 to 5 , wherein the amorphous thermoplastic resin to be molded first has a VICAT softening temperature of 95°C or higher. The method for producing a two-color molded article according to any one of claims 1 to 6 , wherein the amorphous thermoplastic resin to be molded first is a thermoplastic resin composition containing a flame retardant and/or a colorant. The method for producing a two-color molded article according to any one of claims 1 to 7 , wherein the thickness t1 of the surface layer and the thickness t2 of the base layer satisfy the formula (3).
0.2≦t1/t2≦4 (3) The method for producing a two-color molded article according to any one of claims 1 to 8 , wherein the two-color molded article is a design material for automobiles. The automobile design material is center console, instrument panel, air conditioner panel, audio panel, display parts, tail lamp garnish, front lamp garnish, pillar garnish, front grill, rear grill, license garnish, or license plate garnish. Item 9. A method for producing a two-color molded article according to Item 9 . The method for producing the two-color molded product according to any one of claims 1 to 8 , wherein the two-color molded product is office equipment or home appliances.

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