CN112166021A - Two-color injection molded body - Google Patents

Abstract

The purpose of the present invention is to provide a two-color injection molded article which is free from coating or HC, has little environmental burden, and is excellent in surface hardness, appearance, weather resistance and impact resistance. The two-color injection molded article of the present invention is characterized by having a surface layer containing a methacrylic resin and by having a brightness L of 0.01 to 2.5 in SCE measurement.

Description

Two-color injection molded body

Technical Field

The present invention relates to a two-color injection molded article.

Background

Conventionally, molded articles such as polycarbonate or ABS resin subjected to hard coat treatment, ASA or ABS resin painted in black tone have been used for interior and exterior members of automobiles. However, the hard coating treatment (HC treatment) has problems of defects due to the formation of coating spots and low productivity, and the coating treatment may involve a problem of Volatile Organic Compounds (VOC) contained in the paint. Against the background of such problems, molded articles not subjected to HC treatment or coating are strongly desired from the viewpoint of cost reduction, and studies have been actively made in recent years on the replacement of resins with compounds.

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

However, methacrylic resins tend to have lower mechanical strength than other resins, and are currently hardly used as interior member materials for automobiles or design member materials for front and side surfaces of exterior member materials. Therefore, a two-color molded article is known in which a methacrylic resin is used for the surface layer of the molded article and a different resin is used for reinforcing the base layer. Further, the surface layer is made of a methacrylic resin, whereby a glossy and high appearance can be expressed.

As a technique for improving impact resistance by using a resin having good appearance as a surface layer and reinforcing a base layer with a different resin, patent document 1 or patent document 2 discloses a two-layer injection molded article.

However, when a thermoplastic resin other than a methacrylic resin is used for the base layer of the two-color molded article, for example, the contact surface between the surface layer of the two-color molded article and the base layer deteriorates due to the deterioration with time, which causes a problem of appearance defects.

In order to eliminate the weather resistance deterioration of the base layer, for example, patent document 3 discloses a technique of performing a hard coat treatment on the surface of a two-color molded article to block ultraviolet rays.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 9-85779.

Patent document 2: japanese patent laid-open No. 11-157018.

Patent document 3: japanese patent laid-open No. 63-153703.

Disclosure of Invention

Problems to be solved by the invention

In patent document 1, although the impact strength is improved, in the examples, polypropylene is used for the surface layer and an elastomer is used for the base material (base layer), and there is a risk of weather deterioration. Further, weather resistance is not described or suggested for the problem or means for solving the problem.

In patent document 2, ASA resins (acrylonitrile, styrene, and acrylic rubber copolymers) are used for the surface layer, and the core layer is formed of a resin composition containing at least an epoxy compound, and although there are descriptions about improvement of mechanical strength and double layer peeling resistance between the surface layer and the core layer, there is a risk that appearance, weather resistance, and surface hardness of a double layer molded article are deteriorated.

In addition, in patent document 3, productivity is low due to the hard coating treatment, and weather resistance of the contact surface between the surface layer and the base layer is likely to deteriorate due to the use of a transparent methacrylic resin.

Under the circumstances described above, an object of the present invention is to provide a two-color injection molded article which is free from coating or HC, has a small environmental burden, and is excellent in surface hardness, appearance, weather resistance and impact resistance, in view of the problems of the prior art described above.

Means for solving the problems

The present inventors have made intensive studies to solve the above problems, and as a result, have found that the problems of the prior art can be solved by controlling the brightness L in measurement of SCE (Specular Component outside) to 0.01 or more and 2.5 or less by providing a two-color injection molded article having a surface layer containing a methacrylic resin, and have completed the present invention.

That is, the present invention is as follows.

[1] A two-color injection molded article characterized by having a surface layer containing a methacrylic resin and by having a brightness L of 0.01 to 2.5 in SCE measurement.

[2] The two-color injection molded article according to [1], which further comprises a base layer comprising a thermoplastic resin having a Vicat Softening Temperature (Vicat Softening Temperature) of 100 ℃ or higher.

[3] The two-color injection molded article according to [1] or [2], which further comprises a base layer containing a thermoplastic resin selected from the group consisting of methacrylic resins, polycarbonate resins, ABS resins (acrylonitrile, butadiene-styrene copolymers), AS resins (acrylonitrile, styrene copolymers), MBS resins (methyl methacrylate, butadiene-styrene copolymers), AAS resins (acrylonitrile, acrylate rubbers, styrene copolymers), ASA resins (acrylonitrile, styrene, acrylate rubber copolymers) and AES resins (acrylonitrile, ethylene-propylene-diene, styrene).

[4] The two-color injection molded article according to [3], wherein the thermoplastic resin is one or more selected from the group consisting of polycarbonate resins and ABS resins (acrylonitrile, butadiene-styrene copolymers).

[5] The two-color injection-molded article according to any one of [2] to [4], wherein the thickness t1 (unit: mm) of the surface layer and the thickness t2 (unit: mm) of the base layer satisfy the relationship represented by the following formula (1).

0.9≤t1/t2≤3 (1)

[6] The two-color injection-molded article according to any one of [1] to [5], wherein the methacrylic resin has a weight-average molecular weight of 50000 to 300000 as measured by Gel Permeation Chromatography (GPC), and the proportion of a component having a molecular weight of 1/5 or less of a peak top molecular weight Mp obtained from the GPC elution curve of the methacrylic resin is 6 to 50% relative to the total area of the GPC elution curve of the methacrylic resin.

[7] The two-color injection molded article according to any one of [1] to [6], which is a design material for two-wheeled vehicles or automobiles.

[8] A two-color injection molded article according to [7], which is a design material for automobile exterior.

[9] A two-color injection-molded article according to [8], wherein it is a Tail lamp decoration (Tail lamp garnish), a Rear lamp decoration (Rear lamp garnish), a Front lamp decoration (Front lamp garnish), a Pillar decoration (Pillar garnish), a Front grill (Front grill), a Rear grill (Rear grill), a License plate decoration (License grill), a Wheel center cover (Wheel center cap), a License plate decoration (Number plate garnish), a Door Rear mirror cover (Door mirror) or a sliding Door Pillar decoration (Slide glass).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a two-color injection molded article which is free from coating or HC, has a small environmental burden, and is excellent in surface hardness, appearance, weather resistance and impact resistance can be provided.

Drawings

FIG. 1A is a diagram illustrating the reflow in the appearance evaluation of examples.

Fig. 1B is an explanatory view of a weld in the appearance evaluation of the example.

Fig. 1C is an explanatory view of sink marks in the appearance evaluation of the examples.

Detailed Description

Hereinafter, specific embodiments of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. The following embodiments are illustrative of the present invention, and are not intended to limit the present invention to the following. The present invention can be modified as appropriate within the scope of the present invention.

In the present specification, the monomer component before polymerization may be referred to as "monomer" or simply "monomer". The constituent unit constituting the polymer may be referred to as a "monomer unit" or simply as a "unit".

The two-color injection molded article of the present embodiment is characterized by having a surface layer containing a methacrylic resin and by having a brightness L of 0.01 to 2.5 in SCE measurement. The two-color injection molded article of the present embodiment preferably further comprises a base layer, and more preferably the surface layer is in contact with the base layer. The two-color injection molded article of the present embodiment is preferably a two-layer laminate of the surface layer and the base layer.

[ methacrylic resin ]

The methacrylic resin contained in the surface layer will be described in detail below.

The methacrylic resin may be a homopolymer composed of a methacrylate monomer unit (monomer unit derived from a "methacrylate monomer"), or a copolymer containing a methacrylate monomer unit and another vinyl monomer unit copolymerizable with the methacrylate monomer (monomer unit derived from another vinyl monomer). Among them, a copolymer is preferable.

(methacrylate monomer)

The methacrylate ester monomer is not particularly limited as long as the effect of the present invention can be achieved, and preferable examples thereof include monomers represented by the following general formula (I).

[ chemical formula 1]

(in the general formula (I), R₁The hydrocarbon group is a hydrocarbon group having 1 to 18 carbon atoms, and the hydrogen atom on the carbon of the hydrocarbon group may be substituted with a hydroxyl group or a halogen group. )

The methacrylate ester monomer is not particularly limited, but examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, t-butylcyclohexyl methacrylate, benzyl methacrylate, and 2,2, 2-trifluoroethyl methacrylate. Among them, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and the like are more preferable, and methyl methacrylate is particularly preferable, from the viewpoint of easy handling or easy availability. The above-mentioned methacrylate ester monomers may be used alone or in combination of two or more.

When the methacrylic resin is a copolymer, the content of the methacrylate ester monomer unit is preferably 80 to 99.9% by mass, more preferably 88 to 99% by mass, and still more preferably 90 to 98% by mass, based on the total amount of the methacrylic resin. When the content of the methacrylate monomer unit is 80% by mass or more, the heat resistance tends to be further improved. Further, when the content of the methacrylate monomer unit is 99.9% by mass or less, the fluidity tends to be further improved.

(other vinyl monomers)

The other vinyl monomer is not particularly limited, but a preferable example thereof is an acrylate monomer represented by the following general formula (II).

[ chemical formula 2]

(in the general formula (II), R₂The hydrocarbon group is a hydrocarbon group having 1 to 18 carbon atoms, and the hydrogen atom on the carbon of the hydrocarbon group may be substituted with a hydroxyl group or a halogen group. )

The above-mentioned acrylate monomer is not particularly limited, but examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, phenyl acrylate, 2-ethylhexyl acrylate, t-butylcyclohexyl acrylate, benzyl acrylate, and 2,2, 2-trifluoroethyl acrylate. Among them, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate and the like are more preferable from the viewpoint of easy handling or easy availability, and methyl acrylate is particularly preferable.

The vinyl monomer other than the acrylate monomer represented by the general formula (II) copolymerizable with the methacrylate monomer is not particularly limited, but examples thereof include α, β -unsaturated acids such as acrylic acid and methacrylic acid; unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid, itaconic acid, cinnamic acid, and alkyl esters thereof; styrene monomers such as 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-tert-butylstyrene, and isopropenylstyrene (α -methylstyrene); aromatic vinyl compounds such as 1-vinylnaphthalene, 2-vinylnaphthalene, 1-diphenylethylene, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene and the like; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; n-substituted maleimides such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide; amides such as acrylic acid amide and methacrylic acid amide; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, etc. both terminal hydroxyl groups of ethylene glycol or its oligomer are esterified with acrylic acid or methacrylic acid; neopentyl glycol di (meth) acrylate, and the like in which the hydroxyl groups of two alcohols are esterified with acrylic acid or methacrylic acid; a polyol derivative such as trimethylolpropane or pentaerythritol esterified with acrylic acid or methacrylic acid; multifunctional monomers such as divinylbenzene, and the like.

One of the above-mentioned acrylate monomers represented by the general formula (II) and another vinyl monomer such as another vinyl monomer other than the acrylate monomer represented by the general formula (II) may be used alone, or two or more of them may be used in combination.

The content of the monomer unit derived from another vinyl monomer is preferably 0.1 to 20% by mass, more preferably 1.0 to 15% by mass, even more preferably 1.5 to 12% by mass, and particularly preferably 2.0 to 10% by mass, based on the total amount of the methacrylic resin. When the content of the monomer unit derived from another vinyl monomer is 0.1% by mass or more, the fluidity and heat resistance tend to be further improved. Further, when the content of the monomer unit derived from another vinyl monomer 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 processability, a vinyl monomer other than the above-mentioned vinyl monomers 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 are described.

The methacrylic resin preferably has a weight average molecular weight (Mw) of 50000 to 300000 as measured by Gel Permeation Chromatography (GPC). When the weight average molecular weight of the methacrylic resin is in the above range, the balance among fluidity, mechanical strength and solvent resistance is achieved, and good molding processability tends to be maintained. 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 50000 or more, more preferably 60000 or more, further preferably 70000 or more, further more preferably 80000 or more, and further preferably 90000 or more. From the viewpoint that the methacrylic resin exhibits good fluidity, the weight average molecular weight (Mw) of the methacrylic resin is preferably 300000 or less, more preferably 250000 or less, still more preferably 230000 or less, still more preferably 210000 or less, and still more preferably 180000 or less.

The methacrylic resin preferably has a molecular weight distribution (Mw/Mn) of 1.6 to 6.0, more preferably 1.7 to 5.0, and still more preferably 1.8 to 5.0. When the molecular weight distribution of the methacrylic resin is within the above range, the balance between the molding flow and the mechanical strength tends to be more excellent. Herein, Mw represents a weight average molecular weight, and Mn represents a number average molecular weight.

Examples of the method for controlling the molecular weight distribution of the methacrylic resin include a method of adding a chain transfer agent or an initiation/termination agent (iniferter) in stages at the time of production of the methacrylic resin, a method of separately polymerizing a low molecular weight component and a high molecular weight component and melt-blending them, and the like, which will be described later.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the methacrylic resin can be measured by GPC, specifically, by the method described in the examples below.

Specifically, a calibration curve is prepared from the elution time and the weight average molecular weight using a standard methacrylic resin having a previously known monodisperse weight average molecular weight and obtainable as a reagent and an analytical gel column from which a high molecular weight component is eluted, and then the weight average molecular weight (Mw) and the number average molecular weight (Mn) of a predetermined methacrylic resin to be measured can be determined based on the obtained calibration curve. The 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 of the molecular weights 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 of molecular weights in weight fraction.

(ratio of components having a molecular weight of 1/5 or less with a peak top molecular weight (Mp))

From the viewpoint of solvent resistance and fluidity, the proportion of the component 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 preferably 3 to 50%, more preferably 4 to 50%, further preferably 6 to 50%, further preferably 7 to 45%, further preferably 8 to 43%, further preferably 9 to 40%, further more preferably 10 to 38% with respect to the total area of the GPC elution curve of the methacrylic resin. 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, the molding flowability tends to be further improved, and appearance defects such as sink marks and weld seams in the surface layer tend to be suppressed. Further, the solvent resistance tends to be further improved by setting the proportion of components having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) in the methacrylic resin to 50% or less.

The "proportion (%) of a component having a molecular weight of 1/5 or less at the peak top molecular weight (Mp)" means a proportion of a region area corresponding to a component having a molecular weight of 1/5 or less at the peak top molecular weight (Mp) when the entire region area of the GPC elution curve is 100%, and can be measured by the method described in the examples described later. The "peak top molecular weight (Mp)" refers to the weight molecular weight of a peak in a GPC elution curve. When a plurality of peaks are present in the GPC elution curve, the molecular weight of the peak indicating the weight molecular weight present in the largest amount is referred to as 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 the formation of a foam-like appearance defect called a silver streak during molding.

(method for producing methacrylic resin)

The methacrylic resin can be produced by any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among them, bulk polymerization, solution polymerization and suspension polymerization are preferable, and suspension polymerization is more preferable.

The polymerization temperature may be an optimum polymerization temperature, which is appropriately selected according to the polymerization method, and is preferably 50 ℃ to 100 ℃, and more preferably 60 ℃ to 90 ℃.

In the production of the methacrylic resin, a polymerization initiator may be used. Although not particularly limited, examples of the polymerization initiator include organic peroxides such as di-t-butyl peroxide, lauroyl peroxide, decanoyl peroxide, stearyl peroxide, benzoyl peroxide, t-butyl peroxy neodecanoate, t-butyl peroxy pivalate, dilauroyl peroxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate, 1-bis (t-butyl peroxy) -3,3, 5-trimethylcyclohexane, cyclohexane peroxide, 2, 5-dimethyl-2, 5-bis (benzoylperoxy) hexane, and 1, 1-bis (t-butyl peroxy) cyclohexane; azo-based general radical polymerization initiators such as azobisisobutyronitrile, azobisisovaleronitrile, 1-azobis (1-cyclohexanecarbonitrile), 2 ' -azobis-4-methoxy-2, 4-azobisisobutyronitrile, 2 ' -azobis-2, 4-dimethylvaleronitrile, 2 ' -azobis-2-methylbutyronitrile and 2- (carbamoylazo) isobutyronitrile. These may be used alone or in combination of two or more. These radical initiators may be combined with an appropriate reducing agent to be used as a redox-type initiator.

These radical polymerization initiators and/or redox initiators are usually used in the range of 0 to 1 part by mass relative to 100 parts by mass of the total amount of all monomers used in the polymerization of the methacrylic resin, and can be appropriately selected in consideration of the temperature at which the polymerization is carried out and the half-life of the polymerization initiator.

When the bulk polymerization method, the cast polymerization method, or the suspension polymerization method is selected as the method for polymerizing the methacrylic resin, it is preferable to polymerize the methacrylic resin using an organic peroxide as a polymerization initiator from the viewpoint of preventing the methacrylic resin from being colored. Examples of such organic peroxides include those similar to those described above, and among them, lauroyl peroxide, decanoyl peroxide, tert-butylperoxy-2-ethylhexanoate, and the like are preferable, and lauroyl peroxide is more preferable.

When a methacrylic resin is polymerized by a solution polymerization method at a high temperature of 90 ℃ or higher, it is preferable to use, as a polymerization initiator, an organic peroxide, an azodiinitiator, or the like, which has a 10-hour half-life temperature of 80 ℃ or higher and is soluble in an organic solvent to be used. Examples of such organic peroxides and azodiinitiators include those similar to those described above, and among them, 1-bis (t-butylperoxy) -3,3, 5-trimethylcyclohexane, cyclohexane peroxide, 2, 5-dimethyl-2, 5-bis (benzoylperoxy) hexane, 1-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) isobutyronitrile, and the like are preferable.

When a methacrylic resin is produced, the molecular weight of the methacrylic resin can be controlled as necessary. The method for controlling the molecular weight of the methacrylic resin is not particularly limited, but examples thereof include a method of changing a polymerization method or polymerization conditions, a method of selecting a polymerization initiator, and a method of adjusting the amount of a chain transfer agent, an initiation/termination agent, and the like. These molecular weight control methods may be used in one method or in combination of two or more methods.

Although not particularly limited, examples of the initiation-transfer terminator include dithiocarbamates, triphenylmethylazobenzene, tetraphenylethane derivatives, and the like.

The chain transfer agent is not particularly limited, but examples thereof include alkyl mercaptans, dimethylacetamide, dimethylformamide, triethylamine and the like. Among them, alkyl thiols are preferable from the viewpoint of handling and stability. The alkyl mercaptans are not particularly limited, but examples thereof include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan, 2-ethylhexyl thioglycolate (2-ethylhexyl thioglycolate), ethylene glycol dimercaptoacetate, trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate), and the like.

The chain transfer agent and the transfer initiation terminator can be added as appropriate depending on the molecular weight of the intended methacrylic resin (a), and the molecular weight can be adjusted by adjusting the amounts of the chain transfer agent and the transfer initiation terminator added. In general, the amount of the monomer is in the range of 0.001 to 5 parts by mass based on 100 parts by mass of the total amount of all monomers used in the polymerization of the methacrylic resin (a).

Examples of the method for producing a methacrylic resin having a 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 in the range of 6 to 50% include a method of melt-blending a low-molecular-weight methacrylic resin and a high-molecular-weight methacrylic resin, a method of producing a methacrylic resin by a multistage polymerization method, and the like. When the methacrylic resin having Mp and a molecular weight of 1/5 or less is produced in a proportion of 6 to 50%, the method is not particularly limited, but from the viewpoint of quality stability, a multistage polymerization method is more preferably used.

In the case of using the multistage polymerization method, first, it is preferable to polymerize a methacrylate monomer and other vinyl monomers in the first polymerization stage to produce a polymer (i) having a weight average molecular weight of 5000 to 50000 as measured by GPC. Subsequently, the polymerization system is maintained at a temperature higher than the polymerization temperature in the first stage for a certain period of time. Thereafter, it is preferable to further polymerize the methacrylate monomer with other vinyl monomer in the presence of the polymer (i) to produce a polymer (ii) having a weight average molecular weight of 60000 to 350000. When the methacrylic resin is a homopolymer, homopolymerization is performed in the first and second polymerization stages without using any other vinyl monomer. In addition, when the methacrylic resin is a mixture of a homopolymer and a copolymer, homopolymerization may be performed in the first polymerization stage, and copolymerization may be performed in the second polymerization stage.

From the viewpoint of improving polymerization stability during production, fluidity of a methacrylic resin, mechanical strength of a resin molded product, and relaxation of molecular orientation on the surface of the molded product, the content of the polymer (i) is preferably 5 to 50% by mass relative to the total amount of the methacrylic resin, and the content of the polymer (ii) is preferably 95 to 50% by mass relative to the total amount of the methacrylic resin. In view of the balance among 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 the polymer (i)/the polymer (ii) is more preferably 7 to 47% by mass/93 to 53% by mass, still 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, and still more preferably 15 to 40% by mass/85 to 60% by mass.

The polymer (i) is preferably a polymer containing 80 to 100% by mass of a methacrylate monomer unit and 0 to 20% by mass of another vinyl monomer unit, more preferably a polymer containing 90 to 100% by mass of a methacrylate monomer unit and 0 to 10% by mass of another vinyl monomer unit, and further preferably a polymer containing 95 to 100% by mass of a methacrylate monomer unit and 0 to 5% by mass of another vinyl monomer unit. The ratio of the monomer unit constituting the polymer (i) can be adjusted by controlling the amount of the monomer to be added in the polymerization step of the polymer (i) in the multistage polymerization. The polymer (i) preferably contains a small amount of other vinyl monomers, and may contain no other vinyl monomers.

From the viewpoints of suppression of defects such as crazing during molding, polymerization stability, and flowability, the weight average molecular weight of the polymer (i) is preferably 5000 to 50000, more preferably 10000 to 45000, even more preferably 18000 to 42000, and particularly preferably 20000 to 40000. The weight average molecular weight of the polymer (i) can be controlled by adjusting the amounts of the chain transfer agent and the transfer initiation terminator by using these, and appropriately changing the polymerization conditions, as described above. The weight average molecular weight of the polymer (i) can be measured by GPC in the same manner as described above.

The polymer (ii) is preferably a polymer containing 80 to 99.9 mass% of a methacrylate monomer unit and 0.1 to 20 mass% of another vinyl monomer unit, more preferably a polymer containing 90 to 99.9 mass% of a methacrylate monomer unit and 0.1 to 10 mass% of another vinyl monomer unit, and further preferably a polymer containing 92.5 to 99.8 mass% of a methacrylate monomer unit and 0.2 to 7.5 mass% of another vinyl monomer unit. The ratio of the monomer unit constituting the polymer (ii) can be adjusted by controlling the amount of the monomer to be added in the polymerization step of the polymer (ii) in the multistage polymerization.

The weight average molecular weight of the polymer (ii) is preferably 60000 to 350000, more preferably 100000 to 320000, even more preferably 130000 to 300000, and even more preferably 150000 to 270000, from the viewpoint of solvent resistance and fluidity. The weight average molecular weight of the polymer (ii) can be controlled by adjusting the amounts of the chain transfer agent and the transfer initiation terminator as described above and by appropriately changing the polymerization conditions. The weight average molecular weight of the polymer (ii) can be measured by GPC in the same manner as described above.

The multistage polymerization method described above can easily control the respective compositions of the polymer (i) and the polymer (ii), suppress temperature rise due to heat generated during polymerization, and stabilize the viscosity in the system. In this case, the raw material composition mixture of the polymer (ii) may be brought into a state of starting partial polymerization before the polymerization of the polymer (i) is not completed, but a method of temporarily carrying out curing (in this case, maintaining a temperature higher than the polymerization temperature in the system) and adding the raw material composition mixture of the polymer (ii) after completion of the polymerization is preferable. By carrying out the curing in the first stage, not only the polymerization is completed, but also unreacted monomers, initiators, chain transfer agents, and the like can be removed or deactivated, thereby not adversely affecting the polymerization in the second stage. As a result, the intended weight average molecular weight can be obtained.

The polymerization temperature may be produced by appropriately selecting an optimum polymerization temperature according to the polymerization method, and is preferably 50 ℃ or higher and 100 ℃ or lower, and more preferably 60 ℃ or higher and 90 ℃ or lower. The polymerization temperatures of the polymer (i) and the polymer (ii) may be the same or different.

The temperature to be raised during curing is preferably 5 ℃ or higher, more preferably 7 ℃ or higher, and still more preferably 10 ℃ or higher than the polymerization temperature of the polymer (i). The time for holding at the temperature at which the temperature is raised during curing is preferably 10 minutes to 180 minutes, and more preferably 15 minutes to 150 minutes.

(method of kneading additives or colorants)

Examples of the method for obtaining a methacrylic resin composition by kneading a methacrylic resin with various additives or colorants described later include a method of kneading and producing the methacrylic resin composition by using a kneader such as an extruder, a heating roll, a kneader, a roll mixer, or a banbury mixer. In particular, kneading using an extruder is preferable in view of productivity. The methacrylic resin composition may be in the form of pellets.

The kneading temperature may be in the range of 150 to 350 ℃ as a standard, depending on the preferable processing temperature of the methacrylic resin.

After obtaining the methacrylic resin composition, a two-color injection molded article can be obtained by performing two-color molding or the like using the methacrylic resin composition. The methacrylic resin composition may be a methacrylic resin alone or a mixture of a methacrylic resin and additives, colorants, or the like.

[ thermoplastic resin ]

The thermoplastic resin contained in the base layer will be described below.

The thermoplastic resin contained in the primer layer is not particularly limited, and examples thereof include methacrylic resins, polystyrene resins, polycarbonate resins, Syndiotactic polystyrene resins, ABS resins (acrylonitrile, butadiene-styrene copolymers), AS resins (acrylonitrile, styrene copolymers), MBS resins (methyl methacrylate, butadiene-styrene copolymers), AAS resins (acrylonitrile, acrylate rubbers, styrene copolymers), ASA resins (acrylonitrile, styrene, acrylate rubber copolymers), AES resins (acrylonitrile, ethylene-propylene-diene, styrene), biodegradable resins, and modified polyphenylene ether resins. Among them, at least one selected from the group consisting of methacrylic resins, polycarbonate resins, ABS resins, AS resins, MBS resins, AAS resins, ASA resins, and AES resins is preferable, and polycarbonate resins, ABS resins, ASA resins, and AES resins are more preferable from the viewpoint of impact resistance. These may be used alone or in combination of two or more.

In addition, from the viewpoint of adhesion to the methacrylic resin of the surface layer, an amorphous resin is particularly preferable, and a polystyrene resin, a polycarbonate resin, an ABS resin, an AS resin, an ASA resin, and an AES resin are more preferable.

The thermoplastic resin may be a polymer alloy obtained by mixing a plurality of resins, preferably a polymer alloy containing polycarbonate and an ABS resin, and more preferably a polymer alloy consisting of only polycarbonate and an ABS resin.

The thermoplastic resin of the base layer may contain a colorant described later.

The thermoplastic resin is more preferably a thermoplastic resin having a vicat softening point temperature of 100 ℃.

The thermoplastic resin having a vicat softening point temperature of 100 ℃ or higher is not particularly limited, and examples thereof include heat-resistant acrylic resins, polystyrene resins, polycarbonate resins, syndiotactic polystyrene resins, ABS resins (acrylonitrile, butadiene-styrene copolymers), AS resins (acrylonitrile, styrene copolymers), MBS resins (methyl methacrylate, butadiene-styrene copolymers), AAS resins (acrylonitrile, acrylate rubbers, styrene copolymers), ASA resins (acrylonitrile, styrene, acrylate rubber copolymers), AES resins (acrylonitrile, ethylene-propylene-diene, styrene), biodegradable resins, and modified polyphenylene ether resins. Among them, at least one selected from the group consisting of heat-resistant acrylic resins, polycarbonate resins, ABS resins, AS resins, MBS resins, AAS resins, ASA resins, and AES resins is preferable, and polycarbonate resins, ABS resins, ASA resins, and AES resins are more preferable from the viewpoint of impact resistance. These may be used alone or in combination of two or more.

In addition, from the viewpoint of adhesion to the methacrylic resin of the surface layer, an amorphous resin is particularly preferable, and a polystyrene resin, a polycarbonate resin, an ABS resin, an AS resin, an ASA resin, and an AES resin are more preferable.

The thermoplastic resin may be a polymer alloy obtained by mixing a plurality of resins, preferably a polymer alloy containing polycarbonate and an ABS resin, and more preferably a polymer alloy consisting of only polycarbonate and an ABS resin.

The thermoplastic resin of the base layer may contain a colorant described later.

The above thermoplastic resin has a vicat softening point temperature of 100 ℃ or higher, and therefore tends to suppress appearance defects caused by reflow, more preferably 110 ℃ or higher, and still more preferably 115 ℃ or higher.

The vicat softening point temperature can be measured by the method described in the examples described later.

(method of kneading additives or colorants)

Examples of the method for obtaining the thermoplastic resin composition by kneading the thermoplastic resin contained in the base layer with various additives or colorants described later include a method of kneading and producing the thermoplastic resin composition by using a kneading machine such as an extruder, a heating roll, a kneader, a roll mixer, or a banbury mixer. In particular, kneading using an extruder is preferable in view of productivity. The thermoplastic resin composition may be in the form of pellets.

The kneading temperature may be in the range of 150 to 350 ℃ as a standard, depending on the preferable processing temperature of the thermoplastic resin.

After obtaining the thermoplastic resin composition, a two-color injection molded article can be obtained by performing two-color molding or the like using the thermoplastic resin composition. The thermoplastic resin composition may be a thermoplastic resin alone or a mixture of a thermoplastic resin and additives, colorants, or the like.

[ other additives ]

Various other additives may be added as necessary to the methacrylic resin of the surface layer and the thermoplastic resin of the primer layer constituting the two-color injection molded article of the present embodiment.

Examples of the additive include antistatic agents such as polyether-based, polyether ester amide-based, alkylsulfonate, and alkylbenzenesulfonate; stabilizers such as antioxidants, ultraviolet absorbers, heat stabilizers, and light stabilizers; a flame retardant; a flame retardant aid; a curing agent; a curing accelerator; a conductivity-imparting agent; a stress relaxation agent; a crystallization accelerator; a hydrolysis inhibitor; an impact-imparting agent; a compatibilizing agent; a nucleating agent; a fortifier; an enhancer; a flow modifier; a sensitizer; a rubbery polymer; a thickener; an anti-settling agent; an anti-sagging agent; a filler; defoaming agents; a coupling agent; a rust inhibitor; antibacterial and antifungal agents; an anti-fouling agent; 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 applications. Further, a rubbery copolymer may be added as a stress relaxation agent or an impact imparting agent.

When a methacrylic resin is used for the base layer, a rubber copolymer is preferably added from the viewpoint of impact resistance.

(Heat stabilizer)

Examples of the heat stabilizer include, but are not particularly limited to, antioxidants such as hindered phenol antioxidants and phosphorus processing stabilizers. Among them, a hindered phenol antioxidant is preferable. Although not particularly limited, examples of such a heat stabilizer include pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], thiodiethylene bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, N '-hexane-1, 6-diylbis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionamide ], 3', 5, 5 '-hexa-t-butyl-a, a' - (mesityl-2, 4, 6-triyl) tri-p-cresol, and mixtures thereof, 4, 6-bis (octylthiomethyl) o-cresol, 4, 6-bis (dodecylthiomethyl) o-cresol, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate ], hexamethylenebis [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-xylene) 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-triazin-2-ylamine) phenol, and the like, preferably pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]. These may be used alone or in combination of two or more.

(ultraviolet absorber)

Examples of the ultraviolet absorber include, but are not particularly limited to, benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, oxybenzophenone compounds, phenol compounds, oxazole compounds, malonate compounds, cyanoacrylate compounds, lactone compounds, salicylate compounds, and benzoxazinone compounds. Among them, benzotriazole compounds and benzotriazine compounds are preferable. These may be used alone or in combination of two or more.

In addition, from the viewpoint of obtaining excellent molding processability, the vapor pressure (P) of the ultraviolet absorber at 20 ℃ is preferably 1.0X 10^-4Pa or less, more preferably 1.0X 10^-6Pa or less, more preferably 1.0X 10^-8Pa or less. Here, "excellent moldability" means that, for example, a small amount of an ultraviolet absorber or the like is attached to the surface of a mold during injection molding, or a small amount of an ultraviolet absorber or the like is attached to a roller or the like during film molding. When the ultraviolet absorber adheres to the roller, the ultraviolet absorber eventually adheres to the surface of the intended molded article, and there is a risk of deterioration in appearance and optical characteristics, and therefore, when the molded article is used as an optical material, it is particularly important that the molding processability is excellent.

From the viewpoint of preventing bleeding, the melting point (Tm) of the ultraviolet absorber is preferably 80 ℃ or higher, more preferably 100 ℃ or higher, further preferably 130 ℃ or higher, and further more preferably 160 ℃ or higher.

From the viewpoint of preventing bleeding, when the temperature is raised from 23 ℃ to 260 ℃ at a rate of 20 ℃/min, the mass reduction rate of the ultraviolet absorber is preferably 50% or less, more preferably 30% or less, still more preferably 15% or less, still more preferably 10% or less, and still more preferably 5% or less.

(flame retardant)

The flame retardant is not particularly limited, but examples thereof include cyclic nitrogen compounds, phosphorus flame retardants, silicone flame retardants, caged silsesquioxane or a partially cleaved structure thereof, silica flame retardants, and the like.

The kneading method in the case of mixing various additives is not particularly limited, and may be carried out by the above-mentioned method.

[ coloring agent ]

The skin layer and/or the substrate layer may contain a colorant.

The colorant is not particularly limited, but is preferably a colorant selected from the group consisting of anthraquinone dyes, heterocyclic compound dyes, and perinone dyes from the viewpoint of weather resistance. The anthraquinone-based dyes are represented by color indexes, and examples thereof include Solvent Violet (Solvent Violet)36, Solvent Green (Solvent Green)3, Solvent Green (Solvent Green)28, Solvent Blue (Solvent Blue)94, Solvent Blue (Solvent Blue)97, and Disperse Red (Disperse Red) 22. The heterocyclic compound-based dye is represented by a color index, and examples thereof include Disperse Yellow (Disperse Yellow) 160. The perinone-based dye is expressed by a color index, and examples thereof include Solvent red (Solvent red) 179.

As other coloring agents, carbon BLACK, Ketjen BLACK, lion king BLACK (LIONITE BLACK, ライオナイトブラック), carbon nanotube, titanium oxide, calcium carbonate, talc, kaolin, mica, wollastonite, carbon nanotube, and the like can be used.

The above-mentioned coloring agents may be used singly or in combination of two or more.

The content of the colorant in the surface layer is preferably 0.1 to 2 parts by mass per 100 parts by mass of the methacrylic resin, from the viewpoint of increasing the depth of the jet-blackness by the methacrylic resin as the surface layer. When the amount is 0.1 parts by mass or more, the concealing property is expressed, and when the amount is 2 parts by mass or less, bleeding or deterioration of weather resistance can be suppressed. More preferably 0.1 to 1.7 parts by mass, still more preferably 0.2 to 1.6 parts by mass, and yet more preferably 0.3 to 1.5 parts by mass.

[ Properties of two-color injection-molded article ]

Hereinafter, the characteristics of the two-color injection molded article of the present embodiment will be described.

(Brightness L of two-color injection molded article)

The "brightness L" of the two-color injection molded article of the present embodiment refers to the brightness value L in the color values in the color system of la a b employed in JIS Z8729, and the "SCE method" refers to a method of measuring a color by removing specularly reflected light from a light trap using a spectrophotometer in accordance with JIS Z8722.

The brightness L in the SCE measurement of the two-color injection molded article of the present embodiment is 0.01 or more and 2.5 or less, preferably 0.01 or more and 2.3 or less, more preferably 0.01 or more and 2.0 or less, further preferably 0.01 or more and 1.5 or less, and particularly preferably 0.01 or more and 1.2 or less. When L is in the above range, light transmission to the underlayer can be suppressed, and the weather-resistant deterioration of the interface between the underlayer and the surface layer can be reduced.

In order to express the brightness L, the colorant is preferably added to the methacrylic resin contained in the surface layer. In particular, a two-color injection molded article having a higher appearance and excellent weather resistance can be obtained by making the methacrylic resin contained in the surface layer a jet black color.

In addition, even when a colorant is not added to the surface layer, the addition of the colorant to the underlayer makes it possible to adjust the brightness L, and when L of the two-color injection molded article is within the above range, light absorption by the colorant is caused, and the weathering degradation of the underlayer tends to be reduced.

(relationship between the thickness of the surface layer of the molded article and the thickness of the base layer)

The two-color injection molded article of the present embodiment preferably satisfies the relationship represented by the following formula (1) between the surface layer thickness t1 (unit: mm) and the base layer thickness t2 (unit: mm).

0.9≤t1/t2≤3 (1)

When the molded article has the relationship represented by the above formula (1), the molded article is excellent in appearance or mechanical strength.

t1/t2 is preferably 1.0 to 2.8, more preferably 1.1 to 2.6, and still more preferably 1.2 to 2.5. When t1/t2 is 1 or more, the appearance such as sink marks and weld seams of the surface layer tends to be eliminated, and when t1/t2 is 3 or less, the strength of the base layer tends to be maintained.

The thickness of the two-color injection molded article as a whole is preferably 4mm or less, more preferably 3.5mm or less, and still more preferably 3mm or less. When the thickness is 4mm or less, the weight of the member material can be reduced or the material cost can be reduced.

[ method for producing two-color injection molded article ]

The two-color injection molded article of the present embodiment can be produced, for example, as described below, and is preferably produced by a two-color molding method.

First, in order to form the base layer, a thermoplastic resin composition containing a thermoplastic resin in a pellet form is charged into a mold cavity of an injection molding machine as necessary. In this case, it is more preferable to use a mold having a mold cavity with a shape corresponding to the shape of the molded body, and two or more gates for improving the flow of the resin and reducing the molding deformation. In particular, in the case of molding a thermoplastic resin having a high heat resistance temperature or mechanical strength, molding with two or more gates is effective. The kind of the gate is preferably a needle gate, a side gate, or the like.

Next, the methacrylic resin composition as the surface layer was injection-molded by the injection molding machine under predetermined conditions. At this time, as the mold, a mold cavity having a shape corresponding to the shape of the molded body is used, and in order to suppress generation of a weld on the surface, a mold having one gate is preferably used.

The position of the gate in the mold is preferably a position in contact with a portion of the finally obtained molded body which is covered with another member and cannot be visually confirmed, and the type of the gate is preferably a side gate, a fan gate, a wing (tab) gate, a hot runner valve gate, or the like. Thus, the two-color injection molded article of the present embodiment can be obtained.

In order to obtain a long molded article, the length of the two-color injection molded article is preferably 100mm or more. More preferably 110mm or more, and still more preferably 120mm or more.

The two-color injection molded article may be produced by sandwich molding, and in this case, the base layer is a core layer.

The mold temperature at the time of injection molding of the surface layer is preferably adjusted to a range of vicat-65 ℃ to vicat-5 ℃ relative to the vicat softening point temperature of the methacrylic resin to be molded. The mold temperature is more preferably in the range of Vicat-60 to Vicat-10 ℃, still more preferably in the range of Vicat-55 to Vicat-15 ℃, and most preferably in the range of Vicat-50 to Vicat-20 ℃. By adjusting the content to this range, a two-color injection molded article having excellent appearance can be obtained.

When a polycarbonate-based resin is used as the thermoplastic resin, the mold temperature at the time of injection molding of the polycarbonate-based resin is preferably adjusted to a range of vicat-110 ℃ to vicat-20 ℃ relative to the vicat softening point temperature of the polycarbonate-based resin. The mold temperature is preferably in the range of Vicat-100 to Vicat-30 ℃ and more preferably in the range of Vicat-90 to Vicat-40 ℃. By adjusting the content to this range, a two-color injection molded article having excellent appearance can be obtained.

When an ABS resin is used as the thermoplastic resin, the mold temperature at the time of injection molding of the ABS resin is preferably adjusted to a range of vicat-75 ℃ to vicat-5 ℃ with respect to the vicat softening point temperature of the ABS resin. The mold temperature is more preferably in the range of Vicat-70 to Vicat-10 ℃, still more preferably in the range of Vicat-65 to Vicat-15 ℃, and most preferably in the range of Vicat-60 to Vicat-20 ℃. By adjusting the content to this range, a two-color injection molded article having excellent appearance can be obtained.

When a polymer alloy of a polycarbonate resin and an ABS resin (PC/ABS resin) is used as the thermoplastic resin, the mold temperature at the time of injection molding of the polymer alloy of the Polycarbonate (PC) resin and the ABS resin is preferably adjusted to a range of vicat-100 ℃ to vicat-10 ℃ relative to the vicat softening point temperature of the molded PC/ABS resin. The mold temperature is preferably in the range of Vicat-90 to Vicat-15 ℃ and more preferably in the range of Vicat-80 to Vicat-20 ℃. By adjusting the content to this range, a two-color injection molded article having excellent appearance can be obtained.

In addition, the molding method of the present invention can perform insert molding in which a molded body corresponding to the base layer, which is separately molded, is inserted into a mold to mold the surface layer, in addition to two-color molding in which the movable mold is rotated to continuously mold the surface layer after the base layer is molded.

[ use of two-color injection molded article ]

The two-color injection molded article of the present embodiment can be suitably used for various applications requiring surface hardness, high appearance, weather resistance and impact resistance. Although not particularly limited, such applications include furniture, household goods, storage/stocking goods, building materials such as walls and roofs, toys and amusement equipment, interesting applications such as marble panels (パチンコ panels), medical and welfare goods, OA equipment, AV equipment, battery electric equipment, lighting equipment, vehicle body members of structures of ships and airplanes, vehicle members, and the like, and particularly, the applications are suitably applied to vehicle applications such as vehicle body members and vehicle members, optical applications, and electric and electronic applications. Examples of optical applications include various lenses, touch panels, and transparent bases for solar cells.

In the fields of optical communication systems, optical switching systems, and optical measurement systems, the present invention can also be used as a waveguide, an optical fiber, a coating material for an optical fiber, a lens for an LED, a lens cover for EL lighting, and the like.

Examples of the electric and electronic applications include a display device such as a personal computer, a game machine, a television, a car navigation device, and an electronic paper, a printer, a copier, a scanner, a facsimile machine, an electronic organizer, a PDA, an electronic desktop computer, an electronic dictionary, a camera, a video camera, a mobile phone, a battery pack, a drive or a reader for a storage medium, a mouse, a numeric keypad, a CD player, an MD player, and a portable radio/audio player. In particular, the present invention can be suitably used for design members of housings of televisions, personal computers, car navigation systems, electronic paper, and the like.

In particular, it is preferably used as a design material for a motorcycle or an automobile, and more preferably used as a design material for an automobile. As the automotive design material, for example, an automotive exterior design material and an automotive interior design material can be cited, but from the viewpoint of more favorably utilizing the operational effects of the present invention, an automotive exterior design material is preferable. As the design material for the automobile exterior trim of the present embodiment, for example, a tail lamp trim, a rear lamp trim, a front lamp trim, a pillar trim, a front grill, a rear grill, a license plate trim, a wheel center cover, a license plate trim, a door mirror cover, and a sliding door pillar trim are preferable. These applications are generally thin-walled strip members, and design-oriented applications are important.

Examples

The present embodiment will be described in detail below with reference to examples, but the present embodiment is not limited to the examples described below.

[ raw materials used in examples and comparative examples ]

The raw materials used for the production of the two-color injection molded article are as follows.

(raw Material for methacrylic resin)

Methyl Methacrylate (MMA): manufactured by Asahi chemical Co., Ltd. (2,4-di-methyl-6-tert-butylphenol) manufactured by Zhou-Shi chemical Co., Ltd.) was added as a polymerization inhibitor).

Methyl Acrylate (MA): mitsubishi chemical (4-methoxyphenol (4-Methoxyphenol) manufactured by Kaikou chemical industry was added as a polymerization inhibitor in an amount of 14 ppm).

Ethyl Acrylate (EA): chemical system Mitsubishi.

Cyclohexyl maleimide: japanese catalyst.

Styrene: asahi Kasei (Asahi Kasei) K.K.

N-octyl mercaptan (n-octylmercaptan): prepared from Akema (アルケマ).

2-ethylhexyl thioglycolate (2-ethylhexyl thioglycolate): prepared from Asoma.

Lauroyl peroxide (lauroyl peroxide): made of Japanese oil and fat.

Tricalcium phosphate (calcium phosphate): manufactured by japan chemical industry, as a suspending agent.

Calcium carbonate (calcium calabonate): the white stone is industrially prepared and used as a suspending agent.

Sodium lauryl sulfate (sodium lauryl sulfate): and plain-chemical, used as a suspension aid.

(thermoplastic resin)

PC/ABS: techniace H-270(テクニエース H-270), color number 901 (manufactured by japan a & L (japan エイアンドエル)), vicat softening point temperature of 130 ℃.

PC-1: iipilon S-3000UR (ユーピロン S-3000UR), color number 9001 (made of Mitsubishi engineering plastics), and Vicat softening point temperature of 148 ℃.

PC-2: iipilon S-3000, transparent (made of Mitsubishi engineering plastics), and has a Vicat softening point temperature of 148 ℃.

Coloring (2) PC-2: 100 parts by mass of PC-2 is matched with B-2: 0.0005 part by mass, B-3: 0.001 parts by mass, B-5: 0.001 parts by mass of a colorant. The vicat softening point temperature was 148 ℃.

Coloring (3) PC-2: 100 parts by mass of PC-2 is matched with B-1: 0.1 part by mass, B-2: 0.025 parts by mass, B-3: 0.15 part by mass, B-4: 0.05 parts by mass, C-A1: 0.02 parts by mass of a colorant. The vicat softening point temperature was 148 ℃.

ABS-1: stylac ABS183(スタイラック ABS183), color number S133ST (black) (manufactured by Asahi Kasei corporation), Vicat softening point temperature 114 ℃.

ABS-2: stylac ABS220, color number S133ST (black) (manufactured by Asahi Kasei corporation), Vicat softening point temperature 98 ℃.

ABS-3: 100 parts by mass of Stylac ABS185 (manufactured by Asahi Kasei Co., Ltd.) was mixed with B-1: 0.1 part by mass, B-2: 0.03 part by mass, B-3: 0.2 part by mass, B-4: 0.05 parts by mass, C-A1: 0.02 parts by mass of a colorant. Vicat softening point temperature 124 ℃.

[ measurement and evaluation methods ]

Method for measuring 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 apparatus and conditions.

A measuring device: gel permeation chromatography (HLC-8320GPC, manufactured by Tosoh corporation).

Column: TSKgel SuperH 25001 root, TSKgel SuperHM-M2 root, TSKguardcolumn SuperH-H1 root, in series.

In this column, the high molecular weight elutes early and the low molecular weight elutes late.

A detector: an RI (differential refraction) detector.

Detection sensitivity: 3.0 mV/min.

Column temperature: at 40 ℃.

Sample preparation: 0.02g of a solution of the resin in 10mL of tetrahydrofuran.

Injection amount: 10 μ L.

Developing agent: tetrahydrofuran, flow rate; 0.6 mL/min.

As Calibration curve standard samples, the following 10 types of Polymethyl methacrylate (Poly methacrylate Calibration Kit PL 2020-0101M-M-10) having known monodisperse weight peak molecular weights and different molecular weights were used.

Since each of the polymethyl methacrylates used in the calibration curve as the standard sample is a single-peak material, (Mp) is expressed as a peak molecular weight, and is distinguished from the expression "peak top molecular weight" in the case where there are a plurality of peaks.

	Peak molecular weight (Mp)
		Standard test specimen 1	1916000
Standard specimen 2	625500
		Standard specimen No. 3	298900
Standard test specimen 4	138600
		Standard test specimen 5	60150
Standard specimen 6	27600
		Standard specimen 7	10290
Standard specimen 8	5000
		Standard specimen 9	2810
Standard test specimen 10	850

Under the above conditions, the RI detection intensity with respect to the elution time of the thermoplastic resin was measured.

Based on the area of the region in the GPC elution curve and a calibration curve of a cubic approximation formula, the weight average molecular weight (Mw), the molecular weight distribution (Mw/Mn), the GPC peak molecular weight (Mp), and the proportion (%) of components having a molecular weight of 1/5 or less of the GPC peak top molecular weight (Mp) of the methacrylic resin were determined.

Dupont impact Strength >

A DuPont drop impact tester (using a Toyo essence machine, a drop height of 1000mm at maximum, a drop weight of 12.7mm at an interval of 25mm, a diameter of 12.7mm, a pedestal of 12.7mm, a drop weight of 100-1000 g) was used to measure 50% impact energy impact strength at 23 ℃ in an environment according to JIS K7211-1 (2006). The larger the value of the impact strength, the more excellent the impact resistance. The test surface had to be subjected to an impact from the surface layer side and evaluated.

Brightness & lt III

The two-color injection molded articles obtained in examples and comparative examples were measured for brightness L by the SCE method (10 ° field/D65 illuminant) using a spectrophotometer ("CM-700D" manufactured by konica minolta japan, コニカミノルタジャパン). The lower the brightness L, the darker the color, and the two-color injection molded article having high appearance and excellent weather resistance was obtained.

Evaluation of appearance

(remelting)

The two-color injection molded article obtained was evaluated for appearance based on the length of remelting (remelting) generated in a semicircular shape from the vicinity of the gate of the base layer. Here, the reflow means that when the surface layer is formed after the formation of the base layer, a melting trace of the base layer is generated between the surface layer and the base layer (fig. 1A). In fig. 1A to C, for convenience of explanation, only the side gates provided in the central portion having a width of 70mm on the same side as the side gates of the surface layer, which are used in examples 11 and 21, are shown among the side gates of the base layer provided at two locations.

Remelting judgment standard

O (excellent): no appearance defects (remelt).

Δ (good): the appearance defect is less than 10 mm.

X (poor): the appearance defect is more than 10 mm.

(weld)

Appearance evaluation was performed according to the length of a weld (trace of collision between resins) formed on the flow end side of the obtained two-color injection molded body. Here, the weld refers to a defect that is caused to form streaks near the tip of the surface layer (near the end of 70mm width on the side opposite to the side gate) during the surface layer molding. The weld bead is often generated at a position where the resin flowing near the side surface of the mold merges with the resin flowing in the center of the mold.

Weld judgment reference

O (excellent): no welding seam.

Δ (good): the length of the welding seam is less than 10 mm.

X (poor): the length of the welding seam is more than 10 mm.

(sink mark)

The appearance of the flow end side sink marks (deformation) of the obtained two-color injection molded article was evaluated based on the reduction rate of the wall thickness. The wall thickness was measured at the gate side and at the flow end side, and the rate of decrease in wall thickness was calculated and evaluated. Here, sink marks mean that a thin portion is generated in the vicinity of the end of the skin layer when the skin layer is molded.

Wall thickness reduction ratio (%): (thickness of gate sidewall-thickness of flow tip sidewall) x 100/thickness of gate sidewall

Sink mark determination criterion

O (excellent): the reduction rate of the wall thickness is less than 3%.

Δ (good): the reduction rate of the wall thickness is 3% or more and less than 6%.

X (poor): the reduction rate of the wall thickness is more than 6%.

The molded article was subjected to appearance evaluation from the three viewpoints, and subjected to overall appearance evaluation based on the following "x" to "x" judgments.

Excellent: all the above appearance evaluations were evaluated as ∘.

O (slightly superior): any of the above appearance evaluations was Δ.

Δ (good): any two of the above appearance evaluations were Δ.

X (poor): any of the above appearance evaluations was x.

< V. evaluation of surface Pencil hardness >

The measurement was carried out in accordance with JIS K5600, and the surface pencil hardness of the two-color injection molded article was used as an index.

< VI weather resistance >

First, an exposure test of a two-color injection molded article was performed by a method of JIS K7350-4. The exposure conditions were such that the temperature of the black panel was set to 63. + -. 3 ℃, the time of spraying water was set to (18. + -. 0.5) minutes, the time of spray cessation was set to (102. + -. 0.5) minutes, and the total exposure time was 2000 hours. Under this condition, the surface layer side of the two-color injection molded body was exposed. The design surface was washed with water after exposure and prepared for the following evaluation of weather resistance.

The weather resistance was evaluated from the color difference before and after the above exposure test. As the color difference, the value of Δ E (Delta-E) is used. The color difference was measured by measuring L a b of the initial surface layer of the two-color injection molded article and the surface layer of the exposed same molded article in the SCE method (10 ° field/D65 light source) using a spectrophotometer ("CM-700D" manufactured by konica minolta japan) and calculating the color difference Δ E.

The weathering resistance was judged by the following evaluation of Δ E after 2000 hours exposure.

O (excellent): delta E is less than 3.

Δ (good): delta E is more than or equal to 3 and less than 5.

X (poor): delta E is more than or equal to 5.

< VII. comprehensive evaluation >

The two-color injection molded article was subjected to comprehensive evaluation according to the following criteria.

Excellent: the pencil hardness on the surface was H or more, the weather resistance was O determination, the overall appearance was O determination, and the DuPont impact strength was 15 kg/cm or more, all of which were satisfied.

O (slightly superior): the pencil hardness on the surface was H or more, the weather resistance was O, the comprehensive appearance evaluation was Delta, and the DuPont impact strength was 15 kg/cm or more, all of which were satisfied.

Δ (good): the surface pencil hardness is H or more, the overall appearance is evaluated as O or Delta, the weather resistance is evaluated as Delta, and/or the DuPont impact strength is 7 kg/cm or more and less than 15 kg/cm.

X (poor): the pencil hardness of the surface is less than H, the DuPont impact strength is less than 5kg cm, the weather resistance is judged by x, and the overall evaluation of the appearance is judged by x, which is in accordance with any one or more of the cases.

< VIII. Heat resistance >

The Vicat Softening Temperature (VST) of each resin of the surface layer and the base layer of examples and comparative examples described below was measured in accordance with ISO 306B 50 using an HDT test apparatus (heat distortion tester) (manufactured by toyo seiki corporation). The load was 50N and the rate of temperature rise was 50 ℃/hr.

< production example A1 (production of methacrylic resin (A-1) >)

Into a vessel equipped with a stirrer, ion-exchanged water: 2kg, tricalcium phosphate: 65g, calcium carbonate: 39g, sodium lauryl sulfate: 0.39g, thereby obtaining a mixed solution (a). Next, into a 60L reactor, ion-exchanged water: 26kg, warmed to 80 ℃, and charged with the mixture (a), methyl methacrylate: 21.2kg, methyl acrylate: 0.43kg, lauroyl peroxide: 27g and n-octyl mercaptan: 62 g.

Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80 ℃ and, after an exothermic peak was observed, the temperature was raised to 92 ℃ at a rate of 1 ℃/min and aging was carried out for 60 minutes to substantially complete the polymerization reaction.

Subsequently, after cooling to 50 ℃ and charging of 20 mass% sulfuric acid for dissolving the suspending agent, the polymerization reaction solution was passed through a 1.68mm mesh sieve to remove aggregates, and the obtained bead polymer was washed, dehydrated and dried to obtain polymer fine particles.

The obtained polymer fine particles were melt-kneaded using a twin-screw extruder having a diameter of 30mm set at 240 ℃, and the strands were cooled and cut to obtain resin pellets (methacrylic resin (a-1)).

The weight average molecular weight of the obtained resin particles was 10.2 ten thousand, and the molecular weight distribution (Mw/Mn) was 1.85. The structural unit was MMA/MA 98 mass%/2 mass%. The proportion (%) of components having a molecular weight of 1/5 or less and an Mp value was 4.6%.

The Vicat softening point temperature was 110 ℃.

< production example A2 (production of methacrylic resin (A-2) >)

Into a vessel equipped with a stirrer, ion-exchanged water: 2kg, tricalcium phosphate: 65g, calcium carbonate: 39g, sodium lauryl sulfate: 0.39g, thereby obtaining a mixed solution (b).

Next, into a 60L reactor, ion-exchanged water: 26kg, warmed to 80 ℃ and charged with the mixture (b) and methyl methacrylate: 3.76kg, ethyl acrylate: 0.1kg, lauroyl peroxide: 27g, 2-ethylhexyl thioglycolate: 62 g.

Thereafter, suspension polymerization was carried out while maintaining about 80 ℃. An exothermic peak was observed 80 minutes after the start of charging the raw materials. Thereafter, the temperature was raised to 92 ℃ at a rate of 1 ℃/min, and then the temperature was maintained at 92 ℃ to 94 ℃ for 30 minutes. Thereafter, the temperature was decreased at a rate of 1 ℃/min to 80 ℃, and then, methyl methacrylate: 17.4kg, ethyl acrylate: 1.35kg, lauroyl peroxide: 23g, n-octyl mercaptan: 35g, and suspension polymerization was continued while maintaining about 80 ℃. An exothermic peak was observed 105 minutes after the start of charging the raw materials.

Thereafter, the temperature was raised to 92 ℃ at a rate of 1 ℃/min, and then aged for 60 minutes to substantially complete the polymerization reaction.

Subsequently, after cooling to 50 ℃ and charging of 20 mass% sulfuric acid for dissolving the suspending agent, the polymerization reaction solution was passed through a 1.68mm mesh sieve to remove aggregates, and the obtained bead polymer was washed, dehydrated and dried to obtain polymer fine particles.

The obtained polymer fine particles were melt-kneaded using a twin-screw extruder having a diameter of 30mm set at 230 ℃, and the strands were cooled and cut to obtain resin pellets (methacrylic resin (a-2)).

The weight average molecular weight of the obtained beads was 11.8 ten thousand, the peak top molecular weight (Mp) was 12.5 ten thousand, and the molecular weight distribution (Mw/Mn) was 2.45. The structural unit was MMA/EA, 93.5 mass%/6.5 mass%. The proportion (%) of components having a molecular weight of 1/5 or less and an Mp value was 13.5%. The Vicat softening point temperature was 103 ℃.

< production example A3 (production of methacrylic resin (A-3) >)

Into a vessel equipped with a stirrer, ion-exchanged water: 2kg, tricalcium phosphate: 65g, calcium carbonate: 39g, sodium lauryl sulfate: 0.39g, thereby obtaining a mixed solution (c).

Next, into a 60L reactor, ion-exchanged water: 26kg, warmed to 80 ℃, and charged with the mixed solution (c), methyl methacrylate: 17.3kg, cyclohexylmaleimide: 1.77kg, styrene: 1.88kg, lauroyl peroxide: 27g and n-octyl mercaptan: 43 g. Thereafter, the suspension polymerization was carried out for 60 minutes while maintaining at about 77 ℃ and then, after raising the temperature to about 80 ℃, the suspension polymerization was carried out for 75 minutes, and after an exothermic peak was observed, the temperature was raised to 92 ℃ at a rate of 1 ℃/min and aging was carried out for 120 minutes to substantially complete the polymerization reaction.

Subsequently, after cooling to 50 ℃ and charging of 20 mass% sulfuric acid for dissolving the suspending agent, the polymerization reaction solution was passed through a 1.68mm mesh sieve to remove aggregates, and the obtained bead polymer was washed, dehydrated and dried to obtain polymer fine particles.

The obtained polymer fine particles were melt-kneaded using a twin-screw extruder having a diameter of 26mm set at 240 ℃ and the strands were cooled and cut to obtain resin pellets [ methacrylic resin (A-3) ].

The weight average molecular weight of the obtained resin particles was 12.6 ten thousand, and the molecular weight distribution (Mw/Mn) was 1.93. The structural unit was MMA/CMI/St 83/8/9 mass%. The proportion (%) of components having a molecular weight of 1/5 or less and an Mp value was 5.5%. The Vicat softening point temperature was 117 ℃.

[ examples 1 to 21 ] [ comparative examples 1 to 7]

When the methacrylic resin was pelletized at the blending ratio shown in table 2, the coloring agent shown in table 1 was added to adjust the color, and a molded article was produced by the method for producing a two-color injection molded article described later and evaluated.

[ Table 1]

[ method for producing two-color injection molded article ]

(injection Molding)

Pellets of a methacrylic resin and a thermoplastic resin were fed into a two-color injection molding machine to mold a two-color injection molded article (70 mm wide by 150mm long, ribs 5mm high on the long side 150mm long, the thickness of the 70mm by 150mm face was the same as that of the ribs, the surface layer was 0.5 to 3mm, and the base layer was 0.5 to 3mm) as an evaluation molded article.

The surface layer gate was provided with a side gate at the center of 70mm in width. The gate of the base layer was provided with one side gate at the center portion of 70mm in width and a second side gate on the opposite side of the first gate. In addition, the gate of the base layer can select both one gate and two gates. The molding conditions were set as follows.

An injection molding machine: manufactured by Sumitomo heavy machinery industry, SE-280D-CI (mold clamping force 280t, two-color molding).

Conditions of injection

Temperature of the die: at 70 ℃.

Filling speed: 100 mm/s.

Pressure maintaining time: for 10 sec.

Cooling time: for 20 sec.

Molding cycle of each layer: 50 sec.

Molding cycle of base layer + surface layer: for 100 sec.

Temperature of formation

Methacrylic resin: 260 ℃ or 270 ℃.

PC：300℃。

PC/ABS：280℃。

ABS: 260 ℃ or 270 ℃.

In example 10, the gate of the base layer was changed to two side gates, and injection molding was performed.

In example 21, sandwich molding was performed under the following conditions.

Pellets of a methacrylic resin and a thermoplastic resin were fed into a molding machine and molded into a molded article (70 mm in width × 150mm in length, ribs 5mm in height were provided on the long side 150mm in length, the thickness of the surface 70mm × 150mm was the same as that of the ribs, the surface layer was 0.5 to 3mm, and the base layer was 0.5 to 3mm) as a molded article for evaluation.

The surface layer gate was provided with a side gate at the center of 70mm in width. The gate of the core layer was provided with a side gate at the center of 70mm in width, and the core layer was molded after the surface layer was molded.

The molding conditions were set as follows.

An injection molding machine: JT220RAD-2M (mold clamping force 220t, sandwich molding) manufactured by Japan Steel works.

Conditions of injection

Temperature of the die: at 70 ℃.

Filling speed: 100 mm/s.

Pressure maintaining time: for 10 sec.

Cooling time: for 20 sec.

Molding cycle of each layer: 50 sec.

Molding cycle of base layer + surface layer: for 100 sec.

Temperature of formation

Methacrylic resin: at 260 ℃.

PC：300℃。

In example 1, the methacrylic resin of the surface layer was adjusted in color so that L is controlled within the range of claim 1, and therefore, the weather resistance was good. On the other hand, since the thickness ratio of the surface layer to the base layer is out of the more preferable range, the weld appearance is Δ, but other physical properties are at a practical level.

In example 2, since the thickness ratio of the surface layer to the base layer was slightly out of the preferable range, the appearance of sink marks or welds was Δ, but other physical properties were at a practical level.

In example 3 or 4, since the ratio of the weight average molecular weight of the methacrylic resin in the surface layer and the component having a molecular weight of 1/5 or less having a peak top molecular weight (Mp) was in a preferable range, a molded article having a higher appearance than that of example 1 was obtained, and since the L x value was also suitable, a two-color injection molded article having excellent weather resistance was obtained.

In example 5, the amount of the coloring agent in the methacrylic resin of the surface layer was slightly small, and the L value was close to the upper limit of the range of claim 1, and therefore the weather resistance was Δ, but other physical properties were at a practical level.

In example 6, the impact resistance was lowered because the thickness ratio of the surface layer to the base layer exceeded the preferable range, but other physical properties were at a practical level.

In example 7, the thickness of the base layer was made thinner than that of example 1 in order to reduce the thickness of the two-color injection molded article, and therefore the sink mark of the surface layer was Δ, and the impact resistance was slightly lowered, but the other physical properties were at a practical level.

In example 8, since the ratio of the weight average molecular weight of the methacrylic resin in the surface layer and the component having a molecular weight of 1/5 or less having a peak top molecular weight (Mp) was in a preferable range and PC/ABS was used for the base layer, a two-color injection molded article having excellent surface hardness, high appearance, weather resistance and impact resistance and being thinner than example 1 was obtained.

In example 9, since the thickness ratio of the surface layer to the base layer was in a more preferable range, a molded article having excellent surface hardness, high appearance, weather resistance and impact resistance was obtained.

In example 10, two side gates were used for molding the base layer of example 7, and therefore a molded article having a higher appearance and excellent impact resistance was obtained.

In example 11, ABS having a vicat softening point temperature close to 100 ℃ was used for the base layer, and L value was close to the upper limit of the range of claim 1, so that weather resistance was Δ and reflow was Δ, but other physical properties were at a practical level.

In example 12, the weight average molecular weight of the methacrylic resin of the surface layer and the ratio of the component having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) were in a preferable range, and therefore the evaluation of the reflow was good, and the weather resistance was Δ because the L value was close to the upper limit of the range of claim 1, but other physical properties were in practical level.

In example 13, since the value of L is close to the upper limit of the range of claim 1, the weather resistance is Δ and the reflow is Δ, but other physical properties are at a practical level.

Other physical properties were at practical levels.

In example 14, the thickness ratio or L value of the surface layer to the base layer was within a suitable range, and a two-color injection molded article was obtained which was excellent in surface hardness, high appearance and impact resistance.

In example 15, a two-color injection molded article was used as the base layer, which had an ABS having a vicat softening point temperature of 124 ℃, an L value within a suitable range, and excellent surface hardness, high appearance and impact resistance.

In example 16, since the value of L is close to the upper limit of the range of claim 1, the weather resistance is Δ and the reflow is Δ, but other physical properties are at a practical level.

In example 17, the weight average molecular weight of the methacrylic resin of the surface layer and the ratio of the component having a molecular weight of 1/5 or less of the peak top molecular weight (Mp) were in a preferable range, and therefore the evaluation of the reflow was good, and the weather resistance was Δ because the L value was close to the upper limit of the range of claim 1, but other physical properties were in practical level.

In example 18, a two-color injection molded article having excellent surface hardness, high appearance and impact resistance was obtained since the transparent PC was used as the base layer and the L value was within the range of claim 1.

In example 19, a two-color injection molded article excellent in practical use was obtained in the same manner as in example 7, although a heat-resistant acrylic was used for the surface layer.

In example 20, ABS having a vicat softening point temperature of 98 ℃ was used for the base layer, and the L value was close to the upper limit of the range of claim 1, and therefore, the weather resistance was Δ, but other physical properties were at a practical level.

In example 21, the sink mark was Δ and the impact strength was slightly lowered as compared with example 1 by performing the sandwich molding, but other physical properties were at a practical level.

In comparative example 1, since the methacrylic resin of the surface layer was transparent, the value of L was out of the range of claims, and the weather resistance was not at a practical level.

In comparative example 2, since the surface layer used polycarbonate, the molding flowability was poor, the appearance of the surface layer was not at a practical level, and the surface hardness was not at a practical level. Furthermore, since the value of L is out of the scope of claims, the weather resistance is also not at a practical level.

In comparative example 3, since ABS having vicat softening point temperature of 98 ℃ was used for the base layer, L value, which is out of the scope of claims, the weather resistance or the reflow evaluation was not at a practical level.

In comparative example 4, the value of L is out of the range of claims, and the weather resistance or the evaluation of reflow is not at a practical level.

In comparative examples 5 and 6, the value of L is out of the range of claims, and the weather resistance is not at a practical level.

In comparative example 7, the impact strength was not at a practical level because it was a single layer.

Industrial applicability

The use of the two-color injection molded article of the present embodiment can be industrially applied to all uses requiring no coating, surface hardness, high appearance, weather resistance and impact resistance.

Description of reference numerals

1: a surface layer; 2: a base layer; 3: and a side gate.

Claims (9)

1. A two-color injection-molded article characterized in that,

the sheet has a surface layer containing a methacrylic resin, and has a brightness L of 0.01 to 2.5 in SCE measurement.

2. The two-color injection molded body according to claim 1,

it further has a base layer containing a thermoplastic resin having a Vicat softening point temperature of 100 ℃ or higher.

3. Two-color injection molded body according to claim 1 or 2,

the base layer further comprises a thermoplastic resin, the thermoplastic resin is one or more selected from the group consisting of a methacrylic resin, a polycarbonate resin, an ABS resin, an AS resin, an MBS resin, an AAS resin, an ASA resin and an AES resin, the ABS resin is an acrylonitrile/butadiene/styrene copolymer, the AS resin is an acrylonitrile/styrene copolymer, the MBS resin is a methyl methacrylate/butadiene/styrene copolymer, the AAS resin is an acrylonitrile/acrylate rubber/styrene copolymer, the ASA resin is an acrylonitrile/styrene/acrylate rubber copolymer, and the AES resin is an acrylonitrile/ethylene/propylene/diene/styrene copolymer.

4. A two-color injection molded body according to claim 3,

the thermoplastic resin is one or more selected from the group consisting of polycarbonate resin and ABS resin, and the ABS resin is acrylonitrile and butadiene-styrene copolymer.

5. A two-color injection molded body according to any one of claims 2 to 4,

the thickness t1 of the surface layer and the thickness t2 of the base layer satisfy the relationship represented by the following formula (1), and the units of t1 and t2 are mm,

0.9≤t1/t2≤3 (1)。

6. a two-color injection molded body according to any one of claims 1 to 5,

the methacrylic resin has a weight average molecular weight of 50000 to 300000 as measured by gel permeation chromatography GPC,

the ratio of a component 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 to the total area of the GPC elution curve of the methacrylic resin is 6 to 50%.

7. A two-color injection molded body according to any one of claims 1 to 6,

it is a design material for two-wheeled vehicles or automobiles.

8. A two-color injection molded body according to claim 7,

which is a design material for automobile exterior trim.

9. A two-color injection molded body according to claim 8,

it is a tail lamp decoration, a rear lamp decoration, a front lamp decoration, a pillar decoration, a front grille, a rear grille, a license plate decoration, a wheel center cover, a license plate decoration, a door rearview mirror cover or a sliding door pillar decoration.

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