WO2021075551A1

WO2021075551A1 - Resin composition, resin molded article containing same, and method for manufacturing resin molded article

Info

Publication number: WO2021075551A1
Application number: PCT/JP2020/039104
Authority: WO
Inventors: 信平岡崎; 杉生　大輔; 洋劉; 札場　哲哉; 秀一黒井
Original assignee: 本田技研工業株式会社; 東洋アルミニウム株式会社
Priority date: 2019-10-18
Filing date: 2020-10-16
Publication date: 2021-04-22
Also published as: CN114514284A; JPWO2021075551A1; JP7385671B2; CN114514284B

Abstract

Provided is a resin composition that is used for manufacturing injection molded articles and that is capable of suppressing tainting of metal molds. This resin composition is used for manufacturing injection molded articles, and contains a thermoplastic resin and aluminum flake particles, wherein the aluminum flake particles have a coupling agent at least partially adhered to the surfaces thereof.

Description

A resin composition, a resin molded product containing the resin composition, and a method for producing the resin molded product.

The present invention relates to a resin composition, a resin molded product containing the same, and a method for producing the resin molded product.

In an injection molded product, a weld line, also called a welding line, may be formed at a position corresponding to the portion where the molten resin joins in the mold. This weld line may cause a poor appearance in the injection molded product and may cause a structural defect. As a means for preventing the formation of weld lines, a heat-and-cool method is known in which injection molding is performed by heating the mold temperature to a temperature equal to or higher than the glass transition temperature of the resin used as a raw material for the injection molded product.

On the other hand, the resin composition used for producing the injection-molded article is an aluminum pigment for the purpose of giving the injection-molded article a high-class feel and differentiating it from other injection-molded articles. It is known to use a resin composition containing the above. However, when an injection molded product is obtained by using the resin composition as a raw material and performing injection molding using the heat and cool method, the formation of weld lines is prevented, but the aluminum pigment is contained in the mold. It is known that the uneven distribution on the surface of the molten resin causes the resin to adhere to the mold and thus contaminate the mold. On the other hand, JP-A-2016-010957 (Patent Document 1) and JP-A-2014-185328 (Patent Document 2) describe the above-mentioned gold by coating the aluminum flake particles constituting the aluminum pigment with a resin. It proposes to control mold contamination.

Japanese Unexamined Patent Publication No. 2016-010957 Japanese Unexamined Patent Publication No. 2014-185328

However, the techniques disclosed in Patent Document 1 and Patent Document 2 are required to be further improved in order to suppress mold contamination. This is because, in the techniques disclosed in Patent Document 1 and Patent Document 2, the resin coating the aluminum flake particles may melt in the high temperature mold, and the resin melts around the aluminum flake particles. This is because it is presumed that it is insufficient to prevent the aluminum flake particles from being unevenly distributed on the surface of the molten resin by mixing with the molten resin. Therefore, in injection molding in which the formation of weld lines is prevented by using the heat and cool method, a technique for suppressing mold contamination when a resin composition containing an aluminum pigment or the like is used as a raw material is still realized. It has not, and its development is coveted.

In view of the above circumstances, an object of the present invention is to provide a resin composition capable of suppressing mold contamination, a resin molded body containing the resin composition, and a method for producing the resin molded body.

The present inventors have completed the present invention through repeated diligent studies in order to solve the above problems. Specifically, although the detailed mechanism is unknown, it was found that the coupling agent acts effectively on suppressing mold contamination among the innumerable additives contained in this type of resin composition. I found out. Based on this finding, when injection molding using the heat and cool method is performed using a resin composition containing a thermoplastic resin and aluminum flake particles having a coupling agent attached to at least a part of the surface, The present invention was reached with the idea that mold contamination can be suppressed.

That is, the present invention has the following features.
The resin composition according to the present invention is a resin composition used for producing an injection molded product, the resin composition contains a thermoplastic resin and aluminum flake particles, and the aluminum flake particles are the same. Coupling agent is attached to at least a part of the surface.

The coupling agent is preferably a silane coupling agent.
The coupling agent is more preferably an amino silane coupling agent.

The coupling agent is preferably contained in an amount of 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the aluminum flake particles.

The aluminum flake particles are preferably contained in an amount of 0.5 parts by mass or more and 230 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin in a state where the coupling agent is attached to the surface.

The thermoplastic resin is preferably one or more resins selected from the group consisting of acrylonitrile-butadiene-styrene resin, styrene-acrylonitrile copolymer, polystyrene and polyethylene.

The resin molded product according to the present invention contains the above resin composition.
The method for producing a resin molded product according to the present invention is a step of preparing the resin composition and maintaining the inner wall surface of the resin composition at a temperature at least 70 ° C. or higher higher than the glass transition temperature of the thermoplastic resin. It includes a step of injection-injecting into a mold and a step of obtaining a resin molded product by cooling the resin composition in the mold.

According to the present invention, it is possible to provide a resin composition capable of suppressing mold contamination, a resin molded body containing the resin composition, and a method for producing the resin molded body.

Hereinafter, an embodiment according to the present invention (hereinafter, also referred to as “the present embodiment”) will be described in more detail. In the present specification, the notation in the form of "A to B" means the upper and lower limits of the range (that is, A or more and B or less), and when the unit is not described in A and the unit is described only in B, A The unit of and the unit of B are the same.

[Resin composition]
The resin composition according to this embodiment is a resin composition used for producing an injection molded product. The resin composition contains a thermoplastic resin and aluminum flake particles. A coupling agent is attached to at least a part of the surface of the aluminum flake particles. The resin composition having such characteristics can suppress mold contamination when injection molding using the heat and cool method is performed. Hereinafter, each feature of the resin composition according to the present embodiment will be described.

The resin composition is a resin composition used for producing an injection molded product as described above. The "injection molded product" refers to a molded product obtained by applying a conventionally known injection molding method to a resin composition containing a thermoplastic resin. Specifically, it refers to a molded product obtained by heating and fluidizing the resin composition in a cylinder provided in a conventionally known injection molding machine, injecting the resin composition into a mold, and cooling the resin composition in the mold. .. Further, in the present specification, the “resin molded product” means an injection molded product obtained by applying an injection molding method to the resin composition according to the present embodiment.

<Thermoplastic resin>
The resin composition according to the present embodiment contains a thermoplastic resin and aluminum flake particles as described above. As used herein, the term "thermoplastic resin" means a resin that can be used in the above-mentioned injection molding method by being softened by heating. Therefore, as long as the resin is softened by heating and can be used in the above-mentioned injection molding method, even a resin generally included in the concept of "thermosetting resin" is treated as "thermoplastic resin" in the present specification. It shall be.

The thermoplastic resin contained in the above resin composition is, for example, acrylonitrile-butadiene-styrene resin (ABS resin), acrylonitrile-styrene-acrylate resin (ASA resin), acrylonitrile-ethylene-propylene-diene-styrene resin (AES resin). Rubber reinforced resins such as polystyrene (PS resin), styrene-acrylonitrile copolymer (AS resin), styrene-maleic anhydride copolymer, (meth) acrylic acid ester-styrene copolymer and other styrene-based (co) Polymer; Olefin resin such as polyethylene (PE resin) and polypropylene; Cyclic polyolefin resin; Polyester resin; Polyamide resin; Polycarbonate resin; Polyarylate resin; Polyacetal resin; Polyvinyl chloride, Ethylene-vinyl chloride polymer, Poly Vinyl chloride resin such as vinylidene chloride; (meth) acrylic resin such as (co) polymer using one or more (meth) acrylic acid esters such as polymethyl methacrylate (PMMA); polyphenylene ether; polyphenylene sulfide; Fluororesin such as polytetrafluoroethylene and polyvinylidene fluoride; liquid crystal polymer; imide resin such as polyimide, polyamideimide and polyetherimide; ketone resin such as polyetherketone and polyetheretherketone;polysulfone, polyethersulfone and the like Polysulfonate resin; urethane resin; polyvinyl acetate; polyethylene oxide; polyvinyl alcohol; polyvinyl ether; polyvinyl butyral; phenoxy resin; photosensitive resin; biodegradable plastic and the like.

The above-mentioned various thermoplastic resins may be contained alone in the above-mentioned resin composition, or may be contained by mixing two or more kinds. Here, the term "(meth) acrylic" as used herein means at least one of acrylic and methacrylic. The term "(meth) acrylo" shall also mean at least one of acrylo and methacrylo.

The thermoplastic resin is preferably one or more resins selected from the group consisting of ABS resin, AS resin, PS resin and PE resin. As a result, a resin molded product having a desired shape can be molded from the resin composition with good yield, and the resin molded product can be applied to various uses.

The weight average molecular weight (Mw) of the thermoplastic resin is preferably 2000 to 7000000, more preferably 2000 to 1000000. Further, as the thermoplastic resin, it is preferable to use a thermoplastic resin having a glass transition temperature of 280 ° C. or lower, and more preferably to use a thermoplastic resin having a glass transition temperature of 150 ° C. or lower. Even when the thermoplastic resin has at least one of the above-mentioned weight average molecular weight and the above-mentioned glass transition temperature, a resin molded product having a desired shape can be molded from the above-mentioned resin composition with good yield. It can be applied to various uses.

<Aluminum flake particles>
The resin composition according to the present embodiment contains a thermoplastic resin and aluminum flake particles as described above. A coupling agent is attached to at least a part of the surface of the aluminum flake particles. As used herein, the term "aluminum flake particles" refers to particles containing aluminum and having a flat flake shape. That is, the aluminum flake particles may be flake-shaped particles made of aluminum or flake-shaped particles made of an aluminum alloy, and may be a base of a metal (such as copper, nickel, iron, tin or an alloy thereof). It may be flaky particles obtained by depositing aluminum on a base material of a material or a non-metal (ceramic particles such as alumina and titania, glass or mica). These aluminum flake particles can be obtained by a conventionally known method. The surface of the aluminum flake particles is preferably smooth from the viewpoint of exhibiting the desired surface glossiness, whiteness and brilliance in the resin composition.

In the resin composition, the aluminum flake particles are preferably contained in an amount of 0.5 parts by mass or more and 230 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin in a state where the coupling agent described later is attached to the surface thereof. .. When the aluminum flake particles are contained in the above-mentioned range with respect to 100 parts by mass of the thermoplastic resin, the resin composition can more sufficiently suppress mold contamination. Here, when the resin composition is not prepared in the form of a masterbatch as described later, in the resin composition, the aluminum flake particles are in a state where the coupling agent described later is attached to the surface thereof, and the thermoplastic resin 100 is attached. It is preferably contained in an amount of 0.5 parts by mass or more and 50 parts by mass or less with respect to parts by mass.

When the resin composition is not prepared in the form of a masterbatch as described later, when the content of aluminum flake particles is less than 0.5 parts by mass, the desired surface glossiness cannot be obtained in the resin composition. Tend. Further, when the content of the aluminum flake particles exceeds 50 parts by mass, the dispersibility of the aluminum flake particles in the thermoplastic resin deteriorates, so that sufficient strength cannot be obtained in the resin molded product obtained from the above resin composition. Tend. From the viewpoint of more fully exerting the effects of the present invention, when the resin composition is not prepared in the form of a masterbatch as described later, the aluminum flake particles have the thermoplasticity in a state where the coupling agent is attached to the surface thereof. It is more preferable that the resin is contained in an amount of 0.5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the resin.

On the other hand, the above resin composition may be prepared in the form of a masterbatch as described later. In this case, the content of the aluminum flake particles is preferably 5 parts by mass or more and 230 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin in a state where the coupling agent described later is attached to the surface thereof.

The average particle size (D50) of the aluminum flake particles is preferably 2 to 150 μm, and more preferably 5 to 50 μm. The aluminum flake particles preferably have an average thickness (t) of 0.01 to 10 μm, more preferably 0.08 to 1.6 μm. Further, the aluminum flake particles preferably have an average aspect ratio of 5 to 2500, and more preferably 10 to 150.

Here, the "average aspect ratio" means the ratio of the average particle size (D50) of the aluminum flake particles to the average thickness (t), and specifically, the average particle size (D50) (unit) of the aluminum flake particles. Can be obtained from the formula of μm) / average thickness (t) of aluminum flake particles (unit: μm).

The average particle size (D50) and average thickness (t) of the aluminum flake particles were obtained by applying an injection molding method to the resin composition when the resin composition was used as a measurement object and by applying an injection molding method to the resin composition. Can be obtained by the following measurement methods, respectively.

The average particle size (D50) and average thickness (t) of the aluminum flake particles can be obtained by the following method when the resin composition is used as the measurement target. That is, the particle size of the aluminum flake particles is measured by observing the pellets of the resin composition using a scanning electron microscope (SEM), and the particle size of the aluminum flake particles is measured based on the particle size of the 50 or more particles. Calculate the average particle size. When it is difficult to observe the particle size of the aluminum flake particles by the pellets, a flat surface is formed by polishing the surface of the pellets, or the pellets are made into a film by using a hot press machine, and SEM is used for these. The average particle size of the aluminum flake particles can be calculated. The average thickness of the aluminum flake particles can also be calculated by measuring 50 or more aluminum flake particles using SEM in the same manner as the measurement of the average particle size. Even when it is difficult to observe the thickness of the aluminum flake particles by the pellet, the surface of the pellet is polished or made into a film in the same manner as the measurement of the average particle size, and the average thickness of the aluminum flake particles is measured by SEM. Can be calculated.

The average particle size (D50) and average thickness (t) of the aluminum flake particles are calculated by calculating the average particle size and the average thickness of the aluminum flake particles using the resin composition as the measurement target when the resin molded body is the measurement target. It can be the same as the method. When it is difficult to measure the resin molded product as it is, the surface of the resin molded product is cut to form a flat cross section, and the cross section is observed by SEM to obtain the above average particle size and average thickness. Can be done.

(Coupling agent)
A coupling agent is attached to at least a part of the surface of the aluminum flake particles. The coupling agent has an action of binding the inorganic compound and the organic compound via itself by having a reactive group that chemically bonds with the inorganic compound and a reactive group that chemically bonds with the organic compound in one molecule. Refers to a compound that has. As a result, the adhesion between the aluminum flake particles and the thermoplastic resin can be enhanced, and when the above resin composition is used for injection molding, the aluminum flake particles are unevenly distributed on the surface of the molten thermoplastic resin in the mold. Can be suppressed.

Here, when the coupling agent "adheres" to the surface of the aluminum flake particles, the coupling agent is chemically bonded to the surface of the aluminum flake particles by a reactive group that chemically bonds with the above-mentioned inorganic compound of the coupling agent. Means to do.

The coupling agent is preferably a silane coupling agent. The example silane coupling _{_{_{agent, R A -Si (OR B)}}} 3 or _{_{_{_{R A -SiR B (OR B)}}}} 2 (R A,: alkyl group having 2 to 18 carbon atoms, an aryl group or an alkenyl group, _{R B} : It is preferable to use a silane coupling agent represented by the chemical formula (alkyl group having 1 to 3 carbon atoms). Further, _RA preferably has a functional group. _{Examples of the functional group of RA} include an amino group, a ureido group, an epoxy group, a sulfide group, a vinyl group, a (meth) acryloxy group, a mercapto group, a ketimino group, a glycidyl group, a phenyl group, an imidazole group and an isocyanate group. can do. The coupling agent is more preferably an amino silane coupling agent.

Specific examples of silane coupling agents include γ-methacryloxypropyltrimethoxysilane, vinyltricrolsilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyl-tris (β-methoxyethoxy) silane, and vinylmethoxysilane. , Vinyltrimethoxysilane, vinylethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxy Silane, 3-mercaptopropyltrimethoxysilane, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propaneamine, N, N'-bis [3- (trimethoxysilyl) propyl ] Ethylenediamine, tetraisocyanasilane, monomethyltriisocyanatesilane and the like can be mentioned.

Further, as the above-mentioned coupling agent, a titanium (titanate) -based coupling agent, a zirconia-based coupling agent, an aluminum-based coupling agent, or the like can also be used. Specific titanate-based coupling agents include, for example, isopropylisostearoyl diacrylic titanate, isopropyltriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, and tetra (2,2-diallyloxymethyl-1-butyl) bis (di-). Tridecyl) phosphite titanate and the like can be mentioned. Specific examples of the zirconia-based coupling agent include tetranormal propoxyzirconium, tetranormalbutoxyzirconium, zirconium tetraacetylacetone, zirconium tributoxyacetylacetone, zirconium tributoxystearate, and zirconyl acetate. Specific examples of the aluminum-based coupling agent include acetoalkoxyaluminum diisopropyrate, zircoaluminate, alkylacetate aluminum diisopropirate, and acetoalkoxyaluminum diisopropyrate.

The coupling agent is preferably contained in an amount of 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the aluminum flake particles. The coupling agent is more preferably contained in an amount of 0.15 to 3 parts by mass, more preferably 0.2 to 2 parts by mass, based on 100 parts by mass of the aluminum flake particles. When the content of the coupling agent is in the above range, the adhesion between the aluminum flake particles and the thermoplastic resin can be further improved.

When the content of the coupling agent is less than 0.1 parts by mass with respect to 100 parts by mass of the aluminum flake particles, the adhesion between the aluminum flake particles and the thermoplastic resin tends to be insufficient. When the content of the coupling agent exceeds 10 parts by mass with respect to 100 parts by mass of the aluminum flake particles, the aluminum flake particles tend to easily aggregate.

The method of adhering the coupling agent to the surface of the aluminum flake particles is not particularly limited as long as the effect of the present invention is not adversely affected, and a conventionally known method can be used. For example, by kneading the coupling agent and the aluminum flake particles using a conventionally known kneader, mixer or stirrer, the coupling agent can be adhered to the surface of the aluminum flake particles. In this case, an organic solvent can be appropriately added. As the organic solvent, for example, one selected from the group consisting of ethanol, isopropyl alcohol, toluene, xylene, MEK, methanol, hexane, butanol, acetone, ethylene glycol, methyl cellosolve and butyl cellosolve can be used alone. It is also possible to use a mixed solvent in which two or more kinds selected from the group consisting of the above-mentioned organic solvents are mixed.

Further, when the coupling agent and the aluminum flake particles are kneaded using a conventionally known kneader or the like, it is preferable to add deionized water as needed. This makes it easier for the coupling agent to adhere to the surface of the aluminum flake particles. The amount of deionized water added can be 0.03 to 3 parts by mass with respect to 100 parts by mass of the aluminum flake particles. For the purpose of promoting the adhesion reaction of the coupling agent to the surface of the aluminum flakes, the temperature inside the cylinder of the kneader containing the coupling agent and the aluminum flake particles is heated to 20 to 80 ° C., or the kneading is performed. The temperature of the kneaded product containing the coupling agent and the aluminum flake particles obtained by using the machine can be heated to 20 to 80 ° C.

(Organic compounds such as fatty acids)
The aluminum flake particles have one or more organic compounds selected from the group consisting of fatty acids such as oleic acid and stearic acid, aliphatic amines, aliphatic amides, aliphatic alcohols and ester compounds attached to the surface thereof. May be good. These organic compounds can improve the surface glossiness by suppressing unnecessary oxidation of the surface of aluminum flake particles. The organic compound may be added as a grinding aid when obtained by grinding aluminum flake particles from aluminum powder. The content of the organic compound is preferably less than 2 parts by mass with respect to 100 parts by mass of the aluminum flake particles.

When an organic compound such as a fatty acid is attached to the surface of the aluminum flake particles, the coupling agent and the organic compound are mixed on the surface of the aluminum flake particles by a chemical equilibrium. Or it is presumed that it exists as a coexisting layer.

(Other additives)
The resin composition according to the present embodiment may further contain the following additives depending on the purpose, as long as the effects of the present invention are not adversely affected. Additives include, for example, mica, color pigments, phosphorescent pigments, color dyes, colorants such as fluorescent dyes, fillers, antioxidants, antioxidants, heat stabilizers, weather stabilizers, UV absorbers, infrared absorbers. Agents, photochromic agents, antifouling agents, antistatic agents, plasticizers, lubricants, flame retardants, optical brighteners, light diffusers, crystal nucleating agents, flow modifiers, impact modifiers, pigment dispersants, etc. be able to.

[Manufacturing method of resin composition]
The resin composition according to this embodiment can be produced by a conventionally known method. For example, the above resin composition can be obtained by the following production method. That is, first, by kneading the coupling agent and the aluminum flake particles using a kneader or the like as described above, the aluminum flake particles to which the coupling agent adheres to the surface (hereinafter, “aluminum flake particles adhering to the coupling agent”). ”) Is prepared. Next, the coupling agent-attached aluminum flake particles and the above-mentioned thermoplastic resin are selected from the group consisting of a Banbury mixer, a single-screw vented extruder, a twin-screw vented extruder, a kneader, a roll, and a feeder ruder. The resin composition can be obtained by melt-kneading using the melt-kneading machine. The temperature at the time of melt-kneading may be appropriately selected based on the glass transition temperature of the resin used as the thermoplastic resin, and may be, for example, 100 to 300 ° C.

Here, the resin composition obtained by the above-mentioned production method is a masterbatch in which a predetermined amount of aluminum flake particles is filled in a thermoplastic resin for the purpose of obtaining better dispersibility of aluminum flake particles in a resin molded product described later. It can be prepared as a form of. In this case, the content of the aluminum flake particles in the resin composition may be 5 parts by mass or more and 230 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin in a state where the coupling agent is attached to the surface thereof. preferable.

[Resin molded product]
The resin molded product according to the present embodiment contains the above resin composition. This makes it possible to provide resin molded products having various shapes having brilliant properties without contaminating the mold. In the resin molded body, the formation of weld lines is also suppressed. The resin molded body is a resin molded body having a brilliant property, for example, a housing of an electronic device such as a notebook computer or a mobile phone, a housing of a household electric machine such as a vacuum cleaner, a fan, a telephone, a printer, or a housing of an office device. It is suitable for applications such as interior and exterior parts of automobiles, miscellaneous goods, and housing equipment. The resin molded product can be applied not only to the final product but also as a part in the product. Therefore, it can be applied not only to the above-mentioned applications but also to a wide range of applications.

[Manufacturing method of resin molded product]
The method for producing a resin molded product according to the present embodiment includes a step of preparing the resin composition (first step) and a temperature at which the resin composition is at least 70 ° C. higher than the glass transition temperature of the thermoplastic resin. Including a step of injection-injecting into a mold in which the inner wall surface is maintained (second step) and a step of obtaining a resin molded product by cooling the resin composition in the mold (third step). By the method for producing a resin molded product having such characteristics, it is possible to obtain resin molded products having various shapes that have brilliance and suppress the formation of weld lines without contaminating the mold. Become. Hereinafter, each step of the first step to the third step will be described.

<First step>
The first step is a step of preparing the resin composition. Specifically, in this step, the resin composition can be prepared by executing the method for producing the resin composition described above.

<Second step>
The second step is a step of injecting the resin composition into a mold having an inner wall surface maintained at a temperature at least 70 ° C. or higher higher than the glass transition temperature of the thermoplastic resin. Specifically, in this step, a mold for injection molding is first prepared according to a conventionally known heat and cool method, and the temperature of the inner wall surface of the mold is adjusted by using a conventionally known mold temperature adjusting means. The temperature is at least 70 ° C. higher than the glass transition temperature of the thermoplastic resin. Next, the thermoplastic resin contained in the resin composition is melted by heating in a cylinder of a conventionally known injection molding machine or the like. Finally, the resin composition containing the molten thermoplastic resin is injected and injected into the mold whose inner wall surface is maintained at the above temperature.

This makes it possible to prevent the formation of weld lines in the resin molded product obtained by this production method. Further, since the adhesion between the aluminum flake particles and the thermoplastic resin is improved by the coupling agent, it is possible to prevent the aluminum flake particles from being unevenly distributed on the surface of the molten thermoplastic resin in the mold.

Here, the temperature of the inner wall surface of the mold is preferably a temperature 70 ° C. or higher higher than the glass transition temperature of the thermoplastic resin as described above, and is higher than the glass transition temperature of the thermoplastic resin by 80 ° C. or more. It is more preferable that the temperature is higher than, for example, 90 ° C. The upper limit of the temperature of the inner wall surface of the mold may be the same as the molding temperature of the thermoplastic resin. The glass transition temperature of the thermoplastic resin can be measured by using a differential thermal analysis method (DTA: Differential thermal analysis).

<Third step>
The third step is a step of obtaining a resin molded product by cooling the resin composition in the mold. Specifically, in this step, the resin composition injected and injected into the mold is cooled according to a conventionally known heat and cool method. After that, a resin molded product can be obtained by splitting the mold. Since the resin molded product is manufactured by using the heat and cool method, it is possible to prevent the formation of weld lines. Furthermore, since the adhesion between the aluminum flake particles and the thermoplastic resin is improved by the coupling agent, it is possible to prevent the aluminum flake particles from being unevenly distributed on the surface of the molten thermoplastic resin in the mold, and the metal is divided. It is possible to prevent the mold from being contaminated by aluminum flake particles. Since the resin molded product is prevented from being unevenly distributed on the surface of the molten resin of the aluminum flake particles, high smoothness can be obtained on the surface of the resin molded product.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Manufacturing of resin composition (master batch)]
The resin compositions of Examples 1 to 3 and Comparative Examples 1 to 2 were produced by using the following methods.

<Example 1>
Aluminum paste prepared in the form of a paste containing aluminum flake particles having an average particle size (d50) of 21 μm and an average thickness (t) of 0.5 μm (trade name (product number): “5422NS”, manufactured by Toyo Aluminum Co., Ltd.) , Solid content (500 g) was dispersed in 2 L of mineral spirit to obtain a dispersion. Aluminum flake particles were obtained by filtering and washing this dispersion. Next, the above aluminum flake particles, 3 g of deionized water and 3 g of γ-aminopropyltriethoxysilane (trade name (product number): "KBE-903", manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 60 g of isopropyl alcohol. The treated solution was put into a commercially available kneader mixer. Further, these were kneaded in the above kneader mixer for 1 hour to obtain a coupling agent-attached aluminum flake particle dispersion having a solid content of 55% by mass.

730 g (solid content 400 g) of the above-mentioned coupling agent-attached aluminum flake particle dispersion and 1600 g of acrylonitrile-butadiene-styrene resin (ABS resin, trade name (product number): "GA-501", manufactured by Nippon A & L Inc., glass transition Temperature: 90 ° C.) was mixed using a mixer to obtain a mixture. A resin composition formed into pellets by kneading and granulating this mixture using an extruder (trade name: "ZSK type twin-screw extruder", manufactured by Coperion Co., Ltd.) at a temperature inside the cylinder of 190 ° C. to 220 ° C. Manufactured a product (masterbatch). The content of the aluminum flake particles in this resin composition was 25 parts by mass with respect to 100 parts by mass of the thermoplastic resin in a state where the coupling agent was attached to the surface.

<Example 2>
The resin composition (masterbatch) was obtained by carrying out the same method for producing a resin composition as in Example 1 except that the amount of deionized water contained in the above treatment solution was 1 g and the amount of γ-aminopropyltriethoxysilane was 1 g. ) Was manufactured.

<Example 3>
By executing the same method for producing a resin composition as in Example 1 except that the amount of deionized water contained in the above treatment solution was 25 g and the amount of γ-aminopropyltriethoxysilane was 25 g, the resin composition (masterbatch) was carried out. ) Was manufactured.

<Comparative example 1>
A treatment solution containing the above-mentioned coupling agent for the aluminum flake particles contained in the dispersion liquid in which the above-mentioned aluminum paste (trade name (product number): "5422NS", manufactured by Toyo Aluminum K.K., solid content 500 g) is dispersed in the mineral spirit. An aluminum flake particle dispersion having a solid content of 55% by mass was prepared from the above dispersion without kneading. Next, the above aluminum flake particle dispersion (solid content 400 g) and the same ABS resin as in Example 1 are mixed to obtain a mixture, and the above mixture is used in the same extruder as in Example 1 and is the same as in Example 1. A resin composition (masterbatch) formed into pellets was produced by kneading and granulating under the conditions.

<Comparative example 2>
A resin-coated aluminum paste containing aluminum flake particles having an average particle size (d50) of 21 μm and an average thickness (t) of 0.5 μm, and the surface of the aluminum flake particles coated with an acrylic resin (trade name (product number)). : "FZ5422", manufactured by Toyo Aluminum Co., Ltd.) was prepared. Next, this resin-coated aluminum paste (solid content 400 g) is mixed with the same ABS resin as in Example 1 to obtain a mixture, and the above mixture is used in the same extruder as in Example 1 and under the same conditions as in Example 1. A resin composition (masterbatch) formed into pellets was produced by kneading and granulating with.

[Manufacturing of resin molded products]
Next, by carrying out each of the following steps, from the resin compositions of Examples 1 to 3 and Comparative Examples 1 to 2, the corresponding Examples 1 to 3 and Comparative Examples 1 to 1 to The resin molded products of Comparative Example 2 were produced respectively.

First, 42 g of the resin composition (masterbatch) and 800 g of the ABS resin are put into a twin-screw extruder with a vent and a diameter of 20 mm (trade name: "ZSK type twin-screw extruder", manufactured by Coperion Co., Ltd.). Was melt-mixed and extruded at a temperature in the cylinder of 220 ° C. to prepare a molding resin composition having an aluminum flake particle content of 1% by mass (first step). Next, using an injection molding machine (trade name: "FNX220III", manufactured by Nissei Resin Industry Co., Ltd.), the resin composition for molding has a rectangular shape of width 120 mm × length 150 mm × thickness 5 mm and has a plurality of through holes. Was injected into a plate molding die having the above (second step).

In the second step, the temperature inside the cylinder provided in the injection molding machine was set to 240 ° C. On the other hand, plate molding dies heated to 80 ° C, 120 ° C, 130 ° C, 140 ° C, 150 ° C, 160 ° C, 170 ° C, 180 ° C, 190 ° C and 200 ° C, respectively, are prepared and injected. The above molding resin composition was injection-injected from the molding machine into each plate molding die.

Further, using a commercially available low-temperature oil temperature controller and water-cooled temperature controller, the temperature of the inner wall surface of each plate molding die is set to 30 ° C. to cool the molding resin composition in the die, and then the molding resin composition is cooled. A resin molded body was manufactured by dividing each plate molding die (third step). That is, for plate molding in which the temperature of the inner wall surface is heated to 80 ° C., 120 ° C., 130 ° C., 140 ° C., 150 ° C., 160 ° C., 170 ° C., 180 ° C., 190 ° C. and 200 ° C. by executing the third step. Each resin molded body (10 pieces in total) molded using a mold was manufactured.

Here, since the above-mentioned plate molding die has a plurality of through holes, a portion where the molten resin joins is generated in the die. Therefore, when injection molding is performed without using the heat-and-cool method and without heating the inner wall temperature of the mold to at least 70 ° C. or higher than the glass transition temperature of the ABS resin, the molten resin is formed in the mold in the resin molded body. Weld lines may be formed at the points corresponding to the merging parts.

[Evaluation of resin molded product]
<Visual confirmation of weld line formation>
Whether or not a weld line was formed on the surface of each of the resin molded products of Examples 1 to 3 and Comparative Examples 1 to 2 was visually observed. As a result, Examples 1 to 3 and Comparative Examples obtained by using a plate molding die in which the temperature of the inner wall surface was heated to 160 ° C. or higher, which is at least 70 ° C. or higher than the glass transition temperature of the ABS resin. No weld line was observed on the surface of each of the resin molded products of 1 to 2 of Comparative Example 2. On the other hand, on the surfaces of the resin molded bodies of Examples 1 to 3 and Comparative Examples 1 to 2 obtained by using a plate molding die in which the temperature of the inner wall surface was heated to 150 ° C. or lower, Weld lines were observed in both cases.

<Confirmation of mold contamination>
A transparent adhesive tape having a length of 80 mm and a width of 24 mm (trade name: "Cellotape (registered trademark)", manufactured by Nichiban Co., Ltd.) on the surfaces of the resin molded bodies of Examples 1 to 3 and Comparative Examples 1 to 2. ), And by rubbing the tape with your fingertips, the transparent adhesive tape is brought into close contact with the surfaces of the resin molded bodies of Examples 1 to 3 and Comparative Examples 1 to 2, and then from the surface. The transparent adhesive tape was peeled off so as to be peeled off at 180 degrees. Next, the transparent adhesive tape peeled off from the surface of the resin molded product was attached to a black mount, and a digital microscope (trade name: "VHX-6000", manufactured by KEYENCE CORPORATION) was used at a magnification of 500 times. The number of aluminum flake particles adhering to the transparent adhesive tape was determined. The evaluation was performed in one field of view (400 μm × 600 μm) and ranked based on the following criteria. The results are shown in Table 1. Here, the number of aluminum flake particles adhering to the transparent adhesive tape shows a positive correlation with the number of aluminum flake particles that cause mold contamination due to uneven distribution on the surface of the molten resin in the mold. Is presumed. Therefore, the resins of Examples 1 to 3 and Comparative Examples 1 to 2 are obtained by determining the number of aluminum flake particles adhering to the transparent adhesive tape and ranking them based on the following criteria. It is possible to evaluate whether or not the composition can suppress mold contamination when injection molding using the heat and cool method is performed.

A: It is estimated that the number of aluminum flake particles is 3 or less, and mold contamination can be suppressed more sufficiently.
B: The number of aluminum flake particles is 4 to 10, and it is estimated that mold contamination can be suppressed.
C: It is estimated that the number of aluminum flake particles is 11 or more, and the suppression of mold contamination is insufficient.

[Discussion]
From the above, the resin compositions of Examples 1 to 3 and the resin molded product containing the same were injection-molded using a mold heated to at least 70 ° C. or higher than the glass transition temperature of the thermoplastic resin. In this case, the formation of weld lines can be prevented in the same manner as in the conventional (Comparative Examples 1 and 2) resin molded products. Further, according to Table 1, the resin compositions of Examples 1 to 3 and the resin molded product containing the same are injected using a mold heated to at least 70 ° C. or higher than the glass transition temperature of the thermoplastic resin. It is understood that when molding is performed, it is possible to suppress uneven distribution of aluminum flake particles on the surface of the molten resin as compared with Comparative Example 1 and Comparative Example 2, and thus mold contamination can be suppressed.

Although the embodiments and examples of the present invention have been described above, it is planned from the beginning that the configurations of the above-described embodiments and examples are appropriately combined.

It should be considered that the embodiments and examples disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

Claims

A resin composition used in the production of injection molded products.
The resin composition contains a thermoplastic resin and aluminum flake particles.
The aluminum flake particles are a resin composition in which a coupling agent is attached to at least a part of the surface thereof.
The resin composition according to claim 1, wherein the coupling agent is a silane coupling agent.
The resin composition according to claim 1 or 2, wherein the coupling agent is an amino-based silane coupling agent.
The resin composition according to any one of claims 1 to 3, wherein the coupling agent is contained in an amount of 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the aluminum flake particles.
Claims 1 to 4, wherein the aluminum flake particles are contained in an amount of 0.5 parts by mass or more and 230 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin in a state where the coupling agent is attached to the surface. The resin composition according to any one of the following items.
The thermoplastic resin is one or more resins selected from the group consisting of acrylonitrile-butadiene-styrene resin, styrene-acrylonitrile copolymer, polystyrene and polyethylene, according to any one of claims 1 to 5. The resin composition described.
A resin molded product containing the resin composition according to any one of claims 1 to 6.
The step of preparing the resin composition according to any one of claims 1 to 6, and the step of preparing the resin composition.
A step of injecting the resin composition into a mold in which the inner wall surface is maintained at a temperature at least 70 ° C. or higher higher than the glass transition temperature of the thermoplastic resin.
A method for producing a resin molded product, which comprises a step of obtaining a resin molded product by cooling the resin composition in the mold.