ASA-based graft copolymer and resin composition using the same

Abstract

To provide an ASA-based graft copolymer which can improve or hold both impact resistance and color development property when a matrix resin such as polycarbonate and the ASA-based graft copolymer are used in combination, and a resin composition using the same.SOLUTION: An ASA-based graft copolymer has a seed, a core layer and a shell layer in this order. Here, the average particle diameter of an internal virtual particle component composed of the seed and the core layer is 60-90 nm, and the thickness of the core layer is 7-18 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to ASA-based graft copolymers and resin compositions using the same. [Background technology]

[0002] Polycarbonate is a resin widely used in the manufacture of automobiles, electronic components, and other products due to its many desirable physical properties, including impact resistance, colorfastness, transparency, strength, flame retardancy, electrical properties, and heat resistance. However, polycarbonate alone has a high melt viscosity and poor moldability, and is known to have a particularly large thickness dependence on impact resistance.

[0003] To complement these properties, polycarbonate is sometimes used in the form of an alloy with, for example, ASA (acrylate-styrene-acrylonitrile) resin. ASA-based resins are also provided as ASA-based graft copolymers having the form of particles (specifically, virtual particles) composed of, for example, a seed, core layer, and shell layer.

[0004] On the other hand, resin compositions containing various resins such as polycarbonate, ABS (acrylonitrile butadiene styrene), PBT (polybutylene terephthalate), and SAN (styrene acrylonitrile) resin as matrix resins, along with ASA-based graft copolymers, are known (Patent Documents 1 and 2).

[0005] However, it has been pointed out that the ASA-based graft copolymer constituting the resin composition reduces the inherent good color development of polycarbonate, for example, when polycarbonate is used as the matrix resin. This reduction in color development makes it difficult to obtain a satisfactory appearance from the resulting resin composition.

[0006] While such improvements in appearance can be achieved through painting, for example, there is a growing demand to avoid painting altogether, given the impact of environmental burdens, exemplified by recent trends such as carbon neutrality and the SDGs. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6029029 [Patent Document 2] Patent No. 5948716 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the above-mentioned problems, and its objective is to provide an ASA-based graft copolymer and a resin composition using the same that can improve or maintain both impact resistance and color development when using a matrix resin such as polycarbonate and an ASA-based graft copolymer in combination. [Means for solving the problem]

[0009] The present invention relates to an ASA-based graft copolymer having a seed layer, a core layer, and a shell layer in that order, The average particle diameter of the internal virtual particle portion composed of the seed and core layer is 60-90 nm. The core layer has a thickness of 7 to 18 nm and is an ASA-based graft copolymer.

[0010] In one embodiment, the thickness of the core layer is 8 to 16 nm.

[0011] In one embodiment, the average particle diameter of the internal virtual particle portion is 65 nm to 80 nm.

[0012] In one embodiment, the seed contains styrene units, the core layer contains acrylate units, and the shell layer contains acrylonitrile units.

[0013] The present invention also provides a resin composition containing the above ASA graft copolymer and a matrix resin.

[0014] In one embodiment, the matrix resin is composed of at least one resin selected from the group consisting of polycarbonate, poly(styrene-acrylonitrile), polybutylene terephthalate, and polyethylene terephthalate.

[0015] In one embodiment, the matrix resin is polycarbonate.

Advantages of the Invention

[0016] According to the present invention, a resin composition can be obtained in which the reduction of impact resistance and color development is prevented by combining with a matrix resin. As a result, a resin molded body having an excellent appearance can be easily provided by omitting a coating treatment such as painting. Furthermore, by omitting the coating treatment, the use of materials that cause environmental loads such as solvents can be avoided or reduced.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail.

[0018] (ASA graft copolymer) The ASA graft copolymer of the present invention has a seed, a core layer, and a shell layer in this order.

[0019] The seed has a form of fine particles that constitute the central portion in the virtual particles described later.

[0020] Examples of materials that make up the seeds include those derived from aromatic vinyl compounds, vinyl cyanide compounds, alkyl (meth)acrylate compounds, and combinations thereof (hereinafter, these may be collectively referred to as seed-forming materials).

[0021] Examples of aromatic vinyl compounds include styrene, α-styrene, p-styrene, and vinyltoluene, as well as combinations thereof.

[0022] Examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile, as well as combinations thereof.

[0023] Examples of alkyl (meth)acrylate compounds include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, 2-ethylhexyl methacrylate, methyl ethyl ethyl ethyl methacrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate, as well as combinations thereof.

[0024] In forming the seeds, the seed-forming material may optionally contain a crosslinking agent and / or emulsifier. Examples of crosslinking agents include divinylbenzene, 3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, allyl acrylate, allyl methacrylate, trimethylolpropane triacrylate, tetraethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, triallyl isocyanurate, triarylamine, and diallylamine, as well as combinations thereof. Emulsifiers are not particularly limited and include those known in the art.

[0025] In the present invention, the material constituting the seed is preferably composed of an aromatic vinyl compound and a crosslinking agent, or preferably contains styrene units as a whole, for the reason that the impact resistance and transparency of the resulting resin composition are improved.

[0026] The size of the seeds is not particularly limited, but it is preferable that they have a predetermined average particle size for the purpose of more uniform dispersion in the matrix resin described later as an ASA-based graft copolymer. The average particle size of the seeds is preferably 24 nm to 76 nm, more preferably 28 nm to 74 nm, even more preferably 40 nm to 65 nm, and most preferably 45 nm to 60 nm. Having the average particle size of the seeds within this range allows for good impact resistance to be imparted to the resulting resin composition when used in the form of an alloy with a matrix resin such as polycarbonate.

[0027] The core layer acts as an intermediary between the seed and the shell layer, and together with the seed, the core layer constitutes the internal virtual particle portion in the ASA-based graft copolymer of the present invention.

[0028] Herein, the term "internal virtual particle portion" as used herein refers to the portion corresponding to a theoretical virtual particle (also called a core particle) obtained by attaching a core layer to a seed. For example, the internal virtual particle portion includes any of the following: (1) a state in which part or all of the outer surface of the seed is surrounded by the material constituting the core layer; (2) a state in which one particle of the material constituting the core layer is attached to one seed particle (referred to as a seed particle); and (3) a state in which one or more seed particles and one or more particles of the material constituting the core layer are attached to each other, forming a single particle as a whole; and any combination thereof.

[0029] In the ASA-based graft copolymer of the present invention, the average particle diameter of the internal virtual particle portion (composed of the seed and core layers) is 60 nm to 90 nm, preferably 65 nm to 80 nm. If the average particle diameter of the internal virtual particle portion falls below 60 nm or exceeds 90 nm, the resulting mixture of the ASA-based graft copolymer and matrix resin (resin composition) may have reduced impact resistance.

[0030] The material constituting the core layer is an acrylic rubber, obtained, for example, by polymerization of alkyl acrylate (hereinafter sometimes referred to as the core layer-forming material) and a crosslinking agent.

[0031] Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate, as well as combinations thereof. More specific examples of alkyl acrylates include n-butyl acrylate and 2-ethylhexyl acrylate, as well as combinations thereof.

[0032] The crosslinking agent that may be used for the core layer is the same as that that may be used for the seed layer. In addition, during the polymerization of the alkyl acrylate and the crosslinking agent, polymerization initiators and / or emulsifiers known in the art may be added together with them.

[0033] Thus, it is preferable that the material constituting the core layer contains acrylate units due to the alkyl acrylate mentioned above.

[0034] The thickness of the core layer is 7 nm to 18 nm, preferably 8 nm to 16 nm. If the core layer thickness is less than 7 nm, the resulting mixture of ASA-based graft copolymer and matrix resin (resin composition) may have reduced impact resistance. If the core layer thickness exceeds 18 nm, the resulting mixture of ASA-based graft copolymer and matrix resin (resin composition) may have poor color development and an undesirable appearance.

[0035] The thickness of the core layer can be measured and calculated, for example, using a microtrac particle size distribution analyzer, during the fabrication stage of the ASA-based graft copolymer of the present invention. That is, the thickness of the core layer is first calculated by the average particle size (R) of the seed alone. s The particle diameter distribution is measured using a particle diameter distribution analyzer, and then, at the stage when the core layer is added to the seed (the stage when the internal virtual particle portion is created), the average particle diameter (R) of the internal virtual particle portion is measured again using the particle diameter distribution analyzer. n ) are measured, and finally the difference between them (R n -R s This can be obtained by calculating ).

[0036] The shell layer is primarily applied to the core layer (or internal virtual particle portion) and constitutes part or all of the outer surface of the ASA-based graft copolymer.

[0037] Examples of materials that constitute the shell layer include those derived from aromatic vinyl compounds, vinyl cyanide compounds, alkyl (meth)acrylate compounds, and combinations thereof (hereinafter, these may be collectively referred to as shell-forming materials). Specific examples of shell-forming materials are the same as those for seed-forming materials described above.

[0038] In forming the shell layer, the shell-forming material may contain crosslinking agents and / or emulsifiers as needed. The crosslinking agents and emulsifiers that may be used for the shell layer are the same as those that may be used for the seed.

[0039] Furthermore, in order to enhance the polymerization reactivity during the formation of the shell layer and to ensure that the resulting ASA-based graft copolymer has an appropriate refractive index, the shell layer-forming material may contain, in addition to the crosslinking agent and / or emulsifier, other components (A) such as alkyl methacrylate and α-methylstyrene, or combinations thereof.

[0040] From the viewpoint of improving compatibility with matrix resins such as polycarbonate, the graft copolymer of the present invention preferably has a shell layer composed of a vinyl cyanide compound and an aromatic vinyl compound, and more preferably contains acrylonitrile units.

[0041] The thickness of the shell layer is 7 nm to 18 nm, preferably 8 nm to 16 nm. If the shell layer thickness is less than 7 nm, the impact resistance of the resin composition obtained by using it in combination with a matrix resin may decrease. If the shell layer thickness exceeds 18 nm, the transparency of the resin composition obtained by using it in combination with a matrix resin may decrease.

[0042] The thickness of the shell layer can be measured and calculated, for example, using a microtrac particle size distribution analyzer during the fabrication stage of the ASA-based graft copolymer of the present invention. That is, the thickness of the shell layer is calculated by using a microtrac particle size distribution analyzer at the stage in which the core layer is applied to the seed (the stage in which the internal virtual particle portion is fabricated) to determine the average particle diameter (R) of the internal virtual particle portion. n The average particle diameter (R) of the ASA-based graft copolymer was measured, and then, at the stage when the shell layer was applied to the core layer (or internal virtual particle portion) (the stage when the ASA-based graft copolymer was fabricated), the particle diameter distribution analyzer was used again to measure the average particle diameter (R) of the ASA-based graft copolymer. Z ) are measured, and finally the difference between them (R Z -R n This can be obtained by calculating ).

[0043] The ASA-based graft copolymer of the present invention can be prepared, for example, as follows.

[0044] First, a seed-forming material, a crosslinking agent, and an emulsifier as needed are added to an aqueous medium (e.g., water) and stirred for a predetermined time. These materials polymerize to form particles, ultimately creating a latex in which the seeds are dispersed in the aqueous medium. In this latex, the obtained seeds can be used directly in the next step without any particular separation.

[0045] Next, the seed obtained above (existing in the form of latex), a core-forming material, a crosslinking agent, and a polymerization initiator as needed are added to a further aqueous medium (e.g., water) under stirring, thereby conferring a core layer to the seed in the aqueous medium (i.e., forming an internal virtual particle portion).

[0046] Subsequently, by adding a shell-forming material and a crosslinking agent, and optionally an emulsifier and / or other component (A), and stirring for a predetermined time, particles can be obtained in which a shell layer is formed on the outside of the core layer (internal virtual particle portion). These particles are then coagulated or aggregated by means known in the art.

[0047] In this way, an ASA-based graft copolymer having a seed layer, a core layer, and a shell layer in that order can be obtained.

[0048] The resulting ASA-based graft copolymer can be used, for example, as a resin additive to improve the physical properties of a matrix resin, as described later. In particular, the ASA-based graft copolymer of the present invention is useful as a resin additive for polycarbonate because it can improve both the impact resistance and color development of the resulting resin composition.

[0049] (Resin composition) The resin composition of the present invention contains the above-mentioned ASA-based graft copolymer and a matrix resin.

[0050] Examples of matrix resins that can constitute the resin composition include polycarbonate, poly(styrene-acrylonitrile), polybutylene terephthalate, and polyethylene terephthalate, as well as combinations thereof. Polycarbonate is particularly preferred as the matrix resin because it can more effectively improve both the impact resistance and color development of the resulting resin composition.

[0051] The content of the ASA-based graft copolymer and matrix resin in the resin composition of the present invention is not particularly limited, but for example, 0.5 to 40 parts by mass, preferably 0.5 to 30 parts by mass of ASA-based graft copolymer is mixed with 60 to 99.5 parts by mass, more preferably 70 to 99.5 parts by mass of matrix resin. By having the ASA-based graft copolymer and matrix resin in these ranges, the resulting resin composition can improve both impact resistance and color development without impairing the various physical properties inherent in the matrix resin.

[0052] The resin composition of the present invention may also contain other additives as needed. Examples of other additives include: Examples of the additives include activators, heat stabilizers, antioxidants, light stabilizers, pigments, dyes, anti-scratch agents, flame retardants, antibacterial agents, mold release agents, nucleating agents, plasticizers, compatibilizers, and inorganic additives, as well as combinations thereof. The content of other additives that can be included in the resin composition is not particularly limited and can be appropriately selected by those skilled in the art within the range that does not inhibit the above effects of the present invention.

[0053] According to the resin composition of the present invention, by taking advantage of its excellent impact resistance and color development property, a resin molded body having a good appearance can be produced without the need for coating treatments such as painting. The obtained resin molded body is useful, for example, as automotive parts, electronic and electrical parts, and / or building materials.

Examples

[0054] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

[0055] In addition, evaluations were performed in each example and comparative example by the following methods.

[0056] [ (Core particle diameter) From the latex containing the obtained core particles, the average particle diameter of the core particles (corresponding to the average particle diameter (R n )) of the internal virtual particle portion) was measured using a Microtrac particle size distribution measuring device (manufactured by Nikkiso Co., Ltd. (UPA-EX150)). This average particle diameter was referred to as the core particle diameter. From the viewpoint of impact resistance, the core particle diameter is preferably 60 to 90 nm, more preferably 65 to 88 nm. Also, from the viewpoint of appearance, the core particle diameter is preferably 90 nm or less, more preferably 80 nm or less.

[0057] (Core thickness) Subtracting the average particle diameter (R n ) of the seed measured in advance from the core particle diameter (average particle diameter (R S )) obtained above (R n - R sThe core thickness was calculated. From the viewpoint of impact resistance, a core thickness of 7 nm or more is preferable, and 8 nm or more is more preferable. Also, from the viewpoint of appearance, a core particle diameter of 18 nm or less is preferable, and 16 nm or less is more preferable.

[0058] (Graft rate) One g of the ASA-based graft copolymer, isolated from latex containing the ASA-based graft copolymer described later, was added to 80 mL of acetone and heated under reflux at 65-70°C for 3 hours. The resulting suspension of acetone solution was centrifuged at 14,000 rpm for 30 minutes using a centrifuge (Hitachi Koki Co., Ltd. "CR21E") to separate the precipitated component (acetone-insoluble component) from the acetone solution (acetone-soluble component). The precipitated component (acetone-insoluble component) was then dried, and its mass (Y(g)) was measured. The graft rate was calculated using the following formula (1). In formula (1), Y is the mass (g) of the acetone-insoluble component of the ASA-based graft copolymer, X is the total mass (g) of the ASA-based graft copolymer used to determine Y, and the rubber fraction is the solid content concentration in the aqueous dispersion of core particles containing seeds used in the production of the ASA-based graft copolymer. Graft rate (mass %) = {(YX × rubber fraction) / X × rubber fraction} × 100 (1)

[0059] Furthermore, a grafting ratio of 80% or more is preferable from the viewpoint of impact resistance, and 84% or more is more preferable.

[0060] (Impact resistance) A resin composition was used to form molded parts measuring 80 mm in length, 10 mm in width, and 4 mm in thickness using an injection molding machine (Toshiba Machine Co., Ltd., "IS55FP-1.5A") under conditions of cylinder temperature 200°C to 270°C and mold temperature 60°C. These molded parts were used as Charpy impact test molded parts (Ma1). For molded parts (Ma1), the Charpy impact strength (impact direction: edgewise) of the molded part (Type B1, with notch: Shape A single notch) was measured at a test temperature of 23°C in accordance with ISO 179-1:2013. A higher Charpy impact strength indicates superior impact resistance.

[0061] (transparency) A resin composition pellet was injected using an injection molding machine (Toshiba Machine Co., Ltd., "IS55FP-1.5A") under conditions of cylinder temperature 260°C and mold temperature 60°C to form molded products measuring 100 mm in length, 100 mm in width, and 3 mm in thickness. These molded products were used as transparency evaluation molded products (Molded product (Ma2)). The total light transmittance (Tt) of the molded product (Ma2) was measured using a haze meter (Nippon Denshoku Industries Co., Ltd. (NDH2000)). A higher total light transmittance was judged to indicate higher transparency.

[0062] (Color development) During melt-mixing, 1.6 parts by mass of carbon black masterbatch (Koshigaya Chemical Industry Co., Ltd. (ROYALBLACK919P)) was added to color the resin composition pellets. These pellets were then injected into a molded product measuring 100 mm in length, 100 mm in width, and 3 mm in thickness using a Toshiba Machine Co., Ltd. "IS55FP-1.5A" injection molding machine under conditions of cylinder temperature 260°C and mold temperature 60°C. This product was used as a molded product for color development evaluation (molded product (Ma3)). The lightness (L*:SCE) of the molded product (Ma3) was measured using a spectrophotometer (Konica Minolta Japan, Inc. (CM-26d)). A lower lightness value was judged to indicate higher color development.

[0063] (Score (Impact Resistance)) The impact resistance values ​​of the resin compositions obtained above were classified according to the following criteria and evaluated as impact resistance scores for the obtained resin compositions: <Score of resin composition (impact resistance)> 0 points... The impact resistance of the resin composition is 42 kJ / m². 2 The score was less than [value missing]. Resin compositions exhibiting this score have significantly inferior impact resistance compared to 100% polycarbonate resin compositions. Two points... The impact resistance of the resin composition is 42 kJ / m². 2 More than 49kJ / m 2 The score was less than [value missing]. Resin compositions exhibiting this score can be used as substitutes for polycarbonate applications. 4 points... The impact resistance of the resin composition is 49 kJ / m² 2 More than 55kJ / m 2The score was less than [amount missing]. Resin compositions exhibiting this score are excellent as polycarbonate alternatives. 8 points... The impact resistance of the resin composition is 55 kJ / m². 2 That concludes the findings. The resin compositions exhibiting this score are superior as alternatives to polycarbonate.

[0064] (Score (Appearance)) The transparency values ​​of the resin compositions obtained above were classified according to the following criteria and evaluated as an appearance score for the obtained resin compositions: <Score of resin composition (appearance)> 0 points... The transparency of the resin composition was less than 44%. Resin compositions with this score have significantly poor transparency. 2 points... The transparency of the resin composition was between 44% and 47%. Resin compositions exhibiting this score have excellent transparency. 4 points... The transparency of the resin composition was between 47% and 51%. Resin compositions showing this score have better transparency. 8 points... The transparency of the resin composition was 51% or higher. Resin compositions showing this score exhibit even better transparency.

[0065] (Manufacturing Example 1: Seed (A1) Production) 338.5 parts by mass of water were added to a reactor equipped with a reagent injection container, a condenser, a jacket heater, and a stirrer. Further, 90 parts by mass of styrene, 10 parts by mass of divinylbenzene (crosslinking agent), and 3 parts by mass of sodium dodecylbenzenesulfonate (emulsifier) ​​were added and stirred, and while the mixture was dispersed in water as oil droplets, the mixture was purged with nitrogen gas. Then, an aqueous solution of 61.5 parts by mass of water, 1 part by mass of potassium persulfate, and 61.5 parts by mass of water was added, and the mixture was stirred at 60°C for 180 minutes to obtain seed (A1) in the form of latex.

[0066] The average particle size of the obtained seed (A1) was measured from the latex using a Microtrac particle size distribution analyzer (UPA-EX150, manufactured by Nikkiso Co., Ltd.). The results are shown in Table 1.

[0067] (Manufacturing Example 2: Seed (A2) Production) Latex containing seed (A2) was prepared in the same manner as in Production Example 1, except that the amount of sodium dodecylbenzenesulfonate, an emulsifier, was changed to 4 parts by mass. The average terminal form of the obtained seed (A2) was then measured. The results are shown in Table 1.

[0068] (Manufacturing Example 3: Production of Seed (A3)) A latex containing seeds (A3) was prepared in the same manner as in Production Example 1, except that the amount of sodium dodecylbenzenesulfonate, an emulsifier, was changed to 2 parts by mass, and the average particle size (R) of the obtained seeds (A3) was measured. s The terminal form was measured. The results are shown in Table 1.

[0069] (Manufacturing Example 4: Production of Seed (A4)) A latex containing seeds (A4) was prepared in the same manner as in Production Example 1, except that the amount of sodium dodecylbenzenesulfonate, an emulsifier, was changed to 5 parts by mass, and the average particle size (R) of the obtained seeds (A4) was measured. s The terminal form was measured. The results are shown in Table 1.

[0070] (Manufacturing Example 5: Seed (A5) Production) A latex containing seed (A5) was prepared in the same manner as in Production Example 1, except that the amount of sodium dodecylbenzenesulfonate, an emulsifier, was changed to 1 part by mass, and the average particle size (R) of the obtained seed (A5) was measured. s The terminal form was measured. The results are shown in Table 1.

[0071] (Manufacturing Example 6: Preparation of Seed (A6)) A latex containing seed (A6) was prepared in the same manner as in Production Example 1, except that the amount of sodium dodecylbenzenesulfonate, an emulsifier, was changed to 0.1 parts by mass, and the average particle size (R) of the obtained seed (A6) was measured. s The terminal form was measured. The results are shown in Table 1.

[0072] [Table 1]

[0073] (Example 1: Preparation of ASA-based graft copolymer (B1)) In a reactor equipped with a reagent injection container, a condenser, a jacket heater, and a stirrer, 109.199 parts by mass of distilled water were added, and then latex (13.824 parts by mass as solid content) containing seed 1A obtained in Production Example 1 was added and stirred. After purging with nitrogen gas, a mixture of 10.176 parts by mass of n-butyl acrylate, 0.076 parts by mass of allyl methacrylate, 0.046 parts by mass of pentaerythritol triallyl ether, and 0.031 parts by mass of t-butyl hydroperoxide was added dropwise over 110 minutes at 75°C, and stirred for a further 20 minutes to obtain core particles in the form of latex with a core layer attached to seed (A1).

[0074] A portion of the latex containing the obtained core particles was separated, and the core particle diameter (including its score (impact resistance) and score (appearance)) and core thickness (including its score (impact resistance) and score (appearance)) of the obtained core particles were measured and evaluated. The results are shown in Table 2.

[0075] Next, a mixture of 67.64 parts by mass of styrene and 8.36 parts by mass of acrylonitrile was added dropwise to the remaining core particles in the latex over 150 minutes, and the mixture was stirred for 20 minutes. This yielded a latex containing ASA-based graft copolymer (B1) in which a shell layer was imparted to the core particles. The evaluation results of this ASA-based graft copolymer (B1) are shown in Table 2.

[0076] Next, 100 parts by mass of ASA-based graft copolymer (B1) latex was added to 200 parts by weight of hot water in which a coagulant (calcium chloride (2.5 parts by mass)) was dissolved at 1%, causing the ASA-based graft copolymer (B1) to coagulate and aggregate. Then, the coagulated and aggregated ASA-based graft copolymer (B1) was redispersed in water to form a slurry, and any remaining emulsifier residue in the ASA-based graft copolymer (B1) was dissolved in the water and washed. After that, the slurry was dewatered using a dewatering machine or the like, and the resulting solid was dried using an air-flow dryer or the like to isolate the ASA-based graft copolymer (B1).

[0077] (Examples 2-10 and Comparative Examples 1-5: Preparation of ASA-based graft copolymers (B2)-(B10) and (BC1)-(BC5)) Latex containing core particles was prepared in the same manner as in Example 1, except that the latex of seed (A1) obtained in Production Example 1 was used, or the latex of seed (A2) or (A3) obtained in Production Example 2 or 3 was used instead of the latex of sheet (A1), and the amount of each component added was set as shown in Table 2. Latex containing ASA-based graft copolymers (B2) to (B10) and (BC1) to (BC5), in which a shell layer was attached to the core particles, was obtained in the same manner as in the preparation of ASA-based graft copolymer (B1) in Example 1.

[0078] The core particle diameter and core thickness of the obtained core particles, as well as the graft ratios of the ASA-based graft copolymers (B2) to (B10) and (BC1) to (BC5), were measured and evaluated. The results are shown in Table 2.

[0079] [Table 2]

[0080] (Reference Example 1: Preparation of acrylonitrile-styrene copolymer) A monomer mixture consisting of 120 parts by mass of distilled water, 0.60 parts by mass of calcium phosphate, 0.003 parts by mass of potassium alkenylsuccinate, 0.18 parts by mass of 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 0.33 parts by mass of 1,1-di(t-hexylperoxy)cyclohexane, 0.17 parts by mass of t-dodecyl mercaptan, 87 parts by mass of styrene, and 13 parts by mass of acrylonitrile was used in the reactor. The mixture was heated from a starting temperature of 65°C for 6 hours while sequentially adding a portion of the distilled water, and then raised to 120°C. It was then held at 120°C for 0.5 hours. After that, unreacted monomers were removed by vacuum treatment, and the polymer was removed from the reactor. After dehydration, an acrylonitrile-styrene copolymer was obtained. The composition ratio of acrylonitrile units in the obtained acrylonitrile-styrene copolymer was 11% by mass, and the mass-average molecular weight was 170,000.

[0081] (Example 11: Preparation of resin composition (C1)) Resin composition (C1) was obtained by melt-kneading 12.5 parts by mass of the ASA-based graft copolymer (B1) obtained in Example 1, 75 parts by mass of polycarbonate (manufactured by Mitsubishi Engineering Plastics Corporation (S-2000F); weight-average molecular weight 22,000; PC), and 12.5 parts by mass of the acrytonitrile-styrene copolymer obtained in Reference Example 1.

[0082] The obtained resin composition (C1) was evaluated for impact resistance, transparency, color development, overall score (impact resistance), and overall score (appearance) according to the above method and criteria. The results are shown in Table 3.

[0083] (Examples 12-20 and Comparative Examples 6-10: Preparation of resin compositions (C2)-(C10) and (CC1)-(CC5)) Resin compositions (C2) to (C10) and (CC1) to (CC5) were obtained in the same manner as in Example 11, except that the ASA-based graft copolymers (B2) to (B10) or (BC1) to (BC5) obtained in Examples 2 to 10 or Comparative Examples 1 to 5 were used instead of the ASA-based graft copolymer (B1) obtained in Example 1, and the respective addition amounts were set as shown in Table 3.

[0084] The obtained resin compositions (C2) to (C10) and (CC1) to (CC5) were evaluated for impact resistance, transparency, color development, overall score (impact resistance), and overall score (appearance) according to the above method and criteria. The results are shown in Table 3.

[0085] [Table 3]

[0086] As shown in Table 3, the resin compositions (C1) to (C10) prepared in Examples 11 to 20 all had scores of 2 to 8 for both "impact resistance" and "appearance," indicating that they were excellent in both impact resistance and appearance. In contrast, the resin compositions (CC1) to (CC5) obtained in Comparative Examples 6 to 10 had an overall score of 0 for either "impact resistance" or "appearance," meaning that while one of them was excellent in impact resistance or appearance, the other was inferior.

[0087] In contrast to the trends shown in Table 3, as shown in Table 2, the ASA-based graft copolymers (B1) to (B10) produced in Examples 1 to 10 had core thickness and core particle diameter within an optimal range, demonstrating an excellent balance between impact resistance and appearance.

[0088] In contrast, the ASA-based graft copolymer (BC1) obtained in Comparative Example 1 had poor impact resistance because its core thickness was too thin. The ASA-based graft copolymer (BC2) obtained in Comparative Example 2 had poor transparency because its core thickness was too thick. Furthermore, the ASA-based graft copolymer (BC3) obtained in Comparative Example 3 had poor impact resistance because its core particle size was too small. The ASA-based graft copolymer (BC4) obtained in Comparative Example 4 had poor impact resistance because its core particle size was too large. The ASA-based graft copolymer (BC5) obtained in Comparative Example 5 had even larger particle size, resulting in even worse impact resistance. [Industrial applicability]

[0089] The present invention is useful in core technology fields such as resin molding, automotive, electronics and electrical engineering, and construction.

Claims

1. An ASA-based graft copolymer having a seed layer, a core layer, and a shell layer in that order, The average particle diameter of the internal virtual particle portion composed of the seed and the core layer is 60 to 90 nm. The thickness of the core layer is 7 to 18 nm. An ASA-based graft copolymer in which the seed contains styrene units, the core layer contains acrylate units, and the shell layer contains acrylonitrile units.

2. The ASA-based graft copolymer according to claim 1, wherein the thickness of the core layer is 8 to 16 nm.

3. The ASA-based graft copolymer according to claim 1, wherein the average particle diameter of the internal virtual particle portion is 65 nm to 80 nm.

4. The ASA-based graft copolymer according to claim 1, wherein the seed-forming material constituting the seed is solely a compound having styrene units.

5. A resin composition comprising an ASA-based graft copolymer and a matrix resin according to any one of claims 1 to 4.

6. The resin composition according to claim 5, wherein the matrix resin is composed of at least one resin selected from the group consisting of polycarbonate, poly(styrene-acrylonitrile), polybutylene terephthalate, and polyethylene terephthalate.

7. The resin composition according to claim 5, wherein the matrix resin is polycarbonate.

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