Patent Description:
The present invention relates to a thermoplastic resin composition, and particularly, to a thermoplastic resin composition having excellent appearance characteristics.

In general, graft copolymers including a styrene-based monomer unit and an acrylonitrile-based monomer unit which are grafted onto an acrylic rubber polymer are excellent in terms of weather resistance, staining resistance, and aging resistance. Thermoplastic resin compositions including the graft copolymer are used in various fields such as automobiles, ships, leisure products, building materials, horticultural products, and the like, and the usage thereof is rapidly increasing. Among them, decorative sheets made of the thermoplastic resin composition including the graft copolymer exhibit excellent processing stability compared to decorative sheets made of conventional thermoplastic resin compositions including PVC or PP and do not include heavy metal components, and therefore, they have attracted attention as environmentally friendly materials. However, the decorative sheets have a problem in which pressure marks are left during the storage process or the dimensions of the sheet are deformed (expanded or reduced) during processing. Also, when an adhesive is used for adhesion to the base material, the decorative sheets are melted due to having poor chemical resistance.

<CIT> discloses a thermoplastic resin composition which includes: a graft copolymer including a C4 to C10 alkyl (meth)acrylate-based monomer unit, a styrene-based monomer unit, and a vinyl cyan-based monomer unit; a first styrene-based copolymer including a C1 to C3 alkyl-substituted styrene-based monomer unit and a vinyl cyan-based monomer unit; and a second styrene-based copolymer including an unsubstituted styrene-based monomer unit and a vinyl cyan-based monomer unit.

<CIT> discloses a graft copolymer composition and a thermoplastic resin composition comprising the same.

<CIT> discloses a thermoplastic resin composition for blow molding and a molded article using the same. The thermoplastic resin composition for blow molding comprises: <NUM> parts by weight of a basic resin including (A) <NUM> to <NUM> wt% of a diene graft copolymer, (B) <NUM> to <NUM> wt% of an aromatic vinyl compound-cyanide vinyl compound copolymer, (C) <NUM> to <NUM> wt% of an alpha-methyl styrene copolymer and (D) <NUM> to <NUM> wt% of an N-phenyl maleimide copolymer; and (E) <NUM> to <NUM> parts by weight of inorganic particles which are zinc sulfide, titanium dioxide, talc or a combination thereof.

Therefore, there is a need to develop a thermoplastic resin composition having improved appearance characteristics.

The present invention is directed to providing a thermoplastic resin composition that can be used to manufacture a thermoplastic resin molded article having remarkably excellent appearance characteristics due to harmoniously achieving hardness, impact resistance, and heat resistance.

The present invention is also directed to providing a thermoplastic resin composition that can be used to manufacture a thermoplastic resin molded article having excellent weather resistance.

The above problems are solved in accordance with the subject-matter of the independent claims. Further embodiments result from the subclaims and the following detailed description.

One aspect of the present invention provides a thermoplastic resin composition which comprises: a first graft copolymer including a first acrylic rubber polymer; a second graft copolymer including a second acrylic rubber polymer; and a first styrene-based copolymer including an alkyl-substituted styrene-based monomer unit and an acrylonitrile-based monomer unit, a second styrene-based copolymer including an alkyl-unsubstituted styrene-based monomer unit and an acrylonitrile-based monomer unit, and an inorganic pigment, wherein the inorganic pigment is TiO<NUM>; wherein the first acrylic rubber polymer has an average particle diameter larger than that of the second acrylic rubber polymer, the first graft copolymer is included in a larger amount than the second graft copolymer, and the sum of the first graft copolymer and the second graft copolymer is <NUM> parts by weight or less with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, and the first styrene-based copolymer and the second styrene-based copolymer, and wherein, with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, the first styrene-based copolymer, and the second styrene-based copolymer, <NUM> to <NUM> parts by weight of the first styrene-based copolymer and <NUM> to <NUM> parts by weight of the second styrene-based copolymer are included.

A thermoplastic resin composition according to the present invention can be used to manufacture a thermoplastic resin molded article having remarkably excellent appearance characteristics due to harmoniously achieving hardness, impact resistance, and heat resistance. In addition, the thermoplastic resin composition according to the present invention can be used to manufacture a thermoplastic resin molded article having excellent weather resistance.

Terms and words used in this specification and claims should not be interpreted as being limited to commonly used meanings or meanings in dictionaries, and, based on the principle that the inventors can appropriately define concepts of terms in order to describe their invention in the best way, the terms and words should be interpreted with meanings and concepts which are consistent with the technological scope of the present invention.

As used herein, the term "average particle diameter" may refer to an arithmetic average particle diameter in the particle size distribution as measured by a dynamic light scattering method, specifically, an average particle diameter measured in the scattering intensity distribution. Also, the average particle diameter may be measured by a dynamic light scattering method, specifically, by using a Nicomp <NUM> instrument (manufacturer: PSS Nicomp).

As used herein, the term "average particle diameter" may be measured by transmission electron microscopy (TEM) analysis. Specifically, the average particle diameter may be calculated as an average value by numerically measuring the size of particles on the high magnification image of TEM. In this case, a specific measurement method is as follows.

As used herein, the term "acrylic rubber polymer" may refer to a polymer formed by crosslinking polymerization of a (meth)acrylate-based monomer and one or more selected from the group consisting of a styrene-based monomer and an acrylonitrile-based monomer. Specifically, the acrylic rubber polymer may be a core formed by crosslinking polymerization of a (meth)acrylate-based monomer and one or more selected from the group consisting of a styrene-based monomer and an acrylonitrile-based monomer to form a seed and then crosslinking polymerization of a (meth)acrylate-based monomer in the presence of the seed.

As used herein, the term "(meth)acrylate-based monomer" may be one or more selected from the group consisting of an acrylate-based monomer and a methacrylate-based monomer. The acrylate-based monomer may refer to one or more selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, <NUM>-ethylhexyl acrylate, nonyl acrylate, isononyl acrylate, and decyl acrylate. The methacrylate-based monomer may refer to one or more selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, <NUM>-ethylhexyl methacrylate, nonyl methacrylate, isononyl methacrylate, and decyl methacrylate. As the (meth)acrylate-based monomer, butyl acrylate is preferred.

As used herein, the term "styrene-based monomer" may encompass both an alkyl-substituted styrene-based monomer and an alkyl-unsubstituted styrene-based monomer. The alkyl-substituted styrene-based monomer may refer to one or more selected from the group consisting of α-methylstyrene, p-methylstyrene, and <NUM>,<NUM>-dimethylstyrene. As the alkyl-substituted styrene-based monomer, α-methylstyrene is preferred. The alkyl-unsubstituted styrene-based monomer may refer to one or more selected from the group consisting of styrene, <NUM>-fluorostyrene, <NUM>-chlorostyrene, <NUM>-chlorostyrene, <NUM>-bromostyrene, and <NUM>-bromostyrene. As the alkyl-unsubstituted styrene-based monomer, styrene is preferred.

As used herein, the term "acrylonitrile-based monomer" may be one or more selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile, and <NUM>-chloroacrylonitrile. As the acrylonitrile-based monomer, acrylonitrile is preferred.

As used herein, the term "(meth)acrylate-based monomer unit" may be a unit derived from a (meth)acrylate-based monomer.

As used herein, the term "styrene-based monomer unit" may be a unit derived from a styrene-based monomer.

As used herein, the term "alkyl-substituted styrene-based monomer unit" may be a unit derived from an alkyl-substituted styrene-based monomer.

As used herein, the term "alkyl-unsubstituted styrene-based monomer unit" may be a unit derived from an alkyl-unsubstituted styrene-based monomer.

As used herein, the term "acrylonitrile-based monomer unit" may be a unit derived from an acrylonitrile-based monomer.

In the present invention, a weight-average molecular weight may be measured as a relative value with respect to a standard polystyrene (PS) specimen by gel permeation chromatography (GPC, Waters Breeze) using tetrahydrofuran (THF) as an eluent.

A thermoplastic resin composition according to an embodiment of the present invention comprises: a first graft copolymer including a first acrylic rubber polymer; a second graft copolymer including a second acrylic rubber polymer; and a first styrene-based copolymer including an alkyl-substituted styrene-based monomer unit and an acrylonitrile-based monomer unit, a second styrene-based copolymer including an alkyl-unsubstituted styrene-based monomer unit and an acrylonitrile-based monomer unit, and an inorganic pigment, wherein the inorganic pigment is TiO<NUM>; wherein the first acrylic rubber polymer has an average particle diameter larger than that of the second acrylic rubber polymer, the first graft copolymer is included in a larger amount than the second graft copolymer, and the sum of the first graft copolymer and the second graft copolymer is <NUM> parts by weight or less with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, and the first styrene-based copolymer and the second styrene-based copolymer, and wherein, with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, the first styrene-based copolymer, and the second styrene-based copolymer, <NUM> to <NUM> parts by weight of the first styrene-based copolymer and <NUM> to <NUM> parts by weight of the second styrene-based copolymer are included.

Since the thermoplastic resin composition includes both the first graft copolymer and the second graft copolymer, all of weather resistance, impact resistance, hardness, and surface glossiness may be improved. Specifically, the first graft copolymer may improve the impact resistance and weather resistance of the thermoplastic resin composition by including a first acrylic rubber polymer having a large average particle diameter. The second graft copolymer may improve the hardness, weather resistance, and surface glossiness of the thermoplastic resin composition by including a second acrylic rubber polymer having a small average particle diameter.

The first acrylic rubber polymer has an average particle diameter larger than that of the second acrylic rubber polymer, and the average particle diameter of the first acrylic rubber polymer may be <NUM> to <NUM> or <NUM> to <NUM>, with the range of <NUM> to <NUM> being preferred, as measured by a dynamic light scattering method or transmission electron microscopy (TEM) analysis. Specifically, the average particle diameter thereof may be <NUM> to <NUM> or <NUM> to <NUM>, with the range of <NUM> to <NUM> being preferred, as measured by a dynamic light scattering method. Also, the average particle diameter thereof may be <NUM> to <NUM> or <NUM> to <NUM>, with the range of <NUM> to <NUM> being preferred, as measured by TEM analysis. When the above-described range is satisfied, especially, the impact resistance and weather resistance of the thermoplastic resin composition can be improved.

The second acrylic rubber polymer has an average particle diameter smaller than that of the first acrylic rubber polymer, and the average particle diameter of the second acrylic rubber polymer may be <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, with the range of <NUM> to <NUM> being preferred, as measured by a dynamic light scattering method or TEM analysis. Specifically, the average particle diameter thereof may be <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, with the range of <NUM> to <NUM> being preferred, as measured by a dynamic light scattering method. Also, the average particle diameter thereof may be <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, with the range of <NUM> to <NUM> being preferred, as measured by TEM analysis. When the above-described range is satisfied, especially, the hardness, weather resistance, and surface glossiness of the thermoplastic resin composition can be improved.

The first graft copolymer includes the first acrylic rubber polymer and may specifically include the first acrylic rubber polymer and a styrene-based monomer unit and an acrylonitrile-based monomer unit, both of which are grafted onto the first acrylic rubber polymer. The second graft copolymer includes the second acrylic rubber polymer and may specifically include the second acrylic rubber polymer and a styrene-based monomer unit and an acrylonitrile-based monomer unit, both of which are grafted onto the second acrylic rubber polymer.

The first graft copolymer may be formed by graft polymerization of the first acrylic rubber polymer with a styrene-based monomer and an acrylonitrile-based monomer, and the second graft copolymer may be formed by graft polymerization of the second acrylic rubber polymer with a styrene-based monomer and an acrylonitrile-based monomer.

Meanwhile, since the thermoplastic resin composition includes the first styrene-based copolymer, heat resistance and chemical resistance may be improved, and, especially, heat resistance may be substantially improved. Specifically, the first styrene-based copolymer may improve heat resistance by including an alkyl-substituted styrene-based monomer unit and improve chemical resistance by including an acrylonitrile-based monomer unit. Also, the first styrene-based copolymer particularly improves the heat resistance of the thermoplastic resin composition by producing a synergistic effect with a weight ratio of the first graft copolymer and the second graft copolymer, which is to be described below, and allows hardness, impact resistance, and heat resistance to be harmoniously achieved, and thus a thermoplastic resin molded article having excellent appearance characteristics may be manufactured.

The first styrene-based copolymer may be a non-grafted copolymer and may be selected from the group consisting of an α-methylstyrene/acrylonitrile copolymer and an α-methylstyrene/styrene/acrylonitrile copolymer.

Meanwhile, the thermoplastic resin composition may include the first graft copolymer in an amount larger than that of the second graft copolymer while the sum of the first graft copolymer and the second graft copolymer is <NUM> parts by weight or less, and preferably, <NUM> to <NUM> parts by weight, <NUM> parts by weight or less, or <NUM> to <NUM> parts by weight, with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, and the first styrene-based copolymer. When the above-described condition is satisfied, the hardness, impact resistance, and heat resistance of the thermoplastic resin composition are harmoniously achieved, and thus a thermoplastic molded article having remarkably excellent appearance characteristics can be manufactured. When the thermoplastic resin composition includes the first graft copolymer in an amount larger than that of the second graft copolymer while the sum of the first graft copolymer and the second graft copolymer exceeds <NUM> parts by weight with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, and the first styrene-based copolymer, a relatively small amount of the first styrene-based copolymer is included, and thus hardness is substantially degraded. Accordingly, hardness, heat resistance, and impact resistance are not harmoniously achieved, and thus the manufacture of a thermoplastic resin molded article having excellent appearance characteristics is not possible. In addition, when the thermoplastic resin composition includes the first graft copolymer so that the sum of the first graft copolymer and the second copolymer is <NUM> parts by weight or less with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, and the first styrene-based copolymer, but the amount of the first graft copolymer is the same as or smaller than that of the second graft copolymer, impact resistance is degraded, and accordingly hardness, heat resistance, and impact resistance are not harmoniously achieved. As a result, the manufacture of a thermoplastic resin molded article having excellent appearance characteristics is not possible.

The thermoplastic resin composition may include the first graft copolymer and the second graft copolymer in a weight ratio of <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>, with the weight ratio of <NUM>:<NUM> to <NUM>:<NUM> being preferred. When the above-described condition is satisfied, the hardness and impact resistance of the thermoplastic resin composition are not only excellent but also harmoniously achieved, and thus a thermoplastic molded article having remarkably excellent appearance characteristics can be manufactured.

Meanwhile, the thermoplastic resin composition further includes a second styrene-based copolymer including an alkyl-unsubstituted styrene-based monomer unit and an acrylonitrile-based monomer unit to improve processability.

The thermoplastic resin composition further includes the second styrene-based copolymer, with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, the first styrene-based copolymer, and the second styrene-based copolymer, <NUM> to <NUM> parts by weight of the first styrene-based copolymer and <NUM> to <NUM> parts by weight of the second styrene-based copolymer are included, and preferably, <NUM> to <NUM> parts by weight of the first styrene-based copolymer and <NUM> to <NUM> parts by weight of the second styrene-based copolymer may be included. When the above-described range is satisfied, processability can be improved while maintaining the heat resistance of the thermoplastic resin composition at a specific level or higher.

The second styrene-based copolymer may be a non-grafted copolymer and may be a styrene/acrylonitrile copolymer.

Meanwhile, the thermoplastic resin composition according to the embodiment of the present invention further includes an inorganic pigment to improve weather resistance. The thermoplastic resin composition may include the inorganic pigment in an amount of <NUM> to <NUM> parts by weight or <NUM> to <NUM> parts by weight with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, and the first styrene-based copolymer, with the range of <NUM> to <NUM> parts by weight being preferred. Also, when the thermoplastic resin composition further includes the second styrene-based copolymer, the inorganic pigment may be included in an amount of <NUM> to <NUM> parts by weight or <NUM> to <NUM> parts by weight with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, the first styrene-based copolymer, and the second styrene-based copolymer, with the range of <NUM> to <NUM> parts by weight being preferred. When the above-described range is satisfied, not only weather resistance can be improved, but also excellent whitening characteristics can be realized.

The inorganic pigment isTiO<NUM>. As TiO<NUM>, commercially available products may be used, and specifically, one or more of TiONA <NUM> commercially available from Dupont, Ti-Pure R350 commercially available from Chemours Company, and TIOXIDE TR48 commercially available from Venator Materials PLC. may be used.

Meanwhile, the thermoplastic resin composition according to the embodiment of the present invention may further include one or more additives selected from the group consisting of an anti-dripping agent, a flame retardant, an antibacterial agent, an antistatic agent, a stabilizer, a releasing agent, a thermal stabilizer, a UV stabilizer, an inorganic additive, a lubricant, an antioxidant, a photostabilizer, a pigment, a dye, and an inorganic filler.

It is preferable that the thermoplastic resin composition according to the embodiment of the present invention includes one or more selected from the group consisting of a lubricant, an antioxidant, and a UV stabilizer.

A molded article formed of the thermoplastic resin composition according to the embodiment of the present invention may be a sheet, preferably, a decorative sheet for furniture.

<NUM> parts by weight of styrene, <NUM> parts by weight of acrylonitrile, <NUM> parts by weight of sodium dodecyl sulfate as an emulsifier, <NUM> parts by weight of ethylene glycol dimethacrylate as a crosslinking agent, <NUM> parts by weight of allyl methacrylate as a grafting agent, <NUM> parts by weight of KOH as an electrolyte, and <NUM> parts by weight of distilled water were batch-added to a nitrogen-substituted reactor. Afterward, the temperature inside the reactor was raised to <NUM>, and <NUM> parts by weight of potassium persulfate as an initiator was batch-added to the reactor to initiate polymerization, and the polymerization was performed for <NUM> hours and then terminated. As a result, a styrene/acrylonitrile rubber polymer having an average particle diameter of <NUM>, as measured by a dynamic light scattering method, was obtained as a seed.

Polymerization was performed while continuously adding, to the seed-containing reactor, a mixture including <NUM> parts by weight of butyl acrylate, <NUM> parts by weight of sodium dodecyl sulfate as an emulsifier, <NUM> parts by weight of ethylene glycol dimethacrylate as a crosslinking agent, <NUM> parts by weight of allyl methacrylate as a grafting agent, <NUM> parts by weight of distilled water, and <NUM> parts by weight of potassium persulfate as an initiator at <NUM> and a constant rate for <NUM> hours. After the continuous addition was terminated, polymerization was further performed for another <NUM> hour. As a result, a butyl acrylate rubber polymer having an average particle diameter of <NUM>, as measured by a dynamic light scattering method, was obtained as a core.

<NUM> parts by weight of styrene, <NUM> parts by weight of acrylonitrile, and <NUM> parts by weight of distilled water were added to the core-containing reactor. Polymerization was performed while continuously adding, to the reactor, each of a first mixture including <NUM> parts by weight of potassium rosinate as an emulsifier and <NUM> parts by weight of t-butylperoxy ethylhexyl carbonate as an initiator and a second mixture including <NUM> parts by weight of disodium pyrophosphate, <NUM> parts by weight of dextrose, and <NUM> parts by weight of ferrous sulfate as activators at <NUM> and a constant rate for <NUM> hours. After the continuous addition of the first and second mixtures was terminated, polymerization was further performed in the reactor at <NUM> for another <NUM> hour. Then, the polymerization was terminated by cooling the reactor to <NUM>. As a result, graft copolymer latex was obtained.

The graft copolymer latex was added to an aqueous calcium chloride solution containing <NUM> parts by weight of calcium chloride, coagulated at <NUM> and atmospheric pressure for <NUM> minutes, aged at <NUM> for <NUM> minutes, dehydrated, washed, and then dried with <NUM> hot air for <NUM> minutes, thereby obtaining graft copolymer powder.

<NUM> parts by weight of butyl acrylate, <NUM> parts by weight of sodium dodecyl sulfate as an emulsifier, <NUM> parts by weight of ethylene glycol dimethacrylate as a crosslinking agent, <NUM> parts by weight of allyl methacrylate as a grafting agent, <NUM> parts by weight of KOH as an electrolyte, and <NUM> parts by weight of distilled water were batch-added to a nitrogen-substituted reactor. Afterward, the temperature inside the reactor was raised to <NUM>, and then <NUM> parts by weight of potassium persulfate as an initiator was batch-added to initiate polymerization, and the polymerization was performed for <NUM> hours and then terminated. As a result, a butyl acrylate rubber polymer having an average particle diameter of <NUM>, as measured by a dynamic light scattering method, was obtained as a seed.

Polymerization was performed while continuously adding, to the seed-containing reactor, a mixture including <NUM> parts by weight of butyl acrylate, <NUM> parts by weight of sodium dodecyl sulfate as an emulsifier, <NUM> parts by weight of ethylene glycol dimethacrylate as a crosslinking agent, <NUM> parts by weight of allyl methacrylate as a grafting agent, <NUM> parts by weight of distilled water, and <NUM> parts by weight of potassium persulfate as an initiator at <NUM> and a constant rate for <NUM> hours. After the continuous addition was terminated, polymerization was further performed in the reactor for another <NUM> hour and then terminated. As a result, a butyl acrylate rubber polymer having an average particle diameter of <NUM>, as measured by a dynamic light scattering method, was obtained as a core.

<NUM> parts by weight of styrene, <NUM> parts by weight of acrylonitrile, and <NUM> parts by weight of distilled water were added to the core-containing reactor, and polymerization was performed while continuously adding, to the reactor, each of a first mixture including <NUM> parts by weight of potassium rosinate as an emulsifier, <NUM> parts by weight of t-dodecyl mercaptan as a molecular weight controlling agent, and <NUM> parts by weight of t-butylperoxy ethylhexyl carbonate as an initiator and a second mixture including <NUM> parts by weight of disodium pyrophosphate, <NUM> parts by weight of dextrose, and <NUM> parts by weight of ferrous sulfate as activators at <NUM> and a constant rate for <NUM> hours. After the continuous addition of the first and second mixtures was completed, polymerization was further performed in the reactor at <NUM> for another <NUM> hour and then terminated by cooling the reactor to <NUM>. As a result, graft copolymer latex was obtained.

Information on components used in Examples and Comparative Examples is as follows.

The above-described components were mixed in contents shown in Tables <NUM> to <NUM> below and stirred to prepare thermoplastic resin compositions.

Each of the thermoplastic resin compositions of Examples and Comparative Examples was input into a twin-screw extrusion kneader set at <NUM> to prepare a pellet. A physical property of the pellet was evaluated by a method described below, and results thereof are shown in Tables <NUM> to <NUM> below.

The pellet prepared in Experimental Example <NUM> was injection-molded to prepare a specimen. Physical properties of the specimen were evaluated by methods described below, and results thereof are shown in Tables <NUM> to <NUM> below.

The pellet prepared in Experimental Example <NUM> was extruded through a film extruder to form a <NUM>-mm film. Physical properties of the film were evaluated by methods described below, and results thereof are shown in Tables <NUM> to <NUM> below.

In the above equation, L', a', and b' are the L, a, and b values measured in the CIE LAB color coordinate system after irradiating the thermoplastic resin molded article with light under SAE J1960 conditions for <NUM>,<NUM> hours, and L<NUM>, a<NUM>, and b<NUM> are the L, a, and b values measured in the CIE LAB color coordinate system before the light irradiation.

Referring to Tables <NUM> to <NUM>, the thermoplastic resin compositions of Examples <NUM> to <NUM>, which included a first graft copolymer in an amount larger than that of a second graft copolymer, exhibited excellent impact strength compared to the thermoplastic resin compositions of Comparative Examples <NUM> and <NUM> which included a first graft copolymer and a second graft copolymer in the same amounts, and realized appropriate levels of hardness and a heat deflection temperature. Accordingly, in the case of the thermoplastic resin compositions of Examples <NUM> to <NUM>, hardness, impact resistance, and heat resistance were harmoniously achieved, and thus an excellent film appearance was exhibited. However, the thermoplastic resin compositions of Comparative Examples <NUM> and <NUM> were excellent in hardness and a heat deflection temperature but exhibited an impact strength of less than <NUM>·cm/cm, and thus hardness, impact resistance, and heat resistance were not harmoniously achieved, resulting in a substantially degraded film appearance.

The thermoplastic resin composition of Example <NUM>, which included both a first styrene-based copolymer and a second copolymer as non-grafted copolymers, exhibited excellent hardness, but the impact strength, heat deflection temperature, and weather resistance thereof were slightly degraded as compared to the thermoplastic resin composition of Example <NUM> which included only a first styrene-based copolymer as a non-grafted copolymer. However, all of hardness, impact strength, and a heat deflection temperature were maintained at appropriate levels and thus harmoniously achieved, resulting in an excellent film appearance.

Meanwhile, the thermoplastic resin composition of Example <NUM>, which included only a first styrene-based copolymer as a non-grafted copolymer, exhibited slightly degraded hardness compared to the thermoplastic resin composition of Comparative Example <NUM> which included only a second styrene-based copolymer as a non-grafted copolymer, but all of hardness, impact strength, and a heat deflection temperature were maintained at appropriate levels. Accordingly, in the case of the thermoplastic resin composition of Example <NUM>, hardness, impact resistance, and heat resistance were harmoniously achieved, resulting in an excellent film appearance. However, the thermoplastic resin composition of Comparative Example <NUM> was excellent in hardness and impact strength but exhibited a substantially degraded heat deflection temperature such as <NUM>, and thus hardness, impact resistance, and heat resistance were not harmoniously achieved, resulting in a substantially degraded film appearance.

The thermoplastic resin compositions of Examples <NUM> and <NUM>, in which the sum of first and second graft copolymers was <NUM> parts by weight, maintained appropriate levels of hardness, impact strength, and a heat deflection temperature. Accordingly, in the case of the thermoplastic resin compositions of Examples <NUM> and <NUM>, hardness, impact resistance, and heat resistance were harmoniously achieved, resulting in an excellent film appearance.

The thermoplastic resin compositions of Comparative Examples <NUM> to <NUM>, in which the sum of first and second graft copolymers was <NUM> parts by weight, <NUM> parts by weight, and <NUM> parts by weight, respectively, were excellent in impact strength and a heat deflection temperature but exhibited degraded hardness. Accordingly, hardness, impact resistance, and heat resistance were not harmoniously achieved, resulting in a degraded film appearance.

In addition, the thermoplastic resin composition of Comparative Example <NUM>, which included a first graft copolymer in an amount smaller than that of a second graft copolymer, exhibited substantially degraded hardness and impact strength despite including a first styrene-based copolymer as a non-grafted copolymer. Accordingly, hardness, impact resistance, and heat resistance were not harmoniously achieved, resulting in a substantially degraded film appearance.

In addition, the thermoplastic resin composition of Comparative Example <NUM>, which included a first graft copolymer in an amount smaller than that of a second graft copolymer, exhibited a substantially degraded heat deflection temperature compared to the thermoplastic resin composition of Comparative Example <NUM> due to including no first styrene-based copolymer as a non-grafted copolymer. Also, in the case of the thermoplastic resin composition of Comparative Example <NUM>, like the thermoplastic resin composition of Comparative Example <NUM>, hardness, impact resistance, and heat resistance were not harmoniously achieved, resulting in a substantially degraded film appearance.

Meanwhile, the thermoplastic resin compositions of Examples <NUM> and <NUM>, which further included TiO<NUM> compared to the thermoplastic resin composition of Example <NUM>, exhibited substantially improved weather resistance compared to the thermoplastic resin composition of Example <NUM>, but the hardness, heat deflection temperature, and impact strength thereof were not greatly affected, and thus a film appearance was still excellent. The thermoplastic resin composition of Example <NUM>, which included TiO<NUM> in an amount larger than that in the thermoplastic resin composition of Example <NUM>, exhibited slightly degraded impact strength, but the weather resistance thereof was improved.

Claim 1:
A thermoplastic resin composition comprising:
a first graft copolymer including a first acrylic rubber polymer;
a second graft copolymer including a second acrylic rubber polymer;
a first styrene-based copolymer including an alkyl-substituted styrene-based monomer unit and an acrylonitrile-based monomer unit,
a second styrene-based copolymer including an alkyl-unsubstituted styrene-based monomer unit and an acrylonitrile-based monomer unit, and
an inorganic pigment,
wherein the inorganic pigment is TiO<NUM>;
wherein the first acrylic rubber polymer has an average particle diameter larger than that of the second acrylic rubber polymer,
the first graft copolymer is included in a larger amount than the second graft copolymer,
the sum of the first graft copolymer and the second graft copolymer is <NUM> parts by weight or less with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, the first styrene-based copolymer and the second styrene-based copolymer, and
wherein, with respect to <NUM> parts by weight of the sum of the first graft copolymer, the second graft copolymer, the first styrene-based copolymer, and the second styrene-based copolymer, <NUM> to <NUM> parts by weight of the first styrene-based copolymer and <NUM> to <NUM> parts by weight of the second styrene-based copolymer are included.