TECHNICAL FIELD

The present invention relates to the first to third inventions below.

The first invention relates to a graft copolymer which has good moldability and good continuous moldability and with which a molded article having excellent impact resistance can be produced and a method for producing the graft copolymer. The first invention also relates to a method for producing a rubbery polymer with which the above graft copolymer can be produced, a thermoplastic resin composition including the graft copolymer, and a molded article produced using the thermoplastic resin composition.

The second invention relates to a method for producing a graft copolymer having excellent production stability and excellent storage stability, a method for producing a thermoplastic resin composition in which the graft copolymer is used, and a method for producing a molded article in which the thermoplastic resin composition is used.

The third invention relates to a graft copolymer which has good moldability and with which a molded article having excellent impact resistance and excellent appearance can be produced and a method for producing the graft copolymer. The third invention also relates to a method for producing a rubbery polymer with which the above graft copolymer can be produced, a thermoplastic resin composition including the graft copolymer, and a molded article produced using the thermoplastic resin composition.

BACKGROUND ART

Thermoplastic resins have been used in various fields, such as automobiles, housing and building materials, electrical and electronic equipment, and OA instruments (e.g., printers). Among the thermoplastic resins, an ABS resin and an ASA resin, which are produced by mixing a styrene-acrylonitrile copolymer resin, an α-methylstyrene-acrylonitrile copolymer resin, a styrene-acrylonitrile-phenylmaleimide copolymer resin, or the like with a graft copolymer prepared by grafting a monomer capable of enhancing compatibility with the above resin to a rubbery polymer, have been widely used because of their excellent impact resistance and fluidity.

In particular, an ASA resin produced using constituents such as an alkyl (meth)acrylate rubber, which is a saturated rubber, as a rubbery polymer has good weather resistance but lower impact resistance than an ABS resin. In order to enhance the impact resistance of an ASA resin, there have been proposed an ASA resin that includes an alkyl (meth)acrylate rubber having a specific particle size (PTL 1) and an ASA resin that includes alkyl (meth)acrylate rubbers having different particle sizes (PTL 2).

In PTL 1, large particles are formed by seed polymerization. This results in an excessively long production time and poor productivity. Furthermore, small acrylate rubber particles may also be formed, which degrade moldability.

In PTL 2, large particles are formed by coagulation using an acidic-group-containing copolymer latex. This results in excellent productivity but an impact resistance lower than that of an acrylate rubber having a uniform and large particle size. Furthermore, it is necessary to increase the content of a rubbery polymer in a thermoplastic resin composition for enhancing the impact resistance of the ASA resin to a sufficiently high level. Increasing the proportion of the rubbery polymer may degrade moldability.

PTL 1: Japanese Patent 5805066

PTL 2: Japanese Patent Publication 2012-214734 A

SUMMARY OF INVENTION

An object of the first invention is to provide a graft copolymer which has good moldability and good continuous moldability and with which a thermoplastic resin molded article having excellent impact resistance can be produced, a method for producing the graft copolymer, a thermoplastic resin composition including the graft copolymer, and a molded article produced using the thermoplastic resin composition. Another object of the first invention is to provide a method for producing a rubbery polymer with which the above graft copolymer can be produced.

The inventors of the first invention found that the above objects may be attained by a graft copolymer produced using a rubbery polymer mixture including a rubbery polymer and a specific hydrophobic substance, the rubbery polymer produced by polymerizing an alkyl (meth)acrylate and a multifunctional monomer copolymerizable with the alkyl (meth)acrylate.

The summary of the first invention is as follows.

[1] A graft copolymer (B-I) produced by grafting at least one vinyl monomer (b-I) selected from the group consisting of an aromatic vinyl, an alkyl (meth)acrylate, and a vinyl cyanide to a rubbery polymer mixture including a rubbery polymer (A-I) and a hydrophobic substance, the rubbery polymer (A-I) including an alkyl (meth)acrylate unit and a multifunctional monomer unit copolymerizable with an alkyl (meth)acrylate, the hydrophobic substance having a kinematic viscosity of 5 mm2/s or more at 40° C. or a kinematic viscosity of 2 to 4 mm2/s at 100° C., a principal constituent of the hydrophobic substance being a hydrocarbon.

[2] The graft copolymer (B-I) according to [1], wherein the amount of the multifunctional monomer unit is 0.1 to 5.0 parts by mass relative to 100 parts by mass of the total amount of the alkyl (meth)acrylate unit and the multifunctional monomer unit.

[3] The graft copolymer (B-I) according to [1] or [2], wherein the ratio between the rubbery polymer (A-I) and the vinyl monomer (b-I) is such that the proportion of the rubbery polymer (A-I) is 10% to 90% by mass and the proportion of the vinyl monomer (b-I) is 90% to 10% by mass (with the total proportion of the rubbery polymer (A-I) and the vinyl monomer (b-I) being 100% by mass).

[4] The graft copolymer (B-I) according to any one of [1] to [3], wherein the rubbery polymer mixture is a polymerization product produced by polymerizing a miniemulsion containing the alkyl (meth)acrylate, the multifunctional monomer, the hydrophobic substance, an emulsifier, and water.

[5] The graft copolymer (B-I) according to [4], wherein the amount of the hydrophobic substance is 0.1 to 10 parts by mass relative to 100 parts by mass of the alkyl (meth)acrylate.

[6] The graft copolymer (B-I) according to [4] or [5], wherein the rubbery polymer (A-I) included in the polymerization product has a volume-average particle size of less than 1000 nm.

[7] A thermoplastic resin composition comprising the graft copolymer (B-I) according to any one of [1] to [6].

[8] A molded article produced using the thermoplastic resin composition according to [7].

[9] A method for producing a rubbery polymer (A-I), the method comprising a miniemulsion formation step in which a mixture (a-I) containing an alkyl (meth)acrylate, a multifunctional monomer copolymerizable with the alkyl (meth)acrylate, a hydrophobic substance, an emulsifier, and water is formed into a miniemulsion, the hydrophobic substance having a kinematic viscosity of 5 mm2/s or more at 40° C. or a kinematic viscosity of 2 to 4 mm2/s at 100° C., a principal constituent of the hydrophobic substance being a hydrocarbon, and a polymerization step in which the miniemulsion is polymerized.

[10] A method for producing a graft copolymer (B-I), the method comprising grafting at least one vinyl monomer (b-I) selected from the group consisting of an aromatic vinyl, an alkyl (meth)acrylate, and a vinyl cyanide to a rubbery polymer (A-I) produced by the method for producing a rubbery polymer (A-I) according to [9].

[11] A method for producing a thermoplastic resin composition, the method comprising using a graft copolymer (B-I) produced by the method for producing a graft copolymer (B-I) according to [10].

[12] A method for producing a molded article, the method comprising using a thermoplastic resin composition produced by the method for producing a thermoplastic resin composition according to [11].

An object of the second invention is to provide a method for producing a graft copolymer having excellent production stability and excellent storage stability; a thermoplastic resin composition using the graft copolymer and being capable of producing a thermoplastic resin molded article having excellent impact resistance with good moldability; and a method for producing a molded article of the thermoplastic resin composition.

The inventors of the second invention found that the above objects may be attained by a graft copolymer produced using a rubbery polymer prepared by polymerizing a pre-emulsion that is formed using a mixture containing an alkyl (meth)acrylate, a multifunctional monomer copolymerizable with the alkyl (meth)acrylate, an oil-soluble initiator having a predetermined number of carbon atoms, an emulsifier, and water.

The summary of the second invention is as follows.

[13] A method for producing a graft copolymer (B-II), the method comprising a miniemulsion formation step in which a mixture (a-II) containing an alkyl (meth)acrylate, a multifunctional monomer copolymerizable with the alkyl (meth)acrylate, an oil-soluble initiator having 16 or more carbon atoms, an emulsifier, and water is formed into a miniemulsion, a polymerization step in which the miniemulsion is polymerized to form a rubbery polymer (A-II), and a graft polymerization step in which at least one vinyl monomer (b-II) selected from the group consisting of an aromatic vinyl, an alkyl (meth)acrylate, and a vinyl cyanide is grafted to the rubbery polymer (A-II) in order to produce a graft copolymer (B-II).

[14] The method for producing a graft copolymer (B-II) according to [13], wherein the amount of the multifunctional monomer is 0.1 to 5.0 parts by mass relative to 100 parts by mass of the total amount of the alkyl (meth)acrylate and the multifunctional monomer.

[15] The method for producing a graft copolymer (B-II) according to [13] or [14], wherein the ratio between the rubbery polymer (A-II) and the vinyl monomer (b-II) is such that the proportion of the rubbery polymer (A-II) is 10% to 90% by mass and the proportion of the vinyl monomer (b-II) is 90% to 10% by mass (with the total proportion of the rubbery polymer (A-II) and the vinyl monomer (b-II) being 100% by mass).

[16] The method for producing a graft copolymer (B-II) according to any one of [13] to [15], wherein the amount of the oil-soluble initiator used is 0.001 to 5 parts by mass relative to 100 parts by mass of the alkyl (meth)acrylate.

[17] The method for producing a graft copolymer (B-II) according to any one of [13] to [16], wherein the amount of the emulsifier used is 0.01 to 1.0 parts by mass relative to 100 parts by mass of the alkyl (meth)acrylate.

[18] A method for producing a thermoplastic resin composition, the method comprising using a graft copolymer (B-II) produced by the production method according to any one of [13] to [17].

[19] A method for producing a molded article, the method comprising molding a thermoplastic resin composition produced by the production method according to [18].

[20] A graft copolymer (B-II) produced by grafting at least one vinyl monomer (b-II) selected from the group consisting of an aromatic vinyl, an alkyl (meth)acrylate, and a vinyl cyanide to a rubbery polymer (A-II) produced by miniemulsion polymerization of a mixture (a-II) containing an alkyl (meth)acrylate, a multifunctional monomer copolymerizable with the alkyl (meth)acrylate, an oil-soluble initiator having 16 or more carbon atoms, an emulsifier, and water.

[21] A thermoplastic resin composition comprising the graft copolymer (B-II) according to [20].

[22] A molded article produced by molding the thermoplastic resin composition according to [21].

An object of the third invention is to provide a graft copolymer which has good moldability and with which a thermoplastic resin molded article having excellent impact resistance and excellent appearance can be produced, a method for producing the graft copolymer, a thermoplastic resin composition including the graft copolymer, and a molded article produced using the thermoplastic resin composition. Another object of the third invention is to provide a method for producing a rubbery polymer with which the above graft copolymer can be produced.

The inventors of the third invention found that the above objects may be attained by a graft copolymer that includes a rubbery polymer and a graft layer, the rubbery polymer being produced by polymerizing a pre-emulsion containing specific two alkyl (meth)acrylates, a multifunctional monomer copolymerizable with the alkyl (meth)acrylates, an emulsifier, and water.

The summary of the third invention is as follows.

[23] A graft copolymer (B-III) comprising a rubbery polymer (A-III) and a graft layer (g), the rubbery polymer (A-III) being a polymerization product produced by polymerizing a pre-emulsion containing an alkyl (meth)acrylate, a multifunctional monomer copolymerizable with the alkyl (meth)acrylate, an emulsifier, and water, the graft layer (g) being formed by grafting at least one vinyl monomer selected from the group consisting of an aromatic vinyl, an alkyl (meth)acrylate, and a vinyl cyanide to the rubbery polymer (A-III), the alkyl (meth)acrylate including an alkyl (meth)acrylate having 1 to 11 carbon atoms and an alkyl (meth)acrylate having 12 to 30 carbon atoms.

[24] The graft copolymer (B-III) according to [23], wherein the amount of the alkyl (meth)acrylate having 12 to 30 carbon atoms is 0.1 to 50 parts by mass relative to 100 parts by mass of the total amount of the alkyl (meth)acrylate having 1 to 11 carbon atoms and the alkyl (meth)acrylate having 12 to 30 carbon atoms.

[25] A graft copolymer (B-III) according to [23] or [24], wherein the amount of the multifunctional monomer is 0.1 to 5.0 parts by mass relative to 100 parts by mass of the total amount of the alkyl (meth)acrylate and the multifunctional monomer.

[26] The graft copolymer (B-III) according to any one of [23] to [25], wherein the graft layer (g) is produced by polymerizing the vinyl monomer with the rubbery polymer (A-III) such that the proportion of the rubbery polymer (A-III) is 10% to 90% by mass and the proportion of the vinyl monomer is 90% to 10% by mass (with the total proportion of the rubbery polymer (A-III) and the vinyl monomer being 100% by mass).

[27] The graft copolymer (B-III) according to any one of [23] to [26], wherein the rubbery polymer (A-III) included in the polymerization product of the pre-emulsion has a volume-average particle size of less than 1000 nm.

[28] A thermoplastic resin composition comprising the graft copolymer (B-III) according to any one of [23] to [27].

[29] A molded article produced using the thermoplastic resin composition according to [28].

[30] A method for producing a rubbery polymer (A-III), the method comprising a step in which a pre-emulsion is prepared using an alkyl (meth)acrylate, a multifunctional monomer copolymerizable with the alkyl (meth)acrylate, an emulsifier, and water, and a step in which the emulsion is polymerized, the alkyl (meth)acrylate including an alkyl (meth)acrylate having 1 to 11 carbon atoms and an alkyl (meth)acrylate having 12 to 30 carbon atoms.

[31] A method for producing a graft copolymer (B-III), the method comprising grafting at least one vinyl monomer (b-III) selected from the group consisting of an aromatic vinyl, an alkyl (meth)acrylate, and a vinyl cyanide to a rubbery polymer (A-III) produced by the method for producing a rubbery polymer (A-III) according to [30] in order to form a graft layer (g).

[32] A method for producing a thermoplastic resin composition, the method comprising using a graft copolymer (B-III) produced by the production method according to [31].

[33] A method for producing a molded article, the method comprising using a thermoplastic resin composition produced by the production method according to [32].

ADVANTAGEOUS EFFECTS OF INVENTION

The graft copolymer according to the first invention enables the production of a thermoplastic resin composition having good moldability and good continuous moldability and a molded article having excellent impact resistance.

According to the second invention, a graft copolymer having excellent production stability and excellent storage stability may be produced. According to the second invention, a thermoplastic resin composition having excellent moldability may be produced using the graft copolymer. Furthermore, a molded article having excellent impact resistance may be produced using the thermoplastic resin composition.

The graft copolymer according to the third invention enables the production of a thermoplastic resin composition having good moldability and a molded article having excellent impact resistance and excellent appearance.

