Method for producing conjugated diene polymer and method for producing graft copolymer

Abstract

The present invention relates to a method for preparing a conjugated diene-based polymer and a method for preparing a graft copolymer, and more particularly, to a method for preparing a conjugated diene-based polymer, which can increase the particle size of a conjugated diene-based polymer without an additional process such as expansion by agglomeration or an increase in polymerization time; and a method for preparing a graft copolymer, which can further improve the impact strength of a resin composition from a conjugated diene-based polymer having an increased particle size.

Description

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0176493 filed on December 16, 2022, the entire contents of which are incorporated into this specification by reference. Technical Field

[0003] The invention relates to a method for preparing a conjugated diene polymer and a method for preparing a graft copolymer. Background Art

[0004] Acrylonitrile-butadiene-styrene (ABS) copolymers are prepared by graft copolymerization of styrene and acrylonitrile on butadiene rubber polymers. ABS copolymers have excellent impact resistance, chemical resistance, thermal stability, colorability, fatigue resistance, rigidity and processing properties when compared to conventional high impact polystyrene (HIPS), and are used for parts such as interior and exterior materials of automobiles, office equipment, and various electrical and electronic products or toys.

[0005] The rubber polymer included in the ABS copolymer is generally prepared by emulsion polymerization of a conjugated diene-based monomer, and the particle size of the rubber polymer in the rubber polymer latex including the rubber polymer prepared by emulsion polymerization has a very significant influence on the final physical properties.

[0006] Generally, if the particle size of the rubber polymer increases, the impact strength of the resin composition containing the ABS copolymer increases, and a lot of efforts to increase the particle size of the rubber polymer are still going on. According to one aspect of a method for increasing the particle size of the rubber polymer, after polymerizing the rubber polymer having a small particle size, the particle size is increased by an additional process such as enlargement by agglomeration, or by increasing the polymerization time in the process of preparing the rubber polymer. However, if the rubber polymer is prepared like this, the increase in productivity is limited due to the increase in the additional process and the polymerization time, and there is a defect that it shows limitations in increasing the particle size of the rubber polymer.

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] (Patent Document 1) JP 1996-259777 A Summary of the invention

[0010] Technical issues

[0011] The present invention is designed to solve the problems mentioned in the above background technology, and aims to provide a method for preparing a conjugated diene polymer, which can increase the particle size of the conjugated diene polymer without additional processes such as enlargement by agglomeration or increasing the polymerization time.

[0012] Furthermore, another object of the present invention is to provide a method for preparing a graft copolymer, which can further improve the impact strength of a resin composition through a conjugated diene-based polymer having an increased particle size.

[0013] Technical Solution

[0014] In order to solve the above-mentioned tasks, the present invention provides a method for preparing a conjugated diene polymer and a method for preparing a graft copolymer.

[0015] (1) The present invention provides a method for preparing a conjugated diene polymer, comprising the step (S10): polymerizing a conjugated diene monomer in the presence of a sulfate and a carbonate, wherein the sulfate and the carbonate are injected at a weight ratio of 1:0.08 to 9.2.

[0016] (2) The present invention provides the method for preparing a conjugated diene polymer according to (1), wherein the sulfate and the carbonate are injected at a weight ratio of 1:0.1 to 9.0.

[0017] (3) The present invention provides the method for producing a conjugated diene polymer according to (1) or (2), wherein the sulfate is an alkali metal sulfate.

[0018] (4) The present invention provides the method for producing a conjugated diene polymer according to any one of (1) to (3), wherein the carbonate is an alkali metal carbonate.

[0019] (5) The present invention provides a method for preparing a conjugated diene polymer according to any one of (1) to (4), wherein the sulfate and the carbonate are injected at 0.3 to 1.5 parts by weight based on 100 parts by weight of the conjugated diene monomer.

[0020] (6) The present invention provides the method for preparing a conjugated diene polymer according to any one of (1) to (5), wherein the conjugated diene polymer prepared in step (S10) has an average particle size of 50 nm to 500 nm.

[0021] (7) The present invention provides the method for preparing a conjugated diene polymer according to any one of (1) to (6), wherein the conjugated diene polymer prepared in step (S10) has an average particle size of 300 nm to 500 nm.

[0022] (8) The present invention provides a method for preparing a graft copolymer, comprising the step (S20): injecting an aromatic vinyl monomer and a vinyl cyanide monomer in the presence of a conjugated diene polymer latex prepared according to any one of (1) to (7) to prepare a graft copolymer latex containing the graft copolymer.

[0023] (9) The present invention provides a method for preparing a graft copolymer according to (8), wherein step (S20) is carried out by injecting 50 wt % to 70 wt % of the conjugated diene polymer latex, 10 wt % to 40 wt % of the aromatic vinyl monomer and 1 wt % to 20 wt % of the vinyl cyanide monomer based on the solid content, based on the total amount of the conjugated diene polymer, the aromatic vinyl monomer and the vinyl cyanide monomer.

[0024] (10) The present invention provides a conjugated diene polymer prepared according to any one of (1) to (7).

[0025] (11) The present invention provides a graft copolymer prepared according to (8) or (9).

[0026] (12) The present invention provides a graft copolymer comprising the conjugated diene-based polymer according to (10), an aromatic vinyl-based monomer unit and a vinyl cyanide-based monomer unit.

[0027] (13) The present invention provides a resin composition comprising the graft copolymer according to (11) or (12) and a styrene-based copolymer.

[0028] Beneficial Effects

[0029] If a conjugated diene-based polymer is prepared according to the method for preparing a conjugated diene-based polymer of the present invention, the particle size of the conjugated diene-based polymer can be increased without an additional process such as enlargement by agglomeration or increasing the polymerization time.

[0030] Furthermore, if a graft copolymer is prepared according to the method for preparing a graft copolymer of the present invention, the impact strength of the resin composition can be further improved by the conjugated diene-based polymer having an increased particle size. DETAILED DESCRIPTION

[0031] Hereinafter, the present invention will be described in more detail to help understanding of the present invention.

[0032] It should be understood that the words or terms used in the specification and claims of the present invention should not be understood as the meanings defined in common dictionaries. It will be understood that based on the inventors can appropriately define the meanings of the words to best illustrate the principles of the present invention, the words or terms should be understood to have the same meanings as they are in the technical concept of the present invention.

[0033] The term "monomer unit" in the present invention may refer to a component or structure derived from a monomer or the substance itself, and in a specific embodiment, may refer to a repeating unit formed in a polymer by the injected monomer participating in the polymerization reaction during the polymerization process of the polymer.

[0034] The term "composition" used in the present invention includes reaction products and decomposition products formed from materials of corresponding composition, as well as mixtures containing materials of corresponding composition.

[0035] The invention provides a method for preparing a conjugated diene polymer.

[0036] According to one embodiment of the present invention, the method for preparing the conjugated diene polymer may include the step (S10): polymerizing the conjugated diene monomer in the presence of sulfate and carbonate, wherein the sulfate and carbonate may be injected at a weight ratio of 1:0.08 to 9.2.

[0037] According to one embodiment of the present invention, the polymerization in step (S10) is a step of preparing a conjugated diene-based polymer latex containing a conjugated diene-based polymer, and the polymerization in step (S10) may be performed by emulsion polymerization.

[0038] According to one embodiment of the present invention, the conjugated diene monomer can be one or more selected from 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, isoprene and 2-phenyl-1,3-butadiene, more specifically, it can be 1,3-butadiene.

[0039] According to one embodiment of the present invention, in step (S10), the total amount of conjugated diene monomers can be injected in batches before initiating polymerization, or a part can be injected before initiating polymerization and the remaining amount can be injected in the process of carrying out polymerization. In carrying out step (S10), if the conjugated diene monomers are injected in batches by being divided into a point before initiating polymerization and a point in the process of carrying out polymerization, the effect of increasing the average particle diameter of the conjugated diene polymer and improving the particle size uniformity of the conjugated diene polymer prepared can be obtained. In a specific embodiment, in step (S10), the conjugated diene monomers can be injected with 30% to 70% by weight or 40% to 60% by weight before initiating polymerization, and injected with 30% to 70% by weight or 40% to 60% by weight in the process of carrying out polymerization. In a more specific embodiment, in step (S10), the conjugated diene monomer can be injected at 30 wt % to 70 wt % or 40 wt % to 60 wt % before initiating the polymerization, injected at 15 wt % to 35 wt % or 20 wt % to 30 wt % at a point where the polymerization conversion rate is 40 wt % to 60 wt %, and injected at 15 wt % to 35 wt % or 20 wt % to 30 wt % at a point where the polymerization conversion rate is 65 wt % to 80 wt %.

[0040] According to one embodiment of the present invention, the emulsion polymerization in step (S10) may be carried out in the presence of an emulsifier, and the emulsifier may be a fatty acid emulsifier or a fatty acid dimer emulsifier.

[0041] According to one embodiment of the present invention, based on 100 parts by weight of the conjugated diene monomer, the amount of the emulsifier in step (S10) can be 0.1 parts by weight to 10.0 parts by weight, 0.8 parts by weight to 8.0 parts by weight, or 1.0 parts by weight to 6.0 parts by weight. Within this range, the effect of preparing a conjugated diene polymer having an average particle size suitable for ensuring impact resistance can be obtained.

[0042] According to one embodiment of the present invention, in step (S10), the total amount of the emulsifier can be injected in batches, or a portion can be injected before initiating polymerization and the remaining amount can be injected during the polymerization. In the step (S10), if the emulsifier is injected in batches by dividing into a point before initiating polymerization and a point during the polymerization, the effect of improving the particle size uniformity of the prepared conjugated diene polymer can be obtained, while increasing the average particle size of the conjugated diene polymer. In a specific embodiment, in step (S10), a portion of the emulsifier can be injected before initiating polymerization and the remaining amount can be injected during the polymerization.

[0043] According to one embodiment of the present invention, step (S10) can be carried out by free radical polymerization using an initiator for emulsion polymerization, specifically, a water-soluble initiator, a peroxide initiator, a redox initiator or an azo initiator. The water-soluble initiator can be potassium peroxide or ammonium peroxide, and the redox initiator can be, for example, one or more selected from tert-butyl hydroperoxide, diisopropylbenzene hydroperoxide and isopropylbenzene hydroperoxide, in which case, the effect of providing a stable polymerization environment can be obtained. In addition, if a redox initiator is used, step (S10) can be carried out by additionally including ferrous sulfate, dextrose and sodium pyrophosphate as a redox catalyst.

[0044] According to one embodiment of the present invention, based on 100 parts by weight of the conjugated diene monomer, the amount of the initiator in step (S10) can be 0.01 parts by weight to 5.00 parts by weight, 0.05 parts by weight to 3.00 parts by weight, or 0.1 parts by weight to 1.0 parts by weight. Within this range, the effect of preparing a conjugated diene polymer having an average particle size suitable for ensuring impact resistance can be obtained.

[0045] According to one embodiment of the present invention, in step (S10), the total amount of the initiator can be injected in batches before initiating polymerization, or a part can be injected before initiating polymerization and the remaining part can be injected during the polymerization. In the step (S10), if the initiator is injected in batches by dividing into a point before initiating polymerization and a point during the polymerization, the effect of increasing the average particle size of the conjugated diene polymer and improving the particle size uniformity of the conjugated diene polymer can be obtained.

[0046] According to one embodiment of the present invention, step (S10) may be performed in the presence of a molecular weight regulator, and the molecular weight regulator may be a mercaptan molecular weight regulator, specifically, tert-dodecyl mercaptan.

[0047] According to one embodiment of the present invention, based on 100 parts by weight of the conjugated diene monomer, the amount of the molecular weight regulator in step (S10) can be 0.01 parts by weight to 5.00 parts by weight, 0.05 parts by weight to 3.00 parts by weight, or 0.1 parts by weight to 1.0 parts by weight. Within this range, a conjugated diene polymer having an average particle size suitable for ensuring impact resistance can be prepared.

[0048] According to one embodiment of the present invention, in step (S10), the total amount of molecular weight regulator can be injected in batches before initiating polymerization, or a part can be injected before initiating polymerization and the remaining amount can be injected during the polymerization. In the step (S10), if the molecular weight regulator is injected in batches at a point before initiating polymerization and a point during the polymerization, the effect of improving the particle size uniformity of the prepared conjugated diene polymer can be obtained, while increasing the average particle size of the conjugated diene polymer. In a specific embodiment, in step (S10), a part of the molecular weight regulator can be injected before initiating polymerization and the remaining amount can be injected during the polymerization.

[0049] According to one embodiment of the present invention, the emulsion polymerization in step (S10) can be carried out in an aqueous solvent, and the aqueous solvent can be ion-exchanged water. Therefore, the conjugated diene polymer emulsion polymerized in step (S10) can be obtained in a latex type, wherein the conjugated diene polymer particles are dispersed in the aqueous solvent as a colloidal phase.

[0050] According to one embodiment of the present invention, step (S10) can be carried out in the presence of sulfate and carbonate, in which case, sulfate and carbonate are electrolytes and can play a role in controlling the stability of the conjugated diene polymer latex and the average particle size of the conjugated diene polymer. Specifically, if polymerization is carried out by simultaneously including sulfate and carbonate, the latex stability can be further improved, and the average particle size of the conjugated diene polymer can be easily controlled according to the target level.

[0051] According to one embodiment of the present invention, sulfate and carbonate can be injected at a weight ratio of 1: 0.08 to 9.2. In a specific embodiment, based on the weight ratio (sulfate: carbonate), sulfate and carbonate can be injected at a weight ratio of 1: 0.08 or more, 0.09 or more, 0.10 or more, or 0.11 or more, and 1: 9.20 or less, 9.15 or less, 9.10 or less, 9.05 or less, or 9.00 or less. Within this range, the particle size of the conjugated diene polymer can be controlled to a suitable level, and the impact resistance can be improved.

[0052] According to one embodiment of the present invention, the sulfate may be an alkali metal sulfate. In a specific embodiment, the alkali metal sulfate may be one or more selected from sodium sulfate, potassium sulfate, sodium hydrogen sulfate and potassium hydrogen sulfate, specifically, sodium sulfate.

[0053] According to one embodiment of the present invention, the carbonate may be an alkali metal carbonate. In a specific embodiment, the alkali metal carbonate may be one or more selected from sodium carbonate and potassium carbonate, specifically, potassium carbonate.

[0054] According to one embodiment of the present invention, the sulfate and the carbonate may be sodium sulfate and potassium carbonate, respectively, in which case the latex stability may be further improved and the average particle size of the conjugated diene-based polymer may be easily controlled to a target level.

[0055] According to one embodiment of the present invention, based on 100 parts by weight of conjugated diene monomers, sulfate and carbonate can be injected with 0.3 to 1.5 parts by weight. In a specific embodiment, based on 100 parts by weight of conjugated diene monomers, sulfate and carbonate can be injected with more than 0.1 parts by weight, more than 0.2 parts by weight, more than 0.3 parts by weight, more than 0.4 parts by weight or more than 0.5 parts by weight, and less than 1.5 parts by weight, less than 1.4 parts by weight, less than 1.3 parts by weight, less than 1.2 parts by weight, less than 1.1 parts by weight or less than 1.0 parts by weight. Within the scope, the particle size of the conjugated diene polymer can be further increased. Here, the amount of sulfate and carbonate can be the respective amount of sulfate and carbonate, or the amount of sulfate mixed with carbonate.

[0056] According to one embodiment of the present invention, conjugated diene polymer can have the average particle diameter of 50nm to 500nm.In a specific embodiment, conjugated diene polymer can have more than 50nm, more than 100nm, more than 150nm, more than 200nm, more than 250nm or more than 300nm, and the average particle diameter of below 500nm, below 490nm, below 480nm, below 470nm, below 460nm, below 450nm, below 440nm, below 430nm, below 420nm or below 410nm.Conjugated diene polymer is the conjugated diene polymer with large diameter and can show large diameter by the preparation of step (S10).

[0057] The invention provides a method for preparing a graft copolymer.

[0058] According to one embodiment of the present invention, the preparation method of the graft copolymer may include step (S20): injecting aromatic vinyl monomers and vinyl cyanide monomers in the presence of conjugated diene polymer latex prepared according to the preparation method of the conjugated diene polymer described above and polymerizing to prepare a graft copolymer latex containing the graft copolymer. In a specific embodiment, step (S20) may be a step of grafting the conjugated diene polymer contained in the conjugated diene polymer latex prepared in the graft polymerization step (S10) with aromatic vinyl monomers and vinyl cyanide monomers.

[0059] According to one embodiment of the present invention, the graft polymerization in step (S20) may be performed by emulsion polymerization. In addition, the graft polymerization in step (S20) may be performed in the conjugated diene polymer latex of the latex phase prepared in step (S10).

[0060] According to one embodiment of the present invention, step (S20) can be carried out by free radical polymerization using peroxide, redox or azo initiators that can be used for graft emulsion polymerization. The redox initiator can be, for example, one or more selected from tert-butyl hydroperoxide, diisopropylbenzene hydroperoxide and isopropylbenzene hydroperoxide, in which case, the effect of providing a stable polymerization environment can be obtained. In addition, if a redox initiator is used, ferrous sulfate, dextrose and sodium pyrophosphate can be further included as a redox catalyst.

[0061] According to one embodiment of the present invention, the graft emulsion polymerization in step (S20) can be carried out in an aqueous solvent, and the aqueous solvent can be ion-exchanged water. Therefore, the graft copolymer of the graft polymerization in step (S20) can be obtained in a latex type, wherein the graft copolymer particles are dispersed in the aqueous solvent as a colloidal phase.

[0062] According to one embodiment of the present invention, the aromatic vinyl monomer can be one or more selected from styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 1-vinylnaphthalene, 4-cyclohexylstyrene, 4-(p-methylphenyl)styrene and 1-vinyl-5-hexylnaphthalene, specifically, styrene.

[0063] According to one embodiment of the present invention, the vinyl cyanide monomer may be one or more selected from acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile and α-chloroacrylonitrile, and specifically, may be acrylonitrile.

[0064] According to one embodiment of the present invention, based on the total amount of conjugated diene polymer, aromatic vinyl monomer and vinyl cyanide monomer, the amount of conjugated diene polymer latex injected in step (S20) can be 50 wt % to 70 wt %, specifically, 50 wt % or more, 55 wt % or more or 60 wt %, and 70 wt % or less, 65 wt % or less or 60 wt % or less. Within this range, the impact strength and flexibility of the graft copolymer can be further improved.

[0065] According to one embodiment of the present invention, based on the total amount of conjugated diene polymer, aromatic vinyl monomer and vinyl cyanide monomer, the amount of aromatic vinyl monomer injected in step (S20) can be 10 wt % to 40 wt %, specifically, more than 10 wt %, more than 15 wt %, more than 20 wt %, more than 25 wt % or more than 30 wt %, and less than 40 wt %, less than 35 wt % or less than 30 wt %. Within this range, the effect of improving the dispersibility of the graft copolymer in the resin composition can be obtained while ensuring the mechanical properties of the graft copolymer.

[0066] According to one embodiment of the present invention, based on the total amount of conjugated diene polymer, aromatic vinyl monomer and vinyl cyanide monomer, the amount of the vinyl cyanide monomer injected in step (S20) can be 1 wt % to 20 wt %, specifically, more than 1 wt %, more than 2 wt %, more than 3 wt %, more than 4 wt %, more than 5 wt %, more than 6 wt %, more than 7 wt %, more than 8 wt %, more than 9 wt % or more than 10 wt %, and less than 20 wt %, less than 19 wt %, less than 18 wt %, less than 17 wt %, less than 16 wt %, less than 15 wt %, less than 14 wt %, less than 13 wt %, less than 12 wt %, less than 11 wt % or less than 10 wt %. Within this range, the effect of improving the dispersibility of the graft copolymer in the resin combination can be obtained while ensuring the mechanical properties of the graft copolymer.

[0067] The present invention provides a conjugated diene polymer prepared according to the method for preparing the conjugated diene polymer and a graft copolymer prepared according to the method for preparing the graft copolymer.

[0068] According to one embodiment of the present invention, the graft copolymer may include a conjugated diene-based polymer, an aromatic vinyl-based monomer unit, and a vinyl cyanide-based monomer unit.

[0069] According to one embodiment of the present invention, the conjugated diene polymer may be the same as the conjugated diene polymer described in the preparation method of the graft copolymer, and the aromatic vinyl monomer unit and the vinyl cyanide monomer unit may refer to repeating units formed by the aromatic vinyl monomer and the vinyl cyanide monomer described in the preparation method of the graft copolymer participating in the graft polymerization reaction.

[0070] According to one embodiment of the present invention, the amount of each of the conjugated diene-based polymer, the aromatic vinyl-based monomer unit, and the vinyl cyanide-based monomer unit may be the same as the amount of each component injected during the preparation of the graft copolymer.

[0071] The present invention provides a resin composition comprising the graft copolymer.

[0072] According to one embodiment of the present invention, the resin composition may include a graft copolymer and a styrene copolymer. The styrene copolymer may be a non-graft copolymer comprising an aromatic vinyl monomer, specifically, a copolymer comprising an aromatic vinyl monomer unit and a vinyl cyanide monomer unit. Here, the styrene copolymer may be a matrix resin, which may be mixed with the graft copolymer in the resin composition to form a matrix.

[0073] According to one embodiment of the present invention, the aromatic vinyl monomer forming the aromatic vinyl monomer unit of the styrene copolymer may be one or more selected from styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 1-vinylnaphthalene, 4-cyclohexylstyrene, 4-(p-methylphenyl)styrene and 1-vinyl-5-hexylnaphthalene, specifically, styrene.

[0074] According to one embodiment of the present invention, the vinyl cyanide monomer forming the vinyl cyanide monomer unit of the styrene copolymer may be one or more selected from acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile and α-chloroacrylonitrile, specifically, acrylonitrile.

[0075] According to one embodiment of the present invention, the resin composition may contain 10 wt % to 40 wt %, 15 wt % to 35 wt %, or 20 wt % to 30 wt % of a graft copolymer; and a copolymer containing 60 wt % to 90 wt %, 65 wt % to 85 wt %, or 70 wt % to 80 wt % of aromatic vinyl monomer units and vinyl cyanide monomer units. Within this range, the processing properties of the resin composition containing the graft copolymer can be prevented from deteriorating while maximizing the mechanical properties, especially the impact resistance.

[0076] According to one embodiment of the present invention, the graft copolymer and the styrene copolymer each contain an aromatic vinyl monomer unit and a vinyl cyanide monomer unit. If the types of the aromatic vinyl monomer unit and the vinyl cyanide monomer unit forming each copolymer are the same, the same components can be mixed and dispersed during the extrusion process of the resin composition. In the actual resin composition and the molded product formed therefrom, the conjugated diene polymer can be present in a dispersed form in the matrix formed by the aromatic vinyl monomer unit and the vinyl cyanide monomer unit. Therefore, the amount of the graft copolymer and the styrene copolymer in the resin composition can be determined by the total amount of the aromatic vinyl monomer unit and the vinyl cyanide monomer unit and the amount of the conjugated diene polymer.

[0077] According to one embodiment of the present invention, the resin composition may have an impact strength of 24.0 kgf cmm / cmm or more, 24.5 kgf cmm / cmm or more, or 24.8 kgf cmm / cmm or more, and 30.0 kgf cmm / cmm or less measured at 1 / 4 inch thickness by ASTM D256. Within this range, the effect of excellent impact strength of the resin composition comprising the graft copolymer can be obtained.

[0078] Hereinafter, embodiments of the present invention will be explained in detail so that those skilled in the art can easily carry out the present invention. However, the present invention can be implemented in various other types and is not limited to the embodiments explained herein.

[0079] Example

[0080] Example 1

[0081] <Preparation of Conjugated Diene Polymer Latex>

[0082] Into the nitrogen-substituted polymerization reactor, 70 parts by weight of ion exchange water, 80 parts by weight of 1,3-butadiene, 1.7 parts by weight of potassium oleate, 0.3 parts by weight of tert-dodecyl mercaptan, 0.1 parts by weight of potassium carbonate (K 2 CO 3 ) and 0.9 parts by weight of sodium sulfate (Na 2 SO 4 ), and 0.3 parts by weight of potassium persulfate, and stirred to mix well. Then, the internal temperature of the polymerization reactor was raised to 75°C, 0.1 parts by weight of potassium persulfate was injected at a point where the polymerization conversion rate reached 40%, the temperature was raised to 85°C and a polymerization reaction was carried out. At a point where the polymerization conversion rate reached 50%, 20 parts by weight of 1,3-butadiene was injected, and at a point where the polymerization conversion rate reached 90%, the reaction was terminated to obtain a conjugated diene polymer latex (average particle size: , solid content: 55.3 wt %).

[0083] <Preparation of Graft Copolymer Latex>

[0084] A monomer mixture including 30 parts by weight of styrene, 10 parts by weight of acrylonitrile, 100 parts by weight of ion exchange water, 0.05 parts by weight of tert-butyl hydroperoxide, 0.5 parts by weight of potassium rosinate, and 0.5 parts by weight of tert-dodecyl mercaptan was prepared.

[0085] Separately, an activator mixture containing 0.01 parts by weight of dextrose, 0.01 parts by weight of tetrasodium pyrophosphate, and 0.001 parts by weight of ferrous sulfate was prepared.

[0086] Into the nitrogen-substituted polymerization reactor, 60 parts by weight (based on solid content) of the prepared conjugated diene polymer latex and 10 parts by weight of ion exchange water are injected, and the internal temperature of the polymerization reactor is raised to 55°C. Then, the polymerization reaction is carried out for 2 hours while the monomer mixture and the activator mixture are continuously injected into the polymerization reactor. After the continuous injection is completed, 0.005 parts by weight of dextrose, 0.005 parts by weight of tetrasodium pyrophosphate, 0.0005 parts by weight of ferrous sulfate and 0.1 parts by weight of tert-butyl hydroperoxide are injected into the polymerization reactor, and the internal temperature of the polymerization reactor is raised to 80°C over 1 hour, and the polymerization is terminated to obtain a graft copolymer latex containing a graft copolymer.

[0087] <Preparation of Graft Copolymer Granular Material>

[0088] 2.0 parts by weight of magnesium sulfate (MgSO 4 ), and agglomeration was performed at 85° C. Then, the resultant was aged for 10 minutes while the temperature was raised from 85° C. to 95° C., washed, dehydrated and dried to obtain a graft copolymer particulate material.

[0089] Example 2

[0090] The same method as in Example 1 was carried out to prepare conjugated diene polymer latex, graft copolymer latex and graft copolymer particulate material, except that 0.5 weight parts instead of 0.1 weight parts of potassium carbonate and 0.5 weight parts instead of 0.9 weight parts of sodium sulfate were injected during the preparation of the conjugated diene polymer latex in Example 1.

[0091] Example 3

[0092] The same method as in Example 1 was carried out to prepare conjugated diene polymer latex, graft copolymer latex and graft copolymer particulate material, except that 0.9 weight parts instead of 0.1 weight parts of potassium carbonate and 0.1 weight parts instead of 0.9 weight parts of sodium sulfate were injected during the preparation of the conjugated diene polymer latex in Example 1.

[0093] Comparative Example 1

[0094] The same method as in Example 1 was carried out to prepare conjugated diene polymer latex, graft copolymer latex and graft copolymer particulate material, except that 1.0 weight part instead of 0.1 weight part of potassium carbonate was injected and sodium sulfate was not injected during the preparation of the conjugated diene polymer latex in Example 1.

[0095] Comparative Example 2

[0096] The same method as in Example 1 was carried out to prepare conjugated diene polymer latex, graft copolymer latex and graft copolymer particulate material, except that 0.95 weight parts instead of 0.1 weight parts of potassium carbonate and 0.05 weight parts instead of 0.9 weight parts of sodium sulfate were injected during the preparation of the conjugated diene polymer latex in Example 1.

[0097] Comparative Example 3

[0098] The same method as in Example 1 was performed except that 0.05 parts by weight instead of 0.1 parts by weight of potassium carbonate and 0.95 parts by weight instead of 0.9 parts by weight of sodium sulfate were injected during the preparation of the conjugated diene-based polymer latex in Example 1. However, agglomeration occurred due to deterioration of latex stability during the preparation of the conjugated diene-based polymer latex, and the graft copolymer could not be prepared.

[0099] Comparative Example 4

[0100] The same method as in Example 1 was performed except that potassium carbonate was not injected and 1.0 parts by weight instead of 0.9 parts by weight of sodium sulfate was injected during the preparation of the conjugated diene-based polymer latex in Example 1. However, agglomeration occurred due to deterioration of latex stability during the preparation of the conjugated diene-based polymer latex, and the graft copolymer could not be prepared.

[0101] Comparative Example 5

[0102] The same method as in Example 1 was carried out to prepare conjugated diene polymer latex, graft copolymer latex and graft copolymer particulate material, except that 0.5 weight parts instead of 0.1 weight parts of potassium carbonate and 0.5 weight parts of potassium chloride (KCl) instead of 0.9 weight parts of sodium sulfate were injected during the preparation of the conjugated diene polymer latex in Example 1.

[0103] Comparative Example 6

[0104] In addition to injecting 0.5 parts by weight of potassium carbonate instead of 0.1 parts by weight and 0.5 parts by weight of potassium bicarbonate (KHCO 3 ) instead of 0.9 parts by weight of sodium sulfate, the same method as in Example 1 was carried out to prepare a conjugated diene polymer latex, a graft copolymer latex and a graft copolymer particulate material.

[0105] Comparative Example 7

[0106] In addition to injecting 0.5 parts by weight of potassium carbonate instead of 0.1 parts by weight and 0.5 parts by weight of potassium bisulfite (KHSO 3) instead of 0.9 parts by weight of sodium sulfate, the same method as in Example 1 was carried out to prepare a conjugated diene polymer latex, a graft copolymer latex and a graft copolymer particulate material.

[0107] Comparative Example 8

[0108] In addition to injecting 0.5 parts by weight of potassium carbonate instead of 0.1 parts by weight and 0.5 parts by weight of potassium phosphate (K 3 PO 4 ) instead of 0.9 parts by weight of sodium sulfate, the same method as in Example 1 was carried out to prepare a conjugated diene polymer latex, a graft copolymer latex and a graft copolymer particulate material.

[0109] Comparative Example 9

[0110] The same method as in Example 1 was carried out to prepare conjugated diene polymer latex, graft copolymer latex and graft copolymer particulate material, except that 0.5 weight parts instead of 0.9 weight parts of sodium sulfate and 0.5 weight parts of potassium chloride (KCl) instead of 0.1 weight parts of potassium carbonate were injected during the preparation of the conjugated diene polymer latex in Example 1.

[0111] Comparative Example 10

[0112] In addition to injecting 0.5 parts by weight of sodium sulfate instead of 0.9 parts by weight and 0.5 parts by weight of potassium bicarbonate (KHCO 3 ) instead of 0.1 parts by weight of potassium carbonate, the same method as in Example 1 was carried out to prepare a conjugated diene polymer latex, a graft copolymer latex and a graft copolymer particulate material.

[0113] Comparative Example 11

[0114] In addition to injecting 0.5 parts by weight of sodium sulfate instead of 0.9 parts by weight and 0.5 parts by weight of potassium bisulfite (KHSO) during the preparation of the conjugated diene polymer latex in Example 1, 3 ) instead of 0.1 parts by weight of potassium carbonate, the same method as in Example 1 was carried out to prepare a conjugated diene polymer latex, a graft copolymer latex and a graft copolymer particulate material.

[0115] Comparative Example 12

[0116] In addition to injecting 0.5 parts by weight of sodium sulfate instead of 0.9 parts by weight and 0.5 parts by weight of potassium phosphate (K 3 PO 4) instead of 0.1 parts by weight of potassium carbonate, the same method as in Example 1 was carried out to prepare a conjugated diene polymer latex, a graft copolymer latex and a graft copolymer particulate material.

[0117] Experimental example

[0118] Experimental Example 1

[0119] For the conjugated diene-based polymer latexes prepared in Examples 1 to 3 and Comparative Examples 1 to 12, the average particle diameter was measured by the following method and is shown in Table 1 together with the amount of electrolyte injected during the preparation of the conjugated diene-based polymer latex.

[0120] : 1 g of the conjugated diene-based polymer latex was diluted in 100 g of distilled water, and measured by a dynamic light scattering method using a Nicomp 370HPL device from Particle Sizing Systems (PSS) Co.

[0121] [Table 1]

[0122]

[0123] As shown in Table 1, it can be confirmed that the conjugated diene-based polymers of Examples 1 to 3 prepared according to the present invention showed increased particle size without an additional process such as enlargement by agglomeration or increasing the polymerization time.

[0124] In contrast, it was confirmed that Comparative Example 1 in which only carbonate was injected during polymerization, and Comparative Example 2 in which sulfate and carbonate were injected simultaneously but the proportion of carbonate was excessive, showed insufficient increase in the particle size of the conjugated diene-based polymer.

[0125] Furthermore, although sulfate and carbonate were injected simultaneously, it was confirmed that Comparative Example 3 in which the ratio of sulfate was excessive and Comparative Example 4 in which only sulfate was injected showed agglomeration phenomenon due to deterioration of latex stability.

[0126] In addition, it was confirmed that Comparative Examples 5 to 8 in which carbonate and chloride, bicarbonate, bisulfite and triphosphate were injected, and Comparative Examples 9 to 12 in which sulfate and chloride, bicarbonate, bisulfite and triphosphate were injected instead of sulfate and carbonate, showed insufficient increase in the particle size of the conjugated diene polymer.

[0127] Experimental Example 2

[0128] By using the graft copolymer particle materials prepared in Examples 1 to 3 and Comparative Examples 1 to 12, a resin composition was prepared by the following method, and the resin composition particles were injected at 210° C., and the impact strength thereof was measured by the following method and shown in Table 2.

[0129] <Preparation of resin composition>

[0130] 23 parts by weight of each graft copolymer granular material prepared above, 77 parts by weight of styrene-acrylonitrile copolymer (manufactured by LG Chem, product name 92HR), 1.5 parts by weight of lubricant and 0.3 parts by weight of heat stabilizer were injected into a twin-screw extruder, mixed and extruded at 210°C to obtain resin composition pellets.

[0131] *Impact strength (kgf.cm / cm): According to the ASTM D256 method, a notch was made on a sample having a thickness of 1 / 4 inch, and the notched Izod impact strength was measured at room temperature (23° C.) using an impact strength measuring device (TINIUS OLSEN Co.).

[0132] [Table 2]

[0133]

[0134]

[0135] As shown in Table 2, it can be confirmed that all the resin compositions including the graft copolymers prepared by including the conjugated diene-based polymers of Examples 1 to 3 prepared according to the present invention exhibited excellent impact strength.

[0136] On the contrary, it can be confirmed that in the process of preparing the conjugated diene polymer latex, the resin composition containing the graft copolymer prepared by containing the conjugated diene polymer prepared in Comparative Example 1 and Comparative Example 2 showed poor impact strength, wherein only carbonate was injected as an electrolyte in Comparative Example 1 and sulfate was injected at the same time but in an insufficient amount in Comparative Example 2.

[0137] In addition, although carbonate and sulfate were injected together as electrolytes during the preparation of the conjugated diene polymer latex, in the cases of Comparative Example 3 in which an excessive amount of sulfate was injected and Comparative Example 4 in which only sulfate was injected, agglomeration occurred due to deterioration of latex stability during the preparation of the conjugated diene polymer latex, and therefore, preparation of the graft copolymer and the resin composition was impossible, and measurement of impact strength was impossible.

[0138] In addition, it was confirmed that all the resin compositions containing the graft copolymers prepared by containing the conjugated diene polymers prepared in Comparative Examples 5 to 8 in which carbonate and chloride, bicarbonate, bisulfite and triphosphate were injected, and Comparative Examples 9 to 12 in which sulfate and chloride, bicarbonate, bisulfite and triphosphate were injected as electrolytes instead of sulfate and carbonate during the preparation of the conjugated diene polymer latex, showed poor impact strength.

[0139] Based on these results, it can be confirmed that if a conjugated diene polymer is prepared according to the method for preparing a conjugated diene polymer of the present invention, the particle size of the conjugated diene polymer can be increased without the need for additional processes such as enlargement by agglomeration or increasing the polymerization time. In addition, in the process of preparing a graft copolymer, the conjugated diene polymer with increased particle size can further improve the impact strength of the resin composition.

Claims

1. A method for preparing a conjugated diene polymer, the method comprising: Step (S10): polymerizing the conjugated diene monomer in the presence of sulfate and carbonate, Wherein, the sulfate and the carbonate are injected in a weight ratio of 1:0.08 to 9.

2.

2. The method for preparing a conjugated diene polymer according to claim 1, wherein: The sulfate and the carbonate are injected in a weight ratio of 1:0.1 to 9.

0.

3. The method for preparing a conjugated diene polymer according to claim 1, wherein: The sulfate is an alkali metal sulfate.

4. The method for preparing a conjugated diene polymer according to claim 1, wherein: The carbonate is an alkali metal carbonate.

5. The method for preparing a conjugated diene polymer according to claim 1, wherein: The sulfate and the carbonate are injected at 0.3 to 1.5 parts by weight based on 100 parts by weight of the conjugated diene-based monomer.

6. The method for preparing a conjugated diene polymer according to claim 1, wherein: The conjugated diene-based polymer prepared in step (S10) has an average particle size of 50 nm to 500 nm.

7. The method for preparing a conjugated diene polymer according to claim 1, wherein: The conjugated diene-based polymer prepared in step (S10) has an average particle size of 300 nm to 500 nm.

8. A method for preparing a graft copolymer, the method comprising: Step (S20): injecting an aromatic vinyl-based monomer and a vinyl cyanide-based monomer in the presence of the conjugated diene-based polymer latex prepared according to claim 1 to prepare a graft copolymer latex containing a graft copolymer.

9. The method for preparing a graft copolymer according to claim 8, wherein: Step (S20) is to inject the conjugated diene polymer, the aromatic vinyl monomer and the vinyl cyanide monomer into the mixture. 50 wt % to 70 wt % of the conjugated diene polymer latex based on solid content, 10 to 40 wt% of the aromatic vinyl monomer, and 1 wt % to 20 wt % of the vinyl cyanide monomer.

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