KR100394734B1 - Preparation method of thermoplastic resin composition with excellent impact resistance and natural color - Google Patents

Abstract

PURPOSE: A method for preparing a thermoplastic acrylonitrile-butadiene-styrene resin composition is provided, to improve impact resistance, natural color and gloss. CONSTITUTION: The method comprises the steps of adding a mixture of a graft polymerizable monomer and a molecular weight controller to 40-60 parts by weight of a butadiene rubber polymerization latex having a gel content of 70-90 wt% and an average particle diameter of 0.26-0.38 micrometers and stirring the mixture to allow the monomer and molecular weight controller to be swollen into the particles sufficiently, adding an ion exchange water, a reducing agent, an emulsifier and an initiator, and adding a mixture of an oxidizing agent and a chelating agent to polymerize them until a polymerization conversion rate reaches 90-96 %, thereby obtaining a first graft latex; adding an emulsifier to the first graft latex, and continuously adding a mixture of a graft polymerizable monomer and a molecular weight controller to polymerize them, thereby obtaining a second graft latex; and adding a composition of an oxidizing agent, a reducing agent and a chelating agent to the obtained second graft latex to polymerize them until a final polymerization conversion rate reaches 94-98 %. The molecular weight controller in the steps 1 and 2 is an α-methyl styrene dimer, terpinolene, or their mixture with mercaptans.

Description

Manufacturing method of thermoplastic resin composition excellent in impact resistance and natural color

The present invention relates to a thermoplastic styrene resin composition, and more particularly, to an emulsion polymerization method of acrylonitrile-butadiene rubber-styrene resin (hereinafter referred to as "ABS resin") having excellent impact resistance and natural color and improved gloss. It relates to a resin composition produced by.

ABS resin has good physical properties such as styrene processability, acrylonitrile stiffness, chemical resistance, and butadiene rubber impact resistance, and has excellent appearance characteristics, so it is used very closely in our real life such as electric, electronics, and office equipment. In particular, as the standard of living improves, commercial demands such as the characterization of functions are gradually increasing.

ABS resins are manufactured by superphase superposition-suspension polymerization, emulsion polymerization, etc., and are produced by mixing them alone or according to their properties.However, in the case of continuously produced bulk polymerization, it has advantages such as mass production, low production cost, and excellent natural color. On the other hand, there are disadvantages in that it is difficult to specialize in products, add value, and diversify products such as various colors of products. On the other hand, the emulsion polymerization method is widely used because it can compensate for the shortcomings of the bulk polymerization method, but the emulsion polymerization method has various advantages such as emulsifiers that are added to the polymerization process in the final product and remains solidified. It has a problem that the natural color of the ABS resin is very vulnerable to undergo a separate post-process, such as. Therefore, it is necessary to add white pigment in order to produce visually luxurious color due to the characteristics of ABS resin that produces small quantities of various kinds of various colors such as various colors, and thus, the amount of color pigment should be increased. At the same time, the physical properties of the product may be reduced.

Recently, a lot of research has been conducted to improve the above problems, but it is very difficult to manufacture ABS resins that can satisfy various physical properties. It is limited. For example, in order to improve the natural color of ABS resin, there is a method of minimizing additives such as emulsifiers affecting the color in emulsion polymerization, but the coagulation generated during polymerization is increased, which lowers yield, deteriorates working environment and waste disposal cost. It is very difficult to apply it to actual production, and the method of using water-soluble pyrolysis initiator, which uses relatively little additive, has improved color slightly, but it is difficult to form rubber structure of graft copolymer which is advantageous for impact strength due to water-soluble initiator. There is a problem that the strength is lowered. In addition, there is a method of mixing a resin produced by emulsion polymerization and a resin produced by bulk polymerization, but this has a problem in that the complexity of the process, glossiness, and product quality characteristics are deteriorated. There is a method to improve the impact by lowering the content of acrylonitrile monomer, but this has a problem that the rigidity and chemical resistance of the resin, which is a characteristic of the ABS resin is lowered. Another method is to change the coagulant used in the coagulation process during the post-process and to expand the washing process, but this is not preferable because of the increase of manufacturing cost and environmental problems due to the increase of waste water rather than the improvement of color. Has a problem.

An object of the present invention is to provide a method for producing a thermoplastic resin composition with improved natural color and impact resistance and gloss while maintaining properties such as excellent impact resistance and fluidity of the ABS resin.

As a result of earnest research to achieve the above object, the present inventors have improved the industrially advantageous graft copolymerization method and at the same time appropriately selected the main initiator and the auxiliary initiator used as the redox system, The method of dosing, the choice of polymerization initiator, the type and amount of the reducing agent, the chelating agent and the method of dosing are given to the optimum conditions, and the monomer composition and the dosing method of the graft copolymer are controlled to make the monomer composition of the graft copolymer uniform and butadiene. Acrylonitrile-styrene (hereinafter referred to as "SAN resin") resin grafted to rubber particles has a uniform graft form, thereby obtaining a composition of thermoplastic resin having excellent natural color, impact resistance and improved gloss. Revealed.

That is, in the present invention, in the emulsion graft copolymerization of an aromatic vinyl monomer and an unsaturated nitrile monomer by using a conjugated diene rubber latex as a seed, a part of the mixture of the monomers is first added to butadiene rubber latex and stirred. The monomer mixture was allowed to swell mostly into the particles of the rubbery polymer. Subsequently, the emulsifier used was potassium stearate, sodium stearate, potassium oleate, and the like. As a molecular weight regulator, terpineol alpha metal styrene dimer alone or tertiary decyl mercaptan was used. The polymerization initiators were ferrous sulfate and sodium form. An oil-soluble peroxide-based redox initiator in combination with aldehyde sulfoxylate and sodium ethylenediamine tetraacetate is used. The redox composition is added at an appropriate temperature after adding a portion of ion-exchanged water, an emulsifier, a polymerization initiator, and a molecular weight regulator. The graft reaction is carried out by adding a one-step reaction to carry out the graft reaction by adding, and adding an emulsifier to secure polymerization stability to a minimum amount, and then continuously adding the remaining amount of the graft monomer mixture, a molecular weight regulator and a polymerization initiator. Two-step reaction, and reaction and residual In order to minimize the monomer and shorten the reaction time, the present invention relates to a method for preparing a graft copolymer composition comprising a three-step reaction in which a residual amount of a redox composition is further added to terminate the reaction.

Hereinafter, the present invention will be described in more detail.

The preferred average particle diameter of the rubbery polymer latex usable in the present invention is a conjugated diene-based rubbery polymer latex having 0.26 to 0.38 µm, and the amount thereof used is 40 to 60 parts by weight (hereinafter referred to as "parts"). In addition, the graft monomer is a graft copolymer having 60 to 40 parts of a mixture of monomers composed of 67 to 77% of aromatic vinyl monomers and 33 to 23% of unsaturated nitrile monomers, thereby providing excellent impact resistance, natural color, and improved gloss. The process for preparing the emulsion copolymer is as follows.

In the one-step reaction in the present invention, a mixture of an aromatic vinyl monomer and an unsaturated nitrile monomer, which is a graft monomer, in the presence of 40 to 60 parts of a rubbery polymer latex having a gel content of 70 to 90% by weight and an average particle diameter of 0.26 to 0.38 µm. 10 to 30% of the monomers and the molecular weight modifier alphamethyl styrene dimer or terpinolene or tertiary dodecyl mercaptan mixed with a composition and stirred for 20 to 40 minutes to the monomer and molecular weight regulator into the rubber polymer particles After sufficient swelling, ion-exchanged water, sodium formaldehyde sulfoxylate as a reducing agent, potassium stearate or potassium oleate as an emulsifier, and t-butyl peroxy benzoate which is an oil-soluble peroxide as a polymerization initiator, t-butyl peroxy One or two selected from acetate, isocumyl hydroperoxide and cumene hydroperoxide After the mixed polymerization initiator was added, the mixture was heated to 45 ° C. to 60 ° C., and a composition containing ferrous sulfate and sodium ethylenediaminetetraacetate was added. Most of the graft monomers first introduced in the range of 55 ° C. to 70 ° C. were polymerized, and the conversion rate was 90. The polymerization is carried out to reach 96% by weight to prepare a primary graft latex.

In the two- and three-stage reactions according to the present invention, the remaining amount of emulsifier is added in the presence of the primary graft latex obtained in the first step reaction, and the remaining amount of the graft monomer mixture and the molecular weight regulator alphamethylstyrene dimer or terpinolent After mixing one or more of the mixtures of sheridodecyl mercaptan in advance, the mixture is continuously added over 2 hours to 4 hours with a peroxide oil-soluble polymerization initiator, and the reaction temperature is in the range of 75 to 85 ° C. The redox composition in which ferrous sulfate, sodium formaldehyde sulfoxylate, and sodium ethylenediaminetetraacetate were mixed together with the two-stage reaction and the completion of the two-stage reaction by adjusting the heat of reaction so as to proceed with the graft polymerization, ranged from 75 to 85 ° C. It is a manufacturing method consisting of a three-stage reaction to minimize the unreacted entity and reduce the polymerization time by adding in. The final polymerization conversion rate is 94 to 98%, solid content is 38 to 44% by weight.

The graft copolymer latex obtained above was coagulated with isopropyl alcohol to obtain a white powder, which was dissolved in acetone, centrifuged, and the insolubles were washed, dried and weighed to obtain a graft ratio. The graft ratio can be obtained by the following equation.

The graft ratio for meeting the object of the present invention is preferably 45 to 65% by weight. If the graft ratio is less than 45% by weight, it is difficult to obtain a white powder with a uniform particle size distribution during coagulation and drying, and a fish-eye phenomenon due to unplasticized particles on the surface of a molded product during pressure and injection. ) Is not only lowered in surface glossiness but also in impact resistance. On the other hand, if the content exceeds 65% by weight, the probability of forming a continuous chain of the acrylonitrile monomer, which is a water-soluble monomer, increases, resulting in a decrease in color of the powder and a decrease in natural color and fluidity of the final product. It becomes difficult to get balance.

As the rubbery polymer used in the present invention, polybutadiene and butadiene-styrene copolymer latex may be used. The average particle diameter of these rubber latexes is preferably in the range of 0.26 to 0.38 mu m, more preferably in the range of 0.28 to 0.33 mu m. When the rubber having an average particle diameter of the rubbery polymer is less than 0.26 μm, the surface gloss of the final molded product is excellent, but the impact resistance is deteriorated, which is not preferable. When the average particle diameter exceeds 0.38 μm, it is advantageous to improve the impact strength and flowability. The glossiness is lowered, and in particular, an excessive amount of coagulant is generated during the graft copolymerization, thereby lowering the surface of the final molded product, which is not suitable for the purpose of the present invention.

In the present invention, the content of the rubbery polymer is preferably 40 to 60 parts in the total graft composition on a solids basis. When the rubber polymer content is less than 40 parts, the graft copolymer input ratio must be increased to improve the impact strength when mixing with the matrix SAN resin, and thus the fluidity is easily deteriorated, and the natural color is easily damaged. The graft rate of the polymer cannot be sufficiently increased, and in particular, it is difficult to recover the fine powder due to the adhesion between the particles in the solidification process. As a result, the large particles cause yellowing of the powder due to thermal history in the drying process, which greatly reduces the color and causes the appearance of the final molded product.

As the graft monomer used in the present invention, it is preferable to mix the aromatic vinyl monomer in the range of 67 to 77% by weight and the unsaturated nitrile monomer in the range of 33 to 23% by weight in 60 to 40 parts of the total monomer mixture. If the aromatic vinyl monomer content is more than 77% by weight or the unsaturated nitrile content is less than 23% by weight, the chemical resistance and rigidity of the final product is reduced, making it difficult to improve the surface gloss, and the aromatic vinyl monomer content is less than 67% by weight, and the unsaturated nitrile content If the content exceeds 33% by weight, the homopolymer and the continuous chain of unsaturated nitrile monomers are increased during the graft emulsion polymerization, and a large amount of coagulum is generated, and the color of the final molded product is reduced. In addition, in the amount of the graft monomer mixture, it is preferable to add 10 to 30% to the first stage reaction and 90 to 70% to the second stage reaction. In particular, 10-30% of the monomer mixture added to the first stage reaction is added in the presence of rubbery latex and agitated for 20 to 40 minutes, which infiltrates most of the monomer mixture into the rubber particles, which is advantageous for impact strength. In order to induce a lot of SAN formation (Occlusion SAN), the monomer mixture of 90 to 70% by weight added to the two-stage reaction is continuously added over 2 to 4 hours so that the SAN resin is uniformly grafted on the rubber surface. By inducing this to occur it is possible to improve the natural color by minimizing the continuous chain of the water-soluble monomer while improving the gloss.

When the content of the graft monomer mixture added to the first stage reaction is less than 10%, the impact resistance is lowered. If the content of the graft monomer mixture is more than 30%, the initial reaction is very vigorous, so that temperature control is difficult and polymerization stability is deteriorated. There is a disadvantage that a large amount is generated. In addition, if the input time of the monomer mixture to be added to the two-stage reaction is faster than the above range, the polymerization speed is increased, which lowers the polymerization stability and at the same time hardly induces a uniform graft reaction on the rubber surface. Difficult to cause impact resistance and gloss deterioration. On the other hand, when the input time is later than the above range, productivity is lowered due to the long time of polymerization time, which is very disadvantageous industrially.

As a molecular weight modifier used for this invention, alphamethylstyrene duplexes, terpinolene alone, or these and mercaptans, such as tertiary dodecyl mercaptan, can be mixed and used. Of these, it is preferable to mix terpinolene and tertiary dodecyl mercaptan, in particular tertiary decyl mercaptan for one stage reaction, terpinolene for two stage reaction, or terpinolene for one stage reaction. In this two-stage reaction, tertiary dodecyl mercaptan is used in combination with the object of the present invention, and is particularly important in the present invention. In the case of using the alpha methyl styrene duplex or terpinolene alone in the molecular weight modifier, it is very effective to improve the color, but the graft ratio and the ability to adjust the SAN molecular weight is difficult to control the physical properties, thereby reducing the physical properties such as impact resistance and fluidity. Therefore, in order to improve these problems, it is possible to adjust the physical properties, but the polymerization stability is lowered to form a large amount of coagulant and also acts as a major factor in the increase of manufacturing cost. On the other hand, when mercaptans such as tertiary decyl mercaptan alone are used as molecular weight regulators, the molecular weight control ability is excellent, so that a proper physical balance can be obtained even with a small amount of input, but it causes color deterioration to meet the object of the present invention. it's difficult.

The amount of the molecular weight modifier is preferably 0.02 to 0.35 parts of teridolensilmercaptan, and in the case of terpinolene, it is preferable to use 0.05 to 0.35 parts. However, the molecular weight regulator added to the two-stage reaction is pre-mixed with the graft monomer and then It is good to add continuously over 4 hours. In the case of terpinolene, when using less than 0.05 parts, it is difficult to control the proper graft ratio, which greatly reduces the impact resistance and appearance of the final product.

As the emulsifier used in the present invention, fatty acid salts such as potassium stearate, sodium stearate or potassium oleate and potassium rosinate can be used. In particular, the emulsifier that meets the object of the present invention is preferably potassium stearate or sodium stearate excellent in the color of the emulsifier itself even if remaining in the resin after the post-coagulation process. The amount of these used is preferably 0.1 to 0.5 parts in one step reaction, and 0.2 to 0.8 parts in two step reaction. When the amount of the emulsifier is less than the above range, the polymerization stability is lowered, which is not preferable. On the other hand, when the amount of the emulsifier is used, gas may be generated during molding of the final product.

As the redox-based polymerization initiator used in the present invention, one or more selected from oil-soluble peroxide-based t-butylperoxybenzoate, t-butylperoxyacetate, isocumyl hydroperoxide, cumene hydroperoxide, or Two kinds of flow initiators are possible, but in order to improve the natural color, in the present invention, it is preferable to use t-butylperoxybenzoate or t-butylperoxyacetate having relatively little color degradation by by-products after radical decomposition. The amount of these to be used is preferably 0.05 to 0.15 parts in one step reaction and 0.15 to 0.35 parts in two step reaction in consideration of polymerization property, color improvement and impact resistance. In addition, ferrous sulfate as a redox agent and sodium formaldehyde sulfoxylate and dextrose as a reducing agent can be used, but in the case of test rose, it is easily decomposed even at low temperature, and it is sufficient to act as a reducing agent so that the reaction is uniform. There is a disadvantage that it is easily discolored by heat, and there is an unfavorable problem in improving the color. So, in order to meet the object of the present invention, the use of sodium formaldehyde sulfoxylate is an essential condition. Although sodium pyrophosphate may be used, it is preferable to use sodium ethylenediaminetetraacetate, which serves as a strong chelating agent for metal ions in order to improve the problem that the color of the resin decreases when the metal ions are present in the resin.

The prepared graft latex was solidified with 0.5 to 1.5% sulfuric acid solution, dried to obtain a white powder, and then separately mixed with a styrene-acrylic copolymer (SAN resin) resin prepared by bulk polymerization in an appropriate content for extrusion and injection. ABS resin with excellent impact resistance and natural color and improved glossiness is produced through the process.

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

Example 1

Polybutadiene rubber polymer latex with a gel content of 80% by weight and an average particle diameter of 0.30㎛ in a 30L reaction vessel equipped with a stirrer, a temperature controller, a heating mantle, a cooling circulator, a condenser, a monomer mixture and a continuous input device of a polymerization initiator. 50 parts by weight of solids (hereinafter, "parts" is parts by weight), 2.84 parts of acrylonitrile, 7.16 parts of styrene, and 0.10 parts of tertiary mesyl mercaptan, and slowly stirred for 20 minutes to prepare a monomer and a molecular weight modifier. After sufficiently swelling into particles, 0.1 part of t-butylperoxybenzoate, 0.15 part of potassium stearate, 150 parts of ion-exchanged water, and 0.15 part of sodium formaldehyde sulfoxylate were added, and then the temperature of the reactor was increased to 50 ° C. I was. When the reaction temperature reached 50 ° C., stirring was continued for 10 minutes, and then 0.003 parts of ferrous sulfate and 0.1 parts of tetrasodium ethylenediaminetetraacetate were added to initiate a one-step reaction. When the reaction was initiated by the self-heating and appropriate heating to the temperature inside the reactor to 65 ℃ over 40 minutes, the reaction was continued for 10 minutes and the one-step reaction was terminated. After completion of the one-step reaction, 0.35 parts of potassium stearate was added into the reactor and stirred for 10 minutes. Then, 11.33 parts of acrylonitrile, 28.67 parts of styrene, and 0.3 parts of terpinolen were stirred in a stirred container, followed by stirring with t-butylperoxybenzoate 0.2 The reactor was continuously charged in the same amount for 180 minutes with the reactor, and the reactor temperature was set to 77 ° C. through self-exotherm and reaction heat control to terminate the two-step reaction. After completion of the second reaction, 0.001 part of ferrous sulfate, 0.08 part of sodium formaldehyde sulfoxylate, and 0.1 part of sodium ethylenediaminetetraacetate were added to the reaction temperature to 83 ° C. by natural heating, and the reaction was continued for 30 minutes. After the graft copolymer latex was prepared in a three step reaction, the reaction mixture was cooled by using a cold circulation system, and when the temperature inside the reactor reached 60 ° C, 0.35 parts of 2,6-dit-butyl4-methylphenol was added as an antioxidant. The graft reaction was then terminated. At this time, the polymerization rate after the completion of the polymerization was 97% and the solid content of the obtained latex was 40.1 wt%.

The graft copolymer latex was filtered through a 200 mesh wire mesh, and the coagulum that did not pass through the mesh was measured after drying at 100 ° C. for 6 hours to calculate a coagulum for solids, which was 0.23 wt%. The latex passed through the mesh was coagulated with 1% aqueous sulfuric acid solution, dehydrated and dried to recover the white powder with water content of 0.5% or less, and then 30 parts of powder and 70 parts of SAN resin having a weight average molecular weight of 115000 were mixed with a stabilizer and a lubricant. Then, by pressing and injection molding to prepare a test piece for measuring the physical properties of the physical properties were measured.

Example 2

It is the same as Example 1 except that 0.10 part of terpinolene is used as a molecular weight modifier used for a 1st step reaction, and 0.25 part of tertidodecyl mercaptan is used for a 2 step reaction.

Example 3

The same procedure as in Example 1 was carried out except that 10.8 parts of styrene and 4.2 parts of acrylonitrile were used in the graft monomer mixture and 25.2 parts of styrene and 9.8 parts of acrylonitrile were used in the two-step reaction.

Example 4

It is the same as Example 1 except using t-butyl peroxy acetate as a polymerization initiator.

Example 5

As the molecular weight regulator, all of the 1.2 steps were used in the same manner as in Example 1 except that terpinolene was used, and 0.20 parts for the first step reaction and 0.15 parts for the second step reaction.

Comparative Example 1

Same as Example 1 except using sodium pyrophosphate as a chelating agent and dextrose as a reducing agent and cumene hydroperoxide as a polymerization initiator.

Comparative Example 2

It is the same as Example 1 except using potassium rosinate as an emulsifier.

Comparative Example 3

It is the same as Example 1 except using sodium pyrophosphate as a chelating agent.

Comparative Example 4

Same as Example 1 except using sodium pyrophosphate as the chelating agent and dextrose as the reducing agent.

Comparative Example 5

Example 1 except that sodium pyrophosphate was used as a chelating agent, dextrose as a reducing agent, tertiarydecyl mercaptan as a molecular weight control agent, potassium rosin as an emulsifier, and cumene hydroperoxide as a polymerization initiator. same.

Comparative Example 6

Using butadiene rubber latex used in Example 1 and using graft monomer under the same conditions as 1,2 steps, except for reducing agent, chelating agent and ferrous sulfate, using potassium persulfate which is water-soluble polymerization initiator instead of water-soluble polymerization initiator The modifier is the same as in Example 1, except that 0.10 parts are used in the one-step reaction and 0.20 parts are used in the two-step reaction with tertiarydecyl mercaptan.

Physical property analysis results of Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1 below.

Property measurement method

* Izod impact strength: ASTM D256, kgcm / cm, 23 ℃

* Flow index: ASTM D1238, g / 10min 200 ℃, 5kg

Yellowness: ASTM D1925

* Whiteness: ASTM D1925

As described above, the resin prepared according to the present invention can obtain a thermoplastic resin composition having improved natural color and impact resistance and gloss while maintaining properties such as excellent impact resistance and flowability of the ABS resin.

Claims (5)

i) To the 40 to 60 parts by weight of the butadiene rubbery polymerized latex having a gel content of 70 to 90% by weight, the average particle diameter of 0.26 to 0.38㎛, a mixture of a graft polymerizable monomer and a molecular weight regulator is added and stirred to form a monomer and a molecular weight regulator. Allow to swell sufficiently into; Then ion-exchanged water, a reducing agent, an emulsifier and an initiator; Subsequently, adding a mixture of an oxidizing agent and a chelating agent to perform a polymerization reaction to a polymerization conversion rate of 90 to 96% by weight to obtain a first graft latex; ii) adding an emulsifier to the first graft latex; Subsequently adding and polymerizing the mixed composition of the graft polymerizable monomer and the molecular weight modifier to obtain a second graft latex; And iii) a method of preparing a thermoplastic resin composition comprising the step of re-injecting an oxidizing agent, a reducing agent and a chelating agent composition to the obtained secondary graft latex so that the final polymerization conversion rate is 94 to 98%, wherein the first step And a step 2 molecular weight modifier using alpha methyl styrene duplex or terpinolene alone, or using a mixture of these and merketanes. According to claim 1, wherein the graft monomer is a mixture of aromatic vinyl monomer 66 to 77% by weight, unsaturated nitrile monomer 33 to 23% by weight 10-30% by weight when preparing the first graft latex, secondary graft Method for producing a thermoplastic resin composition excellent in impact resistance and natural color, characterized in that the copolymerization by adding 90 to 70% by weight in the production of latex. The method of claim 1, wherein as the emulsifier, potassium stearate or sodium stearate is used, and the method of preparing a thermoplastic resin composition having excellent impact resistance and natural color, which is divided into 1,2-step reactions. The method of claim 1, wherein the molecular weight modifier is a method for producing a thermoplastic resin composition excellent in impact resistance and natural color, characterized in that 0.02 to 0.35 parts by weight of teridodolyl mercaptan, 0.05 to 0.35 parts by weight of terpinolene are used. . The method of claim 1, wherein the redox composition is a mixture of ferrous sulfate, sodium formaldehyde sulfoxylate, and sodium ethylenediaminetetraacetate, the method of producing a thermoplastic resin composition having excellent impact resistance and natural color.