KR100348751B1 - Thermalplastic Flameproof ABS Resin Compositions having Improved Impact Strength and Thermal-Stability and Method for Preparing thereof - Google Patents

Abstract

The thermoplastic flame retardant acrylonitrile-butadiene rubber-styrene (ABS) resin composition having excellent impact resistance and thermal stability of the present invention is prepared by (i) a rubber having an average particle diameter of 0.28 to 0.33 µm and a gel content of 75 to 85%. 10 to 40% by weight of the graft monomer mixture consisting of 50 to 70 parts by weight of the polymer latex and 50 to 30 parts by weight of the graft monomer mixture consisting of 70 to 80% of styrene and 30 to 20% of acrylonitrile was introduced into the reactor. Preparing a primary graft copolymer latex having a polymerization conversion ratio of 90 to 96% by adding a catalyst mixture, adding a molecular weight regulator, a reducing agent, an emulsifier, a polymerization initiator and ion-exchanged water, and then stirring the reactor. (ii) preparing a secondary graft copolymer latex by continuously adding 90 to 60% of the remaining amount of the graft monomer mixture, a molecular weight regulator and a polymerization initiator to the primary graft copolymer latex over 2 to 5 hours, respectively. step; And (iii) styrene / acrylonitrile having an acrylonitrile content of 24 to 32%, a weight average molecular weight of 90,000 to 250,000, and a molecular weight distribution of 1.7 to 2.2 in the secondary graft copolymer latex ( SAN) mixing and processing the resin and the flame retardant.

Description

Thermoplastic Flameproof ABS Resin Compositions having Improved Impact Strength and Thermal-Stability and Method for Preparing Achievements}

Field of invention

The present invention relates to a thermoplastic flame retardant acrylonitrile-butadiene rubber-styrene (ABS) resin composition having excellent impact resistance and thermal stability, and a method of manufacturing the same. More specifically, the present invention controls the balance of rubber particle size, rubber morphology and graft ratio of graft copolymer in preparing graft copolymer using industrially advantageous emulsion polymerization, and acrylonitrile- The present invention relates to a thermoplastic flame-retardant ABS resin composition having improved impact strength and thermal stability by controlling the acrylonitrile content and molecular weight of a SAN resin when mixed with a styrene (SAN) resin, and a method of manufacturing the same.

Background of the Invention

In general, ABS resins have a relatively good balance of physical properties such as impact resistance, mechanical strength, heat resistance, moldability, and glossiness, and thus are widely used in various applications such as electric and electronic parts, office equipment, and automobile parts. In the case where the use of double flame retardancy is required, a separate flame retardant function is given and used. The method for preparing the flame retardant is prepared by graft copolymerization of a flame retardant monomer in a polymerization step by emulsion polymerization and by a separate process. There is a method for producing a flame retardant by mixing the graft copolymer and SAN resin in the extrusion process.

The manufacturing method of flame retardant graft copolymer in the graft copolymerization step can improve the compatibility when extruded with SAN resin to improve the problems such as layer separation, but the impact resistance and fluidity of the graft copolymer are reduced. Problems occurred and commercial application was limited due to difficulty in diversification and high addition of products. Therefore, most of the flame retardant ABS resin manufacturing method is a method of producing by mixing the flame retardant prepared in a separate process in the extrusion process with the graft copolymer and SAN resin.

Flame retardant ABS resin, which is produced by mixing and processing flame retardant, graft copolymer, and SAN resin in the extrusion process, has advantages of relatively good balance of physical properties and processing stability, and thus is widely used in injection molding products requiring flame retardancy such as small monitors and office equipment. . However, since it is not excellent in impact resistance and thermal stability, when applied to moldings such as large-sized monitors or applications requiring special impact resistance, cracks are generated during the injection molding process, and gas generation and heat in the appearance of the injection molded products are caused. Problems such as discoloration occur and its use is very limited.

There are a number of known methods to solve these problems, which include mixing rubbers with large rubber particle sizes to produce a graft copolymer to improve impact resistance and then mixing and processing a flame retardant and a SAN resin. How to increase the dosage of the graft copolymer, and the method of increasing the molecular weight of the SAN resin is the mainstream.

However, in the first method, when a large rubber having an average rubber particle diameter of 0.40 μm or more is used, it is difficult to raise the graft rate sufficiently with the problem that it is difficult to uniformly form the grafted SAN on the rubber surface when preparing the graft copolymer. Therefore, in general ABS resin, impact resistance and fluidity may be improved, but in flame retardant ABS resin, it is difficult to expect improvement of the physical properties, and there is a disadvantage in that yield is increased due to the amount of coagulation generated during polymerization. The method of increasing the second graft copolymer dosage can improve the impact resistance, but there are many problems in using the fluidity and the heat deformation temperature. In addition, the method of using a SAN resin having a third high molecular weight may slightly improve the impact resistance, but due to the large drop in fluidity, the thermal deformation temperature and fluidity of the flame-retardant ABS resin are maintained as it is due to problems such as unmolding in actual injection molding. It was not sufficiently improved to satisfy both impact resistance and thermal stability at the same time.

In order to solve the conventional problems as described above, the present inventors make the rubber structure of the graft copolymer in the graft copolymer having a high rubber content so that the graft SAN has an appropriate balance on the inside and the surface of the rubber particle, and especially the rubber SAN grafted on the surface produces a high rubber content graft copolymer that increases the number without length, thereby preventing the rubber surface from being exposed and at the same time increasing the graft rate, and appropriately adjusting the acrylonitrile content and molecular weight. By adjusting and processing the adjusted SAN resin, it gives sufficient compatibility with graft copolymer and flame retardant, and minimizes deformation and thermal discoloration of rubber due to reaction with flame retardant during extrusion and strong stress of extruder. To develop a method for producing this excellent thermoplastic flame retardant ABS resin composition Reached.

SUMMARY OF THE INVENTION An object of the present invention is to prepare a thermoplastic flame retardant ABS resin composition having improved impact strength and thermal stability by controlling the acrylonitrile content and molecular weight of acrylonitrile / styrene (SAN) resin and mixing and processing with a graft copolymer and a flame retardant. It is to provide.

It is another object of the present invention to provide a method for preparing a thermoplastic flame retardant ABS resin composition having improved compatibility of graft copolymers and flame retardants and excellent impact resistance and thermal stability by using a SAN resin in which acrylonitrile content and molecular weight are appropriately controlled. It is to.

Another object of the present invention is to provide flame retardancy, impact resistance and thermal stability by using an industrially advantageous emulsion polymerization and optimizing the balance of the rubber particle size, the rubber form of the graft copolymer and the graft rate in the preparation of the graft copolymer It is to provide a method for producing an excellent thermoplastic flame retardant ABS resin composition.

It is still another object of the present invention to provide a method for preparing a thermoplastic flame retardant ABS resin composition having excellent impact resistance, which is made of a graft copolymer in which the amount of coagulum is not increased during polymerization and thus the yield is not decreased.

The above and other objects of the present invention can be achieved by the present invention described below. Hereinafter, the content of the present invention will be described in detail.

The thermoplastic flame retardant acrylonitrile-butadiene rubber-styrene (ABS) resin composition having excellent impact resistance and thermal stability of the present invention is (i) a rubbery polymer latex having an average particle diameter of 0.28 to 0.33 µm and a gel content of 75 to 85%. 10 to 40% by weight of the graft monomer mixture consisting of 50 to 30 parts by weight of the graft monomer mixture consisting of ˜70 parts by weight and 70 to 80% of styrene and 30 to 20% of acrylonitrile was added to the reactor, and the molecular weight regulator Preparing a primary graft copolymer latex having a polymerization conversion ratio of 90 to 96% by adding a catalyst mixture after adding a reducing agent, an emulsifier, a polymerization initiator, and ion-exchanged water with stirring. (ii) preparing a secondary graft copolymer latex by continuously adding 90 to 60% of the remaining amount of the graft monomer mixture, a molecular weight regulator and a polymerization initiator to the primary graft copolymer latex over 2 to 5 hours, respectively. And (iii) styrene / acryl with an acrylonitrile content of 24 to 32%, a weight average molecular weight of 90,000 to 250,000, and a molecular weight distribution of 1.7 to 2.2 in the secondary graft copolymer latex. Nitrile (SAN) resin and flame retardant are prepared by the step of mixing. The SAN resin may be applied by appropriately mixing SAN resins having different molecular weights in consideration of balance of fluidity and impact resistance.

The process for preparing the thermoplastic flame retardant ABS resin composition of the present invention is described in detail below:

(1) Preparation of First Graft Copolymer

50 to 30 parts by weight of a graft monomer mixture composed of 70 to 80% of styrene and 30 to 20% of acrylonitrile in the presence of 50 to 70 parts by weight of a rubbery polymer having an average particle diameter of 0.28 to 0.33 µm and a gel content of 75 to 85%. A portion of 10 to 40% by weight, 0.01 to 0.15 parts by weight of a molecular weight regulator, 0.15 to 0.45 parts by weight of dextrose, 0.4 to 1.5 parts by weight of an emulsifier, 0.03 to 0.15 parts by weight of a polymerization initiator and ion exchanged water are added. While stirring them, the temperature is raised to 50-60 ° C. and the stirring is continued for 10 to 30 minutes to allow most monomers to swell and penetrate into the rubber particles. As a catalyst, a catalyst mixture in which 0.001 to 0.008 parts by weight of ferrous sulfate and 0.05 to 0.30 parts by weight of tetrasodium parophosphate is mixed is added to initiate a reaction. The temperature of the first graft copolymerization reaction is preferably 65 to 75 ° C, and the reaction is continued for 0 to 30 minutes while maintaining the temperature to prepare a first graft copolymer latex having a polymerization conversion rate of 90 to 96%. .

(2) Preparation of Second Graft Copolymer

In the presence of the first graft copolymer latex prepared in the first step, the remaining graft monomer mixture 90-60% and the molecular weight regulator 0.05-0.35 parts by weight are mixed and stirred and continuously added over 2 to 5 hours. . The remaining amount of 0.10 to 0.45 parts by weight of the polymerization initiator is continuously added simultaneously with the graft monomer to prepare a secondary graft copolymer latex.

The polymerization initiator is also applied continuously to the graft monomer mixture over a period of 2 to 5 hours to participate in the graft reaction at a constant rate by a small amount of the polymerization initiator in which a small amount of the graft monomer is added together. . The temperature of the secondary graft copolymerization reaction is preferably 65 to 75 ° C., and the reactor temperature is maintained at 65 to 75 ° C. for 20 to 60 minutes after the addition of the continuously added graft monomer and the polymerization initiator is completed. When the final polymerization conversion reaches 95 to 98% by forced cooling to terminate the polymerization to obtain a second high rubber content graft copolymer latex having a solid content of 38 to 44% by weight.

In addition, in order to meet the object of the present invention, the graft ratio of the graft copolymer prepared in the first and second steps should be 50 to 90%. If the graft rate is lower than this, it is difficult to obtain a white powder having a uniform particle size distribution during solidification and drying, and in particular, the rubber efficiency is lowered by the flame retardant and the SAN resin and the flame retardant during extrusion, so that the impact resistance is hardly improved. On the other hand, when exceeding the above range, rather than reducing the interfacial adhesion in the process of mixing with the matrix SAN resin may result in a decrease in physical properties, in particular, the fluidity is severely degraded is not preferable to meet the physical properties of the present invention.

(3) Preparation of flame retardant ABS resin composition

The secondary graft copolymer latex is coagulated with 0.5-1.5% sulfuric acid or phosphoric acid aqueous solution and dried to obtain a white powder. Styrene / acrylonitrile (SAN) resin having an acrylonitrile content of 24 to 32%, a weight average molecular weight of 90,000 to 250,000, and a molecular weight distribution of 1.7 to 2.2 in the graft copolymer; The flame retardant is mixed to prepare a flame retardant ABS resin composition of the present invention excellent in impact resistance and thermal stability.

In the mixing of the graft copolymer, the SAN resin and the flame retardant, 25 to 45 parts by weight of the graft copolymer, 75 to 55 parts by weight of the SAN resin and 15 to 30 parts by weight of the flame retardant may be added, and an additional stabilizer and lubricant may be added. Can be.

Each component used in the process for producing the flame-retardant resin composition of the present invention is as follows.

Rubbery polymer latex

The rubbery polymer latex used in the present invention includes polybutadiene rubbery latex and the like, and the average particle diameter of the rubbery latex is preferably in the range of about 0.28 to 0.33 µm. More preferably, the distribution of rubber particles having a particle size of 0.15 μm or less is less than 10 wt%, and the distribution of rubber particles having a particle size of 0.50 μm or more is less than 10 wt%, while the average particle diameter is about 0.28 to 0.33 μm. It has a range. This has a disadvantage in that the rubber efficiency decreases when the rubber particle diameter is less than 0.28 μm and the impact strength is lowered. On the other hand, when the rubber particle diameter exceeds 0.33 μm, it is difficult to uniformly form graft SAN on the rubber surface during graft copolymerization. This is because the surface is increased and the flame retardant during the mixing process with the flame retardant lowers the rubber efficiency and consequently results in a decrease in physical properties. On the other hand, when rubber particles of about 0.15 μm or more are contained in 10 wt% or more, the rubber is difficult to absorb energy sufficiently to the external stress, and there is a disadvantage in that fluidity is lowered due to surface area difference. On the other hand, when the rubber particles of about 0.50 μm or more contain 10% by weight or more, the graft monomers are hardly grafted to the rubber surface during graft copolymerization, so that the exposed rubber surface increases, thereby increasing the rubber Deformation occurs and a problem that the impact resistance is lowered by the flame retardant.

In addition, the gel content of the rubbery polymer is preferably 75 to 85% by weight. If the gel content is less than 75% by weight, the polymerization of the rubber proceeds more than necessary in the rubber, the shape of the rubber is likely to change, which may impede the appearance of the final molded article, and it is difficult to expect an improvement in impact resistance. On the other hand, if it exceeds 85% by weight, it is difficult to achieve an appropriate graft reaction in the rubber object and an appropriate reaction balance in the rubber surface of the present invention, so that it is difficult to expect an improvement in impact resistance and fluidity.

In the present invention, the content of the rubbery polymer is preferably in the range of 50 to 70 parts by weight of the total graft, based on solid content. When the content of the rubbery polymer is less than 50 parts by weight, as the graft monomer increases, the polymerization rate increases, and as a result, the polymerization stability may decrease, and a large amount of coagulum may occur. In addition, when the content exceeds 70 parts by weight, the graft monomer is reduced, and the graft rate cannot be sufficiently increased, and the graft reaction proceeds unevenly on the inside and the surface of the rubber particles, thereby reducing the rubber structure of the graft copolymer of the present invention. It cannot be obtained and the impact strength falls.

Graft Monomer Mixture

The graft monomer mixture used in the present invention consists of 70 to 80% by weight of styrene and 30 to 20% by weight of acrylonitrile. The composition ratio of the styrene and acrylonitrile is an important condition in the present invention, and because of this condition, the graft copolymer has a rubber structure in which graft SAN is formed in an appropriate composition and size on the inside and outside of the rubber. Increase the compatibility of the to improve the impact strength and fluidity. If the input ratio of styrene and acrylonitrile in the graft monomer mixture is more than that suggested by the present invention, the balance of impact strength and fluidity cannot be simultaneously improved due to the difference in the composition of graft SAN inside and outside the rubber. In particular, when the content of acrylonitrile is excessively added, impact resistance and fluidity are difficult to be improved, and at the same time, the amount of styrene is decreased, so that the mechanical strength and the heat deformation temperature are lowered, thereby making it impossible to achieve the object of the present invention.

In the present invention, the graft monomer mixture is preferably 10 to 40% by weight in the first stage graft reaction, and 90 to 60% by weight in the second stage reaction. When the ratio of the graft monomer mixture is out of the range set forth in the present invention, the composition and the balance of the graft monomer are not appropriate in and out of the rubber, so that the rubber structure of the graft copolymer is difficult to obtain.

When the monomer mixture added to the first stage graft reaction exceeds the above range (10 to 40% by weight), the graft reaction proceeds more than necessary in the rubber to excessively swell the rubber particles, and the polymerization system is caused by a rapid reaction. It is difficult to obtain a graft copolymer having a structure in which graft SAN is uniformly polymerized on the surface of rubber particles due to a lack of graft monomer continuously added in a second step. On the other hand, when the monomer mixture used in the first step graft reaction is used less than the above range, the SAN formed in the rubber, which is advantageous for impact strength, cannot be sufficiently obtained, and thus the object of the present invention cannot be achieved.

Molecular weight regulator

Molecular weight modifiers that can be used in the present invention include mercaptans such as alphamethylstyrene duplexes, terpinolene or tertidodecyl mercaptan. Among these, tertiary dodecyl mercaptan, which can sufficiently control the graft reaction, is preferable.

The molecular weight modifier is preferably 0.02 to 0.25 parts by weight in the first step, 0.01 to 0.35 parts by weight in the second step. When used in excess of the above range, it is difficult to expect impact resistance because the graft ratio, which is an important physical property in the present invention, cannot be sufficiently raised, and in particular, a uniform white powder cannot be obtained during solidification, thereby lowering the appearance of the final molded product. On the other hand, if less than the above range is used is not preferred because the fluidity is greatly reduced due to excessive graft rate.

In the first step, the molecular weight modifier is preferably added in a batch, and in the second step, the graft monomer mixture is mixed with the graft monomer mixture in advance and preferably added continuously for 2 to 5 hours.

Emulsifier

Emulsifiers used in the present invention include fatty acid salts such as potassium stearate, sodium stearate or potassium oleate, potassium rosin or a mixture thereof. Preferably, potassium stearate, potassium rosinate or potassium stearate and an emulsifier in which potassium rosinate is 1: 3 mixed. This has the advantage that the physical properties of the thermoplastic resin are not severely degraded by the emulsifier even if they remain in the resin after the post-processing such as coagulation.

The emulsifier is preferably used in 0.5 to 1.5 parts by weight. If it is used in an amount 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 excessively, problems such as gas generation during molding of the final product may be undesirable.

Polymerization initiator

Polymerization initiators that can be used in the first and second stages of the present invention include one fat-soluble initiator selected from t-butylperoxide, cumene hydroperoxide and t-butylperoxybenzoate. The polymerization initiator is relatively less physical property degradation by the by-products after radical decomposition, it is easy to improve the polymerization rate even at low temperatures, and the graft reaction occurs uniformly inside and outside the rubber.

The polymerization initiator is added in an amount of 0.03 to 0.15 parts by weight in the first step reaction, and 0.10 to 0.45 parts by weight in the second step reaction. In the method of adding the polymerization initiator, in the second step simultaneously with the graft monomer It is preferable to continuously add a polymerization initiator each over 2 to 5 hours. If the amount of the polymerization initiator used in the first and second steps exceeds the range of the preferred amount of use, there is a problem that the stability of the polymerization system due to a sudden reaction is deteriorated. In particular, when the amount of the polymerization initiator continuously added in the second step exceeds the desired content, the color of the final molded product may be reduced, and heat of the resin during extrusion may be caused by unreacted radicals that do not participate in the reaction. It is not preferable because it may lead to stability deterioration. On the other hand, when the polymerization initiator is used less than the range of the preferred amount of use, the reaction rate may be inhibited and excess unreacted monomer may come out. Particularly, in the second step, a uniform graft reaction cannot be expected on the rubber surface. The graft ratio cannot be sufficiently improved to satisfy the object of the present invention.

Reductant and Catalyst Mixtures

Reducing agents that can be used in the first step of the present invention is dextrose, it is preferably added to 0.15 ~ 0.45 parts by weight. Dextrose easily decomposes even at low temperatures, and serves as a reducing agent to make the reaction uniform.

In the first step of the present invention, the catalyst mixture to be added after the graft monomer is sufficiently swollen into the rubber is formed by mixing and dissolving the catalyst and the chelating agent. Here, the preferred one used as the catalyst is ferrous sulfate and is dissolved in the aqueous solution at 0.001 to 0.008 parts by weight, and the preferred one used as the chelating agent is tetrasodium parophosphate and 0.05 to 0.30 parts by weight in the aqueous solution. do.

The ferrous sulfate functions to decompose the oil-insoluble polymerization initiator into radicals capable of polymerization even at low temperatures, and the reducing agent dextrose reduces the ferrous sulfate, which is oxidized after radical decomposition, to restore its original function. In addition, the chelating agent tetrasodium parophosphate performs a function to make the unstable ferrous sulfate into a stable structure, thereby increasing the polymerization rate sufficiently even by adding a small amount of ferrous sulfate, as well as stable polymerization. It functions to induce. When the amount of each of the reducing agent, catalyst and chelating agent exceeds the desired amount of use, there is a problem of lowering the color of the final product and increasing the amount of coagulant generated due to excessive reaction amount during the polymerization. In addition, when the polymerization is less than the above-mentioned preferred amount of use, it is difficult to expect a uniform reaction at the same time as the polymerization rate decreases.

Styrene / Acrylonitrile (SAN) Resin

The SAN resin used in the present invention may be prepared by bulk polymerization or suspension polymerization, which is a conventional manufacturing method, and is used as a matrix in the flame retardant ABS resin composition of the present invention. The SAN resin is preferably used by mixing two or more kinds of SAN resins having an acrylonitrile content of 24 to 32%, a weight average molecular weight of 90,000 to 250,000, and a molecular weight distribution of 1.7 to 2.2.

When the acrylonitrile content contained in the SAN resin is less than the above range, it is somewhat advantageous for fluidity and thermal stability, but the impact resistance is easily lowered, and the rigidity and heat deformation temperature are lowered, so that the physical properties of the present invention are difficult to meet. . On the other hand, in the case of exceeding the above range, the general ABS resin is advantageous in improving the impact resistance, but when the mixed operation with the flame retardant, the impact resistance is severely deteriorated, in particular fluidity and thermal stability is not preferable. On the other hand, when the molecular weight is less than the above range, it is difficult to improve the impact resistance, and when the molecular weight is higher than the above range, the fluidity decrease is severe, which is not preferable.

Flame retardant

Flame retardants used in the method for preparing the flame retardant ABS resin composition of the present invention include tetrabromo bisphenol A and antimony trioxide, which are flame retardants used in the production of conventional flame retardant ABS.

The manufacturing process of the present invention can be more clearly understood by the following examples, the following examples are merely illustrative purposes of the present invention and are not intended to limit the scope of the invention.

Example

Example 1

(1) Preparation of Primary Graft Copolymer Latex

In a 30L reactor equipped with a stirrer, a thermostat, a heating mantle, a cooling circulator, a condenser, a graft monomer mixture, and a continuous dosing device of a polymerization initiator, a polybutadiene rubber polymer latex having a gel content of 80% and an average particle diameter of 0.30 μm was 60 parts by weight based on solids, 3.0 parts by weight of acrylonitrile, 9.0 parts by weight of styrene, 0.05 parts by weight of terdodecyl mercaptan, 0.1 parts by weight of cumene hydroperoxide, 0.2 parts by weight of potassium stearate, 0.6 parts by weight of potassium rosinate, and 140 parts by weight of ion-exchanged water was added, and the temperature of the reactor was increased to 60 ° C. When the temperature inside the reactor reached 60 ° C, stirring was continued for 20 minutes to allow the graft monomer and the polymerization initiator molecular weight regulator to swell sufficiently into the rubbery polymer particles, followed by 0.003 parts by weight of ferrous sulfate and 0.15 part of tetrasodium parophosphate. Part by weight was added to initiate the first step reaction. When the reaction is started, the internal temperature of the reactor is increased to 70 ° C. over 20 minutes by self-heating, proper cooling and heating, and the polymerization is continued for 10 minutes to reach the polymerization conversion rate of 93% or more, and then the reaction is terminated. Primary graft copolymer latex was prepared.

(2) Preparation Step of Secondary Graft Copolymer Latex

In the presence of the prepared primary graft copolymer latex 7.0 parts by weight of acrylonitrile, 21.0 parts by weight of styrene, 0.14 parts by weight of terdodosilylcapcaptan in a stirrable container and stirred for 10 minutes, cumene hydroperoxide The second stage reaction was carried out by continuously adding 150 parts at a reaction temperature of 70 ° C. with 0.17 parts by weight. At this time, when the graft monomer mixture and the polymerization initiator are added, the reaction is continued for 40 minutes, and then forcedly cooled to reach the reactor temperature of 60 ° C., which is an antioxidant of 2,2-methylene-bis (4-methyl-6-t- Butyl) phenol was added 0.6 parts by weight and the reaction was terminated. At this time, the polymerization rate after the completion of the polymerization in the step was 97%, the solid content of the latex obtained here was 40.3%. The graft latex was solidified with an aqueous solution of 0.7% sulfuric acid, washed, and dried to obtain a white powder having a pH of 6.

(3) Preparation of ABS resin composition

30% by weight of the graft copolymer prepared in (1) and (2), 70% by weight of the SAN resin, and 23 parts by weight of a flame retardant were mixed in the amounts shown in Table 1 below. 1.0 parts by weight of calcium stearate and ethylene bis stearoid as stabilizers were added and extrusion molded to prepare specimens for measuring physical properties. The results of the evaluation of physical properties are shown in Table 3 below. In addition, the weight average molecular weight and acrylonitrile content of the SAN resin to be applied was applied differently as described in Table 2 below.

division Example Comparative Example One 2 3 4 5 6 One 2 3 Average particle diameter of rubber latex 0.30 0.30 0.30 0.30 0.30 0.30 0.35 0.40 0.35 Graft Monomer (wt%) 1 reaction Styrene 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 Acrylo -nitrile 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 2 reactions Styrene 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 Acrylo -nitrile 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 Molecular weight regulator (part by weight) First reaction 0.05 0.07 0.02 0.05 0.05 0.05 0.05 0.05 0.09 Second reaction 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.15 Graft Rate (%) 60 63 70 60 60 60 56 49 49 Coagulation amount (%) 0.10 0.08 0.08 0.10 0.10 0.10 0.18 0.26 0.26 SAN resin used SAN-1 SAN-1 SAN-1 SAN-1 / SAN-2 = 70/30 SAN-1 / SAN-3 = 70/30 SAN-1 / SAN-4 = 70/30 SAN-1 SAN-1 SAN-5 Flame retardant (parts by weight) 23 23 23 23 23 23 23 23 23

SAN-1 SAN-2 SAN-3 SAN-4 SAN-5 Molecular Weight Weight average molecular weight 130,000 190,000 130,000 90,000 130,000 Molecular weight distribution 1.87 1.88 2.10 1.80 2.15 Acrylonitrile content (w%) 27 27 31 25 35

Example 2-3

In the first and second graft reaction was carried out in the same manner as in Example 1 except that the molecular weight regulator content was changed as shown in Table 1, the results are shown in Table 3.

Example 4-6

The SAN resin mixed with the graft copolymer prepared in Example 1-3 was carried out in the same manner as in Example 1 except for mixing as described in Table 1 above, and the results are shown in Table 3.

Comparative Example 1

Except for changing the average particle diameter of the rubbery polymer latex as shown in Table 1 was carried out in the same manner as in Example 1, the results are shown in Table 3.

Comparative Example 2

Except for changing the average particle diameter of the rubbery polymer latex as shown in Table 1 was carried out in the same manner as in Example 1, the results are shown in Table 3.

Comparative Example 3

SAN resin was carried out in the same manner as in Comparative Example 1 except that SAN-5 was applied, and the results are shown in Table 3.

In order to evaluate the stability of the graft copolymer latex prepared according to Examples 1 to 6 and Comparative Examples 1 to 3, the coagulum which failed to pass by filtering the graft copolymer latex through a mesh of about 200 mesh. After dehydration with water and dried to calculate the amount of coagulation by the following formula 1 shown in Table 1 below:

According to Examples 1 to 6 and Comparative Examples 1 to 3, the graft copolymer latex was coagulated with isopropyl alcohol, dehydrated and dried to obtain a white powder, dissolved in acetone, centrifuged, and the insoluble was washed and dried. The basis weight was used to calculate the graft ratio according to the following Equation 2:

The specimens of the resin compositions prepared according to Examples 1 to 6 and Comparative Examples 1 to 3 were notched in accordance with ASTM D-256 (1/4 "notched, unit kg · cm / cm, 23 ° C). The flow index (g / 10min) was measured at 200 ° C and 5kg according to ASTM D-1238, and the heat deflection temperature was measured according to ASTM D-1525, and the injection retention thermal stability was 10 minutes at 230 ° C. It was measured by the retention, flame retardancy was measured according to the UL 94 VB flame retardant regulations and the results are shown in Table 3.

Example Comparative Example One 2 3 4 5 6 One 2 3 Izod impact strength (1/4 ″ notched) ASTM D256 kgcm / cm, 23 ℃ 19 21 23 27 22 17 16 14 12 Flow Index (200 ° C 5Kg) ASTM D-1238 6.5 6.1 5.6 5.1 6.2 7.5 6.6 6.8 4.9 Heat Deflection Temperature (℃) (ASTM D-1525) 88 88 88 88 89 87 88 88 89 Injection residence thermal stability (230 ℃ 10 minutes dE) 2.5 2.5 2.6 2.6 2.7 2.3 3.1 3.3 3.8 Flame retardant (1/16 ″) UL-94 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0

As can be seen from Table 3, the resin composition of the present invention prepared in Examples 1 to 6 has a high thermal stability compared to the resin composition prepared in Comparative Example as the injection residence thermal stability of 2.3 to 2.7, Notch Izod It can be seen that the impact strength is generally improved compared to Comparative Examples 1 to 3. In the comparative example, the average particle diameter of the rubbery polymer latex is not included in the preferred range proposed by the present invention. As a result, the graft SAN is not uniformly formed on the rubber surface during graft copolymerization, thereby increasing the exposed rubber surface. And when mixed with a flame retardant and processing, the rubber efficiency is lowered and thereby the impact resistance is lowered.

The present invention utilizes an industrially advantageous emulsion polymerization and optimizes the balance of the rubber particle size, the rubber form of the graft copolymer and the graft rate in the production of the graft copolymer, the yield of coagulation is not increased during the polymerization, the yield is increased It is possible to increase productivity without deterioration and to provide a method for producing a thermoplastic resin composition which can improve impact resistance and thermal stability while maintaining the heat deformation temperature.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (4)

(i) Graft monomer mixture 50 consisting of 50 to 70 parts by weight of a rubbery polymer latex having an average particle diameter of 0.28 to 0.33 µm and a gel content of 75 to 85%, and 70 to 80% of styrene and 30 to 20% of acrylonitrile. 10 to 40% by weight of the total graft monomer mixture consisting of ˜30 parts by weight is added to the reactor, the reactor is heated while stirring and adding a molecular weight regulator, a reducing agent, an emulsifier, a polymerization initiator and ion-exchanged water, and then a catalyst mixture is Preparing a primary graft copolymer latex having a polymerization conversion ratio of 90 to 96%; (ii) preparing a secondary graft copolymer latex by continuously adding 90 to 60% of the remaining amount of the graft monomer mixture, a molecular weight regulator and a polymerization initiator to the primary graft copolymer latex over 2 to 5 hours, respectively. step; And (iii) Styrene / acrylonitrile (SAN) having an acrylonitrile content of 24 to 32%, a weight average molecular weight of 90,000 to 250,000, and a molecular weight distribution of 1.7 to 2.2 in the secondary graft copolymer latex. ) Mixing and processing the resin and the flame retardant; A method for producing a thermoplastic flame-retardant acrylonitrile-butadiene rubber-styrene (ABS) resin composition having excellent impact resistance and thermal stability. The method of claim 1, wherein the graft copolymer has a graft ratio of 50% to 90%, and has excellent impact resistance and thermal stability. The method of claim 1, wherein the molecular weight modifier is selected from the group consisting of alpha methyl styrene duplex, terpinolene or tercydodecyl mercaptan, in the first step to 0.01 to 0.15 parts by weight and in the second step 0.05 to 0.35 It is added in parts by weight, the reducing agent is dextrose and 0.15 to 0.45 parts by weight, the emulsifier is composed of fatty acid salts, such as potassium stearate, sodium stearate or potassium oleate, potassium rosin and mixtures thereof It is selected from the group, in the first step 0.5 to 1.5 parts by weight, the polymerization initiator is one fat-soluble initiator selected from the group consisting of t- butyl peroxide, cumene hydroperoxide and t- butyl peroxy benzoate , 0.03 to 0.15 parts by weight in the first step and 0.10 to 0.45 parts by weight in the second step, and the catalyst mixture is sulfuric acid A method for producing a thermoplastic flame-retardant ABS resin composition having excellent impact resistance and thermal stability, comprising 0.001 to 0.008 parts by weight of ferrous iron and 0.05 to 0.30 parts by weight of tetrasodium parophosphate. A thermoplastic flame retardant ABS resin composition having excellent impact resistance and thermal stability, which is prepared by the method of claim 1.