KR100429062B1 - Thermoplastic Resin Composition With Good Transparent and Impact Strength and Method for Preparing the Same - Google Patents

Abstract

In the method for producing a thermoplastic resin composition of the present invention, the azo polymerization initiator is dissolved in a monomer mixture (B) made of an aromatic vinyl monomer, an unsaturated nitrile monomer, and an alkyl methacrylate monomer, and then the rubber polymer (A), A first step of graft polymerization by adding the emulsifier, the molecular weight regulator and ion-exchanged water to the reactor and raising the temperature to 50-80 ° C; When the polymerization conversion rate in the first step reaches 90% or more, a water-soluble polymerization initiator is added to the reactor, and the monomer mixture (B) as in the first step is divided into several times for 1-5 hours or continuously. The second step of the graft polymerization is further added.

Description

Thermoplastic resin composition with good transparent and impact strength and method for preparing the same

Field of invention

The present invention relates to a methylmethacrylate-acrylonitrile-butadiene-styrene resin (hereinafter transparent ABS resin) excellent in transparency and impact resistance, and a method of manufacturing the same. More specifically, the present invention is prepared by graft polymerization by adding a portion of the monomer mixture in the presence of polybutadiene latex and an oil-soluble initiator, and graft polymerization by adding the remaining amount of the monomer mixture and the water-soluble initiator, which are added in the above steps at a certain point in time. The present invention relates to a thermoplastic resin composition having excellent transparency and impact resistance, and a method of manufacturing the same.

Background of the Invention

ABS resin has various properties such as styrene stiffness, acrylonitrile stiffness and chemical resistance, butadiene impact resistance, and excellent physical properties and appearance characteristics, and is widely used in automobiles, electrical and electronic products, office equipment, home appliances, and toys. However, ABS resin has a disadvantage in that the use is limited because of poor transparency.

The reason why the ABS resin is opaque is that light is refracted and scattered at the interface due to the difference in refractive index between the matrix resin in the continuous phase and the rubber phase in the dispersed phase, and the wavelength of visible light is scattered according to the rubber particle size. In general, polystyrene resins have a high refractive index, and the rubber phase has a low refractive index. Therefore, in order to give transparency to the ABS resin, it is necessary to match the refractive index of the rubber phase with the matrix resin that is continuous and to minimize the scattering of light in the visible region by appropriately adjusting the size of the used rubber particles.

In order to solve such a problem, butadiene-based rubber is used as a seed, and a methacrylic acid alkyl ester monomer is added to the vinylaromatic monomer and the unsaturated nitrile monomer to match the refractive index of the rubbery polymer and the graft polymer, thereby maintaining transparency while maintaining impact resistance. A method for producing ABS resin with excellent natural colors has been developed.

However, in the polymerization process, when graft polymerization is performed using a water-soluble initiator alone, the glossiness is good because a graft structure of a core-shell type is formed by the hydrophilic group of methylacrylic acid alkyl ester which is the main raw material of transparent ABS. Since the thickness of the shell is not sufficiently thick, there is a problem that the impact strength is lowered. On the other hand, when an oil-soluble initiator using a combination of redox initiators is used, the emulsification system becomes unstable due to a decrease in the polymerization rate of the hydrophilic monomer methylmethacrylate alkyl ester, thereby causing a large amount of coagulant, and also a redox initiator. There is a problem that the natural color is reduced by the residual of the metal ions used in the.

Japanese Patent 62-84109 discloses a method of using SBR rubber having different rubber particle sizes. However, Japanese Patent No. 62-84109 also secures transparency and impact resistance, but the glass transition temperature of SBR rubber is low, and the impact resistance is inferior because the size and particle distribution of the rubber are inappropriate. In addition, when using an azo oil-soluble initiator alone, there is a problem in that the impact resistance is lowered because the graft ratio, which is the efficiency of graft polymerization, is lowered due to the decrease in the polymer grafted to the shell.

On the other hand, the inventors of the present invention, in order to overcome the above problems, in the first step, a mixture of styrene-based monomers, unsaturated nitrile-based monomers and alkyl methacrylate monomers is used to form a polymer in the rubber using an azo oil-soluble initiator in a butadiene-based rubber. To improve the impact resistance, and to maintain excellent impact resistance by appropriately graft polymerization of the styrene monomer, the unsaturated nitrile monomer and the alkyl methacrylate monomer to the rubber outer layer by using the water-soluble initiator in the second step. While developing a thermoplastic resin composition excellent in both transparency and natural color.

An object of the present invention is to provide a method for producing a thermoplastic resin composition excellent in transparency and natural color while maintaining excellent mechanical properties, thermal properties and impact resistance of the ABS resin.

Another object of the present invention is to provide a thermoplastic resin composition excellent in transparency and impact resistance.

The above and other objects of the present invention can be achieved by the present invention described below.

The thermoplastic resin composition of the present invention comprises a graft polymerization of a rubbery polymer (A), a monomer mixture (B) consisting of an aromatic vinyl compound, an unsaturated nitrile compound, and an alkyl methacrylate ester using a oil-soluble azo polymerization initiator in rubber. Stage 1; When the polymerization conversion rate is 90% or more, the monomer mixture is graft-polymerized on the rubber surface using a water-soluble polymerization initiator to prepare a graft copolymer having a core-shell structure. Detailed description is as follows.

(1) First step

The oil-soluble azo polymerization initiator is dissolved in a monomer mixture (B) consisting of an aromatic vinyl compound, an unsaturated nitrile compound, and an alkyl methacrylate, and then introduced into a reactor together with a rubbery polymer, an emulsifier, a molecular weight regulator, and ion-exchanged water, and the polymerization temperature is increased. Graft polymerization is carried out at 50-80 ° C. In the first step, the oil-initiator is mainly used to induce the polymerization in the rubber polymer to improve the impact resistance.

(2) second stage

When the polymerization conversion rate in the first step reaches 90% or more, a water-soluble polymerization initiator is added to the reactor at once, and the same monomer mixture (B) added in the first step is divided into several times or continuously for 1-5 hours. It is supplied and subjected to graft polymerization. In the second step, a graft copolymer having a core-shell structure surrounded by a graft monomer is produced under the influence of the water-soluble initiator.

Hereinafter, each component of this invention is demonstrated in detail.

(A) rubbery polymer

The rubbery polymer is a diene rubbery polymer having an average particle diameter of 0.2 to 0.5 µm and a gel content of 70 to 90% by weight, and particularly preferably polybutadiene rubber latex. The rubbery polymer is used at 40-60 parts by weight based on solids. When the diene rubber polymer is used in an amount less than 40 parts by weight, the polymerization stabilization drops sharply and coagulates, and the impact reinforcing effect is remarkably lowered. When it is used in excess of 60 parts by weight, a sufficient graft layer is not formed. Deterioration of the degree and the problem of drying defects due to the formation of coarse particles during the solidification process occurs.

(B) monomer mixture

The monomer mixture is 30-70% by weight of alkyl methacrylate monomer, 10-40% by weight of aromatic vinyl monomer, and 1-20% by weight of unsaturated nitrile monomer, which are combined so that the refractive index is the same as that of the rubbery polymer. . When the ratio of the monomer mixture is out of the above range, there is a problem that haze (HAZE) is increased due to the difference in refractive index between the rubbery polymer and the graft polymer.

In the present invention, the monomer mixture is used in an amount of 40 to 60 parts by weight, and in the first step, 10-40% by weight of the azo-based polymerization initiator is dissolved, and in the second step, the remaining amount is 90-60% by weight. do.

When the monomer mixture is used in less than 10% in the first step, the impact strength is lowered by reducing the graft polymer inside the rubbery polymer. On the other hand, when used in excess of 30%, the reaction stability is deteriorated due to the increase in the graft polymer inside the rubbery polymer, so that a large amount of coagulum is generated, and the rubber layer is not exposed because the shell layer outside the rubbery polymer is not sufficiently formed. There is a problem that the polymer is increased and the natural color and impact strength are lowered.

In a second step, the monomer mixture is added in the range of 1-5 hours. When the input time is less than 1 hour, the heat of reaction is difficult to control due to the increase in the amount of monomers to be added per unit time, there is a problem that the quality of the unstable as well as the generation of coagulum increases. In addition, when the continuous dosing time is 5 hours or more, the polymerization time is long, there is a problem that the productivity is lowered.

(C) oil-soluble polymerization initiator

As the oil-soluble polymerization initiator, azo initiators such as azobisisobutylonitrile, azobis dimethyl vareronitrile, azobis inobareric acid, azobis cyclohexane carbonitrile, and dimethyl azobis isobutylate are used. Most preferred is azobis isobutyl nitrile. The oil-soluble azo polymerization initiator is used in the first step.

In the present invention, the oil-soluble azo polymerization initiator is used in an amount of 0.03-0.2 parts by weight.

(D) Water-soluble polymerization initiator

Potassium peroxydisulfate is used as the water-soluble polymerization initiator. The water-soluble polymerization initiator is added in the second step, so that the graft copolymer of the core-shell structure surrounded by the graft monomer is formed on the rubber surface.

In the present invention, the water-soluble polymerization initiator is used in the range of 0.3-0.8 parts by weight, more preferably in the range of 0.4-0.7 parts by weight.

(E) emulsifier

As the emulsifier, a saturated fatty acid having 12 to 18 carbon atoms is substituted with potassium or sodium ions. Specific examples thereof include sodium lauryl acid, sodium myristicate, sodium stearate, potassium lauryl acid, potassium myristicate, potassium stearate and the like. In the present invention, the emulsifier is preferably used in 0.5-1.0 parts by weight based on the total weight of the mixture of the monomer and the rubbery polymer. If the emulsifier is used in less than 0.5 parts by weight, there is a problem that the polymerization stability is lowered to increase the amount of coagulated product. On the other hand, when it is used in excess of 1.0 parts by weight, there is a problem that gas generation and yellowing is increased due to the increase in the amount of residual emulsifier during molding the final product. In addition, when using an unsaturated emulsifier, the natural color of the final product is lowered by the color of the emulsifier itself.

(F) molecular weight modifier

The molecular weight modifier is selected from the group consisting of mercaptans, terpinolenic and alphamethyl styrene oligomers. The molecular weight modifier of the present invention preferably uses 0.3-1.0 parts by weight, more preferably 0.4-0.7 parts by weight based on the total weight of the mixture of monomers and the rubbery polymer. If the total amount of the molecular weight regulator is less than 0.3 parts by weight, the appearance and impact resistance of the final product is lowered due to the lowering of the graft ratio control ability, and when it is used in excess of 1.0 parts by weight, the polymerization rate is slowed and productivity is lowered. , Due to excessive graft rate control, there is a problem that the physical properties such as impact resistance is lowered.

The ion-exchange water input amount in the graft copolymerization of the present invention is preferably an emulsion polymerization condition in which the concentration range is 20-50% based on the total solids. In the present invention, the polymerization temperature is not limited, and a normal range of 50-80 ° C. is suitable. If it is less than 50 ° C., the polymerization reaction rate is slow and not practical. On the other hand, when the polymerization temperature is 80 ° C. or higher, the polymerization system is used. The amount of coagulum increased due to the deterioration in stability.

The graft polymerization composition prepared by the above method obtains graft ABS powder through coagulation, dehydration and drying, and then mixed with a SAN resin for transparent ABS to obtain an excellent transparency, natural color and impact resistance through an extrusion and injection process. A thermoplastic ABS resin composition is provided. The SAN resin for transparent ABS has good compatibility with the graft polymer, and the refractive index difference is preferably 0.004-0.006.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Example 1

First step: After dissolving 0.1 parts by weight of azobisisobutylnitrile (AIBN) in 10 parts by weight of methyl methacrylate, 4 parts by weight of styrene and 1 part by weight of acrylonitrile, 50 parts by weight of polybutadiene rubber latex (based on solid content), 150 parts by weight of ion-exchanged water, 0.7 parts by weight of potassium stearic acid, and 0.5 parts by weight of tert-dodecyl mercaptan were added to the reaction vessel and sufficiently stirred. Then, the internal temperature of the reactor was raised to 70 ° C, polymerization was carried out for 1 hour, and the conversion rate was To reach 90%.

Second step: After the first step reaction proceeds, 0.4 parts by weight of potassium peroxydisulfate (KPS) is added to the reactor at a time, and then the monomer mixture stored in a separate container capable of continuous feeding is continuously and continuously for 3 hours. It was supplied and the graft polymerization was performed. The monomer mixture was used by quantitatively mixing 25 parts by weight of methyl methacrylate, 7 parts by weight of styrene, and 3 parts by weight of acrylonitrile. After the graft polymerization was performed and the continuous feeding was completed, the reaction was terminated after aging for 1 hour.

After the reaction was completed, the graft polymerization latex was cooled to room temperature, solidified, dehydrated, and dried to obtain graft ABS powder. The graft ABS powder is mixed with a rubber-based polymer having excellent compatibility with a weight average molecular weight of 120,000 and having a refractive index difference of 0.004 to 0.006, and a SAN resin, a stabilizer, and a lubricant for transparent ABS, followed by melt extrusion and injection molding. The final transparent ABS resin was prepared.

Example 2

The combination ratio of 50 parts by weight of the monomer mixture is 65% by weight of methyl methacrylate (MMA), 25% by weight of styrene monomer (SM), 10% by weight of acrylonitrile monomer (AN), and the monomer of the first and second steps. The polymerization was carried out in the same manner as in Example 1, except that the charge ratio was 10/90.

Example 3

The combination ratio of the 50 parts by weight of the monomer mixture was 60% by weight of methyl methacrylate (MMA), 30% by weight of styrene monomer (SM), 10% by weight of acrylonitrile monomer (AN), and the monomers of the first and second steps. The polymerization was carried out in the same manner as in Example 1, except that the charge ratio was 20/80.

Example 4

The polymerization was carried out in the same manner as in Example 2, except that the amount of the rubbery polymer was 40 parts by weight and the monomer addition time was added over 5 hours in the second step.

Example 5

The addition amount of the rubbery polymer was 60 parts by weight, the monomer input ratio of the first step and the second step was 30/70, and the same as in Example 2 except that the monomer input time was added over 1 hour in the second step. The polymerization was carried out by the method.

Comparative Example 1

The polymerization was carried out in the same manner as in Example 2, except that the amount of the rubbery polymer was set to 30 parts by weight and the monomer addition time was added over 1 hour in the second step.

Comparative Example 2

The polymerization was carried out in the same manner as in Example 3, except that rosin soap was used as an emulsifier.

Comparative Example 3

The polymerization was carried out in the same manner as in Example 2, except that the monomer input ratios of the first and second stages were 20/80, and the initiator in the second stage was AIBN, which is an oil-soluble initiator.

Comparative Example 4

The polymerization was carried out in the same manner as in Comparative Example 3, except that the first stage of the initiator was water-soluble potassium peroxydisulfate (KPS), and the second stage of the initiator was an oil-soluble AIBN.

Comparative Example 5

The polymerization was carried out in the same manner as in Comparative Example 3, except that the first and second stage initiators all used potassium peroxydisulfate (KPS).

Table 1 summarizes the composition, monomer injection time, and initiator type of each monomer to be added to each example.

Rubber polymer Monomer combination ratio MMA / SM / AN Monomer input ratio 2 step monomer injection time Emulsifier Class Initiator Type First step 2nd step Example One 50 70/22/8 30/70 3 K-ST AIBN KPS 2 50 65/25/10 10/90 3 K-ST AIBN KPS 3 50 60/30/10 20/80 3 K-ST AIBN KPS 4 40 62/25/10 10/90 5 K-ST AIBN KPS 5 60 62/25/10 30/70 One K-ST AIBN KPS Comparative Example One 30 62/25/10 10/90 One K-ST AIBN KPS 2 50 60/30/10 20/80 3 Rosin soap AIBN KPS 3 50 62/25/10 20/80 3 K-ST AIBN AIBN 4 50 62/25/10 20/80 3 K-ST KPS AIBN 5 50 62/25/10 20/80 3 K-ST KPS KPS

* K-ST: Potassium Stearate

* KPS: Potassium Peroxydisulfate

For the standard specimens prepared in Example 1-5 and Comparative Example 1-5, the physical properties were measured by the measurement method specified below and the results are shown in Table 2.

The graft rate (%) of the polymer was measured as [(graft gum-rubber content) / rubber content] × 100, and the coagulant generation rate (%) was measured as (dry coagulation content / polymerized solids) × 100.

(1) IZOD impact strength (kgcm / cm) was based on ASTM D-256 (1/8 "notched).

(2) Yellowness (YI): Measured using a spectrophotometer in accordance with the standard of ASTM D1925.

(3) Total light transmittance (%): It was measured with a color computer measuring instrument of Suga Instrument Co., Ltd. in Japan and determined to be (sample transmission light / sample irradiation light) × 100.

(4) HAZE (%): A value obtained by dividing the transmitted transmitted light by the total light transmittance (%) calculated above. (Dispersive transmitted light / total light transmittance) × 100

Polymer property Molded product properties Graft Rate (%) Coagulation amount (%) Impact strength Yellow Degree (YI) Total light transmittance (%) HAZE (%) Example One 80 0.1 18 2 90 3 2 85 0.1 20 2 90 3 3 83 0.2 18 2 90 3 4 80 0.2 18 2 90 3 5 88 0.1 20 2 90 3 Comparative Example One 70 5.0 12 2 90 3 2 82 0.2 18 10 80 5 3 70 3.0 10 6 85 5 4 75 4.0 11 3 88 4 5 65 0.5 10 2 90 3

From the results of Table 2, in Comparative Example 1 using a rubbery polymer less than the scope of the present invention, a large amount of coagulum generated, the impact strength was very low. Comparative Example 2 using the rosin soap as an emulsifier showed a significantly high value of yellowness, the transparency of the resin was reduced. In Comparative Example 3 using the oil-soluble initiator AIBN as the second stage initiator, a large amount of coagulum was also generated, and it was found that not only the impact strength of the resin but also the transparency of the resin was very low. In the case of Comparative Example 4 using KPS, which is a water-soluble initiator in the first stage, and AIBN, which is an oil-soluble initiator in the second stage, the coagulation rate was high, and thus the impact strength of the resin was low. In Comparative Example 5 using the water-soluble initiator in the first step, the impact strength was similarly reduced.

The present invention is a thermoplastic resin composition having excellent transparency and natural color while maintaining excellent mechanical properties, thermal properties and impact resistance by polymerizing by using an azo oil-soluble initiator as a first step and a water-soluble initiator in a second step. And it has the effect of the invention to provide a method for producing the same.

Simple modifications or changes of the present invention can be easily made 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 (5)

The azo polymerization initiator is dissolved in a monomer mixture (B) consisting of an aromatic vinyl monomer, an unsaturated nitrile monomer, and an alkyl methacrylate monomer, and then, together with the rubbery polymer (A), an emulsifier, a molecular weight regulator and ion-exchanged water. A first step of graft polymerization by introducing into the reactor and raising the temperature to 50-80 ° C .; When the polymerization conversion rate in the first step reaches 90% or more, a water-soluble polymerization initiator is added to the reactor, and the monomer mixture (B) as in the first step is divided into several times for 1-5 hours or continuously. A second step of graft polymerization by further adding; Method for producing a thermoplastic resin composition, characterized in that consisting of. The rubbery polymer (A) is used in 40-60 parts by weight, the monomer mixture (B) is 30-70% by weight alkyl methacrylate monomer, 10-40% by weight aromatic vinyl compound and unsaturated nitrile compound 1-20% by weight, 40-60 parts by weight, 10-40% by weight of the monomer mixture (B) is used in the first step, 90-60% by weight is used in the second step Method for producing a resin composition. According to claim 1, wherein the azo polymerization initiator is used in 0.03-0.2 parts by weight, the water-soluble polymerization initiator is used in 0.3-0.8 parts by weight, the emulsifier is used in 0.5-1.0 parts by weight, the molecular weight regulator is 0.3-1.0 parts by weight Method for producing a thermoplastic resin composition, characterized in that it is used. The method of claim 1, wherein the rubber polymer has a mean particle size of 0.2 to 0.5㎛ a method for producing a thermoplastic resin composition. delete