KR20040053961A - Method of Preparing Thermoplastic Resin Composition with Good Heat Resistance and Good Transparence - Google Patents

Abstract

PURPOSE: A method for preparing a thermoplastic resin composition is provided, to improve heat resistance and transparency with deterioration of mechanical properties and impact resistance of an ABS resin. CONSTITUTION: The method comprises the steps of graft polymerizing a butadiene-based rubber latex having an average diameter of 0.2-0.5 micrometers, a monomer mixture comprising an aromatic vinyl compound, an unsaturated nitrile compound, an alkyl methacrylate and an alkyl acrylate in the ratio of 10-40 : 1-20 : 50-80 : 1-10 by weight and having a haze of final resin of 4 or less, and a fat-soluble oxidation reduction polymerization initiator; and adding a water-soluble thermally decomposable polymerization initiator and the rest of the monomer mixture when a conversion rate of graft polymerization reaches 90 % or more, to graft copolymerize them, wherein the monomer mixture is added by 10-30 wt% and 70-90 wt% at the first step and the second step, respectively.

Description

Method for preparing thermoplastic resin composition having excellent heat resistance and transparency {Method of Preparing Thermoplastic Resin Composition with Good Heat Resistance and Good Transparence}

Field of invention

The present invention relates to a method for producing a methylmethacrylate-acrylonitrile-butadiene-styrene resin (hereinafter transparent ABS resin) excellent in heat resistance and transparency. More specifically, the present invention is a primary graft polymerization by adding a monomer mixture and an oil-soluble initiator in which the refractive index is the same as the refractive index of the rubbery polymer to the rubber latex, and the second graft polymerization by adding a water-soluble initiator and the monomer mixture It relates to a method for producing a thermoplastic resin composition excellent in heat resistance and transparency consisting of steps.

Background of the Invention

In general, ABS resin is widely used in various applications such as automobiles, electronics, office equipment, home appliances, toys, stationery, etc. due to its physical strength and beautiful appearance such as styrene processability, acrylonitrile stiffness and chemical resistance, butadiene impact resistance, etc. There is an advantage in that it is used, but there is a disadvantage in that it is restricted in use due to opacity.

Transparency resins mainly used for products requiring transparency include SAN, PC, GPPS, and PMMA, but SAN, GPPS, and PMMA have advantages of excellent transparency and low price, but their use is limited due to their low impact resistance. In the case of the PC, there is an advantage of excellent transparency and impact resistance, but the price is expensive, and there is a limit of its development due to the disadvantage of lowering chemical resistance.

Transparent ABS has a higher impact strength than other transparent resins such as SAN and PMMA and has a lower price than PCs. Recently, the use of transparent ABS for transparent materials has been actively developed. The reason why the ABS resin exhibits transparency is that the refractive index of the rubber in the dispersed phase matches the refractive index of the matrix resin in the continuous phase, thereby minimizing the scattering and refraction of light at the interface between the continuous phase and the divided phase. Therefore, in order to impart transparency to the ABS resin, it is necessary to match the refractive index of the rubber phase with that of the continuous matrix resin and to minimize the scattering of light in the visible region by appropriately adjusting the size of the used rubber particles.

The main purpose of the existing transparent ABS is mainly used for products that have a visual characteristic by making the shape of the product transparent, but recently, in addition to these uses, it has given functionality such as high transparency, whitening resistance, scratch resistance, and heat resistance to the existing transparent ABS products. The use of giving characteristics is required in the market. In order to meet the needs of these applications, researches to have additional functions in the transparent ABS have been actively conducted recently.

As such, the transparent ABS is mainly used as an exterior material of home appliances, but in recent years, its use has been expanded to functional materials, and as the use of the transparent ABS is expanded, a characteristic suitable for the intended use is required. As the weight becomes lighter, high impact characteristics are required, transparency level equivalent to that of PC and PMMA is required, and transparent ABS having excellent heat resistance that can be used even in high temperature products is required.

In this conventional technique, when graft polymerization is performed using a water-soluble initiator alone, a glossiness is good because a graft structure of a core-shell type is formed by a hydrophilic group of methylacrylic acid alkyl ester, which is the main raw material of transparent ABS. The thickness of the shell is not thick enough, the impact strength is lowered. In addition, the oil-soluble initiator by the conventional redox initiator combination is excellent in impact strength, but there is a problem that the transparency is inferior to the transparent ABS of the core-shell structure.

Japanese Patent No. 62-84109 discloses a method of securing transparency by using SBR rubber having different rubber particle sizes. However, the glass transition temperature of the SBR rubber is low, the size and particle distribution of the rubber is inadequate, and the impact resistance is inferior. In most cases, the depolymerization of the chain of polymerized MMA molecules occurs when used at a high temperature, so that the high temperature Use is limited.

On the other hand, the present inventors use a peroxide-based insoluble initiator combination in the first step in the butadiene-based rubber, the size and content of which is controlled in order to overcome the above problems, styrene monomer, unsaturated nitrile monomer, methacrylic acid alkyl ester monomer And adding a small amount of alkyl acrylate monomer to form a polymer in the rubber to improve impact resistance, and in the second step graft polymerization, the monomer is a rubber outer shell in combination with the monomer used in the first step using a water-soluble initiator. It has been developed to produce a thermoplastic resin composition having excellent heat resistance and transparency while performing polymerization so as to graft the layer appropriately while maintaining excellent mechanical properties, impact resistance and the like of the ABS resin.

An object of the present invention is to provide a method for producing a thermoplastic resin composition excellent in heat resistance while maintaining the excellent mechanical properties of the ABS resin.

Another object of the present invention is to provide a method for producing a thermoplastic resin composition excellent in transparency.

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

The method for producing a thermoplastic resin having excellent heat resistance and transparency according to the present invention is an aromatic vinyl compound, an unsaturated nitrile compound, an alkyl methacrylate, an alkyl acrylate, and an alkyl acrylate graft monomer in a butadiene rubber latex having an average particle diameter of 0.2-0.5 μm. Graft polymerization by adding a monomer mixture having 10 to 40% by weight, 1 to 20% by weight, 50 to 80% by weight and 1 to 10% by weight, and an oil-soluble redox polymerization initiator, respectively; And a second step of graft copolymerization by adding a water-soluble pyrolytic polymerization initiator and the monomer mixture when the conversion rate of the first step graft polymerization reaches 90% or more, and the monomer mixture is 10-30 weight in the first step. %, It is characterized in that the 90-70% by weight in the second step. Hereinafter, each step of the present invention will be described in detail.

(1) First step

In the first step, aromatics are ion-exchanged water, emulsifiers, molecular weight regulators and graft monomers in the presence of 40 to 60 parts by weight (based on solids) of rubbery polymer having an average particle diameter of 0.2 to 0.5 µm and a gel content of 70 to 90% by weight. The combination ratio of vinyl compound, unsaturated nitrile compound, alkyl methacrylate and alkyl acrylate is 10 to 40% by weight, 1 to 20% by weight, 50 to 80% by weight and 1 to 10% by weight, respectively. A monomer mixture combined with the same refractive index was added to a reactor with 0.05 to 0.30 parts by weight of a peroxide-based oil-soluble initiator, and the temperature was raised to 50 to 80 ° C., followed by 0.001-0.01 parts by weight of a starting catalyst, 0.05-0.5 parts by weight of a reducing agent, and 0.1-0.4 parts by weight of a mixture of a complex ion agent is added to the one-step graft polymerization.

As the rubbery polymer, butadiene rubber having an average particle diameter of 0.2 to 0.5 mu m is preferable, and is used in the present invention at 40 to 60 parts by weight. When the amount of rubber used is less than 40 parts by weight, the average distance between the particle size and the particle diameter of the rubber is far, and the impact reinforcing effect is remarkably lowered. There is a problem of poor drying due to failing to form a layer, the gloss decreases, and the formation of coarse particles during the solidification process.

The graft monomer mixture of the present invention comprises an aromatic vinyl compound, an unsaturated nitrile compound, an alkyl methacrylate, and an alkyl acrylate, and the combination ratio is 10 to 40% by weight, 1 to 20% by weight, and 50 to 80% by weight, respectively. And 1 to 10% by weight.

If the ratio of the aromatic vinyl monomer, unsaturated nitrile monomer, alkyl methacrylate monomer, and alkyl acrylate monomer mixture used in the graft polymerization is out of the above range, HAZE increases due to the difference in refractive index between the rubbery polymer and the graft polymer. There is a problem, and it is preferable to combine so that the HAZE of the final resin is 4 or less.

If the alkyl acrylate is used more than 10% there is a problem that a large amount of coagulation occurs by increasing the reaction rate.

In the alkyl acrylate, the carbon number of the alkyl group applicable to the transparent ABS is preferably 1 to 5, and the lower the carbon number of the alkyl group, the heat resistance is improved.

In the present invention, the graft monomer mixture is divided into 10-30% by weight in the first step and 90-70% by weight in the second step. If the amount of the monomer combination used in the first stage graft emulsion polymerization is less than 10%, the impact strength decreases due to the decrease of the graft polymer inside the rubbery polymer, and if it is more than 30%, the graft polymer inside the rubbery polymer is increased. Due to this, there is a problem in that the reaction stability is lowered, so that a large amount of coagulum is generated, and that the shell layer outside the rubbery polymer is not sufficiently formed, and thus the glossiness is decreased by the increase of the exposed rubbery polymer, and the natural color and impact strength are lowered.

Oil-soluble redox initiators used in the first stage graft polymerization of the present invention include hydroperoxide-based initiators such as cumene hydroperoxide, azo oil-soluble initiator, diisopropylbenzene hydroperoxide and tertiary butyl hydroperoxide. Among these, it is preferable to use cumene hydroperoxide. The oil-soluble redox initiator is used in an amount of 0.05 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight.

As the molecular weight modifier used in the present invention, mercaptans and terpinolenic or alphamethyl styrene oligomers are used, and merketanes are preferably used. The amount of the molecular weight modifier is preferably used 0.1 to 1.0 parts by weight, more preferably 0.3 to 0.7 parts by weight based on the total weight of the rubbery polymer latex and monomer mixture of the graft polymer. If the total amount of the molecular weight regulator is less than 0.1 parts by weight, there is a problem that the appearance and impact resistance of the final product is lowered and the fluidity of the product is lowered due to the lowering of the ability to control the graft ratio. Due to the slow speed, productivity decreases and excessive graft ratio control causes physical properties such as impact resistance to deteriorate and gas generated by the oligomer.

The starting catalyst is ferrous sulfate, the amount used is 0.001 to 0.01 parts by weight, more preferably 0.002 to 0.007 parts by weight. When using the starting catalyst 0.01 parts by weight or more, there is a problem that the yellowness of the natural color is increased.

As the reducing agent, sodium sulfoxylate formaldehyde is preferable, and the amount is 0.05 to 0.5 parts by weight.

The complex ion agent is capable of detecting ions by coordinating two or more multidentate ligands, and serves to improve the natural color by separating the remaining starting catalyst from the product using ethylene diamine tetraacetic acid, and adding 0.1 to 0.4 parts by weight. Used.

As the emulsifier, a saturated fatty acid having 12 to 18 carbon atoms is substituted with potassium or sodium ions. Examples of the emulsifier include sodium lauryl acid, sodium myristic acid, sodium stearic acid, potassium lauric acid, Potassium myristic acid, potassium stearic acid, and the like may be used, and the amount of use is generally 0.5 to 1.0 parts by weight based on the total weight of the mixture of the monomer and the rubbery polymer. If the amount of the emulsifier is less than 0.5 parts by weight, there is a problem in that the amount of coagulated product is increased due to deterioration of the polymerization stability. If the amount of the emulsifier is more than 1.0 part by weight, the generation of gas and yellowing are increased due to the increase in the amount of residual emulsifier in forming the final product. have. In addition, when using an unsaturated emulsifier, there is a problem that the natural color of the final product is lowered by the color of the emulsifier itself.

The polymerization temperature in the graft copolymerization of the present invention is not limited, and a range of 50 to 80 ° C. under ordinary conditions is suitable. If the polymerization temperature is less than 50 ° C, the polymerization reaction rate is slow and not practical, and if the polymerization temperature is 80 ° C or higher, there is a problem in that the amount of coagulated product increases due to the deterioration of the stability of the polymerization system.

(2) second stage

When the polymerization conversion rate reaches a predetermined stage in the first stage, the second stage graft polymerization is performed.

In the second stage, when the conversion rate of the graft polymerization of the first stage reaches 90% or more, 90 to 70 wt% of the same monomer mixture as the first stage graft polymer is used by using 0.20 to 0.50 parts by weight of the water-soluble pyrolytic polymerization initiator. Graft polymerization was performed by dividing or continuously feeding several times for 5 hours to prepare a graft copolymer having a core-shell structure surrounded by a graft monomer.

The water-soluble pyrolytic initiator is added to the reactor in a batch, and Potassium peroxydisulfate is used. The amount of the water-soluble pyrolytic initiator of the present invention is preferably 0.3 to 0.8 parts by weight, more preferably 0.4 to 0.7 parts by weight. Under the influence of the water-soluble initiator, a graft copolymer having a rubber surface surrounded by a graft monomer is prepared to provide excellent impact resistance, heat resistance, and transparency of the final ABS resin.

In the second stage graft polymerization, when the continuous addition time of the aromatic vinyl monomer, the unsaturated nitrile monomer, the alkyl methacrylate monomer, and the alkyl acrylate mixture is less than 1 hour, the heat of reaction is increased due to the increase of the amount of monomer introduced per unit time. Difficult to control, there is a problem of increasing quality instability and coagulation occurs, if the continuous input time is more than 5 hours, there is a problem that the productivity of the polymer is reduced due to a long polymerization time.

The graft polymer prepared by the above method has excellent transparency due to a small refractive index difference between the matrix and the rubber component, and exhibits excellent transparency when the refractive index difference is less than 0.003.

The graft polymerized latex prepared by the above method was obtained by coagulation, dehydration, and drying to obtain a powder, and then mixed with a SAN resin for transparent ABS having good compatibility with the graft polymer and having a refractive index difference of 0.004 to 0.006. ABS resin with excellent transparency, natural color and impact resistance is manufactured through the process.

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 1

(1) First step

In a 10L glass reaction vessel, a stirring impeller, a temperature control thermometer, a mantle, and a cooling water circulator are prepared, followed by 50 parts by weight of polybutadiene rubber latex having an average particle diameter of 0.3 µm (based on solids), 120 parts by weight of ion-exchanged water, and potassium stearic acid 0.7 parts by weight, 10 parts by weight of methyl methacrylate, 3 parts by weight of styrene, 1 part by weight of acrylonitrile, 0.5 parts by weight of methyl acrylate, 0.3 parts by weight of terrestrial dodecyl mercaptan and cumene hydroperoxide (Initiator 1) 0.2 The parts by weight were added to the reaction vessel and stirred well, and the reactor internal temperature was raised to 60 ° C. Next, 0.003 parts by weight of ferrous sulfate, 0.2 parts by weight of sodium sulfoxylate formaldehyde, and 0.1 parts by weight of ethylenediamine tetraacetic acid were added to carry out polymerization for 1 hour so that the conversion reached 90%.

(2) Second step

After the one-stage reaction was carried out, 0.5 parts by weight of potassium peroxydisulfate (initiator 2) was added to the reactor at a time and a two-stage graft polymerization was performed. After the monomer used in the two-stage graft polymerization, 24 parts by weight of methyl methacrylate, 8 parts by weight of styrene, 3 parts by weight of acrylonitrile and 1 part by weight of methyl acrylate were weighed and stored in a separate container capable of continuous supply. The mixture was well mixed and continuously fed for 3 hours continuously to carry out the graft polymerization. After the continuous feeding was completed, the reaction was terminated after aging for 1 hour. After completion of the reaction, the graft polymerization latex was cooled to room temperature, solidified, dehydrated, and dried to obtain graft ABS powder.

(3) Manufacture of transparent ABS resin

The graft ABS powder prepared above is mixed with a rubber polymer and a SAN resin for a transparent ABS having a refractive index difference of 0.004 to 0.006, a stabilizer and a lubricant, and then melt-extrusion and injection molding process. After the final transparent ABS resin was prepared. At this time, the graft ABS powder adjusted the content of the SAN resin to 28% rubber content in the transparent ABS product during melt extrusion. The physical properties of the prepared transparent ABS resin were measured by the specified physical property measurement method, and the results are shown in Table 2.

Example 2

Except that 3% ethyl acrylate was used as the alkyl acrylate monomer was carried out in the same manner as in Example 1.

Example 3

The same procedure as in Example 1 was carried out except that 3% butyl acrylate was used as the alkyl acrylate monomer.

Example 4

40 parts by weight of a rubbery polymer was used, and the same procedure as in Example 1 was carried out except that 3% of methyl acrylate was used.

Example 5

60 parts by weight of a rubbery polymer was used, and the same procedure as in Example 1 was carried out except that 3% of methyl acrylate was used.

Comparative Examples 1 and 2

The same procedure as in Example 1 was carried out except that methyl acrylate was used at 0% and 15%, respectively.

Comparative Examples 3 to 4

Methyl acrylate was used in the same manner as in Example 1 except for using 3% and using only peroxide-based redox initiators (initiator 1) or only potassium peroxydisulfate (initiator 2).

Rubbery polymer (%) Alkyl acrylate Monomer combination ratio Initiator Type Initiator 1 Initiator 2 Example One 50 Methyl acrylate 70/22/7/1 Initiator 1 Initiator 2 2 50 Ethyl acrylate 68/22/7/3 Initiator 1 Initiator 2 3 50 Butyl acrylate 68/22/7/3 Initiator 1 Initiator 2 4 40 Methyl acrylate 68/22/7/3 Initiator 1 Initiator 2 5 60 Methyl acrylate 68/22/7/3 Initiator 1 Initiator 2 Comparative example One 50 - 71/22/7/0 Initiator 1 Initiator 2 2 50 Methyl acrylate 56/22/7/15 Initiator 1 Initiator 2 3 50 Methyl acrylate 68/22/7/3 Initiator 1 Initiator 1 4 50 Methyl acrylate 68/22/7/3 Initiator 2 Initiator 2

The physical properties of the transparent ABS resin prepared above were evaluated by the following method, and the results are shown in Table 2.

Assessment Methods

1) Graft Rate (%) = Graft Gum-Rubber Content × 100

Rubber content

2) COAGULUM amount (%) = dry COAGULUM amount × 100

Polymerized Solids

3) IZOD Impact Strength (㎏ · ㎝ / ㎝): ASTM D-256 (1/8 "NOTCHED)

4) Transparency: Measured by a color computer measuring instrument from SUGAINSTRUMENT, Japan, and the results are expressed as total light transmittance and HAZE.

Total light transmittance (%) = specimen transmitted light x 100

Specimen light

HAZE (%) = diffuse transmitted light x 100

Total light transmittance

5) Vicat Softening Temperature (℃): ASTM D 1525 (Load Cell: 5kg)

Polymer property Molded product properties Vicat (℃) Graft Rate (%) Amount of coagulation product (%) Impact strength Yellow road Total light transmittance HAZE Example One 85 0.1 20 5 91 1.5 100 2 85 0.1 23 5 91 2 95 3 85 0.1 25 5 91 2 95 4 80 0.1 20 5 91 1.5 100 5 90 0.1 25 5 91 2 100 Comparative example One 85 0.1 20 6 91 5 85 2 85 10.0 10 6 90 6 105 3 90 10.0 25 6 91 2 100 4 70 0.1 5 6 91 2 100

As shown in Table 2, Comparative Example 1, which does not use alkyl acrylate, was found to have low transparency and heat resistance, and Comparative Example 2, which used more than alkyl acrylate, had excellent heat resistance, but the amount of coagulant generated. It was high and also the impact strength was found to be reduced. In addition, Comparative Example 3 using only an oil-soluble initiator was excellent in impact strength, but it was confirmed that the amount of coagulant generated was low in reaction stability. Comparative Example 4 using only a water-soluble initiator was found to have the lowest impact strength.

The present invention is the ABS resin by adding the alkyl acrylate monomer to the graft monomer mixture in the first step, and the first graft polymerization using the oil-soluble initiator, and the second graft polymerization using the water-soluble initiator in the second step, The invention has the effect of providing a method for producing a thermoplastic resin composition having excellent heat resistance and transparency while maintaining excellent mechanical properties, impact resistance and the like.

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 (6)

Butadiene-based rubber latex having an average particle diameter of 0.2-0.5 µm has a combination ratio of aromatic vinyl compounds, unsaturated nitrile compounds, alkyl methacrylates, and alkyl acrylates of 10 to 40% by weight and 1 to 20% by weight, respectively. Graft polymerization by adding a monomer mixture and an oil-soluble redox polymerization initiator such that 50-80 wt% and 1-10 wt% of the final resin haze (HAZE) is 4 or less; And A second step of graft copolymerization by adding a water-soluble pyrolytic polymerization initiator and the monomer mixture when the conversion rate of the first step graft polymerization reaches 90% or more; It consists of, the monomer mixture is 10-30% by weight in the first step, 90-70% by weight in the second step of producing a thermoplastic resin composition excellent in heat resistance and transparency, characterized in that the input. The method of claim 1, wherein the butadiene-based rubber latex is 40-60 parts by weight, and the monomer mixture is used in an amount of 60-40 parts by weight. The method for producing a thermoplastic resin composition having excellent heat resistance and transparency according to claim 1, wherein the alkyl group of the alkyl acrylate has 1 to 5 carbon atoms. The method of claim 1, wherein the continuous mixing time of the monomer mixture in the second step is 1 to 5 hours. The method of claim 1, wherein the first step is to use a peroxide-based oil-soluble initiator and the second step to use a Potassium hydro persulfate-based water-soluble initiator, characterized in that the dosage is 0.1 to 0.3 and 0.3-0.8 parts by weight, respectively A method for producing a thermoplastic resin composition excellent in heat resistance and transparency. The method for producing a thermoplastic resin composition having excellent heat resistance and transparency according to claim 1, wherein a difference in refractive index between the matrix component and the rubber component of the produced resin is 0.003 or less.