KR20030046759A - Thermoplastic Resin Composition Having Good Chemical Resistance in Painting - Google Patents

Abstract

PURPOSE: A thermoplastic resin composition for painting is provided, to improve paintability and chemical resistance by employing SAN copolymers having different distribution of molecular weight and different composition of monomers. CONSTITUTION: The thermoplastic resin composition comprises (A) 20-50 parts by weight of a graft copolymer resin prepared by emulsion graft polymerization of 45-65 parts by weight of a rubber latex having an average particle size of 0.28-0.33 micrometers and a gel content of 65-85%; and (B) 50-80 parts by weight of a SAN copolymer resin comprising (b1) 50-80 wt% of a SAN copolymer resin containing 25-35 wt% of acrylonitrile and having a mass average molecular weight of 130,000-150,000, and (b2) 20-50 wt% of a SAN copolymer resin containing 25-35 wt% of acrylonitrile and having a mass average molecular weight of 80,000-100,000. Optionally the composition comprises further 0.5-5 parts by weight of paraffin-based wax based on 100 parts by weight of the resin composition.

Description

Thermoplastic Resin Composition Having Good Chemical Resistance in Painting}

Field of invention

The present invention relates to a thermoplastic composition having excellent chemical resistance. More specifically, the present invention is a graft copolymer (acrylonitrile-butadiene-styrene copolymer), two types of SAN copolymer resins having different monomer compositions and molecular weight distributions, and a thermoplastic composition for coating having excellent chemical resistance. It is about.

Background of the Invention

In general, ABS resin has excellent impact resistance, processability, and mechanical strength, and has been widely used for various purposes including electric and electronic housings and interior and exterior materials of automobiles, and its range is gradually expanded for automobiles and motorcycles. have.

In general, however, ABS resins are not resistant to various chemicals, so when manufactured in a molding method such as injection molding or vacuum molding, and actually used as a product, mechanical contact of the contacting part in the product may be caused by chemical contact. There is a problem in use that the strength is reduced to cause damage or softening of the product. This problem is known to be more pronounced when the residual stress is present in the product due to poor moldability during injection molding or vacuum molding.

In order to solve the above problems, to improve the chemical resistance of the ABS resin itself and to minimize the residual stress that can be generated during processing, by adjusting the molecular weight of the resin to improve the fluidity to lower the residual stress, or graft ABS resin It is common to choose a method of increasing the chemical resistance by increasing the content of.

However, when the fluidity is improved as described above, the residual stress is reduced due to the decrease in molecular weight, but the crack resistance of the resin is reduced, so that the crack proceeds more rapidly when the chemical is affected. The chemical resistance of the product itself is lowered.

In addition, in the case of increasing the content of the graft ABS resin, the fluidity is lowered, there is a problem that the productivity is reduced due to the overload during extrusion processing, the strength of the product is lowered. In particular, because of the low fluidity during injection molding requires high-temperature processing in the production of the product, there is a disadvantage that the physical properties of the product due to discoloration due to high temperature and deterioration of the resin itself.

As another method for increasing chemical resistance, a method of increasing acrylonitrile content in the ABS resin may also be used. However, in this case, there is a limit in that the change in the fluidity of the resin and the color change during processing are greatly changed. In order to solve the problem of reduced fluidity may be introduced lubricants as additives, it may lead to the peeling phenomenon of the molded product according to the use of the lubricant and lower the strength of the weld line. In addition, when the transition to the surface, paintability, printability, etc. are degraded, and if it is severe, the surface may bleed white or whitening may occur when a force is applied.

In order to solve the above problems, the present inventors use a SAN copolymer having a different monomer composition and molecular weight distribution in a graft copolymer prepared by emulsion polymerization to obtain a coating thermoplastic composition having excellent chemical resistance and paintability. It is early to develop.

An object of the present invention is to provide a thermoplastic resin composition excellent in chemical resistance.

Another object of the present invention is to provide a thermoplastic resin composition having excellent paintability.

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

The thermoplastic resin composition for coating according to the present invention is a SAN having 20-50 parts by weight of (A) graft copolymer resin and (B) (b ₁ ) acrylonitrile content of 25-35% by weight and a weight average molecular weight of 130,000-150,000. SAN copolymer resin 50-80 consisting of 50-80% by weight of copolymer resin and (b ₂ ) SAN copolymer resin having 25-35% by weight of acrylonitrile content and a weight average molecular weight of 80,000-100,000. Consisting of parts by weight and optionally 0.5-5 parts by weight of (C) paraffin wax and (D) lubricant. Detailed description of each of these components is as follows.

(A) Graft Copolymer

Graft copolymer resins are prepared by graft polymerization of aromatic vinyl compound monomers such as styrene and unsaturated nitrile compound monomers such as acrylonitrile in the presence of butadiene-based rubbery polymers. Can be prepared.

It is preferable to manufacture the graft copolymer resin of this invention by the emulsion polymerization method. This is because the graft copolymer resin produced by bulk polymerization has advantages such as mass production and reduction of manufacturing cost, but cannot produce a resin having various physical properties, and in particular, cannot produce a resin having a high rubber content.

The graft copolymer resin is a graft emulsion polymerization by adding a radical generating initiator such as a pyrolysis initiator and a redox initiator to acrylonitrile and styrene monomer using a butadiene-based rubbery polymer having a rubber particle diameter of mostly 0.1-1.0 μm. After proceeding, the fine powder is obtained through a solidification, dehydration and drying process, and then prepared by mixing the SAN copolymer resin and a suitable amount separately prepared. At this time, by adjusting rubber particle size, rubber content, rubber particle distribution, acrylonitrile content and molecular weight of SAN copolymer resin used, and adding various additives, it is possible to produce products with various physical properties that meet the needs of the consumer. Can be.

The butadiene-based rubbery polymer is preferably a rubber latex having an average particle diameter of 0.28-0.33 μm and a gel content of 65-85% by weight, and a grafting rate of 40-80% by adding styrene and acrylonitrile monomer thereto. The emulsion graft polymerization is carried out so as to be. In the present invention, the graft copolymer resin is used at 20-50 parts by weight.

(B) SAN copolymer resin

(b ₁ ) SAN copolymer resin having a weight average molecular weight of 130,000-150,000

The SAN copolymer resin (b ₁ ) used in the present invention uses a SAN copolymer resin having an acrylonitrile content of 25-35% by weight and a weight average molecular weight of 130,000-150,000.

The SAN copolymer resin (b ₁ ) is preferably prepared by suspension polymerization or bulk polymerization of styrene monomer and acrylonitrile monomer, and most preferably by block polymerization. When the additive content is high during the polymerization manufacturing process, it is easy to cause appearance defects such as bubbles in the molded product during injection molding, and when the SAN copolymer resin contains gel, it protrudes on the surface of the final molded product. Since there is a problem of lowering the quality of the SAN, a SAN copolymer resin prepared by the bulk polymerization method with less additive content and less gel generation is used.

(b ₂ ) SAN copolymer resin having a weight average molecular weight of 80,000-100,000

The SAN copolymer resin (b ₂ ) used in the present invention uses a SAN copolymer resin having an acrylonitrile content of 25-35% by weight and a weight average molecular weight of 80,000-100,000.

The SAN copolymer resin may be prepared by a conventional method by copolymerizing 65-78% by weight of styrene and 35-22% by weight of acrylonitrile, and in particular, the SAN air prepared by the bulk polymerization method having a low additive content and low gel generation Preference is given to using copolymer resins.

If the weight average molecular weight is 80,000 or less, there is a problem that the impact resistance is significantly lowered, and if the weight average molecular weight is 110,000 or more, the fluidity is lowered, which may cause unmolding, poor bubble generation, etc. during injection molding of a complicated structure.

The total amount of the SAN copolymer resin used in the present invention is 50-80 parts by weight, and 50-80% by weight and 20-50% by weight of the SAN copolymer resin (b ₁ ) and the SAN copolymer resin (b ₂ ), respectively. Use in proportions.

If the low molecular weight SAN resin is 20 parts by weight or less based on the total resin 100, the flow index is lowered, resulting in poor workability.

(C) Paraffin Wax Compound

The paraffin wax compound of the present invention is added to improve chemical resistance, impact resistance, thermal stability and processability.

Specific examples of the paraffin wax compound include polyethylene wax, polypropylene wax, ethylene propylene copolymer wax, oxidized polyethylene wax, oxidized polypropylene wax, and oxidized ethylene propylene copolymer wax. . It may also include acid-modified polyolefin waxes or polyolefin waxes modified with aromatic monomers.

When hydrocarbon-based compounds are used in resin processing, a layer of thin hydrocarbon compound is formed on the surface of the resin due to differences in fluidity and compatibility. As a result, since the blocking ability of the resin to the gas and chemicals is improved, not only chemical resistance but also discoloration phenomenon during processing is improved. In addition, hydrocarbon compounds present in the resin surface layer act as an external lubricant to improve the processing performance of the resin, and some also act as an internal lubricant to improve the dispersion of the rubber components and the inside of the polymer chain to improve the mechanical properties of the resin.

The paraffin wax compound is preferably a polyethylene wax having a molecular weight in the range of 3,000-6,000 and a melting point of 125-135 ° C.

If the molecular weight of the paraffin wax is less than 3,000, there is a disadvantage in that the chemical resistance is reduced due to the lack of the ability to block gas and chemicals. If the molecular weight exceeds 6,000, the compatibility is greatly reduced and the ability as a lubricant in the resin is degraded. The surface and external appearance characteristics of resin fall.

It is preferable to use the paraffin wax compound used for this invention in 0.5-5 weight part. If the content of the paraffin wax compound is 5 parts by weight or more, undesired phenomena such as physical properties of the resin, lowering of heat resistance, peeling, yellowing, gas generation, and extrusion workability appear.

(D) lubricant

In the present invention, the external lubricant and the internal lubricant can be selectively used in addition to the above components. In general, the lubricant is added to improve processability of the resin composition, and serves to smooth and gloss the surface of the final product. The inner lubricant serves to reduce the viscosity of the melt is impregnated inside the polymer, the outer lubricant serves to reduce the extrusion load between the polymer melt in the extruder and the metal surface.

In the present invention, magnesium stearate is used as the external lubricant, and ethylene bis fatty acid amide is preferably used as the internal lubricant.

The amount of the lubricant used in the present invention is preferably 0.2-2.0 parts by weight based on 100 parts by weight of the base resin. If the amount of lubricant is less than 0.2 part by weight, it is difficult to expect uniform dispersion in the SAN resin in which the rubber particles in the extrusion process are used as a matrix, and the release property from the mold is reduced during injection molding, resulting in release cracking or pin whitening. It lowers the value of the product. On the other hand, if the amount of the lubricant is used in excess of 2.0 parts by weight, it is expected that the uniform dispersion of the rubber particles in the extrusion process and the improvement of flowability, impact resistance, etc., but the heat resistance is lowered.

In addition to the above components, the present invention may add other additives such as inorganic additives, pigments, and dyes in appropriate amounts as necessary.

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

The graft copolymer resin, SAN copolymer resin, and additives used in the following Examples and Comparative Examples are as follows.

Graft copolymer resin

An ABS resin having a rubber particle diameter of 0.3 μm, a gel content of 78% by weight, and a graft ratio of 60% was used (rubber latex content of 58% by weight).

SAN copolymer resin

SAN copolymer resin (1)

The acrylonitrile was 30 weight% and the weight average molecular weight was 700,000.

SAN copolymer resin (2)

The acrylonitrile was 28 weight% and the weight average molecular weight was 90,000.

SAN copolymer resin (3)

The acrylonitrile was 28 weight% and the weight average molecular weight was 120,000.

SAN copolymer resin (4)

It was 25 weight% of acrylonitrile, and the weight average molecular weight was 140,000.

SAN copolymer resin (5)

The acrylonitrile was 24 weight% and the weight average molecular weight was 170,000.

Paraffin wax

Polyethylene wax having a weight average molecular weight of 4,000 and a melting point of 132 ° C was used.

Lubricant

Magnesium stearate was used as the external lubricant, and ethylene bis fatty acid amide was used as the internal lubricant.

Examples 1-5 and Comparative Examples 1-6

Each component is added to the graft copolymer resin and the SAN copolymer resin, which are basic resins, in the amounts shown in Table 1 below, and the cylinder temperature is set at 220 ° C., and the biaxial with L / D = 29 and φ = 45 mm. After extruding using an extruder, the extrudate was prepared in pellet form.

Example Comparative Example One 2 3 4 5 One 2 3 4 5 6 Graft Copolymer Resin 25 25 30 30 25 30 30 25 25 25 25 SAN copolymer resin (One) - - - - - - - - - 20 - (2) 20 20 20 20 20 - 70 55 20 - 20 (3) - - - - - - - - - - 55 (4) 55 55 50 50 55 70 - 20 - 55 - (5) - - - - - - - - 55 - - PE wax - 2.0 1.0 - 1.0 - - - - - - Lubricant Internal lubricant 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Outside 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

The physical properties of the pellets prepared in Examples and Comparative Examples were injection molded to measure impact strength, flow index, chemical resistance and paintability, and are shown in Table 2.

(1) Notched Izod impact strength was measured based on ASTM D256 (1/4 ", 23 ° C) (unit kg · cm / cm).

(2) The flow index was measured by ASTM D1238 (5Kg, 200 ° C).

(3) Chemical resistance evaluation: In a 10 oz injection machine, 127 mm × 12.7 mm × 3 mm specimens were molded using a 1-gate system, and the curvature was 0.75% using the molded specimens. JIG used directly as produced. After the molded specimen was fixed in JIG, the chemical (polyglycol ether) was applied to the center of the specimen, and the time until cracks occurred and completely separated was measured.

(4) Coating: After molding 100mm × 100mm × 3.0mm specimen, apply urethane paint (commercially available plastic paint) with spray gun on sprayed gun and apply it on the surface of specimen. The defective phenomenon which occurred is visually determined.

○: Good (No coating erosion occurs)

△: Normal (partly erosion of paint)

×: Poor (Overall coating erosion)

The impact strength, flow index, chemical resistance and paintability of the measured specimens are shown in Table 2.

Example Comparative Example One 2 3 4 5 One 2 3 4 5 6 Notched Izod Impact Strength 25 26 28 28 26 29 22 24 28 23 26 Chemical resistance 4 minutes 30 seconds 5 minutes 50 seconds 4 minute, 20 seconds 4 minutes 30 seconds 5 minute, 10 seconds 4 minute 40 seconds 2 minutes 15 seconds 2 minutes 30 seconds 4 minutes 50 seconds 2 minute, 20 seconds 2 minutes 30 seconds Paintability ○ ○ ○ ○ ○ △ △ ○ × × △

In Comparative Example 1 using only the SAN copolymer resin (4) as a SAN copolymer resin from the results of Table 2, the chemical resistance was excellent, but the flow index was very low, the SAN copolymer resin SAN copolymer In Comparative Example 2 using only the resin (2), it was found that the chemical resistance and the impact strength were very low and the paintability was also low.

Also in Comparative Example 3 in which the content of the SAN copolymer resin (2) was increased, the impact strength and the chemical resistance were lowered.

In the case of Comparative Example 4, which is a combination of the SAN copolymer resin (5) and the SAN copolymer resin (2), it was found that the chemical resistance was increased but the paintability was decreased.

Chemical resistance also in the case of Comparative Example 5 which is a combination of SAN copolymer resin (4) and SAN copolymer resin (1) and in Comparative Example 6 which is a combination of SAN copolymer resin (2) and SAN copolymer resin (3) And paintability fell.

The present invention provides a thermoplastic resin composition having excellent impact strength, fluidity and chemical resistance by using a graft copolymer resin and a styrene-acrylonitrile copolymer (SAN copolymer) having different molecular weight and acrylonitrile content as a base resin. It has the effect of the invention.

Simple modifications and variations 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 (3)

(A) 20-50 parts by weight of a graft copolymer resin prepared by emulsion graft polymerization using 45-65 parts by weight of rubber latex having an average particle size of 0.28-0.33 µm and a gel content of 65-85% by weight. ; And (B) 50-80% by weight of a SAN copolymer resin having (b ₁ ) acrylonitrile content of 25-35% by weight and a weight average molecular weight of 130,000-150,000 and (b ₂ ) 25-35% by weight of acrylonitrile content 50-80 parts by weight of a SAN copolymer resin composed of 20-50% by weight of a SAN copolymer resin having a weight average molecular weight of 80,000-100,000; A thermoplastic resin composition, characterized in that consisting of. The thermoplastic resin composition according to claim 1, wherein the graft copolymer resin (A) has a graft ratio of 40-80%. The thermoplastic resin composition of claim 1, further comprising 0.5-5 parts by weight of (D) paraffin wax, optionally based on 100 parts by weight of the resin composition.