KR20020055522A - Thermoplastic Resin Composition With Excellent Fatigue Strength - Google Patents

Abstract

PURPOSE: Provided is a thermoplastic resin composition excellent in fatigue strength, fluidity, and impact strength, which can be used for electric and electronic parts, parts of cars, and operation parts of electric home appliances. CONSTITUTION: The thermoplastic resin composition comprises: 20-40pts.wt. of a graft copolymer resin comprising 60-90wt% of a graft copolymer resin having an average particle diameter of 0.20-0.40 micrometer and 40-10wt% of a graft copolymer resin having an average particle diameter of 0.1-0.20 micrometer; 60-80pts.wt. of an SAN resin comprising 20-40pts.wt. of an SAN resin having 30-40wt% of acrylonitrile and a weight average molecular weight of 140,000-180,000 and 40-60pts.wt. of an SAN resin having 30-40wt% of the acrylonitrile and a weight average molecular weight of 70,000-120,000; 0.2-0.6pts.wt. of a metal lubricant such as calcium stearate, barium stearate, magnesium stearate; 1.0-2.0pts.wt. of an inside lubricant such as polyethylene wax or ethylene bis stearoamide.

Description

Thermoplastic Resin Composition With Excellent Fatigue Strength

Field of invention

The present invention relates to a thermoplastic resin composition excellent in fatigue strength. More specifically, the present invention relates to an ABS resin prepared by mixing and processing an acrylonitrile-butadiene-styrene graft copolymer prepared by an emulsion polymerization method and an acrylonitrile-styrene copolymer (SAN resin) prepared separately. The present invention relates to a thermoplastic resin composition having excellent fatigue strength and mechanical properties by mixing SAN resins having different monomer compositions and molecular weight distributions.

Background of the Invention

ABS resin has a relatively good combination of physical properties such as impact resistance, mechanical strength, molding processability, etc., and is widely used in electric and electronic parts and automobile parts.

In recent years, industrialization has accelerated and the range of using plastic materials has been widened, and in response, efforts have been made to improve the durability of plastics. Among them, fatigue strength, which is a measure of durability of plastics, is becoming an important property of plastic materials, and products that require high fatigue strength are increasing.

Particularly, products requiring fatigue strength are required as various components such as bobbin sleeves or parts in which load and stress concentration are generated among working parts of home appliances. Bobbin sleeve is a thin cylindrical extruded product used in the textile industry for practical use, and because it is repeatedly used for a long time over 5 months in a thin molded state, durability and fatigue resistance are required in terms of product characteristics. If mechanical properties such as durability and fatigue resistance are not satisfied, cracks may appear on the surface of the product during long-term use, resulting in product defects.

As such, ABS products for bobbin sleeves must be manufactured to withstand the fatigue of long-term use without losing mechanical strength even in a thin film state by using a high content of rubber and ultra high molecular weight SAN.

On the other hand, the fatigue strength of the parts in which the load and stress concentration occur among the working parts of home appliances requires more complex physical properties. These parts may be destroyed by vibration generated during use or transportation, or the plastic strength may be weakened during vibration, causing breakage even with a small impact. The fatigue phenomenon is known to be greatly influenced not only by the mechanical stress applied to the material such as the magnitude of the repeated load or the vibration speed but also by the chemical structure of the material itself or the additives added.

In general, the ABS resin is prepared by graft polymerization of an styrene monomer and an acrylonitrile monomer in an unsaturated nitrile compound, which are representative as aromatic vinyl compounds in the presence of a butadiene rubbery polymer. In addition, the ABS resin can obtain the desired resin by controlling the physical properties of the rubbery polymer, graft polymer, and matrix polymer used.

Graft copolymer resins are usually produced by block polymerization, block polymerization, suspension polymerization, emulsion polymerization, etc., and are produced by mixing alone or in accordance with properties. By the way, the graft copolymer resin produced by the bulk polymerization has advantages such as mass production and reduction of manufacturing cost, but there is a problem in that a resin having various physical properties cannot be manufactured and a resin having a particularly high rubber content cannot be manufactured. Therefore, the most used one is by emulsion polymerization method.

The graft copolymer resin prepared by the emulsion polymerization method uses a butadiene-based rubbery polymer having a rubber particle diameter of mostly 0.1 to 1.0 µm to add radical generating initiators such as pyrolysis initiators and redox initiators to acrylonitrile and styrene monomers. After the graft polymerization proceeds to coagulation, dehydration and drying to obtain fine powder, and then separately mixed SAN resin and the appropriate amount is prepared by processing. At this time, by adjusting the rubber particle size, the rubber content, the rubber particle distribution and the acrylonitrile content, molecular weight, etc. of the SAN resin to be used, a variety of physical properties can be produced by adding various additives.

However, parts that require fatigue strength while demanding external appearance such as home appliances require optimal rubber content and molecular weight control and composition control of SAN resin.

On the contrary, the present inventors have a high acrylonitrile content and high molecular weight SAN resin in the SAN resin in the process of mixing the graft copolymer resin and the SAN resin with different rubber particle size of the graft copolymer resin to overcome the above problems By using an appropriate amount of mixed with a high acrylonitrile content and a low molecular weight SAN resin has led to the development of a thermoplastic resin composition having good balance of mechanical properties such as excellent fatigue strength, high rigidity and fluidity.

An object of the present invention is to use a graft copolymer resin of different graft copolymer resin prepared by the emulsion polymerization method, and a SAN resin having different acrylonitrile content and molecular weight in the SAN resin used as a matrix. It is for providing the thermoplastic resin composition excellent in fatigue strength by mixing and using.

Another object of the present invention is to provide a thermoplastic resin composition excellent in fatigue strength, flowability and impact strength at the same time.

The above and other objects of the present invention can be achieved by the following description.

The thermoplastic resin composition having excellent fatigue strength of the present invention is (A) 60-90 wt% of a large particle size graft copolymer resin (A ₁ ) having an average particle diameter of 0.20-0.40 μm and a small particle size of 0.1-0.20 μm. particle size of the graft copolymer resin (a ₂₎ 40-10 parts by weight of the graft copolymer resin consisting of 20 to 40% by weight; (B) 20-40 parts by weight of a SAN resin (B ₁ ) having an acrylonitrile content of 30-40% by weight and a weight average molecular weight of 140,000-180,000, and an average of 300,000% by weight of an acrylonitrile content of 70,000 It is characterized by consisting of 60-80 parts by weight of SAN resin consisting of 40-60 parts by weight of SAN resin (B ₂ ) of -120,000.

The thermoplastic resin composition having excellent fatigue strength of the present invention has a large particle size graft copolymer resin (A ₁ ) having an average particle diameter of 0.20-0.40 μm and a small particle size graft copolymer resin having an average particle diameter of 0.1-0.20 μm (A ₂ ) SAN resin (B ₁ ) having an acrylonitrile content of 30-40% by weight and a weight average molecular weight of 140,000-180,000, and an acrylonitrile content of 30-40% by weight with a weight average molecular weight It is manufactured by injection molding through a kneading process of mixing and melting 70,000-120,000 SAN resin (B ₂ ) at a predetermined ratio.

The graft copolymer resin (A) is 45 to 60 parts by weight of a graft monomer mixture composed of acrylonitrile and styrene monomer in 45 to 60 parts by weight (based on solids) of rubber latex composed of rubber having an average rubber particle diameter of 0.20 to 0.40 μm. 60 to 90 parts by weight of a large particle size graft copolymer resin (A ₁ ) prepared by a conventional emulsion polymerization method for grafting parts and 45 to 60 parts by weight of a rubber latex composed of rubber having an average rubber particle diameter of 0.10 to 0.20 μm (solid content It consists of a small particle size graft copolymer resin (A ₂ ) 40-10% by weight prepared by a conventional emulsion polymerization method for grafting 45 to 60 parts by weight of a graft monomer mixture composed of acrylonitrile and styrene monomer. The graft copolymer resin (A) is used in the present invention 20 to 40 parts by weight.

When the amount of the large-diameter graphene polymer (A ₁ ) is less than 60% by weight, the amount of the small-diameter rubber is increased to increase the rigidity, but the impact strength is lowered, and the fatigue strength is lowered due to the impact strength. When the amount of light used is 90% by weight, the impact strength due to the increase of the large particle size rubber increases, but the stiffness due to the small particle size decreases relatively, thus affecting the decrease in the fatigue strength. Therefore, the large-diameter graphene polymer (A ₁ ) is preferably used in the range of 60-90% by weight.

In addition, when the graft copolymer resin (A) is used in an amount of less than 20 parts by weight, the stiffness is increased, but the impact resistance is easily lowered because the graft copolymer resin and the SAN resin are mixed. If it is more than 40 parts by weight, impact strength is increased, but fluidity and rigidity are deteriorated, so the mechanical properties of ABS resin and the purpose of the present invention cannot be met.

On the other hand, SAN resin (B) is manufactured by normal suspension polymerization, emulsion polymerization, or block polymerization method. The SAN resin is 30-40% by weight of acrylonitrile content and 20-40 parts by weight of SAN resin (B ₁ ) having a weight average molecular weight of 140,000-180,000, and acrylonitrile content of 30-40% by weight and weight average molecular weight SAN resin (B ₂ ) which is 700,000-100,000. The said weight part is the value shown with respect to 100 weight part of sum total with a copolymer resin.

It is preferable to use 60-80 weight part of said SAN resin (B) with respect to 100 weight part of sum total with a graft copolymer resin.

When the weight average molecular weight is 140,000-180,000, the amount of SAN resin (B ₁ ) is less than 20 parts by weight, there is a problem that the fatigue strength characteristics due to the molecular weight decreases, if more than 40 parts by weight, the stiffness and fatigue strength characteristics by increasing the molecular weight Is increased, but it is difficult to obtain a beautiful appearance quality due to the decrease in fluidity.

When the amount of the SAN resin (B ₂ ) having a weight average molecular weight of 70,000-10,000 is less than 40 parts by weight, the fatigue strength characteristics are improved due to the increase in molecular weight, but the fluidity is deteriorated. However, there is a problem that the stiffness and fatigue strength characteristics are reduced.

In addition, when the content of acrylonitrile in the composition of each SAN is less than 30%, the tensile properties are reduced, fatigue strength is lowered, and when it is 40% or more, workability is poor and it is difficult to obtain beautiful appearance quality.

In the mixing of the graft copolymer resin and the SAN resin, a metal lubricant is added to improve uniform dispersion and release property of rubber particles. As the metal lubricant, stearate-based metal lubricants such as calcium stearate, barium stearate and magnesium stearate are used. In addition, internal lubricant is added to improve the physical properties by reducing friction between resins. As the internal lubricant, polyethylene wax or ethylene bis stearoamide is added. The use range of the lubricant is preferably 0.2 to 0.6 parts by weight for the metal lubricant, 1.0 to 2.0 parts by weight for the internal lubricant.

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

(A ₁ ) large particle size graft copolymer resin, (A ₂ ) small particle size graft copolymer resin, (B ₁ ) SAN resin, (B ₂ ) SAN resin, metal used in the following Examples and Comparative Examples The specifications of lubricant and internal lubricant are as follows.

(A ₁ ) large particle size graft copolymer resin

A rubber particle diameter of 0.3 mu m and a rubber content of 60 wt% were used.

(A ₂ ) Small particle size graft copolymer resin

A rubber particle diameter of 0.1 mu m and a rubber content of 50% by weight were used.

(B ₁ ) SAN resin

SAN resin having an acrylonitrile content of 35% by weight and a weight average molecular weight of 150,000 was used.

(B ₂ ) SAN resin

A SAN resin having an acrylonitrile content of 32% by weight and a weight average molecular weight of 80,000 was used.

(C) metal lubricants

0.4 parts by weight of magnesium stearate was used as a metal lubricant based on 100 parts by weight of the base resin composed of the graft copolymer resin (A) and the SAN resin (B).

(D) internal lubricant

Ethylene bis stearamide was used in an amount of 2.0 parts by weight based on 100 parts by weight of the base resin.

Example 1-5

A large particle size graft copolymer resin (A ₁ ) having a rubber particle diameter of 0.3 μm and a rubber content of 60 wt%, a small particle size graft copolymer resin having a rubber particle diameter of 0.1 μm and a rubber content of 50 wt% ( a _2), a 35% by weight of acrylonitrile content and having a weight average molecular weight of 150,000 of SAN resin (B _1), 32% by weight of the nitrile content of acrylic and base made of SAN resin (B ₂₎ of the 80,000 weight average molecular weight 0.4 parts by weight of magnesium stearate (lubricant 1) and 2.0 parts by weight of ethylene bis stearamide (lubricant 2) were mixed with 100 parts by weight of the resin, and melted using a twin screw extruder having an L / D = 32 and a diameter of 45 mm. Pellets were prepared by kneading extrusion at -220 ° C.

Comparative Example 1-5

Specimens were prepared in the same manner as in Example 1-5 except for changing the composition of each component as described in Table 1.

ingredient Example Comparative Example One 2 3 4 5 One 2 3 4 5 (A ₁ ) large particle size graft copolymer resin 20 25 20 15 15 30 0 45 20 20 (A ₂ ) Small particle size graft copolymer resin 10 15 5 10 10 0 30 0 10 10 (B ₁ ) SAN resin 20 20 20 35 15 20 20 20 50 0 (B ₂ ) SAN resin 50 40 55 40 60 50 50 35 20 70 (C) metal lubricants 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 (D) internal lubricant 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

Physical properties of the pellets prepared above were measured by injection molding, and in the case of Examples, the physical properties were measured under the conditions shown in the following table. Izod notched impact strength was measured according to ASTM D256, and the flow index was measured based on ASTM D1238. In addition, the tensile strength was based on ASTM D638.

In the case of fatigue strength, it was measured by repeatedly applying a constant load or by repeatedly applying a tensile of a certain size. It was measured by the number of cycles until fracture and used a method such as tensile fatigue and bending fatigue depending on the purpose. The experiment is required to apply a constant stress repeatedly. Instron's universal tensile tester (5816 model) was used. Detailed test conditions are as follows. (① Measurement temperature conditions: Room temperature, ② Frequency: 10Hz, ③ Load ratio ( R): 0.1 (amplitude, that is, the ratio of minimum load to 100KG maximum load), ④ Specimen: tensile test specimen (W = 12.90mm, L = 58.00mm, T = 3.25mm, area = 41.93mm2)

Properties Example Comparative Example One 2 3 4 5 One 2 3 4 5 Izod notch impact strength (23 ° C, 1/4 ", kgcm / cm) 28 35 25 25 25 30 10 15 35 15 Fluidity (5 kg, 200 ° C, g / 10min) 3.0 2.5 3.5 2.5 4.0 3.0 3.0 5.0 1.0 6.0 Tensile Strength (kg / cm ² ) 450 430 450 450 450 450 500 500 450 450 Fatigue Strength (Max Stress, MPa) 30 35 35 30 30 20 10 20 35 15

As a result of measuring the physical properties, the comparative example 1 in which only the large-diameter graft copolymer resin was used and the small-diameter graft copolymer resin was not used had high impact strength, but the fatigue strength decreased. In Comparative Example 2, in which only a small particle size graft copolymer resin was used and no large particle size graft copolymer resin was added, the impact strength and fatigue strength were remarkably decreased, and a small particle size graft copolymer resin was used. In Comparative Example 3 containing relatively less SAN resin (B ₂ ), the fluidity and the tensile strength were high, but the impact strength and the fatigue strength were low. In Comparative Example 4, the impact strength and the fatigue strength are excellent, but there is a problem in that the fluidity is excessively reduced, so that molding is likely to occur in the molding process of the molded article. Lastly, in Comparative Example 5 without using the SAN resin (B ₁ ), the fluidity was high, but the impact strength and the fatigue strength were very low.

The present invention uses graft copolymer resins having different rubber particle sizes of graft copolymer resins prepared by emulsion polymerization method, and mixes SAN resins having different acrylonitrile content and molecular weight among SAN resins used as a matrix. The thermoplastic resin composition can be widely used in electrical and electronic parts, automobile parts, etc., which is excellent in fatigue strength and maintains high rigidity, and can be used as a material for operating parts of home appliances that require fatigue strength characteristics. Has a useful effect to provide.

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 (3)

(A) Large particle size graft copolymer resin (A ₁ ) having an average particle diameter of 0.20-0.40 μm (A ₁ ) 60-90 wt% and small particle size graft copolymer resin (A ₂ ) having an average particle diameter of 0.1-0.20 μm 40 20-40 parts by weight of graft copolymer resin consisting of -10% by weight; (B) 20-40 parts by weight of a SAN resin (B ₁ ) having an acrylonitrile content of 30-40% by weight and a weight average molecular weight of 140,000-180,000, and an average of 300,000% by weight of an acrylonitrile content of 70,000 60-80 parts by weight of SAN resin consisting of 40-60 parts by weight of SAN resin (B ₂ ) which is -120,000; Thermoplastic resin composition excellent in fatigue strength, characterized in that consisting of. The method according to claim 1, wherein 0.2 to 0.6 parts by weight of the metal lubricant and 1.0 to 2.0 parts by weight of the internal lubricant are further added to the components, and the metal lubricant is a stearate metal of calcium stearate, barium stearate, magnesium stearate. It is selected from the group consisting of a lubricant, the inner lubricant is polyethylene wax or ethylene bis stearoamide (ethylene bis stearoamide), characterized in that the excellent fatigue strength thermoplastic resin composition. Molded article manufactured using the resin composition of claim 1.