KR100909099B1 - Polypropylene-Polystyrene Blend Composition with Enhanced Stiffness and Scratch Resistance - Google Patents

Abstract

The present invention is a composition comprising a certain amount of crystalline ethylene-propylene copolymer, ethylene-α-olefin copolymer, polystyrene, styrene copolymer elastomer, inorganic filler, and modified polypropylene, the composition is incompatible polypropylene Polypropylene-polystyrene blend composition, which improves the compatibility of polystyrene with polystyrene, maintains flexural modulus, heat deformation temperature and scratch resistance equivalent to that of the conventional one, and at the same time has excellent impact strength and improves price competitiveness. will be.

Description

Polypropylene-Polystyrene Blend of Improved Stiffness and Scratch Resistance}

The present invention is a composition comprising a certain amount of crystalline ethylene-propylene copolymer, ethylene-α-olefin copolymer, polystyrene, styrene copolymer elastomer, inorganic filler and modified polypropylene, the composition is incompatible with polypropylene The present invention relates to a polypropylene-polystyrene blend composition which is particularly useful for automobile exterior parts by improving the compatibility of polystyrene to maintain flexural modulus, heat deformation temperature, and scratch resistance equivalent to or higher than the conventional one, and at the same time, having excellent impact strength and improving cost competitiveness. .

Polypropylene is a rubbery material. Specifically, ethylene-propylene rubber, ethylene-butene rubber, ethylene-octene rubber, EPDM rubber, etc. are mainly used for automobile exterior parts, especially bumpers, through compounding with fillers. It should have a low coefficient of linear expansion in order to minimize the excellent impact strength and shrinkage with temperature change.

In order to satisfy the low temperature impact strength, a high content of rubber phase must be added, and it is essential to add a certain amount of filler to ensure a low coefficient of linear expansion. At this time, the addition of a large amount of rubbery phase and an appropriate amount of filler to the polypropylene has problems such as stiffness reduction, surface gloss reduction, scratch resistance reduction, etc., so that it is difficult to be applied to automotive exterior parts that do not require painting. It is true that coverage is very limited due to poor adhesion.

Meanwhile, although general-purpose polystyrene has excellent stiffness and heat resistance, it is not easy to be applied as a vehicle exterior material due to its weak impact strength, and thus acrylonitrile-butadiene- copolymerized with acrylic rubber and butadiene rubber in general-purpose polystyrene It is made of styrene resin (ABS), acrylate-styrene-acrylonitrile resin (ASA) and the like and has been used as automotive exterior parts.

Although polystyrene copolymers have excellent physical properties such as high stiffness, high gloss, high impact, heat sealability, and low coefficient of linear expansion, they are more expensive than polyolefin resins, in particular, polypropylene resins. The scope of application is difficult to expand.

Thus, various studies on polypropylene-polystyrene blends have been continuously conducted in order to highlight the advantages of the two resins and to compensate for the disadvantages. However, polypropylene, which is a crystalline resin, and polystyrene, which is an amorphous resin, do not have compatibility with each other, resulting in a sharp decrease in physical properties when blending the two resins.In order to solve this problem, an appropriate compatibilizer is used to improve the interfacial bonding strength of the two resins. You have to.

Compatibilizers to improve the compatibility of both resins include polypropylene resins grafted with unsaturated carboxylic acid or acid anhydride, styrene-butadiene-styrene block copolymers, styrene-ethylene-butylene block copolymers, and styrene-ethylene- Propylene-styrene block copolymers Styrene copolymers and the like have been mainly used.

The present invention is intended to provide a new low-cost material that can replace a lot of expensive materials to be able to be applied to the automotive material as a material showing a low cost and similar physical properties instead of expensive materials due to the improvement of automotive structural design capability. The present invention provides a new polypropylene-polystyrene blend composition having a relatively simple manufacturing process, having a suitable physical property to be applied to automotive exterior materials, and added with a compatibilizer.

The present invention (a) 30 to 70% by weight of the crystalline ethylene-propylene copolymer; (b) 5 to 20 weight percent ethylene-α-olefin copolymer having an octene content of 25 to 50% by weight, a Mooney viscosity of 5 to 50 ML1 + 4 (121 ° C), and a glass transition temperature of -65 to -50 ° C. %; (c) 5 to 30 weight percent of polystyrene; (d) 5 to 20% by weight of a styrene copolymer elastomer having a styrene content of 0.5 to 50% by weight; (e) 5 to 30% by weight of an inorganic filler having an average particle size of 0.5 to 10 µm; And (f) 1 to 10% by weight of modified polypropylene grafted with unsaturated carboxylic acid or acid anhydride, which is characterized by a polypropylene-polystyrene blend composition having excellent rigidity and scratch resistance.

In addition, the present invention has another feature of the automotive exterior material manufactured by applying the polypropylene-polystyrene blend composition.

The polypropylene-polystyrene blend composition of the present invention has high stiffness, scratch resistance, high impact resistance, excellent moldability and thermal properties, and thus can be widely used in automobile exterior parts, especially side mirror peripheral parts and home appliances.

The present invention (a) crystalline ethylene-propylene copolymer; (b) an ethylene-α-olefin copolymer having an octene content of 25 to 50% by weight, a Mooney viscosity of 5 to 50 ML1 + 4 (121 ° C), and a glass transition temperature of -65 to -50 ° C; (c) polystyrene; (d) a styrene copolymer elastomer having a styrene content of 0.5 to 50% by weight; (e) inorganic fillers having an average particle size of 0.5 to 10 μm; And (f) a polypropylene-polystyrene blend composition comprising a fixed amount of modified polypropylene grafted with unsaturated carboxylic acids or acid anhydrides.

Such a polypropylene-polystyrene blend composition has flexural modulus, heat deformation temperature and scratch resistance equivalent to or higher than that of each of conventional polypropylene, polystyrene, and the like, and at the same time has excellent impact strength, and is particularly useful for automobile exterior materials.

Looking more specifically at the polypropylene-polystyrene blend composition according to the present invention.

(a) The crystalline ethylene-propylene copolymer is generally used in the art and is not particularly limited, but specifically, the content of the ethylene monomer is 1 to 10% by weight, preferably 3 to 8% by weight, and a weight average molecular weight Is 100,000 to 400,000 g / mol, and the isotactic index of propylene in the copolymer is at least 96%, preferably at least 97% by C13-NMR measurement, and a melt flow index of 0.5 at a temperature of 2.16 kg and 230 ° C. It is good to use what is-100 g / 10min, Preferably it is 5-40g / 10min.

In this case, when the ethylene monomer content is less than 1% by weight, the impact strength of the molded product is lowered. When the content of the ethylene monomer is more than 10% by weight, the rigidity and scratch resistance of the molded product is lowered. When the weight average molecular weight is less than 100,000 g / mol, the mechanical property decreases. And, if it exceeds 400,000 g / mol, molded article appearance quality problems occur. In addition, when the isotactic index is less than 96%, the rigidity and surface hardness of the molded article are not satisfactory, and when the melt flow index is less than 5 g / 10 minutes, fluidity and formability are deteriorated, and when the isotactic index is less than 40 g / 10 minutes, In this case, the impact property of the molded article is significantly reduced.

The crystalline ethylene-propylene copolymer is used in an amount of 30 to 70 wt%, preferably 45 to 65 wt%, but if it is less than 30 wt%, moldability is lowered, and if it exceeds 70 wt%, impact strength is lowered.

(b) The ethylene-α-olefin copolymer is generally used in the art, and is not particularly limited, but may be specifically copolymerized under a metallocene catalyst. This ethylene-α-olefin copolymer has an octene content of 20 to 50% by weight, preferably 30 to 45% by weight, and a Mooney viscosity of 5 to 50 ML1 + 4 at 121 ° C., preferably 20 to 40 ML1 + 4. The glass transition temperature is -65 ~ -50 ℃, preferably -60 to -55 ℃ range can be used.

When the octene content is less than 20% by weight, the impact compensating effect is reduced, and when the content of the octene is more than 50% by weight, rigidity, scratch resistance and moldability problems occur. When exceeding, since there exists a problem of inferior workability, it is preferable to maintain the said range. Moreover, when glass transition temperature is less than -65 degreeC, rigidity and heat resistance will fall, and when exceeding -50 degreeC, there exists a problem that low temperature impact resistance falls.

The ethylene-α-olefin copolymer is used in the range of 5 to 20% by weight, preferably 8 to 15% by weight. When the amount is less than 5% by weight, the impact strength is lowered. Since heat resistance falls, it is preferable to maintain the said range.

(c) Polystyrene is generally used in the art, and general-purpose polystyrene polymerized with styrene monomers alone may be used. These polystyrenes specifically have a weight average molecular weight of 20,000 to 100,000 g / mol, preferably 50,000 to 70,000 g / mol, and a melt flow index of 0.1 to 100 g / 10 minutes (230 ° C., 2.16 kg). 5-30 g / 10min. Is used. If the weight average molecular weight is less than 20,000 g / mol leads to a decrease in stiffness and scratch resistance, when the weight average molecular weight exceeds 100,000 g / mol impact impact problem occurs, if the melt flow index is less than 0.1 g / 10 minutes workability If it falls and exceeds 100 g / 10min, the problem that impact strength falls occurs is preferable to maintain the said range.

(d) Styrene copolymer elastomer having a styrene content of 0.5 to 50% by weight, preferably 10 to 30% by weight, can be used generally in the art, and if the styrene content is less than 0.5% by weight, rigidity And scratch resistance falls, and when it exceeds 50 weight%, impact strength and heat resistance are inferior. Specifically, the styrene copolymer elastomer may use styrene-ethylene-butylene-styrene, styrene-butadiene-styrene, styrene-butadiene-butylene-styrene elastomers, and preferably, styrene-ethylene-butylene-styrene elastomer It is good to use

The styrene copolymer elastomer is used in the range of 5 to 20% by weight, preferably 8 to 15% by weight. When the amount is less than 5% by weight, the impact strength drops, and when the amount exceeds 20% by weight, the strength and heat resistance decreases. It is preferable to maintain the above range because there is a problem.

(e) Inorganic fillers having an average particle size of 0.5 to 10 μm are added for rigid reinforcement. When the average particle size is less than 0.5 μm, feeding problems and dispersibility decrease during compounding, and exceed 10 μm. In this case, a problem of deterioration of physical properties occurs, so it is preferable to maintain the above range. The inorganic fillers are generally used in the art, and specifically, talc, olastonite, barium sulfate, calcium carbonate, silica, whiskers, and the like may be used.

Since the inorganic filler is used in the range of 5 to 30% by weight, preferably 15 to 25% by weight, when the amount is less than 5% by weight, the stiffness and heat resistance are lowered, and when the amount exceeds 30% by weight, the impact strength is lowered. It is preferable to maintain the above range.

(f) Modified polypropylenes grafted with unsaturated carboxylic acids or acid anhydrides are polypropylenes containing unsaturated carboxylic acids such as maleic anhydride, maleic acid, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, cinamic acid, citraconic acid, and the like. Grafted with acid or acid anhydride can be used. The graft ratio is 0.5 to 5% by weight, preferably 1 to 3% by weight, and the graft ratio is less than 0.5% by weight, the compatibility between the resin is lowered, if it exceeds 5% by weight the physical properties are lowered in the above range It is desirable to maintain. In addition, the modified polypropylene may have a weight average molecular weight of 2,000 to 50,000 g / mol, preferably 5,000 to 30,000 g / mol, and when it is out of the above range, the physical properties are deteriorated to maintain the above range desirable.

The modified polypropylene is used in an amount of 1 to 10% by weight, preferably 3 to 5% by weight. If the amount is less than 1% by weight, the modified polypropylene may not function properly as a compatibilizer. And disadvantages in terms of economics, it is desirable to maintain the above range.

In the case of using only the styrene copolymer elastomer alone, the compatibility with polypropylene is reduced, resulting in deterioration of physical properties. Therefore, the mixture is used simultaneously with the polypropylene having polarity while being compatible with the modified polypropylene (f). In this case, the compatibility between the two resins is exhibited without deteriorating the mechanical properties.

In addition, in order to improve the performance and processing characteristics of the molded article, additives commonly used in the art, specifically, primary and secondary antioxidants, ultraviolet absorbers, light stabilizers, pigments, dispersants, nucleating agents, processing lubricants and coupling agents, etc. are added. Can be used. Such additives may be added and used within the range of maintaining the physical properties for which the present invention is aimed. Specifically, the additive is used in the range of 0.1 to 5 parts by weight based on 100 parts by weight of the polypropylene-polystyrene blend composition. If it is less than 0.1 part by weight, the inherent purpose of the additive cannot be performed, and if it exceeds 5 parts by weight, it is preferable to maintain the above range because a problem of deterioration of physical properties of the product occurs.

On the other hand, the polypropylene-polystyrene blend composition of the present invention can be produced by performing a method commonly used in the art bar to look more specifically, after mixing uniformly in a super mixer, uniaxial and biaxial It can manufacture using melt kneading machines, such as an extruder, a short-barrier mixer, and a need. The present invention uses a twin screw extruder to prepare a sample under the conditions of rotational speed 100 ~ 300 rpm at a temperature of 180 ~ 220 ℃. At this time, the temperature and the number of rotations can be appropriately adjusted according to the composition ratio of the components presented above.

The composition prepared in this manner has a flexural modulus (kg _f / cm ² ) of 20,000 ~ 24,000, IZOD impact strength (23 ℃) (kg _f · cm / cm) of 10 ~ 14 range, heat deformation temperature ( ° C) is 120 to 125, and scratch resistance (water supply) is maintained in the range of 3.0 to 3.5.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Examples 1-4 and Comparative Examples 1-5

Next, a polypropylene-polystyrene blend composition is prepared according to the composition ratio of the following Table 9 using the raw materials shown in Tables 3 to 8, and the resin composition is injected at a cylinder temperature of 220 ° C. and a mold temperature of 50 ° C. using an injection molding machine. Molded to prepare a test piece.

The test specimens prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were measured using the following physical property measurement methods, and the results are shown in Table 7 below. At this time, the results of the physical properties of the seven specimens were measured to represent the average value excluding the upper limit and the lower limit, the test method for this is as follows.

[Measurement of physical properties]

(1) Flexural modulus: measured according to ASTM D 790. The specimen thickness was 6.2 mm, the measurement speed was 10 mm / min, and the measurement unit was kg _f / cm ² .

(2) Izod impact strength was measured according to ASTM D256. The specimen thickness was 6.2 mm, and the notch was measured using a notch, and the unit of measurement was kg _f ㅇ cm / cm.

(3) Heat deflection temperature: measured according to ASTM D648. Specimen thickness was 6.2 mm, measured under 4.6 kg _f stress, and the measurement unit was ℃.

(4) Scratch resistance: Measured according to JIS K3718. After scratching the surface of the test piece produced using a scratch-resistant measuring instrument under the conditions of Table 1, the surface state is evaluated by Table 2.

In addition, Tables 3 to 8 show the physical properties of the components used in Examples 1 to 4 and Comparative Examples 1 to 5 in detail.

As shown in Table 9, the polypropylene-polystyrene blend composition prepared in Examples 1 to 4 according to the present invention is the use of the polypropylene and polystyrene of Comparative Examples 1 to 8, respectively, and the physical property ranges of the present invention. Compared with the case of using a component deviating from, it was confirmed that the impact strength, flexural modulus, heat deformation temperature, and scratch resistance equal to or more than the conventional, and particularly excellent impact strength.

Claims (7)

(a) 30 to 70% by weight of the crystalline ethylene-propylene copolymer; (b) 5 to 20 wt% of an ethylene-α-olefin copolymer having an octene content of 25 to 50 wt%, a Mooney viscosity of 5 to 50 ML1 + 4 (121 ° C), and a glass transition temperature of -65 to -50 ° C; %, (c) 5 to 30% by weight of polystyrene; (d) 5 to 20% by weight of a styrene copolymer elastomer having a styrene content of 0.5 to 50% by weight; (e) 5 to 30% by weight of an inorganic filler having an average particle size of 0.5 to 10 µm; And (f) 1 to 10% by weight of modified polypropylene grafted with unsaturated carboxylic acid or acid anhydride Polypropylene-polystyrene blend composition excellent in rigidity and scratch resistance, characterized in that it comprises. The polypropylene-polystyrene blend composition of claim 1, wherein the polystyrene has a weight average molecular weight of 20,000 to 100,000 g / mol and a melt flow index of 0.1 to 100 g / 10 minutes (230 ° C., 2.16 kg). . The polypropylene-polystyrene blend composition of claim 1, wherein the styrene copolymer elastomer is selected from styrene-ethylene-butylene-styrene, styrene-butadiene-styrene and styrene-butadiene-butylene-styrene elastomers. 2. The polypropylene-polystyrene blend composition of claim 1, wherein the inorganic filler is selected from talc, olastonite, barium sulfate, calcium carbonate and silica. The method of claim 1, wherein the modified polypropylene is A polypropylene-polystyrene blend composition, characterized in that the polypropylene homo- or copolymer is grafted with an unsaturated carboxylic acid or acid anhydride in the range of 0.5 to 5.0% by weight. The polypropylene-polystyrene blend composition of claim 1, further comprising an antioxidant, a ultraviolet absorber, a light stabilizer, a pigment, a dispersant, a nucleating agent, a processing lubricant, a coupling agent, a coloring agent, and a nucleating agent. An automotive exterior material manufactured by applying the polypropylene-polystyrene blend composition of any one of claims 1 to 6.