KR20200039300A - Polypropylene resin composition for an automotive exterior part and article foam-molded therefrom - Google Patents

Abstract

The present invention relates to a polypropylene resin composition and a molded article produced therefrom. The polypropylene resin composition according to an embodiment of the present invention is not only excellent in mechanical properties, but also has a good appearance of a foamed surface, and can produce a foam-molded article excellent in water resistance after coating. Therefore, the polypropylene resin foam-molded article according to an embodiment of the present invention can be effectively used for automotive exterior materials, etc. The polypropylene resin composition includes polypropylene-based resins, polyethylene-based resins, thermoplastic elastomers, inorganic fillers and blowing agents.

Description

Polypropylene resin composition for automobile exterior material and foamed molded article manufactured therefrom {Polypropylene resin composition for an automotive exterior part and article foam-molded therefrom}

The present invention relates to a polypropylene resin composition and a molded article produced therefrom. In detail, the present invention relates to a foamed molded article for a vehicle exterior material having a polypropylene resin composition for a vehicle exterior material and a foam molding formed therefrom, as well as having excellent mechanical properties, good appearance of a foam surface, and excellent water resistance after painting. will be.

In order to improve the fuel efficiency of automobiles and reduce carbon dioxide, studies on automobile weight reduction have been continuously conducted. In this regard, research on low specific gravity materials such as plastic materials for replacing metal materials has been actively conducted.

Conventionally, polyvinylchloride has been widely used as a vehicle interior material such as a door trim or dashboard, but polyvinyl chloride has a problem of discharging harmful substances in a specific environment, and is a kind of thermoplastic polyolefin-based polypropylene. Attempts have been made to use as a material for automotive interior materials. For example, Korean Patent No. 1843748 discloses a polypropylene resin composition for automobile interior materials having excellent appearance after foam injection using sodium phosphate-based nucleating agent.

On the other hand, while various automobile interior materials have been developed using a low specific gravity plastic material such as polypropylene, research on applying plastic materials to automotive exterior materials is still limited. For example, Korean Patent No. 1845448 discloses a polypropylene resin composition for interior and exterior materials of automobiles including a polypropylene resin, a fiber reinforcement agent, and a foaming agent.

However, the foamed plastic material generally has a problem in that water resistance is poor after coating parts by a gas used during foaming. For example, when an automobile exterior material made of foamed plastic is exposed to a certain temperature and humidity after painting, there may be a case in which appearance defects such as projections occur on the painting surface.

Accordingly, there is a demand for development of a polypropylene resin composition for an automotive exterior material having a good appearance on a foamed surface and excellent water resistance after painting.

Republic of Korea Patent No. 1843748 Republic of Korea Patent No. 1845448

Accordingly, it is an object of the present invention to provide a polypropylene resin composition capable of producing a foamed molded article having excellent mechanical properties, good appearance of a foamed surface, and excellent water resistance after painting.

Another object of the present invention is to provide a molded article manufactured by foam molding from the above polypropylene resin composition, specifically, a polypropylene resin foam molded article suitable for use as an exterior material for automobiles.

According to an embodiment of the present invention for achieving the above object, based on the total weight of the components (A) to (D) below, (A) 32 to 90% by weight of a polypropylene-based resin; (B) 1 to 15% by weight of a polyethylene-based resin; (C) 1 to 20% by weight of a thermoplastic elastomer; And (D) 1 to 20% by weight of an inorganic filler, and further comprising (E) 1 to 5 parts by weight of a blowing agent with respect to 100 parts by weight of the components (A) to (D), but a polypropylene-based resin (A). ), Based on the total weight of the components (A) to (D), (A1) 30 to 60% by weight of the first ethylene-propylene block copolymer resin; (A2) 1 to 15% by weight of a second ethylene-propylene block copolymer resin; And (A3) 1 to 15% by weight of a rubber-containing polypropylene resin, wherein the second ethylene-propylene block copolymer resin has a lower melt index than the first ethylene-propylene block copolymer resin. A resin composition is provided.

The first ethylene-propylene block copolymer resin (A1) may have a melt index of 50 to 70 g / 10 min when measured at 210 ° C under a load of 2.16 kg.

The second ethylene-propylene block copolymer resin (A2) may have a melt index of 20 to 30 g / 10 min when measured at 210 ° C under a load of 2.16 kg.

Preferably, the rubber-containing polypropylene resin (A3) is a rubber-made polypropylene (R-TPO) resin produced directly in a reactor, and the melt index is 5 to 15 when measured at 210 ° C under a load of 2.16 kg. It can be g / 10 minutes.

The polyethylene-based resin (B) is at least one selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (linear low density polyethylene; LLDPE), When measured at 190 ° C under a 2.16 kg load, the melt index may be between 2.0 and 5.0 g / 10 min.

The thermoplastic elastomer (C) is a rubber or styrene-olefin-based rubber copolymerized with ethylene and α-olefin having 4 to 8 carbon atoms, and may have a melt index of 0.5 to 20.0 g / 10 minutes when measured at 190 ° C under a load of 2.16 kg. Specifically, the thermoplastic elastomer (C) is ethylene-1-butene rubber, ethylene-butylene rubber, ethylene-1-pentene rubber, ethylene-1-hexene rubber, ethylene-1-heptene rubber, and ethylene-1-octene rubber. It may be one or more selected from the group consisting of styrene-ethylene-butylene-styrene rubber, styrene-butadiene-styrene rubber, styrene-isoprene-styrene rubber and styrene-butadiene rubber. .

The inorganic filler (D) may be at least one selected from the group consisting of talc, mica, wollastonite, clay, calcium carbonate, and barium sulfate.

The blowing agent (E) may be a master batch of azodicarbonamide with low density polyethylene (LDPE) as the matrix.

The polypropylene resin composition according to an embodiment of the present invention, with respect to 100 parts by weight of the components (A) to (D), 3 parts by weight or less of heat stabilizer, reinforcing material, filler, weathering stabilizer, antistatic agent, lubricant, slip agent, It may further include at least one additive (F) selected from the group consisting of nucleating agents, flame retardants, pigments and dyes.

Specifically, the polypropylene resin composition according to an embodiment of the present invention, with respect to 100 parts by weight of the components (A) to (D), may further include 0.05 to 0.2 parts by weight of the heat stabilizer, the heat stabilizer is tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylnate), 1,3,5-trimethyl-tris (3,5-di-t-butyl-4-hydroxy benzene) and tris ( It may be one or more selected from the group consisting of 2,4-di-t-butylphenyl) phosphite.

According to another embodiment of the present invention, there is provided a polypropylene resin foam molded article produced by foam molding the above polypropylene resin composition.

The polypropylene resin foamed molded article according to the embodiment of the present invention may have a density of 0.8 g / cm ³ or less, a flexural strength of 25 MPa or more, a flexural modulus of 1,500 MPa or more, and an IZOD impact strength at room temperature of 100 J / m or more.

Preferably, the polypropylene resin foam molded article is an automotive exterior material.

The polypropylene resin composition according to the embodiment of the present invention is not only excellent in mechanical properties, but also has a good appearance of a foamed surface, and can produce a foamed article excellent in water resistance after painting. Therefore, the polypropylene resin foamed molded article according to an embodiment of the present invention can be effectively used as an exterior material for automobiles.

1 is a photograph showing the surface state after coating the specimen of Example 1 and testing the water resistance.
2 is a photograph showing the surface state after coating the specimen of Comparative Example 2 and testing the water resistance.
3 is a photograph of the thickness of the skin layer observed by an optical microscope after coating the specimen of Example 1.

Hereinafter, the present invention will be described in more detail.

Polypropylene resin composition according to an embodiment of the present invention, based on the total weight of the components (A) to (D) below, (A) 32 to 90% by weight of a polypropylene-based resin; (B) 1 to 15% by weight of a polyethylene-based resin; (C) 1 to 20% by weight of a thermoplastic elastomer; And (D) 1 to 20% by weight of an inorganic filler, and further comprising (E) 1 to 5 parts by weight of a blowing agent with respect to 100 parts by weight of the components (A) to (D), but a polypropylene-based resin (A). ), Based on the total weight of the components (A) to (D), (A1) 30 to 60% by weight of the first ethylene-propylene block copolymer resin; (A2) 1 to 15% by weight of a second ethylene-propylene block copolymer resin; And (A3) 1-15% by weight of a rubber-containing polypropylene resin, wherein the second ethylene-propylene block copolymer resin has a lower melt index than the first ethylene-propylene block copolymer resin.

(A) Polypropylene resin

Polypropylene-based resin (A) in the polypropylene resin composition according to an embodiment of the present invention, based on the total weight of the above components (A) to (D), (A1) 30 to 60% by weight of the first ethylene -Propylene block copolymer resin; (A2) 1 to 15% by weight of a second ethylene-propylene block copolymer resin; And (A3) 1 to 15% by weight of a rubber-containing polypropylene resin. Here, the second ethylene-propylene block copolymer resin (A2) has a lower melt index than the first ethylene-propylene block copolymer resin (A1).

The first ethylene-propylene block copolymer resin (A1) is a main component of the polypropylene resin composition according to an embodiment of the present invention, based on the total weight of the components (A) to (D), 30 to 60% by weight Content. The higher the content of the first ethylene-propylene block copolymer resin (A1), the better the appearance of the molded product produced through foam injection, but if it exceeds the above range, the water resistance of the molded product after painting is not preferable.

The first ethylene-propylene block copolymer resin (A1) preferably has a melt index of 50-70 g / 10 min when measured at 210 ° C under a load of 2.16 kg according to ASTM D1238. More preferably, the melt index of the first ethylene-propylene block copolymer resin (A1) may be 55 to 65 g / 10 minutes. When the melt index of the first ethylene-propylene block copolymer resin (A1) is within this range, a uniform foam can be obtained. If the melt index is less than 50 g / 10 min, the flowability of the resin composition may deteriorate and the appearance of the molded product may be poor. If the melt index exceeds 70 g / 10 min, the mechanical properties of the molded product It may degrade.

In addition, the first ethylene-propylene block copolymer resin (A1) may include a solvent extract in the range of 10 to 15% by weight. At this time, xylene is preferable as the solvent. The solvent extract in the first ethylene-propylene block copolymer resin (A1) may have a viscosity of 5 dl / g or more, preferably 5-9 dl / g.

On the other hand, the second ethylene-propylene block copolymer resin (A2) serves to ensure that each resin is mixed well when blending the polypropylene resin composition according to an embodiment of the present invention. The second ethylene-propylene block copolymer resin (A2) may be included in an amount of 1 to 15% by weight based on the total weight of the components (A) to (D). If the content of the second ethylene-propylene block copolymer resin (A2) is less than 1% by weight, the effect of mixing each resin is negligible, and when it exceeds 15% by weight, there is a possibility that the workability and flexural modulus of the resin composition decrease. It is not desirable.

The second ethylene-propylene block copolymer resin (A2) has a lower melt index than the first ethylene-propylene block copolymer resin (A1). Specifically, the second ethylene-propylene block copolymer resin (A2) preferably has a melt index of 20 to 30 g / 10 min when measured at 210 ° C under a load of 2.16 kg according to ASTM D1238. More preferably, the melt index of the second ethylene-propylene block copolymer resin (A2) may be 22 to 28 g / 10 minutes. When the melt index of the second ethylene-propylene block copolymer resin (A2) is within this range, a uniform foam can be obtained.

In addition, the second ethylene-propylene block copolymer resin (A2) may include a solvent extract in the range of 10 to 15% by weight. At this time, xylene is preferable as the solvent. The second ethylene-propylene block copolymer resin (A2) may have an ethylene content of 5 to 11% by weight.

The rubber-containing polypropylene resin (A3) is preferably a rubber-made polypropylene (R-TPO) resin produced directly in a reactor. The rubber-containing polypropylene resin (A3) is contained in an amount of 1 to 15% by weight, preferably 5 to 15% by weight, based on the total weight of the components (A) to (D). When the content of the rubber-containing polypropylene resin (A3) is less than 1% by weight, the surface appearance may be poor after coating of the molded article or the water resistance may not be sufficiently improved. On the other hand, when the content of the rubber-containing polypropylene resin (A3) exceeds 15% by weight, the impact strength is improved, but the flexural modulus may be lowered.

The rubber-containing polypropylene resin (A3) may have a melt index of 5 to 15 g / 10 minutes when measured at 210 ° C under a load of 2.16 kg according to ASTM D1238. Preferably, the melt index of the rubber-containing polypropylene resin (A3) may be 7 to 13 g / 10 minutes. When the melt index of the rubber-containing polypropylene resin (A3) is less than 5 g / 10 min, the flowability of the resin composition may deteriorate, resulting in poor appearance of the molded product, and when the melt index exceeds 15 g / 10 min. , Mechanical properties such as impact strength of molded products may be deteriorated.

Further, the rubber-containing polypropylene resin (A3) may include 20% by weight or more, preferably 20 to 30% by weight of a solvent extract. At this time, xylene is preferable as the solvent.

(B) Polyethylene resin

The polypropylene resin composition according to an embodiment of the present invention includes a polyethylene-based resin (B). In this case, the polyethylene-based resin (B) is at least one selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (linear low density polyethylene; LLDPE) You can. As the polyethylene-based resin (B), high-density polyethylene is most preferred.

The polyethylene-based resin (B) is contained in an amount of 1 to 15% by weight, preferably 5 to 10% by weight, based on the total weight of the components (A) to (D). If the content of the polyethylene-based resin (B) is less than 1% by weight, the surface appearance may be poor after coating of the molded article or the water resistance may not be sufficiently improved. On the other hand, when the content of the polyethylene-based resin (B) exceeds 15% by weight, the compatibility with the polypropylene-based resin (A) is poor and uniform extrusion may be difficult and the flexural modulus of the molded product may be deteriorated.

The polyethylene resin (B) may have a melt index of 2.0 to 5.0 g / 10 minutes when measured at 190 ° C under a 2.16 kg load according to ASTM D1238. Preferably, the melt index of the polyethylene-based resin (B) may be 2.0 to 4.0 g / 10 minutes. If the melt index of the polyethylene-based resin (B) is less than 2.0 g / 10, the flowability of the resin composition may deteriorate, and the appearance of the molded product may be poor. If the melt index exceeds 5.0 g / 10, the resin composition upon foaming There is a possibility that the foaming efficiency is lowered because the melting tension of is lowered.

The polyethylene-based resin (B) preferably has a narrow molecular weight distribution (MWD) of 6.5 or less as measured by gel permeation chromatography (GPC). More preferably, the polyethylene-based resin (B) has a molecular weight distribution of 4.0 to 6.0.

(C) thermoplastic elastomer

The polypropylene resin composition according to an embodiment of the present invention includes a thermoplastic elastomer (C). At this time, the thermoplastic elastomer (C) may be a rubber or a styrene-olefin-based rubber copolymerized with ethylene and α-olefin having 4 to 8 carbon atoms. Specifically, the thermoplastic elastomer (C) is ethylene-1-butene rubber, ethylene-butylene rubber, ethylene-1-pentene rubber, ethylene-1-hexene rubber, ethylene-1-heptene rubber, and ethylene-1-octene rubber. It may be one or more selected from the group consisting of styrene-ethylene-butylene-styrene rubber, styrene-butadiene-styrene rubber, styrene-isoprene-styrene rubber and styrene-butadiene rubber. . As the thermoplastic elastomer (C), ethylene-1-octene rubber is most preferred.

The thermoplastic elastomer (C) is contained in an amount of 1 to 20% by weight based on the total weight of the components (A) to (D). If the content of the thermoplastic elastomer (C) is less than 1% by weight, the impact strength of the foamed molded article may not be sufficient, so it may not be suitable for use as an automotive exterior material. On the other hand, if the content of the thermoplastic elastomer (C) exceeds 20% by weight, the rigidity of the foamed molded article is poor, which is undesirable.

The thermoplastic elastomer (C) may have a melt index of 0.5 to 20.0 g / 10 minutes when measured at 190 ° C under a load of 2.16 kg according to ASTM D1238. Preferably, the melt index of the thermoplastic elastomer (C) may be 0.5 to 15.0 g / 10 minutes. If the melt index of the thermoplastic elastomer (C) is too low, poor molding or appearance defects such as flow marks may occur. If the melt index is too high, mechanical properties such as impact strength of the molded product may deteriorate.

(D) inorganic filler

The polypropylene resin composition according to an embodiment of the present invention includes an inorganic filler (D). The inorganic filler (D) may be at least one selected from the group consisting of talc, mica, wollastonite, clay, calcium carbonate, and barium sulfate. Talc is most preferred as the inorganic filler (D).

The inorganic filler (D) is contained in an amount of 1 to 20% by weight based on the total weight of the components (A) to (D). If the content of the inorganic filler (D) is less than 1% by weight, the physical properties of the foamed molded article by the inorganic filler and the effect of increasing the foaming rate are low, which is undesirable. On the other hand, if the content of the inorganic filler (D) exceeds 20% by weight, the rigidity of the foamed molded body is increased, but the impact strength is rapidly lowered, which is not suitable for use as an automotive exterior material.

(E) blowing agent

The polypropylene resin composition according to an embodiment of the present invention further includes a blowing agent (E). The blowing agent (E) is pre-mixed with the components (A) to (D) described above and then decomposed in the cylinder of the injection molding machine to generate gases such as carbon dioxide gas and nitrogen, azodicarbonamide, dinitro Organic chemical blowing agents such as dinitrosopentatetramine, dinitrosopentamethylenetetramine (DPT), and p, p-oxybisbenzenesulfonylhydrazide (OBSH) are preferred. Do. The foaming agent (E) is most preferably a master batch of azodicarbonamide with low density polyethylene (LDPE) as the matrix.

The blowing agent (E) is added in an amount of 1 to 5 parts by weight, preferably 2 to 4 parts by weight, based on 100 parts by weight of the components (A) to (D). If the content of the foaming agent (E) is less than 1 part by weight, it is difficult to expect a sufficient foaming effect, and when it exceeds 5 parts by weight, it is not preferable because there is a possibility of negatively affecting the strength of the foamed molded article.

(F) additive

The polypropylene resin composition according to the embodiment of the present invention may further include a conventional additive (F) within a range not departing from the scope of the present invention. For example, the polypropylene resin composition may include, but is not limited to, heat stabilizers, reinforcing materials, fillers, weathering stabilizers, antistatic agents, lubricants, slip agents, nucleating agents, flame retardants, pigments and dyes. At this time, the additive (F) may be added in an amount of 3 parts by weight or less based on 100 parts by weight of the components (A) to (D).

Preferably, the polypropylene resin composition according to an embodiment of the present invention may further include a heat stabilizer to increase its heat stability. At this time, the heat-resistant stabilizer, based on 100 parts by weight of the components (A) to (D), may be added in an amount of 0.05 to 0.2 parts by weight, preferably 0.05 to 0.1 parts by weight. If the content of the heat stabilizer is less than 0.05 parts by weight, heat resistance is lowered during extrusion / injection processing, resulting in reduced foaming efficiency due to oxidation and poor appearance. On the other hand, when the content of the heat stabilizer exceeds 0.2 parts by weight, the heat stabilizer may elute or the economics of the product may deteriorate, which is not preferable.

As the above heat stabilizer, a phenol-based antioxidant, a phosphite-based antioxidant, or the like may be used. Specifically, tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylate), tetra Keith (methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate) methane, 1,3,5-trimethyl-tris (3,5-di-t-butyl-4-hydroxy benzene) And tris (2,4-di-t-butylphenyl) phosphite, but is not limited thereto.

There is no particular limitation on the method for manufacturing the polypropylene resin composition according to the embodiment of the present invention, and the method for manufacturing the polypropylene resin composition known in the art to which the present invention pertains may be used as it is or by appropriately modifying it.

Preferably, the resin components (A to C) constituting the polypropylene resin composition according to the embodiment of the present invention, an inorganic filler (D) and, if necessary, an additive (F) are melt-blended. For example, these components are put into a single-screw / two-screw extruder as necessary, and melt-blended at a temperature of 170 to 250 ° C to pelletize.

Subsequently, the obtained polypropylene resin pellets and the master batch type blowing agent (E) are added to a kneader such as a kneader, roll, or Banbury mixer as necessary, followed by dry blending at room temperature. , It is possible to prepare a polypropylene resin composition according to an embodiment of the present invention.

According to another embodiment of the present invention, there is provided a polypropylene resin foamed molded article produced by foam molding the polypropylene resin composition of the present invention.

There is no particular limitation on a method for producing a molded article from a polypropylene resin composition according to an embodiment of the present invention, and methods known in the art to which the present invention pertains can be used. For example, a polypropylene resin foamed molded article may be manufactured by molding the polypropylene resin composition according to an embodiment of the present invention by a conventional method such as foam injection molding, foam extrusion molding, foam press molding, and the like. Of these, foam injection molding is most preferred.

Preferably, the polypropylene resin composition according to an embodiment of the present invention can be foamed and injection molded to produce a foamed molded article. In this case, foam injection molding may be performed under conditions such as an injection temperature of 170 to 250 ° C, a mold temperature of 10 to 100 ° C, an injection speed of 10 to 300 mm / sec, and an injection pressure of 10 to 200 MPa.

The foam injection molding machine, unlike a general injection molding machine, has a shut-off nozzle to maintain the gas phase pressure dissolved and dispersed in the cylinder and a gate valve that allows gas to be trapped inside the mold. ) Must be installed. And for a high foaming rate, a high injection speed is required to increase the pressure difference between the cylinder and the mold.

Recently, in order to maximize the foaming rate in the mold, a core-back method in which a part of the mold is advanced / retracted, and after injection is completed, a part of the mold is retracted and foamed Use The foam produced by this method has a non-foaming layer formed on the surface to have a beautiful appearance, and a high-magnification foam made of uniform and fine foam pores is generated inside, and is excellent in lightness and rigidity.

The polypropylene resin foamed molded article according to the embodiment of the present invention has a beautiful appearance and excellent water resistance after painting, a density of 0.8 g / cm ³ or less, a flexural strength of 25 MPa or more, a flexural modulus of 1,500 MPa or more, and a room temperature of 100 J / m or more IZOD has impact strength.

The polypropylene resin foamed molded article according to the embodiment of the present invention is not only excellent in mechanical properties, but also has good foam surface appearance and excellent water resistance after painting, and thus can be effectively used as an automotive exterior material.

Example

Hereinafter, the present invention will be described in more detail through examples and comparative examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited to them.

The resins and compounds used in the following examples and comparative examples are as follows.

-Polypropylene resin A1: Ethylene-propylene block copolymer resin (melting index 60 g / 10 min, solvent extract content 12 wt%, solvent extract viscosity 8 dl / g)

-Polypropylene resin A2: Ethylene-propylene block copolymer resin (melting index 25 g / 10 min; solvent extract content 10 wt%, ethylene content 8 wt%)

-Polypropylene resin A3: R-TPO resin (melting index 10 g / 10 min, solvent extract content 24 wt%)

-Polyethylene resin B: High density polyethylene (melting index 2.2 g / 10 min, number average molecular weight 21,800, weight average molecular weight 118,000)

-Thermoplastic elastomer C: Ethylene-1-octene rubber (melting index 13 g / 10 min)

-Inorganic filler D: fine powder talc having an average particle diameter of 1 to 2 mu m

-Foaming agent E1: Azodicarbonamide masterbatch with low density polyethylene as matrix

-Foaming agent E2: inorganic foaming agent mainly containing sodium bicarbonate

-Additive F: tetrakis (methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate) methane or tris (2,4-di-t-butylphenyl) phosphite

Manufacturing example

The resin and inorganic fillers of the type and content (unit: parts by weight) shown in Table 1 below are melt-blended at 220 ° C. in a twin screw extruder and pelletized. A specimen was prepared for.

In addition, the pellets and foaming agent obtained above were dried and blended at room temperature using a ribbon mixer, followed by foam injection molding using a core-back method in an Engel E-MAX 440 / 180PRO injection machine to prepare specimens of ASTM standards. Did.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Polypropylene resin (A1) 48 48 62 62 Polypropylene resin (A2) 10 10 10 10 Polypropylene resin (A3) 7 7 - - Polyethylene resin (B) 7 7 - - Thermoplastic elastomer (C) 16 16 16 16 Inorganic filler (D) 12 12 12 12 Foaming agent (E1) 3 - - 3 Foaming agent (E2) - 3 3 - Heat stabilizer (F) 0.1 0.1 0.1 0.1

Test example

The injection molded specimens and the foam injection molded specimens of the polypropylene resin obtained in each of the Examples and Comparative Examples were tested in the following manner. The results are shown in Tables 2 and 3 below.

(1) density

It was measured according to ASTM D 792.

(2) Melt index (g / 10 min)

The melt index of the polypropylene resin was measured at 230 ° C under a load of 2.16 kg according to ASTM D1238, and the melt index of a polyethylene resin and a thermoplastic elastomer was measured at 190 ° C under a 2.16 kg load.

(3) Flexural modulus and flexural strength

It was measured according to ASTM D790. Specimen specifications were 12.7 mm x 127 mm x 6.4 mm, and the crosshead speed under test conditions was 30 mm / min.

(4) IZOD impact strength

It was measured at room temperature (23 ° C) and low temperature (-10 ° C) according to ASTM D256.

(5) Coating water resistance

After painting the foamed specimen, it was impregnated in a water bath maintained at 40 ° C for 10 days. Changes in the appearance of the specimens were visually observed and indicated as ○ if the surface was good and × if it was poor.

unit Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 density g / cm3 0.98 0.98 0.98 0.98 Flexural strength MPa 41 41 43 43 Flexural modulus MPa 2,150 2,150 2,320 2,320 Izod impact strength (23 ℃) J / m 210 210 185 185

unit Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 density g / cm3 0.76 0.75 0.77 0.76 Flexural strength (retention rate,%) MPa 29
(70.7) 28
(68.3) 30
(69.8) 29
(67.4) Flexural modulus (retention ratio,%) MPa 1,630
(75.8) 1,615
(75.1) 1,660
(71.6) 1,640
(70.7) Izod impact strength (23 ℃)
(Retention rate,%) J / m 116
(55.2) 112
(53.3) 88
(47.6) 83
(44.9) Water resistance after painting ○ × × △

As can be seen from Tables 1 to 3, in the case of Example 1 containing rubber-containing polypropylene resin (A3) and polyethylene-based resin (B) at the same time, mechanical after foaming compared to Comparative Examples 2 and 3 not containing them The retention rate of the characteristics was high. In addition, in the case of Example 1 using the azodicarbonamide blowing agent (E1), water resistance after coating was better than Comparative Example 1 using the inorganic blowing agent (E2) (see FIGS. 1 and 2).

Moreover, the foamed molded article prepared from the polypropylene resin composition of Example 1 containing rubber-containing polypropylene resin (A3) and polyethylene-based resin (B) at the same time and using an azodicarbonamide blowing agent (E1) had excellent mechanical properties. In addition, the thickness of the skin layer during coating was uniform (see FIG. 3), and water resistance after coating was excellent. Therefore, the polypropylene resin foamed molded article according to the embodiment of the present invention can be effectively used for exterior materials of automobiles.

Claims (14)

Based on the total weight of the components (A) to (D) below, (A) 32 to 90% by weight of a polypropylene-based resin; (B) 1 to 15% by weight of a polyethylene-based resin; (C) 1 to 20% by weight of a thermoplastic elastomer; And (D) 1 to 20% by weight of an inorganic filler, and further comprising (E) 1 to 5 parts by weight of a blowing agent with respect to 100 parts by weight of the components (A) to (D), but a polypropylene-based resin (A). ), Based on the total weight of the components (A) to (D), (A1) 30 to 60% by weight of the first ethylene-propylene block copolymer resin; (A2) 1 to 15% by weight of a second ethylene-propylene block copolymer resin; And (A3) 1 to 15% by weight of a rubber-containing polypropylene resin, wherein the second ethylene-propylene block copolymer resin has a lower melt index than the first ethylene-propylene block copolymer resin. Resin composition.
The polypropylene resin composition according to claim 1, wherein the first ethylene-propylene block copolymer resin (A1) has a melt index of 50 to 70 g / 10 min when measured at 210 ° C under a load of 2.16 kg.
The polypropylene resin composition according to claim 1, wherein the second ethylene-propylene block copolymer resin (A2) has a melt index of 20 to 30 g / 10 min when measured at 210 ° C under a load of 2.16 kg.
The rubber-containing polypropylene resin (A3) is a rubber-made polypropylene resin (R-TPO) produced directly in a reactor, and has a melt index of 5 when measured at 210 ° C under a load of 2.16 kg. Polypropylene resin composition, characterized in that ~ 15 g / 10 minutes.
The polyethylene resin (B) is at least one selected from the group consisting of high-density polyethylene, low-density polyethylene and linear low-density polyethylene, the melt index is 2.0 ~ 5.0 g when measured at 190 ℃ with a 2.16 kg load Polypropylene resin composition characterized in that it is / 10 minutes.
The thermoplastic elastomer (C) is a rubber or styrene-olefin-based rubber in which ethylene and α-olefin having 4 to 8 carbon atoms are copolymerized, and the melt index is 0.5 to 20.0 g when measured at 190 ° C under a load of 2.16 kg. Polypropylene resin composition characterized in that it is / 10 minutes.
The thermoplastic elastomer (C) is ethylene-1-butene rubber, ethylene-butylene rubber, ethylene-1-pentene rubber, ethylene-1-hexene rubber, ethylene-1-heptene rubber and ethylene-1- One or more selected from the group consisting of octene rubber or one selected from the group consisting of styrene-ethylene-butylene-styrene rubber, styrene-butadiene-styrene rubber, styrene-isoprene-styrene rubber and styrene-butadiene rubber. The polypropylene resin composition characterized by the above.
The polypropylene resin composition according to claim 1, wherein the inorganic filler (D) is at least one selected from the group consisting of talc, mica, wollastonite, clay, calcium carbonate and barium sulfate.
The polypropylene resin composition according to claim 1, wherein the blowing agent (E) is a master batch of azodicarbonamide with low density polyethylene (LDPE) as a matrix.
The method according to claim 1, wherein the components (A) to (D) with respect to 100 parts by weight of 3 parts by weight or less heat stabilizer, reinforcing material, filler, weathering stabilizer, antistatic agent, lubricant, slip agent, nucleating agent, flame retardant, pigment and dye A polypropylene resin composition further comprising at least one additive (F) selected from the group consisting of.
The component according to claim 10, further comprising 0.05 to 0.2 parts by weight of the heat stabilizer with respect to 100 parts by weight of the components (A) to (D), and the heat stabilizer is tetrakis -Hydroxy) hydrosilylnate), tetrakis (methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate) methane, 1,3,5-trimethyl-tris (3,5-di- Polypropylene resin composition, characterized in that at least one member selected from the group consisting of t-butyl-4-hydroxy benzene) and tris (2,4-di-t-butylphenyl) phosphite.
A polypropylene resin foamed molded article produced by foam molding the polypropylene resin composition according to claim 1.
The method of claim 12, 0.8 g / cm ³ A polypropylene resin foamed molded article characterized by having the following density, a flexural strength of 25 MPa or more, a flexural modulus of 1,500 MPa or more, and a normal temperature IZOD impact strength of 100 J / m or more.
The polypropylene resin foamed molded article according to claim 12, which is an exterior material of automobiles.

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