KR102166536B1 - 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 manufactured therefrom. The polypropylene resin composition according to an embodiment of the present invention not only has excellent mechanical properties, but also has a good appearance on the foaming surface, and can produce a foamed molded article having excellent water resistance after painting. Therefore, the polypropylene resin foam molded article according to an embodiment of the present invention can be effectively used for exterior materials of automobiles.

Description

Polypropylene resin composition for an automotive exterior part and article foam-molded 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 manufactured therefrom. In detail, the present invention relates to a polypropylene resin composition for automobile exterior materials and foam-molded products therefrom, and has excellent mechanical properties, good appearance of the foam surface, and excellent water resistance after painting. will be.

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

Conventionally, polyvinylchloride has been widely used as interior materials for automobiles such as door trims and dashboards, but polyvinyl chloride has a problem of releasing harmful substances in a specific environment, so polypropylene, a kind of thermoplastic polyolefin. Attempts are being made to use as a material for automobile interior materials. For example, Korean Patent No. 1843748 discloses a polypropylene resin composition for automobile interior materials having excellent appearance after foam injection using a sodium phosphate-based nucleating agent.

On the other hand, while various automobile interior materials are being developed using low-gravity plastic materials such as polypropylene, research on applying plastic materials to automobile exterior materials has yet to achieve limited results. For example, Korean Patent No. 1845448 discloses a polypropylene resin composition for automobile interior and exterior materials comprising a polypropylene resin, a fiber reinforcing agent, and a foaming agent.

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

Accordingly, there is a need for development of a polypropylene resin composition for automobile exterior materials having good appearance on the foaming surface and having excellent water resistance after painting.

Korean Patent No. 1843748 Korean 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 the foaming 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 following components (A) to (D), (A) 32 to 90% by weight of a polypropylene resin; (B) 1 to 15% by weight of a polyethylene resin; (C) 1 to 20% by weight of a thermoplastic elastomer; And (D) 1 to 20% by weight of an inorganic filler, and, based on 100 parts by weight of components (A) to (D), (E) further comprises 1 to 5 parts by weight of a foaming agent, polypropylene resin (A ) Is, based on the total weight of components (A) to (D), (A1) 30 to 60% by weight of a 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 minutes when measured at 210°C with 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 minutes when measured at 210° C. with a load of 2.16 kg.

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

Polyethylene 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 (LLDPE), When measured at 190°C with a load of 2.16 kg, the melt index may be 2.0-5.0 g/10 minutes.

The thermoplastic elastomer (C) is a rubber or styrene-olefin-based rubber in which ethylene and an α-olefin having 4 to 8 carbon atoms are copolymerized, and the melt index may be 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 at least one selected from the group consisting of or at least 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 inorganic filler (D) may be at least one selected from the group consisting of talc, mica, wollastonite, clay, calcium carbonate, and barium sulfate.

The foaming agent (E) may be a master batch of azodicarbonamide using LDPE as a matrix.

Polypropylene resin composition according to an embodiment of the present invention, based on 100 parts by weight of components (A) to (D), 3 parts by weight or less of a heat-resistant stabilizer, a reinforcing material, a filler, a weathering stabilizer, an antistatic agent, a lubricant, a slip agent, It may further include one or more additives (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 may further include 0.05 to 0.2 parts by weight of a heat-resistant stabilizer, based on 100 parts by weight of components (A) to (D), and the heat-resistant 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 manufactured by foam molding the above polypropylene resin composition.

The polypropylene resin foam molded article according to an 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 a room temperature IZOD impact strength of 100 J/m or more.

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

The polypropylene resin composition according to an embodiment of the present invention not only has excellent mechanical properties, but also has a good appearance on the foaming surface, and can produce a foamed molded article having excellent water resistance after painting. Therefore, the polypropylene resin foam 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 a surface condition after coating the specimen of Example 1 and performing a water resistance test.
2 is a photograph showing a surface condition after coating the specimen of Comparative Example 2 and performing a water resistance test.
3 is a photograph showing the thickness of the skin layer with 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 following components (A) to (D), (A) 32 to 90% by weight of a polypropylene resin; (B) 1 to 15% by weight of a polyethylene resin; (C) 1 to 20% by weight of a thermoplastic elastomer; And (D) 1 to 20% by weight of an inorganic filler, and, based on 100 parts by weight of components (A) to (D), (E) further comprises 1 to 5 parts by weight of a foaming agent, polypropylene resin (A ) Is, based on the total weight of components (A) to (D), (A1) 30 to 60% by weight of a 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) Polypropylene resin

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

The first ethylene-propylene block copolymer resin (A1) preferably has a melt index of 50 to 70 g/10 min when measured at 210°C with 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 minutes, the flowability of the resin composition may be lowered and the appearance of the molded article may be poor.If the melt index exceeds 70 g/10 minutes, the mechanical properties of the molded article It can be degraded.

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 preferred 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 to 9 dl/g.

Meanwhile, the second ethylene-propylene block copolymer resin (A2) serves to allow each resin to be well mixed 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 insignificant, and if it exceeds 15% by weight, the processability and flexural modulus of the resin composition may be lowered. 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 minutes when measured at 210°C with 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 preferred 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-containing polypropylene (reactor made thermoplastic polyolefin; R-TPO) resin produced directly in the 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). If the content of the rubber-containing polypropylene resin (A3) is less than 1% by weight, the surface appearance after coating of the molded article may be poor 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 decrease.

The rubber-containing polypropylene resin (A3) may have a melt index of 5 to 15 g/10 minutes when measured at 210°C with 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. If the melt index of the rubber-containing polypropylene resin (A3) is less than 5 g/10 minutes, the flowability of the resin composition may decrease and the appearance of the molded article may be poor, and if the melt index exceeds 15 g/10 minutes , Mechanical properties such as impact strength of molded products may be deteriorated.

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

(B) Polyethylene resin

The polypropylene resin composition according to an embodiment of the present invention includes a polyethylene-based resin (B). At this time, 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 (LLDPE). I can. High-density polyethylene is most preferred as the polyethylene resin (B).

The polyethylene-based resin (B) is included 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 after coating of the molded article may be poor or the improvement in water resistance may not be sufficient. On the other hand, if the content of the polyethylene-based resin (B) exceeds 15% by weight, uniform extrusion may be difficult due to poor compatibility with the polypropylene-based resin (A), and the flexural modulus of the molded product may be lowered.

Polyethylene resin (B) may have a melt index of 2.0 to 5.0 g/10 minutes when measured at 190°C with a load of 2.16 kg 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 be lowered and the appearance of the molded article may be poor.If the melt index exceeds 5.0 g/10, the resin composition during foaming There is a possibility that the foaming efficiency decreases because the melt tension of is lowered.

The polyethylene-based resin (B) preferably has a narrow molecular weight distribution (MWD) of 6.5 or less when measured by gel permeation chromatography (GPC). More preferably, the polyethylene 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 in which ethylene and an α-olefin having 4 to 8 carbon atoms are copolymerized or a styrene-olefin rubber. 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 at least one selected from the group consisting of or at least one 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 included in an amount of 1 to 20% by weight, based on the total weight of 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 is insufficient, and thus it may not be suitable for use as an automobile exterior material. On the other hand, if the content of the thermoplastic elastomer (C) exceeds 20% by weight, the stiffness of the foamed molded article is lowered, which is not preferable.

The thermoplastic elastomer (C) may have a melt index of 0.5 to 20.0 g/10 minutes when measured at 190°C with 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, molding defects or appearance defects such as flow marks may occur, and if the melt index is too high, mechanical properties such as impact strength of the molded product may be deteriorated.

(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. As the inorganic filler (D), talc is most preferred.

The inorganic filler (D) is included in an amount of 1 to 20% by weight, based on the total weight of components (A) to (D). If the content of the inorganic filler (D) is less than 1% by weight, the effect of improving the physical properties of the foamed molded article by the inorganic filler and increasing the foaming rate is low, which is not preferable. On the other hand, when the content of the inorganic filler (D) exceeds 20% by weight, the stiffness of the foamed molded article is increased, but the impact strength is rapidly deteriorated, which is not suitable for use as an automobile exterior material.

(E) blowing agent

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

The foaming 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 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 if it exceeds 5 parts by weight, it is not preferable because it may negatively affect 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 a heat-resistant stabilizer, a reinforcing material, a filler, a weather stabilizer, an antistatic agent, a lubricant, a slip agent, a nucleating agent, a flame retardant, a pigment, a dye, etc., but is not limited thereto. 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 components (A) to (D).

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

As the above heat-resistant stabilizer, a phenol-based antioxidant, a phosphite-based antioxidant, etc. can be used, specifically tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylnate), tetra Keith (methylene (3,5-di-t-butyl-4-hydroxyhydrocinamate) methane, 1,3,5-trimethyl-tris (3,5-di-t-butyl-4-hydroxy benzene) And tris (2,4-di-t-butylphenyl) may be one or more selected from the group consisting of phosphite, but is not limited thereto.

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

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

Subsequently, the obtained polypropylene resin pellets and the foaming agent (E) in the form of a master batch were added as needed in a kneader such as a kneader, roll, or Banbury mixer, and then dry blended 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 foam molded article manufactured by foam molding the polypropylene resin composition of the present invention.

There is no particular limitation on a method of manufacturing a molded article from the polypropylene resin composition according to an embodiment of the present invention, and a method known in the art may be used. For example, a polypropylene resin foam 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, and foam press molding. Among these, foam injection molding is most preferred.

Preferably, the polypropylene resin composition according to an embodiment of the present invention may be foamed and molded to manufacture a foamed molded article. In this case, the 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.

Unlike general injection molding machines, the foam injection molding machine has a shut-off nozzle for maintaining the pressure of the gas phase dissolved and dispersed in the cylinder and a gate valve for trapping the gas 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 retracted and foamed after the injection is completed, using a movable injection machine that can advance/retreat a part of the mold. Use The foam produced by this method has an unfoamed layer formed on the surface and has a beautiful appearance, and a foam having a high magnification consisting of uniform and fine foamed pores is produced inside, and is excellent in light weight and rigidity.

The polypropylene resin foam molded article according to an 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. It has IZOD impact strength.

The polypropylene resin foam molded article according to an embodiment of the present invention not only has excellent mechanical properties, but also has a good appearance on the foaming surface, and has excellent water resistance after painting, so that it can be effectively used as an automobile 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 thereto.

Resins and compounds used in Examples and Comparative Examples below 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% by weight, ethylene content 8% by weight)

-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 with an average particle diameter of 1 to 2 µm

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

-Foaming agent E2: Inorganic foaming agent whose main component is sodium bicarbonate

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

Manufacturing example

After melt-blending resins and inorganic fillers of the type and content (unit: parts by weight) as shown in Table 1 below at 220°C in a twin screw extruder to pelletize, measure mechanical properties using a TOYO injection molding machine (clamp force: 180 tons) A specimen was prepared for it.

In addition, after drying and blending the pellets and foaming agent obtained above at room temperature using a ribbon mixer, foam injection molding using a core-back method in an Engel E-MAX 440/180PRO injection machine to prepare a specimen of ASTM standard I 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-resistant stabilizer (F) 0.1 0.1 0.1 0.1

Test example

Injection-molded specimens and foam injection-molded specimens of 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, respectively.

(1) density

It was measured according to ASTM D 792.

(2) melt index (g/10min)

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

(3) Flexural modulus and flexural strength

It was measured according to ASTM D790. The specimen size was 12.7 mm × 127 mm × 6.4 mm, and the speed of the crosshead was 30 mm/min under the test conditions.

(4) IZOD impact strength

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

(5) Painting water resistance

After coating the foamed specimen, it was impregnated for 10 days in a water bath maintained at 40°C. Changes in the appearance of the specimen were observed with the naked eye, and if the surface condition was good, it was marked as ○ and if it was bad, it was marked as x.

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

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

Claims (14)

Based on the total weight of the following components (A) to (D), (A) 32 to 90% by weight of a polypropylene resin; (B) 1 to 15% by weight of a polyethylene resin; (C) 1 to 20% by weight of a thermoplastic elastomer; And (D) 1 to 20% by weight of an inorganic filler, and, based on 100 parts by weight of components (A) to (D), (E) further comprises 1 to 5 parts by weight of a foaming agent, polypropylene resin (A ) Is, based on the total weight of components (A) to (D), (A1) 30 to 60% by weight of a 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 minutes 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 minutes when measured at 210° C. under a load of 2.16 kg.
The method of claim 1, wherein the rubber-containing polypropylene resin (A3) is a rubber-containing polypropylene resin (reactor made thermoplastic polyolefin; R-TPO) produced directly in the reactor, and has a melt index of 5 when measured at 210°C with a load of 2.16 kg. Polypropylene resin composition, characterized in that ~ 15 g / 10 minutes.
The method of claim 1, wherein the polyethylene-based resin (B) is at least one selected from the group consisting of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, and has a melt index of 2.0 to 5.0 g when measured at 190°C with a load of 2.16 kg. Polypropylene resin composition, characterized in that /10 minutes.
The method of claim 1, wherein the thermoplastic elastomer (C) is a rubber or styrene-olefin-based rubber in which ethylene and an 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 /10 minutes.
The method of claim 6, wherein 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- At least one 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 Polypropylene resin composition, characterized in that 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 foaming agent (E) is a master batch of azodicarbonamide made of low-density polyethylene (LDPE) as a matrix.
According to claim 1, 3 parts by weight or less of a heat-resistant stabilizer, reinforcing material, filler, weather stabilizer, antistatic agent, lubricant, slip agent, nucleating agent, flame retardant, pigment and dye based on 100 parts by weight of components (A) to (D). Polypropylene resin composition, characterized in that it further comprises one or more additives (F) selected from the group consisting of.
The method of claim 10, further comprising 0.05 to 0.2 parts by weight of a heat-resistant stabilizer based on 100 parts by weight of components (A) to (D), and the heat-resistant stabilizer is tetrakis (methylene (3,5-di-t-butyl-4 -Hydroxy)hydrosilylnate), tetrakis(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, characterized in that at least one selected from the group consisting of a polypropylene resin composition.
A polypropylene resin foam molded article manufactured by foam molding the polypropylene resin composition according to any one of claims 1 to 11.
The method of claim 12, 0.8 g/cm ³ Polypropylene resin foam molded article, characterized in that it has a density below, 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.
The polypropylene resin foam molded article according to claim 12, which is an exterior material for an automobile.

Images