KR101551019B1 - Polypropylene resin composition - Google Patents

Abstract

(A) from 65 to 75% by weight of a highly crystalline polypropylene base resin; (B) 15-25% by weight of at least one rubber elastomer selected from the group consisting of ethylene-butene rubber (EBR), ethylene-octene rubber (EOR) and mixtures thereof; (C) 5 to 10% by weight of an inorganic filler; And (D) 1.5 to 3.5% by weight of a blowing agent.
The polypropylene resin composition according to the present invention improves the appearance of a molded article by improving surface curvature and has excellent mechanical properties such as high rigidity and therefore can be usefully applied to automobile exterior materials, particularly roof racks, and further, Thereby contributing to the weight saving of the automobile.

Description

TECHNICAL FIELD The present invention relates to a polypropylene resin composition,

The present invention relates to a polypropylene resin composition, and more particularly, to a polypropylene resin composition which comprises at least one member selected from the group consisting of ethylene-butene rubber (EBR), ethylene-octene rubber (EOR) A rubber elastomer, an inorganic filler and a foaming agent are contained in a predetermined amount to improve the surface curve to improve the appearance of the molded article, and the mechanical properties such as low specific gravity and high rigidity are also excellent, To a polypropylene resin composition for automobile exterior materials.

'Loop rack' refers to a luggage compartment or a load carrier temporarily installed on a vehicle roof to load luggage which is bulky and can not be loaded in the trunk or the interior of the vehicle.

'Roof rack cover' is currently manufactured by injection molding technology using ABS (acrylonitrile-butadiene-styrene resin). ABS materials are widely used for automotive parts because of their excellent moldability, rigidity, impact resistance, chemical resistance and scratch resistance. However, the ABS material has a disadvantage in that the basic chemical resistance of the amorphous resin is deteriorated and cracks or cracks may occur due to foreign materials exposed to the car wash or the outside.

On the other hand, polypropylene resins are widely used as automobile parts because they have excellent moldability, impact resistance, chemical resistance, low specific gravity and low cost. However, since the molding shrinkage ratio is larger than that of the ABS material, the mold production is separately required and the appearance of the molded article is deformed.

Accordingly, there is a need to develop a resin composition having excellent mechanical properties such as impact strength and rigidity, excellent moldability, and excellent appearance of molded articles in which the incidence of surface defects (sink marks) is reduced.

Korean Patent No. 10-1299316 discloses a crystalline olefin resin; Polyolefin elastomer; Talc; And an acicular calcium meta-silicate filler. The polypropylene resin composition has polypropylene which can be used for manufacturing automotive interior / exterior materials because of its excellent mechanical properties and resistance to stretch. However, such a resin composition has excellent surface properties due to less damage to friction or impact, and shrinkage such as surface bending may occur during injection molding, so that the moldability is still limited.

As a polypropylene resin composition which can be used as an automobile exterior material, it has an excellent appearance of a molded product by improving the surface bending that can occur during injection molding, and has a low specific gravity and excellent mechanical properties, The development of a polypropylene resin composition which is more suitable for automobile exterior materials is urgently required.

1: Korea Patent No. 10-1299316

Accordingly, the present inventors have found that when a high-crystalline polypropylene base resin is mixed with at least one rubber elastic body selected from the group consisting of ethylene-butene rubber, ethylene-octene rubber and a mixture thereof with a predetermined amount of an inorganic filler and a foaming agent, It has been found that it has excellent mechanical properties such as rigidity and excellent workability and has an appearance of an excellent molded article by improving the surface curvature (sink mark), thereby completing the present invention.

Accordingly, an object of the present invention is to provide a polypropylene resin composition having improved physical properties such as improved surface bending due to excellent moldability and processability and high rigidity.

Another object of the present invention is to provide an automobile exterior material made of the polypropylene resin composition.

In order to solve the above problems, the present invention provides a resin composition comprising (A) 65 to 75% by weight of a highly crystalline polypropylene base resin; (B) 15-25% by weight of at least one rubber elastomer selected from the group consisting of ethylene-butene rubber, ethylene-octene rubber and mixtures thereof; (C) 5 to 10% by weight of an inorganic filler; And (D) 1.5 to 3.5% by weight of a blowing agent.

The present invention also provides an automobile exterior material made of the polypropylene resin composition.

The polypropylene resin composition according to the present invention can be advantageously applied to exterior materials such as roof racks of automobiles, because it has physical properties such as improved surface bending due to excellent formability and processability and high rigidity.

Also, since the polypropylene resin composition according to the present invention has a low specific gravity, the polypropylene resin composition can contribute to the improvement of the fuel consumption due to the weight saving of the vehicle.

Fig. 1 shows photographs of specimens prepared according to Comparative Example 4 (left) and Example 1 (right).

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

(A) 65 to 75% by weight of a highly crystalline polypropylene base resin; (B) 15-25% by weight of at least one rubber elastomer selected from the group consisting of ethylene-butene rubber, ethylene-octene rubber and mixtures thereof; (C) 5 to 10% by weight of an inorganic filler; And (D) 1.5 to 3.5% by weight of a blowing agent.

The base resin (A) is preferably a high-crystalline polypropylene as a base material for a polypropylene resin composition for automotive exterior materials, and it preferably contains 65 to 75% by weight based on the total weight of the polypropylene resin composition.

Specifically, the highly crystalline polypropylene preferably has a high crystallinity with an isotactic index (measured by ¹³ C-NMR) of 97% or more, and preferably has a melt flow index of 10 to 60 g / _{10 min} 230 deg. C, 2.16 kg). When the melt flow index of the highly crystalline polypropylene is less than 10 g / _{10 min} , there is a limit in that the moldability is poor. When the melt flow index exceeds 60 g / _{10 min} , the mechanical strength such as impact strength and rigidity of the polypropylene resin is reduced, This is because there is a limit to use as a material for interior materials.

It is preferable that the high crystalline polypropylene contains 65 to 75% by weight based on the total weight of the polypropylene. When the content of the highly crystalline polypropylene is less than 65% by weight, the rigidity is deteriorated. The impact resistance is lowered and it is unsuitable as a material for automobile exterior materials.

Next, the rubber elastomer (B) includes at least one member selected from the group consisting of ethylene-butene rubber (EBR), ethylene-octene rubber (EOR) It is recommended that the melt flow index is 5 to 35 g / _{10 min} (190 DEG C, 2.16 kg). If the melt flow index is less than 5 g / _{10 min} , there is a problem that the moldability is poor and the appearance may be poor. When the melt flow index is more than 35 g / _{10 min} , there is a problem that the IZOD impact strength is lowered. It is good.

The rubber elastomer is preferably used in an amount of 15 to 25% by weight based on the total weight of the polypropylene resin composition. When the rubber elastic body is less than 15% by weight, the impact properties are lowered and the molding shrinkage rate deviation hardly affects. When the rubber elastic body is more than 25% by weight, the molding shrinkage rate deviation is improved but mechanical properties such as rigidity are lowered. It is good to do.

The inorganic filler (C) used in the present invention may be magnesium whisker. Here, whiskers are needle-shaped fibrous bodies, and inorganic fillers are used as reinforcing agents and are dispersed in a highly crystalline polypropylene resin in the shape of an inorganic needle.

The inorganic filler preferably has an average diameter of 0.5 to 1.5 탆 and an average fiber length of 30 to 50 탆. When the average diameter is less than 0.5 탆, there is a problem of stiffness degradation. When the average diameter is more than 1.5 탆, there is a problem of shrinkage rate deviation. Similarly, when the average fiber length is less than 30 탆, there is a problem of stiffness degradation. It is preferable to use an inorganic filler within the above range because there is a problem of variation in shrinkage ratio.

The inorganic filler preferably includes 5 to 10% by weight based on the total weight of the polypropylene resin composition. When the amount of the inorganic filler is less than 5% by weight, there is a problem that the rigidity is reduced. When the inorganic filler is more than 10% by weight, there is a problem that the specific gravity is increased.

The (D) foaming agent used in the present invention may be a chemical foaming agent or a physical foaming agent, and the type of foaming agent is not particularly limited. The foaming agent is also used in the form of a master batch. The decomposition temperature of the foaming agent is in the range of 150 to 220 ° C. When the resin having a decomposition temperature of less than 150 ° C. is used, there is a problem that a smooth extrusion process can not be carried out. It is preferable to use a foaming agent having the characteristics within the above range.

The foaming agent is preferably used in an amount of 1.5 to 3.5% by weight based on the total weight of the polypropylene resin composition. When the amount of the blowing agent is less than 1.5% by weight, the porous structure, which is the effect of the blowing agent, is not well formed. When the amount exceeds 3.5% by weight, foaming gas is generated on the surface of the molded product, It is preferable to include a foaming agent within the range.

The resin composition of the present invention may further contain additives such as a flame retardant, a lubricant, an antioxidant, a light stabilizer, a releasing agent, a pigment, an antistatic agent, an antibacterial agent, a processing aid, a metal deactivator, , A fluorine-based drip inhibitor, and a coupling agent.

The polypropylene resin composition according to the present invention composed of the above-mentioned components can be used widely as a material for automobile exterior materials such as roof racks because it can have the appearance of a molded article equivalent to ABS resin by using a foaming agent in polypropylene.

Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example  1-4

The polypropylene resin composition was prepared by blending the polypropylene resin composition according to the composition ratios shown in Table 1 for 5 minutes at room temperature. The composition was dry-blended and extruded using a twin-screw extruder (manufacturer: SM, diameter: 45) To prepare pellets for the polypropylene resin composition. GRADE: C # 850 MT of Dongjin Semichem Co., Ltd. was used as a foaming agent. The pellet-like composition was extruded from a specimen for physical property measurement and a specimen for appearance evaluation (evaluation of Sink Mark) of Examples 1 to 4 by setting an 210 ° C in an injection molding machine (manufacturer: LG warrior, mold clamping force: 140 ton).

Comparative Example  1-5

In the same manner as in Examples 1 to 4, test pieces for physical property measurement and specimens for appearance evaluation (Sink Mark evaluation) of Comparative Examples 1 to 5 were injected according to the composition ratios shown in Table 1 below.

Polypropylene resin composition (unit:% by weight) division Highly crystalline PP ^{1 )} Rubber elastic body ^{2 )}
(EBR, EOR) Inorganic filler ^{3 )}
(Magnesium whisker) Foaming agent ^{4 )} Additive ^{5 )} ABS  content room
city
Yes One 72 16 6.5 2.5 3.0 - 100 2 68 20 6.5 2.5 3.0 - 100 3 68 18 8.5 2.5 3.0 - 100 4 65 21 8.5 2.5 3.0 - 100 ratio
School
Yes One - - - - - 100 100 2 88 - 6.5 2.5 3.0 - 100 3 78.5 16 - 2.5 3.0 - 100 4 74.5 16 6.5 - 3.0 - 100 5 69.5 16 6.5 5 3.0 - 100 1) Melt index (230 DEG C, 2.16 kg) 45 g / 10 min
2) Melt index (190 ° C, 2.16 kg) 6 g / 10 min
3) Inorganic filler Average diameter 0.7 탆, average fiber length 35 탆
4) Foaming agent: GRADE: C # 850MT from Dongjin Semichem Co.
5) Additives: Songwon Industry's GRADE: SONGNOX 11B

The physical properties of the test pieces for measuring physical properties and test pieces for appearance measurement prepared according to Examples 1 to 4 and Comparative Examples 1 to 5 were measured by the following methods and the physical properties thereof are shown in Table 3 below.

The physical properties of the test pieces for measuring physical properties and test pieces for appearance measurement prepared according to Examples 1 to 4 and Comparative Examples 1 to 5 were measured in the following manner and physical properties are shown in Table 3 below.

Experimental Example : Measurement of physical properties

The physical properties shown in Table 3 below represent the average values of the five specimens except for the upper limit and the lower limit, and the test method is as follows.

(1) Specific gravity measurement: A flexural specimen according to ASTM D790 was cut to prepare a specimen for measuring specific gravity, and the specimen was measured by ASTM D792 method. The measurement equipment used was a DENSITY METER (manufacturer: MIRAGE, measuring range: 200 g / 0.0001 g).

(2) Flexural strength / flexural modulus measurement: Measured according to ASTM D790 method. The test speed (Crosshead speed) is 10 mm / min. The measuring equipment used was INSTRON UTM.

(3) Impact strength measurement: Measured according to ASTM D256 method. (-30 < 0 > C). The measuring equipment used was a YASUDA impact tester.

In order to be used as a material for automobile exterior materials, the physical properties must satisfy the specified specifications. If any one of the items fails to meet the specification, it is judged that the product can not be used as a material for automobile exterior due to problems in actual use after molding.

To be applied as a material for automotive exterior materials, division Item Required property unit importance 0.955 or less - Flexural modulus Over 1,850 MPa Impact strength (-30 ℃) 30 or more J / m Heat deformation temperature (1.84 MPa) 115 or more ℃ Exterior Good without sink -

Physical property measurement result division importance Flexural modulus Impact strength
(Low temperature 30 ° C) HDT
(1.84 MPa) Exterior
(Sink Mark) Acceptance judgment unit - MPa J / m ℃ - - room
city
Yes One 0.945 2,030 40.7 124 Good pass 2 0.945 1,920 44.8 122 Good pass 3 0.955 2,180 40.5 127 Good pass 4 0.955 1,990 46.2 122 Good pass ratio
School
Yes One 1.060 2,210 43.0 118 Good pass 2 0.955 2,370 17.0 128 Good fail 3 0.915 1,511 55.8 102 Good fail 4 0.955 1,870 38.2 118 Visual defects
(Sink Mark generation) fail

From the results shown in Table 3, it was confirmed that the polypropylene resin compositions of Examples 1 to 4 satisfied all of the specific gravity, rigidity, impact resistance, and appearance characteristics (sink mark). In the case of Comparative Example 1, both the mechanical properties and appearance (sink mark) of the current ABS material were satisfactory as compared with those of Examples 1 to 4.

On the other hand, in the case of Comparative Example 2, the rubber elastic body was excluded. The mechanical stiffness and the appearance (Sink Mark) were favorable, but the impact strength was unsatisfactory. In the case of Comparative Example 3, the moldability was satisfied except for the inorganic filler, but the impact strength and appearance (sink mark) were satisfactory, but the mechanical properties were unsatisfactory. In the case of Comparative Example 4, only the blowing agent was used, and the result did not satisfy the required characteristics of the Sink Mark.

Fig. 1 is a photograph of a specimen prepared according to Comparative Example 4 (left) and Example 1 (right), whereby the specimen manufactured according to the present invention has an excellent appearance with an improved Sink Mark Was visually confirmed.

As described above, the polypropylene resin compositions of Examples 1 to 4 according to the present invention were improved in surface curvature in comparison with Comparative Examples 1 to 5, It has been confirmed that it can be effectively applied to materials for automobile exterior materials, particularly roof rack covers, because it has excellent appearance and excellent mechanical properties such as low specific gravity and high rigidity.

Claims (9)

(A) 65 to 75% by weight of a highly crystalline polypropylene base resin;
(B) 15-25% by weight of at least one rubber elastomer selected from the group consisting of ethylene-butene rubber (EBR), ethylene-octene rubber (EOR) and mixtures thereof;
(C) 5 to 10% by weight of an inorganic filler; And
(D) 1.5 to 3.5% by weight of a foaming agent;
Lt; / RTI >
Wherein the rubber elastic body has a melt flow index of 5 to 35 g / _{10 min} (190 캜, 2.16 kg).
The polypropylene resin composition according to claim 1, wherein the (A) highly crystalline polypropylene has a melt flow index of 10 to 60 g / _{10 min} (230 DEG C, 2.16 kg).
The polypropylene resin composition according to claim 1, wherein (A) the highly crystalline polypropylene is an ethylene-polypropylene copolymer.
delete The method of claim 1, wherein the inorganic filler is selected from the group consisting of magnesium whisker ). ≪ / RTI >
The polypropylene resin composition according to claim 1 or 5, wherein the inorganic filler has an average diameter of 0.5 to 1.5 占 퐉 and an average fiber length of 30 to 50 占 퐉.
The polypropylene resin composition according to claim 1, wherein the foaming agent is a masterbatch of a chemical foaming agent or a physical foaming agent.
The polypropylene resin composition according to any one of claims 1 to 7, wherein the decomposition temperature of the blowing agent is 150 to 220 ° C.
An automobile exterior member made of the polypropylene resin composition according to any one of claims 1 to 3, 5 and 7.

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