KR20130053648A - Poly propylene composition for injection foaming molding with supercritical fluid - Google Patents

Abstract

PURPOSE: A polypropylene resin composition is provided to be useful for foam injection molding, to prevent shrinkage phenomenon, and to increase the thickness of a dog house. CONSTITUTION: A polypropylene resin composition for injection molding using a supercritical fluid, using a supercritical fluid as a foaming agent comprises a propylene-ethylene block copolymer which consists of a propylene homopolymer and propylene-ethylene random copolymer rubber; an ethylene-propylene block copolymer which consists of an ethylene-propylene random copolymer or ethylene-propylene random copolymer and ethylene-propylene copolymer rubber; an elastomer of ethylene-olefin random copolymer; and inorganic filler. [Reference numerals] (AA) Example 1; (BB) Comparative example 1; (CC) Comparative example 2

Description

Poly propylene composition for injection foaming molding with supercritical fluid

The present invention relates to a polypropylene resin composition used for foam injection molding using a supercritical fluid.

Automobile exterior parts are parts that are mounted for the purpose of differentiating the vehicle concept from other vehicles and have a great influence on the design of the car. In particular, the side garnish is applied to the door portion of the SUV and vans to give a sense of luxury of the vehicle. Most of these side garnishes have a flat plate shape, and a shock resistant plastic material is applied to prevent damage during mounting, and the manufacturing method is manufactured by a general injection method. The rear side of the garnish has a dog house part into which a fastener can be inserted so as to be press-fitted into a hole processed in a vehicle door part, and a rib structure for preventing deformation and reinforcing rigidity.

However, the dog house (Rib house) and the rib (Rib) is caused by shrinkage of the product surface causes the deterioration of the product, it is designed and manufactured to a thickness of less than 1/2 of the product thickness. Due to such a relatively thin thickness there is a problem that is easily broken when mounting and detaching the vehicle door.

Accordingly, the present inventors have a dog house located on the rear side of the vehicle exterior parts to be mounted on the vehicle and the vehicle, and the shrinkage on the surface of the product in reinforcing ribs to prevent deformation such as warping and bending. Efforts have been made to resolve points that occur and are easily broken.

As a result, a foam injection molding method using a supercritical fluid was applied, and the present invention was completed by developing a thermoplastic resin composition applied to the foam injection molding method.

An object of the present invention is to reduce the weight of a part by applying a foam injection molding method using a supercritical fluid.

In order to achieve the above object, the present invention

Propylene-ethylene block copolymer (A) consisting of a propylene homopolymer portion (A-1) and a propylene-ethylene random copolymer rubber portion (A-2);

An ethylene-propylene random copolymer (B-1) alone or an ethylene-propylene block copolymer (B) consisting of an ethylene-propylene random copolymer (B-1) and an ethylene-propylene copolymer rubber (B-2);

Elastomers (C) of ethylene-octene random copolymer rubber; And

Inorganic fillers (D);

It is characterized by a polypropylene resin composition for foam injection molding using a supercritical fluid containing as a blowing agent.

The resin composition of the present invention is useful for foam injection molding using a supercritical fluid as a blowing agent.

Since the resin composition of the present invention is supercritical foam injection molding and there is no shrinkage phenomenon, it is possible to increase the thickness of the dog house, thereby increasing the mountability and improving work efficiency.

The present invention has a small number of foam cells pointed out as a problem in the conventional TPO injection molding method by the supercritical foam molding, the uniform cell foaming is not made, there is an effect capable of overcoming the limitations in weight loss and physical properties.

The resin composition of the present invention is applied to the vehicle side garnish ash due to supercritical foam molding to reduce weight, thereby increasing fuel economy and producing an environment-friendly vehicle.

1 is a scanning micrograph of a molded article obtained by supercritical foam injection molding of the polypropylene resin compositions of Examples 1 and Comparative Examples 1 and 2. FIG.
FIG. 2 is a photograph of a side garnish prepared by supercritical foam injection molding of the polypropylene resin composition of Example 1. FIG.
3 is a photograph of a vehicle to which the side garnish of FIG. 2 is applied.

The present invention relates to polypropylene resin compositions useful for supercritical foam injection molding using supercritical fluids as blowing agents.

In the present invention, by supercritical foam injection molding of a polypropylene resin composition having a specific composition, the foaming gas solubility is increased in the molded article, so that a large number of foam cells having a uniform size are present, thereby making it possible to manufacture a lightweight molded article.

Referring to each of the components used to constitute the polypropylene resin composition for supercritical foam injection molding according to the present invention will be described in detail.

In the present invention, propylene-ethylene block copolymer (A) and ethylene-propylene random copolymer (B-1) or ethylene-propylene block copolymer (B) are used as main resin components. The propylene-ethylene block copolymer (A) described above is a copolymer composed of a propylene homopolymer portion (A-1) and a propylene-ethylene random copolymer rubber portion (A-2). The ethylene-propylene block copolymer (B) described above is a copolymer composed of an ethylene-propylene random copolymer (B-1) and an ethylene-propylene copolymer rubber (B-2).

The resin used in the present invention, that is, propylene-ethylene block copolymer (A), ethylene-propylene random copolymer (B-1), or ethylene-propylene block copolymer (B), has a melt flow index (230). ℃, 2.16 kg load measurement) is in the range of 5 to 100 g / 10 min, preferably 5 to 50 g / 10 min. If the melt flow index of the resin is too low, the fluidity of the resulting composition may be low, and if too high, the melt strength may be directly related to the impact strength and foaming properties of the resulting composition. Particularly preferably, the melt flow index of the propylene-ethylene block copolymer (A) is in the range of 25-50 g / 10 min, and the melt of the ethylene-propylene random copolymer (B-1) or the ethylene-propylene block copolymer (B) is melted. The flow index is in the range of 5-25 g / 10 min.

The resin composition of the present invention is polymerized with various catalysts in order to increase the gas solubility in the resin matrix to generate a lot of foam cells, so that the content of ethylene comonomer in the propylene homopolymer main chain is in the range of 0.5 to 5% by weight. Ethylene-propylene random copolymer (B-1) alone or an ethylene-propylene block copolymer (B) composed of the above-mentioned ethylene-propylene random copolymer (B-1) and ethylene-propylene copolymer rubber (B-2) use.

In the present invention, an elastomer of ethylene-α-olefin random copolymer rubber is used as the elastomer. Preferably, an ethylene-α-olefin random copolymer rubber containing 20 to 50% by weight of α-olefin having 4 to 12 carbon atoms is used as the elastomer. The α-olefins of this random copolymer are, for example, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1- Decene, 1-undecene, 1-dodecene, etc. are mentioned, Preferred are 1-butene, 1-octene. In consideration of the foaming properties of the resin composition, the melt flow index of the elastomer is in the range of 0.5 to 10 g / 10 min (190 ° C., 2.16 kg load), and preferably 0.5 to 5 g / 10 min (190 ° C., 2.16 kg load). Range.

In the present invention, the inorganic filler serves to improve the rigidity of the polypropylene resin composition and to improve the foaming properties as the foaming nucleating agent. Specifically, the inorganic filler may be silica, talc, glass fiber, mica, calcium carbonate, barium sulfate, mica, crystalline calcium silicate, clay, carbon nanotubes (CNT), etc., each of which may be used alone. Or you may use it in combination of 2 or more type. Preferred inorganic fillers include silica, talc, glass fibers, mica and calcium carbonate, with talc being particularly preferred. The average particle diameter of the inorganic filler is preferably 1 to 10 µm, and more preferably in the range of 1 to 5 µm in order to allow a lot of foaming nucleation to be formed. If the average particle diameter of the inorganic filler is 1 μm or less, the rigidity reinforcing effect is small, and the impact resistance is weakened. If the average particle diameter exceeds 10 μm, there is a problem that fine foaming is prevented due to interference with foaming nucleation.

In the present invention, a supercritical fluid is used as a blowing agent for foam injection molding. Supercritical fluids include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, hexane and heptane; Alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; And at least one organic gas selected from the group consisting of halogenated hydrocarbons such as chlorodifluoromethane, dichloromethane, dichlorofluoromethane, trichlorofluoromethane, chloroethane, dichlorotrifluoroethane and perfluorocyclobutane. And / or one or more selected from the group consisting of gases such as carbon dioxide, nitrogen and air. As the blowing agent, methane, butane, carbon dioxide, or nitrogen is preferable, and nitrogen is more preferable in view of foaming efficiency or nucleation. These blowing agents are mixed and dispersed with the resin in a high temperature and high pressure condition having a supercritical state, and the rapid pressure drop causes thermodynamic destabilization, resulting in bubble nucleation and growth, and finally a product having a large number of cells (or bubbles) is produced. . The addition amount of the blowing agent is selected according to the type of foaming agent and the target foaming ratio, and generally it is preferably used in the range of 0.3 to 5 parts by weight based on 100 parts by weight of the polypropylene resin composition, more preferably 0.5 to 2 parts by weight. It is. If the amount of the blowing agent is too small, the foaming efficiency is low and there is no weight reduction effect. If the amount of the foaming agent is used too much, there is a problem in that physical property degradation due to excessive foaming occurs severely and bubbles appear in the appearance.

In addition to the above components, the resin composition of the present invention may further include various additives such as heat stabilizers, antistatic agents, weather stabilizers, antioxidants, fatty acid metal salts, lubricants, slip agents, pigments, and the like, as necessary.

The polypropylene resin composition is prepared by melt kneading the composition components as described above. In this case, the kneader may use a single screw extruder, a twin screw extruder, a banbury mixer, a kneader, or the like. In one embodiment, to obtain a blend by mixing the components in each content range, then the blend is added to the twin screw extruder (EMSTS32, Screw Dia .: Ø32, L / D: 40) at once And it knead | mixed under the cylinder temperature of 210 degreeC, the extrusion amount of 30 kg / hour, and the screw rotation speed of 250 rpm, and manufactured the polypropylene resin composition.

The present invention will now be described in more detail with reference to the following examples, but the present invention is not limited thereto.

EXAMPLES Preparation of Polypropylene Resin Composition

Example 1 and Comparative Examples 1 and 2

In the composition ratio shown in Table 1 below, each component was added to the twin screw extruder (EMS STS32, Screw Dia .: Ø32, L / D: 40) at once, and the cylinder temperature was 210 ° C, the extrusion amount 30kg / hour, and the screw. The polypropylene resin composition was prepared by melt kneading under a rotation speed of 250 rpm.

[Experimental Example]

Experimental Example 1. Preparation of specimen and measurement of physical properties

The polypropylene resin compositions prepared in Examples and Comparative Examples 1 and 2 were foam injection-molded by adding 0.9 wt% of a supercritical fluid (nitrogen gas) as a blowing agent. At this time, the injection was produced by measuring the physical properties using an Engel injection machine (150 tons of clamping force: VICTORY 150).

Melt flow index, flexural modulus, and Izod impact strength of the obtained injection specimens are shown in Table 1 below.

division Example 1 Comparative Example 1 Comparative Example 2 Composition
(weight%)  PP-1 34 34  PP-2 20  PP-3 54  PP-4 20  Elastomer-1 8  Elastomer-2 20 20 12  Talc-1 25 25  Talc-2 25  Black Masterbatch One One One Property evaluation  Melt Flow Index (g / 10min) 15 38 25  Flexural modulus (kg / ㎠) 18,200 18,700 17,800  Impact strength (room temperature, kg ㎝ / cm) 11.2 6.3 5.2  Exterior ○ X X  Cell uniformity ○ X X [Composition Components]
PP-1: Propylene-ethylene block copolymer with melt flow index of 30 g / 10 min (230 ° C, 2.16 kg load), Samsung Total
PP-2: Propylene-ethylene block copolymer with melt flow index of 40 g / 10 min (230 ° C, 2.16 kg load), Samsung Total
PP-3: Propylene-ethylene block copolymer with melt flow index of 100 g / 10 min (230 ° C, 2.16 kg load), Samsung Total
PP-4: Ethylene-propylene random copolymer with melt flow index of 5 g / 10 min (230 ° C, 2.16 kg load), Samsung Total
Elastomer-1: Ethylene-octene random copolymer rubber with a melt flow index of 13 g / 10 min (190 ° C., 2.16 kg)
Elastomer 2: Ethylene-octene random copolymer rubber with a melt flow index of 1.0 g / 10 min (190 ° C., 2.16 kg)
Talc-1: Talc with an average particle size of 4 μm
Talc-2: Talc with an average particle size of 12 μm

[Properties]
Appearance: ○ Uniform appearance, X appearance is uneven
Cell uniformity: ○ Cells are uniform in size, X cells are uneven in size

Experimental Example 2. Application of Side Garnish and Automobile

The polypropylene resin composition of Example 1 was supercritical foam injection molded to prepare a side garnish.

The weight of the product produced by the general TPO injection method is 870 g, the weight of the product produced by the supercritical foam injection molding method by applying the resin composition of the present invention was 650 g, it was possible to obtain a 25% weight savings. The weight reduction of 1.2 kg can be achieved per vehicle, contributing to the improvement of automobile fuel economy and the production of eco-friendly vehicles. In addition, 25% material savings are also a benefit.

In addition, unlike mass-produced products, since there is no shrinkage on the surface, the thickness of the dog house may be increased on the back to increase the mounting property and work efficiency.

Claims (7)

Propylene-ethylene block copolymer (A) consisting of a propylene homopolymer portion (A-1) and a propylene-ethylene random copolymer rubber portion (A-2);
An ethylene-propylene random copolymer (B-1) alone or an ethylene-propylene block copolymer (B) consisting of an ethylene-propylene random copolymer (B-1) and an ethylene-propylene copolymer rubber (B-2);
Elastomers (C) of ethylene-olefin random copolymer rubbers; And
Inorganic fillers (D);
A polypropylene resin composition for foam injection molding using a supercritical fluid as a blowing agent, comprising:
The method of claim 1,
20 to 50% by weight of the propylene block copolymer (A);
10 to 30% by weight of the ethylene-propylene random copolymer (B-1) alone or the ethylene-propylene block copolymer (B);
10 to 30% by weight of elastomer (C) of the ethylene-olefin random copolymer rubber; And
10-30 wt% of inorganic filler (D);
A polypropylene resin composition for foam injection molding using a supercritical fluid as a blowing agent, comprising:
3. The method according to claim 1 or 2,
The supercritical fluid used as the blowing agent is a polypropylene resin composition, characterized in that selected from the group consisting of methane, butane, carbon dioxide, and nitrogen.
3. The method according to claim 1 or 2,
The propylene-ethylene block copolymer (A), the ethylene-propylene random copolymer (B-1), or the ethylene-propylene block copolymer (B) may have a melt flow index of 5 to 100 g / 10 min (230 ° C.). A polypropylene resin composition characterized by the above.
3. The method according to claim 1 or 2,
The elastomer (C) is a polypropylene resin composition, characterized in that the melt flow index is 0.5 ~ 10 g / 10min (190 ℃, 2.16kg load).
3. The method according to claim 1 or 2,
The inorganic filler (D) is a polypropylene resin composition, characterized in that selected from silica, talc, glass fibers, mica and calcium carbonate.
3. The method according to claim 1 or 2,
The inorganic additive (D) is a polypropylene resin composition, characterized in that talc having an average particle diameter of 1 to 10 ㎛.

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