KR101357908B1 - Polypropylene resin composition for microcellular injection molding - Google Patents

Abstract

The present invention provides a polyolefin resin composition for fine injection foam having excellent mechanical properties, dimensional stability and appearance and having a fine cell size and a uniform cell distribution.

Description

Polypropylene resin composition for microcellular injection molding

The present invention relates to a polypropylene resin composition for fine injection foam, and more particularly, to polyolefin resin for fine injection foam having improved heat resistance, rigidity, dimensional stability, excellent surface appearance, fine cell size and uniform cell distribution. It relates to a composition.

Plastic foaming technology was developed in the 1960s and is still used for various purposes. It mainly uses chemical foaming agents to create small bubbles in plastic products, such as heat blocking, sound absorption, sink mark removal, light weight, and product cost reduction. It can provide advantages.

As a method of obtaining a thermoplastic foamed product, the method of manufacturing by the micro foaming method using a chemical foaming agent or a physical foaming agent is known. Chemical foaming is a low molecular weight organic foaming agent which generally decomposes under molding temperature to generate nitrogen or carbon dioxide gas, and is a method of foam molding above the decomposition temperature. However, these foamed products are expensive, the foam cell size is large and non-uniform, and there is a concern that problems such as discoloration and odor generation occur due to residual decomposition residues of the foaming agent.

The micro foaming process is a technique for forming a product by forming micro bubbles or cells (5-100 micrometers) inside a polymer material of a plastic product, and is a physical process mainly using a supercritical fluid. In injection molding, supercritical fluid nitrogen or carbon dioxide is injected into the middle of the cylinder of the injection molding machine to make a polymer / gas melt with a single phase and then injected into a mold. As it occurs, the gas is formed into a nucleus to form micro pores at the micro level, and a process of forming while forming a fine cell in the composition. This process is an environmentally friendly process technology that does not use chemical blowing agents or freons used in existing structural foaming processes. It not only reduces the weight of a product but also improves plastic flowability, moldability, injection pressure, low temperature molding and molding. It is known as a technique which can realize a cycle shortening, a sink mark of a molded article, a curvature improvement, etc.

In Japanese Patent Application Laid-Open No. 2010-83124, after closing the fine foaming mold, the counter pressure is added to the cavity, the raw material melt is injected into the molding machine, and the high-pressure gas is injected to form fine bubbles. It is claimed that by providing a process and forming system that adds a pulse, cosmetic defects can be avoided.

Japanese Patent Application Laid-Open No. 2010-241997 discloses a weathering agent having a structure of at least one selected from polypropylene resins, polyolefin waxes, alkyl groups, hydroxy alkyl groups, alkoxy groups, and hydroxy alkoxy groups having a curing property and having a melt tension of 2 cN or more. An injection foamed molded article having excellent light weight and good weather stability as a polypropylene resin composition for injection foam molding.

US Pat. No. 6,884,823 B1 describes a fine injection foaming process by adjusting the pressure reduction and shear rate.

Korean Patent Laid-Open Publication No. 10-2005-0111986 introduces a resin composition in which glass fibers, minerals and sulfone amide-based plasticizers are added to a polyamide resin to improve dimensional stability and heat resistance, and improve flowability and surface.

However, in the case of large injection molding products, problems such as warpage and deformation occur due to differences in shrinkage in the longitudinal and transverse directions.

The present invention is to solve the problems of the prior art as described above, the object of the present invention is excellent in mechanical properties such as rigidity, impact resistance, heat resistance, dimensional stability and surface appearance, injection having a fine cell size and uniform cell distribution It is to provide a polyolefin resin composition for foaming.

In order to achieve the above object, the present invention provides at least one compound (A) 25 selected from the group consisting of propylene homopolymer and propylene-ethylene block copolymer having a melt index of 5 to 100 g / 10 min (230 ° C., 2.16 kg). 63 wt%, 5-20 wt% of organic peroxide masterbatch (B) containing polypropylene resin (B-1) and peroxydicarbonate (B-2), 15-35 wt% of glass fiber (C), average Provided is a polypropylene resin composition for fine injection foam containing 5 to 25% by weight of a plate-shaped inorganic filler (D) having a particle diameter of 1 to 10 μm, and 2 to 10% by weight of maleic anhydride grafted polypropylene (E). .

The organic peroxide master batch (B) may include 0.01 to 2.0 parts by weight of peroxydicarbonate (B-2) based on 100 parts by weight of polypropylene resin (B-1).

The molecular weight distribution of the polypropylene resin (B-1) is a ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn) measured by gel permeation chromatography (GPC) method is 4 to 15 days. Can be.

Melt index of the polypropylene resin (B-1) may be 0.5 ~ 100g / 10min.

The peroxydicarbonate (B-2) is diethyl peroxy dicarbonate, dipropyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, dibutyl peroxy dicarbonate, ethylhexyl peroxy dicarbonate, dioctyl peroxy dicarbonate, di (4 It may be at least one selected from the group consisting of -t- butylcyclohexyl) peroxydicarbonate, dimyriyl peroxydicarbonate, and dicetyl peroxydicarbonate.

The glass fibers (C) may have a diameter of 10 to 13 μm and a length of 3 to 3.5 mm.

The plate-shaped inorganic filler (D) may be one or more selected from the group consisting of silica, talc, mica and cray.

The sum total of the said glass fiber (C) and plate-shaped inorganic filler (D) may be 30 to 45 weight% with respect to the whole polypropylene resin composition.

The maleic anhydride grafted polypropylene (E) may be grafted with 0.1 to 5% by weight maleic anhydride.

The polypropylene resin composition of the present invention may further contain a blowing agent.

The blowing agent may be selected from aliphatic hydrocarbons such as propane, butane, isobutane, pentane, hexane and heptane; Alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane and / or gas such as carbon dioxide and nitrogen.

The blowing agent may be 0.5 to 2% by weight based on the polypropylene resin composition.

The fine injection foam product manufactured using the polypropylene resin composition of the present invention has excellent mechanical properties and dimensional stability such as rigidity, impact resistance, heat resistance, etc., has fine and uniform size of bubbles, and has excellent surface appearance characteristics. It is very useful as a material of various uses, such as a material for automobile interior and exterior materials, such as a shroud, an engine cover, and a material for a housing of a home appliance.

The present invention is a polypropylene 25 to 63% by weight of at least one compound (A) selected from the group consisting of a propylene homopolymer and a propylene-ethylene block copolymer having a melt index of 5 to 100 g / 10 minutes (230 ° C., 2.16 kg). 5-20 weight% of organic peroxide masterbatch (B) containing resin (B-1) and peroxydicarbonate (B-2), 15-35 weight% of glass fiber (C), and an average particle diameter of 1-10 micrometers Provided is a polypropylene resin composition for fine injection foam containing 5 to 25% by weight of a plate-shaped inorganic filler (D) and 2 to 10% by weight of maleic anhydride grafted polypropylene (E).

The propylene-ethylene block copolymer is a copolymer composed of a propylene homopolymer portion (A-1) and a propylene-ethylene random copolymer rubber (A-2) portion.

The melt index of the propylene homopolymer and block copolymer (melt flow index, 230 ° C., 2.16 kg load measurement) is preferably 5 to 100 grams / 10 minutes. If their melt index is less than 5 g / 10 minutes, the injection moldability of the resulting composition may be lowered, and if it is 100 g / 10 minutes or more, the melt strength may be directly related to the impact strength and foaming properties of the resulting composition.

The polypropylene resin composition of the present invention contains an organic peroxide masterbatch (B) to improve the melt viscosity of the composition to improve the foaming effect. The content is preferably 5 to 20% by weight with respect to the total resin composition, and when the content is less than 5% by weight, the effect of improving the melt viscosity of the composition is insignificant, and when it exceeds 20% by weight, molding may be difficult.

The organic peroxide masterbatch contains polypropylene resin (B-1) and peroxydicarbonate (B-2), and peroxydicarbonate (B-2) 0.01 to 2.0 with respect to 100 parts by weight of polypropylene resin (B-1). It includes parts by weight. The polypropylene resin (B-1) uses a heterophasic propylene copolymer obtained by dispersing an ethylene propylene copolymer dispersed in a polypropylene homopolymer.

The molecular weight distribution of the polypropylene resin (B-1) is a ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) method (Mw / Mn) is 4-15. It is preferable. When the molecular weight distribution is less than 4, the flowability during injection molding processing is poor, and appearance is poor, and when it exceeds 15, polypropylene resin having an ultra high molecular weight and organic peroxide react to form a gel, resulting in poor appearance. Become.

The polypropylene resin (B-1) has a wide range of melt index (ASTC D1238) under a load condition of 230 ° C. and 2.16 kg load, preferably a melt index of 0.5 to 100 g / 10 min, more preferably 1.0 to It is appropriate to be in the range of 60 g / 10 min, most preferably 3 to 50 g / 10 min. If the melt index of the polypropylene resin is less than 0.5 g / 10 min, the injection molding processability is lowered, and if it exceeds 100 g / 10 min, the impact strength is significantly lowered.

Although there is no restriction | limiting in particular in the kind of peroxydicarbonate (B-2) which is an organic peroxide used here, Preferably, diethyl peroxy dicarbonate, dipropyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, dibutyl peroxy dicarbonate, At least one selected from the group consisting of ethylhexyl peroxy dicarbonate, dioctyl peroxy dicarbonate, di (4-t-butylcyclohexyl) peroxy dicarbonate, dimyrisil peroxy dicarbonate, and dicetyl peroxy dicarbonate can be used. Can be.

The content of the peroxydicarbonate (B-2) is preferably 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the polypropylene resin (B-1), more preferably 0.05 to 1.0 parts by weight. If the content is less than 0.01 parts by weight, the effect of the melt viscosity characteristics is insignificant, and if the content is more than 2.0 parts by weight, the gel content is increased to deteriorate the appearance.

In the present invention, the glass fiber (C) in the form of fibers is used to greatly improve the mechanical properties of the polypropylene-based resin composition and at the same time improve the foaming properties as the foaming nucleating agent. In order to avoid the plate-like inorganic filler (D) is used in combination. Specific examples of the plate-shaped inorganic fillers include mica, talc, silicates, clays, mica, and the like.

The glass fiber may be used with a diameter of 10 ~ 13 ㎛, length of 3 ~ 3.5 mm, the content is preferably 15 to 35% by weight relative to the total resin composition. When the content is less than 15% by weight, the flexural modulus is lowered, and when the content is more than 35% by weight, there is a high possibility of problems of warpage and deformation due to shrinkage anisotropy of the resin composition.

It is preferable that the said plate-shaped inorganic filler is 1-10 micrometers in average particle diameter. If the thickness is less than 1 μm, the manufacturing cost is greatly increased. If the thickness is more than 10 μm, there is a disadvantage in that deflection and deformation improvement are insufficient.

In the present invention, the plate-shaped inorganic filler includes 5 to 25% by weight with respect to the total resin composition, if the content is less than 5% by weight is insufficient deflection, deformation improvement, if the content exceeds 25% by weight the surface properties after molding It becomes bad.

In the present invention, the glass fiber and the plate-shaped inorganic filler must be used in parallel, and the sum thereof is preferably 30 to 45% by weight based on the total composition. If the content is less than 30% by weight, the stiffness and heat resistance is insufficient, if the content exceeds 45% by weight the surface becomes extremely poor after the molding of the product is not preferred because it causes a decrease in fluidity.

The maleic anhydride grafted polypropylene (E) contained in the composition of the present invention serves to increase the interfacial adhesion between the glass fiber and the polypropylene resin, and maleic anhydride with respect to the total weight of the polypropylene resin grafted with maleic anhydride. The thing grafted by 0.1-5 weight% can be used. If it is 0.1 wt% or less, it may not play a role as a compatibilizer between the glass fiber and the polypropylene resin, and if it is 5 wt% or more, the compatibility between the compatibilizer and the polypropylene resin may be poor and mechanical properties may be greatly reduced.

The maleic anhydride-grafted polypropylene resin is used 2 to 10% by weight based on the total weight of the composition of the present invention, more preferably 3 to 5% by weight. When used at less than 2% by weight, glass fibers are not well dispersed in polypropylene, and when it is more than 10% by weight, polypropylene grafted with maleic anhydride has a very small molecular weight, which lowers the mechanical properties of the composition. .

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 of the present invention can be prepared by melt kneading each component, for example, by using a kneader such as a single screw extruder, a twin screw extruder, a banbury mixer, a kneader, or the like. have.

It is preferable to make the polypropylene resin composition of this invention foam by adding a foaming agent. As the blowing agent, aliphatic hydrocarbons such as propane, butane, isobutane, pentane, hexane and heptane; At least one selected from the group consisting of alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane and / or gases such as carbon dioxide and nitrogen can be used. Carbon dioxide and nitrogen are especially preferable, and nitrogen is more preferable especially in terms of foaming efficiency or nucleation.

These blowing agents are dispersed and dispersed with the resin under high temperature and high pressure in a supercritical fluid state and cause rapid thermodynamic destabilization, resulting in bubble nucleation and growth, resulting in a product having multiple cells (or bubbles). . The addition amount of the blowing agent is selected by the kind of the blowing agent and the target expansion ratio, and in general, it is preferably 0.3 to 5% by weight, more preferably 0.5 to 2% by weight based on the polypropylene resin composition.

The present invention can be further illustrated by the following examples, and the following examples are intended to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

Example

Preparation Example (Organic Peroxide Masterbatch Preparation)

Polypropylene resin (weight ratio molecular weight (Mw) and number average molecular weight (Mn) measured by gel permeation chromatography (GPC) method (Mw / Mn) of 7.4, ethylene content of 4 mol%, nuclear magnetic resonance penta 100 parts by weight of a high stereoregular heterophasic propylene copolymer having a stereoregularity index of 96% and 1.0 part by weight of an organic peroxide (di (4-t-butylcyclohexyl) peroxydicarbonate) as an antioxidant 0.05 parts by weight of tetrakis [methylene (3,5-ditetrabutyl-4-hydroxy) hydrosinameth] methane, 0.05 parts by weight of tris (2,4-di-tetrabutyl-phenyl) phosphite, and calcium stearate 0.05 After adding the parts by weight, the mixture was kneaded in a Henschel mixer for 10 minutes, extruded with a temperature gradient from 160 ° C to 220 ° C with a twin screw extruder, cooled, and solidified to obtain a pellet-like resin composition.

Examples 1 to 4

Propylene-ethylene block copolymer (PP-1, BJ700, Samsung Total) with a melt index of 30 grams / 10 minutes (230 ° C, 2.16 kg load) and propylene-ethylene block copolymer with a melt index of 60 grams / 10 minutes (PP- 2, BI961, Samsung Total), talc having an average particle size of 4㎛ (Talk-1, KR8500, Gyeonggi), the organic peroxide masterbatch obtained in the above preparation and maleic anhydride graft polypropylene in the amounts shown in Table 1, respectively Mixing gave a blend. This blend is poured into the main hopper in a twin screw extruder (SM PLATEK, screw diameter 30Ф), and the side of the glass fiber (ECS03T-480 / F9, NEG) having a length of 3 mm and a fiber diameter of 13 μm is prevented from being broken by screw shearing force. It was put into a side feeder. A polypropylene resin composition was prepared by kneading at a cylinder temperature of 210 ° C., an extrusion amount of 30 kg / hour, and a screw rotation speed of 250 rpm.

Comparative Example 1

Each component was mixed in the amounts shown in Table 2 without using an organic peroxide masterbatch to prepare a polypropylene resin composition in the same manner as in Example.

Comparative Examples 2-3

The glass fiber and talc content was adjusted to the content shown in Table 2 below to prepare a polypropylene resin composition in the same manner as in the above examples.

Comparative Example 4

A polypropylene resin composition was prepared in the same manner as in Example 1 by using talc (Talk-2, NA-400, Cots) having an average particle size of 12 micrometers and mixing the components in the amounts shown in Table 2 below.

Comparative Example 5

Melting index of 110 grams / 10 minutes (230 ℃, 2.16 kg load) using a propylene-ethylene block copolymer (PP-3, BI995, Samsung Total) and by mixing each component to the content shown in Table 2 below Table 2 A polypropylene resin composition was prepared at the content shown in.

(Preparation and Properties Measurement of Injection Property Specimen)

After the polypropylene resin compositions obtained in Examples and Comparative Examples were manufactured using TOYO (180 ton) injection molding machines, required specimens for measuring physical properties were obtained, and the resulting flexural modulus, Izod impact strength, heat deformation temperature, etc. Was measured and the results are shown in Tables 1-2. The measurement / evaluation items of the physical properties and the measuring method are as follows.

 (1) flexural modulus

And measured at room temperature according to ASTM D790. The specific flexural modulus was obtained by dividing the flexural modulus by the density.

(2) IZOD impact strength

Was measured with a notched specimen at room temperature according to ASTM D256.

(3) Heat deformation temperature

It was measured under a 4.6 kg load in accordance with ASTM D648.

(Observation / analysis of fine injection foam molding and molded products)

To the polypropylene resin compositions obtained in Examples and Comparative Examples, 0.7 wt% of nitrogen gas was added as a blowing agent, and a fine injection foam molding was applied to an engine cover, which is one of automobile parts, using a clamping force of 850 tons (Dongshin Hydraulic). It was. It can be divided into injection machine / molding part, fine foaming system, and gas counter pressure system. A gas counter pressure and core back system were used to ensure a uniform foaming cell and good appearance quality with an appropriate foaming rate. The injection conditions were set at an injection temperature of 220 ° C, a mold temperature of 55 ° C, an injection pressure of 250bar, a counter pressure of 35bar, and the core back speed was adjusted. Afterwards, the appearance of the molded foam and the warpage / deformation were observed. In addition, the cell distribution and the cell average diameter were confirmed for some cross sections of the molded article using a scanning electron microscope.

Example 1 Example 2 Example 3 Example 4 Composition (% by weight) PP-1 30 25 25 20 PP-2 27 27 27 27 Fiberglass 25 25 25 25 Talc-1 10 10 15 15 Organic Peroxide Masterbatch 5 10 5 10 Maleic Anhydride Polypropylene 3 3 3 3 Evaluation Flexural modulus
(kg / cm2) 64,900 60.000 66,100 63,700 Izod impact strength
(kgcm / cm) 11.1 12.1 9.3 9.8 Heat Deflection Temperature (℃) 162 160 163 162 Molded product appearance Good Good Good Good Molded Product Warpage / Deformation
Whether none none none none Cell average diameter
(탆) 80-100 70 to 90 80-100 70 to 90 Cell uniformity ○ ○ ○ ○

Comparative Example 1 Comparative Example
2 Comparative Example
3 Comparative Example
4 Comparative Example
5 Composition (% by weight) PP-1 30 30 20 30 30 PP-2 32 42 17 27 PP-3 27 Fiberglass 25 10 25 25 25 Talc-1 10 10 30 10 Talc-2 10 Organic Peroxide Masterbatch - 5 5 5 5 Maleic Anhydride Polypropylene 3 3 3 3 3 Evaluation Flexural modulus
(kg / cm2) 65,500 42,000 74,000 63,200 65,100 Izod impact strength
(kgcm / cm) 9.8 7.3 6.8 10.6 9.2 Heat deformation temperature (캜) 163 154 165 162 162 Molded product appearance Bad Good Bad Bad Bad Molded Product Warpage / Deformation
Whether none none none none none Cell average diameter
(탆) 160-180 100-120 160-180 140-160 200 ~ 220 Cell uniformity X ○ X X X

○: excellent foaming cell uniformity, X: foaming cell nonuniformity

The polypropylene resin composition of the present invention has a flexural modulus of 47,000 kg / cm2 or more when evaluated according to ASTM D790, an impact strength of 9 kgcm / cm or more when evaluated according to ASTM D256, and is heated under a 4.6KG load based on ASTM D648. Since it satisfies the deformation temperature of 140 ° C. or higher, it can be seen that the present invention can be preferably applied to automobile parts by a fine injection foaming method.

In addition, as a result of comparing the above Examples and Comparative Examples, it can be seen that the polypropylene resin compositions for fine injection foam of Examples 1 to 4 corresponding to the present invention have improved physical properties compared to Comparative Example 2. In addition, compared to the polypropylene resin compositions of Comparative Example 1, Comparative Examples 3 to 5, the appearance of the molded article was good, and the cell sizes generated after foaming were also relatively fine and uniform.

Claims (12)

25 to 63% by weight of one or more compounds (A) selected from the group consisting of a propylene homopolymer and a propylene-ethylene block copolymer having a melt index of 5 to 100 g / 10 minutes (230 ° C., 2.16 kg),
5-20 weight% of organic peroxide masterbatch (B) containing a polypropylene resin (B-1) and a peroxydicarbonate (B-2),
15-35 weight% of glass fibers (C),
5-25 weight% of plate-shaped inorganic fillers (D) with an average particle diameter of 1-10 micrometers, and
2-10 wt% maleic anhydride grafted polypropylene (E)
Polypropylene resin composition for fine injection foam containing. The fine injection foam according to claim 1, wherein the organic peroxide masterbatch (B) comprises 0.01 to 2.0 parts by weight of peroxydicarbonate (B-2) based on 100 parts by weight of polypropylene resin (B-1). Polypropylene resin composition. The molecular weight distribution of the polypropylene resin (B-1) is a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) method. ) Is 4 to 15, polypropylene resin composition for fine injection foam. The polypropylene resin composition for fine injection foam according to claim 1, wherein the melt index of the polypropylene resin (B-1) is 0.5 to 100 g / 10 min. The method of claim 1, wherein the peroxydicarbonate (B-2) is diethyl peroxy dicarbonate, dipropyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, dibutyl peroxy dicarbonate, ethylhexyl peroxy dicarbonate, dioctyl perox Polypropylene resin for fine injection foaming, characterized in that it is at least one member selected from the group consisting of cidicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, dimyrisil peroxydicarbonate, and dicetyl peroxydicarbonate. Composition. The polypropylene resin composition for fine injection foam according to claim 1, wherein the glass fiber (C) has a diameter of 10 to 13 µm and a length of 3 to 3.5 mm. The polypropylene resin composition for fine injection foam according to claim 1, wherein the plate-shaped inorganic filler (D) is at least one selected from the group consisting of silica, talc, mica and cray. The fine injection foamed polypropylene resin composition according to claim 1, wherein the total of the glass fiber (C) and the plate-shaped inorganic filler (D) is 30 to 45% by weight based on the total polypropylene resin composition. The polypropylene resin composition for fine injection foam according to claim 1, wherein the maleic anhydride grafted polypropylene (E) is grafted with 0.1 to 5% by weight of maleic anhydride. The polypropylene resin composition for fine injection foaming according to any one of claims 1 to 9, further comprising a blowing agent. 11. The method of claim 10, wherein the blowing agent is one or more aliphatic hydrocarbons selected from the group consisting of propane, butane, isobutane, pentane, hexane and heptane; At least one alicyclic hydrocarbon selected from the group consisting of cyclobutane, cyclopentane and cyclohexane and / or at least one member selected from the group consisting of at least one gas selected from the group consisting of carbon dioxide and nitrogen Solvent polypropylene resin composition. The polypropylene resin composition for fine injection foam according to claim 10, wherein the blowing agent is 0.5 to 2 wt% based on the polypropylene resin composition.