KR101357937B1 - Polypropylene resin composition for microcellular injection molding - Google Patents

Abstract

The present invention provides a polypropylene resin composition for fine injection foam having excellent 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, comprising at least one compound selected from the group consisting of a propylene homopolymer and a propylene-ethylene block copolymer, an organic peroxide masterbatch, an elastomer and an inorganic filler. It relates to a polypropylene resin composition for fine injection foaming.

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 the decomposition residues of the blowing agent.

The micro foaming method using a physical foaming agent is a technique for forming a product by forming a micro-sized bubble or cell (5-100 micrometers) inside a polymer material of a plastic product, and mainly using a supercritical fluid. Process. During injection molding, supercritical fluid nitrogen or carbon dioxide is injected into the cylinder part of the injection molding machine to make a polymer / gas melt with a single phase, and then injected into a mold, which causes thermodynamic instability due to rapid pressure reduction. The gas is formed into a nucleus to form micro pores at the micro level, and refers to a method of forming while forming fine cells 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 shortening of a cycle, a sink mark of a molded article, a warpage improvement, and the like.

Japanese Patent Application Laid-Open No. 2002-264164 discloses a thermoplastic resin composition and an injection foam, in which the thermoplastic resin contains a mixture of polycarboxylic acid and a carbonated salt or a decomposition product thereof in the injection foam molding method of a thermoplastic resin for supplying a physical blowing agent in the middle of a cylinder. It relates to the molding method and mentions that a molded article having an excellent surface appearance can be obtained.

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 which is molded by controlling pressure reduction and shear rate.

However, in the case of injection processes based on these methods, the application of the exterior parts is still not applied all over the world without overcoming the problem of molding surface defects such as gas swirl marks or gas blisters. .

The present invention is to solve the problems of the prior art as described above, an object of the present invention is to provide a polypropylene resin composition for injection foam having excellent surface appearance and having a fine cell size and uniform cell distribution.

In order to achieve the above object, the present invention, at least one compound (A) selected from the group consisting of propylene homopolymer and propylene-ethylene block copolymer; Organic peroxide masterbatch (B); Elastomers (C); And it provides a fine injection foam polypropylene resin composition comprising an inorganic filler (D).

The melt index of the propylene homopolymer and the propylene-ethylene block copolymer may be 5 to 100 g / 10 min (230 ° C., 2.16 kg).

The organic peroxide masterbatch (B) contains polypropylene resin (B-1) and peroxydicarbonate (B-2), and peroxydicarbonate (B-2) based on 100 parts by weight of polypropylene resin (B-1). ) May comprise 0.01 to 2.0 parts by weight.

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.

The polypropylene resin (B-1) may have a melt index of 0.5 to 100 g / 10 min.

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 elastomer (C) may be an ethylene-α-olefin random copolymer rubber having a content of α-olefin of 20 to 50% by weight.

The elastomer (C) may be a melt index of 0.1 ~ 10g / 10 minutes (190 ℃, 2.16 kg load).

The inorganic filler (D) may be one or more selected from the group consisting of silica, talc, glass fibers, mica, calcium carbonate and cray.

The inorganic filler (D) may contain talc having an average particle diameter of 1 to 10 micrometers.

The polypropylene resin composition for fine injection foam 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 it may be one or more selected from the group consisting of a gas such as carbon dioxide and nitrogen.

The fine injection foamed product manufactured using the polypropylene resin composition of the present invention has a fine and uniform size of bubbles and has excellent surface appearance characteristics, and thus can be used for various applications such as automobile interior and exterior materials, and housing materials for home appliances. Very useful as a material.

The present invention provides at least one compound (A) selected from the group consisting of propylene homopolymers and propylene-ethylene block copolymers; Organic peroxide masterbatch (B); Elastomers (C); And it provides a fine injection foam polypropylene resin composition comprising an inorganic filler (D).

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 min, the injection moldability of the resulting composition may be reduced, and if it is 100 g / 10 min or more, the melt strength directly related to the impact strength and foaming properties of the resulting composition may be insufficient.

The polypropylene resin composition of the present invention contains an organic peroxide masterbatch to improve the melt viscosity of the composition to improve the foaming effect. 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) may be a heterophasic propylene copolymer obtained by dispersing an ethylene propylene copolymer in a dispersed phase 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 30 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.

The elastomer (C) included in the resin composition of the present invention preferably contains an ethylene and an α-olefin having 4 to 12 carbon atoms, and the content of the α-olefin is an ethylene-α-olefin random copolymer rubber having 20 to 50% by weight. Do. The α-olefin of this random copolymer is, for example, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1 -Decene, 1-undecene, 1-dodecene, and the like, preferably 1-butene, 1-octene, two or more ethylene-α You may use together -olefin random copolymer rubber.

The elastomer (C) preferably has a melt index of 0.1 to 10 grams / 10 minutes (190 degrees, 2.16 kilogram load) with respect to the foaming properties of the resin composition, and more preferably 0.5 to 5 grams / 10 minutes. If the melt index is less than 0.1 gram / 10 minutes, the flowability during the injection molding process is greatly reduced, and if the melt index exceeds 10 grams / 10 minutes, the impact strength is significantly reduced.

The inorganic filler (D) used in the present invention is used to improve the rigidity of the polypropylene resin composition and to improve the foaming properties as a foaming nucleating agent. Specific examples thereof include calcium carbonate, barium sulfate, mica and crystals. Calcium silicate, talc, glass fiber, silicates, clay, etc. are mentioned. Among these, talc and clay are preferable. 1-10 micrometers is preferable and, as for the average particle diameter of talc, it is more preferable that it is the range of 1-5 micrometers so that many foaming nucleation may be formed. An inorganic filler can be used individually by 1 type, and can also be used in combination of 2 or more type.

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; Alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; And at least one selected from the group consisting of gases such as carbon dioxide and nitrogen. 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 the rapid pressure drop causes 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 foaming ratio, and generally 0.3 to 5 parts by weight with respect to 100 parts by weight of the polypropylene resin composition, more preferably 0.5 to 2 parts by weight.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

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) hydroxynameth] methane, 0.05 parts by weight of tris (2,4-di-tetrabutyl-phenyl) phosphite, calcium stearate After adding 0.05 parts by weight, the mixture was kneaded with a Henschel mixer for 10 minutes, extruded with a temperature gradient from 160 ° C to 220 ° C with a twin screw extruder, and then cooled and solidified to obtain a pellet-like resin composition.

Examples 1 to 2

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 a propylene-ethylene block copolymer with a melt index of 60 grams / 10 minutes (PP-2 BI961 Samsung Total), ethylene-octene random copolymer rubber (elastomer-1, ENGAGE 8842, DuPont Dow) with a melt index of 1.0 gram / 10 minutes (190 degrees, 2.16 kilograms), talc with an average particle size of 4 micrometers -1, KR8500, Gyeonggi Industry Co., Ltd.) and the organic peroxide masterbatch obtained in the preparation example were mixed with the composition shown in Table 1 below, and the mixture was introduced into a twin screw extruder (SM PLATEK, screw diameter 30Ф) at once and the cylinder temperature was 210 ° C. And kneading at an extrusion amount of 30 kg / hour and a screw rotation speed of 250 rpm to prepare a polypropylene resin composition.

Comparative Example 1

Propylene-ethylene block copolymer (PP-1, BJ700, Samsung Total) with a melt index of 30 grams / 10 minutes (230 ° C, 2.16 kg load), propylene with a melt index of 100 grams / 10 minutes (230 ° C, 2.16 kg load) -Ethylene block copolymer (PP-3, BI995, Samsung Total), elastomer (elastomer-1, ENGAGE 8842, DuPont Dow) with a melt index of 1.0 g / 10 min (190 degrees, 2.16 kg load) and an average particle size of 4 microns The talc with talc (Talc-1, KR8500, Gyeonggi) was mixed with the composition shown in Table 1 below, and the mixture was introduced into a twin screw extruder (SM PLATEK, screw diameter 30Ф) at once, and the cylinder temperature was 210 deg. A polypropylene resin composition was prepared by kneading at 250 rpm for a time and a screw speed.

Comparative Example 2

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 a propylene-ethylene block copolymer with a melt index of 60 grams / 10 minutes (PP- 2, BI961, Samsung Total), an elastomer with a melt index of 18 grams / 10 minutes (Elastomer-2, ENGAGE 8137, DuPont Dow) and talc having an average particle size of 4 micrometers (Talc-1, KR8500, Unemployment) The mixture was mixed in the composition shown in the above, and this mixture was put into a twin screw extruder (SM PLATEK, screw diameter 30?) At once and kneaded under a cylinder temperature of 210 ° C., an extrusion amount of 30 kg / hour, and a screw rotation speed of 250 rpm to prepare a polypropylene resin composition.

Comparative Example 3

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 a propylene-ethylene block copolymer with a melt index of 60 grams / 10 minutes (PP- 2, BI961, Samsung Total), elastomers having a melt index of 1.0 gram / 10 min (elastomer-1, ENGAGE 8842) and talc (talc-2, NA-400, Cots) having an average particle size of 12 micrometers are shown in Table 1 below. The mixture was mixed in the composition, and this mixture was put into a twin screw extruder (SM PLATEK, screw diameter 30?) At once, and kneaded at a cylinder temperature of 210 deg.

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

0.7 wt% nitrogen gas content was added to the polypropylene resin compositions obtained in Examples and Comparative Examples and applied to a front door side garnish, which is one of automotive exterior parts, using a clamping force of 850 tons (Dongshin Hydraulic). Molding was carried out. 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 200 ° C, a mold temperature of 55 ° C, an injection pressure of 250bar, a counter pressure of 35bar, and the core back speed was adjusted. Since the appearance of the foamed molded article was observed, the density was also measured. 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 Comparative Example 1 Comparative Example 2 Comparative Example 3 Composition (% by weight) PP-1 20 15 20 20 20 PP-2 32 32 37 37 PP-3 - - 37 - - Elastomer 1 18 18 18 18 Elastomer 2 - - 18 - Talc-1 25 25 25 25 - Talc-2 - - 25 Organic Peroxide Masterbatch 5 10 - - - Evaluation Molded product appearance Good Good Bad Bad Bad Density Reduction After Foaming (%) 14 19 8 11 9 Cell average diameter
(탆) 80-100 70 to 90 200 ~ 220 200 ~ 220 160-180 Cell uniformity ○ ○ X X X

○: excellent foam cell uniformity,

X: foam cell non-uniform

As a result of comparing the above Examples and Comparative Examples, the polypropylene resin compositions for fine injection foaming of Examples 1 to 2 according to the present invention have a good appearance of molded articles and relatively fine and uniform cell sizes generated after foaming. In the polypropylene resin compositions of Comparative Examples 1 to 3, a problem arises in that a swirl mark is generated in the appearance of the molded article, and it is confirmed that the cell size is also relatively large and nonuniform.

Claims (12)

At least one compound (A) selected from the group consisting of propylene homopolymers and propylene-ethylene block copolymers; Organic peroxide masterbatch (B); Elastomers (C); And inorganic filler (D),
The organic peroxide masterbatch (B) contains polypropylene resin (B-1) and peroxydicarbonate (B-2), and peroxydicarbonate (B-2) based on 100 parts by weight of polypropylene resin (B-1). ) 0.01 to 2.0 parts by weight,
The elastomer (C) is a polypropylene resin composition for fine injection foam, characterized in that the content of the α-olefin is 20 to 50% by weight of ethylene-α-olefin random copolymer rubber. The polypropylene resin composition for fine injection foam according to claim 1, wherein the melt index of the propylene homopolymer and the propylene-ethylene block copolymer is 5 to 100 g / 10 min (230 ° C., 2.16 kg). delete 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 polypropylene resin (B-1) has a melt index of 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 A polypropylene resin composition 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. . delete The polypropylene resin composition for fine injection foam according to claim 1, wherein the elastomer (C) has a melt index of 0.1 to 10 g / 10 minutes (190 DEG C, 2.16 kg load). According to claim 1, wherein the inorganic filler (D) is polypropylene resin composition for fine injection foam, characterized in that at least one selected from the group consisting of silica, talc, glass fiber, mica, calcium carbonate and cray. The polypropylene resin composition for fine injection foam according to claim 1, wherein the inorganic filler (D) contains talc having an average particle diameter of 1 to 10 micrometers. The polypropylene resin composition for fine injection foaming according to any one of claims 1, 2, 4 to 6, and 8 to 10, further comprising a blowing agent. The method of claim 11, 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 at least one selected from the group consisting of at least one gas selected from the group consisting of carbon dioxide and nitrogen.