JPH0649257A - Resin composition for producing crosslinked foamed polypropylene - Google Patents

Abstract

PURPOSE:To provide the subject composition containing a specific copolymer composition, a low-density PE and a foaming agent at specific ratios, having excellent mechanical properties, heat-resistance, formability of sheet and fabricability and useful as an interior trim for automobile, heat-insulation material, sound-damping material, etc. CONSTITUTION:The objective composition contains (A) 10-90wt.% of a propylene-ethylene random copolymer composition having an ethylene content of 0.2-8.0wt.% and a melt-flow rate of 3-7g/10min and composed of (i) 10-80wt.% of a propylene-ethylene random copolymer having a melt-flow rate of 0.3-3g/10min and (ii) 90-20wt.% of a propylene-ethylene random copolymer having a melt-flow rate of 5-30g/10min, (B) 90-10wt.% of a linear low-density PE and (C) 1-30 pts.wt. (based on 100 pts.wt. of A+B) of a foaming agent such as azodicarbonamide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a polypropylene crosslinked foamed sheet used as an interior material for automobiles, a cushioning material for sports goods and food packaging, a heat insulating material, a sound deadening material, and other exterior materials. More specifically, it has mechanical properties and heat resistance peculiar to polypropylene, especially heat resistance,
The present invention relates to a resin composition for a polypropylene crosslinked foam which is excellent in high-temperature strength and excellent in processability at high temperature such as high-speed lamination processing and vacuum molding.

[0002]

2. Description of the Related Art Polypropylene foam is excellent in mechanical strength, flexibility, texture, heat resistance, chemical resistance, etc., and is used as an interior material for automobiles, a heat insulating material, a cushioning material for sports goods and food packaging, It is also widely used as a sound deadening material and exterior material. As a polypropylene foam, a composition comprising about 70% by weight of polypropylene and about 30% by weight of low-density polyethylene has been used so far. However, the foam cells during foaming tend to be large and non-uniform, and Since the foaming agent starts to decompose at about 170 ° C., it is not suitable for foaming polypropylene resin having a high melting point.

On the other hand, since a foaming agent having a high decomposition temperature produces a small amount of gas, a large amount of foaming agent is required to obtain a foam having a sufficiently high expansion ratio, which is not economical. In addition, the field of use of polypropylene foam is diversifying, and when it is used for automobile interior materials, for example, a high expansion ratio and a thin foam foam sheet are required, and the manufacturing process also requires high speed at high temperatures. Although lamination processing has become necessary, the heat resistance and high temperature strength of conventional polypropylene foams are insufficient. Therefore, an object of the present invention is to solve the problems of the polypropylene foam, and to provide a resin composition for polypropylene crosslinked foam which is excellent in heat resistance and high temperature strength and can be processed at high speed.

[0004]

In view of the above problems, the inventors of the present invention have conducted extensive studies and as a result, compared with a propylene-ethylene random copolymer having a relatively low melt flow rate (hereinafter abbreviated as MFR). It is possible to solve the above problems by blending a relatively high propylene-ethylene random copolymer at a predetermined ratio and using a propylene-ethylene random copolymer composition having an MFR value in a specific range as a raw material for a foam. Heading, completed the present invention.

That is, the present invention has an ethylene content of 0.2-
8.0% by weight of propylene-ethylene random copolymer composition (A) 10 to 90% by weight, linear low density polyethylene (B) 90 to 10% by weight, and a total of 100 parts by weight of the above (A) and (B). In contrast, the propylene-ethylene random copolymer composition (A) containing 1 to 30 parts by weight of a foaming agent (C) has a melt flow rate (hereinafter abbreviated as MFR) of 0.3 to 3 g / 10 minutes. 10 to 80% by weight of the propylene-ethylene random copolymer resin (a) and 90 to 20% by weight of the propylene-ethylene random copolymer (b) having a melt flow rate of 5 to 30 g / 10 min. The melt flow rate of (A) is 3 to 7 g / 10.
The present invention provides a resin composition for polypropylene crosslinked foam, which is characterized in that

The present invention will be described in detail below. In the present invention, the propylene-ethylene random copolymer used in the propylene-ethylene random copolymer composition (A) means that a repeating unit derived from propylene and a repeating unit derived from ethylene are randomly copolymerized. It is polymerized. The ethylene content in the propylene-ethylene random copolymer is preferably 0.2 to 8.0% by weight, particularly preferably 0.5 to 5.0% by weight. Propylene-
When the ethylene content in the ethylene random copolymer is less than 0.2% by weight, sheet moldability, foam physical properties at room temperature,
If the cross-linking efficiency and the like are not sufficient, and if it exceeds 8.0% by weight, the heat resistance of the foam at high temperature, mechanical properties, secondary workability (especially high-speed lamination processing at high temperature, vacuum forming), etc. are deteriorated.

The propylene-ethylene random copolymer composition, which is the component (A) of the resin composition of the present invention, has a relatively low MFR (low MFR) value as the propylene-ethylene random copolymer (a). ) And those with a relatively high MFR (high MFR) value (b)
It is used in combination so as to have an FR value.

Specifically, the low MFR propylene-ethylene random copolymer has an MFR of 0.3 to 3 g / 10.
Min, preferably 1-2 g / 10 min.
MF as FR propylene-ethylene random copolymer
R of 5 to 30 g / 10 minutes, preferably 6 to 20 g / 10 minutes is used. The blending ratio of both is such that the low MFR copolymer (a) is 10 to 80% by weight, preferably 20 to 60% by weight, and the high MFR copolymer (b) is 90 to 20% by weight, preferably 80 to 40% by weight. %, MF after kneading of both
R is 3 to 7 g / 10 minutes. If the MFR after kneading is less than 3 g / 10 minutes, it becomes difficult to form a sheet, and 7 g /
If it exceeds 10 minutes, problems such as deterioration of mechanical properties of the foam will occur.

In the present invention, the linear low density polyethylene (LLDPE) as the component (B) is ethylene and has 4 to 8 carbon atoms.
Is a linear copolymer with α-olefin. Above α
Examples of olefins include butene-1, 4-methylpentene-1, hexene-1, octene-1 and the like. Further, the content of ethylene in the LLDPE is 9
It is 0 mol% or more. Such LLDPE is usually 0.91
It has a density of 0 to 0.940 g / cm ³ and a melt index (190 ° C., 2.16 kg load) of 0.7 to 60 g / 10 minutes, of which 0.5 to 10 g / 10 minutes, particularly 1.0 to 7 g /
A melt index of 10 minutes is preferred.

In the present invention, the mixing ratio of the propylene-ethylene random copolymer composition (A) and the linear low density polyethylene (B) is such that (A) is 10 to 90.
% By weight, 90 to 10% by weight of (B), preferably 20 to 80% by weight of (A) and 80 to 20% by weight of (B).
Is. When the propylene-ethylene random copolymer composition (A) exceeds 90% by weight (the linear low density polyethylene (B) is 10% by weight or less), the cell nonuniformity is exhibited during foaming. Become. When the propylene-ethylene random copolymer composition (A) is 10% by weight or less (the linear low density polyethylene (B) is 90% by weight).
Above), heat resistance and mechanical properties at high temperature deteriorate.

The foaming agent (C) used in the resin composition of the present invention is a compound which is liquid or solid at room temperature and decomposes or vaporizes when heated above the melting point of the resin composition. Any material can be used as long as it does not substantially interfere with molding into a sheet or a crosslinking reaction, but a decomposition temperature in the range of 180 to 270 ° C. is particularly preferable. Specific examples of such a foaming agent include azodicarbonamide, azodicarboxylic acid metal salt, dinitrosopentamethylenetetramine, hydrazodicarbonamide, p-toluenesulfonyl semicarbazide, and s-trihydrazinotriazine.

The blending amount of the foaming agent (C) is selected according to the type of the foaming agent and the expansion ratio, but it is usually the component (A) (propylene-ethylene random copolymer composition) and the component (B). (Linear low density polyethylene) Total 100
It is used in the range of 1 to 30 parts by weight with respect to parts by weight.

In the present invention, in addition to the above-mentioned propylene-ethylene random copolymer resin composition (A), linear low density polyethylene (B) and foaming agent (C), a crosslinking reaction is carried out smoothly and efficiently. Therefore, it is preferable to add a crosslinking aid. Specific examples of such a crosslinking aid include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, bentaerythritol pentaacrylate, diallyl phthalate, diallyl maleate and the like. The amount of the crosslinking aid added is 0.5 to 5.0 parts by weight with respect to 100 parts by weight of the resin component,
It is preferably 1.0 to 3.0 parts by weight.

In the present invention, in order to further improve the properties of the polyolefin crosslinked foam, other compounding agents,
Specifically, a rubber substance, another resin, a pigment, various fillers, a flame retardant substance, an antioxidant and the like can be appropriately mixed. Next, a method for producing a polypropylene crosslinked foamed product using the composition comprising the above components will be described.

Usually, first, a propylene-ethylene random copolymer (a) 10 to 8 having an MFR of 0.3 to 3 g / 10 min.
180 to 230% by weight of 0% by weight and 90 to 20% by weight of propylene-ethylene random copolymer (b) having an MFR of 5 to 30 g / 10 minutes using a Henschel mixer, an extruder or the like.
Melt kneading at a temperature of C to prepare a propylene-ethylene random copolymer resin composition (A) having an MFR of 3 to 7 g / 10 minutes. Next, the resin composition (A),
The linear low-density polyethylene (B), the foaming agent (C), and optionally an organic peroxide, a crosslinking aid, and other compounding agents are kneaded with a Henschel mixer, an extruder, or the like. At this time, the melt-kneading temperature needs to be lower than the decomposition temperature of the foaming agent. The preferable melt-kneading temperature is 160 to 1
It is 75 ° C.

In the present invention, the propylene-ethylene random copolymer resin composition (A) is not prepared by previously melt-kneading the components (a) and (b).
The resin composition of the present invention can be prepared by collectively kneading (a), (b), (B), (C) and other optional components.

Next, the kneaded product of the resin composition of the present invention is extruded from a die such as an extruder to form a molded product such as a sheet. At this time, it is necessary to mold the sheet so that the foaming agent does not decompose and foaming does not occur. The initial decomposition temperature of the foaming agent is about 175 ° C, and the temperature of the die is 160 to 1
It is preferable to control in the range of 75 ° C.

Next, the molding is subjected to a crosslinking treatment.
As the method for forming the crosslinked structure, in addition to the method using an organic peroxide, conventionally used methods such as irradiation with ionizing radiation such as α-ray, β-ray (electron beam) and γ-ray and heating. Can be adopted. Among these methods, the method by irradiation of ionizing radiation is preferable, and the crosslinking by electron beam irradiation is most preferable. The irradiation dose of radiation varies depending on the types and amounts of the organic peroxide and the cross-linking auxiliary compounded if desired, and the degree of cross-linking, but is generally 0.1.
˜50 Mrad, preferably 1-30 Mrad. 0.1 Mrad
If the amount is less than 50 Mrad, the resin composition will be significantly deteriorated and the physical properties of the foam will be deteriorated. Foaming of the crosslinked polyolefin resin composition for crosslinked foam is performed at a temperature higher than the melting point of the resin component, preferably 200 ° C or higher, more preferably 230 to 280 ° C.
It can be carried out by heating to the temperature. The heating time required for foaming is usually 0.5 to 5 minutes.

[0019]

A propylene-ethylene random copolymer composition in which the low MFR propylene-ethylene random copolymer (a) and the high MFR propylene-ethylene random copolymer (b) are melt-kneaded to have an MFR of 3 to 7 g / 10 minutes. (A)
The resin composition for polypropylene crosslinked foams of the present invention containing the linear low density polyethylene (B) and the foaming agent (C) has mechanical properties and heat resistance peculiar to polypropylene, and particularly heat resistance, It has excellent high-temperature strength, good sheet formability, and high-speed lamination at high temperatures.
It is a foam that has excellent secondary processability during vacuum molding and high-temperature physical properties. The reason why such effects can be obtained in the resin composition of the present invention is not necessarily clear, but the molecular weight distribution of the entire resin composition becomes suitable due to an increase in the polypropylene low molecular weight region component, heat resistance, mechanical properties, It is considered that the balance of physical properties such as secondary workability (particularly vacuum formability and lamination work) has been improved.

[0020]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the following examples. The components used in Examples and Comparative Examples are as follows.

(1) Propylene-ethylene random copolymer composition (RPP-1 to RPP-6) Raw material low MFR propylene-ethylene random copolymer (low MFR-PP) and high MFR propylene-ethylene random copolymer The following 4 as a combination (high MFR-PP)
Use the types (i to iv) at the ratios shown in Table 1,
The mixture was melt-kneaded at 200 ° C. using an extruder to prepare 6 types of propylene-ethylene random copolymer compositions (RPP-1 to RPP-6) having MFR values shown in Table 1.

(I) Low MFR-PP-1: ethylene 3.0
Weight% content, manufactured by Tonen Chemical Co., Ltd., MFR (230 ° C, 2.
16 kg load) 1.0 g / 10 minutes; (ii) Low MFR-PP-2: containing 3.0% by weight of ethylene,
Tonen Chemical Co., Ltd., MFR (230 ℃, 2.16kg load) 0.
5 g / 10 min; (iii) High MFR-PP-1: containing 3.0% by weight of ethylene, manufactured by Tonen Chemical Co., Ltd., MFR (230 ° C., 2.16 kg load) 9.0 g / 10 min; (iv) High MFR- PP-2: Contains 3.0% by weight of ethylene,
Tonen Chemical Co., Ltd., MFR (230 ℃, 2.16kg load) 1
5.0 g / 10 minutes.

(2) Propylene-ethylene random copolymer (RPP-7 to RPP-9) Propylene-ethylene random copolymer for comparative examples (R
PP) has an ethylene content of 3.0% by weight,
MFR (230 ℃, 2.16kg load) is 3g / 10min (R
PP-7), 5 g / 10 min (RPP-8) and 7 g /
Three kinds of 10 minutes (RPP-9) (Tonen Chemical Co., Ltd.)
Manufactured) was used.

[0024]

[Table 1]

(3) Linear low density polyethylene (LLDP
E) GMM-1810H, manufactured by Nippon Unicar Co., Ltd., melt index (190 ° C, 2.16 kg load) 1.0 g / 10 minutes, density 0.
920 g / cm ³ . (4) Foaming agent Azodicarbonamide.

Examples 1 to 4 and Comparative Examples 1 to 5 Propylene-ethylene random copolymer compositions (RPP-1 to RPP-6) whose composition is shown in Table 2 and propylene-ethylene random copolymer (RPP) -7 to RPP-
9), linear low-density polyethylene (LLDPE), and 10 parts by weight of a foaming agent, 3 parts by weight of a cross-linking aid, 0.5 of an antioxidant.
500 parts by weight using a Henschel mixer
After mixing for 2 minutes, feed to the extruder at an extrusion temperature of 170
Extruded at ° C and pelletized.

The diameter of the pellet is 50 m in a sheet extruder.
Extruded at a temperature of 170 ° C from a die of m, thickness 1.2 mm
The sheet of was produced. Next, add 8Mrad (80
The degree of crosslinking (gel fraction) is 40 by irradiating with an electron beam of 0 KV).
It was set to% by weight. Then, it was placed in an air oven at 250 ° C. for 2 minutes to decompose the foaming agent and foam it. For each crosslinked foamed sheet thus obtained, tensile strength at 180 ° C., tensile elongation, foam density, sheet formability,
Table 2 shows the results of measuring and evaluating the vacuum formability and the settling property.

[0028]

[Table 2]

The methods for measuring the physical properties shown in Table 1 are as follows. (1) Tensile strength: The values in the longitudinal direction (MD) / width direction (TD) measured in JIS K6767 (180 ° C.) in the longitudinal direction (MD) and the width direction are shown. (2) Tensile elongation: The value of MD / TD measured in the longitudinal direction (MD) and the width direction according to JIS K6767 (180 ° C). (3) Sheet formability: The following criteria were evaluated according to the temperature rise during kneading, pressure fluctuation / torque fluctuation, pre-foaming, and the degree of roughening of the raw sheet surface. ○ …… No, △ …… Small, × …… Large.

(4) Vacuum formability: 25 cm × 25 cm ×
A 3mm foam sheet is clamped on a mold with a diameter of 60mm, and the surface temperature (heat label) of the sheet is 180 ° C.
Heating (heater temperature 300 ° C., heating for 28 seconds), vacuum is applied to the gap between the softened sheet and the mold, and molding is performed.
The value (H / 60) obtained by dividing the depth H (mm) of the sheet drawn into the mold by the diameter of the mold (60 mm) was taken as the limiting drawing ratio, and evaluated according to the following criteria. ○ …… Limit drawing ratio 0.75 or more, △ …… Limit drawing ratio 0.6 to 0.75, × …… Limit drawing ratio 0.6 or less.

(5) Settling property: 25 kg / cm ² , 180
The thickness of the foam after lamination processing under the processing conditions of 10 ° C. and 10 seconds was compared with the thickness before lamination processing and evaluated according to the following criteria. ○: No reduction in thickness, △: Reduction in thickness is small, ×: Reduction in thickness is large.

As is clear from Table 2, MF obtained by melt-kneading a low MFR propylene-ethylene random copolymer and a high MFR propylene-ethylene random copolymer.
The compositions of Examples 1-4 containing the R3-7 g / 10 min propylene-ethylene random copolymer composition had MF.
R is in the range of 3 to 7 g / 10 minutes, but Comparative Example 3, which does not contain both a low MFR copolymer and a high MFR copolymer,
Crosslinking as compared to the compositions of Comparative Examples 1 and 2 which contained both the low MFR copolymer and the high MFR copolymer but whose MFR was outside the range of 3 to 7 g / 10 min. Foam sheet tensile strength, tensile elongation, sheet formability, vacuum formability,
Also, the settling property is good and the heat resistance strength is improved.

[0033]

The resin composition for a polyolefin crosslinked foamed sheet of the present invention comprises a propylene-ethylene random copolymer having a relatively low MFR and a propylene-ethylene random copolymer having a relatively high MFR. It comprises a copolymer composition, a linear low density polyethylene, and a foaming agent. In the foam resin composition of the present invention, without substantially impairing the mechanical properties and heat resistance peculiar to polypropylene, the formability of the sheet, the high-speed lamination process at high temperature, and the secondary processability during vacuum forming are excellent. By utilizing its surface characteristics, flexibility, heat resistance and mechanical characteristics, interior materials of automobiles (door trim panels, instrument panel, ceiling panels, etc.), cushioning materials for sports equipment and food packaging, heat insulation It is suitable for use as materials, sound deadening materials, and other exterior materials.

Claims (1)

[Claims] 1. A propylene-ethylene random copolymer composition (A) 10 to 90 having an ethylene content of 0.2 to 8.0% by weight.
% By weight, 90 to 10% by weight of the linear low density polyethylene (B), and 1 to 30 parts by weight of the foaming agent (C) based on 100 parts by weight of the total of (A) and (B), The propylene-ethylene random copolymer composition (A) has a melt flow rate of 0.3 to 3 g / 10 min, a propylene-ethylene random copolymer (a) of 10 to 80% by weight, and a melt flow rate of 5 to 30 g / 10 min. Of propylene-ethylene random copolymer (b) of 90 to 20% by weight, and the composition (A) has a melt flow rate of 3 to 7 g.
The resin composition for polypropylene crosslinked foams, wherein the resin composition has a viscosity of 10 minutes.