JPH0465442A - Foaming cross-linked polyolefin resin composition - Google Patents

Abstract

PURPOSE:To provide the composition containing propylene-ethylene random copolymer having a melt flow rate adjusted by degradation and having excellent moldability without damaging the mechanical characteristics and thermal resistance thereof and useful for automotive interiors, etc. CONSTITUTION:The objective composition (A) 10-90 wt.% of propylene-ethylene random copolymer having a melt flow rate adjusted by degradation and having an ethylene content of 0.2-8.0 wt.%, (B) 90-10 wt.% of linear low density polethylene, (C) a foaming agent in an amount of 1-30 pts. wt. per 100 pts. wt. of the total amount of the components A and B. The component A preferably has a melt flow rate of 0.3-30 g/10 min before the degradation and 5-100 g/10 min, the increase of the melt flow rate due to the degradation being preferably >=g/10 min.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a resin composition for crosslinked polyolefin foam, and in particular, a resin composition that improves the moldability of sheets without substantially impairing the mechanical properties and heat resistance specific to polypropylene. The present invention relates to a resin composition for crosslinked polyolefin foams that provides foams with excellent mechanical properties, excellent secondary processability, and high heat resistance.

[Prior art and problems to be solved by the invention] Polyolefin foams have excellent mechanical strength, flexibility, texture, heat resistance, chemical resistance, etc., and are used as interior materials for automobiles, insulation materials,
It is widely used in cushioning materials for sporting goods and food packaging, as well as other sound-deadening materials and exterior materials.

Among them, polyethylene foam has a low melting point and is therefore flexible.
Excellent texture, elongation, etc. On the other hand, polypropylene foam has excellent mechanical strength such as tensile strength and bending strength, as well as heat resistance, and has a high melting point, so molecular scission progresses considerably during foaming, resulting in large and uneven cells. easy to become.

Moreover, ordinary blowing agents start to decompose at about 170°C, so they are not suitable for polypropylene resins, which have a high melting point.Furthermore, blowing agents with high decomposition temperatures generate only a small amount of gas, so they are not suitable for use with polypropylene resins, which have a high melting point. In order to obtain a high foaming ratio, a large amount of foaming agent is required, which poses the problem of being uneconomical.

Therefore, propylene-ethylene random copolymers with relatively low melting points are used, but in secondary processing of foam, such as vacuum forming and stamping forming,
A foam that can be molded at a temperature of 130 to 200°C and has a heat resistance that can withstand this temperature has not yet been obtained. That is, until now, there has been no composition that provides foamed materials with excellent moldability and high heat resistance for raw notebooks.

Therefore, the object of the present invention is to provide a polypropylene sheet with excellent formability, good mechanical properties, excellent secondary processability, and high heat resistance without substantially impairing the mechanical properties and heat resistance specific to polypropylene. An object of the present invention is to provide a resin composition for crosslinked polyolefin foam that provides a foam.

[Means to solve the problem]

As a result of intensive research in view of the above problems, the present inventors have developed a composition containing a propylene-ethylene random copolymer whose melt flow rate has been adjusted by degradation, linear low-density polyethylene, and a blowing agent. discovered that it is possible to provide a foam that has excellent moldability of raw sheets, good mechanical properties, and excellent secondary processability without substantially impairing the mechanical properties and heat resistance specific to polypropylene, The present invention was conceived.

That is, the resin composition for a crosslinked polyolefin foam of the present invention comprises (a) a propylene-ethylene random copolymer having a melt flow rate adjusted by degradation and having an ethylene content of 0.2 to 8.0% by weight, 10 to 90% by weight; %, (b) 90-10% by weight of linear low density polyethylene, (
c) The propylene-ethylene random copolymer (a)
+ It is characterized in that it contains 1 to 30 parts by weight of a blowing agent based on a total of 100 parts by weight of the linear low-density polyethylene ('b).

The present invention will be explained in detail below.

In the present invention, (a) the propylene-ethylene random copolymer is a copolymer randomly copolymerized with a repeating unit derived from propylene and a repeating unit derived from ethylene. The ethylene content in the propylene-ethylene random copolymer is 0.2 to 8.0% by weight, preferably 0.5 to 5.0% by weight.

If the ethylene content in the propylene-ethylene random copolymer is less than 0.2% by weight, the sheet formability, physical properties of the foam at room temperature, crosslinking efficiency, etc. will be insufficient, and if it exceeds 8.0% by weight, the ethylene content will be insufficient. The physical properties of the foam at high temperatures, secondary processability, etc. deteriorate.

In the present invention, as such a propylene-ethylene random copolymer, the melt flow rate (
Use one adjusted to 230°C (12, 16 kg load).

The propylene-ethylene random copolymer before degradation preferably has a melt flow rate of 0.3 to 30 g/10 min. A more preferable melt flow rate is 1.
0 to 20 g/10 minutes.

The melt flow rate of the propylene-ethylene random copolymer after degradation is preferably 5 to 100 g/10 min. A more preferable melt flow rate is 9 to 50 g/1
It is 0 minutes.

Furthermore, the increase in melt flow rate due to degradation is 2g/1
It is preferable that the time is 0 minutes or more. If the increase in melt flow rate is less than 2 g/10 minutes, the moldability at low temperatures is not good. A more preferable increase in melt flow rate is 5 to 20
g/10 minutes.

Note that the method of degradation is not particularly limited, and may be a method using an organic peroxide, a method using ionizing radiation, or the like.

In the case of degradation with an organic peroxide, for example, the undegraded propylene-ethylene random copolymer is heated in an extruder at 170 to 250°C in the presence of the organic peroxide to 0.5
This may be carried out by melt-kneading for ~5 minutes.

The organic peroxide preferably has a decomposition temperature of 170°C or higher, such as methyl ethyl ketone peroxide, t-butyl peroxyisopropyl carbonate, dicumyl peroxide, cumene hydroperoxide, 2,5-dimethyl -2,5-di(t-butylperoxy)hexane, 2,5-dimethyl 2,5-di(t-butylperoxy)hexyne-3, and di-t-butylperoxyphthalate.

These organic peroxides are used depending on the desired melt flow rate, and are usually used in a proportion of about 0.01 to 0.5 parts by weight per 100 parts by weight of homopolypropylene.

Further, when the degradation is carried out by irradiation with ionizing radiation, α rays, β rays (electron beams), γ rays, etc. can be used as the ionizing radiation. Among these, gamma rays are preferred.

In the present invention, (b) linear low density polyethylene is a linear copolymer of ethylene and a substitute olefin having 4 to 8 carbon atoms. Examples of the above-mentioned olefins include 4-methylpentene-1,1-butene and 1-hexene. Further, the content of ethylene in the linear low density polyethylene is 90 mol% or more, preferably 95 mol% or more. Such linear low density polyethylene typically has a density of 0.910 to 0.940 g/apr and a density of 0.7
~60g/10min melt index (ML JIS
K7210, load 2.16 kg, 190°C).

The blending ratio of (a) propylene-ethylene random copolymer and (b) linear low-density polyethylene as described above is (al propylene-ethylene random copolymer + (b)
) Assuming 100% by weight of linear low density polyethylene (a)
(b) 10 to 90% by weight of propylene-ethylene random copolymer, preferably 30 to 80% by weight, and (b) 90 to 10% by weight of linear low density polyethylene, preferably 7% by weight;
It is 0 to 20% by weight. (a) If the propylene-ethylene random copolymer is less than 10% by weight ((b) if the linear low density polyethylene is more than 90% by weight), the mechanical strength and heat resistance, which are the characteristics of polypropylene resin, will not be sufficient. (a) If the propylene-ethylene random copolymer exceeds 90% by weight ((b) if the linear low-density polyethylene contains less than 10% by weight), the low-temperature formability of the raw sheet and the foam's Processability, etc. is not sufficient.

In the present invention, the blowing agent (c) is a compound that is liquid or solid at room temperature, or decomposes or vaporizes when heated above the melting point of polypropylene, and substantially inhibits forming such as sheeting and crosslinking reactions. Any material can be used as long as it does not interfere with the decomposition temperature or 180 to 270°.
C range is preferred.

Specific examples thereof include azodicarbonamide, azodicarboxylic acid metal salt, dinitrosopentamethylenetetramine, hydrazodicarbonamide, p-toluenesulfonyl semicarbazide, and s-h hydrazinotriazine. These blowing agents include (a) propylene-
It is used in the range of 1 to 30 parts by weight, based on the total of 100 parts by weight of the ethylene random copolymer + (b) linear low-density polyethylene (hereinafter referred to as the resin component), and it can be used as desired depending on the type and expansion ratio of each. The amount of mixture can be changed.

In the present invention, in addition to the above-mentioned (a) propylene-ethylene random copolymer, (b) linear low-density polyethylene and blowing agent, a peroxide may be added in order to carry out a crosslinking reaction. However, when the crosslinking reaction is carried out using ionizing radiation, it is not necessary to use an organic peroxide. When using an organic peroxide, it is preferable that the decomposition temperature is about 150°C or higher. Specific examples include methyl ethyl ketone peroxide (182°C), t-butylperoxyisopropyl carbonate (153°C) ), dicumyl peroxide (171″C), cumene hydroperoxide (25
5°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (179°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane- 3
(193°C), sheet t-butyl peroxyphthalate (159°C), etc. These organic peroxides are used in an amount of 0.01 to 1.0 parts by weight, preferably 0.05 to 0.5 parts by weight, based on 100 parts by weight of the resin component.

Further, in order to carry out the crosslinking reaction smoothly and efficiently, it is preferable to add a crosslinking aid. Examples of crosslinking coagents that can be used in the present invention include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol pentaacrylate, diallyl phthalate, diallyl maleny 1, and the like. The amount of the crosslinking aid added is 0.5 to 100 parts by weight of the resin component.
The amount is 5.0 parts by weight, preferably 1.0 to 3.0 parts by weight.

In the other invention, various other compounding agents, specifically rubber substances, other resins, pigments, various fillers, flame retardant substances, Antioxidants and the like may be appropriately mixed.

Next, a method for producing a polyolefin crosslinked foam using a composition consisting of the above-mentioned components will be described.

First, as mentioned above, (a) propylene-ethylene random copolymer, (b) linear low-density polyethylene, (c) blowing agent, and organic peroxides, crosslinking aids, and other ingredients blended as necessary. The ingredients are kneaded using a kneader, Henschel mixer, extruder, etc. At this time, the melt-kneading temperature must be lower than the decomposition temperature of the blowing agent. The preferred melt-kneading temperature is 160 to 180°C.

Thereafter, the mixed material is extruded from a die such as an extruder and formed into a molded product such as a sheet. At this time, set the temperature of the dice to 16
It is preferable to control the temperature within the range of 0 to 180°C.

The molded article obtained in this way is then crosslinked, or
As for the formation method of the crosslinked structure, in addition to the method using organic peroxide as mentioned above, there are conventional methods such as irradiation with ionizing radiation such as alpha rays, beta rays (electron beams), and γ rays, and methods using heating. It is possible to adopt the method described. Among these methods, a method by irradiation with ionizing radiation is preferred, and crosslinking by irradiation with an electron beam is particularly preferred. The amount of radiation irradiated varies depending on the type and amount of organic peroxide and crosslinking aid, and the degree of crosslinking, but is generally 0.1 to 50 Mr.
ad, preferably 1 to 30 Mrad.

The thus crosslinked resin composition for crosslinked polyolefin foam is foamed at a temperature higher than the melting point of the resin component, preferably 200°C or higher, more preferably 230 to 280°C.
This can be done by heating to a temperature of °C. The heating time required for foaming is usually 0.5 to 5 minutes.

[For production]

The resin composition for a crosslinked polyolefin foam of the present invention contains a propylene-ethylene random copolymer whose melt flow rate has been adjusted by degradation, linear low-density polyethylene, and a blowing agent.

Such a composition has excellent moldability of the raw sheet without substantially impairing the mechanical properties and heat resistance peculiar to polypropylene, and can also produce a foam with good mechanical properties and excellent secondary processability. give.

The reason why such an effect is obtained is not necessarily clear, or it may be that the propylene-ethylene random copolymer, which has improved secondary processability without lowering the melting point through degradation, and the propylene-ethylene random copolymer This is thought to be because the composition is made with linear low-density polyethylene, which has excellent compatibility and good moldability.

〔Example〕

The present invention will be explained in more detail by the following specific examples.

Example 1 and Comparative Example 1 100 parts by weight of a propylene-ethylene random copolymer (ethylene content 3.0% by weight) with a melt flow rate (VFR 230°C 2, 16 kg load) Ig/10 minutes,
0.05 parts by weight of organic peroxide was put into an extruder, and 19
The mixture was kneaded at 0°C for 2 minutes, and the VFR was adjusted to 9 g/10 minutes.

70 parts by weight of the thus obtained propylene-ethylene random copolymer (cRRPP■) and linear low density polyethylene (LLDPE, melt index (
Ml, 190°C, 12, 16 kg load) 2.5, density o, 920 g/al) 30 parts by weight, 15 parts by weight of azodicarbonamide as a blowing agent, 2.0 parts by weight of crosslinking aid, and 0 parts by weight of antioxidant. After mixing for 2 minutes at 500 rpm using a Henschel mixer, the mixture was fed into an extruder and pressed at an extrusion temperature of 170° C. to form pellets.

This pellet was fed to a sheet forming machine, and the extrusion temperature was 170.
°C and extruded to create a sheet with a thickness of 1.0 mm.

This sheet was then irradiated with an electron beam at a dose of 8 Mrad to effect crosslinking. Thereafter, it was placed in an air oven at 250°C for 2 minutes to decompose the foaming agent and cause foaming.

For each crosslinked foam sheet obtained in this way, density after foaming, gel fraction, tensile strength, tensile elongation and tear strength at 23°C, tensile strength and tensile elongation at high temperature (130°C) and heat-resistant dimensional stability were measured.

Furthermore, the moldability of the obtained crosslinked foam sheet was visually evaluated according to the following criteria.

◎, Appearance is very good.

○ Appearance is good.

△ Appearance is somewhat poor.

×・Appearance is poor.

The results are shown in Table 1 along with the composition of the resin component.

In addition, in Example 1, the MFR was reduced to 9 g/1 due to degradation.
Instead of the propylene-ethylene random copolymer that had been used for 0 minutes, a 4-propylene-ethylene random copolymer (RPP■, ethylene content 3% by weight) was used that had a VFR of 9 g/10 minutes without degradation. As Comparative Example 1, the composition was similarly made into a crosslinked foam sheet, and the density after foaming, gel fraction, tensile strength at 23°C, tensile elongation and tear strength,
Tensile strength and tensile elongation at high temperature (130"C),
Heat resistant dimensional stability and sheet formability were measured.

The results are also shown in Table 1.

Example 2 and Comparative Example 2 100 parts by weight of propylene-ethylene random copolymer (ethylene content 1% by weight) with a melt flow rate (MFR 230°C 2, 16 kg load) Ig/10 minutes and 0.08 parts by weight of organic peroxide Put the parts by weight into the extruder and heat at 190°.
The mixture was kneaded at C for 2 minutes, and the MFR was adjusted to 15 g/10 minutes.

70 parts by weight of the thus obtained propylene-ethylene random copolymer (cRRPP■), linear low density polyethylene (LLDPE), melt index (M+
, 190°C12, 16kg load) 2.5, density 0.
920g/d), 15 parts by weight of abdicarbonamide as a blowing agent, 2.0 parts by weight of a crosslinking aid, and 0.5 parts by weight of an antioxidant were added, and the mixture was mixed at 500 rpm+ using a Henschel mixer. After mixing for a minute, the mixture was fed into an extruder and extruded at an extrusion temperature of 170°C to form pellets.

This pellet was fed to a sheet forming machine, and the extrusion temperature was 170.
°C and extruded to create a sheet with a thickness of 1.0 mm.

Next, this sheet was irradiated with an electron beam at a dose of 12 MradO to perform crosslinking. Thereafter, it was placed in an air oven at 250°C for 2 minutes to decompose the foaming agent and cause foaming.

For each crosslinked foam sheet obtained in this way, density after foaming, gel fraction, tensile strength, tensile elongation and tear strength at 23°C, tensile strength and tensile elongation at high temperature (130°C) and heat-resistant dimensional stability were measured.

The moldability of the sheet was evaluated using the same criteria as in Example 1.

The results are shown in Table 1 along with the composition of the resin component.

In addition, in Example 2, the MFR was reduced to 15 g/
Instead of the propylene-ethylene random copolymer with a 10-minute treatment time, a propylene-ethylene random copolymer (RPP■,
Comparative Example I
Similarly, a cross-linked foam sheet was prepared, and the density after foaming, gel fraction, tensile strength, tensile elongation and tear strength at 23°C, tensile strength and tensile elongation at high temperature (130°C), and heat resistant dimensional stability were determined. The properties and sheet formability were measured.

The results are also shown in Table 1.

(1), the value measured by LIS K6767,
Values in the longitudinal direction (MD) and width direction (TD) are shown.

(2) It is a value measured according to JIS 6767, and shows the value in the longitudinal direction (MD) and width direction (TD).

(3) It is a value measured according to JIS K6767, and shows the value in the longitudinal direction (MD) and width direction (TD).

(4) Values were measured according to JIS K6767, and the values are shown in the longitudinal direction (MD) and width direction (TD).

(5) Values were measured according to JIS K6767, and the values are shown in the longitudinal direction (MD) and width direction (TD).

(6) Longitudinal direction (after being left at 120°C for 22 hours)
MD) 7 The shrinkage rate (%) in the width direction (TD) was measured.

As is clear from Table 1, the composition of Example 1.2:
Comparative example 1 using the same MFR but not degraded.
Compared to composition No. 2, the resulting crosslinked foam has good tensile strength, tensile elongation, tear strength, tensile strength and tensile elongation at high temperatures, and is also excellent in heat-resistant dimensional stability. Furthermore, the moldability of the sheet was also good.

〔Effect of the invention〕

As detailed above, the resin composition for crosslinked polyolefin foam of the present invention contains a propylene-ethylene random copolymer whose melt flow rate has been adjusted by degradation, linear low-density polyethylene, and a blowing agent. It becomes. This composition has excellent sheet formability without substantially impairing the mechanical properties and heat resistance specific to polypropylene, and has good mechanical properties and excellent secondary processability, making it possible to form highly heat-resistant foams. give.

Such a resin composition for polyolefin crosslinked foam is
Utilizing its surface properties, flexibility, heat resistance, and mechanical properties, it is suitable for use in automobile interior materials, sporting goods, cushioning materials for food packaging, heat insulation materials, sound deadening materials, and other exterior materials. It is.

Applicant: Tonen Petrochemical Co., Ltd.

Claims (3)

[Claims] (1) (a) 10 to 90% by weight of a propylene-ethylene random copolymer with an ethylene content of 0.2 to 8.0% by weight, whose melt flow rate was adjusted by degradation, and (b) linear low-density polyethylene. and (c) 1 to 30 parts by weight of a blowing agent based on a total of 100 parts by weight of the propylene-ethylene random copolymer (a) + the linear low density polyethylene (b). A resin composition for a crosslinked polyolefin foam, characterized by: (2) In the resin composition for polyolefin crosslinked foam according to claim 1, the propylene-ethylene random copolymer has a melt flow rate of 0.3 to 30 before degradation.
g/10 minutes, and the melt flow rate after degradation is 5~
100 g/10 minutes, and an increase in melt flow rate due to degradation of 2 g/10 minutes or more. (3) The resin composition for polyolefin crosslinked foam according to claim 1 or 2, characterized in that the propylene-ethylene random copolymer is degraded by heating after adding an organic peroxide. A resin composition for a crosslinked polyolefin foam.