JP2002128935A - Ethylenic resin composition for foaming and open cell foam comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylenic resin composition excellent in foam molding properties and particularly in open cell foaming properties, and an open cell foam obtainable by heating the same. SOLUTION: The ethylenic resin composition employed comprises an ethylenic resin mixture comprising an ethylene/α-olefin copolymer (A) and a crosslinked polyethylenic resin (B) and satisfying (a)-(d) below and a foaming agent (C) having a gas yield of at least 170 ml/g as measured at 210 deg.C: (a) a 1,2,4- trichlorobenzene-insoluble content at 135 deg.C of 0.1-10 wt.%, (b) a melt index of 0.5-10 g/10 min, (c) an activation energy of flow at 160-220 deg.C of at most 35 kJ/mol, (d) a melt tension, as measured using a dice having a length/diameter ratio of 8/2.095 under a condition of a stretch ratio of 5 at 140 deg.C, is at least 5 times the melt tension of (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene resin composition having excellent foam moldability, especially excellent open cell foamability, and an open cell foam obtained by heating the same.

[0002]

2. Description of the Related Art Foams of polyethylene resin are widely used mainly for cushioning materials, cushioning materials, shock absorbing materials and the like. In recent years, from the viewpoint of environmental protection, there has been an increasing demand for replacing a polyurethane foam or a soft vinyl chloride resin foam with another resin foam, and a polyethylene resin has been receiving attention as a substitute material. JP-A-10-110055 proposes a polyethylene resin composition that is recyclable and suitable for foam molding.

[0003] However, since foams obtained from polyethylene resins are generally closed-cell foams, their flexibility is inferior to polyurethane foams and soft vinyl chloride resin foams. Also, Japanese Patent Application Laid-Open No. 10-1
It is difficult to obtain an open-cell foam even if a polyethylene-based resin composition which is recyclable as proposed in Japanese Patent Publication No. 10055 and is suitable for foam molding is used.
As a method for obtaining a polyethylene-based open-cell foam, there is a method in which closed-cell foam is compressed between two rolls to break bubbles, but this method requires a post-process and is economically disadvantageous. Was.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to an ethylene resin composition for foaming which is recyclable and suitable for foaming moldability, especially for moldability of an open-cell foam, and an open-cell foam comprising the same. It provides the body.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an ethylene-based resin composition having a specific composition has foam moldability, particularly moldability of an open-cell foam. And found that the present invention was completed.

That is, the present invention provides an ethylene resin mixture ((A)) comprising an ethylene / α-olefin copolymer (A) and a crosslinked polyethylene resin (B) and satisfying the following (a) to (d): + (B)) and a blowing agent (C) having a gas generation amount of 170 ml / g or more when measured at 210 ° C., and the ethylene-based resin mixture (A) / (B) has a weight ratio of 99.5 / 0.5 to 60/40, and the ethylene-based resin mixture ((A) + (B)) / foaming agent (C) has a weight ratio of 95/5 to 80/20. The present invention relates to an ethylene-based resin composition for foaming and an open-cell foam comprising the same.

(A) 0.1 to 10% by weight of an insoluble component when dissolved in 1,2,4-trichlorobenzene at 135 ° C. (b) 190 ° C., 2.% by weight according to JIS K7210 1
Melt index measured at 6 kg load is 0.5 g /
10 minutes or more and 10 g / 10 minutes or less (c) The flow activation energy (ΔH) in the range of 160 to 220 ° C. is 35 kJ / mol or less (d) The ratio of length (L) to diameter (D) is 8/2. The present invention will be described in more detail below with a melt tension measured at 140 ° C. and a draw ratio of 5 using a die having a draw ratio of at least 5 times the melt tension of the ethylene / α-olefin copolymer (A). explain.

The ethylene / α-olefin copolymer resin (A) used in the ethylene resin composition for foaming of the present invention.
May be any copolymer as long as it is a copolymer of ethylene and an α-olefin, for example, linear low-density polyethylene, linear medium-density polyethylene, linear ultra-low-density polyethylene, and further α-olefin content. 50% by weight or less of an ethylene / propylene copolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / octene copolymer, and the like. These may be used alone or in combination of two or more. You may.

[0009] Ethylene / α-olefin copolymer (A)
May be obtained by a general production method without any particular limitation. Examples of such a method include production using a general catalyst such as a titanium-based catalyst, a vanadium-based catalyst, and a metallocene-based catalyst. can do.

As the ethylene / α-olefin copolymer resin (A) used in the ethylene resin composition for foaming of the present invention, a foam having particularly excellent flexibility can be obtained. Density is 0.910 g / cm ³
The following linear low density polyethylenes are preferred. In addition, the melt index is preferably in the range of 0.1 to 10 g / 10 minutes when measured at 190 ° C. under a load of 2.16 Kg in accordance with JIS K7210 because of particularly excellent foam molding. It is preferably in the range of 0.5 to 5 g / 10 minutes.

The crosslinked polyethylene resin (B) used in the ethylene resin composition for foaming of the present invention is an ethylene homopolymer or an ethylene / α-olefin copolymer resin. The above methods may be used in combination, and there is no particular limitation on the method of crosslinking when forming a crosslinked polyethylene resin, and examples include a method of crosslinking using an electron beam, a method of crosslinking using a radical generator, and the like.

When the crosslinked polyethylene resin (B) is prepared by using an electron beam, the foam obtained from the ethylene resin composition for foaming of the present invention is excellent in foamability and has an open-cell foam. Therefore, it is preferable to set the irradiation amount of the electron beam to 2 to 10 Mrad and to perform crosslinking in the presence of an inert gas such as nitrogen gas.

When the crosslinked polyethylene resin (B) is prepared using a radical generator, the foam obtained from the ethylene resin composition for foaming of the present invention is excellent in foaming properties and has an open cell foam. 2 x 10 radical generators per 100 g of polyethylene resin
It is preferable that after addition in a range of ^-4 to 10 × 10 ^-4 mol and homogenous kneading, crosslinking is performed under static conditions.

Further, since the foam obtained from the ethylene-based resin composition for foaming of the present invention tends to be an open-cell foam, the crosslinked polyethylene resin (B) is heated at 135 ° C.
Insoluble components (gel fraction) in the crosslinked polyethylene resin (B) when dissolved in 2,4-trichlorobenzene to prepare a 0.1% solution and filtered through a Teflon filter having a pore size of 0.45 μm Is preferably 10% by weight or more.

The ethylene / α-olefin copolymer (A) and the crosslinked polyethylene resin (B) used in the ethylene resin composition for foaming of the present invention are obtained by mixing an ethylene resin mixture ((A) + (B)) is (a) 1
0.1 to 10% by weight of an insoluble component when dissolved in 1,2,4-trichlorobenzene at 35 ° C;
(B) 190 ° C, 2.1 according to JIS K7210
Melt index measured at 6 kg load is 0.5 g /
10 minutes or more and 10 g / 10 minutes or less, (c) 160 to 220
The activation energy (ΔH) of the flow in the range of ° C. is 3
The melt tension measured at 140 ° C. and a draw ratio of 5 using a die having a ratio of length (L) to diameter (D) of 8 / 2.095 is 5 kJ / mol or less. -At least 5 times the melt tension of the olefin copolymer (A).

Here, the ethylene mixture ((A) +
(B)) was dissolved in 1,2,4-trichlorobenzene at 135 ° C. to prepare a 0.1% solution having a pore size of 0.4%.
If the insoluble component is less than 0.1% by weight or exceeds 10% by weight when filtered through a 5-micron Teflon filter, the foamable ethylene resin composition obtained will have poor foaming moldability.

The ethylene-based mixture ((A) +
(B)) according to JIS K7210 at 190 ° C.
When the melt index measured under a load of 2.16 kg is less than 0.5 g / 10 minutes, it is difficult for the resulting ethylene-based resin composition for foaming to obtain an open-cell foam. If it exceeds 10 g / 10 minutes, it will be difficult to obtain a molded sheet from the resulting ethylene-based resin composition for foaming.

Further, an ethylene-based mixture ((A) +
(B)) is (A) / (B) in a weight ratio of 99.5 / 0.
It is preferably in the range of 5-60 / 40, more preferably 99.5-80 / 25 in weight ratio. on the other hand,
Deviating from this range is not preferable because foam molding failure occurs.

When the flow activation energy (ΔH) of the ethylene-based mixture ((A) + (B)) in the range of 160 to 220 ° C. exceeds 35 kJ / mol, the obtained ethylene-based resin composition for foaming is This is not preferable because the resulting foam has remarkable adhesion.

The flow activation energy (ΔH) in the present invention may be determined by any method. For example, a cone-disk dynamic viscoelasticity measuring device (trade name: SR, manufactured by Rheometrics Co., Ltd.) -2000)
Frequency 0.01Hz-1 at each temperature of 160-220 ° C
The shear storage modulus G ′ and the shear loss modulus G ″ in the range of 00 Hz were measured, and the measured values were determined according to a known method (for example, the method described on page 91 of the course rheology) using a reference temperature of 160 ° C. It can be obtained by the formula.

Activation energy of flow (ΔH) = 2.3
03R * (dlogT / d (1 / T)) where aT is the shift amount on the horizontal axis, T is the absolute temperature, and R is the gas constant of 0.008314 kJ.

The ethylene-based mixture ((A) + (B)) was prepared by using a die having a length (L) / diameter (D) ratio of 8 / 2.095 and a draw ratio of 5 at 140 ° C. When the melt tension measured in step (a) is less than 5 times the melt tension of the ethylene / α-olefin copolymer (A), the obtained ethylene resin composition for foaming is difficult to foam mold.

The foaming agent (C) used in the ethylene resin composition for foaming of the present invention has an amount of generated gas at 210 ° C. of 170 ml / g or more. When the amount of the generated gas at 210 ° C. of the blowing agent is less than 170 ml / g, the obtained ethylene-based resin composition for foaming has poor foamability. The foaming agent (C) is not particularly limited, and is, for example, a vinyl acetate AW # containing azodicarbonamide as a main component.
9 (manufactured by Eiwa Chemical Co., Ltd.).

The amount of gas generated by the foaming agent in the present invention means that 0.1 g of the foaming agent is placed in a test tube having an internal volume of 90 ml,
After evacuating, the mixture was heated in a heating furnace set at 210 ° C. for 5 minutes, and the pressure difference before the decomposition of the blowing agent and the pressure difference (ΔP) after the decomposition of the blowing agent were determined by a manometer when the blowing agent was completely decomposed. It can be determined from the measured value by the following equation (1).

Evolved gas amount = Internal volume (ml) × (ΔP / 760 mmHg) / Sample weight (g) (1) The ethylene resin composition for foaming of the present invention has an ethylene / α
-An ethylene resin mixture ((A) +) comprising an olefin copolymer (A) and a crosslinked polyethylene resin (B)
(B)) and the amount of gas generated at 210 ° C. was 17
The foaming agent (C) is 0 ml / g or more, and the weight ratio of the ethylene-based resin mixture ((A) + (B)) / the foaming agent (C) is in the range of 95/5 to 80/20. If the ratio is outside the above range, the obtained ethylene-based resin composition for foaming cannot have good foamability.

As a method for producing the open-cell foam of the present invention, it is desirable that after kneading the foaming agent, the foam is once formed into a sheet or rod shape, and then foamed in a heating furnace. Here, when forming into a sheet or rod shape, the temperature must be lower than the decomposition temperature of the used foaming agent. The heating furnace to be used is not limited, and a batch type, a continuous type, or a salt bath can be used. In particular, an open-cell foam can be more easily obtained.

The ethylene resin composition for foaming of the present invention comprises:
If necessary, for example, calcium carbonate, mica, talc, silica, barium sulfate, calcium sulfate, kaolin, clay, pyroferrite, bentonite, selesanite, zeolite, nepheline cinite, attapulgite, wollastonite, ferrite, calcium silicate, Inorganic fillers such as magnesium carbonate, dolomite, antimony trioxide, titanium oxide, iron oxide, molybdenum disulfide, graphite, gypsum, glass beads, glass powder, glass balloon, glass fiber, quartz, quartz glass, and organic and inorganic pigments You may mix. Also, foaming aid, crystal nucleating agent, clarifying agent, anti-blocking agent,
Release agents, antistatic agents, slip agents, antifogging agents, lubricants, heat stabilizers, ultraviolet light stabilizers, light stabilizers, weathering stabilizers, fungicides, rust inhibitors, ion trap agents, flame retardants, difficult A combustion aid or the like may be added as necessary.

Further, the ethylene resin composition for foaming of the present invention may contain another rubber or a thermoplastic resin without departing from the object of the present invention. Examples of such rubber include natural rubber, acrylonitrile butadiene rubber, butadiene rubber, isoprene rubber, styrene butadiene rubber, silicone rubber, polynorbornene rubber, and chloroprene rubber.Examples of the thermoplastic resin include ethylene-ethyl acrylate copolymer. Polymer,
Examples thereof include polybutene, acid-modified polyolefin, polyamide, styrene-based thermoplastic elastomer, and polyolefin-based thermoplastic elastomer.

[0029]

EXAMPLES The present invention will be described below with reference to examples, but these are merely examples, and the present invention is not limited to these examples.

Hereinafter, various measurements in Examples and Comparative Examples will be described.

[Amount of Gas Generated by Blowing Agent] The amount of gas generated by the blowing agent is 0.1 g of the blowing agent with an internal volume of 90 m.
After putting in a test tube and evacuating, heating in a heating furnace set at 210 ° C. for 5 minutes, the pressure before and after the heating was measured by a manometer, and the pressure was determined by the following formula (1) from the measured value. .

Generated gas amount = (internal volume × (pressure after heating−pressure before heating) / 760) / sample weight (g) (1)-Measurement of insoluble component amount (gel fraction)-crosslinked polyethylene, The ethylene-based resin mixture was dissolved in 1,2,4-trichlorobenzene at 135 ° C. to prepare a 0.1% solution. When this solution was filtered through a Teflon (registered trademark) filter having a pore size of 0.45 μm, The weight of insoluble components that could not be filtered was measured and determined.

Melt Index 190 ° C., 2.16 Kg according to JIS K7210
It measured under the load of.

-Activation Energy of Flow- Using a conical disk type dynamic viscoelasticity measuring device (SR-2000, manufactured by Rheometrics Co., Ltd.) at 160 ° C. and 190 ° C.
℃, frequency at each temperature of 220 ℃ 0.01Hz ~ 100H
The shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ in the range of z are determined, and these are determined by the following formula using 160 ° C. as a reference temperature and a known method (method described on page 91 of the course rheology). it can.

Activation energy of flow (ΔH) = 2.3
03R * (dlogT / d (1 / T)) where aT is the shift amount on the horizontal axis, T is the absolute temperature, and R is the gas constant of 0.008314 kJ.

Melting Tension A length (L) / diameter (D) ratio of 8/2. Was measured by a capillary viscometer (manufactured by Toyo Seiki Co., Ltd., trade name: Capillograph) set at a barrel diameter of 9.55 mm and a temperature of 140 ° C. A 095 die was mounted, and the load required for drawing was measured under the conditions of a plunger descending speed of 10 mm / min and a drawing speed of 1 m / min, that is, a draw ratio of 5, and this was taken as a melt tension (MS).

-Measurement of expansion ratio- Specific gravity (SA) before foam molding and specific gravity (S) after foam molding
B) was replaced with an underwater replacement hydrometer (NADA Electroni)
(SA) / (SB) was determined as the expansion ratio ER.

-Evaluation of open cells of foam- [0038] The surface of the obtained foam was shaved, and a test piece cut into 5 cm long × 5 cm wide × 1 cm high was prepared, and a 5 kg load was applied to the test piece in water. After standing for 10 minutes, the load was removed and it was determined whether or not water absorption was observed. If water absorption is observed, the foam has open cells.

○: Open-cell foam ×: Closed-cell foam Example 1 High-density polyethylene (Nipolon Hard # 5110, manufactured by Tosoh Corporation, melt index: 0.9 g / 10
5) ^10-4 mol of α, α'-bis (t-butylperoxy-m-isopropyl) benzene (manufactured by NOF CORPORATION, trade name: Perbutyl P) as a peroxide was added to 100 g of the mixture. Was kneaded by a roll mill kneader. The high-density polyethylene was crosslinked by heating the obtained kneaded material with a compression molding machine set at 190 ° C. for 15 minutes to obtain a crosslinked polyethylene resin. Then, the crosslinked polyethylene resin was finely crushed by a freezing and crushing machine. The insoluble component of the obtained crosslinked polyethylene resin was 73% by weight.

30 g of the obtained crosslinked polyethylene resin and linear low-density polyethylene (manufactured by EXXON, trade name E
XACT3028, density 0.8980 g / cm3, melt index: 1.1 g / 10 min, Mw / Mn:
1.8, melt tension: 20 mN) 470 g, hindered phenol-based heat stabilizer (manufactured by Ciba-Geigy, trade name Irganox 1010) 3 g, phosphorus-based heat stabilizer (manufactured by Ciba-Geigy, trade name: Irgafos 168) 3 g of the mixture was kneaded with a roll mill kneader having a surface temperature of 100 ° C. for 15 minutes to prepare an ethylene-based mixture, and azodicarbonamide (trade name: Vinyl Hole AC # LQ, manufactured by Eiwa Chemical Co., Ltd., as a foaming agent, amount of generated gas: 210 ml) / G) and kneaded for 3 minutes to obtain an ethylene resin composition for foaming.

At that time, the insoluble component of the ethylene-based mixture was 2.1% by weight, and the melt index was 1.0 g /
10 minutes, the activation energy of flow (ΔH) is 29
kJ / mol and the melt tension was 230 mN.

After the obtained roll sheet was compression molded at 100 ° C., it was placed in an oven preheated to 200 ° C. for 7 minutes to obtain a foam.

The obtained foam had an expansion ratio of 12 and had open cells.

Example 2 High-density polyethylene (Nipolon Hard # 5110, manufactured by Tosoh Corporation, melt index: 0.9 g / 10)
5) ^10-4 mol of α, α'-bis (t-butylperoxy-m-isopropyl) benzene (manufactured by NOF CORPORATION, trade name: Perbutyl P) as a peroxide was added to 100 g of the mixture. Low density polyethylene (EXACT4051, trade name EXACT4051, density 0.8986 g)
/ Cm3, melt index: 2.3 g / 10 minutes,
Mw / Mn: 1.9) and peroxide α, α'-bis (t-
Butyl peroxy-m-isopropyl) benzene (manufactured by NOF CORPORATION, trade name: Perbutyl P) was 5.3 × 10 ⁻⁴ mol.
An ethylene resin composition for foaming was prepared in the same manner as in Example 1 except that a crosslinked polyethylene resin (the insoluble component was 2.1% by weight) was obtained by addition to obtain a foam.

At this time, the insoluble component of the ethylene-based mixture was 2.1% by weight, and the melt index was 2.1 g / g.
10 minutes, the activation energy of flow (ΔH) is 29
kJ / mol, and the melt tension was 230 mN.

The foam obtained had an expansion ratio of 11 and had open cells.

Example 3 An ethylene / α-olefin copolymer resin (A) was used as a linear low-density polyethylene (EXACT, trade name EXACT).
4024, density 0.8884 g / cm3, melt index: 3.7 g / 10 min, Mw / Mn: 1.8, melt tension: 10 mN), except that the ethylene-based resin composition for foaming was used in the same manner as in Example 1. The product was adjusted to obtain a foam.

At this time, the insoluble component of the ethylene-based mixture was 2.1% by weight, and the melt index was 3.7 g /
10 minutes, the activation energy of flow (ΔH) is 29
kJ / mol, and the melt tension was 230 mN.

The foam obtained had an expansion ratio of 10 and had open cells.

Example 4 15 g of a cross-linked polyethylene and azodicarbonamide as a blowing agent (manufactured by Eiwa Kasei Co., Ltd., trade name VINHALL AC # L)
Q, the amount of generated gas: 210 ml / g) was replaced by azodicarbonamide (trade name: Vinyl Hole SW # 5, manufactured by Eiwa Chemical Co., Ltd., generated gas amount: 180 ml / g).
An ethylene resin composition for foaming was prepared in the same manner as in Example 1 to obtain a foam.

At that time, the insoluble component of the ethylene-based mixture was 1.0% by weight, and the melt index was 3.7 g /
10 minutes, the activation energy of flow (ΔH) is 29
kJ / mol, and the melt tension was 130 mN.

The foam obtained had an expansion ratio of 9,
It had open cells.

Comparative Example 1 The blowing agent was azodicarbonamide (manufactured by Eiwa Chemical Co., Ltd., trade name: Vinyl Hole AC # LQ, amount of generated gas: 210 ml /
g) was replaced with p, p'-oxybisbenzenesulfonylhydrazine (manufactured by Sankyo Kasei Co., Ltd., trade name: CellMike S, generated gas amount: 155 ml / g) by the same method as in Example 1. An ethylene resin composition for foaming was prepared to obtain a foam.

In this case, the insoluble component of the ethylene-based mixture was 2.1% by weight, and the melt index was 1.1 g / g.
10 minutes, the activation energy of flow (ΔH) is 29
kJ / mol, and the melt tension was 230 mN.

The foam obtained had an expansion ratio of 10 and had closed cells.

Comparative Example 2 Peroxide α, α'-bis (t-butylperoxy-m-
0.5 × 10 ⁻⁴ mol instead of 5 × 10 ⁻⁴ mol of isopropyl) benzene (manufactured by NOF CORPORATION, trade name: Perbutyl P)
An ethylene resin composition for foaming was prepared in the same manner as in Example 1 except that the crosslinked polyethylene resin (insoluble component was 0% by weight) was adjusted to 10 ^-4 mol, and a foam was obtained.

At this time, the insoluble component of the ethylene-based mixture was 0% by weight, and the melt index was 1.1 g / 10
And the activation energy of flow (ΔH) is 29 kJ
/ Mol and the melt tension was 70 mN.

The foam obtained had an expansion ratio of 7,
It had closed cells. The foam cells were also non-uniform.

Comparative Example 3 Example 1 except that no crosslinked polyethylene resin was used.
The ethylene resin composition for foaming was prepared in the same manner as described above to obtain a foam.

At this time, the insoluble component of the ethylene mixture was 0% by weight, and the melt index was 1.1 g / 10
And the activation energy of flow (ΔH) is 29 kJ
/ Mol, and the melt tension was 20 mN.

The foam obtained has an expansion ratio of 6,
It had closed cells. The foam cells were also non-uniform.

[0062]

[Table 1]

[0063]

The ethylene resin composition for foaming of the present invention is excellent in foam moldability, particularly open cell foamability, whereby an open cell foam of ethylene resin can be easily obtained.

Claims (2)

[Claims] 1. An ethylene / α-olefin copolymer (A)
And a cross-linked polyethylene resin (B), the following (a)
Ethylene resin mixture ((A) +) satisfying (d)
(B)) and the amount of gas generated at 210 ° C. was 17
The ethylene-based resin mixture (A) / (B) has a weight ratio of 99.5 /
0.5 to 60/40, and the ethylene-based resin mixture ((A) + (B)) / foaming agent (C) has a weight ratio of 95 /
An ethylene-based resin composition for foaming, which is in the range of 5 to 80/20. (A) Insoluble components when dissolved in 1,2,4-trichlorobenzene at 135 ° C. are 0.1% by weight or more and 10% by weight or less. (B) 190 ° C., 2.1 in accordance with JIS K7210.
Melt index measured at 6 kg load is 0.5 g /
10 minutes or more and 10 g / 10 minutes or less (c) The flow activation energy (ΔH) in the range of 160 to 220 ° C. is 35 kJ / mol or less (d) The ratio of the length (L) to the diameter (D) is 8 The melt tension measured at 140 ° C. and a draw ratio of 5 using a dice of /2.095 is at least 5 times the melt tension of the ethylene / α-olefin copolymer (A). 2. An open-cell foam obtained by heating and foaming the ethylene-based resin composition for foaming according to claim 1.