JP2012107222A - Ethylene resin composition, crosslinked foam, member for footwear, and footwear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylene resin composition capable of providing a crosslinked foam which is lightweight and has a large impact resilience.SOLUTION: The ethylene resin composition includes: ≥10 wt.% and ≤90 wt.% of an ethylene-α-olefin copolymer (A1) which has a density of ≥900 kg/mand ≤940 kg/m, a melt flow rate of ≥0.01 g/10 min and ≤5 g/10 min, and a flow activation energy of <40 kJ/mol; and ≥10 wt.% and ≤90 wt.% of an ethylene-α-olefin copolymer (A2) which has a density of ≥800 kg/mand <880 kg/m, and a melt flow rate of ≥0.01 g/10 min and ≤5 g/10 min; and ≥0.1 pt.wt and ≤10 pts.wt of a crosslinking agent (B) and ≥1 pt.wt and ≤50 pts.wt of a foaming agent (C) based on 100 pts.wt of the total weight of the (A1) and the (A2).

Description

  The present invention relates to an ethylene resin composition, a cross-linked foam, a footwear member, and footwear.

  Cross-linked foam made of ethylene resin is widely used as daily goods, flooring materials, sound insulation materials, heat insulating materials, footwear materials (outer sole (lower bottom), midsole (upper bottom), insole (insole), etc.) Is used. For example, Patent Document 1 describes a foam obtained by crosslinking and foaming an ethylene-vinyl acetate copolymer, and Patent Document 2 is obtained by crosslinking and foaming an ethylene-α-olefin copolymer. Foam is described.

Japanese Patent Publication No. 3-2657 Japanese Patent Laid-Open No. 10-182866

However, the foam obtained by crosslinking and foaming the ethylene-vinyl acetate copolymer is required to be lightweight. Moreover, the foam obtained by crosslinking and foaming the ethylene-α-olefin copolymer has insufficient rebound resilience.
Under such circumstances, the problem to be solved by the present invention is an ethylene resin composition capable of obtaining a crosslinked foam having a light weight and high impact resilience, and a crosslinked foam obtained by heating the ethylene resin composition. Another object of the present invention is to provide a footwear member having a layer made of the foam, and a footwear having the footwear member.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the present invention
It has a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 20 carbon atoms, has a density of 900 kg / m ³ or more and 940 kg / m ³ or less, and a melt flow rate of 0 An ethylene-α-olefin copolymer (A1) having a flow activation energy of less than 40 kJ / mol (A1) of 10% by weight to 90% by weight;
Monomer units and the number of carbon atoms based on ethylene and a monomer unit based on 3-20 of α- olefin, the density is less than 800 kg / ^{m 3} or more 880 kg / ^{m 3,} a melt flow rate of 0 10 wt% or more and 90 wt% or less of ethylene-α-olefin copolymer (A2) that is 0.01 g / 10 min or more and 5 g / 10 min or less (provided that ethylene-α-olefin copolymer (A1) and ethylene- the total weight with the α-olefin copolymer (A2) is 100% by weight),
For a total weight of 100 parts by weight of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2),
Cross-linking agent (B) 0.1 parts by weight or more and 10 parts by weight or less,
The present invention relates to an ethylene resin composition containing 1 part by weight or more and 50 parts by weight or less of a foaming agent (C).

  INDUSTRIAL APPLICABILITY According to the present invention, an ethylene resin composition capable of obtaining a light-weight and high impact resilience crosslinked foam, a crosslinked foam obtained by heating the ethylene resin composition, and footwear having a layer comprising the crosslinked foam A footwear having the member and the footwear member can be provided.

It is a perspective view of the test piece for tear strength measurement.

[Ethylene-α-olefin copolymer (A1)]
The ethylene-α-olefin copolymer (A1) used in the present invention is a copolymer having a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 20 carbon atoms. is there. Examples of the α-olefin include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and 1-decene, and preferably 1-butene and 1-hexene.

  Examples of the ethylene-α-olefin copolymer (A1) include an ethylene-1-butene copolymer, an ethylene-4-methyl-1-pentene copolymer, an ethylene-1-hexene copolymer, and ethylene-1. -Octene copolymer, ethylene-1-decene copolymer, ethylene-1-butene-4-methyl-1-pentene copolymer, ethylene-1-butene-1-hexene copolymer, ethylene-1-butene -1-octene copolymer can be used, and from the viewpoint of excellent tensile strength at break, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-butene- A 1-hexene copolymer, more preferably an ethylene-1-butene-1-hexene copolymer and an ethylene-1-hexene copolymer.

  In the ethylene-α-olefin copolymer (A1), the content of all monomer units in the ethylene-α-olefin copolymer (A1) is 100% by weight, and the ethylene-based monomer unit is 50% by weight. % Or more is preferable.

The density of the ethylene-α-olefin copolymer (A1) is 900 kg / m ³ or more and 940 kg / m ³ or less. From the viewpoint of maintaining the rigidity of the crosslinked foam, it is preferably 905 kg / m ³ or more, more preferably 907 kg / m ³ or more. Further, since a soft foam can be obtained, the density is preferably 930 kg / m ³ or less, more preferably 925 kg / m ³ or less. The density is measured by an underwater substitution method described in JIS K7112-1980.

The melt flow rate (hereinafter sometimes referred to as “MFR”) of the ethylene-α-olefin copolymer (A1) is 0.01 g / 10 min or more and 5 g / 10 min or less. Since a foam having a high expansion ratio can be obtained, the MFR is preferably 0.05 g / 10 min or more, more preferably 0.1 g / 10 min or more, and further preferably 0.15 g / 10 min or more. It is. Further, in order to obtain a crosslinked foam having excellent tensile fracture strength and excellent fatigue resistance, the MFR is preferably 3.0 g / 10 min or less, more preferably 2.5 g / 10 min or less. It is. The MFR is measured by the A method according to JIS K7210-1995 under conditions of a temperature of 190 ° C. and a load of 21.18N. In the measurement of the MFR, a sample in which about 1000 ppm of an antioxidant is blended in advance with an ethylene-α-olefin copolymer is usually used.

  The flow activation energy of the ethylene-α-olefin copolymer (A1) (hereinafter sometimes referred to as “Ea”) is less than 40 kJ / mol, preferably 38 kJ / mol or less. From the viewpoint of obtaining a foam having a uniform cell size, it is preferably 10 kJ / mol or more, more preferably 20 kJ / mol or more.

The flow activation energy (Ea) is a master curve showing the dependence of the melt complex viscosity (unit: Pa · second) at 190 ° C. on the angular frequency (unit: rad / second) based on the temperature-time superposition principle. Is a numerical value calculated by the Arrhenius equation from the shift factor (a _T ) at the time of creating the value, and is a value obtained by the following method. That is, the melt complex viscosity-angular frequency curve of the ethylene-α-olefin copolymer at temperatures of 130 ° C., 150 ° C., 170 ° C. and 190 ° C. (T, unit: ° C.) The unit of the angular frequency is rad / sec.) Is superposed on the melt complex viscosity-angular frequency curve of the ethylene-α-olefin copolymer at 190 ° C. based on the temperature-time superposition principle. The shift factor (a _T ) is determined for each melt complex viscosity-angular frequency curve. From each temperature (T) and the shift factor (aT) at each temperature (T), a linear approximation of [ln (a _T )] and [1 / (T + 273.16)] by the least square method ( (Equation (I) below) is calculated. Next, Ea is obtained from the slope m of the linear equation and the following equation (II).
ln (a _T ) = m (1 / (T + 273.16)) + n (I)
Ea = | 0.008314 × m | (II)
a _T : Shift factor Ea: Activation energy of flow (unit: kJ / mol)
T: Temperature (unit: ° C)
For the calculation, commercially available calculation software may be used. As the calculation software, Rheos V. manufactured by Rheometrics is used. 4.4.4.
The shift factor (a _T ) is obtained by moving the logarithmic curve of the melt complex viscosity-angular frequency at each temperature (T) in the log (Y) = − log (X) axis direction (however, the Y axis Is the melt complex viscosity, and the X-axis is the angular frequency.), And the amount of movement when superimposed on the melt complex viscosity-angular frequency curve at 190 ° C. The logarithmic curve of melt complex viscosity-angular frequency at each temperature (T) shifts the angular frequency by a _T times and the melt complex viscosity by 1 / a _T times for each curve. Moreover, the correlation coefficient when calculating | requiring (I) Formula by the least squares method from the value of four points | pieces, 130 degreeC, 150 degreeC, 170 degreeC, and 190 degreeC is usually 0.99 or more.

  The melt complex viscosity-angular frequency curve is measured using a viscoelasticity measuring apparatus (for example, Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), and usually geometry: parallel plate, plate diameter: 25 mm, plate interval: 1. It is performed under the conditions of 5 to 2 mm, strain: 5%, angular frequency: 0.1 to 100 rad / sec. The measurement is performed in a nitrogen atmosphere, and for the measurement, it is preferable to use a sample in which an appropriate amount of antioxidant (for example, 1000 ppm) is blended in advance with an ethylene-α-olefin copolymer.

[Ethylene-α-olefin copolymer (A2)]
The ethylene-α-olefin copolymer (A2) used in the present invention is a copolymer having a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 20 carbon atoms. is there. Examples of the α-olefin include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and 1-decene, and preferably 1-butene and 1-hexene.

  Examples of the ethylene-α-olefin copolymer (A2) include an ethylene-1-butene copolymer, an ethylene-4-methyl-1-pentene copolymer, an ethylene-1-hexene copolymer, and ethylene-1. -Octene copolymer, ethylene-1-decene copolymer, ethylene-1-butene-4-methyl-1-pentene copolymer, ethylene-1-butene-1-hexene copolymer, ethylene-1-octene From the viewpoint of excellent tensile strength at break and the like, preferred are ethylene-1-butene copolymer, ethylene-1-hexene copolymer, and the like. A polymer, an ethylene-1-butene-1-hexene copolymer, and an ethylene-1-octene copolymer, and more preferably ethylene-1-butene-1-hexene. Polymers, ethylene-1-hexene copolymer, an ethylene-1-octene copolymer.

The density of the ethylene -α- olefin copolymer (A2) is less than 800 kg / ^{m 3} or more 880 kg / ^{m 3.} The density of the ethylene-α-olefin copolymer (A2) is preferably 875 kg / m ³ or less from the viewpoint of maintaining the rigidity of the crosslinked foam. In the case of producing a crosslinked foam having a predetermined hardness, a lighter foam can be produced as the density of the ethylene-α-copolymer used for producing the foam is higher. Therefore, the density of the ethylene -α- olefin copolymer (A2) is preferably 820 kg / m ³ or more, more preferably 830 kg / m ³ or more, more preferably 840 kg / m ³ or more, particularly preferably 850 kg / m ³ That's it.

  The melt flow rate (MFR) of the ethylene-α-olefin copolymer (A2) is 0.01 g / 10 min or more and 5 g / 10 min or less. The melt flow rate of the ethylene-α-olefin copolymer (A2) is preferably 3.5 g / 10 min or less, more preferably 2.5 g / 10 min or less, from the viewpoint of increasing the tensile strength at break of the crosslinked foam. More preferably, it is 1.5 g / 10 minutes or less. Moreover, since a crosslinked foamed body can be manufactured easily, Preferably it is 0.1 g / 10min or more, More preferably, it is 0.3 g / 10min or more, More preferably, it is 0.5 g / 10min or more.

[Crosslinking agent (B)]
The crosslinking agent (B) used in the present invention is preferably an organic peroxide. Among the melting points of the ethylene-α-olefin copolymer (A1) and the melting point of the ethylene-α-olefin copolymer (A2), an organic peroxide having a 1-minute half-life temperature that is higher than the higher temperature is suitable. For example, dicumyl peroxide, 1,1-ditertiary butyl peroxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-ditertiary butyl peroxyhexane, 2,5 Examples thereof include dimethyl-2,5-ditertiary butyl peroxyhexyne, α, α-ditertiary butyl peroxyisopropylbenzene, tertiary butyl peroxyketone, tertiary butyl peroxybenzoate, and the like.
An organic peroxide having a 1 minute half-life temperature of 120 to 220 ° C is preferred, and an organic peroxide having a temperature of 140 to 190 ° C is more preferred.

[Foaming agent (C)]
The foaming agent (C) used in the present invention is preferably a pyrolytic foaming agent. Of the melting point of the ethylene-α-olefin copolymer (A1) and the melting point of the ethylene-α-olefin copolymer (A2), a thermal decomposition type foaming agent having a decomposition temperature equal to or higher than the higher temperature is more preferable. For example, azodicarbonamide, barium azodicarboxylate, azobisbutylnitrile, nitrodiguanidine, N, N-dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide, 4- Toluenesulfonyl hydrazide, 4,4′-oxybis (benzenesulfonylhydrazide) azobisisobutyronitrile, 4,4′-oxybisbenzenesulfonyl semicarbazide, 5-phenyltetrazole, trihydrazinotriazine, hydrazodicarbonamide, Sodium hydrogen carbonate etc. can be mentioned, These are used individually or in combination of 2 or more types. Among these, azodicarbonamide or sodium hydrogen carbonate is preferable.

  Pyrolytic foaming agents having a decomposition temperature of 120 to 240 ° C. are preferred. The decomposition temperature of the thermally decomposable foaming agent can be determined by a method based on JIS K0064.

[Ethylene resin composition]
The ethylene resin composition of the present invention has an ethylene-α-olefin copolymer (A1) of 10% by weight to 90% by weight,
10% by weight or more and 90% by weight or less of ethylene-α-olefin copolymer (A2) (however, the total weight of ethylene-α-olefin copolymer (A1) and ethylene-α-olefin copolymer (A2)) Is 100% by weight),
For a total weight of 100 parts by weight of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2),
Cross-linking agent (B) 0.1 parts by weight or more and 10 parts by weight or less,
1 part by weight or more and 50 parts by weight or less of the foaming agent (C) is contained.

  The content of the ethylene-α-olefin copolymer (A1) contained in the ethylene resin composition is such that a crosslinked foamed body is produced using the ethylene resin composition and has a high tensile breaking strength and is lightweight. From the viewpoint of obtaining a foam, it is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 60% by weight or more (provided that ethylene-α-olefin copolymer (A1) and ethylene- The total weight with the α-olefin copolymer (A2) is 100% by weight). Further, the content of the ethylene-α-olefin copolymer (A1) is preferably 85% by weight or less because a crosslinked foam having high impact resilience is obtained.

  The content of the crosslinking agent (B) contained in the ethylene resin composition is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, because a crosslinked foam having a high tensile breaking strength is obtained. More preferably, it is 0.7 parts by weight or more (provided that the total weight of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2) is 100 parts by weight). Moreover, since the crosslinked foamed body with high tear strength is obtained, Preferably it is 5 weight part or less, More preferably, it is 3 weight part or less.

  The content of the foaming agent (C) contained in the ethylene resin composition is preferably 3 parts by weight or more from the viewpoint of reducing the weight of the crosslinked foamed material (however, the ethylene-α-olefin copolymer (A1)). ) And the ethylene-α-olefin copolymer (A2) in a total weight of 100 parts by weight). Since a cross-linked foam having a high tensile breaking strength is obtained, the amount is preferably 30 parts by weight or less, more preferably 25 parts by weight or less, and still more preferably 20 parts by weight or less.

  The ethylene resin composition may contain a foaming aid as necessary. Examples of the foaming aid include compounds mainly composed of urea; metal oxides such as zinc oxide and lead oxide; higher fatty acids such as salicylic acid and stearic acid; and metal compounds of the higher fatty acids. The content of the foaming aid is preferably 0.1 to 30% by weight, more preferably 1 to 20% by weight, where the total weight of the foaming agent and the foaming aid is 100% by weight.

The ethylene resin composition may contain a crosslinking aid. As the crosslinking aid, a compound having a plurality of double bonds in the molecule is preferably used. Examples of the crosslinking aid include N, N′-m-phenylene bismaleimide, toluylene bismaleimide, triallyl isocyanurate, triallyl cyanurate, p-quinone dioxime, nitrobenzene, diphenylguanidine, divinylbenzene, ethylene glycol. Examples include dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and allyl methacrylate. Moreover, you may use these crosslinking adjuvants in combination of multiple.
The content of the crosslinking aid is 0.01 to 4.0 parts by weight based on 100 parts by weight of the total weight of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2). It is preferable that it is 0.05-2.0 weight part.

  If necessary, the ethylene resin composition comprises a heat stabilizer, a weathering agent, a lubricant, an antistatic agent, a filler and a pigment (metal oxide such as zinc oxide, titanium oxide, calcium oxide, magnesium oxide, silicon oxide; Various additives such as carbonates such as magnesium and calcium carbonate; fiber materials such as pulp) may be contained.

  The ethylene resin composition may contain a thermoplastic resin different from the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2) as necessary. Examples of the thermoplastic resin include high pressure method low density polyethylene, high density polyethylene, polypropylene, polyvinyl acetate, polybutene, and the like.

[Ethylene-unsaturated ester copolymer (D)]
An ethylene resin composition comprising an ethylene-unsaturated ester system having a monomer unit based on at least one unsaturated ester selected from a vinyl carboxylate and an unsaturated carboxylic acid alkyl ester, and a monomer unit based on ethylene It is preferable to contain a copolymer (D). Since the crosslinked foam obtained by heating the ethylene resin composition containing the ethylene-unsaturated ester copolymer (D) is excellent in adhesiveness, the foam can be easily laminated with other layers. Examples of the carboxylic acid vinyl ester include vinyl acetate and vinyl propionate, and the unsaturated carboxylic acid alkyl ester includes methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, and n-acrylate. -Butyl, t-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate and the like. .

  The ethylene-unsaturated ester copolymer (D) is preferably an ethylene-vinyl acetate copolymer, an ethylene-methyl methacrylate copolymer, an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer. It is a coalescence.

  The melt flow rate (MFR) of the ethylene-unsaturated ester copolymer (D) is usually 0.1 to 100 g / 10 min. The MFR is measured by the A method according to JIS K7210-1995 under conditions of a temperature of 190 ° C. and a load of 21.18N.

  In the ethylene-unsaturated ester copolymer (D), the content of monomer units based on the unsaturated ester is the content of all monomer units in the ethylene-unsaturated ester copolymer (D). If the amount is 100% by weight, it is usually 2 to 50% by weight. The content is measured by a known method. For example, the content of monomer units based on vinyl acetate is measured according to JIS K6730-1995.

  The ethylene-unsaturated ester copolymer (D) is produced, for example, by a bulk polymerization method or a solution polymerization method using a radical initiator.

When the ethylene resin composition of the present invention contains an ethylene-unsaturated ester copolymer (D), an ethylene-α-olefin copolymer (A1) and an ethylene-α-olefin copolymer (A2). The content of the ethylene-unsaturated ester copolymer (D) is preferably 1 part by weight or more and 250 parts by weight or less based on 100 parts by weight of the total weight.
The content of the ethylene-unsaturated ester copolymer (D) is preferably 20% from the viewpoint of adhesiveness when a crosslinked foam obtained by heating the ethylene resin composition and another layer are laminated. Part or more, more preferably 30 parts by weight or more, still more preferably 40 parts by weight or more, particularly preferably 50 parts by weight or more, and most preferably 60 parts by weight or more. Further, from the viewpoint of reducing the weight of the crosslinked foam, it is preferably 200 parts by weight or less, more preferably 150 parts by weight or less, still more preferably 100 parts by weight or less, and particularly preferably 80 parts by weight or less.

  The ethylene resin composition comprises an ethylene-α-olefin copolymer (A1), an ethylene-α-olefin copolymer (A2), a cross-linking agent (B) and a foaming agent (C), and, if necessary, an ethylene- The saturated ester copolymer (D) and other components are preferably melt-mixed by a mixing roll, a kneader, an extruder or the like at a temperature at which the foaming agent (C) is not decomposed.

(Crosslinked foam)
The crosslinked foam of the present invention is obtained by heating the ethylene resin composition. Specifically, by supplying an ethylene resin composition into a mold and heating and pressurizing (holding pressure) the resin composition in the mold, the resin composition is crosslinked and foamed to obtain a crosslinked foam. be able to. When the ethylene resin composition is supplied into the mold, the ethylene resin composition plasticized by an injection molding machine or the like may be supplied into the mold.

The cross-linked foam can be produced using a pressure press machine or an injection molding machine.
Examples of a method for producing a crosslinked foam using a pressure press include a production method including the following steps.
Supplying an ethylene resin composition into a mold;
A step of forming a plasticized and crosslinked intermediate (i) by pressurizing and heating the ethylene resin composition in the mold, and a foaming of the intermediate (i) by opening the mold to form a crosslinked foam Forming process

The ethylene resin composition supplied into the mold is preferably an ethylene resin composition obtained in advance by the following treatment.
First, an ethylene-α-olefin copolymer (A1), an ethylene-α-olefin copolymer (A2), a crosslinking agent (B), a foaming agent (C), and an ethylene-unsaturated ester copolymer as required. The mixture with the polymer (D) and other components is a 1 minute half-life temperature of the crosslinking agent (B), a decomposition temperature of the blowing agent (C), and an ethylene-α-olefin. It is preferable to plasticize with a mixing roll, a kneader, an extruder or the like at a temperature which is higher than the higher one of the melting point of the copolymer (A1) and the melting point of the ethylene-α-olefin copolymer (A2). The temperature for plasticizing the mixture is preferably 90 to 150 ° C, more preferably 100 to 140 ° C, and still more preferably 105 to 130 ° C. The plasticized mixture is cooled to obtain an ethylene resin composition. The obtained ethylene resin composition is supplied to a mold.

The ethylene resin composition in the mold is pressurized and heated by a pressure press or the like to form the plasticized and crosslinked intermediate (i). The temperature at which the ethylene resin composition is heated is equal to or higher than the one-minute half-life temperature of the cross-linking agent (B), equal to or higher than the decomposition temperature of the foaming agent (C), and an ethylene-α-olefin copolymer ( The temperature is preferably equal to or higher than the higher melting point of the melting point of A1) and the melting point of the ethylene-α-olefin copolymer (A2). It is preferable that the temperature which heats an ethylene resin composition is 130-220 degreeC, More preferably, it is 140-190 degreeC, More preferably, it is 150-180 degreeC.
The melting point here refers to a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, and 8 to 12 mg of sample is packed in an aluminum pan and held at 150 ° C. for 2 minutes, and then 40 ° C. at 5 ° C./min. The temperature at the melting peak position of the highest temperature among melting peaks observed when the temperature is lowered to 150 ° C. and held at 40 ° C. for 2 minutes and then increased to 150 ° C. at 5 ° C./min.

The mold clamping pressure is preferably 50 to 300 kgf / cm ² , and the pressure holding time is preferably about 10 to 60 minutes.
Next, when the mold is opened, the intermediate (i) foams and a crosslinked foam can be obtained.

Next, a manufacturing method using an injection molding machine will be described.
The method includes the following steps.
A first step of heating the ethylene resin composition in a cylinder of an injection molding machine to form a plasticized intermediate (ii);
The plasticized intermediate (ii) is fed to a mold, and the intermediate (ii) is crosslinked by pressurizing and heating the intermediate (ii) in the mold to produce a plasticized and crosslinked intermediate ( a second step of forming iii) and a third step of foaming intermediate (iii) by opening the mold to form a crosslinked foam

The ethylene resin composition supplied into the cylinder of the injection molding machine is preferably an ethylene resin composition obtained in advance by the following treatment.
First, an ethylene-α-olefin copolymer (A1), an ethylene-α-olefin copolymer (A2), a crosslinking agent (B), a foaming agent (C), and an ethylene-unsaturated ester copolymer as required. The mixture with the polymer (D) and other components is a 1 minute half-life temperature of the crosslinking agent (B), a decomposition temperature of the blowing agent (C), and an ethylene-α-olefin. It is preferable to plasticize with a mixing roll, a kneader, an extruder or the like at a temperature which is higher than the higher one of the melting point of the copolymer (A1) and the melting point of the ethylene-α-olefin copolymer (A2). The temperature for plasticizing the mixture is preferably 90 to 150 ° C, more preferably 100 to 140 ° C, and still more preferably 105 to 130 ° C. The plasticized mixture is cooled to obtain an ethylene resin composition. The obtained ethylene resin composition is supplied into a cylinder of an injection molding machine.

  The temperature at which the ethylene resin composition is heated in the first step is not more than the 1 minute half-life temperature of the crosslinking agent (B), not more than the decomposition temperature of the foaming agent (C), and ethylene-α- It is preferable that the temperature is equal to or higher than the higher one of the melting point of the olefin copolymer (A1) and the melting point of the ethylene-α-olefin copolymer (A2). It is preferable that the temperature which heats an ethylene resin composition is 90-150 degreeC, More preferably, it is 100-140 degreeC, More preferably, it is 105-130 degreeC.

Intermediate (ii) is fed to the mold and intermediate (ii) in the mold is pressurized and heated to cross-link intermediate (ii) to form a plasticized and cross-linked intermediate (iii) To do. The mold temperature is equal to or higher than the 1 minute half-life temperature of the cross-linking agent (B), equal to or higher than the decomposition temperature of the foaming agent (C), and the melting point of the ethylene-α-olefin copolymer (A1). The temperature is preferably equal to or higher than the higher melting point of the melting points of the ethylene-α-olefin copolymer (A2). The mold temperature is preferably 130 to 220 ° C, more preferably 140 to 210 ° C, and still more preferably 150 to 200 ° C. The mold clamping pressure is preferably 50 to 300 kgf / cm ² , and the pressure holding time is preferably about 10 to 60 minutes.

  Finally, the intermediate (iii) is foamed by opening the mold to obtain a crosslinked foam.

The crosslinked foam obtained by the above-described method may be referred to as an organic peroxide crosslinked foam. The organic peroxide crosslinked foam can be further compressed to obtain a compressed crosslinked foam. The compression crosslinked foam is obtained by applying a load of 30 to ²⁰⁰ kg / cm ² to the organic peroxide crosslinked foam usually at 130 to 200 ° C. for 5 to 60 minutes. The compression-crosslinked foam of the present invention is more suitable for a midsole that is a kind of footwear member.
In the present invention, the organic peroxide crosslinked foam and the compressed crosslinked foam are collectively referred to as a crosslinked foam.

  The cross-linked foam of the present invention can be laminated with other layers to produce a multilayer laminate. The material constituting the other layers includes vinyl chloride resin material, styrene copolymer rubber material, olefin copolymer rubber material (ethylene copolymer rubber material, propylene copolymer rubber material, etc.), natural Examples include leather materials, artificial leather materials, and cloth materials. At least one material selected from these materials is used.

  As a manufacturing method of a multilayer laminated body, the method of bonding the said crosslinked foam and the other layer shape | molded separately by heat bonding or a chemical adhesive etc. is mention | raise | lifted, for example. The chemical adhesive is preferably a urethane chemical adhesive or a chloroprene chemical adhesive. Further, before the cross-linked foam and other layers are bonded with these chemical adhesives, an overcoat agent called a primer may be applied to the cross-linked foam and / or other layers.

  The crosslinked foam of the present invention can be suitably used as a member for footwear such as shoes and sandals in the form of a single layer or multiple layers. Examples of the footwear member include an outer sole (lower bottom), a midsole (upper bottom), and an insole (sole). Moreover, the crosslinked foam of this invention is used also for building materials, such as a heat insulating material and a shock absorbing material, besides the member for footwear.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples.
(1) Density of copolymer (unit: kg / m ³ )
It was measured by an underwater substitution method described in JIS K7112-1980.

(2) Melt flow rate of copolymer (MFR, unit: g / 10 min)
According to JIS K7210-1995, it measured by A method on the conditions with a temperature of 190 degreeC and a load of 21.18N.

(3) Activation energy of flow of copolymer (Ea, unit: kJ / mol), dynamic complex viscosity (η ^* ₁₀₀ ) at an angular frequency of 100 rad / sec
Using a viscoelasticity measuring device (Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), the dynamic viscosity-angular frequency curve of the copolymer was measured at 130 ° C, 150 ° C, 170 ° C and 190 ° C under the following measurement conditions. . Next, from the obtained dynamic viscosity-angular velocity curve, Rheometrics R. The activation energy (Ea) of the flow was determined using 4.4.4. Further, the dynamic complex viscosity (η ^* ₁₀₀ ) of the copolymer at an angular frequency of 100 rad / sec and 190 ° C. was measured.
<Measurement conditions>
Geometry: Parallel plate Plate diameter: 25mm
Plate spacing: 1.5-2mm
Strain: 5%
Angular frequency: 0.1 to 100 rad / sec Measurement atmosphere: Under nitrogen

(4) Melting point of copolymer (unit: ° C)
Using a differential scanning calorimeter DSC-7 type apparatus manufactured by PerkinElmer, 8-12 mg of a sample was packed in an aluminum pan, held at 150 ° C. for 2 minutes, then cooled to 40 ° C. at 5 ° C./min, and at 40 ° C. The temperature at the melting peak position showing the highest temperature among melting peaks observed when the temperature was raised to 150 ° C. at 5 ° C./min after holding for 2 minutes was taken as the melting point.

(5) Density of crosslinked foam (unit: kg / m ³ )
The density of the crosslinked foam was measured according to ASTM-D297. It shows that a crosslinked foam is lightweight, so that this value is small.

(6) Rebound resilience of crosslinked foam (unit:%)
In accordance with JIS K 6400, the resilience of the crosslinked foam was measured.

(7) Hardness of crosslinked foam (unit: none)
The hardness of the surface (mold installation surface) of the obtained crosslinked foam was measured with a C method hardness tester in accordance with ASTM-D2240.

(8) Tensile strength at break of crosslinked foam (unit: kg / cm)
After slicing the cross-linked foam to a thickness of 2 mm, it was punched into the shape of a JIS No. 2 dumbbell to produce a test piece. The test piece was pulled at a speed of 500 mm / min, and the maximum load F (kg) when the test piece broke was divided by the thickness of the test piece to obtain the tensile breaking strength.

(9) Tear strength of crosslinked foam (unit: N)
After the crosslinked foam was sliced to a thickness of 10 mm, a rectangular sample piece having a length of 40 mm and a width of 15 mm was prepared. Subsequently, a test piece was prepared by making a notch with a depth of 15 mm in the longitudinal direction at the center in the thickness direction as shown in FIG. 1 on one side in the longitudinal direction of the rectangular sample piece. The test piece was torn by opening the cut and pulling each part formed by cutting the cross-linked foam at a speed of 50 mm / min in the direction of 180 degrees. The maximum load F (N) when the test piece was torn was measured.

[Example 1]
Ethylene-1-hexene copolymer Enable 2703CH (manufactured by Exxson: density 924 kg / m ³ , MFR = 0.3 g / 10 min, Ea = 36.7 kJ / mol, melting point = 119 ° C .; hereinafter referred to as PE-1 ) And 67 wt% ethylene-1-octene copolymer Engage 8150 (The Dow Chemical Company, density: 868 kg / m ³ , MFR = 0.5 g / 10 min, melting point = 54 ° C .; hereinafter, PE-2 And 33% by weight,
For a total weight of 100 parts by weight of PE-1 and PE-2,
67 parts by weight of ethylene-vinyl acetate copolymer COSMOTHENE H2181 (manufactured by The Polyolefin Company, MFR = 2.0 g / 10 min, melting point = 89 ° C .; hereinafter referred to as EVA-1),
1.2 parts by weight of dicumyl peroxide (1 minute half-life temperature 175 ° C.)
7.5 parts by weight of azodicarbonamide (trade name Cellmic C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.), which is a thermal decomposition type foaming agent,
17 parts by weight of heavy calcium carbonate,
1.7 parts by weight of stearic acid,
1.7 parts by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 125 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to obtain a crosslinked foam. It was. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

[Example 2]
Ethylene-1-hexene copolymer Sumikacene E FV203 (manufactured by Sumitomo Chemical Co., Ltd .: density 908 kg / m ³ , MFR = 2.0 g / 10 min, Ea = 34.1 kJ / mol, melting point = 115 ° C .; hereinafter PE— 3)), 67% by weight, PE-2, 33% by weight,
For a total weight of 100 parts by weight of PE-3 and PE-2,
67 parts by weight of EVA-1,
1.2 parts by weight of dicumyl peroxide (1 minute half-life temperature 175 ° C.)
7.5 parts by weight of azodicarbonamide (trade name Cellmic C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.), which is a thermal decomposition type foaming agent,
17 parts by weight of heavy calcium carbonate,
1.7 parts by weight of stearic acid,
1.7 parts by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 125 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to obtain a crosslinked foam. It was. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

[Example 3]
60% by weight of PE-3, 40% by weight of PE-2,
For a total weight of 100 parts by weight of PE-3 and PE-2,
Dicumyl peroxide (1 minute half-life temperature 175 ° C.) 0.7 parts by weight,
4.5 parts by weight of azodicarbonamide (trade name CELLMIC C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.) which is a thermal decomposition type foaming agent;
10 parts by weight of heavy calcium carbonate,
1 part by weight of stearic acid,
1 part by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 125 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to obtain a crosslinked foam. It was. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

[Comparative Example 1]
100 parts by weight of EVA-1,
Dicumyl peroxide (1 minute half-life temperature 175 ° C.) 0.7 parts by weight,
3.1 parts by weight of azodicarbonamide (trade name CELLMIC C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.) which is a thermal decomposition type foaming agent;
10 parts by weight of heavy calcium carbonate,
1 part by weight of stearic acid,
1 part by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 115 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to obtain a crosslinked foam. It was. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

[Comparative Example 2]
PE-1 67% by weight, ethylene-1-octene copolymer Engage 8480 (The Dow Chemical Company, density: 901 kg / m ³ , MFR = 0.9 g / 10 min, Ea = 59.8 kJ / mol, melting point = 97 ° C .; hereinafter referred to as PE-4) 33 wt%
For a total weight of 100 parts by weight of PE-1 and PE-4,
EVA-1 67% by weight,
1.2 parts by weight of dicumyl peroxide (1 minute half-life temperature 175 ° C.)
7.5 parts by weight of azodicarbonamide (trade name Cellmic C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.), which is a thermal decomposition type foaming agent,
17 parts by weight of heavy calcium carbonate,
1.7 parts by weight of stearic acid,
1.7 parts by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 125 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to obtain a crosslinked foam. It was. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

[Comparative Example 3]
60% by weight of PE-3, 40% by weight of PE-4,
For a total weight of 100 parts by weight of PE-3 and PE-4,
Dicumyl peroxide (1 minute half-life temperature 175 ° C.) 0.7 parts by weight,
4.5 parts by weight of azodicarbonamide (trade name CELLMIC C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.) which is a thermal decomposition type foaming agent;
10 parts by weight of heavy calcium carbonate,
1 part by weight of stearic acid,
1 part by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 125 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to obtain a crosslinked foam. It was. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

[Comparative Example 4]
PE-3 67% by weight, PE-4 33% by weight,
For a total weight of 100 parts by weight of PE-3 and PE-4,
67 parts by weight of EVA-1,
1.2 parts by weight of dicumyl peroxide (1 minute half-life temperature 175 ° C.)
7.5 parts by weight of azodicarbonamide (trade name Cellmic C-1; decomposition temperature 206 ° C., manufactured by Sankyo Kasei Co., Ltd.), which is a thermal decomposition type foaming agent,
17 parts by weight of heavy calcium carbonate,
1.7 parts by weight of stearic acid,
1.7 parts by weight of zinc oxide,
Using a roll kneader, kneading was performed under the conditions of a roll temperature of 125 ° C. and a kneading time of 5 minutes to obtain a resin composition. The resin composition is filled in a 12 cm × 12 cm × 2.0 cm mold, and the resin composition is heated and pressurized ethylene under the conditions of a temperature of 165 ° C., an hour of 30 minutes, and a pressure of 150 kg / cm ² to form a crosslinked foamed product. Got. The physical property evaluation results of the obtained crosslinked foam are shown in Table 2.

Claims (5)

It has a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 20 carbon atoms, has a density of 900 kg / m ³ or more and 940 kg / m ³ or less, and a melt flow rate of 0 An ethylene-α-olefin copolymer (A1) having a flow activation energy of less than 40 kJ / mol (A1) of 10% by weight to 90% by weight;
Monomer units and the number of carbon atoms based on ethylene and a monomer unit based on 3-20 of α- olefin, the density is less than 800 kg / ^{m 3} or more 880 kg / ^{m 3,} a melt flow rate of 0 10 wt% or more and 90 wt% or less of ethylene-α-olefin copolymer (A2) that is 0.01 g / 10 min or more and 5 g / 10 min or less (provided that ethylene-α-olefin copolymer (A1) and ethylene- the total weight with the α-olefin copolymer (A2) is 100% by weight),
For a total weight of 100 parts by weight of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2),
Cross-linking agent (B) 0.1 parts by weight or more and 10 parts by weight or less,
An ethylene resin composition containing 1 part by weight or more and 50 parts by weight or less of a foaming agent (C). The ethylene resin composition according to claim 1,
At least selected from a carboxylic acid vinyl ester and an unsaturated carboxylic acid alkyl ester, based on 100 parts by weight of the total weight of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin copolymer (A2). An ethylene resin composition containing 1 to 250 parts by weight of an ethylene-unsaturated ester copolymer (D) having a monomer unit based on one kind of unsaturated ester and a monomer unit based on ethylene .   A crosslinked foam obtained by heating the ethylene resin composition according to claim 1.   The member for footwear which has a layer which consists of a crosslinked foamed body of Claim 3.   Footwear comprising the member for footwear according to claim 4.

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