JP2008001792A - Method for producing foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing foam composed of a polyethylene-based resin and excellent in foamy properties and strength. <P>SOLUTION: The method for producing the foam comprises thermally expanding a resin composition by irradiating ionizing radiation having 1-20 Mrad radiation values to an ethylene-based resin composition containing (A) an ethylene-α-olefin copolymer having 0.1-5 g/10 min melt flow rate (MFR) measured under conditions of 190°C temperature and 21.28N load defined by JIS K-7210, having 900-935 kg/m<SP>3</SP>density and 5-25 molecular-weight distribution (Mw/Mn) and ≥40 kJ/mol activation energy (Ea) of flow and (B) a heat-decomposition type foaming agent having 100-240°C decomposition temperature and containing the component B in an amount of 1-40 pts.wt. based on 100 pts.wt. component A. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an ethylene resin foam.

  Foams made of ethylene resins such as linear low-density polyethylene and high-pressure method low-density polyethylene are excellent in flexibility and heat insulating properties, and thus are used in various applications as buffer materials or heat insulating materials. As a method of manufacturing a foam made of such an ethylene resin, an ethylene resin, a foaming agent and a peroxide are melt-mixed at a temperature at which the foaming agent and the peroxide are not decomposed, and then molded into a sheet. After that, the sheet is crosslinked by heating to a temperature at which the peroxide is decomposed, and then the sheet is heated to foam above the decomposition temperature of the foaming agent, or the ethylene resin and the foaming agent are combined. A method is known in which a sheet is melt-mixed at a temperature that does not decompose and formed into a sheet, the sheet is irradiated with an electron beam to crosslink the sheet, and then the sheet is heated to a temperature higher than the decomposition temperature of the foaming agent to foam. (For example, refer to Patent Document 1).

JP-A-7-286059

However, foams produced using conventional ethylene-based resins such as linear low density polyethylene have not always been satisfactory in terms of cell properties and strength.
Under such circumstances, the problem to be solved by the present invention is to provide a method for producing a foam made of a polyethylene resin and having excellent cell properties and strength.

  According to the present invention, it is possible to provide a method for producing a foam made of a polyethylene resin and having excellent cell properties and strength. The production method of the present invention is suitable for producing a foam having a high expansion ratio.

That is, the present invention relates to a method for producing a foam by heating and foaming a resin composition formed by irradiating the following ethylene resin composition with ionizing radiation having an irradiation amount of 1 to 20 Mrad.
[Ethylene resin composition]
An ethylene-based resin composition component (A) containing the following component (A) and component (B), wherein the content of the component (B) is 1 to 40 parts by weight per 100 parts by weight of the component (A): JIS K7210 The melt flow rate (MFR) measured under the conditions of a specified temperature of 190 ° C. and a load of 21.18 N is 0.1 to 5 g / 10 minutes, the density is 900 to 935 kg / m ³ , and the molecular weight distribution (Mw / Mn) is 5 to 25, and the flow activation energy (Ea) is 40 kJ / mol or more, an ethylene-α-olefin copolymer component (B): a thermal decomposition type having a decomposition temperature of 100 to 240 ° C. Blowing agent

  The ethylene-α-olefin copolymer of component (A) used in the present invention is an ethylene-α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. . Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4 -Methyl-1-pentene, 4-methyl-1-hexene and the like can be mentioned, and 1-butene, 1-hexene and 1-octene are preferable. Moreover, said C3-C20 alpha olefin may be used independently and may use 2 or more types together.

  Examples of the ethylene-α-olefin copolymer of component (A) include an ethylene-propylene copolymer, an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer, and an ethylene-1-octene copolymer. Preferred are ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-butene-1-hexene copolymer, ethylene-1-butene-1-octene copolymer. It is a coalescence.

  The content of the monomer unit based on ethylene in the ethylene-α-olefin copolymer of the component (A) is usually from 50 to 50% based on the total weight (100% by weight) of the ethylene-α-olefin copolymer. 99% by weight. The content of the monomer unit based on the α-olefin having 3 to 20 carbon atoms is usually 1 to 50% by weight with respect to the total weight (100% by weight) of the ethylene-α-olefin copolymer.

  The ethylene-α-olefin copolymer of component (A) has a long chain branch, and such an ethylene-α-olefin copolymer is a conventional ethylene-α-olefin that has been used for foams. Compared with a copolymer, the flow activation energy (Ea) is high, and is usually 40 kJ / mol or more. The Ea of the ethylene-α-olefin copolymer that has been used in conventionally known foams is usually lower than 40 kJ / mol.

  The flow activation energy (Ea) of the ethylene-α-olefin copolymer of the component (A) is preferably 45 kJ / mol or more, more preferably 50 kJ / mol or more, from the viewpoint of enhancing the bubble property. More preferably, it is 60 kJ / mol or more. Further, from the viewpoint of increasing strength, the Ea is preferably 100 kJ / mol or less, and more preferably 90 kJ / mol or less.

The flow activation energy (Ea) of the component (A) ethylene-α-olefin copolymer is the angle of the melt complex viscosity (unit: Pa · sec) at 190 ° C. based on the temperature-time superposition principle. It is a numerical value calculated by the Arrhenius type equation from the shift factor (a _T ) when creating a master curve showing frequency (unit: rad / sec) dependency, and is a value obtained by the following method. That is, an ethylene-α-olefin copolymer at each temperature (T, unit: ° C.) for four temperatures including 190 ° C. among temperatures of 130 ° C., 150 ° C., 170 ° C., 190 ° C., and 210 ° C. The melt complex viscosity-angular frequency curve (melt melt viscosity unit is Pa · sec, angular frequency unit is rad / sec) based on the temperature-time superposition principle at each temperature (T). For each melt complex viscosity-angular frequency curve, the shift factor (a _T ) at each temperature (T) obtained when superimposed on the melt complex viscosity-angular frequency curve of the ethylene copolymer at 190 ° C. is obtained. , and each of the temperature (T), a first-order approximation of from shift factor and (a _T), by the method of least squares and [ln (a _T)] and [1 / (T + 273.16) ] at each temperature (T) Formula (Formula (I) below) is calculated. Next, Ea is obtained from the slope m of the linear expression and the following expression (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 complex viscosity of the melt, and the X axis is the angular frequency.), And the amount of movement when superposed on the melt complex viscosity-angular frequency curve at 190 ° C., in the superposition, melting at each temperature (T) The logarithmic curve of complex viscosity-angular frequency shifts the angular frequency _aT times and the melt complex viscosity 1 / _aT times.
In addition, when obtaining the linear approximation formula (I) obtained from the shift factors and temperatures at four temperatures including 190 ° C. from 130 ° C., 150 ° C., 170 ° C., 190 ° C., and 210 ° C. by the method of least squares. The correlation coefficient is usually 0.99 or more.

  The above-mentioned melt complex viscosity-angular frequency curve is measured using a viscoelasticity measuring apparatus (for example, Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics). Usually, geometry: parallel plate, plate diameter: 25 mm, plate interval: It is performed under the conditions of 1.5 to 2 mm, strain: 5%, angular frequency: 0.1 to 100 rad / sec. The measurement is performed in a nitrogen atmosphere, and it is preferable that an appropriate amount of an antioxidant (for example, 1000 ppm) is blended in advance with the measurement sample.

  The melt flow rate (MFR) of the ethylene-α-olefin copolymer of component (A) is 0.1 to 5 g / 10 min. The melt flow rate is preferably 0.2 g / 10 min or more from the viewpoint of improving the lightness of the foam. Moreover, from a viewpoint of improving a bubble property and intensity | strength, Preferably it is 4 g / 10min or less. The MFR is measured under the conditions of a load of 21.18 N and a temperature of 190 ° C. in the method defined in JIS K7210-1995.

The density of the ethylene -α- olefin copolymer component (A), in view of enhancing the light weight of the foam, preferably 935 kg / m ³ or less, more preferably 930 kg / m ³ or less. From the viewpoint of reducing the stickiness of the foam, preferably 900 kg / m ³ or more, more preferably 905 kg / m ³ or more. In addition, this density is measured according to the A method in the method prescribed | regulated to JISK7112-1999.

  The molecular weight distribution (Mw / Mn) of the ethylene-α-olefin copolymer of the component (A) is 5 to 25. The molecular weight distribution is preferably 6 or more, more preferably 7 or more, from the viewpoint of enhancing the lightness of the foam. The M molecular weight distribution is preferably 25 or less, more preferably 20 or less, and still more preferably 17 or less, from the viewpoint of increasing the strength of the foam. The molecular weight distribution (Mw / Mn) is a value obtained by obtaining a weight average molecular weight (Mw) and a number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography, and dividing Mw by Mn ( Mw / Mn).

The ethylene-α-olefin copolymer of component (A) has a melt complex viscosity of η ^* (unit: Pa · sec) at a temperature of 190 ° C. and an angular frequency of 100 rad / sec, from the viewpoint of enhancing low-temperature extrusion characteristics, and JIS In the method defined in K7210-1995, a melt flow rate measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N as MFR (unit: g / 10 minutes) satisfies the following formula (1). ,
η ^* <1550 × MFR ^−0.25 −420 Formula (1)
More preferably, the following formula (1-2) is satisfied,
η ^* <1500 × MFR ^−0.25 −420 Formula (1-2)
More preferably, the following formula (1-3) is satisfied,
η ^* <1450 × MFR ^−0.25 −420 Formula (1-3)
It is particularly preferable that the following formula (1-4) is satisfied.
η ^* <1350 × MFR ^−0.25 −420 Formula (1-4)

The melt complex viscosity η ^* was obtained in the measurement of 190 ° C. melt complex viscosity-angular frequency among the measurements performed to determine the flow activation energy (Ea) of the ethylene-α-olefin copolymer. It is a melt complex viscosity at an angular frequency of 100 rad / sec.

  As a method for producing the ethylene-α-olefin copolymer of component (A), for example, a promoter component such as an organoaluminum compound, an organoaluminum oxy compound, a boron compound, and an organozinc compound is supported on a particulate carrier. It has a solid particulate promoter component (hereinafter referred to as component (i)) and a ligand having a structure in which two cyclopentadienyl type anion skeletons are bonded to each other by a crosslinking group such as an alkylene group or a silylene group. Examples thereof include a method in which ethylene and an α-olefin are copolymerized in the presence of a polymerization catalyst using a metallocene complex (hereinafter referred to as component (b)) as a catalyst component.

  Examples of the solid particulate promoter component include a component in which methylalumoxane is mixed with porous silica, a component in which diethyl zinc, water, and fluorinated phenol are mixed with porous silica.

More specific examples of the solid particulate promoter component include component (a) diethylzinc, component (b) fluorinated phenol, component (c) water, component (d) porous silica and component (e) trimethyldisilazane. The promoter support component (a) obtained by contacting (((CH ₃ ) ₃ Si) ₂ NH) can be mentioned.

  Examples of the fluorinated phenol of component (b) include pentafluorophenol, 3,5-difluorophenol, 3,4,5-trifluorophenol, 2,4,6-trifluorophenol and the like. From the viewpoint of increasing the fluid activation energy (Ea) and molecular weight distribution (Mw / Mn) of the component (A), it is preferable to use two types of fluorinated phenols having different fluorine numbers. The molar ratio with the phenol having a small number of fluorine is usually 20/80 to 80/20, and the higher the molar ratio is preferable.

The amount of component (a), component (b) and component (c) used is the molar ratio of the amount of each component used: component (a): component (b): component (c) = 1: y: z Then, it is preferable that y and z satisfy the following formula.
| 2-y-2z | ≦ 1
Y in the above formula is preferably a number of 0.01 to 1.99, more preferably a number of 0.10 to 1.80, and still more preferably a number of 0.20 to 1.50. Most preferably, the number is 0.30 to 1.00.

  The amount of the component (d) used relative to the component (a) is such that the number of moles of zinc atoms contained in the particles obtained by contacting the component (a) and the component (d) is 0.00 per gram of the particles. The amount is preferably 1 mmol or more, and more preferably 0.5 to 20 mmol. The amount of the component (e) to be used with respect to the component (d) is preferably an amount that makes the component (e) 0.1 mmol or more per 1 g of the component (d), and an amount that becomes 0.5 to 20 mmol More preferably.

  The metallocene complex includes a zirconocene complex in which two indenyl groups are bonded by an ethylene group, a dimethylmethylene group or a dimethylsilylene group, and a zirconocene in which two methylindenyl groups are bonded by an ethylene group, a dimethylmethylene group or a dimethylsilylene group. Complex A zirconocene complex in which two methylcyclopentadienyl groups are bonded by ethylene, dimethylmethylene or dimethylsilylene groups, and two dimethylcyclopentadienyl groups are bonded by ethylene, dimethylmethylene or dimethylsilylene groups The zirconocene complex etc. which were made can be mention | raise | lifted. Moreover, as a metal atom of a component (b), a zirconium and hafnium are preferable, and also as a remaining substituent which a metal atom has, a diphenoxy group and a dialkoxy group are preferable. The component (b) is preferably ethylenebis (1-indenyl) zirconium diphenoxide.

  In the polymerization catalyst comprising the above-described solid particulate promoter component and the metallocene complex, an organoaluminum compound may be used in combination as a catalyst component as appropriate. Examples of the organoaluminum compound include triisobutylaluminum, trinormal Examples include octyl aluminum.

The amount of the metallocene complex used is preferably 5 × 10 ^{−6 to} 5 × 10 ⁻⁴ mol per 1 g of the solid particulate promoter component. The amount of the organoaluminum compound used is preferably such that the aluminum atom of the organoaluminum compound is 1 to 2000 mol per mol of the metal atom of the metallocene complex.

  In addition, in the polymerization catalyst using the solid particulate promoter component and the metallocene complex, an electron donating compound may be used as a catalyst component as appropriate. Examples of the electron donating compound include triethylamine, Examples thereof include tri-normal octylamine.

  When two types of fluorinated phenols having different numbers of fluorine are used as the component (b) fluorinated phenol, it is preferable to use an electron donating compound.

  The amount of the electron-donating compound used is usually 0.1 to 10 mol% with respect to the number of moles of aluminum atoms in the organoaluminum compound used as the catalyst component, and the molecular weight distribution (Mw / From the viewpoint of increasing Mn), the amount used is preferably higher.

  More specifically, as a method for producing the ethylene-α-olefin copolymer of component (A), a catalyst obtained by contacting the promoter support (a), the crosslinked bisindenylzirconium complex and the organoaluminum compound. In the presence of, there is a method of copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms.

  The polymerization method is preferably a continuous polymerization method involving molding of ethylene-α-olefin copolymer particles, such as continuous gas phase polymerization, continuous slurry polymerization, and continuous bulk polymerization, preferably continuous gas phase. Polymerization. The gas phase polymerization reaction apparatus is usually an apparatus having a fluidized bed type reaction tank, and preferably an apparatus having a fluidized bed type reaction tank having an enlarged portion. A stirring blade may be installed in the reaction vessel.

  As a method for supplying each component of the polymerization catalyst used for the production of the component (A) ethylene-α-olefin copolymer to the reaction vessel, usually, an inert gas such as nitrogen or argon, hydrogen, ethylene or the like is used. Then, a method of supplying in a state free from moisture, or a method of supplying each component in a solution or slurry after dissolving or diluting each component in a solvent is used. Each component of the polymerization catalyst may be supplied individually, or arbitrary components may be supplied in contact in advance in any order.

  Moreover, it is preferable to carry out prepolymerization before carrying out the main polymerization and to use the prepolymerized prepolymerized catalyst component as a catalyst component or catalyst for the main polymerization. Different α-olefins may be used in the main polymerization and the prepolymerization, and it is preferable to prepolymerize the α-olefin having 4 to 12 carbon atoms with ethylene, and the α-olefin having 6 to 8 carbon atoms. It is more preferable to prepolymerize with ethylene.

  The polymerization temperature is usually lower than the temperature at which the ethylene-α-olefin copolymer melts, preferably 0 to 150 ° C, more preferably 30 to 100 ° C, and even more preferably 50 to 90 ° C. is there. From the viewpoint of expanding the molecular weight distribution (Mw / Mn) of the ethylene-α-olefin copolymer, a higher polymerization temperature is preferable.

  The polymerization time is usually 1 to 20 hours (as an average residence time in the case of a continuous polymerization reaction). From the viewpoint of expanding the molecular weight distribution (Mw / Mn) of the ethylene-α-olefin copolymer, it is preferable that the polymerization time (average residence time) is long.

  Further, for the purpose of adjusting the melt fluidity of the copolymer, hydrogen may be added to the polymerization reaction gas as a molecular weight regulator, and an inert gas may be allowed to coexist in the polymerization reaction gas. The molar concentration of hydrogen in the polymerization reaction gas with respect to the molar concentration of ethylene in the polymerization reaction gas is usually 0.1 to 3 mol% as the molar concentration of ethylene in the polymerization reaction gas is 100 mol%. Further, from the viewpoint of extending the molecular weight distribution (Mw / Mn) of the ethylene-α-olefin copolymer, it is preferable that the molar concentration of hydrogen in the polymerization reaction gas is high.

  Examples of the thermally decomposable blowing agent for component (B) used in the present invention include azodicarbonamide (ADCA), 4,4′-oxybis (benzenesulfonylhydrazide), p-toluenesulfonylhydrazide, N, N′-dinitroso. Organic thermal decomposition foaming agents such as pentamethylenetetramine, barium azodicarboxylate, nitroguanidine, 5-phenyltetrazole, trihydrazinotriazine, hydrazodicarbonamide, p-toluenesulfonyl semicarbazide; sodium bicarbonate, anhydrous sodium citrate, etc. These are inorganic pyrolytic foaming agents, and these can be used alone or in combination of two or more. Preferably, it is azodicarbonamide (ADCA).

  The decomposition temperature of the pyrolyzable foaming agent of component (B) is usually 100 to 240 ° C, and preferably 130 to 240 ° C.

  The content of the component (B) in the ethylene resin composition containing the component (A) and the component (B) is 1 to 40 parts by weight, preferably 2 to 30 parts by weight per 100 parts by weight of the component (A). Part.

  In the ethylene-based resin composition containing the component (A) and the component (B), a foaming aid, a crosslinking agent, a crosslinking aid, a heat stabilizer, a weathering stabilizer, a pigment, a filler, a lubricant, You may contain well-known additives, such as an antistatic agent and a flame retardant.

  Examples of the foaming aid include metal oxides such as zinc oxide and lead oxide; metal carbonates such as zinc carbonate; metal chlorides such as zinc chloride; urea; zinc stearate, lead stearate, dibasic lead stearate , Metal soaps such as zinc laurate, zinc 2-ethylhexoate, dibasic lead phthalate; organotin compounds such as dibutyltin dilaurate and dibutyltin dimale; tribasic lead sulfate, dibasic lead phosphite, base And inorganic salts such as lead sulfite.

  The ethylene-based resin composition containing the component (A) and the component (B) is obtained by decomposing the component (A), the component (B), and other components blended as necessary, by decomposing the foaming agent of the component (B). After mixing with a known method, for example, a tumbler blender, Henschel mixer, etc., at a temperature lower than the temperature, it is further melt-kneaded with a single-screw extruder, multi-screw extruder, etc., or by melt-kneading with a kneader, Banbury mixer, etc. can get.

  In the method for producing a foam of the present invention, a resin composition obtained by irradiating an ethylene resin composition containing the component (A) and the component (B) with ionizing radiation is heated and foamed.

  As ionizing radiation with which the ethylene-based resin composition containing the component (A) and the component (B) is irradiated, α rays, β rays, γ rays, electron beams, neutron rays, X rays and the like are used. Of these, cobalt-60 γ rays and electron beams are preferred.

  The irradiation with ionizing radiation is performed using a known ionizing radiation irradiation apparatus, and the irradiation amount is usually 1 to 20 Mrad, preferably 2 to 15 Mrad.

  The ethylene-based resin composition containing the component (A) and the component (B) is usually molded into a desired shape at a temperature lower than the decomposition temperature of the foaming agent of the component (B) before irradiating with ionizing radiation. . For example, as a method of forming into a sheet, a method of forming into a sheet form with a calender roll, a method of forming into a sheet form with a press molding machine, a method of forming into a sheet form by melt extrusion from a T die or an annular die, etc. It is done.

  As a method of heating and foaming a resin composition formed by irradiating ionizing radiation, any known method can be applied, and ethylene-based methods such as a vertical hot air foaming method, a horizontal hot air foaming method, a horizontal chemical liquid foaming method, It is preferable to apply a method capable of continuously heating and foaming a sheet made of a resin composition. The heating temperature is a temperature equal to or higher than the decomposition temperature of the foaming agent of component (B), and preferably 5 to 50 ° C. higher than the decomposition temperature of the foaming agent. The heating time is usually 3 to 5 minutes when heated in an oven.

  The foam obtained by the present invention is excellent in cell properties and strength, and has good lightness. Therefore, it is used as a buffer material, a heat insulating material, a sound insulating material, a heat insulating and cold insulating material, and the like.

Hereinafter, the present invention will be described with reference to examples and comparative examples.
The physical properties in Examples and Comparative Examples were measured according to the following methods.

(1) Melt flow rate (MFR, unit: g / 10 minutes)
In the method defined in JIS K7210-1995, the measurement was performed under the conditions of a load of 21.18 N and a temperature of 190 ° C.

(2) Density (Unit: kg / m ³ )
The density was measured according to the A method in the method defined in JIS K7112-1999.

(3) Molecular weight distribution (Mw / Mn)
The measurement was performed under the following conditions (1) to (7) using a gel permeation chromatograph (GPC) method. The weight average molecular weight (Mw) in terms of polystyrene and the number average in terms of polystyrene using a calibration curve prepared in advance using standard polystyrene with a narrow molecular weight distribution (TSO STANDARD POLYSTYRNE manufactured by Tosoh Corporation) whose molecular weight distribution can be regarded as monodisperse. The molecular weight (Mn) was determined, and the molecular weight distribution (Mw / Mn) was determined from them.
(1) Equipment: Waters 150C manufactured by Water
(2) Separation column: TOSOH TSKgelGMH-HT
(3) Measurement temperature: 145 ° C
(4) Carrier: Orthodichlorobenzene
(5) Flow rate: 1.0 mL / min
(6) Injection volume: 500 μL
(7) Detector: Differential refraction

(4) Flow activation energy (Ea, unit: kJ / mol)
Using a viscoelasticity measuring device (Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), a melt complex viscosity-angular frequency curve at 130 ° C., 150 ° C., 170 ° C. and 190 ° C. was measured under the following measurement conditions. From the obtained melt complex viscosity-angular frequency curve, calculation software Rhios V. The activation energy (Ea) was determined using 4.4.4.
<Measurement conditions>
Geometry: Parallel plate Plate diameter: 25mm
Plate spacing: 1.2-2mm
Strain: 5%
Angular frequency: 0.1 to 100 rad / sec Measurement atmosphere: Under nitrogen

(5) Melt complex viscosity (η ^* , unit: Pa · sec)
The melt complex viscosity at 190 ° C. at an angular frequency of 100 rad / sec was determined from the measurement result of the melt complex viscosity at 190 ° C.-angular frequency obtained when the above (4) flow activation energy was measured.

(6) Foaming ratio (unit: times)
The density was calculated by the following formula from the density of the resin and the density of the foam obtained by the above (2) density method.
Foaming ratio = resin density / foam density

(7) Tensile properties ASTM D1822 type L type dumbbell-shaped test pieces are punched from the foam, and a tensile test is carried out under the conditions of a grip distance of 30 mm and a tensile speed of 50 mm / min. Tensile fracture strength (unit: N) and tensile The breaking elongation (unit:%) was determined. The greater these values, the better the strength.

(8) Properties of foam The properties of the foam were visually evaluated as follows.
○: The uniformity of the bubble shape is high.
X: The uniformity of bubble shape is low.

Example 1
(1) Preparation of promoter support A solid product was obtained in the same manner as in Example 10 (1) and Component (A) of JP-A-2003-171415.

(2) Preliminary polymerization In an autoclave with a stirrer having an internal volume of 210 liters, which was previously purged with nitrogen, 0.68 kg of the above solid product, 80 liters of butane, 0.02 kg of 1-butene, and 3 liters as hydrogen at normal temperature and pressure were charged. Thereafter, the autoclave was raised to 30 ° C. Further, ethylene was charged for 0.03 MPa as the gas phase pressure in the oat clave, and after the system was stabilized, 216 mmol of triisobutylaluminum and 72.5 mmol of racemic-ethylenebis (1-indenyl) zirconium diphenoxide were added to perform polymerization. Started. While raising the temperature to 30.7 ° C. and supplying ethylene and hydrogen continuously, prepolymerization was carried out at 50 ° C. for a total of 4 hours. After completion of the polymerization, purging with ethylene, butane, hydrogen gas, etc., the remaining solid is vacuum-dried at room temperature, and 14.2 g of ethylene / 1-butene copolymer per 1 g of the solid product obtained in (1) above. A prepolymerized catalyst component having been prepolymerized was obtained.

(3) Continuous gas phase polymerization Using the above prepolymerization catalyst component, ethylene and 1-hexene were copolymerized in a continuous fluidized bed gas phase polymerization apparatus. The polymerization conditions were a temperature of 75.4 ° C., a total pressure of 2 MPa, a gas linear velocity of 0.28 m / s, a hydrogen molar ratio to ethylene of 0.835%, and a 1-hexene molar ratio to ethylene of 1.96%. In order to keep the gas composition constant, ethylene, hexene-1, and hydrogen were continuously supplied. Further, the pre-polymerization catalyst component and triisobutylaluminum were continuously supplied at a constant ratio so that the total powder weight of the fluidized bed was maintained at 80 kg and the average polymerization time was 3.4 hr. By polymerization, a powder of an ethylene-1-hexene copolymer (hereinafter referred to as PE-1) was obtained with a polymerization efficiency of 23.4 kg / hr.

(4) Granulation of ethylene-1-hexene copolymer powder The PE-1 powder obtained above was fed with an LCM50 extruder manufactured by Kobe Steel, Ltd., at a feed rate of 50 kg / hr, a screw rotation speed of 450 rpm, and a gate opening of 4. The pellets of PE-1 were obtained by granulation under conditions of 0.2 mm, a suction pressure of 0.2 MPa, and a resin temperature of 200 to 230 ° C. Table 1 shows the physical properties of PE-1 pellets.

(5) Molding of foam 100 parts by weight of PE-1 pellets, 20 parts by weight of azodicarbonamide (trade name Cellmice CE; decomposition temperature 208 ° C., manufactured by Sankyo Kasei Co., Ltd.), and 1.5 parts by weight of zinc stearate After being kneaded with a Brabender at a temperature of 130 to 140 ° C., the obtained kneaded material is put into a mold on a press at 130 ° C., heated for 5 minutes, and then pressurized and cooled to perform a thickness of 2 mm. A crosslinked and unfoamed sheet was obtained. Next, the sheet was irradiated with an electron beam of 4.5 Mrad by an electron beam accelerator to obtain an unfoamed crosslinked sheet. The crosslinked sheet was heated in an oven at 215 ° C. to obtain a foam. Table 2 shows the physical properties of the obtained foam.

Example 2
A foam was obtained in the same manner as in Example 1 except that the electron beam irradiation amount was changed to 4.8 Mrad. Table 2 shows the physical properties of the obtained foam.

Example 3
(1) Preparation of promoter support A solid product was obtained in the same manner as in Example 10 (1) and Component (A) of JP-A-2003-171415.

(2) Preliminary polymerization After charging 0.73 kg of the above solid product, 80 liters of butane, 0 kg of 1-butene, and 0 liter as hydrogen at normal temperature and normal pressure into an autoclave with a stirrer having an internal volume of 210 liters previously substituted with nitrogen The autoclave was raised to 30 ° C. Further, ethylene was charged for 0.03 MPa as the gas phase pressure in the oat clave, and after the system was stabilized, 160 mmol of triisobutylaluminum and 101.2 mmol of racemic-ethylenebis (1-indenyl) zirconium diphenoxide were added for polymerization. Started. While raising the temperature to 30.6 ° C. and continuously supplying ethylene and hydrogen, prepolymerization was carried out at 50.3 ° C. for a total of 4 hours. After completion of the polymerization, purging with ethylene, butane, hydrogen gas, etc., the remaining solid is vacuum dried at room temperature, and 16.0 g of ethylene / 1-butene copolymer per 1 g of the solid product obtained in the above (1). A prepolymerized catalyst component having been prepolymerized was obtained.

(3) Continuous gas phase polymerization Using the above prepolymerization catalyst component, ethylene and 1-hexene were copolymerized in a continuous fluidized bed gas phase polymerization apparatus. The polymerization conditions were a temperature of 87.2 ° C., a total pressure of 2 MPa, a gas linear velocity of 0.25 m / s, a hydrogen molar ratio to ethylene of 1.451%, and a 1-hexene molar ratio to ethylene of 1.09%. In order to keep the gas composition constant, ethylene, hexene-1, and hydrogen were continuously supplied. Further, the pre-polymerization catalyst component and triisobutylaluminum were continuously supplied at a constant ratio so that the total powder weight of the fluidized bed was maintained at 80 kg and the average polymerization time was 3.7 hr. By polymerization, a powder of an ethylene-1-hexene copolymer (hereinafter referred to as PE-2) was obtained at a polymerization efficiency of 21.6 kg / hr.

(4) Granulation of ethylene-1-hexene copolymer powder The PE-2 powder obtained above was fed with an LCM50 extruder manufactured by Kobe Steel, Ltd. at a feed rate of 50 kg / hr, a screw rotation speed of 450 rpm, and a gate opening of 4. The pellets of PE-2 were obtained by granulation under the conditions of 0.2 mm, a suction pressure of 0.2 MPa, and a resin temperature of 200 to 230 ° C. Table 1 shows the physical properties of PE-2 pellets.

(5) Molding of foam 100 parts by weight of PE-2 pellets, 20 parts by weight of azodicarbonamide (manufactured by Sankyo Kasei Co., Ltd., Cellmic CE; decomposition temperature 208 ° C.), and 1.5 parts by weight of zinc stearate After being kneaded with a Brabender at a temperature of 130 to 140 ° C., the obtained kneaded material is put into a mold on a press at 130 ° C., heated for 5 minutes, and then pressurized and cooled to perform a thickness of 2 mm. A crosslinked and unfoamed sheet was obtained. Next, the sheet was irradiated with an electron beam of 3.5 Mrad by an electron beam accelerator to obtain an unfoamed crosslinked sheet. The crosslinked sheet was heated in an oven at 215 ° C. to obtain a foam. Table 2 shows the physical properties of the obtained foam.

Comparative Example 1
(1) Preparation of solid catalyst component A solid product was obtained in the same manner as in Example 16 (1) of JP-A-11-322833.

(2) Prepolymerization After replacing an internal volume 210L autoclave equipped with a stirrer with nitrogen, 1.55 kg of the above solid product at room temperature, 100L of butane, and 2.63 mol of triethylaluminum were added. After the addition of butane, the tank internal temperature was 27.3 ° C. and the tank internal pressure was 0.30 MPaG. Next, hydrogen was added until the internal pressure of the tank reached 1.37 MPaG, and then the temperature in the tank was raised to 40 ° C. The ethylene supply was started simultaneously with the temperature rise. Ethylene was charged at an average of 2.6 kg / h. After completion of the temperature increase, polymerization was allowed to proceed at an average temperature of 39.7 ° C. and an average pressure of 1.85 MPaG. The supply was stopped 10.8 hours after the start of the supply of ethylene, and the reaction was stopped. Thereafter, butane was flushed, nitrogen drying was performed for 3 hours, classification was performed using a 36-mesh wire net under a nitrogen atmosphere to remove coarse particles, and a prepolymerized catalyst was obtained. The mass ratio of the prepolymer to the solid product (1) (prepolymer / solid product) was 15.6 g / g.

(3) Continuous gas phase polymerization Copolymerization of ethylene and 1-butene was carried out in a continuous fluidized bed gas phase reactor. The polymerization conditions were as follows: reactor temperature 89 ° C., reactor pressure 2.0 MPaG, hold-up 80 kg, gas flow rate in the reactor 28 cm / s, gas composition ethylene 58 mol%, 1-butene 22.6 mol%, Hydrogen was 10.6 mol% and nitrogen was 8.8 mol%, and the above prepolymerized catalyst was supplied at 32.2 g / hr and triethylaluminum at 80 mmol / hr. By polymerization, an ethylene-1-butene copolymer powder (hereinafter referred to as PE-3) was obtained at a polymerization efficiency of 22.4 kg / hr. PE-3 powder was granulated with a 30 mm extruder to obtain PE-3 pellets. The physical properties of PE-3 pellets are shown in Table 1.

(3) Molding of foam 100 parts by weight of PE-3 pellets, 20 parts by weight of azodicarbonamide (trade name Celmic CE; decomposition temperature 208 ° C., manufactured by Sankyo Kasei Co., Ltd.), and 1.5 parts by weight of zinc stearate After being kneaded with a Brabender at a temperature of 130 to 140 ° C., the obtained kneaded product is put into a mold on a 140 ° C. press and heated for 5 minutes. A crosslinked and unfoamed sheet was obtained. Next, the sheet was irradiated with an electron beam of 4.5 Mrad by an electron beam accelerator to obtain an unfoamed crosslinked sheet. The crosslinked sheet was heated in an oven at 215 ° C. to obtain a foam. Table 2 shows the physical properties of the obtained foam.

Comparative Example 2
A foam was obtained in the same manner as in Comparative Example 1 except that the electron beam irradiation amount was changed to 5.0 Mrad. Table 2 shows the physical properties of the obtained foam.

Claims (3)

The manufacturing method of the foam which heat-foams the resin composition formed by irradiating the following ethylene-type resin composition with ionizing radiation with the irradiation amount of 1-20 Mrad.
[Ethylene resin composition]
An ethylene-based resin composition component (A) containing the following component (A) and component (B), wherein the content of the component (B) is 1 to 40 parts by weight per 100 parts by weight of the component (A): JIS K7210 The melt flow rate (MFR) measured under the conditions of a specified temperature of 190 ° C. and a load of 21.18 N is 0.1 to 5 g / 10 minutes, the density is 900 to 935 kg / m ³ , and the molecular weight distribution (Mw / Mn) is 5 to 25, and the flow activation energy (Ea) is 40 kJ / mol or more, an ethylene-α-olefin copolymer component (B): a thermal decomposition type having a decomposition temperature of 100 to 240 ° C. Blowing agent The ethylene-based resin composition containing the following component (A) and component (B), and the content of the component (B) is 1 to 40 parts by weight per 100 parts by weight of the component (A); A resin composition formed by irradiating ionizing radiation.
Component (A): Melt flow rate (MFR) measured under conditions of a temperature of 190 ° C. and a load of 21.18 N specified in JIS K7210 is 0.1 to 5 g / 10 min, and a density is 900 to 935 kg / m. ³ , an ethylene-α-olefin copolymer component (B) having a molecular weight distribution (Mw / Mn) of 5 to 25 and a flow activation energy (Ea) of 40 kJ / mol or more: a decomposition temperature of 100 Pyrolytic foaming agent having a temperature of ~ 240 ° C A foam formed by heating and foaming the resin composition according to claim 2.