JP2010150525A - Ethylene-based resin for foam molding and foamed body - Google Patents

Abstract

The present invention provides an ethylene-based resin for foam molding capable of obtaining a foam molded article having an increased expansion ratio without excessively reducing the impact strength of linear low density polyethylene.
An ethylene-based resin for foam molding that satisfies all of the following conditions.
(A) Density is 890-930 kg / m ³
(B) Melt flow rate (MFR) is 0.1 to 10 g / 10 min (c) Flow activation energy (Ea) is less than 50 kJ / mol (d) Mz / Mw is 3.5 or more (e) (Mz /Mw)/(Mw/Mn)≧2.0
(F) The ratio of the amount of the eluted resin at 100 ° C. or higher measured by the temperature rising elution fractionation method is less than 1% by weight (provided that the weight of the ethylene resin is 100% by weight)
(G) Melt tension at 150 ° C. is 4 to 30 cN
[Selection figure] None

Description

  The present invention relates to an ethylene resin for foam molding and a 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. These foams can be molded by injecting a physical foaming agent such as butane gas or carbon dioxide during the kneading and melting of the resin in the extruder, and releasing the pressure during extrusion to allow foaming without foaming, resin, heat The decomposable foaming agent and peroxide are melt-mixed at a temperature at which the blowing agent and the peroxide are not decomposed and formed into a sheet, and then heated to a temperature at which the peroxide decomposes to crosslink the sheet, A method in which the sheet is heated to a temperature higher than the decomposition temperature of the foaming agent, or a resin and a foaming agent are melt-mixed at a temperature at which the foaming agent does not decompose and molded into a sheet, and then the sheet is irradiated with an electron beam. Then, so-called cross-linking foaming is known in which the sheet is cross-linked, and then the sheet is heated to foam above the decomposition temperature of the blowing agent.
Although linear low density polyethylene is superior in strength to high pressure method low density polyethylene, it is more difficult to obtain a foamed molded article having a high expansion ratio than high pressure method low density polyethylene. Therefore, it has been proposed to blend and foam linear low density polyethylene and high pressure method low density polyethylene (see Patent Documents 1 and 2).

JP 60-222222 A JP-A-5-247247

However, in the above resin composition, although the expansion ratio is improved by blending the high-pressure method low-density polyethylene, the impact strength may be greatly reduced, which is not always satisfactory.
Under such circumstances, the present invention can solve the above-described problems and obtain a foamed molded article having an increased expansion ratio without excessively reducing the impact strength of linear low density polyethylene. The present invention provides an ethylene resin for foam molding and a foam formed by foaming the resin.

  INDUSTRIAL APPLICABILITY According to the present invention, an ethylene-based resin for foam molding capable of obtaining a foam having an increased expansion ratio without excessively reducing the impact strength of linear low-density polyethylene, and foaming the resin. A foam can be provided.

The first of the present invention relates to an ethylene resin for foam molding that satisfies all of the following conditions.
(A) Density is 890-930 kg / m ³
(B) Melt flow rate (MFR) is 0.1 to 10 g / 10 min (c) Flow activation energy (Ea) is less than 50 kJ / mol (d) Mz / Mw is 3.5 or more (e) (Mz /Mw)/(Mw/Mn)≧2.0
(F) The ratio of the amount of the eluted resin at 100 ° C. or higher measured by the temperature rising elution fractionation method is less than 1% by weight (provided that the weight of the ethylene resin is 100% by weight)
(G) Melt tension at 150 ° C. is 4 to 30 cN

  The second of the present invention relates to a foam formed by foaming the above-mentioned ethylene-based resin.

  The ethylene resin of the present invention is a copolymer resin containing a monomer unit based on ethylene and a monomer unit based on an α-olefin. Examples of the α-olefin 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 etc. are mention | raise | lifted and these may be used independently and 2 or more types may be used together. The α-olefin is preferably an α-olefin having 3 to 20 carbon atoms, more preferably an α-olefin having 4 to 8 carbon atoms, and still more preferably 1-butene and 1-hexene. , At least one α-olefin selected from 4-methyl-1-pentene.

  In addition to the above-mentioned monomer units based on ethylene and monomer units based on α-olefin, the ethylene-based resin has monomer units based on other monomers within a range not impairing the effects of the present invention. You may do it. Examples of other monomers include conjugated dienes (for example, butadiene and isoprene), non-conjugated dienes (for example, 1,4-pentadiene), acrylic acid, acrylic acid esters (for example, methyl acrylate and ethyl acrylate), and methacrylic acid. Methacrylic acid esters (for example, methyl methacrylate and ethyl methacrylate), vinyl acetate and the like.

  Examples of the ethylene resin include an ethylene-1-butene copolymer resin, an ethylene-1-hexene copolymer resin, an ethylene-4-methyl-1-pentene copolymer resin, and an ethylene-1-octene copolymer. Resin, ethylene-1-butene-1-hexene copolymer resin, ethylene-1-butene-4-methyl-1-pentene copolymer resin, ethylene-1-butene-1-octene copolymer resin, etc. It is done. Preferably, ethylene-1-butene copolymer resin, ethylene-1-hexene copolymer resin, ethylene-4-methyl-1-pentene copolymer resin, ethylene-1-butene-1-hexene copolymer resin It is.

  The content of monomer units based on ethylene in the ethylene-based resin is usually 50 to 99.5% by weight, preferably 80 to 99%, based on the total weight (100% by weight) of the ethylene-based resin. % By weight. The content of monomer units based on α-olefin is usually 0.5 to 50% by weight, preferably 1 to 20% by weight based on the total weight (100% by weight) of the ethylene-based resin. %.

The density of the ethylene-based resin is 890 to 930 kg / m ³ (condition (a)). The density of the ethylene-based resin is preferably 890 kg / m ³ or more, more preferably 900 kg / m ³ or more, from the viewpoint of increasing rigidity. Moreover, from a viewpoint of improving the lightweight property of a foam, Preferably it is 930 kg / m < ³ > or less, More preferably, it is 925 kg / m < ³ > or less. The density is measured according to an underwater substitution method defined in JIS K7112-1980 after annealing described in JIS K6760-1995.

  The melt flow rate (MFR) of the ethylene-based resin is 0.1 to 10 g / 10 minutes (condition (b)). The MFR of the ethylene-based resin is preferably 0.5 g / 10 minutes or more, more preferably 0.7 g / 10 minutes or more, from the viewpoint of reducing the extrusion load during the molding process. Moreover, from a viewpoint of raising the impact strength of a foam, Preferably it is 5 g / 10min or less, More preferably, it is 4 g / 10min or less. The melt flow rate is a value measured by the A method under the conditions of a temperature of 190 ° C. and a load of 21.18 N according to the method defined in JIS K7210-1995.

  The flow activation energy (Ea) of the ethylene-based resin is less than 50 kJ / mol (condition (c)). The Ea of the ethylene-based resin is preferably 40 kJ / mol or less, more preferably 35 kJ / mol or less, from the viewpoint of increasing impact strength.

The flow activation energy (Ea) is a master curve showing the dependence of the melt complex viscosity (unit: Pa · sec) at 190 ° C. on the angular frequency (unit: rad / sec) 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, 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. Based on the temperature-time superposition principle, the melt complex viscosity-angular frequency curve of the ethylene copolymer at 190 ° C. is obtained for each melt complex viscosity-angular frequency curve at each temperature (T). The shift factor (a _T ) at each temperature (T) obtained when superposed on the angular frequency curve is obtained, and the respective temperature (T) and the shift factor (a _T ) at each temperature (T) From the above, a first-order approximate expression (formula (I) below) of [ln (a _T )] and [1 / (T + 273.16)] is calculated by the method of least squares. 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 1.2 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 ratio (hereinafter, “Mz / Mw”) of the Z-average molecular weight (hereinafter sometimes referred to as “Mz”) and the weight-average molecular weight (hereinafter sometimes referred to as “Mw”) of the ethylene-based resin. Is 3.5 or more (condition (d)). From the viewpoint of impact strength, Mz / Mw is preferably 4.5 or more. Further, from the viewpoint of workability and impact strength, Mz / Mw is preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less.

  Ratio (hereinafter, “Mw / Mn”) of weight average molecular weight (hereinafter sometimes referred to as “Mw”) and number average molecular weight (hereinafter sometimes referred to as “Mn”) of the ethylene-based resin. Is preferably 3 or more, more preferably 4 or more from the viewpoint of improving the extrusion processability. From the viewpoint of impact strength, Mw / Mn is preferably 15 or less, more preferably 10 or less, and even more preferably 8 or less. Mw / Mn and Mz / Mw are obtained from the number average molecular weight (Mn), weight average molecular weight (Mw) and Z average molecular weight (Mz) measured by gel permeation chromatography (GPC) method. Value.

  Mw / Mn and Mz / Mw of the ethylene-based resin can be controlled by the following method. For example, when the ethylene resin of the present invention is produced by continuously performing a process for producing a component having a high molecular weight and a process for producing a component having a low molecular weight, the hydrogen concentration or polymerization temperature in each production process. It is a method to change. Specifically, when the conditions for producing a component having a high molecular weight are the same, the Mw / Mn of the resulting ethylene resin increases when the hydrogen concentration or the polymerization temperature in producing the component having a low molecular weight is increased. Similarly, the Mz / Mw of the ethylene-based resin can be increased by lowering the hydrogen concentration when producing a component having a high molecular weight or lowering the polymerization temperature. The Mz / Mw of the ethylene resin can also be increased by increasing the time of the step of producing a component having a high molecular weight and increasing the content of the ultrahigh molecular weight component in the ethylene resin.

  Mz / Mw represents the molecular weight distribution of the high molecular weight component contained in the ethylene-based resin. Mz / Mw smaller than Mw / Mn means that the molecular weight distribution of the high molecular weight component is narrow and the molecular weight is very low. This means that the component ratio of the high molecular weight is small, and that Mz / Mw is larger than Mw / Mn means that the molecular weight distribution of the high molecular weight component is wide and the ratio of the component having a very high molecular weight is large. The ethylene-based resin of the present invention satisfies (Mz / Mw) / (Mw / Mn) ≧ 2.0 (condition (e)). From the viewpoint of increasing the expansion ratio and impact strength, preferably (Mz / Mw) / (Mw / Mn) ≧ 2.5.

In the ethylene-based resin of the present invention, when the weight of the ethylene-based resin is 100% by weight, the ratio of the amount of the eluted resin at 100 ° C. or higher measured by the temperature rising elution fractionation method is less than 1% by weight (provided that The sum of the weights of the ethylene-based resins eluted up to 140 ° C. is 100% by weight) (condition (f)).
The elution resin component at 100 ° C. or higher in the temperature rising elution fractionation method for ethylene resin means a high-density component. When the ethylene-based resin contains a high-density component and a low-density component, these have different crystallization start temperatures, which causes rough skin during film formation, and as a result, the resulting film is inferior in transparency. . The ratio of the amount of resin eluted at 100 ° C. or higher in the temperature rising elution fractionation method is preferably less than 0.5% by weight, more preferably less than 0.1% by weight.

  The ratio of the amount of the eluted resin at 100 ° C. or higher of the ethylene resin measured by the temperature rising elution fractionation method can be controlled as follows. For example, when the ethylene-based resin of the present invention is produced by continuously performing a process for producing a component having a high molecular weight and a process for producing a component having a low molecular weight, α for the ethylene concentration in each production process. -A method of changing the olefin concentration. Specifically, the ratio of the short chain branched structure introduced into the polymer chain can be increased by increasing the ratio of the α-olefin concentration to the ethylene concentration in the polymerization reactor. Since a polymer having a molecular structure with a high proportion of short chain branches has a thin crystal structure, it can be dissolved at a lower temperature. In addition to controlling the ratio of the α-olefin concentration to the ethylene concentration, the ethylene resin of the present invention can also be produced by producing a component having a high molecular weight and a component having a low molecular weight using two types of complexes. In this case, an ethylene-based resin that melts at a lower temperature can be provided by selecting a complex having a higher copolymerization property of α-olefin with respect to ethylene.

The ethylene-based resin of the present invention has a melt tension of 4 to 30 cN at 150 ° C. (condition (g)).
The melt tension in the ethylene-based resin means some degree of molecular entanglement in the molten state, and the higher the entanglement, the higher the melt tension. When the molecular weight of the ethylene-based resin is large, it is easy to be entangled, and when the molecular weight is low, the entanglement is small.
The melt tension of the ethylene-based resin can be controlled by the following method. For example, when the ethylene resin of the present invention is produced by continuously performing a process for producing a component having a high molecular weight and a process for producing a component having a low molecular weight, the hydrogen concentration or polymerization temperature in each production process. Alternatively, the polymerization time is changed. Specifically, when producing a component having a high molecular weight, it is possible to increase the melt tension by lowering the hydrogen concentration, lowering the polymerization temperature, and increasing the polymerization time, and producing a component having a low molecular weight. In the case of carrying out, the melt tension can be increased by lowering the hydrogen concentration, lowering the polymerization temperature, and shortening the polymerization time. Further, when the proportion of the component having a high molecular weight is larger than that of the component having a low molecular weight, the melt tension can be increased.
The melt tension at 150 ° C. of the ethylene-based resin of the present invention is 4 to 30 cN. If the melt tension is too low, it tends to be difficult to obtain a molded article having a high expansion ratio because foam breakage occurs during foam molding, so the melt tension of the ethylene-based resin is preferably 4.5 cN or more, More preferably, it is 5 cN or more. On the other hand, if the melt tension is too high, it tends to be difficult to swell during bubble growth due to the inflow of gas, and it becomes difficult to obtain a molded article having a high expansion ratio. Therefore, it is preferably 20 cN or less, more preferably 15 cN or less.

The ethylene resin of the present invention preferably has a swell ratio (SR) of 1.4 to 1.9 from the viewpoint of obtaining a foam having a high expansion ratio. SR is a method in which the diameter D of the extruded strand is measured when the melt flow rate is measured by the method A under the conditions of a load of 21.18 N and a temperature of 190 ° C. according to the method defined in JIS K7210-1995. Is the ratio D / D0 of the diameter D0 of the orifice.
The swell ratio (SR) is an index of the melt elasticity of the resin and indicates how much the diameter of the strand extruded from the measuring machine expands more than the nozzle diameter of the orifice when measuring the melt flow rate. In terms of molecular structure, the relationship between the molecular weight distribution and the long chain branching is strong, the broader the molecular weight distribution and the larger the number of long chain branches, the larger the SR.

  The ethylene resin of the present invention is a polymer obtained by polymerizing ethylene and α-olefin under the same polymerization conditions using any catalyst selected from Ziegler catalysts, metallocene catalysts, etc. When the molecular weights are compared, it can be produced by combining two or more known olefin polymerization catalysts whose molecular weights are greatly different. In addition, a process for producing a high molecular weight ethylene / α-olefin copolymer using one known olefin polymerization catalyst capable of producing a high molecular weight ethylene / α-olefin copolymer, By a known polymerization method such as a liquid phase polymerization method, a slurry polymerization method, a gas phase polymerization method, a high pressure ion polymerization method using a plurality of reactors including a step of producing a molecular weight ethylene / α-olefin copolymer, It can also be produced by copolymerizing ethylene and an α-olefin. These polymerization methods may be either batch polymerization methods or continuous polymerization methods.

When the ethylene-based resin of the present invention is produced using a plurality of reactors, the high molecular weight component and the low molecular weight component are successively produced in different reactors. When polymerizing in such a continuous process, polymerized particles that pass through some reactors in a very short time (hereinafter sometimes referred to as short-pass polymerized particles) exist in the polymerized particles. To do. In order to prevent the occurrence of such short path polymerized particles, when the ethylene resin of the present invention is produced in a continuous process using a plurality of reactors, a high molecular weight component is produced in the first polymerization reactor. Then, it is preferable to connect two or more reactors to produce a low molecular weight component. On the other hand, when producing the ethylene-based resin of the present invention by batch polymerization, a low molecular weight component and a high molecular weight component can be produced in two reactors, respectively.

When producing the ethylene-based resin of the present invention by batch polymerization, a single reactor is used instead of a plurality of reactors, and the hydrogen concentration in the reactor is changed over time, so that a high molecular weight component and a low molecular weight are obtained. The components can also be manufactured sequentially.

When the ethylene-based resin of the present invention is produced using two or more kinds of olefin polymerization catalysts, the olefin polymerization catalyst used is a polymer of ethylene and α-olefin under the same polymerization conditions using each catalyst. When the molecular weights of the obtained polymers are compared, it is preferable to use a combination of catalysts whose molecular weights are greatly different. In addition, as a catalyst for polymerization, both of a catalyst for producing a high molecular weight component and a catalyst for producing a low molecular weight component have a long activation energy of less than 50 kJ / mol. It is important to select a catalyst capable of producing an ethylene-based resin having a small chain branching structure. When a long chain branching structure is present in the high molecular weight component, the surface of the molded body tends to be rough due to the component having a long relaxation time, and the appearance tends to deteriorate. Further, when a long chain branched structure is present in the low molecular weight component, the impact strength tends to be reduced.

When the ethylene resin of the present invention is produced with one kind of polymerization catalyst, suitable catalysts include, for example, 0.8 to 1.4% by weight of titanium atom, magnesium atom, halogen atom and 15-50% by weight ester. The solid catalyst component which contains a compound and whose specific surface area by BET method is 80 m < ² > / g or less can be mentioned. The ester compound contained in the solid catalyst component is preferably a dialkyl phthalate from the viewpoint of polymerization activity. The solid catalyst component is obtained by reducing a titanium compound (ii) represented by the following general formula [I] with an organomagnesium compound (iii) in the presence of an organosilicon compound (i) having a Si—O bond. It can be obtained as a contact product of the resulting solid component (a), halogenated compound (b) and phthalic acid derivative (c).

  In the case of using a single polymerization catalyst and performing multistage polymerization using a plurality of reactors, the polymerization conditions in at least one of the plurality of reactors are the polymerization conditions of the reactors. It is preferable from the viewpoint of increasing the expansion ratio that the intrinsic viscosity of the ethylene-based resin obtained when the polymerization using the catalyst to be used is 3 or more. Polymerization is performed so that the proportion of the high molecular weight component polymerized under the polymerization reaction conditions giving the high molecular weight component in the ethylene resin of the present invention is 0.5 wt% or more and 10 wt% or less. Is preferable from the viewpoints of expansion ratio and surface smoothness.

Furthermore, when multistage polymerization is performed using one kind of polymerization catalyst, the degree of short chain branching (the number of branches per 1000 carbons) of the resin component obtained in the polymerization tank giving the high molecular weight component is 6 or more and 20 or less. It is preferable from the viewpoint of the lightness of the molded article obtained using the ethylene-based resin of the present invention.

［式中、Ｍ²は元素周期律表の第４族の遷移金属原子を表し、Ｘ²、Ｒ³およびＲ⁴は、それぞれ独立に、水素原子、ハロゲン原子、炭素原子数１〜２０の置換されていてもよいハイドロカルビル基、炭素原子数１〜２０の置換されていてもよいハイドロカルビルオキシ基、炭素原子数１〜２０の置換シリル基または炭素原子数１〜２０の置換アミノ基であり、複数のＸ²は互いに同じであっても異なっていてもよく、複数のＲ³は互いに同じであっても異なっていてもよく、複数のＲ⁴は互いに同じであっても異なっていてもよく、Ｑ²は、下記一般式（ＩＩＩ）で表される架橋基を表す。

（式中、ｎは１〜５の整数であり、Ｊ²は元素周期律表の第１４族の原子を表し、Ｒ⁵は、水素原子、ハロゲン原子、炭素原子数１〜２０の置換されていてもよいハイドロカルビル基、炭素原子数１〜２０の置換されていてもよいハイドロカルビルオキシ基、炭素原子数１〜２０の置換シリル基または炭素原子数１〜２０の置換アミノ基であり、複数のＲ⁵は互いに同じであっても異なっていてもよい。）］ When the ethylene-based resin of the present invention is produced with two or more kinds of polymerization catalysts including a polymerization catalyst that provides a high molecular weight component and a polymerization catalyst that provides a low molecular weight component, examples of suitable catalysts include the following. It is done.
Examples of the polymerization catalyst that gives a high molecular weight component include transition metal compound polymerization catalysts represented by the following general formula (II).

[Wherein, M ² represents a transition metal atom of Group 4 of the periodic table, and X ² , R ^3, and R ⁴ are each independently a hydrogen atom, a halogen atom, or a substitution of 1 to 20 carbon atoms. Optionally substituted hydrocarbyl group, optionally substituted hydrocarbyloxy group having 1 to 20 carbon atoms, substituted silyl group having 1 to 20 carbon atoms, or substituted amino group having 1 to 20 carbon atoms The plurality of X ² may be the same or different from each other, the plurality of R ³ may be the same or different from each other, and the plurality of R ⁴ may be the same or different from each other. Q ² represents a crosslinking group represented by the following general formula (III).

(In the formula, n is an integer of 1 to 5, J ² represents an atom of Group 14 of the periodic table, and R ⁵ is a hydrogen atom, a halogen atom, or a substituted carbon atom having 1 to 20 carbon atoms. An optionally substituted hydrocarbyl group, an optionally substituted hydrocarbyloxy group having 1 to 20 carbon atoms, a substituted silyl group having 1 to 20 carbon atoms, or a substituted amino group having 1 to 20 carbon atoms. The plurality of R ⁵ may be the same or different from each other.

On the other hand, as a polymerization catalyst that gives a low molecular weight component, for example, there are two groups having a cyclopentadiene type anion skeleton having a substituent, and the groups having this cyclopentadiene type anion skeleton are not bonded to each other. And transition metal compound polymerization catalysts in which the central metal is a Group 4 transition metal atom. When a polymerization catalyst component in which cyclopentazine type anion skeletons are bonded to each other is used, the resulting polymer has a long chain branch, and the strength tends to decrease.

Moreover, it is preferable that the following conditions are satisfied with respect to the mixing ratio Cat1: Cat2 = x: y of the polymerization catalyst (Cat1) that provides a high molecular weight component and the polymerization catalyst (Cat2) that provides a low molecular weight component. The polymerization activity (g / g) per gram of Cat1 and Cat2 when the polymerization was carried out using each catalyst alone under the same polymerization conditions as those used for polymerization using the mixed catalyst components was A _Cat1. , when the _{a Cat2, a Cat1 · x /} a Cat2 · y from the viewpoint of improving the expansion ratio of the resulting ethylene-based resin is preferably 0.005 or more. Further, from the viewpoint of kneading load _{reduction, A Cat1 · x / A Cat2} · y is preferably 0.12 or less.

The conditions for producing the ethylene-based resin of the present invention using the polymerization catalyst (Cat 1) that gives a high molecular weight component and the polymerization catalyst (Cat 2) that gives a low molecular weight component are the polymerization conditions for polymerizing using the mixed catalyst components. From the viewpoint of increasing the melt tension, it is preferable that the intrinsic viscosity [η] of the ethylene-based resin obtained when the polymerization is carried out using Cat 1 under the same polymerization conditions.

When a metallocene catalyst is used as the polymerization catalyst component, a known activation promoter component, carrier and the like can be used in combination.

  The ethylene-based resin of the present invention can be used for various moldings with other resins as necessary. Examples of the other resin include an ethylene resin different from the ethylene resin of the present invention.

  The foaming agent used at the time of manufacturing the foamed molded product is not particularly limited, and a known physical foaming agent or a pyrolytic foaming agent can be used. A plurality of foaming agents may be used in combination.

  Physical foaming agents include air, oxygen, nitrogen, carbon dioxide, ethane, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, isohexane, cyclohexane, heptane, ethylene, propylene, water, petroleum ether, Examples include methyl chloride, ethyl chloride, monochlorotrifluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane and the like. Among these, carbon dioxide, nitrogen, n-butane, isobutane, n-pentane or isopentane is preferably used from the viewpoint of economy and safety.

  Examples of the pyrolytic foaming agent include inorganic foaming agents such as ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, anhydrous monosodium citrate; azodicarbonamide, barium azodicarboxylate, Azobisbutyronitrile, nitrodiguanidine, N, N-dinitropentamethylenetetramine, N, N'-dimethyl-N, N'-dinitrosotephthalamide, p-toluenesulfonyl hydrazide, p-toluenesulfonyl cellcarbazide, Organic foams such as p, p'-oxybisbenzenesulfonyl hydrazide, azobisisobutyronitrile, p, p'-oxybisbenzenesulfonyl semicarbazide, 5-phenyltetrazole, trihydrazinotriazine, hydrazodicarbonamide Agents and the like. Among these, azodicarbonamide, sodium hydrogen carbonate, and p′-oxybisbenzenesulfonyl hydrazide are preferably used from the viewpoints of economy and safety. It is particularly preferable to use a foaming agent containing azodicarbonamide and sodium hydrogencarbonate because a molding temperature range is wide and an extruded foam molded product having fine bubbles is obtained.

  When using a thermal decomposition type foaming agent, the thermal decomposition type foaming agent whose decomposition temperature is 120-240 degreeC normally is used. When using a thermal decomposition type foaming agent having a decomposition temperature higher than 200 ° C., it is preferable to use the foaming aid in combination with a decomposition temperature lowered to 200 ° C. or lower. As foaming aids, 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 soap such as zinc laurate, zinc 2-ethylhexoate, and dibasic lead phthalate; Organotin compounds such as dibutyltin dilaurate and dibutyltin dimale; Tribasic lead sulfate, dibasic lead phosphite, basic Examples thereof include inorganic salts such as lead sulfite.

  When using a pyrolyzable foaming agent, a masterbatch composed of a pyrolyzable foaming agent, a foaming aid and a resin is usually used. The type of resin used in the masterbatch is not particularly limited as long as the effect of the present invention is not inhibited, but it is an ethylene-α-olefin copolymer constituting the foam of the present invention, or a high pressure method low density polyethylene. Is preferred. The blending ratio of the total amount of the pyrolyzable foaming agent and foaming aid contained in the masterbatch to the resin is usually 5 to 90% by weight.

  When a foaming agent is used, a foam having finer bubbles can be obtained by using a foaming nucleating agent in combination. Foam nucleating agents include talc, silica, mica, zeolite, calcium carbonate, calcium silicate, magnesium carbonate, aluminum hydroxide, barium sulfate, aluminosilicate, clay, quartz powder, diatomaceous earth inorganic fillers; polymethyl methacrylate, polystyrene Examples of beads having a particle diameter of 100 μm or less; metal salts such as calcium stearate, magnesium stearate, zinc stearate, sodium benzoate, calcium benzoate, aluminum benzoate, and magnesium oxide, and combinations of two or more thereof May be.

  Although the addition amount of a foaming agent is suitably set by the kind of foaming agent to be used and the foaming ratio of the molded article to be produced, it is usually 1 to 100 parts by weight with respect to 100 parts by weight of the resin constituting the foam.

  The ethylene-based resin of the present invention may contain known additives such as a crosslinking agent, a heat stabilizer, a weather stabilizer, a pigment, a filler, a lubricant, an antistatic agent, and a flame retardant as necessary.

  The ethylene resin of the present invention can be used as a resin composition by kneading in advance with other components blended as necessary. In kneading, there are known methods, for example, a method of mixing with a tumbler blender, a Henschel mixer, etc., and then a melt kneading with a single screw extruder or a multi-screw extruder, or a method of melt kneading with a kneader or a Banbury mixer. Yes, a resin composition can be obtained by these.

  The manufacturing method of the foam of this invention is not specifically limited. For example, in the case of a method for producing a non-crosslinked foam, an ethylene-based resin for foam molding or an ethylene-based resin composition for foam molding containing the resin and a thermally decomposable foaming agent is converted into a single-screw screw extruder or a twin-screw screw extruder. This is a method of melt-kneading with a known molding machine such as the above and extruding it into the atmosphere from a die attached to the tip of the molding machine. The temperature of the extruder is usually 120-280 ° C, and the temperature of the die is usually 100-260 ° C. The molten extruded product immediately after being extruded from the die is foamed. An extruded foam as a final product can be obtained by cooling the extruded foamed molded body in a molten state with a cooling roll, a cooling mandrel, cooling air, cooling water, or the like. The die can be selected from a slit type, a circular slit type, a circular type, a modified type, and the like according to the purpose. A gear pump may be provided between the molding machine and the die for stabilizing the extrusion amount. A static mixer or the like may be installed between the extruder and the die for the purpose of kneading the resin and the foaming agent. In the case of using a physical foaming agent, after melting an ethylene resin for foam molding, or an ethylene resin composition for foam molding containing the resin and a thermal decomposition type foaming agent, the physical foaming agent is supplied from a physical foaming agent supply port of a molding machine. Inject the blowing agent.

For example, when producing a crosslinked foamed product, ionizing radiation is irradiated to the ethylene-based resin composition for foam molding containing the ethylene-based resin of the present invention and a pyrolytic foaming agent. As the ionizing radiation, 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.
Irradiation with ionizing radiation is performed using a known ionizing radiation irradiation apparatus, and the irradiation amount is usually 10 to 200 kGy, preferably 10 to 100 kGy.
The resin composition is usually formed into a desired shape at a temperature lower than the decomposition temperature of the thermally decomposable foaming agent 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 thermally decomposable foaming agent, and preferably 5 to 50 ° C. higher than the decomposition temperature of the thermally decomposable foaming agent. The heating time is usually 3 to 5 minutes when heated in an oven.

  In addition to ionizing radiation, a cross-linked foam can also be produced by using a cross-linking agent such as a radical generator. As the crosslinking agent, an organic peroxide having a decomposition temperature equal to or higher than the flow start temperature of the copolymer is preferably used. For example, dicumyl peroxide, 1,1-ditertiary butyl peroxy-3,3 , 5-trimethylcyclohexane, 2,5-dimethyl-2,5-ditertiary butyl peroxyhexane, 2,5-dimethyl-2,5-ditertiary butyl peroxyhexine, α, α-ditertiary butyl peroxy Examples thereof include isopropylbenzene, tertiary butyl peroxyketone, and tertiary butyl peroxybenzoate.

  When a crosslinking agent is used, an ethylene resin composition obtained by melt-kneading an ethylene resin, a thermally decomposable foaming agent and a crosslinking agent at a temperature at which the thermally decomposable foaming agent and the crosslinking agent do not decompose is heated and heated. The foam can be obtained by pressing.

  In the case of crosslinking with ionizing radiation or a crosslinking agent, the expansion ratio and strength can be increased by using a crosslinking aid. The crosslinking aid is for increasing the degree of crosslinking of the crosslinking type thermoplastic resin composition and improving the mechanical properties of the thermoplastic resin composition. A compound having a plurality of double bonds in the molecule is preferred. 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 addition amount of the crosslinking aid can be selected in the range of 0.01 to 4.0 parts by mass with respect to 100 parts by mass in total of the thermoplastic resin. Preferably it is 0.05-2.0 mass parts. If it is less than 0.01 part by mass, the effect of adding a crosslinking aid hardly appears, and if it exceeds 4 parts by mass, it is not economically advantageous.

  In the composition of the present invention, if necessary, a resin / rubber component such as high pressure method low density polyethylene, high density polyethylene, polypropylene, polyvinyl acetate, and polybutene is blended within a range that does not impair the performance of the present invention. Also good.

The ethylene resin of the present invention is suitable for the production of a foam excellent in expansion ratio and impact strength, and the foam formed by molding the ethylene resin includes a cushioning material, a heat insulating material, a sound insulating material, a heat insulation and cold insulation material, and the like. Used for.

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) Density (Unit: Kg / m ³ )
The density was measured according to the underwater substitution method defined in JIS K7112-1980. The sample was annealed according to JIS K6760-1995.

(2) Melt flow rate (MFR, unit: g / 10 minutes)
The melt flow rate was measured by the A method under the conditions of a load of 21.18 N and a temperature of 190 ° C. according to the method defined in JIS K7210-1995.

(3) Swell ratio (SR)
According to the method specified in JIS K7210-1995, when the melt flow rate is measured by the method A under the conditions of a load of 21.18 N and a temperature of 190 ° C., the diameter D of the extruded strand is measured. The ratio D / D0 with D0 was SR. If SR is about 1.4 to 1.9, it is estimated that the foamability is good.

(4) Intrinsic viscosity ([η], unit: dl / g)
A tetralin solution (hereinafter referred to as a blank solution) in which 2,6-di-t-butyl-p-cresol (BHT) is dissolved at a concentration of 0.5 g / L and the resin so that the concentration becomes 1 mg / ml. A solution dissolved in a blank solution (hereinafter referred to as a sample solution) was prepared. The falling time of the blank solution and the sample solution at 135 ° C. was measured with an Ubbelohde viscometer. The intrinsic viscosity [η] was determined from the falling time by the following formula.
[Η] = 23.3 × log (ηrel)
ηrel = sample solution fall time / blank solution fall time

(5) Flow activation energy (Ea, unit: kJ / mol)
Using a viscoelasticity measuring device (Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), melt complex viscosity-angular frequency curves at 130 ° C., 150 ° C., 170 ° C. and 190 ° C. were measured under the following measurement conditions. Next, from the obtained melt complex viscosity-angular frequency curve, calculation software Rhios V.R. manufactured by Rheometrics is used. Using 4.4.4, a master curve of the melt complex viscosity-angular frequency curve at 190 ° C. was created, and the activation energy (Ea) of the flow was determined.
<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: Nitrogen

(6) Molecular weight distribution (Mw / Mn, Mz / Mw)
Using gel permeation chromatograph (GPC) method, measure z-average molecular weight (Mz), weight-average molecular weight (Mw) and number-average molecular weight (Mn) under the following conditions (1) to (8) Mw / Mn and Mz / Mw were obtained. The baseline on the chromatogram is a stable horizontal region with a sufficiently long retention time than the appearance of the sample elution peak and a stable horizontal region with a sufficiently long retention time than the solvent elution peak was observed. A straight line formed by connecting the points.
(1) Equipment: Waters 150C manufactured by Waters
(2) Separation column: TOSOH TSKgelGMH6-HT 2
(3) Measurement temperature: 152 ° C
(4) Carrier: Orthodichlorobenzene
(5) Flow rate: 1.0 mL / min
(6) Injection volume: 500 μL
(7) Detector: Differential refraction
(8) Molecular weight reference material: Standard polystyrene

(7) Measurement of elution resin amount of 100 ° C. or higher measured by temperature rising elution fractionation method The measurement was performed under the following conditions using the following apparatus.
Apparatus: CFC T150A type manufactured by Mitsubishi Chemical Corporation Detector: Magna-IR550 manufactured by Nicole Japan Co., Ltd.
Wavelength: Data range 2982 to 2842 cm ^-1 Column: UT-806M manufactured by Showa Denko Co., Ltd. Solvent: Orthodichlorobenzene Flow rate: 60 ml / hour Sample concentration: 100 mg / 25 ml
Sample injection volume: 0.8ml
Loading conditions: The temperature was lowered from 140 ° C. to 0 ° C. at a rate of 1 ° C./1 minute, and then left for 30 minutes to start elution from the 0 ° C. fraction.
Data acquisition conditions: In the temperature range of 85 ° C. to 105 ° C., data on the amount of elution was acquired in increments of 1 ° C. Thereafter, the temperature was raised to 140 ° C. and then data on the amount of elution was acquired.

(8) Melt tension (MT, unit: cN)
Using a melt tension tester manufactured by Toyo Seiki Seisakusho, an orifice with a diameter of 2.09 mmφ and a length of 8 mm is obtained by filling a molten resin filled in a 9.5 mmφ barrel at 150 ° C. with a piston descending speed of 5.5 mm / min. The molten resin thus extruded was wound up at a winding speed of 40 rpm / min using a winding roll having a diameter of 150 mmφ, and the tension value immediately before the molten resin broke was taken as the value of the melt tension.

(9) Tensile impact strength (unit: kJ / m ² )
Measurement of tensile impact strength was performed at 23 ° C. in the form of an S-type dumbbell according to ASTM D1822-61T. The sample piece was molded by hot pressing at 150 ° C., stored in a temperature-controlled room at 23 ° C. and 50% humidity for 24 hours or more, and then used for measurement.
The higher the value, the higher the impact strength of the foam.

Example 1
(1-1) Preparation of solid catalyst component 80 L of hexane, 20.6 kg of tetraethoxysilane and 2.2 kg of tetrabutoxytitanium were charged into a 200 L reactor equipped with a nitrogen-substituted stirrer and baffle plate and stirred. Next, 50 L of a dibutyl ether solution of butyl magnesium chloride (concentration: 2.1 mol / L) was added dropwise to the stirred mixture over 4 hours while maintaining the temperature of the reactor at 5 ° C. After completion of the dropwise addition, the mixture was stirred at 5 ° C. for 1 hour and further at 20 ° C. for 1 hour and filtered to obtain a solid component. Next, the obtained solid component was washed with 70 L of toluene three times, and 63 L of toluene was added to the solid component to obtain a slurry.
A reactor having an internal volume of 210 L equipped with a stirrer was replaced with nitrogen, a solid component toluene slurry was charged into the reactor, and 14.4 kg of tetrachlorosilane and 9.5 kg of di (2-ethylhexyl) phthalate were charged, The mixture was stirred at 105 ° C. for 2 hours. Subsequently, solid-liquid separation was performed, and the obtained solid was washed 3 times with 90 L of toluene at 95 ° C. 63 L of toluene was added to the solid, the temperature was raised to 70 ° C., 13.0 kg of TiCl ₄ was added, and the mixture was stirred at 105 ° C. for 2 hours. Next, solid-liquid separation was performed, and the obtained solid was washed 6 times with 90 L of toluene at 95 ° C., and further washed twice with 90 L of hexane at room temperature. The solid after washing was dried to obtain a solid catalyst component.
(1-2) Preparation of Preliminary Polymerization Catalyst (XA-1) An autoclave with a stirrer with an internal volume of 3 L was sufficiently dried, the autoclave was evacuated, 490 g of butane and 260 g of 1-butene were charged, and the temperature was raised to 55 ° C. Next, ethylene was added so that the partial pressure was 1.0 MPa. Polymerization was initiated by injecting 1.7 mmol of triethylaluminum and 194.4 mg of the solid catalyst component produced in (1-1) with argon. Ethylene was continuously supplied from the cylinder so that the pressure was constant, and polymerization was performed at 55 ° C. until the weight reduction amount of the cylinder became 70.0 g. After the polymerization, the supply of ethylene was stopped, the inside of the system was purged, and then pressurized with argon gas, and the prepolymerized powder was collected in an ampoule purged with nitrogen and sealed. When the intrinsic viscosity [η] was measured for a part of the recovered prepolymerized powder and the degree of short chain branching was examined by IR, [η] = 12.5, the degree of short chain branching per 1000 carbons was 6.9. Met.

(1-3) Main polymerization The autoclave with a stirrer having an internal volume of 3 L was sufficiently dried, the autoclave was evacuated, 620 g of butane and 130 g of 1-butene were charged, and the temperature was raised to 70 ° C. Next, ethylene was added so that the partial pressure was 0.6 MPa, and hydrogen was added so that the partial pressure was 0.25 MPa. Polymerization was started by injecting 5.40 g of prepolymerized catalyst (XA-1) produced in 1.7 mmol of triethylaluminum and (1-2) with argon. Ethylene was continuously supplied from a cylinder so that the pressure was constant, and polymerization was performed at 70 ° C. for 3.5 hours. 92 g of ethylene-1-butene copolymer (hereinafter referred to as ethylene resin (A1)) was obtained by polymerization. The physical property values of the ethylene-based resin (A1) are shown in Tables 1 and 2.

Comparative Example 1
(2-1) Preparation of Preliminary Polymerization Catalyst (XA-2) An autoclave with a stirrer with an internal volume of 3 L was sufficiently dried, the autoclave was evacuated, charged with 550 g of butane and 200 g of 1-butene, and heated to 55 ° C. Next, ethylene was added so that the partial pressure was 0.6 MPa. Polymerization was initiated by injecting 1.7 mmol of triethylaluminum and 193.7 mg of the solid catalyst component produced in Example 1 (1-1) with argon. Ethylene was continuously supplied from the cylinder so that the pressure was constant, and polymerization was performed at 55 ° C. until the weight reduction amount of the cylinder reached 19.0 g. After the polymerization, the supply of ethylene was stopped, the inside of the system was purged, and then pressurized with argon gas, and the prepolymerized powder was collected in an ampoule purged with nitrogen and sealed. When a limiting viscosity [η] was measured for a part of the recovered prepolymerized powder and the degree of short chain branching was examined by IR, [η] = 8.1 and the degree of short chain branching per 1000 carbons was 11.5. Met.

(2-2) Main polymerization An autoclave with a stirrer with an internal volume of 3 L was sufficiently dried, the autoclave was evacuated, 530 g of butane and 105 g of 1-butene were charged, and the temperature was raised to 70 ° C. Next, hydrogen was added so that the partial pressure was 0.5 MPa and hydrogen was 0.2 MPa. Polymerization was started by injecting 4.44 g of prepolymerized catalyst (XA-2) produced in 1.7 mmol of triethylaluminum and (2-1) with argon. Ethylene was continuously supplied from a cylinder so that the pressure was constant, and polymerization was carried out at 70 ° C. for 2 hours. By polymerization, 208.5 g of ethylene-1-butene copolymer (hereinafter referred to as ethylene resin (A2)) was obtained. The physical properties of the ethylene resin (A2) are shown in Table 1.

Comparative Example 2
(3-1) Preparation of prepolymerized catalyst (XA-3) An autoclave with a stirrer with an internal volume of 3 L was sufficiently dried, the autoclave was evacuated, 490 g of butane and 260 g of 1-butene were charged, and the temperature was raised to 55 ° C. Next, ethylene was added so that the partial pressure was 1.0 MPa. Polymerization was initiated by injecting 5.4 mmol of triethylaluminum and 326.4 mg of the solid catalyst component produced in Example 1 (1-1) with argon. Ethylene was continuously supplied from the cylinder so that the pressure was constant, and polymerization was carried out at 55 ° C. until the weight loss of the cylinder reached 48.9 g. After the polymerization, the supply of ethylene was stopped, the inside of the system was purged, and then pressurized with argon gas, and the prepolymerized powder was collected in an ampoule purged with nitrogen and sealed. When a limiting viscosity [η] was measured for a part of the recovered prepolymerized powder and the degree of short chain branching was examined by IR, [η] = 9.1, and the degree of short chain branching per 1000 carbons was 10.4. Met.

(3-2) Main polymerization The autoclave with a stirrer with an internal volume of 3 L was sufficiently dried, the autoclave was evacuated, 620 g of butane and 130 g of 1-butene were charged, and the temperature was raised to 70 ° C. Next, ethylene was added so that the partial pressure was 0.6 MPa, and hydrogen was added so that the partial pressure was 0.2 MPa. Polymerization was initiated by injecting 1.775 g of triethylaluminum and 3.75 g of the prepolymerized catalyst (XA-3) produced in (3-1) with argon. Ethylene was continuously supplied from a cylinder so that the pressure was constant, and polymerization was carried out at 70 ° C. for 3 hours. By polymerization, 197 g of an ethylene-1-butene copolymer (hereinafter referred to as ethylene resin (A3)) was obtained. The physical properties of the polymer (A3) are shown in Table 1.

Comparative Example 3
Tables 1 and 2 show physical property values of linear low density polyethylene (Sumikasen-L FS240 manufactured by Sumitomo Chemical Co., Ltd .; hereinafter referred to as ethylene resin (A4)).

Claims (5)

An ethylene-based resin for foam molding that satisfies all of the following conditions.
(A) Density is 890-930 kg / m ³
(B) Melt flow rate (MFR) is 0.1 to 10 g / 10 min (c) Flow activation energy (Ea) is less than 50 kJ / mol (d) Mz / Mw is 3.5 or more (e) (Mz /Mw)/(Mw/Mn)≧2.0
(F) The ratio of the amount of the eluted resin at 100 ° C. or higher measured by the temperature rising elution fractionation method is less than 1% by weight (provided that the weight of the ethylene resin is 100% by weight)
(G) Melt tension at 150 ° C. is 4 to 30 cN An ethylene resin composition for foam molding comprising the ethylene resin for foam molding according to claim 1 and a pyrolytic foaming agent. The ethylene resin composition for foam molding according to claim 2, further comprising a crosslinking agent. A foam formed by foaming the ethylene-based resin for foam molding according to claim 1. The foam formed by foaming the ethylene-type resin composition for foam molding of Claim 2 or 3.