JP2008024768A - Silane-modified ethylene polymer and pipe comprising the same - Google Patents

Abstract

[Purpose] A novel silane-modified ethylene polymer obtained by graft-modifying an ethylene polymer with an organic unsaturated silane compound with a low number of terminal vinyl groups, excellent thermal stability, low flow activation energy, and high melt tension. And a pipe formed by crosslinking the silane-modified ethylene polymer.
A silane-modified ethylene polymer obtained by graft-modifying an ethylene polymer having a small number of terminal vinyl groups and a high melt tension with an organic unsaturated silane compound is used.
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Description

  The present invention relates to a silane-modified ethylene polymer and a pipe comprising the same. More specifically, the present invention relates to an ethylene polymer having a high melt tension and excellent molding processability as compared with conventionally known ethylene polymers. The present invention relates to a silane-modified ethylene polymer composed of a coalescence and a pipe excellent in all aspects of crosslinking efficiency, heat distortion resistance and mechanical properties by crosslinking the silane-modified ethylene polymer.

  Conventionally, pipes made of polyvinyl chloride have been used for the water supply hype and metal pipes such as copper pipes have been used for the hot water supply pipe. However, there has been a problem that the durability of the pipes made of polyvinyl chloride and copper is short. . In particular, copper pipes have the disadvantages of rusting and water leakage due to long-term use, and poor workability due to the low flexibility of pipes. In recent years, flexible polyolefin pipes have been used. is there. Moreover, since pressure resistance and creep resistance at high temperatures are required for water supply and hot water supply applications, silane-crosslinked polyethylene pipes that have been improved in heat resistance and cold resistance by crosslinking polyolefin are used.

  As a method for producing a crosslinked polyethylene pipe, a resin composition obtained by blending polyethylene with an organic peroxide such as dicumyl peroxide at a temperature at which the organic oxide does not decompose is used. A method of extruding into a pipe shape while heating at a decomposition temperature or higher is disclosed (for example, see Patent Document 1).

  In addition, a silane compound, an organic peroxide and a silanol condensation catalyst are blended with polyethylene, and the resulting composition is extruded into a pipe shape while heating, and the resulting pipe is exposed to a moisture-containing environment to cause silane crosslinking. A method of advancing the reaction is also disclosed (see, for example, Patent Documents 2 and 3).

  Furthermore, by using so-called metallocene catalysts prepared from metallocene compounds and aluminoxanes, it becomes possible to produce ethylene copolymers having a very narrow molecular weight distribution of 2 to 3, and these metallocene catalysts have recently been obtained. A crosslinked pipe using polyethylene having a narrow molecular weight distribution has been proposed (see, for example, Patent Document 4).

Japanese Patent Publication No. 45-35658 JP-A-57-170913 JP 57-59724 A Japanese Patent Laid-Open No. 10-193468

  However, in the methods proposed in Patent Documents 1 to 3, polyethylene used as a raw material is an ethylene polymer polymerized by a Ziegler catalyst or a chromium catalyst, and is sufficiently crosslinked due to a wide molecular weight distribution. It was difficult to add a large amount of silane compound, organic peroxide and silanol condensation catalyst. Also, the silane cross-linked pipe molded in this way has problems such as a strange odor derived from unsaturated silane compounds when water is passed through, and the viscosity of the resin is too high even during pipe extrusion, so the die outlet As a result, a large amount of eyes and spots were generated, and it was difficult to stably operate the pipe extrusion for a long time.

  In the method proposed in Patent Document 4, the molecular weight distribution of polyethylene obtained by the metallocene catalyst is narrow, so that the crosslinking characteristics and crosslinking efficiency are high, but the extrusion moldability is very poor, and in the actual extrusion process A good pipe surface cannot be obtained. That is, in the case of an ethylene polymer obtained by a metallocene catalyst, it is preferable in terms of a uniform cross-linked body, but due to the narrow molecular weight distribution, especially in the pipe extrusion process, the fluidity is insufficient, so that shear heat generation in the extruder is generated. However, there is a problem in actual production because there is a risk that the cross-section of the extruded pipe partially deteriorates in the extruder and the surface condition of the extruded pipe deteriorates to cause a decrease in mechanical strength.

  The present invention solves the above-mentioned problems. An ethylene polymer having a low number of terminal vinyl groups, excellent thermal stability, low flow activation energy, and high melt tension is graft-modified with an organic unsaturated silane compound. It is an object of the present invention to provide a novel silane-modified ethylene polymer and a pipe formed by crosslinking the silane-modified ethylene polymer. The pipe of the present invention is excellent in mechanical properties, has little odor in running water, and can solve the conventional problems without problems such as an increase in the load on the extruder, heat generation, and eye contact during pipe forming.

  As a result of intensive studies on the above-mentioned problems, the present inventor is excellent in the extrudability of pipes and molding by using a novel silane-modified ethylene polymer obtained by modifying an ethylene polymer having specific performance. It has been found that the post-crosslinked pipe has excellent characteristics, and the present invention has been completed.

That is, the present invention comprises a repeating unit derived from ethylene by an organic unsaturated silane compound, or a repeating unit derived from ethylene and a repeating unit derived from an α-olefin having 3 to 8 carbon atoms. ) To (F), a silane-modified ethylene polymer obtained by graft-modifying an ethylene polymer, and a pipe obtained by crosslinking the silane-modified ethylene polymer It is.
(A) The density (d) measured by the density gradient tube method in accordance with JIS K6760 is 925 kg / m ³ or more and 970 kg / m ³ or less.
(B) The melt flow rate (MFR) measured at 190 ° C. and a 2.16 kg load is 0.3 g / 10 min or more and 10 g / 10 min or less.
(C) The number of terminal vinyls is 0.2 or less per 1000 carbon atoms,
(D) The relationship between the melt tension (MS ₁₆₀ (mN)) measured at 160 ° C. and MFR satisfies the following formula (1).

MS ₁₆₀ > 90-130 × log (MFR) (1)
(E) The relationship between the melt tension (MS ₁₉₀ (mN)) measured at 190 ° C. and MS ₁₆₀ satisfies the following formula (2).

MS ₁₆₀ / MS ₁₉₀ <1.8 (2)
(F) The relationship between the flow activation energy (E _a (kJ / mol)) and the density (d) satisfies the following formula (3).

_{127-0.107d <E a <88-0.060d (3} )
The present invention is described in detail below.

  The silane-modified ethylene polymer of the present invention is composed of a repeating unit derived from ethylene, or a repeating unit derived from ethylene and a repeating unit derived from an α-olefin having 3 to 8 carbon atoms. An ethylene polymer satisfying (F) is graft-modified with an organic unsaturated silane compound.

  Examples of the ethylene polymer include an ethylene homopolymer composed of a repeating unit derived from ethylene, or an ethylene-α-olefin composed of a repeating unit derived from ethylene and a repeating unit derived from an α-olefin having 3 to 8 carbon atoms. A copolymer is mentioned. Here, the repeating unit derived from an α-olefin having 3 to 8 carbon atoms is derived from an α-olefin having 3 to 8 carbon atoms, which is a monomer, and is contained in the ethylene-α-olefin copolymer. Examples of the α-olefin having 3 to 8 carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-butene. . You may use together at least 2 types of these C3-C8 alpha olefins. When the α-olefin has more than 8 carbon atoms, the melting point and crystallinity of the ethylene polymer are lowered, so that the melting point and crystallinity of the silane-modified ethylene polymer are low. It will be inferior in heat resistance and rigidity.

The ethylene polymer has a density (d) of 925 kg / m ³ or more and 970 kg / m ³ or less, preferably 925 kg, measured by a density gradient tube method in accordance with (A) JIS K6760 (1995). / M ³ or more and 940 kg / m ³ or less. When the density is less than 0.925 kg / m ³ , the insertion of the tertiary carbon produced by the insertion of α-olefin becomes non-uniform, and the graft modification with the organic unsaturated silane compound proceeds non-uniformly. It becomes a system polymer. As a result, mechanical strength and appearance are poor when a crosslinked pipe or the like is used. Furthermore, when a low-density silane-modified ethylene polymer is used as a pipe, there is a problem that the antioxidant is eluted from the pipe when water is passed at a high temperature and long-term oxidation resistance is lowered. On the other hand, when it exceeds 970 kg / m ³ , the product is excellent in heat resistance and rigidity, but inferior in impact strength.

  The ethylene polymer (B) has a melt flow rate (hereinafter referred to as MFR) measured at 190 ° C. and a load of 2.16 kg, of 0.3 g / 10 min to 10 g / 10 min, preferably 1 g. / 10 minutes or more and 8 g / 10 minutes or less, more preferably 2 g / 10 minutes or more and 7 g / 10 minutes or less. Here, when the MFR is less than 0.3 g / 10 min, it becomes difficult to mold the silane-modified ethylene polymer when it is extruded into a pipe or the like. On the other hand, when it exceeds 10 g / 10 minutes, the mechanical strength of the silane-modified ethylene polymer and the pipe made thereof is insufficient.

  The ethylene-based polymer is 0.2 or less per 1000 carbon atoms, preferably 0.1 or less. Here, when the number of terminal vinyls exceeds 0.2 per 1000 carbon atoms, there arises a problem of thermal deterioration, particularly yellowing, during the molding process of the silane-modified ethylene polymer.

Here, as a method for measuring the number of terminal vinyls in the present invention, a film prepared by hot-pressing an ethylene polymer and then cooling with ice was used to measure 4000 cm ⁻¹ to 4,000 cm ⁻¹ with a Fourier transform infrared spectrophotometer (FT-IR). It measured in the range of 400 cm < ^-1 >, and computed using the following formula.

Number of terminal vinyls per 1000 carbon atoms (pieces / 1000 C) = a × A / L / d
(In the formula, a is an absorptivity coefficient, A is an absorbance of 909 cm ⁻¹ attributed to terminal vinyl, L is a film thickness, and d is a density. Note that a is 1000 carbons from ¹ H-NMR measurement. was determined from a calibration curve prepared using samples confirmed terminal number vinyl per atom. ^{1 H-NMR} measurement, NMR measurement apparatus (manufactured by JEOL Ltd., (trade name) GSX400) using deuterated benzene And a mixture of o-dichlorobenzene at 130 ° C. The number of terminal vinyls per 1000 carbon atoms was calculated from the integral ratio of the peak attributed to methylene and the peak attributed to terminal vinyl. Based on tetramethylsilane (0 ppm), a peak with a chemical shift of 1.3 ppm was attributed to methylene and a peak at 4.8 to 5.0 ppm was attributed to terminal vinyl. )
In the ethylene polymer, the relationship between the melt tension (mN) measured in (D) 160 (hereinafter referred to as MS ₁₆₀ ) and MFR satisfies the following formula (1), and preferably the following formula: (4) is satisfied.

MS ₁₆₀ > 90-130 × log (MFR) (1)
MS ₁₆₀ > 110-130 × log (MFR) (4)
Here, when the relationship between MS ₁₆₀ and MFR does not satisfy the above formula (1), the moldability when the silane-modified ethylene polymer is used as a pipe is poor, it becomes difficult to control the thickness of the pipe, and the dimensions are accurate. You can't get a controlled pipe.

MS ₁₆₀ (mN) in the present invention uses a die having a length of 8 mm and a diameter of 2.095 mm, an inflow angle of 90 °, a shear rate of 10.8 s ⁻¹ , a draw ratio of 47, and a measurement temperature of 160 ° C. When the maximum stretch ratio was less than 47, the value measured at the highest stretch ratio that did not break was designated as MS ₁₆₀ .

The ethylene-based polymer has a relationship between (E) melt tension (mN) measured at 190 ° C. (hereinafter referred to as MS ₁₉₀ ) and MS ₁₆₀ satisfies the following formula (2), preferably The following formula (5) is satisfied.

MS ₁₆₀ / MS ₁₉₀ <1.8 (2)
MS ₁₆₀ / MS ₁₉₀ <1.7 (5)
Here, when the relationship between MS ₁₆₀ and MS ₁₉₀ does not satisfy the above formula (2), the melt tension of the silane-modified ethylene polymer greatly changes depending on the temperature. Strict adjustment of the temperature is required, and as a result, the moldable range is narrowed.

In addition, MS ₁₉₀ (mN) in the present invention uses a die having a length of 8 mm and a diameter of 2.095 mm, an inflow angle of 90 °, a shear rate of 10.8 s ⁻¹ , a draw ratio of 47, and a measurement temperature of 190 ° C. When the maximum stretch ratio was less than 47, the value measured at the highest stretch ratio that did not break was designated as MS ₁₉₀ .

The ethylene polymer, (F) fluidized activation energy (kJ / mol) (hereinafter referred to as E _a.) And relationships between the density, which satisfies the following formula (3), preferably The following formula (6) is satisfied.

_{127-0.107d <E a <88-0.060d (3} )
_{127-0.107d <E a <87-0.060d (6} )
Here, if it is _{E a} is (127-0.107d) below, problems in workability of the silane-modified ethylene polymer is produced. On the other hand, if it is E _a is (88-0.060d) or more, the temperature dependency of the melt viscosity of the silane-modified ethylene polymer is increased, it requires tight regulation of the molding temperature, and thus of the pipe forming The moldable range at the time becomes narrow.

Incidentally, E _a in the present invention can be determined by substituting a shift factor obtained by dynamic viscoelasticity measurement of 160 ° C. to 230 ° C. to Arrhenius equation.

Since the ethylene polymer becomes a silane-modified ethylene polymer having excellent mechanical strength, (G) weight average molecular weight / number average molecular weight (hereinafter referred to as M _w / M _n ) is 2 or more and 6 or less. Preferably, it is 2 or more and 5 or less. M _w / M _n can be calculated by measuring a weight average molecular weight (M _w ) and a number average molecular weight (M _n ), which are standard polyethylene equivalent values, by gel permeation chromatography (GPC). it can.

  The ethylene polymer satisfying the above requirements (A) to (F), preferably further satisfying (G) may be any one as long as it belongs to the category of the ethylene polymer, and is obtained by any method. However, for example, it can be arbitrarily made according to the manufacturing conditions of the embodiment of the present invention to be described later or the minor variation of the condition factors.

  More specifically, for example, as a metallocene compound, two cyclopentadienyl groups are cross-linked with a cross-linking group consisting of a chain of two or more atoms, or cross-linked with a cross-linking group consisting of a chain of two or more atoms. Bridged biscyclopentadienyl zirconium complex (hereinafter referred to as component (a)), bridged (cyclopentadienyl) (fluorenyl) zirconium complex and / or bridged (indenyl) (fluorenyl) zirconium A method of polymerizing ethylene or copolymerizing ethylene and an α-olefin having 3 to 8 carbon atoms in the presence of a metallocene catalyst using a complex (hereinafter referred to as component (b)) can be used.

  Specific examples of the component (a) include, for example, 1,1,3,3-tetramethyldisiloxane-1,3-diyl-bis (cyclopentadienyl) zirconium dichloride, 1,1-dimethyl-1-silaethane- 1,2-diyl-bis (cyclopentadienyl) zirconium dichloride, propane-1,3-diyl-bis (cyclopentadienyl) zirconium dichloride, butane-1,4-diyl-bis (cyclopentadienyl) zirconium Dichloride, cis-2-butene-1,4-diyl-bis (cyclopentadienyl) zirconium dichloride, 1,1,2,2-tetramethyldisilane-1,2-diyl-bis (cyclopentadienyl) zirconium Dichlorides such as dichloride and dimethyl and diethyl forms of the above transition metal compounds Dihydro derivative, diphenyl body, can be exemplified dibenzyl body.

  Specific examples of the component (b) include, for example, diphenylmethylene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (2-trimethylsilyl-1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride. Diphenylmethylene (1-cyclopentadienyl) (2,7-dimethyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (1-cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) Zirconium dichloride, isopropylidene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, isopropylidene (1-cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, dipheni Silanediyl (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, dimethylsilanediyl (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (1-indenyl) (9-fluorenyl) zirconium dichloride Diphenylmethylene (2-phenyl-1-indenyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (2-phenyl-1-indenyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, etc. Examples thereof include dimethyl, diethyl, dihydro, diphenyl, and dibenzyl isomers of dichloride and the above transition metal compounds. Moreover, the compound which substituted the zirconium atom of the said transition metal compound by the titanium atom or the hafnium atom can also be illustrated.

  Moreover, the quantity of the component (b) with respect to a component (a) does not have a restriction | limiting in particular, It is preferable that it is 0.0001-100 times mole, Most preferably, it is 0.001-10 times mole.

  As the metallocene catalyst using component (a) and component (b), a catalyst comprising component (a), component (b) and an organoaluminum compound (hereinafter referred to as component (c)), component (a) and Catalyst comprising component (b) and aluminoxane (hereinafter referred to as component (d)), catalyst comprising component (c), component (a), component (b) and protonate (hereinafter referred to as component (c)) A catalyst comprising at least one salt selected from a component (e)), a Lewis acid salt (hereinafter referred to as component (f)) or a metal salt (hereinafter referred to as component (g)); Catalyst comprising component (c), catalyst comprising component (a), component (b), component (d) and inorganic oxide (hereinafter referred to as component (h)), component (a) and component ( at least one selected from b), component (h), component (e), component (f), and component (g) A catalyst comprising a salt of the above, a catalyst further comprising component (c), a catalyst comprising component (a), component (b), clay mineral (hereinafter referred to as component (i)), and component (c), component Examples of the catalyst include (a), component (b), and a clay mineral treated with an organic compound (hereinafter referred to as component (j)), preferably component (a) and component (b). And a catalyst comprising the component (j) can be used.

  Here, the clay mineral that can be used as the component (i) and the component (j) is fine particles mainly composed of microcrystalline silicate. Most of the clay minerals have a layered structure as a structural feature, and it can be mentioned that the layers have negative charges of various sizes. In this respect, it is greatly different from a metal oxide having a three-dimensional structure such as silica or alumina. These clay minerals are generally of a large layer charge, with pyrophyllite, kaolinite, dickite and talc groups (negative charge per chemical formula is approximately 0), smectite groups (negative charge per chemical formula is from about 0.25). 0.6), vermiculite group (negative charge per chemical formula is approximately 0.6 to 0.9), mica group (negative charge per chemical formula is approximately 1), brittle mica group (negative charge per chemical formula is approximately 2) It is classified. Each group shown here includes various clay minerals, and examples of the clay mineral belonging to the smectite group include montmorillonite, beidellite, saponite, hectorite and the like. Further, a plurality of the above clay minerals can be mixed and used.

  The organic compound treatment in component (j) refers to introducing an organic ion between clay mineral layers to form an ionic complex. Examples of the organic compound used in the organic compound treatment include N, N-dimethyl-n-octadecylamine hydrochloride, N, N-dimethyl-n-eicosylamine hydrochloride, N, N-dimethyl-n-docosylamine hydrochloride, N, N-dimethyloleylamine hydrochloride, N, N-dimethylbehenylamine hydrochloride, N-methyl-bis (n-octadecyl) amine hydrochloride, N-methyl-bis (n-eicosyl) amine hydrochloride, N-methyl -Dioleylamine hydrochloride, N-methyl-dibehenylamine hydrochloride, N, N-dimethylaniline hydrochloride can be exemplified.

The catalyst comprising component (a), component (b) and component (j) can be obtained by contacting component (a), component (b) and component (j) in an organic solvent. The method of adding component (b) to the contact product of component (j) and component (b), the method of adding component (a) to the contact product of component (b) and component (j), component (a) and component (b) ) And a method of adding the contact product of component (a) and component (b) to component (j).
As the contact solvent, aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane, nonane, decane, cyclopentane or cyclohexane, aromatic hydrocarbons such as benzene, toluene or xylene, ethyl ether or n-butyl ether And ethers such as methylene chloride and chloroform, 1,4-dioxane, acetonitrile and tetrahydrofuran.

  About a contact temperature, it is preferable to select between 0-200 degreeC and to process.

  The amount of each component used is 0.0001 to 100 mmol, preferably 0.001 to 10 mmol of component (a) per 1 g of component (j).

  The contact product of component (a), component (b) and component (j) prepared in this way may be used without washing, or may be used after washing. Further, when the component (a) or the component (b) is a dihalogen, it is preferable to further add the component (c). Further, component (c) can be added for the purpose of removing impurities in component (j), polymerization solvent and olefin.

  When producing the ethylene polymer used for the silane-modified ethylene polymer of the present invention, the polymerization temperature is preferably -100 to 120 ° C, and particularly considering productivity, 20 to 120 ° C, more preferably 60 to 120 ° C. It is preferable to carry out in the range. The polymerization time is preferably in the range of 10 seconds to 20 hours, and the polymerization pressure is preferably in the range of normal pressure to 300 MPa. The polymerizable monomer is ethylene alone or ethylene and an α-olefin having 3 to 8 carbon atoms. When ethylene is an α-olefin having 3 to 8 carbon atoms, ethylene and α-olefin having 3 to 8 carbon atoms are used. As the olefin supply ratio, ethylene / C3-C8 α-olefin (molar ratio) of 1 to 200, preferably 3 to 100, and more preferably 5 to 50 can be used. It is also possible to adjust the molecular weight using hydrogen during polymerization. The polymerization can be carried out by any of batch, semi-continuous and continuous methods, and can be carried out in two or more stages by changing the polymerization conditions. In addition, the ethylene copolymer can be obtained by separating and recovering from the polymerization solvent by a conventionally known method after the completion of the polymerization and drying.

  Polymerization can be carried out in a slurry state, a solution state, or a gas phase state. In particular, when the polymerization is performed in a slurry state, an ethylene-based copolymer having a powder particle shape is efficiently and stably produced. Can do. Further, the solvent used for the polymerization may be any organic solvent that is generally used, and specific examples include benzene, toluene, xylene, propane, isobutane, pentane, hexane, heptane, cyclohexane, gasoline, and the like, propylene, Olefin itself such as 1-butene, 1-hexene and 1-octene can also be used as a solvent.

  The silane-modified ethylene polymer of the present invention is obtained by graft-modifying the ethylene polymer with an organic unsaturated silane compound, and the silane-modified ethylene polymer is imparted with crosslinkability by the modification. is there.

In graft modification, the radicals in the ethylene polymer generated by the action of the organic peroxide react with the organic unsaturated silane compound, and the silane modified ethylene polymer grafted with the organic silane compound group on the ethylene polymer. It is preferable to combine. The silane-modified ethylene polymer of the present invention is suitable for use as a crosslinked pipe, and the organic unsaturated silane compound is preferably one having crosslinkability. The organic unsaturated silane compound is preferably a compound having silane crosslinkability. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltris ( Examples of the method for producing the silane-modified ethylene polymer of the present invention include, for example, blending the ethylene polymer, an organic peroxide, and the organic unsaturated silane compound, followed by extrusion. Examples thereof include a method of heating by a machine to decompose an organic peroxide into radicals and graft-modify an organic unsaturated silane compound to an ethylene polymer. Examples of the organic peroxide at this time include dicumyl peroxide, 2,5-dimethyl-2,5-di- (t-butyl-oxy) -hexyne-3, 1,3-bis- (t-butyl). -Oxy-isopropyl) -benzene, t-butylcumyl peroxide, 4,4, -di- (t-butylperoxy) valeric acid-butyl ester, 1,1-di- (tert-butylperoxy) -3 , 3,5-trimethylcyclohexanexin-3, benzoyl peroxide, dicyclobenzoperoxide, di-t-butyl peroxide, lauroyl peroxide, di-t-butylperoxyisophthalate, double bond group in the molecule And a compound having a peroxide group. Dicumyl peroxide is particularly economical and preferred.

  In addition, when graft modification is performed, the graft modification efficiency is excellent, and the problem of organic peroxide odor generation hardly occurs. Therefore, the organic peroxide is 0.005 to 100 parts by weight of the ethylene polymer. It is preferable to use 5 parts by weight, particularly preferably 0.007 to 1 part by weight, more preferably 0.01 to 0.5 part by weight. Further, since a silane-modified ethylene polymer having excellent crosslinking efficiency can be efficiently produced, it is preferable to use 0.1 to 10 parts by weight of an organic unsaturated silane compound with respect to 100 parts by weight of the ethylene polymer. The amount is preferably 0.3 to 5 parts by weight, more preferably 0.5 to 4 parts by weight.

  The silane-modified ethylene polymer of the present invention has crosslinkability because it has a silane group, and it is possible to improve heat deformation resistance and mechanical properties by performing crosslinking, particularly as a pipe. Goodness is excellent.

  As a method for crosslinking the silane-modified ethylene-based ethylene polymer of the present invention, for example, a silanol condensation catalyst is blended with the silane-modified ethylene-based polymer, and the water is at room temperature to about 130 ° C, preferably at room temperature to 100 ° C. In contact with moisture in water vapor or in a humid atmosphere for about 1 minute to 1 week, preferably about 10 minutes to 1 day. Examples of the silanol condensation catalyst include dibutyltin dilaurate, stannous acetate, stannous caprylate, tin naphthenate, zinc caprylate, iron 2-ethylhexanoate, cobalt naphthenate, tetrabutyl ester titanate, and ethylamine. And dibutylamine, especially dibutyltin dilaurate, dibutyltin diacetate, and dibutyl octate.

  The pipe formed by crosslinking the silane-modified ethylene polymer of the present invention is excellent in heat distortion resistance and mechanical properties. Examples of the method for producing the pipe include ethylene polymers and organic peroxides. A product, an organounsaturated silane compound, a silanol condensation catalyst, melt-mixed with an extruder, and then formed into a pipe, and the resulting pipe is crosslinked in the presence of hot water, hot water or steam to form a pipe; ethylene Extruded a polymer, organic peroxide, and organic unsaturated silane compound once to obtain a silane-modified ethylene polymer, and a silanol condensation catalyst was added to the silane-modified ethylene polymer to form a pipe. , A method in which hot water or steam is cross-linked in the presence to form a pipe; a pipe is formed with a silane-modified ethylene polymer, and hot water, hot water or steam containing a silanol condensation catalyst is used. Examples include the method of exposing and cross-linking pipes in the presence to make pipes that are particularly excellent in quality. Among them, ethylene polymers, organic peroxides, and organic unsaturated silane compounds are extruded once. This is a method of forming a silane-modified ethylene-based polymer, adding a silanol condensation catalyst to the silane-modified ethylene-based polymer and forming a pipe, and then crosslinking the resulting pipe in the presence of hot water, hot water or steam to form a pipe. It is preferable.

  In addition, when a pipe is used, a pipe in which cross-linking is efficiently generated is obtained. Therefore, 0.001 to 10 parts by weight of a silanol condensation catalyst is used with respect to 100 parts by weight of a silane-modified ethylene polymer. Is preferred.

  The pipe obtained by the present invention preferably has a gel fraction of 65% by weight or more. The gel fraction has a high value when the organic unsaturated silane compound is uniformly grafted in the ethylene polymer and the silane group is uniformly crosslinked by a silanol condensation catalyst. Empirically, silane cross-linked pipes with a high gel fraction are known to have excellent mechanical strength such as short-term and long-term hot internal pressure creep. To obtain a high gel fraction in conventional ethylene-based polymers Needs to use a large amount of an organic unsaturated silane compound. Moreover, conventionally, even if a high gel fraction is achieved in a silane crosslinked pipe using an ethylene-based polymer, the hot internal pressure creep property is not satisfactory. On the other hand, the pipe obtained by the present invention can obtain a high gel fraction even if the grafting rate of the graft-modified ethylene polymer by the organic unsaturated silane compound is low, and can achieve sufficient mechanical properties.

  The gel fraction in the present invention is obtained by cutting 10 g of the pipe after crosslinking, extracting with a Soxhlet extractor using a xylene solvent as a solvent, measuring the remaining amount of extraction, and calculating by the following formula. .

Gel fraction (%) = (remaining extraction amount (g) / 10 (g)) × 100
In the silane-modified ethylene polymer and pipe of the present invention, a known phenol stabilizer, organic phosphite stabilizer, organic thioether stabilizer, stabilizer such as metal salt of higher fatty acid, pigment, weathering agent, Additives added to polyolefins such as dyes, nucleating agents, lubricants such as calcium stearate, inorganic fillers such as carbon black, talc, and glass fiber, reinforcing materials, flame retardants, neutron blocking agents, and the like. It is possible to add in the range which is not. In the pipe, an adsorbent such as activated carbon may be added in order to suppress elution of the unreacted organic unsaturated silane compound, silanol condensation catalyst, and organic peroxide from the pipe.

  Examples of the phenol-based stabilizer include 2,6-di-t-butyl-4-methylphenol, 2,6-di-cyclohexyl-4-methylphenol, 2,6-diisopropyl-4-ethylphenol, 2,6 -Di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol, 2,6-dicyclohexyl 4-n-octylphenol, 2-isopropyl-4-methyl-6 -T-butylphenol, 2-t-butyl-2-ethyl-6-t-octylphenol, 2-isobutyl-4-ethyl-6-t-hexylphenol, 2-cyclohexyl-4-n-butyl-6-isopropylphenol Tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrocinnamate) methane, 2,2, -methyl Bis (4-methyl-6-tert-butylphenol), 4,4, -butylidenebis (3-methyl-6-tert-butylphenol), 4,4, -thiobis (3-methyl-6-tert-butylphenol), 2 , 2, -thiobis (4-methyl-6-tert-butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxyphenyl) benzylbenzene 1,3,5-tris (2-methyl-4-hydroxy-5-tert-butylphenol) methane, tetrakis (methylene (3,5-di-butyl-4-hydroxyphenyl) propionate) methane, β- (3 , 5-Di-t-butyl-4-hydroxylphenol) propionic acid alkyl ester, 2,2, -oxamide bis (ethyl-3- (3,5-di-t-) Til-4-hydroxyphenyl) propionate, tetrakis (methylene (2,4-di-t-butyl-4-hydroxyl) propionate), n-octadecyl-3- (4, -hydroxy-3,5-di-t- Butylphenyl) propionate, 2,6-di-tert-butyl-p-cresol, 2,4,6-tris (3,5, di-tert-butyl-4, -hydroxybenzylthiono-1,3,5-triazine, 2, 2, -methylenebis (4-methyl-6-tert-butylphenol), 4,4-methylenebis (2,6-di-tert-butylphenol), 2,2-methylenebis (6- (1-methylcyclohexyl) -p- Cresol), bis (3,5-bis (4-hydroxy-3-tert-butylphenyl) butyric acid) glycol ester, 4,4-buty Redenbis (6-t-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-tris (2,6- Dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1 , 3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanate, 1,3,5-tris ((3,5-di-t-butyl-4-hydroxyphenyl) propionyl Oxyethyl) isocyanurate, 2-octylthio-4,6-di (4-hydroxy-3,5-di-t-butyl) phenoxy-1,3,5-triazine, 4,4, -thiobis (6-t -Butyl- - cresol), and the like.

  Examples of organic phosphite stabilizers include trioctyl phosphite, trilauryl phosphite, tridecyl phosphite, octyl diphosphite, tris (2,4-di-t-butylphenyl) phosphite, triphenyl phosphite. , Tris (butoxyethyl) phosphite, tris (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, tetra (tridecyl) -1,1,3-tris (2-methyl-5-tert-butyl-4- Hydroxyphenyl) butanediphosphite, tetra (tridecyl) -4,4, -butylidenebis (3-methyl-6-tert-butylphenol) diphosphite, tris (3,5-di-tert-butyl-4-hydroxyphenyl) phos Fight, Tris (mono or dinonylphenyl) Phosphite, hydrogenated-4,4,4-isopropylidenediphenol polyphosphide, bis (octylphenyl) bis (4,4, -butylidenebis (3-methyl-6-tert-butylphenol)) 1,6-hexaneol Diphosphide, phenyl-4,4, -isopropylidene diphenol pentaerythritol diphosphide, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphide, bis (2,6-di-t- Butyl-4methylphenyl) pentaerythritol diphosphide, tri ((4,4, -isopropylidenebis (2-t-butylphenol)) phosphide, di (nonylphenyl) pentaerythritol diphosphide, tris (1,3- Di-stearoyloxyisopropyl) phosphite, 4,4 -Isopropylidenebis (2-t-butylphenol) di (nonylphenyl) phosphide, 9,10-di-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, tetrakis (2,4-di-) t-butylphenyl) -4,4, -biphenylene diphosphide and the like.

  Examples of the organic thioether-based stabilizer include dialkylthiopropionates such as dilauryl-, dimyristyl-, and distearyl- and polyhydric alcohols of alkylthiopropionic acid such as butyl-, octyl-, lauryl-, stearyl-, and the like. , Esters of trimethylolethane, trimethylolpropane, pentaerythritol, trishydroxyethyl isocyanurate) (for example, pentaerythritol tetralauryl thiopropionate). More specifically, dilauryl thiopropionate, dimyristyl thiopropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, distearyl thiodibutyrate and the like can be mentioned.

  Examples of higher fatty acid metal salts include stearic acid, oleic acid, lauric acid, caprylic acid, arachidic acid, palmitic acid, behenic acid, and other alkaline earth metal salts such as magnesium, calcium, and barium salts, and cadmium. Salts, zinc salts, lead salts, sodium salts, potassium salts, lithium salts and the like are used. Magnesium stearate, magnesium laurate, magnesium palmitate, calcium stearate calcium oleate, barium stearate, barium laurate, barium laurate, magnesium, zinc stearate, zinc calcium oleate, zinc stearate, zinc laurate, Examples thereof include lithium stearate, sodium stearate, sodium palmitate, sodium laurate, potassium stearate, potassium laurate, and calcium 12-hydroxystearate.

  The silane-modified ethylene polymer of the present invention is a silane-modified copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms, and the density and melt flow rate are in a specific range, In addition, the relationship between the melt tension measured at 160 ° C. and the melt tension measured at 190 ° C., the activation energy of flow, and the molecular weight distribution are in a specific relationship, so that extrudability, shape retention, and pressure-resistant creep characteristics are excellent. . Since the cross-linked pipe of the present invention is a cross-linked product of the above-mentioned molded product composed of the silane-modified ethylene polymer, it is excellent in both thermal stability and pressure-resistant creep characteristics. For this reason, hot water supply, water supply, floor heating and road heat are used. It can be suitably used as a bridging pipe for tinging.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, commercially available reagents were used.

  Preparation of the clay mineral [component (j)] treated with the organic compound, preparation of the ethylene polymer production catalyst, production of the ethylene polymer and solvent purification were all carried out in an inert gas atmosphere. Preparation of clay mineral [component (j)] treated with an organic compound, preparation of an ethylene polymer production catalyst, solvent used for the production of the ethylene polymer, etc. are all purified, dried and removed in advance by known methods. What used oxygen was used. Components (a) and (b) were synthesized and identified by known methods. A hexane solution (0.714M) of triisobutylaluminum manufactured by Tosoh Finechem Co., Ltd. was used.

  Furthermore, various physical properties of the ethylene-based polymer in the examples were measured by the following methods.

-Measurement of molecular weight and molecular weight distribution-
The weight average molecular weight (M _w ), the number average molecular weight (M _n ), and the ratio of the weight average molecular weight to the number average molecular weight (M _w / M _n ) were measured by gel permeation chromatography (GPC). Tosoh Co., Ltd. HLC-8121GPC / HT is used as the GPC apparatus, Tosoh Co., Ltd. TSKgel GMHhr-H (20) HT is used as the column, the column temperature is set to 140 ° C., and 1 is used as the eluent. Measurement was performed using 2,4-trichlorobenzene. A measurement sample was prepared at a concentration of 1.0 mg / ml, and 0.3 ml was injected and measured. The calibration curve of molecular weight is calibrated using a polystyrene sample having a known molecular weight. In addition, _Mw and _Mn were calculated | required as a value of linear polyethylene conversion.

~ Measurement of density ~
The density (d) was measured by a density gradient tube method in accordance with JIS K6760 (1995).

The number of terminal vinyls is 4000 cm ⁻¹ to 400 cm of a film prepared by hot-pressing an ethylene polymer using a SPECTRUM ONE Fourier transform infrared spectrophotometer (FT-IR) manufactured by Perkin Elmer, and then cooling with ice. It measured in the range of ^-1 and computed using the following formula.

-Measurement of the number of terminal vinyl-
Number of terminal vinyls per 1000 carbon atoms (pieces / 1000 C) = a × A / L / d
In the formula, a represents an absorptivity coefficient, A represents an absorbance of 909 cm ⁻¹ attributed to terminal vinyl, L represents a film thickness, and d represents a density. In addition, a was calculated | required from the analytical curve created using the sample which confirmed the number of terminal vinyls per 1000 carbon atoms from < ¹ > H-NMR measurement. ¹ H-NMR measurement was performed at 130 ° C. in a mixed solvent of deuterated benzene and o-dichlorobenzene using GSX400 manufactured by JEOL. The number of terminal vinyls per 1000 carbon atoms was calculated from the integral ratio of the peak attributed to methylene and the peak attributed to terminal vinyl. With respect to each peak, tetramethylsilane was used as a standard (0 ppm), and a peak with a chemical shift of 1.3 ppm was attributed to methylene, and a peak with 4.8 to 5.0 ppm was attributed to terminal vinyl.

The ethylene polymer used for the measurement of melt tension (MS ₁₆₀ , MS ₁₉₀ ) and flow activation energy (E _a ) is Irganox 1010 ^™ (manufactured by Ciba Specialty Chemicals) 500 ppm, Irgaphos 168 ^™ (manufactured by Ciba Specialty Chemicals Co., Ltd.) 1,500 ppm was added, and an internal mixer (manufactured by Toyo Seiki Co., Ltd., trade name: Labo Plast Mill) was used at 190 ° C. under a nitrogen stream. , And kneaded for 30 minutes at a rotation speed of 30 rpm.

~ Calculation of flow activation energy ~
The activation energy (E _a ) of the flow was determined by using a disk-disk rheometer (trade name: MCR-300, manufactured by Anton Paar Co., Ltd.) at each of 150 ° C., 170 ° C., and 190 ° C. at an angular velocity of 0.1. The shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ in the range of ˜100 rad / s were determined, and the shift factor of the horizontal axis at a reference temperature of 150 ° C. was determined and calculated according to the Arrhenius equation.

~ Measurement of melt tension ~
Melt tension was adjusted so that the inflow angle was 90 ° on a capillary viscometer with a barrel diameter of 9.55 mm (Toyo Seiki Seisakusho Co., Ltd., trade name: Capillograph) and a dice with a length of 8 mm and a diameter of 2.095 mm. Wearing and measuring. In MS ₁₆₀ , the temperature was set to 160 ° C., the piston lowering speed was set to 10 mm / min, the stretch ratio was set to 47, and the load (mN) required for take-up was MS ₁₆₀ . When the maximum draw ratio was less than 47, the load (mN) required for taking up at the highest draw ratio that did not break was MS ₁₆₀ . The load (mN) measured by the same method with the temperature set at 190 ° C. was designated as MS ₁₉₀ .

~ Evaluation of thermal stability ~
The thermal stability of the ethylene polymer is as follows. The ethylene polymer was added with no heat stabilizer, and an internal mixer (trade name: Labo Plast Mill, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used under a nitrogen stream. Evaluation was made by calculating the yellowing degree (ΔYI) by the method described in JIS K 7105 by leaving the pelletized material after kneading at 30 ° C. and 30 rpm for 30 minutes and leaving it in an oven set at 120 ° C. for 96 hours. did. ΔYI is the amount of change in yellowness determined by the following formula. The smaller the ΔYI, the better the thermal stability.

ΔYI = YI−YI ₀
(Wherein, YI is the yellowness after heat treatment in an oven, YI ₀ is the yellowness before heating in an oven.)
~ Gel fraction ~
10 g of a silane cross-linked pipe is cut, extracted with a Soxhlet extractor using a xylene solvent for 10 hours, the remaining amount of extraction is measured, and the following formula is obtained.

Gel fraction (%) = (remaining extraction amount (g) / 10 (g)) × 100
~ 95 ° C hot internal pressure creep ~
A circumferential stress of 5.5 MPa was applied to the silane crosslinked pipe in warm water of 95 ° C., and the time until cracking and leakage occurred was evaluated.

~ Odor ~
Appearance was evaluated using a silane cross-linked pipe, and the odor of water after the silane cross-linked pipe was immersed in 50 ° C. warm water for 24 hours was evaluated (good, good, bad).

Example 1
[Preparation of ethylene polymer production catalyst]
63 mg (160 μmol) of 1,1,3,3-tetramethyldisiloxane-1,3-diylbis (cyclopentadienyl) zirconium dichloride (component (a)) was suspended in 17.6 mL of hexane, and triisobutylaluminum ( 22.4 mL of a hexane solution (0.714M) of component (c)) was added to obtain a contact product of component (a) and component (c). 4.0 g of the modified hectorite (component (l)) prepared in Example 1 [Preparation of clay mineral {component (j)} treated with an organic compound]) was added to this contact product, and the mixture was heated at 60 ° C. for 3 hours. After stirring, the solution was left to stand to remove the supernatant, and washed with a hexane solution (0.03M) of triisobutylaluminum. Further, a hexane solution (0.15 M) of triisobutylaluminum was added to form a catalyst slurry (100 g / L).

In the catalyst slurry prepared above, 5 mol% of diphenylmethylene (1-cyclopentadienyl) with respect to 1,1,3,3-tetramethyldisiloxane-1,3-diylbis (cyclopentadienyl) zirconium dichloride. 5.6 mg (8.4 μmol) of (2,7-di-tert-butyl-9-fluorenyl) zirconium dichloride (component (b)), 6.7 mL of hexane, and a hexane solution of triisobutylaluminum (0.714 M) A solution consisting of 18 mL was added and stirred at room temperature for 6 hours. Let stand and remove the supernatant, wash with hexane solution of triisobutylaluminum (0.03M), add hexane solution of triisobutylaluminum (0.15M) and finally add 100g / L catalyst slurry. Obtained.
[Production of ethylene polymer]
30 L of hexane and 25.0 mL of a hexane solution (0.714M) of triisobutylaluminum were introduced into a 50 L autoclave, and the internal temperature of the autoclave was raised to 85 ° C. To this autoclave, 1.875 mL of the catalyst slurry was added, and an ethylene / hydrogen mixed gas (hydrogen: containing 700 ppm) was introduced until the partial pressure reached 1.2 MPa to initiate polymerization. During the polymerization, an ethylene / hydrogen mixed gas was continuously introduced so that the partial pressure was maintained at 1.2 MPa. The polymerization temperature was controlled at 85 ° C. After 90 minutes from the start of the polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 2,250 g of polymer was obtained. Table 1 shows the density, MFR, terminal vinyl number, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , E _a , and ΔYI of the obtained ethylene polymer.

  The obtained ethylene copolymer powder was mixed with the amount of vinyltrimethoxysilane and the amount of dicumyl peroxide described in Table 1 and extruded using a single screw extruder at an extrusion temperature of 200 ° C. 0.01 parts by weight of dioctyltin dilaurate and 0.4 parts by weight of Irganox 1010 (trade name) are mixed with 100 parts by weight of the resulting pellet, and a pipe molding machine (resin temperature 200 ° C., L / D22, compression) A pipe having a nominal diameter of 13 was formed using a ratio of 3.0).

  This pipe was immersed in 90 ° C. hot water for 9 hours to crosslink to form a silane crosslinked pipe of the present invention. The resulting silane crosslinked pipe had a high gel fraction and excellent mechanical properties. Moreover, the appearance and smell of the silane cross-linked pipe were satisfactory. The evaluation results of the pipe are shown in Table 2.

Example 2
[Production of ethylene polymer]
30 L of hexane and 25.0 mL of a hexane solution (0.714M) of triisobutylaluminum were introduced into a 50 L autoclave, and the internal temperature of the autoclave was raised to 85 ° C. To this autoclave, 1.875 mL of the catalyst slurry was added, and an ethylene / hydrogen mixed gas (hydrogen: 1000 ppm included) was introduced until the partial pressure reached 1.2 MPa to initiate polymerization. During the polymerization, an ethylene / hydrogen mixed gas was continuously introduced so that the partial pressure was maintained at 1.2 MPa. The polymerization temperature was controlled at 85 ° C. After 90 minutes from the start of the polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 2,250 g of polymer was obtained. Table 1 shows the density, MFR, terminal vinyl number, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , E _a , and ΔYI of the obtained ethylene polymer.

  Using the obtained ethylene polymer, the same operation as in Example 1 was performed to obtain a silane cross-linked pipe. The resulting silane cross-linked pipe had a high gel fraction and excellent mechanical strength. Moreover, the appearance and smell of the silane cross-linked pipe were satisfactory.

Example 3
[Preparation of ethylene-based copolymer production catalyst]
10 mol% of isopropylidene (1-cyclopentadienyl) (2,7-di-tert) with respect to 1,1,3,3-tetramethyldisiloxane-1,3-diylbis (cyclopentadienyl) zirconium dichloride -A solution consisting of 9.7 mg (17.8 μmol) of butyl-9-fluorenyl) zirconium dichloride (component (b)), 5.4 mL of hexane, and 2.5 mL of a hexane solution of triisobutylaluminum (0.714 M) was added. Except for the above, preparation was carried out in the same manner as in Example 3 [Preparation of ethylene polymer production catalyst].
[Production of ethylene copolymer]
30 L of hexane and 25.0 mL of a hexane solution (0.714M) of triisobutylaluminum were introduced into a 50 L autoclave, and the internal temperature of the autoclave was raised to 85 ° C. To this autoclave, 1.875 mL of the catalyst slurry was added, and an ethylene / hydrogen mixed gas (hydrogen: containing 2500 ppm) was introduced until the partial pressure reached 1.2 MPa to initiate polymerization. During the polymerization, an ethylene / hydrogen mixed gas was continuously introduced so that the partial pressure was maintained at 1.2 MPa. The polymerization temperature was controlled at 85 ° C. After 90 minutes from the start of the polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 2,275 g of polymer was obtained. Table 1 shows the density, MFR, terminal vinyl number, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , E _a , and ΔYI of the obtained ethylene polymer.

  Using the obtained ethylene polymer, the same operation as in Example 1 was performed to obtain a silane cross-linked pipe. The resulting silane cross-linked pipe had a high gel fraction and excellent mechanical strength. In addition, the appearance and smell of the silane cross-linked pipe were satisfactory.

Comparative Example 1
[Production of ethylene polymer]
30 L of hexane and 2.0 mL of a hexane solution of triisobutylaluminum (0.714 M) were introduced into a 50 L autoclave, and the internal temperature of the autoclave was raised to 90 ° C. To this autoclave, 1812.5 mg of Ineosilicas Cr catalyst (EP350) was added, hydrogen gas was introduced until the partial pressure reached 1.0 MPa, and ethylene gas was introduced until the partial pressure reached 1.0 MPa. Polymerization was started. During the polymerization, ethylene gas was continuously introduced so that the ethylene partial pressure was maintained. The polymerization temperature was controlled at 90 ° C. After 90 minutes from the start of the polymerization, the internal pressure of the autoclave was released, and the contents were suction filtered. After drying, 3575 g of polymer was obtained. Table 1 shows the density, MFR, terminal vinyl number, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , E _a , and ΔYI of the obtained ethylene polymer. As a result of evaluating the ΔYI of the ethylene polymer, the number of terminal vinyls per 1,000 carbon atoms exceeded 0.2, and it was confirmed that the ethylene polymer was inferior in thermal stability.

  Using the obtained ethylene polymer, the same operation as in Example 1 was performed to obtain a silane cross-linked pipe. The obtained silane cross-linked pipe had a high gel fraction, but was inferior in product appearance (surface skin) and hot internal pressure creep characteristics.

Comparative Example 2
Table 1 shows the density, MFR, number of terminal vinyls, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , and E _a of the metallocene catalyst ethylene / 1-octene copolymer (AF1840) commercially available from Dow Chemical. Show. The present ethylene copolymer deviates from the requirements of the formulas (1) and (3).

  A 100 L drum was molded from the obtained polyethylene using a blow molding machine (manufactured by Nippon Steel Works) having a 115 mmφ extrusion screw, and the moldability and the drop strength were measured.

  Using the obtained ethylene polymer, the same operation as in Example 1 was performed to obtain a silane cross-linked pipe. The obtained silane cross-linked pipe had a high gel fraction, but was inferior in product appearance (surface skin) and hot internal pressure creep characteristics.

Comparative Example 3
Table 1 shows the density, MFR, number of terminal vinyls, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , and E _a of the high-pressure method LDPE (Petrocene 360) commercially available from Tosoh Corporation. The present ethylene polymer deviates from the requirements of the formulas (2) and (3).
Using the obtained ethylene polymer, the same operation as in Example 1 was performed to obtain a silane cross-linked pipe. The obtained silane cross-linked pipe had a high gel fraction, but was inferior in product appearance (surface skin) and hot internal pressure creep characteristics.

Comparative Example 4
Density, MFR, number of terminal vinyls, M _w / M _n , MS ₁₆₀ , MS ₁₉₀ , commercially available high-density polyethylene (RS1000 manufactured by Nippon Polyethylene Co., Ltd., MFR = 0.1 g / 10 min, density 953 kg / m ³ ) the E _a shown in Table 1. Using the obtained ethylene polymer, the same operation as in Example 1 was performed to obtain a silane cross-linked pipe. The obtained silane cross-linked pipe had a high gel fraction, but was inferior in product appearance (surface skin) and hot internal pressure creep characteristics.

Claims (9)

The organic unsaturated silane compound is composed of a repeating unit derived from ethylene, or a repeating unit derived from ethylene and a repeating unit derived from an α-olefin having 3 to 8 carbon atoms, and the following (A) to (F): A silane-modified ethylene polymer obtained by graft-modifying a satisfactory ethylene polymer.
(A) The density (d) measured by the density gradient tube method in accordance with JIS K6760 is 925 kg / m ³ or more and 970 kg / m ³ or less.
(B) The melt flow rate (MFR) measured at 190 ° C. and a 2.16 kg load is 0.3 g / 10 min or more and 10 g / 10 min or less.
(C) The number of terminal vinyls is 0.2 or less per 1000 carbon atoms,
(D) The relationship between the melt tension (MS ₁₆₀ (mN)) measured at 160 ° C. and MFR satisfies the following formula (1).
MS ₁₆₀ > 90-130 × log (MFR) (1)
(E) The relationship between the melt tension (MS ₁₉₀ (mN)) measured at 190 ° C. and MS ₁₆₀ satisfies the following formula (2).
MS ₁₆₀ / MS ₁₉₀ <1.8 (2)
(F) The relationship between the flow activation energy (E _a (kJ / mol)) and the density (d) satisfies the following formula (3).
_{127-0.107d <E a <88-0.060d (3} ) 2. The ethylene polymer according to claim 1, wherein the ethylene polymer further satisfies (G) a weight average molecular weight / number average molecular weight (M _w / M _n ) of 2 or more and 6 or less. The silane-modified ethylene polymer described. The ethylene polymer is an ethylene polymer satisfying (A ') a density (d) measured by a density gradient tube method in accordance with JIS K6760 is 925 kg / m ³ or more and 940 kg / m ³ or less. The silane-modified ethylene polymer according to claim 1 or 2, characterized in that Ethylene polymer 100 consisting of a repeating unit derived from ethylene or consisting of a repeating unit derived from ethylene and a repeating unit derived from an α-olefin having 3 to 8 carbon atoms and satisfying the following (A) to (F) The organic peroxide 0.005 to 5 parts by weight and the organic unsaturated silane compound 0.1 to 10 parts by weight are blended with respect to parts by weight, and the grafting reaction of the organic unsaturated silane compound is performed. Item 4. A method for producing a silane-modified ethylene polymer according to any one of Items 1 to 3.
(A) The density (d) measured by the density gradient tube method in accordance with JIS K6760 is 925 kg / m ³ or more and 970 kg / m ³ or less.
(B) The melt flow rate (MFR) measured at 190 ° C. and a 2.16 kg load is 0.3 g / 10 min or more and 10 g / 10 min or less.
(C) The number of terminal vinyls is 0.2 or less per 1000 carbon atoms,
(D) The relationship between the melt tension (MS ₁₆₀ (mN)) measured at 160 ° C. and MFR satisfies the following formula (1).
MS ₁₆₀ > 90-130 × log (MFR) (1)
(E) The relationship between the melt tension (MS ₁₉₀ (mN)) measured at 190 ° C. and MS ₁₆₀ satisfies the following formula (2).
MS ₁₆₀ / MS ₁₉₀ <1.8 (2)
(F) The relationship between the flow activation energy (E _a (kJ / mol)) and the density (d) satisfies the following formula (3).
_{127-0.107d <E a <88-0.060d (3} ) A pipe formed by crosslinking a pipe made of the silane-modified ethylene polymer according to claim 1. 6. The pipe according to claim 5, wherein the gel fraction is 65% by weight or more. The pipe according to claim 5, wherein the pipe is a water supply pipe, a hot water supply pipe, or a heating pipe. A silane-modified ethylene polymer obtained by blending the silane-modified ethylene polymer according to any one of claims 1 to 3 with a silanol condensation catalyst into a pipe shape, and then at room temperature to 100 ° C in water, in water vapor or in a humid atmosphere. The method for producing a pipe according to claim 5, wherein the crosslinking is performed. The method for producing a pipe according to claim 8, wherein 0.001 to 10 parts by weight of a silanol condensation catalyst is used with respect to 100 parts by weight of the silane-modified ethylene polymer according to any one of claims 1 to 3.