JP7099850B2 - Polyethylene resin composition and its pipe - Google Patents

Description

The present invention relates to a polyethylene-based resin composition and a pipe thereof.

Conventionally, a crosslinked body obtained by cross-linking a polyethylene resin is easy to form and crosslink. For example, a tubular body such as a pipe, a hose and a tube, an insulating coating material used for a conductor such as an electric wire and a cable, various containers, and It is used for various purposes such as sheets. For example, pipes (cross-linked polyethylene pipes) that can be used in the construction field have higher creep characteristics at high temperatures, longer durability, and better workability than vinyl chloride pipes and copper pipes that are also used in the construction field. It is excellent in that it is good, and in recent years, cross-linked polyethylene pipes are being used more and more in the construction field, specifically for water supply / drainage, hot water supply, heating and the like.

Here, as one of the typical methods for producing such a crosslinked polyethylene, a silane compound such as vinylalkoxysilane is melt-kneaded with a polyolefin and graft-polymerized, and then the silane-modified polyethylene is desired. There is known a method of forming a shape and subjecting it to conditions such as exposure to warm water or high-temperature steam to promote cross-linking in the presence of a catalyst to cause cross-linking (see, for example, Patent Documents 1 to 5).

Patent No. 3532106 Japanese Unexamined Patent Publication No. 2011-11497 Japanese Unexamined Patent Publication No. 2007-120764 Japanese Unexamined Patent Publication No. 2010-150299 Japanese Unexamined Patent Publication No. 2012-136596

By the way, the cross-linked polyethylene body (hereinafter, also referred to as silane cross-linked polyethylene) obtained by the above-mentioned conventional technique cannot be said to have sufficient flexibility, for example. Specifically, for example, when silane cross-linked polyethylene is molded into a pipe, for example, when the pipe is bent and used, more specifically, when the pipe is bent and installed for hot water supply or floor heating, workability is achieved. However, it cannot be said that the conventional silane cross-linked polyethylene has sufficient flexibility. Further, since the silane cross-linked polyethylene is used for a long period of time, it has been required to have sufficient durability at the same time.

The present invention has been made in view of the above problems, and is a polyethylene-based resin composition containing silane cross-linked polyethylene having sufficient durability while improving flexibility, and a pipe made of the polyethylene-based resin composition. The purpose is to provide.

As a result of diligent studies to solve the above-mentioned problems, the present invention can solve the above-mentioned problems by preparing a polyethylene-based resin composition having the composition shown below and having specific properties. I found it and came up with the present invention.

That is, the present invention is as follows.
[1]
It contains silane cross-linked polyethylene, at least one phenolic antioxidant, and at least one phosphorus-based antioxidant.
The gel fraction is 30% or more,
A polyethylene-based resin characterized in that the ratio of the total amount of components eluted at 95 ° C. or lower to the total elution amount is 90% or more in the measurement using cross-separation chromatography of xylene-dissolved components in the gel fraction measurement. Composition.
[2]
The polyethylene-based resin composition has an MFR of 0.1 or more and 10 or less, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in GPC measurement is 2.0 or more and 10 or more. The polyethylene-based resin composition according to the above [1], which is produced by using the following ethylene-based polymer.
[3]
The polyethylene-based resin composition according to the above [1] or [2], which contains 5 to 500 ppm of tin element in the polyethylene-based resin composition.
[4]
In any of the above [1] to [3], the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount is 30% or less in the measurement using the cross fractionation chromatography of the xylene-dissolved components. The polyethylene-based resin composition according to the above.
[5]
The polyethylene-based resin composition according to the above [4], wherein the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount is 27% or less in the measurement using the xylene-dissolved component cross fractionation chromatography.
[6]
The above-mentioned [1] to [5], wherein the ratio of the total amount of the components eluted at 95 ° C. or lower to the total elution amount is 93% or more in the measurement using the xylene-dissolving component cross fractionation chromatography. Polyethylene resin composition.
[7]
A pipe made of the polyethylene-based resin composition according to any one of the above [1] to [6].

According to the present invention, it is possible to provide a polyethylene-based resin composition containing silane cross-linked polyethylene having sufficient durability while improving flexibility, and a pipe made of the polyethylene-based resin composition.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in more detail, but the present invention is not limited to this, and various embodiments are made without departing from the gist thereof. It can be transformed.
[Polyethylene-based resin composition]
The polyethylene-based resin composition of the present embodiment contains a silane-crosslinked polyethylene, at least one phenol-based antioxidant, and at least one phosphorus-based antioxidant, and has a gel content of 30% or more. In the measurement using cross-separation chromatography of xylene-dissolved components in gel fraction measurement (hereinafter, "cross-separation chromatography" is also referred to as "CFC"), the total amount of components eluted at 95 ° C or lower with respect to the total elution amount. Is characterized by a ratio of 90% or more. According to the polyethylene-based resin composition of the present embodiment, sufficient durability can be provided while improving flexibility. In addition, in this specification, when it is simply described as "polyethylene resin composition", it refers to the polyethylene resin composition after undergoing the cross-linking step, and the notation "polyethylene resin composition before cross-linking" or ". When described as "before cross-linking" as in "polyethylene-based resin composition (before cross-linking)", it refers to a polyethylene-based resin composition before undergoing a cross-linking step.

Here, the polyethylene-based resin composition of the present embodiment contains silane cross-linked polyethylene having cross-linked via a silane compound, and specifically, the silane cross-linked polyethylene is grafted with the silane compound by a free radical generator. It is obtained by cross-linking the copolymerized polyethylene-based polymer in the presence of a silane condensation catalyst and water.

-Gel fraction-
The polyethylene-based resin composition of the present embodiment has a gel fraction of 30% or more, preferably 50% or more, and more preferably 65% or more. The ethylene-based polymer can be improved in brittleness, mechanical strength and heat resistance by cross-linking with silane, but when the gel content is less than 30%, the ethylene-based polymer is close to non-crosslinking in which the ethylene-based polymer is not sufficiently cross-linked. It shows properties and cannot fully exhibit its performance as a polyethylene-based resin composition (after cross-linking). The gel fraction of the polyethylene-based resin composition can be controlled by the amount of the silanol condensation catalyst charged and the crosslinking time. Specifically, the gel is gelled by increasing the amount of the silanol condensation catalyst and lengthening the crosslinking time. The fraction can be increased.

Here, the gel fraction in the present embodiment is a value measured according to the estimation of the degree of cross-linking by measuring the JIS K 6796-1998 cross-linked polyethylene (PE-X) pipe and the joint-gel content. Specifically, 1.0 g of the polyethylene-based resin composition of the present embodiment is cut and the sample is extracted in a flask using a xylene solvent for 8 hours. Then, the remaining amount of extraction after extraction is measured and calculated by the following formula.
G = (sample mass before extraction) / (sample mass before extraction) × 100
G: Gel fraction

-Measurement using CFC of xylene dissolving component in gel fraction measurement-
The polyethylene-based resin composition of the present embodiment is the total amount of components eluted at 95 ° C. or lower with respect to the total elution amount in the measurement using CFC of the xylene-dissolving component in the gel fraction measurement (hereinafter, also simply referred to as CFC measurement). The ratio of is 90% or more.

Here, the xylene-dissolving component in the gel fraction measurement is a xylene solution obtained by removing the remaining amount of extraction of the polyethylene-based resin composition in the gel fraction measurement, and then precipitated after cooling the solution to 25 ° C. It is a component that can be obtained by filtering and separating the component, and can be said to be a component that is not sufficiently involved in cross-linking in the polyethylene-based resin composition. In the present embodiment, in the CFC measurement, the ratio of the total amount of the components eluted at 95 ° C. or lower to the total elution amount is 90% or more, so that the flexibility of the polyethylene-based resin composition can be improved. Specifically, although the reason is not clear, among the xylene-dissolving components in the polyethylene-based resin composition, the component that elutes above 95 ° C. in the CFC measurement is relatively crystalline and has a relatively high molecular weight. Since it is a highly rigid component, it is presumed that the ratio of the total amount of the components eluted at 95 ° C. or lower in the CFC measurement affects the flexibility of the polyethylene resin composition. In the present embodiment, since the total amount of the components eluted at 95 ° C. or lower in the CFC measurement is within a predetermined range, the components having a relatively high crystallinity and the high molecular weight are reduced, and the polyethylene-based resin composition is prepared. It is presumed that the flexibility can be improved.

In the polyethylene-based resin composition of the present embodiment, in the CFC measurement, the ratio of the total amount of the components eluted at 95 ° C. or lower to the total elution amount is preferably 93% or more, more preferably 95% or more. be. In the present embodiment, in the CFC measurement, the total amount of the components eluted in the predetermined temperature range is the integrated amount of the components eluted in the predetermined range, and is also referred to as the integrated elution amount.

Further, in the polyethylene-based resin composition of the present embodiment, in the CFC measurement, the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount is preferably 30% or less, more preferably 27% or less. Yes, more preferably 25% or less.

In the polyethylene-based resin composition, when the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount is more than 30% in the CFC measurement, a large amount of low molecular weight components are present in the polyethylene-based resin composition. .. Therefore, when a polyethylene-based resin composition is formed into a pipe and used for floor heating, for example, if the pipe is used for a long period of time, low molecular weight substances gradually elute into the warm water in the pipe and the hot water is used. When the viscosity increases or the hot water cools, these low molecular weight components precipitate and adhere to the inside of the pump, which puts a load on the circulating pump. In the polyethylene-based resin composition of the present embodiment, in the CFC measurement, the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount is 30% or less, so that the low molecular weight substance eluted in the warm water in the pipe. Can be reduced, which can contribute to energy saving.

In the measurement using CFC of the xylene-dissolved component in the gel fraction measurement, the ratio of the total amount of components eluted at 80 ° C or lower to the total elution amount and the ratio of the total amount of components eluted at 95 ° C or lower to the total elution amount are Although not particularly limited, it can be controlled by the catalyst used, the slurry concentration when polymerizing the ethylene-based polymer by slurry polymerization, and the cooling method after melt-kneading the polyethylene-based resin composition before cross-linking. Specifically, by using a supported metallocene catalyst during the polymerization of the ethylene polymer, the ratio of the total amount of components eluted at 80 ° C. or lower to the total elution amount is reduced, and at 95 ° C. or lower with respect to the total elution amount. The proportion of the total amount of eluted components can be increased. Further, by lowering the slurry concentration at the time of polymerization of the ethylene polymer, the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount can be reduced. Further, the polyethylene-based resin composition before crosslinking is melt-kneaded and cooled after molding, for example, by gently contacting it with a liquid having a specific heat of 2.0 J / g / ° C or higher and a temperature of 10 ° C or higher and 50 ° C or lower. By doing so, the ratio of the total amount of the components eluted at 95 ° C. or lower to the total elution amount can be increased. The xylene-dissolved component in the gel fraction measurement is a xylene solution obtained by removing the remaining amount of extraction of the polyethylene-based resin composition in the gel fraction measurement, and the component precipitated after cooling the solution to 25 ° C. It can be obtained by filtration separation.

Here, the "cross fractionation chromatography" is a device that combines a temperature-increasing elution fractionation unit (hereinafter, also referred to as "TREF unit") for performing crystalline separation and a GPC unit for performing molecular weight separation, and is a TREF. It is a device capable of analyzing the interrelationship between the composition distribution and the molecular weight distribution by directly connecting the unit and the GPC unit. The measurement in the TREF unit may be referred to as the measurement in the CFC.

The measurement by the TREF unit is performed as follows based on the principle described in "Journal of Applied Polymer Science, Vol 26, 4217-4231 (1981)". The xylene-dissolving component in the polyethylene-based resin composition to be measured is completely dissolved in orthodichlorobenzene. Then, it is cooled at a constant temperature to form a thin polymer layer on the surface of the inert carrier. At this time, the component having high crystallinity is crystallized first, and then the component having low crystallinity is crystallized as the temperature decreases. Next, when the temperature is gradually increased, the components having low crystallinity are eluted in order from the components having high crystallinity, and the concentration of the eluted components at a predetermined temperature can be detected.

The elution amount and the elution integrated amount of the xylene-dissolved component in the polyethylene-based resin composition at each temperature can be obtained by measuring the elution temperature-elution amount curve as follows from the TREF unit. The temperature profile of the column is as follows: First, the column containing the filler is heated to 140 ° C., and a sample solution (for example, concentration: 16 mg / 8 mL) in which the xylene-dissolving component is dissolved in ortodichlorobenzene is introduced and held for 120 minutes. ..

Next, the temperature is lowered to 40 ° C. at a temperature lowering rate of 0.5 ° C./min and then held for 20 minutes to deposit the sample on the surface of the filler. After that, the temperature of the column is sequentially raised at a heating rate of 20 ° C./min. The temperature rises from 40 ° C to 80 ° C at 10 ° C intervals, from 80 ° C to 85 ° C at 5 ° C intervals, from 85 ° C to 90 ° C at 3 ° C intervals, and from 90 ° C to 100 ° C. The temperature is raised at 1 ° C intervals, and from 100 ° C to 120 ° C, the temperature is raised at 10 ° C intervals. After holding the sample at each temperature for 20 minutes, the temperature is raised to detect the concentration of the sample eluted at each temperature. Then, the elution temperature-elution amount curve is measured from the values of the elution amount (mass%) of the sample and the in-column temperature (° C.) at that time, and the elution amount and the elution integral amount at each temperature are obtained. More specifically, it can be measured by the method described in Examples.

-Antioxidant-
The polyethylene-based resin composition of the present embodiment contains, but is not limited to, at least one phenol-based antioxidant and at least one phosphorus-based antioxidant. By containing these antioxidants, deterioration of the resin during processing after molding can be suppressed, and therefore, durability that can withstand long-term use can be sufficiently provided.

The phenolic antioxidant is not particularly limited, but is, for example, dibutylhydroxytoluene, pentaerythyl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3-3. Examples thereof include (3,5-di-t-butyl-4-hydroxyphenyl) propionate.

The content of the phenolic antioxidant is not particularly limited, but is preferably 0.05% by mass or more and 3.0% by mass or less, more preferably 0.1% by mass or more, with respect to the polyethylene-based resin composition. It is 0% by mass or less.
The phenolic antioxidant and the phosphorus-based antioxidant described later can be contained in the polyethylene-based resin composition of the present embodiment by being contained in the polyethylene-based resin composition before crosslinking.

Phosphorus-based antioxidants include tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene-di-phosphonite, tris (2,4-di-t-butylphenyl) phosphite, and rhinoceros. Examples thereof include click neopentane tetraylbis (2,4-t-butylphenylphosphite).

The content of the phosphorus-based antioxidant is not particularly limited, but is preferably 50 ppm or more and 3000 ppm or less, and more preferably 100 ppm or more and 2000 ppm or less with respect to the polyethylene-based resin composition.

-Tin element-
The polyethylene-based resin composition of the present embodiment can contain a tin element, and the content thereof is preferably 5 to 500 mass ppm in the polyethylene-based resin composition. The content of the tin element is more preferably 10 ppm or more and 300 ppm or less, and further preferably 20 ppm or more and 200 ppm or less. If the content of the tin element is less than 5 ppm, cross-linking tends not to proceed sufficiently in the polyethylene-based resin composition, and if it exceeds 500 ppm, in the extruder during extrusion of the polyethylene-based resin composition before cross-linking. The tin element tends to be locally present, and if the tin element is locally present, cross-linking proceeds locally and the appearance is deteriorated.
The tin element can be mainly derived from a silanol condensation catalyst used for obtaining silane cross-linked polyethylene in a polyethylene-based resin composition.

[[Method for manufacturing polyethylene-based resin composition]]
The polyethylene-based resin composition of the present embodiment is obtained before cross-linking with respect to grafted polyethylene, which is a silane-modified ethylene-based polymer, in the presence of a silanol condensation catalyst when or after obtaining the grafted polyethylene. It can be produced by molding the polyethylene-based resin composition of No. 1 and then cross-linking the polyethylene-based resin composition before crosslinking in the presence of water or water vapor.

More specifically, the polyethylene-based resin composition of the present embodiment is formed by melt-kneading a silanol condensation catalyst together with grafted polyethylene, which is a silane-modified ethylene-based polymer, or an ethylene-based polymer and silanol. The master batch obtained by melt-kneading the condensation catalyst is melt-kneaded and molded (polyethylene-based resin composition before cross-linking), and then the molded product (polyethylene-based resin composition before cross-linking) is watered (preferably). It can be manufactured by exposing it to hot water) or water vapor. By exposing the molded body (polyethylene resin composition before cross-linking) to water (preferably warm water) or water vapor, the silyl groups of the entire molded body are cross-linked to obtain a polyethylene resin composition (after cross-linking) containing silane cross-linked polyethylene. Obtainable.

The melt-kneading for obtaining the polyethylene-based resin composition before crosslinking is not particularly limited and can be carried out by a known method. For example, the resin temperature during melt-kneading is 170 ° C to 240 ° C. be able to.

The polyethylene-based resin composition before cross-linking can contain various additives including the above-mentioned phenol-based antioxidant and phosphorus-based antioxidant, and the various additives are used when obtaining grafted polyethylene. It is contained in, or when an ethylene polymer and a silanol condensation catalyst are melt-kneaded to obtain a master batch, or a grafted polyethylene and a silanol condensation catalyst are melt-kneaded or a grafted polyethylene and a master batch are melt-kneaded. It can be contained when obtaining a polyethylene-based resin composition before cross-linking. Among various additives, phenol-based antioxidants and phosphorus-based antioxidants are preferably not contained when obtaining grafted polyethylene, and more specifically, an ethylene-based polymer and a silanol condensation catalyst are kneaded. It is contained when obtaining a masterbatch, or when melt-kneading a grafted polyethylene and a silanol condensation catalyst or melt-kneading a grafted polyethylene and a masterbatch to obtain a polyethylene-based resin composition before cross-linking. It is preferable to let it.

The above-mentioned grafted polyethylene contains an ethylene-based polymer, an organic peroxide of 0.01 parts by mass or more and 5.0 parts by mass or less, and 0.1 parts by mass or more with respect to 100 parts by mass of the ethylene-based polymer. By melt-kneading an organic unsaturated silane compound of 20 parts by mass or less with an extruder, the organic peroxide is decomposed into radicals, and the organic unsaturated silane compound can be grafted onto an ethylene polymer to produce the product. ..

The organic peroxide is not particularly limited, but for example, dicumyl peroxide, 2,5-dimethyl-2,5-di- (t-butyl-oxy) -hexin-3, 1,3-bis- ( t-butyl-oxy-isopropyl) -benzene, t-butylcumyl peroxide, 4,4, -di- (t-butylperoxy) valeric acid-butyl ester, 1,1-di- (t-butylperoxy) ) -3,3,5-trimethylcyclohexanexin-3, benzoyl peroxide, dicyclobenzo peroxide, di-t-butyl peroxide, lauroyl peroxide, di-t-butylperoxyisophthalate, and in the molecule. Examples thereof include compounds having a double bond group and a peroxide group. Among these, dicumyl peroxide is economical and preferable.

The organic unsaturated silane compound is not limited as long as it can be silane crosslinked, and is, for example, vinyltrimethixylsilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, vinylmethyldimethoxysilane, and vinyltris. Examples include (β-methoxyethoxy) silane. Such an organic unsaturated silane compound can react with radicals in an ethylene-based polymer generated by the action of an organic peroxide and graft to the ethylene-based polymer.

The ethylene-based polymer is not particularly limited, but is preferably a copolymer of ethylene and an α-olefin copolymerizable with ethylene. The α-olefin is not particularly limited, and examples thereof include α-olefins having 3 to 20 carbon atoms. The α-olefin can be represented by H ₂ C = CHR, in which R is a linear or branched aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group, or an aromatic group. Indicates a hydrocarbon group.

Specific examples of the α-olefin include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-. Examples include tridecene and 1-tetradecene. Further, further specific examples of the α-olefin include, but are not limited to, vinylcyclohexane, styrene and derivatives thereof. Further, the α-olefin may have a non-conjugated unsaturated bond, and the α-olefin is not particularly limited, but for example, a non-conjugated polyene such as 1,5-hexadiene or 1,7-octadien can be used. It can also be used.

The α-olefin is not particularly limited, but propylene and 1-butene are preferable from the viewpoint of increasing the amount of tertiary carbon that the organic unsaturated silane compound as a cross-linking agent easily reacts with. Moreover, the above-mentioned copolymer may be a ternary random polymer. As the comonomer contained in the copolymer, one type may be used alone, or two or more types may be used in combination.

The ethylene polymer preferably has an MFR of 0.1 g / 10 min or more and 10.0 g / 10 min or less, more preferably 0.5 g / 10 min or more and 5.0 g / 10 min or less, and further preferably 3. It is 0 g / 10 min or more and 5.0 g / 10 min or less. When the MFR of the ethylene polymer is 0.1 g / 10 min or more, the moldability is excellent and the surface of the molded product becomes smooth. In addition, since the resin pressure during melt molding and the heat generation of the share can be reduced, deterioration of the resin during molding can be suppressed, and decomposition of the resin is less likely to occur in the extruder, so that smoke is generated during processing. It is less likely to occur. On the other hand, when the MFR is 10.0 g / 10 min or less, the molded product has excellent durability.

The MFR of the ethylene-based polymer can be controlled by the temperature at the time of polymerization, the amount of hydrogen added, and the like. Specifically, the MFR of the ethylene polymer can be controlled to be increased by increasing the temperature at the time of polymerization or increasing the amount of hydrogenation. Further, the above MFR can be measured by the method described in Examples.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in the GPC measurement of the ethylene polymer is preferably 3.0 or more and 10.0 or less. It is more preferably 3.0 or more and 7.0 or less, and further preferably 3.0 or more and 4.0 or less. When Mw / Mn is 3.0 or more and 10.0 or less, the moldability at the time of melt molding is excellent. The molecular weight distribution of the ethylene-based polymer can be controlled by the catalyst used at the time of production, the residence time in the reactor at the time of polymerization, and the like. In addition, the molecular weight distribution can be measured by the method described in Examples.

In the polyethylene-based resin composition before cross-linking, the content of the silanol condensation catalyst is preferably 50% by mass or more and 1000% by mass or less, more preferably 100% by mass or more and 700 with respect to 100 parts by mass of the ethylene-based polymer. The mass is ppm or less, and more preferably 100 mass ppm or more and 500 mass ppm or less. By setting the content of the silanol condensation catalyst to 50% by mass or more, the crosslinking reaction can be sufficiently advanced, and by setting the content to 1000% by mass or less, the polyethylene-based resin composition before crosslinking can be extruded. It is possible to prevent the catalyst from being locally present in the extruder. If the catalyst is locally present, cross-linking proceeds locally and the appearance deteriorates.

The silanol condensation catalyst is not particularly limited, but is limited to dibutyltin dilaurate, dibutyltin dioctate, dibutyltin acetate, dibutyltin diacetate, dibutyltin malee, dibutyltin phthalate, and dibutyltin bis (2-ethylhexanoe). ), Dibutyl tin bis (one lidecyl malee), dibutyl tin bis (one benzyl malee), dibutyl tin dimethoxide, dibutyl tin bis (nonylphenoxide), dibutyl tin oxide, dibutyl tin bis (acetyl acetylnate), dibutyl tin Bis (ethyl acetylate), reaction product of dibutyl tin oxide and silicate compound, reaction product of dibutyl tin oxide and phthalate ester, tributyl tin dilaurate (TBTDL), dioctyl tin diacetate, dioctyl tin dilaurate, Dioctyl tin-bis (isooctyl maleate), dioctyl tin-bis (isooctyl thioglycolate), dioctyl tin maleate, dioctyl tin bis (ethyl malee), dioctyl tin dineodecanoate, dioctyl tin oxide, acetic acid Tin, stannous octanoate, tin naphthenate, tin stearate (II), tin (II) octate, tin dineodecanoate, stannous cabrylate, tin bisneodecanoate, tin bis (2-ethylhexanoic acid) , Tin (II) 2,4 pentanionate, acetylacetonate tin (II) and the like, with dioctyl tin dilaurate being particularly preferred.

In addition to the above, the polyethylene-based resin composition before cross-linking includes known organic thioether-based stabilizers, stabilizers such as metal salts of higher fatty acids: pigments, weather-resistant agents, dyes, nucleating agents, and lubricants such as calcium stearate; Inorganic fillers such as carbon black, talc, and glass fiber, or compounding agents added to polyolefins such as reinforcing materials, flame retardants, and neutron blocking agents can be added within a range that does not impair the object of the present invention. Further, an adsorbent such as activated carbon may be added in order to suppress the elution of unreacted organic unsaturated silane compound, silanol condensation catalyst, and organic peroxide from the polyethylene resin composition (molded body after cross-linking). ..

The polyethylene-based resin composition before crosslinking preferably contains at least 90% by mass of the ethylene-based polymer in the polyethylene-based resin composition before crosslinking, more preferably at least 92% by mass, and more preferably. At least 94% by weight. The upper limit of the content of the ethylene-based polymer in the polyethylene-based resin composition before crosslinking is less than 100% by mass, but the polyethylene-based polymer before crosslinking depends on the physical characteristics required for the polyethylene-based resin composition after crosslinking. The content of the above-mentioned antioxidant, catalyst, etc. contained in the resin composition varies, and the upper limit thereof also differs accordingly. The content of the ethylene polymer in the polyethylene resin composition before cross-linking means the content of the component derived from the ethylene polymer in the polyethylene resin composition after cross-linking.

[[[Method for producing ethylene polymer]]]
The method for producing an ethylene-based polymer includes a polymerization step of polymerizing at least ethylene and the above-mentioned α-olefin in the presence of a metallocene catalyst or a Ziegler-Natta catalyst. When a metallocene catalyst is used as the catalyst, a supported metallocene catalyst obtained from at least a carrier substance, an organic aluminum compound, a borate compound having active hydrogen, a cyclopentadiene compound, and a transition metal compound of Group IV of the periodic table, and a liquid. In the presence of a co-catalyst, at least ethylene and the above-mentioned α-olefin can be polymerized to produce an ethylene-based polymer.

When the above-mentioned supported metallocene catalyst is used as the catalyst used in the method for producing an ethylene polymer, other metallocene catalysts, Ziegler-Natta catalysts, Phillips catalysts and the like can also be used. By using the supported metallocene catalyst, the amount of low molecular weight components in the ethylene polymer can be reduced. The metallocene catalyst is not particularly limited, but for example, those described in JP-A-2006-273977 can be preferably used.

The supported metallocene catalyst can be prepared from at least a carrier substance, an organic aluminum compound, a borate compound having active hydrogen, a cyclopentadiene compound, and a transition metal compound of Group IV of the Periodic Table.

The average particle size of the carrier substance is preferably 1.0 μm or more and 20 μm or less, more preferably 1.0 μm or more and 15 μm or less, and further preferably 2.0 μm or more and 10 μm or less. When the average particle size is 1.0 μm or more, the obtained polymer particles tend to be suppressed from scattering and adhering. Further, when the average particle size is 20 μm or less, the carrier substance remaining in the ethylene-based polymer tends to suppress the deterioration of the smoothness of the surface of the crosslinked product. Further, when polyethylene is extruded, the carrier substance remaining in the polyethylene tends to be clogged in the filter of the extruder to increase the pressure and suppress the deterioration of the smoothness of the surface of the crosslinked body. The particle size distribution of the carrier substance is preferably as narrow as possible, and the particle size distribution can be adjusted by removing fine powder particles and coarse powder particles by sieving, centrifugation, or cyclone.

The compressive strength of the carrier substance is preferably 1.0 MPa or more and less than 10 MPa, more preferably 1.0 MPa or more and less than 8.0 MPa, and further preferably 2.0 MPa or more and less than 6.0 MPa. When the compressive strength is 1.0 MPa or more, it is crushed and reduced in size during catalyst synthesis or feeding, and tends to suppress scattering and adhesion of the obtained polymer particles. When the compressive strength is less than 10 MPa, the probability that the carrier substance remains in the ethylene-based polymer without being crushed during the polymerization increases, and the problem that the smoothness of the crosslinked surface is impaired tends to be suppressed. be.

Further, the obtained supported metallocene catalyst may be washed with a decantation, filtration or the like using an inert solvent for the purpose of removing organoaluminum compounds, borate compounds, etc. that are not supported on the carrier. can. When producing an ethylene polymer, it is preferable to carry out decantation and / or filtration at least once in order to reduce the low molecular weight components generated by the side reaction.

Further, the chlorine content in the catalyst is preferably 50% by mass or less, more preferably 20% by mass or less, still more preferably 5.0% by mass or less, and less preferably.

The liquid co-catalyst is a liquid co-catalyst and is a substance that increases the activity of the supported metallocene catalyst. The liquid co-catalyst is not particularly limited, but can be prepared from, for example, an organic magnesium compound and a methylhydropolysiloxane.

The Ziegler-Natta catalyst that can be used as a catalyst in the method for producing an ethylene polymer is not particularly limited, but a compound containing a silane compound, organic magnesium, and titanium can be prepared as a main raw material. More specifically, it can be obtained by preparing from trichlorosilane, organic magnesium, n-butyl alcohol, organic aluminum, and titanium tetrachloride.

When preparing the Ziegler-Natta catalyst, when reacting organic magnesium with a silane compound such as trichlorosilane, slowly add organic magnesium (eg, n-heptane solvent, etc.) for 1 hour or longer, preferably 2 hours or longer. It is preferable to add. Further, when preparing the Ziegler-Natta catalyst, since by-products, unreactants and the like are mixed in the solvent after the reaction is completed, it is preferable to perform the washing operation three times or more after the reaction. Similarly, it is preferable to perform washing at least once after each reaction with an alcohol such as n-butyl alcohol and a compound containing titanium such as organoaluminum and titanium tetrachloride.

The chlorine content in this solid catalyst is 70% or less, preferably 65% or less, and more preferably 60% or less.

The polymerization method in the polymerization step is not particularly limited, and examples thereof include a slurry polymerization method, a gas phase polymerization method, and a solution polymerization method. By these polymerization methods, ethylene or a monomer containing ethylene is (co). Can be polymerized. Among these, a slurry polymerization method capable of efficiently removing heat of polymerization is preferable. In the slurry polymerization method, an inert hydrocarbon medium can be used as the polymerization medium, and the olefin itself can also be used as the polymerization medium.

The inert hydrocarbon medium is not particularly limited, and is, for example, an aliphatic hydrocarbon such as propane, butane, isobutane, pentane, isopentan, hexane, heptane, octane, decane, dodecane, kerosene; cyclopentane, cyclohexane, and methylcyclo. Aliphatic hydrocarbons such as pentane; aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as ethyl chloride, chlorbenzene and dichloromethane and mixtures thereof.

Among the above-mentioned inert hydrocarbon media, it is more preferable to use a hydrocarbon medium having 6 or more and 10 or less carbon atoms in the polymerization step. When the number of carbon atoms is 6 or more, the low molecular weight component that reacts with the cross-linking agent and lowers the pressure resistance and durability is relatively easy to dissolve, and the ethylene polymer is separated from the ethylene polymer in the step of separating the polymerization medium. Tends to be easily removed from. When the number of carbon atoms is 10 or less, the amount of low molecular weight components (medium) remaining in the ethylene polymer is reduced, the adhesion of polyethylene powder to the reaction vessel is suppressed, and industrially stable operation is performed. There is a tendency to do it.

The polymerization temperature in the polymerization step is preferably 30 ° C. or higher and 100 ° C. or lower, more preferably 35 ° C. or higher and 95 ° C. or lower, and even more preferably 40 ° C. or higher and 90 ° C. or lower. If the polymerization temperature is 30 ° C. or higher, industrially efficient production tends to be possible. On the other hand, when the polymerization temperature is 100 ° C. or lower, continuous stable operation tends to be possible.

The polymerization pressure in the polymerization step is preferably normal pressure or more and 2 MPa or less, more preferably 0.1 MPa or more and 1.5 MPa or less, and further preferably 0.3 MPa or more and 1.2 MPa or less.

The slurry concentration in the polymerization step is preferably 40% or less, more preferably 35% or less. The higher the slurry concentration, the more industrially efficient production becomes possible, but the lower limit of the slurry concentration in producing the ethylene-based polymer for obtaining the polyethylene-based resin composition of the present embodiment is particularly high. do not have. On the other hand, when the slurry concentration exceeds 40%, the concentration of the low molecular weight polymer component dissolved in the solvent increases, and as a result, the amount of the low molecular weight component contained in the ethylene polymer increases. The polyethylene-based resin composition (after cross-linking) produced by using the ethylene-based polymer containing a large amount of low molecular weight components will contain a large amount of low molecular weight components.

The polymerization in the polymerization step can be carried out by any of a batch type, a semi-continuous type, and a continuous type, and it is preferable to carry out the polymerization by a continuous type. In the continuous equation, ethylene gas, solvent, catalyst, etc. are continuously supplied into the polymerization system and continuously discharged together with the generated ethylene-based polymer to suppress a partial high temperature state due to a rapid ethylene reaction. This makes it possible to stabilize the inside of the polymerization system. When ethylene reacts in a uniform state in the system, it is possible to suppress the formation of branches, double bonds and the like in the polymer chain. This makes it easier to obtain an ethylene-based polymer with high cross-linking efficiency, and tends to increase the gel fraction. Therefore, a continuous equation in which the inside of the polymerization system is more uniform is preferable.

The molecular weight of the ethylene-based polymer is not particularly limited, but is adjusted by allowing hydrogen to be present in the polymerization system, changing the polymerization temperature, or the like, as described in Japanese Patent Application Publication No. 3127133. be able to. It is also possible to control the molecular weight within an appropriate range by adding hydrogen as a chain transfer agent into the polymerization system. When hydrogen in the polymerization system is added, the mole fraction of hydrogen is preferably 0 mol% or more and 30 mol% or less, and more preferably 0 mol% or more and 20 mol% or less.

Further, it is preferable that hydrogen is brought into contact with the catalyst in advance and then added into the polymerization system from the catalyst introduction line. Immediately after introducing the catalyst into the polymerization system, the concentration of the catalyst near the outlet of the introduction line is high, and the possibility of a partial high temperature state due to the rapid reaction of ethylene increases, but hydrogen and the catalyst are introduced into the polymerization system. By contacting the catalyst before introduction, it is possible to suppress the initial activity of the catalyst and suppress the formation of low molecular weight components. Therefore, it is preferable to introduce hydrogen into the polymerization system in a state of being in contact with the catalyst.

After the polymerization step, it is preferable to feed wet nitrogen in a liquid to the flash tank for removing unreacted ethylene, comonomer and hydrogen. By feeding wet nitrogen in the liquid, it is possible to suppress post-polymerization in flash tanks with different polymerization conditions (temperature, concentration, etc.), and it is possible to reduce the production of low molecular weight components and low melting point polyethylene. can.

The solvent separation method in the method for producing an ethylene polymer can be carried out by a decantation method, a centrifugation method, a filter filtration method or the like, but a centrifugation method having good separation efficiency between the ethylene polymer and the solvent is more preferable. The amount of the solvent contained in the ethylene-based polymer after solvent separation is not particularly limited, but is 70% by mass or less, more preferably 60% by mass or less, based on the mass (100% by mass) of the ethylene-based polymer. , More preferably 50% by mass or less. By drying and removing the solvent in a state where the solvent contained in the ethylene-based polymer is small, the metal component, the low molecular weight component, and the like contained in the solvent tend to be difficult to remain in the ethylene-based polymer. When these components do not remain, an ethylene-based polymer having excellent hygiene and high cross-linking efficiency can be obtained, and a polyethylene-based resin composition (after cross-linking) having excellent pressure resistance and durability can be easily obtained. Therefore, it is preferable to separate the ethylene polymer and the solvent by a centrifugal separation method.

The drying temperature in the method for producing an ethylene polymer is preferably 50 ° C. or higher and 150 ° C. or lower, more preferably 50 ° C. or higher and 140 ° C. or lower, and further preferably 50 ° C. or higher and 130 ° C. or lower. When the drying temperature is 50 ° C. or higher, efficient drying tends to be possible. On the other hand, when the drying temperature is 150 ° C. or lower, it tends to be possible to dry the ethylene-based polymer in a state of suppressing decomposition.
After that, the dried ethylene polymer is melt-kneaded with an extruder and pelletized.

[Use]
The polyethylene-based resin composition of the present embodiment is not particularly limited, but is not particularly limited, and is used for tubular bodies such as pipes, hoses and tubes, coating materials used for conductors such as electric wires and cables, various containers, sealing materials, films, porous films, and the like. It can be used for various purposes such as sheets. The polyethylene-based resin composition is preferably a tubular body, and more preferably a pipe. The shape of the polyethylene-based resin composition (after cross-linking) for these uses is not particularly limited, but the molded body (polyethylene-based before cross-linking) before making the polyethylene-based resin composition (after cross-linking). The resin composition) may be formed into a desired shape, or may be formed into a polyethylene-based resin composition (after cross-linking) and then molded into a desired shape (for example, cutting).

Hereinafter, the present embodiment will be described in more detail based on the examples, but the present embodiment is not limited to the following examples. First, the measurement methods and evaluation criteria for each physical property and evaluation will be described below.

(Evaluation 1: Gel fraction of polyethylene resin composition)
The gel fraction of each polyethylene-based resin composition (crosslinked body) obtained in Examples and Comparative Examples is the gel fraction of JIS K 6787-1997 cross-linked polyethylene pipe for water supply Annex 7 (regulation). It was measured by the following method according to the test method. The results obtained from the crosslinked products of each Example and Comparative Example are shown in Tables 1 and 2.

Next, a specific method for measuring the gel fraction of the crosslinked product will be described.
(I) A basket made of aluminum or stainless steel, which is a mesh having a hole diameter of 125 μm ± 25 μm, was prepared. (The mass of the car is "m1".)
(Ii) 0.5 g to 1.0 g of the sample sliced or scraped to a thickness of 0.1 mm to 0.2 mm was weighed and placed in the above basket. (The mass of the basket including the sample is "m2".)
(Iii) A basket containing the sample was placed in a flask, a sufficient amount of xylene was added to ensure that the sample was immersed, and then the solvent was boiled vigorously for 8 hours ± 5 minutes.
(Iv) The sample residue and cage were carefully removed from the boiling solvent and the outside of the cage was wiped with a cloth.
(V) The basket containing the residue was completely dried for 3 hours by either of the following methods a) and b).
a) In a vacuum furnace at 140 ° C. ± 2 ° C. under a negative pressure of at least 0.85 Bar (85 KPa) (ie, about 0.15 bar or less in absolute pressure).
b) At 140 ° C ± 2 ° C, with a forced ventilation furnace equipped with an appropriate exhaust system.
(Vi) After cooling sufficiently, the basket and the residue were taken out. (The mass of the basket including the residue is "m3".)
(Vii) The degree of cross-linking to each sample was calculated as a percentage of the mass of the insoluble matter; G1 by the following formula.
(Viii) G1 = (m3-m1) / (m2-m1) × 100
The result is represented by the closest integer.
(Ix) The above operations (i) to (vii) were repeated at least once with a new sample.
(X) The average degree of cross-linking G was obtained by calculation from each result. If there was a difference of 3 points or more between the two individual results, the test was repeated with two new samples.

(Physical characteristics 2: CFC of polyethylene resin composition)
For the polyethylene-based resin compositions obtained in Examples and Comparative Examples, a solution (xylene-dissolving component) after performing the step (vi) of the method for measuring the above-mentioned "gel fraction of polyethylene-based resin composition" was added to 25. The mixture was cooled to ° C., and then the precipitate was collected by filtration. Further, for the product dried in air at 23 ° C. for 10 hours, the elution temperature-elution amount curve by temperature elution fractionation (TREF) was measured as follows, and the elution amount and elution integrated amount at each temperature were measured. I asked. First, the temperature of the column containing the filler was raised to 140 ° C., a sample solution in which the xylene-dissolving component was dissolved in orthodichlorobenzene was introduced, and the mixture was held for 120 minutes.

Next, the temperature was lowered to 40 ° C. at a temperature lowering rate of 0.5 ° C./min and then held for 20 minutes to deposit the sample on the surface of the filler. Then, the temperature of the column was sequentially raised at a heating rate of 20 ° C./min. The temperature rises from 40 ° C to 80 ° C at 10 ° C intervals, from 80 ° C to 85 ° C at 5 ° C intervals, from 85 ° C to 90 ° C at 3 ° C intervals, and from 90 ° C to 100 ° C. The temperature was raised at 1 ° C intervals, and the temperature was raised from 100 ° C to 120 ° C at 10 ° C intervals. After holding at each temperature for 20 minutes, the temperature was raised to detect the concentration of the sample eluted at each temperature. Then, the elution temperature-elution amount curve was measured from the values of the elution amount (mass%) of the sample and the in-column temperature (° C.) at that time, and the elution amount and the elution integral amount at each temperature were obtained.
-Device: Polymer ChaAR Automated 3D analyzer CFC-2
Column: Stainless steel micro ball column (3/8 "od x 150 mm)
Eluent: o-dichlorobenzene (for high performance liquid chromatograph)
Sample solution concentration: Sample 20 mg / o-dichlorobenzene 20 mL
Injection volume: 0.5 mL
Pump flow rate: 1.0 mL / min Detector: Polymer ChAR infrared spectrophotometer IR4
Detected wavenumber: 3.42 μm
Sample dissolution conditions: 140 ° C x 120 min dissolution

(Physical characteristics 3: MFR of ethylene polymer)
For each ethylene-based polymer obtained in Examples and Comparative Examples, JIS K7210
The melt flow rate was measured by code D: 1999 (temperature = 190 ° C., load = 2.16 kg). The results obtained from the ethylene-based polymers of each Example and Comparative Example are shown in Tables 1 and 2.

(Physical characteristics 4: Weight average molecular weight and number average molecular weight of ethylene polymer and their ratio)
A sample solution was prepared by introducing 15 mL of o-dichlorobenzene into 20 mg of each ethylene-based polymer obtained in Examples and Comparative Examples and stirring at 150 ° C. for 1 hour, and gel permeation chromatography (GPC) was performed. Measurements were made. From the measurement results, the weight average molecular weight (Mw), the number average molecular weight (Mn), and their ratio (Mw / Mn) were determined based on a calibration curve (first-order approximation) prepared using commercially available monodisperse polystyrene. The molecular weight in the present invention is a weight average molecular weight. The materials and conditions used for the measurement were as follows. The results obtained from the samples of each Example and Comparative Example are shown in Tables 1 and 2.

Equipment: Waters 150-C ALC / GPC
Detector: RI detector Mobile phase: o-dichlorobenzene (for high performance liquid chromatograph)
Flow rate: 1.0 mL / min Column: One AT-807S manufactured by Showa Denko KK and two TSK-gelGMH-H6 manufactured by Tosoh Corporation were connected.
Column temperature: 140 ° C

The polyethylene-based resin compositions obtained in Examples and Comparative Examples were evaluated as follows.
(Evaluation 1: Oxidation induction time)
The oxidation induction time of the polyethylene-based resin compositions obtained in Examples and Comparative Examples is measured using a differential scanning calorimeter (DSC). DSC-60Plus (manufactured by Shimadzu Corporation) was used for the measurement. First, 5 mg of aluminum oxide was added to an aluminum pan for DSC measurement. This was set on the left side of the DSC-60Plus furnace, and an aluminum pan containing 5 mg of the measurement sample was set on the right side of the furnace. The inner lid was closed, the protective cover was lowered, the temperature was raised to 240 ° C. while flowing nitrogen gas in the furnace at 25 mL / min, and the mixture was allowed to stand for 1 minute in that state before measurement was started. The heating rate was 25 ° C./min. The sampling interval at the time of measurement was set to 0.5 seconds. After 1 minute, nitrogen was switched to oxygen to oxidize the sample. It passes through a point on the chart when nitrogen is switched to oxygen, a straight line with the slope of the chart at that point, and the inflection point before the chart rises and passes through the first peak, and at that inflection point. The oxidation induction time was measured by calculating the time of the intersection with the straight line having the slope of the chart. The results obtained from the crosslinked products of each Example and Comparative Example are shown in Tables 1 and 2.
The oxidation induction time is closely related to the thermal stability and oxidation resistance of the sample, and the longer the oxidation induction time, the better the thermal stability and oxidation resistance.

(Evaluation 2: Appearance of molded product)
The molded articles of the polyethylene-based resin compositions obtained in Examples and Comparative Examples were visually confirmed, and the appearance was evaluated according to the following criteria. The results obtained from the samples of each Example and Comparative Example are shown in Tables 1 and 2.
◯: Good because there is no unevenness due to gel-like substances on the inner and outer surfaces of the molded product.
Δ: The outer and outer surfaces of the molded product have irregularities due to gel-like substances, etc., but only a small part of the surface of the molded product has a slight effect on the overall appearance.
X: There are many irregularities on the outer and outer surfaces of the molded product due to gel-like substances and the like.

(Evaluation 3: Energy saving)
10 g of the polyethylene-based resin composition obtained in Examples and Comparative Examples molded to a thickness of 1 mm and 10 g of distilled water were placed in a container and sealed, and the polyethylene-based resin composition and water were sufficient at 90 ° C. for 5 hours. After vibrating with a shaker so as to come into contact with the water, the viscosity of this water at 90 ° C. was measured by JIS Z8830. This evaluation is for evaluating the load of a circulation pump or the like due to an increase in the viscosity of hot water in contact with the pipe when the polyethylene-based resin composition of the present application is used for a hot water pipe for floor heating. If the viscosity of the hot water is low, the load on the pump is also low, so it can be said that energy saving is high. The results obtained from the samples of each Example and Comparative Example are shown in Tables 1 and 2.

(Evaluation 4: Flexibility)
Pipe 1 (length 900 mm, outer diameter 21.5 mm, inner diameter 16.2 mm) and pipe 2 (length 900 mm, outer diameter 34.0 mm, inner diameter 26.0 mm) of the polyethylene-based resin compositions obtained in Examples and Comparative Examples. Was wound around a tubular cylinder (mandrel) having a diameter of 300 mm without a gap so that the pipe was in contact with the cylinder (mandrel), and the flexibility was evaluated by the degree of winding. The results obtained from the samples of each Example and Comparative Example are shown in Tables 1 and 2.
◯: Both pipe 1 and pipe 2 could be wound without buckling.
Δ: Only pipe 1 could be wound without buckling.
X: Both pipe 1 and pipe 2 buckled and could not be wound.

[Preparation of polymerization catalyst]
(Saturated adsorption amount of Lewis acidic compound on the precursor of carrier [C])
First, spherical silica was prepared as a precursor of the carrier [C]. Next, triethylaluminum (Lewis acidic compound) was prepared as the activator compound (E-1). Spherical silica was heat-treated at 400 ° C. for 5 hours under a nitrogen atmosphere. The average particle size after the heat treatment was 3 μm, the compressive strength was 6 MPa, and the amount of surface hydroxyl groups was 1.85 mmol / g. A silica slurry was obtained by adding 4 g of this heat-treated spherical silica to a glass container having a capacity of 0.2 L under a nitrogen atmosphere, and adding 80 mL of hexane to disperse the silica. 10 mL of a hexane solution of triethylaluminum (concentration 1 mol / L) was added to the obtained silica slurry at 20 ° C. with stirring, and then the mixture was stirred for 2 hours to react triethylaluminum with the surface hydroxyl group of silica to obtain a hexane slurry. .. As a result of quantifying the amount of aluminum in the supernatant of this hexane slurry, the saturated adsorption amount of triethylaluminum with respect to spherical silica was 2.1 mmol / g.

(Preparation of carrier [C])
Spherical silica (40 g) after heat treatment was dispersed in 800 mL of hexane in a nitrogen-substituted capacity 1.8 L autoclave to obtain a slurry. While keeping the obtained slurry at 20 ° C. under stirring, 80 mL of a hexane solution of triethylaluminum (concentration 1M) was added, and then the mixture was stirred for 2 hours to prepare 880 mL of a hexane slurry of carrier [C] on which triethylaluminum was adsorbed.

(Preparation of Transition Metal Compound [D])
As the transition metal compound (D-1), [(Nt-butylamide) (tetramethyl-η5-cyclopentadienyl) dimethylsilane] titanium-1,3-pentadiene (hereinafter abbreviated as "titanium complex"). I prepared. Further, as the organic magnesium compound (D-2), composition formula AlMg ₆ (C ₂ H ₅ ) ₃ (C ₄ H ₉ ) ₁₂ (hereinafter abbreviated as “Mg 1”) was prepared. This Mg1 was synthesized by mixing a predetermined amount of triethylaluminum and dibutylmagnesium in hexane at 25 ° C. 200 mmol of the titanium complex is dissolved in 1000 mL of Isopar (registered trademark) E (manufactured by Exxon Mobile Chemical), 20 mL of a hexane solution of Mg1 (concentration 1 M) is added, and hexane is further added to adjust the titanium complex concentration to 0.1 M, and the transition The metal compound [D] was obtained.

(Preparation of activator [E])
As the activating compound (E-2), bis (taroalkyl hydride) methylammonium-tris (pentafluorophenyl) (4-hydroxyphenyl) borate (hereinafter abbreviated as "borate") was prepared. Further, as the activating compound (E-3), an organoaluminum compound and ethoxydiethylaluminum were prepared. 5.7 g of borate was added to 50 mL of toluene and dissolved to obtain a 100 mM toluene solution of borate. 5 mL of a hexane solution of ethoxydiethylaluminum (concentration 1M) was added to the toluene solution of this volate at 25 ° C., and hexane was further added to adjust the volate concentration in the toluene solution to 80 mM. Then, the activator [E] was prepared by stirring at 25 ° C. for 1 hour.

(Preparation of metallocene-supported catalyst [A])
To 880 mL of the slurry of the carrier [C] obtained by the above operation, 50 mL of the activator [E] obtained by the above operation was added with stirring at 20 ° C., and the reaction was continued for 10 minutes. Next, 40 mL of the transition metal compound component [D] obtained by the above operation was added with stirring, and the reaction was continued for 3 hours to obtain a slurry. Further, the purification operation of removing the supernatant of this slurry, adding hexane and stirring the mixture was carried out three times, and the metallocene-supported catalyst [A] having a chlorine content of 1 mass ppm or less (in Table 1, simply [A]. ] Is shown.) Was prepared.

(Preparation of liquid co-catalyst [B])
The above Mg1 was prepared as the organic magnesium compound [G]. As compound [J], methylhydropolysiloxane (viscosity at 25 ° C., 20 cm Stokes, manufactured by Shinetsu Silicon Co., Ltd.) was used. To a 200 mL flask, add 40 mL of hexane and Mg1 with stirring so that the total amount of Mg and Al is 37.8 mmol, and 40 mL of hexane containing 2.27 g (37.8 mmol) of methylhydropolysiloxane at 25 ° C. Was added with stirring, and then the temperature was raised to 80 ° C. and reacted under stirring for 3 hours to prepare the liquid co-catalyst component [B].

(Preparation of Ziegler catalyst [H])
2740 mL of trichlorosilane (HSICl ₃ ) as a 2 mol / L n-heptane solution was charged into a fully nitrogen-substituted 15 L reactor, kept at 50 ° C. with stirring, and the composition formula AlMg ₆ (C ₂ H ₅ ) ₃ (N-C ₄ H ₉ ) _10.8 (On-C ₄ H ₉ ) Add 7 L of n-heptane solution (5 mol in magnesium equivalent) of the organic magnesium component shown in _1.2 over 3 hours, and further. The reaction was carried out at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the obtained solid was washed with 7 L of n-hexane four times to obtain a slurry. As a result of separating, drying and analyzing this solid, Mg: 8.62 mmol, Cl: 17.1 mmol, and n-butoxy group ( _On -C 4H ₉ ): 0.84 mmol were contained in 1 gram of the solid. Was there.

The slurry containing 500 g of the solid obtained as described above was reacted with 1250 mL of an n-hexane solution of 1 mol / L of n-butyl alcohol at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the obtained solid was washed once with 7 L of n-hexane to obtain a slurry. The slurry was kept at 50 ° C., 500 mL of an n-hexane solution of diethyl aluminum chloride 1 mol / L was added with stirring, and the mixture was reacted for 1 hour. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the obtained solid was washed twice with 7 L of n-hexane to obtain a slurry. The slurry was kept at 50 ° C., 78 mL of an n-hexane solution of 1 mol / L diethylaluminum chloride and 78 mL of an n-hexane solution of 1 mol / L titanium tetrachloride were added, and the mixture was reacted for 1 hour. Further, 234 mL of an n-hexane solution of 1 mol / L diethylaluminum chloride and 234 mL of an n-hexane solution of 1 mol / L titanium tetrachloride were added to this reaction solution, and the reaction was carried out for 2 hours. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the mixture was washed with 7 L of n-hexane four times with the internal temperature maintained at 50 ° C., and the solid catalyst Ziegler catalyst [H] (Table 1). Among them, simply indicated as [H]) was obtained as a hexane slurry solution. The chlorine content of this solid catalyst was 55% by mass.

[Example 1]
(Method for producing ethylene polymer)
Using a Vessel type 340L polymerization reactor equipped with a stirrer, continuous polymerization was carried out under the conditions of a polymerization temperature of 80 ° C., a polymerization pressure of 1 MPa and an average residence time of 2.5 hours. Dehydrated normal hexane 65 L / hour as a solvent, the above-mentioned supported metallocene catalyst [A] as a catalyst 50 mg / hour, liquid co-catalyst [B] 4 mmol / hour in terms of Al atom, 1-with respect to the gas phase concentration of ethylene. Each was supplied so as to have 0.25 mol% of butene and 0.37 mol% of hydrogen, and polymerization was carried out so that the slurry concentration became 35%. Hydrogen was introduced into the reactor after reacting with the supported metallocene catalyst [A]. The polymerization slurry in the polymerization reactor was guided to a flash tank having a pressure of 0.04 MPa and a temperature of 70 ° C. so that the level of the polymerization reactor was kept constant, and unreacted ethylene, 1-butene and hydrogen were separated.

Subsequently, the polymerized slurry in the polymerization reactor was continuously sent to a centrifuge to separate the polymer from other solvents and the like to obtain polyethylene powder. The separated polyethylene powder was dried by high temperature nitrogen blow.

1500 ppm of calcium stearate was added to the obtained polyethylene powder, and TEX-44 manufactured by Japan Steel Works, Ltd. (screw diameter 44 mm, L / D = 35. L: distance from the raw material supply port to the discharge port of the polymerization reactor (m). ), D: Inner diameter (m) of the polymerization reactor; the same shall apply hereinafter), melt-kneaded at a resin temperature of 200 ° C. and granulated to obtain an ethylene-based polymer.

(Manufacturing method of silane grafted polyethylene)
To 100 parts by mass of the above ethylene-based polymer, 5.0 parts by mass of vinyltrimethoxysilane and 0.15 parts by mass of Perhexa 25B (manufactured by Japan Steel Works) as an organic peroxide are mixed, mixed with Henciel, and stocked. A silane grafted polyethylene was obtained by adjusting the resin temperature to about 200 ° C. and performing extrusion compounding and pelletizing using a twin-screw extruder (TEX-28) manufactured by Japan Steel Works, Ltd.

(Method for Producing Silanol Condensation Catalyst-Containing Resin Composition)
Further, with respect to 100 parts by mass of the above ethylene-based polymer, 1.7 parts by mass of dioctyltin dilaurate as a silanol condensation catalyst, 4.1 parts by mass of Irganox1010 (manufactured by BASF) as a phenol-based antioxidant, and Irganox1330 (BASF). 8.3 parts by mass, Irganox 1076 (manufactured by BASF) 4.9 parts by mass, Irgafos 168 (manufactured by BASF) 2.5 parts by mass as a phosphorus-based heat stabilizer, Irganox MD1024 (manufactured by BASF) 5.2 mass By blending 3.4 parts by mass of each part and Dynamer FX9613 (manufactured by 3M), mixing with a Henciel mixer, adjusting the resin temperature to about 200 ° C. using TEX-28, and performing melt kneading and pelletizing. , A master batch of a resin composition containing a silanol condensation catalyst was obtained.

(Manufacturing method of polyethylene-based resin composition)
5.0 parts by mass of the above masterbatch is uniformly mixed with 100 parts by mass of the above silane grafted polyethylene using a Henshell mixer, melt-kneaded, and then cooled with water at 20 ° C. to form a molded product (two types). It was molded into a pipe). The molded product (pipe) was immersed in warm water at 100 ° C. for 12 hours to obtain a polyethylene-based resin composition containing silane cross-linked polyethylene. In the polyethylene-based resin composition (pipe after cross-linking), the pipe 1 had an outer diameter of 21.5 mm and an inner diameter of 16.2 mm, and the pipe 2 had an outer diameter of 34.0 mm and an inner diameter of 26.0 mm.

[Example 2]
As a method for producing an ethylene polymer, continuous polymerization is carried out under the conditions of a polymerization reaction temperature of 82 ° C. and an average residence time of 5 hours, and the above-mentioned Cheegler catalyst [H] is used as a catalyst at 10.0 mg / hour and a liquid co-catalyst [B]. The conditions were the same as in Example 1 except that the polymerization was carried out by supplying each of 10 mmol / hour in terms of Al atom so that hydrogen was 25 mol% with respect to the gas phase concentration of ethylene, and the polyethylene-based resin was used. The composition was obtained.

[Example 3]
The ethylene-based polymer was produced in the same manner as in Example 1 except that the slurry concentration was 45%, to obtain a polyethylene-based resin composition.

[Example 4]
As a method for producing the polyethylene-based resin composition, the same procedure as in Example 1 was carried out except that the amount of dioctyltin dilaurate was 5.6 parts by mass to obtain a polyethylene-based resin composition.

[Example 5]
The ethylene-based polymer was produced in the same manner as in Example 1 except that the polymerization temperature was 65 ° C. and hydrogen was 0 mol%, to obtain a polyethylene-based resin composition.

[Example 6]
The polyethylene-based resin composition was produced in the same manner as in Example 1 except that the polyethylene-based resin composition was melt-kneaded before crosslinking and then cooled with water at 10 ° C. to obtain a polyethylene-based resin composition.

[Example 7]
The polyethylene-based polymer was produced in the same manner as in Example 1 except that 1-butene was 0.32 mol% and hydrogen was 0.29 mol% with respect to the vapor phase concentration of ethylene to obtain a polyethylene-based resin composition. rice field.

[Example 8]
As a method for producing the polyethylene-based resin composition, the same procedure as in Example 7 was carried out except that the amount of dioctyltin dilaurate was 1.2 parts by mass to obtain a polyethylene-based resin composition.

[Example 9]
The ethylene-based polymer was produced in the same manner as in Example 8 except that the slurry concentration was 45%, to obtain a polyethylene-based resin composition.

[Example 10]
The polyethylene-based resin composition was produced in the same manner as in Example 8 except that the polyethylene-based resin composition was melt-kneaded before crosslinking and then cooled with water at 10 ° C. to obtain a polyethylene-based resin composition.

[Example 11]
As a method for producing the silanol condensation catalyst-containing resin composition, the same procedure as in Example 1 was carried out except that the amount of dioctyltin dilaurate was 9.8 parts by mass to obtain a polyethylene-based resin composition.

[Comparative Example 1]
As a method for producing the silanol condensation catalyst-containing resin composition, a polyethylene-based resin composition was obtained in the same manner as in Example 1 except that Irganox 1010, Irganox 1330, and Irganox 1076 as phenolic antioxidants were not used.

[Comparative Example 2]
As a method for producing the silanol condensation catalyst-containing resin composition, the same procedure as in Example 1 was carried out except that Irgafos 168 as a phosphorus-based heat stabilizer was not used to obtain a polyethylene-based resin composition.

[Comparative Example 3]
As a method for producing an ethylene polymer, the slurry concentration is 50% and an average residence time is 5 hours, and as a method for producing a polyethylene resin composition, the polyethylene resin composition is cooled with water at 10 ° C. after melt-kneading before crosslinking. A polyethylene-based resin composition was obtained in the same manner as in Example 2 except for the above.

[Comparative Example 4]
The ethylene-based polymer was produced in the same manner as in Example 1 except that the slurry concentration was 55%, to obtain a polyethylene-based resin composition.

[Comparative Example 5]
The polyethylene-based resin composition was produced in the same manner as in Example 1 except that the polyethylene-based resin composition was melt-kneaded before crosslinking and then cooled with water at 0 ° C. to obtain a polyethylene-based resin composition.

[Comparative Example 6]
The ethylene-based polymer was produced in the same manner as in Example 8 except that the slurry concentration was 55%, to obtain a polyethylene-based resin composition.

[Comparative Example 7]
The polyethylene-based resin composition was produced in the same manner as in Example 8 except that the polyethylene-based resin composition was melt-kneaded before crosslinking and then cooled with water at 0 ° C. to obtain a polyethylene-based resin composition.

According to Tables 1 and 2 above, in Examples 1 to 11, the polyethylene-based resin composition has a predetermined composition, and in CFC measurement, the ratio of the total amount of components eluted at 95 ° C. or lower to the total elution amount. Is 90% or more, so it can be seen that it is superior in terms of thermal stability and flexibility as compared with Comparative Examples 1 to 7.

According to the present invention, it is possible to provide a polyethylene-based resin composition containing silane cross-linked polyethylene having sufficient durability while improving flexibility, and a pipe made of the polyethylene-based resin composition.

Claims (6)

It contains silane cross-linked polyethylene, at least one phenolic antioxidant, and at least one phosphorus-based antioxidant.
The gel fraction is 30% or more,
In the measurement using the cross fractionation chromatography of the xylene-dissolved component in the gel fraction measurement, the ratio of the total amount of the components eluted at 95 ° C. or lower to the total elution amount was 90% or more .
A polyethylene-based resin composition in which the ratio of the total amount of components eluted at 80 ° C. or lower to the total elution amount is 30% or less in the measurement using cross-separation chromatography of xylene-dissolved components in the gel fraction measurement . The polyethylene-based resin composition has an MFR of 0.1 or more and 10 or less, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in GPC measurement is 2.0 or more and 10 or more. The polyethylene-based resin composition according to claim 1, which is produced by using the following ethylene-based polymer. The polyethylene-based resin composition according to claim 1 or 2, wherein the polyethylene-based resin composition contains 5 to 500 ppm of tin element. The polyethylene-based product according to any one of claims 1 to 3 , wherein the ratio of the total amount of the components eluted at 80 ° C. or lower to the total elution amount is 27% or less in the measurement using the xylene-dissolved component cross fractionation chromatography. Resin composition. The polyethylene-based product according to any one of claims 1 to 4 , wherein the ratio of the total amount of the components eluted at 95 ° C. or lower to the total elution amount is 93% or more in the measurement using the xylene-dissolved component cross fractionation chromatography. Resin composition. A pipe made of the polyethylene-based resin composition according to any one of claims 1 to 5 .