JP2019172923A - Polyethylene-based resin composition and pipe thereof - Google Patents

Abstract

To provide a polyethylene resin composition containing silane crosslinked polyethylene having sufficient durability while flexibility is enhanced, and a pipe consisting of the polyethylene resin composition.SOLUTION: The polyethylene resin composition contains silane crosslinked polyethylene, at least one kind of phenol antioxidant, and at least one kind of phosphorus antioxidant, and has gel fraction of 30% or more, and percentage of total amount of a component eluted at 95°C or lower to total eluted amount in a measurement of a xylene soluble component in a gel fraction measurement by using a cross fractionation chromatography of 90% or more. The pipe consists of the polyethylene resin composition.SELECTED DRAWING: None

Description

  The present invention relates to a polyethylene resin composition and its pipe.

  Conventionally, a crosslinked product obtained by crosslinking a polyethylene resin is easy to be molded or crosslinked, for example, tubular bodies such as pipes, hoses and tubes, insulating coating materials used for conductors such as electric wires and cables, various containers, and It is used in various applications 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 workability than vinyl chloride pipes and copper pipes that are also used in the construction field. In recent years, cross-linked polyethylene pipes are being used more frequently in the construction field, specifically for water supply / drainage, hot water supply, and heating.

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

Patent No. 3532106 JP 2011-11497 A JP 2007-120964 A JP 2010-150299 A JP 2012-136596 A

  By the way, the cross-linked polyethylene (hereinafter also referred to as silane cross-linked polyethylene) obtained by the conventional technique as described above cannot be said to have sufficient flexibility, for example. Specifically, for example, when silane-crosslinked polyethylene is formed into a pipe, for example, when the pipe is bent, more specifically, when the pipe is bent and provided for hot water supply or floor heating, workability is improved. However, it cannot be said that conventional silane-crosslinked polyethylene has sufficient flexibility. Furthermore, since silane crosslinked polyethylene is used over 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 a polyethylene resin composition containing a silane-crosslinked polyethylene having sufficient durability while improving flexibility, and a pipe comprising the polyethylene resin composition The purpose is to provide.

  As a result of intensive investigations to solve the above-mentioned problems, the present invention can solve the above problems by using a polyethylene-based resin composition having the following composition and specific properties. As a result, the present invention has been made.

That is, the present invention is as follows.
[1]
Containing silane-crosslinked polyethylene, at least one phenolic antioxidant, and at least one phosphorus antioxidant,
The gel fraction is 30% or more,
A polyethylene resin characterized in that the ratio of the total amount of components eluting at 95 ° C. or less to the total elution amount is 90% or more in the measurement using cross fractionation chromatography of xylene-dissolved components in gel fraction measurement Composition.
[2]
The polyethylene resin composition has an MFR of 0.1 or more and 10 or less, and a 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 The polyethylene resin composition according to the above [1], which is produced using the following ethylene polymer.
[3]
The polyethylene resin composition according to the above [1] or [2], wherein a tin element is contained in the polyethylene resin composition in an amount of 5 to 500 ppm.
[4]
In the measurement using the cross fractionation chromatography of the xylene-dissolved component, the ratio of the total amount of components eluted at 80 ° C. or less to the total elution amount is 30% or less, according to any one of the above [1] to [3] The polyethylene-based resin composition described.
[5]
The polyethylene resin composition according to [4] above, wherein in the measurement using the xylene-soluble component cross fractionation chromatography, the ratio of the total amount of components eluted at 80 ° C. or less to the total amount eluted is 27% or less.
[6]
In the measurement using the xylene-dissolved component cross fractionation chromatography, the ratio of the total amount of components eluted at 95 ° C. or less to the total elution amount is 93% or more, according to any one of [1] to [5] above. Polyethylene resin composition.
[7]
The pipe which consists of a polyethylene-type resin composition in any one of said [1]-[6].

  ADVANTAGE OF THE INVENTION According to this invention, the pipe which consists of a polyethylene-type resin composition containing the silane crosslinked polyethylene provided with sufficient durability while improving a softness | flexibility, and the said polyethylene-type resin composition can be provided.

Hereinafter, a mode for carrying out the invention of the present application (hereinafter referred to as “the present embodiment”) will be described in more detail. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention. Deformation is possible.
[Polyethylene resin composition]
The polyethylene resin composition of the present embodiment contains silane-crosslinked polyethylene, at least one phenolic antioxidant, and at least one phosphorus antioxidant, and has a gel fraction of 30% or more. The total amount of components eluted at 95 ° C. or lower relative to the total elution amount in the measurement using gel fraction measurement of xylene-dissolved components using cross fraction chromatography (hereinafter referred to as “CFC”). The ratio is 90% or more. According to the polyethylene resin composition of the present embodiment, sufficient durability can be provided while improving flexibility. In the present specification, when simply referred to as “polyethylene resin composition”, it refers to a polyethylene resin composition after undergoing a crosslinking step, and the notation “polyethylene resin composition before crosslinking” or “ When it is described as “before crosslinking” as in “polyethylene resin composition (before crosslinking)”, it means a polyethylene resin composition before undergoing a crosslinking step.

  Here, the polyethylene-based resin composition of the present embodiment includes a silane-crosslinked polyethylene having a crosslinking via a silane compound. Specifically, the silane-crosslinked polyethylene is grafted with a silane compound by a free radical generator. The copolymerized ethylene polymer is obtained by crosslinking in the presence of a silanol condensation catalyst and moisture.

-Gel fraction-
The polyethylene 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 polymer can improve brittleness, mechanical strength and heat resistance by silane crosslinking, but is close to non-crosslinking when the ethylene polymer is not sufficiently crosslinked when the gel fraction is less than 30%. It exhibits properties and cannot fully exhibit the performance as a polyethylene resin composition (after crosslinking). The gel fraction of the polyethylene resin composition can be controlled by the amount of the silanol condensation catalyst charged and the crosslinking time. Specifically, the gel fraction can be increased by increasing the amount of silanol condensation catalyst and increasing 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 measurement of JIS K 6696-1998 cross-linked polyethylene (PE-X) pipe and joint-gel content. Specifically, 0.5 g to 1.0 g of the polyethylene resin composition of the present embodiment is cut, and the sample is extracted for 8 hours in a flask using a xylene solvent. And the extraction residual amount after extraction is measured and it calculates | requires by a following formula.
G = (Sample mass before extraction) / (Sample mass before extraction) × 100
G: Gel fraction

-Measurement of xylene-soluble components in gel fraction measurement using CFC-
The polyethylene resin composition of the present embodiment is a total amount of components that elute at 95 ° C. or less with respect to the total elution amount in the measurement using the CFC of the xylene-soluble component in the gel fraction measurement (hereinafter also simply referred to as CFC measurement). Is 90% or more.

  Here, the xylene-dissolved component in the gel fraction measurement refers to the xylene solution obtained by removing the remaining amount of the polyethylene resin composition in the gel fraction measurement, and then the solution is cooled to 25 ° C. and then precipitated. It can be said that it is a component that can be obtained by filtering and separating the component, and is not sufficiently involved in crosslinking in the polyethylene resin composition. In the present embodiment, in the CFC measurement, since the ratio of the total amount of components eluted at 95 ° C. or less to the total amount eluted is 90% or more, the flexibility of the polyethylene resin composition can be improved. Specifically, although the reason is not clear, among the xylene-soluble components in the polyethylene-based resin composition, the components that elute above 95 ° C. in the CFC measurement are relatively crystalline and have a high molecular weight. Since it is a component with high rigidity, it is estimated that the ratio of the total amount of components eluted at 95 ° C. or less in CFC measurement affects the flexibility of the polyethylene resin composition. In this embodiment, the total amount of components eluted at 95 ° C. or lower in the CFC measurement is within a predetermined range, so that the component having a high molecular weight while having relatively crystallinity is reduced, and the polyethylene resin composition It is presumed that flexibility can be improved.

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

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

  In the polyethylene resin composition, in the CFC measurement, when the ratio of the total amount of components eluted at 80 ° C. or less to the total elution amount is more than 30%, the polyethylene resin composition contains many low molecular weight components. . Therefore, when a polyethylene-based resin composition is molded into a pipe and used for floor heating, for example, if the pipe is continuously used for a long period of time, the low molecular weight substance gradually elutes in the warm water in the pipe, When the viscosity rises or when the hot water cools, these low molecular weight components are deposited in the pump and adhere to it, which places a load on the circulating pump. In the polyethylene resin composition of the present embodiment, the ratio of the total amount of components eluted at 80 ° C. or less to the total elution amount is 30% or less in the CFC measurement, so that the low molecular weight material eluted in the warm water in the pipe This can contribute to energy saving.

  In the measurement using the CFC of the xylene-dissolved component in the gel fraction measurement, the ratio of the total amount of components eluting at 80 ° C. or less to the total elution amount and the proportion of the total amount of components eluting at 95 ° C. or less to the total elution amount are Although not particularly limited, it can be controlled by the catalyst used, the slurry concentration when the ethylene polymer is polymerized by slurry polymerization, or the cooling method after melt-kneading the polyethylene resin composition before crosslinking. Specifically, by using a supported metallocene catalyst during the polymerization of the ethylene polymer, the ratio of the total amount of components eluting at 80 ° C. or less to the total elution amount is reduced, and at 95 ° C. or less with respect to the total elution amount. The proportion of the total amount of components to be eluted can be increased. Moreover, the ratio of the total amount of the component eluted at 80 degrees C or less with respect to the total amount of elution can be reduced by making the slurry density | concentration at the time of superposition | polymerization of an ethylene polymer low. In addition, cooling after melt-kneading and molding the polyethylene-based resin composition before crosslinking is gently brought into contact with, for example, 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 performing, the ratio of the total amount of the components eluted at 95 ° C. or less with respect to the total amount of elution can be increased. In addition, the xylene-dissolved component in the gel fraction measurement is the xylene solution obtained by removing the remaining amount of the polyethylene resin composition in the gel fraction measurement. It can be obtained by filtration and separation.

  Here, the “cross fractionation chromatography” is an apparatus that combines a temperature-rise elution fractionating unit (hereinafter also referred to as “TREF unit”) for performing crystalline fractionation and a GPC unit for performing molecular weight fractionation. By directly connecting the part and the GPC part, it is an apparatus capable of analyzing the mutual relationship between the composition distribution and the molecular weight distribution. Note that the measurement at the TREF section may be referred to as the measurement at the CFC.

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

  The elution amount and integrated elution amount at each temperature of the xylene-soluble component in the polyethylene resin composition can be determined by measuring the elution temperature-elution amount curve as follows using a TREF part. The temperature profile of the column is as follows. First, the column containing the packing material is heated to 140 ° C., and a sample solution (for example, concentration: 16 mg / 8 mL) in which xylene-dissolved components are dissolved is introduced and held for 120 minutes. .

  Next, after the temperature is lowered to 40 ° C. at a temperature lowering rate of 0.5 ° C./min, the sample is held for 20 minutes to precipitate the sample on the surface of the filler. Thereafter, the column temperature is sequentially raised at a rate of temperature rise of 20 ° C./min. From 40 ° C to 80 ° C, the temperature is increased at 10 ° C intervals, from 80 ° C to 85 ° C, the temperature is increased at 5 ° C intervals, from 85 ° C to 90 ° C, the temperature is increased at 3 ° C intervals, and from 90 ° C to 100 ° C The temperature is increased at intervals of 1 ° C., and the temperature is increased at intervals of 10 ° C. from 100 ° C. to 120 ° C. The temperature is raised after holding at each temperature for 20 minutes, and the concentration of the sample eluted at each temperature is detected. And the elution temperature-elution amount curve is measured from the value of the elution amount (mass%) of the sample and the temperature in the column (° C.) at that time, and the elution amount and elution integration amount at each temperature are obtained. More specifically, it can be measured by the method described in the examples.

-Antioxidant-
Although it does not specifically limit in the polyethylene-type resin composition of this embodiment, At least 1 type of phenolic antioxidant and at least 1 type of phosphorus antioxidant are contained. By containing these antioxidants, it is possible to suppress deterioration of the resin during processing after molding, and therefore, it is possible to have sufficient durability to withstand use over a long period of time.

  Although it does not specifically limit as a phenol-type antioxidant, For example, dibutylhydroxytoluene, pentaeryristyl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and the like.

Although content of a phenolic antioxidant is not specifically limited, 0.05 mass% or more and 3.0 mass% or less are preferable with respect to a polyethylene-type resin composition, More preferably, 0.1 mass% or more 1. 0% by mass or less.
A phenol antioxidant and the phosphorus antioxidant mentioned later can be contained in the polyethylene resin composition of this embodiment by making it contain in the polyethylene resin composition before bridge | crosslinking.

  Phosphorus antioxidants include tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene-di-phosphonite, tris (2,4-di-t-butylphenyl) phosphite, Click neopentanetetraylbis (2,4-t-butylphenyl phosphite) and the like.

  Although content of a phosphorus antioxidant is not specifically limited, 50 ppm or more and 3000 ppm or less are preferable with respect to a polyethylene-type resin composition, More preferably, they are 100 ppm or more and 2000 ppm or less.

-Tin element-
The polyethylene resin composition of the present embodiment can contain a tin element, and the content thereof is preferably 5 to 500 ppm by mass in the polyethylene resin composition. Further, the content of 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, there is a tendency that the crosslinking is not sufficiently progressed in the polyethylene resin composition, and if it exceeds 500 ppm, in the extruder during the extrusion of the polyethylene resin composition before crosslinking. There exists a tendency for a tin element to exist locally, and when a tin element exists locally, bridge | crosslinking will advance locally and an external appearance will deteriorate.
In addition, a tin element can be mainly derived from the silanol condensation catalyst used in order to obtain the silane crosslinked polyethylene in a polyethylene-type resin composition.

[[Production method of polyethylene resin composition]]
The polyethylene-based resin composition of the present embodiment is obtained by subjecting a grafted polyethylene, which is a silane-modified ethylene-based polymer, to a grafted polyethylene before or after crosslinking by obtaining a silanol condensation catalyst after the grafted polyethylene is obtained. After the polyethylene resin composition is molded, the polyethylene resin composition before cross-linking can be cross-linked in the presence of water or water vapor.

  More specifically, the polyethylene resin composition of the present embodiment is formed by melting and kneading a silanol condensation catalyst together with a grafted polyethylene which is a silane-modified ethylene polymer, or an ethylene polymer and a silanol. A master batch obtained by melt-kneading the condensation catalyst is melt-kneaded and molded (a polyethylene-based resin composition before crosslinking is obtained), and then the molded body (polyethylene-based resin composition before crosslinking) is water (preferably Hot water) or water vapor. A polyethylene-based resin composition (after crosslinking) containing silane-crosslinked polyethylene in which the silyl group of the entire molded body is crosslinked by exposing the molded body (polyethylene resin composition before crosslinking) to water (preferably warm water) or water vapor. Obtainable.

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

  The polyethylene resin composition before cross-linking can contain various additives including the above-mentioned phenolic antioxidants and phosphorus antioxidants, and these additives are used when obtaining grafted polyethylene. Or when the ethylene polymer and silanol condensation catalyst are melt-kneaded to obtain a masterbatch, or the grafted polyethylene and silanol condensation catalyst are melt-kneaded or the grafted polyethylene and masterbatch are melt-kneaded. And can be contained when obtaining a polyethylene resin composition before cross-linking. Among the various additives, the phenolic antioxidant and the phosphorus antioxidant are preferably not contained when obtaining the grafted polyethylene. More specifically, the ethylene polymer and the silanol condensation catalyst are kneaded. To be included when obtaining a master batch, or when melt-kneading grafted polyethylene and silanol condensation catalyst or melt-kneading grafted polyethylene and master batch to obtain a polyethylene resin composition before crosslinking. It is preferable to let them.

  The grafted polyethylene is an ethylene polymer, an organic peroxide of 0.01 parts by weight or more and 5.0 parts by weight or less, and 0.1 parts by weight or more with respect to 100 parts by weight of the ethylene polymer. It can be produced by melting and kneading an organic unsaturated silane compound of 20 parts by mass or less with an extruder so that the organic peroxide is decomposed into radicals and grafting the organic unsaturated silane compound onto an ethylene polymer. .

  The organic peroxide is not particularly limited. For example, 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-tert-butyl peroxide, lauroyl peroxide, di-tert-butyl peroxyisophthalate, and in the molecule The compound which has a double bond group and a peroxide group is mentioned. Of these, dicumyl peroxide is economical and preferred.

  The organic unsaturated silane compound is not limited as long as it can be crosslinked with silane, and examples thereof include vinyltrimethyoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, vinylmethyldimethoxysilane, and vinyltris. (Β-methoxyethoxy) silane is mentioned. Such an organic unsaturated silane compound can react with a radical in an ethylene polymer generated by the action of an organic peroxide and can be grafted to the ethylene polymer.

The ethylene polymer is not particularly limited, but is preferably a copolymer of ethylene and an α-olefin copolymerizable with ethylene. Although it does not specifically limit as the said alpha olefin, For example, a C3-C20 alpha olefin is mentioned. The α-olefin can be represented by H ₂ C═CHR, where R is a linear or branched aliphatic hydrocarbon group having 1 to 18 carbon atoms, an alicyclic hydrocarbon group, or aromatic. A hydrocarbon group is shown.

  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, specific examples of the α-olefin are not particularly limited, and examples thereof include vinylcyclohexane, styrene, and derivatives thereof. Furthermore, the α-olefin may have a non-conjugated unsaturated bond, and the α-olefin is not particularly limited, but examples thereof include non-conjugated polyenes such as 1,5-hexadiene and 1,7-octadiene. It can also be used.

  Although it does not specifically limit as an alpha olefin, A propylene and 1-butene are preferable from a viewpoint that the tertiary carbon with which the organic unsaturated silane compound which is a crosslinking agent reacts easily increases. The copolymer may be a ternary random polymer. As a comonomer contained in a copolymer, 1 type may be used individually and 2 or more types may be used together.

  The ethylene polymer preferably has an MFR of 0.1 g / 10 min to 10.0 g / 10 min, more preferably 0.5 g / 10 min to 5.0 g / 10 min, and even more 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 body becomes smooth. In addition, since the resin pressure during melt molding and shear heat generation can be reduced, it is possible to suppress resin degradation during molding and the like, and it is difficult for resin to decompose in the extruder, so smoke is generated during processing. Less likely to occur. On the other hand, when the MFR is 10.0 g / 10 min or less, the molded article is excellent in durability.

  The MFR of the ethylene polymer can be controlled by the temperature during polymerization, the amount of hydrogen to be added, and the like. Specifically, the MFR of the ethylene polymer can be controlled to increase by increasing the temperature during polymerization or increasing the amount of hydrogenation. The MFR can be measured by the method described in the examples.

  The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) in the GPC measurement of the ethylene polymer is preferably 3.0 or more and 10.0 or less. More preferably, it is 3.0 or more and 7.0 or less, More preferably, it is 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 polymer can be controlled by the catalyst used during production, the residence time in the reactor during polymerization, and the like. Moreover, the said molecular weight distribution can be measured by the method as described in an Example.

  In the polyethylene resin composition before crosslinking, the content of the silanol condensation catalyst is preferably 50 ppm by mass or more and 1000 ppm by mass or less, more preferably 100 ppm by mass or more and 700 ppm or less with respect to 100 parts by mass of the ethylene polymer. The mass is not more than ppm, and more preferably not less than 100 ppm and not more than 500 ppm by mass. By setting the content of the silanol condensation catalyst to 50 mass ppm or more, the crosslinking reaction can sufficiently proceed, and by setting the content to 1000 mass ppm or less, the polyethylene resin composition before crosslinking is extruded. It is possible to prevent the catalyst from being locally present in the extruder. If the catalyst is present locally, the cross-linking proceeds locally and the appearance deteriorates.

  The silanol condensation catalyst is not particularly limited, but dibutyltin dilaurate, dibutyltin dioctoate, dibutyltin acetate, dibutyltin diacetate, dibutyltin maleate, dibutyltin phthalate, dibutyltin bis (2-ethylhexanoe ), Dibutyltin bis (one decyl maleate), dibutyltin bis (benzyl malee), dibutyltin dimethoxide, dibutyltin bis (nonylphenoxide), dibutyltin oxide, dibutyltin bis (acetylacetonate), dibutyltin Bis (ethylacetate acetate), reaction product of dibutyltin oxide and silicate compound, reaction product of dibutyltin oxide and phthalate ester, tributyltin dilaurate (TBTDL), dioctyltin diacetate, dioctyltin dilaurate Dioctyltin-bis (isooctyl maleate), dioctyltin-bis (isooctylthioglycolate), dioctyltin maleate, dioctyltin bis (ethyl maleate), dioctyltin dineodecanoate, dioctyltin oxide , Stannous acetate, stannous octoate, tin naphthenate, tin (II) stearate, tin (II) octate, tin dineodecanoate, stannous cabrylate, tin bisneodecanoate, bis (2-ethylhexane Acid) tin, tin (II) 2,4-pentanedionate, acetylacetonate tin (II) and the like, and dioctyltin dilaurate is particularly preferable.

  In addition to the above, the polyethylene resin composition before cross-linking includes known organic thioether stabilizers, stabilizers such as metal salts of higher fatty acids: lubricants such as pigments, weathering agents, dyes, nucleating agents, calcium stearate; Additives added to polyolefin such as carbon black, talc, glass fiber and other inorganic fillers or reinforcing materials, flame retardants, and neutron blocking agents can be added as long as the object of the present invention is not impaired. Further, an adsorbent such as activated carbon may be added to suppress elution of unreacted organic unsaturated silane compound, silanol condensation catalyst, and organic peroxide from the polyethylene resin composition (molded product after crosslinking). .

  The polyethylene resin composition before cross-linking preferably contains at least 90% by mass of the ethylene polymer in the polyethylene resin composition before cross-linking, more preferably at least 92% by mass, more preferably It is at least 94% by mass. The upper limit of the content of the ethylene polymer in the polyethylene resin composition before cross-linking is less than 100% by mass, but the polyethylene type before cross-linking depends on the physical properties required for the polyethylene resin composition after cross-linking. Content of said antioxidant contained in a resin composition, a catalyst, etc. fluctuate | variate, and the said upper limit differs also by it. The content of the ethylene polymer in the polyethylene resin composition before crosslinking means the content of components derived from the ethylene polymer in the polyethylene resin composition after crosslinking.

[[[Method for producing ethylene polymer]]]
The method for producing an ethylene polymer has a polymerization step of polymerizing at least ethylene and the above 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 support material, an organoaluminum 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 cocatalyst, at least ethylene and the above α-olefin can be polymerized to produce an ethylene polymer.

  When the supported metallocene catalyst is used as the catalyst for the ethylene polymer production method, other metallocene catalysts, Ziegler-Natta catalysts, Phillips catalysts and the like can be used together. By using the supported metallocene catalyst, low molecular weight components in the ethylene polymer can be reduced. Although it does not specifically limit as a metallocene catalyst, For example, the thing of Unexamined-Japanese-Patent No. 2006-273777 can be used conveniently.

  The supported metallocene catalyst can be prepared and prepared from at least a support material, an organoaluminum compound, a borate compound having active hydrogen, a cyclopentadiene compound, and a group IV transition metal compound.

  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 resulting polymer particles tend to be prevented from scattering and adhering. Further, when the average particle diameter is 20 μm or less, the carrier substance remaining in the ethylene polymer tends to suppress a decrease in the smoothness of the crosslinked body surface. In addition, when polyethylene is extruded, the carrier substance remaining in the polyethylene tends to be clogged in the filter of the extruder, thereby increasing the pressure and suppressing a decrease in smoothness of the surface of the crosslinked body. The particle size distribution of the carrier material is preferably as narrow as possible, and the particle size distribution can be adjusted by removing fine particles and coarse particles by sieving, centrifugation, or cyclone.

  The compressive strength of the carrier material 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 still more preferably 2.0 MPa or more and less than 6.0 MPa. When the compressive strength is 1.0 MPa or more, the catalyst particles are crushed and reduced when the catalyst is synthesized or fed, and the resulting polymer particles tend to be prevented from scattering and adhering. When the compressive strength is less than 10 MPa, the carrier material is not crushed during the polymerization, and the probability that it remains in the ethylene-based polymer increases, and the problem that the smoothness of the cross-linked body surface is hindered tends to be suppressed. is there.

  Further, the obtained supported metallocene catalyst may be washed by a method such as decantation or filtration using an inert solvent for the purpose of removing organoaluminum compounds, borate compounds, etc. not supported on the carrier. it can. When producing an ethylene-based polymer, it is preferable to carry out decantation and / or filtration once or more in order to reduce low molecular weight components produced by side reactions.

  Furthermore, the chlorine content in the catalyst is preferably 50 ppm by mass or less, more preferably 20 ppm by mass or less, still more preferably 5.0 ppm by mass or less, and the lower the content, the more preferable.

  The liquid promoter is a liquid promoter and a substance that increases the activity of the supported metallocene catalyst. Although it does not specifically limit as a liquid co-catalyst, For example, it can prepare from an organomagnesium compound and methyl hydropolysiloxane.

  Moreover, 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 prepared from trichlorosilane, organomagnesium, n-butyl alcohol, organoaluminum, and titanium tetrachloride.

  When preparing a Ziegler-Natta catalyst, when reacting a silane compound such as trichlorosilane with organomagnesium, the organomagnesium (eg, n-heptane solvent) is slowly added over 1 hour, preferably over 2 hours. It is preferable to add. Further, when adjusting the Ziegler-Natta catalyst, by-products and unreacted substances are mixed in the solvent after completion of the reaction, it is preferable to perform a washing operation three or more times after the reaction. Similarly, it is preferable to perform washing once or more after each reaction with an alcohol such as n-butyl alcohol, a compound containing titanium such as organic aluminum or titanium tetrachloride.

  The chlorine content in the 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 (co) It can be polymerized. Among these, the slurry polymerization method that can efficiently remove the 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, but examples thereof include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane, hexane, heptane, octane, decane, dodecane, and kerosene; cyclopentane, cyclohexane, methylcyclo Examples thereof include alicyclic hydrocarbons such as pentane; aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as ethyl chloride, chlorobenzene and dichloromethane, and mixtures thereof.

  In the polymerization step, among the above-described inert hydrocarbon media, it is more preferable to use a hydrocarbon media having 6 to 10 carbon atoms. When the number of carbon atoms is 6 or more, the low molecular weight component that reacts with the crosslinking agent to reduce pressure resistance and durability is relatively easily dissolved, and the ethylene polymer is separated in the process of separating the ethylene polymer and the polymerization medium. It tends to be easily removed from. When the number of carbon atoms is 10 or less, the low molecular weight component (medium) remaining in the ethylene-based polymer is reduced, adhesion of polyethylene powder to the reaction vessel is suppressed, and industrially stable operation is achieved. It tends to be possible.

  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 further 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, the stable operation tends to be continuously possible.

  The polymerization pressure in the polymerization step is preferably from normal pressure to 2 MPa, more preferably from 0.1 MPa to 1.5 MPa, and even more preferably from 0.3 MPa to 1.2 MPa.

  The slurry concentration in the polymerization step is preferably 40% or less, more preferably 35% or less. A higher slurry concentration enables industrially efficient production, but the lower limit of the slurry concentration in producing the ethylene polymer for obtaining the polyethylene resin composition of the present embodiment is particularly Absent. 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. A polyethylene resin composition (after crosslinking) produced using an ethylene 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 performed by any of batch, semi-continuous and continuous methods, and it is preferable to perform polymerization in a continuous manner. The continuous system continuously supplies ethylene gas, solvent, catalyst, etc. into the polymerization system and continuously discharges it together with the generated ethylene polymer to suppress partial high-temperature conditions due to rapid ethylene reaction. And the inside of the polymerization system becomes more stable. 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. Thereby, it becomes easy to obtain an ethylene-based polymer having high crosslinking efficiency, and the gel fraction tends to be increased. Therefore, a continuous system in which the inside of the polymerization system becomes more uniform is preferable.

  The molecular weight of the ethylene polymer is not particularly limited, but is adjusted by the presence of hydrogen in the polymerization system, changing the polymerization temperature, etc., as described in the specification of German 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 molar 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.

  Furthermore, it is preferable that hydrogen is added to the polymerization system from the catalyst introduction line after contacting with the catalyst in advance. Immediately after the catalyst is introduced into the polymerization system, the concentration of the catalyst near the outlet of the introduction line is high, and there is an increased possibility of partial high temperatures due to the rapid reaction of ethylene. By bringing into contact before introduction, it is possible to suppress the initial activity of the catalyst, and it is possible to suppress the generation of low molecular weight components. Therefore, it is preferable to introduce hydrogen into the polymerization system in contact with the catalyst.

  After the polymerization step, wet nitrogen is preferably fed into the liquid to a 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 reduce the production of low molecular weight components, low melting point polyethylene, etc. it can.

  The solvent separation method in the method for producing an ethylene polymer can be performed by a decantation method, a centrifugal separation method, a filter filtration method, or the like, but a centrifugal separation method with good separation efficiency between the ethylene polymer and the solvent is more preferable. The amount of the solvent contained in the ethylene polymer after the solvent separation is not particularly limited, but is 70% by mass or less, more preferably 60% by mass or less with respect to the mass (100% by mass) of the ethylene polymer. More preferably, it is 50 mass% or less. By removing the solvent by drying in a state where the amount of the solvent contained in the ethylene polymer is small, metal components and low molecular weight components contained in the solvent tend not to remain in the ethylene polymer. When these components do not remain, an ethylene polymer having excellent hygiene and high crosslinking efficiency is obtained, and a polyethylene resin composition (after crosslinking) having excellent pressure resistance and durability is 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, drying tends to be possible in a state where decomposition of the ethylene-based polymer is suppressed.
Thereafter, 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 a covering material used for tubular bodies such as pipes, hoses and tubes, conductors such as electric wires and cables, various containers, sealing materials, films, porous films, and It can be used for various applications such as sheets. The polyethylene resin composition is preferably a tubular body, more preferably a pipe. The shape of the polyethylene-based resin composition (after crosslinking) for these uses is not particularly limited, but the molded product before the polyethylene-based resin composition (after crosslinking) (polyethylene-based before crosslinking) (Resin composition) may be formed into a desired shape, or may be molded into a desired shape (for example, cutting) after forming a polyethylene resin composition (after crosslinking).

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

(Evaluation 1: Gel fraction of polyethylene resin composition)
The gel fraction of each polyethylene-based resin composition (crosslinked product) obtained in Examples and Comparative Examples is JIS K 6787-1997 Crosslinked polyethylene pipe for water supply Annex 7 (normative) Gel fraction of crosslinked polyethylene pipe for water supply It measured by the following method according to the test method. Tables 1 and 2 show the results obtained from the crosslinked products of the examples and comparative examples.

Next, a specific method for measuring the gel fraction of the crosslinked body will be described.
(I) An aluminum or stainless steel cage having a mesh with a hole diameter of 125 μm ± 25 μm was prepared. (The weight of the car is “m1”.)
(Ii) A sample sliced or scraped to a thickness of 0.1 mm to 0.2 mm was weighed from 0.5 g to 1.0 g and placed in the basket. (The weight of the basket including the sample is “m2”.)
(Iii) The basket containing the sample was placed in the flask, and after adding a sufficient amount of xylene that could be reliably immersed, the solvent was vigorously boiled for 8 hours ± 5 minutes.
(Iv) The sample residue and the basket were carefully removed from the boiling solvent, and the outside of the basket was wiped off with a cloth.
(V) The cage 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. and at a negative pressure of at least 0.85 Bar (85 KPa) (ie, absolute pressure of about 0.15 bar or less).
b) At 140 ° C ± 2 ° C in a forced ventilation oven with appropriate exhaust.
(Vi) Cooled sufficiently and the residue was taken out. (The weight of the basket including the residue is “m3”.)
(Vii) The degree of crosslinking for each sample was calculated as a percentage of the mass of insoluble matter;
(Viii) G1 = (m3−m1) / (m2−m1) × 100
Results are expressed as the closest integer.
(Ix) The above operations (i) to (vii) were repeated at least once with a new sample.
(X) The average crosslinking degree G was calculated 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 again.

(Physical property 2: CFC of polyethylene resin composition)
About the polyethylene-type resin composition obtained by the Example and the comparative example, the solution (xylene soluble component) after performing the process (vi) of the measuring method of said "gel fraction of a polyethylene-type resin composition" is 25. After cooling to 0 ° C., the precipitate was collected by filtration. Furthermore, about what dried this in 23 degreeC air for 10 hours, the elution temperature-elution amount curve by a temperature rising elution fractionation (TREF) was measured as follows, and the elution amount in each temperature, and elution integration amount were calculated | required. Asked. First, the column containing the filler was heated to 140 ° C., and a sample solution in which xylene-dissolved components were dissolved in orthodichlorobenzene was introduced and held for 120 minutes.

Next, after the temperature was lowered to 40 ° C. at a temperature lowering rate of 0.5 ° C./min, the temperature was kept for 20 minutes to deposit the sample on the surface of the filler. Thereafter, the column temperature was sequentially raised at a rate of temperature rise of 20 ° C./min. From 40 ° C to 80 ° C, the temperature is increased at 10 ° C intervals, from 80 ° C to 85 ° C, the temperature is increased at 5 ° C intervals, from 85 ° C to 90 ° C, the temperature is increased at 3 ° C intervals, and from 90 ° C to 100 ° C Until 100 ° C. to 120 ° C., the temperature was increased at 10 ° C. intervals. The temperature was raised after holding at each temperature for 20 minutes, and the concentration of the sample eluted at each temperature was detected. And the elution temperature-elution amount curve was measured from the value of the elution amount (mass%) of the sample and the temperature in the column (° C.) at that time, and the elution amount and elution integration amount at each temperature were obtained.
-Apparatus: Automated 3D analyzer CFC-2 manufactured by Polymer ChAR
Column: Stainless steel microball column (3/8 "o.d x 150mm)
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: Infrared spectrophotometer IR4 manufactured by Polymer ChAR
Detection wave number: 3.42 μm
Sample dissolution conditions: 140 ° C x 120 min dissolution

(Physical property 3: MFR of ethylene polymer)
About each ethylene-type polymer obtained by the Example and the comparative example, it is JIS K7210.
The melt flow rate was measured by code D: 1999 (temperature = 190 ° C., load = 2.16 kg). Tables 1 and 2 show the results obtained from the ethylene polymers of the examples and comparative examples.

(Physical property 4: Weight average molecular weight and number average molecular weight of ethylene-based polymer and ratio thereof)
A sample solution was prepared by introducing 15 mL of o-dichlorobenzene into 20 mg of each ethylene polymer obtained in Examples and Comparative Examples, and stirring at 150 ° C. for 1 hour, and gel permeation chromatography (GPC). Measurements were made. From the measurement results, a weight average molecular weight (Mw), a number average molecular weight (Mn), and a ratio thereof (Mw / Mn) were determined based on a calibration curve (primary approximation) created using commercially available monodisperse polystyrene. In addition, the molecular weight in this 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.

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

The following evaluation was performed about the polyethylene-type resin composition obtained by the Example and the comparative example.
(Evaluation 1: Oxidation induction time)
The oxidation induction time of the polyethylene resin compositions obtained in Examples and Comparative Examples is measured using a differential scanning calorimeter (DSC). DSC-60 Plus (manufactured by Shimadzu Corporation) was used for the measurement. First, 5 mg of aluminum oxide was put into an aluminum pan for DSC measurement. This was set on the left side of the DSC-60 Plus furnace, and an aluminum pan containing 5 mg of a 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 at 25 mL / min in the furnace, and the measurement was started after standing for 1 minute in that state. The heating rate was 25 ° C./min. The sampling interval during measurement was set to 0.5 seconds. After 1 minute, the 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, the chart rises, passes through the inflection point before passing the first peak, and at that inflection point The oxidation induction time was measured by calculating the time of intersection with a straight line having the slope of the chart. Tables 1 and 2 show the results obtained from the crosslinked products of the examples and comparative examples.
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 body)
The molded body of the polyethylene-type resin composition obtained by the Example and the comparative example was confirmed visually, and the external appearance was evaluated by the following reference | standard. The results obtained from the samples of each Example and Comparative Example are shown in Tables 1 and 2.
◯: Good with no irregularities due to gel or the like on the outer surface of the molded body.
Δ: There are irregularities due to gel-like materials on the outer surface of the molded body, but only a small part of the surface of the molded body and the influence on the overall appearance is slight.
X: There are many irregularities due to gels and the like on the outer surface of the molded body.

(Evaluation 3: Energy saving)
10 g of the polyethylene resin composition obtained in Examples and Comparative Examples molded to a thickness of 1 mm and 10 g of distilled water were sealed in a container, and the polyethylene resin composition and water were sufficient for 5 hours at 90 ° C. After being vibrated with a shaker so as to come into contact with this, the viscosity of this water at 90 ° C. was measured according to JIS Z8830. This evaluation is for evaluating the load of a circulation pump or the like due to an increase in viscosity of hot water in contact with a pipe when the polyethylene resin composition of the present application is used for a hot water pipe for floor heating. If the viscosity of 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 shape: 21.5 mm, inner diameter: 16.2 mm) and pipe 2 (length: 900 mm, outer shape: 34.0 mm, inner diameter: 26.0 mm) of polyethylene resin compositions obtained in the examples and comparative examples The pipe was wound around a tubular cylinder (mandrel) having a diameter of 300 mm without any 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.
A: Pipe 1 and pipe 2 could be wound without buckling.
Δ: Only the pipe 1 could be wound without buckling.
X: Both the pipe 1 and the pipe 2 were buckled and could not be wound.

(Preparation of polymerization catalyst)
(Saturated adsorption amount of Lewis acidic compound with respect to precursor of support [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). The 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. Under a nitrogen atmosphere, 4 g of spherical silica after the heat treatment was added to a 0.2 L glass container, and 80 mL of hexane was added and dispersed to obtain a silica slurry. To the obtained silica slurry, 10 mL of a hexane solution of triethylaluminum (concentration 1 mol / L) was added at 20 ° C. with stirring, and then 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 on the spherical silica was 2.1 mmol / g.

(Preparation of carrier [C])
The spherical silica (40 g) after heat treatment was dispersed in 800 mL of hexane in a 1.8 L autoclave purged with nitrogen to obtain a slurry. While maintaining the resulting slurry at 20 ° C. with stirring, 80 mL of a hexane solution of triethylaluminum (concentration 1M) was added, and then stirred for 2 hours to prepare 880 mL of a hexane slurry of carrier [C] adsorbing triethylaluminum.

(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”) Prepared. Furthermore, a composition formula AlMg ₆ (C ₂ H ₅ ) ₃ (C ₄ H ₉ ) ₁₂ (hereinafter abbreviated as “Mg1”) was prepared as the organomagnesium compound (D-2). The Mg1 was synthesized by mixing a predetermined amount of triethylaluminum and dibutylmagnesium at 25 ° C. in hexane. Dissolve 200 mmol of titanium complex in 1000 mL of Isopar (registered trademark) E (manufactured by ExxonMobil Chemical), add 20 mL of hexane solution of Mg1 (concentration 1M), and further add hexane to adjust the concentration of titanium complex to 0.1M, transition Metal compound [D] was obtained.

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

(Preparation of metallocene supported catalyst [A])
50 mL of the activator [E] obtained by the above operation was added to 880 mL of the slurry of the support [C] obtained by the above operation 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 supernatant of this slurry was removed, and a purification operation in which hexane was added and stirred was carried out three times, and a metallocene supported catalyst [A] having a chlorine content of 1 mass ppm or less (in Table 1, simply [A ] Was prepared.

(Preparation of liquid promoter [B])
The Mg1 was prepared as the organomagnesium compound [G]. As compound [J], methylhydropolysiloxane (viscosity at 25 ° C., 20 centistokes, manufactured by Shin-Etsu Silicon Co., Ltd.) was used. To a 200 mL flask, 40 mL of hexane and Mg1 were added with stirring so that the total amount of Mg and Al was 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 the reaction was allowed to proceed with stirring for 3 hours to prepare a liquid promoter 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 15 L reactor sufficiently purged with nitrogen, maintained at 50 ° C. with stirring, and the composition formula AlMg ₆ (C ₂ H ₅ ) ₃ ( _{NC 4} H ₉ ) _10.8 (On-C ₄ H ₉ ) 7 L (5 mol in terms of magnesium) of an organomagnesium component represented by _1.2 was added over 3 hours, and further The reaction was allowed to stir at 50 ° C. for 1 hour. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the resulting solid was washed 4 times with 7 L of n-hexane to obtain a slurry. As a result of separating, drying and analyzing this solid, it contained Mg: 8.62 mmol, Cl: 17.1 mmol, and n-butoxy group (On-C ₄ H ₉ ): 0.84 mmol per gram of the solid. It was.

  The slurry containing 500 g of the solid obtained as described above was reacted with 1250 mL of n-butyl alcohol 1 mol / L n-hexane solution 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 resulting solid was washed once with 7 L of n-hexane to obtain a slurry. The slurry was kept at 50 ° C., and 500 mL of an n-hexane solution of 1 mol / L of diethylaluminum chloride was added with stirring and reacted for 1 hour. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the resulting solid was washed twice with 7 L of n-hexane to obtain a slurry. This slurry was kept at 50 ° C., 78 mL of n-hexane solution of 1 mol / L of diethylaluminum chloride and 78 mL of n-hexane solution of 1 mol / L of titanium tetrachloride were added and reacted for 1 hour. Furthermore, 234 mL of n-hexane solution of 1 mol / L of diethylaluminum chloride and 234 mL of n-hexane solution of 1 mol / L of titanium tetrachloride were added to this reaction solution, and reacted for 2 hours. After completion of the reaction, the supernatant was removed from the reaction solution containing the solid, and the inner temperature was kept at 50 ° C., followed by washing 4 times with 7 L of n-hexane, and the Ziegler catalyst [H], which is a solid catalyst (Table 1). (Indicated simply 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 Bessel type 340L polymerization reactor equipped with a stirrer, continuous polymerization was carried out under 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, 50 mg / hour of the supported metallocene catalyst [A] as a catalyst, 4 mmol / hour of liquid promoter [B] in terms of Al atom, Polymerization was carried out by supplying 0.25 mol% of butene and 0.37 mol% of hydrogen, respectively, so that the slurry concentration was 35%. Hydrogen was reacted with the supported metallocene catalyst [A] and then introduced into the reactor. The polymerization slurry in the polymerization reactor was led 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 polymerization slurry in the polymerization reactor was continuously sent to a centrifuge to separate the polymer from the other solvent and obtain polyethylene powder. The separated polyethylene powder was dried by hot nitrogen blowing.

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

(Method for producing silane-grafted polyethylene)
100 parts by mass of the ethylene-based polymer is blended with 5.0 parts by mass of vinyltrimethoxysilane and 0.15 parts by mass of perhexa 25B (manufactured by NOF Corporation) as an organic peroxide. The silane-grafted polyethylene was obtained by adjusting the resin temperature to about 200 ° C. using a twin screw extruder (TEX-28) manufactured by Nippon Steel, Ltd., and performing extrusion compounding and pelletizing.

(Manufacturing method of silanol condensation catalyst-containing resin composition)
Further, with respect to 100 parts by mass of the ethylene polymer, 1.7 parts by mass of dioctyltin dilaurate as a silanol condensation catalyst, 4.1 parts by mass of Irganox 1010 (manufactured by BASF) as a phenolic antioxidant, Irganox 1330 (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, Irganox MD1024 (manufactured by BASF) 5.2 parts by mass Parts, Dynamer FX9613 (manufactured by 3M), 3.4 parts by mass, respectively, mixed with a Henschel mixer, adjusted to a resin temperature of about 200 ° C. using TEX-28, melt kneaded and pelletized. , Obtain a master batch of silanol condensation catalyst-containing resin composition It was.

(Method for producing polyethylene resin composition)
To 100 parts by mass of the above-mentioned silane-grafted polyethylene, 5.0 parts by mass of the above master batch are uniformly mixed using a Henschel mixer, melt-kneaded, and then cooled with 20 ° C. water to form a molded product (two types) Of pipe). The molded body (pipe) was immersed in warm water at 100 ° C. for 12 hours to obtain a polyethylene-based resin composition containing silane-crosslinked polyethylene. The polyethylene-based resin composition (crosslinked pipe) had a pipe 1 having an outer diameter of 21.5 mm and an inner diameter of 16.2 mm, and the pipe 2 having an outer diameter of 34.0 mm and an inner diameter of 26.0 mm.

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

Example 3
As a method for producing an ethylene polymer, a polyethylene resin composition was obtained in the same manner as in Example 1 except that the slurry concentration was 45%.

Example 4
As a method for producing a polyethylene resin composition, a polyethylene resin composition was obtained in the same manner as in Example 1 except that 1.7 parts by mass of dioctyltin dilaurate was used.

Example 5
As a method for producing the ethylene polymer, a polyethylene resin composition was obtained in the same manner as in Example 1 except that the polymerization temperature was 65 ° C. and the hydrogen was 0 mol%.

Example 6
As a method for producing a polyethylene resin composition, a polyethylene resin composition was obtained in the same manner as in Example 1 except that the polyethylene resin composition before crosslinking was melt-kneaded and cooled with water at 10 ° C.

Example 7
A method for producing an ethylene polymer was carried out 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 gas phase concentration of ethylene to obtain a polyethylene resin composition. It was.

Example 8
As a method for producing a polyethylene resin composition, a polyethylene resin composition was obtained in the same manner as in Example 7 except that dioctyltin dilaurate was changed to 1.2 parts by mass.

Example 9
As a method for producing the ethylene polymer, a polyethylene resin composition was obtained in the same manner as in Example 8 except that the slurry concentration was 45%.

Example 10
A polyethylene resin composition was obtained in the same manner as in Example 8 except that the polyethylene resin composition before crosslinking was melt-kneaded and cooled with water at 10 ° C. as a method for producing the polyethylene resin composition.

Example 11
The production method of the silanol condensation catalyst-containing resin composition was carried out in the same manner as in Example 1 except that dioctyltin dilaurate was changed to 9.8 parts by mass to obtain a polyethylene resin composition.

[Comparative Example 1]
As a method for producing the silanol condensation catalyst-containing resin composition, a polyethylene 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, a polyethylene resin composition was obtained in the same manner as in Example 1 except that Irgafos 168 as a phosphorus heat stabilizer was not used.

[Comparative Example 3]
As a method for producing an ethylene polymer, the slurry concentration is 50% and the average residence time is 5 hours. As a method for producing a polyethylene resin composition, the polyethylene resin composition before crosslinking is melted and kneaded and then cooled with water at 10 ° C. Except having carried out, it carried out similarly to Example 2 and obtained the polyethylene-type resin composition.

[Comparative Example 4]
As a method for producing an ethylene polymer, a polyethylene resin composition was obtained in the same manner as in Example 1 except that the slurry concentration was 55%.

[Comparative Example 5]
As a method for producing a polyethylene resin composition, a polyethylene resin composition was obtained in the same manner as in Example 1 except that the polyethylene resin composition before crosslinking was melt-kneaded and cooled with water at 0 ° C.

[Comparative Example 6]
As a method for producing an ethylene polymer, a polyethylene resin composition was obtained in the same manner as in Example 8 except that the slurry concentration was 55%.

[Comparative Example 7]
As a method for producing a polyethylene resin composition, a polyethylene resin composition was obtained in the same manner as in Example 8 except that the polyethylene resin composition before crosslinking was melt-kneaded and cooled with water at 0 ° C.

  According to Tables 1 and 2, in Examples 1 to 11, the ratio of the total amount of components eluted at 95 ° C. or less with respect to the total elution amount in the CFC measurement in the polyethylene resin composition having a predetermined composition. Since it is 90% or more, it turns out that it is excellent in terms of thermal stability and a softness | flexibility compared with Comparative Examples 1-7.

  ADVANTAGE OF THE INVENTION According to this invention, the pipe which consists of a polyethylene-type resin composition containing the silane crosslinked polyethylene provided with sufficient durability while improving a softness | flexibility, and the said polyethylene-type resin composition can be provided.

Claims (7)

Containing silane-crosslinked polyethylene, at least one phenolic antioxidant, and at least one phosphorus antioxidant,
The gel fraction is 30% or more,
A polyethylene resin characterized in that the ratio of the total amount of components eluting at 95 ° C. or less to the total elution amount is 90% or more in the measurement using cross fractionation chromatography of xylene-dissolved components in gel fraction measurement Composition.   The polyethylene resin composition has an MFR of 0.1 or more and 10 or less, and a 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 The polyethylene resin composition according to claim 1, which is produced using an ethylene polymer which is the following.   The polyethylene resin composition according to claim 1 or 2, wherein the polyethylene element contains 5 to 500 ppm of tin element.   The polyethylene according to any one of claims 1 to 3, wherein the ratio of the total amount of components eluted at 80 ° C or less to the total amount eluted is 30% or less in the measurement using cross fractionation chromatography of the xylene-dissolved component. -Based resin composition.   5. The polyethylene resin composition according to claim 4, wherein in the measurement using the xylene-soluble component cross fractionation chromatography, the ratio of the total amount of components eluted at 80 ° C. or less to the total elution amount is 27% or less.   The polyethylene system according to any one of claims 1 to 5, wherein a ratio of a total amount of components eluted at 95 ° C or lower with respect to a total eluted amount is 93% or more in measurement using the xylene-soluble component cross fractionation chromatography. Resin composition.   The pipe which consists of a polyethylene-type resin composition in any one of Claims 1-6.