JP4928728B2 - Water-crosslinking polyethylene resin raw material, water-crosslinking polyethylene resin composition, and water-crosslinking polyethylene resin molding using them - Google Patents

Description

  The present invention relates to a water-crosslinking polyethylene resin material, a water-crosslinking polyethylene resin composition, and a water-crosslinked polyethylene resin molded article using the same. Specifically, by using specific linear low-density polyethylene resin granules that have a long oxidation induction time, heat aging resistance and storage stability are improved, and handling during storage is improved. The present invention relates to a water-crosslinking polyethylene resin material and a water-crosslinking resin composition that are useful for insulation and the like.

Polyethylene resin material is an important industrial material that is widely used in many technical fields because it is excellent in various physical properties and moldability and is highly economical and adaptable to environmental problems. As a utilization form, a polyethylene resin composition for water crosslinking is heavily used.
Polyethylene resin composition materials for water cross-linking are industrial materials such as pipes and hoses, electrical materials such as coated insulated wires and power cables, and electronic parts due to the ease of cross-linking and high physical properties such as mechanical strength and heat resistance. Wide range of products requiring mechanical strength, heat resistance, long-term durability, electrical characteristics, etc. as molded products such as sheets, films and foams, various machine parts, various daily necessities, and medical materials. Used in various applications.

  In order to produce a cross-linked modified molded article from a polyethylene-based resin, instead of the conventional heat cross-linking method and radiation cross-linking method using a cross-linking agent, due to the simplicity of the cross-linking treatment and inexpensive equipment costs, etc. Since the resin can also be cross-linked, the water cross-linking method has recently been adopted exclusively. In the water cross-linking method, generally, after an unsaturated silane compound is graft-copolymerized in the presence of an organic peroxide on a polyethylene resin. In addition, water crosslinking is performed together with a silanol condensation catalyst in an atmosphere of water, warm water, hot water, or steam.

In the water cross-linking method for polyethylene resins, various improvements have been proposed and disclosed for resin materials, various compounding components, or a mixing method or cross-linking method thereof.
As for the types of polyethylene resins, a method of using these polyethylenes together in order to make use of both the characteristics of high-density polyethylene having excellent mechanical and chemical properties and low-density polyethylene having good moldability (Patent Document 1). , A method using linear low density polyethylene to make use of its economical and mechanical properties (Patent Document 2), a method using granular polyethylene to improve the dispersibility and impregnation of each component (Patent Document 2) 3) is known.
A method of producing a copolymer of ethylene and an unsaturated silane compound is obtained by grafting by melting and kneading polyethylene and an unsaturated silane compound in the presence of an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide. A method of polymerizing (Patent Document 4), a method of randomly copolymerizing polyethylene and an unsaturated silane compound by a high-pressure radical polymerization method (Patent Document 5), and the like are known.
As for the water crosslinking method, a method of melt-kneading an ethylene-unsaturated alkoxysilane copolymer and a composition in which a silanol condensation catalyst is previously melt-mixed with polyethylene at the time of processing a molded body (Patent Document 6), polyethylene and unsaturated silane. Known is a method of melting and kneading a compound, an organic peroxide, and a silanol condensation catalyst all at once during processing of a molded body (Patent Document 7), and various proposals for other mixing methods and melt kneading methods. A lot has already been done.
Moreover, in order to avoid the unnecessary progress of water cross-linking due to moisture or moisture of the outside air, a technique for storing water-absorbing inorganic substances in a mixed manner has been proposed (Patent Document 8).

  As for the shape of the polyethylene resin for water cross-linking, in the case of powder, the bite in the hopper part of the extruder is poor, and the apparent specific gravity is too small to reduce the productivity. Therefore, polyethylene resin pellets are generally used. Yes. However, polyethylene resin pellets have the problem that the dispersibility and impregnation of the unsaturated silane compound, etc. from the liquid are poor and the cross-linking reaction becomes non-uniform. As described above, the use of granular polyethylene has been proposed (Patent Document 3). Recently, polyethylene particles (granules) and pellets are used in combination (Patent Document 9). The use of a linear low density ethylene-α-olefin copolymer in a porous granular form (Patent Document 10) is disclosed.

Polyethylene granules (granules) can be easily produced in the production of linear low-density polyethylene by the medium-low pressure polymerization method, after polymerization of ethylene and comonomer, and before pelletizing by degassing unreacted monomers However, it is general that such a polymerized granular material does not contain an antioxidant from the viewpoint of the production process. For this reason, the granular material has a larger specific surface area than pellets, so it is prone to oxidative degradation due to contact with air at high temperatures, and especially when stored in stock for several weeks to several months, the summer temperature is particularly high. There is a problem that oxidation deterioration progresses depending on the time.
Therefore, as a composition of water-crosslinking polyolefin resin using linear low density polyethylene particles, an unsaturated silane compound, an organic peroxide, a silanol condensation catalyst and an antioxidant are added to the polyethylene particles. A compound composition obtained by blending is generally used (Patent Document 11). In such a conventional composition, various types of mixtures are melt-kneaded at a time when a molded body is processed using a single extruder. The unsaturated silane compound, the organic peroxide, and the silanol condensation catalyst, including the antioxidant, are mixed immediately before the product is molded into the polyethylene powder. Therefore, in the case of a polyethylene-based granule that has not been previously blended with an antioxidant, even if an antioxidant is blended during product molding, it can be obtained if the polyethylene-based granule has already been slightly degraded during storage. The heat aging resistance of the molded body is lowered, and a problem that a large amount of antioxidant is required to obtain the desired heat aging resistance is also derived.

Furthermore, in order to obtain heat aging resistance, an antioxidant is an essential component, and the antioxidant is generally dissolved and mixed uniformly in a liquid unsaturated silane compound, an organic peroxide and a silanol condensation catalyst, It is used by mixing or impregnating polyethylene resin, but mixing an antioxidant that is a radical chain inhibitor into an organic peroxide that is a free radical generator is a mixture of chemical functions that are contradictory. In addition, since the respective functions are reduced due to their chemical properties, long-term storage is difficult.In particular, during the long-term storage of these mixtures in summer, a specific anti-aging agent is used. Attention to control the consumption of the anti-aging agent by performing treatment such as nitrogen gas replacement was indispensable (Patent Document 12).
On the other hand, in order to avoid deterioration due to oxidation or to avoid special storage treatment for long-term storage, it is inevitable that the production of the water-crosslinking polyethylene resin composition must be performed immediately before the molding process. there were.

Japanese Patent Laid-Open No. 52-122401 (Claims and lower part of lower right column on page 1) JP-A-60-250033 (Claims 1. and lower right column on page 1) JP 54-127944 (Claims 1. and lower right column on page 2) JP-A-50-126789 (Claims and lower right column on page 2 to upper left column on page 3) JP 55-9611 (Claims and upper right column on page 3) Japanese Examined Patent Publication No. 48-1711 (Claims and lower column on page 4, right column to middle column on page 5, left column) JP 51-82361 A (Claims) JP-A-6-107802 (summary) JP-A-7-130238 (Abstract) JP-A-8-134147 (summary) JP 2001-114959 A (Summary and right column on page 3) JP 2000-86905 A (summary)

As described above in the description of the background art, the polyethylene-based resin composition material for water cross-linking is made of an electric material such as a coated insulated wire and a power cable because of its easy cross-linking and high physical properties such as mechanical strength and heat resistance. It has been used for a wide range of applications at the beginning, and in response to this, in the water cross-linking method, improvement studies have been continued from various viewpoints. As the shape of the polyethylene resin, pellets and powders or granules ( The selection of the granule and its influence is also an important issue.
And when it can be said to be a preferred embodiment of the recent water crosslinking method, when an unsaturated silane compound, an organic peroxide, and a silanol condensation catalyst are blended into a polyethylene resin particle and water-crosslinked with water or steam (1) Since the granular material has a larger specific surface area than pellets, it is prone to oxidative degradation due to contact with air at high temperatures, and in the case of inventory storage for a period of several weeks to several months, (2) Derived from the problem that a large amount of antioxidant is required to obtain the desired heat aging resistance, (3) ) The compounding of the antioxidant, which is a radical chain inhibitor, into the organic peroxide, which is a free radical generator, is contradictory in terms of chemical action function. (4) Therefore, long-term storage is difficult and long. When storing the period Te uses a specific antioxidant, is inherent the problem it is essential to control the consumption of anti-aging agent is subjected to treatment such as nitrogen gas replacement to the storage container.
Therefore, in such a situation, the present invention solves such various problems as much as possible, and as a result, a high-quality water-crosslinkable polyethylene resin molded article excellent in performance such as heat aging resistance and storage stability, It is another object of the present invention to produce a molded body such as a coated insulated wire and a power cable using the same.

  In order to solve the problems summarized in the above (1) to (4) as much as possible, the inventors of the present invention used an initial oxidation in a water-crosslinking polyethylene resin using a polyethylene resin particle. We think that it is only necessary to suppress deterioration, improve storage stability, improve heat aging resistance, and improve handling during storage. Based on this idea, resin materials and various components or polymerization catalysts, especially resins Considering the particle size and antioxidants of the material from various viewpoints and experimenting with them, and also examining the oxidation control method and storage handling method in detail to suppress the initial oxidative degradation and increase the storage stability. It can be recognized that the initial oxidation-inducing function in polyethylene-based resin granules, especially the oxidation induction time is involved, and that the particle diameter and density or melt fluidity of the granules are also affected. The basic structure of the present invention could be materialized based on the recognition.

In the present invention, basically, as a water-crosslinking polyethylene resin material or a composition using the material, an oxidation induction time (OIT) satisfies a specific time or more, and an average particle size of 0.2 to 1. 5 mm linear low density polyethylene granules or a blend of 50 mass% or more of the granules with other polyolefin resin granules or pellets, and the density and melt fluidity of the granules Etc., the initial oxidative deterioration is suppressed, and the storage stability is improved. Furthermore, an unsaturated alkoxysilane compound and an organic peroxide, which are additive components to the polyethylene resin for water crosslinking, and Since it is not necessary to mix an antioxidant with the silanol condensation catalyst in advance, the handling and workability of these mixed components are excellent during storage, and the storage stability is good, so special storage handling is not essential. It is capable of obtaining raw materials.
By employing such a water-crosslinking polyethylene resin, it is possible to produce a water-crosslinkable polyethylene molded article excellent in heat aging resistance, particularly such a coated insulated wire / power cable.

  In the present invention, the number of fish eyes of the linear low density polyethylene granular material is specified in order to obtain a high-quality molded product as an additional structural requirement, and a specific radical chain inhibitor is 0.001 if necessary. ˜2 parts by mass are mixed, the type of catalyst, carrier and polymerization method or comonomer are specified, and the molded product is applied to a wide range of products such as coated insulated wires and power cables.

  In the paragraph 0011 of the present invention, the main points and characteristics of the basic configuration are outlined. The combination of polyethylene powder and granules (Patent Document 9), surface area, as described in paragraphs 0005 to 0007. Scrutinize each prior art document regarding the resin shape in water-crosslinking polyethylene resins in the use of linear low-density ethylene-α-olefin copolymers in the form of small-sized porous granular materials with a large diameter (Patent Document 10) However, no description relating to the configuration peculiar to the present invention is found or suggested, and the present invention solves the problems (1) to (4) described in paragraph 0009 as much as possible. Absent.

  In the above, the background and background in the creation of the present invention, and the basic configuration and features of the present invention have been described in general. Therefore, the overall configuration of the present invention will be described in detail clearly. The invention is composed of the following invention unit groups, the invention of [1] is the basic invention, and the invention of [2] and below is an invention that embodies or embodies the basic invention. The entire invention group of [1] to [10] is collectively referred to as “the present invention”.

[1] Polyethylene resin raw material for water crosslinking, which satisfies the following properties (a) to (c), and has a mean particle size of 0.2 to 1.5 mm, and is a linear low density polyethylene resin powder 100 to 50% by mass, and another polyolefin resin powder or pellet 0 to 50% by mass, water-crosslinking polyethylene resin raw material.
(A) Density 0.91 to 0.94 g / cm ³
(B) Melt mass flow rate (MFR) 0.1 to 5 g / 10 minutes (c) Oxidation induction time (OIT) at 150 ° C. is 30 minutes or more [2] Fish eye of linear low density polyethylene resin granules However, those having a diameter in the range of 0.1 to 0.3 mm are 70 pieces / g or less, and those having a diameter exceeding 0.3 mm are 10 pieces / g or less. Polyethylene resin raw material.
[3] A linear chain inhibitor having a molecular weight of 300 or more is added in an amount of 0.001 to 2 parts by mass to 100 parts by mass of a linear low density polyethylene resin granule or an admixture thereof with another polyolefin resin granule or pellet. The water-crosslinking polyethylene resin material according to [1] or [2], which is mixed.
[4] Ethylene and 3 to 12 carbon atoms, wherein the linear low density polyethylene resin granules are produced by gas phase polymerization using a chromium-containing catalyst in which at least a chromium compound is supported on a support of a porous inorganic oxide. The water-crosslinking polyethylene resin material according to any one of [1] to [3], which is a copolymer with an α-olefin.
[5] The water-crosslinking polyethylene system according to [4], wherein the inorganic oxide porous carrier has an average particle size of 10 to 50 μm and a carrier having a particle size of 100 μm or more is less than 10%. Resin raw material.
[6] A water-crosslinking polyethylene, wherein the polyethylene resin raw material according to any one of [1] to [5] is blended with an unsaturated alkoxysilane compound, an organic peroxide, and, if necessary, a silanol condensation catalyst. -Based resin composition.
[7] A polyethylene resin composition comprising an unsaturated alkoxysilane compound, an organic peroxide, and, if necessary, a silanol condensation catalyst in the polyethylene resin material according to any one of [1] to [5], A water-crosslinking polyethylene resin composition produced by treatment at a temperature equal to or higher than the decomposition temperature of an oxide.
[8] A water-crosslinked polyethylene resin molded product, which is molded using the water-crosslinking polyethylene resin material or the water-crosslinking polyethylene resin composition according to any one of [1] to [7].
[9] The water-crosslinked polyethylene resin molded body according to [8], wherein the water-crosslinked polyethylene resin molded body is a pipe, a coated steel wire, an electric wire or a power cable.
[10] Electric wire or electric power characterized in that the water-crosslinking polyethylene resin material and / or the water-crosslinking polyethylene resin composition according to any one of [1] to [7] is used for an insulating layer or a coating layer. cable.

  In the present invention, by using a water-crosslinking linear low-density polyethylene resin particle having a specific oxidation induction time or a water-crosslinking polyethylene resin composition using the particle, water crosslinking is performed. Polyethylene resin granules or compositions for polyethylene use have reduced oxidation deterioration, greatly improved heat aging resistance, improved storage stability, handling and workability during storage, and high-quality coated wires and power Forms such as cables can be provided.

As a means for solving the problem, the present invention has been generally described in accordance with the basic configuration of the present invention, but in the following, the embodiments of the invention of the present invention group described above will be specifically described. Will be described in detail.
1. Polyethylene resin for water crosslinking (1) Linear low-density polyethylene resin Compared with high-pressure polyethylene, linear low-density polyethylene resin is produced at low temperature and low pressure with an ion catalyst and has a high melting point and low production cost. Excellent mechanical properties such as tensile strength and impact resistance, and excellent durability such as creep and stress crack resistance, environmental stress crack resistance (ESCR), and relatively wide molecular weight distribution Since it can be said that it is suitable for extrusion molding of power cables and the like, in the present invention, a linear low density polyethylene resin is employed as a main component of the water-crosslinking polyethylene resin.
The linear low density polyethylene resin of the present invention is preferably a linear low density polyethylene produced by a gas phase polymerization method by selecting the particle size of a carrier carrying a chromium-based catalyst. In order to further improve the strength or crosslinkability, a linear low density polyethylene resin is preferably used as a copolymer of ethylene and another α-olefin.

(2) Granule The linear low density polyethylene resin of the present invention is used as a powder, and the powder is also referred to as a granule. In the production of linear low density polyethylene by the medium-low pressure polymerization method, the polyethylene powder is easily obtained after polymerization of ethylene and comonomer and before degassing the unreacted monomer and pelletizing.
In water-crosslinking polyethylene resins, poor biting in the hopper of the extruder occurs in the powder, and the apparent specific gravity is too small to reduce the productivity, and in the pellet, the unsaturated silane compound is liquid because it is liquid. Dispersibility and impregnation in the resin are poor, and the crosslinking reaction becomes non-uniform.

The linear low-density polyethylene resin powder of the present invention has a specific surface area of 1,000 to 3,000 cm ² / g, preferably 1,500 to 2,500 cm ² / g, and a bulk specific gravity of 0.2 to 0.00. 5 g / ml, preferably 0.3 to 0.5 g / ml.
The specific surface area is measured by the BET method under the following conditions.
Equipment used: Okura Riken AMS-8000
Adsorbed gas: 31.1% N ₂ / He
Pretreatment: N ₂ atmosphere at 25 ° C. 60 minutes The bulk specific gravity is measured by the method of JIS K6722 (1995).
A powdered linear low density polyethylene resin having a specific surface area and a bulk specific gravity within this range is liable to oxidatively deteriorate at high temperatures because of its large contact area with air, but controls the oxidation induction time as a requirement of the present invention. It is easy to be effective.

(3) Average particle diameter The average particle diameter of the linear low density polyethylene resin powder in the present invention is defined as 0.2 to 1.5 mm, preferably in the range of 0.2 to 1.0 mm. It is a powder grain shape. Since it is in the form of particles, it is easy to mix, impregnate and disperse unsaturated silane compounds, organic peroxides and silanol condensation catalysts which are essential components for water crosslinking.
If the average particle size is less than 0.2 mm, the handleability of the powder particles may be deteriorated, or the bulk specific gravity may increase and the processability may decrease. If the average particle size exceeds 1.5 mm, the functions of mixing, impregnating, and dispersing components essential for water crosslinking may be deteriorated.
The average particle diameter is measured according to “ASTM D1921 (1996) TEST METHOD A Sieve Designation No. 18, 35, 60, 120, 200”.

(4) Density linear low density polyethylene resin powder particles of the present invention, the density is defined as 0.91~0.94g / cm ^3, preferably 0.915~0.935g / cm ^3.
If the density is less than 0.91 g / cm ³ , the mechanical strength and heat resistance may be lowered. When the density exceeds 0.94 g / cm ³ , flexibility, flexibility, low-temperature characteristics and the like may be deteriorated.
The density is measured by “JIS K6922-1 (1997) JIS K6922-2 (1997 underwater substitution method)”.

(5) Melt mass flow rate (MFR)
The melt mass flow rate of the linear low density polyethylene resin granules of the present invention is 0.1 to 5 g / 10 minutes, preferably 0.1 to 3 g / 10 minutes, and more preferably 0.5 to 2 g / 10. The range of minutes.
When the MFR is less than 0.1 g / 10 min, the extrudability during molding processing deteriorates. When the MFR exceeds 5 g / 10 min, the molding strength deteriorates due to a decrease in mechanical strength of the molded product or a melt tension during molding processing. May occur.
MFR is measured based on “JIS K6922-2 (1997) Condition D (190 ° C. 21.18 N)”.

(6) Oxidation induction time (OIT)
The linear low density polyethylene powder of the present invention has an oxidation induction time (OIT) at 150 ° C. of 30 minutes or longer, preferably 60 minutes or longer, more preferably 120 minutes or longer.
If the OIT is less than 30 minutes, the linear low-density polyethylene powder is likely to be oxidized or deteriorated slightly due to oxidation. May be inferior.
In the linear low-density polyethylene granular material of the present invention, the identification of OIT is an important requirement and feature, which is related to the oxidative degradation and heat aging resistance of the water-crosslinking polyethylene resin, and results in improving them. Bring.
The OIT is measured based on “JIS K6774 (1998) Annex 2 (normative) Thermal Stability Test Method” and uses a thermal analysis method such as a differential thermal analyzer (DTA) or a differential scanning calorimeter (DSC). The time is shown from the time when the test sample is kept in an oxygen atmosphere and oxygen introduction is started to the intersection of the baseline extension line and the tangent line drawn at the maximum slope of the exothermic curve. 1-3, the measurement result of the oxidation induction time of the polyethylene resin raw material used in Examples 1 and 3 and Comparative Example 1 based on this test method is illustrated.

In the linear low density polyethylene resin granular material of the present invention, it is important that the OIT at 150 ° C. satisfies 30 minutes or more. As a method for satisfying OIT at 150 ° C. for 30 minutes or more, i) promptly use this powder before oxidative degradation during storage, ii) not to avoid oxidative degradation during storage. Examples include storage in an atmosphere of active gas, and iii) storage in a storage container that does not become hot and humid, or storage in a low-temperature warehouse. Generally, it is used for storage management and molding after the production of granular materials. This is not always the case before storage.
Therefore, when used in a high-temperature and high-humidity environment, a radical chain inhibitor having a molecular weight of 300 or more is further added to linear low-density polyethylene resin granules or other polyolefin resin granules or pellets. It is desirable that 0.001 to 2 parts by mass, preferably 0.005 to 1.5 parts by mass, and more preferably 0.01 to 1 part by mass are mixed with 100 parts by mass of the mixture. By mixing a radical chain inhibitor having a molecular weight of 300 or more with this polyethylene powder, oxidative deterioration or thermal deterioration during long-term storage of this polyethylene is suppressed, and water-crosslinkable polyethylene produced using this polyethylene resin raw material. The heat aging resistance of the molded body is improved. Moreover, since it is not necessary to mix and store the organic peroxide and the radical chain inhibitor, the handleability during processing is improved.

(7) Radical chain inhibitor
The molecular weight of the radical chain inhibitor is 300 or more, preferably 300 to 3,000, more preferably 400 to 2,000. If the molecular weight is less than 300, the melting point tends to be lowered and stickiness is likely to occur, so that the handleability of the linear low density polyethylene resin granules may be lowered. If the molecular weight is too high, the melting point of the additive is increased, and even if the temperature is high, the linear low density polyethylene resin granules are not dispersed in the linear low density polyethylene resin granules. There is a possibility that it will not affect the prevention of oxidative degradation.
When the addition amount of the radical chain inhibitor is less than 0.001 part by mass, the heat aging performance is not improved, the dispersion tends to be poor, and the deterioration preventing effect may not be expected depending on the storage conditions. When the amount exceeds 2 parts by mass, the mixed radical chain inhibitor may become sticky and the handling of the granular material may be impaired.

  Radical chain inhibitors include phenolic antioxidants, acrylate antioxidants, hindered phenolic antioxidants, hindered piperidine light stabilizers, amine antioxidants, and hindered phenolic oxidations with a thiobisphenol structure. Antioxidants are exemplified, and hindered phenol antioxidants, hindered phenol antioxidants having a thiobisphenol structure, hindered piperidine light stabilizers are preferred, and sulfur antioxidants that do not have a radical chain inhibiting function In addition, phosphorus-based antioxidants, and particularly some phosphorus-based antioxidants that are easily hydrolyzed are not preferable.

  Preferable radical chain inhibitors include, specifically, tetrakis {methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)} methane, octadecyl-3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isosinualate, 4,4-thiobis (6-tert-butyl-3-methylphenol), 3,9- Bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) -propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5 5] undecane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3 5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2-methylene-bis (4-methyl-6-t-butylphenol), 2,2'-methylene-bis (4-ethyl-6-t-butylphenol), 2- {1- (2-hydroxy-3,5-di-t- Pentylphenyl) ethyl} -4,6-di-t-pentylphenyl acrylate, triethylene glycol bis {3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate}, 4,4-butylidenebis ( 6-t-butyl-3-methylphenol), bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxy) Til) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine- 2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], N, N ′, N ″, N ″ ″-tetrakis- [4,6-bis- {butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino} -triazine- 2-yl] -4,7-diazadecane-1,10-diamine, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (2,2,6,6-tetramethyl-4-piperidi ) -1,2,3,4-butanetetracarboxylate, 2- {4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl} -5- (octyloxy) Examples thereof include phenol, and one or more radical inhibitors selected from these may be used in combination.

  The preferred shape of the radical chain inhibitor is a powder or granule having an average particle size of 0.5 mm or less, preferably 0.3 mm or less, more preferably 0.1 mm or less at room temperature, and is preferably liquid or more than 0.5 mm. The shape of the average particle diameter is not preferable from the viewpoint of dispersibility.

(8) Fisheye (FE)
The number of fish eyes of the linear low-density polyethylene resin granular material of the present invention is 70 / g or less in the range of 0.1 to 0.3 mm in diameter and 10 in the range exceeding 0.3 mm in diameter. / G or less, preferably 60 or less FE having a diameter of 0.1 to 0.3 mm, and 7 or less FE having a diameter exceeding 0.3 mm, more preferably 0.1 to 0.3 mm. FE is 50 pieces / g or less, for example, 40 to 10 pieces, and FE having a diameter exceeding 0.3 mm is 5 pieces / g or less, for example, 4 pieces to 1 piece / g, and in some cases, 0 pieces. Although it is ideal that the FE with a diameter of as low as possible is as low as possible, there is a technical limit to reducing it as much as possible.

Fisheye is produced by using ultra-high molecular weight gel components, burns of oxidative degradation products, or porous inorganic oxides of catalyst carriers, etc., which are produced during the production of polyethylene. When the fish eye exceeds the above number due to the average particle size of the carrier being too large or the amount of the carrier being too large due to low catalytic activity, There is a possibility that the ESCR performance and the electrical performance when the crosslinked polyethylene molded body is used will be lowered starting from the carrier.
In the linear low-density polyethylene-based resin of the present invention, it is desirable that the fish eye is defined in order to reduce foreign matter as much as possible and enhance electrical characteristics in the resin composition as the electric wire / power cable covering insulating layer. .
Major factors that cause fish eyes are due to catalyst carriers, catalyst residues, resin burns, fine foreign matter mixed in the process, and the resulting ultra-polymer gel, but mainly controlled the average particle size of the carrier. By using a catalyst, the size and amount of fish eyes can be controlled below a specific level.

The fish eye measurement method of the present invention uses a single-screw extruder having a diameter of 40 to 50 mm and an L / D of 20 to 26, a molding temperature of a cylinder temperature of 160 to 200 ° C. and a die temperature of 180 to 220 ° C., and a compression ratio of 2. After forming an inflation film having a blow ratio of 2 to 3 and a thickness of 20 to 30 μm under conditions of a full flight screw of 5 to 3.5 and a rotation speed of 60 to 80 rpm, it is included in an area of 1,000 to 2,000 cm ² The number of foreign matter (FE) exceeding 0.1 to 0.3 mm and 0.3 mm in diameter is counted and measured, and expressed as the number per measured film weight (g).

(9) Other polyolefins In the water-crosslinking polyethylene resin raw material of the present invention, in order to improve various properties such as heat resistance, flexibility and electrical performance, linear low-density polyethylene resin granules. You may be comprised with the mixture of 100-50 mass% and the granular material of another polyolefin resin, or 0-50 mass% of pellets.
Other polyolefin resins are low density polyethylene, linear low density polyethylene different from the main component, high density polyethylene, ultra low density polyethylene with a density of less than 0.910 g / cm ³ , ethylene and vinyl ester, α, β Random, block, or graft copolymers with one or more selected from comonomers such as saturated carboxylic acids, α, β-unsaturated carboxylic esters, vinyl silanes, acid anhydrides, polypropylene, propylene and ethylene and / or Or the block and / or random copolymer with other (alpha) -olefin, the homopolymer of (alpha) -olefin, those copolymers, Furthermore, these mixtures etc. are mentioned.

2. Production method of linear low density polyethylene resin granules The production method of the linear low density polyethylene resin granules of the present invention may be obtained by mechanically pulverizing the pellets, but the powder obtained directly from the plant A copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms produced by gas phase polymerization using a chromium-containing catalyst in which at least a chromium compound is supported on a porous inorganic oxide carrier is preferably used. preferable.

(1) Gas phase polymerization method The gas phase polymerization method is not particularly limited, but preferably, for example, JP-A-51-112891 and JP-A-61-106610 and the above-mentioned Patent Document 10 are used. The method using the chromium containing catalyst shown by each gazette, such as (Unexamined-Japanese-Patent No. 8-134147), is mentioned. Although described in detail in the production method in this patent document, the polymerization temperature is 30 to 110 ° C., preferably 75 to 95 ° C., the pressure is 5 to 70 atm, preferably 10 to 50 atm. It can be produced by gas phase polymerization.
By using such a gas phase polymerization method, it is possible to easily obtain a granule-like linear low-density polyethylene resin granular material having an average particle diameter of 0.2 to 1.5 mm according to the present invention. In addition, before the step of packing in a container or bag in-line, a powdery or granular radical chain inhibitor having a molecular weight of 300 or more is added in an amount of 0.001 to 100 parts by mass with respect to 100 parts by mass of the polyethylene resin granular material. It is preferable to mix 2 parts by mass in order to prevent oxidative degradation.

(2) Chromium-containing catalyst By using a chromium-containing catalyst, a linear low-density polyethylene having a broad molecular weight distribution and good extrudability can be obtained as compared with titanium-based catalysts and metallocene-based catalysts. The linear low density polyethylene produced by the method of the present invention has a higher number of unsaturated carbon bonds in the polyethylene molecule than the linear low density polyethylene produced by the titanium-based catalyst. This is effective for controlling the oxidation induction time.
The chromium-containing catalyst is a supported catalyst in which a chromium compound is essential, and a chromium compound and a titanium compound and / or a fluorine compound are supported on a dry carrier, and then the resulting composite composition is 100 in an inert gas or dry air. It is formed by drying at a temperature of ˜300 ° C. and then used after being activated in dry air or dry oxygen at a temperature of 250 to 1,000 ° C. for about 6 hours.
Examples of the chromium compound include chromium oxide (CrO ₃ ), chromium acetylacetonate, chromic nitrate, chromic acetate, chromic chloride, chromic sulfate and ammonium chromate, bis (cyclopentadienyl) chromium ( II) and these magnesium-titanium composites.

(3) Carrier
As the carrier of the inorganic oxide porous material supporting the chromium-containing catalyst, the average particle size is 10 μm to 50 μm, and the support having a particle size of 100 μm or more is less than 10%, preferably the average particle size is 20 μm or more and 50 μm. The carrier having a particle size of less than 100 μm or more is desirably less than 5%, more preferably, the carrier having a particle size of less than 20 μm is less than 30%.
Specifically, the average particle size is, for example, preferably in the range of 20 to less than 50 μm or less than 30 to 50 μm, and the carrier having a large particle size of 100 μm or more is less than 10% or less than 8 to 5%. Further, the carrier having a large particle size of 0 to less than 4%, more preferably 90 μm or more is preferably less than 10%, and particularly preferably the carrier having a large particle size of 80 μm or more is less than 10%. Although preferred, it is technically difficult to obtain one having such a particle size range.

If the average particle size of the carrier is less than 10 μm, it is too fine as a carrier, so that it is not easy to handle, and convection in a fluidized bed in gas phase polymerization is insufficient, which may impair the polymerization stability. If the average particle size exceeds 50 μm, the environmental stress crack resistance (ESCR property) and electrical performance when the water-crosslinked polyethylene molded body is obtained may be lowered starting from the inorganic oxide porous body.
If the carrier having a particle diameter of 100 μm or more is 10% or more, the ESCR property and the electrical performance may be similarly lowered.
Further, in some applications, when melt molding using an extruder, a screen mesh is inserted into a die plate to remove minute foreign matter, but when the carrier having a particle size of less than 20 μm is 30% or more, The carrier can easily pass through the screen mesh and be mixed, and the performance of the water-crosslinked polyethylene molded product may be reduced.
The average particle size is a value obtained by measuring the particle size distribution using a laser diffraction / scattering type particle size distribution measuring device and obtained by an arithmetic average diameter. As a measuring device, for example, LA-920 type manufactured by Horiba, Ltd. is used. It is preferable because of its excellent measurement accuracy.
As the inorganic oxide porous material, one having a specific surface area of 50 to 1,000 m ² / g, a pore diameter of 50 to 500 mm, and a pore volume of 0.5 to 3.0 cc / g is preferably selected. .

  Inorganic oxide porous materials include talc, silica, titania, alumina, magnesia, silica titania, silica alumina, silica magnesia, silica chromia, silica chromia titania, silica titania alumina, tria, zirconia, silanized silica, aluminum phosphate gel And other inorganic oxide porous bodies similar to these, and a mixture of these carriers, and silica is particularly preferable.

(4) Comonomer The linear low density polyethylene of the present invention is basically a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, preferably an α-olefin having 3 to 10 carbon atoms. Is selected.
Examples of the α-olefin include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, and the like, and one or more kinds of comonomers are selected from these comonomers. be able to. The content of these comonomer is 1 to 30% by mass of comonomer with respect to 70 to 99% by mass of ethylene, preferably 2 to 25% by mass of comonomer with respect to 75 to 98% by mass of ethylene. Preferably, 3 to 20% by mass of the comonomer is copolymerized with respect to 80 to 97% by mass of ethylene.
Preferred copolymers are ethylene-propylene copolymer, ethylene-propylene-1-butene copolymer, ethylene-propylene-1-hexene copolymer, ethylene-1-butene copolymer, ethylene-4-methyl. Binary or ternary copolymers such as -1-pentene copolymer and ethylene-1-hexene copolymer can be used.

The amount of comonomer introduced greatly affects the density of the linear low density polyethylene. As the amount of comonomer increases, the density of linear low density polyethylene decreases proportionally, so to maintain the proper MFR and density in the range of 0.91 to 0.94 g / cm ³ , It is necessary to adjust the amount of the comonomer in consideration of the kind of the comonomer and the polymerization amount, but this can be easily designed by adjusting a conventional polymerization technique.
Furthermore, the density varies depending on the type of comonomer. For example, if propylene, 1-butene, 1-hexene and the number of carbon atoms increase, short chain branching becomes longer, and the density tends to decrease monotonously. In consideration of various circumstances corresponding to such subtle changes, a linear low density polyethylene MFR and a density in the range of 0.91 to 0.94 g / cm ³ can be polymerized.

  In order to increase the crosslinking efficiency of the crosslinking agent as a response to the peroxide crosslinking as a crosslinking agent, in addition to silanol crosslinking, crosslinking such as butadiene, divinylbenzene, pentadiene, particularly in the case of short-chain branched α-olefins It is also possible to introduce a monomer as a comonomer, which increases the usefulness as a water-crosslinkable polyethylene molded product.

3. Water-crosslinking polyethylene resin composition The water-crosslinking polyethylene resin composition of the present invention is a mixture of linear low-density polyethylene resin granules or granules thereof with other polyolefin resin granules or pellets. This is a water-crosslinking polyethylene resin composition obtained by blending an unsaturated alkoxysilane compound, an organic peroxide, and, if necessary, a silanol condensation catalyst with a polyethylene resin material made of a product.
In another embodiment, a water-crosslinking polyethylene resin composition comprising an unsaturated alkoxysilane compound and an organic peroxide and, if necessary, a silanol condensation catalyst in the polyethylene resin raw material is mixed with an organic peroxide. It is a polyethylene resin composition for water crosslinking produced by treatment at a temperature equal to or higher than the decomposition temperature.

4). Molded product The water-crosslinking polyethylene-based resin molded product of the present invention is a molded product characterized by being extruded and water-crosslinked using, for example, a water-crosslinking polyethylene-based resin material or composition. Examples include water distribution or drainage pipes or coated steel wires, and electric wires or power cables.
Particularly preferred examples include electric wires and power cables obtained by crosslinking a water-crosslinking polyethylene resin material or composition as an insulating layer and / or a coating layer.
In addition, it can be used for electronic parts, molded articles such as sheets, films and foams, various machine parts, various daily necessities, and medical materials.

5. Water cross-linking method (1) Silane cross-linking method The water cross-linking method involves extruding an unsaturated alkoxysilane compound and an organic peroxide together with a resin raw material or resin composition at a temperature equal to or higher than the decomposition temperature of the organic peroxide. After obtaining a saturated alkoxysilane graft resin composition, a silanol condensation catalyst and a water-crosslinkable resin composition containing a silanol condensation catalyst, which is kneaded by extrusion molding after mixing a resin raw material or composition, are suitable at the time of molding. A method of obtaining a molded product by mixing with a resin (two-step Sioplas method), an unsaturated alkoxysilane compound, an organic peroxide, and a silanol condensation catalyst are simultaneously mixed with a resin raw material or composition, followed by decomposition of the organic peroxide. There is a method of forming a molded product by molding at a temperature higher than the temperature (one-step Monosil method).

In the water cross-linking method, if the water cross-linkable linear low-density polyethylene resin raw material of the present invention or the composition thereof is used to increase the decomposition temperature of the organic peroxide or higher, a mixing method or the like Is not particularly limited. For example, an unsaturated alkoxysilane compound and an organic peroxide are mixed with a linear low density polyethylene in advance and then introduced into an extruder, and then a silanol condensation catalyst and a linear low density are mixed with a side feeder. A method in which a mixture of a density polyethylene-based resin raw material or a composition thereof is charged and molded with the same extruder, an unsaturated alkoxysilane compound and an organic peroxide are mixed with a linear low-density polyethylene-based resin raw material or a composition thereof. Later, it was put into an extruder to obtain an unsaturated alkoxysilane-grafted linear low-density polyethylene-based resin or a composition thereof, and subsequently the resin or the composition thereof was And a method of melt-kneading is molded using a first with a mixture of silanol catalyst and linear low density polyethylene second extruder, a known water crosslinking method various may be used.
Further, in the case of water cross-linking, the heat aging resistance and molding processability of the molded product can be improved by mixing an antioxidant or an anti-scratch additive.

(2) Unsaturated silane compound As an unsaturated silane compound used for water bridge | crosslinking by this invention, an unsaturated alkoxysilane compound is used preferably and the following are illustrated.
γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyl-tris- (2-methoxyethoxy) silane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, Vinyltriacetoxysilane, allyltriethoxysilane, allylmethyldiethoxysilane, diallyldimethoxysilane, allylphenyldiethoxysilane, methoxyvinyldiphenylsilane, dodecenyldipropoxysilane, didecenyldimethoxysilane, didodecenylmethoxysilane , Cyclohexenyltrimethoxysilane, hexenylhexoxydimethoxysilane, vinyl-tri-n-butoxysilane, hexenyl-tri-n-butoxysilane, vinyl- Lith (n-butoxy) silane, vinyl-tris (n-pentoxy) silane, vinyl-tris (n-hexoxy) silane, vinyl-tris (n-heptoxy) silane, vinyl-tris (n-octoxy) silane, vinyl- Tris (n-dodecyloxo) silane, vinyl-bis (n-butoxy) methylsilane, vinyl-bis (n-pentoxy) methylsilane, vinyl-bis (n-hexoxy) methylsilane, vinyl- (n-butoxy) dimethylsilane, vinyl -(N-pentoxy) dimethylsilane, allyl dipentoxy silane, butenyl didecoxy silane, decenyl didecoxy silane, dodecenyl trioctoxy silane, heptenyl triheptoxy silane, allyl tripropoxy silane, Divinyldiethoxysilane, diallyl-di-n-butoxy Lan, pentenyltripropoxysilane, allyl-di-n-butoxysilane, s-butenyltriethoxysilane, β-methacryloxyethyl-tris (n-butoxy) silane, γ-methacryloxypropyl-tris (n-dodecyl) Silane etc. are mentioned.
The unsaturated alkoxysilane is blended in an amount of 0.1 to 10 parts by mass, preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the resin raw material or composition.

(3) Organic peroxide The free radical generator as an organic peroxide is an additive for generating free radicals used for initiating grafting of a silane compound.
As the organic peroxide used in the present invention, free radical sites can be generated in the polyolefin resin under graft reaction conditions, and the half-life is shorter than 6 minutes, preferably shorter than 1 minute at the reaction temperature. Arbitrary compounds having the following can be used, and typical examples include dicumyl peroxide, di-t-butyl peroxide, benzoyl peroxide, 2,5-di (peroxybenzoate) hexyne-3, and the like.
The organic peroxide is blended in an amount of 0.01 to 0.75 parts by weight, preferably 0.02 to 0.3 parts by weight, based on 100 parts by weight of the resin raw material or composition.

(4) Silanol condensation catalyst The silanol condensation catalyst used in the present invention is used as a catalyst for promoting dehydration condensation between silanols of silicone, and is dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diolate, acetic acid. Stannous, lead naphthenate, cobalt naphthenate, zinc caprylate, iron 2-ethylhexanoate, titanate, tetrabutyl titanate, tetranonyl titanate, bis (acetylacetonitrile) di-isopropyltitanium-ethylamine Hexylamine, dibutylamine, pyridine and the like.
The compounding quantity of a silanol condensation catalyst is about 0.001-10 mass parts with respect to 100 mass parts of resin raw materials or compositions, and 0.05-5 mass parts is preferable.

6). Other Additives The water-crosslinkable linear low-density polyethylene resin raw material of the present invention or the composition thereof includes an antioxidant, a slip agent, and a neutralizing agent that are generally used for polyethylene resins depending on applications. In addition, a light-resistant agent, an ultraviolet absorber, an anti-scratch agent, a copper damage inhibitor, an antistatic agent, a color pigment, a filler, and the like can be appropriately mixed during the molding process.
When the resin raw material or composition of the present invention is used outdoors, weather resistance is improved by mixing 0.1 to 5 parts by mass of carbon black with respect to 100 parts by mass of the resin raw material or composition. In particular, in order to ensure extrusion stability during molding over a long period of time, slip agents such as aliphatic amides, fatty acid metal salts, vinylidene fluoride-based additives, silicone-based additives, and anti-scratch agents are used as resin raw materials or compositions. Extrusion stability is improved by mixing 0.01 to 0.3 parts by mass with respect to 100 parts by mass. When color pigments or fillers are mixed, special attention is required because there is a concern that the electrical characteristics may be affected by aggregation.
Furthermore, in order to avoid unnecessary progress of water crosslinking due to moisture or moisture of the outside air, a water-absorbing inorganic substance may be mixed and stored.

In the following, examples and comparative examples to be compared are presented to clarify the configuration and effects of the present invention, and to demonstrate the significance of the configuration of the present invention.
[Example 1]
(1) Production of linear low-density polyethylene powder a. Production of Solid Catalyst Component Commercially available porous silica (Silopol 948 manufactured by Grace Japan Co., Ltd.) was prepared in accordance with the method of “ASTMD1921 (1996) TEST METHOD A”. The fine particles were passed through a 230 (mesh 63 μm) mesh sieve, and silica (SiO ₂ -1) on the fine particle side that passed through was used. The average particle size of the SiO ₂ -1 was measured using a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba, Ltd., and the dispersion solvent was distilled water-refractive index 1.0-shape factor 1.0. As a result, the average particle diameter in terms of the arithmetic average diameter was 45 μm, and the particle size of 100 μm or more was 0%.
400 g of the classified silica SiO ₂ -1 obtained above was introduced into a 3 liter glass flask, and then 4 g of CrO ₃ was dissolved in 2 liter of distilled water and added for 15 minutes. Next, after removing the supernatant, when nitrogen gas was introduced while heating and the mixture became powdery, the temperature was raised to 150 ° C. and further dried for 4 hours to obtain chromium-supporting silica. This supported silica contained 0.2% by mass of chromium.
Next, 400 g of this dry carrier was introduced into a 3 liter flask, 1 liter of isopentane and 100 g of isopropyl titanate were introduced, and the mixture was stirred at 50 ° C. for 2 hours, and then isopentane was distilled off. Further, 1 g of (NH ₄ ) ₂ SiF ₆ was added and dried at 150 ° C. for 1 hour under a nitrogen gas flow. After returning to room temperature, it was transferred to a firing tube under nitrogen, and further dried at 150 ° C. under nitrogen in a firing furnace for 1 hour, then the gas was switched from nitrogen to dry air, 350 ° C. for 2 hours, and further at 750 ° C. for 4 hours. Baked for hours. After the calcination, the gas was switched to nitrogen gas, and then slowly returned to room temperature to obtain a solid catalyst carrying chromium and titanium. This catalyst contained 3.5% by mass of titanium.

B. Polymerization of Linear Low Density Polyethylene Using the above solid catalyst, 0.10 ppm of oxygen in a mixed gas of ethylene and 1-butene (1-butene / (ethylene + 1-butene) = 7.5 mol%) fluid Polymerization was performed at a temperature of 90 ° C., a total pressure of 20 atm and a residence time of 3.5 hours while maintaining the concentration of MFR 0.7 g / 10 min, a density of 0.922 g / cm ³ , and an average particle size of 0.67 mm. A low-density polyethylene (ethylene-1-butene copolymer) powder was obtained.

C. Control of oxidation induction time Tetrakis {methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)} methane as a radical chain inhibitor in 100 parts by mass of the above-mentioned linear low density polyethylene powder (AO-1 molecular weight 1,178) 0.05 part by mass was added, and the mixture was mixed for 3 minutes at 200 rpm in a nitrogen atmosphere using a super mixer to prepare a linear low density polyethylene resin raw material. Subsequently, the resin raw material was stored in a gear oven at a temperature of 90 ° C. for 96 hours to facilitate high-temperature storage.

(2) Measurement a. Measurement of Oxidation Induction Time The obtained linear low-density polyethylene resin raw material was compression-molded using a flat die at a pressure of 8 MPa—temperature of 150 ° C.—heating time of 2 minutes, and then pressure of 8 MPa—average cooling rate of 60 The sheet was rapidly cooled to room temperature at ± 30 K / min to prepare a 0.3 mm compression molded sheet.
A 5 ± 0.1 mg test piece was cut out from the compression molded sheet to obtain a measurement sample, and the oxidation induction time was measured under the following conditions. After confirming that there was no change of 0.2 mW or more in the 120-minute exothermic curve, the measurement was terminated.
Measurement item: Oxidation induction time Standard number: JIS K6774 (1998) Annex 2 (normative) Conforms to thermal stability test method Measuring instrument: Thermal Analyst 2000 manufactured by Du Pont Instruments
Measurement temperature: 150 ° C

B. Evaluation of Flexibility A compression molded sheet having a thickness of 4 mm is prepared from the above-mentioned linear low-density polyethylene resin raw material according to the compression molding conditions of “JIS K6922-2 (1997)” using a flat die at a pressure of 5 MPa. did. A strip-shaped test piece having a width of 10 mm and a length of 80 mm was punched from the obtained compression-molded sheet to obtain a measurement test piece, and the flexural modulus was measured under the following conditions. The results are shown in Table 1.
Measurement item: Flexural modulus standard number: JIS K7171 (1994)
Test equipment: Shimadzu Corporation, Autograph AG-20kNG
Test speed: 2 mm / min Measurement environment: Temperature 23 ° C. Humidity 50%

C. Evaluation of heat aging resistance According to the compression molding conditions of “JIS K6922-2 (1997)”, the linear low density polyethylene resin raw material was compressed into a compression molded sheet having a thickness of 1 mm using a flat die at a pressure of 5 MPa. Created. Dumbbell-shaped No. 3 was punched out from the obtained compression molded sheet to obtain a test specimen for measurement, and tensile strength and elongation were measured under the following conditions. The results are shown in Table 1.
Measurement item: Tensile strength (maximum tensile strength) Elongation standard number: JIS C3005 (2000) 4.16 (tensile of insulator and sheath)
Test equipment: Tensilon UTM-III-100 manufactured by Toyo Baldwin
Tensile speed: 200 mm / min Measurement environment: Temperature 23 ° C. Humidity 50%
Subsequently, the test piece was subjected to a heat test under the following conditions, the tensile strength and elongation after the test were measured, and the residual rate from before each test was calculated to evaluate the heat aging resistance. The results are shown in Table 1.
Measurement item: Tensile strength (maximum tensile strength) Elongation standard number: JIS C3005 (2000) 4.17 (heating)
Heating conditions: Heating temperature 90 ± 2 ° C. Heating time 96 hours Test equipment: Tensilon UTM-III-100 manufactured by Toyo Baldwin
Tensile speed: 200 mm / min Measurement environment: Temperature 23 ° C. Humidity 50%
Residual rate: (Residual rate) = (Average of measured values after heating) / (Average of measured values before heating) (%)

D. Evaluation of electrical characteristics The electrical characteristics were evaluated under the following conditions using the sheet having a thickness of 1 mm. The results are shown in Table 1.
Standard number: JIS C2110 (1994) Short-time breakdown test Measurement condition: In oil Upper spherical electrode Lower 25 mmφ electrode Measurement item: Dielectric breakdown strength

[ Reference Example 2 ]
In Example 1, using a titanium catalyst without using CrO ₃ , polymerization was performed by appropriately adjusting the concentration of the mixed gas of ethylene and 1-butene, the polymerization temperature, the polymerization pressure, and the residence time, and MFR 4.9 g / 10 min. A linear low-density polyethylene (ethylene-1-butene copolymer) powder having a density of 0.935 g / cm ³ and an average particle size of 0.72 mm was obtained.
To 100 parts by mass of the obtained linear low-density polyethylene granules, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (AO-2 molecular weight 481) 0.10 as a radical chain inhibitor Mass parts were added, and 0.05 parts by mass of calcium stearate was added as a neutralizing agent. A linear low-density polyethylene resin raw material was prepared in the same manner as in Example 1, and stored in a gear oven.
The oxidation induction time of the obtained linear low density polyethylene resin raw material was measured in the same manner as in Example 1. After confirming that the exothermic curve did not change by 0.2 mW or more in 120 minutes, the measurement was terminated. Subsequently, the linear low density polyethylene resin raw material was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
In Example 1, the oxidation induction time was measured in the same manner as in Example 1 without mixing the linear chain inhibitor with the linear low-density polyethylene powder and without storing it in a gear oven. The oxidation induction time was 73 minutes.
Subsequently, the linear low-density polyethylene powder was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[ Reference Example 4 ]
In Reference Example 2 , the linear low-density polyethylene powder was not mixed with a radical chain inhibitor, and 0.05 part by weight of calcium stearate was added as a neutralizing agent, and the sample was not stored in a gear oven. The oxidation induction time was measured in the same manner as in 1. The oxidation induction time was 162 minutes.
Subsequently, the linear low-density polyethylene powder was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[ Reference Example 5 ]
In Example 1, a commercially available porous silica support (Grace Japan K.K./Silopol 952) was used (SiO ₂ -2). This SiO ₂ -2 has an average particle size of 129 μm and 1
The particle size of 00 μm or more was 73%. Using this SiO ₂ -2, the conditions were appropriately adjusted in the same manner as in Example 1 to obtain a solid catalyst on which chromium and titanium were supported, and then the conditions were appropriately adjusted in the same manner as in Example 1 to obtain MFR0. A linear low-density polyethylene (ethylene-1-butene copolymer) granular material having a density of 0.7 g / 10 minutes, a density of 0.920 g / cm ³ , and an average particle diameter of 0.68 mm was obtained.
To 100 parts by mass of the obtained linear low-density polyethylene powder, 0.05 part by mass of the radical chain inhibitor AO-1 was added, and the linear low-density polyethylene resin raw material was obtained in the same manner as in Example 1. Prepared and stored in gear oven. For the obtained linear low density polyethylene resin raw material, the oxidation induction time was measured in the same manner as in Example 1, and after confirming that there was no change of 0.2 mW or more in the 120 minute-exothermic curve, the measurement was completed. did.
Subsequently, the linear low density polyethylene resin raw material was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, the linear low-density polyethylene powder was not mixed with a radical chain inhibitor and stored in a gear oven, and the oxidation induction time was measured in the same manner as in Example 1. The oxidation induction time was not observed and was 0 minutes.
Subsequently, the linear low-density polyethylene powder was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
In Example 1, MFR 8.2 g / 10 min, density 0.938 g / cm ³ , average particle size 0. 0, produced by a gas phase polymerization method using a titanium catalyst as a linear low density polyethylene powder. A 68 mm linear low density polyethylene (ethylene-1-butene copolymer) granular material was used.
Example 1 To 100 parts by mass of the linear low-density polyethylene powder, 0.05 part by mass of the radical chain inhibitor AO-1 was added, and 0.05 part by mass of calcium stearate was added as a neutralizing agent. In the same manner as above, a linear low-density polyethylene resin raw material was prepared and stored in a gear oven. For the obtained linear low density polyethylene resin raw material, the oxidation induction time was measured in the same manner as in Example 1, and after confirming that there was no change of 0.2 mW or more in the 120 minute-exothermic curve, the measurement was completed. did.
Subsequently, the linear low density polyethylene resin raw material was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
In Example 1, octadecyl-3- (3,5-di-t-butyl was used as a radical chain inhibitor produced by a slurry polymerization method using a titanium catalyst without using a linear low-density polyethylene granular material. Using high density polyethylene pellets with MFR of 1.4 g / 10 min and density of 0.952 g / cm ³ to which 0.05% by mass of (4-hydroxyphenyl) propionate (AO-3 molecular weight 531) was added, Similarly, it was stored in a gear oven.
The oxidation induction time of the high-density polyethylene pellets was measured in the same manner as in Example 1, and after confirming that there was no change of 0.2 mW or more in the 120-minute exothermic curve, the measurement was terminated.
Subsequently, the linear low density polyethylene resin raw material was evaluated for flexibility, heat aging resistance, and electrical characteristics in the same manner as in Example 1. The results are shown in Table 1.

[Example 6]
In Example 1, 0.01 part by mass of the radical chain inhibitor AO-1 was added to 100 parts by mass of the linear low density polyethylene powder, and the linear low density polyethylene resin was obtained in the same manner as in Example 1. Raw materials were prepared and stored in a gear oven.
The oxidation induction time of the obtained linear low density polyethylene resin raw material was measured in the same manner as in Example 1. The oxidation induction time was 207 minutes.
This linear low density polyethylene resin raw material is mixed with 98.3% by mass of vinyl trimethoxysilane 1.5% by mass, dicumyl peroxide 0.1% by mass and radical chain inhibitor AO-1 0.1% by mass. Then, using a twin screw extruder with a diameter of 65 mm, kneading was carried out at a resin temperature of 200 ° C., a screw rotation speed of 40 rpm, and an extrusion rate of 50 kg / hour to obtain a silane graft linear low density polyethylene.
Subsequently, after mixing 98.9% by mass of the linear low-density polyethylene resin raw material with 1.0% by mass of dibutyltin dilaurate and 0.1% by mass of the radical chain inhibitor AO-1, Using a twin screw extruder, kneading was carried out at a resin temperature of 200 ° C., a screw speed of 40 rpm, and an extrusion rate of 50 kg / hour to obtain a linear low density polyethylene masterbatch containing dibutyltin dilaurate.

100 parts by mass of the above silane-grafted linear low-density polyethylene composition and 5 parts by mass of the masterbatch are mixed, and a full-flight screw with a compression ratio of 3.0 is used in a single screw extruder having a caliber of 20 mm-L / D20. A sheet having a thickness of 1 mm was prepared by extruding from a die having a thickness of 1 mm at a temperature of 210 ° C., a screw speed of 50 rpm, and a width of 50 mm.
The obtained sheet was conditioned in warm water at a temperature of 80 ° C. for 24 hours, and then water was removed to obtain a water-crosslinked sheet having a degree of crosslinking of 51%, which was measured based on the method of “JIS C3005 (2000)”. Heat aging resistance was evaluated in the same manner as in Example 1 except that the obtained water-crosslinked sheet was used under heating conditions of 150 ° C. and heating time of 14 days. The results are shown in Table 2.

[Example 7]
In Example 6, the oxidation induction time was measured in the same manner as in Example 1 without adding a radical chain inhibitor to the linear low density polyethylene powder and without storing it in a gear oven. The oxidation induction time was 73 minutes.
Using this linear low density polyethylene powder, a linear low density polyethylene masterbatch containing silane-grafted linear low density polyethylene and dibutyltin dilaurate was obtained in the same manner as in Example 6.
Subsequently, a sheet having a thickness of 1 mm was prepared in the same manner as in Example 6, and then a water-crosslinked sheet was obtained. Using the obtained water cross-linked sheet, heat aging resistance was evaluated in the same manner as in Example 6. The results are shown in Table 2.

[Comparative Example 4]
In Example 6, the linear low-density polyethylene granular material was not mixed with a radical chain inhibitor and stored in a gear oven, and the oxidation induction time was measured in the same manner as in Example 1. The oxidation induction time was not observed and was 0 minutes.
Using this linear low-density polyethylene powder, a linear low-density polyethylene masterbatch containing silane-grafted linear low-density polyethylene and dibutyltin dilaurate was obtained in the same manner as in Example 6.
Subsequently, a sheet having a thickness of 1 mm was prepared in the same manner as in Example 6 to obtain a water-crosslinked sheet. Using the obtained water cross-linked sheet, heat aging resistance was evaluated in the same manner as in Example 6. The results are shown in Table 2.

[Example 8]
In Example 1, 0.01 part by mass of the radical chain inhibitor AO-1 was added to 100 parts by mass of the linear low density polyethylene powder, and the linear low density polyethylene resin was obtained in the same manner as in Example 1. Raw materials were made and stored in a gear oven.
For the obtained linear low-density polyethylene resin raw material, the oxidation induction time was measured in the same manner as in Example 1. The oxidation induction time was 207 minutes.
Subsequently, 70% by mass of the above-mentioned linear low-density polyethylene resin raw material was added to low-density polyethylene pellets having a density of 0.920 g / cm ³ at an MFR of 0.3 g / 10 minutes (LD1: 100% of the polyethylene pellets as an antioxidant). 30 parts by mass (including 0.05 part by mass of 2,6-di-t-butyl-4-hydroxytoluene), and using a single screw extruder with a diameter of 40 mm, resin temperature 200 ° C.-screw rotation speed The mixture was kneaded at 80 rpm and pelletized to obtain a linear low density polyethylene resin composition.
Subsequently, the flexibility, heat aging resistance, and electrical characteristics were evaluated using the resin composition in the same manner as in Example 1. The results are shown in Table 3.

[Evaluation of Examples and Comparative Examples]
In Example 1 , the average particle diameter, density and MFR of the present invention are satisfied, and since the radical chain inhibitor is mixed with the linear low density polyethylene powder, the powder mixture is heated at a high temperature. Even after long-term storage, the oxidation induction time is long (120 minutes or more), and the heat aging resistance is excellent.
In Example 3 , the average particle diameter, density and MFR of the present invention are satisfied, and the linear low-density polyethylene powder is not mixed with a radical chain inhibitor, but is not stored at a high temperature for a long time. Oxidation induction time is long and heat aging resistance is maintained.
Since Comparative Example 1 was stored for a long time at a high temperature without mixing a radical chain inhibitor into the linear low-density polyethylene powder, the oxidation induction time was extremely short and the heat aging resistance was poor.
In Comparative Example 2, since the MFR of the present invention is significantly higher, the elongation (before the heating test), which is mechanical strength, is inferior. Moreover, since the FE is relatively large, the electrical characteristics are somewhat inferior.
In Comparative Example 3, since the density of the present invention is increased and pellets are used, the flexural modulus is high and the flexibility is inferior.
In Example 6, the average particle diameter, density and MFR of the present invention were satisfied, and since the radical chain inhibitor was mixed with the linear low density polyethylene powder, the powder mixture was heated at a high temperature. Even after long-term storage, the oxidation induction time is long, and the water-crosslinked polyethylene molded article is excellent in heat aging resistance.
In Example 7, the average particle diameter, density, and MFR of the present invention are satisfied, and the linear low-density polyethylene powder is not mixed with a radical chain inhibitor, but is not stored at a high temperature for a long time. Oxidation induction time is long, and heat aging resistance is maintained as a water-crosslinked polyethylene molded article.
In Comparative Example 4, since the linear low-density polyethylene powder was stored for a long time at a high temperature without admixing the radical chain inhibitor, the oxidation induction time was extremely short, and the water-crosslinked polyethylene molded article was inferior in heat aging resistance.
Example 8 is an example of a composition satisfying the respective regulations of the average particle diameter, density and MFR of the present invention and mixed with low density polyethylene as another polyolefin. Because it contains a radical chain inhibitor, it excels in heat aging resistance.

  When considering the results of each example and each comparative example in the above, the polyethylene-based resin for water crosslinking and the composition in each example of the present invention that satisfy each regulation in the configuration of the present invention, It is clear that heat aging resistance and electrical properties are excellent, and that storage stability is also good. And it is also clear that each provision of the structural requirements in the water-crosslinking polyethylene resin of the present invention and its composition has significance and has been verified by experimental data.

This is a measurement example of the oxidation induction time of the polyethylene resin raw material used in Example 1 based on “JIS K6774 (1998) Annex 2 (normative) Thermal Stability Test Method”. This is a measurement example of the oxidation induction time of the polyethylene resin raw material used in Example 3 based on “JIS K6774 (1998) Annex 2 (normative) thermal stability test method”. The numerical value in the figure represents the measured value (minute) of the oxidation induction time. This is a measurement example of the oxidation induction time of the polyethylene resin raw material used in Comparative Example 1 based on “JIS K6774 (1998) Annex 2 (normative) Thermal Stability Test Method”.

Claims (6)

A raw material for blending an unsaturated alkoxysilane compound, an organic peroxide, and a silanol condensation catalyst into a water-crosslinking polyethylene resin composition, which satisfies the following properties (a) to (c): 100 to 50% by mass of linear low-density polyethylene resin granules having an average particle size of 0.2 to 1.5 mm, and 0 to 50% by mass of other polyolefin resin granules or pellets , Low-density polyethylene resin granular material containing at least a chromium compound supported by a porous inorganic oxide carrier having an average particle size of 10 to 50 μm and a carrier having a particle size of 100 μm or more of less than 10% catalytic gas-phase polymerization in the produced polyethylene resin composition material for water crosslinking, wherein isosamples used.
(A) Density 0.91 to 0.94 g / cm ³
(B) Melt mass flow rate (MFR) 0.1 to 5 g / 10 minutes (c) Oxidation induction time (OIT) at 150 ° C. is 30 minutes or more 0.001 to 2 parts by mass of a radical chain inhibitor having a molecular weight of 300 or more is mixed with 100 parts by mass of a linear low-density polyethylene resin granule or an admixture thereof with other polyolefin resin granules or pellets. The water-crosslinking polyethylene resin composition raw material according to claim 1, characterized in that: A polyethylene resin composition obtained by blending an unsaturated alkoxysilane compound and an organic peroxide and, if necessary, a silanol condensation catalyst into the polyethylene resin composition raw material according to claim 1 or 2, A water-crosslinking polyethylene resin composition produced by treatment at a temperature equal to or higher than the decomposition temperature of a product. A water-crosslinked polyethylene resin molded article, which is molded using the water-crosslinking polyethylene resin composition raw material or the water-crosslinking polyethylene resin composition according to any one of claims 1 to 3 . The water-crosslinked polyethylene resin molded body according to claim 4, wherein the water-crosslinked polyethylene resin molded body is a pipe, a coated steel wire, an electric wire or a power cable. An electric wire comprising the water-crosslinking polyethylene resin composition raw material and / or the water-crosslinking polyethylene resin composition according to any one of claims 1 to 5 used for an insulating layer or a coating layer. Or power cable.

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