JP3069093B1 - Silane-crosslinked polyolefin resin composition and insulating cable - Google Patents

Abstract

An object of the present invention is to provide a silane-crosslinked polyolefin resin composition having excellent molding surface smoothness and heat resistance, and an insulated cable from which a water crosslinking step is eliminated. SOLUTION: The mixture is composed of a mixture of 45 to 99 parts by weight of a linear medium-low density polyethylene having a dispersity (Mw / Mn) of 4 or more and 1 to 55 parts by weight of a low-density or high-density polyethylene having an average density of 0.1 to 0.5 parts by weight. 915 g / cm ^{3 to} 0.935 g /
cm ³ , 0.1 to 5 parts by weight of an organic unsaturated silane represented by the general formula RR′SiY ₂ , 0.01 to 0.5 parts by weight of a free radical generator and 0.01 of a silanol condensation catalyst In a silane cross-linked polyolefin resin composition obtained by melt-mixing the base polymer, the base polymer comprises a mixture of 5 to 100 parts by weight of a granulated polymer and 95 to 0 parts by weight of a pellet-shaped polymer. A silane crosslinked polyolefin resin composition having a heat deformation ratio (JIS K6723) of 40% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a base polymer,
The present invention relates to a silane crosslinked resin composition obtained by melt-mixing an organic unsaturated silane, a free radical generator and a silanol condensation catalyst, and an insulated cable coated with an electric wire using the composition.

[0002]

2. Description of the Related Art As a simple method for crosslinking polyethylene, chemical crosslinking, electron beam irradiation crosslinking and hot water crosslinking (which proceed using an organic silane compound as a medium) are widely known, and one of them is hot water crosslinking. Has the advantages that the cost of a crosslinking apparatus is much lower than that of chemical crosslinking or electron beam irradiation crosslinking, and that crosslinking can be easily controlled. As a typical example of the hot water cross-linked polyethylene, the polyolefin is subjected to a graft reaction with an organic unsaturated silane in the presence of a free radical generator to perform silane grafting, and then the silane grafter is subjected to a silanol condensation catalyst in the presence of a silanol condensation catalyst. The so-called silane crosslinking method of crosslinking by contact with moisture is generally known. For example, it is disclosed in JP-B-48-1711 and JP-A-57-49109.

[0003] However, the hot water cross-linking, in which the equipment cost is lower than other cross-linking methods, is missed in that much time and cost are required for the cross-linking treatment.
An electric wire coated with a water-crosslinkable resin composition undergoes a very slow cross-linking reaction at room temperature. Therefore, it is necessary to promote cross-linking in hot water of about 80 ° C. or a high-temperature and high-humidity tank. Even if it is promoted, it takes about one day, and the investment cost of the crosslinking treatment equipment is enormous. For this reason, even if the equipment cost is very low, the advantage will be diminished if a large cost is applied to the crosslinking treatment cost.

[0004] For this reason, various attempts have been made to reduce the time required for the cross-linking treatment of an electric wire extruded with a water-crosslinkable resin. For example, a method is known in which a catalyst or an auxiliary agent is added to a modified silane compound to promote cross-linking, which is disclosed in JP-A-57-208006 and JP-A-62-106.
No. 947. In addition, a method of increasing the contact with moisture during the crosslinking of the water-crosslinked resin-coated electric wire to shorten the crosslinking time is also known and disclosed in Japanese Patent Application Laid-Open No. 60-254520. Further, Japanese Patent Application Laid-Open No. 4-331241 discloses a method of shortening the crosslinking treatment time by promoting the diffusion of water into the water-crosslinked resin by performing the crosslinking treatment of the water-crosslinked resin-coated electric wire in an ultrasonic atmosphere. I have. However, all of the above methods only shorten the time of the crosslinking treatment by hot water or steam treatment, and do not eliminate the water crosslinking step.

In addition, hot water crosslinked polyethylene has a disadvantage that the effect of improving heat resistance and the like is lower than that of chemical crosslinking or electron beam irradiation crosslinking. Therefore, examples of using a linear medium-low-density polyethylene for a base resin in order to effectively improve heat resistance are increasing. However, when a linear medium-low-density polyethylene having a higher melting point and a higher melt viscosity than a low-density polyethylene or the like is used as a base resin, heat is generated in the extruder to cause early crosslinking, or the molding surface becomes rough due to friction with a die. There was a problem. Japanese Patent Application Laid-Open No. 7-130238 discloses an example using only a linear medium-low-density polyethylene as a raw material. However, the above method provides stable workability and does not eliminate the water crosslinking step.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and provides a silane-crosslinked polyolefin resin composition which is particularly excellent in the smoothness and heat resistance of a molding surface. It is another object of the present invention to provide an insulated cable capable of sheathing an electric wire extrusion-coated with a silane-crosslinked polyolefin resin composition immediately after coating.

[0007]

Means for Solving the Problems The present inventors have conducted intensive searches to solve the above-mentioned problems, and as a result, have found that the problems can be solved by using a specific crosslinked polyolefin. That is, the present invention comprises a mixture of 45 to 99 parts by weight of a linear medium and low density polyethylene having a dispersity (Mw / Mn) of 4 or more and 1 to 55 parts by weight of a low density or high density polyethylene, and having an average density of 0 to 0. 0.915 g / cm ^{3 to} 0.935
g / cm ³ and a general formula RR′Si
Y2 (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R 'is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y) Crosslinked polyolefin resin composition obtained by melt-mixing 0.1 to 5 parts by weight of an organic unsaturated silane, 0.01 to 0.5 parts by weight of a free radical generator and 0.01 to 0.2 parts by weight of a silanol condensation catalyst Silane cross-linking, wherein the base polymer comprises a mixture of 5 to 100 parts by weight of a granulated polymer and 95 to 0 parts by weight of a pelletized polymer, and has a heat deformation ratio (JIS K 6723) of 40% or less after melt mixing. Insulation of wire coating with polyolefin resin composition
It is an edge cable . In addition, the present invention provides a method for preparing a dispersion degree (Mw / Mn).
Is 4 or more, a linear medium-low density polyethylene 75 to 99.
Parts by weight and an ethylene-ethyl acrylate copolymer (EE
A), ethylene-vinyl acetate copolymer (EV
A), ethylene-methyl methacrylate copolymer (EM
MA) a hydrogenated block obtained by hydrogenating a block copolymer consisting of at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound A mixture of 1 to 25 parts by weight of a polyolefin selected from the group consisting of a copolymer and a mixture thereof;
A base polymer which is ^{5g / cm 3 ~0.935g / cm 3} , the general formula RR'SiY2 (R is a monovalent olefinically unsaturated hydrocarbon group, Y represents an organic group which can be hydrolyzed, R 'is an aliphatic Organic unsaturated silane represented by a monovalent hydrocarbon group other than unsaturated hydrocarbon or the same as Y) 0.1 to 5
Parts by weight, a free radical generator 0.01 to 0.5 parts by weight and a silanol condensation catalyst 0.01 to 0.2 parts by weight are melt-mixed. 5-10
An insulated cable comprising a mixture of 0 parts by weight and a pellet-shaped polymer of 95 to 0 parts by weight, and coated with a silane-crosslinked polyolefin resin composition having a heat deformation ratio (JIS K 6723) of 40% or less after melt mixing. It is. Also, the present invention
An insulated cable in which an electric wire is coated with the silane-crosslinked polyolefin resin composition and then coated with a sheath material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The linear medium-low-density polyethylene used for the base polymer of the present invention is prepared by using various catalysts such as a Ziegler catalyst, a chromium catalyst, etc. It is a copolymer with an α-olefin containing ethylene as a main component by various polymerization methods such as a polymerization method and a suspension polymerization method. As the α-olefin, C ₃ -C ₁₂
For example, propylene, butene-1, pentene-1, octene-1, 4-methylpentene-1, 4-methylhexene-1, 4,4-dimethylpentene-1, nonene-1,
Decene-1, undecene-1, dodecene-1 and the like can be mentioned. The polyethylene used for the base polymer of the present invention is a high density polyethylene or a low density polyethylene. High density polyethylene is a Ziegler catalyst,
It is an ethylene polymer obtained by various polymerization methods such as a gas phase method, a solution method, and a suspension polymerization method at medium to low pressure or high pressure using various catalysts such as a chromium-based catalyst. Low-density polyethylene is an ethylene polymer produced by high-pressure radical polymerization by a tubular method or an autoclave method. The base polymer of the present invention comprises 5 to 100 parts by weight of a granulated polymer and 9
It must be a mixture of 5 to 0 parts by weight. If the amount of the granulated polymer is less than 5 parts by weight, the dispersibility of the organic silane compound is reduced, which causes local crosslinking.

The base polymer of the present invention has a dispersity (Mw).
/ Mn) is 4 or more.
5 to 99 parts by weight and high density or low density polyethylene 1
55 parts by weight of the mixture, the average density of the mixture being 0.915
a ^{g / cm 3 ~0.935g / cm 3} . When a linear medium-low-density polyethylene having a degree of dispersion of less than 4 is used, poor appearance is likely to occur. The average density when mixed is 0.91
When the amount is less than 5 g / cm ³ or the mixing number of the low-density polyethylene exceeds 55 parts by weight, heat resistance is lowered,
If the average density when mixed exceeds 0.935 g / cm ³ , it becomes hard and unsuitable for producing thick electric wires and cables.

The polyolefin used in the base polymer of the present invention includes ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), and at least one polyolefin. Hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of a polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound, for example, Examples include hydrogenated styrene-isoprene block copolymer (SEPS) and hydrogenated styrene-butadiene block copolymer (SEBS). The base polymer of the present invention is a mixture of 75 to 99 parts by weight of a linear medium-low-density polyethylene having a dispersity (Mw / Mn) of 4 or more and 1 to 25 parts by weight of the above-mentioned polyolefin. It is 915 g / cm ^{3 to} 0.935 g / cm ³ . When the average density is less than 0.915 g / cm ³ or when the number of mixed parts of the polyolefin exceeds 25 parts by weight, the heat resistance is reduced, and when the average density exceeds 0.935 g / cm 3, it becomes hard and produces thick electric wires and cables. Not suitable for

The organic unsaturated silane of the present invention is one which is grafted to the base resin so as to be a cross-linking point between the base resins. Examples of the organic unsaturated silane used in the present invention include a compound represented by the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R 'is an aliphatic unsaturated hydrocarbon group. A compound represented by a monovalent hydrocarbon group other than hydrogen or the same as Y) is used. It is desirable to use an organic unsaturated silane represented by the general formula RSiY _{3 in} which R ′ is the same as Y, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, allyltriethoxysilane. Examples include silane. The amount of these additives is from 0.1 to 5% by weight, preferably from 0.7 to 3% by weight, based on the total weight of the polymer. 0.1% by weight
If it is less than 5%, sufficient grafting does not occur, and if it exceeds 5% by weight, molding failure occurs and it is not economical.

The free radical generator of the present invention acts as an initiator for a silane grafting reaction. The free radical generator used in the present invention includes various organic peroxides and peresters having a strong polymerization initiating action, such as dicumyl peroxide, α, α'-bis (t-butylperoxydiisopropyl) benzene, Di-t-butyl peroxide, t-butyl cumyl peroxide, di-benzoyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylperoxypivalate, t -Butylperoxy-2-ethylhexanoate and the like. The amount of these additives is 0.01 to 0.5% by weight, preferably 0.05 to 0.2% by weight, based on the total weight of the polymer. 0.0
If the amount is less than 1% by weight, a sufficient silane grafting reaction does not proceed.

The silanol condensation catalyst of the present invention includes dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, and stearic acid. Organic metal compounds such as lead, zinc stearate, cadmium stearate, barium stearate, calcium stearate and the like can be mentioned. These additives may be added in an amount of 0.01 to 0.2% by weight, preferably 0.02 to 0.1% by weight, based on the total weight of the polymer.
% By weight. If the amount is less than 0.01% by weight, a sufficient crosslinking reaction does not proceed. If the amount exceeds 0.2% by weight, crosslinking occurs locally in the extruder at the time of extrusion, and the appearance is significantly deteriorated.

As other additives, if desired, commonly used additives such as antioxidants, neutralizers, ultraviolet absorbers, antistatic agents, pigments, dispersants, thickeners, metal deterioration inhibitors, A fungicide, a flow regulator, other inorganic fillers, or the like, or other synthetic resins can be contained.

The crosslinked polyolefin resin composition of the present invention has extremely excellent heat deformation properties and can be used for various applications. If a post-crosslinking treatment step such as steam treatment or hot water treatment after extrusion is performed, the heat resistance is further improved, but this step can be omitted. Therefore, it is particularly suitable for the production of insulated cables that require heat resistance and flexibility, and can be covered with a sheath material without performing a water crosslinking step after covering the electric wires. For this purpose, it is necessary that the heating deformation ratio immediately after extrusion is 40% or less. As the sheath material, a vinyl chloride resin composition or the like is used.

[0016]

The following examples illustrate the invention, but are by way of example only and the invention is not limited thereto.

The base polymer, unsaturated organic silane compound, free radical generator and silanol catalyst are shown in Tables 1-3.
And the tape was extruded using an extruder. The extruded tape was used to evaluate the heating deformation rate. In addition, the wire was extruded with the same composition as when the tape was extruded, and the smoothness of the molded surface was evaluated.

The raw materials used are as follows. (1) L-LDPE (1): linear low-density polyethylene (density: 0.918 g / cm ³ , dispersion degree 4.5) (granular) (2) L-LDPE (2): linear medium-low density polyethylene (Density: 0.917 g / cm ³ , dispersity 7.8) (pellet) (3) L-LDPE (3): linear medium-low density polyethylene (density: 0.919 g / cm ³ , dispersity 3.9) (pellet) (4) L-LDPE (4): linear medium-low density polyethylene (density: 0.902 g / cm ³ , dispersity 5) (pellet) (5) L-LDPE (5): linear medium-low Density polyethylene (density; 0.925 g / cm ³ , dispersity 5) (pellet) (6) L-LDPE (6): linear medium-low density polyethylene (density: 0.920 g / cm ³ , dispersity 3.6) ( (6) LDPE: Low density polyethylene (density: 0.923g)
/ cm ³ ) (7) HDPE: high-density polyethylene (density; 0.950 g)
/ cm ³ ) (8) EEA: ethylene-ethyl acrylate copolymer (EA content; 23% by weight) (density;
(0.935 g / cm ³ ) (9) EVA: ethylene-vinyl acetate copolymer (VA content; 25% by weight) (density: 0.950 g / cm ³ ) (10) VTMOS: vinyl trimethoxysilane (11) DCP: dik Mil peroxide (12) DBTDL: dibutyltin dilaurate

The evaluation method is as follows. (13) Appearance of tape extrusion (confirmation of presence or absence of bumps): 50mmφ
Extruder 130-160-180-190-180 ℃ L / D: 20, compression ratio 3.5, tape die: width 100mm, lip interval 1mmt, screw rotation speed 40rpm Tape appearance (bubble) evaluation: ○>△> × , The level of ○ was judged to be acceptable. (14) Heat deformation ratio (%): JIS K 6723
by. (15) Coated wire extrusion appearance (Evaluation of molding surface): Extruder with 50mmφ 130-160-180-190-180 ℃ L / D: 24, compression ratio 4.0, conductor diameter 0.8mmφ, coating thickness 1.00mm
φ Screw rotation speed 40 rpm Appearance evaluation of the coated electric wire: ○>△> ×, and the level of ○ was accepted. (16) Ease of winding after covering the wire (confirmation of cable flexibility): Winding evaluation of the covered wire: ○>△> ×
The level of ○ was judged as passed.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

As is clear from Tables 1 to 3, Examples 1 to
No. 5 has good extrusion processability and smoothness of the molding surface, and shows very excellent heat resistance. That is, the heat deformation ratio is 40% or less immediately after the extrusion, and the crosslinking treatment step can be omitted. In addition, it can be seen that good workability and heat resistance are obtained by using any of the crosslinking methods.
On the other hand, all of the comparative examples have difficulty in smoothness, and the extrusion processability and heat resistance are not balanced.

[0024]

According to the present invention, it is possible to obtain a silane-crosslinked polyolefin having excellent molding surface smoothness and excellent heat resistance. Hanging can be performed. As a result, not only is the productivity of the product significantly improved, but also the production cost is greatly reduced, which greatly contributes to the production of the insulated cable.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01B 7/02 H01B 7/02 F

Claims (3)

(57) [Claims] 1. A mixture of 45 to 99 parts by weight of a linear medium and low density polyethylene having a degree of dispersion (Mw / Mn) of 4 or more and 1 to 55 parts by weight of a low density or high density polyethylene having an average density of 0 0.915 g / cm ^{3 to} 0.935 g /
cm ³ and a general formula RR′SiY 2
(R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R ′ is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y). 0.1 to 5 parts by weight of an organic unsaturated silane, 0.01 to 0.5 parts by weight of a free radical generator and 0.0 of a silanol condensation catalyst
In a silane crosslinked polyolefin resin composition obtained by melt-mixing 1 to 0.2 parts by weight, a base polymer is a mixture of 5 to 100 parts by weight of a granulated polymer and 95 to 0 parts by weight of a pellet-shaped polymer, It was noted that the wire was coated with a silane-crosslinked polyolefin resin composition having a post-heating deformation ratio (JIS K 6723) of 40% or less.
Insulated cable . 2. 75 to 99 parts by weight of a linear medium-low-density polyethylene having a dispersity (Mw / Mn) of 4 or more, ethylene-ethyl acrylate copolymer (EEA),
Vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), at least 1
Hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of a polymer block mainly composed of two vinyl aromatic compounds and at least one polymer block mainly composed of a conjugated diene compound, and And a mixture of 1 to 25 parts by weight of a polyolefin selected from the group consisting of mixtures having an average density of 0.915 g / cm ^{3 to} 0.1.
A base polymer of 935 g / cm ³ ,
R'SiY2 (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, R 'is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y)
A silane crosslink obtained by melt-mixing 0.1 to 5 parts by weight of an organic unsaturated silane represented by the formula, 0.01 to 0.5 parts by weight of a free radical generator and 0.01 to 0.2 parts by weight of a silanol condensation catalyst. In the polyolefin resin composition, the base polymer is composed of a mixture of 5 to 100 parts by weight of a granulated polymer and 95 to 0 parts by weight of a pellet-shaped polymer, and a heat deformation ratio after melt mixing (JIS K 6723) is 40% or less. Conducting wire coating with a silane-crosslinked polyolefin resin composition
Insulated cable which is characterized in that Tsu. 3. The insulated cable according to claim 1, wherein
An insulated cable, wherein an electric wire is coated with a silane-crosslinked polyolefin resin composition and then coated with a sheath material.