JP3359572B2 - Silane cross-linked polyolefin resin composition and insulated cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a base polymer,
A silane-grafted resin composition obtained by reacting an organic unsaturated silane and a free radical generator to form a silane graftmer, and then melt-mixing a carrier polymer A containing a silanol condensation catalyst and the like, and an insulation obtained by coating a wire with this composition. It is about cables.

[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, JP-B-48-1711, JP-A-57-
No. 49109 discloses this.

[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. Also, a method of increasing the contact with moisture during the crosslinking of the water-crosslinked resin-coated electric wire and shortening the crosslinking time is known, which is disclosed in JP-A-60-254520 and JP-A-60-26510. .
Further, a method of shortening the time of the crosslinking treatment by promoting the diffusion of water into the inside of the water-crosslinking resin by performing the crosslinking treatment of the water-crosslinking resin-coated electric wire in an ultrasonic atmosphere is disclosed in JP-A-Hei.
It is disclosed by Japanese Patent Publication No. 31241. 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.

[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 relates to a base polymer having the general formula RR'S
iY ₂ (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), and is reacted with an organic unsaturated silane and a free radical generator to form a silane graft. A silane-crosslinked polyolefin resin composition melt-mixed with a carrier polymer A containing a silanol condensation catalyst and an antioxidant, wherein the base polymer has a dispersity (Mw / Mn) of 4 or more. includes a density polyethylene, and an average density of ^{0.915g / cm 3 ~0.935g / cm 3} , a silane crosslinked polyolefin resin composition heated deformation ratio after melt mixing (JIS K 6723) is not more than 40% is there.
Preferably, the base polymer comprises 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 polyethylene,
Alternatively, 75 to 99 parts by weight of a linear medium-low-density polyethylene having a dispersity (Mw / Mn) of 4 or more, an ethylene-ethyl acrylate copolymer (EEA), and an ethylene-vinyl acetate copolymer (EVA) A block copolymer comprising ethylene-methyl methacrylate copolymer (EMMA), 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 silane-crosslinked polyolefin resin composition comprising a mixture of 1 to 25 parts by weight of a polyolefin selected from the group consisting of a hydrogenated block copolymer obtained by hydrogenation and a mixture thereof. More preferably, it is a silane crosslinked polyolefin resin composition in which the carrier polymer A is selected from the group consisting of polyethylene, polypropylene, and a copolymer of ethylene and an α-olefin, and the amount of the carrier polymer A is 2 to 5% by weight. Further, 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, C3 to C1
2, 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. The polyethylene used for the base polymer of the present invention is a high density polyethylene or a low density polyethylene. High-density polyethylene uses various catalysts such as Ziegler-based catalysts and chromium-based catalysts, and ethylene polymers obtained by various polymerization methods such as gas phase method, solution method, suspension polymerization method, etc. at medium to low pressure or high pressure It is. 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 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
g / cm ³ as a ~0.935g / cm ³ are preferred. When a linear medium-low-density polyethylene having a degree of dispersion of less than 4 is used, poor appearance is likely to occur. On the other hand, if the average density when mixed is less than 0.915 g / cm ³ or the number of parts of the low-density polyethylene exceeds 55 parts by weight, heat resistance is reduced, and the average density when mixed is 0.935 g.
If it exceeds / cm ³ , it becomes hard and is not suitable for manufacturing 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 degree of dispersion (Mw / Mn) of 4 or more and 1 to 25 parts by weight of the above-mentioned polyolefin. It is preferably from 915 g / cm ^{3 to} 0.935 g / cm ³ . If the average density is less than 0.915 g / cm ³ or the number of parts of the polyolefin exceeds 25 parts by weight, heat resistance is reduced, and the average density is 0.93 g / cm ^3.
If it exceeds 5 g / cm ³ , it becomes hard and is not suitable for producing thick electric wires and cables.

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. The organic unsaturated silane used in the present invention is 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. Monovalent hydrocarbon groups other than hydrogen or
The same compound as used for 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,
Vinyl triethoxy silane, vinyl tributoxy silane, allyl trimethoxy silane, allyl triethoxy silane and the like can be mentioned. 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. If the amount is less than 0.1% by weight, sufficient grafting does not occur, and if the amount 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 it is less than 1% by weight, a sufficient silane grafting reaction does not proceed, and if it exceeds 0.5% by weight, the extrudability decreases and the molding surface deteriorates.

The carrier polymer A can be added by kneading and granulating a silanol condensation catalyst and an antioxidant with the carrier polymer A of the present invention. The carrier polymer A must also be in a particulate form and a solid compatible with the base polymer to be crosslinked. The carrier polymer A of the present invention is usually in the form of granules or granules in the form of pellets, and the preferred form is pellets. The carrier polymer A used in the present invention is, for example, polyethylene, polypropylene, a copolymer of ethylene and an α-olefin, and the α-olefin is, for example, propylene, butene-1, pentene-1, octene-1 of C3 to C12. , 4-methylpentene-1, 4-methylhexene-1, 4,4-dimethylpentene-1, nonene-1, decene-1, undecene
1, dodecene-1 and the like, and mixtures thereof.

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.

The amount of the carrier polymer A is in the range of 2 to 5% by weight. If the amount is less than 2% by weight, a sufficient crosslinking reaction does not occur. If the amount exceeds 5% by weight, molding failure (scorch or unstable ejection) occurs, and it is not economical. As other additives, if desired, commonly used additives such as antioxidants, neutralizers, ultraviolet absorbers,
Antistatic agent, pigment, dispersant, thickener, metal deterioration inhibitor,
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 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.

[0017]

The following examples illustrate the invention, but are by way of example only and the invention is not limited thereto. << Production of Carrier Polymer A >> The carrier polymer A, a silanol condensation catalyst, an antioxidant and the like were kneaded and granulated according to the compounding ratio shown in Table 1 using a pressure kneader.

<< Production of Silane Graft Mer >> Next, a polyolefin base polymer, an unsaturated organic silane compound and a free radical generator were blended in the ratios shown in Tables 2 to 4 to produce a silane graft mer.

The produced silane graftmer and carrier polymer A were mixed in the ratios shown in Tables 5 to 7, and a tape was extruded using an extruder. The heating deformation rate immediately after extrusion of this extruded tape was evaluated. 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 results are shown in Tables 5 to 7.

The raw materials used are as follows. (1) EEA: ethylene-ethyl acrylate copolymer (E
(A content: 23% by weight) (density: 0.935 g / cm ³ ) (2) EVA: ethylene-vinyl acetate copolymer (VA
(Content: 25% by weight) (density: 0.950 g / cm ³ ) (3) EMMA: ethylene-methyl methacrylate copolymer (EA content: 17% by weight) (density: 0.930 g / cm ³ ) (4) VTMOS: Vinyltrimethoxysilane (5) DCP: dicumyl peroxide (6) LDPE: low density polyethylene (density: 0.925 g / c
^{m 3, MI; 1.5g / 10min} ) (7) PP: polypropylene (homopolymer, MI (230 °
(8) DBTDL: dibutyltin dilaurate (9) Antioxidant: phenolic antioxidant / Irganox 1010 (manufactured by Ciba Geigy) (10) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Chemical Industries, Ltd.) (11) L-LDPE (1): linear medium-low density polyethylene (density; 0.917 g / cm ³ , dispersity 7.8) (12) L-LDPE (2): Linear medium and low density polyethylene (density: 0.919 g / cm ³ , dispersity 3.9) (13) L-LDPE (3): linear medium and low density polyethylene (density: 0.902 g / cm ³ , dispersity 5) (14) L-LDPE (4): linear medium and low density polyethylene (density: 0.925 g / cm ³ , dispersity 5) (15) LDPE: low density polyethylene (density: 0.923 g / c)
m ³ ) (16) HDPE: high density polyethylene (density; 0.950 g / c
m ³ )

The evaluation method is as follows. (17) Appearance of tape extrusion (confirmation of presence or absence of bumps): Extruder of 50mmφ 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 (Bullet) Evaluation: The order of △>△> × was given, and the level of ○ was judged as acceptable. (18) Heat deformation ratio (%): JIS K 6723
by. (19) 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 1.00mmφ Screw speed 40 rpm Coating Appearance evaluation of the electric wire: ○>△> ×, in order, and the level of “O” was accepted. (20) Ease of winding after covering the wire (confirmation of the flexibility of the cable): Winding evaluation of the covered wire: In the order of △>△> ×, the level of ○ was accepted.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

As is clear from the table, Examples 1 to 5 have good extrusion processability and smoothness of the molding surface, and show extremely 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. On the other hand, all of the comparative examples have difficulty in smoothness, and the extrusion processability and heat resistance are not balanced.

[0030]

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.

Claims (7)

(57) [Claims] 1. A base polymer having the 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) The base polymer is dispersed in a silane-crosslinked polyolefin resin composition melt-mixed with a carrier polymer A containing a silanol condensation catalyst and an antioxidant by reacting an organic unsaturated silane and a free radical generator to form a silane graftmer. comprises degrees molecular weight distribution (Mw / Mn) linear in low density polyethylene which is a 4 or more, and an average density of ^{0.915g / cm 3 ~0.935g / cm 3} ,
A silane crosslinked polyolefin resin composition having a heat deformation ratio after melting and mixing (JIS K 6723) of 40% or less. 2. The base polymer has a degree of dispersion (Mw / Mn).
Is 4 or more, a linear medium-low density polyethylene 45 to 99.
The silane-crosslinked polyolefin resin composition according to claim 1, comprising a mixture of 1 part by weight and 1 to 55 parts by weight of polyethylene. 3. The base polymer has a degree of dispersion (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 The silane-crosslinked polyolefin resin composition according to claim 1, comprising a mixture of 1 to 25 parts by weight of a polyolefin selected from the group consisting of a copolymer and a mixture thereof. 4. The carrier polymer A is polyethylene,
The silane-crosslinked polyolefin resin composition according to claim 1, which is selected from the group consisting of polypropylene and a copolymer of ethylene and α-olefin. 5. The silane-crosslinked polyolefin resin composition according to claim 1, wherein the amount of the carrier polymer A is 2 to 5% by weight. 6. An insulated cable obtained by coating an electric wire with the silane-crosslinked polyolefin resin composition according to claim 1. 7. An insulated cable, wherein an electric wire is coated with the silane-crosslinked polyolefin resin composition according to claim 1 and then coated with a sheath material.