JP3354498B2 - Silane crosslinkable polyolefin resin composition and insulated cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a base polymer,
Silane cross-linked resin composition produced by a method capable of silane cross-linking in a single step with a carrier polymer A containing a high concentration of an organic unsaturated silane or the like and a carrier polymer B containing a silanol condensation catalyst or the like, and an insulated cable using the same It is about.

[0002]

2. Description of the Related Art Polyethylene is used in many industrial fields because of its excellent mechanical properties, electrical properties, chemical resistance, weather resistance, cold resistance and the like. It is often used in the field of electric power and insulated cables.
Cross-linking treatment is often performed to improve stracking resistance, weather resistance, and the like. Recently, cross-linked polyethylene has been increasingly used for high-voltage cables from the viewpoint of easy maintenance and cost reduction.

[0003] 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. One of them is hot water crosslinking. Compared with chemical crosslinking and electron beam irradiation crosslinking, the cost of the crosslinking apparatus is much lower and the crosslinking is 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-57-49
No. 109 publication.

[0004] However, hot water crosslinking requires much man-hours compared to other crosslinking methods which are highly useful in terms of equipment cost. For example, after producing a coated electric wire by extrusion coating a silane cross-linked polyolefin resin, wound on a drum,
Next, the drum is left in a hot water or a high-temperature and high-humidity bath at about 80 ° C. to perform a crosslinking treatment. After the treatment, a step of putting the drum in a drying chamber to dry the coated electric wire, sheathing the wound wire, and winding the wound wire around a shipping drum is performed. Further, as a problem in this step, there is corrosion of the drum at the time of the cross-linking treatment, which causes an increase in cost.

[0005] There have been various attempts to shorten the time required for the cross-linking treatment of electric wires extruded with a water-crosslinkable resin. For example, a method of adding a catalyst or an auxiliary agent to a modified silane compound to promote crosslinking is known, and is disclosed in JP-A-57-208006 and JP-A-62-106947.
No. 6,086,045. Further, 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, which is disclosed in JP-A-60-254520 and JP-A-60-26510. I have. Furthermore, a method of shortening the time of the crosslinking treatment by promoting the diffusion of water into 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-4-331.
No. 241. However, all of the above methods only shorten the time of the crosslinking treatment by hot water or steam treatment, and do not eliminate and shorten 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.

[0007]

[0008] The present invention has solved these aforementioned problems, in particular those providing smoothness and excellent heat resistance silane crosslinkable polyolefin resin composition forming the surface. Further, in wire was extrusion coated with the silane crosslinkable <br/> polyolefin resin composition to remove the cross-linking treatment step, there is provided an insulated cable which may immediately sheath seat.

[0008]

According to the present invention, there is provided a polymer having the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon) under the condition that (1) a base polymer and (2) substantially no water is present. 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 an organic unsaturated silane represented by Y) and a free radical generator. and carrier polymer a, and (3) a silanol condensation catalyst and silane crosslinkable polyolefin resin composition comprising a carrier polymer B which contains an antioxidant, base polymer density 0.910
A melt index of 0.5 in ~0.945g / cm ³
Made linear in the low-density polyethylene 5 g / 10min, heat deformation rate immediately after extrusion (JIS K 6723) can silane-crosslinked, characterized in that 40% or less of polyolefin <br/> fin resin composition It is. In a preferred embodiment, the base polymer is a linear medium-low-density polyethylene having a density of 0.910 to 0.945 g / cm ³ and a melt index of 0.5 to 5 g / 10 min. The melt viscosity is 6500-15000 poise and the die swell is 1.50 or more (under 200 ° C., using a capillary having a diameter of 1 mm and a length of 10 mm, 240
c- ¹ ) or a base polymer having a melt viscosity of 6500 to 15000 poise and a die swell of 1.50 or more (under a condition of 200 ° C., a capillary having a diameter of 1 mm and a length of 10 mm). Use 240se
c and a linear in the low density polyethylene 45 and 90 parts by weight of the measurement) at a shear rate of ^-1, linear in the silane crosslinkable consisting of a mixture of low density polyethylene 10 to 55 parts by weight with from 9000 to 11000 poise a polyolefin resin composition. In a more preferred embodiment, the carrier polymer A is an ethylene-ethyl acrylate copolymer (E
EA), ethylene-methyl methacrylate copolymer (E
MMA), 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 carrier polymer B is selected from the group consisting of polyethylene, polypropylene, and a copolymer of ethylene and α-olefin, and the total amount of the carrier polymers A and B is 3 to 15% by weight. a silane crosslinkable polyolefin resin composition is. Further, the present invention is an insulated cable in which an electric wire is coated with such a silane crosslinkable polyolefin resin composition, in which the electric wire is coated, a water cross-linking step after coating is eliminated, and the sheath is immediately sheathed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The linear medium-low-density polyethylene used in the base polymer of the present invention refers to a gas-phase method, a solution method, and a suspension method using various catalysts such as a Ziegler-based catalyst and a chromium-based catalyst. It is a copolymer with an α-olefin containing ethylene as a main component by various polymerization methods such as a synthesis method, and has a density of 0.910 to 0.945 g / cm ³ and a melt index of 0.5 to 5 g / 10 min. is there. Examples of the α-olefin include C3-C12 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 density of the linear medium-low density polyethylene used is 0.910 g /
If it is less than ³ cm ³ , the heat resistance is reduced, and 0.945
Exceeding g / cm ³ causes a reduction in extrusion processability.

The melt viscosity of the base polymer of the present invention is 6
500-15000 poise, die swell is 1.50
Above (measured at a shear rate of 240 sec ^-1 using a capillary of 1 mm in diameter and 10 mm in length at 200 ° C.)
Are preferred. The melt viscosity of the base polymer is 65
Less than 00 poise or more than 15,000 poise causes poor appearance. Also, when the die swell is less than 1.50, the appearance is similarly deteriorated. More preferably, the linear medium-low-density polyethylene 45 to 6500 to 10000 poise and the die swell is 1.50 or more.
It is a base polymer comprising a mixture of 90 parts by weight and 10 to 55 parts by weight of a linear medium-low density polyethylene having 9000 to 11,000 poise. Melt viscosity is 9000-1
If the addition amount of the linear low-density polyethylene of 1,000 poise is less than 10 parts by weight, the effect of improving heat resistance is reduced. On the other hand, if it exceeds 55 parts by weight, the extrusion processability is reduced.

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 free radical generator and the silane can be added to the carrier polymer A by swelling the carrier polymer A of the present invention with a liquid mixture in which the free radical generator is dissolved in the silane. At this time, in order to add silane at a high concentration, preheating of the carrier polymer A is necessary, but the temperature must be lower than the crystal melting point so that the polymer does not melt. Also, the carrier polymer A must be in solid form and be solid and compatible with the crosslinkable base polymer and silane. What is compatibility?
It means that the carrier polymer A must not readily react with the silane and must be dispersible or soluble in the base polymer. Suitable carrier polymers A are non-hygroscopic. That is, it is preferred that the water absorption be relatively slow to minimize the potential for premature hydrolysis and condensation of the silane. In any case, the carrier polymer A should be substantially free of water. 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 includes ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), and a polymer mainly composed of at least one vinyl aromatic compound. A hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of a united block and a polymer block mainly composed of at least one conjugated diene compound, for example, a hydrogenated styrene-isoprene block copolymer (SEPS) ), Hydrogenated styrene-butadiene block copolymer (SEBS) and the like, and mixtures thereof.

The carrier polymer B can be added by kneading and granulating a silanol condensation catalyst and an antioxidant with the carrier polymer B of the present invention. Also, the carrier polymer B must be in particulate form and a solid compatible with the base polymer to be crosslinked. The carrier polymer B of the present invention is usually in the form of granules or granules in the form of pellets, the preferred form being pellets. The carrier polymer B 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.

Examples of the silanol condensation catalyst of the present invention include 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. Also, a silanol condensation catalyst must be added to the carrier polymer B. This is because the addition to the carrier polymer A promotes oligomerization by condensation of silane and causes deterioration in appearance.

The antioxidant of the present invention is generally used when processing a polyolefin and is not particularly limited, but must be added to the carrier polymer B. This is because the addition to the carrier polymer A inhibits crosslinking by scavenging radicals. Even when other additives are added, additives that may inhibit crosslinking must be added to the carrier polymer B.

The added amount of the carrier polymer is such that the total amount of the carrier polymers A and B is in the range of 3 to 15% by weight. If the amount is less than 3% by weight, sufficient grafting will not occur, and if it exceeds 15% by weight, molding failure will occur and it will not be economical. As other additives, if desired, additives usually used, for example, neutralizers, ultraviolet absorbers, antistatic agents, pigments, dispersants, thickeners, metal deterioration inhibitors, antifungal agents, flow control agents , Other inorganic fillers, etc.
Alternatively, another synthetic resin 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 it is possible to cover the electric wire and then apply a sheath without performing a water crosslinking step. For this purpose, it is necessary that the heating deformation ratio immediately after extrusion is 40% or less.

[0020]

The following examples illustrate the invention, but are by way of example only and the invention is not limited thereto. An example will be described below. << Production of Carrier Polymer A >> According to the compounding ratio as shown in Table 1, first, the carrier polymer A is charged into a super mixer, stirred and mixed, and preheated to 80 ° C. Next, a liquid mixture in which a free radical generator was dissolved in an unsaturated silane was charged into a supermixer and impregnated with the carrier polymer A for 10 minutes while stirring. << Production of Carrier Polymer B >> The carrier polymer B, a silanol condensation catalyst, an antioxidant, and the like were kneaded and granulated according to the compounding ratio shown in Table 2 using a pressure kneader.

The raw materials used are as follows. (1) EEA: ethylene-ethyl acrylate copolymer (E
(A content: 23% by weight) (2) SEPS: hydrogenated styrene-isoprene block copolymer (styrene content: 30% by weight) (3) L-LDPE (1): linear low-density polyethylene (density: 0.924 g) / cm ³ , MI;
(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 Co., Ltd.) (10) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Chemical Industries, Ltd.) (11) L-LDPE (2): linear medium-low-density polyethylene (density: 0.917 g / cm ³ , MI; 0.7 g / 10 min) (12) L-LDPE ( 3): Linear medium and low density polyethylene (density: 0.919 g / cm ³ , MI; 2 g / 10 min) (13) L-LDPE (4): Linear medium and low density polyethylene (density: 0.920 g / cm ³⁾ , MI; 2 g / 10 min) (14) L-LDPE (5): linear medium-low density polyethylene (density; 0.920 g / cm ³ , MI; 4 g / 10 min) (15) L-LDPE (6): straight Linear medium-low-density polyethylene (density: 0.925 g / cm ³ , MI; 1.7 g / 10 min) (16) L-LDPE (7): linear medium-low-density polyethylene (density: 0.924 g / cm ³ , MI; (17) L-LDPE (8): linear medium-low density polyethylene (density; 0.920 g / cm ³ , MI; 1 g / 10 min)

The evaluation method is as follows. (18) Silane impregnation: The impregnation when the VTMOS / DCP liquid mixture was heated and stirred by a super mixer was evaluated. ：: good impregnating property, ×: no impregnating property (19) Measurement of Melt Viscosity and Die Swell by Capillograph Melt viscosity and die swell were measured using a Capillograph manufactured by Toyo Seiki. The measurement was performed at 200 ° C., and the measured range was a shear rate of 20 to 6000 sec ⁻¹ , and the numerical values in the text and the table are those at 240 sec ⁻¹ . (20) Tape extrusion appearance (confirmation of the 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 (Bull) Evaluation: The order of ○>△> × was given, and the level of ○ was passed. (21) Heat deformation ratio (%): JIS K 6723
by. (22) 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 ○ was accepted.

A polyolefin base polymer having the composition shown in Tables 3 and 4, a carrier polymer A and a carrier polymer B were mixed at a ratio shown in Tables 5 to 7, and a tape was extruded using an extruder. The heat deformation rate 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.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

[0029]

[Table 6]

[0030]

[Table 7]

As is clear from the table, Examples 1 to 3 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.

[0032]

According to the present invention, it is possible to obtain an excellent silane crosslinkable polyolefin excellent heat resistance in smoothness of the molded surface, reducing the water crosslinking process when used in wire coating, immediately Can be sheathed. 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 (8)

(57) [Claims] (1) a base polymer; (2) a compound represented by the general formula RR'SiY ₂ (R is 1
Olefinic 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 the free radical generator carrier polymer were contained a, and (3) a silanol condensation catalyst and silane crosslinkable polyolefin resin composition comprising a carrier polymer B which contains an antioxidant, base polymer density 0. It is made of linear medium-low-density polyethylene having a melt index of 0.5 to 5 g / 10 min at 910 to 0.945 g / cm ³ , and has a heating deformation ratio (JIS K 6723) immediately after extrusion of 40% or less. a silane crosslinkable polyolefin resin composition. 2. The base polymer having a density of 0.910
0.945g / cm ³ a melt index from 0.5 to 5
g / 10 min linear low-density polyethylene having a melt viscosity of 6500 to 1 when used alone or in combination of two or more.
5000 a poise and die swell of 1.50 or more is (200 ° C. under conditions of a diameter of 1 mm, 240 sec measured at a shear rate of ^-1 using a capillary length 10 mm) according to claim 1 silane crosslinkable polyolefin according Resin composition. 3. The base polymer has a melt viscosity of 6500.
~ 15000 poise and 1.50 die swell
(Measured at a shear rate of 240 sec ^-1 using a capillary having a diameter of 1 mm and a length of 10 mm at 200 ° C.)
45 to 90 parts by weight of a linear medium-low density polyethylene of
Linear in low density polyethylene 10-55 mixture according to claim 1 silane crosslinkable polyolefin resin composition according consisting of parts with 000 to 11,000 poise. 4. A polymer block mainly composed of an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), at least one vinyl aromatic compound,
4. A hydrogenated block copolymer obtained by hydrogenating a block copolymer composed of a polymer block mainly composed of at least one conjugated diene compound, and a hydrogenated block copolymer selected from the group consisting of mixtures thereof . silane crosslinkable polyolefin resin composition according to any one. 5. The carrier polymer B is polyethylene,
Polypropylene, ethylene and α over any one in serial <br/> mounting of silane crosslinkable polyolefin resin composition of claim 1 selected from the group consisting of copolymerization of olefins. 6. The total amount of carrier polymers A and B is 3
Silane crosslinkable polyolefin resin composition according to any one of claims 1 to 5 is 15%. 7. insulated cable, wherein the performing the wire coated with the silane crosslinkable polyolefin resin composition according to any one of claims 1 to 6 8. perform wire coated with silane crosslinkable polyolefin resin composition according to any one of claims 1 to 6, to remove the water crosslinking step after coating, characterized in that immediately over the sheath And insulated cable.