JPH0820703A - Soft silane graftmer and production of insulated wire - Google Patents

Abstract

PURPOSE:To obtain a soft silane graftmer which has mechanical characteristics greatly inhibited from lowering at high temps. by reacting a base polymer comprising specific ethylene copolymers and a low-density PE with an org. unsatd. silane and a free-radical generater. CONSTITUTION:This soft silane graftmer is obtd. by reacting 100 pts.wt. base polymer with 1-5 pts.wt. org. unsatd. silane and 0.1-1 pt.wt. free-radical generater. The base polymer comprises an ethylene-propylene- ethylidenenorbornene terpolymer having a molar ratio of ethylene to propylene of (70:30)-(90:10)(A), an ethylene-propylene binary copolymer having a molar ratio of ethylene to propylene of (70:30)-(90:10)(B), 15-45wt.% low-density PE (C), and 10-20wt.% at least one resin selected from among an ethylene-alpha-olefin copolymer, an ethylene-ethyl acrylate coplymer, and an ethylene-methyl methacrylate copolymer (D) provided the sum of amts. of components A and B is 35-75wt.% and the wt. ratio of component A to component B is (2:1)-(4:1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition of a polyolefin-based rubber insulated wire and a method for producing the same, in which deterioration of mechanical properties at a high temperature (250 ° C.) is significantly suppressed.

[0002]

2. Description of the Related Art Conventionally, as a simple method for crosslinking polyolefin such as polyethylene or ethylene propylene rubber, after graft-reacting an organic unsaturated silane with the polyolefin in the presence of a free radical generator, silane-grafting is performed. A so-called silane cross-linking method is generally known in which the silane grafter is brought into contact with water in the presence of a silanol condensation catalyst to cross-link it. For example, JP-B-48-1711 and JP-A-57-49109 are available. Although a polyolefin rubber insulated wire having rubber elasticity can be manufactured by this method, the fact is that it is difficult to put into practical use due to the following problems. That is, the polyolefin having rubber elasticity generally has a low softening temperature of around 40 ° C., and the pellets of the polyolefin cause blocking at the throat portion of the extruder hopper during storage or during extrusion,
Pellets adhered to the screw feed section of the extruder, and the amount of extrusion varied or the amount of extrusion gradually decreased.

As another method, a polyolefin-based rubber insulated wire can be manufactured by passing a vulcanization process of rubber. However, due to its low mechanical strength and the vulcanization process, the manufacturing speed of the cable is increased. Financial problems are inevitable. In other words, immediately after extrusion coating, an external force is applied in the take-up machine or the winding drum to cause permanent deformation of the coating layer. Therefore, it is necessary to take sufficient cooling process and vulcanization process. For this reason, it is necessary to slow down the cable manufacturing linear velocity and to remarkably lengthen the cooling water tank, which inevitably causes economic problems. In order to solve such a problem, as seen in JP-A-3-56517,
A system using an ethylene-propylene-diene terpolymer and an ethylene-methylmethacrylate copolymer as a base resin was invented, and a resin composition having good processability and good rubber elasticity was provided. However, these resin compositions show remarkable deterioration in mechanical properties at high temperatures (250 ° C.) and break in a heat elongation test at 250 ° C. For this reason, it could not be used in applications requiring such heat resistance.

[0004]

SUMMARY OF THE INVENTION The present invention has solved these problems, and it is a polyolefin-based rubber having a rubber-like flexibility that remarkably suppresses deterioration of mechanical properties at high temperatures (250 ° C.), and It is intended to provide an insulated electric wire coated with the polyolefin rubber.

[0005]

The present invention provides the following (a) to (f):
(A) + (b) = 35-75
Weight% (however, (a) :( b) = 2: 1 to 4: 1), (c) is 1
5 to 45 wt% and (d) 10 to 20 wt% of the base polymer (a) + (b) + (c) + (d) = 100 parts by weight,
A flexible silane graftmer obtained by reacting 1 to 5 parts by weight of (e) and 0.1 to 1 part by weight of (f). (a) The molar ratio of ethylene and propylene is 70/30 to 90.
/ 10 terpolymer with ethylidene norbornene (b) The molar ratio of ethylene and propylene is 70/30 to 90
/ 10 binary copolymer (c) at least low density polyethylene (d) at least selected from copolymers of ethylene and α-olefins, ethylene-ethyl acrylate copolymers, ethylene-methyl methacrylate copolymers One or more kinds of resin (e) organic unsaturated silane (f) free radical generator, and low-density polyethylene in the form of pellets and / or powder, which is a flexible silane graftmer, and further said flexible silane graft The method for producing an insulated wire is characterized in that a mer is extrusion-coated on a conductor in the presence of a silanol condensation catalyst and brought into contact with water to crosslink.

The terpolymer of the component (a) of the present invention, which has a molar ratio of ethylene to propylene of 70/30 to 90/10 and ethylidene norbornene, is added for the purpose of imparting flexibility to the resin composition. It The binary copolymer having a molar ratio of ethylene and propylene of component (b) of 70/30 to 90/10 maintains the flexibility of the resin composition and suppresses the reduction of the grafting ratio of silane to crosslink. It is added for the purpose of improving the degree. The addition amount of these (a) + (b) is 35 to 75% by weight, preferably 45 to 65% by weight of the base polymer. If it is less than 35% by weight, the desired flexibility cannot be obtained.
When it is 5% by weight or more, the workability becomes poor and the product becomes expensive, which is not practical. Further, the ratio of the component (a) to the component (b) is (a) :( b) = 2: 1 to 4: 1, preferably (a) :( b) =
3: 1. If the amount of the component (b) is less than the above range, the degree of cross-linking will be lowered, and if it exceeds the above range, the workability will be poor, which is not practical.

The low density polyethylene as the component (c) of the present invention is added for the purpose of maintaining mechanical properties at high temperature (250 ° C). The addition amount of these is 15 of the base polymer.
˜45 wt%, preferably 25-35 wt%. 1
If it is 5% by weight or less, desired mechanical properties at high temperature (250 ° C.) cannot be obtained, and if it is 45% by weight or more, flexibility is lowered. Further, the powder type of the component (c), when an appropriate amount of the organic unsaturated silane and the free radical generator is added and reacted, the organic unsaturated silane which is a liquid substance is impregnated, and a small amount is added for uniform dispersion. Is preferred.

At least one resin selected from the copolymer of ethylene and α-olefin, the ethylene-ethyl acrylate copolymer and the ethylene-methyl methacrylate copolymer, which is the component (d) of the present invention, is , (A) component and (b)
It is added for the purpose of improving the compatibility of the component and the component (c) and maintaining the balance between flexibility and mechanical properties. The amount of these added is 10 to 20% by weight of the base polymer,
It is preferably 12 to 17% by weight. If it is 10% by weight or less, the desired compatibilizing effect cannot be obtained, and if it is 20% by weight or more, the mechanical properties and the degree of crosslinking are deteriorated.

The organic unsaturated silane of the component (e) of the present invention is
The base resin is grafted to the base resin as crosslink points as possible. The organic unsaturated silane used in the present invention has the general formula RR'SiY ₂ (R is a monovalent olefin unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R'is an aliphatic unsaturated hydrocarbon. Other than monovalent hydrocarbon groups or compounds represented by Y) are used. It is desirable to use an organic unsaturated silane in which R'is the same as Y and is represented by the general formula RSiY ₃ , and examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, and allyltriethoxy. Examples include silane. The addition amount of these is 1 to 5 parts by weight, preferably 2.5 to 3.5 parts by weight, based on 100 parts by weight of the base polymer. If the amount is less than 1 part by weight, sufficient grafting does not occur, and if the amount is more than 5 parts by weight, molding defects occur and it is not economical.

The free radical generator of the component (f) of the present invention acts as an initiator of the silane grafting reaction. As the free radical generator used in the present invention, various organic peroxides having a strong polymerization initiation action are used. The addition amount of these is 0.1 to 1 part by weight, preferably 0.1 to 0.3 part by weight, based on 100 parts by weight of the base polymer. If the amount is less than 0.1 parts by weight, the silane grafting reaction will not proceed sufficiently, and if the amount is more than 1 part by weight, the extrusion processability will deteriorate and the molding surface will deteriorate. As the other additive, the flexible composition of the present invention may optionally contain a commonly used additive such as an antioxidant, a neutralizer, an ultraviolet absorber, an antistatic agent, a pigment, a dispersant, a lubricant, and a thickener. Further, a foaming agent, a metal deterioration preventing agent, an antifungal agent, a flow controlling agent, etc., a flame retardant of phosphorus and phosphine derivatives, other inorganic fillers, etc., or other synthetic resin may be contained.

[0011]

EXAMPLES Examples will be described below. First, the base polymer was kneaded and granulated using a pressure kneader according to the blending ratios shown in Table 1 and Table 2. This mixture is mixed with an organic unsaturated silane and a free radical generator, and kneaded at an extrusion temperature of 120 to 180 ° C. using a single screw extruder,
The strand was cut and granulated to obtain a silane graftmer. The obtained silane grafter and catalyst masterbatch (100 parts by weight of low-density polyethylene, 1 part by weight of dibutyltin dilaurate and an antioxidant kneaded into pellets) were mixed at a ratio of 19: 1, The mixture was kneaded using a single-screw extruder, extruded into a tape having a thickness of 1 mm and a width of 100 mm, and then immersed in warm water to perform a crosslinking treatment. Using this tape-shaped sample, various test pieces for measurement were prepared.
Using this test piece, a gel fraction, a tensile test and a heat elongation test were carried out. Also, using a tape-shaped sample after extrusion,
A press sheet having a thickness of m was prepared, and the hardness of the composition was measured using this press sheet. In addition, the extrusion processability during extrusion was evaluated.

Table 1 Example Comparative Example 1 2 3 4 1 2 3 4 Compounding agent EPDM 40 50 35 45 55 60 50 EPR 15 15 10 15 50 23 18 LDPE 28 20 38 24 35 30 30 EMMA 15 13 15 16 15 13 15 Powder LDPE 2 2 2 2 2 VTMOS 3 3 3 3 3 3 3 3 DCP 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Evaluation item Tensile strength (MPa) 17 16 18 17 18 16 13 17 Stretch (%) 550 600 540 540 49 520 550 520 Gel fraction (%) 78 77 76 76 84 69 81 78 Allowable elongation (%) 100 105 95 110 100 Fracture fracture 105 Permanent elongation (%) 10 15 10 15 15 − − 15 Hardness (JIS A) 85 81 87 83 86 77 73 83 Workability ○ ○ ○ ○ × ○ △ △ Overall evaluation ○ ○ ○ ○ × × × ×

Table 2 Comparative Example 5 6 7 8 9 10 11 12 Combination drug EPDM 40 25 55 25 40 45 45 35 EPR 15 30 10 10 15 15 20 10 LDPE 28 20 55 30 25 20 35 HDPE 30 EMMA 15 15 13 10 15 13 15 13 Powder LDPE 2 2 2 2 VTMOS 3 3 3 3 0.5 10 3 3 DCP 0.2 0.2 0.2 0.2 0.2 0.2 0.05 3 Evaluation item Tensile strength (MPa) 18 17 15 18 12 17 10 14 Elongation (%) 500 490 570 450 600 440 520 230 Gel fraction (%) 75 80 70 75 52 80 47 90 Allowable elongation (%) 110 115 Break 90 Break Break Break Break Permanent elongation (%) 15 15 − 10 − − − − Hardness (JIS A) 95 84 82 97 85 84 81 88 Workability ○ △ ○ ○ △ △ ○ × Overall evaluation × × × × × × × ×

In the examples and comparative examples, the following were used and compounded. (1) Ethylene-propylene-diene terpolymer (EP
DM) (2) Ethylene-propylene binary copolymer (EPR) (3) Low density polyethylene (LDPE) (4) High density polyethylene (HDPE) (5) Ethylene-methyl methacrylate copolymer (EMM
A) (6) Powder low density polyethylene (powder LDPE) (7) Vinyltrimethoxysilane (VTMOS) (8) Dicumyl peroxide (DCP) The evaluation method was as follows. (1) Tensile strength and elongation are according to JIS K6760. (2) Gel fraction is 120 ° C., 20 hours, xylene immersion method (3) Allowable elongation is according to IEC 540A. Elongation between marked lines after 15 minutes at 250 ° C. and 20 N / cm ² (4) Permanent elongation is according to IEC 540A. Elongation between marked lines after 5 minutes at 250 ° C (5) Hardness is according to JIS K6301. (90 or less was accepted) (6) Workability was 50 mmφ single screw extruder 120-150-170-180-
170 ° C L / D: 20 compression ratio 3.5 tape die thickness 1mm The evaluation was in the order of ○>△> ×, and the level of ○ was passed.

[0015]

As is apparent from the table, Examples 1 to 4
The material shown in 1) retains flexibility, passes the heat elongation test at 250 ° C., and exhibits very excellent mechanical properties and processability. On the other hand, the comparative examples are all flexible, 2
The heat extensibility at 50 ° C and workability are not balanced. As described above, according to the present invention, it is possible to obtain an insulated electric wire that remarkably suppresses deterioration of mechanical properties at high temperature (250 ° C.) and has rubber-like flexibility.

Claims (3)

[Claims] 1. A composition comprising the following components (a) to (f), wherein (a) + (b) = 35 to 75% by weight (where (a) :( b)
= 2: 1 to 4: 1), (c) 15 to 45% by weight, (d) 1
0 to 20% by weight of base polymer (a) + (b) + (c) +
1 to 5 parts by weight of (e) with respect to (d) = 100 parts by weight and
A flexible silane graftmer, characterized by reacting (f) with 0.1 to 1 part by weight. (a) The molar ratio of ethylene and propylene is 70/30 to 90.
/ 10 terpolymer with ethylidene norbornene (b) The molar ratio of ethylene and propylene is 70/30 to 90
/ 10 binary copolymer (c) at least low density polyethylene (d) at least selected from copolymers of ethylene and α-olefins, ethylene-ethyl acrylate copolymers, ethylene-methyl methacrylate copolymers At least one resin (e) organic unsaturated silane (f) free radical generator 2. The low density polyethylene comprises pellets or /
And the flexible silane graft mer according to claim 1, which is a powder. 3. A method for producing an insulated wire, which comprises extrusion-coating a flexible silane graftmer according to claim 1 on a conductor in the presence of a silanol condensation catalyst and bringing the conductor into contact with water to crosslink the same.