JP3344918B2 - Flame retardant polyolefin composition and power cable using the composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant polyolefin composition, particularly to a coating material for electric wires and cables,
The present invention relates to a low-smoke and low-toxic flame-retardant polyolefin composition that can be used as a building material such as wallpaper.

[0002]

2. Description of the Related Art Polyolefin resins have flexibility,
In addition, it is widely used in various fields because of its low price compared to other materials. Also, since it has excellent electrical insulation properties, it is used in large quantities as a wire coating material.

[0003] A flame-retardant polyolefin composition having a flame retardancy obtained by blending a flame retardant with such a polyolefin resin is known. Does not include
Attention has been focused on flame-retardant polyolefin compositions that emit less toxic gas and smoke when burned.

[0004] Polyolefin resins include polyethylene, polypropylene and its copolymer ethylene /
Vinyl acetate copolymer (EVA), ethylene / ethyl acrylate copolymer (EEA) and the like are widely used, but these polyrefin resins are inherently easily flammable and make these resins flame-retardant. Therefore, it is necessary to add a flame retardant, a flame retardant auxiliary, and the like.

As the flame retardant, bromine-based and chlorine-based halogen-based flame retardants are known to have a high flame-retardant effect. The request cannot be answered. On the other hand, with other phosphorus-based flame retardants, metal hydroxide-based flame retardants, metal hydrate-based flame retardants, metal oxide-based flame retardants, etc., the polyolefin resin composition has a sufficient flame retardancy (in particular, an oxygen index of 28 or more). In order to provide (1), a large amount of a flame retardant and a flame retardant auxiliary must be added. For example, it is necessary to add at least about 150 parts by weight of the flame retardant to 100 parts by weight of the resin.

However, polyolefin resins containing such large amounts of flame retardants and the like are inferior in mechanical properties and workability, and have many practical problems particularly in applications requiring sufficient mechanical properties.

[0007] Accordingly, there is a need for flame-retardant polyolefins that have even better flame retardancy without containing halogen and have excellent mechanical properties. In addition, when used as an insulating coating for power cables, its electrical characteristics are also important.

[0008]

Accordingly, the present invention relates to a polyolefin resin material containing no halogen, which has sufficient flame retardancy, mechanical properties and workability, and is used as a wire covering material. It is an object of the present invention to provide a flame-retardant polyolefin composition exhibiting suitable electrical characteristics.

[0009]

As a result of the research by the present inventors,
When a composite metal hydroxide flame retardant containing two or more metals is used in a polyolefin resin in combination with a silicone compound as a flame retardant aid, excellent flame retardancy is obtained due to its synergistic effect, and therefore, mechanical properties are impaired. It is possible to obtain a flame-retardant polyolefin composition that does not require such a flame retardant amount, has excellent mechanical and electrical properties, and can meet the demand for non-halogenation, low toxic gasification and low smoke generation. Was found.

Accordingly, the present invention relates to a polyolefin resin 10
8 parts by weight of a composite metal hydroxide as a flame retardant per 0 parts by weight
A low-smoke and low-toxic flame-retardant polyolefin composition comprising 0 to 150 parts by weight and 1 to 10 parts by weight of a silicone compound as a flame retardant aid.

In one preferred embodiment of the flame-retardant polyolefin composition of the present invention, the flame retardant has the formula Mg _1-x M
⁺² _x (OH) ₂ complex metal hydroxide (wherein, M
⁺² is at least one selected from the group of divalent metal ions of Mn ⁺² , Fe ⁺² , Co ⁺² , Ni ⁺² , Cu ⁺² and Zn ⁺² , and x is
0.001 ≦ x ≦ 0.9).

In another preferred embodiment of the flame-retardant polyolefin composition of the present invention, the polyolefin resin comprises:
It consists of at least one selected from polyethylene, polypropylene, ethylene / ethyl acrylate copolymer and ethylene / vinyl acetate copolymer.

The flame-retardant polyolefin composition of the present invention comprises
It preferably has an oxygen index of 28 or more.

The present invention also provides a power cable having the flame-retardant polyolefin composition of the present invention as an insulating layer or a sheath.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin resin which is the base of the flame-retardant polyolefin composition of the present invention includes polyethylene having low density, medium density and high density, ethylene and propylene, butene-1, pentene-1, hexene-. 1,4
A copolymer with an α-olefin having 3 to 12 carbon atoms such as methylpentene-1, octene-1, and decene-1, ethylene / propylene rubber (EPM), ethylene / propylene / diene monomer rubber (EPDM), Copolymers of ethylene with a polar group-containing monomer such as vinyl acetate, ethyl acrylate, methacrylic acid, ethyl methacrylate, and maleic acid, and arbitrary mixtures of these polyolefin resins can be given.

Of these, polyethylene, polypropylene, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer and mixtures thereof are particularly preferred.

As the flame retardant used in the flame-retardant polyolefin composition of the present invention, a composite metal hydroxide containing a plurality of metals is used. The composite metal hydroxide has the function of imparting flame retardancy by dissociating and absorbing heat during combustion of water and the function of imparting flame retardancy by the carbonization promoting catalytic effect of the composite metal. I do.

Such a composite metal hydroxide is represented by the formula
A composite metal hydroxide represented by Mg _1-x M ⁺² _x (OH) ₂ (where M
⁺² is at least one selected from the group of divalent metal ions of Mn ⁺² , Fe ⁺² , Co ⁺² , Ni ⁺² , Cu ⁺² and Zn ⁺² , and x is
It is a number satisfying 0.001 ≦ x ≦ 0.9). Preferred specific examples of the composite metal hydroxide represented by the formula Mg _1-x M ⁺² _x (OH) ₂ include the formulas Mg _1-x Ni ⁺² _x (OH) ₂ , Mg _1-x Mn
⁺² _x (OH) ₂ and a composite metal hydroxide represented by Mg _1-x Fe ⁺² _x (OH) ₂ .

Such a composite metal hydroxide can be provided in the form of being coated with another metal hydroxide represented by M based on magnesium hydroxide,
The metal represented by M, for example, Ni has an effect of extracting hydrogen in hydrocarbons derived from a vaporized polymer component, and such an effect can provide a flame retardant and low smoke generating effect of the composition. .

The amount of the composite metal hydroxide added is as follows:
The range is 80 parts by weight to 150 parts by weight with respect to 00 parts by weight. If the amount is less than 80 parts by weight, the effect of imparting flame retardancy is not sufficient, and if it exceeds 150 parts by weight, the processing properties of the composition and the mechanical properties of the product are significantly reduced. Preferably it is in the range of 100 to 120 parts by weight.

In the flame-retardant polyolefin composition of the present invention, a silicone compound flame retardant aid is used together with the composite metal hydroxide flame retardant. Silicone compounds used as flame retardant aids include Si-O bonded to organic groups.
Examples of such a silicone compound include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, modified silicone oils such as epoxy-modified, alkyl-modified, amino-modified, carboxy-modified, alcohol-modified, and ether-modified, and dimethyl. Silicone rubbers such as polysiloxane rubber and methylvinylpolysiloxane rubber; silicone resins such as methyl silicone resin and ethyl silicone resin;

These silicone compounds have a bond Si-
Compounds containing O and having bonded Si-C are generated during combustion, and these structures serve as a barrier for heat transfer. This barrier effect and the synergistic effect of imparting flame retardancy by thermal condensation at the time of forming a carbonized layer are obtained. Thus, the amount of the composite metal hydroxide flame retardant can be reduced to maintain the mechanical properties of the composition, and to reduce the generation of CO when the composition is burned.

The silicone compound is added in an amount of 1 to 10 parts by weight based on 100 parts by weight of the polyolefin resin. If it is less than 1 part by weight, the synergistic effect of imparting flame retardancy obtained with the composite metal hydroxide is not sufficient, and if it exceeds 10 parts by weight, the thermal stability of the composition becomes insufficient. Preferably, 2 to 8 parts by weight, particularly preferably 3 to 5 parts by weight, is added to 100 parts by weight of the polyolefin resin.

When a silicone compound which is solid at room temperature such as silicone rubber or silicone resin is used, it is preferable to use finely divided silicone powder in consideration of dispersibility in the resin composition. As such a silicone powder, an ordinary commercially available silicone powder can be used.

The silicone powder may be added to the composition as it is, but known coupling agents such as silane coupling agents such as vinyltriethoxysilane and γ-mercaptopropyltriethoxysilane, Surface-treat silicone powder in advance using a titanium coupling agent such as stearoyl titanate, a higher fatty acid coupling agent such as stearic acid, maleic acid, or oleic acid, or blend a coupling agent into the composition. Thereby, the adhesion between the silicone powder and the polyolefin resin can be improved, and the mechanical properties of the obtained polyolefin composition can be improved.

The composition of the present invention may further contain, if desired, inorganic fillers such as magnesium oxide, aluminum oxide, zirconium oxide, titanium oxide, silicon carbide, mica, and the like, as long as the desired effects are not impaired. ,
Plasticizers such as fatty acids such as oleic acid or metal salts thereof, mineral oils, waxes, softeners such as paraffins, esters,
Other additives such as antioxidants such as amides, coloring agents, antioxidants, ultraviolet absorbers, lubricants, stabilizers, and crosslinking agents may be added.

The method for producing the composition of the present invention is not particularly limited, and the composition can be produced by a known method. A polyolefin resin, a composite metal hydroxide flame retardant, a silicone compound flame retardant auxiliary and, if desired, any of the above-mentioned components are blended, and these are mixed with a usual Banbury mixer, tumbler, pressure kneader, kneading extruder. ,
The mixture is kneaded with a kneader such as a twin-screw extruder or a roll to produce a molded product, and then, if desired, can be crosslinked by heating, crosslinking with water in warm water, or irradiating an electron beam or high-energy radiation.

The flame-retardant polyolefin composition of the present invention comprises
In addition to excellent flame retardancy, it does not contain halogen, has low smoke emission and low toxic gas generation, so it can be widely used for building materials such as wallpaper, various consumer products, etc. The synergistic effect of the silicone compound reduces the amount of flame retardant required to obtain the required flame retardancy, and has excellent mechanical properties.Therefore, insulation of power cables that require sufficient mechanical properties in addition to the above properties It can be suitably used for coating and the like.

The power cable having an insulating coating made of the composition of the present invention can be manufactured by a known method for manufacturing a resin insulating coated cable such as extrusion coating using an extruder and a crosshead.

For example, the power cable of the present invention is formed by providing an internal semiconductive layer made of polyethylene, conductive carbon, and a crosslinking agent on a conductor, and further providing an insulating layer made of the composition of the present invention on the inner semiconductive layer. Further, an outer semiconductive layer similar to the inner semiconductive layer is provided thereon and cross-linked (these two or three layers can be extruded simultaneously), and a shielding tape and a holding tape are wound around these cables. Turned and provided with a sheath made of XLPE containing a flame retardant and a cross-linking agent, extruded an insulating layer made of the composition of the present invention on a conductor, and twisted three cross-linked cables together with an intervening material (aramid fiber, etc.) It is possible to adopt a form in which a pressing tape is wound and a sheath similar to the above is coated thereon.

[0031]

The present invention will be further described with reference to the following examples.

Example The components shown in Table 1 were blended in the amounts (parts by weight) also shown in Table 1, and kneaded with a kneader at a temperature of 90 ° C. for 5 minutes.
The mixture is pressed at 160 ° C. for 40 minutes by a press machine for 20 minutes.
Heat molding was performed at 0 kgf / cm ² to obtain a 2 mm-thick sheet comprising the composition of the present invention.

With respect to the sheet sample obtained above, tensile strength (JIS K 6301), elongation (JIS K 6301), hardness (JIS K 6301) and specific gravity were measured as initial physical properties. In addition, volume resistivity (JIS K 6911) as electrical characteristics,
Dielectric tangent (tanδ, JIS K 6911), dielectric constant (ε, JIS K 6911)
11) and the AC breakdown voltage were measured for oxygen index (JIS K 7201) as a measure of flame retardancy. Table 2 shows the results.

Comparative Examples 1 to 4 Polyolefin resin sheets were produced in the same manner as in the Examples, using the components and amounts shown in Table 1. The mechanical properties and the electrical properties of the sheet were measured in the same manner as in the examples. Table 2 shows the results.

[0035]

[Table 1]

[0036]

[Table 2] As shown in Table 2, the composition of the present invention using the composite metal hydroxide and the silicone compound (Example) was compared with Comparative Example 1 using only the metal hydroxide-based flame retardant magnesium hydroxide. Since the amount of flame retardant is reduced, the mechanical properties are improved (especially tensile strength and elongation), and the flame retardancy (oxygen index) is significantly superior due to the synergistic effect of the composite metal hydroxide and the silicone compound. I have.

Comparative Example 2 used only the composite metal hydroxide. Although the flame retardancy was maintained by increasing the amount of the flame retardant as compared with the composition of the present invention, the mechanical properties ( In particular, tensile strength and elongation) are remarkably inferior.

Comparative Examples 3 and 4 each used a composite metal hydroxide and zinc stannate or carbon black as a flame retardant aid in the same amounts as in the examples, but were compared with the composition of the present invention. Both have poor flame retardancy. Further, since the composition of Comparative Example 4 using carbon black is blackened, it cannot be used for the identification color formulation used for the insulator-coated electric wire and the like.

The composition of the present invention also had sufficient electrical properties to be used as an insulation coating on power cables.

FIG. 1 shows the relationship between the heat generation rate and the time measured by the corn calorimeter for the samples obtained in the examples and comparative examples. As can be seen from the figure, the rise of the curve of the sample of the example is slower than that of any of the samples of the comparative example, that is, the ignition time is slower, the heat generation rate at the same time is lower, and the flame retardancy is excellent. it is obvious. In particular, the lower heat generation rate compared to the sample of Comparative Example 2 in which only the same composite metal hydroxide as in the example was used in an increased amount,
This is considered to indicate that Si-O contained in the silicone compound flame retardant aid and the Si-C-containing compound generated by burning the compound have a high heat insulating effect, and serve as a barrier for heat transfer.

[0041]

Industrial Applicability The flame-retardant polyolefin composition of the present invention exhibits excellent flame retardancy and mechanical properties, and contains no halogen, so that it is excellent in safety, mechanical properties, and processability. Power cable insulation as a composition,
It can be suitably used for various building materials. In the flame-retardant polyolefin composition of the present invention, superior flame retardancy is obtained as compared with the case where a known composite metal hydroxide is used in combination with zinc stannate or carbon black in an equal amount.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between heat generation rate and time measured by a corn calorimeter for the samples obtained in Examples and Comparative Examples.

Claims (5)

(57) [Claims] 1. A composite metal hydroxide as a flame retardant is used in an amount of 80 to 150 parts by weight and a silicone compound as a flame retardant aid is used in an amount of 1 to 10 based on 100 parts by weight of a polyolefin resin.
A flame-retardant polyolefin composition comprising parts by weight. 2. The flame retardant is a composite metal hydroxide represented by the formula Mg _1-x M ⁺² _x (OH) ₂ (wherein M ⁺² is Mn ⁺² , Fe ⁺² , C
o ⁺² , Ni ⁺² , Cu ⁺² and Zn ⁺² are at least one selected from the group of divalent metal ions, and x is a number satisfying 0.001 ≦ x ≦ 0.9) The flame-retardant polyolefin composition according to claim 1, characterized in that: 3. The polyolefin resin is polyethylene,
3. The method according to claim 1, wherein the material comprises at least one selected from the group consisting of polypropylene, ethylene / ethyl acrylate copolymer and ethylene / vinyl acetate copolymer.
3. The flame-retardant polyolefin composition according to item 1. 4. The flame-retardant polyolefin composition according to claim 1, wherein the oxygen index is 28 or more. 5. A power cable having the flame-retardant polyolefin composition according to claim 1 as an insulating layer or a sheath.