JP3063759B2 - Flame retardant polyolefin resin 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 resin composition which is extruded as an insulating coating or a sheath for electric wires and cables.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of safety and hygiene,
Non-halogen flame-retardant resin compositions have been used as insulating coatings or sheath materials for cables that have low smoke emission in the event of fire and do not generate harmful gases such as hydrogen halide. These resin compositions generally use a metal hydrate such as magnesium hydroxide or aluminum hydroxide as a flame retardant, and red phosphorus or a phosphoric acid compound as a flame retardant aid. However, these resin compositions have the following problems.

1) The flame retardant effect of the metal hydrate itself is not so large as compared with the halogen-based flame retardant, and it is necessary to increase the filling amount in order to impart sufficient flame retardancy. Increasing the filling amount of the metal hydrate decreases the compatibility between the metal hydrate and the polymer molecule, increases the shear viscosity of the resin composition, increases the torque during extrusion molding, and increases the appearance of the molded product. Becomes rough, and it is necessary to lower the forming linear velocity. 2) When the filling amount of the metal hydrate is increased, the hardness and the flexural modulus of the resin composition are increased, resulting in a hard-to-handle electric cable. This is because, in addition to the hardness of the metal hydrate itself, the metal hydrate is preferentially filled into the amorphous portion of the base polymer, so that the amorphous portion that should impart flexibility to the resin composition is It is thought to decrease.

[0004] 3) Since polyolefin resins are inherently low in compatibility with metal hydrates and inorganic fillers, resin compositions containing these compounds have low extensional viscosities when melted. As a result, it becomes impossible to withstand the elongation deformation generated at the time of extrusion, and the surface of the molded product becomes rough when the processing linear velocity at the time of extrusion processing increases. 4) It is better to narrow the molecular weight distribution of the polyolefin resin used in order to achieve a balance between the large amount of metal hydrates and inorganic fillers and the mechanical properties of the final product (electric wire coating), but the extrusion torque is high and the processing wire is high I can't speed up. A resin having a narrow molecular weight distribution does not decrease the shear viscosity even if the shear rate is increased, so that the extrusion torque during high-speed extrusion is increased and the processability is reduced.

[0005] On the other hand, if the amount of the metal hydrate is reduced in order to enhance the extrudability and flexibility, the flame retardancy of the resin composition decreases. In particular, when based on a polyolefin resin containing no polar monomer, the carbonization rate is low,
Since heat generation and combustion continue for a long time, the flame retardancy is extremely reduced.

6) Therefore, in order to maintain flame retardancy even when the metal hydrate loading is reduced, a flame retardant aid such as red phosphorus may be added. The resin composition is colored reddish-brown and changes the color tone of the white or colored coating. 7) Since magnesium hydroxide emits water of crystallization at a higher temperature than aluminum hydroxide, foaming due to water release can be suppressed even when the temperature rises at a high shear rate, and brucite ore is used as a raw material. Crushed products are resistant to C
O2 whitening (magnesium hydroxide reacts with water and carbon dioxide in the air to produce magnesium carbonate,
White spots may be formed on the surface of the molded product, which is preferably used because of its excellent resistance to this phenomenon), but it develops a reddish-brown color due to the high temperature during compounding and extrusion, and the resin composition Deteriorate color tone. Although the cause is not clear, it is considered that impurities existing in the brucite influence.

[Problems to be solved by the invention]

The present invention is excellent in extrusion processability while maintaining high flame retardancy without containing halogen or phosphorus, has a good molded product surface during extrusion molding, and is hardly colored during compounding or extrusion. It is an object to obtain a flame-retardant polyolefin resin composition.

[Means for Solving the Problems]

In view of the above various problems, the present inventors have conducted intensive studies on measures for achieving both high flame retardancy and good extrusion processability. Was completed. The following physical properties of the materials constituting the present invention are values measured based on the following standards and conditions. a) Molecular weight distribution (MWD): The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC), and Mw / Mn
I asked more. b) MFR: temperature 190 based on JIS K7210
The die diameter is 2.095m under the condition of ° C and load of 2.16kg.
m. c) Die swell ratio: Measured at a temperature of 200 ° C. based on the method described in JIS K7199. The dies used had a capillary length (l) and diameter (d) ratio (l / d) of 4. d) Viscosity: Measured at a temperature of 25 ° C. using an Ubbelohde viscometer according to ASTM D-445-46T.

In the present invention, (A-1) a linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin is blended in an amount of 30 to 80% by weight, and (A-2) ethylene-vinyl acetate copolymer is used. A combined amount of at least one selected from the group consisting of a copolymer, an ethylene-ethyl acrylate copolymer and an ethylene-methyl acrylate copolymer, and (A-3) a low-density polyethylene obtained by a high-pressure polymerization method; (B-1) 50 to 70% by weight of a polyolefin resin mixture,
A flame-retardant polyolefin resin composition comprising 140 parts by weight and (C) 2 to 10 parts by weight of a polysiloxane. (Claim 1)

The resin composition comprises (A-1), (A-2), (A-
By adding (B-1) and (C) with the combination of 3) as a base polymer, good mechanical properties of (A-1), (A-2)
Flame retardant which has the flexibility of (A-3) and the extrudability of (A-3)
(B-1), a flame-retardant auxiliary (C), and by the synergistic action of (A-2),
Expresses high flame retardancy.

In order to maintain the mechanical properties when adding metal hydrates and inorganic fillers, it is preferred that (A-1) be contained in the polyolefin resin in an amount of 30% by weight or more. Extrudability deteriorates. In order to improve the extrudability, (A-2) and / or (A-3)
It is preferred that the polyolefin resin contains 20% by weight or more, but if it exceeds 70% by weight, the mechanical properties of the resin composition deteriorate.

The present invention also relates to (A-1) a linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin in an amount of 30 to 80% by weight, and (A-2) ethylene-vinyl acetate. Copolymer, at least one selected from the group consisting of ethylene-ethyl acrylate copolymer or ethylene-methyl acrylate copolymer, and (A-3) a combined amount of low-density polyethylene by high-pressure polymerization 20-70% by weight
The polyolefin resin mixture contains (B-1) 50 to 140 parts by weight of a metal hydrate, (B-2) 10 to 60 parts by weight of an inorganic filler, and (C) 2 to 10 parts by weight of a polysiloxane. Provided is a flame-retardant polyolefin resin composition characterized by the following: (Claim 2) (B-2) is replaced with (B-1)
By coexisting in the resin, the resin component is diluted and the flame retardant effect can be enhanced.

Further, the present invention relates to (A-1) ethylene and α-
The α-olefin in the olefin copolymer is at least one selected from the group consisting of butene-1, hexene-1, 4-methylpentene-1 and octene-1. (Claim 3)

LLDPE containing these α-olefins as comonomers has a particularly good balance between strength and flexibility.
When combined with (A-2) and / or (A-3) and mixed with (B-1) and (C) and / or (B-2), it has excellent mixing and extrusion processability, To form a resin composition having excellent mechanical properties and flame retardancy.

In the present invention, the density of (A-1) is 0.880
0.920, the molecular weight distribution is in the range of 3.0 to 6.0, and the MFR is in the range of 0.5 to 2.0. (Claim 4) As (A-1), as described above, if a polymer having a low density, a relatively wide molecular weight distribution and a high molecular weight component is selected among polyolefin resins, a resin composition is obtained. On the other hand, when filled with a metal hydrate, an inorganic filler or the like, flexibility is not lost, extrudability is good, and mechanical properties required for wire coating can be provided.

Further, the present invention relates to a method for producing vinyl acetate (hereinafter abbreviated as VA), ethyl acrylate (hereinafter abbreviated as EA) or methyl acrylate (hereinafter MA) contained in (A-2).
), The MFR of (A-2) is in the range of 0.5 to 5.0, and the die swell ratio is in the range of 1.2 to 2.5. It is characterized by. (Claim 5) The amount of the polar comonomer contained in (A-2) is 10%
With the above, flexibility and flame retardancy can be improved. As the amount of polar comonomer increases, (A
Since the compatibility with -1) is reduced, the content is preferably suppressed to 25% by weight or less. Further, by setting the MFR and the die swell ratio of (A-2) in the above ranges, good extrudability can be maintained.

Further, the present invention is characterized in that (A-2) is EVA. (Claim 6) EVA is EEA or EMA
It has a higher carbonization rate and is suitable for improving flame retardancy. Moreover, it is inexpensive and easily available, and is preferable from the viewpoint of economy.

Further, according to the present invention, the density of (A-3) is 0.91
0 to 0.920, an MFR of 0.5 to 2.0, and a die swell ratio of 1.2 to 2.5.
(Claim 7) By setting the density, MFR and die swell ratio of (A-3) in the above-mentioned ranges, it is possible to make it difficult to cause a rough surface phenomenon at the time of resin composition extrusion.

Next, the present invention is characterized in that magnesium hydroxide or aluminum hydroxide is used as (B-1). (Claim 8) In order to exert a sufficient flame retardant effect as a resin composition, the addition amount of (B-1) is preferably 50 parts by weight or more, and in order to maintain good extrusion processability of the resin composition. It is preferable that the addition amount be 140 parts by weight or less.

The present invention is characterized in that (B-1) is filled with 50 to 140 parts by weight of magnesium hydroxide or aluminum hydroxide, and (B-2) is filled with 10 to 60 parts by weight of calcium carbonate. . (Claim 9) Regarding (B-1), the above range is preferable for the same reason as described above. The addition amount of (B-2) is preferably 10 parts by weight or more in order to contribute to the flame retardant effect, and is preferably 60 parts by weight or less in order not to adversely affect the extrusion processability.

In the present invention, (B-1) is magnesium hydroxide, and its average particle size (D50) is 1.0-7.
It is characterized by using brucite ore having a content of Mg (OH) ₂ of 85 to 95% by weight with a size of 0 μm. (Claim 10) As (B-1), magnesium hydroxide having a high dehydration reaction temperature is preferable from the viewpoint of preventing foaming during extrusion. Further, by setting the average particle size of magnesium hydroxide in the above range, the degree of skin roughness during extrusion can be reduced. Further, the use of the above-mentioned brucite ore as a raw material as magnesium hydroxide can reduce the resistance to CO ₂ whitening.

Further, the present invention is characterized in that (B-2) is (heavy) calcium carbonate having an average particle diameter (D50) of 1.0 to 7.0 μm. (Claim 11) By setting the average particle diameter of (B-2) within the above range, the degree of skin roughness during extrusion can be suppressed to a low level.

Next, according to the present invention, (C) has a viscosity of 6000
It is an organopolysiloxane in the range of 範 囲 25000 cSt. (Claim 12) If the viscosity of (C) is less than 6000 cSt, bleeding from the resin composition is likely to occur, which is not preferable. On the other hand, 25000c
If it is higher than St, it is difficult to disperse the mixture during mixing of the materials, and the quality of the compound is deteriorated. The addition amount of (C) is preferably 2 parts by weight or more in order to contribute to the improvement of the flame retardancy. However, if it exceeds 10 parts by weight, the improvement of the flame retardancy levels off and the cost is increased, which is not preferable. .

Further, the present invention is characterized in that (C) is dimethylpolysiloxane. (Claim 13) Dimethylsiloxane has a higher flame-retardant effect than other organopolysiloxanes, and suppresses red-brown discoloration of a resin composition caused by addition of magnesium hydroxide made from brucite ore. There are also unique effects.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Among the polyolefin mixtures constituting the flame-retardant polyolefin resin composition of the present invention, (A-1)
LLDPE obtained by copolymerizing ethylene and α-olefin
As a single site catalyst represented by a metallocene catalyst, or a so-called Ziegler catalyst (titanium,
A multisite catalyst typified by a chromium-based catalyst or the like can be used. Butene
LLDP using 1, hexene-1,4-methylpentene-1 or octene-1 as an α-olefin comonomer
E is preferred, but considering the flexibility of the resin composition,
Hexene-1, 4-methylpentene-1, octene-1
The use of a bulky comonomer such as is preferred because the lamella is thin and contributes to flexibility. The density of the polymer used in (A-1) is preferably in the range of 0.880 to 0.920, but in consideration of oil resistance performance, low-density polymers are disadvantageous, and those less than the above described range have poor performance. High risk of starting. For example, when a resin having a density of less than 0.880 is used, the oil resistance required for the electric wire covering material specified in JIS C3005 cannot be satisfied. If the density exceeds 0.920, it becomes hard when a metal hydrate or the like is added, and the flexibility when the wire is made into an insulating coating or the like becomes poor. The molecular weight distribution (MWD) of the polymer is monodisperse (MWD).
= 1), the material strength tends to increase, which is effective for increasing the filling of the filler. However, the decrease in the shear viscosity at the time of high shear is small, the extrusion torque increases, and the processability deteriorates. On the other hand, a broader molecular weight distribution results in a higher content of low molecular weight components, resulting in a higher efficiency of lowering the shear viscosity during high shear and contributing to a reduction in screw torque during high speed extrusion, thus improving extrusion processability. Strength decreases. Therefore (A
The molecular weight distribution of the polymer used in -1) is 3.0 to 6.0 in consideration of the balance between processability and material strength.
Is optimal. The MFR of a polymer is a measure of the average molecular weight. If the MFR is small, the amount of the high molecular weight component increases, and extrusion processing becomes difficult. On the other hand, if the MFR is large, the low molecular weight component becomes excessive and the material strength is reduced. Therefore,
In order to obtain the strength characteristics specified in “Technical standards and handling details of electrical appliances”, the MFR of the polymer used in (A-1)
Is preferably in the range of 0.5 to 2.0. Examples of the polymer (A-1) meeting the above-mentioned conditions of density, molecular weight distribution and MFR include, for example, butene-1 or hexene-
A resin polymerized by a gas phase method using 1 as a comonomer;
-Resin polymerized by a solution polymerization method using methylpentene-1 or octene-1 as a comonomer, and resin polymerized by a high-pressure ion polymerization method using butene-1 or hexene-1 as a comonomer.

Next, as (A-2), EVA, EEA,
EMA can be used, but the polar comonomers VA, E
A, MA added amount is 5 to 25% by weight, MFR is 0.5 to
Particularly preferred are polymers having a swell ratio in the range of 1.2 to 2.5. The copolymer having these polar groups has a smaller total heat generation in the filler-filled system than the ethylene homopolymer, and is suitable for use in flame-retardant materials. In particular, in consideration of material properties (strength and the like) at the time of use, those having an average molecular weight that provides the above-mentioned MFR range are preferable. If the content of the polar group is too low, the effect of reducing the calorific value is reduced, and if it is too high, the compatibility with the blend partner LLDPE is reduced and the material properties are reduced. In addition, since the polar group reduces the crystallinity of the polyethylene skeleton, the higher the content is, the more the flexibility can be improved. However, the too high content is not preferable because the properties are deteriorated as described above.

Further, (A-3) is a low-density polyethylene produced by a high-pressure polymerization method and having a density of 0.910 to 0.92.
0, MFR 0.5-2.0, swell ratio 1.2-
Those in the range of 2.5 are particularly preferred. (A-3) is (A-2)
Since it is inexpensive as compared with the above, if the ratio of (A-2) is reduced by adding (A-3), it is advantageous in terms of cost. However, the ratio of (A-3) to (A-2) preferably does not exceed 66% in order to prevent a decrease in flame retardancy. In the polyolefin resin mixture of the present invention, the ratio PR of the polar comonomer required for exhibiting the flame retardant effect to the total resin components PR
(Polarity) is preferably from 7 to 12% by weight. Therefore, considering the polar monomer content of (A-2), (A-1), (A-2) and (A-2)
What is necessary is just to determine the ratio of -3).

(A-2) and (A-3) have a long-chain branch and are effective in reducing the shear viscosity during high shear. Therefore, an increase in torque when the extruder screw is rotated at high speed during high-speed extrusion can be suppressed. In addition, since it has a long chain branch, the tension (melt tension) at the time of melting is high, which is effective in reducing the skin roughening phenomenon that occurs immediately after passing through an extrusion die. In the extrusion of a filler-filled material, this roughening phenomenon often becomes a problem, because the melt-tension of the filler-filled material is low. As a countermeasure, the effect of a long-chain branched polymer having a high melt tension is required. However, when the degree of branching is low, the melt tension is low and ineffective, so that the degree of branching must be within the specified range. The die swell ratio is an index for conveniently evaluating the number of long-chain branches. The resin having a larger number of branches has a larger die swell ratio. A resin having a large number of long-chain branches has a high frequency of entanglement between molecules, resulting in a resin material having a high melt tension.

As the metal hydrate (B-1) used in the present invention, magnesium hydroxide or aluminum hydroxide is suitable, and these can be used alone or as a mixture. Considering the heating temperature during processing, the release of adsorbed water peaks at about 250 ° C. for aluminum hydroxide. Air bubbles tend to be generated in the molded product due to the release of moisture in the temperature range before and after the temperature. For this reason, in the case of a material used for high-speed extrusion processing in which the processing temperature tends to increase, it is preferable to use magnesium hydroxide. Hydrate-based fillers are said to have a tendency to lower the insulation resistance of the material due to their hygroscopicity, but the use of a material that has been sufficiently surface-treated with stearic acid or the like will lower the insulation resistance. Can be prevented. Magnesium hydroxide may react with water and carbon dioxide in the air to form magnesium carbonate and form white spots on the molded product surface. It has an effect of suppressing white spot formation (so-called CO2 whitening resistance), and is thus preferable.

As the inorganic filler (B-2) used in the present invention, talc, clay, magnesium oxide, magnesium carbonate, calcium carbonate and the like used in resin molding materials can be used. Of these, calcium carbonate is particularly preferred because it is less likely to cause secondary aggregation. Calcium carbonate is considered to play a role in improving the dispersibility of the metal hydrate when blended with the (B-1) metal hydrate that easily causes secondary aggregation.

When polysiloxane is used in combination with (B-1) or (B-2), in order to enhance the flame retardant effect, the addition amount of the above-mentioned inorganic filler may be reduced by its addition. And has an advantageous effect on extrudability. (C) used in the present invention
Straight polysiloxane. Organopolysiloxanes such as modified systems are suitable. The present inventor has found that, among them, a so-called straight type methyl hydrogen polysiloxane, dimethyl polysiloxane and the like have a high flame retarding effect. In addition, it has been found that the straight polysiloxane has a unique effect of suppressing red-brown discoloration of the resin composition that occurs when magnesium hydroxide made from brucite ore is used as a raw material. Among straight polysiloxanes, dimethyl polysiloxane is particularly preferred because it has the highest flame retardancy improving effect. Polysiloxane has a viscosity of 6000-25000c
It is preferably in the range of St. The viscosity is 6000
If it is less than cSt, bleeding from the material occurs, which is not preferable. On the other hand, if it exceeds 25000 cSt, it becomes difficult to disperse the material during mixing, and the quality of the compound deteriorates.

The flame-retardant resin composition of the present invention contains an antioxidant, a copper damage inhibitor, an ultraviolet absorber, an ultraviolet shielding agent, carbon and other coloring pigments as long as its properties are not impaired.
An additive generally used for a resin molding material may be blended. In particular, DL-α-tocopherol (vitamin E) is used as an antioxidant, and an organic skeleton-based hindered amine-based ultraviolet absorber is used as an ultraviolet absorber. Therefore, it is preferable.
In particular, DL-α-tocopherol is effective at a low addition amount and has a function of suppressing the attack of oxygen radicals on the carbon skeleton itself. Therefore, a large amount of conventional antioxidants (such as bisphenols) and ultraviolet absorbers are added. It is possible to suppress an increase in cost of the resin composition due to the above.

The resin composition of the present invention is melt-mixed in a compounding equipment such as a commonly used twin-screw kneading extruder, kneading kneader, kneading roll, etc., and granulating into an appropriate shape as required. Can be manufactured. Insulation of an electric wire or cable or coating of a sheath or the like using the pellets or the like thus produced can be performed using an extruder or the like according to a usual method. As for (C), as described above, even when a resin and a filler such as a metal hydrate or an inorganic filler are added in the same manner as other additives, a surface treatment agent is added to the filler in advance. Even if the filler is used at the time of mixing, it is also effective in improving the processability at the time of extrusion.

The flame-retardant resin composition according to the present invention was measured and evaluated according to the following specifications and conditions. 1) Tensile properties: A press sheet having a thickness of 1 mm is prepared from the resin composition, and is subjected to a method specified in JIS C3005,
JIS No. 3 dumbbells were punched out and pulled at room temperature at a pulling speed of 20.
Tensile was performed at 0 mm / min, and tensile strength and elongation at break were measured.
For use as a cable insulating material or a sheath material, the tensile strength and the elongation at break are preferably 10 MPa or more and 350% or more, respectively.

2) Flexural modulus: A standard test piece was prepared by the method specified in JIS K7171, and the test speed was 50 mm.
/ Min. The flexural modulus is an index indicating the flexibility of the insulating material or the sheath material, and is preferably 350 MPa or less in consideration of the ease of handling of the cable.

3) Shear viscosity: Based on JIS K7199, set temperature 200 ° C., die has orifice diameter 0.5
The measurement was performed at a shear rate of 3000 / sec using a capillary rheometer with a diameter of 8 mm and a land length of 8 mm, and the true viscosity was calculated by performing Ravinovich correction from the apparent shear viscosity. A resin material having a lower shear viscosity under a high shear rate can suppress an increase in extrusion torque during high-speed extrusion, which is advantageous for extrusion processing.
It is preferable to take a value equal to or less than c.

4) Extruded appearance: The molded product extruded using a capillary rheometer in the measurement of the shear viscosity described in the preceding section was evaluated by measuring the average surface roughness based on the method specified in JIS B0601. The average surface roughness Ra of the cable material is preferably 5 μm or less.

5) Oxygen index: Measured according to JIS K7201. The index of flame retardancy is preferably 27 or more.

6) Electric wire burning test: A 150 mmφ extruder was used to coat a stranded wire conductor having an outer diameter of 6 mm with a 1.5 mm thick sheath of a resin composition at a set temperature of 170 ° C. and an outer diameter of 9.4.
mm cable was produced. About this cable,
A combustion test was performed according to the method specified in ISC3005. In the evaluation, in accordance with the technical standards and handling details of electric appliances, a case where self-extinguishing within 60 seconds was represented by ○, and other cases were represented by ×.

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples. Example 1 LLDPE-1, EVA-1 and LDP shown in Table 1
E-1 was treated with dimethylpolysiloxane having a viscosity of 25,000 cps, magnesium hydroxide (average particle diameter of 3.5 μm).
m, with a raw material of brucite ore having a Mg (OH) 2 content of 85 to 95% by weight) and calcium carbonate (average particle size 1.2 μm) in a weight part shown in Table 2 with difficulty in mixing. A flammable polyolefin resin composition was obtained. From this composition, a press sheet was formed by a 10-ton press at 180 ° C., and a cable was produced by the method described in the section of the electric wire combustion test. The characteristics were measured. The results are shown in Table 2.

Examples 2 to 3 and Comparative Examples 1 to 3 A polyolefin resin composition was obtained in the same manner as in Example 1 except that the polyolefin resins shown in Table 1 were used and the types and the number of parts of the compounding materials were changed to Table 2. Was. A press sheet and a cable were prepared from this composition, and the above characteristics were measured. The results are shown in Table 2.

[0042]

[Table 1]

[0043]

[Table 2]

In the flame-retardant resin compositions of Examples 1 to 3, all of the above-mentioned properties are within the preferred ranges, and the materials defined by the present invention are characterized by mechanical properties, extrudability, Indicates that the flame retardancy is balanced. Comparative Example 1 shows that the polyolefin resin mixture contained (A-2)
Although it is an example which does not contain, when compared with Example 4, despite the fact that the equivalent amount of the flame retardant and the flame retardant auxiliary are blended,
Failed the wire burning test. The reason for this is that, in Example 4, although (A-2) having a polar group is effective in reducing the total calorific value during combustion in the presence of a flame retardant and a flame retardant auxiliary. It is considered that Comparative Example 1, which does not include (A-2), does not have this effect. Comparative Example 1
Material has a high flexural modulus and lacks flexibility, but reduces the crystallinity of the polyethylene skeleton and improves flexibility (A-
This is because 2) is not included. Further, the material of Comparative Example 1 is:
Although the shear viscosity at the time of melting is high and the average roughness value of the surface exhibiting an extruded appearance is large, (A-2) having long chain branching is not contained and L
Because only LDPE is the base polymer, the shear viscosity at the time of high shear increases, and the effect of maintaining the tension during melting due to long chain branching is small. .

Since the resin composition of Comparative Example 2 does not contain (B-1), it has a low oxygen index and does not pass the electric wire burning test. Comparative Example 3 does not include the flame retardant aid (C), and thus has a low oxygen index and does not pass the electric wire combustion test. The resin composition of Example 6 is excellent in flame retardancy and extrudability, but since the VA content of EVA contained as (A-2) is as high as 30% by weight, the tensile strength is reduced.

[0046]

The flame-retardant polyolefin resin composition of the present invention has a high degree of flame retardancy even without containing halogen or phosphorus, has excellent extrudability, and hardly causes problems such as surface roughness during high-speed extrusion. When used as an insulator or sheath for electric wires and cables, it is possible to produce electric wires and cables at low cost, which have low smoke emission at the time of fire and do not generate harmful gases such as hydrogen halide. Further, the flame-retardant polyolefin resin composition of the present invention is suitable for electric wires because it is hardly colored at the time of material mixing or extrusion, and can be used for a wider range of electric wires and cables.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01B 3/44 H01B 3/44 M 3/46 3/46 D // (C08L 23/08 83:04) (56) References JP-A-62-104853 (JP, A) JP-A-6-200091 (JP, A) JP-A-61-228046 (JP, A) JP-A-2-255584 (JP, A) JP-A-10-7913 (JP, A) JP-A-8-295764 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 23/08 C08L 83/04 C08K 3/22 C08K 3/26 H01B 3 / 00 H01B 3/44 H01B 3/46

Claims (13)

(57) [Claims] (A-1) The compounding amount of a linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin is 30 to
80% by weight, (A-2) ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer or ethylene-
(B-3) a polyolefin resin mixture having a blending amount of at least one selected from the group consisting of methyl acrylate copolymer and (A-3) a low-density polyethylene obtained by a high-pressure polymerization method of 20 to 70% by weight, -1) A flame-retardant polyolefin resin composition comprising 50 to 140 parts by weight of a metal hydrate and 2 to 10 parts by weight of a polysiloxane (C). 2. The amount of (A-1) a linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin is 30 to 8%.
0% by weight, (A-2) at least one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer or ethylene-methyl acrylate copolymer, and (A-3) (B-1) 50 to 140 parts by weight of a metal hydrate and (B-2) an inorganic filler 10 are added to a polyolefin resin mixture containing 20 to 70% by weight of a low-density polyethylene obtained by high-pressure polymerization. A flame-retardant polyolefin resin composition characterized by containing about 60 parts by weight and (C) 2 to 10 parts by weight of a polysiloxane. (A-1) The α-olefin in the linear low-density polyethylene obtained by copolymerizing ethylene and an α-olefin is butene-1, hexene-1, 4-methylpentene-1 or octene- The at least one member selected from the group consisting of 1 or 2,
The flame-retardant polyolefin resin composition according to claim 2. 4. The density of (A-1) is from 0.880 to 0.92.
0, molecular weight distribution is 3.0-6.0, MFR is 0.5-
The resin composition according to claim 1 or 2, wherein the resin composition is in a range of 2.0. 5. The content of vinyl acetate, ethyl acrylate or methyl acrylate contained in (A-2) is 10 to 25% by weight, and the MFR of (A-2) is 0.5 to 5% by weight.
The resin composition according to claim 1 or 2, wherein the die swell ratio is in the range of 1.2 to 2.5. 6. The resin composition according to claim 1, wherein (A-2) is an ethylene-vinyl acetate copolymer. 7. The method according to claim 1, wherein the density of (A-3) is 0.910 to 0.92.
0, MFR 0.5-2.0, die swell ratio 1.2
The resin composition according to claim 1, wherein the resin composition is in a range of from 2.5 to 2.5. 8. The resin composition according to claim 1, wherein magnesium hydroxide or aluminum hydroxide is used as (B-1). 9. The resin composition according to claim 1, wherein magnesium hydroxide or aluminum hydroxide is used as (B-1) and calcium carbonate is used as (B-2). (B-1) is magnesium hydroxide,
The average particle diameter (D50) is 1.0 to 7.0 μm, and M
The resin composition according to claim 1, wherein a brucite ore having a g (OH) ₂ content of 85 to 95% by weight is used as a raw material. (B-2) has an average particle diameter (D50) of 1.0
3. The resin composition according to claim 1, wherein the resin composition is calcium carbonate having a thickness of 7.0 to 7.0 μm. 4. 12. (C) having a viscosity of 6,000 to 25,000.
The resin composition according to claim 1, wherein the resin composition is an organopolysiloxane having a cSt range. 13. The resin composition according to claim 1, wherein (C) is dimethylpolysiloxane.