Flame-retardant resin composition

Abstract

The purpose of the present invention is to provide a resin composition that has excellent flame retardancy and that also has excellent fluidity and mechanical properties. A flame-retardant resin composition according to the present invention comprises: 20-30 wt% of an ethylene vinyl acetate copolymer (EVA) resin (A); 1-10 wt% of maleic-anhydride-modified polyethylene (B); 50-70 wt% of magnesium hydroxide particles (C); 1-5 wt% of an acrylic-modified silicone resin (D); and 1-10 wt% of an ethylene / propylene-based thermoplastic elastomer (TPO resin) (E).

Description

Flame-retardant resin composition

[0001] The present invention relates to a flame-retardant resin composition.

[0002] Conventionally, as a flame-retardant resin composition used to form an insulating layer of an insulated wire or cable, the following Patent Document 1 describes a flame-retardant resin composition having (A) a density of 0.880 to 0.908 g / cm 3 and (B) 30 to 60% by weight of a linear very low density polyethylene having a melt flow rate (MFR) of 0.5 to 4.0 g / 10 min at 190°C under a load of 2.16 kg, (A) 40 to 70% by weight of an ethylene-vinyl acetate copolymer (EVA) or ethylene-ethyl acetate copolymer (EEA) containing a comonomer content of 12 to 25% by weight and having a melt flow rate (MFR) of 0.1 to 5.0 g / 10 min at 190°C under a load of 2.16 kg, and (C) 80 to 160 parts by weight of magnesium hydroxide added to 100 parts by weight of the resins (A+B) as a flame retardant.

[0003] Furthermore, the following Patent Document 2 discloses a flame retardant (D) containing an ethylene polymer (A), an acid-modified thermoplastic resin (B), polyethylene (C), and a flame retardant (D), wherein the ethylene polymer (A) contains an ethylene-α-olefin polymer and an ethylene-unsaturated carboxylic acid ester copolymer, the acid-modified thermoplastic resin (B) is at least one thermoplastic resin selected from the group consisting of maleic anhydride-modified thermoplastic resins and maleic acid-modified thermoplastic resins, and the polyethylene (C) has a viscosity of 0.950 g / cm 3 or more, wherein the content of the ethylene polymer (A) is 40% by mass or more and 85% by mass or less, the content of the acid-modified thermoplastic resin (B) is 10% by mass or more and 30% by mass or less, and the content of the polyethylene (C) is 5% by mass or more and 30% by mass or less, based on 100 parts by mass of the total of the ethylene polymer (A), the acid-modified thermoplastic resin (B), and the polyethylene (C), and the flame retardant (D) is blended in an amount of 80 parts by mass or more and 96 parts by mass or less, based on 100 parts by mass of the total of the ethylene polymer (A), the acid-modified thermoplastic resin (B), and the polyethylene (C).

[0004] Furthermore, Patent Document 3 listed below proposes a halogen-free flame-retardant resin composition containing a base polymer containing 50 to 90 parts by mass of either an ethylene-vinyl acetate copolymer or an ethylene-butene copolymer and 10 to 50 parts by mass of low-density polyethylene, and containing, per 100 parts by mass of the base polymer, 1 to 10 parts by mass of amorphous silica and 10 to 150 parts by mass of a halogen-free flame retardant.

[0005] 2004-10811 publication 2015-151415 publication 2018-92889 publication

[0006] The flame-retardant resin compositions described in Patent Documents 1 to 3 contain a high proportion of a metal hydroxide such as magnesium hydroxide as a flame retardant. Therefore, these resin compositions have problems such as poor fluidity and mechanical properties. An object of the present invention is to provide a resin composition that has excellent flame retardancy as well as excellent fluidity and mechanical properties.

[0007] (1) The flame-retardant resin composition of the present invention is characterized by comprising: (A) 20 to 30% by weight of an olefin polymer; (B) 1 to 10% by weight of an acid-modified polyolefin; (C) 50 to 70% by weight of a flame retardant; (D) 1 to 5% by weight of a modified silicone; and (E) 1 to 10% by weight of an olefin thermoplastic elastomer.

[0008] (2) In the flame-retardant resin composition of the present invention, the component (D) preferably comprises a silicone modified by having an organic group in the side chain that is compatible with polyethylene and polypropylene.

[0009] (3) In the flame-retardant resin composition of the present invention, the component (D) preferably comprises a silicone modified by having an acrylic group or a vinyl acetate group on the side chain.

[0010] (4) In the flame-retardant resin composition of the present invention, the component (E) preferably comprises an ethylene / propylene thermoplastic elastomer.

[0011] (5) In the flame-retardant resin composition of the present invention, the component (E) preferably comprises the ethylene / propylene thermoplastic elastomer in which an ethylene-propylene copolymer is dispersed in polypropylene.

[0012] (6) In the flame-retardant resin composition of the present invention, it is preferable that the component (A) comprises an ethylene (co)polymer and / or a propylene (co)polymer, the component (B) comprises an acid-modified polyethylene and / or an acid-modified polypropylene, the component (C) comprises an inorganic flame retardant, the component (D) comprises a silicone modified by having an organic group compatible with polyethylene and polypropylene in its side chain, and the component (E) comprises an ethylene / propylene thermoplastic elastomer.

[0013] (7) In the flame-retardant resin composition of the present invention, it is more preferable that the component (A) comprises an ethylene (co)polymer, the component (B) comprises an acid-modified polyethylene, the component (C) comprises a metal hydroxide, the component (D) comprises a silicone modified by having an acrylic group or a vinyl acetate group in the side chain, and the component (E) comprises the ethylene / propylene-based thermoplastic elastomer in which an ethylene-propylene-based copolymer is dispersed in polypropylene.

[0014] (8) In the flame-retardant resin composition of the present invention, it is particularly preferred that the component (A) comprises an ethylene-vinyl acetate copolymer, the component (B) comprises maleic anhydride-modified polyethylene, the component (C) comprises magnesium hydroxide or aluminum hydroxide, and the component (D) comprises a silicone modified by having an acrylic group in the side chain.

[0015] The flame-retardant resin composition of the present invention has excellent flame retardancy, as well as excellent flowability and mechanical properties.

[0016] The flame-retardant resin composition of the present invention contains, as essential components, (A) an olefin polymer, (B) an acid-modified polyolefin, (C) a flame retardant, (D) a modified silicone, and (E) an olefin thermoplastic elastomer.

[0017] <(A) Olefin Polymer> Examples of the olefin polymer constituting the flame-retardant resin composition of the present invention as component (A) include, but are not limited to, olefin homopolymers such as polyethylene and polypropylene; and olefin copolymers such as ethylene vinyl ester copolymers, ethylene (meth)acrylic acid copolymers, ethylene (meth)acrylic acid ester copolymers, propylene vinyl ester copolymers, propylene (meth)acrylic acid copolymers, and propylene (meth)acrylic acid ester copolymers. Of these, ethylene vinyl ester copolymers are preferred, and ethylene vinyl acetate (EVA) copolymers are particularly preferred. The content of component (A) in the flame-retardant resin composition of the present invention is 20 to 30% by weight.

[0018] <(B) Acid-Modified Polyolefin> The acid-modified polyolefin constituting the flame-retardant resin composition of the present invention as component (B) is a polyolefin to which at least one modifying monomer selected from unsaturated organic acids and their derivatives has been grafted. Examples of the polyolefin to which the modifying monomer is grafted include polyethylene and polypropylene.

[0019] Examples of functional groups introduced by the modifying monomer include functional groups having a C═O bond, such as a carbonyl group (>C═O), a carboxyl group (—COOH), an ester group, an acid anhydride group, an amide group, and an imide group.

[0020] Preferred modifying monomers include unsaturated dicarboxylic acids, unsaturated dicarboxylic acid anhydrides, and unsaturated dicarboxylic acid derivatives. Specific examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Specific examples of unsaturated dicarboxylic acid anhydrides include maleic anhydride and itaconic anhydride. Specific examples of unsaturated dicarboxylic acid derivatives include monomethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, diethyl fumarate, maleic acid monoamide, maleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. These can be used alone or in combination of two or more. Of these, maleic anhydride is preferred. An example of a method for preparing acid-modified polyolefins is a method in which a polyolefin, an antioxidant, a modifying monomer, and an organic peroxide are mixed in an extruder, heated to react, and then granulated into pellets or granules.

[0021] By including a certain proportion of component (B), the resin composition of the present invention has good mechanical properties (high tensile strength and high modulus of elasticity). The content of component (B) in the flame-retardant resin composition of the present invention is 1 to 10% by weight. If the content of component (B) is too low, the resulting resin composition will not have good mechanical properties (see Comparative Example 3 described below). On the other hand, if the content of component (B) is too high, the fluidity of the resin composition will be impaired (see Comparative Example 4 described below), and extrusion processability, etc., may be reduced.

[0022] <(C) Flame Retardant> The flame retardant constituting the flame-retardant resin composition of the present invention as component (C) is preferably an inorganic flame retardant, and particularly preferably a metal hydroxide. Metal hydroxides decompose and dehydrate when heated, and the resulting moisture can lower the temperature of the resin composition and suppress its combustion. Suitable metal hydroxides include magnesium hydroxide and aluminum hydroxide. The particle surfaces of the metal oxide constituting the flame retardant are preferably surface-treated with a fatty acid, a silane coupling agent, or the like.

[0023] The content of component (C) in the flame-retardant resin composition of the present invention is 50 to 70% by weight. If the content of component (C) is too low, the resulting resin composition will not have good flame retardancy (see Comparative Example 5 below). On the other hand, if the content of component (C) is too high, the fluidity of the resin composition will be impaired and the mechanical properties will be reduced (see Comparative Example 6 below).

[0024] <(D) Modified Silicone> The modified silicone constituting the flame-retardant resin composition of the present invention as component (D) can be a silicone (polysiloxane) modified by having an organic group compatible with polyethylene and polypropylene in the side chain. Examples of the organic group in the side chain include an acrylic group and a vinyl acetate group. By including such a modified silicone, the flame-retardant resin composition of the present invention can exhibit excellent fluidity due to the silicone (polysiloxane structure) for a long period of time.

[0025] By including a certain proportion of component (D), the resin composition of the present invention has good fluidity (improved extrusion properties). The content of component (D) in the flame-retardant resin composition of the present invention is 1 to 5 wt %. If the content of component (D) is too low, the resulting resin composition will not have good fluidity (see Comparative Example 7 below). On the other hand, if the content of component (D) is too high, the resin composition will have good fluidity and mechanical properties (see Comparative Example 8 below), but the component (D) will precipitate (bleed out) on the surface of the resin composition, causing poor appearance such as cloudy surfaces in the final product, which is not preferred.

[0026] <(E) Olefin-Based Thermoplastic Elastomer> The olefin-based thermoplastic elastomer constituting the flame-retardant resin composition of the present invention as component (E) is a thermoplastic elastomer containing a hard segment of polyolefin and a soft segment of aliphatic rubber.

[0027] Here, examples of the hard segment (polyolefin) include polypropylene or polyethylene, with polypropylene being preferred. Examples of the soft segment (aliphatic rubber) include ethylene-propylene copolymer (EPM) and ethylene-propylene-diene copolymer (EPDM). By using polyethylene or polypropylene as the hard segment and EPM or EPDM as the soft segment, an ethylene / propylene thermoplastic elastomer can be constructed.

[0028] Examples of methods for producing an olefin-based thermoplastic elastomer include a method of mechanically blending a polyolefin with an aliphatic rubber, a method of polymerizing an olefin in the presence of an aliphatic rubber, etc. The latter method can produce an olefin-based thermoplastic elastomer (ethylene / propylene-based thermoplastic elastomer) in which an aliphatic rubber, an ethylene-propylene copolymer (EPM or EPDM), is finely dispersed in a polyolefin (polypropylene or polyethylene).

[0029] By containing the olefin-based thermoplastic elastomer, the flame-retardant resin composition of the present invention has excellent mechanical properties (high elastic modulus).

[0030] The content of component (E) in the flame-retardant resin composition of the present invention is 1 to 10% by weight. If the content of component (E) is too low, the resulting resin composition will not have good mechanical properties (high elastic modulus) (see Comparative Example 1 described below). On the other hand, if the content of component (E) is too high, the tensile strength of the resulting resin composition will be reduced (see Comparative Example 2 described below).

[0031] <Optional Components> In addition to the above-described components (A) to (E), the flame-retardant resin composition of the present invention may contain stabilizers (light stabilizers, antioxidants, processing stabilizers), various additives (processability improvers, dispersants, copper inhibitors, antistatic agents, lubricants, fillers), and the like, within limits that do not impair the properties of the resin composition of the present invention.

[0032] <Method for Producing Resin Composition> The flame-retardant resin composition of the present invention can be produced by blending the essential components [components (A) to (E)] and optional components in predetermined proportions, followed by melt-kneading.

[0033] <Uses of Resin Composition> The flame-retardant resin composition of the present invention can be suitably used as an insulating coating material for various electric wires and cables.

[0034] Examples of the present invention will be described below, but the present invention is not limited to these examples. Here, the (A) olefin polymer, (B) acid-modified polyolefin, (C) flame retardant, (D) modified silicone, (E) olefin thermoplastic elastomer, and optional components used to produce the resin compositions of the examples and comparative examples are as follows.

[0035] (A1) Olefin polymer: Ethylene vinyl acetate copolymer (EVA) resin (density = 0.95 g / cm 3 , vinyl acetate content = 25 wt%, MFR (2.16 kg) = 5.0 g / 10 min]

[0036] (B1) Acid-modified polyethylene: Maleic anhydride-modified polyethylene (density = 0.94 g / cm 3 , maleic anhydride content = 0.4 wt%, MFR (2.16 kg) = 1.8 g / 10 min]

[0037] (C1) Flame retardant: Magnesium hydroxide particles surface-treated with fatty acid, average particle size = 1.1 μm

[0038] (D1) Modified silicone: Acrylic silicone resin in which an acrylic group is graft-polymerized onto the main chain silicone (silicone content: 70% by weight)

[0039] (E1) Olefin-based thermoplastic elastomer: Ethylene / propylene-based thermoplastic elastomer in which an ethylene-propylene-based copolymer is dispersed in polypropylene (TPO resin, density = 0.88 g / cm 3 , MFR (2.16 kg) = 0.25g / 10min]

[0040] (F1) Optional component: Carbon black-containing masterbatch

[0041] Examples 1 to 9 and Comparative Examples 1 to 8 According to the formulations shown in Table 1 below, the components were melt-kneaded to obtain resin compositions of the present invention and comparative resin compositions.

[0042] <Evaluation> The following evaluation tests were carried out on each of the resin compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 8. The measurement methods, evaluation methods, and evaluation criteria are as follows. The results are also shown in Table 1.

[0043] (1) Flame Retardancy Using a heated press (Toho Machinery, TBD-50 model), the resin composition was pressed at 180°C for 2 minutes to form a 3 mm thick sheet. A test piece (JIS K 7201, Test Piece Type IV, Table 2) was prepared from the resulting sheet-like molded product, and the oxygen index (LOI) was measured in accordance with JIS K 7201, except that this test piece was used. An oxygen index (LOI) of more than 35 was evaluated as "pass," and an LOI of 35 or less was evaluated as "fail."

[0044] (2) Fluidity The melt mass-flow rate (MFR) was measured in accordance with JIS K 7210. Here, the measurement temperature was 200°C and the load was 211.68 N (21.6 kg). Those for which the MFR could be measured were rated as "passed," and those for which the MFR was too low to be measured were rated as "failed."

[0045] (3) Mechanical Properties (Tensile Test) The resin composition was pressed at 180°C for 2 minutes using a heated press (Toho Machinery, TBD-50 model) to form a sheet having a thickness of 1 mm. No. 3 dumbbell test pieces were prepared from the resulting sheet-like molded body. Using this test piece, a tensile test was performed at a tensile speed of 200 mm / min using a tensile tester (Shimadzu Corporation, Autograph AGS-X) to measure the tensile strength and elongation at break. A tensile strength of 10 MPa or more was evaluated as "pass," and a tensile strength of less than 10 MPa was evaluated as "fail."

[0046] (4) Mechanical Properties (Elastic Modulus) Using a rheometer (MCR302, manufactured by Anton Paar), the change in complex viscosity of the resin composition was measured under conditions of a temperature of 70°C, a frequency of 10 Hz, and a strain of 0.5%, and the storage modulus was calculated. A sample with an elastic modulus (70°C) of 20 MPa or more was evaluated as "pass", and a sample with an elastic modulus of less than 20 MPa was evaluated as "fail".

[0047]

Claims

1. A flame-retardant resin composition containing: (A) 20-30% by weight of an olefin polymer; (B) 1-10% by weight of an acid-modified polyolefin; (C) 50-70% by weight of a flame retardant; (D) 1-5% by weight of a modified silicone; and (E) 1-10% by weight of an olefin thermoplastic elastomer.

2. The flame-retardant resin composition according to claim 1, wherein component (D) is a silicone modified by having an organic group on the side chain that is compatible with polyethylene and polypropylene.

3. A flame-retardant resin composition according to claim 2, wherein component (D) is a silicone modified by having an acrylic group or a vinyl acetate group on the side chain.

4. A flame-retardant resin composition according to any one of claims 1 to 3, wherein component (E) comprises an ethylene / propylene thermoplastic elastomer.

5. The flame-retardant resin composition according to claim 4, wherein said component (E) comprises an ethylene / propylene thermoplastic elastomer in which an ethylene-propylene copolymer is dispersed in polypropylene.

6. A flame-retardant resin composition according to claim 1, wherein the (A) component is an ethylene (co)polymer and / or a propylene (co)polymer, the (B) component is an acid-modified polyethylene and / or an acid-modified polypropylene, the (C) component is an inorganic flame retardant, the (D) component is a silicone modified by having an organic group on its side chain that is compatible with polyethylene and polypropylene, and the (E) component is an ethylene / propylene thermoplastic elastomer.

7. A flame-retardant resin composition according to claim 6, wherein the (A) component is an ethylene (co)polymer, the (B) component is an acid-modified polyethylene, the (C) component is a metal hydroxide, the (D) component is a silicone modified by having an acrylic group or a vinyl acetate group on the side chain, and the (E) component is the ethylene / propylene thermoplastic elastomer in which an ethylene-propylene copolymer is dispersed in polypropylene.

8. A flame-retardant resin composition according to claim 7, wherein the (A) component is an ethylene-vinyl acetate copolymer, the (B) component is a maleic anhydride modified polyethylene, the (C) component is magnesium hydroxide or aluminum hydroxide, and the (D) component is a silicone modified by having an acrylic group in the side chain.

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