JP2008037927A - Flame-retardant resin composition and insulated wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-retardant resin composition using resin material with low crystallinity, imparting a sufficient flame-retardancy and a proper adhesion with a conductor and attaining a high tensile strength at break after crosslinking. <P>SOLUTION: The flame-retardant resin composition comprises 240-300 pts.mass of magnesium hydroxide surface treated with vinyl silane based coupling agent compounded with 100 pts.mass of a base resin comprising 50-70 pts.mass of an α-olefin copolymer with more than 1.0 g/10 min of melt flow rate and more than 30 MPa of tensile strength, 30-50 pts.mass of an ethylene-vinyl acetate copolymer with more than 30 mass% of acetic acid content, and/or an ethylene-acrylate rubber with more than 30 mass% of methylacrylate content. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a halogen-free flame-retardant resin composition that is excellent in high flame retardancy, electrical insulation, and water resistance, and is suitable as a coating material for electric appliances and the like, and an insulated wire using the same.

UL certification is required for electric wires for electronic equipment. The flame retardancy is required to be very high flame retardancy by the VW-1 combustion test method shown in UL94.
Conventionally, as a halogen-free flame retardant resin composition, polyolefin such as ethylene / vinyl acetate copolymer (hereinafter abbreviated as EVA) and ethylene / ethyl acrylate copolymer (hereinafter abbreviated as EEA). A resin containing a flame retardant such as magnesium hydroxide or aluminum hydroxide and a flame retardant aid such as melamine cyanurate or zinc hydroxystannate is known (for example, see Patent Document 1).
It is also known to improve the mechanical properties of a resin composition using magnesium hydroxide surface-treated with a silane coupling agent or stearic acid (for example, see Patent Document 2).
Furthermore, an insulated wire obtained by coating a flame retardant composition obtained by adding a large amount of metal hydrate to an acid copolymer such as EVA or acrylic rubber on a conductor and then crosslinking the coating with an electron beam has been proposed. (For example, refer to Patent Document 3).

In such a halogen-free flame-retardant resin composition, no harmful halogen compound is generated during incineration, and an insulated wire having a coating layer made of this resin composition conforms to the UL1581 standard. It exhibits high flame retardancy that passes the prescribed VW-1 combustion test, has good mechanical properties and workability, and is used, for example, as an insulator or sheath of an insulated wire for electronic equipment.
JP 2000-294036 A JP 2000-195336 A JP 2004-339317 A

Halogen-free highly flame retardant materials require the addition of a large amount of metal hydrate such as magnesium hydroxide (200 to 300 parts by mass), so a base resin capable of filling a large amount of metal hydrate is selected. Is done. Examples of such resins include resin blends such as EVA, EEA, EP rubber, styrene elastomer, and ethylene / acrylic rubber (hereinafter abbreviated as AEM) having low crystallinity.
However, by using this type of resin, the acid component of the resin and the hydroxyl group on the surface of the conductor form hydrogen bonds, thereby increasing the adhesion, and for example, removing the end portion of the wire when connecting the wire and the connector. There was a problem that the workability of the harness deteriorated, such as difficult work.
In addition, in order to obtain flexibility, these electric wires are usually made of stranded conductors. However, if the adhesiveness with the coating resin is excessively strong, a coating residue may be formed on the conductor or the conductor may be cut. May occur.

In addition, in a halogen-free flame-retardant resin composition, a polyolefin having a low crystallinity and a high filler filling property is used as a main component of the resin as a means for reducing the adhesion to the conductor without impairing the high flame retardancy. It is also possible. However, the polyolefin resin has a low flame retardant effect obtained when magnesium hydroxide is added as compared with EVA or AEM, and therefore the amount of flame retardant added is 240 parts by mass or more with respect to 100 parts by mass of the resin.
The polyolefin resin has a mechanical property after irradiation of 10.3 MPa unless the melt mass flow rate (hereinafter abbreviated as MFR) defined in JIS K6922-1 is 1.0 g / 10 min or more and the tensile strength is not 30 MPa or more. The above cannot be achieved. Similarly, magnesium hydroxide must have a mechanical property improved by electron beam irradiation using a vinylsilane coupling agent.

  The present invention has been made in view of the above circumstances, uses a resin material having low crystallinity, provides sufficient flame retardancy and appropriate conductor adhesion, and can achieve high tensile fracture strength after crosslinking. The purpose is to provide goods.

In order to achieve the above object, the present invention provides EVA and / or methyl having an MFR of 1.0 g / 10 min or more and an α-olefin copolymer having a tensile strength of 30 MPa or more and an acetic acid content of 30 mass% or more. It is characterized in that 240 to 300 parts by mass of magnesium hydroxide surface-treated with a vinyl silane coupling agent is blended with 100 parts by mass of a base resin consisting of 30 to 50 parts by mass of AEM having an acrylate content of 30% by mass or more. Provided is a flame retardant resin composition.
The flame retardant resin composition of the present invention is preferably crosslinked.

  Further, the present invention is characterized in that the above-mentioned flame retardant resin composition according to the present invention is coated on a conductor, and the coating composed of the flame retardant resin composition is crosslinked by electron beam irradiation. Provide insulated wires.

  The flame-retardant resin composition of the present invention uses a resin material having low crystallinity, provides sufficient flame retardancy and appropriate conductor adhesion, and can achieve high tensile breaking strength after crosslinking.

  The flame retardant resin composition of the present invention contains 50 to 70 parts by mass of an α-olefin copolymer having an MFR of 1.0 or more and a tensile strength of 30 MPa or more, and EVA and / or methyl acrylate having an acetic acid content of 30% by mass or more. It is obtained by blending 240 to 300 parts by mass of magnesium hydroxide surface-treated with a vinylsilane coupling agent in 100 parts by mass of a base resin consisting of 30 to 50 parts by mass of AEM having an amount of 30% by mass or more.

  In order to achieve UL 105 ° C. heat resistance and tensile strength of 10.3 MPa with a material having low crystallinity, it is necessary to crosslink the resin composition by irradiating it with an electron beam. From this point, the flame-retardant resin composition of the present invention contains EVA or AEM having a higher crosslinking efficiency than the nonpolar resin such as polyethylene in the base resin. In addition, the flame retardant resin composition of the present invention contains 50% or more of an α-olefin copolymer having a weak adhesion to a conductor. In particular, in order to supplement heat resistance and tensile strength, a high-strength α-olefin copolymer is combined with magnesium hydroxide treated with a vinyl silane coupling agent having a high crosslinking efficiency by electron beam irradiation. Only by combining them in a limited way, the goal could be achieved.

  Examples of the α-olefin copolymer having an MFR of 1.0 or more and a tensile strength of 30 MPa or more used in the flame-retardant resin composition of the present invention include an ethylene-α-olefin copolymer and a propylene-α-olefin copolymer. Of these, ethylene-α-olefin copolymers are preferable, and commercially available products include TAFMER (registered trademark) A-1085 (trade name, manufactured by Mitsui Chemicals, Inc.).

  As EVA used in the flame retardant resin composition of the present invention, acetic acid content of 30% by mass or more, EVA alone, EVA with ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer ( EBA), a resin to which an ethylene-acrylic acid ester copolymer such as ethylene-methyl acrylate copolymer (EMA) is added, and the like, and it is preferable to use EVA alone. These resins contain oxygen in the molecule and generate nonflammable gas when the polymer is thermally decomposed during combustion. By using this as a constituent component of the base resin, self-extinguishing properties during combustion Is obtained.

  As AEM used for the flame retardant resin composition of the present invention having a methyl acrylate content of 30% by mass or more, 30 to 70% by mass of ethylene and 30 to 70 acrylic acid esters such as methyl acrylate and butyl acrylate. A copolymer with mass%, particularly a copolymer with methyl acrylate is preferred. Furthermore, a terpolymer having ethylene-methyl acrylate as a main component and an unsaturated organic acid ester as a third component is particularly effective. As this, a commercially available product can be used, and examples thereof include Baymac (VAMAC: trade name, manufactured by DuPont). This acrylic rubber is blended for the purpose of improving heat resistance, mechanical strength, flame retardancy, and flexibility.

  In the flame-retardant resin composition of the present invention, the blending amount of the α-olefin copolymer in 100 parts by mass of the base resin is in the range of 50 to 70 parts by mass. When the blending amount of the α-olefin copolymer is less than 50 parts by mass, the conductor adhesion of the flame retardant resin composition is increased, and the harness workability of the insulated wire is deteriorated. On the other hand, when the blending amount of the α-olefin copolymer exceeds 70 parts by mass, the flame retardancy of the resulting resin composition deteriorates and the tensile strength decreases.

  In the flame-retardant resin composition of the present invention, the blending ratio of EVA and / or AEM in 100 parts by mass of the base resin is in the range of 30 to 50 parts by mass. When the blending amount of EVA and / or AEM is less than 30 parts by mass, the blending amount of the α-olefin copolymer increases, the flame retardancy of the resulting resin composition is deteriorated, and the crosslinking efficiency by electron beam irradiation is increased. It becomes worse and the tensile strength decreases. On the other hand, when the blending amount of EVA and / or AEM exceeds 50 parts by mass, the blending amount of the α-olefin copolymer decreases, and the conductor adhesion of the flame retardant resin composition increases.

  As the flame retardant in the flame retardant resin composition of the present invention, magnesium hydroxide surface treated with a vinyl silane coupling agent (hereinafter simply referred to as water) has a large effect of imparting flame retardancy and excellent affinity with the base resin. (Referred to as magnesium oxide). The magnesium hydroxide preferably has an average particle diameter of 0.7 to 1.3 μm, and the amount of vinylsilane coupling agent present on the surface of the magnesium hydroxide particles is about 0.1 to 2% by mass. is there. As the vinyl silane coupling agent, vinyl trimethoxy silane, vinyl triethoxy silane and the like are preferable.

  In the flame-retardant resin composition of the present invention, the amount of magnesium hydroxide is in the range of 240 to 300 parts by mass with respect to 100 parts by mass of the base resin. When the blending amount of magnesium hydroxide is less than 240 parts by mass, the flame retardancy of the obtained flame retardant resin composition becomes insufficient. On the other hand, when the compounding amount of magnesium hydroxide exceeds 300 parts by mass, the mechanical properties, particularly the tensile strength, of the obtained flame-retardant resin composition is deteriorated.

  In the flame retardant resin composition of the present invention, in addition to the essential components described above, flame retardant aids, antioxidants, ultraviolet absorbers, copper damage inhibitors, antistatic agents, lubricants, processing aids, colorants, inorganic Additives such as fillers can be appropriately blended.

  The flame retardant resin composition of the present invention may be cross-linked. By performing the crosslinking, the heat resistance and wear resistance of the obtained flame-retardant resin composition are improved. As the cross-linking method, an electron beam cross-linking method in which an electron beam is irradiated after molding or a chemical cross-linking in which a cross-linking agent is preliminarily blended with a flame retardant resin composition and then heated and cross-linked is employed.

When the molded article made of the flame-retardant resin composition of the present invention is thin, such as an insulator such as an insulated wire for electronic equipment or a sheath, electron beam crosslinking with an irradiation dose of 1 to 30 Mrad is preferable, and a thick molded article In this case, chemical crosslinking is preferred.
Organic peroxides such as dicumyl peroxide and di-tert-butyl peroxide are used as the crosslinking agent used for chemical crosslinking, and unsaturated acrylates such as zinc acrylate and triallyl isocyanurate are used as the crosslinking aid. A compound is used.

  The insulated wire of the present invention has an insulator made of the flame retardant resin composition described above or an insulator and a sheath, and the flame retardant resin composition is coated on a conductor or an insulator by a known extrusion coating method. An insulator or a sheath is formed by coating, or an insulator or a sheath is crosslinked by irradiation with an electron beam or heating after coating. The thickness of the insulator of this insulated wire is 0.05 to 0.8 mm, and the thickness of the sheath is 0.05 to 0.8 mm.

Since the flame-retardant resin composition of the present invention does not contain a halogen element such as chlorine, no harmful halogen-containing gas is generated when a molded product made of the flame-retardant resin composition is incinerated. Moreover, the insulated wire which shows high flame retardance and made this composition a coating layer passes the VW-1 combustion test prescribed | regulated to UL1581.
Furthermore, the mechanical properties are good, the tensile breaking strength is 10 MPa or more, and the tensile breaking elongation is 150% or more.
In addition, those subjected to crosslinking improve characteristics such as heat resistance, wear resistance and hardness.
Hereinafter, the effects of the present invention will be demonstrated by examples.

The resin compositions having the blending compositions (units: parts by mass) shown in Table 1 (Examples 1 to 8) and Table 2 (Comparative Examples 1 to 10) were blended and kneaded at 180 ° C. for 5 minutes. In that case, in addition to each compounding component described in Table 1 and Table 2, 5 mass parts stearic acid and 2 mass parts antioxidant were added with respect to 100 mass parts of base resins as a processing aid.
After kneading, extrusion coating was performed on the conductor of AWG26 (7 / 0.16TA) with an extruder to form a coating with an insulation thickness of 0.25 mm. Subsequently, this was irradiated with an electron beam with an irradiation dose of 15 Mrad, and the insulator was electron beam cross-linked.
The following evaluation was performed about the obtained insulated wire.

Evaluation items (acceptance criteria)
・ Tensile strength at break (passed 10MPa or more)
-Tensile elongation at break (over 150% passed)
・ Flame retardancy (UL 1581 standard VW-1 combustion test, 5 out of 5 passed)
-Conductor adhesion (passed 2kg / 10mm or less)

The tensile strength at break and the tensile elongation at break were measured according to the methods described in UL1581.
The conductor adhesion force was measured by pulling out the conductor leaving the insulated wire covering 10 mm. The insulation wire is left 10 mm, the other part is removed, and the conductor is exposed, and a sample is used. A plate having a hole larger than the outer diameter of the conductor and smaller than the outer diameter of the plate is used. The specimen conductor was passed from above to below, pulled downward at a pulling speed of 100 mm / min, and the pulling force was measured.

In Tables 1 and 2, the following commercially available products were used as the blending components.
As EVA, EV180 (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd., block PP, MFR = 0.3) was used.
As AEM, VAMAC DP (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd., MA content of 30% by mass or more) was used.
As the α-olefin copolymer, Tafmer (registered trademark) A-1085 (manufactured by Mitsui Chemicals) was used.
As the magnesium hydroxide, Kisuma 5L (trade name, manufactured by Kyowa Chemical Co., Ltd.) was used.

  In Examples 1 to 8 according to the present invention shown in Table 1, sufficient flame retardancy and appropriate conductor adhesion were obtained, and high tensile fracture strength was achieved after crosslinking.

On the other hand, Comparative Example 1 shown in Table 2 has a composition in which the α-olefin copolymer is more than the range of the present invention and EVA is insufficient, and the flame retardancy and the tensile elongation at break are rejected. .
In Comparative Example 2, the α-olefin copolymer was more than the range of the present invention and AEM was insufficient, and the flame retardancy and tensile strength at break were unacceptable.
In Comparative Example 2, the α-olefin copolymer was more than the range of the present invention, and the total amount of EVA + AEM was insufficient, and the flame retardancy and the tensile strength at break were unacceptable.
Comparative Example 4 has a composition in which the α-olefin copolymer is less than the range of the present invention and the total amount of EVA + AEM is excessive, and the flame retardancy and strength are passed, but the conductor adhesion strength Was too high to be rejected.
In Comparative Example 5, the α-olefin copolymer is less than the range of the present invention, EVA is excessive, and the flame retardancy is passed, but the conductor adhesion is too high and the test is rejected. The elongation at break failed.
In Comparative Example 6, the α-olefin copolymer is less than the range of the present invention, and the AEM is excessive, and the flame retardancy is passed, but the conductor adhesion is too high and the test is rejected. The breaking strength was rejected.
In Comparative Example 7 and Comparative Example 8, the amount of magnesium hydroxide was less than the range of the present invention, and the flame retardancy was rejected.
In Comparative Example 9 and Comparative Example 10, magnesium hydroxide was added in excess, and the flame retardancy passed, but the tensile strength at break or tensile elongation at break failed.

Claims (3)

  50 to 70 parts by mass of an α-olefin copolymer having a melt mass flow rate of 1.0 g / 10 min or more and a tensile strength of 30 MPa or more as defined in JIS K6922-1, and an ethylene / vinyl acetate copolymer having an acetic acid content of 30% by mass or more. Magnesium hydroxide 240 to 300 mass parts surface-treated with a vinylsilane coupling agent on 100 parts by mass of a base resin composed of 30 to 50 parts by mass of an ethylene / acrylic rubber having a polymer and / or methyl acrylate content of 30 mass% or more A flame retardant resin composition comprising a part.   The flame retardant resin composition according to claim 1, which is crosslinked. An insulated wire, wherein the flame retardant resin composition according to claim 1 is coated on a conductor, and the coating made of the flame retardant resin composition is crosslinked by electron beam irradiation.