JP4754187B2 - Flame retardant composition and wire excellent in heat resistance and voltage resistance characteristics - Google Patents

Description

  The present invention has a heat-resistant and voltage-resistant characteristic in a well-balanced manner, for example, a flame-retardant composition suitable as an insulator for electrical equipment wiring and automobile harness, and a coating made of the flame-retardant composition Related to electrical wires.

Olefin polymers such as polyethylene and ethylene-propylene rubber have been widely used as insulators for insulated wires since they are inexpensive and have good processability. However, since the olefin polymer itself is flammable, it is necessary to impart flame retardancy from the viewpoint of safety and fire resistance. As a method for imparting flame retardancy, for example, a method of adding a flame retardant is generally employed, but by adding an additive such as a flame retardant, mechanical strength and withstand voltage characteristics are greatly increased. It will be reduced. Therefore, for example, Patent Document 1 and Patent Document 2 disclose nonpolar olefin polymers having excellent voltage resistance characteristics such as polyethylene and ethylene-propylene rubber, and additives such as ethylene-vinyl acetate and ethylene-ethyl acrylate. A method for preventing deterioration of various properties due to the addition of an additive such as a flame retardant is disclosed by mixing a polar olefin polymer having an excellent affinity with a suitable ratio.

In recent years, the demand for materials that can be used in a high-temperature atmosphere has increased, and it has become a problem to impart high heat resistance to flame retardant compositions. Thus, for example, Patent Document 3 and Patent Document 4 disclose a method of adding hydrotalcites and additives such as antioxidants and metal deactivators to improve heat resistance by synergistic effects thereof. ing.

JP-A-8-180737 Japanese Patent No. 3092294 Japanese Patent Laid-Open No. 5-214175 Japanese Patent No. 3289424

However, as in Patent Document 1 and Patent Document 2 described above, the effect of improving the heat resistance cannot be obtained only by selecting a specific polymer, even if the mechanical strength and the withstand voltage characteristics can be prevented from being lowered. . In addition, although Patent Document 3 and Patent Document 4 have a description for improving heat resistance, there is no description on withstand voltage characteristics. In the first place, hydrotalcite is a crystal formed by ionic bond between an anion layer and a cation layer. In addition, since the crystal water is contained in the crystal, the withstand voltage characteristic is deteriorated, and when the additive as described above is added in a large amount in order to express high heat resistance, The withstand voltage characteristics are lowered due to problems in the properties and molecular structure. Furthermore, when hydrotalcites or the above-mentioned additives are added, the mechanical strength tends to be lowered. Thus, it has been difficult to obtain a flame retardant composition having both heat resistance and withstand voltage characteristics in a well-balanced manner with the conventional technology.

  The present invention has been made to solve such problems of the prior art, and an object of the present invention is to provide a flame retardant composition having a good balance of heat resistance and withstand voltage characteristics. .

In order to achieve the above object, a flame retardant composition according to claim 1 of the present invention comprises an olefin polymer and a hydroxide of a group 2 or group 3 metal element with respect to 100 parts by weight of the olefin polymer. A flame retardant composition comprising 150 parts by weight, 2 to 50 parts by weight of an oxide of a group 2 or 3 metal element, and 2 to 50 parts by weight of a hydrotalcite compound , the flame retardant The composition has a heat of crystal melting of 10 J / g or more and 50 J / g or less .
The flame retardant composition according to claim 2 is characterized in that 5 to 70 parts by weight of a halogen flame retardant is further blended with 100 parts by weight of the olefin polymer.
The flame retardant composition according to claim 3 is characterized in that the metal element hydroxide of the group 2 or 3 is at least one selected from magnesium hydroxide and aluminum hydroxide, and the group 2 or 3 The metal element oxide is at least one selected from zinc oxide and magnesium oxide.
According to a fourth aspect of the present invention, there is provided an electric wire provided with a coating made of the above flame retardant composition, wherein the flame retardant composition is crosslinked.

The flame retardant composition according to the present invention has excellent heat resistance by combining a specific amount of an oxide of a group 2 or 3 metal element and an inorganic substance having an ion exchange function in an olefin polymer. Can be obtained. This effect is even higher when a halogen-based additive is added. Further, by adding a specific amount of a hydroxide of a group 2 or group 3 metal element, the withstand voltage characteristics are improved, and an oxide or ion exchange function of the group 2 or group 3 metal element, or Even if other additives and the like are added, it is possible to suppress a decrease in withstand voltage characteristics. Thus, according to the present invention, it is possible to obtain a flame retardant composition having a good balance between heat resistance and withstand voltage characteristics.
Moreover, since the softness | flexibility can be improved because the crystal melting heat amount of the said flame-retardant composition shall be 50 J / g or less, the flame-retardant composition suitable for the use for which flexibility is required is obtained. be able to.
Moreover, the flame retardant composition which has higher flame retardance can be obtained by further adding 5-70 weight part of halogenated flame retardants. Therefore, this flame retardant composition is suitable as a covering material for insulated wires, for example, which requires a VW-1 vertical combustion test conformity specified in UL standards.

  Hereinafter, each component which comprises the flame-retardant composition of this invention is demonstrated.

(A) Olefin polymer
Examples of the olefin polymer used in the present invention include polyethylene, ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, ethylene methyl methacrylate copolymer, and ethylene-α olefin copolymer. Examples thereof include polymers and ethylene propylene rubber. Examples of the α olefin include 1-hexene, 1-butene, 4-methyl-1-pentene and the like. These may be used alone or in combination. Among these, it is preferable to contain a nonpolar olefin polymer such as polyethylene or ethylene propylene rubber. If such a non-polar olefin polymer is contained, it is possible to suppress a decrease in the withstand voltage characteristics due to the base polymer itself, so that the withstand voltage characteristics of the flame retardant composition can be improved.

(B) Group 2 or Group 3 Metal Element Hydroxide In the present invention, a Group 2 or Group 3 metal element hydroxide is used for the purpose of improving withstand voltage characteristics by the action as an insulating filler. Is blended. Examples of the hydroxide of the group 2 or group 3 metal element include magnesium hydroxide, calcium hydroxide, barium hydroxide, and aluminum hydroxide. These may be used alone or in combination. Among these, magnesium hydroxide and aluminum hydroxide are preferable because they greatly contribute to the improvement of the flame retardancy of the flame retardant composition, and even when a large amount is blended, there is little decrease in heat resistance. Further, a hydroxide that acts as an acid acceptor, such as magnesium hydroxide or calcium hydroxide, is preferable because it improves heat resistance when an appropriate amount is blended. Further, as the hydroxide of the metal element of Group 2 or Group 3, it is preferable that the particle size is fine and the particle shape is uniform because the effect of improving the withstand voltage characteristic is high.

  The above-mentioned group 2 or group 3 metal element hydroxide is blended in an amount of 10 to 150 parts by weight per 100 parts by weight of the olefin polymer. When the blending amount of the hydroxide is less than 10 parts by weight, the effect of improving the withstand voltage characteristics as an insulating filler is insufficient, and when it exceeds 150 parts by weight, the mechanical strength and heat resistance are lowered. .

(C) Group 2 or Group 3 Metal Element Oxide In the present invention, an oxide of a Group 2 or Group 3 metal element is blended for the purpose of improving heat resistance by the action as an acid acceptor. . Examples of Group 2 or Group 3 metal element oxides include magnesium oxide, calcium oxide, barium oxide, and zinc oxide. These may be used alone or in combination.

  The above-mentioned oxide of the group 2 or group 3 metal element is blended in an amount of 2 to 50 parts by weight with respect to 100 parts by weight of the olefin polymer. When the compounding amount of the oxide is less than 2 parts by weight, the effect of improving the heat resistance as an acid acceptor is insufficient, and when it exceeds 50 parts by weight, the mechanical strength and withstand voltage characteristics are deteriorated.

(D) Inorganic substance having ion exchange function In the present invention, an inorganic substance having an ion exchange function is blended for the purpose of improving heat resistance. Accordingly, long-term heat resistance can be improved by incorporating halogen ions and metal ions that promote deterioration into an inorganic substance having an ion exchange function and inactivation. Examples of inorganic substances having an ion exchange function include hydrotalcite compounds, smectites, kaolins, and swellable mica. These may be used alone or in combination.

  The inorganic substance having the ion exchange function described above is blended in an amount of 2 to 50 parts by weight with respect to 100 parts by weight of the olefin polymer. When the blending amount of the inorganic substance having an ion exchange function is less than 2 parts by weight, the effect of improving the heat resistance is insufficient, and when it exceeds 50 parts by weight, the mechanical strength and withstand voltage characteristics are deteriorated.

  These Group 2 or Group 3 metal element hydroxides, Group 2 or Group 3 metal element oxides, and inorganic substances having an ion exchange function include, for example, higher fatty acids such as lauric acid, stearic acid, and oleic acid, Alternatively, the surface treatment can be performed with a surface treatment agent such as a higher fatty acid metal salt such as aluminum, magnesium or calcium salt, a silane coupling agent or a titanate surface treatment agent. These surface treatment agents are preferably used in order to improve the affinity and dispersibility with the olefin polymer and improve the mechanical strength and the like. These surface treatment agents may be used alone or in combination of two or more. Moreover, when surface-treating, what was surface-treated beforehand may be used, and a surface treatment agent may be mix | blended with an untreated or surface-treated thing, and surface treatment may be performed.

(E) Halogen Flame Retardant The flame retardant composition of the present invention has the above-described (b) group 2 or group 3 metal element hydroxide functioning as a flame retardant. For example, it has flame retardant properties that pass the horizontal combustion test specified in the UL standard), but in addition to the components (a) to (d) above, further adding a halogen flame retardant, The flame retardancy can be further improved, and a higher level of flame retardancy (for example, flame retardancy that passes the VW-1 vertical combustion test defined in the UL standard) can be imparted. Examples of the halogen-based flame retardant include ethylene bis (tetrabromophthalimide), ethylene bis (pentabromodiphenyl), perchlorocyclopentadecane, and the like. These may be used alone or in combination.

  The halogen-based flame retardant is preferably blended in an amount of 5 to 70 parts by weight with respect to 100 parts by weight of the olefin polymer. When the blending amount of the halogen-based flame retardant is less than 5 parts by weight, the effect of improving the flame retardancy is not sufficient, and the more advanced flame retardancy (for example, passes the VW-1 vertical combustion test defined in the UL standard). Flame retardancy) cannot be obtained, and when it exceeds 70 parts by weight, mechanical strength and withstand voltage characteristics are degraded.

  In the present invention, in addition to the above components, various additives that are conventionally used in electric wires and cables may be blended within a range that does not impair the object of the present invention. Examples of such additives include flame retardant aids, anti-aging agents, cross-linking agents, cross-linking aids, lubricants, softeners, dispersants, colorants, and the like.

Examples of the flame retardant aid include antimony trioxide, zinc sulfide, zinc borate, zinc stannate, and a molybdenum compound. Among these, it is preferable to use antimony trioxide, and higher flame retardancy can be imparted by using it together with a halogen-based flame retardant.

These flame retardant aids are preferably blended in an amount of 5 to 40 parts by weight with respect to 100 parts by weight of the olefin polymer. If the blending amount of the flame retardant aid is less than 5 parts by weight, the effect as a flame retardant aid is not sufficient, and if it is 40 parts by weight or more, the mechanical strength and the withstand voltage characteristics are lowered.

Examples of the anti-aging agent include amine-based, phenol-based, phosphorus-based and sulfur-based anti-aging agents. These may be used alone or in combination. Among these, it is preferable to use a phenol-based anti-aging agent and a sulfur-based anti-aging agent in combination, and by providing a synergistic effect of a radical scavenging effect and a peroxide decomposition effect, a higher heat resistance is imparted, and bleed-out and coloring properties are improved. There is no pollution. Examples of the phenolic antioxidant include monophenols such as 2,6-di-t-butyl-4-methylphenol, 2,2′-methylene-bis- (4-methyl-6-t-butylphenol), and the like. Bisphenols such as 4,4′-thiobis- (6-t-butyl-3-methylphenol), thiobisphenols such as tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanate Examples include hindered phenols such as nurate, and sulfur-based anti-aging agents such as thioethers such as dilauryl thiodipropionate, imidazoles such as 2-mercaptobenzimidazole, nickel dibutyldithiocarbamate, etc. And thiocarbamate aging inhibitors. Of these, the combination of a hindered phenol anti-aging agent and an imidazole anti-aging agent is more preferable, and the highest effect of improving heat resistance is exhibited. Examples of the hindered phenol antioxidant include tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 1,1,3-tris- (2-methyl-4-hydroxy). -5-t-butylphenyl) butane, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, and the like. Examples of the imidazole anti-aging agent include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, 4,5-mercaptomethylbenzimidazole, and zinc salts thereof.

  These antioxidants are preferably blended in a total of 2 to 30 parts by weight with respect to 100 parts by weight of the olefin polymer. When the blending amount of the anti-aging agent is less than 2 parts by weight, the effect as an anti-aging agent is not sufficient, and when it exceeds 30 parts by weight, the withstand voltage characteristic is lowered.

  The flame retardancy of the present invention is obtained by adequately blending the above-described constituent materials with a known kneader such as a roll, kneader, Banbury, uniaxial kneader, or biaxial kneader. A composition can be obtained.

In the present invention, the heat of crystal fusion of the flame retardant composition thus obtained is preferably 50 J / g or less. If the amount of heat of crystal fusion of the flame retardant composition is 50 J / g or less, the flexibility can be improved, so that a flame retardant composition suitable for applications requiring flexibility can be obtained.

  An electric wire according to another embodiment of the present invention is formed by subjecting the above flame-retardant composition to extrusion coating on the conductor circumference by a known method, and then appropriately crosslinking to improve the heat resistance of the flame-retardant composition. Can be obtained.

  The crosslinking method is not particularly limited. For example, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 1,3-bis (t-butylperoxyisopropyl) benzene, 1,1-bis (t -Butylperoxy) -3,3,5-trimethylcyclohexane, chemical crosslinking method using an organic peroxide such as dicumyl peroxide as a crosslinking agent, X-ray, γ-ray, electron beam, proton beam, deuteron beam, Examples include an irradiation crosslinking method using ionizing radiation such as α rays and β rays. In addition, about the crystal heat of fusion mentioned above, when performing bridge | crosslinking, it is preferable that the crystal heat of fusion of the flame-retardant composition after bridge | crosslinking is 50 J / g or less.

  Examples of the present invention will be described below together with comparative examples. Details of each compounding material used in this example are as shown in Table 5.

The blended materials shown in Table 5 were sufficiently kneaded with a twin-screw kneader according to the number of blending parts shown in Tables 1 to 4, and the obtained flame retardant composition was pelletized. This pellet was supplied to a 25 mmφ extruder with L / D = 24, and tin-plated annealed copper stranded wire (0... 0) of American Wire Gauge (AWG) 28 under the temperature conditions of cylinder 70 to 100 ° C. and head 110 ° C. 4φ) was coated on the circumference of the conductor with a thickness of 0.35 mm. Then, it was chemically crosslinked under the conditions of 210 ° C. and 0.4 MPa to produce an electric wire having a finished outer diameter of 1.1 mmφ.

Here, using a total of 26 types of electric wires obtained in this way as samples, mechanical strength (tensile breaking strength, tensile breaking elongation), heat resistance, withstand voltage characteristics (dielectric breakdown voltage), flame retardancy, flexibility Each sex was evaluated. The results are shown in Tables 1 to 4 together with the number of blended parts of each blended material.

The evaluation method is as follows.
(Mechanical strength)
Based on UL758.14, the tensile strength at break and the tensile elongation at break were evaluated. As a pass / fail criterion, a sample having a tensile strength at break of 10 MPa or more and a tensile elongation at break of 150% or more was determined to be acceptable.
(Heat-resistant)
Reference was made to the heat resistance test (rated at 125 ° C. and rated at 150 ° C.) of UL758.14. Put into a gear oven set at 158 ° C (rated 125 ° C) and 180 ° C (rated 150 ° C), take out every 7 days, measure the tensile elongation at break, and the tensile elongation at break after aging is 50% or more The number of days that can be retained was measured. As a pass / fail standard, a rating of 125 ° C. was determined to be 35 days or more, and a rating of 150 ° C. was determined to be 21 days or more.
(Withstand voltage characteristics)
The dielectric breakdown voltage in water was used for evaluation. The applied AC voltage was increased, and the voltage at the time of dielectric breakdown was measured. Measurement was performed with the number of samples n = 10, and the average value was calculated. As a pass / fail criterion, a product having a dielectric breakdown voltage of 10 kV or higher was determined to be acceptable.
(Flame retardance)
Evaluation was performed using UL758.39 (horizontal combustion test) and UL758.41 (VW-1 combustion test).
(Flexibility)
As shown in FIG. 1 (A), the wire 1 having a length of 500 mm is used as a sample, the marked lines s and s ′ are drawn at a distance of 50 mm on the left and right from the center c, and the covering 1a is peeled off only 10 mm on both ends of the wire 1. The conductor 1b is exposed. Next, as shown in FIG. 1 (B), the ends of the conductors 1b are aligned and bundled, and suspended so that the center c of the electric wire 1 is placed on the mandrel 3 having a diameter of 2.0φ. A load of 0.98 N (100 g) is applied to the bound portion of the conductor 1b. Then, after applying the load, the distance L between the marked lines s and s ′ after one minute is measured. As a criterion for evaluation, it was determined that the distance L between the marked lines was less than 5 mm, especially soft, 5-10 mm soft, and 10 mm or more hard. Moreover, in the table | surfaces, the thing below 5 mm was shown as (double-circle), the thing 5-10 mm is (circle), and the thing 10 mm or more was shown as (triangle | delta).

  Further, the heat of crystal melting was measured for the above-mentioned 26 kinds of samples. The measurement method was a differential scanning calorimetry (DSC) apparatus, where the temperature of the sample was raised from room temperature to 300 ° C., and the total endotherm was measured to obtain the heat of crystal fusion.

  Of the above examples, Examples 1 and 2 do not contain a halogen flame retardant, and Examples 3 to 19 contain a halogen flame retardant. All of the examples passed the horizontal combustion test, and it was confirmed that they usually have the necessary flame retardancy. Especially Examples 3-19 which mix | blended the halogenated flame retardant passed the VW-1 vertical combustion test, and it was confirmed that it has especially high flame retardance.

  In addition, the electric wires according to this example all show acceptable values for heat resistance and withstand voltage characteristics, and have a good balance of heat resistance and withstand voltage characteristics, as well as mechanical strength (strength and elongation). It was also confirmed that it was excellent.

Especially about Example 5 containing an ethylene-propylene-diene copolymer which is a nonpolar olefin polymer as an olefin polymer, Examples 3 and 4 which do not contain a nonpolar olefin polymer. It was confirmed that it was excellent in withstand voltage characteristics as compared with.

  When Examples 3, 6, 7, and 8 are compared with Comparative Example 1, a comparative example in which a hydroxide of a metal element of Group 2 or Group 3 is blended exceeding the range (10 to 150 parts by weight) of the present invention. 1 is inferior in mechanical strength and heat resistance compared to Examples 3, 6, 7 and 8, and any value of mechanical strength test (strength, elongation) and heat resistance test (125 ° C rating, 150 ° C rating) It was also confirmed that the acceptable level was not reached. Further, when Examples 3, 6, 7, and 8 are compared with Comparative Example 2, Comparative Example 2 in which a hydroxide of a metal element of Group 2 or Group 3 is not blended is found in Examples 3, 6, 7, and 8. It was confirmed that the withstand voltage characteristic was inferior to that of the test, and the withstand voltage characteristic test value did not reach the acceptable level.

  When Examples 3, 9, 10, 11 and Comparative Example 3 are compared, Comparative Example 3 in which an oxide of a metal element belonging to Group 2 or Group 3 exceeds the range of the present invention (2 to 50 parts by weight) Was inferior to the withstand voltage characteristics compared to Examples 3, 9, 10, and 11, and it was confirmed that the value of the withstand voltage characteristic test did not reach the acceptable level. In addition, when Examples 3, 9, 10, and 11 are compared with Comparative Example 4, Comparative Example 4 that does not contain an oxide of a Group 2 or Group 3 metal element is similar to Examples 3, 9, 10, and 11. It was confirmed that the heat resistance was inferior to that of the heat resistance test (rated at 125 ° C. and rated at 150 ° C.) and did not reach the acceptable level.

  Comparing Examples 3, 12, and 13 with Comparative Example 5, Comparative Example 5 in which the inorganic substance having an ion exchange function was blended exceeding the range of the present invention (2 to 50 parts by weight) , 13 is inferior to the withstand voltage characteristic, and it was confirmed that the value of the withstand voltage characteristic test did not reach the acceptable level. Further, when Examples 3, 12, and 13 were compared with Comparative Example 6, Comparative Example 6 in which an inorganic substance having an ion exchange function was not blended was inferior in heat resistance compared to Examples 3, 12, and 13, and heat resistance. It was confirmed that the value of the test (150 ° C rating) did not reach the acceptable level.

  Further, when Examples 3 and 14 are compared with Example 15, Examples 3 and 14 in which the heat of crystal fusion of the flame retardant composition falls within the preferred range (50 J / g or less) of the present invention can be flexible. Although the flexibility was excellent, Example 15 in which the heat of crystal fusion of the flame-retardant composition exceeded the preferable range of the present invention (50 J / g or less) was not problematic in practical use. It was slightly hard and poor in flexibility.

  Further, when Examples 3, 17, 18 and Example 16 are compared, Example 16 in which the halogen-based flame retardant is blended exceeding the preferable range of the present invention (5-70 parts by weight) is problematic in practical use. However, the mechanical strength and withstand voltage characteristics were slightly poor.

  Further, when Examples 3, 19, and 20 were compared, it was confirmed that the value of the heat resistance test was decreased as the blending amount of the antioxidant was decreased.

  As described above in detail, according to the present invention, a flame retardant composition having a good balance between heat resistance and withstand voltage characteristics can be obtained. Therefore, this flame retardant composition is suitable as an electrical device wiring or an insulator for an automobile harness. Further, the usage is not limited to these, and for example, it can be used as an insulating coating material for a cord-shaped heater, a constituent material for a tube, and the like.

It is the schematic showing the method of a flexibility test.

Explanation of symbols

1 electric wire 1a covering 1b conductor 2 weight 3 mandrel

Claims (4)

Olefin-based polymer, Group 2 or Group 3 metal element hydroxide 10 to 150 parts by weight, Group 2 or Group 3 metal element oxide 2 to 50 parts by weight with respect to 100 parts by weight of the olefin polymer And 2 to 50 parts by weight of a hydrotalcite compound, wherein the heat of crystal melting of the flame retardant composition is 10 J / g or more and 50 J / g or less. A flame retardant composition. The flame retardant composition according to claim 1, wherein 5 to 70 parts by weight of a halogen flame retardant is further blended with 100 parts by weight of the olefin polymer. The Group 2 or Group 3 metal element hydroxide is at least one selected from magnesium hydroxide and aluminum hydroxide, and the Group 2 or Group 3 metal element oxide is zinc oxide and magnesium oxide. The flame retardant composition according to claim 1, wherein the flame retardant composition is at least one selected from the group consisting of: An electric wire comprising a coating made of the flame retardant composition according to any one of claims 1 to 3, and the flame retardant composition being cross-linked.

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