JPS624067B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-resistant crosslinked polyolefin composition with improved heat aging resistance at high temperatures. Polyolefin has excellent weather resistance, mechanical properties,
Due to its electrical properties, it is widely used as an electrical insulating material, but because of its poor heat deformation resistance, cross-linking is recommended when used as an electrical insulating material that is used continuously at high temperatures of 120°C or higher. It is necessary to take such measures to improve heat deformation resistance. However, even if the heat deformation resistance is simply improved by crosslinking, unless the resistance to oxidation of the polyolefin itself is improved, it will not be possible to obtain a product that can withstand continuous use at high temperatures. In this respect, conventional crosslinked polyolefins have poor heat aging resistance at high temperatures, and are unsatisfactory for use as electrical insulating materials that are continuously used at high temperatures. For this reason, silicone rubber and fluorine-based resins, which are unavoidably expensive but can withstand high temperatures of 180°C or higher, have been used in the past. In view of the above points, an object of the present invention is to provide a crosslinked polyolefin that can withstand long-term continuous use at high temperatures. That is, the present invention provides the following features: (1) a polyolefin is blended with a benzimidazole anti-aging agent and b 4,4'-bis(α-dimethylbenzyl) diphenylamine, and the blending ratio of components a and b is at right angles as shown in the drawings. Coordinates [100 parts of polyolefin (parts by weight,
The same applies hereinafter)), and the y-axis is the number of parts of component b relative to 100 parts of polyolefin], point A is 2,1, point B is 12,0, etc.
5. A heat-resistant crosslinked polyolefin composition characterized by being in a range surrounded by points C 12, 6 and points D 1, 6, and (2) the composition further contains c zinc oxide, cadmium oxide, lead oxide and The present invention relates to a heat-resistant crosslinked polyolefin composition in which at least one metal oxide selected from the group consisting of magnesium oxide is blended in an amount of 10 parts or less per 100 parts of the polyolefin. The present invention provides polyolefin with the above-mentioned components a and b as antioxidants, and furthermore, in addition to these, C.
It is characterized in that the ingredients are blended in the above-mentioned specific proportions, and in such a combination of antioxidants, a remarkable synergistic effect is exhibited between each ingredient, resulting in excellent heat aging resistance at high temperatures. A crosslinked polyolefin is obtained. In addition, the antioxidant consisting of two or three components has less inhibition of crosslinking, less volatilization at high temperatures, good compatibility with resins, and no risk of bleeding. The above components a, b and c are individually known as antioxidants for rubbers and plastics, but a combination of two components a and b or a combination of three components a, b and c is The fact that polyolefins exhibit a remarkable mutual effect on heat aging resistance at high temperatures was discovered for the first time in the present invention. However, in the present invention, inexpensive polyolefin is heated to 120 to 150°C.
It has become possible to withstand continuous use for long periods of time at moderately high temperatures, and it has become possible to use it in place of conventionally used expensive materials such as silicone rubber and fluoroplastics. The value is extremely large. Examples of the benzimidazole anti-aging agent used as component a in the present invention include 2-mercaptobenzimidazole and a zinc salt of 2-mercaptobenzimidazole. Component b, 4,4'-(α-dimethylbenzyl)diphenylamine, has the formula; This is shown in . The blending ratio of the a and b components to the polyolefin is as follows: point A 2, 1, point B 12, 1 on the rectangular coordinates.
0.5, within the range surrounded by points C 12, 6 and points D 1, 6 (hereinafter referred to as blending region). When the blending ratio of component a and (or) component b is less than the blending range, the mutual effect on heat aging resistance will not be sufficiently exhibited, whereas when it is higher than the blending range, the effect will improve compared to the increase in the blending amount. This is economically disadvantageous because it is not carried out, and moreover, undesirable phenomena such as crosslinking inhibition and bleeding tend to occur. From this point of view, in the present invention, the blending ratios of components a and b are as follows: A ¹ point 2.5.1, B ¹ point 12.1, C point 1 in rectangular coordinates.
The range surrounded by 2, 6 and D ¹ point 2.5, 6 (hereinafter referred to as blending area), especially A ¹ point 2.5, 1, B ² points 6, 1, C ¹ point 6, 3, and D ²
It is preferable to be in the range surrounded by points 2, 5 and 3 (hereinafter referred to as blending region). In the present invention, in addition to the a and b components, zinc oxide Zno and cadmium oxide are used as the c component.
It has been found that heat aging resistance is further improved when one or more of Cdo, lead oxide Pbo, and magnesium oxide M _g o is blended in an amount of 10 parts or less per 100 parts of polyolefin. If the blending ratio of component c is more than 10 parts, the effect will not be improved as compared to an increase in the blending amount, which is not preferable. The preferred blending ratio of component c is 3 to 6 parts. When component c is used in combination with components a and b, the additive effect of components a, b, and c on heat aging resistance is most pronounced when the blending ratio of components a and b is in the above blending range, especially in the blending range. This is preferable because it is economical and does not cause undesirable phenomena such as crosslinking inhibition or bleeding. As the polyolefin used in the present invention, a blend of polyethylene and an ethylene-propylene-nonconjugated diene terpolymer is suitable, but polyethylene, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, ethylene -Propylene copolymer, ethylene-propylene-
It is also possible to use one type or a blend of two or more types of ethylene copolymers such as non-conjugated diene terpolymers and ethylene-α-olefin copolymers. In the present invention, the polyolefin can be crosslinked by a conventional crosslinking method such as a method using a crosslinking agent such as an organic peroxide or a method using electron beam irradiation. As the organic peroxide crosslinking agent, any commonly used organic peroxide crosslinking agent can be used, such as dicumyl peroxide, benzoyl peroxide, cumene hydroperoxide, 1,1
-bis(t-butylperoxy)-3,3,5-
Examples include trimethylcyclohexane. These crosslinking agents are used in amounts ranging from 1 to 100 parts per 100 parts of polyolefin.
Preferably, 6 parts are used. If the proportion of the crosslinking agent is less than the above range, sufficient crosslinking will not be carried out, and if it is greater than the above range, it will not only result in over-crosslinking, resulting in a decrease in thermal stability, but also a large amount of decomposition residue of the crosslinking agent, which may damage the resin surface. Blooming occurs.
The crosslinking agent may be used in combination with commonly used crosslinking aids such as ethylene dimethacrylate and triallylisocyanurate, if necessary. In addition to the above-mentioned components, the composition of the present invention includes clay,
Inorganic fillers such as talc, aluminum hydroxide, and calcium carbonate; flame retardants such as chlorine and bromine;
Flame retardant aids such as zinc borate, barium metaborate, antimony oxide, carbon black, colorants,
A lubricant or the like may be added as appropriate. Since the heat-resistant crosslinked polyolefin composition of the present invention has excellent heat aging resistance at high temperatures, it is suitably applied to electrical insulation materials that are used continuously for long periods of time at high temperatures of, for example, about 120 to 150°C. Next, the composition of the present invention will be explained with reference to Examples and Comparative Examples. Examples 1 to 2 and Comparative Examples 1 to 4 The chemicals shown in Table 2 were blended with the standard formulation shown in Table 1, thoroughly kneaded in an oven roll at 110 to 130°C, and then heated at 175°C and 150 kg/kg. cm ² for 15 minutes to crosslink and create a sheet with a thickness of 1 mm. In order to examine the heat aging resistance of the resulting sheet at high temperatures, the elongation (%) after aging at 180°C for 7 days was measured in accordance with the UL 150°C class standard. Measurement from elongation to elongation was performed in accordance with JIS K 6301.
In addition, the elongation before aging and the remaining elongation rate (%) after aging were determined. In addition, those whose elongation after aging was less than 50% were considered to be brittle. These results are shown in Table 2. Furthermore, the second
The compounding ratio of each drug in the table is polyolefin.
This is the number of copies per 100 copies (the same applies below).

【table】

【table】

【table】

[Table] As is clear from Table 2, when zinc oxide, 2-mercaptobenzimidazole or its zinc salt, and 4,4-bis(α-dimethylbenzyl)diphenylamine are used together (Examples 1 and 2)
2,2,4-trimethyl-1, which has remarkable heat aging resistance, has been conventionally used as an effective anti-aging agent for polyolefins in place of 4,4'-bis(α-dimethylbenzyl)diphenylamine. , 2-dihydroquinoline or 4,4'-thio-bis(6-t-butyl-m-cresol) (Comparative Examples 1 to 4) had poor heat aging resistance. Examples 3 to 11 and Comparative Examples 5 to 10 Sheets were prepared in the same manner as in Examples 1 to 2, except that the chemicals shown in Table 3 were added to the standard formulation shown in Table 1, and the elongation before and after aging was measured. was measured. The results are also listed in Table 3.

【table】

[Table] As is clear from Table 3, when using zinc oxide, 2-mercaptobenzimidazole zinc salt, and 4,4'-bis(α-dimethylbenzyl) diphenylamine in combination, 2-mercaptobenzimidazole zinc salt and , 4′-bis(α-dimethylbenzyl)diphenylamine is within the blending range (Examples 3 to 11),
The heat aging resistance is superior when the blending ratio of 2-mercaptobenzimidazole zinc salt and 4,4'-bis(α-dimethylbenzyl)diphenylamine is lower than the blending range (Comparative Examples 9 to 10). In addition, when using two components together, zinc oxide and 2-mercaptobenzimidazole zinc salt or 4,4'-bis(α-dimethylbenzyl)diphenylamine (Comparative Examples 5 to 8), it is important to consider how much of the latter component is mixed. However, it can be seen that the heat aging resistance is not good. Examples 12-22 Sheets were prepared in the same manner as in Examples 1-2, except that the chemicals shown in Table 4 were added to the standard formulation shown in Table 1, and the elongation before and after aging was measured. The results are also listed in Table 4. Note that the results of Example 1 are also listed in Table 4 for reference.

[Table] As is clear from Table 4, the blending ratio of 2-mercaptobenzimidazole zinc salt and 4,4'-bis(α-dimethylbenzyl)diphenylamine is within the range of the blending range; When outside, the effect of adding zinc oxide is not so pronounced, but 2-mercaptobenzimidazole zinc salt and 4,4'-bis(α-dimethylbenzyl)
The effect of adding zinc oxide is particularly significant when the blending ratio with diphenylamine is within the blending range, especially within the range. Examples 23-31 and Comparative Example 11 Sheets were prepared in the same manner as Examples 1-2, except that the agents shown in Table 5 were added to the standard formulation shown in Table 1, and the elongation before and after aging was measured. did. The results are also listed in Table 5.

[Table] As is clear from Table 5, as the proportion of zinc oxide increases, the heat aging resistance improves (Examples 23 to 28), but when it exceeds 9 parts, it does not improve any further (Comparative Example 11). ). Excellent heat aging resistance is also exhibited when cadmium oxide, lead oxide or magnesium oxide is blended instead of zinc oxide (Examples 29 to 31).

[Brief explanation of the drawing]

The drawing shows component a (benzimidazole anti-aging agent) and component (4,4'-
These are rectangular coordinates showing the blending ratio of bis(α-dimethylbenzyl)diphenylamine).

Claims (1)

[Scope of Claims] 1. A benzimidazole-based anti-aging agent a and b4,4'-bis(α-dimethylbenzyl) diphenylamine are blended into a polyolefin, and the blending ratio of components a and b is expressed on a rectangular coordinate [on the x-axis]. The number of parts by weight of component a relative to 100 parts by weight of polyolefin is taken, and the number of parts by weight of component a relative to 100 parts by weight of polyolefin is plotted on the y-axis.
A point 2, 1, B in [take parts by weight of ingredients]
Point 12,0.5, C point 12,6 and D point 1,6
A heat-resistant crosslinked polyolefin composition characterized by being in the range surrounded by . 2 The blending ratio of components a and b is A ¹ point 2.5.1, B ¹ point 12.1, C point 1 on the rectangular coordinates.
2,6 and D1 ^point 2.5,6. 3 The blending ratio of components a and b is A ¹ point 2.5.1, B ² point 6.1, C ¹ point 6.3 in rectangular coordinates.
and D ² points 2.5, 3. 4 Polyolefin is polyethylene and ethylene-
The composition according to claim 1, 2 or 3, which is a blend with a propylene-nonconjugated diene terpolymer. 5. The composition according to claim 1, 2, 3 or 4, wherein component a is 2-mercaptobenzimidazole or a zinc salt of 2-mercaptobenzimidazole. 6. The composition according to claim 1, 2, 3, 4 or 5, further comprising an organic peroxide. 7 The blending ratio of organic peroxide is higher than that of polyolefin.
The composition according to claim 6, in an amount of 1 to 6 parts by weight per 100 parts by weight. 8 polyolefin, a benzimidazole anti-aging agent, b 4,4'-bis(α-dimethylbenzyl) diphenylamine and c at least one metal selected from the group consisting of zinc oxide, cadmium oxide, lead oxide and magnesium oxide. The oxide is blended, and the blending ratio of components a and b is determined on a rectangular coordinate [the x-axis is the number of parts by weight of the component a relative to 100 parts by weight of the polyolefin, and the y-axis is the proportion of the polyolefin.
A point 2,1, B point 12,0.5, C point 1 in 100 parts by weight of component b]
It is in the range surrounded by points 2, 6 and D points 1, 6,
A heat-resistant crosslinked polyolefin composition, characterized in that the blending ratio of component c is 10 parts by weight or less based on 100 parts by weight of the polyolefin. 9 The blending ratio of components a and b is A ¹ point 2.5.1, B ¹ point 12.1, C point 1 in rectangular coordinates.
9. The composition according to claim 8, which is in the range surrounded by 2, 6 and D ¹ point 2, 5, 6. 10 The blending ratio of components a and b is A ¹ point 2.5.1, B ² point 6.1, C ¹ point 6.
The composition according to claim 9, which is in the range surrounded by points 2.5 and ³ . 11. The composition according to claim 8, 9 or 10, wherein the blending ratio of component c is 3 to 6 parts by weight based on 100 parts by weight of the polyolefin. 12 Claims 8 and 9, in which the polyolefin is a blend of polyethylene and an ethylene-propylene-nonconjugated diene terpolymer,
The composition according to item 10 or 11. 13 Claims 8, 9, and 1, wherein component a is 2-mercaptobenzimidazole or a zinc salt of 2-mercaptobenzimidazole
The composition according to item 0, item 11 or item 12. 14 Claims 8, 9, 10, and 11 further contain an organic peroxide.
The composition according to item 1, item 12 or item 13. 15 The blending ratio of organic peroxide is higher than that of polyolefin.
15. The composition according to claim 14, in an amount of 1 to 6 parts by weight per 100 parts by weight.