JPS6239161B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a molded article of a flame-retardant and radiation-resistant polymer composition having excellent flame retardancy and radiation resistance. Hydrocarbon polymers, such as polyethylene, polypropylene, ethylene-propylene copolymers,
Polybutadiene, butadiene-styrene copolymers, polystyrene, polyisoprene, and other hydrocarbon polymers are easily flammable, and when deemed necessary for disaster prevention, it is desirable to use them after being subjected to flame-retardant treatment. It is well known that various flame retardants and flame retardant methods have been proposed for this purpose. Examples of flame retardants include organic flame retardants such as chlorine or brominated paraffin, halogen-substituted aliphatic compounds such as chlorinated polyethylene, and halogen-substituted aromatic compounds such as hexapromobenzene and decabromodiphenyl ether. , triphenyl phosphate, tris(2,3-dibromopropyl) phosphate, and many other compounds such as aluminum hydroxide are known as inorganic flame retardants.
Among them, halogen-substituted aromatic compounds such as bromine are known to be thermally stable and highly effective as flame retardants for hydrocarbon polymers. However, in the case of the so-called additive type flame retardant exemplified here, there is no chemical bond between the flame retardant and the polymer. Therefore, during long-term use, the flame retardant properties of the flame retardant polymer molded product often deteriorate because the flame retardant oozes out onto the surface of the molded product or evaporates at high temperatures. Considering that a flame retardant polymer molded product actually encounters a fire, if the flame retardant has a small molecular weight and is additive, it will evaporate from the molded product before the polymer ignites due to flames or heat. Since it volatilizes, a situation arises in which the flame retardant effect is significantly reduced. For this reason, measures such as adding an excessive amount in advance may be taken, but adding a large amount of flame retardant will affect the mechanical properties such as strength and electrical properties such as insulation performance of the flame retardant polymer molded product. This causes a significant decrease in the amount of water. On the other hand, additive flame retardants with high molecular weights, such as chlorinated polyethylene, have been proposed.
In this case, there is little leaching from the resin or volatilization at high temperatures, which occurs with the low molecular weight ones mentioned above. However, these high molecular weight flame retardants are compatible only with resins having very similar molecular structures, and the compatibility between resins with different structures is very poor. Moreover, even if it appears to be mixed on the surface, it is often only dispersed non-uniformly, and the flame retardant effect is also poor. The inventors have previously discovered that flame retardants do not have such drawbacks commonly found in flame retardants, i.e., there is no leaching or volatilization of flame retardants from formulated compositions, and good compatibility with a wide range of polymers. We proposed a new flame retardant method using polymerizable phosphoric acid esters as a new flame retardant method for hydrocarbon polymers, which shows that effective flame retardant effects can be obtained even when used in small amounts. However, in the flame retardant hydrocarbon polymer composition obtained by this flame retardant method, the polymerizable phosphate ester flame retardant blended into the composition is However, a new problem has arisen in that when a molded article of the composition is used under conditions of high humidity, its flame retardancy decreases due to a hydrolysis reaction. Incidentally, in recent years, power generation using light water-cooled nuclear reactors has become widespread, and there is a strong demand for improving the fire resistance of electric wires and cables used around the reactor in order to ensure safety. Around the reactor,
Electric wires and cables are sometimes used in environments where there are multiple deterioration factors such as high humidity and radiation, and the flame retardant treatment of insulation materials must be done in a manner suitable for this environment. In other words, the flame retardant must be non-leaching, highly moisture resistant, and must not impair the radiation resistance of the base hydrocarbon polymer. From the above points of view, the present inventors have conducted intensive studies on making flame retardant hydrocarbon polymers using polymerizable compounds, and as a result, the general formula The brominated phenyl ester of acrylic acid represented by (in the formula, n = 3, 4 or 5) has sufficient polymerization reactivity, and this polymer is sufficient in the hydrocarbon polymer that serves as the base material. The inventors have discovered that the material has the ability to provide excellent moisture resistance and flame retardancy. On the other hand, polymerizable flame retardants such as those mentioned above exhibit an effective flame retardant effect only when they are turned into polymers, so they are generally used as radiation resistance imparting agents for hydrocarbon polymers. Addition of an antioxidant with a strong radical scavenging effect is not preferable because it inhibits the polymerization of the flame retardant and reduces the flame retardant effect. Furthermore, due to this polymerization inhibiting effect, the polymerizable flame retardants left unreacted will gradually react when exposed to a radiation environment, promoting radiation deterioration of the base hydrocarbon polymer. It has been shown that this has an adverse effect. For this reason, a radiation resistance imparting agent that can be used in combination with a polymerizable flame retardant must not inhibit the polymerization of the polymerizable flame retardant. Based on this request, the present inventors conducted basic studies on the radiation reactions of various compounds, and found that pyrene and nickel dialkyl diothicarbamate or pyrene and 4-benzoyloxy -Electrically insulating hydrocarbon type that has excellent performance in both flame retardancy and radiation resistance when a mixture with 2,2,6,6-tetramethylpyridine in a specific range is used together with the above polymerizable flame retardant. It has been discovered that a polymer composition can be obtained, and the present invention has been achieved. The hydrocarbon polymers targeted by the present invention are polymers whose main component is a monomer consisting of carbon and hydrogen, such as ethylene, propylene, butene, isobutene, butadiene, isoprene, styrene, α-methylstyrene, or A mixture of these. In addition, the polymers referred to in the present invention include various derivatives of the above monomers, acrylic acid and its esters, methacrylic acid and its esters, vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, vinyl chloride,
Copolymers with vinyl monomers such as vinylidene chloride, vinyl bromide, acrylonitrile, acrylamide, vinyl acetate, and mixtures of these with the above-mentioned hydrocarbon polymers also belong to the scope of the present invention. In addition, the general formula

[Formula] Specific examples of polymerizable flame retardants represented by (in the formula, n = 3, 4 or 5) include bromine, 2, 3, 4-,
Tribromophenyl acrylate in the 2, 3, 5-, 2, 3, 6, 2, 4, 6- or 3, 4, 5- position, 2, 3, 4, 5- or 2,
Mention may be made of tetrabromphenyl acrylate and pentabromphenyl acrylate in the 3, 5, and 6 positions. Pyrene, nickel dialkyldithiocarbamate and 4-
Commercially available benzoyloxy-2,2,6,6-tetramethylpiperidine can be used as is. Further, examples of the alkyl of nickel dialkyldithiocarbamate include ethyl, n-butyl, and the like. The amount of the flame retardant added to the hydrocarbon polymer depends on the type of hydrocarbon polymer and the required degree of flame retardancy, but 5 to 60 parts by weight of the flame retardant is added to 100 parts by weight of the polymer. part is used. However, since the flame retardant has a large flame retardant effect, it is not necessary to add a significantly excessive amount, and in general, addition of about 10 to 30 parts by weight is sufficient. In the present invention, it is preferable to use antimony trioxide in an amount of 1/2 to 1/3 times the antimony atomic weight per 1 bromine atom in the added flame retardant, as this further promotes flame retardancy. On the other hand, if the amount of the radiation resistance imparting agent used in combination with the polymerizable flame retardant is too small, the effect will be small, and if it is added in a large amount, the flame retardance of the composition will decrease. The amount is 0.5 to 20 parts by weight per 100 parts by weight of the combined product. In addition, the radiation resistance imparting agent pyrene and nickel dialkyldithiocarbamate or 4-benzoyloxy-
The most effective mixing ratio with 2,2,6,6-tetramethylpiperidine is in the range of 1:2 to 1:0.1 by weight. In order to obtain the flame-retardant and radiation-resistant polymer composition molded article according to the present invention, first, a hydrocarbon polymer, a polymerizable flame retardant, and a radiation resistance imparting agent are mixed by various known methods, for example, in the form of granules, powders, etc. A powder or granular flame retardant may be added to a polymer in the form of flakes or blocks, mixed in a mixer, and kneaded using a hot roll, Brabender, or the like. Thereafter, the polymerizable flame retardant blended after molding is polymerized by a desired molding method.
As a means for this polymerization, for example, a radical generator is added to the composition immediately before the composition is molded, and the radical generator is heated and polymerized at the same time as the molding. Alternatively, after molding the composition, there is a method of irradiating the shaped molded article with ionizing radiation to polymerize it. Irradiation before molding is not preferred because crosslinking occurs in the hydrocarbon polymer, making subsequent molding of the composition difficult. Ingredients such as fillers, plasticizers, dyes, pigments, heat stabilizers, antistatic agents, lubricants and similar substances can also be incorporated into the flame retardant composition used in the present invention. In addition, the composition molded article as used in the present invention does not mean a specific shape at all, but refers to, for example, an insulator layer, a sheath layer, and other various excipients in sheets, films, electric wires, cables, etc. It is something. Examples are shown below, in which oxygen index was adopted as a method of indicating flame retardancy. The method for measuring this value is standardized in JIS K7201 or ASTM D2863-70, and according to these, the oxygen index of a polymer material is measured if the sample burns continuously for 3 minutes or more, or if the combustion length It is calculated from the minimum oxygen concentration required for the flame to continue burning for more than 50 mm. In the following examples, all parts and percentages are by weight unless otherwise specified. Examples 1-2, Comparative Examples 1-2 5 parts of zinc white, 0.5 part of sulfur, 1 part of stearic acid to 100 parts of ethylene propylene rubber (EPDM)
parts, poly(2,2,4-trimethyl-1,2 dihydroquilinone) 1.5 parts, antimony trioxide 10 parts,
100 parts of talc, 2, 4, 6- as a polymeric flame retardant
30 parts of tribromophenyl acrylate (Example 1) or pentabromophenyl acrylate (Example 2), 5 parts of pyrene as a radiation resistance imparting agent,
120 parts of nickel dibutyldithiocarbamate
The mixture was mixed into ethylene propylene rubber on two rolls at .degree. C., and then the roll temperature was lowered to room temperature, and 3 parts of dicumyl peroxide and 6 parts of di-t-butyl peroxide were mixed as radical generators. This mixture was heated at 175°C for 30 minutes at 100°C.
It was compression molded into a sheet with a thickness of 3 mm or 2 mm at kg/cm ² . From the obtained 3mm thick sheet, width 6.5
A strip of 150 mm in length was cut out and the oxygen index of each sample was measured. Also, from a sheet with a thickness of 2 mm,
Punch out JIS No. 3 dumbbells and place them in the air at room temperature 5x
After irradiating with gamma rays at a dose rate of 10 ⁵ rad/hr, each sample obtained was subjected to a tensile test method (20℃, tensile rate
500mm/min) to measure radiation resistance. The results obtained are shown in Table 1. Comparative Example 1 in the same table shows the results when decabromodiphenyl ether was added instead of the polymerizable flame retardant so that the bromine content was the same as in Example 1, and no radiation resistance imparting agent was added. It can be seen that according to the method of the present invention, a flame-retardant composition molded article having a high oxygen index and excellent radiation resistance can be obtained. In addition, as Comparative Example 2, when decabrom diphenyl ether and a radiation resistance imparting agent having the same composition as that used in Examples 1 and 2 were added, sufficient flame retardance was obtained with an oxygen index of 2, 4, and 5. No molded article of the composition was obtained.

[Table] Examples 3 to 4 In Examples 1 and 2, the same procedure as in Example 1 was used except that 5 parts of pyrene and 2 parts of 2,2,6,6-tetramethylpiperidine were used as radiation resistance imparting agents. Sample sheets were obtained, and oxygen index and radiation resistance tests were conducted on each sample. The results obtained are summarized in Table 2.

[Table] As is clear from the above table, it can be seen that excellent flame-retardant and radiation-resistant polymer composition molded articles similar to those of Examples 1 and 2 were obtained. Example 5 For 100 parts of polyethylene (PE), 0.5 parts of lead stearate, 0.5 parts of paraffin wax, 0.5 parts of poly(2,2,4-trimethyl-1,2 dihydroquinoline), 10 parts of antimony trioxide, 15 parts of Lorane Plus 25, 20 parts of pentabromophenylacrate as a polymerizable flame retardant, 5 parts of pyrene as a radiation resistance imparting agent, and 2 parts of nickel dibutyldithiocarbamate were mixed into polyethylene on two rolls at 110°C. Thereafter, 3 parts of dicumyl peroxide was further mixed in as a radical generator.
This mixture was heated at 160℃ for 30 minutes to a thickness of 3 cm at 100Kg/ ^cm2.
It was compression molded into a sheet of mm. Width 65 from this sheet
mm, and 150 mm long strips were cut out. These samples were subjected to oxygen index measurements and radiation resistance tests. The results obtained are shown in Table 3.

[Table] As is clear from the comparison with a comparative example using decabrom diphenyl ether as a bromine-containing flame retardant, according to the method of the present invention, a molded composition with excellent flame retardancy and radiation resistance can be obtained. You can see what you can get. Example 6 In Example 5, the oxygen index value and the results of the radiation resistance test when the radiation resistance imparting agent was 5 parts of pyrene and 2 parts of 2,2,6,6-tetramethylpiperidine are shown in Table 4. Ta.

[Table] As is clear from the comparison with the comparative example shown in Table 3, it can be seen that according to the method of the present invention, a molded composition having excellent flame retardancy and radiation resistance can be obtained. Example 7 In Example 5, the oxygen index value and radiation resistance test results when the hydrocarbon thermoplastic polymer was ethylene-vinyl acetate copolymer (EVA, vinyl acetate content 15 wt%) are shown in Table 5. Indicated.

[Table] As is clear from the comparison with a comparative example using decabrom diphenyl ether as a bromine-containing flame retardant, according to the method of the present invention, a molded composition with excellent flame retardancy and radiation resistance can be obtained. You can see what you can get. Example 8 After kneading each composition of Examples 1, 2, 3, 5 and Comparative Example 1 with a roll, each composition was extruded onto an annealed copper stranded wire having a cross-sectional area of 2 mm ² to a thickness of 8 mm. After extrusion coating using a machine, the wire was vulcanized at 160°C for 30 minutes in a steam can to obtain an insulated wire. Next, we conducted insulation resistance, AC withstanding voltage tests, IPCEA vertical combustion tests, and radiation resistance tests by self-diameter winding after 200 Mrad irradiation on each of the obtained insulated wires, and the results obtained are listed below. 6. As is clear from the table, according to the method of the present invention, an insulated wire with excellent properties can be obtained.

[Table] As explained above, according to the method of the present invention, a molded article of a hydrocarbon polymer composition having excellent flame retardant properties and radiation resistance properties can be obtained, and its industrial value is extremely large. It is something.

Claims (1)

[Scope of Claims] 1. The polymerization ratio of pyrene and nickel dialkyldithiocarbamate or 4-benzoyloxy-2,2,6,6-tetramethylpiperidine to 100 parts by weight of the hydrocarbon polymer is 1:2 to 1. :0.1
Mixtures ranging from 0.5 to 20 parts by weight and general formula After forming a composition characterized by blending 5 to 60 parts by weight of a polymerizable flame retardant represented by the formula (wherein n=3, 4 or 5) into a desired excipient, 1. A method for producing a flame-retardant, radiation-resistant polymer composition molded article, which comprises performing a treatment of polymerizing a polymerizable flame retardant.