CS232310B1 - Self-extinguishing material for low-voltage electrical engineering - Google Patents

Abstract

The invention relates to flame retardant materials for low-current electrical engineering based on polyphenylene oxide in a mixture with styrene plastics and polyolefins, stabilizers, flame retardants and other additives. The material contains 0.05 to 3 parts by weight of guanidine derivatives, 0.2 to 5 parts by weight of molybdenum trioxide and 2 to 20 parts by weight of triphenyl phosphates or substituted triphenyl phosphates and is characterized by good electrical properties, in particular a low dissipation factor.

Description

The invention relates to a self-extinguishing material suitable for low-current electrical engineering based on polyphenylene oxide in a mixture with other polymers, with the addition of stabilizers, flame retardants, possibly pigments, lubricants and other additives.

Pure poly(2,6-dimethyl-1,4-phenylene oxide) is characterized by excellent electrical properties in a wide range of temperatures and frequencies, very good dimensional stability, considerable heat resistance, self-ignition and good mechanical strength, which together with excellent resistance to moisture, acids, alkalis and alcohols predetermines it for use in the electrical industry. However, its use in pure form is very limited due to the high viscosity of the melt. The usual solution to this problem is to mix polyphenylene oxide with other polymers, of which clear or tough polystyrene is most often used in combination with smaller amounts of rubbers and polyolefins. These mixtures have very good flow and mechanical properties, but the addition of other polymers leads to a decrease in thermo-oxidative stability and deterioration of electrical properties. The high polystyrene content in the mixtures also causes the material to be flammable. For most applications, this means adding flame retardants in addition to stabilizers, which further significantly worsens the electrical properties, especially the dissipation factor.

In mixtures prepared with nitrogenous bases according to ČS 159 032, this problem can be solved by adding some common metal oxides according to ČS. author's certificate No. 232 308. An even more significant improvement in the electrical properties of stabilized mixtures can be achieved according to ČS 201 766 by using substituted guanidines or biguanidines as substances suppressing undesirable changes in the properties of polyphenylene oxide in the mixture during heat treatment. Their use is also suitable for mixtures retarded by organic halogen derivatives or elemental red phosphorus, usually used as flame retardants.

However, for special applications in the electrical industry, in some cases it is not recommended to use the above-mentioned flame retardants due to the possible corrosion of electrical components, or the formation of toxic fumes in the event of a breakdown of the device in which the material was used. Conventional flame retardants from the group of triaryl phosphates, which would be the most advantageous since they do not exhibit the aforementioned unpleasant effects, cannot be used in this case, since it has been shown that in combination with guanidines or biguanidines in mixtures containing more than 40 parts by weight of polystyrene, the electrical properties do not improve (especially at laboratory temperature) to the same extent as without the use of the aforementioned retardants, and in addition, the self-extinguishing property is not sufficient. This means that a material with originally excellent properties cannot be prepared in a self-extinguishing treatment of satisfactory quality. It has now been found that this can be achieved by a ternary combination of substituted guanidines or biguanidines, triaryl phosphates and molybdenum trioxide.

The subject of the invention is a self-extinguishing material for low-current electrical engineering based on polyphenylene oxide in a mixture with styrene plastics and polyolefins, stabilizers and flame retardants from the group of triphenyl phosphates in combination with molybdenum trioxide and optionally other additives such as pigments or lubricants, the material containing: 0.05 to 3 parts by weight of guanidine (1) (I) or biguanidine (11) derivatives

R ² - N

N - R ² .C - H - C.

(II)

R ³ - N

7 where R to R are hydrogen, methyl, ethyl, phenyl, tolyl or xylyl, 0.2 to 5 parts by weight of molybdenum trioxide and 2 to 20 parts by weight of triphenyl phosphate or substituted triphenyl phosphates.

Polyphenylene oxide is understood as poly(2,6-dimethyl-1,4-phenylene oxide). The main component of the mixture may be any of the following polymers, or their combinations: styrene plastic, for example clear polystyrene, tough polystyrene or terpolymer of acrylonitrile, butadiene and styrene, polyolefins, for example polyethylene, polypropylene, ethylene-propylene copolymer (with properties of a thermoplastic or elastomer), polyisobutylene, and also ethylene-propylenediene * rubber or butyl rubber. The total content of these modifying polymers may range from 1 to 70% by weight, calculated on the mixture with polyphenylene oxide. The material also contains thermo-oxidative stabilizers, additives to improve resistance to atmospheric aging, and possibly also pigments, lubricants and the like.

The addition of molybdenum trioxide together with guanidine or biguanidine derivatives to mixtures of retarded triaryl phosphates achieves good material flammability. At the same time, there is a marked improvement in the electrical properties, especially the value of the dissipation factor at higher temperatures, compared to the material prepared with the addition of other nitrogen bases and triphenyl phosphate as a flame retardant or substituted triphenyl phosphates. Substituted triphenyl phosphates are understood to be phosphates in which at least one hydrogen of the phenyl groups is substituted by alkyls, such as methyl, ethyl, propyl, isopropyl or tert-butyl. Thus, for example, triphenyl phosphate, tricresyl phosphate, isopropylphenyl-diphenyl phosphate, 4,4-diethyldiphenylphenyl phosphate can be used.

The invention will be illustrated by the following examples. The parts in the examples are by weight.

Example

To a mixture of 50 parts of poly(2,6-dimethyl-1,4-phenylene oxide), 43 parts of clear polystyrene, ethylene-propylene rubber, 2 parts of zinc oxide, 1 part of phosphorous acid tris(4-(1*-phenyl)ethylphenyl ester) as a stabilizer and 7 parts of triphenyl phosphate was added in case A: 0.5 part of N,N'-dimethylhexaethylenediamine, in case B and C 0.5 part of dimethylguanidine. Mixture C also contained 5 parts by weight of molybdenum oxide MoOj.

To prepare these and the samples given in the next example, powdered polyphenylene oxide was used, the viscosity number of which was 56.5 ml/g measured in chloroform at a concentration of 0.3 g/100 ml of solution at a temperature of 25 °C.

After thorough homogenization, the mixture was melted on a laboratory screw extruder and the extruded strand granulated. Plates were pressed from the granulate and test specimens were prepared from them by mechanical machining for determining the basic mechanical, electrical and thermal properties. The measured values of the compared materials are given in Table I.

Example 2

To a mixture of 50 parts of poly(2,6-dimethyl-1,4-phenylene oxide), 48 parts of high-density polystyrene, 2 parts of polyethylene, 5 parts of titanium dioxide, a stabilizer consisting of: 1.2 parts of tris(nonylphenyl phosphite) and 0.2 parts of ditert.butyl-4-methylphenol and 5 parts of isopropylphenyl diphenyl phosphate were added in case A: 3 parts of 8-phenyloctylamine-1, in cases B and C: 3 parts of phenyl-o-tolylxylylguanidine, Mixture C also contained 0.2 parts of molybdenum oxide. The material was processed and evaluated in the same way as in the previous example, the measurement results are given in Table 11.

Table 1

Property Measurement temperature Mixture A Mixture B Mixture C dissipation factor, 50 Hz 23 2.5.10 ^-3 7,2.10 ^-3 3,2.10 ^-3 100 11.0.10 ^-3 5,9.10 ^-3 5,2.10 ^-3 ČSN 346466 150 690.10 ^-3 27,4.10 ^-3 33,8.10 ^-3 specific internal resistance [ílcm] 23 2,5.10 ¹⁶ 3,1.10 ¹⁶ 2,8.10 ¹⁶ ČSN 346460 flammability, UL 94 [s] - 21 41 19 classification V - 1 does not comply V - 1 tensile strength [líPa] microbodies with working cross section 23 51.2 51.7 50.9 parts 1 mm ² , deformation speed 50 mm/min notch toughness [j/cm ² ] 23 0.75 0.79 0.74

ČSN 640612, type 3 test specimens

Vicet softening point [°c] 135 133 135 ČSN 64 05 21, method B

Table II

Property Measurement temperature [°c] Mixture A Mixture B Mixture C dissipation factor, 50 Hz 23 2,4.10 ^-3 4.3.10 ^-3 3.0.10 ^-3 100 16,3.10 ^-3 11.0.10 ^-3 5,7.10 ^-3 150 110.0.10 ^-3 68.0.10 ^-3 40.5.10 ^-3 specific internal resistance (pcm) 23 1,8.10 ¹⁶ 1,7.10 ¹⁶ · 1,7.10 ¹⁶ flammability [s] - 18.2 42.5 ’9.4 classification V - 1 does not comply V - 1 tensile strength [MPa] 23 49.7 50.3 49.6 notched toughness fj/cm ² ] 23 0.71 0.73 0.68 softening point according to Vlčata °C- - 135 134 134

Claims (2)

SUBJECT OF THE INVENTION 2323IO Flame retardant low-voltage electrical polyphenylene oxide electrical material and mixtures thereof with styrene plastics and polyolefins, stabilizers, flame retardants from the triphenyl phosphate group in combination with molybdenum trioxide and optionally other additives such as pigments or lubricants, characterized in that it contains 0.05 to 3 parts by weight of guanidine derivatives (I) N - C - N (I) or biguanidine (II) R ² - N N - R ³ (II) 3_ 'N - R ⁶ where r' to R? is hydrogen, methyl, ethyl, phenyl, tolyl or xylyl, 0.2 to 5 parts by weight of molybdenum trioxide and 2 to 20 parts by weight of triphenylphosphates or substituted triphenylphosphates.