IE45793B1 - Flameproofed polyamide compositions - Google Patents

Abstract

These compositions contain a polyamide, a flame-retardant agent which is a halogen compound and cadmium oxide. Shaped articles made from these compositions exhibit both a flame-retardant nature and an increased arc tracking resistance.

Description

The present invention relates to flameproofed polyamide compositions.

Various means have been proposed for imparting a flame-resistant character to polyamides. For example halogenated products in combination with certain inorganic oxides, such as those derived from arsenic, bismuth and antimony, have frequently been added (see, for example, French Patent No. 1,563 952). In fact, the use of halogenated derivatives makes it possible to impart effective fire-resistance to the polyamides. However, it has been found that the articles manufactured from these compositions exhibit a fairly low arcing resistance (in terms of Standard Specification NF C 26,220). This is significant since a high arcing resistance is a necessity in numerous applications, in particular in the electrical or electronics industries.

The present invention is intended to provide polyamide-based compositions which enable articles exhibiting both good fire-resistance and good arcing resistance to be produced. These compositions comprise a halogenated derivative and cadmium oxide.

According to the present invention, there is provided a polyamide composition which contains a halogenated f lame proof ing agent and cadmium oxide.

' The polyamide can be selected from the various polymers of this type which are available. They can be, for example, products obtained by polycondensation of diacids and diamines, or by bomopolycondenoation of amino-acids, or by polymerisation of lactams, especially the polyhexamethyleno adipamides and the polycaprolactams.

The halogenated flameproofing agents may be those 5 described in British Specification No. 1208065 and French Patent No. 1439030. Thus they should, in general, be capable of providing hydrogen halide at combustion temperatures. They are usually chlorinated and brominated derivatives of monocyclic or polycyclic hydrocarbons of aliphatic or aromatic character.

Amongst these products, there may be mentioned especially decabromodiphenyi, tetrabrowinated bisphenol, decabromodiphenyl oxide, hexabromobsnzene, pentabromotoluene, the chlorinated derivatives of diphenyl or also the product obtained by reacting 2 mols of liexachlorocyclopentadicne with one mol of cyclooctadiene. This product corresponds to the empirical formula C28^'I12C'112 nn<^ generally assigned the following structural formula: Cl r Cl Cl .ci 1 C1C.1 Jc.tel ' Cl L Cl - Cl ci Generally the composition contains from 5 to 25 % by weight of the flameproofing agent and from 0.2 tc 20 % by weight of cadmium oxide, based on the weight of ths composition.

The amount of fLameproofing agent (halogenated derivative) is preferably from 10 to 20 % by weight of the total weight of the composition.

The flame-resistant effect of the halogenated c, derivatives can be.advantageously reinforced by the use of - 3 certain inorganic compounds, such as the abovementioned oxides or zinc borate. In general, the proportion of inorganic additive does not exceed 40% of the weight of the halogenated derivative.

Both the 'amorphous variety and the crystalline variety of cadmiiim oxide can be used. In general, it is desirable to uge ai) anhydrous product in order to prevent any liberation of water during the moulding of the composition The oxide is preferably used in the form of a powder of a particle sise which does not exceed 100 for example from 5 to 100/Λ.

The compositions according to the invention can of course also contain adjuvants generally used in this type of composition. It is thus possible to incorporate into these compositions reinforcing or gelling fillers, such as glass fibres or asbestos fibres, glass microspheres, kaolin, talc, silica, micas, bentonites or bentones. Glass fibres are the most commonly employed fillers: the diameter of the fibres is generally from 1 to 10# and their length from 2 to 6 ®m. Articles possessing improved mechanical properties can be obtained by using fibres which are sized, for example with epoxy resins, polyester, polyurethanes or vinyl polymers.

When fillers such as those mentioned above are used, their amount, in general, represents from 20 to 50% of the total weight of the composition.

Other additives can also be used, such as lubricants, - 4 43793 agents for increasing the impact strength, antistatic agents and crystallising agents. These various additives, as well as their use, are widely described in the literature.

The compositions of this invention can be converted into finished or semi-finished articles by application of the usual injection or extrusion techniques. In general, the conversion is carried out within a temperature range from 200 to 320°C. The articles obtained are fire-resistant, on exposure to a flame do not lead to the formation of droplets of molten material which may be burning, and exhibit an excellent arcing resistance (according to Standard NF/C 26,220). Although the fields of use of articles of this kind are very varied, these articles are thus particularly suitable for uses in the industries concerned with electricity, namely the electrical, electronics, household electrical appliances, radio and automobile industries.

The following Example further illustrates this invention.

EXAMPLE 3,650 g of a polyhexamethylene adipamide having an average molecular weight of 20,000 and a viscosity index of 145 (determined by Standard Specification ISO R 307), 950 g of the halogenated conpound of the enpirical formula ciaH12C1l2 83 described previously, 100 g of zinc borate of the formula: ZnO. 3 BjOg. 3.5 HjO, 100 g of antimony trioxide and 200 g of cadmium oxide are introduced into a mechanical mixer. - 5 After homogenisation at ambient temperature (25°C), the composition is introduced irfco a single-screw laboratory extruder, the screw of which has a diameter of 45 mm and a length of 900 mm. This extruder is equipped with a cylindrical die having a diameter of 3 mm.

The temperatures are as follows: 250 - 260°C in t the feed zone, 270 - 275°C in the melting and compression zones and 260°C at the die.

The throughput of the machine is 15 kg/hour.

The strand obtained is cut into granules and stored so as to be protected from moisture.

Test pieces of 127 x 12.7 x 1.6 mm are injectionmoulded between 270 and 290 °C and are subjected to the Underwriters Laboratories UL 94 (vertical) test [as described in document 9750-1 of the Bureau de Normalisation des Mati^res Plastiques] in order to measure the degree of flameproofing; the classification 94 VO is obtained.

The test for measuring the arcing resistance, as defined in the Standard NF 26,220, is also carried out; an index of more than 425 Volts is obtained.

By way of comparison, if cadmium oxide is not used, the value obtained is 350 Volts, the classification also being 94 VO in the flameproofing test.

Claims (7)

1. WE CLAIM

1. A polyamide composition which contains a halogenated flameproofing agent and cadmium oxide.

2. A composition according to claim 1 which contains from 5 to 25% by weight of said flameproofing agent and from 0.2 to 20% by weight of cadmium oxide, based on the weight of the composition.

3. A composition according to claim 1 or 2, in which the flamepyoofing agent is a brominated or chlorinated aliphatic or aromatic monocyclic or polycyclic hydrocarbon.

4. A composition according to claim 3, in whieh the flameproofing agent has the empirical formula c ig H i2 c ^12' and is obtained from 2 mols of hexachlorocyclopentadiene and one mol of cyclooctadiene.

5. A composition according to any one of claims 1 to 4 in which the cadmium oxide has a particle size from 5 to 100z«..

6. A composition according to claim 5, substantially as hereinbefore described.

7. A shaped article obtained from a composition as claimed in any one of the preceding claims.