DK148773B - FIRE-RESISTANT POLYAMIDE PLASTIC MATERIALS BASED ON RED PHOSPHORES AND FIRE-RESISTANT POLYAMIDE PLASTIC MATERIALS CONTAINING SUCH AN AGENT - Google Patents

Description

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The present invention relates to a flame retardant for red phosphorus based polyamide plastics and flame retardant polyamide plastics material containing such agent.

5 Numerous patents describe the use of phosphorus for fire retardant plastics, red phosphorus being in fact a very good fire retardant. Thus, in a given activity, it is necessary to use lesser amounts of red phosphorus than e.g. halogen compounds.

10 Further, the use of red phosphorus leads to better mechanical properties and does not interfere with the electrical properties of the plastic materials into which it is incorporated.

However, its use is limited by some accompanying hazards: Risk of contamination and difficulty in a fully-15 continuous safe processing. Thus, the presence of traces of water in almost all polymeric materials, under the influence of the heat needed to form these polymers, induces the formation of highly toxic phosphines which spontaneously ignite in the air.

20 Andreev and Kataradze have found that the phosphines can be oxidized in the presence of copper oxide (Memoirs de l'Acdémie des Sciences d'URSS 1948 LX No. 7). However, the copper oxide also oxidizes the red phosphorus.

In order to remedy these disadvantages, FR Patent No. 2574394 proposes incorporating, in the thermoplastic material, which may be glass fiber reinforced, red phosphorus impregnated with a lactam containing 4-12 carbon atoms, e.g. caprolactam, in an amount of 1-20 wt. relative to the polymer.

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However, this method has the significant disadvantage that the hygroscopy of the lactams as well as the presence of water in the mixture induces the formation of the highly toxic phosphines which spontaneously ignite in the air, especially at the temperatures at which the polymers are processed.

DE Publication No. 2,308,104 describes thermoplastic red phosphorus fire-retardant compositions containing metal oxides to prevent any release of phosphines during storage at ambient temperature. However, the addition of metal oxides is not sufficient to prevent the release of phosphines formed at high temperature.

Various products such as waxes and metal salts of fatty acids have been proposed for wrapping red 15 phosphorus grains, thereby isolating them from any contact with copper oxide in particular, thus reducing the release of phosphines.

However, the presence of certain wrapping agents can damage the mechanical properties of the molded articles obtained from the said moldings. 1 2 3 4 5 6 7 8 9 10 11

It's from BE. Patent Specification No. 842,698, cf. DK Ans. no.

2 2515/76, it is known that in order to fire various plastics 3 materials by means of red phosphorus, without being able to detect a release of phosphines, a wrapping of the red phosphorus grains in a polyurethane can be carried out. 6, selected so that the layer of envelope material about the red phosphorus grains at the forming temp. 8 ratios of the thus fire-retardant material 9 undergoes the least possible degradation. Here, it is proposed to use as a wrapping material that should not have a melting point or softening point below 90 ° C, such as, for example, a polycarbonate (mp, on the order of 230 ° C), a phenolic resin (mp higher than 150 ° C). C), a polyimide resin (does not melt) or a polyester which, in that context, is a substantially thermosettable, unsaturated compound (which, in principle, does not melt once cured). These envelopes are polymeric materials which, due to their high melting point or non-melting, are not flexible. Thus, the 5 can simultaneously act as filler, which may prove to be a disadvantage. These polymeric materials should - due to their high melting point or non-melting - be either deposited on the phosphorus in the form of a solution (which causes problems with recovery of the solvent) or deposited on the phosphorus during completion of the polymerization of the monomers. in the presence of the phosphorus, which causes problems with the control of the polymerization reaction.

Thus, there is the problem of finding a new wrap material which, on the one hand, allows red phosphorus to be introduced into the plastic material in question without substantial phosphine release at the high temperatures required for the subsequent conversion of the plastic material and which at the other hand is stable under these transformation conditions, but is flexible so that, by acting as a filler, it will not be able to degrade the mechanical properties of the eventually formed articles and which are finally easy to use during the manufacturing process.

It has now been found that this problem can be solved if fire-retardants of the kind described in the preamble of claim 1 are used and which are peculiar to the characterizing part of claim 1.

The flame retardant polyamide plastics materials of the invention, especially for use in the manufacture of molded articles, are characterized by the characterizing part of claim 3.

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By "red phosphorus" is meant here all the colored allotropic varieties which are marketed under the term red phosphorus and which may contain as stabilizers up to 3¾ oxides or metal salts.

The red phosphorus takes the form of particles with an average diameter of less than 200 µm. The use of grains having a diameter of only a few µm allows for the fire retardation of spun blanks for use in the manufacture of textiles.

The polyesters used in the compositions of the invention are well known.

Products which are solid at ambient temperature are selected and have a melting point between 50-90 ° C. The degree of polymerization is low or medium high, preferably corresponding to a molecular weight of 500-2000. Such polyesters can be prepared by polycondensation of aliphatic diols with aliphatic dicarboxylic acids used alone or in admixture.

Such polyesters are e.g. described in V.V. Korshak and S.V. Vinogradova "Polyesters" Edition Pergamon Press, 1965.

The present compositions can be prepared simply by mixing the two components in the cold state and subsequently heating the mixture to a temperature slightly above the melting point of the polyester. It is found that the polyester homogeneously envelops the phosphorus grains. 1 2 3 4 5 6

The polyesters can also be deposited on the surface of the phosphorus 2 grains. For this purpose one can use one of the number 3 rich encapsulation methods which e.g. is described in "A 4 Cyclopedia of Polymer Science and Technology" vol. 8 p.

5 179, Interscience Publishers. These methods are essentially of a chemical or physical nature. Among the most common methods may be mentioned: coacervation in aqueous or interfacial layer, organic phase precipitation by addition of a non-solvent, dry atomization, the use of fluidized bed, polymerization in interface or in situ in gas phase or in liquid phase, vacuum -5 deposition, electrostatic deposition, and numerous other methods based on methods of phase separation or interface reaction.

For the protection obtained by the polyester to be satisfactory, the amount used should be 5-50% by weight 10%. relative to the enveloped red phosphorus.

Furthermore, it is known that addition to the present metal oxide agent stabilizes red phosphorus and commercially red phosphorus usually contains such compounds. The addition of metal oxides enables a possible reduction of the possible release of phosphines. The metal oxides that lead to the best results are the oxides of copper, zinc, silver, iron, antimony, vanadium, tin, titanium, cadmium or magnesium, but copper and / or cadmium oxide is preferred.

The amounts of metal oxide used may vary according to the amount of polyester used, according to the processing conditions of the synthetic resins, and according to their nature.

You can use up to 100% by weight. metal oxide, calculated on the red phosphorus. 1 2 3 4 5 6

The polyamides to be flame retardant can, if desired, be machined together with various fillers when they are machined 3 to form molded blanks. There may be 4 reinforcing fillers such as glass fibers, fill 5 fabrics to obtain special properties of the 6 molded blanks, or inert fillers such as kaolin or talc, antioxidants, various stabilizers, dyes or pigments. An amount (usually) of the fire retardant of 0.2 - 20% by weight is used (as a rule). in relation to the plastic material to obtain a suitable fire-retardant effect.

The use of encapsulated red phosphorus grains provides 5 numerous advantages, including: ease of handling before and during introduction into the polymers, reduction of the risk of contamination during the manufacture of the resins, and, in particular, exclusion of the release of phosphines during the main processing; when working here at 10 temperatures above 200 ° C.

The invention is further illustrated by the following examples, in which, as polyamide to be made flame retardant, a polyamide 6-6 has been selected whose moisture absorption, apart from cellulose molding, is among the highest for polymeric materials, hence the effect of heat and the presence of red phosphorus would lead to the greatest release of phosphines.

EXAMPLE 1

660 g of a red phosphorus powder with a 20 to 30 µm average granulometry are mixed with 400 g of an ethylene glycol polysaccharide of molecular weight approx. 3650 and with a granulometry of less than 500 ^ υπι and m.p. ca. 72 ° C. These powders are intimately mixed on a roller for 20 minutes. The mixture is placed in an oven at 120 ° C for three hours at a pressure of 20 mmHg. Plates are obtained which are broken into pieces with dimensions of between 300 µm and 6 mm. It is found that the pieces do not release red phosphorus powder by rubbing and that the phosphorus grains have been shrouded.

The following product is prepared by simple mixing in a mechanical mixer: 7 1A8773 4 412.5 g of polyhexamethylene adipamide having an average molecular weight of 20,000, whose viscosity number o according to the ISO R 307 standard is 145 ml / g at the concentration X xc 0.005 g / ml of polyamide in 90¾ aqueous formic acid, 12.5 g of copper oxide, and 575 g of the above mixture of red phosphorus and polyester (mixture A).

This mixture was kneaded for 10 minutes at 16 ο / min, then introduced into a press and a rod extruded.

10 A laboratory theory single screw press is used, each screw having a length of 900 mm and a diameter of 45 mm. This press is equipped with a cylindrical nozzle with a diameter of 3.5 mm. The temperatures are as follows: 255 ° C at the material entrance, 270 - 275 ° C in the center of the press and 260 ° C at the nozzle. The worm turns at 45 rpm. giving a rate of 15 kg / hour. Throughout the operation, attempts were made at various locations around the press to determine the possible presence of phosphines by means of a tube. . All of these tests are negative.

EXAMPLE 2

Example 1 is followed, however, by preparing the following mixture: 25 4 375 g of a polyhexamethylene adipamide-based mold having a mean molecular weight of 20,000 and a viscosity of 145 ml / g containing 30¾ glass fibers, 148253 825 g of mixture A, and 100 g of cadmium oxide.

This mixture is mixed for 10 minutes at 16 ο / min, and then introduced into the press.

5 The same air analyzes by means of the DRAEGER tube above the nozzle, at the feeding funnel and at the granulator lead to a finding of the absence of phosphines.

EXAMPLE 3

Proceed as in Example 1, except for the 575 g of 60/40.

The red phosphorus and polyester mixture is replaced by 575 g of a 60/40 red phosphorus and polyester mixture prepared as in Example 1, however, using a polyethylene glycol polyadipate having m.p. 65 ° C and an average molecular weight of 2000 (mixture B).

No release of phosphines was found.

EXAMPLE 4

Proceed as in Example 2, however using 525 g of mixture B.

Phosphine delivery was lower than 0.1 ppm.

EXAMPLE 5

Proceed as in Example 1, however mixing: 4495 g of polyhexamethylene adipamide 492.5 g of a 70/30 mixture of red phosphorus and polyse-bacate of ethylene glycol of the same kind as used in Example 1 (mixture C), and 9 12.5 g of copper oxide.

no release of phosphines is found.

EXAMPLE 6

Proceed as in Example 1, however, mixing: 4450 g of polyhexamethylene adipamide molding compound 450 g of mixture C 100 g of cadmium oxide.

No release of phosphines is found.