Self-extinguishing flame resistant polyamide moulding compositions containing from 0.1 to 20% by weight of at least one glycoluril and/or reaction product of glycoluril as a flame-proofing agent.

Various processes have already been proposed to render thermoplastic 
plastics materials flame-resistant and fire-retardant. The most frequently 
used process comprises admixing with the resin a flame-resisting and 
fire-retardant agent. Red phosphorus and compounds containing halogen and 
nitrogen are well known fire-retardant agents. 
Pulverised red phosphorus or halogen compounds together with 
synergistically active metal compounds are presently used on a commercial 
scale as fireproofing agents for polyamide moulding compositions. These 
fireproofing agents and the use thereof are described, for example, in 
U.S. Pat. No. 3,418,267, German Auslegeschrift Nos. 1.694,494 and 
1,931,387 and in German Offenlegungsschrift No. 2,544,219. 
Halogen compounds have the disadvantage of reducing the creep resistance of 
the polyamide moulding compositions and, in the event of combustion, of 
releasing hydrogen halide which may cause considerable corrosion in the 
surroundings of the fire. Moulding compositions containing halogen 
compounds also release hydrogen halide to a slight extent at elevated 
temperatures required in processing machines and the hydrogen halide may 
damage the machines. Moreover, the synergistically active metal compounds, 
such as, for example, antimony trioxide are toxic. 
Pulverulent red phosphorus has to be handled carefully, because it can lead 
to dust explosions in the presence of air upon contact with hot metal 
surfaces. 
A further disadvantage can be the ready formation of toxic 
phosphorus-hydrogen compounds which can take place at the elevated 
processing temperatures of the moulding compositions by a reaction of the 
phosphorus with polyamides. Numerous additional procedural steps have been 
recommended, as described, for example, in German Auslegeschrift Nos. 
2,308,104; 2,625,673 and 2,625,691 in order to improve this development as 
far as possible. 
Finally, the inherent red colour of phosphorus impairs the adjustment of 
light colour shades in the moulding compositions. The large quantity of 
white pigments which is required to conceal the red colour of the 
phosphorus entails a deterioration of the mechanical properties. 
Furthermore, it has been proposed to add melamine (German Auslegeschrift 
No. 1,694,254), cyanuric acid (U.S. Pat. No. 3,980,618) and melamine and 
cyanuric acid (U.S. Pat. No. 4,001,177) in order to render polyamide 
moulding compositions flame-proof. 
By adding melamine, a satisfactory flame-proofing is achieved, but the 
melamine may sublime under the moulding conditions and may be deposited on 
the mould. This phenomenon is termed "flattening out". In this event, the 
moulding becomes spotted or is detached, which is undesirable. 
It is for this reason that the products do not always have a satisfactory 
appearance. 
By adding cyanuric acid, the mechanical properties of the moulding are 
impaired even with small quantities of flameproofing agent and 
considerable bloom phenomena are observed. When adding cyanuric acid and 
melamine, it is necessary to add at least 10 parts by weight to 100 parts 
by weight of polyamide resin in order to achieve a satisfactory 
flameproofing. In this case as well, the "flattening out" and "blooming" 
phenomena are considerable. 
Surprisingly by using the flameproofing agent according to the present 
invention, it is possible to provide a polyamide resin composition which 
shows a satisfactory flame resistance and is suitable in particular for 
the production of mouldings having light colours, because all the 
components are practically colourless or white. 
Thus, the present invention provides self-extinguishing, flame proof, 
thermoplastic polyamide moulding compositions which optionally contain up 
to 60% by weight, based on the total moulding compositions, of reinforcing 
materials and/or fillers and optionally other conventional aids and/or 
additives, and which are characterised in that they contain from 0.1 to 
20% by weight, based on the total moulding compositions, of glycolurils 
and/or reaction products of glycolurils as flameproofing agents. 
The following may be used as thermoplastic polyamide resins: polyamides 
which are obtained by the polymerisation of a lactam having at least five 
ring members or of a corresponding .epsilon.-aminocarboxylic acid, for 
example .epsilon.-caprolactam, aminocaproic acid, enatholactam, 
7-aminohexanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 
.alpha.-pyrrolidone and piperidone, also polyamide resins which are 
obtained by the polycondensation of aliphatic diamines such as 
hexamethylenediamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, 
isophoronediamine, 1,3- and 1,4-bisaminocyclohexane, 
bisamino-cyclohexyl-alkanes, xylylenediamine and aliphatic or aromatic 
dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, 
dodecane dicarboxylic acid, glutaric acid, cyclohexanedicarboxylic acid, 
isophthalic acid and terephthalic acid. 
Polyamides which are prepared from the above-mentioned aliphatic 
dicarboxylic acid and aromatic diamines, for example, 1,3- and 
1,4-diaminobenzene, and polyamide mixtures and copolyamides of all the 
components mentioned, so far as aliphatic or partly-aliphatic polyamides 
are produced can be rendered flame-proofed according to the invention. 
Polyamide-6 and polyamide-6,6 are particularly preferred. 
The polyamide resin may also contain other resins, e.g. polyesters, 
polyolefins, polytetrafluoroethylene, ABS, AS or ethylene-vinyl acetate 
copolymers in quantities as high as 50% by weight, based on polyamides. 
Glycolurils of the following general formula (I) are preferably used as 
flameproofing agents: 
##STR1## 
wherein 
R.sup.1 and R.sup.2 may be the same or different and independently of each 
other represent hydrogen, an aliphatic preferably C.sub.1 -C.sub.20 or an 
aromatic preferably C.sub.6 -C.sub.10 radical, and R.sup.3 represents 
hydrogen, an aliphatic preferably C.sub.1 -C.sub.20, a cycloaliphatic 
preferably C.sub.4 -C.sub.15, an araliphatic preferably C.sub.7 -C.sub.15 
or an aromatic preferably C.sub.6 -C.sub.15 radical. 
The radicals R.sup.1, R.sup.2 and R.sup.3 in the glycolurils of the general 
formula (I) may be completely or partly substituted with halogen (cl, Br) 
an C.sub.1 -C.sub.4 alkoxy group, or hydroxy. However, R.sup.1 preferably 
is not substituted, and preferably represents hydrogen, a C.sub.1 -C.sub.4 
-alkyl or phenyl group, and most preferably represents hydrogen or a 
methyl group. 
R.sup.3 is preferably unsubstituted and represents hydrogen, an aliphatic 
C.sub.1 -C.sub.6, a cycloaliphatic C.sub.5 -C.sub.6, an araliphatic 
C.sub.7 -C.sub.10 or an optionally C.sub.1 -C.sub.4 alkylene-substituted 
phenyl radical. R.sup.3 most preferably represents hydrogen. 
The preparation of the glycolurils of the general formula (I) is known in 
the literature and may be carried out by reacting a dicarbonyl compound, 
for example, glyoxal and an optionally substituted urea, optionally in the 
presence of an acid catalyst like hydrochloric acid. 
Salts of the following general formula (II) may preferably be used as 
reaction products of the glycolurils 
##STR2## 
wherein 
R.sup.1 and R.sup.2 are as defined above, 
R.sup.4 represents hydrogen, an amino group, or an optionally with a 
halogen atom (chlorine, bromine) substituted aliphatic C.sub.1 -C.sub.20, 
preferably C.sub.1 -C.sub.6, cycloaliphatic C.sub.4 -C.sub.17, preferably 
C.sub.5 -C.sub.6, araliphatic C.sub.7 -C.sub.17, preferably C.sub.7 
-C.sub.10, or aromatic C.sub.6 -C.sub.15, preferably C.sub.6 -C.sub.10, 
radical, R.sup.5 represents hydrogen, an aliphatic C.sub.1 -C.sub.20, 
preferably C.sub.1 -C.sub.6, cycloaliphatic C.sub.4 -C.sub.15, preferably 
C.sub.5 -C.sub.6, araliphatic C.sub.7 -C.sub.15, preferably C.sub.7 
-C.sub.10, or aromatic C.sub.6 -C.sub.15, preferably C.sub.6 -C.sub.10, 
radical, and 
n represents an integer of from 1 to 4, preferably from 2 to 4. 
R.sup.1 and R.sup.2 most preferably represents hydrogen or a methyl radical 
and R.sup.5 most preferably represents hydrogen. 
Glycoluril salts of glycoluril or dimethylglycoluril and melamine and/or 
2-methyl- and/or 2-phenyl-4,6-diamino-1,3,5-triazine are particularly 
preferred. The glycoluril salts prepared from 1 mol of glycoluril and 2 
mols or 4 mols of melamine, i.e. R.sup.4 represents NH.sub.2, are used as 
a particularly preferred salt of the general formula (II). 
These glycoluril salts from glycolurils and the corresponding triazine 
derivatives are optionally prepared under elevated pressure at 
temperatures of from 20.degree. to 130.degree. C., preferably in suitable 
solvents and preferably in water. 
Glycolurils or reaction products of the glycolurils are added to the 
polyamide resin in a quantity of from 0.1 to 20% by weight, preferably of 
from 0.5 to 15% by weight. When using glycolurils, a quantity of from 0.1 
to 5% by weight, preferably from 0.5 to 3% by weight is sufficient for 
flame-proofing. However, the reaction products of the glycolurils are 
added to the polyamide resin in a quantity of from 0.1 to 20% by weight, 
preferably from 1 to 20, most preferably from 3 to 15% by weight. Of 
course, mixtures of glycolurils and the reaction products of glycolurils 
may also be used. It is also possible to add other flameproofing agents, 
for example, halogen compounds or red phosphorus, to the moulding 
composition. 
The polyamide moulding compositions according to the present invention may 
contain up to 60% by weight of reinforcing materials and fillers. The 
following are used reinforcing materials and fillers: glass fibres, carbon 
fibres, asbestos fibres, glass beads, talcum, mica, wollastonite, 
microvit, chalk, silicon dioxide, graphite, gypsum and other conventional 
additives, such as pigments and dyes, e.g. cadmium sulphide, 
phthalocyanines and titanium dioxide. 
Copper compounds or a mixture of a copper compound and an alkali metal 
halide may be added in quantities of from 0.001 to 1% by weight as 
additional flameproofing agents to the polyamide moulding compositions 
according to the present invention. 
Suitable copper compounds include organic and inorganic copper salts. The 
following are mentioned as examples: copper(I)chloride, 
copper(II)sulphate, copper(I)iodide, copper(II)phosphate, 
copper(II)acetate, copper(II)stearate, copper(II)benzoate and 
copperchelate compounds. Suitable alkali metal halides include potassium 
iodide, potassium bromide, sodium chloride and sodium bromide. 
Aromatic and/or higher aliphatic carboxylic acids and the alkali metal or 
alkaline-earth metal salts thereof, e.g. sodium stearate, calcium 
stearate, isophthalic acid and terephthalic acid, may be worked into the 
polyamide resin compositions according to the invention as aids and 
additives in quantities of from 0.1 to 1% by weight. 
It is also possible to add any known antistatic agents such as conductive 
carbon black or quaternary ammonium salts. 
The additives may be added to the polyamide resin according to the most 
varied known processes, preferably before moulding. The simplest process 
comprises admixing the additives dry with the polyamide resin. The 
dry-mixed material may then be melted and extruded for the production of 
granulates. The additives may also be admixed with the plasticised 
polyamide resin composition in the extruder using known metering 
apparatus. It is also possible initially to produce master-batch 
granulates by admixing large quantities of the additives with the 
polyamide resin and then to mix these master-batch granulates with the 
polyamide resin. 
The mouldings may be produced by moulding the composition or the granulates 
using various moulding machines, in particular injection moulding 
machines, extruding machines, pressing machines or the like. The additives 
may also be worked in using the moulding machine. 
Usually the additives are dosed to the polyamide at the processing 
temperature which is usually at least 10.degree. C., but not more than 
30.degree. C., above the softening temperature of the polyamide. For 
example, in case of polyamide-6,6, the processing temperature is below 
270.degree. C., whereas in the case of polyamide-6, temperatures of below 
250.degree. C. are sufficient. 
The polyamide resin compositions according to the present invention do not 
only exhibit an outstanding flame resistance, outstanding mechanical 
properties and an outstanding workability, but can be produced in light 
colours.