Flameproof compositions of polycondensation products

A self-extinguishing thermoplastic composition containing at least one polycondensation product, and a flame retardant which comprises a mixture of melamine with at least one adduct of an isocyanate and a lactam wherein the proportion of adduct, based on the mixture of melamine and adduct, amounts to 5-25% by weight.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a self-extinguishing thermoplastic 
composition comprising a thermoplastic polycondensation product and to a 
process for the preparation thereof. 
2. Discussion of Related Art 
Formulations of halogen compounds, and in most cases these compounds being 
in combination with antimony trioxide, are recommended as flame retardants 
for the manufacture of flameproof polycondensation products. Typical 
representatives of such halogen compounds are perbrominated aromatics, 
such as decabromodiphenyl oxide, polymers thereof, such as 
polytribromophenylene oxide, as well as, for example, 
perchloropentacyclodecane. The use of such products as flame retardants 
has been described in U.S. Pat. No. 3,418,267, German Published 
Applications DE-AS 1,694,494 and DE-AS 1,931,387, German Laid-Open 
Application DE-OS 2,544,219, and German Patent DE 2,937,379 C 2. 
In spite of advances in the art afforded by the utilization of these 
halogen compounds as flame retardants, their use is accompanied by 
considerable drawbacks. Such drawbacks have been dealt with in detail in 
British Patent 0044 419 B1 and in German Patent 3,208,486 C 2. An 
especially grave disadvantage resides in that when using perbrominated 
aromatics, such as decabromodiphenyl oxide or decabromodiphenyl, toxic 
compounds are formed during their combustion, such as dioxins and furans, 
so that in the case of a fire, grave injuries can occur. 
In addition to the halogen compounds, it is also known to use elemental red 
phosphorus for rendering thermoplastics, particularly polyamide, 
flameproof. This mode of operation is set forth in German Published 
Application DE-AS 1,173,641 and U.S. Pat. No. 3,951,908. 
Here again, a number of drawbacks must be tolerated, such as the effect on 
the color and electrical values. British Patent 0044 419 B1 provides 
information on these aspects. 
Finally, a number of nitrogen-containing compounds are utilized as flame 
retardants in thermoplastics. These involve melamine, as well as melamine 
derivatives. Such have been suggested, inter alia, in U.S. Pat. No. 
4,263,203, German Patent DE 2,937,379 C 2, British Patent 0044 419 B1, and 
German Published Application DE-AS 1,694,254. As disclosed in the 
specifications of the aforementioned patents, nitrogen-containing 
compounds exhibit a number of advantages over the previously mentioned 
products. 
However, in most cases, processing stability is inadequate, especially when 
the higher-melting polyamide and polyester types, such as polyamide 6,6 
and polybutylene terephthalate, are rendered flameproof. In particular, 
nitrogen-containing compounds are unsuitable for mineral- and 
glass-fiber-reinforced polyamide and polyester synthetic resins, to be 
utilized in the industrial field. Besides lacking temperature stability, 
such nitrogen-containing flame retardants have the drawback in that they 
do not melt with the polymer melt but rather are present therein only as 
extremely fine particles. In the usual case, a dispersant must be 
additionally used in order to obtain a maximally fine, uniform 
distribution. This situation results in a decrease in the mechanical 
values during the use of these flame retardants, especially in the impact 
resistance property. 
The advantage displayed by the use of melamine cyanurate, as compared with 
melamine in accordance with the patent specifications, resides in a 
reduction in the so-called plate-out due to the sublimation of melamine at 
processing temperatures. However, the use of melamine cyanurate does lead 
to increased dripping. This makes it even difficult to stay within the 
customary flame retardance test UL 94-V0 (in accordance with testing 
standard by Underwriters Laboratories Inc., dated Feb. 1, 1974). 
Melamine display greater temperature stability than melamine cyanurate. 
However, practical application thereof is hindered, in addition to the 
aforementioned tendency toward sublimation leading to plate-out, it is 
also hindered by the lower hydrolysis stability of melamine. When boiling 
melamine-treated polyamide test rods, the flame retarding effect which was 
initially present, is diminished. 
German Patent 3,208,486 C 2 describes the use of a reaction product of 
cyanuric acid with 2 to 2.35 moles of melamine and, respectively, whereby 
melamine derivatives having the above-described deficiencies are to be 
avoided. However, the admixture rates in order to attain 
self-extinguishing properties in accordance with UL 94 are relatively 
high. Furthermore, the data relate especially to polyamide 6,6 rather than 
to glass-fiber-reinforced thermoplastics, of which the flameproofing 
thereof has gained increasing importance. 
OBJECT AND SUMMARY OF THE INVENTION 
The present invention has as its object to develop highly flameproof, 
thermoplastically processable compositions of polycondensation products, 
as well as suitable methods for their production, which exhibit advantages 
over flameproof polycondensation products manufactured heretofore. 
It is surprising and could not be foreseen that, by adding an adduct of an 
isocyanate and a lactam, e.g. caprolactam, in conjunction with melamine, 
flammability is reduced. It was especially surprising that such adducts in 
a mixture with melamine reduce flammability even if an excess of lactam is 
present therein. As is known, monomeric lactams raise the flammability of 
polyamides considerably. 
It was furthermore surprising that these novel flame retardants, added in 
powder form, were distributed in the molding compositions in a very fine 
and uniform fashion, even without the addition of dispersants, as compared 
with the case of the nitrogen compounds of melamine which do not melt in 
the polyamide matrix (as illustrated in Tables 1-3 below). Especially 
noticeably in the case in which melamine cyanurate is the flame retarding 
agent, it is present in a highly nonuniform distribution pattern. 
Therefore, the present invention relates to self-extinguishing, 
thermoplastic compositions of at least one thermopolastic polycondensation 
product, characterized in that they contain as the flame retardant, a 
mixture of melamine with at least one adduct of an isocyanate and a 
lactam, wherein the proportion of the adduct, based on the mixture of the 
melamine and adduct, amounts to 5-25% by weight. 
Thermoplastic polycondensation products according to the present invention 
are understood to define reaction products having been derived from two or 
more chemical compounds wherein these compounds in each case exhibit at 
least two reacting groups which can react with the reactive groups of 
their co-reactants and yield, after reaction has occurred, 
thermoplastically processable polymers. Such polycondensation products can 
also be formed by causing a molecule containing two different reactive 
groups to react with other molecules containing reactive groups 
corresponding therewith. Of course, in order to produce the products to be 
rendered flameproof according to the present invention, it is also 
possible for the compounds containing two different groups, capable of 
reacting with each other, to react and thereby resulting in the formation 
of condensation products. 
On the other hand, thermoplastic polycondensation products which can be 
treated to be flameproof in accordance with the present invention can also 
be formed by ring-opening polymerization of rings which contain hetero 
atoms. 
Thermoplastic polycondensation products that are suitable according to the 
present invention can also be formed by a combination of these reaction 
possibilities. It is also feasible to utilize mixtures of different 
polycondensation products and mixtures thereof with other thermoplastic 
synthetic resins. Preferred thermoplastic condensation products are 
polyamides and polyesters, as well as mixtures thereof. 
Suitable polyamides are all of the thermoplastically processable 
polyamides, in the pure form or in a mixture with auxiliary additives, 
such as fillers, stabilizers, plasticizers, etc. Polyamides useable in 
accordance with the present invention are: polycondensation products of 
diamines and dicarboxylic acids, polycondensation products of 
.omega.-aminocarboxylic acids, polylactams, as well as copolyamides 
derived from these components. In addition to homopolymeric polyamides and 
mixed polyamides, it is also possible to flameproof, in accordance with 
the present invention, polyamide alloys, as well as mixtures thereof, or 
the so-called "blends" thereof, with other polymers. In this context, 
these alloys or blends can likewise be one or several polyamides, or a 
polyester, such as polyethylene terephthalate or polybutylene 
terephthalate, as well as other thermoplastics. Low-melting polyamides, 
such as polyaminoundecanoic acid as well as polylaurolactam and alloys 
with these polyamides are likewise suited for the flameproofing treatment 
according to the present invention. The essential feature in this case, is 
that the processing of such thermoplastics be performed at temperatures of 
below 300.degree. C., if at all possible. 
Suitable isocyanates are aliphatic, cycloaliphatic, aromatic and 
alkylaromatic mono-, di- and polyisocyanates which, in turn, can contain 
hereto atoms, such as oxygen or nitrogen. Examples of these isocyanates 
are: tetramethylene-, hexamethylene-, octamethylenediisocyanate, 
4,4'-methylenebis(cyclohexyldiisocyanate), 2,4-toluylenediisocyanate, 
2,6-toluylenediisocyanate, .omega.,.omega.-diisocyanatodimethylbenzene, 
4,4'-methylenebis(phenylisocyanate), di- and polyisocyanates by reaction 
of diols and polyols with diisocyanates, and the like. The isocyanates to 
be used in accordance with the present invention are not limited to the 
above exemplary listing. 
The thermoplastic polycondensation products can contain the auxiliary 
agents which are customarily used in processing, such as lubricants, 
fillers and reinforcing agents, antioxidants, etc., wherein these 
additives can also be used in mixtures, depending on the required 
utilization. Since such additives usually affect the flame retarding 
characteristic of the polyamide molding compositions, an increased 
proportion of flame retardant to be utilized may become necessary. 
The proportion of isocyanate-lactam adduct in the flame retardant can 
fluctuate within the above-indicated limits. In case of nonreinforced 
polyamide, this proportion is in the higher range of 10-25% in the mixture 
with melamine; whereas in case of a reinforced material requiring a higher 
total dosage of flame retardant, this proportion is comparatively lower. 
It is preferred to utilize melamine in maximally finely divided form. 
The thermoplastic compositions of the present invention preferably contain 
an adduct of a diisocyanate and a lactam. A preferred lactam is 
.epsilon.-caprolactam. 
In an especially preferred thermoplastic composition according to the 
present invention, the adduct consists of .epsilon.-caprolactam and 
hexamethylene diisocyanate in a molar ratio of 0.2 to 0.5 mole of 
hexamethylene diisocyanate to 1 mole of .epsilon.-caprolactam. 
The amount of the mixture of melamine with the aforementioned adduct, 
utilized as the flame retardant, can vary within a wide range. Preferably, 
the quantity of flame retardant is 2-30% by weight, based on the entire 
composition. 
The flame retardant according to the present invention can also be utilized 
with other flame retardants, e.g., melamine cyanurate, but in this case 
the proportion of the melamine cyanurate in the mixture should not exceed 
25%. 
Incorporation of the flame retarding mixture can be performed in a 
conventional manner by means of using the devices commonly used in a 
compounding operation, for example by introducing the finished powder 
mixture of both components in separate connecting pipes into a twin screw 
extruder and granulating into a homogeneous composition. It is also 
possible to premix the melamine with the starting granules and to 
introduce the lactam-isocyanate component in powder form or as a liquid 
via an additional, separate connecting pipe into the extruder. In this 
procedure, it is also possible to add the isocyanate and lactam separately 
instead of as an already produced lactam-isocyanate adduct. 
Finally, a masterbatch can be produced in a first step, for example based 
on polyamide 6, containing a high content of flame retarding mixture, e.g. 
50%. With such a masterbatch, reinforced polyamides and comparable 
polymers can be preferably treated, whereby advantages result from the 
distribution of the flame retardant in the polyamide matrix and therefore 
resulting in a substantial improvement in the impact resistance of the 
thus-treated composition. Besides the usual stearates (Ca, Mg, Zn), it is 
also possible to utilize with advantage amides, such as bis-stearylamide 
and toluenesulfonamides (for example the mixture of ortho- and para-), as 
processing aids and, respectively, lubricants for the production of 
correspondingly highly filled masterbatches. 
A special advantage resides in that the flame retardant present in the 
polymerization composition surprisingly cannot be washed out to any 
measurable extent by boiling water. The corresponding test results are set 
forth in Table 5. 
With the aid of the flame retardant of the present invention, thermoplastic 
compositions can be produced which exhibit flameproofing characteristics 
corresponding to the norms. The flame retardant treatment in accordance 
with the present invention is superior in many respects to the flame 
retarding finishings known heretofore. The compositions exhibit 
considerably diminished plate-out. They can be manufactured in 
light-colored, almost colorless grades with good electrical values. During 
processing or in case of combustion, pollution effects, as known from the 
flame retardants based on phosphorus and halogen, are not to be expected. 
The various methods for incorporation of the flame retardants will be 
described in the following examples. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is described in detail in the Examples and Tables 
below. The following abbreviations are employed: 
FR agent=flame retardant agent 
M=melamine 
MC=melamine cyanurate 
VN=reaction product of 3 moles of .epsilon.-caprolactam and 1 mole of 
hexamethylene diisocyanate 
VH=processing aid 
The testing and measured values cited in these examples are determined as 
follows: 
1. Flammability 
Test rods with the dimensions of 126 x 12.6 mm having a thickness of 1.6 
and, respectively, 3.2 mm are stored prior to testing at 23.degree. C. and 
50% relative atmospheric humidity for 24 hours and subsequently tested in 
accordance with Underwriters Laboratories Inc. (UL) Subject 94 (vertical 
burning test for classifying materials). 
Decisive criteria for classification according to V2 and V0, respectively, 
are the burning period and the dripping characteristic, especially to the 
effect whether the wad ignites during dripping (V2) or whether it does not 
ignite (V0). 
The Tables indicate, in addition to this UL-94 classification, that the 
entire burning period for the 2 x 5=10 rods in seconds, and the number of 
drops (drop number) resulting in total in the testing of 10 rods, in order 
to clarify the differences in the burning characteristic. 
2. Processing Criteria 
The Tables contain data which are to yield information on the 
dispersion/distribution of the flame retardant in the polymer matrix. For 
this purpose, the test specimen is viewed in translucent light, and the 
degree of distribution of the flame retardant which, in the normal case is 
not melted, is evaluated. 
The column "Unmolding" contains data on the unmoldability during injection 
molding of the compositions treated with the flame retardants. Finally, 
the Tables also contain information regarding the residues in the 
injection mold which are to yield explanations regarding the sublimation 
of the flame retardants during processing. 
3. Mechanical Properties 
The tensile strength and tensile impact resistance are measured analogously 
to DIN 53455 and, respectively, DIN 53448 on a flat rod, 126 x 12.6 x 1.6 
mm, without and, respectively, with cut-out notch 6 mm after a storage 
period of 24 hours at 23.degree. C. and 50% relative atmospheric humidity. 
The quantities indicated in the examples are set forth either in moles or 
in weights. Insofar as parts are mentioned, these are parts by weight.

EXAMPLE 1 (COMATIVE EXAMPLE) 
2 kg of polyamide 6,6 having a relative viscosity .eta..sub.rel =2.7 is 
injection molded, after pre-drying in a vacuum dryer at 70.degree. C., for 
12 hours on a screw injection molding machine model Arburg Allrounder 
221-75-350 into test specimens having the dimension of 126 x 12.6 x 1.6 
mm. The resultant test specimens are tested in accordance with the 
procedure indicated under (1) and (2), and the results are set out in 
Table 1. As can be seen from Table 1, the composition exhibits an 
unfavorable burning behavior as compared with the products according to 
the present invention. 
EXAMPLE 2 
In a reactor, .epsilon.-caprolactam is melted under nitrogen and such an 
amount of hexamethylene diisocyanate (HDI) is added under vacuum in 
metered quantities that 1 mole of HDI is made to react per 3 moles of 
.epsilon.-caprolactam. The thus-obtained adduct is discharged, after 
cooling, as a melt into moistureproof containers and later on ground into 
a powder under addition of nitrogen. 
This powder, denoted as VN hereinbelow, is mixed thoroughly with finely 
divided melamine having an average threshold particle size of 60 .mu.m, 1 
part of VN being provided per 9 parts of melamine. 
Eight parts of this pulverulent flame retardant mixture is then thoroughly 
mixed as a so-called dry blend with 92 parts of polyamide 6,6 granules, as 
described in Example 1, and injection molded to test specimens analogously 
to Example 1. 
Table 1 shows that the composition according to the present invention 
exhibits a very good dispersion of the flame retardant and is to be 
classified as self-extinguishing according to UL 94 V0. 
EXAMPLE 3 
The procedure of Example 2 is followed. The proportion of flame retardant 
component VN in the mixture with melamine is increased from 10 parts to 15 
parts. 
As indicated by Table 1, the resultant compositions are to be classified as 
self-extinguishing according to UL 94 V0; they exhibit a very good 
dispersion of the flame retardant. 
EXAMPLE 4 
The process of Example 2 is carried out with the difference that finely 
divided melamine having an average threshold particle size of 60 .mu.m is 
utilized as the flame retardant. Table 1 shows that the resultant test 
specimens are likewise self-extinguishing in accordance with UL 94 V0 but 
exhibit poor dispersion of the flame retardant and leave residues in the 
mold. 
EXAMPLE 5 
The mold of operation likewise corresponds to Example 2. The flame 
retardant incorporated is finely divided melamine cyanurate having an 
average threshold particle size of 90 .mu.m. The thus-produced test 
specimens show a less favorable burning characteristic corresponding to 
the classification UL 94 V2, and a markedly poorer dispersion of the flame 
retardant. 
EXAMPLE 6 (COMATIVE EXAMPLE) 
2 kg of polyamide 6 with a relative viscosity .eta..sub.rel =2.6 is 
predried in the same manner as in Example 1 and injection molded to test 
specimens having the dimension of 126 x 12.6 x 1.6 mm. 
The results of the test, performed in the same way as in Examples 1-5, are 
listed in Table 2. The resultant composition shows an adverse burning 
characteristic as compared with the products according to the present 
invention. 
EXAMPLE 7 
1.84 kg of polyamide 6 as in Example 6 is thoroughly mixed with 0.16 kg of 
pulverulent flame retardant mixture corresponding to Example 2 and 
injection molded into test specimens as in Example 6. 
The results set forth in Table 2 demonstrate that the composition obtained 
according to the present invention is to be classified as 
self-extinguishing according to UL 94 V0; it has a reduced dripping 
tendency during the flammability test, and shows a good dispersion of the 
flame retardant. 
EXAMPLE 8 (COMATIVE EXAMPLE) 
The procedure of Example 7 is followed except that finely divided melamine 
cyanurate having an average threshold particle size of 90 .mu.m is used as 
the flame retardant. The resultant composition shows a poorer dispersion 
of the flame retardant, as compared with the composition according to this 
invention, an increased dripping tendency during burning, and can be 
classified only according to UL 94 V2. 
EXAMPLE 9 (COMATIVE EXAMPLE) 
The procedure of Example 7 is performed with the difference that finely 
divided melamine having an average threshold particle size of 60 .mu.m is 
incorporated as the flame retardant. The thus-obtained composition 
exhibits the same disadvantages with respect to the composition of the 
present invention in a similar way as in Example 8. 
EXAMPLE 10 (COMATIVE EXAMPLE) 
The process is conducted as described in Example 7. The flame retardant 
utilized is a powdery mixture of the components melamine, melamine 
cyanurate, zinc borate, and calcium stearate in the ratio of 
6:1.2:0.64:0.16. Eight parts by weight of this flame retardant mixture is 
mixed thoroughly with 92 parts by weight of polyamide 6 corresponding to 
Example 6 and injection molded into test specimens as in Example 7. A 
reduced drop number is determined in the flammability test. The 
classification is UL V0. Dispersion is markedly poorer as compared with 
the product according to the present invention. 
EXAMPLE 11 (COMATIVE EXAMPLE) 
2 kg of polyamide 6,6, reinforced with 30 parts by weight of glass fiber, 
is injection molded into test specimens having the dimension 126 x 12.6 x 
3.2 mm. 
As shown in Table 3, the thus-obtained molded products burn through 
entirely in the UL 94 test. 
EXAMPLES 12 AND 13 
3 kg of polyamide 6,6, reinforced with 30 parts by weight of glass fiber, 
is thoroughly mixed with 1 kg of flame retardant mixture according to 
Example 2 and injection molded into test specimens as in Example 11. The 
resultant composition corresponds in both examples to classification UL 
V0. The composition contains 22.5 parts by weight of glass fiber and 25 
parts by weight of flame retardant mixture. 
In order to improve the dispersion of the flame retardant and to test its 
thermal stability, test specimens from Example 12 are comminuted and again 
injection molded. As can be seen from Table 3, the good flameproofing 
properties remain preserved, and the dispersion of the flame retardant is 
improved in Example 13. 
EXAMPLE 14 (COMATIVE EXAMPLE) 
2.325 kg of polyamide 6,6, reinforced with 30 parts by weight of glass 
fiber, is thoroughly mixed with 0.675 kg of finely divided melamine having 
an average threshold particle size of 60 .mu.m, and injection molded into 
test specimens as in Example 11. The test specimens contain 23.25 parts by 
weight of glass fiber. Table 3 shows that the resultant composition 
exhibits a substantially less favorable burning characteristic than the 
composition of the present invention according to Examples 12 and 13. Only 
classification UL V2 is reached. Furthermore, marked residues are observed 
in the mold, and surface flaws are found due to sublimation of the flame 
retardant. 
EXAMPLE 15 (COMATIVE EXAMPLE) 
3 kg of polyamide 6,6, reinforced with 30 parts by weight of glass fiber, 
is thoroughly mixed with 1 kg of pulverulent flame retardant consisting of 
90 parts by weight of finely divided melamine cyanurate having an average 
threshold particle size of 90 .mu.m and 10 parts by weight of a reaction 
product (adduct) according to Example 2, and injection molded into test 
specimens as in Example 11. The test specimens contain 22.5 parts by 
weight of glass fibers. 
As in Example 14, the resultant compositions cannot be classified according 
to UL V0 and exhibit surface flaws on account of the sublimation of 
melamine cyanurate. In contrast to the products according to this 
invention, pronounced residues in the form of coatings are found in the 
mold. 
EXAMPLE 16 
2 kg of polyamide 6,6, reinforced with 50 parts by weight of glass fiber, 
are thoroughly mixed with 2 kg of flame retardant batch and injection 
molded into test specimens according to Example 11. 
The flame retardant batch is present in granular form, containing 50 parts 
by weight of polyamide 6 with a relative viscosity .eta..sub.rel =2.6 and 
50% by weight of flame retardant mixture according to Example 2. 
The resultant composition contains 25% by weight of glass fiber and 
corresponds to the classification UL V0. The test specimens show a good 
dispersion of the flame retardant; only very minor residues can be found 
in the mold. Example 15 demonstrates that the combination of melamine 
cyanurate with the adduct of this invention leads to increased 
flammability and does not make a V0 classification possible. In contrast 
thereto, this can be done with the combination of melamine with the adduct 
of the present invention from Example 2, at the same quantitative ratios, 
as demonstrated by Examples 12, 13, and 16. 
EXAMPLE 17 
3.2 kg of polyamide 6, reinforced with 50 parts by weight of glass fiber, 
is thoroughly mixed with 0.8 kg of flame retardant mixture according to 
Example 2 and injection molded as described in Example 11. The molded 
articles contain 40 parts by weight of glass fiber and 20 parts by weight 
of flame retardant. Classification corresponds to UL V0 at 3.2 mm. 
EXAMPLE 18 
2.64 kg of polyamide 6, reinforced with 30 parts by weight of finely 
divided kaolin having an average threshold particle size of 100 .mu.m, is 
thoroughly mixed with 0.36 kg of flame retardant mixture according to 
Example 2 and injection molded as described in Example 11. 
The results are light-brown test specimens having a thickness of 3.2 mm 
with a content of 26.4 parts by weight of kaolin and 12 parts by weight of 
flame retardant mixture. The dispersing ability of the flame retardant is 
very good. Classification corresponds to UL V0. 
EXAMPLE 19 
3.3 kg of polyamide 6 with a viscosity of .eta..sub.rel =2.6 is thoroughly 
mixed with 0.7 kg of polyamide 12 (standard brand) and 1 kg of flame 
retardant batch as utilized in Example 16 and injection molded to test 
specimens as in Example 11. Test rods result which, besides having a light 
color, show good flexibility and surface and, with a thickness of 3.2 mm, 
correspond to the classification UL V0. 
EXAMPLE 20 
3.68 kg of polyamide 6 as in Example 19 is thoroughly mixed with 0.32 kg of 
flame retardant mixture of 90 parts by weight of finely divided melamine 
having a threshold particle size of 60 .mu.m and 10 parts by weight of an 
adduct of 3 moles of .epsilon.-caprolactam and 1 mole of 
4,4'-methylenebis(phenylisocyanate) and injection molded as described in 
Example 11. The resultant test specimens having a thickness of 3.2 mm 
correspond to classification UL V0. The flame retardant is well dispersed; 
no residues are observed in the mold. 
EXAMPLE 21 (COMATIVE EXAMPLE) 
2 kg of polyamide 11 having a viscosity of .eta..sub.rel =3.2 is injection 
molded as described in Example 1 into test specimens having a thickness of 
1.6 mm. The white, homogeneous test specimens result in a UL 94 
classification of V2. The entire burning time is 21 seconds, the drop 
number is 43. 
EXAMPLE 22 
1.8 kg of polyamide 11 having the viscosity indicated in Example 21 is 
mixed with 0.2 kg of flame retardant mixture according to Example 2 into a 
dry blend and injection molded as in Example 21 into test rods of a 
thickness of 1.6 mm. The testing mold shows no residues whatever, the test 
specimens are homogeneous and correspond to UL classification V0. The 
entire burning period is 7 seconds, the drop number is 13. 
EXAMPLE 23 (COMATIVE EXAMPLE) 
2 kg of polybutylene terephthalate (PBTP) having a viscosity of 
.eta..sub.rel =3.3 is injection molded analogously as described in Example 
1. Homogeneous test specimens are the result, having a thickness of 3.2 
mm, which cannot be classified under UL 94. The entire burning time is 89 
seconds, the drop number is above 120. 
EXAMPLE 24 
1.6 kg of PBTP corresponding to Example 23 is mixed thoroughly with 0.4 kg 
of flame retardant batch as described in Example 16 and injection molded 
as disclosed in Example 23. The injection molded test specimens contain 10 
parts by weight of flame retardant mixture VN and 10 parts by weight of 
polyamide 6. They correspond to UL V0 with a thickness of 3.2 mm. The 
entire burning time is 16 seconds, the drop number is 18. The rods show 
homogeneous appearance. 
EXAMPLE 25 
2.55 kg of polyamide 12 (basic type, unstabilized) is mixed thoroughly with 
0.45 kg of flame retardant and injection molded analogously to Example 1. 
The powdery flame retardant is a thorough mixture of 85 parts of an adduct 
formed from a mixture of 2 moles of .epsilon.-caprolactam with 1 mole of 
laurolactam together with a mixture of 0.8 mole of hexamethylene 
diisocyanate with 0.2 mole of 2,4-toluylene diisocyanate. The resultant 
test specimens correspond, as contrasted to polyamide 12 not provided with 
flame retardant, to the classification UL V0 with a layer thickness of 1.6 
mm. 
EXAMPLE 26 
2 kg of polyamide 6,6 with a relative viscosity .eta..sub.rel =2.8, 
provided with 20 parts by weight of glass microbeads having a maximum 
grain size of 3,000 .mu.m, is mixed thoroughly with 0.5 kg of flame 
retardant batch in granular form as described in Example 16, and injection 
molded into parts having a wall thickness of 5.2 mm. These injection 
molded parts are subjected to the incandescent wire test DIN VDE 0471, 
part 2 at 750.degree. C. and 850.degree. C. In both cases, the 
incandescent wire test is passed. 
In order to test resistance against boiling water, the following 
experiments are carried out: 
EXAMPLE 27 (COMATIVE EXAMPLE) 
1.8 kg of polyamide 6, granulated, is thoroughly mixed with 0.2 kg of 
finely divided melamine and processed as described in Examples 1 and 4. 
The thus-obtained test specimens having a thickness of 1.6 mm are 
self-extinguishing and correspond to UL 94 V0. 
EXAMPLE 28 
1.6 kg of polyamide 6,6, granulated, as used in Example 1, is mixed with 
0.4 kg of flame retardant batch according to Example 16 and processed into 
test specimens having a thickness of 1.6 mm. The test specimens are 
self-extinguishing according to UL 94 V0. 
Test rods according to Examples 27 and 28 are dipped for 5 hours into 
boiling water and, after drying and conditioning, are again subjected to 
the burning test. The results are set out in Table 5. 
It is found that the melamine-treated test specimens no longer correspond 
to the UL 94 V0 classification. In contrast thereto, the flame retardant 
effect is preserved in the test specimens treated in accordance with this 
invention, even under the influence of boiling water. 
TABLE 1 
__________________________________________________________________________ 
PA 6,6 Nonreinforced 
Proprotions in % by Weight 
UL 94 
Burning 
Drop 
of Mixture Classi- 
Time for 
Number 
Polymer Flame Retardant 
fication 
10 Rods 
for 10 
Disper- 
Unmold- 
Residues 
Example 
PA 6,6 
M VN MC 1.6 mm 
(sec) 
Rods sion 
ing in Mold 
__________________________________________________________________________ 
1 100 -- -- -- V2 8 20 + None 
2 92 7.2 
0.8 
-- V0 0 16 ++ + None 
3 92 6.8 
1.2 
-- V0 0 19 ++ + None 
4 92 8 -- -- V0 0 24 - + Minor 
5 92 -- -- 8 V2 5 20 - + Minor 
__________________________________________________________________________ 
+ = Good 
++ = Very Good 
- = Bad 
TABLE 2 
__________________________________________________________________________ 
PA 6 Nonreinforced 
Proprotions in % by Weight 
UL 94 
Burning 
Drop 
of Mixture Classi- 
Time for 
Number 
Polymer Flame Retardant 
fication 
10 Rods 
for 10 
Disper- 
Unmold- 
Residues 
Example 
PA 6,6 
M VN MC VH 1.6 mm 
(sec) 
Rods sion 
ing in Mold 
__________________________________________________________________________ 
6 100 -- 
-- -- -- V2 9 28 + None 
7 92 6.8 
1.2 
-- -- V0 2 15 + + None 
8 92 -- 
-- 8 -- V2 0 35 - + None 
9 92 8 -- -- -- V2 4 30 - + Minor 
10 92 6 -- 1.2 
0.8.sup.1 
V0 21 7 - + None 
__________________________________________________________________________ 
.sup.1 Zinc borate Calcium stearate Mixture 4:1 
+ = Good 
- = Bad 
TABLE 3 
__________________________________________________________________________ 
PA 6,6 Glass-Fiber Reinforced 
UL 94 
Burning 
Drop 
Proprotions in % by Weight of Mixture 
Classi- 
Time Number 
Ex- Polymer.sup.1 
Glass 
Flame Retardant 
fication 
for 10 
for 10 
Disper- 
Residue 
ample 
PA 6,6 
PA 6 
Fiber 
M VN MC 3.2 mm 
Rods Rods sion 
in Mold 
__________________________________________________________________________ 
11 100 -- -- -- -- -- n.c. 
b.h. n.c. 
12 52.5 
-- 22.5 
22.5 
2.5 
-- V0 3 0 - Minor 
13 52.5 
-- 22.5 
22.5 
2.5 
-- V0 4 0 + Minor 
14 54.25 
-- 23.25 
22.5 
-- -- V2 129 5 -- Marked 
15 52.5 
-- 22.5 
-- 2.5 
22.5 
V2 93 3 -- Marked 
16 25 25 25 .sup. 22.5.sup.2 
.sup. 2.5.sup.2 
-- V0 14 0 + Very 
Minor 
__________________________________________________________________________ 
.sup.1 Examples 12-15 with PA 6,6/30% by weight glass fiber. Example 16 
with PA 6,6/50% by weight glass fiber and flame retardant batch with PA 6 
matrix 
.sup.2 As flame retardant batch (50% by weight PA 6) 
+ = Good 
- = Bad 
-- = Very Bad 
n.c. = Not Classifiable 
b.h. = Burns Through to Holder 
TABLE 4 
______________________________________ 
Tensile Strength Test According to DIN 53445.sup.1 
Tensile Impact Resistance Test Analogously to DIN 53448.sup.1 
(Cut Notch 6 mm Diameter) 
Proportions in % 
by Weight of Mixture 
N/mm.sup.2 
kJ/m.sup.2 
Example 
Polymer Polymer M VN MC .sigma.s 
a.sub.ZL 
______________________________________ 
1 PA 6,6 100 -- -- -- 79.2 89.6 
2 " 92 7.2 0.8 -- 70.0 48.8 
5 " 92 -- -- 8 57.2 35.5 
21 PA 11 100 -- -- -- 48.6 210.6 
22 " 90 9 1 -- 47.0 128.7 
______________________________________ 
.sup.1 Measurements on Flat Rod 126 .times. 12.6 .times. 1.6 mm 
TABLE 5 
__________________________________________________________________________ 
Resistance to Boiling Water 
After Storage 
Proportions in % by Weight of 
Without Storage 
for 5 Hours 
Mixture in Boiling Water 
in Boiling Water 
Polymer Flame Retardant 
UL BD UL BD 
Example 
PA 6,6 
PA 6 
M VN Class. 
sec 
DN Class. 
sec 
DN 
__________________________________________________________________________ 
27 90 -- 10 -- V0 0 28 V2 4 22 
28 80 10.sup.1 
.sup. 9.sup.1 
1.sup.1 
V0 0 17 V0 0 14 
__________________________________________________________________________ 
.sup.1 As flame retardant batch (50% by weight PA 6) 
BD = Burning duration, in total for 2 .times. 5 rods 
DN = Drop number, in total for 2 .times. 5 rods