Polyamideimides prepared by reacting either lactams or polyamides with polyisocyanates and anhydrides using a lactam as an additive

This invention relates to new polyamide imides and to the use thereof as thermoplasts.

This invention relates to new polyamide imides and to the use thereof as 
thermoplasts. 
It is known that aliphatic-aromatic polyamide imides may be obtained by 
reacting polyisocyanates with cyclic polycarboxylic acid anhydrides and 
lactams (DAS No. 17 70 202) or polyamides (DAS No. 19 56 512). The 
reaction products are distinguished by high softening temperatures and 
favourable elasticity values and are used as high temperature-resistant 
coatings, for example in the field of electrical insulating lacquers. 
It has now been found that polyamide imides which are obtained by the 
condensation of organic polyisocyanates, such as aliphatic, 
aliphatic-aromatic and aromatic diisocyanates, with cyclic polycarboxylic 
acid anhydrides and lactams or polyamides at temperatures of from 
0.degree. to 400.degree. C., optionally in a solvent, are thermoplasts 
having excellent properties providing these polymers additionally contain 
from 0.1 to 20%, by weight, preferably from 0,2 to 15%, by weight, most 
preferably from 1 to 10% by weight corresponding to the following general 
formula: 
##STR1## 
wherein 
n is the number 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18. 
n denotes preferred in formula (1) the numbers n=5 (caprolactam), n=11 
(azacyclotridecan-2-on laurinlactame), n=10 and n=12, mostly preferred the 
number n=10 and n=11 or mixtures thereof, especially preferred are all 
mixtures mentioned before admixed with caprolactame. 
Caprolactam and azacyclotridecan-2-one (n=11), preferably in admixture, are 
preferred. 
It has also been found that these polyamide imides may be produced, for 
example, in solvents and subsequently concentrated, optionally in vacuo, 
in an evaporation extruder at temperatures of from 250.degree. to 
400.degree. C. 
The reaction products are distinguished by favourable mechanical 
properties, such as impact strength, tensile strength, moduli of 
elasticity and dimensional stability under heat. It is surprising that the 
polyamide imides according to the present invention may be processed at 
the high temperatures which are required for the extrusion and 
injection-moulding of polyimides. 
In general, it is only possible to use residues of very high thermal 
stability, for example 4,4'-substituted diphenyl esters, as the amino 
component in imides for applications of the type in question. It is also 
surprising that the polymers according to the present invention do not 
become brittle and infusible under these conditions, particularly during 
concentration in the extruder, as is the case with reaction products of 
polyisocyanates and cyclic polycarboxylic acid anhydrides. 
According to the present invention, it is possible with advantage to use 
polyisocyanates of the type described, for example, in DE-OS No. 17 70 
202. 
Particular preference is attributed to phosgenated condensates of aniline 
and formaldehyde having a polyphenylene-methylene structure, technical 
mixtures of tolylene diisocyanates, m-phenylene diisocyanate and the 
symmetrical compounds 4,4'-diisocyanatodiphenyl methane, 
4,4'-diisocyanatodiphenyl ether, naphthylene-(1,5)-diisocyanate, 
p-phenylene diisocyanate, 4,4'-diisocyanatodiphenyl methane, analogous 
hydroaromatic diisocyanates, such as 4,4'-diisocyanatodicyclohexyl 
methane, and also aliphatic diisocyanates containing from 2 to 12 carbon 
atoms, such as hexamethylene diisocyanate, diisocyanates derived from 
isophorone and mixtures thereof. 
Instead of using the isocyanates, it is also possible to use compounds 
which react as isocyanates under the reaction conditions, preferably the 
addition compounds with phenols and lactams, for example phenol, technical 
cresol mixtures and caprolactam or mixtures of the amines corresponding to 
the isocyanates and aliphatic and aromatic carbonic acid esters, for 
example carbonic acid diethyl ester, carbonic acid diphenyl ester and 
ethylene carbonate, which may have been partially reacted, or even 
polycarbodiimides and isocyanato-isocyanurates of the described 
polyisocyanates. Monofunctional isocyanates, such as phenyl isocyanate, 
tolyl isocyanate, cyclohexyl isocyanate, stearyl isocyanate, 
.omega.,.omega.,.omega.-trifluoroethyl isocyanate and 3,5-trifluoromethyl 
phenyl isocyanate, or the corresponding amines, may also be used for 
regulating molecular weight. 
The cyclic polycarboxylic acid anhydrides used in accordance with the 
present invention may be compounds of the type described in DE-OS No. 17 
02 02 and DE-OS No. 25 42 706, preferably polycarboxylic acid anhydrides 
corresponding to the following general formula: 
##STR2## 
wherein 
R.sup.1 represents an optionally substituted C.sub.2 -C.sub.20 aliphatic 
radical, a C.sub.5 -C.sub.10 cycloaliphatic radical, an aliphatic-aromatic 
radical containing from 1 to 10 carbon atoms in the aliphatic portion and 
from 6 to 10 carbon atoms in the aromatic portion or an aromatic radical 
containing from 6 to 10 carbon atoms which, in addition to the cyclic 
anhyride group, also contains at least one other cyclic anhydride group or 
a carboxyl group. 
Butane tetracarboxylic acid dianhydride, cyclopentane tetracarboxylic acid 
dianhydride, pyromellitic acid dianhydride, benzophenone tetracarboxylic 
acid dianhydride and especially trimellitic acid anhydride are mentioned 
as examples. 
Instead of using the carboxylic acid anhydrides, it is also possible to use 
derivatives, such as alkyl esters or phenyl esters or the polycarboxylic 
acid themselves which are converted into the acid anhyrides during the 
reaction. 
Carboxylic acid which react monofunctionally under the reaction conditions, 
such as phthalic acid or its anhydride, benzoic acid or palmitic acid, 
which in addition may be substituted by alkyl or halogen, such as fluorine 
or chlorine, are used for regulating molecular weight. 
Lactams suitable for use in accordance with the present invention, are for 
example, those corresponding to the following general formula: 
##STR3## 
wherein X represents an integer of from 2 to 20. 
Caprolactam is preferably used. 
The lactams may be replaced by or used in combination with polyamides of 
the type described in DE-AS No. 19 56 512, for example polycarpoic amide 
(nylon-6), polydodecanoic acid amide and polyamides of dicarboxylic acids, 
such as adipic acid, sebacic acid, oxalic acid, dibutyl malonic acid, 
isophthalic acid and terephthalic acid, and diamines, such as ethylene 
diamine, hexamethyl diamine, decamethylene diamines and m- and p-phenylene 
diamine. Polycaproic amide (nylon-6) and polyhexamethylene adipamide 
(nylon-6,6) are preferably used. 
The lactams which the polyamide imides according to the present invention 
are intended to contain either individually or in admixture in quantities 
of from 0.2 to 15%, by weight, correspond to the following general 
formula: 
##STR4## 
wherein n represents an integer of from 4 to 18. 
It is preferred to use caprolactam and lauric lactam 
(azacyclotridecan-2-one), preferably in admixture. 
The production of the polymers according to the present invention may be 
carried out in solvents, as described in DE-AS No. 17 70 202. The solvents 
preferably used are phenols, such as phenol, and technical mixtures of o-, 
m- and p-cresols. 
To produce the imide thermoplasts according to the present invention, the 
reaction components are maintained at from 0.degree. to 400.degree. C. for 
from a few minutes to several hours in the presence or absence of solvent. 
The course of the reaction may be followed, for example, from the 
evolution of gas, from the increase in viscosity and from the IR-spectra. 
The lactam used in the production of the polyamide imide may be the same 
lactam which the end product is intended to contain. In that case, it is 
possible, instead of additionally adding the same lactam, to carry our 
production and concentration in such a way that the quantity required in 
accordance with the present invention remains present in the reaction 
product, for example by suitably selecting the quantity of lactam, the 
reaction times, temperatures and the pressure at which concentration is 
carried out. 
The additional lactams according to the present invention (n.gtoreq.4) may 
be added either at the beginning of or during the reaction. In this 
connection, it is important to bear in mind that the additional lactams 
may have to be used in an excess relative to the required final content 
because partial incorporation into the polymer may occur. 
In one preferred embodiment which avoids these difficulties, the lactams 
are only added on completion of condensation or, more preferably, in the 
phase preceding concentration and post-condensation in the extruder. 
It is occasionally advantageous to carry out the production reaction in 
several stages or to add the individual components in a different sequence 
or at different temperatures. Thus, the polymer may be prepared in a 
phenolic solvent, subesequently precipitated from the solution using a 
non-solvent, such as methanol, and optionally post-condensed in an 
extruder. In one preferred embodiment, the polymer is prepared in a 
solvent, optionally concentrated in the reaction vessel itself to form a 
still-fluid solution or a casting resin, the lactam wherein n.gtoreq.4 is 
introduced and the rest of the concentration process is carried out, 
optionally with post-condensation, in an evaporation extruder, optionally 
in vacuo, at temperatures of from 240.degree. to 400.degree. C., 
preferably from 280.degree. to 340.degree. C. 
In a special embodiment of the invention for example during the production 
of the polymer in a phenolic solvent (e.g. phenol/technical 
cresole-mixture) after the polymerisation the reaction mixture is kept for 
additional 0,5 to 10 hours, preferably 1 to 6 hours at a temperature of 
200.degree. to 250.degree. C., preferably 210.degree. to 220.degree. C. 
These temperatures can be reached by a partial evaporation of the solvent 
or by applying a pressure up to about 5 bars. 
In general, 1 val of carboxylic acid or cyclic carboxylic acid anhydride is 
reacted per val of isocyanate and from 0.5 to 2 val of lactam or amide per 
val of carboxylic acid anhydride, although significant deviations from 
these quantities are also possible. In addition to this quantity of lactam 
or amide, from 0.2 to 15%, by weight, preferably from 1 to 8%, by weight, 
of lactam wherein n.gtoreq.4 is used in the manner described. In another 
possible embodiment, excess isocyanate is reacted with di- or 
tri-carboxylic acids, such as adipic acid, terephthalic acid, isophthalic 
acid or trimesic acid, and excess carboxylic acid with polyfunctional 
alcohols, such as ethylene glycol, neopentyl glycol, hexane diol, 
trimethylol propane, tris-hydroxyethyl isocyanurate, tris-hydroxyethyl 
urazole and polyesters containing terminal hydroxy groups. 
The production of the polymers according to the present invention may be 
influenced by catalysts, for example by amines, such as triethylamine, 
1,4-diazabicyclo(2,2,2)-octane, N-ethyl morpholine, N-methyl imidazole and 
2-methyl imidazole, by inorganic and organic metal compounds, especially 
compounds of iron, lead, zinc, tin, copper, cobalt and titanium such as 
iron-(III) chloride, cobalt acetate, lead oxide, lead acetate, tin 
octoate, dibutyl tin dilaurate, copper acetylacetonate, titanium 
tetrabutylate, alkali metal phenolates and sodium cyanide, and by 
phosphorus compounds, such as trialkyl phosphine and methyl phospholine 
oxide. 
The polyamide imides according to the present invention are distinguished 
by the particular tensile strength, moduli of elasticity and dimensional 
stability under heat thereof. The properties thereof may be varied to suit 
the various applications by altering the stoichiometric ratios, the degree 
of condensation and by the addition of low molecular weight and high 
molecular weight components, such as fillers, pigments, anti-agers, 
lubricants, plasticizers and other polymers.

EXAMPLE 1 
565 g of caprolactam, 87 g of a technical mixture of 80 parts of 2,4- and 
20 parts of 2,6-tolylene diisocyanate, 1125 g of 4,4'-diisocyanatodiphenyl 
methane and 960 g of trimellitic acid anhydride are stirred in 1875 g of a 
phenol/cresol (1:1) mixture first for 2 hours at 170.degree. C. then for 2 
hours at 190.degree. C. and finally for 4 hours at 205.degree. C. 1300 g 
of the solvent mixture are then distilled off in vacuo and the residue 
stirred for 1 hour at 210.degree. C. The polyamide imide is obtained in 
the form of an approximately 80% melt. The viscosity .eta..sup.25, as 
measured using a 15% solution in cresol, amounts to 670 mPas. 
69 g of dodecane lactam are stirred into the melt. A brittle resin is 
obtained on cooling which, after size reduction, is concentrated and 
condensed to completion in a Welding evaporation extruder at a maximum 
barrel temperature of 300.degree. C. and under a pressure of 135 mbar. The 
condensation product is a light brown, transparent resin having a relative 
viscosity .eta., as measured using a 1% solution in cresol at 25.degree. 
C., of 2.10. 
The thus-produced polymer is injection-moulded at temperatures of the order 
of 300.degree. C. Test specimens having a notched impact strength of 8 
kJ/m.sup.2, a tensile strength of 116 mPa, a modulus of elasticity in 
tension of 3510 MPa and a Vicat softening temperature of 176.degree. C. 
are obtained. 
EXAMPLE 2 
5000 g of an 80% polyamide imide resin produced in accordance with Example 
1 are melted and 240 g of 12-dodecane lactam are added to the resulting 
melt. The homogenized melt is concentrated in a Welding evaporation 
extruder at a maximum barrel temperature of 310.degree. C. and under a 
pressure of 165 mbar. A transparent, brown resin is obtained, its relative 
viscosity .eta. amounting to 1.86, as measured using a 1% solution in 
cresol at 25.degree. C. 
Injection moulding at temperatures of about 300.degree. C. produced test 
specimens having an impact strength of 82 kJ/m.sup.2, a tensile strength 
of 105 MPa, modulus of elasticity in tension of 3480 MPa and a Vicat 
softening temperature of 174.degree. C. 
EXAMPLE 3 
5000 g of an 80% polyamide imide resin produced in accordance with Example 
1 are melted and 80 g of dodecane lactam and 40 g of a technical mixture 
of nonyl phenols added to the resulting melt. The melt solidifies on 
cooling to form a brittle resin which is size reduced and concentrated in 
a Welding evaporation extruder at a maximum barrel temperature of 
310.degree. C. and under a pressure of 90 mbar. The imide polymer is 
obtained in the form of a transparent, elastic resin having a relative 
viscosity .eta. of 2.40. 
EXAMPLE 4 
113 g of caprolactam, 200 g of 4,4'-diisocyanatodiphenyl methane, 52.5 g of 
trimellitic acid anhydride and 52.5 g of 
bis-[4-isocyanatocyclohexyl]-methane are introduced into 640 g of 
phenol/cresol (1:1). The reaction mixture is stirred for 2 hours at 
170.degree. C., for 2 hours at 190.degree. C. and for 4 hours under gentle 
reflux at about 200.degree. C. 520 g of the solvent mixture are then 
distilled off in vacuo. The residue is then post-condensed for 1 hour at 
215.degree. C., giving an approximately 80% melt of the polyamide imide 
resin. The visocosity .eta..sup.25 of a 15% solution in cresol amounts to 
720 mPas. 15 g of 12-dodecane lactam are stirred into the melt. A sample 
of the thus-produced polymer is evaporated in a stream of nitrogen at from 
250.degree. to 300.degree. C., giving a transparent, fusible resin having 
a relative viscosity .eta. of 1.73, as measured using a 1% solution in 
cresol at 25.degree. C. 
EXAMPLE 5 
33.9 g of nylon-6,6 (polyhexamethylene adipamide) are dissolved in 210 g of 
a technical cresol mixture. 112.5 g of 4,4'-diisocyanatodiphenyl methane, 
8.7 g of 2,4-tolylene diisocyanate and 96 g of trimellitic acid anhydride 
are then introduced and the reaction mixture is stirred for 2 hours at 
170.degree. C., for 2 hours at 190.degree. C. and for 4 hours at 
205.degree. C. 140 g of the solvent mixture are then distilled off in 
vacuo, followed by stirring for 1 hour at 215.degree. C. for further 
condensation. A light brown, clear melt of the polyamide imide resin 
having a solids content of approximately 75%, by weight, is obtained. A 
15% solution in cresol has a viscosity .eta..sup.25 of 580 mPas. 3.8 g of 
.omega.-dodecane lactam are introduced into 100 g of the resulting melt. 
Concentration in a stream of nitrogen at from 250.degree. to 300.degree. 
C. produces a transparent, fusible resin having a relative viscosity .eta. 
of 1.82. 
EXAMPLE 6 
904 g of caprolactam are introduced into 3000 g of phenol/cresol (1:1) at 
room temperature, followed by the introduction at 120.degree. C. of 1780 g 
of 4,4'-diisocyanatodiphenyl methane, 139 g of a technical mixture of 80% 
of 2,4- and 20% of 2,6-tolylene diisocyanate, 19 g of phenyl isocyanate 
and 1536 g of trimellitic acid anhydride. After stirring for 2 hours at 
170.degree. C., for 2 hours at 190.degree. C. and for 4 hours at 
205.degree. C., 1780 g of the solvent mixture are distilled off in vacuo 
and the residue maintained at 215.degree. C. for 1 hour. 110 g of 
12-dodecane lactam are then introduced. A clear, brittle resin having a 
solids content of approximately 75%, by weight, is obtained on cooling. A 
15% solution in cresol has a viscosity .eta..sup.25 of 570 mPas. 
The imide resin is concentrated in a ZSK screw extruder at a maximum barrel 
temperature of 320.degree. C. and under a pressure of 400 mbar. A clear, 
elastic polymer is obtained, having a relative viscosity .eta. of 2.16, as 
measured using a 1% solution in cresol at 25.degree. C.