CA1120192A - Aliphatic polyamides - Google Patents

Abstract

Case 3-11407/ZFO/+
Canada ALIPHATIC POLYAMIDES
Abstract of the Disclosure The polyamides according to the invention are mainly transparent (amorphous), but in some cases also partially crystalline. They have a reduced specific viscosity (0.5 % in m-cresol at 25°C) of at least 0.3 dl/g, and consist of recurring structural elements of the formula I

(I) in which R1 and R2 are monovalent aliphatic or cyclo-aliphatic radicals, and Z is a bivalent aliphatic radical.
The dicarboxylic acid structural radicals are derived in particular from adipic acid. The polyamides have high glass transition temperatures, and have a low water absorption and also good stability to hydrolysis. They can be processed into moulded articles (for example by the injection moulding process and extrusion process).

Description

~ 0 ~9 Z

The invention relates to novel, predominantly transparent, aliphatic polyamides, to processes for producing them, and to their use for producing moulded articles.
From the French Patent Specification No. 1,476,146 are known aliphatic polyamides from decane-l,10-di-carboxylic acid and trimethylhexamethylenediamine, particularly a mixture of 2,2,4- and 2,4,4-trimethyl-hexamethylenediamine. These prior known aliphatic poly-amides have relatively low glass transition temperatures, and leave much to be desired with regard to absorption of water and to dimensional stability. Furthermore, the properties of these known aliphatic polyamides, especially the mechanical and electrical properties, become severely impaired under the action of moisture. These known poly-amides swell in the presence of moisture, and their original hardness and tensile strength decrease sharply.
The object of the present invention was therefore the production of novel aliphatic polyamides free from these disadvantages.
The novel polyamides according to the invention have a reduced specific viscosity (referred to in the following also as reduced solution viscosity) of at least 0.3 dl/g, pre.ferably of 0.3 to about 3.0 dl/g, and particularly of ,' ~

about 0.4 to 2.0 dl/g, measured on A 0. 5 % solutlon in m-cresol at 25 C, and they consist o~ identlcal or different recurrlng structural elements of the formula I
O O
HN CH ~CH2)8 1 (I) Rl R2 -in which Rl and R2 independently of one another are straight-chain or branched-chain alkyl havlng 3-20 C atoms or cyclo-alkyl ha~ing 4-12 C atoms, and Z is an allphatic radical having at least 2 C atoms.
The following may be mentioned as examples of straight-chaln o~ branched-chain alkyl groups dsnoted by R
or R2: the n-propyl, lsopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl, n-hexyl, 3-heptyl, n-heptyl, n-octyl, ~-nonyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl and eicosane groups.
Rl and R2 are preferably identical radicals per re-curring struatural element, especially isopropyl or straight-chain o~ branched-chain alkyl groups having 5-ll C
atoms, or cycloalkyl groups ha~ing 5-8 C atoms.
In partlcular preferred polyamides are those in which Z is fitralght-chain or branched-chain alkylene having

2-12 C atoms. ~specially pxeferred polyamides are those in which Z is optionally branched-chain alkylene having 4-lO C atoms. Examples of alkylene groups of this type are the tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, decamethylene and dodeca-methylene groups.
Preferred polyamides are those in which ~1 and R2 per recurring structural element of the formula I are each isopropyl or stralght-chain or branched-chain alkyl .B

having 5-11 C atoms, or are each cycloalkyl having 5-8 C atoms, and Z is straight-chain or branched-chain alkylene having 4-10 C atoms. More particularly pre-ferred polyamides are those in which Rl and R2 are each n-pentyl~ 3-pentyl, n-hexyl, 3-heptyl or cyclohexyl, cycloheptyl or cyclooctyl, and Z is -(CH2)4-.
Further preferred polyamides according to the invention are the following four special types:
1. Transparent polyamides which consist of recurring structural elements of the formula IV

NH-CH-(CH2)8-C~H-NH-CO-(CH2)4 ~ (IV), l CH3 ~ CH3 CH3 ~ CH3 and which have a reduced specific viscosity (0.5%
in m-cresol at 25C) preferably of about 1.1 dl/g.
2. Transparent polyamides which consist of recurring structural elements of the formula V
t NH-CH-(CH2)8-~H-NH-CO (CH2)4 ~ (V) and which have a reduced specific viscosity (0.5%
in m-cresol at 25C) preferably of about 0.75 dl/g.

3. Partially crystalline polyamides which consist of recurring structural elements of the formula VI

¦ . ( 2)8 CH NH - CO - (CH2~4 - CO
CH CH
- /\ /\ -ethyl n-butyl ethyl n-butyl and which have a reduced specific viscosity (0.5%

, . . . ~ .... . .. . . ..

in m-cresol at 25C) preferably of about o.6 dl/g.

4. Transparent polyamides which consist of recurring structural elements of the formula VII

~ NH-CH-(CH2)8-~H-NH-CO-(CH~)8 ~ (VII), and which have a reduced specific viscosity (0.5%
in m-cresol at 25C) preferably of about 0.7 dl/g.
The polyamides according to the invention can be produced by reacting a diamine of the formula II
H2N-CH-(CH2)8-CH NH2 (II) Rl, R2 with a dicarboxylic acid of the formula III
HOOC-Z-COOH (III), or with an amide-forming derivative thereof, wherein Rl, R2 and Z have the meanings given under the formula I.
It is possible to use in the reaction according to the invention also different diamines of the formula II and different dicarboxylic acids of the formula III.
As amide-forming derivatives of the dicarboxylic acid of the formula III, there can be used for example the corresponding dihalides, particularly the dichlorides, dinitriles and dialkyl esters or diaryl esters, especially dialkyl esters having 1-4 C atoms in each of the alkyl moieties and diphenyl esters.
The reaction of the diamines of the formula II with the dicarboxylic acids of the formula III, or with amide-forming derivatives thereof, can be performed by methods known per se. The preferred production process is the ll'~O~9Z

_ 5 _ melt polycondensation process in several stages. In this case, essentially stoichiometric amounts of diamine of the formula II and dicarboxylic acid of the formula III, or salts from the stated diamines and dicarboxylic acids, are pre-condensed under pressure at temperatures of about 220 to 300C in the melt, advantageously under inert gas, such as nitrogen. For this pre-condensation reaction there are advantageously used salts of the aforementioned type, which are produced in a preliminary stage frorn essentially stoichiometric amounts of diamine of the formula II, or of mixtures thereof, and dicarboxylic acids of the formula III in suitable inert organic solvents. Suitable inert organic solvents are for example: cycloaliphatic alcohols such as cyclopentanol and cyclohexanol, and particularly aliphatic alcohols having up to 6 C atoms, such as methanol, ethanol, n-propanol, butanols, pentanols and hexanols, and also mixtures of such solvents with water. The pre-condensate can be subsequently further condensed, at temperatures of between about 220 and 300C under normal pressure, and advantageously likewise in an inert-gas atmosphere, until the polyamides according to the invention have been formed. It can be of advantage under certain circumstance to apply a vacuum after completion of the polycondensation reaction.
The polyamides according to the invention can be produced also by melt polycondensation of diamines of the formula II and essentially stoichiometric amounts of an amide-forming derivative of the dicarboxylic acids of the formula III, for example activated esters, especially diphenyl esters. The r~action temperatures are in general between about 220 and 300C. And, finally, the polyamides ~ gz according to the invention can optionally also be produced, in a manner known per se, by polycondensation in solution or by inerfacial surface polycondensation.
The dicarboxylic acids of the formula III and the diamines of the formula II are known or can be produced by methods known per se. The diamines of the formula II
can be produced in a particularly simple manner by catalytically hydrogenating in the 3,12-position correspondingly substituted 1,2-diaza-1,5,9-cyclododeca-triens or 1,2-diazacyclododecanes in the presence of an inert organic solvent.
The polyamides according to the invention have high glass transition temperatures. They are distinguished in particular by a low water absorption, good stability to hydrolysis and improved dimensional stability.
Furthermore, the properties of the polyamides according to the invention, such as the mechanical and electrical properties, are only slightly affected by the action of moisture.
The polyamides according to the invention are in general transparent. Some of them however lose their transparency in consequence of partial crystallinity.
An example of this is the polyamide according to Example 12, which is based on adipic acid and 6,15-diamino-5,1~-diethyleicosane.
The polyamides according to the invention can be processed, by methods know per se, into moulded articles of the most varied kind (amorphous and crystalline), for example by the injection-moulding process and the extrusion process. They are particularly suitable for producing transparent apparatus and parts of apparatus from the melt, Further fields of application are for example their -` ll'~O19Z
.

use as adhesives for organic materials, such as leather and textiles, or for the production of lacquers. In the case of partially crystalline polyamides, they can be used to produce filaments.

. .

~'~019Z

Example_l A solution of 10.0 g of 5,14-diaminooctadecane in ethanol is added at 50C to a solution of 5,11-adipic acid in 30 ml of ethanol. The reaction mixture is sub-sequently cooled to 0C, whereupon the formed salt precipitates from the solution. The salt is filtered off, and dried in vacuo at 90C; yield: 14.7 g (97 %
of theory).
10 g of this salt is sealed under nitrogen into a bomb tube and heated for 3 hours at 260C. After cooling to 20-25C, the pre-condensate is removed from the tube and transferred to a condensing tube which is provided with a device for introducing nitrogen. The pre-condensate is melted down at 260C under nitrogen, and is held at this temperature for 10 hours as nitrogen is being passed through. The polycondensate on cooling solidifies to form a transparent substance. The reduced solution viscosity of the resulting polyamide, measured on a 0.5% solution in m-cresol at 25C, is 0.83 dl/g; glass transition temperature, determined by means of differential calorimetry (DSC), is 87C.
With the aid of a hydraulic press, there is produced from the polyamide at 200C a sheet approximately 0.3 mm thick. This is stored for 1 week at 20-25C with 65%
relative humidity, and after this time the sheet has absorbed 0.7 % by weight of water. No further water is absorbed on further storage under the stated conditions.
Examples 2 - 8 Using the method described in Example 1, further polyamides are produced from adipic acid and different diamines, and are subsequently processed into sheets. The il'~U19Z

reaction components and also the properties of the polyamides obtained are surnmarised in Table 1.
Example 9 9.54 g of diphenyl adipate and 10.0 g of 4,13-diamino-3,14-diethylhexadecane are sealed under nitrogen into a bomb tube, and pre-condensed at 220C for 4 hours.
The pre-condensate which has formed is then heated in a second reaction vessel for 2 hours at 260C under normal pressure and with the passing through of nitrogen.
For the purpose of effecting complete removal of the phenol which has been split off, the melt is maintained at 260C for a further 2 hours under a reduced pressure of 14 Torr. The melt on cooling solidifies to form a transparent substance. The polyamide obtained is then processed, in the manner described in Example 1, into the form of a sheet, the properties of which are given in Table 1.
Examples 10 - 14 In a manner analogous to that described in Example 9, further polyamides are produced from diphenyl adipate and different diamines, and these polyamides are processed into sheets. The reaction components and also the properties of the polyamides obtained are summarised in Table 1.
Example lS
A mixture of 5.00 g of l,10-diamino-1,10-dicyclo-hexyldecane and 3.022 g of sebacic acid are sealed under nitrogen into a bomb tube, and heated for 3 hours at 260C.
After cooling to room temperature, the pre-condensate is polycondensed in a condensing tube for 8 hours at 260C
whilst nitrogen is being passed through. The properties of the polyamide are listed in Table 1.

Example 16 Example 15 is repeated with the difference that, in place o~ l,10-diamino-1,10-dicyclohexyldecane, there is used an equivalent amount of 3,12-diamino-2,13-dimethyltetradecane. The properties are shown in Table 1.
Examples 17 - 18 Polyamides from equivalent amounts of dodecandioic acid (1 ? 12) and in each case a diamine are produced under the reaction conditions described in Example lS.
Composition and properties of the pol.yamides are summarised in Table 1.

11'~0192 ~ a~
~ O O O O O O O O O O O O O O O O O

'~

~ O Oo~ ~ O _ æ ~ O ~0 0 ~ ~ ~ O ~ ~ ~ ~ ~0 ,~0.

a ~n~ ~ _ O O .,, O , O O ~ O a~ ~o co _ o. . ~ Ir~

_ ~

¦ c o ~ c ~ c o o C ~D 8 ~ 8~ C C ~ ~ 8 _ C~ C a:l C _~ o ~I C~ 7 0 U~ O ~ L~ 0 0 0 0 ~ C~ ~ ~ O ~ ~ ._ ~ ~ G ~ G

~ _ _ ~ ~ ~ ~c ~

V ._ ~, o O O _ ~ O = O ._ 1~1 ~ ~0 ~ ~0 ~ ~ ~ ~ ~ ~0 ~0 ~ ~ 0~ ~ ~ O Cl _ ¦ O ~o O

C
N ~ O- O = ~ ~ ~ ~ _ 8 _ ~ _ ~ r~

.

0~92 The dlamines used in the above Examples can be pro-duced as f~llows:
a) 4,13-Diaminohexadecane 942 g ~3,79 mols) of 3,12-dlpropyl-1,2-dlaza-1,5,9-cyclododecatrlene ~diastereoisomerlc mlxture) is dissolved in 3800 ml of t-butanol ln an autoclave fltted with a stirrer. After the addition of 90 g of a rhodium~aluminlum oxide catalyst (5~ by weight of Rh), hydrogen is injected up to a pressure o 130-150 bars, and hydrogenation is per-formed at 150-180 C untll the absorption o~ hydrogen ls finished. After coollng, the e~ces~ hydrogen ls released, the suspenslon i8 drawn by suctlon out of the autoclave, and the catalyst ls flltered off with suction through a small amount of flltering auxlliary sold by ~ohns-Manville Sales Corp. ~U.S.~.) under the trademark "Hyflo".
The flltrate is concentrated ln a rotary evapora~or, ~nd the product is purifled by di~tillation~
There is obtained as the main fraction 462 g ~48~ of theory) of 4,13-diaminohexadecane as colourless oil ~b.p.
132-135 C/0.01 Torr; n20 ; 1.4590; IR (liquid) inter alia bands at 3278 and 1613 cm ).
b) 5,14-DiaminooctadeCane If there is used in the manner described under a), in-stead of 942 g ~3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatrlene, 208 g (0.75 mol) of 3,12-dibutyl-1,2-diaza-1,5,9-cyclododecatriene (diastereoisomeric mixture) and correspondingly reduced amounts of catalyst and solvent, the procedure otherwise being the same, there is obtained as the main fraction 132.8 g (62.3 % of theory) of 5,14-diaminooctadecane as colourless oil (b.p. 149 C/0.001 Torr;
nD = 1.4593~ I~ (liquid) inter alia bands at 3333, 3267 and 1613 cm ).

ll'~Ol9Z

c) 6~15-Diaminoeicosane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 220 g (0.71 mol) of 3,12-dipentyl-1,2-diazacyclododecane (diastereoisomeric mixture~ and correspondingly reduced amounts of catalyst and solvent, with otherwise the same procedure, there is obtained, as the main fraction, 136 g (61.3 % of theory) of 6,15-diaminoeicosane as colourless oil lb.p.
167-170C/0.001 Torr; n20 = 1.4603; IR (liquid) inter alia bands at 3378, 3289 and 1613 cm 1].
d) 7,16-Diaminodocosane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 190 g (0.56 mol) of 3,12-dihexyl-1,2-diazacyclododecane (diatereoisomeric mixture) and correspondingly reduced amounts of catalyst and solvent, with otherwise the same procedure, there is obtained as main fraction 130 g (68% of theory) of 7,16-diaminodocosane as colourless oil ~b.p. 184C/0.02 - 0.005 Torr; ~ = 1.4624;
IR (liquid) inter alia bands at 3355, 3278 and 1613 cm l.
e) 10~19-Diaminooctacosane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-l,S,9-cyclododecatriene, 100 g (0.24 mol) of crude 3,12-dinonyl-1,2-diaza-1,5,9-cyclododecatriene (diastereo-isomeric mixture) and correspondingly reduced amounts of catalyst and solvent, with otherwise the same procedure, there is obtained, as the main fraction, 40.4 g (40 %
of theory) of 10,19-diaminooctacosane [m.p. 33-37C;
IR (CH2C12) inter alia bands at 3225 and 1582 cm 1].

0~9Z

f) 12,21-Diaminodotrlacontane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 100 g (0.21 mol) of crude 3,12-diundecyl-1,2-diaza-1,5,9-cyclododecatriene (di-astereoisomeric mixture) and correspondingly reduced amounts of catalyst and solvent, with the procedure otherwise being the same~ there is obtained 64.3 g (64 % of theory) of 12,21-diaminodotriacontane [m.p.
45-46C; IR (CH2C12) inter alia bands at 3174 and 1582 cm ].
g) 3~12-Diamino-2~13-dimethyltetradecane If there are used in the manner described under a), intead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 250 g (1 mol) of 3,12-diiso-propyl-1,2-diaza-1,5,9-cyclododecatriene (diastereo-isomeric mixture) and correspondingly reduced amounts of catalyst and solvent, with the procedure otherwise being the same, there is obtained, as the main fraction, 238 g (92 % of theory) of 3,12-diamino-2,13-dimethyltetradecane as colourless oil [b.p. 106-109C/0.01 Torr; n20 = 1.4600;
IR (liquid) inter alia bands at 3355, 3278 and 1613 cm l.
h) 4~13-Diamino-3,14-diethylhexadecane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 49 g (0.159 mol) of 3,12-di-(3-pentyl)-1,3-diazacyclododecane and correspondingly reduced amounts of catalyst and solvent, there is obtained, after chromatographic purification and distillation, 26.8 g (54 % of theory) of 4,13-diamino-3,14-diethyl-hexadecane as colourless oil [b.p. 141-143C/0.004 Torr;
n20 = 1.4666; IR (liquid) inter alia bands at 3378, , 11'~0~9Z ' 3278 and 1613 cm 1].
i) l~10-Diamino-l,10-dicyclohexyldecane If there are used in the manner described ~Inder a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 328.5 g (1 mol) of 3,12-dicyclo-hexyl-1,2-diaza-1,5,9-cyclododecatriene (diastereoisomeric mixt~ure) and correspondingly reduced amounts of catalyst and solvent, using otherwise the same procedure, there is obtained, as the main fraction, 304 g (90 % of theory) of l,10-diamino-1,10-dicyclohexyldecane as colourless oil [b.p. 190-193C/0.05 Torr; n20 = 1.4944; IR (liquid) inter alia bands at 3355, 3278 and 1613 cm ~.
k) 6~15-Diamino-5~16-diethyleicosane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 74.8 g (0.2 mol) of 3,12-di-(3-heptyl)-1,2-diazacyclododecane (diastereoîsomeric mixture) and correspondingly reduced amounts of catalyst and solvent, using otherwise the same procedure, there is obtained, after chromatographic purification and distillation, 29.9 g (40 % of theory) of 6,15-diamino-

5,16-diethyleicosane as colourless oil [b.p. 170C/0.01 Torr; nD - 1.466 ; IR (liquid) inter alia bands at 3278 and 1613 cm l.
1) 4,13-Diamino-2~15-dimethYlhexadecane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 400 g (1.45 mols) of 3,12-diisobutyl-1,2-diaza-1,5,9-cyclododecatriene (diastereo-isomeric mixture) and correspondingly reduced amounts of .... . .. . . .

11'~0192 catalyst and solvent, with otherwise the same procedure,there is obtained, as the main fraction, 261 g (63 %
of theory) oE 4,13-diamino-2,15-dimethylhexadexane as colourless oil ~b.p. 168-172C/0.4 Torr; n20 = 1.4561;
IR (liquid) inter alia bands at 3289, 3205 and 1600 cm 1~.
m~ O-Diamino-l~lO-dicyclopentyldecane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 200 g (0.666 mol) of crude 3,12-dicyclopentyl-1,2-diaza-1,5,9-cyclododecatriene (diastereoisomeric mixture) and correspondingly reduced amounts of catalyst and solvent, with the procedure otherwise being the same, there is obtained, after chromatographic purification and distillation, 39.2 g (19 % of theory) of l,10-diamino-1,10-dicyclopentyldecane as colourless oil [b.p. 174-178C/0.002 Torr; nD = 1.4885;
IR (liquid) inter alia bands at 3355, 3278 and 1613 cm 1].
The 1,2-diaza-1,5,9-cyclododecatrienes and 1,2-diaza-cyclododecanes used as starting materials are produced by the processes described in the German Offenlegungs-schriften Nos. 2,330,097 and 2,549,403.
n) l,10-Diamino-l~10-dicycloheptyldecane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 106 g (0.3 mol) of 3,12-dicyclo-heptyl-1,2-diaza-1,5,9-cyclododecatriene (diastereo-isomeric mixture) and correspondingl~ reduced amounts of catalyst and solvent, with otherwise the same procedure, there is obtained, after chromatographic purification,and 63 g (58 % of theory) of l,10-diamino-1,10-dicycloheptyl-decane as colourless oil (nD`= 1.5018; IR (liquid) inter .. . .. . . . . . . .. ...

0 ~ 2 alia bands at 3390, 3310 and 3618 cm ].

o) l~10-Diamino-l,10-dicyclooctyldecane If there are used in the manner described under a), instead of 942 g (3.79 mols) of 3,12-dipropyl-1,2-diaza-1,5,9-cyclododecatriene, 65 g (0.168 mol) of 3,12-dicyclo-octyl-1,2-diazacyclododecane and correspondingly reduced amounts of catalyst and solvent, with otherwise the same procedure, there is obtained, after chromatographic purification, 43.6 g (66 % of theory) of l,10-diamino-l,10-dicyclooctyldecane as colouriess oil (n20 = 1.5050;
IR (liquid) inter alia bands at 3333, 3278 and 1613 cm 1).

Claims (11)

- 18 -

1. An aliphatic polyamide which has a reduced specific viscosity of at least 0.3 dl/g, measured on a 0.5% solution of m-cresol at 25° C, and which consists of identical or different recurring structural elements of the formula I

(I) in which R1 and R2 independently of one another are straight-chain or branched-chain alkyl having 3-20 C atoms, or cycloalkyl having 4-12 C atoms, and Z is an aliphatic aliphatic having at least 2 C atoms.

2. A polyamide according to Claim 1, in which R1 and R2 per recurring structural element of the formula I are each identical alkyl or cycloalkyl groups.

3. A polyamide according to Claim 1, in which Z is optionally branched-chain alkylene having 2-12 C atoms.

4. A polyamide according to Claim 1, in which Z is optionally branched-chain alkylene having 4-10 C atoms.

5. A polyamide according to Claim 1, in which R1 and R2 per recurring structural element of the formula I are each isopropyl, or straight-chain or branched-chain alkyl having 5-11 C atoms, or are each cycloalkyl having 5-8 C atoms, and Z is optionally branched-chain alkylene having 4-10 C atoms.

6. A polyamide according to Claim 1, in which R1 and R2 are each n-pentyl, 3-pentyl, n-hexyl, 3-heptyl or cyclohexyl, and Z is -(CH2)4-.

7. A transparent polyamide according to Claim 1, which consists of recurring structural elements of the formula IV

(IV), and which has a reduced specific viscosity (0.5% in m-cre-sol at 25° C) preferably of about 1.1 dl/g.

8. A transparent polyamide according to Claim 1, which consists of recurring structural elements of the formula V

(V), and which has a reduced specific viscosity (0.5 % in m-cre-sol at 25° C) preferably of about 0.75 dl/g.

9. A partially crystalline polyamide according to Claim 1, which consists of recurring structural elements of the formula VI

(VI), and which has a reduced specific viscosity (0.5% in m-cre-sol at 25° C) preferably of about 0.6 dl/g.

10. A transparent polyamide according to Claim 1, which consists of recurring structural elements of the formula VII

(VII), and which has a reduced specific viscosity (0.5% in m-cre-sol at 25° C) preferably of about 0.7 dl/g.

11. A process for producing a polyamide according to Claim 1, which process comprises reacting a diamine of the formula II

(II) with a dicarboxylic acid of the formula III

HOOC-Z-COOH (III), or with an amide-forming derivative thereof, wherein R1, R2 and Z have the meanings given under the formula I.