GB2194540A

GB2194540A - Impact-resistant polyamide alloys

Info

Publication number: GB2194540A
Application number: GB08720043A
Authority: GB
Inventors: Torre Hans Dalla; Manfred Hoppe
Original assignee: EMS Inventa AG; Inventa AG fuer Forschung und Patentverwertung
Current assignee: Inventa AG fuer Forschung und Patentverwertung; Uhde Inventa Fischer AG
Priority date: 1986-08-26
Filing date: 1987-08-25
Publication date: 1988-03-09
Anticipated expiration: 2007-08-25
Also published as: DE3728334A1; JP2559759B2; FR2603293B1; FR2635329B1; IT1211738B; JPH0641296A; FR2603293A1; JPS6361040A; GB2194540B; FR2635329A1; IT8748327A0; DE3728334C2; CH671022A5; GB8720043D0

Description

GB2194540A 1

SPECIFICATION

Impact-resistant polyamide alloys FIELD OF THE INVENTION 5

The invention relates to thermoplastic mouldable, impact-resistant polyamide alloys comprising copolyamides. It relates in particular to low-viscosity polyamide alloys which are readily pro cessed in injection moulding or extrusion apparatus.

BACKGROUND OF THE INVENTION 10

US-A-2696482 describes an amorphous polyamide derived from bis(4aminocyclohexyl)meth- ane and isophthalic acid, which is unsuitable for processing in, for example, injection moulding because its viscosity is too high.

DE-B-1795464 discloses a process for the preparation of amorphous copolyamides from combinations of alkyl-group-substituted hexamethylenediamines, isophthalic acid and terephthalic 15 acid. These products also have viscosities so high that they are difficult to work.

US-A-3597400 describes an amorphous copolyamide derived from bis(4aminocyclohexyl)meth- ane, hexamethylenedia mines, isophthalic acid and terephthalic acid, in which the compositions having high proportions of bis(4-aminocyclohexyl)methane clearly exhibit high melt viscosities and therefore lend themselves poorly to processing, e.g. by injection moulding; however, even at low 20 diamine concentrations, viscosities are still sufficiently high that the preparation of large moulded parts is difficult.

According to US-A-4369305, viscosities below 30,000 poise at 280'C and at a shear value of 101 dyn/CM2, are obtained if a copolyamide composition contains particular proportions of iso- and terephthalic acids, very low proportions of bis(4- aminocyclohexyl)methane and this in a 25 particular mixture of isomers, viz. at least 59% by weight trans/trans or cis/trans isomers.

It may be deduced that bis(4-aminocyclohexyl)methane is responsible for the high viscosities and the highly viscous properties which are observed.

US-A-4536541 describes an amorphous copolyamide which again includes a low amount of bis (4-aminocyclohexl)methane isomers and is modified for impact- resistance with a particular 30 ethylene/ propylene/diene copolymer (EPDM) activated with succinic acid.

It is known that if impact-resistant modifiers of this type are worked into polyamides, they considerably increase the melt viscosity (US-A-4174538, DE-B-1242606), so that the processing of such polyamides is again made more difficult. By contrast, a reduction of the amount of bis(4 a minocyclohexyl) methane in the amorphous copolyamide has the effects of reducing the heat 35 distortion temperature and of a deterioration of certain mechanical properties, e.g. impact and tensile strengths.

GB-A-0998439 describes the introduction of modified polyolefines and polyacrylates into linear partial ly-crystalli ne polyamides, for improving impact resistance; impact resistance modification using particular reactive copolyolefines is described in detail in DE-A- 2722270 for the polyam- 40 ides PA 6 and PA 66. However, partially-crystalline polyamides have a very low melt viscosity; the increase in viscosity due to the modification causes no problems on processing thermoplas tic compositions of this type.

US-A-4339555 describes the modification of homopolyamides with particular copolyolefines which contain in addition urea derivatives, for the improvement of the melt and to facilitate 45 removal from a mould.

GB-A-2170209 discloses a transparent copolyamide derived from a dicarboxylic acid such as isophthalic acid and a diamine component partially or wholly constituted by bis (4-amino-3,5 diethylcyclohexyl)-methane as well as other polyamide-forming components. British Patent Appli cation No. 8629928 (Serial No.) discloses a similar product, but in which the principal 50 diamine is bis(4-amino-3-ethyl-5-methy[cyclohexyl)methane.

OBJECT OF THE INVENTION The invention has the object of overcoming the given disadvantages for polyamide and copoly- amide alloys, and to find particular read ily-workable, low viscosity alloys having good properties 55 in use.

SUMMARY OF THE INVENTION

Thermoplastic mouldable, impact-resistant polyamide alloys, according to the invention, com- prise 60 a) at least 20% by weight of an amorphous copolyamide derived from an optionally alkyl substituted hexamethylenediamine, a bis(4-aminocyclohexyl)C,-4 alkane substituted adjacent to the amino groups, and a dicarboxylic acid, and b) up to 80% by weight of a modified copolyolefine.

2 GB2194540A 2 DESCRIPTION OF THE INVENTION

Unexpectedly, it has been shown that hexamethylenediamine and isophthalic acid andlor deri- vatives thereof with, optionally, terephthalic acid, or an aliphatic dicarboxylic acid give readily workable amorphous copolyamides, if an additional amine component is used which is not bis(4 aminocyclohexyi)methane but rather a homologue thereof, substituted immediately adjacent to the 5 amino -groups, in the 3- and/or 5- position. The amino groups of such diamines are sterically influenced by the substituents; this factor, and the choice of a suitable mixture of isomers, allow the viscosity of the copolyamide to be satisfactorily regulated. Desirably influencing the viscosity in this way, by the introduction of particular substituents and isomer mixtures, was not predicta ble. Many of the amorphous copolyamides of this type are novel. 10 It has also been found that the combination of such copolyamides with modified copolyo- lefines, e.g. ehthylene/propylene and/or ethylene/ 1 -butene copolymerisates or mixtures thereof, gives readily-workable impact-resistant alloys which, owing to their readily-controllable viscosi ties, allow the preparation of moulded bodies having large surface area, e.g. in injection-moulding processes, and also of extremely thin-walled articles by extrusion processes. 15 Another theory has been that the weight proportion of terephthalic acid can decisively influ- ence the viscosity of the alloys according to the invention.

Cycloaliphatic amines which can be used in the invention are diamines such as, e.g.

bis(4-amino-3-methyi-5-ethylcyclohexyi) methane, bis(4-amino-3,5-diethylcyclohexyi)methane, 20 bis(4-amino-3-methyi-5-isopropylcyclohexyi) methane, bis(4-amino-3,5-diisopropylcyclohexyi)methane, bis(4-amino-3,5-dimethylcyclohexyi)methane, bis(4-amino-3-methylcyclohexyi)methane, bis(4-amino-3-ethylcyclohexyi)methane, and 25 bis (4-amino-3-isopropylcyclohexyl) methane.

Other diamines may be used, e.g. diamines having further alkyl substituents on the cyclohex- ane rings or in which, if desired, the -CH,group between the cyclohexane rings is replaced by a C,-, alkylene chain such as ethylene, propylene, isopropylene or butylene. In general, it is preferred that the alkyl groups on the cyclohexane rings have 1 to 8, more preferably 1 to 4, 30 and more preferably 1 to 3, carbon atoms. It is especially preferred that these alkyl groups should comprise a combination of methyl with ethyl or isopropyl groups. If appropriate, mixtures of diamines, and various isomeric mixtures of particular diamines may be used.

The use of such diamines not only reduces the viscosity of the copolyamide and of the copolyamide alloy, but also gives further advantages, i.e. (a) greatly increased shaped retention 35 of the moulded compositions on heating, owing to considerably higher glass transition tempera tures, (b) increased stiffness, also in the conditioned state, (c) improved cold impact resistance, (d) reduced water uptake and (e) higher heat distortion temperature. Further, the polyamide alloys according to the invention exhibit a particularly low permeability to oxygen.

The content of the diamine in the copolyamide which is used is varied in order to obtain a 40 particular desired viscosity, but should be at least 2% by weight of the total diamine content. In similar manner, the viscosity of the polymer increases with increasing amounts of terephthalic acid, whose effective upper limit is 10% by weight.

The copolyamide is preferably derived from 20 to 48 (more preferably 25 to 45) mol % of the hexamethylene-diamene, 2 to 30 (more preferably 5 to 25) mol % of the substituted cycloalipha- 45 tic diamine, and 50% acid, e.g. 40 to 50 mol % isophthalic acid and 0 to 10 mol % terephthalic acid. In practice, there may be a small excess of diamine with respect to acid.

The modified copolyolefine provide improved impact resistance in the polyamide alloys accord- ing to the -invention. The copolyolefine preferably comprises a copolymer of ethylene with a C3-W ethylenically-unsaturatect a-olefine, more preferably ethylene/ 1 -butene, and/or a copolymer of 50 ethylene with a higher (3-16) homologue, more preferably ethylene/propylene; each copolymer is usually grafted with 0.05 to 1.0% by weight maleic acid anhydride or another ethylenically unsaturated dicarboxylic acid, or an anhydride thereof. The copolyolefine is used in an amount of up to 80% by weight of the novel composition, the minimum amount being 0. 01, 0.1 or, preferably, 2% by weight. 55 The polyamide alloys according to the invention can contain further components such as fillers, reinforcing agents, pigments, dyes, heat stabilisers, anti-oxidants, UV protective agents, plasticis ers and nucleation agents. They can also be alloyed or mixed with further polyarnides or foreign polymers.

The novel polyamide alloys can be moulded to give articles which are particularly suitable for 60 processing in-extrusion and injection moulding machines, inter alia for the preparation of large surface area or large volume moulded parts, such as are used in, for example, vehicle bodies or as machine covers or as protective parts. They can also be used for the preparation of dimensionally stable apparatus components, and for the preparation of wire and lightwave guide claddings and other moulded parts having very low wall thickness and cross-sectional dimen- 65 3 GB2194540A 3 sions.

The polyamide alloys according to the invention and their preparation will now be illustrated in the following Examples 1 to 5. Examples 6 to 9 are comparative; reference may be made to US A-4369305 and US-A-4536541. The comparative Examples show that the use of non-substi tuted bis(4-aminocyclohexyl) methane gives very high, poorly-controllable melt viscosities, so that 5 it is almost impossible to process the alloys in injection moulding procedures.

For the products of the Examples, solution viscosities were measured as a 0.5% w/v solution in m-cresol, melt viscosities were measured at 270"C/122.6 N. TG=glass transition point.

Example 1 10

376.5 g isophthalic acid (47.7 mol %), 395.5 g of a 60% aqueous hexamethylenediamine solution (43.0 mol %), 118.0 bis(4-amino-3,5-diethylcyclohexyl)methane (7. 8 mol %) and 8.7 g benzoic acid (1.5 mol %) were weighed into a reaction vessel, at 180"C, and then heated for 1 hour at 250'C with stirring, under a nitrogen screen. The water of reaction (c. 182.0 ml) obtained in polycondensation was separated and collected, and the temperature was then main- 15 tained at 285'C for about 4.5 hours.

The resultant polymer was completely transparent, had a solution viscosity of 1.529 and a melt viscosity of 912 Pa.s. TG was 138C.

The polymer thus prepared was mixed with 20% by weight of an ethylene/propylene-ethy- lene/1-butene copolymerisate mixture grafted with maleic acid anhydride (melting point 49C or 20 700C) and extruded in a laboratory extruder, type Netsal 5730/N 110, at a mass temperature of about 2600C.

The polymer strand was cooled in water, granulated and dried. TG was then 138"C and the melt viscosity 1342 Pa.s (270OC/122.6 N).

25 Example 2

357.3 g isophthalic acid (42.6 mol %), 66.8 g tertbutylisophthalic acid (6.4 mol %), 15.0 g benzoic acid (2.4 mol %), 40.0 g terephthalic acid (4.8 mol %), 102.0 g bis(4-amino-3-methyl-5 ethylcyclohexyl) methane. (6.9 mol %) and 254.0 g hexamethylenediamine (43.3 mol %) were introduced into a reaction vessel and gradually heated to 180'C with stirring, under a nitrogen 30 screen. After separating the water of reaction, the reaction mixture was heated to 285'C for 3 hours and cooled.

The glass-clear polycondensation product had a solution viscosity qrel=1. 628 and a melt viscosity of 1212 Pa.s. TG was 152'C.

After co-extrusion with 20% by weight of the modified copolyolefine mixture described in 35 Example 1, the viscosity rose to 1520 Pa.s. TG was still 152C.

A test body prepared therefrom had a water uptake of only 2. 1 % after storage in water at 25'C for 3 months.

Example 3 40

273.0 g isophthalic acid (39.9 mol %), 85.0 g dodecanedicarboxylic acid (8.9 mol %), 125.0 g hexamethylenediamine (26.1 mol %) and 333.0 g bis(4-amino-3,5- diethylcyclohexyl) methane (25.1 mol %) were polycondensed at 2850C.

The relative solutiop viscosity of the transparent polycondensate was 1. 504, the melt viscosity was 680 Pa.s, and TG was 165C. 45 After extrusion with 20% by weight of an ethylene/propylene/1-butene polyolefine mixture grafted with maleic acid anhydride, the viscosity of the alloy was 836 Pa. s, and TG was 159'C.

Example 4

21.3 kg isophthalic acid (42.42 mol %), 3.4 kg terephthalic acid (6.86 mol %), 26.15 kg of a 50 60.4% aqueous hexamethylenediamine solutuion (45 mol %), 3.58 kg bis(4- amino-3-methylcyclo hexyl)methane (4.97 mol %), 400 g stearic acid (0.74 mol %) and 5 1 water were heated in a 1 aut oclave with stirring to 260'C. After releasing pressure in the autoclave, the content was polycondensed under nitrogen at 290'C, the polycondensate was taken off as a strand through a water bath, and granulated. 55 The glass-clear granulate had a solution viscosity of 1.589, a melt viscosity of 1158 Pa.s and TG of 143'C.

Test bodies prepared therefrom exhibited an impact resistance according to DIN 53453 of no break, and a notched impact resistance of 1.9 U/M2. The bending E modulus according to DIN 53452 was 2754 N/mm2 and the flexural strength at break 153 N/MM2. The water' uptake was 60 29% after-30 days storage in water at 250C.

The amorphous copolyamide was mixed with 20% by weight of the copolyolefine mixture given in Example 3, extruded and comminuted. The melt viscosity of the granulate was 1410 Pa.s and TG was 142'C.

Test bodies prepared from the granulate exhibited an impact resistance of no break according 65 4 GB2194540A 4 to DIN 53453 and a notched impact resistance of 44.0 U/M2 at 2WC and 16 Uftn2 at -40'C, a bending E modulus of 1911 N/mm2 (dry) and 1903 N/MM2 (conditioned) according to DIN 43457, a tensile strength at break (dry) of 58.7 N/MM2 and an elongation at break of 150%.

The water uptake was only 2.5% after 30 days storage in water at 2WC.

5 Example 5

2.8 kg isophthalic acid (41.1 mol %), 0.52 kg terephthalic acid (7.4 mol %), 2.07 kg hexamethylenediamine (43.4 mol %), 0.83 kg (7.1 mol %) bis(4-amino-3,5- diethylcyclohexyi)- methane and 50 9 (1 mol %) benzoic acid were polycondensed in a 20 1 autoclave at 28WC.

The resultant polycondensate had a solution viscosity of 1.574, a melt viscosity of 840 Pa.s 10 and TG of 140'C.

Text bodies prepared therefrom exhibited an impact resistance of no break and notched impact resistance of 2.3 U/m2 (DIN 53453), as well as a bending E modulus of 3080 N/MM2 (dry) and of 2334 N/MM2 (conditioned) according to DIN 53457.

After compounding with 12% by weight of the copolyolefine mixture described in Examples 3 15 and 4, test bodies prepared from the composition were measured to have an impact resistance of no break, a notched impact resistance at 2WC of 30.5 W/m2 (dry) and at -400C of 12 U/M2, a bending E modulus of 2360 M/mm2 (dry) and 2400 N/mM2 (conditioned), and a flexural strength at break of 100 N/MM2.

20 Example 6 (Comparative) Bis(4-a m inocyclohexyl) methane having an isomeric distribution of 36% by weight trans/trans, 45% by weight cis/trans and 9% by weight cis/cis was used.

15.0 kg isophthalic acid (44.14 mol %), 1.60 kg terephthalic acid (4.7 mol %) 10.3 kg hexamethylenediamine (43.3 mol %), 3 kg bis (4-aminocyclohexyl) methane (6.97 mol %) and 0.22 25 kg benzoic acid (0.89 mol %) were polycondensed in a 20 1 autoclave at 28WC. The copolyam ide was drawn off as a transparent strand and granulated.

The copolyamide had a solution viscosity of 1.539 and a high melt viscosity of 2974 Pa.s. TG was 13WC.

Test bodies exhibited a flexural strength of 165 N/mM2, an impact resistance of no break 30 (60%) and 53 U/M2 (40%), a notched impact resistance of 1.6 U/m2, a bending E modulus of 3100 N/mM2 and a tensile strength at break of 102 N/MM2 (50%) and 70 N/Mm2 (50%).

After co-extrusion with 20% by weight of the modified copolyolefine mixture described in Example 3, the viscosity rose to 5200 Pa.s. At this melt viscosity value, test bodies could not be prepared without problems, and only with great difficulty. 35 TG was 130'C. The flexural strength break was 95 N/mm2, the impact resistance test gave no break, notched impact resistance was 45.9 U/M2, the bending E modulus was 2140 N/mM2 and the tensile strength at break 57 N/mrn'.

Example 7 (Comparative) 40 Bis(4-aminocyclohexyl)rnethane having an isomeric distribution of 54% by weight trans/trans, 40% by weight cis/trans and 6% by weight cis/cis was used.

2.98 kg isophthalic acid (44.0 mol %), 0.34% by weight terephthalic acid (5.0 mol %), 2,07 kg hexamethylenediamine (43.7 mol %), 0.55 kg (6.5 mol %) bis(4- aminocyclohexyi) methane and 40 g benzoic acid (0.8 mol %) were polycondensed in a 20 1 autoclave to give a transparent 45 copolyamide.

The viscosity rose extremely quickly and the autoclave could only be emptied with difficulty.

The relative solution viscosity was 1.68 and the melt viscosity 7640 Pa.s.

After extrusion with 20% by weight of the copolyolefine mixture described in Example 3, a highly viscous polymer alloy was obtained, whose melt viscosity was greater than 10,000 Pa.s. 50 No useful injection moulded bodies could be prepared, because they could not fill the mould.

Example 8 (Comparative) 2.905 kg isophthalic acid (135 mol %), 1.240 kg terephthalic acid (15 mol %), 2.800 kg (48 mol %) hexamethylenediamine, 0.220 kg (2 mol %) bis(4- aminocyclohexyi)methane and 0.005 kg 55 (0.03 mol %) stearic acid were polycondensed in a 20 1 autoclave at 28WC.

The resultant polycondensate had a solution capacity of 1.512, a melt viscosity of 3240 Pa.s and TG of 126'C.

Particularly by contrast with the analogous procedure of Example 5, no test bodies could be produced. The viscosity was such that they could not be alloyed. 60 Example 9 (Comparative) 4.780 kg (42 mol %) isophthalic acid, 0.910 kg (8 mol %) terephthalic acid, 3.600 kg (45 mol %) hexamethylenediamine, 0.720 kg (5 mol %) bis(4-aminocyclohexyi)methane and 0.030 kg (0.15 mol %) stearic acid were polycondensed in a 20 1 autoclave at 280'C. 65 GB2194540A 5 The resultant polycondensate had a solution viscosity of 1.47, a melt viscosity of 2900 Pa.s and TG of 133'C.

Particularly by contrast with the analogous procedure of Example 5, no test bodies could be produced. The viscosity was such that they could not be alloyed.

5

Claims

1. A thermoplastic mouldable, impact-resistant polyamide alloy, which comprises a) at least 20% by weight of an amorphous copolyamide derived from an optionally alkyl substituted hexamethylenediamine, a bis(4-aminocyclohexyl) C,-, alkane substituted adjacent to the amino groups, and a dicarboxylic acid, and 10 b) a modified copolyolefine, in an amount of up to 80% by weight.

2. An alloy according to claim 1, wherein each cyclohexyl group has an alkyl substituent in the 3- and/or 5-positions and optionally also at further positions.

3. An alloy according to claim 2, wherein the or each alkyl substituent has 1 to

4 carbon atoms. 15 4. An alloy according to claim 3, wherein the alkyl substituents comprise a combination of methyl with ethyl or isopropyl groups.

5. An alloy according to any preceding claim, wherein the p roportion of the substituted bis(4- aminocyclohexyl)alkane diamine content of the copolyamide is at least 2% by weight.

6. An alloy according to any preceding claim, wherein the dicarboxylic acid comprises iso- 20 phthalic acid and/or a derivative thereof and, optionally, terephthalic acid, the amount of tere phthalic acid in the amorphous copolyamide being from 0 to 10 mol %.

7. An alloy according to any preceding claim, wherein the modified copolyolefine is a co- polymer of ethylene with a C,_1, a-olefine and/or copolymer of ethylene with a C3-16 homologue, each copolymer being grafted with an ethylenically-unsaturated dicarboxylic acid or anhydride 25 thereof.

8. An alloy according to claim 7, wherein the copolymer is of ethylene with 1-butene and of ethylene with propylene.

9. An alloy according to any preceding claim, wherein the copolyamide is derived from 20 to 48 mol % of the hexamethylenediamine, 2 to 30 mol % of the substituted cycloaliphatic 30 diamine, and 50 mol % of the acid.

10. An alloy according to any preceding claim, which comprises 20 to 98% by weight of the copolyamide and 2 to 80 % by weight of the copolyolefine.

11. An alloy according to claim 1, substantially as exemplified herein.

12. An article manufactured from an alloy according to any preceding claim. 35 Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.