GB2218105A

GB2218105A - Polyamide

Info

Publication number: GB2218105A
Application number: GB8915343A
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: 1989-07-04
Publication date: 1989-11-08
Anticipated expiration: 2007-08-25
Also published as: GB2218105B; GB8915343D0

Abstract

An amorphous copolyamide is derived from an optionally alkyl-substituted hexamethylenediamine, a bis (4-aminocyclohexyl) C1-4 alkane substituted adjacent to the amino groups, and a dicarboxylic acid.

Description

IMPACT-PESISTANT POLY'IDE ALLOYS FIELD OF THE INVENTION The invention relates to thermoplastic mouldable, impact-resistant polyamide alloys comprising copolyamides. It relates in particular to low-viscosity polyamide alloys which are readily processed in injection moulding or extrusion apparatus.

BACKGROUND OF THE INTENTION US-A-2696482 describes an amorphous polyamide derived from bis(4-aminocyclohexyl)methane 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 acid. These products also have viscosities so high that they are difficult to work.

US-A-3597400 describes an amorphous copolyamide derived from bis (4-aminocyclohexyl)methane, hexamethylenediamines, 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 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 2800C and at a shear value of 105 dy-n/cm-, 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 particular mixture 0 isomers, viz. at least 5 b" weight trans /trans or cs,rans Se It may be educed that bis(4-aminocyclohex=')met;-iane 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-aminocyclohexyl)methane isomers and is modified for impactresistance with a particular ethylene/propylene/diene copolymer (EPDM.) activated with succ nic 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-aminocyclohexyl)methane in the amorphous copolyamide has the effects of reducing the heat 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 partially-crystalline polyamides, for improving impact resistance; impact resistance modification using particular reactive copolyolefines is described in detail in DE-A-2722270 for the polyamides 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 thermoplastic compositions of this type.

US-A-4339555 describes the modification of homopolyamides with particular copolyolefines which contain in addition urea derivatives, for the improveet of the melt and to facilitate 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 constitted by bis (4-amino-3,5-diethylcyclohexyl) -methane as w=- other Folyamide-forming components. British Patent Application No. 8629928 (Serial No. ) discloses a similar product, but in which the principal diamine is bis (4-amino-3-ethyl-5-methylcyclohexyl)methane.

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

SUMMARY OF THE INVENTION Thermoplastic mouldable, impact-resistant polyamide alloys, according to the invention, comprise 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 b) up to 80% by weight of a modified copolyolefine.

DESCRIPTION OF THE INVENTION Unexpectedly, it has been shown that hexamethylenediamine and isophthalic acid and/or derivatives 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-aminocyclohexyl)methane but rather a homologue thereof, substituted immediately adjacent to the amino groups, in the 3- and/or 5 posltion. The amino groups of such diamines are sterically influenced by the substituents; this factor, anc 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 predictable.Many of the amorthous copolya:rie o this type are cel.

It has also been found that the combination ol such copolyamides with modified copolyolefines, e.g.

ethylene/propylene and/or ethylene/l-butene copolymerisates or mixtures thereof, gives readily-workable impact-resistant alloys which, owing to their readily-controllable viscosities, 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.

Another theory has been that the weight proportion of terephthalic acid can decisively influence 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-methyl-5-ethylcyclohexyl) methane, bis(4-amino-3,5- iethylcyclohexyl)methane, bis (4-amino-3-methyl-5-isopropylcyclohexyl)methane, bis (4-amino-3 ,S-diisopropylcyclohexyl)methane, bis (4-amino-3 , 5-dimethylcyclohexyl) methane, bis(4-amino-3-methylcyclohexyl)methane, bis(4-amino-3-ethylcyclohexyl)methane, and bis (4-amino-3-isopropylcyclohexyl)methane.

Other diamines may be used, e.g. diamines having further alkyl substituents on the cyclohexane rings or in which, if desired, the -CH2- group between the cyclohexane rings is replaced by a C 2-4 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, 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 varous somerlc m tllres c; cf particular cia.;ir.es ma :na UStl.

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 shape retention of the moulded compositions on heating, owing to considerably higher glass transition temperatures, (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 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 hexamethylenediamine, 2 to 30 (more preferably 5 to 25) mol % of the substituted cycloaliphatic diamine, and 50 mol % 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 according to the invention. The copolyolefine preferably comprises a copolymer of ethylene with a C 3-16 ethylenicallyunsaturated a-olefine, more preferably ethylene/1-butene, and/or a copolymer of ethylene with a higher (C316) homologue, more preferably ethylene/propylene; each copolymer is usually grafted with 0.05 to 1.0% by weight maleic acid anhydride or another ethylenlcally- unsaturated dicarboxylic acid, or an anhydride threof.

The copolyolefine is used in an amount of up to 6 by weight of the novel composition, the minimum amount being 0.01, 0.1 or, preferably, 2% by weight.

The polyamide alloys according to the invention can contain further components such as fillers, reinforcing agents, pigments, dyes, heat stabilisers, anti-oxidants, W protective agents, plasticisers and nucleation agents.

They can also be alloyed or mixed with further polyamides or foreign polymers.

The novel polyamide alloys can be moulded to give articles which are particularly suitable for 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 dimensions.

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-substituted bis (4-aminocyclohexyl)methane gives very high, poorly-controllable melt viscosities, so that 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 2700C/122.6 N. TG = glass transition point.

Example 1 3.5 c wscht.a~;c acid (4. .w- ^E !, 393.5 G a 603 aqueous hexamethylenediamine solution (43.C 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 1800C, and then heated for 1 hour at 2500C 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 maintained at 2850C 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 1380C.

The polymer thus prepared was mixed with 20% by weight of an ethylene/propylene-ethylene/1-butene copolymerisate mixture grafted with maleic acid anhydride (melting point 490C or 700C) and extruded in a laboratory extruder, type Netstal 5730/N 110, at a mass temperature of about 2600C.

The polymer strand was cooled in water, granulated and dried. TG was then 1380C and the melt viscosity 1342 Pa.s (27000/122.6 N).

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 1800C with stirring, under a nitrogen screen. After separating the water of reaction, the reaction mixture was heated to 2850C for 3 hours and cooled.

The glass-clear polycondensation product had a solution viscosity #rel = 1.628 and a melt viscosity of 1212 Pa.s. TG was 15200.

After co-extrusicn with 205 by weight of the modified copolyolefine mixture described in Example 1, the viscosity rose to 1520 Pa.s. TG was still 152 C.

A test body prepared therefrom had a water uptake of only 2.1% after storage in water at 250C for 3 months.

Example 3 273.0 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 solution viscosity of the transparent polycondensate was 1.504, the melt viscosity was 680 Pa.s, and TG was 1650C.

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 1590C.

Example 4 21.3 kg isophthalic acid (42.42 mol %), 3.4 kg terephthalic acid (6.86 mol %), 26.15 kg of a 60.4% aqueous hexamethylenediamine solution (45 mol %), 3.58 kg bis(4-amino-3-methylcyclohexyl)methane (4.97 mol %), 400 g stearic acid (0.74 mol %) and 5 1 water were heated in a 150 1 autoclave with stirring to 2600C. After releasing pressure in the autoclave, the content was polycondensed under nitrogen at 2900C, the polycondensate was taken off as a strand through a water bath, and granulated.

The glass-clear granulate had a solution viscosity of 1.589, a melt viscosity of 1158 Pa.s and TG of 1430C.

Test bodies prepared therefrom exhibited an impact resistance according to DIN 53453 of no break, and a notched impact resistance of 1.9 kJ/m2. The bending E modulus according to DIN 53452 was 2754 N/mm2 and the pleura: strength at break 153 N/mm. . The water uptake s--s 29% aLter 300 as storage in water at 25C.

The amorphous copolyamide was mixed with 20w 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 1420C.

Test bodies prepared from the granulate exhibited an impact resistance of no break according to DIN 53453 and 2 a notched impact resistance of 44.0 kJ/m2 at 230C and 16 kJ/m at -40 C, a bending E modulus of 1911 N/mm (dry) and 1903 N/mm (conditioned) according to DIN 43457, a tensile strength at break (dry) of 58.7 N/mm and an elongation at break of 150%. The water uptake was only 2.5% after 30 days storage in water at 250C.

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 t), 0.83 kg (7.1 mol t ) bis(4-amino-3,5-diethylcticlohexJl)methane and 50 g (1 mol %) benzoic acid were polycondensed in a 20 1 autoclave at 2850C.

The resultant polycondensate had a solution viscosity of 1.574, a melt viscosity of 840 Pa.s and TG of 1400C.

Text bodies prepared therefrom exhibited an impact resistance of no break and a notched impact resistance of 2.3 kJ/m (DIN 53453), as well as a bending E modulus of 3080 N/mm2 (dry) and of 2334 N/mm (conditioned) according to DIN 53457.

After compounding with 12% by weight of the copolyolefine mixture described in Examples 3 and 4, test bodies prepared from the composition were measured to have an impact resistance of no break, a notched impact resistance at 230C of 30.5 kJ/m2 (dry) and at -40 C of 12 kJ/m2, a bending E modulus of 2360 M/mm2 (dry) and 2420 N/mm (conditioned) , and a f'exurai strength at break of Example 6 (Comparative) Bis (4-aminocyclohexyl) 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 kg benzoic acid (0.89 mcl i) were polycondensed in a 20 1 autoclave at 2800C. The copolyamide 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 135 C.

Test bodies exhibited a flexural strength of 165 N/mm, an an impact resistance of no break (60%) and 53 kJ/m2 (40%), a notched impact resistance of 1.6 kJ/m21 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.

TG was 1300C. The flexural strength break was 95 N/mm , the impact resistance test gave no break, notched impact resistance was 45.9 kJ/m , the bending E modulus was 2140 N/mm and the tensile strength at break 57 N/mm .

Example 7 (Comparative) Bis (4-aminocyclohexyl)methane 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 mcl %), 0.349 b weight terephthallc acid (5.0 ol Y), 2.G kg heya- methylenediamine (43.7 mol %), 0.55 kg (6.5 mol t) bis (4-aminocyclohexyl)methane and 40 g benzoic acid (0.8 mol %) were polycondensed in a 20 1 autoclave to give a transparent 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. No useful injection moulded bodies could be prepared, because they could not fill the mould.

Example 8 (Comparative) 2.905 kg isophthalic acid (35 mol %), 1.240 kg terephthalic acid (15 mol %), 2.800 kg (48 mol %) hexamethylenediamine, 0.220 kg (2 mol %) bis(4-aminocyclohe:cyl)methane and 0.005 kg (0.03 mol %) stearic acid were polycondensed in a 20 1 autoclave at 2800C.

The resultant polycondensate had a solution capacity of 1.512, a melt viscosity of 3240 Pa.s and TG of 1260C.

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.

Example 9 (Comparative) 4.780 kg (42 mol %) isophthalic acid, 0.910 kg (8 mol t) terephthalic acid, 3.600 kg (45 mol %) hexamethylenediamine, 0.720 kg (5 mol %) bis(4-aminocyclohexyl)methane and 0.030 kg (0.15 mol %) stearic acid were polycondensed in a 20 1 autoclave at 2800C.

The resultant polycondensate had a scluticn viscosity of 1.47, a melt viscosity o' 2900 Pa.s and TG of 1330C.

The viscosity was such that they could not be alloyed.

Claims

1. An amorphous ccpolaride derIved fr an optionally rn alkyl-substituted he-amethylenediamine1 G bis(4-aminocyclohexyl)-C1 alkane substituted adjacent to the amino groups, and a dicarboxylic acid.

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

3. A copolyamide according te claim 2, wherein the or each alkyl substituent has 1 to 4 carbon atoms.

4. A copolyamide according to claim 3, wherein the alkyl substituents comprise a combination of methyl ethyl or isopropyl groups.

5. A copolyamide according to any preceding claim, comprising at least 2% by weight of the substituted bis (4-aminocyclohexyl) alkane.

6. A copolyamide according to any preceding claim, wherein the dicarboxylic acid comprises isophthalic acid and/or a derivative thereof and, optionally, terephthalic acid, the amount of terephthalic acid in the amorphous copolyamide being from 0 to 10 mol %.

7. A copolyamide according to any preceding claim, which is derived from 20 to 48 mol % of the hexamethylenediamine, 2 to 30 mol % of the bis(4-aminocyclohexyl)alkane, and 50 mol % of the dicarboxylic acid.

8. A copolyamide according to claim 1, substantially as exemplified herein.