IE45632B1 - Copolyamides based on hexamethyleneadipamide - Google Patents

Abstract

1533230 Copolyamides RHONE POULENC INDUSTRIES 27 June 1977 [28 June 1976] 26847/77 Heading C3R Copolyamides are derived from hexamethylene diamine and the following molar percentages of acid or ester: (a) 50 to 90% adipic, (b) 2 to 40% hexahydroterephthalic and (c) 40 to 2% terephthalic. They may be processed similarly to nylon 66 but have a higher Tg, lower moisture absorption and better dimensional stability and their mechanical properties are less affected by humidity.

Description

The present invention relates to copolyamides having improved dimensional stability to heat and to humidity and an increased Young's modulus.

Linear polyamides of high molecular weight possess 5 numerous physical and chemical properties which make them suitable for the production of a variety of shaped articles, such as fibres, films and moulded objects. Polyhexamethyleneadipamides have thus undergone a very important development.

However, these polymers also exhibit a certain number 10 of disadvantages, the seriousness of which depends on the intended use. Examples of such disadvantages are: a not inconsiderable shrinkage on moulding, a significant water absorption and, correspondingly, an insufficient dimensional stability to humidity and mechanical properties which are affected by the ambient humidity, and a sharp drop in the modulus at temperatures in the region of 25O°C.

Many patent specifications describe polyamides which contain different groupings, such as aromatic polyamides or linear polyamides modified, for example, by polyether groupings, whioh make it possible for some of the properties to be improved but which inevitably result in significant modifications to other properties.

United States Patent No. 2,965,616 describes a polyhexamethyleneadipamide having a higher melting point obtained by replacing 15 to 50% mols of the adipic acid by hexahydro40632 - 3 terephthalic acid.

French Patent No. 2,052,875 discloses copolyamides of terephthalic acid, hexahydroterephthalic acid and polymethylenediamine containing 6 to 12 carbon atoms. Small amounts of other copolymerisable components, such as hexamethyleneadipamide, can be used to lower the melting point of this copolyamide. However, the melting point still remains high, of the order of 300 to 360°C, and the copolyamide cannot be processed according to the methods customarily used for polyhexamethyleneadipamide.

Copolyamides which are suitable for processing by extrusion, spinning or injection have now been found according to this invention. They are obtained by subjecting hexamethylenediamine to a condensation reaction with specific dicarboxylic acids or their esters or other derivatives which can form copolyamides. These acids or esters are (a) adipic acid or an ester thereof, (b) hexahydroterephthalic acid or an ester thereof, and (c) terephthalic acid or an ester thereof, and they are reacted with the hexamethylenediamine in the respective proportions of 50 to 90 mol%, 2 to 40 mol %, and 2 to 40 mol %, based on the total of components (a), (b) and (c). In order that the copolyamide can be processed similarly to polyhexamethyleneadipamide and have the desired properties, it is necessary to react component (a) in an amount of 50 to 9o mol °/°, preferably 60 to 80 mol %, based on the total of components (a), (b) and (c).

The total amount of terephthalic acid and hexahydroterephthalic acid reacted will be from 50 to 10 mol %, preferably 40 to 20 %, based on the total of components (a), (b) and (c). The molar percentages of each of these two non-linear acids in relation to each other can vary, but they will *. 43633 - 4 usually be 80% to 20% and' 20% to 80%, preferably 65% to 35% and 35% to 65%, respectively, based on these two acids.

In addition to the three acid (or ester) components specified for this invention, it is possible to have present minor amounts of other dicarboxylic acids or esters thereof such that the properties of the polymer obtained thereby are not substantially modified by the additional acid or ester.

The copolyamides according to the invention can be prepared by any conventional process customarily used for obtaining polyhexamethyleneadipamide. For example, it is possible to use the process which consists of first reacting equimolar quantities of hexamethylenediarnine with a mixture of the -acids, in an aqueous solution, in order to obtain the salts. The aqueous solution of these salts is then subjected to the action of heat and pressure in order to effect the condensation reaction leading to the copolyamide.

It is thus possible tnemploy a process wherein the hexamethylenediarnine is reacted with a mixture of the three acids. It is also possible to prepare the salt of each acid with hexamethylenediarnine individually, and then mix the solutions of the three salts obtained before carrying out the condensation reaction.

According to the present invention it is possible to react the hexamethylene diamine with esters particularly Cl to C6 Alkyl Esters, Of the specified acids. When the esters of the acids with low-boiling alcohols are used, an aminolysis of the esters with hexamethylenediarnine is carried out. Conveniently after removing the alcohols formed, the polycondensation reaction is then carried out ih the usual manner.

A chain-terminating agent is generally used in order 456 3 2 - 5 to control the molecular weight of the copolyamide obtained. The amount of such an agent employed depends on the desired molecular weight range. However 0.1 to 2 mol % is generally employed, based on the salts.

The chain-terminating agent is preferably a carboxylic acid or aliphatic amine.

Various additives can be added to the polymerisation mixture if desired. Examples of such additives include antioxidants, stabilisers, light stabilisers and antistatic agents.

Any apparatus employed in conventional polycondensation processes can be used. For example, it is possible to use a continuous apparatus, such as that used for the manufacture of polyhexamethyleneadipamide, or a discontinuous apparatus, laboratory processes in sealed tubes are also suitable.

The polycondensation reaction is generally carried out at 25O°C to 32O°C under pressures of 5 to 20 kg/cm2. To obtain significant degrees of polymerisation it is often preferable to carry out the reaction in the absence of oxygen, for example in the presence of nitrogen.

In general, the copolyamides obtained after the polycondensation reaction are extruded in the form of ribbons or strands into a cooling zone and then converted into a powder or granules by grinding or granulation.

The eopolyamides according to the invention generally exhibit a glass transition temperature which can be greater than that of nylon 6,6 by 10 to 40°C. Because of this, when the copolyamides of the present invention are processed by a technique similar to that for nylon 6,6, the drop in the modulus is less noticeable. The principal advantage of the 43633 - 6 copolyamides of the present invention is the permanence of their physical and mechanical properties in the moist state, in particular for relative humidities in the region of 50 %. Compared with nylon 6,6, their absorption of moisture is a little lower, their dimensional stability is improved and their mechanical properties are markedly less affected by a relative humidity of 0% to 50%, which corresponds to the conditions under which they are commonly used.

Bie copolyamides according to the invention are particularly suitable for producing mechanical or electrical parts, the use of which at relatively high temperatures, as well as under hygrometric conditions where the relative humidity is 0 to 50%, requires the mechanical properties to remain consistent.

The characteristics of these copolyamides also make it possible for textile yarns having good mechanical characteristics to be obtained by spinning.

In the Examples which follow, and which further illustrate the present invention, the copolyamides are dried at 110°C in an oven under a pressure of about 10 mm Hg for 5 hours before injection-moulding test pieces for comparison.

The intrinsic viscosities are obtained for solutions of 0.5 g of the polymer in 100 cm^ of m-cresol at 25°C (recommendation ISO/R 307).

The thermal transitions are obtained by differential thermal analysis under nitrogen using temperature variations of 10°C/minute.

The glass transition temperature Tg°C is measured on a pendulum torsion apparatus. 4S632 - 7 The hardness properties are measured on a Shore D durometer in accordance with recommendation ISO/R 868.

The mechanical characteristics under tension were determined using test pieces of the type H3 according to standard specification Norme Frangais (NF) T 51,034 (rate of traction 14 mm/minute) on a Lhomargy tensometer.

The mechanical bending characteristics Were determined using test bars of 80 x 10 x 4 mm according to recommendation ISO 178.

The dynamic torsion moduli were determined using test bars of 80 x 10 x 4 mm on an automatic pendulum apparatus.

The conditioning of the test pieces is carried out in the following manner: % relative humidity: test pieces kept in a desiccator containing P-0,. and at 25°C for 24 hours after moulding. z □ % relative humidity: test pieces kept in a desiccator containing a saturated solution of sodium bichromate and at 25°C until equilibrium is attained. 100 % relative humidity: test pieces kept in water at 80% for 7 days and then in water at 25°C until equilibrium is attained.

EXAMPLE 1: The salt of terephthalic acid and hexamethylenediamine (salt 6T) is obtained in the following manner: A 10 litre three-necked round-bottomed flask Which is equipped with a glass blade stirrer, a condenser and a nitrogen bubbler is charged, at ambient temperature, with 1,162 g (10 mols) of hexamethylenediamine and 2,800 cm of water. - 8 After the hexamethylenediamine has dissolved, whilst stirring, the temperature is brought to 50°C and 1,662 g of terephthalic acid are added in portions, in the course of one hour.

The mixture is kept under reflux for forty minutes after the end of the addition of the acid. The composition is then cooled to about 0°C by means of an iced water bath.

The salt which precipitates is filtered off on No. 3 glass frit and dried.

The product thus obtained is suspended in 2.5 litres of methanol under reflux, whilst stirring. After cooling to 20°C, the mixture is again filtered.

The precipitate is dried and washed with methanol and then dried to constant weight in an oven at 60°C in vacuo. 2,675 g of salt 6T (yield 94,6 %) are thus obtained.

The pH of a 10 % strength solution at 20°C is equal to 7.25. Melting point: 28O°C. The microanalysis is as follows: C %: 58.34-57.92 (59.57) H % : 7.87-8.00 (7.80) N % : 9.51-9.46 (9.92) 0 % : 23.23-23.06 (22,69).

The salt of hexahydroterephthalic acid and hexamethylenediamine (salt 6HT) is obtained in the following manner: A 10 litre three-necked round-bottomed flask equipped as indicated above is charged with 6 litres of 2-propanol and 600 g (3.571 mols) of hexahydroterephthalic acid. 405 g of hexamethylene diamine in 405 g of 2-propanol are then ruh in, whilst stirring and bringing the mixture to the reflux temperature.

The salt precipitates. Stirring under reflux is maintained for 30 minutes after the end of the addition. -45632 - 9 The mass is then cooled to 20°C by means of a water bath.

The salt is filtered off on a No. 3 frit, dried and 3 washed with four times 250 cm of 2-propanol. It is then dried to constant weight in an oven at 60°C in vacuo.

The salt is obtained in a yield of 99 %. The pH of a 10 % strength solution in water at 20°C is 7.36.

Melting point: 217°C. The microanalysis is as follows: C % : 58.45-58.71 (58.33) H % : 9.63-9.35 (9.72) N % : 9.91-10.01 (9.72) 0 % : 22.25-22.33 (22.22).

The salt of adipic acid and hexamethylenediarnine (salt N) used is the product employed industrially for the preparation of polyamide 66.

The following charges: SALT N SALT 6T SALT 6HT 19.68 g (0.075 mol) 4.59 g (0.01625 mol) 2.52 g (0.00875 mol) benzoic acid : 0.244 g (0.002 mol) are introduced into a glass tube (length 45 cm., internal diameter 1.8 cm., and thickness 0.6 cm.).

After flushing with nitrogen, the tube is sealed and placed in an oven, kept at 280°c, for 4 hours.

After cooling, the tube is opened and connected to an apparatus which enables the tube to be put under a vacuum or under a stream of nitrogen.

The tube is flushed with nitrogen and then kept under a stream of nitrogen in an oven at 320°C for 30 minutes.

The stream of nitrogen is stopped and then a pressure of less than 10 mm of mercury is established in the course of 30 minutes, whilst keeping the oven at 32O°C. The tube is kept sr 450 J* -10in the oven at 32O°C under a pressure of less than 10 mmHg for 10 minutes. The vacuum is broken with nitrogen and the tube is cooled under a stream of nitrogen. After cooling, the polymer is obtained by breaking the tube.

A hard, opaque white polyamide is obtained which exhibits an intrinsic viscosity of 0.9, a melting point (Tf°c) of 264°C and a crystallisation point (Tc°C), on cooling, of 225°C. EXAMPLES 2 to 7: Various copolyamides were obtained by the process described in Example 1. Table I summarises their properties compared vzith those Of polyamide 66.

TABLE I mol % of :intrinbenzoic :sic Example COMPOSITION OP POLYAMIDE IN MOL % OF SALTS acid relative to the salts visco- sity dcl/g Tf°C Tc°C SALT N SALT 6T SALT 6HT Compar- ison 100 0 2 1 260 218 2 75 16.25 8.75 2 0.9 268 225 3 75 12.5 12.5 2 0.97 268 229 4 75 8.75 16.25 2 0.88 267 238 5 50 32.5 17.5 2 1.34 273 248 650 25 25 2 - 275 248 7 80 13 7 0.6 1.09 263 218 EXAMPLE 8: A 1 litre autoclave provided with a spiral stirrer, heating system which operates by the circulation of heating fluid, temperature probes, a system of side-tubes which makes distillation under pressure possible and a supply of nitrogen is charged with: 43632 - 11 SALT N SALT 6T SALT 6HT 330.56 g (1.260 mol) 76.23 g (0.270 mol) 77.86 g (0.270 mol) acetic acid distilled water 1.3 g (0.0216 mol) and 456 g The mass is heated to 80°C and flushed with nitrogen whilst putting the autoclave under a pressure of 5 bars and then decompressing it. The valves of the autoclave are then shut and the mass is heated to 2l0°C in the course of 30 minutes, whilst stirring (75 r.p.m.). A pressure of 18 bars is reached. The water is distilled off under 18 bars in the course of two hours, whilst raising the temperature of the mass to 26O°C. Distilling off the water, with progressive decomposition, is continued for 90 minutes, whilst reducing the stirring to 10 r.p.m. and progressively raising the temperature of the mass to 285°C The polymer is homogenised under a stream of nitrogen and with slow stirring for one hour, whilst raising the Stirring is stopped and the polymer is drawn off into a tank of cool water, whilst exerting a pressure of 5 bars of nitrogen on the molten mass.

An opaque white copolyamide is obtained which exhibits the following characteristics: intrinsic viscosity : 0.91 dcl/g melting point : 279°C crystallisation point, on cooling : 248°c Shore D hardness at 0 % relative humidity : 88 Tg°C at 0 % relative humidity : 66 % linear contraction on moulding : 1.5 3632 % absorption of Water at 50 % relative : 1,3 humidity linear dimensional variation between 0 % and 50 % relative humidity : + 0.09 % Linear dimensional variation between 0 % and 100 % relative humidity : + 1.38 % breaking stress under tension, 0 % relative humidity, 25°C 2 : 7.2 DaN/mm apparent bending modulus of elasticity 0 % relative humidity, 25°C : 237 DaN/mm2 50 % relative humidity, 25°C : 220 DaN/mm2 EXAMPLES 9 to Hi Various copolyamides were obtained by the process described in Example 8 using temperatures of 270°C to 29O°C at the end of the decompression and of 275 to 295°C at the end of the homogenisation.

The compositions of the salts used in preparing these polyamides as well as some of their properties compared to those of nylon 66 are given in Table II: 43632 Η- Π w ω ο Η ο <Ο ο 3 3 Ό 0 Η 1 Ό χΐ «Ο σι ο ο ο σ» Β (-· ω σ κ φ σι Η t’ σι Ο a Η σ» σι to ο « σ» σι ►3 σι W Η Η « • to to to ο ο Η ρι ·. ω ω ο Η* σι Η to to to to co Ό *4 σ» W \Ο φ to to to to to σι GJ to ω 00 ΙΟ σι Φ cn σ» tn ω σ> σ» ω ο Η to to • σ» +· ω σι Φ ϋ 00 W Η Η ω to U) σι Ο 00 00 >> Η rt n S' o ro ζυ ϊχ ο Η 8,3 ϋο pi φ ω μ Η ρ. > Ρ Ο Ρ Ω Φ ft Η* ΓΤ % Ο own η ω οι οι Ό Ο ο ω η· Hi Η & < Η· Qj 01 ο ο W ο X 01 ifl Ρ· rt η· Ο ,4 Hl ra ο >3 rt ο Ϊ4 Ο Η· Ο C Ο 3 F w ο & δ·§ ίΤ5· (U Φ Ω Φ I Η FK Q tf < 3 & $ C ® « Φ ΑΙ Ρ> Η' μ ° Γ+ H I “ Η· ρ> Ρ 3 Η· Pj rt » Φ » Η» Η· pi Φ (+ π- < 3 ρ.

MJ Φ Η Ο Η· Φ Ρ· Ρ 3 ω φ ρ. 0) Ο Κ I - 14 45 6 3 2 Η Η Η1 Ο Φ Compar- ison Example Μ *0 Ό σι . g) o O ο Ο o σι 3 Ml 0 OH· 3 Hi Ch ft Ό H ® ?o Η* Φ to to fl> ω σ» Οι GV (H tu h* Ol fl s Η Ρ- Ω (+ (+ 3 0 P- «· 01 »o 0 H σι 3 0 3 to Η* O GV σν ο h ra 01 w Oi fl 1 p- 3* ο ω3 g ϋ Ρ· H p) P> 0, φ x* *4 σι σι Ζ Η· Η H· 1 • • • X.rt P> 3 ίο. φ η 3 kJ ftiQ 3 * H* to <(fl to Φ rf oi H 0 o O io 01 51 w 1 to to to H U H > fcj w ω ffi w ts >g H •ο to o Ο οι Ό O 0 w non O Hi O 3 P- 3 a 3 ro rt· > mb* H H 0 0 3 rt 3 01 (0 Oj W M ft 3 • p- a to w H* a Ω H· r to φ «4 P- 3 ο o ω 01 (+tQ o kJ w fU 0 H* Cu si 1 w 3 X ro ο o 00 *J · σ a M a*< W P> S 3 Q Ol o o o 1 Ο Μ Η P Η o o o r rt 3 3 ο O □ o •4 GV H· 01 H· o ο n 0 a ρ. o n kJ ft· Hl ft 0 k- O 0 H ω 0) w a \ ΡΟ 0 ω ω to 3 3 Oi tO pj Φ 00 to •4 O to H Οι 01 Ol ό I ο o o o σι - 0 o - 15 45632 EXAMPLE 12: A copolyamide was prepared as in Example 8, but the temperature of the mass was raised to 29O°C at the end of decompression and to 295°C at the end of homogenisation and the following were charged: salt N : 216 g (0.823 mol) salt 6T : 151 g (0.535 mol) salt 6HT : 83.1 g (0.288 mol) acetic acid : 1.19 g (0.02 mol) and distilled water 440 g intrinsic viscosity Tf°c 15 Tc°C contraction on moulding absorption of water at 50% relative humidity dimensional variation between 20 0 % and 50 % relative humidity The polymer obtained exhibited the following characteristics : : 0.92 dcl/g : 290°C : 256°C : 1.43 % : 1.4% : + 0.26 : 82°C

Claims (7)

1. CIAIMS:1. A copolyamide obtainable by polycondensing hexamethylene diamine with (a) adipic acid or an ester thereof, (b) hexahydrcterephthalic acid or an ester thereof and (c) 5 terephthalic acid or an ester thereof, components (a), (b) and (c) being reacted with the hexamethylenediarnine as a mixture and in respective amounts of 50 to 90 mol %,

2. To 40 mol %, and 40 to 2 mol %, based on the total of components (a) , (b) and (c). 10 2. A copolyamide according to Claim 1, in which the respective amounts of components (a), (b) and (c) are 60 to 80 mol %, 7 to 26 mol %, and 26 to 7 mol %, based on the total of components (a), (b) and (c),

3. A copolyamide according to Claim 1 or 2 in which the 15 amounts of components (b) and (c) are, respectively, 65 to 35 mol % and 35 to 65 mol %, based on these two components.

4. A copolyamide according to any one of the preceding Claims obtained by carrying out the polycondensation in the presence of a chain-terminating agent. 20

5. A copolyamide according to Claim I substantially as described in any one- of the Examples.

6. A shaped article whenever obtained from a copolyamide as claimed in any one of the preceding Claims.

7. An article according to Claim 6 in the form of a yarn 25 obtained by spinning a copolyamide as claimed in any one of Claims 1 to 5: