WO1993004110A1

WO1993004110A1 - Process for manufacturing high-resistance foils made of aromatic copolyamides and use of the same

Info

Publication number: WO1993004110A1
Application number: PCT/EP1992/001880
Authority: WO
Inventors: Cynthia Bennett; Werner Roth
Original assignee: Hoechst Aktiengesellschaft
Priority date: 1991-08-21
Filing date: 1992-08-18
Publication date: 1993-03-04
Also published as: EP0599944A1; JPH06510311A; MX9204834A; DE4127603A1

Abstract

According to a process for manufacturing high-resistance foils made of aromatic copolyamides, (a) a solution of an aromatic copolyamid is at first prepared; (b) this solution is poured on a solid substrate; (c) the poured foil is pre-dried in order to remove part of the solvent; (d) coagulation is carried out in a precipitating agent; and (e) the foil is finally dried in order to remove the coagulating agent and the residual amide solvent. This process is characterized in that the dimension retention factor D in the longitudinal and/or transverse direction is greater than or equal to 0.9 during process steps (c), (d) and (e).

Description

Process for the production of high-strength films from aromatic copolyamides and their use

The present invention relates to a process for the production of high-strength films from aromatic copolyamides and their use, in particular as

Carrier for magnetic storage media, as an electrical insulating material and as a carrier for flexible printed circuits.

Aromatic polyamides are known as heat-resistant, infusible materials for foils and fibers. Those in which the amide bonds on the aromatic rings are oriented coaxially or almost parallel to one another have rigid, rod-shaped molecules which lead to high intrinsic strengths and elastic modulus values. Para-linked homopolyamides such as poly-p-phenylene terephthalamide (PPTA) are not sufficiently soluble in organic solvents and have to be processed into films using solutions in concentrated sulfuric acid (e.g. JP / A 02/133 434), which poses particular problems in handling (occupational safety , Corrosion) and waste disposal.

Attempts have therefore been made to circumvent these difficulties by developing polyamides with good solubility in amide solvents. For example, films made from aromatic copolyamides are described which have been produced with considerable proportions of diamines such as 3,4'-diaminodiphenyl ether and 2-chlorophenylenediamine (EP-A-0 045 934, EP-A-0 090 499).

Such copolyamides have sufficient solubility in amide solvents, but have the disadvantage that the monomers are relatively expensive. The asymmetrical 3,4'-diaminodiphenyl ether is only accessible via relatively cumbersome processes and the 2-chlorophenylenediamine only via the sulfate, the separation of which in turn leads to major waste problems. Aromatic copolyamides from the recurring structural units of the formulas are therefore more advantageous

A -OC-Ar-CO- B -OC-Ar ¹ -CO-

C -HN-Ar ² -NH-

D -HN-Ar ³ -NH-

E -HN-Ar ⁴ -Z-Ar ⁵ -HN- where the sums of the molar proportions of the structural units A + B and the molar proportions of the structural units C + D + E are essentially the same size, the molar fraction of the structural unit B 0 to 5% of the total the molar fraction of the structural units is A + B, the number of diamine components C + D + E per molecule is ≥ 2, the number of diamine components D + E ≠ 0, and where -Ar- and -Ar ² - divalent aromatic radicals (arylene radicals) mean whose

Valence bonds in para- or - in the case of linearly fused benzene rings - are in a comparable coaxial or parallel position and these arylene radicals are optionally substituted by one or two inert radicals such as lower alkyl, alkoxy or halogen, -Ar ¹ - a divalent, aromatic radical (arylene radicals ) means whose valence bonds are in the meta- or - in the case of linearly fused benzene rings - in a comparable angled position and are optionally substituted by one or two inert radicals such as lower alkyl, alkoxy or halogen, -Ar ³ - a biphenylene structure of formula I.

has or has the meaning of -Ar ¹ -,

-Ar ⁴ - a para-phenylene structure of formula II

owns

-Ar ⁵ - a para-phenylene structure of the formula II or a meta-phenylene structure of the formula III

owns

-Z- a two-valued link selected from

Means -C (CH-) ₂ - and -CO-NH- and

R, R ¹ , R ² and R ^{3 are the} same or different and are H, lower alkyl, lower alkoxy or halogen.

Preferred arylene radicals for Ar and Ar ² are the following divalent compounds represented by the formula:

Preferred arylene radicals for Ar ¹ are the following divalent compounds represented by the formula:

These aromatic copolyamides, in amide solvents, can be processed into films, fibers, fiber pulp, films and membranes (DE-A-35 10655, EP-A-0 199 090, EP-A-0 322 837, EP-A-0 364 891, EP-A-0 364 892, EP-A-0 364 893). Amide solvents are understood to mean all those solvents which are able to dissolve aromatic, polymeric amides. High-boiling, in particular N-substituted amides have proven suitable. Examples include: N-methylpyrrolidone, dimethylformamide, dimethylacetamide, N-N'-dimethylimidazolidin-2-one or N-methylcaprolactam.

The lower alkyl or alkoxy radicals mentioned are preferably C ₁ -C ₆ -, particularly preferably C ₁ -C ₄ -, very particularly preferably C ₁ - or C ₂ -alkyl or alkoxy radicals. The halogen radicals mentioned are preferably fluorine, chlorine,

Bromine or iodine residues, especially chlorine residues.

The divalent aromatic aryl residues -Ar- and Ar ² - have valence bonds in the para position. If these arylenes are condensed, so-called annelated ring systems, the two valence bonds are in a coaxial, that is, as parallel as possible position on the first and the last to

System belonging to the aromatic ring. Examples include 2,6-naphthylene, 2,6-anthrylene or 2,8-naphthacylene or 4,4'-biphenylene or 4,4 "-terphenylene. The angled arylene radicals Ar ¹ are benzene rings with

Valence bonds in meta position. In the case of the fused systems, the two bonds on the first and last ring of the aromatic system are in an angled, non-coaxial position. Examples include 1,3-phenylene, 2,5-, 2,7- or 2,8-naphthylene, 2,5-, 2,7- or 2,8-anthrylene or 4,3'-biphenylene or 4, 2 "terphenylene.

Films made from the above-mentioned copolyamides (cf. EP-A-0 303 949) are highly heat-resistant, dimensionally stable, have good electrical insulation and have good strengths and elastic modulus values (230 MPa or 5.0 GPa) even without special process steps that are comparable to eg high strength stretched

Are polyethylene terephthalate films. However, such PET films are far less heat-stable. Films from aromatic copolyamides are usually produced as follows:

a) preparing a solution of the aromatic copolyamide in one

suitable amide solvents such as N-methylpyrrolidone or dimethylacetamide, if appropriate in the presence of a solvent, such as a halide of the first or second group of the periodic system, or by direct synthesis from the monomers in a suitable solvent such as N-methylpyrrolidone or dimethylacetamide, if appropriate in the presence of one reactive solvent such as CaO (converted to CaCl ₂ ),

b) pouring the solution of the aromatic copolyamide onto a solid

Carrier,

c) predrying to remove part of the solvent and

Consolidation of the layer,

d) coagulation in a precipitant for the polymer which contains the amide

Is able to dissolve solvent and any solvent that is present,

e) removal of the coagulant and residual amide solvent by a drying step.

The casting (b) can on a flat structure such as a metal, plastic or glass plate. For continuous, industrial production, however, a roller or a moving belt is more suitable as a solid support. The surface of the solid support should be resistant to the casting solution.

Predrying (c) solidifies the cast polymer layer, which facilitates handling during coagulation and also economically recovers the amide solvent used, e.g. by condensation. This predrying can be caused by the action of

Heat, if necessary, apply vacuum. A well-suited method for continuous production is the transfer of a heated one Gas flow, such as nitrogen or air. Depending on the solvent used, layer thickness, gas flow and temperature, sufficient pre-drying can be achieved within 2 to 60 minutes. Predrying is sufficient if approx. 50 to 99% of the amide solvent has been removed and the layer contains no bubbles.

The coagulation (d) is carried out in a liquid medium in which the aromatic copolyamide is insoluble, but the amide solvent and any solvent auxiliaries present are soluble. The separation from the carrier can take place before the coagulation, provided that the layer is sufficiently solid after predrying, but it can also be done only after immersion in the coagulation bath. Water or water / solvent mixtures, optionally with suitable additives, e.g. Complexing agents for the dissolving agents can be used. Suitable solvents are all those which can be mixed with the amide solvent, which dissolve any solvent which may be present and which do not dissolve the copolyamide. For example, water / acetone mixtures are suitable. Mixtures with the amide solvent itself can also be used if there is sufficient precipitant in the mixture. In this case, several baths with a concentration gradient should be used. In the coagulation bath, the solvents and a large part of the amide solvent still present are removed.

The drying (e) serves to remove the coagulant and amide solvent as completely as possible and is carried out at elevated temperature, if appropriate also under vacuum. The necessary conditions depend on the film thickness and the choice of amide solvent and coagulant. If the dimensional stability of the film is required at a high temperature, high drying temperatures, eg 200 ° C to 400 ° C, should be selected, as this increases the operating temperature of the thermal shrinkage. As already described in EP-A-0 303 949, stretching of such copolyamide films at temperatures ≥ 280 ° C. after the final drying (e) achieves extraordinarily high strengths and elastic modulus values (eg 800 MPa or 19 GPa at 1.5 times stretching).

Technically, film materials with high strengths are of interest, among other things, because they have smaller film thicknesses with the same machinability, i.e. Safe running during manufacture, processing and use, e.g. allow when winding and winding.

A continuous stretching process at temperatures ≥ 280 ° C is, however, quite complex in terms of equipment. In addition to, for example, lubrication problems in the continuously operating stretching frame, the temperature uniformity required for successful stretching over the entire film width is very difficult due to convection in a stretching frame which is open at both ends.

The object of the present invention was therefore to find a less technically complex process for producing films from aromatic copolyamides with increased strength.

It has now surprisingly been found that ensuring dimensional stability, i.e. preventing shrinkage during the final drying process (e) already increases the strength and the modulus of elasticity by more than 30% and 50%, respectively. Already measures that

Limiting shrinkage, but not completely preventing it, has an effect here.

In addition, it was found that the strength and modulus of elasticity can be increased even further if the film is stretched when wet. This stretching can take place before and / or in the coagulation bath. Both measures can be implemented without great technical effort, in particular without the high stretching temperatures customary hitherto.

To better understand the measures according to the invention, the definition of a dimensional constancy factor D is useful:

D

Depending on the design, D can be the same or different in the longitudinal and transverse directions of the film.

According to the processing method according to the prior art (EP-A-0 303 949 without stretching), D is approximately 0.7 to 0.8. Are the dimensions according to the

Keeping the invention constant, D is 1.0. If a wet stretching according to the invention is carried out, D> 1.0.

If a material that is stronger only in the running direction (production direction) is required, it is sufficient if D is ≥ 0.9 in the longitudinal direction. In a continuous

In the process, this can be achieved by leading guide rollers in front of or in the coagulation bath relative to the solid casting support (usually a roller or belt). This process measure usually results in a transverse shrinkage of the film at the same time, which means a reduction in the D values in the transverse direction. Such films are particularly strong in the longitudinal direction and particularly splice-resistant in the transverse direction.

The latter is very surprising since films with a high longitudinal orientation usually splice very easily, i.e. have low toughness in the transverse direction.

If isotropic but increased strength properties are required in both directions, D should be the same in the longitudinal and transverse directions and ≥ 0.9. For D = 1.0, the film web should be led to the dryer without great tension. To prevent longitudinal shrinkage, the entrance and exit path speed should be the same. Cross-shrinkage can be prevented, for example, by lateral guidance of the film web.

Films that are even firmer in both directions can be obtained by a combination of longitudinal and transverse stretching in front of and / or in the coagulation bath with the dimensional stability described above in the dryer. The longitudinal stretching is expediently carried out as already described (for example by means of different roller speeds) and the transverse stretching according to the customary tenter technique, with no elevated temperatures in the tenter being required in the case of the moist film web. The dimensions achieved after stretching should then be maintained during drying.

The films which are produced by the process according to the invention are used in areas where strength and / or thermal stability are required. Above all as tape material, e.g. as a carrier for magnetic tapes or

Wrap insulation for cables allows the very high strength to further reduce the film thickness and save space accordingly. The high heat resistance is necessary for various coating techniques e.g. Sputtering, metal vapor deposition and also important for electrical insulation. Other areas of application are acoustic membranes, solid and heat-resistant

Adhesive tapes, cover materials, carrier tapes for thermal printing processes, conveyor belts, etc.

The invention is explained in more detail below with the aid of examples. The following abbreviations mean:

TPC - terephthalolyl chloride

PPD - para-phenylenediamine

DMB - 3,3'-dimethylbenzidine BAPOB 1, 4-bis - [(4-aminophenoxy) benzene]

DADPM 4,4'-diaminodiphenylmethane

NMP - N-methylpyrrolidone

The mechanical properties E modulus, tensile strength and elongation at break of strip samples were determined on the films produced (inventive and comparative examples) in a tensile testing machine in accordance with DIN 53 455. The sample width was 15 mm and the clamping length was 100 mm. The modulus of elasticity was determined as a secant module between 0.4 and 0.6% elongation at a test speed of 10 mm / min, the tensile strength and elongation at 100 mm / min.

The inherent viscosity

was determined at a concentration of 0.5% in NMP at 25 ° C. (η _rel means the relative viscosity, C the concentration in g / dl).

example 1

A solution of 5.0% by weight of an aromatic copolyamide made from TPC,

PPD, DMB and BAPOB in a molar ratio of 1: 0.25: 0.5: 0.25 was produced and had an η _inh of 5.9 dl / g and 1.7% by weight of CaCl ₂ in NMP was brought to 90 ° C warmed and spread with a squeegee on a glass plate. The glass plate was placed in a forced-air drying cabinet (130 ° C.) for 20 minutes to remove part of the solvent. Thereafter, the polymer concentration was approximately 35

% By weight. The glass plate was placed in a water bath and the polymer layer removed as a film. After a total of 10 minutes in a water bath, the film was removed, clamped in a tenter and 10 minutes at 250 ° C in dried in a convection oven. The film obtained had a thickness of 20 μm and a residual NMP content 0,0 0.02%.

The mechanical properties of the high-strength film were measured (see Table 1).

Example 2 (comparative example)

The solution from Example 1 was processed into the film as described in Example 1, but with the difference that the drying was free-hanging without a tenter. During this drying, the film shrank evenly in the longitudinal and transverse directions. She had only 76% of her initial dimensions.

The modulus of elasticity and the strength of the film were lower than in the film according to Example 1 (cf. Table 1).

Example 3

A solution of 5.5% by weight of an aromatic copolyamide made from TPC, PPD, DMB and BAPOB in a molar ratio of 1.0: 0.25: 0.375: 0.375 and 1.9% CaCl ₂ in NMP was made as processed into a film in Example 1. After the first treatment in a circulating air dryer ("predrying" 130 ° C), the polymer concentration was approx. 85%.

The mechanical properties of the 26 μm thick film obtained are given in Table 1.

Example 4 (comparative example)

The solution from Example 3 was processed as in Example 2. After drying, the film was 73% of its original size. Mechanical properties see p. Table 1. Example 5

A solution of 3.0% by weight of an aromatic copolyamide which was prepared from TPC, PPD, DMB and BAPOB in a molar ratio of 1.0: 0.375: 0.5: 0.125 and 1.2% by weight of CaCl ₂ in NMP was processed similarly as in Example 1. However, the predrying time in the circulating air dryer was 15 minutes instead of 20 minutes. After this pretreatment, the polymer concentration was approximately 50%. The rest of the processing was carried out as in Example 1. A high-strength film with a thickness of 21 μm was obtained. The mechanical properties are summarized in Table 1.

Example 6 (comparative example)

The solution from Example 5 was processed as in Example 5, but without the use of a tenter during drying. Therefore, the dimensional stability was not guaranteed during drying, so that the film only had 70% of its original dimensions afterwards. The mechanical

The strength of the film was lower than that of the film according to Example 5.

Example 7

A solution of 10 wt .-% of an aromatic copolyamide, which was prepared from TPC, PPD, DMB and DADPM in a molar ratio of 1.0: 0.25: 0.40: 0.35 and an η _{in h} of 3.9 dl / g and 3.5% CaCl ₂ in NMP, were heated to 170 ° C and spread with a doctor knife on a glass plate. The layer was pre-dried in a forced air drying cabinet at 130 ° C. for 20 minutes. The glass plate was placed with the layer in water to detach the layer. After a total of 10 minutes in a water bath, the film was removed into a

Clamping frame clamped and dried for 10 minutes at 250 ° C in a circulating air drying cabinet. The mechanical properties of the 30 μm thick film were measured (see Table 1). Example 8

The solution from Example 7 was processed as in Example 7, with the difference that the drying was carried out at 250 ° C. without a tenter, the The film shrank. After drying, the film was wavy and was only 70% of the original size. The mechanical properties of the film were measured (see Table 1). Example 9

A solution of 6.0% by weight of an aromatic copolyamide, which had the same composition as in Example 1 and had an η _inh of 6.6 dl / g and 1.8% CaCl ₂ in NMP, was added using a casting machine processed a film. For this purpose, the solution, which was heated to 90 ° C., was poured through a slot die onto a stainless steel belt rotating in a hot air duct and predried at 130 ° C. The dwell time in the hot air duct was approx. 20 minutes. Then the polymer layer was detached from the tape, passed through a water bath at room temperature and then a dryer at 250 ° C. and wound up. At the exit of the after-dryer, the web speed was 91% of that of the stainless steel belt and the web width of the film was 78% of the casting width.

The mechanical properties of the high-strength film were measured (see Table 2).

Example 10

A solution of an aromatic copolyamide as described in Example 9, but with an η _inh of 6.9 dl / g, was processed in a similar manner to that in Example 9, but with a different web speed ratio. After

After drying, the web speed was 110% of that of the stainless steel belt and the web width of the film was 61% of the casting width.

The mechanical properties of the high-strength film were measured (cf.

Table 2).

Example 11

A solution of a copolyamide as in Example 9, but with an η _inh of 6.9 dl / g, was processed in a similar manner to that in Example 9, but with a different web speed ratio. After drying, the web was Speed 169% of that of the stainless steel belt and the web width of 57% of the initial width.

The mechanical properties of the films according to Examples 9, 10 and 11 are summarized in Table 2.

Example 12

A film was made as in Example 10, but with an additional one

Stretching step in the transverse direction before drying. After the first water bath, the film was swollen in a mixture of 70% NMP and 30% water and then stretched in the transverse direction by 150% of its initial width. The NMP was then removed in another water bath and the film was dried. The last steps were carried out under constant dimensions. Thus, D in the transverse direction was now 0.61 x 1.5 = 0.91. The modulus of elasticity in the transverse direction was 9.0 GPa (without transverse extension: 3.5 GPa).

Claims

1. Process for the production of films from high-strength, aromatic copolyamides soluble in an amide solvent from the recurring structural units of the formulas

A -OC-Ar-CO-

B -OC-Ar ¹ -CO-

C -HN-Ar ² -NH- D -HN-Ar ³ -NH-

E -HN-Ar ⁴ -Z-Ar ⁵ -HN- where the sums of the molar proportions of the structural units A + B and the molar proportions of the structural units C + D + E are essentially the same size, the molar fraction of the structural unit B 0 to 5% of the total the molar fraction of the structural units is A + B, the number of diamine components C + D + E per molecule ≥ 2, the number of diamine components D + E ≠ 0, and where

one or two inert radicals such as lower alkyl, alkoxy or halogen is substituted,

-Ar ³ - a biphenylene structure of formula I.

has or has the meaning of -Ar ¹ -, -Ar ⁴ - a para-phenylene structure of the formula II

owns

owns

-Z- a two-valued link selected from

-C (CH ₃ ) ₂ - and -CO-NH- means and

R-, R ¹ -, R ² - and R ³ - are identical or different and denote H, lower alkyl, lower alkoxy or halogen, whereby a) a solution of an aromatic copolyamide is first prepared, this solution b) is poured onto a solid support, the cast film is c) predried in order to remove part of the solvent, d) coagulation is carried out in a precipitant and e) the film is finally sealed, Dries for the purpose of removing the coagulant and the remaining amide solvent, characterized in that the dimensional constancy factor D in process steps c), d) and e) is ≥ 0.9 in the longitudinal and / or transverse direction.

2. The method according to claim 1, characterized in that the

Predry 50 to 99% of the amide solvent.

3. The method according to claim 1 or 2, characterized in that

the dimensional constancy factor D over the process steps c), d) and e) in the longitudinal and / or transverse direction is in the range from 0.9 to 2.0.

4. The method according to one or more of claims 1 to 3,

characterized in that the pre-dried but still moist film is stretched following process step c).

5. The method according to one or more of claims 1 to 4,

characterized in that the film is detached from the solid support after process step c) or d).

6. The method according to one or more of claims 1 to 3,

characterized in that the film in process steps b) to d) is guided without great tension.

7. The method according to claim 6, characterized in that the

tension-free guidance is achieved by synchronizing the entry and exit path speed.

8. The method according to one or more of claims 1 to 7, characterized in that the amide solvent is selected from one or more compounds of the group N-methylpyrrolidone, dimethylformamide, dimethylacetamide, N.N-dimethylimidazolidione and N-methylcaprolactam.

9. The method according to one or more of claims 1 to 8,

characterized in that the amide solvent contains a solvent.

10. The method according to claim 9, characterized in that the

Solvent is selected from one or more halides of the first or second group of the periodic system.

11. The method according to one or more of claims 1 to 10,

characterized in that the coagulation (d) begins on the solid support.

12. High-strength film made from an aromatic copolyamide, available

according to a method according to one or more of the claims

1 to 11.

13. Use of the high-strength film according to claim 12 as a high-strength

heat-resistant carrier for magnetic storage.

14. Use of the high-strength film according to claim 12 as a heat-resistant electrical insulating material.

15. Use of the high-strength film according to claim 12 as a carrier for flexible printed circuits.