DE4127603A1 - METHOD FOR PRODUCING HIGH-STRENGTH FILMS FROM AROMATIC COPOLYAMIDES AND THE USE THEREOF - Google Patents

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

The present invention relates to a method for producing high-strength films from aromatic copolyamides and their use, in particular as Carrier for magnetic storage media, as electrical insulating material and as a carrier for flexible printed circuits.

Aromatic polyamides are considered heat-resistant, infusible materials for Films and fibers known. Those in which the amide bonds to the aromatic rings are oriented coaxially or almost parallel to one another, have rigid, rod-shaped molecules that are too high intrinsic Strengths and elastic modulus values.

Para-linked homopolyamides such as poly-p-phenylterephthalamide (PPTA) are not sufficiently soluble in organic solvents and have to be dissolved processed into foil in concentrated sulfuric acid (e.g. JP / A 02/1 33 434), which poses special problems in handling (occupational safety, Corrosion) and waste disposal.

One therefore tried to avoid these difficulties by: Developed polyamides with good solubility in amide solvents. So are For example, films made from aromatic copolyamides described with considerable amounts of diamines such as 3,4′-diaminodiphenyl ether and 2- Chlorphenylenediamine were prepared (EP-A-00 45 934, EP-A-00 90 499). Such copolyamides have sufficient solubility in amide solvents, have the disadvantage, however, that the monomers are relatively expensive. The unsym Metric 3,4'-diaminodiphenyl ether is only through relatively cumbersome procedures  accessible and the 2-chlorophenylenediamine only via the sulfate, the Separation in turn leads to major waste problems.

Aromatic copolyamides from the recurring are therefore more advantageous Structural units of the formulas

A -OC-Ar-CO-
B -OC-Ar¹-CO-
C -HN-Ar²-NH-
D -HN-Ar³-NH-
E -HN-Ar⁴-Z-Ar⁵-HN-

wherein 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 structural unit B is 0 to 5% of the sum of the molar proportions of structural units A + B,
the number of diamine components C + D + E per molecule is 2,
the number of diamine components is D + E ≠ 0, and where
-Ar- and Ar ² - mean divalent aromatic radicals (arylene radicals) whose valence bonds are in para- or - in the case of linearly fused benzene rings - in a comparable coaxial or parallel position and where these arylene radicals are optionally substituted by one or two inert radicals such as lower alkyl, alkoxy or halogen are substituted,
-Ar ¹ - means a divalent, aromatic radical (arylene radicals), the valence bonds of which are in a meta- or - in the case of linearly fused benzene rings - in a comparable angled position and optionally substituted by one or two inert radicals such as lower alkyl, alkoxy or halogen,
-Ar³- a biphenylene structure of formula I.

has or has the meaning of -Ar¹-,
-Ar⁴- a para-phenylene structure of the formula II

owns
-Ar⁵- 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

-O-, -S-, -CH₂-,

-C (CH₃) ₂- and -CO-NH-

means 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 shown in formulas:

Preferred arylene radicals for Ar 1 are the following, represented in formulas divalent connections:

These aromatic copolyamides, in amide solvents, can be converted into films, Process fibers, fiber pulp, films and membranes (DE-A-35 10 655, EP-A 01 99 090, EP-A-03 22 837, EP-A-03 64 891, EP-A-03 64 892, EP-A-03 64 893).

Amide solvents are understood to mean all those solvents which are capable of are to dissolve aromatic, polymeric amides. Have proven to be suitable boiling, especially N-substituted amides proven. For example, be here called: 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 annellated ring systems, then the two valence bonds are in a coaxial, that is, as parallel as possible position on the first and last aromatic ring belonging to the system. Examples include 2,6-naphthylene, 2,6-anthrylene or 2,8-naphthacylene or 4,4'-biphenylene or 4,4 '' - terphenylene.

The angled arylene residues Ar ¹ are benzene rings with valence bonds in the 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 copolyamides mentioned above (cf. EP-A-03 03 949) are high heat-resistant, dimensionally stable, good electrical insulation and already have  good strength and modulus of elasticity (230 MPa or 5.0 GPa), which is comparable to e.g. B. high strength stretched Are polyethylene terephthalate films. However, such PET films are far more extensive less heat stable.

Usually, films made from aromatic copolyamides are as follows produced:

• a) preparing a solution of the aromatic copolyamide in a suitable amide solvent such as N-methylpyrrolidone or dimethylacetamide, optionally 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 a reactive solvent such as CaO (is 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,
• c) coagulation in a precipitant for the polymer that contains the amide Solvent and any solvent present is able to extract
• e) removal of the coagulant and residual amide solvent by a Drying step.

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

Predrying (c) solidifies the cast polymer layer, which facilitates handling during coagulation and also a economic recovery of the amide solvent used, e.g. B. by Condensation allowed. This predrying can be caused by the action of Heat, if necessary, apply vacuum. A good one The method for continuous production is the transfer of a heated one Gas flow, e.g. B. nitrogen or air. Depending on the solvent used, Layer thickness, gas flow and temperature, adequate predrying can be reached within 2 to 60 minutes. The predrying is over sufficient if approx. 50 to 99% of the amide solvent has been removed and the Layer does not contain bubbles.

The coagulation (d) takes place in a liquid medium in which the aromatic Copolyamide is insoluble, but the amide solvent and, if appropriate existing solvents are soluble. The separation from the carrier can be carried out before coagulation, provided that the layer after predrying is sufficiently firm, but it can also only after immersion in the Coagulation bath take place. Can be used as an economic coagulant Water or water / solvent mixtures, optionally with suitable ones Additives, e.g. B. complexing agents for the dissolving agents can be used. As Solvents are all those which mix with the amide solvent leave, dissolve any solvent and the copolyamide not solve. For example, water / acetone mixtures are suitable. Also Mixtures with the amide solvent itself can be used if there is sufficient precipitant in the mixture. In this case, there should be several Baths with a concentration gradient can be used. In the coagulation bath become the solvent and a large part of the amide solvent still present removed by means.  

The drying (e) serves to remove the coagulum as completely as possible agent and amide solvent and takes place at elevated temperature also under vacuum. The necessary conditions depend on the Film thickness and the choice of amide solvent and coagulant. Becomes the dimensional stability of the film at high temperature is required high drying temperatures, e.g. B. 200 ° C to 400 ° C to choose, as this is the Increase operating temperature of the thermal shrink.

As already described in EP-A-03 03 949, one can be reached by a the final drying (e) of such copolyamide Films at temperatures of 280 ° C extremely high strength and E- Module values (e.g. 800 MPa or 19 GPa with 1.5 times stretching).

Technically, film materials with high strengths are one of the reasons for this interesting, because they have smaller film thicknesses with the same machinability, d. H. Reliability in the manufacture, processing and use, e.g. B. at Allow winding and winding.

A continuous stretching process at temperatures of 280 ° C is however quite expensive in terms of equipment. In addition to, for example, lubrication problems in the continuously operating stretching frame is the one for successful stretching necessary temperature uniformity across the entire width of the film convection in a wide-open frame that is open at both ends hardly possible.

The object of the present invention was therefore one less technically elaborate process for the production of films from aromatic Co to find polyamides with increased strength.  

It has now surprisingly been found that ensuring the dimensions constancy, d. H. a prevention of shrinkage during the final Drying process (s) already an increase in the strength and the modulus of elasticity causes over 30% or 50%. Already measures that Limiting shrinkage, but not completely preventing it, has an effect here.

In addition, it was found that strength and modulus of elasticity are still further let it increase if the film is stretched when wet. These Stretching can take place before and / or in the coagulation bath.

Both measures are without great technical effort, especially without the usual high stretching temperatures can be achieved.

The definition is for a better understanding of the measures according to the invention a dimension constancy factor D:

Depending on the version, D can be equal to or in the longitudinal and transverse directions of the film to be different.

According to the processing method according to the prior art (EP-A-03 03 949 without stretching) D is approx. 0.7 to 0.8. Are the dimensions according to the Keeping the invention constant, D is 1.0. If an inventive wet stretching is carried out, D <1.0.

If a material that is firmer only in the direction of travel (production direction) is required, then it is sufficient if D is 0.9 in the longitudinal direction. In a continuous This can be done by leading guide rollers before or in the process Coagulation bath compared to the fixed casting support (usually a roller or  Band) can be achieved. This process measure is usually achieved at the same time a transverse shrinkage of the film, which leads to a reduction in the D values means in the transverse direction. Such films are particularly strong in the longitudinal direction and particularly splice-stable in the transverse direction.

The latter is very surprising, since usually films with a high length Orientation spliced very easily, d. H. low transverse toughness exhibit.

Become isotropic but increased strength properties in both directions required, D should be equal in the longitudinal and transverse directions and 0.9. For D = 1.0 the film web should be fed to the dryer without great tension will. In order to prevent longitudinal shrinkage, the entrance and exit path speed should be the same. A transverse shrink can e.g. B. by a lateral guidance of the film web can be prevented.

Films that are even firmer in both directions can be combined with a combination of Longitudinal and transverse stretching in front of and / or in the coagulation bath with the above dimensional stability can be obtained in the dryer. The longitudinal Stretching is expediently carried out as already described (for example by different roller speeds) and the transverse stretching after the usual tenter technology, with no increase in the wet film web Temperatures in the tent are required. Then during drying the dimensions achieved after stretching are retained.

The films which are produced by the process according to the invention find use in areas where strength and / or thermal stability be requested. Especially as tape material, e.g. B. as a carrier for magnetic tapes or winding insulation for cables allows the very high strength another Reduction of the film thickness and a corresponding space saving. The height Heat resistance is for different coating techniques such. B. 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 driving, 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 films produced (inventive and comparative examples) were the mechanical properties modulus of elasticity, tensile strength and elongation at break Strip samples determined in a tensile testing machine according to DIN 53 455. The Sample width was 15 mm and the clamping length was 100 mm. The modulus was as a secant module between 0.4 and 0.6% elongation at a test speed speed of 10 mm / min, the tensile strength and elongation at 100 mm / min determined.  

The inherent viscosity

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

Example 1

A solution of 5.0% by weight of an aromatic copolyamide which was produced from TPC, PPD, DMB and BAPOB in a molar ratio of 1: 0.25: 0.5: 0.25 and an η _inh of 5.9 dl / g and 1.7% by weight of CaCl ₂ in NMP, was heated to 90 ° C. and spread onto a glass plate using a doctor blade. The glass plate was placed in a forced air oven (130 ° C) for 20 minutes to remove part of the solvent. The polymer concentration was then 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 dried in a forced-air drying cabinet at 250 ° C. for 10 minutes. The film obtained had a thickness of 20 μm and a residual NMP content of 0.02%.

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

Example 2 (comparative example)

The solution from Example 1 became a film as described in Example 1 processed, but with the difference that the drying free hanging without Tenter frame took place. The film shrank during this drying  evenly in the longitudinal and transverse directions. She only owned 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 (see 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 in Table 1 given.

Example 4 (comparative example)

The solution from Example 3 was processed as in Example 2. After Drying was 73% of its original size. Mechanical properties s. Table 1.

Example 5

A solution of 3.0% by weight of an aromatic copolyamide made 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 contained 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 Use of a tenter during drying. That's why it was Dimensional stability during drying is not guaranteed, so that the film afterwards only had 70% of their original dimensions. The mechanical The strength of the film was lower than that of the film according to Example 5.

Example 7

A solution of 10% by weight 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 _inh of 3.9 dl / g and 3.5% CaCl ₂ in NMP, were heated to 170 ° C and spread with a doctor blade on a glass plate. The layer was predried 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, clamped in a tenter and dried in a circulating air dryer for 10 minutes at 250 ° C. 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 sub decided that the drying took place at 250 ° C without stenter, the Foil shrank. After drying, the film was wavy and only had  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 circulating 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 (cf. 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 as in Example 9, but with a different web speed ratio. After the final 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 the final drying, the web speed was 169% of that of the stainless steel belt and the web width was 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 transversely by 150% of its original width. The NMP was then removed in another water bath and the film dried. The last steps were carried out under constant dimensions.

Thus it was D in the transverse direction now 0.61 · 1.5 = 0.91. The modulus of elasticity in the transverse direction was 9.0 GPa (without transverse stretch: 3.5 GPa).  

Table 1

Table 2

Claims (15)

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-Ar¹-CO-
C -HN-Ar²-NH-
D -HN-Ar³-NH-
E -HN-Ar⁴-Z-Ar⁵-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 structural unit B is 0 to 5% of the sum of the molar proportions of structural units A + B,
the number of diamine components C + D + E per molecule is 2,
the number of diamine components is D + E ≠ 0, and where
-Ar- and Ar ² - mean divalent aromatic radicals (arylene radicals) whose valence bonds are in para- or - in the case of linearly fused benzene rings - in a comparable coaxial or parallel position and where these arylene radicals are optionally substituted by one or two inert radicals such as lower alkyl, alkoxy or halogen are substituted,
-Ar ¹ - means a divalent, aromatic radical (arylene radicals), the valence bonds of which are in a meta- or - in the case of linearly fused benzene rings - in a comparable angled position and optionally substituted by one or two inert radicals such as lower alkyl, alkoxy or halogen,
-Ar³- a biphenylene structure of formula I. has or has the meaning of -Ar¹-,
-Ar⁴- a para-phenylene structure of the formula II owns
-Ar⁵- a para-phenylene structure of the formula II or a meta-phenylene structure of the formula III owns
-Z- a divalent link selected from -O-, -S-, -CH₂-, -C means (CH₃) ₂- and -CO-NH 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) pre-dried in order to remove part of the solvent, d) coagulation is carried out in a precipitant and e) the film is finally sealed, for the purpose of removing the coagulant and the remaining amide solution by means of drying, characterized in that the dimensional constant factor D over the process steps c), d) and e) in the longitudinal and / or transverse direction is 0.9. 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 via process steps c), d) and e) in the longitudinal and / or transverse direction in the range from 0.9 to 2.0 lies. 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 after process step c). 5. The method according to one or more of claims 1 to 4, characterized in that the film after process step c) or d) is released from the solid support.   6. The method according to one or more of claims 1 to 3, characterized in that the film in the process steps b) to d) is performed without great tension. 7. The method according to claim 6, characterized in that the tension-free guidance through synchronization of the inputs and Output path speed is reached. 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 is a dissolving aid contains. 10. The method according to claim 9, characterized in that the Solvents are selected from one or more halogens that 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) is still on the solid carrier begins. 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 heat-resistant electrical insulation material. 15. Use of the high-strength film according to claim 12 as a carrier for flexible printed circuits.