JPH0144142B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing aromatic polyamide films with improved electrical and physical properties. More specifically, by stretching an aromatic polyamide film containing a specific amount of water in wet steam at 50°C or higher, it is possible to achieve industrially advantageous continuous wet stretching, and at the same time improve electrical and physical properties. The present invention relates to a technology for obtaining an aromatic polyamide film with excellent properties. Aromatic polyamides have excellent heat resistance and mechanical properties, and include P-phenylene terephthalamide, halogen-substituted P-phenylene terephthalamide, m-phenylene terephthalamide,
-Phenylene isophthalamide-based polymers and m-phenylene isophthalamide-based polymers are polymeric materials that have been widely used in various fields such as fibers and synthetic papers, and have attracted particular attention in recent years. Fully aromatic polyamides are generally infusible or the melting temperature and decomposition temperature of the polymer are close to each other, so it is difficult to melt-mold them, and they are generally processed by dry molding or wet molding from dope using an amide solvent. The manufacturing of molded products is being carried out. A comparison of the processes for manufacturing films by the above-mentioned wet molding method or dry molding method from the viewpoint of economics, technology, and film performance is as follows. That is, in the dry molding method, the solvent is removed in a heated atmosphere, and the solvent used for molding wholly aromatic polyamide generally has a high boiling point and a large latent heat of vaporization. In particular, depending on the type of solvent, the affinity is so strong that some may even form complexes with the polymer, so if a dry molding method is used, it may take a long time to remove the solvent at high temperatures. It is an economically disadvantageous process. If a wet molding method is adopted, the above-mentioned difficulties in film production by a dry method can be overcome. However, films obtained from conventional wet-forming processes generally have significantly inferior film performance compared to those from dry processes. One of the biggest technical challenges when adopting a wet method is the selection of a coagulation bath. That is,
Even if special consideration is given to the coagulation performance, coagulation time, coagulation temperature, etc. of the coagulation bath, there is a problem in that the film is still non-uniform and it is difficult to produce a film with excellent mechanical and electrical performance. Thus, high-performance films made of wholly aromatic polyamides have not yet been established on the market, and poly-m
- Heat-resistant insulating paper obtained by paper-making from fibers and pulp made of phenylene isophthalamide is used. However, it is often difficult for some insulating papers to maintain their insulating function in electric fields of several thousand volts. As a result of intensive studies on the coagulation properties of aromatic polyamide films during molding, the present inventors selected the polymer concentration and solubilization aid concentration in the aromatic polyamide composition, and decided to introduce them into the aqueous coagulation bath. Therefore, we discovered an industrially extremely advantageous manufacturing method,
I've already suggested it. However, aromatic polyamide films generally have low mechanical properties in an unstretched state and may not always exhibit satisfactory performance. Possible methods for stretching the aromatic polyamide film include dry heat stretching at a high temperature of around 300°C or higher, swelling heat stretching in an aqueous amide solvent at around 60 to 80°C, and the like. When the dry heat stretching method is applied to an aromatic polyamide film, the conventional wet-formed film is extremely brittle, and cannot be stretched in practice even if stretching conditions such as stretching humidity and processing time are varied. Although it is possible to stretch dry-formed films, dry-formed films contain organic solvents that pose a risk of explosion, so there are problems with stable stretching over long periods of time. This method also requires high temperatures and is economically disadvantageous. On the other hand, when the swelling hot stretching method is applied to films, not only wet-formed films but also dry-formed films tend to swell and become opaque in the swelling solution. It was difficult. Stretching methods to solve these problems include JP-A No. 52-56169, No. 53-42265, No. 53-42266, No. 53
-42267 and 53-42268, etc., propose a method in which an aromatic polyamide film is treated and impregnated with an aqueous solution containing an amide solvent and/or an ionic metal salt, stretched at room temperature, and then washed and dried. However, this method not only requires washing with water after stretching, but also requires handling the film impregnated with highly corrosive compounds such as amide solvents and ionic metal salts, making the stretching method extremely disadvantageous in terms of equipment. can be,
This is not necessarily a satisfactory method in industrial production. Taking these points into consideration, the present inventors investigated various methods for producing aromatic polyamide films that are advantageous for industrial production and have excellent electrical and physicochemical properties. The present invention was developed based on the new knowledge that aromatic polyamide films can be stretched extremely easily in wet steam at temperatures above a certain temperature. That is, the present invention provides an aromatic polyamide film containing at least 40% by weight of water and substantially no components other than water, using a tenter to heat it with wet steam at 50°C or higher (hereinafter referred to as "wet steam"). This is a method of producing an aromatic polyamide film by stretching it at least in the width direction by a factor of 1.1 or more in steam (referred to as "steam"). More preferably, the composition ratio of the aromatic polyamide composition is according to the following formula: 0.5≧a/a+b≧0.05...(1) c/a≧0.1...(2) [In the above formulas (1) and (2), a represents parts by weight of the aromatic polyamide, b represents parts by weight of the amide solvent, and c represents parts by weight of the solubilization aid. ] An aromatic polyamide film with a moisture content of 40% by weight or more obtained by a wet molding method in which an aromatic polyamide composition represented by the formula is introduced into aqueous coagulation is uniaxially or This is a method for producing an aromatic polyamide film by stretching in biaxial directions. The aromatic polyamide polymer used in the present invention has the general formula It is an aromatic polyamide-based polymer containing the repeating structural unit shown in either alone or in the form of a copolymer, preferably an aromatic polyamide-based polymer containing 75 mol% or more of the repeating structural unit. Here, Ar ₁ and Ar ₂ may be the same or different, and have the following structural formula as a typical example. Here, R is lower alkyl, lower alkoxy, halogen or nitro group, n is an integer from 0 to 4 including O and 4, and x is One type selected from the following, where Y represents hydrogen or a lower alkyl group. When carrying out the present invention, it is necessary that the aromatic polyamide film contains at least 40% by weight of water. If the water content is less than 40% by weight, the stretchability, especially the stretchability in wet steam, will be markedly reduced and it cannot be used. The amount of water contained in aromatic polyamide film is 40% by weight
It is sufficient if the content is more than 60% by weight, but more preferably 60% by weight or more. Although the upper limit is not particularly limited, a water content of 250 to 300% by weight is the upper limit for film formation. In carrying out the present invention, it is necessary that the aromatic polyamide film contains at least 40% by weight of water, but solvents other than water, such as N,N'-dimethylacetamide, An amide solvent such as N-methyl-2-pyrrolidone may be included if necessary. The hydrous aromatic polyamide film can be obtained by (1) dry-wet film forming method or (2) wet film-forming method. Regarding the method for producing an aromatic polyamide film by a dry-wet film forming method, the aromatic polyamide film
The moisture content is determined by casting the amide solvent composition, removing the solvent in an atmosphere of 150 to 250°C, and washing with water.
It is possible to obtain an aromatic polyamide film of 40% by weight or more. As a method for providing an aromatic polyamide film having a predetermined water content used in the method of the present invention, it is particularly preferable to use the following wet film forming method in terms of industrial production and film properties. That is, the composition ratio of the aromatic polyamide composition is expressed by the following formula: 0.5≧a/a+b≧0.05...(1) c/a≧0.1...(2) [In the above formulas (1) and (2), a is aromatic. Parts by weight of the polyamide, b represents parts by weight of the amide solvent, and c represents parts by weight of the solubilization aid. ] A wet film forming method in which an aromatic polyamide composition represented by the following formula is introduced into an aqueous coagulation bath is particularly preferred for obtaining the film of the present invention. The amide solvents used here include tetramethylurea, hexamethylphosphoramide, N,N
-dimethylacetamide, N-methylpyrrolidone-2, N-methylpiveridone-2, N,N-dimethylethyleneurea, N,N,N',N'-tetramethylmalonic acid amide, N-methylcaprolactam, N-acetylpyrrolidine, N,N-diethylacetamide, N-ethylpyrrolidone-2, N,
Examples include N-dimethylpropionic acid amide, N,N-dimethylisobutylamide, N,N-dimethylpropylene urea, N,N-dimethylformamide, and mixtures thereof. A particularly preferred amide solvent is N-methylpyrrolidone-2 (hereinafter referred to as
N,N-dimethylacetamide (hereinafter abbreviated as DMAC) and a mixture thereof can be mentioned. Preferably used solubilizing aids include salts of metals of Groups and/or Groups of the Periodic Table and ammonium halides. Such salts are dissolved in the polymer solution and serve to enhance the stability of the solution, as described in, for example, Japanese Patent Publication No. 35-16027. Preferred solubilization aids include lithium chloride, calcium chloride, and magnesium chloride, with calcium chloride being particularly preferred. In the aromatic polyamide composition used in the present invention, the aromatic polyamide (A), amide solvent (B), and solubilization aid (c) must have the following relationship. 0.5≧a/a+b≧0.05 …(1) c/a≧0.1 …(2) In the above formulas (1) and (2), a is parts by weight of the aromatic polyamide, and b is parts by weight of the amide solvent. , and c represent parts by weight of the solubilization aid. In the above formula (1), if a/a+b<0.05, sufficient moldability for the purpose of film molding cannot be obtained, and the amount of amide solvent used is large, so that the effects of the present invention cannot be fully enjoyed. Can not do it. On the other hand, when a/a+b>0.5, the viscosity of the resulting composition solution becomes extremely high, and it is often difficult to handle. In the above formula (2), it is necessary that c/a≧0.1. It is often difficult to ensure sufficient solution stability when c/a<0.1. The preferred range is c/a ≧0.15. In addition, as a general tendency, the state of the aromatic polyamide composition at room temperature varies depending on the type and amount of solubilization aid used, so the type and amount of solubilization aid used should be preferably selected depending on the purpose. This is very important. In addition, if the amount of solubilizing aid used is too large, for example, c/a>0.6, the solution viscosity of the composition will increase significantly, the coagulability will tend to be impaired, and moisture absorption during operation will become a problem. Not recommended for handling. Therefore, in practice, the amount of solubilization aid is preferably
0.1≦c/a≦0.6, particularly preferably 0.15≦c/a≦0.5
It is. The method for producing the aromatic polyamide composition used in the method of the present invention is not particularly limited, but typical examples include (a) redissolution method and (b) solution polymerization-neutralization method. The redissolution method is a method in which aromatic polyamide, amide solvent, and solubilization aid that have been isolated in advance are mixed in a predetermined ratio and redissolved. A typical method is to dissolve the solubilization aid in an amide solvent and then mix the polymer with the mixture, preferably while cooling. Depending on the type and amount of solubilization aid used, the entire amount may not be dissolved in the amide solvent alone, but it often dissolves uniformly when the polymer is further mixed. Alternatively, it is also possible to further mix and pulverize the solubilization aid powder and the polymer powder as necessary, and then mix them thoroughly with the amide solvent while cooling. The composition of the present invention can also be prepared by a solution polymerization-neutralization method. Using an amide solvent,
It is known to subject an aromatic diamine and an aromatic diacid halide to a polymerization reaction to prepare a polymer solution (see, for example, Japanese Patent Publication No. 14399/1983). It is also known to prepare a stable polymer solution by subsequently neutralizing the hydrogen halide produced in the polymerization solution to produce the plasticizing aid of the present invention (see, for example, Japanese Patent Publication No. 15027/1982). ). Furthermore, a production method using a prepolymer has been proposed as an excellent method for preparing the aromatic polyamide composition of the present invention by a solution polymerization-neutralization method (Japanese Patent Application No.
(See Publication No. 46745). This method is preferable because it allows the composition ratio of the solubilizing aid in the stock solution composition to be controlled. In addition to the above-mentioned solution polymerization method, an interfacial polymerization method (Japanese Patent Publication No. 13247/1983) may also be used as a method for producing the aromatic polyamide that is the object of the present invention. It goes without saying that any aromatic polyamide having the above-mentioned structural units can be used as the target aromatic polyamide, but aromatic polyamides that are particularly preferably used in the present invention and have great effects are also used. is at least 75 repeating units
It is poly-m-phenylene isophthalamide obtained by reacting m-phenylene diamine and isophthalic acid halide such as isophthalic acid chloride by a method such as solution polymerization or interfacial polymerization, and if necessary, it can be copolymerized. The components include P-phenylenediamine, benzidine,
4,4'-diaminodiphenyl ether, 3,4'-
Examples include diaminodiphenyl ether, gysylylene diamine, toluene diamine, 4,4'-diaminodiphenyl sulfone, and acid components include terephthalic acid chloride, 1,4-naphthalenedicarboxylic acid chloride, and 2,6-naphthalenedicarboxylic acid chloride. Acid chloride, diphenyl sulfone-4,
Typical examples include dicarboxylic acid hydrides such as 4'-dicarboxylic acid chloride and 4,4'-diphenylcarboxylic acid chloride. A suitable stock solution composition when such a polymer is used in the present invention will be described below. When 0.25≦a/a+b≦0.336 0.1≦c/a When 0.336≦a/a+b≦0.5 0.028/a+b×a−0.84<c/a The stock solution composition that satisfies the above composition has high thermal stability and moderate It exhibits a suitable solution viscosity and can be preferably used in the present invention. The preferred polymer concentration when using this type of aromatic polyamide is 0.3
≦a/a+b≦0.5, more preferably 0.336<a/a+b≦0.45. In the method of the present invention, the wholly aromatic polyamide composition prepared as described above may contain the following additives, modifiers, etc., as necessary: light stabilizer, heat stabilizer, etc. Stabilizers, antioxidants, crosslinking agents, combustion agents, ultraviolet rays and breakers, antistatic agents, matting agents, coloring agents such as dyes and pigments, various organic and inorganic fillers or reinforcing materials, and various other materials. Plasticizers, solution viscosity modifiers, etc. The composition used in the present invention is usually in the form of a viscous liquid or semi-solid at room temperature. However, as shown in the examples, even if it is semi-solid at room temperature, it should flow easily at temperatures above 80°C and ensure proper fluidity in the temperature range up to the boiling point of the solvent used. The solution has good thermal stability. Therefore, film molding using a melt molding machine is also possible in addition to the conventional wet molding method. The molding temperature varies depending on the composition ratio of the aromatic polyamide composition used and the molding method applied, but 60
It is preferably selected from the range of ~180°C. If the molding temperature is lower than 60°C, the solution viscosity of the composition will be high, making it difficult to obtain a homogeneous film, and sufficient productivity may not be obtained. On the other hand, if the temperature exceeds 180°C, coloring of the molded product and foaming due to moisture in the composition may occur, which may cause operational problems. The aromatic polyamide composition of the present invention can be molded by a wet method or an air discharge wet method. The composition extruded through a slit nozzle or T-die is formed into a film by a wet method. The wet molding method applied to the present invention is the following two methods. Wet molding method - A method in which the stock solution composition is directly introduced into a coagulation bath and molded Aerial discharge - Wet molding method The stock solution composition is once placed in air,
A method in which a gaseous medium such as water vapor or nitrogen is introduced into the coagulation bath. In the present invention, a wet molding method is generally applied when an aromatic polyamide composition with a low solution viscosity is used, and an air discharge-wet molding method is often applied when the solution viscosity is relatively high. However, the method is not necessarily limited, and a more preferable molding method can be selected depending on the purpose of film production and the physical properties of the stock composition. In the present invention, the air-discharge one-wet molding method has extremely significant effects in the following points compared to conventionally known molding methods. Because it enables molding with extremely high polymer concentrations, the amount of expensive amide solvents used is small. A molding method similar to melt molding can be applied, and it is possible to provide a molding method with extremely high productivity, such as improved extrusion speed. A homogeneous, highly transparent film can be stably produced up to a relatively large thickness. Energy costs of manufacturing are reduced. When dry molding is performed from a stock composition containing a solubilizing aid, a wet washing step is required and the process is complicated. In contrast, the method of the present invention basically consists of only a wet molding step, and the process is simple. As the coagulating bath, at least one bath having the following composition is preferably used for forming the aromatic polyamide film of the present invention. (i) Inorganic salt aqueous solution (ii) Organic solvent aqueous solution (iii) Mixed aqueous solution of (i) and (ii) For the purpose of facilitating the stretching process of the method of the present invention and producing a transparent and strong film, coagulation is of course necessary. This is a particularly important factor, and by combining the above-mentioned aromatic polyamide composition and the above-mentioned coagulation bath, the following stretching becomes possible and a high-performance film can be obtained. Typical compounds contained in the inorganic salt aqueous solution are CaCl ₂ , BaCl ₂ , ZnCl ₂ , MgCl ₂ ,
_NaCl2 , KCl, _AlCl3 , _SnCl2 , _NiCl2 , _SrCl2 ,
LiCl, CcBr ₂ , LiBrCa(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ , Al
(NO ₃ ) ₂ , Cc(SCN) ₂ , KSCN, NaSCN, etc. can be mentioned. Preferred inorganic salts include
Examples include CaCl ₂ , MgCl ₂ and ZnCl ₂ , with LiCl ₂ and CaCl ₂ being particularly preferred. It is also generally advantageous for the solubilization aid in the aromatic polyamide composition and the inorganic salt in the coagulation bath to be the same compound. Although the preferred inorganic salt concentration varies depending on the type of inorganic salt, the composition or composition ratio of the aromatic polyamide composition, molding conditions, etc., an aqueous solution containing 20% by weight or more of the above-mentioned inorganic salt is preferable. When such a coagulation bath is used, it is possible to produce a film with excellent mechanical performance. Furthermore, although the coagulation bath composition, temperature, and immersion time are not constant depending on the desired thickness and transparency of the film, the preferred coagulation bath temperature when using an aqueous inorganic salt solution is 40 to 11°C. An organic solvent aqueous solution can also be used as the coagulation bath. As organic solvents, various alcohols,
Amide solvents can also be used. Among various alcohols, alkylene glycol is one of the organic solvents that can be preferably selected. As typical alkylene glycols, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, etc. can be used. The concentration of the polyalkylene glycol or glycerin aqueous solution varies depending on the composition or composition ratio of the aromatic polyamide composition, molding method, or conditions, but generally an aqueous solution of 30% by weight or more can be used. Suitable temperature conditions also vary depending on other factors.
Selected from the range of 30°C to coagulation bath boiling point. In preferred embodiments of the present invention, multi-stage coagulation baths are often used. As a multi-stage coagulation bath, it is possible to use systems with different inorganic salt aqueous solutions at different concentrations and temperatures, systems with completely different coagulation compositions, etc., depending on the needs, but from an industrial standpoint, it is possible to use a combination of coagulation systems of the same type. A multi-stage coagulation bath is preferred. After the organic solvent and inorganic salt are removed in a water washing process, the film thus obtained has a water content of 40% by weight or more, usually 80% by weight or more.
A homogeneous transparent film of 200% by weight can be obtained. In the conventional state of the art, it was believed that it was impossible to stretch a film formed by wet molding in a wet bath, but in the wet steam of the method of the present invention, an aromatic polyamide film with a water content of 40% by weight or more can be stretched at 50°C. The film can be easily stretched. The method of the present invention consists in stretching in humid steam at a temperature of 50°C or higher. Moist steam as used in the method of the present invention refers to an atmosphere with a relative humidity of 80% or more. Also, the temperature of wet steam is
The temperature is preferably 50°C or higher, preferably 80°C or higher. If the temperature of the wet steam is less than about 50° C., the stretchability is lowered, the stress required for stretching becomes extremely large, it is difficult to obtain a large stretching ratio, and the final film performance is undesirable. Furthermore, the stretching ratio is 1.1 times or more, preferably
Considering the performance of the film, it is necessary to perform sequential two-axis and simultaneous two-axis processing at a rate of 1.3 times or more. When the stretching ratio is less than about 1.1 times, the mechanical properties are low, especially the elongation is low and unstable. From the viewpoint of film homogeneity, etc., the stretching ratio is preferably 1.3 times or more, and preferably 2.3 times or less. Of course, it is possible to stretch 2.5 times or more depending on the purpose, but from the viewpoint of long-term stability of continuous stretching and balance of mechanical properties of the obtained film, the preferred range of the stretching ratio is 1.3 to 2.5 times. I can say that. Furthermore, the so-called steam stretching in wet steam is characterized by continuous tenter stretching. In other words, for uniaxial stretching, stretching in hot water or an organic solvent-water bath is fully possible for industrial production, but biaxial stretching in the direction perpendicular to this is usually carried out by a tenter method, and stretching in a bath is also possible. is extremely difficult in terms of equipment. Therefore, the method of substantial wet stretching is achieved for the first time by the method of the present invention, and its significance is extremely important. Therefore, the uniaxial direction is roller stretching in hot water, and the biaxial direction is the sequential biaxial stretching method of the method of the present invention, stretching in wet steam, or the simultaneous biaxial stretching method of the present invention method, in wet steam. This can be said to be a preferred embodiment. By drying the stretched film obtained as described above under a fixed length, an aromatic polyamide with excellent electrical and mechanical properties can be obtained. In addition, by heat-treating under tension if necessary, the film can be made to have the desired strength, elongation, and electrical insulation performance. According to the method of the present invention, a film with excellent transparency, toughness, heat resistance, and electrical insulation properties can be produced continuously and economically. The method of the present invention is effective in the conventionally known aromatic polyamide film production method, but its effectiveness is particularly remarkable in the production method of aromatic polyamide films based on m-phenylene isophthalamide polymers. . That is, as a method for forming an aromatic polyamide film mainly made of m-phenylene isophthalamide-based polymer, a solution composition consisting of an amide-based solvent and an aromatic polyamide is generally cast onto a steel belt in the form of a film. After evaporating most of the solvent in a hot air dryer, the desolubilization aid is then introduced into water.
Methods of desolvation have been proposed (Tokkai 1973).
-42561, 52-57253, 52-152973, etc.).
However, as described above, these methods require a high boiling point organic solvent to be removed by heat, so a large amount of heat is required and the energy cost is high. Furthermore, the above thermal evaporation is followed by water washing, and finally the desolubilization aid and solvent are removed, so the process consists of a dry and wet two-step process. . Furthermore, in film formation by this method, as mentioned above, it is suggested that it is necessary to pre-treat the film in an aqueous solution containing an amide solvent and/or an ionic metal salt before stretching. When such stretching is carried out, not only is there a disadvantage that an additional process such as washing with water is required after stretching, but also the problem of corrosion of the equipment remains. However, if the method of the present invention is employed, the amount of amide organic solvent used relative to the polymer is small because the aromatic polyamide composition is highly concentrated. In addition, since the film can basically be manufactured only by the wet method, energy costs are also reduced.
The process is also simplified. The ability to produce a high-performance aromatic polyamide film as described above by the method of the present invention is said to be based on the exquisite balance between the composition of the aromatic polyamide stock solution and the composition of the coagulation bath. It's no exaggeration. Japanese Patent Publication No. 47-41743 proposes a method for forming transparent fibers, tapes, etc. by introducing a solution composition consisting of an aromatic polyamide and an amide solvent into a coagulation bath consisting of an aqueous calcium chloride solution. There is. However, it is stated that if this stock solution composition contains 3% or more of a solubilizing aid such as calcium chloride, the performance of the molded product will deteriorate rapidly. On the other hand, in the method of the present invention, the composition ratio of the polymer and the solubilizing aid such as calcium chloride in the aromatic polyamide composition is specified and made compatible with the coagulation bath, thereby substantially affecting the coagulation property during molding. It does not have any adverse effects, but rather has the effect of greatly improving coagulation properties, making it possible to form transparent and dense films. In particular, the excellent coagulation properties ensured by the stock solution composition and coagulation bath composition of the present invention make the structure of the formed film dense and strong, and at the same time impart high transparency. As a result, it is possible to perform wet stretching, which has been considered difficult with conventionally known wet-formed films, and to provide a film that can be easily stretched in wet steam and exhibits excellent performance. In other words, for polymers containing 75 mol% or more of repeating units of poly-m-phenylene isophthalamide, using wet molding can only yield a stretched film with a thickness of about 20 μ at most, which is of practical use. In contrast, with the method of the present invention, high performance films of 25μ or more can be easily produced. In particular, the ability to stably produce stretched films with a thickness of 50 μm or more is much higher than the conventional wet film forming technology and deserves special mention. The aromatic polyamide film obtained by the method of the present invention has a wide range of uses such as industrial materials, insulating materials, and laminated structural materials. Hereinafter, specific examples of the present invention will be illustrated by way of Examples. Further, the excellent solubility of the aromatic polyamide obtained by the method of the present invention and the excellent mechanical properties of the fiber obtained therefrom will be shown together with comparative examples. ηinh in Examples and Comparative Examples
is a solution of 0.5g of polymer dissolved in 100ml of concentrated sulfuric acid.
It is the logarithmic viscosity at 30℃. Example 1 Poly-m-phenylene isophthalamide was used as the aromatic polyamide, and N- as the amide solvent.
Methyl-2-pyrrolidone, as a solubilization aid
An aromatic polyamide composition having the following composition was prepared using _CaCl2 . a/a+b=0.33 c/a=0.20 The above composition was 0.1 mm wide using a 30 m/m extruder.
It was extruded from a 400 mm T-die onto a casting roller at 110°C and introduced into a 43% by weight calcium chloride aqueous solution at 90°C. Subsequently, after washing in cold water of 10°C or lower, stretching was performed between rollers in 1.5 times the machine direction (MD) in hot water of 95°C. This film contained 130% water by weight. Hold the film at both ends with clips at 95℃ and 100% relative humidity.
Stretch it 1.7 times in the transverse direction (TD) at a speed of 1.5 m/min, and then stretch it at 150°C while holding it at a constant length with a clip.
It was dried in a hot air dryer at 200°C to obtain a 25μ film. The mechanical properties of the obtained film are strength: 17.4 Kg/mm ² in MD direction, 16.4 Kg/mm ² in TD direction, elongation 120% in MD direction, 110% in TD direction, and initial Young's modulus of 364 Kg/mm ² in MD direction, 379 in TD direction.
It was strong and well-balanced with Kg/ ^mm2 . For comparison, the uniaxially stretched film of Example 1 was stretched 1.7 times in the TD direction at a speed of 1.5 m/min while holding both ends of the film with clips at room temperature in the atmosphere. During stretching, the film is stretched at 2 speeds per minute.
The film broke more than once, and the surface of the part that could barely be stretched turned white and devitrified. Examples 2 to 4 In the same manner as in Example 1, the coagulation conditions and water washing conditions were varied, and uniaxial roller stretched films in hot water with different water contents were used and stretched and dried in continuous wet steam in the same manner as in Example 1. I went. The results obtained are shown in Table 1.

[Table] Example 5 The film obtained in Example 1 and having a water content of 130% by weight was stretched in various types of wet steam to determine the maximum stretching ratio. The results are shown in Table 2.

[Table] Example 10 An aromatic polyamide having the following composition using poly-m-phenylene isophthalamide as the aromatic polyamide, N-methyl-2-pyrrolidone as the amide solvent, and CaCl ₂ as the solubilization aid. The composition was prepared. a/a+b=0.2, c/a=0.2 The above composition was cast onto a glass plate using a doctor knife, and N-methyl-
After a portion of 2-pyrrolidone was removed by evaporation, the sample was immersed in water. A film with a water content of 90% by weight that was naturally peeled off from a glass plate was sequentially biaxially stretched 1.9 times in a saturated steam atmosphere at 90°C. After stretching, it was dried under a fixed length to obtain a 30μ film. The mechanical properties of the obtained film were strength 17.8Kg/mm ² , elongation 78%, and Young's modulus 375Kg/mm ²
It was excellent. Examples 11 to 16 In Example 10, various aromatic polyamides were used and various compositions were adjusted to obtain water-containing aromatic polyamide films. These films were similarly stretched at 90°C in a saturated steam atmosphere and dried under a fixed length to obtain various films. The obtained film was of excellent quality as shown in Table 3.

【table】

【table】

Claims (1)

[Scope of Claims] 1. An aromatic polyamide film containing at least 40% by weight of water and containing substantially no components other than water is heated to 1.1 times or more in wet steam at 50°C or higher using a tenter. A method for producing an aromatic polyamide film, which comprises stretching at least in the width direction. 2 An aromatic polyamide film containing at least 40% by weight of water has a composition ratio of the following formula: 0.5≧a/a+b≧0.05...(1) c/a≧0.1...(2) [The above formula ( In 1) and (2), a represents parts by weight of the aromatic polyamide, b represents parts by weight of the amide solvent, and c represents parts by weight of the solubilization aid. ] The method for producing an aromatic polyamide film according to claim 1, which is obtained by a wet molding method in which an aromatic polyamide composition represented by the following is introduced into an aqueous coagulation bath. 3. The method for producing an aromatic polyamide film according to claim 1 or 2, wherein the aromatic polyamide is a polymer in which at least 75 mol% of the structural units are m-phenylene isophthalamide.