JPS63152641A - Para-oriented aromatic polyamide flame-retardant film and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled film having high strength and modulus and excellent flame-retardance and fastness, by forming an optically anisotropic dope containing a para-oriented aromatic polyamide to the form of a film, converting and coagulating the film, contacting with a flame-retardant and drying the product. CONSTITUTION:The objective film having a density of >=1.37g/cm<3> and Young's modulus of >=500kg/mm<2> can be produced by (1) casting an optically anisotropic dope containing (i) a para-oriented aromatic polyamide having a logarithmic viscosity etainh of >=2.5 and (ii) a solvent selected from concentrated sulfuric acid having a concentration of >=96wt.%, chlorosulfuric acid and fluorosulfuric acid on a substrate keeping the optical anisotropy, (2) leaving the film until the film is converted to an optically isotropic dope by moisture-absorption and/or heating, (3) removing the solvent from the film after coagulation, (4) contacting the obtained film with a liquid containing one or more kinds of flame-retardants selected from aliphatic (cyclic) phosphoric acid esters and aromatic phosphoric acid esters and (5) drying the film at >=50 deg.C under con trolled shrinkage.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a flame-retardant film made of para-oriented aromatic polyamide and a method for producing the same, and more particularly, to A para-oriented aromatic compound that exhibits excellent mechanical properties in both the direction (hereinafter abbreviated as TD force direction) and the width direction (hereinafter abbreviated as TD force direction), and has flame retardancy with a limiting oxygen index (L, O, I) exceeding 35. This invention relates to a polyamide flame-retardant film and its manufacturing method.

(Prior art) Polyparaphenylene terephthalamide (hereinafter referred to as PPTA)
Para-coordination type aromatic polyamides, typified by It is a polymer material that is attracting particular attention. It has also been reported that fibers spun from concentrated solutions exhibiting optical anisotropy exhibit high strength and modulus, and have already been put into industrial use. In addition, several examples of molding PPTA into films have been proposed (for example, Japanese Patent Publication No. 56-45421, Japanese Patent Publication No. 5717886, etc.).

It is very difficult to impregnate flame retardant into these para-oriented aromatic polyamide molded products due to their high crystallinity and dense structure. Until now, as a method for making aromatic polyamide flame retardant, impregnation of undried fibers swollen in water with additives such as flame retardants has been proposed, as disclosed in JP-A-50-12322 and JP-A-49-75824. , No. 53-35020 and Japanese Patent Publication No. 56-33487.

However, for para-oriented aromatic polyamide fibers, the only technology disclosed is wet spinning into a high-temperature coagulation bath using a spinning dope with a low polymer concentration, and the yarn obtained by this method has no voids. It has a large amount of carbon, a low density, and a significantly low strength. This is because the premise is to create porous fibers with many voids and a density of about 1.35 g/aJ or less, which is easy to impregnate.

In addition, since the porous fibers with many voids are impregnated with flame retardant, they lack robustness. There are, but it's still not enough.

On the other hand, no technology has yet been disclosed for impregnating a para-oriented aromatic polyamide film with a flame retardant. In particular, it has been thought that it would be impossible to impregnate a para-oriented aromatic polyamide film, which has excellent mechanical performance due to its dense and highly oriented structure, with a flame retardant without impairing the mechanical performance.

(Problems to be Solved by the Invention) The object of the present invention is to provide a flame-retardant polymer having high strength and high modulus, which is flame-retardant, and has excellent robustness of the flame-retardant effect. The purpose of the present invention is to provide a film and a method for producing the same.

(Means for Solving the Problems) As a result of intensive research into a method for obtaining such a film, the present inventors have developed an optically anisotropic dope of para-configured aromatic polyamide onto a support surface in the form of a film. After that,
A special method in which an undried film with a moisture content of 50% by weight or more obtained by isotroping, then coagulation, and removal of the solvent is brought into contact with a liquid containing a flame retardant, and then dried, provides excellent mechanical properties. It was discovered that a film exhibiting these properties and excellent in flame retardancy and fastness could be obtained, and after further research, the present invention was completed.

That is, the first aspect of the present invention is made of a substantially para-coarticulated aromatic polyamide having a logarithmic viscosity ηinh 2°5 or more, a density force of 37 g/cn1 or more, and a Young's modulus of 500 kg/mm2 or more. and at least 0.1% by weight of one or more flame retardants selected from the group consisting of aliphatic phosphoric esters, aliphatic cyclic phosphoric esters, and aromatic phosphoric esters based on the total weight of the film. This is a para-oriented aromatic polyamide flame-retardant film characterized by containing phosphorus.

The second aspect of the present invention is a para-steroidal aromatic polyamide having a logarithmic viscosity ηinh of 2.5 or more and at least one solvent selected from the group consisting of concentrated sulfuric acid, chlorosulfuric acid, and fluorosulfuric acid at a concentration of 96% by weight or more. An optically anisotropic dope comprising: is formed into a film on a supporting surface while maintaining its optical anisotropy, until the dope is substantially converted into an optically isotropic dope by moisture absorption and/or heating. After standing, the film containing a water content of 50 MN% or more obtained by solidifying and substantially removing the solvent is brought into contact with a liquid containing a flame retardant, and then the shrinkage is limited at a temperature of 50"C or more. This is a method for producing a partially oriented aromatic polyamide flame retardant film, which is characterized in that it is dried while drying.

The flame retardant contained in the para-articulated aromatic polyamide H flame retardant film of the present invention is preferably selected from aliphatic phosphoric esters, aliphatic cyclic phosphoric esters and aromatic phosphoric esters.

These typical flame retardants are D(c2o)3p=o, (H2CO)3P=O1, etc., and some of the hydrogen atoms in the aliphatic substituents and aromatic substituents are replaced with halogens. There may be. Flame retardancy is usually achieved by selecting one of these compounds and diffusing it into the film, but it is also possible to diffuse and impregnate two or more compounds. In general, non-esterified phosphoric acid compounds such as phenylphosphonic acid are also effective as flame retardants, but these compounds are highly acidic and the loosely oriented aromatic polyamide film itself may be used during impregnation or for various applications. may deteriorate during use.

The objective of the present invention is high flame retardancy (for example, 0°1 is 3
5 or more), the amount of iTE should be at least 0.1%, more preferably 0.1% based on the total weight of the film.
The flame retardant mentioned above must be included to provide 3 imti 1% phosphorus. Furthermore, in order to ensure high N flammability fastness, it is preferable that the flame retardant is sufficiently impregnated not only in the surface layer of the film but also in the center.

The individually oriented aromatic polyamide used in the present invention is substantially composed of units selected from the group consisting of the following structural units.

NHArI NH-"(I) -CO-A r2- CO--(n)-NH-Ar
3--Co-...(I[[)where A r 1 ,
A r 2 and Ar 3 are each a divalent aromatic group,
(I) and (If) when present in the polymer are substantially equimolar.

In the polyamide film of the present invention, in order to ensure good mechanical performance, Arc, Ar2 and Ar3 are each so-called 1, disjointly oriented groups.

Here, the term "discretely oriented" means that the bonds that grow the molecular chain are located coaxially or parallel to the opposite direction of the aromatic nucleus. Specific examples of such divalent aromatic groups include paraphenylene, 4,4'-biphenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-
Examples include naphthylene and 2,5-pyrylidine. They may be substituted one or more with non-reactive groups such as halogen, lower alkyl, nitro, methoxy, sulfonic acid, cyan groups, etc. All of Ar1, Ar2 and Ar3 may be two or more types, and may be the same or different.

The polymer used in the present invention can be produced from diamines, dicarboxylic acids, and aminocarboxylic acids corresponding to each unit by a method known so far. Specifically, there is a method in which a carboxylic acid group is first induced into an acid halide, an acid imidazolide, an ester, etc. and then reacted with an amino group, or a method in which an amino group is induced into an isocyanate group and then reacted with a carboxylic acid group. As for the polymerization method, so-called low-temperature solution polymerization method, interfacial polymerization method, melt polymerization method, solid phase polymerization method, etc. can be used.

The para-oriented aromatic polyamide used in the present invention includes:
Groups other than those mentioned above are copolymerized with about 10 mol% or less,
Other polymers may also be blended.

The most typical para-oriented aromatic polyamide of the present invention is poly-p-phenylene terephthalamide (P
PTA) and poly-p-benzamide.

The polymerization degree of the individually oriented aromatic polyamide of the present invention is usually 2.5 or more, preferably 3.5 or more logarithm, because if it is too low, a film with good mechanical properties, which is the object of the present invention, cannot be obtained. A polymer having a degree of polymerization giving a viscosity η1nh (value measured at 30° C. by dissolving 0.5 g of polymer in 100 ml of sulfuric acid) is selected.

The film of the present invention has a density of 1.37 g/cm3 or more, more preferably 1.39 g/cm3! It has a density of more than

This is the density necessary to ensure the above-mentioned mechanical properties of the film, and is also the density that can maintain the preferred fastness of the flame retardant.

The film of the present invention has a Young's modulus of 500 kg, /+m
2 or more, more preferably 700 kg/mm2 or more. This is a necessary condition in order for the film of the present invention to be difficult to deform due to external forces, or to be strong even if it is thin.

Next, a method for obtaining a para-oriented aromatic polyamide film impregnated with such a flame retardant will be described.

Suitable solvents for preparing the optically anisotropic dope used in forming the film of the present invention include sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, or mixtures thereof at a concentration of 96% by weight or more. The sulfuric acid may be 100% or more, that is, fuming sulfuric acid, or trihalogenated acetic acid or the like may be mixed and used as long as the effects of the present invention are not impaired.

The polymer concentration in the dope used in the present invention is at room temperature (
A concentration that exhibits optical anisotropy at a temperature of about 20° C. to 30° C. or higher is preferably used, and specifically, it is used at a concentration of about 9% by weight or more, preferably about toiit% or more. At polymer concentrations below this range, ie, polymer concentrations that do not exhibit optical anisotropy at room temperature or higher temperatures, the formed film often does not have desirable mechanical properties. Although the upper limit of the polymer concentration of the dope is not particularly limited, it is usually 20% by weight or less, and preferably 16% by weight or less for PPTA with particularly high ηtnh.

The dope used in the present invention may contain additives such as fillers, light removal agents, ultraviolet stabilizers, heat stabilizers, antioxidants, and melting aids, as long as they do not significantly impair the solubility of the polymer in the dope. may be mixed.

Whether the dope is optically anisotropic or optically isotropic can be determined by a known method, such as the method described in Japanese Patent Publication No. 50-8474, but the critical point depends on the type of solvent, temperature, polymer It depends on the concentration, degree of polymerization of the polymer, content of non-solvent, etc., so by investigating these relationships in advance, you can create an optically anisotropic dope and change the conditions to make it an optically isotropic dope. It is possible to change from tropic to optically isotropic.

To obtain the film of the present invention, for example, the dope is formed into a film on a support surface, and then the dope is converted from optically anisotropic to optically isotropic prior to solidification.

In order to convert optical anisotropy to optical isotropy, specifically, before solidifying an optically anisotropic dope formed into a film on a support surface, the concentration of the solvent forming the dope is lowered by absorbing moisture. The dope can be transformed into an optically isotropic region by changing the solubility of the solvent and the polymer concentration, or the dope can be heated to transform it into an optically isotropic region simultaneously or sequentially, or the dope can be transformed into an optically isotropic region by heating and moisture absorption. This can be achieved by using them together.

The dope can be made to absorb moisture, for example, by leaving it in the air for a certain period of time or more.

The air in this case preferably has a relative humidity of 50% or more.

Further, actively applying humidification to a normal humid atmosphere is a desirable embodiment because it shortens the time until optical isotropy is achieved, and when heating is used in combination, the heating temperature can be lowered. If the relative humidity exceeds 99%, water will condense on the dope at low temperatures, leading to polymer precipitation.
Relative humidity of 100% or more can also be used at temperatures of 45° C. or higher, although the flatness of the film may be lost.

In addition, in a method that uses heating simultaneously with moisture absorption or after moisture absorption, for example, when sulfuric acid is used as a solvent, the temperature at which optical anisotropy substantially disappears and the dope converts to optical isotropy is: Polymer concentration, degree of polymerization, sulfuric acid concentration,
Although it varies depending on the thickness of the dope and the degree of moisture absorption,
Generally, the temperature is preferably about 45°C or higher, and when considering the decomposability of the polymer, it is generally desirable that the upper limit is not too high, and the temperature of the film-like dope should be selected to the extent that it does not exceed 200°C. desirable.

Although the mechanism of optical isotropy caused by this moisture absorption is not necessarily clear, it is probably because the liquid crystal region of the PPTA-solvent system is considerably reduced due to the decrease in polymer concentration and solvent concentration due to moisture absorption. This moisture absorption alone is sufficient to achieve optical isotropy, but if this is further accompanied by heating, isotropy can be achieved in a short period of time. This method is particularly effective when the dope is thick.

In the present invention, the dope coagulating liquid that can be used is, for example, dilute sulfuric acid containing about 70% by weight or less of water, aqueous sodium hydroxide solution containing about 20% by weight or less, aqueous ammonia, about 5% by weight or less
These include 0% by weight or less sodium chloride aqueous solution and calcium chloride aqueous solution. The temperature of the coagulation bath is not particularly limited, and is usually in the range of about -5°C to 50°C.

Since the coagulated film as it is contains acid, it is necessary to wash and remove the acid as much as possible in order to produce a film whose mechanical properties are less likely to deteriorate due to heating. Specifically, it is desirable to remove the acid content to about sooppm or less. Water is usually used as the cleaning liquid, but if necessary, hot water may be used, or washing may be performed by neutralizing with an alkaline aqueous solution and then washing with water. Cleaning is carried out, for example, by running the film in a cleaning liquid or by spraying the cleaning liquid.

In the present invention, the film produced in this manner is maintained at a moisture content of at least 50% by weight or more, preferably 80% by weight or more without being dried, and is brought into contact with a liquid containing a flame retardant. I have to let it happen.

When the water content is less than 50% by weight, the product is in a so-called half-dried or dried state, and the diffusion rate of the flame retardant from the liquid containing the flame retardant is significantly reduced, making it impossible to impregnate the flame retardant to a practical level.

The flame retardant impregnation treatment is carried out by bringing the film into contact with a solution of the above impregnating agent. The flame retardant particles are preferably dispersed in molecular form in the flame retardant solution, and the flame retardant-containing liquid is most preferably an aqueous solution. Even non-water-soluble flame retardants can be impregnated in the form of emulsions, dispersions, or colloids, but from the viewpoint of easy impregnation to the inside of the film, 0.1μ or less, preferably 0.
．． It is preferable that particles having a particle size of 0.01 μm or less are dispersed. Stabilize these emulsions, dispersions, etc.
Alternatively, additives such as surfactants may be added to improve flame retardancy. If the flame retardant is unnecessary or poorly soluble in water, the flame retardant can be dissolved in a water-soluble organic solvent such as acetone, methanol, dimethylformamide, N-methylpyrrolidone, dimethylacetamide, or a mixed solution of these and water. It can also be used in a dispersed manner.

Impregnation can be carried out by immersing the film in a liquid containing an impregnating agent, or by spraying or showering. The impregnation temperature can be set arbitrarily between room temperature and the boiling point of the impregnating agent-containing liquid, but a high temperature is preferable. The impregnating agent concentration is also arbitrary between 0.1 and 99ffi1%.

Since impregnation with a flame retardant is generally diffusion-limited, the impregnation temperature, time, and impregnation concentration should be determined depending on the desired degree of flame retardancy. The content of the flame retardant that exhibits a flame retardant effect is approximately 0.1% by weight or more based on the dry film of phosphorus.

The film rendered flame retardant in this way is dried, if necessary, after washing off the flame retardant adhering to the surface, but it can also be stretched prior to drying if desired. That is,
1.01 in one or two directions of wet film before drying
By stretching the film by about 1.4 times, the mechanical properties of the film can be improved.

The film must be dried under tension, at a constant length, or slightly stretched while limiting shrinkage of the film. If a film that tends to shrink with the removal of a cleaning solution (e.g., water) is dried without any restriction on shrinkage, microscopically non-uniform structure formation (crystallization, etc.) may occur. The resulting film may lose its flatness or curl. To dry while controlling shrinkage, for example, a tenter dryer or drying between metal frames can be used.

Other conditions related to drying are not particularly limited.
Any method can be selected from methods using heated gas (air, nitrogen, argon, etc.) or room temperature gas, methods using radiant heat such as electric heaters or infrared lamps, and dielectric heating methods.

In the present invention, it is important that the drying temperature of the film is 50°C or higher. This is because drying at a temperature below 50° C. results in insufficient densification of the film structure (low density), resulting in insufficient flame retardant fastness. The drying temperature is preferably 100 to 300°C.

(Example) Examples and reference examples (manufacturing examples of PPTA) of the present invention are shown below, but these reference examples and examples are for explaining the present invention, and are not intended to limit the present invention. .

In addition, unless otherwise specified in the examples, parts by weight or mW
Shows %.

The logarithmic viscosity ηinh in the examples is 98% sulfuric acid 100 m (l
The viscosity of the dope was measured using a B-type viscometer at a rotational speed of 1 rpm. The strength and elongation and modulus were measured using a dial gauge held in the hand.The film sample was cut into a 100NXIO dragon rectangle using a constant speed elongation type strength and elongation +1 machine, and the initial grip length was 30 mm and the tensile speed was 30+n/min. Load at -
It was calculated from the elongation curve taken five times. Density was measured at 30°C by density gradient tube method using carbon tetrachloride-toluene.

Approximately 50 mg to 100 m of film containing flame retardant
g Accurately weigh and place in a platinum basket.

This is combusted in an oxygen stream, and the gas generated by the combustion is introduced into a mixed solution of 10 ml of 0.01N caustic soda and 10 ml of water and absorbed. Water is added to the above solution that has absorbed the combustion gas, and the volume is adjusted to exactly 50 ml. This solution was passed through an ion chromatogram (Guionesox Model 10 manufactured by Guionesox) to measure the phosphorus content. At that time, the separation column used was a column filled with TSK gel-anion pw (manufactured by Toyo Soda Co., Ltd.), and the eluent was a 0.0015 mol/l sodium bicarbonate aqueous solution and 0.0012 mol/l.
A 1:l mixed solution of sodium carbonate aqueous solution was used. Alternatively, the quantification of phosphorus was performed based on a phosphorus-containing calibration curve prepared by performing the above operation in advance using a known amount of potassium dihydrogen phosphate. .

Measurement of limit oxygen index〉 The limit oxygen index (L, 0.1), which is an index of flame retardancy, was measured using a flame retardancy tester (manufactured by Suga Test Instruments Co., Ltd., 0N- 1), and the film itself was used as a test piece. A is the lowest oxygen flow rate at which the test piece can burn continuously for 3 minutes or more or 5ω or more.
(427 m1n), and the nitrogen flow rate at this time is B (=11.
4-A) If (l/m1n), then L, O, I are L, O, I= (A/ (A+B)) xio.

is the value represented by .

Example 1 A PPTA polymer having an ηinh of 5.5 was dissolved in 99.7% sulfuric acid at a polymer concentration of 12.0% to obtain a dope with optical anisotropy at 60°C. The viscosity of this dope was measured at room temperature and was found to be 14,500 poise. In order to facilitate film formation, this dope was kept at about 70° C. and heated under vacuum. In this case as well, it has optical anisotropy as above,
The viscosity was 4200 poise. This dope is passed through a filter from the tank, passed through a gear pump while keeping it at about 70°C, and passed through a 1.5m bent pipe to the die, and is heated to 0.3mm.
The cast dope was cast from a die with a slit of X3001- onto a Hastelloy belt with a mirror surface, and air at about 90°C, which is about 95% of the relative temperature, was blown onto the cast dope to achieve an optical isodynamic ratio of about 1. Hold it on the belt for a minute, then
Together with the belt, it was introduced into a 20% by weight aqueous sulfuric acid solution at 0° C. and coagulated. The coagulated film was then peeled off from the belt and washed by running it in a water tank at about 20° C. via rotating rollers (residence time: about 3 minutes) to obtain a film with a moisture content of about 400% by weight.

This film was impregnated with the flame retardant by contacting it with a 10% aqueous solution of Ni-19A (manufactured by Meisei Kagaku Kogyo Co., Ltd., registered trademark, chemical structure is listed in the footnotes of Table 1) for 5 minutes at 50°C. After that, the obtained flame retardant film was washed with water and
It was sandwiched between two 15 cm stainless steel frames and dried for a fixed length in an air oven maintained at 200°C. The measurement results of the obtained film are shown in Table 1.

The following margin is Comparative Example 1. Once the 400% water content film obtained in Example 1 is
After drying at 20°C to a moisture content of about 30% by weight,
Impregnation treatment was carried out under the same conditions as in Example 1, and drying was carried out under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 2 After impregnating the 400% water-containing film obtained in Example 1 with the flame retardant shown in Example 1 under the conditions of Example 1,
The obtained film was sandwiched between two stainless steel frames of about IQ cm x 15 cm and air-dried at room temperature (about 23° C.). The results are shown in Table 1.

Example 2 After impregnating the 400% water-containing film obtained in Example 1 with the flame retardant shown in Example 1 under the conditions of Example 1,
The obtained film was sandwiched between two stainless steel frames of about 10 cm x 15 marks, and dried for a fixed length in an air oven maintained at 100°C. The results are shown in Table 1.

Comparative Example 3 The film obtained in Example 1 was dried at 120° C. to a moisture content of 5%, and then the film was dried under the same conditions as Example 2! i
It was brought into contact with the fuel and the containing liquid and dried.

The results are shown in Table 1.

Example 3 The gel-like coagulated film obtained in Example 1 was immersed in a 15% acetone solution of triphenyl phosphate (abbreviated as TPP), and the obtained film was cut into a size of about 10 cm x 15 cm.
It was sandwiched between two stainless steel frames and heated at 50°C for 60 minutes, and then the surface was washed with A7Ton and dried in an air oven maintained at 150°C. The results are shown in Table 1. Example 4 The films obtained in Example 1.2 and Comparative Example 2 were kept in boiling water for 30,60,90 minutes to evaluate the fastness of the flame retardant. The results are shown in Table 2. The results showed that the film of the present invention maintained excellent flame retardancy even after treatment with boiling water.

Table 2 shows that a PPTA film that was not subjected to any flame retardant treatment showed a glue, O, I of about 28, burned when brought into contact with a cigarette lighter flame, and exhibited self-extinguishing properties when the lighter was moved away. On the other hand, the film of the present invention having L, O, and I of about 35 or more did not emit any flame even when the flame of a lighter was brought close to it.

(Effects of the Invention) The film of the present invention has good mechanical properties expressed by high strength and high modulus.

This is a novel film that has excellent flame retardancy with a value of 0.1 exceeding 35, and also has excellent flame retardant fastness.

Furthermore, the film of the present invention has heat resistance and a high dielectric constant. The film of the present invention takes advantage of these performance characteristics and is useful as an insulator for capacitors, a coating material for electric wires and optical fibers, and is particularly useful as a flame-retardant member for these electrical machine-related applications. be.

Claims (2)

[Claims] (1) Made of substantially para-oriented aromatic polyamide with a logarithmic viscosity ηinh of 2.5 or more, and a density of 1.37 g/cm
^3 or more, and a Young's modulus of 500 kg/mm^2 or more, and one or more selected from the group consisting of aliphatic phosphoric esters, aliphatic cyclic phosphoric esters, and aromatic phosphoric esters. A para-oriented aromatic polyamide flame-retardant film, characterized in that it contains a flame retardant such that at least 0.1% by weight of phosphorus is contained in the total weight of the film. (2) a para-oriented aromatic polyamide with a logarithmic viscosity ηinh of 2.5 or more, and concentrated sulfuric acid with a concentration of 96% by weight or more,
An optically anisotropic dope containing at least one solvent selected from the group consisting of chlorosulfuric acid and fluorosulfuric acid is formed into a film on a support surface while maintaining optical anisotropy, and is subjected to moisture absorption and/or heating. A liquid containing a flame retardant and a film containing 50% by weight or more of water obtained by allowing the dope to stand until it is substantially converted into an optically isotropic dope, solidifying it, and substantially removing the solvent. in contact with
A method for producing a para-oriented aromatic polyamide flame-retardant film, which is then dried at a temperature of 50° C. or higher while controlling shrinkage.