JPH0118090B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new method for molding aromatic polyamide. More specifically, the present invention relates to a method of emulsifying a sulfuric acid solution of aromatic polyamide to obtain aromatic polyamide fibers, films, powders, microdispersions, etc. formed therefrom. Aromatic polyamide is a material with excellent heat resistance and mechanical properties, but it is difficult to melt and has poor solubility, so there are only a limited number of solvents available for its use. There were major difficulties in molding. The present inventor has researched various ways to utilize aromatic polyamide as a material for composite materials while taking advantage of its good properties. It was desired to develop a technology for forming thinner or more minute shapes, and as a result of various experiments, we focused on emulsification of aromatic polyamide solutions, and as a result of intensive research, we arrived at the present invention. That is, the present invention provides an emulsion obtained by dispersing a sulfuric acid solution of an aromatic polyamide and a hydrophobic solvent in the presence of a surfactant having an HLB (hydrophile lipophile balance) value of 2 or more at a temperature range of 90°C or less. This is an emulsion molding method for aromatic polyamide, which is characterized by contacting with a poor solvent for aromatic polyamide and molding and solidifying. According to the present invention, aromatic polyamide ultrafine fibers, ultrathin films, microfibril networks, water,
Microdispersions in liquid materials such as organic liquids and solutions,
Aromatic polyamides can be molded into various shapes such as fine dispersions in solids such as polymer compounds and oligomers. In the present invention, aromatic polyamide is a diamine residue represented by the general formula -NH-Ar ₁ -NH- (1) (Ar ₁ in the formula is a divalent aromatic group), and the general formula -CO −Ar ₂ −CO− …(2) (Ar ₂ in the formula is a divalent aromatic group) and the dicarboxylic acid residue represented by the general formula NH−Ar ₃ −CO− …(3) (In the formula (Ar ₃ is a divalent aromatic group) is a polyamide in which one or more residues selected from the aminocarboxylic acid residues represented by are bonded by an amide bond, and the aromatic polyamide Examples of aromatic moieties, Ar ₁ , Ar 2 and Ar ₃ in the above general formulas (1), ( ₂ ) and (3) include m-phenylene, 3,4'-biphenylene, 1,3 - Naphthylene, 1,6-naphthylene, 1,7-naphthylene,
2,4-pyridylene,

[Formula] (where X is -CH ₂ -, -O-, -NH-, -CO-, -SO ₂ -, etc.), but preferred are 4,4'-biphenylene, 1,4-naphthylene,
1,5-naphthylene, 2,6-naphthylene, 2,
5-pyridylene,

[Formula] (where X' is -CH ₂ CH ₂ -, -N=N-,

【formula】

[Formula] -CH=N-),

[Formula] (where Y is -SO ₂ -, -CO-, -CH ₂ -), p-phenylene is particularly preferred, and one or more of these can be selected and used. These aromatic moieties include halogen atoms, alkyl groups, alkoxy groups,
It may contain an inert group such as a nitro group or a cyano group or an alkoxycarbonyl group as a nuclear substituent. Further, Ar ₁ , Ar ₂ or Ar ₃ may be partially replaced by aliphatic or especially alicyclic hydrocarbon groups as long as the properties of the aromatic polyamide are not seriously impaired. The degree of polymerization of the aromatic polyamide is not particularly limited and is appropriately selected depending on the application. Generally 0.2g/dl
A relative viscosity (ηrel) value of 0.1 or higher is used as the viscosity measured at 30°C for a 97% sulfuric acid solution. The sulfuric acid used to form the sulfuric acid solution of the aromatic polyamide is preferably 96% or more sulfuric acid or fuming sulfuric acid, and in order to minimize hydrolysis during dissolution, the concentration is preferably as high as possible.
A concentration of 98% or higher is preferred. In addition, hydrogen fluoride, fluorosulfuric acid, chlorosulfuric acid,
It is also possible to add antimony pentafluoride, trifluoroacetic acid, and the like. The concentration of aromatic polyamide in a sulfuric acid solution of aromatic polyamide is not limited as long as it remains fluid and can be emulsified, but generally a range of 0.1 to 30% by weight, particularly 0.5 to 20% by weight is conveniently used. Ru. The hydrophobic solvent used in the present invention is a liquid substance that has poor compatibility with sulfuric acid and is difficult to react with sulfuric acid, and preferably aliphatic, alicyclic and/or aromatic hydrocarbons. may be substituted with a halogen such as fluorine, chlorine, bromine, or iodine, a nitro group, an alkoxy group, or a phenoxy group. Examples include pentane, hexane, heptane, octane, cyclohexane, decalin, tetralin, ligroin, liquid paraffin, benzene, toluene, xylene, ethylbenzene, anisole, carbon tetrachloride, chloroform, ethane bromide, tetrachloroethane, chloro These include benzene, dichlorobenzene, bromobenzene, dibromobenzene, chloranisole, nitrobenzene, and nitrotoluene. A soluble polymer compound may be added to these solvents if necessary. For example, various materials such as polyolefins, polystyrenes, polyvinyl chlorides, polysulfones, and nitrocellulose can be used. The surfactant used in the present invention is an anionic, nonionic, cationic, and/or amphoteric surfactant with an HLB value of approximately 2 or more, and has the desired emulsification state, desired shape after solidification, and purpose. You can choose according to your needs. Here, the HLB value is a value that is a guideline for the balance between hydrophilicity and hydrophobicity of a surfactant, and there are various calculation methods and estimation methods, but it can be calculated based on various known methods, such as Davies' arithmetic. There are various methods such as Cliffin's method, Kawakami and Oda's method (Kogyo Materials 19 (4) 48 (1971)), and it can be estimated from these methods. In the present invention, an HLB value of 2 or more is required in order to control the emulsification state or obtain a stable emulsification state. Examples of these include polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, and polyoxyethylene nonyl phenyl ether. , nonionic surfactants such as polyoxyethylene octyl phenyl ether, sodium ethyl lauryl alcohol sulfate, sodium oleate, potassium oleate, potassium stearate, sodium stearate, potassium perfluorodecanoate, dodecane sulfonic acid, dodecane sulfone Anionic surfactants such as sodium acid, dodecylbenzenesulfonic acid, sodium dodecylbenzenesulfonate, sodium decyl sulfate, sodium dodecyl sulfate, polyoxyethylene dodecyl phenyl ether sulfonic acid, decyl ammonium bromide, decyl trimethylammonium bromide, hexadecyl Cationic surfactants such as trimethylammonium bromide and dodecyltrimethylammonium chloride, N-dodecyl-N,N-
These include amphoteric surfactants such as dimethylglycine. The emulsion of the present invention is produced by mixing the sulfuric acid solution of the aromatic polyamide, the hydrophobic solvent, and the surfactant using a known method, such as mechanical stirring, shearing, vibration, or ultrasonication, at a temperature of 90°C or less and hydrophobic. It is obtained by emulsifying a solvent and a sulfuric acid solution at a temperature range that maintains a fluid state capable of emulsification. Above this range, the aromatic polyamide and surfactant are severely decomposed and altered by sulfuric acid, which is undesirable.
The amount of each of the above components depends on the type of emulsion, for example, dispersion type in a hydrophobic solvent in a sulfuric acid solution, dispersion type in a sulfuric acid solution in a hydrophobic solvent, or molding into a fiber, film, or microdispersion. The appropriate selection is made depending on whether the Generally, the amount of surfactant is
It is 0.05 to 20% by weight, preferably 0.3 to 15% by weight, and the mixing ratio of the hydrophobic solvent and sulfuric acid can be arbitrarily used depending on the purpose and can be used in a wide range from 0.2:99.8 to 99.8:0.2. When the above-mentioned emulsion is brought into contact with a poor solvent and solidified by molding, the poor solvent is preferably water, or an organic solvent soluble in sulfuric acid such as methanol, ethanol, ethylene glycol, acetone, or a mixture thereof. Also, emulsions of water and hydrophobic hydrocarbons, and emulsions containing salts, acids, or alkalis can also be used. When the emulsion is brought into contact with these poor solvents and molded and solidified, various desired shapes can be obtained. That is, they include fibrous materials, film materials, powder materials, and microdispersed materials in liquids and solids. Various methods and devices can be applied to obtain various desired solidified products. For example, the emulsion can be extruded through pores and brought into contact with a poor solvent immediately or after passing through a vacuum or gas phase to obtain molded products in the form of fibers or rods of various thicknesses. Especially conventional 8~
Although aromatic polyamide fibers can only be obtained with a diameter of 9 μm or more, even ultrafine fibers with a diameter of 7 to 8 μm or less can be easily molded. Alternatively, the emulsion can be extruded from a nozzle, applied or cast to form a film, and then brought into contact with a poor solvent to form a film. Alternatively, the emulsion may be finely dispersed in the poor solvent while or after being brought into contact with the poor solvent by mechanical stirring, shearing force, vibration force, ultrasonic irradiation, etc. can do. The above-mentioned finely dispersed particles are generally several microns in size or even 1 micron or less in size, and this is an excellent method for obtaining such minute aromatic amide dispersed particles. Such a microdispersion can be separated using a method such as centrifugation and dried to form a powder, or the dispersion medium can be replaced with a desired liquid such as water or an organic liquid to form a microdispersion therein. I can do it. In addition, the above-mentioned finely dispersed material can be used as a dispersion medium to substitute a polymerizable liquid monomer and polymerize as it is, or it can be replaced with a liquid medium in which a polymer compound has been dissolved and then reprecipitated in a poor solvent, or the liquid medium can be By evaporating it, and furthermore,
The finely dispersed material can be finely dispersed in a polymer compound by mixing the finely dispersed material with a solution in which the polymer compound is dissolved and simultaneously reprecipitating the polymer compound. Further, finely dispersed inorganic or organic powders can also be obtained. The fibers, films, powders, or microdispersions thus obtained can be used in various polymeric compounds such as polyamides, polyesters, polyphenylene sulfides, polyethers, polysulfones, polystyrenes, polyolefins, polymethacrylates, It can be used as a composite material with many existing polymer compounds such as polyvinyl chloride, rubber, epoxy resin, phenol resin, and unsaturated polyester resin, or it can be used as is as a heat-resistant fiber, film, or paper-like material. Can be used. In particular, since the microdispersion of the present invention can be very homogeneously finely dispersed in various polymeric compounds, it can serve as a reinforcing material for these polymeric compounds when used in a small amount, or it can also be used as a crystalline material. It can also be used as a crystal nucleating agent for polypropylene compounds. Example 1 Polyparaphenylene terephthalamide 30 with a relative viscosity of 3.40 obtained by reacting paraphenylene diamine and terephthalic acid dichloride using a known solution polymerization method.
g in 200 ml of 99.3% concentrated sulfuric acid, add and dissolve 10 g of polyoxyethylene nonyl phenyl ether (HLB value 5.7), and then dissolve in toluene.
300 ml was added and emulsified using a homogenizer. The emulsification temperature was set to 65°C or higher and 80°C or lower. The resulting emulsion was cooled and then a portion thereof was dropped into cold water and vigorously stirred. As a result, extremely finely dispersed polyparaphenylene terephthalamide was obtained. The supernatant liquid was removed by centrifugation, and water was added again for washing. When the resulting microdispersion was observed under a polarizing microscope, flakes of several microns or less and needle-like objects of 1 micron or less in diameter were observed. Further, when observed with an electron microscope, aggregates of microfibrils with a diameter of several hundred angstroms were also observed. Example 2 A portion of the emulsion of Example 1 was extruded into water through a hole having a diameter of 0.46 mm, and then dispersed using a homogenizer, followed by ultrasonic irradiation for 10 minutes.
The obtained microdispersion was repeatedly washed with water by centrifugation to remove the supernatant, then washed with ethylene glycol, and finally ultrasonic irradiation was performed again in ethylene glycol for 10 minutes. This microdispersion
There were many flakes with a size of 1 μm or less, and when observed using an electron microscope, aggregates of microfibrils with a diameter of several hundred angstroms were also observed. Example 3 A portion of the microdispersion in ethylene glycol obtained by the method of Example 2 was taken, and the solvent was further replaced with orthochlorophenol. Polyethylene terephthalate was added and dissolved in this orthochlorophenol, and this solution was reprecipitated in methanol. The precipitate was washed repeatedly with methanol and then dried. When the resulting composite with polyethylene terephthalate was observed under a polarizing microscope equipped with a heating plate while heating, it was found that even after the polyethylene terephthalate had melted (at 260°C or higher), unmelted acicular or granular particles remained homogeneous. A dispersed state was observed. The slow cooling crystallization behavior of this composite was investigated using a Differential Scanning Calorimeter. As a result, from a state heated above the melting point of polyethylene terephthalate,
Under conditions of cooling at a rate of 0.degree. C./min, the half-width of the exothermic peak due to crystallization was 7.5.degree. C., which was an extremely sharp peak. In the same measurement, polyethylene terephthalate alone had a half-width of 19°C. This indicates that the dispersion of the present invention promoted the crystallization of polyethylene terephthalate and exhibited a rapid crystallization phenomenon. Note that the composite obtained in this experiment was weighed, dissolved again in orthochlorophenol, filtered, and insoluble matter was separated, and this insoluble matter was thoroughly washed with ethanol and then dried. This insoluble material was confirmed to be polyparaphenylene terephthalamide by infrared spectroscopy and elemental analysis, and the amount of this insoluble material was about 0.4% by weight based on polyethylene terephthalate. Comparative Example 1 A sulfuric acid solution of polyparaphenylene terephthalamide was prepared in the same manner as used in Example 1, and the solution was poured into cold water and vigorously stirred without adding surfactant or toluene. As a result, granular or elongated solidified matter of about 0.5 to several millimeters was precipitated, and a fine dispersion like that in Example 1 could not be obtained. Comparative Example 2 Cetyl alcohol (HLB value
1.3) Using 10 g, an attempt was made to emulsify polyparaphenylene terephthalamide with a sulfuric acid solution and toluene in the same manner as in Example 1, but a stable emulsion state could not be obtained and the product separated into two phases. Example 4 An experiment similar to Example 1 was conducted using polyoxyethylene nonyl phenyl ether with an HLB value of 10.9. The obtained emulsion was dropped into water and stirred vigorously to obtain a microdispersion having a size slightly larger than that of Example 1, but approximately the same size. Example 5 28 g of polyparaphenylene terephthalamide (relative viscosity 2.79) was dissolved in 120 ml of 98.5% concentrated sulfuric acid,
Dissolve 6g of sodium dodecylbenzenesulfonate (HLB approx. 37) in this, and then dissolve 50g of chlorobenzene.
ml and 100 ml of hexane were added, stirred, and then emulsified using a homogenizer. A portion of the resulting viscous emulsion was extruded through 0.1 mm diameter pores and dropped into water, which was then vigorously stirred to obtain a microdispersion. When this object was observed with a polarizing microscope, the diameter was
There were many needle-like objects with a diameter of 1 μm or less. Example 6 A portion of the emulsion of Example 5 was applied onto a glass plate, heated slightly, and then immersed in water. This was gently washed with water, left to dry, and finally heated and dried under reduced pressure to obtain flakes. Example 7 30 g of polyparaphenylene terephthalamide (relative viscosity 3.5) was dissolved in 170 g of 99.9% concentrated sulfuric acid, and 5 g of polyoxyethylene nonyl phenyl ether (HLB value 12.6) and dodecylbenzenesulfonic acid (HLB value approximately 12) were dissolved in this. 300 ml of toluene in which 100 g of polystyrene was dissolved was added to emulsify. The emulsion was extruded through a 0.15 mm pore and stretched while immersed in water. The obtained fibrous material was taken out of the water and air-dried. When this was washed again with toluene and then heated and dried, a thin fiber of approximately 4 μm was obtained. Example 8 A portion of the microdispersion obtained in Example 4 was taken and filtered through a fine glass funnel. After washing with water, it was dried as it was. After drying, the film-like or paper-like material adhering to the glass funnel surface was peeled off. When this film-like or paper-like material was observed under a polarizing microscope, it was observed as a network-like object consisting of entangled fine needles or fibrils with a diameter of 1 μm or less. Example 9 A portion of the emulsion obtained in Example 1 was
Push it out into water through a 0.2 mm hole, disperse it with a homogenizer, then remove the supernatant liquid by centrifugation, repeat the process of washing with water, then washing with acetone, and finally soaking it in acetone. Ultrasonic irradiation was performed. 25 g of epoxy resin (Epikote 1001) was dissolved in this, and then 7 g of phthalic anhydride and 0.2 g of dimethylaniline were added and heated. This solution was then applied onto a glass plate and the acetone was evaporated.
After evaporating the acetone, it was heated to 120°C for 2 hours to obtain a cured product. When this was observed with a polarizing microscope, it was observed that microscopic objects of several μm or less were homogeneously dispersed.

Claims (1)

[Claims] 1. A sulfuric acid solution of an aromatic polyamide and a hydrophobic solvent are dispersed in the presence of a surfactant with an HLB (hydrophile lipophile balance) value of 2 or more at a temperature range of 90°C or less. 1. A method for emulsion molding an aromatic polyamide, which comprises contacting an emulsion with a poor solvent for the aromatic polyamide and molding and solidifying the emulsion. 2. The method for emulsion molding aromatic polyamide according to claim 1, wherein the aromatic polyamide is a linearly oriented aromatic polyamide. 3. The method for emulsion molding aromatic polyamide according to claim 1, wherein the surfactant is anionic and/or nonionic. 4. The method for emulsion molding an aromatic polyamide according to claim 1, wherein the emulsion is an emulsion in which a sulfuric acid solution of the aromatic polyamide is dispersed in a hydrophobic solvent.