JP4736493B2 - Process for producing aromatic polyamide composition, composition and film comprising the same - Google Patents

Description

  The present invention relates to a method for producing an aromatic polyamide composition excellent in dispersibility of inert particles, having no coarse protrusions, and excellent in suppressing the aggregation of inert particles, a composition and a film comprising the same. The film to be used can be suitably used for a magnetic recording medium.

  In recent years, in order to increase the density of information recording, metals such as Co, Ni, Cr, and Fe and their alloys have been formed on a film substrate by methods such as vacuum deposition, sputtering, and ion plating. Recording media are being actively developed. Since the metal thin film type magnetic layer is much thinner than the conventional coating type, the surface form of the base film used is the surface form of the magnetic layer as it is. For this reason, when the surface roughness of the base film is rough, for example, the output is reduced and the dropout is increased. On the other hand, if the film surface is completely mirrored to improve these electromagnetic conversion characteristics, slipping with each equipment is bad in the film manufacturing process and magnetic tape processing process, and the film is wrinkled and running resistance is high. Problems such as film cutting occur. As means for solving these problems, slipping is imparted by adding inert particles and forming protrusions on the film surface. However, since the dispersibility of the added inert particles is poor, coarse aggregates are formed in the polymer, and there are problems that many coarse protrusions appear on the surface of the obtained film and dropout increases.

As a method for suppressing coarse agglomerates in the film, for example, as a dispersion method of the inert particles, the dispersion is performed with a stirring-type disperser, a ball mill, a sand mill, an ultrasonic disperser or the like until the particle diameter is 5 nm or more and 500 nm or less. A method to do this has been proposed. (See Patent Document 1)
Further, the inert particles are added to the solvent at a speed not exceeding 0.1% by volume of the solvent while the solvent flows at a speed of 10 to 1000 m / min, or the dispersion is mixed with the ultrasonic homogenizer. A method of adding the amount of dispersion added to the solvent at a rate not exceeding 0.1% of the amount of solvent per minute is disclosed. (See Patent Document 2)
However, the method of simply dispersing the inert particle slurry mechanically with a ball mill, an ultrasonic disperser, or the like, or the method of controlling the method of adding the inert particles has some improvement effect on the formation of aggregates. However, it was not satisfactory enough to cope with the higher density of information recording.
JP 60-127523 A JP-A-10-139895

  The present invention solves such problems, and provides an aromatic polyamide composition production method, a composition, and a film comprising the same, which suppress the formation of coarse aggregates and have excellent dispersibility of inert particles. It is aimed.

An object of the present invention is to produce a dispersion containing a compound having a dissociation constant (pKa) of 5.0 or less and inert particles having an average particle diameter of 1 nm or more when an aromatic polyamide is produced from dicarboxylic acid dichloride and a diamine. The dispersion medium of the dispersion is an organic solvent, and the content of the compound having a dissociation constant (pKa) of 5.0 or less in the dispersion is 0 with respect to the inert particles. It can be achieved by a method for producing an aromatic polyamide composition characterized in that it is added so that the content of inert particles is 0.001 to 10% by weight with respect to the aromatic polyamide. .

  The present invention provides an aromatic polyamide composition by adding a dispersion containing a compound having a dissociation constant (pKa) of 5.0 or less and an inert particle having an average particle diameter of 1 nm or more in the production of the aromatic polyamide. The formation of coarse aggregates of the inert particles therein can be suppressed, and the inert particles can be uniformly dispersed to reduce the coarse protrusions and reduce the aggregation rate. Further, the obtained film has few coarse protrusions and can be suitably used for digital recording materials such as computer data tapes and video camera tapes for outdoor use, as well as for video and audio.

The aromatic polyamide of the present invention is produced from dicarboxylic acid dichloride and diamine.
Examples of the dicarboxylic acid dichloride used in the present invention include terephthalic acid dichloride, isophthalic acid dichloride, 4,4′-diphenyldicarboxylic acid dichloride, 2,6′-naphthalenedicarboxylic acid dichloride, 2-chloroterephthalic acid dichloride, 2, Examples include 5'-dichloroterephthalic acid dichloride, 2,6'-dichloroterephthalic acid dichloride, and the like. Among these, 2-chloroterephthalic acid dichloride is preferable from the viewpoint of improving the solubility of the polymer in the solvent and the hygroscopicity.

  Examples of the diamine include p-phenylenediamine, m-phenylenediamine, 2,4′-diaminochlorobenzene, 2,6′-naphthylenediamine, 4,4′-biphenylenediamine, and 4,4′-diaminodiphenyl ether. 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 2-chloro-p-phenylenediamine, 2,5′-dichloro-p-phenylenediamine, 2,6 Examples include '-dichloro-p-phenylenediamine, 4,4'-oxydianiline, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone. Of these, 2-chloro-p-phenylenediamine or 4,4'-diaminodiphenyl ether is preferable from the viewpoint of improving the solubility of the polymer in a solvent, hygroscopicity, and rigidity. These diamines can be used alone or in combination of two or more.

  Examples of the method for producing an aromatic polyamide in the present invention include a low temperature solution polymerization method, an interfacial polymerization method, a method of direct polymerization using a dehydration catalyst, and the like. Among these, the low temperature solution polymerization method is preferable from the viewpoint of easily obtaining a polymer having a high degree of polymerization. In this case, it is synthesized by solution polymerization in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), or dimethylformamide (DMF). Moreover, you may superpose | polymerize in presence of calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate etc. as a dissolution aid.

  As the polymerization tank used for the polymerization reaction, in the case of a vertical polymerization tank, stirring blades such as a double helical ribbon type, a paddle type, and a propeller type can be used. In the case of a kneader, a fishtail type or a zet type blade attached can be used.

In the present invention, dicarboxylic acid dichloride or dicarboxylic acid and hydrogen chloride by-produced by the reaction of diamine are converted into inorganic neutralizers such as calcium hydroxide, calcium carbonate, lithium carbonate, or ethylene oxide, propylene oxide, ammonia, triethylamine. Alternatively, neutralization may be performed with an organic neutralizing agent such as triethanolamine or diethanolamine. The polymerization step and the neutralization step can be performed in the same tank.

  The obtained polymer solution may be used as it is as a film-forming stock solution. However, the polymer is once isolated by reprecipitation, etc., and redissolved in an inorganic solvent such as the above organic solvent or sulfuric acid to prepare a film-forming stock solution. Also good. In the film-forming stock solution, an inorganic salt such as calcium chloride, magnesium chloride, lithium chloride, lithium bromide, or lithium nitrate may be added as a dissolution aid. Moreover, antioxidants and other additives may be blended to such an extent that the physical properties of the film are not impaired. The solvent in the film-forming stock solution is preferably 70% by weight or more and 97% by weight or less with respect to the polymer solution.

  When the intrinsic viscosity ηinh of the aromatic polyamide produced by the above method (value measured at 30 ° C. in a 100 ml solution of 0.5 g of polymer in sulfuric acid) is 0.5 dl / g or more when processed into a film It has sufficient strength and is preferable.

  The dispersion containing inert particles in the present invention contains a compound having a dissociation constant (pKa) of 5.0 or less from the viewpoints of dispersibility of inert particles, reduction of coarse protrusions of the resulting film, and reduction of aggregation rate. There is a need. The dissociation constant (pKa) is preferably 3.0 or less, more preferably 1.0 or less. In the case of a compound having a dissociation constant (pKa) exceeding 5.0, the dispersibility of the inert particles is poor, and the resulting film has a large number of coarse protrusions and a high aggregation rate of the inert particles.

  The compound having a dissociation constant (pKa) of 5.0 or less in the present invention is not particularly limited, and examples thereof include formic acid, tartaric acid, acetic acid, hydrochloric acid, sulfuric acid, and malic acid. Among these, acid compounds are preferable from the viewpoint of dispersibility of the inert particles, and more preferable are formic acid, tartaric acid, hydrochloric acid, and sulfuric acid. Hydrochloric acid having a constant (pKa) of −8.0 is preferred.

The content of the compound having a dissociation constant (pKa) of 5.0 or less in the dispersion of the present invention is in the range of the inert particles from the viewpoint of the dispersibility of the inert particles, the coarse protrusions of the obtained film, and the aggregation rate. It is preferably 1200 ppm or less, more preferably 1000 ppm or less, and still more preferably 50 ppm or less. When the content exceeds 1200 ppm, not only the dispersibility effect of the inert particles does not change, but also the agglomeration of the inert particles occurs, which may be inferior to the coarse film projections.

  A method for incorporating a compound having a dissociation constant (pKa) of 5.0 or less in the present invention into a dispersion containing inert particles is not particularly limited. For example, pure water or a dispersion medium of the dispersion may be used in advance. The method of adding to a dispersion after diluting to 0.01 to 10weight% can be mentioned. When the compound concentration exceeds 10% by weight, the inert particles may aggregate when added to the dispersion.

  In the dispersion containing inert particles in the present invention, the average particle diameter of the inert particles needs to be 1 nm or more from the viewpoint of dispersibility of the inert particles, reduction of coarse protrusions, and reduction of the aggregation rate. Preferably it is 1-1000 nm, More preferably, it is 10-100 nm. If the average particle diameter of the inert particles is outside this range, the dispersibility of the inert particles is inferior, and the resulting film has a large number of coarse protrusions and a high aggregation rate.

  In the present invention, when the aromatic polyamide is produced, the amount of the dispersion containing the inert particles is preferably set such that the content of the inert particles is less than that of the aromatic polyamide from the viewpoint of running property and reduction of coarse protrusions. The content is preferably 001 to 10% by weight, and preferably 0.01 to 5.0% by weight. When the film is less than 0.001% by weight, the running property is poor, and when it exceeds 10% by weight, the particles form coarse aggregates and the coarse protrusions increase.

  The dispersion medium of the dispersion containing inert particles in the present invention is preferably an organic solvent from the viewpoint of the dispersibility of the inert particles and the coarse protrusions of the film. For example, N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), etc. can be mentioned. Among these, N-methylpyrrolidone (NMP) is preferable from the viewpoint of dispersibility of the inert particles.

  The inert particles in the present invention are not particularly limited. For example, silicon oxide, acid value titanium, acid value aluminum, colloidal silica, calcium carbonate, acid value zirconium, calcium sulfide, barium sulfide, zeolite and other metal compounds, carbon black, metal Examples thereof include inorganic particles such as fine powders, and organic particles such as silicon particles, polyimide particles, crosslinked copolymer particles, crosslinked polyester particles, and Teflon (registered trademark) particles. Among them, inorganic particles are preferable from the viewpoint of the effect of the present invention, and colloidal silica is particularly preferable.

  In the present invention, before adding a dispersion containing a compound having a dissociation constant (pKa) of 5.0 or less and an inert particle having an average particle diameter of 1 nm or more to an aromatic polyamide, the dispersion of the inert particles is It may be mechanically dispersed with a homogenizer, ultrasonic disperser, stirring disperser, ball mill, sand mill, etc., and the inert particle dispersion is filtered with a filter or the like to remove the pre-aggregated inert particles. May be.

  In the present invention, a method for adding a dispersion containing a compound having a dissociation constant (pKa) of 5.0 or less and an inert particle having an average particle diameter of 1 nm or more to an aromatic polyamide is not particularly limited. A method of adding before the polymerization of the polyamide or a method of adding it after the completion of the polymerization can be mentioned, and can be appropriately selected according to the purpose.

  As described above, the present invention provides an inert particle by adding a dispersion containing a compound having a dissociation constant (pKa) of 5.0 or less and an inert particle having an average particle diameter of 1 nm or more to an aromatic polyamide. It is possible to obtain an aromatic polyamide composition and a film having excellent dispersibility, no coarse protrusions, and excellent agglomeration rate of inert particles. The reason why the dispersibility of the inert particles is improved by incorporating a compound having a dissociation constant (pKa) of 5.0 or less in the dispersion of inert particles is not clear, but is estimated as follows. An inert particle has an interface around the particle in the dispersion medium, and the interface is considered to have a specific charge. By adding and containing a specific compound, the charge is changed and the inert particle It is thought to affect dispersibility.

  The polymer solution comprising the aromatic polyamide composition and the solvent thus produced is processed into a film by a so-called solution casting method as a film-forming stock solution. The solution casting method includes a dry-wet method, a dry method, a wet method, and the like. Any method may be used, but here, the dry-wet method will be described as an example.

  In the case of forming a film by a dry-wet method, the film-forming stock solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is evaporated from the thin film layer and dried until the thin film has self-holding properties. . The drying conditions are preferably room temperature to 220 ° C. and within 60 minutes, more preferably room temperature to 200 ° C.

  The dried film is peeled off from the support, subjected to desalting, desolvation, longitudinal stretching, etc. in a coagulation bath (usually aqueous), and further stretched, dried and heat-treated in a tenter to form a film. . The draw ratio is defined as a surface ratio (defined by a value obtained by dividing the film area after stretching by the film area before stretching. Less than 1 means relaxation), preferably 0.8 or more and 8.0 or less, and 1.1 or more and 5 0.0 or less is more preferable.

  Moreover, a laminated film may be sufficient as the film which consists of an aromatic polyamide composition of this invention. For example, in the case of two layers, the polymerized aromatic polyamide solution may be divided into two, and different particles may be added and then laminated. The same applies to the case of three or more layers. As a lamination method, for example, a well-known technique such as lamination in a die, lamination in a composite pipe, or once forming one layer, another layer is formed thereon. There are methods.

The coarse protrusions of the film comprising the aromatic polyamide composition of the present invention are preferably 20 pieces / cm ² or less, more preferably 10 pieces / cm ² or less, and further preferably 5 pieces / cm ² or less.
The magnetic layer of the high-density recording medium to which the film of the present invention is applied is not particularly limited, but is preferably a ferromagnetic metal thin film layer. As a means for forming the ferromagnetic metal thin film layer, for example, a vacuum deposition method, a sputtering method, or an ion plating method is preferably used, but a magnetic layer made of ferromagnetic powder and an organic binder may be formed by a coating method. As the ferromagnetic metal material, a metal such as Co, Ni, Cr, or Fe, or an alloy containing these as a main component can be used.

  After forming the magnetic layer, it is preferable to apply diamond-like coating and lubrication protective layer from the viewpoint of improving the durability of the magnetic recording medium. Further, a backcoat layer may be provided in order to improve the runnability by the surface opposite to the magnetic layer.

  The magnetic recording medium obtained in this way can be reduced in size and thinned, can record large amounts of data with compactness, and of course, for video and audio, there are few dimensional changes due to humidity and temperature. It is particularly suitable as a digital recording material such as a computer data tape. Moreover, since it is excellent in running property and electromagnetic conversion characteristics under high temperature and high humidity, it can be suitably used for video camera tapes for outdoor use.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to this. In addition, the measurement of the characteristic in an Example is as follows.
(1) Average particle diameter of inert particles (nm)
Inert particles are uniformly dispersed in NMP to form a slurry, which is measured with a centrifugal sedimentation type particle size measuring device (SA-CP2 type, manufactured by Shimadzu Corporation). The obtained particle size distribution was plotted on a logarithmic probability paper, and the median diameter at the point where the cumulative percentage was 50% was defined as the average particle size of the inert particles.
(2) Coarse protrusions (pieces / 100cm ² )
Foreign matter is observed and marked in the range of 100 cm ² of the film surface of the prepared film under polarized light with a stereomicroscope. The height of the marked foreign substance is observed using a multiple interferometer at a wavelength of 546 nm, and the number of interference fringes is counted. Those having a single ring or more were regarded as coarse protrusions.
(3) Aggregation rate (%)
The film surface of the prepared film was photographed at 10 points under the following conditions using a field emission scanning reflection electron microscope (UHR-FE-SEM), and the number of aggregated units (a group of aggregated particles of 2 or more) The value when counted as one) and the total number of particles (the number of all particles forming protrusions on the film surface regardless of the presence or absence of aggregation) were counted, and the aggregation rate was determined from the following formula. The lower the aggregation rate, the better the dispersibility of the inert particles in the film.
Apparatus: Hitachi, Ltd. S-900H
Acceleration voltage: 5 kV
Sample preparation: direct method, Ag shadowing, tilt angle 5 °
Magnification: From the photograph obtained 30,000 times, the aggregation rate was determined from the following formula.
Aggregation rate (%) = (number of aggregation units / total number of particles) × 100
Example 1
Hydrochloric acid having a dissociation constant (pKa) of 8.0 was adjusted to a concentration of 0.2% using pure water. Next, in a dispersion in which 10 parts by weight of colloidal silica particles having an average particle diameter of 70 nm and 90 parts by weight of N-methylpyrrolidone (NMP) are dispersed, the above hydrochloric acid aqueous solution is adjusted to have a hydrochloric acid concentration of 30 ppm with respect to the colloidal silica particles. Added and included.

  Next, using a polymerization jacket with a cooling jacket having an anchor type stirring blade, 2-chloro-p-phenylenediamine corresponding to 85 mol% as an aromatic diamine component in N-methylpyrrolidone (NMP), 15 mol % Of 4,4′-diaminodiphenyl ether was dissolved, and the dispersion was added as an inert particle to 0.05% by weight based on the polymer. To this was added 2-chloroterephthalic acid dichloride corresponding to 98.4 mol% with respect to the aromatic diamine, and polymerization was started while stirring at a linear velocity of 4.0 m / sec. As the temperature of the solution increased, the stirring speed was lowered stepwise so that the temperature in the tank could be kept at 35 ° C. or lower, and finally the linear speed was set to 2.0 m / second, followed by stirring for 2 hours to complete the polymerization. The by-produced hydrogen chloride was neutralized with lithium carbonate to obtain a polymer solution having a polymer concentration of 10.5 wt% and a solution viscosity of 3610 poise.

After passing this stock solution through a 5 μm cut filter, it is cast on a belt with a surface defect frequency of 30 μm or more of 0.006 / mm ² and heated with hot air at 180 ° C. for 2 minutes to evaporate the solvent. The film having self-holding property was continuously peeled from the belt. Next, the film was introduced into a water tank (3 tanks) with an NMP concentration gradient, water extraction of the residual solvent and the inorganic salt generated by neutralization was performed, water was dried and heat-treated with a tenter, and the thickness was 6 μm. Film was obtained. During this time, the film was stretched 1.2 times and 1.3 times in the longitudinal direction and the width direction, respectively, dried and heat-treated at 280 ° C. for 1.5 minutes, and then slowly cooled at a rate of 20 ° C./second. The aggregation rate and coarse protrusions of the obtained aromatic polyamide film were evaluated and the characteristics are shown in Table 1. Both the agglomeration rate of the film and the coarse protrusions were good.

Examples 2-5
An aromatic polyamide composition was produced in the same manner as in Example 1 except that the dispersion of inert particles and the compounds contained in the dispersion were changed as shown in Table 1, and a film was obtained. The coarse protrusions and aggregation rate of the obtained aromatic polyamide film were evaluated in the same manner as in Example 1. Table 1 shows the inert particles used, the compounds contained in the dispersion of inert particles, and the film properties. Each of Examples 2 to 5 was within the scope of the present invention, and both the coarse protrusions and the aggregation rate of the film were good.

Comparative Example 1
A dispersion of inert particles in which 10 parts by weight of colloidal silica particles having an average particle diameter of 70 nm and 90 parts by weight of N-methylpyrrolidone (NMP) were dispersed was obtained.

  Next, after adding the dispersion of the above-mentioned inert particles as the inert particles so as to be 0.05% by weight with respect to the polymer in the same manner as in Example 1, the aromatic polyamide composition in the same manner as in Example 1. To obtain a film. Table 1 shows the characteristics of the obtained aromatic polyamide film. The compound of the present invention contained in the dispersion of inert particles was not added, and both the coarse protrusions and the aggregation rate of the film were poor.

Comparative Examples 2 and 3
An aromatic polyamide composition was produced in the same manner as in Example 1 except that the inert particles used and the compounds contained in the dispersion of the inert particles were changed as shown in Table 1, and a film was obtained. The coarse protrusions and aggregation rate of the obtained aromatic polyamide film were evaluated in the same manner as in Example 1. Table 1 shows the inert particles used, the compounds contained in the dispersion of inert particles, and the film properties. In Comparative Example 2, the dissociation constant (pKa) of the compound contained in the dispersion of inert particles was outside the range of the present invention, and both the coarse protrusions and the aggregation rate of the film were poor. In Comparative Example 3, the dispersion medium of the dispersion of inert particles was outside the scope of the present invention, and both the coarse protrusions and the aggregation rate of the film were poor.

Claims (3)

In the production of aromatic polyamides from dicarboxylic acid dichloride and diamine, a production method using a dispersion containing a compound having a dissociation constant (pKa) of 5.0 or less and inert particles having an average particle diameter of 1 nm or more. The dispersion medium of the dispersion is an organic solvent, and the content of the compound having a dissociation constant (pKa) of 5.0 or less in the dispersion is greater than 0 and 1200 ppm or less with respect to the inert particles. And adding the inert particles such that the content of the inert particles is 0.001 to 10% by weight with respect to the aromatic polyamide. An aromatic polyamide composition obtained by the production method according to claim 1 . A film comprising the aromatic polyamide composition according to claim 2 .