JPS59603B2 - Method for producing short fibers and/or pulp particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to short fibers and/or fibers with excellent heat resistance, mechanical properties, etc.
Or it relates to a method of producing pulp particles.

More specifically, the present invention relates to a method for industrially producing fifurlated short fibers and/or pulp particles suitable for use as synthetic paper raw materials, resin reinforcing materials, friction materials, and the like. Conventional technology
Fully aromatic polyamides, such as poly(paraphenylene terephthalamide) and poly(metaphenylene isophthalamide), have excellent heat resistance, mechanical properties, electrical properties, etc., and are useful for pulp particles (fifrites), fibers, films, sheet materials, It is known to be useful as a raw material for resins and laminated materials.

For example, Japanese Patent Publication No. 47-2489 describes high strength and high modulus fibers obtained from poly(paraphenylene terephthalamide) or its copolymer, and Japanese Patent Publication No. 47-123602 describes Synthetic papers using fifrits of non-melting wholly aromatic polyamides such as poly(metaphenylene isophthalamide) have been described.

However, the above-mentioned high-strength, high-modulus fibers require special measures and equipment to be cut into short fibers, and are difficult to use as they are in fields such as synthetic paper raw materials and friction materials.

On the other hand, poly(metaphenylene isophthalamide) fifrit is considered to be suitable as a raw material for heat-resistant synthetic paper, but it has the problem of poor strength because it is not substantially oriented, and it is also used as a resin reinforcing material. , there is a problem that it is unsuitable for the field of friction materials, etc. OBJECTS OF THE INVENTION The main object of the present invention is to produce short fibers and/or pulp particles different from conventional wholly aromatic polyamide fibers and fifrites by fibrillating an oriented molded product.

Another object of the present invention is to produce fifurlated short fibers and/or pulp particles made of a rigid wholly aromatic polyamide suitable as a synthetic paper raw material, a resin reinforcement material, a friction material, etc.

Components of the Invention The present invention relates to a molded article having molecular orientation formed from an optically anisotropic solution of a rigid wholly aromatic polyamide mainly composed of the following repeating units [1], and which is sheared by mechanical operation. This is a method for producing short fibers and/or pulp particles, which is characterized by applying force to crush the molded product into threads to form fibrils.

[However, in the formula, Arl and Ar2 represent a mixture thereof.

] “Rigid wholly aromatic polyamide” used in the present invention
Although poly(paraphenylene terephthalamide) is preferable, it may also be one in which some of the hydrogen atoms in the aromatic nucleus are replaced with chlorine.

This wholly aromatic polyamide must have a degree of polymerization of 1.5 or more in terms of intrinsic viscosity (ηInh).

Note that the intrinsic viscosity (ηInll) referred to here refers to the polymer taken out as a powder from the polymer composition and 0.0
．． The value was measured at 30° C. at a concentration of 57/100ml. Many of the rigid wholly aromatic polyamides used in the present invention can be made into a solution by various methods.

That is, a solution can also be prepared by mixing with a suitable solvent or a solubilizing agent under conditions such as suitable temperature and pressure. Alternatively, since these polymers are generally poorly soluble, a polymerized system prepared by a solution polymerization method from a monomer system with a mixing ratio corresponding to the polymer composition or a mixed system after polymerization can be directly used as X or as a by-product. HCl
It is also possible to use a neutralized system for molding. Furthermore, it is known that one of the attributes of such rigid polymers is that they give optically anisotropic solutions in a specific solvent system, at a specific concentration range, and at a specific temperature range (Japanese Patent Publication No. 47-248
No. 9, West German Patent Publication No. 1810426,
(See US Pat. No. 3,671,542), it is possible to obtain a molded article having molecular orientation from such an optically anisotropic solution by a wet or dry solution molding method.

Molded products having molecular orientation that can be used in the present invention are limited to those obtained from optically anisotropic solutions, and even if the same polymer is produced from an isotropic solution, it is difficult to fifuryl, so it is not preferred.

In other words, in an optically anisotropic solution, the solution structure is already in a state of considerable molecular orientation or a state in which molecular orientation is more likely to occur, and the obtained molded product has molecular orientation and is easily fifurlated. A molded article made from an optically anisotropic solution is used. The optically anisotropic solution referred to here is described in, for example, Japanese Patent Application Laid-Open No. 47-39458, but one simple method for determining this is that the solution looks milky to the naked eye and is polarized under a polarizing microscope. When the child is rotated and observed, there is no angle at which the field of view becomes completely dark. Such an optically anisotropic solution can be made to have properties such as fluidity, castability, and stringability suitable for solution molding by appropriately selecting the composition ratio, temperature, additives, etc. A polymer solution having such optical anisotropy may be introduced into an aqueous precipitation system and precipitated as fine particles, but it may be passed through a nozzle, slit, etc. in the form of a lump, granule, powder, filament, or string. It may be extruded into a coagulation bath or coagulation atmosphere in the form of a shape, a film, a sheet, or a spray. Pulp particles and/or short fibers can also be produced by further stretching and heat-treating the obtained molded product to enhance orientation and crystallization, or by crushing it into filaments without any treatment to form fifuryls. Can be done. In the method of the present invention, the molding conditions such as the nozzle diameter, slit width, extrusion speed, type and temperature of the coagulation system, winding speed, desolvation, desalting speed and timing, or heat treatment of the molded product are adjusted appropriately. By combining,
Pulp particles and/or pulp particles obtained by crushing the molded product into threads later.
Alternatively, various properties of the short fibers, particularly their shape and mechanical properties, can be controlled, and under appropriate conditions, the length of the short fibers and their distribution can also be controlled to a certain extent.

In the method of the present invention, the molded article is coagulated, desalted, or desolventized in an inert gas atmosphere, a steam atmosphere, or an aqueous coagulation bath containing water, an aqueous calcium chloride solution, or an organic solvent, if necessary. It can be performed. The optically anisotropic solution made of rigid wholly aromatic polyamide may contain a relatively high boiling point solvent such as N-methylpyrrolidone or hexamethylphosphoramide, or an inorganic salt such as lithium chloride or calcium chloride. There is.

In this case, it is also possible to form the film into a film using a T-die wet method, such as in the production of cellophane, but after extrusion, a part of the solvent is removed with hot air and then introduced into an aqueous coagulation bath at an appropriate timing. It is preferable to form a film-like product by removing the solvent and desalting in a bath. On the other hand, some of these solutions may undergo gelation or phase separation at high temperatures, so in the inflation method, calendar method, etc., after being molded at a high temperature, they are desolvated and desalted in an appropriate coagulation bath. You can also do this. Furthermore, since some optically anisotropic solutions change from a solution state to a paste state or a semi-solid state at low temperatures, it is also possible to obtain molded products while cooling. In any case, the molded product should have molecular orientation. The [molded product with molecular orientation] referred to in the present invention only needs to have a structure in which molecules are oriented internally, and macroscopically it can be in the form of a lump, granule, powder, sheet, film, or membrane. It can take various forms such as , string-like, filament-like, etc.

According to the research conducted by the present inventors, molded articles made of rigid wholly aromatic polyamides such as those described above, such as poly(paraphenylene terephthalamide), and which have molecular orientation properties, have extremely relaxed orientation once the molecules have been oriented. Because it is easy to form a higher-order structure that is difficult to form, it creates areas along the orientation direction with a low molecular chain density and weak lateral bonding force, and when a moderate mechanical shearing force is applied to this area, it becomes extremely easy to fifuryl. It was found that the desired short fibers and/or pulp particles could be formed.

Therefore, in the present invention, molded products obtained (or in the process of being obtained) by the various methods described above are subjected to stretching or stretching before or after desolvation and desalting, or at the same time as necessary. After rolling or further heat treatment, mechanical shearing force is applied to crush the material into threads to form fifurls.

In the present invention, in order to crush the molded product into filiforms to form fibrils, for example, crushing, grinding, extrusion, impact,
It is necessary to apply mechanical shearing force such as beating.

As means for applying shearing force, various grinders, mills, pulverizers, etc. can be used. Furthermore, since this process has considerable similarities with adjustments in paper manufacturing, various heaters, di-jordans, refiners, etc. can also be applied. Additionally, parts of the wood chipper grinder in pulp production can also be used. The above-described step of applying mechanical shearing force to the oriented molded product to crush it into threads can be performed simultaneously with the production of the molded product.

For example, in the case of solution molding, it can be carried out simultaneously with or after desolvation and desalination, or after heat treatment, by a wet method or a dry method. Furthermore, it is also possible to mix the molded product as it is into a resin or the like and crush it into threads by the shearing force applied during kneading. Effects of the Invention According to the method of the present invention as described above, by selecting the structure of the polymer and the composition of the polymer solution used for molding,
Traditionally, these rigid polymers were considered to have a disadvantage of being oriented in the longitudinal direction and easily tearing in the longitudinal direction (easily forming into fifurls).
By reversing this molding problem, useful pulp particles and/or short fibers can be produced in a simple process.

Moreover, it is possible to mold with a higher polymer concentration than when using an optically isotropic solution, and since it tends to be more easily oriented, the molded products obtained therefrom are extremely easy to fifuril and break into threads. An even greater advantage is that many of the fibrous materials made of rigid wholly aromatic polyamides specified in the present invention have high rigidity, so it is difficult to obtain short fibers by cutting the spun yarn into short lengths. However, unlike the cutting machine that requires special measures and equipment, the method of the present invention allows short fibers or short fiber precursors to be obtained extremely easily. The pulp particles and/or short fibers obtained in the present invention can be formed into a strong sheet-like material such as heat-resistant insulating paper by taking advantage of their fifurlicity and excellent heat-resistant mechanical properties.

In addition to a large surface area due to fifrillation, it has high mechanical properties, especially high modulus and strength, and has a lower specific gravity than glass fiber, carbon fiber, metal fiber, etc., so it is also useful for reinforcing resins. be. Moreover, it can also be used as a friction material by utilizing the above-mentioned characteristics. EXAMPLES The present invention will be explained below using examples.

In the examples, the organic polar solvents were hexamethylphosphoramide (HMPA) and N-methylpyrrolidone (NMPA), respectively.
P) and abbreviations are used. Example 1 Paraphenylenediamine 5661y was dissolved in a mixed solvent consisting of 50ml of HMPA and NMPlOOml, lithium carbonate 38687 was added thereto, and after cooling in an ice bath, terephthalic acid chloride powder 106297 was added to carry out a polymerization reaction.

An optically anisotropic solution was obtained after about 30 minutes. Poly(paraphenylene terephthalamide) thus obtained
The intrinsic viscosity was 2.75. This solution contains approximately 7.5% by weight polymer. This solution was passed through a slit with a width of 6 mu and a thickness of 0.17 nm at 100°C for 50 min.
A membrane was obtained by extrusion into a calcium chloride bath at 100° C. at a speed of m/min. When this film-like material was observed under a microscope, a striped pattern was observed in the vertical direction, indicating that the molecules were oriented. When this film-like material was vigorously stirred with water in a homomixer, it was fifurlated and short fibers were obtained. Example 2 Poly(paraphenylene terephthalamide) (intrinsic viscosity 5
．． 5) 1007 was dissolved in 400y of sulfuric acid at 85°C to obtain an optically anisotropic solution.

This solution was heated at 85°C using a slit similar to that used in Example 1, passing through a 5 mm air layer and applying it to a rolling roller at 3°C.
The resulting film was stirred in a homomixer with an aqueous NaHCO3 solution. Filter the resulting mixture;
A short fibrous material was obtained by washing with water and further pulverizing in a ball mill. Further, short fibrous material was obtained even when the film-like material was neutralized and washed before being applied to the homomixer, heat-treated at 450 DEG C. under tension-F, and then ground in a ball mill. Furthermore, by cutting the film-like material heat-treated at 450'C as described above into 10 mm lengths and kneading it with so-called raw resin of unsaturated polyester, it was possible to obtain a molded article in which short fibers were dispersed fairly uniformly. Example 3 Paraphenylenediamine 10.817 and paraphenylenediamine 2HC118.117 were combined into HMPA4OO
A paste exhibiting optical anisotropy prepared by polymerization reaction with terephthalic acid chloride 40,877 in a mixed solvent of NMP and 200 ml was rolled with a rolling roller for 10 minutes.
After forming into a film at 0°C, NaHCO
Pulp-like particles were prepared by stirring while neutralizing with 3 aqueous solution.

The particles were fibrous. Example 4 An optically anisotropic solution prepared by polymerization and neutralization in the same manner as in Example 1 was heated for 15 minutes using a drum-type solution casting film manufacturing apparatus.
A part of the solvent was removed on a metal drum while supplying dry nitrogen gas at 0° C. to form a film.

This film-like material was dehydrated by applying water to a heater (beater), washed with water, and dried to obtain short fibers. Example 5 An optically anisotropic solution prepared in the same manner as in Example 1 was added to a coagulation bath of Ca
The film was formed by a wet casting method using a Cl2 aqueous solution.

Short fibers were obtained by crushing the obtained film in a grinder. Example 6 In the same manner as in Example 3, paraphenylenediamine 21.637 and paraphenylenediamine.2HC118. I1y and HMPA6OOml
The polymerization reaction mixture obtained by polymerizing with terephnoyl chloride 61.217 in a mixed solvent of , Dehydrochlorination in a CaCl2 aqueous solution containing Ca(0H)2 with a second stage roller,
The film-like material obtained by further rolling while removing the solvent was introduced into a homomixer and stirred to produce short fibers.

Example 7 An optically anisotropic solution prepared in the same manner as in Example 1 was introduced in the form of a thread into a homomixer through a nozzle with a diameter of 0.5 mTL, and was stirred and ground to prepare fibrous pulp particles.

Example 8 Paraphenylene diamine 5.6607 was dissolved in a mixed solvent consisting of 50 ml of HMPA and NMPlOOml, and after cooling on ice, 10.678 f of terephthalic acid chloride was added to start the polymerization reaction. A molded product mainly consisting of films and blocks obtained by colliding a non-optically anisotropic solution with a wall under a nitrogen stream using centrifugal force is stirred with water in a homomixer, washed with an aqueous Na2cO3 solution, and then washed with water. , dehydrated and dried to obtain short fibers and pulp particles.

Claims (1)

[Scope of Claims] 1 A molded article having molecular orientation formed from an optically anisotropic solution of a rigid wholly aromatic polyamide mainly composed of the following repeating units [I] is sheared by mechanical operation. A method for producing short fibers and/or pulp particles, which comprises applying force to crush the molded product into threads to form fibrils. ▲There are mathematical formulas, chemical formulas, tables, etc.▼……[I] [However, Ar_1 and Ar_2 in the formula are ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ mathematical formulas, chemical formulas,
There are tables, etc. ▼ or a mixture of these. ].