JPS63165514A - Production of pulp granules - Google Patents

Abstract

PURPOSE:To obtain the titled granules outstanding in heat resistance, mechanical properties, etc., suitable as a raw material for synthetic paper, resin reinforcer, etc., by forming, under specified conditions, an optically isotropic solution of p-aromatic polyamide followed by applying a mechanical shear force on the resultant formed product to make it into fibrillated threads. CONSTITUTION:An optically isotropic solution of p-aromatic polyamide [pref., poly-(p-phenylene terephthalamide)] is extruded at a draft ratio >=1.8 (pref. >=2.0) to carry out a wet forming. Thence, a mechanical shear force (e.g., grinding, mashing, impacting) is applied on the resultant product to make fibrillated threads, thus obtaining the objective pulp granules.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing pulp particles with excellent heat resistance, mechanical properties, etc. The present invention relates to a method for industrially producing highly fibrillated pulp particles suitable for such uses.

(Prior art) Poly (p-phenylene terephthalamide), poly (
Aromatic polyamides such as (m-phenylene isophthalamide) are known to be useful as pulp particles (fibrids), fibers, films, sheet materials, etc., which have excellent heat resistance, mechanical properties, and electrical properties. There is.

For example, Japanese Patent Publication No. 50-8474 describes a fiber with high strength and high modulus obtained from an optically anisotropic solution of para-aromatic polyamide, and also describes an optically anisotropic dope of para-aromatic polyamide. Fibrids obtained directly from

Furthermore, Japanese Patent Publication No. 59-603 discloses that a film-like material or monofilament is once obtained from an optically anisotropic dope of a para-aromatic polyamide, and then the formed material is fibrillated by mechanical shearing force to produce pulp particles. Discloses how to obtain. However, the disclosure in this publication is limited to using a film-like material or monofilament as a starting material, which has a low density and is brittle and easily disintegrated, and furthermore, it was found that the degree of fibrillation was not necessarily at a satisfactory level. . In addition, in the statement of opposition to the publication, he showed that fibrillated pulp particles could be produced by once making multifilaments from optically anisotropic dope and beating them, which resulted in qualitative changes from the state of the art at the time of filing the patent application. It clearly shows the progress that has been made in the past, and most of the progress has been made from optically isotropic doping.
This indicates that only particles that are not fibrillated or not fibrillated at all can be produced.

(Problems to be Solved by the Invention) In view of the above-mentioned current state of the prior art, an object of the present invention is to provide a method for producing highly fibrillated para-aromatic polyamide pulp particles.

(Means for Solving the Problems) In order to achieve the above object, the present invention is directed to a para-aromatic polyamide, which has conventionally been considered impossible to prepare highly fibrillated pulp particles. As a result of intensive research on the production of pulp particles from an optically isotropic solution, it was found that by once molding the solution at a high draft rate and applying mechanical shearing force to the resulting molded product, it was possible to produce pulp particles with a surprisingly high degree of It was discovered that it is possible to produce fibrillated pulp particles, and based on this knowledge, the present invention was completed.

That is, the present invention involves applying mechanical shearing force to a molded product obtained by molding an optically isotropic solution of para-aromatic polyamide at a draft ratio of 1.8 or more to form a fibrillated filament. A method for producing pulp particles characterized by:

In the present invention, the para-aromatic polyamide means that the amide bond is in the para-position of the aromatic ring or in a similar orientation position (4,4
'-biphenylene, 1,5-naphthalene, 2,6-rifthalene, etc., consisting essentially of repeating units bonded with coaxial or parallel orientations in opposite directions, such as poly(p -phenylene terephthalamide) (hereinafter abbreviated as PPTA), poly (p-benzamide), poly (4,4'-benzanilide terephthalamide), poly (p-phenylene-4,4'-
Examples include aromatic polyamides having a structure close to a poly-balanced orientation type or a para-orientation type, such as poly (p-phenylene-2,6-naphthalene dicarbonamide) and poly (p-phenylene-2,6-naphthalene dicarbonamide). These polyamides are
It is convenient to produce it from an aromatic diamine and an aromatic dicarboxylic acid chloride by a conventionally known low temperature solution polymerization method. In particular, poly(p-phenylene teretalamide) can be polymerized from a simple heptamer, is inexpensive, and is therefore preferred from an industrial standpoint.

In the present invention, the degree of polymerization of the para-aromatic polyamide is
If it is too low, pulp particles with good mechanical properties cannot be obtained, so it is preferably 2.5 or more, more preferably 3.
．． A polymer having a degree of polymerization that gives a logarithmic viscosity η1nh of 5 or more (value measured at 30° C. by dissolving 0.5 g of polymer in 100 taps of sulfuric acid) is selected.

In the present invention, it is necessary to prepare an optically isotropic solution of the above para-aromatic polyamide. Can it be used? The medium is dimethylacetamide.

N-methylpyrrolidone, hexamethylphosphoramide,
These include so-called amide type polar solvents such as N~acetylpyrrolidinetetramethylurea, systems in which lithium chloride, calcium chloride, etc. are dissolved therein, and acid solvents such as sulfuric acid, methanesulfonic acid, and chlorosulfonic acid. The optically isotropic solution can be used as the polymerization reaction solution as it is or after neutralization, concentration, dilution, etc., or it can be used by once isolating the polymer obtained in the polymerization reaction and then redissolving it in the solvent. It can also be used as Whether a solution is optically isotropic or not can be determined by, for example,
This can be investigated using the method disclosed in Japanese Patent Publication No. 50-8474. The polymer concentration in the optically isotropic solution is not particularly limited, but it is usually 1 to 1 in the case of an amide type solvent.
It is used in a range of 1 to 13% by weight when used as an acid solvent.

In addition, as a special method, an optically anisotropic dope of para-aromatic polyamide is made once, and then it is extruded by heating, humidifying, adding a non-solvent, etc. with optical force immediately before molding. There is.

The method of the present invention is characterized by the use of para-aromatic polyamide, which has superior molecular orientation and greater strength than pulp particles made from meta-aromatic polyamide, and is used as a resin reinforcing material and friction material. It is also useful as In addition, pulp particles prepared from optically anisotropic dope of para-aromatic polyamide have excessive molecular orientation, and when paper is made from pulp particles, the pulp particles further fibrillate even in the paper state. It has been found that the paper has the disadvantage of relatively low paper strength.

In the present invention, it is necessary to mold the optically isotropic solution with a draft ratio of 1.8 or more. Here, the draft rate refers to the ratio of the drawing speed from the coagulation bath to the linear speed of extruding the optically isotropic solution from pores, gouers, slits, etc. By increasing the draft ratio to more than 1.8, it is possible to obtain a molded product having an appropriate molecular orientation to obtain pulp particles that are easily fibrillated and have a large paper strength after paper making. The draft rate is preferably 2.0 or more.

The extruded solution at a certain draft rate is wet-formed and
In this case, after once passing through a non-coagulating fluid N (for example, an air layer), or directly from the molding die, it is introduced into a coagulating bath. The above-mentioned draft rate is defined as the ratio of the drawing speed from the coagulation bath to the linear speed at which the material is extruded from a forming die (for example, a die or a spinneret). The coagulation bath is selected from water, an aqueous solution of an amide type solvent, an aqueous sulfuric acid solution, ethylene glycol, methanol, acetone, and the like. Although the temperature of the coagulation bath is not particularly limited, it is preferable that it be as low as possible because it is easier to obtain a large draft rate for -C.

The molded product obtained by coagulation is preferably washed to remove the solvent and dried, but if necessary, it can be transferred to the next step without washing or without drying after washing. be. A conventional method can be used for washing and drying.

The molding thus obtained must then be subjected to mechanical shearing forces to form a fibrillated thread. Mechanical shearing force can be applied through processes such as crushing, grinding, impact, and beating, such as various grinders, mills,
A crusher, beater, dijordan, refiner, etc. can be used.

(Examples) Hereinafter, the present invention will be explained in more detail using Examples, but the Examples are not intended to limit the present invention.

Example 6.48 g of para-phenylenediamine was dissolved in a mixed solvent consisting of 200 ml of hexamethylphosphoramide and 100 ml of N-methylpyrrolidone, and 12.18 g of terephthalic acid dichloride powder was added to carry out a polymerization reaction. Ta. A viscous optically isotropic solution was obtained after stirring for several minutes.

After degassing the solution of poly(p-phenylene terephthalamide) obtained in this way, it was extruded into water at 50°C through a spinneret with a hole of 0.2 m diameter, and a coagulation bath was applied at a draft rate of 1.8. The coagulated thread was pulled out from the (water) and wound up. The obtained filament was washed with neutralized water. When a portion of it was dried and the logarithmic viscosity was measured, it was 3.3.

Next, the filament was subjected to a beater together with water to obtain a fibrillated filament.

This fibril thread-like material could be used alone to make paper from a slurry dispersed in water, and strong paper was obtained.

Example 2 Poly(p-phenylene terephthalamide) having a logarithmic viscosity of 5.1 was dissolved in 99.7% by weight sulfuric acid to give a concentration of 4% by weight to obtain an optically isotropic dope. 0.1 mm diameter hole 2
The dope was discharged from a spinneret with 0.4% by weight.
The yarn was coagulated with an aqueous sulfuric acid solution and taken out from the coagulation bath at a draft rate of 2.1. The yarn material was neutralized with alkali, washed with water, and dried.

After cutting the obtained yarn into approximately 3C11 length,
It was fibrillated by applying it to a grinder.

When the product is observed under an optical microscope, a large number of fibrils (
It had a filamentous structure with branches.

Strong paper is obtained from these pulp particles, and nylon 6
When kneaded with 6 resin, the rigidity of the resin increases.

Ta.

Example 3 A 10% by weight optically anisotropic dope was prepared from poly(p-phenylene terephthalamide) having a logarithmic viscosity of 4.0 and concentrated sulfuric acid having a concentration of 99% or more. 0.07m of this dope
It was once discharged into the air from a spinneret having 50 holes with a diameter of +s, and after traveling about 5 c+m, it was introduced into a coagulation bath (water at 10° C.). Here, the spinneret was heated to about 85°C, and moist hot air (about 110°C, 90% RH) was applied to the dope flow running in the air.
) was sprayed so that the running dope was completely optically isotropic under static conditions before entering the coagulation bath. The speed at which the filament was drawn out from the funnel-shaped coagulation bath was adjusted so that the draft ratio was 2.7.

The coagulated filament was washed with water, dried, cut into about 6 lengths, and beaten with water in a beater. After beating for about 1 hour, fibrillated threads were obtained.

This thread-like material could be easily made into paper using a Tappi standard paper machine, and the dry paper had a strength of 0.8 kg/mj.

Comparative Example 1 In Example 3, the spinneret temperature was set at 35 to 40°C,
Example 3 was repeated except that the blowing of hot air was stopped and the optically anisotropic dope was solidified.

Although a fibrillated filament was obtained, the dry paper produced had a strength of only 0.4 kg/-.

Comparative Example 2 In Example 3, a filament was produced with a draft ratio of 1.5 and beaten with a beater. The degree of fibrillation was small and paper-making properties were poor.

Example 4 In Example 3, instead of the spinneret, a 0.3 mj x 3.2 cm slit heated to 85° C. was used to extrude into a film, and the film was made optically isotropic and solidified by humidifying heat. The trough ratio was set to 2.1. Other conditions are Example 3
I made it the same as

The obtained film-like material was cut into three lengths and beaten with water in a beater to obtain a fibrillated thread-like material.

The filamentous material has excellent paper-making properties and has a dry paper strength of 0.7 kg/mj.
It was big.

Example 5 In Example 3, the optically anisotropic dope was extruded from a 60°C slit die at a draft rate of 2.4, cast onto a tantalum belt, and blown with moist hot air at 110°C and 90% Rf. The film was soaked for optical isotropy, and then introduced into water at 15°C for coagulation to obtain a transparent film.The draft rate here refers to the speed at which the film is removed from the coagulation bath (=movement of the tank belt). speed) divided by the extrusion line speed from the goo.

After the obtained film was neutralized and washed with water, it was
% and then constant length drying.

The film was cut into approximately 20 square pieces, and then beaten with water using a beater to obtain a fibrillated filament. This filamentous material had good paper-making properties and high paper strength (dry strength).

(Effects of the Invention) The pulp particles, i.e., fibrillated filaments obtained by the present invention, can be made into strong sheet-like materials such as heat-resistant insulating paper by taking advantage of their fibrillarity and excellent heat-resistant mechanical properties. . In particular, since it has excellent paper strength, it is suitable as electrical insulating paper for heavy electric motors and the like. In addition, it can also be used as a friction material and a reinforcing material for resins.

Claims (1)

[Claims] Pulp particles characterized by applying mechanical shearing force to a molded product obtained by molding an optically isotropic solution of para-aromatic polyamide at a draft ratio of 1.8 or more to form a fibrillated filament. manufacturing method