JPH0234972B2 - FUIBURITSU DONOSEIZOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing fibrids made of synthetic polymers. More specifically, a solution of a synthetic polymer is introduced into a precipitant that is a non-solvent for the polymer and has an affinity for the solvent in the solution, and the polymer is precipitated while applying a shearing action to the solution. The present invention relates to improvements in the method of manufacturing fibrids by.

Prior Art It has been known for a long time to produce pulp-like particles called "fibrids" from synthetic polymers.
-5732 publication etc., by stirring a precipitant at high speed, introducing a polymer solution into the precipitant, and precipitating the polymer while applying shearing action (and beating action),
A method of manufacturing a fibrid is disclosed.

In addition, as an apparatus for efficiently performing precipitation when producing fibrids according to such a method,
Devices such as those described in Japanese Patent Publication No. 40-9044 and Japanese Patent Application Laid-Open No. 52-151621 are known, but these precipitation devices also use high-speed rotating bodies as means for applying shearing action, and the rotating bodies Because of this, it is necessary to vigorously stir and mix the mixture system of the polymer solution, precipitant, and precipitate, and therefore the power required to produce the fibrid is extremely large.

Furthermore, in the above-mentioned method and apparatus, it is known that the physical properties of the fibrid and the paper-like material made using the same change slightly depending on the absolute shear rate and the time required to cause precipitation. In order to obtain fibrids, it is necessary to control these conditions to appropriate conditions, but in reality it is difficult to always maintain these conditions within an appropriate range, and no matter how you adjust these conditions, the fibrids that can be obtained It is difficult to manufacture products with small variations in size and quality. Furthermore, the fibrid produced in this manner has a problem in that the physical properties of the paper-like sheet made using the fibrid, particularly the electrical insulation properties, are not necessarily sufficient.

Purpose of the Invention The purpose of the present invention is to solve the various problems in the conventional fibrid manufacturing method as described above, to significantly reduce the power consumption during fibrin manufacturing, and to make the obtained fibrs uniform in size. It is an object of the present invention to provide a method for easily producing a fibrid which can form a paper-like sheet with good physical properties when paper-formed using the fibrid.

Composition of the Invention As a result of repeated research to achieve the above-mentioned object, the present inventors have discovered that fibrils can be produced by mixing a certain amount of gas into a system in which a polymer solution and a precipitant are brought into contact with each other and precipitated. The present invention was achieved based on the discovery that power consumption during production is significantly reduced, the resulting fibrils have less variation, and the physical properties of sheets made using the same are improved.

That is, the present invention provides a method for producing fibrids by introducing a polymer solution into a precipitant and precipitating the polymer while applying a shearing action to the solution, in which the precipitation system is changed to a mixed phase of gas and liquid. This method is characterized by:

The polymer used in the present invention may be any fiber-forming polymer that can be dissolved in an appropriate solvent, but aromatic polyamides that have good heat resistance and can easily form good fibrils are preferred. is particularly suitable. Examples of such suitable aromatic polyamides include the following.

(a) A condensation polyamide of a dicarboxylic acid having an aromatic ring, preferably a highly active derivative such as an acid halide, and a diamine having an aromatic ring; For example, as the dicarboxylic acid, one or two kinds of isophthalic acid, terephthalic acid, etc. In addition to the above, diamines include metaphenylenediamine, paraphenylenediamine,
One or more of 3,4'- or 4,4'-diaminodiphenyl ether, 3,4'- or 4,4'-diaminodiphenylmethane, xylylene diamine, N-methyl paraphenylene diamine, etc. A homopolyamide or copolyamide obtained by reacting and condensing both in substantially equimolar amounts; Among such condensed polyamides, the most preferable one is polymetaphenylene isophthalamide or metaphenylene isophthalamide and metaphenylene. Examples include copolymers with terephthalamide.

(b) A polyamide obtained by activating and condensing an aminocarboxylic acid having an aromatic ring; for example, a homopolyamide using para- or meta-aminobenzoic acid, para-aminomethylbenzoic acid, etc. as the aminocarboxylic acid, or two types thereof Copolyamide obtained by co-condensation of the above aminocarboxylic acids; preferred among such condensed polyamides is poly(para-aminobenzoic acid).

(c) A polyamide obtained by co-condensing the above (a) and (b); Preferred examples of such co-condensing polyamides include polyamides obtained by condensing three components: metaphenylene diamine, isophthalic acid chloride, and para-aminobenzoic acid chloride hydrochloride. Examples include polyamide.

The above-mentioned polymer may contain mica particles or other inorganic substance fine particles, if necessary.

In the present invention, the solvent for dissolving the polymer to form a solution is not particularly limited as long as it can dissolve the polymer, and may be either an inorganic solvent or an organic solvent.

When the polymer is an aromatic polyamide, an inorganic solvent such as sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, hydrogen fluoride, or N-methyl-2-pyrrolidone,
Organic solvents such as NN'-dimethylformamide, NN'-dimethylacetamide, dimethyl sulfoxide, and tetramethylurea are used, but in the case of polymetaphenylene isophthalamide-based polymers,
Polar amide solvents such as N-methyl-2-pyrrolidone or NN'-dimethylacetamide are particularly preferred.

The concentration of the polymer in the solution varies depending on the type of polymer, the degree of polymerization of the polymer, etc., but is generally preferably 2 to 15% by weight.

On the other hand, as the precipitant, a liquid is used that has an affinity for the solvent in the polymer solution but is a non-solvent for the polymer.

When an organic solvent is used as the solvent, the precipitant that can be used may be water alone, a water-organic solvent mixture, glycerin, ethylene glycol, a glycerin-water mixture, ether, or the like. These precipitants include calcium chloride, lithium chloride,
It may also contain an inorganic salt such as magnesium chloride.

Among these, as a precipitant for a polymer solution in which a polymetaphenylene isophthalamide-based aromatic polyamide is dissolved in an amide-based solvent, a precipitant containing the amide-based solvent in an amount of 50% by weight or less, particularly 10 to 40% by weight is used. Aqueous solutions are best.

When producing fibrids, it is necessary to use a precipitation device that stirs the precipitant at high speed, removes the solvent from the polymer solution introduced into the precipitant, and at the same time applies a strong shearing action. As such a precipitation device, a continuous precipitation device in which a stator of a specific shape and a turbine blade-shaped rotor are combined as described in JP-A-52-151621 is particularly preferred.

In the present invention, when producing a fibrid by applying a precipitant to a polymer solution as described above, the precipitation system is a mixed phase of gas and liquid (vapor-liquid mixed phase). Air is economical as the gas used here, but other gases such as carbon dioxide may also be used.

In order to make the precipitation system into a gas-liquid mixed phase, the gas may be mixed or dissolved in the precipitant in advance and then introduced into the precipitation apparatus, or the gas may be introduced into the precipitation apparatus at the same time as the precipitant and polymer solution. It's okay. In addition, the introduction method may be to use compressed gas, or the precipitation device may be devised to draw gas (air) into the precipitation system from the outside, or even gas may be introduced into the precipitation system. It is also possible to dissolve it and generate gas during precipitation. The point is that liquid and gas need only be mixed in the precipitation system, and any means or method can be used.

The amount of gas introduced is 5 to 100% relative to the precipitant.
The amount is preferably about % by volume, and particularly preferably within the range of 10 to 50% by volume.

At this time, Japanese Patent Publication No. 40-9044 and JP-A-52-
In a precipitation device of the type described in Publication No. 151621,
It is effective to rotate the rotor at a high speed, such as 5000 rpm or higher, to mix in the gas in the precipitation system, which is subjected to a very large shearing action, and is less effective when the rotor is rotated at a low speed.

Effects of the Invention According to the present invention as described above, when producing a fibrid by introducing and dispersing a polymer solution into a precipitant in a system having a shearing action,
The power required during precipitation is significantly reduced, good fibrids of uniform size and quality are obtained, and the physical properties of paper-like sheets made using the fibrs are also good.

This means that in the gas-liquid mixed phase, the apparent viscosity of the system decreases, the power required to stir the system at high speed decreases, and the time required for precipitation changes, so the shape and size of the fibrids obtained will change. changes, reducing variations in fibrid size and quality, and
It is believed that the physical properties of paper-like sheets made using the fibrid are also improved.

Therefore, the fibrids produced according to the present invention can be mixed with reinforcing fibers, particularly heat-resistant aromatic polyamide fibers, to form paper-like sheets with excellent physical properties such as strength and elongation, heat resistance, and electrical insulation properties. .

Examples Next, examples and comparative examples of the present invention will be described in detail. Although these examples all relate to fibrils of polymetaphenylene isophthalamide, it goes without saying that the present invention is not limited thereto.

Example 1 Polymetaphenylene isophthalamide was produced by the interfacial polymerization method described in Japanese Patent Publication No. 47-10863. This polymer had an intrinsic viscosity (IV) of 1.35 when dissolved in N-methyl-2-pyrrolidone and was found to contain no inorganic salt at all. This polymer was dissolved in N-methyl-2-pyrrolidone to a polymer concentration of 12.5% by weight to obtain a polymer solution for precipitation.

On the other hand, N-methyl-2-pyrrolidone was added to water at a concentration of 30% by weight to prepare an aqueous solution, which was used as a precipitant.

Using this polymer solution and precipitant,
- Precipitation device described in Publication No. 151621 (however, the diameter is 15 mm)
A fibrid was produced using the method described in the same publication.

At this time, the above N-methyl-2-pyrrolidone aqueous solution was added to the precipitation apparatus for 60 parts by volume of the polymer solution.
Supply at a rate of 1800 parts by volume, and increase the number of rotations of the rotor.
A fibrid was prototyped with a speed of 10,000 rpm. on the other hand,
A similar experiment was conducted by mixing and supplying 200 to 450 parts by volume of air to 1800 parts by volume of the above N-methyl-2-pyrrolidone aqueous solution.

The results of these experiments are shown in FIGS. 1-3. Figure 1 shows data on the load on the electric motor in the precipitation equipment. By mixing these, this can be reduced to around 100A, resulting in a significant reduction in power requirements.

Also, Figure 2 shows the state of the viscosity distribution of fibrids.
It can be seen that the content of particles larger than 80 meshes is small, and the content of small particles smaller than 80 meshes is also small, indicating that the variation in particle size in the produced fibrillated particles is small.

Figure 3 shows 60 parts by weight of this fibrid and a fineness of 2.
Polymetaphenylene isophthalamide fiber with denier and cut length of 4 mm (registered trademark "Konex")
40 parts by weight was mixed to make paper at a pressure of 200Kg/cm ² and a temperature of
This shows the physical properties of a paper-like sheet made by heating under pressure at 300℃, but the paper made using a fibrid made by mixing air has electrical insulation properties (as indicated by dielectric breakdown voltage BVD) and strength. This shows that it has excellent physical properties such as elongation.

Example 2 Using the same polymer solution and precipitant as in Example 1,
60 parts by weight of polymer solution, 1800 parts by volume of precipitant, and 180 to 432 parts by volume of air were added to the apparatus described in JP-A-52-151621.
Capacity parts were introduced separately. Note that air was introduced from a position deviated by 180° toward the axis from the position serving as the polymer solution inlet of the apparatus.

The results of these experiments are shown in FIGS. 4-6.
FIG. 4 shows the power required for the precipitation apparatus, and FIG. 5 shows the freeness (water content) of the obtained fibrids and the content of fibrids with a small particle size of 150 mesh or less. Furthermore, FIG. 6 shows the physical properties of a paper-like sheet made by using this fibrid and mixing it with polymetaphenylene isophthalamide fiber in the same manner as in Example 1.

These figures show that by introducing air into the precipitation system, the power required for the precipitation device is reduced, the proportion of small particles in the resulting fibrids is reduced, and the freeness (water content) is changed. Not having a good time,
It is also clear that the paper-like sheets made from this have good physical properties, and those with a large amount of air introduced have particularly excellent electrical insulation properties.

[Brief explanation of drawings]

Figures 1 to 6 are diagrams for explaining the effects of the present invention, and Figures 1 and 4 respectively show the amount of air mixed into the precipitant and the load (current ), Figures 2 and 5 are diagrams showing the relationship between the amount of air mixed into the precipitant and the characteristics of the fibrids obtained, and Figures 3 and 6 are diagrams showing the relationship between the amount of air mixed in the precipitant and the characteristics of the fibrids produced, respectively. FIG. 3 is a diagram showing the relationship between the amount of air mixed into the precipitant and the physical properties of a paper-like sheet made using the fibrid.

Claims (1)

[Claims] 1. A method for producing a fibrid by introducing a polymer solution into a precipitant and precipitating the polymer while applying a shearing action to the solution, in which the precipitation system is converted into a mixed phase of gas and liquid. A method for producing a fibrid, characterized by: 2. The method for producing a fibrid according to claim 1, wherein the mixing ratio of the liquid precipitant and gas in the precipitation system is adjusted so that the gas accounts for 5 to 100% by volume of the liquid. 3. Claims 1 or 2, wherein the polymer solution is an amide solvent solution of an aromatic polyamide, the precipitant is an aqueous solution of the amide solvent, and the gas is air. Method of manufacturing the described fibrids.