JPH01148810A - Production of polybenzimidazole pulpy particle - Google Patents

Abstract

PURPOSE:To obtain the title pulpy particles having excellent sheet forming properties, by injecting a polybenzimidazole solution into a specific precipitant by a solution shearing method. CONSTITUTION:A polybenzimidazole containing at least about >=85mol% recurring units expressed by the formula (Ar1 is tetrafunctional aromatic residue, etc., forming benzimidazole ring in pair at the o-positions of the aromatic nucleus; Ar2 is bifunctional aromatic residue, etc.) is dissolved in an amide based polar solvent to provide a polymer solution, which is then injected into a precipitant stirred at a high speed to precipitate pulpy particles. (A) An aqueous solution containing of calcium chloride in >=25wt.% calcium chloride concentration at >=30 deg.C temperature or (B) an aqueous solution containing 50-90wt.% N-methylpyrrolidone-2 is used as the precipitant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing polybenzimidazole pulp particles having excellent heat resistance. More specifically, the present invention relates to a method for industrially producing polybenzimidazole pulp-like particles suitable for use in heat-resistant synthetic paper and resin molded articles from a polybenzimidazole solution by a so-called solution shearing method.

BACKGROUND OF THE INVENTION Polybenzimidazole has been known to be useful as a raw material for fibers and other molded products having excellent heat resistance and nitrogen properties. For example, poly(2,2'-metaphenylene-5,51-bibenzimidazole) provides fibers with excellent heat resistance and is widely used for flame-resistant applications.

On the other hand, in the field of heat-resistant synthetic paper, aramid synthetic paper is used, but with the advancement of advanced materials for space and aircraft applications, products with higher heat resistance and flame resistance have been required in recent years. Therefore, polybenzimidazole synthetic paper, which has better flame resistance than aramid, has been eagerly awaited.

Incidentally, pulp-like particles, which are generally raw materials for synthetic paper, can be broadly classified into two methods. Namely, shearing method from polymer solution and high orientation! This is a method of beating l\11 or a polymer. Regardless of which method is applied, in order to obtain high-performance pulp particles, the final pulp particles must have as high mechanical strength and electrical insulation as possible through paper making and heat-pressure calendering. It is desirable that the paper-like sheet has flame resistance.

Regarding aramid (fully aromatic polyamide), when producing pulp-like particles of aramid polymer by the solution shearing method, water or an amide polar solvent (aramid solvent) (
Generally, an aqueous coagulation bath such as amide solvent (hereinafter abbreviated as amide solvent) is used, and the solvent concentration is 5 to 30% by weight.

However, in the case of polybenzimidazole, using the above-mentioned coagulant causes rapid coagulation and precipitation, so-called poor coagulation properties, resulting in insufficient mechanical strength of the pulp-like particles, and ultimately The properties of synthetic papers obtained by calendering often fail to meet the required standards.

The main purpose of the present invention is to eliminate the above-mentioned drawbacks in producing pulp-like particles from a polybenzimidazole solution by a solution shearing method, and to improve coagulation properties in the process of forming bulb-like particles (precipitation and coagulation). The object of the present invention is to provide a method for obtaining polybenzimidazole pulp particles of good quality.

1 shellfish! The object of the present invention as described above is to dissolve polybenzimidazole, in which about 85 mol% or more of the repeating units are represented by the following general formula (I), in at least one solvent, and to dissolve the resulting polymer solution. In the so-called solution shearing method (precipitation method) in which the precipitant is brought into contact with a precipitant that is stirred at high speed and precipitated as pulp-like particles, the precipitant contains: a) Calcium chloride 21 degrees Celsius is 25% by weight or more and the temperature is 30 degrees Celsius or more; an aqueous solution of calcium chloride, or b) N
- an aqueous solution containing 50 to 90% by weight of methylpyrrolidone-2.

The polybenzimidazole used in the method of the present invention is one in which the repeating units represented by the above general formula (I) account for 85 mol% or more of the total repeating units of the polymer,
Ar+ in the formula includes aromatic residues such as eg.

One or more hydrogen atoms in these aromatic residues may be substituted with a monovalent functional group such as -CI or -CH3.

Such polybenzimidazole itself is conventionally known,
For example, U.S. Pat. No. 3,526,693, 3.61
It is described in detail in issues such as No. 9,453.

The polybenzimidazole particularly preferably used in the method of the invention consists essentially of 2,2'-metaphenylene-5,
It is a polymer composed of 5'-bibenzimidazole units.

The degree of polymerization of polybenzimidazole varies depending on the use of the pulp particles, but is generally preferably 0.6 or more in terms of η1nh (intrinsic viscosity).

Note that ηinh here is a value measured at a concentration of 0.59/dj in sulfuric acid at 30°C.

In the method of the present invention, the polybenzimidazole may contain various colorants, stabilizers, fillers, etc., and may also be mixed with other polymers having a common solvent.

In order to produce pulp-like particles by the method of the present invention, the above-mentioned polybenzimidazole is dissolved in at least one kind of amide solvent, and the resulting solution (dope) is formed into pulp-like particles (fibrids) by the method described below. However, each step will be sequentially explained below.

B. Preparation of polybenzimidazole solution As the amide solvent for dissolving polybenzimidazole, the following can be used: N, N, N', N'-tetramethylurea (TMU), N, N- Dimethylacetamide (
DMAC), N,N-diethylacetamide (DEAC)
), N,N-dimethylpropionamide (DMPR>,
N,N-dimethylbutyramide (NMBA), N,N-
Dimethylisobutyramide (HMIB), N-methylpiperidine-2 (NMP), N-ethylpyrrolidone-2 (
NEP), N-methylcaprolactam (NMC), N
-Acetylpyrrolidine (NAPR), N-acetylpiperidine, N-methylpiperidine-2 (NMPD),
N.

N'-dimethylethylene urea (DMI), N.

N'-dimethylpropylene urea, N, N, N'.

N'-tetramethylmalonamide, N-acetylpyrrolidone, etc.

In these amide solvents, NMP, DMAC.

DMF, NMC, NAPR, TMU, and DMI are preferred. Particularly preferably used are NMP and DMAC.
,DMI.

These may be used alone or as a mixed solvent.

In addition, lithium chloride, calcium chloride, magnesium chloride, ammonium chloride, and zinc chloride are added to the above solvent for the purpose of increasing the ability to dissolve the polymer.

Inorganic salts such as lithium nitrate, calcium nitrate, magnesium nitrate, ammonium nitrate, zinc nitrate, etc. can be added. Among these inorganic salts, lithium chloride and calcium chloride are particularly preferred.

The amount of the inorganic salt added varies depending on the type of inorganic salt, polymer concentration, etc., but can be selected from the range of 0.1 to 6% (by weight) for boat fishing. If it is less than 0.1%, the effect of addition is small, and if it exceeds 6%, it is not only excessive for the purpose of stabilizing the solution, but also deteriorates wet coagulation properties. In view of the balance between solution stabilization and wet coagulation, the preferred addition amount is 0.
It is 5 to 4%, particularly preferably 1 to 3%.

Polybenzimidazole is dissolved in the above amide solvent (if necessary in the coexistence of the above inorganic salt), and the polymer is dissolved.
To prepare a stock solution for molding (dope), for example, a method is adopted in which a polymer is added to a solvent at room temperature and then dissolved until it reaches around the boiling point of the solvent, with stirring under normal pressure or pressure, or with stirring without Wt. I can do it.

The polymer concentration in the dope is generally preferably about 10 to 30% (by weight).

The obtained dope can be used for forming bulb-shaped particles after defoaming and filtration if necessary.

B. Pulp-like granules In the production of pulp-like particles, the polybenzimidazole solution prepared by the method described above and the coagulant described below are made to act under shear stress, and the pulp-like particles are formed under favorable coagulation conditions. Particles can be precipitated.

As the coagulant, an aqueous calcium chloride solution having a substantially calcium chloride concentration of 25% by weight or more and a temperature of 30° C. or more, preferably 50° C. or more is used. If the calcium chloride concentration is 25% by weight or less, the improvement in coagulation is insufficient, and if the temperature is less than 30°C, the rate of coagulation of the pulp-like particles produced is slow. The concentration of calcium chloride in the coagulation bath is preferably 30 to 50% by weight, particularly preferably 37 to 4% by weight.
It is 5% by weight. A still more preferable coagulation bath temperature is 60~
The temperature is 120°C, and can be particularly preferably selected from a temperature range of 70 to 110°C.

The above calcium chloride aqueous solution may further contain a certain amount of other salts as necessary, such as lithium chloride, calcium chloride, magnesium MA, ammonium chloride, zinc chloride, lithium nitrate, calcium chloride, magnesium nitrate, and ammonium nitrate.

It is also possible to contain zinc nitrate, and it is also possible to preferably improve coagulation properties or control the coagulation rate by using a mixed system containing an amide solvent or the like.

In addition, in the method of the present invention, NMP is used as a coagulant at 50 to 9
It is also possible to use a coagulant consisting essentially of an aqueous solution containing 0w%. NMP+! If 1 degree is less than 50% by weight,
The coagulation properties of the obtained pulp particles are insufficiently improved, and on the other hand, when the amount exceeds 90% by weight, the coagulation rate of the pulp particles produced is extremely slow. A particularly preferred precipitant has an NMP degree of 60 to 85% by weight.

The above NMP aqueous solution may further contain a certain amount of inorganic salts, such as lithium chloride, magnesium chloride,
Ammonium chloride, zinc chloride, lithium nitrate, calcium nitrate, magnesium nitrate.

It can also contain ammonium nitrate and zinc nitrate.
Furthermore, it is also possible to preferably improve coagulation properties or control the coagulation rate by using a mixed system containing a solvent other than an amide solvent, for example, an alcohol solvent such as ethylene glycol, glycerin, or polyethylene glycol.

In the method of the present invention, in order to form pulp-like particles from a solution, the coagulant is stirred at high speed, and at the same time, any pulping apparatus that can sufficiently generate shearing action or beating action can be used to remove the solvent from the introduced solution. Although such a device can be used, it is preferably equipped with a stirring blade that can rotate at high speed. In addition, as for the device type, either a tank type or a channel agitation type can be applied, but in particular, the
A pipe stirring type continuous precipitation device combining a rotor and a stator as described in No. 47695 is preferred.

Since the pulp-like particles obtained by the above method often contain a solvent and/or inorganic salts therein, it is preferable to wash them with water or the like, if necessary. As the cleaning method, the displacement cleaning method described in European Patent Application No. 851037481 is preferably used.

C. Paper making The pulp-like particles obtained by the method of the present invention can be made into useful synthetic paper even when made alone, but even better synthetic paper can be made by mixing short fibers and making paper. You can. In order to produce synthetic paper from pulp-like particles and short fibers by the method of the present invention, it is preferable to make paper using a Fourdrinier method or a cylinder method, as in the case of paper making for conventionally known natural valves and synthetic valves. .

As short fibers, conventionally known 1 [(for example, Japanese Patent Publication No. 1973-
Various types of fibers 1) described in Publication No. 10718 can be used, but in order to take full advantage of the extremely good heat resistance of the pulp-like particles produced by the method of the present invention, fibers with high heat resistance that can withstand a working temperature of 200°C or higher are used. preferable.

Examples of such highly heat-resistant mu include various aramid fibers, polyimide fibers, polyamideimide fibers, polybenzimidazole fibers, carbon fibers, and ceramic fibers.

When making paper using pulp-like particles according to the method of the present invention,
The amount of pulp particles used is 20 to 95% by weight, preferably 40 to 60% by weight, based on the sheet.

When the content of pulp-like particles is less than 20%, physical properties such as strength and elongation deteriorate. On the other hand, when the content is more than 95%, various properties such as strength and elongation deteriorate.

2. Manufacture of molded products After drying, the pulp-like particles or paper sheets obtained as described above are placed in a heat compression mold and heated under pressure to obtain excellent thermal and mechanical properties. It can be made into a molded product such as a motsu board.

The thermal compression temperature varies depending on the pulp particles and the polymer composition of the sheet, but can be appropriately selected from the temperature range of 150 to 500°C. The pressure of application also depends on the polymer composition, but is usually 50 to 1000 Kg/CI! It is.

It has been reported in the literature that the polybenzimidazole having the above structure constituting the pulp-like particles has a glass transition point of 435°C. On the other hand, when the present inventor conducted a thermal threat analysis (TGA) of this product, it was found that thermal decomposition of the polymer cannot be ignored when kept at 435°C or higher for 10 hours or more even in an inert atmosphere as well as in air. As it progresses,
I learned that it gradually becomes carbonized. Therefore, molded products (engineering plastics), thick synthetic papers, and the like inevitably tend to become brittle if they are subjected to such high-temperature treatment for a long time.

When the polybenzimidazole pulp-like particles obtained by the method of the present invention are used for paper making or heat pressing to produce synthetic paper, molded products, etc., if necessary, the polybenzimidazole pulp-like particles can be used at a heat pressing temperature of 320°C or higher and lower than 435°C. Shows thermocompression bondability.

Effects of the Invention According to the method of the present invention as described above, useful polybenzimidazole pulp particles can be produced by suitably combining and selecting various factors such as polymer skeleton/composition, coagulant composition/conditions, etc. I can do it.

The pulp-like particles obtained by the method of the present invention have excellent heat resistance, flame resistance, and paper-making properties, and are therefore useful as raw materials for heat-resistant synthetic papers and molded products. It is particularly useful for heat-resistant synthetic paper that takes advantage of its flame resistance.

EXAMPLES The present invention will be explained below with reference to Examples. In the examples, the intrinsic viscosity ηinh is a value measured at 30° C. at a polymer concentration of 0.5 g/dl.

Example 1 (Preparation of polybenzimidazole solution) ηinh is 0.
7 poly(2,2'-metaphenylene-5,5'-
bibenzimidazole) 22.5g, lithium chloride 2
．． 0 g and 77.5 g of NMP were placed in an eggplant-shaped flask equipped with a reflux condenser and heated to 200 to 210°C to dissolve them. The obtained solution was filtered and used for the following production of pulp-like particles.

(Manufacture of pulp-like particles) The solution (dope) obtained above is made of a combination of a stator with baffles and a turbine blade-shaped rotor, a coagulant, a supply port for the solution, and pulp-like particles after coagulation. The dope was simultaneously fed at 5009/min and the coagulant was fed at 5Ky/min into a conduit stirring type continuous precipitator equipped with a slurry discharge port, and a slurry of pulp-like particles was taken out from the discharge port. The coagulant consisted of a 40% by weight aqueous calcium chloride solution, and the temperature was 85°C. Further, the rotation speed of the rotor was 7.00 Or, p, m.

The slurry after precipitation was drained using a centrifuge, and most of the coagulant was taken out as a filtrate. The cake consisting of pulp-like particles was roughly washed with water to finally obtain a pulp-like particle slurry solution.

(Manufacture of sheet) 2.5 g of pulp-like particles obtained above (as solid content)
Paper was made from a slurry containing 0.3 g of aramid fiber "Technora"(copolybalaphenylene/3.4'-oxydiphenylene terephthalamide fiber) cut into lengths of 5III and 1 m using a Tarapee standard sheet machine. The obtained sheet had good drainage of water from the wire mesh and was uniform with few spots.

This sheet was hot pressed at 350° C. and 300:9/ci to obtain synthetic paper with a thickness of about 100 μm.

(Manufacture of molded product) 2.5 g of the bulb-shaped particles obtained above (as solid content)
and polyether aramid fiber "Technora"(copolyparaphenylene/3.4'-oxydiphenylene terephthalamide fiber) cut into lengths of 5 m. Paper was made from a slurry containing 0.39 using a Tarapy standard sheet machine. . The obtained sheet had good drainage of water from the wire mesh and was uniform with few spots.

After drying, slit this sheet and set it in a mold.
Heat pressed at 90℃ and 50ONg/cd,
A plate-shaped resin composition having a thickness of approximately 2 mm was obtained.

Example 2 The same polybenzimidazole solution as in Example 1 was prepared by combining a stator with baffles and a turbine blade rotor, and equipped with a coagulant and dope supply port and a valve-shaped particle slurry discharge port after coagulation. A dope at 500 g/min and a coagulant at 5 kg/min were simultaneously fed into a conduit stirring type continuous precipitator, and a slurry of pulp-like particles was taken out from an outlet.

The coagulant consisted of a 40% by weight aqueous calcium chloride solution, and the temperature was 85°C. Also, the rotation speed of the rotor is
7,0OOr, p, m, te was carried out.

The slurry after precipitation was drained using a centrifuge, and most of the coagulant was taken out as a filtrate. The cake consisting of pulp-like particles was further washed with water to finally obtain a bulb-like particle slurry solution.

Next, 2.5 g of the obtained bulb-shaped particles (as solid content)
Paper was made from a slurry containing 0.3 g of polyether aramid fiber "Technora"(copolyparaphenylene/3.4'-oxydiphenylene terephthalamide fiber) cut into 5 m lengths using a Tarapy standard sheet machine. . The obtained sheet had good drainage of water from the wire mesh and was uniform with few spots.

This sheet was hot pressed under the same conditions as in Example 1 to obtain a good synthetic paper with a thickness of about 100 μm.

Example 3 22.5 g of polybenzimidazole with ηinh of 0.7 as in Example 1, 2.0 g of lithium chloride, and NMP77
5 g was placed in an eggplant-shaped flask equipped with a reflux condenser and heated to 200-210°C to dissolve.

The resulting solution was filtered and subjected to bulbing.

This solution (dope) is transferred to a conduit-stirred continuous precipitation system consisting of a combination of a stator with baffles and a turbine blade-shaped rotor, and equipped with a supply port for coagulant and stock solution, and a valve-shaped slurry discharge port after coagulation. On the occasion, dope 5
009/min, a 70% by weight aqueous NMP aqueous solution 5K was simultaneously supplied as a solid agent at room temperature, and a slurry of pulp-like particles was taken out from the outlet. Note that the rotation speed of the rotor was 7.00 Or, p, l.

The slurry that had undergone bulbing was deliquified using a centrifuge, and most of the coagulant was taken out as a filtrate.

The cake consisting of pulp-like particles was further washed with water to finally obtain a bulb-like particle slurry solution.

Patent applicant Teijin Kaisha Ltd.

Claims (3)

[Claims] (1) Approximately 85 mol% or more of the repeating units have the following general formula (I), ▲a mathematical formula, a chemical formula, a table, etc.▼...(I) In the formula, Ar_1 is a tetravalent aromatic residue, and It can form a benzimidazole ring by forming a pair at the ortho position of the aromatic nucleus, and Ar_2 is a divalent aromatic residue. Ar_1 and Ar
The hydrogen atom on the aromatic residue of _2 may be substituted with another functional group. Polybenzimidazole represented by is dissolved in at least one type of amide polar solvent, and the resulting polymer solution is heated to: a) a calcium chloride concentration of 25% by weight or more and a temperature of 30%;
℃ or higher, or b) an aqueous solution containing 50 to 90% by weight of N-methylpyrrolidone-2, introduced into a coagulant that is stirred at high speed and precipitated as pulp-like particles. A method for producing polybenzimidazole pulp particles, characterized by: (2) The production method according to claim (1), wherein the polybenzimidazole is poly(2,2'-metaphenylene-5,5'-bibenzimidazole). (3) The manufacturing method according to claim (1), in which an aqueous calcium chloride solution having a calcium chloride concentration of 30 to 50% by weight is used as a coagulant.