JPS6232123A - Method for producing para-oriented aromatic polyamide fine particles - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing para-oriented aromatic polyamide fine particles. In particular, the present invention relates to an improved method for producing highly para-oriented aromatic polyamide fine particles used as reinforcing fillers for plastics, rubber, etc. or as raw materials for compression molding.

[Conventional technology]

Generally, the polymer particles are Merck, alumina.

It is already known that, like inorganic particles such as glass powder, they are used for the purpose of reinforcing plastics, rubber, etc., or improving quality such as dimensional stability and heat resistance.

Generally, the particle size of such particles has a large effect on the physical properties of the product, and in order to obtain a high modifying effect, it is desirable to have a fine particle size. In addition, in recent years, especially with the advancement of composite technology, there has been a strong demand for materials with excellent heat resistance, dimensional stability, chemical resistance, etc.

Aromatic polyamides, especially para-oriented aromatic polyamides, are rigid and have excellent dimensional stability, heat resistance, chemical resistance, impact resistance, etc., as expected from their structure, so they are suitable for polymer particles. It is a material that is highly anticipated as a reinforcing filler used in the form of , and as a raw material for compression molding.

Aromatic polyamides are obtained in high yields as polymers with a high degree of polymerization from the corresponding aromatic diamines and aromatic dibasic acid-rides by the so-called low-temperature solution polymerization method (see, for example, Japanese Patent Publication No. 35-14399).

It is already known that particles can be obtained from such aromatic [IJ amide], for example, in the aforementioned Japanese Patent Publication No. 35-143
No. 99 discloses that it can be obtained by pouring a polymerization solution obtained by low-temperature solution polymerization into a coagulant such as water and stirring.

However, when such a method is applied to a matrix-oriented aromatic polyamide, the matrix-oriented aromatic polyamide has a fast solidification rate, high crystallinity, and rigidity, so although it can be obtained as a granular material, the above-mentioned Particles with the desired fine particle size cannot be obtained.

In addition, reducing the concentration of the aromatic polyamide oriented in the solution in order to make the particles finer has a finer effect, but it is not sufficient, and it is necessary to use a large amount of solvent. Due to the drawbacks, this is not a method that can be adopted industrially.

On the other hand, it is a well-known fact that mechanical pulverization means such as a slurry mill, a grinder, and a hammer mill can be applied as a general method for obtaining particles from isolated and purified polymers. However, when such a method is applied to para-oriented aromatic polyamide, the degree of polymerization decreases due to the frictional heat of the mechanical crushing operation, or deterioration due to decomposition occurs. In addition, because it is inherently rigid and has excellent impact resistance, a large amount of energy is required to make particles of sufficiently small size, making this method extremely impractical for industrial use. do not have.

[Problem that the invention seeks to solve]

The present invention has been extremely difficult to achieve with prior art. It is an object of the present invention to provide a method for easily and efficiently manufacturing highly fine particles of para-oriented aromatic polyamide. The diameter of the particles obtained by the present invention is at most 200 μm or less, particularly 100 μm or less.

In general, oriented aromatic boria atoms have poor solubility in solvents, have a strong cohesive force, and are rigid. Therefore, even when the above-mentioned low-temperature solution polymerization is carried out, it usually gives an r-shaped or cheese-like solidified product (hereinafter referred to as "polymerized solidified dope"), and in some cases, it may have rubber-like elasticity. It may also become a polymerized and solidified dope as shown.

When trying to obtain particles from such a polymerized and solidified dope by the conventional method of pulverizing it while contacting with a coagulant, the dope coagulates and precipitates as hard, coarse particles before it is sufficiently pulverized, resulting in fine particles. It becomes difficult to obtain as

On the other hand, even when applying a dope in the form of a solution in which the once isolated para-oriented aromatic polyamide is dissolved in a solvent,
Although there is a slight difference in the degree, it can only be obtained as coarse particles, and 200 μm as the objective of the present invention.
Thereafter, it becomes almost impossible to obtain highly fine particles, especially particles of 100 μm or less.

In view of this, the present inventors have conducted extensive studies on the state of dissolution of para-oriented aromatic polyamide in additives, its aggregation mechanism, formation of precipitates, etc. Dogue and the dope, which is once dissolved in a solvent and then cooled and solidified, surprisingly maintain a stable solid form in a non-coagulating atmosphere, and do not separate and release the polymerization solvent and agglomerate even if left for a long time. / IJ Although mom-ko is considered to be in a so-called solid solution state solvated in a solvent, it can be coarsely crushed and mechanically pulverized;
Furthermore, it was surprisingly discovered that as the grinding progresses, it is possible to homogenize the material into fine particles while losing the elastic properties of a roll-like or cheese-like shape. The present invention was completed based on this knowledge.

[Means for solving problems]

The present invention provides a solidified solution (hereinafter simply referred to as "solidified dope") consisting essentially of a para-oriented aromatic polyamide and a solvent capable of dissolving the para-oriented aromatic polyamide.
This is a method for producing para-oriented aromatic polyamide fine particles, which comprises pulverizing the para-oriented aromatic polyamide fine particles in a non-coagulating atmosphere to a particle size of 200 μm or less, washing and removing the solvent, and then drying.

In the present invention, "para-oriented aromatic polyamide" refers to a polyamide in which an aromatic group having a divalent bond located at the H position is linked, and specifically, the aromatic group is a polyamide in which a divalent bond is located at the H position. 1,4-phenylene () 4.
such as 4'-biphenylene, 1,4--)-phthylene,
It means an aromatic group arranged coaxially in the opposite direction from the aromatic ring, or arranged in a parallel axis opposite direction, such as 1,5-naphthylene and 2,6-naphthylene. These aromatic groups may contain one or more lower alkyl groups such as methyl and ethyl groups, halogen groups such as methoxy, ethyl, chloro, and chloro groups.

Typical of these para-oriented aromatic polyamides are: If parapenzamide, Polyno phenylene terephthalamide +/') -4a 4'-diaminopenzanilide terephthalamide r%po! J-
N*N'-p-phenylene bis(p-benzamide) terephthalamide, polyphenylene 2.
6-naphthalinamide, copolynographenylene/4
．． 4'-(3,3'-dimethylbiphenylene)-terephthalamide, ? ! Sori--'! Examples include loroparaphenylene diphthalamide.

Of these, 90 moles of the repeating units constituting the phenylene terephthalamide, or -limer,
Colimer having a strength of 1/4 or more and /#raphenylene terephthalamide units is preferable from the viewpoint of dimensional stability, heat resistance, and chemical resistance.

The solvent capable of dissolving the above-mentioned /4'-oriented aromatic polyamide may be any solvent as long as it can substantially dissolve the polymer, and specifically, N,N-dimethylacetamide, N-methyl - One or more so-called amide type solvents such as 2-pyrrolidone, N-acetylpyrrolidine, hexamethylphosphoramide, etc., and a solvent with lithium chloride, calcium chloride, etc. added thereto, or a concentration of 95
Concentrated sulfuric acid, hydrochloric acid, methanesulfonic acid, etc. with a weight ratio or higher can be mentioned.

In the following invention, a solidified product of a solution prepared from the above para-oriented aromatic polyamide and a solvent, that is, a solidified dope, is used.

Solidifying the solution into a dope can be easily achieved by once dissolving the resulting solution, usually by cooling it. The temperature at that time varies depending on the type of solvent used, the dope concentration, that is, the concentration of para-oriented aromatic polyamide in the solution, etc., and cannot be generally specified. In the present invention, the temperature does not particularly matter, as long as it is a solidified product.

The dope concentration is not particularly limited in the method of the present invention, but in general, a higher concentration has advantages such as giving a solidified product even at a higher temperature and using less solvent when producing particles. preferable. It is usually carried out in a range of 5 to 40% by weight, but is not limited to this.

In general, the low-temperature solution polymerization method disclosed in Japanese Patent Publication No. 35-14399 mentioned above is used to produce a 9-way oriented aromatic polyamide, especially when all or more than 95 moles of the divalent aromatic groups constituting the polymer chain are When applied to oriented aromatic polyamides such as those with flat phenylene groups and polymerized at industrially important high concentrations, the polymerization reaction product is almost always solidified in the form of glue or cheese. (Hereinafter, such a glue-like or cheese-like polymerization reaction solidified product will be simply referred to as "polymerization solidified dope").

The polymerized solidified dope is a solidified dope that can be applied in the present invention, and is a particularly useful solidified dope because it can be obtained simultaneously with the polymerization operation.

In order to obtain fine particles of para-oriented aromatic polyamide by the method of the present invention, it is essential to crush the solidified dope in a non-coagulating atmosphere.

If the solidified dope is exposed to a coagulating atmosphere, especially an aqueous medium such as water, before pulverization, the solvent will be desorbed from the solidified dope, the polymer will coagulate and precipitate, and strong coarse particles or lumps will be formed. As a result, it becomes impossible to obtain sufficiently fine particles as in the conventional method.

Under a non-coagulating atmosphere, the solidified dope itself is very stable and does not separate the solvent and coagulate.

By pulverizing the solidified dope while maintaining its solvated state with the solvent, the solidified dope can be easily made into fine particles, which is the most important feature of the present invention.

Furthermore, in the present invention, the crushed particles obtained from the solidified dope are particles that still contain the solvated solvent, and the polymer in the particles is only removed by washing and removing the solvent as described below. As a result of the coagulation and precipitation, even finer oriented aromatic polyamide particles are obtained.

The term "non-coagulant atmosphere" as used in the present invention refers to an atmosphere in which desorption or dilution of the solvent from the solidified dope does not substantially occur. Specifically, it is in a gas such as nitrogen, oxygen, helium, or air with a relative humidity of at least 60 degrees or less, or in a dehydrated liquid medium that is insoluble in the solvent that forms the solidified dope. Specific examples of the liquid medium include hydrocarbons such as hexane and heptane, alkyl esters of aliphatic carboxylic acids, and the like.

The method of pulverization is not particularly limited in the present invention, and any general-purpose means may be used as long as it can pulverize the particles to the desired particle size in the above-mentioned non-coagulating atmosphere.

Examples of specific methods for crushing the polymerized and solidified dope include:
T-bahammer mill, cod? - It is also useful to use commonly used crushing equipment such as Lumir, Shaw crusher, Henschel mixer, etc., or to extrude through a specified sieve grid using a twin-screw mixed kneader, etc. be.

The degree of pulverization varies somewhat depending on the purpose of use of the resulting oriented aromatic polyamide fine particles, but in order to satisfy the application to recent advanced composite material technology, it is necessary to increase the size of the final particles. It is necessary to form particles of 100 μm or less, and for this purpose, in the method of the present invention, the solidified dope is pulverized to at least a particle size of 200 μm or less.

The temperature during pulverization is not particularly limited in the present invention, as long as it is maintained so that the solidified dope does not become a solution due to frictional heat or the like. It is possible to heat it if necessary, and cooling it is also of course permitted.

Usually due to high temperature, decomposition denaturation of the solvent.

Or, there is a possibility of coloring of the polymer.

Preferably, the temperature is 100°C or less.

The particles from the solidified dope crushed by K in this way still contain the solvent, so the particles may be compressed or stuck together by squeezing, etc., but the subsequent removal of the solvent or washing with water may cause the particles to stick together. Since it is easily dispersed by stirring or the like, there is no particular problem in the method of the present invention.

The particles from the ground solidified dope are then washed free of solvent.

In the present invention, the cleaning means is not particularly limited, and may be carried out by any commonly used means.

Specifically, examples thereof include a method in which a detergent is added to the particles, stirred, and then the polymer particles are filtered in a batch manner, and a countercurrent or cocurrent multistage washing method in which the particles are washed while continuously supplying a detergent. The extent of such cleaning depends on the amount of polymer required.
It may be determined as appropriate depending on the degree of I-manufacturing.

The particles thus washed are dehydrated prior to drying, and then dried. Deliquoring is usually carried out by conventional methods such as filtration, compression treatment, centrifugation, etc. Of course, any general-purpose means can be used as the drying means.

As polyamide is pulverized while being solvated by the solvent, the pulverization itself is extremely easy, and the pulverized particles that still contain the solvent have poor cohesiveness, and even if they do coagulate, they will not coagulate. By removing the solvent with a detergent, detergent, etc., it will easily disperse and become fine particles, and as a result of the removal of the solvent, the polymer molecules will coagulate and precipitate, resulting in particles that are even finer than the solidified dope particle size at the time of crushing. As particles, oriented aromatic polyamide particles can be obtained.

〔Example〕

The method of the present invention will be explained in more detail with reference to Examples below.

In the workings, unless otherwise specified, all limits are expressed in % by weight.

In addition, the particle size of the solidified Dogu after pulverization and the finally obtained iJ? The particle size of the oriented aromatic polyamide fine particles represents the value measured using a Tyler standard sieve.

Measuring method of intrinsic viscosity〉 Intrinsic viscosity (η1nh) is measured by adding concentrated sulfuric acid of 9&5% by weight.
(01=0.2, f/dt) A solution in which a polymer or fiber is dissolved is measured at 30°C by a conventional method.

An・ηrsL ηlnh =□ Example 1 In a polymerization vessel equipped with a stirrer, 250% of N,N-dimethylacetamide and 8.5 k5F of lithium chloride and para-
9 was added to phenylenediamine IQ, 8' and dissolved, and then 20.3 g of powdered terephthalic acid chloride was added at once to carry out polymerization. About 3 minutes after the addition, stirring became difficult, so stirring was stopped and the mixture was allowed to stand for 30 minutes, to obtain a polymerized and solidified dope that solidified into a cheese shape.

A portion of 5 kJ of the solidified dope was put into a hammer mill equipped with a 100 mesh (opening 147 μm) wire mesh screen and sealed with nitrogen, stirred and crushed for 30 minutes, and passed through the screen to form the crushed solidified dope. 2 kIi was obtained.

The resulting pulverized product was then put into a household mixer together with water and stirred. The obtained slurry was placed in a cylindrical filter with a 400-mesh (opening 38 μm) wire mesh screen attached to the bottom, separated by F, and the particles on the screen were collected and poured into water for washing. Washed repeatedly.

The obtained washed particles were collected and dried in a hot air dryer at 150°C.

The dry particles of poly-paraphenylene terephthalamide thus obtained had an average particle diameter of 49 μm and an intrinsic viscosity of 7.36 when sieved through a Tyler standard sieve.

Comparative Example 1 This comparative example shows a method for producing particles using a conventionally known method of pulverizing particles together with a coagulant.

Polymerization obtained in Example 1--p.3 to 9,'10! of water into a Henschel mixer with an internal volume of 201 cm,
The mixture was stirred for 30 minutes and pulverized. This Henschel mixer is equipped with a vertical blade at a distance of 5 m from the vessel wall.

After the pulverization operation was completed, the contents were taken out and washed and dried in the same manner as in Example 1 to obtain particles.

The obtained particles were sieved using a Tyler standard sieve, and the average particle diameter was 295 μm, 100 mesh (opening 147 μm).
The sieve content of the particles that passed through m) was 5.7% of the amount of charged particles.

The intrinsic viscosity of the polymer of the obtained particles is 7.74.
Met.

When compared with this comparative example, it is clear that the method of the present invention can efficiently produce fine particles, proving that it is an excellent production method.

Comparative Example 2 In this comparative example, isolated 7'b'? A method for producing oriented aromatic polyamide by mechanical grinding is shown.

The particles having an average particle diameter of 295 μm obtained in Comparative Example 1 were placed in a Wiley-type pulverizer, and pulverized for 1 hour. During crushing,
The temperature inside the aircraft reached approximately 200°C due to frictional heat. As a result of sieving the obtained pulverized product, the average particle size was 124 μm, 150 mesh, and the particles passing through the screen (opening 104 μm) accounted for 37.2% of the particles input during pulverization.

The intrinsic viscosity of these particles was 4.78, and the decrease in intrinsic viscosity was greater than expected.

In this mechanical pulverization method, the intrinsic viscosity is extremely high, probably due to polymer decomposition;
It was also revealed that the efficiency was low. In contrast, in the method of the present invention, almost no decrease in intrinsic viscosity was observed, and it was demonstrated that polymer particles with a high degree of polymerization could be obtained.

Example 2 Using the polymerization machine used in Example 1, 15.5 kl of calcium chloride was added to 200 & N-methyl-2-pyrrolidone.
F, para-phenylenediamine 9 was stirred and dissolved in 8.64 ml, and then powdered terephthalic acid chloride of 9 was added at once to 16.24 ml to carry out polymerization.

As in Example 1, stirring became difficult about 3 minutes after the addition, and about 1 hour after the stirring was stopped, a cheese-like solidified dope was obtained. Clearance between the side wall filled with flow and the paddle is 0
．． It is continuously fed into a two-shaft continuous kneader (2-inch KRC kneader made by Kurimoto Iron Works) certified by the Japanese government, and the remaining water is discharged from a discharge section equipped with a perforated plate with many holes of 0.15 mm diameter. It was discharged so that the time was 10 minutes. At that time, the emissions are 0.1
Although it was obtained as a seemingly continuous string-like substance through a hole of 5 mwφ, it was easily granulated by pouring it into water and then stirring it with a commonly used household mixer.

The slurry thus obtained was washed and dried in the same manner as in Example 1 to obtain fine particles.

The average particle diameter of the obtained particles was 78 μm, and the intrinsic viscosity was 6.
It was 84.

Example 3 Polyno with an intrinsic viscosity (η1nh) of 7.05! Laphenylentele 7 talamide was added to 99% while maintaining the jacket temperature at 800% so that the I remer concentration was 18.7%.
．． Add to 7% concentrated sulfuric acid and dissolve with stirring to prepare a dope. It was confirmed by polarizing microscopy observation under crossed Nicols that this dope exhibits optical anisotropy. The viscosity of the dope at 80°C was 575° poise.

Next, an aqueous ethylene glycol solution at -15° C. was fed into the jacket while stirring to solidify by cooling, thereby obtaining a coarsely crushed solidified dope.

This solidified dope was discharged using the equipment and conditions used in Example 2, except that it was cooled by sending an ethylene glycol aqueous solution at -15°C to the salmon, and after being put into water, it was used for household use. After stirring with a mixer, the same water washing and drying as in Example 1 were performed.

The average particle diameter of the obtained particles was 92 μm, and the intrinsic viscosity was 6.
It was 12.

Procedural amendment (voluntary) October 76, 1985

Claims (1)

[Claims] 1. A solidified solution consisting of a substantially para-oriented aromatic polyamide and a solvent capable of dissolving the para-oriented aromatic polyamide is heated in a non-coagulating atmosphere so that the particle size becomes 200 μm or less. 1. A method for producing para-oriented aromatic polyamide fine particles, which is characterized by crushing the particles, washing and removing the solvent, and then drying. 2. The manufacturing method according to claim 1, wherein 90 mol% or more of the repeating units constituting the para-oriented aromatic polyamide are paraphenylene terephthalamide units. 3. The production method according to claim 1, wherein the solidified product is a polymerization reaction solidified product of para-oriented aromatic polyamide obtained by a low-temperature solution polymerization method. 4. The solvent is one or more amide type solvents selected from N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-acetylpyrrolidine to which lithium chloride or calcium chloride is added. The manufacturing method according to claim 1. 5. The manufacturing method according to claim 1, wherein the solvent is sulfuric acid with a concentration of 95% by weight or more.