JPH0299523A - Production of para-orientated aromatic polyamide particle - Google Patents

Abstract

PURPOSE:To obtain the title particles useful as reinforcing filler for rubber, etc., having excellent adhesiveness by grinding a solidified substance of a solution of para-orientated aromatic polyamide in a noncoagulable atmosphere, removing a solvent by washing to give undried particles, bringing a solution of a specific copolymer into contact with the undried particles and heat treating. CONSTITUTION:In a polymerizer, lithium chloride and para-phenylenediamine are dissolved in a solvent such as N,N-dimethylacetamide, incorporated with terephthalic acid chloride and polymerization is carried out to give a solidified substance of a solution comprising a para-orientated aromatic polyamide and a solvent capable of dissolving the polyamide. Then the solidified material is ground in a noncoagulable atmosphere and the solvent is removed by washing to give undried particles, which which a solution or dispersion of a copolymer having a constituent units shown by formula I (R is H or 1-5C alkyl; m is >=1 integer) and formula II (n is >=1 integer) is brought into contact and then the particles are dried and/or heat-treated to give the aimed polymer particles.

Description

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

[Conventional technology]

In general, polymer particles are used to reinforce plastics, rubber, etc., as well as inorganic particles such as talc, alumina, and glass powder.
Alternatively, it is already known that it is used for the purpose of improving properties such as dimensional stability, heat resistance, and electrical properties.

In general, the adhesion of such particles to matrix resins such as plastics and rubber has a large effect on the physical properties of the product, as well as the particle size. At the same time, it is necessary to improve adhesiveness. 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 halides by a so-called low-temperature solution polymerization method (see, for example, Japanese Patent Publication No. 14399/1983).

It is already known that particles can be obtained from such aromatic polyamides. For example, in the above-mentioned Japanese Patent Publication No. 3514399, a polymer solution obtained by low-temperature solution polymerization is
It is disclosed that it can be obtained by pouring into a coagulant such as water and stirring.

However, when such a method is applied to para-oriented aromatic polyamide, para-oriented aromatic polyamide has a fast solidification rate, high crystallinity, and rigidity, so although it can be obtained as granules, it can be used as a fine material for the purpose described above. It cannot be obtained as particles of particle size.

In addition, reducing the concentration of para-oriented aromatic polyamide in the solution for the purpose of microfabrication has been shown to have a microfabrication effect, but it is not sufficient, and a large amount of solvent must be used. Due to its drawbacks, this method cannot be adopted industrially.

On the other hand, it is a well-known fact that mechanical crushing means such as a ball 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, since wood is 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.

In contrast to these conventional particle manufacturing methods, what is the difference between para-oriented aromatic polyamide? The solidified product of 8 liquids is pulverized in a non-coagulating atmosphere,
After that, a method of washing and removing the solvent is described, for example, in JP-A No. 6.
This method was proposed in Japanese Patent No. 2-32123, and it was possible to efficiently obtain sufficiently fine particles. however,
It has been found that such particles have a new problem in that they have insufficient adhesion to matrix resins and the like.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned drawbacks, namely, by improving the adhesion to the matrix resin, and by making fine para-oriented aromatic polyamide particles with excellent adhesion to the matrix resin, which has been extremely difficult to achieve with conventional techniques. It was done in order to obtain.

For the purpose of improving adhesion, the present inventor conducted intensive studies on particles obtained by pulverizing solidified solutions of para-oriented aromatic polyamides, and found that undried particles obtained by removing the solvent from the particles by washing Particles are in a swollen state and only become fine when dried, and it was discovered that various compounds can be impregnated in the form of solutions or dispersions in the swollen state, and after further study, the present invention was completed. It is.

[Means for solving problems]

That is, the gist of the present invention is as follows.

A solidified solution consisting essentially of a para-oriented aromatic polyamide and a solvent capable of dissolving the para-oriented aromatic polyamide is pulverized in a non-coagulating atmosphere, and then the undried particles from which the solvent has been washed away are mixed with A method for producing para-oriented aromatic polyamide particles characterized by contacting a solution or dispersion of a copolymer having constitutional units represented by formulas (1) and [2] and then drying and/or heat-treating the particles. -CH2-C-+-(2] C0N11□ However, in formula (13, (2), R is hydrogen or has 5 carbon atoms
The following alkyl groups, m and n represent integers of 1 or more.

In the present invention, in the "para-oriented aromatic polyamide" position 2
It refers to a polyamide formed by linking aromatic groups in which a valent bond is located, and specifically, the aromatic group is a polyamide in which a divalent bond is located in 1,4-phenylene (paraphenylene) or 4,4'- coaxially opposite from the aromatic ring, such as biphenylene, 1,4-naphthylene, or 1,5-naphthylene, 2.
It refers to aromatic groups which are arranged in opposite directions along parallel axes, such as 6-naphthylene. These aromatic groups may contain one or more lower alkyl groups such as methyl group and ethyl group, halogen groups such as methoxy group, ethoxy group, and chloro group.

Typical of these para-oriented aromatic polyamides are poly-parabenzamide, poly-paraphenylene terephthalamide, poly-4,4'diaminobenzanilide terephthalamide, poly-N,N'-p-phenylene bis(p -benzamide) terephthalamide, poly-paraphenylene-2,6-naphthalamide, copoly-paraphenylene/4.4'-(3,3'-dimethylbiphenylene)-terephthalamide, poly-2-chloro-paraphenylene terephthalamide Examples include amides. Among these, poly-paraphenylene terephthalamide or 90 mol% or more of the repeating units constituting the polymer are
A copolymer having paraphenylene terephthalamide units is preferred from the viewpoint of dimensional stability, heat resistance, and chemical resistance.

The solvent capable of dissolving the para-oriented aromatic polyamide as described above may be any solvent as long as it substantially dissolves the polymer, and specifically, N, N-dimethylacel-amide, N-methyl-2 - One or more so-called amide type solvents such as pyrrolidone, N-acetylpyrrolidine, hexamethylphosphoramide, etc., and a solvent with lithium chloride, calcium chloride, etc. added thereto, or a concentration of 95%
Concentrated sulfuric acid, hydrofluoric acid, methanesulfonic acid, etc. in a concentration of % by weight or more can be mentioned.

In the present 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.

A solidified dope solution can be easily achieved by first 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 the 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 a higher concentration of -C has the advantage that a solidified product can be obtained even at a higher temperature, and that less solvent is used when producing particles. It is preferable because there is. Usually, it is carried out in the range of 5 to 40%, but it is not limited to this.

Generally, the low-temperature solution polymerization method disclosed in Japanese Patent Publication No. 35-14399 is used to prepare para-oriented aromatic polyamides.
All of the divalent aromatic groups that make up the polymer chain,
When applied to para-oriented aromatic polyamides in which 95 mol% or more of para-phenylene groups are polymerized at industrially important high concentrations, the polymerization reaction product is in the form of a gel or cheese in most cases. obtained as a solidified product (hereinafter, such a gel-like or cheese-like polymerization reaction solidified product will be referred to as
(simply referred to as "polymerized 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 particles of para-oriented aromatic polyamide by the method of the present invention, it is essential to grind 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 and the polymer will coagulate and precipitate, forming strong coarse particles or lumps. 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 dope while maintaining its solvated state, the solidified dope can be easily made into fine particles.

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 coagulation and precipitation, finer para-oriented aromatic polyamide particles are obtained.

The term "non-coagulant atmosphere" as used in the present invention refers to an atmosphere in which desorption, dilution, etc. of the solvent from the solidified dope does not substantially occur. Specifically, it refers to gases such as nitrogen, oxygen, helium, or air with a relative humidity of 60% or less, or in a dehydrated liquid medium that is insoluble in the solvent that forms the solidified dope.Liquid Specific examples of the 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.

Specifically, methods for crushing the solidified dope or polymerized solidified dope include methods using commonly used crushing equipment or machines such as a hammer mill, ball mill, Shaw crusher, Henschel mixer, etc., or twin-screw kneading. A method of extruding through a specified sieve-like lattice using a niegoo or the like is also useful.

The degree of pulverization varies somewhat depending on the purpose of use of the obtained para-oriented aromatic polyamide fine particles, but in order to satisfy the application to recent advanced composite material technology, the final particle size should preferably be 500 μm or less. is preferably 250 μm or less.

The temperature during grinding is Ig! The present invention is not particularly limited as long as the solidified dope is maintained so as not to become a solution by heat rubbing or the like. It is also possible to heat as necessary, and cooling is also of course allowed. Normally,
Depending on the high temperature, there is a possibility of decomposition and modification of the solvent or coloring of the polymer, so the temperature is preferably 100°C or less.

The particles from the solidified dope crushed 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 washing is performed while continuously supplying a detergent. The degree of such washing may be appropriately determined depending on the required degree of purification of the polymer.

The cleaning agent used in the present invention is not particularly limited, and includes, for example, alcohols such as methyl alcohol and ethyl alcohol, halogenated hydrocarbons, ethers,
Water or any other material may be used, but water is usually used for economical reasons.

In the method of the present invention, the particles thus washed are
After the liquid is removed as necessary, it is necessary to contact the solution or dispersion of the copolymer having the structural units represented by formulas [1] and [2]. Formula used in the present invention [
Copolymers having structural units 1] and [2] can be easily obtained by anionically polymerizing an acrylamide derivative represented by CH,=C-CONH2 as a monomer under conditions where so-called hydrogen transfer polymerization occurs. can.

The molecule 1 (MW) of such a copolymer is not particularly limited in the present invention, but is usually 1000 to 50
oooo is used. Further, the ratio of the β-alanine unit represented by formula [1] and the acrylamide unit represented by formula [2] may be 10 to 90% by weight, and usually the acrylamide unit represented by formula [2] is 10 to 90% by weight. A copolymer containing 40 to 60% by weight of units is used. Such copolymers are usually water-soluble, and as the proportion of β-alanine units represented by 2[1] increases, the solubility in water decreases.

In the present invention, an aqueous solution or dispersion of the above-mentioned copolymer is used. Such an aqueous solution or dispersion can be obtained by a conventional method, and the copolymer may be poured into water while stirring. In some cases, an aqueous solution may be added to a general-purpose solvent such as acetone, alcohol, or ether, stirred, and a dispersion obtained by adding a surfactant or the like as necessary. can.

The concentration of such an aqueous solution or dispersion may be appropriately selected depending on the processing method, processing speed, liquid (water) retention rate of undried particles, desired adhesion amount, etc., but is generally 0.1 to 20% by weight. or more.

The method of bringing the undried particles into contact with the solution or dispersion of the epoxy compound is not particularly specified in the present invention, but generally, the undried particles are brought into contact with the aqueous solution or dispersion of the above-mentioned copolymer. A method in which the slurry is made into a slurry and then separated by filtration, a method in which the aqueous solution or dispersion is showered or sprinkled on the undried particles, or a method in which the above-mentioned copolymer is directly poured into the slurry of the washed particles and stirred. may also be adopted.

The aqueous solution or dispersion of the above-mentioned copolymer may contain, for example, a dispersant, an antistatic agent, a rubber latex, an additive, etc., as long as the solution or dispersion does not adversely affect the effects of the present invention, such as reacting sensitively with the above-mentioned copolymer. It may also contain various processing agents such as sticky agents, light stabilizers, and antioxidants.

In the present invention, the amount of the above-mentioned copolymer attached to the particles is not particularly limited, but is usually 0.05 to 10
It is preferable to do this within a range of % by weight. In other words, it is essential that the above-mentioned copolymer exists in the surface layer of the particles in order to improve adhesion, but even if the amount is extremely small on the dry particles, it will have an effective effect. , even if the adhesion rate is higher than this, the effects of the present invention will not be particularly impaired. The amount of adhesion can be easily adjusted by adjusting the concentration of the aqueous solution or dispersion to be brought into contact and the amount of retained liquid.

In the method of the invention, the undried particles brought into contact with the aqueous solution or dispersion as described above are then dried.

Regarding drying, there are no special restrictions in the method of the present invention, and conventional means can be used. For example, box-type dryers or fluidized dryers that dry undried particles by blowing hot air batchwise or continuously, infrared lamps, far-infrared heaters,
Any method such as drying using a high frequency dielectric heating device or the like may be used.

The drying temperature may also be within a normally employed range. In addition, the above-mentioned copolymer used in the present invention has 170
It is known that intermolecular crosslinking occurs at a temperature of 170°C or higher, and if necessary, if intermolecular crosslinking is not allowed to occur, drying can be carried out at a temperature of 170°C or lower.
The temperature range is 160°C.

On the other hand, the present invention is not limited to intermolecular crosslinking of the above-mentioned adhered copolymer, and in this case, the purpose can be easily achieved by drying at a temperature of 170'C or higher. .

In addition, in drying, excessively high temperature is undesirable because it causes deterioration and severe coloring of the para-oriented aromatic polyamide and the above-mentioned copolymer that constitute the particles, and the drying temperature is usually about 300°.
Often selected as C or below.

Following drying, additional heat treatments may also be useful and may be performed. For the reasons mentioned above, the temperature in this case is
The temperature is in the range of about 140 to 300°C, and the treatment time is usually preferably carried out in the range of 10 seconds to 60 minutes, but is not particularly limited thereto.

The para-oriented aromatic polyamide particles thus obtained by the method of the present invention have a fine particle size and contain the above-mentioned copolymer in the surface layer and inside. It has a high adhesive strength with the resin and exhibits an extremely high reinforcing effect, and this effect cannot be obtained by simply applying the above-mentioned copolymer to dry para-oriented aromatic polyamide particles, but the particles produced by the method of the present invention It is distinguished from Although the exact reason for this difference in effect is unknown, in the method of the present invention, the above-mentioned copolymer is contacted in an undried swollen state and then densified, so the copolymer is inside the particles. This is presumed to be due to the captured anchor effect.

〔Example〕

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

In the examples, % represents weight % unless otherwise specified.

The particle size of the solidified dope after pulverization and the particle size of the finally obtained para-oriented aromatic polyamide particles are determined by Tyler (
(Tyler) represents the value measured with a standard sieve.

Measuring method of intrinsic viscosity〉 Intrinsic viscosity (ηtnh) of para-oriented aromatic polyamide is determined by dissolving a solution of the polymer in 98.5% by weight concentrated sulfuric acid at a concentration (C) = 0.2 g/a. is 10g/for formic acid
Measure the solution dissolved in step a at 30°C using a conventional method.

2n·ηreal ηinh=Characteristics of Composite Material> The properties of a composite material using para-oriented aromatic polyamide particles obtained by the method of the present invention are determined by the following measurement method.

Nylon 66 resin (manufactured by Asahi Kasei Corporation, Leona (300s)
) was compounded so that the particle content was 30% by weight, a test piece was prepared by injection molding, and the following physical properties were measured.

Bending strength and flexural modulus: A test piece was prepared according to ASTM D790, and the measurement conditions were also tested according to the same standard.

Izot impact: Measurement was performed using a notched test piece according to ASTM D256.

Example 1 8.5 kg of lithium chloride and 10.8 kg of para-phenylenediamine were added and dissolved in 250 kg of N,N-dimethylacetamide in a polymerization vessel equipped with a stirrer, and then 20.5 kg of powdered terephthalic acid chloride was added. Polymerization was carried out by adding 3 kg at once. 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 kg of this solidified dope was placed in a hammer mill fitted with a wire mesh screen of 100 meshes (openings of 147 μm) and sealed with nitrogen, and pulverized with stirring for 30 minutes.
3.2 kg of crushed solidified dope was obtained through a screen.

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

Next, a water slurry is prepared so that the concentration of cleaning particles is 10%, and β- expressed by the formula [1] is added to this slurry.
A random copolymer (intrinsic viscosity = 0.59) containing 40% by weight of alanine units and 60% by weight of acrylamide units represented by formula [2] was added, and the concentration (weight%) of the random copolymer was 0. .1%, 0.2%, 0.5%, 1
．． Each slurry liquid was obtained so that the concentration was 0%. Next, each slurry liquid was stirred at room temperature for 30 minutes, and then dehydrated using a center type dehydrator to a moisture content of 350%.
It was dried for 165 hours in a hot air dryer at 0°C.

When the obtained dry particles were sieved using a lighter standard sieve, they were found to be fine particles with an average particle size of 43 μm. Table 1 shows the results of characterizing the composite material using these particles. It was proved that the composite material using the particles of the present invention has excellent bending properties and impact resistance properties as a result of the improved adhesion of the particles.

Comparative Example 1 Particles obtained in the same manner as in Example 1 except that the random copolymer in Example 1 was not added (average particle size 4)
Characteristics of the composite material were evaluated using 2μm). The physical properties of the obtained composite material are as listed in Table 1, and all physical property values were inferior to the composite material using the particles of the present invention.

Examples 2 to 4 Using the polymerization machine used in Example 1, 15.5 kg of calcium chloride was added to 200 kg of N-methyl-2-pyrrolidone.
Stir and dissolve 8.64 kg of para-phenylenediamine,
Next, 16.24 kg of powdered terephthalic acid chloride was added all at once to carry out polymerization.

As in Example 1, stirring became difficult approximately 3 minutes after addition, and a cheese-like solidified dope was obtained approximately 1 hour after stirring was stopped. This solidified dope is roughly crushed and discharged, and the crushed material is then disposed of with a clearance of 0 between the plate wall filled with nitrogen flow and the paddle.
．． Continuously put it into a 5 mm two-axis continuous type knee goo (2 inch KRC knee goo manufactured by Kurimoto Iron Works), and 0.15 an
The solution was discharged from a discharge section equipped with a perforated plate having a large number of holes of φ so that the residence time was 10 minutes. At that time, the discharged material was obtained as a seemingly continuous string-like material from the 0.15anφ hole, but it was easily turned into particles by putting it into water and stirring it with a commonly used household mixer. did.

The thus obtained slurry was washed in the same manner as in Example 1, and then dehydrated using a Centor dehydrator to obtain undried particles with a moisture content of 320%.

On the other hand, a 1% by weight aqueous solution of the random copolymer shown in Table 2 was prepared, and the undried particles were added to this aqueous solution.
After stirring for 0 minutes, remove the liquid using a centor dehydrator and reduce the moisture content to 350.
%) and then dried at a temperature of 180"C as in Example 1.

The average particle diameter of the obtained dry particles was 78 μm, and the amount of random copolymer attached was about 3.5% by weight.

The physical properties of the composite materials using these particles are shown in Table 2, and all exhibited excellent properties.

Comparative Example 2 Dry particles were obtained by the same treatment as in Example 2 except that no random copolymer was added. The physical properties of the composite material using these particles are listed in Table 2.

Below is a blank space Example 5 Poly-paraphenylene terephthalamide having an intrinsic viscosity (η1nh) of 7.05 was used at a polymer concentration of 18. A dope was prepared by adding to 99.7% by weight concentrated sulfuric acid and dissolving with stirring so that the concentration was 7% by weight while maintaining the jacket temperature at 80°C. It was confirmed by polarizing microscopy observation under crossed Nicols that this dope exhibits optical anisotropy. 8 again
The viscosity of the dope at 0°C was 5750 poise.

Next, an aqueous ethylene glycol solution at -15° C. was fed into the jacket while stirring, and the mixture was cooled and solidified to obtain a coarsely crushed solidified dope.

Except that this solidified dope was cooled by feeding an ethylene glycol aqueous solution at -15°C into the jacket.
The entire material was discharged using the equipment and conditions used in Example 2, poured into water, and stirred with a household mixer. Dry particles having an amount of 1.8% by weight and an average particle size of 92 μm were obtained.

The bending strength of the composite material using these particles is x670kg/c
i, the flexural modulus was 3580 kg/crA, and the Izod impact was 4.4 kg-cm/cm.

〔Effect of the invention〕

The para-oriented aromatic polyamide particles obtained by the production method of the present invention are fine particles and have extremely excellent adhesive properties.As a result, they can be used as reinforcing materials for composite materials to improve the mechanical properties of the materials, especially their impact properties and bending properties. It is possible to dramatically increase the Furthermore, it is not only possible to modify the particles themselves by taking advantage of their heat resistance, chemical resistance, and flame retardancy, but also to use them extremely effectively as compression molding materials.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] (1) Undried particles obtained by pulverizing a solidified solution consisting essentially of a para-oriented aromatic polyamide and a solvent capable of dissolving the para-oriented aromatic polyamide in a non-coagulating atmosphere, and then washing and removing the solvent. The production of para-oriented aromatic polyamide particles, which comprises contacting with a solution or dispersion of a copolymer having structural units represented by the following formulas [1] and [2], followed by drying and/or heat treatment. Method ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [1] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [2] However, in formulas [1] and [2], R is hydrogen or an alkyl group with 5 or less carbon atoms. , m, and n represent integers of 1 or more.