JP5592201B2 - Aromatic polyamide particles having improved chemical resistance and method for producing the same - Google Patents

Description

  The present invention relates to an aromatic polyamide particle having improved chemical resistance and a method for producing the same. More specifically, the present invention relates to a method for efficiently producing aromatic polyamide particles that have high chemical resistance and can be suitably used even in an environment where an NMP solvent is used.

  Sliding formed on the surface of a film formed from a composition in which a solid lubricant such as PTFE, a fluorinated polymer represented by PTFE, graphite, molybdenum disulfide, etc. is blended with a binder resin such as an epoxy resin or a polyamide-imide resin Members are known. Especially, the film which consists of polyamideimide resin or a polyimide resin is used suitably for sliding members, such as a motor vehicle, from the point which has the outstanding heat resistance. On the other hand, it is known to add an antiwear agent in order to achieve both the strength of the coating film and the friction / wear characteristics. As an abrasion resistance imparting agent, organic particles are superior in that they are lighter than metals and do not damage the mating material. Among them, polyamide resins, aromatic polyamide resins, etc. that are excellent in heat resistance are used (for example, patents). Literature 1, 2 etc.). Binder resins such as polyamide-imide resins are often used in NMP solvent systems, and when aromatic polyamide resins are used as additives, particles cannot be used because they dissolve or swell to increase the viscosity of the paint. .

JP 2005-120213 A JP 2008-106086 A

  An object of the present invention is to provide aromatic polyamide particles having excellent chemical resistance while maintaining the high heat resistance inherent in aromatic polyamides, and suitable for use in an environment where a solvent, particularly an NMP solvent is used. It is to provide a manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that when aromatic polyamide particles are heat-treated under specific conditions, desired aromatic polyamide particles can be obtained, and the present invention has been achieved. .

That is, according to the present invention, aromatic polyamide particles comprising an aromatic polyamide, wherein the aromatic polyamide is copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, and are determined by wide-angle X-ray diffraction. Also provided is an aromatic polyamide particle having improved chemical resistance, wherein the crystallinity of the particle is 8 to 35%.

Also, aromatic polyamide particles made of an aromatic polyamide, wherein the aromatic polyamide is copolyparaphenylene, 3,4′-oxydiphenylene terephthalamide, a temperature range T (° C.) satisfying the following formula: A process for producing aromatic polyamide particles with improved chemical resistance, characterized by heat treatment in the inside, is provided.
350 ≦ T <Tmq-30
(However, Tmq represents the melting point or pseudo melting point of the aromatic polyamide.)

  Since the aromatic polyamide particles of the present invention have an appropriate degree of crystallinity, they exhibit excellent high chemical resistance and can be suitably used even in an environment where a solvent is used. For this reason, even when added to a coating material containing a solvent (including paints), etc., the aromatic polyamide particles are agglomerated or swollen to increase the viscosity of the coating material and spray it. In such a case, nozzle clogging does not occur, and even when this is applied, there is an effect that application can be performed smoothly.

Hereinafter, embodiments of the present invention will be described in detail.
The aromatic polyamide used in the present invention may be a meta-type aromatic polyamide or a para-type aromatic polyamide, but the para-type aromatic polyamide is particularly preferable in terms of strength, heat resistance, and chemical resistance. preferable. The para-type aromatic polyamide is composed of an aromatic homopolyamide represented by the following formula (1) or an aromatic copolyamide at 80 mol% or more, preferably 90 mol% or more of the repeating units constituting the polyamide. Is.
—NHAr ₁ —NHCO—Ar ₂ —CO— (1)

Here, Ar ₁ and Ar ₂ represent an aromatic group, and among them, those composed of the same or different aromatic groups selected from the following formula (2) are preferable. However, the hydrogen atom of the aromatic group may be substituted with a halogen atom, a lower alkyl group, a phenyl group, or the like.

  Regarding the method for producing such an aromatic polyamide particle molded body and the molded body characteristics, for example, British Patent No. 1501948, US Pat. Nos. 3,733,964, 3,767,756, and 3,869,429, Japan Patents such as JP-A-49-10032, JP-A-47-10863, JP-A-58-144152, JP-A-4-65513 and the like are described in detail. Examples thereof include phenylene terephthalamide, copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, and the like.

  The para-type aromatic polyamide is preferably an isotropic solution that is soluble in an organic solvent. As long as the para-type aromatic polyamide is dissolved, the solution (dope) may be an organic solvent dope after solution polymerization or a separately obtained para-type aromatic polyamide dissolved in an organic solvent. . In particular, those after solution polymerization reaction is preferable.

  As a polymerization solvent for the para-type aromatic polyamide, generally known aprotic organic polar solvents are used. For example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N, N- Dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylpropionamide, N, N-dimethylbutyramide, N, N-dimethylisobutyramide, N-methylcaprolactam, N, N- Dimethylmethoxyacetamide, N-acetylpyrrolidine, N-acetylpiperidine, N-methylpiperidone-2, N, N′-dimethylethyleneurea, N, N′-dimethylpropyleneurea, N, N, N ′, N′-tetramethyl Malonamide, N-acetylpyrrolidone, N, N, N ′, N′-tetramethylurea, dimethyl Sulfoxide, and the like. Specific products include Technora (registered trademark) (manufactured by Teijin Techno Products), Twaron (registered trademark) (manufactured by Teijin Aramid BV), and the like.

  In the present invention, it is important that the crystallinity obtained by wide-angle X-ray diffraction is 8 to 35%, and the crystallinity is preferably 8 to 30%, more preferably 8 to 20%. By making the aromatic polyamide particles having such crystallinity, the chemical resistance is remarkably improved, and even if the aromatic polyamide particles are contained as an additive in a binder resin containing an NMP solvent, the particles Does not dissolve or swell and the viscosity of the coating material (including paint) increases. If the crystallinity is low, sufficient chemical resistance cannot be obtained. If an attempt to increase the crystallinity is higher than the above, the decomposition of the polymer proceeds by a heat treatment described later, and the chemical resistance is lowered.

  The average particle diameter of the aromatic polyamide particles used in the present invention is usually 5 to 100 μm. Such aromatic polyamide particles may be produced by the methods described in JP-A-2005-120213 and JP-A-2008-106086. In other words, the aromatic polyamide may be formed into fibers by solution spinning and then pulverized and powdered. The shape may be spherical, pulp-like, flake-like, needle-like, fibrous. Etc. may be mixed.

The aromatic polyamide particles described above can be produced by high-temperature heat treatment as described below. The heat treatment temperature at this time needs to be within a temperature range T (° C.) satisfying the following formula with respect to the melting point or pseudo melting point Tmq of the aromatic polyamide particles measured by the measurement method described later.
350 ≦ T <Tm _q −30
(However, Tm _q represents the melting point or pseudo melting point of the aromatic polyamide.)

  The aromatic polyamide particles thus obtained preferably have a crystallinity obtained by wide-angle X-ray diffraction of 4% or less, more preferably 2-3%. When the degree of crystallinity exceeds 4%, it is difficult to pulverize and isolate the aromatic polyamide, and then pulverize it, and there is a possibility that uniform particles having a particle diameter of 5 to 100 μm cannot be obtained. .

  When the heat treatment temperature T (° C.) is less than 350 ° C., the effect of improving the chemical resistance by the heat treatment cannot be obtained. On the other hand, when the heat treatment temperature T (° C.) is Tmq−30 ° C. or higher, the fiber itself is greatly deteriorated even in a short time treatment, and uniform treatment becomes difficult. A preferable heat treatment temperature is 350 ° C. or higher and lower than 440 ° C., more preferably 350 ° C. or higher and lower than 400 ° C.

  The aromatic polyamide particles obtained in this way are made into a composition containing a resin and a solvent, and this is used as a coating material (including paint) for machine parts, electrical and electronic parts, buildings, precision machine parts, etc. It can be applied or sprayed. At this time, the aromatic polyamide particles of the present invention have high chemical resistance, and even if a solvent, particularly NMP (N-methyl-2-pyrrolidone) is contained, the aromatic polyamide particles aggregate or swell. Thus, the viscosity of the coating material is not increased, nozzle clogging does not occur when spraying the coating material, and smooth application can be performed even when this is applied.

  As said solvent, the mixed solvent etc. which added aromatic solvents, such as xylene, ketone solvents, such as methyl ethyl ketone, and ester solvents, such as ethyl acetate, to NMP can be used. Examples of the resin include polyamideimide, polyamide, and polyimide.

  As described above, after coating or spraying, a composition containing the aromatic polyamide particles of the present invention and a resin is formed on the surface of the mechanical component or the like. In this case, in the composition, The aromatic polyamide particles are uniformly dispersed without agglomeration to coat the surface. For this reason, it is possible to impart excellent wear resistance to mechanical parts and the like.

Further, the composition may contain a solid lubricant, which can impart high slidability to mechanical parts and the like in addition to wear resistance.
The above-mentioned solid lubricant can be used by selecting an appropriate one from known ones, but by dispersing the solid lubricant in the resin and forming a lubricating film on the surface of the sliding member, a friction coefficient is obtained. Can be reduced, and the conformability can be ensured. In addition, sulfides such as molybdenum disulfide (MoS ₂ ) and tungsten disulfide (WS ₂ ), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene. It is preferable to select from copolymers, tetrafluoroethylene-ethylene copolymers, fluorine compounds such as polyvinylidene fluoride and polychlorotrifluoroethylene, graphite (graphite), graphite fluoride and the like.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the measuring method of the physical property used in the Example is as follows.
(1) Crystallinity The crystallinity was determined from the diffraction intensity curve of wide-angle X-ray diffraction by the following method. According to the crystallinity calculation method by peak separation described in Rigaku Electric Co., Ltd. “X-ray Handbook” (issued February 21, 2000, 3rd edition), the peak of the amorphous component and the crystalline component were separated from the total scattering curve, It was determined from the ratio of the scattering intensity of the crystal component in the scattering intensity.
(2) NMP solution viscosity Particles were stirred in an NMP solution at 80 ° C for 30 minutes, and the viscosity was determined with a vibration viscometer.
(3) Presence or absence of generation of aggregates To confirm whether swelling or aggregation occurred when the particles were immersed in an NMP solvent, the particles were immersed in an NMP solution for 300 hours, and then passed through a 150 mesh wire mesh. It was visually judged whether there was any residue. The case where there was no residue was indicated as ◯, and the case where there was a residue was indicated as x.
(4) Spray property With respect to 100 parts by weight of particles, polyamideimide (manufactured by Hitachi Chemical Co., Ltd., trade name HPC-5000) 600 parts by weight, polytetrafluoroethylene (manufactured by Daikin Industries, Ltd., trade name: Lubron L2) 180 weight A coating material consisting of parts was prepared and sprayed onto a metal surface from a nozzle having a hole diameter of 1.0 mm for 20 minutes.
(5) Weight reduction rate The weight reduction rate by heat-treating the particles was measured from the weight before and after the heat treatment.

[Example 1]
Para-type aromatic polyamide particles (Technola manufactured by Teijin Techno Products) having a crystallinity of 2.14% and a particle size of 5 μm were used.
(Measurement of melting point and pseudo melting point Tmq)
It is not clear whether the polymer has a true melting point Tm, that is, since this polymer is a copolymerized polymer, the melting point range is wide and an accurate Tm cannot be determined.
However, the melting start temperature of this polymer can be observed by a flow tester, DTA, or DSC. Here, the melting start temperature (temperature at the intersection of the base line and the endothermic peak gradient) detected at a rate of temperature increase of 10 ° C./min of DTA in a nitrogen atmosphere is defined as pseudo melting point Tmq. It is defined similarly in DSC.
In the flow tester, when Tmq is reached, the polymer flows out from a nozzle having a diameter of 1 mm or more and a flow path of 10 mm or less under an extrusion pressure of 100 kg / cm ² or more. However, at the same time, crosslinking proceeds and the outflow is interrupted. The determination of Tmq is ensured by the combined use of the above DTA, DSC, and flow tester.
The pseudo melting point Tmq thus determined was 470 ° C.
Not limited to the above, when the para-type aromatic polyamide particles have a clear melting point due to a crystallization peak by DTA or DSC, the temperature is used.
(Chemical resistance improvement treatment)
The particles were subjected to a dry heat treatment in an oven at 350 ° C. for 30 minutes. Table 1 shows the physical properties of the obtained particles.

[Example 2]
In Example 1, it implemented like Example 1 except having changed the temperature at the time of a chemical-resistance improvement process from 350 degreeC to 400 degreeC. Table 1 shows the physical properties of the obtained particles.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the chemical resistance improvement treatment was not performed in Example 1, that is, the obtained particles were used for measurement as they were. Table 1 shows the physical properties of the obtained particles.

[Comparative Example 2]
In Example 1, it implemented like Example 1 except having changed the temperature at the time of a chemical-resistance improvement process from 350 degreeC to 300 degreeC. Table 1 shows the physical properties of the obtained particles.

[Comparative Example 3]
In Example 1, it implemented like Example 1 except having changed the temperature at the time of a chemical-resistance improvement process from 350 degreeC to 450 degreeC. Table 1 shows the physical properties of the obtained particles.

  The aromatic polyamide particles of the present invention have good heat resistance, exhibit excellent chemical resistance, and can be used without problems even in an environment where a solvent is used. Etc.) and the like. The coating material containing the aromatic polyamide particles of the present invention does not cause nozzle clogging when sprayed, and can be applied smoothly even when applied.

Claims (8)

An aromatic polyamide particle comprising an aromatic polyamide, wherein the aromatic polyamide is copolyparaphenylene, 3,4'-oxydiphenylene terephthalamide, and the crystallinity of the particle determined by wide-angle X-ray diffraction is Aromatic polyamide particles having improved chemical resistance, characterized by being 8 to 35%. Aromatic polyamide particles composed of an aromatic polyamide , wherein the aromatic polyamide is copolyparaphenylene, 3,4'-oxydiphenylene terephthalamide, within a temperature range T (° C.) satisfying the following formula: A method for producing aromatic polyamide particles having improved chemical resistance, characterized by heat treatment.
350 ≦ T <Tmq-30
(However, Tmq represents the melting point or pseudo melting point of the aromatic polyamide.) The method for producing aromatic polyamide particles having improved chemical resistance according to claim 2 , wherein the degree of crystallinity of the aromatic polyamide particles before heat treatment determined by wide-angle X-ray diffraction is 4% or less. A composition comprising the aromatic polyamide particles according to claim 1 and a resin. A composition comprising the aromatic polyamide particles according to claim 1 , a resin, and a solid lubricant. A composition comprising the aromatic polyamide particles according to claim 1 , a resin, and a solvent. The composition according to any one of claims 4 to 6 , wherein the resin is a polyamide-imide resin. The coating material which consists of a composition in any one of Claims 4-7 .