JP2005126833A - Carbon fiber coated with wholly aromatic condensation polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon fiber having an improved affinity for a resin and a solvent and to provide a method for producing the carbon fiber. <P>SOLUTION: The carbon fiber is coated with a wholly aromatic condensation polymer in an amount of 0.01-100 pts. wt. based on 100 pts. wt. of the carbon fiber. The method for producing the carbon fiber is provided. The wholly aromatic condensation polymer is preferably a wholly aromatic azole satisfying formula (A) or formula (B) [wherein, X<SP>1</SP>and X<SP>2</SP>are each independently selected from the group consisting of O, S and NH; Ar<SP>1</SP>denotes a 6-20C tetravalent aromatic group; and Ar<SP>2</SP>denotes a 6-20C bivalent aromatic group]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carbon fiber whose surface is coated with a wholly aromatic condensation polymer and a method for producing the same.

As a report example of coating the surface of carbon fiber with a polymer, there is a report example of improving the surface wettability by coating the surface of ultrafine carbon fibrils with a polyolefin such as polystyrene, polyethylene, polyacrylic acid or the like. (Patent Document 1)
In addition, there is a report example in which a carbodiimide reagent is attached to the carbon fiber surface to improve the adhesion at the interface with a thermoplastic resin such as polyamide or polycarbonate (Patent Document 2).

  In addition, there is a report example in which the surface of a potassium titanate whisker is coated with an organopolysiloxane to improve the stability with the polycarbonate resin interface (Patent Document 3).

  In addition, there is a report that polybenzoxazole is polymerized in the presence of single-walled carbon nanotubes to improve mechanical properties (Non-Patent Document 1), but there is no report on the surface modification of the carbon fiber itself.

In addition, it is known as a known technique that the surface of the glass fiber is surface-treated with a silane coupling agent to improve the adhesion with the polymer as a matrix.
Japanese Patent Laid-Open No. 3-287821, pages 3-4 JP-A-5-106163, pages 3-4 JP-A-6-320992, pages 5-10 Macromolecules, 35, 9039-9043 (2002).

  When producing a composition of carbon fiber and resin, the carbon fiber has poor adhesion and affinity with the resin and solvent, and it has been difficult to achieve improvement in the mechanical strength of the composition. The main problem of the present invention is to improve the affinity with resins and solvents.

  This invention provides the carbon fiber which improved the affinity with resin and a solvent by previously coat | covering the surface of carbon fiber with resin highly compatible with resin which has a matrix. Moreover, this invention provides the manufacturing method of the carbon fiber which coat | covered the surface.

  According to the present invention, it is possible to provide a carbon fiber having improved affinity with a resin and a solvent, and it is possible to provide a resin composition in which carbon fibers, more preferably ultrafine carbon fibers, are highly dispersed.

Hereinafter, the specific contents of the present invention will be described in detail.
(About carbon fiber)
The carbon fiber used in the present invention, more preferably the ultrafine carbon fiber (N), specifically has a diameter of 300 nm or less, preferably 0.3 to 250 nm, more preferably 0.4 to 100 nm. . Those having a diameter of 0.3 nm or less are substantially difficult to produce, and those having a diameter of 300 nm or more have little effect of improving dispersion in a solvent.

  Moreover, although there is no upper limit as a preferable value of the aspect ratio, it is preferable that it is 100,000 or less in terms of the current product, the lower limit is 5.0 or more, 10.0 or more, more preferably 50.0 or more.

  As the shape of the ultrafine carbon fiber, a graphene sheet is wound in a cylindrical shape or a conical shape, and this cylinder may be a single layer or a plurality of layers. In addition, graphene sheets stacked in a cup shape may be used. That is, in the present invention, single-walled carbon nanotubes, multi-walled carbon nanotubes, cup-stacked carbon nanotubes, and carbon nanohorns are preferable.

  Examples of methods for producing these ultrafine carbon fibers include conventionally known gas phase flow methods, catalyst-supported gas phase flow methods, laser ablation methods, high pressure carbon monoxide methods, arc discharge methods, and the like. It is not done.

(Pretreatment of carbon fiber)
Further, when the carbon fiber is coated with the wholly aromatic condensation polymer, it is preferable that the carbon fiber is previously subjected to physical treatment and / or chemical treatment.

  As a preferable example of the chemical treatment, it is preferable to use a mixed solution of nitric acid and sulfuric acid, a mixed solution of sulfuric acid and hydrogen peroxide, and it is more preferable to perform the treatment in the presence of ultrasonic waves.

  Preferable examples of physical treatment include ball mill, bead mill, ultrasonic treatment, strong shearing treatment and the like.

(All aromatic condensation polymers)
The wholly aromatic condensation polymer in the present invention is a linear molecule having a rigid last name in which the structural unit of the molecular chain mainly consists of an aromatic ring. For example, wholly aromatic polyamide, wholly aromatic polyimide, wholly aromatic polyester , Polybenzoxazole, polybenzimidazole, polybenzothiazole, polypyridobisimidazole, and the like. Among these, wholly aromatic azoles such as polybenzoxazole, polybenzimidazole, polybenzothiazole, and polypyridobisimidazole are preferable.

(All aromatic condensation polymers)
As the wholly aromatic condensation polymer, the following formulas (A) and (B)

(A)
(B)
[In the above formulas (A) and (B), X ¹ and X ² are each independently selected from the group consisting of O, S and NH, and Ar ¹ represents a tetravalent aromatic group having 6 to 20 carbon atoms. Ar ² represents a divalent aromatic group having 6 to 20 carbon atoms. ]
It is preferably a wholly aromatic azole composed of each of the structural units.

  In the wholly aromatic condensation polymer, (A) and (B) may be used alone or in combination, and the molar ratio of (A) :( B) is appropriately set at an arbitrary ratio of 0: 100 to 100: 0. You can choose.

Ar ¹ in the above formulas (A) and (B) each independently represents a tetravalent aromatic group having 6 to 20 carbon atoms.

[Y is O, S, SO, SO2, NH, selected from any of C _{(CH 3) 2.} ]
However, it is not limited to this. 1 or more of hydrogen atoms of these aromatic groups are each independently halogen groups such as fluorine, chlorine, bromine; alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, hexyl group; A cycloalkyl group having 5 to 10 carbon atoms such as a cyclopentyl group and a cyclohexyl group; an aromatic group having 6 to 10 carbon atoms such as a phenyl group may be substituted.

Ar ² in the above formulas (A) and (B) each independently represents a divalent aromatic group having 6 to 20 carbon atoms, and specific examples thereof include a metaphenylene group, a paraphenylene group, an orthophenylene group, 2,6-naphthylene group, 2,7-naphthylene group, 4,4'-isopropylidenediphenylene group, 4,4'-biphenylene group, 4,4'-diphenylene sulfide group, 4,4'-diphenylene A sulfone group, 4,4′-diphenylene ketone group, 4,4′-diphenylene ether group, 3,4′-diphenylene ether group, metaxylylene group, paraxylylene group, orthoxylylene group and the like can be mentioned. 1 or more of hydrogen atoms of these aromatic groups are each independently halogen groups such as fluorine, chlorine, bromine; alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, hexyl group; A cycloalkyl group having 5 to 10 carbon atoms such as a cyclopentyl group and a cyclohexyl group; an aromatic group having 6 to 10 carbon atoms such as a phenyl group may be substituted. In addition, the structural unit of the above formula (A) and / or (B) may be a copolymer composed of two or more aromatic groups.

Of these, a paraphenylene group and a 2,6-naphthylene group are preferable.
As a preferred wholly aromatic condensation polymer, specifically, polybenzobisoxazole, that is, a wholly aromatic azole represented by (A) is used.

Or polybenzobisthiazole,

Can be preferably exemplified.

  These wholly aromatic condensation polymers can be produced by a conventionally known method such as a solution polymerization method or a melt polymerization method. As the degree of polymerization of the polymer, the inherent viscosity ηinh measured at 30 ° C. in a solution of 0.5 g / 100 ml in 98% by weight concentrated sulfuric acid is 0.05 to 100 (dl / g), preferably 1.0. Those between ˜80 (dl / g) are preferred.

(Regarding the method for producing the wholly aromatic condensation polymer of the present invention)
The wholly aromatic condensation polymer as described above can be industrially produced with good productivity by the following method according to the present invention.

That is, the following formulas (C) and (D)
(C)
(D)
(In the above formulas (C) and (D), X ¹ and X ² are each independently selected from the group consisting of O, S and NH, and Ar ¹ represents a tetravalent aromatic group having 6 to 20 carbon atoms. And (C) and (D) may be hydrochlorides.)
At least one selected from the group consisting of an aromatic amine derivative represented by the formula:
R ¹ —O ₂ C—Ar ² —CO ₂ —R ¹ ′ (E)
(Ar ² represents each independently a divalent aromatic group having 6 to 20 carbon atoms, and R ¹ and R ¹ ′ each independently represent hydrogen or an aromatic group having 6 to 20 carbon atoms.)
And a method in which the obtained reaction product is dissolved in an organic solvent and the carbon fiber component is filtered and isolated.

^Ar 1, Ar ² in the formula (C) (D) is the same as ^Ar 1, Ar ² described with respect to the composition of the wholly aromatic azole respectively, also, ^R 1, ^{R 1} in the general formula (D) ' Each independently represents hydrogen or a monovalent aromatic group having 6 to 20 carbon atoms, and specific examples of the aromatic unit include phenylene group, naphthalene group, biphenylene group, isopropylidene diphenyl group, diphenyl ether group, diphenyl sulfide group, A diphenylsulfone group, a diphenylketone group, and the like. One or more hydrogen atoms of these aromatic groups are each independently a halogen group such as fluorine, chlorine or bromine; an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group or a hexyl group; It may be substituted with a C5-C10 cycloalkyl group such as a cyclopentyl group or a cyclohexyl group; an alkoxycarbonyl group such as a methoxycarbonyl group or an ethoxycarbonyl group.

The number of moles of each monomer (reaction component) is the above formula (1)
The following mathematical formula (1)
0.8 ≦ (c + d) /e≦1.2 (1)
[Wherein c is an aromatic amine derivative represented by the above formula (C), d is an aromatic amine derivative represented by the above formula (D), and e is an aromatic dicarboxylic acid represented by the above formula (E). This is the number of moles of each charged acid derivative. ]
When (c + d) / e is preferably smaller than 0.8 or larger than 1.2, it may be difficult to obtain a polymer having a sufficient degree of polymerization. The lower limit of (c + d) / e is suitably 0.9 or more, more preferably 0.93 or more, and even more preferably 0.95 or more. Moreover, as an upper limit of (c + d) / e, 1.1 or less is suitable, More preferably, it is 1.07 or less, More preferably, it is 1.05 or less. Therefore, it can be said that the optimum range of c / d in the present invention is 0.95 ≦ c / d ≦ 1.05.

  (C) and (D) may be used alone or in combination, and the molar ratio of (C) :( D) can be appropriately selected at an arbitrary ratio of 0: 100 to 100: 0.

  For the reaction, either a reaction performed in a solvent or a solvent-free heating and melting reaction can be employed. For example, it is preferable to carry out a heating reaction in a reaction solvent described later with stirring. The reaction temperature is preferably 50 ° C to 500 ° C, more preferably 100 ° C to 350 ° C. This is because if the temperature is lower than 50 ° C., the reaction does not proceed, and if the temperature is higher than 500 ° C., side reactions such as decomposition tend to occur. Although the reaction time depends on temperature conditions, it is usually 1 hour to several tens of hours. The reaction can be carried out from under pressure to under reduced pressure.

  The reaction usually proceeds even without a catalyst, but a transesterification catalyst may be used if necessary. Examples of transesterification catalysts used in the present invention include antimony compounds such as antimony trioxide, stannous acetate, tin octylate, dibutyltin oxide, tin compounds such as dibutyltin diacetate, alkaline earth metal salts such as calcium acetate, sodium carbonate Examples thereof include phosphorous acids such as alkali metal salts such as potassium carbonate, diphenyl phosphite, triphenyl phosphite and the like. In addition, it is preferable to use various additives such as an antioxidant in the reaction.

In the carbon fiber coated with the wholly aromatic condensation polymer of the present invention, the carbon fiber (N) is preliminarily added to the above-mentioned (C), (D), and (E), which are polymerization raw materials, before the reaction. ) / (X) ≦ 100 (3)
[Wherein (x) represents the sum of parts by weight of aromatic diamine (C), aromatic dicarboxylic acid diaryl ester (D), and aromatic dicarboxylic acid derivative (E), and (n) represents carbon fiber (N ) Parts by weight. ]
It is preferable to carry out the reaction by adding at a ratio satisfying.
Carbon fiber (N) here is synonymous with what was mentioned previously.

  When the weight ratio (n) / (x) is less than 0.001, it may be difficult to isolate the carbon fiber component from the polymer. On the other hand, if the weight ratio (n) / (x) is greater than 100, the coating of the carbon fiber polymer is not sufficient, which is not preferable. In the study by the present inventors, in the above formula (3), a range of 0.01 ≦ (n) / (x) ≦ 10 is preferable, and a range of 0.01 ≦ (n) / (x) ≦ 1.0. Is particularly preferred.

  At this time, it is preferable to use carbon fibers that have been previously subjected to physical treatment and / or chemical treatment as described above. As a preferable example of the chemical treatment, it is preferable to use a mixed solution of nitric acid and sulfuric acid, a mixed solution of sulfuric acid and hydrogen peroxide, and it is more preferable to perform the treatment in the presence of ultrasonic waves.

  Further, it is preferable to use a carbon fiber dispersion liquid in which carbon fibers are dispersed in a solvent by physical treatment such as ball mill, bead mill, homogenizer, ultrasonic treatment, and strong shearing treatment.

  The above reaction can be carried out without a solvent, but if necessary, phosphoric acid, polyphosphoric acid, phosphorus pentoxide, 1-methyl-2-pyrrolidone, 1-cyclohexyl-2-pyrrolidone, dimethylacetamide, diphenyl A solvent such as sulfone, dichloromethane, chloroform or tetrahydrofuran may be used. These solvents may be used alone or in combination of two or more.

  The total aromatic azole containing carbon fiber obtained by the above method is dissolved in methanesulfonic acid, sulfuric acid, 1-methyl-2-pyrrolidone, 1-cyclohexyl-2-pyrrolidone, dimethylacetamide, etc. Carbon fibers coated with the wholly aromatic polyester of the invention can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is explained in full detail, this invention is not limited at all by these Examples.

Centrifugation: A personal centrifuge Chibitan manufactured by MILLIPORE was used.
Amount of wholly aromatic azole coating the carbon fiber: The carbon fiber coated with the wholly aromatic azole was 1500 ° C. at a temperature rising rate of 10 ° C./min in Air using a differential thermal scanning calorimeter, TG-8120 manufactured by Rigaku Corporation. It is the value calculated | required from the ratio of the weight reduction derived from decomposition | disassembly of a total aromatic azole and carbon fiber.

[Reference Example 1: Acid treatment of carbon fiber]
After adding 30 parts by weight of sulfuric acid to 1 part by weight of carbon nanotube VGCF manufactured by Showa Denko KK, 10 parts by weight of nitric acid was slowly dropped. After the completion of the dropping, it was treated with a 28 kHz ultrasonic wave in a 70 ° C. warm water bath for 1 hour. The solution after completion of the reaction was diluted with 100 parts by weight of water, isolated by suction filtration with a Teflon (registered trademark) membrane filter having a pore size of 0.22 μm and washed with water.

[Example 1]
To 9.37 parts by weight of polyphosphoric acid, 0.21306 parts by weight of 4,6-diaminoresorcinol dihydrochloride was added and stirred at 176 mmHg and 80 ° C. for 24 hours. The reaction product was cooled to 60 ° C. and 6.82 parts by weight of phosphorus pentoxide, 0.16613 parts by weight of terephthalic acid and 0.23421 parts by weight of the carbon fiber obtained in Reference Example 1 were added at 100 ° C. for 2 hours, 140 ° C. For 18 hours. The obtained reactant was added to 100 parts by weight of water and reprecipitated. The precipitate was washed three times with 100 parts by weight of sulfuric acid and suction filtered and washed with a membrane filter made of Teflon (registered trademark) having a pore diameter of 0.22 μm to isolate 0.21 part by weight of carbon fiber coated with wholly aromatic azole. . When 0.1 part by weight of the coated carbon fiber thus obtained is dispersed in 100 parts by weight of 98% sulfuric acid with ultrasonic waves, and subjected to a centrifugal separation treatment with a centrifugal acceleration of 51000 m / s ² for 1 minute. The obtained precipitate was 0.02 part by weight, and it was confirmed that 0.08 part by weight of carbon fiber was compatibilized in sulfuric acid. When the same treatment was performed in 100 parts by weight of methanesulfonic acid, the obtained precipitate was 0.01 parts by weight, and 0.09 parts by weight of carbon fiber was compatibilized in methanesulfonic acid. I was able to confirm.

  Further, the result of measurement with a differential thermal scanning calorimeter balance was 8.39 wt% of the total aromatic azole coated with carbon fiber.

[Comparative Example 1]
Precipitation obtained when 0.1 part by weight of Showa Denko carbon fiber (VGCF) was dispersed in 100 parts by weight of 98% sulfuric acid with ultrasonic waves and subjected to a centrifugal separation at a centrifugal acceleration of 51000 m / s ² for 1 minute. The product was 0.08 part by weight, and it was confirmed that 0.02 part by weight of carbon fiber was compatibilized in sulfuric acid. When the same treatment was performed in 100 parts by weight of methanesulfonic acid, the resulting precipitate was 0.07 parts by weight, and 0.03 parts by weight of carbon fibers were compatibilized in methanesulfonic acid. I was able to confirm.
The results are summarized in Table 1 below.

Claims (11)

  Carbon fiber coated with 0.01 to 100 parts by weight of a wholly aromatic condensation polymer with respect to 100 parts by weight of carbon fiber.   The carbon fiber according to claim 1, wherein the carbon fiber is a carbon nanotube. The wholly aromatic condensation polymer is represented by the following formula (A) and / or (B):
(A)
(B)
[In the above formulas (A) and (B), X ¹ and X ² are each independently selected from the group consisting of O, S and NH, and Ar ¹ represents a tetravalent aromatic group having 6 to 20 carbon atoms. Ar ² represents a divalent aromatic group having 6 to 20 carbon atoms. ]
The carbon fiber according to any one of claims 1 and 2, wherein the carbon fiber is a wholly aromatic azole that satisfies the following conditions. The wholly aromatic azole represented by (A) is

And or


The carbon fiber according to claim 3, wherein The wholly aromatic azole represented by (B)

And or

The carbon fiber according to claim 3, wherein Following formula (C), (D)
(C)
(D)
(In the above formulas (C) and (D), X ¹ and X ² are each independently selected from the group consisting of O, S and NH, and Ar ¹ represents a tetravalent aromatic group having 6 to 20 carbon atoms. And at least one selected from the group consisting of the aromatic amine derivatives represented by (C) and (D) may be hydrochlorides) and the hydrochlorides thereof, and the following formula (E):
R ¹ —O ₂ C—Ar ² —CO ₂ —R ¹ ′ (E)
(Ar ² represents each independently a divalent aromatic group having 6 to 20 carbon atoms, and R ¹ and R ¹ ′ each independently represent hydrogen or an aromatic group having 6 to 20 carbon atoms.)
At least one aromatic dicarboxylic acid derivative represented by:
Following formula (1)
0.8 ≦ (c + d) /e≦1.2 (1)
[Wherein c is an aromatic amine derivative represented by the above formula (C), d is an aromatic amine derivative represented by the above formula (D), and e is an aromatic dicarboxylic acid represented by the above formula (E). This is the number of moles of each charged acid derivative. ]
Is coated with the wholly aromatic condensation polymer according to any one of claims 1 to 3, wherein the obtained reaction product is dissolved in an organic solvent, and the carbon fiber component is filtered and isolated. Carbon fiber manufacturing method.   The method for producing a carbon fiber coated with a wholly aromatic condensation polymer according to claim 6, wherein carbon fiber is added in advance to the polymerization raw material to polymerize the wholly aromatic condensation polymer.   The method for producing carbon fiber according to claim 6 or 7, wherein carbon fiber subjected to surface treatment in a mixed solution of nitric acid and sulfuric acid is used.   The carbon fiber production method according to claim 6 or 7, wherein a carbon fiber dispersion liquid in which carbon fibers are dispersed in a solvent by a physical treatment such as a ball mill, a bead mill, or a homogenizer is used. The aromatic amine derivative represented by (C) is

Or its dihydrochloride and / or

Or the aromatic dicarboxylic acid derivative which is the dihydrochloride and represented by (E) is a terephthalic acid, The manufacturing method of the carbon fiber of any one of Claims 6-9. The aromatic amine derivative represented by (D) is

Or its dihydrochloride and / or

Or the aromatic dicarboxylic acid derivative which is the dihydrochloride and represented by (E) is a terephthalic acid, The manufacturing method of the carbon fiber of any one of Claims 6-9.