JP2775982B2 - Sized carbon fiber - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a sized carbon fiber, and more particularly to a sized carbon fiber suitable for a composite material using a resin having excellent heat resistance as a matrix.

[Related Art] Conventionally, carbon fiber composite materials have been used for aircraft materials by utilizing the high specific strength and specific rigidity of carbon fibers. Phenolic resins and epoxy resins are mainly used as matrix resins, but with the speeding-up of aircraft and application to primary structural materials (wings, fuselage, etc.), these materials have heat resistance, water resistance and high temperature. There was a problem in the impact property when absorbing water. In order to improve the above characteristics, in recent years, resins having excellent heat resistance, for example, bismaleimide resin, polyether ketone resin, polyether sulfone resin, polyphenylene sulfide resin, polyether imide resin, polyamide imide resin and the like were used. Material development is underway.

In order for the composite material composed of these resins and carbon fibers to exhibit excellent physical properties, the adhesiveness of the interface between the matrix resin and the carbon fibers is improved, and the carbon fibers are sized to improve workability. Is usually the case.

The term "workability" as used herein mainly refers to the fact that by imparting convergence to carbon fibers, fuzzing is prevented, that quality and workability are good, and that the compatibility between the carbon fibers and the matrix resin is good. is there.

By the way, carbon fibers sized with a heat-resistant resin such as a polyimide resin, a polyamideimide resin, or a polyetherimide resin for the above purpose are known (for example, JP-A-53-121871, JP-A-61-75880). JP-A-62-299580). However, if these sized carbon fibers are not flexible and too hard,
Threading work in the weaving process or prepreg process becomes difficult. Conversely, if the sizing adhesion amount is reduced to facilitate the threading operation, the sizing properties of the yarn are insufficient and the fluff is likely to be generated, such as sufficient workability of the carbon fiber and physical properties of the composite material. Was not.

[Problems to be Solved by the Invention] In view of the above, the present inventors have developed excellent processability and physical properties of composite materials using carbon fibers as reinforcing fibers, particularly composite materials using a resin having excellent heat resistance as a matrix. As a result of intensive studies on the carbon fibers to be developed, the present invention has been reached. That is, the object of the present invention is to provide a specific sizing agent on the carbon fiber surface, for example, the above-mentioned bismaleimide resin, polyetherketone resin, polyethersulfone resin, polyphenylenesulfide resin, polyetherimide resin, polyamide An object of the present invention is to provide a carbon fiber which exhibits excellent workability and physical properties of a composite material in a composite material using a heat-resistant resin such as an imide resin as a matrix.

[Means for Solving the Problems] The above object of the present invention is represented by the formula A. Structural unit of B. Formula An aromatic polyamide-imide copolymer composed of a structural unit of the formula C and a structural unit of the formula Ar (where Z is a trifunctional aromatic group in which two of the three functional groups are bonded to adjacent carbon atoms) Group, Ar is an allyl group, R ₁ is an alkyl group having 1 to 4 carbon atoms, b is 0, 1 or 2, and x is an integer of 1 to 500). .

That is, the carbon fiber of the present invention uses a specific aromatic polyamideimide-based resin (hereinafter abbreviated as PAI-based resin) as a sizing agent.

The PAI-based resin is mainly composed of the three units represented by A, B and C, and preferably has a substantially equimolar ratio between the A unit and the (B + C) unit.
It has a structure in which A units and B units or C units are alternately connected. The preferred composition ratio of the B unit and the C unit as the diamine residue is 0.05 to 1 mol of the B unit and C
The unit is arbitrarily selected from the range of 0.95 to 0 mol.

Further, it is preferable that the component Ar of the B unit and the C unit be a mixture of two units having the following structure and composition ratio.

Where X is Or Y is a direct bond, -O -, - S -, - SO 2, R ₂ is an alkyl group having 1 to 4 carbon atoms, a fluorine-substituted alkyl group or a phenyl group, Q is a direct bond, -CO-, -O-,-
S- or -CH ₂ -, a is 0 or an integer from 1 to 4 and R ₁ and b, are as described above.

If the Ar ₁ unit in Ar exceeds 70 mol%, the resulting PAI
The thermal properties and mechanical strength of the base resin tend to decrease, which is not preferable. On the other hand, if the content of Ar ₂ units in Ar exceeds 95 mol%, the thermal characteristics or mechanical strength of the obtained PAI resin tends to decrease, which is not preferable. Accordingly, Ar ₁ and Ar ₂ proportions preferably Ar ₁ 5 to 70 mol%, more preferably 20 to 50 mol%, preferably Ar ₂ 95 to 30 mol%, more preferably 30 to 5
It is selected from the range of 0 mol%.

Note that Z in the A unit is a trifunctional aromatic group in which two of the three functional groups are bonded to adjacent carbons. And so on.

A ′ unit in the case where the imide bond in the above A unit remains in the state of an amic acid bond as its ring-closing precursor Is a part of the A unit, for example, 50 mol% or less, preferably 30 mol% or less.
The case where it exists as mol% or less is also included in the scope of the present invention.

In the above B unit An example of Specific examples of the above Ar ₁ unit are It is.

Specific examples of the above Ar ₂ unit are, for example, And their side chain-substituted derivatives.

the above B composed of specific examples of a unit, an Ar ₁ unit and an Ar ₂ unit
As a specific example of the unit, (Where x represents 1 to 500, preferably 1 to 10, and more preferably 1 to 4). These are mixed and used within a range satisfying the preferred constitutional conditions of Ar ₁ / Ar _2. Sometimes. In particular, x =
1 is useful.

Among them, the following can be mentioned as specific structural formulas of preferred PAI resins.

Here, m and n are selected within a range that satisfies the preferable constitutional conditions of Ar ₁ / Ar ₂ , and a more preferable range is m / n.
n = 1/8 to 1/2, which is Ar ₁ / Ar ₂ = 20/80 to 50/50
(Molar ratio).

In the PAI-based resin of the present invention, the imide unit may remain as a partially opened amic acid bond,
Most have a closed-ring structure, and the value of the logarithmic viscosity (ηinh) measured at 30 ° C. in a N-methylpyrrolidone solvent at a polymer concentration of 0.5% by weight is preferably 0.20 or more, more preferably 0.25 or more. It is a polymerization degree polymer.

As a means for attaching the PAI resin as a sizing agent to carbon fibers, the following method is usually preferably used. In other words, PAI should be adjusted to a concentration at which the desired amount of adhesion can be obtained.
This is a method in which a system resin is dissolved in a solvent, immersion treatment is performed while carbon fibers are continuously run in the solvent, and then the solvent is removed by drying.

Examples of the solvent used at this time include diethylene glycol dimethyl ether, N, N-dimethylformamide, N, N-diketylacetamide, N-methylpyrrolidone and the like.

The amount of the sizing agent may be appropriately adjusted depending on whether the carbon fibers are long fibers or short fibers, but preferably 0.1% by weight or more, more preferably 0.2% by weight, based on the fiber weight.
That is all. In addition, when this adhesion amount exceeds 5% by weight,
In some cases, the carbon fibers become too hard, resulting in poor workability.

Known carbon fibers (including graphite fibers) are used as the carbon fibers in the present invention. Specifically, pitch-based carbon fiber, rayon-based carbon fiber, acrylonitrile-based carbon fiber, and the like are preferable. Among them, acrylonitrile-based carbon fiber is particularly preferable.

The carbon fibers preferably have an elongation of 1.6% or more. That is, in order to use not only as a secondary structural material of an aircraft but also as a primary structural material, as a strand physical property, the strength is preferably 485 kg / mm ² or more and the elongation is 1.6% or more, more preferably the strength is 540 kg / mm. mm ² or more, the more than 1.8% elongation is obtained.

The matrix resin used for the carbon fiber of the present invention is not particularly limited, but is preferably a heat-resistant resin, and is usually a bismaleimide resin, a polyetheretherketone resin, a polyethersulfone resin, a polyphenylenesulfide resin, or a polyphenylenesulfide resin. Examples thereof include an ether imide resin and a polyamide imide resin. Among these, a bismaleimide resin is particularly preferred from the viewpoint of workability and the like.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples. In this example, the torsional stiffness, strand properties and composite properties were measured according to the following methods.

(1) Torsional stiffness Cut about 15 cm of carbon fiber, apply a 25 g load, apply 10 turns of torsion, leave it to stand, and measure the torsional angle from the beginning. The larger the twist angle, the harder the feel of the carbon fiber.

(2) Strand physical properties Tensile strength, tensile elongation and tensile modulus were measured in accordance with the JIS-760 resin-impregnated strand test method. In addition,
As the resin formulation, "BAKELITE" ERL4221 / 3 boron fluoride monoethylamine / acetone-100 / 3/4 (parts by weight) was mixed well and used.

(3) Composite properties Preparation of composite test pieces First, a resin drum coated with a resin to be combined with carbon fiber on silicon-coated paper was wound around a steel drum with a circumference of about 2.7 m, and then pulled out of the creel onto the resin film. The carbon fiber was wound up through a traverse, arranged, and further covered with the resin film from above the fiber.Then, the resin was impregnated into the fiber by rotating and pressing with a pressure roll, and the width was 300 mm and the length was 300 mm. A unidirectional prepreg 2.7 m long is manufactured.

At this time, the drum is heated to 50 to 60 ° C to improve the resin impregnation between the fibers, and the fiber weight of the prepreg is adjusted to 200 g / m by adjusting the rotation speed of the drum and the feed speed of the traverse. ^2. A prepreg having a resin amount of about 35% by weight was prepared.

The prepreg prepared in this manner is cut, laminated, and heat-cured at 180 ° C. and 70 kg / cm ² for 2 hours using an autoclave to measure a tensile strength of about 1 mm in wall thickness or interlayer shear strength (ILSS). A cured plate having a thickness of about 2 mm was prepared for measurement.

Measurement of tensile strength and ILSS The above hardened plate was used as a test piece having a width of 12.7 mm and a length of 230 mm for tensile strength, and a thickness of about 1.2 mm and a length of 50 mm was applied to both ends of the test piece.
A tab made of GFRP was adhered (a strain gauge for measuring elastic modulus and breaking strain was attached to the center of the test piece as necessary), and measurement was performed at a load speed of 1 mm / min using an autograph manufactured by Shimadzu.

The ILSS test specimen was 12.7 mm wide and 28 mm long. The measurement was performed at a load speed of 2.5 mm / min using a normal three-point bending test jig with the support span set to four times the test specimen thickness. did.

Reference Example 1. (Production of polyamide imide resin A; PAI-A) 4,4'-diaminodiphenyl ether 180.2 g (0.9 mol) and terephthaloyl-m-aminoanilide 103.9 g
(0.3 mol) was dissolved in 3000 g of N, N-dimethylacetamide. This was cooled to −10 ° C. with dry ice / acetone, and 252.7 g (1.2 mol) of trimellitic anhydride monochloride was gradually added. After stirring was continued for 1 hour, 121.4 g of triethylamine was added, and the mixture was further stirred for 2 hours.

Next, 150 ml of pyridine and 300 ml of acetic anhydride were added,
Stirred overnight at room temperature. The PAI polymerization solution thus obtained is
The polymer was gradually poured into water under high-speed stirring to precipitate the polymer, followed by washing / dehydration, and further, at 150 ° C. in a hot air drier for 5 hours.
After drying at 200 ° C. for 3 hours, a polyamideimide-A powder was obtained. The logarithmic viscosity (measured at a concentration of 0.5% in N-methylpyrrolidone at 30 ° C.) of the polymer was 0.60.

Reference Example 2. (Production of polyamide imide resin B; PAI-B) In Reference Example 1, 204.2 g (1.02 mol) of 4,4'-diaminodiphenyl ether and 62.4 g (0.18 mol) of terephthaloyl-m-aminoanilide were used. Otherwise, polymerization was carried out in substantially the same manner as in Reference Example 1 to obtain a polyamideimide resin B powder (logarithmic viscosity = 0.72).

Examples 1-2 A carbon fiber consisting of 12,000 filaments sized with an epoxy resin was dried with N, N dimethylformamide and acetone after removing the sizing agent.

Using the raw carbon fiber, the PAI-A and PAI-
B was successively immersed in an NN dimethylformamide solution, and then dried at 180 ° C. to give a size. The results are shown in Table 1.

The amount of the sizing agent attached was 0.8% by weight, the generation of fluff was small, and the feeling was good.

For these carbon fibers, composite test specimens were prepared using maleimide resin as the matrix.
Tensile strength (shown as a value converted to a volume content of carbon fiber of 60%) and interlaminar shear strength (ILSS) were evaluated. The results are shown in Table 1.

As seen in Table 1, in the maleimide resin,
High tensile strength and ILSS were obtained.

Note that, specifically, a maleimide resin having the following composition was used.

BT2562F (Mitsubishi Gas Chemical BT Resin): 90 parts by weight Ep828 (Hetrochemicals): 10 parts by weight Dicumyl peroxide: 0.2 parts by weight Comparative Examples 1-2 Epoxy-sized carbon fibers and the size removal thereof in Example 1 A composite test piece was prepared and evaluated in the same manner as in Example 1 for the non-size raw carbon fiber thus obtained. As shown in Table 1, the results were inferior to ILSS.

Comparative Example 3 Amoco's PAI resin "Toron" 4000T was used for the non-size raw carbon fiber of Example 1. Was attached in the same manner as in Example 1. The strand properties and strand properties of the sized carbon fiber were measured and are shown in Table 1.

As shown by the results, the strand physical properties of the raw carbon fiber sized with the epoxy resin and the non-sized carbon fiber obtained by removing the size of the raw carbon fiber have a tensile strength of about 570k.
g / mm ² , and the tensile modulus of elasticity is about 30 t / mm ² , and despite the fact that there is almost no difference from the physical properties of the product of the present invention, the torsional stiffness is high and the feeling is hard, and the composite physical properties (tensile Strength and
ILSS) was also low.

[Effect of the Invention] The carbon fiber of the present invention uses a specific PAI-based resin as a sizing agent, and thereby has excellent processability and physical properties of the composite material, especially in a composite material using a heat-resistant resin as a matrix resin. You can get things.

Claims (4)

(57) [Claims] 1. The formula A. Structural unit of B. Formula An aromatic polyamide-imide copolymer composed of a structural unit of the formula C and a structural unit of the formula Ar (where Z is a trifunctional aromatic group in which two of the three functional groups are bonded to adjacent carbon atoms) A group, Ar is an allyl group, R ₁ is an alkyl group having 1 to 4 carbon atoms, b is 0, 1 or 2, and x is an integer of 1 to 500). 2. The aromatic polyamide-imide copolymer is composed of the structural units represented by the formulas A, B and C, and the ratio of each structural unit is 1 mol of A unit and 1 mol of (B + C) units. The C unit is 0.95 to 0.05 mol per mol of the B unit.
0 mol, and has a structure in which the A unit and the B unit or the C unit are alternately connected, and furthermore, Ar represents the formula of the B unit and the C unit as a whole. To 0.05 to 0.70 mol of a divalent residue (Ar ₁ ) of the formula 2. The sized carbon fiber according to claim 1, wherein the divalent residue (Ar ₂ ) is 0.95 to 0.30 mol. Where X in the formula is Y is a direct bond, -O -, - S -, - SO 2, R ₁ and R ₂ are an alkyl group having 1 to 4 carbon atoms, a fluorine-substituted alkyl group or a phenyl group, Q is a direct bond, —CO—, —O
-, - S- or -CH ₂ -, a is 0 or an integer of 1 to 4, b is an integer of 0, 1 or 2, x is an integer of 1 to 500. 3. The method according to claim 1, wherein the amount of the sizing agent is set to be 0.
The sized carbon fiber according to claim (1) or (2), which is 1% by weight or more. 4. The sized carbon fiber according to claim 1, wherein the carbon fiber has an elongation of 1.6% or more.