JP2937570B2 - Sizing agent for carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sizing agent for carbon fibers. Carbon fiber is used as a reinforcing material for composite materials. The carbon fibers are inherently low in elongation and brittle. Therefore, the carbon fibers are liable to fluff in the weaving process or the like, and have poor handling properties. Then, in order to improve the handleability, the carbon fiber is treated with a sizing agent. The present invention relates to an improvement in such a sizing agent for carbon fibers, and more particularly to a sizing agent for carbon fibers which can be easily desized by washing with water.

[0002]

2. Description of the Related Art Various types of aqueous sizing agents for epoxy resin aqueous emulsions have been proposed as sizing agents for carbon fibers (Japanese Patent Publication No. 57-49675, Japanese Patent Publication No. Sho 62-62).
34876, JP-B-62-56266, JP-B-62-5
6267, JP-B-63-48989).

[0003] However, these conventional sizing agents for carbon fibers have the disadvantage that, even if the sizing property of the carbon fibers can be improved, sufficient smoothness cannot be imparted to the carbon fibers. If the smoothness of the carbon fiber is insufficient, the carbon fiber tends to fluff in the weaving step or the like, and the speed in the weaving step or the like cannot be increased.

[0004] Further, these conventional carbon fiber sizing agents include, when carbon fibers treated with them are used as a reinforcing material for a composite material whose matrix is a resin other than an epoxy resin, the composite material has desired physical properties. Has the drawback that it cannot be used. When a conventional epoxy resin aqueous emulsion type sizing agent is applied to carbon fiber, it is difficult to remove it from the carbon fiber by a simple means of washing with water, and the sizing agent is also brought into the composite material together with the carbon fiber. As a result, when the matrix of the composite material is an epoxy resin,
Since the carbon fiber has good wettability with the matrix, the obtained composite material can exhibit desired physical properties.However, when the matrix of the composite material is a resin other than an epoxy resin, for example, an unsaturated polyester resin In the case of a vinyl ester resin, a polyamide resin, a polycarbonate resin, a phenol resin, or the like, the carbon fibers have poor wettability with the matrix, so that the obtained composite material cannot exhibit the expected physical properties. .

[0005] A sizing agent for carbon fibers can impart sufficient sizing and smoothness to carbon fibers, and at the same time, desizing by a simple means of washing with water, and wetting between the carbon fibers and a general matrix. Therefore, it is required that the composite material obtained can exhibit desired physical properties.

[0006]

The problem to be solved by the present invention is that a conventional sizing agent for carbon fibers cannot impart sufficient convergence and smoothness to carbon fibers, and the sizing agent cannot be easily washed with water. It is difficult to desizing by some means, and it is not possible to make a composite material intended for a general matrix exhibit the desired physical properties.

[0007]

Means for Solving the Problems Thus, the present inventors have
As a result of intensive studies from the above viewpoints, it has been found that those containing a specific polyether polyester obtained by subjecting two specific components to an ester forming reaction in a specific molar ratio range are correctly suitable.

[0008] That is, the present invention relates to a method for preparing a compound obtained by subjecting the following component A and component B to an ester formation reaction at a component / B component ratio of 0.5 to 1.3 / 1.0 (molar ratio). And a polyether polyester having a free hydroxyl group. Component A: dicarboxylic acid or ester-forming derivative thereof Component B: polyether polyol having 3 to 7 hydroxyl groups in the molecule

In the present invention, the component A is a dicarboxylic acid or an ester-forming derivative thereof, such as an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, or an ester-forming derivative thereof.

The aromatic dicarboxylic acids or their ester-forming derivatives include 1) aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid and naphthalenedicarboxylic acid; 2) dimethyl ester and diethyl ester of the above aromatic dicarboxylic acids. , Bishydroxyethyl esters, etc., lower alkyl esters or bishydroxyalkyl esters of the aromatic dicarboxylic acids, 3) aromatic dihalides or acid anhydrides such as isophthalic dichloride, terephthalic dichloride, phthalic anhydride and the like. .

Examples of the aliphatic dicarboxylic acid or its ester-forming derivative include 1) a saturated aliphatic dicarboxylic acid such as malonic acid, succinic acid, maleic acid, adipic acid and sebacic acid or an unsaturated aliphatic dicarboxylic acid; Lower alkyl esters or bishydroxyalkyl esters of the saturated aliphatic dicarboxylic acids or unsaturated aliphatic dicarboxylic acids, such as dimethyl esters, diethyl esters, bishydroxyethyl esters, etc. of the above saturated aliphatic dicarboxylic acids or unsaturated aliphatic dicarboxylic acids; ) Acid anhydrides such as succinic anhydride and maleic anhydride.

Further, alicyclic dicarboxylic acids or their ester-forming derivatives include: 1) saturated alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and cyclohexene-1,2-dicarboxylic acid or unsaturated alicyclic acids; Dicarboxylic acid, 2) dimethyl ester, diethyl ester of the above-mentioned saturated alicyclic dicarboxylic acid or unsaturated alicyclic dicarboxylic acid,
Lower alkyl esters or bishydroxyalkyl esters of the saturated alicyclic dicarboxylic acid or unsaturated alicyclic dicarboxylic acid, such as bishydroxyethyl ester;

The component A is a dicarboxylic acid or an ester-forming derivative thereof as exemplified above, and among them, an aromatic dicarboxylic acid or an ester-forming derivative thereof is preferable, and terephthalic acid, isophthalic acid, phthalic acid,
Naphthalenedicarboxylic acids or their lower alkyl esters are particularly preferred.

In the present invention, the component B contains 3 to 7 in the molecule.
Polyether polyols having 3 to 7 active hydrogens in the molecule, such as polyether polyols obtained by polyalkoxylating a nitrogen-containing compound having 3 to 7 active hydrogens in the molecule, and 3 to 7 active hydrogens in the molecule. And polyether polyols obtained by polyalkoxylating a polyhydric alcohol having the formula (I), and polyether polyols having 3 to 7 hydroxyl groups in the molecule obtained by condensing the polyhydric alcohol.

Examples of the nitrogen-containing compound having 3 to 7 active hydrogens in the molecule include 1) alkanolamines such as triethanolamine and tetraethanolethylenediamine, 2) alkylenediamines such as ethylenediamine and hexamethylenediamine, 3) ) Polyalkylene polyamines such as diethylenetriamine and pentamethylenehexamine; 4) aromatic polyamines such as phenylenediamine and toluenediamine; 5) p-aminophenol and m-
And aromatic aminophenols such as aminophenol.

Examples of the polyhydric alcohol having 3 to 7 active hydrogens in the molecule include aliphatic polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol and sorbitol. Examples of the polyether polyol having 3 to 7 hydroxyl groups in a molecule obtained by condensing an alcohol include polyglycerin such as diglycerin and triglycerin.

The B component is present in the molecule as exemplified above in 3 to 3 parts.
Among these are polyether polyols having 7 hydroxyl groups, and among these, a nitrogen-containing compound or a polyhydric alcohol having 3 to 5 active hydrogens in the molecule is a compound having 2 to 2 carbon atoms.
Those obtained by polyalkoxylation with the alkylene oxide of No. 4 are preferred.

The alkylene oxide used for the polyalkoxylation in the component B is ethylene oxide, propylene oxide, butylene oxide, etc., which can be reacted in a block or random manner. Preferably, the content is 35% by weight or more.
It is particularly preferred that the content be% by weight. This is because the obtained polyether polyester has improved water-removability. The B component preferably has a molecular weight (weight average molecular weight by GPC, the same applies hereinafter) of 2,000 to 20,000, more preferably 5,000.
Particularly preferred are those of ~ 15,000. This is for facilitating the progress of the ester formation reaction with the component A and for preventing the resulting polyether polyester from gelling.

The polyether polyester in the present invention has a free hydroxyl group in the molecule obtained by subjecting the above-mentioned component A and component B to an ester-forming reaction at a specific molar ratio. The molar ratio is A component / B component = 0.5 to 1.3 / 1.0, but 0.6 to 1.1.
/1.0 is preferable. 0.5 / 1.0 molar ratio
If it is smaller than that, the component B remains unreacted and the molecular weight of the obtained polyether polyester also becomes small, so that the convergence imparted to the carbon fiber is insufficient. Conversely, the molar ratio is 1.3
If the ratio is greater than /1.0, crosslinking occurs during the ester formation reaction, and the resulting polyether polyester tends to gel, resulting in poor handling.

The polyether polyester in the present invention preferably has a molecular weight of 3,000 to 50,000,
000 to 40,000, further 10,000 to 300
00 is particularly preferred. The polyether polyester in the present invention preferably has a polyoxyalkylene portion occupying 70 to 98% by weight in the molecule thereof and an oxyethylene portion occupying 34 to 80% by weight in the polyoxyalkylene portion. In any case, the handleability of the polyether polyester is improved, and the polyether polyester has better convergence, smoothness, and water-removability.

The sizing agent for carbon fibers of the present invention comprises the polyether polyester thus obtained. The sizing agent may also contain surfactants and other auxiliary components depending on the desired performance. The polyether polyester readily dissolves in normal or warm water. Usually, the sizing agent is prepared and used as an aqueous solution containing 0.1 to 50% by weight of the polyether polyester, and the aqueous solution is stable at room temperature for a long time.

The sizing agent for carbon fiber of the present invention is made into an aqueous solution, and can be attached to the carbon fiber by an immersion method, a spray method or the like. After the adhesion, the sizing process is completed by squeezing with a roller and drying with a heater. The amount of the carbon fiber sizing agent attached to the carbon fibers can be adjusted by the concentration of the aqueous solution of the carbon fiber sizing agent and the squeezing ratio after the attachment. The attached amount is preferably 0.1 to 10% by weight, more preferably 0.5 to 5.0% by weight, as a polyether polyester based on carbon fibers.
This is for imparting better convergence and smoothness to the carbon fiber.

The sizing agent for carbon fibers of the present invention is PAN
It is extremely effective for carbon fibers based on pitch or pitch. The sizing agent for carbon fibers of the present invention uniformly coats the surface of these carbon fibers, sufficiently binds the carbon fibers, and imparts sufficient smoothness to the carbon fibers. The carbon fibers to which the sizing agent for carbon fibers of the present invention is adhered have almost no fluffing or breakage of single yarns in the weaving step or the like, so that the process speed can be increased and productivity is remarkably improved. Further, the sizing agent for carbon fibers of the present invention can be easily removed from the attached carbon fibers by a simple means of washing with water. It is not necessary to take troublesome means such as organic solvent treatment or heat treatment, and damage to carbon fibers caused by these means can be prevented. Moreover, when the carbon fiber sizing agent of the present invention is used as a reinforcing material for a composite material by using the carbon fiber which has been washed and removed as described above, the adhesiveness between the matrix and the matrix in the composite material is impaired. Since there is no intervening substance, the physical properties of a composite material using a general resin as a matrix can be improved as expected.

Hereinafter, examples and the like will be described in order to make the configuration and effects of the present invention more specific, but the present invention is not limited to these examples.・ Test Category 1 {Synthesis of polyether polyol (B component)} ・ ・ Synthesis of B-1 120 g (2 mol) of ethylenediamine in an autoclave
And 476 g of propylene oxide at 70 ° C.
(8.2 mol) was reacted for 50 minutes, 13.0 g of potassium hydroxide was added as a catalyst in a nitrogen gas atmosphere, and then dehydrated at 120 ° C. × 10 mmHg for 1.5 hours. Next, after returning to normal pressure under a nitrogen gas atmosphere, 115 to 110
3480 g of propylene oxide at 4 ° C x 5 kg / cm ²
(60 mol) was reacted for 6 hours, and further kept at the same temperature and pressure for 1 hour. And 120-125 ℃ × 5-6kg
6468 g (147 mol) of ethylene oxide under / cm ²
Was allowed to react for 4 hours, and further kept at the same temperature and pressure for 1 hour. After the reaction, neutralize the remaining potassium hydroxide,
Dehydration was performed at 100 ° C. × 5 mmHg for 1.5 hours, followed by filtration to obtain B-1. B-1 had a hydroxyl value of 42.6 and a molecular weight of 5260.

Synthesis of B-2 184 g (2 mol) of glycerin was charged into an autoclave, and 12.0 g of potassium hydroxide was added as a catalyst.
A mixture of 6380 g (145.0 mol) of ethylene oxide and 3480 g (60.0 mol) of propylene oxide was reacted at 110 to 120 ° C. × 5 to 6 kg / cm ² for 10 hours, and further reacted at the same temperature and pressure for 1 hour. Held. The remaining potassium hydroxide was neutralized and filtered to obtain B-2. B-2 had a hydroxyl value of 34.2 and a molecular weight of 4950.

Synthesis of B-3 to B-8 B-3 to B-8 were obtained in the same manner as in B-1 and B-2. Table 1 summarizes the contents of B-1 to B-8.

[0027]

[Table 1]

In Table 1, b-1: ethylenediamine, b-2: glycerin, b-
3: triethanolamine, b-4: diaminodiphenylmethane, b-5: trimethylolpropane, b-6:
Pentaerythritol, b-7: sorbitol Bonding state: Bonding state of ethylene oxide and propylene oxide used EO / PO: Weight ratio of ethylene oxide / propylene oxide used

Test Category 2 (Synthesis of Polyether Polyester) Example 1 Using dimethyl terephthalate (A-1) as A component, A-1 / B-2 = 1.0 / 1.0 (molar ratio) ) And potassium hydroxide as a catalyst was added.
The reaction was carried out at 40 ° C. × 1 mmHg for 6 hours, during which time methanol was distilled off. Next, the reaction product was cooled to 100 ° C., potassium hydroxide was neutralized with phosphoric acid, dehydrated, and filtered to obtain a polyether polyester (Example 1). This polyether polyester had a molecular weight of 24,800.

The components A and B used in Examples 2 to 8 and Comparative Examples 1 to 3 and their molar ratios were changed,
In the same manner as in Example 1, polyether polyesters (Examples 2 to 8 and Comparative Examples 1 to 3) were obtained. Example 1
Tables 2 and 3 summarize the contents of Comparative Examples 1 to 8 and Comparative Examples 1 to 3.

Comparative Example 4 An ester-forming reaction product of phthalic anhydride (2 mol) and polyethylene glycol (molecular weight 1,000, 1 mol) was neutralized with triethanolamine to obtain a polyether polyester (Comparative Example 4). Was. This polyether polyester had an oxyethylene portion of 88% by weight and a molecular weight of 1,100.

Comparative Example 5 5 parts by weight of a solid epoxy resin (Epicoat 1001, manufactured by Yuka Shell Co., Ltd.) and a liquid epoxy resin (Epicoat 828,
After heating and mixing at 90 ° C. with 10 parts by weight of Yuka Shell Co., Ltd., polyoxyethylene (85 mol) was used as a surfactant.
Nonylphenyl ether (5 parts by weight) was added and dispersed in water to obtain an epoxy resin aqueous emulsion type sizing agent.

[0033]

[Table 2]

[0034]

[Table 3]

In Tables 2 and 3, A-1: dimethyl terephthalate, A-2: dimethyl isophthalate, A-32,6-dimethylnaphthalenedicarboxylate, A-4: terephthalic acid / isophthalic acid = 0.8. /0.2 (molar ratio), A-5: terephthalic acid / adipic acid = 0.8 / 0.2 (molar ratio) mixture A / B: A component / B component (molar ratio) EO: oxy % By weight of oxyethylene portion in alkylene * 1: Gelation during ester formation reaction

Test Category 3 (Evaluation and Measurement) The performance of each of the aqueous emulsion sizing agents of Examples 1 to 8 and Comparative Examples 3 to 5 obtained in Test Category 2 was as follows. Was evaluated or measured, and the results are shown in Table 4. The polyether polyesters of Comparative Examples 1 and 2 were not used because they were gelled.

Attachment to carbon fiber 3.0% by weight aqueous solution of each polyether polyester or 3.0% aqueous epoxy resin emulsion type sizing agent
A weight% (equivalent to epoxy resin) aqueous emulsion was prepared. In each prepared aqueous solution or aqueous emulsion, an unsized carbon fiber obtained from polyacrylonitrile fiber (tensile strength 350 kg / mm ² , tensile modulus 28 ton / m 2)
m ² , 3000 filaments) were continuously immersed, and the squeezing conditions were adjusted so that the adhesion amount of the polyether polyester or epoxy resin to the carbon fiber was 3.0% by weight, and the oven was continuously heated at 120 ° C. Dried through.

Evaluation of convergence The rubbing test between fibers was performed using a rubbing tester manufactured by Toyo Seiki Co., Ltd. under a load of 100 g / 3000 filaments.
The inner angle was 35 degrees, twisted once, the rubbing length was 20 mm, and reciprocating motion was performed at a speed of 100 times / minute. In addition, the rubbing test between the fiber and the metal was performed using a TM-type conjugation tester manufactured by Daiei Chemical Seiki Co., Ltd.
Load 100g / 3000 filament, θ = 150 degree,
A chrome-plated metal comb with a rubbing length of 30 mm was reciprocated at a speed of 150 times / min. In each case, the number of times of rubbing leading to cutting was evaluated.

Evaluation of smoothness The coefficient of friction (F / F) between fibers was 5.1 cm in diameter.
A carbon fiber is wound around a cylinder having a length of 7.6 cm, a carbon fiber is wound thereon in parallel with the above-mentioned winding direction, a load (T ₁ ) is applied to the cylinder, and the cylinder is rotated, and the tension (T ₂ ) at this time is applied. 20
It measured under conditions of ° C x 65% RH. The coefficient of friction (F / M) between the fiber and the metal was similarly measured without winding the carbon fiber around a cylinder.

Evaluation of water-removability The carbon fiber bundle to which polyether polyester or epoxy resin is adhered is immersed in water at 50 ° C. at a bath ratio of 1 to 30, and
After leaving it for 0 minutes, wash it gently with running water.
After drying for 0 minutes, FT-IR spectrum analysis (AT
R method) under the same conditions. In the case of polyether polyester, the IR spectrum wave number before and after water washing is 110.
The difference in absorbance due to the ether bond at 0 cm ^-1 was compared.
The difference in absorbance due to an aromatic ring of 15 cm ^-1 was compared, and the water washability of the polyether polyester or epoxy resin was evaluated according to the following criteria. 5: Not at all 4; Almost no remaining 3; Very slight remaining 2; Slightly remaining 1;

..Measurement of bending strength The carbon fiber bundle dried and washed after the above was cut into a fiber length of 4 mm with a cutter, and then 20 parts by weight of chopped fiber obtained by cutting and 80 parts by weight of 6,6-nylon resin. And kneaded and extruded with an extruder to produce pellets. The pellets were injection molded, and the bending strength of the molded product was measured.

[0042]

[Table 4]

[0043]

As is clear from the above, the present invention described above can impart convergence and smoothness to the carbon fiber and can be removed from the carbon fiber by a simple means of washing with water. There is an effect that a composite material using fibers as a reinforcing material can exhibit desired physical properties.

Claims (4)

(57) [Claims] 1. The following A component and B component are combined with A component / B
For carbon fiber, characterized by containing a polyether polyester having a free hydroxyl group in a molecule obtained by an ester forming reaction at a component = 0.5 to 1.3 / 1.0 (molar ratio). Sizing agent. Component A: dicarboxylic acid or ester-forming derivative thereof Component B: polyether polyol having 3 to 7 hydroxyl groups in the molecule 2. The sizing agent for carbon fibers according to claim 1, wherein the component A is an aromatic dicarboxylic acid or an ester-forming derivative thereof. 3. The method according to claim 1, wherein the component B comprises a nitrogen-containing compound or a polyhydric alcohol having 3 to 5 active hydrogen atoms in the molecule.
The sizing agent for carbon fibers according to claim 1 or 2, which is polyalkoxylated with the alkylene oxide (4). 4. A polyether polyester having a molecular weight of 30.
4. The sizing agent for carbon fibers according to claim 1, wherein the sizing agent is in the range of 00 to 50,000.