JP5561180B2 - Carbon fiber bundles for aqueous processes - Google Patents

Description

  The present invention relates to a carbon fiber bundle having processability into chopped fibers, bundling properties suitable for handling of chopped fibers, and opening properties suitable for water-based processes represented by papermaking processes.

  Carbon fiber reinforced composite material with carbon fiber and matrix resin is excellent in lightness, mechanical properties, electrical conductivity and dimensional stability, etc., so it can be used in automobiles, aircraft, electrical / electronic equipment, optical equipment, sporting goods, and construction. It is used in a wide range of materials and other fields.

  Many molding methods are known for carbon fiber composite materials. One method for obtaining a base material used for molding is to process carbon fibers by an aqueous process typified by a wet papermaking process. For example, chopped fibers are dispersed in an aqueous medium and processed into paper or nonwoven fabric, and then various resins are used as a base material to form a composite material base material. An electrode base material of a fuel cell is manufactured by this paper making process.

  In the wet papermaking process, paper is made by dispersing chopped fibers in an aqueous dispersion medium. In order to improve the quality of paper products, it is required to have carbon fiber bundling and openability in an aqueous dispersion medium. Convergence is important in making the fiber length uniform at the time of cutting and processability when feeding chopped fibers. The spreadability is a characteristic for dispersing the fiber bundle at the single fiber level, and directly affects the papermaking quality. The better the convergence and spreadability of the carbon fiber bundle, the better the mechanical and conductive properties of the carbon fiber reinforced composite material.

  From such a background, in a carbon fiber bundle used for an aqueous process, a specific resin is usually attached as a sizing agent to improve the bundling property and the spreadability.

  Patent Document 1 discloses an aqueous process carbon fiber to which a sizing agent mainly composed of a surfactant is attached. Patent Document 2 discloses a carbon fiber for papermaking in which a hydrophilic compound composed of polyoxyalkylene and an aliphatic hydrocarbon is attached as a sizing agent. Further, Patent Document 3 discloses a carbon fiber to which a sizing agent composed of a surfactant having an HLB value of 9 to 17 and a polyvinyl alcohol-based water-soluble thermoplastic resin is attached.

  However, it is not easy to achieve both convergence and spreadability. In particular, when trying to obtain a paper with a high basis weight by increasing the carbon fiber concentration in the aqueous dispersion medium, the fiber spreadability is insufficient, There is a problem that the quality of the base material is deteriorated due to agglomeration and the mechanical properties of the molded product cannot be fully exhibited.

  By the way, urethane resin is often used as a fiber sizing agent because it is excellent in elasticity, toughness, adhesiveness and the like. For example, Patent Document 4 discloses a carbon fiber bundle using polyether polyurethane or polyester polyurethane resin as a sizing agent.

  Although this fiber bundle is intended to improve adhesion to thermoplastic resin by attaching a polyester polyurethane resin with a breaking elongation of 400% or less, the disclosure also suggests that it exhibits excellent properties in an aqueous process. It has not been done.

  Further, Patent Document 5 discloses a carbon fiber chopped strand that uses a mixture of an aromatic polyurethane and a non-aromatic polyurethane as a sizing agent and is excellent in handleability, mechanical properties of the composite material, and conductivity.

  However, it is neither disclosed nor suggested that the carbon fiber chopped strand described in Patent Document 5 exhibits excellent properties in an aqueous process.

  Patent Document 6 discloses a carbon fiber bundle in which a sizing agent having a specific solubility parameter (SP value) is attached to carbon fibers. Adhesion with a rubber-containing resin is improved by using a sizing agent having a specific range of SP values.

International Publication No. 2006/018139 Pamphlet JP 2006-219808 A JP 2000-54269 A JP 2007-231441 A JP 2003-247127 A JP 2003-247127 A

  Thus, there is a demand for a carbon fiber bundle that achieves both convergence and spreadability with an aqueous dispersion medium. In the case of a carbon fiber reinforced composite material, the greater the proportion of carbon fiber, the better the mechanical properties and conductivity. Therefore, a better substrate can be obtained if it can be processed at a high carbon fiber concentration. In addition, handleability when manufacturing and processing a fiber bundle is also important, and winding around a bobbin and processability during processing are characteristics that are always required for the fiber bundle.

  An object of the present invention is to provide a carbon fiber bundle that has good handleability when producing and processing a fiber bundle, is excellent in bundling properties, and is excellent in openability in an aqueous dispersion medium even at a high concentration. .

As a result of intensive studies to achieve the above object, the present inventors have found the following carbon fiber bundle that can achieve the above-mentioned problems. That is, the present invention relates to a carbon fiber bundle comprising carbon fibers and a sizing agent, wherein the sizing agent comprises a water-soluble polyurethane resin having an SP value of 11.2 to 13.4, and the sizing agent is the carbon fiber. It is the carbon fiber bundle for aqueous processes which has adhered to the fiber in the ratio of 0.5-7 mass%.

  The carbon fiber bundle of the present invention is excellent in handleability when manufacturing and processing the fiber bundle, and further achieves both the fiber convergence and the openability in the aqueous dispersion medium, when the carbon fiber concentration is increased. However, uniform dispersion at the single fiber level is possible, and a papermaking substrate excellent in mechanical properties and conductivity can be obtained.

It is the schematic explaining the measuring method of the drape value of a carbon fiber bundle.

  The carbon fiber bundle of the present invention is obtained by attaching a water-soluble polyurethane resin having an SP value of 11.2 to 13.4 to carbon fibers. First, these components will be described.

  As the carbon fiber, PAN-based, pitch-based, rayon-based, and the like can be used, but PAN-based carbon fiber is preferable from the viewpoint of the balance between strength and elastic modulus of the obtained molded product. These are available as commercial products. The carbon fiber may be subjected to a surface treatment in order to improve adhesion to the sizing agent and form a uniform film. Examples of surface treatment include chemical oxidation, electrolytic oxidation, or gas phase oxidation in the liquid phase, but the electrolytic oxidation in which the carbon fiber is used as the anode in the aqueous electrolyte solution is simple and suppresses the decrease in strength. preferable. The electrolytic treatment solution is not particularly limited, and examples thereof include inorganic acids such as sulfuric acid and nitric acid, inorganic bases such as potassium hydroxide and sodium hydroxide, and inorganic salts such as ammonium sulfate, ammonium carbonate and sodium carbonate.

  A carbon fiber bundle is a form in which single fibers (filaments) of carbon fibers are bundled, and the number of filaments is usually about 1,000 to 60,000. From the viewpoint of handling and opening properties of carbon fibers, 3,000 to 40,000 are preferable. More preferably, it is 6,000 to 24,000.

  As for the diameter of the carbon fiber (filament) which comprises a carbon fiber bundle, 3-15 micrometers is preferable, More preferably, it is 5-10 micrometers.

  In addition, the carbon fiber bundle of the present invention may contain a small amount of other fiber types as long as the object of the invention is not impaired. Examples of other fiber types include carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, metal fiber, and other high-strength and high-modulus fibers. Also good.

  The sizing agent of the present invention comprises a water-soluble polyurethane resin, and the water-soluble polyurethane resin is composed of a polyol unit and a urethane unit. This water-soluble polyurethane resin can be obtained by condensing a polyol with a diisocyanate. The polyol constitutes a polyol unit, and the diisocyanate constitutes a urethane unit. From the viewpoint of water solubility, the polyol needs to contain polyalkylene glycol. Moreover, in addition to polyalkylene glycol, the polyol can use together 1 type or multiple types chosen from polyester polyol, polycaprolactone polyol, and polycarbonate polyol.

  Since the condensation of diisocyanate and polyol is a polyaddition (addition polymerization) reaction and does not involve the formation and separation of low molecules, the mass ratio of the polyol unit and the urethane unit constituting the sizing agent of the present invention should be The mass ratio of the constituent raw materials is reflected. That is, the mass% of each unit in the present invention is the mass% of each raw material with respect to the total mass of the polyol and diisocyanate that are the raw materials. As a mass% of a polyol, 94-99.2 mass% is preferable.

  The polyalkylene glycol that can be used in obtaining the sizing agent of the present invention needs to be hydrophilic in order that the carbon fiber bundle exhibits high openability in the aqueous dispersion medium, for example, polyethylene glycol (PEG), Examples include polypropylene glycol (PPG), PEG / PPG block polymer, PEG / PPG random polymer, and the like. Of these, polyethylene glycol is preferable. In particular, the weight average molecular weight of the polyalkylene glycol is preferably 4,000 or more and 21,000 or less from the viewpoint of the balance between the handleability of the carbon fiber bundle, the bundling property, and the spreadability in the aqueous dispersion medium. The polyalkylene glycol component varies in hydrophilicity and film flexibility depending on the molecular weight. When the molecular weight is in an appropriate range, it is possible to obtain a sizing agent that is more excellent in convergence and handling properties while exhibiting high fiber opening.

  In addition, the polyalkylene glycol component can also be used by mixing a plurality of types having different weight average molecular weights. In this case, the weight average molecular weight of the polyalkylene glycol can be obtained by the following formula.

  Here, Mw represents a weight average molecular weight, and W represents mass% of the polyalkylene glycol component.

  In addition to polyalkylene glycol, one or more kinds selected from polyester polyol, polycaprolactone polyol, and polycarbonate polyol can be used in combination as the polyol component. The polyester polyol can be obtained by dehydration condensation of glycol and carboxylic acid. Examples of glycols that can be used for dehydration condensation include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanediol, and the like. Examples of the dicarboxylic acid component include adipic acid, succinic acid, azelaic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, diphenic acid, ubidic acid, 2-methylterephthalic acid, 4-methylphthalic acid, naphthalenedicarboxylic acid, etc. Is mentioned.

  The polycaprolactone polyol is a polyol using ε-caprolactone and various alcohols as raw materials. For example, DIC Corporation polylite OD-X-2155, OD-X-640, OD-X-2586, Daicel Chemical Co., Ltd. Plaxel 205, 210, 220, 303, 305, etc. are available as commercial products. is there.

  The polycarbonate polyol is a polyol having a carbonate structure in the molecular chain. For example, Plaxel CD CD205, CD210, CD220 manufactured by Daicel Chemical Industries, Ltd. are commercially available.

  Moreover, the compound which has other hydroxyl groups except water can be contained in the range which does not impair the handleability of a sizing agent, bundling property, and fiber opening property. Examples of such compounds include ethylene glycol, propylene glycol, butylene glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, catechol, bisphenol A, and the like.

  Diisocyanates that can be used in obtaining the sizing agent of the present invention include phenyl diisocyanate, methylene diphenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, dimer acid diisocyanate, norbornene diisocyanate, dicyclohexylmethane. Diisocyanate etc. are mentioned. From the viewpoint of flexibility and toughness of the film, tolylene diisocyanate or isophorone diisocyanate is preferable.

  As described above, in the present invention, the urethane unit constituting the polyurethane resin used for the sizing agent is preferably composed of tolylene diisocyanate or isophorone diisocyanate. "" Means that the diisocyanate component is 90% by mass or more of the total diisocyanate component.

  In the aqueous dispersion medium, the sizing agent is water-soluble and the SP value is in the range of 11.2 to 13.4 in order to exhibit high fiber opening properties even when the carbon fiber bundle is at a high concentration. is important. Here, “water-soluble” means “dissolving” in water at a molecular level, that is, a uniform liquid phase. As a polyurethane-based sizing agent, for example, as described in Patent Document 4, a polyurethane resin dispersed in water is widely used. Specifically, the polyurethane resin is self-emulsified or emulsified with a surfactant. Here, emulsification is a phenomenon in which one of two liquids that do not dissolve each other becomes fine particles and is dispersed in the other liquid to form an emulsion (Japanese Standards Association 3rd edition JIS Industrial Term Dictionary p1352). That is, the state in which the polyurethane resin is “emulsified” and “dissolved” in water is greatly different.

  In polyurethane sizing agents emulsified in water, polyurethane itself has a low affinity with water, so even if it is treated in an aqueous dispersion medium after forming a film on the surface of the carbon fiber bundle, it shows almost no fiber opening. . In order to exhibit good fiber opening properties, it is important that the sizing agent and water are compatible, and it is necessary to use a water-soluble polyurethane-based sizing agent.

  On the other hand, for example, when a sizing agent having high water solubility such as a surfactant is attached to the carbon fiber, the sizing agent dissolves in water too early and the opening property is insufficient, or the sizing agent from the surface of the carbon fiber. Is lost rapidly and re-agglomerates, and the quality is lowered particularly when paper making with high basis weight is performed. That is, it is important that the water solubility of the sizing agent is appropriately controlled in order to increase the paper weight of the paper.

  The SP value (solubility parameter) is defined by the square root of the heat of evaporation per volume, but is a numerical value used as a measure of the solubility of the two components. The smaller the difference between the two SP values, the greater the solubility. In the carbon fiber bundle of the present invention, when the SP value of the water-soluble polyurethane resin is in the range of 11.2 to 13.4, the water-solubility is appropriately controlled and high fiber opening property is exhibited. Preferably it is 12.3-13.3. If it is outside this range, the water-solubility is insufficient or too high, and the spreadability is lowered.

In the present invention, the SP value is calculated based on the method of Fedors (Polymer Engineering and Science, vol. 14, No. 2, p 147 (1974)). For example, the SP value of a polyurethane resin represented by the following chemical formula is calculated as follows.

The polyurethane of the formula (1) is composed of a polyol unit and a urethane unit. The polyol unit contains 10 methylene groups (—CH ₂ —) and 6 ethers (—O—). The urethane units, one is a methyl group (-CH _3), 2 pieces A bromide (-CONH-) is phenylene are included one. The molar heat of vaporization Δei and the molar volume Δvi of each unit are shown in Table 1 according to the above literature.

Here, the SP value of each unit is expressed by the following equation.

Since the values of ΣΔei and ΣΔvi are as shown in Table 1, the SP value is 9.503 for the polyol unit and 15.362 for the urethane unit by applying the respective values to the above equation . Since the polyurethane of formula (1) contains one polyol unit and one urethane unit, the SP value is ((9.503 × 1) + (15.362 × 1)) / 2, which is 12.433. It becomes.

  In the present invention, the constituent component of the polyurethane resin used for the sizing agent may contain a small amount of other units as long as the object of the present invention is not impaired. Examples of other units include polyamines such as low molecular weight alkylene glycol, cyclohexanediol, and hexamethylenediamine.

  The sizing agent in this invention can be manufactured with the following method, for example. That is, polyisocyanate is advanced by adding diisocyanate to a polyol that has been sufficiently dried under reduced pressure at an appropriate temperature. At that time, an organic tin compound, a tertiary amine, or the like may be used as a reaction catalyst. When a polyester polyol is used as the polyol, a dicarboxylic acid and an alkylene glycol are heated under reduced pressure to undergo dehydration condensation to form a polyester polyol, and then a polyalkylene glycol is added thereto and cooled to an appropriate temperature. Add diisocyanate.

  In the present invention, the adhesion amount of the sizing agent to the carbon fiber is in the range of 0.5 to 7% by mass with respect to 100% by mass of the carbon fiber bundle from the viewpoint of the balance between the bundling property and the spreadability. is important. When the adhesion amount is less than this lower limit, film formation becomes insufficient, and the converging property and opening property of the carbon fiber bundle are insufficient. On the other hand, when the upper limit is exceeded, the fiber bundle is hard and the handleability is insufficient, and the cost is disadvantageous. Preferably it is 1-5 mass%, More preferably, it is 1.2-3 mass%.

  The sizing agent used in the present invention includes an antifoaming agent, an emulsifier, an antiseptic, a slime inhibitor, a cross-linking agent, an antioxidant, a heat stabilizer, an epoxy resin, an acrylic resin, and the like, as long as the object of the present invention is not impaired. Ingredients such as thermoplastic resins may be included. Moreover, a well-known sizing agent can also be added.

  Carbon fiber sizing treatment is usually performed by immersing a continuous carbon fiber bundle in a solution or dispersion liquid (sizing liquid) of a sizing agent in an aqueous medium, or dripping, spraying or spraying the sizing liquid onto the carbon fiber, and then drying the dispersion medium.・ Proceed by removing.

  When the carbon fiber bundle of the present invention is used in a papermaking process, the roving, which is a continuous fiber to which the sizing agent is attached, is a chopped fiber cut with a known cutting machine such as a guillotine cutter. Although the length of this chopped fiber is not specifically limited, It is preferable to cut to about 1-20 mm. By making the cut length within this range, it is possible to obtain a base material excellent in the balance of paper processability, mechanical properties and conductive properties.

  The carbon fiber bundle of the present invention preferably has a rape value (bundle hardness) of 5 to 20 cm from the viewpoint of facilitating winding of a roving onto a bobbin and suppressing generation of fluff at the time of cutting. When the drape value is in this range, winding of the roving onto the bobbin becomes easy. In addition, generation of fuzz during cutting, winding around the cutter, and miscut induction due to shift of the cut surface can be prevented.

  In addition, the sizing agent used in the present invention can maintain the openability even when the concentration of carbon fibers in the aqueous dispersion medium is increased, and can prevent re-aggregation of single fibers once dispersed. Since the sizing agent has a high affinity for the aqueous dispersion medium and at the same time has an excellent affinity for carbon fibers, it is considered that an excellent opening property has been developed.

  Since the carbon fiber bundle to which the sizing agent of the present invention is attached is excellent in bundling property and spreadability in an aqueous dispersion medium, a carbon fiber sheet uniformly dispersed at a single fiber level can be obtained by a papermaking process. . This carbon fiber sheet can be suitably used for an electrode material, a planar heating element, a static electricity removing sheet, and the like. In addition, a carbon fiber composite material having excellent mechanical characteristics and conductive characteristics can be produced using a known resin as a base material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, the following Example does not restrict | limit this invention.

  The measurement method of various characteristics of the carbon fiber used in the description of the present invention is as follows.

(1) Adhering amount of sizing agent About 5 g of carbon fiber to which the sizing agent was attached was collected and put into a heat-resistant container. Next, this container was dried at 120 ° C. for 3 hours, cooled to room temperature while taking care not to absorb moisture, and the weight of the weighed carbon fiber was set to W ₁ (g). Subsequently, the entire container was placed in a nitrogen atmosphere at 450 ° C. After heating for 15 minutes, the mixture was cooled to room temperature while taking care not to absorb moisture, and the weight of the weighed carbon fiber was defined as W ₂ (g). Through the above treatment, the amount of the sizing agent attached to the carbon fiber was determined by the following equation.
Adhering amount (% by weight) = 100 × {(W ₁ −W ₂ ) / W ₂ }.

(2) Evaluation of convergence The carbon fiber bundle is cut, and about 70 g of chopped fibers [weighing value M (g)] is collected and put into a 500 mL graduated cylinder. Next, this graduated cylinder is a rubber sheet having a thickness of 4 mm. Then, after tapping treatment from a height of 2.54 cm to 60 times, the volume V (mL) of the chopped fiber in the graduated cylinder was read. Through this treatment, the filling bulk density was determined by the following equation.
D: Filled bulk density D = M / V
The number of measurements was three, and the average bulk density obtained by dividing the filling bulk density by the number of measurements was evaluated in four stages A to D. A to C are acceptable and D is unacceptable.
A: The average bulk density is 0.35 or more.
B: The average bulk density is 0.25 or more and less than 0.35.
C: The average bulk density is 0.2 or more and less than 0.25.
D: The average bulk density is less than 0.2.

(3) Evaluation of spreadability (A) Evaluation of spreadability (normal)
0.05 g of chopped fiber cut to a length of 6 mm is put into 300 ml of water, stirred gently for 20 seconds, and then allowed to stand for 20 seconds. The dispersion state of the carbon fibers was visually observed, and the spreadability was evaluated in four stages A to D. A to B are acceptable and C to D are unacceptable.
A: The number of unopened bundles is less than two.
B: The number of unopened bundles is 2 or more and less than 5.
C: The number of unopened bundles is 5 or more and less than 10.
D: The number of unopened bundles is 10 or more.

(B) Opening evaluation (high concentration)
2 g of chopped fiber cut to a length of 6 mm is put into a container with a diameter of 150 mm containing 1000 mL of water, stirred gently for 60 seconds, and then allowed to stand for 60 seconds. Water was filtered off and three small pieces of 2 cm × 2 cm were cut out from the obtained sheet-like carbon fiber, and the number of unopened bundles was measured by microscopic observation. Observation was performed on both the front and back sides of the small piece, and the spreadability was evaluated in four stages A to D from the total number of unopened bundles. A to C are acceptable and D is unacceptable.
A: The number of unopened bundles is less than 5.
B: The number of unopened bundles is 6 or more and less than 9.
C: The number of unopened bundles is 10 or more and less than 19.
D: The number of unopened bundles is 20 or more.

(4) Measurement of drape value In an atmosphere of 23 ± 5 ° C., a carbon fiber bundle cut to 30 cm was fixed to the end of a rectangular parallelepiped base, and at this time, the carbon fiber bundle was fixed to protrude 25 cm from the end of the base. . That is, as shown in FIG. 1, a portion 5 cm from the end of the carbon fiber bundle was placed at the end of the table. After leaving still in this state for 30 minutes, the shortest distance between the tip of the carbon fiber not fixed to the table and the side surface of the table was measured to obtain the drape value. The number of measurements was n = 5, and an average value was adopted.

(5) Measurement of elution amount of sizing agent The sizing agent was diluted with water to prepare a 4 wt% aqueous solution or aqueous dispersion. A filter paper (No. 2 filter paper manufactured by ADVANEC, diameter 90 mm) was immersed in this for 1 minute, and then dried under reduced pressure at 60 ° C. for 2 hours to attach a sizing agent to the filter paper. The amount of sizing agent deposited was calculated from the weight of the filter paper before and after sizing agent deposition. Next, the filter paper was immersed in 250 mL of water to elute the sizing agent. The dry weight of the filter paper after 1 minute and after 5 minutes was measured, and the dissolution rate of the sizing agent from the filter paper was calculated.

Reference Example 1 Preparation of Sizing Agent Aqueous Solution (a-1) 1 mol (91.99 parts by weight) of polyethylene glycol (PEG) (weight average molecular weight 2000) was heated to 120 ° C., and 1 mol of tolylene diisocyanate (TDI) (8 (.01 part by weight) was added and stirred to obtain a PEG-TDI polyadduct. The obtained polyaddition product was diluted with water to a concentration of 10% by mass to obtain an aqueous sizing agent solution (a-1).

Reference Example 2 Preparation of Sizing Agent Aqueous Solution (a-2) A sizing agent aqueous solution (a-2) was obtained in the same manner as in Reference Example 1, except that PEG having a weight average molecular weight of 4,000 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol (95.83 parts by weight) of PEG and 1 mol (4.17 parts by weight) of TDI.

Reference Example 3 Preparation of Sizing Agent Aqueous Solution (a-3) A sizing agent aqueous solution (a-3) was obtained in the same manner as in Reference Example 1, except that PEG having a weight average molecular weight of 6,200 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol (97.27 parts by weight) of PEG and 1 mol (2.73 parts by weight) of TDI.

Reference Example 4 Preparation of Sizing Agent Aqueous Solution (a-4) A sizing agent aqueous solution (a-4) was obtained in the same manner as in Reference Example 1, except that PEG having a weight average molecular weight of 7,000 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol (97.57 parts by weight) of PEG and 1 mol (2.43 parts by weight) of TDI.

Reference Example 5 Preparation of Sizing Agent Aqueous Solution (a-5) A sizing agent aqueous solution (a-5) was obtained in the same manner as in Reference Example 1 except that PEG having a weight average molecular weight of 10,000 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol (98.29 parts by weight) of PEG and 1 mol (1.71 parts by weight) of TDI.

Reference Example 6 Preparation of Sizing Agent Aqueous Solution (a-6) A sizing agent aqueous solution (a-6) was obtained in the same manner as in Reference Example 1, except that PEG having a weight average molecular weight of 20,000 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol of PEG (99.14 parts by weight) and 1 mol of TDI (0.86 parts by weight).

Reference Example 7 Preparation of Sizing Agent Aqueous Solution (a-7) A sizing agent aqueous solution (a-7) was obtained in the same manner as in Reference Example 1 except that PEG having a weight average molecular weight of 25,750 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol (99.33 parts by weight) of PEG and 1 mol (0.67 parts by weight) of TDI.

Reference Example 8 Preparation of Sizing Agent Aqueous Solution (a-8) A sizing agent aqueous solution (a-8) was obtained in the same manner as in Reference Example 1, except that PEG having a weight average molecular weight of 31,500 was used. The raw material ratio for obtaining the PEG-TDI polyadduct was 1 mol (99.45 parts by weight) of PEG and 1 mol (0.55 parts by weight) of TDI.

Reference Example 9 Preparation of Sizing Agent Aqueous Solution (a-9) 1 mol (97.56 parts by weight) of PEG having a weight average molecular weight of 10,000 and 1 mol (2.44 parts by weight) of methylenediphenylene diisocyanate (MDI) Polyaddition was carried out in the same manner as in Example 1, and diluted to 10% by mass with water to obtain an aqueous sizing agent solution (a-9).

Reference Example 10 Preparation of Sizing Agent Aqueous Solution (a-10) 1 mol (98.35 parts by weight) of PEG having a weight average molecular weight of 10,000 and 1 mol (1.65 parts by weight) of hexamethylene diisocyanate (HDI) were used as reference examples. In the same manner as in No. 1, polyaddition was performed, and the mixture was diluted to 10% by mass with water to obtain an aqueous sizing agent solution (a-10).

Reference Example 11 Preparation of Sizing Agent Aqueous Solution (a-11) Instead of PEG having a weight average molecular weight of 2,000, 1 mol (98.29 parts by weight) of polypropylene glycol (PPG) having a weight average molecular weight of 10,000 was used. A sizing agent aqueous solution (a-11) was obtained in the same manner as in Reference Example 1 except that the amount was 1 mol (1.71 parts by weight) to obtain a PEG-TDI polyadduct.

Reference Example 12 Preparation of Sizing Agent Aqueous Solution (a-12) 1.2 mol of ethylene glycol and 0.6 mol of terephthalic acid were heated and stirred at 180 ° C. and dehydrated and condensed until the acid value became 1 or less. 2-hydroxyethyl) (BHET) was obtained.

  A mixture of 0.4 mol (92.45 parts by weight) of PEG having a weight average molecular weight of 10,000 and 0.6 mol (3.53 parts by weight) of BHET was heated to 120 ° C., and 1 mol of TDI (4.03 parts by weight) was heated. And stirred to obtain a PEG / BHET-TDI polyadduct. The obtained polyaddition product was diluted with water to a concentration of 10% by mass to obtain an aqueous sizing agent solution (a-12).

Reference Example 13 Preparation of Sizing Agent Aqueous Solution (a-13) A sizing agent aqueous solution (a-13) was obtained in the same manner as in Reference Example 12 except that PEG having a weight average molecular weight of 7,000 was used. The raw material ratio for obtaining the PEG / BHET-TDI polyadduct was as follows: PEG 0.4 mol (89.55 parts by weight), BHET 0.6 mol (4.88 parts by weight), TDI 1 mol (5.57 parts by weight). )Met.

Reference Example 14 Preparation of Sizing Agent Aqueous Solution (a-14) 1.2 mol of ethylene glycol and 0.6 mol of adipic acid were heated and stirred at 180 ° C., and dehydrated and condensed until the acid value was 1 or less. 2-Hydroxyethyl) (BHEA) was obtained.

  A mixture of 0.4 mol (92.71 parts by weight) of PEG having a weight average molecular weight of 10,000 and 0.6 mol (3.26 parts by weight) of BHEA was heated to 120 ° C., and 1 mol of TDI (4.04 parts by weight) was heated. Was added and stirred to obtain a PEG / BHEA-TDI polyadduct. The obtained polyaddition product was diluted with water to a concentration of 10% by mass to obtain an aqueous sizing agent solution (a-14).

Reference Example 15 Preparation of Sizing Agent Aqueous Solution (a-15) 1.2 mol of ethylene glycol and 0.6 mol of succinic acid were heated and stirred at 180 ° C., dehydrated and condensed until the acid value became 1 or less, and bis succinate ( 2-hydroxyethyl) (BHES) was obtained.

  A mixture of 0.4 mol (93.07 parts by weight) of PEG having a weight average molecular weight of 10,000 and 0.6 mol (2.88 parts by weight) of BHES was heated to 120 ° C., and 1 mol of TDI (4.05 parts by weight) was heated. Was added and stirred to obtain a PEG / BHEA-TDI polyadduct. The obtained polyadduct was diluted with water to a concentration of 10% by mass to obtain an aqueous sizing agent solution (a-15).

Reference Example 16 Preparation of Sizing Agent Aqueous Solution (a-16) A sizing agent aqueous solution (a-16) was obtained in the same manner as in Reference Example 12 except that 1 mol of isophorone diisocyanate (IPDI) was used as the diisocyanate. The raw material ratio for obtaining the PEG / BHET-IPDI polyadduct was as follows: PEG 0.4 mol (91.43 parts by weight), BHET 0.6 mol (3.49 parts by weight), IPDI 1 mol (5.08 parts by weight) )Met.

Reference Example 17 Preparation of Sizing Agent Aqueous Solution (a-17) A sizing agent aqueous solution (a-17) was obtained in the same manner as in Reference Example 1, except that 1 mol of isophorone diisocyanate (IPDI) was used as the diisocyanate. The raw material ratio for obtaining the PEG-IPDI polyadduct was 1 mol (97.83 parts by weight) of PEG and 1 mol (2.17 parts by weight) of IPDI.

Reference Example 18 Preparation of Aqueous Sizing Agent Solution (a-18) Using 0.1 mole (71.28 parts by weight) of PEG having a weight average molecular weight of 10,000 and 0.9 moles of BHET (16.31 parts by weight) BHET was obtained, and a sizing agent aqueous solution (a-18) was obtained in the same manner as in Reference Example 15 except that 1 mol (12.41 parts by weight) of TDI was used to obtain a PEG / BHET-TDI polyaddition product. .

Reference Example 19 Preparation of Sizing Agent Aqueous Solution (a-19) According to Reference Example 1 of Patent Document 1 (International Publication No. 2006/018139 Pamphlet), the number average molecular weight 600 represented by the following chemical formula (I), HLB 11.3 A surfactant (A) prepared by mixing 80 parts by weight of polyoxyethylene oleyl ether and 20 parts by weight of polyoxyethylene alkyl ether having a number average molecular weight of 1300 and HLB17 represented by the following chemical formula (II) is 20% by weight. It prepared to aqueous solution and obtained sizing agent aqueous solution (a-19).
_{C 18 H 35 O- (CH 2} CH 2 O) 8 -H (I)
_{C 12 H 25 O- (CH 2} CH 2 O) 25 -H (II).

Example 1
A continuous bundle of carbon fibers (T700S-12K manufactured by Toray Industries, Inc.) was immersed in an aqueous solution prepared by adjusting the aqueous sizing agent solution (a-1) of Reference Example 1 to a concentration of 3.5%, and the sizing agent was adhered thereto, and a hot air dryer was used. For 2 minutes at 170 ° C. The obtained carbon fiber bundle to which the sizing agent was adhered was cut into a length of 6 mm to obtain chopped fibers. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 2
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-2) of Reference Example 2 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 3
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-3) of Reference Example 3 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 4
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-4) of Reference Example 4 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 5
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-5) of Reference Example 5 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 6
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-6) of Reference Example 6 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 7
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-7) of Reference Example 7 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 8
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-8) of Reference Example 8 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 9
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-9) of Reference Example 9 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 10
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-10) of Reference Example 10 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 11
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-11) of Reference Example 11 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 12
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-12) of Reference Example 12 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 13
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-13) of Reference Example 13 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 14
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-14) of Reference Example 14 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 15
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-15) of Reference Example 15 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 16
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-16) of Reference Example 16 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 17
A chopped fiber was obtained in the same manner as in Example 1 except that the concentration of the aqueous sizing agent solution (a-5) in Reference Example 5 was adjusted to 2.0%. The adhesion amount of the sizing agent was 1.4% by mass. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Example 18
Chopped fibers were obtained in the same manner as in Example 1 except that the sizing agent aqueous solution (a-5) in Reference Example 5 was adjusted to a concentration of 1.2%. The adhesion amount of the sizing agent was 0.7% by mass. The properties of the obtained carbon fiber bundle are summarized in Table 2.

Comparative Example 1
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-17) of Reference Example 16 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundles are summarized in Table 3. Out of the SP value range, the fiber-opening property at a particularly high concentration was insufficient.

Comparative Example 2
A chopped fiber was obtained in the same manner as in Example 1 except that the sizing agent (a-18) of Reference Example 17 was used as the sizing agent aqueous solution. The properties of the obtained carbon fiber bundles are summarized in Table 3. Since the range of the SP value is out of the range, the openability is greatly insufficient.

Comparative Example 3
A continuous bundle of carbon fibers (T700S manufactured by Toray Industries, Inc.) was immersed in an aqueous solution prepared by adjusting the aqueous sizing agent solution (a-19) of Reference Example 19 to a concentration of 3.5%. Dry at 2 ° C. for 2 minutes. The obtained sizing agent-attached carbon fiber bundle was cut into a length of 6 mm to obtain chopped fibers. At this time, the adhesion amount of the sizing agent adhered to the obtained chopped fiber was 2.2% by mass. The properties of the obtained carbon fiber bundles are summarized in Table 3. The resulting carbon fiber bundles were inferior in opening property, and in particular, the lack of opening at a high concentration was remarkable.

Comparative Example 4
According to Example 1 of Patent Document 4 (Japanese Patent Application Laid-Open No. 2007-231441), hydrated AP-40 (manufactured by DIC, 22.5% suspension) was used as a sizing agent, and chopped fiber in the same manner as Example 1. Got. The properties of the obtained carbon fiber bundles are summarized in Table 3. The obtained carbon fiber bundle showed almost no opening property.

Comparative Example 5
According to Example 2 of Patent Document 4 (Japanese Patent Laid-Open No. 2007-231441), chopped in the same manner as in Comparative Example 6 except that Hydran AP-30F (manufactured by DIC, 20% suspension) was used as the sizing agent. Fiber was obtained. The properties of the obtained carbon fiber bundles are summarized in Table 3. The obtained carbon fiber bundle showed almost no opening property.

Comparative Example 6
According to Example 3 of Patent Document 4 (Japanese Patent Laid-Open No. 2007-231441), the same procedure as in Comparative Example 6 was conducted except that Hydran AP-20 (DIC, 29.5% suspension) was used as the sizing agent. To obtain chopped fibers. The properties of the obtained carbon fiber bundles are summarized in Table 3. The obtained carbon fiber bundle showed almost no opening property.

Comparative Example 7
According to Example 4 of Patent Document 4 (Japanese Patent Laid-Open No. 2007-231441), chopped in the same manner as in Comparative Example 6 except that Hydran HW-140SF (DIC, 25% suspension) was used as the sizing agent. Fiber was obtained. The properties of the obtained carbon fiber bundles are summarized in Table 3. The obtained carbon fiber bundle showed almost no opening property.

  In addition, the elution amount of the sizing agent was measured in order to confirm that the film made of water-soluble polyurethane was excellent in the opening property in the aqueous dispersion medium. The results are shown in Table 4. The water-soluble sizing agent is eluted in water at a constant rate, and most of the water-soluble sizing agent is eluted after 5 minutes. It can be seen that the film formed by the sizing agent shows water solubility. That is, the carbon fiber bundles shown in the examples are considered to have obtained high fiber opening properties because the water solubility of the sizing agent is appropriately controlled. On the other hand, in Comparative Examples 4 to 7, it can be seen that even when the filter paper to which the sizing agent is adhered is immersed in water for 5 minutes, the elution amount is small and the film once formed is hardly soluble in water. That is, it is considered that since the water solubility of the sizing agent is low, the affinity for water is insufficient, the fiber bundle is not dispersed, and the fiber opening property is hardly exhibited.

  From the examples in Table 2 and the comparative examples in Table 3 and Table 4, the following is clear.

  That is, in the polyurethane-based sizing agent whose SP value is appropriately controlled as shown in the examples, the handling property, the bundling property and the opening property of the carbon fiber are controlled in a well-balanced manner, and in particular, the concentration of the carbon fiber bundle is increased. Even if it shows, it shows a good spreadability. In addition, since the drape value can be controlled within an appropriate range, it can be said that a carbon fiber bundle that is easy to wind on a bobbin, has less fuzz, and has excellent handleability is obtained.

1 Carbon fiber bundle 2 Rectangular base 3 Drape value

Claims (7)

In a carbon fiber bundle having carbon fibers and a sizing agent, the sizing agent is made of a water-soluble polyurethane resin having an SP value of 11.2 to 13.3, and the sizing agent is 0.5 to A carbon fiber bundle for an aqueous process attached at a rate of 7% by mass. The carbon fiber bundle for water-based processes according to claim 1, wherein the sizing agent is a water-soluble polyurethane containing a polyethylene glycol unit having a weight average molecular weight of 4,000 to 21,000. The carbon fiber bundle for aqueous processes according to claim 1 or 2, wherein in the sizing agent, the isocyanate constituting the urethane unit is tolylene diisocyanate. The carbon fiber bundle for aqueous processes according to any one of claims 1 to 3, wherein in the sizing agent, the isocyanate constituting the urethane unit is isophorone diisocyanate. The carbon fiber bundle for aqueous processes according to any one of claims 1 to 4, wherein the drape value is 2 to 20 cm. The carbon fiber bundle for aqueous processes according to any one of claims 1 to 5, wherein the carbon fiber bundle is composed of 1,000 to 60,000 single fibers. The carbon fiber bundle for aqueous processes according to any one of claims 1 to 6, wherein the carbon fiber bundle is a chopped fiber having a fiber length of 1 to 20 mm.

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