JP2019173216A - Manufacturing method of non-woven fabric and manufacturing method of composite material - Google Patents

Abstract

To provide a manufacturing method of a non-woven fabric which is made of carbon fibers and has a good formation.SOLUTION: A manufacturing method of a non-woven fabric comprises the steps of: adding a nonionic thickner to an aqueous dispersion containing carbon fibers and a nonionic dispersant, and performing papermaking using the aqueous dispersion with the thickner added.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a nonwoven fabric and a method for producing a composite material.

  Composite materials in which organic materials such as resins and carbon fibers are combined are used in various fields. Examples of such a composite material include carbon fiber reinforced plastic (CFRP) including a resin and a carbon cloth in which carbon fibers are plain woven.

  On the other hand, from the viewpoint of effective use of resources, a method for reusing carbon fibers taken out from a used composite material has been studied. For example, a method of manufacturing a nonwoven fabric in which carbon fibers taken out from a composite material are dispersed in water and manufacturing carbon fibers randomly arranged (wet papermaking method) has been studied.

  In the case of producing a carbon fiber nonwoven fabric by a wet papermaking method, the surface of the carbon fiber is hydrophobic, so that it is difficult to disperse in water and it is difficult to obtain a nonwoven fabric with good formation. Then, using a dispersing agent in order to improve the water dispersibility of carbon fiber is examined. For example, Patent Document 1 describes that a conductive paper is prepared by mixing a dispersion in which carbon nanotubes are dispersed in water together with a specific surfactant with pulp.

JP 2010-13312 A

The method described in Patent Document 1 uses a nano-sized carbon material, and does not use a carbon fiber having a length of millimeter to centimeter.
Furthermore, even if the carbon fibers can be dispersed well in water using a dispersant, it has been clarified by the present inventors that a nonwoven fabric produced using the carbon fibers is not always excellent in formation. .

  An object of this invention is to provide the manufacturing method of the nonwoven fabric from which the nonwoven fabric of a carbon fiber with favorable formation is obtained in view of the said situation. Another object of the present invention is to provide a method for producing a composite material using a nonwoven fabric produced by this method.

Specific means for solving the problems include the following aspects.
<1> A step of adding a nonionic adhesive to an aqueous dispersion containing carbon fibers and a nonionic dispersant, and a step of carrying out papermaking using the aqueous dispersion to which the adhesive has been added. The manufacturing method of the nonwoven fabric provided.
<2> The method for producing a nonwoven fabric according to <1>, wherein the carbon fiber is extracted from a composite material containing carbon fiber and a resin.
<3> A method for producing a composite material, comprising: a step of producing a non-woven fabric by the method for producing a non-woven fabric according to <1> or <2>; and a step of combining the non-woven fabric with a resin.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the nonwoven fabric from which the nonwoven fabric of a carbon fiber with favorable formation is obtained is provided. Moreover, according to this invention, the manufacturing method of the composite material using the nonwoven fabric manufactured by this method is provided.

3 is a photographed image of a nonwoven fabric produced in Example 2. 4 is a photographed image of a nonwoven fabric produced in Comparative Example 2. It is a picked-up image of the nonwoven fabric produced in Comparative Example 4.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.
In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
In the present specification, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.

<Nonwoven Fabric Manufacturing Method>
The method for producing a nonwoven fabric of the present disclosure includes a step of adding a nonionic adhesive to an aqueous dispersion containing carbon fibers and a nonionic dispersant, and papermaking using the aqueous dispersion to which the adhesive has been added. And a step of carrying out the method.

  In the method of manufacturing a nonwoven fabric using a dispersion in which raw materials such as carbon fibers are dispersed in water as in the method of the present disclosure (wet papermaking method), the stock solution of the dispersion is diluted with water before being supplied to the papermaking machine. Since the viscosity is lowered, a viscosity agent is added to adjust the viscosity to be suitable for papermaking.

  As a result of the study by the present inventors, a nonwoven fabric obtained by using a non-ionic adhesive added to an aqueous dispersion containing carbon fibers and a nonionic dispersion is at least one of the dispersion and the adhesive. It was found that the formation of carbon fibers in the nonwoven fabric was less agglomerated and uneven in distribution than the nonwoven fabric obtained by using non-nonionic material, and the formation was good.

  The timing of adding a sticky agent to an aqueous dispersion containing carbon fiber and a dispersant is before the step of carrying out paper making using the aqueous dispersion (for example, after diluting the aqueous dispersion). It may be simultaneous with the step of carrying out papermaking using a liquid, or a combination thereof. Moreover, the frequency | count in particular of adding a viscous agent to an aqueous dispersion liquid is not restrict | limited, You may be 1 time or multiple times.

(Carbon fiber)
The length of the carbon fibers used for the production of the nonwoven fabric (average value of 100 when the length is not constant) is not particularly limited, and can be selected from a range of 1 mm to 1000 mm, for example. From the viewpoint of easy papermaking of the carbon fiber, the length of the carbon fiber is preferably 50 mm or less.

  The thickness of the carbon fibers used for the production of the nonwoven fabric (the average value of 100 when the thickness is not constant) is not particularly limited, and can be selected from a range of 3 μm to 10 μm, for example.

  If necessary, the carbon fibers may be subjected to a surface treatment. By applying a surface treatment to the surface of the carbon fiber, for example, when a composite material is produced by combining the manufactured nonwoven fabric with a resin, the strength and formability of the resulting composite material can be improved.

  In the present disclosure, the “surface treatment” of the carbon fiber means a treatment for improving the adhesion of the surface of the carbon fiber to the resin. There are no particular restrictions on the mechanism of adhesion due to the surface treatment of carbon fiber, such as mechanical bonding (anchor effect, etc.), physical interaction (intermolecular force, etc.), chemical interaction (covalent bond, hydrogen bond, etc.), etc. Any of these may be used, or a combination thereof may be used.

  Examples of the method for performing the surface treatment on the carbon fiber include a method for introducing an oxygen-containing functional group by an oxidation treatment, a method for imparting a surface treatment agent, and the like, and any of them may be applied. When the surface treatment of carbon fiber is performed using a surface treatment agent, specific examples of the surface treatment agent include a coupling agent, a sizing agent, a surfactant, and a nitriding agent. Among these, a coupling agent is preferable and a silane coupling agent is more preferable from the viewpoint of achieving both the strength and formability of the composite material.

  In an embodiment of the method of the present disclosure, one extracted from a composite material including carbon fiber and resin (regenerated carbon fiber) may be used as the carbon fiber. In general, carbon fibers taken out from a composite material are in a state where a bundling body (strand) is not formed through a regeneration process (including cases where a part of the bundling body is formed) or a sizing agent is attached. It is difficult to make a plain weave because it is not in a state (including the case where a sizing agent is partly attached), but suitable for the production of nonwoven fabrics (particularly, the production of nonwoven fabrics by a wet method). . Examples of the composite material from which the carbon fiber is taken out include used CFRP.

  Whether or not the carbon fiber is taken out from the composite material is determined by, for example, whether or not the carbon fiber forms a converging body, whether or not the sizing agent is attached to the surface of the carbon fiber, and the like. be able to.

  The method for taking out the carbon fiber from the composite material is not particularly limited, and can be selected from general methods. For example, a method of immersing a composite material in a treatment solution that can dissolve the resin contained in the composite material and dissolving the resin (dissolution method), a method of heating the composite material to thermally decompose the resin (thermal decomposition method), a composite Examples include a method of electrolyzing a material to decompose a resin (electrolysis method). From the viewpoint of suppressing the deterioration of the extracted carbon fiber, a dissolution method is preferable. Moreover, it is preferable to use the carbon fiber taken out by the melt | dissolution method also from a dispersible viewpoint when manufacturing a nonwoven fabric by the wet method mentioned later.

(Dispersant)
The dispersant used in the method of the present disclosure is not particularly limited as long as it is nonionic and can improve the dispersibility of carbon fibers in water. A dispersing agent can be selected from well-known materials, such as a water-soluble polymer and surfactant, for example. Only one type of dispersant may be used or two or more types may be used in combination.

  The method for determining whether or not the dispersant is nonionic is not particularly limited. For example, it can be confirmed by calculating the required amount of cation by a method as described in Examples described later.

  Specific examples of the dispersant include polyalkylene oxide such as polyethylene oxide, polyacrylamide, polyamine, polyacrylic acid, polyacrylic acid ester, polyvinylamine, polyethyleneimine, naphthalenesulfonic acid condensate, polyurethane, and alumina compound. . If possible, the dispersant may be a modified or copolymerized product.

(Viscous)
The dispersant used in the method of the present disclosure is not particularly limited as long as it is nonionic and can adjust the viscosity of the aqueous dispersion containing carbon fiber and the dispersant. A sticky agent can be selected from well-known materials, such as a water-soluble polymer, for example. Only 1 type or 2 or more types of adhesives may be used together. In addition, the same type of stickers and dispersants may be used, or different types may be used.

  The method for determining whether or not the adhesive is nonionic is not particularly limited. For example, it can be confirmed by calculating the required amount of cation by a method as described in Examples described later.

  Specific examples of the sticking agent include polyalkylene oxides such as polyethylene oxide, polysaccharides such as carboxymethyl cellulose, starch and carrageenan, vinyl acetate, polylactic acid, polyglycolic acid, polyacrylamide, gelatin and the like. The sticking agent may be modified or copolymerized if possible.

  The method for carrying out the step of making the carbon fiber is not particularly limited. For example, it may be carried out by supplying an aqueous dispersion containing carbon fiber and a dispersant and added with a sticking agent to a papermaking machine. The amount of the carbon fiber, the dispersant and the sticking agent contained in the aqueous dispersion is not particularly limited, and can be selected according to the type, amount, papermaking conditions, and the like of each component.

  An aqueous dispersion may contain components other than carbon fiber, a dispersing agent, and a viscosity agent as needed. For example, you may contain a binder, an antifoamer, etc.

  The thickness of the nonwoven fabric obtained by the method of the present disclosure is not particularly limited and can be selected depending on the application. For example, the range may be 5 mm to 100 mm.

  A nonwoven fabric may also contain components other than carbon fiber as needed. For example, resin fibers may be included.

  The nonwoven fabric may be further subjected to surface treatment as necessary, but from the viewpoint of maintaining the formability of the composite material, it is not subjected to surface treatment or to the extent that the shapeability of the composite material is not impaired. It is preferable.

<Production method of composite material>
The manufacturing method of the composite material of this indication includes the process of manufacturing a nonwoven fabric with the manufacturing method of the nonwoven fabric mentioned above, and the process of combining the said nonwoven fabric with resin.

  The type of resin used in the above method is not particularly limited, and can be selected according to the use of the composite material. For example, urethane acrylate resin, epoxy resin, phenol resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, thermosetting polyimide resin, polyamide resin, polypropylene resin, polyester resin, polyvinyl chloride resin, polyvinylidene chloride resin , Polyvinyl acetate resin, polystyrene resin, polyethylene resin, polyurethane resin, acrylic resin, polyether ether ketone resin, polyetherimide resin, Teflon resin, acrylonitrile butadiene styrene resin, polyacetal resin, polycarbonate resin, cyclic polyolefin resin, modified polyphenylene ether Resins, polysulfone resins, polyamideimide resins, polyphenylene sulfide resins and the like can be mentioned. Resin used for manufacture of a composite material may be only 1 type, or 2 or more types of combinations may be sufficient as it.

  The method for combining the nonwoven fabric and the resin is not particularly limited, and can be selected from general methods. For example, it can be carried out by impregnating a nonwoven fabric with a resin. Or it can carry out by melting the resin fiber in the nonwoven fabric manufactured using the carbon fiber and the resin fiber. You may perform the hardening process etc. of resin compounded with carbon fiber as needed.

  The composite material may be formed into a desired shape as necessary. For example, the composite material may be formed into a three-dimensional shape by taking advantage of the excellent shapeability of the nonwoven fabric.

  Hereinafter, the present disclosure will be specifically described by way of examples. However, the present disclosure is not limited to these examples.

(1) Production of non-woven fabric In a 1,000 mL mixer vessel (TESCOM Co., Ltd.), 0.66 g of carbon fiber (length: 10 mm), 0.1 g of binder fiber (Toray Co., Ltd .: Vinylon), Table 1 Were added to distilled water to give a total of 500 g. The dispersant was added in the form of an aqueous solution, and the solid content to be added was 0.06 g. Similarly, the sticky agent was also added in the form of an aqueous solution, and the solid content to be added was 0.06 g. Furthermore, 1 drop of antifoaming agent (Meisei Chemical Industry Co., Ltd .: Foamless P-8) was added and stirred with a mixer for 2 minutes. Thereafter, 500 g of water (concentration: 80 ppm) containing the same adhesive as described above was added, and the mixture was stirred for 1 second for a short time 20 times to obtain an aqueous dispersion of carbon fibers. The used dispersants and adhesives are as follows.

Dispersant 1: Alcox CP-B2 (Meisei Chemical Industry Co., Ltd.)
Dispersant 2: Meika Surf BP-25 (Meisei Chemical Co., Ltd.)
Dispersant 3: Pamall S-300 (Meisei Chemical Co., Ltd.)
Dispersant 4: VS-87E (Meisei Chemical Co., Ltd.)

Adhesive 1: Alcox SK (Meisei Chemical Co., Ltd.)
Adhesive 2: Alcox SW (Meisei Chemical Co., Ltd.)
Sticky 3: High Form 202 (Kurita Industry Co., Ltd.)
Sticky agent 4: Pamall P-270H (Meisei Chemical Co., Ltd.)

The obtained dispersion was put into a round standard sheet machine (Kumaya Riki Kogyo Co., Ltd.). After water injection of 6,000 mL, the mixture was sufficiently stirred and filtered to obtain a circular nonwoven fabric having a diameter of 160 mm. The nonwoven fabric was compressed at 300 MPa for 1 minute while being sandwiched between filter papers, and dehydrated. The non-woven fabric after dehydration was dried with a box dryer set at 105 ° C. to obtain a carbon fiber non-woven fabric having a basis weight of 33 g / m ² .

(2) Determination of Ionicity of Dispersant Dispersant 1 was added to distilled water and stirred for 1 minute to prepare a dispersant solution (concentration: 0.1% by mass). To 50 g of this solution, 10.0 g of a cationic colloid titration reagent methyl glycol chitosan solution (Wako Pure Chemical Industries, Ltd.) diluted to N / 400 (required cation; −0.0025 meq / g) was added for 1 minute. Stir. To this, 4 drops of toluidine blue (Wako Pure Chemical Industries, Ltd.) as an indicator was dropped with a dropper and stirred for 10 seconds until uniformly mixed, and it was confirmed that the solution became blue showing cationicity. Subsequently, while continuing stirring, 0.1 g of N / 400 (cation required amount; +0.0025 meq / g) polyvinyl potassium sulfate solution (Wako Pure Chemical Industries, Ltd.) was dropped with a micropipette as an anionic colloid titration reagent. Stir for 10 seconds. Thereafter, it was confirmed that there was no change in the color of the solution. Similarly, the step of dropping 0.1 g of N / 400 potassium polyvinyl sulfate solution and observing the color of the solution was repeated until a change in the color of the solution was confirmed. After a total of 10.0 g was added dropwise, the color of the solution became light purple, and after the addition of 10.1 g, the color of the solution changed to reddish purple indicating anionic property, so the addition at the time when the color change of the solution started The amount (10.0 g) was taken as the isoelectric point. From the difference in mass between the charged N / 400 methyl glycol chitosan solution and the N / 400 potassium potassium sulfate solution added to the isoelectric point, the required cation amount of the solution was calculated. As a result, it was 0 meq / g, and the dispersant was judged to be nonionic.

  The required amount of cation was similarly calculated for the dispersants 2 to 4. When the cation requirement was a positive value, it was determined to be anionic, and when the cation requirement was a negative value, it was determined to be cationic. The results are shown in Table 1.

(3) Judgment of ionicity of the sticking agent The cation requirement amount of the sticking agents 1 to 4 was calculated in the same manner as described above to judge the ionicity. The results are shown in Table 1.

(4) Evaluation of formation In the dark room, the produced nonwoven fabric was mounted on the backlight of the LED light source which set the brightness of the center part to 3,200 lux (Tritech Co., Ltd .: TREVIEWER A4-520). Then, the nonwoven fabric was image | photographed with the single-lens reflex camera (Canon Co., Ltd .: EOS Kiss X7) which turned off the automatic light control from the front (perpendicular to the cross section) of the nonwoven fabric. The captured image was taken into a personal computer and analyzed with analysis software (Adobe Systems Inc .: Adobe Photoshop CC 2017). Specifically, the analysis range was a non-woven fabric portion (circular shape with a diameter of 160 mm), and a histogram was created based on the brightness of the transmitted light of the non-woven fabric. The value of the standard deviation of the created histogram was evaluated as the formation evaluation index (formation variation), and evaluated according to the following three criteria. The results are shown in Table 1.

A: The standard deviation is 15 or less, and the texture of the nonwoven fabric is uniform.
B: The standard deviation is more than 15 and 40 or less, and unevenness of texture exists in the whole nonwoven fabric.
C: The standard deviation is more than 40, and the texture of the nonwoven fabric is extremely uneven.

  In Table 1, “-” indicates that the non-woven fabric could not be produced due to significant aggregation of the carbon fibers in the dispersion.

  As shown in Table 1, the non-woven fabric of the example using both nonionic and non-dispersing agents as the dispersant and the sticker is more suitable than the non-woven fabric of the comparative example in which at least one of the dispersant and the sticker is not nonionic. Evaluation was good.

  Also, a photographed image of the nonwoven fabric produced in Example 2 (FIG. 1), a photographed image of Comparative Example 2 in which the adhesive was changed to an anionic one in Example 2 (FIG. 2), and a dispersant in Example 2. From the comparison with the photographed image of Comparative Example 4 (FIG. 3) in which the nonionic material was changed to the anionic one, the non-woven fabric produced by using the nonionic material for both the dispersant and the sticker had a better texture. I know that there is.

Claims (3)

  A non-woven fabric comprising: a step of adding a nonionic adhesive to an aqueous dispersion containing carbon fiber and a nonionic dispersant; and a step of making a paper using the aqueous dispersion to which the adhesive is added. Production method.   The manufacturing method of the nonwoven fabric of Claim 1 whose said carbon fiber is taken out from the composite material containing carbon fiber and resin.   The manufacturing method of a composite material provided with the process of manufacturing a nonwoven fabric with the manufacturing method of the nonwoven fabric of Claim 1 or Claim 2, and the process of combining the said nonwoven fabric with resin.