JP2017222786A - Fiber-resin composite body and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fiber-resin composite body which can simply improve mechanical characteristics of a resin by general-purpose treatment, and to provide a fiber-resin composite body.SOLUTION: A fiber-resin composite body is produced by a method including the following steps (A) to (C): (A) a step of applying a liquid composition containing a cellulose nanofiber and a solvent onto a hydrophilic and porous base material; (B) a step of removing the solvent from the base material after the liquid composition has been applied; and (C) a step of compounding the base material after the solvent has been removed with a resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fiber-resin composite and a method for producing the same, and more particularly to a technique for improving mechanical properties of a resin material using cellulose nanofibers as a reinforcing material.

  Cellulose nanofiber (CNF) has physical properties that are lightweight, high in strength, and low in thermal expansion, and has attracted attention as a reinforcing material that improves the mechanical properties of the resin. CNF is an ultrafine fiber having a fiber diameter of 4 to 100 nm and a length of micro order. When these fibers are intertwined with each other, a large structure is formed and the overall strength is expressed.

  Since the cellulose fiber has a hydroxyl group in the side chain, the affinity for the resin is not good. Therefore, the dispersibility of cellulose nanofibers in the resin is poor, and if the dispersibility is poor, the mechanical properties of the resin may not be sufficiently improved. Thus, conventionally, there has been proposed a technique for improving the affinity with a resin by modifying a hydroxyl group of a cellulose fiber with an acid anhydride, or using a modified cellulose nanofiber modified with a resin (for example, Patent Document 1). And Patent Document 2).

JP 2009-293167 A Japanese Patent No. 5656100

  However, the technique for increasing the affinity with the resin by chemical modification of the hydroxyl group of the cellulose fiber requires advanced techniques and complicated processing. For this reason, if it is attempted to improve the mechanical properties of the resin using CNF, it is possible that an advanced and expensive facility is required or the price of the product is increased.

  This invention is made | formed in view of the said subject, and provides the manufacturing method of the fiber-resin composite which can improve the mechanical characteristic of resin simply by a general purpose process, and a fiber-resin composite. One purpose.

  The present disclosure employs the following means in order to solve the above problems.

The first configuration is a method for producing a fiber-resin composite including the following steps (A) to (C).
(A) The process of apply | coating the liquid composition containing a cellulose nanofiber and a solvent to a hydrophilic and porous base material.
(B) The process of removing the said solvent from the said base material after apply | coating the said liquid composition.
(C) The process of combining the said base material after removing the said solvent, and resin.

  In the manufacturing method having the above-described structure, a liquid composition containing cellulose nanofibers (CNF) and a solvent (hereinafter also referred to as “CNF-containing liquid”) is applied to a hydrophilic and porous substrate, and then the substrate Remove the solvent from Thereby, CNF adheres on the base-material surface in the state intertwined. In addition, since the base material to which CNF is attached is porous, when the base material to which CNF is attached and the resin are combined, the resin enters the fine gaps of the base material, thereby separating the resin and CNF. It can be integrated while being suppressed. Thereby, the outstanding mechanical characteristic can be shown. Moreover, according to the said method, the resin composite excellent in the mechanical characteristic can be obtained by a simple method by combining a general purpose process.

  The second configuration is a fiber-resin composite in which cellulose nanofibers are contained in a resin matrix, and the resin matrix includes a porous substrate having the cellulose nanofibers attached to the surface thereof. And a fiber-resin composite.

  In the fiber-resin composite having the above-described configuration, the resin matrix can contain a base material with CNF attached to the surface, so that the resin can be used without using advanced techniques such as chemical modification treatment of CNF. CNF can be contained in the resin matrix while suppressing separation between CNF and CNF. Therefore, a resin composite having excellent mechanical properties can be obtained by a simple method.

The flowchart which shows an example of the manufacturing method of a fiber-resin composite. The schematic diagram which shows an example of a fiber-resin composite.

  Below, the fiber-resin composite of this indication and its manufacturing method are explained in detail. The manufacturing method includes the following steps (A) to (C).

<Process (A)>
Step (A) is a step of applying a CNF-containing liquid to a hydrophilic and porous substrate.
(CNF-containing liquid)
The CNF-containing liquid is a liquid composition in which cellulose nanofibers (CNF) are dispersed or dissolved in a solvent. CNF is obtained by defibrating cellulose fibers. The kind of cellulose fiber is not particularly limited, and examples thereof include cellulose fiber derived from pulp, cotton, regenerated fiber (for example, rayon, acetate fiber, etc.), sea squirt, and cellulose synthetic bacteria. As a method for obtaining cellulose nanofibers by defibrating cellulose fibers, known methods can be applied. Specifically, for example, a method of removing lignin and hemicellulose from cellulose fibers and then mechanically using a refiner, a high-pressure homogenizer, a grinder, a kneader, a bead mill, etc .; TEMPO oxidation, ozone treatment, enzyme treatment, etc. And a method of defibrating by weakening the interaction between cellulose crystals.

  In addition, the state in which the cellulose fiber has been fibrillated to become the cellulose nanofiber refers to, for example, a case where the average fiber diameter of the cellulose nanofiber is in the range of 2 to 500 nm. The average fiber diameter of the cellulose nanofiber is preferably 2 to 200 nm, more preferably 4 to 100 nm. The fiber diameter of the cellulose nanofiber can be measured by observing with an electron microscope.

  The CNF-containing liquid is preferably a dispersion in which CNF is dispersed in a dispersion medium as a solvent. The dispersion medium is preferably an aqueous solvent from the viewpoint of uniformly dispersing CNF by suppressing aggregation of CNF, and examples thereof include water, alcohol, or a mixed solvent of water and alcohol. As the CNF-containing liquid, it is preferable to use an aqueous dispersion in which CNF is dispersed in water from the viewpoints of dispersibility and availability.

  The CNF concentration in the CNF-containing liquid is appropriately selected in consideration of viscosity and the like, but is preferably in the range of 0.1 to 10% by mass. If the CNF concentration is less than 0.1% by mass, the effect of reinforcing the resin by CNF is difficult to obtain, and if it is higher than 10% by mass, the viscosity of the CNF-containing liquid becomes too high and the handling becomes difficult. The CNF concentration is more preferably 0.3 to 5% by mass, and further preferably 0.5 to 3% by mass.

  The CNF-containing liquid may contain other components other than CNF and the solvent as long as the effects of the present disclosure are not impaired. Examples of such other components include various resins, additives, organic fillers, and inorganic fillers. These content ratios can be appropriately selected according to the types of other components. The blending ratio of other components is preferably 5% by mass or less, and more preferably 1% by mass or less.

(Base material)
The material of the substrate is not particularly limited as long as it is hydrophilic and porous. Here, the hydrophilicity generally means a property having a high affinity with water molecules, and refers to a property that is opposed to water repellency that repels water. Here, when water can permeate or hold in the thickness direction of the substrate, the substrate is said to be hydrophilic. When the substrate is hydrophilic, when the CNF-containing liquid is applied to the substrate, the solvent in the CNF-containing liquid is absorbed by the substrate, so that the CNF adheres to the surface by drying it. A material is obtained. Further, the CNF-containing liquid wets and spreads over the entire surface of the base material, and CNF can be uniformly attached to the base material surface. Thereby, high intensity | strength and rigidity can be provided uniformly over the whole resin matrix. “Porosity” means having a large number of fine pores (gaps).

  The hydrophilic and porous substrate is preferably paper, woven fabric or non-woven fabric. By using these materials as the base material, a thin, light, and rigid resin composite can be produced at low cost without requiring advanced techniques and facilities. These are all materials made of fibers, but are usually formed using fibers thicker than CNF (for example, 1 μm or more).

  Paper is generally a sheet-like flake manufactured using vegetable fibers (pulp) as a material and glued while entangled fibers. In addition, the fiber diameter used for paper is thicker than CNF, for example, is 1-100 micrometers. As the paper used as the base material, paper used for various purposes can be applied. Specifically, for example, printing / information paper, packaging paper, sanitary paper, industrial hybrid paper, household hybrid paper, newspaper Etc. The paper as the base material may be either Japanese paper or Western paper.

  The paper as the base material may be produced by dispersing fibers in water and making paper, and then dehydrating and drying the paper, or may be produced by a dry method that does not use water. . In the former case, the paper after dehydration and drying may be used as the base material, or the paper containing the water after paper making and before dehydration and drying may be used as the base material.

  The woven fabric is a sheet-like fabric woven by combining fibers (yarns) vertically and horizontally. The weaving method is not particularly limited, and examples thereof include plain weave, twill weave and satin weave. A nonwoven fabric is a sheet-like fabric in which fibers are intertwined by mechanical or chemical treatment without being woven. The nonwoven fabric may be produced by any method, for example, a fleece forming method such as a dry method, a wet method, or a spun bond method; a fleece bonding method such as a thermal bond method, a chemical bond method, or a needle punch method. It is done. The type of fiber constituting the woven fabric and the non-woven fabric is not particularly limited. For example, natural fibers such as cotton, silk, hemp, mohair, wool, and cashmere; recycled fibers such as acetate, rayon, and cupra; nylon, polyester, polyurethane, and the like Synthetic fibers, and the like.

  The color and pattern of paper, woven fabric and non-woven fabric are not particularly limited. For example, printing may be performed on paper, woven fabric, and non-woven fabric, or a pattern made of leaves, flowers (fresh flowers, pressed flowers, dried flowers, etc.), colored paper, yarn, wool yarn, and the like may be included. Or a handwritten pattern, a character, etc. may be attached | subjected. A resin composite excellent in design can be obtained by using a material with a color, a pattern, or letters as a base material. In addition, various variations of patterns, colors, and letters can be easily applied to paper, woven fabric and non-woven fabric, and it is possible to manufacture resin composites with excellent decorativeness and aesthetics by a simple method. .

  The magnitude | size of a base material is suitably selected according to the use application etc. of a resin composite. The shape of the substrate is preferably a sheet. The thickness of the base material is appropriately selected according to the desired mechanical properties (strength, rigidity, etc.) of the obtained resin composite, but the resin composite has high strength and rigidity while improving the handleability of the base material. From the viewpoint of obtaining the above, it is preferably in the range of 10 to 1500 μm, more preferably in the range of 20 to 500 μm. As the base material, it has a high immobilization ability for CNF attached to the surface, a thin base material, a higher strength resin composite, a high degree of freedom in selection, and availability. Among the above, paper can be particularly preferably used for reasons such as ease.

  The method for applying the CNF-containing liquid to the substrate is not particularly limited. For example, a shower method, a spray method, a dip (immersion) method, a paddle (liquid accumulation) method, a brush coating, a roller brush coating, a roll coater method, an offset printing method. Various methods such as an inkjet printing method can be applied. At this time, in order to increase the application amount of the CNF-containing liquid, for example, it is also effective to apply the CNF-containing liquid to the substrate a plurality of times. The thickness of the CNF-containing liquid to be applied to the substrate is appropriately selected, but is preferably in the range of 0.5 to 10 mm from the viewpoint of achieving both the dripping prevention and the reinforcing effect by CNF, and 1 to 8 mm. It is more preferable to set the range. The CNF-containing liquid may be applied to only one surface of the substrate or may be applied to both surfaces.

<Process (B)>
A process (B) is a process of removing a solvent from the base material after apply | coating a CNF containing liquid. The base material is dried by this step, and the base material fixed on the base material surface can be obtained by entanglement of CNF on the base material surface. The method for removing the solvent is not particularly limited, and examples thereof include natural drying, air drying, heat drying, and reduced pressure drying. Heat drying with hot air, a thermostatic bath, a hot plate or the like is preferable. Although the heating temperature at this time can be suitably selected according to the kind of a solvent, a base material, a heating method, etc., Preferably it is 20-150 degreeC, More preferably, it is 30-100 degreeC. The heating time is preferably 3 to 60 minutes, more preferably 5 to 30 minutes.

  In order to further increase the mechanical strength of the resulting composite, a step for reinforcement such as a stretching step or a pressurizing step may be added after removing the solvent.

<Process (C)>
Step (C) is a step of combining the base material and the resin after removing the solvent.
(resin)
Examples of the resin used for compounding with CNF include thermoplastic resins and thermosetting resins. A thermoplastic resin is a resin whose plasticity is reversibly maintained when cooling and heating are repeated. Therefore, it can be softened by heating to exhibit plasticity and can be molded, and solidifies when cooled. Specific examples of the thermoplastic resin include, for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polytetrafluoroethylene, acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, acrylic resin, Examples thereof include polyamide, polyacetal, polyester, and modified polyphenylene ether. The resin may be either transparent or opaque, but is preferably a transparent resin from the viewpoint of making it possible to visually recognize colors, patterns, characters, and the like attached to the base material.

  A thermosetting resin is a resin that undergoes a reaction by heating a low molecular weight solid or liquid compound and cures irreversibly. Specific examples of the thermosetting resin include, for example, epoxy resins, phenol resins, melamine resins, urea resins, urethane resins, silicone resins, unsaturated polyester resins, diallyl phthalate resins, thermosetting polyimides, alkyd resins, and the like. In addition, resin may be used individually by 1 type and may be used in combination of 2 or more type.

  As the resin used for the composite, a thermosetting resin can be preferably used, and an unsaturated polyester resin, an epoxy resin, a polyamide resin, a phenol resin or an acrylic resin is preferable, and an epoxy resin is particularly preferable. The matrix in the fiber-resin composite may contain a conventionally known additive together with the resin. Examples of such additives include curing agents, colorants, antioxidants, polymerization initiators, flame retardants, antistatic agents, antifoaming agents, leveling agents, and inorganic fillers. The blending ratio of the additive can be appropriately selected within a range not impairing the effects of the present disclosure.

  There is no particular limitation on the method of combining the resin to which the CNF-attached substrate (hereinafter also referred to as “CNF-attached substrate”) and the resin are used. For example, a part or the whole of the CNF-attached substrate is impregnated with a liquid resin. By making it, the composite which has a CNF adhesion base material in a resin matrix is formed, and the method of hardening resin after that is mentioned.

  Only one CNF-adhering substrate may be used for compounding with the resin, but from the viewpoint of further increasing the strength and rigidity of the obtained fiber-resin composite, a plurality of CNF-adhering substrates are used. It is preferable to integrate the laminated body laminated with a resin. In the manufacturing method of the present disclosure, the resin enters the fine gaps of the base material, so that the plurality of base materials with CNF attached to the surface can be integrated with the resin.

  As a method for integrating the laminated body with resin, for example, a plurality of ones obtained by impregnating a liquid resin on one base material after applying and drying a CNF-containing liquid are prepared, and these are overlapped. A method of laminating the above substrates; a method of laminating a plurality of CNF-attached substrates to form a laminate, and then impregnating the laminate with a resin; a combination thereof, and the like.

  When the resin is cured, in order to further increase the strength and rigidity of the obtained composite, a curing process may be performed while compressing the plurality of laminated CNF-adhering substrates. By performing the compression operation, it becomes easy for the resin to uniformly flow into the fine gaps of the base material, and the formation of voids inside the molded body can be suppressed. When the fiber-resin composite is a molded body, it is molded into a target shape when the resin is cured. As a molding method, a commonly used method can be applied, and examples thereof include compression molding, injection molding, hollow molding, and vacuum molding. In the case of using a thermoplastic resin, as in the case of a thermosetting resin, a liquid resin impregnated in a CNF adhering substrate is cooled and cured while being compressed or the like according to a desired mold. Thus, a fiber-resin composite as a final product may be manufactured. Alternatively, an intermediate as a fiber-resin composite is prepared by impregnating a CNF adhering substrate with a liquid resin, and once cooled and cured, and this intermediate is heated and softened according to a desired mold. The fiber-resin composite as the final product may be produced by cooling and curing while compressing.

  According to the above method, a resin composite that is superior in strength and rigidity can be obtained by a simple operation such as reducing the thickness of the substrate to which CNF is adhered and increasing the number of laminated layers. In addition, there is an advantage that the resin composite obtained can be finely adjusted so as to have desired mechanical properties depending on the thickness of the base material and the number of layers, and a reinforced resin suitable for the application can be easily designed.

  In FIG. 1, one Embodiment of the manufacturing method of the fiber-resin composite of this indication is shown. In this embodiment, paper, woven fabric, or nonwoven fabric is used as the hydrophilic and porous substrate. First, in the process of step S11, a CNF-containing liquid is applied on the surface of the base sheet. Here, the CNF-containing liquid is applied only to one side of the base sheet. However, the CNF-containing liquid may be applied to both sides of the sheet. In the subsequent process of step S12, the solvent is completely removed from the substrate sheet coated with the CNF-containing liquid, and the substrate sheet is dried. In the present embodiment, a plurality of sheets (hereinafter also referred to as “CNF-attached sheets”) are produced.

  In the subsequent process of step S13, a laminated body in which a plurality of CNF-attached sheets are laminated is integrated with a resin. Here, a plurality of impregnated liquid resins are prepared from at least one of the CNF adhering surface and the CNF non-adhering surface of the CNF adhering sheet, and they are laminated. The resin is preferably impregnated from the CNF non-adhering surface of the CNF adhering sheet in that the resin can be filled in the holes of the base material without any gap. Thereafter, in the process of step S14, the resin is cured while compressing the laminate of the CNF-attached sheets. Thereby, a fiber-resin composite in which a plurality of laminated CNF-attached sheets are integrated so as to cover the entire sheet with a hard resin matrix is obtained.

  In FIG. 2, the schematic diagram of the fiber-resin composite 10 obtained by the manufacturing method of the said FIG. 1 is shown. The fiber-resin composite 10 includes a resin matrix 13 and a porous substrate 11 having cellulose nanofibers 12 attached to the surface thereof. The resin matrix 13 includes a plurality of (three in FIG. 2) base materials 11 stacked, and the resin matrix 13 contains CNF.

  The fiber-resin composite of the present disclosure can be applied to various uses. Specifically, for example, automobile members (for example, exterior parts such as bodies and bumpers, interior parts such as dashboards and panels), railway members, marine members (for example, hulls), aviation-related members, home appliances Materials (for example, casings), building materials (for example, wall materials, flooring materials, fittings, ducts, vibration control and seismic isolation materials), furniture materials, housing equipment (for example, unit baths and septic tanks), Examples include household items, household goods (for example, smartphone covers and stationery), sports / leisure items, medical members, containers / packaging members, and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
A 1% by weight cellulose nanofiber aqueous suspension was applied to one surface of a 10 cm × 5 cm Japanese paper with a spatula so as to have a thickness of 4 to 5 mm. Subsequently, the Japanese paper coated with the cellulose nanofiber aqueous suspension was placed on a hot plate heated to around 60 ° C. and dried by removing moisture to obtain a CNF-attached sheet having CNF attached to the surface of the Japanese paper. . The same operation as above was repeated to prepare two CNF-attached sheets. Each of the two CNF-attached sheets was impregnated with a mixture of an epoxy resin (prepolymer) and a curing agent from the back side on the CNF-attached side (surface on the non-CNF-attached side). Two CNF adhering sheets impregnated with the resin were superposed and placed in a mold, and the resin was cured by heating and compression at 30 ° C. and a surface pressure of 0.1 MPa. As a result, a fiber-resin composite having a thickness of about 1 to 2 mm having two CNF-attached sheets inside the resin matrix was obtained as a resin molded body.

[Comparative Example 1]
A resin molded body was produced in the same manner as in Example 1 except that the CNF-containing liquid was not applied to the Japanese paper and the Japanese paper was not dried.

  About the resin molding of Example 1 and Comparative Example 1, both bending strength (rigidity) was compared by bending a resin molding to the up-down direction with a bare hand. As a result, it was found that the sample of Example 1 was less bent than the sample of Comparative Example 1 and was excellent in rigidity.

[Examples 2 and 3]
Except for changing the number of laminated CNF-attached sheets to 5 and 10, respectively, resin molded bodies were produced by the same operation as in Example 1, and the rigidity was compared by the same method as described above. As a result, the greater the number of laminated CNF-attached sheets, the higher the rigidity of the resin molded body. From the above, it was found that according to the production method including the steps (A) to (C), the mechanical properties of the resin can be improved by a simple method using a general-purpose treatment.

  DESCRIPTION OF SYMBOLS 10 ... Fiber-resin composite, 11 ... Base material, 12 ... Cellulose nanofiber, 13 ... Resin matrix.

Claims (6)

A method for producing a fiber-resin composite, comprising the following steps (A) to (C).
(A) The process of apply | coating the liquid composition containing a cellulose nanofiber and a solvent to a hydrophilic and porous base material.
(B) The process of removing the said solvent from the said base material after apply | coating the said liquid composition.
(C) The process of combining the said base material after removing the said solvent, and resin.   The method for producing a fiber-resin composite according to claim 1, wherein the substrate is paper, woven fabric, or nonwoven fabric.   The method for producing a fiber-resin composite according to claim 1, wherein the resin is a thermosetting resin.   The said process (C) is a process of compounding by integrating the laminated body by which the said base material after removing the said solvent was laminated | stacked with the said resin. The manufacturing method of the fiber-resin composite of description. A fiber-resin composite in which cellulose nanofibers are contained in a resin matrix,
A fiber-resin composite comprising a porous substrate having the cellulose nanofibers attached to the surface thereof in the resin matrix.   The fiber-resin composite according to claim 5, wherein the substrate is paper, woven fabric, or nonwoven fabric.

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