JP2017106130A - Carbon short fiber unwoven fabric and composite body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon short fiber unwoven fabric excellent in processability without damaging dispersibility of a carbon short fiber during heating or heating pressing treatment when manufacturing a carbon fiber reinforced thermoplastic resin composite body and during hot press processing for manufacturing a molded article from the carbon fiber reinforced thermoplastic resin composite body and a composite body by laminating the carbon short fiber unwoven fabric and a thermoplastic resin film.SOLUTION: There is provided a carbon short fiber unwoven fabric containing a carbon short fiber, a thermoplastic resin fiber and a fibrillation cellulose fiber and a composite body by laminating the carbon short fiber unwoven fabric and a thermoplastic resin film.SELECTED DRAWING: None

Description

  The present invention relates to a carbon short fiber nonwoven fabric and a composite formed by laminating a carbon short fiber nonwoven fabric and a thermoplastic resin film.

  Carbon fiber reinforced resin composite formed by combining carbon fiber and resin has strength and elastic modulus comparable to metal materials, but has a smaller specific gravity than metal materials, so the weight of members can be reduced, In addition, it has no rust problem and is resistant to acids and alkalis, so it is used in electronic equipment materials, electrical equipment materials, civil engineering materials, building materials, automotive materials, aircraft materials, and various manufacturing industries. Used in manufacturing parts such as robots and rolls.

  The carbon fiber reinforced resin composite is a composite in which a carbon fiber fabric such as a long fiber woven fabric, a spread fabric, a unidirectional web, and a short fiber nonwoven fabric is combined with a resin such as a thermosetting resin or a thermoplastic resin. It is. The most common carbon fiber reinforced resin composite is a composite of a long fiber nonwoven fabric and a thermosetting resin, but it is difficult to design, is not a homogeneous material, has a long molding time, is expensive, etc. There was a problem.

  As a carbon fiber reinforced resin composite that has solved these problems, a carbon fiber reinforced thermoplastic resin composite in which a nonwoven fabric containing carbon short fibers (carbon short fiber nonwoven fabric) and a thermoplastic resin is combined has been proposed ( For example, refer to Patent Documents 1 to 6). By using a carbon short fiber nonwoven fabric, homogeneity is enhanced, and by using a thermoplastic resin, easy design and processability are obtained, it is inexpensive, and recycling is possible.

  Carbon fiber reinforced thermoplastic resin composites include composites of carbon short fiber nonwoven fabrics containing carbon short fibers and thermoplastic resin powders or fibers, thermoplastic resins or thermoplastic resins melted in carbon short fiber nonwoven fabrics. Known are composites formed by combining the above solutions and dispersions, composites formed by laminating short carbon fiber nonwoven fabrics and thermoplastic resin films, and the like. When manufacturing these carbon fiber reinforced thermoplastic resin composites, a heating or heating and pressing treatment is performed. In addition, the carbon fiber reinforced thermoplastic resin composite is formed into a molded product by being subjected to heat and pressure processing (hot press processing) as it is or in combination with other materials. Conventional carbon short fiber nonwoven fabrics are carbon short fiber nonwoven fabrics containing carbon short fibers and thermoplastic resin powders or fibers, carbon short fiber nonwoven fabrics containing only carbon short fibers, and the like. There has been a problem that the thermoplastic resin in the carbon short fiber nonwoven fabric flows due to pressure processing or the like, the dispersibility of the carbon short fibers is lost, and a uniform carbon fiber reinforced thermoplastic resin composite or molded product cannot be obtained. In particular, in a composite formed by laminating a short carbon fiber nonwoven fabric and a thermoplastic resin film, this problem occurs when the melting point of the thermoplastic resin film is higher than the melting point of the thermoplastic resin in the short carbon fiber nonwoven fabric. It was easy to occur.

JP 2013-208791 A JP 2013-202891 A JP 2011-21303 A JP 2004-43985 A JP 2011-194852 A JP 2014-224333 A

  An object of the present invention is to disperse short carbon fibers during heating or heat-pressure treatment during the production of a carbon fiber reinforced thermoplastic resin composite and during hot press processing for producing a molded product from the carbon fiber reinforced thermoplastic resin composite. It is to provide a composite comprising a carbon short fiber nonwoven fabric excellent in processability and a laminate of the carbon short fiber nonwoven fabric and a thermoplastic resin film.

  The above problems can be solved by the following invention.

(1) A carbon short fiber nonwoven fabric comprising carbon short fibers, thermoplastic resin fibers, and fibrillated cellulose fibers.

(2) The short carbon fiber nonwoven fabric according to (1), wherein the fibrillated cellulose fiber is 2 to 20% by mass with respect to all the fibers in the nonwoven fabric.

(3) A composite formed by laminating the short carbon fiber nonwoven fabric according to (1) or (2) and a thermoplastic resin film.

  According to the present invention, the short carbon fibers are dispersed at the time of heating or heat pressure treatment at the time of producing the carbon fiber reinforced thermoplastic resin composite and at the time of hot press processing for producing a molded product from the carbon fiber reinforced thermoplastic resin composite. A carbon short fiber nonwoven fabric excellent in processability that does not lose its properties can be obtained. Since the composite formed by laminating the carbon short fiber nonwoven fabric and the thermoplastic resin film of the present invention maintains the uniformity of the carbon short fibers of the carbon short fiber nonwoven fabric in heating or heat-pressing treatment and heat press processing. A uniform carbon fiber reinforced thermoplastic resin composite can be obtained.

  The carbon short fiber nonwoven fabric of the present invention is a nonwoven fabric comprising carbon short fibers, thermoplastic resin fibers, and fibrillated cellulose fibers.

  Examples of the carbon short fibers include PAN-based carbon short fibers using polyacrylonitrile as a raw material and pitch-based carbon short fibers using pitch as a raw material. The fiber diameter of the short carbon fibers is preferably 3 to 20 μm, and more preferably 5 to 15 μm. Moreover, it is preferable that the fiber length of a carbon short fiber is 1-30 mm, and it is more preferable that it is 3-12 mm.

  The thermoplastic resin fiber is added to prevent the carbon short fibers from being detached from the nonwoven fabric and to impart strength to the carbon short fiber nonwoven fabric. Thermoplastic resin fibers include non-crystalline polyvinyl alcohol (vinylon) short fibers, polyester core-sheath fibers whose surfaces have a low melting point, unstretched polyester fibers, polycarbonate (PC) fibers, polyolefin fibers, and low melting points on the surface. Polyolefin core-sheath fibers that have been formed, polyolefin fibers whose surface is made of acid-modified polyolefin, aliphatic polyamide fibers, unstretched polyphenylene sulfide fibers, polyether ketone ketone fibers, and the like.

  The melting point of the thermoplastic resin fiber is preferably 60 to 260 ° C, more preferably 60 to 230 ° C, still more preferably 60 to 180 ° C, and particularly preferably 80 to 160 ° C. When the melting point of the thermoplastic resin fiber is within this temperature range, the heat treatment in the nonwoven fabric manufacturing process imparts binding properties and imparts strength to the carbon short fiber nonwoven fabric.

  The fiber diameter of the thermoplastic resin fiber is preferably 3 to 40 μm, and more preferably 5 to 20 μm. Moreover, it is preferable that the fiber length of a thermoplastic resin fiber is 1-20 mm, and it is more preferable that it is 3-12 mm.

  In the short carbon fiber nonwoven fabric of the present invention, in addition to the short carbon fiber, by using the fibrillated cellulose fiber and the thermoplastic resin fiber in combination, at the time of heating or heat press treatment and hot press processing, It is possible to obtain a carbon short fiber non-woven fabric excellent in processability that does not lose dispersibility.

  The fibrillated cellulose fiber is not a film shape, but a fiber shape having a portion finely divided mainly in a direction parallel to the fiber axis, and at least a part thereof is a cellulose fiber having a fiber diameter of 1 μm or less. The aspect ratio of length to width is preferably 20 to 100,000. Moreover, it is preferable that modified drainage is 0-770 ml, and it is more preferable that it is 0-600 ml. Furthermore, the mass average fiber length is preferably 0.1 to 2 mm. The modified freeness in the present invention is that a wire mesh (made by PULP AND PAPER RESEARCH INSTITUTE OF CANADA) having a wire diameter of 0.14 mm and an aperture of 0.18 mm is used as a sieve plate, and the sample concentration is 0.1%. It is a freeness measured in accordance with JIS P8121 (1995 edition).

  The degree of fibrillation of fibrillated cellulose can also be grasped by the dispersion viscosity at a low concentration. As the viscosity increases, fibrillation progresses, but if the viscosity is too high, the fiber length may be too short. The viscosity of the fibrillated cellulose dispersion (concentration 0.5% by mass) is 50 to 200 cp when a B-type viscometer (rotor No. 2, rotor rotation speed 60 rpm, temperature 23 to 25 ° C.) is used. Is preferred.

  If the content of the fibrillated cellulose fiber is too small, the dispersibility of the short carbon fibers may be lost if the heating temperature is too high during the heating or heating / pressing treatment and during the hot press processing. On the other hand, if the content of fibrillated cellulose fibers is too large, the fibrillated celluloses form a dense structure after being dehydrated during the production of the nonwoven fabric, forming a film, and into the carbon short fiber nonwoven fabric during hot press processing. It becomes difficult for the thermoplastic resin film to enter. Moreover, a void may be seen in the composite body which laminates | stacks a carbon short fiber nonwoven fabric and a thermoplastic resin fiber. The content of the fibrillated cellulose fiber is preferably 2 to 20% by mass, more preferably 2 to 15% by mass, and 5 to 15% by mass with respect to all the fibers in the nonwoven fabric. Further preferred.

  Cellulose materials for fibrillated cellulose fibers include vegetable pulp, solvent-spun cellulose, semi-synthetic cellulose and the like. Examples of plant pulp include woody pulp such as kraft pulp (KP), dissolved pulp (DP), and dissolved kraft pulp (DKP) using hardwood (L material) and softwood (N material). Moreover, non-woody pulps such as straw, hemp, cotton, and cotton linter are also included. As a commercially available product, serisch (registered trademark, manufactured by Daicel FineChem) can be mentioned. The crystal form of the cellulose material includes type I, type II, type III, type IV, and the like. From the viewpoint of heat resistance, type I and type II are preferable, and type I is more preferable. As the type I cellulose material source, non-woody pulp such as cotton pulp, cotton linter pulp, hemp pulp, kenaf pulp, etc., which is obtained from pulp with reduced lignin and hemicellulose content, L material or N material, And wood pulps such as KP, DP and DKP with a reduced content of hemicellulose. In particular, a cotton material is preferable.

  To obtain fibrillated cellulose, the cellulosic material is first dispersed in water and mechanically ground. And the fiber of a cellulose material is defibrated and a microfibril is formed. Examples of the device for defibrating the cellulose material include a disc refiner, a stone mill type grinder, a high-pressure homogenizer, a ball mill, an underwater counter collision method device, and an ultrasonic crusher. These devices can be used in appropriate combination.

  The content ratio (mass basis) of the short carbon fiber and the thermoplastic resin fiber is preferably 8.5: 0.5 to 5: 4, more preferably 8: 1 to 6: 3. . By setting the content ratio of the short carbon fiber and the thermoplastic resin within the above range, the strength of the short carbon fiber nonwoven fabric, the composite, and the molded product can be increased.

  The short carbon fiber nonwoven fabric in the present invention is preferably a wet papermaking nonwoven fabric produced by a wet papermaking method. In the wet papermaking method, first, short carbon fibers, thermoplastic resin fibers, and fibrillated cellulose fibers are uniformly dispersed in water, and then passed through processes such as screen (removal of foreign matters, lumps, etc.), and the final fiber concentration is reduced to 0. The slurry adjusted to 0.01 to 0.50% by mass is made by a paper machine to obtain a wet paper. In order to make the dispersibility of the fibers uniform, chemicals such as dispersants, antifoaming agents, hydrophilic agents, antistatic agents, polymer thickeners, mold release agents, antibacterial agents, bactericides, etc. may be added during the process. is there.

  As the paper machine, for example, a paper machine using a paper net such as a long net, a circular net, or an inclined wire alone, or a combination paper machine in which two or more paper nets of the same type or different types are installed online is used. be able to. In addition, when the nonwoven fabric has a multilayer structure of two or more layers, a paper making method in which wet papers made by each paper machine are laminated, or after one layer is formed, fibers are dispersed on the layer. The nonwoven fabric can be produced by a casting method in which the slurry is cast to form a laminate. When casting the slurry in which the fibers are dispersed, the previously formed layer may be either a wet paper state or a dry state. In addition, two or more dry layers can be heat-sealed to form a multilayered nonwoven fabric.

  In the present invention, when the nonwoven fabric has a multilayer structure, it may have a multilayer structure in which the fiber blend of each layer is the same, or may have a multilayer structure in which the fiber blend of each layer is different. In the case of a multilayer structure, since the fiber concentration of the slurry can be lowered by lowering the basis weight of each layer, the formation of the nonwoven fabric is improved, and as a result, the uniformity of the formation of the nonwoven fabric is improved. Moreover, even when the formation of each layer is non-uniform | heterogenous, it can compensate by laminating | stacking. Furthermore, the papermaking speed can be increased, and the operability can be improved.

  In the wet papermaking method, a wet papermaking nonwoven fabric in sheet form is obtained by drying wet paper produced by a papermaking net with a Yankee dryer, air dryer, cylinder dryer, suction drum dryer, infrared dryer, or the like. When the wet paper is dried, it is brought into close contact with a hot roll such as a Yankee dryer and dried by heat and pressure to improve the smoothness of the contacted surface. Hot-pressure drying means that wet paper is pressed against a hot roll with a touch roll or the like and dried. The surface temperature of the hot roll is preferably 100 to 180 ° C, more preferably 100 to 160 ° C, and still more preferably 110 to 160 ° C. The pressure is preferably 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

  The composite of the present invention is a composite formed by laminating a carbon short fiber nonwoven fabric and a thermoplastic resin film. The composite can be produced by superposing a carbon short fiber nonwoven fabric and a thermoplastic resin film, and subjecting them to heat treatment or heat pressure treatment. A molded product can be produced by subjecting this composite to hot pressing (hot pressing).

  Examples of the thermoplastic resin of the thermoplastic resin film include polyolefin resins such as polyethylene resin, polypropylene resin and polybutylene resin; methacrylic resins such as polymethyl methacrylate resin; polystyrene resins such as polystyrene resin, ABS resin and AS resin; polyethylene Polyester resins such as terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene terephthalate resin, polyethylene naphthalate (PEN) resin, poly 1,4-cyclohexyldimethylene terephthalate (PCT) resin; 6-nylon Polyamide (PA) resin such as resin, 6,6-nylon resin; polyvinyl chloride resin; polyoxymethylene (POM) resin; polycarbonate (PC) resin; polyphenylene sulfide (PP Modified polyphenylene ether (PPE) resin; polyetherimide (PEI) resin; polysulfone (PSF) resin; polyethersulfone (PES) resin; polyketone resin; polyarylate (PAR) resin; polyether nitrile (PEN) resin Polyetherketone (PEK) resin; Polyetheretherketone (PEEK) resin; Polyetherketoneketone (PEKK) resin; Polyimide (PI) resin; Polyamideimide (PAI) resin; Fluorine (F) resin; Liquid crystalline polymer resin: polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, polyisoprene, or fluorine-based thermoplastic elastomer; or a copolymer resin or modified resin thereof; ionomer Resins. Among these resins, one type or two or more types can be used. From the viewpoint of combustibility, PC, PPS, PEEK, PEI and the like are preferable.

  Examples of the ionomer resin include an ethylene ionomer resin obtained by neutralizing a part of the carboxyl group of the ethylene-unsaturated carboxylic acid copolymer resin with a metal ion. A product obtained by neutralizing 10 mol% or more, preferably 10 to 90 mol%, of a carboxyl group with a metal ion is used. Examples of the metal ions include polyvalent metal ions such as alkali metals such as lithium and sodium, and alkaline earth metals such as zinc, magnesium and calcium.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples. In the examples, all parts and percentages are by mass unless otherwise specified.

(Production of fibrillated cellulose)
The linter pulp (mass average fiber length: 1.2 mm) was subjected to a grinding treatment using a mascolloider (registered trademark, apparatus name: MKZA12) manufactured by Masuko Sangyo Co., Ltd. to produce fibrillated cellulose. The viscosity of the fibrillated cellulose dispersion (concentration: 0.5 mass%) was measured with a B-type viscometer (rotor No. 2, rotor rotational speed 60 rpm, temperature 23 to 25 ° C.), and was 80 cp.

(Short carbon fiber)
Carbon short fiber: Fiber diameter 7μm, fiber length 6mm

(Thermoplastic fiber)
Thermoplastic resin fiber: Fiber diameter 4.5 μm, fiber length 3 mm, unstretched PET fiber

(Nonwoven fabric manufacturing)
With the fiber blending ratio shown in Table 1, the fiber is dispersed in water at a dispersion concentration of 0.2 mass% for 5 minutes to form a 25 cm × 25 cm size wet paper with a 90 mesh metal wire. It dried with the Yankee dryer of 0 degreeC, and obtained the carbon short fiber nonwoven fabric of basic weight 27g / m < ² >.

(Manufacture of complex)
The front and back of the carbon short fiber nonwoven fabric produced in the examples and comparative examples were sandwiched between thermoplastic resin (PEEK) films, heated and pressed with a hot press machine at a temperature of 360 ° C., 10 MPa for 5 minutes, and then cooled to room temperature. .

  The following evaluation was performed on the carbon short fiber nonwoven fabrics and composites produced in Examples and Comparative Examples, and the results are shown in Table 2.

(State when manufacturing non-woven fabric)
On the surface of the metal wire, the dispersibility of the carbon short fibers was confirmed, and the presence or absence of detachment of the carbon short fibers until the wet paper formed with the metal wires was dried with a Yankee dryer was observed (before drying). . In addition, the presence or absence of carbon short fibers after drying with a Yankee dryer was also confirmed (after drying).

(Composite state)
After the composite was formed with a hot press, the short carbon fiber flow (flow) was generated around the short carbon nonwoven fabric, and the presence or absence of warpage of the composite and the occurrence of voids were observed.

  In the carbon short fiber nonwoven fabric of Comparative Example 1 containing carbon short fibers and thermoplastic resin fibers, when the state of the composite was observed, a flow of carbon short fibers was generated around the nonwoven fabric. On the other hand, since the short carbon fiber nonwoven fabrics of Examples 1 to 9 contain short carbon fibers, thermoplastic resin fibers, and fibrillated cellulose fibers, the flow of short carbon fibers was suppressed.

  When Examples 1-9 are compared, in the carbon short fiber nonwoven fabrics of Example 2 and Example 3 in which the content of fibrillated cellulose fibers is less than 3% by mass based on the total fibers of the nonwoven fabric, the state of the composite is When observed, the flow of short carbon fibers was somewhat, and the nonwoven fabric before drying was easy to break, but it was at a usable level. Further, in the carbon short fiber nonwoven fabric of Example 6 in which the content of fibrillated cellulose fibers is more than 15% by mass based on the total fibers of the nonwoven fabric, the state of the composite was observed, and there was no flow of carbon short fibers. However, although it was at a usable level, a small amount of void was confirmed.

  When Examples 1 to 9 were compared, as the content of the thermoplastic resin fibers decreased, the carbon short fibers after drying slightly desorbed, but were at a usable level. Further, when the content of the thermoplastic resin fiber is increased, detachment of the short carbon fiber after drying is suppressed, but although it is at a usable level, the composite is easily warped.

  From the comparison between Example 4 and Comparative Example 2, it was confirmed that the cellulose fibers were fibrillated to suppress the detachment of the carbon short fibers, and the flow of the carbon short fibers did not occur in the composite.

  In the carbon short fiber nonwoven fabric of Comparative Example 3 containing carbon short fibers and fibrillated cellulose fibers, there was no flow of carbon short fibers in the composite, but the carbon short fibers were removed both before and after drying. There was much separation, and it was a useless level.

  The carbon short fiber nonwoven fabric and composite of the present invention can be used for manufacturing parts such as electronic equipment materials, electrical equipment materials, civil engineering materials, building materials, automobile materials, aircraft materials, robots and rolls used in various manufacturing industries, etc. It is.

Claims (3)

  A carbon short fiber nonwoven fabric comprising carbon short fibers, thermoplastic resin fibers, and fibrillated cellulose fibers.   2. The carbon short fiber nonwoven fabric according to claim 1, wherein the fibrillated cellulose fiber is 2 to 20% by mass with respect to all the fibers in the nonwoven fabric.   A composite formed by laminating the carbon short fiber nonwoven fabric according to claim 1 or 2 and a thermoplastic resin film.