JP2018012312A - Carbon short fiber reinforcement film and method for producing carbon short fiber reinforcement structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon short fiber reinforcement film excellent in productivity and workability and a method for producing a carbon short fiber reinforcement structure.SOLUTION: There are provided a method for producing a carbon short fiber reinforcement film which includes heating and pressurizing a laminate of a non-woven fabric containing a carbon short fiber and a thermoplastic film from both surfaces of the laminate with a roll to integrate the non-woven fabric and the thermoplastic film or a method for producing a carbon short fiber reinforcement structure which includes sticking a plurality of the carbon short fiber reinforcement films, where the non-woven fabric contains microfibrillated cellulose.SELECTED DRAWING: None

Description

  The present invention relates to a carbon short fiber reinforced film and a method for producing a carbon short fiber reinforced structure.

  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, there is no problem of rusting like metal plates such as iron, and since it has the property of being resistant to acids and alkalis, electronic device materials, electrical device materials, civil engineering materials, building materials, automotive materials, Used in aircraft materials, manufacturing parts such as robots and rolls used in various manufacturing industries.

  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 woven 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 solves these problems, a method (for example, Patent Document 1) in which short carbon fibers are kneaded with a thermoplastic resin and used as a material for injection molding as a composite is known. The fibers are prone to breakage during kneading, and the fiber length is shortened, so that sufficient characteristics cannot be obtained, and it is difficult to obtain a film-like structure of several hundred microns or less. On the other hand, a method has been proposed in which a non-woven fabric containing carbon short fibers (carbon short fiber non-woven fabric) is prepared in advance, and the carbon short fiber non-woven fabric and a thermoplastic resin are combined by a hot press molding method (patent). Since the processing method is based on single wafers, there is a problem that productivity is inferior. Moreover, the subject that it was not able to handle like the film excellent in the designability suitable for the vacuum forming method etc. occurred.

JP 07-156146 A JP 2013-208791 A JP 2013-202891 A JP 2011-21303 A JP 2004-43985 A JP 2011-194852 A JP 2014-224333 A

  The subject of this invention is providing the manufacturing method of the carbon short fiber reinforced film and carbon short fiber reinforced structure excellent in productivity and workability.

  The above problems can be solved by the following invention.

(1) A carbon short fiber reinforced film in which the nonwoven fabric and the thermoplastic film are integrated by performing heat and pressure treatment with rolls from both sides of the laminate of the nonwoven fabric and the thermoplastic film containing carbon short fibers. In the manufacturing method, the nonwoven fabric contains microfibrillated cellulose, The manufacturing method of the carbon short fiber reinforced film characterized by the above-mentioned.

(2) A carbon short fiber reinforced film is obtained by integrating the nonwoven fabric and the thermoplastic film by heat and pressure treatment with rolls from both sides of the laminate of the nonwoven fabric and the thermoplastic film containing carbon short fibers. A method for producing a carbon short fiber reinforced structure, wherein the nonwoven fabric contains microfibrillated cellulose in a method for producing a carbon short fiber reinforced structure in which a plurality of carbon short fiber reinforced films are bonded together Method.

  According to the present invention, in order to obtain a continuous carbon short fiber reinforced film, by laminating a plurality of carbon short fiber reinforced films as a single layer as it is, without impairing the fiber length of the carbon short fiber, A carbon short fiber reinforced structure excellent in predetermined thickness, physical properties and processability can be obtained.

  As the nonwoven fabric (carbon short fiber nonwoven fabric) containing carbon short fibers in the present invention, a wet nonwoven fabric or a dry nonwoven fabric produced by a wet method or a dry method can be used. And a carbon short fiber nonwoven fabric can contain a thermoplastic short fiber, a thermoplastic emulsion, etc. as a binder. With this binder, strength can be easily imparted to the carbon short fiber nonwoven fabric.

  Examples of short carbon fibers include PAN-based carbon fibers made from polyacrylonitrile and pitch-based carbon short fibers made from pitches. The fiber diameter of the short carbon fibers is preferably 3 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. In addition, the fiber length of the short carbon fibers is preferably 3 mm or more and 40 mm or less in the case of a wet nonwoven fabric, and is preferably 20 mm or more and 120 mm or less in the case of a dry nonwoven fabric.

  In the present invention, recycled carbon short fibers can be used as the carbon short fibers. Commonly used carbon fiber prepregs are impregnated with epoxy resins such as aircraft and sports, and removal of the resin is indispensable for recycling the carbon fibers. As a removal method, a method of sintering and removing in an inert gas such as argon or nitrogen or in water vapor is known. In particular, the sintering method using superheated steam is an effective method that is inexpensive and does not pollute the environment because the superheated steam returns to water when heat is taken away in the atmosphere. Structures made of carbon fiber prepreg have various forms such as an angle ply laminate, and are usually cut to a certain size, then sintered, removed from the thermosetting resin, and cut. In this case, recycled carbon short fibers having different fiber lengths are obtained.

  A method for producing a dry nonwoven fabric will be described. First, carbon short fibers defibrated in the atmosphere are spread on a web and dispersed by the card method or the like. At this time, when the thermoplastic short fibers are used in combination as the binder, the fibers are defibrated and dispersed together with the carbon short fibers and subjected to heat treatment. Moreover, when using a thermoplastic emulsion together as a binder, a thermoplastic emulsion is provided to the web of a short carbon fiber, and it heat-processes. The binder is used to give strength and make a dry nonwoven fabric.

  The manufacturing method of a wet nonwoven fabric is demonstrated. First, short carbon fibers are defibrated in water, and then rolled up with a papermaking net such as a circular net, short net, long net, or slanted short net, and dried, heat treated, etc. to obtain a wet nonwoven fabric. And like a dry type nonwoven fabric, it gives strength with binders, such as a thermoplastic short fiber and a thermoplastic emulsion, and makes it a wet nonwoven fabric.

  In the present invention, any of a dry nonwoven fabric and a wet nonwoven fabric can be used. However, when a thin nonwoven fabric is used, it is preferable to use a wet nonwoven fabric having excellent fiber dispersibility. Moreover, when using a thick nonwoven fabric, it is preferable to use a dry nonwoven fabric which is simple for the production method and advantageous for providing thickness.

  Examples of thermoplastic short fibers include amorphous polyvinyl alcohol (vinylon) short fibers, polyester core-sheath short fibers whose surfaces have a low melting point, unstretched polyester short fibers, polycarbonate (PC) short fibers, polyolefin short fibers, Polyolefin core-sheath short fiber whose surface has a low melting point, polyolefin short fiber whose surface is made of acid-modified polyolefin, aliphatic polyamide short fiber, unstretched polyphenylene sulfide short fiber, polyether ketone ketone short fiber, etc. Resin short fibers may be mentioned.

  As the thermoplastic emulsion, an emulsion of a resin having thermoplasticity such as an acrylic resin, a styrene acrylic resin, an acid-modified polyolefin, a polyolefin containing an acid-modified α-olefin, an ionomer, or a chlorinated polyolefin is used.

  The melting point of the thermoplastic resin is preferably 60 ° C. or higher and 260 ° C. or lower, more preferably 60 ° C. or higher and 230 ° C. or lower, further preferably 60 ° C. or higher and 180 ° C. or lower, and more preferably 80 ° C. or higher and 160 ° C. or lower. It is particularly preferable that the temperature is not higher than ° C.

  The fiber diameter of the thermoplastic short fiber is preferably 3 μm or more and 40 μm or less, and more preferably 5 μm or more and 20 μm or less. Further, the fiber length of the thermoplastic short fibers is preferably 1 mm or more and 120 mm or less, and more preferably 3 mm or more and 40 mm or less.

  The content ratio of the short carbon fibers and the binder (based on mass basis, short carbon fibers: binder) is preferably 8.5: 0.0 to 5: 4, and 8.5: 0.5 to 5: 4 is more preferable, and 8: 1 to 6: 3 is still more preferable. Although the binder is not an essential component, the strength of the carbon short fiber reinforced film and the carbon short fiber reinforced structure can be easily increased by setting the content ratio of the short carbon fiber and the binder within the above range. .

  In the method for producing a carbon short fiber reinforced film of the present invention, the nonwoven fabric and the thermoplastic film are integrated by subjecting the laminate of the carbon short fiber nonwoven fabric and the thermoplastic film to heat and pressure treatment with rolls. Further, in the method for producing a carbon short fiber reinforced structure of the present invention, the nonwoven fabric and the thermoplastic film are integrated by performing heat and pressure treatment with rolls from both sides of the laminate of the carbon short fiber nonwoven fabric and the thermoplastic film. To produce a carbon short fiber reinforced film, and a plurality of the carbon short fiber reinforced films are bonded together. In these steps, for example, when PEEK is used, since the melting point of PEEK is around 350 ° C., a superheater of 400 ° C. or higher is required. In the present invention, since the carbon short fiber nonwoven fabric contains microfibrillated cellulose, the dispersibility of the carbon short fibers does not collapse in the carbon short fiber nonwoven fabric during the heat and pressure treatment or when the carbon short fiber reinforced film is bonded. The short carbon fiber does not break. As a result, a continuous carbon short fiber reinforced film can be obtained with high productivity. The carbon short fiber reinforced film obtained in the present invention can be used as a carbon short fiber reinforced structure with a single layer. Furthermore, a carbon short fiber reinforced structure can also be obtained by laminating a plurality of carbon short fiber reinforced films. In the present invention, by containing microfibrillated cellulose, a carbon short fiber reinforced structure excellent in predetermined thickness, physical properties and processability is obtained without impairing the fiber length of the carbon short fiber even at the time of bonding. be able to.

  The microfibrillated cellulose 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. Further, the modified freeness is preferably from 0 ml to 770 ml, more preferably from 0 ml to 600 ml. Furthermore, the mass average fiber length is preferably 0.1 mm or more and 2 mm or less. 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 microfibrillated 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. When the viscosity of the microfibrillated cellulose dispersion (concentration 0.5% by mass) is a B-type viscometer (rotor No. 2, rotor rotational speed 60 rpm, temperature 23 ° C. or higher and 25 ° C. or lower), 50 cp or more and 200 cp The following is preferable.

  If the content of the microfibrillated cellulose fiber is too small, the dispersibility of the carbon short fiber may be lost when the heating temperature is too high during the production of the carbon short fiber reinforced film or the carbon short fiber reinforced structure. is there. Conversely, if the content of the microfibrillated cellulose fiber is too large, the microfibrillated cellulose forms a dense structure at the time of carbon short fiber nonwoven fabric production, and becomes a film, and at the time of carbon short fiber reinforced film production or carbon At the time of manufacturing the short fiber reinforced structure, it becomes difficult for the thermoplastic film to enter the carbon short fiber nonwoven fabric. In addition, voids may be seen in the short carbon fiber reinforced film. The content of the microfibrillated cellulose is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less with respect to all the fibers in the short carbon fiber nonwoven fabric. preferable.

  Cellulose materials for microfibrillated cellulose 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.

  In order to obtain microfibrillated 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.

  In the method for producing a carbon short fiber reinforced film of the present invention, a carbon short fiber reinforced film is produced by laminating and integrating a carbon short fiber nonwoven fabric and a thermoplastic film.

  The thermoplastic resin of the thermoplastic film includes polyolefin resins such as polyethylene resin, polypropylene (PP) resin and polybutylene resin; methacrylic resins such as polymethyl methacrylate resin; polystyrene resins such as polystyrene resin, ABS resin and AS resin. Polyester resins such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene terephthalate resin, polyethylene naphthalate (PEN) resin, poly 1,4-cyclohexyldimethylene terephthalate (PCT) resin; 6 -Polyamide (PA) resin such as nylon resin and 6,6-nylon resin; polyvinyl chloride resin; polyoxymethylene (POM) resin; polycarbonate (PC) resin; polyphenylene sulfide ( PS) resin; modified polyphenylene ether (PPE) resin; polyetherimide (PEI) resin; polysulfone (PSF) resin; polyethersulfone (PES) resin; polyketone resin; polyarylate (PAR) resin; polyether nitrile (PEN) Polyetherketone (PEK) resin; Polyetheretherketone (PEEK) resin; Polyetherketoneketone (PEKK) resin; Polyimide (PI) resin; Polyamideimide (PAI) resin; Fluorine (F) resin; Liquid crystalline polyester resin Liquid crystal polymer resins such as polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, polyisoprene or fluorine, etc .; or copolymer resins and modified resins thereof; Mer 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 mol% or more and 90 mol% or less of the 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.

  The carbon short fiber nonwoven fabric and the thermoplastic film are continuously heated and pressurized from both sides to become a carbon short fiber reinforced film. The roll method is excellent as a method of continuously heating and pressurizing. As the heating temperature, a temperature around the melting point of the thermoplastic film is appropriate, but attention should be paid to temperature changes or fluctuations during operation or in a pressurized place. Or the thermoplastic film is torn or the permeability of the thermoplastic film into the carbon short fiber nonwoven fabric is uneven. Therefore, the temperature fluctuation is preferably within 1 ° C, more preferably within 0.5 ° C. . As the pressurization, the linear pressure is preferably 10 N / mm or more and 600 N / mm or less. The speed is preferably 1 m / min or more and 100 m / min or less, and more preferably 3 m / min or more and 40 m / min or less. These conditions need to be appropriately adjusted depending on the material to be selected.

  The rolls are arranged in pairs on both sides of the laminate, but a single pair or a plurality of pairs may be used. Moreover, about the super engineering plastics-type thermoplastic film, the apparatus for preheating can be provided. As a laminate, a laminate composed of one layer of carbon short fiber nonwoven fabric and one layer of thermoplastic film, a laminate in which thermoplastic films are arranged on both sides of one layer of carbon short fiber nonwoven fabric, and one layer of thermoplastic film Laminated body in which carbon short fiber nonwoven fabrics are arranged on both sides, a laminated body in which a plurality of carbon short fiber nonwoven fabrics and a plurality of thermoplastic films are alternately arranged, a laminate in which a plurality of carbon short fiber nonwoven fabrics and a plurality of thermoplastic films are randomly arranged Examples include the body. However, if the produced short carbon fiber reinforced film is too thick, it is difficult to wind it into a roll. Therefore, the thickness of the short carbon fiber reinforced film is preferably 20 μm or more and 500 μm or less, preferably 30 μm or more. More preferably, it is 250 μm or less.

  As the roll, since the surface temperature needs to be maintained with high accuracy in the roll axis direction, a jacket chamber having a heat pipe function and an electromagnetic induction heating method capable of forming a multilayer heating layer in the roll axis direction are used. It is preferable to use a combined roll. As such a roll, Tokuden's induction heating jacket roll (registered trademark) is excellent in continuous production, and in the case of batch or semi-batch production, induction heating jacket roll (registered trademark). The induction heating jacket plate manufactured by Tokuden Co., Ltd., which has the same principle as (1), is excellent.

  The carbon short fiber reinforced film obtained in the present invention can be used as a carbon short fiber reinforced structure with a single layer. Furthermore, a carbon short fiber reinforced structure can also be obtained by laminating a plurality of carbon short fiber reinforced films. The short carbon fiber reinforced film obtained in the present invention can be cut and used. For the bonding, a molding process such as hot press molding or vacuum molding can be used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples. All parts and percentages in the examples are based on mass unless otherwise specified.

(Preparation of microfibrillated cellulose)
The linter pulp (mass average fiber length: 1.2 mm) was subjected to a grinding treatment using a mass colloider (registered trademark, apparatus name: MKZA12) manufactured by Masuko Sangyo Co., Ltd., to produce microfibrillated cellulose. Furthermore, it processed 4 times at 50 Mpa using the high pressure homogenizer (MC2 made from BOS). The viscosity of the microfibrillated cellulose dispersion (concentration: 0.5% by mass) was measured with a B-type viscometer (rotor No. 2, rotor rotational speed 60 rpm, temperature 23 ° C. or higher and 25 ° C. or lower). It was.

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

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

<Examples 1-4 and Comparative Example 1>
(Manufacture of carbon short fiber nonwoven fabric)
With the fiber blending ratio shown in Table 1, the fiber was dispersed in water for 5 minutes at a dispersion concentration of 0.2% by mass, and then spun at a speed of 3 m / min with a 90 mesh circular paper machine. The carbon short fiber non-woven fabric having a basis weight of 25 g / m ² , a thickness of 150 μm, a width of 40 cm, and a length of 100 m was prepared and wound into a roll.

(Manufacture of carbon short fiber reinforced film 1)
A carbon short fiber nonwoven fabric and a thermoplastic film (resin: PEEK) 100 μm were sandwiched between roll pairs heated to 360 ° C. at a speed of 5 m / min and a linear pressure of 150 N / mm to produce a carbon short fiber reinforced film having a thickness of 115 μm.

(Manufacture of carbon short fiber reinforced film 2)
A roll of carbon short fiber nonwoven fabric 2 and a thermoplastic film (resin: unstretched PP, manufactured by Toyobo, ToyoTac (registered trademark) E-100, melting point 160 ° C.) 100 μm heated to 210 ° C., at a speed of 5 m / min, A carbon short fiber reinforced film having a thickness of 115 μm was produced by sandwiching at a linear pressure of 80 N / mm.

(Manufacture of carbon short fiber reinforced resin composite)
The obtained carbon short fiber reinforced films 1 and 2 were each cut and bonded together by a hot press method, and 5 pieces of 80 mm long and 10 mm wide test pieces were cut out as a carbon short fiber reinforced structure having a thickness of 4 mm. After heat treatment at 150 ° C. for 3 hours, it was cooled and its flexural modulus was measured with a universal material testing machine (TSE Co., Ltd., device name: Autocom (registered trademark, AutoCOM) AC-100). It was measured. The average results are shown in Table 2.

<Comparative example 2: PEEK injection molded body>
After compounding carbon short fibers and PEEK resin at a mass ratio of 15/85 and kneading them with a biaxial stretching machine, a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was produced by an injection molding method. Was subjected to a heat treatment at 280 ° C. for 3 hours, and after cooling, the flexural modulus was measured in the same manner as in Example 1, and the average values are shown in Table 2.

<Comparative Example 3: PP injection molded article>
After compounding carbon short fibers and homotype PP resin at a mass ratio of 20/80 and kneading them with a biaxial stretching machine, a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was produced by an injection molding method. This was subjected to heat treatment at 150 ° C. for 3 hours, and after cooling, the flexural modulus was measured in the same manner as in Example 1, and the average values are shown in Table 2.

  In Comparative Example 1 in which the carbon short fiber nonwoven fabric does not contain microfibrillated cellulose, the carbon short fiber nonwoven fabric cannot withstand the momentum of the thermoplastic film that enters during the heat and pressure treatment, and contains the thermoplastic short fibers. In spite of this, it broke and could not produce a carbon short fiber reinforced film. On the other hand, in Examples 1-4 in which the carbon short fiber nonwoven fabric contains microfibrillated cellulose, a carbon short fiber reinforced film could be produced without depending on the presence or absence of thermoplastic short fibers.

  Moreover, when the carbon fiber reinforced resin composite produced in Examples 1 to 4 and the injection-molded product containing carbon short fibers (Comparative Examples 2 and 3) are compared, the carbon short fibers produced in Examples 1 to 4 are used. It was found that the reinforced resin composite had an improved flexural modulus.

  As described above, the short carbon fiber reinforced films obtained in the examples can be wound with a roll, and can be bonded together to produce a carbon fiber reinforced resin structure. In addition, the obtained carbon fiber reinforced resin composite also had excellent physical properties.

  The carbon short fiber reinforced film and carbon short fiber reinforced structure obtained in the present invention are manufactured parts such as electronic equipment materials, electrical equipment materials, civil engineering materials, building materials, automobile materials, robots and rolls used in various manufacturing industries. Etc. are available.

Claims (2)

  In the method for producing a carbon short fiber reinforced film in which the nonwoven fabric and the thermoplastic film are integrated by subjecting the laminate of the nonwoven fabric containing the carbon short fibers and the thermoplastic film to heat and pressure treatment with rolls from both sides. The method for producing a carbon short fiber reinforced film, wherein the nonwoven fabric contains microfibrillated cellulose.   By heating and pressing with a roll from both sides of a laminate of a nonwoven fabric and a thermoplastic film containing carbon short fibers, the nonwoven fabric and the thermoplastic film are integrated to produce a carbon short fiber reinforced film, Furthermore, in the method for producing a carbon short fiber reinforced structure in which a plurality of the carbon short fiber reinforced films are bonded together, the nonwoven fabric contains microfibrillated cellulose.