JP6702536B2 - Short carbon fiber reinforced film and short carbon fiber reinforced structure manufacturing method - Google Patents

Description

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

The carbon fiber reinforced resin composite obtained by compositing carbon fiber and resin has strength and elastic modulus comparable to that of a metal material, but has a smaller specific gravity than the metal material, so that the weight of the member can be reduced, Also, unlike metal plates such as iron, which have no rusting problem and are resistant to acids and alkalis, electronic equipment materials, electrical equipment materials, civil engineering materials, building materials, automobile materials, It is used in aircraft materials, robots used in various manufacturing industries, and manufacturing parts such as rolls.

The carbon fiber reinforced resin composite is a composite of carbon fiber cloth such as long fiber woven cloth, open-woven cloth, unidirectional web, and short fiber non-woven cloth, and resin such as thermosetting resin and thermoplastic resin. Is. The most common carbon fiber reinforced resin composite is a composite of long fiber woven fabric and thermosetting resin, but it is difficult to design, it is not a homogeneous material, molding time is long, expensive, etc. There was a problem.

As a carbon fiber reinforced resin composite that solves these problems, a method is known in which short carbon fibers are kneaded with a thermoplastic resin and used as an injection molding material as a composite (for example, Patent Document 1). The fibers are easily broken during kneading, and the fiber length becomes short, so that not only sufficient characteristics cannot be obtained, but also it is difficult to obtain a film-like structure having a size of several hundreds of 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 short carbon fiber non-woven fabric and the thermoplastic resin are combined by a hot press molding method (Patent (See References 2 to 7) and the processing method using a single wafer, there is a problem that productivity is inferior. Further, there is a problem that it cannot be handled like a film having a good design property suitable for a vacuum forming method or the like.

Japanese Patent Laid-Open No. 07-156146 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 provide a method for producing a short carbon fiber reinforced film and a short carbon fiber reinforced structure which are excellent in productivity and processability.

The above problems can be solved by the following inventions.

(1) A carbon short fiber reinforced film in which the nonwoven fabric and the thermoplastic film are integrated by heat and pressure treatment with a roll from both sides of a laminate of the nonwoven fabric containing the carbon short fibers and the thermoplastic film The method for producing a short carbon fiber reinforced film, wherein the nonwoven fabric contains microfibrillated cellulose.

(2) A short carbon fiber reinforced film is obtained by integrally heating the nonwoven fabric and the thermoplastic film by heating and pressing with a roll from both sides of the laminate of the nonwoven fabric containing the short carbon fibers and the thermoplastic film. A method for producing a carbon short fiber reinforced structure, which is produced by further laminating a plurality of the carbon short fiber reinforced films, wherein the non-woven fabric contains microfibrillated cellulose. Method.

According to the present invention, in order to obtain a continuous carbon short fiber reinforced film, by sticking a single layer or by stacking a plurality of carbon short fiber reinforced films as they are, without impairing the fiber length of the carbon short fibers, It is possible to obtain a short carbon fiber reinforced structure excellent in predetermined thickness, physical properties and workability.

As the non-woven fabric containing carbon short fibers (carbon short fiber non-woven fabric) in the present invention, a wet non-woven fabric or a dry non-woven fabric manufactured by a wet method or a dry method can be used. The short carbon fiber non-woven fabric may contain thermoplastic short fibers, a thermoplastic emulsion or the like as a binder. With this binder, strength can be easily imparted to the short carbon fiber nonwoven fabric.

Examples of the short carbon fibers include PAN-based carbon fibers made of polyacrylonitrile as a raw material and pitch-based short carbon fibers made of pitches as a raw material. 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. Further, 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. Generally used carbon fiber prepregs are impregnated with epoxy resin for aircraft, sports, etc., and removal of the resin is indispensable for recycling carbon fibers. As a removing method, a method of sintering and removing in an inert gas such as argon or nitrogen or in steam 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 heat of the superheated steam returns to water when heat is removed in the atmosphere. The structure made of carbon fiber prepreg has various forms such as an angle ply laminated body, and it is usually cut to a certain size, then subjected to a sintering treatment to remove the thermosetting resin and then cut. In this case, recycled carbon short fibers having different fiber lengths can be obtained.

A method for manufacturing a dry nonwoven fabric will be described. First, carbon short fibers disintegrated in the air are spread on a web and dispersed by the card method or the like. At this time, when thermoplastic short fibers are also used as a binder, the short fibers are defibrated and dispersed together with the short carbon fibers, and heat treatment is performed. When a thermoplastic emulsion is also used as a binder, the web of short carbon fibers is provided with the thermoplastic emulsion and heat treated. A binder is used to give strength and make a dry non-woven fabric.

A method for manufacturing a wet type nonwoven fabric will be described. First, short carbon fibers are defibrated in water, and then they are made up by a paper net such as a cylinder, a short net, a long net, and an inclined short net, and dried and heat-treated to obtain a wet non-woven fabric. Then, similarly to the dry non-woven fabric, a binding material such as thermoplastic short fibers or a thermoplastic emulsion is used to impart strength to form a wet non-woven fabric.

In the present invention, either a dry nonwoven fabric or a wet nonwoven fabric can be used, but when a thin nonwoven fabric is used, it is preferable to use a wet nonwoven fabric having excellent fiber dispersibility. When a thick non-woven fabric is used, it is preferable to use a dry non-woven fabric, which has a simple manufacturing method and is advantageous in providing a thickness.

As the thermoplastic short fibers, non-crystalline polyvinyl alcohol (vinylon) short fibers, polyester core-sheath short fibers whose surface has a low melting point, unstretched polyester short fibers, polycarbonate (PC) short fibers, polyolefin short fibers, Thermoplastic polyolefin core-sheath short fibers whose surface has a low melting point, polyolefin short fibers whose surface is made of acid-modified polyolefin, aliphatic polyamide short fibers, undrawn polyphenylene sulfide short fibers, polyetherketoneketone short fibers, etc. The short fiber of resin is mentioned.

As the thermoplastic emulsion, an emulsion of a resin having a thermoplasticity such as an acrylic resin, a styrene acrylic resin, an acid-modified polyolefin, a polyolefin containing an acid-modified α-olefin, an ionomer, and 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 80°C or higher and 160°C or higher. It is particularly preferable that the temperature is not higher than °C.

The fiber diameter of the thermoplastic short fibers is preferably 3 μm or more and 40 μm or less, more preferably 5 μm or more and 20 μm or less. 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 the mass, short carbon fibers: binder) is preferably 8.5:0.0 to 5:4, and 8.5:0.5 to. The ratio is more preferably 5:4, further preferably 8:1 to 6:3. 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 carbon short fiber and the binder within the above range. ..

In the method for producing a short carbon fiber reinforced film of the present invention, the nonwoven fabric and the thermoplastic film are integrated by subjecting the laminate of the short carbon fiber nonwoven fabric and the thermoplastic film to heat and pressure treatment with a roll from both sides. Further, in the method for producing a short carbon fiber reinforced structure of the present invention, the nonwoven fabric and the thermoplastic film are integrated by heating and pressing with a roll from both sides of the laminate of the short carbon fiber nonwoven fabric and the thermoplastic film. To produce a short carbon fiber reinforced film, and further, a plurality of the short carbon fiber reinforced films are stuck 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 short carbon fiber nonwoven fabric contains microfibrillated cellulose, the dispersibility of the short carbon fiber fibers in the short carbon fiber nonwoven fabric does not collapse during the heating and pressure treatment or the bonding of the short carbon fiber reinforced film. The short carbon fiber does not break. As a result, a continuous short carbon fiber reinforced film can be obtained with good productivity. The short carbon fiber reinforced film obtained in the present invention can also be used as a short carbon fiber reinforced structure in a single layer. Furthermore, a short carbon fiber reinforced structure can also be obtained by stacking and bonding a plurality of short carbon fiber reinforced films. In the present invention, by containing the microfibrillated cellulose, even at the time of this bonding, a short carbon fiber reinforced structure having a predetermined thickness, physical properties and processability is obtained without impairing the fiber length of the short carbon fiber. be able to.

The microfibrillated cellulose is not a film-like but a fibrous having mainly finely divided portions 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 and width is preferably 20 to 100,000. Further, the modified freeness is preferably 0 ml or more and 770 ml or less, and more preferably 0 ml or more and 600 ml or less. Further, the mass average fiber length is preferably 0.1 mm or more and 2 mm or less. In the modified freeness of the present invention, a wire mesh having a wire diameter of 0.14 mm and an opening of 0.18 mm (PULP AND PAPER RESEARCH INSTITUTE OF CANADA) was used as the sieve plate except that the sample concentration was 0.1%. It is the freeness measured according to JIS P8121 (1995 version).

The degree of fibrillation of microfibrillated cellulose can be grasped by the viscosity of the dispersion liquid at a low concentration. The higher the viscosity is, the more the fibrillation progresses, but if the viscosity is too high, the fiber length may be too short. The viscosity of the dispersion liquid of microfibrillated cellulose (concentration 0.5% by mass) is 50 cp or more and 200 cp when a B-type viscometer (rotor No. 2, rotor rotation speed 60 rpm, temperature 23° C. or higher and 25° C. or lower) is used. The following is preferable.

If the content of the microfibrillated cellulose fibers is too low, the dispersibility of the short carbon fibers may be disrupted when the heating temperature is too high during the production of the short carbon fiber reinforced film or during the production of the short carbon fiber reinforced structure. is there. On the contrary, if the content of the microfibrillated cellulose fibers is too high, during the production of the carbon short fiber nonwoven fabric, the microfibrillated cellulose forms a dense structure with each other to form a film, and during the production of the carbon short fiber reinforced film or the carbon. During the production of the short fiber reinforced structure, it becomes difficult for the thermoplastic film to penetrate into the carbon short fiber nonwoven fabric. Further, voids may be seen in the carbon short fiber reinforced film. The content of the microfibrillated cellulose is preferably 0.5% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, based on all the fibers in the carbon short fiber nonwoven fabric. preferable.

Examples of the cellulose material for the microfibrillated cellulose include plant pulp, solvent-spun cellulose, semi-synthetic cellulose and the like. Examples of the plant pulp include wood pulp such as kraft pulp (KP) using hardwood (L material) and softwood (N material), dissolving pulp (DP), and dissolving kraft pulp (DKP). Further, non-wood pulp such as straw, hemp, cotton and cotton linter is also included. Examples of commercially available products include Serish (registered trademark, manufactured by Daicel Finechem). The crystal form of the cellulosic material includes I type, II type, III type, IV type and the like, but from the viewpoint of heat resistance, I type and II type are preferable, and I type is more preferable. The type I cellulosic material source is a non-wood pulp such as cotton pulp, cotton linter pulp, hemp pulp, kenaf pulp, etc., lignin obtained from pulp, L material or N material having a reduced content of lignin and hemicellulose. And wood pulp such as KP, DP and DKP having a reduced content of hemicellulose. In particular, a cotton material is preferable.

To obtain microfibrillated cellulose, the cellulosic material is first dispersed in water and mechanically ground. Then, the fibers of the cellulosic material are defibrated to form microfibrils. Examples of the apparatus for defibrating the cellulosic material include a disc refiner, a stone mill type grinder, a high pressure homogenizer, a ball mill, an underwater counter collision method apparatus, and an ultrasonic crusher. These devices can also be used in appropriate combination.

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

Examples of the thermoplastic resin of the thermoplastic film include polyolefin resins such as polyethylene resin, polypropylene (PP) resin and polybutylene resin; methacrylic resins such as polymethylmethacrylate resin; polystyrene resins such as polystyrene resin, ABS resin and AS resin. Polyester resin such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene terephthalate resin, polyethylene naphthalate (PEN) resin, poly 1,4-cyclohexyl dimethylene 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 (PPS) resin; modified polyphenylene ether (PPE) Resin; Polyetherimide (PEI) Resin; Polysulfone (PSF) Resin; Polyethersulfone (PES) Resin; Polyketone Resin; Polyarylate (PAR) Resin; Polyethernitrile (PEN) Resin; Polyetherketone (PEK) Resin; Polyether ether ketone (PEEK) resin; Polyether ketone ketone (PEKK) resin; Polyimide (PI) resin; Polyamideimide (PAI) resin; Fluorine (F) resin; Liquid crystal polymer resin such as liquid crystal polyester resin; Polystyrene type, polyolefin Examples thereof include thermoplastic elastomers such as system-based, polyurethane-based, polyester-based, polyamide-based, polybutadiene-based, polyisoprene-based, and fluorine-based thermoplastic elastomers; or copolymer resins or modified resins thereof; ionomer resins and the like. Among these resins, one kind or two or more kinds can be used. From the viewpoint of flammability, PC, PPS, PEEK, PEI and the like are preferable.

Examples of the ionomer resin include an ethylene-based ionomer resin obtained by neutralizing a part of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer resin with a metal ion. A carboxyl group of 10 mol% or more, preferably 10 mol% or more and 90 mol% or less neutralized 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 short carbon fiber nonwoven fabric and the thermoplastic film are continuously heated and pressed from both sides to become a short carbon fiber reinforced film. The roll method is excellent as a method of continuously heating and pressurizing. The heating temperature is preferably around the melting point of the thermoplastic film, but it is necessary to be careful about temperature changes or fluctuations during operation or at a pressurizing place. The temperature fluctuation is preferably 1° C. or less, more preferably 0.5° C. or less, since the thermoplastic film is torn or the permeability of the thermoplastic film into the short carbon fiber nonwoven fabric becomes uneven. .. The pressure applied is preferably 10 N/mm or more and 600 N/mm or less in linear pressure. 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 selected material.

The rolls are arranged in pairs on both sides of the laminate, but a single pair may be used or a plurality of pairs may be used. Further, for the super engineering plastic type thermoplastic film, a device for preheating can be provided. As the laminate, a laminate comprising one layer of short carbon fiber nonwoven fabric and one layer of thermoplastic film, a laminate comprising one layer of short carbon fiber nonwoven fabric and thermoplastic films disposed on both sides of the one layer of short carbon fiber nonwoven fabric, and one layer of thermoplastic film A laminate in which short carbon fiber nonwoven fabrics are arranged on both sides, a laminate 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 The body etc. are mentioned. However, if the thickness of the produced short carbon fiber reinforced film becomes too thick, it becomes 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, and 30 μm or more. It is more preferably 250 μm or less.

As the roll, it is necessary to keep the surface temperature in the roll axial direction with high accuracy.Therefore, a jacket chamber having a heat pipe function and an electromagnetic induction heating method capable of forming a multilayer heating layer in the roll axial direction are provided. It is preferred to use a combination of rolls. As such a roll, the induction heating jacket roll (registered trademark) manufactured by Tokuden Co., Ltd. is superior in the case of continuous production, and the induction heating jacket roll (registered trademark) in the case of batch type or semi-batch type production. The same as the above), the induction heating jacket plate manufactured by Tokuden Co. is excellent.

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

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 by mass unless otherwise specified.

(Preparation of microfibrillated cellulose)
The linter pulp (mass average fiber length 1.2 mm) was subjected to grinding treatment using a Masuko Sangyo Co., Ltd. mass colloider (registered trademark, device name: MKZA12) to produce microfibrillated cellulose. Furthermore, it processed 4 times at 50 MPa using a high pressure homogenizer (MC2 by BOS). When the viscosity of the dispersion liquid of microfibrillated cellulose (concentration: 0.5% by mass) was measured with a B-type viscometer (rotor No. 2, rotor rotation speed 60 rpm, temperature 23° C. or higher and 25° C. or lower), it was 170 cp. It was

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

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

<Examples 1 to 4 and Comparative Example 1>
(Manufacture of short carbon fiber nonwoven fabric)
The fibers were mixed in water at a dispersion concentration of 0.2 mass% for 5 minutes at the fiber blending ratio shown in Table 1, and were made up with a 90 mesh cylinder paper machine at a speed of 3 m/min to a surface temperature of 150°C. Was dried with a Yankee dryer for 10 seconds to prepare a carbon short fiber nonwoven 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, and wound into a roll.

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

(Production of short carbon fiber reinforced film 2)
A short carbon fiber non-woven fabric 2 and a thermoplastic film (resin: unstretched PP, Toyobo, Toyo Tac (registered trademark) E-100, melting point 160° C.) 100 μm, heated at 210° C., with a roll pair, a speed of 5 m/min, It was sandwiched at a linear pressure of 80 N/mm to produce a carbon short fiber reinforced film having a thickness of 115 μm.

(Production of short carbon fiber reinforced resin composite)
Each of the obtained short carbon fiber reinforced films 1 and 2 was cut and bonded by a hot pressing method, and as a short carbon fiber reinforced structure having a thickness of 4 mm, five test pieces having a length of 80 mm and a width of 10 mm were cut out. After being heat-treated at 150°C for 3 hours, it is cooled and its bending elastic modulus is measured by a universal material testing machine (TSE Co., Ltd., device name: Autocom (registered trademark, AutoCOM) AC-100). It was measured. The average value results are shown in Table 2.

<Comparative Example 2: PEEK injection molded article>
A short carbon fiber and a PEEK resin were compounded at a mass ratio of 15/85 and kneaded with a biaxial stretching machine, and then a test piece having a length of 80 mm, a width of 10 mm and a thickness of 4 mm was prepared 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 value is shown in Table 2.

<Comparative Example 3: PP injection molded body>
A short carbon fiber and a homotype PP resin were compounded at a mass ratio of 20/80 and kneaded with a biaxial stretching machine, and then a test piece having a length of 80 mm, a width of 10 mm and a thickness of 4 mm was prepared by an injection molding method. This was heat-treated 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 value is shown in Table 2.

In Comparative Example 1 in which the carbon short fiber non-woven fabric does not contain microfibrillated cellulose, the carbon short fiber non-woven fabric cannot withstand the momentum of the thermoplastic film that enters during the heat and pressure treatment and contains the thermoplastic short fiber. However, the carbon short fiber reinforced film could not be manufactured due to breakage. On the other hand, in Examples 1 to 4 in which the carbon short fiber nonwoven fabric contained the microfibrillated cellulose, the carbon short fiber reinforced film could be manufactured regardless of the presence or absence of the thermoplastic short fibers.

In addition, comparing the carbon fiber reinforced resin composites produced in Examples 1 to 4 with the injection molded articles containing carbon short fibers (Comparative Examples 2 and 3), the carbon short fibers produced in Examples 1 to 4 were compared. It was found that the reinforced resin composite had a higher flexural modulus.

As described above, the short carbon fiber reinforced films obtained in the examples can be wound by a roll, and further bonded to each other so that a carbon fiber reinforced resin structure can also be produced, which has excellent processability, In addition, the obtained carbon fiber reinforced resin composite also had excellent physical properties.

The short carbon fiber reinforced film and the short carbon fiber reinforced structure obtained in the present invention are manufacturing parts such as electronic equipment materials, electric equipment materials, civil engineering materials, building materials, automobile materials, robots used in various manufacturing industries, rolls, etc. It can be used for etc.

Claims (2)

In a method for producing a carbon short fiber reinforced film in which the nonwoven fabric and the thermoplastic film are integrated by heat and pressure treatment with a roll from both sides of a laminate of the nonwoven fabric containing the carbon short fibers and the thermoplastic film A method for producing a short carbon fiber reinforced film, wherein the non-woven fabric contains microfibrillated cellulose. By heating and pressurizing with a roll from both sides of a laminate of a nonwoven fabric containing a short carbon fiber and a thermoplastic film, a carbon short fiber reinforced film is produced by integrating the nonwoven fabric and the thermoplastic film, Furthermore, in the method for producing a short carbon fiber reinforced structure in which a plurality of the short carbon fiber reinforced films are laminated, the nonwoven fabric contains microfibrillated cellulose, wherein the short carbon fiber reinforced structure is produced.