JP2018123268A - Fiber-reinforced plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide fiber-reinforced plastic that is excellent in mold releasability, and can combine excellent mechanical property with excellent flowability when shaped.SOLUTION: The fiber-reinforced plastic is provided which includes a reinforcement fiber and a matrix resin, and contains at least one or more mold release agents, and in which tanδ(ave) is 0.01-0.25, and tanδ(max)-tanδ(ave) is 0.15 or more when the tanδ(ave) denotes an average value of viscoelastic characteristics tanδ represented by expression (1) of the fiber-reinforced plastic in the temperature range of T-30(°C) to T-10(°C), and the tanδ(max) denotes the maximum value of the viscoelastic characteristics tanδ of the fiber-reinforced plastic in the temperature range of T-10(°C) to T+10(°C).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fiber reinforced plastic.

Fiber reinforced plastics are widely used in various fields such as aircraft members, automobile members, wind turbine members for wind power generation, and sports equipment. The fiber reinforced plastic is shaped by preheating the fiber reinforced plastic with an IR heater to a temperature exceeding the melting point (or glass transition point) of the matrix resin, and then pressurizing and cooling with a press molding machine equipped with a mold. Therefore, a compression molding method (stamping molding) is generally performed in which a desired shape is formed and solidified.
The fiber reinforced plastic is formed, for example, by stacking and integrating a plurality of prepreg base materials in which a reinforced fiber is impregnated with a thermoplastic resin.

  Examples of the prepreg base material include those obtained by impregnating a thermoplastic resin with a continuous reinforcing fiber having a long fiber length in one direction and impregnating it with a thermoplastic resin. With a fiber reinforced plastic formed with a prepreg base material using such continuous long reinforcing fibers, a structural material having excellent mechanical properties can be produced. However, since the fiber reinforced plastic is a continuous reinforcing fiber, the fluidity at the time of shaping is low, and it is difficult to form a complicated shape such as a three-dimensional shape by stamping. For this reason, when the fiber reinforced plastic is used, the structural material to be manufactured is mainly limited to those having a nearly planar shape.

As a method of increasing the fluidity at the time of shaping, for example, by laminating a plurality of prepreg base materials in which a reinforcing fiber aligned in one direction is impregnated with a thermoplastic resin, and further, a notch intersecting with the fiber axis is formed, A method (I) in which they are integrated into a fiber reinforced plastic has been proposed (Patent Document 1). Since the fiber reinforced plastic obtained by the method (I) has a cut formed in the prepreg base material and the reinforcing fibers are divided, good fluidity can be obtained at the time of shaping. In addition, the mechanical property isotropic property is obtained by laminating a plurality of prepreg base materials so that the fiber axis direction is shifted by 45 ° in a plan view so that the fiber axis direction of the reinforcing fiber is not biased in a specific direction. A fiber reinforced plastic having good and low variation can be obtained. Anisotropy can also be controlled by laminating with the fiber axis direction aligned in an arbitrary direction.
However, the method (I) is not yet sufficient in terms of manufacturing simplicity and cost. In particular, in industrial production of fiber reinforced plastics and structural materials (molded products), it is important that they can be manufactured more easily and at low cost. Further, in order to obtain a structural material having a more complicated shape, it is important to increase the fluidity at the time of shaping the fiber reinforced plastic.
When manufacturing a structural material by shaping a fiber reinforced plastic into a complicated shape such as a three-dimensional shape, a relatively short reinforcing fiber generally having a fiber length of 100 mm or less is required to ensure fluidity during shaping. Is used. However, when the fiber length of the reinforcing fiber is shortened, the mechanical properties of the structural material after shaping tend to be lowered.

Moreover, as a method for increasing the fluidity at the time of shaping, there is a method in which discontinuous reinforcing fibers are randomly arranged. For example, a method of dispersing a plurality of prepreg pieces cut out from a narrow tape-like prepreg base material at a predetermined length on a plane and integrating them by press molding to form a sheet-like fiber reinforced plastic (II ) Is disclosed (Patent Document 2).
However, in the method (II), the prepreg pieces are dispersed by flying the prepreg pieces by air or by diffusing the prepreg pieces in a liquid fluid and depositing them. It is extremely difficult to uniformly disperse the prepreg pieces so as to face in random directions. Therefore, even in the same sheet, the fiber reinforced plastic has different mechanical properties such as strength depending on the location and orientation. In many cases, the structural material is required to have little variation in mechanical properties such as strength and to have isotropic mechanical properties or to have controlled anisotropy. However, in the method (II), it is difficult to obtain a fiber reinforced plastic with good mechanical property isotropy or with controlled anisotropy and less mechanical property variation.
In addition, fiber reinforced plastics are also required to have good heat resistance. In general, the heat resistance of fiber reinforced plastics is greatly influenced by the heat resistance of trix resin in the fiber reinforced plastics. Usually, the mechanical properties of a single resin tend to decrease at a temperature equal to or higher than the glass transition temperature of the resin. Similarly, in fiber reinforced plastics, mechanical properties tend to decrease at temperatures higher than the glass transition temperature of the matrix resin. In order to minimize the deterioration of the mechanical properties, it is necessary to uniformly disperse the reinforcing fibers in the matrix resin in the fiber reinforced plastic. However, in the above method, only the molten matrix resin flows into the gaps between the deposited prepreg pieces in the step of heating and integrating the deposited prepreg pieces. Therefore, in the obtained fiber reinforced plastic, a resin-rich portion is locally generated. Under the influence of this resin-rich part, the fiber reinforced plastic obtained by the method (II) has a problem of poor heat resistance.

  Further, the fiber reinforced plastic obtained by the method (I) has a problem that when a stress is generated in a direction along the cut shape, the cut portion becomes a starting point of breakage and mechanical properties are lowered. In addition, since only the resin is present in the cut portion, heat resistance is inferior at a temperature equal to or higher than the glass transition temperature of the matrix resin as in the method (II) disclosed in Patent Document 2. There's a problem.

Patent Document 3 discloses a method (III) for producing a fiber-reinforced plastic by dispersing reinforcing fibers by papermaking. In the fiber reinforced plastic obtained by the method (III), since the reinforcing fibers are dispersed almost uniformly, the mechanical properties are excellent in isotropy, there are few variations, and the heat resistance is also good.
However, in the fiber reinforced plastic obtained by the method (III), the reinforcing fibers are intertwined three-dimensionally, so that the fluidity during molding is inferior. Also, the manufacturing process is extremely complicated and inferior in cost. In addition, when an attempt is made to produce a fiber-reinforced plastic having a high reinforcing fiber content by the method (III), it is necessary to make paper with a denser reinforcing fiber. However, when trying to impregnate such a high-density paper-reinforced reinforcing fiber with a matrix resin, among the reinforcing fibers entangled three-dimensionally, the reinforcing fibers oriented particularly in the thickness direction (impregnation direction) Since it bears the stress of the pressing force, no pressure is transmitted to the resin, making impregnation extremely difficult. In addition, when the fiber length of the reinforcing fiber is long, the three-dimensional entanglement becomes strong, so that impregnation is similarly difficult.

The following have been proposed as fiber reinforced plastics that can obtain a structural material having high mechanical properties while using discontinuous reinforcing fibers.
(1) It is composed of reinforcing fibers having a fiber length of 5 to 100 mm and a thermoplastic resin, and the average value of tan δ ′ within the range of the melting point of the thermoplastic resin ± 25 ° C. is 0.01 ≦ tan δ ′ (average value) ≦ 0. 2. A fiber reinforced plastic satisfying .2 (Patent Document 4). tan δ ′ is defined by the following two expressions.
tan δ = G ″ / G ′
tan δ ′ = Vf × tan δ / (100−Vf)
(Where Vf is the volume fraction (%) of the reinforced fiber in the fiber reinforced plastic, G ′ is the storage elastic modulus (Pa) of the fiber reinforced plastic, and G ″ is the loss elastic modulus of the fiber reinforced plastic ( Pa).)
The fiber reinforced plastic of (1) has good mechanical properties because tan δ ′ (average value) is controlled within a specific range.
However, in the fiber reinforced plastic of (1), as shown in Examples 1 and 2, tan δ ′ is almost even in the state heated to the melting point of nylon resin (melting point: 225 ° C.) which is a thermoplastic resin. It has not changed. Since Vf / (100−Vf) is constant, the fact that tan δ ′ has hardly changed means that the value of tan δ itself has hardly changed, but the value of tan δ is also in the temperature range above the melting point. If the properties as a small and elastic body are large, the fluidity of the reinforcing fibers and thermoplastic resin will not be sufficiently high when heated during shaping, and the reinforcing fibers will be cut and shortened during shaping. There is a risk that the mechanical properties of the subsequent structural material will be insufficient.

In addition, when a fiber reinforced plastic is manufactured or when a molded product is formed from the fiber reinforced plastic, molding is performed using a mold or the like, so that excellent mold releasability is also required. If the releasability from the metal is poor, the work efficiency is lowered, and if a part of the fiber reinforced plastic is left unreleased on the metal surface at the time of release, it may cause a poor appearance.
As a technique for improving the releasability of the fiber reinforced plastic from the metal surface, a technique for applying a release agent to the metal surface (Reference 5), or a technique for compounding a mold release component such as a wax component into the matrix resin by extrusion kneading. (Reference 6). However, in the method of applying a release agent to the metal surface, if the mold surface temperature is high, the release performance gradually deteriorates after the release agent is applied. There is a problem that the work efficiency is lowered. Further, in the method of blending a release component such as a wax component into a matrix resin by extrusion kneading, the release component is dispersed in the resin by a shearing force at the time of extrusion kneading, and the above methods (I) to (III) In the fiber reinforced plastic produced by the above method, since the dispersibility of the release component in the matrix resin is insufficient, there is a problem that the release performance of the release property is inferior.

International Publication No. 2014/142061 JP 07-164439 A International Publication No. 2010/013645 International Publication No. 2012/140793 JP2015-51629A JP 2002-179895 A

  An object of the present invention is to provide a fiber reinforced plastic that is excellent in releasability and that can achieve both excellent mechanical properties and excellent fluidity during shaping.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by giving the fiber-reinforced plastic a specific viscoelastic property and containing a release agent. It came to be completed. That is, the gist of the present invention resides in the following (1) to (5).
(1) A fiber reinforced plastic containing reinforcing fibers and a matrix resin,
Contains at least one release agent,
The following formula of fiber reinforced plastic in the temperature range of T-30 (° C.) to T-10 (° C.) (where T is the melting point of the matrix resin or, if not, the glass transition temperature): The average value of the viscoelastic property tan δ represented by 1) is tan δ (ave), and the maximum value of the viscoelastic property tan δ in the temperature range of T−10 (° C.) to T + 10 (° C.) is tan δ (max). At this time, tan δ (ave) is 0.01 to 0.25, and tan δ (max) −tan δ (ave) is 0.15 or more.
tan δ = G ″ / G ′ (1)
However, the symbols in the formula (1) have the following meanings.
G '': loss modulus,
G ′: storage elastic modulus.
(2) The fiber reinforced plastic according to (1), wherein the average fiber length of the reinforcing fibers is 1 to 100 mm.
(3) The fiber-reinforced plastic according to (1) or (2), wherein the release agent is a higher fatty acid ester and / or a higher fatty acid salt.
(4) The fiber reinforced plastic according to any one of the above (1) to (3), comprising 0.01 to 4 parts by mass of the release agent with respect to 100 parts by mass of the matrix resin.
(5) The fiber reinforced plastic according to any one of (1) to (4), wherein the matrix resin is a thermoplastic resin.

  The fiber-reinforced plastic of the present invention is excellent in releasability and can achieve both excellent mechanical properties and excellent fluidity during shaping.

It is the schematic diagram which showed 1 process of the measuring method of orientation degree pf. It is the schematic diagram explaining the process by the image processing software in calculation of the dispersion parameter dp. It is the top view which showed an example of the prepreg base material used for the manufacturing method of the fiber reinforced plastics of this invention. It is the top view which showed the other example of the prepreg base material used for the manufacturing method of the fiber reinforced plastics of this invention. It is the perspective view which showed a mode that material (A) was pressurized with a pair of press roll. It is the schematic diagram which showed an example of the double belt type heating pressurization machine.

The fiber-reinforced plastic of the present invention is a fiber-reinforced plastic containing reinforcing fibers and a matrix resin, and contains at least one release agent. More specifically, a fiber reinforced plastic containing a reinforced fiber and a matrix resin,
It contains at least one release agent and has a temperature range of T-30 (° C.) to T-10 (° C.) (where T is the melting point of the matrix resin, or the glass transition temperature when it does not have a melting point). The viscoelastic property tan δ represented by the following formula (1) in the fiber reinforced plastic in tan δ (ave), the viscoelasticity in the temperature range of T−10 (° C.) to T + 10 (° C.). When the maximum value of the characteristic tan δ is tan δ (max), tan δ (ave) is 0.01 to 0.25, and tan δ (max) −tan δ (ave) is 0.15 or more. is there.
tan δ = G ″ / G ′ (1)
However, the symbols in the formula (1) have the following meanings.
G '': loss modulus,
G ′: storage elastic modulus.

(Reinforced fiber)
The reinforcing fiber is not particularly limited, and for example, a reinforcing fiber having an inorganic fiber, an organic fiber, a metal fiber, or a hybrid structure in which these are combined can be used. One type of reinforcing fiber may be used alone, or two or more types may be used in combination.

  Examples of the inorganic fiber include carbon fiber, graphite fiber, silicon carbide fiber, alumina fiber, tungsten carbide fiber, boron fiber, and glass fiber. Examples of the organic fibers include aramid fibers, high density polyethylene fibers, other general nylon fibers, and polyester fibers. Examples of metal fibers include fibers such as stainless steel and iron, and carbon fibers coated with metal may be used. Of these, carbon fibers are preferred in view of mechanical properties such as the strength of the structural material that is the final molded product.

It does not specifically limit as carbon fiber, A polyacrylonitrile (PAN) type | system | group carbon fiber, a PITCH type | system | group carbon fiber, etc. are mentioned.
A preferred carbon fiber is a carbon fiber having a strand tensile strength measured in accordance with JIS R7601 (1986) of 1.0 GPa or more and 9.0 GPa or less and a strand tensile elastic modulus of 150 GPa or more and 1000 GPa or less.
More preferred carbon fibers are carbon fibers having a strand tensile strength of 1.5 GPa or more and 9.0 GPa or less measured according to JIS R7601 (1986) and a strand tensile modulus of 200 GPa or more and 1000 GPa or less.

The average fiber length of the reinforcing fibers in the fiber reinforced plastic is preferably 1 to 100 mm, more preferably 3 to 70 mm, further preferably 5 to 50 mm, particularly preferably 10 to 50 mm, and most preferably 10 to 35 mm.
In general, the longer the reinforcing fiber, the more structural material excellent in mechanical properties can be obtained. However, the fluidity is lowered particularly during stamping molding, so that it becomes difficult to obtain a structural material having a complicated three-dimensional shape. When the average fiber length of the reinforcing fibers is not more than the upper limit value, excellent fluidity can be obtained at the time of shaping, and the reinforcing fibers and the matrix resin can easily flow. Therefore, it is easy to obtain a complicated three-dimensional structural material such as a rib or a boss. Moreover, if the average fiber length of the reinforcing fibers is not less than the lower limit value, a structural material having excellent mechanical properties can be produced.

(Measurement method of average fiber length)
The resin in the fiber reinforced plastic is burned off, and only the reinforcing fiber is taken out, and the fiber length of the reinforcing fiber is measured with calipers or the like. The measurement is performed on 100 randomly selected reinforcing fibers, and the average fiber length is calculated as the mass average of them.
1-50 micrometers is preferable and, as for the average fiber diameter of a reinforced fiber, 5-20 micrometers is more preferable.

(Matrix resin)
The matrix resin may be a thermoplastic resin or a thermosetting resin. A matrix resin may be used individually by 1 type, and may use 2 or more types together.
As the matrix resin, a thermoplastic resin is preferable. Since a thermoplastic resin generally has a higher toughness value than a thermosetting resin, it is easy to obtain a structural material having excellent strength, particularly impact resistance, by using a thermoplastic resin as a matrix resin. In addition, the shape of the thermoplastic resin is determined by cooling and solidification without chemical reaction. Therefore, when a thermoplastic resin is used, molding can be performed in a short time, and the productivity of fiber reinforced plastic and structural material is excellent.

The thermoplastic resin is not particularly limited, and polyamide resin (nylon 6 (melting point: 225 ° C.), nylon 66 (melting point: 260 ° C.), nylon 12 (melting point: 175 ° C.), nylon MXD6 (melting point: 237 ° C.), etc. ), Polyolefin resin (low density polyethylene (melting point: 95 to 130 ° C.), high density polyethylene (melting point: 120 to 140 ° C.), polypropylene (melting point: 165 ° C.), etc.), modified polyolefin resin (modified polypropylene resin (melting point: 160). ˜165 ° C.)), polyester resin (polyethylene terephthalate, polybutylene terephthalate, etc.), polycarbonate resin (glass transition temperature: 145 ° C.), polyamideimide resin, polyphenylene oxide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin Polyetherimide resin, polystyrene resin, ABS resin, polyphenylene sulfide resin, liquid crystal polyester resin, a copolymer of acrylonitrile and styrene, a copolymer of nylon 6 and nylon 66 and the like.
Examples of the modified polyolefin resin include a resin (acid-modified polypropylene resin) obtained by modifying a polyolefin resin with an acid such as maleic acid.
A thermoplastic resin may be used individually by 1 type, may use 2 or more types together, and uses 2 or more types as a polymer alloy is very good.
The thermoplastic resin is selected from the group consisting of polyolefin resin, modified polypropylene resin, polyamide resin and polycarbonate resin from the viewpoint of the balance of adhesiveness with reinforcing fiber, impregnation into reinforcing fiber and raw material cost of thermoplastic resin. It is preferable to include at least one selected.

The thermosetting resin is not particularly limited, and examples thereof include an epoxy resin, a phenol resin, an unsaturated polyester resin, a urethane resin, a urea resin, a melamine resin, and an imide resin.
A thermosetting resin may be used individually by 1 type, and may use 2 or more types together.
The thermosetting resin is preferably an epoxy resin, a phenol resin, an unsaturated polyester resin, or an imide resin from the viewpoint of developing the mechanical properties of the fiber reinforced plastic after the thermosetting resin is cured, and the fiber reinforced plastic. From the viewpoint of ease of production, an epoxy resin and an unsaturated polyester resin are more preferable.

(Release agent)
The release agent is not particularly limited, and examples thereof include higher fatty acid esters, higher fatty acid metal salts, higher fatty acids, paraffin wax, beeswax, olefinic wax, olefinic wax having a carboxy group and / or a carboxylic anhydride group, and silicone. Examples thereof include oils, organopolysiloxanes, aliphatic amines, and ethylene bisamide compounds. Of these, higher fatty acid esters and higher fatty acid metal salts are preferred. A mold release agent may be used individually by 1 type, and may use 2 or more types together.
The higher fatty acid ester is preferably a partial ester or a total ester of a monovalent or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. Examples of such monohydric or polyhydric alcohols include ethylene glycol, glycerin, dipentaerythritol, tripentaerythritol, sorbitan, and the like. Examples of such saturated fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, and montanic acid. Of these, stearic acid and montanic acid are preferable.

The higher fatty acid metal salt is preferably a partially saponified or total saponified product of the higher fatty acid ester, or a salt of a saturated fatty acid having 10 to 30 carbon atoms and a metal element. Examples of such saturated fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, and montanic acid. Of these, stearic acid and montanic acid are preferable. Examples of such metal elements include calcium, magnesium, sodium, lithium, barium, zinc, and aluminum.
As the higher fatty acid, a substituted or unsubstituted saturated fatty acid having 10 to 30 carbon atoms is preferable, and an unsubstituted saturated fatty acid having 10 to 30 carbon atoms is more preferable. Examples of such higher fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, and montanic acid. Of these, stearic acid and montanic acid are preferable.

  Although it does not specifically limit as quantity of the mold release agent in the fiber reinforced plastics of this invention, It is preferable that 0.01-4 mass parts of mold release agents are contained with respect to 100 weight part of matrix resins, and 0.02-2. Mass parts are more preferred, 0.03 to 1 parts by mass are more preferred, and 0.05 to 0.5 parts by mass are most preferred.

The fiber-reinforced plastic of the present invention may be blended with other additives depending on the required characteristics of the target structural material.
Examples of other additives include flame retardants, weather resistance improvers, antioxidants, heat stabilizers, ultraviolet absorbers, plasticizers, lubricants, colorants, compatibilizers, non-fibrous fillers, conductive fillers, Surfactant etc. are mentioned and you may use a thermoplastic resin as another additive.

In the fiber reinforced plastic of the present invention, tan δ (ave) is 0.01 to 0.25, and tan δ (max) −tan δ (ave) is 0.15 or more. By satisfying the above ranges, tan δ (ave) and tan δ (max) -tan δ (ave) respectively, excellent release characteristics due to the effect of the release agent, excellent mechanical properties, and excellent shaping It is possible to achieve both fluidity.
“Tan δ (ave)” is a temperature range of T-30 (° C.) to T-10 (° C.) (where T is the melting point of the matrix resin, or the glass transition temperature when no melting point is present). It is an average value of the viscoelastic property tan δ of the fiber reinforced plastic.
“Tan δ (max)” is the maximum value of the viscoelastic property tan δ in the temperature range of T−10 (° C.) to T + 10 (° C.).
The viscoelastic property tan δ is expressed by the following formula (b1).
tan δ = G ″ / G ′ (b1)
(Where G ″ is the loss modulus (Pa) and G ′ is the storage modulus (Pa).)
The tan δ (ave) of the fiber reinforced plastic of the present invention is 0.01 to 0.25, preferably 0.02 to 0.20, and more preferably 0.03 to 0.15. When tan δ (ave) is extremely low (close to zero), it is close to a completely elastic body, meaning that the property is far from the plastic material, and mechanical properties and fluidity as a plastic material cannot be expected. However, if tan δ (ave) is equal to or greater than the lower limit, a fiber-reinforced plastic having a good balance between mechanical properties and flow properties can be obtained, and excellent release properties due to the effect of the release agent can be exhibited. If tan δ (ave) is not more than the upper limit, a structural material having excellent mechanical properties can be produced.
The tan δ (max) -tan δ (ave) of the fiber reinforced plastic of the present invention is 0.15 or more, preferably 0.25 or more, and more preferably 0.35 or more. If tan δ (max) −tan δ (ave) is equal to or more than the lower limit value, excellent fluidity can be obtained at the time of shaping. .
When tan δ (max) −tan δ (ave) is extremely large, that is, tan δ (max) is extremely large, only the matrix resin flows during molding, and the reinforcing fibers do not follow the flow of the matrix resin. In this respect, tan δ (max) −tan δ (ave) of the fiber reinforced plastic of the present invention is preferably 1.5 or less, and more preferably 0.9 or less.
The tan δ of the fiber reinforced plastic becomes smaller as the dispersibility of the reinforced fiber is higher. The tan δ of the fiber reinforced plastic can be adjusted, for example, by adjusting the clearance between the belts during pressurization in the fiber reinforced plastic manufacturing method described later. As the clearance becomes narrower, the dispersibility of the reinforcing fibers in the fiber-reinforced plastic improves, and tan δ tends to decrease. For example, by adjusting the fiber volume content (Vf) of the reinforcing fiber in the fiber reinforced plastic, the value of tan δ (max) −tan δ (ave) can be adjusted. As Vf of the fiber reinforced plastic is higher, tan δ (max) tends to be smaller.
In addition, the entanglement between the reinforcing fibers and the friction between the reinforcing fibers in the fiber reinforced plastic also affect the tan δ (max).
In addition, when a polymer alloy has a plurality of melting points and glass transition temperatures, one melting point or glass transition temperature T satisfying the range of tan δ (ave) and tan δ (max) -tan δ (ave) of the present invention is provided. What is necessary is just to have more.

The fiber volume content (Vf) of the reinforcing fiber in the fiber-reinforced plastic of the present invention is preferably 5 to 70% by volume, more preferably 10 to 60% by volume, still more preferably 15 to 50% by volume, and 25 to 45% by volume. % Is most preferred. If the Vf of the reinforcing fiber is not more than the upper limit value, the interface strength is not easily lowered due to a decrease in toughness, and the fluidity at the time of molding is hardly lowered. If Vf of the reinforcing fiber is equal to or higher than the lower limit value, mechanical properties required as a fiber reinforced plastic are easily obtained.
The Vf value of the fiber reinforced plastic means the volume ratio of the reinforced fiber to the total volume of other components such as the reinforced fiber, the matrix resin, the release agent, and other additives in the fiber reinforced plastic. Since the Vf value measured based on JIS K7075 varies depending on the amount of voids present in the fiber reinforced plastic, the present invention employs a fiber volume content that does not depend on the amount of voids present.

(Orientation degree pf)
The orientation degree pf of the reinforcing fiber in the direction orthogonal to the thickness direction in the fiber reinforced plastic of the present invention is preferably 0.001 to 0.8. pf is an index representing the orientation state of the reinforcing fibers in the direction orthogonal to the thickness direction in the fiber reinforced plastic. When pf is “0”, it means that the reinforcing fibers are oriented in an ideal state in a direction orthogonal to the thickness direction of the fiber-reinforced plastic. It shows that the higher the value of pf is, the higher the degree of disturbance of the reinforcing fibers is toward the outer side of the surface orthogonal to the thickness direction.
Although it depends on the fiber length of the reinforcing fiber, as the value of pf is larger, fluidity at the time of shaping is less likely to be obtained due to entanglement between the reinforcing fibers and friction between the reinforcing fibers. That is, the more the reinforcing fibers are distorted in the outward direction of the surface perpendicular to the thickness direction, the more entanglement between the reinforcing fibers and the friction between the reinforcing fibers occur, and the fluidity at the time of shaping is difficult to obtain. When the average fiber length of the reinforcing fibers is 1 mm to 100 mm, if pf is 0.8 or less, excellent fluidity can be easily obtained during shaping, and a structural material having excellent mechanical properties can be easily obtained. The lower limit of pf is not particularly limited on the physical properties of the fiber reinforced plastic. However, it is difficult to set pf to 0, and 0.001 or more is a realistic value. The upper limit of pf is preferably 0.5, more preferably 0.3, and further preferably 0.15.

(Measurement method of pf)
As shown in FIG. 1, a measurement sample 2210 having a width of 2 mm is cut out from a fiber reinforced plastic 2200 having a thickness of 2 mm, and measurement is performed as follows.
In the measurement sample 2210, the width direction is the x direction, the thickness direction is the y direction, and the length direction is the z direction.

<Measured integral value in x direction>
The measurement sample 2210 is irradiated with X-rays in the x direction to obtain a one-dimensional orientation profile derived from diffraction on the 002 plane of graphite. A one-dimensional orientation profile derived from diffraction on the 002 plane of graphite is obtained by a method of obtaining a profile in the circumferential direction at the 002 diffraction portion using analysis software after capturing an image using a two-dimensional detector. In the case of a one-dimensional detector, a one-dimensional orientation profile derived from diffraction on the 002 plane of graphite can also be obtained by fixing the detector at 002 diffraction and rotating the sample 360 °.
Next, an actual measurement integrated value Sx in the x direction is calculated from the obtained one-dimensional orientation profile by the following equation (b2).
However, in the formula (b2), I (δ) is the intensity at the azimuth angle δ with reference to the z direction on the yz plane in the one-dimensional orientation profile.
Sx takes the maximum value when the reinforcing fibers are fully oriented in the x direction. The value of Sx becomes small because the reinforcing fiber has an inclination from the x direction. Factors for reducing Sx include a component in the thickness direction in the inclination of the reinforcing fiber with respect to the x direction and a component in a plane perpendicular to the thickness direction. That is, both the component in the yz plane and the component in the xz plane in the inclination of the reinforcing fiber with respect to the x direction cause Sx to decrease. In pf, in order to evaluate the degree of disturbance of the reinforcing fiber toward the outer side of the surface orthogonal to the thickness direction, the following operation is performed to remove the influence of the component in the xz plane on the inclination of the reinforcing fiber. .

<Predicted integral value in x direction>
The measurement sample 2210 is irradiated with X-rays in the y direction to obtain a one-dimensional orientation profile derived from diffraction on the 002 plane of graphite. Next, I (ψ) is normalized by the following equation (b3) to calculate the fiber ratio G (ψ) at the azimuth angle ψ.
However, in the formula (b3), I (ψ) is the intensity at the azimuth angle ψ relative to the z direction on the xz plane in the one-dimensional orientation profile.
Next, a predicted integral value F in the x direction is calculated by the following equation (b4).
However, Va is the fiber volume content (Vf) of the reinforcing fiber in the measurement sample 2210. Vb is the fiber volume content (Vf) of the reinforcing fiber in the standard sample for correction described later. A (ψ) is an intensity correction coefficient.

The intensity correction coefficient A (ψ) is obtained as follows.
As a standard sample for correction, a UD material having a thickness of 2 mm in which reinforcing fibers are aligned in one direction so as to be completely oriented in the z direction is prepared, and this is used as a 0 ° material. The reinforcing fiber and the matrix resin used for the standard sample are the same type as the measurement sample 2210. Va that is the fiber volume content (Vf) of the reinforcing fiber in the measurement sample 2210 and Vb that is the fiber volume content (Vf) of the reinforcing fiber in the standard sample for correction are the same or different. May be.
Next, as a further standard sample, a 15 ° material is produced in the same manner as the 0 ° material, except that the reinforcing fibers are aligned in one direction so that the azimuth angle ψ is completely oriented in the direction of 15 °. Similarly, 30 ° material, 45 ° material, 60 in which reinforcing fibers are aligned in one direction so that the azimuth angle ψ is completely oriented in each direction of 30 °, 45 °, 60 °, 75 °, and 90 °. A ° material, a 75 ° material, and a 90 ° material are prepared.
Next, a standard measurement sample having a width of 2 mm is cut out from each standard sample in the same manner as the measurement sample 2210. X-rays are incident on the standard measurement sample in the x direction to obtain a one-dimensional orientation profile derived from diffraction on the 002 plane of graphite. In the one-dimensional orientation profile of the standard measurement sample derived from the 90 ° material, the strength is a substantially constant value. From the one-dimensional orientation profile of each standard measurement sample, the integral value S (ψ) of the strength I (ψ, δ) of the material at the azimuth angle ψ is calculated by the following equation (b5).
However, I (ψ, δ) is the intensity at the azimuth angle δ for the standard measurement sample with the azimuth angle ψ.
The integral value S (ψ) has a relationship of S (ψ) = S (π−ψ). Plotting with ψ on the horizontal axis and S (ψ) on the vertical axis and plotting a normal distribution approximation in the range of ψ from 0 ° to 180 ° is defined as the intensity correction coefficient A (ψ) at the azimuth angle ψ.

<Predicted integral intensity of correction in x direction>
The predicted integral value F in the x direction and the actually measured integral value Sx do not necessarily match. Therefore, the integral value correction coefficient B (Sx) is calculated using the standard sample.
A standard measurement sample is cut out from each standard sample in the same manner as the calculation of the intensity correction coefficient A (ψ). For each standard measurement sample, the actual measurement integrated value Sx (α) is calculated by the above-described method for calculating the actual measurement integrated value in the x direction. Α is 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, and 90 °. Further, for each standard measurement sample, the predicted integrated value F (α) in the x direction is obtained by the above-described method for calculating the predicted integrated value in the x direction. When the horizontal axis represents Sx (α) and the vertical axis represents Sx (α) / F (α), there is a high correlation, and a linear approximation is defined as an integral correction coefficient B (Sx).
The predicted integrated value F in the x direction is multiplied by the integral correction coefficient B (Sx) to obtain the predicted integrated intensity F ′ for correction in the x direction.

<Calculation of pf>
Pf is calculated by the following equation (b6).

(Elliptic divergence coefficient ec)
The elliptical divergence coefficient ec of the orientation profile of the reinforcing fiber on the surface orthogonal to the thickness direction in the fiber reinforced plastic of the present invention is preferably 1 × 10 ^{−5 to} 9 × 10 ⁻⁵ . ec is an index representing the dispersibility of the two-dimensional orientation of the reinforcing fibers in the plane orthogonal to the thickness direction in the fiber-reinforced plastic of the present invention. ec is a deviation coefficient from the approximate ellipse of the orientation profile described above.
In the fiber reinforced plastic in which the reinforcing fibers are randomly oriented, the larger the ec, the greater the variation in mechanical properties. If ec is 9 × 10 ⁻⁵ or less, it is easy to suppress variations in mechanical properties. The ec of the fiber reinforced plastic of the present invention is preferably 8.5 × 10 ⁻⁵ or less, and more preferably 8 × 10 ⁻⁵ or less.
The preferred lower limit of ec is not particularly limited in terms of mechanical properties of the fiber reinforced plastic. However, for example, as the fiber length of the reinforcing fiber becomes longer, the difficulty of manufacturing a fiber reinforced plastic having a small ec value increases. Increasing the fiber length of the reinforcing fiber improves the mechanical properties, but the value of ec tends to increase accordingly, and the variation in mechanical properties increases. Considering the balance between the mechanical properties and the variation thereof, the preferable lower limit value of ec according to the average fiber length of the reinforcing fiber is as follows, which is realistic from the viewpoint of production. When the average fiber length of the reinforcing fibers is 1 to 3 mm, ec is preferably 1 × 10 ⁻⁵ or more. When the average fiber length of the reinforcing fibers is more than 3 mm and 10 mm or less, ec is preferably 1.5 × 10 ⁻⁵ or more. When the average fiber length of the reinforcing fibers is more than 10 mm and not more than 35 mm, ec is preferably 2 × 10 ⁻⁵ or more. When the average fiber length of the reinforcing fibers is more than 35 mm and not more than 70 mm, ec is preferably 3 × 10 ⁻⁵ or more. When the average fiber length of the reinforcing fibers is more than 70 mm and 100 mm or less, ec is preferably 4 × 10 ⁻⁵ or more.

(Measurement method of ec)
The profile of the intensity I (ψ) at the azimuth angle ψ measured when obtaining the predicted integral value in the x direction in the measurement of pf is approximated by an ellipse Ia (ψ) represented by the following equation (b7).
However, in Formula (b7), a is an ellipse major axis. b is the minor axis of the ellipse. β is the rotation angle.
A, b, and β when Ia (ψ) is closest to I (ψ) may be numerically calculated so that the degree of deviation R from the ellipse represented by the following equation (b8) is minimized. The minimum value of the divergence degree R at that time is defined as ec.

(Dispersion parameter dp)
The dispersion parameter dp of the reinforcing fiber in the cross section in the thickness direction of the fiber reinforced plastic of the present invention is preferably 100-80. dp is an index representing the three-dimensional dispersion of reinforcing fibers in the fiber-reinforced plastic. The dp of “100” means that the reinforcing fibers are dispersed in the matrix resin in an ideal state. It means that the smaller the value of dp, the higher the proportion of reinforcing fibers that are locally aggregated, and the higher the proportion of resin-rich portions.
The smaller the value of dp and the worse the dispersibility of the reinforcing fibers, the worse the heat resistance. If dp is 80 or more, good heat resistance is easily obtained. The dp of the fiber reinforced plastic of the present invention is more preferably 84 or more, and even more preferably 88 or more. The upper limit value of dp of the fiber reinforced plastic of the present invention is 100 as a theoretical value. A practical upper limit value of dp is 98 from the viewpoint of manufacturing.
The fluidity at the time of shaping of the fiber reinforced plastic is caused by the flow of the resin at the time of shaping or the sliding of the resin layer. Therefore, the higher the flowability of the resin in the fiber reinforced plastic, the higher the fluidity is obtained when shaping. That is, the smaller the dp, the higher the fluidity during shaping. In the fiber reinforced plastic of the present invention, by controlling pf within the above-described range, high fluidity is exhibited even if the value of dp is high.

(Measurement method of dp)
The dp can be measured by processing a cross-sectional photograph in the thickness direction of the sample piece cut out from the fiber reinforced plastic using image editing software.
Specifically, for example, a sample piece is cut out from fiber reinforced plastic, and a cross-sectional photograph of the sample piece is taken. For example, an optical microscope can be used for taking a cross-sectional photograph. From the viewpoint that the accuracy of evaluation by dp becomes higher, the dot pitch in the resolution at the time of photographing is preferably 1/10 or less of the diameter of the reinforcing fiber, and more preferably 1/20 or less.
Next, the cut photograph is processed as follows using image editing software.
In the cut photograph, a portion corresponding to a rectangular range of 2 mm in the thickness direction and 1.5 mm in the direction orthogonal to the thickness direction in the cross section of the sample piece is set as a processing target image. The image editing software binarizes the reinforcing fiber portion, the resin portion, and the void portion in the processing target image. For example, in a processing target image in which the reinforcing fiber portion is white, the resin portion is gray, and the void portion is black, the binarization is performed with the reinforcing fiber portion being black and the resin portion and the void portion being green.
As shown in FIG. 2, the unit regular hexagonal H of the reinforcing fiber C is completely dispersed in the cut surface of the fiber reinforced plastic having a radius of reinforcing fiber of r (μm) and a fiber volume content of Vf (volume%). The length La of one side is obtained by the following formula (b9).
In the reinforcing fiber portion of the processing target image after binarization, it is assumed that the reinforcing fibers are completely theoretically dispersed as shown in FIG. Then, as shown in FIG. 2, the radius of the reinforcing fiber is increased by the length Le represented by the following formula (b10), and binarization is performed by image editing software so that the radius of the reinforcing fiber becomes La. The later reinforcing fiber part is expanded. Note that Le is a distance that is half of the distance at which the distance between the outer wall surfaces of adjacent reinforcing fibers is the farthest in a state where the reinforcing fibers are ideally dispersed. If the expansion processing described above is performed when the reinforcing fibers are actually dispersed ideally in the reinforcing fiber portion after binarization, the reinforcing fiber portion occupies the entire area of the processing target image.
After expansion processing by the image editing software, dp is calculated by the following equation (b11).
However, in Formula (b11), S1 is an area of the reinforcing fiber portion after the expansion processing in the processing target image. S2 is the entire area of the processing target image.
The thickness of the fiber reinforced plastic of the present invention is preferably 0.1 to 10.0 mm, more preferably 0.25 to 6.0 mm, and further preferably 0.4 to 4.0 mm. When the thickness is equal to or less than the upper limit value, the matrix resin hardly protrudes during pressurization in the production of the fiber reinforced plastic, and thickness control is easy. If the thickness is equal to or greater than the lower limit, shear stress is likely to be applied at the time of pressurization in the production of fiber reinforced plastic, and it becomes easy to randomize the reinforced fibers and control the isotropy and anisotropy of mechanical properties.

(Manufacturing method of fiber reinforced plastic)
As a method for producing the fiber-reinforced plastic of the present invention, there is a method having the following steps (i) to (iii) from the viewpoint that tan δ (ave) and tan δ (max) -tan δ (ave) can be easily controlled to the above-described ranges. preferable.
(I) A step of obtaining a material (A) including a prepreg base material in which a reinforcing fiber aligned in one direction is impregnated with a matrix resin and a cut is formed so as to intersect the fiber axis.
(Ii) Using a pressurizing device that presses substantially uniformly in a direction orthogonal to the traveling direction of the material (A), so that the fiber axis direction of the reinforcing fiber intersects the traveling direction, and the material (A) The process of pressurizing in the state heated to the temperature T more than a glass transition temperature, when not having melting | fusing point of the said matrix resin, making it run in one direction.
(Iii) A step of cooling the material (A) pressed by the pressing device to obtain a fiber reinforced plastic.

{Process (i)}
In step (i) in the method for producing a fiber-reinforced plastic of the present invention, a material (A) containing a prepreg base material is obtained. The material (A) may be a single layer material composed of only one prepreg base material, or may be a prepreg laminate in which two or more prepreg base materials are laminated.
The prepreg base material used in step (i) is obtained by impregnating a matrix resin into reinforcing fibers aligned in one direction. In the prepreg base material, additives may be blended according to the required characteristics of the target structural material.
The prepreg base material used in the step (i) has a cut formed so as to intersect the fiber axis. Thereby, in the said prepreg base material, the long reinforced fiber arranged in one direction is parted by cutting, and the fiber length is set to 1-100 mm.
When a sheet-like fiber-reinforced plastic is formed by dispersing and integrating prepreg pieces, which are generally called random materials, cut out from a prepreg base material, mechanical properties vary, making it difficult to design parts. On the other hand, in the method according to steps (i) to (iii), a fiber reinforced plastic is obtained by using a prepreg base material with a cut, and therefore, mechanical properties are better than those in the case of using a random material, and variations thereof are also observed. Can be small.

The shape of the cut formed in the prepreg base material used in the method for producing the fiber-reinforced plastic of the present invention is not particularly limited, and may be, for example, linear, curved, or polygonal.
The angle of the cut formed on the prepreg base material used for the fiber reinforced plastic manufacturing method of the present invention with respect to the fiber axis of the reinforcing fiber is not particularly limited, but the angle θ formed by the fiber axis of the reinforcing fiber and the cut is 0 ° <θ. An incision (hereinafter also referred to as an incision (b)) that satisfies <90 ° and an incision (hereinafter also referred to as an incision (c)) in which the angle θ satisfies −90 ° <θ <0 ° are formed. It is preferable. The angle θ is positive counterclockwise with respect to the fiber axis of the reinforcing fiber in plan view.
In the prepreg base material used in the present invention, the angle θ formed by the fiber axis of the reinforcing fiber and the cut is 0 ° <θ <90 ° (hereinafter also referred to as a cut (b)), and the angle θ is the same. A notch that satisfies −90 ° <θ <0 ° (hereinafter also referred to as notch (c)) is formed. The angle θ is positive counterclockwise with respect to the fiber axis of the reinforcing fiber in plan view.

In the prepreg base material used in step (i), a plurality of cuts (b) are formed in the fiber axis direction of the reinforcing fibers (hereinafter also referred to as region (B)), and the cuts (c) are reinforced. It is preferable that a plurality of regions (hereinafter also referred to as region (C)) formed in the fiber axis direction of the fibers are alternately formed in a direction perpendicular to the fiber axis of the reinforcing fiber. As described above, in the prepreg base material used in step (i), a straight notch that descends to the left in a plan view in a state in which the fiber axis direction of the reinforcing fibers aligned in one direction is the lateral direction. Regions (B) in which a plurality of (b) are formed and regions (C) in which a plurality of linear notches (c) are formed alternately in the direction perpendicular to the fiber axis of the reinforcing fibers. It is preferable that
In the prepreg base material, the region (B) and the region (C) are alternately formed in the direction orthogonal to the fiber axis of the reinforcing fiber, so that the random fiber axis direction of the reinforcing fiber in the entire base material in the step (ii). Occurs more uniformly, and the deviation of the reinforcing fibers in the fiber axis direction is reduced. For this reason, undulation and warpage are less likely to occur in the fiber reinforced plastic, and the winding diameter when wound is reduced. Further, a fiber reinforced plastic having excellent mechanical properties and isotropic properties can be obtained.
In addition, the aspect in which the region (B) and the region (C) are alternately formed in the direction orthogonal to the fiber axis of the reinforcing fiber is the region (B) composed of one row of cuts (b) and an example of the cut ( It is not limited to the aspect in which the area | region (C) which consists of c) is formed alternately. A mode in which a region (B) consisting of two rows of cuts (b) and a region (C) consisting of two examples of cuts (c) are alternately formed, or a region (B) consisting of three rows of cuts (b) ) And regions (C) formed by three cuts (c) may be alternately formed.

The angle θ of each cut (b) in the region (B) is preferably 10 ° to 89 °, more preferably 25 ° to 89 °. If the angle θ of each cut (b) in the region (B) is within the above range, randomization of the reinforcing fibers in the fiber axis direction is likely to occur more uniformly.
The angle θ for each cut (b) in the region (B) may be the same or different. The angle θ for each cut (b) in the region (B) is preferably the same in that randomization of the reinforcing fibers in the fiber axis direction tends to occur more uniformly.
The length of the cut (b) is not particularly limited and can be set as appropriate. It is preferable that the length of each notch (b) is the same. Note that the lengths of the respective cuts (b) may be different from each other.
The number of cuts (b) in the fiber axis direction of the reinforcing fibers in the region (B) is not particularly limited, and may be appropriately determined so that the lengths of the reinforcing fibers divided by the cutting become a desired length.
The number of rows of cuts (b) in the region (B) may be one row or two or more rows.

The angle θ of each notch (c) in the region (C) is preferably −89 ° to −10 °, more preferably −89 ° to −20 °. If the angle θ of each cut (c) in the region (C) is within the above range, randomization of the reinforcing fibers in the fiber axis direction is likely to occur more uniformly.
The angle θ for each notch (c) in the region (C) may be the same or different. The angle θ for each cut (c) in the region (C) is preferably the same in that randomization of the reinforcing fibers in the fiber axis direction is more likely to occur more uniformly.
In terms that the randomization of the reinforcing fiber in the fiber axis direction is more likely to occur more uniformly, the absolute value of the angle θ of each notch (b) in the region (B) and the angle θ of each notch (c) in the region (C). More preferably, the absolute value of is the same. The absolute value of the angle θ of each notch (b) in the region (B) may be different from the absolute value of the angle θ of each notch (c) in the region (C). The difference is preferably as small as possible.
The length of the cut (c) is not particularly limited and can be set as appropriate. It is preferable that the length of each notch (c) is the same. In addition, the length of each notch (c) may each differ.
The length of the cut (c) is preferably the same as the length of the cut (b). Note that the length of the cut (c) and the length of the cut (b) may be different.
The number of cuts (c) in the fiber axis direction of the reinforcing fibers in the region (C) is not particularly limited, and may be appropriately determined so that the lengths of the reinforcing fibers divided by the cutting become a desired length.
The number of rows of cuts (c) in the region (C) may be one row or two or more rows. The number of rows of cuts (c) in region (C) is preferably the same as the number of rows of cuts (b) in region (B).

The relationship between the region (B) and the region (C) in the prepreg substrate is that the region (C) is reversed when the region (B) is inverted so as to be symmetrical with respect to the direction perpendicular to the fiber axis of the reinforcing fiber. ) Is preferred. Thereby, randomization of the reinforcing fiber in the fiber axis direction is likely to occur more uniformly.
The end of the notch (b) closest to the region (C) in the region (B) and the end of the notch (c) closest to the region (B) in the region (C) are the fiber axes of the reinforcing fibers. It is preferable that the directions are staggered. Thereby, randomization of the reinforcing fiber in the fiber axis direction is likely to occur more uniformly.
The length in the direction orthogonal to the fiber axis of the reinforcing fiber in the region (B) and the length in the direction orthogonal to the fiber axis of the reinforcing fiber in the region (C) are preferably the same.

Specific examples of the prepreg base material include the prepreg base material 12 illustrated in FIG. 3.
In the prepreg base material 12, the reinforcing fibers 13 aligned in one direction are impregnated with the matrix resin 14, and the notches (b) 15 and the notches (c) 16 are formed so as to intersect the fiber axis of the reinforcing fibers 13. ing. The cut (b) 15 is a cut in which the angle θ formed with the fiber axis of the reinforcing fiber 13 is 0 ° <θ <90 °. The cut (c) 16 is a cut in which the angle θ formed with the fiber axis of the reinforcing fiber 13 is −90 ° <θ <0 °.
In the prepreg base material 12, a region (B) 17 including a plurality of cuts (b) 15 formed in a row in the fiber axis direction of the reinforcing fibers 13, and a plurality of rows in a row formed in the fiber axis direction of the reinforcing fibers 13. Regions (C) 18 composed of the notches (c) 16 are alternately formed in a direction perpendicular to the fiber axis of the reinforcing fibers 13. That is, in the prepreg base material 12, the rows made of the cuts (b) 15 and the rows made of the cuts (c) 16 are alternately formed in a direction perpendicular to the fiber axis of the reinforcing fibers 13.
Further, the prepreg base material may be the prepreg base material 12A illustrated in FIG.
The prepreg base 12 </ b> A is the same as the prepreg base 12 except that it includes a region (B) 17 </ b> A instead of the region (B) 17 and a region (C) 18 </ b> A instead of the region (C) 18. The region (B) 17A is the same as the region (B) 17 except that two rows of cuts (b) 15 are formed in the fiber axis direction of the reinforcing fibers 13. The region (C) 18A is the same as the region (C) 18 except that two rows of cuts (c) 16 are formed in the fiber axis direction of the reinforcing fibers 13. In the prepreg base material 12 </ b> A, the rows made of the cuts (b) 15 and the rows made of the cuts (c) 16 are alternately formed in every two rows in the direction perpendicular to the fiber axis of the reinforcing fibers 13.

  The preferable range of the length of the reinforcing fiber cut by the cutting in the prepreg base material used in the method for producing the fiber-reinforced plastic of the present invention is the same as the preferable range of the fiber length of the reinforcing fiber in the fiber-reinforced plastic described above. .

The fiber volume content (Vf) in the prepreg base material used in the method for producing a fiber-reinforced plastic of the present invention is preferably 5 to 70% by volume, more preferably 10 to 60% by volume, and further preferably 15 to 50% by volume. Most preferred is 25 to 45 volume percent. When Vf is equal to or greater than the lower limit, a structural material having sufficient mechanical properties is easily obtained. If Vf is not more than the upper limit value, good fluidity can be easily obtained at the time of shaping.
In addition, the Vf value of a prepreg base material means the volume ratio of the reinforced fiber with respect to the total volume of other components, such as a reinforced fiber in a prepreg base material, a matrix resin, a mold release agent, and another additive. Since the Vf value measured based on JIS K7075 is a value that varies depending on the amount of voids present in the fiber prepreg substrate, the fiber volume content does not depend on the amount of voids present in the fiber reinforced plastic manufacturing method of the present invention. Adopt rate.

As for the thickness of the prepreg base material used for the manufacturing method of the fiber reinforced plastics of this invention, 50-500 micrometers is preferable. If the thickness of a prepreg base material is more than a lower limit, handling of a prepreg base material will become easy. In addition, when two or more prepreg base materials are laminated to obtain a material (A) having a desired thickness, it is possible to suppress an increase in the number of prepreg base materials, and thus productivity is increased. If the thickness of the prepreg base material is less than or equal to the upper limit, voids (voids) inside the prepreg base material generated during the production of the prepreg base material can be suppressed, and a fiber-reinforced plastic having sufficient mechanical properties can be obtained. Cheap.
In the fiber reinforced plastic manufacturing method of the present invention, the thickness of the prepreg base material has little influence on the strength of the structural material finally obtained.
The manufacturing method of the prepreg base material used for the manufacturing method of the fiber reinforced plastic of this invention is not specifically limited, A well-known method is employable. As the prepreg substrate, a commercially available prepreg substrate may be used. Examples of the method for forming the cut into the prepreg base material include a method using a laser marker, a cutting plotter, a die cutting, and the like. The method using a laser marker is preferable in that it can be processed at a high speed even when cutting a complicated shape such as a curved line or a zigzag line. The method using a cutting plotter is preferable in that processing is easy even with a large prepreg base material of 2 m or more. The method using a punching die is preferable because it can be processed at high speed.

When the material (A) is a prepreg laminate, in the prepreg laminate, it is preferable to form a resin layer by laminating a resin sheet between the prepreg substrates to be laminated. Thereby, fluidity | liquidity improves in a process (ii), the isotropy and anisotropy of a mechanical physical property are controlled, and it becomes easy to obtain the fiber reinforced plastic with few variations in a mechanical physical property.
It does not specifically limit as resin used for the said resin layer, For example, the same thing as the matrix resin used for a prepreg base material is mentioned. The matrix resin used for the resin layer is preferably the same resin as the matrix resin used for the prepreg substrate. The resin used for the resin layer may be a resin different from the matrix resin used for the prepreg base material.
When the material (A) is a prepreg laminate, the aspect of laminating a plurality of prepreg substrates in the step (i) is such that the fiber axis direction of the reinforcing fibers in the prepreg substrates in the step (ii) is the material (A It suffices if it intersects with the traveling direction of
As a specific example of the lamination mode of the prepreg laminate of the material (A), for example, an embodiment in which two or more prepreg substrates are aligned and laminated such that the fiber axes of the reinforcing fibers of each prepreg substrate are in the same direction. Is mentioned. Since the direction of the fiber axis of the reinforcing fiber of each prepreg base material is aligned in the above aspect, the direction of the fiber axis of the reinforcing fiber intersects the traveling direction of the material (A) for each prepreg base material in the step (ii). It is easy to control their angular relationship.

Moreover, it is good also as an aspect from which the direction of the fiber axis of a reinforced fiber has shifted | deviated between each prepreg base material which forms a prepreg laminated body. That is, when laminating a plurality of prepreg base materials, it is not always necessary to strictly control the angles of the prepreg base materials so that the directions of the fiber axes of the reinforcing fibers of the prepreg base materials are completely aligned.
Further, even when there is a deviation in the fiber axis direction of the reinforcing fiber between the laminated prepreg base materials, the fiber axis direction of the reinforcing fiber for the prepreg base material of 66% or more with respect to the number of laminated layers in the prepreg laminated body. The deviation is preferably 40 ° or less, and more preferably 10 ° or less. In step (ii), the smaller the deviation in the fiber axis direction of the reinforcing fiber between the prepreg base materials, the more the angular relationship between the traveling direction of the material (A) and the fiber axis direction of the reinforcing fiber of each prepreg base material. It becomes easy to control.

  2-16 are preferable and, as for the number of lamination | stacking of the prepreg base material in the prepreg laminated body of material (A), 4-12 are more preferable. If the number of laminated prepreg base materials is equal to or greater than the lower limit, a fiber-reinforced plastic having sufficient mechanical properties can be easily obtained. If the number of laminated prepreg base materials is equal to or less than the upper limit, the laminating work becomes easy and the productivity is excellent.

  The material (A) preferably contains at least one release agent. If the material (A) contains at least one release agent, the material (A) cooled in the step (iii) is excellent in releasability with a pressurizing device, and a fiber reinforced plastic is used. A fiber-reinforced plastic having excellent releasability from a molding die during molding can be produced. The release agent may be contained in the prepreg base material, the resin film containing the release agent may be disposed between the surface of the prepreg base material and the prepreg laminate, and the release agent is in a particle or liquid state. May be added. Since the release agent of the material (A) is dispersed in the step (ii), the dispersibility and arrangement of the release agent in the material (A) have little influence on the obtained fiber reinforced plastic.

  The thickness of the material (A) is preferably 0.25 to 6.0 mm, more preferably 0.4 to 6.0 mm, and still more preferably 0.5 to 4.0 mm. If the thickness of the material (A) is at least the lower limit value, a fiber-reinforced plastic having sufficient mechanical properties can be easily obtained. If the thickness of the material (A) is less than or equal to the upper limit value, the direction of the fiber axis of the reinforcing fiber in the material (A) is more likely to be randomized by pressurization in the step (ii), and mechanical properties areotropic and anisotropic. It is easy to obtain a fiber reinforced plastic with controlled properties and little variation in mechanical properties.

{Process (ii)}
In the step (ii), the material (A) is applied to the material (A) by using a pressurizing apparatus capable of pressurizing the material (A) in the thickness direction so that the pressurization is substantially uniform over the direction orthogonal to the traveling direction of the material (A). While traveling in one direction, when the melting point is higher than the melting point of the matrix resin, or when it does not have a melting point, the pressure is applied in a state heated to a temperature T equal to or higher than the glass transition temperature.
In the step (ii), the direction of the fiber axis of the reinforcing fiber in the material (A) is made to intersect the traveling direction of the material (A) when the pressure is applied by the pressing device. Thereby, the reinforced fiber cut | disconnected by cutting with the matrix resin flows, and the direction of the fiber axis of a reinforced fiber changes in various directions. As a result, the direction of the fiber axis of the reinforcing fiber in the material (A) is randomized. Further, by improving the dispersibility of the reinforcing fibers, it is possible to obtain a fiber-reinforced plastic in which tan δ is controlled to be within the above range. In addition, since the dispersibility of the releasing agent is also improved, a fiber reinforced plastic having excellent releasing property can be obtained.
In step (ii), the angle φ formed by the direction orthogonal to the traveling direction of the material (A) and the direction of the fiber axis of the reinforcing fiber in the material (A) is preferably −20 ° to 20 °, and −5 to 5 °. Is more preferable. Thereby, the direction of the fiber axis of the reinforcing fiber is more easily randomized and the dispersibility of the reinforcing fiber is further improved. In step (ii) in the method for producing a fiber reinforced plastic of the present invention, the angle φ formed by the fiber axis directions of all the reinforcing fibers is −20 ° to 20 ° with respect to the direction orthogonal to the traveling direction of the material (A). It is preferable to do so.
In addition, when the prepreg laminate is used as the material (A), the condition of the angle φ is such that 66% or more of the reinforcing fibers in the prepreg base material are satisfied with respect to the number of laminated prepreg laminates. Also good.

The angle θ formed by the direction orthogonal to the traveling direction of the material (A) and the direction of the fiber axis of the reinforcing fiber is the traveling of the material (A) when the material (A) is pressed while traveling in the step (ii). It is an angle formed by the direction perpendicular to the direction and the direction of the fiber axis of the reinforcing fiber in the prepreg base material in the material (A). The angle θ is positive in the counterclockwise direction when the material (A) is viewed from above and negative in the clockwise direction.
When using a pressurizing device comprising at least a pair of press rolls in which the axial direction of the roll coincides with a direction orthogonal to the traveling direction of the material (A) as the pressurizing device in step (ii), the angle θ And an angle formed by the direction of the fiber axis of the reinforcing fiber in the prepreg base material in the material (A).
A preferable range of the temperature T in the step (ii) in the present invention is a temperature equal to or higher than the melting point of the matrix resin impregnated in the prepreg base material, or a temperature equal to or higher than the glass transition temperature of the matrix resin when the matrix resin does not have a melting point. It is. When the material (A) includes two or more kinds of matrix resins, the temperature T is based on the highest temperature among the melting points or glass transition temperatures of the matrix resins.
Although the temperature T varies depending on the type of the matrix resin, 150 to 450 ° C. is preferable and 200 to 400 ° C. is more preferable as long as the matrix resin melts. When the temperature T is in the above range, it is easy to flow the reinforcing fibers together with the matrix resin, and it is easy to obtain a fiber reinforced plastic in which the isotropy and anisotropy of the mechanical properties are controlled and the mechanical properties are less varied.

In step (ii) in the method for producing a fiber-reinforced plastic of the present invention, the material (A) may be preheated before the material (A) is heated to the temperature T. When preheating is performed, a preferable range of the preheating temperature and a preheating method are preferably 150 to 400 ° C, and more preferably 200 to 380 ° C. In the preheating stage, the matrix resin of the material (A) may be melted or not melted.
The method for preheating the material (A) is not particularly limited, and examples thereof include a method using an IR heater, a circulating hot air oven, and the like.

The clearance between the belts immediately below the rolls at the point where the pressure is applied by the pair of press rolls is preferably 30 to 80%, more preferably 40 to 70% with respect to the thickness of the material (A). If the clearance between the belts is equal to or greater than the lower limit value, it is easy to suppress the material (A) from being excessively crushed and deformed, and a fiber-reinforced plastic having a desired shape can be easily obtained. If the clearance between the belts is not more than the upper limit value, the dispersibility of the reinforcing fibers is improved, and a fiber reinforced plastic having a small tan δ value and excellent mechanical properties is easily obtained. In addition, the clearance between press means the distance of the press surfaces which contact | connects material (A) when it pressurizes. For example, when a double belt type heating and pressing machine is used, the clearance between the presses is the distance between the belts. When pressing the material (A) directly with a pair of press rolls, the clearance between the presses is the distance between the roll outer peripheral surfaces.
The following can be considered as factors that improve the dispersibility of the reinforcing fibers by reducing the clearance between the belts at the point where the pressure is applied by the pair of press rolls. At the point where the pressure is applied by the pair of press rolls, the thickness of the material (A) is temporarily reduced at the portion sandwiched between the belts. At this time, in the vicinity of the belt in the thickness direction of the material (A), the flow rates of the reinforcing fibers and the matrix resin become approximately the same as the belt speed by following the running of the belt. On the other hand, the flow rates of the reinforcing fibers and the matrix resin in the central portion in the thickness direction of the material (A) are pushed back by pressurization immediately before the press roll and become faster by being pushed by pressurization immediately after the press roll. It is considered that the dispersibility of the reinforcing fibers is improved by the shearing force due to the difference in the flow velocity in the thickness direction in the material (A).
The time for pressurizing the material (A) is preferably 0.1 to 30 minutes, and more preferably 0.5 to 10 minutes.

The travel speed of the material (A) in the step (ii) is preferably 0.1 to 25 m / min, more preferably 0.2 to 20 m / min, and further preferably 0.5 to 15 m / min. When the traveling speed of the material (A) is equal to or higher than the lower limit value, the productivity is increased. If the travel speed of the material (A) is not more than the upper limit value, it is easy to obtain a fiber reinforced plastic that is excellent in isotropy of mechanical properties and has little variation in mechanical properties.
Controlling the clearance, pressing time, and temperature T of the material (A) in step (ii) not only makes the mechanical properties of the resulting fiber-reinforced plastic excellent in isotropic properties, The anisotropy of physical properties can be controlled as desired.
In the step (ii) of the present invention, the material (A) is traveled in one direction by a pressurizing device including at least a pair of press rolls in which the axial direction of the roll is orthogonal to the travel direction of the material (A). The step (ii-1) of applying pressure while heating to the temperature T is preferable.

In step (ii-1), as shown in FIG. 5, the axial direction of the pair of press rolls 10 coincides with the orthogonal direction X with respect to the traveling direction of the material (A). The pair of press rolls 10 pressurize the material (A) 100 while being heated to the temperature T while traveling in one direction. At this time, the material (A) 100 is pressurized so that the fiber axis direction Y of the reinforcing fiber 110 in the material (A) 100 intersects the traveling direction of the material (A).
In the pair of press rolls, the axial directions of the upper and lower press rolls are the same.
As a method of heating the material (A) to the temperature T in the step (ii-1), a method of applying pressure while heating the material (A) using a heating roll as a press roll is preferable.
If the state where the material (A) is heated to the temperature T can be secured only by heating before pressing the material (A) and pressurizing with the press roll, use a press roll having no heating function. Also good. In addition, in the case where the material (A) can be heated to the temperature T with only a heating roll used as a press roll, preheating may not be performed.
In the step (ii-1), only one stage of the pair of press rolls may be used, or two or more stages may be used. When two or more press rolls that are paired vertically are provided in the step (ii-1), the axial direction of all the press rolls is made to coincide with the orthogonal direction X with respect to the traveling direction of the material (A).
In the step (ii-1), the material (A) is heated while being moved so as to pass between at least a pair of press rolls while being sandwiched between at least a pair of belts, and the material (A) is heated by the at least a pair of press rolls. It is preferable to use a double belt type heating and pressurizing machine that pressurizes. In this case, it is preferable that a release paper or a release film is disposed between the material (A) and the belt, or a release treatment is performed on the belt surface in advance. The material of the belt is not particularly limited, and metal is preferable in terms of heat resistance and durability.
In addition, a process (ii-1) is not limited to the aspect performed using the said double belt type heating pressurization machine. For example, it is good also as an aspect which presses the said material (A) with a pair of press roll, running a strip | belt-shaped material (A), without pinching with a pair of belt. In this case, it is preferable that the clearance between the pair of press rolls is within the above-described range.
Step (ii) is not limited to an embodiment using a pressurizing device including at least a pair of press rolls. For example, it is good also as an aspect pressed with the pressurization apparatus which presses with a plane and a press roll, the pressurization apparatus by the press panel pressed with a plane and a plane, and a pressurization apparatus provided with a some spherical press.

{Process (iii)}
In step (iii), the material (A) pressurized by the pressure device in step (ii) is cooled to obtain a fiber reinforced plastic. When the matrix resin is a thermoplastic resin, the temperature of the material (A) is lowered to below the melting point of the matrix resin or below the glass transition temperature and solidified to obtain a fiber reinforced plastic.
When a prepreg laminate is used as the material (A), the fiber reinforced plastic obtained has a sheet shape in which the prepreg base materials are bonded together. Therefore, even when a prepreg laminate is used, the obtained fiber reinforced plastic is easy to handle.
The method for cooling the material (A) is not particularly limited, and examples thereof include a method using a hot water roll. You may employ | adopt the method of cooling by allowing material (A) to cool.
The cooling time is preferably 0.5 to 30 minutes.

[Example of embodiment]
Hereinafter, an example of using the double belt type heating and pressurizing machine 1 illustrated in FIG. 6 (hereinafter simply referred to as the heating and pressing machine 1) will be described as an example of an embodiment for carrying out the process (ii-1) and the process (iii). . In addition, the aspect which implements a process (ii) and a process (iii) is not limited to the aspect using the heating-pressing machine 1. FIG.
The heating and pressing machine 1 includes a pair of belts 12 that travel in one direction with the belt-shaped material (A) 100 sandwiched from above and below, a pair of IR heaters 14 that preheat the material (A) 100, and a preheated material. (A) A pair of press rolls 10 that sandwich and press 100 from above and below, and three stages, and a pair of hot water rolls 16 that sandwich and cool the material (A) 100 pressed by the press roll 10 from above and below. And a winding roll 18 for winding the cooled and solidified fiber reinforced plastic 120.
The pair of press rolls 10 pressurizes the material (A) 100 while rotating in a direction to send the material (A) 100 passing between the pair of press rolls 10 to the downstream side. In the heating and pressing machine 1, the axial direction of the pair of press rolls 10 coincides with the orthogonal direction X with respect to the traveling direction of the supplied material (A) 100. The pair of hot water rolls cool the material (A) 100 while rotating in a direction to send the material (A) 100 passing between them to the downstream side.

Each of the pair of belts 12 is wound around and mounted on a drive roll 20 provided upstream of the IR heater 14 and a driven roll 22 provided downstream of the hot water roll 16. Moved. The material (A) 100 travels when the pair of belts 12 rotates while holding the material (A) 100 therebetween.
In the aspect using this heating and pressurizing machine 1, as the step (ii-1), a band-shaped material (such as the direction of the fiber axis of the reinforcing fiber in the material (A) 100 intersects the traveling direction of the material (A) 100. A) 100 is continuously supplied to the heating and pressing machine 1. Specifically, the strip-shaped material (A) 100 in which the direction of the fiber axis of the reinforcing fiber intersects the length direction is continuously supplied to the heating and pressing machine 1 in the length direction.
In the heating and pressurizing machine 1, the material (A) 100 is preheated by the IR heater 14 while traveling so as to pass between the pair of press rolls 10 while being sandwiched by the pair of belts 12. A) Pressurization with 100 heated to temperature T. Thereby, in the material (A) 100, the matrix resin and the reinforcing fiber flow, the direction of the fiber axis of the reinforcing fiber is randomized, and the dispersibility of the reinforcing fiber is improved. In this example, it is preferable that the clearance between the belts is within the above range at each point where the material (A) 100 is pressed by each of the pair of press rolls 10 arranged in three stages.
Further, in this example, it is preferable to use a heating roll as the press roll 10 and pressurize the material (A) 100 simultaneously with heating to the temperature T. In addition, when the material (A) 100 can be pressurized by the press roll 10 while being heated to the temperature T only by preheating with the IR heater 14, the material (A) 100 is not heated by the press roll 10 without being heated. Only may be performed.
Next, as the step (iii), the material (A) 100 pressed by the press roll 10 is caused to travel so as to pass between the pair of hot water rolls 16 while being sandwiched between the pair of belts 12. The belt-shaped fiber reinforced plastic 120 is obtained by cooling with the roll 16.

The obtained fiber reinforced plastic 120 is peeled off from the pair of belts 12 on the downstream side of the driven roll 22 and then wound around the winding roll 18 via the guide roll 24.
A double belt type heating and pressing machine such as the heating and pressing machine 1 is advantageous in that a series of steps from heating and pressing to cooling of the material (A) can be easily performed.
In the fiber-reinforced plastic of the present invention described above, a release agent is contained, and tan δ (ave) and tan δ (max) -tan δ (ave) are controlled within a specific range. In addition, both excellent mechanical properties and excellent fluidity during shaping can be achieved.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Measurement of viscoelastic properties (tan δ)]
A disk having a diameter of 25 mm was cut out from the fiber reinforced plastic obtained in each example with a water jet cutter to prepare a test specimen.
As a test apparatus, a rheometer (product name “AR-G2”) manufactured by TA Instruments was used. Two parallel plates made of aluminum with a diameter of 25 mm were attached, and mapping was performed to remove residual torque. By performing this “mapping”, it is possible to measure with high accuracy. After adjusting the zero point of the parallel plate gap at the melting point of the matrix resin of the test specimen (165 ° C. when the matrix resin is polypropylene, 225 ° C. when nylon 6 is used), it is applied to the lower plate of the upper and lower parallel plates. The test body was set, and the upper plate was lowered to a position where the entire surface was in contact with the test body. The gap (clearance) between the upper and lower parallel plates at this time was taken as the thickness of the test specimen at the time of measurement. From a temperature 30 ° C lower than the melting point, which is the measurement start temperature (135 ° C when the matrix resin is polypropylene, 195 ° C when nylon 6 is used), with the clearance kept constant, under the following measurement conditions, two parallel sheets A constant strain was applied across the test body with the plate, and the storage elastic modulus G ′ and the loss elastic modulus G ″, which were responses at that time, were recorded. A value obtained by dividing the loss elastic modulus G ″ by the storage elastic modulus G ′ was defined as tan δ.
(Measurement condition)
Frequency: 1Hz,
Strain: 0.1%
Measurement temperature range: 30 ° C. lower than the melting point of the matrix resin to 10 ° C. higher than the melting point of the matrix resin (135 ° C. to 175 ° C. when the matrix resin is polypropylene, 195 to 235 when the matrix resin is nylon 6) ℃)
Temperature increase rate: 2 ° C / min,
Measurement point: Every 30 seconds (every 1 ° C).
[Liquidity during shaping]
The fluidity during shaping of the fiber reinforced plastic obtained in each example was evaluated by the following method.
A plate-like product having a length of 78 mm and a width of 78 mm was cut out from the obtained fiber-reinforced plastic. The plate-like material is stacked to a thickness of about 4 mm, and when the matrix resin is polypropylene, heated at 230 ° C. for 10 minutes using a mini test press (product name: MP-2FH), 145 ° C. Pressing was performed for 60 seconds under the condition of 5 MPa. Further, when the matrix resin is nylon 6, it was heated at 290 ° C. for 10 minutes and then pressed at 200 ° C. and 5 MPa for 60 seconds. The initial thickness h _A (mm) before press molding and the final thickness h _B (mm) after press molding were measured, and the fluidity was evaluated by the ratio h _A / h _{B obtained} by dividing the initial thickness by the final thickness. In addition, there is a phenomenon called a spring back, in which the thickness of the fiber reinforced plastic increases due to the residual stress of the reinforced fiber due to the softening of the fiber reinforced plastic matrix resin. When the fiber reinforced plastic spring-backed by heating could not be pressed to the initial thickness h _A (mm) by press molding under the above conditions, x was recorded.

[Bending properties]
<Measurement of bending strength, coefficient of variation (CV value), 80 ° C. bending strength retention>
The fiber reinforced plastic obtained in each example was cut into a 300 mm square, and this was overlapped by 2 mm in thickness in the same direction (so that the direction of MD, TD, etc. was the same when laminated). The laminate is placed in a 300 mm square and 15 mm deep stamping mold, heated to 200 ° C. when the matrix resin is polypropylene and 250 ° C. when the matrix resin is nylon 6, and then subjected to a multi-stage press (Shinfuji). When the matrix resin is polypropylene and the matrix resin is nylon 6, the compression molding machine manufactured by Metal Industries Co., Ltd., product name: SFA-50HH0), and when the matrix resin is nylon 6, it is 2 from both sides at a pressure of 0.1 MPa with a panel surface of 250 ° C. Heated and pressurized for minutes. Then, it cooled to room temperature with the same pressure, and obtained the fiber-reinforced plastic board of plate shape 2mm in thickness. A bending test piece having a length of 100 mm and a width of 25 mm was cut out from the obtained fiber-reinforced plastic plate with a wet cutter, and a bending strength was measured by performing a three-point bending test according to a test method specified in JIS K7074. At this time, the longitudinal direction of the bending test piece coincides with the MD direction (direction of 90 ° with respect to the roll axial direction) at the time of manufacturing the fiber reinforced plastic, and with the TD direction (axial direction of the roll). Six of each were prepared, a total of 12 tests were performed, and the average value was recorded as the bending strength. As a testing machine, an Instron universal testing machine 4465 type was used. The test was performed at room temperature (23 ° C.) and 80 ° C. Furthermore, the standard deviation is calculated from the measured value of bending strength at room temperature (23 ° C), and the standard deviation is divided by the average value, thereby calculating the coefficient of variation (CV value, unit:%), which is a variation index. did.
The ratio σ _{80 °} C./σ _RT (unit:%) was calculated as the 80 ° C. bending strength retention. However, σ _{80 ° C.} is the bending strength measured at 80 ° C. σ _RT is the bending strength measured at room temperature.
In addition, regarding Comparative Examples 5 to 7 having no clear MD direction and TD direction at the time of production, an arbitrary direction was evaluated as the MD direction, and a direction orthogonal to the direction was evaluated as the TD direction.

[Release evaluation]
The releasability of the fiber reinforced plastic obtained in each example was evaluated by the following method.
The fiber reinforced plastic obtained in each example was cut into 180 mm squares, and this was laminated in the same direction (in the same direction when MD, TD, etc. were laminated) by a thickness of 6 mm, 125 ° C. higher than the melting point of the matrix resin. Throw in a far-infrared heater type heating device (NGK Kiln Tech Co., Ltd., product name: H7GS-71289) set to a high temperature (290 ° C when the matrix resin is polypropylene, 350 ° C when the matrix resin is nylon 6). And heated for 5 minutes. Using a 300t press machine (manufactured by Kawasaki Yoko Co., Ltd.) to which a stamping mold (lower mold is concave, upper mold is convex) having a depth of 310 mm and a depth of 40 mm, the mold temperature is 90 ° C. and the molding pressure is 18 MPa. Then, a fiber reinforced plastic in which the resin was melted by heating was charged in the central part of the lower mold of the mold and pressed for 1 minute to obtain a stamped molded product having a 310 mm square and a thickness of 2 mm. The mold surface was pressed without performing a release treatment such as application of a release agent. Further, the time from when the fiber reinforced plastic was taken out of the far infrared heater type heating device until it was pressed was 25 seconds. After the upper and lower molds attached to the press machine were opened and opened, the stamping molded product was removed from the mold by protruding the ejector pins. At this time, if the ejector pin broke through the stamped molded product and could not be removed from the mold, it was possible to remove the mold by ejecting the ejector pin, but a part of the stamped molded product was left on the mold surface. Was recorded as △, and when it was possible to remove the mold without any problem, it was recorded as ◯.

[Evaluation of pf and ec]
According to the pf measurement method and ec measurement method described above, pf and ec were measured. For the X-ray diffraction measurement, an X-ray diffraction apparatus (manufactured by Rigaku Corporation, TTR-III) equipped with a fiber sample stage was used, the measurement sample was placed on the stage, and the target was Cu. Specifically, while irradiating X-rays from above the measurement sample, the measurement sample is rotated about its thickness direction, and a diffracted X-ray is emitted by a detector arranged at a diffraction angle 2θ = 24.5 °. I took it in. A standard sample having a Vf of 35% by volume was used.

[Evaluation of dp]
A sample piece of 3 cm square was cut out from the fiber reinforced plastic and embedded in a techno bit 4000 manufactured by Kulzer. After the techno bit 4000 was cured, it was polished and mirror-finished so that the cross section of the sample piece was exposed.
Next, a cross-sectional photograph of the sample piece was taken under the following conditions.
(Shooting conditions)
Device: Olympus Industrial Optical Microscope BX51M
Lens magnification: 500 times Shooting dot pitch: 0.17 μm
In the obtained cross-sectional photograph, a portion corresponding to a range of (thickness direction × 0.5 mm in a direction orthogonal to the thickness direction) in the cross section of the sample piece was used as a processing target image. Using the software Fair-Roof as image editing software, dp was calculated according to the dp measurement method described above. The calculation of dp was performed at five points in the cross section of each sample piece, and the average value was obtained.

[Production Example 1: Production of prepreg substrate A]
For 100 parts by mass of polyamide 6 resin (UBE nylon manufactured by Ube Industries, product number: 1013B, specific gravity 1.14), a saponified product of montanic acid part as a release agent (Luwas OP, calcium montanate and montanic acid ester manufactured by BASF) , Saponification value of 110 to 130 mgKOH / g) and 0.2 part by mass of the mixture were premixed, and a film having a basis weight of 48 g / m ² was produced using an extruder and a T-die. did.
Carbon fiber (Pyrofil CF tow, manufactured by Mitsubishi Rayon Co., Ltd., product number: TR 50S15L, carbon fiber diameter 7 μm, number of filaments: 15,000, toe weight: 1.0 g / m, specific gravity 1.82) in one direction and flat A fiber sheet having a basis weight of 75 g / m ² was obtained by aligning in a shape.
The fiber sheet is sandwiched from both sides of the fiber sheet, and heated and pressurized by passing a calender roll a plurality of times to impregnate the fiber sheet with a fiber volume content (Vf) of 33% by volume and a basis weight of 170 g / m ^2. A prepreg substrate A having a theoretical thickness of 125 μm was prepared.

[Production Example 2: Production of prepreg base material B]
A prepreg base material B was produced in the same manner as in Production Example 1 except that a film consisting only of polyamide 6 resin (UBE nylon manufactured by Ube Industries, product number: 1013B, specific gravity 1.14) was produced. This prepreg base material has a fiber volume content (Vf) of 33% by volume, a basis weight of 170 g / m ² , and a theoretical thickness of 125 μm. Note that the prepreg base material B does not contain a release agent.

[Production Example 3: Production of prepreg base material C]
A prepreg was prepared in the same manner as in Production Example 1 except that a film having a basis weight of 38 g / m ² consisting only of acid-modified polypropylene resin (Modick manufactured by Mitsubishi Chemical Corporation, product number: P958V, MFR: 50, specific gravity 0.91) was produced. A substrate C was produced. This prepreg base material has a fiber volume content (Vf) of 33% by volume, a basis weight of 151 g / m ² , and a theoretical thickness of 125 μm. Note that the prepreg base material C does not contain a release agent.

[Production Example 4: Production of prepreg base material D]
A prepreg substrate D was produced in the same manner as in Production Example 3, except that the basis weight of the film was 29 g / m ² and the basis weight of the fiber sheet was 110 g / m ² . This prepreg base material has a fiber volume content (Vf) of 49% by volume, a basis weight of 167 g / m ² , and a theoretical thickness of 123 μm. The prepreg base material D does not contain a release agent.

[Example 1]
From the prepreg substrate A obtained in Production Example 1, a rectangular prepreg substrate of 300 mm (0 ° direction with respect to the fiber axis) × 900 mm (90 ° direction with respect to the fiber axis) was cut out. Using a cutting plotter (L-2500 cutting plotter made by Rezac), the prepreg base material was cut with a depth to cut the reinforcing fiber, to obtain a prepreg base material with a cut. In the cutting process, as shown in FIG. 5, a region (B) in which a plurality of cuts (b) in which the angle θ formed by the fiber axis of the reinforcing fiber and the cut is + 45 ° are formed in a line in the fiber axis direction of the reinforcing fiber (B). And regions (C) in which a plurality of cuts (c) having an angle θ of −45 ° are formed in a row in the fiber axis direction of the reinforcing fiber are alternately formed in a direction perpendicular to the fiber axis of the reinforcing fiber. Was carried out as follows. The angle θ is positive in the counterclockwise direction with respect to the fiber axis of the reinforcing fiber in plan view. The fiber length of the reinforcing fiber divided by the cutting was 25 mm.
Four of the prepreg base materials with cuts were laminated so that the fiber axes of the reinforcing fibers were in the same direction to obtain a prepreg laminate. The thickness of the prepreg laminate was 0.5 mm.
Reinforcing fibers in the prepreg laminate with respect to the direction orthogonal to the running direction of the prepreg laminate (the axial direction of the press roll) in the double belt type heating and pressurizing machine illustrated in FIG. 6 where the upper and lower belts are driven at 0.8 m / min. A plurality of prepreg laminates were continuously charged so that the angle φ formed by the fiber axis direction of the prepreg laminate was 0 ° and no gap was formed before and after each prepreg laminate. In the double belt type heating and pressurizing machine, the prepreg laminate is heated by a two-stage press roll having a roll temperature of 380 ° C. and a belt clearance of 300 μm immediately below the roll to melt the thermoplastic resin. did. After that, a 1.5 m cooling section provided with a one-stage hot water roll having a roll temperature of 30 ° C. and a clearance between belts of 300 μm immediately below the roll was passed, and the thermoplastic resin was solidified to obtain a fiber reinforced plastic. The apparent traveling speed of the prepreg laminate is the same as the belt driving speed.
The obtained fiber reinforced plastic had a thickness of 0.5 mm and a basis weight of 680 g / m ² .

[Example 2]
A fiber reinforced plastic was obtained in the same manner as in Example 1 except that the clearance between the belts immediately below the rolls during heating and cooling was 400 μm. The obtained fiber reinforced plastic had a thickness of 0.5 mm and a basis weight of 680 g / m ² .

[Comparative Example 1]
A fiber reinforced plastic was obtained in the same manner as in Example 1 except that the prepreg base material B obtained in Production Example 2 was used. The obtained fiber reinforced plastic had a thickness of 0.5 mm and a basis weight of 680 g / m ² .

[Comparative Example 2]
Fiber reinforced plastic in the same manner as in Example 1 except that the prepreg base material C obtained in Production Example 3 was used, the roll temperature during heating and pressing was 270 ° C., and the belt driving speed was 1.0 m / min. Got. The obtained fiber reinforced plastic had a thickness of 0.5 mm and a basis weight of 600 g / m ² .

[Comparative Example 3]
A fiber reinforced plastic was obtained in the same manner as in Comparative Example 2 except that the prepreg base material D obtained in Production Example 4 was used and the belt driving speed was changed to 0.5 m / min. The obtained fiber reinforced plastic had a thickness of 0.5 mm and a basis weight of 670 g / m ² .

[Comparative Example 4]
In Comparative Example 4, a fiber reinforced plastic is produced by the method (I).
A 300 mm square prepreg base material was cut out from the prepreg base material C obtained in Production Example 3, and cut using linear cutting at regular intervals using a cutting plotter (product name: L-2500). An intruded prepreg substrate was obtained. In the cutting process, the fiber length of the carbon fiber is 25.0 mm, the cutting length is 20.0 mm, and the angle formed by the fiber axis of the reinforcing fiber and the cutting in the part inside the part of 5 mm from the periphery of the prepreg base material. All the θ were applied to + 45 °. Sixteen notched prepreg base materials, the fiber direction of each notched prepreg base material is 0 ° / 45 ° / 90 ° / −45 ° / −45 ° / 90 ° / 45 ° / 0 ° from above. Lamination was carried out so that / 0 ° / 45 ° / 90 ° / −45 ° / −45 ° / 90 ° / 45 ° / 0 °. The laminated prepreg base materials with cuts are spot-welded with an ultrasonic welder (manufactured by Emerson Japan, product name: 2000LPt) to produce a quasi-isotropic ([0/45/90 / -45] s2) prepreg. A laminate was produced.
The prepreg laminate was placed in a stamping die of 300 mm square and 15 mm depth, heated to 200 ° C., and then placed in a multi-stage press (compression molding machine manufactured by Shinto Metal Industry, product name: SFA-50HH0). The plate was heated and pressurized at a pressure of 0.1 MPa for 2 minutes with a 200 ° C. surface. Thereafter, the laminate was cooled to room temperature under the same pressure, and a plate-like fiber reinforced plastic having a thickness of 2 mm was obtained.

[Comparative Example 5]
In Comparative Example 5, a fiber reinforced plastic is produced by the method (II).
The prepreg base material D obtained in Production Example 4 was slit into a strip shape having a width of 15.0 mm, and then continuously cut to a length of 25.0 mm using a guillotine type cutting machine. A chopped strand prepreg of 0 mm was obtained. 244 g of the obtained chopped strand prepreg was weighed and individually dropped from a 30 cm height into a 300 mm square and 15 mm deep stamping die, and laminated so that the fiber orientation was random. .
After the stamping die on which the chopped strand prepreg is laminated is heated to 200 ° C., it is 0.1 MPa by a multi-stage press machine (compression molding machine manufactured by Shinfuji Metal Industry Co., Ltd., product name: SFA-50HH0) at 200 ° C. Heated and pressurized for 2 minutes at pressure. Thereafter, the laminate was cooled to room temperature under the same pressure, and a plate-like fiber reinforced plastic having a thickness of 2 mm was obtained.

[Comparative Example 6]
In Comparative Example 6, a fiber reinforced plastic is produced by the method (III).
Using a rotary cutter, carbon fiber (Pyrofil TR 50S manufactured by Mitsubishi Rayon) was cut into 6 mm to obtain chopped carbon fiber. Similarly, the fiber which consists of acid-modified polypropylene resin (Mitsubishi Chemical make Modic P958V, MFR50) was cut into 3 mm, and the chopped polypropylene fiber was obtained. 0.74 kg of chopped polypropylene fiber was added to 110 kg of an aqueous polyethylene oxide solution having a mass concentration of 0.12%, and the mixture was sufficiently stirred using a stirrer. Subsequently, 0.37 kg of chopped carbon fiber was added and stirred for 10 seconds to obtain a dispersion. The obtained dispersion was poured into a 100 cm square mesh frame, and after the polyethylene oxide aqueous solution was filtered, moisture was completely removed in a dryer at 120 ° C. to obtain a fiber volume content of 20 vol% (fiber mass content of 33 mass). %) And a basis weight of 1.11 kg / m ² was obtained. The obtained prepreg base material was cut into 30 cm square, and two sheets were stacked to obtain a prepreg laminate. The prepreg laminate was placed in a 300 mm square and 15 mm deep stamping die, heated to 200 ° C., and then placed in a multi-stage press (compression molding machine manufactured by Shindo Metal Industries, product name: SFA-50HH0). The plate was heated and pressurized at a pressure of 0.1 MPa for 2 minutes with a 200 ° C. surface. Thereafter, the prepreg laminate was cooled to room temperature under the same pressure to obtain a plate-like fiber reinforced plastic having a thickness of 2 mm.

The evaluation results of each example are shown in Table 2.
In addition, “DBP randomization” in Table 1 means a method of randomizing the fiber axis direction of the reinforcing fiber by pressurization with a double belt type heating and pressurizing machine.

11: Double belt type heating and pressing machine 12, 12A: Prepreg base material 13: Reinforcing fiber 14: Matrix resin 15: Cutting (b)
16: Cutting (c)
17, 17A: Region (B)
18, 18A: Region (C)
110: Press roll 112: Belt 114: IR heater 116: Hot water roll 118: Winding roll 120: Drive roll 122: Follower roll 124: Guide roll 1100: Material (A)
1110: Reinforcing fiber 1120: Fiber reinforced plastic X: Direction perpendicular to the running direction of the material (A) Y: Fiber axis direction of the reinforcing fiber

Claims (5)

A fiber reinforced plastic comprising reinforced fibers and a matrix resin,
Contains at least one release agent,
The following formula of fiber reinforced plastic in the temperature range of T-30 (° C.) to T-10 (° C.) (where T is the melting point of the matrix resin or, if not, the glass transition temperature): The average value of the viscoelastic property tan δ represented by 1) is tan δ (ave), and the maximum value of the viscoelastic property tan δ in the temperature range of T−10 (° C.) to T + 10 (° C.) is tan δ (max). At this time, tan δ (ave) is 0.01 to 0.25, and tan δ (max) −tan δ (ave) is 0.15 or more.
tan δ = G ″ / G ′ (1)
However, the symbols in the formula (1) have the following meanings.
G '': loss modulus,
G ′: storage elastic modulus.   The fiber reinforced plastic according to claim 1, wherein an average fiber length of the reinforcing fibers is 1 to 100 mm.   The fiber-reinforced plastic according to claim 1 or 2, wherein the release agent is a higher fatty acid ester and / or a higher fatty acid salt.   The fiber-reinforced plastic according to any one of claims 1 to 3, comprising 0.01 to 4 parts by mass of the release agent with respect to 100 parts by mass of the matrix resin.   The fiber reinforced plastic according to any one of claims 1 to 4, wherein the matrix resin is a thermoplastic resin.