WO2020196531A1

WO2020196531A1 - Matrix resin film for fiber-reinforced resins, prepreg, carbon fiber-reinforced resin molded body and method for producing carbon fiber-reinforced resin molded body

Info

Publication number: WO2020196531A1
Application number: PCT/JP2020/013045
Authority: WO
Inventors: 宏和飯塚; 正嗣大槻; 真一郎鈴木; 陽平田; 雄介菊本
Original assignee: 藤森工業株式会社
Priority date: 2019-03-25
Filing date: 2020-03-24
Publication date: 2020-10-01
Also published as: JPWO2020196531A1; TW202041381A; TWI748385B; JP7426378B2

Abstract

A matrix resin film for fiber-reinforced resins, which comprises a first layer in one surface, while comprising a second layer in the other surface, and which is configured such that: the first layer is formed of a first resin composition; the first resin composition contains a base material that is composed of a maleic acid-modified polyolefin and a crosslinking agent; a second resin composition; the solid content concentration of the main material contained in the first resin composition is from 70% by mass to 99.5% by mass (inclusive) relative to the total mass of the first resin composition; the solid content concentration of the crosslinking agent contained in the first resin composition is from 0.5% by mass to 30% by mass (inclusive) relative to the total mass of the first resin composition; and the solid content concentration of the main material contained in the second resin composition is from 80% by mass to 100% by mass (inclusive) relative to the total mass of the second resin composition.

Description

Method for manufacturing matrix resin film for fiber reinforced resin, prepreg, carbon fiber reinforced resin molded body, and carbon fiber reinforced resin molded body

The present invention relates to a matrix resin film for a fiber reinforced resin, a prepreg, a carbon fiber reinforced resin molded body, and a method for producing a carbon fiber reinforced resin molded body.
The present application claims priority based on Japanese Patent Application No. 2019-057349 filed on March 25, 2019, the contents of which are incorporated herein by reference.

In recent years, a molded body using carbon fiber reinforced resin (hereinafter, sometimes abbreviated as CFRP) as a forming material has been proposed. CFRP is lighter than metal materials but has high mechanical strength. Therefore, the CFRP molded body is adopted as, for example, a metal substitute part.

A molded body using CFRP is obtained by molding a prepreg having a semi-cured curable resin and carbon fiber which is a reinforcing fiber, and curing the curable resin. CFRP prepregs are produced, for example, by impregnating a carbon fiber woven fabric with a solution of curable resin, then removing the solvent from the solution, and then semi-curing the curable resin (eg, Patent Document). 1).

Japanese Unexamined Patent Publication No. 01-272416

In the method described in Patent Document 1 described above, when the carbon fiber is impregnated with the curable resin, when the inside of the obtained prepreg is observed in detail, the curable resin cannot be sufficiently impregnated and voids are formed. There may be. When a molded body is manufactured using a prepreg having such voids, if the voids are exposed on the surface of the prepreg, minute recesses remain on the surface of the molded body, which causes a poor appearance. Further, the fiber-reinforced resin molded product to be produced is required to have high shear strength.

The present invention has been made in view of such circumstances, and is a matrix resin film for fiber reinforced resin, a prepreg, and a carbon fiber reinforced resin molded body capable of producing a molded body having high shear strength and few voids. , And a method for producing a carbon fiber reinforced resin molded body.

That is, the present invention has adopted the following configuration.
[1] A matrix resin film for a fiber-reinforced resin having a first layer on one surface and a second layer on the other surface, wherein the first layer is composed of a first resin composition. The second layer is composed of a second resin composition having a lower content of a cross-linking agent than the first resin composition, and the first resin composition is cross-linked with a main agent made of maleic acid-modified polyolefin. The second resin composition contains a main agent made of maleic acid-modified polyolefin, and the solid content concentration of the main agent contained in the first resin composition is the first resin composition. It is 70% by mass or more and 99.5% by mass or less with respect to the total amount, and the solid content concentration of the cross-linking agent contained in the first resin composition is 0.5% by mass with respect to the total amount of the first resin composition. % Or more and 30% by mass or less, and the solid content concentration of the main agent contained in the second resin composition is 80% by mass or more and 100% by mass or less with respect to the total amount of the second resin composition. Matrix resin film for resin.
[2] The matrix resin film for a fiber reinforced resin according to [1], which has a thickness of 30 μm or more and 200 μm or less.
[3] The matrix resin film for fiber reinforced resin according to [1] or [2], wherein the melt viscosity of the maleic acid-modified polyolefin is 1000 mPa · s or more and 50,000 mPa · s or less at 180 ° C.
[4] The method according to any one of [1] to [3], wherein the graft modification rate of the maleic acid-modified polyolefin with maleic anhydride or maleic acid is 0.5% by mass or more and 2.5% by mass or less. Matrix resin film for fiber reinforced resin.
[5] The matrix resin film for a fiber reinforced resin according to any one of [1] to [4], wherein the cross-linking agent is an epoxy resin.
[6] The matrix resin film for a fiber reinforced resin according to [5], wherein the epoxy compound constituting the epoxy resin has a weight average molecular weight of 300 or more and 50,000 or less.
[7] The matrix resin for fiber-reinforced resin according to [5] or [6], wherein the cross-linking agent is at least one selected from the group consisting of novolak type, phenol type, bisphenol A type, and bisphenol F type. the film.
[8] A prepreg in which the matrix resin film for fiber reinforced plastic according to any one of [1] to [7] and carbon fibers are laminated.
[9] The prepreg according to [7], wherein the surface provided with the second layer is laminated so as to be in contact with the carbon fibers.
[10] The prepreg according to [8] or [9], wherein the carbon fibers are continuous fibers.
[11] A carbon fiber reinforced resin molded body in which the prepreg according to any one of [8] to [10] is laminated.
[12] A method for producing a carbon fiber reinforced resin molded body in which the prepregs according to [11] are laminated, wherein the prepregs are laminated to obtain a laminated body, and the obtained laminated body is stampable molded. A method for producing a carbon fiber reinforced resin molded product, comprising.

According to the present invention, a matrix resin film for a fiber reinforced resin, a prepreg, a carbon fiber reinforced resin molded body, and a method for manufacturing a carbon fiber reinforced resin molded body, which enable the production of a molded body having high shear strength and few voids. Can be provided.

It is a schematic diagram of the cross section of the matrix resin film for a fiber reinforced resin. It is the schematic sectional drawing which shows the prepreg. It is explanatory drawing explaining the manufacturing process of a prepreg. It is explanatory drawing explaining the manufacturing process of a prepreg. It is explanatory drawing explaining the manufacturing process of a prepreg. It is explanatory drawing explaining the manufacturing process of a prepreg. It is explanatory drawing explaining the manufacturing process of a prepreg.

Hereinafter, the present invention will be described based on a preferred embodiment.

<Matrix resin film for fiber reinforced plastic>
The matrix resin film for fiber reinforced plastics of the present embodiment (hereinafter, may be referred to as “resin film”) has a first layer on one surface and a second layer on the other surface. FIG. 1 shows a schematic view of a cross section of the resin film 11 of the present embodiment. The resin film 11 includes a first layer 11A and a second layer 11B.

The first layer is composed of the first resin composition. The second layer is composed of a second resin composition having a lower content of the cross-linking agent than the first resin composition. The first resin composition contains a main agent composed of maleic acid-modified polyolefin and a cross-linking agent. The second resin composition contains a main agent composed of maleic acid-modified polyolefin.

≪Main agent; Maleic acid-modified polyolefin≫
The first resin composition and the main agent constituting the second resin composition have thermoplasticity. The maleic acid-modified polyolefin used as the main agent of the present embodiment is obtained by graft-modifying an unmodified polyolefin resin with either or both of maleic anhydride and maleic acid.
Hereinafter, the “unmodified polyolefin resin” means a maleic anhydride or a polyolefin resin that has not been graft-modified with maleic acid.

Examples of the method for producing a maleic acid-modified polyolefin include the following two methods.
(1) A method of graft-modifying an unmodified polyolefin resin with maleic anhydride or maleic acid by melt-kneading.
(2) A method of copolymerizing an olefin monomer and an acid functional group-containing monomer. Either one or both of maleic anhydride and maleic acid is used as the "acid functional group-containing monomer".

The graft modification is preferably carried out in the presence of a radical polymerization initiator such as an organic peroxide or an aliphatic azo compound.

In the composition of the maleic acid-modified polyolefin, the olefin monomer when copolymerized with maleic anhydride or maleic acid, or the olefin monomer constituting the unmodified polyolefin resin, includes ethylene, propylene, 1-butene, isobutylene, 1-hexene, and the like. One or more of 1-octene, α-olefin and the like can be mentioned.

Examples of the unmodified polyolefin resin include polyethylene, polypropylene, poly-1-butene, polyisobutylene, a copolymer of ethylene and propylene, a copolymer of propylene and 1-butene, and a random mixture of propylene and ethylene or α-olefin. Examples thereof include one or more types such as a copolymer, a block copolymer of propylene and ethylene or α-olefin.
Among them, polypropylene-based resins such as homopolypropylene which is a homopolymer of propylene, a block copolymer of propylene-ethylene, a random copolymer of propylene-ethylene, and a propylene-1-butene copolymer are preferable.
That is, in the present embodiment, the maleic acid-modified polypropylene-based resin is preferable as the maleic acid-modified polyolefin.

Since the monomer constituting the maleic acid-modified polyolefin contains 1-butene, the molecular movement of the main agent and the cross-linking agent constituting the resin film is promoted when the resin film is heated. When the main agent and the cross-linking agent have functional groups capable of reacting with each other, the chances of the functional groups of the main agent and the cross-linking agent coming into contact with each other increase, and as a result, the durability of the resin film and the adhesion to the adherend are further improved. To do.

When the maleic acid-modified polyolefin contains unreacted maleic acid or maleic anhydride, the adhesive strength may decrease. Therefore, as the main agent constituting the resin film, unreacted maleic acid or maleic anhydride-modified polyolefin containing no maleic anhydride is preferable.
In the present embodiment, it is preferable to use maleic acid-modified polyolefin obtained by removing unreacted maleic acid or maleic anhydride from the products obtained by the above-mentioned production methods (1) and (2) as a main agent. ..

-Graft modification rate The graft modification rate of maleic anhydride or maleic acid-modified polyolefin with maleic anhydride is 0.5% by mass or more and 3.0% by mass or less, and 0.5% by mass or more and 2.5% by mass or less. Is preferable. The "graft denaturation rate" refers to a value obtained by measuring by the following method.

(Measurement method 1)
A film having a thickness of about 100 μm was prepared by hot-pressing a pellet-shaped sample of maleic anhydride, and the content of maleic acid (maleic acid content) was obtained from the absorption peak appearing at 1780 cm ^-1 in the infrared absorption spectrum and the separately obtained calibration curve. Mass%) is calibrated, and the obtained value is taken as the content rate (mass%) of total maleic anhydride. Let A be the obtained value.

After dissolving the pellet-shaped measurement sample in boiling xylene, the measurement sample is reprecipitated in methanol from the obtained solution. The precipitate is then vacuum dried at 80 ° C. for 6 hours to give a powdery sample.

The content of maleic anhydride contained in the obtained sample is calibrated by the same method as above, and the obtained value is taken as the content of maleic anhydride grafted on the polyolefin in the sample (mass%). Let B be the obtained value.

The content of graft-modified maleic anhydride (B) was divided by the content of total maleic anhydride (A), and the obtained value was expressed as a percentage ((B / A) × 100). The graft denaturation rate (mass%) of maleic anhydride in the sample.

Further, the graft denaturation rate may be measured by the following method.

(Measurement method 2)
The measurement sample of the maleic acid-modified polyolefin is dissolved in boiling xylene, and then the measurement sample is reprecipitated in acetone from the obtained solution. The precipitate is then vacuum dried at 80 ° C. for 6 hours to give a powdery sample.

The obtained sample is heat-pressed to prepare a film having a thickness of 100 μm. In the infrared absorption spectrum of the obtained film, the ratio of the absorption peak appearing at 1780 cm ^-1 to the absorption peak of polypropylene appearing at 840 cm ^-1 and the calibration curve of Ide et al. (Reference: Polymer Chemistry 25,167, 1968). From, the graft modification rate (mol%) is calculated by the following formula.
[Graft denaturation rate] = [1780 cm ^-1 absorbance] / [840 cm ^-1 absorbance] x 1.30

The obtained graft denaturation rate (mol%) can be converted into a graft denaturation rate (mass%) based on a separately obtained calibration curve.
For example, a plurality of mixtures of polypropylene and maleic anhydride are prepared while changing the composition, and each mixture is heat-pressed to prepare a film having a thickness of 100 μm. By measuring the graft denaturation rate (mol%) of each of the obtained films, a calibration curve showing the correspondence between the content rate (mass%) of maleic anhydride contained in the film and the graft denaturation rate (mol%). Can be created. "

(Measurement method 3)
The acid value of the measurement sample of maleic acid-modified polyolefin can be obtained by an oxidation measurement method based on JIS K 0070, and the graft modification rate (mass%) can be obtained by converting the obtained acid value by the following formula. Good.
[Graft denaturation rate] = [Acid value of maleic acid-modified polyolefin] ÷ 11.4

The following samples and reagents are used for measuring the acid value.
Sample amount: 1-2 g (fine scale)
Solvent: Xylene (special grade reagent)
Indicator: Phenolphthalein titrate: 0.05 mol / L KOH benzyl alcohol solution. Titrate in advance with 0.1 ml / L hydrochloric acid to determine the correct concentration.

First, a sample and 70 ml of solvent are added to a 100 ml Erlenmeyer flask, an air-cooled tube is attached, and the sample is heated in an oil bath at 135 ° C. for 15 minutes to obtain a xylene solution of the sample.

Then, 3 drops of the indicator are added to the obtained sample and titrated on a hot stirrer at about 100 ° C. The end point of the titration is when the light red color continues for 30 seconds.
A blank test is also performed by the same method, and the acid value is calculated from the following formula.
The acid value _{(mgKOH / g) = [(} V 1 -V o) × N × 56.11] / S
V ₁ : Titrate volume of sample (ml)
V ₀ : Amount of titrant in blank test (ml)
N: Concentration of titrant (mol / L)
S: Sample mass (g)

-Melting Viscosity The melt viscosity of the maleic acid-modified polyolefin at a measurement temperature of 180 ° C. is preferably 1000 mPa · s or more and 50,000 mPa · s or less, and more preferably 5000 mPa · s or more and 20000 mPa · s or less. The upper and lower limits of the melt viscosity can be arbitrarily combined.

In the present specification, the melt viscosity refers to a value measured by a method conforming to JIS K7199. Specifically, it refers to a value when measurement is performed using a rheometer (manufactured by AntonioPaar, device name: physicaMCR301) at a measurement temperature of 180 ° C., a strain amplitude of 3%, and a frequency of 1 Hz.

The melting point of the maleic acid-modified polyolefin is preferably 60 ° C. or higher and 130 ° C. or lower. The melting point is preferably 70 ° C. or higher and 120 ° C. or lower, more preferably 75 ° C. or higher and 110 ° C. or lower, and further preferably 80 ° C. or higher and 100 ° C. or lower.

The weight average molecular weight of the maleic acid-modified polyolefin is not particularly limited, but is, for example, 10,000 to 800,000, preferably 50,000 to 650000, more preferably 80,000 to 550000, and even more preferably 100,000 to 450,000.

≪Crosslinking agent; Epoxy group-containing resin≫
Next, the first resin composition and the cross-linking agent constituting the second resin composition will be described. Examples of the epoxy group-containing resin used as a cross-linking agent include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol type epoxy resin, novolac type epoxy resin, phenol novolac type epoxy resin, glycidyl ether type epoxy resin, and glycidyl amine type epoxy resin. And so on. The phenoxy resin is a polyhydroxypolyether resin synthesized from bisphenols and epichlorohydrin. The phenoxy resin can be used as a cross-linking agent when it has an epoxy group derived from epichlorohydrin as a raw material in its structure.

As the epoxy group-containing resin, a phenol-type epoxy resin, a novolac-type epoxy resin, and a phenol novolac-type epoxy resin are preferable, and a phenol novolac-type epoxy resin is more preferable.

Further, as the epoxy group-containing resin, bisphenol A type epoxy resin and bisphenol F type epoxy resin are also preferable. Here, the bisphenol A type epoxy resin means an epoxy resin having a bisphenol A skeleton. Similarly, the bisphenol F type epoxy resin means an epoxy resin having a bisphenol F skeleton.

A bisphenol type epoxy resin such as a bisphenol A type epoxy resin and a bisphenol F type epoxy resin is a compound having a bisphenol compound as a basic structure and an epoxy group introduced into a part of the structure. Since the bisphenol compound has two phenolic hydroxyl groups, the bisphenol type epoxy resin is usually a bifunctional epoxy resin having a bisphenol skeleton.

In the present specification, the phenol novolac type epoxy resin is a compound having a phenol novolac resin as a basic structure and an epoxy group introduced into a part of the structure. The phenol novolac resin is generally also simply referred to as "novolak" and is obtained by condensing a phenolic compound and formaldehyde. The amount of epoxy group introduced per molecule in the phenol novolac type epoxy resin is not particularly limited, but by reacting an epoxy group raw material such as epichlorohydrin with the phenol novolac resin, a large number of phenols present in the phenol novolac resin are present. Since a large number of epoxy groups are introduced into the sex hydroxyl group, it is usually a polyfunctional epoxy resin.

The phenolic compound constituting the phenol novolak resin may be any compound having a phenolic hydroxyl group, and a compound having no active hydrogen other than the hydroxyl group is preferable. Specific examples of the phenolic compound include monophenolic compounds such as phenol (hydroxybenzene), cresol and naphthol, and bisphenol compounds such as bisphenol A, bisphenol E and bisphenol F. The phenol novolac resin and the phenol novolac type epoxy resin constructed by using the bisphenol compound have a bisphenol skeleton.

As the cross-linking agent, a phenol novolac type epoxy resin having a bisphenol skeleton is preferable, and a phenol novolac type epoxy resin having a bisphenol A skeleton or bisphenol F is particularly preferable.

The epoxy equivalent of the epoxy group-containing resin is preferably 100 to 300, more preferably 200 to 300. The epoxy equivalent (g / eq) corresponds to the weight average molecular weight of the epoxy group-containing resin per epoxy group, and the smaller this value is, the more epoxy groups are contained in the epoxy group-containing resin. By using an epoxy group-containing resin having a relatively small epoxy equivalent as a cross-linking agent, the maleic acid-modified polyolefin as a main agent can be sufficiently cross-linked even if the amount of the epoxy group-containing resin added is relatively small.

The weight average molecular weight of the epoxy group-containing resin constituting the cross-linking agent is preferably 300 or more and 50,000 or less, and preferably 10,000 or less. When the weight average molecular weight of the epoxy compound is 50,000 or less, the epoxy compound easily diffuses and moves easily in the main agent. Therefore, when the weight average molecular weight of the epoxy group-containing resin is not more than the above upper limit value, the reaction probability between the epoxy group of the cross-linking agent (epoxide group-containing resin) and the substituent of the main agent (maleic acid-modified polyolefin) increases. ..

Further, when the weight average molecular weight of the epoxy group-containing resin is not more than the above upper limit value, when a fiber reinforced resin is obtained using a matrix resin film for fiber reinforced resin, the epoxy group contained in the cross-linking agent is replaced with the surface of the fiber. The reaction probability with the group increases.

As a result, the strength of the carbon fiber reinforced resin molded body is improved.

As specific examples of the phenol novolac type epoxy resin, jER (registered trademark) 154, jER (registered trademark) 157S70, jER (registered trademark) 157S65 manufactured by Mitsubishi Chemical Co., Ltd .; EPICLON (registered trademark) N-730A manufactured by DIC Co., Ltd. , EPICLON (registered trademark) N-740, EPICLON (registered trademark) N-770, EPICLON (registered trademark) N-775 (all of which are trade names) and the like can also be used.

In addition to the main agent and the cross-linking agent, the matrix resin film for the fiber-reinforced resin appropriately contains an additive, an additional resin, a plasticizer, a stabilizer, a colorant and the like which are miscible with the main agent and the cross-linking agent. Can be done.

(Mixing ratio)
In the present embodiment, the solid content concentration of the main agent contained in the first resin composition is 70% by mass or more and 99.5% by mass or less with respect to the total amount of the first resin composition.
In the present embodiment, the solid content concentration of the cross-linking agent contained in the first resin composition is 0.5% by mass or more and 30% by mass or less with respect to the total amount of the first resin composition.

In the present embodiment, the solid content concentration of the main agent contained in the second resin composition is 80% by mass or more and 100% by mass or less with respect to the total amount of the second resin composition. The solid content concentration of the cross-linking agent contained in the second resin composition is smaller than the concentration of the cross-linking agent contained in the first resin composition, and is lower than the concentration of the cross-linking agent contained in the first resin composition. It is preferably 15% by mass less, more preferably 10% by mass less, and particularly preferably 5% by mass less. Further, the content of the cross-linking agent in the second resin composition may be 0% by mass.

-Resin film As a method of forming the resin film of the present embodiment, a second sheet is formed by melt extrusion, and a coating liquid of a first resin composition containing a main agent and a cross-linking agent is formed on the second sheet. There is a method of applying and drying.

The film thickness of the resin film after drying is preferably 30 μm or more and 200 μm or less. The film thickness of the resin sheet is preferably 20 μm or more and 150 μm or less, more preferably 30 μm or more and 100 μm or less, and most preferably 40 μm or more and 80 μm or less.

The ratio of the thickness of the first layer to the sum of the thicknesses of the first layer and the second layer is preferably 0.4 or less, more preferably 0.3 or less, and preferably 0.05 or more and 0.07 or more. ..

As the coating liquid, a coating liquid in which the main agent and the cross-linking agent are dissolved in a solvent is preferable. As the solvent, an organic solvent having excellent drying property after coating, in addition to the solubility of the main agent and the cross-linking agent, is preferable. The boiling point of the solvent is preferably, for example, 150 ° C. or lower.

Specific examples of the solvent include aromatics such as toluene, xylene, anisole, ethylbenzyl ether, cresylmethyl ether, diphenyl ether, dibenzyl ether, phenetol, butylphenyl ether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, simene and mesitylene. Group solvent;
Aliphatic solvent such as n-hexane;
Ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, 2-heptanone;
Ester solvents such as methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate;
Examples thereof include alcohol solvents such as methanol, ethanol, isopropyl alcohol, ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol.

As the solvent used in the coating liquid, one of the above-mentioned solvents may be used alone, or two or more of them may be used in combination.

In the case of a mixed solvent in which two or more kinds of solvents are used in combination, it is also preferable to use a combination of an organic solvent that dissolves the main agent well and an organic solvent that dissolves the cross-linking agent well. As such a combination, a combination of toluene that dissolves the main agent well and methyl ethyl ketone that dissolves the cross-linking agent well is preferable.

The method for producing the coating liquid using the mixed solvent may be a method of dissolving the main agent and the cross-linking agent in the mixed solvent, or a method of mixing the solution of the main agent and the solution of the cross-linking agent.

The mixing ratio in the mixed solvent is not particularly limited as long as the main agent and the cross-linking agent can be dissolved well. For example, when toluene and methyl ethyl ketone are combined, the mass ratio is preferably 60 to 95: 5 to 40, more preferably 70 to 90:10 to 30.

Further, the resin film may be produced by melt extrusion using a known sheet die or T die. In such a method, the resin film to be produced is likely to be thickened as compared with the method of applying and drying the above-mentioned coating liquid.

The resin film of the present embodiment may include layers other than the first layer and the second layer as long as the effects of the present embodiment are not impaired. When the other layer is provided, the other layer is preferably a polyolefin-based layer.

<Prepreg>
The present embodiment is a prepreg in which the resin film of the present embodiment and carbon fibers are laminated.
FIG. 2 is a schematic cross-sectional view showing the prepreg of the present embodiment. As shown in FIG. 2, the prepreg 1 of the present embodiment includes a resin layer 10 and a carbon fiber layer 20.

In prepreg 1, the resin layer 10 contains the above-mentioned main agent and cross-linking agent.

(Carbon fiber)
The carbon fiber layer 20 is composed of a plurality of carbon fibers 29 buried in the resin layer 10. The gaps 20a of the plurality of carbon fibers 29 are impregnated with the main agent and the cross-linking agent constituting the resin layer 10.

(Manufacturing method of prepreg)
2 to 7 are explanatory views for explaining the manufacturing process of the prepreg.
First, as shown in FIG. 3, the carbon fiber sheet 21 is sandwiched between a pair of resin films 11 and pressed and bonded together.

(Resin film)
The resin film is used as the resin film 11.

(Continuous fiber sheet)
(Continuous fiber)
In the present embodiment, the carbon fibers are preferably continuous fibers.
Continuous carbon fiber is a general term for fibrous carbon materials composed of substantially only carbon elements. As the carbon fiber, commonly known carbon fibers such as pitch-based carbon fiber and PAN-based carbon fiber can be used.

In the present embodiment, the carbon fiber as the continuous carbon fiber may be a single fiber or a twisted yarn. Here, the continuous fiber means a bundle of fibers continuous over the entire length of the prepreg.

Further, the continuous fiber may be a woven fabric or a knitted fabric formed by using carbon fiber which is a continuous fiber. As the woven fabric, commonly known weaving methods such as plain weave, twill weave (oblique weave), and satin weave can be adopted.

As the continuous fiber, a woven fabric using PAN-based carbon fiber as the carbon fiber is preferable.
The carbon fiber sheet 21 is a molded body in which carbon fibers are molded into a sheet shape. As the carbon fiber sheet 21, for example, a woven fabric having the same shape as the above-mentioned carbon fiber can be mentioned.

As shown in FIG. 3, the resin film 11 is pressure-bonded to the carbon fiber sheet 21 to obtain a laminate 1B composed of the resin film 11, the carbon fiber sheet 21, and the resin film 11.

Next, as shown in FIG. 4, the resin film 11 is heated and melted in a temperature range equal to or higher than the softening point (softening temperature) of the resin film 11 and lower than the reaction start temperature of the cross-linking agent contained in the resin film 11. Further, the molten resin film 11 is pressed toward the carbon fiber sheet 21. The "softening point of the resin film 11" is a softening point of the matrix resin for fiber reinforced resin constituting the resin film 11.

As a result, in the laminate 1B, the resin constituting the resin film 11 is melted and penetrates into the gaps 20a of the plurality of carbon fibers 29 constituting the carbon fiber sheet 21. As a result, prepreg 1 is generated.

The obtained prepreg 1 may be cooled after pressurization. In the resin sheet 11 that has been heated until it melts, the cross-linking agent contained in the resin sheet 11 may unintentionally undergo a cross-linking reaction due to heating, and curing may proceed. By cooling the prepreg 1, the unintended cross-linking reaction as described above can be suppressed or stopped.

An embodiment of a method for producing a prepreg will be described with reference to FIG. In the present embodiment, as shown in FIG. 5, when the carbon fiber sheet 21 is sandwiched between the pair of resin films 11, the second layer 11B is laminated so as to be in contact with the carbon fiber sheet 21, and is pressed and bonded.

In such an embodiment, when the resins constituting the second layer 11B of each of the pair of resin films are melted, the melted resin has a low content of a cross-linking agent, so that it has high fluidity and is a carbon fiber sheet. It is easy to impregnate 21. Therefore, the generation of voids can be suppressed.

An embodiment of a method for producing a prepreg will be described with reference to FIG. In the present embodiment, as shown in FIG. 6, when the carbon fiber sheet 21 is sandwiched between the pair of resin films 11, the first layer 11A is laminated so as to be in contact with the carbon fiber sheet 21, and is pressed and bonded.

In such an embodiment, the cross-linking agents contained in the first layer 11A of each of the pair of resin films are easily cross-linked inside the carbon fiber sheet 21, and the strength of the manufactured molded product can be increased.

An embodiment of a method for producing a prepreg will be described with reference to FIG. In the present embodiment, as shown in FIG. 7, when the carbon fiber sheet 21 is sandwiched between the pair of resin films 11, the first layer 11A and the second layer 11B are laminated so as to be in contact with the carbon fiber sheet 21. Then pressurize and stick.

When a resin film provided with a first layer and a second layer is used, the cross-linking agent contained in the resin sheet is easily dispersed when laminated with carbon fibers and pressed, and can be cured in a short time.

The prepreg produced using the resin sheet of the present embodiment tends to have a gradient in the concentration of the cross-linking agent in the depth direction.

<Carbon fiber reinforced resin molded body>
The present embodiment is a carbon fiber reinforced resin molded body in which the prepreg of the present embodiment is laminated. In the following description, the carbon fiber reinforced resin molded body may be simply referred to as a “molded body”.

<Manufacturing method of carbon fiber reinforced resin molded body>
The method for producing a carbon fiber reinforced resin molded product of the present embodiment includes a step of laminating prepregs to obtain a laminated body and a step of stampable molding the obtained laminated body.

The obtained prepreg 1 of the present embodiment is used as a stampable sheet. The prepreg 1 can be molded by heating to produce a molded body. Specifically, the molded body is formed by performing so-called stampable molding, in which only one prepreg 1 or a laminated body obtained by laminating a plurality of prepregs 1 is heated and softened, and the softened prepreg 1 is pressed by a mold to be molded. Can be manufactured.

Further, the prepreg 1 is heated to a temperature equal to or higher than the reaction start temperature of the cross-linking agent contained in the resin layer 10, so that the cross-linking reaction between the main agent constituting the resin layer 10 and the cross-linking agent proceeds and the prepreg 1 is cured. As a result, the desired molded body can be obtained.

According to the prepreg having the above configuration, it is possible to manufacture a carbon fiber reinforced resin molded body having good mechanical strength and appearance by using the carbon fiber reinforced resin as a forming material.

Further, according to the above-mentioned manufacturing method of the carbon fiber reinforced resin molded body, a high quality carbon fiber reinforced resin molded body can be easily manufactured.

Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to such an example. The various shapes and combinations of the constituent members shown in the above-mentioned examples are examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.

(Measurement method of graft denaturation rate)
A pellet-shaped sample of maleic anhydride was heat-pressed to prepare a film having a thickness of about 100 μm, and the amount of maleic acid was calibrated from the absorption peak appearing at 1780 cm ^-1 in the infrared absorption spectrum, and the obtained value was the total maleic anhydride. The amount was taken. The obtained value was designated as A.

After dissolving the pellet-shaped measurement sample in boiling xylene, the measurement sample was reprecipitated in methanol from the obtained solution. Then, the precipitate was vacuum dried at 80 ° C. for 6 hours to obtain a powdery sample.

The amount of maleic anhydride contained in the obtained sample was calibrated by the same method as above, and the obtained value was used as the amount of maleic anhydride grafted on the polyolefin in the sample. The obtained value was designated as B.

The amount of maleic anhydride (B) that has been graft-modified is divided by the total amount of maleic anhydride (A), and the value obtained is expressed as a percentage ((B / A) x 100). The graft modification rate (mass%) of the maleic anhydride-modified polyolefin by acid was used.

(Examples 1 to 4, Comparative Examples 1 and 2)
A resin film was produced according to the configuration shown in Table 1. Specifically, a toluene solution of a maleic acid-modified polypropylene resin as a main agent and a cross-linking agent was applied by bar coating on a PET base film that had been subjected to a mold release treatment, and dried to obtain a resin film. .. The film thickness of each resin film was the film thickness shown in Table 1.

The carbon fiber sheets shown in Table 1 were sandwiched between the two obtained resin films to form a laminate, and the obtained laminate was heated and pressed under the following conditions to produce a prepreg. The thickness of the prepreg is shown in Table 1, respectively.
Heating: 180 ° C
Pressure: 30cm ² corners per 0.5t load time: 1 minute

Each material shown in Table 1 is as follows.

Maleic acid PP: Graft modification rate by maleic acid 1.2%, weight average molecular weight = 120,000, melting point = 80 ° C.
CF1: Carbon fiber plain woven fabric (trade name: Trading Card Cloth CO-6363, manufactured by Toray Industries, Inc.)
Epoxy: Special novolak type epoxy resin (epoxy equivalent 200, softening point 70 ° C). It contains a bisphenol A skeleton in the molecule and contains an epoxy group with a novolak structure.

(Evaluation of resin permeability to carbon fibers in prepreg)
The resin permeability of the obtained prepreg was evaluated as follows.
First, the prepreg 1 was cut in a direction intersecting the fiber direction of the carbon fibers to form a surface in which both the carbon fibers and the resin were present in the cross section of the prepreg 1 and the carbon fibers looked circular.

Next, a magnified image was taken at a magnification of 20 times using an electron microscope (Keyence Digital Microscope VHX) in a range of 100 μm × 100 μm. The obtained image was image-processed using the image processing software attached to the electron microscope used, and the porosity was calculated. The method of calculating the porosity was as follows.

Regarding the image obtained by shooting, the region excluding the carbon fiber that looks circular was regarded as the resin portion or the gap portion where the resin did not penetrate.

The boundary between the resin part and the gap part was judged from the change in brightness of the image. That is, the set of parts where the contrast is suddenly darker than the vicinity where the contrast is adjacent is regarded as the gap part, and the other parts are regarded as the resin part. Here, the sudden darkening means a point where the brightness becomes three times or less when the movement corresponding to 0.5 μm is performed from an arbitrary point. The set of the parts where the certain range is darkened is defined as the gap part.

In more detail, it was done as follows.
First, orthogonal coordinate axes (x-axis, y-axis) were set in the obtained image. Next, the brightness of the pixels constituting the image was determined discretely along the x-axis at intervals of 0.5 μm in the cross section. Of the plurality of points for which the brightness was obtained, the boundary point between the gap portion and the resin portion was defined as the boundary point between two adjacent points having a difference of 3 times or more in brightness.

The same operation was performed in the entire image area at intervals of 0.5 μm in the y-axis direction, and the boundary line between the gap portion and the resin portion was drawn from the obtained multiple boundary points. The side with high brightness was the resin part and the side with low brightness was the gap part across the drawn boundary line.

By image processing using image processing software, the area Sp of the resin portion and the area Sv of the gap portion were obtained from the region excluding the carbon fibers that appeared to be circular in the captured image.

Using the obtained areas Sv and Sp, the ratio of the gap portion was calculated as a percentage from the following formula (1).
Percentage of voids = area Sv / (area Sv + area Sp) x 100 ... Equation (1)

The above imaging, image processing, and calculation of the ratio of the gap portion were performed a total of 5 times, and the average value (n = 5) of the obtained ratio of the gap portion was defined as the "porosity".

Using the determined porosity, the resin permeability of the prepreg to the carbon fibers was evaluated according to the following items. “◎”, “○” and “△” were evaluated as non-defective products, and “×” was evaluated as defective products. The results are shown in Table 1.
"⊚": The porosity was less than 1%.
"○": The porosity was 1% or more and less than 2%.
"Δ": The porosity was 2% or more and less than 5%.
"X": The porosity was 5% or more.

(Evaluation of shear strength at the interface between carbon fiber and resin)
The interfacial shear strength was evaluated using a composite material interface characteristic evaluation device (manufactured by Toei Sangyo Co., Ltd., model number "HM410"). Specifically, using the microdroplet method, the carbon fibers and the resin constituting the test piece of the prepreg to be measured were sandwiched between the blades of the device and installed in the device.
Next, the carbon fiber was run at a speed of 0.12 mm / min on the apparatus, the maximum pull-out load F when the carbon fiber was pulled out from the prepreg was measured, and the interfacial shear strength τ was calculated by the following formula.
τ = F / πDL

In the above formula
F: Maximum stress (N) generated when the resin film is peeled from the carbon fiber.
D: Diameter of one carbon fiber (m)
L: Diameter (m) of the thermoplastic resin in the axial direction of the carbon fiber
Represent each.

The interfacial shear strength was evaluated according to the following criteria. The results are shown in Table 1.
"◎": Interfacial shear strength is 30 MPa or more.
"○": Interfacial shear strength is 20 MPa or more and less than 30 MPa.
"Δ": Interfacial shear strength is 10 MPa or more and less than 20 MPa.
"X": Interfacial shear strength is less than 10 MPa.

As a result of the evaluation, it was found that the prepreg of the example had fewer voids and the interfacial shear strength was higher than that of the prepreg of the comparative example.

1 ... prepreg, 10 ... resin layer, 11 ... resin film, 20 ... carbon fiber layer, 20a ... gap, 21 ... carbon fiber sheet, 29 ... carbon fiber

Claims

A matrix resin film for a fiber reinforced plastic having a first layer on one surface and a second layer on the other surface.
The first layer is composed of the first resin composition and
The second layer is composed of a second resin composition having a lower content of the cross-linking agent than the first resin composition.
The first resin composition contains a main agent composed of maleic acid-modified polyolefin and a cross-linking agent.
The second resin composition contains a main agent composed of maleic acid-modified polyolefin and contains.
The solid content concentration of the main agent contained in the first resin composition is 70% by mass or more and 99.5% by mass or less with respect to the total amount of the first resin composition.
The solid content concentration of the cross-linking agent contained in the first resin composition is 0.5% by mass or more and 30% by mass or less with respect to the total amount of the first resin composition.
A matrix resin film for a fiber reinforced resin in which the solid content concentration of the main agent contained in the second resin composition is 80% by mass or more and 100% by mass or less with respect to the total amount of the second resin composition.
The matrix resin film for fiber reinforced resin according to claim 1, which has a thickness of 30 μm or more and 200 μm or less.
The matrix resin film for a fiber reinforced resin according to claim 1 or 2, wherein the melt viscosity of the maleic acid-modified polyolefin is 1000 mPa · s or more and 50,000 mPa · s or less at 180 ° C.
The matrix for a fiber-reinforced resin according to any one of claims 1 to 3, wherein the graft modification rate of the maleic acid-modified polyolefin with maleic anhydride or maleic acid is 0.5% by mass or more and 2.5% by mass or less. Resin film.
The matrix resin film for fiber reinforced resin according to any one of claims 1 to 4, wherein the cross-linking agent is an epoxy resin.
The matrix resin film for a fiber-reinforced resin according to claim 5, wherein the epoxy compound constituting the epoxy resin has a weight average molecular weight of 300 or more and 50,000 or less.
The matrix resin film for a fiber-reinforced resin according to claim 5 or 6, wherein the cross-linking agent is at least one selected from the group consisting of novolak type, phenol type, bisphenol A type, and bisphenol F type.
A prepreg in which the matrix resin film for fiber reinforced resin according to any one of claims 1 to 7 and carbon fibers are laminated.
The prepreg according to claim 8, wherein the surface provided with the second layer is laminated so as to be in contact with the carbon fibers.
The prepreg according to claim 8 or 9, wherein the carbon fiber is a continuous fiber.
A carbon fiber reinforced resin molded body in which the prepreg according to any one of claims 8 to 10 is laminated.
A method for producing a carbon fiber reinforced resin molded body in which the prepreg is laminated according to claim 11.
The process of laminating prepregs to obtain a laminate,
A method for producing a carbon fiber reinforced resin molded product, comprising a step of stampable molding the obtained laminate.