JP6944804B2 - Manufacturing method of prepreg for fiber reinforced plastic molding - Google Patents

Description

The present invention relates to a method for producing a prepreg for molding a fiber reinforced plastic using a crosslinkable phenoxy resin composition containing cellulose nanofibers.

Fiber reinforced plastic (FRP), which is a composite of plastic and reinforced fiber material, is a material widely used from sports and leisure products to structural materials in the aeronautical and space fields because of its light weight and high strength. As the reinforcing fiber material, in addition to glass fiber and carbon fiber, organic fiber such as aramid has been mainly used so far.

Cellulose fiber, which is a kind of organic fiber, has been studied for use as a reinforcing fiber material for a long time. Cellulous nanofibers, which have been introduced in recent years and are made by defibrating and refining cellulose fibers, are materials that can effectively utilize forest resources, which are abundant unused resources in Japan, and because they can be thermally recycled, carbon fibers and glass. It is a material that is attracting much attention as an advanced material that is more environmentally friendly than materials that are difficult to dispose of or recycle, such as fibers.

At present, technological development for blending this cellulose nanofiber with a thermoplastic resin as a reinforcing fiber material and using it as a resin material for automobiles and the like is being actively studied (for example, Patent Document 1 and Patent Document 2).

One of the problems in using cellulose nanofibers is that cellulose nanofibers are inferior in heat resistance in terms of their manufacturing method and material as compared with carbon fibers and the like. For this reason, not only highly heat-resistant thermoplastic resins such as nylon, which require a high-temperature and long-term process, but also thermoplastic resins such as polyolefin resins, which have a relatively low melting temperature, can be blended and molded. There is a problem that the cellulose nanofibers are thermally deteriorated depending on the conditions and the resin material is discolored.

Japanese Unexamined Patent Publication No. 2016-79311 WO2011 / 126038

INDUSTRIAL APPLICABILITY According to the present invention, a homogeneous fiber-reinforced plastic molded body having good impregnation property of a matrix resin composition into a reinforcing fiber base material and having no defects such as voids can be obtained even if a large amount of cellulose nanofibers are contained. With the goal.

The method for producing a fiber-reinforced plastic molding prepreg of the present invention is a method for producing a fiber-reinforced plastic molding prepreg containing a reinforcing fiber base material and a resin composition adhering to the reinforcing fiber base material.
In the method for producing a prepreg for molding a fiber-reinforced plastic of the present invention, the resin composition is applied to the reinforcing fiber base material by using a powder coating method to apply the resin composition to the reinforcing fiber base material. It includes a step of adhering.
In the method for producing a prepreg for molding fiber reinforced plastics of the present invention, the resin composition is in the form of powder, and the phenoxy resin (A), epoxy resin (B), cross-linking agent (C), and cellulose nanofibers ( It is a crosslinkable phenoxy resin composition containing D).

In the method for producing a fiber-reinforced plastic molding prepreg of the present invention, the epoxy resin (B) may be a crystalline epoxy resin, and the epoxy resin (B) and the phenoxy resin in the crosslinkable phenoxy resin composition. The compounding ratio (A: B) with (A) may be in the range of 100: 10 to 100: 85.

In the method for producing a fiber-reinforced plastic molding prepreg of the present invention, the cross-linking agent (C) may be an aromatic acid dianhydride, and the cross-linking phenoxy resin composition is the same as the phenoxy resin (A). The acid anhydride group of the cross-linking agent (C) may be blended in the range of 0.9 to 1.4 mol with respect to 1 mol of the secondary hydroxyl group.

In the method for producing a fiber-reinforced plastic molding prepreg of the present invention, the content of the cellulose nanofibers (D) in the crosslinkable phenoxy resin composition may be in the range of 0.1 to 20% by weight. ..

The method for producing a fiber-reinforced plastic molded product of the present invention is a method for producing a fiber-reinforced plastic molded product containing a reinforcing fiber base material and a matrix resin adhering to the reinforcing fiber base material.
In the method for producing a fiber-reinforced plastic molded product of the present invention, the phenoxy resin composition is cured by heating the fiber-reinforced plastic molding prepreg obtained by any of the above methods for producing a fiber-reinforced plastic molding prepreg. The process of obtaining the fiber reinforced plastic molded body without the matrix resin.
Includes.

In the method for producing a fiber-reinforced plastic molding prepreg of the present invention, a powdery phenoxy resin composition having crosslinkability and containing cellulose nanofibers is applied to a reinforcing fiber base material by a powder coating method. This makes it possible to obtain a fiber-reinforced plastic molding prepreg capable of forming a fiber-reinforced plastic molded body of good quality without defects such as voids even if a large amount of cellulose nanofibers are blended.

Hereinafter, embodiments of the present invention will be described in detail.

[Manufacturing method of prepreg for fiber reinforced plastic molding]
A method according to an embodiment of the present invention is a fiber-reinforced plastic molding prepreg containing a reinforcing fiber base material and a resin composition attached to the reinforcing fiber base material (hereinafter, referred to as "FRP molding prepreg"). It is a manufacturing method (which may be described). The method for producing a prepreg for FRP molding according to the present embodiment is a powder-like phenoxy resin composition obtained by applying a crosslinkable phenoxy resin composition to a reinforcing fiber base material using a powder coating method. It includes a step of adhering an object to a reinforcing fiber base material.

First, the crosslinkable phenoxy resin composition used in the method of the present embodiment will be described, and then the coating on the reinforcing fiber base material by the powder coating method will be described.

<Crosslinkable phenoxy resin composition>
The crosslinkable phenoxy resin composition used in the present embodiment contains a phenoxy resin (A), an epoxy resin (B), a crosslinking agent (C), and cellulose nanofibers (D).

(Phenoxy resin)
The phenoxy resin (A) is preferably solid at room temperature and has a melt viscosity at 200 ° C. of 10,000 Pa · s or less. The melt viscosity is preferably 1,000 Pa · s or less, and more preferably 500 Pa · s or less. If the melt viscosity exceeds 10,000 Pa · s, the fluidity of the resin during the molding process is lowered, and the resin is not sufficiently distributed and causes voids, which is not preferable.

The phenoxy resin (A) is a thermoplastic resin obtained by a condensation reaction between a dihydric phenol compound and epihalohydrin or a polyaddition reaction between a divalent phenol compound and a bifunctional epoxy resin, and is conventionally used in a solvent or in a solvent-free manner. It can be obtained by a known method. The average molecular weight, as the mass average molecular weight (Mw), is usually 10,000 to 200,000, preferably 20,000 to 100,000, and more preferably 30,000 to 80,000. If Mw is too low, the strength of the molded product is inferior, and if it is too high, workability and workability are likely to be inferior. In addition, Mw shows the value measured by gel permeation chromatography and converted using the standard polystyrene calibration curve.

The hydroxyl group equivalent (g / eq) of the phenoxy resin (A) is usually 1000 or less, preferably 750 or less, and more preferably 500 or less. If the hydroxyl group equivalent is too high, the crosslink density may be insufficient and the heat resistance may be lowered, which is not preferable.

The glass transition temperature (Tg) of the phenoxy resin (A) is preferably in the range of 65 ° C. to 160 ° C., preferably in the range of 70 ° C. to 150 ° C., and more preferably in the range of 80 ° C. to 150 ° C. Is. When the Tg of the phenoxy resin (A) is lower than 65 ° C., the moldability is improved, but the Tg of the crosslinked cured product is less likely to be 120 ° C. or higher. If the Tg of the phenoxy resin (A) is higher than 160 ° C., the melt viscosity becomes high and molding becomes difficult, and as a result, press molding at a higher temperature is required. The Tg of the phenoxy resin (A) was measured in the range of 20 to 280 ° C. using a differential scanning calorimetry device (DSC) under a heating condition of 10 ° C./min, and was calculated from the peak value of the second scan. It is a numerical value.

The phenoxy resin (A) is not particularly limited as long as it satisfies the above physical properties, but is a bisphenol A type phenoxy resin (for example, Phenototo YP-50, Phenototo YP-50S, Phenoto manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.). Tote YP-55U), bisphenol F type phenoxy resin (for example, Phenotote FX-316 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), bisphenol A and bisphenol F copolymerized phenoxy resin (for example, YP-70 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) ), Special phenoxy resins such as brominated phenoxy resins, phosphorus-containing phenoxy resins, and sulfone group-containing phenoxy resins (for example, Phenototo YPB-43C, Phenototo FX293, YPS-007, etc. manufactured by Nippon Steel & Sumitomo Metal Corporation). Can be mentioned. These can be used alone or in combination of two or more.

The phenoxy resin (A) is preferably blended with an epoxy resin (B), a cross-linking agent (C), a cellulose nanofiber (D), an inorganic filler or other materials in a polymer state, and for example, bisphenol A. It may be obtained by blending a bifunctional epoxy resin such as a solid epoxy resin and a prepolymer of a phenoxy resin such as a diol compound such as bisphenol A and polymerizing them at the time of molding.

(Epoxy resin)
In the present embodiment, the epoxy resin (B) is blended together with the phenoxy resin (A). When the epoxy resin (B) coexists, the melt viscosity can be reduced to improve the moldability, and the physical properties (strength, heat resistance) of the crosslinked cured product can also be improved.

In the phenoxy resin composition, the blending amount of the epoxy resin (B) is preferably in the range of 10 to 85 parts by weight with respect to 100 parts by weight of the phenoxy resin (A). That is, the compounding ratio (A: B) of the epoxy resin (B) and the phenoxy resin (A) is preferably 100: 10 to 100: 85. If the blending amount of the epoxy resin (B) exceeds 85 parts by weight, the effect of improving Tg by cross-linking curing becomes small, and if the amount of the epoxy resin (B) is larger than that of the phenoxy resin (A), the epoxy resin (B) is used. ) Will take a long time to cure, which is not preferable. Further, even if the blending amount of the epoxy resin (B) is less than 10 parts by weight, the effect of improving Tg by cross-linking curing becomes small, and the effect of reducing the viscosity by blending the epoxy resin (B) cannot be obtained. The blending amount of the epoxy resin (B) is more preferably in the range of 20 to 83 parts by weight, and most preferably in the range of 30 to 80 parts by weight with respect to 100 parts by weight of the phenoxy resin (A).

As the epoxy resin (B), a conventionally known epoxy resin can be used without particular limitation as long as it is a bifunctional or higher functional epoxy resin, but a solid epoxy resin having a softening point is suitable. As such an epoxy resin (B), a bisphenol type epoxy resin (for example, Epototo YD-011, YDF-2001, YSLV-80XY, etc. manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), a biphenyl type epoxy resin (for example, manufactured by Mitsubishi Chemical Co., Ltd.) YX-4000, etc.), Biphenyl aralkyl type epoxy resin (for example, NC-3000 manufactured by Nippon Kayaku Co., Ltd.), Diphenyl ether type epoxy resin (for example, YSLV-80DE manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), Bisphenol sulfide type epoxy resin (For example, YSLV-120TE manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), hydroquinone type epoxy resin (for example, Epototo YDC-1312 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), thioether type epoxy resin (for example, YSLV120TE manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) , Phenol novolac type epoxy resin (for example, Epototo YDPN-638 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), Orthocresol Novolac type epoxy resin (for example, Epototo YDCN-701 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), Aralkyl naphthalenediol novolac type Epoxy resin (for example, ESN-355 manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), triphenylmethane type epoxy resin (for example, EPPN-502H manufactured by Nippon Kayaku Co., Ltd.), naphthalene type epoxy resin (for example, HP manufactured by DIC Co., Ltd.) -4770, HP-5000, etc.), dicyclopentadiene type epoxy resin (for example, HP-7200 manufactured by DIC Co., Ltd.), etc., but these are not limited, and two or more kinds thereof are mixed. You may use it.

Among the above solid epoxy resins, the epoxy resin exhibiting crystallinity is not only advantageous for high filling of cellulose nanofibers (D) because it can be handled as a powder, but also has a high temperature above its melting point. The epoxy resin (B) is particularly preferable because it exhibits fluidity.
The crystalline epoxy resin preferably has a low chlorine content, a melting point in the range of 75 ° C. to 145 ° C., and a melt viscosity at 150 ° C. of 2.0 Pa · s or less. When the melt viscosity exceeds 2.0 Pa · s, the moldability of the phenoxy resin composition deteriorates, and the cured product or matrix when used as a fiber-reinforced plastic molded product (hereinafter, may be referred to as “FRP molded product”). It is not preferable because the homogeneity of the resin is inferior.

Preferred crystalline epoxy resins include, for example, Epototo YSLV-80XY, YSLV-70XY, YSLV-120TE, YDC-1312 manufactured by Nippon Kayaku Corporation, YX-4000, YX-4000H, YX-8800 manufactured by Mitsubishi Chemical Corporation. Examples thereof include YL-6121H, YL-6640, etc., HP-4032, HP-4032D, HP-4700, etc. manufactured by DIC Corporation, NC-3000 manufactured by Nippon Kayaku Co., Ltd., and the like.

(Crosslinking agent)
As the cross-linking agent (C) used in the present embodiment, one having two or more functional groups that react with the OH group of the phenoxy resin (A) can be used, but an acid anhydride is preferable. It is understood that the acid anhydride has two functional groups because it produces two carboxyl groups by hydrolysis.

The acid anhydride as the cross-linking agent (C) is not particularly limited as long as it is solid at room temperature and does not have much sublimation property, but it is phenoxy from the viewpoint of imparting heat resistance and reactivity of the FRP molded product. An aromatic acid anhydride having two or more acid anhydrides that react with the hydroxyl group of the resin (A) is preferable. In particular, aromatic compounds having two acid anhydride groups, such as pyromellitic anhydride, are preferably used because the crosslink density of trimellitic anhydride is higher than that of hydroxyl groups and the heat resistance is improved.

Aromatic acid dianhydrides are also phenoxy resins such as 4,4'-oxydiphthalic acid, ethylene glycol bisuanhydrotrimerite, 4,4'-(4,4'-isopropyridenediphenoxy) diphthalic anhydride. The aromatic acid dianhydride having compatibility with (A) and the epoxy resin (B) has a large effect of improving Tg and is more preferable. In particular, aromatic acid dianhydrides having two acid anhydride groups, such as pyromellitic anhydride, have improved cross-linking density and heat resistance as compared with, for example, phthalic anhydride having only one acid anhydride group. It is preferably used because it improves the properties. That is, the aromatic acid dianhydride has good reactivity because it has two acid anhydride groups, and a crosslinked cured product having sufficient strength for demolding can be obtained in a short molding time, and the phenoxy resin (A). The final crosslink density can be increased in order to generate four carboxyl groups by the esterification reaction with the secondary hydroxyl group inside.

The blending amount of the cross-linking agent (C) is usually in the range of 0.9 to 1.4 mol of the acid anhydride group with respect to 1 mol of the secondary hydroxyl group of the phenoxy resin (A), and is preferably 1. It is in the range of 0 to 1.3 mol. If the amount of the acid anhydride group is too small, the acid anhydride group reactive with respect to the secondary hydroxyl group of the phenoxy resin (A) is insufficient, so that the crosslink density becomes low and the rigidity of the cured product is inferior. The acid anhydride becomes excessive with respect to the secondary hydroxyl group of the phenoxy resin (A), and the unreacted acid anhydride adversely affects the curing characteristics and the cross-linking density.

The reaction of the phenoxy resin (A), the epoxy resin (B) and the cross-linking agent (C) is an esterification reaction between the secondary hydroxyl group in the phenoxy resin (A) and the acid anhydride group of the cross-linking agent (C), and further. It is crosslinked and cured by the reaction between the carboxyl group generated by this esterification reaction and the epoxy group of the epoxy resin (B). A phenoxy resin crosslinked product can also be obtained by reacting the phenoxy resin (A) with the cross-linking agent (C), but the coexistence of the epoxy resin (B) reduces the melt viscosity of the phenoxy resin composition and enhances moldability. In addition, a crosslinkable phenoxy resin composition suitable for obtaining a crosslinked cured product having excellent properties such as expression of Tg higher than that of a phenoxy resin and improvement of mechanical strength by promoting a crosslinking reaction and improving a crosslinking density. It becomes. In the present embodiment, although the epoxy resin (B) coexists, the main component is the phenoxy resin (A) which is a thermoplastic resin, and the secondary hydroxyl group and the acid of the cross-linking agent (C) are used as the main components. It is considered that the esterification reaction with the anhydride group is prioritized.

(Cellulose nanofiber)
Cellulose nanofiber (D) is cellulose and / or lignocellulosic having a length of 5 μm or more and a fiber diameter of 0.004 to 0.1 μm obtained by defibrating and / or refining cellulose. It is a fine organic fiber composed.

The blending amount of the cellulose nanofibers (D) in the phenoxy resin composition is in the range of 0.1 to 20% by weight, preferably in the range of 0.1 to 10% by weight, more preferably 0.1 to 7% by weight. It is in the range of%, most preferably in the range of 0.1 to 5% by weight. If the blending amount of the cellulose nanofibers (D) is less than 0.1% by weight, the effect of addition cannot be obtained. On the other hand, if the blending amount of the cellulose nanofibers (D) exceeds 20% by weight, the melt viscosity of the phenoxy resin composition becomes too high, and the impregnation property and moldability deteriorate, which is not preferable.

As the cellulose nanofiber (D) used in the present embodiment, one that has been defibrated as nanofibers in advance may be used, or cellulose as a raw material is defibrated and refined in a defibrated resin. It may be a plastic one.

The pre-defibrated cellulose nanofibers (D) are dispersed in water or an organic solvent (for example, Nanoforest manufactured by Chuetsu Pulp & Paper Co., Ltd.) or powdered (for example, Daicel Phychem Co., Ltd.). (Cerish, etc.), and any of these can be used, but the powdery one is preferable because the step of removing the dispersion medium can be simplified.

On the other hand, when cellulose is defibrated and / or finely divided in a defibrating resin to obtain cellulose nanofibers (D), the raw material cellulose can be used as a defibrating material and / or a finening material. If there is no particular limitation, for example, pulp, cotton, paper, regenerated cellulose fiber such as rayon or acetate, bacterial cellulose and the like can be used. Further, these celluloses may have a surface chemically modified, if necessary.
Further, as the cellulose as the micronizing material, cellulose powder obtained by crushing the cellulose and having a constant particle size distribution may be used. For example, KC Flock (registered trademark) manufactured by Nippon Paper Chemicals Co., Ltd. and Asahi Kasei Chemicals Co., Ltd. Examples thereof include Theoras (registered trademark) and Abyssel (registered trademark) manufactured by FMC.

The cellulose nanofiber (D) used in this embodiment may be modified. The modification may be a chemical modification or a physical modification. In the case of chemical modification, even modified cellulose nanofibers obtained by defibrating and / or refining cellulose to produce nanofibers, and then further adding a modifying compound and reacting with the nanofibers. good. Here, as the modified compound, for example, a functional group such as an alkyl group, an acyl group, an acylamino group, a cyano group, an alkoxy group, an aryl group, an amino group, an aryloxy group, a silyl group or a carboxyl group is chemically added to the cellulose nanofiber. Examples thereof include compounds that can be modified by binding with each other.

Further, the modified compound may be modified by physically adsorbing to the cellulose nanofibers instead of the chemical bond. Examples of the physically adsorbed compound include a surfactant, and any of anionic, cationic, and nonionic compounds may be used, but it is preferable to use a cationic surfactant.

(Arbitrary ingredient)
Further, in the phenoxy resin composition used in the present embodiment, in addition to the above essential components, an optional component such as a curing accelerator can be added.
The curing accelerator is not particularly limited as long as it is solid at room temperature and does not have sublimation properties. For example, a tertiary amine such as triethylenediamine, 2-methylimidazole, 2-phenylimidazole, 2- Examples thereof include imidazoles such as phenyl-4-methylimidazole, organic phosphines such as triphenylphosphine, and tetraphenylborone salts such as tetraphenylphosphonium tetraphenylborate. These curing accelerators may be used alone or in combination of two or more.

Further, the phenoxy resin composition includes other thermoplastic resin powders such as polyolefin resin, acrylonitrile-butadiene-styrene resin, acrylic resin, polyvinyl chloride resin, and polyvinylidene chloride resin as long as the physical properties of the crosslinked cured product are not impaired. , Polyethylene terephthalate resin, polyamide resin, polyphenylene ether resin and its modified products, polyphenylene sulfide resin, polyether sulfone resin, polyetherimide resin, polyether ketone resin, liquid crystal polyester resin, natural rubber, synthetic rubber and other powders, silica Various inorganic fillers such as, alumina, and talc, extender pigments, colorants, antioxidants, ultraviolet inhibitors, and other additives can also be blended.

(Preparation of phenoxy resin composition)
The preparation of the phenoxy resin composition used in the present embodiment is not particularly limited, but there is no need to remove the solvent and the storage stability is excellent. Therefore, a method for obtaining the phenoxy resin composition as a mixture of powders. Is preferable, and for example, the following three methods can be mentioned.

First preparation method:
As the first preparation method, a blender such as a Henschel mixer in which the phenoxy resin (A), the epoxy resin (B), the cross-linking agent (C), the cellulose nanofibers (D), and other additives are all powdered. Is a method of blending and mixing using.

Second preparation method:
The second preparation method is a production method in which the cellulose nanofibers (D) are dispersed in the liquid. First, the dispersion medium in the dispersion liquid of the cellulose nanofibers (D) is phenoxy resin (A) or epoxy. The resin (B) is replaced with a soluble dispersion medium. Next, the phenoxy resin (A) and the epoxy resin (B) are blended and kneaded to remove the substituted dispersion medium, and then the powder pulverized to a predetermined particle size is blended with the remaining material such as the cross-linking agent (C). The method.

Third preparation method:
As a third preparation method, cellulose nanofibers (D) obtained by defibrating and / or refining cellulose in a defibrating resin are mixed with a phenoxy resin (A), an epoxy resin (B), and a cross-linking agent (C). How to do it. In this method, cellulose nanofibers (D) are defibrated and / or refined in water or an organic solvent in order to defibrate and / or refine cellulose in a defibrating resin to obtain cellulose nanofibers (D). ), It is not necessary to remove the medium used for miniaturization. That is, since the fibers are directly defibrated and / or finely divided in the defibrating resin, the cellulose nanofibers (D) can be produced without going through a complicated process of removing water and an organic solvent. Therefore, the cellulose nanofibers (D) can be easily dispersed in the resin, and the phenoxy resin composition and the FRP molded product using the composition can be easily produced.

Examples of the defibrated resin include epoxy resin, modified epoxy resin, polyester resin, vinyl resin and the like, but epoxy resin or modified epoxy resin is preferable, and phenoxy resin (A) and cross-linking agent (C) are particularly preferable as the resin composition. It is preferable to use the same epoxy resin as the epoxy resin (B) blended together with the defibrating resin.

When defibrating and / or refining cellulose using a defibrating resin, the ratio of the defibrating resin to cellulose can be arbitrarily changed. Since it is further compounded with the phenoxy resin composition after miniaturization, the effect of strengthening the resin is higher when the cellulose concentration with respect to the defibrated resin is higher to some extent in advance. On the other hand, if the ratio of the defibrated resin is too small, a sufficient effect of refining cellulose cannot be obtained. The ratio of cellulose to the total amount of defibrated resin and cellulose is preferably in the range of 10% by weight to 90% by weight, more preferably in the range of 30% by weight to 70% by weight, and 40% by weight to 60% by weight. The range of is most preferable.

Although it is difficult to strictly define the state in which the cellulose nanofibers (D) are defibrated, for example, the fiber diameter of cellulose is in the defibrated range of 0.004 to 0.1 μm. It means a state in which the presence of resin between each fiber can be confirmed by electron microscope observation or the like.

The phenoxy resin composition obtained as described above becomes a crosslinked cured product containing cellulose nanofibers (D) by heating and curing. In the crosslinked cured product, the cellulose nanofibers (D) form a large number of bonding points in the cured product to form a network structure, so that the crosslinked cured product is not only useful as a matrix resin for an FRP molded product described later, but also the cellulose nanofibers. The crosslinked cured product itself containing (D) can also be seen as an FRP molded body reinforced with short fibers. The heat treatment temperature for cross-linking and curing the phenoxy resin composition is, for example, preferably in the range of 150 to 240 ° C., more preferably in the range of 160 ° C. to 220 ° C., and most preferably in the range of 180 ° C. to 200 ° C. If the heat treatment temperature exceeds the upper limit temperature, excessive heat is applied, which may cause decomposition of the resin and thermal deterioration of the cellulose nanofibers. If the heat treatment temperature is lower than the lower limit temperature, the melt viscosity of the phenoxy resin composition is high. Therefore, the moldability is deteriorated. The molding time is usually 30 to 60 minutes, but even for a short time of about 10 minutes, the molding time is different from that of the cross-linking agent (C) using the secondary hydroxyl group of the phenoxy resin (A) as the main component. By the reaction, the strength for demolding can be obtained. However, in order to complete the curing reaction of the epoxy resin (B), it is preferable to post-cure the epoxy resin (B) at a temperature in the range of 200 to 250 ° C. for about 30 to 60 minutes.

Such a crosslinked cured product has a Tg of at least 120 ° C. or higher, preferably 160 ° C. or higher, and more preferably 180 ° C. or higher. Therefore, it is also applicable to applications requiring high heat resistance such as automobiles. Can be done. If the Tg is less than 120 ° C., the heat resistance and the thermal decomposition stability will be insufficient. Here, the Tg of the crosslinked cured product was measured in the range of 20 to 280 ° C. using a differential scanning calorimetry device (DSC) under a heating condition of 10 ° C./min, and was calculated from the peak value of the second scan. It is a numerical value.

<Coating on reinforced fiber base material by powder coating method>
The prepreg for FRP molding is obtained by adhering the crosslinkable phenoxy resin composition to a reinforcing fiber base material in a powder state by a powder coating method.
In the powder coating method, each component constituting the phenoxy resin composition is adhered to the reinforcing fiber base material in a fine powder state, so that the phenoxy resin (A), the epoxy resin (B) and the cross-linking agent (C) are used. Each component other than the cellulose nanofiber (D), such as other additives, is crushed into a fine powder. For pulverization, it is preferable to use a pulverizer / mixer such as a low-temperature drying pulverizer (centri-dry mill), but the pulverization is not limited thereto. Further, at the time of crushing, each of the above components may be crushed and then mixed with the cellulose nanofibers (D), or these components and the cellulose nanofibers (D) may be mixed and then crushed. Is preferable. In this case, it is advisable to set the pulverization conditions so that the fine powder of each component has a predetermined average particle size. The average particle size of the fine powder containing the phenoxy resin (A), the epoxy resin (B), the cross-linking agent (C), and other additives is, for example, in the range of 10 to 100 μm, preferably in the range of 40 to 80 μm. Yes, more preferably in the range of 40-50 μm. When the average particle size exceeds 100 μm, the energy when the fine powder collides with the reinforcing fiber base material increases in the adhesion to the reinforcing fiber base material by powder coating in an electrostatic field, and the adhesion rate to the reinforcing fiber base material increases. Will decrease. If it is less than 10 μm, the fine powder is scattered by the accompanying airflow and the adhesion efficiency is lowered, and the fine powder floating in the atmosphere may cause deterioration of the working environment.

The powder coating method includes a fluidized coating method using a fluidized bed and an electrostatic coating method using an electrostatic field. In the present embodiment, either method can be used, but the reinforcing fiber base material can be used. An electrostatic coating method using an electrostatic field is preferable because of the uniformity of adhesion to the surface.

The amount of the fine powdered phenoxy resin composition adhered to the reinforcing fiber base material is coated so that the resin ratio (RC) is in the range of 20 to 50% by weight, preferably 25 to 40% by weight. It is in the range of 25 to 30% by weight, more preferably in the range of 25 to 30% by weight. If the RC exceeds 50% by weight, the mechanical properties such as the tensile and bending elastic modulus of the FRP molded product will decrease, and if it is less than 20% by weight, the amount of resin adhered will be extremely small. The impregnation of the matrix resin into the material becomes insufficient, and both the thermal and mechanical characteristics become low.

The powder-coated fine powder phenoxy resin composition is fixed to the reinforcing fiber base material by heating and melting. Cold coating in which the powder is applied and then heat-sealed, and preheated reinforcing fibers are used. Either hot coating, in which powder is applied or fused to the base material, may be used. By melting the phenoxy resin composition in the form of a fine powder on the surface of the reinforcing fiber base material by this heat melting, the adhesion to the base material is enhanced and the coated resin powder is prevented from falling off. However, at this stage, the phenoxy resin composition is concentrated on the surface of the reinforcing fiber base material, and does not reach the inside of the reinforcing fiber base material as in the molded product after heat and pressure molding. The heating time after powder coating is not particularly limited as long as the phenoxy resin composition can maintain fluidity and reactivity, but 1 to 2 minutes is suitable. That is, by performing the heat treatment in a much shorter time than at the time of molding, the phenoxy resin (A), the epoxy resin (B), etc. are heated to the reinforcing fiber base material without reacting the cross-linking agent (C) with the resin component. It is fixed by fusion and prevents powder from falling off. The melting temperature is in the range of 150 to 240 ° C., preferably in the range of 160 to 220 ° C., more preferably in the range of 180 to 200 ° C. If the melting temperature exceeds the upper limit, the curing reaction may proceed, and if it falls below the lower limit, heat fusion becomes insufficient, and the fine powdered phenoxy resin composition falls off when the prepreg for FRP molding is handled. , Dropping out, etc. occur.

For the reinforcing fiber base material, for example, carbon fiber, glass fiber, aramid fiber, boron fiber, alumina fiber, mineral fiber, silicon carbide fiber and the like can be used, but when the electrostatic coating method is used, the reinforcing fiber base material must have conductivity. Therefore, carbon fiber is preferable. The form of the reinforcing fiber base material is not particularly limited, and is, for example, a unidirectional material, a cloth such as plain weave or twill weave, a three-dimensional cloth, a chopped strand mat, a tow made of thousands or more filaments, or a non-woven fabric. Etc. can be used. These reinforcing fiber base materials can be used alone or in combination of two or more.

<Manufacturing of FRP molded products>
The FRP molded product can be easily manufactured by individually or laminating the FRP molding prepregs produced as described above, heating and pressurizing them. Further, when laminating, a metal foil such as aluminum or stainless steel can be laminated between layers or the outermost layer. The FRP molding prepreg can perform shaping and cross-linking and curing of the resin at the same time by pressure molding with a hot press to form a matrix resin which is a cross-linked cured product of the phenoxy resin composition.
As long as the molding using the prepreg for FRP molding is heat and pressure molding, various molding methods such as autoclave molding and hot press molding using a mold are appropriately used according to the size and shape of the target FRP molded body. It can be selected and implemented. The molding temperature is preferably in the range of 150 to 240 ° C., more preferably in the range of 160 ° C. to 220 ° C., and most preferably in the range of 180 ° C. to 200 ° C. If the molding temperature exceeds the upper limit temperature, excessive heat is applied, which may cause decomposition of the resin and thermal deterioration of the cellulose nanofiber (D). If the temperature is lower than the lower limit temperature, the phenoxy resin composition may be decomposed. Since the melt viscosity of the matrix resin is increased, the impregnation property of the matrix resin into the reinforcing fiber base material is deteriorated. The molding time is usually 30 to 60 minutes, but even for a short time of about 10 minutes, the molding time is different from that of the cross-linking agent (C) using the secondary hydroxyl group of the phenoxy resin (A) as the main component. By the reaction, the strength for demolding can be obtained. However, in order to complete the curing reaction of the epoxy resin (B), it is preferable to post-cure the epoxy resin (B) at a temperature in the range of 200 to 250 ° C. for about 30 to 60 minutes.

The FRP molded product obtained by heat-press molding the FRP molding prepreg contains a matrix resin which is a crosslinked cured product of the phenoxy resin composition and a reinforcing fiber base material. In the FRP molded product, the matrix resin and the reinforcing fiber base material are firmly bonded to give characteristics such as predetermined strength. Since the Tg of this matrix resin is at least 120 ° C. or higher, preferably 160 ° C. or higher, and more preferably 180 ° C. or higher, it can be applied to applications requiring high heat resistance, such as automobiles. If the Tg is less than 120 ° C., the heat resistance and the thermal decomposition stability will be insufficient. Here, the Tg of the matrix resin is measured in the range of 20 to 280 ° C. using a differential scanning calorimetry device (DSC) under a heating condition of 10 ° C./min, and is a numerical value calculated from the peak value of the second scan. Is.

The FRP molded product can be suitably used for various purposes. For example, industrial machinery parts, general machinery parts, automobile parts, transportation parts such as railways and ships, aerospace parts, electronic / electrical parts, construction / civil engineering materials, sports / leisure goods, housing parts for wind power generation, etc. Can be mentioned. Further, for example, it can be suitably used for storing natural gas or for a high pressure vessel such as a hydrogen gas cylinder of a fuel cell vehicle.

Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto.

The raw materials used in Examples and Comparative Examples are as follows.

<Phenoxy resin>
A-1: Bisphenol A type phenoxy resin (YP-50 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), Mw = 60,000, hydroxyl group equivalent: 284, Tg: 84 ° C.)
<Epoxy resin>
B-1: Tetramethylbisphenol F type crystalline epoxy resin; (YSLV-80XY (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), epoxy equivalent: 192, melting point: 72 ° C.)
<Crosslinking agent>
C-1: Ethylene glycol bisanhydrotrimeritate (TMEG) (acid anhydride equivalent: 207)
<Cellulose nanofiber>
Product name: Serish, manufactured by Daicel FineChem

[Example 1]
100 parts by weight of (A-1) as the phenoxy resin (A), 30 parts by weight of (B-1) as the epoxy resin (B), and 73 parts by weight of (C-1) as the cross-linking agent (C), respectively. By pulverizing, classifying, and then mixing, a powder having an average particle diameter D ₅₀ of 80 μm [the average particle diameters of (A), (B), and (C) are almost the same] was obtained. This powder and 10 parts by weight of the cellulose nanofiber (D) were dry-blended with a Henschel mixer to prepare a phenoxy resin composition. Next, a phenoxy resin composition was applied to a defibrated plain weave reinforced fiber base material made of carbon fiber (STANDARD Modulus type HTS40 3K manufactured by Toho Tenax Co., Ltd.) under the conditions of an electric charge of 70 kV and a sprayed air pressure of 0.32 MPa in an electrostatic field. Was powder coated. Then, the powder-coated reinforcing fiber base material was heated and melted in an oven at 170 ° C. for 1 minute to heat-fuse the resin to obtain a prepreg for FRP molding. The resin ratio (RC) of the obtained prepreg for FRP molding was 27%.
Thirteen FRP molding prepregs thus obtained were stacked on a Teflon (registered trademark) sheet and pressed at 5 MPa for 10 minutes with a press machine heated to 200 ° C. to prepare an FRP laminated plate, which was cut with a diamond cutter. The cross section of the steel was observed with a scanning electron microscope, but no internal defects such as voids due to poor impregnation were found. Further, the glass transition point (Tg) of the matrix resin of the FRP laminated plate was measured at a temperature rising rate of 10 ° C./min using a TMA6100 type thermomechanical measuring device manufactured by Seiko Instruments Inc. and found to be 125 ° C.

As described above, by using the prepreg for FRP molding obtained by powder-coating the crosslinkable phenoxy resin composition on the reinforcing fiber base material, there are no defects such as voids in the matrix resin after molding. An FRP molded product of good quality can be obtained.

Claims (4)

A method for producing a fiber-reinforced plastic molding prepreg containing a reinforcing fiber base material and a resin composition attached to the reinforcing fiber base material.
A step of adhering the resin composition to the reinforcing fiber base material by applying the resin composition to the reinforcing fiber base material by using a powder coating method is included.
The resin composition is in the form of powder and is substantially composed of a phenoxy resin (A), an epoxy resin (B), a cross-linking agent (C), and a cellulose nanofiber (D). The content is in the range of 0.1 to 20% by weight, and the compounding ratio (A: B) of the epoxy resin (B) and the phenoxy resin (A) is 100: 10 to 100:85. The crosslinkability is within the range, and the acid anhydride group of the cross-linking agent (C) is blended in the range of 0.9 to 1.4 mol with respect to 1 mol of the secondary hydroxyl group of the phenoxy resin (A) . A method for producing a prepreg for forming a fiber-reinforced plastic, which comprises the phenoxy resin composition of. The method for producing a fiber-reinforced plastic molding prepreg according to claim 1, wherein the epoxy resin (B) is a crystalline epoxy resin. Manufacturing method of the crosslinking agent (C) is a prepreg for fiber-reinforced plastic molding according to claim 1 or 2 Ru aromatic dianhydride der. A method for producing a fiber-reinforced plastic molded body containing a reinforcing fiber base material and a matrix resin adhering to the reinforcing fiber base material.
The matrix resin is cured by heating the fiber-reinforced plastic molding prepreg obtained by the method for producing a fiber-reinforced plastic molding prepreg according to any one of claims 1 to 3. The process of obtaining the fiber reinforced plastic molded body,
A method for manufacturing a fiber reinforced plastic molded article including.