Vacuum bag molding system, method for producing reinforced fiber composite molded body, and polyvinyl alcohol film

Abstract

The present invention provides a vacuum bag molding system, with which it is possible to reduce the use of auxiliary materials such as a breather and a release film in autoclave molding or the like of a reinforced fiber composite material, with which a gap is not likely to be left between a bagging film and a molding material at the time of exhaust from a vacuum bag, thereby achieving excellent workability, and which enables molding of a molded body that has good surface properties. This vacuum bag molding system includes: a vacuum bag; and a vacuum valve for exhausting the inside of the vacuum bag. A molding material, which is disposed on a mold directly or indirectly with another intermediary member, is housed inside the vacuum bag. The vacuum bag has a bagging film which is a polyvinyl alcohol film having a surface that is not embossed.

Description

Vacuum bag molding system, method for manufacturing reinforced fiber composite molded body, and polyvinyl alcohol film

[0001] The present invention relates to a vacuum bag molding system, a reinforced fiber composite molded article, and a polyvinyl alcohol film.

[0002] Composite materials are known in which fibers such as natural fibers and carbon fibers are solidified with a matrix such as resin. Various molding methods are used to mold such composite materials depending on the final shape and properties. Among these molding methods, autoclave molding offers a high degree of freedom in terms of materials and shapes, making it the molding method that best brings out the characteristics and performance of composite materials.

[0003] A typical procedure for autoclave molding is outlined as follows: Prepreg, in which reinforcing fibers (reinforcing fibers) are impregnated with a thermosetting resin, is cut into a predetermined shape. A release agent is applied to a mold having the desired shape, and the required number of prepregs are stacked in predetermined positions inside the mold. A release film and a breather are placed, in that order, on the surface of the stacked prepregs, and these are then covered and sealed with a bagging film. By covering and sealing with the bagging film in this manner, a vacuum bag is formed. The air inside the vacuum bag is evacuated, creating a vacuum inside the vacuum bag, which improves adhesion of the stacked prepregs to the mold. The thermosetting resin is then cured while being heated and pressurized in an autoclave, resulting in a fiber-reinforced composite molded product.

[0004] While autoclave molding produces high-quality molded articles, it requires numerous auxiliary materials (e.g., release films, breathers, bagging films, etc.). Consequently, problems include high production costs, long molding cycle times, and the generation of large amounts of waste secondary materials after molding. Without a breather, the air inside the vacuum bag typically cannot be fully evacuated, or gaps tend to remain between the bagging film and the molding material after evacuation. If gaps remain between the bagging film and the molding material, the process must be redone, resulting in poor workability. Furthermore, when a mold release film is not used and the molding material is directly covered with a bagging film, it is typically difficult to peel the bagging film from the resulting molded article.

[0005] In response to this situation, Patent Document 1 describes that by using an embossed vacuum bag film (bagging film), air is exhausted through the raised pattern when it is sucked in, eliminating the need for a breather. Patent Document 2 describes that by using a multifunctional film in which a flexible barrier film or release coating is laminated on the composite side of the vacuum bag film, it is possible to replace multiple layers with a single material. However, these technologies do not result in a fundamental improvement because, while the function of the breather or release film is transferred to the bagging film, a process of subjecting the bagging film to special treatment is required.

[0006] International Publication No. WO 2022 / 103727 International Publication No. WO 2021 / 257530

[0007] An object of the present invention is to provide a vacuum bag molding system that can reduce the use of secondary materials such as breathers and release films in autoclave molding of reinforced fiber composite materials, that is easy to work with as it is less likely to leave gaps between the bagging film and the molding material when the vacuum bag is vented, and that enables the molding of molded articles with good surface properties, a method for producing reinforced fiber composite molded articles using such a vacuum bag molding system, and a polyvinyl alcohol film that makes such a vacuum bag molding system possible.

[0008] As a result of extensive research, the present inventors have found that a polyvinyl alcohol film having an unembossed surface has excellent release properties for cured reinforced fiber composite materials (reinforced fiber composite moldings), etc., and as a result of further research, they have found that if a bagging film made of this film is used, autoclave molding, etc. can be performed without using a breather or release film.

[0009] That is, the present invention relates to [1] to

[11] . [1] A vacuum bag molding system comprising a vacuum bag and a vacuum valve for evacuating the inside of the vacuum bag, the inside of the vacuum bag containing a molding material placed on a mold directly or via another member, and the vacuum bag having a bagging film which is a polyvinyl alcohol film whose surface is not embossed; [2] A polyvinyl alcohol film having a Young's modulus of 50 to 350 N / mm at 23°C / 50% RH°C. ２ [3] The vacuum bag molding system of [1] or [2], wherein the polyvinyl alcohol film has an average thickness of 20 to 100 μm; [4] The vacuum bag molding system of any of [1] to [3], wherein the bagging film is directly laminated on the surface of the molding material; [5] A method for producing a reinforced fiber composite molded product using the vacuum bag molding system of any of [1] to [4], wherein the molding material is an uncured reinforced fiber composite material, the method comprising the steps of: evacuating air from the vacuum bag through the vacuum valve; and heat-curing the uncured reinforced fiber composite material contained in the vacuum bag in an autoclave; [6] The method for producing a reinforced fiber composite molded product of [5], wherein the bagging film and the uncured reinforced fiber composite material are in close contact with each other after the step of evacuating air from the vacuum bag through the vacuum valve; [7] A polyvinyl alcohol film used as a bagging film in the vacuum bag molding system of any of [1] to [4];

[0010] According to the present invention, there are provided a vacuum bag molding system that can reduce the use of secondary materials such as breathers and release films in autoclave molding of reinforced fiber composite materials, that is less likely to leave gaps between the bagging film and the molding material when the vacuum bag is vented, that is excellent in workability, and that enables the molding of molded articles with good surface properties, a method for producing reinforced fiber composite molded articles using such a vacuum bag molding system, and a polyvinyl alcohol film that enables such a vacuum bag molding system.Furthermore, according to the present invention, molded articles can be produced using fewer secondary materials, and the step of installing secondary materials, which is required in conventional methods, is omitted.

[0011] Fig. 1 is a schematic cross-sectional view showing a vacuum bag molding system according to a first embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing a vacuum bag molding system according to a second embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing a vacuum bag molding system according to a third embodiment of the present invention. Fig. 4 is a schematic cross-sectional view for explaining a method for producing a carbon material composite molded body using the vacuum bag molding system according to the first embodiment of the present invention.

[0012] In this specification, a numerical range described using "to" means that the numerical values ​​described before and after "to" are included as the upper and lower limits. In addition, in this specification, the upper and lower limit values ​​of numerical ranges (content, physical properties, etc.) can be combined as appropriate. In this specification, polyvinyl alcohol may be abbreviated as "PVA," polyvinyl alcohol film as "film," uncured reinforced fiber composite material as "prepreg," and autoclave molding as "AC molding."

[0013] A vacuum bag molding system is a system for performing molding using a vacuum bag (e.g., AC molding, etc.). A vacuum bag is a device that has a shape that can be evacuated to create a vacuum. The vacuum bag may be, for example, bag-shaped, but is not limited to bag-shaped. The vacuum bag may be composed of, for example, only a bagging film, or may be composed of a bagging film and other components (e.g., a mold, etc.). A vacuum state does not necessarily refer to a complete vacuum state, but may refer to a state where the pressure is sufficiently reduced compared to atmospheric pressure. A vacuum state may be, for example, a state of 0.1 atmospheres or less, or a state of 0.01 atmospheres or less, or 0.001 atmospheres or less. A molding material is a material to be molded, such as an uncured reinforced fiber composite material. An uncured reinforced fiber composite material is a semi-cured material in which fibers are impregnated with a thermosetting resin. A reinforced fiber composite material is a material obtained by combining reinforcing fibers with other materials (e.g., resin), and a reinforced fiber composite molded product is a molded product of a reinforced fiber composite material. A reinforcing fiber is a fiber (a reinforcing material) that reinforces a material or molded product.

[0014] A vacuum bag molding system according to one embodiment of the present invention comprises a vacuum bag and a vacuum valve for evacuating the inside of the vacuum bag, the inside of the vacuum bag containing a molding material that is placed on a mold directly or via another member, and the vacuum bag having a bagging film that is a polyvinyl alcohol film whose surface is not embossed.

[0015] This vacuum bag molding system can reduce the use of secondary materials such as breathers and release films in autoclave molding of reinforced fiber composite materials, is less likely to leave gaps between the bagging film and the molding material when the vacuum bag is evacuated, and enables the molding of molded articles with good surface properties. The reasons for these effects are not clear, but the following are thought to be the reasons.

[0016] PVA films have excellent releasability for molded articles obtained from molding materials, such as cured reinforced fiber composite materials (reinforced fiber composite molded articles). This is thought to be due to the low affinity between PVA and the resins used in the molding materials (especially thermosetting resins such as epoxy resins). However, when PVA films are embossed, releasability is reduced. As described in Patent Document 1, embossing a nylon bagging film has the advantage that the raised pattern formed on the bagging film serves as an air passage during decompression. However, because PVA films are relatively flexible, when embossed PVA films are used, the raised pattern is easily crushed when the vacuum bag is decompressed and the film is brought into close contact with the molding material. Conversely, the increased surface area of ​​the PVA film due to embossing is thought to increase adhesion to the molding material, thereby reducing releasability. Furthermore, since the PVA film itself has excellent releasability from molded articles as described above, even if the PVA film is not embossed, it is likely that an air passage will remain to the end when the vacuum bag is decompressed, and it is therefore possible to sufficiently vent the air without using a breather.

[0017] Furthermore, PVA film is considered to be a film with an appropriate balance of flexibility and strength for use as a bagging film. That is, when the PVA film is evacuated from the vacuum bag, it stretches sufficiently to conform to the shape of the molding material, which is the filler, and therefore highly conforms to the shape of the molding material, making it unlikely for gaps to remain between the bagging film and the molding material. Furthermore, PVA film has sufficient strength and is unlikely to break even when stretched to a certain extent, making it suitable for use as a bagging film. Furthermore, PVA film is highly flexible and has excellent release properties for the molding material, making it easy to remove air bubbles (voids) remaining between the molding material and the film upon evacuation. Thus, PVA film has high conformability, is unlikely to leave gaps between the bagging film and the molding material, is not embossed, and can be used by directly laminating it to the surface of the molding material. Therefore, it is considered possible to mold a molded product with excellent surface properties. Note that if a breather is placed between the bagging film and the molding material, the shape of the breather surface may be transferred to the molded product, resulting in reduced surface properties. Furthermore, if gaps remain between the bagging film and the molding material and molding is performed with wrinkles, the shape of the wrinkles will be transferred to the molded product, which can reduce surface properties. Furthermore, with this vacuum bag molding system, the bagging film has high conformability when exhausting air from the vacuum bag, making it difficult for gaps to form between the bagging film and the molding material, which provides advantages such as good workability, less resin accumulation during molding, and uniform thermal curing.

[0018] Furthermore, PVA film has low air permeability and excellent moisture permeability under high humidity conditions, so when a vacuum bag is made using PVA film, it is possible to maintain a vacuum while allowing moisture inside the molding material to escape to the outside of the vacuum bag, and therefore PVA film is considered to be suitable for the vacuum bag molding system of the present invention.

[0019] Furthermore, the vacuum bag molding system according to one embodiment of the present invention can reduce the use of secondary materials such as breathers and release films, thereby reducing waste, shortening the molding cycle, and suppressing contamination caused by breathers and the like. While the vacuum bag molding system according to one embodiment of the present invention does not preclude the use of breathers, release films, and the like, it is preferable to not use breathers or release films from the perspective of reducing waste. The vacuum bag molding system may not use breathers or release films. Furthermore, the vacuum bag molding system may use only PVA film as the secondary film material. Furthermore, PVA film has the advantages of being easily degraded in the environment, being less likely to accumulate in living organisms, and being easily biodegradable, making it possible to replace fluoropolymers, which have traditionally been used as release films. This technology is also useful as a replacement for conventional technology in which nylon film was used as a bagging film. For example, PVA film is softer (less rigid) than nylon film, so gaps are less likely to remain between the PVA film bagging film and the molding material during evacuation from the vacuum bag, and any wrinkles that may occur are easily smoothed out.

[0020] <PVA Film> First, a PVA film used as a bagging film in a vacuum bag forming system according to one embodiment of the present invention will be described.

[0021] (PVA) The PVA film contains PVA as a main component. The main component refers to the component with the largest content by mass. The lower limit of the PVA content in the PVA film is preferably 51% by mass, more preferably 60% by mass, and even more preferably 80% by mass. The upper limit of the PVA content in the PVA film may be 100% by mass, 99%, 95%, or 90% by mass.

[0022] PVA consists of vinyl alcohol units (-CH ２It is a polymer having a vinyl alcohol unit (—CHOH—). The PVA may have a monomer unit other than the vinyl alcohol unit. As the PVA, one produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. The polymerization and saponification can be carried out by conventionally known methods.

[0023] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate, with vinyl acetate being preferred.

[0024] The vinyl ester polymer is preferably one obtained by using only one or more vinyl ester monomers as the monomer, more preferably one obtained by using only one vinyl ester monomer as the monomer, but may also be a copolymer of one or more vinyl ester monomers with other monomers copolymerizable therewith.

[0025] Examples of other monomers copolymerizable with vinyl ester monomers include ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; acrylic acid or a salt thereof; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, methacrylic acid, and the like. Methacrylic acid esters such as n-propyl acrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or a salt thereof, and N-methylolacrylamide or a derivative thereof. acrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or a salt thereof, N-methylolmethacrylamide or a derivative thereof; N-vinylamides such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether vinyl ethers such as butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or a salt, ester, or acid anhydride thereof; itaconic acid or a salt, ester, or acid anhydride thereof; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate.The vinyl ester polymers and polyvinyl alcohols may have monomer units derived from one or more of these other monomers.

[0026] When the vinyl ester polymer is a copolymer, it is preferably a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate. The content of the monomer unit derived from the other monomer copolymerizable with vinyl acetate contained in the (co)polymer is preferably 15 mol % or less, more preferably 10 mol % or less, and even more preferably 4 mol % or less, when the vinyl ester unit contained in the copolymer is taken as 100 mol %.

[0027] The degree of polymerization of PVA is not particularly limited and is, for example, 500 to 8,000. The lower limit of the degree of polymerization of PVA may be 1,000, 1,500, or 2,000. The upper limit of the degree of polymerization of PVA may be 6,000, 4,000, 3,000, or 2,000. Here, the degree of polymerization of polyvinyl alcohol means the viscosity average degree of polymerization (Po) measured in accordance with the description of JIS K6726-1994, and is calculated by the following formula from the intrinsic viscosity [η] (dl / g) measured in water at 30°C after resaponifying and purifying polyvinyl alcohol: Po=([η]×10 ４ / 8.29) （１／０．６２）

[0028] The degree of saponification of the PVA is not particularly limited and is, for example, 70 to 100 mol%. The lower limit of the degree of saponification of the PVA may be 80 mol%, 90 mol%, 95 mol%, 97 mol%, or 98 mol%. Here, the degree of saponification of the PVA refers to the ratio (mol%) of the number of moles of vinyl alcohol units to the total number of moles of vinyl alcohol units and monomer units (typically vinyl ester units) that can be converted to vinyl alcohol units by saponification. The degree of saponification of the PVA can be measured in accordance with the description of JIS K6726-1994.

[0029] (Other Components) In addition to PVA as the main component, the PVA film may contain water, a plasticizer, a surfactant, a filler, starch, a polymer other than PVA, and the like, as long as the effects of the present invention are not impaired.

[0030] The inclusion of a plasticizer in the PVA film gives the film particularly good flexibility. As a result, the film stretches appropriately and easily conforms to the shape of the molding material when the pressure is reduced in the vacuum bag. This excellent conformability also reduces the formation of air bubbles (voids) remaining between the molding material and the film when the pressure is reduced.

[0031] As the plasticizer, polyhydric alcohols such as ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, trimethylolpropane, and sorbitol are preferred from the viewpoint of being less likely to bleed out onto the surface of the water-soluble film, and at least one selected from the group consisting of ethylene glycol, glycerin, diglycerin, propylene glycol, and diethylene glycol is more preferred.

[0032] The content of the plasticizer contained in the PVA film can be adjusted appropriately depending on the shape and surface properties of the molded body. The lower limit of the content of the plasticizer in the PVA film may be 0 parts by mass, preferably 1 part by mass, more preferably 3 parts by mass, or may be 5 parts by mass or 10 parts by mass, relative to 100 parts by mass of PVA. By setting the content of the plasticizer in the PVA film to be equal to or greater than the lower limit, it is possible to increase the flexibility of the PVA film. On the other hand, the upper limit of the content of the plasticizer is preferably 25 parts by mass, more preferably 20 parts by mass, or may be 15 parts by mass, 10 parts by mass, or 8 parts by mass, relative to 100 parts by mass of PVA. By setting the content of the plasticizer in the PVA film to be equal to or less than the upper limit, it is possible to increase the strength of the PVA film.

[0033] Examples of the surfactant include anionic surfactants, nonionic surfactants, etc. When the PVA film contains a surfactant, the releasability from the film-forming roll and the drying roll during film production is improved, and the film can be produced with good productivity.

[0034] The anionic surfactants include R ａ -O-SO ３ － (R ａan alkyl sulfate salt having an anion represented by the formula (R is an alkyl group) (sodium lauryl sulfate, sodium dodecyl sulfate, etc.); ａ -O-(R ｂ O) ｎ -SO ３ － (R ａ is an alkyl group, R ｂ and the like). Examples of the alkylene sulfonate include polyoxyalkylene alkyl ether sulfates having an anion represented by the formula (wherein ⁻ is an alkylene group) (such as polyoxyethylene isotridecyl ether sodium sulfate, polyoxyethylene lauryl ether sodium sulfate, and polyoxyethylene polyoxypropylene lauryl ether sodium sulfate); dialkyl sulfosuccinates such as dialkyl sulfosuccinate and sodium di-2-ethylhexyl sulfosuccinate; alkyl sulfonates (linear or branched alkyl sulfonates) such as octyl sulfate, lauryl sulfate, sodium lauryl sulfonate, and sodium lauryl sulfoacetate; alpha olefin sulfonates such as alpha olefin sulfonate and sodium tetradecene sulfonate; linear or branched alkyl benzene sulfonates such as alkyl benzene sulfonate and sodium dodecyl benzene sulfonate; and condensates of naphthalene sulfonates and formaldehyde such as sodium naphthalene sulfonate-formaldehyde condensate.

[0035] The content of the anionic surfactant in the PVA film is not limited as long as it does not affect the effects of the present invention, and is, for example, 0.5 to 1.5 parts by mass per 100 parts by mass of PVA.

[0036] Examples of nonionic surfactants include alkyl ether types (straight-chain or branched alkyl ether types) such as polyoxyethylene alkyl ethers (polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, etc.) and polyoxypropylene alkyl ethers; ester types such as polyoxyethylene sorbitan fatty acid esters; ester ether types such as polyoxyethylene sorbitan monolaurate; amino ether types such as polyoxyethylene lauryl amino ether; alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether; alkyl ester types such as polyoxyethylene laurate; alkyl amine types such as polyoxyethylene lauryl amino ether; alkyl amide types such as polyoxyethylene lauric acid amide; polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; alkanolamide types such as lauric acid diethanolamide and oleic acid diethanolamide; and allyl phenyl ether types such as polyoxyalkylene allyl phenyl ether.

[0037] The content of the nonionic surfactant in the PVA film is not limited as long as it does not affect the effects of the present invention, and is, for example, 0.3 to 1.2 parts by mass per 100 parts by mass of PVA.

[0038] The lower limit of the total content of PVA and optional components such as water, plasticizer, and surfactant in the PVA film may be, for example, 90 mass%, 95 mass%, 98 mass%, 99 mass%, 99.5 mass%, or 99.9 mass%, and the upper limit of the total content of PVA and optional components such as water, plasticizer, and surfactant in the PVA film may be 100 mass%.

[0039] The PVA film may contain a filler, which can improve the mechanical strength and handling properties of the film.

[0040] Examples of fillers include carbon black, metal powder, silica, alumina, calcium carbonate, titanium dioxide, talc, mica, clay minerals such as bentonite, etc. Among these, talc, mica, and clay minerals are preferred.

[0041] The upper limit of the filler content in the PVA film is preferably 20 parts by mass, more preferably 10 parts by mass, relative to 100 parts by mass of PVA, and the lower limit of the filler content in the PVA film may be 0 parts by mass, 0.1 parts by mass, 0.5 parts by mass, or 1 part by mass, relative to 100 parts by mass of PVA.

[0042] Examples of starch include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and sago starch; and processed starches that have been subjected to etherification, esterification, oxidation, or the like, with processed starches being preferred.

[0043] The lower limit of the starch content in the PVA film is preferably 1 part by mass, more preferably 2 parts by mass, per 100 parts by mass of PVA. Having a starch content equal to or greater than the lower limit makes it possible to increase the mechanical strength of the film. The upper limit of the starch content in the PVA film is preferably 15 parts by mass, more preferably 10 parts by mass, per 100 parts by mass of PVA. Having a starch content equal to or less than the upper limit improves processability during film production.

[0044] The polymer other than PVA is preferably a water-soluble polymer because of its affinity with PVA, and examples thereof include dextrin, gelatin, glue, casein, shellac, gum arabic, polyacrylic acid amide, sodium polyacrylate, polyvinyl methyl ether, a copolymer of methyl vinyl ether and maleic anhydride, a copolymer of vinyl acetate and itaconic acid, polyvinylpyrrolidone, cellulose, acetyl cellulose, acetyl butyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and sodium alginate.

[0045] The upper limit of the content of the water-soluble polymer other than PVA in the PVA film is preferably 15 parts by mass, more preferably 10 parts by mass, relative to 100 parts by mass of PVA, and the lower limit of the content of the water-soluble polymer other than PVA in the PVA film may be 0 parts by mass, 0.1 parts by mass, 0.5 parts by mass, or 1 part by mass, relative to 100 parts by mass of PVA.

[0046] The PVA film may further contain other components in addition to the above-mentioned components, such as antioxidants, ultraviolet absorbers, lubricants, crosslinking agents, colorants, preservatives, and antifungal agents, as long as the effects of the present invention are not impaired.

[0047] (Coating Layer) The PVA film (bagging film) may have a coating layer formed by applying an emulsion solution to the inner surface (the inner surface in a vacuum bag state). To provide the coating layer on the film, a coating treatment method using a liquid coating agent can be used, for example, a roll coater method, an air doctor method, a blade coater method, a spray method, a dipping method, etc.

[0048] Examples of coating agents used to provide the coating layer include styrene-based resin emulsions, emulsions containing a (meth)acrylic acid ester / styrene copolymer, (meth)acrylic resin emulsions, aqueous polyvinyl alcohol solutions, polyvinyl alcohol-based emulsions, aqueous solutions of silicone-based water repellents, and silicone-based emulsions.

[0049] Of these, any one selected from the group consisting of styrene-based resin emulsions, emulsions containing a (meth)acrylic acid ester / styrene copolymer, (meth)acrylic resin emulsions, aqueous polyvinyl alcohol solutions, and polyvinyl alcohol-based emulsions is preferred.

[0050] The dispersant for dispersing the microparticles contained in the emulsion is not particularly limited, but PVA is preferred because it has strong adhesion to the PVA film body (portions other than the coating layer), prevents peeling of the coating layer, and has excellent peelability from the molded article. The PVA is appropriately selected from the PVAs used in the PVA films.

[0051] The average particle size of the fine particles contained in the emulsion is not particularly limited, but may be, for example, 0.020 to 0.5 μm.

[0052] The amount of coating in the coating process for providing the coating layer is not particularly limited, but for example, the amount of microparticles contained in the emulsion is 0.005 to 0.050 g / m per side. ２ may be.

[0053] The surface of the coating layer provided on the PVA film may further be coated with a powder. Examples of the powder include organic powders and inorganic powders. Examples of the organic powder include starch. Examples of the starch include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and sago starch; and processed starches that have been etherified, esterified, oxidized, or water-repellent treated. Among these, processed starches are preferred, and water-repellent processed starches are more preferred. Examples of the inorganic powder include silica, heavy, light, or surface-treated calcium carbonate, aluminum hydroxide, aluminum oxide, titanium oxide, diatomaceous earth, barium sulfate, calcium sulfate, zeolite, zinc oxide, silicic acid, silicates, mica, magnesium carbonate, kaolin, clays such as halloysite, pyroferrite, and sericite, and talc. These may be used alone or in combination of two or more.

[0054] Although there is no limitation on the average particle size of the powder, when the average particle size of the powder is within a specific range, the surface irregularities are appropriately formed, and the releasability from the molded body is improved. Therefore, the lower limit of the average particle size of the powder is preferably 5 μm, more preferably 10 μm. On the other hand, the upper limit of the average particle size of the powder is preferably 30 μm, more preferably 20 μm.

[0055] The amount of powder attached to the PVA film is, for example, 0.1 to 100 mg / m ３ The upper limit of the amount of adhesion is 50 mg / m ３ It may be 30 mg / m ３ The lower limit of the amount of adhesion is 0.5 mg / m ３ and may be 1 mg / m３ may be.

[0056] The powder may be applied to one side or both sides of the PVA film, although it may be preferable to apply it to both sides in order to obtain good releasability regardless of the orientation of the film.

[0057] In one embodiment of the present invention, the PVA film may not have a coating layer. For example, the PVA film may be a single-layer film. In one layer of the single-layer PVA film, PVA and other optional components are substantially uniformly present. In addition, the amount of powder attached to the PVA film is 10 mg / m. ３ It may be less than 1 mg / m ３ It may be 0.1 mg / m or less, ３ It may be 0.1 mg / m or less, ３ In this way, even when the PVA film is a single-layer film or a film having substantially no powder attached to its surface, it can be used as a bagging film that can fully exhibit the above-mentioned effects.

[0058] (Physical properties, etc.) The lower limit of the Young's modulus of the PVA film at 23°C / 50% RH is 50 N / mm ２ is preferred, and 100 N / mm ２ More preferably, 150 N / mm ２ On the other hand, the upper limit of the Young's modulus is 350 N / mm ２ is preferable, and 300 N / mm ２ When the Young's modulus of the PVA film is in the above range, the film exhibits particularly sufficient flexibility, and the film has improved conformability when used as a bagging film. The lower limit of the Young's modulus is 200 N / mm ２ The upper limit of the Young's modulus may be 250 N / mm ２ , 200 N / mm ２ , 150 N / mm ２ or 100 N / mm ２The Young's modulus of the PVA film can be adjusted by, for example, the thickness of the film, the type and content of the plasticizer, the type of PVA, etc.

[0059] The average thickness of the PVA film is not particularly limited as long as the effects of the present invention are not impaired, but the lower limit is preferably 20 μm, more preferably 25 μm. By making the average thickness of the PVA film equal to or greater than the lower limit, the strength, peelability, workability, etc. of the PVA film can be improved. On the other hand, the upper limit is preferably 100 μm, more preferably 80 μm, and even more preferably 60 μm. By making the average thickness of the PVA film equal to or less than the upper limit, the followability, workability, etc. can be improved. The lower limit of the average thickness of the PVA film may be 30 μm or 40 μm. The upper limit of the average thickness of the PVA film may be 40 μm or 30 μm. The average thickness of the PVA film is the average value of the thicknesses at any five locations.

[0060] The PVA film may be a stretched film or a non-stretched film, but is preferably a non-stretched film. By using a non-stretched PVA film as a bagging film, effects such as followability can be more fully achieved. The non-stretched film refers to a film that has not substantially been subjected to a stretching treatment. The non-stretched film may be a film whose length-based stretching ratio is 1.0 times or more and 1.1 times or less, or a stretched film whose length-based stretching ratio is 1.00 times or more and 1.01 times or less.

[0061] The surface of the PVA film used as the bagging film is not embossed. Embossing is a processing method in which a film is generally formed and then nipped between an embossing roll and a rubber roll while applying heat and pressure. Since the surface of the PVA film is not embossed, it has a high level of surface smoothness.

[0062] <Vacuum Bag Molding System> A vacuum bag molding system according to one embodiment of the present invention includes a vacuum bag and a vacuum valve. The vacuum bag contains a molding material that is placed on a mold directly or via another member. The vacuum bag molding system may also include a hose connecting the inside and outside of the vacuum bag. A breather, a release film, etc. may also be placed inside the vacuum bag. A detailed description will be given below with reference to the drawings.

[0063] (Vacuum Bag Molding System of FIG. 1) The vacuum bag molding system of FIG. 1, which is a first embodiment, includes a mold 10, a bagging film 13, and a vacuum valve 14. Specifically, in the vacuum bag molding system of FIG. 1, a molding material 12 is placed on the mold 10 (the central portion of the mold 10) with a release agent 11 interposed therebetween, and a bagging film 13 is placed so as to cover the molding material 12. The peripheral portion where the mold 10 and the bagging film 13 overlap is sealed with a sealing tape 16, which is an example of a sealing member. In the vacuum bag molding system of FIG. 1, a vacuum bag 15 is formed by the mold 10 and the bagging film 13, and the molding material 12 is contained inside this vacuum bag 15. The molding material 12 is placed on the mold 10 with the release agent 11 interposed therebetween, and the mold 10 also constitutes a part of the vacuum bag 15. Furthermore, in order to evacuate the inside of the vacuum bag 15, the vacuum valve 14 is arranged inside the vacuum bag 15 so that the connection point (exhaust port) with an exhaust device (not shown) is exposed from the vacuum bag 15. In other words, when the vacuum valve 14 is evacuated, the inside of the vacuum bag 15, which is the space sealed with the sealing tape 16 between the mold 10 and the bagging film 13, becomes a vacuum state.

[0064] Although the mold 10 is shown as a plate in FIG. 1 , its shape can be changed appropriately depending on the shape of the target molded product. The PVA film used as the bagging film 13 has excellent conformability, so it can be applied to molding using molds with complex shapes having uneven portions. The material of the mold 10 is not particularly limited, and metal molds such as aluminum and steel, pearl board molds, FRP (Fiber Reinforced Plastics) molds, etc. can be used.

[0065] The release agent 11 is applied to the mold 10 (the surface on which the molding material 12 is placed) in order to improve the releasability of the molded body (the molding material 12 after molding) from the mold 10. The release agent 11 does not have to be applied. That is, the molding material 12 may be placed directly on the mold 10, or may be placed via another member such as the release agent 11. Instead of or together with the release agent 11, a release film may be placed between the mold 10 and the molding material 12.

[0066] As the release film, a PVA film, a polymethylpentene film, a polyolefin film, or the like can be used, with a PVA film being preferred. Specific and preferred forms of the PVA film used as the release film are the same as those of the PVA film described above as the bagging film. As described above, the PVA film has good releasability from the molding material and the resulting molded article. Therefore, the PVA film may be disposed as a release film at a position in contact with the molding material 12. Examples of the position in contact with the molding material 12 include the position between the mold 10 and the molding material 12, and the position between the molding material 12 and the bagging film 13.

[0067] The molding material 12 is placed in the central portion of the mold 10. That is, the molding material 12 is not placed in the peripheral portion of the mold 10 (the portion where the vacuum valve 14 and sealing tape 16 in FIG. 1 are provided). The molding material 12 is the material of the target molded body, and an example thereof is an uncured reinforced fiber composite material. However, the vacuum bag molding system of one embodiment of the present invention can also be applied to molding materials other than reinforced fiber composite materials. The molding material 12 may be a material containing a resin or a material containing a thermosetting resin. As the resin contained in the uncured reinforced fiber composite material and other molding materials, thermosetting resins such as epoxy resins and phenolic resins are preferred, and epoxy resins are more preferred. Such resins have particularly good releasability from PVA films. Conventionally known molding materials can be used as the molding material 12.

[0068] The bagging film 13 is the PVA film whose surface is not embossed, as described above. In the vacuum bag molding system of FIG. 1 , the bagging film 13 is placed directly on the surface (top surface) of the molding material 12, and the mold 10 and the bagging film 13 form a vacuum bag 15. As described above, PVA film has good peelability and conformability to the molding material 12 or the molded article molded from the molding material 12. Furthermore, when a PVA film is used as the bagging film 13, it can be sufficiently vented without the need for a breather. For this reason, a configuration in which the bagging film 13 is directly laminated on the surface of the molding material 12 is a preferred embodiment. In this configuration, there is no need to place secondary materials (such as a release film or breather) between the molding material 12 and the bagging film 13, which has the advantage of further reducing the use of secondary materials and shortening the molding cycle. Note that, as in the vacuum bag molding system of other embodiments (e.g., the embodiment of FIG. 3 ), a secondary material (such as a release film 19) may be placed between the molding material 12 and the bagging film 13.

[0069] The vacuum bag molding system of FIG. 1 includes a vacuum valve 14 for evacuating the vacuum bag 15 and isolating the inside and outside of the vacuum bag 15. That is, the vacuum valve 14 is provided so as to evacuate the vacuum bag 15 and maintain a vacuum state inside the vacuum bag 15. One opening of the vacuum valve 14 is connected to the interior space of the vacuum bag 15, and the other opening (exhaust port) is connected to an exhaust device (not shown) such as a vacuum pump located outside the vacuum bag 15. In the vacuum bag system of FIG. 1, the main body of the vacuum valve 14 is located inside the vacuum bag 15. In another embodiment, the vacuum valve 14 may be located outside the vacuum bag 15, as in the vacuum bag forming system of FIG. 2 described below. When the vacuum valve 14 is installed inside the vacuum bag 15, a minimal slit may be made in the vacuum bag 15 (typically, the bagging film 13 constituting the vacuum bag 15) to expose the exhaust port of the vacuum valve 14 to the outside of the vacuum bag 15 and reinforce the slit to prevent leakage. When the vacuum valve 14 is installed outside the vacuum bag 15, a hose 17 is provided to connect the inside and outside of the vacuum bag 15, and the vacuum valve 14 is installed on the outside, as shown in FIG.

[0070] In the vacuum bag molding system of Fig. 1, as described above, the peripheral portion where the mold 10 and the bagging film 13 overlap is sealed with a sealing tape 16 (sealant tape) as an example of a sealing member. That is, the sealing tape 16 that bonds the mold 10 and the bagging film 13 together is used as the sealed portion of the vacuum bag 15. Note that, as another form of the sealed portion, the portion where the bagging films 13 overlap each other may be sealed with the sealing tape 16, as in the vacuum bag molding system of Fig. 2 described below. Furthermore, the sealing means is not limited to the method using the sealing tape 16, and an adhesive or the like may also be used. Alternatively, the bagging films 13 may be bonded together directly by thermocompression or the like.

[0071] The sealing portion (sealing tape 16 in the vacuum bag molding system of FIG. 1 ) is preferably provided at a position (e.g., 10 cm to 50 cm) that is appropriately spaced from the molding material 12. By appropriately spacing the molding material 12 and the sealing portion (e.g., the position of the sealing tape 16), it becomes particularly difficult for the vacuum bag 15 (bagging film 13) to break or for air to become trapped. By not spacing the molding material 12 and the sealing portion too far apart, workability can be improved.

[0072] (Vacuum Bag Molding System of FIG. 2) The vacuum bag molding system of FIG. 2, which is a second embodiment, includes a mold 10, a bagging film 13, and a vacuum valve 14. In the vacuum bag molding system of FIG. 2, similar to the vacuum bag molding system of FIG. 1, a molding material 12 is placed on the mold 10 with a release agent 11 interposed therebetween. However, the mold 10 is placed on a first bagging film 13 with a breather 18 interposed therebetween, and a second bagging film 13 is placed so as to cover the molding material 12. The peripheral portion where the two bagging films 13 overlap is sealed with a sealing tape 16, which is an example of a sealing member. In this way, in the vacuum bag molding system of FIG. 2, a vacuum bag 15 is formed by two bagging films 13, and the molding material 12 and the like are contained inside this vacuum bag 15. In such a configuration, for example, the mold 10 with the molding material 12 placed therein may be placed in a vacuum bag 15 previously prepared in a cylindrical or bag shape, and the open portion may be sealed, or the mold 10, molding material 12, etc. may be placed in this order on the first bagging film 13, and finally covered with the second bagging film 13, and the peripheral portion where the two bagging films 13 overlap may be sealed. The vacuum bag 15 in the configuration of Fig. 2 may be formed by folding one bagging film 13 and sealing the periphery. Alternatively, the bagging films 13 may be directly bonded to each other by thermocompression or the like.

[0073] 2 also includes a hose 17 that connects the inside and outside of the vacuum bag 15. In the vacuum bag molding system of Fig. 2, the vacuum valve 14 is disposed outside the vacuum bag 15. The tip of the hose 17 located on the outside side of the vacuum bag 15 is connected to the vacuum valve 14.

[0074] The vacuum bag molding system of FIG. 2 includes a breather 18 disposed inside the vacuum bag 15. The breather 18 is connected to the tip of a hose 17 located inside the vacuum bag 15. The vacuum bag molding system according to one embodiment of the present invention is able to exhaust air from inside the vacuum bag 15 more easily than conventional methods, ensuring good workability without the use of a breather. However, this does not preclude the use of a breather. By disposing the breather 18 inside the vacuum bag 15 and connecting the tip of the hose 17 located inside the vacuum bag 15 to the breather 18, as in the vacuum bag molding system of FIG. 2, exhaust performance is improved, particularly when molding large or complex molded articles. A conventionally known breather can be used as the breather 18. For example, the breather 18 can be made of a nonwoven fabric, such as a breather cloth.

[0075] In the vacuum bag molding system of Figure 2, the breather 18 is disposed within the vacuum bag 15 so as not to come into contact with the molding material 12. Specifically, the breather 18 is disposed on the back side of the mold 10 (the side of the mold 10 opposite to the side on which the molding material 12 is disposed). Alternatively, the breather 18 may be disposed in a corner or the like inside the vacuum bag 15 so as not to come into contact with the molding material 12. If the molding material 12 and the breather 18 are in contact with each other, the surface shape of the breather 18 may be transferred to the molding material 12 when air is discharged from the vacuum bag 15. Therefore, even when the breather 18 is used, by disposing the breather 18 inside the vacuum bag 15 so as not to come into contact with the molding material 12, a molded product with better surface properties can be produced.

[0076] (Vacuum bag molding system of Figure 3) The vacuum bag molding system of Figure 3, which is a third embodiment, differs from the vacuum bag molding system of Figure 1 only in that a release film 19 is placed between the molding material 12 and the bagging film 13.

[0077] As described above, the molding material 12 and the bagging film 13, which is a PVA film, have good releasability, so there is no need to place a release film between them, but a release film may be placed. As described above, examples of the release film 19 include PVA film, polymethylpentene film, and polypropylene film, with PVA film being preferred. The specific and preferred forms of the PVA film used as the release film 19 placed between the molding material 12 and the bagging film 13 are the same as the specific and preferred forms of the PVA film described above as the bagging film.

[0078] <Method for manufacturing reinforced fiber composite> A method for manufacturing a reinforced fiber composite according to one embodiment of the present invention is a method for manufacturing a reinforced fiber composite molded body using the vacuum bag molding system according to one embodiment of the present invention, in which the molding material is an uncured reinforced fiber composite material, and the method includes a step (step B) of evacuating the air inside the vacuum bag through the vacuum valve, and a step (step C) of heat-curing the uncured reinforced fiber composite material contained in the vacuum bag using an autoclave.

[0079] According to this method for producing a reinforced fiber composite molding, when the air is discharged from the vacuum bag, gaps are unlikely to remain between the bagging film and the molding material (reinforced fiber composite material), which reduces the need to repeatedly vacuum and release to the atmosphere to eliminate the gaps, resulting in good operability. Furthermore, the bagging film has excellent conformability to the uncured reinforced fiber composite material under vacuum or during pressure and heat curing, making it possible to produce a reinforced fiber composite molding with an excellent surface.

[0080] The method for producing a reinforced fiber composite may further include a step of assembling a vacuum bag molding system (step A). ​​The step of assembling the vacuum bag molding system (step A) includes, for example, a step (step A-1) of placing an uncured reinforced fiber composite material (molding material) on a mold directly or via another member, and a step (step A-2) of using a bagging film and a vacuum valve to create a vacuum bag that contains the uncured reinforced fiber composite material (molding material) placed on the mold directly or via another member and to which the vacuum valve is attached.

[0081] In other words, a method for manufacturing a vacuum bag molding system, which includes the steps of: placing an uncured reinforced fiber composite material (molding material) on a mold, either directly or via another member (step A-1); and using a bagging film and a vacuum valve, creating a vacuum bag to which the uncured reinforced fiber composite material (molding material) placed on the mold, either directly or via another member, and to which the vacuum valve is attached (step A-2). is also an aspect of the present invention.

[0082] The following will explain the steps of assembling the vacuum bag molding system (Step A) in order.

[0083] In step A-1, an uncured fiber-reinforced composite material is placed on a mold directly or via another member. Before placing the uncured fiber-reinforced composite material, a release agent may be applied to the surface of the mold, or a release film may be placed on the surface of the mold.

[0084] The material and shape of the mold are as described above and are not particularly limited. The PVA film has excellent conformability, so it can be applied to complex shapes with uneven portions.

[0085] The uncured reinforced fiber composite material is a material in which reinforcing fibers are impregnated with a matrix resin. The reinforced fiber composite material placed in the mold is basically uncured, but may be partially cured or semi-cured.

[0086] The type of matrix resin is not particularly limited, but is usually a thermosetting resin. Examples of the matrix resin include epoxy resin, phenol resin, unsaturated polyester resin, cyanate ester resin, phenol-formaldehyde resin, and melamine resin, with epoxy resin being preferred.

[0087] The matrix resin may contain various known curing agents depending on the type of resin. For example, when the matrix resin is an epoxy resin, examples of the curing agent include amines, amides, imidazoles, and acid anhydrides.

[0088] Examples of reinforcing fibers (fibrous products) used in reinforced fiber composite materials include artificially produced fibers such as carbon fiber, glass fiber, ceramic fiber, aramid fiber, boron fiber, basalt fiber, steel fiber, nylon fiber, fiber mat, scrim, and woven fabric; natural fibers such as flax, hemp, jute, ramie, kenaf, sisal, bamboo, silk, cotton, and wood; and semi-natural fibers such as cellulose nanofiber. Two or more of these reinforcing fibers (fibrous products) may be used in combination.

[0089] The reinforcing fiber (fibrous product) is preferably a carbon fiber or a natural fiber, more preferably a carbon fiber. That is, the reinforced fiber composite material may be a carbon fiber composite material, and the reinforced fiber composite molded product obtained by the production method may be a carbon fiber composite molded product.

[0090] The release agent to be applied to the surface of the mold is not particularly limited and can be selected depending on the materials of the mold and prepreg. Examples of the release agent include silicone-based, acrylic-based, urethane-based, urethane acrylate-based materials, fluoropolymer-based materials, and combinations thereof.

[0091] In step A-2, a bagging film and a vacuum valve are used to create a vacuum bag containing uncured reinforced fiber composite material placed on a mold directly or via another member, and the vacuum valve is attached to the bagging film. For example, in the production of a vacuum bag molding system having the structure shown in Figure 1, the uncured reinforced fiber composite material placed on a mold directly or via another member is covered with the bagging film and sealed with sealing tape to form a vacuum bag. At this time, a vacuum valve is installed inside the vacuum bag so that air can be discharged in the next step.

[0092] In the fabrication of a vacuum bag molding system having the structure shown in FIG. 2 , for example, a cylindrical or bag-shaped vacuum bag may first be fabricated using a bagging film. An uncured reinforced fiber composite material, which has been placed on a mold directly or via another member, is placed inside the vacuum bag, and the vacuum bag is then sealed with sealing tape. Alternatively, an uncured reinforced fiber composite material, which has been placed on a mold directly or via another member, may be placed between the bagging films, and the bagging films may then be sealed together with sealing tape to form a vacuum bag. In the fabrication of a vacuum bag molding system having the structure shown in FIG. 2 , a breather may also be placed inside the vacuum bag, and a hose may be provided connecting the inside and outside of the vacuum bag, connected to a vacuum valve, to allow air to be discharged in the next process.

[0093] In step A-2, if necessary, other auxiliary materials such as a release film can be placed at an appropriate position in the vacuum bag.

[0094] In step B, the air inside the vacuum bag is discharged through the vacuum valve. At this time, the vacuum valve is connected to an exhaust device, and the air inside the vacuum bag is discharged. If a gap remains between the vacuum bag (bagging film) and the molding material after the exhaust, the gap can be eliminated by returning a small amount of air into the vacuum bag and then discharging it again. Furthermore, if wrinkles occur in the vacuum bag (bagging film) due to the exhaust, the wrinkles can be eliminated by similarly returning a small amount of air into the vacuum bag, smoothing out the wrinkles, and discharging it again.

[0095] As shown in Figure 4, after step B (a step of evacuating the air inside the vacuum bag 15 through the vacuum valve 14), it is preferable that the bagging film 13 and the uncured reinforced fiber composite material (molding material 12) are in close contact with each other. Figure 4 shows the state after step B in the method for producing a reinforced fiber composite molded product using the vacuum bag molding system of Figure 1. By using a PVA film with high conformability as the bagging film 13 and by placing the bagging film 13 directly on the uncured reinforced fiber composite material (molding material 12), it is possible to achieve a state in which the bagging film 13 and the uncured reinforced fiber composite material (molding material 12) are in close contact with each other. By performing step C in this state in which the bagging film 13 and the uncured reinforced fiber composite material (molding material 12) are in close contact with each other, a reinforced fiber composite molded product with a particularly good surface shape can be obtained. Furthermore, the bagging film 13, which is a PVA film whose surface is not embossed, has good peelability, so even after performing step C while the bagging film 13 and the uncured reinforced fiber composite material (molding material 12) are in close contact, the bagging film 13 can be sufficiently peeled off, resulting in good workability.

[0096] In step C, the uncured reinforced fiber composite material contained in the vacuum bag is heat-cured using an autoclave. Step C can be carried out in the same manner as conventionally known autoclave molding. That is, the pressure and temperature inside the autoclave can be adjusted in accordance with the shape and properties of the desired molded body, taking into account the curing temperature and curing rate of the thermosetting resin that constitutes the uncured reinforced fiber composite material used, while referring to the manufacturing conditions for general reinforced fiber composite molded bodies.

[0097] <Other Embodiments> The present invention is not limited to the above-described embodiments, and the configuration can be changed without departing from the spirit of the present invention. For example, the vacuum bag molding system of the present invention can also be used to mold molding materials other than reinforced fiber composite materials. The vacuum bag molding system of the present invention and the method for manufacturing a reinforced fiber composite molded article of the present invention can also be applied to molding methods other than autoclave molding.

[0098] According to the present invention, it is possible to produce a reinforced fiber composite molding that requires fewer secondary materials than conventional moldings and has good surface properties. Such reinforced fiber composite moldings can be used in a wide range of applications, from aircraft such as airplanes and helicopters to vehicles such as motorcycles and automobiles, wind power generation blades, and leisure goods such as fishing rods, golf shafts, and rackets.

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The evaluation methods used in the following examples and comparative examples are shown below.

[0100] <Young's modulus of film> The film was conditioned overnight at 23°C / 50% RH, cut into the following sample sizes, and the stress and elongation up to break were determined using an autograph (Autograph AG-X, manufactured by Shimadzu Corporation). Young's modulus was determined using the following formula: Young's modulus (N / mm ２ ) = (stress value at 4% strain - stress value at 3% strain) x 100 (formula) Sample size: Width 25 mm x length 100 mm Autograph measurement conditions: Chuck width: 25 mm Temperature / humidity: 23°C / 50% RH (using a thermostatic bath) Tensile speed: 100 mm / min

[0101] <Workability> When producing a reinforced fiber composite molding, if a gap remained between the bagging film and the prepreg (uncured reinforced fiber composite material) after the air inside the vacuum bag was discharged, the following procedure was carried out to eliminate the gap. The vacuum valve was operated to return a small amount of air, and wrinkles caused by the remaining gap were smoothed out and the pressure was reduced. The above procedure was carried out until the gap disappeared. If this procedure was carried out 0 to 1 time, it was rated A, and if it was carried out 2 or more times, it was rated B. The fewer the number of times the procedure was carried out, the less time and effort required for setting up was saved and the better the workability.

[0102] <Followability to prepreg (uncured reinforced fiber composite material)> When producing a reinforced fiber composite molded product, the gaps remaining between the bagging film and the prepreg after the air inside the vacuum bag was initially discharged were rated A if the number of gaps was small and the gaps were small, and B if the number of gaps was large and the gaps were large. The fewer the number of gaps and the smaller the gaps, the better the followability of the bagging film to the prepreg.

[0103] <Surface Properties of Reinforced Fiber Composite Molding> The arithmetic mean roughness Ra (μm) of the surface of the obtained reinforced fiber composite molding was measured using a laser microscope. A straight line perpendicular to the longitudinal direction was drawn in the longitudinal center of the 480x measurement image (longitudinal direction (LD) approximately 529 μm and width direction (TD) approximately 706 μm), the surface roughness was measured on the line, and Ra (TD) on the line was automatically calculated in the device. Measurements were taken at different locations, and a total of five locations were measured, and the average value was used as the analytical value. Detailed measurement and analysis conditions are as follows. Ra was evaluated as A for 1 μm or less and B for more than 1 μm. A indicates better surface properties. Measurement device: VK-X3000 (manufactured by Keyence Corporation) Measurement sample: 10 cm x 10 cm Measurement conditions: basic measurement, pitch 1.00 μm, step approximately 25 to 140 (adjusted appropriately depending on the sample) Analysis conditions: tilt correction: none, DCL / BCL: none, measurement type: roughness, cutoff: λs = none, λc = none, end effect correction: enabled, double Gaussian: OFF, stylus mode: OFF, number of reference lengths: 1, load length rate for calculating cutting level difference: Rmr1 25%, Rmr2 75%

[0104] [Production Example 1] A film-forming solution with a volatile content of 68%, consisting of 100 parts by mass of PVA (degree of polymerization 2,400, degree of saponification 99.4 mol%), 13 parts by mass of glycerin as a plasticizer, 0.1 parts by mass of lauric acid diethanolamide as a surfactant, and water, was melt-extruded from a T-die onto a metal roll at 90°C, dried, and then heat-treated with a heat-treatment roll at a surface temperature of 120°C to obtain a PVA film with an average thickness of 50 μm. The obtained PVA film was subjected to a surface coating treatment. A methyl methacrylate / styrene copolymer was applied to both sides of the PVA film by a dipping method at a rate of 0.020 g / m per side. ２The film was then dried with hot air at 100°C for 30 seconds to obtain a film (PVA-1). For the surface coating treatment, an emulsion of a methyl methacrylate / styrene copolymer (methyl methacrylate unit / styrene unit (molar ratio) = 50 / 50) having an average particle size of 0.1 µm (particles of the methyl methacrylate / styrene copolymer dispersed in water at a concentration of 30% by mass) was added to an aqueous solution containing 1.5% by mass of PVA having a degree of polymerization of 2400 and a degree of saponification of 99.2 mol%, so that the [PVA] / [methyl methacrylate / styrene copolymer] (mass ratio) was 3 / 1. This was used as the coating solution. The Young's modulus of the film (PVA-1) was 240 N / mm ２ It was.

[0105] [Production Example 2] Powder was attached to both sides of the film (PVA-1) obtained in Production Example 1 (powder treatment) to produce film (PVA-2). In the powder treatment, water-repellent processed starch was used, and the powder was attached by electronic spraying. The Young's modulus of film (PVA-2) was 240 N / mm ２ It was.

[0106] [Production Example 3] This film was the same as Production Example 1 except that the average thickness was changed to 25 μm and the same powder treatment as described in Production Example 2 was performed. This was designated as film (PVA-3). The Young's modulus of film (PVA-3) was 115 N / mm ２ It was.

[0107] [Production Example 4] A film-forming solution with a volatile content of 55%, consisting of 100 parts by mass of PVA (degree of polymerization 1,700, degree of saponification 98.5 mol%), 5 parts by mass of glycerin as a plasticizer, 0.1 parts by mass of lauric acid diethanolamide as a surfactant, and water, was melt-extruded from a T-die onto a metal roll at 90°C, dried, and then heat-treated with a heat-treatment roll at a surface temperature of 120°C to obtain a PVA film with an average thickness of 25 μm, which was designated film (PVA-4). No surface coating treatment was performed on film (PVA-4). The Young's modulus of film (PVA-4) was 60 N / mm ２ It was.

[0108] [Production Example 5] Both sides of the film (PVA-1) obtained in Production Example 1 were embossed to produce a film (PVA-5). The embossing conditions were as follows: Embossing roll: Material: carbon steel, Handle: silk, Temperature: 100-110°C Back roll: Material: cotton, Temperature: No temperature control, Pressure: 5 MPa / 140 cm, Speed: 12 m / min

[0109] [Production Example 6] Film (PVA-6) was obtained by embossing both surfaces of the film (PVA-3) obtained in Production Example 3. The embossing conditions were the same as those in Production Example 5.

[0110] [Production Example 7] The film (PVA-4) obtained in Production Example 4 was embossed on both sides to obtain a film (PVA-7). The embossing conditions were the same as in Production Example 5.

[0111] [Reference Example 1] A commercially available nylon film (NA1400-2, manufactured by National Aerospace Supply Company, average thickness 50 μm) was prepared. The Young's modulus of this nylon film was 630 N / mm ２ It was.

[0112]

[0113] Example 1 An uncured carbon fiber composite material (three layers of TR3523-381GMX (manufactured by Mitsubishi Chemical Corporation)) in which carbon fibers were impregnated with epoxy resin was placed on a flat mold. Before placing the uncured carbon fiber composite material, a mold release agent (Curecoat QP7050, manufactured by Chukyo Chemical Industry Co., Ltd.) was applied to the surface of the mold that would come into contact with the uncured carbon fiber composite material. The mold was covered with a film (PVA-1) used as a bagging film to form a vacuum bag, and a vacuum valve for venting air was installed inside the vacuum bag, which was then sealed with sealing tape. A small cut was made in the vacuum bag to expose the tip of the vacuum valve for venting air to the outside of the vacuum bag, and a vacuum bag molding system was produced.

[0114] A vacuum hose was connected to the vacuum valve for exhausting air from the vacuum bag molding system, and the air inside the vacuum bag was evacuated using a vacuum device. This was then placed in an autoclave. Heat curing was performed inside the autoclave while reducing the pressure inside the vacuum bag of the vacuum bag molding system (125°C for 4 hours, autoclave internal pressure: 3.5 MPa). After heat curing was complete, the vacuum bag molding system was removed from the autoclave and allowed to cool to room temperature. The vacuum bag was then released to atmospheric pressure, and the carbon fiber composite molded body was removed, yielding a carbon fiber composite molded body (an example of a reinforced fiber composite molded body). The evaluation results for the workability, conformability to the prepreg, and surface properties of the reinforced fiber composite molded body are shown in Table 2. The surface Ra of the carbon fiber composite molded body was 0.17 μm.

[0115] [Example 2] A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-2) was used as the bagging film. The evaluation results are shown in Table 2.

[0116] [Example 3] A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-3) was used as the bagging film. The evaluation results are shown in Table 2.

[0117] [Example 4] A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-4) was used as the bagging film. The evaluation results are shown in Table 2.

[0118] [Example 5] A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that film (PVA-2) was used as the bagging film and that film (PVA-2) was laminated as a release film on the front side of the uncured carbon fiber composite material (the side of the uncured carbon fiber composite material opposite to the surface that contacts the mold) when the uncured carbon fiber composite material was laminated on a flat mold. The evaluation results are shown in Table 2.

[0119] Example 6 A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-2) was used as the bagging film, and a polymethylpentene (TPX) film (Opulent (registered trademark), manufactured by Mitsui Chemicals, Inc.) was laminated as a release film on the surface side of the uncured carbon fiber composite material (the side of the uncured carbon fiber composite material opposite to the surface that contacts the mold) when the uncured carbon fiber composite material was laminated on the flat mold. The evaluation results are shown in Table 2.

[0120] Example 7 A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-2) was used as the bagging film, and a polypropylene (PP) film (A2000, manufactured by Cytec Industries Incorporated) was laminated as a release film on the front side of the uncured carbon fiber composite material (the side of the uncured carbon fiber composite material opposite to the surface that contacts the mold) when the uncured carbon fiber composite material was laminated on the flat mold. The evaluation results are shown in Table 2.

[0121] Comparative Example 1 A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-5) was used as the bagging film. The evaluation results are shown in Table 2.

[0122] Comparative Example 2 A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-6) was used as the bagging film. The evaluation results are shown in Table 2.

[0123] Comparative Example 3 A vacuum bag molding system was produced and a carbon fiber composite molded product was obtained in the same manner as in Example 1, except that a film (PVA-7) was used as the bagging film. The evaluation results are shown in Table 2.

[0124] Comparative Example 4 A vacuum bag molding system was prepared in the same manner as in Example 1, except that the nylon film of Reference Example 1 was used as the bagging film. When the air inside the vacuum bag was suctioned using a pressure reducing device, the air inside the vacuum bag could not be sufficiently discharged, and many gaps remained between the bagging film and the carbon fiber composite material, making molding impossible. The evaluation results are shown in Table 2.

[0125] Comparative Example 5 A vacuum bag molding system was fabricated in the same manner as in Example 1, except that the nylon film of Reference Example 1 was used as the bagging film, a polymethylpentene (TPX) film (Opulent (registered trademark), manufactured by Mitsui Chemicals, Inc.) was laminated as a release film on the front side of the uncured carbon fiber composite material (the side of the uncured carbon fiber composite material opposite to the side that contacts the mold) when the uncured carbon fiber composite material was laminated onto the flat mold, and a breather was laminated on the back side of the mold (the side of the mold opposite to the side on which the uncured carbon fiber composite material was placed). The evaluation results are shown in Table 2. The Ra of the surface of the carbon fiber composite molded product was 6.10 μm.

[0126]

[0127] Examples 1 to 7, which used a non-embossed PVA film as the bagging film, each exhibited excellent workability, prepreg conformability, and surface quality of the reinforced fiber composite molded body (carbon fiber composite molded body). Meanwhile, Comparative Examples 1 to 3, which used an embossed PVA film, exhibited strong adhesion between the film and the molded body after curing, preventing peeling. It can be seen that the presence or absence of embossing has a greater impact on peelability than the surface coating or powder treatment. Furthermore, Comparative Example 4, which used a nylon film as the bagging film, was unable to fully evacuate the air inside the vacuum bag, leaving many gaps between the bagging film and the carbon fiber composite material, resulting in failure to mold the body. In other words, when a nylon film was used as the bagging film without a release film or breather, molding of a reinforced fiber composite molded body (carbon fiber composite molded body) was not possible. On the other hand, surprisingly, Examples 1 to 4, which were formed using a non-embossed PVA film as a bagging film and without a release film or breather, were superior in all evaluation items to Comparative Example 5, which used a nylon film bagging film and a polymethylpentene film release film and breather.

[0128] The vacuum bag molding system of the present invention can be suitably used for autoclave molding of reinforced fiber composite materials.

[0129] REFERENCE SIGNS LIST 10 Mold 11 Mold release agent 12 Molding material 13 Bagging film 14 Vacuum valve 15 Vacuum bag 16 Sealing tape (sealing portion) 17 Hose 18 Breather 19 Mold release film

Claims

1. A vacuum bag molding system comprising a vacuum bag and a vacuum valve for evacuating the inside of the vacuum bag, wherein the inside of the vacuum bag contains a molding material that is placed on a mold directly or via another member, and the vacuum bag has a bagging film that is a polyvinyl alcohol film whose surface is not embossed.

2. The Young's modulus of the polyvinyl alcohol film at 23°C / 50% RH is 50 to 350 N / mm ２ 2. The vacuum bag forming system of claim 1, wherein:

3. The vacuum bag molding system according to claim 1 or 2, wherein the average thickness of the polyvinyl alcohol film is 20 to 100 μm.

4. A vacuum bag molding system according to claim 1 or 2, wherein the bagging film is directly laminated on the surface of the molding material.

5. A method for producing a reinforced fiber composite molding using the vacuum bag molding system described in claim 1, wherein the molding material is an uncured reinforced fiber composite material, and the method comprises the steps of: evacuating the air inside the vacuum bag through the vacuum valve; and heat-curing the uncured reinforced fiber composite material contained in the vacuum bag using an autoclave.

6. A method for producing a reinforced fiber composite molding as described in claim 5, wherein the bagging film and the uncured reinforced fiber composite material are in close contact after the step of evacuating the air inside the vacuum bag through the vacuum valve.

7. A polyvinyl alcohol film used as a bagging film in the vacuum bag forming system of claim 1.

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