Method for producing molded body

Abstract

Provided is a method for producing a molded body capable of reducing solid waste. A method for producing a molded body, the method including, in the following order, a step for accommodating a molding material in a vacuum bag having a water-soluble bagging film, a step for curing the molding material, and a step for dissolving the bagging film in water.

Description

Method for manufacturing a molded body

[0001] The present invention relates to a method for manufacturing a molded body.

[0002] Molded bodies in which reinforcing materials such as natural fibers and carbon fibers are solidified with a base material (matrix) such as resin are known. In such molded bodies, various molding methods are selected according to the final form and characteristics. Among the molding methods, autoclave molding has a high degree of freedom in materials and shapes and is the molding method that is most likely to bring out the characteristics and performance of the molded body.

[0003] A typical procedure outline of autoclave molding is as follows. A prepreg in which a thermosetting resin is impregnated in fibers (reinforcing fibers) serving as a reinforcing material is cut into a predetermined shape. A mold having a desired shape is coated with a release agent, and the necessary number of prepregs are laminated at predetermined positions inside the mold. A release film and a breather are sequentially arranged on the surface of the laminated prepregs, and these are covered and sealed with a bagging film. By covering and sealing with such a bagging film, a vacuum bag is formed. By discharging the air inside the vacuum bag and bringing the inside of the vacuum bag into a vacuum state, the adhesion of the laminated prepregs to the mold is enhanced. Then, the molded body is obtained by curing the thermosetting resin while heating and pressurizing in an autoclave.

[0004] Generally, resin films such as nylon films are used for the bagging films used in autoclave molding. Patent Document 1 describes a film made of a resin composition mainly composed of a polyamide resin and a thermoplastic elastomer as a bagging film used in autoclave molding.

[0005] Japanese Unexamined Patent Application Publication No. 2016-190404

[0006] Autoclave molding is a method capable of manufacturing high-quality molded bodies, but there are problems in the treatment of the auxiliary materials used. Many auxiliary materials (release films, breathers, bagging films, etc.) used in autoclave molding become waste and are not reused after molding. Since these auxiliary materials are in the form of films, they are likely to take up a lot of space and there is a limit to making them smaller, and a dedicated waste space is required.

[0007] This invention was made based on these circumstances, and the object of this invention is to provide a method for manufacturing molded articles that enables the reduction of solid waste.

[0008] In other words, the present invention relates to [1] to [8]. [1] A method for manufacturing a molded article, comprising in this order: a step of containing a molding material in a vacuum bag having a water-soluble bagging film; a step of curing the molding material; and a step of dissolving the bagging film in water. [2] The method for manufacturing a molded article according to [1], wherein in the containing step, the molding material is contained such that the bagging film is in contact with the surface of the molding material. [3] The method for manufacturing a molded article according to [1] or [2], wherein the molding material comprises a curable resin and a reinforcing material. [4] The method for manufacturing a molded article according to [3], wherein the curable resin is a thermosetting resin. [5] The method for manufacturing a molded article according to any one of [1] to [4], wherein the bagging film mainly comprises a water-soluble polymer. [6] The method for manufacturing a molded article according to [5], wherein the water-soluble polymer is polyvinyl alcohol. [7] The method for manufacturing a molded article according to [6], wherein the degree of saponification of the polyvinyl alcohol is 70 to 98 mol%. [8] A method for producing the molded article according to [6] or [7], wherein the content of vinyl alcohol units relative to the total monomer units of the polyvinyl alcohol is 70 to 98 mol%.

[0009] The method for manufacturing molded articles according to the present invention makes it possible to reduce solid waste.

[0010] Figure 1 is a schematic cross-sectional view showing a state in which the molding material is contained in a vacuum bag in a method for manufacturing a molded article according to one embodiment of the present invention. Figure 2 is a schematic cross-sectional view showing a state in which the molding material is contained in a vacuum bag in a method for manufacturing a molded article according to an embodiment different from Figure 1.

[0011] In this specification, numerical ranges indicated using "~" include the values ​​indicated before and after "~" as the lower and upper limits, respectively. In this specification, the upper and lower limits of numerical ranges (content, physical properties, etc.) can be combined as appropriate. In this specification, "main component" refers to the component with the highest content by mass. Polyvinyl alcohol may be abbreviated as "PVA," and polyvinyl alcohol film may be abbreviated as "PVA film."

[0012] A vacuum bag is a container that has a shape that creates a vacuum inside when the contents are evacuated. A vacuum bag may be, for example, a bag shape, but is not limited to that shape. A vacuum bag may be composed solely of a water-soluble bagging film, or it may be composed of a water-soluble bagging film and other components (e.g., a mold). A vacuum state does not refer only to a completely vacuum state, but 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. Furthermore, "molding material" refers to the material before curing, and "molded body" refers to the cured product after curing.

[0013] A method for manufacturing a molded article according to one embodiment of the present invention includes, in this order, the steps of: placing a molding material in a vacuum bag having a water-soluble bagging film; curing the molding material; and dissolving the bagging film in water.

[0014] According to this method for manufacturing molded products, the bagging film is dissolved in water after the molding material has hardened, thus reducing the amount of bagging film that would normally become solid waste, leading to space savings in disposal areas (waste storage areas, etc.). The following provides a detailed explanation of each step.

[0015] <Containment Process> In the method for manufacturing the molded product, first, the molding material is contained in a vacuum bag having a water-soluble bagging film. In other words, the molding material is contained in a vacuum bag having a water-soluble bagging film. The bagging film will be explained in detail below.

[0016] (Bagging Film) The bagging film is a water-soluble film. Preferably, the bagging film contains a water-soluble polymer as its main component. Examples of water-soluble polymers include polyvinyl alcohol (PVA), polyacrylic acid, polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, polyvinylamide, polyamine, protein, starch, etc. One or more water-soluble polymers can be used.

[0017] The water-soluble polymer is preferably PVA. In other words, the bagging film is preferably a PVA film. A film containing PVA as the main component (PVA film) has moderate hardness, making it easy to work with and easily soluble in water. Furthermore, PVA films have excellent conformability to the molding material, allowing for the production of molded articles with a good surface appearance. In addition, PVA has low affinity for the base material used in the molding material (especially thermosetting resins such as epoxy resins), which has the advantage of being easy to remove with water after obtaining the molded article.

[0018] PVA stands for vinyl alcohol unit (-CH ２ It is a polymer having -CHOH-). PVA may have monomer units other than vinyl alcohol units. As PVA, a vinyl ester polymer obtained by polymerizing vinyl ester monomers and then saponifying that polymer can be used. Polymerization and saponification can be carried out by conventionally known methods.

[0019] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versaticate, with vinyl acetate being preferred.

[0020] The degree of polymerization of PVA is not particularly limited, and may be, for example, 500 to 8,000, 1,000 to 6,000, or 1,500 to 4,000. Here, the degree of polymerization of PVA refers to the viscosity-average degree of polymerization (Po) measured in accordance with the description in JIS K6726-1994, and is determined by the following formula from the intrinsic viscosity [η] (deciliters / g) measured in water at 30°C after resaponification and purification of polyvinyl alcohol.

[0021] The degree of saponification of PVA is not particularly limited, and is usually 70 to 100 mol%, may be 70 to 99.9 mol%, and preferably 70 to 98 mol%. By having a degree of saponification of 70 to 98 mol%, the appropriate hardness, water solubility, etc. of the PVA film can be particularly optimized in a well-balanced manner. From the viewpoint of water solubility, etc., the upper limit of the degree of saponification is more preferably 95 mol%, even more preferably 93 mol%, and even more preferably 91 mol%. From the viewpoint of flexibility, etc., the lower limit of the degree of saponification is more preferably 75 mol%, even more preferably 78 mol%, even more preferably 80 mol%, and may be 82 mol%, 84 mol%, or 86 mol%. The degree of saponification refers to the ratio (mol%) of moles of vinyl alcohol units to the total number of moles of monomer units (typically vinyl ester units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification. The degree of saponification of PVA can be measured in accordance with the description in JIS K6726-1994.

[0022] The PVA may contain modified PVA, or it may be modified PVA alone. Using modified PVA tends to increase the water solubility of the PVA film after curing of the molding material. Modified PVA refers to PVA that has monomer units derived from monomers other than vinyl esters. Modified PVA may also be a saponified product of modified polyvinyl ester. Furthermore, modified PVA may be obtained by post-modifying unmodified PVA.Other monomers include, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, their salts, or their anhydrides; unsaturated sulfonic acids such as acrylamide alkyl sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, their salts, or their anhydrides; ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, and 2-butyl acrylate. Acrylic acid esters such as -ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamide Acrylamide derivatives such as dopropyldimethylamine or its salts, N-methylolacrylamide or its derivatives; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or its salts, methacrylamidepropyldimethylamine or its salts, N-methylolmethacrylamide or its derivatives; N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-prop Examples include vinyl ethers such as polyvinyl ether, i-propyl vinyl ether, n-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 esters; itaconic acid esters; vinyl silyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate.

[0023] As the modified PVA, acid-modified PVA such as carboxylic acid-modified PVA, sulfonic acid-modified PVA, and phosphate-modified PVA is preferred, and at least one selected from the group consisting of sulfonic acid-modified PVA and carboxylic acid-modified PVA is more preferred. Using such modified PVA tends to increase the water solubility of the PVA film after obtaining the molded article.

[0024] Sulfonic acid-modified PVA is PVA having a sulfo group. The sulfo group may be in the form of a salt or an anhydride. Sulfonic acid-modified PVA may have monomer units derived from the unsaturated sulfonic acid, its salt, or its anhydride, or it may have a sulfo group introduced by post-modification. It is preferable that sulfonic acid-modified PVA has monomer units derived from an unsaturated sulfonic acid, its salt, or its anhydride.

[0025] Carboxylic acid-modified PVA is PVA having a carboxyl group. The carboxyl group may be in the form of a salt or an anhydride. Carboxylic acid-modified PVA may have monomer units derived from the unsaturated carboxylic acid, its salt, or its anhydride, or it may have a carboxyl group introduced by post-modification. It is preferable that carboxylic acid-modified PVA has monomer units derived from an unsaturated carboxylic acid, its salt, or its anhydride.

[0026] The modified PVA is preferably a saponified product of a modified polyvinyl ester (a copolymer of a vinyl ester and another monomer other than a vinyl ester). In other words, it is preferable that the modified PVA is not modified by post-modification. The main chain of the modified PVA may consist of vinyl alcohol units, arbitrary vinyl ester units, and units derived from other monomers. The other monomers are preferably monomers having acidic groups (sulfo groups, carboxyl groups, phosphate groups, etc.). The acidic groups may be in the form of salts or anhydrides. Examples of monomers having acidic groups include the unsaturated sulfonic acid, its salt or anhydride, the unsaturated carboxylic acid, its salt or anhydride, etc.

[0027] The degree of modification in modified PVA is, for example, 0.1 to 10 mol%. The lower limit of the degree of modification may be 0.5 mol% or 1 mol%. The upper limit of the degree of modification may be 5 mol% or 3 mol%. The degree of modification refers to the ratio of monomer units derived from monomers other than vinyl ester to the total monomer units constituting the modified PVA.

[0028] The upper limit of the content of vinyl alcohol units relative to the total monomer units in PVA may be 100 mol%, but 98 mol% is preferred, 95 mol% is more preferred, and 93 mol% is even more preferred. The lower limit of the content is preferably 70 mol%, more preferably 75 mol%, even more preferably 78 mol%, and even more preferably 80 mol% or 84 mol%. In this way, the presence of monomer units other than vinyl alcohol units (vinyl ester units and monomer units derived from other monomers other than vinyl esters) in an appropriate amount tends to reduce the crystallinity of the PVA film and increase the water solubility of the PVA film after curing of the molding material.

[0029] The lower limit of the water-soluble polymer content in the bagging film is preferably 50% by mass, more preferably 60% by mass, and even more preferably 80% by mass. The upper limit of the water-soluble polymer content in the bagging film may be 100% by mass, or 99% by mass, 95% by mass, or 90% by mass.

[0030] In addition to the water-soluble polymer as the main component, the bagging film may also contain water, plasticizers, surfactants, fillers, polymers other than water-soluble polymers, etc., as long as they do not impair the effects of the present invention.

[0031] As plasticizers, 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 cause bleed-out to the film surface, and it is more preferable that at least one is selected from the group consisting of ethylene glycol, glycerin, diglycerin, propylene glycol, and diethylene glycol.

[0032] The amount of plasticizer contained in the bagging film can be appropriately adjusted according to the desired shape and surface properties of the molded article. The lower limit of the plasticizer content in the bagging film may be 0 parts by mass, preferably 1 part by mass, more preferably 3 parts by mass, and may also be 5 or 10 parts by mass per 100 parts by mass of water-soluble polymer. By setting the plasticizer content in the bagging film to be above the lower limit, the flexibility of the bagging film can be increased. On the other hand, the upper limit of the plasticizer content is preferably 35 parts by mass, more preferably 30 parts by mass, even more preferably 25 parts by mass, and even more preferably 20 parts by mass per 100 parts by mass of water-soluble polymer. By setting the plasticizer content in the bagging film to be below the upper limit, the strength of the bagging film can be increased.

[0033] The surfactant is not particularly limited as long as it does not impair the effects of the present invention, and examples include cationic surfactants, anionic surfactants, and nonionic surfactants.

[0034] The lower limit of the total content of water-soluble polymers and optional components such as water, plasticizers, and surfactants in the bagging film may be, for example, 90% by mass, or 95% by mass, 98% by mass, 99% by mass, 99.5% by mass, or 99.9% by mass. The upper limit of the total content of water-soluble polymers and optional components such as water, plasticizers, and surfactants in the bagging film may be 100% by mass.

[0035] The bagging film may contain a filler. By including a filler, the mechanical strength and handling properties of the bagging film can be improved.

[0036] Examples of fillers include carbon black, metal powder, silica, alumina, calcium carbonate, titanium dioxide, talc, mica, and clay minerals such as bentonite.

[0037] The bagging film may further contain other components besides those described above, as long as they do not interfere with the effects of the present invention. Examples of other components include antioxidants, ultraviolet absorbers, lubricants, crosslinking agents, colorants, preservatives, and fungicides.

[0038] The surface of the bagging film may be physically and / or chemically treated as necessary, provided that the effects of the present invention are not impaired. Examples of physical treatments include embossing. Examples of chemical treatments include surface treatments to prevent blocking inside the film roll.

[0039] There are no particular restrictions on the thickness of the bagging film, and it can be appropriately selected considering factors such as ease of handling during molding and water solubility. The average thickness of the bagging film can be, for example, 20 to 200 μm. From the viewpoint of ease of handling during molding, the lower limit of the average thickness is preferably 25 μm, and more preferably 30 μm. On the other hand, from the viewpoint of water solubility, the upper limit of the average thickness is preferably 160 μm, more preferably 140 μm, and may also be 100 μm.

[0040] The bagging film may be a stretched film or an unstretched film, but an unstretched film is preferred. By using an unstretched film as the bagging film, effects such as conformability are fully achieved. An unstretched film is a film that has not undergone substantially any stretching treatment. An unstretched film may be a film with a length-based stretching ratio of 1.0x or more and 1.1x or less, or a film with a length-based stretching ratio of 1.00x or more and 1.01x or less.

[0041] In the case of the bagging film, it is preferable that the film heated at 130°C for 2 hours completely dissolves in water at 99°C or lower, more preferably in water at 90°C or lower, even more preferably in water at 70°C or lower, and even more preferably in water at 50°C or lower. Further, in the bagging film, it is preferable that the film heated at 130°C for 2 hours completely dissolves in water at 25°C or higher, and more preferably in water at 30°C or higher.

[0042] (Vacuum bag) The vacuum bag has a water-soluble bagging film and has a space capable of accommodating a molding material inside. Usually, the vacuum bag has a part that can be evacuated and a part that can be sealed. The part that can be evacuated may be a vacuum valve or the like described later. The part that can be sealed may be a part where a sealing member or the like described later is provided.

[0043] There is no particular limitation on the method of accommodating the molding material in the vacuum bag. For example, as shown in FIG. 1, there is a method of accommodating the molding material 3 in a bag-shaped vacuum bag 2 formed from the bagging film 1. In this embodiment, the molding material 3 is placed on the mold 4, and the mold 4 is also placed in the vacuum bag 2 together with the molding material 3. After accommodating the molding material 3 or the like in the vacuum bag 2, the vacuum bag 2 is sealed with a sealing member 5 such as a sealing tape. The sealing means is not limited to the method using a sealing tape, and an adhesive or the like may be used, or alternatively, the bagging films 1 may be directly bonded by thermocompression bonding or the like. Further, a vacuum valve 6 is provided on the vacuum bag 2 so that the air inside the vacuum bag 2 can be discharged. In order to obtain the state where the molding material 3 is accommodated in the vacuum bag 2 as shown in FIG. 1, the mold 4, the molding material 3, and the second bagging film 1 are arranged in this order on the first bagging film 1, and the vacuum bag 2 may be produced by sealing the bagging films 1 with the sealing member 5.

[0044] Note that, for the formation of the vacuum bag, a water-soluble bagging film and other bagging films may be used in combination. From the viewpoint of reducing solid waste after obtaining the molded body, it is preferable that all of the bagging films used are water-soluble.

[0045] Also, as shown in FIG. 2, after placing the molding material 3 on the mold 4, the molding material 3 is covered with the bagging film 1, and the space between the mold 4 and the bagging film 1 is sealed with the sealing member 5, so that a method of manufacturing the vacuum bag 2 in which the molding material 3 is accommodated can also be adopted. In the form of FIG. 2, the vacuum bag 2 in which the molding material 3 is accommodated is formed by the bagging film 1 and the mold 4. Also in the form of FIG. 2, the vacuum bag 2 is provided with a vacuum valve 6.

[0046] (Molding Material) The molding material is the material of the target molded body. Usually, the molding material contains a curable resin, and it is preferable that the curable resin and a reinforcing material are included. As a typical form of the molding material, there is an example in which a fibrous reinforcing material is impregnated with a curable resin. The curable resin to be arranged is uncured, but it may be partially cured or semi-cured.

[0047] The curable resin is preferably a thermosetting resin. Examples of the thermosetting resin include epoxy resin, phenol resin, unsaturated polyester resin, cyanate ester resin, phenol-formaldehyde resin, melamine resin, etc., and epoxy resin is preferable. The water-soluble bagging film has particularly good mold release properties with respect to such resins.

[0048] The thermosetting resin may contain various known curing agents. For example, when the curable resin is an epoxy resin, examples of the curing agent include amines, amides, imidazoles, acid anhydrides, etc.

[0049] As the reinforcing material, various reinforcing fibers can be used. Examples of the reinforcing fibers include artificially generated 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 linen, hemp, jute, ramie, kenaf hemp, sisal hemp, bamboo, silk, cotton, and wood; and semi-natural fibers such as cellulose nanofiber. Two or more of these reinforcing fibers may be used in combination.

[0050] As the reinforcing fiber, carbon fiber or natural fiber is preferred, and carbon fiber is more preferred. The molded article obtained by the method for manufacturing a molded article according to one embodiment of the present invention may be a reinforced fiber composite molded article or a carbon fiber composite molded article.

[0051] Considering the strength and dimensional stability of the molded object in each direction, a fibrous reinforcing material impregnated with a thermosetting resin (prepreg) may be used as the molding material.

[0052] The molding material may be in contact with the water-soluble bagging film that constitutes the vacuum bag. Both the configurations in Figures 1 and 2 show the molding material 3 in contact with the bagging film 1. Normally, a release film is placed between the molding material and the bagging film to facilitate the removal of the bagging film after obtaining the molded product. However, in this manufacturing method, the bagging film can be removed by dissolving it with water after obtaining the molded product, so a release film does not need to be placed. Not using a release film has advantages such as improved work efficiency and reduced waste.

[0053] (Other auxiliary materials, etc.) In this manufacturing method, a release film may be placed between the molding material and the bagging film. As the release film, fluororesin (polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene hexafluoropropylene copolymer, etc.), PVA film, polymethylpentene film, polyolefin (polyethylene, polypropylene, etc.) film, etc. can be used. As the release film, a water-soluble film similar to that of the bagging film can be used. When using a release film, if it is the same type or a different type of water-soluble release film as the bagging film, the release film can be dissolved at the same time as the bagging film in the process of dissolving the bagging film in water. It is preferable to use a release film containing the same type of water-soluble polymer as the bagging film, as this facilitates recovery and reuse after dissolution. The specific form and preferred form of the water-soluble release film are the same as those described above for the water-soluble bagging film. On the other hand, a release film that does not dissolve in water can also be used.

[0054] Although the mold 4 in Figures 1 and 2 is shown as a plate, its shape can be appropriately changed according to the desired shape of the molded product. The method for manufacturing the molded product can also be applied to molding using molds with complex shapes that have uneven surfaces. The material of the mold is not particularly limited, and metal molds such as aluminum and steel, pearl board molds, FRP (Fiber Reinforced Plastics) molds, etc., can be used.

[0055] A release agent may be placed between the mold and the molding material. That is, a release agent may be applied to the mold surface (the surface on which the molding material is placed) and the molding material may be placed on top of it. The molding material may be placed directly on the mold or via other components such as a release agent. There are no particular restrictions on the release agent, and it can be selected according to the material of the mold or prepreg. Examples of release agents include silicone-based, acrylic-based, urethane-based, urethane acrylate-based materials, fluoropolymer-based materials, or combinations thereof.

[0056] In this manufacturing method, a breather may be placed inside the vacuum bag for efficient disposal. When a breather is used, its placement is not particularly limited, for example, between the mold and the molding material, between the molding material and the bagging film, or between the mold and the bagging film. The breather may be placed in only one location or in multiple locations. Conventional breathers can be used as the breather. For example, a nonwoven fabric called a breather cloth can be used as the breather. The breather can be made of one or more layers of nonwoven fabric.

[0057] On the other hand, in this manufacturing method, it is not necessary to place a breather inside the vacuum bag. In particular, when PVA film is used as the water-soluble bagging film, the PVA film has good release and conformability to the molding material or the molded article formed from the molding material, and when PVA film is used as the bagging film, sufficient exhaust is possible even without placing a breather.

[0058] After placing the molding material in a vacuum bag and sealing the vacuum bag, the air inside the vacuum bag is expelled through a vacuum valve. For example, the vacuum valve may be connected to an exhaust device to expel the air from the vacuum bag.

[0059] <Curing Process> The molding material is placed in a vacuum bag, the vacuum bag is evacuated, and then the molding material inside the vacuum bag is cured. By curing the molding material, the desired molded body is obtained. The curing of the molding material may be done by thermosetting. The curing of the molding material can be carried out in the same way as conventionally known autoclave molding, etc. That is, after referring to the general manufacturing conditions for molded bodies, for example, the curing temperature and curing rate of the thermosetting resin that constitutes the uncured molding material used should be considered, and the pressure and temperature inside the autoclave should be adjusted according to the desired shape and properties of the molded body.

[0060] When heating is performed during the curing process, the heating temperature is preferably below the decomposition temperature of the bagging film. When the bagging film is mainly composed of PVA, the upper limit of the heating temperature is preferably 200°C, more preferably 180°C, and even more preferably 150°C. The lower limit of the heating temperature is preferably 110°C.

[0061] When an autoclave is used in the curing process, the internal pressure of the autoclave is preferably above atmospheric pressure, more preferably 0.2 MPa or higher, and even more preferably 0.3 MPa or higher. The pressurization time is preferably 60 minutes or more, and more preferably 120 minutes or more.

[0062] <Dissolution Process> After the molding material has hardened, the bagging film is dissolved in water. This process allows the bagging film to be recovered as an aqueous solution. Therefore, this manufacturing method can reduce solid waste and, as a result, save space in the waste disposal area.

[0063] There are no particular restrictions on the method of dissolving the bagging film with water. The bagging film covering the molded body formed from the hardened molding material may be dissolved by directly spraying water onto it, the entire vacuum bag containing the molded body may be immersed in water, or the bagging film may be peeled off the molded body and the bagging film may be immersed in water.

[0064] In one embodiment of the present invention, the bagging film covering the molded body may be dissolved with water. In other words, the bagging film constituting the vacuum bag containing the molded body may be dissolved with water while the vacuum bag is still in place. Dissolving the bagging film covering the molded body with water eliminates the need to peel off the bagging film, thus improving work efficiency. Alternatively, the bagging film covering the molded body may be brought into contact with water to partially dissolve it, then peeled off, and the peeled bagging film may be dissolved in water. Methods for bringing the bagging film into contact with water include pouring water on it or immersing it in water. When the bagging film covering the molded body is brought into contact with water in this way, the adhesion between the bagging film and the molded body decreases due to the partial dissolution of the bagging film, making it easier to peel off the bagging film and improving work efficiency. In particular, bagging film is generally strongly adhered to molded bodies and can be difficult to peel off. Therefore, this method, which involves dissolving at least a portion of the bagging film covering the molded body with water, is useful as it has the advantage of eliminating the need for or facilitating the removal process.

[0065] When dissolving bagging film by immersion in water, the water may be agitated or water pressure may be applied to dissolve the bagging film. This allows the bagging film to dissolve quickly.

[0066] The water used to dissolve the bagging film may be an aqueous solution or aqueous dispersion containing other components besides water.

[0067] The lower limit of the water temperature used to dissolve the bagging film is preferably 25°C, more preferably 30°C, and even more preferably 40°C. By setting the water temperature above the lower limit, the bagging film can be dissolved in a short time. On the other hand, the upper limit of the water temperature may be, for example, 99°C, or 90°C, 70°C, 60°C, or 50°C. By setting the water temperature below the upper limit, it is possible to reduce costs and save energy in the manufacturing of molded products.

[0068] The molded articles obtained by this manufacturing method can be widely applied to a variety of products, from aircraft such as airplanes and helicopters, to vehicles such as motorcycles and automobiles, wind turbine blades, fishing rods, golf shafts, rackets, and other leisure goods.

[0069] <Other Embodiments> The present invention is not limited to the embodiments described above, and its configuration can be modified without altering the essence of the invention. For example, the method for manufacturing a molded article of the present invention can be applied to molding methods other than autoclave molding.

[0070] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0071] [Manufacturing Example 1] (Manufacturing of Bagging Film A) An aqueous solution containing 100 parts by mass of PVA (degree of polymerization 1,700, degree of saponification 88.0 mol%, unmodified PVA), 15 parts by mass of glycerin as a plasticizer, 1.0 part by mass of sodium alkyl sulfonate as an anionic surfactant, 0.5 parts by mass of polyoxyethylene alkyl ether as a nonionic surfactant, and 3.0 parts by mass of starch, with a PVA content of 11.0% by mass, was prepared as a film-forming stock solution. The film-forming stock solution was cast onto a metal drum at 60°C and dried for 20 minutes. The dried film was peeled off the surface of the metal drum to produce bagging film A with an average thickness of 35 μm.

[0072] [Production Example 2] (Production of Bagging Film B) Bagging film B was produced in the same manner as in Production Example 1, except that the PVA was changed to itaconic acid-modified PVA (saponified copolymer of vinyl acetate and itaconic acid) with a degree of polymerization of 1,700, a degree of saponification of 88.0 mol%, and an itaconic acid modification amount of 1.3 mol%.

[0073] [Production Example 3] (Production of Bagging Film C) Bagging film C was produced in the same manner as in Production Example 1, except that PVA was changed to AMPS-modified PVA (saponified copolymer of vinyl acetate and AMPS) with a degree of polymerization of 1,700, a degree of saponification of 88.0 mol%, and an AMPS ((meth)acrylamide alkyl sulfonic acid) modification amount of 2.0 mol%.

[0074] [Manufacturing Example 4] (Manufacturing of Bagging Film D) Bagging film D was manufactured in the same manner as in Manufacturing Example 1, except that the PVA was changed to unmodified fully saponified PVA with a degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and no modification.

[0075] Table 1 shows the bagging films A to D that were produced in the above manufacturing example and used in the example.

[0076]

[0077] [Example 1] An uncured carbon fiber composite material (three layers of W-3101-A / Q-1120E (manufactured by Teijin Limited)), in which carbon fibers are impregnated with epoxy resin, was placed on a flat mold as the molding material. Before placing the uncured carbon fiber composite material, a release agent (ChemLease 2166, manufactured by ChemTrend Japan Co., Ltd.) was applied to the surface of the mold on which the uncured carbon fiber composite material would be placed. The mold was covered with bagging film A to form a vacuum bag, a vacuum valve for air release was installed inside the vacuum bag, and the vacuum bag was sealed with sealing tape. A small cut was made in the vacuum bag to expose the tip of the vacuum valve for air release to the outside of the vacuum bag.

[0078] A vacuum hose was connected to the vacuum valve for air discharge of the vacuum bag, and the air inside the vacuum bag was sucked out 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 (130°C for 2 hours, with an autoclave pressure of 0.5 MPa). After heat curing, the vacuum bag was removed from the autoclave and allowed to cool to room temperature. When the vacuum bag was immersed in a bath of 40°C water, the bagging film completely dissolved. The appearance of the resulting molded body was good.

[0079] [Example 2] The same procedure as in Example 1 was followed until the molding material was heat-cured, except that bagging film B was used instead of bagging film A. After heat curing, the vacuum bag was removed from the autoclave and allowed to cool to room temperature. When the vacuum bag was immersed in a bath of water at 40°C, the bagging film completely dissolved. The appearance of the resulting molded body was good.

[0080] [Example 3] The procedure for heat curing of the molding material was the same as in Example 1, except that bagging film C was used instead of bagging film A. After heat curing, the vacuum bag was removed from the autoclave and allowed to cool to room temperature. When the vacuum bag was immersed in a bath of water at 30°C, the bagging film completely dissolved. The appearance of the resulting molded body was good.

[0081] [Example 4] The procedure for heat curing of the molding material was the same as in Example 1, except that bagging film D was used instead of bagging film A. After heat curing, the vacuum bag was removed from the autoclave and allowed to cool to room temperature. When the vacuum bag was immersed in a bath of water at 80°C, the bagging film completely dissolved. The appearance of the resulting molded body was good.

[0082] 1. Bagging film 2. Vacuum bag 3. Molding material 4. Mold 5. Sealing component 6. Vacuum valve

Claims

1. A method for manufacturing a molded article, comprising the steps of: placing a molding material in a vacuum bag having a water-soluble bagging film; curing the molding material; and dissolving the bagging film in water, in this order.

2. The method for manufacturing a molded article according to claim 1, wherein in the receiving step, the molded material is received such that the bagging film is in contact with the surface of the molded material.

3. The method for manufacturing a molded article according to claim 1, wherein the molding material includes a curable resin and a reinforcing material.

4. The method for manufacturing a molded article according to claim 3, wherein the curable resin is a thermosetting resin.

5. A method for producing a molded article according to any one of claims 1 to 4, wherein the bagging film mainly contains a water-soluble polymer.

6. The method for producing a molded article according to claim 5, wherein the water-soluble polymer is polyvinyl alcohol.

7. The method for producing a molded article according to claim 6, wherein the degree of saponification of the polyvinyl alcohol is 70 to 98 mol%.

8. The method for producing a molded article according to claim 6, wherein the content of vinyl alcohol units relative to the total monomer units of the polyvinyl alcohol is 70 to 98 mol%.

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