Prepreg and method for producing furan resin

Abstract

This furan resin satisfies condition (a). Condition (a): 10g of the furan resin and 0.33g of a p-toluenesulfonic acid (PTSA) aqueous solution (55%) are mixed to obtain a mixture. The mixture is treated at 120°C for one hour and then pulverized to prepare a sample. The IR spectrum of the sample is measured using Fourier transform infrared spectroscopy (FT-IR). When the transmittance at the maximum absorption peak in the range from 1545 cm-1 to 1560 cm-1 is noted as R1, and the transmittance at the maximum absorption peak in the range from 1645 cm-1 to 1662 cm-1 is noted as R2, R1 / R2 > 1.000 is satisfied.

Description

[Technical Field]

[0001] The present invention relates to a furan resin, a resin composition, and a method for producing a furan resin. More specifically, the present invention relates to a furan resin, a resin composition containing a furan resin, a prepreg in which a fiber substrate is impregnated with the resin composition containing a furan resin, a panel using the prepreg, a cured product of the resin composition containing a furan resin, and a method for producing a furan resin. [Background technology]

[0002] Furan resin is a curable resin having a furan ring, and is known to be synthesized by a self-condensation reaction of furfuryl alcohol or a condensation reaction of furfuryl alcohol with aldehydes and / or phenols.

[0003] For example, Patent Document 1 discloses a method for producing a copolymer of furfuryl alcohol and formaldehyde, which includes a dissolution step of adding paraformaldehyde to furfuryl alcohol and stirring the mixture under alkaline conditions at a heating temperature not exceeding 100°C to dissolve the paraformaldehyde in the furfuryl alcohol, and a polymerization step of adding an acid catalyst to the solution obtained in the dissolution step to polymerize the solution, and exemplified formaldehyde scavengers such as urea, acetamide, methylacetamide, dimethylurea, and toluenesulfonamide.

[0004] Patent Document 2 also discloses the hydroxymethylation of furfuryl alcohol using an acid catalyst. The examples in Patent Document 2 disclose that furfuryl alcohol, paraformaldehyde, and adipic acid were charged into a reactor, the reactor was purged with nitrogen, heated to 117°C, and pressurized with nitrogen to polymerize the reaction mixture. It also discloses that the remaining free formaldehyde was removed using an aqueous urea solution and an aqueous NH3 solution. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-1356 [Patent Document 2] US Patent Application Publication No. 2010 / 0062276 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional techniques disclosed in Patent Documents 1 and 2 have room for improvement in terms of improving the flame retardancy of the furan resin. [Means for solving the problem]

[0007] The present inventors conducted extensive research to solve the problems and found that highly flame-retardant furan resins tend to have a characteristic FT-IR spectrum in their cured products. As a result of further research, they devised a new index using the FT-IR spectrum of a cured furan resin and found that controlling this index can effectively improve the flame retardancy of furan resins, thereby completing the present invention.

[0008] According to the present invention, the following furan resin and related technology are provided.

[0009] [1] A furan resin that satisfies the following condition (a): Condition (a): 10 g of the furan resin was mixed with 0.33 g of an aqueous solution of paratoluenesulfonic acid (PTSA) (55%) to obtain a mixture. The mixture was then treated at 120°C for 1 hour and pulverized to prepare a sample. The IR spectrum of the sample was measured using Fourier transform infrared spectroscopy (FT-IR), and the peak at 1545 cm -1 ~1560cm -1 The transmittance of the maximum absorption peak in the range of 1645 cm -1 ~1662cm -1 When the transmittance of the maximum absorption peak in this range is R2, R1 / R2>1.000. [2] The furan resin according to [1], A furan resin having a mass average molecular weight (Mw) of 300 to 2000. [3] A resin composition comprising the furan resin according to [1] or [2]. [4] A resin composition comprising the furan resin according to [1] or [2], the resin composition being in the form of a film. [5] A prepreg in which the resin composition according to [3] or [4] is impregnated into a fiber substrate. [6] A panel using the prepreg described in [5]. [7] A cured product of the resin composition according to [3] or [4]. [8] Step 1: Mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, dissolving the mixture by heating to a pH of 4 or less, and then polymerizing the furfuryl alcohol with the aldehydes; a step 2 of obtaining a polymer by removing the remaining furfuryl alcohol monomer and aldehyde monomer under a condition where the polymerization reaction is suppressed by adding a neutralizing agent; Step 3: adding urea to react with the polymer; A method for producing a furan resin, comprising: [9] In the method for producing a furan resin according to [8], A method for producing a furan resin, wherein in step 1, the heating temperature is 80°C or higher.

[10] In the method for producing a furan resin according to [8] or [9], In the step 2, the remaining furfuryl alcohol monomer and the aldehyde monomer are removed by distillation under reduced pressure.

[11] In the method for producing a furan resin according to any one of [8] to

[10] , The step 1 is a method for producing a furan resin, which is carried out under atmospheric pressure. [Effects of the Invention]

[0010] According to the present invention, a furan resin capable of improving flame retardancy is provided. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a diagram showing the FT-IR spectrum of the furan resin of Example 1. [Figure 2] FIG. 1 shows the FT-IR spectrum of the furan resin of Example 2. [Figure 3] FIG. 1 shows the FT-IR spectrum of the furan resin of Example 3. [Figure 4] FIG. 1 is a diagram showing the FT-IR spectrum of the furan resin of Comparative Example 1. [Figure 5] FIG. 1 is a diagram showing the FT-IR spectrum of the furan resin of Comparative Example 2. [Figure 6] FIG. 1 is a diagram showing the FT-IR spectrum of the furan resin of Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] In this specification, unless otherwise specified, the expression "a to b" in the description of a numerical range means from a to b. For example, "1 to 5 mass %" means "1 mass % to 5 mass %."

[0014] <Furan resin> The furan resin of this embodiment is a novel resin that satisfies the following condition (a), and will hereinafter be referred to as "furan resin (A)."

[0015] Condition (a): 10 g of the furan resin was mixed with 0.33 g of an aqueous solution of paratoluenesulfonic acid (PTSA) (55%) to obtain a mixture. The mixture was then treated at 120°C for 1 hour and pulverized to prepare a sample. The IR spectrum of the sample was measured using Fourier transform infrared spectroscopy (FT-IR), and the peak at 1545 cm -1 ~1560cm -1 The transmittance of the maximum absorption peak in the range of 1645 cm -1 ~1662cm -1 When the transmittance of the maximum absorption peak in this range is R2, R1 / R2>1.000.

[0016] This makes it possible to obtain a furan resin (A) that can improve flame retardancy. Conventional furan resins use urea to capture formaldehyde used in their synthesis, but the urea is simply mixed with the furan resin without forming a chemical bond, and the urea does not enter the crosslinked structure even after curing. In contrast, the furan resin (A) of the present embodiment satisfies condition (a) and incorporates urea into the cured product. That is, in the present embodiment, urea enters the crosslinked structure of the furan resin, and nitrogen is released during combustion to generate inert gas, thereby suppressing oxidative decomposition. This is thought to improve flame retardancy compared to conventional furan resins.

[0017] Under condition (a), 1545 cm -1 ~1560cm -1 The range is preferably 1553 cm -1 ~1559cm -1 1645cm -1 ~1662cm -1 The range is preferably 1646 cm -1 ~1660cm -1 is.

[0018] In condition (a), the furan resin and the aqueous solution of paratoluenesulfonic acid (PTSA) (55%) may be mixed by hand using a spatula or disposable chopsticks, provided that the two are mixed uniformly. Furthermore, under condition (a), the furan resin can be cured by treating the mixture for 1 hour at 120° C. The heating method is not particularly limited, but the mixture may be dropped onto an aluminum cup and cured in a dryer set at 120° C. In addition, in the condition (a), the pulverization method may be any method that allows the FT-IR measurement to be performed appropriately, and a hammer, a mortar, or the like may be used.

[0019] In the condition (a), R1 / R2>1.000, preferably R1 / R2>1.003, and more preferably R1 / R2>1.005.

[0020] The furan resin (A) satisfying the condition (a) can be realized by adjusting the production method thereof, such as a method of reacting urea with a furan resin (polymer) obtained by polymerization, as will be described in detail later.

[0021] The mass average molecular weight (Mw) of the furan resin (A) is preferably 300 to 2,000, more preferably 500 to 1,800, and even more preferably 700 to 1,500.

[0022] The mass average molecular weight of the furan resin (A) can be determined by gel permeation chromatography (GPC) measurement using polystyrene as a standard substance.

[0023] The viscosity of the furan resin (A) at 25° C. is preferably 200 to 1500 mPa·s, more preferably 500 to 800 mPa·s. By adjusting the viscosity of the furan resin (A) at 25°C to fall within the above range, the moldability and processability of the furan resin (A) can be improved, and molded articles with improved flame retardancy can be obtained. The viscosity of the furan resin (A) can be measured, for example, using a RE-85 type viscometer manufactured by Toyo Sangyo.

[0024] <Method for producing furan resin (A)> The method for producing the furan resin (A) includes the following steps 1 to 3. Step 1: A step of mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, dissolving the mixture by heating to a pH of 4 or less, and then carrying out a polymerization reaction between the furfuryl alcohol and the aldehydes. Step 2: A step of obtaining a polymer by adding a neutralizing agent to suppress the polymerization reaction and removing the remaining furfuryl alcohol monomer and aldehyde monomer. Step 3: Adding urea to react with the polymer Each step will be described in detail below.

[0025] [Process 1] Step 1 is a step of mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, dissolving the mixture by heating to a pH of 4 or less, and then allowing the furfuryl alcohol and the aldehydes to undergo a polymerization reaction. That is, since furfuryl alcohol is a liquid, the acid catalyst is a solid, and paraformaldehyde is a solid, they are heated and dissolved to obtain a mixed solution in order to mix them uniformly. The pH (25°C) of the mixed solution (polymerization solution) of pH 4 or less is 4 or less, and preferably 2.3 to 3.8. By adjusting the pH (25°C) of the mixed solution to 4 or less, the polymerization rate can be increased. The pH (25°C) of the mixed solution is controlled by adjusting the amount of acid catalyst added, for example.

[0026] Furfuryl alcohol and the acid catalyst may be mixed in advance, or the acid catalyst may be further added after paraformaldehyde is added and mixed with furfuryl alcohol. By mixing furfuryl alcohol, an acid catalyst, and paraformaldehyde in sequence, a rapid reaction can be suppressed and uniform polymerization can be achieved.

[0027] After mixing furfuryl alcohol, an acid catalyst, and an aldehyde, the heating temperature in step 1 is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, and particularly preferably 110°C or higher, in order to obtain a homogeneous mixed solution and promote polymerization. On the other hand, the heating temperature is preferably 130°C or lower, and more preferably 120°C or lower, in order to prevent unreacted formaldehyde from volatilizing and sublimating, adhering to the reflux tube, and clogging it, thereby suppressing separation and the generation of unreacted substances.

[0028] The heating in step 1 may be carried out in two stages. For example, in the first stage, the temperature may be maintained at a constant temperature in the range of 80°C or higher and lower than 110°C, and then the temperature may be increased, and in the second stage, the temperature may be maintained at a constant temperature in the range of 110°C or higher and 130°C or lower. The temperature setting can be appropriately set depending on the degree of evaporation and dissolution of paraform.

[0029] The acid catalyst may be an inorganic acid or an organic acid. Specific examples include inorganic acids such as phosphoric acid, sulfuric acid, hydrochloric acid, xylenesulfonic acid, and paratoluenesulfonic acid; and organic acids such as acetic acid, lactic acid, succinic acid, glutaric acid, levulinic acid, crotonic acid, and adipic acid. These may be used alone or in combination of two or more. Among these, organic acids are preferred, and adipic acid is more preferred.

[0030] The amount of the acid catalyst added is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 7 parts by mass, and even more preferably 0.3 to 5 parts by mass, relative to 100 parts by mass of furfuryl alcohol. By setting the amount of the acid catalyst to be equal to or greater than the above-mentioned lower limit, the polymerization reaction can be sufficiently activated and the reaction time can be shortened. On the other hand, by setting the amount of the acid catalyst to be equal to or less than the above-mentioned upper limit, the pot life of the furan resin (A) can be maintained at a good level.

[0031] The aldehydes are not particularly limited as long as they can release formaldehyde under the reaction conditions, but preferred examples include a 30 to 50% aqueous formaldehyde solution, trioxymethylene, and paraformaldehyde, and among these, it is preferable to use paraformaldehyde. Furfuryl alcohol is reacted with an aldehyde, and the amount of the aldehyde used per mole of furfuryl alcohol is preferably 0.8 moles or more, more preferably 0.9 to 3.0 moles, and even more preferably 1.0 to 2.5 moles. Setting the molar ratio to 0.9 or more leads to a reduction in the content of residual furfuryl alcohol, while setting the molar ratio to 3.0 or less can prevent excess aldehydes from precipitating in the reflux tube and clogging the reflux tube.

[0032] Step 1 is preferably carried out without heating, for example, at an ambient temperature of 15 to 30°C. Furthermore, step 1 is preferably carried out under atmospheric pressure (in air, under normal pressure). The mixing method is not particularly limited, and any known method can be used. The mixing time is not particularly limited, and may be, for example, 0.1 to 3 hours.

[0033] The production method of this embodiment does not include the step of adding paraformaldehyde to furfuryl alcohol and dissolving the paraformaldehyde in furfuryl alcohol under alkaline conditions before step 1.

[0034] [Process 2] Step 2 is a step in which the polymerization reaction is suppressed by adding a neutralizing agent, and the remaining furfuryl alcohol monomer and aldehyde monomer are removed to obtain a polymer.

[0035] That is, the polymerization reaction can be suppressed by neutralizing the reaction mixture by adding a neutralizing agent. The amount of neutralizing agent added should be such that the pH of the polymerization solution exceeds 4, but the pH is preferably 4.5 or higher, and more preferably 5 or higher and 7 or lower. Neutralizing agents include bases such as sodium hydroxide, potassium hydroxide, and ammonia.

[0036] Furthermore, in order to remove the remaining furfuryl alcohol monomer and aldehyde monomer, the polymerization liquid to which the neutralizing agent has been added may be distilled under reduced pressure. This makes it possible to remove the furfuryl alcohol and aldehydes that remain unpolymerized.

[0037] The reduced pressure distillation is preferably carried out at a temperature of 100 to 150°C under a pressure of 0 to 100 torr.

[0038] During vacuum distillation, water is gradually added to the system, and furfuryl alcohol and formaldehyde can be efficiently removed by steam distillation. Alternatively, alcoholic solvents such as methanol and ethanol, ketone solvents such as acetone and MIBK, and hydrocarbon solvents such as hexane and heptane may be used instead of water. Only one of these solvents may be used, or two or more may be used.

[0039] [Process 3] In step 3, urea is added to react with the polymer. This allows urea to be incorporated into the polymer, yielding the furan resin (A). Whether or not urea has reacted with the polymer can be confirmed by FT-IR of the cured product of the furan resin (A).

[0040] In step 3, the reaction temperature is preferably 40°C or higher, more preferably 45°C or higher, and is preferably 70°C or lower, more preferably 60°C or lower.

[0041] The reaction time in step 3 is appropriately set taking into consideration the temperature conditions and the like, but can be about 0.5 to 3 hours.

[0042] Step 3 is preferably carried out under atmospheric pressure (in air, under normal pressure).

[0043] By the above steps, the furan resin (A) can be obtained. The resulting furan resin (A) may be diluted with water or a solvent to reduce the viscosity, for example, to improve the impregnation into glass cloth, etc. Examples of the solvent include one or more selected from alcohol solvents such as methanol, ethanol, and isopropyl alcohol; acetone, methyl isobutyl ketone (MIBK), and the like.

[0044] <Resin composition> The resin composition of the present embodiment contains a furan resin (A), which can improve the flame retardancy of a molded article made using the resin composition.

[0045] (acid catalyst) The resin composition preferably contains an acid catalyst in order to effectively cure the furan resin (A). Examples of the acid catalyst include those similar to those listed in the above step 1. Among them, inorganic acids such as phosphoric acid, sulfuric acid, hydrochloric acid, xylenesulfonic acid, and paratoluenesulfonic acid are preferred.

[0046] Furthermore, the resin composition may contain known compounds depending on the application. Examples of known compounds include additives such as curable resins other than the furan resin (A), thermoplastic resins, curing agents, curing accelerators, coupling agents, fillers, reinforcing fibers, elastomers, pigments, flame retardants, and adhesion promoters. Only one of these may be contained, or two or more may be contained.

[0047] (coupling agent) Examples of the coupling agent include silane coupling agents such as vinyl silane coupling agents, epoxy silane coupling agents, cationic silane coupling agents, and amino silane coupling agents, titanate coupling agents, and silicone oil coupling agents, etc. Only one type of coupling agent may be used, or two or more types may be used. Specific examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-(2aminoethyl)-3-aminopropylsilanol, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, N-phenylγ-aminopropyltriethoxysilane, N-phenylγ-aminopropyltrimethoxysilane, and N-β(aminoethyl)γ-aminopropyltriethoxysilane. Examples of silane coupling agents include silane, N-6-(aminohexyl)3-aminopropyltrimethoxysilane, N-(3-(trimethoxysilylpropyl)-1,3-benzenedimethanane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and vinyltriethoxysilane. The silane coupling agent may contain only one type, or two or more types. Of these, vinylsilane, epoxysilane, mercaptosilane, and aminosilane are preferred.

[0048] (Leveling agent) Examples of the leveling agent include acrylic leveling agents and silicon leveling agents. Examples of the acrylic leveling agent include polymers using only one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, allyl acrylate, allyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, or copolymers using two or more of these. Examples of the silicon-based leveling agent include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, polyester-modified polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyether-modified polymethylalkylsiloxane, polyether-modified siloxane, polyester-modified hydroxyl group-containing polydimethylsiloxane, polyether-modified hydroxyl group-containing polydimethylsiloxane, etc. One or a combination of two or more of these can be used. Of these, polyether-modified polydimethylsiloxane is preferred.

[0049] The leveling agent is preferably used in an amount of 2% by mass or less, and more preferably in an amount of 0.01% by mass or more and 1.0% by mass or less, based on the total amount of the resin composition.

[0050] The resin composition of this embodiment may contain water or a solvent (e.g., an organic solvent), and the solvent may be selected depending on the intended use. For example, in order to improve the impregnation ability into glass woven fabric or the like, the furan resin (A) may be diluted with water or a solvent such as methanol to reduce the viscosity. However, from the viewpoints of ease of distribution and handling as a resin composition, suppression of VOC emissions in the working environment, and the like, the resin composition of this embodiment may be substantially free of a solvent (e.g., an organic solvent).

[0051] [Manufacturing method] The resin composition of the present embodiment can be produced by mixing the above components by a known method.

[0052] When the resin composition is in the form of a varnish, the solid content of the resin composition may be, for example, 30% by mass to 90% by mass, more preferably 40% by mass to 85% by mass, which results in a resin composition with excellent workability and film-forming properties.

[0053] The varnish-like resin composition can be prepared by mixing and stirring the above-mentioned components using various mixers, such as those used in ultrasonic dispersion, high-pressure collision dispersion, high-speed rotation dispersion, bead mill dispersion, high-speed shear dispersion, and rotation-revolution dispersion.

[0054] [Application] The resin composition can be cured and used suitably for molded articles, which will be described later. The resin composition can also be used as an impregnation or binder, in which it is used by impregnating various substrates such as organic fibers, metals, and glass.

[0055] <Resin film> Next, the resin film of this embodiment will be described. The resin film of this embodiment can be obtained by forming the above-mentioned resin composition in a varnish form into a film. The resin film is preferably in a B-stage (semi-cured) state. For example, the resin film of this embodiment can be obtained by removing the solvent and water from a coating film obtained by applying a varnish-like resin composition. In such a resin film, the solvent and water content can be 5% by mass or less based on the entire resin film. In this embodiment, the solvent removal step can be carried out under conditions of, for example, 60°C to 110°C and 5 to 30 minutes. This allows the solvent and water to be sufficiently removed while suppressing the progress of curing of the furan resin (A).

[0056] The resin film of this embodiment may be composed of a resin film alone, or may be composed so as to contain a fiber base material inside.

[0057] <Prepreg> The prepreg of this embodiment is obtained by impregnating a fiber substrate with the resin composition. For example, the prepreg can be used as a sheet-like material obtained by impregnating a fiber substrate with the resin composition and then semi-curing the material.

[0058] In this embodiment, the method for impregnating the resin composition into the fiber substrate is not particularly limited, but examples include a method of immersing the fiber substrate in the resin varnish, a method of applying the resin varnish to the fiber substrate using various coaters, a method of spraying the resin varnish onto the fiber substrate using a sprayer, and a method of laminating both sides of the fiber substrate with the resin film made of the resin composition.

[0059] Examples of the fiber substrate include glass fiber substrates such as woven glass cloth and nonwoven glass cloth, inorganic fiber substrates such as woven or nonwoven cloth containing an inorganic compound other than glass as a component, and organic fiber substrates made of organic fibers such as aromatic polyamideimide resin, polyamide resin, aromatic polyester resin, polyester resin, polyimide resin, fluororesin, etc. Among these substrates, the use of a glass fiber substrate typified by woven glass cloth in terms of strength can improve the mechanical strength and heat resistance of the printed wiring board.

[0060] The thickness of the fiber base material is not particularly limited, but is preferably 50 μm to 350 μm, more preferably 70 μm to 300 μm, and even more preferably 90 μm to 270 μm. Use of a fiber base material having such a thickness can further improve the handleability during prepreg production. When the thickness of the fiber substrate is equal to or less than the upper limit, the impregnation of the resin composition into the fiber substrate is improved, and the occurrence of strand voids and a decrease in insulation reliability can be suppressed. On the other hand, when the thickness of the fiber substrate is equal to or more than the lower limit, the strength of the prepreg using the fiber substrate can be improved.

[0061] As the glass fiber substrate, for example, a glass fiber substrate formed of one or more types of glass selected from E glass, S glass, D glass, T glass, NE glass, UT glass, L glass, HP glass, and quartz glass is preferably used.

[0062] The thickness of the prepreg is not particularly limited, but is preferably 50 μm to 400 μm, more preferably 70 μm to 350 μm, and even more preferably 90 μm to 320 μm.

[0063] The prepreg is then fully cured and can be suitably used for panels and the like used as wall materials and ceiling materials for buildings and transport equipment.

[0064] The B stage refers to a state in which 5 to 90% of the resin composition has cured (semi-cured), and the C stage refers to a state in which more than 90% of the resin composition has cured (completely cured). The degree of curing can be confirmed by immersing the resin in methanol to dissolve the uncured resin, drying it, and then measuring the weight.

[0065] <Molded product / cured product> The molded article of the present embodiment is made using a cured product of the resin composition and is suitable for applications requiring flame retardancy, such as transportation equipment such as automobiles, aircraft, railroad vehicles, and ships, and various parts and structural members for buildings, office equipment, general-purpose machines, household electrical appliances, and electrical equipment.

[0066] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0067] The present invention will be described in detail based on examples and comparative examples, but the present invention is not limited to these examples.

[0068] (1) Synthesis of furan resin (A) Example 1 Furfuryl alcohol, paraform (92%), and adipic acid were added to a reaction vessel at room temperature and pressure in the amounts (parts by weight) shown in Table 1. The mixture was heated to 117°C while stirring. After 1 hour and 40 minutes, the paraform and adipic acid dissolved and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.1 (25°C). For pH measurements, the solution was mixed with pure water in a 1:1 ratio by mass. The reaction was continued at a temperature of 117°C ± 3°C for 5 hours and 10 minutes. When the viscosity reached 342 mPa·s, cooling was initiated. Once the temperature had dropped below 100°C, 50% aqueous sodium hydroxide solution was added to neutralize the mixture. The pH was then 5.6 (25°C). The pressure in the reaction vessel was reduced to 80 torr while the temperature was raised. The mixture was then heated at 140°C and 80 torr for 1 hour while simultaneously undergoing steam distillation (143.1 parts by mass of water, added dropwise over 1 hour). After cooling to 100°C, water was added. Then, water-1 and urea were added in the amounts shown in Table 1, and the mixture was allowed to react at 55°C. Finally, water-2 was added to adjust the viscosity to that shown in Table 1, yielding furan resin (A-1).

[0069] <Example 2> Furfuryl alcohol, paraform (92%), and adipic acid were added to a reaction vessel at room temperature and pressure in the amounts (parts by mass) shown in Table 1. The mixture was heated to 105°C while stirring. After 5 hours and 40 minutes, the paraform and adipic acid dissolved and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.1 (25°C). The temperature was then raised to 117°C ± 3°C for 5 hours and 25 minutes. When the viscosity reached 311 mPa·s, cooling was initiated. Once the temperature had dropped below 100°C, 25% aqueous potassium hydroxide solution was added to neutralize the mixture. The pH at this point was 5.6 (25°C). The pressure inside the reaction vessel was reduced to 80 torr while the temperature was raised, and the mixture was heated to 140°C and 80 torr for 1 hour. After cooling to 100°C, water was added. Water-1 and urea were then added in the amounts shown in Table 1, and the mixture was allowed to react at 55°C. Finally, water-2 was added to adjust the viscosity to that shown in Table 1, to obtain furan resin (A-2).

[0070] Example 3 Furfuryl alcohol, paraform (92%), and adipic acid were added to a reaction vessel at room temperature and pressure in the amounts (parts by mass) shown in Table 1. The mixture was heated to 100°C while stirring. After 9 hours and 20 minutes, the paraform and adipic acid dissolved and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.1 (25°C). The temperature was then raised to 117°C ± 3°C for 7 hours and 15 minutes, and the mixture was allowed to react until the viscosity reached 302 mPa·s. Cooling was initiated, and once the mixture had cooled below 100°C, 25% aqueous potassium hydroxide solution was added to neutralize the mixture. The pH at this point was 5.6 (25°C). The pressure inside the reaction vessel was reduced to 80 torr while the temperature was raised, and the mixture was heated to 140°C and 80 torr for 1 hour. After cooling to 100°C, water was added. Water-1 and urea were then added in the amounts shown in Table 1, and the mixture was allowed to react at 55°C. Finally, water-2 was added to adjust the viscosity to that shown in Table 1, to obtain furan resin (A-3).

[0071] <Comparative Example 1> Furfuryl alcohol, paraform (92%), and adipic acid were added to a reaction vessel at room temperature and pressure in the amounts (parts by weight) shown in Table 1. The mixture was heated to 117°C while stirring. After 2 hours and 20 minutes, the paraform and adipic acid dissolved and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.3 (25°C). For pH measurements, the solution was mixed with pure water in a 1:1 mass ratio. The reaction was continued at a temperature of 117°C ± 3°C for 8 hours and 30 minutes. When the viscosity reached 347 mPa·s, cooling was initiated. Once the temperature had dropped below 100°C, 25% aqueous potassium hydroxide solution was added to neutralize the solution. The pH was then 5.6 (25°C). The pressure in the reaction vessel was reduced to 80 torr while the temperature was raised, and the mixture was heated to 140°C at 80 torr for 1 hour. After cooling to 100°C, water was added. Thereafter, water-1 was further added in the amount shown in Table 1, and the viscosity was adjusted to the value shown in Table 1, to obtain a furan resin (B-1).

[0072] <Comparative Example 2> Furfuryl alcohol, paraform (92%), and adipic acid were added to a reaction vessel at room temperature and pressure in the amounts (parts by weight) shown in Table 1. The mixture was heated to 117°C while stirring. After 2 hours and 20 minutes, the paraform and adipic acid dissolved and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.3 (25°C). For pH measurements, the solution was mixed with pure water in a 1:1 mass ratio. The reaction was continued at a temperature of 117°C ± 3°C for 9 hours and 15 minutes. When the viscosity reached 305 mPa·s, cooling was initiated. Once the temperature had dropped below 100°C, 25% aqueous potassium hydroxide solution was added to neutralize the solution. The pH was then 5.6 (25°C). The pressure in the reaction vessel was reduced to 80 torr while the temperature was raised, and the mixture was heated to 140°C at 80 torr for 1 hour. After cooling to 100°C, water was added. Thereafter, water-1 was further added in the amount shown in Table 1, and the viscosity was adjusted to the value shown in Table 1, to obtain a furan resin (B-2).

[0073] <Comparative Example 3> Furfuryl alcohol, paraform, and adipic acid were added to a reaction vessel at room temperature and pressure in the amounts (parts by weight) shown in Table 1. The mixture was heated to 117°C while stirring. After 2 hours and 10 minutes, the paraform and adipic acid dissolved and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.3 (25°C). For pH measurements, the solution was mixed with pure water in a 1:1 mass ratio. The reaction was continued at a temperature of 117°C ± 3°C for 5 hours and 10 minutes. When the viscosity reached 306 mPa·s, cooling was initiated. Once the temperature had dropped below 100°C, 25% aqueous potassium hydroxide solution was added to neutralize the solution. The pH was then 5.6 (25°C). The pressure in the reaction vessel was reduced to 80 torr while the temperature was raised, and the mixture was heated to 140°C at 80 torr for 1 hour. After cooling to 100°C, water was added. Thereafter, water-1 was further added in the amount shown in Table 1, and the viscosity was adjusted to the value shown in Table 1, to obtain a furan resin (B-3).

[0074] (2) Analysis and measurement of furan resin The resulting furan resins were subjected to FT-IR measurement under the following conditions. The results are shown in Table 1 and Figures 1 to 6. Figure 1 shows the FT-IR spectrum of the furan resin (A-1) synthesized in Example 1, Figure 2 shows the furan resin (A-2) synthesized in Example 2, Figure 3 shows the furan resin (A-3) synthesized in Example 3, Figure 4 shows the furan resin (B-1) synthesized in Comparative Example 1, Figure 5 shows the furan resin (B-2) synthesized in Comparative Example 2, and Figure 6 shows the furan resin (B-3) synthesized in Comparative Example 3.

[0075] <Measurement conditions> 10 g of each furan resin was mixed with 0.33 g of a 55% aqueous solution of paratoluenesulfonic acid (PTSA) to obtain a mixture, which was then treated at 120°C for 1 hour and then crushed to prepare a sample. The IR spectrum of the sample was measured using Fourier transform infrared spectroscopy (FT-IR). -1 ~1560cm -1 The transmittance of the maximum absorption peak in the range of 1645 cm -1 ~1662cm -1 The transmittance of the maximum absorption peak in this range was taken as R2. Fourier transform infrared spectroscopic analysis measuring device: Thermo Scientific FT-IR Nicolect iS20 was used, and the single reflection ATR method was used.

[0076] (3) Prepreg fabrication To 100 parts by mass of each furan resin, 1.5 parts by mass of an amino group-containing silane coupling agent, 0.5 parts by mass of a leveling agent, 5 parts by mass of water, and an acid curing agent in the amount shown in Table 1 were added and mixed to obtain a varnish. The resulting varnish was coated with a glass woven fabric (Cloth type #7781, E glass, basis weight 298 g / m 2 ) to impregnate the glass woven fabric with varnish, and then the glass woven fabric was taken out and hung up and dried in a hot air dryer at 100°C to prepare four sheets. The four sheets were then stacked with spacers (1 mm) between them and pressed at 120°C for 1 hour to obtain a prepreg.

[0077] (4) Evaluation of prepreg Test pieces measuring 125 mm in length, 13 mm in width, and 1.2 mm in thickness were prepared from the obtained prepreg, and measurements were made in accordance with the UL94 (standard established by Underwriters Laboratories Inc., USA) vertical flame test. Specifically, with the test specimen held perpendicular to the lengthwise direction, the specimen was exposed to a flame from below for 10 seconds, and the burning time (t1 (seconds)) from when the flame was removed until the flame went out was measured. Once the flame had gone out, the specimen was exposed to the flame again for 10 seconds, and the burning time (t2 (seconds)) from when the flame was removed until the flame went out was measured and evaluated based on the following criteria. V-0: At least one of t1 and t2 is 10 seconds or less and (t1+t2)≦50 seconds V-1: At least one of t1 and t2 is 30 seconds or less and (t1+t2)≦250 seconds

[0078] [Table 1]

[0079] This application claims priority based on Japanese Patent Application No. 2024-026683, filed February 26, 2024, the disclosure of which is incorporated herein in its entirety.

Claims

1. A prepreg in which a resin composition containing a furan resin is impregnated into a fiber substrate, the resin composition satisfying the following condition (a): Condition (a): 10 g of the furan resin is mixed with 0.33 g of a 55% aqueous solution of paratoluenesulfonic acid (PTSA) to obtain a mixture. The mixture is then treated at 120°C for 1 hour and pulverized to prepare a sample. The IR spectrum of the sample is measured using Fourier transform infrared spectroscopy (FT-IR). When R1 is the transmittance of the maximum absorption peak in the range of 1545 cm -1 to 1560 cm -1 and R2 is the transmittance of the maximum absorption peak in the range of 1645 cm -1 to 1662 cm -1 , R1 / R2 > 1.

000.

2. The prepreg according to claim 1, The furan resin has a mass average molecular weight (Mw) of 300 to 2,000.

3. A panel using the prepreg according to claim 1 or 2.

4. a step 1 of mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, heating and dissolving the mixture to a pH of 4 or less, and then allowing a polymerization reaction between the furfuryl alcohol and the aldehydes to proceed; a step 2 of obtaining a polymer by removing the remaining furfuryl alcohol monomer and aldehyde monomer under a condition where the polymerization reaction is suppressed by adding a neutralizing agent; Step 3: adding urea to react with the polymer; Including, In the step 1, the amount of the aldehyde per mole of the furfuryl alcohol is 0.8 moles or more and 1.9 moles or less.

5. The method for producing a furan resin according to claim 4, In the step 1, the heating temperature is 80°C or higher.

6. The method for producing a furan resin according to claim 4 or 5, In the step 2, the remaining furfuryl alcohol monomer and the aldehyde monomer are removed by vacuum distillation.

7. The method for producing a furan resin according to claim 4 or 5, The method for producing a furan resin, wherein the step 1 is carried out under atmospheric pressure.

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