Furan resin, resin composition, and method for producing furan resin

Abstract

To provide a furan resin that can improve flame retardancy. [Solution] The furan resin of the present invention satisfies the following condition (a). Condition (a): 10 g of the furan resin and 0.33 g of a 55% aqueous solution of p-toluenesulfonic acid (PTSA) are mixed to obtain a mixture. The mixture is treated at 120°C for 1 hour, and then pulverized to prepare a sample. The IR spectrum of the sample is measured using Fourier transform infrared spectroscopy (FT-IR) and measured at 1555 cm⁻¹. -1 Let R1 be the transmittance of the nearby absorption peak, at 1655 cm. -1 When R2 is the transmittance of the nearby absorption peak, R1 / R2 > 1.000.

Description

[Technical Field]

[0001] This invention relates to furan resin, resin compositions, and methods for producing furan resin. More specifically, it relates to furan resin, resin compositions containing furan resin, prepregs in which a resin composition containing furan resin is impregnated into a fibrous substrate, panels using prepregs, cured products of resin compositions containing furan resin, and methods for producing furan resin. [Background technology]

[0002] Furan resins are curable resins containing a furan ring and are known to be synthesized by the self-condensation reaction of furfuryl alcohol, or by the 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. The method discloses a dissolution step in which paraformaldehyde is added to furfuryl alcohol and stirred under alkaline conditions at a heating temperature not exceeding 100°C to dissolve the paraformaldehyde in furfuryl alcohol, and a polymerization step in which an acid catalyst is added to the solution obtained in the dissolution step to polymerize the copolymer. Examples of formaldehyde scavenging agents are given, including urea, acetamide, methylacetamide, dimethylurea, and toluenesulfonamide.

[0004] Furthermore, Patent Document 2 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 polymerization was carried out by applying nitrogen pressure to the reactor. It also discloses that the remaining free formaldehyde was removed with an aqueous urea solution and an aqueous NH3 solution. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-1356 [Patent Document 2] U.S. Patent Application Publication No. 2010 / 0062276 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the conventional technologies disclosed in Patent Documents 1 and 2 had room for improvement in terms of enhancing flame retardancy using furan resin. [Means for solving the problem]

[0007] The inventors conducted diligent research to solve the problem and discovered that furan resins with high flame retardancy tend to have a unique FT-IR spectrum in their cured products. Further investigation led to the development of a new index using the FT-IR spectrum of cured furan resins. By controlling this index, the flame retardancy of furan resins can be effectively improved, thus completing the present invention.

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

[0009] [1] A furan resin that satisfies the following condition (a): Condition (a): Mix 10 g of the furan resin with 0.33 g of 55% p-toluenesulfonic acid (PTSA) aqueous solution to obtain a mixture. Treat the mixture at 120°C for 1 hour, then pulverize to prepare a sample. Measure the IR spectrum of the sample using Fourier transform infrared spectroscopy (FT-IR) and obtain a value of 1545 cm⁻¹. -1 ~1560cm -1 Let R1 be the transmittance of the maximum absorption peak in the range of 1645cm. -1 ~1662cm -1 When R2 is the transmittance of the maximum absorption peak within the specified range, R1 / R2 > 1.000. [2] The furan resin described in [1], A furan resin having a mass average molecular weight (Mw) of 300 to 2000. [3] A resin composition containing the furan resin according to [1] or [2]. [4] A resin composition containing the furan resin according to [1] or [2], which is 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 according to [5]. [7] A cured product of the resin composition according to [3] or [4]. [8] Step 1 of mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, heating and dissolving to make the pH 4 or less, and then proceeding with the polymerization reaction between the furfuryl alcohol and the aldehydes; Step 2 of adding a neutralizing agent to suppress the polymerization reaction and obtaining a polymer from which the remaining furfuryl alcohol monomer and aldehyde monomer have been removed; Step 3 of adding urea and reacting it with the polymer; A method for producing a furan resin, comprising the above steps. [9] In the method for producing a furan resin according to [8], In Step 1, the heating temperature is 80°C or higher. A method for producing a furan resin.

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

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

[10] , Step 1 is carried out under atmospheric pressure. A method for producing a furan resin. [Advantages of the Invention]

[0010] According to the present invention, a furan resin with improved flame retardancy is provided. [Brief Description of the Drawings]

[0011] [Figure 1]It is a diagram showing the FT-IR spectrum of the furan resin of Example 1. [Figure 2] It is a diagram showing the FT-IR spectrum of the furan resin of Example 2. [Figure 3] It is a diagram showing the FT-IR spectrum of the furan resin of Example 3. [Figure 4] It is a diagram showing the FT-IR spectrum of the furan resin of Comparative Example 1. [Figure 5] It is a diagram showing the FT-IR spectrum of the furan resin of Comparative Example 2. [Figure 6] It is a diagram showing the FT-IR spectrum of the furan resin of Comparative Example 3.

Mode for Carrying Out the Invention

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

[0013] In this specification, the notation "a~b" in the description of a numerical range represents a to b unless otherwise specified. For example, "1~5 mass%" means "1 mass% or more and 5 mass% or less".

[0014] <Furan Resin> The furan resin of this embodiment is a novel resin that satisfies the following condition (a). Hereinafter, it will also be described as "furan resin (A)".

[0015] Condition (a): Mix 10 g of the furan resin and 0.33 g of an aqueous solution of p-toluenesulfonic acid (PTSA) (55%) to obtain a mixture. After treating the mixture at 120 °C for 1 hour, it is pulverized to prepare a sample. The IR spectrum of the sample is measured using Fourier transform infrared spectroscopy measurement (FT-IR), and the transmittance of the maximum absorption peak in the range of 1545 cm -1 ~1560 cm -1 is defined as R1, and when the transmittance of the maximum absorption peak in the range of 1645 cm -1 ~1662 cm -1 is defined as R2, R1 / R2 > 1.000.

[0016] As a result, a furan resin (A) with improved flame retardancy can be obtained. Here, in the conventional furan resin, urea is used to capture formaldehyde used in the synthesis process. However, urea is only mixed with the furan resin and does not form a chemical bond. Even when cured, urea did not enter the crosslinked structure. In contrast, the furan resin (A) of the present embodiment satisfies condition (a) and incorporates urea into its cured product. That is, in the present embodiment, urea enters the crosslinked structure of the furan resin, and when burning, nitrogen desorbs to generate an inert gas, thereby suppressing oxidative decomposition. Therefore, it is presumed that the flame retardancy can be improved compared to the conventional furan resin.

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

[0018] In condition (a), the mixing method of the furan resin and the para-toluenesulfonic acid (PTSA) aqueous solution (55%) only needs to be uniformly mixed, and it may be manually mixed using a spatula or a stirring rod. Also, in condition (a), the furan resin can be cured by treating the mixture at 120°C for 1 hour. The heating method is not particularly limited, but it may be dropped onto an aluminum cup and cured in a dryer set at 120°C. Also, in condition (a), the grinding method only needs to be suitable for performing FT-IR measurement, and a hammer, mortar, etc. may be used.

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

[0020] A furan resin (A) that satisfies condition (a) can be produced by adjusting its manufacturing method. Details will be described later, but one example is a method in which urea is reacted with a furan resin (polymer) obtained by polymerization.

[0021] The mass-average molecular weight (Mw) of the furan resin (A) is preferably 300 to 2000, more preferably 500 to 1800, and even more preferably 700 to 1500.

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

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

[0024] <Method for manufacturing furan resin (A)> The method for producing furan resin (A) includes the following steps 1 to 3. Step 1: A process in which furfuryl alcohol, an acid catalyst, and aldehydes are mixed at room temperature, heated to dissolve and reduce the pH to 4 or below, and then the polymerization reaction between the furfuryl alcohol and the aldehydes is carried out. Step 2: A process to obtain a polymer by adding a neutralizing agent to suppress the polymerization reaction and removing the remaining furfuryl alcohol monomer and aldehyde monomer. Step 3: Add urea and react it with the polymer. The details of each step are explained below.

[0025] [Process 1] Step 1 involves mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, heating and dissolving them to a pH of 4 or lower, and then proceeding with the polymerization reaction between the furfuryl alcohol and the aldehydes. In other words, since furfuryl alcohol is a liquid, the acid catalyst is a solid, and paraformaldehyde is a solid, a mixed solution is obtained by heating and dissolving them to ensure uniform mixing. The pH (at 25°C) of the mixed solution (polymerization solution) with a pH of 4 or lower is 4 or lower, and it is preferable to have a pH of 2.3 to 3.8. By setting the pH (at 25°C) of the mixed solution to 4 or lower, the polymerization rate can be increased. The pH (at 25°C) of the mixed solution is controlled by adjusting the amount of acid catalyst added, etc.

[0026] The furfuryl alcohol and the acid catalyst may be mixed beforehand, or paraformaldehyde may be added and mixed with the furfuryl alcohol, and then the acid catalyst may be added further. By sequentially mixing furfuryl alcohol, an acid catalyst, and paraformaldehyde, rapid reactions can be suppressed, and uniform polymerization can be achieved.

[0027] After mixing furfuryl alcohol, an acid catalyst, and aldehydes, 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 especially preferably 110°C or higher, in order to obtain a homogeneous mixed solution and to allow polymerization to proceed. 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 causing blockage, thereby suppressing separation and the generation of unreacted substances.

[0028] Furthermore, the heating in step 1 may be carried out in two stages. For example, in the first stage, the temperature may be kept constant in the range of 80°C or higher and less than 110°C, and then the temperature may be increased, and in the second stage, the temperature may be kept constant in the range of 110°C or higher and 130°C or lower. The temperature setting can be appropriately adjusted according to the degree of paraform volatilization and dissolution.

[0029] The acid catalyst can be an inorganic acid or an organic acid. Specifically, examples include inorganic acids such as phosphoric acid, sulfuric acid, hydrochloric acid, xylene sulfonic acid, and p-toluenesulfonic 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 individually or in combination of two or more. Among these, organic acids are preferred, and adipic acid is more preferred.

[0030] The amount of 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, per 100 parts by mass of furfuryl alcohol. By adding an amount of acid catalyst above the lower limit, the polymerization reaction can be sufficiently activated and the reaction can be shortened. On the other hand, by adding an amount of acid catalyst below the upper limit, the pot life of the furan resin (A) can be well maintained.

[0031] The aldehydes used are not particularly limited as long as they can release formaldehyde under the reaction conditions, but preferred examples include a 30-50% aqueous solution of formaldehyde, trioxymethylene, and paraformaldehyde, with paraformaldehyde being the most suitable. The aldehydes are reacted with furfuryl alcohol, and it is preferable to use 0.8 moles or more, more preferably 0.9 to 3.0 moles, and even more preferably 1.0 to 2.5 moles of aldehydes per mole of furfuryl alcohol. Setting the molar ratio to 0.9 or higher helps to reduce the amount of remaining furfuryl alcohol. On the other hand, setting the molar ratio to 3.0 or lower can prevent excess aldehydes from precipitation in the reflux tubing and blocking it.

[0032] Step 1 is non-heating and is preferably carried out at an ambient temperature of, for example, 15 to 30°C. Furthermore, it is preferable to carry out step 1 under atmospheric conditions (air, normal pressure). Furthermore, the mixing method is not particularly limited, and known methods can be used. Also, the mixing time is not particularly limited, but for example, it may be 0.1 to 3 hours.

[0033] Furthermore, the manufacturing 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 process to obtain a polymer by adding a neutralizing agent to suppress the polymerization reaction and then removing the remaining furfuryl alcohol monomer and aldehyde monomer.

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

[0036] Furthermore, to remove any remaining furfuryl alcohol monomer and aldehyde monomer, the polymerized solution may be further treated with a neutralizing agent and then distilled under reduced pressure. This makes it possible to remove the furfuryl alcohol and aldehydes that remain without polymerization.

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

[0038] By gradually adding water to the system during vacuum distillation, furfuryl alcohol and formaldehyde can be efficiently removed by steam distillation. Alternatively, alcohol-based solvents such as methanol and ethanol, ketone-based solvents such as acetone and MIBK, and hydrocarbon-based solvents such as hexane and heptane may be used instead of water. One of these may be included, or two or more may be included.

[0039] [Process 3] Step 3 is a step in which urea is added and reacted with the polymer. As a result, the urea is incorporated into the polymer, and furan resin (A) can be obtained. Whether or not the urea has reacted with the polymer can be confirmed by FT-IR of the cured furan resin (A).

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

[0041] The reaction time in step 3 is set appropriately considering the temperature and other factors, but can be approximately 0.5 to 3 hours.

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

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

[0044] <Resin composition> The resin composition of this embodiment includes furan resin (A). This makes it possible to improve the flame retardancy of molded articles using the resin composition.

[0045] (Acid catalyst) The resin composition preferably contains an acid catalyst, as this allows for effective curing of the furan resin (A). Examples of acid catalysts include those listed in step 1 above. Among these, inorganic acids such as phosphoric acid, sulfuric acid, hydrochloric acid, xylene sulfonic acid, and p-toluenesulfonic acid are preferred.

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

[0047] (Coupling agent) Examples of the coupling agents mentioned above include vinyl silane coupling agents, epoxy silane coupling agents, cationic silane coupling agents, and aminosilane coupling agents, as well as titanate coupling agents and silicone oil type coupling agents. The coupling agent may consist of only one type or two or more types. Specific compounds used as silane coupling agents include, for example, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-silanol, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, N-phenylγ-aminopropyltriethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane Examples include 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, vinyltriethoxysilane, etc. The silane coupling agent may consist of only one type or two or more types. Of these, vinylsilane, epoxysilane, mercaptosilane, and aminosilane are preferred.

[0048] (Leveling agent) Examples of leveling agents include acrylic-based leveling agents and silicone-based leveling agents. Examples of the acrylic leveling agents mentioned above include polymers using only one of the following, or copolymers using two or more of the following: 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, cyclohexyl metharylate, etc. As the above-mentioned silicon-based leveling agent, for example, one or more of the following can be used in combination: polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, polyester-modified polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyether-modified polymethylalkylsiloxane, polyether-modified siloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyether-modified hydroxyl-containing polydimethylsiloxane, etc. Of these, polyether-modified polydimethylsiloxane is preferred.

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

[0050] The resin composition of this embodiment may contain water and a solvent (such as an organic solvent), and the solvent may be selected depending on the application. For example, to improve impregnation into glass woven fabrics and the like, the furan resin (A) may be diluted with water or a solvent such as methanol to reduce its viscosity. However, from the viewpoint of ease of distribution and handling of the resin composition and suppression of VOC generation in the work environment, the resin composition of this embodiment may be substantially free of solvents (such as organic solvents).

[0051] [Manufacturing method] The resin composition of this embodiment is obtained by mixing the above components by a known method.

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

[0053] A varnish-like resin composition can be prepared by mixing and stirring the above-mentioned components using various mixers, such as ultrasonic dispersion, high-pressure impact dispersion, high-speed rotation dispersion, bead mill, high-speed shear dispersion, and rotational dispersion.

[0054] [Application] The resin composition, upon curing, is suitably used in molded products as described later. Furthermore, the resin composition can be applied to impregnation and binder applications, where it is used to impregnate 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, which is in the form of a varnish, into a film. The resin film is preferably in the B stage (semi-cured). For example, the resin film of this embodiment can be obtained by removing 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 of the total resin film. In this embodiment, for example, the solvent removal step may be carried out under conditions of 60°C to 110°C for 5 to 30 minutes. This makes it possible to sufficiently remove the solvent and water while suppressing the curing of the furan resin (A).

[0056] The resin film of this embodiment may be composed of the resin film alone, or it may be configured to include a fibrous substrate inside.

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

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

[0059] Examples of the above-mentioned fiber substrates include glass fiber substrates such as glass fiber cloth and glass nonwoven cloth, inorganic fiber substrates such as cloth or nonwoven cloth composed of inorganic compounds other than glass, and organic fiber substrates composed of organic fibers such as aromatic polyamide-imide resin, polyamide resin, aromatic polyester resin, polyester resin, polyimide resin, and fluororesin. Among these substrates, using a glass fiber substrate, such as glass woven cloth, in terms of strength can improve the mechanical strength and heat resistance of printed circuit boards.

[0060] The thickness of the fiber substrate 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. By using a fiber substrate with such a thickness, handling during prepreg manufacturing can be further improved. If the thickness of the fiber substrate is below the above upper limit, the impregnation of the resin composition in the fiber substrate is improved, and the occurrence of strand voids and a decrease in insulation reliability can be suppressed. Furthermore, if the thickness of the fiber substrate is above the above lower limit, the strength of the prepreg using it can be improved.

[0061] As the glass fiber substrate mentioned above, a glass fiber substrate formed from 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 as panels for walls, ceilings, and other materials in buildings and transportation equipment.

[0064] Stage B represents a state where 5-90% of the resin composition has hardened (partially hardened), while Stage C represents a state where more than 90% of the resin composition has hardened (fully hardened). The degree of hardening can be confirmed by immersing the unhardened resin in methanol to dissolve it, then drying and determining its weight.

[0065] <Molded product / cured product> The molded articles of this embodiment use cured resin compositions and are suitable for applications where flame retardancy is required. Specifically, examples include transportation equipment such as automobiles, aircraft, railway vehicles, and ships; and various parts and structural components of buildings, office equipment, general-purpose machinery, household electrical appliances, and electrical equipment.

[0066] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

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

[0068] (1) Synthesis of furan resin (A) <Example 1> At room temperature and pressure, furfuryl alcohol, paraform (92%), and adipic acid were added to the reaction vessel in the proportions (parts by mass) shown in Table 1, and the temperature was raised to 117°C while stirring. After 1 hour and 40 minutes, it was confirmed that the paraform and adipic acid had dissolved and a homogeneous solution had been formed, and the pH was measured and confirmed to be pH 3.1 (25°C). For the pH measurement, a mixture of the solution and pure water in a 1:1 mass ratio was used. The reaction was carried out at a solution temperature of 117°C ± 3°C for 5 hours and 10 minutes, and when the viscosity reached 342 mPa·s, cooling was started, and when the temperature fell below 100°C, 50% aqueous sodium hydroxide solution was added to neutralize it. The pH at that time was 5.6 (25°C). The temperature in the reaction vessel was raised while the pressure was reduced to 80 torr, and while heating at 140°C and 80 torr for 1 hour, steam distillation (143.1 parts by mass of water was added dropwise over 1 hour) was also performed. After cooling to 100°C, water was added. Then, water-1 and urea were added in the proportions shown in Table 1, and the mixture was reacted at 55°C. Finally, water-2 was added to adjust the viscosity to the level shown in Table 1, and furan resin (A-1) was obtained.

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

[0070] <Example 3> At room temperature and pressure, furfuryl alcohol, paraform (92%), and adipic acid were added to a reaction vessel in the proportions (parts by mass) shown in Table 1. The mixture was heated while stirring until it reached 100°C. After 9 hours and 20 minutes, the paraform and adipic acid were dissolved, and a homogeneous solution was confirmed. The pH was then measured and confirmed to be 3.1 (at 25°C). The mixture was further heated to 117°C ± 3°C for 7 hours and 15 minutes until the viscosity reached 302 mPa·s. Cooling was then started, and when the temperature dropped below 100°C, 25% potassium hydroxide aqueous solution was added to neutralize the mixture. The pH at this point was 5.6 (at 25°C). The mixture in the reaction vessel was heated while the pressure was reduced to 80 torr, and heated at 140°C and 80 torr for 1 hour. After cooling to 100°C, water was added. Subsequently, water-1 and urea were added in the proportions shown in Table 1, and the mixture was reacted at 55°C. Finally, water-2 was added to adjust the viscosity to that shown in Table 1, and furan resin (A-3) was obtained.

[0071] <Comparative Example 1> At room temperature and pressure, furfuryl alcohol, paraform (92%), and adipic acid were added to the reaction vessel in the proportions (parts by mass) shown in Table 1, and the temperature was raised to 117°C while stirring. After 2 hours and 20 minutes, it was confirmed that the paraform and adipic acid had dissolved and a homogeneous solution had been formed, and the pH was measured and confirmed to be pH 3.3 (25°C). For pH measurement, a mixture of the solution and pure water in a 1:1 mass ratio was used. The reaction was carried out at a solution temperature of 117°C ± 3°C for 8 hours and 30 minutes, and when the viscosity reached 347 mPa·s, cooling was started, and when the temperature fell below 100°C, 25% potassium hydroxide aqueous solution was added to neutralize it. The pH at that time was 5.6 (25°C). The temperature inside the reaction vessel was raised while the pressure was reduced to 80 torr, and heated at 140°C and 80 torr for 1 hour. After cooling to 100°C, water was added. Subsequently, water-1 was added in the proportions shown in Table 1, and the viscosity was adjusted to match the viscosity shown in Table 1 to obtain furan resin (B-1).

[0072] <Comparative Example 2> At room temperature and pressure, furfuryl alcohol, paraform (92%), and adipic acid were added to the reaction vessel in the proportions (parts by mass) shown in Table 1, and the temperature was raised to 117°C while stirring. After 2 hours and 20 minutes, it was confirmed that the paraform and adipic acid had dissolved and a homogeneous solution had been formed. The pH was then measured and confirmed to be pH 3.3 (25°C). For the pH measurement, a mixture of the solution and pure water in a 1:1 mass ratio was used. The reaction was carried out at a solution temperature of 117°C ± 3°C for 9 hours and 15 minutes. When the viscosity reached 305 mPa·s, cooling was started, and when the temperature fell below 100°C, 25% potassium hydroxide aqueous solution was added to neutralize it. The pH at this time was 5.6 (25°C). The temperature inside the reaction vessel was raised while the pressure was reduced to 80 torr, and the mixture was heated at 140°C and 80 torr for 1 hour. After cooling to 100°C, water was added. Subsequently, water-1 was added in the proportions shown in Table 1, and the viscosity was adjusted to match the viscosity shown in Table 1 to obtain furan resin (B-2).

[0073] <Comparative Example 3> At room temperature and pressure, furfuryl alcohol, paraform, and adipic acid were added to the reaction vessel in the proportions (parts by mass) shown in Table 1, and the temperature was raised to 117°C while stirring. After 2 hours and 10 minutes, it was confirmed that the paraform and adipic acid had dissolved and a homogeneous solution had been formed. The pH was then measured and confirmed to be pH 3.3 (25°C). For the pH measurement, a mixture of the solution and pure water in a 1:1 mass ratio was used. The reaction was carried out at a solution temperature of 117°C ± 3°C for 5 hours and 10 minutes. When the viscosity reached 306 mPa·s, cooling was started, and when the temperature fell below 100°C, 25% potassium hydroxide aqueous solution was added to neutralize it. The pH at this point was 5.6 (25°C). The temperature inside the reaction vessel was raised while the pressure was reduced to 80 torr, and the mixture was heated at 140°C and 80 torr for 1 hour. After cooling to 100°C, water was added. Subsequently, water-1 was added in the proportions shown in Table 1, and the viscosity was adjusted to match the viscosity shown in Table 1 to obtain furan resin (B-3).

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

[0075] <Measurement conditions> A mixture was obtained by mixing 10 g of each furan resin with 0.33 g of a 55% aqueous solution of p-toluenesulfonic acid (PTSA). This mixture was treated at 120°C for 1 hour, and then pulverized to prepare the sample. The IR spectrum of the sample was measured using Fourier transform infrared spectroscopy (FT-IR). 1545 cm⁻¹ -1 ~1560cm -1 Let R1 be the transmittance of the maximum absorption peak in the range of 1645cm. -1 ~1662cm -1 R2 was defined as the transmittance of the maximum absorption peak within the specified range. Fourier transform infrared spectroscopy was performed using a Thermo Scientific FT-IR Nicolect iS20 instrument, employing the single-reflection ATR method.

[0076] (3) Preparation of prepregs Varnish was obtained by adding and mixing 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 the acid curing agent in the proportions shown in Table 1 to 100 parts by mass of each furan resin. The resulting varnish was then applied to a glass woven fabric (cloth type #7781, E glass, basis weight 298g / m²). 2 After immersing the glass woven fabric in varnish, four sheets were prepared by removing the fabric and drying it in a 100°C hot air drying apparatus while it was suspended. Then, the four sheets were laminated with a spacer (1 mm) in between, and pressed at 120°C for 1 hour to obtain a prepreg.

[0077] (4) Evaluation of prepregs From the obtained prepreg, test specimens measuring 125 mm in length, 13 mm in width, and 1.2 mm in thickness were prepared and measured in accordance with the UL94 (standard established by Under Writers Laboratories Inc. in the United States) vertical combustion test. Specifically, with the test specimen held perpendicular to its length, the flame was applied from below the specimen for 10 seconds. The burning time (t1 (seconds)) from the time the flame was removed until it extinguished was measured. After the flame extinguished, the flame was applied again for 10 seconds, and the burning time (t2 (seconds)) from the time the flame was removed until it extinguished was measured. The results were then evaluated based on the following criteria. V-0: At least one of t1 or t2 is 10 seconds or less AND (t1+t2) ≤ 50 seconds V-1: At least one of t1 or 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 on 26 February 2024, and incorporates all of its disclosures herein.

Claims

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

000.

2. The furan resin according to claim 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 claim 1 or 2.

4. A resin composition comprising the furan resin according to claim 1 or 2, wherein the resin composition is in the form of a film.

5. A prepreg in which the resin composition according to claim 3 or 4 is impregnated into a fibrous substrate.

6. A panel using the prepreg described in claim 5.

7. A cured product of the resin composition according to claim 3 or 4.

8. Step 1 involves mixing furfuryl alcohol, an acid catalyst, and aldehydes at room temperature, heating and dissolving them to a pH of 4 or lower, and then proceeding with the polymerization reaction between the furfuryl alcohol and the aldehydes. Step 2 involves adding a neutralizing agent to suppress the polymerization reaction and then removing the remaining furfuryl alcohol monomer and aldehyde monomer to obtain a polymer. Step 3 involves adding urea and reacting it with the polymer, A method for producing furan resin, including the resin itself.

9. In the method for producing furan resin according to claim 8, A method for producing furan resin, wherein the heating temperature in step 1 is 80°C or higher.

10. In the method for producing furan resin according to claim 8 or 9, The above-mentioned step 2 is a method for producing furan resin, wherein the remaining furfuryl alcohol monomer and aldehyde monomer are removed by vacuum distillation.

11. In the method for producing furan resin according to any one of claims 8 to 10, Step 1 is a method for producing furan resin, carried out under atmospheric pressure.

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