Method for producing phenol resin

Abstract

A method for producing a phenol resin includes, in the following order: a decomposition step for heating and pressurizing a mixture 1 containing a phenol resin cured product, phenol, and an alkali catalyst 1, and decomposing the phenol resin cured product to obtain a phenol composition containing phenols; and a synthesis step for synthesizing a phenol resin using the phenols. The phenols have a weight-average molecular weight (Mw) of 3000 or less as measured by the following <Method 1>. <Method 1> The phenol composition is dissolved in THF, filtered through a filter having a pore size of 0.2 um, and the filtrate is used as a THF-soluble fraction. Next, the THF-soluble fraction is subjected to GPC measurement under the following conditions, and the weight-average molecular weight (Mw) is calculated. (Conditions) Eluent: THF, calibration curve: polystyrene equivalent, detector: differential refractometer, flow rate: 1 mL / min, temperature: 40°C

Description

Method for producing phenolic resin

[0001] The present invention relates to a method for producing a phenolic resin.

[0002] A phenolic composition containing phenols is used as a raw material for resins such as phenolic resins, polycarbonate resins, epoxy resins, and aromatic polyester resins. As technologies related to the chemical recycling of phenolic resins, those of Patent Document 1 and Patent Document 2 can be cited.

[0003] Patent Document 1 describes a method of decomposing a cured phenolic resin containing an organic filler in a solution containing phenols and separating the organic filler. According to the above method, it is described that the organic filler can be easily separated from the cured phenolic resin containing the organic filler.

[0004] Patent Document 2 describes a method for co-producing an inorganic substance and a phenolic compound from a composite material containing an inorganic substance and a cured thermosetting resin, which includes the following steps 1 to 4. Step 1: A step of contacting a composite material containing an inorganic substance and a cured thermosetting resin with a treatment liquid containing a metal alkoxide and an organic solvent to obtain a decomposition liquid A containing an inorganic substance and a phenolic compound. Step 2: A step of solid-liquid separating the decomposition liquid A obtained in Step 1 into a crude inorganic substance B and a dissolution liquid C containing a phenolic compound. Step 3: A step of washing the crude inorganic substance B obtained in Step 2 to obtain an inorganic substance. Step 4: A step of separating a phenolic compound from the dissolution liquid C obtained in Step 2. According to the above method, it is described that a chemical recycling method can be provided that does not damage the decomposition tank due to corrosion and suppresses coloring of the obtained inorganic substance and thermosetting resin.

[0005] Japanese Patent Application Laid-Open No. 2005-054138 Japanese Patent Application Laid-Open No. 2024-017469

[0006] The present invention provides a method for producing a phenolic resin that can obtain a phenolic resin composition with improved hardness.

[0007] According to the present invention, a method for producing a phenolic resin as shown below is provided.

[0008] [1] A method for producing a phenol resin, comprising the steps of: a decomposition step of heating and pressurizing a mixture 1 containing a cured phenol resin, phenol, and an alkaline catalyst 1 to decompose the cured phenol resin and obtain a phenol composition containing phenols; and a synthesis step of synthesizing a phenol resin using the phenols, wherein the weight-average molecular weight (Mw) of the phenols, as measured by the following <Method 1>, is 3000 or less. <Method 1> The phenol composition is dissolved in THF and filtered through a filter with a pore size of 0.2 μm, and the filtrate is used as the THF-soluble component. The THF-soluble component is then measured by GPC under the following conditions, and the weight-average molecular weight (Mw) of the phenols is calculated. (Conditions) Eluent: THF Calibration curve: Polystyrene equivalent Detector: Differential refractometer Flow rate: 1 ml / min Temperature: 40°C [2] The method for producing a phenol resin according to [1], wherein in the decomposition step, the mixture 1 is heated to 200°C or higher. [3] The method for producing a phenol resin according to claim [1] or [2], wherein in the decomposition step, the mixture 1 is pressurized at 0.5 MPa or more. [4] The method for producing a phenol resin according to any one of [1] to [3], wherein the decomposition step is carried out in a subcritical state. [5] The method for producing a phenol resin according to any one of [1] to [4], wherein the content of the alkali catalyst 1 in the mixture 1 is 0.1 parts by mass or more and 40 parts by mass or less when the total amount of the cured phenol resin is 100 parts by mass. [6] The method for producing a phenol resin according to any one of [1] to [5], wherein the alkali catalyst 1 comprises one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal phenolates and alkaline earth metal phenolates. [7] The method for producing a phenol resin according to any one of [1] to [6], wherein the mixture 1 further comprises water. [8] The method for producing a phenol resin according to [7], wherein the amount of the phenol resin cured product in the mixture 1 is 5 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the total amount of the phenol and the water.[9] The method for producing a phenol resin according to any one of [1] to [8], wherein the content of the phenol in the mixture 1 is 50 parts by mass or more and 1500 parts by mass or less per 100 parts by mass of the cured phenol resin.

[10] The method for producing a phenol resin according to any one of [1] to [9], wherein the content of water in the mixture 1 is 0 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the cured phenol resin.

[11] The method for producing a phenol resin according to any one of [1] to

[10] , wherein in the synthesis step, a mixture 2 containing the phenols contained in the phenol composition, formaldehyde, and a catalyst is heated.

[12] The method for producing a phenol resin according to

[11] , wherein the catalyst is an alkaline catalyst 2.

[13] The method for producing a phenol resin according to

[12] , wherein the alkaline catalyst 2 contains one or more selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

[14] The method for producing a phenol resin according to

[11] , wherein the catalyst is an acid catalyst.

[15] A method for producing a phenol resin according to any one of [1] to

[14] , further comprising a neutralization step of neutralizing the alkali catalyst 1 before the synthesis step, and a step of removing the neutralized salt obtained by the neutralization step.

[16] A method for producing a phenol resin according to

[15] , wherein the alkali catalyst 1 comprises one or more selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

[17] A method for producing a phenol resin according to any one of [1] to

[16] , wherein the decomposition step is carried out continuously using a continuous reaction apparatus.

[0009] According to the present invention, a method for producing a phenolic resin can be obtained that yields a phenolic resin composition with improved hardness.

[0010] The present invention will be described below based on embodiments. In these embodiments, unless otherwise specified, "A to B" indicating a numerical range represents A or greater and B or less.

[0011] <Method for Producing Phenolic Resin> The method for producing phenolic resin according to this embodiment includes, in this order: a decomposition step in which a mixture 1 containing a cured phenolic resin, phenol, and an alkaline catalyst 1 is heated and pressurized to decompose the cured phenolic resin and obtain a phenolic composition containing phenols; and a synthesis step in which a phenolic resin is synthesized using the phenols. The weight-average molecular weight (Mw) of the phenols, as measured by the following <Method 1>, is 3000 or less. <Method 1> The phenolic composition is dissolved in THF and filtered through a filter with a pore size of 0.2 μm, and the filtrate is used as the THF-soluble component. Next, the THF-soluble component is measured by GPC under the following conditions, and the weight-average molecular weight (Mw) of the phenols is calculated. (Conditions) Eluent: THF Calibration curve: Polystyrene equivalent Detector: Differential refractometer Flow rate: 1 ml / min Temperature: 40°C

[0012] The method for producing phenolic resin according to this embodiment includes a decomposition step in which phenol and an alkaline catalyst are added to a cured phenolic resin, and the cured phenolic resin is heated and pressurized to decompose it and obtain a phenolic composition, and a synthesis step in which a phenolic resin is synthesized using the phenols contained in the obtained phenolic composition. By setting the weight-average molecular weight of the phenols to below a predetermined upper limit, the hardness of the phenolic resin composition containing the obtained phenolic resin can be improved.

[0013] Although the reason is not clear, by reducing the weight-average molecular weight (Mw) of phenols to below a predetermined value, i.e., by reducing the molecular weight, a phenol resin composition with improved hardness can be obtained using the phenol resin production method of this embodiment. When a phenol resin is produced using a phenol composition containing phenols with a weight-average molecular weight (Mw) exceeding a predetermined value, i.e., phenols with a high molecular weight, it is thought that the hardness of the resulting phenol resin composition will decrease compared to when phenols with a weight-average molecular weight (Mw) below a predetermined value are used, for example, due to reasons such as polymerization and increased viscosity.

[0014] Note that "synthetic phenol" refers to synthesized phenol, not a decomposition product of a cured phenol resin. Furthermore, in the method for producing the phenol resin of this embodiment, "phenols" include phenols containing one aromatic ring (such as phenol), bisphenols containing two aromatic rings (such as bisphenol A, bisphenol F, and methyl adducts of bisphenol F), and phenols containing three or more aromatic rings. In this embodiment, bisphenol F means one or more selected from the group consisting of 2,2'-methylenediphenol, 2,4'-methylenediphenol, and 4,4'-methylenediphenol.

[0015] In the method for producing the phenol resin of this embodiment, the phenol composition includes phenols, preferably one or more selected from the group consisting of phenols derived from the decomposition products of the cured phenol resin and phenol, and more preferably one or more selected from the group consisting of phenols containing one aromatic ring (such as phenol), bisphenols containing two aromatic rings (such as bisphenol A and bisphenol F), and phenols containing three or more aromatic rings. Note that even if the cured phenol resin is decomposed, it is difficult to decompose it down to phenols containing one aromatic ring, so the decomposition products of the cured phenol resin mainly contain phenols containing two or more aromatic rings.

[0016] Furthermore, in this specification, phenols derived from the decomposition products of phenol resin cured products are referred to as regenerated phenols. The phenols of this embodiment include regenerated phenols, and the phenol composition of this embodiment includes regenerated phenols.

[0017] The method for producing the phenolic resin in this embodiment includes a decomposition step and a synthesis step. First, the decomposition step will be described.

[0018] <Decomposition Process> In the decomposition process, a mixture 1 containing a phenol resin cured product, phenol, and an alkaline catalyst 1 is heated and pressurized to decompose the phenol resin cured product and obtain a phenol composition containing phenols. The components contained in the mixture 1 are described in detail below.

[0019] (Cured Phenolic Resin) Mixture 1 contains a cured phenolic resin. There are no particular restrictions on the cured phenolic resin, but examples include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin; unmodified resol phenolic resins and resol-type phenolic resins such as oil-modified resol phenolic resins modified with tung oil, linseed oil, walnut oil, etc. The cured phenolic resin may also be a composite material containing reinforcing fibers, fillers, additives, etc. Furthermore, there are no particular restrictions on the cured phenolic resin as long as it is a cured phenolic resin as described above, and products containing the cured phenolic resin may be used. For example, examples include molding materials and sealing materials containing a phenolic resin composition containing the above phenolic resin and an inorganic filler, or laminates manufactured by impregnating an inorganic or organic substrate with the above phenolic resin, and metal-clad laminates in which metal foil is bonded to these laminates, etc., that contain the cured phenolic resin.

[0020] Furthermore, the cured phenolic resin product in the decomposition process includes cured products of the phenolic resin composition. The phenolic resin composition may include one or two selected from the group consisting of phenolic resins obtained from synthetic phenols and resins obtained from recycled phenols. When the phenolic resin composition includes resins obtained from recycled phenols, the environmental impact can be further reduced.

[0021] It is preferable that the cured phenolic resin is pulverized before the decomposition process. The average particle size of the cured phenolic resin after pulverization is preferably 1 mm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. By keeping the average particle size of the cured phenolic resin after pulverization below the above upper limit, the decomposition rate of the cured phenolic resin can be further improved.

[0022] The content of the phenol resin cured product in mixture 1 is preferably 5 parts by mass or more and 80 parts by mass or less, more preferably 6 parts by mass or more and 70 parts by mass or less, even more preferably 7 parts by mass or more and 60 parts by mass or less, and even more preferably 8 parts by mass or more and 50 parts by mass or less, when the total amount of mixture 1 is 100 parts by mass.

[0023] (Alkali Catalyst 1) Mixture 1 contains alkali catalyst 1. From the viewpoint of further improving the decomposition properties of the cured phenolic resin, alkali catalyst 1 preferably contains one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal phenolates, and alkaline earth metal phenolates. The alkali metal hydroxide preferably contains one or more selected from the group consisting of potassium hydroxide and sodium hydroxide. The alkaline earth metal hydroxide preferably contains one or more selected from the group consisting of beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide, and more preferably contains calcium hydroxide. The alkali metal phenolates and alkaline earth metal phenolates preferably contain one or more selected from the group consisting of sodium phenolate, potassium phenolate, and calcium phenolate. When producing a novolac-type phenolic resin in the synthesis process described later, an acid catalyst is used in the synthesis of the novolac-type phenolic resin, so it is necessary to neutralize the alkali catalyst 1 remaining in the phenolic composition before synthesis. Therefore, from the viewpoint of promoting neutralization more smoothly, it is preferable to use a catalyst as the alkali catalyst 1 that includes one or more selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, more preferably an alkaline earth metal hydroxide with weaker alkalinity, and even more preferably calcium hydroxide.

[0024] The content of alkali catalyst 1 in mixture 1 is preferably 0.1 parts by mass to 40 parts by mass, more preferably 0.2 parts by mass to 35 parts by mass, even more preferably 0.3 parts by mass to 30 parts by mass, and even more preferably 0.5 parts by mass to 25 parts by mass, when the total amount of the cured phenolic resin is 100 parts by mass. By having an alkali catalyst 1 content above the above lower limit, the decomposition rate of the cured phenolic resin can be further improved, and the molecular weight of the resulting phenolic composition can be further reduced.

[0025] (Phenol) Mixture 1 contains phenol. In the decomposition process, phenol acts as a solvent for decomposing the phenol resin cured product, and also remains in the phenol composition after the decomposition of the phenol resin cured product. Therefore, as will be described later, it also becomes a material for the phenol resin obtained by synthesizing the phenol composition of this embodiment.

[0026] The phenol content in mixture 1 is preferably 50 parts by mass or more and 1500 parts by mass or less, more preferably 100 parts by mass or more and 1200 parts by mass or less, even more preferably 100 parts by mass or more and 900 parts by mass or less, and even more preferably 100 parts by mass or more and 600 parts by mass or less, based on 100 parts by mass of the phenol resin cured product. By having a phenol content in the mixture above the lower limit, the phenol composition can be made lower in molecular weight. By having a phenol content in the mixture below the upper limit, the recycling rate of the phenol composition can be further improved. In this specification, the recycling rate means the proportion of recycled phenols among the phenols contained in the phenol composition.

[0027] (Water) Mixture 1 may further contain water. The inclusion of water can further improve the solubility of the alkaline catalyst in the mixture when the alkaline catalyst contains an alkaline earth metal hydroxide.

[0028] The water content in mixture 1 is preferably 0 to 150 parts by mass, more preferably 0 to 140 parts by mass, even more preferably 1 to 130 parts by mass, even more preferably 2 to 120 parts by mass, and even more preferably 3 to 110 parts by mass, based on 100 parts by mass of the phenol resin cured product.

[0029] When mixture 1 contains water, the content of the phenol resin cured product in mixture 1 is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 5.5 parts by mass or more and 90 parts by mass or less, and even more preferably 6.0 parts by mass or more and 80 parts by mass or less, or 6.5 parts by mass or more and 70 parts by mass or less, based on 100 parts by mass of the total content of phenol and water.

[0030] In the decomposition process, the temperature and pressure used to heat and pressurize mixture 1 are preferably 200°C to 700°C and 0.5 MPa to 40.0 MPa, more preferably 213°C to 629°C and 0.6 MPa to 36.6 MPa, and even more preferably 255°C to 560°C and 1.0 MPa to 24.4 MPa, since the critical temperature of phenol is 421°C and the critical pressure is 6.1 MPa. By heating and pressurizing mixture 1 within the above range, the mixture containing phenol can be brought to a supercritical or subcritical state, further improving the decomposition properties of the phenol resin cured product. That is, from the viewpoint of further improving the decomposition properties of the phenol resin cured product, it is preferable to carry out the decomposition process of this embodiment in a supercritical or subcritical state, and more preferably in a subcritical state. Furthermore, the pressure applied depends on the amount of water and phenol contained in mixture 1. When the ratio of phenol content to water content in mixture 1 (P / W) is less than 10, the pressure is preferably 3.8 MPa or higher, and when P / W is 10 or higher, the pressure is preferably less than 3.8 MPa.

[0031] In the decomposition process, the steps of heating and pressurizing mixture 1 are preferably performed for 1 minute to 400 minutes, more preferably 2 minutes to 300 minutes, even more preferably 3 minutes to 200 minutes, and even more preferably 4 minutes to 100 minutes. Performing the steps of heating and pressurizing mixture 1 for a time greater than or equal to the lower limit can further improve the decomposition properties of the phenol resin cured product. Performing the steps of heating and pressurizing mixture 1 for a time less than or equal to the upper limit can further improve productivity.

[0032] The reaction apparatus used for the decomposition process is not particularly limited, but for example, a batch-type reactor or a continuous-type reactor can be used, and preferably the process is carried out continuously using a continuous-type reactor.

[0033] The phenol composition obtained by the decomposition process will be described in detail. The phenol composition contains phenols, and the weight-average molecular weight (Mw) of the phenols, as measured by the following Method 1, is 3000 or less. Method 1 The phenol composition is dissolved in THF, filtered through a 0.2 μm pore size filter, and the filtrate is used as the THF-soluble component. Next, the THF-soluble component is measured by GPC under the following conditions to determine the weight-average molecular weight (Mw) of the phenols. (Conditions) Eluent: THF Calibration curve: Polystyrene equivalent Detector: Differential refractometer Flow rate: 1 ml / min Temperature: 40°C

[0034] The weight-average molecular weight (Mw) of the phenols measured by Method 1 above is 3000 or less, preferably 2500 or less, more preferably 2000 or less, even more preferably 1500 or less, and still more preferably 1000 or less, from the viewpoint of further improving the hardness of the phenol resin composition containing the obtained phenol resin. Even more preferably it is 550 or less, even more preferably 530 or less, even more preferably 500 or less, even more preferably 450 or less, even more preferably 430 or less, even more preferably 420 or less, and still more preferably 410 or less. There is no lower limit to the weight-average molecular weight (Mw) of the phenols measured by Method 1 above, but it may be, for example, 94 or more, 100 or more, or 110 or more. Furthermore, the weight-average molecular weight (Mw) of the phenols measured by the above-mentioned Method 1 is preferably 94 to 3000, more preferably 94 to 2500, even more preferably 94 to 2000, even more preferably 94 to 1500, and even more preferably 94 to 1000, from the viewpoint of being able to further improve the hardness of the phenol resin composition containing the obtained phenol resin. Even more preferably, it is 94 to 550, even more preferably 94 to 530, even more preferably 94 to 500, even more preferably 94 to 450, even more preferably 100 to 430, even more preferably 110 to 420, and even more preferably 110 to 410.

[0035] The number-average molecular weight (Mn) of phenols measured by Method 2 below is preferably 1000 or less, more preferably 900 or less, even more preferably 800 or less, even more preferably 700 or less, even more preferably 600 or less, and even more preferably 550 or less, from the viewpoint of further improving the hardness of the phenol resin composition containing the obtained phenol resin. Even more preferably it is 300 or less, even more preferably 250 or less, even more preferably 200 or less, even more preferably 180 or less, even more preferably 160 or less, and even more preferably 150 or less, from the viewpoint of obtaining a phenol resin composition having the same hardness as a phenol resin composition containing a phenol resin obtained using synthetic phenol. There is no lower limit to the number-average molecular weight (Mn) of phenols measured by Method 2 below, but it may be, for example, 94 or more, or 100 or more. Furthermore, the number-average molecular weight (Mn) of phenols measured by <Method 2> below is preferably 94 to 1000, more preferably 94 to 900, even more preferably 94 to 800, even more preferably 94 to 700, even more preferably 94 to 600, and even more preferably 94 to 550, from the viewpoint of further improving the hardness of the phenol resin composition containing the obtained phenol resin. Even more preferably, it is 94 to 300, even more preferably 94 to 250, even more preferably 94 to 200, even more preferably 100 to 180, even more preferably 100 to 160, and even more preferably 100 to 150.

[0036] <Method 2> The phenol composition is dissolved in THF, filtered through a 0.2 μm pore size filter, and the filtrate is used as the THF-soluble component. Next, the THF-soluble component is subjected to GPC measurement under the following conditions to determine the number-average molecular weight (Mn) of the phenols. (Conditions) Eluent: THF Calibration curve: Polystyrene equivalent Detector: Differential refractometer Flow rate: 1 ml / min Temperature: 40°C

[0037] The phenol content in the phenol composition of this embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, when the total amount of the phenol composition is considered as 100% by mass, and may also be less than 100% by mass and 95% by mass or less. By having a phenol content in the phenol composition that is above the above lower limit, the hardness of the phenol resin composition containing the phenol resin obtained using the phenol composition can be further improved. The phenol content in the phenol composition can be calculated by subtracting the water content and ash content from the total amount of the phenol composition.

[0038] <Synthesis Process> In the synthesis process, a mixture containing the phenol composition obtained in the decomposition process, formaldehyde, and a catalyst is heated and pressurized to synthesize a phenol resin. By changing the catalyst used, resol-type phenol resin or novolac-type phenol resin can be synthesized.

[0039] (When synthesizing resol-type phenolic resin) In a method for synthesizing resol-type phenolic resin, the catalyst preferably includes an alkali catalyst 2. Examples of alkali catalyst 2 include alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, sodium carbonate, aqueous ammonia, tertiary amines such as triethylamine, hexamethylenetetramine, and the like, and preferably includes one or more selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, and more preferably includes one or two selected from the group consisting of potassium hydroxide and sodium hydroxide.

[0040] In a method for synthesizing resol-type phenolic resins, for example, a mixture containing the phenolic composition of this embodiment, formaldehyde, and the above-mentioned alkaline catalyst can be heated and pressurized to synthesize a resol-type phenolic resin. Heating can preferably be performed at a temperature of 50°C to 150°C, more preferably 60°C to 100°C. The heating time can preferably be performed for 30 minutes to 500 minutes, more preferably 60 minutes to 250 minutes.

[0041] (When synthesizing novolac-type phenolic resin) In a method for synthesizing novolac-type phenolic resin, the catalyst preferably includes an acid catalyst. Examples of acid catalysts include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, phosphorous acid, oxalic acid, and p-toluenesulfonic acid; zinc acetate and lead naphthenate, which contain divalent metal ions when dissolved in phenol; and organic acids, preferably including oxalic acid. Furthermore, if high ortho novolac is desired, zinc acetate is preferably included. In addition, since an acid catalyst is used in the method for synthesizing novolac-type phenolic resin, it is preferable to neutralize any alkaline catalyst remaining in the phenolic composition that was used in the method for producing the phenolic composition (decomposition step of the cured phenolic resin) before the step of synthesizing the phenolic resin. Neutralization can be carried out, for example, when using oxalic acid, until the pH of the phenolic composition is about 3 to 8, and after neutralization, it is preferable to remove the salt produced by filtration.

[0042] Furthermore, as a method for curing the novolac-type phenolic resin, it is preferable to incorporate a curing agent such as hexamethylenetetramine (hexamine) after the process of synthesizing the phenolic resin.

[0043] In a method for synthesizing a novolak-type phenol resin, for example, by heating and pressurizing a mixture containing the phenol composition of the present embodiment, phenol, formaldehyde, the acid catalyst described above, and a curing agent, a novolak-type phenol resin can be synthesized. The heating can preferably be carried out at a temperature of 60°C or higher and 120°C or lower, more preferably 80°C or higher and 100°C or lower. The heating time can be 30 minutes or longer and 500 minutes or shorter, more preferably 60 minutes or longer and 300 minutes or shorter.

[0044] <Other steps> As described above, when producing a novolak-type phenol resin in the synthesis step, since an acid catalyst is used in the synthesis of the novolak-type phenol resin, it is necessary to neutralize the alkali catalyst 1 remaining in the phenol composition before synthesis. Also, the process of removing the alkali catalyst 1 remaining in the phenol composition may be included in the synthesis of the resol-type phenol resin. Therefore, the method for producing the phenol resin of the present embodiment may further include a neutralization step of neutralizing the alkali catalyst 1 before the synthesis step and a step of removing the neutralization salt obtained by the neutralization step.

[0045] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can also be adopted. Also, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the range that does not impair the effects of the present invention are included in the present invention.

[0046] Hereinafter, the present embodiment will be described in detail with reference to examples and the like. Note that the present embodiment is not limited to the descriptions of these examples.

[0047] As the cured phenol resin used in the production of the phenol composition, the following phenol resins and cured phenol resin molding materials were used. - Novolac-type phenol resin molding material (containing glass filler (GF)): manufactured by Sumitomo Bakelite Co., Ltd., product name: PM-9640 - Novolac-type phenol resin (13% hexamine, no GF): manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-51794 - Novolac-type phenol resin (7% hexamine, no GF): manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-217 - Resole-type phenol resin (no GF): manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-961A These phenol resins and phenol resin molding materials were placed in a dryer and cured by heating at 120°C for 2 hours, and then further cured by heating at 200°C for 1 hour. After that, they were pulverized by a pulverizer and sieved to obtain a cured phenol resin with an average particle diameter of 50 μm.

[0048] <Example 1> (Production of Phenol Composition)1000 parts by mass of a cured phenol resin obtained from a novolac-type phenol resin molding material (containing GF), 107 parts by mass of calcium hydroxide, 693 parts by mass of water, and 2773 parts by mass of phenol were charged into an autoclave (internal volume: 6 L). Then, while stirring at a rotation speed of 300 rpm, the temperature and pressure inside the container were increased, and it was held for 10 minutes under the conditions of a container internal temperature of 300°C and a container internal pressure of 6.1 MPa. While being held under the conditions of a container internal temperature of 300°C and a container internal pressure of 6.1 MPa, the inside of the container was in a subcritical state. Table 1 shows the ratio (M / R) of the content M of the alkali catalyst to the content R of the cured phenol resin, and the ratio (P / R) of the content P of phenol to the content R of the cured phenol resin. Subsequently, 1000 parts by mass of the high-pressure reaction composition obtained inside the above container and 1000 parts by mass of water were added to a 5 L three-neck flask equipped with a stirrer. Then, it was kept at 60°C and oxalic acid was further added to adjust the pH to 5. Next, 1000 parts by mass of methyl ethyl ketone (MEK) was further added to the three-neck flask to extract the phenol composition with MEK, and MEK was removed by vacuum distillation to obtain a black liquid phenol composition.

[0049] (Weight-average molecular weight (Mw) and number-average molecular weight (Mn)) The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the phenols obtained in Example 1 were measured according to the following method. The results are shown in Table 1. <Method> The phenol composition was dissolved in THF at 25°C and 50 RH for 5 minutes by ultrasonic irradiation to a concentration of 0.3% by mass, filtered through a 0.2 μm pore size filter (Cytiva, product name: Whatman Puradisc 25, filter material: PTFE, membrane filter), and the filtrate was used as the THF-soluble matter. Next, the THF-soluble matter was measured by GPC under the following conditions to determine the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the phenols. The peak area was calculated as follows. In the elution curve, a straight line was drawn connecting the point where the rise from baseline began as the starting point and the point where the oligomer peak returned to baseline as the endpoint of the oligomer. Similarly, a straight line was drawn connecting the point where the phenol peak began to rise from baseline as the starting point and the point where the elution peak returned to baseline as the endpoint of the phenol. The sum of the areas enclosed by the two peak curves and the straight line was calculated. (Conditions) Measurement device: Product name HLC-8320 (manufactured by Tosoh Corporation) Column: Product name TSKgel G1000HXL, G2000HXL x 2, G3000HXL (manufactured by Tosoh Corporation) Eluent: THF Calibration curve: Polystyrene equivalent (Standard product: Product name TSKstandard POLYSTYRENE, manufactured by Tosoh Corporation, molecular weight range: 500 to 1,090,000, number of data points: 12) and phenol Detector: Differential refractometer Flow rate: 1 ml / min Temperature: 40°C

[0050] (Production of resol-type phenolic resin) 1000 parts by mass of the phenolic composition obtained in the above (production of phenolic composition), 862 parts by mass of 37% formalin (manufactured by Kanto Chemical Co., Ltd., product name: formaldehyde solution special grade), and 50 parts by mass of aqueous sodium hydroxide solution (manufactured by Kanto Chemical Co., Ltd., product name: 48% sodium hydroxide solution first grade) were charged into a reaction vessel and reacted at 80°C for 2 hours. Then, water was removed by vacuum distillation to obtain the phenolic resin.

[0051] (Hardness evaluation of cured products using resol-type phenolic resin) Using the obtained resol-type phenolic resin, a resin varnish was prepared by adjusting the phenolic resin content with acetone to 30% by mass. This varnish was impregnated into an aramid fiber substrate measuring 120 mm × 10 mm × 1 mm thick, and then dried and cured in an oven at 190°C for 30 minutes to obtain test specimens. The obtained test specimens were evaluated as follows. The results are shown in Table 1. Rockwell hardness (HRD): The hardness of the obtained test specimens was measured on the H scale according to the method in accordance with JIS Z 2245. A higher Rockwell hardness (HRD) value indicates a more hard test specimen.

[0052] <Examples 2-27, Comparative Examples 1-5> Except for the types of phenol resin cured products and alkali catalysts, the amounts of alkali catalyst, water, and phenol, and the temperature, pressure, and decomposition time during the production of the phenol composition, the production of the phenol composition and the phenol resin were carried out and evaluated in the same manner as in Example 1. The results are shown in Table 1 or 2.

[0053] <Reference Example 1> For comparison, a resol-type phenolic resin was also produced using a phenolic resin composition made with commercially available synthetic phenol. Furthermore, a cured product was prepared using the obtained resol-type phenolic resin and its hardness was evaluated. (Preparation of resol-type phenolic resin) Specifically, 1000 parts by mass of commercially available synthetic phenol (manufactured by Kanto Chemical Co., Ltd., product name: Special Grade Phenol), 1294 parts by mass of 37% formalin (manufactured by Kanto Chemical Co., Ltd., product name: Special Grade Formaldehyde Solution), and 50 parts by mass of sodium hydroxide aqueous solution (manufactured by Kanto Chemical Co., Ltd., product name: 48% Sodium Hydroxide Solution Grade 1) were charged into a reaction vessel and reacted at 100°C for 2 hours. Then, water was removed by vacuum distillation to obtain a resol-type phenolic resin. A cured product was prepared in the same manner as in Example 1 and its hardness was evaluated. The results are shown in Table 2.

[0054]

[0055]

[0056] In Tables 1 and 2, GF refers to glass filler; M / R is the ratio of the alkali catalyst content M to the phenol resin curing content R; P / R is the ratio of the phenol content P to the phenol resin curing content R; W / R is the ratio of the water content W to the phenol resin curing content R; and R / (W+P) is the ratio of the phenol resin curing content R to the sum of the water content W and the phenol content P.

[0057] This application claims priority based on Japanese Patent Application No. 2024-169364, filed on 27 September 2024, and incorporates all of its disclosures herein.

Claims

1. A method for producing a phenol resin, comprising: a decomposition step of heating and pressurizing a mixture 1 containing a cured phenol resin, phenol, and an alkaline catalyst 1 to decompose the cured phenol resin and obtain a phenol composition containing phenols; and a synthesis step of synthesizing a phenol resin using the phenols, wherein the weight-average molecular weight (Mw) of the phenols, as measured by the following <Method 1>, is 3000 or less. <Method 1> The phenol composition is dissolved in THF, filtered through a filter with a pore size of 0.2 μm, and the filtrate is used as the THF-soluble component. Next, the THF-soluble component is measured by GPC under the following conditions, and the weight-average molecular weight (Mw) of the phenols is calculated. (Conditions) Eluent: THF Calibration curve: Polystyrene equivalent Detector: Differential refractometer Flow rate: 1 ml / min Temperature: 40°C 2. The method for producing a phenol resin according to claim 1, wherein in the decomposition step, the mixture 1 is heated to 200°C or higher.

3. The method for producing a phenolic resin according to claim 1 or 2, wherein in the decomposition step, the mixture 1 is pressurized to 0.5 MPa or more.

4. A method for producing a phenol resin according to any one of claims 1 to 3, wherein the decomposition step is carried out in a subcritical state.

5. The method for producing a phenol resin according to any one of claims 1 to 4, wherein the content of the alkali catalyst 1 in the mixture 1 is 0.1 parts by mass or more and 40 parts by mass or less when the total amount of the phenol resin cured product is 100 parts by mass.

6. The method for producing a phenol resin according to any one of claims 1 to 5, wherein the alkali catalyst 1 comprises one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal phenolates, and alkaline earth metal phenolates.

7. A method for producing a phenol resin according to any one of claims 1 to 6, wherein the mixture 1 further contains water.

8. The method for producing a phenol resin according to claim 7, wherein the content of the phenol resin cured product in the mixture 1 is 5 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the total content of the phenol and the water.

9. A method for producing a phenol resin according to any one of claims 1 to 8, wherein the content of the phenol in the mixture 1 is 50 parts by mass or more and 1,500 parts by mass or less, based on the content of 100 parts by mass of the cured phenol resin.

10. A method for producing a phenol resin according to any one of claims 1 to 9, wherein the water content in the mixture 1 is 0 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the phenol resin cured product.

11. A method for producing a phenol resin according to any one of claims 1 to 10, wherein in the synthesis step, a mixture 2 containing the phenols contained in the phenol composition, formaldehyde, and a catalyst is heated.

12. The method for producing a phenol resin according to claim 11, wherein the catalyst comprises an alkaline catalyst 2.

13. The method for producing a phenol resin according to claim 12, wherein the alkali catalyst 2 comprises one or more selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

14. The method for producing a phenol resin according to claim 11, wherein the catalyst includes an acid catalyst.

15. A method for producing a phenol resin according to any one of claims 1 to 14, further comprising a neutralization step of neutralizing the alkaline catalyst 1 before the synthesis step, and a step of removing the neutralized salt obtained by the neutralization step.

16. The method for producing a phenol resin according to claim 15, wherein the alkali catalyst 1 comprises one or more selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

17. A method for producing a phenol resin according to any one of claims 1 to 16, wherein the decomposition step is carried out continuously using a continuous reaction apparatus.

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