Amorphous powder of benzoxazine compound and method for producing same

Abstract

The present invention addresses the problem of providing a novel form of benzoxazine compounds represented by chemical formula (A), the novel form being capable of solving issues related to handleability, productivity, safety when using an organic solvent, and environmental load in conventional forms of benzoxazine compounds represented by chemical formula (A). As a solution, provided is amorphous powder of a benzoxazine compound represented by chemical formula (A).

Description

Amorphous powder of benzoxazine compound and method for producing the same

[0001] The present invention relates to an amorphous powder of a benzoxazine compound having a specific chemical structure and a method for producing the same.

[0002] Benzoxazine compounds are compounds synthesized by reacting phenols, amines, and formaldehyde, and are known as thermosetting resin raw materials in which the benzoxazine ring undergoes ring-opening polymerization and cures without generating volatile by-products upon heating. They are used as raw materials for molded bodies, liquid crystal alignment agents, semiconductor encapsulation resin compositions, etc. that can be used as materials for insulating substrates. Conventionally, benzoxazine compounds are generally known to have the problem of relatively high curing temperatures. Therefore, in order to lower the curing temperature, catalysts, polymerization accelerators, and highly reactive benzoxazine compounds have been developed in recent years. As such a highly reactive benzoxazine compound, for example, a benzoxazine compound having a thiol group introduced into its structure is known to be able to cure at low temperatures and melt at low temperatures (Patent Document 1). A benzoxazine compound represented by Chemical Formula (A) that can be synthesized by reacting 4,4'-biphenol, formaldehydes, and cysteamine (hereinafter sometimes referred to as benzoxazine compound (A)) is known as one type of benzoxazine compound having a thiol group introduced into its chemical structure. It is known that after the synthesis reaction of benzoxazine compound (A), post-treatment is performed and it is isolated by distillation operation and obtained as a varnish dissolved in a solvent (Patent Document 2).

[0003] International Publication No. 2022 / 163553 Japanese Patent Application Laid-Open No. 2024-077640

[0004] In the form of benzoxazine compound (A) isolated by distillation, although it has a low melting point, energy and equipment are required to maintain a high temperature in order to keep it in a fluid molten state. However, when it cools, it solidifies like a resin, making it difficult to remove from manufacturing equipment, handle, weigh, and transport. As a thermosetting resin with high reactivity, benzoxazine compound (A) has the problem that repeated heating and melting during handling can cause some of the reaction to proceed before it can be used as a raw material. When obtained as a varnish, the manufacturing efficiency relative to the volume of the reaction equipment is low, limiting the versatility of processing as a raw material for curable resin compositions. Furthermore, the large amount of organic solvent used poses problems in terms of safety and environmental impact. The present invention aims to provide a new form of benzoxazine compound (A) that solves these problems.

[0005] As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention discovered that the above-mentioned problems can be solved by providing the benzoxazine compound (A) in the form of an amorphous powder, and thus completed the present invention.

[0006] The present invention is as follows: 1. An amorphous powder of a benzoxazine compound represented by chemical formula (A). 2. The powder according to 1, wherein, in a gel permeation chromatography measurement using a differential refractometer as a detector, the peak area of ​​the benzoxazine compound represented by chemical formula (A) is in the range of 75 to 100 area % of the peak area of ​​all detected components. 3. A method for producing the powder according to 1 or 2, comprising a reaction step in which 4,4'-biphenol, formaldehydes, and cysteamine or a salt thereof are reacted in the presence of an aliphatic ester solvent having 4 to 7 carbon atoms at a temperature in the range of 15 to 60°C while precipitating a solid of the benzoxazine compound represented by chemical formula (A).

[0007] Because the benzoxazine compound (A) is an amorphous powder, the present invention allows for easy separation and purification of the benzoxazine compound (A) obtained by the synthesis reaction, as well as easier handling, weighing, and transportation, contributing to improved manufacturing efficiency. Furthermore, it expands processing versatility, such as allowing the benzoxazine compound (A) to be directly mixed and melted as a raw material for curable resin compositions. Moreover, since the use of organic solvents when used as a raw material for curable resin compositions can be minimized, safe handling is possible, and the environmental impact is reduced, making it extremely useful.

[0008] This figure shows a chart of differential scanning calorimetry (DSC) data for the amorphous powder of benzoxazine compound (A) obtained in Example 1.

[0009] <Amorphous Powder of Benzoxazine Compound Represented by Chemical Formula (A)> In the amorphous powder of the benzoxazine compound represented by chemical formula (A) of the present invention, amorphousness can be confirmed by the absence of an endothermic peak indicating crystalline melting in differential scanning calorimetry (DSC). In gel permeation chromatography using a differential refractometer as a detector, the amorphous powder of the benzoxazine compound represented by chemical formula (A) of the present invention preferably has a peak area of ​​75 to 100 area % relative to the peak area of ​​all detected components. Conventionally, even if the organic solvent contained in the reaction-finished mixture after post-treatment was removed by distillation, only a viscous substance or a solid that had cooled and solidified could be obtained. However, it is considered that the benzoxazine compound (A) can now be obtained as an amorphous powder partly because the peak area value of the benzoxazine compound represented by chemical formula (A) is above the lower limit of the above range. The lower limit of this range is more preferably 78 area % or more, and even more preferably 80 area % or more. The upper limit of such a range may be 98% or less, or 95% or less. The lower and upper limits of the range mentioned above can be arbitrarily combined to form a numerical range.

[0010] <Method for producing amorphous powder of benzoxazine compound represented by chemical formula (A)> The present invention provides a method for producing amorphous powder of benzoxazine compound represented by chemical formula (A), which includes a reaction step in which 4,4'-biphenol, formaldehydes, and cysteamine or a salt thereof are reacted in the presence of an aliphatic ester solvent having 4 to 7 carbon atoms at a temperature in the range of 15 to 60°C while precipitating a solid of the benzoxazine compound represented by chemical formula (A). In this reaction, the reaction equation when formaldehyde is used as the formaldehyde is as follows.

[0011] (Cysteamine or its salt) The cysteamine used as a raw material for synthesizing the benzoxazine compound (A) in the present invention may be cysteamine itself, or, if necessary, as a solution in an aliphatic ester solvent having 4 to 7 carbon atoms. Examples of cysteamine salts include cysteamine hydrochloride. The amount of cysteamine or its salt used is preferably in the range of 2.0 to 4.0 moles, more preferably in the range of 2.0 to 3.5 moles, even more preferably in the range of 2.0 to 3.0 moles, and particularly preferably in the range of 2.0 to 2.8 moles per mole of 4,4'-biphenol.

[0012] (Formaldehydes) Specifically, examples of formaldehydes include aqueous formaldehyde solutions, 1,3,5-trioxane, and paraformaldehyde. The amount of formaldehyde used is preferably in the range of 4.0 to 8.0 moles, more preferably 4.2 to 6.0 moles, even more preferably 4.2 to 5.5 moles, and particularly preferably 4.2 to 5.0 moles, per mole of 4,4'-biphenol, when converted to the amount of formaldehyde that participates in the synthesis reaction of the benzoxazine compound (A). For example, 1 mole of trioxane participates in the reaction as 3 moles of formaldehyde.

[0013] (Reaction Solvent) In the reaction step of the present invention, it is preferable to use an aliphatic ester solvent having 4 to 7 carbon atoms as the reaction solvent. Among these, an aliphatic ester solvent having 4 to 6 carbon atoms is more preferable, an acetate ester solvent having 4 to 6 carbon atoms is even more preferable, and an acetate ester solvent having 6 carbon atoms is particularly preferable. Specific examples of aliphatic ester solvents having 4 to 7 carbon atoms include ethyl acetate, propyl acetate (n-propyl acetate, isopropyl acetate), butyl acetate (n-butyl acetate, isobutyl acetate, sec-butyl acetate, t-butyl acetate), amyl acetate, isoamyl acetate, ethyl propionate, butyl propionate, and ethyl butyrate. Among these, ethyl acetate, propyl acetate (n-propyl acetate, isopropyl acetate), butyl acetate (n-butyl acetate, isobutyl acetate, sec-butyl acetate, t-butyl acetate), or amyl acetate are preferred; ethyl acetate, propyl acetate (n-propyl acetate, isopropyl acetate), or butyl acetate (n-butyl acetate, isobutyl acetate, sec-butyl acetate, t-butyl acetate) are more preferred; ethyl acetate or butyl acetate (n-butyl acetate, isobutyl acetate, sec-butyl acetate, t-butyl acetate) is even more preferred; and butyl acetate (n-butyl acetate, isobutyl acetate, sec-butyl acetate, t-butyl acetate) is particularly preferred. Among butyl acetate, n-butyl acetate is particularly preferred. The chemical formula for butyl acetate is C ６ H １２ O ２ Therefore, it corresponds to an aliphatic ester solvent having 6 carbon atoms. Among these aliphatic ester solvents, one type or a combination of two or more types can be used, but it is preferable to use only one type. As a condition for obtaining the amorphous powder of the present invention, when carrying out the reaction while precipitating a solid, the amount of aliphatic ester solvent having 4 to 7 carbon atoms used is preferably in the range of 1.2 to 4.0 times the weight of 4,4'-biphenol, more preferably in the range of 1.2 to 3.5 times the weight, and even more preferably in the range of 1.2 to 3.0 times the weight.

[0014] (Catalyst) In the present invention, a catalyst is not particularly necessary to promote the reaction, but an acid catalyst or a base catalyst may be used as needed. In this case, examples of usable acid catalysts include concentrated hydrochloric acid, hydrochloric acid gas, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, benzoic acid, and mixtures thereof, and examples of usable base catalysts include sodium hydroxide, sodium carbonate, triethylamine, triethanolamine, and mixtures thereof. Among these, p-toluenesulfonic acid and sodium hydroxide are preferred, and sodium hydroxide is more preferred.

[0015] (Reaction Conditions and Method) The reaction conditions and method for obtaining the amorphous powder of the present invention will now be described. The reaction temperature is preferably in the range of 15 to 60°C, more preferably in the range of 17 to 55°C, and even more preferably in the range of 20 to 50°C. By carrying out the reaction in this temperature range, the benzoxazine compound (A) can be synthesized with high selectivity, and the reaction is carried out while precipitating the solid benzoxazine compound (A), which contributes to obtaining the amorphous powder of the present invention. The reaction temperature may be kept constant within the above range, or the temperature may be changed within the above range as the reaction progresses. When the reaction temperature is changed, it is preferable to carry out the reaction in the first stage at a low temperature range of 15 to 45°C, and then in the second stage at a temperature range of 45 to 60°C. It is more preferable to carry out the reaction in the first stage at a low temperature range of 15 to 45°C, and then in the second stage at a temperature range of 45 to 55°C. The reaction time varies depending on the amount of raw materials used, the size of the reaction scale, the reaction temperature, the catalyst, and other conditions, and therefore cannot be stated definitively, but it can be carried out in the range of 2 to 50 hours. When the reaction is carried out while changing the reaction temperature, it is preferable to carry out the reaction for 1 to 30 hours in the range of 15 to 45°C in the first stage, and then carry out the reaction for 1 to 20 hours in the range of 45 to 60°C in the first stage. The selectivity of the benzoxazine compound (A) at the end of the reaction is preferably such that the peak area of ​​the benzoxazine compound represented by chemical formula (A) is in the range of 75 to 100 area % of the peak area of ​​all detected components, as measured by gel permeation chromatography using a differential refractometer as the detector for the reaction solution. The lower limit of this range is more preferably 78 area % or more, and even more preferably 80 area % or more. The upper limit of this range may be 98 area % or less, or 95 area % or less. The lower and upper limits of the range described above can be arbitrarily combined to form a numerical range. We believe that one reason we were able to obtain the benzoxazine compound (A) as an amorphous powder is that the peak area value of the benzoxazine compound represented by the chemical formula (A) is above the lower limit of the above range.

[0016] The reaction pressure may be carried out under atmospheric pressure, or under pressurized or reduced pressure. There are no restrictions on the method of mixing the raw materials: 4,4'-biphenol, formaldehydes, and cysteamine. For example, (i) a method in which cysteamine is mixed with a mixture containing 4,4'-biphenol and formaldehydes and the reaction is carried out; (ii) a method in which 4,4'-biphenol is mixed with a mixture containing formaldehydes and cysteamine. These mixtures may contain the solvent and catalyst mentioned above, and there are no restrictions on the method of mixing the catalyst, but it is preferable to mix the catalyst before mixing the cysteamine. In the production method of the present invention, there are no restrictions on the method of mixing the remaining raw materials with the mixture of raw materials, but from the viewpoint of reaction selectivity and suppressing the generation of high molecular weight by-products, it is preferable to mix continuously or intermittently rather than mixing all at once. In the reaction step of the production method of the present invention, it is preferable to continuously stir the reaction solution. The reaction may include a procedure to remove water originating from the raw materials or water generated during the reaction from the system. The procedure for removing the water generated from the reaction solution is not particularly limited and can be carried out by azeotropic distillation of the generated water with the solvent system in the reaction solution. The generated water can be removed from the reaction system using, for example, an isobaric dropping funnel with a stopcock, a Diebroth condenser, or a Dean-Stark apparatus.

[0017] (Post-processing) The reaction-end mixture containing the solid benzoxazine compound (A) obtained in the reaction step may be isolated as is by a filtration step to separate the solid. However, before the filtration step, a washing step may be performed to wash the solid by adding water, an alkaline aqueous solution prepared by dissolving sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, etc. in water, an aliphatic ester solvent with 4 to 7 carbon atoms used in the reaction, or other organic solvents to the reaction-end mixture. A sodium hydroxide aqueous solution is preferred as the alkaline aqueous solution used for washing, and its concentration is preferably in the range of 1 to 10% by weight. An aliphatic ester solvent with 4 to 7 carbon atoms used in the reaction is preferred as the organic solvent used for washing, and it is more preferable to use the same type of solvent as the solvent used in the reaction step from the viewpoint of ease of solvent recycling. After washing with the alkaline aqueous solution, it is preferable to wash with water to prevent alkali from remaining. When washing with water or an alkaline aqueous solution, these are mixed with the reaction-completed mixture, stirred, and the aqueous layer and the oil layer containing the solid benzoxazine compound (A) are separated, and the aqueous layer is removed. When washing with an organic solvent, it is preferable to mix the organic solvent with the reaction-completed mixture and separate the filtrate from the desired powdered solid in a filtration step. There are no restrictions on the amount of water, alkaline aqueous solution, or organic solvent used for washing, but from the viewpoint of limiting the amount of the desired powdered solid obtained and the volume of the manufacturing equipment, it is preferable to use the minimum amount in consideration of the washing effect. For example, when using an aliphatic ester solvent having 4 to 7 carbon atoms, and especially butyl acetate among them, the amount used is preferably in the range of 0.1 to 3.0 times the weight of the amount of 4,4'-biphenol used in the reaction step, more preferably in the range of 0.1 to 2.0 times the weight, even more preferably in the range of 0.1 to 1.5 times the weight, and particularly preferably in the range of 0.1 to 0.8 times the weight. If the amount of aliphatic ester solvent having 4 to 7 carbon atoms used in the reaction step is relatively large within the aforementioned range, the amount of aliphatic ester solvent having 4 to 7 carbon atoms mixed for washing can be reduced, and it is preferable to appropriately adjust the amount used for washing according to the amount used in the reaction step.The powdered solid separated by the filtration process may be subjected to a drying process, which involves heating and / or reducing the pressure as needed to remove the solvent. When carrying out the above-mentioned reaction process, washing process, filtration process, drying process, and other conventional purification methods, it is preferable to do so under an inert gas atmosphere such as nitrogen or argon, or in an atmosphere with less oxygen than air, in order to suppress oxidation, deterioration, discoloration, etc., due to the effects of oxygen.

[0018] The present invention will be further described in detail below with reference to examples. <Analysis Method> 1. Confirmation of the remaining amount of the raw material compound in the reaction solution (liquid chromatography: LC) The remaining amount of the raw material compound, 4,4'-biphenol (hereinafter sometimes referred to as BP), was calculated using a calibration curve of BP prepared in advance by this analysis method. Apparatus: Prominence UFLC (liquid chromatography) manufactured by Shimadzu Corporation Pump: LC-20AD Column oven: CTO-20A Detector: SPD-20A Column: HALO C18 (inner diameter 3 mm, length 75 mm) Oven temperature: 50℃ Flow rate: 0.7 mL / min. Mobile phase: (A) 0.2 vol% aqueous acetic acid solution, (B) tetrahydrofuran gradient Conditions: (B) vol% Method: 10% (0 min.) → (5 min.) → 20% (5 min.) → (8 min.) → 100% (4 min.) Sample injection volume: 7 μL Detection wavelength: 254 nm Measurement sample: 0.1 g of reaction solution was diluted with tetrahydrofuran to 50 mL to prepare the sample solution. 2. Analysis of reaction solution composition and purity (gel permeation chromatography: GPC) The selectivity of benzoxazine compound (A) in the reaction solution and the purity of the obtained benzoxazine compound (A) were expressed as the area percentage of benzoxazine compound (A) obtained by this analysis. Apparatus: HLC-8320 / Tosoh Corporation Detector: Differential refractometer (RI) Flow rate: 1.0 mL / min. Elutate: Tetrahydrofuran Temperature: 40°C Sample: 0.03 g of the benzoxazine compound (A)-containing composition was diluted 600-fold with tetrahydrofuran. For the analysis of the reaction solution and filtrate, 0.2 g of the solution was diluted 260-fold with tetrahydrofuran to prepare the sample solution. 3. Differential Scanning Calorimetry (DSC) The obtained benzoxazine compound (A) powder was analyzed by differential scanning calorimetry (DSC) under the following conditions. [Measurement conditions] Apparatus: DSC7020 / Hitachi High-Tech Science Co., Ltd. Heating rate: 10°C / min. Measurement temperature range: 30-300°C Measurement atmosphere: Nitrogen 50 mL / min. Sample: 3 mg

[0019] <Comparative Example 1> 231 g (2.0 mol) of cysteamine hydrochloride was added to a 2 L four-necked flask, and then 165 g (2.0 mol) of 48% NaOH aqueous solution was slowly added over 5 minutes while stirring, while confirming the temperature rise. After confirming that the pH of the aqueous layer was 9-10, 140 g (4.3 mol) of paraformaldehyde (purity: 92%) was added in small amounts over 30 minutes. During this time, the temperature of the reaction system was confirmed to rise from 30°C to 42°C. After that, the mixture was air-cooled while stirring, and after confirming that the temperature had dropped to 30°C, stirring was continued at 30°C for 1 hour. Then, 508 g of butyl acetate (2.8 times the weight of 4,4'-biphenol) and 184 g of 4,4'-biphenol were added to the flask. After that, the liquid temperature was raised to 60°C and the reaction was carried out for 7 hours, and LC analysis of the reaction solution showed that the remaining BP was 6.4%. Therefore, the reaction was continued at 70°C for 5 hours. The remaining BP was 1.1%, and since almost all of the raw materials had been consumed, the reaction was terminated. The selectivity of the benzoxazine compound (A) in the reaction solution at the end of the reaction by GPC was 68%. After lowering the temperature of the liquid in the flask to 40°C, 400 g of pure water was added to wash the organic layer of the reaction solution, and after stirring for 30 minutes, it was allowed to stand to confirm the separation of the organic layer and the aqueous layer, and then the aqueous layer was removed. This washing operation was repeated four times, and it was confirmed that the pH of the aqueous layer was 7-8. After that, the solvent was removed by distillation under reduced pressure at 60°C. The distillation residue after distillation accumulated at the bottom of the flask and became a solid mass when cooled. Butyl acetate was added to obtain a varnish containing 15% by weight of solids, yielding 291 g of yellow varnish. The purity of the obtained benzoxazine compound (A) was 64 area%.

[0020] <Example 1> 559 g of BP, 470 g (14.4 mol) of paraformaldehyde (purity: 92%), and 1000 g of n-butyl acetate (1.8 times the weight of BP) were charged into a 5 L four-necked flask. 466 g (6.0 mol) of cysteamine was added over 60 minutes in small portions while stirring, while monitoring the temperature rise. During this time, the temperature of the liquid in the flask rose from 20°C to 41°C. The liquid temperature was then maintained at 40°C and stirred for 4 hours, after which it was heated to 50°C and stirred for another 10 hours to complete the reaction. Solid precipitates formed in the reaction solution from the time of cysteamine addition until the end of the reaction, and the reaction solution was in a slurry state. At the end of the reaction, the residual rate of BP by LC analysis of the reaction solution was 4.1%, and the selectivity of benzoxazine compound (A) by GPC was 81.3%. After lowering the temperature of the liquid in the flask to 40°C, 500 g of 3% NaOH aqueous solution was added to wash the organic layer of the reaction slurry, and the mixture was stirred for 15 minutes. After standing, the separation of the organic and aqueous layers was confirmed, and the aqueous layer was removed. This washing procedure was then repeated seven times using pure water. At the end of washing, the residual BP in the reaction solution by LC was 1.4%, and the selectivity of benzoxazine compound (A) by GPC was 80.6%. The slurry state was maintained throughout the washing procedure, similar to the post-reaction state. Subsequently, 1000 g of n-butyl acetate was added to the slurry after washing and stirred. The slurry state remained even after adding n-butyl acetate solvent and stirring. The solid in the flask was filtered off by centrifugal filtration, and the obtained solid was dried at 30°C for 15 hours. 280 g of white powder was obtained after drying. The purity of benzoxazine compound (A) in this obtained powder was 81 area%. Differential scanning calorimetry (DSC) measurements of the obtained powder using the above analytical method did not reveal any endothermic peaks due to crystal melting, thus indicating that the powder was amorphous. The differential scanning calorimetry (DSC) data is shown in Figure 1.

[0021] In Comparative Example 1, a conventional method for producing benzoxazine compound (A), the reaction solution at the end of the reaction was in a solution state. The benzoxazine compound (A) isolated by distillation accumulated at the bottom of the flask and, upon cooling, solidified into a lump, making it difficult to remove from the production equipment, handle, measure, and transport. While this form can be dissolved in a solvent and handled as a varnish, varnish has low production efficiency relative to the volume of the reaction equipment, limits the versatility of processing as a raw material for curable resin compositions, and uses a large amount of organic solvent, posing problems in terms of safety and environmental impact. Furthermore, both the benzoxazine compound (A) isolated by distillation and the prepared varnish were yellow, posing problems in terms of color. In Example 1, a specific example of the present invention, the reaction proceeded while solid precipitation occurred, and the reaction selectivity at the end of the reaction was improved, making it possible to obtain benzoxazine compound (A) as an amorphous powdery solid. Furthermore, it was revealed that the obtained benzoxazine compound (A) powder is white and, compared to those obtained by conventional manufacturing methods, does not have a yellowish tint, thus providing a powder with superior hue.

Claims

1. An amorphous powder of a benzoxazine compound represented by chemical formula (A).

2. The powder according to claim 1, wherein, in a gel permeation chromatography measurement using a differential refractometer as a detector, the peak area of ​​the benzoxazine compound represented by chemical formula (A) is in the range of 75 to 100 area % of the peak area of ​​all detected components.

3. A method for producing a powder according to claim 1 or 2, comprising a reaction step of reacting 4,4'-biphenol, formaldehydes and cysteamine or a salt thereof in the presence of an aliphatic ester solvent having 4 to 7 carbon atoms at a temperature in the range of 15 to 60°C while precipitating a solid of the benzoxazine compound represented by the chemical formula (A).

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