A method for synthesizing a low softening point, fast-curing phenolic resin

Abstract

The present application relates to a kind of low softening point, the synthesis method of fast curing phenolic resin, it includes the following steps: 1) in reactor, phenol, basic catalyst, nitrogen atmosphere, temperature is raised to 40-70 ℃, under stirring condition, add formaldehyde aqueous solution, then at 50-70 ℃, 60-240 min is reacted, obtain resin A;2) in reactor, phenol, the resin A obtained in step 1) and acidic catalyst are added, temperature is raised to 90-100 ℃, under stirring condition, add formaldehyde aqueous solution, then at 90-100 ℃, 60-240 min is reacted, reduced pressure distillation, obtain immediately.The method synthesizes a new phenolic resin, makes it have lower softening point, faster poly speed, improves the crosslinking density of polymer, to improve the heat resistance of polymer.

Description

Technical Field

[0001] This invention belongs to the field of phenolic resin synthesis technology, specifically relating to a method for synthesizing a low softening point, rapidly curing phenolic resin. Background Technology

[0002] Phenolic resin is the earliest type of synthetic resin to be industrialized. Due to its abundant and inexpensive raw material sources, relatively simple production processes and equipment, and unique properties such as heat resistance, ablation resistance, electrical insulation, and good dimensional stability, it has become an indispensable material in transportation, textiles, construction, and defense industries.

[0003] The electronics industry is developing rapidly, and the rapid development of electronic materials has placed higher performance demands on phenolic resins. Besides short gelation time and excellent mechanical properties, phenolic resins must also contain as few impurities as possible to minimize their impact on the electrical properties of electronic materials. Compared with other ablation-resistant materials, high-molecular-weight phenolic resins have higher molecular structure order, lower steric hindrance, faster curing speed, higher degree of curing, faster product molding, and superior quality. They also possess excellent mechanical and heat resistance properties, making them a major development direction for general-purpose phenolic resins in recent years and a field of intense research both domestically and internationally.

[0004] Bender, Burke, and others studied the effects of various catalysts, or the introduction of halides and multi-component composite catalysts, such as ZnO / MgBr2, ZnO / MgBr2, and Mn(Ac), on the ortho- and para-position structures and contents of phenolic resins. Subsequently, Fraser discovered that divalent metal ion catalysts are very effective in forming ortho-position structures. Using weak acid salts of divalent metals, especially their acetates, as catalysts can both leverage the electrophilic substitution effect of the ortho-position hydroxyl groups in the phenol ring and guide ortho-position condensation. Zhang Qiaoling et al. synthesized a high-ortho-position thermoplastic phenolic resin using zinc acetate and hydrochloric acid as catalysts in a two-step addition process.

[0005] Currently, most domestic methods for synthesizing high-ortho-phenolic resins use zinc acetate and manganese sulfate as the primary catalyst, and hydrochloric acid, sulfuric acid, and oxalic acid as the secondary catalyst, employing a one-step or two-step addition method. The synthesized phenolic resins exhibit low softening points and short polymerization rates. However, this method carries inherent risks during synthesis. Furthermore, the use of zinc acetate and manganese sulfate as the primary catalyst introduces a large amount of metal ions, failing to meet the requirements for electronic-grade phenolic resins and necessitating multiple subsequent water washes, resulting in waste. Simultaneously, the large amount of metal ions easily causes the resin product to absorb water, leading to a decline in finished product performance.

[0006] Therefore, it is essential to find new modification methods. This invention utilizes the characteristics of star polymers—low softening point and fast polymerization rate—to synthesize a novel phenolic resin, giving it a lower softening point and a faster polymerization rate. Summary of the Invention

[0007] In view of this, the purpose of this invention is to overcome the deficiencies of the prior art and provide a method for synthesizing phenolic resin with a low softening point and rapid curing. This method involves reacting phenol and formaldehyde aqueous solution under alkaline conditions to obtain a phenolic resin of water-soluble polyhydroxymethylphenol, which is then synthesized with phenol and formaldehyde under acidic conditions to obtain the final phenolic resin.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for synthesizing a low softening point, rapidly curing phenolic resin, comprising the following two steps (synthetic route see...). Figure 1 ):

[0010] 1) Synthesis of water-soluble phenolic resin:

[0011] Phenol and alkaline catalyst are added to the reactor, nitrogen gas is introduced, stirring is started, and the temperature is raised to 40-70℃ under nitrogen atmosphere. Formaldehyde aqueous solution is added under stirring, and then the reaction is carried out at 50-70℃ for 60-240 min to obtain resin A.

[0012] 2) Synthesis of low softening point, fast-curing phenolic resin:

[0013] Phenol, resin A obtained in step 1), and acidic catalyst are added to the reactor. Stirring is started, and the temperature is raised to 90-100℃. Formaldehyde aqueous solution is added under stirring conditions, and then the reaction is carried out at 90-100℃ for 60-240 minutes. The phenol is removed by vacuum distillation to 140-190℃, thus obtaining a low softening point and fast-curing phenolic resin.

[0014] Specifically, in step 1), the mass ratio of phenol, formaldehyde aqueous solution, and alkaline catalyst is 1:2~3.5:0.005~0.11.

[0015] Furthermore, the alkaline catalyst may be one or a mixture of two or more of the following: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, barium hydroxide, triethylamine, dimethylethanolamine, triethanolamine, triisopropanolamine, etc.

[0016] Specifically, in step 2), the mass ratio of phenol, formaldehyde aqueous solution, and acidic catalyst is 1:0.5-0.8:0.005~0.02. The amount of resin A added is 8%-30% of the mass of phenol.

[0017] Furthermore, the acidic catalyst can be one or a mixture of two or more of the following: oxalic acid, phosphoric acid (50-85%), hydrochloric acid (30-50%), sulfuric acid (20%-98%), and p-toluenesulfonic acid. Acid concentration refers to the mass percentage.

[0018] Specifically, in steps 1) and 2), the formaldehyde aqueous solution has a mass percentage concentration of 18%-55%.

[0019] Furthermore, in steps 1) and 2), the formaldehyde aqueous solution can be added dropwise over 60-150 minutes.

[0020] Furthermore, in step 2), the temperature can be raised to 90-100℃ within 60-100 minutes.

[0021] The present invention also provides a low softening point, fast-curing phenolic resin synthesized by the above method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention provides a method for synthesizing a low-softening-point, rapidly curing phenolic resin. The method involves reacting phenol and formaldehyde aqueous solutions under alkaline conditions to obtain a water-soluble polyhydroxymethylphenol phenolic resin, which is then synthesized with phenol and formaldehyde under acidic conditions to obtain the final phenolic resin. This invention utilizes the characteristics of star polymers—low softening point and fast polymerization rate—to synthesize a novel phenolic resin with a lower softening point and faster polymerization rate. Attached Figure Description

[0024] Figure 1 This invention provides a synthetic route for a low softening point, rapidly curing phenolic resin.

[0025] Figure 2 The GPC spectrum of the phenolic resin synthesized in Example 4 is shown below.

[0026] Figure 3 The image shows the GPC spectrum of the phenolic resin synthesized in Example 5. Detailed Implementation

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. That is, the scope of protection of the invention is not limited to the technical solutions listed in the embodiments.

[0028] Example 1

[0029] The synthesis of water-soluble phenolic resin is as follows:

[0030] Add 100g of phenol and 7g of triethylamine to a 500ml three-necked flask, purge with nitrogen, add a magnetic stir bar, start stirring, heat to 70℃ under nitrogen atmosphere, add 300g of formaldehyde aqueous solution (37%) dropwise over 90min under stirring, and after the addition is complete, keep the reaction at 70℃ for 120min to obtain a brownish-red blocky liquid, which is denoted as resin A.

[0031] Resin A test results: Free phenol 1.5%, solid content 48%, infinitely water soluble.

[0032] Example 2

[0033] The synthesis of water-soluble phenolic resin is as follows:

[0034] Add 100g of phenol and 2g of sodium hydroxide to a 500ml three-necked flask, purge with nitrogen, add a magnetic stir bar, start stirring, heat to 70℃ under nitrogen atmosphere, add 300g of formaldehyde aqueous solution (37%) dropwise over 90min under stirring, and after the addition is complete, react at 60℃ for 120min to obtain a brownish-red blocky liquid, which is denoted as resin B.

[0035] Resin A test results: Free phenol 1.3%, solid content 48%, infinitely water soluble.

[0036] Example 3

[0037] The synthesis of water-soluble phenolic resin is as follows:

[0038] Add 100g of phenol and 11g of dimethylethanolamine to a 500ml three-necked flask, purge with nitrogen, add a magnetic stir bar, start stirring, heat to 70℃ under nitrogen atmosphere, and add 280g of formaldehyde aqueous solution (37%) dropwise over 90min while stirring. After the addition is complete, react at a constant temperature of 65℃ for 120min to obtain a brownish-red blocky liquid, which is denoted as resin C.

[0039] Resin A test results: Free phenol 1.6%, solid content 46%, infinitely water soluble.

[0040] Example 4

[0041] The synthesis of low softening point, fast-curing phenolic resin is as follows:

[0042] Add 984g of phenol and 100g of resin A to a 2000ml three-necked flask, add a magnetic stir bar, and start stirring. Under stirring conditions, add 15g of oxalic acid, heat to 90℃, and add 550g of formaldehyde aqueous solution (37%) dropwise over 60min. After the addition is complete, heat to 98℃ and keep the temperature constant for 3h. After the reaction is complete, heat to 140-180℃ and start vacuum distillation to remove phenol and water, obtaining a blocky solid, which is the low softening point, fast-curing phenolic resin.

[0043] Tests on the obtained resin: softening point 85℃, polymerization rate (150℃, 10% added six times): 50s, metal ions 200ppm.

[0044] Figure 2 The GPC spectrum of the phenolic resin synthesized in this embodiment is shown in the figure. As shown in the figure, the molecular weight is about 800, indicating that the phenolic resin was successfully synthesized.

[0045] Example 5

[0046] The synthesis of low softening point, fast-curing phenolic resin is as follows:

[0047] Add 984g of phenol and 100g of resin C to a 2000ml three-necked flask, add a magnetic stir bar, and start stirring. Under stirring conditions, add 12g of oxalic acid, raise the temperature to 96-98℃, and add 600g of formaldehyde aqueous solution (37%) dropwise over 60min. After the addition is complete, maintain the temperature for 3h. After the reaction is complete, raise the temperature to 140-180℃ and start vacuum distillation to remove phenol and water, obtaining a yellow blocky solid, which is the low softening point, fast-curing phenolic resin.

[0048] The resulting resin was tested for softening point 87℃ and polymerization rate (150℃, 10% added six times): 32s.

[0049] Figure 3 The GPC spectrum of the phenolic resin synthesized in this embodiment is shown. This figure illustrates the successful synthesis of the phenolic resin.

[0050] Example 6

[0051] The synthesis of low softening point, fast-curing phenolic resin is as follows:

[0052] Add 984g of phenol and 100g of resin C to a 2000ml three-necked flask, add a magnetic stir bar, and start stirring. Under stirring conditions, add 5g of p-toluenesulfonic acid, heat to 96-98℃, and add 630g of formaldehyde aqueous solution (37%) dropwise over 60min. After the addition is complete, keep the temperature constant for 3h. After the reaction is complete, heat to 140-180℃ and start vacuum distillation to remove phenol and water, obtaining a brown blocky solid, which is the low softening point, fast-curing phenolic resin.

[0053] The resulting resin was tested as follows: softening point 92℃, polymerization rate (150℃, 10% added six times): 26s, molecular weight 900.

[0054] Example 7

[0055] The synthesis of low softening point, fast-curing phenolic resin is as follows:

[0056] Add 1000g of phenol and 100g of resin A to a 2000ml three-necked flask, add a magnetic stir bar, and start stirring. Under stirring conditions, add 8g of hydrochloric acid aqueous solution (37%), heat to 96-98℃, and add 600g of formaldehyde aqueous solution (37%) dropwise over 60min. After the addition is complete, maintain the temperature for 3h. After the reaction is complete, heat to 140-180℃ and start vacuum distillation to remove phenol and water, obtaining a yellow-brown blocky solid, which is the low softening point, fast-curing phenolic resin.

[0057] The resulting resin was tested as follows: softening point 90℃, polymerization rate (150℃, 10% added six times): 26s, molecular weight 890.

Claims

1. A process for the synthesis of a low softening point, fast curing phenolic resin, characterized in that, The method comprises the following steps: 1) adding phenol, alkaline catalyst into a reactor, heating to 40-70℃ under nitrogen atmosphere, adding aqueous formaldehyde solution under stirring, then reacting at 50-70℃ for 60-240min to obtain resin A; 2) adding phenol, resin A obtained in step 1) and acidic catalyst into a reactor, heating to 90-100℃, adding aqueous formaldehyde solution under stirring, then reacting at 90-100℃ for 60-240min, and distilling under reduced pressure to obtain the product; In step 1), the mass ratio of phenol, aqueous formaldehyde solution and alkaline catalyst is 1:2-3.5:0.005-0.11; In step 2), the mass ratio of phenol, aqueous formaldehyde solution and acidic catalyst is 1:0.5-0.8:0.005-0.02; the amount of resin A added is 8%-30% of the mass of phenol; In steps 1) and 2), the mass concentration of aqueous formaldehyde solution is 18%-55%.

2. The process for the synthesis of low softening point, fast curing phenol formaldehyde resin as claimed in claim 1, wherein, The alkaline catalyst is one or a mixture of two or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, barium hydroxide, triethylamine, dimethyl ethanolamine, triethanolamine and triisopropanolamine.

3. The process for the synthesis of low softening point, fast curing phenol formaldehyde resin as claimed in claim 1, wherein, The acidic catalyst is one or a mixture of two or more of oxalic acid, phosphoric acid, hydrochloric acid, sulfuric acid and p-toluenesulfonic acid.

4. The process for the synthesis of low softening point, fast curing phenol formaldehyde resin as claimed in claim 1, wherein, In steps 1) and 2), the aqueous formaldehyde solution is added dropwise within 60-150min.

5. The process for the synthesis of low softening point, fast curing phenol formaldehyde resin as claimed in claim 1, wherein, In step 2), the temperature is raised to 90-100℃ within 60-100min.

6. The low-softening-point, fast-curing phenolic resin synthesized by the method of any one of claims 1 to 5.

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