Preparation method of low-absorbance phenol-biphenylene phenolic resin

Abstract

The invention discloses a preparation method of low-absorbance phenol-biphenylene phenolic resin, which comprises the following steps: mixing raw materials including phenol, biphenyl compounds and a cocatalyst, and introducing inert gas from the bottom of a reaction container to carry out condensation polymerization, thereby obtaining the low-absorbance phenol-biphenylene phenolic resin. According to the invention, the inert gas is forcibly filled in the reaction process to take away the micromolecular by-products, and the cocatalyst is combined to improve the reaction efficiency and selectivity, so that the purification step is simplified, the molecular weight distribution of the product is controllable, the production efficiency is improved, and the cost is reduced. The prepared phenol-biphenylene phenolic resin shows the characteristic of low absorbance, especially has high transparency at the wavelength of 400nm, and widens the application in the fields of optics, coatings and the like.

Description

Technical Field

[0001] This invention relates to a method for preparing low absorbance phenol-biphenyl phenolic resin, belonging to the field of phenolic resin preparation technology. Background Technology

[0002] Epoxy resins are widely used in electrical and electronic components, structural composite materials, adhesives, and coatings due to their processability and the excellent electrical properties, heat resistance, adhesion, and moisture resistance (water resistance) of their cured products. Among these, phenol-biphenylene oxide resins with a biphenyl structure and their corresponding epoxy resins have gained recognition in the electronic packaging materials industry due to their excellent heat resistance, moisture resistance, flame retardancy, and impact resistance. However, the reported preparation methods for phenol-biphenylene oxide resins typically involve adding a biphenyl dimethyl substitute, phenol, and an acid catalyst to a reaction vessel and preparing the resin through addition and condensation reactions under reflux condensation conditions. However, this method results in a high phenol feed ratio and high resin absorbance, which can negatively impact the resin's performance in ultraviolet LED applications, especially in packaging applications where lower absorbance at a wavelength (400 nm) is desired.

[0003] Japanese Patent JP2006124492A discloses a biphenyl phenol-formaldehyde resin with a specific molecular weight distribution. The method described in this invention is carried out under reflux condensation conditions, involving neutralization, water washing to remove acid, and reduced pressure to remove solvent and unreacted phenol, yielding a biphenyl phenol-formaldehyde resin with a degree of polymerization n = 1-6. The target product is then obtained through recrystallization. However, this method is complex, employs recrystallization, results in a narrow molecular weight distribution range for the product, low product yield, and difficult byproduct treatment, failing to meet the cost control and environmental protection requirements of industrial production. Summary of the Invention

[0004] To address the shortcomings of existing biphenyl phenol-formaldehyde resin preparation technologies, the present invention aims to provide a method for preparing low-absorbance phenol-biphenylene phenol-formaldehyde resin. This preparation process is simple, allows for flexible control of the molecular weight distribution of phenol-biphenylene phenol-formaldehyde resin, and produces a product with low absorbance (400 nm) and high yield.

[0005] To achieve the above-mentioned technical objectives, this invention provides a method for preparing a low-absorbance phenol-biphenyl phenol-formaldehyde resin. The method involves mixing raw materials including phenol, biphenyl compounds, and a co-catalyst, and then introducing an inert gas through the bottom of a reaction vessel to carry out a polycondensation reaction, thereby obtaining the resin. The biphenyl compounds have the following structural formula:

[0006]

[0007] Wherein, X1 and X2 are both selected from one of -Cl, -Br, -OH, -OCH3, -OC2H5; X1 and X2 may be the same or different.

[0008] The chemical reaction process of this invention is as follows:

[0009]

[0010] The technical solution of this invention mainly involves the simultaneous polycondensation reaction of the ortho- or para-hydrogen at the phenolic hydroxyl group on phenol with X1 and X2 on biphenyl compounds. During the reaction, introducing an inert gas from the bottom not only prevents oxidation of the phenol but also removes small molecule products, promoting the reaction. Furthermore, with the assistance of a co-catalyst, the selectivity and yield of the reaction are improved, and the resulting product has low absorbance, meeting the requirements of the packaging field for low absorbance at a wavelength (400 nm).

[0011] Furthermore, the inventors discovered that the present invention can control the molecular weight distribution of the product by controlling the phenol feeding ratio. The higher the phenol feeding ratio, the narrower the molecular weight distribution of the product. The technical solution of the present invention can achieve low absorbance of products with different molecular weight distributions.

[0012] Further optimization is made, with X1 and X2 being the same.

[0013] As a preferred embodiment, the molar ratio of phenol to biphenyl compound is (2-10):1; more preferably (2-4):1. When the phenol and biphenyl compound are within the scope of this invention, a higher yield of the product can be obtained while reducing the generation of byproducts.

[0014] As a preferred embodiment, the co-catalyst is at least one selected from sodium hypophosphite, sodium hypophosphite, mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol.

[0015] As a preferred embodiment, the amount of the co-catalyst is 0.05–3 wt% of the total weight of the raw materials; more preferably, it is 0.3–1.5 wt%. In this invention, if the amount of catalyst is too small, the reaction proceeds slowly, and the intermediate products cannot be completely converted; while when the amount of catalyst exceeds 1.5 wt%, its effect on promoting the reaction process no longer changes significantly. As a preferred embodiment, when X1 and X2 are selected from one of -OH, -OCH3, and -OC2H5, the raw materials also include an acid catalyst. Adding an acid catalyst can further facilitate the polycondensation reaction.

[0016] As a preferred embodiment, the acid catalyst is at least one selected from hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid; the amount of the acid catalyst is 0.15 to 1.5 wt% of the weight of the biphenyl compound. More preferably, the amount of p-toluenesulfonic acid is 0.75 to 1.0 wt%.

[0017] As a preferred embodiment, the condensation reaction is performed under the following conditions: temperature of 40–150°C and time of 1–12 h. More preferably, the temperature is 80–100°C and the time is 1–3 h.

[0018] As a preferred embodiment, the flow rate of the inert gas is 10–120 ml / min; more preferably 20–60 ml / min. The inert gas flow rate affects the reaction process. By introducing inert gas from the bottom of the container, small molecules generated in the reaction can be carried away, which can promote the reaction and reduce the phenol feed ratio, thus obtaining a product with low absorbance. As a preferred embodiment, the inert gas is at least one of nitrogen, helium, neon, and argon.

[0019] As a preferred embodiment, after the polycondensation reaction is completed, the mixture is washed with an immiscible organic solvent and water to obtain an aqueous phase and an organic phase. The aqueous phase is dehydrated and the co-catalyst is recovered for recycling. The organic phase is washed with water until neutral, and then the organic solvent and unreacted phenol are removed under heating and reduced pressure. The product is then vacuum dried to obtain the phenol-bisphenol A phenolic resin product. This invention utilizes the difference in solubility and polarity between the co-catalyst and the phenol-bisphenol A phenolic resin, and a mixed solution of organic solvent and water can effectively separate both, as well as water-soluble impurities.

[0020] As a preferred embodiment, the organic solvent is at least one selected from 4-methyl-2-pentanone, toluene, xylene, methyl isobutyl ketone, cyclohexane, ethyl acetate, dichloromethane, and tetrahydrofuran.

[0021] As a preferred embodiment, the amount of organic solvent used is 10 to 300 wt% of the total weight of the raw materials, more preferably 100 to 300 wt%.

[0022] Compared with existing technologies, the innovativeness and beneficial technical effects of the present invention are as follows:

[0023] 1) The preparation process of this invention effectively removes small molecule byproducts generated during the reaction by using an inert gas (such as nitrogen) for strong priming, simplifying subsequent purification steps and significantly improving production efficiency. Simultaneously, with the assistance of a co-catalyst, the selectivity and yield of the reaction are improved, resulting in more controllable molecular weight distribution, which is beneficial for preparing resin products with stable performance and uniform quality. Furthermore, the recovery and reuse of the catalyst not only reduces production costs but also reduces waste emissions, conforming to the principles of green chemistry and sustainable development.

[0024] 2) This invention prepares a phenol-biphenol-formaldehyde resin product through a simple process. This resin exhibits significant low absorbance characteristics, especially at a wavelength of 400 nm, where the absorbance is ≤0.4. The transparency of the resin is significantly improved, making it particularly suitable for encapsulation applications requiring low absorbance at 400 nm. More importantly, this technology achieves flexible control over the resin's molecular weight distribution, allowing adjustment of resin properties such as thermal stability, mechanical strength, or viscosity according to different application requirements. This greatly expands the resin's application range and meets the market demand for high-performance resin materials.

[0025] 3) The preparation method provided by the present invention does not require recrystallization and is not limited to the molecular weight distribution of the product, and can obtain phenol-biphenol aldehyde resin with low absorbance. Attached Figure Description

[0026] Figure 1 This is the ultraviolet absorption spectrum of the product in Example 1. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments; these embodiments are only for better understanding of the present invention, and not for limiting the scope of protection of the present invention.

[0028] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0029] The instruments and testing conditions used for the performance testing of this invention are as follows:

[0030] Softening point determination: FP900 thermal analyzer, Mettler, UK;

[0031] Absorbance test: UV-2600 UV-Vis spectrophotometer, Shimadzu, Japan. Test conditions: Prepare a 50% tetrahydrofuran solution of resin and place it in a cuvette. Test wavelength range: 200-800 nm.

[0032] Molecular weight determination: Gel permeation chromatography (GPC): LC-20A, Shimadzu, Japan; test conditions: pressure 39-42 bar, temperature 35℃, mobile phase tetrahydrofuran, flow rate 1 ml / min, injection volume 20 μL.

[0033] Example 1

[0034] 605 g (2.5 mol) of 4',4-bis(methoxymethyl)biphenyl, 893 g (9.5 mol) of phenol, 4.5 g of p-toluenesulfonic acid, and 0.44 g of sodium hypophosphite were added to a reaction flask equipped with a stirrer, thermometer, and condenser. Nitrogen gas was purged from the bottom of the container at a rate of 40 mL / min. The mixture was heated and stirred, and the temperature was slowly increased to 90 °C for 3 h. After the reaction was completed, 1500 mL of 4-methyl-2-pentanone and 300 mL of deionized water were added and stirred for 20 min. After standing and separating the layers, the organic solvent phase was collected and washed with hot water until neutral. The solvent was then recovered by vacuum distillation, and the solid was dried to obtain a light orange-yellow transparent solid.

[0035] Hydroxyl equivalent 210.9, softening point 111.3℃, molecular weight distribution D = 1.305, absorbance 0.256 (400nm). Product yield: 99.2%.

[0036] Example 2

[0037] 605 g (2.5 mol) of 4',4-bis(methoxymethyl)biphenyl, 1410 g (15 mol) of phenol, 6.0 g of p-toluenesulfonic acid, and 2.3 g of mercaptoacetic acid were added to a reaction flask equipped with a stirrer, thermometer, and condenser. Nitrogen gas was purged from the bottom of the container at a rate of 40 mL / min. The mixture was heated and stirred, and the temperature was slowly increased to 90 °C for 2 h. After the reaction was completed, 1500 mL of 4-methyl-2-pentanone and 30 mL of deionized water were added and stirred for 20 min. After standing and separating the layers, the solvent phase was collected and washed with hot water until neutral. The solvent was then recovered by vacuum distillation and dried to obtain a light orange-yellow transparent solid.

[0038] Hydroxyl equivalent 200.6, softening point 133.5℃, molecular weight distribution D = 1.13, absorbance 0.367 (400nm). Product yield: 98.8%.

[0039] Example 3

[0040] 675 g (2.5 mol) of 4',4-bis(methoxyethyl)biphenyl, 893 g (9.5 mol) of phenol, 4.5 g of p-toluenesulfonic acid, and 0.44 g of sodium hypophosphite were added to a reaction flask equipped with a stirrer, thermometer, and condenser. Nitrogen gas was purged from the bottom of the container at a rate of 20 mL / min. The mixture was heated and stirred, and the temperature was slowly increased to 80 °C for 3 h. After the reaction was completed, 1500 mL of 4-methyl-2-pentanone and 300 mL of deionized water were added and stirred for 20 min. After standing and separating the layers, the organic solvent phase was collected and washed with hot water until neutral. The solvent was then recovered by vacuum distillation, and the solid was dried to obtain a light orange-yellow transparent solid.

[0041] Hydroxyl equivalent 224.9, softening point 113.3℃, ​​molecular weight distribution D = 1.28, absorbance 0.253 (400nm). Product yield: 98.2%.

[0042] Example 4

[0043] 535 g (2.5 mol) of 4',4-dihydroxymethylbiphenyl, 893 g (9.5 mol) of phenol, 4.5 g of p-toluenesulfonic acid, and 0.44 g of sodium hypophosphite were added to a reaction flask equipped with a stirrer, thermometer, and condenser. Nitrogen gas was purged from the bottom of the container at a rate of 60 mL / min. The mixture was heated and stirred, and the temperature was slowly increased to 100 °C for 3 h. After the reaction was completed, 1500 mL of 4-methyl-2-pentanone and 300 mL of deionized water were added and stirred for 20 min. After standing and separating the layers, the organic solvent phase was collected and washed with hot water until neutral. The solvent was then recovered by vacuum distillation, and the solid was dried to obtain a light orange-yellow transparent solid.

[0044] Hydroxyl equivalent 197.6, softening point 108.3℃, molecular weight distribution D = 1.27, absorbance 0.251 (400nm). Product yield: 99.3%.

[0045] Comparative Example 1 (No strong emission + no co-catalyst)

[0046] Under nitrogen protection, 605 g (2.5 mol) of 4',4-bis(methoxymethyl)biphenyl, 893 g (9.5 mol) of phenol, and 4.5 g of p-toluenesulfonic acid were added to a reactor equipped with a stirrer, thermometer, and condenser. The mixture was heated and stirred, and the temperature was slowly increased to 90°C for 3 hours. After the reaction was completed, the procedure was the same as in Example 1.

[0047] Hydroxyl equivalent 217.7, softening point 68.6℃, molecular weight distribution D = 1.323, absorbance 1.24 (400nm). Product yield: 98.4%.

[0048] Comparative Example 2

[0049] The only difference between this comparative example and Example 1 is that sodium hypophosphite, a co-catalyst, is not added; all other steps and conditions are the same, resulting in an orange-yellow transparent solid.

[0050] Hydroxyl equivalent 196.39, softening point 108.2℃, molecular weight distribution D = 1.313, absorbance 0.537 (400nm). Product yield: 98.7%.

[0051] Comparative Example 3

[0052] The only difference between this comparative example and Example 1 is that nitrogen gas was changed from container purging to nitrogen protection and a stirrer was used for stirring. The remaining steps and conditions were the same, and an orange-yellow transparent solid was obtained.

[0053] Hydroxyl equivalent 216.39, softening point 69.0℃, molecular weight distribution D = 1.490, absorbance 0.657 (400nm). Product yield: 98.7%.

[0054] The test results of Examples 1-4 and Comparative Examples 1-3 were statistically analyzed, and the results are shown in Table 1.

[0055] Table 1 Performance data of phenol-biphenylacetic acid resin

[0056]

[0057]

[0058] Note: Mn is the number-average molecular weight, and Mw is the weight-average molecular weight.

[0059] As can be seen from the comparison of the data in Table 1 between Example 1 and Comparative Examples 1 to 3, when nitrogen is not introduced from the bottom or no co-catalyst is added, the softening point of the product obtained by the present invention will decrease, while the absorbance will increase significantly.

[0060] The above embodiments are only for better explaining the principles and practical applications of the present invention, so that those skilled in the art can better understand and utilize the present invention, and are not intended to limit the patent scope of the present invention. All equivalent modifications made using the content of the present invention are within the patent protection scope of the present invention.

Claims

1. A method for preparing a low-absorbance phenol-biphenol-formaldehyde resin, characterized in that: The raw materials, including phenol, biphenyl compounds, and a co-catalyst, are mixed, and an inert gas is introduced from the bottom of the reaction vessel to carry out a polycondensation reaction, thereby obtaining the product; the biphenyl compounds have the following structural formula: Wherein, X1 and X2 are both selected from one of -Cl, -Br, -OH, -OCH3, -OC2H5; X1 and X2 may be the same or different.

2. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 1, characterized in that: The molar ratio of phenol to biphenyl compounds is (2-10):

1.

3. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 2, characterized in that: The co-catalyst is at least one selected from sodium hypophosphite, sodium hypophosphite, mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol.

4. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 3, characterized in that: The amount of the co-catalyst is 0.05 to 3 wt% of the total weight of the raw materials.

5. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 1, characterized in that: When X1 and X2 are selected from one of -OH, -OCH3 and -OC2H5, the raw material also includes an acid catalyst.

6. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 5, characterized in that: The acid catalyst is at least one of hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid; The amount of acid catalyst used is 0.15 to 1.5 wt% of the weight of the biphenyl compound.

7. A method for preparing a low-absorbance phenol-biphenol-formaldehyde resin according to any one of claims 1 to 6, characterized in that: The conditions for the polycondensation reaction are: temperature 40–150°C, time 1–12 h.

8. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 7, characterized in that: The flow rate of the inert gas is 10–120 ml / min.

9. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 8, characterized in that: The inert gas is at least one of nitrogen, helium, neon, and argon.

10. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 1, characterized in that: After the polycondensation reaction is completed, the mixture is washed with an immiscible organic solvent and water to obtain an aqueous phase and an organic phase. The aqueous phase is dehydrated and the co-catalyst is recovered for recycling. The organic phase is washed with water until neutral, and then the organic solvent and unreacted phenol are removed under heating and reduced pressure. The mixture is then vacuum dried to obtain the phenol-biphenyl phenol-formaldehyde resin product.

11. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 10, characterized in that: The organic solvent is at least one selected from 4-methyl-2-pentanone, toluene, xylene, methyl isobutyl ketone, cyclohexane, ethyl acetate, dichloromethane, and tetrahydrofuran.

12. The method for preparing a low absorbance phenol-biphenol-formaldehyde resin according to claim 10 or 11, characterized in that: The amount of the organic solvent used is 10 to 300 wt% of the total weight of the raw materials.

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