High-performance modified o-cresol formaldehyde resin as well as preparation method and application thereof

Abstract

The invention relates to high-performance modified o-cresol formaldehyde resin as well as a preparation method and application thereof. The preparation method adopts a step-by-step polymerization and molecular design strategy, takes organic acid as a catalyst, performs controllable polycondensation by adding formaldehyde in batches and introducing a molecular weight regulator (such as phenol and p-tert-butylphenol), and finally stabilizes the tail end of a molecular chain by adopting an end capping technology. The method successfully synthesizes the modified o-cresol formaldehyde resin with high ortho-position structure content and narrow molecular weight distribution (the molecular weight distribution index PDI is less than or equal to 2.0). When epoxidation is carried out by using the epoxy resin as an intermediate, the reaction efficiency is high, side reactions are few, and the obtained epoxy resin shows the excellent characteristics of high epoxy value and low hydrolyzed chlorine. The finally cured product shows higher glass transition temperature, lower water absorption, improved toughness and excellent dielectric properties, and comprehensively meets the harsh requirements of high-end electronic packaging materials, copper-clad plates and high-performance composite materials on heat resistance, reliability and electrical insulation.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis and modification technology, specifically to a method for preparing a modified o-cresol resin with a high ortho-position structure and narrow molecular weight distribution. Background Technology

[0002] o-Cresol-formaldehyde epoxy resin is an important polymer material produced by reacting o-cresol-formaldehyde resin with epichlorohydrin. Due to its excellent heat resistance, dielectric properties, and adhesive strength, it has become an indispensable key material in semiconductor packaging, high-performance electronic laminates, and other fields. The final properties of o-cresol-formaldehyde epoxy resin largely depend on the molecular structure of its intermediate—o-cresol-formaldehyde resin.

[0003] Traditional methods for producing o-cresylform resins have the following problems, leading to limitations in the performance of their epoxidized products: 1. Wide molecular weight distribution: Traditional acid-catalyzed condensation polymerization reactions struggle to control the uniformity of molecular chain growth, resulting in resins containing both low-molecular-weight oligomers and ultra-high-molecular-weight fractions. Epoxidation of the low-molecular-weight fraction leads to uneven crosslinking density and decreased heat resistance in the cured product; the ultra-high-molecular-weight fraction may result in incomplete epoxidation, leaving residual phenolic hydroxyl groups, which worsens the product's hydrolytic stability and dielectric properties. 2. Low proportion of ortho-position structures: Both ortho and para-positions of phenolic hydroxyl groups can react with formaldehyde. Molecular chains with higher ortho-position structures exhibit better flexibility, and the network structure of the cured epoxidized product can better dissipate energy under stress, thus imparting higher toughness to the material. Traditional catalytic systems have low ortho-selectivity. 3. Residual catalyst metal ions: Some metal salt catalysts remain in the resin, entering the final product after epoxidation, severely impairing the electrical insulation properties and long-term damp heat resistance of the cured epoxy resin.

[0004] Therefore, modifying the molecular structure of o-cresol resin to synthesize intermediates with regular structure, narrow molecular weight distribution, high ortho ratio, and high purity (low metal ion residue) is a key prerequisite and a technical challenge in the preparation of high-performance o-cresol epoxy resin. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a modified o-cresphenolic resin with a regular molecular structure. This resin has the characteristics of high ortho-position structure, narrow molecular weight distribution and low metal ion content. The epoxidation product prepared with it as an intermediate has a more uniform and dense cross-linked network structure after curing, thus exhibiting excellent heat resistance, low water absorption, high toughness and excellent electrical insulation properties.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned modified o-cresol resin.

[0007] Another object of the present invention is to provide an epoxy resin obtained by epoxidation of the above-mentioned modified o-cresol resin and its application.

[0008] The technical solution of the present invention is as follows: A method for preparing a high-ortho, narrow-distribution modified o-cresol formaldehyde resin, characterized by employing stepwise polymerization and end-capping technology, comprising the following steps: Stage 1 - Prepolymerization (Generating a Controllable Prepolymer): o-Cresol and a first portion of formaldehyde are reacted at 70-80°C for 2-4 hours in the presence of an acidic catalyst. The acidic catalyst is one or more of oxalic acid, p-toluenesulfonic acid, or hydrochloric acid in any proportion. Its function is to efficiently catalyze the formation of a high-ortho-methylene bond. The molar ratio of o-cresol to the first portion of formaldehyde is 1:(0.4-0.6).

[0009] Second stage - Chain growth and molecular weight control: A second portion of formaldehyde is slowly added to the product obtained in the first stage, while a molecular weight regulator is added simultaneously. The molecular weight regulator is a compound containing a single phenolic hydroxyl group, such as phenol, p-tert-butylphenol, or p-nonylphenol. The amount added is 1%-5% of the total molar amount of o-cresol. The temperature is controlled at 80-90℃ during this stage, and the reaction lasts for 2-4 hours.

[0010] The third stage - end-capping reaction: After the reaction is complete, an end-capping agent is added, and the reaction is carried out at 90-100℃ for 1-2 hours to eliminate residual hydroxymethyl and free formaldehyde, ensuring the stability of the molecular chain ends. The end-capping agent is phenol or the above-mentioned molecular weight regulator.

[0011] Post-processing: After the reaction is complete, the system is neutralized to weakly acidic with organic acid, the catalyst metal ions are thoroughly removed by washing with water, and finally the modified o-cresol resin is obtained by dehydration under reduced pressure.

[0012] Preferably, the total molar ratio of o-cresol to formaldehyde is 1:(0.7-0.9).

[0013] Preferably, the addition of the molecular weight regulator and the capping agent effectively controls the growth of the molecular chain through their steric hindrance effect and difference in reactivity, so that the ratio of the weight-average molecular weight to the number-average molecular weight of the resulting resin is less than or equal to 2.0, preferably less than or equal to 1.8.

[0014] The beneficial effects of this invention are: 1. Superior Molecular Structure: High ortho-selectivity of methylene bonds is ensured through organic acid catalysts and a stepwise feeding process. The introduction of molecular weight regulators and end-capping technology precisely controls the molecular chain length and terminal groups, resulting in a resin with a narrow molecular weight distribution and highly regular structure.

[0015] 2. High epoxidation efficiency and excellent product quality: The narrow distribution of resin intermediates makes the epoxidation reaction more uniform and thorough, with fewer side reactions, resulting in a stable epoxy value, low organic chlorine content, and low hydrolytic chlorine content in the final epoxy resin.

[0016] 3. High heat resistance and low water absorption: The uniform cross-linked network results in a higher glass transition temperature of the cured material, and the dense network significantly reduces water absorption, providing excellent reliability in humid heat.

[0017] 4. High toughness: The high ortho structure gives the molecular chain a certain degree of flexibility, making the solidified material less prone to cracking when subjected to mechanical or thermal stress, and improving its impact resistance.

[0018] 5. Excellent electrical properties: The extremely low metal ion residue and regular molecular structure result in lower dielectric constant and dielectric loss factor of the cured material, and better insulation performance.

[0019] 6. Controllable process, suitable for industrialization: The preparation method has clear steps, easy-to-control parameters, stable product quality, and is suitable for large-scale production. Detailed Implementation

[0020] Example 1 Add 540g of o-cresol (5mol), 162g of 37% formaldehyde aqueous solution (2mol formaldehyde), and 5.4g of p-toluenesulfonic acid to the reaction vessel. Heat to 80℃ and react for 2.5 hours.

[0021] Slowly add a second batch of 121.5g of 37% formaldehyde aqueous solution (1.5mol formaldehyde), while simultaneously adding 9.4g of phenol (as a molecular weight regulator, accounting for 2% of the molar amount of o-cresol) in portions over 1 hour. After the addition is complete, continue the reaction at 85℃ for 3 hours.

[0022] An additional 5.4g of phenol was added as a capping agent, and the reaction was carried out at 95°C for 1.5 hours.

[0023] The solution was neutralized to pH 6 with oxalic acid, and washed five times with deionized water at 80°C until the conductivity of the aqueous phase was <10 μS / cm. Finally, the solution was dehydrated under reduced pressure at 180°C / -0.098 MPa to obtain modified resin A.

[0024] Example 2 Add 540g of o-cresol (5mol), 162g of 37% formaldehyde aqueous solution (2mol formaldehyde), and 5.4g of p-toluenesulfonic acid to the reaction vessel. Heat to 80℃ and react for 2.5 hours.

[0025] Slowly add a second batch of 121.5 g of 37% formaldehyde aqueous solution (1.5 mol formaldehyde), while simultaneously adding 16.5 g of p-tert-butylphenol (as a molecular weight regulator, accounting for 2% of the molar amount of o-cresol) in portions over 1 hour. After the addition is complete, continue the reaction at 85°C for 3 hours.

[0026] Add an additional 7.5g of p-tert-butylphenol as a capping agent and react at 95°C for 1.5 hours.

[0027] The solution was neutralized to pH 6 with oxalic acid, and washed five times with deionized water at 80°C until the conductivity of the aqueous phase was <10 μS / cm. Finally, the solution was dehydrated under reduced pressure at 180°C / -0.098 MPa to obtain modified resin B.

[0028] Example 3 Add 540g of o-cresol (5mol), 243g of 37% formaldehyde aqueous solution (3mol formaldehyde), and 5g of p-toluenesulfonic acid to the reaction vessel. Heat to 80℃ and react for 3 hours.

[0029] Slowly add a second batch of 81g of 37% formaldehyde aqueous solution (1 mol of formaldehyde), while simultaneously adding 9.4g of phenol (as a molecular weight regulator, accounting for 2% of the molar amount of o-cresol) in portions over 1 hour. After the addition is complete, continue the reaction at 85°C for 3 hours.

[0030] An additional 5.4g of phenol was added as a capping agent, and the reaction was carried out at 95°C for 1.5 hours.

[0031] The solution was neutralized to pH 6 with oxalic acid, and washed five times with deionized water at 80°C until the conductivity of the aqueous phase was <10 μS / cm. Finally, the solution was dehydrated under reduced pressure at 180°C / -0.098 MPa to obtain modified resin C.

[0032] Example 4 Add 540g of o-cresol (5mol), 243g of 37% formaldehyde aqueous solution (3mol formaldehyde), and 5g of p-toluenesulfonic acid to the reaction vessel. Heat to 80℃ and react for 3 hours.

[0033] Slowly add a second batch of 81g of 37% formaldehyde aqueous solution (1 mol of formaldehyde), while simultaneously adding 18.8g of phenol (as a molecular weight regulator, accounting for 4% of the molar amount of o-cresol) in portions over 1 hour. After the addition is complete, continue the reaction at 85°C for 3 hours.

[0034] An additional 5.4g of phenol was added as a capping agent, and the reaction was carried out at 95°C for 1.5 hours.

[0035] The solution was neutralized to pH 6 with oxalic acid, and washed five times with deionized water at 80°C until the conductivity of the aqueous phase was <10 μS / cm. Finally, the solution was dehydrated under reduced pressure at 180°C / -0.098 MPa to obtain modified resin D.

[0036] Comparative Example 1 Add 470g of o-cresol (5.0mol), 405g of 37wt% formaldehyde aqueous solution (5.0mol formaldehyde) and 7.0g of oxalic acid to the reaction vessel.

[0037] The mixture was heated to 100℃±2℃ at a rate of 3℃ / min and refluxed for 5 hours.

[0038] After the reaction was complete, the mixture was cooled to 80°C and neutralized to pH 7.0 with a 10 wt% sodium hydroxide solution. It was then washed three times with hot water at 70°C. Finally, it was dehydrated at 180°C / -0.095 MPa for 1 hour to obtain resin E. This comparative example represents the most traditional production process.

[0039] Comparative Example 2 Add 470g of o-cresol (5mol), 162g of 37% formaldehyde aqueous solution (2mol formaldehyde), and 5g of p-toluenesulfonic acid to the reaction vessel. Heat to 80℃ and react for 2.5 hours.

[0040] Slowly add a second batch of 121.5g of 37% formaldehyde aqueous solution (1.5mol formaldehyde). After the addition is complete, continue the reaction at 85℃ for 3 hours.

[0041] An additional 4.7g of phenol was added as a capping agent, and the reaction was carried out at 95°C for 1.5 hours.

[0042] The solution was neutralized to pH 6 with oxalic acid, and washed five times with deionized water at 80°C until the conductivity of the aqueous phase was <10 μS / cm. Finally, the solution was dehydrated under reduced pressure at 180°C / -0.098 MPa to obtain modified resin F.

[0043] Comparative Example 3 Add 470g of o-cresol (5.0mol), 405g of 37wt% formaldehyde aqueous solution (5.0mol formaldehyde) and 5.0g of concentrated sulfuric acid to the reaction vessel.

[0044] The mixture was heated to 100℃±2℃ at a rate of 3℃ / min and refluxed for 5 hours.

[0045] After the reaction was complete, the mixture was cooled to 80°C and neutralized to pH 7.0 with a 10 wt% sodium hydroxide solution. It was then washed twice with hot water at 70°C. Finally, it was dehydrated at 180°C / -0.095 MPa for 1 hour to obtain resin G.

[0046] Performance testing and characterization involved rigorous testing of all resin samples, with standardized evaluation of epoxidation and curing.

[0047] PDI Adjacent percentage (%) Electrical conductivity (µs / cm) Epoxy value (eq / 100g) Hydrolyzed chlorine (ppm) Tg (°C) of solidified product Water absorption rate of solidified material (%) Resin A 1.74 92.5 12 0.45 380 176 0.33 Resin B 1.79 91.8 14 0.44 410 174 0.35 Resin C 1.80 93.1 18 0.45 395 172 0.34 Resin D 1.86 92.0 11 0.46 350 178 0.38 Resin E 3.72 65.3 105 0.43 850 162 0.72 Resin F 2.30 91.5 15 0.44 520 165 0.45 Resin G 3.50 64.8 350 0.42 970 160 0.85 The test results fully demonstrate that the modified resin intermediate of the present invention can significantly improve the overall performance of its epoxidation product and its final cured product.

Claims

1. A method for preparing high-performance modified o-cresylformaldehyde resin, characterized in that, The stepwise polymerization and molecular weight control technology includes the following steps: o-Cresol and the first batch of formaldehyde undergo a pre-condensation reaction in the presence of an acidic catalyst; A second batch of formaldehyde and a molecular weight regulator are added to the product obtained in step a to carry out a chain growth reaction. The molecular weight regulator is a compound containing a single phenolic hydroxyl group. A capping agent is added to carry out a capping reaction to eliminate residual active groups; d. The reaction product is neutralized, washed with water, and dehydrated to obtain the modified o-cresol resin.

2. The method according to claim 1, characterized in that, The molar ratio of o-cresol to the first batch of formaldehyde in step a is 1:(0.4-0.6); the molar ratio of the total amount of formaldehyde to o-cresol in steps a and b is (0.7-0.9):

1.

3. The method according to claim 1, characterized in that, The acidic catalyst is one or more of oxalic acid, p-toluenesulfonic acid, or hydrochloric acid in any proportion.

4. The method according to claim 1, characterized in that, The temperature of the pre-condensation reaction is 70-80℃, and the reaction time is 2-4h.

5. The method according to claim 1, characterized in that, The chain growth reaction is carried out at a temperature of 80–90°C for 2–4 hours.

6. The method according to claim 1, characterized in that, The molecular weight regulator is one of phenol, p-tert-butylphenol, and p-nonylphenol, and its addition amount is 1%-5% of the total moles of o-cresol.

7. The method according to claim 1, characterized in that, The end-capping reaction is carried out at a temperature of 90-100℃ for 1-2 hours.

8. The method according to claim 1, characterized in that, The capping agent mentioned in step c is phenol.

9. The method according to claim 1, characterized in that, In step d, the conductivity of the aqueous extract of the final product is reduced to less than 20 μS / cm by washing with water.

10. A modified o-cresol formaldehyde resin prepared by the method according to any one of claims 1-9, characterized in that, Its molecular weight distribution index is less than or equal to 2.

0.

11. An epoxy resin, prepared by epoxidation reaction of the modified o-cresol resin of claim 10 and epichlorohydrin.

12. An epoxy resin composition comprising the epoxy resin of claim 11 and a curing agent.

13. A cured product of the epoxy resin composition of claim 11, used in electronic packaging materials, copper-clad laminate prepregs, or high-performance composite materials.