Dynamically toughened phenolic resin, emulsion, preparation method and application

Abstract

The invention discloses a dynamically toughened phenolic resin, an emulsion, a preparation method and an application, and belongs to the technical field of high polymer material synthesis. The dynamically toughened phenolic resin is formed by chemical grafting of DMMn and phenolic resin, the structural formula of the dynamically toughened phenolic resin contains a specific acetal chain segment, and the dynamically toughened phenolic resin has dynamic toughening and latent curing functions. The invention provides two synthesis methods which are respectively used for preparing the dynamically toughened phenolic resin through an alkaline prepolymerization-acidic grafting-alkaline termination or acidic copolymerization-alkaline aldehyde supplement process. The dynamically toughened phenolic resin emulsion is prepared from the resin, an emulsifier, a hydrophobic organic solvent and water through emulsification and desolvation processes. The emulsion can be used for preparing a water-based heat-vulcanized primer, and the obtained product is low in VOC content and good in film flexibility, has high bonding strength and excellent medium resistance after being bonded with rubber in a heat-vulcanized manner, and is particularly suitable for bonding of automobile rubber metal parts. The technical problem that the traditional water-based phenolic resin is poor in toughness and difficult to consider the crosslinking density at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a dynamically toughened phenolic resin, emulsion, preparation method, and application. Background Technology

[0002] Phenolic resins are widely used in rubber-metal hot vulcanization bonding due to their excellent mechanical strength, heat resistance, and adhesive properties. However, traditional solvent-based phenolic resins suffer from high VOC emissions and significant safety risks. Waterborne formulations are an inevitable trend, but waterborne phenolic resins, especially emulsion types, face challenges such as emulsification difficulties, poor storage stability, and inherently rigid resins leading to brittle coatings and easy cracking on flexible substrates. While attempts have been made to toughen phenolic resins through physical blending or chemical grafting of flexible segments, these often come at the cost of sacrificing the crosslinking density and resistance to media in the final cured product. Chinese invention patent CN103012704B discloses a method for preparing toughened thermosetting phenolic resins, using glycidyl tert-carbonate as a toughening agent to participate in the polymerization reaction, becoming part of the resin and improving its inherent toughness; however, it does not achieve a simultaneous increase in toughening and crosslinking density.

[0003] Therefore, developing a waterborne phenolic resin system that is easy to emulsify, stable in storage, and possesses excellent toughness, high adhesive strength, and high final crosslinking density has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as high VOC emissions from solvent-based phenolic resins, difficulty in emulsifying waterborne phenolic resins, poor toughness, and difficulty in balancing crosslinking density and toughness, and to provide a dynamically toughened phenolic resin, emulsion, preparation method, and application.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a dynamically toughened phenolic resin, the general structural formula of which is as follows:

[0006] Wherein, R1 is hydroxyl, hydroxymethyl, or (CH2O). x -CH3, where x is an integer from 0 to 8; R represents CH2 or (CH2O). y -CH2, where y is an integer from 0 to 8; and at least one of R and R1 is an acetal segment; R2 is a hydrogen atom, hydroxymethyl, or alkyl group; R3 represents a hydrogen atom, a hydroxyl group, and a carbon atom. 15 Aliphatic side chains and their modified products; m is an integer between 0 and 8.

[0007] The dynamically toughened phenolic resin provided by this invention forms a structure containing specific acetal segments by chemically grafting DMMn onto the phenolic resin. The introduced acetal segments act as flexible segments at room temperature, significantly improving the flexibility and crack resistance of the resin dry film. Under subsequent heat vulcanization conditions, these segments can hydrolyze in an acidic environment, releasing formaldehyde to promote more complete cross-linking and curing of the resin, improving the resistance of the final adhesive network to various media. Furthermore, the toughening segments themselves are dynamically consumed, thus fundamentally and synergistically resolving the contradiction between the high brittleness of waterborne phenolic resin coatings and insufficient final cross-linking density.

[0008] Secondly, the present invention provides a first method for synthesizing the above-mentioned dynamically toughened phenolic resin, characterized by comprising the following steps: S1: Under the action of an alkaline catalyst, phenolic compounds and aldehyde compounds are reacted at a temperature of 80-90℃ for 1-2 hours to form a first-order phenolic resin prepolymer. S2: Add an acid regulator to the first-stage phenolic resin to make the pH of the system 5-6.5, add DMMn to carry out a grafting reaction, and react at 50-70℃ for 1-2 hours to form a dynamically toughened phenolic resin intermediate. S3: Add an alkali adjuster to the dynamically toughened phenolic resin intermediate to make the pH of the system 7-8, and dehydrate to obtain the dynamically toughened phenolic resin.

[0009] Thirdly, the present invention provides a second method for synthesizing the above-mentioned dynamically toughened phenolic resin, characterized by comprising the following steps: S1: Under the action of an acidic catalyst, 70-80% of the total mass of phenolic and aldehyde compounds are reacted at a temperature of 80-90℃ for 0.5-3 hours to form a methyl phenolic resin prepolymer. S2: Add DMMn to the methyl phenolic resin to carry out a grafting reaction, and react at 60-75℃ for 0.5-1.5h to form a dynamically toughened phenolic resin intermediate. S3: Add an alkali adjuster to the dynamically toughened phenolic resin intermediate to adjust the pH of the system to 7.5-8.5, add the remaining aldehyde compound, and stir continuously at 60-75°C for 1.5-3 hours to obtain the dynamically toughened phenolic resin after dehydration.

[0010] Furthermore, in DMMn, n is an integer from 3 to 5, and the weight ratio of the phenolic compound to DMMn is 100:(5-50).

[0011] Furthermore, the phenolic compounds include one or more of phenol, resorcinol, pyrogallol, cashew phenol, and alkylphenols.

[0012] Furthermore, the aldehyde compounds include one or more of formaldehyde, paraformaldehyde, and acetaldehyde.

[0013] Fourthly, the present invention provides a dynamically toughened phenolic resin emulsion, characterized in that it is prepared from the dynamically toughened phenolic resin as described in claim 1, an emulsifier, a hydrophobic organic solvent and water, and has a solid content of 10% to 40%; the amount of the emulsifier is 5-12% of the dry weight of the dynamically toughened phenolic resin.

[0014] Fifthly, the present invention provides a method for preparing the above-mentioned emulsion, comprising the following steps: S1: Dissolve the dynamically toughened phenolic resin in a hydrophobic organic solvent to form a homogeneous resin oil phase system; S2: Mix and disperse the emulsifier with water to form a homogeneous aqueous system; S3: The resin oil phase system is dispersed in the aqueous phase system, emulsified, and the hydrophobic organic solvent is removed under vacuum to obtain the dynamically toughened phenolic resin emulsion.

[0015] Sixthly, the present invention provides an application of a dynamically toughened phenolic resin emulsion for preparing an aqueous hot-curing adhesive primer; the aqueous hot-curing adhesive primer comprises, by weight, the following components: 5-15 parts of dynamically toughened phenolic resin emulsion, 5-15 parts of polymer latex, 1-5 parts of acid scavenger, 5-12 parts of inorganic filler, 0.5-2 parts of pH adjuster, 0-1 part of vulcanizing agent, 0.05-0.25 parts of dispersant, 0.05-0.25 parts of defoamer, and 65-73 parts of deionized water.

[0016] Further, the polymer latex includes one or more of carboxylated nitrile butadiene latex, carboxylated styrene-butadiene latex, chloroprene latex, styrene-acrylic emulsion, and pure acrylic emulsion; the acid scavenger includes one or more of zinc oxide, magnesium oxide, zinc phosphate, and zinc molybdate; the inorganic filler includes one or more of titanium dioxide and barium sulfate; the pH adjuster includes one or more of ammonia, 2-amino-2-methyl-1-propanol, and barium hydroxide; the vulcanizing agent includes one or more of sulfur, selenium, and polymaleimide; and the water-based additives include one or more of dispersants, defoamers, wetting agents, and thickeners.

[0017] In a seventh aspect, the present invention provides a method for preparing the above-mentioned water-based hot-curing adhesive primer, comprising the following steps: Mix and grind 30-40% of the total weight of acid absorber, inorganic filler, vulcanizing agent, dispersant and deionized water, and add it to the dynamic toughening phenolic resin emulsion; then add polymer latex, defoamer and the remaining deionized water, mix evenly to obtain the water-based hot vulcanizing adhesive base.

[0018] Beneficial effects 1. This invention introduces acetal segments into phenolic resin through chemical grafting of DMMn, achieving dynamic toughening and imparting toughness to the resin at room temperature. During vulcanization, the acidic environment promotes the hydrolysis of acetal segments, releasing formaldehyde to further promote cross-linking, thus balancing toughness and final cross-linking density.

[0019] 2. Through a specific combination of emulsifiers and external emulsification process, dynamically toughened phenolic resin can be stably dispersed in the aqueous phase, has a long shelf life at 25°C, does not require a large amount of organic co-solvents, and has strong process adaptability. 3. It adopts a water-based system with extremely low VOC emissions, which solves the pollution and safety problems of solvent-based phenolic resins and meets environmental protection regulations.

[0020] 4. The water-based hot vulcanizing adhesive base formulated with this emulsion has good adhesion to metal substrates, flexible film formation, high vulcanization bonding strength when combined with the top adhesive, and excellent resistance to media. It is particularly suitable for high-strength bonding requirements of automotive parts. Detailed Implementation

[0021] The claims of the present invention will be further described in detail below with reference to specific embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the protection scope of the claims of the present invention.

[0022] Unless otherwise specified, the following embodiments are all conventional experimental methods and operating procedures in the art.

[0023] Example 1 The preparation method of dynamically toughened phenolic resin includes the following steps: S1: Add 94g of phenol and 36g of paraformaldehyde to the reactor, then add 2g of barium hydroxide, stir and heat to 80-85℃, react for 1.5h to obtain a methyl phenolic resin prepolymer. S2: Cool the system to 60℃, adjust the pH to 5.5 with phosphoric acid, add 20g DMM4, and keep the reaction at 60℃ for 1.5h to form a dynamically toughened phenolic resin intermediate. S3: Add ammonia to adjust the pH to 7.5, start vacuum distillation to dehydrate, and obtain the dynamically toughened phenolic resin.

[0024] The preparation method of dynamically toughened phenolic resin emulsion includes the following steps: S1: Take 200g of the above dynamically toughened phenolic resin, dissolve it in 300g of 4-methyl-2-pentanone, stir evenly to form a resin oil phase system; S2: Dissolve 4g sodium dodecylbenzenesulfonate and 6g polyvinyl alcohol in 400g deionized water and stir until completely dissolved to form an aqueous phase system; S3: Turn on the emulsifier, set the speed to 3000 r / min, control the emulsification temperature at 40℃, slowly drip the resin oil phase system into the aqueous phase system, and continue emulsification for 15 min after the addition is complete to obtain the emulsion semi-finished product; place the emulsion semi-finished product in a distillation apparatus, remove 4-methyl-2-pentanone under vacuum until the output is about 300g, adjust the solid content to 30%, and obtain the dynamically toughened phenolic resin emulsion.

[0025] The DMM4, with a content of ≥98%, was purchased from Suzhou Senfida Chemical Co., Ltd. The DMM3-5, with a content of ≥98% and a distillation range of 150-220℃, was purchased from Jinan Hanbai Chemical Co., Ltd.

[0026] Example 2 The specific implementation method is the same as in Example 1, except that in the preparation method of dynamically toughened phenolic resin, in step S1, the amount of paraformaldehyde added is 45g, and in step S2, the acid catalyst phosphoric acid is replaced with oxalic acid, and DMM4 is replaced with DMM3-5.

[0027] Example 3 The preparation method of dynamically toughened phenolic resin includes the following steps: S1: Add 94g of phenol and 2g of phosphoric acid to the reaction vessel, heat to 85℃, add 27g of paraformaldehyde, and react for 1 hour; S2: Cool to 60℃, add 40g DMM4, and react for 1 hour; S3: Adjust the pH to 8.0 with ammonia, add the remaining 9g of paraformaldehyde, react at 70℃ for 2h, dehydrate, and obtain the dynamically toughened phenolic resin.

[0028] The preparation method of the dynamically toughened phenolic resin emulsion is the same as in Example 1, and the dynamically toughened phenolic resin emulsion is obtained.

[0029] Example 4 The specific implementation method is the same as in Example 3, except that in the preparation method of dynamically toughened phenolic resin, in step S1, the amount of paraformaldehyde added is 33.75g, the acid catalyst phosphoric acid is replaced with p-toluenesulfonic acid, and DMM4 is replaced with DMM3-5; in step S3, the remaining amount of paraformaldehyde added is 11.25g.

[0030] Comparative Example 1 The specific implementation method is the same as in Example 1, except that in the preparation method of dynamically toughened phenolic resin, DMM4 is replaced with DMM2 in step S1.

[0031] Comparative Example 2 The specific implementation method is the same as in Example 2, except that in the preparation method of dynamically toughened phenolic resin, oxalic acid and DMM3-5 are not added in step S2.

[0032] Comparative Example 3 Referring to existing technology, Chinese invention patent CN1243065C, pyrogallol / resorcinol is dissolved in 250g of water in a 2000ml resin polymerization pot equipped with a stirrer, nitrogen inlet, and reflux condenser. Phosphoric acid is added, and the mixture is heated at 95℃ while 75% of the formalin solution is slowly added. Then FBS is added, and the mixture is heated for another 15 minutes, followed by the slow addition of the remaining formalin. After the addition is complete, the mixture is heated at 95℃ for another 30 minutes, and the remaining dilution water is added. The mixture is then filtered and packaged to obtain water-soluble phenolic resin.

[0033] The phenolic resins obtained in Examples 1-3 and Comparative Examples 1-3 were used to prepare water-based hot-curing adhesive primers according to the proportions in Table 1.

[0034] Table 1

[0035] The carboxylated styrene-butadiene latex, model number GenFlo 3060, was purchased from Shanghai Xintema Chemicals Co., Ltd. The defoamer was BYK 011 and was purchased from BYK Chemical Co., Ltd. The dispersant is DSP28, purchased from Resox Chemicals (Shanghai) Co., Ltd.

[0036] The preparation method of water-based hot-curing adhesive primer includes the following steps: The acid absorber, inorganic filler, vulcanizing agent, dispersant and deionized water totaling 30-40 wt% are ground by a grinder to obtain a mother liquor. The mother liquor is added to the dynamic toughening phenolic resin emulsion composition and stirred and mixed. Polymer latex, defoamer and the remaining deionized water are added and stirred and mixed evenly to obtain the water-based hot vulcanizing adhesive base.

[0037] Performance testing 1. Performance testing of dynamically toughened phenolic resin emulsion Storage stability: Observe its storage stability at 25 degrees Celsius.

[0038] Media resistance: 1.5 g of each of the 30% solids content dynamically toughened phenolic resin emulsions were cured at 155°C for 15 min. The cured resins were then immersed in water and ethylene glycol, respectively, and their solubility was observed over 7 days to characterize their media resistance. The results are shown in Table 2. Table 2

[0039] The emulsions of Examples 1-4 of this invention exhibit significantly better storage stability and media resistance than the emulsions of Comparative Examples 1-3, indicating that the chemical grafting of DMMn is crucial for emulsion stability and media resistance.

[0040] 2. Flexible substrate bending test 2. Perform ASTM D4145-10 (2022) "Standard Test Method for Flexibility of Pre-coated Metal Sheets". Degrease a 50mm × 150mm aluminum sheet and pre-dry it in an 80℃ forced-air drying oven for 20 min. Apply the primer provided in the application examples and comparative examples using a pneumatic spray gun, controlling the film thickness to 10μm. After spraying, dry it in a 70℃ oven for 3 min. Fix the 6-20mm end of the sample in a vise and slowly bend the free end to 180° (0T bend), ensuring the coating is on the outside. Use a magnifying glass to check for coating cracking. Perform a tape peel test: apply tape along the bend → press → quickly peel at 90° → check for tape residue. Perform 1T, 2T, and 3T bends step by step until no cracking / peeling occurs, and determine the minimum passing T value (e.g., no defects at 2T). The test results are shown in Table 3. Table 3

[0041] As shown in Table 3, the flexibility of phenolic resin after dynamic toughening is significantly improved.

[0042] 3. Test of adhesion of test pieces Prepare a long strip of polished iron. Pre-bake the test substrate in an 80 ℃ forced-air drying oven for 20 min. Apply the same coating process to the products provided in Application Examples 1-3 and Comparative Examples 1-3: use a pneumatic spray gun to spray onto the middle part of the substrate, controlling the film thickness at 10 μm; after coating, place it in an 80 ℃ oven to dry for 3 min. Then, brush on the hot-curing adhesive POLYTON 8021, controlling the adhesive film thickness at 20 μm, dry at 80 ℃ for 20 min, and place it together with NR55 rubber in a vulcanization mold. Vulcanize at 165 ℃ and 10 MPa for 7 min to complete the vulcanization and bonding. After the test piece is vulcanized and bonded, cool it at 25 ℃ for 2 h to eliminate rubber thermal stress. Perform rubber peeling and read the percentage of rubber failure area in the total bonded area. The results are shown in Table 4.

[0043] Table 4

[0044] Table 5 shows that the adhesive products provided in Application Examples 1-3 of this invention have better adhesion than the adhesive products provided in Comparative Examples 1-3.

[0045] 4. Media resistance test The test substrate was pre-dried in an 80 °C forced-air drying oven for 10 min. The products provided in Application Examples 1-4 and the commercially available Megum W9300 were coated using the same process: a pneumatic spray gun was used to spray the coating onto the center of the substrate, controlling the film thickness to 10 μm; POLYTON 815GB was brushed on, controlling the film thickness to 10 μm. After coating, the substrate was dried in an 80 °C oven for 3 min. Then, POLYTON 829GB hot-curing adhesive was brushed on, controlling the adhesive film thickness to 20 μm, and dried at 80 °C for 20 min. The substrate and NR55 rubber were then placed in a vulcanization mold and vulcanized at 165 °C and 10 MPa for 7 min to complete the vulcanization and bonding. After vulcanization and bonding, the test pieces were cooled at 25 °C for 2 h to eliminate rubber thermal stress.

[0046] Tie the two ends of the rubber together to expose the bonding interface. Place the workpiece in pure ethylene glycol at 100°C for 240 h and then remove it. Peel the rubber and record the failure mode. R represents rubber failure, RC represents failure of the bonding surface between rubber and top adhesive, CP represents failure of the bonding surface between base adhesive and top adhesive, and M represents failure of the base adhesive bonded to metal. The results are shown in Table 5.

[0047] Table 5

[0048] The MEGUM W 9300 was purchased from Dow Chemical Company; The POLYTON 815GB and POLYTON 829GB mentioned are products currently sold by the applicant.

[0049] Table 5 shows that the base adhesive products provided in Application Examples 1-3 of the present invention have better resistance to media than the base adhesive products provided in Application Comparative Examples 1-5.

Claims

1. A dynamically toughened phenolic resin, characterized in that, The structural formula of the dynamically toughened phenolic resin is as follows: Wherein, R1 is hydroxyl, hydroxymethyl, or (CH2O). x -CH3, where x is an integer from 0 to 8; R represents CH2 or (CH2O). y -CH2, where y is an integer from 0 to 8; and at least one of R and R1 is an acetal segment; R2 is a hydrogen atom, hydroxymethyl, or alkyl group; R3 represents a hydrogen atom, a hydroxyl group, and a carbon atom. 15 Aliphatic side chains and their modified products; m is an integer between 0 and 8.

2. A method for preparing dynamically toughened phenolic resin according to claim 1, characterized in that, Includes the following steps: S1: Under the action of an alkaline catalyst, phenolic compounds and aldehyde compounds are reacted at a temperature of 80-90℃ for 1-2 hours to form a first-order phenolic resin prepolymer. S2: Add an acid regulator to the methyl phenolic resin to make the pH of the system 5-6.5, add DMMn to carry out a grafting reaction, and react at 50-70℃ for 1-2 hours to form a dynamically toughened phenolic resin intermediate. S3: Add an alkali adjuster to the dynamically toughened phenolic resin intermediate to make the pH of the system 7-8, and dehydrate to obtain the dynamically toughened phenolic resin.

3. A method for preparing dynamically toughened phenolic resin according to claim 1, characterized in that, Includes the following steps: S1: Under the action of an acidic catalyst, 70-80% of the total mass of phenolic and aldehyde compounds are reacted at a temperature of 80-90℃ for 0.5-3 hours to form a methyl phenolic resin prepolymer. S2: Add DMMn to the methyl phenolic resin to carry out a grafting reaction, and react at 60-75℃ for 0.5-1.5h to form a dynamically toughened phenolic resin intermediate. S3: Add an alkali adjuster to the dynamically toughened phenolic resin intermediate to make the pH of the system 7.5-8.5, add the remaining aldehyde compound, and stir continuously at 60-75℃ for 1.5-3 hours to obtain the dynamically toughened phenolic resin after dehydration.

4. The method for preparing dynamically toughened phenolic resin according to claim 2 or 3, characterized in that, In the DMMn, n is an integer from 3 to 5, and the weight ratio of the phenolic compound to the DMMn is 100:5-50.

5. The method for preparing dynamically toughened phenolic resin according to claim 2 or 3, characterized in that, The phenolic compounds include one or more of phenol, resorcinol, pyrogallol, cashew phenol, and alkylphenol; the aldehyde compounds include one or more of formaldehyde, paraformaldehyde, and acetaldehyde.

6. A dynamically toughened phenolic resin emulsion, characterized in that, It is prepared from the dynamically toughened phenolic resin as described in claim 1, an emulsifier, a hydrophobic organic solvent, and water, with a solid content of 10-40%; the amount of the emulsifier is 5-12% of the dry weight of the dynamically toughened phenolic resin.

7. A method for preparing a dynamically toughened phenolic resin emulsion according to claim 6, characterized in that, Includes the following steps: S1: Dissolve the dynamically toughened phenolic resin in a hydrophobic organic solvent to form a homogeneous resin oil phase system; S2: Mix and disperse the emulsifier with water to form a homogeneous aqueous system; S3: The resin oil phase system is dispersed in the aqueous phase system, emulsified, and the hydrophobic organic solvent is removed under vacuum to obtain the dynamically toughened phenolic resin emulsion.

8. A preparation method according to claim 7, characterized in that, The emulsification process is carried out at a temperature of 20-60℃ and at a rotation speed of 1000-7000 r / min.

9. An application of the dynamically toughened phenolic resin emulsion according to claim 6, characterized in that, This product is used to prepare a water-based hot-curing adhesive base. The water-based hot-curing adhesive base, by weight, comprises the following components: 5-15 parts of dynamically toughened phenolic resin emulsion, 5-15 parts of polymer latex, 1-5 parts of acid scavenger, 5-12 parts of inorganic filler, 0.5-2 parts of pH adjuster, 0-1 part of vulcanizing agent, 0.05-0.25 parts of dispersant, 0.05-0.25 parts of defoamer, and 65-73 parts of deionized water.

10. The application of the dynamically toughened phenolic resin emulsion according to claim 9, characterized in that, The preparation steps of the water-based hot-curing adhesive primer are as follows: Mix and grind 30-40% of the total weight of acid absorber, inorganic filler, vulcanizing agent, dispersant and deionized water, and add it to the dynamic toughening phenolic resin emulsion; then add polymer latex, defoamer and the remaining deionized water, mix evenly to obtain the water-based hot vulcanizing adhesive base.

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