Preparation method of silicon-modified toughened epoxy resin emulsifier

Abstract

The invention relates to the technical field of epoxy resin, in particular to a preparation method of a silicon-modified toughened epoxy resin emulsifier. Comprising the following steps: reacting double-hydroxyl-terminated polysiloxane with first anhydride to obtain carboxyl-terminated polysiloxane; the carboxyl-terminated polysiloxane and polyethylene glycol are subjected to a reaction, and polyethylene glycol modified carboxyl-terminated polysiloxane is obtained; reacting the polyethylene glycol modified carboxyl-terminated polysiloxane with a second anhydride to obtain a carboxyl-terminated polyethylene glycol intermediate; and adding epoxy resin and a catalyst into the carboxyl-terminated polyethylene glycol intermediate for reaction. The emulsifier provided by the invention can be used for preparing an epoxy emulsion of 0 VOC, and simultaneously endows resin with excellent protective performance and mechanical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and specifically, to a preparation method of a silicone-modified toughened epoxy resin emulsifier. Background Art

[0002] Epoxy resin is a high-performance polymer material with excellent properties in many aspects. It shows extremely strong adhesion to materials such as metals, ceramics, glass, and wood. In terms of chemical properties, epoxy resin is resistant to acids, alkalis, salts, and various solvents, especially showing outstanding resistance to alkaline media, and is widely used in the anti-corrosion of chemical equipment and marine engineering. However, traditional epoxy resins have environmental problems, with a low HLB value and a dependence on organic solvents, resulting in VOC emissions. For this reason, the waterborne technology has become the focus. Currently, waterborne modification is carried out through mechanical methods, chemical modification methods, phase inversion methods, and curing agent emulsification methods. Among them, the phase inversion method refers to uniformly mixing an emulsifier and epoxy resin under high shear force conditions. Currently, in order to have good compatibility with epoxy resin and certain reaction activity, and not migrate to the surface after curing, most epoxy resin emulsifiers are designed as reactive emulsifiers, but most of them are difficult to balance the protective performance and mechanical properties.

[0003] Chinese invention patent CN113150263 B prepares an epoxy active emulsifier through three-step reactions: ① Esterification of an acid anhydride and a polyether to generate product A-1 (molar ratio ≥ 1), ② Neutralizing product A-1 with potassium hydroxide / sodium to obtain A-2, ③ Ring-opening reaction of A-2 and an epoxy resin containing a bis-epoxy group to finally obtain the emulsifier. This method reduces the amount of emulsifier used, and the obtained epoxy resin dispersion system has high stability and good corrosion resistance of the coating; however, the residue of small molecule bases may damage the water resistance and salt spray resistance of the paint film, and there are potential defects. Chinese invention patent application CN113881018A improves the process of non-ionic epoxy emulsifiers: mixing polyethylene glycol and a catalyst and then dropping the epoxy resin dilution solution, and removing the solvent by reduced pressure distillation after holding the reaction. By optimizing the ratio, the free polyethylene glycol is reduced to obtain a high molecular weight emulsifier. The emulsifier has excellent performance (strong emulsification, low toxicity, and low pollution), but the process requires a large amount of solvent and needs to be removed by reduced pressure, the process is cumbersome and not environmentally friendly enough, and further optimization is required. Summary of the Invention

[0004] The first aspect of the present invention provides a preparation method of a silicone-modified toughened epoxy resin emulsifier, including the following steps:

[0005] S1, reacting a polyorganosiloxane terminated with dihydroxy groups with a first acid anhydride to obtain a polyorganosiloxane terminated with carboxyl groups;

[0006] S2, reacting the polyorganosiloxane terminated with carboxyl groups with polyethylene glycol (PEG) to obtain a polyethylene glycol-modified polyorganosiloxane terminated with carboxyl groups;

[0007] S3. React the polyethylene glycol-modified carboxyl-terminated polysiloxane with the second anhydride to obtain a carboxyl-terminated polyethylene glycol intermediate;

[0008] S4. Add epoxy resin and a catalyst to the carboxyl-terminated polyethylene glycol intermediate for reaction.

[0009] The temperature of the reaction in S1 is 50 - 70 °C, and the time is 1 - 3 h.

[0010] The temperature of the reaction in S2 is 80 - 100 °C, and the time is 2 - 5 h.

[0011] The temperature of the reaction in S3 is 110 - 120 °C.

[0012] The reaction in S4 ends when the acid value is less than 5 mgKOH / g.

[0013] The research of the present invention finds that when the second anhydride is an aliphatic anhydride with a carbon chain length greater than 10, the water resistance, salt spray resistance, and impact resistance of the epoxy resin can be effectively improved. Using a long-chain anhydride as an intermediate for the reaction between hydroxyl and epoxy groups, the long-chain anhydride can well increase the toughness of the epoxy resin. Since it is block-copolymized in the epoxy resin emulsifier molecule, after the epoxy resin cures into a film, it can be evenly distributed in the cured epoxy resin system, and can well improve the toughness of the epoxy resin.

[0014] The second anhydride includes an aliphatic anhydride with a carbon chain length greater than 10.

[0015] Optionally, the aliphatic anhydride is prepared by reacting an aliphatic dibasic acid with acetic anhydride.

[0016] Optionally, the aliphatic anhydride includes at least one of polyazelaic anhydride, sebacic anhydride, and behenic anhydride.

[0017] The first anhydride includes at least one of phthalic anhydride, maleic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and nadic anhydride.

[0018] The number-average molecular weight of the dihydroxy-terminated polysiloxane is 400 - 2000.

[0019] Optionally, the number-average molecular weight of the dihydroxy-terminated polysiloxane is 550 - 1000.

[0020] The weight-average molecular weight of the polyethylene glycol is 800 - 3000.

[0021] Optionally, the weight-average molecular weight of the polyethylene glycol is 1000 - 2000.

[0022] The epoxy resin includes at least one of the following grades: E-44, E-51, E20, E12, and E06.

[0023] The molar ratio of the dihydroxy-terminated polysiloxane to the first anhydride is 1:(1.4 - 3).

[0024] Optionally, the molar ratio of the dihydroxy-terminated polysiloxane to the first anhydride is 1:(1.4 - 2.4).

[0025] The molar ratio of the polyethylene glycol, the second anhydride, and the epoxy resin is 1:(0.5 - 3):(1 - 5).

[0026] Optionally, the molar ratio of the polyethylene glycol, the second anhydride, and the epoxy resin is 1:(0.5 - 3):(1 - 3).

[0027] Beneficial effects

[0028] 1. The present invention designs and synthesizes a silicon-containing block epoxy resin emulsifier. By utilizing the wettability of polysiloxane to inorganic fillers, the wettability of the resin itself to pigments and fillers is improved, the use of dispersants is reduced, and at the same time, the heat resistance of the resin is enhanced.

[0029] 2. When the second anhydride is an aliphatic anhydride with a carbon chain length greater than 10, the water resistance, salt spray resistance, and impact resistance of the epoxy resin can be effectively improved.

[0030] 3. When the second anhydride is at least one of polyazelic anhydride, polysebacic anhydride, and polyeicosanoic anhydride, the glass transition temperature of the epoxy resin can be further increased.

[0031] 4. After the emulsifier prepared in the present invention is blended with the liquid epoxy resin, it can be used as the main agent of the waterborne epoxy zinc-rich coating. It has good wettability to zinc powder without adding dispersants, and excellent mechanical properties and protective properties.

[0032] 5. The emulsifier prepared in the present invention can be used together with the liquid epoxy resin to prepare a waterborne emulsion by the phase inversion method, avoiding the use of organic solvents and obtaining a 0VOC waterborne epoxy emulsion. Specific embodiments

[0033] In this example, the dihydroxy-terminated polydimethylsiloxane, PEG, epoxy resin, polysebacic anhydride, and polyazelic anhydride involved are not limited to manufacturers; the reaction reaches the theoretical acid value when the acid value no longer decreases.

[0034] Example 1

[0035] A preparation method of a silicone-modified toughened epoxy resin emulsifier comprises the following steps: Add 27.5 g of dihydroxy-terminated polydimethylsiloxane (number-average molecular weight 550) into a three-necked flask, heat it to 60 °C, add 14.8 g of phthalic anhydride, react for 3 h. When the reaction reaches the theoretical acid value, the intermediate obtained is carboxylated polysiloxane. Add 100 g of PEG (weight-average molecular weight 1000) into the carboxylated polysiloxane synthesized above, raise the temperature to 90 °C, react for 3 h. When the acid value is measured to be less than 5 mgKOH / g, the product obtained is polyethylene glycol-modified carboxylated polysiloxane. Add 140 g of polysebacic anhydride (molecular weight 2000) into the polyethylene glycol-modified carboxylated polysiloxane synthesized above. After adding the anhydride, the reaction temperature rises to 120 °C. When the reaction reaches the theoretical acid value, the product obtained is end-carboxylated polyethylene glycol. Add 44 g of epoxy resin E-44 and 0.1 g of triphenylphosphine into the above end-carboxylated polyethylene glycol product, react for 1 h. When the acid value is measured to be less than 5 mgKOH / g, the reaction reaches the end point.

[0036] Example 2

[0037] A preparation method of a silicone-modified toughened epoxy resin emulsifier comprises the following steps: Add 50 g of dihydroxy-terminated polydimethylsiloxane (number-average molecular weight 1000) into a three-necked flask, heat it to 60 °C, add 15.4 g of hexahydrophthalic anhydride, react for 2 h. When the acid value is measured to reach the theoretical value, the intermediate obtained is carboxylated polysiloxane. Add 200 g of PEG (weight-average molecular weight 2000) into the carboxylated polysiloxane synthesized above, raise the temperature to 90 °C, react for 4 h. When the acid value is measured to be less than 5 mgKOH / g, the product obtained is polyethylene glycol-modified carboxylated polysiloxane. Add 120 g of polynonanoic anhydride into the polyethylene glycol-modified carboxylated polysiloxane synthesized above. After adding the anhydride, the reaction temperature rises to 120 °C. When the reaction reaches the theoretical acid value, the product obtained is end-carboxylated polyethylene glycol. Add 51 g of epoxy resin E-51 into the above end-carboxylated polyethylene glycol product. Add 0.2 g of triphenylphosphine, react for 1 h. When the acid value is measured to be less than 5 mgKOH / g, the reaction reaches the end point.

[0038] Example 3

[0039] A preparation method of a silicon-modified toughened epoxy resin emulsifier comprises the following steps: Add 50 g of dihydroxy-terminated polydimethylsiloxane (number-average molecular weight 1000) into a three-necked flask, heat it to 60 °C, add 15.2 g of tetrahydrophthalic anhydride, react for 2 h, measure the acid value to reach the theoretical value, and the obtained intermediate is carboxylated polysiloxane. Add 200 g of PEG (weight-average molecular weight 2000) into the carboxylated polysiloxane synthesized above, raise the temperature to 90 °C, react for 4 h, and when the measured acid value is less than 5 mgKOH / g, the obtained product is polyethylene glycol-modified carboxylated polysiloxane. Add 120 g of polyazelic anhydride into the polyethylene glycol-modified carboxylated polysiloxane synthesized above. After adding the anhydride, the reaction temperature rises to 120 °C. After the reaction reaches the theoretical acid value, the obtained product is end-carboxylated polyethylene glycol. Add 100 g of epoxy resin E-20 and 0.3 g of triphenylphosphine into the above end-carboxylated polyethylene glycol product, react for 1 h, and when the measured acid value is less than 5 mgKOH / g, the reaction reaches the end point.

[0040] Comparative Example 1

[0041] A preparation method of an epoxy resin emulsifier comprises the following steps: Add 80 g of PEG (weight-average molecular weight 1000) into a three-necked flask, then add 25.6 g of hexahydrophthalic anhydride, raise the temperature to 100 °C, react for 3 h, add 84 g of epoxy resin E-51 and 0.24 g of triphenylphosphine, and then continue to react at 100 °C for 1 h.

[0042] Comparative Example 2

[0043] A preparation method of an epoxy resin emulsifier comprises the following steps: Add 50 g of dihydroxy-terminated polydimethylsiloxane (molecular weight 1000) into a three-necked flask, heat it to 60 °C, add 15.4 g of hexahydrophthalic anhydride, react for 2 h, measure the acid value to reach the theoretical value, and the obtained intermediate is carboxylated polysiloxane. Add 200 g of PEG (weight-average molecular weight 2000) into the carboxylated polysiloxane synthesized above, raise the temperature to 90 °C, react for 4 h, and when the measured acid value is less than 5 mgKOH / g, the obtained product is polyethylene glycol-modified carboxylated polysiloxane. Add 14.8 g of phthalic anhydride into the polyethylene glycol-modified carboxylated polysiloxane synthesized above. After adding the anhydride, the reaction temperature rises to 120 °C. After the reaction reaches the theoretical acid value, the obtained product is end-carboxylated polyethylene glycol. Add 51 g of epoxy resin E-51 and 0.2 g of triphenylphosphine into the above end-carboxylated polyethylene glycol product, react for 1 h, and when the measured acid value is less than 5 mgKOH / g, the reaction reaches the end point.

[0044] Comparative Example 3

[0045] A preparation method of an epoxy resin emulsifier comprises the following steps: Add 200 g of PEG (weight-average molecular weight 2000) into a three-necked flask, heat it to 120 °C, add 120 g of polyazelaic anhydride, react for 3 h. After adding the acid anhydride, the reaction temperature rises to 120 °C. After the reaction reaches the theoretical acid value, the obtained product is carboxyl-terminated polyethylene glycol. In the above carboxyl-terminated polyethylene glycol product, add 51 g of epoxy resin E-51 and 0.2 g of triphenylphosphine, react for 1 h. When the acid value is measured to be less than 5 mg KOH / g, the reaction reaches the end point.

[0046] Performance test method

[0047] Preparation method of waterborne epoxy emulsion: Take 15 g of the epoxy resin emulsifier prepared in the example and the comparative example respectively, then add 100 g of liquid epoxy resin E-51, mix evenly at 65 °C, and then dropwise add 115 g of deionized water within 1 h under stirring to obtain a milky viscous emulsion, which is the waterborne epoxy resin. Then add 67 g of curing agent 1 (Handai 2622) and 48 g of curing agent 2 (Handai 6815), disperse evenly and add deionized water to adjust to a suitable construction viscosity. Take the waterborne epoxy emulsion, scrape it on the pretreated cold-rolled steel plate with a 200-micron wire bar, cure it at room temperature for 7 days, and conduct tests. The test results are shown in Table 1.

[0048] Water resistance: Immerse 2 / 3 of the specimen in a normal-temperature water bath for 48 h, and observe whether the paint film blisters, rusts, and turns white;

[0049] Salt spray resistance: Seal the back and edges of the sample plate, put it into a neutral salt spray chamber to observe, and record the time when the paint film rusts;

[0050] Adhesion: Cross-cut method;

[0051] Impact resistance: Conduct according to the provisions of GB / T1732;

[0052] Glass transition temperature: Differential scanning calorimetry (DSC).

[0053] Performance test data

[0054] Table 1

[0055]

[0056]

Claims

1. A preparation method of a silicon-modified toughened epoxy resin emulsifier, characterized in that, It includes the following steps: The dihydroxy-terminated polysiloxane reacts with the first anhydride to obtain a carboxyl-terminated polysiloxane; the carboxyl-terminated polysiloxane reacts with polyethylene glycol to obtain a polyethylene glycol-modified carboxyl-terminated polysiloxane; the polyethylene glycol-modified carboxyl-terminated polysiloxane reacts with the second anhydride to obtain a carboxyl-terminated polyethylene glycol intermediate; Epoxy resin and a catalyst are added to the carboxyl-terminated polyethylene glycol intermediate for reaction.

2. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 1, characterized in that, The second anhydride includes an aliphatic anhydride with a carbon chain length greater than 10.

3. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 2, wherein, The aliphatic anhydride is prepared by reacting an aliphatic dibasic acid with acetic anhydride.

4. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 3, wherein, The aliphatic anhydride includes at least one of polyazelic anhydride, sebacic anhydride, and eicosanoic anhydride.

5. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 1, characterized in that, The first anhydride includes at least one of phthalic anhydride, maleic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and nadic anhydride.

6. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 5, wherein, The number-average molecular weight of the dihydroxy-terminated polysiloxane is 400 - 2000.

7. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 6, characterized in that, The weight-average molecular weight of the polyethylene glycol is 800 - 3000.

8. The preparation method of the silicone-modified toughened epoxy resin emulsifier according to claim 7, characterized in that, The epoxy resin includes at least one of the following grades: E-44, E-51, E20, E12, and E06.

9. The preparation method of the silicon-modified toughened epoxy resin emulsifier according to claim 1, characterized in that The molar ratio of the dihydroxy-terminated polysiloxane to the first anhydride is 1:(1.4 - 3).

10. The preparation method of the silicon-modified toughened epoxy resin emulsifier according to claim 1, characterized in that, The molar ratio of the polyethylene glycol, the second anhydride, and the epoxy resin is 1:(0.5 - 3):(1 - 5).

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