Method for synthesizing UV-cured flexible vinyl resin in microreactor

Abstract

The invention belongs to the technical field of resin synthesis, and discloses a method for synthesizing UV-cured flexible vinyl resin by a microreactor. The method comprises the following steps: (1) preparing a reaction liquid: mixing binary acid, a solvent, methacrylic acid, epoxy resin, a catalyst and a polymerization inhibitor to obtain the reaction liquid; and (2) adding the reaction liquid into a microreactor for reaction to obtain the UV-cured flexible vinyl resin. The micro-reactor device is used, the problem that the temperature of a reaction system is not controlled due to a strong exothermic reaction is solved, gel curing of products due to too high temperature is avoided, the reaction rate is also improved, a target product can be synthesized within extremely short time, and due to the fact that the temperature of the reaction system is constant, the diffusion rate is high, the reaction selectivity is high and side reaction products are few, the yield is high. Therefore, the synthesized product is colorless.

Description

Technical Field

[0001] The invention belongs to the technical field of resin synthesis, and particularly relates to a method for synthesizing UV-curing flexible vinyl resin using a microreactor. Background Art

[0002] Vinyl resin has the advantages of good mechanical properties and corrosion resistance of epoxy resin. Due to the generation of hydroxyl groups in the ring-opening reaction, it has good adhesion to metal surfaces and wettability to pigments. The two ends of the molecule contain extremely active double bonds, which can quickly cure to reach the strength required for use. Therefore, it is widely used in the fields of anti-corrosion pipelines, aviation, automobiles, electrical insulation, etc. At present, the more mature processes for synthesizing vinyl resins mostly use autoclave reactors for synthesis. However, for this highly exothermic reaction, autoclave reactor synthesis has the following disadvantages: the large amount of heat generated by the reaction cannot be transferred in time, the temperature of the reaction system cannot be controlled, the local temperature is too high, the product is easy to gel and solidify, the diffusion rate of the reaction system is slow, the reaction time is long, and side reaction products are easy to synthesize.

[0003] Therefore, there is an urgent need to provide a new synthesis method for vinyl resins, which makes the reaction temperature controllable, the by-products generated well, and the target product conversion rate high. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for synthesizing UV-curable flexible vinyl resin using a microreactor. The method of the present invention uses a microreactor to effectively control the reaction temperature and reduce the generation of by-products, and can also shorten the reaction time, reduce energy consumption, and achieve a high conversion rate of the target product.

[0005] The present invention uses epoxy resin, methacrylic acid and adipic acid as reaction raw materials to synthesize flexible vinyl resin in a microreactor. The use of a microreactor can effectively solve the problem of difficult temperature control during the reaction process, ensure that the temperature of the reaction system is constant during the reaction time, and reduce the generation of side reaction products; it can also increase the reaction rate, prevent the target product from yellowing, and improve the quality and performance of the synthesized target product.

[0006] The invention provides a method for synthesizing UV-curable flexible vinyl resin by using a microreactor.

[0007] Specifically, a method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0008] (1) Preparation of reaction solution: mixing dibasic acid, solvent, methacrylic acid, epoxy resin, catalyst, and polymerization inhibitor to obtain a reaction solution;

[0009] (2) adding the reaction solution into a microreactor for reaction to obtain the UV-curable flexible vinyl resin.

[0010] Preferably, in step (1), the dibasic acid comprises adipic acid.

[0011] Preferably, in step (1), the solvent comprises 1,4-dioxane.

[0012] Preferably, in step (1), the molar ratio of methacrylic acid, dibasic acid and epoxy resin is 0.85:(0.05-0.2):(0.5-2), and more preferably 0.85:0.1:1.

[0013] Preferably, in step (1), the catalyst comprises tetrabutylammonium bromide.

[0014] Preferably, in step (1), the mass of the catalyst is 0.5-1.5% of the total mass of methacrylic acid, dibasic acid and epoxy resin, and more preferably 0.8-1%.

[0015] Preferably, in step (1), the inhibitor comprises p-hydroxyanisole.

[0016] Preferably, in step (1), the mass of the polymerization inhibitor is 0.1-0.5% of the total mass of methacrylic acid, dibasic acid and epoxy resin, and more preferably 0.1-0.2%.

[0017] Preferably, in step (2), the reaction solution is loaded into a stainless steel syringe, and a high-pressure microinjection pump is used to push the reaction solution in the syringe into the microreactor.

[0018] Preferably, the high-pressure microinjection pump is a Havard injection pump.

[0019] Preferably, the microreactor is made of polytetrafluoroethylene tube (PTFE) or stainless steel tube (316L), the microreactor tube diameter is 1.5-2 mm, and the tube length is 3.5-5 m.

[0020] Preferably, the micro mixer is a Y-shaped stainless steel mixer or a T-shaped stainless steel mixer.

[0021] Preferably, in step (2), the reaction temperature is 140-160°C, more preferably 145-155°C. Specifically, for example, it is 140°C, 150°C, or 160°C.

[0022] Preferably, in step (2), the reaction time is 5-10 min, more preferably 6-8 min, specifically, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min.

[0023] Preferably, in step (2), the reaction pressure is 0.5-0.7 MPa.

[0024] Preferably, in step (2), after the reaction is completed, the product is collected and the solvent is removed by rotary evaporation. About 1 g of the product after the solvent is removed is placed in a conical flask, dissolved in acetone, and the acid value of the product is measured. The acid value of the product is in the range of 1-3 mg / g.

[0025] The reaction equation involved in the above UV curing flexible vinyl resin synthesis process is:

[0026]

[0027] “or” means “or”, n is an integer greater than 0, “Cat” means catalyst, and △ means heating.

[0028] Preferably, the UV curable flexible vinyl resin, reactive diluent and photoinitiator are mixed, sprayed, and then cured under ultraviolet light to form a film.

[0029] Preferably, the weight ratio of UV-curable flexible vinyl resin, reactive diluent and photoinitiator is 65-70:(25-35):(1-8), and more preferably 65:30:5.

[0030] Preferably, the photoinitiator is Irgacure 1173.

[0031] Preferably, the wavelength of the ultraviolet light is 365nm and the power is 2KW.

[0032] Preferably, it is sprayed on a polished tinplate sheet.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The present invention uses a microreactor device to solve the problem that the temperature of the reaction system is uncontrolled due to a strong exothermic reaction, avoids the product from gelling due to excessive temperature, and improves the reaction rate. The target product can be synthesized in a very short time. Since the temperature of the reaction system is constant, the diffusion rate is fast, the reaction selectivity is high, and there are fewer side reaction products, the color of the synthesized product is colorless. Epoxy resin is used as a raw material to react with methacrylic acid and adipic acid, and long-chain fatty dibasic acid is introduced into the product, so that the flexibility of the vinyl resin is improved after curing. The molecular weight of the product is measured by GPC (gel permeation chromatography), and it is found that the molecular weight distribution of the synthesized product in the microreactor is narrower than that in the kettle reactor, indicating that there are fewer side reaction products.

[0035] (2) The present invention uses epoxy resin, methacrylic acid, adipic acid as raw materials, tetrabutylammonium bromide as a catalyst, and p-hydroxyanisole as a polymerization inhibitor to synthesize vinyl resin in a microreactor, and investigates the effects of reaction temperature and residence time on acid value. Compared with the synthesis of vinyl resin in a tank reactor, the present invention has the advantages that the temperature of the reaction system is accurately controlled in the microreactor to avoid the phenomenon of excessive local temperature, the efficient mass transfer and heat transfer rate greatly increases the reaction rate, improves the product selectivity, reduces the content of side reaction products, and improves the carboxyl conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of the micro-reaction device used in the present invention;

[0037] Figure 2 This is the infrared spectrum of the vinyl resin synthesized in Example 8 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0039] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0040] Example 1

[0041] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0042] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 140°C, the total flow rate of the reaction solution to 3.16 mL / min, the pressure to 0.5 MPa, the reaction residence time to 5 min, and the acid value of the target product is measured to be 125 mg / g.

[0043] Example 2

[0044] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0045] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 150°C, the total flow rate of the reaction solution to 3.16 mL / min, the pressure to 0.5 MPa, the reaction residence time to 5 min, and the acid value of the target product is measured to be 107 mg / g.

[0046] Example 3

[0047] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0048] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 160°C, the total flow rate of the reaction solution to 3.16 mL / min, the pressure to 0.7 MPa, the reaction residence time to 5 min, and the acid value of the target product is measured to be 98 mg / g.

[0049] Example 4

[0050] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0051] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 150°C, the total flow rate of the reaction solution to 2.63 mL / min, the pressure to 0.5 MPa, the reaction residence time to 6 min, and the acid value of the target product to be measured to be 42.7 mg / g.

[0052] Example 5

[0053] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0054] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 150°C, the total flow rate of the reaction solution to 2.26 mL / min, the pressure to 0.5 MPa, the reaction residence time to 7 min, and the acid value of the target product to be measured to be 17.41 mg / g.

[0055] Example 6

[0056] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0057] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 150°C, the total flow rate of the reaction solution to 1.98 mL / min, the pressure to 0.5 MPa, the reaction residence time to 8 min, and the acid value of the target product to be measured to be 9.92 mg / g.

[0058] Example 7

[0059] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0060] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 150°C, the total flow rate of the reaction solution to 1.76 mL / min, the pressure to 0.5 MPa, the reaction residence time to 9 min, and the acid value of the target product to be measured to be 3.9 mg / g.

[0061] Example 8

[0062] A method for synthesizing UV-curable flexible vinyl resin using a microreactor comprises the following steps:

[0063] Take 3.21 g of adipic acid and 22 g of solvent 1,4-dioxane to completely dissolve the adipic acid, then add 50 g of epoxy resin (bisphenol A type epoxy resin), 15.33 g of methacrylic acid, 0.793 g of catalyst tetrabutylammonium bromide, and 0.158 g of inhibitor p-hydroxyanisole, mix well to obtain a reaction solution, inject the reaction solution into a syringe, and use a high-pressure micro-injection pump to push the reaction solution in the syringe into the microreactor, control the reaction temperature to 150°C, the total flow rate of the reaction solution to 1.58 mL / min, the pressure to 0.5 MPa, the reaction residence time to 10 min, and the acid value of the target product to be measured to be 1.61 mg / g.

[0064] Product effect testing

[0065] 1. Infrared spectroscopy analysis

[0066] Figure 1 This is a schematic diagram of the structure of the micro-reaction device used in the present invention; Figure 1 The "reaction liquid" in the equation means the reaction liquid, and "Heating" means heating. The syringe pump pushes the syringe to make the reaction liquid pass through the T-type mixer and mix quickly and evenly, and react quickly in the 2mm tetrafluoroethylene tube. Because the vinyl resin has a large molecular weight and high viscosity, it is easy to block the pipeline during the reaction. Therefore, choose Figure 1 The simple microreactor not only saves synthesis costs, but also greatly improves the reaction conversion rate.

[0067] Figure 2 This is the infrared spectrum of the vinyl resin synthesized in Example 8 of the present invention. Figure 2 The horizontal axis represents the wave number in cm -1 .

[0068] The product prepared in Example 8 was subjected to infrared spectroscopy analysis. The structure of the product was analyzed using a Nicolet 6700 spectrometer. KBr pellets were used to prepare the sample and the transmittance of the product was measured. The scanning range was 400-4000 cm -1 , the results are as follows Figure 2 shown.

[0069] From the infrared spectrum, we can see that at 1613cm -1 The carbon-carbon double bond stretching vibration peak appeared, indicating that a carbon-carbon double bond was introduced into the synthesized product during the reaction. -1 The absorption peak of methylene appears at 1715cm, indicating that the introduction of methylene into the product increases the flexibility of the resin after curing. Compared with the infrared spectrum of epoxy resin, the synthetic product has an absorption peak of 1715cm -1 The characteristic absorption peak of carbonyl in esters and 3449 cm -1The characteristic absorption peak of hydroxyl at 871cm indicates that the epoxy group reacts with the carboxyl group to generate an ester group and a hydroxyl group. -1 The characteristic absorption peak of the epoxy group disappeared, indicating that the epoxy group and the carboxyl group underwent a ring-opening reaction, and the reaction was relatively complete, which was consistent with the result shown by the measured acid value.

[0070] 2. Film forming performance test

[0071] The vinyl resin synthesized in Example 8 (also called adipic acid-modified vinyl resin) was mixed evenly with a reactive diluent and a photoinitiator Irgacure 184, with a mass ratio of the vinyl resin, the reactive diluent and the photoinitiator being 70:25:5, and then sprayed on a polished tinplate sheet, which was placed in a UV curing machine (2kW, wavelength λ=365nm) to form a film, and the pencil hardness was measured according to GB / T6739-2006, the adhesion was measured according to GB / T9286-1998, and the flexibility was measured according to the standard GB / T1731-1993, and the results are shown in Table 1. A control group was also set up, and the performance of the film was tested by using a commercially available vinyl resin instead of the vinyl resin synthesized in Example 8.

[0072] Table 1: Coating properties

[0073]

[0074] Table 1 shows that the product synthesized by the microreactor has improved flexibility after curing compared with the commercially available vinyl resin, while the pencil hardness and adhesion are not reduced. The curing performance of the coating film meets the expected requirements.

[0075] In the present invention, the change of acid value is selected as the basis for judging whether the reaction is good or bad, and the data of cured film is the performance data of the product. Because the flexible vinyl resin is synthesized in the microreactor, the temperature is heated evenly, the reaction rate is fast, the reaction conversion rate is more than 98%, the synthetic by-products are less, the molecular weight distribution is uniform, and the cured film flexibility is better. The change of acid value in the present invention represents the degree of reaction, and the larger the acid value, the lower the reaction conversion rate. The acid value data in the embodiments of the present invention are the conversion rates of the corresponding vinyl resin reactions. Because the viscosity of the synthetic product is relatively large, there are some residual raw materials and products in the microreactor, and the yield of the vinyl resin cannot well represent the reaction degree of the vinyl resin. Therefore, the change of the more intuitive acid value is selected to represent the influence of different reaction conditions on the reaction degree in the embodiment.

Claims

1. A method for synthesizing UV-curable flexible vinyl resin using a microreactor, characterized in that: The following steps are involved: (1) Preparation of reaction solution: mixing dibasic acid, solvent, methacrylic acid, epoxy resin, catalyst, and polymerization inhibitor to obtain a reaction solution; (2) adding the reaction solution into a microreactor for reaction to obtain the UV-curable flexible vinyl resin.

2. The method according to claim 1, characterized in that In step (1), the dibasic acid includes adipic acid.

3. The method according to claim 1, characterized in that In step (1), the molar ratio of methacrylic acid, dibasic acid and epoxy resin is 0.85:(0.05-0.2):(0.5-2).

4. The method according to claim 1, characterized in that: In step (1), the catalyst comprises tetrabutylammonium bromide.

5. The method according to claim 1, characterized in that In step (1), the mass of the catalyst is 0.5-1.5% of the total mass of methacrylic acid, dibasic acid and epoxy resin.

6. The method according to claim 1, characterized in that In step (1), the polymerization inhibitor comprises p-hydroxyanisole; and / or the mass of the polymerization inhibitor is 0.1-0.5% of the total mass of methacrylic acid, dibasic acid and epoxy resin.

7. The method according to claim 1, characterized in that In step (2), the reaction solution is loaded into a stainless steel syringe, and a high-pressure micro-injection pump is used to push the reaction solution in the syringe into the microreactor.

8. The method according to claim 1, characterized in that The microreactor is made of polytetrafluoroethylene tube or stainless steel tube, the diameter of the microreactor tube is 1.5-2mm, and the tube length is 3.5-5m.

9. The method according to claim 1, characterized in that: In step (2), the reaction temperature is 140-160° C.; and / or, in step (2), the reaction time is 5-10 min.

10. The method according to claim 1, characterized in that The UV curable flexible vinyl resin, reactive diluent and photoinitiator are mixed, sprayed, and then cured under ultraviolet light to form a film.

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