Method for preparing a (meth)acrylate monomer

Abstract

The present invention relates to a method for preparing a (meth)acrylate monomer with high performance and high economic value. The present invention uses pentaerythritol and (meth)acrylic acid as the main compounds, first conducts an esterification reaction, and after reaching a certain acid value, adds one or two of a certain amount of chain extenders adipic acid and itaconic acid. After washing with water and removing the solvent, a (meth)acrylate monomer with relatively low price but excellent performance is obtained. The synthesized monomer has a relatively high functionality, and the coating after UV curing has relatively high hardness and gloss. Due to the addition of different amounts of chain extenders, the viscosity of the (meth)acrylate monomer ranges from 1000 to 15000 cps / 25 °C, and the properties such as flexibility, hardness, and adhesion of the coating after UV curing are all very good, which can expand the application range of the (meth)acrylate monomer.

Description

Technical Field

[0001] The present invention relates to a method for preparing (meth)acrylate monomers, belonging to the technical field of organic synthesis. Background Art

[0002] With the strengthening of environmental awareness, the coating industry has been continuously researching and developing new technologies to reduce the use of traditional solvent-based coatings and lower the emission of VOCs.

[0003] UV curing technology has the advantages of low energy consumption, low volatile content, no pollution, fast film-forming speed, and high film quality, becoming a new generation of green technology. In UV coatings, (meth)acrylate monomers account for a relatively large proportion, about 20 - 50%. Acrylate monomers can not only adjust the viscosity of UV coatings but also improve the performance of UV coatings. (Meth)acrylate monomers can be simply classified according to the number of functional groups into: monofunctional, difunctional, and polyfunctional monomers. Monomers with different numbers of functional groups have a great influence on the performance of coatings and can change properties such as the adhesion, hardness, flexibility, and light transmittance of coatings. The viscosity of (meth)acrylate monomers also affects the scope of use of the monomers. In some application scenarios, (meth)acrylate monomers with higher viscosity are required. However, since most monomers are compounds with relatively small molecular weights, their viscosities are generally small, usually ranging from a dozen to over a hundred. The viscosity of PETA (pentaerythritol triacrylate) is about 400 - 700 cps / 25°C, and the viscosity of higher-viscosity DPHA (dipentaerythritol hexaacrylate) is about 6000 - 8000 cps / 25°C. In some ink printing scenarios, this limits the application of most monomers.

[0004] Due to reasons such as raw material shortage, few manufacturers, and low production, the price of DPHA is high. The price of PETA is lower, but its low viscosity narrows its application range. Summary of the Invention

[0005] The purpose of the present invention is to provide a synthesis scheme for (meth)acrylate monomers.

[0006] The present invention uses (meth)acrylic acid and pentaerythritol under the action of a catalyst to first esterify into pentaerythritol (meth)acrylate, and then by adding a dibasic acid as a chain extender, synthesize (meth)acrylate monomers with ultra-high functionality and ultra-high viscosity. Since the prices of raw materials pentaerythritol and dibasic acid are relatively low, the price of the synthesized acrylate monomer can be 10,000 - 15,000 yuan / ton cheaper than DPHA. Conducting a photocuring performance test on the synthesized (meth)acrylate monomer, it is found that the hardness, curing speed, and adhesion of the cured film are all higher than those of DPHA. As the content of the chain extender increases, the viscosity can reach 1000 - 15000 cps / 25°C, which greatly increases the competitiveness of this product.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a (meth)acrylate monomer, comprising the following steps:

[0009] (1) Synthesis of pentaerythritol (meth)acrylate: Add a certain amount of pentaerythritol, a water-carrying agent, a catalyst, an inhibitor, and (meth)acrylic acid into a four-necked flask equipped with a stirrer, a thermometer, a water separator, and a condenser. Adjust the reaction temperature to 70-120°C and the reaction time to 4-6 h. After measuring that the acid value in the flask reaches the theoretical value, cool down to obtain pentaerythritol (meth)acrylate;

[0010] (2) Preparation of the (meth)acrylate monomer: After the temperature of the solution in step (1) drops to 40-50°C, add a certain amount of dibasic acid to the reaction kettle, continue to heat up to 70-120°C, reflux for 4-6 h, take a sample to measure the acid value, and stop the reaction after reaching the theoretical value;

[0011] (3) Washing with water and desolvation: Add the material in step (2) into a pear-shaped separating funnel, add a certain amount of solvent and shake well, then add soda ash and liquid alkali with a certain concentration in sequence to wash the excessive acid, control the temperature within a certain range. After the pH of the lower layer of water in the separating funnel is > 7, carry out vacuum desolvation. After the residual solvent < 200 ppm, obtain the finished product of the (meth)acrylate monomer.

[0012] As a preferred solution, the water-carrying agent is at least one or a mixture of several of toluene, cyclohexane, n-heptane, and n-hexane.

[0013] As a preferred solution, the catalyst is at least one or a mixture of several of p-toluenesulfonic acid and concentrated sulfuric acid.

[0014] As a preferred solution, the inhibitor is one or a mixture of several of p-methoxyphenol, phenothiazine, or hydroquinone.

[0015] As a preferred solution, the molar ratio of pentaerythritol to (meth)acrylic acid is 1:3-3.5.

[0016] In step (2), the dibasic acid is at least one or a mixture of several of adipic acid, itaconic acid, aconitic acid, and malonic acid. The molar amount of the dibasic acid added: 2n(dibasic acid) ≤ 4n(pentaerythritol) - n((meth)acrylic acid).

[0017] As a preferred solution, the mass concentration of the soda ash (sodium carbonate) in step (3) is 5-18%, and the mass concentration of the liquid alkali (sodium hydroxide) is 2-25%.

[0018] The beneficial effects of the present invention are as follows: The present invention provides a method for synthesizing (meth)acrylate monomers with low cost and high performance. Compared with the existing DPHA, with the change of the content of the chain extender dibasic acid, the viscosity of this monomer can be adjusted from 1000 to 15000 cps / 25°C, and the properties such as photocuring performance, speed, adhesion, and scratch resistance are all significantly improved. Moreover, the cost is reduced by 10000 - 15000 yuan per ton, which has good economic value and broad market prospects. Detailed implementation manners

[0019] The following further illustrates the present invention in conjunction with embodiments, but the embodiments do not constitute a limitation to the scope of protection required by the present invention: Embodiment 1

[0020] 1. A preparation method of (meth)acrylate monomers, which comprises the following steps:

[0021] (1) Synthesis of pentaerythritol (meth)acrylate: Add 136 g of pentaerythritol, 94 g of toluene, 11 g of methanesulfonic acid, 0.25 g of p-hydroxyanisole, and 230 g of acrylic acid into a four-necked flask equipped with a stirrer, a thermometer, a water separator, and a condenser. Adjust the reaction temperature to 110°C and the reaction time to 4 h. After measuring that the acid value in the flask reaches 20 mgKOH / g, cool down to obtain pentaerythritol (meth)acrylate;

[0022] (2) Preparation of (meth)acrylate monomers: After the temperature of the solution in step (1) drops to 40°C, add 35 g of adipic acid to the reaction kettle, continue to heat up to 110°C, reflux for 3 h, take a sample to measure the acid value, and stop the reaction after it reaches 15 mgKOH / g;

[0023] (3) Washing and solvent stripping: Add the materials in step (2) into a pear-shaped separatory funnel, add 200 g of toluene after shaking well, add 150 g of sodium carbonate with a mass concentration of 15% and 80 g of sodium hydroxide with a mass concentration of 5% in sequence to wash the excessive acid, control the temperature at 45°C. After the pH of the lower layer of water in the separatory funnel is >7, carry out solvent stripping under negative pressure. After the residual solvent <200 ppm, obtain a (meth)acrylate monomer finished product with a viscosity of 7000 cps / 25°C.

[0024] 2. Performance Test: Take the above-prepared (meth)acrylate monomer, add 3% of photoinitiator 1173, and cure it under a crawler-type ultraviolet lamp with a power of 2 kW and a curing time of 4 s per time to obtain a cured film. Prepare a DPHA cured film under the same conditions for comparison. Use a QHQ-A portable pencil hardness tester and refer to GB / T 6739–2006 "Paints and varnishes - Determination of film hardness by pencil test" to measure the pencil hardness of the coating film. Use a QFH coating film cross-cutting instrument from Tianjin Jingke Material Testing Machine Factory, and use Scotch610 tape for the tape. Refer to GB / T 9286-1998 "Cross-cut test for paints and varnishes film" to measure the adhesion of the coating film by the cross-cut test method. Refer to the national standard GB / T 1731-1993 "Method for the determination of flexibility of paint films" to detect the performance of both, and the results are shown in Table 1 below.

[0025] Table 1 Performance Test and Comparison

[0026] Performance Test Methacrylate monomer DPHA Hardness 2H H Flexibility ＞7 ＞7 Surface drying time Twice Twice Adhesion Grade 0 Grade 0 Wear resistance No trace Slight scratch Example

[0027] 1. A preparation method of a (meth)acrylate monomer, which comprises the following steps:

[0028] (1) Synthesis of pentaerythritol (meth)acrylate: Add 136 g of pentaerythritol, 100 g of toluene, 80 g of cyclohexane, 12 g of concentrated sulfuric acid, 0.3 g of hydroquinone, and 252 g of acrylic acid into a four-necked flask equipped with a stirrer, a thermometer, a water separator, and a condenser. Adjust the reaction temperature to 95 °C and the reaction time to 5 h. After measuring that the acid value in the flask reaches 35 - 40 mgKOH / g, cool down to obtain pentaerythritol (meth)acrylate.

[0029] (2) Preparation of (meth)acrylate monomer: After the temperature of the solution in step (1) drops to 50 °C, add 80 g of itaconic acid to the reaction kettle, continue to heat up to 100 °C, and reflux for 4 h. Take a sample to measure the acid value, and stop the reaction when it reaches 15 - 20 mgKOH / g.

[0030] (3) Washing and solvent stripping: Add the materials in step (2) into a pear-shaped separating funnel, add 200 g of toluene and shake well. Then add 160 g of sodium carbonate with a mass concentration of 15% and 70 g of sodium hydroxide with a mass concentration of 20% in sequence to wash the excessive acid. Control the temperature at 35 °C. After the pH of the lower layer of water in the separating funnel is > 7, perform negative pressure solvent stripping. When the residual solvent < 200 ppm, obtain a (meth)acrylate monomer finished product with a viscosity of 12000 cps / 25 °C.

[0031] 2. Performance Test: Take the above-prepared (meth)acrylate monomer, add 3% of photoinitiator 1173, and cure it under a crawler-type ultraviolet lamp with a power of 2 kW and a curing time of 4 s per time to obtain a cured film. Prepare a DPHA cured film under the same conditions for comparison. Use a QHQ-A portable pencil hardness tester and refer to GB / T 6739–2006 "Paints and varnishes - Determination of film hardness by pencil test" to measure the pencil hardness of the coating film. Use a QFH coating film cross-cutting instrument from Tianjin Jingke Material Testing Machine Factory, and use Scotch610 tape for the tape. Refer to GB / T 9286-1998 "Paints and varnishes - Cross-cut test of coating films" to measure the adhesion of the coating film by the cross-cut test method. Refer to the national standard GB / T 1731-1993 "Determination of flexibility of coating films" to detect the flexibility of both. The results are shown in Table 2 below.

[0032] Table 2 Performance Test and Comparison

[0033] Performance Test Methacrylate monomer DPHA Hardness 4H H Flexibility ＞7 ＞7 Surface drying time Once Twice Adhesion Grade 0 Grade 0 Wear resistance No trace Slight scratch 。

[0034] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a (meth)acrylate monomer, characterized in that, it comprises the following steps: Synthesis of pentaerythritol (meth)acrylate: Add a certain amount of pentaerythritol, water-carrying agent, catalyst, inhibitor, and (meth)acrylic acid into a four-necked flask equipped with a stirrer, thermometer, water separator, and condenser. Adjust the reaction temperature to 70 - 120 °C and the reaction time to 4 - 6 h. After measuring that the acid value in the flask reaches the theoretical value, cool down to obtain pentaerythritol (meth)acrylate; Preparation of (meth)acrylate monomer: After the temperature of the pentaerythritol (meth)acrylate solution prepared in step (1) drops to 40 - 50 °C, add a certain amount of dibasic acid to the reaction kettle, continue to heat up to 70 - 120 °C, reflux for 4 - 6 h, take a sample to measure the acid value, and stop the reaction after reaching the theoretical value; Washing and solvent stripping: Add the material in step (2) into a pear-shaped separating funnel, add a certain amount of solvent and shake well, then add soda ash and liquid alkali with a certain concentration in sequence to wash the excessive acid, control the temperature within a certain range. After the pH of the lower layer of water in the separating funnel is > 7, carry out solvent stripping under negative pressure. After the residual solvent < 200 ppm, obtain the finished product of (meth)acrylate monomer.

2. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, the water-carrying agent is at least one or a mixture of several of toluene, cyclohexane, n-heptane, and n-hexane; the catalyst is at least one or a mixture of several of p-toluenesulfonic acid and concentrated sulfuric acid; the inhibitor is one or a mixture of several of p-methoxyphenol, phenothiazine, or hydroquinone.

3. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, the molar ratio of pentaerythritol to (meth)acrylic acid in step (1) is: 1:3 - 3.

5.

4. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, the dibasic acid in step (2) is at least one or a mixture of several of adipic acid, itaconic acid, aconitic acid, and malonic acid.

5. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, the molar amount of the dibasic acid added in step (2): 2n(dibasic acid) ≤ 4n(pentaerythritol) - n((meth)acrylic acid).

6. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, the concentration of soda ash in step (3) is 5 - 18%, accounting for 40 - 70%, and the concentration of liquid alkali is 2 - 25%, accounting for 30 - 60%.

7. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, the temperature in step (3) is controlled at 25 - 55 °C.

8. The preparation method of the (meth)acrylate monomer according to claim 1, characterized in that, it comprises the following steps: (1)Synthesis of pentaerythritol (meth)acrylate: In a four-necked flask equipped with a stirrer, thermometer, water separator and condenser, add 136 g of pentaerythritol, 94 g of toluene, 11 g of methanesulfonic acid, 0.25 g of p-hydroxyanisole, and 230 g of (meth)acrylic acid. Adjust the reaction temperature to 110 °C and the reaction time to 4 h. After measuring that the acid value in the flask reaches 20 mgKOH / g, cool down to obtain pentaerythritol (meth)acrylate; (2)Preparation of (meth)acrylate monomer: After the temperature of the pentaerythritol (meth)acrylate solution in step (1) drops to 40 °C, add 35 g of adipic acid to the reaction kettle, continue to heat up to 110 °C, reflux for 3 h, take a sample to measure the acid value, and stop the reaction after it reaches 15 mgKOH / g; (3)Washing and solvent stripping: Add the material in step (2) to a pear-shaped separating funnel, add 200 g of toluene after shaking well, add 150 g of sodium carbonate with a mass concentration of 15% and 80 g of liquid alkali with a mass concentration of 5% in sequence to wash the excessive acid, control the temperature at 45 °C. After the pH of the lower layer of water in the separating funnel is > 7, carry out negative pressure solvent stripping. After the residual solvent < 200 ppm, obtain the (meth)acrylate monomer finished product with a viscosity of 7000 cps / 25 °C.

9. The preparation method of the (meth)acrylate monomer as described in claim 1, characterized in that, it includes the following steps: (1)Synthesis of pentaerythritol (meth)acrylate: In a four-necked flask equipped with a stirrer, thermometer, water separator and condenser, add 136 g of pentaerythritol, 100 g of toluene, 80 g of cyclohexane, 12 g of concentrated sulfuric acid, 0.3 g of hydroquinone, and 252 g of (meth)acrylic acid. Adjust the reaction temperature to 95 °C and the reaction time to 5 h. After measuring that the acid value in the flask reaches 35 - 40 mgKOH / g, cool down to obtain pentaerythritol (meth)acrylate; (2)Preparation of (meth)acrylate monomer: After the temperature of the pentaerythritol (meth)acrylate solution in step (1) drops to 50 °C, add 80 g of itaconic acid to the reaction kettle, continue to heat up to 100 °C, reflux for 4 h, take a sample to measure the acid value, and stop the reaction when it reaches 15 - 20 mgKOH / g; (3)Washing and solvent stripping: Add the material in step (2) to a pear-shaped separating funnel, add 200 g of toluene after shaking well, add 160 g of sodium carbonate with a mass concentration of 15% and 70 g of liquid alkali with a mass concentration of 5% in sequence to wash the excessive acid, control the temperature at 35 °C. After the pH of the lower layer of water in the separating funnel is > 7, carry out negative pressure solvent stripping. After the residual solvent < 200 ppm, obtain the (meth)acrylate monomer finished product with a viscosity of 12000 cps / 25 °C.