Acrylate monomer, preparation method thereof and application in photocurable coating

Abstract

The present invention discloses an acrylate monomer, a preparation method thereof and an application of the acrylate monomer in a photocurable coating. The structural formula (I) of the acrylate monomer is as follows: wherein R1 is a C1-C4 straight-chain alkyl group or H; R2 and R3 are independently a C1-C4 alkyl group or R2, R3 and N are bridged to form a C4-C5 heterocyclic group; the acrylate monomer prepared by the present invention can improve the ultraviolet light curing effect and the photocuring speed, and does not require the addition of an additional hydrogen donor auxiliary agent, and can effectively suppress the oxygen inhibition problem in the free radical system.

Description

Technical Field

[0001] The invention belongs to the field of photocurable coatings, and in particular relates to an acrylate monomer and a preparation method thereof and application thereof in photocurable coatings. Background Art

[0002] Radiation curing includes ultraviolet curing (UV) and electron beam curing (EB), which are widely used in the field of coatings due to their advantages of energy saving, environmental protection, high curing efficiency, good economic benefits, and no VOCs emissions. UV-curing coatings are generally composed of four parts: oligomers, monomers, photoinitiators, and additives. Monomers, also known as active diluents, are small organic molecules containing polymerizable functional groups. They not only dissolve and dilute oligomers and adjust the viscosity of the system, but also participate in the photocuring process, affecting the photocuring speed, the pigment wettability of the coating, the adhesion properties of the coating, and the various properties of the cured film. They are an important component of photocuring coatings.

[0003] Compared with electron beam curing, UV curing has a faster curing rate and is easier to operate, so UV curing is often used in the field of radiation curing. UV curing systems are divided into free radical systems and cationic systems. The most commonly used in UV curing systems is the free radical system. The photoinitiators used in the free radical system are divided into cleavage-type free radical photoinitiators (Type I photoinitiators) and hydrogen-abstracting free radical photoinitiators (Type II photoinitiators). During the UV curing process, since the stable state of oxygen in the air is the excited triplet state, the oxygen in this state will interact with the active free radicals generated during the photocuring process, quenching the active free radicals, thereby inhibiting the polymerization reaction, resulting in incomplete curing of the photocured coating or even stickiness, and greatly reduced surface performance.

[0004] In order to solve the problem of active free radicals quenched by oxygen in the air, the prior art usually adds hydrogen donor additives to the UV curing system, such as hydrogen donor active amines or compounds containing active α-H structures. Hydrogen donor additives can effectively reduce the peroxides formed by oxygen and free radicals in the oxygen inhibition process into active free radicals, allowing the polymerization reaction to continue. However, when hydrogen donor additives are added to cleavage-type free radical photoinitiators, the hydrogen donor additives will interact with the cleavage-type free radical photoinitiators, affecting the storage stability of the cleavage-type free radical photoinitiators; adding hydrogen donor additives to hydrogen abstraction-type free radical photoinitiators does not solve the oxygen inhibition problem well.

[0005] Therefore, it is of great significance to develop a functional monomer that can improve the UV curing effect without the need for additional hydrogen donor additives. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides an acrylate monomer, which can improve the ultraviolet light curing effect and the photocuring speed, and does not require the addition of an additional hydrogen donor auxiliary agent. The acrylate monomer can effectively reduce the peroxide formed by oxygen and free radicals in the oxygen inhibition process into active free radicals, thereby solving the oxygen inhibition problem in the free radical system. At the same time, the acrylate monomer can be used as a hydrogen donor to provide active hydrogen for the Type II photoinitiator system so that the photocuring system can achieve a good curing effect.

[0007] The object of the present invention is to provide an acrylate monomer, the structural formula (I) of the acrylate monomer is as follows:

[0008]

[0009] Among them, R1 is a C1-C4 straight-chain alkyl group or H; R2 and R3 are independently a C1-C4 alkyl group or R2, R3 and N are bridged to form a C4-C5 heterocyclic group.

[0010] Another object of the present invention is to provide a method for preparing an acrylate monomer, comprising the following steps:

[0011] Step S1. Mix acrylic acid, a polymerization inhibitor, a 3-hydroxymethyloxetane compound and a Lewis base catalyst, and react at elevated temperature to obtain a compound of formula (III). The structure of the 3-hydroxymethyloxetane compound is shown in formula (II):

[0012]

[0013] Wherein, R1 is a C1-C4 straight chain alkyl group or H;

[0014] Step S2. The compound of formula (III), an acetal amide compound dissolved in a solvent, a strong acid catalyst, and a polymerization inhibitor are mixed, the temperature is raised for reaction, and the crude product is separated and purified to obtain an acrylate monomer of formula (I). The structure of the acetal amide compound is shown in formula (IV):

[0015]

[0016] Wherein, R2 and R3 are independently C1-C4 alkyl or R2, R3 and N are bridged to form a C4-C5 heterocyclic group, and R4 is a C1-C5 alkyl.

[0017] Preferably, in step S1, the Lewis base catalyst is selected from one or more of triphenylphosphine, n-butylammonium bromide, chromium acetate, triethylamine, and N,N-dimethylbenzylamine.

[0018] More preferably, in step S1, the Lewis base catalyst is selected from chromium acetate. The chromium acetate catalytic reaction used in the present invention has a higher yield, which may be due to the fact that chromium acetate forms a complex intermediate state with acrylic acid and 3-hydroxymethyloxetane compounds during the catalytic reaction, thereby reducing the reaction activation energy.

[0019] Preferably, in step S2, the strong acid catalyst is selected from one or more of p-toluenesulfonic acid, methanesulfonic acid, boron trifluoride etherate, scandium trifluoromethanesulfonate, and yttrium trifluoromethanesulfonate.

[0020] More preferably, in step S2, the strong acid catalyst is selected from one or more of scandium trifluoromethanesulfonate and yttrium trifluoromethanesulfonate. The catalytic reaction of scandium trifluoromethanesulfonate and yttrium trifluoromethanesulfonate used in the present invention has a higher yield, which may be due to the fact that scandium trifluoromethanesulfonate or yttrium trifluoromethanesulfonate forms a complex intermediate with the compound of formula (III) and the acetalamide compound during the catalytic reaction, thereby reducing the reaction activation energy.

[0021] Preferably, in step S1, the molar ratio of the acrylic acid, the 3-hydroxymethyloxetane compound, the Lewis base catalyst and the polymerization inhibitor is 1-1.05:1:0.001-0.005:0.001-0.002.

[0022] Preferably, in step S1, the temperature-raising reaction is to raise the temperature to 80-120° C. and react for 3-8 hours.

[0023] Preferably, in step S2, the molar ratio of the compound of formula (III), the acetal amide compound, the strong acid catalyst and the polymerization inhibitor is 1-1.1:1:0.001-0.01:0.001-0.005.

[0024] Preferably, in step S2, the temperature-raising reaction is to raise the temperature to 50-100° C. and react for 3-8 hours.

[0025] Preferably, the polymerization inhibitor is selected from one or more of hydroquinone, methyl hydroquinone, tert-butyl hydroquinone, 2,6-di-tert-butyl hydroquinone, N,N'-diphenyl-p-phenylenediamine, phenothiazine, and N-nitroso-cyclohexylhydroxylamine.

[0026] Preferably, in step S2, the solvent is selected from one or more of chloroform, dichloromethane, tetrahydrofuran and toluene.

[0027] Another object of the present invention is to provide an application of the above-mentioned acrylate monomer in a photocurable coating.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The acrylate monomer provided by the present invention can be used to prepare a coating to effectively increase the curing speed of the coating and inhibit oxygen inhibition; when used with a Type II photoinitiator, no additional additives are required to achieve a good curing effect and curing speed;

[0030] (2) The acrylate monomer prepared by the present invention provides raw materials for the industrialization of LED curing, and the acrylate monomer has excellent pigment wettability, which can broaden its application in colored systems. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0032] TPO: diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide;

[0033] DETX: 2,4-diethylthioxanthone;

[0034] ACMO: acryloylmorpholine;

[0035] IBOA: isobornyl acrylate;

[0036] TPGDA: tripropylene glycol diacrylate;

[0037] TMPTA: trimethylolpropane triacrylate;

[0038] B-296: difunctional polyurethane acrylate, Guangdong Boxing New Materials Technology Co., Ltd.;

[0039] B-590H: polyester acrylate, Guangdong Boxing New Material Technology Co., Ltd.;

[0040] MEHQ: methyl parahydroxyanisole;

[0041] Dispersants were purchased from Lubrizol Corporation.

[0042] Example 1: Preparation of acrylate monomers.

[0043] Step S1. In a 250 ml straight four-necked flask, acrylic acid (1.01 mol), hydroquinone (0.001 mol), and triphenylphosphine (0.001 mol) were added, and the temperature was slowly raised to 80° C. while stirring, and 3-hydroxyethyl ether (1 mol) was added dropwise. The addition was maintained for about 1 hour. The temperature of the addition process was controlled at 90±10° C. When the reaction was no longer exothermic, the reaction system was placed at 105±2° C. for insulation, and samples were taken every 1 hour to measure the acid value. When the acid value was less than 5 mgKOH / g, the crude product was passed through a silica gel column in an eluent of ethyl acetate: petroleum ether (v / v) = 1:10 to obtain compound A1 with a yield of 76.4%.

[0044] Step S2. In a 500 ml straight four-necked flask, add N,N-dimethylformamide diethyl acetal (1 mol) and tetrahydrofuran (100 g). After the solid N,N-dimethylformamide diethyl acetal is dissolved, add p-toluenesulfonic acid (0.001 mol), hydroquinone (0.001 mol), add compound A1 (1.02 mol), slowly heat to 60°C and react for 3 hours, then place in a 50°C water bath for rotary evaporation, and the crude product is passed through a silica gel column in an eluent of ethyl acetate: cyclohexane (v / v) = 1:9 to obtain a colorless, clear and transparent liquid, namely compound M1, with a yield of 77.3%. The NMR data are characterized as follows: 1 H-NMR (CDCl3, 400MHz), δ (ppm): 6.31 (d, 1H, CH2), 6.08 (m, 1H, CH), 5.85 (s, 1H, C H),5.61(d,1H,CH2),3.60-3.90(m,6H,CH2),2.27(s,6H,CH3),2.08(m,1H,CH).

[0045]

[0046] Example 2: Preparation of acrylate monomers.

[0047] Step S1. In a 250 ml straight four-necked flask, add acrylic acid (1.05 mol), hydroquinone (0.002 mol), and n-butylammonium bromide (0.005 mol), slowly heat to 80°C while stirring, add oxetane-3-methanol (1 mol) dropwise, and keep the addition for about 1 hour. The temperature of the addition process is controlled at 90±10°C. When the reaction is no longer exothermic, the reaction system is placed at 105±2°C for insulation, and samples are taken every 1 hour to measure the acid value. When the acid value is less than 5 mgKOH / g, the crude product is passed through a silica gel column in an eluent of ethyl acetate: petroleum ether (v / v) = 1:10 to obtain compound A1 with a yield of 76.4%.

[0048] Step S2. In a 500 ml straight four-necked flask, add 1-(dimethoxymethyl)piperidine (1 mol) and tetrahydrofuran (100 g). After the solid 1-(dimethoxymethyl)piperidine is dissolved, add methanesulfonic acid (0.01 mol), hydroquinone (0.005 mol), add compound A1 (1.1 mol), slowly heat to 60°C and react for 6 hours, then place in a 50°C water bath for rotary evaporation, and the crude product is passed through a silica gel column in an eluent of ethyl acetate: cyclohexane (v / v) = 1:9 to obtain a colorless, clear and transparent liquid, namely compound M2, with a yield of 75.4%. The NMR data are characterized as follows: 1 H-NMR (C DCl3, 400MHz), δ (ppm): 6.39 (d, 1H, CH2), 6.13 (m, 1H, CH), 5.81 (s, 1H, CH), 5.78 (d, 1H, C H2),3.63-3.91(m,6H,CH2),2.48(m,4H,CH2),2.18(m,1H,CH),1.59-1.55(m,6H,CH2).

[0049]

[0050] Example 3: Preparation of acrylate monomers.

[0051] Step S1. In a 250 ml straight four-necked flask, add acrylic acid (1.0 mol), hydroquinone (0.001 mol), and N,N-dimethylbenzylamine (0.003 mol), slowly heat to 80°C while stirring, add 3-ethyl-3-oxetanol (1 mol) dropwise, and keep the addition for about 1 hour. The temperature of the addition process is controlled at 90±10°C. When the reaction is no longer exothermic, the reaction system is placed at 105±2°C for insulation, and samples are taken every 1 hour to measure the acid value. When the acid value is less than 5 mgKOH / g, the crude product is passed through a silica gel column in an eluent of ethyl acetate: petroleum ether (v / v) = 1:9 to obtain compound A2 with a yield of 72.9%.

[0052] Step S2. In a 500 ml straight four-necked flask, add N,N-dimethylformamide diethyl acetal (1 mol) and tetrahydrofuran (100 g). After the solid N,N-dimethylformamide diethyl acetal is dissolved, add boron trifluoride etherate (0.005 mol), hydroquinone (0.003 mol), add compound A2 (1.06 mol), slowly heat to 60 ° C and react for 6 hours, then place in a 50 ° C water bath for rotary evaporation, and the crude product is passed through a silica gel column in an eluent of ethyl acetate: cyclohexane (v / v) = 1:8 to obtain a colorless, clear and transparent liquid, namely compound M3, with a yield of 71.1%. The NMR data are characterized as follows: 1H-NMR (CDCl3, 400MHz), δ (ppm): 6.35 (d, 1H, CH2), 6.09 (m, 1H, CH), 5.85 (s, 1H, CH), 5.65 (d, 1H, CH2), 4. 10(s,2H,CH2),3.90(s,2H,CH2),3.68(s,2H,CH2),2.29(s,6H,CH3),1.69(m,2H,CH2),0.96(t,3H,CH3).

[0053]

[0054] Example 4: Preparation of acrylate monomers.

[0055] The triphenylphosphine in Example 1 was replaced by chromium acetate, and p-toluenesulfonic acid was replaced by scandium trifluoromethanesulfonate, while the other steps remained unchanged, to obtain compound A1 with a yield of 87.9%; and compound M1 with a yield of 92.8%.

[0056] Example 5: Preparation of acrylate monomers.

[0057] The n-butylammonium bromide in Example 2 was replaced by chromium acetate, the methanesulfonic acid was replaced by yttrium trifluoromethanesulfonate, and the other steps remained unchanged to obtain compound A1 with a yield of 88.5%; and compound M2 with a yield of 93.1%.

[0058] Preparation of light-curing coatings:

[0059] Table 1. Composition of coatings.

[0060]

[0061] Preparation of photocurable coating: 50 g of oligomer, 50 g of monomer, 2 g of photoinitiator and 0.5 g of hydrogen donor auxiliary agent in Table 1 were mixed and stirred to obtain photocurable coating.

[0062] Performance test of light-curing coatings:

[0063] The coatings prepared in Examples 6-11 were coated onto PC sheets using a 12 μm wire rod and cured using a 300 mJ medium pressure mercury lamp or a 2000 mJ 395 nm LED lamp. The curing time was recorded and the surface dryness of the coatings after curing was judged by finger touch method, where "NG" means that the coatings are sticky and incompletely cured; "OK" means that the coatings are completely cured and completely dry. The coatings cured by the medium pressure mercury lamp were tested for adhesion, hardness, wear resistance and chemical resistance.

[0064] Adhesion test: refer to GB 1720-1979 (1989) "Determination of adhesion of paint films", the grid spacing is 2mm, the smaller the adhesion grade value, the better the adhesion.

[0065] Wear resistance test: The vibration wear resistance performance is tested using the German ROSLER vibration wear tester.

[0066] Chemical resistance test: Determined in accordance with GB / T 1763-1979.

[0067] Table 2. Test results of coating properties of Examples 6-11 and Comparative Examples 1-12.

[0068]

[0069]

[0070] As can be seen from Table 2, the acrylate monomers M1 to M3 prepared in the present invention are compounded with TPO / DETX photoinitiators, and the coatings can be dried on the surface under irradiation with a mercury lamp or an LED lamp; in Comparative Examples 1 to 8, under the conditions of mercury lamp irradiation and TPO photoinitiation, ACMO, TPGDA, and TMPTA can all be dried on the surface, but IBOA does not dry on the surface; under the conditions of mercury lamp irradiation and DETX photoinitiation, ACMO, TPGDA, TMPTA, and IBOA do not dry on the surface; under the conditions of LED lamp irradiation, ACMO, TPGDA, TMPTA, and IBOA do not dry on the surface; in Comparative Examples 9 to 12, under the conditions of DETX+N,N-dimethylbenzylamine, the mercury lamp curing of ACMO, TPGDA, and TMPTA all dried on the surface, and the LED curing of TMPTA dried on the surface. It shows that the acrylate monomers M1-M3 prepared by the present invention have excellent curing performance under mercury lamp / LED irradiation, and their LED curing performance is better than ACMO and trifunctional monomer TMPTA. This performance provides key materials for photocuring systems that require high curing speed and low viscosity such as inkjet printing and 3D printing. In addition, the acrylate monomers M1-M3 prepared by the present invention can achieve good curing effects in hydrogen abstraction type photoinitiator systems without the need to add additional hydrogen donor additives.

[0071] Pigment wettability test:

[0072] 40g of B-590H, 20g of TMPTA, 15g of the monomer in Table 3, 4g of photoinitiator TPO, 2g of dispersant 24000, 18g of red powder, and 0.1g of inhibitor MEHQ were mixed uniformly, ground to less than 10 microns with a three-roll mill, and the fineness was tested with a fineness tube; then the ground sample was placed on an offset printing machine, printed on paper, and then cured with a 1000mJ energy medium-pressure mercury lamp. After complete curing, the color density of the coating was tested with a color density meter. The higher the color density value and the brighter the color, the better the wettability of the monomer to the pigment.

[0073] Table 3. Pigment wetting test results of coatings made from different monomers.

[0074] sample monomer Color Density Example 12 M1 2.55 Example 13 M2 2.53 Embodiment 14 M3 2.60 Comparative Example 13 ACMO 2.35 Comparative Example 14 IBOA 2.20 Comparative Example 15 TPGDA 2.22 Comparative Example 16 TMPTA 2.10

[0075] As can be seen from Table 3, in Examples 12 to 14, the formula contains monomers M1 to M3, and the color density values ​​are all above 2.50, while the color density of ACMO is 2.35, and the color densities of IBOA, TPGDA, and TMPTA are all less than 2.30, indicating that the acrylate monomers M1 to M3 prepared in the present invention have good pigment wettability.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, the technicians can still modify or replace the specific implementation mode of the present invention with equivalents, but these modifications or changes do not deviate from the scope of protection of the pending claims of the present application.

Claims

1. An acrylate monomer, characterized in that: The structural formula (I) of the acrylic acid ester monomer is shown below: Wherein, R1 is a C1~C4 straight chain alkyl or H; R2 and R3 are independently a C1~C4 alkyl.

2. An acrylate monomer, characterized in that: The structural formula (V) of the acrylic acid ester monomer is as follows:

3. A method for preparing an acrylate monomer, characterized in that: The steps include: Step S1. Mix acrylic acid, a polymerization inhibitor, a 3-hydroxymethyloxetane compound and a Lewis base catalyst, and react at elevated temperature to obtain a compound of formula (III). The structure of the 3-hydroxymethyloxetane compound is shown in formula (II): Wherein, R1 is a C1~C4 straight chain alkyl or H; Step S2. The compound of formula (III), an acetal amide compound dissolved in a solvent, a strong acid catalyst, and a polymerization inhibitor are mixed, the temperature is raised for reaction, and the crude product is separated and purified to obtain an acrylate monomer of formula (I). The structure of the acetal amide compound is shown in formula (IV): Wherein, R2 and R3 are independently C1~C4 alkyl, and R4 is C1~C5 alkyl.

4. A method for preparing an acrylate monomer, characterized in that: The steps include: Step S1. Mixing acrylic acid, a polymerization inhibitor, oxetane-3-methanol and a Lewis base catalyst, and heating the mixture to react to obtain a compound of formula (VI); Step S2. mixing the compound of formula (VI), 1-(dimethoxymethyl)piperidine dissolved in a solvent, a strong acid catalyst, and a polymerization inhibitor, reacting at elevated temperature, and separating and purifying the crude product to obtain a single acrylate of formula (V); 5. The method for preparing an acrylate monomer according to any one of claims 3 to 4, characterized in that: In step S1, the Lewis base catalyst is selected from one or more of triphenylphosphine, n-butylammonium bromide, chromium acetate, triethylamine, and N,N-dimethylbenzylamine.

6. The method for preparing an acrylate monomer according to any one of claims 3 to 4, characterized in that: In step S1, the Lewis base catalyst is selected from chromium acetate.

7. The method for preparing an acrylate monomer according to any one of claims 3 to 4, characterized in that: In step S2, the strong acid catalyst is selected from one or more of p-toluenesulfonic acid, methanesulfonic acid, boron trifluoride etherate, scandium trifluoromethanesulfonate, and yttrium trifluoromethanesulfonate.

8. The method for preparing an acrylate monomer according to claim 7, wherein: In step S2, the strong acid catalyst is selected from one or more of scandium trifluoromethanesulfonate and yttrium trifluoromethanesulfonate.

9. The method for preparing an acrylate monomer according to claim 3, wherein: In step S1, the molar ratio of the acrylic acid, 3-hydroxymethyloxetane compound, Lewis base catalyst and inhibitor is 1-1.05:1:0.001-0.005:0.001-0.002; the temperature-raising reaction is carried out by heating the temperature to 80-120° C. and reacting for 3-8 hours.

10. The method for preparing an acrylate monomer according to claim 4, characterized in that: In step S1, the molar ratio of acrylic acid, oxetane-3-methanol, Lewis base catalyst and inhibitor is 1-1.05:1:0.001-0.005:0.001-0.002; the temperature-raising reaction is carried out by heating the temperature to 80-120° C. and reacting for 3-8 hours.

11. The method for preparing an acrylate monomer according to claim 3, characterized in that: In step S2, the molar ratio of the compound of formula (III), the acetal amide compound, the strong acid catalyst and the inhibitor is 1-1.1:1:0.001-0.01:0.001-0.005; the temperature-raising reaction is carried out by heating the temperature to 50-100° C. and reacting for 3-8 hours.

12. The method for preparing an acrylate monomer according to claim 4, characterized in that: In step S2, the molar ratio of the compound of formula (VI), 1-(dimethoxymethyl)piperidine, strong acid catalyst and polymerization inhibitor is 1-1.1:1:0.001-0.01:0.001-0.005; the temperature-raising reaction is carried out by heating the temperature to 50-100° C. and reacting for 3-8 hours.

13. The method for preparing an acrylate monomer according to any one of claims 3 to 4, characterized in that: The polymerization inhibitor is selected from one or more of hydroquinone, methyl hydroquinone, tert-butyl hydroquinone, 2,6-di-tert-butyl hydroquinone, N,N'-diphenyl-p-phenylenediamine, phenothiazine, and N-nitroso-cyclohexylhydroxylamine.

14. Use of the acrylate monomer according to any one of claims 1 to 2 in a photocurable coating.

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