LU500719B1

LU500719B1 - UV-LED Curing Varnish and Preparation Method thereof

Info

Publication number: LU500719B1
Application number: LU500719A
Authority: LU
Inventors: Minghui He; Linjuan Yan; Zihan Jiang; Xingyan Yan; Guangxue Chen; Linyi Chen
Original assignee: Huagong Liyan Guangdong New Material Tech Co Ltd
Priority date: 2021-10-11
Filing date: 2021-10-11
Publication date: 2022-04-11

Abstract

The invention provides a UV-LED curing varnish and a preparation method thereof, and relates to the technical field of curing oils. The UV-LED curing varnish comprises the following raw material components in percentage by mass: 40-80% of polyurethane acrylate prepolymer, 5-25% of acrylate monomer, 1-5% of photoinitiator and the balance of solvent. The UV-LED curing varnish provided by the invention takes polyurethane acrylate prepolymer, acrylate monomer and photoinitiator in a specific proportion as main raw materials, and reacts under the action of photoinitiator to obtain the UV-LED curing varnish with a polymer network structure, which has low viscosity and high solid content, and can significantly improve the speed and quality of varnish.

Description

DESCRIPTION UV-LED Curing Varnish and Preparation Method thereof

TECHNICAL FIELD The invention relates to the technical field of curing oil, in particular to a UV-LED curing varnish and a preparation method thereof.

BACKGROUND With the improvement of people's consumption level, higher requirements are put forward for the quality of printed matter. Printing and polishing can effectively improve the quality of printed matter. Printing glazing can not only improve the surface smoothness and enhance the surface glossiness of printed matter, but also protect printed matter, which is the most commonly used method of surface finishing processing technology of printed matter. With the enhancement of people's awareness of environmental protection, various countries have successively formulated environmental protection laws and regulations on VOC emission, and people pay more and more attention to green gloss oil. Among them, UV-LED curing gloss oil has the characteristics of fast curing speed, energy saving, superior performance and green environmental protection, which has been supported by relevant environmental laws and regulations and has been vigorously promoted in the printing industry.

The viscosity of UV-LED curing varnish will affect the speed and quality of varnish, and the solid content determines the final glossiness and smoothness of printed matter. Therefore, it is expected to develop a UV-LED curing varnish with low viscosity and high solid content to improve the quality of printed matter.

In view of this, the present invention is specially proposed.

SUMMARY The first purpose of the present invention is to provide a UV-LED curing varnish to alleviate the technical problems of high viscosity and low solid content in the prior art.

The UV-LED curing varnish provided by the invention comprises the following raw material components in percentage by mass: 40-80% of polyurethane acrylate prepolymer, 5-25% of acrylate monomer, 1-5 % of photoinitiator and the balance of solvent.

> LU500719 Furthermore, it comprises the following raw material components in percentage by mass: 45-80% of polyurethane acrylate prepolymer, 5-20% of acrylate monomer, 2-5% of photoinitiator and the balance of solvent.

Furthermore, it comprises the following raw material components in percentage by mass: 50-65% of polyurethane acrylate prepolymer, 10-15% of acrylate monomer, 3-5% of photoinitiator and the balance of solvent.

Furthermore, the acrylate monomer comprises at least one of tripropylene glycol diacrylate, hexanediol diacrylate or trimethylolpropane triacrylate.

Furthermore, the acrylate monomer is a mixture of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate; Preferably, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is (1-5): (2-4): (2-4); Further preferably, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is (2-4): (2-4): (2-4).

Furthermore, it also comprises the following raw material components in percentage by mass: 0.5-1.5% of leveling agent and 0.5-1.5% of defoamer.

Furthermore, the solvent is a mixed solution of ethanol and acetone; Preferably, the mass ratio of ethanol to acetone is (1-5): 1; Further preferably, the mass ratio of ethanol to acetone is 4: 1.

Furthermore, the number average molecular weight of the polyurethane acrylate prepolymer is 4000-5000.

Furthermore, the photoinitiator comprises 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 2- methyl -2-(4- morpholinyl) -1-[4- (methylthio) phenyl ]-1- acetone or 2- hydroxy -2- methyl -1- phenyl-.

And/or the leveling agent comprises at least one of acrylic resin or modified polysiloxane; And/or the defoaming agent comprises at least one of emulsified silicone oil or polyoxypropylene glycerol ether.

The second purpose of the present invention is to provide a preparation method of UV-LED curing varnish, which has simple production process, easily available raw materials and low cost, and is suitable for large-scale production. The prepared UV-LED curing varnish has low viscosity and high solid content, and has broad application prospects.

The method for preparing UV-LED curing varnish provided by the invention comprises the following steps: firstly, dissolving polyurethane acrylate prepolymer in a solvent, then adding acrylate monomer, photoinitiator, optional leveling agent and optional defoamer, and uniformly mixing to obtain the UV-LED curing varnish.

Compared with the prior art, the invention has the following beneficial effects: The UV-LED curing varnish provided by the invention takes polyurethane acrylate prepolymer, acrylate monomer and photoinitiator in a specific proportion as main raw materials, and reacts under the action of photoinitiator to obtain the UV-LED curing varnish with a polymer network structure, which has low viscosity and high solid content, and can significantly improve the speed and quality of varnish.

The method for preparing the UV-LED curing varnish provided by the invention has simple production process, easily available raw materials and low cost, and is suitable for large-scale production; and the prepared UV-LED curing varnish has low viscosity and high solid content, and has broad application prospects.

DESCRIPTION OF THE INVENTION The embodiments of the present invention will be described in detail with examples below, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If the specific conditions are not indicated in the examples, they shall be carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used are conventional products that can be obtained through commercial purchase without indicating the manufacturer.

According to the first aspect of the invention, the invention provides a UV-LED curing varnish, which comprises the following raw material components in percentage by mass: 40-80% of polyurethane acrylate prepolymer, 5-25% of acrylate monomer, 1-5% of photoinitiator and the balance of solvent.

As a film forming agent, the properties of polyurethane acrylate prepolymer play an important role in curing process and properties of curing film. The curing polyurethane acrylate prepolymer has high wear resistance, adhesion, flexibility, excellent optical properties and weatherability.

As reactive diluent, acrylate monomer is mainly used to promote curing speed and adjust the viscosity of varnish. The acrylate monomer can be selected, but is not limited to tripropylene glycol diacrylate, hexanediol diacrylate or trimethylolpropane triacrylate.

Under the irradiation of ultraviolet light, photoinitiators will produce active intermediate substances with the ability of initiating polymerization, which will cause crosslinking reaction between polyurethane acrylate prepolymer and acrylate monomer.

The solvent can fully dissolve polyurethane acrylate prepolymer and reduce the viscosity of UV-LED curing varnish.

Among them, the polyurethane acrylate prepolymer can be, but not limited to, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%; For example, the crosslinking agent can be, but is not limited to, 5%, 10%, 15%, 20% or 25%; The photoinitiator can be, for example, but not limited to, 1%, 2%, 3%, 4% or 5%; For example, the solvent can be, but 1s not limited to, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%.

The UV-LED curing varnish provided by the invention takes polyurethane acrylate prepolymer, acrylate monomer and photoinitiator in a specific proportion as main raw materials, and reacts under the action of photoinitiator to obtain the UV-LED curing varnish with a polymer network structure, which has low viscosity and high solid content, and can significantly improve the speed and quality of varnish.

In a preferred embodiment, it comprises the following raw materials in percentage by mass: 45-80% of polyurethane acrylate prepolymer, 5-20% of acrylate monomer, 2- 5% of photoinitiator and the balance of solvent.

The UV-LED curing varnish provided by the invention has the characteristics of high glossiness, high adhesive force and excellent performance by adjusting the proportion among the components and cooperating among the components.

In a preferred embodiment, it comprises the following raw materials in percentage by mass: 50-65% of polyurethane acrylate prepolymer, 10-15% of acrylate monomer, 3- 5% of photoinitiator and the balance of solvent.

In a preferred embodiment, the acrylate monomer comprises at least one of tripropylene glycol diacrylate, hexanediol diacrylate or trimethylolpropane triacrylate.

In a preferred embodiment, the acrylate monomer is a mixture of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate; Preferably, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is (1-5): (2-4): (2-4); Further preferably, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is (2-4): (2-4): (2-4).

The acrylate monomer was reacted with tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate in a specific ratio, and the reaction speed was fast. The UV-LED curing varnish obtained had good softness.

The mass of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate can be, but not limited to, 1: 2: 2, 2: 2: 3, 1: 2: 3, 3: 4: 4 or 5: 4: 4, In a preferred embodiment, it also comprises the following raw materials in percentage by mass: 0.5-1.5% of leveling agent and 0.5-1.5% of defoamer.

Leveling agent can increase the fluidity of UV-LED curing varnish and improve the gloss of UV-LED curing varnish.

The defoaming agent can reduce the surface tension of UV-LED curing varnish and inhibit the foam generated during the production and use of UV-LED curing varnish.

The leveling agent can be, for example, but not limited to 0.5%, 0.6%, 0.7%, 0.8%,

0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%. For example, the defoaming agent can be, but is not limited to, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or

1.5%.

In a preferred embodiment, the solvent is a mixed solution of ethanol and acetone; Preferably, the mass ratio of ethanol to acetone is (1-5): 1; Further preferably, the mass ratio of ethanol to acetone is 4: 1.

Ethanol and acetone have lower boiling points in organic solvents, among which the boiling point of ethanol is 78°C and the boiling point of acetone is 56°C. The mixture of ethanol and acetone can fully dissolve the polyurethane acrylate prepolymer, reduce the viscosity of the system, and the lowest viscosity can reach 100cps. Meanwhile, the solvent is easy to volatilize, and the VOC residue of the curing coating is low.

The mass ratio of ethanol to acetone can be, but not limited to, 1: 1, 2: 1, 3: 1, 4: 1 or 5:1.

In a preferred embodiment, the number average molecular weight of the polyurethane acrylate prepolymer is 4000-5000.

Among them, the number average molecular weight of the polyurethane acrylate prepolymer can be, for example, but not limited to, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900 or 5000.

In a preferred embodiment, the photoinitiator comprises 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 2- methyl -2-(4- morpholinyl) -1-[4- (methylthio) phenyl ]-1- acetone or 2- hydroxy -2- methyl-1.

In a preferred embodiment, the leveling agent comprises at least one of acrylic resin or modified polysiloxane.

In a preferred embodiment, the defoaming agent comprises at least one of emulsified silicone oil or polyoxypropylene glycerol ether.

According to the second aspect of the invention, the invention provides a preparation method of UV-LED curing varnish, which comprises the following steps: firstly, dissolving polyurethane acrylate prepolymer in a solvent, then adding acrylate monomer, photoinitiator, optional leveling agent and optional defoamer, and uniformly mixing to obtain the UV-LED curing varnish.

In order to facilitate a clearer understanding of the present invention, the following will further explain the technical scheme of the present invention in combination with examples and comparative examples.

Example 1 The embodiment provides a UV-LED curing varnish, which comprises the following raw materials in percentage by mass: 40% of polyurethane acrylate prepolymer, 25% of tripropylene glycol diacrylate, 1% of 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 0.5% of acrylic resin, 0.5% of emulsified silicone oil, 22% of ethanol and 11% of acetone. The mass ratio of ethanol to acetone is 2: 1.

Example 2 The embodiment provides a UV-LED curing varnish which comprises the following raw materials in percentage by mass: 80% of polyurethane acrylate prepolymer, 5% of tripropylene glycol diacrylate, 5% of 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 1.5% of acrylic resin, 1.5% of emulsified silicone oil, 5.6% of ethanol and 1.1% of acetone. The mass ratio of ethanol to acetone is 4: 1.

Example 3 The embodiment provides a UV-LED curing varnish which comprises the following raw materials in percentage by mass: 45% of polyurethane acrylate prepolymer, 20% of tripropylene glycol diacrylate, 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 0.8% of acrylic resin, 0.8% of emulsified silicone oil, 15.7% of ethanol and acetone. The mass ratio of ethanol to acetone is 1: 1.

Example 4 The embodiment provides a UV-LED curing varnish, which comprises the following raw materials in percentage by mass: 50% of polyurethane acrylate prepolymer, 15% of tripropylene glycol diacrylate, 3% of 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 1.5% of acrylic resin, 1.5% of emulsified silicone oil, 21.75% of ethanol, and 1.5% of acrylic resin. The mass ratio of ethanol to acetone is 3: 1.

Example 5 The embodiment provides a UV-LED curing varnish which comprises the following raw material components in percentage by mass: 65% of polyurethane acrylate prepolymer, 10% of tripropylene glycol diacrylate, 3% of 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 1% of acrylic resin, 1% of emulsified silicone oil, 16% of ethanol and 4% of acetone. The mass ratio of ethanol to acetone is 4: 1.

Example 6

The embodiment provides a UV-LED curing varnish which comprises the following raw material components in percentage by mass: 49% of polyurethane acrylate prepolymer, 10% of tripropylene glycol diacrylate, 3% of 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 1% of acrylic resin, 1% of emulsified silicone oil, 30% of ethanol and 6% of acetone. The mass ratio of ethanol to acetone 1s 5: 1.

Example 7 This example provides a UV-LED curing varnish, which is different from Example in that acrylate monomers include 2% tripropylene glycol diacrylate, 4% hexanediol diacrylate and 4% trimethylolpropane triacrylate, that is, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is 1: 2: 2.

Example 8 This example provides a UV-LED curing varnish, which is different from Example 5 in that acrylate monomers include 5% tripropylene glycol diacrylate, 2% hexanediol diacrylate and 3% trimethylolpropane triacrylate, that is, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is 5: 2: 3.

Example 9 This example provides a UV-LED curing varnish, which is different from Example 5 in that acrylate monomers include tripropylene glycol diacrylate 4%, hexanediol diacrylate 3% and trimethylolpropane triacrylate 3%, that is, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is 4 3: 3.

The methods for preparing UV-LED curing varnish provided in Examples 1 to 9 include the following steps: firstly, dissolving polyurethane acrylate prepolymer in solvent, then adding acrylate monomer, photoinitiator, leveling agent and defoamer, and mixing uniformly to obtain UV-LED curing varnish.

Comparative example 1 This comparative example provides a UV-LED curing varnish, which is different from Example 5 in that ethanol and acetone are replaced by toluene.

Comparative example 2

This comparative example provides a UV-LED curing varnish, which is different from Example 5 in that tripropylene glycol diacrylate is replaced by 2- phenoxyethyl acrylate.

Comparative example 3 This comparative example provides a UV-LED curing varnish. Different from Example 5, the content of each component 1s outside the scope of the present invention.

The comparative example provides a UV-LED curing varnish, which comprises the following raw materials in percentage by mass: polyurethane acrylate prepolymer 33%, tripropylene glycol diacrylate 33%, 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone 10%, acrylic resin 10%, emulsified silicone oil 10%, ethanol 3.2% and acetone 0.0%. The mass ratio of ethanol to acetone is 4: 1.

Comparative example 4 This comparative example provides a UV-LED curing varnish, which is different from Example 5 in that the mass ratio of ethanol to acetone is not within the protection range of this invention.

The comparative example provides a UV-LED curing varnish, which comprises the following raw materials in percentage by mass: 65% of polyurethane acrylate prepolymer, 10% of tripropylene glycol diacrylate, 3% of 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 1% of acrylic resin, 1% of emulsified silicone oil, 18% of ethanol and 2% of acetone. The mass ratio of ethanol to acetone is 9: 1.

The preparation methods of UV-LED curing varnish provided in Comparative Examples 1 to 4 are the same as those in Example 5.

Test case Test the performance of UV-LED cured varnish provided by each example and comparative example, and the specific methods are as follows: (1) Viscosity measurement: Measure with a rotary viscometer at 25°C.

(2) Curing test: scratch the surface of the coating with a needle, and then observe the scratch with a magnifying glass. If the scratch is serrated, it indicates that it has been cured.

(3) Gloss measurement: measure the glossiness with a glossmeter, and select an angle of 60.

(4) Adhesion test: use 3M adhesive tape for peel test (100-grid test), and evaluate its adhesion by coating peeling area. (5) Solid content measurement: measure the solid content according to GB/T 1725-

2007. (6)VOC content test: according to ISO1180-1/2:2000 Standard for Determination of Volatile Organic Compounds (VOC) Content in Color Paints and Related Paints. The performance test results of UV-LED cured varnish provided by each example and comparative example are shown in Table 1.

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It can be seen from the data in Table 1 that the UV-LED curing varnish provided in Embodiments 1 to 9 of the present invention 1s yellowish in appearance, and can be completely cured under the UV-LED light source for 2 seconds. After curing, the scratches are found to be jagged. After curing, the coating has strong adhesion, does not fall off, and the viscosity can be as low as 100cps. The glossiness of the coating is over 85%, and the solid content is over 95%. The residual VOC in the coating is not detected, which is up to the environmental protection standard.

Comparison between Comparative Example 1 and Example 5 shows that replacing the mixed solution of ethanol and acetone with toluene, due to the relatively high boiling point of toluene, the solvent in the coating is not easy to volatilize, the coating is difficult to cure, the VOC content is high, and the glossiness and solid content are also greatly reduced.

Comparison between Comparative Example 2 and Example 5 shows that the polyurethane acrylate prepolymer of the present invention is replaced by 2- phenoxyethyl acrylate, which leads to the change of the morphology of the polymer network structure product generated by the reaction, which further affects the performance of UV-LED curing varnish, and the coating is incompletely cured, the adhesion is poor, and the glossiness and solid content are also greatly reduced.

Comparing the third comparative example with the fifth example, it can be seen that changing the content of each component of the present invention is not within the scope of protection of the present invention, which leads to the change of the morphology of the polymer network structure product generated by the reaction, and further affects the performance of UV-LED curing varnish, with incomplete curing of the coating, poor adhesion, and greatly reduced glossiness and solid content.

Comparing the fourth comparative example with the fifth comparative example, it can be seen that changing the mass ratio of ethanol and acetone in the present invention is not within the protection range of the present invention, which leads to an increase in the viscosity of UV-LED cured varnish, and a significant decrease in the gloss and solid content of the cured coating.

Finally, it should be noted that the above embodiments are only used to 1llustrate the technical scheme of the present invention, but not to limit it.

Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that the technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; However, these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of each embodiment of the present invention.

Claims

1. A UV-LED curing varnish, which is characterized by comprising the following raw material components in percentage by mass: 40-80% of polyurethane acrylate prepolymer, 5-25% of acrylate monomer, 1-5% of photoinitiator and the balance of solvent.

2. The UV-LED curing varnish according to claim 1, which is characterized by comprising the following raw material components in percentage by mass: 45-80% of polyurethane acrylate prepolymer, 5-20% of acrylate monomer, 2-5% of photoinitiator and the balance of solvent.

3. The UV-LED curing varnish according to claim 1, which is characterized by comprising the following raw material components in percentage by mass: 50-65% of polyurethane acrylate prepolymer, 10-15% of acrylate monomer, 3-5% of photoinitiator and the balance of solvent.

4. The UV-LED curing varnish according to any one of claims 1-3, wherein the acrylate monomer comprises at least one of tripropylene glycol diacrylate, hexanediol diacrylate or trimethylolpropane triacrylate.

5. The UV-LED curing varnish according to claim 4, wherein the acrylate monomer is a mixture of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate; preferably, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is (1-5): (2-4): (2-4); further preferably, the mass ratio of tripropylene glycol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate is (2-4): (2-4): (2-4).

6. The UV-LED curing varnish according to any one of claims 1-3, which is characterized by further comprising the following raw material components in percentage by mass: 0.5-1.5% of leveling agent and 0.5-1.5% of defoamer.

7. The UV-LED curing varnish according to claim 1, wherein the solvent is a mixed solution of ethanol and acetone; preferably, the mass ratio of ethanol to acetone is (1-5): 1; further preferably, the mass ratio of ethanol to acetone is 4: 1.

8. The UV-LED curing varnish according to any one of claims 1-3, wherein the number average molecular weight of the polyurethane acrylate prepolymer is 4000-5000.

9. The UV-LED curing varnish according to claim 6, wherein the photoinitiator comprises 2- hydroxy -4-(2- hydroxyethoxy) -2- methylphenylacetone, 2- methyl -2-(4- morpholinyl) -1-[4- (methylthio) phenyl ]-1- acetone or at least one of 1-phenyl-2- hydroxy-2-methyl-1-propanone; and/or the leveling agent comprises at least one of acrylic resin or modified polysiloxane; and/or the defoaming agent comprises at least one of emulsified silicone oil or polyoxypropylene glycerol ether.

10. A method for preparing the UV-LED curing varnish according to any one of claims 1 to 9, which is characterized by comprising the following steps: firstly dissolving polyurethane acrylate prepolymer in a solvent, then adding acrylate monomer, photoinitiator, optional leveling agent and optional defoamer, and mixing uniformly to obtain the UV-LED curing varnish.