A kind of UV adhesive and preparation method thereof

Abstract

The invention discloses a UV adhesive and a preparation method thereof. The UV adhesive comprises a photoacid generator with a weight content of 0.5-3% and a carbonate compound with a weight content of 0.5-2%. The structure of the photoacid generator is shown in formula (I): wherein n is 1-18. The invention adds a photoacid generator with a specific structure into the UV adhesive so that the UV adhesive does not photolyze to generate acid under the irradiation of an LED lamp, but photolyzes to generate a strong acid under the irradiation of a UV mercury lamp. The strong acid reacts with the carbonate compound to release carbon dioxide, thereby quickly reducing the adhesion between the UV adhesive and a glass substrate, thereby achieving the effect of photodegradation debonding.

Description

Technical Field

[0001] The present invention belongs to the field of adhesives, and in particular relates to a UV adhesive and a preparation method thereof. Background Art

[0002] When cutting a mobile phone glass panel, it is usually necessary to bond multiple pieces of glass together. During the cutting process, in order to ensure that the glass panel does not break and the cut shape is intact, UV adhesive is usually used to bond the glass. The specific process is: after applying UV adhesive on the glass panel, attach the glass, UV cure and bond it, and then place the bonded glass panel in the cutting fluid for cutting. After the cutting is completed, use solvents or strong acids and alkalis to remove the glue. However, when using solvents or strong acids and alkalis for debonding, it is difficult for the solvents or strong acids and alkalis to penetrate into the bonding interface between the UV adhesive and the glass panel in a short period of time, resulting in a long debonding time. It is even impossible for the solvents or strong acids and alkalis to completely penetrate into the bonding interface between the UV adhesive and the glass panel, resulting in residual glue on the glass panel. Summary of the Invention

[0003] To address the shortcomings of the existing technology, the present invention discloses a UV adhesive. By adding a photoacid generator with a specific structure to the UV adhesive, the adhesive does not photolyze to produce acid under LED light irradiation, but instead photolyzes to produce a strong acid under UV mercury lamp irradiation. The strong acid reacts with a carbonate compound to release carbon dioxide, rapidly reducing the adhesion between the UV adhesive and the glass substrate, achieving photodegradation and debonding. Debonding can be achieved by simply bubbling the glass panel with a UV mercury lamp after the glass panel is cut, rather than penetrating the adhesive into the bonding interface after cutting. Furthermore, the acid generator is used to prepare the UV adhesive without affecting the adhesive properties of the UV adhesive.

[0004] The present invention aims to provide a UV adhesive, characterized in that the UV adhesive comprises 0.5-3% by weight of a photoacid generator and 0.5-2% by weight of a carbonate compound, wherein the structure of the photoacid generator is shown in formula (I):

[0005]

[0006] Formula (I)

[0007] Among them, n is 1~18.

[0008] A UV adhesive solution containing the photoacid generator described in formula (I) is applied to a glass panel, and then the glass is attached. After curing and bonding under an LED light, the panel is placed in cutting fluid for cutting and then irradiated with a mercury lamp. Under the irradiation of the UV mercury lamp, the UV adhesive photolyzes to produce a strong acid, which reacts with a carbonate compound to release carbon dioxide, thereby rapidly reducing the adhesion between the UV adhesive and the glass substrate. The panel is then boiled in hot water for 10 minutes until the adhesive layer is completely removed. This process is simple and fast, greatly saves time and energy, and reduces the use of solvents or strong bases.

[0009] Preferably, the structural formula (I) of the photoacid generator is as follows:

[0010]

[0011] Formula (I)

[0012] Among them, n is 1~8.

[0013] Preferably, the carbonate compound is selected from at least one of ethylene carbonate and propylene carbonate.

[0014] Preferably, the UV adhesive further comprises 25-44% polyurethane acrylate, 15-25% acrylic resin, and 20-53% acrylic monomer.

[0015] Polyurethane acrylate is an oligomer commonly used in the preparation of UV adhesives. However, polyurethane acrylate is prone to produce gaps during the UV curing process of UV adhesives, resulting in a decrease in the adhesion between the UV adhesive and the glass panel. In severe cases, bubbles and voids may even appear, which in turn affects the moisture and heat resistance of the UV adhesive. During experiments, the inventors unexpectedly discovered that the photoacid generator prepared by the present invention, when combined with a carbonate compound and an acrylate monomer selected from ethoxylated trimethylolpropane triacrylate and polyethylene glycol diacrylate, can effectively solve the problem of gaps easily generated during UV curing when preparing a UV adhesive using polyurethane acrylate, thereby improving the adhesion of the UV adhesive to the glass panel and the moisture and heat resistance of the UV adhesive, and reducing the curing time of the UV adhesive. This may be due to the fact that the molecular structure of the photoacid generator contains benzene rings and carbonyl groups, the molecular chains of ethylene carbonate or propylene carbonate also contain heterocycles, and the molecular chains of ethoxylated trimethylolpropane triacrylate and polyethylene glycol diacrylate contain long chain structures. The interaction between the long and short chain structures and the different ring structures reduces the shrinkage of the UV adhesive during the curing process, improves the adhesion of the UV adhesive to the glass panel and the moisture and heat resistance of the UV adhesive.

[0016] Preferably, the acrylic resin is selected from at least one of epoxy acrylate, modified epoxy acrylate, and polyester acrylate.

[0017] Preferably, the acrylate monomer is selected from ethoxylated trimethylolpropane triacrylate and polyethylene glycol diacrylate.

[0018] More preferably, the weight ratio of the ethoxylated trimethylolpropane triacrylate to the polyethylene glycol diacrylate is 1:1.3-3.

[0019] Preferably, the UV adhesive further comprises 2-10% of a photoinitiator.

[0020] Preferably, the photoinitiator is selected from TPO.

[0021] Another object of the present invention is to provide a method for preparing the above-mentioned photoacid generator, comprising the following steps:

[0022] 4-Hydroxybenzophenone, an acid-binding agent and a solvent are mixed, stirred at low temperature, a sulfonyl halide compound is added dropwise, and the temperature is raised to react to obtain a compound of formula (I). The structure of the sulfonyl halide compound is shown in formula (II):

[0023]

[0024] Formula (II)

[0025] Wherein, X is chlorine or fluorine, and n is 1 to 18.

[0026] Preferably, the molar ratio of the 4-hydroxybenzophenone to the sulfonyl halide compound is 1:1.5-5.

[0027] Preferably, the acid binding agent is selected from one of triethylamine, potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate.

[0028] Preferably, the molar ratio of the acid binding agent to the sulfonyl halide compound is 1:1.

[0029] Preferably, the solvent is selected from tetrahydrofuran, acetonitrile and chloroform.

[0030] Preferably, the low temperature is -30-0°C.

[0031] Preferably, the temperature-raising reaction time is 12-24 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 .Ultraviolet absorption spectra of different photoacid generators in acetonitrile solvent. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction 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 making creative efforts should fall within the scope of protection of the present invention.

[0034] TPO: diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide;

[0035] B-151: modified epoxy acrylate, from Guangdong Boxing New Material Technology Co., Ltd.

[0036] B-206: polyurethane acrylate, from Guangdong Boxing New Material Technology Co., Ltd.

[0037] PAG101: photoacid generator, from Zhejiang Yangfan New Materials Co., Ltd.

[0038] TX-F: Patent CN107501235B describes a photoacid generator compound TX-F that is sensitive to 395nm LED light sources. Its structure is shown below: .

[0039] Example 1: Preparation of photoacid generator.

[0040] 4-Hydroxybenzophenone (0.01 mol) and anhydrous potassium carbonate (0.015 mol) were added to 60 ml of acetonitrile and stirred at -10°C for 5 minutes. Trifluoromethylsulfonyl chloride (0.015 mol) was then added dropwise. After stirring for 5 minutes, the mixture was allowed to react at room temperature for 12 hours. The solvent was evaporated, and the mixture was passed through a column (eluent: ethyl acetate:petroleum ether (v / v) = 1:9). After the solvent was evaporated, the mixture was dried in a vacuum oven. M1 was obtained as a pale yellow powder with a yield of 69.70%. 1 H-NMR (CDCl3, 400MHz), δ (ppm): 7.70-7.80 (m, 4H, Ar-H), 7.40~7.55 (m, 4H, Ar-H).

[0041] The product M1 was dissolved in acetonitrile solution at a certain concentration and tested by UV-visible absorption spectrum (see Appendix Figure 1 ), its maximum absorption wavelength was measured to be 212nm (ε reached 10 5 L . mol -1. cm -1 )、246nm(ε reaches 10 4 L . mol -1. cm -1), which has no ultraviolet absorption after 310~410nmnm.

[0042] The solution was irradiated by a medium pressure mercury lamp with a light intensity of 20 mW / cm 2 After irradiation for 10 minutes, the mass spectrum ESI-MS(-) showed a peak of M=148.7, which was the molecular ion peak of perfluoromethanesulfonate, proving that M1 produced sulfonic acid after irradiation.

[0043]

[0044] M1

[0045] Example 2: Preparation of photoacid generator.

[0046] To 20 ml of acetonitrile, add 4-hydroxybenzophenone (0.01 mol) and anhydrous potassium carbonate (0.015 mol) and stir at -15°C for 5 minutes. Perfluorooctanesulfonyl fluoride (0.015 mol) is then added dropwise. Stir for 5 minutes and allow to react at room temperature for 12 hours. The solvent is evaporated, and the mixture is passed through a column (eluent: ethyl acetate:petroleum ether (v / v) = 1:9), dried, and dried in a vacuum oven. M2 is obtained as a pale yellow powder with a yield of 44.51%. 1 H-NMR (CDCl3, 400MHz), δ (ppm): 7.72-7.85 (m, 4H, Ar-H), 7.45~7.60 (m, 4H, Ar-H).

[0047] The product M2 was dissolved in acetonitrile solution at a certain concentration and tested by UV-visible absorption spectrum. Figure 1 ), and its maximum absorption wavelength was found to be 212 nm (10 5 L . mol -1. cm -1 )、246nm(10 4 L . mol -1. cm -1 ), which has no ultraviolet absorption after 310~410nmnm.

[0048] The solution was placed under a medium pressure mercury lamp with a light intensity of 20 mW / cm 2 After irradiation for 10 minutes, the mass spectrum ESI-MS(-) showed a peak of M=498.7, which was the molecular ion peak of perfluorooctane sulfonate, proving that M2 produced sulfonic acid after irradiation.

[0049]

[0050] M2

[0051] Preparation of UV adhesive:

[0052] Table 1. Composition of UV adhesives in parts by weight.

[0053]

[0054] Preparation of UV adhesive: Polyurethane acrylate B206, acrylic resin B151, photoinitiator (TPO), carbonate compound, acrylic monomer and photoacid generator as shown in Table 1 were mixed and stirred to obtain UV adhesive.

[0055] Performance test of UV adhesive:

[0056] The UV adhesives prepared in Examples 3-5 and Comparative Examples 1-5 were coated onto a glass substrate using a 12μm wire rod. Another piece of glass was then placed over the adhesive and pressed until no bubbles formed between the glass substrates. The adhesives were then cured using a 395nm LED lamp at 300mJ. The cured UV adhesives were then tested for adhesion and cure time.

[0057] ① First, test the bonding performance between the glass substrates. At this time, tear the two bonded glasses by hand. If the two glasses cannot be broken apart, the bonding performance between the two glasses is OK. If they can be broken apart, the bonding performance between the two glasses is NG.

[0058] ②Then place the bonded glass under a 1000mJ medium-pressure mercury lamp for irradiation to test the photolysis ability of the glue between the glass substrates. That is, by observing the glass after being irradiated by the mercury lamp, if the two originally bonded glasses can be directly separated, then the photolysis performance of the glue is OK, otherwise it is NG.

[0059] ③ Place the prepared UV photodissolved glue in an 80℃ oven for 3 days. If the glue does not gel, the stability is OK. Otherwise, the stability is NG. The test results are shown in Table 2.

[0060] Adhesion test: The adhesion of the cured film was measured according to the cross-cut test method of GB / T9286-88 paint film, which is divided into 6 levels (0-5), with level 0 being the best and level 5 being the worst.

[0061] Curing time: Record the curing time of the UV adhesive. Touch the surface of the adhesive layer with your finger. If it feels a little sticky but there is no adhesive on your finger, the surface is considered dry.

[0062] Table 2. UV adhesive performance test results of Examples 3-5 and Comparative Examples 1-5.

[0063]

[0064] As shown in Table 2, the UV adhesive prepared in the present invention has the advantages of fast curing speed and good bonding performance, and the glue undergoes photolysis after irradiation with a mercury lamp.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not 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, technicians can still modify or replace the specific implementation methods of the present invention with equivalents, but these modifications or changes do not depart from the scope of protection of the pending claims of the present application.

Claims

1. A UV adhesive, characterized in that: The UV adhesive comprises 0.5-3% by weight of a photoacid generator and 0.5-2% of a carbonate compound, 25-44% of polyurethane acrylate, 15-25% of an acrylate resin, 20-53% of an acrylate monomer and 2-10% of a photoinitiator. The structure of the photoacid generator is shown in formula (I): Formula (I) Where n is 1 to 18; The acrylic resin is selected from at least one of epoxy acrylate and polyester acrylate; The acrylic ester monomer is selected from ethoxylated trimethylolpropane triacrylate and polyethylene glycol diacrylate.

2. The UV adhesive according to claim 1, characterized in that: The carbonate compound is selected from at least one of ethylene carbonate and propylene carbonate.

3. The UV adhesive according to claim 1, characterized in that: The weight ratio of the ethoxylated trimethylolpropane triacrylate to the polyethylene glycol diacrylate is 1:1.3-3.

4. The UV adhesive according to claim 1, characterized in that: The preparation method of the photoacid generator comprises the following steps: 4-Hydroxybenzophenone, an acid-binding agent and a solvent are mixed, stirred at low temperature, a sulfonyl halide compound is added dropwise, and the temperature is raised to react to obtain a compound of formula (I). The structure of the sulfonyl halide compound is shown in formula (II): Formula (II) Wherein, X is chlorine or fluorine, and n is 1-18.

5. The UV adhesive according to claim 4, characterized in that: The molar ratio of the 4-hydroxybenzophenone to the sulfonyl halide compound is 1:1.5-5.

6. The UV adhesive according to claim 4, characterized in that: The acid binding agent is selected from one of triethylamine, potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate.

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