Process for the preparation of an enol-terminated mercapto compound and use thereof

Abstract

The present application relates to the field of new curing agent, specifically relates to a kind of preparation method and application of enol-terminated mercapto compound, the enol-terminated mercapto compound is obtained by enol and mercapto compound mixed reaction, the molar ratio of hydroxyl and mercapto of enol and mercapto compound is (0.01-0.75):1;Specific application, enol-terminated mercapto compound is mixed with polyurethane acrylate, diluent monomer, photoinitiator, polymerization inhibitor to obtain UV glue, the UV glue prepared by enol-terminated mercapto compound, 80 ℃ storage time >80d, light solidification time <120s, and without affecting the curing condition, can greatly improve the shelf life of UV glue.

Description

Technical Field

[0001] This invention relates to the field of novel curing agents, specifically to a method for preparing and applying an enol-terminated thiol compound. Background Technology

[0002] With the increasing environmental awareness and the development of high technology, UV curing technology has received widespread attention. As one of the application areas of UV curing technology, UV curing adhesives have developed rapidly due to their advantages such as low odor, fast curing speed, high bonding strength, and low production energy consumption, and have broad application prospects in the fields of optics, electronics, and precision instruments.

[0003] Thiol compounds possess characteristics such as high refractive index, rapid low-temperature curing, and high gloss, making them widely used as UV curing aids in adhesives, inks, and coating materials. However, due to their high reactivity, UV adhesives using thiol compounds currently suffer from poor storage stability and short-term gelation. Current methods typically involve adding larger doses of stabilizers or using low-activity diluent monomers to reduce reactivity and extend the shelf life of UV adhesives. However, increasing the stabilizer further inhibits initiator activity, leading to longer UV curing times. Furthermore, the stabilizer polymers do not provide structural support, resulting in decreased adhesive strength. Excessive addition of diluent monomers also leads to a decrease in the mechanical properties of the cured adhesive. Existing methods for modifying thiol compounds include self-made silicone-modified thiol compounds and combined modification with epoxy adhesives; however, these methods all suffer from poor stability and complex modification processes. Therefore, providing a new thiol compound is one of the urgent problems to be solved in this field. Summary of the Invention

[0004] This invention addresses numerous problems in existing technologies by providing a method for preparing and applying an enol-terminated thiol compound. The enol-terminated thiol compound is obtained by reacting an enol with a thiol compound, wherein the molar ratio of hydroxyl to thiol groups in the enol compound and thiol compound is (0.01-0.75):1. In specific applications, the enol-terminated thiol compound is mixed with polyurethane acrylate, a diluent monomer, a photoinitiator, and a polymerization inhibitor to obtain a UV adhesive. The UV adhesive prepared from the enol-modified thiol compound has a storage time of >80 days at 80°C and a light curing time of <120 seconds, effectively improving the problem of unstable storage in existing UV adhesives. Compared to existing technologies, this method is simpler to operate, significantly improves storage stability, does not affect curing time, meets the requirements of practical applications, and is of great significance for improving the stability of UV adhesives.

[0005] The specific technical solution of the present invention is as follows: An enol-terminated thiol compound is obtained by reacting a thiol compound, an enol, and sodium ethoxide, wherein the molar ratio of hydroxyl to thiol groups in the enol and thiol compound is (0.01-0.75):1. Furthermore, the molar ratio of hydroxyl to mercapto groups in the enol and mercapto compounds is (0.1-0.7):1; Furthermore, the molar ratio of hydroxyl to mercapto groups in the enol and mercapto compounds is (0.25-0.5):1.

[0006] The thiol compounds mentioned above are pentaerythritol tetrathiopropionate, pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane trithiopropionate, 1,6-hexanedithiol, 2,2-dimethylpropane-1,3-dithiol, dipentaerythritol hexa(3-mercaptopropionate), 2,2-bis(mercaptomethyl)1,3-propanedithiol, 2,3-dimercapto-1-propanol (3-mercaptoacetate), and 2,3-dimercapto-1-propanol (2-mercaptoacetate). The mercapto compound is selected from one or more of the following: trimethylolpropane bis(3-mercaptopropionate), trimethylolpropane tri(3-mercaptoacetate), trimethylolethane tri(3-mercaptoacetate), pentaerythritol tetrakis(3-mercaptobutyrate), pentaerythritol tetra(2-mercaptoacetate), and 1,3,5-trimercaptomethyl-2,4,6-trimethylbenzene; and the mercapto compound can be used alone or in combination, preferably containing two or more mercapto groups.

[0007] Preferably, the enol is one or more of the following: 3-hexenol, 3-octenol, 2,7-octadienol, 2-dodecenol, 1,19-nonadienol, S-androstenol, trans-10,cis-12-hexadecadienol, isopentenol, cyclopentadienol, cyclohexadienol, 2,3-butadien-1,4-diol, 2-(6-methoxynaphthyl)propenol, 3-phenyl-2-propen-1-ol, methpropenol, and propenol.

[0008] Furthermore, the thiol compound is selected from pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetra(2-mercaptoacetate), and dipentaerythritol hexa(3-mercaptopropionate); the enol is selected from allyl alcohol and methacrylate. Sodium ethoxide is used as a catalyst at a weight fraction of 0.1%-1% of the mercapto compound.

[0009] In addition, the inventors also provided a method for preparing the above-mentioned enol-terminated thiol compound, the specific steps of which are as follows: A thiol compound and sodium ethoxide were added to a reaction vessel, and the reaction temperature was controlled at 40-90℃. An enol was added dropwise to the thiol compound at a rate of 0.02-0.1 L / min. The mixture was stirred at 500 rpm for 10 min-6 h to obtain an enol-terminated thiol compound.

[0010] The thiol compounds obtained above can reduce the high reactivity of thiol compounds, and thiol compounds containing hydroxyl groups at the end are obtained through the addition reaction of double bonds and thiol groups. The hydroxyl groups can be used in the next step of UV adhesive to crosslink with other components without changing the crosslinking density. The above-mentioned enol-terminated thiol compounds can improve the stability of UV adhesives.

[0011] The applicant further obtained a corresponding UV adhesive using the aforementioned enol-terminated thiol compound, the composition of which, by weight, is as follows: Enol-terminated thiol compounds, 0.01–40 parts; Dilute monomer: 0.01–40 parts; Photoinitiator: 0.01–10 parts; Polymerization inhibitor: 0.0001–10 parts; 0.01 to 70 parts of polyurethane acrylic resin; The polyurethane acrylate resin has a functionality of 1-3 and a molecular weight of 1000-3000.

[0012] The diluting monomers mentioned therein are one or more of the following: hydroxyethyl methacrylate, 1,6-hexanediol diacrylate, acrylate, isobornyl acrylate, carboxyacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, dipropylene glycol diacrylate, dipropylene glycol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

[0013] Preferably, the photoinitiator is one or more of 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-hydroxy-2-methylphenylpropanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, or 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone.

[0014] Preferably, the polymerization inhibitor is one or more of 4-methoxy-1-naphthol, p-benzoquinone, 2,5-di-tert-butylhydroquinone, pyrogallol, triphenyl phosphite, pentaerythritol diisodecyl diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, and 4-tert-butylcatechin.

[0015] Furthermore, the UV adhesive has the following composition by weight: 1-30 parts of enol-terminated thiol compound; Dilute monomer: 1-20 parts; Photoinitiator: 1-5 parts; Polymerization inhibitor: 0.0001–5 parts; 30-70 parts of polyurethane acrylic resin.

[0016] The preparation method of the above-mentioned UV adhesive includes the following steps: Add photoinitiator and polymerization inhibitor to the prepolymerized modified mercapto compound according to the above dosage, mix at 20-40℃ for 10 min-1 h, then add diluent monomer and polyurethane acrylic resin in sequence, react at 30-80℃ for 10 min-1 h, and degas at room temperature to obtain UV adhesive.

[0017] When applying the above-mentioned UV adhesive, it can be cured under ultraviolet light irradiation with a wavelength of 200-400nm and an irradiation time of 1-70s.

[0018] In summary, the technical solution of this invention modifies thiol compounds with enols, introducing unsaturated double bonds and hydroxyl groups into the molecular structure, and using highly reactive groups for end-capping to reduce the reactivity of the thiol compounds, thereby improving stability. Simultaneously, the end groups of the end-capped compound can participate in the crosslinking system, improving mechanical properties. The UV adhesive prepared from enol-modified thiol compounds exhibits a heat storage time of >80 days at 80℃, a light curing time of <120 seconds, and a tensile strength ≥9 MPa; it effectively improves the storage instability problem of existing UV adhesives while enhancing their mechanical properties. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] To further illustrate the present invention, the following embodiments provide a detailed description. Unless otherwise specified, all raw materials used in the following embodiments of the present invention are commercially available products. Example 1

[0021] The preparation method of enol-terminated thiol compounds and corresponding UV-curable adhesives, including the specific raw material composition and preparation steps, is as follows: (1) At room temperature and with stirring at 500 rpm, 10 parts by weight of pentaerythritol tetra(3-mercaptopropionate) were added to the reactor, and 0.1% sodium ethoxide was added according to the weight of pentaerythritol tetra(3-mercaptopropionate). Then, allyl alcohol was added dropwise at a rate of 0.05 L / min according to a molar ratio of hydroxyl to mercapto group of 0.25:1. After the addition was completed, the reaction was carried out at 60 °C for 60 min to obtain an enol-terminated mercapto compound. (2) Under stirring conditions of 500 rpm, add 1 part by weight of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 0.0001 part by weight of 4-methoxy-1-naphthol to the enol-terminated thiol compound obtained in step (1) above, and mix at 30°C for 30 min. Then, 70 parts by weight of polyurethane acrylic resin U600 and 20 parts by weight of trimethylolpropane triacrylate were added, and the mixture was reacted at 40°C for 30 minutes to obtain a mixture. After standing and degassing, the target UV-curable adhesive was obtained. Example 2

[0022] A method for preparing an enol-terminated thiol compound and its corresponding UV-curable adhesive is disclosed. The only difference between this method and Example 1 is that the thiol compound is 20 parts by weight of pentaerythritol tetra(2-mercaptoacetate); the amount of polyurethane acrylic resin U600 added is 60 parts by weight; and the other components, amounts, and preparation methods are the same as in Example 1. Example 3

[0023] A method for preparing an enol-terminated thiol compound and its corresponding UV-curable adhesive differs from Example 1 only in that pentaerythritol tetra(3-mercaptopropionate) and allyl alcohol are added in a ratio of 0.3:1 for hydroxyl to thiol groups, and the amount of 2,4,6-trimethylbenzoyl diphenylphosphine oxide added is 1.5 parts by weight. Other components, amounts, and preparation methods are the same as in Example 1. Example 4

[0024] A method for preparing an enol-terminated thiol compound and its corresponding UV-curable adhesive differs from Example 1 only in that the amount of polyurethane acrylic resin U600 added is 70 parts by weight, and the amount of 2,4,6-trimethylbenzoyl diphenylphosphine oxide added is 1.5 parts by weight. Other components, amounts, and preparation methods are the same as in Example 1. Example 5

[0025] A method for preparing an enol-terminated thiol compound and its corresponding UV-curable adhesive differs from Example 1 only in that the thiol compound is 20 parts by weight of pentaerythritol hexa(3-mercaptopropionate); methacrylic alcohol is added at a molar ratio of hydroxyl to thiol of 0.4:1; the amount of polyurethane acrylic resin U600 added is 60 parts by weight; the diluent monomer is 20 parts by weight of pentaerythritol tetraacrylate; the polymerization inhibitor is 0.0001 parts by weight of 2,5-di-tert-butylhydroquinone; and the other components, amounts, and preparation methods are the same as in Example 1.

[0026] Comparative Example 1

[0027] The specific raw material composition and preparation steps of a method for preparing a UV-curable adhesive are as follows: (1) Under stirring conditions at 500 rpm, 10 parts by weight of pentaerythritol tetra(3-mercaptopropionate), 1 part by weight of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and 0.0001 parts by weight of polymerization inhibitor 4-methoxy-1-naphthol were added and mixed at 30°C for 30 min.

[0028] (2) Under stirring conditions of 500 rpm, the mixture obtained in step (1) is added with 70 parts by weight of polyurethane acrylic resin U600 and 20 parts by weight of trimethylolpropane triacrylate. The mixture is reacted at 40°C for 30 min to obtain a mixture. After standing, the mixture is degassed to obtain the UV-curable adhesive.

[0029] The units for the components in the table below are "parts by weight".

[0030]

[0031] The UV-curable adhesives of Examples 1-5 and Comparative Example 1 were subjected to various performance tests according to the following methods: 80℃ Storage Stability: Place the prepared UV adhesive in a light-proof glass bottle, put it in an 80℃ oven, and observe it periodically to see if it gels and record the gelation status.

[0032] Curing time test: The curing agent prepared in each example was applied to a glass slide with a coating thickness of 0.5 mm. A stopwatch was used to time the curing. After curing, a PET plastic sheet was used to touch the coating surface. When the PET had no adhesion to the coating, it indicated that the coating was surface dry.

[0033] Tensile strength test: The prepared UV adhesive is added into a dumbbell mold with a diameter of 150*10*4mm, and cured into a strip by a ZT1365 box-type UV curing machine. The tensile strength of the strip is tested on a universal tensile testing machine. Six strips are used at a time for parallel data and the average value is taken.

[0034] Shear strength test: Apply the prepared UV adhesive to one end of a 100*20*4mm transparent glass sheet, and overlap it with another glass sheet (overlap area is 20mm*10mm). After overlapping, fix it with a clip and place it in a ZT1365 box-type UV curing machine for pre-curing for 2s. Remove the clip and cure for 1min. Test the tensile and shear strength on a universal tensile testing machine. Take 6 parallel data at a time and take the average value.

[0035] Pencil hardness: The pencil hardness was measured according to the pencil hardness evaluation method specified in JIS-K5400.

[0036] The curing time, thermal storage stability at 80℃, pencil hardness, tensile strength, and shear strength of the cured adhesives of Examples 1-5 and Comparative Example 1 were tested, and the results are shown in the table below.

[0037] As shown in the table above, the UV adhesive prepared by the present invention has good storage stability, good hardness, and good impact resistance. Compared with conventional UV adhesive (Comparative Example 1), the mechanical properties of the UV adhesive obtained by enol-terminated thiol compound are all improved.

[0038] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention, but rather to represent selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A UV adhesive prepared from an enol-terminated thiol compound, characterized in that: Its composition by weight is as follows: Enol-terminated thiol compounds, 0.01–40 parts; Dilute monomer: 0.01–40 parts; Photoinitiator: 0.01–10 parts; Polymerization inhibitor: 0.0001–10 parts; 0.01 to 70 parts of polyurethane acrylic resin; The polyurethane acrylate resin has a functionality of 1-3 and a molecular weight of 1000-3000. The enol-terminated thiol compound is obtained by reacting an enol with a thiol compound and sodium ethoxide to obtain a modified enol-terminated thiol compound; wherein the molar ratio of hydroxyl to thiol groups in the enol and thiol compound is (0.25-0.5):1; the thiol compound is selected from pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), or dipentaerythritol hexa(3-mercaptopropionate); the enol is selected from allyl alcohol or methacrylate.

2. The UV adhesive prepared from the enol-terminated thiol compound according to claim 1, characterized in that, The preparation method of the enol-terminated thiol compound is as follows: A thiol compound and sodium ethoxide were added to a reaction vessel, and the reaction temperature was controlled at 40-90℃. An enol was added dropwise to the thiol compound at a rate of 0.02-0.1 L / min. The mixture was stirred at 500 rpm for 10 min-6 h to obtain an enol-terminated thiol compound.

3. The UV adhesive prepared from the enol-terminated thiol compound according to claim 1 or 2, characterized in that, Sodium ethoxide is used as a catalyst at a weight fraction of 0.01%-1% of the mercapto compound.

4. The UV adhesive prepared from the enol-terminated thiol compound according to claim 1, characterized in that: The diluting monomer is one or more of the following: hydroxyethyl methacrylate, 1,6-hexanediol diacrylate, isobornyl acrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, dipropylene glycol diacrylate, dipropylene glycol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

5. The UV adhesive prepared from the enol-terminated thiol compound according to claim 1, characterized in that: Its composition by weight is as follows: 1-30 parts of enol-terminated thiol compound; Dilute monomer: 1-20 parts; Photoinitiator: 1-5 parts; Polymerization inhibitor: 0.0001–5 parts; 30-70 parts of polyurethane acrylic resin.

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