A UV curing multifunctional adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, and discloses a UV-curable multifunctional adhesive and a preparation method thereof. The multifunctional adhesive is formed by mixing polyurethane acrylate as a main raw material, adding auxiliary agents such as a dispersant, and introducing a diol chain extender having a block biphenyl-phosphorus-containing flame retardant mechanism alternating structure into a polyurethane acrylate oligomer structure, which can not only utilize the strong stability of the rigid biphenyl structure to improve the stability of the polyurethane acrylate molecular chain and improve its heat resistance, but also the introduction of the phosphorus-containing flame retardant can greatly enhance the flame retardant property of the adhesive, and due to the chain extension reaction of the diol chain extender, a large amount of unsaturated olefinic substituents can be contained in the prepared polyurethane acrylate structure, a higher cross-linking reaction can be generated during the UV curing process, so that the cohesive energy of the adhesive is greatly improved, thereby showing more excellent bonding performance.

Description

Technical Field

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

[0002] UV curing adhesive is an adhesive that cures by ultraviolet light irradiation. It is mainly composed of liquid oligomers (prepolymers), reactive diluent monomers (reactive diluents), photoinitiators and other additives. Under the irradiation of ultraviolet light, the photoinitiator absorbs light energy and decomposes into free radicals or cations, which triggers the polymerization reaction of the oligomers and reactive diluent monomers to form a polymer chain, thereby achieving curing. UV curing adhesives have the following significant characteristics: fast curing speed, environmental friendliness, long storage life and other advantages, so they have been more and more widely used in recent years. Polyurethane acrylate is an important product in UV curing adhesives. It combines the advantages of polyurethane and acrylate and has unique performance and application value. It has been widely used in automobile manufacturing, electronic appliances, furniture manufacturing, construction, aerospace and other fields.

[0003] However, with the continuous deepening of application, the defects of polyurethane acrylate adhesives have gradually emerged. The biggest problem is the flame retardancy. In the current context of frequent fires, the flame retardancy of materials has received more and more attention, which has also directly affected the application of polyurethane acrylate in the field of UV-curing adhesives. In addition, due to the poor high temperature resistance of polyurethane acrylate, it will gradually decompose in a high temperature working environment. These decomposed volatiles will have a negative impact on the service life of some precision devices. These defects have greatly hindered the further application of polyurethane acrylate. Therefore, it is of great significance to prepare UV-curing polyurethane acrylate adhesives with better comprehensive performance. Summary of the invention

[0004] In order to solve the problems mentioned in the background technology, the object of the present invention is to provide a UV curing multifunctional adhesive and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a UV-curable multifunctional adhesive comprises the following raw materials in parts by weight:

[0007]

[0008] The preparation method comprises the following steps:

[0009] The first step is to add polyurethane acrylate oligomer, diluent, leveling agent and dispersant into a mixing kettle, control the stirring rate to 1000-1500r / min, and mechanically stir and mix for 30-60min at room temperature to form a precursor;

[0010] The second step is to adjust the rotation speed to 500-1000r / min, continue to add the photoinitiator to the mixing kettle, stir at room temperature for 20-40min in the dark, then add the thixotropic agent to the mixing kettle, continue to stir and mix for 30-40min, discharge the material, and store in the dark.

[0011] As a further embodiment of the present invention, the specific preparation method of the polyurethane acrylate oligomer comprises the following steps:

[0012] Step S1, vacuum dehydrating the polyglycol, then mixing it with the diisocyanate, stirring evenly, controlling the heating rate to be 2-3°C / min, raising the temperature to 50-60°C, and adding an organic tin compound catalyst. After the addition, continue to raise the temperature to 60-70°C, and keep the temperature for 3-6 hours to form a prepolymer;

[0013] Step S2, lowering the temperature to 50-55°C, then adding the diol chain extender to the prepolymer, raising the temperature to 70-80°C, keeping the temperature for chain extension polymerization for 6-9 hours, stopping heating, cooling and discharging the material, and obtaining the polyurethane acrylate oligomer.

[0014] As a further embodiment of the present invention, in step S1, the polyol is polyether diol or polytetramethylene diol; the diisocyanate is hexamethylene diisocyanate, isophorone diisocyanate or toluene diisocyanate; and the organotin compound catalyst is stannous octoate or dibutyltin dilaurate.

[0015] As a further embodiment of the present invention, in step S2, the specific preparation method of the diol chain extender comprises the following steps:

[0016] Step SS1, dissolving 2,5-dibromoadipic acid in tetrahydrofuran solvent, then adding a condensing agent and a accelerator to the reaction solution, stirring and activating for 30-60 minutes, then continuing to add a hydroxyphosphorus flame retardant intermediate, stirring at room temperature for 4-8 hours after the addition, to obtain a chain extension connector;

[0017] Step SS2, adding magnolol and toluene to a polymerization kettle filled with nitrogen and mixing, then adding a sodium hydroxide aqueous solution with a mass fraction of 20-25% to the polymerization kettle, turning on the heating, raising the temperature to 50-60°C, and keeping the temperature for 1-2 hours, then adding the chain extender connector to the polymerization kettle, after adding, further raising the temperature to 70-80°C, keeping the temperature for 8-12 hours, cooling and discharging, and the diol chain extender can be obtained.

[0018] As a further embodiment of the present invention, in step SS1, the condensing agent is dicyclohexylcarbodiimide; and the accelerator is 4-dimethylaminopyridine or N-hydroxysuccinimide.

[0019] As a further embodiment of the present invention, in step SS1, the hydroxyphosphorus-based flame retardant intermediate is 2,6,7-trioxa-1-phosphabicyclo (2.2.2) octane-4-methanol-1-oxide or 2-hydroxyethyl dimethyl phosphate.

[0020] As a further embodiment of the present invention, in step SS1, the molar ratio of the 2,5-dibromoadipic acid to the hydroxyphosphorus-based flame retardant intermediate is 1:1-2.

[0021] As a further embodiment of the present invention, in step SS2, the molar ratio of magnolol to the chain extension linker is 1:0.8-0.9.

[0022] In the above technical scheme, the active substituted carboxyl groups in the structure of 2,5-dibromohexanedioic acid are firstly activated by using a condensing agent and a accelerator, and then condensed with the active substituted hydroxyl groups in the structure of a hydroxyphosphorus-based flame retardant intermediate to obtain a chain extension linker. Subsequently, sodium hydroxide is used as a catalyst to catalyze the continuous substitution reaction between the halogen substituents in the chain extension linker structure and the phenolic hydroxyl groups in the magnolol structure to obtain a diol chain extender having a block alternating structure. By controlling the dosage ratio of the raw materials, the prepared diol chain extender can be hydroxyl-terminated. Therefore, the diol chain extender can participate in the chain extension cross-linking reaction in the subsequent synthesis process of the polyurethane acrylate prepolymer to obtain a polyurethane acrylate oligomer.

[0023] As a further embodiment of the present invention, the diluent is an acrylate diluent; the thixotropic agent is fumed silica; the leveling agent is any one of BYK-310, BYK-315N or BYK-333; the dispersant is BYK-985 or BYK-9077; and the photoinitiator is benzoin dimethyl ether.

[0024] A UV curing multifunctional adhesive is prepared by adopting the preparation method.

[0025] Beneficial effects of the present invention:

[0026] The present invention realizes the chain extension polymerization of polyurethane acrylate by preparing a diol chain extender having an alternating structure of block biphenyl-phosphorus-containing flame retardant mechanism, and then introduces the above-mentioned block structure into the polyurethane acrylate oligomer structure. On the one hand, the rigid biphenyl structure has strong stability, which can improve the stability of the polyurethane acrylate molecular chain and improve its heat resistance, and the introduction of the phosphorus-containing flame retardant structure can greatly enhance the flame retardant property of the adhesive, and this chemical connection method can avoid the precipitation phenomenon of the flame retardant, ensuring that the adhesive has a long-term flame retardant property. On the other hand, due to the chain extension reaction of the diol chain extender, the prepared polyurethane acrylate structure will contain a large amount of unsaturated alkenyl substituents, and a higher cross-linking reaction will be generated in the subsequent UV curing process, so that the cohesive energy of the adhesive is greatly improved, thereby showing more excellent bonding performance, and the increase in the molecular chain cross-linking density will limit the movement of the molecular chain, so it is also beneficial to the improvement of the high temperature resistance of the adhesive.

[0027] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0029] Figure 1 This is the infrared test image of the diol chain extender. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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 are within the scope of protection of the present invention.

[0031] Preparation Example 1

[0032] Preparation of diol chain extender:

[0033] Step SS1, dissolving 0.8 g of 2,5-dibromohexanedioic acid in tetrahydrofuran solvent, then adding 0.2 g of dicyclohexylcarbodiimide and 0.06 g of 4-dimethylaminopyridine to the resulting reaction solution, stirring and activating for 40 min after the addition, then continuing to add 0.9 g of 2,6,7-trioxa-1-phosphabicyclo (2.2.2) octane-4-methanol-1-oxide, stirring at room temperature for 6 h after the addition, to obtain a chain extension connector;

[0034] Step SS2, add 0.5g of magnolol and toluene to a polymerization kettle filled with nitrogen and mix well, then add 10mL of a 20% sodium hydroxide aqueous solution to the polymerization kettle, turn on the heating, raise the temperature to 50°C, keep warm for 2h, then add 1g of a chain extender connector to the polymerization kettle, after adding, further raise the temperature to 80°C, keep warm for 9h, cool and discharge, and the diol chain extender can be obtained.

[0035] Figure 1 This is the infrared analysis test chart of the diol chain extender, where 3346cm -1 The characteristic absorption peak at 3023cm is the characteristic absorption peak of the end-capped hydroxyl group. -1 The characteristic absorption peak at 1748 cm is the characteristic absorption peak of the carbon-hydrogen group of the unsaturated olefinic substituent. -1 The characteristic absorption peak at 1030 cm is the characteristic absorption peak of the ester group C=O produced by the esterification reaction. -1 The characteristic absorption peak that appears at is the characteristic absorption peak of the ether bond CO produced by the substitution reaction.

[0036] Preparation Example 2

[0037] Preparation of polyurethane acrylate oligomers:

[0038] Step S1, vacuum dehydrating 5g of polytetramethylene glycol with a number average molecular weight of 1000, then mixing with 3g of isophorone diisocyanate, stirring evenly, controlling the heating rate to be 2°C / min, raising the temperature to 60°C, and adding 0.1g of dibutyltin dilaurate. After the addition, continue to raise the temperature to 70°C, and keep warm for 4h to form a prepolymer;

[0039] Step S2, lowering the temperature to 55°C, then adding 0.5g of diol chain extender to the prepolymer, raising the temperature to 75°C, keeping the temperature for chain extension polymerization for 8h, stopping heating, cooling and discharging the material to obtain polyurethane acrylate oligomer.

[0040] The preparation method of the diol chain extender is shown in Preparation Example 1.

[0041] Example 1

[0042] A UV curing multifunctional adhesive comprises the following raw materials in parts by weight:

[0043]

[0044] The preparation method of the multifunctional adhesive comprises the following steps:

[0045] In the first step, polyurethane acrylate oligomer, diluent, leveling agent BYK-310 and dispersant BYK-985 are added to a mixing kettle, the stirring rate is controlled to be 1000 r / min, and mechanical stirring is performed for 60 minutes at room temperature to form a precursor material;

[0046] The second step is to adjust the rotation speed to 500r / min, continue to add the photoinitiator benzoin dimethyl ether into the mixing kettle, stir at room temperature for 40 minutes under light-proof conditions, then add the fumed silica into the mixing kettle, continue to stir and mix for 40 minutes, discharge the material, and store it in a dark place.

[0047] The preparation method of polyurethane acrylate oligomer is shown in Preparation Example 2; hydroxyethyl acrylate is selected as the diluent, and the following are the same.

[0048] Example 2

[0049] A UV curing multifunctional adhesive comprises the following raw materials in parts by weight:

[0050]

[0051] The preparation method of the multifunctional adhesive comprises the following steps:

[0052] The first step is to add polyurethane acrylate oligomer, diluent, leveling agent BYK-333 and dispersant BYK-9077 into a mixing kettle, control the stirring rate to 1000r / min, and mechanically stir and mix for 40 minutes at room temperature to form a precursor;

[0053] The second step is to adjust the rotation speed to 1000r / min, continue to add the photoinitiator benzoin dimethyl ether into the mixing kettle, stir at room temperature for 30 minutes under light-proof conditions, then add the fumed silica into the mixing kettle, continue to stir and mix for 30 minutes, discharge the material, and store it in a dark place.

[0054] Example 3

[0055] A UV curing multifunctional adhesive comprises the following raw materials in parts by weight:

[0056]

[0057]

[0058] The preparation method of the multifunctional adhesive comprises the following steps:

[0059] The first step is to add polyurethane acrylate oligomer, diluent, leveling agent BYK-333 and dispersant BYK-9077 into a mixing kettle, control the stirring rate to 1500r / min, and mechanically stir and mix for 30 minutes at room temperature to form a precursor;

[0060] The second step is to adjust the rotation speed to 1000r / min, continue to add the photoinitiator benzoin dimethyl ether into the mixing kettle, stir at room temperature for 20 minutes under light-proof conditions, then add the fumed silica into the mixing kettle, continue to stir and mix for 30 minutes, discharge the material, and store it in a dark place.

[0061] Comparative Example 1

[0062] A UV curing multifunctional adhesive comprises the following raw materials in parts by weight:

[0063]

[0064] The preparation method of the multifunctional adhesive comprises the following steps:

[0065] The first step is to add polyurethane acrylate oligomer, diluent, leveling agent BYK-333 and dispersant BYK-9077 into a mixing kettle, control the stirring rate to 1000r / min, and mechanically stir and mix for 40 minutes at room temperature to form a precursor;

[0066] The second step is to adjust the rotation speed to 1000r / min, continue to add the photoinitiator benzoin dimethyl ether into the mixing kettle, stir at room temperature for 30 minutes under light-proof conditions, then add the fumed silica into the mixing kettle, continue to stir and mix for 30 minutes, discharge the material, and store it in a dark place.

[0067] The preparation method of the polyurethane acrylate oligomer is different from that of Preparation Example 2 in that the diol chain extender is replaced by the conventional end-capping agent hydroxyethyl methacrylate, and the rest are the same.

[0068] Test Case

[0069] The adhesives in the embodiments and comparative examples were tested for performance, and the results are recorded in the following table:

[0070] Table 1 - Performance test results

[0071] 180° peel strength / N / 25mm Limiting oxygen index / % Phenomenon Example 1 2.89 32.1 No obvious phenomenon Example 2 2.94 32.2 No obvious phenomenon Example 3 2.93 32.1 No obvious phenomenon Comparative Example 1 1.86 20.7 Curly, yellowing

[0072] The 180° peel strength test method refers to the standard GB / T 2792-1998;

[0073] The limiting oxygen index test method is: evenly apply the adhesive on the glass plate, irradiate it with ultraviolet light until it is completely cured, remove the film, and cut it into film samples that meet the specifications, referring to the standard GB / T 2406.2-2009;

[0074] The film samples were placed in a temperature environment of 120°C and taken out after 72 hours. The surface phenomena of the film samples were observed and their high temperature resistance was evaluated.

[0075] According to the test results, the adhesive prepared using the polyurethane acrylate oligomer prepared in Preparation Example 2 of the present invention as the main raw material has good bonding performance, excellent high temperature resistance, good flame retardant performance, and strong functionality. However, when the polyurethane acrylate oligomer prepared using a conventional capping agent is used as the main raw material, the various properties of the adhesive are significantly reduced.

[0076] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a UV-curable multifunctional adhesive, characterized in that: The invention comprises the following raw materials in parts by weight: The preparation method comprises the following steps: The first step is to add polyurethane oligomer, diluent, leveling agent and dispersant into a mixing kettle, control the stirring rate to 1000-1500r / min, and mechanically stir and mix for 30-60min at room temperature to form a precursor; Step 2: Adjust the speed to 500-1000r / min, continue to add the photoinitiator to the mixing kettle, stir at room temperature for 20-40min under light-proof conditions, then add the thixotropic agent to the mixing kettle, continue to stir and mix for 30-40min, discharge the material, and store it in a dark place; The specific preparation method of the polyurethane oligomer comprises the following steps: Step S1, vacuum dehydrating the polyglycol, then mixing it with the diisocyanate, stirring evenly, controlling the heating rate to be 2-3°C / min, raising the temperature to 50-60°C, and adding an organic tin compound catalyst. After the addition, continue to raise the temperature to 60-70°C, and keep the temperature for 3-6 hours to form a prepolymer; Step S2, lowering the temperature to 50-55°C, then adding the diol chain extender to the prepolymer, raising the temperature to 70-80°C, keeping the temperature to carry out chain extension polymerization for 6-9 hours, stopping heating, lowering the temperature and discharging the material, and obtaining a polyurethane oligomer; The specific preparation method of the diol chain extender comprises the following steps: Step SS1, dissolving 2,5-dibromoadipic acid in tetrahydrofuran solvent, then adding a condensing agent and a accelerator to the reaction solution, stirring and activating for 30-60 minutes, then continuing to add a hydroxyphosphorus flame retardant intermediate, stirring at room temperature for 4-8 hours after the addition, to obtain a chain extension connector; Step SS2, adding magnolol and toluene to a polymerization kettle filled with nitrogen and mixing, then adding a sodium hydroxide aqueous solution with a mass fraction of 20-25% to the polymerization kettle, turning on the heating, raising the temperature to 50-60°C, and keeping the temperature for 1-2 hours, then adding the chain extender connector to the polymerization kettle, after adding, further raising the temperature to 70-80°C, keeping the temperature for 8-12 hours, cooling and discharging, and the diol chain extender can be obtained.

2. The method for preparing a UV curable multifunctional adhesive according to claim 1, characterized in that: In step S1, the polyol is polyether diol or polytetramethylene diol; the diisocyanate is hexamethylene diisocyanate, isophorone diisocyanate or toluene diisocyanate; and the organotin compound catalyst is stannous octoate or dibutyltin dilaurate.

3. The method for preparing a UV curable multifunctional adhesive according to claim 1, characterized in that: In step SS1, the condensing agent is dicyclohexylcarbodiimide; and the accelerator is 4-dimethylaminopyridine or N-hydroxysuccinimide.

4. The method for preparing a UV curable multifunctional adhesive according to claim 1, characterized in that: In step SS1, the hydroxyphosphorus-based flame retardant intermediate is 2,6,7-trioxa-1-phosphabicyclo (2.2.2) octane-4-methanol-1-oxide or 2-hydroxyethyl dimethyl phosphate.

5. The method for preparing a UV curable multifunctional adhesive according to claim 1, characterized in that: In step SS1, the molar ratio of the 2,5-dibromoadipic acid to the hydroxyphosphorus-based flame retardant intermediate is 1:1-2.

6. The method for preparing a UV curable multifunctional adhesive according to claim 1, characterized in that: In step SS2, the molar ratio of magnolol to the chain extension linker is 1:0.8-0.

9.

7. The method for preparing a UV curable multifunctional adhesive according to claim 1, characterized in that: The diluent is an acrylate diluent; the thixotropic agent is fumed silica; the leveling agent is any one of BYK-310, BYK-315N or BYK-333; the dispersant is BYK-985 or BYK-9077; and the photoinitiator is benzoin dimethyl ether.

8. A UV curable multifunctional adhesive, characterized in that: The method is prepared according to any one of claims 1 to 7.

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