UV (ultraviolet) curing organosilicone structural adhesive for bonding low-polarity base material as well as preparation method and use method of UV curing organosilicone structural adhesive

Abstract

The invention relates to the technical field of adhesives, in particular to a UV-cured organosilicone structural adhesive for bonding low-polarity base materials and a preparation method and a use method of the UV-cured organosilicone structural adhesive. The acrylic pressure-sensitive adhesive prepared by the invention comprises the following substances: 70-90 parts of organic silicon photosensitive resin, 5-20 parts of a diluent, 1-10 parts of a coupling agent, 1-10 parts of a photoinitiator and 1-5 parts of an auxiliary photoinitiator, the organic silicon photosensitive resin is an acrylic acid modified siloxane polymer; acrylic acid or methacrylic acid groups are grafted on a main chain of the organic silicon photosensitive resin, and meanwhile, the organic silicon photosensitive resin contains part of silicon hydroxyl or alkoxy groups. A photocuring reaction group and a group with good adhesion to a base material are introduced, so that the defects of long curing time and poor colloid storage stability of the existing organic silicon adhesive are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and specifically to a UV-curable silicone structural adhesive for bonding low-polarity substrates, and its preparation and usage methods. Background Art

[0002] Ultraviolet (UV) curing is an advanced technology for surface treatment of materials that emerged in the 1960s. It is collectively referred to as radiation curing (Rad Tech) with electron beam (EB) curing. It uses ultraviolet light to initiate the rapid polymerization and cross-linking of chemically active liquid materials, instantaneously curing them into solid materials. The industrial production of electron beam (EB) curing is restricted to a certain extent due to the complex equipment, high technical requirements, and large cost investment. Ultraviolet (UV) curing technology is relatively mature, with a lower equipment investment cost, and is suitable for industrial automation production. At the same time, ultraviolet (UV) curing is also an industrial technology with the characteristics of "5E": efficient, enabling, economical, energy saving, and environmentally friendly. Therefore, the photocuring technology will be more widely applied and developed.

[0003] Ultraviolet (UV) curable adhesives apply the photocuring technology to the polymer field to achieve bonding, fixing, sealing, and three-proofing of substrates. In addition to UV adhesives, the most common photocuring products are UV coatings and UV inks. Their greatest feature is the fast curing rate, generally between several seconds and dozens of seconds, and the fastest can be cured within 0.05 - 0.1 s, making them the fastest drying and curing among various coatings, inks, and adhesives currently. This can meet the production requirements of large-scale automated production lines, greatly improving production efficiency and saving the space for stacking semi-finished products.

[0004] Generally, the drying and curing time of solvent-based or thermosetting coatings, inks, and adhesives requires several hours or even days, and a large production workshop is needed to stack semi-finished products. UV adhesives are usually applicable to a variety of substrates, such as paper, wood, plastic, metal, leather, stone, glass, ceramics, etc., and are particularly suitable for some heat-sensitive materials (such as paper, plastic, or electronic components, etc.). UV adhesives cure rapidly at room temperature, and their energy consumption is only 1 / 10 - 1 / 5 of that of thermosetting formula products. Photocuring only requires the radiant energy to excite the photoinitiator, unlike thermosetting which requires heating the substrate, materials, and the surrounding space, and also evaporating the diluting solvent or water, consuming a large amount of energy.

[0005] Another advantage of UV adhesives is that they basically do not contain volatile solvents. The active diluents used are all high-boiling organic acrylic monomers, and they all participate in cross-linking polymerization during curing and become part of the cross-linked network structure. Therefore, they do not cause air pollution, reduce the harm to the human body and the risk of fire, and are an environmentally friendly product.

[0006] In industrial applications, adhesives often encounter low-polarity surfaces with very low surface energy, such as silicone rubber, polypropylene, polystyrene, etc. Conventional polyurethane adhesives, epoxy adhesives, and acrylic adhesives cannot achieve good adhesion to low-polarity surfaces such as silicone rubber. According to the principle of polarity similarity, using low-polarity silicone-based adhesives to bond these surfaces will have certain effects, such as moisture-curing silicone adhesives, but they have disadvantages such as long curing time and poor storage stability of the colloid.

[0007] Chinese Patent No. CN116731667A discloses a UV-curable silicone pressure-sensitive adhesive material, its preparation method and application. By using the method of condensation grafting of an acrylic polymer containing an alkoxysilyl functional group and a UV-curing group, a terminal hydroxyl silicone polymer and an MQ tackifying silicone resin, the compatibility and phase stability between the acrylic polymer and the silicone polymer are improved, and high-strength and high-performance pressure-sensitive adhesives are obtained by UV curing without an external cross-linking agent, solving the problems of low cross-linking degree, low performance, complex production process and high preparation cost in the existing UV light-curable silicone pressure-sensitive adhesives.

[0008] Although this invention introduces that the photoinitiation principle is through the curing of acrylic radicals, the photosensitive resin synthesized is solvent-based and belongs to the technical field of pressure-sensitive adhesives, and it cannot be used in 100% solids content solvent-free adhesives.

[0009] To solve the above problems, the present invention provides a UV-curable silicone structural adhesive for bonding low-polarity substrates and its preparation and use methods. Summary of the Invention

[0010] The purpose of the present invention is to provide a UV-curable silicone structural adhesive for bonding low-polarity substrates and its preparation and use methods to solve the problems raised in the above background technology.

[0011] To solve the above technical problems, the present invention provides the following technical solution: A UV-curable silicone structural adhesive for bonding low-polarity substrates, calculated by weight components, includes the following substances:

[0012] 70-90 parts of silicone photosensitive resin, 5-20 parts of diluent, 1-10 parts of coupling agent, 1-10 parts of photoinitiator, 1-5 parts of co-photoinitiator;

[0013] The silicone photosensitive resin is a silicone acrylate polymer.

[0014] Preferably, the main chain of the acrylic modified silicone polymer is a siloxane chain structure, and the side chain or end group contains acrylic groups or methacrylic groups. The number average molecular weight is between 4000 and 10000. The (meth)acrylic groups on the molecular chain include monofunctional and difunctional groups, and the structure is:

[0015]

[0016] Preferably, the synthesis route of the acrylic modified silicone polymer is as follows: Add 1 mol of diphenylmethane diisocyanate and 0.1% by mass of dibutyltin dilaurate into a three-necked flask, heat up to 40 °C, and dropwise add 1 mol of pentaerythritol triacrylate containing the inhibitor p-hydroxyanisole (-NCO:-OH = 2:1, molar ratio). After addition, continue to react at 40 °C for 4 h. When the -NCO content reaches the predetermined value, dropwise add 1 mol of hydroxyl and methoxy terminated hydroxy silicone oil (-NCO:-OH = 1:1, molar ratio). Under nitrogen protection, heat up to 70 - 75 °C and react until the -NCO content is zero, then stop the reaction to obtain the photocurable acrylic modified silicone polymer.

[0017] Preferably, the diluent is one or a combination of photosensitive silicone oligomers and photosensitive acrylic active monomers.

[0018] Preferably, the photosensitive acrylic active monomer has a main chain of carbon chain structure, and the (meth)acrylic groups on the molecular chain include monofunctional, difunctional, polyfunctional and highly functional groups.

[0019] Preferably, the coupling agent is selected from at least one of titanate coupling agents and silane coupling agents.

[0020] Preferably, the photoinitiator is a free radical photoinitiator, including one or a combination of α-hydroxy ketone derivatives, acylphosphine oxides, α-amino ketone derivatives, benzil and its derivatives, acetophenone derivatives, thioxanthone and its derivatives, anthraquinone and its derivatives, and other photoinitiators.

[0021] Preferably, the co-photoinitiator contains one or a combination of tertiary amine compounds and active amines.

[0022] The present invention provides a preparation method of a UV-curable silicone structural adhesive for bonding low-polarity substrates, which is used to prepare any of the above UV-curable silicone structural adhesives for bonding low-polarity substrates. The preparation steps are as follows:

[0023] Weigh a quantitative amount of silicone photosensitive resin, diluent, photoinitiator, and co - photoinitiator as needed in a yellow light laboratory. Stir and mix them using a blender and degas, then add a coupling agent, continue to disperse, stir, and degas. Finally, fill them into a brown single - component rubber tube and seal for storage away from light.

[0024] The present invention also provides a method for using a UV - curable silicone structural adhesive for bonding low - polarity substrates. Use any of the above - mentioned UV - curable silicone structural adhesives for bonding low - polarity substrates. Before processing, the surface of the low - polarity substrate needs to be treated using a VUV processor and a vacuum plasma processor.

[0025] More optimally, the basic parameters of the VUV processor are: a 172 - nm ultraviolet lamp, a working voltage of 15 V; an irradiation distance of 5 mm; the atmosphere is: nitrogen at 19 L / min and compressed air at 2.5 L / min; the time is 3 - 5 min.

[0026] More optimally, the basic parameters of the vacuum plasma processor are: oxygen 50%, argon 50%, and the duration is 3 - 5 min.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0028] (1) The present invention provides a preparation and use method of a UV - curable silicone structural adhesive for bonding low - polarity substrates. The silicone photosensitive resin in the present invention has acrylic or methacrylic acid groups grafted on the main chain, and at the same time contains partial silicon hydroxyl groups or alkoxy groups. The photo - curable reaction groups and groups with good adhesion to the substrate are introduced.

[0029] (2) The bonding process method described in the present invention treats low - polarity surfaces such as the silicone rubber surface, and the treatment technologies include Plasmas, VUV, etc.

[0030] (3) In the bonding process method described in the present invention, the mechanical properties of the bonded test specimens are significantly improved after heating. Description of the Drawings

[0031] Figure 1 It is a structural diagram of the (meth) acrylic acid group on the molecular chain of the acrylic - modified siloxane polymer. Detailed Embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0033] The present invention verifies the performance and usage characteristics of this structural adhesive with several examples and control groups.

[0034] Example 1

[0035] This example provides a UV-curable silicone structural adhesive for bonding low-polarity substrates and its preparation method, including a single component, 70 parts of silicone photosensitive resin, 5 parts of diluent, 3 parts of coupling agent, 1 part of photoinitiator, and 1 part of co-photoinitiator;

[0036] The silicone photosensitive resin is an acrylic-modified siloxane polymer with a molecular weight of 4000 - 10000. The diluent is a photosensitive acrylic active monomer, the coupling agent is a silane coupling agent, the photoinitiator is 184 photoinitiator, and the co-photoinitiator is a tertiary amine compound.

[0037] This example prepares a UV-curable silicone structural adhesive for bonding low-polarity substrates. The specific steps are as follows:

[0038] Weigh a quantitative amount of silicone photosensitive resin, diluent, photoinitiator, and co-photoinitiator as needed in a yellow light laboratory. Use a stirrer or homogenizer to stir at 2000 r / min for 3 min. After mixing evenly, add the coupling agent and continue to stir at 2000 r / min for 2 min. After mixing evenly, defoam (negative pressure -0.1 MPa), and finally fill it into a brown single-component glue tube and store it sealed and away from light.

[0039] This example prepares a usage method of a UV-curable silicone structural adhesive for bonding low-polarity substrates, including the surface treatment technology of low-polarity substrate silicone rubber (PDMS) substrates. The specific steps are as follows:

[0040] UV light source: 365 nm LED light source, light intensity is 380 mW / cm 2 , total energy is 13.68 J / cm 2 .

[0041] Plasmas surface treatment: 50% oxygen, 50% argon, duration 5 min.

[0042] VUV surface treatment: The basic parameters of the VUV treatment machine are: 172 nm ultraviolet lamp, working voltage 15 v; irradiation distance 5 mm; atmosphere: nitrogen 19 L / min and compressed air 2.5 L / min; time 5 min.

[0043] Example 2

[0044] This example provides a UV-curable silicone structural adhesive for bonding low-polarity substrates and its preparation method, including a single component, 80 parts of silicone photosensitive resin, 12 parts of diluent, 3 parts of coupling agent, 2 parts of photoinitiator, and 5 parts of co-photoinitiator;

[0045] The silicone photosensitive resin is an acrylic acid modified siloxane polymer with a molecular weight of 4000 - 10000. The diluent is a photosensitive acrylic acid based active monomer, the coupling agent is a silane coupling agent, the photoinitiator is Irgacure 184, and the co - photoinitiator is a tertiary amine compound.

[0046] This example prepares a UV - curable silicone structural adhesive for bonding low - polarity substrates. The specific steps are as follows:

[0047] Weigh a quantitative amount of silicone photosensitive resin, diluent, photoinitiator, and co - photoinitiator as required in a yellow - light laboratory. Use a stirrer or homogenizer to stir at 2000 r / min for 3 min. After mixing evenly, add the coupling agent and continue to stir at 2000 r / min for 2 min. After mixing evenly, defoam (negative pressure - 0.1 MPa), and finally fill it into a brown single - component glue tube and store it sealed and away from light.

[0048] This example describes the usage method of a UV - curable silicone structural adhesive for bonding low - polarity substrates, including the surface treatment technology of low - polarity substrate silicone rubber (PDMS) substrates. The specific steps are as follows:

[0049] UV light source: 365 nm LED light source, light intensity is 380 mW / cm 2 , total energy is 13.68 J / cm 2 .

[0050] Plasmas surface treatment: oxygen 50%, argon 50%, duration 5 min.

[0051] VUV surface treatment: The basic parameters of the VUV treatment machine are: 172 nm ultraviolet lamp, working voltage 15 v; irradiation distance 5 mm; atmosphere: nitrogen 19 L / min and compressed air 2.5 L / min; time is 5 min.

[0052] Example 3

[0053] This example provides a UV - curable silicone structural adhesive for bonding low - polarity substrates and its preparation method, including a single component, 90 parts of silicone photosensitive resin, 20 parts of diluent, 3 parts of coupling agent, 5 parts of photoinitiator, and 10 parts of co - photoinitiator;

[0054] The silicone photosensitive resin is an acrylic acid modified siloxane polymer with a molecular weight of 4000 - 10000. The diluent is a photosensitive acrylic acid based active monomer, the coupling agent is a silane coupling agent, the photoinitiator is Irgacure 184, and the co - photoinitiator is a tertiary amine compound.

[0055] This example prepares a UV - curable silicone structural adhesive for bonding low - polarity substrates. The specific steps are as follows:

[0056] Weigh a quantitative amount of silicone photosensitive resin, diluent, photoinitiator, and co - photoinitiator as needed in the yellow light laboratory. Stir at 2000 r / min for 3 min using a blender or homogenizer. After mixing evenly, add the coupling agent and continue to stir at 2000 r / min for 2 min. After mixing evenly, defoam (negative pressure -0.1 MPa), and finally fill it into a brown single - component rubber tube and store it sealed in the dark.

[0057] This example describes the usage method of a UV - curable silicone structural adhesive for bonding low - polarity substrates, including the surface treatment technology of low - polarity substrate silicone rubber (PDMS) substrates. The specific steps are as follows:

[0058] UV light source: 365 nm LED light source, light intensity is 380 mW / cm 2 , total energy is 13.68 J / cm 2 .

[0059] Plasmas surface treatment: Oxygen 50%, argon 50%, duration 5 min.

[0060] VUV surface treatment: The basic parameters of the VUV treatment machine are as follows: 172 nm ultraviolet lamp, working voltage 15 v; irradiation distance 5 mm; atmosphere: nitrogen 19 L / min and compressed air 2.5 L / min; time 5 min.

[0061] Control group 1

[0062] Refer to the preparation raw materials and preparation process in Example 2, and prepare a UV - curable silicone structural adhesive for bonding low - polarity substrates without adding a coupling agent.

[0063] Control group 2

[0064] Refer to the preparation raw materials and preparation process in Example 2, and prepare a UV - curable silicone structural adhesive for bonding low - polarity substrates without adding a co - photoinitiator.

[0065] Perform performance tests on the UV - curable silicone structural adhesives for bonding low - polarity substrates prepared in Examples 1 - 3 and Control groups 1 and 2 above. The test results are shown in Table 1 below.

[0066] Table 1 Performance test table of structural adhesives in each example and control group

[0067]

[0068]

[0069] Note: * represents that the shear strength failure mode is PC substrate failure;

[0070] **It represents that the shear strength failure mode is the failure of the PDMS substrate.

[0071] Conclusion: It can be seen from the test results of Example 1, Example 2 and Example 3 that the photosensitive resin and the diluent play a key role in the properties of hardness, tensile strength and elongation at break. The diluent is a small molecule. Increasing its dosage can significantly increase the hardness of the cured adhesive film, while the elongation at break decreases and the tensile strength increases.

[0072] It can be seen from the shear tests of the three groups of examples that for the low-polarity substrate PDMS, the maximum shear strength can reach 1.1 MPa without treatment. After VUV and Plasmas treatments respectively, the maximum shear strength can reach 1.9 MPa and 1.6 MPa, an increase of 73% and 45%. After 72 hrs of high temperature and high humidity at 65 °C / 90% RH, the strength increases, and in Example 2, the shear strength reaches 3.4 MPa. After 500 hrs of high temperature and high humidity aging, the strength slightly increases to 3.9 MPa, and PDMS substrate failure occurs. This is mainly because the photosensitive resin contains some hydroxyl groups and urethane bonds, which will produce a certain degree of crosslinking and form hydrogen bonds under heating and humid conditions, thus enhancing the bonding strength.

[0073] It can be seen from the comparison between Control Group 1 and Example 2 that the coupling agent enhances the bonding strength to a certain extent, and this extent can be more reflected after 500 hrs of high temperature and high humidity aging.

[0074] It can be seen from the comparison between Control Group 2 and Example 2 that the co-initiator has little influence on the bonding strength because its main function is to improve the light irradiation efficiency, shorten the light irradiation time during production, and thus improve the production efficiency.

[0075] It can be seen from the PC / PC test data of the examples and the control groups that this structural adhesive has good bonding performance for non-low-polarity substrates such as untreated PC, and substrate failure occurs in some cases.

[0076] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made under the inventive concept of the present invention, using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A UV-curable silicone structural adhesive for bonding low-polarity substrates, characterized in that: The components by weight include the following substances: 70-90 parts of organosilicon photosensitive resin, 5-20 parts of diluent, 1-10 parts of coupling agent, 1-10 parts of photoinitiator, 1-5 parts of auxiliary photoinitiator; The organosilicon photosensitive resin is an acrylic acid-modified siloxane polymer.

2. The UV curable silicone structural adhesive for bonding low polarity substrates according to claim 1, characterized in that: The main chain of the acrylic modified siloxane polymer is a silicon oxygen chain structure, the side chain or the terminal group contains an acrylic acid group or a methacrylic acid group, the number average molecular weight is between 4000 and 10000, and the (meth) acrylic acid group on the molecular chain contains monofunctionality and difunctionality.

3. The UV curable silicone structural adhesive for bonding low polarity substrates according to claim 2, characterized in that: The synthetic route of the acrylic modified siloxane polymer is as follows: 1 mol of diphenylmethane diisocyanate and 0.1% by mass of dibutyltin dilaurate are added into a three-necked flask, the temperature is raised to 40° C., 1 mol of pentaerythritol triacrylate (-NCO:-OH=2:1, molar ratio) containing a polymerization inhibitor p-hydroxyanisole is added dropwise, after the addition is completed, the reaction is continued at 40° C. for 4 hours, when the -NCO content reaches a predetermined value, 1 mol of hydroxy silicone oil terminated with hydroxyl and methoxy groups (-NCO:-OH=1:1, molar ratio) is added dropwise, the temperature is raised to 70-75° C. under nitrogen protection, the reaction is stopped when the -NCO content is zero, and the photosensitive acrylic modified siloxane polymer is obtained.

4. The UV curable silicone structural adhesive for bonding low polarity substrates according to claim 1, characterized in that: The diluent is one or more combinations of photosensitive siloxane oligomers and photosensitive acrylic active monomers.

5. The UV curable organic silicon structural adhesive for bonding low polarity substrates according to claim 4, characterized in that: The photosensitive acrylic active monomer comprises a main chain structure of a carbon chain, and the (meth) acrylic groups on the molecular chain include monofunctional, difunctional, multifunctional and high-functional.

6. The UV curable silicone structural adhesive for bonding low polarity substrates according to claim 1, characterized in that: The coupling agent is selected from at least one of a titanate coupling agent and a silane coupling agent.

7. The UV curable organic silicon structural adhesive for bonding low polarity substrates according to claim 1, characterized in that: The photoinitiator is a free radical photoinitiator, including one or more combinations of α-hydroxy ketone derivatives, acyl phosphine oxide compounds, α-amino ketone derivatives, benzil and its derivatives, acetophenone derivatives, thioxanthone and its derivatives, anthraquinone and its derivatives, and other photoinitiators.

8. The UV curable silicone structural adhesive for bonding low polarity substrates according to claim 1, characterized in that: The auxiliary photoinitiator comprises one or more combinations of tertiary amine compounds and active amines.

9. A method for preparing a UV-curable organic silicon structural adhesive for bonding low-polarity substrates, for preparing any one of claims 1 to 8, characterized in that: The preparation steps are: In the Huangguang laboratory, weigh a certain amount of organic silicon photosensitive resin, diluent, photoinitiator, and auxiliary photoinitiator as needed. Use a blender to mix and degas, then add the coupling agent, continue to disperse, stir and degas, and finally put it into a brown single-component rubber tube and seal it to avoid light.

10. A method for using a UV-curable organic silicon structural adhesive for bonding low-polarity substrates, using any one of the UV-curable organic silicon structural adhesives for bonding low-polarity substrates as claimed in claims 1 to 8, characterized in that: Before processing, the surface of the low-polarity substrate needs to be treated with a VUV processor or a vacuum plasma processor.

11. The method for using the UV curable organic silicon structural adhesive for bonding low polarity substrates according to claim 10, characterized in that: The basic parameters of the VUV treatment machine are: 172nm ultraviolet lamp, working voltage 15V; irradiation distance 5mm; atmosphere: nitrogen 19L / min and compressed air 2.5L / min; time is 3-5min.

12. The method for using the UV-curable organic silicon structural adhesive for bonding low-polarity substrates according to claim 10, characterized in that: The basic parameters of the vacuum plasma treatment machine are: 50% oxygen, 50% argon, and a duration of 3-5 minutes.

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