A solvent-free UV curing adhesive and a preparation method thereof
By pre-preparing rosin ester preplasticized slurry and amphiphilic siloxane oligomers, combined with specific sequential mixing and multi-stage degassing treatment, the problems of high viscosity and poor compatibility of solvent-free UV curing adhesives were solved, achieving lower viscosity, higher stability and better curing performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- MIDGOLD SILICONE (YICHANG) CO LTD
- Filing Date
- 2026-02-10
- Publication Date
- 2026-06-02
Smart Images
Figure CN122127940A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coating preparation, and more particularly to a solvent-free UV-curable adhesive and its preparation method. Background Technology
[0002] Ultraviolet (UV) curing adhesives are widely used due to their fast curing speed, low energy consumption, and high production efficiency. Solvent-free UV curing adhesives have become an important development direction. They are composed entirely of active components that can participate in the photocuring reaction, achieving zero emissions of volatile organic compounds.
[0003] In existing technologies, to further endow products with bio-based properties and utilize their rigid structure to improve performance, the introduction of rosin or its derivatives (such as rosin acrylate) as raw material components into solvent-free systems has become a valuable technical approach. However, some drawbacks still exist in its application. For example, solvent-free UV-curable adhesives using rosin have issues with high viscosity and compatibility. Specifically, the inherent rigid hydrogenated phenanthrene ring structure of rosin molecules and the difference in polarity between rosin and common acrylate resins cause prominent technical contradictions in solvent-free high-solids-content systems: on the one hand, the introduction of rosin components leads to a sharp increase in system viscosity, making preparation and construction processes such as mixing, degassing, and dispensing difficult and increasing energy consumption; on the other hand, the poor compatibility between the rosin phase and the main resin phase easily leads to stratification during storage and phase separation after curing, thereby affecting the transparency, uniformity, final mechanical properties, and long-term reliability of the adhesive layer.
[0004] Therefore, a solvent-free UV-curable adhesive and its preparation method are proposed to solve the problems of high viscosity and poor compatibility of solvent-free UV-curable adhesives using rosin. Summary of the Invention
[0005] The purpose of this invention is to provide a solvent-free UV-curable adhesive and its preparation method, thereby solving the problems of high viscosity and poor compatibility of solvent-free UV-curable adhesives using rosin.
[0006] To achieve this objective, the present invention adopts the following technical solution: A method for preparing a solvent-free UV-curable adhesive, the method comprising the following steps: Step S1: Prepare a flowable rosin ester preplasticized slurry, an amphiphilic siloxane oligomer bridging the acrylate phase and the rosin phase, and a completely homogeneous acrylate resin mixture, respectively. Step S2: Premix the amphiphilic siloxane oligomer with the acrylate resin mixture. After mixing, add rosin ester preplasticizing slurry to obtain adhesive a. Degas adhesive a to obtain adhesive b. Then cool and filter adhesive b and encapsulate and seal it to obtain solvent-free UV curable adhesive.
[0007] The rosin ester preplasticized slurry is obtained according to the following steps: Under nitrogen protection, isodecyl acrylate, antioxidant 1076, and TPO (photoinitiator TPO) are heated to the first temperature and stirred. Then, rosin acrylate is slowly added and stirred until the system is completely dissolved and transparent. Under the condition of maintaining a slight positive pressure in the reaction system, a vacuum is drawn to (-0.05)-(-0.08) MPa at the first temperature and maintained for 3-10 min. Heating is stopped, and the system temperature is reduced to ≤40℃ to obtain rosin ester preplasticized slurry.
[0008] The first temperature is 60-70℃, the mass ratio of isodecyl acrylate, antioxidant 1076, TPO and rosin acrylate is (48-52):(0.4-0.6):(4.0-5.0):(43-47), and the viscosity of the rosin ester preplasticized slurry is 2000-5000 mPa. s.
[0009] The amphiphilic siloxane oligomers are obtained according to the following steps: Under dry nitrogen, acryloyloxypropyltrimethoxysilane, HEA, and polymerization inhibitor are mixed evenly with aqueous mother liquor, and the total water content of the system is 50-150 ppm. After stirring evenly, zirconium acetylacetonate is added to the system, and the reaction is stirred at a second temperature. After the reaction starts, the actual viscosity and actual FTIR (Fourier transform infrared spectrum) of the system are monitored every 15-20 min. The stirring reaction is stopped when the actual viscosity and actual FTIR reach the target values simultaneously. Subsequently, the material is degassed and de-gasified at 38-40℃ and vacuum degree ≤-0.095MPa, and the material residence time is 20-50s to obtain amphiphilic siloxane oligomers.
[0010] The second temperature is 28-32℃, the target viscosity is 150-400 mPa·s, the target FTIR is the peak intensity of the silane characteristic peak reduced to 60-80% of the peak intensity at the beginning of the reaction, the mass ratio of acryloyloxypropyltrimethoxysilane, HEA and the polymerization inhibitor is 6:(1.4-1.6):(0.01-0.03), the amount of zirconium acetylacetonate added is 0.3-0.7% of the total mass of acryloyloxypropyltrimethoxysilane, HEA and the polymerization inhibitor, the polymerization inhibitor is hydroquinone monomethyl ether, the aqueous mother liquor is isodecyl acrylate solution, and the water content of the isodecyl acrylate solution is 950-1050 ppm.
[0011] The acrylate resin mixture is obtained according to the following steps: Under normal temperature and nitrogen conditions, aliphatic polyurethane acrylate oligomer, HDDA, PO-NPGDA, photoinitiator, leveling agent and defoamer are stirred at a stirring speed of 100-200 rpm for 30-45 minutes until completely homogeneous to obtain an acrylate resin mixture.
[0012] The mass ratio of the aliphatic polyurethane acrylate oligomer, HDDA, PO-NPGDA, photoinitiator, leveling agent, and defoamer is (33-37):(18-22):(7-9):(4.8-5.2):(0.4-0.6):(0.2-0.4). The photoinitiator is a mixture of 2-isopropylthioxanthone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, with a mass ratio of (1.0-1.8):(3.0-3.8). The leveling agent is a polyether-modified siloxane, and the defoamer is a defoaming polysiloxane.
[0013] Step S2 specifically includes the following steps: Step S21: Heat the acrylate resin mixture to a third temperature and stir it with the amphiphilic siloxane oligomer at the third temperature for 10-15 minutes. Then add rosin ester preplasticized slurry to the system and stir at a stirring speed of 2000-3000 for 20-30 minutes. After stirring, obtain adhesive a. Step S22: Place adhesive solution a in a planetary mixer degasser, stir at the fourth temperature and at a revolution speed of 5-10 rpm, and evacuate to (-0.06)-(-0.08) MPa and maintain for 3-10 min; then switch the vacuum degree between (-0.08)-(-0.10) MPa and (-0.04)-(-0.06) MPa 3-5 times, and maintain each state for 30-50 s; then adjust the vacuum degree to ≤-0.097 MPa, and stir at the fourth temperature at a revolution speed of 15-20 rpm and a rotation speed of 30-50 rpm for 15-30 min. After stirring, let it stand at the fourth temperature for 5-15 min under a vacuum degree of ≤-0.097 MPa, and then cool it to below room temperature at a rate of 2-3℃ / min to obtain adhesive solution b; Step S23: After coarse filtration and fine filtration, the adhesive solution b is filled into an opaque container under a nitrogen atmosphere and sealed to obtain a solvent-free UV curing adhesive.
[0014] In step S21, the third temperature is 38-40℃; in step S22, the fourth temperature is ≤35℃; in step S23, the coarse filtration uses a 100-mesh filter bag, and the fine filtration uses a 5-10μm filter.
[0015] A solvent-free UV-curable adhesive, wherein the solvent-free UV-curable adhesive is prepared by the preparation method described above.
[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a solvent-free UV-curable adhesive and its preparation method. By designing a process of independently preparing key components and then mixing them sequentially, it effectively solves the inherent high viscosity and compatibility problems of rosin-based solvent-free systems. On one hand, by pre-thermoplasticizing the rosin component, it is transformed into a medium-to-low viscosity and stable slurry, significantly reducing the energy consumption and operational difficulty of subsequent overall mixing. On the other hand, by synthesizing amphiphilic siloxane oligomers and pre-anchoring them in the bulk phase during the mixing stage, their migration to the two-phase interface is promoted, thereby enhancing the compatibility and interfacial stability between the rosin and acrylate phases at the microscopic level. Furthermore, a specific feeding sequence and a multi-stage vacuum degassing procedure further ensure uniform dispersion of components and a defect-free adhesive solution. The final product, while maintaining a high bio-based content, exhibits lower application viscosity, excellent storage stability, higher cured film transparency, and more balanced mechanical properties, with overall performance significantly superior to the control product obtained using a one-time mixing process. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.
[0019] Figure 1 This is a schematic flowchart of the preparation method in this invention. Detailed Implementation
[0020] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0021] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.
[0022] Example 1: Please see Figure 1 The method for preparing a solvent-free UV-curable adhesive in this embodiment is characterized by comprising the following steps: Step S1: Prepare a flowable rosin ester preplasticized slurry, an amphiphilic siloxane oligomer bridging the acrylate phase and the rosin phase, and a completely homogeneous acrylate resin mixture, respectively. Step S2: Premix the amphiphilic siloxane oligomer with the acrylate resin mixture. After mixing, add rosin ester preplasticizing slurry to obtain adhesive a. Degas adhesive a to obtain adhesive b. Then cool and filter adhesive b and encapsulate and seal it to obtain solvent-free UV curable adhesive.
[0023] Specifically, step S1 involves preparing a flowable rosin ester preplasticized slurry, an amphiphilic siloxane oligomer bridging the acrylate phase and the rosin phase, and a completely homogeneous acrylate resin mixture. Rosin ester preplasticized slurry is obtained according to the following steps: Under nitrogen protection, isodecyl acrylate, antioxidant 1076, and TPO are heated to the first temperature and stirred. Then, rosin acrylate is slowly added and stirred until the system is completely dissolved and transparent. Under the condition of maintaining a slight positive pressure in the reaction system, a vacuum is drawn to (-0.05)-(-0.08) MPa at the first temperature and maintained for 3-10 min. Heating is stopped, and the system temperature is reduced to ≤40℃ to obtain rosin ester preplasticized slurry.
[0024] The first temperature is 60-70℃, and the mass ratio of isodecyl acrylate, antioxidant 1076, TPO and rosin acrylate is (48-52):(0.4-0.6):(4.0-5.0):(43-47). The viscosity of the rosin ester preplasticized slurry is 2000-5000 mPa. s.
[0025] It should be noted that in the step of obtaining the rosin ester preplasticized slurry, the mixture of isodecyl acrylate, antioxidant 1076, TPO and rosin acrylate is heated to a first temperature and continuously stirred at this temperature. The molecular thermal motion of the isodecyl acrylate monomer, which serves as the dispersion medium, is intensified, and its interaction with the surface of the solid rosin acrylate particles is enhanced. This gradually penetrates and destroys the strong van der Waals forces and possible crystallization regions generated by the rigid hydrogenated phenanthrene ring structure between rosin ester molecules. During this process, the mobility of the rosin ester molecular chain segments increases, gradually untangling and dispersing. The solid rosin acrylate particles gradually become smaller and disappear, and the entire system changes from turbid to a completely transparent and homogeneous liquid. Subsequently, a short-term vacuum treatment is performed under an inert atmosphere that maintains a slight positive pressure in the system. This process mainly removes the gas dissolved in the liquid monomer and the air bubbles entrained during stirring, further ensuring the compactness and storage stability of the slurry, and providing a rosin component precursor with low gas content and controllable flowability for subsequent processes.
[0026] It is known that pre-plasticization significantly reduces the processing difficulty of rosin esters; specifically, pre-plasticization transforms acrylic rosin esters, which are originally solid or have extremely high viscosity at room temperature, into rosin esters that still have good fluidity below 40°C, with a viscosity of 2000-5000 mPa. The homogeneous slurry effectively alters the physical form of rosin components in subsequent mixing, transforming it from a component requiring extremely high mechanical energy to disperse into a standardized liquid raw material that is easy to measure, transport, and mix, thus laying the physical foundation for the smooth progress of the entire preparation process.
[0027] It is understandable that solvent-free UV-curable adhesives using rosin have a high viscosity problem, stemming from the high bulk viscosity of rosin due to its rigid molecular structure and the difficulty of direct dispersion in solvent-free systems. This step, by utilizing heat and the dissolving effect of active monomers in a separate process, effectively reduces the processing viscosity of the rosin phase, optimizing its state before final mixing. This transforms the subsequent blending process with acrylate resins and other mixtures from struggling to disperse extremely high viscosity to relatively easy mixing between viscous liquids, thus significantly reducing the overall energy consumption and mixing difficulty of the process, and providing a pretreatment solution for solving the high viscosity problem.
[0028] It is worth noting that the specific operational procedures of the plasticizing step described above are based on the material characteristics of rosin acrylate and the solvent-free system. Specifically, rosin acrylate is difficult to flow at room temperature, and direct mixing is inefficient and uneven. Heating to a first temperature of 60-70°C can effectively soften and dissolve the rosin ester, while avoiding premature decomposition of antioxidant 1076 or TPO or thermal oxidative yellowing of the rosin components due to excessively high temperatures. In addition, isodecanoacrylate serves as both a plasticizing solvent and a subsequent reactive component, and its dosage can maintain the total solids content of the system while ensuring sufficient dissolution of the rosin ester. After complete dissolution, a slight positive pressure is applied at the same temperature. The short-term vacuum treatment under these conditions aims to rapidly remove gas by taking advantage of the low viscosity of the material at high temperatures, when bubbles are easily removed. At the same time, maintaining a slight positive pressure prevents the introduction of new oxygen and moisture by air backflow, thereby reducing bubble defects at the source and improving the stability of the rosin ester preplasticized slurry. This ensures the production of a high-performance final product. In addition, the vacuum treatment stage is carried out at the first temperature to take advantage of the optimal time window when the material viscosity is lowest and the bubble migration resistance is minimal. This efficiently removes dissolved and encapsulated gases, significantly reducing the degassing burden under the high viscosity state of the final adhesive and improving the storage stability and uniformity of the rosin ester preplasticized slurry.
[0029] Amphiphilic siloxane oligomers are obtained according to the following steps: Under dry nitrogen, acryloyloxypropyltrimethoxysilane, HEA, and polymerization inhibitor are mixed evenly with an aqueous mother liquor, and the total water content of the system is 50-150 ppm. After stirring evenly, zirconium acetylacetonate is added to the system, and the reaction is stirred at a second temperature. After the reaction starts, the actual viscosity and actual FTIR of the system are monitored every 15-20 minutes. The stirring reaction is stopped when the actual viscosity and actual FTIR reach the target values simultaneously. Subsequently, the material is de-devoured and degassed in a short-path thin-film evaporator at 38-40°C and a vacuum degree ≤-0.095 MPa, with a material residence time of 20-50 s, to obtain amphiphilic siloxane oligomers. The method of de-devouring and degassed by the short-path thin-film evaporator is well known to those skilled in the art and will not be described in detail in this embodiment.
[0030] The second temperature is 28-32℃, the target viscosity is 150-400 mPa·s, the target FTIR is the reduction of the peak intensity of the silane characteristic peak to 60-80% of the peak intensity at the beginning of the reaction, the mass ratio of acryloyloxypropyltrimethoxysilane, HEA (2-hydroxyethyl acrylate) to the polymerization inhibitor is 6:(1.4-1.6):(0.01-0.03), the amount of zirconium acetylacetonate added is 0.3-0.7% of the total mass of acryloyloxypropyltrimethoxysilane, HEA and polymerization inhibitor, the polymerization inhibitor is hydroquinone monomethyl ether, the aqueous mother liquor is isodecyl acrylate solution, and the water content of the isodecyl acrylate solution is 950-1050 ppm.
[0031] It should be noted that in the process of obtaining amphiphilic siloxane oligomers, under the action of the catalyst zirconium acetylacetonate, in a second temperature environment of 28-32℃, the methoxy group of the raw material acryloyloxypropyltrimethoxysilane and the hydroxyl group of HEA undergo an alcoholysis reaction. At the same time, the 50-150ppm water content in the system will induce partial hydrolysis of silane groups to generate silanols. Then, silanols condense with each other or with unreacted alkoxy groups. These reactions cause silane molecules to be connected through Si-O-Si or Si-OC bonds, and the molecular weight increases slowly, so the viscosity of the system gradually increases over time. By monitoring the viscosity and Fourier transform infrared spectroscopy in real time, the reaction is actively terminated when the actual viscosity reaches the target viscosity and the actual FTIR reaches the target FTIR. Subsequently, the material is rapidly degassed and degassed under high temperature and high vacuum thin film evaporation conditions to remove small molecule by-products, and finally, a structurally controllable amphiphilic siloxane oligomer is obtained.
[0032] It is known that, under the action of the above steps, a siloxane oligomer with predetermined amphiphilicity is prepared, which plays the role of a highly efficient interface compatibilizer. Specifically, the molecular structure of this oligomer contains polymerizable acryloyloxy groups with polarity similar to the acrylate phase, as well as siloxane segments with good compatibility with the non-polar rosin phase. This allows the oligomer to spontaneously migrate and accumulate in the interface region between the rosin phase and the acrylate resin phase during subsequent mixing. Through its amphiphilic structure, it effectively reduces the interfacial tension between the two phases and enhances the interfacial bonding strength through chemical bonding and physical entanglement, thus becoming a key component for bridging the two phases.
[0033] It is understandable that solvent-free UV-curable adhesives using rosin suffer from poor compatibility due to the polarity difference and thermodynamic incompatibility between the rosin phase and the main acrylate phase. This can easily lead to uneven mixing, storage stratification, and phase separation after curing. This step, by pre-synthesizing amphiphilic siloxane oligomers, provides an efficient molecular bridge between the two incompatible phases. When these oligomers are introduced into the system, they can effectively improve the thermodynamic stability and adhesion of the two-phase interface, thereby inhibiting the tendency of phase separation, improving the storage stability of the adhesive and the uniformity of the cured adhesive layer, and providing a chemical means to solve the compatibility problem.
[0034] It is worth noting that the specific operational procedures described above are based on the characteristics of silane chemical reactions and the functionality of amphiphilic siloxane oligomers. Specifically, the mass ratio of acryloyloxypropyltrimethoxysilane to HEA is 6:(1.4-1.6) to balance the reactive functional groups and amphiphilic structural units of the final product. The second temperature of 28-32℃ is to minimize side reactions and raw material volatilization while ensuring an appropriate reaction rate. Viscosity and FTIR characteristic peak intensity are used as dual endpoint control indicators because viscosity can directly reflect the increase in molecular weight, while FTIR can microscopically monitor the conversion degree of key functional groups (-OCH3). The combination of the two ensures the consistency of the structure of different batches of products. The subsequent thin-film devolatilization process at 38-40℃ and ≤-0.095MPa utilizes the high mass transfer efficiency of low-viscosity materials under high vacuum and large specific surface area. It can remove the reaction byproduct methanol and residual trace water in a very short time, thereby terminating the reaction, purifying the product, and ensuring its storage stability, laying the foundation for its subsequent stabilizing effect.
[0035] The acrylate resin mixture is obtained according to the following steps: Under normal temperature and nitrogen conditions, aliphatic polyurethane acrylate oligomer, HDDA, PO-NPGDA, photoinitiator, leveling agent and defoamer are stirred at a stirring speed of 100-200 rpm for 30-45 minutes until completely homogeneous to obtain an acrylate resin mixture.
[0036] The mass ratio of aliphatic polyurethane acrylate oligomer, HDDA, PO-NPGDA, photoinitiator, leveling agent, and defoamer is (33-37): (18-22): (7-9): (4.8-5.2): (0.4-0.6): (0.2-0.4). The photoinitiator is a mixture of 2-isopropylthioxanthone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, with a mass ratio of (1.0-1.8): (3.0-3.8). The leveling agent is polyether-modified siloxane, and the defoamer is defoaming polysiloxane.
[0037] It should be noted that in the step of obtaining the acrylate resin mixture, by applying mechanical stirring at 100-200 rpm, the liquid components such as aliphatic polyurethane acrylate oligomers, HDDA (1,6-hexanediol diacrylate), and PO-NPGDA (propoxylated neopentyl glycol diacrylate) form a continuous mixed liquid phase. Meanwhile, the photoinitiator, leveling agent, and defoamer, as solid components, are gradually wetted, dispersed, and eventually dissolved under the shear force of this liquid phase. In this process, the energy provided by mechanical stirring overcomes the van der Waals forces between the molecules of each component, promoting diffusion and mixing at the molecular scale. In particular, it fully deagglomerates solid particles such as photoinitiators and dissolves them into the mixed solution of monomers and oligomers, so that the material gradually transforms from a multiphase, turbid or heterogeneous system containing solid particles into a single, transparent, and completely homogeneous liquid mixture, i.e., the acrylate resin mixture.
[0038] It is known that in this step, the various acrylate resins, reactive diluent monomers, and key additives that constitute the main body of the final cured network are pre-mixed into a homogeneous solution without concentration gradients and undissolved solids. This provides a stable and predictable reaction and dispersion medium for the subsequent introduction of amphiphilic siloxane oligomers and rosin ester preplasticized slurry, ensuring the uniform distribution of photoinitiators in the system. This lays a solid foundation for obtaining a cured adhesive layer with uniform curing and consistent performance.
[0039] Understandably, while the above steps do not directly reduce viscosity or improve compatibility, they provide a homogenized starting point for the entire preparation system, thus providing a technical solution to the technical problem. The completely homogeneous acrylate resin mixture avoids the uneven curing problem that may be caused by excessive local concentration of photoinitiator, and also eliminates the potential interference to subsequent precision filtration and the purity of the final product caused by the presence of solid particles. Furthermore, the acrylate resin mixture creates a mother liquor environment free of internal defects for the effective anchoring of amphiphilic siloxane oligomers and the uniform dispersion of the rosin phase. This allows subsequent processes aimed at solving high viscosity and compatibility problems to be carried out on a stable composition, thereby improving the reliability of the overall process and the performance consistency of the final product.
[0040] It is worth noting that in the above steps, the main components such as aliphatic polyurethane acrylate oligomers and HDDA already have good flowability and miscibility at room temperature, and can be mixed without heating. Maintaining room temperature can avoid unnecessary thermal history and prevent photoinitiators or monomers from prepolymerizing or changing in performance during the mixing stage. Nitrogen protection is used to isolate oxygen and prevent free radicals that may be generated during stirring from initiating premature polymerization. In addition, aliphatic polyurethane acrylate oligomers provide a flexible framework as the main film-forming substance, while HDDA and PO-NPGDA act as reactive diluents to adjust viscosity and reactivity. The dosage of both can obtain a suitable operating viscosity in the subsequent mixing stage. The combination of a stirring time of 30-45 min and a rotation speed of 100-200 rpm is designed to provide sufficient shear and diffusion time to ensure that all components, especially solid photoinitiators, can be completely dissolved and uniformly dispersed at the molecular level, thereby obtaining a reliable acrylate resin mixture.
[0041] Specifically, in step S2, the amphiphilic siloxane oligomer and the acrylate resin mixture are premixed. After the mixing is completed, rosin ester preplasticizing slurry is added and mixed to obtain adhesive a. Adhesive a is degassed to obtain adhesive b. Then, adhesive b is cooled, filtered, and encapsulated to obtain solvent-free UV curable adhesive.
[0042] Step S2 specifically includes the following steps: Step S21: Heat the acrylate resin mixture to a third temperature and stir it with the amphiphilic siloxane oligomer at the third temperature for 10-15 minutes. Then add rosin ester preplasticized slurry to the system and stir at a stirring speed of 2000-3000 for 20-30 minutes. After stirring, obtain adhesive a. Step S22: Place adhesive solution a in a planetary mixer degasser, stir at the fourth temperature and at a revolution speed of 5-10 rpm, and evacuate to (-0.06)-(-0.08) MPa and maintain for 3-10 min; then switch the vacuum degree between (-0.08)-(-0.10) MPa and (-0.04)-(-0.06) MPa 3-5 times, and maintain each state for 30-50 s; then adjust the vacuum degree to ≤-0.097 MPa, and stir at the fourth temperature at a revolution speed of 15-20 rpm and a rotation speed of 30-50 rpm for 15-30 min. After stirring, let it stand at the fourth temperature for 5-15 min under a vacuum degree of ≤-0.097 MPa, and then cool it to below room temperature at a rate of 2-3℃ / min to obtain adhesive solution b; Step S23: After coarse filtration and fine filtration, the adhesive solution b is filled into an opaque container under a nitrogen atmosphere and sealed to obtain a solvent-free UV curing adhesive.
[0043] In step S21, the third temperature is 38-40℃; in step S22, the fourth temperature is ≤35℃; in step S23, coarse filtration uses a 100-mesh filter bag, and fine filtration uses a 5-10μm filter.
[0044] It should be noted that in step S2, the acrylate resin mixture is first heated to a third temperature of 38-40°C to reduce its viscosity. Then, it is premixed with amphiphilic siloxane oligomers. This process allows the hydrophilic ends (acrylate groups) of the oligomers to have sufficient opportunity to anchor with the main resin phase through polar interaction. Next, rosin ester preplasticized slurry is added and subjected to high-speed shear stirring. During this process, the hydrophobic siloxane segments of the pre-anchored amphiphilic siloxane oligomers migrate to and adsorb at the interface of the newly formed rosin phase droplets under shear force, forming a stable interface layer. This disperses the high-viscosity rosin slurry, and the entire system achieves macroscopic homogeneity, resulting in adhesive solution a. The subsequent multi-stage degassing treatment gradually removes the gas mixed and dissolved in adhesive solution a through the synergy of vacuum and mechanical stirring. Finally, the purity is ensured by cooling and locking, and filtration, completing the transformation from adhesive solution b to solvent-free UV-curable adhesive.
[0045] It is understood that step S2, through specific sequential mixing and multi-stage degassing, achieves the dual effect of efficient interfacial compatibilization and obtaining an extremely defect-free adhesive. The sequential mixing steps ensure that the amphiphilic siloxane oligomers can be pre-positioned in the host phase, so that they can efficiently migrate to the interface to play a compatibilizing role when the rosin phase is added. The multi-stage degassing, through a combination of stages, different vacuum levels, and stirring methods, specifically removes bubbles of different sizes and sources. The specific sequential mixing ensures the microscopic stability of the multiphase system from a chemical and physical perspective, while the multi-stage degassing ensures the macroscopic integrity and reliability of the final product from an engineering perspective. Together, they determine the final performance and quality of the cured adhesive.
[0046] Understandably, step S2, by optimizing the feeding sequence, increases the compatibilization efficiency of the amphiphilic siloxane oligomer, enabling the high-viscosity rosin phase to be uniformly dispersed and stably exist in the host phase with relatively reasonable energy consumption. This synergistically solves the problems of mixing difficulty and poor compatibility. Moreover, this specific mixing sequence is the key to maximizing the compatibilization efficiency of the amphiphilic siloxane oligomer, ensuring that the amphiphilic siloxane oligomer has sufficient time to pre-disperse and anchor in the host phase (i.e., the acrylate phase). Thus, when the hydrophobic rosin phase is added, it can efficiently migrate to the two-phase interface and form a stable transition layer in situ, thereby improving compatibility and reducing the overall mixing difficulty. The multi-stage degassing treatment specifically addresses the bubble problem, which is particularly troublesome due to high viscosity and multi-phase interfaces. It prevents curing defects, uneven performance, and unstable storage caused by the presence of bubbles, ensuring that the uniform structure achieved in the aforementioned steps can be completely transformed into the excellent performance of the final product.
[0047] It is worth noting that the specific order of mixing the amphiphilic siloxane oligomer with the acrylate resin mixture first, and then adding the rosin ester preplasticized slurry, is based on the kinetic principle of interfacial chemistry, aiming to create optimal interfacial enrichment conditions for the amphiphilic siloxane oligomer. The third temperature of 38-40℃ can moderately reduce the overall viscosity of the system without excessively initiating thermal side reactions, which is conducive to uniform mixing and subsequent degassing. The degassing process adopts a multi-stage combination of slow-to-fast, pulsed loosening, gentle deep degassing, and static cooling, which can address the specific difficulties in degassing high-viscosity, multiphase systems. The initial low-vacuum slow stirring steadily removes large bubbles, the vacuum pulse uses pressure changes to weaken the adhesion of microbubbles on the interface, the subsequent high vacuum combined with gentle stirring achieves deep degassing, and the final static cooling locks in a bubble-free state. The above multi-stage degassing treatment aims to achieve the ultimate degassing effect with the lowest thermomechanical stress, ensuring the optical and mechanical integrity of the cured adhesive.
[0048] The following is a comparison of the various properties of this Example 1 with those of solvent-free UV curable adhesives in the prior art, as detailed in Table 1.
[0049] Table 1 As shown in Table 1, to address the high viscosity issue, Example 1 uses an independent pre-plasticization step to convert solid or high-viscosity rosin acrylate into a homogeneous slurry with good flowability under the action of heating and active monomers. This pretreatment reduces the final mixing viscosity of the adhesive by approximately 44-65% compared to the one-time mixing method in the comparative example, significantly reducing mixing energy consumption and improving construction rheology. To address the poor compatibility issue, Example 1 uses an in-situ synthesized siloxane oligomer with an amphiphilic structure as a customized compatibilizer. By employing a specific sequence of first mixing with the acrylate resin and then adding the rosin slurry, it ensures that the compatibilizer can be pre-anchored in the main phase and subsequently migrate efficiently to the two-phase interface, thereby forming a stable transition layer at the microscopic level. Macroscopically, this results in a significant improvement in the storage stability of the adhesive (no stratification, small viscosity changes), a significant increase in the transparency of the cured film (light transmittance increased by approximately 2-5%, haze reduced by approximately 3-6%), and improvements in mechanical properties such as adhesion.
[0050] In the above data, the comparative data represents the average value after multiple tests of solvent-free UV-curable adhesives in the prior art. The preparation method of solvent-free UV-curable adhesives in the prior art is as follows: First, all formulation components, including solid or extremely high viscosity rosin acrylate, aliphatic polyurethane acrylate oligomers, various acrylate reactive diluent monomers, photoinitiators, and additives, are simultaneously added to the same mixing container, either all at once or in groups. Then, under room temperature or moderate heating conditions, a high-speed disperser or homogenizer is turned on, and the mixture is subjected to prolonged, strong mechanical shearing at high speeds to forcibly break down rosin solid clumps and disperse them into the main resin phase until a macroscopically homogeneous mixture is obtained. After mixing, the resulting adhesive solution is transferred to a degassing device and degassed under a certain vacuum and continuous stirring to attempt to remove air bubbles. Finally, the adhesive solution is cooled, filtered, and filled to obtain the final product.
[0051] The test data for Example 1 were obtained based on three specific Examples a, b, and c.
[0052] Example a is as follows: To prepare a rosin ester preplasticized slurry, 50.0 g of isodecanyl acrylate, 0.5 g of antioxidant 1076, and 4.5 g of photoinitiator TPO were heated to 65°C and stirred. 45.0 g of rosin acrylate was slowly added, and the mixture was stirred until completely transparent. Under a slightly positive pressure, a vacuum was applied at 65°C to -0.07 MPa and maintained for 5 minutes. Heating was then stopped, and the mixture was cooled to below 40°C to obtain a slurry with a viscosity of 3200 mPa·s. To prepare an amphiphilic siloxane oligomer, 6.0 g of acryloyloxypropyltrimethoxysilane, 1.5 g of 2-hydroxyethyl acrylate, and 0.02 g of hydroquinone monomethyl ether (polymer inhibitor) were prepared. g of silane was mixed with isodecyl acrylate mother liquor containing 1000 ppm water, and the total water content of the system was controlled to be 100 ppm. After stirring evenly, 0.03 g of zirconium acetylacetonate catalyst was added, and the mixture was stirred at 30 °C. The viscosity and FTIR spectrum of the system were monitored. The reaction was stopped when the viscosity reached 280 mPa·s and the intensity of the silane characteristic peak decreased by 30%. The material was then devolatilized for 30 s in a thin-film evaporator at 40 °C and a vacuum degree ≤ -0.097 MPa to obtain oligomers. An acrylate resin mixture was prepared by taking 35.0 g of aliphatic polyurethane acrylate oligomer and 20.0 g of 1,6-hexanediol diacrylate. 8.0 g of propoxylated neopentyl glycol diacrylate, 1.5 g of photoinitiator 2-isopropylthioxanthone, 3.5 g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 0.5 g of polyether-modified siloxane leveling agent, and 0.3 g of defoaming polysiloxane defoamer were stirred at 150 rpm for 40 min under nitrogen protection at room temperature until completely homogeneous. Sequential mixing and degassing were then performed. The acrylate resin mixture was heated to 39°C and stirred with amphiphilic siloxane oligomers for 12 min. Rosin ester preplasticized slurry was then added, and the mixture was subjected to high-speed shearing at 2500 rpm for 25 min to obtain adhesive solution a. Adhesive solution a was transferred... The mixture was transferred to a planetary agitator and deaerated at a controlled temperature of 33°C. First, it was deaerated at 8 rpm and a vacuum of -0.07 MPa for 8 minutes. Then, the vacuum was switched between -0.09 MPa and -0.05 MPa four times, each time for 40 seconds. The vacuum was then increased to -0.098 MPa and stirred at 18 rpm and 40 rpm for 22 minutes. After stirring, it was allowed to stand for 10 minutes. Finally, it was cooled to below 25°C at a rate of 2.5°C / min to obtain adhesive b. Adhesive b was coarsely filtered through a 100-mesh filter bag and then finely filtered through an 8μm filter element. It was then filled and sealed under a nitrogen atmosphere to obtain a solvent-free UV-curable adhesive.
[0053] The performance test results of Example a are as follows: the viscosity of the adhesive is 3200 mPa·s, the viscosity increases by 12% after 7 days of accelerated storage at 50℃, and there is no delamination; the pencil hardness of the cured film is 3H, the adhesion of the film to the glass substrate is 0, the light transmittance is 92% and the haze is 1.5% with a thickness of 1 mm.
[0054] Example b is as follows: To prepare a rosin ester preplasticized slurry, 48.0 g of isodecanyl acrylate, 0.5 g of antioxidant 1076, and 4.0 g of TPO were heated to 68°C, and 47.0 g of rosin acrylate was added. After dissolving and clarifying, the mixture was degassed at 68°C and -0.07 MPa for 5 min. After cooling, a slurry with a viscosity of approximately 4100 mPa·s was obtained. To prepare an amphiphilic siloxane oligomer, 6.0 g of acryloyloxypropyltrimethoxysilane, 1.6 g of 2-hydroxyethyl acrylate, and 0.03 g of hydroquinone monomethyl ether were added to a mother liquor with a water content of 1000 ppm to bring the total water content to 120 ppm. 0.035 g of zirconium acetylacetonate was then added. The mixture was reacted at 31°C until the viscosity reached 380 mPa·s and the FTIR silane peak intensity decreased by 35%. It was then devolatilized using a thin-film evaporator. An acrylate resin mixture was prepared by taking 33.0 g of aliphatic polyurethane acrylate oligomer, 22.0 g of 1,6-hexanediol diacrylate, 7.0 g of propoxylated neopentyl glycol diacrylate, 1.8 g of 2-isopropylthioxanthone, and 3.2 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. The leveling agent and defoamer were the same as in Example a. The mixture was thoroughly mixed at room temperature. The sequential mixing and defoaming processes were the same as in Example a, except that the third temperature was 40°C and the fourth temperature was 34°C.
[0055] The performance test results of Example b are as follows: the viscosity of the adhesive is 4100 mPa·s, the viscosity increases by 18% after 7 days of storage at 50℃, and there is no delamination; the pencil hardness of the cured film is 4H, the adhesion is grade 0, the light transmittance is 90%, and the haze is 2.2%.
[0056] Example c is as follows: The formulation of the rosin ester preplasticized slurry is the same as in Example a; to prepare the amphiphilic siloxane oligomer, 6.0 g of acryloyloxypropyltrimethoxysilane, 1.4 g of 2-hydroxyethyl acrylate, and 0.01 g of hydroquinone monomethyl ether were taken, and the total water content was controlled to 80 ppm by controlling the mother liquor. 0.025 g of zirconium acetylacetone was added, and the mixture was reacted at 29 °C until the viscosity reached 180 mPa·s and the FTIR silane peak intensity decreased by 25%. After devolatilization, the oligomer was obtained; acrylate was prepared. The resin mixture consists of 37.0 g of aliphatic polyurethane acrylate oligomer, 18.0 g of 1,6-hexanediol diacrylate, 9.0 g of propoxylated neopentyl glycol diacrylate, 1.0 g of 2-isopropylthioxanthone, and 3.8 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, with the same additives as before. The mixture is prepared at room temperature. The sequential mixing and degassing process is the same as in Example a, except that the third temperature is 38°C and the fourth temperature is 32°C.
[0057] The performance test results of Example c are as follows: the viscosity of the adhesive is 2800 mPa·s, the viscosity increases by 10% after 7 days of storage at 50℃, and there is no delamination; the pencil hardness of the cured film is 2H, the adhesion is grade 0, the light transmittance is 93%, and the haze is 1.0%.
[0058] Based on the three specific examples a, b, and c, the main differences between examples a, b, and c are primarily reflected in the raw material ratios. Example b uses a higher proportion of rosin acrylate and a slightly higher amount of HEA, while example c uses a lower amount of HEA and catalyst, and a different photoinitiator ratio. Secondly, in terms of process parameters, the first temperature, second temperature, reaction endpoint viscosity, FTIR conversion target, and mixing and degassing temperature of each example are all specifically adjusted. Ultimately, these differences lead to distinctions in performance: Example b, due to its highest rosin content, exhibits the highest hardness and relatively high viscosity and haze; Example c, due to a lower degree of compatibilizer reaction and an adjusted main resin ratio, exhibits the lowest viscosity, best light transmittance, and moderate hardness; Example a, as a balanced ratio, achieves a moderate and balanced performance in all aspects.
[0059] Example 2: This embodiment describes a solvent-free UV-curable adhesive, which is prepared using the method described in Example 1.
[0060] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do 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 solvent-free UV-curable adhesive, characterized in that, The preparation method includes the following steps: Step S1: Prepare a flowable rosin ester preplasticized slurry, an amphiphilic siloxane oligomer bridging the acrylate phase and the rosin phase, and a completely homogeneous acrylate resin mixture, respectively. Step S2: Premix the amphiphilic siloxane oligomer with the acrylate resin mixture. After mixing, add rosin ester preplasticizing slurry to obtain adhesive a. Degas adhesive a to obtain adhesive b. Then cool and filter adhesive b and encapsulate and seal it to obtain solvent-free UV curable adhesive.
2. The method for preparing the solvent-free UV-curable adhesive according to claim 1, characterized in that, The rosin ester preplasticized slurry is obtained according to the following steps: Under nitrogen protection, isodecyl acrylate, antioxidant 1076, and TPO are heated to the first temperature and stirred. Then, rosin acrylate is slowly added and stirred until the system is completely dissolved and transparent. Under the condition of maintaining a slight positive pressure in the reaction system, a vacuum is drawn to (-0.05)-(-0.08) MPa at the first temperature and maintained for 3-10 min. Heating is stopped, and the system temperature is reduced to ≤40℃ to obtain rosin ester preplasticized slurry.
3. The method for preparing the solvent-free UV-curable adhesive according to claim 2, characterized in that, The first temperature is 60-70℃, the mass ratio of isodecyl acrylate, antioxidant 1076, TPO and rosin acrylate is (48-52):(0.4-0.6):(4.0-5.0):(43-47), and the viscosity of the rosin ester preplasticized slurry is 2000-5000 mPa. s.
4. The method for preparing the solvent-free UV-curable adhesive according to claim 1, characterized in that, The amphiphilic siloxane oligomers are obtained according to the following steps: Under dry nitrogen, acryloyloxypropyltrimethoxysilane, HEA, and polymerization inhibitor are mixed evenly with aqueous mother liquor, and the total water content of the system is 50-150 ppm. After stirring evenly, zirconium acetylacetonate is added to the system, and the reaction is stirred at a second temperature. After the reaction starts, the actual viscosity and actual FTIR of the system are monitored every 15-20 minutes. The stirring reaction is stopped when the actual viscosity and actual FTIR reach the target values simultaneously. Subsequently, the material is degassed and de-gasified at 38-40℃ and vacuum degree ≤-0.095MPa, and the material residence time is 20-50s to obtain amphiphilic siloxane oligomers.
5. The method for preparing the solvent-free UV-curable adhesive according to claim 4, characterized in that, The second temperature is 28-32℃, the target viscosity is 150-400 mPa·s, the target FTIR is the peak intensity of the silane characteristic peak reduced to 60-80% of the peak intensity at the beginning of the reaction, the mass ratio of acryloyloxypropyltrimethoxysilane, HEA and the polymerization inhibitor is 6:(1.4-1.6):(0.01-0.03), the amount of zirconium acetylacetonate added is 0.3-0.7% of the total mass of acryloyloxypropyltrimethoxysilane, HEA and the polymerization inhibitor, the polymerization inhibitor is hydroquinone monomethyl ether, the aqueous mother liquor is isodecyl acrylate solution, and the water content of the isodecyl acrylate solution is 950-1050 ppm.
6. The method for preparing the solvent-free UV-curable adhesive according to claim 1, characterized in that, The acrylate resin mixture is obtained according to the following steps: Under normal temperature and nitrogen conditions, aliphatic polyurethane acrylate oligomer, HDDA, PO-NPGDA, photoinitiator, leveling agent and defoamer are stirred at a stirring speed of 100-200 rpm for 30-45 minutes until completely homogeneous to obtain an acrylate resin mixture.
7. The method for preparing the solvent-free UV-curable adhesive according to claim 6, characterized in that, The mass ratio of the aliphatic polyurethane acrylate oligomer, HDDA, PO-NPGDA, photoinitiator, leveling agent, and defoamer is (33-37):(18-22):(7-9):(4.8-5.2):(0.4-0.6):(0.2-0.4). The photoinitiator is a mixture of 2-isopropylthioxanthone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, with a mass ratio of (1.0-1.8):(3.0-3.8). The leveling agent is a polyether-modified siloxane, and the defoamer is a defoaming polysiloxane.
8. The method for preparing the solvent-free UV-curable adhesive according to claim 1, characterized in that, Step S2 specifically includes the following steps: Step S21: Heat the acrylate resin mixture to a third temperature and stir it with the amphiphilic siloxane oligomer at the third temperature for 10-15 minutes. Then add rosin ester preplasticized slurry to the system and stir at a stirring speed of 2000-3000 for 20-30 minutes. After stirring, obtain adhesive a. Step S22: Place adhesive solution a in a planetary mixer degasser, stir at the fourth temperature and at a revolution speed of 5-10 rpm, and evacuate to (-0.06)-(-0.08) MPa and maintain for 3-10 min; then switch the vacuum degree between (-0.08)-(-0.10) MPa and (-0.04)-(-0.06) MPa 3-5 times, and maintain each state for 30-50 s; then adjust the vacuum degree to ≤-0.097 MPa, and stir at the fourth temperature at a revolution speed of 15-20 rpm and a rotation speed of 30-50 rpm for 15-30 min. After stirring, let it stand at the fourth temperature for 5-15 min under a vacuum degree of ≤-0.097 MPa, and then cool it to below room temperature at a rate of 2-3℃ / min to obtain adhesive solution b; Step S23: After coarse filtration and fine filtration, the adhesive solution b is filled into an opaque container under a nitrogen atmosphere and sealed to obtain a solvent-free UV curing adhesive.
9. The method for preparing the solvent-free UV-curable adhesive according to claim 8, characterized in that, In step S21, the third temperature is 38-40℃; in step S22, the fourth temperature is ≤35℃; in step S23, the coarse filtration uses a 100-mesh filter bag, and the fine filtration uses a 5-10μm filter.
10. A solvent-free UV-curable adhesive, characterized in that, The solvent-free UV-curable adhesive is prepared using the preparation method described in any one of claims 1-9.