Acrylic emulsion, emulsion preparation method, and acrylic ester pressure-sensitive adhesive
By using a mixture of decanol polyoxyethylene ether glucoside and fatty alcohol polyoxyethylene ether sodium carboxylate as emulsifiers, and combining it with a semi-continuous pre-emulsification method, the problem of poor compatibility between emulsifiers and the matrix in acrylic pressure-sensitive adhesives was solved, thereby improving the density and light transmittance of the emulsion film.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG HENGHE YONGSHENG GRP CO LTD
- Filing Date
- 2026-02-27
- Publication Date
- 2026-06-09
AI Technical Summary
The existing emulsifiers used in acrylic pressure-sensitive adhesives have poor molecular structure and poor compatibility with the pressure-sensitive adhesive matrix. During film formation, they are prone to microphase separation, resulting in increased haze of the adhesive layer, poor film density, and impaired light transmittance.
A mixture of decanol polyoxyethylene ether glucoside and fatty alcohol polyoxyethylene ether sodium carboxylate was used as an emulsifier, and the dispersion particle size of the monomers in the pre-emulsion was controlled by a semi-continuous pre-emulsification method to ensure that the emulsifier molecules are uniformly dispersed in the polymer network when the emulsion forms a film, thus avoiding microphase separation.
It improves the film density and light transmittance of the emulsion, reduces the haze of the pressure-sensitive adhesive layer, and enhances the mechanical properties and light transmittance of the pressure-sensitive adhesive layer.
Smart Images
Figure CN122167642A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of acrylic pressure-sensitive adhesive technology, and more particularly to an acrylic emulsion, an emulsion preparation method, and an acrylic pressure-sensitive adhesive. Background Technology
[0002] Acrylic pressure-sensitive adhesives are pressure-sensitive adhesive systems mainly composed of acrylic soft and hard monomers as polymer raw materials, supplemented by functional monomers through processes such as emulsion polymerization. They are currently the most widely used pressure-sensitive adhesive systems.
[0003] Existing emulsifiers used in acrylic pressure-sensitive adhesives are typically nonionic emulsifiers, such as alkylphenol polyoxyethylene ethers, and anionic emulsifiers, such as sodium dodecyl sulfate. However, the molecular structures of these emulsifiers have poor compatibility with the acrylic polymer matrix, and they tend to separate hydrophilic and hydrophobic phases. This easily leads to microphase separation during film formation, resulting in increased haze, poor film density, and impaired light transmittance. Summary of the Invention
[0004] The purpose of this invention is to provide an acrylic emulsion, an emulsion preparation method, and an acrylic pressure-sensitive adhesive, aiming to solve the problems of poor compatibility between the molecular structure of the emulsifier in existing acrylic pressure-sensitive adhesives and the pressure-sensitive adhesive matrix, which easily leads to microphase separation during film formation, resulting in increased haze of the adhesive layer, poor film density, and impaired light transmittance.
[0005] To address the aforementioned technical problems, the first aspect of this invention provides an acrylic emulsion, the raw materials for which, by weight, are: The mixture contains 95-100 parts water, 70-75 parts soft monomers, 20-23 parts hard monomers, 3-5 parts functional monomers, 2-2.5 parts emulsifier, 1.5-2.5 parts crosslinking agent, 0.3-0.5 parts initiator, and 0.3 parts defoamer; the emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate.
[0006] In the acrylic emulsion, the soft monomer is at least one of isooctyl acrylate and butyl acrylate.
[0007] In the acrylic emulsion, the hard monomer is at least one of methyl methacrylate and styrene.
[0008] In the acrylic emulsion, the ratio of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate by weight is 1:(1-1.5).
[0009] In the acrylic emulsion, the functional monomer is at least one of hydroxyethyl acrylate and N-hydroxymethylacrylamide.
[0010] In the acrylic emulsion, the crosslinking agent is at least one of trimethylolpropane triacrylate and polycarbodiimide.
[0011] A second aspect of this invention provides a method for preparing an acrylic emulsion, comprising the following steps: S001. Add emulsifier and 65-70 parts of water to the reaction vessel, stir and mix evenly to obtain the base liquid; S002. Add 25 parts of water to the stirrer, then add the soft monomer, hard monomer, functional monomer and crosslinking agent to the stirrer, stir and disperse evenly to obtain a pre-emulsion; S003. Mix 0.2 parts of initiator and 3 parts of water evenly to obtain initiator solution A, and mix 0.1 to 0.3 parts of initiator and 2 parts of water evenly to obtain initiator solution B; S004. After the temperature inside the reactor rises to 80-85°C, add 5% of the total mass of the pre-emulsion and initiator solution A dropwise into the reactor. After the addition is completed, keep the reactor warm. S005. After the heat preservation in step S004 is completed, continue to add the remaining pre-emulsion and initiator solution B to the reactor. After the addition is completed, keep the reactor warm. S006. After the heat preservation in step S005 is completed, the temperature inside the reactor is reduced to below 50°C. After adjusting the pH value of the emulsion, defoamer and crosslinking agent are added to the emulsion. After stirring and mixing evenly, the emulsion is filtered to obtain the acrylic emulsion.
[0012] Furthermore, in step S002, the crosslinking agent is trimethylolpropane triacrylate; in step S006, the crosslinking agent is polycarbodiimide.
[0013] A third aspect of the present invention provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion.
[0014] In the acrylate pressure-sensitive adhesive, the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.
[0015] The beneficial effects of this invention are: The first aspect of this invention provides an acrylic emulsion suitable for acrylate pressure-sensitive adhesives. The acrylic emulsion is based on soft and hard monomers, compounded with functional monomers, crosslinking agents, initiators, and defoamers. At the same time, by using decanol polyoxyethylene ether glucoside and fatty alcohol polyoxyethylene ether carboxylate as emulsifiers, the emulsifier molecules can be uniformly dispersed in the polymer network during film formation, rather than agglomerating to form independent phase regions. This can suppress microphase separation and avoid the increase of haze and damage to light transmittance of the pressure-sensitive adhesive layer.
[0016] The second aspect of the present invention provides a method for preparing an acrylic emulsion. By using a semi-continuous pre-emulsification method to control the dispersion particle size of the monomers in the pre-emulsion, it is possible to ensure that the latex particles are of uniform size after polymerization. This allows the latex particles to be tightly packed when the emulsion forms a film, thereby avoiding pores and defects caused by particle agglomeration, resulting in a pressure-sensitive adhesive layer with low haze and high light transmittance. Attached Figure Description
[0017] Figure 1 This is a flowchart of the method for preparing acrylic emulsion provided by the present invention. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not 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 creative effort are within the scope of protection of the present invention.
[0019] The first aspect of this invention provides an acrylic emulsion, which can be used to prepare acrylic pressure-sensitive adhesives. Specifically, the acrylic emulsion, by weight, comprises the following raw materials: Water 95-100 parts, soft monomer 70-75 parts, hard monomer 20-23 parts, functional monomer 3-5 parts, emulsifier 2-2.5 parts, crosslinking agent 1.5-2.5 parts, initiator 0.3-0.5 parts, defoamer 0.3 parts. In the aforementioned acrylic emulsions, soft monomers impart flexibility and tackiness. When used to prepare acrylic pressure-sensitive adhesives, these emulsions provide the adhesive layer with excellent initial tack, holding power, and flexibility, ensuring its ability to adhere to various interfaces. Hard monomers, with their higher glass transition temperature compared to soft monomers, provide rigid support to the adhesive layer, balancing the tackiness of the soft monomers and preventing deformation and flow under tension or high-temperature conditions. They also enhance the peel strength of the adhesive, preventing adhesion and residue. Functional monomers participate in crosslinking reactions, strengthening the adhesion, water resistance, and stability of the adhesive layer to the substrate. Crosslinking agents construct a three-dimensional network structure during polymerization, improving the strength, solvent resistance, high-temperature resistance, and creep resistance of the emulsion film, thereby preventing deformation or failure of the adhesive layer. Emulsifiers can reduce the interfacial tension between oil and water, disperse the oil phase monomers into tiny droplets, prevent particle aggregation during polymerization, and improve the compatibility of the emulsion with the acrylate polymer matrix, thereby improving film transparency and density.
[0020] Furthermore, the emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate.
[0021] Specifically, among the emulsifiers mentioned above, the hydrophobic segment of decanol polyoxyethylene ether glucoside is a long-chain fatty alcohol, similar to the carbon chain structure of acrylate monomers, resulting in stronger compatibility. The hydrophilic segment of decanol polyoxyethylene ether glucoside is a glucoside group, with a flexible spatial structure that can form weak interactions with the polymer molecular chain, thereby reducing the tendency for separation between the hydrophilic and hydrophobic segments. The hydrophobic segment of sodium fatty alcohol polyoxyethylene ether carboxylate is a long-chain fatty alcohol, synergistically complementing the hydrophobic structure of decanol polyoxyethylene ether glucoside. The hydrophilic segment of sodium fatty alcohol polyoxyethylene ether carboxylate is a sodium carboxylate group, with moderate polarity, avoiding interfacial repulsion caused by excessively strong hydrophilicity. Therefore, this invention uses decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate as emulsifiers, and the combination of the two can improve the matching degree between the emulsifier molecular structure and the acrylate polymer matrix, so that the emulsifier molecules can be uniformly dispersed in the polymer network during emulsion film formation, rather than agglomerating to form independent phase regions. This can suppress microphase separation and avoid the increase of haze and damage to light transmittance of the pressure-sensitive adhesive layer.
[0022] Furthermore, sodium fatty alcohol polyoxyethylene ether carboxylate is an anionic emulsifier, which can give the emulsion particles a negative charge and prevent particle aggregation through electrostatic repulsion, thereby ensuring the stability of the emulsion during storage and polymerization, and avoiding uneven film formation caused by excessively large particles. Decanol polyoxyethylene ether glucoside can form a flexible hydration film on the surface of latex particles, providing steric hindrance, which can further reduce particle aggregation and make the emulsion particles smaller and more uniform. When uniform and fine emulsion particles form a film, they can be tightly packed to form a continuous and dense pressure-sensitive adhesive layer, thereby avoiding porosity and defects caused by particle aggregation. This not only improves the mechanical properties of the pressure-sensitive adhesive layer, but also reduces light scattering in the pores and improves the light transmittance of the pressure-sensitive adhesive layer.
[0023] In an optional embodiment, the soft monomer is at least one of isooctyl acrylate and butyl acrylate. The soft monomer described above has a lower glass transition temperature, enabling the pressure-sensitive adhesive layer using the acrylic emulsion to maintain high elasticity at room temperature, quickly wetting the surface of the adhered object to form an effective bond, while simultaneously imparting a sticky but not rigid characteristic to the pressure-sensitive adhesive layer, ensuring no residue upon peeling.
[0024] In an optional embodiment, the hard monomer is at least one of methyl methacrylate and styrene. Of the hard monomers described above, methyl methacrylate imparts hardness and weather resistance to the pressure-sensitive adhesive layer using the acrylic emulsion; while styrene enhances the cohesive strength and high-temperature resistance of the pressure-sensitive adhesive layer.
[0025] In a preferred embodiment, the ratio of decanol polyoxyethylene ether glucoside to sodium fatty alcohol polyoxyethylene ether carboxylate is 1:(1-1.5) by weight. The hydrophilic segment of decanol polyoxyethylene ether glucoside is highly hydrophilic; excessive use can increase the hygroscopicity of the pressure-sensitive adhesive layer, leading to whitening and decreased peel strength with prolonged use. Conversely, the hydrophilic segment of sodium fatty alcohol polyoxyethylene ether carboxylate is highly polar; excessive use reduces its compatibility with the acrylate polymer matrix. During emulsion film formation, the emulsifier easily precipitates from the pressure-sensitive adhesive layer, forming micro-aggregates and causing slight microphase separation. This can result in light scattering and impaired light transmittance of the pressure-sensitive adhesive layer.
[0026] This invention discovers that when the weight ratio of decanol polyoxyethylene ether glucoside and fatty alcohol polyoxyethylene ether carboxylate is within the aforementioned range, the steric hindrance of decanol polyoxyethylene ether glucoside and the electrostatic repulsion generated by fatty alcohol polyoxyethylene ether carboxylate can form a dual stabilizing effect. This not only prevents emulsion particle aggregation but also reduces the impact of the environment on the emulsion, resulting in fine and uniform emulsion particles. Furthermore, within the aforementioned ratio range, the hydrophobic segments of the two emulsifiers are perfectly compatible with the acrylate matrix, while the hydrophilic segments have complementary polarities. This ensures that during emulsion film formation, the emulsifiers are uniformly dispersed in the pressure-sensitive adhesive layer without significant micro-phase separation, thereby reducing the haze of the pressure-sensitive adhesive layer and improving its light transmittance.
[0027] In optional embodiments, the functional monomer is at least one of hydroxyethyl acrylate and N-hydroxymethylacrylamide. Specifically, the molecular structure of hydroxyethyl acrylate contains hydroxyl groups, which can form strong hydrogen bonds with polar groups on the substrate surface, thereby improving the adhesion of the pressure-sensitive adhesive layer to the substrate. Moreover, the hydroxyl groups can react with the crosslinking agent polycarbodiimide to form stable chemical bonds, thus participating in the construction of a three-dimensional network structure and preventing stringing and residue phenomena in the pressure-sensitive adhesive layer due to insufficient cohesion.
[0028] The molecular structure of N-hydroxymethylacrylamide contains an amide group and a hydroxymethyl group. The hydroxymethyl group can undergo a condensation reaction with the hydroxyl group of hydroxyethyl acrylate and the carboxyl group on the polymer chain, while the amide group can undergo free radical polymerization with the unsaturated double bond of the crosslinking agent trimethylolpropane triacrylate. This significantly improves the tensile strength and tear resistance of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is not easily deformed or flowed at high temperatures.
[0029] In an optional embodiment, the crosslinking agent is at least one of trimethylolpropane triacrylate and polycarbodiimide.
[0030] Specifically, the molecular structure of trimethylolpropane triacrylate contains three unsaturated double bonds. Under the action of an initiator, it can polymerize simultaneously with soft monomers, hard monomers, and functional monomers to quickly form a preliminary cross-linked polymer skeleton. This avoids excessive linear growth of molecular chains during polymerization, which can lead to uncontrolled emulsion viscosity. At the same time, it can provide basic cohesive force for the pressure-sensitive adhesive layer and prevent the pressure-sensitive adhesive layer from tensile fracture.
[0031] Polycarbodiimide can react with the carboxyl and hydroxyl groups in acrylic emulsions, reducing the exposure of hydrophilic groups in the pressure-sensitive adhesive layer, making the pressure-sensitive adhesive layer less prone to whitening and tack degradation in humid environments.
[0032] In an optional embodiment, the initiator may be ammonium persulfate. The defoamer may be BYK-024 defoamer.
[0033] like Figure 1 As shown, a second aspect of the present invention provides a method for preparing an acrylic emulsion, comprising the following steps: S001. Add emulsifier and 65-70 parts of water to the reaction vessel, stir and mix evenly to obtain the base liquid; S002. Add 25 parts of water to the stirrer, then add the soft monomer, hard monomer, functional monomer and crosslinking agent to the stirrer, stir and disperse evenly to obtain a pre-emulsion; S003. Mix 0.2 parts of initiator and 3 parts of water evenly to obtain initiator solution A, and mix 0.1 to 0.3 parts of initiator and 2 parts of water evenly to obtain initiator solution B; S004. After the temperature inside the reactor rises to 80-85°C, add 5% of the total mass of the pre-emulsion and initiator solution A dropwise into the reactor. After the addition is completed, keep the reactor warm. S005. After the heat preservation in step S004 is completed, continue to add the remaining pre-emulsion and initiator solution B to the reactor. After the addition is completed, keep the reactor warm. S006. After the heat preservation in step S005 is completed, the temperature inside the reactor is reduced to below 50°C. After adjusting the pH value of the emulsion, defoamer and crosslinking agent are added to the emulsion. After stirring and mixing evenly, the emulsion is filtered to obtain the acrylic emulsion.
[0034] This invention uses a semi-continuous pre-emulsification method to control the dispersion particle size of monomers in the pre-emulsion, which ensures that the latex particles are of uniform size after polymerization. This allows the latex particles to be tightly packed when the emulsion forms a film, thereby avoiding pores and defects caused by particle aggregation, resulting in a pressure-sensitive adhesive layer with low haze and high light transmittance.
[0035] Furthermore, in step S002, the crosslinking agent is trimethylolpropane triacrylate.
[0036] In step S006, the crosslinking agent is polycarbodiimide, which can react stepwise with the residual carboxyl and hydroxyl groups in the emulsion after the polymerization reaction, thereby reducing the exposure of hydrophilic groups. Furthermore, the post-crosslinking reaction between polycarbodiimide and carboxyl and hydroxyl groups can fill the crosslinking gaps of trimethylolpropane triacrylate, making the three-dimensional network structure in the acrylate polymer matrix more compact, thereby improving the solvent resistance and long-term stability of the pressure-sensitive adhesive layer.
[0037] A third aspect of the present invention provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion.
[0038] Specifically, the base film layer can be a PET release film. The acrylic emulsion and photoinitiator are mixed and coated onto the surface of the PET release film to a thickness of 20±2 μm, and then dried at 105℃ for 3 minutes. After drying, the pressure-sensitive adhesive layer is cured using a 365nm LED UV curing machine (light intensity 80~120mW / cm², curing energy 300~400mJ / cm²), resulting in the finished acrylic pressure-sensitive adhesive film.
[0039] In the aforementioned acrylic pressure-sensitive adhesive, the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. All of the above-mentioned photoinitiators are water-based, and when two photoinitiators are combined, the light response range covers 250–400 nm, accommodating different types of ultraviolet light sources. Regardless of the thickness of the adhesive layer, simultaneous curing of the surface and interior is achieved, thus avoiding the problem of incomplete curing of the pressure-sensitive adhesive layer. Furthermore, when the above-mentioned photoinitiators are combined, the yellowing index of the pressure-sensitive adhesive layer after long-term use is low, far superior to a single photoinitiator system, making the acrylic pressure-sensitive adhesive suitable for applications with high appearance requirements (such as food packaging labels).
[0040] To further illustrate the acrylic emulsion and acrylic pressure-sensitive adhesive provided by the present invention, the following examples and comparative examples are provided. The sources of some of the raw materials used in the following examples and comparative examples are as follows: Decanol polyoxyethylene ether glucoside (Shanghai Fakai Chemical), sodium fatty alcohol polyoxyethylene ether carboxylate (AEC-9Na, Jining Fangyu Chemical), polycarbodiimide (Bolino), 2-hydroxy-2-methyl-1-phenyl-1-propanone (Shanghe), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (Plutosil), dodecylphenol polyoxyethylene ether (Yuanlian Chemical), sodium dodecyl sulfate (Guangzhou Yuanda).
[0041] Example 1 This embodiment provides an acrylic emulsion, the raw materials for which, by weight, are: 95 parts water, 70 parts isooctyl acrylate, 20 parts methyl methacrylate, 2 parts emulsifier, 2 parts hydroxyethyl acrylate, 1 part N-hydroxymethylacrylamide, 1 part trimethylolpropane triacrylate, 0.5 parts polycarbodiimide, 0.3 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0042] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:1.
[0043] This embodiment also provides a method for preparing an acrylic emulsion, including the following steps: S001. Add emulsifier and 65 parts of water to the reaction vessel, stir and mix evenly to obtain the base liquid; S002. Add 25 parts of water to the mixer, then add the soft monomer, hard monomer, functional monomer, and trimethylolpropane triacrylate to the mixer and stir to disperse evenly to obtain a pre-emulsion. S003. Mix 0.2 parts of initiator and 3 parts of water evenly to obtain initiator solution A, and mix 0.1 parts of initiator and 2 parts of water evenly to obtain initiator solution B; S004. After the temperature inside the reactor rises to 80°C, add 5% of the total mass of the pre-emulsion and initiator solution A dropwise into the reactor. After the addition is completed, keep the reactor warm. S005. After the heat preservation in step S004 is completed, continue to add the remaining pre-emulsion and initiator solution B to the reactor. After the addition is completed, keep the reactor warm. S006. After the heat preservation in step S005 is completed, the temperature inside the reactor is reduced to 45°C, the pH value of the emulsion is adjusted to 7.2, and then defoamer and polycarbodiimide are added to the emulsion. After stirring and mixing evenly, the emulsion is filtered to obtain the acrylic emulsion.
[0044] This embodiment also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this embodiment. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0045] Example 2 This embodiment provides an acrylic emulsion, the raw materials for which, by weight, are: 100 parts water, 75 parts isooctyl acrylate, 23 parts methyl methacrylate, 3 parts hydroxyethyl acrylate, 2 parts N-hydroxymethylacrylamide, 2.5 parts emulsifier, 1.5 parts trimethylolpropane triacrylate, 1 part polycarbodiimide, 0.5 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0046] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:1.5.
[0047] This embodiment also provides a method for preparing an acrylic emulsion, including the following steps: S001. Add emulsifier and 70 parts of water to the reaction vessel, stir and mix evenly to obtain the base liquid; S002. Add 25 parts of water to the mixer, then add the soft monomer, hard monomer, functional monomer, and trimethylolpropane triacrylate to the mixer and stir to disperse evenly to obtain a pre-emulsion. S003. Mix 0.2 parts of initiator with 3 parts of water to obtain initiator solution A, and mix 0.3 parts of initiator with 2 parts of water to obtain initiator solution B. S004. After the temperature inside the reactor rises to 80°C, add 5% of the total mass of the pre-emulsion and initiator solution A dropwise into the reactor. After the addition is completed, keep the reactor warm. S005. After the heat preservation in step S004 is completed, continue to add the remaining pre-emulsion and initiator solution B to the reactor. After the addition is completed, keep the reactor warm. S006. After the heat preservation in step S005 is completed, the temperature inside the reactor is reduced to 45°C, the pH value of the emulsion is adjusted to 7.5, and then defoamer and polycarbodiimide are added to the emulsion. After stirring and mixing evenly, the emulsion is filtered to obtain the acrylic emulsion.
[0048] This embodiment also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this embodiment. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0049] Example 3 This embodiment provides an acrylic emulsion, the raw materials for which, by weight, are: 98 parts water, 72 parts isooctyl acrylate, 21.5 parts methyl methacrylate, 2.5 parts hydroxyethyl acrylate, 1.5 parts N-hydroxymethylacrylamide, 2.2 parts emulsifier, 1 part trimethylolpropane triacrylate, 1 part polycarbodiimide, 0.4 parts ammonium persulfate, and 0.3 parts BYK-024 defoamer.
[0050] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:1.2.
[0051] This embodiment also provides a method for preparing an acrylic emulsion, including the following steps: S001. Add emulsifier and 68 parts of water to the reaction vessel, stir and mix evenly to obtain the base liquid; S002. Add 25 parts of water to the mixer, then add the soft monomer, hard monomer, functional monomer, and trimethylolpropane triacrylate to the mixer and stir to disperse evenly to obtain a pre-emulsion. S003. Mix 0.2 parts of initiator and 3 parts of water evenly to obtain initiator solution A, and mix 0.2 parts of initiator and 2 parts of water evenly to obtain initiator solution B; S004. After the temperature inside the reactor rises to 80°C, add 5% of the total mass of the pre-emulsion and initiator solution A dropwise into the reactor. After the addition is completed, keep the reactor warm. S005. After the heat preservation in step S004 is completed, continue to add the remaining pre-emulsion and initiator solution B to the reactor. After the addition is completed, keep the reactor warm. S006. After the heat preservation in step S005 is completed, the temperature inside the reactor is reduced to 45°C, the pH value of the emulsion is adjusted to 7.0, and then defoamer and polycarbodiimide are added to the emulsion. After stirring and mixing evenly, the emulsion is filtered to obtain the acrylic emulsion.
[0052] This embodiment also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this embodiment. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0053] Comparative Example 1 This comparative example provides an acrylic emulsion, the raw materials for which, by weight, are: 95 parts water, 85 parts isooctyl acrylate, 5 parts methyl methacrylate, 2 parts emulsifier, 2 parts hydroxyethyl acrylate, 1 part N-hydroxymethylacrylamide, 1 part trimethylolpropane triacrylate, 0.5 parts polycarbodiimide, 0.3 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0054] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:1.
[0055] This comparative example also provides a method for preparing an acrylic emulsion, which is the same as the method provided in Example 1.
[0056] This comparative example also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this comparative example. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0057] Comparative Example 2 This comparative example provides an acrylic emulsion, the raw materials for which, by weight, are: 95 parts water, 55 parts isooctyl acrylate, 35 parts methyl methacrylate, 2 parts emulsifier, 2 parts hydroxyethyl acrylate, 1 part N-hydroxymethylacrylamide, 1 part trimethylolpropane triacrylate, 0.5 parts polycarbodiimide, 0.3 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0058] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:1.
[0059] This comparative example also provides a method for preparing an acrylic emulsion, which is the same as the method provided in Example 1.
[0060] This comparative example also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this comparative example. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0061] Comparative Example 3 This comparative example provides an acrylic emulsion, the raw materials for which, by weight, are: 95 parts water, 70 parts isooctyl acrylate, 20 parts methyl methacrylate, 2 parts emulsifier, 2 parts hydroxyethyl acrylate, 1 part N-hydroxymethylacrylamide, 1 part trimethylolpropane triacrylate, 0.5 parts polycarbodiimide, 0.3 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0062] The emulsifier is a mixture of dodecylphenol polyoxyethylene ether and sodium dodecyl sulfate, with the ratio of alkylphenol polyoxyethylene ether and sodium dodecyl sulfate being 1:1 by weight.
[0063] This comparative example also provides a method for preparing an acrylic emulsion, which is the same as the method provided in Example 1.
[0064] This comparative example also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this comparative example. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0065] Comparative Example 4 This comparative example provides an acrylic emulsion, the raw materials for which, by weight, are: 95 parts water, 70 parts isooctyl acrylate, 20 parts methyl methacrylate, 2 parts emulsifier, 2 parts hydroxyethyl acrylate, 1 part N-hydroxymethylacrylamide, 1 part trimethylolpropane triacrylate, 0.5 parts polycarbodiimide, 0.3 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0066] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:0.6.
[0067] This comparative example also provides a method for preparing an acrylic emulsion, which is the same as the method provided in Example 1.
[0068] This comparative example also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this comparative example. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0069] Comparative Example 5 This comparative example provides an acrylic emulsion, the raw materials for which, by weight, are: 95 parts water, 70 parts isooctyl acrylate, 20 parts methyl methacrylate, 2 parts emulsifier, 2 parts hydroxyethyl acrylate, 1 part N-hydroxymethylacrylamide, 1 part trimethylolpropane triacrylate, 0.5 parts polycarbodiimide, 0.3 parts initiator (ammonium persulfate), and 0.3 parts BYK-024 defoamer.
[0070] The emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate, with a weight ratio of 1:2.2.
[0071] This comparative example also provides a method for preparing an acrylic emulsion, which is the same as the method provided in Example 1.
[0072] This comparative example also provides an acrylic pressure-sensitive adhesive, comprising, from bottom to top, a base film layer (PET release film) and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion provided in this comparative example. The total amount of the photoinitiator is 2.3% of the water content in the acrylic emulsion, and the photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, wherein the weight ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 1.5:0.8.
[0073] The acrylic pressure-sensitive adhesives provided in the above embodiments and comparative examples were subjected to performance tests, including light transmittance, haze, 180° peel strength (with stainless steel plate), holding power, and initial tack. The test results are shown in the table below.
[0074] The 180° peel strength test of the acrylic pressure-sensitive adhesive was conducted in accordance with the standard GB / T 2792-2014 Test Method for Peel Strength of Adhesive Tapes.
[0075] The tackiness of acrylic pressure-sensitive adhesives was tested according to the standard GB / T4851-2014, "Test Method for Tackiness of Adhesive Tapes".
[0076] The initial tack of acrylic pressure-sensitive adhesive was tested according to the standard GB / T 4852-2002 Initial Tack Test Method for Pressure-Sensitive Adhesive Tapes (Rolling Ball Method).
[0077] The transmittance and haze of acrylic pressure-sensitive adhesive were determined according to the standard GB / T2410-2023 "Determination of transmittance and haze of plastics".
[0078]
[0079] Comparing Comparative Example 1 with Example 1, it was found that the acrylic pressure-sensitive adhesive provided in Comparative Example 1 had poorer tackiness and lower peel strength than that provided in Example 1. Furthermore, its light transmittance and haze were also poor. This is because the acrylic emulsion used in the acrylic pressure-sensitive adhesive of Comparative Example 1 contained an excess of soft monomers and an insufficient amount of hard monomers. This resulted in insufficient rigidity support for the pressure-sensitive adhesive layer, causing the polymer molecular chains to easily creep and deform at high temperatures, leading to poor tackiness. Simultaneously, the insufficient hard monomers resulted in insufficient cohesion within the pressure-sensitive adhesive layer, making it prone to cohesive failure during peeling and failing to form effective adhesive strength, thus resulting in lower peel strength. Moreover, the excess of soft monomers caused uneven particle size distribution in the emulsion, leading to loose particle aggregation and the formation of micropores during film formation. This resulted in enhanced light scattering, increased haze, and decreased light transmittance.
[0080] Comparing Comparative Example 2 with Example 1, it was found that the performance of the acrylic pressure-sensitive adhesive provided in Comparative Example 2 was inferior to that of the acrylic pressure-sensitive adhesive provided in Example 1. This is because the acrylic emulsion used in the acrylic pressure-sensitive adhesive of Comparative Example 2 had insufficient soft monomers and excessive hard monomers, resulting in a higher glass transition temperature of the acrylic emulsion. Consequently, the pressure-sensitive adhesive layer lacked flexibility at room temperature, failing to quickly wet the surface of the adhered object, and its initial tack was significantly reduced. Simultaneously, the excessive hard monomers increased the brittleness of the adhesive layer, preventing it from fully adhering to the substrate surface during bonding. This resulted in weak interfacial forces, making it prone to interfacial damage during peeling, and its peel strength was significantly lower than that of Example 1.
[0081] Comparing Comparative Example 3 with Example 1, it was found that the performance of the acrylic pressure-sensitive adhesive provided in Comparative Example 3 was inferior to that of the acrylic pressure-sensitive adhesive provided in Example 1. This is because the acrylic emulsion used in the acrylic pressure-sensitive adhesive of Comparative Example 3 uses a traditional emulsifier. The molecular structure of traditional emulsifiers has poor compatibility with the acrylic polymer matrix, and a strong tendency for hydrophilic and hydrophobic phase separation. During film formation, the emulsifier aggregates to form independent phase regions, causing severe microphase separation. Therefore, the acrylic pressure-sensitive adhesive has high haze and low light transmittance. Moreover, the poor compatibility between the emulsifier and the acrylic polymer matrix leads to insufficient film density, which affects the peel strength and tack of the acrylic pressure-sensitive adhesive.
[0082] Comparing Comparative Example 4 with Example 1, it was found that the performance of the acrylic pressure-sensitive adhesive provided in Comparative Example 4 was inferior to that of the acrylic pressure-sensitive adhesive provided in Example 1. This is because the acrylic emulsion used in the acrylic pressure-sensitive adhesive of Comparative Example 4 had a higher proportion of the emulsifier decanol polyoxyethylene ether glucoside in the emulsifier compound system, which increased the repulsion between the hydrophilic segment of the emulsifier and the polymer matrix, resulting in slight phase separation during film formation and enhanced light scattering. In addition, the excessive glucoside increased the hygroscopicity of the adhesive layer, indirectly affecting the light transmittance. Moreover, the imbalance of the emulsifier ratio disrupted the dual stabilizing effect of steric hindrance and electrostatic repulsion, causing the emulsion particles to agglomerate, resulting in uneven particle size and loose film packing with pore defects. At high temperatures, the pores expanded, reducing the cohesive force of the adhesive layer. Therefore, the tackiness of the acrylic pressure-sensitive adhesive was inferior to that of Example 1.
[0083] Comparing Comparative Example 5 with Example 1, it was found that the performance of the acrylic pressure-sensitive adhesive provided in Comparative Example 5 was inferior to that of the acrylic pressure-sensitive adhesive provided in Example 1. This is because the acrylic emulsion used in Comparative Example 5 had a higher proportion of sodium fatty alcohol polyoxyethylene ether carboxylate emulsifier in the emulsifier compound system, which reduced its compatibility with the acrylic polymer matrix. During emulsion film formation, the emulsifier easily precipitated from the pressure-sensitive adhesive layer, forming micro-aggregates and causing slight microphase separation, which in turn led to light scattering and impaired the light transmittance of the pressure-sensitive adhesive layer. Furthermore, excessive anionic emulsifier resulted in an excessively high surface charge density of the emulsion particles, leading to excessive repulsive forces between particles during film formation and weak bonding within the pressure-sensitive adhesive layer. At high temperatures, the slippage between emulsion particles caused displacement of the adhesive layer. Therefore, although the tackiness of the acrylic pressure-sensitive adhesive was better than other comparative examples, it was still far inferior to the 48-hour displacement-free performance of Example 1.
[0084] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. An acrylic emulsion, characterized in that, The raw materials for its preparation, by weight, include: The mixture contains 95-100 parts water, 70-75 parts soft monomers, 20-23 parts hard monomers, 3-5 parts functional monomers, 2-2.5 parts emulsifier, 1.5-2.5 parts crosslinking agent, 0.3-0.5 parts initiator, and 0.3 parts defoamer; the emulsifier is a mixture of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate.
2. The acrylic emulsion according to claim 1, characterized in that, The soft monomer is at least one of isooctyl acrylate and butyl acrylate.
3. The acrylic emulsion according to claim 1, characterized in that, The hard monomer is at least one of methyl methacrylate and styrene.
4. The acrylic emulsion according to claim 1, characterized in that, The ratio of decanol polyoxyethylene ether glucoside and sodium fatty alcohol polyoxyethylene ether carboxylate by weight is 1:(1-1.5).
5. The acrylic emulsion according to claim 1, characterized in that, The functional monomer is at least one of hydroxyethyl acrylate and N-hydroxymethylacrylamide.
6. The acrylic emulsion according to claim 1, characterized in that, The crosslinking agent is at least one of trimethylolpropane triacrylate and polycarbodiimide.
7. A method for preparing an acrylic emulsion as described in any one of claims 1-6, characterized in that, Includes the following steps: S001. Add emulsifier and 65-70 parts of water to the reaction vessel, stir and mix evenly to obtain the base liquid; S002. Add 25 parts of water to the stirrer, then add the soft monomer, hard monomer, functional monomer and crosslinking agent to the stirrer, stir and disperse evenly to obtain a pre-emulsion; S003. Mix 0.2 parts of initiator and 3 parts of water evenly to obtain initiator solution A, and mix 0.1 to 0.3 parts of initiator and 2 parts of water evenly to obtain initiator solution B; S004. After the temperature inside the reactor rises to 80-85°C, add 5% of the total mass of the pre-emulsion and initiator solution A dropwise into the reactor. After the addition is completed, keep the reactor warm. S005. After the heat preservation in step S004 is completed, continue to add the remaining pre-emulsion and initiator solution B to the reactor. After the addition is completed, keep the reactor warm. S006. After the heat preservation in step S005 is completed, the temperature inside the reactor is reduced to below 50°C. After adjusting the pH value of the emulsion, defoamer and crosslinking agent are added to the emulsion. After stirring and mixing evenly, the emulsion is filtered to obtain the acrylic emulsion.
8. The method for preparing the acrylic emulsion according to claim 7, characterized in that, In step S002, the crosslinking agent is trimethylolpropane triacrylate; in step S006, the crosslinking agent is polycarbodiimide.
9. An acrylic pressure-sensitive adhesive, characterized in that, From bottom to top, it includes a base film layer and a pressure-sensitive adhesive layer; the raw materials for preparing the pressure-sensitive adhesive layer include a photoinitiator and the acrylic emulsion according to any one of claims 1-6.
10. The acrylic pressure-sensitive adhesive according to claim 9, characterized in that, The photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.