Water-based adhesive as well as preparation method and application thereof

Abstract

The invention relates to the field of adhesives, and discloses a water-based adhesive and a preparation method and application thereof.According to the water-based adhesive, 2-ethylhexyl acrylate and ethyl acrylate serve as soft monomers, and an adhesion enhancing monomer, a crosslinking monomer, a seed emulsion matched with the glass transition temperature and a compound system of a reactive type and an anionic emulsifier are compounded; auxiliary agents such as an initiator are used; an emulsion polymerization core-shell process is adopted for preparation, and monomer uniform polymerization and adhesive performance regulation and control can be achieved. The prepared water-based adhesive has excellent high and low temperature viscosity and peelability, has no adhesive residue at high temperature and no debonding at low temperature, can avoid short-time sticking of labels, can be widely applied to the field of permanent movable adhesive labels, and has environmental protection property and practicability.

Description

Technical Field

[0001] This invention relates to the field of adhesives, and particularly to an aqueous adhesive, its preparation method, and its application. Background Technology

[0002] Currently, water-based adhesives are widely used in label bonding applications. However, existing water-based adhesives have the following limitations in their environmental adaptability: Firstly, the cross-linking density of the polymer adhesive system is insufficient. Under high temperatures, the adhesive layer is prone to softening and its cohesive strength decreases, resulting in adhesive residue when the label is peeled off, thus failing to achieve a permanent removable application. Secondly, the film-forming and wetting properties of their water-based dispersion system are sensitive to low temperatures. At low temperatures, the rate of water evaporation slows down, the adhesive film formation is insufficient, and the activity of polymer chain segments decreases, leading to adhesive performance degradation and weak label adhesion. Overall, the performance cannot simultaneously meet the requirements for stable adhesion and removability under multiple temperature ranges.

[0003] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a water-based adhesive, its preparation method and application, aiming to solve the problems of high-temperature residue and low-temperature non-stickiness of water-based adhesives.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A water-based adhesive, by weight, comprises the following components: 250-400 parts isooctyl acrylate, 100-300 parts ethyl acrylate, 10-30 parts adhesion-enhancing monomer, 5-40 parts styrene, 20-50 parts vinyl acetate, 1-5 parts crosslinking monomer, 0.05-1 part dodecyl mercaptan, 5-20 parts seed emulsion, 4-15 parts emulsifier, 400-600 parts deionized water, 1-5 parts sodium persulfate, and 0.1-1 parts sodium carbonate.

[0006] The water-based adhesive further contains 30 to 100 parts of methyl methacrylate or methyl acrylate.

[0007] The water-based adhesive, wherein the adhesion-enhancing monomer comprises 5 to 20 parts of acrylic acid or methacrylic acid and 5 to 10 parts of hydroxyethyl acrylate.

[0008] The water-based adhesive, wherein the crosslinking monomer is one of acrylamide, glycidyl methacrylate, or hydroxyethyl acryloyl urea.

[0009] The water-based adhesive, wherein the glass transition temperature of the seed emulsion is 40–45°C.

[0010] The water-based adhesive wherein the emulsifier is a compound product of 3 to 10 parts of reactive emulsifier and 1 to 5 parts of anionic emulsifier.

[0011] The aqueous adhesive, wherein the reactive emulsifier is Adico's SR-10; and the anionic emulsifier is one or more of sodium dodecyl sulfonate, ester succinate, and fatty alcohol polyoxyethylene ether salt.

[0012] A method for preparing a water-based adhesive includes the following steps: S1. Preparation of pre-emulsion: Add 97-100% by weight of emulsifier, sodium carbonate, and 20-40% by weight of deionized water to a pre-emulsion kettle, mix and stir evenly. Add all of the isooctyl acrylate, ethyl acrylate, adhesion-enhancing monomer, crosslinking monomer, styrene, vinyl acetate and dodecyl mercaptan to the pre-emulsion kettle, stir evenly, and prepare the pre-emulsion. S2. Add the remaining deionized water, emulsifier and sodium carbonate to the reactor; heat to 78-82°C, then add 1-10% by weight of the pre-emulsion, all of the seed emulsion, and 30-70% by weight of sodium persulfate. S3. After keeping warm for 15-20 minutes, add the remaining pre-emulsion and sodium persulfate dropwise over 2-5 hours. After the addition is complete, keep warm for 20-60 minutes, then cool down to 72°C to treat the residual monomers. Cool down to below 45°C, add defoamer, wetting agent, and preservative, neutralize and discharge to obtain the above-mentioned water-based adhesive.

[0013] An application of a water-based adhesive, wherein the above-mentioned water-based adhesive is applied to a removable adhesive label.

[0014] Beneficial effects: This invention provides a water-based adhesive, its preparation method, and its application. It solves the technical problems of traditional water-based adhesives, such as high-temperature residue, low-temperature non-stickiness, and labels that are easy to stick but difficult to peel off, through the following technical means. The resulting labels, while ensuring no glue overflow and long-term adhesion without peeling, achieve stable peelability under high and low temperature conditions, greatly expanding the application scenarios of the product.

[0015] 1. The combined use of reactive emulsifiers and anionic emulsifiers can reduce the surface tension of the system and reduce the generation of emulsion bubbles. It is compatible with different types of coating methods and high-speed coating speeds, avoiding problems such as misaligned or incorrect labeling caused by bubbles or uneven coating, thus balancing production efficiency and labeling yield.

[0016] 2. By controlling the ratio of hard monomers such as methyl methacrylate, styrene, vinyl acetate, and methyl acrylate, the room temperature tack and high temperature tack of the product are improved, the stability of the adhesive layer structure is enhanced, and the risk of adhesive overflow is reduced.

[0017] 3. Corona treatment of film substrates such as PP synthetic paper, 75μm synthetic paper, and transparent BOPP (or a base coating process, with corona treatment offering better cost-effectiveness) can increase the dyne value of the substrate surface to above 38 (above 42 is even better), significantly improving the wetting and adhesion of the adhesive layer to the substrate.

[0018] 4. When combined with adhesion-enhancing monomers containing functional groups such as acrylic acid, hydroxyethyl acrylate, and methacrylic acid, their polar functional groups can form hydrogen bonds or chemical bonds with the substrate, further strengthening the adhesion between the adhesive layer and the film material and preventing the label from peeling off.

[0019] 5. By introducing trace amounts of crosslinking monomers such as acrylamide, glycidyl methacrylate, and hydroxyethylacrylurea compounds, a moderate crosslinking network can be constructed inside the adhesive layer, significantly improving the cohesive strength of the adhesive layer. This avoids the problem of residual adhesive caused by softening and migration of the adhesive layer under high temperature conditions, and retains the peelability of the label due to the controllable degree of crosslinking, thus meeting the requirement of no residual adhesive peeling after long-term high-temperature bonding.

[0020] 6. The hard-core, soft-shell structure of latex particles is prepared by seed emulsion polymerization. The rigidity of the core layer ensures that the adhesive layer does not soften at high temperatures, while the flexibility of the shell layer maintains the adhesiveness and activity of the adhesive layer at low temperatures. This allows the adhesive to maintain stable bonding and peelability under complex high and low temperature conditions, breaking through the environmental limitations of traditional water-based adhesives. Detailed Implementation

[0021] This invention provides a water-based adhesive, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following embodiments are provided to further illustrate the invention in detail. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0022] This invention provides an aqueous adhesive, comprising the following components by weight: 250-400 parts isooctyl acrylate, 100-300 parts ethyl acrylate, 10-30 parts adhesion-enhancing monomer, 30-100 parts methyl methacrylate / methyl acrylate, 5-40 parts styrene, 20-50 parts vinyl acetate, 1-5 parts crosslinking monomer, 0.05-1 part dodecyl mercaptan, 5-20 parts seed emulsion, 4-15 parts emulsifier, 400-600 parts deionized water, 1-5 parts sodium persulfate, and 0.1-1 parts sodium carbonate.

[0023] The first aspect of this invention solves the problem of high-temperature adhesive residue: by adding a trace amount of crosslinking monomers, a moderately crosslinked network is formed after the adhesive film is formed, significantly improving the cohesive strength of the adhesive layer and avoiding adhesive residue caused by softening and cohesive failure of the adhesive layer under high-temperature conditions; at the same time, the degree of crosslinking is controllable, and peelability will not be lost due to excessive crosslinking. Furthermore, by controlling the proportion of hard monomers (methyl methacrylate, styrene, vinyl acetate, methyl acrylate), the room-temperature tack and high-temperature tack of the adhesive are improved, enhancing the high-temperature stability of the adhesive layer, reducing the risk of adhesive layer migration to the substrate under high-temperature conditions, and achieving the effect of label peeling off without residue even after long-term high-temperature bonding.

[0024] The second aspect of this invention addresses the problem of low-temperature non-stick properties: isooctyl acrylate and ethyl acrylate, as soft monomers, provide excellent low-temperature flexibility and initial tack to the adhesive, ensuring that the polymer chain segments retain sufficient activity at low temperatures and preventing the adhesive layer from becoming brittle and losing its stickiness; simultaneously, the combination with an appropriate amount of hard monomers forms an interpenetrating structure of soft and hard segments, balancing low-temperature tack and high-temperature stability. The use of emulsifiers reduces the surface tension of the system and decreases air bubbles, ensuring that the adhesive can still fully wet the label substrate at low temperatures, thus improving initial tack and holding power at low temperatures.

[0025] The third aspect of this invention solves the problem of labels being immovable: the added adhesion-enhancing monomer can form hydrogen bonds or chemical bonds with the polar groups of the surface to be bonded, thereby enhancing the adhesion between the adhesive layer and the label film substrate. It also controls the bonding strength within the peelable range, preventing the label from becoming stuck and impossible to remove in a short time. A small amount of seed emulsion can optimize the emulsion particle size and film-forming properties of the adhesive, improving the uniformity and controllable peelability of the adhesive layer, further ensuring the label can be removed without residue.

[0026] In some embodiments, the adhesion-enhancing monomer includes 5-20 parts of acrylic acid or methacrylic acid and 5-10 parts of hydroxyethyl acrylate. The carboxyl functional groups contained in the acrylic acid or methacrylic acid molecules can form strong hydrogen bonds with polar groups (such as ester groups) on the surface of the substrate to be adhered to, and can also physically adsorb or chemically bond with active sites on the surface of the label film substrate (after corona treatment), providing a basic substrate adhesion for the adhesive. The above-mentioned addition amount ensures sufficient polar interaction sites to prevent the label from lifting and falling off, and also prevents the adhesive layer from becoming too hydrophilic and losing water resistance due to excessive carboxyl content, thereby causing the adhesive layer to absorb moisture and lose its stickiness at low temperatures. The 5-10 parts of hydroxyethyl acrylate have both hydroxyl and acrylate double bonds in their molecular chains. These double bonds can participate in the copolymerization reaction of acrylate monomers, anchoring the hydroxyl groups to the main chain of the adhesive polymer. The hydroxyl groups can form intramolecular or intermolecular hydrogen bond networks with carboxyl groups, and can also synergistically crosslink with the functional groups of crosslinking monomers. This not only improves the cohesive strength of the adhesive layer, but also further strengthens the interfacial bonding between the adhesive layer and the film substrate. The above-mentioned addition amount works synergistically with the carboxyl groups of acrylic acid or methacrylic acid to avoid excessive hardness of the adhesive layer due to excessive hydroxyl groups, which would damage the flexibility and initial tack of the adhesive layer at low temperatures. Ultimately, this ensures that the adhesive maintains adhesion, peelability, and tack stability under both high and low temperature conditions in label applications.

[0027] In some embodiments, the crosslinking monomer is one of acrylamide, glycidyl methacrylate, or hydroxyethyl acryloyl urea. The amide group in the acrylamide molecule can form a strong hydrogen bond network with the carboxyl and hydroxyl groups of monomers such as acrylic acid and hydroxyethyl acrylate in the adhesive system. Simultaneously, its active double bonds can participate in emulsion polymerization, constructing a mildly crosslinked structure between polymer molecular chains. This crosslinking method is mild and controllable, improving the cohesive strength of the adhesive layer and avoiding residue problems caused by adhesive layer softening and cohesive failure at high temperatures, while preventing embrittlement of the adhesive layer due to excessive crosslinking, ensuring adhesion and flexibility at low temperatures. The epoxy groups of glycidyl methacrylate can react with the carboxyl and hydroxyl groups in the system to form stable chemical crosslinks. Compared to hydrogen bond crosslinking, its chemical crosslinking network has stronger high-temperature resistance, enhancing the structural stability of the adhesive under high-temperature conditions. Furthermore, the reaction specificity of the epoxy groups can control the degree of crosslinking, preventing excessive bonding between the adhesive layer and the substrate, which could lead to a stuck and difficult-to-peel adhesive. Hydroxyethyl acryloylurea compounds possess vinyl, hydroxy, and acryloylurea groups. The vinyl groups can anchor to the polymer backbone, the hydroxyl groups can participate in the construction of intermolecular hydrogen bonds, and the acryloylurea groups can form multiple cross-linking sites, achieving a synergistic effect of physical and chemical cross-linking. While improving the cohesive strength of the adhesive layer and solving the problem of high-temperature adhesive residue, it can also optimize the interfacial bonding force between the adhesive layer and the film substrate after corona treatment, ensuring that the label does not peel off, can be peeled off, and leaves no adhesive residue under complex temperature ranges.

[0028] In some embodiments, the glass transition temperature of the seed emulsion is 40–45°C. During the emulsion polymerization stage, the seed emulsion with a glass transition temperature of 40–45°C can serve as the core of the polymerization reaction, providing stable reaction sites for subsequent monomer grafting and polymerization. This ensures that the soft and hard monomers in the pre-emulsion are uniformly coated on the surface of the seed emulsion particles during polymerization, forming latex particles with controllable particle size and uniform distribution. It also avoids problems such as abnormal viscosity and decreased emulsion stability caused by excessively high glass transition temperature of the seed emulsion, or latex particle adhesion and demulsification during polymerization caused by excessively low glass transition temperature. This ensures the stability of the reaction during the pre-emulsion drop addition and heat preservation stages, and improves the storage and coating adaptability of the final emulsion. Furthermore, the moderate glass transition temperature balances the rigidity and toughness of the adhesive layer, forming a complementary core-shell structure with soft monomers such as isooctyl acrylate and hard monomers such as methyl methacrylate in the system. This not only enhances the cohesive strength of the adhesive layer by leveraging the rigidity of the seed emulsion, preventing softening and residue formation under high-temperature conditions, but also ensures sufficient chain activity at low temperatures, maintaining good initial tack and holding power. This solves the problems of high-temperature residue and low-temperature non-tack issues associated with traditional water-based adhesives. Simultaneously, the seed emulsion strengthens the interfacial adhesion between the adhesive layer and the corona-treated film substrate, ensuring that labels do not peel off or detach after automated high-speed labeling, and leaving no residue upon peeling.

[0029] In some embodiments, the emulsifier is a compound product of 3-10 parts of a reactive emulsifier and 1-5 parts of an anionic emulsifier. Specifically, the reactive emulsifier is Adico's SR-10; the anionic emulsifier is one or more of sodium dodecyl sulfonate, ester succinate, and fatty alcohol polyoxyethylene ether salt. The active groups of SR-10 can participate in copolymerization and graft onto the polymer backbone, avoiding the decrease in water resistance and adhesion of the adhesive layer caused by emulsifier migration, while reducing the surface tension of the system and reducing bubbles, making it suitable for automated high-speed labeling processes. The aforementioned anionic emulsifier can further improve the dispersion stability of the emulsion and enhance the wetting ability of the adhesive to the label film substrate. When compounded with SR-10, it not only ensures the stability of the polymerization process but also optimizes the tack and peelability of the adhesive under high and low temperature conditions.

[0030] This invention also provides a method for preparing an aqueous adhesive, comprising the following steps: S1. Preparation of the pre-emulsion: Add 97–100% by weight of reactive emulsifier, anionic emulsifier, sodium carbonate, and 20–40% by weight of deionized water to a pre-emulsion reactor, mix and stir until homogeneous. Then add all of the isooctyl acrylate, ethyl acrylate, adhesion-enhancing monomer, crosslinking monomer, styrene, vinyl acetate, and dodecyl mercaptan to the pre-emulsion reactor and stir until homogeneous to prepare the pre-emulsion. This step ensures uniform dispersion of the monomers, forming a stable pre-emulsion system.

[0031] S2. Add the remaining deionized water, reactive emulsifier, anionic emulsifier, and sodium carbonate to the reactor; heat to 78–82°C, then add 1–10% by weight of pre-emulsion, seed emulsion, and 30–70% by weight of sodium persulfate. Introducing a small amount of pre-emulsion, seed emulsion, and some initiator not only creates a stable polymerization environment but also anchors the latex particle size through the seed emulsion. The small amount of pre-emulsion and initiator can initiate the initial polymerization.

[0032] S3. After maintaining the temperature for 15-20 minutes, add the remaining pre-emulsion and sodium persulfate dropwise over 2-5 hours to control the polymerization rate and prevent localized overheating that could lead to emulsion demulsification or abnormal performance. After the addition is complete, maintain the temperature for 20-60 minutes to ensure the polymerization reaction proceeds fully. Cool to 72°C to treat residual monomers, reducing residual impurities in the adhesive, improving the product's environmental friendliness, and preventing post-migration. Cool to below 45°C, add defoamer, wetting agent, and preservative, neutralize, and discharge to obtain the aforementioned water-based adhesive.

[0033] This invention also provides an application of the water-based adhesive, wherein the water-based adhesive is coated onto release paper, dried at 105°C for 3–6 minutes, and then transferred to a substrate (film / paper). Specifically, the basis weight of the dried water-based adhesive is 20 g / m². 2 More specifically, when the selected substrate is a membrane material, the membrane material can be corona-treated to increase its surface tension, so that its dyne value reaches 38 or above, and 42 or above is even better.

[0034] To further illustrate the water-based adhesive, its preparation method, and its application provided by the present invention, the following examples and comparative examples are provided.

[0035] Example 1 Weigh out the following components by weight: 400 parts isooctyl acrylate, 100 parts ethyl acrylate, 5 parts acrylic acid, 5 parts hydroxyethyl acrylate, 30 parts methyl methacrylate, 5 parts styrene, 20 parts vinyl acetate, 1 part hydroxyethyl acryloyl urea compound, 0.2 parts dodecyl mercaptan, 10 parts seed emulsion, 6 parts reactive emulsifier (SR-10), 3 parts anionic emulsifier (fatty alcohol polyoxyethylene ether salt), 500 parts deionized water, 2 parts sodium persulfate, and 1 part sodium carbonate.

[0036] Preparation of pre-emulsion: Add emulsifier, 0.8 parts sodium carbonate, and 160 parts deionized water to a pre-emulsion kettle, mix and stir evenly. Add all of isooctyl acrylate, ethyl acrylate, acrylic acid, hydroxyethyl acrylate, styrene, vinyl acetate, methyl methacrylate, hydroxyethyl acryloyl urea compound, and dodecyl mercaptan to the pre-emulsion kettle and stir evenly to prepare a pre-emulsion.

[0037] Add the remaining deionized water, emulsifier, and sodium carbonate to the reactor, heat to 80°C, and then add 5% by weight of pre-emulsion, 10 parts by weight of seed emulsion, and 1 part by weight of sodium persulfate.

[0038] After the reaction is complete, keep the temperature at 80-82℃ for 15 minutes, then add the remaining pre-emulsion and sodium persulfate dropwise over 3 hours. After the dropwise addition is complete, keep the temperature at 80-82℃ for 30 minutes to treat the residual monomers, then cool the temperature to below 45℃, add defoamer, wetting agent, and preservative, neutralize and discharge the material to obtain the water-based adhesive.

[0039] The prepared water-based adhesive was coated onto release paper and dried at 105℃ for 3 minutes, with a dry adhesive basis weight of 20 g / m². 2 It can be prepared by covering it onto a corona-treated film material.

[0040] Example 2 Weigh out the following components by weight: 400 parts isooctyl acrylate, 100 parts ethyl acrylate, 8 parts methacrylic acid, 10 parts hydroxyethyl acrylate, 60 parts methyl methacrylate, 10 parts styrene, 40 parts vinyl acetate, 2 parts acrylamide, 0.6 parts dodecyl mercaptan, 15 parts seed emulsion, 6 parts reactive emulsifier (SR-10), 4 parts anionic emulsifier (sodium dodecyl sulfonate), 500 parts deionized water, 3 parts sodium persulfate, and 0.7 parts sodium carbonate.

[0041] Preparation of pre-emulsion: Add emulsifier, 0.3 parts sodium carbonate, and 160 parts deionized water to a pre-emulsion kettle, mix and stir evenly. Add all of the following to the pre-emulsion kettle: isooctyl acrylate, ethyl acrylate, methacrylic acid, hydroxyethyl acrylate, styrene, vinyl acetate, methyl methacrylate, acrylamide, and dodecyl mercaptan, and stir evenly to prepare the pre-emulsion.

[0042] Add the remaining deionized water, emulsifier, and sodium carbonate to the reactor, heat to 80°C, and then add 8% by weight of pre-emulsion, 15 parts by weight of seed emulsion, and 2 parts by weight of sodium persulfate.

[0043] After the reaction is complete, keep the temperature at 80-82℃ for 15 minutes, then add the remaining pre-emulsion and sodium persulfate dropwise over 4 hours. After the dropwise addition is complete, keep the temperature at 80-82℃ for 40 minutes to treat the residual monomers, then cool the temperature to below 45℃, add defoamer, wetting agent, and preservative, neutralize and discharge the material to obtain the water-based adhesive.

[0044] The prepared water-based adhesive was coated onto release paper and dried at 105℃ for 5 minutes, with a dry adhesive basis weight of 20 g / m². 2 It can be prepared by covering it onto a corona-treated film material.

[0045] Example 3 Weigh out the following components by weight: 300 parts isooctyl acrylate, 200 parts ethyl acrylate, 15 parts acrylic acid, 5 parts hydroxyethyl acrylate, 40 parts methyl acrylate, 20 parts styrene, 50 parts vinyl acetate, 4 parts glycidyl methacrylate, 0.4 parts dodecyl mercaptan, 8 parts seed emulsion, 8 parts reactive emulsifier (SR-10), 4 parts anionic emulsifier (ester succinate), 600 parts deionized water, 4 parts sodium persulfate, and 1 part sodium carbonate.

[0046] Preparation of pre-emulsion: Add emulsifier, 0.8 parts sodium carbonate, and 150 parts deionized water to a pre-emulsion kettle, mix and stir evenly. Add all of isooctyl acrylate, ethyl acrylate, acrylic acid, hydroxyethyl acrylate, styrene, vinyl acetate, methyl acrylate, glycidyl methacrylate, and dodecathiol to the pre-emulsion kettle and stir evenly to prepare the pre-emulsion.

[0047] Add the remaining deionized water, emulsifier, and sodium carbonate to the reactor, heat to 80°C, and then add 15% by weight of pre-emulsion, 8 parts by weight of seed emulsion, and 3 parts by weight of sodium persulfate.

[0048] After the reaction is complete, keep the temperature at 80-82℃ for 20 minutes, then add the remaining pre-emulsion and sodium persulfate dropwise over 3 hours. After the dropwise addition is complete, keep the temperature at 80-82℃ for 50 minutes to treat the residual monomers, and then cool the temperature to below 45℃. Add defoamer, wetting agent, and preservative, neutralize and discharge the material to obtain the water-based adhesive.

[0049] The prepared water-based adhesive was coated onto release paper and dried at 105℃ for 3 minutes, with a dry adhesive basis weight of 20 g / m². 2 It can be prepared by covering it onto a corona-treated film material.

[0050] Example 4 Weigh out the following components by weight: 250 parts isooctyl acrylate, 250 parts ethyl acrylate, 20 parts methacrylic acid, 10 parts hydroxyethyl acrylate, 90 parts methyl methacrylate, 40 parts styrene, 20 parts vinyl acetate, 5 parts hydroxyethyl acryloyl urea compound, 0.6 parts dodecyl mercaptan, 20 parts seed emulsion, 10 parts reactive emulsifier (SR-10), 5 parts anionic emulsifier (fatty alcohol polyoxyethylene ether salt), 600 parts deionized water, 4 parts sodium persulfate, and 1 part sodium carbonate.

[0051] Preparation of pre-emulsion: Add emulsifier, 0.5 parts sodium carbonate, and 200 parts deionized water to a pre-emulsion kettle, mix and stir evenly. Add all of the following to the pre-emulsion kettle: isooctyl acrylate, ethyl acrylate, methacrylic acid, hydroxyethyl acrylate, styrene, vinyl acetate, methyl methacrylate, hydroxyethyl acryloyl urea compound, and dodecyl mercaptan, and stir evenly to prepare the pre-emulsion.

[0052] Add the remaining deionized water, emulsifier, and sodium carbonate to the reactor, heat to 80°C, and then add 15% by weight of pre-emulsion, 20 parts by weight of seed emulsion, and 3 parts by weight of sodium persulfate.

[0053] After the reaction is complete, keep the temperature at 80-82℃ for 15 minutes, then add the remaining pre-emulsion and sodium persulfate dropwise over 4 hours. After the dropwise addition is complete, keep the temperature at 80-82℃ for 30 minutes to treat the residual monomers, then cool the temperature to below 45℃, add defoamer, wetting agent, and preservative, neutralize and discharge the material to obtain the water-based adhesive.

[0054] The prepared water-based adhesive was coated onto release paper and dried at 105℃ for 3 minutes, with a dry adhesive basis weight of 20 g / m². 2 It can be prepared by covering it onto a corona-treated film material.

[0055] Comparative Example 1 The adhesion-enhancing monomer in Comparative Example 1 was 10 parts of acrylic acid, and the rest was the same as in Example 1.

[0056] Comparative Example 2 Comparative Example 2 did not add crosslinking monomers, and was otherwise the same as Example 1.

[0057] Comparative Example 3 The emulsifier in Comparative Example 3 was 9 parts of anionic emulsifier (sodium dodecyl sulfonate), and the rest was the same as in Example 1.

[0058] Comparative Example 4 Comparative Example 4 added 50 parts of styrene and 70 parts of vinyl acetate, and the rest was the same as in Example 1.

[0059] Performance testing (1) 180° peel strength test: The test was conducted according to the FTM1.SS test method. The test objects were the label samples (75μm synthetic paper) prepared by Examples 1-4 and Comparative Examples 1-4. Test method: Test strips with a size of 175×25 (mm) were placed under standard conditions of 23℃±2℃ and 50%RH±5%RH for 4 hours, then attached to a clean standard steel plate. The test strips were pressed twice in each direction at a speed of 10mm / s using a test roller. After 20 minutes, the strips were peeled 180° at a peeling speed of 300mm / min. Three test strips were made for each sample, and the average value was taken. The results are shown in Table 1.

[0060] Table 1 Results of 180° Peel Strength Test

[0061] (2) Ring initial adhesion test: The test was conducted according to the FTM9.SS test method. The test objects were the label samples (75μm synthetic paper) prepared by Examples 1-4 and Comparative Examples 1-4.

[0062] Test Method: After placing a 175×25 (mm) test strip under standard conditions of 23℃±2℃ and 50%RH±5%RH for 4 hours, remove the sample material, with the adhesive side facing out, and form a ring by holding both ends. Clamp the end of the ring 10mm into the tension gauge clamp, with the ring hanging vertically downwards, and clamp a 25mm×30mm strip into the lower clamp. At a speed of 300mm / min, bring the ring to complete contact with the test plate (contact area 25mm×25mm), and immediately restore it at a speed of 300mm / min. Record the maximum force value of the ring and the test plate at the point of separation. Prepare three test strips for each sample, record the data, and take the average value. The results are shown in Table 2.

[0063] Table 2 Results of Ring Initial Tack Test

[0064] (3) Residual adhesive and peeling test: A 25mm×200mm sample was randomly taken from the tapes prepared in Examples 1-4 and Comparative Examples 1-4 respectively. The substrate was removed, and the sample was attached to a new, uncontaminated PET bottle in a ring (360°). The sample was tightly attached without air bubbles. After placing the sample in an oven at 60°C for 1D / 7D, the sample was slowly and quickly torn off. The presence of residual adhesive and peeling were observed. The results are shown in Table 3.

[0065] Table 3

[0066] Results Analysis This invention verifies the performance advantages of water-based adhesives through four sets of examples with different formulations. Each example uses isooctyl acrylate and ethyl acrylate as soft monomers, combined with hard monomers such as methyl methacrylate / methyl acrylate, styrene, and vinyl acetate. It also incorporates adhesion-enhancing monomers composed of acrylic acid / methacrylic acid and hydroxyethyl acrylate, specific types of crosslinking monomers, a seed emulsion with a glass transition temperature of 40–45°C, and a compound system of Adico SR-10 reactive emulsifier and anionic emulsifier. A core-shell preparation process is used to prepare the water-based adhesive at a concentration of 20 g / m³. 2 Labels are made by applying dry adhesive by weight to release paper and transferring it to a corona-treated film. Performance data shows that the 180° peel strength of Examples 1-4 is in the range of 6–11 N / 25 mm, the initial tack is 9–14 N / 25 mm, and the initial tack at 0°C remains at 2–7 N / 25 mm. After being placed in a 60°C oven for 1 and 7 days, there is no adhesive residue and no peeling. The peel strength is suitable for the requirements of permanently removable labels, indicating that the water-based adhesive provided by this invention can effectively solve the problems of high-temperature residue and low-temperature non-stickiness of traditional water-based adhesives.

[0067] Comparative Example 1: Since only 10 parts of acrylic acid were added as an adhesion-enhancing monomer, the lack of synergistic crosslinking reinforcement from hydroxyethyl acrylate resulted in insufficient interfacial bonding between the adhesive layer and the substrate. Therefore, the 180° peel strength was lower than that of Example 1, the initial tack at low temperature was reduced, and the label was prone to slight peeling.

[0068] Comparative Example 2: Due to the lack of crosslinking monomers, the cohesive strength of the adhesive layer is insufficient, and adhesive layer migration is prone to occur at high temperatures. Therefore, the 180° peel strength is relatively high, and as the high temperature storage time is prolonged, the residual adhesive phenomenon changes from slight to obvious, and the peeling difficulty increases.

[0069] Comparative Example 3: Due to the absence of reactive emulsifiers and the addition of only anionic emulsifiers, the emulsion dispersion stability and substrate wettability decreased, resulting in lower initial tack and peel strength. The initial tack at low temperatures was only 1N / 25mm, and the labels were prone to peeling due to emulsion bubbles during high-speed labeling.

[0070] Comparative Example 4: Excessive hard monomers (styrene, vinyl acetate) resulted in an overly rigid adhesive layer with insufficient toughness. Although there was no adhesive residue, the initial tack at low temperatures dropped sharply to 1N / 25mm, and the 180° peel strength was too high, making it more difficult to peel off the label.

[0071] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A water-based adhesive, characterized in that, The product comprises the following components by weight: 250-400 parts isooctyl acrylate, 100-300 parts ethyl acrylate, 10-30 parts adhesion-enhancing monomer, 5-40 parts styrene, 20-50 parts vinyl acetate, 1-5 parts crosslinking monomer, 0.05-1 part dodecyl mercaptan, 5-20 parts seed emulsion, 4-15 parts emulsifier, 400-600 parts deionized water, 1-5 parts sodium persulfate, and 0.1-1 parts sodium carbonate.

2. The water-based adhesive according to claim 1, characterized in that, Water-based adhesives also contain 30 to 100 parts of methyl methacrylate or methyl acrylate.

3. The water-based adhesive according to claim 1, characterized in that, The adhesion-enhancing monomer comprises 5 to 20 parts of acrylic acid or methacrylic acid and 5 to 10 parts of hydroxyethyl acrylate.

4. The water-based adhesive according to claim 1, characterized in that, The crosslinking monomer is one of acrylamide, glycidyl methacrylate, or hydroxyethylacrylurea.

5. The water-based adhesive according to claim 1, characterized in that, The glass transition temperature of the seed emulsion is 40–45°C.

6. The water-based adhesive according to claim 1, characterized in that, The emulsifier is a compound product of 3 to 10 parts of reactive emulsifier and 1 to 5 parts of anionic emulsifier.

7. The water-based adhesive according to claim 6, characterized in that, The reactive emulsifier is Adico's SR-10; the anionic emulsifier is one or more of sodium dodecyl sulfonate, ester succinate, and fatty alcohol polyoxyethylene ether salt.

8. A method for preparing a water-based adhesive, characterized in that, Includes the following steps: S1. Preparation of pre-emulsion: Add 97-100% by weight of emulsifier, sodium carbonate, and 20-40% by weight of deionized water to a pre-emulsion kettle, mix and stir evenly. Add all of the isooctyl acrylate, ethyl acrylate, adhesion-enhancing monomer, crosslinking monomer, styrene, vinyl acetate and dodecyl mercaptan to the pre-emulsion kettle, stir evenly, and prepare the pre-emulsion. S2. Add the remaining deionized water, emulsifier and sodium carbonate to the reactor; heat to 78-82°C, then add 1-10% by weight of the pre-emulsion, all of the seed emulsion, and 30-70% by weight of sodium persulfate. S3. After keeping warm for 15-20 minutes, add the remaining pre-emulsion and sodium persulfate dropwise over 2-5 hours. After the addition is complete, keep warm for 20-60 minutes, cool down to 72°C, and treat the residual monomers. Cool down to below 45°C, add defoamer, wetting agent, and preservative, neutralize and discharge the material to obtain the water-based adhesive as described in any one of claims 1-7.

9. An application of a water-based adhesive, characterized in that, The water-based adhesive as described in any one of claims 1-7 is applied to removable adhesive labels.

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