Composite glue and anti-curling copper plate paper composite aluminum plated paper and production method thereof

Abstract

The application discloses a kind of composite glue and anti-curling copper-based paper composite aluminum-plated paper and its production method, the following weight parts of each raw material is used when the composite glue is prepared: acrylate hard monomer 12-18 parts, acrylate soft monomer 36-45 parts, acrylic acid 1-3 parts, initiator 0.1-0.4 parts, emulsifier 0.5-2 parts, defoaming agent 0.1-0.6 parts, pH regulator 0.5-2.5 parts, penetrating agent 0.5-1 part, modified cellulose nanocrystal 2-5 parts, vinyl silane coupling agent 0.05-0.25 parts and deionized water 45-80 parts.The advantage is that modified cellulose nanocrystal, vinyl silane coupling agent and penetrating agent are added in the formula, and the proportion of soft and hard monomer usage is increased at the same time, when the copper-based paper with low grammage is compounded with aluminum-plated PET film, the composite glue can make the aluminum-plated paper prepared have better stiffness and folding resistance, the anti-curling effect is good, and the on-machine requirement of high-speed printing machine is met.

Description

Technical Field

[0001] This invention belongs to the technical field of composite adhesives and their application in the production of metallized paper for packaging, specifically relating to a composite adhesive and anti-curling coated paper composite metallized paper and its production method. Background Technology

[0002] Composite adhesives are adhesives used to bond several layers of films of different materials together. Based on the type of solvent, they are generally classified into solvent-based composite adhesives, water-based composite adhesives, and solvent-free composite adhesives. Metallized paper is a high-grade packaging material formed by bonding an aluminized carrier film and coated paper (base paper) together with a composite adhesive, and then peeling off the carrier film. It is widely used in tobacco, alcohol, cosmetics, and gift industries where aesthetics, environmental friendliness, and anti-counterfeiting features are crucial.

[0003] Currently, the composite adhesives used in the production of metallized paper are mostly water-based composite adhesives with acrylic polymers as the main component. However, when using coated paper as the base paper, due to the low adhesive and water absorption of coated paper itself and its paper weight of 170g / m², it is difficult to achieve the desired effect. 2 Due to factors such as lower stiffness at medium to low basis weights, metallized paper products produced using conventional water-based adhesives and lamination processes are prone to curling. If the curling of coated paper laminated with metallized paper exceeds 5mm, it cannot meet the requirements of high-speed printing presses. Therefore, it is necessary to innovate the formulation of the adhesive and apply it to the production of metallized paper to solve the curling problem of laminated metallized paper products using medium to low basis weight coated paper as the base paper, while maintaining folding endurance and good adhesion to the metallized layer. Summary of the Invention

[0004] This invention provides a composite adhesive and anti-curling coated paper composite aluminized paper and its production method, aiming to overcome the above-mentioned problems existing in the prior art.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] On one hand, the present invention provides a composite adhesive, which is prepared using the following raw materials in parts by weight: 12-18 parts of acrylate hard monomers, 36-45 parts of acrylate soft monomers, 1-3 parts of acrylic acid, 0.1-0.4 parts of initiator, 0.5-2 parts of emulsifier, 0.1-0.6 parts of defoamer, 0.5-2.5 parts of pH adjuster, 0.5-1 part of penetrant, 2-5 parts of modified cellulose nanocrystals, 0.05-0.25 parts of vinyl silane coupling agent, and 45-80 parts of deionized water; wherein the modified cellulose nanocrystals are cellulose nanocrystals modified with vinyl silane coupling agent.

[0007] The composite adhesive provided by this invention is a water-based adhesive with a solid content of approximately 45-55%. It is mainly used in the production process of metallized paper using transfer film technology. It is coated onto the surface of the metallized layer of a PET film and laminated with the base paper. This composite adhesive serves to bond the metallized layer and the base paper. When the base paper is medium-to-low basis weight coated paper, the metallized paper obtained after bonding using this composite adhesive exhibits good stiffness and excellent anti-curling effect, meeting the requirements for high-speed printing presses. This invention mainly uses modified cellulose nanocrystals and vinyl silane coupling agents to modify the properties of the composite adhesive. The mass ratio of acrylate soft monomers to acrylate hard monomers is appropriately increased, optimally at 2.5-3.0:1 (currently, conventional water-based composite adhesives using acrylates as the main component in metallized paper production typically control the soft and hard monomer ratio between 1.25-2.0). This results in better adhesion, folding endurance after film curing, and enhancement of the stiffness of the composite metallized paper. The penetrant component in the composite adhesive helps the adhesive solution to wet and penetrate the coated paper during film formation, making the adhesive film bond with the coated paper stronger and improving the stiffness of the composite metallized paper.

[0008] Based on the above technical solutions, the present invention can also make the following specific or better choices.

[0009] Specifically, the modified cellulose nanocrystals are prepared by the following method: cellulose nanocrystals are mixed with ethanol at a ratio of 1g:80-120mL and stirred to obtain a dispersion for later use; a vinyl silane coupling agent is mixed with ethanol at a volume ratio of 1:55-75 to obtain a coupling modifier for later use; the dispersion is placed in an open container and magnetically stirred under a water bath at 45-55℃, and then the coupling modifier is added dropwise to the dispersion. The ratio of cellulose nanocrystals to vinyl silane coupling agent is 1g:4-8mL. After the addition is complete, the reaction is kept at a constant temperature for 4-8 hours. Finally, the temperature is lowered to 40℃ and filtered to obtain the filter residue. After rinsing with ethanol, the residue is placed in a vacuum drying oven for thorough drying to obtain the modified cellulose nanocrystals.

[0010] It should be noted that, in the modification of cellulose nanocrystals in this invention, the silanol groups formed by the gradual hydrolysis of the vinylsilane coupling agent undergo a silanol condensation reaction with the active hydroxyl groups on the surface of the cellulose nanocrystals, resulting in a stable bond. The number of active hydroxyl groups on the surface of the modified cellulose nanocrystals is greatly reduced (with sufficient modification and an excess of vinylsilane coupling agent, but considering steric hindrance, not all active hydroxyl groups participate in the reaction). During dispersion, its tendency to aggregate due to the easy formation of hydrogen bonds by surface hydroxyl groups is improved. At the same time, its compatibility with non-polar polyacrylate is enhanced, which is beneficial for its uniform and stable dispersion in polyacrylic acid resin. Furthermore, this invention uses a vinylsilane coupling agent with active double bonds, which is also a reactive monomer that can participate in the polymerization of polyacrylate and stably bind with the polyacrylate molecular chains in the emulsion. The modified cellulose nanocrystals become crosslinking centers, enhancing the cohesive force of the polymer. In addition, the cellulose nanocrystals themselves have relatively high rigidity, which can ultimately significantly improve the strength of the composite film.

[0011] Specifically, the vinyl silane coupling agent is one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane.

[0012] Preferably, vinyltriethoxysilane is the best choice for modifying cellulose nanocrystals, and vinyltris(β-methoxyethoxy)silane is the best choice for vinyl silane coupling agent used in composite adhesive formulations.

[0013] Specifically, the acrylate hard monomer is methyl methacrylate, and the acrylate soft monomer is any one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate.

[0014] Specifically, the initiator is one or more of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0015] Preferably, the emulsifier is one or more of sodium dodecyl sulfate, sodium dioctyl sulfosuccinate, and sodium dodecylbenzene sulfonate.

[0016] Specifically, the penetrant is fatty alcohol polyoxyethylene ether.

[0017] Preferably, the defoamer is a mineral oil-based defoamer, and the pH adjuster is ammonia.

[0018] The present invention also provides a method for producing the above-mentioned composite adhesive, which specifically includes the following steps:

[0019] S1. Pre-emulsification: Add 100% of the formula amount of acrylate hard monomers, acrylate soft monomers and acrylic acid, 60-70% of the formula amount of emulsifier and 25-35% of the formula amount of deionized water into an emulsification tank, stir and emulsify to obtain a pre-emulsion for later use.

[0020] S2. Prepolymerization: Prepare an initiator solution with a mass concentration of 5-8 wt% by dissolving 100% of the initiator in an appropriate amount of deionized water and set aside. Add 30-40% of the deionized water and 10-20% of the emulsifier to the reactor, stir and heat to 80°C and maintain the temperature. Then add 15-30% of the pre-emulsion to the reactor and dropwise add 20-35% of the initiator solution. After the dropwise addition is complete, keep the reaction at the temperature for 20-30 minutes and then cool down to 55-60°C.

[0021] S3. Polymerization and molding: Add all the remaining pre-emulsion to the reactor, stir and heat to 80°C and maintain it, add 45-55% of the initiator solution dropwise, and after the dropwise addition is complete, keep the temperature and react for 30-60 minutes;

[0022] S4. Polymerization Modification: Thoroughly mix the remaining emulsifier, deionized water, and 100% of the formulated amount of modified cellulose nanocrystals to obtain Mixture 1, set aside; mix 100% of the formulated amount of vinyl silane coupling agent and an appropriate amount of ethanol to obtain Mixture 2, set aside; add Mixture 1 dropwise to the reaction solution after the end of S3 heat preservation, and simultaneously add the remaining initiator solution. After the addition is complete, keep the reaction at the heat for more than 30 minutes, and continue to add Mixture 2 dropwise. After the addition is complete, keep the reaction at the heat for 25-35 minutes; after the addition of vinyl silane coupling agent, it participates in the polymerization reaction through its vinyl double bond and enters the polymer chain segment, while the other active end is gradually hydrolyzed into silanol active groups. Since the active hydroxyl groups on the modified cellulose nanocrystals have been basically consumed and the acrylate chain segments are spatially confined, the silanol active groups are retained and become active sites that strongly bind to the active hydroxyl groups on the aluminum-plated layer or base paper when the composite adhesive is cured;

[0023] S5. Compounding: After the S4 heat preservation reaction is completed, cool the reactor to 45-50℃, use a pH adjuster to adjust the pH of the emulsion in the reactor to 7.0-8.0, then add the prescribed amount of defoamer and penetrant, stir and mix well to obtain the final product.

[0024] On the other hand, the present invention also provides an anti-curling coated paper composite aluminized paper, which has a basis weight of 135-170 g / m³. 2 Medium-low grammage coated paper is used as the base paper, and vacuum-metallized PET film is used as the base film. The metallized layer of the base film is transferred to the surface of the base paper through a transfer film process and the PET film is peeled off. The metallized layer is bonded to the base paper with the aforementioned composite adhesive.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention adds appropriate amounts of vinyl silane coupling agent-modified cellulose nanocrystals, vinyl silane coupling agent, and penetrant to the composite adhesive formulation, while appropriately increasing the proportion of soft and hard monomers. This ensures that when the composite adhesive is used to laminate coated paper with aluminized PET film using medium-low basis weight coated paper as the base paper, the resulting coated paper-metallized paper has good stiffness and folding resistance, good anti-curling effect, and meets the requirements of high-speed printing presses.

[0027] The modified cellulose nanocrystals used in this invention employ a vinyl silane coupling agent as the modifier. After modification, the number of active hydroxyl groups on the surface of the cellulose nanocrystals is greatly reduced. On the one hand, this reduces their hydrogen bonding with themselves and water, allowing the modified cellulose nanocrystals to better diffuse into the oily particles and distribute evenly in the polyacrylate after being added to the reaction system during the preparation of the composite adhesive. On the other hand, the silane coupling agent bound to the surface of the modified cellulose nanocrystals has vinyl groups, which can participate in the polymerization reaction of the polyacrylate, enabling the cellulose nanocrystals to be stably bonded to the polyacrylate. This avoids the possible migration and aggregation of the cellulose nanocrystals and allows the polymer molecules to form a cross-linked network, increasing the mechanical strength of the composite adhesive film.

[0028] To prevent the composite adhesive formed after the addition of modified cellulose nanocrystals from having excessively high viscosity in the reaction system during production and insufficient folding resistance and adhesion of the adhesive film during use, this invention significantly increases the amount of soft monomers and appropriately reduces the viscosity of the system. At the same time, a small amount of vinyl silane coupling agent is added in the final stage of the polymerization reaction during the production of the composite adhesive and allows it to participate in the polymerization. The vinyl silane coupling agent dispersed on the polyacrylate retains the active silanol ends during subsequent film formation, which can generate a strong bonding effect with both the paper base and the aluminized layer, effectively increasing the adhesion of the composite adhesive.

[0029] The production method of the composite adhesive provided by this invention is divided into several steps, including pre-emulsification, pre-polymerization, polymerization molding, polymerization modification and compounding. The key modifying raw materials are added at a specific time during emulsion polymerization. The design is ingenious and reasonable. The final results show that the performance of the obtained composite adhesive can meet the requirements and achieve the purpose of improving the composite adhesive. Detailed Implementation

[0030] The technical solutions provided by the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To avoid unnecessary details, unless otherwise specified, all raw materials used in the following examples are commercially available products, and all methods used are conventional methods in the art.

[0032] The modified cellulose nanocrystals used in the following examples were all prepared by the following methods:

[0033] Cellulose nanocrystals and ethanol were mixed and dispersed at a ratio of 1 g: 100 mL to obtain a dispersion for later use. Vinyltriethoxysilane and ethanol were mixed at a volume ratio of 1:60 to obtain a coupling modifier for later use. The dispersion was placed in an open container and magnetically stirred in a water bath at 50 °C. The coupling modifier was then added dropwise to the dispersion at a ratio of 1 g: 8 mL for cellulose nanocrystals and vinyltriethoxysilane. After the addition was complete, the mixture was kept at this temperature for 6 h. Finally, the temperature was lowered to 40 °C and the mixture was filtered to obtain the residue. After rinsing with ethanol, the residue was dried thoroughly in a vacuum drying oven to obtain the modified cellulose nanocrystals.

[0034] Example 1

[0035] A composite adhesive, wherein the following raw materials are used in its preparation in parts by weight:

[0036] The composition includes: 12 parts of acrylate hard monomers (methyl methacrylate), 36 parts of acrylate soft monomers (ethyl acrylate and butyl acrylate in a mass ratio of 1:1), 1 part of acrylic acid, 0.1 part of initiator (ammonium persulfate), 0.5 part of emulsifier (sodium dodecyl sulfate), 0.1 part of DF-691 (mineral oil defoamer), 0.8 parts of ammonia (pH adjuster), 0.5 parts of fatty alcohol polyoxyethylene ether (penetrating agent), 2 parts of modified cellulose nanocrystals, 0.05 parts of vinyltris(β-methoxyethoxy)silane, and 45 parts of deionized water.

[0037] The preparation method of the above-mentioned composite adhesive includes the following steps:

[0038] S1. Pre-emulsification: Add 100% of the formula amount of acrylate hard monomers, acrylate soft monomers and acrylic acid, 60% of the formula amount of emulsifier and 25% of the formula amount of deionized water into an emulsification tank, stir and emulsify to obtain a pre-emulsion for later use.

[0039] S2. Prepolymerization: Prepare an initiator solution with a mass concentration of 5wt% by dissolving 100% of the initiator in an appropriate amount of deionized water for later use; add 30% of the deionized water and 10% of the emulsifier to the reactor, stir and heat to 80℃ and maintain the temperature, then add 15% of the pre-emulsion to the reactor, and dropwise add 20% of the initiator solution. After the dropwise addition is completed, keep the temperature for 20-25 minutes and then cool down to 55-60℃.

[0040] S3. Polymerization and molding: Add all the remaining pre-emulsion to the reactor, stir and heat to 80°C and maintain it, add 55% of the initiator solution dropwise, and after the dropwise addition is complete, keep the temperature and react for 30-40 minutes;

[0041] S4. Polymerization modification: Thoroughly mix the remaining emulsifier, deionized water, and 100% of the formulated amount of modified cellulose nanocrystals to obtain mixture one, and set aside; mix 100% of the formulated amount of vinyltris(β-methoxyethoxy)silane and an appropriate amount of ethanol (volume ratio 1:20) to obtain mixture two, and set aside; add mixture one dropwise to the reaction solution after the end of S3 heat preservation, and simultaneously add the remaining initiator solution. After the addition is completed, keep the reaction at the heat for more than 30 minutes, and continue to add mixture two dropwise. After the addition is completed, keep the reaction at the heat for 25-35 minutes;

[0042] S5. Compounding: After the S4 heat preservation reaction is completed, the reaction vessel is cooled to 45℃. The pH of the emulsion in the reaction vessel is adjusted to 7.0-8.0 using a pH adjuster. Then, the prescribed amount of defoamer and penetrant is added, stirred and mixed, cooled to below 40℃, and filtered out to obtain the final product.

[0043] Example 2

[0044] A composite adhesive, wherein the following raw materials are used in its preparation in parts by weight:

[0045] The composition includes 14 parts of acrylate hard monomers (methyl methacrylate), 40 parts of acrylate soft monomers (ethyl acrylate and butyl acrylate in a mass ratio of 1:1.5), 2 parts of acrylic acid, 0.2 parts of initiator (ammonium persulfate), 1 part of emulsifier (sodium dodecyl sulfate), 0.3 parts of DF-691 (mineral oil defoamer), 1.5 parts of ammonia (pH adjuster), 0.6 parts of fatty alcohol polyoxyethylene ether (penetrating agent), 3 parts of modified cellulose nanocrystals, 0.1 parts of vinyltris(β-methoxyethoxy)silane, and 60 parts of deionized water.

[0046] The preparation method of the above-mentioned composite adhesive includes the following steps:

[0047] S1. Pre-emulsification: Add 100% of the formula amount of acrylate hard monomers, acrylate soft monomers and acrylic acid, 65% of the formula amount of emulsifier and 30% of the formula amount of deionized water into an emulsification tank, stir and emulsify to obtain a pre-emulsion for later use.

[0048] S2. Prepolymerization: Prepare an initiator solution with a mass concentration of 5wt% by dissolving 100% of the initiator in an appropriate amount of deionized water for later use; add 35% of the deionized water and 15% of the emulsifier to the reactor, stir and heat to 80℃ and maintain the temperature, then add 20% of the pre-emulsion to the reactor, and dropwise add 25% of the initiator solution. After the dropwise addition is completed, keep the temperature for 25-30 minutes and then cool down to 55-60℃.

[0049] S3. Polymerization and molding: Add all the remaining pre-emulsion to the reactor, stir and heat to 80°C and maintain it, add 50% of the initiator solution dropwise, and after the dropwise addition is complete, keep the temperature and react for 35-45 minutes;

[0050] S4. Polymerization modification: Thoroughly mix the remaining emulsifier, deionized water, and 100% of the formulated amount of modified cellulose nanocrystals to obtain mixture one, and set aside; mix 100% of the formulated amount of vinyltris(β-methoxyethoxy)silane and an appropriate amount of ethanol (volume ratio 1:25) to obtain mixture two, and set aside; add mixture one dropwise to the reaction solution after the end of S3 heat preservation, and simultaneously add the remaining initiator solution. After the addition is complete, keep the reaction at the heat for more than 30 minutes, and continue to add mixture two dropwise. After the addition is complete, keep the reaction at the heat for 30-35 minutes.

[0051] S5. Compounding: After the S4 heat preservation reaction is completed, the reaction vessel is cooled to 45℃. The pH of the emulsion in the reaction vessel is adjusted to 7.0-8.0 using a pH adjuster. Then, the prescribed amount of defoamer and penetrant is added, stirred and mixed, cooled to below 40℃, and filtered out to obtain the final product.

[0052] Example 3

[0053] A composite adhesive, wherein the following raw materials are used in its preparation in parts by weight:

[0054] The composition includes: 16 parts of acrylate hard monomers (methyl methacrylate), 42 parts of acrylate soft monomers (ethyl acrylate, butyl acrylate, and isooctyl acrylate in a mass ratio of 1:1:1), 3 parts of acrylic acid, 0.3 parts of initiator (ammonium persulfate), 1.5 parts of emulsifier (sodium dodecyl sulfate), 0.4 parts of DF-691 (mineral oil defoamer), 2 parts of ammonia (pH adjuster), 0.8 parts of fatty alcohol polyoxyethylene ether (penetrating agent), 4 parts of modified cellulose nanocrystals, 0.15 parts of vinyltris(β-methoxyethoxy)silane, and 70 parts of deionized water.

[0055] The preparation method of the above-mentioned composite adhesive includes the following steps:

[0056] S1. Pre-emulsification: Add 100% of the formula amount of acrylate hard monomers, acrylate soft monomers and acrylic acid, 70% of the formula amount of emulsifier and 35% of the formula amount of deionized water into an emulsification tank, stir and emulsify to obtain a pre-emulsion for later use.

[0057] S2. Prepolymerization: Prepare an initiator solution with a mass concentration of 6wt% by dissolving 100% of the initiator in an appropriate amount of deionized water for later use; add 35% of the deionized water and 15% of the emulsifier to the reactor, stir and heat to 80℃ and maintain the temperature, then add 25% of the pre-emulsion to the reactor, and dropwise add 30% of the initiator solution. After the dropwise addition is completed, keep the temperature for 25-30 minutes and then cool down to 55-60℃.

[0058] S3. Polymerization and molding: Add all the remaining pre-emulsion to the reactor, stir and heat to 80°C and maintain it, add 50% of the initiator solution dropwise, and after the dropwise addition is complete, keep the temperature and react for 40-45 minutes;

[0059] S4. Polymerization modification: Thoroughly mix the remaining emulsifier, deionized water, and 100% of the formulated amount of modified cellulose nanocrystals to obtain mixture one, and set aside; mix 100% of the formulated amount of vinyltris(β-methoxyethoxy)silane and an appropriate amount of ethanol (volume ratio 1:30) to obtain mixture two, and set aside; add mixture one dropwise to the reaction solution after the end of S3 heat preservation, and simultaneously add the remaining initiator solution. After the addition is completed, keep the reaction at the heat for more than 30 minutes, and continue to add mixture two dropwise. After the addition is completed, keep the reaction at the heat for 25-35 minutes;

[0060] S5. Compounding: After the S4 heat preservation reaction is completed, the reaction vessel is cooled to 50℃. The pH of the emulsion in the reaction vessel is adjusted to 7.0-8.0 using a pH adjuster. Then, the prescribed amount of defoamer and penetrant is added, stirred and mixed, and cooled to below 40℃. The mixture is then filtered and discharged to obtain the final product.

[0061] Example 4

[0062] A composite adhesive, wherein the following raw materials are used in its preparation in parts by weight:

[0063] The composition includes: 18 parts of acrylate hard monomers (methyl methacrylate), 45 parts of acrylate soft monomers (ethyl acrylate, butyl acrylate and isooctyl acrylate in a mass ratio of 1.5:1:0.5), 3 parts of acrylic acid, 0.4 parts of initiator (ammonium persulfate), 2 parts of emulsifier (sodium dodecyl sulfate), 0.6 parts of DF-691 (mineral oil defoamer), 2.5 parts of ammonia (pH adjuster), 1 part of fatty alcohol polyoxyethylene ether (penetrating agent), 5 parts of modified cellulose nanocrystals, 0.25 parts of vinyltris(β-methoxyethoxy)silane, and 80 parts of deionized water.

[0064] The preparation method of the above-mentioned composite adhesive includes the following steps:

[0065] S1. Pre-emulsification: Add 100% of the formula amount of acrylate hard monomers, acrylate soft monomers and acrylic acid, 70% of the formula amount of emulsifier and 35% of the formula amount of deionized water into an emulsification tank, stir and emulsify to obtain a pre-emulsion for later use.

[0066] S2. Prepolymerization: Prepare an initiator solution with a mass concentration of 6wt% by dissolving 100% of the initiator in an appropriate amount of deionized water for later use; add 40% of the deionized water and 20% of the emulsifier to the reactor, stir and heat to 80℃ and maintain the temperature, then add 30% of the pre-emulsion to the reactor, and dropwise add 35% of the initiator solution. After the dropwise addition is completed, keep the reaction temperature for 20-30 minutes, and then cool down to 55-60℃.

[0067] S3. Polymerization and molding: Add all the remaining pre-emulsion to the reactor, stir and heat to 80°C and maintain it, add 45% of the initiator solution dropwise, and after the dropwise addition is complete, keep the temperature and react for 45-60 minutes;

[0068] S4. Polymerization modification: Thoroughly mix the remaining emulsifier, deionized water, and 100% of the formulated amount of modified cellulose nanocrystals to obtain mixture one, and set aside; mix 100% of the formulated amount of vinyltris(β-methoxyethoxy)silane and an appropriate amount of ethanol (volume ratio 1:30) to obtain mixture two, and set aside; add mixture one dropwise to the reaction solution after the end of S3 heat preservation, and simultaneously add the remaining initiator solution. After the addition is complete, keep the reaction at the heat for more than 30 minutes, and continue to add mixture two dropwise. After the addition is complete, keep the reaction at the heat for 30-35 minutes.

[0069] S5. Compounding: After the S4 heat preservation reaction is completed, the reaction vessel is cooled to 50℃. The pH of the emulsion in the reaction vessel is adjusted to 7.0-8.0 using a pH adjuster. Then, the prescribed amount of defoamer and penetrant is added, stirred and mixed, and cooled to below 40℃. The mixture is then filtered and discharged to obtain the final product.

[0070] Comparative Example 1

[0071] Compared to Example 4, the composite adhesive formulation does not include modified cellulose nanocrystals and vinyltris(β-methoxyethoxy)silane, and the amount of deionized water is adjusted to 70 parts. The corresponding preparation method lacks step S4 (polymerization modification), and only adaptive adjustments are made to other steps. For example, 30% of the formulated emulsifier is added during prepolymerization in S2, all remaining initiator solution is added dropwise in S3, and excess deionized water is added in S5.

[0072] Comparative Example 2

[0073] Compared to Example 4, the composite adhesive formulation does not include vinyltris(β-methoxyethoxy)silane, and the amount of deionized water is adjusted to 77 parts. The corresponding preparation method lacks the steps of preparing and adding the second mixture in step S4 of the polymerization modification.

[0074] Comparative Example 3

[0075] Compared to Example 4, the composite adhesive formulation does not contain modified cellulose nanocrystals, and the amount of deionized water is adjusted to 72 parts. The corresponding preparation method lacks the steps of preparing and adding mixture two in step S4 of the polymerization modification. The corresponding preparation method also lacks the steps of preparing and adding mixture one in step S4 of the polymerization modification. Other steps are only adjusted adaptively; for example, 30% of the formulated emulsifier is added during prepolymerization in S2, 55% of the initiator solution is added in S3, and the remaining initiator and mixture two are added immediately after the heat preservation in S3 in S4. Excess deionized water is added in S5.

[0076] Comparative Example 4

[0077] Compared to Example 4, the composite adhesive formulation does not contain fatty alcohol polyoxyethylene ether (penetrating agent), while other aspects remain unchanged.

[0078] Composite adhesive performance testing

[0079] The composite adhesives prepared in each embodiment and comparative example were characterized. The appearance of the prepared composite adhesives was observed, and their viscosity, mechanical stability, and peel strength were tested. Viscosity was measured at room temperature using an SNB-2 digital viscometer. For mechanical stability testing, the emulsion sample was placed in a 15mL centrifuge tube and centrifuged at 3000rpm for 15 minutes at room temperature. After standing, the presence of stratification, demulsification, or precipitation was observed. If no stratification, emulsion breaking, or precipitation occurred, the mechanical stability test was passed; otherwise, it failed. For peel strength testing, the national standard GB / T 2791-1995 "Adhesives T Peel Strength Test Method Flexible Materials to Flexible Materials" was used. Two PET films were used as flexible materials, with a sample length of 200mm, a width of 25±0.5mm, and an adhesive application rate of 6g / m². 2 The specific results are shown in the table below:

[0080]

[0081] As can be seen from the test results in the table above, the composite adhesives prepared in each embodiment of the present invention have excellent properties and can meet the adhesive bonding requirements of aluminized PET film and base paper in the transfer film process. The composite adhesive corresponding to Comparative Example 1 did not contain modified cellulose nanocrystals and vinyltris(β-methoxyethoxy)silane. Although the adhesive particles in the solution were finer and more uniform (the more obvious the blue light, the smaller the particle size), the viscosity was lower and the film cohesion and rigidity were insufficient after curing due to the lack of hard monomers and the absence of modified nanocellulose for crosslinking and reinforcement, resulting in lower peel strength. The composite adhesive corresponding to Comparative Example 2, compared to Example 4, did not contain vinyltris(β-methoxyethoxy)silane. During curing, the lack of silanol active groups between the adhesive and the substrate resulted in a decrease in peel strength. In Comparative Example 3, the lack of crosslinking and reinforcement from modified cellulose nanocrystals resulted in lower viscosity. The insufficient film cohesion and rigidity after curing also led to a decrease in peel strength. In Comparative Example 4, the absence of a penetrant, which has a certain emulsifying effect, may have weakened the emulsifying effect and increased viscosity. However, its absence also reduced the wetting and penetration of the adhesive to the substrate, resulting in a slight decrease in peel strength.

[0082] The present invention also uses the composite adhesives prepared in the above embodiments and comparative examples for the production of coated paper composite metallized paper in the transfer film process, with a basis weight of 135-170 g / m³. 2 The base paper is coated paper, and the base film is vacuum-metallized PET film. The base film is transferred to the surface of the base paper through a transfer film process and the PET film is peeled off. The metallized layer is bonded to the base paper with the aforementioned composite adhesive.

[0083] In specific production implementation, the quantitative measure is 150g / m 2 Coated paper is used as the base paper. Before lamination, it can be corona treated on a corona equipment (corona voltage 15-20kV, current 10-15A to enhance surface adhesion). A coating and gluing machine is used to coat the aluminized layer of the aluminized PET film with the corresponding composite adhesive from the examples, comparative examples, and commercially available materials. The amount of adhesive applied is controlled at 6g / m². 2 The base paper and base film are then laminated in a laminating machine, and then dried, cured, and the PET film is peeled off to obtain anti-curling coated paper laminated with aluminized paper.

[0084] The anti-curling coated paper composite aluminized paper was tested for curling resistance and folding endurance. Multiple test samples were provided for each type of composite adhesive and the resulting aluminized paper. The test results were averaged, and the final results are shown below:

[0085]

[0086] In the table above, commercially available composite adhesive refers to water-based composite adhesives commonly used in the production of composite metallized paper when using high-grammage paper as the base paper; during the warpage test, the paper sample is placed flat on a horizontal platform, and the vertical distance between the edge or highest point of the paper sample and the reference surface is measured. Before the test, the paper sample is stored in the standard environment and method in the printing workshop for a certain period of time (more than 24 hours); in the folding endurance test, "color bursting" refers to the cracking, peeling, or partial detachment of the metallized layer, resulting in the exposure of the substrate, while "slight color bursting" refers to the presence of slight cracking of the metallized layer, without detachment and with inconspicuous white exposure.

[0087] As can be seen from the data in the table above, the anti-curling coated paper composite aluminized paper made using the composite adhesive of the present invention can have its curling degree controlled to below 5mm and has good folding resistance. The composite adhesive can increase the stiffness of the composite aluminized paper with medium and low grammage coated paper as the base material and reduce curling, so as to meet the requirements of high-speed printing presses.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite adhesive, characterized in that, The following raw materials are used in the preparation: 12-18 parts of acrylate hard monomers, 36-45 parts of acrylate soft monomers, 1-3 parts of acrylic acid, 0.1-0.4 parts of initiator, 0.5-2 parts of emulsifier, 0.1-0.6 parts of defoamer, 0.5-2.5 parts of pH adjuster, 0.5-1 part of penetrant, 2-5 parts of modified cellulose nanocrystals, 0.05-0.25 parts of vinyl silane coupling agent, and 45-80 parts of deionized water; the modified cellulose nanocrystals are cellulose nanocrystals modified with vinyl silane coupling agent, and the mass ratio of acrylate soft monomers to acrylate hard monomers is 2.5-3.0:

1.

2. The composite adhesive according to claim 1, characterized in that, The modified cellulose nanocrystals were prepared by the following method: cellulose nanocrystals and ethanol were mixed and dispersed by stirring at a ratio of 1g:80-120mL to obtain a dispersion for later use; vinyl silane coupling agent and ethanol were mixed at a volume ratio of 1:55-75 to obtain a coupling modifier for later use; the dispersion was placed in an open container and magnetically stirred under a water bath at 45-55℃, and then the coupling modifier was added dropwise to the dispersion. The ratio of cellulose nanocrystals to vinyl silane coupling agent was 1g:4-8mL. After the addition was completed, the reaction was kept at a constant temperature for 4-8 hours. Finally, the temperature was lowered to 40℃ and filtered to obtain the filter residue. After rinsing with ethanol, the residue was placed in a vacuum drying oven and dried thoroughly to obtain the modified cellulose nanocrystals.

3. The composite adhesive according to claim 2, characterized in that, The vinyl silane coupling agent is one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane.

4. The composite adhesive according to claim 1, characterized in that, The acrylate hard monomer is methyl methacrylate, and the acrylate soft monomer is any one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate.

5. The composite adhesive according to claim 1, characterized in that, The initiator is one or more of ammonium persulfate, sodium persulfate, and potassium persulfate.

6. The composite adhesive according to claim 1, characterized in that, The emulsifier is one or more of sodium dodecyl sulfate, sodium dioctyl sulfosuccinate, and sodium dodecylbenzene sulfonate.

7. The composite adhesive according to claim 1, characterized in that, The penetrant is fatty alcohol polyoxyethylene ether.

8. A composite adhesive according to any one of claims 1 to 7, characterized in that, The defoamer is a mineral oil-based defoamer, and the pH adjuster is ammonia.

9. A method for producing a composite adhesive as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Pre-emulsification: Add 100% of the formula amount of acrylate hard monomers, acrylate soft monomers and acrylic acid, 60-70% of the formula amount of emulsifier and 25-35% of the formula amount of deionized water into an emulsification tank, stir and emulsify to obtain a pre-emulsion for later use. S2. Prepolymerization: Prepare an initiator solution with a mass concentration of 5-8 wt% by dissolving 100% of the initiator in an appropriate amount of deionized water and set aside. Add 30-40% of the deionized water and 10-20% of the emulsifier to the reactor, stir and heat to 80°C and maintain the temperature. Then add 15-30% of the pre-emulsion to the reactor and dropwise add 20-35% of the initiator solution. After the dropwise addition is complete, keep the reaction at the temperature for 20-30 minutes and then cool down to 55-60°C. S3. Polymerization and molding: Add all the remaining pre-emulsion to the reactor, stir and heat to 80°C and maintain it, add 45-55% of the initiator solution dropwise, and after the dropwise addition is complete, keep the temperature and react for 30-60 minutes; S4. Polymerization modification: Thoroughly mix the remaining emulsifier, deionized water, and 100% of the formulated amount of modified cellulose nanocrystals to obtain mixture one, and set aside; mix 100% of the formulated amount of vinyl silane coupling agent and an appropriate amount of ethanol to obtain mixture two, and set aside; add mixture one dropwise to the reaction solution after the end of S3 heat preservation, and simultaneously add the remaining initiator solution. After the addition is complete, keep the reaction at the heat for more than 30 minutes, and continue to add mixture two dropwise. After the addition is complete, keep the reaction at the heat for 25-35 minutes. S5. Compounding: After the S4 heat preservation reaction is completed, cool the reactor to 45-50℃, use a pH adjuster to adjust the pH of the emulsion in the reactor to 7.0-8.0, then add the prescribed amount of defoamer and penetrant, stir and mix well to obtain the final product.

10. A type of anti-curling coated paper composite aluminized paper, characterized in that, With a quantitative amount of 135-170 g / m 2 The base paper is medium-low grammage coated paper, and the base film is vacuum-metallized PET film. The base film is transferred to the surface of the base paper through a transfer film process and the PET film is peeled off. The metallized layer is bonded to the base paper with the composite adhesive described in any one of claims 1 to 8.

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