Emulsion type movable pressure-sensitive adhesive and preparation method thereof

Abstract

The invention discloses an emulsion type movable pressure-sensitive adhesive and a preparation method thereof. The pressure-sensitive adhesive is prepared from the following raw materials: nano polymer microspheres, a soft monomer, an aliphatic ring hard monomer, a fluorine-containing acrylate monomer, a functional monomer, a cross-linking agent, a pH regulator, an emulsifier, an initiator and water. The preparation method of the pressure-sensitive adhesive comprises the following steps: 1, adding nano polymer microspheres, a soft monomer, an aliphatic ring hard monomer, a fluorine-containing acrylate monomer, a functional monomer, a cross-linking agent, an emulsifier and an initiator into 1 / 2-2 / 3 weight of water, and uniformly mixing to obtain a pre-emulsion; and 2, adding the rest water and the pH regulator into a reaction kettle, heating to 80-90 DEG C, slowly dropwise adding the pre-emulsion, continuing to react for 0.5-1.5 hours after dropwise adding is completed, and cooling after the reaction is completed. The removable pressure-sensitive adhesive disclosed by the invention has the advantages of excellent water resistance, good removable performance, energy conservation, environment friendliness, simple preparation process and the like, and has a very good application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pressure sensitive adhesive, and particularly relates to an emulsion type removable pressure sensitive adhesive and a preparation method thereof. BACKGROUND

[0002] Pressure sensitive adhesive is a viscoelastic body with liquid viscosity and solid elasticity, and its applications mainly include adhesive tapes, adhesive films, labels and protective films. At present, the global production of pressure sensitive adhesive has exceeded one million tons, and it is widely used in the electronic, electrical, aviation and packaging industries, and is a very important industrial material.

[0003] At present, the pressure sensitive adhesive applied in actual production mainly includes solvent type, hot melt type and emulsion type. The solvent type pressure sensitive adhesive usually contains more than 50% of solvent, which seriously pollutes the environment and has safety hazards in the production process. Although the hot melt type pressure sensitive adhesive does not contain solvent, its production and coating temperature are both above 130°C, which has very high energy consumption, and the hot melt type pressure sensitive adhesive usually uses unsaturated styrene-isoprene-styrene copolymer as the base material, which has poor aging resistance. Compared with the solvent type and hot melt type pressure sensitive adhesive, the emulsion type pressure sensitive adhesive is very friendly to the environment, the production process is safe, the energy consumption is relatively low, and the obtained pressure sensitive adhesive has excellent aging resistance, so it has been widely studied and applied.

[0004] However, the traditional emulsion type pressure sensitive adhesive has large viscosity, low elasticity, strong molecular polarity and low crosslinking degree, and is prone to cold flow, so that the bonding area gradually increases with time, and it is difficult to peel off the interface bonding strength, even if it can be peeled off, there is residual adhesive on the surface of the bonded object, which is difficult to meet the repeated use requirement or affects the appearance of the bonded object. At the same time, the traditional emulsion type pressure sensitive adhesive generally has poor water resistance, which also leads to the easy whitening of the emulsion type pressure sensitive adhesive.

[0005] For example, the Chinese patent application with the publication number CN113292951A discloses a solvent type peelable acrylate pressure sensitive adhesive and a preparation method thereof, but the solvent type has large environmental pollution. Only crosslinking agent and heat conducting filler are used in the preparation process of the pressure sensitive adhesive, but the heat conducting filler is in lamellar shape, which can increase the contact area and reduce the peeling performance.

[0006] For example, the Chinese patent application with the publication number CN104877588A discloses an emulsion type peelable pressure sensitive adhesive film and a preparation method thereof, which uses a low surface energy fluorosilicon monomer, has certain removable performance compared with the conventional acrylate emulsion pressure sensitive adhesive, but does not use crosslinking agent, and has low crosslinking density, which will also cause cold flow problem under high temperature condition. SUMMARY

[0007] To address the problems existing in the background technology, the present invention provides an emulsion-type removable pressure-sensitive adhesive and its preparation method. The removable pressure-sensitive adhesive of the present invention has the advantages of excellent water resistance, good removability, energy saving and environmental protection, and simple preparation process, and has a very good application prospect.

[0008] The technical solution adopted to achieve the above-mentioned objectives of this invention is as follows: An emulsion-type removable pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: 0.5-2 parts of nanopolymer microspheres 20 parts of soft monomer 5-15 parts of aliphatic ring hard monomer 1-5 parts of fluorinated acrylate monomer 0.1-0.5 parts of functional monomer Crosslinking agent 0.5-2 parts pH adjuster 0.01-0.05 parts Emulsifier 0.3-0.7 parts Initiator 0.05-0.3 parts 24-45 parts water.

[0009] Furthermore, the nanopolymer microspheres are at least one of polystyrene microspheres and polymethyl methacrylate microspheres.

[0010] Furthermore, the particle size of the nanopolymer microspheres is 100-800 nm. Preferably, the particle size of the nanopolymer microspheres is 500-800 nm.

[0011] The inclusion of nanopolymer microspheres in this invention is primarily due to the significant impact of the adhesive area on the peel performance of pressure-sensitive adhesives. The addition of nanopolymer microspheres effectively reduces the contact area, resulting in better peel performance and improved reusability. Furthermore, the high glass transition temperatures of polystyrene and polymethyl methacrylate, coupled with their low viscosity and high elasticity, effectively mitigate the problem of increased adhesive strength and difficulty in peeling caused by cold flow in the pressure-sensitive adhesive.

[0012] Furthermore, the soft monomer is at least one selected from butyl acrylate and isooctyl acrylate. Preferably, the soft monomer is butyl acrylate, which has a higher glass transition temperature and elasticity compared to isooctyl acrylate, thereby obtaining a pressure-sensitive adhesive with excellent peel performance.

[0013] Furthermore, the alicyclic hard monomer is at least one selected from cyclohexyl methacrylate and isobornyl methacrylate. Preferably, the alicyclic hard monomer is isobornyl methacrylate.

[0014] This invention utilizes rigid alicyclic hard monomers, which, compared to traditional hard monomers, exhibit lower viscosity and higher elasticity. This reduces creep of pressure-sensitive adhesive molecules and wetting of the bonding surfaces, further minimizing low cold flow. Furthermore, these alicyclic hard monomers have lower polarity and stronger hydrophobicity, making the pressure-sensitive adhesive easier to peel and providing better water resistance.

[0015] Furthermore, the fluorinated acrylate monomer is at least one selected from trifluoroethyl acrylate, hexafluorobutyl acrylate, and dodecafluoroheptyl methacrylate. Preferably, the fluorinated acrylate monomer is dodecafluoroheptyl methacrylate.

[0016] This invention utilizes low surface energy fluorinated acrylate monomers. Due to the low surface energy of these monomers, wetting properties and adhesive strength can be further reduced, thereby improving the peelability of the pressure-sensitive adhesive. Simultaneously, the superior self-cleaning and hydrophobic properties of fluorinated materials significantly improve the water resistance of the pressure-sensitive adhesive.

[0017] Furthermore, the functional monomer is at least one of acrylic acid and methacrylic acid.

[0018] Furthermore, the crosslinking agent is one of N-hydroxymethylacrylamide and hydroxyethyl acrylate.

[0019] This invention adds such crosslinking agents during the preparation of emulsion-type pressure-sensitive adhesives, which can improve the degree of crosslinking of the pressure-sensitive adhesive. The increased degree of crosslinking can, on the one hand, increase the cohesive energy density of the pressure-sensitive adhesive, thereby improving elasticity, reducing cold flow, and thus improving peel performance; on the other hand, it can reduce the permeability of water molecules, thereby improving the water resistance of the pressure-sensitive adhesive.

[0020] Furthermore, the pH adjuster is at least one of sodium bicarbonate and sodium carbonate.

[0021] Furthermore, the emulsifier is one of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate (CAS No.: 52556-42-0) or 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate (CAS No.: 184719-88-8). This invention uses a reactive emulsifier, which, compared to traditional emulsifiers, significantly reduces the hydrophilicity of the resulting pressure-sensitive adhesive and further improves its water resistance.

[0022] Furthermore, the initiator is at least one of ammonium persulfate and potassium persulfate.

[0023] A method for preparing an emulsion-type removable pressure-sensitive adhesive includes the following steps: S1. Take the following components by weight: nanopolymer microspheres, soft monomers, aliphatic ring hard monomers, fluorinated acrylate monomers, functional monomers, crosslinking agents, pH adjusters, emulsifiers, initiators, and water. S2. Add nanopolymer microspheres, soft monomers, aliphatic ring hard monomers, fluorinated acrylate monomers, functional monomers, crosslinking agents, emulsifiers and initiators to 1 / 2-2 / 3 of the weight of water, mix evenly to obtain a pre-emulsion; S3. Add the remaining water and pH adjuster to the reaction vessel, heat to 80-90°C, then slowly add the pre-emulsion dropwise. After the addition is complete, continue the reaction for 0.5-1.5 hours. After the reaction is complete, cool to obtain the emulsion-type removable pressure-sensitive adhesive.

[0024] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention uses water as a medium to prepare an environmentally friendly pressure-sensitive adhesive with good water resistance and portability through emulsion polymerization.

[0025] 2. This invention uses nanopolymer microspheres to prepare pressure-sensitive adhesive, which can effectively reduce the contact area of ​​the pressure-sensitive adhesive and improve its elasticity, thereby obtaining a removable pressure-sensitive adhesive with excellent peel performance, improving its reusability, and ensuring that there is no adhesive residue or white shadow on the adhered object, reducing its impact on the appearance of the adhered object.

[0026] 3. In the preparation of the pressure-sensitive adhesive, the present invention uses a hydrophobic rigid aliphatic ring hard monomer, which can reduce creep and cold flow, and at the same time improve the water resistance of the pressure-sensitive adhesive.

[0027] 4. The present invention uses fluorinated acrylate monomers in the preparation of pressure-sensitive adhesive, which can further reduce its adhesive strength and water resistance.

[0028] 5. In the preparation of pressure-sensitive adhesive, the present invention adds a suitable crosslinking agent, which can not only improve the crosslinking density and reduce the cold flow phenomenon, but also further improve the water resistance. Attached Figure Description

[0029] Figure 1 This is a peeling effect diagram of the emulsion-type removable pressure-sensitive adhesive prepared in Example 4 after bonding the cardboard.

[0030] Figure 2 This is a peeling effect diagram of the emulsion-type pressure-sensitive adhesive prepared in Comparative Example 3 after bonding the cardboard. Detailed Implementation

[0031] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0032] Example 1 An emulsion-type removable pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: 0.5 parts of polystyrene microspheres (100 nm) 20 parts butyl acrylate 5 parts of cyclohexyl methacrylate 1 part trifluoroethyl acrylate 0.1 parts acrylic acid 0.5 parts of N-hydroxymethylacrylamide Sodium bicarbonate 0.01 parts 0.3 parts of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate 0.05 parts ammonium persulfate 24 parts water.

[0033] The preparation method of the above-mentioned emulsion-type removable pressure-sensitive adhesive is as follows: 1. Add polystyrene microspheres (100 nm), butyl acrylate, cyclohexyl methacrylate, trifluoroethyl acrylate, acrylic acid, N-hydroxymethylacrylamide, sodium allyl hydroxypropyl sulfonate and ammonium persulfate to 18 parts of water, stir and mix evenly to obtain a pre-emulsion. 2. Add the remaining 6 parts of water and sodium bicarbonate to the reaction vessel, heat to 80°C, and then slowly add the pre-emulsion dropwise. The addition of the pre-emulsion is completed in 2 hours. Continue the reaction for 1.5 hours. After the reaction is completed, cool to obtain the emulsion-type removable pressure-sensitive adhesive.

[0034] Example 2 An emulsion-type removable pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: Two portions of polymethyl methacrylate microspheres (800 nm) 20 parts of isooctyl acrylate 15 parts of isoborneol methacrylate 5 parts hexafluorobutyl acrylate 0.5 parts methacrylic acid 2 parts hydroxyethyl acrylate Sodium carbonate 0.05 parts 0.7 parts of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate. 0.3 parts potassium persulfate 45 parts water.

[0035] The preparation method of the above-mentioned emulsion-type removable pressure-sensitive adhesive is as follows: 1. Add polymethyl methacrylate microspheres (800 nm), isooctyl acrylate, isobornyl methacrylate, hexafluorobutyl acrylate, methacrylic acid, hydroxyethyl acrylate, 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate and potassium persulfate to 30 parts of water, stir and mix evenly to obtain a pre-emulsion; 2. Add the remaining 15 parts of water and sodium carbonate to the reaction vessel, heat to 90°C, and then slowly add the pre-emulsion dropwise. The addition of the pre-emulsion is completed after 2 hours. Continue the reaction for 0.5 hours, and then cool after the reaction to obtain the emulsion-type removable pressure-sensitive adhesive.

[0036] Example 3 An emulsion-type removable pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: 1 part of polystyrene microspheres (500 nm) 20 parts of isooctyl acrylate 10 parts of isoborneol methacrylate 3 parts of dodecafluoroheptyl methacrylate 0.3 parts methacrylic acid 1 part of N-hydroxymethylacrylamide Sodium bicarbonate 0.03 parts 0.5 parts of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate 0.2 parts potassium persulfate 30 parts water.

[0037] The preparation method of the above-mentioned emulsion-type removable pressure-sensitive adhesive is as follows: 1. Add polystyrene microspheres (500 nm), isooctyl acrylate, isobornyl methacrylate, dodecafluoroheptyl methacrylate, methacrylic acid, N-hydroxymethylacrylamide, acryloxynonylphenol polyoxyethylene ether ammonium sulfate and potassium persulfate to 20 parts of water, stir and mix evenly to obtain a pre-emulsion. 2. Add the remaining 10 parts of water and sodium bicarbonate to the reaction vessel, heat to 85°C, and then slowly add the pre-emulsion dropwise. The addition of the pre-emulsion is completed in 2 hours. Continue the reaction for 1 hour. After the reaction is completed, cool to obtain the emulsion-type removable pressure-sensitive adhesive.

[0038] Example 4 An emulsion-type removable pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: One part of polystyrene microspheres (800 nm) 20 parts of isooctyl acrylate 12 parts of isoborneol methacrylate 4 parts of dodecafluoroheptyl methacrylate 0.3 parts methacrylic acid 1.5 parts of N-hydroxymethylacrylamide Sodium bicarbonate 0.04 parts 0.6 parts of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate 0.2 parts ammonium persulfate 36 portions of water.

[0039] The preparation method of the above-mentioned emulsion-type removable pressure-sensitive adhesive is as follows: 1. Add polystyrene microspheres (800 nm), isooctyl acrylate, isobornyl methacrylate, dodecafluoroheptyl methacrylate, methacrylic acid, N-hydroxymethylacrylamide, acryloxynonylphenol polyoxyethylene ether ammonium sulfate and ammonium persulfate to 24 parts of water, stir and mix evenly to obtain a pre-emulsion; 2. Add the remaining 12 parts of water and sodium bicarbonate to the reaction vessel, heat to 85°C, and then slowly add the pre-emulsion dropwise. The addition of the pre-emulsion is completed after 2 hours. Continue the reaction for 1 hour. After the reaction is completed, cool to obtain the emulsion-type removable pressure-sensitive adhesive.

[0040] Comparative Example 1 The preparation method of the pressure-sensitive adhesive in this comparative example is the same as that in Example 4. The difference between the formulation of the pressure-sensitive adhesive in this comparative example and that in Example 4 is that polystyrene microspheres are not added.

[0041] Comparative Example 2 The preparation method of the pressure-sensitive adhesive in this comparative example is the same as that in Example 4. The difference between the formulation of the pressure-sensitive adhesive in this comparative example and that in Example 4 is that the crosslinking agent N-hydroxymethylacrylamide is replaced with glycidyl methacrylate.

[0042] Comparative Example 3 The preparation method of the pressure-sensitive adhesive in this comparative example is the same as that in Example 4. The difference between the formulation of the pressure-sensitive adhesive in this comparative example and that in Example 4 is that polystyrene microspheres are not added, and the crosslinking agent N-hydroxymethylacrylamide is replaced with glycidyl methacrylate.

[0043] Comparative Example 4 The preparation method of the pressure-sensitive adhesive in this comparative example is the same as that in Example 4. The difference between the formulation of the pressure-sensitive adhesive in this comparative example and that in Example 4 is that the fluorinated monomer dodecafluoroheptyl methacrylate is replaced with isooctyl acrylate.

[0044] Comparative Example 5 The preparation method of the pressure-sensitive adhesive in this comparative example is the same as that in Example 4. The difference between the formulation of the pressure-sensitive adhesive in this comparative example and that in Example 4 is that the aliphatic ring hard monomer isoborneol methacrylate is replaced with methyl methacrylate.

[0045] The pressure-sensitive adhesives prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to the following performance tests: Peel performance: The pressure-sensitive adhesive was coated on the PET film, and the 180° peel force was tested according to the national standard GB / 2792-1998. Adhesion performance: The pressure-sensitive adhesive was coated on the PET film and the holding power was tested according to GB / 4851-1998; White shadow situation: The pressure-sensitive tape was pasted on a standard 304 mirror stainless steel plate and left at room temperature for 7 days. The adhesive film was then slowly removed from the steel plate, and the white shadow situation was observed on the surface of the pasted steel plate with the naked eye. Water absorption performance: The pressure-sensitive adhesive was soaked in distilled water at room temperature for 48 hours, and the water absorption rate was calculated by differential method.

[0046] The performance test results are shown in Table 1 below: Table 1 Performance Indicators of Pressure-Sensitive Adhesives

[0047] As shown in Table 1, the removable pressure-sensitive adhesive of the present invention has good peel performance. After being adhered to the steel plate surface, there is no residue or white shadow after peeling, which meets the requirements for the use of removable pressure-sensitive adhesives. Moreover, the removable pressure-sensitive adhesive of the present invention has good water resistance. The peel effect of the removable pressure-sensitive adhesive prepared in Example 4 after bonding to the cardboard is shown in Table 1. Figure 1 ,Depend on Figure 1 It can be seen that it has excellent portability.

[0048] In Comparative Example 1, the pressure-sensitive adhesive, due to the absence of polystyrene microspheres during preparation, exhibited reduced elasticity, increased viscosity, a large contact area, significant cold flow, high peel strength, severe adhesive residue, and poor peel performance. However, the presence of a crosslinking agent minimized the impact on holding power and resulted in low water absorption.

[0049] In the preparation of the pressure-sensitive adhesive of Comparative Example 2, the crosslinking effect of glycidyl methacrylate was not as good as that of N-hydroxymethyl acrylate. The effect of the enamide is that the network crosslinking density formed synergistically with the polystyrene microspheres decreases, the viscosity of the adhesive increases, the holding power decreases significantly, and the water absorption rate increases significantly. In Comparative Example 3, the pressure-sensitive adhesive, due to the absence of polystyrene microspheres and the poor crosslinking effect of the crosslinking agent, failed to synergistically form a crosslinking network with the polystyrene microspheres. This resulted in a more pronounced cold flow phenomenon, further increased peel force, and continued deterioration of holding power, ultimately leading to the worst peel performance and water resistance in the resulting pressure-sensitive adhesive. The peel performance of the pressure-sensitive adhesive prepared in Comparative Example 3 after bonding to the cardboard is shown in the figure. Figure 2 ,Depend on Figure 2 It is evident that its portability is very poor.

[0050] In the preparation of the pressure-sensitive adhesive in Comparative Example 4, the low surface energy fluorinated acrylate monomer dodecafluoroheptyl methacrylate was replaced with the more polar isooctyl acrylate, resulting in high polarity and peel strength of the pressure-sensitive adhesive, but poor water resistance.

[0051] In the preparation of Comparative Example 5, the hydrophobic rigid aliphatic ring hard monomer isoborneol methacrylate was replaced with the conventional hard monomer methyl methacrylate, which resulted in a decrease in the elasticity of the pressure-sensitive adhesive, an increase in viscosity, and a deterioration in its peel performance.

Claims

1. An emulsion-type removable pressure-sensitive adhesive, characterized in that... It is prepared from the following raw materials in parts by weight: 0.5-2 parts of nanopolymer microspheres 20 parts of soft monomer 5-15 parts of aliphatic ring hard monomer 1-5 parts of fluorinated acrylate monomer 0.1-0.5 parts of functional monomer Crosslinking agent 0.5-2 parts pH adjuster 0.01-0.05 parts Emulsifier 0.3-0.7 parts Initiator 0.05-0.3 parts 24-45 parts water.

2. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The nanopolymer microspheres are at least one of polystyrene microspheres and polymethyl methacrylate microspheres.

3. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The particle size of the aforementioned nanopolymer microspheres is 100-800 nm.

4. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The soft monomer is at least one of butyl acrylate and isooctyl acrylate.

5. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The alicyclic hard monomer is at least one of cyclohexyl methacrylate and isobornyl methacrylate.

6. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The fluorinated acrylate monomer is at least one of trifluoroethyl acrylate, hexafluorobutyl acrylate, and dodecafluoroheptyl methacrylate.

7. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The functional monomer is at least one of acrylic acid and methacrylic acid.

8. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The crosslinking agent is one of N-hydroxymethylacrylamide and hydroxyethyl acrylate.

9. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The pH adjuster is at least one of sodium bicarbonate and sodium carbonate.

10. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The emulsifier is one of sodium 3-allyloxy-2-hydroxy-1-propanesulfonate or ammonium sulfate of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether.

11. The emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that: The initiator is at least one of ammonium persulfate and potassium persulfate.

12. A method for preparing the emulsion-type removable pressure-sensitive adhesive according to claim 1, characterized in that... Includes the following steps: S1. Take the following components by weight: nanopolymer microspheres, soft monomers, aliphatic ring hard monomers, fluorinated acrylate monomers, functional monomers, crosslinking agents, pH adjusters, emulsifiers, initiators, and water. S2. Add nanopolymer microspheres, soft monomers, aliphatic ring hard monomers, fluorinated acrylate monomers, functional monomers, crosslinking agents, emulsifiers and initiators to 1 / 2-2 / 3 of the weight of water, mix evenly to obtain a pre-emulsion; S3. Add the remaining water and pH adjuster to the reaction vessel, heat to 80-90°C, then slowly add the pre-emulsion dropwise. After the addition is complete, continue the reaction for 0.5-1.5 hours. After the reaction is complete, cool to obtain the emulsion-type removable pressure-sensitive adhesive.

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