Composite pressure-sensitive adhesive for protective film and preparation method of composite pressure-sensitive adhesive

Abstract

The invention relates to the technical field of adhesives, and discloses a composite pressure-sensitive adhesive for a protective film and a preparation method thereof.The pressure-sensitive adhesive is formed by mixing an acrylate polymerized emulsion serving as a base material with auxiliary materials such as a wetting agent and a defoaming agent, a cross-linking agent is added in the polymerization process of acrylate monomers, and a cross-linking polymerization reaction is achieved; according to the present invention, the cross-linking reaction can increase the density of the formed acrylic resin molecular chain so as to effectively improve the cohesive energy, such that the adhesion property of the acrylate pressure-sensitive adhesive is enhanced, and the increase of the molecular chain density can hinder the movement of the molecular chain so as to easily improve the high temperature resistance of the pressure-sensitive adhesive. In addition, the cross-linking agent structure contains a large number of rigid double-ring structures, and the structures can improve the stability of acrylate molecular chains, so that the high temperature resistance of the pressure-sensitive adhesive is further enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly relates to a composite pressure-sensitive adhesive for a protective film and a manufacturing method thereof. Background Art

[0002] In the fields of industrial manufacturing and consumer electronics, as a core material for surface protection, the protective film is widely used in fields such as construction and electronic products. Especially in the field of electronic products, attaching a protective film can effectively prevent scratches that occur during manufacturing and use, and can also reduce pollution such as dust and grease, which can play a positive role in both the appearance and service life of electronic products. During the use of the protective film, pressure-sensitive adhesive is required to achieve adhesion to the object to be protected.

[0003] Due to the high transparency and low haze characteristics of acrylate pressure-sensitive adhesive, most of the current protective films use acrylate resin pressure-sensitive adhesive to achieve adhesion to objects. However, the acrylate pressure-sensitive adhesive has poor adhesion, which is not very beneficial for objects that require firm adhesion. In addition, since electronic products will inevitably generate heat during long-term use, the pressure-sensitive adhesive needs to work continuously at a relatively high temperature for a long time. However, the acrylate pressure-sensitive adhesive generally shows poor high-temperature aging resistance and will age and fall off in a long-term high-temperature environment, resulting in phenomena such as curling of the protective film.

[0004] Since acrylate pressure-sensitive adhesive is prepared by free radical polymerization of different acrylate monomers, the comprehensive performance of the pressure-sensitive adhesive can be improved by adjusting the monomers. Therefore, the present invention designs a pressure-sensitive adhesive with good bonding performance and high-temperature resistance, which can be directly used for the protective film. Summary of the Invention

[0005] In order to solve the problems mentioned in the background art, the purpose of the present invention is to provide a composite pressure-sensitive adhesive for a protective film and a manufacturing method thereof.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A composite pressure-sensitive adhesive for a protective film is made of the following raw materials measured by weight parts:

[0008] 40 - 60 parts of acrylate polymerization emulsion, 1 - 2 parts of wetting agent, 0.5 - 1 part of defoaming agent, 1 - 3 parts of curing agent, 20 - 35 parts of organic solvent.

[0009] As a further solution of the present invention, the preparation method of the acrylate polymerization emulsion includes the following steps:

[0010] Step 1: According to parts by weight, add 30 - 45 parts of soft monomer, 3 - 6 parts of hard monomer, 2 - 5 parts of functional monomer, and 1 - 2 parts of crosslinking agent to 80 - 120 parts of deionized water. Stir mechanically to mix evenly, add 0.5 - 1 part of emulsifier, and continue to stir and mix evenly to form an emulsion.

[0011] Step 2: Take 3 - 5% of the total mass of the emulsion as the seed solution, add it to 40 - 50 parts of deionized water. After adding, raise the temperature to 65 - 75°C, then add 0.1 - 0.2 part of initiator. After adding, stir for 20 - 40 min, continue to add the remaining amount of the emulsion and 0.3 - 0.6 part of initiator, and raise the temperature to 82 - 85°C. Keep stirring and polymerize for 2 - 4 h, then stop heating and cool down to discharge, and that's it.

[0012] As a further solution of the present invention, in Step 1, the soft monomer is selected from at least one of isooctyl acrylate or butyl acrylate; the hard monomer is selected from methyl methacrylate; the functional monomer is at least one of acrylic acid or 2 - hydroxyethyl acrylate; the emulsifier is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate.

[0013] As a further solution of the present invention, in Step 1, the preparation method of the crosslinking agent is as follows:

[0014] Step S1: Add bicyclo[2.2.2]oct - 5 - ene - 2,3 - dicarboxylic anhydride, dihydrosilane compound, and absolute ethanol to a reaction kettle, introduce nitrogen for protection, start stirring. After forming a uniform reaction solution, start heating and raise the temperature to 70 - 75°C. Add a platinum catalyst to the reaction kettle under stirring conditions. After adding, keep stirring for 4 - 8 h, then evaporate to remove the solvent, collect the product, and form a linker.

[0015] Step S2: Add the linker, 3 - allyloxy - 1,2 - propanediol, and N,N - dimethylformamide to a polymerization kettle, purge air with nitrogen, and continue to add a phase transfer catalyst to the polymerization kettle. After adding, raise the temperature to 80 - 100°C, keep stirring and heat - insulating for 12 - 18 h, then evaporate the solvent. After the product undergoes a purification process, the crosslinking agent can be obtained.

[0016] As a further solution of the present invention, in Step S1, the dihydrosilane compound is decamethyl - dihydropentasiloxane or 1,1,3,3,5,5,7,7 - octamethyltetrasiloxane.

[0017] As a further solution of the present invention, in Step S1, the molar ratio of bicyclo[2.2.2]oct - 5 - ene - 2,3 - dicarboxylic anhydride to the dihydrosilane compound is 2:1.

[0018] As a further solution of the present invention, in step S2, the phase transfer catalyst is p-toluenesulfonic acid.

[0019] In the above technical solution, first, bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride and dihydrosilane compound are used as reactants. Under the action of a platinum catalyst, the unsaturated alkenyl functional groups in their structures can undergo a hydrosilylation reaction with Si-H. By controlling the amounts of the two, a siloxane derivative containing two equivalents of acid anhydride groups in its structure, that is, a linker, can be prepared. Then, using 3-allyloxy-1,2-propanediol as a chain extender, under the action of a phase transfer catalyst, the acid anhydride groups in their structures can undergo successive ring-opening esterification with active hydroxyl substituents to form a polymeric substance connected by ester bonds. Since its structure contains a large number of unsaturated alkenyl substituents that can participate in free radical polymerization reactions, cross-linking polymerization of acrylate monomers can be achieved, so it can be used as a cross-linking agent.

[0020] As a further solution of the present invention, in step two, the initiator is potassium persulfate or ammonium persulfate.

[0021] As a further solution of the present invention, the wetting agent is alkyl polyoxyethylene ether; the defoaming agent is NYK-065; the curing agent is a polyisocyanate curing agent; the organic solvent is ethyl acetate.

[0022] A method for preparing a composite pressure-sensitive adhesive for a protective film, comprising the following steps:

[0023] First step, weigh and prepare all raw materials according to parts by weight;

[0024] Second step, add the acrylate polymerization emulsion to an organic solvent, set the stirring rate to 800 - 1500 r / min, mechanically stir and mix for 20 - 40 min, then add the wetting agent and the curing agent, stir for 5 - 10 min, continue to add the defoaming agent, stir evenly, and let stand for 1 - 2 h to obtain the pressure-sensitive adhesive.

[0025] The beneficial effects of the present invention:

[0026] By adding a cross-linking agent during the polymerization of acrylate monomers, the present invention realizes a cross-linking polymerization reaction. The cross-linking reaction will increase the density of the formed acrylate resin molecular chains, thereby effectively increasing the cohesive energy and enhancing the bonding performance of the acrylate pressure-sensitive adhesive. In addition, the increase in the molecular chain density can also hinder the movement of the molecular chains, which is beneficial to improving the high-temperature resistance of the pressure-sensitive adhesive. Furthermore, the cross-linking agent structure contains a large number of rigid bicyclic structures, and this structure can improve the stability of the acrylate molecular chains, thereby further enhancing the high-temperature resistance of the pressure-sensitive adhesive.

[0027] Of course, it is not necessary for any product implementing the present invention to achieve all the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 Infrared test chart of the crosslinking agent. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] Embodiment 1

[0032] A composite pressure-sensitive adhesive for a protective film is prepared from the following raw materials measured by weight parts:

[0033] 40 parts of acrylate polymerization emulsion, 1 part of wetting agent alkyl polyoxyethylene ether, 0.5 part of defoaming agent NYK-065, 1 part of curing agent isophorone diisocyanate trimer, and 20 parts of organic solvent ethyl acetate.

[0034] The preparation method of the pressure-sensitive adhesive includes the following steps:

[0035] First step, weigh and prepare all the raw materials according to the weight parts;

[0036] Second step, add the acrylate polymerization emulsion into the organic solvent ethyl acetate, set the stirring rate at 800 r / min, mechanically stir and mix for 40 min, then add the wetting agent alkyl polyoxyethylene ether and the curing agent isophorone diisocyanate trimer, stir for 5 min, continue to add the defoaming agent NYK-065, stir evenly, and stand for 1 h to obtain the pressure-sensitive adhesive.

[0037] The preparation method of the acrylate polymerization emulsion includes the following steps:

[0038] Step 1: Add 35 parts by weight of isooctyl acrylate, 4 parts of methyl methacrylate, 3 parts of acrylic acid, and 1.5 parts of crosslinking agent to 100 parts of deionized water. Stir mechanically and mix evenly. Add 0.6 part of sodium dodecyl sulfate and continue to stir and mix evenly to form an emulsion.

[0039] Step 2: Take 5% of the total mass of the emulsion as the seed solution and add it to 50 parts of deionized water. After adding, raise the temperature to 70 °C, then add 0.1 part of potassium persulfate. After adding, stir for 30 min, continue to add the remaining amount of the emulsion and 0.5 part of potassium persulfate, and raise the temperature to 83 °C. Keep stirring and polymerize for 3 h, then stop heating and cool down to discharge the product.

[0040] The preparation method of the crosslinking agent is as follows:

[0041] Step S1: Add 0.3 g of bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, 0.3 g of decamethyldihydrofivesiloxane, and anhydrous ethanol to the reaction kettle. Protect with nitrogen, start stirring. After forming a uniform reaction solution, start heating and raise the temperature to 70 °C. Add 0.01 g of platinum catalyst to the reaction kettle under stirring conditions. After adding, keep stirring for 6 h, then evaporate to remove the solvent and collect the product to form a linker.

[0042] Step S2: Add 0.2 g of linker, 0.02 g of 3-allyloxy-1,2-propanediol, and N,N-dimethylformamide to the polymerization kettle. Purge with nitrogen to remove air, and continue to add 0.01 g of p-toluenesulfonic acid to the polymerization kettle. After adding, raise the temperature to 90 °C, keep stirring and heat for 16 h, then evaporate the solvent. After the product undergoes a purification process, the crosslinking agent can be obtained.

[0043] Figure 1 This is the infrared test chart of the crosslinking agent. Among them, a C-H characteristic absorption peak attributed to unsaturated carbon-carbon double bonds appears at 3053 cm -1 A C-H characteristic absorption peak attributed to saturated C-H appears at 2800 - 3000 cm -1 Characteristic absorption peaks of C=O in the ester group and C=O of the carboxyl group generated by ring-opening esterification reaction appear at 1765 cm -1 and 1716 cm -1 respectively. A Si-O characteristic absorption peak appears at 1098 cm -1

[0044] Example 2

[0045] A composite pressure-sensitive adhesive for a protective film is prepared from the following raw materials measured by weight:

[0046] ​50 parts of acrylate polymer emulsion, 1.5 parts of wetting agent alkyl polyoxyethylene ether, 0.6 part of defoaming agent NYK-065, 2 parts of curing agent isophorone diisocyanate trimer, 30 parts of organic solvent ethyl acetate.

[0047] The preparation method of the pressure-sensitive adhesive comprises the following steps:

[0048] First step, weigh and prepare each raw material according to the weight parts;

[0049] Second step, add the acrylate polymer emulsion into the organic solvent ethyl acetate, set the stirring rate to 1000 r / min, mechanically stir and mix for 30 min, then add the wetting agent alkyl polyoxyethylene ether and the curing agent isophorone diisocyanate trimer, stir for 8 min, continue to add the defoaming agent NYK-065, stir evenly, and let stand for 1 h to obtain the pressure-sensitive adhesive.

[0050] The preparation method of the acrylate polymer emulsion is the same as that in Example 1.

[0051] Example 3

[0052] A composite pressure-sensitive adhesive for a protective film is made of the following raw materials measured by weight parts:

[0053] 60 parts of acrylate polymer emulsion, 2 parts of wetting agent alkyl polyoxyethylene ether, 1 part of defoaming agent NYK-065, 3 parts of curing agent isophorone diisocyanate trimer, 35 parts of organic solvent ethyl acetate.

[0054] The preparation method of the pressure-sensitive adhesive comprises the following steps:

[0055] First step, weigh and prepare each raw material according to the weight parts;

[0056] Second step, add the acrylate polymer emulsion into the organic solvent ethyl acetate, set the stirring rate to 1500 r / min, mechanically stir and mix for 20 min, then add the wetting agent alkyl polyoxyethylene ether and the curing agent isophorone diisocyanate trimer, stir for 10 min, continue to add the defoaming agent NYK-065, stir evenly, and let stand for 2 h to obtain the pressure-sensitive adhesive.

[0057] The preparation method of the acrylate polymer emulsion is the same as that in Example 1.

[0058] Comparative Example 1

[0059] A composite pressure-sensitive adhesive for a protective film is made of the following raw materials measured by weight parts:

[0060] 50 parts of acrylate polymerization emulsion, 1.5 parts of wetting agent alkyl polyoxyethylene ether, 0.6 parts of defoaming agent NYK-065, 2 parts of curing agent isophorone diisocyanate trimer, 30 parts of organic solvent ethyl acetate.

[0061] The preparation method of the pressure-sensitive adhesive comprises the following steps:

[0062] First step, weigh and prepare each raw material according to the weight parts;

[0063] Second step, add the acrylate polymerization emulsion into the organic solvent ethyl acetate, set the stirring rate at 1000 r / min, mechanically stir and mix for 30 min, then add the wetting agent alkyl polyoxyethylene ether and the curing agent isophorone diisocyanate trimer, stir for 8 min, continue to add the defoaming agent NYK-065, stir evenly, and let stand for 1 h to obtain the pressure-sensitive adhesive.

[0064] The difference in the preparation method of the acrylate polymerization emulsion from that in Example 1 is that the cross-linking agent is replaced with a conventional cross-linking agent N,N'-methylenebisacrylamide, and the rest are the same.

[0065] Comparative Example 2

[0066] A composite pressure-sensitive adhesive for protective film is made of the following raw materials measured by weight parts:

[0067] 50 parts of acrylate polymerization emulsion, 1.5 parts of wetting agent alkyl polyoxyethylene ether, 0.6 parts of defoaming agent NYK-065, 2 parts of curing agent isophorone diisocyanate trimer, 30 parts of organic solvent ethyl acetate.

[0068] The preparation method of the pressure-sensitive adhesive comprises the following steps:

[0069] First step, weigh and prepare each raw material according to the weight parts;

[0070] Second step, add the acrylate polymerization emulsion into the organic solvent ethyl acetate, set the stirring rate at 1000 r / min, mechanically stir and mix for 30 min, then add the wetting agent alkyl polyoxyethylene ether and the curing agent isophorone diisocyanate trimer, stir for 8 min, continue to add the defoaming agent NYK-065, stir evenly, and let stand for 1 h to obtain the pressure-sensitive adhesive.

[0071] The difference in the preparation method of the acrylate polymerization emulsion from that in Example 1 is that the cross-linking agent is removed, and the rest are the same.

[0072] Performance test

[0073] The pressure-sensitive adhesives in the examples and comparative examples were coated on the surface of a PET film with a thickness of 60 μm and placed in a temperature environment of 80 °C until they were completely cured to form a glue film.

[0074] Referring to the standard GB / T 2792-2014, a 180° peel strength test was carried out.

[0075] High-temperature resistance test method: The glue film was placed in a temperature environment of 150 °C. After 24 hours, it was taken out and the change on the surface of the glue film was observed to evaluate the high-temperature resistance. The test results are recorded in the following table:

[0076] 180° peel strength / gf / 25 mm Phenomenon Example 1 19.6 No obvious phenomenon Example 2 19.9 No obvious phenomenon Example 3 19.7 No obvious phenomenon Comparative Example 1 19.1 Edge curling Comparative Example 2 15.4 Yellowing, curling, cracking

[0077] According to the test results, the pressure-sensitive adhesive prepared with the acrylate polymerization emulsion crosslinked and polymerized by using the crosslinking agent of the present application as the main substance has excellent bonding performance and high-temperature resistance. Although the conventional crosslinking agent can improve the bonding performance of the acrylate pressure-sensitive adhesive to a certain extent, the improvement effect on the high-temperature resistance is limited.

[0078] In this article, specific examples were used to elaborate on the principles and implementation methods of the present invention. The descriptions of the above examples are only used to help understand the method and its core idea of the present invention, including the best mode, and also enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

[0079] The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite pressure-sensitive adhesive for a protective film, characterized in that, It is made from the following raw materials measured by weight parts: 40 - 60 parts of acrylate polymer emulsion, 1 - 2 parts of wetting agent, 0.5 - 1 part of defoaming agent, 1 - 3 parts of curing agent, 20 - 35 parts of organic solvent.

2. The composite pressure-sensitive adhesive for a protective film according to claim 1, characterized in that, The preparation method of the acrylate polymer emulsion includes the following steps: Step 1: By weight parts, add 30 - 45 parts of soft monomer, 3 - 6 parts of hard monomer, 2 - 5 parts of functional monomer and 1 - 2 parts of crosslinking agent to 80 - 120 parts of deionized water, mechanically stir and mix evenly, add 0.5 - 1 part of emulsifier, and continue to stir and mix evenly to form an emulsion; Step 2: Take 3 - 5% of the total mass of the emulsion as the seed liquid, add it to 40 - 50 parts of deionized water. After adding, raise the temperature to 65 - 75 °C, then add 0.1 - 0.2 part of initiator. After adding, stir for 20 - 40 min, continue to add the remaining amount of emulsion and 0.3 - 0.6 part of initiator, and raise the temperature to 82 - 85 °C. Continuously stir and polymerize for 2 - 4 h, then stop heating and cool down to discharge, and that's it.

3. The composite pressure-sensitive adhesive for a protective film according to claim 2, characterized in that, In Step 1, the soft monomer is selected from at least one of isooctyl acrylate or butyl acrylate; the hard monomer is selected from methyl methacrylate; the functional monomer is at least one of acrylic acid or 2 - hydroxyethyl acrylate; the emulsifier is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate.

4. The composite pressure-sensitive adhesive for a protective film according to claim 2, characterized in that, In Step 1, the preparation method of the crosslinking agent is as follows: Step S1: Add bicyclo[2.2.2]oct - 5 - ene - 2,3 - dicarboxylic anhydride, dihydrosilane compound and absolute ethanol to the reaction kettle, introduce nitrogen for protection, start stirring. After forming a uniform reaction solution, start heating, raise the temperature to 70 - 75 °C, add platinum catalyst to the reaction kettle under stirring conditions. After adding, continuously stir for 4 - 8 h, then evaporate and remove the solvent, collect the product to form a linker; Step S2: Add the linker, 3 - allyloxy - 1,2 - propanediol and N,N - dimethylformamide to the polymerization kettle, pass nitrogen to discharge air, and continue to add a phase transfer catalyst to the polymerization kettle. After adding, raise the temperature to 80 - 100 °C, keep stirring for 12 - 18 h, then evaporate the solvent, and the product is subjected to a purification process to obtain the crosslinking agent.

5. The composite pressure-sensitive adhesive for a protective film according to claim 4, characterized in that, In Step S1, the dihydrosilane compound is decamethyl - dihydropentasiloxane or 1,1,3,3,5,5,7,7 - octamethyltetrasiloxane.

6. The composite pressure-sensitive adhesive for a protective film according to claim 4, wherein, In Step S1, the molar ratio of bicyclo[2.2.2]oct - 5 - ene - 2,3 - dicarboxylic anhydride to the dihydrosilane compound is 2:

1.

7. The composite pressure-sensitive adhesive for a protective film according to claim 4, wherein In Step S2, the phase transfer catalyst is p - toluenesulfonic acid.

8. The composite pressure-sensitive adhesive for a protective film according to claim 2, characterized in that, In Step 2, the initiator is potassium persulfate or ammonium persulfate.

9. The composite pressure-sensitive adhesive for a protective film according to claim 1, characterized in that, The wetting agent is alkyl polyoxyethylene ether; the defoaming agent is NYK - 065; the curing agent is a polyisocyanate curing agent; the organic solvent is ethyl acetate.

10. A method for preparing a composite pressure-sensitive adhesive for a protective film as described in claim 1, characterized in that, It includes the following steps: The first step: Weigh and prepare each raw material according to weight parts; Step 2: Add the acrylate polymer emulsion into an organic solvent, set the stirring rate at 800 - 1500 r / min, mechanically stir and mix for 20 - 40 min, then add a wetting agent and a curing agent, stir for 5 - 10 min, continue to add an antifoaming agent, stir evenly, and let stand for 1 - 2 h to obtain the pressure-sensitive adhesive.

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