Preparation method of peelable emulsion

Abstract

The invention relates to the field of polymer emulsions, in particular to a preparation method of a peelable emulsion. The method comprises the following steps: stirring glycidyl methacrylate, amino-terminated silicone oil and a sodium sheet in a dark place at room temperature for reaction, and filtering to obtain double-bond modified silicone oil; splitting the vinyl monomer into a first monomer and a second monomer, and dispersing the double-bond modified silicone oil into the first monomer to obtain a third monomer; carrying out ultrasonic emulsification on a second monomer, an emulsifier and water to prepare a pre-emulsion, and adding the pre-emulsion, the cross-linking monomer aqueous solution and the first ammonium persulfate aqueous solution into a reaction kettle to form a nuclear phase emulsion; dropwise adding a third monomer and a second ammonium persulfate aqueous solution into the nuclear phase emulsion to form a core-shell emulsion; and naturally cooling the core-shell emulsion, adjusting the pH value to 7-8 by using ammonia water, and filtering to obtain the peelable emulsion. The preparation method of the peelable emulsion provided by the invention aims to solve the problem that the performance of a peelable coating is weakened due to the fact that the dosage of a stripping aid is large.

Description

Technical Field

[0001] The present invention relates to the field of polymer emulsions, and in particular to a method for preparing a strippable emulsion. Background Art

[0002] The export of wind turbine towers and blades in my country has formed a scale effect. However, wind turbine towers and blades are easily damaged by bumps, scratches, rain, etc. during sea transportation. In order to avoid damage to the surface of wind turbine towers and blades, a feasible method is to spray a peelable coating on their surface for temporary protection, and then tear off the peelable coating when they are delivered for use. At present, peelable coatings have been widely used for temporary protection of ship painting, offshore oil platforms, glass / metal curtain walls, parts machining, welding, etc. Peelable coatings can prevent the coated surface from being stepped on, bumped, scratched, and other mechanical damage and rain erosion. It has moderate adhesion and can be easily peeled off from the coated surface after use, thereby greatly saving the various costs of reworking and repairing the surface.

[0003] Strippable coatings are water-based coatings composed of film formers, stripping agents, fillers, and additives. Acrylic resin emulsions are often used as film formers. Due to their good adhesion, in order to achieve a good stripping effect, low-surface-energy organic silicon, organic fluorine substances, or powders such as calcium carbonate are usually added as stripping agents. The low adhesion between the stripping agent and the substrate is used to reduce the overall adhesion of the coating. Due to the lack of compatibility between the stripping agent and the film former, it is an island structure in the coating, and the coating as a whole presents a discontinuous distribution of strong adhesion and weak adhesion, so a large amount of stripping agents are usually added. However, the excessive introduction of stripping agents often weakens the mechanical and water-resistant properties of the coating.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the present disclosure is to provide a method for preparing a strippable emulsion, which aims to overcome the problem that the performance of the strippable coating is weakened due to the excessive amount of stripping agent used.

[0006] Other features and advantages of the present disclosure will become apparent from the following detailed description, or may be learned in part by the practice of the present disclosure.

[0007] According to one aspect of an embodiment of the present disclosure, a method for preparing a strippable emulsion is provided, comprising: reacting glycidyl methacrylate, amino-terminated silicone oil and sodium flakes under stirring at room temperature in the dark, filtering to obtain double-bond modified silicone oil; splitting a vinyl monomer into a first monomer and a second monomer, and dispersing the double-bond modified silicone oil in the first monomer to obtain a third monomer; preparing a pre-emulsion by ultrasonic emulsification of the second monomer, an emulsifier and water, and adding the pre-emulsion, a cross-linking monomer aqueous solution and a first ammonium persulfate aqueous solution to a reactor to form a core phase emulsion; dropping the third monomer and the second ammonium persulfate aqueous solution into the core phase emulsion to form a core-shell emulsion; naturally cooling the core-shell emulsion, adjusting the pH to 7-8 with aqueous ammonia, and filtering to obtain a strippable emulsion.

[0008] According to some embodiments of the present disclosure, based on the aforementioned scheme, the molar ratio of the glycidyl methacrylate to the amino-terminated silicone oil is (1-2):1.

[0009] According to some embodiments of the present disclosure, based on the aforementioned scheme, the amine value of the amino-terminated silicone oil is 0.15-0.3 mL·1N HCl / g.

[0010] According to some embodiments of the present disclosure, based on the aforementioned scheme, the vinyl monomer is a mixture of methyl methacrylate and butyl acrylate; the mass ratio of the methyl methacrylate to the butyl acrylate is 1:(0.8-1.5).

[0011] According to some embodiments of the present disclosure, based on the aforementioned scheme, the mass ratio of the double bond modified silicone oil to the vinyl monomer is (1-2):200.

[0012] According to some embodiments of the present disclosure, based on the aforementioned scheme, the emulsifier is a mixture of sodium dodecyl sulfate and OP-10; the mass ratio of the sodium dodecyl sulfate to the OP-10 is 2:1; the amount of the sodium dodecyl sulfate and the OP-10 is 1 to 4% of the mass of the vinyl monomer.

[0013] According to some embodiments of the present disclosure, based on the aforementioned scheme, the cross-linking monomer is N,N-methylenebisacrylamide, and the amount of the N,N-methylenebisacrylamide is 0.5-1.5% of the mass of the vinyl monomer; the cross-linking monomer aqueous solution is an N,N-methylenebisacrylamide aqueous solution, and the concentration of the N,N-methylenebisacrylamide aqueous solution is 3-7%.

[0014] According to some embodiments of the present disclosure, based on the aforementioned solution, the mass proportion of ammonium persulfate in the first aqueous ammonium persulfate solution and the second aqueous ammonium persulfate solution is the same, and the mass of the ammonium persulfate is 2-3% of the mass of the vinyl monomer.

[0015] According to some embodiments of the present disclosure, based on the aforementioned scheme, the adding of the pre-emulsion, the cross-linking monomer aqueous solution and the ammonium persulfate aqueous solution into the reactor to form a core phase emulsion comprises: adding the pre-emulsion into the reactor and heating the temperature to 75°C; simultaneously dropping the cross-linking monomer aqueous solution and the ammonium persulfate aqueous solution into the pre-emulsion within 1 hour, and keeping the temperature for reaction for 2 hours to form the core phase emulsion.

[0016] According to some embodiments of the present disclosure, based on the aforementioned scheme, the step of adding the third monomer and the second aqueous ammonium persulfate solution into the core phase emulsion to form a core-shell emulsion comprises: simultaneously adding the third monomer and the second aqueous ammonium persulfate solution into the core phase emulsion within 1 hour, and reacting at the same temperature for 2 hours to form the core-shell emulsion.

[0017] The exemplary embodiments of the present disclosure may have some or all of the following beneficial effects:

[0018] In the technical solutions provided in some embodiments of the present disclosure, on the one hand, glycidyl methacrylate containing highly reactive double bonds is grafted onto terminal aminosilane by utilizing the room temperature ring-opening reaction of epoxy groups and amino groups, and double-bond modified silicone oil with low surface energy is introduced in situ into the polyacrylate polymer chain, thereby reducing the overall polarity of the polyacrylate molecules at the micromolecular level and weakening their intrinsic adhesion, thereby effectively reducing the amount of stripping agent used, avoiding its influence on the overall performance of the coating, and giving it excellent strippability; on the other hand, a core-shell emulsion polymerization method is used to introduce a pre-crosslinked monomer N,N-methylenebisacrylamide into the core phase to crosslink the acrylate polymer chain and effectively improve its mechanical properties, while double-bond modified silicone oil is introduced into the shell phase to utilize its long molecular chain to physically entangle with the polyacrylate molecular chain, thereby enhancing the interaction between the latex particles and the density of the emulsion film, and also improving its mechanical properties.

[0019] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0021] Figure 1 A schematic flow chart schematically illustrates a method for preparing a strippable emulsion in an exemplary embodiment of the present disclosure.

[0022] Figure 2 A transmission electron microscope image of the core-shell structured peelable emulsion prepared in exemplary embodiment 1 of the present disclosure is shown.

[0023] In order to further illustrate the solutions of the implementation scheme of the present disclosure, various embodiments of the present disclosure are described below. DETAILED DESCRIPTION

[0024] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more comprehensive and complete and will fully convey the concept of the example embodiments to those skilled in the art.

[0025] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0026] The export of wind turbine towers and blades in my country has formed a scale effect. However, wind turbine towers and blades are easily damaged by bumps, scratches, rain, etc. during sea transportation. In order to avoid damage to the surface of wind turbine towers and blades, a feasible method is to spray a peelable coating on their surface for temporary protection, and then tear off the peelable coating when they are delivered for use. At present, peelable coatings have been widely used for temporary protection of ship painting, offshore oil platforms, glass / metal curtain walls, parts machining, welding, etc. Peelable coatings can prevent the coated surface from being stepped on, bumped, scratched, and other mechanical damage and rain erosion. It has moderate adhesion and can be easily peeled off from the coated surface after use, thereby greatly saving the various costs of reworking and repairing the surface.

[0027] Strippable coatings are water-based coatings composed of film formers, stripping agents, fillers, and additives. Acrylic resin emulsions are often used as film formers. Due to their good adhesion, in order to achieve a good stripping effect, low-surface-energy organic silicon, organic fluorine substances, or powders such as calcium carbonate are usually added as stripping agents. The low adhesion between the stripping agent and the substrate is used to reduce the overall adhesion of the coating. Due to the lack of compatibility between the stripping agent and the film former, it is an island structure in the coating, and the coating as a whole presents a discontinuous distribution of strong adhesion and weak adhesion, so a large amount of stripping agents are usually added. However, the excessive introduction of stripping agents often weakens the mechanical and water-resistant properties of the coating.

[0028] Therefore, the present disclosure provides a method for preparing a strippable emulsion, which aims to overcome the problem that the performance of the strippable coating is weakened due to the excessive amount of stripping agent used to a certain extent.

[0029] The implementation details of the technical solution of the embodiment of the present disclosure are elaborated in detail below.

[0030] Figure 1 The schematic diagram of the process of preparing a strippable emulsion in an exemplary embodiment of the present disclosure is shown schematically. Figure 1 As shown, the method for preparing the strippable emulsion includes steps S101 to S105:

[0031] Step S101, reacting glycidyl methacrylate, amino-terminated silicone oil and sodium flakes under stirring at room temperature in the dark, and filtering to obtain double-bond modified silicone oil;

[0032] Step S102, splitting the vinyl monomer into a first monomer and a second monomer, and dispersing the double bond modified silicone oil in the first monomer to obtain a third monomer;

[0033] Step S103, preparing a pre-emulsion by ultrasonic emulsification of the second monomer, the emulsifier and water, and adding the pre-emulsion, the cross-linking monomer aqueous solution and the first ammonium persulfate aqueous solution into a reactor to form a core phase emulsion;

[0034] Step S104, adding the third monomer and the second ammonium persulfate aqueous solution dropwise into the core phase emulsion to form a core-shell emulsion;

[0035] Step S105, naturally cooling the core-shell emulsion, adjusting the pH to 7-8 with aqueous ammonia, and filtering to obtain a strippable emulsion.

[0036] In the technical solutions provided in some embodiments of the present disclosure, on the one hand, glycidyl methacrylate containing highly reactive double bonds is grafted onto terminal aminosilane by utilizing the room temperature ring-opening reaction of epoxy groups and amino groups, and double-bond modified silicone oil with low surface energy is introduced in situ into the polyacrylate polymer chain, thereby reducing the overall polarity of the polyacrylate molecules at the micromolecular level and weakening their intrinsic adhesion, thereby effectively reducing the amount of stripping agent used, avoiding its influence on the overall performance of the coating, and giving it excellent strippability; on the other hand, a core-shell emulsion polymerization method is used to introduce a pre-crosslinked monomer N,N-methylenebisacrylamide into the core phase to crosslink the acrylate polymer chain and effectively improve its mechanical properties, while double-bond modified silicone oil is introduced into the shell phase to utilize its long molecular chain to physically entangle with the polyacrylate molecular chain, thereby enhancing the interaction between the latex particles and the density of the emulsion film, and also improving its mechanical properties.

[0037] In one embodiment of the present disclosure, in step S101, the molar ratio of glycidyl methacrylate to the amino-terminated silicone oil is (1-2): 1. The amine value of the amino-terminated silicone oil is 0.15-0.3 mL·1N HCl / g.

[0038] In one embodiment of the present disclosure, the vinyl monomer in step S102 is a mixture of methyl methacrylate and butyl acrylate, and the mass ratio of methyl methacrylate to butyl acrylate is 1:(0.8-1.5).

[0039] In one embodiment of the present disclosure, when the double bond modified silicone oil is dispersed in the first monomer in step S102, the mass ratio of the double bond modified silicone oil to the vinyl monomer is (1-2):200.

[0040] In one embodiment of the present disclosure, the emulsifier in step S103 is a mixture of sodium dodecyl sulfate and OP-10, the mass ratio of sodium dodecyl sulfate to OP-10 is 2:1, and the amount of sodium dodecyl sulfate and OP-10 is 1-4% of the mass of the vinyl monomer.

[0041] In one embodiment of the present disclosure, the crosslinking monomer in step S103 is N,N-methylenebisacrylamide, and the amount of N,N-methylenebisacrylamide is 0.5-1.5% of the mass of the vinyl monomer. The crosslinking monomer aqueous solution is N,N-methylenebisacrylamide aqueous solution, and its concentration is 3-7%.

[0042] In one embodiment of the present disclosure, in step S104, the pre-emulsion, the cross-linking monomer aqueous solution and the first ammonium persulfate aqueous solution are added to the reactor to form a core phase emulsion. The specific process is: first, the pre-emulsion is added to the reactor and the temperature is raised to 75° C., and then the cross-linking monomer aqueous solution and the first ammonium persulfate aqueous solution are simultaneously added dropwise into the pre-emulsion within 1 hour, and the reaction is kept warm for 2 hours to form a core phase emulsion.

[0043] In one embodiment of the present disclosure, in step S105, the third monomer and the second ammonium persulfate aqueous solution are added dropwise into the core phase emulsion to form a core-shell emulsion. The specific process is: the third monomer and the second ammonium persulfate aqueous solution are added dropwise into the core phase emulsion at the same time within 1 hour, and the reaction is kept warm for 2 hours to form the core-shell emulsion.

[0044] It should be noted that the mass ratio of ammonium persulfate in the first ammonium persulfate aqueous solution and the second ammonium persulfate aqueous solution is the same, and the mass of ammonium persulfate is 2-3% of the mass of the vinyl monomer. Then, during preparation, an ammonium persulfate aqueous solution with the above mass ratio can be prepared first, and then divided into the first ammonium persulfate aqueous solution and the second ammonium persulfate aqueous solution, and the amount of the first ammonium persulfate aqueous solution and the second ammonium persulfate aqueous solution is 2:1.

[0045] Example 1

[0046] (1) 0.01 mol of glycidyl methacrylate, 0.01 mol of amino-terminated silicone oil with an amine value of 0.15, and 0.5 g of clean sodium flakes were added to a single-mouth bottle, stirred and reacted for 12 h at room temperature in the dark, and filtered to obtain double-bond modified silicone oil.

[0047] (2) Weigh 33.34 g of methyl methacrylate and 26.66 g of butyl acrylate and mix them. Divide the mixed monomer into two parts in a ratio of 1:1, which are respectively referred to as the second monomer and the first monomer. Disperse 0.6 g of double bond-modified silicone oil in the first monomer to obtain the third monomer.

[0048] (3) A 250 mL reactor equipped with a stirring and reflux device was heated to 75° C. The second monomer, 1.2 g of sodium dodecyl sulfate, 0.6 g of OP-10 and 30 g of water were ultrasonically emulsified to prepare a pre-emulsion. Within 1 hour, 6 g of a 5% aqueous solution of N,N-methylenebisacrylamide and 30 g of a 3.34% aqueous solution of ammonium persulfate were simultaneously added dropwise into the reactor. The reaction was kept warm for 2 hours to form a core phase emulsion.

[0049] (4) The remaining 15 g of 3.34% ammonium persulfate aqueous solution and the third monomer were simultaneously added dropwise into the reactor within 1 hour, and the reaction was kept warm for 2 hours to form a core-shell emulsion. The emulsion was cooled naturally, the pH was adjusted to 7-8 with ammonia water, and the material was filtered out.

[0050] (5) Take 60 parts of the product emulsion, add 3 parts of calcium carbonate stripping agent, 0.6 parts of silica filler, 10 parts of sepiolite filler, 0.3 parts of defoamer, and 0.3 parts of thickener in sequence while stirring, and mix and compound to prepare a water-based peelable coating. Spray the coating on the tinplate sheet, and test the peel strength and tensile strength after the coating is completely dry.

[0051] Example 2

[0052] (1) 0.01 mol of glycidyl methacrylate, 0.01 mol of amino-terminated silicone oil with an amine value of 0.2, and 0.5 g of clean sodium flakes were added to a single-mouth bottle, stirred and reacted for 12 h at room temperature in the dark, and filtered to obtain double-bond modified silicone oil.

[0053] (2) Weigh 50 g of methyl methacrylate and 50 g of butyl acrylate, mix them, and divide them into two parts in a ratio of 1:1, which are respectively referred to as the second monomer and the first monomer. Disperse 0.5 g of double bond-modified silicone oil in the first monomer to obtain the third monomer.

[0054] (3) A 500 mL reactor equipped with a stirring and reflux device was heated to 75° C. The second monomer, 0.67 g of sodium dodecyl sulfate, 0.33 g of OP-10 and 50 g of water were ultrasonically emulsified to prepare a pre-emulsion. Within 1 hour, 20 g of a 3% aqueous solution of N,N-methylenebisacrylamide and 50 g of a 2.22% aqueous solution of ammonium persulfate were simultaneously added dropwise into the reactor. The reaction was kept warm for 2 hours to form a core phase emulsion.

[0055] (4) The remaining 25 g of 2.22% ammonium persulfate aqueous solution and the third monomer were simultaneously added dropwise into the reactor within 1 hour, and the reaction was kept warm for 2 hours to form a core-shell emulsion. The emulsion was cooled naturally, the pH was adjusted to 7-8 with ammonia water, and the material was filtered out.

[0056] (5) According to the same formula as in Example 1, the product emulsion was prepared into a water-based peelable coating, and the coating was sprayed on a tinplate sheet. After the coating was completely dry, the peel strength and tensile strength were tested.

[0057] Example 3

[0058] (1) 0.02 mol of glycidyl methacrylate, 0.01 mol of amino-terminated silicone oil with an amine value of 0.3, and 0.5 g of clean sodium flakes were added to a single-necked bottle, stirred and reacted for 12 h at room temperature in the dark, and filtered to obtain double-bond modified silicone oil.

[0059] (2) Weigh 40 g of methyl methacrylate and 60 g of butyl acrylate, mix them, and divide them into two parts in a ratio of 1:1, which are respectively referred to as the second monomer and the first monomer. Disperse 0.75 g of double bond-modified silicone oil in the first monomer to obtain the third monomer.

[0060] (3) A 500 mL reactor equipped with a stirring and reflux device was heated to 75° C. The second monomer, 2.67 g of sodium dodecyl sulfate, 1.33 g of OP-10 and 50 g of water were ultrasonically emulsified to prepare a pre-emulsion. Within 1 hour, 21.4 g of a 7% aqueous solution of N,N-methylenebisacrylamide and 50 g of a 3.34% aqueous solution of ammonium persulfate were simultaneously added dropwise into the reactor. The reaction was kept warm for 2 hours to form a core phase emulsion.

[0061] (4) The remaining 25 g of 3.34% ammonium persulfate aqueous solution and the third monomer were simultaneously added dropwise into the reactor within 1 hour, and the reaction was kept warm for 2 hours to form a core-shell emulsion. The emulsion was cooled naturally, the pH was adjusted to 7-8 with ammonia water, and the material was filtered out.

[0062] (5) According to the same formula as in Example 1, the product emulsion was prepared into a water-based peelable coating, and the coating was sprayed on a tinplate sheet. After the coating was completely dry, the peel strength and tensile strength were tested.

[0063] The present disclosure also provides comparative examples.

[0064] Comparative Example 1

[0065] (1) Weigh 33.34 g of methyl methacrylate and 26.66 g of butyl acrylate, mix them, and divide them into two parts in a ratio of 1:1, which are respectively recorded as the second monomer and the first monomer.

[0066] (2) A 250 mL reactor equipped with a stirring and reflux device was heated to 75° C. The second monomer, 1.2 g of sodium dodecyl sulfate, 0.6 g of OP-10 and 30 g of water were ultrasonically emulsified to prepare a pre-emulsion. Within 1 hour, 6 g of a 5% aqueous solution of N,N-methylenebisacrylamide and 30 g of a 3.34% aqueous solution of ammonium persulfate were simultaneously added dropwise into the reactor. The reaction was kept warm for 2 hours to form a core phase emulsion.

[0067] (3) The remaining 15 g of 3.34% ammonium persulfate aqueous solution and the third monomer were simultaneously added dropwise into the reactor within 1 hour, and the reaction was kept warm for 2 hours to form a core-shell emulsion. The emulsion was cooled naturally, the pH was adjusted to 7-8 with ammonia water, and the material was filtered out.

[0068] (4) According to the same formula as in Example 1, the product emulsion was prepared into a water-based peelable coating, and the coating was sprayed on a tinplate sheet. After the coating was completely dry, the peel strength and tensile strength were tested.

[0069] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not contain double-bond modified silicone oil, and the other contents remain unchanged.

[0070] Comparative Example 2

[0071] In Comparative Example 2, according to the process formula of Comparative Example 1, the amount of calcium carbonate stripping agent in step (4) was changed to 6 parts, and the other contents remained unchanged.

[0072] The mechanical properties and peel strength of the coatings prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were tested using a universal tensile testing machine. The results are shown in Table 1:

[0073] Table 1 Comparison of properties of the strippable emulsions prepared in the examples and comparative examples

[0074]

[0075] From the perspective of mechanical properties, it can be seen from Comparative Examples 1 and 2 in Table 1 that when the amount of calcium carbonate is doubled, the tensile strength drops sharply by 60%, indicating that too much calcium carbonate is very detrimental to the mechanical properties of the coating.

[0076] From the comparison of Examples 1 to 3 with Comparative Example 1 in Table 1, it can be seen that the introduction of silicone oil slightly reduces the mechanical properties of the coating. As the silicone oil content increases, the tensile strength of the coating decreases continuously. When the silicone oil content is 1%, the tensile strength decreases the most, reaching 21%.

[0077] Therefore, increasing the amount of calcium carbonate stripping agent and silicone oil will reduce the tensile strength, but in comparison, increasing the amount of silicone oil in the present disclosure has a smaller negative impact on the mechanical strength of the coating.

[0078] From the perspective of peeling strength, it can be seen from Table 1 that, taking Comparative Example 1 as the control group, when the amount of calcium carbonate in Comparative Example 2 was doubled, the peeling strength of the coating decreased by 32%.

[0079] In Example 2, only 0.5% silicone oil was introduced, and the coating peel strength dropped sharply by 43%. The amount of silicone oil was further increased, and in Example 3, the amount of silicone oil was 0.75%, and the coating peel strength dropped by 51%. In Example 1, the amount of silicone oil was 1%, and the coating peel strength dropped by 58%.

[0080] This also shows that the introduction of silicone oil in the present disclosure can significantly reduce the peel strength of the coating and improve its strippability, and the effect is far better than adding calcium carbonate as a stripping aid.

[0081] Figure 2 The transmission electron microscope image of the core-shell structure strippable emulsion prepared by the exemplary embodiment 1 of the present disclosure is shown. The strippable emulsion includes a shell layer 201 of the core-shell emulsion and a core layer 202 of the core-shell emulsion, and the core-shell structure latex particles in the strippable emulsion contain an N,N-methylenebisacrylamide cross-linked network in the core 202 and a low-polarity silicone oil segment in the shell 201.

[0082] Based on the above method, the present invention, on the one hand, modifies silicone oil by covalent grafting reaction of epoxy group of glycidyl methacrylate with terminal amino silicone oil, so as to graft active double bonds onto silicone oil molecules, and introduces low-polarity silicone oil molecules into the molecular side chains of polyacrylate by in-situ core-shell emulsion polymerization, thereby reducing the overall polarity of polyacrylate molecules and weakening their intrinsic adhesion, thereby reducing the amount of release agent used and avoiding the adverse effect of adding too much release agent on mechanical properties.

[0083] On the other hand, core-shell structured latex particles containing an N,N-methylenebisacrylamide cross-linked network in the core and low-polarity silicone oil segments in the shell were prepared by core-shell emulsion polymerization. This not only improved the mechanical properties of the emulsion itself, but also reduced the polarity at the molecular level, effectively improving its strippability.

[0084] The water-based strippable coating prepared by using the strippable emulsion has better mechanical properties and strippable properties.

[0085] Through the above embodiments, the purpose of the present invention is fully and effectively achieved. Those skilled in the art can understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Although the present invention has been described with respect to the most practical and preferred embodiments currently considered, it should be understood that the present invention is not limited to the disclosed embodiments, and any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

[0086] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. The present disclosure is intended to cover any variations, uses or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not disclosed in the present disclosure.

[0087] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for preparing a strippable emulsion, characterized in that: include: Glycidyl methacrylate, amino-terminated silicone oil and sodium flakes are reacted under stirring at room temperature in the dark, and filtered to obtain double-bond modified silicone oil; Splitting the vinyl monomer into a first monomer and a second monomer, and dispersing the double bond modified silicone oil in the first monomer to obtain a third monomer; preparing a pre-emulsion by ultrasonic emulsification of the second monomer, the emulsifier and water, and adding the pre-emulsion, the cross-linking monomer aqueous solution and the first ammonium persulfate aqueous solution into a reaction kettle to form a core phase emulsion; adding the third monomer and the second aqueous ammonium persulfate solution dropwise into the core phase emulsion to form a core-shell emulsion; The core-shell emulsion is naturally cooled, the pH value is adjusted to 7-8 with aqueous ammonia, and the strippable emulsion is obtained by filtration.

2. The method for preparing a strippable emulsion according to claim 1, characterized in that: The molar ratio of the glycidyl methacrylate to the amino-terminated silicone oil is (1-2):

1.

3. The method for preparing a strippable emulsion according to claim 1, characterized in that: The amine value of the amino-terminated silicone oil is 0.15-0.3 mL·1N HCl / g.

4. The method for preparing a strippable emulsion according to claim 1, characterized in that: The vinyl monomer is a mixture of methyl methacrylate and butyl acrylate; the mass ratio of the methyl methacrylate to the butyl acrylate is 1:(0.8-1.5).

5. The method for preparing a strippable emulsion according to claim 1, characterized in that: The mass ratio of the double bond modified silicone oil to the vinyl monomer is (1-2):

200.

6. The method for preparing a strippable emulsion according to claim 1, characterized in that: The emulsifier is a mixture of sodium dodecyl sulfate and OP-10; the mass ratio of the sodium dodecyl sulfate to the OP-10 is 2:1; the amount of the sodium dodecyl sulfate and the OP-10 is 1-4% of the mass of the vinyl monomer.

7. The method for preparing a strippable emulsion according to claim 1, characterized in that: The crosslinking monomer is N,N-methylenebisacrylamide, and the amount of the N,N-methylenebisacrylamide is 0.5-1.5% of the mass of the vinyl monomer; the crosslinking monomer aqueous solution is N,N-methylenebisacrylamide aqueous solution, and the concentration of the N,N-methylenebisacrylamide aqueous solution is 3-7%.

8. The method for preparing a strippable emulsion according to claim 1, characterized in that: The mass proportion of ammonium persulfate in the first ammonium persulfate aqueous solution and the second ammonium persulfate aqueous solution is the same, and the mass of the ammonium persulfate is 2-3% of the mass of the vinyl monomer.

9. The method for preparing a strippable emulsion according to claim 1, characterized in that: The pre-emulsion, the cross-linking monomer aqueous solution and the ammonium persulfate aqueous solution are added into a reaction kettle to form a core phase emulsion, comprising: Add the pre-emulsion into the reactor and heat it to 75°C; The crosslinking monomer aqueous solution and the ammonium persulfate aqueous solution are simultaneously added dropwise into the pre-emulsified liquid within 1 hour, and the mixture is kept warm for 2 hours to form the core phase emulsion.

10. The method for preparing a strippable emulsion according to claim 1, characterized in that: The step of dropwise adding the third monomer and the second aqueous ammonium persulfate solution into the core phase emulsion to form a core-shell emulsion comprises: The third monomer and the second aqueous ammonium persulfate solution are simultaneously added dropwise into the core phase emulsion within 1 hour, and the reaction is kept warm for 2 hours to form the core-shell emulsion.

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