A method for preparing an acrylate protective film

Abstract

This invention discloses a method for preparing an acrylic protective film in the field of pressure-sensitive adhesive technology. The steps are as follows: S1, acid-free acrylic pressure-sensitive adhesive, HDI trimer curing agent, and self-made catalyst are mixed evenly in a mass ratio of 10:0.75-1.25:0.75-1.25; S2, then evenly coated on a 50μm transparent PET substrate, baked at 140℃ for 1 min, and then a release film is attached. The dry adhesive thickness is 10μm, thus obtaining the acrylic protective film. The acid-free acrylic pressure-sensitive adhesive prepared by this invention, combined with HDI trimer curing agent and self-made catalyst, can achieve rapid curing of acrylic pressure-sensitive adhesive without affecting the activation period of acrylic pressure-sensitive adhesive. It does not require the attachment of a release film, and the film layer can be directly attached after coating, thus achieving direct coating and direct removal of the coating process.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive adhesive technology, specifically to a method for preparing an acrylate protective film. Background Technology

[0002] With the rapid development of the 3C electronics industry, the demand for protective films used in the production process and on the shipped surface of 3C electronic products is also increasing. Commonly used protective films consist of a film material (PET, BOPP, PE, etc.) and an adhesive layer. Depending on the adhesive material, protective films can be classified as acrylic protective films, silicone protective films, and polyurethane protective films. Among these, acrylic protective films are widely used in the 3C electronics industry due to their stable performance, easily adjustable adhesion, and excellent adhesion and weather resistance.

[0003] Currently, most acrylic protective films use acrylic pressure-sensitive adhesives combined with isocyanate curing agents during the coating process. After coating, a release film needs to be laminated for post-curing to achieve the target adhesion, which affects delivery speed and occupies more warehouse resources. Because most acrylic pressure-sensitive adhesives used in protective films on the market are acid-containing adhesives, they can only be used with relatively low-activity isocyanate curing agents such as TDI adducts and IPDI trimers. Using highly active HDI trimers results in a shorter activation period for the acrylic pressure-sensitive adhesive, affecting its coating performance. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] Therefore, the object of the present invention is to provide a method for preparing an acrylate protective film to solve the problems mentioned in the background art.

[0006] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0007] A method for preparing an acrylate protective film, comprising the following steps:

[0008] S1. Mix the acid-free acrylic pressure-sensitive adhesive, HDI trimer curing agent, and self-made catalyst evenly in a mass ratio of 10:0.75-1.25:0.75-1.25;

[0009] S2. Then, the adhesive is evenly coated onto a 50μm transparent PET substrate, baked at 140℃ for 1 minute, and then the release film is attached. The thickness of the dry adhesive coating is 10μm, thus obtaining the acrylic protective film.

[0010] The preparation method of the self-made catalyst is as follows:

[0011] Weigh out 4-5% toluene, 84-88% glacial acetic acid, and 8-12% catalyst stock solution by mass ratio;

[0012] The toluene, glacial acetic acid, and catalyst stock solution weighed above were respectively added into a 500mL three-necked flask equipped with a stirrer, and the mixture was stirred thoroughly and evenly to obtain the self-made catalyst.

[0013] The catalyst stock solution is one or more of bismuth isooctanoate, bismuth neodecanoate, zinc isooctanoate, zinc neodecanoate, stannous octanoate, and dibutyltin dilaurate.

[0014] In a preferred embodiment of the method for preparing an acrylate protective film according to the present invention, the method for preparing the acid-free acrylate pressure-sensitive adhesive is as follows:

[0015] Weigh out 34-38% soft monomer, 1-3% hard monomer, 1-2% functional monomer, 0.04-0.06% initiator, and 55-65% solvent by mass ratio.

[0016] Mix all soft monomers, hard monomers, functional monomers and 30-35% of the total amount of the above initiators to obtain mixed monomers;

[0017] Add 40-44% of the total amount of the above solvent to the reaction vessel, heat to the solvent stable reflux temperature of 75-85℃, and then add the mixed monomer dropwise to the reaction vessel at the solvent reflux temperature for 2-4 hours. After the mixed monomer is added, keep the reaction at the solvent reflux temperature for 2-4 hours.

[0018] The remaining initiator was dissolved in a portion of the solvent in three separate portions and then added to the reaction vessel. After each addition, the reaction was maintained at the solvent reflux temperature for 0.5-3 hours.

[0019] After the reaction is complete, the temperature is lowered to below 50°C. The remaining solvent is then added and stirred until homogeneous to obtain the acid-free acrylate pressure-sensitive adhesive.

[0020] In a preferred embodiment of the method for preparing an acrylate protective film according to the present invention, the soft monomer is one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

[0021] In a preferred embodiment of the method for preparing an acrylate protective film according to the present invention, the hard monomer is one or more of methyl acrylate, methyl methacrylate, and vinyl acetate.

[0022] In a preferred embodiment of the method for preparing an acrylate protective film according to the present invention, the functional monomer is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate.

[0023] In a preferred embodiment of the method for preparing an acrylate protective film according to the present invention, the initiator is one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, and benzoyl peroxide.

[0024] In a preferred embodiment of the method for preparing an acrylate protective film according to the present invention, the solvent is one or both of ethyl acetate and toluene.

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

[0026] 1. The present invention provides an acid-free acrylic pressure-sensitive adhesive that, when combined with an HDI trimer curing agent and a self-made catalyst, enables rapid curing of the acrylic pressure-sensitive adhesive without affecting its activation period. It eliminates the need for a release film; the film layer can be directly bonded after coating, allowing for direct coating and removal. This eliminates the need for a release film, reducing the cost of release materials, and also eliminates the need for post-curing, enabling timely delivery without consuming excessive time and warehousing resources.

[0027] 2. The reason why rapid curing can be achieved is that, on the one hand, the HDI trimer curing agent has high reactivity, and on the other hand, the self-made catalyst can efficiently catalyze the reaction between the HDI trimer curing agent and the acrylic pressure-sensitive adhesive, further improving the curing speed, thereby achieving rapid curing of the pressure-sensitive adhesive and enabling direct application and collection. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0029] Figure 1 Performance parameter test diagrams of the acrylate protective films prepared in Examples 1-4 and Comparative Examples 1-2 provided by the present invention. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] Example 1

[0032] S1. Preparation of acid-free acrylate pressure-sensitive adhesive: 152.7g of isooctyl acrylate, 28.3g of ethyl acrylate, 12.2g of vinyl acetate, 6.8g of hydroxyethyl acrylate, and 0.08g of azobisisobutyronitrile were added to a 250mL beaker and stirred until homogeneous to obtain a mixed monomer.

[0033] 124.5 g of ethyl acetate was added to a 1 L four-necked flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was heated in a constant temperature water bath until the solvent was stable under reflux (temperature 78℃). At the solvent reflux temperature, the mixed monomers were added dropwise to the reaction flask evenly using a constant pressure dropping funnel. The addition took 2 hours. After the addition was completed, the reaction was kept at the solvent reflux temperature for 2 hours.

[0034] The first initiator was added by completely dissolving 0.04 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 0.5 h. The second initiator was added by completely dissolving 0.04 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 0.5 h. The third initiator was added by completely dissolving 0.08 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 2 h.

[0035] After the reaction is complete, the temperature is lowered to below 50°C. Then, 171.5g of ethyl acetate is added and the mixture is stirred thoroughly.

[0036] S2. Preparation of homemade catalyst: 16g of toluene, 299g of glacial acetic acid, 12g of bismuth isooctanoate and 23g of bismuth neodecanoate were respectively put into a 500mL three-necked flask equipped with a stirrer and stirred thoroughly for 10min to obtain the homemade catalyst.

[0037] S3. Preparation of acrylate protective film: Mix 20g of the acid-free acrylate pressure-sensitive adhesive prepared above with 2g of curing agent HT-100 (HDI trimer) and 2g of self-made catalyst evenly. Use a wire bar coater to evenly coat the acrylate pressure-sensitive adhesive onto a 50μm PET film. After baking at 140℃ for 1min, attach the release film to obtain an acrylate protective film with a dry film thickness of 10μm.

[0038] Example 2

[0039] S1. Preparation of acid-free acrylate pressure-sensitive adhesive: 154.8g of isooctyl acrylate, 32.4g of butyl acrylate, 13.6g of methyl acrylate, 7.5g of hydroxyethyl methacrylate, and 0.1g of azobisisovalerate were added to a 250mL beaker and stirred until homogeneous to obtain a mixed monomer.

[0040] 96.4 g of ethyl acetate and 28.1 g of toluene were added to a 1 L four-necked flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was heated in a constant temperature water bath until the solvent was stable under reflux (temperature 80℃). At the solvent reflux temperature, the mixed monomers were added dropwise to the reaction flask evenly using a constant pressure dropping funnel. The addition took 3 hours. After the addition was completed, the reaction was kept at the solvent reflux temperature for 2 hours.

[0041] First initiator addition: Dissolve 0.06 g of azobisisovalerate in 1.2 g of ethyl acetate completely and add to the reaction flask. Incubate at reflux for 1 h. Second initiator addition: Dissolve 0.06 g of azobisisovalerate in 1.2 g of ethyl acetate completely and add to the reaction flask. Incubate at reflux for 1 h. Third initiator addition: Dissolve 0.1 g of azobisisovalerate in 1.5 g of ethyl acetate completely and add to the reaction flask. Incubate at reflux for 2 h.

[0042] After the reaction is complete, the temperature is lowered to below 50°C. Then, 180.6g of ethyl acetate is added and the mixture is stirred thoroughly.

[0043] S2. Preparation of homemade catalyst: 14g of toluene, 305g of glacial acetic acid, 10g of zinc isooctanoate and 20g of zinc neodecanoate were respectively put into a 500mL three-necked flask equipped with a stirrer and stirred thoroughly for 10min to obtain the homemade catalyst.

[0044] S3. Preparation of acrylate protective film: Mix 20g of the acid-free acrylate pressure-sensitive adhesive prepared above with 1.5g of curing agent N3390 (HDI trimer) and 2.5g of self-made catalyst evenly. Use a wire bar coater to evenly coat the acrylate pressure-sensitive adhesive onto a 50μm PET film. After baking at 140℃ for 1min, attach the release film to obtain an acrylate protective film with a dry film thickness of 10μm.

[0045] Example 3

[0046] S1. Preparation of acid-free acrylate pressure-sensitive adhesive: 148.6g of isooctyl acrylate, 25.7g of butyl acrylate, 15.6g of ethyl acrylate, 10.8g of methyl methacrylate, 5.8g of hydroxypropyl acrylate, and 0.09g of azobisisobutyronitrile were added to a 250mL beaker and stirred until homogeneous to obtain a mixed monomer.

[0047] 128.6 g of ethyl acetate was added to a 1 L four-necked flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was heated in a constant temperature water bath until the solvent was stable under reflux (temperature 78 °C). At the solvent reflux temperature, the mixed monomers were added dropwise to the reaction flask using a constant pressure dropping funnel. The addition took 2 hours. After the addition was completed, the reaction was kept at the solvent reflux temperature for 3 hours.

[0048] The first initiator was added by completely dissolving 0.08 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux for 0.5 h. The second initiator was added by completely dissolving 0.08 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux for 0.5 h. The third initiator was added by completely dissolving 0.09 g of azobisisobutyronitrile in 1.5 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux for 3 h.

[0049] After the reaction is complete, the temperature is lowered to below 50°C. Then, 178.9g of toluene is added and the mixture is stirred thoroughly.

[0050] S2. Preparation of homemade catalyst: 17g of toluene, 315g of glacial acetic acid, 25g of stannous octoate and 15g of dibutyltin dilaurate were respectively put into a 500mL three-necked flask equipped with a stirrer and stirred thoroughly for 10min to obtain the homemade catalyst.

[0051] S3. Preparation of acrylate protective film: Mix 20g of the acid-free acrylate pressure-sensitive adhesive prepared above with 2g of curing agent HT-100 (HDI trimer) and 1.5g of self-made catalyst evenly. Use a wire bar coater to evenly coat the acrylate pressure-sensitive adhesive onto a 50μm PET film. After baking at 140℃ for 1min, attach the release film to obtain an acrylate protective film with a dry film thickness of 10μm.

[0052] Example 4

[0053] S1. Preparation of acid-free acrylate pressure-sensitive adhesive: 163.5g of butyl acrylate, 24.8g of ethyl acrylate, 11.6g of vinyl acetate, 7.2g of hydroxybutyl acrylate, and 0.07g of benzoyl peroxide were added to a 250mL beaker and stirred until homogeneous to obtain a mixed monomer.

[0054] Add 85.7g of ethyl acetate and 39.6g of toluene to a 1L four-necked flask equipped with a stirrer, thermometer, and reflux condenser. Heat the mixture in a constant temperature water bath until the solvent is stable under reflux (temperature 81℃). Under the solvent reflux temperature, add the mixed monomers dropwise evenly to the reaction flask using a constant pressure dropping funnel. The dropwise addition takes 3 hours. After the dropwise addition is completed, keep the reaction at the solvent reflux temperature for 3 hours.

[0055] First initiator addition: Dissolve 0.05 g of benzoyl peroxide completely in 1.2 g of toluene and add to the reaction flask. Incubate at reflux for 1 hour. Second initiator addition: Dissolve 0.05 g of benzoyl peroxide completely in 1.2 g of toluene and add to the reaction flask. Incubate at reflux for 1 hour. Third initiator addition: Dissolve 0.07 g of benzoyl peroxide completely in 1.5 g of toluene and add to the reaction flask. Incubate at reflux for 3 hours.

[0056] After the reaction is complete, the temperature is lowered to below 50°C. Then, 178.9g of ethyl acetate is added and the mixture is stirred thoroughly.

[0057] S2. Preparation of homemade catalyst: 19g of toluene, 338g of glacial acetic acid, 28g of bismuth isooctanoate and 17g of dibutyltin dilaurate were respectively put into a 500mL three-necked flask equipped with a stirrer and stirred thoroughly for 10min to obtain the homemade catalyst.

[0058] S3. Preparation of acrylate protective film: Mix 20g of the acid-free acrylate pressure-sensitive adhesive prepared above with 2.5g of curing agent N3390 (HDI trimer) and 2.5g of self-made catalyst evenly. Use a wire bar coater to evenly coat the acrylate pressure-sensitive adhesive onto a 50μm PET film. After baking at 140℃ for 1min, attach the release film to obtain an acrylate protective film with a dry film thickness of 10μm.

[0059] Comparative Example 1

[0060] S1. Preparation of acid-free acrylate pressure-sensitive adhesive: 152.7g of isooctyl acrylate, 28.3g of ethyl acrylate, 12.2g of vinyl acetate, 6.8g of hydroxyethyl acrylate, and 0.08g of azobisisobutyronitrile were added to a 250mL beaker and stirred until homogeneous to obtain a mixed monomer.

[0061] 124.5 g of ethyl acetate was added to a 1 L four-necked flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was heated in a constant temperature water bath until the solvent was stable under reflux (temperature 78℃). At the solvent reflux temperature, the mixed monomers were added dropwise to the reaction flask evenly using a constant pressure dropping funnel. The addition took 2 hours. After the addition was completed, the reaction was kept at the solvent reflux temperature for 2 hours.

[0062] First initiator was added by completely dissolving 0.04 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 0.5 h. Second initiator was added by completely dissolving 0.04 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 0.5 h. Third initiator was added by completely dissolving 0.08 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 2 h.

[0063] After the reaction is complete, the temperature is lowered to below 50°C. Then, 171.5g of ethyl acetate is added and the mixture is stirred thoroughly.

[0064] S2. Preparation of acrylate protective film: Mix 20g of the acid-free acrylate pressure-sensitive adhesive prepared above with 2g of curing agent HT-100 (HDI trimer), and coat the acrylate pressure-sensitive adhesive evenly on a 50μm PET film using a wire bar coater. After baking at 140℃ for 1min, a release film is attached to obtain an acrylate protective film with a dry film thickness of 10μm.

[0065] Comparative Example 2

[0066] S1. Preparation of acid-containing acrylate pressure-sensitive adhesive: 152.7g of isooctyl acrylate, 28.3g of ethyl acrylate, 12.2g of vinyl acetate, 6.8g of hydroxyethyl acrylate, 4.2g of acrylic acid, and 0.08g of azobisisobutyronitrile were added to a 250mL beaker and stirred until homogeneous to obtain a mixed monomer.

[0067] 124.5 g of ethyl acetate was added to a 1 L four-necked flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was heated in a constant temperature water bath until the solvent was stable under reflux (temperature 78℃). At the solvent reflux temperature, the mixed monomers were added dropwise to the reaction flask evenly using a constant pressure dropping funnel. The addition took 2 hours. After the addition was completed, the reaction was kept at the solvent reflux temperature for 2 hours.

[0068] First initiator was added by completely dissolving 0.04 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 0.5 h. Second initiator was added by completely dissolving 0.04 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 0.5 h. Third initiator was added by completely dissolving 0.08 g of azobisisobutyronitrile in 1.2 g of ethyl acetate and then adding it to the reaction flask. The reaction was maintained at reflux temperature for 2 h.

[0069] After the reaction is complete, the temperature is lowered to below 50°C. Then, 171.5g of ethyl acetate is added and the mixture is stirred thoroughly.

[0070] S2. Preparation of acrylate protective film: Mix 20g of the acid-containing acrylate pressure-sensitive adhesive prepared above with 2g of curing agent HT-100 (HDI trimer), and coat the acrylate pressure-sensitive adhesive evenly on a 50μm PET film using a wire bar coater. After baking at 140℃ for 1min, a release film is attached to obtain an acrylate protective film with a dry film thickness of 10μm.

[0071] like Figure 1As shown in the test results, the acid-free acrylic pressure-sensitive adhesive prepared in this invention, when mixed with HDI trimer curing agent and a self-made catalyst, exhibits an activation period of >8 hours, which does not affect actual coating applications. Furthermore, by comparing the peel strength of the acrylic protective film before and after curing, the suitability of the acrylic pressure-sensitive adhesive of this invention for direct coating and collection without post-curing was examined. The peel strength before curing indicates that the acrylic pressure-sensitive adhesive of this invention cures quickly, achieving a low basis weight without curing, thus meeting the requirements for the protective film. Simultaneously, the peel strength after curing shows no significant decrease, indicating that the acrylic pressure-sensitive adhesive cures completely without further post-curing, thereby improving delivery efficiency.

[0072] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing an acrylate protective film, characterized in that, The steps are as follows: S1. Mix the acid-free acrylic pressure-sensitive adhesive, HDI trimer curing agent, and self-made catalyst evenly in a mass ratio of 10:0.75-1.25:0.75-1.25; S2. Then, the adhesive is evenly coated onto a 50μm transparent PET substrate, baked at 140℃ for 1 minute, and then the release film is attached. The thickness of the dry adhesive coating is 10μm, thus obtaining the acrylic protective film. The preparation method of the self-made catalyst is as follows: Weigh out 4-5% toluene, 84-88% glacial acetic acid, and 8-12% catalyst stock solution by mass ratio; The toluene, glacial acetic acid, and catalyst stock solution weighed above were respectively added into a 500mL three-necked flask equipped with a stirrer, and the mixture was stirred thoroughly and evenly to obtain the self-made catalyst. The catalyst stock solution is one or more of bismuth isooctanoate, bismuth neodecanoate, zinc isooctanoate, zinc neodecanoate, stannous octanoate, and dibutyltin dilaurate. The preparation method of the acid-free acrylate pressure-sensitive adhesive is as follows: Weigh out 34-38% soft monomer, 1-3% hard monomer, 1-2% functional monomer, 0.04-0.06% initiator, and 55-65% solvent by mass ratio. Mix all soft monomers, hard monomers, functional monomers and 30-35% of the total amount of the above initiators to obtain mixed monomers; Add 40-44% of the total amount of the above solvent to the reaction vessel, heat to the solvent stable reflux temperature of 75-85℃, and then add the mixed monomer dropwise to the reaction vessel at the solvent reflux temperature for 2-4 hours. After the mixed monomer is added, keep the reaction at the solvent reflux temperature for 2-4 hours. The remaining initiator was dissolved in a portion of the solvent in three separate portions and then added to the reaction vessel. After each addition, the reaction was maintained at the solvent reflux temperature for 0.5-3 hours. After the reaction is complete, the temperature is lowered to below 50°C. The remaining solvent is then added and stirred until homogeneous to obtain the acid-free acrylate pressure-sensitive adhesive.

2. The method for preparing an acrylate protective film according to claim 1, characterized in that, The soft monomer is one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

3. The method for preparing an acrylate protective film according to claim 1, characterized in that, The hard monomer is one or more of methyl acrylate, methyl methacrylate, and vinyl acetate.

4. The method for preparing an acrylate protective film according to claim 1, characterized in that, The functional monomer is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate.

5. The method for preparing an acrylate protective film according to claim 1, characterized in that, The initiator is one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, and benzoyl peroxide.

6. The method for preparing an acrylate protective film according to claim 1, characterized in that, The solvent is one or both of ethyl acetate and toluene.

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