High-solid low-viscosity acrylic pressure-sensitive adhesive and preparation method thereof

Abstract

The invention discloses a high-solid low-viscosity acrylic pressure-sensitive adhesive and a preparation method thereof.The high-solid low-viscosity acrylic pressure-sensitive adhesive is composed of an acrylic polymer, an initiator, a solvent and a 10% tackifying resin methanol solution. The preparation method comprises the following steps: adding monomers butyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, acrylamide and pentaerythritol triacrylate as well as solvents methanol, toluene and ethyl acetate, heating to 67 DEG C, starting reflux, adding an initiator, reacting for 1 hour after initiation, subsequently supplementing the initiator every 2 hours, supplementing for 3 times, cooling to 50 DEG C, adding a 10% tackifying resin methanol solution, stirring for 30 minutes, and then adding an initiator after reaction for 2 hours. According to the highly low-viscosity acrylic acid pressure-sensitive adhesive and the preparation method thereof, the problem of compatibility between a high-methanol-content system and tackifying resin is solved from the molecular level, and the finally prepared pressure-sensitive adhesive is kept clear and transparent at the normal temperature and the low-temperature environment of-10 DEG C.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive adhesive technology, specifically to a high-solids, low-viscosity acrylic pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Acrylic pressure-sensitive adhesives are widely used in packaging, electronics, building materials, medical, and other fields due to their excellent adhesion, weather resistance, and application adaptability. With increasing demands for environmental protection and construction efficiency in industrial production, high-solids, low-viscosity adhesives have become a key development direction. High solids content reduces volatile organic compound (VOC) emissions, complying with environmental policies; low viscosity meets the needs of convenient operation in coating, laminating, and other processes, improving production efficiency.

[0003] In existing technologies, methanol is used as a solvent in some systems to achieve the performance target of high solids and low viscosity. Methanol has a significant viscosity-reducing advantage, which can make high molecular weight acrylic polymers exhibit low viscosity characteristics suitable for construction. Moreover, compared with traditional solvents such as ethyl acetate and toluene, methanol has a lower raw material cost and has obvious economic advantages in industrial production. Therefore, it is considered one of the preferred solvents for high solids and low viscosity acrylic pressure-sensitive adhesives.

[0004] However, methanol has inherent defects in its molecular structure: its weak polarity and tendency to form hydrogen bonds between molecules mean that when the methanol content in an acrylic pressure-sensitive adhesive system is high, adding tackifying resins to improve adhesive strength (such as 180° peel strength) will result in poor compatibility between methanol and the tackifying resins, leading to a cloudy appearance of the adhesive. This defect severely limits the large-scale application of methanol in high-solids, low-viscosity acrylic pressure-sensitive adhesives. Although methanol has advantages such as good viscosity reduction and low cost, the cloudy appearance cannot meet the requirements for clear adhesive appearance in the electronics and packaging industries, thus restricting the market application scope of related products.

[0005] Therefore, how to improve the compatibility between high methanol content systems and tackifying resins while retaining the viscosity-reducing and cost advantages of methanol, and obtain high-solids, low-viscosity acrylic pressure-sensitive adhesives with clear and transparent appearance and excellent bonding performance, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] 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.

[0007] Therefore, the purpose of this invention is to provide a high-solids, low-viscosity acrylic pressure-sensitive adhesive and its preparation method, so as to solve the problems mentioned in the background art.

[0008] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0009] A high-solids, low-viscosity acrylic pressure-sensitive adhesive, by mass percentage, is composed of 75.6-112.5 parts of acrylic polymer, 0.1-1 parts of initiator, 50-90 parts of solvent, and 125.1-151 parts of 10% tackifying resin methanol solution.

[0010] As a preferred embodiment of the high-solids, low-viscosity acrylic pressure-sensitive adhesive of the present invention, the acrylic polymer is composed of 60-80 parts of butyl acrylate, 5-10 parts of methyl acrylate, 10-20 parts of isooctyl acrylate, 0.5-2 parts of acrylamide, and 0.1-0.5 parts of pentaerythritol triacrylate by mass percentage.

[0011] As a preferred embodiment of the high-solids, low-viscosity acrylic pressure-sensitive adhesive of the present invention, the solvent is composed of 30-50 parts methanol, 10-20 parts toluene, and 10-20 parts ethyl acetate by mass percentage.

[0012] As a preferred embodiment of the high-solids, low-viscosity acrylic pressure-sensitive adhesive of the present invention, the 10% tackifying resin methanol solution is composed of 100 parts of rosin acid, 20-40 parts of pentaerythritol, 0.1-1 parts of catalyst, and 5-10 parts of methanol by mass percentage.

[0013] In a preferred embodiment of the high-solids, low-viscosity acrylic pressure-sensitive adhesive described in this invention, the catalyst is zinc stearate.

[0014] As a preferred embodiment of the high-solids, low-viscosity acrylic pressure-sensitive adhesive of the present invention, the specific preparation steps of the 10% tackifying resin methanol solution are as follows:

[0015] In a pressurized stainless steel reactor equipped with a condenser, thermometer, and stirring device, rosin acid, methanol, and catalyst are added.

[0016] The synthesis reaction was carried out under pressure at 160-170℃ for 2 hours, and then pentaerythritol was added, and the reaction was continued at 160-170℃.

[0017] After reacting for 1 hour, the temperature was gradually increased to 210°C, and the reaction was continued for 4 hours. Then, methanol was added as a solution to prepare a 10% methanol solution.

[0018] A method for preparing a high-solids, low-viscosity acrylic pressure-sensitive adhesive, comprising the following steps:

[0019] S1. In a four-necked flask equipped with a condenser, thermometer, and stirring device, add monomers butyl acrylate, methyl acrylate, isooctyl acrylate, acrylamide, and pentaerythritol triacrylate, as well as solvents methanol, toluene, and ethyl acetate.

[0020] S2. Heat to 67°C, reflux begins, add initiator, react for 1 hour after initiation, then add initiator every 2 hours thereafter, after 3 additions, cool down to 50°C.

[0021] S3. Add 10% tackifying resin methanol solution and stir for 30 minutes to obtain the final high-viscosity low-viscosity acrylic pressure-sensitive adhesive.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention solves the compatibility problem between high methanol content systems and tackifying resins at the molecular level by introducing methanol into the reaction during the preparation stage of the tackifying resin and introducing an amphiphilic structure into the acrylic polymer. The pressure-sensitive adhesive obtained in this invention remains clear and transparent at room temperature and -10°C, and no solvent precipitation occurs after being placed at 50°C. This completely overcomes the core defect of turbid adhesives in existing technologies and meets the needs of fields such as electronics and packaging that have strict requirements for appearance.

[0024] 2. This invention retains the excellent viscosity-reducing effect and low-cost advantage of methanol. While achieving high solids content, it maintains low viscosity of the system, ensuring convenient and efficient construction processes such as coating and lamination. It takes into account both environmental protection and construction efficiency, and reduces the raw material cost of industrial production. Furthermore, through the bridging effect of acrylic polymer, the tackifying resin and methanol system form a stable bond, which fully guarantees the adhesive performance of the pressure-sensitive adhesive. The 180° peel strength is not less than 10.2N / 25mm, which meets the requirements of the industry for adhesive strength. Moreover, the performance does not significantly decrease under high and low temperature environments, making it applicable to a wider range of scenarios. Detailed Implementation

[0025] 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.

[0026] Example 1

[0027] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 70 parts butyl acrylate, 5 parts methyl acrylate, 15 parts isooctyl acrylate, 1 part acrylamide, and 0.2 parts pentaerythritol triacrylate, along with solvents: 40 parts methanol, 15 parts toluene, and 15 parts ethyl acetate. Heat to 67°C until reflux begins, then add 0.2 parts initiator. After initiation, react for 1 hour, then add 0.1 parts initiator every 2 hours for a total of 3 times. Cool to 50°C, add 10% tackifying resin methanol solution, and stir for 30 minutes to obtain the final acrylic pressure-sensitive adhesive.

[0028] The 10% tackifying resin methanol solution was prepared as follows: In a pressurized stainless steel reactor equipped with a condenser, thermometer, and stirring device, 100 parts of rosin acid, 6 parts of methanol, and 0.2 parts of zinc stearate catalyst were added. The pressure was increased to 2 MPa, and the reaction was carried out at 160°C for 2 hours. Then, 30 parts of pentaerythritol were added, and the reaction was continued at 160°C for 1 hour. After that, the temperature was gradually increased to 210°C, and the reaction was continued for 4 hours. Then, methanol was added as a solution to prepare a 10% methanol solution for later use.

[0029] Example 2

[0030] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 75 parts butyl acrylate, 10 parts methyl acrylate, 5 parts isooctyl acrylate, 0.5 parts acrylamide, and 0.2 parts pentaerythritol triacrylate, along with solvents: 50 parts methanol, 10 parts toluene, and 10 parts ethyl acetate. Heat to 67°C until reflux begins, then add 0.2 parts initiator. After initiation, react for 1 hour, then add 0.1 parts initiator every 2 hours for a total of 3 times. After this, cool to 50°C, add a 10% tackifying resin methanol solution, and stir for 30 minutes to obtain the final acrylic pressure-sensitive adhesive.

[0031] The 10% tackifying resin methanol solution was prepared as follows: In a pressurized stainless steel reactor equipped with a condenser, thermometer, and stirring device, 100 parts of rosin acid, 6 parts of methanol, and 0.2 parts of zinc stearate catalyst were added. The pressure was increased to 2 MPa, and the reaction was carried out at 160°C for 2 hours. Then, 30 parts of pentaerythritol were added, and the reaction was continued at 160°C for 1 hour. After that, the temperature was gradually increased to 210°C, and the reaction was continued for 4 hours. Then, methanol was added as a solution to prepare a 10% methanol solution for later use.

[0032] Example 3

[0033] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 50 parts butyl acrylate, 20 parts methyl acrylate, 20 parts isooctyl acrylate, 1.5 parts acrylamide, and 0.3 parts pentaerythritol triacrylate, along with solvents: 45 parts methanol, 20 parts toluene, and 5 parts ethyl acetate. Heat to 67-70°C until reflux begins. Add 0.2 parts initiator and react for 1 hour. Then, add 0.1 parts initiator every 2 hours for a total of 3 times. Cool to approximately 50°C and add a 10% tackifying resin methanol solution. Stir for 30 minutes to obtain the final acrylic pressure-sensitive adhesive.

[0034] Comparative Example 1

[0035] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 70 parts butyl acrylate, 5 parts methyl acrylate, 15 parts isooctyl acrylate, 1 part acrylamide, and 2 parts pentaerythritol triacrylate, along with solvents: 40 parts methanol, 15 parts toluene, and 15 parts ethyl acetate. Heat to 67°C until reflux begins, then add 0.2 parts initiator. After initiation, react for 1 hour, then add 0.1 parts initiator every 2 hours thereafter, repeating this process 3 times. Cool to 50°C, add 10% tackifying resin methanol solution, and stir for 30 minutes to obtain the final acrylic pressure-sensitive adhesive.

[0036] The 10% tackifying resin methanol solution was prepared as follows: In a pressurized stainless steel reactor equipped with a condenser, thermometer, and stirring device, 100 parts of rosin acid, 6 parts of methanol, and 0.2 parts of zinc stearate catalyst were added. The pressure was increased to 2 MPa, and the reaction was carried out at 160°C for 2 hours. Then, 30 parts of pentaerythritol were added, and the reaction was continued at 160°C for 1 hour. After that, the temperature was gradually increased to 210°C, and the reaction was continued for 4 hours. Then, methanol was added as a solution to prepare a 10% methanol solution for later use.

[0037] Comparative Example 2

[0038] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 70 parts butyl acrylate, 5 parts methyl acrylate, 15 parts isooctyl acrylate, 1 part acrylamide, and solvents: 40 parts methanol, 15 parts toluene, and 15 parts ethyl acetate. Heat to 67°C until reflux begins, then add 0.2 parts initiator. After initiation, react for 1 hour, then add 0.1 parts initiator every 2 hours thereafter, repeating this process 3 times. Cool to 50°C, add 10% tackifying resin methanol solution, and stir for 30 minutes to obtain the final acrylic pressure-sensitive adhesive.

[0039] The 10% tackifying resin methanol solution was prepared as follows: In a pressurized stainless steel reactor equipped with a condenser, thermometer, and stirring device, 100 parts of rosin acid, 6 parts of methanol, and 0.2 parts of zinc stearate catalyst were added. The pressure was increased to 2 MPa, and the reaction was carried out at 160°C for 2 hours. Then, 30 parts of pentaerythritol were added, and the reaction was continued at 160°C for 1 hour. After that, the temperature was gradually increased to 210°C, and the reaction was continued for 4 hours. Then, methanol was added as a solution to prepare a 10% methanol solution for later use.

[0040] Comparative Example 3

[0041] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 70 parts butyl acrylate, 5 parts methyl acrylate, 15 parts isooctyl acrylate, 0.2 parts pentaerythritol triacrylate, and solvents: 40 parts methanol, 15 parts toluene, and 15 parts ethyl acetate. Heat to 67°C until reflux begins, then add 0.2 parts initiator. After initiation, react for 1 hour, then add 0.1 parts initiator every 2 hours thereafter, for a total of 3 times. Cool to 50°C, add 10% tackifying resin methanol solution, and stir for 30 minutes to obtain the final high-viscosity acrylic pressure-sensitive adhesive.

[0042] The 10% tackifying resin methanol solution was prepared as follows: In a pressurized stainless steel reactor equipped with a condenser, thermometer, and stirring device, 100 parts of rosin acid, 6 parts of methanol, and 0.2 parts of zinc stearate catalyst were added. The pressure was increased to 2 MPa, and the reaction was carried out at 160°C for 2 hours. Then, 30 parts of pentaerythritol were added, and the reaction was continued at 160°C for 1 hour. After that, the temperature was gradually increased to 210°C, and the reaction was continued for 4 hours. Then, methanol was added as a solution to prepare a 10% methanol solution for later use.

[0043] Comparative Example 4

[0044] In a four-necked flask equipped with a condenser, thermometer, and stirrer, add monomers: 70 parts butyl acrylate, 5 parts methyl acrylate, 15 parts isooctyl acrylate, 1 part acrylamide, and 0.2 parts pentaerythritol triacrylate, along with solvents: 40 parts methanol, 15 parts toluene, and 15 parts ethyl acetate. Heat to 67°C until reflux begins, then add 0.2 parts initiator. After initiation, react for 1 hour, then add 0.1 parts initiator every 2 hours thereafter, repeating this process 3 times. Cool to 50°C, add 10% tackifying resin methanol solution, and stir for 30 minutes to obtain the final high-viscosity acrylic pressure-sensitive adhesive.

[0045] The 10% tackifying resin methanol solution was prepared as follows: 100 parts of rosin acid, 35 parts of pentaerythritol and 0.2 parts of zinc stearate catalyst were added to a pressurized stainless steel reactor equipped with a condenser, thermometer and stirring device. The reaction was carried out at 160℃ for 2 hours. The temperature was then gradually increased to 210℃ and the reaction was continued for 4 hours. Methanol was then added as a solution to prepare a 10% methanol solution for later use.

[0046] The acrylic pressure-sensitive adhesives prepared in Examples 1-3 and Comparative Examples 1-4 were coated and their performance was tested.

[0047] Solubility test: The acrylic pressure-sensitive adhesive prepared in the example was placed in a 250L transparent PET bottle and its appearance was observed to see if it was transparent; then it was placed in a -10℃ cold storage for 2 hours and then removed to see if it was transparent; another 250L transparent PET bottle was placed in a 50℃ oven for 24 hours and then removed and placed at room temperature to observe whether solvent was precipitated in the upper layer.

[0048] Performance Testing: Add 1% propylene glycol diglycidyl ether epoxy curing agent, stir for 10 minutes and set aside. Use a 40µm thick wire rod to evenly coat the adhesive onto a 25µm PET substrate, controlling the final dry film thickness to 20-30µm. Place in a 120℃ forced-air oven and dry for 90-120 seconds. After drying, laminate with a PET release film. After lamination, place in a 40℃ oven for 24 hours to stabilize, and then test the performance at room temperature.

[0049] According to the test of the pressure-sensitive adhesive, the appearance at room temperature is transparent, the appearance at -10℃ is transparent, and the appearance at 50℃ shows whether there is solvent precipitation on the upper layer. The 180° peel strength is 1N / 25mm.

[0050] The test results are shown in Table 1.

[0051] Table 1. Performance test results of acrylic pressure-sensitive adhesives prepared in Examples 1-3 and Comparative Examples 1-4

[0052] Is the appearance transparent at room temperature? Is it transparent at -10℃? At 50℃, is there solvent precipitation on the upper layer? 180° peel force (N / 25mm) Example 1 yes yes no 10.5 Example 2 yes yes no 10.7 Example 3 yes yes no 10.2 Comparative Example 1 yes yes no 5.8 Comparative Example 2 yes no no 9.2 Comparative Example 3 yes yes yes 8.2 Comparative Example 4 no -- -- 9.0

[0053] As shown in Table 1, in Comparative Example 1, although the appearance met the requirements after adding too much pentaerythritol triacrylate, the peel strength was low. In Comparative Example 2, without adding pentaerythritol triacrylate, the compatibility at low temperature was very poor. In Comparative Example 3, without adding acrylamide, solvent precipitation occurred at high temperature, mainly because methanol did not have sufficient binding force with the system, was easily volatilized at high temperature, and was difficult to dissolve into the system after returning to room temperature. In Comparative Example 4, tackifying resin was added, but methanol was not added in advance to participate in the synthesis, and the appearance became cloudy at room temperature after the addition.

[0054] 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 high solids, low viscosity acrylic pressure sensitive adhesive, characterized in that, The acrylic acid polymer is composed of 75.6-112.5 parts of butyl acrylate, 0.1-1 part of initiator, 50-90 parts of solvent, and 125.1-151 parts of 10% tackifying resin methanol solution by mass percentage.

2. The high solid low viscosity acrylic pressure sensitive adhesive according to claim 1, characterized in that, The acrylic acid polymer is composed of 75.6-112.5 parts of butyl acrylate, 0.1-1 part of initiator, 50-90 parts of solvent, and 125.1-151 parts of 10% tackifying resin methanol solution by mass percentage.

3. The high solid low viscosity acrylic pressure sensitive adhesive according to claim 1, wherein, The solvent is composed of 30-50 parts of methanol, 10-20 parts of toluene, and 10-20 parts of ethyl acetate by mass percentage.

4. The high solid low viscosity acrylic pressure sensitive adhesive according to claim 1, wherein, The 10% tackifying resin methanol solution is composed of 100 parts of abietic acid, 20-40 parts of pentaerythritol, 0.1-1 part of catalyst, and 5-10 parts of methanol by mass percentage.

5. The high solid low viscosity acrylic pressure sensitive adhesive according to claim 4, wherein, The catalyst is zinc stearate.

6. The high solid low viscosity acrylic pressure sensitive adhesive according to claim 4, wherein, The 10% tackifying resin methanol solution is prepared according to the following steps: In a pressurizable stainless steel reaction kettle equipped with a condenser, a thermometer, and a stirring device, abietic acid, methanol, and a catalyst are added; Under pressure, the synthesis reaction is carried out at 160-170°C for 2h, then pentaerythritol is added, and the reaction is continued at 160-170°C; After 1h of reaction, the temperature is gradually increased to 210°C, and the reaction is continued for 4h, then methanol is added as a solution to prepare a 10% methanol solution.

7. A method for preparing a high-solids, low-viscosity acrylic pressure-sensitive adhesive as described in claim 2, characterized in that, The steps are as follows: S1, in a four-necked flask equipped with a condenser, a thermometer, and a stirring device, monomers butyl acrylate, methyl acrylate, isooctyl acrylate, acrylamide, and pentaerythritol triacrylate, and solvents methanol, toluene, and ethyl acetate are added; S2, the temperature is increased to 67°C, and refluxing begins, then the initiator is added, and after 1h of reaction, the initiator is added every 2h for 3 times, then the temperature is decreased to 50°C; S3, 10% tackifying resin methanol solution is added, and stirred for 30min to obtain the final highly low-tack acrylic pressure-sensitive adhesive.