Degradable acrylic pressure sensitive adhesive and method for preparing the same

Abstract

The present application relates to a kind of degradable acrylic pressure sensitive adhesive and its preparation method, belong to acrylic pressure sensitive adhesive technical field.The raw material of degradable acrylic pressure sensitive adhesive provided by the present application includes polylactic acid, butyl acrylate, isooctyl acrylate, benzoyl peroxide, ethyl acetate, temperature-sensitive microcapsule, tackifier, antioxidant and stabilizer.The degradable acrylic pressure sensitive adhesive of the present application is composed of multiple components, the polylactic acid in which not only gives pressure sensitive adhesive good biodegradability, but also provides appropriate mechanical strength and flexibility;The combination of butyl acrylate and isooctyl acrylate makes the pressure sensitive adhesive have excellent adhesion and weather resistance;The introduction of temperature-sensitive microcapsule, tackifier, antioxidant and stabilizer further improves the performance of pressure sensitive adhesive, improves the degradability of pressure sensitive adhesive.

Description

Technical Field

[0001] This invention belongs to the field of acrylic pressure-sensitive adhesive technology, and relates to a biodegradable acrylic pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Pressure-sensitive adhesives (PSAs) are a class of adhesives that are sensitive to pressure, enabling rapid bonding under pressure. They are widely used in labels, protective films, adhesive tapes, medical patches, and electronic products. The market mainly offers solvent-based PSAs (rubber-based, acrylic-based, SBCs-based, and silicone-based) and emulsion-based PSAs (acrylic-based). Solvent-based PSAs once dominated the market due to their excellent adhesion properties and applicability. However, with increasing environmental awareness, solvent-based adhesives are gradually being restricted due to the potential hazards of volatile organic compounds (VOCs) to the environment and human health.

[0003] Emulsion-based acrylic pressure-sensitive adhesives are gradually becoming the mainstream choice in the market due to their relatively environmentally friendly characteristics. Compared with solvent-based pressure-sensitive adhesives, emulsion-based adhesives release fewer harmful substances during production and use, meeting modern environmental standards. However, despite their good adhesion and weather resistance, emulsion-based acrylic pressure-sensitive adhesives have certain limitations in their polymer structure, especially in terms of biodegradability. Acrylic polymers generally do not possess biodegradable properties, meaning that after use, they can still have a negative impact on the environment, increasing the risk of soil and water pollution. With increasing global emphasis on environmental protection and sustainable development, developing environmentally friendly and biodegradable acrylic pressure-sensitive adhesives has become an important research direction. Summary of the Invention

[0004] The purpose of this invention is to provide a biodegradable acrylic pressure-sensitive adhesive and its preparation method. The biodegradable acrylic pressure-sensitive adhesive of this invention is composed of multiple components. Polylactic acid not only endows the pressure-sensitive adhesive with good biodegradability, but also provides appropriate mechanical strength and flexibility. The combination of butyl acrylate and isooctyl acrylate gives the pressure-sensitive adhesive excellent adhesion and weather resistance. The introduction of temperature-sensitive microcapsules, tackifiers, antioxidants and stabilizers further improves the performance of the pressure-sensitive adhesive and enhances its biodegradability.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A biodegradable acrylic pressure-sensitive adhesive, wherein the acrylic pressure-sensitive adhesive comprises, by weight, 22-28 parts polylactic acid, 28-32 parts butyl acrylate, 41-43 parts isooctyl acrylate, 0.3-0.7 parts benzoyl peroxide, 110-130 parts ethyl acetate, 2.6-3.4 parts thermosensitive microcapsules, 8-12 parts tackifier, 0.5-0.9 parts antioxidant and 0.8-1.2 parts stabilizer.

[0007] Furthermore, the polylactic acid has a weight-average molecular weight of 50,000-150,000.

[0008] Furthermore, the preparation method of the thermosensitive microcapsules includes the following steps:

[0009] S1. Mix N-isopropylacrylamide, sodium dodecyl sulfate and deionized water and stir at 200-800 rpm for 20-30 min to obtain an emulsion;

[0010] S2. Add titanium dioxide to deionized water and sonicate for 15-25 minutes to obtain a suspension;

[0011] S3. Pour the suspension into the emulsion, stir at 300-400 rpm for 20-40 min, add benzoyl peroxide, heat to 55-65℃, stir at 20-40 rpm for 2-4 h, filter with 300 mesh filter cloth to remove the filtrate, wash with deionized water 3 times, dry, and plasma treat to obtain thermosensitive microcapsules.

[0012] Furthermore, the mass ratio of N-isopropylacrylamide to titanium dioxide is 4:8-5.2:0.8-1.2.

[0013] Further, the amount of sodium dodecyl sulfate added in step S1 is 1.2-1.8 wt% of the total mass of N-isopropylacrylamide and titanium dioxide.

[0014] Further, the mass ratio of N-isopropylacrylamide to deionized water in step S1 is 1:4-6.

[0015] Further, in step S2, the mass ratio of titanium dioxide to deionized water is 1:8-10; the average particle size of the titanium dioxide is 20-40 nm.

[0016] Furthermore, the frequency and power of the ultrasonic treatment in step S2 are 35-45kHz and 100-200W, respectively.

[0017] Further, the plasma treatment in step S3 involves introducing a mixture of oxygen and nitrogen, with oxygen accounting for 25-35%, and setting the processing power to 100-200W for 10-20 minutes.

[0018] Furthermore, the preparation method of the acrylic pressure-sensitive adhesive is as follows:

[0019] After preparing the raw materials according to the weight proportions, add polylactic acid, butyl acrylate, and isooctyl acrylate to ethyl acetate and stir at 50-150 rpm for 20-30 minutes. Then add benzoyl peroxide, thickener, antioxidant, and stabilizer. After heating to 55-70℃, continue stirring for 5-7 hours, then cool to 34-40℃. Add temperature-sensitive capsules and stir evenly at 20-50 rpm to remove bubbles, thus obtaining pressure-sensitive adhesive.

[0020] The beneficial effects of this invention are:

[0021] (1) The biodegradable acrylic pressure-sensitive adhesive of the present invention is composed of a variety of components. Polylactic acid not only gives the pressure-sensitive adhesive good biodegradability, but also provides appropriate mechanical strength and flexibility. The combination of butyl acrylate and isooctyl acrylate gives the pressure-sensitive adhesive excellent adhesion and weather resistance. The introduction of thermosensitive microcapsules, tackifiers, antioxidants and stabilizers further improves the performance of the pressure-sensitive adhesive and enhances its biodegradability.

[0022] (2) After plasma treatment, the thermosensitive microcapsules of this invention introduce polar functional groups on their surface, which can not only interact with polylactic acid and butyl acrylate, but also improve the compatibility between the components. This allows the microcapsules to fill the tiny pores and defects in the pressure-sensitive adhesive, improve the internal structure of the pressure-sensitive adhesive, and thus improve its adhesion and uniformity. During the preparation of the thermosensitive microcapsules, N-isopropylacrylamide is polymerized to obtain poly-N-isopropylacrylamide. Sodium dodecyl sulfate is introduced at the same time to promote the uniform dispersion of titanium dioxide in the poly-N-isopropylacrylamide system. When the ambient temperature is lower than the glass transition temperature of poly-N-isopropylacrylamide, the microcapsules remain stable, ensuring that the adhesive performance of the adhesive is not affected under low temperature conditions. When the temperature rises above the melting point of poly-N-isopropylacrylamide, the microcapsules will rupture and release the contained photocatalyst titanium dioxide, thereby promoting the self-degradation of the adhesive and reducing the burden on the environment. Detailed Implementation

[0023] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0024] Example 1

[0025] A biodegradable acrylic pressure-sensitive adhesive, wherein the acrylic pressure-sensitive adhesive of this embodiment comprises, by weight, 22 parts polylactic acid, 28 parts butyl acrylate, 41 parts isooctyl acrylate, 0.3 parts benzoyl peroxide, 110 parts ethyl acetate, 2.6 parts thermosensitive microcapsules, 8 parts tackifier, 0.5 parts antioxidant and 0.8 parts stabilizer.

[0026] The weight-average molecular weight of polylactic acid in this embodiment is 50,000.

[0027] The method for preparing the thermosensitive microcapsules in this embodiment includes the following steps:

[0028] S1. N-isopropylacrylamide, sodium dodecyl sulfate and deionized water were mixed and stirred at 200 rpm for 20 min to obtain an emulsion;

[0029] S2. Add titanium dioxide to deionized water and sonicate for 15 minutes to obtain a suspension;

[0030] S3. Pour the suspension into the emulsion, stir at 300 rpm for 20 min, add benzoyl peroxide, heat to 55℃, stir at 20 rpm for 2 h, then filter with a 300-mesh filter cloth to remove the filtrate, rinse with deionized water 3 times, dry, and plasma treat to obtain thermosensitive microcapsules.

[0031] In this embodiment, the mass ratio of N-isopropylacrylamide to titanium dioxide is 4:8:0.8.

[0032] In this embodiment, the amount of sodium dodecyl sulfate added in step S1 is 1.2 wt% of the total mass of N-isopropylacrylamide and titanium dioxide.

[0033] In this embodiment, the mass ratio of N-isopropylacrylamide to deionized water in step S1 is 1:4.

[0034] In this embodiment, the mass ratio of titanium dioxide to deionized water in step S2 is 1:8; the average particle size of titanium dioxide is 20 nm.

[0035] In this embodiment, the frequency and power of the ultrasonic treatment in step S2 are 35kHz and 100W, respectively.

[0036] In step S3 of this embodiment, the plasma treatment involves introducing a mixture of oxygen and nitrogen, with oxygen comprising 25%, and setting the processing power to 100W for 10 minutes.

[0037] The preparation method of the acrylic pressure-sensitive adhesive in this embodiment is as follows:

[0038] After preparing the raw materials according to the weight proportions, polylactic acid, butyl acrylate, and isooctyl acrylate are added to ethyl acetate and stirred at 50 rpm for 20 minutes. Then, benzoyl peroxide, thickener, antioxidant, and stabilizer are added. The temperature is raised to 60°C and stirred continuously for 5 hours. The temperature is then lowered to 34°C, and temperature-sensitive capsules are added. After stirring evenly at 20 rpm, the bubbles are removed to obtain pressure-sensitive adhesive.

[0039] In this embodiment, the tackifier, antioxidant, and stabilizer are rosin resin, 1010 antioxidant, and calcium stearate, respectively.

[0040] Example 2

[0041] A biodegradable acrylic pressure-sensitive adhesive, wherein the acrylic pressure-sensitive adhesive of this embodiment comprises, by weight, 28 parts polylactic acid, 32 parts butyl acrylate, 43 parts isooctyl acrylate, 0.7 parts benzoyl peroxide, 130 parts ethyl acetate, 3.4 parts thermosensitive microcapsules, 12 parts tackifier, 0.9 parts antioxidant and 1.2 parts stabilizer.

[0042] The weight-average molecular weight of polylactic acid in this embodiment is 150,000.

[0043] The method for preparing the thermosensitive microcapsules in this embodiment includes the following steps:

[0044] S1. N-isopropylacrylamide, sodium dodecyl sulfate and deionized water were mixed and stirred at 800 rpm for 30 min to obtain an emulsion;

[0045] S2. Add titanium dioxide to deionized water and sonicate for 25 minutes to obtain a suspension;

[0046] S3. Pour the suspension into the emulsion, stir at 400 rpm for 40 min, add benzoyl peroxide, heat to 65℃, stir at 40 rpm for 4 h, then filter with a 300-mesh filter cloth to remove the filtrate, rinse with deionized water 3 times, dry, and plasma treat to obtain thermosensitive microcapsules.

[0047] In this embodiment, the mass ratio of N-isopropylacrylamide to titanium dioxide is 5.2:1.2.

[0048] In this embodiment, the amount of sodium dodecyl sulfate added in step S1 is 1.8 wt% of the total mass of N-isopropylacrylamide and titanium dioxide.

[0049] In this embodiment, the mass ratio of N-isopropylacrylamide to deionized water in step S1 is 1:6.

[0050] In this embodiment, the mass ratio of titanium dioxide to deionized water in step S2 is 1:10; the average particle size of titanium dioxide is 40 nm.

[0051] In this embodiment, the frequency and power of the ultrasonic treatment in step S2 are 45kHz and 200W, respectively.

[0052] In this embodiment, the plasma treatment in step S3 involves introducing a mixture of oxygen and nitrogen, with oxygen comprising 35%, and setting the treatment power to 200W for 20 minutes.

[0053] The preparation method of the acrylic pressure-sensitive adhesive in this embodiment is as follows:

[0054] After preparing the raw materials according to the weight proportions, polylactic acid, butyl acrylate, and isooctyl acrylate are added to ethyl acetate and stirred at 150 rpm for 30 minutes. Then, benzoyl peroxide, thickener, antioxidant, and stabilizer are added. The temperature is raised to 60°C and stirred continuously for 7 hours. The temperature is then lowered to 40°C, and temperature-sensitive capsules are added. After stirring evenly at 50 rpm, the bubbles are removed to obtain pressure-sensitive adhesive.

[0055] In this embodiment, the tackifier, antioxidant, and stabilizer are rosin resin, 1010 antioxidant, and calcium stearate, respectively.

[0056] Example 3

[0057] A biodegradable acrylic pressure-sensitive adhesive, wherein the acrylic pressure-sensitive adhesive of this embodiment comprises, by weight, 25 parts polylactic acid, 30 parts butyl acrylate, 42 parts isooctyl acrylate, 0.5 parts benzoyl peroxide, 120 parts ethyl acetate, 3 parts thermosensitive microcapsules, 10 parts tackifier, 0.7 parts antioxidant and 1 part stabilizer.

[0058] The weight-average molecular weight of polylactic acid in this embodiment is 100,000.

[0059] The method for preparing the thermosensitive microcapsules in this embodiment includes the following steps:

[0060] S1. Mix N-isopropylacrylamide, sodium dodecyl sulfate and deionized water and stir at 500 rpm for 25 min to obtain an emulsion;

[0061] S2. Add titanium dioxide to deionized water and sonicate for 20 minutes to obtain a suspension;

[0062] S3. Pour the suspension into the emulsion, stir at 350 rpm for 30 min, add benzoyl peroxide, heat to 60℃, stir at 30 rpm for 3 h, then filter with a 300-mesh filter cloth to remove the filtrate, rinse with deionized water 3 times, dry, and plasma treat to obtain thermosensitive microcapsules.

[0063] In this embodiment, the mass ratio of N-isopropylacrylamide to titanium dioxide is 5:0.7.

[0064] In this embodiment, the amount of sodium dodecyl sulfate added in step S1 is 1.5 wt% of the total mass of N-isopropylacrylamide and titanium dioxide.

[0065] In this embodiment, the mass ratio of N-isopropylacrylamide to deionized water in step S1 is 1:5.

[0066] In this embodiment, the mass ratio of titanium dioxide to deionized water in step S2 is 1:9; the average particle size of titanium dioxide is 30 nm.

[0067] In this embodiment, the frequency and power of the ultrasonic treatment in step S2 are 40kHz and 150W, respectively.

[0068] In this embodiment, the plasma treatment in step S3 involves introducing a mixture of oxygen and nitrogen, with oxygen accounting for 30%, and setting the processing power to 150W for 15 minutes.

[0069] The preparation method of the acrylic pressure-sensitive adhesive in this embodiment is as follows:

[0070] After preparing the raw materials according to the weight proportions, polylactic acid, butyl acrylate, and isooctyl acrylate are added to ethyl acetate and stirred at 100 rpm for 25 minutes. Then, benzoyl peroxide, thickener, antioxidant, and stabilizer are added. The temperature is raised to 65°C and stirred continuously for 6 hours. The temperature is then lowered to 37°C, and temperature-sensitive capsules are added. After stirring evenly at 35 rpm, the bubbles are removed to obtain pressure-sensitive adhesive.

[0071] In this embodiment, the tackifier, antioxidant, and stabilizer are rosin resin, 1010 antioxidant, and calcium stearate, respectively.

[0072] Comparative Example 1

[0073] Based on Example 3, the temperature-sensitive microcapsules were removed, while other conditions remained the same as in Example 3.

[0074] Comparative Example 2

[0075] Based on Example 3, sodium dodecyl sulfate in step S1 of the preparation of temperature-sensitive microcapsules was removed and replaced with an equal weight of deionized water, while other conditions remained the same as in Example 3.

[0076] Comparative Example 3

[0077] Based on Example 3, the plasma treatment in step S3 of the preparation of temperature-sensitive microcapsules was removed, while other conditions remained the same as in Example 3.

[0078] Comparative Example 4

[0079] Based on Example 3, the oxygen content introduced during plasma treatment in step S3 of the thermosensitive microcapsule preparation was changed to 50%, while other conditions remained the same as in Example 3.

[0080] Comparative Example 5

[0081] Based on Example 3, while keeping other conditions the same, the preparation method of the acrylic pressure-sensitive adhesive was modified as follows:

[0082] After preparing the raw materials according to the weight proportions, polylactic acid, butyl acrylate, and isooctyl acrylate are added to ethyl acetate and stirred at 100 rpm for 25 minutes. Then, benzoyl peroxide, thermosensitive capsules, thickener, antioxidant, and stabilizer are added. After heating to 55°C, the mixture is stirred continuously for 6 hours to remove bubbles and obtain pressure-sensitive adhesive.

[0083] The acrylic pressure-sensitive adhesives prepared in Examples 1-3 and Comparative Examples 1-5 were used as samples, and peel strength and degradation tests were performed respectively:

[0084] (1) Peel strength test: The sample was coated on a 50μm thick PET base film to make a 50μm dry adhesive thickness tape. After drying, it was covered with a PET release film (release force 3g-10g) and cured to obtain a pressure-sensitive tape. The 180° peel strength (N / cm) of the tape was tested according to GB / T 2792-2014. The test results are shown in Table 1 below.

[0085] (2) Degradation of samples: The samples were heated at 80°C for 24 hours and 48 hours to simulate the high-temperature degradation environment to test the degradation rate. The degradation rate = (total amount of substance - remaining amount) / total amount of substance × 100%. The test results are shown in Table 1 below.

[0086] Table 1

[0087]

[0088]

[0089] As shown in Table 1, the acrylic pressure-sensitive adhesives prepared in Examples 1-3 of this invention exhibit high peel strength and degradation rate. In Comparative Example 1, the thermosensitive microcapsules were removed. Compared to the improvement effect of the thermosensitive microcapsules on the structure and viscosity of the pressure-sensitive adhesive in Example 3, the peel strength decreased, and the degradation rate decreased due to the lack of photocatalyst participation. In Comparative Example 2, sodium dodecylbenzenesulfonate was removed, which may lead to component dispersion and uneven mixing, thus affecting the final peel strength and degradation rate. Comparative Examples 3 and 4 modified the plasma treatment in Example 3. Without plasma treatment, polar functional groups could not be introduced into the thermosensitive surface to improve the compatibility and viscosity between components, thus affecting the peel strength, but having a smaller impact on the degradation rate. 4. Changing the oxygen content in the plasma treatment to 50% will introduce more polar functional groups onto the microcapsule surface, potentially roughening the surface and even affecting the internal poly-N-isopropylacrylamide structure. This would impact the mechanical strength and stability of the microcapsules, making them more prone to breakage or degradation during application, thus affecting the viscosity of the pressure-sensitive adhesive in practical applications and failing to meet daily usage requirements. Similarly, in Comparative Example 5, directly mixing the components and then heating the mixture at higher temperatures may cause premature breakage of the temperature-sensitive microcapsules or affect their mechanical strength and stability, thus affecting the viscosity and also impacting daily use. Therefore, the acrylic acid prepared in this invention, through the synergistic effect of its components, further improves the performance of the pressure-sensitive adhesive, not only meeting daily usage requirements but also further increasing the degradation rate.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A biodegradable acrylic pressure-sensitive adhesive, characterized in that: The acrylic pressure-sensitive adhesive, by weight, comprises 22-28 parts polylactic acid, 28-32 parts butyl acrylate, 41-43 parts isooctyl acrylate, 0.3-0.7 parts benzoyl peroxide, 110-130 parts ethyl acetate, 2.6-3.4 parts thermosensitive microcapsules, 8-12 parts tackifier, 0.5-0.9 parts antioxidant, and 0.8-1.2 parts stabilizer; The method for preparing the thermosensitive microcapsules includes the following steps: S1. Mix N-isopropylacrylamide, sodium dodecyl sulfate and deionized water and stir at 200-800 rpm for 20-30 min to obtain an emulsion; S2. Add titanium dioxide to deionized water and sonicate for 15-25 minutes to obtain a suspension; S3. Pour the suspension into the emulsion, stir at 300-400 rpm for 20-40 min, add benzoyl peroxide, heat to 55-65℃, stir at 20-40 rpm for 2-4 h, filter with a 300-mesh filter cloth to remove the filtrate, rinse three times with deionized water, dry, and plasma treat to obtain thermosensitive microcapsules; wherein, the plasma treatment involves introducing a mixed gas of oxygen and nitrogen, wherein the oxygen content is 25-35%, and setting the treatment power to 100-200W for plasma treatment for 10-20 min; The preparation method of the acrylic pressure-sensitive adhesive is as follows: After preparing the raw materials according to the weight proportions, add polylactic acid, butyl acrylate, and isooctyl acrylate to ethyl acetate and stir at 50-150 rpm for 20-30 minutes. Then add benzoyl peroxide, thickener, antioxidant, and stabilizer. After heating to 55-70℃, continue stirring for 5-7 hours, then cool to 34-40℃. Add the temperature-sensitive capsules and stir evenly at 20-50 rpm to remove bubbles, thus obtaining the pressure-sensitive adhesive.

2. The biodegradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The polylactic acid has a weight-average molecular weight of 50,000-150,000.

3. The biodegradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The mass ratio of N-isopropylacrylamide to titanium dioxide is 4.8-5.2:0.8-1.

2.

4. The biodegradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The amount of sodium dodecyl sulfate added in step S1 is 1.2-1.8 wt% of the total mass of N-isopropylacrylamide and titanium dioxide.

5. The biodegradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The mass ratio of N-isopropylacrylamide to deionized water in step S1 is 1:4-6.

6. The biodegradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: In step S2, the mass ratio of titanium dioxide to deionized water is 1:8-10; the average particle size of the titanium dioxide is 20-40 nm.

7. The biodegradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The frequency and power of the ultrasonic treatment in step S2 are 35-45kHz and 100-200W, respectively.

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