Degradable acrylic pressure-sensitive adhesive and preparation method thereof

Abstract

The invention relates to a degradable acrylic pressure-sensitive adhesive and a preparation method thereof, and belongs to the technical field of acrylic pressure-sensitive adhesives. The degradable acrylic pressure-sensitive adhesive provided by the invention is prepared from the following raw materials: polylactic acid, butyl acrylate, 2-ethylhexyl acrylate, benzoyl peroxide, ethyl acetate, temperature-sensitive microcapsules, a tackifier, an antioxidant and a stabilizer. The degradable acrylic pressure-sensitive adhesive disclosed by the invention is prepared from a plurality of components, and the polylactic acid not only endows the pressure-sensitive adhesive with good biodegradability, but also provides proper mechanical strength and flexibility; butyl acrylate and 2-ethylhexyl acrylate are combined, so that the pressure-sensitive adhesive has excellent adhesion and weather resistance; due to the introduction of the temperature-sensitive microcapsules, the tackifier, the antioxidant and the stabilizer, the performance of the pressure-sensitive adhesive is further improved, and the degradability of the pressure-sensitive adhesive is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of acrylic pressure-sensitive adhesives and relates to a degradable acrylic pressure-sensitive adhesive and a preparation method thereof. Background Art

[0002] Pressure-sensitive adhesives are a type of pressure-sensitive adhesive that can achieve rapid bonding when pressure is applied. They are widely used in many fields such as labels, protective films, adhesive tapes, medical patches, and electronic products. Pressure-sensitive adhesives on the market mainly include solvent-based pressure-sensitive adhesives (rubber, acrylate, SBCs, silicone) and emulsion-based pressure-sensitive adhesives (acrylate). Solvent-based pressure-sensitive adhesives once dominated the market due to their excellent adhesion and applicability. However, with the increasing awareness of environmental protection, solvent-based adhesives have gradually been restricted due to the potential harm of volatile organic compounds (VOCs) to the environment and human health.

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

[0004] The purpose of the present invention is to provide a degradable acrylic pressure-sensitive adhesive and a preparation method thereof. The degradable acrylic pressure-sensitive adhesive of the present invention is composed of multiple components, wherein the 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 makes the pressure-sensitive adhesive have 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 improves the degradability of the pressure-sensitive adhesive.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A degradable acrylic pressure-sensitive adhesive comprises, by weight, 22-28 parts of polylactic acid, 28-32 parts of butyl acrylate, 41-43 parts of isooctyl acrylate, 0.3-0.7 parts of benzoyl peroxide, 110-130 parts of ethyl acetate, 2.6-3.4 parts of temperature-sensitive microcapsules, 8-12 parts of tackifiers, 0.5-0.9 parts of antioxidants and 0.8-1.2 parts of stabilizers.

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

[0008] Furthermore, the preparation method of the temperature-sensitive microcapsules comprises the following steps:

[0009] S1. After mixing N-isopropylacrylamide, sodium lauryl sulfate and deionized water, stirring at a speed of 200-800 rpm for 20-30 min to obtain an emulsion;

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

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

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

[0013] Furthermore, 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] Furthermore, in step S1, the mass ratio of N-isopropylacrylamide to deionized water is 1:4-6.

[0015] Furthermore, in step S2, the mass ratio of titanium dioxide to deionized water is 1:8-10; and 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] Furthermore, the plasma treatment in step S3 is to introduce a mixed gas of oxygen and nitrogen, wherein the oxygen accounts for 25-35%, and the treatment power is set to 100-200W for plasma treatment for 10-20 minutes.

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

[0019] After preparing the raw materials according to weight proportions, add polylactic acid, butyl acrylate and isooctyl acrylate into ethyl acetate, stir at 50-150 rpm for 20-30 min, then add benzoyl peroxide, tackifier, antioxidant and stabilizer, raise the temperature to 55-70°C, continue stirring for 5-7h, then cool to 34-40°C, add temperature-sensitive capsules, stir evenly at 20-50 rpm, and degas to obtain a pressure-sensitive adhesive.

[0020] Beneficial effects of the present invention:

[0021] (1) The degradable acrylic pressure-sensitive adhesive of the present invention is composed of multiple components, among which 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 makes the pressure-sensitive adhesive have 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 the degradability of the pressure-sensitive adhesive.

[0022] (2) After the temperature-sensitive microcapsules in the present invention are treated with plasma, polar functional groups are introduced on the surface, which can not only interact with polylactic acid and butyl acrylate, etc., but also improve the compatibility between the components, so that the microcapsules can fill the tiny pores and defects in the pressure-sensitive adhesive, improve the internal structure of the pressure-sensitive adhesive, and thus improve its viscosity and uniformity; during the preparation process of the temperature-sensitive microcapsules, N-isopropylacrylamide is polymerized to obtain poly-N-isopropylacrylamide, and 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 bonding performance of the adhesive under low temperature conditions is not affected. When the temperature rises above the melting point of poly-N-isopropylacrylamide, the microcapsules will rupture and release the photocatalyst titanium dioxide contained therein, thereby promoting the self-degradation of the adhesive and reducing the burden on the environment. DETAILED DESCRIPTION

[0023] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0024] Example 1

[0025] A degradable acrylic pressure-sensitive adhesive. The acrylic pressure-sensitive adhesive of this embodiment comprises, by weight, 22 parts of polylactic acid, 28 parts of butyl acrylate, 41 parts of isooctyl acrylate, 0.3 parts of benzoyl peroxide, 110 parts of ethyl acetate, 2.6 parts of temperature-sensitive microcapsules, 8 parts of tackifiers, 0.5 parts of antioxidants and 0.8 parts of stabilizers.

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

[0027] The preparation method of the temperature-sensitive microcapsules of this embodiment comprises the following steps:

[0028] S1. N-isopropylacrylamide, sodium lauryl 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 ultrasonicate for 15 min to obtain a suspension;

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

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

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

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

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

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

[0036] The plasma treatment in step S3 of this embodiment is to introduce a mixed gas of oxygen and nitrogen, wherein the oxygen accounts for 25%, and the treatment power is set to 100W for plasma treatment for 10 minutes.

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

[0038] After preparing the raw materials according to weight portions, add polylactic acid, butyl acrylate and isooctyl acrylate into ethyl acetate, stir at 50 rpm for 20 min, then add benzoyl peroxide, thickener, antioxidant and stabilizer, raise the temperature to 60°C, continue stirring for 5 h, then cool to 34°C, add temperature-sensitive capsules, stir evenly at 20 rpm, and degas to obtain a pressure-sensitive adhesive.

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

[0040] Example 2

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

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

[0043] The preparation method of the temperature-sensitive microcapsules of this embodiment comprises the following steps:

[0044] S1. After mixing N-isopropylacrylamide, sodium lauryl sulfate and deionized water, stirring at 800 rpm for 30 min to obtain an emulsion;

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

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

[0047] The mass ratio of N-isopropylacrylamide to titanium dioxide in this embodiment is 5.2:1.2.

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

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

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

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

[0052] The plasma treatment in step S3 of this embodiment is to introduce a mixed gas of oxygen and nitrogen, wherein the oxygen accounts for 35%, and the treatment power is set to 200W for plasma treatment for 20 minutes.

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

[0054] After preparing the raw materials according to weight portions, add polylactic acid, butyl acrylate and isooctyl acrylate to ethyl acetate, stir at 150 rpm for 30 min, then add benzoyl peroxide, thickener, antioxidant and stabilizer, raise the temperature to 60°C, continue stirring for 7 h, then cool to 40°C, add temperature-sensitive capsules, stir evenly at 50 rpm, and degas to obtain a pressure-sensitive adhesive.

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

[0056] Example 3

[0057] A degradable acrylic pressure-sensitive adhesive. The acrylic pressure-sensitive adhesive of this embodiment comprises, by weight, 25 parts of polylactic acid, 30 parts of butyl acrylate, 42 parts of isooctyl acrylate, 0.5 parts of benzoyl peroxide, 120 parts of ethyl acetate, 3 parts of temperature-sensitive microcapsules, 10 parts of tackifiers, 0.7 parts of antioxidants and 1 part of stabilizers.

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

[0059] The preparation method of the temperature-sensitive microcapsules of this embodiment comprises the following steps:

[0060] S1. N-isopropylacrylamide, sodium lauryl sulfate and deionized water were mixed and stirred at 500 rpm for 25 min to obtain an emulsion;

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

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

[0063] The mass ratio of N-isopropylacrylamide to titanium dioxide in this embodiment is 5:0.7.

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

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

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

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

[0068] The plasma treatment in step S3 of this embodiment is to introduce a mixed gas of oxygen and nitrogen, wherein the oxygen accounts for 30%, and set the treatment power to 150W for plasma treatment for 15 minutes.

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

[0070] After preparing the raw materials according to weight portions, add polylactic acid, butyl acrylate and isooctyl acrylate to ethyl acetate, stir at 100 rpm for 25 min, then add benzoyl peroxide, thickener, antioxidant and stabilizer, heat to 65°C, continue stirring for 6 h, then cool to 37°C, add temperature-sensitive capsules, stir evenly at 35 rpm, and degas to obtain a pressure-sensitive adhesive.

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

[0072] Comparative Example 1

[0073] On the basis of Example 3, the temperature-sensitive microcapsules were removed, and other conditions were the same as those in Example 3.

[0074] Comparative Example 2

[0075] On the basis of Example 3, the sodium dodecyl sulfate in the temperature-sensitive microcapsule preparation step S1 was removed and replaced with an equal weight of deionized water, and the other conditions were the same as those in Example 3.

[0076] Comparative Example 3

[0077] On the basis of Example 3, the plasma treatment in step S3 of preparing the temperature-sensitive microcapsules was removed, and other conditions were consistent with those in Example 3.

[0078] Comparative Example 4

[0079] On the basis of Example 3, the proportion of oxygen introduced during the plasma treatment in the temperature-sensitive microcapsule preparation step S3 was changed to 50%, and the other conditions were consistent with those in Example 3.

[0080] Comparative Example 5

[0081] On the basis of Example 3, keeping other conditions the same, the preparation method of acrylic pressure-sensitive adhesive was changed to:

[0082] After preparing the raw materials according to weight portions, add polylactic acid, butyl acrylate and isooctyl acrylate into ethyl acetate, stir at 100 rpm for 25 min, then add benzoyl peroxide, temperature-sensitive capsules, thickener, antioxidant and stabilizer, heat to 55°C, continue stirring for 6 h, degas, and obtain a pressure-sensitive adhesive.

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

[0084] (1) Peel strength test: The sample was coated on a 50 μm thick PET base film to prepare a tape with a dry adhesive thickness of 50 μm, dried, covered with a PET release film (release force 3 g-10 g), and aged 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 samples: The samples were heated and boiled at 80°C for 24 h and 48 h to simulate a high temperature degradation environment to test the degradation rate. Degradation rate = (total amount of substance - residual amount) / total amount of substance × 100%. The test results are shown in Table 1 below.

[0086] Table 1

[0087]

[0088]

[0089] As can be seen from Table 1, the acrylic pressure-sensitive adhesives prepared in Examples 1-3 of the present invention have high peel strength and degradation rate. In Comparative Example 1, the thermosensitive microcapsules were removed. Compared with the improvement of the structure and viscosity of the pressure-sensitive adhesive by the thermosensitive microcapsules in Example 3, the peel strength decreased, and the degradation rate decreased due to the lack of the participation of the photocatalyst; in Comparative Example 2, sodium dodecylbenzene sulfonate was removed, which may lead to uneven dispersion and mixing of the components, thereby affecting the final peel strength and degradation rate; Comparative Examples 3 and 4 modified the plasma treatment of Example 3. The lack of plasma treatment failed to introduce polar functional groups on the thermosensitive surface to improve the compatibility and viscosity between the components, and thus the peel strength was affected, but the degradation rate was less affected, while in Comparative Example 4, the peel strength was affected, but the degradation rate was less affected. 4 Changing the oxygen ratio in the plasma treatment to 50% will lead to the introduction of more polar functional groups on the surface of the microcapsule, which may cause the surface of the microcapsule to become rough, and may even affect the poly N-isopropyl acrylamide structure inside it, thereby affecting the mechanical strength and stability of the microcapsule, making it easier to break or degrade during the application process, affecting the viscosity of the pressure-sensitive adhesive in actual application, and not meeting the needs of daily use; similarly, in comparative example 5, the components are directly mixed and then heated up. The high temperature may cause the temperature-sensitive microcapsule to break prematurely or affect the mechanical strength and stability of the microcapsule, so the viscosity is affected, which also affects daily use. Therefore, the acrylic acid prepared by the present invention further improves the performance of the pressure-sensitive adhesive through the mutual synergy between the components, not only meeting the needs of daily use, but also further improving the degradation rate.

[0090] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A degradable acrylic pressure-sensitive adhesive, characterized in that: The acrylic pressure-sensitive adhesive comprises, by weight, 22-28 parts of polylactic acid, 28-32 parts of butyl acrylate, 41-43 parts of isooctyl acrylate, 0.3-0.7 parts of benzoyl peroxide, 110-130 parts of ethyl acetate, 2.6-3.4 parts of temperature-sensitive microcapsules, 8-12 parts of tackifiers, 0.5-0.9 parts of antioxidants and 0.8-1.2 parts of stabilizers.

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

3. The degradable acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The preparation method of the temperature-sensitive microcapsule comprises the following steps: S1. After mixing N-isopropylacrylamide, sodium lauryl sulfate and deionized water, stirring at a speed of 200-800 rpm for 20-30 min to obtain an emulsion; S2. Add titanium dioxide to deionized water and ultrasonicate for 15-25 min to obtain a suspension; S3. Pour the suspension into the emulsion, stir at 300-400 rpm for 20-40 min, then add benzoyl peroxide, heat to 55-65°C, stir at 20-40 rpm for 2-4 h, filter with 300 mesh filter cloth to remove the filtrate, rinse with deionized water 3 times, dry, and plasma treat to obtain temperature-sensitive microcapsules.

4. The degradable acrylic pressure-sensitive adhesive according to claim 3, characterized in that: The mass ratio of the N-isopropylacrylamide to titanium dioxide is 4:8-5.2:0.8-1.

2.

5. The degradable acrylic pressure-sensitive adhesive according to claim 3, 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.

6. The degradable acrylic pressure-sensitive adhesive according to claim 3, characterized in that: The mass ratio of N-isopropylacrylamide to deionized water in step S1 is 1:4-6.

7. The degradable acrylic pressure-sensitive adhesive according to claim 3, characterized in that: In step S2, the mass ratio of titanium dioxide to deionized water is 1:8-10; and the average particle size of the titanium dioxide is 20-40 nm.

8. The degradable acrylic pressure-sensitive adhesive according to claim 3, characterized in that: The frequency and power of the ultrasonic treatment in step S2 are 35-45kHz and 100-200W respectively.

9. The degradable acrylic pressure-sensitive adhesive according to claim 3, characterized in that: The plasma treatment in step S3 is to introduce a mixed gas of oxygen and nitrogen, wherein the oxygen accounts for 25-35%, and set the treatment power to 100-200W for plasma treatment for 10-20 minutes.

10. A degradable acrylic pressure-sensitive adhesive according to any one of claims 1 to 9, characterized in that: The preparation method of the acrylic pressure-sensitive adhesive is: After preparing the raw materials according to weight proportions, add polylactic acid, butyl acrylate and isooctyl acrylate into ethyl acetate, stir at 50-150 rpm for 20-30 min, then add benzoyl peroxide, tackifier, antioxidant and stabilizer, raise the temperature to 55-70°C, continue stirring for 5-7h, then cool to 34-40°C, add temperature-sensitive capsules, stir evenly at 20-50 rpm, and degas to obtain a pressure-sensitive adhesive.

Images