Pressure-sensitive adhesive and pressure-sensitive adhesive tape

Abstract

The invention belongs to the technical field of pressure-sensitive adhesives, and particularly relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive tape. According to the pressure-sensitive adhesive disclosed by the invention, the requirements of high adhesive force, high cohesion and low modulus of a double-sided adhesive tape layer are comprehensively considered, the polymerization ratio of butyl acrylate to 2-ethylhexyl acrylate to acrylic acid to hydroxyl-containing acrylate is ingeniously regulated and controlled, the weight-average molecular weight Mw is controlled to be 600000-900000 g / mol, polyacrylate resin is prepared, then proper tackifying resin is screened and matched, and the pressure-sensitive adhesive is prepared. The pressure-sensitive adhesive with excellent comprehensive performance can be obtained, and the required anti-falling performance can be met; the polyacrylate resin is obtained through solution method thermal polymerization, the synthesis process is simple and stable, and the technological process is more stable and reliable; the pressure-sensitive adhesive has lower energy storage modulus at normal temperature, is relatively soft, and has higher stress dispersion capacity when subjected to stress impact; the pressure-sensitive adhesive tape has excellent initial adhesion and adhesive force, the storage modulus in a high-temperature region is not rapidly attenuated, and the pressure-sensitive adhesive tape still has excellent mirror steel plate retention at 85 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of pressure-sensitive adhesive technology, specifically relating to a pressure-sensitive adhesive and a pressure-sensitive adhesive tape. Background Technology

[0002] In recent years, with the rapid development of technology, electronic consumer products such as mobile phones and tablets have become more portable and thinner, which has led to increasingly higher requirements for double-sided pressure-sensitive tapes that play a role in bonding and fixing internal components of electronic products.

[0003] For example, double-sided tape for mobile phone battery compartments is mainly used to secure the easy-tear sticker covering the battery inside the battery compartment. One side adheres to the easy-tear sticker covering the battery, and the other side adheres to the phone casing. During drop tests, the battery must function normally; it should not catch fire, explode, or leak. After disassembling the battery, the double-sided tape must adhere firmly to the fixture, without separation, tearing, or breaking. This requires the adhesive layer on the double-sided tape to have high adhesion, high cohesion, and low modulus to meet excellent drop resistance requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a pressure-sensitive adhesive and pressure-sensitive adhesive tape to solve the above-mentioned technical problems.

[0005] This application provides a pressure-sensitive adhesive, the raw materials for which are prepared by weight include: 100 parts of polyacrylate resin; 12-16 parts of tackifying resin; Hardener 0.16-0.50 parts; The weight-average molecular weight M of the polyacrylate resin w = 600,000-900,000 g / mol; The pressure-sensitive adhesive has a storage modulus of 35,000-45,000 Pa at 25°C and a storage modulus of 10,000-14,000 Pa at 85°C.

[0006] In one embodiment of this application, the tackifying resin is one or more of the following: terpene phenol resin, rosin terpene phenol, rosin pentaerythritol ester, hydrogenated rosin glycerol ester, hydrogenated rosin ester, and rosin glycerol ester.

[0007] In one embodiment of this application, the raw materials for preparing the polyacrylate resin include, by weight: 16-25 parts butyl acrylate; 70-80 parts of 2-ethylhexyl acrylate; Acrylic acid 0.5-1.5 parts; 2-5 parts containing hydroxyl acrylate; 0.25-0.80 parts of thermal initiator; 110-150 parts of ethyl acetate.

[0008] In one embodiment of this application, the hydroxyl-containing acrylate is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0009] In one embodiment of this application, the thermal initiator is one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

[0010] In one embodiment of this application, the method for preparing the polyacrylate resin includes: Add the weighed acrylate monomer and 100-110 parts of ethyl acetate to a reaction vessel equipped with a stirring, reflux and dropping device, and stir for 30-60 minutes under a nitrogen atmosphere; Heat the mixture to 65℃ and add 35%-60% of the thermal initiator to initiate polymerization. The polymerization reaction temperature is controlled at 68-75℃. After 2 hours of polymerization, the remaining thermal initiator was added, and the polymerization reaction continued for another 1.5 hours. The mixture was heated to reflux and reacted for another 2 hours. Then the temperature was lowered, the remaining ethyl acetate was added, and the mixture was cooled to 35°C and filtered to obtain polyacrylate resin.

[0011] In one embodiment of this application, the method for preparing the pressure-sensitive adhesive includes: The tackifying resin was dissolved in an equal part by weight of ethyl acetate by stirring thoroughly to obtain a tackifying resin solution. Add the above tackifying resin solution to the polyacrylate resin, stir thoroughly until homogeneous, and then add the curing agent and stir thoroughly for 30 minutes. Use 200-500 mesh filter bags for filtration, and allow to stand to defoam before coating.

[0012] Accordingly, this application also provides a pressure-sensitive adhesive tape, comprising: Substrate, and pressure-sensitive adhesive layer coated on one or both sides of the substrate; The pressure-sensitive adhesive layer uses the pressure-sensitive adhesive described above.

[0013] In one embodiment of this application, the substrate is 12μm black PET.

[0014] In one embodiment of this application, both sides of the substrate are coated with pressure-sensitive adhesive layers, and the thickness of each pressure-sensitive adhesive layer is 44 μm.

[0015] Accordingly, this application also provides an application of the pressure-sensitive tape described above in electronic products. It is preferably used to secure easy-tear adhesive strips covering batteries inside a mobile phone battery compartment.

[0016] The beneficial effects of this invention are: (1) The pressure-sensitive adhesive of the present invention takes into account the requirements of high adhesion, high cohesion and low modulus of the double-sided tape adhesive layer. It cleverly controls the polymerization ratio of butyl acrylate, 2-ethylhexyl acrylate, acrylic acid and hydroxyl-containing acrylate, and controls the weight average molecular weight Mw = 600000-900000g / mol to prepare polyacrylate resin. Then, it selects and matches suitable tackifying resin to obtain a pressure-sensitive adhesive with excellent comprehensive performance and meets the required anti-drop performance. (2) The polyacrylate resin of the present invention is obtained by solution thermal polymerization, which is simple and stable in synthesis and more stable and reliable in process. (3) The pressure-sensitive adhesive of the present invention has a low storage modulus at room temperature, the adhesive is relatively soft, and has a strong stress dispersion ability when subjected to stress impact. (4) The pressure-sensitive tape of the present invention has excellent initial tack and adhesion. The storage modulus does not decay rapidly in the high-temperature region, and it still has excellent mirror steel plate holding power at 85°C. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention is further illustrated below by way of embodiments, but this does not limit the present invention to the scope of the embodiments described. Experimental methods in the following embodiments that do not specify specific conditions are performed according to conventional methods and conditions, or according to the product instructions. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0018] In the following examples, all raw materials and reagents used are commercially available.

[0019] To address the existing technical problems, one embodiment of this application provides a solution. This solution includes [specific features / methods]. Details are described below.

[0020] Example 1 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1100g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 50min under a nitrogen atmosphere, heat to 65℃ and add 1.2g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 70-75℃. After 2h of polymerization, add the remaining 2.1g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 400g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0021] (2) Dissolve the tackifying resin KB120 in 354g of ethyl acetate and add it to the above polyacrylate resin. Stir for 30 minutes and then add 8g of curing agent L-75. Stir for another 30 minutes and filter with a 200-500 mesh filter bag to obtain pressure-sensitive adhesive liquid. Let it stand to defoam before coating.

[0022] Example 2 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1100g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 60min under a nitrogen atmosphere, heat to 65℃ and add 2g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 68-70℃. After 2h of polymerization, add the remaining 2g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 400g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0023] (2) Dissolve the tackifying resin KB120 in 310g of ethyl acetate and add it to the above polyacrylate resin. Stir for 30 minutes and then add 9.2g of curing agent L-75. Stir for another 30 minutes. Filter with a 200-500 mesh filter bag to obtain pressure-sensitive adhesive liquid. Let it stand to defoam before coating.

[0024] Example 3 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1000g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 50min under a nitrogen atmosphere, heat to 65℃ and add 4g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 70-75℃. After 2h of polymerization, add the remaining 3g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 200g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0025] (2) After dissolving the tackifying resins TP96 and TP7042 in 350g of ethyl acetate, add them to the above polyacrylate resin. Stir for 30 minutes, then add 5g of curing agent L-75 and stir for another 30 minutes. Filter the solution using a 200-500 mesh filter bag to obtain a pressure-sensitive adhesive solution. Let it stand to defoam before coating.

[0026] Example 4 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1000g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 60min under a nitrogen atmosphere, heat to 65℃ and add 3g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 68-70℃. After 2h of polymerization, add the remaining 3g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 400g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0027] (2) After the tackifying resin AS-HD5085 is fully dissolved by stirring with 320g of ethyl acetate, it is added to the above polyacrylate resin. After stirring for 30 minutes, 8.8g of curing agent L-75 is added and stirred for another 30 minutes. The mixture is then filtered through a 200-500 mesh filter bag to obtain a pressure-sensitive adhesive solution. After standing and defoaming, it is ready for coating.

[0028] Example 5 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1200g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 50min under a nitrogen atmosphere, heat to 65℃ and add 2g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 70-75℃. After 2h of polymerization, add the remaining 3g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 300g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0029] (2) Dissolve the tackifying resins KB120 and TP7042 in 384g of ethyl acetate and add them to the polyacrylate resin. Stir for 30 minutes and then add 8g of curing agent L-75. Stir for another 30 minutes and filter with a 200-500 mesh filter bag to obtain the pressure-sensitive adhesive liquid. Let it stand to defoam before coating.

[0030] Comparative Example 1 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1100g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 50min under a nitrogen atmosphere, heat to 65℃ and add 1.2g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 70-75℃. After 2h of polymerization, add the remaining 2.1g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 400g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0031] (2) Dissolve the tackifying resin KB120 in 354g of ethyl acetate and add it to the above polyacrylate resin. Stir for 30 minutes and then add 8g of curing agent L-75. Stir for another 30 minutes and filter with a 200-500 mesh filter bag to obtain pressure-sensitive adhesive liquid. Let it stand to defoam before coating.

[0032] Comparative Example 2 The specific components are shown in the table below: Preparation method: (1) Add acrylate monomer and 1000g of ethyl acetate to a reactor equipped with a stirring, reflux, and dropping device. Stir for 50min under a nitrogen atmosphere, heat to 65℃ and add 1.2g of azobisisobutyronitrile to initiate polymerization. The polymerization reaction temperature is controlled at 70-75℃. After 2h of polymerization, add the remaining 2.1g of azobisisobutyronitrile and react for 1.5h. Heat to reflux and continue the reaction for 2h, then cool down, add 400g of ethyl acetate, cool to 35℃ and filter to obtain polyacrylate resin.

[0033] (2) Dissolve the tackifying resin KB120 in 354g of ethyl acetate and add it to the above polyacrylate resin. Stir for 30 minutes and then add 8g of curing agent L-75. Stir for another 30 minutes and filter with a 200-500 mesh filter bag to obtain pressure-sensitive adhesive liquid. Let it stand to defoam before coating.

[0034] Performance testing The pressure-sensitive adhesives prepared in Examples 1-5 and Comparative Examples 1-2 of this invention were wet-coated onto the release surface of PET release films, and the solvent was dried in an oven to control the dry adhesive thickness to 44 μm. Then, they were laminated to both sides of a 12 μm black PET substrate and cured at 40°C for 3 days to obtain double-sided pressure-sensitive tapes. The physical properties of the above series of double-sided pressure-sensitive tapes were tested, and the test methods are listed below: Adhesion: Peel off one release film of the double-sided pressure-sensitive tape, cover it with 25μm PET, then cut it into 25mm*15cm strips. Peel off the other release film and attach it to the test plates, 304 stainless steel (SUS) and aluminum (AL). Roll it back and forth three times with a 2Kg roller. After standing in a constant temperature and humidity chamber for 20 minutes, use a tensile testing machine at a speed of 300mm / min and 180°... o Directional peel test sample.

[0035] Initial probe adhesion: Fix the sample onto the test ring, ensuring its size covers the circular hole inside the test ring. The probe contacts the sample adhesive surface at a speed of 10±0.1 mm / s, stays for 1.0±0.01 s, and then separates from the adhesive surface at a speed of 10±0.1 mm / s. Record the maximum force required for the probe to separate from the adhesive surface.

[0036] Holding power: According to the national standard test method, the bonding surface is a mirror steel plate. If it does not fall off after 24 hours and there is no visible peeling on the bonding surface, it can be judged as OK.

[0037] Storage modulus: Measured using a TA hybrid rheometer DHR-2. The pressure-sensitive adhesive was applied to the heavy release film, the solvent was dried, and then a light release film was laminated onto it. The film was cured at 40℃ for 3 days to obtain the adhesive film. The release film was removed from the adhesive film, and the film was stacked to a sample with a thickness of 1mm ± 0.05mm, free of wrinkles and bubbles. A circular sample with a diameter of 0.8mm was prepared using a fixture and tested according to the operating procedure. Test conditions: 1Hz, 0.1% strain. Creep recovery test conditions: 40kPa, 25℃, creep 600s, recovery 600s.

[0038] Drop Test: The battery is fully charged according to the standard charging method. Place the battery in the fixture, and after loading, let it stand for at least 12 hours. Drop from a height of 1 meter, dropping 5 times from each of the 6 sides and 4 corners, for a total of 10 drops. This constitutes one cycle, and 5 cycles are required, for a total of 50 drops. After the drop tests, immediately test the battery's OCV1 / IR1, and then after placing it at room temperature for 24 hours, measure OCV2 / IR2 again. Judgment Criteria: The battery should not catch fire, explode, or leak; after disassembling the battery, the double-sided tape should be firmly attached to the fixture.

[0039] The physical property data of pressure-sensitive adhesives and double-sided pressure-sensitive adhesive tapes are summarized below: The monomer composition of polyacrylate resin, the type and amount of tackifying resin, and other factors significantly affect the various physical properties of pressure-sensitive adhesives. As can be seen from the data in the table above, the double-sided pressure-sensitive adhesive tape of this invention exhibits excellent initial tack, adhesion, and holding power. Furthermore, its energy storage modulus at room temperature is between 35,000 and 45,000 Pa; the relatively low modulus ensures the adhesive is relatively soft and has strong stress dispersion ability under stress impact. Simultaneously, the energy storage modulus remains stable at 10,000-14,000 Pa at a high temperature of 85°C, thus demonstrating excellent holding power against the mirror steel plate at 85°C without detachment. Subsequent drop tests verified that all examples 1-5 passed the tests, the battery functioned normally, and after disassembly, the adhesive backing adhered firmly to the fixture.

[0040] In Comparative Example 1, the proportions of butyl acrylate and 2-ethylhexyl acrylate added to the polyacrylate resin deviated significantly from the range proposed in this patent. That is, the content of hard monomers increased and the content of soft monomers decreased. As a result, the designed Tg was too high, the resulting colloidal storage modulus was too high, and the structure was too hard. When subjected to stress impact, it could not disperse stress well. In the drop test, the double-sided pressure-sensitive tape separated from the fixture, and the adhesive backing showed a lot of tearing / pulling.

[0041] In Comparative Example 2, the polyacrylate resin does not contain acrylic acid, resulting in significantly weakened intermolecular chain interactions. This leads to a faster decay of the storage modulus at high temperatures, a softer colloid, poorer cohesion, and easy peeling from the mirror-finished steel plate surface. In drop tests, the double-sided pressure-sensitive tape separated from the fixture, and the protective plate broke upon impact. While this appeared better than Comparative Example 1, it may be related to the relatively lower colloid modulus.

[0042] 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 simple 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 pressure-sensitive adhesive, characterized in that, The raw materials for preparation include, by weight: 100 parts of polyacrylate resin; 12-16 parts of tackifying resin; Hardener 0.16-0.50 parts; The weight-average molecular weight M of the polyacrylate resin w = 600,000-900,000 g / mol; The pressure-sensitive adhesive has a storage modulus of 35,000-45,000 Pa at 25°C and a storage modulus of 10,000-14,000 Pa at 85°C.

2. The pressure-sensitive adhesive according to claim 1, characterized in that, The tackifying resin is one or more of the following: terpene phenol resin, rosin terpene phenol, rosin pentaerythritol ester, hydrogenated rosin glycerol ester, hydrogenated rosin ester, and rosin glycerol ester.

3. The pressure-sensitive adhesive according to claim 1, characterized in that, The raw materials for preparing the polyacrylate resin include, by weight, the following: 16-25 parts butyl acrylate; 70-80 parts of 2-ethylhexyl acrylate; Acrylic acid 0.5-1.5 parts; 2-5 parts containing hydroxyl acrylate; 0.25-0.80 parts of thermal initiator; 110-150 parts of ethyl acetate.

4. The pressure-sensitive adhesive according to claim 3, characterized in that, The hydroxyl-containing acrylate is one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

5. The pressure-sensitive adhesive according to claim 3, characterized in that, The thermal initiator is one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

6. The pressure-sensitive adhesive according to any one of claims 1-5, characterized in that, The method for preparing the polyacrylate resin includes: Add the weighed acrylate monomer and 100-110 parts of ethyl acetate to a reaction vessel equipped with a stirring, reflux and dropping device, and stir for 30-60 minutes under a nitrogen atmosphere; Heat the mixture to 65℃ and add 35%-60% of the thermal initiator to initiate polymerization. The polymerization reaction temperature is controlled at 68-75℃. After 2 hours of polymerization, the remaining thermal initiator was added, and the polymerization reaction continued for another 1.5 hours. The mixture was heated to reflux and reacted for another 2 hours. Then the temperature was lowered, the remaining ethyl acetate was added, and the mixture was cooled to 35°C and filtered to obtain polyacrylate resin.

7. The pressure-sensitive adhesive according to any one of claims 1-5, characterized in that, The preparation method of the pressure-sensitive adhesive includes: The tackifying resin was dissolved in an equal part by weight of ethyl acetate by stirring thoroughly to obtain a tackifying resin solution. Add the above tackifying resin solution to the polyacrylate resin, stir thoroughly until homogeneous, and then add the curing agent and stir thoroughly for 30 minutes. Use 200-500 mesh filter bags for filtration, and allow to stand to defoam before coating.

8. A pressure-sensitive adhesive tape, characterized in that, include: Substrate, and pressure-sensitive adhesive layer coated on one or both sides of the substrate; The pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive as described in any one of claims 1-5.

9. The pressure-sensitive tape as described in claim 8, characterized in that, The substrate is 12μm black PET; The substrate is coated with pressure-sensitive adhesive layers on both sides, and the thickness of each pressure-sensitive adhesive layer is 44 μm.

10. The application of the pressure-sensitive tape as described in claim 8 in electronic products.

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