Polar-solvent-resistant pressure-sensitive adhesive for flexible printing plate as well as preparation method and application of polar-solvent-resistant pressure-sensitive adhesive

Abstract

The invention discloses a polar solvent resistant pressure-sensitive adhesive for a flexographic printing plate and a preparation method and application of the polar solvent resistant pressure-sensitive adhesive. The polar solvent resistant pressure-sensitive adhesive comprises the following raw materials: resin and a solvent, and the mass ratio of the resin to the solvent is 1: 1-7: 3; the resin is a mixture of urethane acrylate, a vinyl unsaturated monomer and an initiator, the urethane acrylate accounts for 50%-80% of the mass of the resin, the vinyl unsaturated monomer accounts for 15%-45% of the mass of the resin, and the initiator accounts for 0.5%-5% of the mass of the resin. The pressure-sensitive adhesive has excellent polar solvent resistance, a flexible printing plate is not damaged by a solvent after being used for a long time, the printing stability is kept, meanwhile, the pressure-sensitive adhesive has high peel strength, and the bonding strength between PET base films is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure-sensitive adhesives, and more specifically, to a polar solvent-resistant pressure-sensitive adhesive for a flexible printing plate, and a preparation method and application thereof. Background Art

[0002] Photosensitive resin flexible printing plates have developed rapidly since they were launched on the market. Currently, the flexible plates on the market include 1.14mm~7.00mm thickness, digital plates, conventional plates, self-flattened dot plates, solvent-resistant plates and other varieties. Flexible plates are composed of resin layers and PET base films, and the base films are bonded to each other by pressure-sensitive adhesives. With the growth of flexible plate sales, some quality problems have also emerged, and the phenomenon of stratification between PET films often occurs. In particular, flexible printing plates used in the liquid crystal panel industry are exposed to various solvents for a long time during the printing process, such as water, N-methylpyrrolidone and other polar solvents. Therefore, each component of the flexible printing plate must have good solvent resistance. In particular, the pressure-sensitive adhesive that bonds the base film to the base film not only needs to have high bonding strength, but also the bonding interface layer needs to have good solvent resistance to prevent the solvent from penetrating into the interface layer between the PET films, resulting in PET stratification and damage to the printing plate.

[0003] Pressure-sensitive adhesives, also known as pressure-sensitive adhesives, refer to an adhesive chemical product that is extremely sensitive to pressure. Pressure-sensitive adhesives are a soft polymer material that achieves bonding through intermolecular forces (cohesive forces) and the adhesion between the substrate. The adhesion can continue to work at room temperature, and it adheres to the surface of the bonded object under light pressure through non-covalent bonds, and there is no residue after being peeled off. Pressure-sensitive adhesives can be divided into two categories: rubber type and resin type. According to the chemical composition, they can be divided into five categories: rubber type pressure-sensitive adhesives, thermoplastic elastomer type pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone type pressure-sensitive adhesives, and polyurethane type pressure-sensitive adhesives. Pressure-sensitive adhesives are in increasing demand in all walks of life due to their excellent properties such as easy production and aging resistance. However, the types of pressure-sensitive adhesives currently produced in industry are relatively single, and they cannot meet market demand in terms of high solvent resistance.

[0004] In order to overcome the shortcomings of existing products, it is necessary to develop a polar solvent-resistant pressure-sensitive adhesive suitable for flexible printing plates to improve the adhesion between PET base films. Summary of the invention

[0005] The purpose of the present invention is to provide a polar solvent-resistant pressure-sensitive adhesive for a flexible printing plate, and a preparation method and application thereof. The pressure-sensitive adhesive has excellent polar solvent resistance, the flexible printing plate is not damaged by the solvent during long-term use, and the printing stability is maintained. At the same time, it has high peel strength and improves the bonding strength between PET base films.

[0006] The technical solution adopted by the present invention to solve the technical problem is: providing a polar solvent resistant pressure sensitive adhesive for a flexible printing plate, the raw materials comprising: resin and solvent, the mass ratio of the resin to the solvent is 1:1-7:3; The resin is a mixture of polyurethane acrylate, vinyl unsaturated monomer and initiator, wherein the mass ratio of polyurethane acrylate to resin is 50% to 80%, the mass ratio of vinyl unsaturated monomer to resin is 15% to 45%, and the mass ratio of initiator to resin is 0.5% to 5%.

[0007] Preferably, the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the polyurethane acrylate is polybutadiene polyurethane acrylate.

[0008] Preferably, in the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the vinyl unsaturated monomer is one or more of lauryl acrylate, lauryl methacrylate, isodecyl acrylate, C16-C18 methacrylate, and 2-ethylhexyl acrylate.

[0009] Preferably, in the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the initiator is one or two of dibenzoyl peroxide, dilauroyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0010] Preferably, the polar solvent-resistant pressure-sensitive adhesive for the flexible printing plate comprises ethyl acetate, butyl acetate or ethylene glycol methyl ether.

[0011] Preferably, in the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the polyurethane acrylate accounts for 59% to 70% of the resin mass ratio; The vinyl unsaturated monomer accounts for 29% to 40% of the resin mass; The mass ratio of the initiator to the resin is 1% to 2%.

[0012] The present invention also provides a method for preparing the polar solvent-resistant pressure-sensitive adhesive for a flexible printing plate, comprising the following steps: Prepare the raw materials of polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to the above-mentioned method, dilute the vinyl unsaturated monomer with a solvent, mix the initiator with the diluted vinyl unsaturated monomer in proportion, stir and dissolve, add the dissolved solution and polyurethane acrylate into a barrel in proportion, stir mechanically at a low speed for 15 to 20 minutes, then add the remaining solvent into the barrel, stir and dilute to the required viscosity, and complete the preparation of the pressure-sensitive adhesive.

[0013] Preferably, in the preparation method, the method for determining the required viscosity is as follows: The required viscosity value depends on the coating method selected during coating. When comma-type scraper coating is used, the viscosity is 200~1000mPa·s; when micro-concave coating is used, the viscosity is 1~1000mPa·s; when slit coating is used, the viscosity is 400~800mPa·s.

[0014] The present invention also provides a method for using the polar solvent-resistant pressure-sensitive adhesive for a flexible printing plate, comprising the following steps: The prepared pressure-sensitive adhesive is coated on the PET base film through a slit coater. After the solvent is volatilized in a high-temperature oven, the PET release film is covered, rolled up, and then aged at room temperature for 5 to 10 days.

[0015] Preferably, in the method of use, the pressure-sensitive adhesive coating thickness is 20-40 μm.

[0016] The present invention has at least the following beneficial effects: 1. The pressure-sensitive adhesive has excellent resistance to polar solvents. The flexible printing plate will not be damaged by solvents during long-term use, thus maintaining printing stability.

[0017] 2. The pressure-sensitive adhesive has high peel strength, which improves the bonding strength between PET base films.

[0018] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail and completely in conjunction with the embodiments below. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the embodiments, it should be particularly noted that the technical solutions and technical features provided in each part of the present invention, including the following description, can be combined with each other without conflict.

[0020] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] The present invention is further described in detail below in conjunction with embodiments, and its specific implementation process is as follows: The invention provides a polar solvent resistant pressure sensitive adhesive for a flexible printing plate. The raw materials include: resin and solvent. The mass ratio of the resin to the solvent is 1:1-7:3. The ratio of the resin to the solvent can be added according to actual application, and the preferred ratio is 1:1-7:3.

[0022] The resin is a mixture of polyurethane acrylate, vinyl unsaturated monomer and initiator, wherein the mass ratio of polyurethane acrylate to resin is 50% to 80%, the mass ratio of vinyl unsaturated monomer to resin is 15% to 45%, the vinyl unsaturated monomer is an active monomer with excellent solvent resistance, the mass ratio of initiator to resin is 0.5% to 5%, and the initiator is a cleavage-type free radical initiator.

[0023] Furthermore, in the polar solvent-resistant pressure-sensitive adhesive for the flexographic printing plate, the polyurethane acrylate is polybutadiene polyurethane acrylate. As the main component of the pressure-sensitive adhesive, polybutadiene polyurethane acrylate is mainly used to improve the solvent resistance of the pressure-sensitive adhesive. It is a low-polarity resin with excellent solvent resistance. At the same time, the polybutadiene polyurethane acrylate also has good adhesion to PET. In this embodiment, a preferred embodiment is that the polybutadiene polyurethane acrylate can be composed of one or more (different number average molecular weights, viscosities and glass transition temperatures) hydroxyl-terminated polybutadiene polyurethane acrylates.

[0024] Furthermore, in the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the vinyl unsaturated monomer is one or more of lauryl acrylate, lauryl methacrylate, isodecyl acrylate, C16-C18 methacrylate, and 2-ethylhexyl acrylate.

[0025] Furthermore, in the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the initiator is one or two of dibenzoyl peroxide, dilauroyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate. The initiator is a cleavage-type free radical initiator, which is not particularly limited as long as it can polymerize the polymer, and is preferably selected from factors such as initiation efficiency and price.

[0026] Furthermore, the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the solvent is ethyl acetate, butyl acetate or ethylene glycol methyl ether. The solvent is not particularly limited as long as it can dissolve the resin, dilute the resin and reduce the viscosity of the resin. The solvent is preferably selected from the perspectives of solvent toxicity, boiling point and price. The solvent plays a role in reducing the viscosity of the resin, which is beneficial to the coating process.

[0027] Furthermore, in the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the polyurethane acrylate accounts for 59% to 70% of the resin mass ratio; The vinyl unsaturated monomer accounts for 29% to 40% of the resin mass; The mass ratio of the initiator to the resin is 1% to 2%.

[0028] The present invention also provides a method for preparing a polar solvent-resistant pressure-sensitive adhesive for a flexible printing plate using the pressure-sensitive adhesive, comprising the following steps: Prepare the raw materials of polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to the above-mentioned method, dilute the vinyl unsaturated monomer with a solvent to facilitate uniform mixing of the vinyl unsaturated monomer and polyurethane acrylate, mix the initiator with the diluted vinyl unsaturated monomer in proportion, completely dissolve the initiator in the monomer, stir and dissolve, add the dissolved solution and polyurethane acrylate into a barrel in proportion, stir mechanically at a low speed for 15 to 20 minutes, then add the remaining solvent into the barrel, stir and dilute to the desired viscosity, and complete the preparation of the pressure-sensitive adhesive.

[0029] The low-speed mechanical stirring speed is 100-400 r / min, preferably 200-250 r / min.

[0030] Furthermore, in the method for preparing the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, the method for determining the required viscosity is as follows: The required viscosity value depends on the coating method selected during coating. When comma-type scraper coating is used, the viscosity is 200~1000mPa·s; when micro-concave coating is used, the viscosity is 1~1000mPa·s; when slit coating is used, the viscosity is 400~800mPa·s.

[0031] The present invention also provides a method for using the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates, comprising the following steps: coating the prepared pressure-sensitive adhesive on a PET base film through a slit coater, volatilizing the solvent in a high-temperature oven, covering the PET release film, winding it up, and then aging it at room temperature for 5 to 10 days, preferably 7 to 9 days.

[0032] The coating method of the coater is preferably slit coating, which has the advantages of good film thickness uniformity, few coating defects, etc.

[0033] The high temperature oven temperature is 100-150°C, preferably 120-140°C.

[0034] Furthermore, in the method of use, the pressure-sensitive adhesive coating thickness is 20~40μm, preferably 30~35μ. If the thickness is too thin, the T-peel strength of the pressure-sensitive adhesive is low; if the thickness is too thick, a large number of bubbles will appear during high-temperature drying, resulting in poor uniformity of the film surface; secondly, the coating is too thick and increases the cost.

[0035] The technical solution of the present invention will be demonstrated below in conjunction with specific embodiments.

[0036] Embodiment 1: In this embodiment, the mass ratio of resin to solvent is 7:3, ethyl acetate is used as the solvent, and the mass ratios of polyurethane acrylate, vinyl unsaturated monomer and initiator in the resin component are 60%, 38% and 2% respectively, wherein polyurethane acrylate is polybutadiene polyurethane propylene, the vinyl unsaturated monomer is isodecyl acrylate, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0037] Embodiment 2: In this embodiment, the mass ratio of resin to solvent is 7:3, ethyl acetate is used as the solvent, and the mass ratios of polyurethane acrylate, vinyl unsaturated monomer and initiator in the resin component are 65%, 33% and 2% respectively, wherein polyurethane acrylate is polybutadiene polyurethane propylene, the vinyl unsaturated monomer is isodecyl acrylate, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0038] Embodiment 3: In this embodiment, the mass ratio of resin to solvent is 1:1, ethyl acetate is used as the solvent, and the mass ratios of polyurethane acrylate, vinyl unsaturated monomer and initiator in the resin component are 60%, 38% and 2% respectively, wherein polyurethane acrylate is polybutadiene polyurethane propylene, the vinyl unsaturated monomer is isodecyl acrylate, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0039] Embodiment 4: In this embodiment, the mass ratio of resin to solvent is 13:7, ethyl acetate is used as the solvent, and the mass ratios of polyurethane acrylate, vinyl unsaturated monomer and initiator in the resin component are 60%, 38% and 2% respectively, wherein polyurethane acrylate is polybutadiene polyurethane propylene, the vinyl unsaturated monomer is lauryl methacrylate, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0040] Embodiment 5: In this embodiment, the mass ratio of resin to solvent is 7:3, ethyl acetate is used as the solvent, and the mass ratios of polyurethane acrylate, vinyl unsaturated monomer and initiator in the resin component are 60%, 38% and 2% respectively, wherein polyurethane acrylate is polybutadiene polyurethane propylene, the vinyl unsaturated monomer is lauric acid acrylate, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0041] Comparative Example 1: This comparative example is a CF membrane produced by a Japanese company.

[0042] Comparative Example 2: This comparative example is acrylic pressure-sensitive adhesive NP-66 produced by Shanghai Lingke Chemical Technology Co., Ltd.

[0043] Comparative Example 3: In this comparative example, the mass ratio of resin to solvent is 6:4, ethyl acetate is used as the solvent, the resin component does not contain vinyl unsaturated monomers, and the mass ratios of polyurethane acrylate and initiator in the resin component are 98% and 2% respectively, wherein the polyurethane acrylate is polybutadiene polyurethane propylene, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0044] Comparative Example 4: In this comparative example, the mass ratio of resin to solvent is 9:1, ethyl acetate is used as the solvent, and the mass ratios of polyurethane acrylate, vinyl unsaturated monomer and initiator in the resin component are 60%, 38% and 2% respectively, wherein polyurethane acrylate is polybutadiene polyurethane propylene, the vinyl unsaturated monomer is isodecyl acrylate, and the initiator is azobisisobutyronitrile and azobisisoheptanenitrile, each accounting for 1% of the resin mass ratio.

[0045] Sample preparation and testing of the adhesion performance of pressure-sensitive adhesive to PET: Tear off the PET release film from the PET base film coated with pressure-sensitive adhesive, use a laminating machine to laminate the PET base film coated with pressure-sensitive adhesive with the PET film, and test after leaving it for 24 hours. Test the T-peel strength of pressure-sensitive adhesive according to GB8808-1988.

[0046] The solvent resistance of pressure-sensitive adhesive is tested according to GB / T 1690-2006, and the swelling rate of pressure-sensitive adhesive is tested in N-methylpyrrolidone (NMP) for 24 hours.

[0047] The measurement results are shown in Table 1: Table 1 Swelling rate and peel strength test results of examples / comparative examples Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 NMP swelling rate (24h) 6.5% 5.5% 4.3% 5.6% 6.7% 20% 30% 4.9% 6.1% Peel strength grade (original) 5.3N / cm 5.0N / cm 4.9N / cm 5.2N / cm 4.8N / cm 2.3N / cm 5.2N / cm 3.4N / cm 5.5N / cm Peel strength grade (immersed in NMP for 24 hours) 4.8N / cm 4.7N / cm 4.5N / cm 4.9N / cm 4.5N / cm 1.8N / cm 2.1N / cm 2.9N / cm 5.2N / cm Comparative Example 1 is a CF film produced by a Japanese company. The product has insufficient adhesion to PET and PET is easily delaminated.

[0048] Comparative Example 2 is acrylic pressure-sensitive adhesive NP-66 produced by Shanghai Lingke Chemical Technology Co., Ltd. This pressure-sensitive adhesive has good adhesion to PET, but has a high swelling rate and poor resistance to polar solvents.

[0049] Comparative Example 3 is a formula without adding vinyl unsaturated monomers. The NMP swelling rate of the formula is low, but because polybutadiene polyurethane acrylate is a low-polarity resin, there are fewer polar groups in the molecular structure and the intermolecular force is small. It is difficult to interact with the PET surface at the molecular level and the peel strength is low.

[0050] Comparative Example 4 is a formula with a reduced solvent ratio. The solvent resistance and peel strength of the formula meet the requirements, but the viscosity of the resin formula is relatively high and it is difficult to apply in actual coating production.

[0051] Examples 1-5 all have good polar solvent resistance, NMP swelling rate is less than 10%, peel strength is greater than 4N / cm, meeting the requirements of flexible printing plates, and after immersion in solvent, the peel strength is not significantly weakened, maintaining the original adhesion.

[0052] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A polar solvent resistant pressure sensitive adhesive for a flexible printing plate, characterized in that: The raw materials include: resin and solvent, wherein the mass ratio of the resin to the solvent is 1:1 to 7:3; The resin is a mixture of polyurethane acrylate, vinyl unsaturated monomer and initiator, wherein the mass ratio of polyurethane acrylate to resin is 50% to 80%, the mass ratio of vinyl unsaturated monomer to resin is 15% to 45%, and the mass ratio of initiator to resin is 0.5% to 5%.

2. The polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to claim 1, characterized in that: The polyurethane acrylate is polybutadiene polyurethane acrylate.

3. The polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to claim 1, characterized in that: The vinyl unsaturated monomer is one or more of lauryl acrylate, lauryl methacrylate, isodecyl acrylate, C16-C18 methacrylate, and 2-ethylhexyl acrylate.

4. The polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to claim 1, characterized in that: The initiator is one or two of dibenzoyl peroxide, dilauroyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

5. The polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to claim 1, characterized in that: The solvent is ethyl acetate, butyl acetate or ethylene glycol methyl ether.

6. The polar solvent-resistant pressure-sensitive adhesive for flexible printing plates according to claim 1, characterized in that: The polyurethane acrylate accounts for 59% to 70% of the resin mass; The vinyl unsaturated monomer accounts for 29% to 40% of the resin mass; The mass ratio of the initiator to the resin is 1% to 2%.

7. A method for preparing a polar solvent-resistant pressure-sensitive adhesive for a flexible printing plate using the method described in claim 1-6, characterized in that: The steps include: The raw materials of the polar solvent-resistant pressure-sensitive adhesive for flexible printing plates are prepared according to any one of claims 1 to 6, the vinyl unsaturated monomer is diluted with a solvent, the initiator and the diluted vinyl unsaturated monomer are mixed in proportion, stirred and dissolved, and the dissolved solution and polyurethane acrylate are added to a barrel in proportion, stirred mechanically at a low speed for 15 to 20 minutes, and then the remaining solvent is added to the barrel, stirred and diluted to the desired viscosity to complete the preparation of the pressure-sensitive adhesive.

8. The preparation method according to claim 7, characterized in that: The required viscosity is determined as follows: The required viscosity value depends on the coating method selected during coating. When comma-type scraper coating is used, the viscosity is 200~1000mPa·s; when micro-concave coating is used, the viscosity is 1~1000mPa·s; when slit coating is used, the viscosity is 400~800mPa·s.

9. A method for using the polar solvent resistant pressure sensitive adhesive for a flexible printing plate as described in claim 1-6, characterized in that: The steps include: The prepared pressure-sensitive adhesive is coated on the PET base film through a slit coater. After the solvent is volatilized in a high-temperature oven, the PET release film is covered, rolled up, and then aged at room temperature for 5 to 10 days.

10. The method of use according to claim 9, characterized in that: The pressure-sensitive adhesive coating thickness is 20-40 μm.