Adhesive capable of being rapidly cured at low temperature, preparation method of adhesive and screen printing plate

Abstract

The invention relates to the field of adhesives, in particular to a low-temperature fast-curing adhesive, a preparation method thereof and a screen printing plate. The low-temperature fast curing adhesive provided by the invention is prepared from the following raw materials: polyamide-imide, epoxy resin, an epoxy resin reactive diluent, a curing agent accelerator, a latent curing agent, a low-temperature curing agent, a defoaming agent and a solvent. The adhesive prepared by the preparation method disclosed by the invention has relatively low thermocuring temperature, and can be cured at the temperature of 120-130 DEG C, so that the energy consumption in the production process is effectively reduced, and the production safety is improved; and the product has high peel strength, and the peel strength is 8N / cm or above.

Description

Technical Field

[0001] The invention relates to the field of adhesives, in particular to an adhesive that cures quickly at low temperatures and a preparation method thereof and a printing screen. Background Art

[0002] Screen printing is a process of printing that uses the characteristics of the screen printing plate that the mesh holes of the image part can pass the ink, while the mesh holes of the non-image part cannot pass the ink. During the printing process, the ink is transferred to the substrate through the mesh holes of the screen printing plate under the action of the scraper to form the desired image. In the processing of printing screens, glue plays a vital role. It can form a strong bond between the screen base and the printing material to ensure the stability and accuracy of the printing process.

[0003] Prior art CN117625117A discloses a polyamide-imide adhesive, the raw materials for its preparation include polyamide-imide resin, epoxy resin and toughening resin, and the obtained polyamide screen film has the advantages of high laser etching precision and high efficiency; Prior art CN117801743A discloses an epoxy adhesive, the raw materials for its preparation include epoxy resin, tackifying resin, film-forming resin, curing agent and photosensitizer, and the product still maintains adhesion to the polyimide base film after high-temperature curing, thereby improving the service life of the printing screen. However, the curing and pressing temperature of the above-mentioned adhesive is 150-200°C, which is relatively high. However, high temperature means high risk factor, high energy consumption and high cost in the pressing process. Therefore, there is an urgent need for an adhesive that can be pressed at low temperature and has excellent bonding performance. Summary of the invention

[0004] In order to solve the above technical problems, the first aspect of the present invention provides a low-temperature fast-curing adhesive, whose preparation raw materials include: polyamideimide, epoxy resin, epoxy resin active diluent, curing agent accelerator, latent curing agent, low-temperature curing agent, defoaming agent and solvent.

[0005] As an implementable case, the raw materials for preparing the low-temperature fast-curing adhesive include, by weight, 15-40 parts of polyamide-imide, 40-60 parts of epoxy resin, 0.05-0.5 parts of epoxy resin active diluent, 5-20 parts of curing agent accelerator, 5-20 parts of latent curing agent, 0.5-3 parts of low-temperature curing agent, 100-200 parts of solvent and 0.05-1 part of defoaming agent.

[0006] As an implementable case, the grades of the polyamide-imide include: one or more of PAI Torlon 4000TF, PAI Torlon 5030HF, PAI Torlon 4203, and PAI Torlon AI-10.

[0007] Furthermore, the heat deformation temperature of the polyamide-imide is 112-145° C., and the brand is PAI TorlonAI-10.

[0008] As an implementable case, the epoxy resin includes: one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, and phenol epoxy resin.

[0009] Furthermore, the epoxy resin is a phenolic epoxy resin.

[0010] Polyamide-imide has excellent heat resistance, mechanical strength and wear resistance, while phenolic epoxy resin has good adhesion and chemical stability. Polyamide-imide and phenolic epoxy resin will undergo chemical cross-linking during the compounding process to form a dense spatial network structure, thereby enhancing the interfacial bonding force and helping to improve the bonding performance of the adhesive; in addition, the imide ring of polyamide-imide will react with the epoxy group of phenolic epoxy resin, and the formed chemical bond or cross-linking structure is conducive to the adhesive to undergo an effective cross-linking and curing reaction at a lower temperature, thereby reducing the hot pressing temperature. The phenolic hydroxyl group in the phenolic epoxy resin can also hydrogen bond with the imide in the polyamide-imide, further promoting the curing reaction and reducing the thermal curing temperature. However, the inventors have found that the thermal deformation temperature of the polyamide-imide needs to be further limited. Too high a thermal deformation temperature is also not conducive to reducing the thermal curing temperature of the adhesive. When the thermal deformation temperature is too low, the adhesive layer formed by the thermal curing of the product may deform at a lower temperature, resulting in a decrease in the mechanical properties of the material, such as strength and hardness. Therefore, the present invention preferably uses a polyamide-imide with a thermal deformation temperature of 112-145°C, which can ensure that the material has a higher bonding strength and achieve the effect of low-temperature thermal curing.

[0011] As an implementable case, the epoxy resin active diluent is a low molecular weight epoxy compound containing one or more epoxy groups in its molecular structure.

[0012] Furthermore, the epoxy resin active diluent includes: one or more of ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, 1,4-butanediol glycidyl ether, diglycidyl ether, and polyethylene glycol diglycidyl ether.

[0013] Furthermore, the epoxy resin active diluent is diglycidyl ether.

[0014] As a bifunctional epoxy resin reactive diluent, diglycidyl ether has good wetting ability and penetration. It can effectively reduce the viscosity of epoxy resin system adhesive, making it easier for adhesive to penetrate into the tiny gap of PI (polyimide) film during coating, thereby improving the bonding strength and sealing performance of adhesive. In addition, the addition of diglycidyl ether can also improve the flexibility and toughness of adhesive. The inventor speculates that it is mainly due to the presence of longer chain segments in the diglycidyl ether molecule, which can form a certain elastic structure during the curing process, so that the adhesive can better absorb and disperse stress when subjected to external force, avoiding the situation of being unable to bond caused by stress concentration; while in the curing process of adhesive, the epoxy group in diglycidyl ether can react rapidly with the functional group in the low temperature curing agent to form a cross-linked network structure, realizing the effect of low temperature thermal curing.

[0015] The present invention does not further limit the type of defoaming agent. Any substance that can effectively eliminate bubbles generated during the processing and make the adhesive more uniform and delicate can be used. Its brands include but are not limited to: one or more of DF-285, DF-214, DF-2416, DF-2655, and DF-233.

[0016] As an implementable case, the curing agent accelerator is at least one of imidazole compounds and their derivatives, urea compounds and their derivatives, organic guanidine compounds and their derivatives, and phosphorus-containing compounds.

[0017] Furthermore, the curing agent accelerator includes: at least one of triphenylphosphine, di-o-tolylguanidine, o-tolylbiguanide, N-(2-hydroxyphenyl)-N',N'-dimethylurea, N-(2-hydroxy-4-nitrobenzene)-N',N'-dimethylurea, and N-(5-chloro-2-hydroxybenzene)-N',N'-dimethylurea.

[0018] Furthermore, the curing agent accelerator is triphenylphosphine.

[0019] As an implementable case, the latent curing agent includes at least one of aromatic diamines, dicyandiamides, and organic hydrazides.

[0020] Furthermore, the latent curing agent includes at least one of 4,4'-diaminodiphenyl sulfone (DDS), 4,4'-diaminodiphenylmethane (DDM), and 4,4'-diaminodiphenyl ether (DDE).

[0021] Furthermore, the latent curing agent is 4,4'-diaminodiphenyl sulfone.

[0022] DDS is a high-performance latent curing agent with relatively low reactivity, but its cured product has high thermal stability and heat resistance. At room temperature, the system composed of DDS, epoxy resin and polyamide-imide is relatively stable, but under heating and other conditions, it can quickly undergo a curing reaction, allowing the adhesive to form a stable cross-linked network structure, thereby improving the strength and heat resistance of the adhesive.

[0023] As an implementable case, the low-temperature curing agent is an imidazole curing agent.

[0024] Furthermore, the low-temperature curing agent is at least one of 2-methylimidazole, 2-ethylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-phenylimidazole.

[0025] Furthermore, the low-temperature curing agent is 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0026] As an imidazole curing agent, 1-cyanoethyl-2-ethyl-4-methylimidazole has the characteristics of low curing temperature, fast curing reaction, small dosage, low toxicity and wide range of applications; 1-cyanoethyl-2-ethyl-4-methylimidazole can catalyze the chemical reaction between epoxy resin and polyamide-imide and accelerate the curing process; by optimizing the curing reaction path and reducing the reaction activation energy, the adhesive can be cured quickly at a lower temperature.

[0027] As an implementable example, the solvent includes an aprotic solvent and a low polarity solvent.

[0028] As an implementable example, the aprotic solvent includes: one of DMAC (N,N-dimethylacetamide), DMF (N,N-dimethylformamide), and NMP (N-methylpyrrolidone).

[0029] As an implementable example, the low polarity solvent includes: EA (ethyl acetate) and / or MEK (methyl ethyl ketone).

[0030] Furthermore, the mass ratio of the aprotic solvent to the low polarity solvent is (1.5-3):1.

[0031] The second aspect of the present invention provides a method for preparing a low-temperature fast-curing adhesive, comprising: dissolving polyamide-imide using a non-protonic solvent; then adding epoxy resin, epoxy resin active diluent, defoamer, curing agent accelerator, latent curing agent, and low-temperature curing agent in sequence at room temperature, stirring for 30-60 minutes, and then adding a low-polarity solvent for dilution to obtain the adhesive.

[0032] The third aspect of the present invention provides a printing screen, which includes: a PI film, a screen and an adhesive layer; the adhesive layer is made by thermally curing an adhesive.

[0033] The preparation method of the printing screen comprises: coating the prepared adhesive on a PI film with a thickness of 2-10 μm to form an adhesive layer with a thickness of 1-10 μm, drying temperature of 80-110°C, drying time of 1-10 min, aging temperature of 40-50°C, aging time of 12-24 h, to form a covering film; laminating the adhesive layer of the covering film with the screen of the screen, and then using a vacuum fast press machine to hot press at 120-130°C and 1-2MPa for 20-60 min, and cutting to obtain the printing screen.

[0034] Beneficial Effects

[0035] (i) The adhesive prepared by the present invention has a relatively low thermal curing temperature and can be cured at 120-130° C., which effectively reduces energy consumption in the production process and improves production safety.

[0036] (ii) The present invention selects polyamide-imide and epoxy resin for compounding, which can ensure that the adhesive has excellent bonding properties.

[0037] (III) The present invention further limits the heat deformation temperature of polyamide-imide to 112-145°C, which can ensure that the adhesive has a high peel strength and achieve the effect of low-temperature thermal curing.

[0038] (IV) In the present invention, diglycidyl ether is preferably used as the reactive diluent for epoxy resin. The epoxy groups in diglycidyl ether can react rapidly with the functional groups in the low-temperature curing agent to form a cross-linked network structure, thereby achieving the effects of low-temperature thermal curing and high peel strength.

[0039] (V) The present invention creatively adopts a technical solution of compounding a curing agent accelerator, a latent curing agent and a low-temperature curing agent, which not only improves the curing efficiency of the adhesive, but also improves the bonding performance of the product and further reduces the thermal curing temperature of the adhesive. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the structure of the printing screen prepared in Example 1-2 and Comparative Example 1-2, wherein: 1-PI film, 2-adhesive layer, 3-screen. DETAILED DESCRIPTION

[0041] Example 1

[0042] The first aspect of this example provides a low-temperature fast-curing adhesive, the raw materials for its preparation, calculated by weight, include: 25 parts of polyamide-imide, 50 parts of epoxy resin, 0.25 parts of epoxy resin reactive diluent, 12 parts of curing agent accelerator, 7.5 parts of latent curing agent, 1.8 parts of low-temperature curing agent, 0.08 parts of defoaming agent and 113 parts of solvent.

[0043] The polyamide-imide is of the brand PAI Torlon AI-10, purchased from Tianzhihong Plastic Chemical Co., Ltd.

[0044] The epoxy resin is a phenolic epoxy resin with a brand name of DEN tm 438, purchased from Kain Chemicals.

[0045] The epoxy resin active diluent is diglycidyl ether.

[0046] The curing agent accelerator is triphenylphosphine.

[0047] The latent curing agent is DDS.

[0048] The low temperature curing agent is 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0049] The defoamer is of the brand DF-233, purchased from Defeng Defoamer Co., Ltd.

[0050] The solvent comprises an aprotic solvent and a low polar solvent in a mass ratio of 75:38; the aprotic solvent is DMF and the low polar solvent is MEK.

[0051] The second aspect of this example provides a method for preparing a low-temperature fast-curing adhesive, comprising: dissolving polyamideimide at 60°C using a non-protonic solvent; then adding epoxy resin, epoxy resin active diluent, defoamer, curing agent accelerator, latent curing agent, and low-temperature curing agent in sequence at room temperature of 25°C, stirring for 30 minutes, and then adding a low-polarity solvent for dilution to obtain the adhesive.

[0052] The third aspect of this example provides a printing screen, which includes: a PI film, a screen and an adhesive layer; the adhesive layer is made by thermal curing of an adhesive.

[0053] The preparation method of the printing screen comprises: coating the prepared adhesive on a 5 μm PI film to form an adhesive layer with a thickness of 5 μm, drying at a temperature of 100°C, drying for 10 minutes, aging at a temperature of 50°C, aging for 24 hours, to form a covering film; laminating the adhesive layer of the covering film to the screen of the screen, and then using a vacuum fast press to perform hot pressing at 120°C and 1MPa for 30 minutes, and cutting to obtain the printing screen.

[0054] Example 2

[0055] The first aspect of this example provides a low-temperature fast-curing adhesive, the raw materials for its preparation, calculated by weight, include: 25 parts of polyamide-imide, 50 parts of epoxy resin, 0.25 parts of epoxy resin active diluent, 12 parts of curing agent accelerator, 7 parts of latent curing agent, 1.5 parts of low-temperature curing agent, 0.08 parts of defoaming agent and 113 parts of solvent.

[0056] The polyamide-imide is of the brand PAI Torlon AI-10, purchased from Tianzhihong Plastic Chemical Co., Ltd.

[0057] The epoxy resin is a phenolic epoxy resin with a brand name of DEN tm 438, purchased from Kain Chemical.

[0058] The epoxy resin active diluent is diglycidyl ether.

[0059] The curing agent accelerator is triphenylphosphine.

[0060] The latent curing agent is DDS.

[0061] The low temperature curing agent is 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0062] The defoamer is of the brand DF-233, purchased from Defeng Defoamer Co., Ltd.

[0063] The solvent comprises an aprotic solvent and a low polar solvent in a mass ratio of 75:38; the aprotic solvent is DMF, and the low polar solvent is MEK.

[0064] The second aspect of this example provides a method for preparing a low-temperature fast-curing adhesive, comprising: dissolving polyamideimide at 60°C using a non-protonic solvent; then adding epoxy resin, epoxy resin active diluent, defoamer, curing agent accelerator, latent curing agent, and low-temperature curing agent in sequence at room temperature of 25°C, stirring for 30 minutes, and then adding a low-polarity solvent for dilution to obtain the adhesive.

[0065] The third aspect of this example provides a printing screen, which includes: a PI film, a screen and an adhesive layer; the adhesive layer is made by thermal curing of an adhesive.

[0066] The preparation method of the printing screen comprises: coating the prepared adhesive on a 5 μm PI film to form an adhesive layer with a thickness of 5 μm, drying at a temperature of 100°C, drying for 10 minutes, aging at a temperature of 50°C, aging for 24 hours, to form a covering film; laminating the adhesive layer of the covering film to the screen of the screen, and then using a vacuum fast press to perform hot pressing at 120°C and 1MPa for 30 minutes, and cutting to obtain the printing screen.

[0067] Comparative Example 1

[0068] The first aspect of this example provides a low-temperature fast-curing adhesive, the raw materials for its preparation, calculated by weight, include: 25 parts of polyamide-imide, 50 parts of epoxy resin, 0.25 parts of epoxy resin active diluent, 12 parts of curing agent accelerator, 7.5 parts of latent curing agent, 0.08 parts of defoaming agent and 113 parts of solvent.

[0069] The polyamide-imide is of the brand PAI Torlon AI-10, purchased from Tianzhihong Plastic Chemical Co., Ltd.

[0070] The epoxy resin is a phenolic epoxy resin with a brand name of DEN tm 438, purchased from Kain Chemicals.

[0071] The epoxy resin active diluent is diglycidyl ether.

[0072] The curing agent accelerator is triphenylphosphine.

[0073] The latent curing agent is DDS.

[0074] The defoamer is of the brand DF-233, purchased from Defeng Defoamer Co., Ltd.

[0075] The solvent comprises an aprotic solvent and a low polar solvent in a mass ratio of 75:38; the aprotic solvent is DMF and the low polar solvent is MEK.

[0076] The second aspect of this example provides a method for preparing a low-temperature fast-curing adhesive, comprising: dissolving polyamideimide at 60°C using a non-protonic solvent; then adding epoxy resin, epoxy resin active diluent, defoaming agent, curing agent accelerator, and latent curing agent in sequence at room temperature of 25°C, stirring for 30 minutes, and then adding a low-polarity solvent for dilution to obtain the adhesive.

[0077] The third aspect of this example provides a printing screen, which includes: a PI film, a screen and an adhesive layer; the adhesive layer is made by thermal curing of an adhesive.

[0078] The preparation method of the printing screen comprises: coating the prepared adhesive on a 5 μm PI film to form an adhesive layer with a thickness of 5 μm, drying at a temperature of 100°C, drying for 10 minutes, aging at a temperature of 50°C, aging for 24 hours, to form a covering film; laminating the adhesive layer of the covering film to the screen of the screen, and then using a vacuum fast press to perform hot pressing at 120°C and 1MPa for 30 minutes, and cutting to obtain the printing screen.

[0079] Comparative Example 2

[0080] The first aspect of this example provides a low-temperature fast-curing adhesive, the raw materials for its preparation, calculated by weight, include: 25 parts of polyamide-imide, 50 parts of epoxy resin, 0.25 parts of epoxy resin active diluent, 12 parts of curing agent accelerator, 7 parts of latent curing agent, 0.08 parts of defoaming agent and 113 parts of solvent.

[0081] The polyamide-imide is of the brand PAI Torlon AI-10, purchased from Tianzhihong Plastic Chemical Co., Ltd.

[0082] The epoxy resin is a phenolic epoxy resin with a brand name of DEN tm 438, purchased from Kain Chemicals.

[0083] The epoxy resin active diluent is diglycidyl ether.

[0084] The curing agent accelerator is triphenylphosphine.

[0085] The latent curing agent is DDS.

[0086] The defoamer is of the brand DF-233, purchased from Defeng Defoamer Co., Ltd.

[0087] The solvent comprises an aprotic solvent and a low polar solvent in a mass ratio of 75:38; the aprotic solvent is DMF and the low polar solvent is MEK.

[0088] The second aspect of this example provides a method for preparing a low-temperature fast-curing adhesive, comprising: dissolving polyamideimide at 60°C using a non-protonic solvent; then adding epoxy resin, epoxy resin active diluent, defoaming agent, curing agent accelerator, and latent curing agent in sequence at room temperature of 25°C, stirring for 30 minutes, and then adding a low-polarity solvent for dilution to obtain the adhesive.

[0089] The third aspect of this example provides a printing screen, which includes: a PI film, a screen and an adhesive layer; the adhesive layer is made by thermal curing of an adhesive.

[0090] The preparation method of the printing screen comprises: coating the prepared adhesive on a 5 μm PI film to form an adhesive layer with a thickness of 5 μm, drying at a temperature of 100°C, drying for 10 minutes, aging at a temperature of 50°C, aging for 24 hours, to form a covering film; laminating the adhesive layer of the covering film to the screen of the screen, and then using a vacuum fast press to perform hot pressing at 120°C and 1MPa for 30 minutes, and cutting to obtain the printing screen.

[0091] The structure of the printing screen prepared in the above-mentioned Examples 1-2 and Comparative Examples 1-2 is as follows: Figure 1 shown.

[0092] Performance Evaluation

[0093] Test objects: printing screens prepared in Examples 1-2 and Comparative Examples 1-2.

[0094] Test item: Peel strength of adhesive layer in printing stencil. See Table 1 for test results.

[0095] Test method: Cut the prepared printing screen into 1 cm wide strips, use a universal tensile testing machine, and pull it up in a 180-degree direction at a test speed of 50.8 mm / min in a measuring environment of 25±5°C and 65±20% RH, with a stretching distance of 70 mm.

[0096] Table 1

[0097] Peel strength (N / cm) Example 1 8.82 Example 2 8.42 Comparative Example 1 4.15 Comparative Example 2 3.83

[0098] Compared with comparative example 1-2, the adhesive prepared in example 1-2 of the present invention can be quickly molded at 120° C. and has a higher peel strength of more than 8 N / cm.

Claims

1. A low temperature fast curing adhesive, characterized in that: The preparation raw materials include: polyamide-imide, epoxy resin, epoxy resin active diluent, curing agent accelerator, latent curing agent, low-temperature curing agent, defoaming agent and solvent; The solvent includes an aprotic solvent and a low polarity solvent.

2. The low temperature fast curing adhesive according to claim 1, characterized in that: The raw materials for preparing the low-temperature fast-curing adhesive include, by weight, 15-40 parts of polyamide-imide, 40-60 parts of epoxy resin, 0.05-0.5 parts of epoxy resin active diluent, 5-20 parts of curing agent accelerator, 5-20 parts of latent curing agent, 0.5-3 parts of low-temperature curing agent, 100-200 parts of solvent and 0.05-1 part of defoaming agent.

3. The low temperature fast curing adhesive according to claim 1, characterized in that: The heat deformation temperature of the polyamide-imide is 112-145°C.

4. The low temperature fast curing adhesive according to any one of claims 1 to 3, characterized in that: The epoxy resin includes: one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, and phenol epoxy resin.

5. The low temperature fast curing adhesive according to claim 1, characterized in that: The epoxy resin active diluent includes one or more of ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, 1,4-butanediol glycidyl ether, diglycidyl ether, and polyethylene glycol diglycidyl ether.

6. The low temperature fast curing adhesive according to claim 1, characterized in that: The curing agent accelerator includes at least one of triphenylphosphine, di-o-tolylguanidine, o-tolylbiguanide, N-(2-hydroxyphenyl)-N',N'-dimethylurea, N-(2-hydroxy-4-nitrobenzene)-N',N'-dimethylurea, and N-(5-chloro-2-hydroxybenzene)-N',N'-dimethylurea.

7. The low temperature fast curing adhesive according to claim 1, characterized in that: The low-temperature curing agent includes at least one of 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-methylimidazole and 2-ethylimidazole.

8. The low temperature fast curing adhesive according to claim 1, characterized in that: The mass ratio of the aprotic solvent to the low-polarity solvent is (1.5-3):

1.

9. A method for preparing a low-temperature fast-curing adhesive according to any one of claims 1 to 8, characterized in that: include: Dissolve the polyamide-imide using a non-protonic solvent; then add epoxy resin, epoxy resin active diluent, defoamer, curing agent accelerator, latent curing agent, low-temperature curing agent in sequence at room temperature, stir for 30-60 minutes, and then add a low-polarity solvent for dilution to obtain the product.

10. A printing screen, characterized in that: The preparation raw materials include the adhesive according to any one of claims 1-8.

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