High-temperature-aging-resistant acrylate pressure-sensitive adhesive and preparation method thereof

Abstract

The invention relates to the technical field of pressure-sensitive adhesives, in particular to a high-temperature-aging-resistant acrylate pressure-sensitive adhesive and a preparation method thereof.The high-temperature-aging-resistant acrylate pressure-sensitive adhesive comprises a linear acrylate pressure-sensitive adhesive layer, and the linear acrylate pressure-sensitive adhesive layer is formed by mixing a plurality of acrylate monomers with different Tg values and a monomer containing an active functional group; azobisisobutyronitrile is used as an initiator, ethyl acetate is used as a solvent, a solution polymerization method is adopted for polymerization, and the linear acrylate pressure-sensitive adhesive with high molecular weight and low Tg value is prepared by regulating and controlling the monomer concentration, the dropping speed and the reaction temperature. Compared with the prior art, the high-temperature-aging-resistant acrylate pressure-sensitive adhesive disclosed by the invention can still keep high viscosity in a long-time high-temperature environment, and is suitable for high-temperature working environments such as insulation protection of high-power electric appliances and the like.

Description

[Technical field]

[0001] The invention relates to the technical field of pressure-sensitive adhesives, and in particular to a high-temperature aging-resistant acrylic pressure-sensitive adhesive and a preparation method thereof. [Background technology]

[0002] Pressure-sensitive tape has the advantages of easy construction and low cost for use as insulation protection for electrical appliances. However, when it comes to insulation protection for high-power electrical appliances, the pressure-sensitive adhesives in the existing technology lose their adhesion due to high-temperature aging. For example, the viscosity of many tapes will decrease by more than 50% within a day under a 120°C environment, and cannot meet this application scenario. [Summary of the invention]

[0003] In order to overcome the above problems, the present invention provides a high temperature aging resistant acrylic pressure sensitive adhesive and a preparation method thereof which can effectively solve the above problems.

[0004] The present invention provides a technical solution to solve the above technical problems: providing a high temperature aging resistant acrylic pressure-sensitive adhesive and a preparation method thereof, comprising a linear acrylic pressure-sensitive adhesive layer, wherein the linear acrylic pressure-sensitive adhesive layer is formed by mixing a plurality of acrylic monomers with different Tg values ​​and a monomer containing an active functional group.

[0005] Preferably, the acrylic acid ester monomer is two or more selected from the group consisting of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate and isooctyl acrylate.

[0006] Preferably, the monomer containing active functional groups is one of methacrylic acid, acrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate and glycidyl acrylate.

[0007] Preferably, the methyl methacrylate is a high Tg value monomer, accounting for 4-10%.

[0008] Preferably, the ethyl acrylate, butyl acrylate and isooctyl acrylate are low Tg value monomers, accounting for 85-95%.

[0009] Preferably, the monomer containing active functional groups accounts for 2-5%.

[0010] Preferably, the linear acrylate pressure-sensitive adhesive layer further comprises an antioxidant, a tackifying resin and a curing agent; based on 100 parts by mass of the linear acrylate pressure-sensitive adhesive layer, the antioxidant content is 0.1-0.6%, the tackifying resin content is 2-6%, and the curing agent content is 0.2-1%.

[0011] A method for preparing a high-temperature aging-resistant acrylic pressure-sensitive adhesive comprises the following steps: using azobisisobutyronitrile as an initiator and ethyl acetate as a solvent, adopting a solution polymerization method, and adjusting the monomer concentration, the dropping speed and the reaction temperature to prepare a linear acrylic pressure-sensitive adhesive with a high molecular weight and a low Tg value.

[0012] Preferably, the dosage of the azobisisobutyronitrile initiator is between 0.1% and 0.3%, and the monomer concentration is between 40% and 55%.

[0013] Preferably, a method for preparing a high temperature aging resistant acrylic pressure-sensitive adhesive comprises the following steps:

[0014] Step S1, taking each monomer into a batching barrel, adding solvent ethyl acetate and initiator, mixing evenly, and pumping into a high-level tank for standby use;

[0015] Step S2, preheating the reaction kettle, passing cold water through the dynamic condenser, adding a certain amount of ethyl acetate, starting the stirring paddle, and stirring for 10 to 20 minutes to remove oxygen;

[0016] Step S3, adding 5-10% of the total amount of the mixed monomers in the header tank into the reactor at one time, and reacting until the mixed liquid in the reactor has a certain viscosity;

[0017] Step S4, uniformly adding the mixed monomers in the high-level tank dropwise; the adding time is 4 to 6 hours;

[0018] Step S5, after the dropwise addition is completed, adding the initiator 1 to 2 times;

[0019] Step S6: After the addition of the initiator is completed, the reaction temperature is increased by 1 to 3°C above the original temperature and the temperature is kept constant for 1.5 to 2.5 hours;

[0020] Step S7, after the heat preservation is completed, cool it down to below 40°C with cold water;

[0021] Step S8: adding tackifying resin, antioxidant and curing agent and mixing them evenly, thus completing the preparation of glue.

[0022] Compared with the prior art, the high temperature aging resistant acrylic pressure-sensitive adhesive of the present invention can still maintain high viscosity in a high temperature environment for a long time, and is suitable for high-temperature working environments such as insulation protection of high-power electrical appliances.

Brief Description of the Drawings

[0023] Figure 1 This is a layered structure diagram of the high temperature aging resistant acrylic pressure-sensitive adhesive of the present invention. [Specific implementation method]

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are limited to relative positions on the specified view, rather than absolute positions.

[0026] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] See also Figure 1 The high temperature aging resistant acrylic pressure-sensitive adhesive of the present invention comprises a linear acrylic pressure-sensitive adhesive layer 20, wherein the linear acrylic pressure-sensitive adhesive layer 20 is formed by mixing acrylic monomers with different Tg (glass transition temperature) values ​​and a monomer containing an active functional group.

[0028] The high temperature aging resistant acrylic pressure-sensitive adhesive of the present invention comprises a substrate layer 10 and a release film 30, wherein the linear acrylic pressure-sensitive adhesive layer 20 is adhered to the substrate layer 10, and the release film 30 is adhered to the linear acrylic pressure-sensitive adhesive layer 20, and the substrate layer 10 and the release film 30 are respectively located on different sides of the linear acrylic pressure-sensitive adhesive layer 20.

[0029] The acrylic acid ester monomer is a combination of two or more of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate and isooctyl acrylate.

[0030] The monomer containing active functional groups is one of methacrylic acid, acrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate and glycidyl acrylate.

[0031] The methyl methacrylate is a high Tg value monomer, accounting for 4-10%.

[0032] The ethyl acrylate, butyl acrylate and isooctyl acrylate are low Tg value monomers, and two or three of them are selected, accounting for 85-95%.

[0033] The monomer containing active functional groups accounts for 2-5%.

[0034] The above-mentioned proportion is the mass proportion of the total mass of the linear acrylic pressure-sensitive adhesive layer 20 .

[0035] Among them, acrylate monomers can be used in a variety of different combinations. The following mainly introduces four preferred combinations:

[0036] Combination 1: Methyl methacrylate: 6%

[0037] Butyl acrylate: 75.5%

[0038] Isooctyl acrylate: 15%

[0039] Hydroxyethyl acrylate: 3.5%.

[0040] Combination 2: Methyl methacrylate: 5%

[0041] Butyl acrylate: 70.5%

[0042] Isooctyl acrylate: 20%

[0043] Acrylic acid: 4.5%.

[0044] Combination 3: Methyl methacrylate: 4%

[0045] Butyl acrylate: 62%

[0046] Isooctyl acrylate: 30%

[0047] Methacrylic acid: 4%.

[0048] Combination 4: Methyl methacrylate: 7%

[0049] Butyl acrylate: 64%

[0050] Isooctyl acrylate: 25%

[0051] Hydroxypropyl acrylate: 4%.

[0052] The contents in the above four combinations are all the mass proportions of a single component to the total mass of acrylate monomers.

[0053] The linear acrylic pressure-sensitive adhesive layer 20 further includes an antioxidant, an anti-aging tackifying resin such as a petroleum resin and a terpene resin, and a curing agent.

[0054] Based on 100 parts by mass of the linear acrylic pressure-sensitive adhesive layer 20, the content of the antioxidant is 0.1-0.6%, the content of the tackifying resin is 2-6%, and the content of the curing agent is 0.2-1%.

[0055] The tackifying resin is one of petroleum resin, terpene resin and terpene phenol resin.

[0056] The antioxidant is one of antioxidants 1010, 1076, 168, 164, etc., or a mixture of several of them.

[0057] The petroleum resin is one or more of C5 petroleum resin and C9 petroleum resin of different colors, and needs to have good compatibility with the glue, otherwise it will not have the effect of increasing viscosity.

[0058] The terpene resin may have a relatively high softening point, such as T130 and T140, which are more suitable, and can improve the viscosity of the tape and also contribute to the cohesion and holding force of the tape.

[0059] The curing agent can be selected from isocyanate curing agents and organic metal salt curing agents, such as Bayer's N3390, N3300, L75, IL1454 and other trimer structure curing agents, preferably HDI structure aliphatic N3390 and N3300 isocyanates, which have better aging resistance.

[0060] Organic metal salt curing agents include organic zinc salts, organic aluminum salts, organic zirconium salts, etc., which react with carboxyl and hydroxyl groups in the glue to produce cross-linking, forming a network structure between the pressure-sensitive adhesive molecules and having good cohesion and adhesion.

[0061] The method for preparing the high temperature aging resistant acrylic pressure-sensitive adhesive adopts azobisisobutyronitrile as an initiator and ethyl acetate as a solvent, adopts a solution polymerization method, and prepares a linear acrylic pressure-sensitive adhesive with a high molecular weight and a low Tg value by regulating process conditions such as monomer concentration, dropping speed and reaction temperature.

[0062] The dosage of azobisisobutyronitrile initiator is between 0.1% and 0.3%, preferably between 0.1% and 0.15%, which reduces the double radical termination of active free radicals, is beneficial to increase the molecular weight, and the adhesive has better cohesive strength.

[0063] The monomer concentration is between 40% and 55%. The higher the monomer concentration, the higher the molecular polymerization degree. However, there is a problem of high viscosity, which is not easy to dissipate heat and may cause explosion and gelation. Therefore, a method of high concentration in the early stage and adding solvent in the later stage is adopted to prepare a pressure-sensitive adhesive with a higher average molecular weight.

[0064] The reaction temperature is between 75 and 83° C. The polymerization reaction is carried out by dropping while stirring. The dropping time of the mixed monomer is 4 to 6 hours. The longer the time, the greater the average molecular weight of the polymer, the more uniform the reaction exotherm, and the generation of branched structure can be prevented.

[0065] Specifically, the method for preparing the high temperature aging resistant acrylic pressure-sensitive adhesive of the present invention comprises the following steps:

[0066] Step S1, weigh each monomer according to the formula into a batching barrel, then add solvent ethyl acetate and initiator, mix evenly, and pump into a high-level tank for standby use.

[0067] Step S2, preheating the reactor to the set reaction temperature, passing cold water through the dynamic condenser, adding a certain amount of ethyl acetate, starting the stirring paddle, and stirring for about 10 to 20 minutes to remove oxygen.

[0068] Step S3, adding 5-10% of the total amount of the mixed monomers in the high-level tank into the reaction kettle at one time, and reacting until the mixed liquid in the kettle has a certain viscosity.

[0069] Step S4, adding the mixed monomers in the high-level tank dropwise at a uniform speed; the adding time is 4 to 6 hours.

[0070] Step S5: After the dropwise addition is completed, the initiator is added 1 to 2 times to improve the monomer conversion rate, with a time interval of 10 to 20 minutes.

[0071] Step S6: After the addition of the initiator is completed, the reaction temperature is increased by 1 to 3°C from the original temperature and the temperature is kept constant for 1.5 to 2.5 hours.

[0072] Step S7: After the heat preservation is completed, cool it with cold water to below 40°C.

[0073] Step S8: adding tackifying resin, antioxidant and curing agent in proportion and mixing evenly to complete the preparation of glue.

[0074] After the linear acrylic pressure-sensitive adhesive with high molecular weight and low Tg value is prepared, it is coated on the substrate layer 10 , and the surface is covered with a release film 30 .

[0075] After high-temperature aging at 130°C / 720h, the high-temperature aging-resistant acrylic pressure-sensitive adhesive of the present invention is bonded to a SUS steel plate, and the 180° peeling force is greater than 7N / 25mm; after high-temperature aging at 120°C / 1500h, the high-temperature aging-resistant acrylic pressure-sensitive adhesive is bonded to a SUS steel plate, and the 180° peeling force is greater than 7N / 25mm.

[0076] Compared with the prior art, the high temperature aging resistant acrylic pressure-sensitive adhesive of the present invention can still maintain high viscosity in a high temperature environment for a long time, and is suitable for high-temperature working environments such as insulation protection of high-power electrical appliances.

[0077] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included in the patent protection scope of the present invention.

Claims

1. A high temperature aging resistant acrylic pressure-sensitive adhesive, characterized in that: The linear acrylate pressure-sensitive adhesive layer is formed by mixing a plurality of acrylate monomers with different Tg values ​​and a monomer containing an active functional group.

2. The high temperature aging resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The acrylic acid ester monomers are two or more of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate and isooctyl acrylate.

3. The high temperature aging resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that: The monomer containing active functional groups is one of methacrylic acid, acrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate and glycidyl acrylate.

4. The high temperature aging resistant acrylic pressure-sensitive adhesive according to claim 2, characterized in that: The methyl methacrylate is a high Tg value monomer, accounting for 4-10%.

5. The high temperature aging resistant acrylic pressure sensitive adhesive according to claim 2, characterized in that: The ethyl acrylate, butyl acrylate and isooctyl acrylate are low Tg value monomers, accounting for 85-95%.

6. The high temperature aging resistant acrylic pressure sensitive adhesive according to claim 3, characterized in that: The monomer containing active functional groups accounts for 2-5%.

7. The high temperature aging resistant acrylic pressure sensitive adhesive according to claim 1, characterized in that: The linear acrylate pressure-sensitive adhesive layer also includes an antioxidant, a tackifying resin and a curing agent; based on 100 parts by mass of the linear acrylate pressure-sensitive adhesive layer, the antioxidant content is 0.1-0.6%, the tackifying resin content is 2-6%, and the curing agent content is 0.2-1%.

8. A method for preparing a high temperature aging resistant acrylic pressure-sensitive adhesive, characterized in that: A linear acrylic pressure-sensitive adhesive with high molecular weight and low Tg value was prepared by solution polymerization using azobisisobutyronitrile as initiator and ethyl acetate as solvent by adjusting the monomer concentration, dropping speed and reaction temperature.

9. The method for preparing the high temperature aging resistant acrylic pressure sensitive adhesive according to claim 8, characterized in that: The dosage of azobisisobutyronitrile initiator is between 0.1 and 0.3%, and the monomer concentration is between 40 and 55%.

10. The method for preparing the high temperature aging resistant acrylic pressure sensitive adhesive according to claim 8, characterized in that: The steps include: Step S1, taking each monomer into a batching barrel, adding solvent ethyl acetate and initiator, mixing evenly, and pumping into a high-level tank for standby use; Step S2, preheating the reaction kettle, passing cold water through the dynamic condenser, adding a certain amount of ethyl acetate, starting the stirring paddle, and stirring for 10 to 20 minutes to remove oxygen; Step S3, adding 5-10% of the total amount of the mixed monomers in the header tank into the reactor at one time, and reacting until the mixed liquid in the reactor has a certain viscosity; Step S4, uniformly adding the mixed monomers in the high-level tank dropwise; the adding time is 4 to 6 hours; Step S5, after the dropwise addition is completed, adding the initiator 1 to 2 times; Step S6: After the addition of the initiator is completed, the reaction temperature is increased by 1 to 3°C above the original temperature and the temperature is kept constant for 1.5 to 2.5 hours; Step S7, after the heat preservation is completed, cool it down to below 40°C with cold water; Step S8: adding tackifying resin, antioxidant and curing agent and mixing them evenly, thus completing the preparation of glue.

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