High-temperature-resistant and high-humidity-resistant acrylic pressure-sensitive adhesive and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant and high-humidity-resistant acrylic pressure-sensitive adhesive and a preparation method thereof, and belongs to the field of adhesives. The pressure-sensitive adhesive comprises butyl acrylate, methyl acrylate, dicyclopentenyl ethoxylated acrylate DCPEA, hydroxyethyl acrylamide, hydroxybutyl acrylate, acrylic acid and hydroxyethyl oxybenzophenone methacrylate, is prepared by taking azodiisobutyronitrile as an initiator and ethyl acetate as a solvent through a special segmented polymerization process, and is prepared by using N, N, N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N ', N', N N, N ', N'-tetra (oxirane methyl)-1, 3-xylylenediamine is used as a curing agent. The molecular weight Mw of the obtained pressure-sensitive adhesive is 80-140 million, the theoretical Tg is-30 DEG C to-36 DEG C, the gel fraction is 60%-75%, the stripping force is larger than 25 N / 25 mm, and the glue viscosity and the solid content meet the relation that the glue viscosity is equal to 5000 + 50 * solid content. And the product meets related standard requirements and is suitable for laminating the road sign reflective film.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more particularly to a high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Pressure-sensitive adhesives (PSA) are specialty adhesives that bond under slight pressure, offering permanent adhesion and ease of use. They are widely used in packaging, medical, electronics, and traffic signage. Acrylic PSAs, due to their excellent weather resistance, transparency, and aging performance, have become the mainstream products in the PSA field, holding over 60% of the market share.

[0003] However, traditional acrylic pressure-sensitive adhesives are prone to problems such as decreased peel strength, insufficient cohesive strength, and adhesive residue in high-temperature and high-humidity environments, limiting their application in harsh environments. Especially in the field of road marking reflective film applications, pressure-sensitive adhesives need to be exposed to the outdoor environment for a long time, enduring various harsh conditions such as extreme temperature changes, rain erosion, and ultraviolet radiation.

[0004] As a crucial component of traffic safety facilities, road sign reflective film needs to maintain excellent adhesion performance over long periods under various harsh weather conditions to ensure the clear visibility and lasting effectiveness of traffic signs. This type of application places extremely high demands on pressure-sensitive adhesives: durable adhesive strength, excellent weather resistance, UV resistance, and resistance to high and low temperatures. According to GB / T 18833-2012 "Road Traffic Reflective Film" and GB / T 25978-2018 "Road Vehicle Signs and Labels" standards, pressure-sensitive adhesives used for road traffic signs must undergo rigorous testing for weather resistance, peel strength, and pull-out force.

[0005] Currently, some high-temperature resistant acrylic pressure-sensitive adhesives on the market are composed of hard monomers, soft monomers, functional monomers, and heat-resistant monomers. After treatment at 180℃ and cooling to room temperature, they leave no residue, do not yellow, are easy to peel, and have good resistance to damp heat. However, these pressure-sensitive adhesives typically have low peel strength, making it difficult to meet the requirements of high-strength bonding, and their durability in high-humidity environments needs improvement.

[0006] In addition, while high-adhesion emulsion-type acrylic pressure-sensitive adhesives have high adhesion (>1800gf / 25mm), their temperature resistance is only 120℃ / 1h, and due to their emulsion system, their wettability and water resistance to the substrate are poor. Solvent-based acrylic pressure-sensitive adhesives, although possessing advantages such as high transparency, excellent weather resistance and heat resistance (-40~200℃), good oil resistance, solvent resistance, and water resistance, still need further improvement in their overall performance under high temperature and high humidity conditions, especially in the application of road marking reflective films.

[0007] Traditional acrylic pressure-sensitive adhesives have shortcomings in UV resistance, while road marking reflective films need to be exposed to sunlight for extended periods, placing higher demands on the UV stability of pressure-sensitive adhesives. Although adding small-molecule UV absorbers can improve UV resistance, these small molecules are prone to migration, leading to performance degradation. While large-molecule UV absorbers can prevent migration, they have poor compatibility with acrylate polymers and are difficult to disperse uniformly in the pressure-sensitive adhesive.

[0008] Furthermore, existing acrylic pressure-sensitive adhesives have limitations in terms of molecular weight control and viscosity adjustment. Excessively high molecular weight leads to increased viscosity and difficulty in coating; conversely, excessively low molecular weight affects cohesive strength and heat resistance. Balancing the relationship between molecular weight, viscosity, and performance is a significant challenge facing existing technologies.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] The purpose of this invention is to provide a high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive and its preparation method, which has suitable peel strength, excellent high-temperature and high-humidity resistance, UV resistance, controllable molecular weight and viscosity characteristics, and excellent comprehensive performance, thereby solving the above-mentioned technical problems existing in the prior art.

[0011] The objective of this invention is achieved through the following technical solution: A high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive, characterized in that the pressure-sensitive adhesive is composed of a main agent and a curing agent, wherein the main agent comprises the following components in weight percentages, the sum of the amounts of the components being 100%, and the components are: methyl acrylate 4-8%, butyl acrylate 15-25%, dicyclopentenyl ethoxyacrylate 3-8%, hydroxyethyl acrylamide 1-3%, hydroxybutyl acrylate 2-5%, acrylic acid 0.5-2%, hydroxyethyloxybenzophenone methacrylate 1-3%, azobisisobutyronitrile 0.5-2%, and solvent 50-70%; The curing agent is N,N,N',N'-tetra(epoxyethylenemethyl)-1,3-phenylenediamine, and its addition amount is 0.5% to 2% of the total weight of the main components.

[0012] Preferably, in the above pressure-sensitive adhesive, the viscosity and solid content of the pressure-sensitive adhesive conform to the following relationship: pressure-sensitive adhesive viscosity = 5000 + 50 × solid content, wherein the solid content ranges from 40% to 45%.

[0013] Preferably, in the above-mentioned pressure-sensitive adhesive, the molecular weight Mw of the pressure-sensitive adhesive is 800,000 to 1,400,000, the theoretical glass transition temperature Tg is -30°C to -36°C, the gel fraction is 60% to 75%, and the 180° peel strength is greater than 25N / 25mm.

[0014] Preferably, in the above pressure-sensitive adhesive, the solvent is ethyl acetate.

[0015] A method for preparing the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive of the present invention, comprising the main components according to the formulation of the present invention, including: Step 1: Mix methyl acrylate, butyl acrylate, dicyclopentenyl ethoxyacrylate, hydroxyethyl acrylamide, hydroxybutyl acrylate, acrylic acid and hydroxyethyloxybenzophenone methacrylate to form a monomer mixture. Add 40-55% of the monomer mixture by weight and a portion of azobisisobutyronitrile to the reaction vessel. Add some solvent to the reaction vessel to adjust the mass concentration of the reaction system to 37-52%. Heat to 75-85°C. Step 2: Add some solvent to the remaining monomer mixture to adjust the mass concentration to 70-90%, and slowly add it dropwise to the reaction system in the reactor over 2 hours; Step 3: After the addition is complete, add azobisisobutyronitrile (AIBN) as an initiator every hour for a total of 3 times. Step 4: Keep the reaction at 75-85℃ for 3 hours, then cool to below 40℃; Step 5: Add the polymerization inhibitor and the remaining solvent, and adjust the solid content of the main agent to 40%–45%; Step 6: Add N,N,N',N'-tetratetra(epoxyethylenemethyl)-1,3-phenylenediamine as a curing agent, mix evenly, and the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive is obtained.

[0016] Preferably, in step 5 of the above method, the polymerization inhibitor is hydroquinone or 4-methoxyphenol, and the amount added is 0.01% to 0.05% of the total weight of all monomers of the main agent.

[0017] Compared with the prior art, the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive and its preparation method provided by the present invention have the following advantages: Excellent high temperature and humidity resistance: By using special heat-resistant monomers, hydroxyethyloxybenzophenone methacrylate (MABP) and dicyclopentenyl ethoxyacrylate (DCPEA), and optimizing the monomer ratio and polymerization process, the pressure-sensitive adhesive maintains excellent adhesion even in high temperature and humidity environments. Tests show that after 24 hours of treatment at 85℃ and 85% relative humidity, there was no peeling or bubbling, and the peel strength retention rate exceeded 90%.

[0018] Durable UV resistance: By using the reactive UV absorber MABP, UV-absorbing groups are directly introduced into the polymer backbone, avoiding the migration problems of small-molecule UV absorbers and providing durable and reliable UV absorption capabilities, enabling the pressure-sensitive adhesive to be used outdoors for extended periods without failure. After 1000 hours of UV aging, the peel strength retention rate exceeds 93%.

[0019] Controllable molecular weight and viscosity characteristics: Through special drop-addition process and initiator replenishment method, the polymerization reaction process is controlled to avoid burst polymerization and gelation, ensuring that the molecular weight of the product is in the range of 800,000 to 1,400,000, and that the viscosity and solid content have a linear relationship: glue viscosity = 5000 + 50 × solid content, which is beneficial to the control of production process and the consistency of product quality.

[0020] Suitable overall performance: The final product has suitable peel strength (greater than 25N / 25mm), high cohesive strength (holding power of more than 168 hours), and excellent heat and solvent resistance, meeting the demanding application requirements of road marking reflective film.

[0021] Broad application prospects: The product is not only suitable for road marking reflective film lamination, but also for other outdoor applications such as car signs and building signs, and has broad market prospects. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the specific content of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, which do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0023] First, the following explanations are provided for the terms that may be used in this article: The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0024] The terms "comprising," "including," "containing," "having," or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.) should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0025] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0026] The term "parts by mass" indicates the mass ratio between multiple components. For example, if component X is described as x parts by mass and component Y as y parts by mass, then the mass ratio of component X to component Y is x:y. One part by mass can represent any mass; for example, one part by mass can be expressed as 1 kg or 3.1415926 kg, etc. The sum of the parts by mass of all components is not necessarily 100 parts; it can be greater than 100 parts, less than 100 parts, or equal to 100 parts. Unless otherwise stated, parts, proportions, and percentages mentioned herein are all measured by mass.

[0027] When concentration, temperature, pressure, size, or other parameters are expressed as numerical ranges, such ranges should be understood to specifically disclose all ranges formed by any pairing of upper limits, lower limits, or preferred values ​​within that range, regardless of whether the range is explicitly stated; for example, if the numerical range "2 to 8" is stated, then that range should be interpreted to include ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4 and 6 to 7", "3 to 5 and 7", "2 and 5 to 7", etc. Unless otherwise stated, the numerical ranges described herein include both their endpoints and all integers and fractions within that range.

[0028] The solution provided by this invention will be described in detail below. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this invention whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0029] This invention provides a high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive, which is made from raw materials comprising the following weight percentages: 4-8% methyl acrylate, 15-25% butyl acrylate, 3-8% dicyclopentenyl ethoxyacrylate (DCPEA), 1-3% hydroxyethyl acrylamide, 2-5% hydroxybutyl acrylate, 0.5-2% acrylic acid, 1-3% hydroxyethyl benzophenone methacrylate (MABP), 0.5-2% azobisisobutyronitrile (AIB), and 50-70% solvent, wherein the sum of the weight percentages of each component is 100%.

[0030] Preferably, the molecular weight (Mw) of the pressure-sensitive adhesive is 800,000 to 1,400,000, the theoretical glass transition temperature (Tg) is -30°C to ~36°C, the gel fraction is 60% to 75%, and the 180° peel strength is greater than 25 N / 25 mm.

[0031] Preferably, the viscosity and solid content of the pressure-sensitive adhesive meet the following relationship: adhesive viscosity = 5000 + 50 × solid content, wherein the solid content ranges from 40% to 45%.

[0032] Preferably, the pressure-sensitive adhesive meets the weather resistance requirements of GB / T 18833-2012 "Road Traffic Reflective Film" and the peel strength and pull-out force requirements of GB / T 25978-2018 "Road Vehicle Signs and Labels".

[0033] The present invention also provides a method for preparing the above-mentioned high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive, comprising the following steps: Step 1, Initial Feeding: Take the main components according to the above formula, and mix the monomers methyl acrylate, butyl acrylate, dicyclopentenyl ethoxyacrylate, hydroxyethyl acrylamide, hydroxybutyl acrylate, acrylic acid, and hydroxyethyloxybenzophenone methacrylate to form a monomer mixture. Add 40-55% of the monomer mixture by weight, along with azobisisobutyronitrile and a portion of the solvent (ethyl acetate), to the reactor. Adjust the mass concentration of the reaction system to 37-52%, and raise the temperature to 75-85°C. The purpose of this step is to establish a suitable initial reaction environment and avoid explosive polymerization. Step 2, Monomer Addition: Add a portion of solvent to adjust the remaining monomer mixture to a mass concentration of 70-90%, and slowly add it dropwise to the reaction system over 2 hours. Using a dropwise addition method allows for control of the reaction rate, avoids localized overheating and explosive polymerization, and ensures uniform molecular weight distribution. Step 3, Initiator Replenishment: After the initial droplet addition is complete, azobisisobutyronitrile (AIBN) is added as the initiator every hour, for a total of 3 times. This staged initiator replenishment method ensures the reaction proceeds fully, improves monomer conversion, and controls the molecular weight within the target range. Azobisisobutyronitrile is a commonly used free radical polymerization initiator with a suitable decomposition temperature (60-80℃) and harmless decomposition products, making it suitable for the polymerization system of this invention.

[0034] Step 4, Incubation Reaction: Incubate the reaction at 75–85°C for 3 hours, then cool to below 40°C. This incubation stage ensures complete reaction of the remaining monomers, improving conversion rate. Step 5, Adjust solids content: Add the polymerization inhibitor and the remaining solvent to adjust the solids content of the main agent to 40%–45%. The addition of the polymerization inhibitor prevents further polymerization during storage and ensures product stability; Step 6, Add curing agent: Add N,N,N',N'-tetratetra(epoxyethylenemethyl)-1,3-phenylenediamine as curing agent, mix evenly, and the high temperature and high humidity resistant acrylic pressure-sensitive adhesive is obtained.

[0035] Preferably, in step 5 of the above method, the polymerization inhibitor is hydroquinone or 4-methoxyphenol, and its addition amount is 0.01% to 0.05% of the total weight of all monomers of the main agent.

[0036] Preferably, in step 6 of the above method, the crosslinking density and the performance of the final product are ensured by precisely controlling the amount of curing agent.

[0037] The aforementioned high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive can be used in the application of road marking reflective film.

[0038] In summary, the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive provided by the embodiments of the present invention has at least the following advantages: Excellent high temperature and humidity resistance: By using special heat-resistant monomers, hydroxyethyloxybenzophenone methacrylate (MABP) and dicyclopentenyl ethoxyacrylate (DCPEA), and optimizing the monomer ratio and polymerization process, the pressure-sensitive adhesive maintains excellent adhesion even in high temperature and humidity environments. Tests show that after 24 hours of treatment at 85℃ and 85% relative humidity, there was no peeling or bubbling, and the peel strength retention rate exceeded 90%.

[0039] Durable UV resistance: By using the reactive UV absorber MABP, UV-absorbing groups are directly introduced into the polymer backbone, avoiding the migration problems of small-molecule UV absorbers and providing durable and reliable UV absorption capabilities, enabling the pressure-sensitive adhesive to be used outdoors for extended periods without failure. After 1000 hours of UV aging, the peel strength retention rate exceeds 93%.

[0040] Controllable molecular weight and viscosity characteristics: Through special drop-addition process and initiator replenishment method, the polymerization reaction process is controlled to avoid burst polymerization and gelation, ensuring that the molecular weight of the product is in the range of 800,000 to 1,400,000, and that the viscosity and solid content have a linear relationship: glue viscosity = 5000 + 50 × solid content, which is beneficial to the control of production process and the consistency of product quality.

[0041] Suitable overall performance: The final product has suitable peel strength (greater than 25N / 25mm), high cohesive strength (holding power of more than 168 hours), and excellent heat and solvent resistance, meeting the demanding application requirements of road marking reflective film.

[0042] Broad application prospects: The product is not only suitable for road marking reflective film lamination, but also for other outdoor applications such as car signs and building signs, and has broad market prospects.

[0043] To more clearly demonstrate the technical solution and its effects provided by the present invention, the following detailed description of the solution provided by the embodiments of the present invention is provided with reference to specific examples.

[0044] Example 1 This embodiment provides a high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive. The main component includes the following raw materials in weight percentage: methyl acrylate 6%, butyl acrylate 20%, dicyclopentenyl ethoxyacrylate (DCPEA) 5%, hydroxyethyl acrylamide 1.5%, hydroxybutyl acrylate 3%, acrylic acid 1%, hydroxyethyl benzophenone methacrylate (MABP) 2%, azobisisobutyronitrile 0.8%, and ethyl acetate 61.5%.

[0045] The preparation method of the above pressure-sensitive adhesive is as follows: Step 1: Add 40% of the total weight of the monomer mixture (including methyl acrylate, butyl acrylate, DCPEA, hydroxyethyl acrylamide, hydroxybutyl acrylate, acrylic acid and MABP mixed in the above proportions) along with 0.2% azobisisobutyronitrile and part of ethyl acetate to the reaction vessel, adjust the mass concentration of the reaction system to 40%, and heat to 80°C. Step 2: Prepare an 80% mass concentration mixture of the remaining 60% monomer mixture and a portion of ethyl acetate, and slowly add it dropwise to the reaction system over 2 hours; Step 3: After the addition is complete, add 0.2% azobisisobutyronitrile as an initiator every hour for a total of 3 times; Step 4: Keep the reaction at 80°C for 3 hours, then cool it to below 40°C; Step 5: Add hydroquinone as a polymerization inhibitor (0.03% of the total weight of the monomers in the main agent) and the remaining ethyl acetate to adjust the solid content of the main agent to 42%; Step 6: Add N,N,N',N'-tetratetra(epoxyethylenemethyl)-1,3-phenylenediamine (1% of the total weight of all components of the main agent) as a curing agent, mix evenly, and obtain high temperature and high humidity resistant acrylic pressure-sensitive adhesive.

[0046] Example 2 This embodiment provides a high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive. The main component includes the following raw materials in weight percentage: methyl acrylate 7%, butyl acrylate 22%, dicyclopentenyl ethoxyacrylate (DCPEA) 4%, hydroxyethyl acrylamide 2%, hydroxybutyl acrylate 3.5%, acrylic acid 1.2%, hydroxyethyl benzophenone methacrylate (MABP) 2.5%, azobisisobutyronitrile 1.2%, and ethyl acetate 57.8%.

[0047] The preparation method of the above pressure-sensitive adhesive is as follows: Step 1: Add 45% of the monomer mixture, 0.3% of azobisisobutyronitrile and part of ethyl acetate to the reactor, adjust the mass concentration of the system to 45%, and heat to 78°C.

[0048] Step 2: Prepare an 85% mass concentration mixture of the remaining 55% monomer mixture with a portion of ethyl acetate, and slowly add it dropwise to the reaction system over 2 hours.

[0049] Step 3: After the addition is complete, add 0.3% azobisisobutyronitrile as an initiator every hour for a total of 3 times.

[0050] Step 4: Keep the reaction at 78°C for 3 hours, then cool it to below 40°C.

[0051] Step 5: Add 4-methoxyphenol (0.025% of the total weight of all monomers in the main agent) as a polymerization inhibitor and the remaining ethyl acetate to adjust the solid content of the main agent to 43%.

[0052] Step 6: Add N,N,N',N'-tetratetra(epoxyethylenemethyl)-1,3-phenylenediamine (accounting for 1.2% of the total weight of all components of the main agent), mix evenly, and obtain a novel high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive.

[0053] Example 3 This embodiment provides a high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive. The main component includes the following raw materials in weight percentage: methyl acrylate 5%, butyl acrylate 18%, dicyclopentenyl ethoxyacrylate (DCPEA) 6%, hydroxyethyl acrylamide 1%, hydroxybutyl acrylate 2.5%, acrylic acid 0.8%, hydroxyethyl benzophenone methacrylate (MABP) 1.5%, azobisisobutyronitrile 1%, and ethyl acetate 65.2%.

[0054] The preparation method of the above pressure-sensitive adhesive is as follows: Step 1: Add 50% of the monomer mixture, 0.25% of azobisisobutyronitrile, and part of ethyl acetate to the reactor, adjust the mass concentration of the system to 42%, and heat to 82°C. Step 2: Prepare a 75% mass concentration mixture of the remaining 50% monomer mixture and a portion of ethyl acetate, and slowly add it dropwise to the reaction system over 2 hours; Step 3: After the addition is complete, add 0.25% azobisisobutyronitrile as an initiator every hour for a total of 3 times; Step 4: Keep the reaction at 82°C for 3 hours, then cool it to below 40°C; Step 5: Add hydroquinone (0.04% of the total weight of all monomers in the main agent) and the remaining ethyl acetate as polymerization inhibitors to adjust the solid content of the main agent to 41%. Step 6: Add N,N,N',N'-tetratetra(epoxyethylenemethyl)-1,3-phenylenediamine (0.8% of the total weight of all components of the main agent) as a curing agent, mix evenly, and obtain high temperature and high humidity resistant acrylic pressure-sensitive adhesive.

[0055] Comparative Example 1 The formulation and process of Example 1 are followed, but without the addition of hydroxyethyloxybenzophenone methacrylate (MABP), and the content of butyl acrylate is increased accordingly.

[0056] Comparative Example 2 The formulation and process of Example 1 are followed, but without adding dicyclopentenyl ethoxyacrylate (DCPEA), and the content of butyl acrylate is increased accordingly.

[0057] Comparative Example 3

[0058] The formulation and process of Example 1 were followed, but conventional benzoyl peroxide (BPO) was used instead of azobisisobutyronitrile (AIBN) as the initiator.

[0059] Comparative Example 4 The formulation and process of Example 1 are followed, but without the curing agent N,N,N',N'-tetra(epoxyethylenemethyl)-1,3-phenylenediamine.

[0060] It can be understood that the above comparative examples 1-4 were designed to compare with the high temperature and high humidity resistant acrylic pressure-sensitive adhesive of the present invention in order to verify the influence of certain components on product performance, and do not belong to the prior art.

[0061] Performance testing: The performance of the pressure-sensitive adhesive samples obtained in Examples 1-3 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1.

[0062] Table 1 shows the performance test results of the pressure-sensitive adhesive:

[0063] Test method description: Molecular weight (Mw): determined by gel permeation chromatography (GPC), using polystyrene as the standard and tetrahydrofuran as the mobile phase.

[0064] Theoretical Tg: Calculated using the Fox formula, which is: 1 / Tg = w1 / Tg1 + w2 / Tg2 + ... + wn / Tgn, where w1 is the weight fraction of monomer i and Tgi is the glass transition temperature of the homopolymer of monomer i.

[0065] Gel fraction: determined by Soxhlet extraction with ethyl acetate as solvent for 24 hours.

[0066] 180° peel force: Measured according to GB / T 2792-2014 standard, with stainless steel plate as the substrate and tensile speed of 300 mm / min.

[0067] Initial tack: Determined according to the rolling ball method of GB / T 4852-2002. The smaller the ball number, the better the initial tack.

[0068] Adhesion holding power: According to GB / T 4851-2014 standard, the detachment time was recorded after hanging a 1kg weight at 80℃.

[0069] High temperature resistance: After treatment at 120℃ for 24 hours, observe the appearance and test the peel force.

[0070] High humidity resistance: After treatment at 85℃ and 85% relative humidity for 24 hours, observe the appearance and test the peel strength.

[0071] Peel strength retention rate after UV aging: The peel strength retention rate was tested after 1000 hours of UV aging according to GB / T 18833-2012 standard.

[0072] Results analysis: As can be seen from the test results in Table 1, the pressure-sensitive adhesives prepared in Examples 1-3 of this invention have excellent comprehensive performance: Molecular weight control: The molecular weight Mw is between 1.18 million and 1.32 million, which meets the requirement of 800,000 to 1.4 million, and the distribution is relatively narrow, indicating that the polymerization reaction is well controlled.

[0073] Glass transition temperature: The theoretical Tg is between -31℃ and -34℃, which meets the requirements of -30℃ to -36℃, ensuring the performance of the pressure-sensitive adhesive over a wide temperature range.

[0074] Gel fraction: A gel fraction between 65% and 72% meets the requirement of 60% to 75%, indicating that the crosslinking density is moderate, with sufficient cohesive strength and good adhesion.

[0075] Peel performance: The peel force at 180° is greater than 25N / 25mm, which meets the application requirements of road marking reflective film.

[0076] Temperature and humidity resistance: Excellent resistance to high temperature and high humidity, maintaining stable bonding performance even in harsh environments.

[0077] Aging resistance: After 1000 hours of UV aging, the peel strength retention rate exceeds 93%, indicating excellent UV resistance.

[0078] In contrast, Comparative Example 1 (without MABP) showed a peel strength retention rate of only 72.4% after UV aging, significantly lower than that of the embodiments of the present invention, indicating that the addition of MABP significantly improved the UV resistance of the pressure-sensitive adhesive. Comparative Example 2 (without DCPEA) showed a significant decrease in high temperature and high humidity resistance, indicating that DCPEA plays an important role in improving the heat resistance and cohesive strength of the pressure-sensitive adhesive. Comparative Example 3 (using BPO initiator) had a lower molecular weight and decreased overall performance, indicating that AIBN initiator is more suitable for the polymerization system of the present invention. Comparative Example 4 (without curing agent) had a lower gel fraction, poor tack, and severe residue and flow at high temperatures, indicating that the curing agent is crucial for forming a three-dimensional cross-linked network and improving cohesive strength.

[0079] Verification of the viscosity-solid content relationship of pressure-sensitive adhesive: The viscosity of the samples from Examples 1-3 at different solid contents was tested, and the results are shown in Table 2.

[0080] Table 2 shows the test results of the viscosity-solid content relationship of the pressure-sensitive adhesive:

[0081] As shown in Table 2, the deviation rate between the measured viscosity and the theoretical viscosity (calculated according to the formula: adhesive viscosity = 5000 + 50 × solid content) of the pressure-sensitive adhesive samples in Examples 1-3 at different solid contents is less than 5%, proving that the viscosity-solid content relationship of the products meets the design requirements and has good consistency and stability. This characteristic is beneficial for controlling the production process and ensuring the consistency of performance of different batches of products.

[0082] Application Examples The pressure-sensitive adhesive prepared in Example 1 was coated onto a 25 μm thick PET film, with a dry adhesive thickness of 25 μm. It was then laminated with reflective film material to produce a road marking reflective film sample. Tests were conducted according to GB / T 18833-2012 "Road Traffic Reflective Film" and GB / T25978-2018 "Road Vehicle Signs and Labels," and the results are as follows: Retroreflection coefficient: According to the GB / T 18833-2012 standard, the retroreflection coefficient of the white reflective film is 650 cd / (lx·m²) (observation angle 0.2°, incident angle -4°), which is higher than the standard requirement of 600 cd / (lx·m²).

[0083] Weather resistance test: After 1000 hours of xenon lamp aging test, the retroreflection coefficient decreased by 18%, which is lower than the standard requirement of 20%; there was no cracking or fading.

[0084] Abrasion resistance test: Using a Taber abrasion tester, after 500g load and 500 cycles of friction, there was no penetrating damage to the surface, and the retroreflection coefficient retention rate was 85%, which is higher than the standard requirement of 80%.

[0085] Color fastness: After solvent (gasoline, alcohol) wiping and high and low temperature cycling tests, the color change ΔE is 2.5, which is lower than the standard requirement of ΔE≤3.

[0086] Impact resistance and flexibility: No cracks were observed in the falling ball impact test, and no fractures were observed in the -20℃ low temperature bending test.

[0087] Peel strength: Tested according to GB / T 25978-2018 standard, the peel strength is 28.5N / 25mm, which is higher than the standard requirement.

[0088] The test results above show that the pressure-sensitive adhesive prepared by this invention fully meets the application requirements of road sign reflective film and has excellent weather resistance, adhesion and durability.

[0089] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive, characterized in that, This pressure-sensitive adhesive consists of a main agent and a curing agent. The main agent comprises the following components by weight percentage, with the sum of the components being 100%. The components are: methyl acrylate 4-8%, butyl acrylate 15-25%, dicyclopentenyl ethoxyacrylate 3-8%, hydroxyethyl acrylamide 1-3%, hydroxybutyl acrylate 2-5%, acrylic acid 0.5-2%, hydroxyethyl benzophenone methacrylate 1-3%, azobisisobutyronitrile 0.5-2%, and solvent 50-70%. The curing agent is N,N,N',N'-tetra(epoxyethylenemethyl)-1,3-phenylenediamine, and its addition amount is 0.5% to 2% of the total weight of the main components.

2. The high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive according to claim 1, characterized in that, The viscosity and solid content of the pressure-sensitive adhesive conform to the following relationship: pressure-sensitive adhesive viscosity = 5000 + 50 × solid content, where the solid content ranges from 40% to 45%.

3. The high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive according to claim 1 or 2, characterized in that, The pressure-sensitive adhesive has a molecular weight (Mw) of 800,000 to 1,400,000, a theoretical glass transition temperature (Tg) of -30°C to -36°C, a gel fraction of 60% to 75%, and a 180° peel strength greater than 25 N / 25 mm.

4. The high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive according to claim 1 or 2, characterized in that, The solvent is ethyl acetate.

5. A method for preparing the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive according to any one of claims 1-4, characterized in that, The main components are taken according to the formulation of any one of claims 1-4, including: Step 1: Mix methyl acrylate, butyl acrylate, dicyclopentenyl ethoxyacrylate, hydroxyethyl acrylamide, hydroxybutyl acrylate, acrylic acid and hydroxyethyloxybenzophenone methacrylate to form a monomer mixture. Add 40-55% of the monomer mixture by weight and a portion of azobisisobutyronitrile to the reaction vessel. Add some solvent to the reaction vessel to adjust the mass concentration of the reaction system to 37-52%. Heat to 75-85°C. Step 2: Add some solvent to the remaining monomer mixture to adjust the mass concentration to 70-90%, and slowly add it dropwise to the reaction system in the reactor over 2 hours; Step 3: After the addition is complete, add azobisisobutyronitrile (AIBN) as an initiator every hour for a total of 3 times. Step 4: Keep the reaction at 75-85℃ for 3 hours, then cool to below 40℃; Step 5: Add the polymerization inhibitor and the remaining solvent, and adjust the solid content of the main agent to 40%–45%; Step 6: Add N,N,N',N'-tetratetra(epoxyethylenemethyl)-1,3-phenylenediamine as a curing agent, mix evenly, and the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive is obtained.

6. The preparation method of the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive according to claim 5, characterized in that, In the method described, the amount of azobisisobutyronitrile added in the four additions is the same, with each addition being one-quarter of the total amount of azobisisobutyronitrile added.

7. The preparation method of the high-temperature and high-humidity resistant acrylic pressure-sensitive adhesive according to claim 5, characterized in that, In step 5, the polymerization inhibitor is hydroquinone or 4-methoxyphenol, and the amount added is 0.01% to 0.05% of the total weight of all monomers.

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