A pressure-sensitive adhesive for self-adhesive PVC film and preparation method thereof

Abstract

The present invention relates to a self-adhesive pressure-sensitive adhesive for PVC film and a preparation method thereof. The inventors have discovered that p-fluorophenylalanine can be used as an antioxidant and tackifier for polyacrylate pressure-sensitive adhesives, and can be used to prepare emulsion-type polyacrylate pressure-sensitive adhesives. The resulting emulsion-type polyacrylate pressure-sensitive adhesive exhibits excellent anti-aging properties, as demonstrated by the fact that its initial tack, sustained tack, and 180° peel strength do not significantly change before and after accelerated aging. The resulting pressure-sensitive adhesive can be used to prepare self-adhesive PVC wallpaper.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a pressure-sensitive adhesive for a self-adhesive PVC film and a preparation method thereof. Background Art

[0002] As people's living standards and aesthetic tastes continue to improve, their inherent demands for interior decoration are also rising, and the proportion of interior decoration costs in construction projects is also increasing. In some high-end building decoration, this cost accounts for over 40% of the total cost. Wallpaper, as an important architectural decoration material, offers advantages such as environmental friendliness, luxurious style, soft texture, rich colors and patterns, and elegant decorative effects. Therefore, it is widely used in interior decoration in homes, hotels, hospitals, KTV entertainment venues, and other places.

[0003] Wallpaper pasting construction used to use polyvinyl alcohol and white latex, which has the following disadvantages:

[0004] (1) When applying wallpaper, the leveling and lubricity are low. After the wallpaper is applied to the wall, the excess glue is not easy to discharge, and the residual glue affects the flatness of the wallpaper.

[0005] (2) After the glue dries, the glue left at the wallpaper seams is difficult to clean, affecting the aesthetic effect;

[0006] (3) The cost of using polyvinyl alcohol and white latex is high, and the residual monomers in the polymerization process will cause air pollution;

[0007] (4) Early starch adhesives had simple production equipment and improper raw material combinations, which resulted in a short shelf life of the product, easy yellowing and mold, and secondary pollution to the environment.

[0008] PVC adhesive wallpaper is made by covering a layer of polyvinyl chloride film on a pure paper base (or non-woven fabric, woven fabric base), and is made through processes such as lamination, embossing, and printing. This type of wallpaper has exquisite printing, good embossing texture, good waterproof and moisture-proof properties, is durable, and easy to maintain. Structurally, a polyvinyl chloride film is covered on a pure paper base, and the film has its own pressure-sensitive adhesive, which is then covered with a protective sticker. When using, tear off the protective sticker and stick it directly on the clean wall. This eliminates the need to handle the wall and apply glue during the construction of ordinary wallpaper, and is therefore very popular among the people. This type of wallpaper is currently the most commonly used and most widely used wallpaper, and can be widely used in all homes and commercial places.

[0009] Pressure-sensitive adhesive (PSA) is a type of adhesive that is sensitive to pressure during bonding, forming a strong bond even with minimal pressure. The bonding force between two surfaces is primarily van der Waals forces, so once the bond is formed, the surface structure remains intact.

[0010] Because PSA is easy to adhere, difficult to peel, can be peeled without damage, has a long-lasting adhesive layer, and is easy to use, it is widely used in many fields such as packaging, automobiles, electrical appliances, aerospace, building materials, medical care, and daily chemicals. It is a type of adhesive commonly used on PVC-coated wallpaper.

[0011] Acrylate PSA has been widely used in various industries due to its excellent pressure sensitivity, adhesion, antioxidant properties, UV radiation resistance, good optical transparency and relatively low production cost, and its output accounts for more than 65% of all pressure-sensitive adhesive output.

[0012] Polyacrylate PSAs are categorized as solvent-based and emulsion-based. Solvent-based PSAs are made by dissolving the pressure-sensitive adhesive in a solvent, coating it on a substrate, and then completely evaporating the solvent from the adhesive coating to create the adhesive tape. The solvents used are mostly industrial-grade ethyl acetate, toluene, and methyl ethyl ketone, which can pollute the environment after evaporation.

[0013] Emulsion-based PSA uses water as the dispersion medium, dispersing the adhesive. After coating, the water evaporates to produce the tape. These adhesives offer advantages such as safety, ease of use, high polymer molecular weight, and pollution-free properties. They have been the fastest-growing polymer emulsion adhesive since the 1980s. Domestic research on acrylic PSAs has primarily focused on emulsion-based PSAs.

[0014] From the composition point of view, the emulsion acrylate PSA system usually includes main components such as acrylate monomer, initiator, emulsifier and dispersion medium. In addition, molecular weight regulators, inhibitors, tackifiers, antioxidants, co-emulsifiers, etc. are sometimes added to ensure good performance and emulsion stability.

[0015] The monomers used in acrylic emulsion polymerization are divided into soft monomers, hard monomers, and functional monomers. Soft monomers refer to monomers with a lower glass transition temperature (Tg), such as butyl acrylate, isooctyl acrylate, ethylene, butadiene, etc. Adding soft monomers can increase the viscoelasticity and rheological properties of the polymer.

[0016] Hard monomers are those monomers that have a higher Tg and can copolymerize with soft monomers, such as methyl methacrylate, styrene, acrylonitrile, vinyl acetate, etc. After copolymerization of hard monomers and soft monomers, the polymer can have better cohesive strength, creep resistance and high temperature resistance.

[0017] Functional monomers are monomers that contain various functional groups and can copolymerize with soft and hard monomers, such as hydroxyethyl acrylate, acrylic acid, carboxyethyl acrylate, and acrylamide. Functional monomers can improve the high-temperature resistance, adhesion, and creep resistance of the copolymer. In addition, adding a small amount of functional monomers can also improve the polymerization process and enhance the stability of the polymerization process. When designing the actual pressure-sensitive adhesive monomer formula, it is necessary to calculate the amount of comonomer according to the FOX equation:

[0018]

[0019] T g ——Glass transition temperature of acrylate copolymers

[0020] w1, w2, w3——the weight fraction of each acrylate monomer involved in the polymerization reaction

[0021] T g1 、T g2 、T g3 ——Glass transition temperature of the homopolymer of the acrylate monomer involved in the polymerization reaction

[0022] The design of the monomer formula requires selecting the appropriate monomer mass ratio based on the FOX formula to keep the glass transition temperature of the copolymer within a certain range.

[0023] Emulsifiers are essential components in emulsion polymerization systems. Essentially, they are surfactants, their chemical structure consisting of a polar hydrophilic group and a nonpolar lipophilic group. Emulsifiers have the ability to reduce surface tension, emulsify, disperse, and solubilize. They not only influence the nucleation of latex particles, the emulsification and polymerization of monomer droplets, and the stability of latex particles during the emulsion's storage period, but also significantly impact film formation, the film's adhesion to various substrates, and the film's mechanical strength.

[0024] Generally speaking, the more emulsifier used, the faster the reaction rate and the larger the molecular weight of the polymer. At the same time, the smaller the particle size of the emulsion, the better the emulsion stability. However, emulsifier molecules can migrate to the surface of the pressure-sensitive adhesive layer, thereby reducing adhesion. The more emulsifier used, the greater the decrease in adhesion. Furthermore, due to the hydrophilicity of the emulsifier, the water resistance and aging resistance of the pressure-sensitive adhesive can be reduced. Therefore, while ensuring the stability of the emulsion polymerization system, the use of emulsifier should be minimized.

[0025] Emulsifiers are divided into two categories:

[0026] ① Ionic emulsifiers. These include sodium lauryl sulfate, sodium lauryl sulfonate, and sodium dodecylbenzene sulfonate. Anionic emulsifiers are less chemically stable, but compared to nonionic emulsifiers, they produce smaller emulsion particles, offer better mechanical stability, and are less likely to form clots during polymerization. Therefore, using anionic emulsifiers makes it easier to produce highly concentrated and stable emulsions.

[0027] ② Non-ionic emulsifiers. These include spam and alkyl polyoxyethylene ethers. Non-ionic emulsifiers have good chemical stability to electrolytes, but they slow down the polymerization process and have weak emulsification ability, making them prone to forming clots during polymerization. They form a dense, solvated monomolecular adsorption layer on the surface of the latex particles, preventing particle aggregation. Using a compounded emulsifier system, two types of emulsifier molecules are alternately adsorbed on the surface of the latex particles, increasing the distance between similar emulsifier molecules, weakening electrostatic repulsion, and increasing the binding energy between the emulsifier molecules and the monomer molecules. This not only makes the emulsion polymerization process more stable, but also improves the storage stability of the emulsion.

[0028] In emulsion polymerization, the initiator is soluble in the continuous phase but insoluble in the monomer. Therefore, normal emulsion polymerization uses water-soluble initiators, while reverse emulsion polymerization uses oil-soluble initiators. Based on the mechanism of free radical generation, emulsion polymerization initiators are generally divided into two categories: thermal decomposition initiators and redox initiators. The most commonly used in acrylic emulsion polymerization are water-soluble, thermal decomposition initiators such as potassium persulfate, ammonium persulfate, and hydrogen peroxide, with concentrations generally ranging from 0.01% to 0.75%.

[0029] The drying film formation of polymer emulsions relies on the mutual dissolution and interpenetration of the polymer latex particles. If the polymer is too hard, its minimum film-forming temperature is high. When the application temperature approaches or falls below the emulsion's temperature, the emulsion will not form a complete film or will form an incomplete film. This can lead to problems such as reduced water resistance, durability, and adhesion to the substrate, poor gloss, microcracks, and uneven color. If the emulsion polymer is too soft, while these disadvantages can be overcome, the film's mechanical properties will be reduced, and it will be susceptible to scratching and stain resistance. The film-forming agent is both soluble in water and compatible with the polymer. It can be proportionally distributed between the water phase and the polymer. The portion of the film-forming agent dissolved in the polymer latex particles actually acts as a plasticizer, reducing the interfacial tension of the emulsion and facilitating the interpenetration and dissolution of the latex particles, resulting in a high-quality film. After the film is formed, the film-forming agent can slowly evaporate, hardening the film, increasing its strength, and gradually restoring its mechanical properties to the desired level. The part of the film-forming aid dissolved in the water phase can slow down the volatilization rate of water, while increasing the fluidity of the emulsion, helping to form a uniform, complete and continuous film, thereby significantly improving the performance of the film.

[0030] Dispersion media are essential for any emulsion polymerization process. The material used as a dispersion medium in emulsion polymerization must meet the following requirements: it must be able to dissolve the emulsifier and initiator; it must aggregate most dissolved emulsifier molecules to form micelles; it must be insoluble or slightly soluble in monomers; it must not inhibit free radical polymerization; it must have a low viscosity to facilitate heat and mass transfer; and it must be able to carry out the polymerization reaction over a wide range of temperatures and pressures. Water is the most commonly used dispersion medium in emulsion polymerization.

[0031] Emulsion acrylic ester PSA is produced by free radical copolymerization of acrylic ester monomers and has been a rapidly developing product in the field of pressure-sensitive adhesives in recent years. The main advantages of emulsion acrylic ester pressure-sensitive adhesives are:

[0032] Low cost, safe and pollution-free;

[0033] The synthesis process is relatively easy and the polymerization reaction time is short;

[0034] The molecular weight of the polymer is relatively high;

[0035] It is easy to obtain a pressure-sensitive adhesive with high solid content and low viscosity.

[0036] Adhesive performance is an important property in the application process of polyacrylate pressure-sensitive adhesive. In the study, the viscosity of polyacrylate pressure-sensitive adhesive was tested, mainly the initial adhesion, holding force and 180° peel strength of the pressure-sensitive tape.

[0037] The indicators that characterize the adhesive properties of pressure-sensitive adhesives are: initial tack T (tack), adhesion A (adhesion), cohesion C (cohesion) and keying K (keying). Generally speaking, these four adhesive performance indicators must meet a certain relationship in order for the pressure-sensitive adhesive to have good adhesion, and this certain relationship is: T <A<C<K。

[0038] Initial tack T generally refers to the force between the pressure-sensitive adhesive product and the surface of the adherend. It is the ability to resist separation when they separate quickly after contact under very light pressure. Therefore, initial tack is also called quick tack.

[0039] Adhesion A also reflects the force between a pressure-sensitive adhesive product and the adherend. Unlike initial tack, adhesion refers to the ability of the pressure-sensitive adhesive product and the adherend to resist separation after a suitable period of time, when applied with appropriate pressure. The 180° peel force is typically used to characterize adhesion A.

[0040] Cohesion C refers to the strength of the adhesive layer of the pressure-sensitive adhesive product itself, which is generally expressed by holding force. The holding force characterizes the ability of the adhesive product to resist shear creep after pasting. This ability is the embodiment of the strength of the adhesive layer.

[0041] In the absence of a primer, tack (K) refers to the bond strength between the adhesive layer and the substrate. In the presence of a primer, it refers to the bond strength between the adhesive layer and the primer, or between the primer and the substrate. During a 180° peel test, the adhesive layer and substrate may sometimes separate. In this case, the measured peel strength is the tack (K). Under normal circumstances, to ensure the peelability of a pressure-sensitive adhesive, the tack (K) must be greater than the adhesive strength, so the tack (K) value cannot be measured.

[0042] The disadvantages of emulsion-based acrylic ester PSAs are poor water resistance and electrical properties, slow drying speed, high energy consumption, and high surface tension, making their coating performance inferior to solvent-based polyacrylate pressure-sensitive adhesives. Therefore, the performance of water-based acrylic ester PSAs must be improved through modification. Crosslinking modification and tackifying resin modification can further increase their viscosity, silicone modification can improve the heat resistance of PSA, and nanoparticle modification can toughen and strengthen the film, increasing cohesion and adhesion. Reactive emulsifiers can not only be used as emulsifiers, but can also participate in polymerization reactions as comonomers, improving adhesive properties and significantly increasing the water resistance of the film and the stability of the emulsion. Mainly available are allyl ether sulfonates (sodium allyl sulfonate), acrylamide sulfonates, maleic acid derivatives, and sodium allyl alkyl sulfosuccinate.

[0043] Aging refers to the migration of small molecules from the film to its surface during use due to various physical and chemical effects such as ultraviolet light exposure and weather changes, resulting in a reduction in mechanical properties such as peel strength, initial adhesion, and holding strength, ultimately rendering the film useless. There are many factors that affect aging, such as the influence of small molecules, double bonds in the polymer backbone, and the content of hard monomers. Small molecules present in polymers migrate to the polymer surface over time and with changes in the surrounding environment, affecting their performance. Double bonds in the backbone easily decompose and break after exposure to ultraviolet light, resulting in a loss of application value due to cohesive failure. Excessive hard monomers in the polymer can cause the film to harden and lose its stickiness after exposure to ultraviolet light outdoors, making it easily fall off the adhered surface, affecting its performance.

[0044] p-Fluorophenylalanine, CAS: 60-17-3, chemical formula: C9H 10 FNO2 is a phenylalanine derivative in which the hydrogen atom at the para position of the benzene ring is replaced by a fluorine atom. It is a non-proteinogenic α-amino acid that is generally incorporated into protein synthesis as a protein synthesis inhibitor. The chemical structure is as follows:

[0045] Summary of the Invention

[0046] The applicant has long been committed to the research of polyacrylate pressure-sensitive adhesives. During the research, we accidentally discovered that p-fluorophenylalanine, a non-protein amino acid, can be used as an antioxidant for polyacrylate pressure-sensitive adhesives to enhance the peel strength, initial adhesion and lasting adhesion of the obtained pressure-sensitive adhesive after aging.

[0047] The present application first discloses the use of p-fluorophenylalanine as an anti-aging agent for emulsion-type polyacrylate pressure-sensitive adhesives, for enhancing their anti-aging ability, thereby enhancing peel strength, initial adhesion and lasting adhesion.

[0048] The chemical structural formula of the p-fluorophenylalanine is as follows:

[0049]

[0050] Secondly, the invention discloses the formula and preparation process of an emulsion type polyacrylate pressure-sensitive adhesive using p-fluorophenylalanine as an anti-aging agent.

[0051] The formula of the emulsion type polyacrylate pressure-sensitive adhesive is as follows:

[0052] The following raw materials are prepared by emulsion polymerization in deionized water according to mass percentage:

[0053] Soft monomer: 30-50%,

[0054] Hard monomer: 15-30%,

[0055] Functional monomer: 1-5%,

[0056] Initiator: 0.1-1%,

[0057] Reactive emulsifier: 0.1-5%,

[0058] Emulsifier: 0.1-5%,

[0059] pH regulator: 0.1-5%,

[0060] Defoaming agent: 0.1-5%,

[0061] Antiaging agent: 0.1-1.5% and solvent;

[0062] The soft monomer is selected from one or more of ethyl acrylate, butyl acrylate, n-octyl acrylate, isooctyl acrylate and isooctyl methacrylate;

[0063] The hard monomer is selected from one or more of methyl methacrylate, methyl methacrylate, vinyl acetate, styrene, acrylonitrile, ethyl methacrylate, and n-butyl methacrylate.

[0064] The functional monomer is selected from one or two of acrylic acid, methacrylic acid, acrylamide, methacrylamide, maleic acid, maleic anhydride, N-hydroxymethyl acrylamide, β-hydroxypropyl acrylate, β-hydroxyethyl acrylate, glycidyl acrylate, and divinylbenzene.

[0065] The initiator is selected from one or two of ammonium persulfate, potassium persulfate, sodium persulfate, and benzoyl peroxide.

[0066] The reactive emulsifier is selected from allyl ether sulfonates, acrylamide sulfonates, and sodium allyl alkyl sulfosuccinate, preferably sodium allyl sulfonate.

[0067] The co-emulsifier is selected from long-chain hydrocarbon hexadecane (HD) or long-chain fatty alcohol, preferably cetyl alcohol (CA) as a co-emulsifier for reducing particle size.

[0068] The pH regulator is selected from one or more of hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, tartaric acid, ammonia water, NaOH aqueous solution, KOH aqueous solution, diethanolamine, triethylamine, and N-methyldiethanolamine.

[0069] The defoaming agent is selected from one of mineral oils 2190 and DF691, and polyethers DF-106 and DF-963, or two or more of them in any proportion.

[0070] The antioxidant is p-fluorophenylalanine.

[0071] The solvent is deionized water.

[0072] The preparation method of the emulsion type polyacrylate pressure-sensitive adhesive is as follows:

[0073] Step 1: Mix the prescribed amount of soft monomer, hard monomer, functional monomer, antioxidant, and co-emulsifier evenly and set aside;

[0074] Step 2: Take out 10% of the total monomer mixture and add all the reactive emulsifier and deionized water. Stir, increase the temperature, and keep the mixture warm for reaction.

[0075] Step 3: Prepare the initiator into an aqueous solution, take out a portion of it to initiate the polymerization reaction, and form a seed emulsion. The emulsion gradually turns blue, keep warm, and react.

[0076] Step 4: Continue to raise the temperature and add the remaining monomer mixture and initiator aqueous solution dropwise at a uniform rate. Raise the temperature and maintain the temperature until the reaction is complete.

[0077] Step 5: After the reaction is completed, the temperature in the reaction device drops below 30°C and the material is discharged.

[0078] Step 6: The pH of the discharged emulsion is adjusted to 7-8 using a pH regulator.

[0079] Finally, the present application discloses the use of the emulsion-type polyacrylate pressure-sensitive adhesive for preparing self-adhesive PVC wallpaper. The wallpaper is prepared by evenly applying the emulsion-type polyacrylate pressure-sensitive adhesive on the PVC wallpaper and applying a protective film.

[0080] The beneficial effects of the present invention are:

[0081] 1. Use of p-fluorophenylalanine as an anti-aging agent for emulsion polyacrylate pressure-sensitive adhesive;

[0082] 2. Use of p-fluorophenylalanine as a tackifier for emulsion-type polyacrylate pressure-sensitive adhesives;

[0083] 3. Optimized formula and preparation process of emulsion polyacrylate pressure-sensitive adhesive containing p-fluorophenylalanine.

[0084] 4. Self-adhesive PVC wallpaper using emulsion-type polyacrylate pressure-sensitive adhesive containing p-fluorophenylalanine as adhesive and its preparation process. DETAILED DESCRIPTION

[0085] The present invention is further described in detail below by way of examples. The following examples are provided to explain the present invention, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0086] Example 1: Preparation of emulsion polyacrylate pressure-sensitive adhesive

[0087]

[0088]

[0089] The preparation method is as follows:

[0090] Step 1: Mix the prescribed amount of isooctyl acrylate, butyl acrylate, methyl methacrylate (MMA), acrylic acid (AA), p-fluorophenylalanine and hexadecanol in a beaker and set aside;

[0091] Step 2: Add 10% of the total monomer mixture to a four-necked flask, along with the entire amount of emulsifier (sodium allyl sulfonate) and an appropriate amount of deionized water. Stir at 300 rpm and gradually raise the temperature to 70°C.

[0092] Step 3: Prepare a 1% aqueous solution of ammonium persulfate as the initiator. Add one-third of this to a four-necked flask to initiate polymerization and form a seed emulsion. The emulsion will gradually turn blue. Keep warm for 15 minutes.

[0093] Step 4: Continue to raise the temperature to 80°C and add the remaining monomer mixture and initiator aqueous solution dropwise at a constant rate over 3 hours. Raise the temperature to 83°C and keep the reaction at this temperature for 1.5 hours.

[0094] Step 5: After the insulation is completed, the temperature in the reaction device is reduced to below 30°C and the material is filtered out.

[0095] Step 6: Adjust the pH value of the discharged emulsion to 7 with ammonia water, dilute to 100% with deionized water, and stir evenly.

[0096] Example 2 Test of the Adhesive Properties of the Four Formula Polyacrylate Pressure-Sensitive Adhesives Obtained in Example 1

[0097] 2.1 Preparation of samples

[0098] Refer to HT / T5054-2016 Water-based acrylic acid pressure-sensitive adhesives for adhesive products, 7.4.2.2 Preparation of samples for protection applications

[0099] Take a 20cm x 30cm piece of corona-treated PVC film with a thickness of 40μm, ensuring the corona surface is facing upward, and place it on a horizontal surface. Place an appropriate amount of the pressure-sensitive adhesive obtained in Recipes 1-4 of Example 1 on one end of the PVC film. Place a 20μm wire rod on top of the adhesive and pull the rod at a constant speed to evenly coat the adhesive on the PVC film. Then, dry the film until it is completely transparent (drying temperature: 105°C, time: 3-5 minutes). This will create a test specimen. Other applicators can also be used to ensure that the specimen meets the requirements.

[0100] Take out the sample, cool it to room temperature, and test its thickness. The total thickness should be 50μm±2μm (i.e. the thickness of the adhesive layer is 10μm±2μm). Otherwise, re-prepare it.

[0101] Place the prepared samples in a laboratory environment with a temperature of 23℃±1℃ and a relative humidity of 50%±5% for 24 hours before conducting application performance tests.

[0102] The prepared samples were taken and the initial tack, sustained tack and 180° peel strength were measured in sequence according to the following methods.

[0103] 2.2 Initial adhesion test

[0104] According to GB / T 31125-2014, the ring method is used. A ring-shaped adhesive tape is placed in contact with a test plate of a specified area under its own weight, and the force required to pull the tape off the test plate is measured.

[0105] Reference method B: Automatic ring initial adhesion performance tester method

[0106] State adjustment and test environment:

[0107] Before preparing the specimens, place the samples and test panels at a temperature of 23°C ± 1°C and a relative humidity of 50% ± 5% for 24 hours. The laboratory temperature is 23°C ± 1°C and the relative humidity is 50% ± 5%.

[0108] Take the sample prepared in 2.1 and make three sample rings. The sample rings should be 25 mm wide and 125 mm in circumference.

[0109] The stainless steel test plate has a thickness of 1.5mm-2.0mm, a width of 24mm, and a length of 100mm. The material is 0Cr18Ni9 test plate specified in GB / T 3280-2007, with a surface roughness of 50±25nm.

[0110] Before the test, wipe the stainless steel test plate with medical gauze dipped in methanol. After the test plate appears clean, repeat the cleaning three times to ensure that the cleaning agent is completely evaporated.

[0111] Test steps:

[0112] Keep the automatic ring tack tester horizontal, connect the power cord, and release the locking lever. Turn on the power switch. Confirm that the upper clamp is in the uppermost position. Loosen the retaining screws and remove the stainless steel test plate. Return the cleaned stainless steel test plate to the test fixture and tighten the retaining screws.

[0113] Remove the release paper covering the specimen. Bend the specimen completely over, taking care not to wrinkle it. Bend the specimen into a teardrop-shaped ring with a circumference of 98 mm, with the adhesive side facing outward.

[0114] Fasten the ends of the specimen ring together with 13 mm wide covering tape.

[0115] Insert the specimen ring into the upper holder, ensuring that the specimen ring is in the proper position to form the upper assembly.

[0116] Zero the dynamometer. Press and hold the "Jog" button to begin the downward movement of the upper assembly. The upper assembly will automatically stop after completing a full cycle. At this point, the dynamometer returns to its initial position.

[0117] A complete cycle begins with the upper assembly moving downward, bringing the specimen ring into contact with the test plate, establishing a bond. Next, the assembly moves upward at a speed of 300 mm / min ± 10 mm / min, with the dynamometer recording the force (in Newtons) required to pull the specimen ring away from the test plate. At the end of the cycle, the upper assembly is fixed to its original position.

[0118] Record the maximum pulling force (in N) required for the sample ring to detach from the stainless steel test plate. Repeat three times for each sample ring and take the average value.

[0119] 2.3 Adhesion test

[0120] According to GB / T4851-2014, Method A: Adhesion test method between adhesive tape and vertical standard steel plate. The specific method is as follows:

[0121] Under the conditions of constant load, temperature of (23±1)°C and relative humidity of (50±5)%, the adhesiveness of the adhesive tape to the standard steel plate is measured by the failure time of the adhesive tape.

[0122] Adhesion to standard steel plate: An adhesive tape is applied to a standard steel plate at a controlled rolling speed. The steel plate is mounted vertically, and a standard mass weight is hung from the free end of the adhesive tape. The time (h) until adhesion failure is measured.

[0123] Sample preparation:

[0124] Place the sample at the center of one end of the test steel plate. Without applying pressure, use the mass of the pressure rod to evenly roll and stick the adhesive tape sample to an area of ​​(12±0.5)mm×(12±0.5)mm. The exposed adhesive part in the free area of ​​the sample can be covered.

[0125] During the rolling process, to prevent damage to the end specimens of the test plate, place another identical test plate or a slightly thinner test plate under the free end of the specimen, aligning it with the end of the test plate. Roll the specimen back and forth along the length of the test area.

[0126] Prepare 3 specimens. Prepare each specimen individually and start the test within 1 minute.

[0127] After pasting the sample, complete the following actions within 1 minute.

[0128] Clamp the grips to the free ends of the specimen, ensuring that the grips fully grip the entire width of the specimen and that the load is evenly distributed.

[0129] Place the entire test specimen on the test stand with the free end of the specimen vertical to ensure that no peeling force acts on the specimen.

[0130] Gently apply the weight to the fixture to avoid shearing the specimen. Record the time it takes for the specimen to completely separate from the test plate. Test each specimen once and convert the result for each specimen to its common logarithm. Obtain the arithmetic mean of all logarithms and then take the inverse logarithm to obtain the time (h).

[0131] 2.4180° peel strength test

[0132] Refer to GB / T2792-2014 Adhesive Tape Peel Strength Test Method.

[0133] Method 1: Test method for 180° peel strength between adhesive tape and stainless steel

[0134] A piece of adhesive tape is stuck on a stainless steel plate, and the stainless steel plate is fixed on a fixture of the tensile testing machine. The other fixture of the testing machine clamps the free end of the adhesive tape at an angle of 180° to the stainless steel plate, and the adhesive tape is pulled apart at a specified rate.

[0135] The peel force was measured as the force required to continuously peel the adhesive tape from the stainless steel plate and converted to peel strength.

[0136] Standard test environment temperature (23±1)℃, relative humidity (50±5)%.

[0137] Prepare the specimen according to step 2.1 and cut a 300mm long and 24mm wide specimen from it. Fold the adhesive side of one end of the specimen along its length to form a folded layer approximately 12mm long. Holding this folded layer, adhere the other end of the specimen to one end of the steel plate, allowing the adhesive tape to naturally rest above the plate (without touching it). Then, mechanically roll the pressing rod back and forth twice to prevent air from entrapped between the adhesive surface and the plate. If any air is trapped, discard the specimen and prepare a new one.

[0138] Each sample is prepared and tested one by one, and the test is completed within 1 minute.

[0139] Peel off 25 mm of the adhesive tape from the steel plate from the folded end of the adhesive tape. Clamp one end of the steel plate in the fixture of the tensile testing machine and clamp the free end of the adhesive tape in the other fixture. Peel the tape off continuously at a rate of (5.0 ± 0.2) mm / s.

[0140] After the load fixture is running, ignore the value obtained when the first 25mm of adhesive tape is mechanically peeled off, and use the average tensile force value obtained by the next 50mm of adhesive tape as the peel force and convert it into peel strength.

[0141] Three specimens were prepared and tested three times. The test results were expressed as the arithmetic mean of the peel strength in N / 24mm.

[0142] 2.5 Aging test

[0143] The test is conducted in accordance with GBT17875-1999, "Test Method for Accelerated Aging of Pressure-Sensitive Adhesive Tapes." The test method is as follows: place the sample prepared in 2.1 in an environment of 66°C and 80% relative humidity for 96 hours, then place it under standard laboratory conditions for a certain period of time (here, 24 hours). After allowing it to return to standard conditions, the initial tack, sustained tack, and 180° peel strength are tested according to methods 2.2-2.4.

[0144] 2.6 Statistical results (n=3)

[0145]

[0146] As can be seen from the data in the table above, the pressure-sensitive adhesive obtained from Formula 1 of Example 1 (without the addition of an antioxidant) shows a decrease in initial tack, sustained tack, and 180° peel strength before and after aging, and the decrease is quite significant. However, for Formulas 2-4 (with the addition of the antioxidant p-fluorophenylalanine in different proportions), the initial tack, sustained tack, and 180° peel strength before and after aging are comparable, with essentially no difference. When the amount of p-fluorophenylalanine added is increased from 1.0% to 1.5%, there is no significant difference in the initial tack, sustained tack, and 180° peel strength of the resulting pressure-sensitive adhesive before and after aging. However, its initial tack, sustained tack, and 180° peel strength before aging increase slightly. This indicates that p-fluorophenylalanine not only has an anti-aging effect, but also has a weaker effect of increasing the adhesion of the pressure-sensitive adhesive.

[0147] Example 3 Preparation of self-adhesive PVC wallpaper

[0148] Any of the emulsion-type polyacrylate pressure-sensitive adhesives shown in 2-4 obtained in Example 1 is evenly coated on the PVC wallpaper according to conventional processes, and a protective film is affixed to obtain the wallpaper.

[0149] The above invention content and embodiments describe the basic principles and main features of the patent application of the present invention and the advantages of the patent application of the present invention. Those skilled in the art should understand that the patent application of the present invention is not limited to the above embodiments. The above embodiments and descriptions describe only the optimal technical solutions of the patent application of the present invention. Without departing from the spirit and scope of the patent application of the present invention, the patent application of the present invention may have various changes and improvements, that is, using p-fluorophenylalanine as an antioxidant and tackifier for polyacrylate pressure-sensitive adhesive, alone or in combination with other additives to prepare polyacrylate pressure-sensitive adhesive, all fall within the scope of the patent application of the present invention. The scope of protection claimed in the patent application of the present invention is defined by the attached claims and their equivalents.

Claims

1. Application of p-fluorophenylalanine as an anti-aging agent for emulsion polyacrylate pressure-sensitive adhesive.

2. Use of p-fluorophenylalanine as a tackifier for emulsion-type polyacrylate pressure-sensitive adhesives.

3. An emulsion-type polyacrylate pressure-sensitive adhesive, characterized in that: The prescription composition of described pressure-sensitive adhesive is as follows: Soft monomer: 30-50%, Hard monomer: 15-30%, Functional monomer: 1-5%, Initiator: 0.1-1%, Reactive emulsifier: 0.1-5%, Emulsifier: 0.1-5%, pH regulator: 0.1-5%, Defoaming agent: 0.1-5%, Antiaging agent: 0.1-1.5% and solvent; The antioxidant is p-fluorophenylalanine.

4. The pressure-sensitive adhesive according to claim 3, wherein The preparation method of the pressure-sensitive adhesive is as follows: Step 1: Mix the prescribed amount of soft monomer, hard monomer, functional monomer, antioxidant, and co-emulsifier evenly and set aside; Step 2: Take out 10% of the total monomer mixture, add all the reactive emulsifier and deionized water; stir, heat, and keep warm for reaction; Step 3: Prepare the initiator into an aqueous solution, take out a portion of it to initiate the polymerization reaction, and form a seed emulsion. The emulsion gradually turns blue, and the solution is kept warm and allowed to react. Step 4: Continue to raise the temperature and dropwise add the remaining monomer mixture and initiator aqueous solution at a uniform rate; raise the temperature and keep warm until the reaction is complete; Step 5: After the reaction is completed, the temperature in the reaction device is lowered to below 30°C and the material is discharged; Step 6: The pH of the discharged emulsion is adjusted to 7-8 using a pH regulator.

5. A self-adhesive PVC wallpaper, characterized in that: The pressure-sensitive adhesive according to any one of claims 3-4 is used as the backing adhesive.

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