Styrene-acrylic-emulsion-containing aqueous pressure-sensitive adhesive composition, adhesive tape, and preparation methods therefor

Abstract

The present invention provides a styrene-acrylic-emulsion-containing aqueous pressure-sensitive adhesive composition, an adhesive tape, and preparation methods therefor. The styrene-acrylic-emulsion-containing aqueous pressure- sensitive adhesive composition comprises an aqueous adhesive matrix and a styrene-acrylic emulsion, wherein the aqueous adhesive matrix is an aqueous acrylic adhesive matrix or a tackifying resin-modified aqueous acrylic adhesive matrix, and the styrene-acrylic emulsion comprises a styrene-acrylate copolymer. An adhesive tape with an adhesive layer prepared from the aqueous pressure- sensitive adhesive composition has a suitable peeling property and a significantly improved cohesion.

Description

[0001] STYRENE-ACRYLIC-EMULSION-CONTAINING AQUEOUS PRESSURESENSITIVE ADHESIVE COMPOSITION, ADHESIVE TAPE, AND PREPARATION METHODS THEREFOR

[0002] Technical Field

[0003] The present invention relates to the technical field of adhesives or adhesive tapes, in particular to a styrene-acrylic-emulsion-containing aqueous pressuresensitive adhesive composition, an adhesive tape made of the aqueous pressuresensitive adhesive composition, and preparation methods therefor.

[0004] Background Art

[0005] Pressure-sensitive adhesives are widely used in products such as adhesive tapes, protective films, and labels. Depending on the dispersion medium of the pressure-sensitive adhesive, pressure-sensitive adhesives can be divided into solvent-based pressure-sensitive adhesives and aqueous pressure-sensitive adhesives. Since solvent-based pressure-sensitive adhesives involve environmental concerns such as substantial evaporation of organic solvents and the problem of a relatively long processing time during processing, aqueous pressure-sensitive adhesives with a simple production process, a low cost, and no pollution are more acceptable to the public at present. Furthermore, aqueous pressure-sensitive adhesives can be divided into aqueous acrylate systems, aqueous silicone systems, aqueous polyurethane systems, etc. Among them, aqueous acrylate systems have a very wide range of applications on the market due to characteristics such as a wide adjustable range and a high performance-to- cost ratio.

[0006] However, most aqueous pressure-sensitive adhesive emulsions on the market have a relatively poor cohesion, causing aqueous pressure-sensitive adhesive products to have defects in adhesion holding power and shear resistance. At present, the method for improving the cohesion of a pressure-sensitive adhesive mainly involves adding a cross-linking agent. Although the use of a cross-linking agent can improve the cohesion of a pressure-sensitive adhesive, the cross-linking agent causes the adhesive tape to have a greatly reduced peeling force and a relatively poor adhesive power. Therefore, investigating new approaches to improve the cohesion of an aqueous pressure-sensitive adhesive has become an important topic. Summary of the Invention

[0007] An object of the present invention is to provide an aqueous pressure-sensitive adhesive composition. The aqueous pressure-sensitive adhesive composition has a suitable peeling property and an improved cohesion without the addition of a cross-linking agent.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned aqueous pressure-sensitive adhesive composition.

[0009] Still another object of the present invention is to provide an aqueous pressuresensitive adhesive tape with an improved cohesion, which has a suitable peeling property, and improved adhesion holding power and shear resistance where the composition is simple.

[0010] The above-mentioned objects of the present invention are achieved by the following technical solution.

[0011] In one aspect, the present invention provides an aqueous pressure-sensitive adhesive composition comprising an aqueous adhesive matrix and a styrene-acrylic emulsion, wherein the aqueous adhesive matrix is an aqueous acrylic adhesive matrix or a tackifying resin-modified aqueous acrylic adhesive matrix, and the styrene-acrylic emulsion comprises a styrene-acrylate copolymer.

[0012] Optionally, the styrene-acrylate copolymer is a random copolymer emulsion or block copolymer emulsion made of styrene and an acrylic monomer.

[0013] Optionally, the aqueous acrylic adhesive matrix is prepared using water, an emulsifier, an initiator, and an acrylic monomer by emulsion polymerization; and the tackifying resin-modified aqueous acrylic adhesive matrix is prepared using the aqueous acrylic adhesive matrix and a tackifying resin, wherein the tackifying resin is one or more of a rosin resin, a terpene resin, and a terpene phenol resin.

[0014] Optionally, based on the total weight of the aqueous pressure-sensitive adhesive composition, the content of the styrene-acrylic emulsion is 2-25%, preferably 5-20%, even preferably 10-15%; and the content of the aqueous acrylic adhesive matrix is 75-98%, preferably 80-95%, even preferably 85-90%.

[0015] Optionally, based on the total weight of the aqueous pressure-sensitive adhesive composition, the content of the styrene-acrylic emulsion is 2-25%, preferably 5-20%, even preferably 5-10%; and the content of the tackifying resin- modified aqueous acrylic adhesive matrix is 75-98%, preferably 80-95%, even preferably 90-95%.

[0016] Optionally, based on the total weight of the styrene-acrylate copolymer, the content of the styrene monomer is 20-90%, preferably 50-90%; and the content of the acrylic monomer is 10-80%, preferably 10-50%. Optionally, the mass ratio of the aqueous acrylic adhesive matrix to the tackifying resin in the tackifying resin-modified aqueous acrylic adhesive matrix is 18 : 1 -3 : 1.

[0017] In another aspect, the present invention provides a method for preparing the above-mentioned aqueous pressure-sensitive adhesive composition, comprising:

[0018] 1) preparing an aqueous acrylic adhesive matrix using water, an emulsifier, an initiator, and an acrylic monomer by emulsion polymerization; or preparing a tackifying resin-modified aqueous acrylic adhesive matrix by adding a tackifying resin to the aqueous acrylic adhesive matrix; and

[0019] 2) preparing an aqueous pressure-sensitive adhesive composition by adding a styrene-acrylic emulsion to the prepared aqueous acrylic adhesive matrix or tackifying resin-modified aqueous acrylic adhesive matrix, and stirring and uniformly mixing the mixture.

[0020] In still another aspect, the present invention provides an aqueous pressuresensitive adhesive tape comprising a substrate and an adhesive layer, wherein the adhesive layer comprises the above-mentioned aqueous pressure-sensitive adhesive composition.

[0021] In a further aspect, the present invention provides a method for preparing an aqueous pressure-sensitive adhesive tape, comprising applying the above- mentioned aqueous pressure-sensitive adhesive composition to at least one side of a substrate to prepare the aqueous pressure-sensitive adhesive tape.

[0022] The present invention can result in the following beneficial technical effects:

[0023] In the present invention, a styrene-acrylic emulsion, as an alternative to common cross-linking agents, is added to the aqueous pressure-sensitive adhesive, enabling the aqueous pressure-sensitive adhesive composition to have a suitable peeling property and an improved cohesion; moreover, the aqueous pressure-sensitive adhesive composition of the present invention can be used to prepare an aqueous pressure-sensitive adhesive tape by a simple preparation method, and the adhesive tape has a suitable peeling property and a significantly improved adhesion holding power and shear resistance (cohesion) without the addition of a cross-linking agent. The problem of a greatly reduced peeling force caused usually when using a cross-linking agent to improve the cohesion of an aqueous pressure-sensitive adhesive composition is solved.

[0024] Brief Description of the Drawings

[0025] Fig. 1 shows a TEM image of a styrene-acrylate emulsion with a core-shell structure according to the present invention. Detailed Description of Embodiments

[0026] In order to make the objects, technical solutions, and advantages of the examples of the present invention more clear, the technical solutions of the present invention will be described clearly and completely with reference to the following specific embodiments. Obviously, the described specific embodiments are some of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without involving any inventive effort fall within the scope of protection of the present invention.

[0027] According to one aspect of the present invention, provided is an aqueous pressure-sensitive adhesive composition comprising an aqueous adhesive matrix and a styrene-acrylic emulsion, wherein the aqueous adhesive matrix is an aqueous acrylic adhesive matrix or a tackifying resin-modified aqueous acrylic adhesive matrix, and the styrene-acrylic emulsion comprises a styrene-acrylate copolymer.

[0028] According to a preferred embodiment of the present invention, the styreneacrylate copolymer is a random copolymer emulsion or block copolymer emulsion made of styrene and an acrylic monomer.

[0029] According to a preferred embodiment of the present invention, the styrene- acrylic emulsion is preferably a styrene-acrylic emulsion with a core-shell structure. The styrene-acrylic emulsion with a core-shell structure has many excellent properties, and the core-shell structure can significantly improve the flowability, water retention, adhesive power, wear resistance, mechanical strength, and elongation properties of the material where the raw material composition is completely the same. For the core-shell structure of the styrene-acrylic emulsion, the core part is a styrene-acrylate copolymer and the shell part is a water-soluble polymer. The water-soluble polymer can be entangled with an outer ring polymer of droplets of the aqueous adhesive matrix, while the styrene in the styrene-acrylic copolymer of the core part has a higher glass transition temperature Tg and can form strong physical cross-linking through agglomeration. Therefore, through the interaction between the styrene-acrylic emulsion with a shell-core structure and the aqueous adhesive matrix, a uniformly mixed aqueous pressure-sensitive adhesive composition with improved shear resistance can be prepared. The styrene in the styrene-acrylic emulsion with a shell-core structure according to the present invention has a glass transition temperature (Tg) of 100-105°C, which can improve the overall Tg to a certain extent, thereby improving the cohesion of the aqueous pressure-sensitive adhesive. The glass transition temperature (Tg) refers to a temperature corresponding to the transition of an amorphous polymer from a glassy state to a highly elastic state. Specifically, a TEM image of the styrene-acrylic emulsion with a shell-core structure according to the present invention is as shown in Fig. 1 .

[0030] According to a preferred embodiment of the present invention, the aqueous acrylic adhesive matrix is prepared using water, an emulsifier, an initiator, and an acrylic monomer by emulsion polymerization; and the tackifying resin-modified aqueous acrylic adhesive matrix is prepared using the aqueous acrylic adhesive matrix and a tackifying resin. Preferably, the tackifying resin is one or more of a rosin resin, a terpene resin, and a terpene phenol resin.

[0031] According to a preferred embodiment of the present invention, based on the total weight of the aqueous pressure-sensitive adhesive composition, the content of the styrene-acrylic emulsion is 2-25%, preferably 5-20%, even preferably 10- 15%; and the content of the aqueous acrylic adhesive matrix is 75-98%, preferably 80-95%, even preferably 85-90%.

[0032] According to a preferred embodiment of the present invention, based on the total weight of the aqueous pressure-sensitive adhesive composition, the content of the styrene-acrylic emulsion is 2-25%, preferably 5-20%, even preferably 5-10%; and the content of the tackifying resin-modified aqueous acrylic adhesive matrix is 75-98%, preferably 80-95%, even preferably 90-95%.

[0033] The content of the styrene-acrylate copolymer in the styrene-acrylic emulsion of the present invention is 20-80%, preferably 20-50%, with the balance being water.

[0034] According to a preferred embodiment of the present invention, based on the total weight of the styrene-acrylate copolymer, the content of the styrene monomer is 20-90%, preferably 50-90%; and the content of the acrylic monomer is 10-80%, preferably 10-50%.

[0035] The acrylic monomer in the above-mentioned aqueous acrylic adhesive matrix is not particularly limited, as long as it can provide the aqueous pressure-sensitive adhesive with a sufficient bonding power. For example, the acrylic monomer in the aqueous acrylic adhesive matrix is one or more of butyl acrylate (n-BA), ethyl acrylate (EA), isooctyl acrylate (2-EHA), acrylic acid (AA), methyl (meth)acrylate (MAA), butyl methacrylate (MBA), isobornyl methacrylate, octadecyl (meth)acrylate, or docosyl (meth)acrylate.

[0036] According to a preferred embodiment of the present invention, the mass ratio of the aqueous acrylic adhesive matrix to the tackifying resin in the tackifying resin- modified aqueous acrylic adhesive matrix is 18 : 1 -3 : 1. In another aspect, the present invention further provides a method for preparing the above-mentioned aqueous pressure-sensitive adhesive composition, comprising:

[0037] 1 ) preparing an aqueous acrylic adhesive matrix using water, an emulsifier, an initiator, and an acrylic monomer by emulsion polymerization; or preparing a tackifying resin-modified aqueous acrylic adhesive matrix by adding a tackifying resin to the aqueous acrylic adhesive matrix; and

[0038] 2) preparing an aqueous pressure-sensitive adhesive composition by adding a styrene-acrylic emulsion to the prepared aqueous acrylic adhesive matrix or tackifying resin-modified aqueous acrylic adhesive matrix, and stirring and uniformly mixing the mixture.

[0039] In the preparation method according to the present invention, the styrene- acrylic emulsion used is well compatible with the aqueous adhesive matrix, such that a uniformly mixed aqueous pressure-sensitive adhesive composition can be easily prepared, that is, the uniformly mixed aqueous pressure-sensitive adhesive composition can be prepared only by simple stirring and mixing. The molecular chain of the styrene-acrylic copolymer in the aqueous pressure-sensitive adhesive composition can be entangled with the molecular chain of the aqueous adhesive matrix to form robust physical cross-linking, so that the cohesive strength of the aqueous pressure-sensitive adhesive composition is greatly improved. Therefore, the aqueous pressure-sensitive adhesive composition of the present invention has excellent adhesion holding power and shear resistance.

[0040] In another aspect, the present invention further provides an aqueous pressuresensitive adhesive tape comprising a substrate and an adhesive layer, wherein the adhesive layer comprises the above-mentioned aqueous pressure-sensitive adhesive composition. The above-mentioned aqueous pressure-sensitive adhesive composition can be applied and dried to form an adhesive layer. The molecular chain of the styrene-acrylic copolymer in the adhesive layer can be entangled with the molecular chain of the aqueous adhesive matrix to form robust physical crosslinking, so that the cohesive strength of the adhesive layer is greatly improved. Therefore, the aqueous pressure-sensitive adhesive tape prepared from the aqueous pressure-sensitive adhesive composition of the present invention has excellent adhesion holding power and shear resistance.

[0041] In another aspect, the present invention further provides a method for preparing an aqueous pressure-sensitive adhesive tape, characterized by comprising applying the above-mentioned aqueous pressure-sensitive adhesive composition to at least one side of a substrate to prepare the aqueous pressure-sensitive adhesive tape. The substrate may be a carrier (such as PET, SUS, or PE) or a release paper.

[0042] The aqueous pressure-sensitive adhesive composition, the aqueous pressuresensitive adhesive tape, and the preparation methods therefor according to the present invention can result in the following beneficial technical effects. That is, in the present invention, a styrene-acrylic emulsion, as an alternative to common cross-linking agents, is added to the aqueous pressure-sensitive adhesive, enabling the obtained aqueous pressure-sensitive adhesive composition to have a suitable peeling property and an improved cohesion; moreover, the aqueous pressure-sensitive adhesive composition of the present invention can be used to prepare an aqueous pressure-sensitive adhesive tape by a simple preparation method, and the tape has a suitable peeling property and a significantly improved adhesion holding power and shear resistance (cohesion) without the addition of a cross-linking agent. The problem of a greatly reduced peeling force caused usually when using a cross-linking agent to improve the cohesion of an aqueous pressuresensitive adhesive composition is solved.

[0043] Examples

[0044] In the examples of the present invention, the following test methods are used to test the peeling force property, static shear property, and micro-shear property.

[0045] 1. Test method

[0046] (1 ) Peeling force test

[0047] In the present invention, the 180° peeling force property of the adhesive composition on stainless steel (SUS) is tested.

[0048] In the present invention, the peeling force is determined at a temperature of 23°C ± 1 °C and a relative humidity of 50% ± 5%. A specimen is cut into a width of 20 cm and adhered to an SUS substrate. The substrate is cleaned with acetone before measurement. Subsequently, the test specimen is rolled onto the substrate by rolling back and forth on the adhesive tape five times with a 4 kg roller at a rolling rate of 10 m / min. Immediately after the rolling treatment, a steel plate is inserted into a fixture that allows the specimen to be tested for the peeling force at an angle of 180°. The peeling force is measured with Zwick tensile tester at a speed of 300 mm / min. The test result of each sample is represented by the average value (N / cm) of three measurements. (2) Static shear test

[0049] The specimen is applied to a specific rigid substrate (here, a specimen testing steel plate) and undergoes a constant shear load. The holding time of the adhesive tape is measured in minutes.

[0050] At room temperature, a 13 mm x 20 mm specimen is bonded to a 5 cm long polished specimen testing steel plate, and the specimen is rolled back and forth twice with a 2 kg roller at a rolling rate of 300 mm / min. Subsequently, a ring hook is fixed to the bottom of the specimen. Then, the specimen testing steel plate is fixed to a front side of a shear test plate with nuts and bolts to ensure a specified angle of 179° ± 1 °. The strength development time should be less than 10 minutes, from specimen rolling to suspension loading. Then, a weight (1 kg) is stably suspended via the ring hook. The time point at which the suspended weight falls as the adhesive tape breaks is measured by an automatic counter, and the mode of bonding failure at break is also recorded.

[0051] A suitable plate suspension system (angle 179° ± 1 °) ensures that the specimen does not peel off from the lower edge of the specimen testing steel plate. This test mainly provides information about the cohesion of the composition. In addition, the test provides information about adhesion to the substrate or provides information about a combination of adhesion and cohesion of the composition.

[0052] In the present invention, the characterization of anti-shear ability is recorded as the failure time combined with the failure mode. There are many failure modes in the static shear test, including adhesion failure (abbreviated as AF), cohesion failure (abbreviated as CF), and anchorage failure (abbreviated as AN). The static shear test in the present invention involves adhesion failure (AF) and cohesion failure (CF). Adhesion failure (AF) means that the failure occurs at the contact interface between the adhesive surface and the adherend, the adhesive layer is peeled off from the adherend as a whole, and there is no adhesive layer left on the adherend, that is, bonding failure occurs. The result of adhesion failure indicates that the adhesive force of the adhesive layer on the adherend is not high enough, but the cohesion of the adhesive layer remains good. Cohesion failure (CF) means that the failure occurs inside the adhesive layer, the adhesive layer breaks from the inside, there is adhesive layer residue on the adherend, and the residual adhesive surface is well bonded with the adherend. The result of cohesion failure indicates that the cohesive force of the adhesive layer is insufficient to provide long-time support, leading to failure under shear. According to the above analysis, the evaluation of the static shear characterization is as follows:

[0053] > 10000 min : ++

[0054] > 1000 min + AF : +

[0055] > 2000 min + CF : +

[0056] 500-2000 min + CF : O

[0057] < 500 min + CF : -

[0058] (3) Micro-shear test

[0059] This test is used to test the micro-shear property of a specimen of the prepared sample at a temperature load of 40°C.

[0060] A specimen cut from the corresponding sample is bonded to a specimen testing steel plate that is heat-treatable, ground, and cleaned with acetone. The bonding method involves attaching a 13 mm x 50 mm adhesive tape to a 10 mm wide specimen testing steel plate, wherein the specimen is protruded from the specimen testing steel plate by 2 mm at the upper edge, such that the bonding area between the specimen and the steel plate is 13 mm x 10 mm. Then, the specimen is rolled back and forth at the bonding position three times with a 2 kg roller at a rolling rate of 10 m / min. The adhesive tape is reinforced in an aligned manner with a robust bonding strip used as a support for a displacement sensor. The sample thus prepared is vertically suspended and fixed via the specimen testing steel plate.

[0061] Measurement: The bottom of the specimen testing steel plate is loaded with a 100 g weight. The test temperature is 40°C and the test duration is 15 minutes. The sliding stroke of the specimen testing steel plate within 15 minutes is measured. The maximum shear displacement is set to 1000 pm. If the displacement exceeds this value, the test is stopped. The smaller the sliding stroke (shear displacement), the higher the cohesion.

[0062] 2. Raw materials and preparation processes used in the examples

[0063] 2.1 Raw materials used in the examples

[0064] The abbreviations, sources, categories, and compositions of the raw materials used in the examples of the present invention are as shown in Table 1 below. Table 1 . Raw materials used in the examples of the present invention and abbreviations thereof

[0065] 2.2 Process for preparing adhesive compositions and adhesive tapes in the examples (1 ) Preparation of aqueous adhesive matrix

[0066] 1 ) Preparation of aqueous acrylic adhesive matrix

[0067] An aqueous adhesive matrix is prepared from water, an emulsifier, an initiator, and various monomers by means of an emulsion polymerization method, wherein the acrylic monomer is made up of 86% of butyl acrylate (n-BA), 10% of isooctyl acrylate (2-EHA), 2% of acrylic acid (AA), and 2% butyl methacrylate (MBA).

[0068] The specific preparation method involves: taking 30 parts of deionized water, 1 part of the emulsifier, and 50 parts of the acrylic monomer to form a mixture, preemulsifying the mixture to obtain a monomer pre-emulsion, then adding 0.5 parts of the initiator, and uniformly stirring the mixture to obtain a monomer dropping liquid; adding 40 parts of deionized water, 0.5 parts of the emulsifier, and 0.1 parts of the initiator to a 500 ml reaction kettle equipped with a thermometer, a stirrer, a nitrogen introduction pipe, and a reflux condenser, and uniformly stirring the mixture to obtain a kettle bottom liquid; heating the kettle bottom liquid to 80°C, slowly dropwise adding the monomer dropping liquid to the kettle bottom liquid, with the dropwise addition of the monomer dropping liquid being controlled to complete in 3.5 hours; after the dropwise addition is complete, controlling the kettle bottom liquid to react at a maintained temperature of 85°C for 60 minutes; subsequently, cooling the kettle bottom liquid to 45°C, adding an appropriate amount of aqueous ammonia to adjust the pH value to 7.5, and then adding 0.3 parts of a wetting agent, 0.5 parts of a defoaming agent, and 0.1 parts of a preservative; and stirring the liquid material for 30 minutes until uniform, and filtering the material with a 205-mesh filter screen to obtain the aqueous acrylic adhesive matrix.

[0069] 2) Preparation of tackifying resin-modified aqueous acrylic adhesive matrix

[0070] A rosin, terpene, or terpene phenol tackifying resin is added to the aqueous acrylic adhesive matrix obtained in 1 ) and stirred for 30 minutes until uniform to obtain the tackifying resin-modified aqueous acrylic adhesive matrix.

[0071] (2) Preparation of the aqueous pressure-sensitive adhesive composition of the present invention

[0072] Various types of styrene-acrylic emulsions are respectively weighed according to the required formulation ratios, respectively added to aqueous adhesive matrices, and stirred for 30 minutes with a stirrer at a speed of 300-500 revolutions / minute at room temperature to obtain homogeneous aqueous pressure-sensitive adhesive compositions of the present invention.

[0073] (3) Preparation of the aqueous pressure-sensitive adhesive tape of the present invention

[0074] The aqueous pressure-sensitive adhesive composition (containing a styrene- acrylic emulsion) obtained in (2) is applied to a 23 pm polyethylene terephthalate (PET) substrate to form an adhesive layer, thus obtaining a single-sided aqueous pressure-sensitive adhesive tape.

[0075] 3. Examples 1 -17 and Comparative Examples 1 -10

[0076] Examples 1 -4

[0077] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 2, and corresponding amounts of KE-1062 were respectively added, mixed, and then fully stirred for 30 minutes. The above- mentioned aqueous pressure-sensitive adhesive composition solution was applied to a PET substrate with a final thickness (the thickness of an adhesive layer) of 50 pm to form an adhesive layer, thereby obtaining a single-sided aqueous acrylic pressure-sensitive adhesive tape. Examples 5-9

[0078] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 2, and corresponding amounts of PE-2184 were respectively added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0079] Examples 10-12

[0080] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 2, and corresponding amounts of YL-1098 were respectively added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0081] Examples 13-15

[0082] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 2, and corresponding amounts of KE-1060 were respectively added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0083] Examples 16 and 17

[0084] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 2, and corresponding amounts of Hariester SK-822E were added, mixed, and then stirred for 30 minutes until uniform to obtain tackifying resin-modified aqueous adhesive matrices. Corresponding amounts of KE-1062 were added to the obtained tackifying resin-modified aqueous adhesive matrix, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0085] Comparative Example 1

[0086] The prepared aqueous acrylic adhesive matrix (100%) was applied to a PET substrate with a final thickness (the thickness of an adhesive layer) of 50 pm to form an adhesive layer, thereby obtaining a single-sided purely aqueous acrylic pressure-sensitive adhesive tape.

[0087] Comparative Examples 2 and 3

[0088] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of aqueous acrylic adhesive matrix were weighed as shown in Table 3, and corresponding amounts of Snowtack 100G were respectively added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0089] Comparative Examples 4 and 5

[0090] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 3, and corresponding amounts of Hariester SK-822E were respectively added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0091] Comparative Examples 6-8

[0092] Based on the total weight of the aqueous pressure-sensitive adhesive composition, different amounts of the aqueous acrylic adhesive matrix were weighed as shown in Table 3, and corresponding amounts of CX-100 were respectively added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0093] Comparative Example 9

[0094] Based on the total weight of the aqueous pressure-sensitive adhesive composition, 99% of the aqueous acrylic adhesive matrix was weighed as shown in Table 3, and 1 % of KE-1062 was added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0095] Comparative Example 10

[0096] Based on the total weight of the aqueous pressure-sensitive adhesive composition, 70% of the aqueous acrylic adhesive matrix was weighed as shown in Table 3, and 30% of KE-1062 was added, mixed, and then fully stirred for 30 minutes. The subsequent steps were the same as the preparation steps in Examples 1 -4.

[0097] Table 2. Contents of components in examples

[0098] Table 3. Contents of components in comparative examples

[0099] 4. Test results

[0100] The aqueous pressure-sensitive adhesive compositions prepared in Examples 1 -17 and Comparative Examples 1 -10 were respectively measured for peeling force property, static shear property, and micro-shear property by means of the above- mentioned peeling force test, static shear test, and micro-shear test methods. The measurement results were as shown in Table 4 below. Table 4. Test results of examples and comparative examples

[0101] As can be seen from Table 4 of the test results of the examples in Table 2 and the comparative examples in Table 3, compared with the static shear property (O) and micro-shear property (205) of the adhesive tape (Comparative Example 1 ) obtained from the purely aqueous acrylic adhesive composition, the adhesive tapes prepared in Examples 1 -17 of the present invention had an improved static shear property (+ or ++) and an improved micro-shear property (5-128); compared with the static shear property (- or O) and micro-shear property (170-269) of the adhesive tapes (Comparative Examples 2-5) obtained from the aqueous acrylic adhesive compositions in which common tackifiers were added, the corresponding properties of the adhesive tapes prepared in Examples 1 -17 of the present invention were better; and compared with the peeling force property (steel: 0.2-1.2), static shear property (++), and micro-shear property (3-13) of the adhesive tapes (Comparative Examples 6-8) obtained from the aqueous pressure-sensitive adhesive compositions in which common cross-linking agents were added, the adhesive tapes prepared in Examples 1 -17 of the present invention had higher peeling forces (steel: 2.9-5.1 ) where the static shear property and micro-shear property were satisfactory.

[0102] By further analyzing the test results in Table 4 above, it was found that when the styrene-acrylic emulsion content of the aqueous pressure-sensitive adhesive composition of the present invention was lower than 2% (Comparative Example 9), the static shear property (O) of the adhesive tape prepared therefrom was poor; and when the styrene-acrylic emulsion content of the aqueous pressure-sensitive adhesive composition of the present invention was higher than 25% (Comparative Example 10), the peeling force property (0.8) and static shear property (O) of the adhesive tape prepared therefrom were poor. In contrast, when the styrene-acrylic emulsion content of the aqueous pressure-sensitive adhesive composition of the present invention was 2-25% and the aqueous acrylic adhesive content was 75- 98%, the adhesive tape obtained therefrom had improved static shear property and micro-shear property (cohesion) and a desired peeling force.

[0103] In addition, the aqueous pressure-sensitive adhesive composition in which the aqueous adhesive matrix was a tackifying resin-modified aqueous adhesive matrix (Examples 16 and 17) had an improved peeling force (5.0) as compared with the aqueous pressure-sensitive adhesive composition comprising the aqueous acrylic adhesive matrix (Examples 1 and 2). In addition, compared with the static shear property (- or O) and micro-shear property (170-269) of the adhesive tapes (Comparative Examples 2-5) obtained from common tackifiers and the aqueous acrylic adhesive matrix, the adhesive tapes (Examples 16 and 17) obtained by adding the styrene-acrylic emulsion and the tackifying resin-modified aqueous adhesive matrix had improved static shear property (++) and micro-shear property (29-70). The technical solution of the present invention is not limited to the above specific embodiments or examples. The above specific embodiments or examples are only illustrative, not restrictive. With the inspiration of the specific embodiments or examples disclosed in the present invention, those skilled in the art may also make various improvements and variations without departing from the subject matter of the present invention and the scope claimed by the claims, and these improvements and variations all fall within the protection of the present invention.

Claims

CLAIMS1. An aqueous pressure-sensitive adhesive composition, characterized by comprising an aqueous adhesive matrix and a styrene-acrylic emulsion, wherein the aqueous adhesive matrix is an aqueous acrylic adhesive matrix or a tackifying resin-modified aqueous acrylic adhesive matrix, and the styrene-acrylic emulsion comprises a styrene-acrylate copolymer.

2. The aqueous pressure-sensitive adhesive composition according to Claim 1 , characterized in that the styrene-acrylate copolymer is a random copolymer emulsion or block copolymer emulsion made of styrene and an acrylic monomer.

3. The aqueous pressure-sensitive adhesive composition according to Claim 1 , characterized in that the aqueous acrylic adhesive matrix is prepared using water, an emulsifier, an initiator, and an acrylic monomer by emulsion polymerization; and the tackifying resin-modified aqueous acrylic adhesive matrix is prepared using the aqueous acrylic adhesive matrix and a tackifying resin, wherein the tackifying resin is one or more of a rosin resin, a terpene resin, and a terpene phenol resin.

4. The aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -3, characterized in that based on the total weight of the aqueous pressure-sensitive adhesive composition, the content of the styrene- acrylic emulsion is 2-25%, preferably 5-20%, even preferably 10-15%; and the content of the aqueous acrylic adhesive matrix is 75-98%, preferably 80-95%, even preferably 85-90%.

5. The aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -3, characterized in that based on the total weight of the aqueous pressure-sensitive adhesive composition, the content of the styrene- acrylic emulsion is 2-25%, preferably 5-20%, even preferably 5-10%; and accordingly, the content of the tackifying resin-modified aqueous acrylic adhesive matrix is 75-98%, preferably 80-95%, even preferably 90-95%.

6. The aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -5, characterized in that based on the total weight of the styreneacrylate copolymer, the content of the styrene monomer is 20-90%, preferably 50- 90%; and the content of the acrylic monomer is 10-80%, preferably 10-50%.

7. The aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -6, characterized in that the mass ratio of the aqueous acrylic adhesive matrix to the tackifying resin in the tackifying resin-modified aqueous acrylic adhesive matrix is 18 : 1 -3 : 1.

8. A method for preparing the aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -7, characterized by comprising:1 ) preparing an aqueous acrylic adhesive matrix using water, an emulsifier, an initiator, and an acrylic monomer by emulsion polymerization; or preparing a tackifying resin-modified aqueous acrylic adhesive matrix by adding a tackifying resin to the aqueous acrylic adhesive matrix; and2) preparing an aqueous pressure-sensitive adhesive composition by adding a styrene-acrylic emulsion to the prepared aqueous acrylic adhesive matrix or tackifying resin-modified aqueous acrylic adhesive matrix, and stirring and uniformly mixing the mixture.

9. An aqueous pressure-sensitive adhesive tape, characterized by comprising a substrate and an adhesive layer, wherein the adhesive layer comprises the aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -7.

10. A method for preparing an aqueous pressure-sensitive adhesive tape, characterized by comprising applying the aqueous pressure-sensitive adhesive composition according to any one of Claims 1 -6 to at least one side of a substrate to prepare the aqueous pressure-sensitive adhesive tape.

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