Aqueous pressure-sensitive adhesive composition having a multimodal particle size distribution

Abstract

The present disclosure is directed to an aqueous adhesive composition. In one embodiment, the aqueous pressure sensitive adhesive composition comprises a plurality of particles having a multimodal particle size distribution. The particles are comprised of (A) a first polymer and (B) a second polymer different from the first polymer. The particles have a d of greater than 450 nm. 50 and a polydispersity index PDi of 0.5 to 2.0.(C) The composition has a solids content of 65.5% by weight or greater.Further disclosed is an article having the aqueous pressure-sensitive adhesive composition.

Description

[Background technology]

[0001] A pressure-sensitive adhesive (PSA) is an adhesive that bonds to a substrate when pressure is applied. PSAs differ from adhesives that are activated, for example, by heat, irradiation, or chemical reactions. Typically, aqueous PSAs are applied to a substrate as an emulsion or dispersion and then dried to remove the liquid carrier.

[0002] Pressure-sensitive adhesives are typically characterized by their adhesiveness and cohesiveness. Adhesion is indicated by the peel strength and / or tackiness of the PSA to the substrate. Cohesiveness is indicated by the shear resistance of the PSA. There is an inverse relationship between adhesiveness and cohesiveness, so that PSA with high adhesiveness has low cohesiveness, and PSA with low adhesiveness has high cohesiveness.

[0003] For example, in coating technologies such as curtain coatings, it is desirable to use aqueous acrylic pressure-sensitive adhesive dispersions having a solids content of more than 65% by weight in order to (i) reduce transportation costs, (ii) improve coating rheology, and (iii) minimize drying energy. However, as the solids content in the aqueous PSA composition increases, the viscosity of the PSA also increases. Similarly, as the solids content in the aqueous PSA composition increases, the risk of polymer particle solidification also increases. The bittiness of the resulting PSA dry layer also increases with increasing solids content.

[0004] As a result, the need for aqueous acrylic pressure-sensitive adhesive compositions having a solid content exceeding 65% by weight and low viscosity has been recognized in this technical field. [Overview of the project]

[0005] This disclosure relates to aqueous adhesive compositions. In one embodiment, the aqueous pressure-sensitive adhesive composition comprises a plurality of particles having a multimodal particle size distribution. The particles consist of (A) a first polymer and (B) a second polymer different from the first polymer. The particles have a diameter greater than 450 nm. 50 (C) The composition has a polydispersity index PDi of 0.5 to 2.0.

[0006] This disclosure provides an article. In one embodiment, the article comprises a first substrate and a layer of dried aqueous pressure-sensitive adhesive composition on the first substrate. The aqueous pressure-sensitive adhesive composition comprises a plurality of particles having a multimodal particle size distribution. The particles consist of (A) a first polymer and (B) a second polymer different from the first polymer. The particles have a diameter greater than 450 nm. 50 (C) The composition has a polydispersity index PDi of 0.5 to 2.0. [Brief explanation of the drawing]

[0007] [Figure 1] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of comparative sample 1. [Figure 2] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of comparative sample 2. [Figure 3] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 1. [Figure 4] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 2. [Figure 5] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 3. [Figure 6] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 4. [Figure 7] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 5. [Figure 8] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 6. [Figure 9]This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 7. [Figure 10] This graph shows the particle size distribution of the aqueous pressure-sensitive adhesive composition of Invention Example 8.

[0008] definition All references to the periodic table refer to the edition published by CRC Press, Inc., 1990–1991. The references to element groups in this table are based on a new notation for numbering groups.

[0009] For the purposes of U.S. patent practice, any referenced patent, patent application, or publication is incorporated by reference in its entirety (or its equivalent U.S. version is incorporated by reference) particularly with respect to definitional disclosures (to the extent that they do not conflict with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0010] Numerical ranges disclosed herein include all values ​​from the lower limit to the upper limit, including the lower and upper limits. In the case of ranges containing explicit values ​​(e.g., 1 or 2, or 3 to 5, or 6 or 7), any sub-ranges between any two explicit values ​​(e.g., the above range of 1 to 7 includes sub-ranges such as 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc.) are also included.

[0011] Unless otherwise stated, implied by the context, or customary in the art, all parts and percentages are based on weight, and all test methods are current as of the filing date of this disclosure.

[0012] When used in this specification, "acrylic monomer" refers to the following structure (I):

[0013] [ka] [In the formula, R1 is a hydroxyl group or C1~C 18This monomer contains an alkoxy group, where R2 is either H or CH3. Examples of acrylic monomers include acrylic acid, methacrylic acid, acrylate, and methacrylate.

[0014] As used herein, the terms “blend” or “polymer blend” refer to a blend of two or more polymers. Such a blend may or may not be miscible (i.e., not phase-separated at the molecular level). Such a blend may or may not be phase-separated. Such a blend may or may not contain one or more domain configurations determined, for example, by transmission electron spectroscopy, light scattering, or X-ray scattering.

[0015] The term "composition" refers to a mixture of materials containing the composition, as well as reaction and decomposition products formed from the materials of the composition.

[0016] The terms “comprising,” “including,” and “having,” and their derivatives, are not intended to exclude the presence of any additional components, steps, or procedures, whether or not they are specifically disclosed. To avoid doubt, all compositions claimed through the use of the term “comprising” may include any additional additives, adjuvants, or compounds, whether polymers or otherwise, unless otherwise stated. In contrast, the term “essentially consisting of” excludes any other components, steps, or procedures from the scope of any subsequent description, except those not essential to the operability. The term “consisting of” excludes any components, steps, or procedures not explicitly described or enumerated. The term “or” refers to the enumerated members individually and in any combination, unless otherwise specified. The use of the singular includes the use of the plural, and vice versa.

[0017] A “polymer” is a compound prepared by polymerizing monomers that provide multiple and / or repeating “units” or “mer units” that constitute a polymer in polymeric form, whether of the same or different types. Therefore, the general term polymer encompasses both the term homopolymer, commonly used to refer to polymers prepared from only one type of monomer, and the term copolymer, commonly used to refer to polymers prepared from at least two types of monomers. It also encompasses all forms of copolymers, such as random, block, etc. The terms “ethylene / α-olefin polymer” and “propylene / α-olefin polymer” refer to the aforementioned copolymers prepared by polymerizing ethylene or propylene with one or more additional polymerizable α-olefin monomers, respectively. While polymers are often described as “made from” one or more specific monomers, “based on” a specific monomer or monomer type, and “containing” a specific monomer content, it should be noted that in this context, the term “monomer” is understood to refer to the polymerized residue of a specific monomer, and not to the non-polymerized species. In general, polymers in this specification are referred to as "units," which are the polymerized forms of the corresponding monomers.

[0018] Test method Adhesion test (peel / tack). Samples are tested on both stainless steel ("stainless steel, SS") and high-density polyethylene ("high-density polyethylene, HDPE") test plates according to the Federation Internationale des fabricants et transformateurs d'Adhesifs et Thermocollants ("FINAT") test method No. 2. Cohesive / shear test: For the shear resistance test of stainless steel plates, FINAT test method No. 8 is used. The type of failure is recorded after the test value: "AF" indicates poor adhesion. "AFB" indicates poor adhesion from the backing material, i.e., the release liner. "CF" indicates poor cohesiveness. "MF" indicates poor mixing. FINAT is the European association of the self-adhesive label industry (Laan van Nieuw-Oost Indie 131-G, 2593BM The Hague, POBox 85612, 2508CH The Hague, The Netherlands). Before the test, the sample strips were applied to the test plate with a residence time of 20 minutes or 24 hours.

[0019] The loop tack test (PSTC Test Method 16) (Pressure Sensitive Tape Council, One Parkview Plaza, Suite 800, Oakbrook Terrace, IL60101, USA) is performed as follows: The loop tack test measures the initial adhesion of the adhesive when it comes into contact with the substrate. The adhesive laminate is tested after being conditioned for at least one day in a controlled environment (22.2–23.3°C (72–74°F), 50% relative humidity). A 2.54 cm (1 inch) wide strip is cut and folded to form a loop, exposing the adhesive surface. This is then mounted between the jaws of an INSTRON® tensile testing machine, and the lower jaw is lowered at a speed of 12 inches / min relative to the substrate so that a 2.54 cm × 2.54 cm (1 inch × 1 inch) square area of ​​adhesive is in contact with the substrate for 1 second. The adhesive is then pulled away, and the peak force that pulls the adhesive away from the substrate is recorded.

[0020] Differential Scanning Calorimetry (DSC). Differential scanning calorimetry (DSC) can be used to measure the melting, crystallization, and glass transition behavior of polymers over a wide range of temperatures. For example, this analysis is performed using a TA Instruments Q1000DSC equipped with an RCS (refrigerated cooling system) and an autosampler. During the test, the nitrogen purge gas flow rate used is 50 ml / min. 3–10 mg of the sample is prepared in a lightweight aluminum pan (approximately 50 mg) by oven-drying the polymer latex at 50°C for 24 hours, then crimped and sealed. The analysis is then performed to determine its thermal properties.

[0021] The thermal behavior of the sample is determined by raising and lowering the sample temperature to create a heat flow versus temperature profile. First, to remove its thermal history, the sample is rapidly heated to 150°C and held isothermally for 5 minutes. Next, the sample is cooled to -90°C at a cooling rate of 10°C / min and held isothermally at -90°C for 5 minutes. Then, the sample is heated to 150°C at a heating rate of 3°C / min (this is the "second heating" gradient). The cooling curve and the second heating curve are recorded.

[0022] The glass transition temperature (Tg) is determined from the DSC heating curve, as described in Bernhard Wunderlich, *The Basis of Thermal Analysis, in Thermal Characterization of Polymeric Materials* 92, 278-279 (Edith A. Turi ed., 2d ed. 1997). Baselines are drawn below and above the glass transition region and extrapolated through the Tg region. The temperature at which the heat capacity of the sample is midway between these baselines is Tg.

[0023] The molecular weight was determined by gel permeation chromatography (GPC) according to the following method. The sample was prepared in tetrahydrofuran (THF) (High Performance Liquid Chromatography (HPLC) grade from Fisher) at a concentration of approximately 2 mg / g of polymer solid per gram. The sample was equilibrated overnight at ambient temperature (approximately 25°C) on a mechanical shaker. Before subjecting the sample solution to size exclusion chromatography (SEC), the sample solution was filtered using a 0.45 micron (μm) polytetrafluoroethylene (PTFE) filter.

[0024] SEC isolation settings SEC separation was performed using a liquid chromatograph consisting of an Agilent 1100 model isocratic pump, vacuum degasser, variable injection size autosampler, and Agilent 1100 HPLC G1362A refractive index detector. Data were processed using Agilent ChemStation, version B.04.03, along with Agilent GPC-Addon, version B.01.01.

[0025] SEC separation was performed in THF (Fisher HPLC grade) at 1 ml / min (mL / min) using an SEC column set consisting of two PLgel MIXED-D columns (available from Agilent) in neat THF, with a narrow fraction of polystyrene standards ranging from 580 Daltons to 371,000 Daltons fitted to a first-order fitting calibration curve. 100 microliters (μL) of sample were subjected to SEC separation.

[0026] SEC separation conditions Column: PLgel MIXED-D column (inner diameter (ID) of 300 × 7.5 millimeters (mm)) and guard (50 mm × 7.5 mm ID), particle size 5 μm Eluent: THF (HPLC grade, Fisher) Flow rate: 1.0 mL / min Sample solvent: THF Sample concentration: approximately 2 mg / g (0.2%) Injection volume of sample solution: 100 μL Calibration: A 10-point calibration curve was constructed (first-order fitting) using a narrow fraction of polystyrene standard with peak molecular weights in the range of 580 Daltons to 371,000 Daltons at a concentration of approximately 0.5 milligrams / milliliter (mg / mL) in THF and used to evaluate the relative molecular weight of the analyzed sample. The detection method is refractive index (RI).

[0027] The number-average molecular weight Mn of the polymer is represented as the first moment of the plot of the number of molecules within each molecular weight range with respect to the molecular weight. In practice, this is the total molecular weight of all molecules divided by the number of molecules and is calculated in the usual way according to the following formula. Mn = Σn i * M i / Σn I = Σw i / Σ(w i / M i ) In the formula,[[]] n i = the number of molecules having molecular weight M i w i = the weight fraction of the material having molecular weight M, and i Σn i = the total number of molecules.

[0028] Mw, which is the weight-average molecular weight, W is calculated in the usual manner according to the formula: M W = Σw i * M i where w i and M i ​​These are the weight fraction and molecular weight of the i-th fraction eluted from the GPC column, respectively. The molecular weight distribution (MWD or M) is the ratio of the averages of these two. w / M n ) is used herein to define the width of the molecular weight distribution.

[0029] As used herein, the term “multimodal particle size distribution” refers to a group of particles having a particle size distribution identified according to a mass fraction characterized by a polydispersity index Q (or “polydispersity index, PDi”).

[0030]

number

[0031] Unlike a unimodal particle size distribution (i.e., a single distribution or Gaussian distribution), a multimodal particle size distribution has at least two prominent maxima that differ by at least 50 nm or at least 100 nm. A unimodal particle size distribution is characterized by a PDi (or Q value) less than 0.3 or a PDi between 0.05 and 0.3, while a multimodal particle size distribution has a PDi (or Q value) greater than 0.3, or a PDi value of 0.4, 0.5, or 0.6 to 1.2, or 1.5 or 2.0. In other words, a multimodal particle size distribution has a PDi (or Q value) between 0.4 and 2.0, or 0.5 to 1.5, or 0.6 to 1.2.

[0032] The particle size distribution is determined by the hydrodynamic radius (R) of the particles. hThe particle size is measured using a CPS Disc Centrifuge Photosedimentometer 24000 (DCP) Particle Size Analyzer, employing differential centrifugal sedimentation techniques within an optically transparent rotating disk. Sedimentation is stabilized by a sucrose gradient (density gradient) within the disk. The rotating disk facilitates sedimentation, and the detector measures only a portion or "difference" of the distribution at a time. Emulsion samples are diluted with DI water containing 0.1% sodium lauryl sulfate. These diluted samples are injected into a rotating disk, and the particle bands are separated and measured as they pass through the detector beam. The turbidity of the fluid near the outer edge of the disk is measured and converted to a weight distribution by Mie Theory light scattering calculations. The reported particle size mode depends on the particle density (or polymer density) and refractive index, calibration standard particle density and diameter, as well as the sucrose gradient and disk speed. The disk centrifuge can determine the particle size of emulsion products in the range of 20 nm to 20 microns. Sample analysis time depends on particle size and density.

[0033] Two discs were used for these analyses. One was a standard disc in which the sample was introduced into the center, and the particles settled outward towards the edge of the disc. Standard discs typically have a density of 1.03 g / cm². 3 It is used for particles with a density exceeding 1.03 g / cm³. Low-density disks typically have a particle density of 1.03 g / cm³. 3 This method is used when the density is less than [amount missing]. The sample is introduced to the outer edge of a low-density disk, and the particles float towards the detector.

[0034] Specific conditions for using low-density disks and Method 1: Three drops in 10 mL of 32% sucrose containing sample dilution SLS. Gradient solution containing 16% to 28% sucrose. Maximum diameter: 3.0 Minimum diameter: 0.09 Disk speed: 24000 RPM Calibration standard diameter: 0.882 microns Calibration standard density: 1.022 g / ml Particle density: 1.029g / ml Particle refractive index: 1.49 Particle absorption: 0.0 Particle non-sphericity: 1.0 Fluid density: 1.086g / ml Fluid refractive index: 1.366

[0035] Specific conditions for using standard disks and Method 2: Add one drop to 10 mL of DI water containing sample dilution SLS. Gradient solution containing 2% to 8% sucrose Maximum diameter: 3.0 microns Minimum diameter: 0.05 microns Disk speed: 22000 RPM Calibration standard diameter: 0.596 microns Calibration standard density: 1.052 g / ml Particle density: 1.06g / ml Particle refractive index: 1.47 Particle absorption: 0.0 Particle non-sphericity: 1.0 Fluid density: 1.015g / ml Fluid refractive index: 1.341

[0036] The solids content of the dispersion is measured by weighing approximately 1 g of the dispersion onto a weighed aluminum pan, recording this initial weight, heating the dispersion in the pan in an oven at 150°C for 30 minutes, and reweighing the sample for the final weight. The solids content is defined as follows:

[0037]

number

[0038] For example, the viscosity of a dispersion with 65.5 wt% solids is measured at 25°C using a Brookfield viscometer model and Brookfield RV-DV-II-Pro viscometer spindle #3, after the dispersion sample has been brought to 25°C using a water bath. Pour the sample into a wide-mouth cup and pour in enough volume so that the spindle is completely submerged in the dispersion when the viscometer device is lowered. Switch on the viscometer and set it to operate at a shear rate of 30 RPM. Monitor the reading for 15 minutes, or until the reading stabilizes, and record the final reading at that point. [Modes for carrying out the invention]

[0039] This disclosure relates to aqueous pressure-sensitive adhesive compositions. In one embodiment, the aqueous pressure-sensitive adhesive composition comprises a plurality of particles having a multimodal particle size distribution. The particles consist of (A) a first polymer and (B) a second polymer different from the first polymer. The particles have a diameter greater than 450 nm. 50 It also has a polydispersity index PDi of 0.5 to 2.0. Composition (C) has a solids content of 65.5% by weight or more.

[0040] In one embodiment, the aqueous pressure-sensitive adhesive composition does not contain a thickener or the thickener is omitted, and the composition has a viscosity of less than 650 cps with a solids content of 65.5% by weight.

[0041] The aqueous pressure-sensitive adhesive composition comprises a plurality of particles, a surfactant, and water. The particles have a multimodal particle size distribution. The particles consist of (A) a first polymer and (B) a second polymer different from the first polymer. The first polymer (A) is an acrylic polymer having a glass transition temperature (Tg) below -20°C. The second polymer (B) is an acrylic polymer having a glass transition temperature (Tg) above -20°C. The second polymer is "different" from the first polymer by having (i) a different monomer type and / or (ii) a different monomer weight percentage and / or (iii) a different Mn and / or (iv) a different Mw and / or (v) a different Tg. As used herein, "acrylic polymer" is a polymer having one or more acrylic monomers in a major amount based on the total weight of the acrylic polymer.

[0042] A surfactant acts as an emulsifier, enabling the formation of droplets of hydrophobic acrylic monomers throughout the aqueous medium. An initiator is then introduced into the emulsified mixture. The initiator reacts with the acrylic monomers dispersed throughout the aqueous medium until all or substantially all of the acrylic monomers have polymerized. The final result is an acrylic dispersion consisting of dispersions of acrylic polymer particles in an aqueous medium, each composed of one or more acrylic monomer subunits.

[0043] The first acrylic polymer has a Tg of less than -20°C, or -80°C to -20°C, or -70°C to -30°C, or -60°C to -35°C. The second acrylic polymer has a Tg of greater than -20°C, or -20°C to 80°C, or -20°C to 60°C, or -20°C to 50°C.

[0044] The first acrylic polymer and the second acrylic polymer are each composed of two or more acrylic monomers. Non-limiting examples of suitable acrylic monomers include acrylic acid (AA), butyl acrylate (BA), ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), octyl acrylate, isooctyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate (MMA), isobutyl methacrylate, octyl methacrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, pentadecyl methacrylate, stearyl methacrylate, n-butyl methacrylate, and C. 12 ~C 18Examples include alkyl methacrylates, cyclohexyl methacrylates, methacrylic acid, and combinations thereof. In addition to acrylic monomers, the first acrylic polymer and the second acrylic polymer may each contain other unsaturated monomers. Unsaturated monomers may include α,β-monoethylene unsaturated dicarboxylic acids with 3 to 6 carbon atoms, such as itaconic acid, fumaric acid, and maleic acid, and anhydrides of monoolefinic unsaturated dicarboxylic acids, such as maleic anhydride and itaconic anhydride, or monoethylene unsaturated sulfonic acids, such as vinyl sulfonic acid, methallyl sulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid. In one embodiment, the second acrylic polymer contains less than 5% monomer units of unsaturated acid comonomers such as acrylic acid and methacrylic acid. In another embodiment, the second acrylic polymer excludes unsaturated acid comonomers. If the monomer units of unsaturated acid comonomers in the second acrylic polymer exceed 5%, a thickening effect may occur when the dispersion is neutralized, which can make handling and processing of the dispersion difficult. Unsaturated monomers include vinyl aromatic monomers such as styrene, α-methylstyrene, vinyltoluene, 4-n-butylstyrene, and 4-tert-butylstyrene, and aliphatic C2-C2 monomers such as vinyl acetate and vinyl propionate. 10 The unsaturated monomers may include vinyl esters of carboxylic acids, or monoethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile. The unsaturated monomers may include amides of monoethylenically unsaturated C3-C8 monocarboxylic acids such as acrylamide and methacrylamide, and hydroxy-C2-C4 alkyl esters of monoethylenically unsaturated C3-C8 monocarboxylic acids, more specifically, C2-C4 hydroxyalkyl acrylates and methacrylates such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate. In some embodiments, the unsaturated monomers are styrene, vinyl acetate, and combinations thereof.

[0045] In one embodiment, the first acrylic polymer includes, in addition to the monomers described above, a small amount of polyethylene unsaturated monomer, which results in crosslinking when the polymer is prepared. Non-limiting examples of polyethylene unsaturated monomers include diesters and triesters of ethylenically unsaturated carboxylic acids, more specifically, bis- and triacrylates of diols or polyols having three or more OH groups; non-limiting examples include bisacrylates and bismethacrylates of ethylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, or polyethylene glycol; vinyl and allyl esters of saturated or unsaturated dicarboxylic acids; vinyl and allyl esters of monoethylenically unsaturated monocarboxylic acids; and polyethylene unsaturated aromatic monomers such as divinylbenzene. The fraction of polyethylene unsaturated monomers does not exceed 1 weight percent, 0.5 weight percent, or 0.1 weight percent based on the total weight of monomers in the monomer mixture.

[0046] The first acrylic polymer has a number-average molecular weight Mn of 50,000 to 5,000,000 daltons, or 50,000 to 1,000,000 daltons, or 50,000 to 500,000 daltons, or 50,000 to 250,000 daltons, or 75,000 to 125,000 daltons, and a weight-average molecular weight Mw of 100,000 to 5,000,000 daltons, or 250,000 to 2,000,000 daltons, or 300,000 to 750,000 daltons. The second acrylic polymer has a number-average molecular weight Mn of 1,000 to 35,000 daltons, or 1,000 to 25,000 daltons, or 2,000 to 10,000 daltons, or 3,000 to 7,500 daltons, and a weight-average molecular weight Mw of 1,000 to 50,000 daltons, or 2,000 to 20,000 daltons, or 3,000 to 10,000 daltons.

[0047] In one embodiment, the ratio of the weight of the first polymer to the weight of the second polymer is 95:5 to 50:50, or 93:7 to 60:40, or 92:8 to 70:30, or 90:10 to 75:25, where the weight of the first polymer is calculated from the total weight of the monomer units of the first polymer, and the weight of the second polymer is calculated from the total weight of the monomer units of the second polymer.

[0048] To prepare an aqueous polymer dispersion, it is possible to use a process for preparing a polymer dispersion having a multimodal particle size distribution. A non-limiting example of a suitable process is the mixing of two or more different polymer dispersions having intrinsic unimodal or multimodal particle size distributions with different average particle sizes. Another suitable process is to prepare a polymer dispersion by free radical aqueous emulsion polymerization of ethylenically unsaturated monomers in the presence of two or more different seed latexes with different average particle sizes. Another suitable process that may be used to prepare a polymer dispersion is to carry out free radical aqueous emulsion polymerization of monomers by a feed process, and if some of the monomers have already undergone polymerization during the polymerization process, a larger amount of emulsifier is added (e.g., surfactant intercept) to initiate the formation of new particles. Another suitable process that may be used to prepare a polymer dispersion is to carry out free radical aqueous emulsion polymerization of monomers by a feed process, and an excess amount of emulsifier is supplied to the polymerization reactor during the polymerization process, resulting in the formation of new particles throughout the polymerization and obtaining a multimodal particle size distribution.

[0049] In one embodiment, the aqueous pressure-sensitive adhesive composition is provided by free-radical aqueous emulsion polymerization of a monomer containing a polymer. In this process, the free-radical aqueous emulsion polymerization of an ethylenically unsaturated monomer is carried out according to a monomer feeding process in which at least one seed latex A is included in the initial packing to the polymerization reactor and at least one further seed latex B is added in the form of an aqueous dispersion during the polymerization process. Seed latex B is added to the polymerization reactor continuously during the monomer feeding. Alternatively, seed latex B is added to the polymerization reactor at predetermined points in time during the monomer feeding, at individual intervals. In one embodiment, seed latex B is added to the polymerization reactor at predetermined points in time when 20% to 60% of the total amount of monomer has been added to the polymerization reactor. The intervals in which seed latex B is added to the polymerization reactor are less than 15 minutes, less than 10 minutes, or less than 5 minutes.

[0050] The term "seed latex" is understood to refer to an aqueous polymer dispersion. The weight-average particle size (weight-average, d) of the seed latex used in the process of the present invention. 50 The particle size is less than 500 nm, or 10-400 nm, or 30-250 nm. The initial seed latex or latex A, located in the polymerization reactor at the start of polymerization, has a weight-average particle size of 30-400 nm. For the additional seed latex B added during the polymerization process, the weight-average particle size is 30-400 nm, or 30-100 nm.

[0051] In one embodiment, the seed polymer is mainly from vinyl aromatic monomers, more specifically from styrene (so-called styrene seed), or mainly from C1-C 10 Alkyl acrylates and / or C1-C 10The seed polymer is composed of alkyl methacrylates, for example, a mixture of butyl acrylate and methyl methacrylate. In addition to these major monomers, which typically constitute at least 80% by weight, more specifically at least 90% by weight, the seed polymer may contain other monomers, more specifically monomers with increased water solubility, in copolymer form. Non-limiting examples include monomers having at least one acidic functional group and / or neutral monomers with increased water solubility. The fraction of such monomers does not generally exceed 20% by weight, more specifically 10% by weight, based on the total amount of monomers constituting the seed polymer, and, if present, typically lies in the range of 0.1% to 10% by weight.

[0052] The first seed polymer A is typically used in amounts of 0.05% to 4% by weight, or 0.2% to 2% by weight, based on the total solids content of the seed polymer relative to the amount of monomer polymerized.

[0053] Seed polymer B, added during the polymerization reaction, is used in amounts of 0.05% to 2% by weight, or 0.1% to 1% by weight, based on the total solid content of the seed polymer relative to the total amount of monomers polymerized.

[0054] It is possible to adjust the maximum particle size of polymer particles in the dispersion through the amount of seed latex A and / or through the ratio of seed latex A to monomer. A smaller fraction of seed latex A based on monomer generally results in larger polymer particles, while a larger amount of seed latex A generally results in smaller polymer particles. The addition time of the second seed latex, and the weight ratio of seed latex B to monomer are used to adjust the particle size and weight fraction of smaller polymer particles in the dispersion, in particular. If the second seed latex B is added earlier, the fraction of smaller polymer particles in the polymer dispersion will be higher. However, at the same time, there is an increase in the diameter of smaller particles, and therefore, the initial addition of seed latex B is d 10The value is larger than in the case of later addition. A similar consideration applies to the amount of seed latex B. A larger ratio of seed latex B to the monomer polymerized results in a larger fraction of smaller polymer particles and a larger particle size distribution. 10 The value becomes larger.

[0055] The particles, composed of (A) a first acrylic polymer and (B) a second acrylic polymer, exhibit a multimodal particle size distribution and d particles exceeding 450 nm. 50 , and has a polydispersity index PDi of 0.5 to 2.0. In one embodiment, particles composed of (A) a first acrylic polymer and (B) a second acrylic polymer have one, some, or all of the following properties. (i) 455nm to 1.0 micron, or 455nm to 800nm ​​d 50 , and / or (ii) PDi of 0.5 to 2.0 or 0.5 to 1.8, and / or (iii) 2.5 to 20.0, or d 2.5 to 10.0 90 / d 10 .

[0056] The aqueous pressure-sensitive adhesive composition contains a surfactant. Suitable surfactants, though not limited to these, include cationic surfactants, anionic surfactants, bipolar surfactants, nonionic surfactants, and combinations thereof. Examples of anionic surfactants include, but are not limited to, sulfonates, carboxylates, and phosphates. Examples of cationic surfactants include, but are not limited to, quaternary amines. Examples of nonionic surfactants include, but are not limited to, block copolymers containing ethylene oxide, and silicone surfactants such as ethoxylated alcohols, ethoxylated fatty acids, sorbitan derivatives, lanolin derivatives, ethoxylated nonylphenol, or alkoxylated polysiloxanes. Suitable commercially available surfactants include, but are not limited to, those sold by The Dow Chemical Company under the trade names TERGITOL® and DOWFAX®, e.g., TERGITOL® 15-S-9 and DOWFAX® 2A1; those sold by BASF SE under the trade name DISPONIL, e.g., DISPONIL FES 77 IS and DISPONIL FES 993; and those sold by Solvay under the trade name AEROSOL, e.g., AEROSOL A-102 and AEROSOL OT-75. The amount of surfactant is typically in the range of 0.1% to 10% by weight, preferably 0.2% to 5% by weight, based on 100% by weight of the polymer or 100% by weight of the monomers constituting the polymer.

[0057] Initiators used in emulsion polymerization are typically water-soluble substances that form free radicals. Water-soluble initiators for emulsion polymerization can be organic or inorganic peroxide compounds, i.e., compounds having at least one peroxide group or hydroperoxide group. Examples include ammonium and alkali metal salts of peroxodisulfate, such as sodium peroxodisulfate, hydrogen peroxide, or organic peroxides such as tert-butyl hydroperoxide. Initiators can also be redox initiator systems. A redox initiator system consists of at least one reducing agent, usually inorganic, and one organic or inorganic oxidizing agent. The oxidizing component may be, for example, one of the peroxide compounds mentioned above. The reducing component consists of reducing agents such as alkali metal salts of sulfite, such as sodium sulfite and sodium bisulfite; alkali metal salts of sulfite, such as sodium disulfite; bisulfite adducts with aliphatic aldehydes and ketones, such as acetone bisulfite; or hydroxymethanesulfinic acid and its salts, BRUGGOLITE FF6 (Bruggeman); or ascorbic acid. Subsequently, a redox initiator system can be used in combination with a soluble metal compound. Typical redox initiator pairs include, for example, ascorbic acid / ferrous sulfate / sodium peroxodisulfate, tert-butyl hydroperoxide / sodium disulfite, and tert-butyl hydroperoxide / sodium hydroxymethanesulfinate.

[0058] The amount of initiator is generally 0.1% to 10% by weight, or 0.3% to 5% by weight, depending on the monomer being polymerized. It is also possible to use two or more different initiators in the same emulsion polymerization.

[0059] Molecular modifiers or chain transfer agents can also be used in polymerization in amounts of 0% to 5% by weight, for example, based on the monomer being polymerized. Using this method, the molecular weight of the polymer can be reduced. By controlling the ratio of monomer to modifier, a specific molecular weight of the polymer dispersion can be targeted, and a higher amount of modifier results in a lower molecular weight polymer. Suitable chemical modifiers include compounds having thiol groups, such as tert-butyl mercaptan, mercaptoethanol, thioglycolic acid, ethyl thioglycolate, mercaptopropyltrimethoxysilane, and tert-dodecyl mercaptan, n-dodecyl mercaptan (n-DDM), 3-mercaptopropionic acid, and their esters, such as methyl 3-mercaptopropionate (MMP) and butyl 3-mercaptopropionate. In one embodiment, the modifier is a transition metal chelate complex, such as a cobalt(II) or (III) chelate complex. The modifier can be added throughout the entire polymerization process, for example, by adding it to the monomer emulsion that is continuously supplied to the reactor. Alternatively, it can be added separately at any point during the reaction, either continuously or at a variable rate. In a preferred embodiment, the modifier is added to the second-stage monomer emulsion (B) to produce a final composition in which the polymer A composition obtained from monomer emulsion (A) has a molecular weight greater than that of polymer B. In a preferred embodiment, the modifier is added to both the first-stage monomer emulsion (A) and the second-stage monomer emulsion (B) to produce a final composition in which the first polymer A composition obtained from monomer emulsion (A) has a molecular weight greater than that of the second polymer B.

[0060] The amount of modifier used to produce polymer A or polymer B may depend on the specific modifier used and the amounts of other components in polymerization. However, in exemplary embodiments, though not limited thereto, if the modifier used in the polymerization step of polymer B is, for example, n-DDM, the amount of modifier may be 0.5% to 20% by weight, or if the modifier used in the present invention is, for example, MMP, the amount of chain transfer agent may be 0.3% to 12% by weight based on the weight of the modifier, as a fraction of the total weight of the modifier and the monomers constituting polymer B. In embodiments where the modifier is n-DDM or MMP, the amount of modifier used to achieve the target Mn is (w) as a fraction of the total weight of the modifier and the monomers constituting polymer B. 調節剤 ) can be estimated according to the following formula, where z 調節剤 This is the molecular weight of the regulator:

[0061]

number

[0062] This process is carried out as a supply process, meaning that at least 95% of the monomers to be polymerized are added to the polymerization reactor under polymerization conditions during polymerization. The addition can be carried out continuously or stepwise. The monomer composition may be changed at least once during the polymerization process to prepare the first polymer A and the second polymer B.

[0063] A preferred procedure involves providing water as an initial packing in the polymerization reactor, adding a portion of the polymerization initiator, and then optionally filling the reactor with water and a first seed latex or latex A in the form of an aqueous dispersion. Subsequently, the monomer to be polymerized is added to the polymerization reactor under polymerization conditions. The addition is typically carried out over a period of at least 30 minutes, or 30 minutes to 10 hours, or 1 hour to 6 hours. As already described, the addition may be carried out at a constant rate, an increasing rate, or a decreasing rate. In one embodiment, the addition is carried out at the start of polymerization while increasing the feed rate. Alternatively, the addition is carried out at a constant rate. The monomer may be added as is. Preferably, the monomer is added in the form of an aqueous monomer emulsion, which contains at least a portion, at least 70% by weight, of the surfactant used in emulsion polymerization. This monomer emulsion typically has a monomer content in the range of 60% to 90%. It is possible to add monomers or monomer emulsions to the polymerization reactor via two or more feed streams, and the monomer compositions of each feed stream can be different from one another. However, generally, it is sufficient to add monomers as a mixture to the polymerization reactor via a single feed stream. When monomers are added to the polymerization reactor in the form of aqueous emulsions, it is beneficial to provide fresh emulsification of the monomers immediately before and in parallel with the addition of monomers to the polymerization reactor, for example, by a continuous method. It is also possible to prepare the monomer emulsion first and then introduce it into the polymerization reactor at the desired addition rate.

[0064] Typically, at least a portion of the entire polymerization initiator is added in parallel with the addition of the monomer. The polymerization initiator may be added, for example, at a constant rate, a decreasing rate, or an increasing rate.

[0065] In one embodiment, an adhesive composition in which particles consist of (A) a first polymer and (B) a second polymer different from the first polymer is prepared using a two-step process. A first monomer solution is provided and polymerized to form polymer A in the first step, optionally in the presence of a modifier. In the second step, a second monomer solution is provided and polymerized to form polymer B in the presence of a modifier. Alternatively, a first monomer solution is provided and polymerized to form polymer B in the first step. In the second step, a second monomer solution is provided and polymerized to form polymer A in the presence of a modifier. The initiators used in each polymerization may be the same or different. Polymerization to form polymer A is carried out using an ammonium or alkali metal salt of peroxodisulfate as the initiator. Alternatively, polymerization to form polymer B is carried out using a redox initiator system. For efficiency, these two steps may be carried out in a single container to prepare a polymer dispersion.

[0066] Emulsion polymerization takes place at temperatures of 30–130°C or 50–90°C. The polymerization pressure is typically in the range of atmospheric pressure, i.e., ambient pressure, but can also be slightly above or below this range, for example, in the range of 800–1500 mbar.

[0067] At the end of the addition of the monomers to be polymerized, or after the conversion of at least 95% of the monomers present in the polymerization reactor, chemical and / or physical deodorization is performed for the purpose of removing unpolymerized monomers. Chemical deodorization is a post-polymerization step initiated by the addition of at least one further polymerization initiator, more specifically by one of the aforementioned redox initiator systems. In one embodiment, the chemical deodorization step may be combined with a second polymerization step such that the supply of initiators continues after the supply of monomers to achieve chemical deodorization. The reduction of residual monomers may also be performed through a combined means of chemical and physical deodorization, in which case physical deodorization is preferably performed after chemical deodorization. The polymer dispersion thus obtained contains less than 1500 ppm, or less than 1000 ppm, or less than 500 ppm of residual monomer species.

[0068] Before the polymer dispersion is used, a base is typically added to adjust the pH to the desired range. Examples of bases used include, but are not limited to, ammonium hydroxide, sodium hydroxide, potassium hydroxide, and triethanolamine. A preferred base is ammonia.

[0069] A. Tackifier In one embodiment, the aqueous pressure-sensitive adhesive composition comprises a tackifier different from the first polymer and the second polymer. Suitable tackifiers include, but are not limited to, rosin resins, including rosin acid and / or rosin esters obtained by esterifying rosin acid with an alcohol or epoxy compound and / or a mixture thereof, non-hydrogenated aliphatic C5 resins, hydrogenated aliphatic C5 resins, aromatically modified C5 resins, terpene resins, hydrogenated C9 resins, (meth)acrylic resins, and combinations thereof. Suitable (meth)acrylic resins as tackifiers are described in U.S. Patent No. 4,912,169, U.S. Patent Application Publication No. 2002 / 055587, and U.S. Patent No. 9,605,188. The aqueous pressure-sensitive adhesive composition contains, based on the total dry weight of the aqueous pressure-sensitive adhesive composition, more than 0% to 50% by weight, or 5% to 40% by weight, or 7% to 30% by weight, or 8% to 15% by weight of the tackifier.

[0070] B. Additives The aqueous pressure-sensitive adhesive composition may further contain one or more optional additives. If additives are present, non-limiting examples of suitable additives include thickeners, defoamers, wetting agents, mechanical stabilizers, pigments, fillers, freeze-thaw agents, neutralizing agents, plasticizers, adhesion promoters, biocides, and combinations thereof.

[0071] In one embodiment, the aqueous pressure-sensitive adhesive composition contains more than 0% to 5% by weight of a thickener, based on the total dry weight of the aqueous pressure-sensitive adhesive composition. Suitable thickeners include, but are not limited to, ACRYSOL®, UCAR®, and CELLOSIZE®, which are available on the market from The Dow Chemical Company in Midland, Michigan.

[0072] In one embodiment, the aqueous pressure-sensitive adhesive composition contains a thickening agent and has a viscosity of 500 cP to 3000 cP.

[0073] C.PSA composition Water-based pressure-sensitive adhesive compositions are Multiple particles having a multimodal particle size distribution, (A) The first polymer and (B) Composed of a second polymer different from the first polymer, d 50 and includes particles having a polydispersity index PDi of 0.5 to 2.0. (C) The composition (i) has a solids content of 65.5% by weight or more. In further embodiments, the composition does not contain a thickener or the thickener is excluded, and the composition (ii) has a viscosity of less than 650 cps.

[0074] In one embodiment, the aqueous pressure-sensitive adhesive composition is (A) A first polymer which is an acrylic polymer, (i) Tg at -80℃ to -20℃, (ii) Mn of 50,000 Daltons to 5,000,000 Daltons, or 50,000 Daltons to 250,000 Daltons. (iii) A first polymer having Mw of 100,000 Daltons to 5,000,000 Daltons, or 300,000 Daltons to 750,000 Daltons, (B) A second polymer different from the first polymer, the second polymer being an acrylic polymer. (i) Tg at -20℃ to 80℃, (ii) Mn of 1,000 Daltons to 35,000 Daltons, or 2,000 Daltons to 10,000 Daltons, (iii) comprising a second polymer having Mw of 1,000 Daltons to 50,000 Daltons, or 3,000 Daltons to 10,000 Daltons, The ratio of the weight of the first polymer to the weight of the second polymer is 95:5 to 50:50 or 90:10 to 75:25. Particles are, (i) 455nm to 1.0 micron, or 455nm to 800nm ​​d 50 , and PDi values ​​of 0.5 to 2.0, or 0.5 to 1.8, and (ii) 2.5 to 20.0, or d 2.5 to 10.090 / d 10 It has, (C) The composition has (i) a solids content of 65.5% to 75% by weight. In further embodiments, the composition is free of or excludes a thickener, and the composition has (ii) a viscosity of less than 650 cps.

[0075] D.Goods This disclosure provides an article comprising a first substrate and a layer of a dried aqueous PSA composition on the first substrate (hereinafter referred to as the PSA layer). The aqueous PSA composition is any aqueous PSA composition as previously disclosed herein and comprises a plurality of particles having a multimodal particle size distribution, the particles are (A) The first polymer and (B) Composed of a second polymer different from the first polymer, The particles are d 50 and has a polyvariance index PDi of 0.5 to 2.0, (C) The composition has (i) a solids content of 65.5% by weight or more. In one embodiment, the composition is free of or excludes a thickener, and composition (ii) has a viscosity of less than 650 cps with a solids content of 65.5% by weight.

[0076] In one embodiment, the article is a pressure-sensitive adhesive article. As used herein, “pressure-sensitive adhesive article” is an article to which a pressure-sensitive adhesive (PSA) is bonded to a first substrate, the PSA having an “effective surface,” the effective surface being an exposed surface effective for contact with a second substrate. The available surface of the PSA may or may not be in contact with a release material. As used herein, “release material” is a material that forms a weak bond with the PSA so that the PSA can be easily removed by hand to expose the effective surface.

[0077] The article includes a first substrate. The first substrate is a film, a cellulose-based material, a woven fabric, a tape, or a release liner, or a combination thereof.

[0078] In one embodiment, the first substrate is a film. Non-limiting examples of films suitable for the first substrate include plastic films (unstretched films, or uniaxially oriented films, or biaxially oriented films) such as propylene polymer films, ethylene polymer films, ethylene / propylene copolymer films, polyester films, poly(vinyl chloride) films, metallized films, polyurethane foams, and polyethylene foams, as well as metal foils such as aluminum foil or copper foil.

[0079] In one embodiment, the first substrate is a cellulose-based material. Non-limiting examples of cellulose-based materials suitable for the substrate include paper (such as kraft paper, crepe paper, and Japanese paper), labels, and cardboard.

[0080] In one embodiment, the first base material is a woven fabric. Non-limiting examples of woven fabrics suitable for the base material include cotton woven fabrics, staple fiber woven fabrics, nonwoven fabrics (such as polyester nonwoven fabrics), vinyl on nonwoven fabrics, and combinations thereof.

[0081] In one embodiment, the first substrate is a release liner. Non-limiting examples of materials suitable for the release liner include fluorocarbon polymers (e.g., polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.), silicone-treated paper or film, and non-polar polymers (e.g., olefin resins such as ethylene-based polymers and propylene-based polymers).

[0082] In one embodiment, the thickness of the first substrate (film, cellulose-based material, woven fabric, tape, or release liner) is 10 microns to 10,000 microns, or 10 microns to 1,000 microns, or 20 microns to 500 microns, or 50 microns to 100 microns, or 100 microns to 200 microns, or 200 microns to 500 microns.

[0083] The PSA layer is formed by applying an aqueous PSA composition to one or both sides of a first substrate and allowing it to dry or cure. The aqueous PSA composition may be any aqueous PSA composition previously disclosed herein. For applying the PSA composition, coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, curtain coaters, slot die coaters, comma coaters, and knife coaters can be used. In one embodiment, the surface of the substrate to which the pressure-sensitive adhesive layer is applied is subjected to surface treatment. Non-limiting examples of suitable surface treatments include primer coating and corona discharge treatment before application of the PSA layer to the substrate surface.

[0084] In one embodiment, the thickness of the PSA layer on the substrate surface is 1 micron to 500 microns, or 10 microns to 110 microns, or 30 microns to 90 microns, or 1 micron to 10 microns, or 10 microns to 50 microns.

[0085] In one embodiment, the article is a multilayer PSA article. As used herein, “multilayer PSA article” includes a substrate and two or more PSA layers such that a first PSA layer is in contact with the substrate and a second PSA layer is in contact with the first PSA layer. The multilayer PSA article may include additional PSA layers, each additional PSA layer in contact with a preceding PSA layer, and the PSA layers are arranged in a stacked manner. For example, the multilayer PSA article may include a third PSA layer, the third PSA layer in contact with and stacked on top of the second PSA layer. The multilayer PSA article may include a fourth PSA layer, the fourth PSA layer in contact with and stacked on top of the third PSA layer. The multilayer PSA article may include a fifth PSA layer, the fifth PSA layer in contact with and stacked on top of the fourth PSA layer. At least one of the PSA layers of a multilayer PSA article is composed of any dry aqueous PSA composition as previously disclosed herein.

[0086] Rather than being limiting, some embodiments of the present disclosure are described in detail below in the following examples. [Examples]

[0087] [Table 1]

[0088] 1. Calculation of estimated polymer Tg Polymers with Mn exceeding 35,000 Da: The polymer Tg (Kelvin) of copolymers with Mn exceeding 35,000 Da, prepared from monomer units of n, can be estimated using the following Fox formula:

[0089]

number

[0090] Polymers with Mn less than or equal to 35,000 Da: The polymer Tg (Kelvin) of copolymers with Mn less than or equal to 35,000 Da, prepared from monomer units of n, can be estimated using the following Flory-Fox formula:

[0091]

number

[0092] The estimated polymer Tg values ​​of monomer units present in the first polymer and / or the second polymer can be calculated using the following "polymer Tg" values ​​in Table A below.

[0093] [Table 2]

[0094] 2. Preparation of comparative samples Comparative sample 1: Polymer composition: 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP)

[0095] Sodium carbonate (0.01% BOM, 0.57 g) in 25 g of water was added as a buffer to a 96°C kettle packing of nitrogen-swept water (259 g) equipped with an overhead stirrer, thermometer, and reflux condenser. Subsequently, ammonium persulfate (0.217% BOM, 5.85 g) in 25 g of water as an initiator, and preform seed packing (starting particle size of 100 nm, 1.251% BOM, 32.8 g) were added to 82.8 g of water to set the initial particle size. The supply and co-feeding of the monomer emulsion were initiated. The monomer emulsion consisted of sodium carbonate (0.02% BOM, 1.4g), itaconic acid (0.2%, 5.2g), acrylic acid (0.8% BOM, 21.0g), disodium ethoxylated alcohol hemiester of sulfosuccinic acid with a strength of 30% in water (0.17%, 14.7g), sodium dodecylbenzenesulfonate with a strength of 22.5% in water (0.21% BOM, 24.8g), butyl acrylate (71.1% BOM, 1870.8g), methyl methacrylate (6.0% BOM, 157.2g), styrene (1.6% BOM, 41.93g), and water (16.8% of the total monomer emulsion, 423g), and was supplied for 75 minutes. A cofeed of ammonium persulfate (0.173% BOM, 4.6g) in 66.5g water was supplied for 75 minutes. The reaction temperature was controlled to 88-90°C. When 50% of the monomer emulsion feed was added, an intercept of sodium dodecylbenzenesulfonate (0.235% BOM, 26.5g) in 16g water was added to the kettle. The high viscosity of the polymerization reaction mixture required dilution by adding an additional 62.5g of water 60 minutes after the start of monomer supply to ensure that stirring of the reaction mixture could be maintained. After the addition of the monomer emulsion was complete, 40g of water was added to the reactor and the reaction mixture was maintained at that temperature. After 15 minutes, the kettle was cooled to 75°C and dilute iron sulfate (0.001% BOM, 0.03g) and tetrasodium ethylenediaminetetraacetate (0.001% BOM, 0.03g) in 8g water were added to the kettle. Next, we began supplying and co-supplying monomer emulsions.The monomer emulsion consisted of tetrasodium 1,1-diphosphonatoethanol (0.002%, 0.1g) with a strength of 33% in water, acetic acid (0.03% BOM, 0.7g), sodium dodecylbenzenesulfonate (0.05% BOM, 5.5g) with a strength of 22.5% in water, butyl acrylate (5% BOM, 131.4g), butyl methacrylate (15% BOM, 394.3g), methyl 3-mercaptopropionate (0.38% BOM, 10.1g), and water (105.8g) for 20 minutes. One co-feed consisted of t-butyl hydroperoxide (0.4% BOM, 85.5g) with a strength of 12.6% in water, and was fed for 50 minutes. The other co-feed consisted of 90 g of water and sodium formaldehyde sulfoxylate dihydrate (0.24% BOM, 8.3 g), which was fed for 50 minutes. The temperature was controlled at 74-76°C during the supply of the monomer emulsion. After the monomer emulsion was finished, 30 g of water was added and the co-feeding continued. After the co-feeding was finished, 20 g of water was added and the batch was cooled to 65°C. The dispersion was then neutralized with 24 g of water containing 28% ammonium hydroxide (17.2 g). After neutralization, the batch was cooled to below 35°C and filtered through a 100-mesh sieve. The maximum reactor stirring was 450 RPM. The final solids content was 64.9%. The particle size distribution measured by Method 2 was polydispersity index = 0.84 and ratio D. 90 / D 10 D 10 =101.5nm, D 50 =362.8nm, and D 90 It had a wavelength of 405.5 nm.

[0096] Comparative sample 2: Monomer composition 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP). Dispersions were prepared according to the process of comparative sample 1, using the following packings instead of the 100 nm preform seed packing and sodium dodecylbenzenesulfonate intercept: 235 nm seeds were added to the initial packing at a solid content of 2.5% relative to the monomer (65.5 g of seeds in 83.2 g of water), and 60 nm seeds were added to the initial packing at a solid content of 0.04% relative to the monomer (1.0 g of seeds in 16.6 g of water). No intercept packing was added. The high viscosity of the polymerization reaction mixture necessitated dilution by adding an additional 62.5 g of water at 60 minutes of monomer supply and another 62.5 g of water at 70 minutes of monomer supply (total 125 g) to ensure that stirring of the reaction mixture could be maintained. The maximum stirring of the reactor was 500 RPM. The final solids content was 64.6% by weight. The particle size distribution measured by Method 2 showed a polydispersity index of 0.47 and a ratio of D 90 / D 10 D 10 =374.5nm, D 50 =620.7nm, and D 90 It had a wavelength of 666.1 nm.

[0097] 3. Preparation of the Invention Invention Example 1: Monomer composition: 80 (80.9 EHA / 8.3 VA / 8.0 MMA / 2.1 Sty / 0.5 AA / 0.2 SVS) / / 20 (97 IBMA / 3 MMP). Using a flask equipped with a mechanical stirrer, a packing consisting of 1.68 g of tetrasodium pyrophosphate, 255 g of deionized water, and 0.68 g of ascorbic acid is heated to 86°C. Next, 39 g of sodium persulfate at a concentration of 6.6% in water is poured into the flask. Then, 26.1 g of polymer seeds with a diameter of 235 nm at a concentration of 25% in water is poured into the flask, followed by 16.3 g of polymer seeds with a diameter of 100 nm at a concentration of 10% in water. Over 4 hours, a monomer emulsion prepared from 24.5 g of a 10% sodium hydroxide aqueous solution, 42.6 g of a 35% solution of sodium sulfate ester of iso-octylphenol ethoxylated with 25 moles of ethylene oxide in water, 10.6 g of a 25.0% sodium vinyl sulfonate aqueous solution, 19.2 g of a 30% sodium lauryl sulfate aqueous solution, 68 g of water, 27.6 g of styrene, 1,079.2 g of 2-ethylhexyl acrylate, 110.4 g of vinyl acetate, 106.8 g of methyl methacrylate, and 7.2 g of acrylic acid is gradually distributed into a flask. At the start, the addition rate for the first 6 minutes is 1.37 g / min. Then, the addition rate is steadily increased to 6.83 g / min over 40 minutes. From the start of emulsion supply, 101.1 g of a 6.6% sodium peroxodisulfate aqueous solution is added at a constant rate over 5 hours, maintaining the reaction medium at 85-87°C. After 52% of the total amount of monomer emulsion (both from the first and second steps) is added to the flask, 50 g of polymer seeds with a diameter of 60 nm and a concentration of 26% in water is poured into the flask.

[0098] After the above supply is complete, the reaction medium is cooled to 75°C. Next, the following three mixtures are supplied to the flask: 93.8 g of an 11% sodium bisulfite aqueous solution over 60 minutes, 88.8 g of an 11% tert-butyl hydroperoxide aqueous solution over 55 minutes, and a monomer emulsion of 0.8 g acetic acid, 32.5 g water, 4 g of a 22% sodium dodecylbenzenesulfonate aqueous solution, 10.1 g methyl 3-mercaptopropionate, and 322.7 g isobutyl methacrylate over 15 minutes. After the addition of the monomer emulsion is complete, the reaction medium is cooled to 55°C over a period of 45 minutes.

[0099] An acrylic emulsion with a solid content of 67.0% and a viscosity of 1512 cP (#3 / 30 RPM) is obtained. The particle size distribution (measured by Method 1) has a polydispersity index of 1.60 and a ratio of D 90 / D 10 D 10 =152.6nm, D 50 =515.7nm, and D 90 It had a wavelength of 976.2 nm. The maximum stirring speed of the reactor was 500 RPM.

[0100] Invention Example 2: Monomer composition 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP). A dispersion was prepared according to the process of Comparative Sample 1, using the following packing instead of the 100 nm preform seed packing and sodium dodecylbenzenesulfonate intercept: 100 nm seeds were added to the initial packing at a solid content of 0.3% relative to the monomer (7.9 g of seeds in 19.6 g of water), and 60 nm seed intercept was added to the reactor at a solid content of 0.8% relative to the monomer (21 g of seeds in 41.1 g of water) at 40% (32% of the total) of the feed for the first monomer emulsion. No additional water was needed to maintain stirring in the polymerization reaction mixture. The maximum stirring speed in the reactor was 350 RPM. The final solid content was 66.8%. The particle size distribution measured by Method 2 had a polydispersity index of 0.76 and a ratio of D 90 / D10 D 10 =175.3nm, D 50 =527.0nm, and D 90 It had a wavelength of 575.2 nm.

[0101] Invention Example 3: Monomer composition 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP). A dispersion was prepared according to the process of Comparative Sample 1, using the following packing instead of the 100 nm preform seed packing and sodium dodecylbenzenesulfonate intercept: 100 nm seeds were added to the initial packing at a solid content of 0.45% relative to the monomer (11.8 g of seeds in 44.4 g of water), and 60 nm seed intercept was added to the reactor at a solid content of 1% relative to the monomer (26.2 g of seeds in 47.7 g of water) at 40% (32% of the total) of the feed for the first monomer emulsion. No additional water was needed to maintain stirring in the polymerization reaction mixture. The maximum stirring speed in the reactor was 400 RPM. The final solid content was 66.8% by weight. The particle size distribution measured by Method 2 had a polydispersity index of 0.74 and a ratio of D 90 / D 10 D 10 =161.8nm, D 50 =458.0nm, and D 90 It had a wavelength of 501.7 nm.

[0102] Invention Example 4: Monomer composition 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP). A dispersion was prepared according to the process of Comparative Sample 1, using the following packings instead of the 100 nm preform seed packing and the sodium dodecylbenzenesulfonate intercept: 235 nm seeds were added to the initial packing at a solid content of 0.4% relative to the monomer (10.5 g of seeds in 19.9 g of water), and 60 nm seeds were added to the initial packing at a solid content of 0.06% relative to the monomer (1.6 g of seeds in 13.4 g of water). When 50% of the first stage monomer had been supplied to the reactor, a packing of 40 nm diameter seeds was added to the reactor at a solid content of 0.4% relative to the monomer (10.5 g of seeds in 31.3 g of water). No additional water was needed to maintain stirring in the polymerization reaction mixture. The maximum stirring speed in the reactor was 450 RPM. The final solids content was 66.8% by weight. The particle size distribution measured by Method 2 had a polydispersity index of 1.06 and a ratio of D 90 / D 10 D 10 =193.1nm, D 50 =535.3nm, and D 90 It had a wavelength of 760.6 nm.

[0103] Invention Example 5: Monomer composition 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP). A dispersion was prepared according to the process of Comparative Sample 1, using the following packing instead of a 100 nm preform seed packing and sodium dodecylbenzenesulfonate intercept: 370 nm seeds were added to the initial packing at a solid content of 2.0% relative to the monomer (52.4 g of seeds in 51.8 g of water), and 60 nm seeds were added to the initial packing at a solid content of 0.06% relative to the monomer (1.6 g of seeds in 13.4 g of water). When 50% of the first stage monomer had been supplied to the reactor, a packing of 40 nm diameter seeds was added to the reactor at a solid content of 0.4% relative to the monomer (10.5 g of seeds in 31.3 g of water). No additional water was needed to maintain stirring in the polymerization reaction mixture. The maximum stirring speed in the reactor was 400 RPM. The final solids content was 66.2% by weight. The particle size distribution measured by Method 2 had a polydispersity index of 1.72 and a ratio of D 90 / D 10 D 10 =92.9nm, D 50 =462.9nm, and D 90 It had a wavelength of 887.8 nm.

[0104] Inventive Example 6: Monomer composition 80 (89.2 BA / 7.5 MMA / 1 AA / 0.3 IA / 2 STY) / / 20 (73.6 BMA / 24.5 BA / 1.9 MMP). A dispersion was prepared according to the process of Comparative Sample 1 using the following filler instead of the 100 nm preform seed filler and the intercept of sodium dodecylbenzenesulfonate: A 235 nm seed was added to the initial filler at 2.0% solids (52.4 g of seed in 74.5 g of water) with respect to the monomer. When 25% of the first stage monomer was fed to the reactor, a 100 nm seed filler was added at 0.6% solids (15.7 g of seed in 30.0 g of water) with respect to the monomer. No additional water needed to be added to the polymerization reaction mixture to maintain stirring. The maximum stirring of the reactor was 400 RPM. The final solids content was 66.4 wt%. The particle size distribution measured by Method 2 was such that the polydispersity index = 0.68 and ratio D 90 / D 10 = 2.8, with D 10 = 248.0 nm, D 50 = 645.7 nm, and D 90 = 684.9 nm.

[0105] Inventive Example 7: Monomer composition 90 (80.7 EHA / 8.0 MMA / 8.3 VA / 0.5 AA / 0.2 SVS / 2.1 STY / 0.17 nDDM) / / 10 (91 IBMA / 5 MMA / 4 MMP). According to the process of Inventive Example 1, a dispersion was prepared using the following modified fillers. The initial filler contained 0.77 g of ascorbic acid instead of 0.68 g of ascorbic acid. The pre-polymerization persulfate filler was 39 g of sodium persulfate at a concentration of 7.5% in water. The monomer emulsion for preparing the first polymer was prepared from 5.5 g of a 50% strength aqueous sodium hydroxide solution, 47.9 g of a 35% solution of the sodium sulfate ester of iso-octylphenol ethoxylated with 25 moles of ethylene oxide in water, 11.9 g of a 25.0% strength aqueous sodium vinyl sulfonate solution, 21.6 g of a 30% strength aqueous sodium lauryl sulfate solution, 87.5 g of water, 31.1 g of STY, 1,0241.1 g of EHA, 124.2 g of VA, 120.2 g of MMA, 2.48 g of n-DDM, and 8.1 g of AA. The monomer emulsion was fed over 4 hours. The initial feed rate for the first 6 minutes was 1.53 g / min. Thereafter, the feed rate was steadily increased to 7.64 g / min over 40 minutes. From the start of emulsion feeding, 152.1 g of a 4.9% strength aqueous sodium peroxydisulfate solution was added at a constant rate over 5 hours. The monomer emulsion for preparing the second polymer was prepared from 0.8 g of acetic acid, 32.5 g of water, 2 g of a 22% strength aqueous sodium dodecylbenzenesulfonate solution, 3.92 g of MMP, 8.12 g of MMA, and 154.4 g of IBMA.

[0106] An acrylic emulsion having a solids content of 66.2% and a viscosity of 972 cP (#3 / 30 RPM) is obtained. The particle size distribution (measured by Method 1) has a polydispersity index = 1.11 and ratio D 90 / D 10 such that D 10 = 194.4 nm, D 50 = 732.0 nm, and D 90 = 1005 nm. The maximum agitation of the reactor was 450 RPM.

[0107] Invention Example 8: Monomer composition 75 (80.9 EHA / 6.0 MMA / 8.3 VA / 0.5 AA / 0.2 SVS / 2.1 STY / 2.0 HEA / 0.01 MMP) / / 25 (61.9 BMA / 22 IBMA / 12.5 BA / 1.5 MMA / 0.5 STY / 0.5 MAA / 1.3 MMP). A dispersion was prepared using the following modified packings according to the process of Invention Example 1. The initial packing contained 0.64 g of ascorbic acid instead of 0.68 g of ascorbic acid. The pre-polymerized persulfate packing was 39 g of sodium persulfate at a concentration of 6.2% in water. The 235 nm and 100 nm seed packings were replaced with 56.3 g of packing consisting only of 235 nm preformed seed packing at a concentration of 26.5% in water. A monomer emulsion for preparing the first polymer was prepared from 4.6 g of a 50% strength sodium hydroxide aqueous solution, 33.8 g of a 33% concentration sodium lauryl alcohol sulfate solution ethoxylated with 30 moles of ethylene oxide in water, 9.9 g of a 25.0% concentration sodium vinyl sulfonate aqueous solution, 5.63 g of DOWFAX® 2A1, 2.1 g of Lutensol TO 6, 87.5 g of water, 25.9 g of STY, 1011.8 g of EHA, 103.5 g of VA, 75.1 g of MMA, 24.8 g of HEA, and 6.8 g of AA. The monomer emulsion was supplied over 4 hours. The initial addition rate for the first 6 minutes was 1.29 g / min. Thereafter, the addition rate was increased to a constant 6.44 g / min over 40 minutes. When 60% of the first-stage monomers had been supplied to the reactor, 0.124 g of MMP packing was mixed into the monomer emulsion. From the start of emulsion supply, 101.1 g of a 6.2% sodium peroxodisulfate aqueous solution was added at a constant rate over 5 hours. A monomer emulsion for preparing the second polymer was prepared from 2.05 g of methacrylic acid, 32.5 g of water, 5 g of a 22% sodium dodecylbenzenesulfonate aqueous solution, 5.55 g of MMP, 6.16 g of MMA, 2.05 g of STY, 51.3 g of BA, 257.4 g of BMA, and 91.5 g of IBMA.

[0108] An acrylic emulsion with a solid content of 67.6% and a viscosity of 2788 cP (#3 / 30 RPM) is obtained. The particle size distribution (measured by Method 1) is polydispersity index = 1.27 and ratio D 90 / D 10 D 10 =222.8nm, D 50 =850.9nm, and D 90 It had a wavelength of 1305 nm. The maximum stirring speed of the reactor was 425 RPM. The final solids content was 67.6% by weight.

[0109] Table 2 below summarizes the characteristics of the comparative samples (CS1-2) and inventive examples (IE1-8), with component amounts expressed as weight percentages based on the dry weight of the pressure-sensitive adhesive composition. Dispersions prepared with a solid content exceeding 65.5% were diluted with water to 65.5% to measure their viscosity at the standardized solid content level.

[0110] [Table 3-1]

[0111] [Table 3-2]

[0112] Equally equal to all other factors, the viscosity of aqueous dispersions generally increases with increasing solid content, especially at solid content exceeding 65% by weight. It is known that blending (i) a high molecular weight, low Tg pressure-sensitive adhesive polymer dispersion with (ii) a low molecular weight, high Tg tackifier dispersion can reduce the solid content of the final dispersion. Furthermore, it is known that the viscosity of aqueous dispersions can be reduced by creating a bimodal particle size distribution (two different particle size modes). CS1 and CS2, as well as IE1 to IE8, each consist of (i) a high molecular weight, low Tg pressure-sensitive adhesive polymer and (ii) a low molecular weight, high Tg tackifier polymer, and (iii) each has a bimodal particle size distribution. However, compared to CS1 / CS2, which cannot achieve a viscosity of less than 650 cP even with a solids content of 65% by weight (64.9% and 64.6% by weight respectively), the ability of IE1-IE8 to exhibit (i) low viscosity (less than 650 cP) and (ii) higher solids content (65.5% by weight) is counterintuitive and unexpected.

[0113] Preparation of PSA articles Samples of aqueous PSA compositions were directly coated onto polyethylene terephthalate (PET) film (60 microns thick) and dried at 80°C for 5 minutes to achieve a dry coating weight of 19-20 grams per square meter. Silicone-treated release paper was laminated with the aqueous pressure-sensitive adhesive coating film to prepare an adhesive laminate.

[0114] The adhesive laminate was conditioned in a controlled environment (22.2-23.3°C (72-74°F), 50% relative humidity) under a weight of 12 kg for at least one day (24 hours) before being subjected to performance testing.

[0115] High-density polyethylene (HDPE) panels purchased from Cheminstruments (510 Commercial Dr., West Chester Township, OH45014) are cleaned and conditioned before use in adhesive testing. Wipe the panels with a lint-free, non-abrasive cloth soaked in isopropanol to remove any adhesive residue from previous tests. Take care not to damage the surface. Once the panel surface appears clean, perform additional wiping with isopropanol. Condition the HDPE panels at 22.2–23.3°C (72–74°F) and 50% relative humidity for a minimum of 4 hours but no more than 24 hours.

[0116] 4. PSA application trial The aqueous PSA composition in the adhesive laminate was completely dried, conditioned in a controlled environment (22.2–23.3°C, 50% relative humidity) in a test chamber, and then performance tests were conducted.

[0117] Table 3 provides the selected dry PSA compositions. Table 3 also provides peel strength, loop tack, and shear data for adhesive laminates containing dry PSA.

[0118] Table 3: Peel adhesion, loop tack, and shear data for adhesive laminates using dried PSA compositions.

[0119] [Table 4] AF - Adhesive failure, CF - Cohesive failure, IE - Example of invention

[0120] This disclosure is not limited to the embodiments and examples contained herein, but is particularly intended to include some embodiments and modified forms of those embodiments, including combinations of elements of different embodiments, to the extent that they fall within the scope of the following claims.

Claims

1. A water-based pressure-sensitive adhesive composition, A plurality of particles having a multimodal particle size distribution, wherein the multimodal particle size distribution is a distribution of a plurality of particles having a particle size distribution that is identified according to a mass fraction characterized by a polydispersity index Q (or PDi), [Math 1] During the ceremony, d 10 is the particle size below which 10% by weight of the polymer particles are located. d 50 is the particle size below which 50% by weight of the polymer particles are located. d 90 is the particle size below which 90% by weight of the polymer particles are located. The aforementioned particles, (A) The first polymer is an acrylic polymer having a glass transition temperature (Tg) of less than -20°C, (B) A second polymer different from the first polymer, which is an acrylic polymer having a glass transition temperature (Tg) above -20°C, and is composed of the above, The aforementioned particles have a d ５０ and has a polyvariance index PDi of 0.5 to 2.0, (C) A water-soluble pressure-sensitive adhesive composition having a viscosity of less than 650 cps and a solids content of 65.5% by weight or more.

2. The particles are d, ranging from 455 nm to 1.0 micron. ５０ The aqueous pressure-sensitive adhesive composition according to claim 1, having the following characteristics.

3. The aforementioned particles have a d of 2.5 to 20.

0. ９０ / d １０ An aqueous pressure-sensitive adhesive composition according to claim 1 or 2, having the following characteristics.

4. The first polymer (A) has a number-average molecular weight Mn of 50,000 Daltons to 5,000,000 Daltons, The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the (B) second polymer has a number-average molecular weight Mn of 1,000 daltons to 35,000 daltons.

5. The first polymer is acrylic acid (AA), butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), octyl acrylate, iso-octyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate (MMA), isobutyl methacrylate, octyl methacrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, pentadecyl methacrylate, stearyl methacrylate, n-butyl methacrylate, C １２ ~C １８ An aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 4, comprising one or more acrylic monomers selected from the group consisting of alkyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and combinations thereof.

6. The second polymer is acrylic acid (AA), butyl acrylate (BA), ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), octyl acrylate, isooctyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate (MMA), isobutyl methacrylate, octyl methacrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, pentadecyl methacrylate, stearyl methacrylate, n-butyl methacrylate, C １２ ~C １８ An aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 5, comprising one or more acrylic monomers selected from the group consisting of alkyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and combinations thereof.

7. The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the second polymer comprises one or more monomer units in an amount of more than 50% by weight having a Tg of -15°C or higher.

8. The aqueous pressure-sensitive adhesive composition according to claim 1, wherein the aqueous pressure-sensitive adhesive composition does not contain a thickening agent, and the aqueous pressure-sensitive adhesive composition has a viscosity of less than 650 cps with a solid content of 65.5% by weight.

9. The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the aqueous pressure-sensitive adhesive composition contains a thickening agent and the aqueous pressure-sensitive adhesive composition has a viscosity of 500 cP to 3000 cP.

10. An aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 9, comprising a surfactant selected from the group consisting of anionic surfactants, cationic surfactants, nonionic surfactants, acid-functional polyethylene, acid-functional polypropylene, and combinations thereof.

11. A water-soluble pressure-sensitive adhesive composition according to any one of claims 1 to 10, comprising a neutralizing agent.

12. Articles, The first substrate and The first substrate comprises a layer of dried aqueous pressure-sensitive adhesive composition, wherein the aqueous pressure-sensitive adhesive composition is A plurality of particles having a multimodal particle size distribution, wherein the multimodal particle size distribution is a distribution of a plurality of particles having a particle size distribution that is identified according to a mass fraction characterized by a polydispersity index Q (or PDi), [Math 2] During the ceremony, d 10 is the particle size below which 10% by weight of the polymer particles are located. d 50 is the particle size below which 50% by weight of the polymer particles are located. d 90 is the particle size below which 90% by weight of the polymer particles are located. The aforementioned particles, (A) The first polymer is an acrylic polymer having a glass transition temperature (Tg) of less than -20°C, (B) A second polymer different from the first polymer, which is an acrylic polymer having a glass transition temperature (Tg) above -20°C, and is composed of the above, The particles have a d50 greater than 450 nm and a polydispersity index PDi of 0.5 to 2.

0. (C) An article wherein the composition has a viscosity of less than 650 cps and a solids content of 65.5% by weight or more.

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