Acrylic adhesive composition containing ethylene vinyl acetate

Abstract

The present disclosure relates to an aqueous pressure-sensitive adhesive composition. In one embodiment, the aqueous pressure-sensitive adhesive composition includes (A) an acrylic dispersion comprising (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than -20°C and (ii) a surfactant. The aqueous pressure-sensitive adhesive composition also includes (B) an ethylene vinyl acetate (EVA) dispersion comprising (i) particles of an ethylene vinyl acetate copolymer having from 10% to less than 50% by weight of a vinyl acetate comonomer, and (ii) a dispersion. Additionally, an article comprising the aqueous pressure-sensitive adhesive composition is disclosed.

Description

[Background technology]

[0001] Pressure-sensitive adhesives ("PSAs") are adhesives that bond to an adherend when pressure is applied. PSAs are distinct from adhesives that are activated by, for example, heat, radiation, or chemical reaction. Typically, water-based 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 their cohesiveness. Adhesion is indicated by the peel strength and / or adhesion of the PSA to the substrate. Cohesion is indicated by the shear resistance of the PSA. Adhesion and cohesion are inversely related; PSAs with high adhesiveness have low cohesion, and PSAs with low adhesiveness have high cohesion.

[0003] However, certain adhesive applications require both high adhesion and high cohesion. It is known to add a tackifier to an acrylic PSA to improve adhesion. However, tackifiers typically reduce cohesion when added to an acrylic PSA. Therefore, the art has recognized a need for an acrylic PSA that has increased cohesion without reducing adhesion. Furthermore, there is a need for an acrylic PSA composition that has increased adhesion without reducing cohesion, without the use of a tackifier. Summary of the Invention

[0004] The present disclosure relates to an aqueous pressure-sensitive adhesive composition. In one embodiment, the aqueous pressure-sensitive adhesive composition includes (A) an acrylic dispersion comprising (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than -20°C and (ii) a surfactant. The aqueous pressure-sensitive adhesive composition also includes (B) an ethylene vinyl acetate (EVA) dispersion comprising (i) particles of an ethylene vinyl acetate copolymer having from 10% to less than 50% by weight of a vinyl acetate comonomer, and (ii) a dispersion.

[0005] The present disclosure provides an article. In one embodiment, the article includes a first substrate and a layer of an aqueous pressure-sensitive adhesive composition on the first substrate. The aqueous pressure-sensitive adhesive composition comprises (A) an acrylic dispersion comprising (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than -20°C and (ii) a surfactant. The aqueous pressure-sensitive adhesive composition also includes (B) an ethylene vinyl acetate (EVA) dispersion comprising (i) particles of an ethylene vinyl acetate copolymer having from 10% to less than 50% by weight of a vinyl acetate comonomer, and (ii) a dispersion.

[0006] definition Any reference to the Periodic Table of the Elements is to that published by CRC Press, Inc., 1990-1991. References to element groups in this table are by the new notation for numbering groups.

[0007] For purposes of United States patent practice, the contents of any referenced patent, patent application, or publication are incorporated by reference in their entirety (or the equivalent United States version thereof is so incorporated by reference), particularly with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0008] Numerical ranges disclosed herein include all values ​​between and including the lower and upper limits, and for ranges containing explicit values ​​(e.g., 1 or 2, or 3-5, or 6, or 7), all subranges between any two explicit values ​​(e.g., the 1-7 range above includes subranges such as 1-2, 2-6, 5-7, 3-7, 5-6, etc.).

[0009] Unless specifically stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are by weight and all test methods are current as of the filing date of this disclosure.

[0010] As used herein, an "acrylic monomer" is defined as having the following structural formula (I):

[0011] [ka] [wherein R1 is a hydroxyl group or a C1-C 18 and R2 is H or CH3. Acrylic monomers include acrylic acid, methacrylic acid, acrylates, and methacrylates.

[0012] As used herein, the terms "blend" or "polymer blend" refer to a blend of two or more polymers. Such blends may or may not be miscible (not phase separated at the molecular level). Such blends may or may not be phase separated. Such blends may or may not contain one or more domain configurations as determined by transmission electron spectroscopy, light scattering, X-ray scattering, and other methods known in the art.

[0013] The term "composition" refers to a mixture of materials that comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0014] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional component, step, or procedure, whether specifically disclosed or not. For the avoidance of doubt, all compositions claimed through the use of the term "comprising" may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless specifically stated to the contrary. In contrast, the term "consisting essentially of" excludes any other component, step, or procedure from the scope of any succeeding description, except those that are not essential to operability. The term "consisting of" excludes any component, step, or procedure not expressly delineated or listed. The term "or," unless otherwise stated, refers to the listed members individually as well as in any combination. The use of the singular includes the use of the plural, and vice versa.

[0015] An "ethylene-based polymer" is a polymer that contains greater than 50 weight percent (wt%) polymerized ethylene monomer (based on the total amount of polymerizable monomers), and may optionally contain at least one comonomer. Ethylene-based polymers include ethylene homopolymers and ethylene copolymers (meaning units derived from ethylene and one or more comonomers). The terms "ethylene-based polymer" and "polyethylene" may be used interchangeably.

[0016] An "olefin-based polymer" or "polyolefin" is a polymer that contains more than 50 weight percent polymerized olefin monomers (based on the total amount of polymerizable monomers) and may optionally include at least one comonomer. A non-limiting example of an olefin-based polymer is an ethylene-based polymer.

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

[0018] A "propylene-based polymer" is a polymer that contains more than 50 weight percent polymerized propylene monomers (based on the total amount of polymerizable monomers) and may optionally contain at least one comonomer. Propylene-based polymers include propylene homopolymers and propylene copolymers (meaning units derived from propylene and one or more comonomers). The terms "propylene-based polymer" and "polypropylene" may be used interchangeably. Non-limiting examples of suitable propylene copolymers include propylene impact copolymers and propylene random copolymers.

[0019] Test Method Adhesion / Cohesion Testing: Samples are tested on both stainless steel ("SS") and high-density polyethylene ("HDPE") test plates according to Federation Internationale des fabricants et transformateurs d' Adhesifs et Thermocollants ("FINAT") Test Method No. 2. Cohesion / Shear Testing: For shear resistance testing of stainless steel plates, FINAT Test Method No. 8 is used. Failure modes are recorded after the test value: "AF" indicates adhesive failure; "AFB" indicates adhesion failure from the backing, i.e., release liner; "CF" indicates cohesive failure; and "MF" indicates mixing failure. Peel Adhesion Testing: Peel strength testing at 90° on high-density polyethylene (HDPE) test plates followed FINAT Test Method No. 2. FINAT is the European Association for the Self-Adhesive Label Industry (Laan van Nieuw-Oost Indie 131-G, 2593 BM The Hague, PO Box 85612, 2508 CH The Hague, The Netherlands). Prior to testing, sample strips were applied to the test plate with a dwell time of 20 minutes.

[0020] Density is measured according to ASTM D792, Method B. Results are recorded in grams per cubic centimeter (g / cc).

[0021] 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 temperature range. For example, a TA Instruments Q1000 DSC equipped with a refrigerated cooling system (RCS) and an autosampler is used to perform this analysis. A nitrogen purge gas flow rate of 50 mL / min is used during testing. Each sample is melt-pressed into a thin film at approximately 175°C, and the molten sample is then air-cooled to room temperature (approximately 25°C). A 3-10 mg, 6 mm diameter specimen is extracted from the cooled polymer, weighed, placed in a lightweight aluminum pan (approximately 50 mg), and crimped shut. Analysis is then performed to determine its thermal properties.

[0022] The thermal behavior of the sample is determined by increasing and decreasing the sample temperature to create a heat flow versus temperature profile. First, the sample is rapidly heated to 180°C to remove its thermal history and held isothermally for 3 minutes. Next, the sample is cooled to -40°C at a cooling rate of 10°C / min and held isothermally at -40°C for 3 minutes. The sample is then heated to 180°C at a heating rate of 10°C / min (this is the "second heat" gradient). A cooling curve and a second heating curve are recorded. The cooling curve is analyzed by setting a baseline endpoint from the onset of crystallization to -20°C. The heating curve is analyzed by setting a baseline endpoint from -20°C to the end of melting. The values ​​obtained are the extrapolated melting onset Tm and extrapolated crystallization onset Tc, the heat of fusion (H f ) (Joules / gram), and the % crystallinity of the polyethylene sample calculated using the following equation: % crystallinity = ((H f ) / 292J / g)x100

[0023] From the second heating curve, the heat of fusion (H f ) (also known as enthalpy of fusion) and peak melting temperature are reported.

[0024] The melting temperature, Tm, is determined from a DSC heating curve by first drawing a baseline between the onset and end of the melting transition. A line tangent to the data on the low-temperature side of the melting peak is then drawn. The point where this line intersects the baseline is the extrapolated melting onset (Tm), as described by Bernhard Wunderlich, *The Basis of Thermal Analysis*, in *Thermal Characterization of Polymeric Materials* 92, 277-278 (Edith A. Turi ed., 2d ed. 1997).

[0025] The glass transition temperature, Tg, is determined from a DSC heating curve where half of the sample acquires a liquid heat capacity, 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 the Tg.

[0026] Loop Tack (PSTC Test Method 16) (Pressure Sensitive Tape Council, One Parkview Plaza, Suite 800, Oakbrook Terrace, IL 60101, USA) is performed as follows: The loop tack test measures the initial adhesive strength when the adhesive contacts the substrate. The adhesive laminate is conditioned for at least one day in a controlled environment (72-74°F (22.2-23.3°C) and 50% relative humidity) before testing. A 1-inch (2.54 cm) wide strip is cut and folded back to form a loop, exposing the adhesive surface. It is then mounted between the jaws of an INSTRON™ tensile tester, and the lower jaw is lowered against the substrate at a rate of 12 inches per minute until a 1-inch x 1-inch (2.54 cm x 2.54 cm) square area of ​​adhesive contacts the substrate for one second. The adhesive is then pulled apart, and the peak force required to pull the adhesive from the substrate is recorded.

[0027] Measure the melt index (MI) (I2) in g / 10 min using ASTM D1238 (190°C / 2.16 kg).

[0028] ASTM D1238 (230°C / 2.16 kg) is used to measure the melt flow rate (MFR) in g / 10 min.

[0029] Melt viscosity is measured at 140°C using a Brookfield viscometer model and a Brookfield RV-DV-II-Pro viscometer spindle 31. The sample is poured into the chamber, which is then inserted into a Brookfield Thermosel and secured in place. The sample chamber has a notch in the bottom that fits the bottom of the Brookfield Thermosel to ensure the chamber does not rotate when the spindle is inserted and rotating. The sample (approximately 8-10 grams of resin) is heated to the required temperature until the molten sample is approximately 1 inch below the top of the sample chamber. The viscometer device is lowered, immersing the spindle into the sample chamber. The lowering continues until the viscometer bracket is flush with the Thermosel. The viscometer is turned on and set to operate at a shear rate that results in a torque reading within 40-60 percent of the total torque capacity, based on the rpm output of the viscometer. Readings are taken every minute for 15 minutes, or until the value stabilizes, at which point the final reading is recorded.

[0030] The viscosity of the emulsion or dispersion is measured at 25°C using a Brookfield viscometer model and a Brookfield RV-DV-II-Pro viscometer spindle #2 or #3. Pour the sample into a wide-mouth cup and pour enough so that the spindle is completely submerged in the dispersion when the viscometer device is lowered. Turn on the viscometer and set it to operate at a shear rate of 12, 30, or 60 RPM. Monitor the reading for 15 minutes or until it stabilizes, at which point record the final reading.

[0031] Molecular weights are determined using gel permeation chromatography (GPC) on a Waters 150°C high temperature chromatography unit equipped with three mixed porosity columns (Polymer Laboratories 103, 104, 105, and 106) operating at a system temperature of 140°C. The solvent is 1,2,4-trichlorobenzene from which an approximately 0.3 weight percent solution of the sample is prepared for injection. The flow rate is 1.0 mL / min, and the injection size is 100 microliters.

[0032] Molecular weight determinations are inferred using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in combination with their elution volumes. Equivalent polyethylene molecular weights are determined using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described in T. Williams & I. M. Ward, "The Construction of a Polyethylene Calibration Curve for Gel Permeation Chromatography Using Polystyrene Fractions," 6 J. Polymer Sci. Pt. B: Polymer Letter 621, 621-624 (1968)), leading to the following equation:

[0033] M polyethylene = a × (M polystyrene) b In this formula, a=0.4316 and b=1.0.

[0034] The number average molecular weight, Mn, of a polymer is expressed as the first moment of a plot of the number of molecules in each molecular weight range against 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 formula:

[0035]

number

[0036] Vicat softening point is determined according to ASTM D1525.

[0037] Volume average particle size analysis was performed using standard procedures with a Beckman Coulter LS13320 laser light scattering particle sizer (Beckman Coulter Inc., Fullerton, California) and the results are reported in microns. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present disclosure relates to an aqueous pressure-sensitive adhesive composition. In one embodiment, the aqueous pressure-sensitive adhesive composition includes (A) an acrylic dispersion comprising (i) an acrylic polymer having a glass transition temperature (Tg) of less than -20°C, and (ii) a surfactant. The aqueous pressure-sensitive adhesive composition also includes (B) an ethylene vinyl acetate (EVA) dispersion. The EVA dispersion comprises (i) an ethylene vinyl acetate copolymer and (ii) a dispersing agent. The ethylene vinyl acetate copolymer contains 10% to less than 50% by weight of a vinyl acetate comonomer and is in the form of particles.

[0039] A. Acrylic dispersion Aqueous PSA compositions include acrylic dispersions. The term "aqueous PSA composition" refers to pressure-sensitive adhesive compositions in which water is the continuous phase, i.e., compositions having an aqueous medium. The acrylic dispersion includes one or more acrylic monomers, excluding the ethylene-based polymer, a surfactant, and water. The surfactant acts as an emulsifier, allowing droplets of the hydrophobic acrylic monomer to form 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 are polymerized. The end result is an acrylic dispersion consisting of a dispersion of acrylic polymer particles in an aqueous medium, where the acrylic polymer particles, excluding the ethylene-based polymer, are composed of one or more acrylic monomer subunits.

[0040] The acrylic polymer has a Tg of less than -20°C, or from -80°C to -20°C, or from -70°C to -30°C, or from -60°C to -40°C, and a Mw of greater than 100,000 Daltons to 10,000,000 Daltons. Non-limiting examples of suitable acrylic monomers include acrylic acid (AA), butyl acrylate (BA), ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), butyl methacrylate (BMA), 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 18Examples of suitable acrylic monomers include alkyl methacrylates, cyclohexyl methacrylates, methacrylic acid, and combinations thereof. In addition to the acrylic monomer, the acrylic polymer may also include monomers such as 2-hydroxyethyl acrylate (2-HEA), styrene (STY), vinyl esters, vinyl acetate, and combinations thereof.

[0041] The acrylic dispersion contains a surfactant. Non-limiting examples of suitable surfactants include cationic surfactants, anionic surfactants, zwitterionic 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 nonylphenols, or alkoxylated polysiloxanes. Commercially available examples of suitable surfactants include, but are not limited to, surfactants sold under the trade names TERGITOL™ and DOWFAX™ by The Dow Chemical Company, such as TERGITOL™ 15-S-9 and DOWFAX™ 2A1, and products sold under the trade name DISPONIL by BASF SE, such as DISPONIL FES 77 IS and DISPONIL FES 993.

[0042] The initiator can be either a thermal initiator or a redox initiator. Examples of thermal initiators include, but are not limited to, ammonium persulfate, sodium persulfate, and potassium persulfate. When the initiator is a redox initiator, the reducing agent can be, for example, ascorbic acid, sulfoxylate, or erythorbic acid, while the oxidizing agent can be, for example, a peroxide or a persulfate.

[0043] In one embodiment, the acrylic dispersion comprises particles of an acrylic polymer having the following properties: (i) two or more monomeric subunits selected from any combination of 2-EHA, MA, MMA, STY, 2-HEA, AA, BA, EA, VA, and BMA; and (ii) Tg between -60°C and -30°C.

[0044] In one embodiment, the acrylic dispersion comprises particles of an acrylic polymer having the following properties: (i) 2-EHA, EA, MMA, and AA monomer subunits, and (ii) Tg between -60°C and -30°C.

[0045] In one embodiment, the acrylic dispersion comprises particles of an acrylic polymer having the following properties: (i) 2-EHA, MMA, STY, 2-HEA, AA, and BA monomer subunits, and (ii) Tg between -60°C and -30°C.

[0046] B. Ethylene vinyl acetate dispersion The aqueous PSA composition includes an ethylene vinyl acetate (EVA) dispersion. The EVA dispersion includes particles of ethylene vinyl acetate copolymer, a dispersing agent, and water. The ethylene vinyl acetate copolymer (or EVA copolymer) consists of (i) ethylene, (ii) vinyl acetate, and (iii) optionally, one or more comonomers. The EVA copolymer contains more than 50% by weight of ethylene monomer. The EVA copolymer contains 10% to less than 50% by weight of vinyl acetate monomer. The weight percentages are based on the total weight of the EVA copolymer. The EVA copolymer is present to the exclusion of ethylene oxide vinyl acetate copolymers (such as ethylene oxide vinyl acetate copolymers made by oxidation of ethylene-vinyl acetate copolymers with oxygen at elevated temperatures) and to the exclusion of vinyl acetate-ethylene copolymers prepared by emulsion polymerization in water.

[0047] It is understood that the particles of EVA copolymer are different from the particles of acrylic polymer present in the acrylic dispersion. In one embodiment, the particles of EVA copolymer have one, some, or all of the following properties: (i) a vinyl acetate content of 15% to 40% by weight, or 17% to 35% by weight, and / or (ii) a volume average particle size of 0.1 microns to 2.0 microns, or 0.2 microns to 1.5 microns, or 0.5 microns to 1.2 microns, and / or (iii) a melt index (MI) of 1 g / 10 min to 600 g / 10 min, or 3 g / 10 min to 600 g / 10 min, or 30 g / 10 min to 550 g / 10 min, or 40 g / 10 min to 500 g / 10 min, and / or (iv) a density between 0.920 g / cc and 0.970 g / cc or between 0.927 g / cc and 0.965 g / cc; and / or (v) a melting point (Tm) of 40°C to 75°C, or 47°C to 73°C, and / or (vi) A Vicat softening point of 20°C to 65°C or 27°C to 62°C.

[0048] In one embodiment, the EVA copolymer comprises (i) ethylene, (ii) vinyl acetate, and (iii) one or more comonomers. Non-limiting examples of suitable comonomers include acrylic acid, methacrylic acid, carbon monoxide, maleic anhydride, glycidyl methacrylate, and unsubstituted alkyl esters of acrylic and methacrylic acid. When any comonomers are present, the total amount of comonomers is greater than 0% to less than 15% by weight, and the total amount of ethylene and vinyl acetate is less than 100% to greater than 85% by weight, based on the total weight of the EVA copolymer. In a further embodiment, the comonomers are present in an amount greater than 0% to less than 8% by weight, and the total amount of ethylene and vinyl acetate is greater than 92% to less than 100% by weight, based on the total weight of the EVA copolymer.

[0049] Commercially available examples of suitable ethylene-vinyl acetate copolymers include, but are not limited to, products sold under the trade name ELVAX™ by The Dow Chemical Company, such as ELVAX™ 220W, ELVAX™ 240W, ELVAX™ 210W, ELVAX™ 150W, ELVAX™ 40W, ELVAX™ 410, ELVAX™ 40W, ELVAX™ 420, ELVAX™ 440, ELVAX™ 440, ELVAX™ 450, ELVAX™ 550, ELVAX™ 265, ELVAX™ 4310, and ELVAX™ 4320.

[0050] In one embodiment, the aqueous pressure-sensitive adhesive composition comprises from 0.1 wt % to 25 wt %, or from 0.1 wt % to 10 wt %, or from 0.2 wt % to 6 wt % of ethylene-vinyl acetate polymer, based on the total dry weight of the aqueous pressure-sensitive adhesive composition.

[0051] The EVA dispersion includes a dispersing agent. The dispersing agent provides colloidal stability for the EVA copolymer in the EVA dispersion. The dispersing agent is selected from long-chain fatty acids having 14 to 40 carbon atoms, anionic surfactants, cationic surfactants, nonionic surfactants, polyethylene with acid functionality, polypropylene with acid functionality, and combinations thereof. In one embodiment, the dispersing agent is a long-chain fatty acid having 14 to 40 carbon atoms, or 16 to 36 carbon atoms, or 18 to 24 carbon atoms, optionally neutralized with a base such as potassium hydroxide, sodium hydroxide, and / or dimethylethanolamine. Non-limiting examples of long-chain fatty acids suitable for dispersing agents include lauric acid (C 12 ), palmitic acid (C 16 ), oleic acid (C 18 ), stearic acid (C 18 ), arachidic acid (C 20 ), erucic acid (C 22 ), behenic acid (C 22 ), and combinations thereof.

[0052] In one embodiment, the dispersant is an anionic surfactant. Non-limiting examples of anionic surfactants suitable for the dispersant include sodium lauryl ether sulfonate, sodium dodecylbenzene sulfonate, C 14 ~C 16 Sodium alpha olefin sulfonate, and DOWFAX™ 2A1 available from The Dow Chemical Company.

[0053] In one embodiment, the dispersant is a cationic surfactant. Non-limiting examples of cationic surfactants suitable for dispersants include stearamidopropyl dimethylamine.

[0054] In one embodiment, the dispersant is a non-ionic surfactant. Non-limiting examples of non-ionic surfactants suitable for dispersants include poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) and poly(ethylene glycol) alkyl ethers.

[0055] In one embodiment, the dispersing agent is an acid-functionalized polyethylene or polypropylene. Non-limiting examples of acid-functionalized polyethylene or polypropylene include ethylene copolymers with acrylic acid, methacrylic acid, maleic acid, or maleic anhydride.

[0056] D. Tackifier In one embodiment, the aqueous pressure-sensitive adhesive composition contains a tackifier. Suitable tackifiers include, but are not limited to, rosin resins, including rosin acids and / or rosin esters obtained by esterifying rosin acids with alcohols or epoxy compounds and / or mixtures thereof, non-hydrogenated aliphatic C5 resins, hydrogenated aliphatic C5 resins, aromatic-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. Pat. No. 4,912,169, U.S. Patent Application Publication No. 2002 / 055587, and U.S. Pat. No. 9,605,188. The aqueous pressure-sensitive adhesive composition contains from greater than 0% to 50% by weight, or from 5% to 40% by weight, or from 7% to 30% by weight, or from 8% to 15% by weight, of the tackifier, based on the total dry weight of the aqueous pressure-sensitive adhesive composition.

[0057] E. Additives The aqueous pressure-sensitive adhesive composition may further comprise one or more optional additives, if present, non-limiting examples of suitable additives include thickeners, defoamers, wetting agents, mechanical stabilizers, pigments, fillers, freeze-thaw agents, neutralizing agents, plasticizers, adhesion promoters, and combinations thereof.

[0058] In one embodiment, the aqueous pressure-sensitive adhesive composition contains greater 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™, commercially available from The Dow Chemical Company, Midland, Michigan.

[0059] In one embodiment, the aqueous pressure-sensitive adhesive composition comprises greater than 0% to 2% by weight of a neutralizing agent, based on the total dry weight of the aqueous pressure-sensitive adhesive composition. Neutralizing agents are used to control pH and provide stability to the formulated pressure-sensitive adhesive composition. Suitable neutralizing agents include, but are not limited to, aqueous ammonia, aqueous amines, and other aqueous inorganic salts.

[0060] C.PSA composition The aqueous PSA composition comprises (A) 40 wt% to 99.9 wt%, or 93 wt% to 99.8 wt%, or 95 wt% to 99.7 wt% of an acrylic dispersion; (B) 10 wt% to 0.1 wt%, or 7 wt% to 0.2 wt%, or 5 wt% to 0.3 wt% EVA dispersion, and (C) 0 wt. %, or greater than 0 wt. % to 50 wt. %, or 5 wt. % to 40 wt. %, or 7 wt. % to 30 wt. %, or 8 wt. % to 15 wt. % of a tackifier, where the weight percentages are based on the total dry weight of the aqueous pressure-sensitive adhesive composition.

[0061] D.Goods The present disclosure provides an article. The article includes a first substrate and a layer of an aqueous PSA composition (hereinafter, "PSA layer") on the first substrate. The aqueous PSA composition may be any of the aqueous PSA compositions previously disclosed herein, and includes (i) an acrylic dispersion (A) composed of an acrylic polymer having a glass transition temperature (Tg) of less than -20°C and (ii) a surfactant, (B) an ethylene vinyl acetate (EVA) dispersion composed of (i) particles of an ethylene vinyl acetate copolymer and (ii) a dispersing agent, and (C) an optional tackifier. The ethylene vinyl acetate copolymer contains from 10% by weight to less than 50% by weight of a vinyl acetate comonomer.

[0062] In one embodiment, the article is a pressure-sensitive adhesive article. As used herein, a "pressure-sensitive adhesive article" is an article in which a pressure-sensitive adhesive (PSA) is adhered to a first substrate, and the PSA has an "available surface," which is an exposed surface available 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, a "release material" is a material that forms a weak bond with the PSA, allowing the PSA to be easily removed by hand to expose the available surface.

[0063] The article includes a first substrate, which can be a film, a cellulosic material, a fabric, a tape, or a release liner, and combinations thereof.

[0064] 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 stretched films, or biaxially stretched films), such as propylene-based polymer films, ethylene-based polymer films, ethylene / propylene copolymer films, polyester films, poly(vinyl chloride) films, metallized films, foam substrates such as polyurethane foam and polyethylene foam, and metal foils such as aluminum foil or copper foil.

[0065] In one embodiment, the first substrate is a cellulosic material. Non-limiting examples of cellulosic materials suitable for the substrate include paper, such as kraft paper, crepe paper, and washi paper, labels, and cardboard.

[0066] In one embodiment, the first substrate is a fabric. Non-limiting examples of fabrics suitable for the substrate include cotton fabric, staple fiber fabric, nonwoven fabric such as polyester nonwoven fabric, vinyl on nonwoven fabric, and combinations thereof.

[0067] In one embodiment, the first substrate is a release liner. Non-limiting examples of materials suitable for release liners 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-based resins such as ethylene-based polymers and propylene-based polymers).

[0068] In one embodiment, the thickness of the first substrate (film, cellulosic material, fabric, tape, or release liner) is from 10 microns to 10,000 microns, or from 10 microns to 1,000 microns, or from 20 microns to 500 microns, or from 50 microns to 100 microns, or from 100 microns to 200 microns, or from 200 microns to 500 microns.

[0069] The PSA layer is formed by applying an aqueous PSA composition to one or both surfaces of a first substrate and allowing it to dry or cure. The aqueous PSA composition may be any of the aqueous PSA compositions disclosed hereinabove. The PSA composition can be applied using a coater, such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, curtain coater, slot die coater, comma coater, or knife coater. In one embodiment, the surface of the substrate to which the pressure-sensitive adhesive layer is applied is subjected to a surface treatment. Non-limiting examples of suitable surface treatments include a primer coating and a corona discharge treatment prior to applying the PSA layer to the substrate surface.

[0070] In one embodiment, the thickness of the PSA layer on the substrate surface is from 1 micron to 500 microns, or from 10 microns to 110 microns, or from 30 microns to 90 microns, or from 1 micron to 10 microns, or from 10 microns to 50 microns.

[0071] In one embodiment, the article is a multilayer PSA article. As used herein, a "multilayer PSA article" includes a substrate and two or more PSA layers, such that a first PSA layer contacts the substrate and a second PSA layer contacts the first PSA layer. The multilayer PSA article may include additional PSA layers, each in contact with the preceding PSA layer, with the PSA layers arranged in a stacked configuration. For example, the multilayer PSA article may include a third PSA layer, which contacts and is stacked on top of the second PSA layer. The multilayer PSA article may include a fourth PSA layer, which contacts and is stacked on top of the third PSA layer. The multilayer PSA article may include a fifth PSA layer, which contacts and is stacked on top of the fourth PSA layer. At least one of the PSA layers of the multilayer PSA article is composed of any of the aqueous PSA compositions previously disclosed herein.

[0072] By way of example, and not by way of limitation, some embodiments of the present disclosure will now be described in detail in the following examples. [Example]

[0073] The materials used in the examples are provided in Tables 1A and 1B below.

[0074] [Table 1]

[0075] [Table 2] * Weight percent of vinyl acetate comonomer based on total weight EVA resin † Contains 1% methacrylic acid.

[0076] A. Melt index (MI)-melt viscosity (Mv) relationship The melt index at 190°C can be estimated from the melt viscosity at 140°C according to the following calculation taken from Shenoy, AV Saini, DR Nadkarni, VM Polymer 1983, 24, 722-728: The MI at a given temperature, say 140°C, can be estimated from the melt viscosity at the same temperature as follows:

[0077]

number

[0078]

number

[0079]

number

[0080] As an example, the MI at 190°C of EAA Honeywell AC 5120 polymer is calculated based on its melt viscosity (6 poise), density (0.93 g / cm3) at 140°C. 3 ), and the glass transition temperature calculated for a copolymer of 85% ethylene and 15% acrylic acid.

[0081] [Table 3] * Estimated monomer composition, wt% based on total weight of material E-ethylene, VA-vinyl acetate, AA-acrylic acid

[0082] 1. Preparation of Acrylic Dispersion A. Acrylic Dispersion 1 Acrylic Dispersion 1 is prepared according to the following procedure: A 4-liter, five-neck reactor equipped with a condenser, mechanical stirrer, temperature-controlled thermocouple, and inlets for initiator and monomer is charged with 540 g of deionized ("DI") water and heated to 87°C under a gentle nitrogen flow. In a separate container, a monomer emulsion is prepared by combining 400 g of DI water, 11.9 g of DISPONIL FES 77, 5 g of TERGITOL™ 15-S-9, 4 g of sodium carbonate, and 2,024 g of a monomer mixture consisting of 71.5 wt% 2-ethylhexyl acrylate ("2-EHA"), 18.5 wt% ethyl acrylate ("EA"), 9 wt% methyl methacrylate ("MMA"), and 1 wt% acrylic acid ("AA"). Next, a solution of a mixture of 1.3 g of sodium carbonate and 8.3 g of ammonium persulfate ("APS" as initiator) in 32 g of DI water is added to the reactor. Immediately after the addition of the sodium carbonate and APS solutions, the monomer emulsion is fed into the reactor. The feeds are continued for 80 minutes. Once the addition of the monomer emulsion is complete, the reaction mixture is cooled to 60°C, after which a solution of tert-butyl hydroperoxide (70%) ("t-BHP") (4.7 g in 23 g of DI water) and 2.8 g of sodium formaldehyde bisulfite in 28 g of DI water are slowly added via two separate feeds over 25 minutes. Once the feeds are complete, the reaction is allowed to cool to room temperature. The resulting Acrylic Dispersion 1 is then filtered through a 325 mesh filter cloth to prepare the composition for subsequent evaluation work. The resulting Acrylic Dispersion 1 contained an acrylic polymer consisting of 71.5 wt% 2-EHA / 18.5 wt% EA / 9 wt% MMA / 1 wt% AA and had a glass transition temperature of −41° C. Weight percentages are based on the total dry weight of the acrylic polymer.

[0083] B. Acrylic Dispersion 2 Acrylic Dispersion 2 is INVISU™ 4100 available from The Dow Chemical Company.

[0084] C. Acrylic Dispersion 3 Acrylic Dispersion 3 is INVISU™ 3000 available from The Dow Chemical Company.

[0085] D. Acrylic Dispersion 4 A flask prepared for semi-continuous emulsion polymerization containing 270 g of water at 90° C. was first charged with sodium peroxodisulfate (1.26 g) in 13 g of deionized water, followed by 21.2 g of seeds consisting of an aqueous dispersion of an acrylic polymer with a 12% solids content and an average particle size of 60 nm. After 2 minutes, the addition of a feed stream containing sodium peroxodisulfate (3.79 g) in 59.8 g of deionized water and monomer emulsion was started and continued at a constant rate over 120 minutes at 90° C. The monomer emulsion consisted of 1250 g of monomers in the weight proportions listed in Table 2, 180 g of a 33% aqueous solution of the sodium salt of the sulfate ester of lauryl alcohol ethoxylated with 30 moles of ethylene oxide, 5.6 g of a 44% aqueous solution of DOWFAX™ 2A1, 6.7 g of a 75% ethanol / water solution of dioctyl sulfosuccinate sodium salt, and 295 g of deionized water. After adding half the weight of the monomer emulsion to the reactor, 72 g of seeds consisting of an aqueous dispersion of an acrylic polymer with a 26% solids content and an average particle size of 60 nm were added to the reactor within 1 minute. After the monomer emulsion and feed streams were completely added to the reactor, an additional 35 g of deionized water was added while the reactor temperature was maintained at 90°C. Next, ammonia (17.9 g of a 4.4% concentration in water) was added to the reactor. Finally, an 8% aqueous solution of tert-butyl hydroperoxide (23 g) and a 10% aqueous solution of sodium formaldehyde sulfoxylate (19.5 g) were added to the reactor at constant rates over 60 minutes at 90° C. After completion of these feed streams, the reactor contents were cooled to room temperature.

[0086] E. Acrylic Dispersion 5 Using a flask equipped with a mechanical stirrer, an initial aqueous charge consisting of 0.51 grams of tetrasodium pyrophosphate, 640 grams of deionized water, 1.80 grams of anhydrous sodium sulfate, and 1.36 grams of ascorbic acid is warmed to 87° C. Next, 28.4 grams of a 19% concentration aqueous solution of sodium persulfate is poured into the flask. Over a 2.0 hour period, an emulsion consisting of 14.7 grams of 50% aqueous sodium hydroxide, 39.4 grams of a 30% sodium sulfate solution of lauryl alcohol ethoxylated with 12 moles of ethylene oxide in water, 21.2 grams of a 25.0% aqueous sodium vinyl sulfonate solution, 28.8 grams of a 22% aqueous sodium dodecylbenzenesulfonate solution, 6.6 grams of itaconic acid, 236 grams of water, 321.2 grams of methyl methacrylate, 55.2 grams of styrene, 1,592.4 grams of 2-ethylhexyl acrylate, 679.3 grams of ethyl acrylate, and 14.4 grams of acrylic acid is gradually added to the flask. Initially, the addition rate is 5.0 grams per minute for the first 5.0 minutes. This rate is then steadily increased to 25.0 grams per minute over a 35 minute period. After a total feed time of 75 minutes, the rate is increased to 35.0 grams per minute. From the start of the emulsion feed, 94 grams of an 11% aqueous solution of sodium peroxodisulfate is added at a constant rate over a 2.3 hour period while maintaining the reactor temperature at 85-87°C.

[0087] After the feeds are complete, a solution of 2.76 grams of sodium bisulfite, 1.8 grams of acetone, and 44.4 grams of water is simultaneously dispensed into the flask over a period of 45 minutes at about 70° C. A pressure-sensitive adhesive copolymer dispersion is produced at 70% by weight solids.

[0088] F. Acrylic Dispersion 6 Using a flask equipped with a mechanical stirrer, a charge consisting of 1.34 g of tetrasodium pyrophosphate, 269 g of deionized water, and 0.68 g of ascorbic acid is warmed to 86° C. Next, 28 g of 6.6% sodium persulfate in water is poured into the flask. Over a period of 4 hours, an emulsion consisting of 24.5 g of 10% aqueous sodium hydroxide, 30 g of a 33% solution of the sodium sulfate ester of lauryl alcohol ethoxylated with 30 moles of ethylene oxide in water, 10.6 g of a 25.0% solution of sodium vinyl sulfonate in water, 5 g of a 44% solution of DOWFAX™ 2A1 in water, 2.2 g of lauryl alcohol ethoxylated with 7 moles of ethylene oxide, 172 g of water, 27.6 g of styrene, 1,079.2 g of 2-ethylhexyl acrylate, 55.2 g of vinyl acetate, 162 g of methyl methacrylate, and 7.2 g of acrylic acid is gradually dispensed into the flask. Initially, the addition rate is 1.42 g / min for the first 6 minutes. The addition rate is then steadily increased to 7.1 g / min over a period of 40 minutes. From the start of the emulsion feed, 148 g of a 5% strength sodium peroxodisulfate solution in water are added at a constant rate over a period of 5 hours, maintaining the reaction medium at 85-87°C.

[0089] After the end of the feed, at approximately 70° C., a solution of 1.38 g of sodium hydrogen sulfite, 0.9 g of acetone, 22.2 g of water and simultaneously 23.8 g of a 5.5% strength solution of tert-butyl hydroperoxide are dispensed into the flask over the course of 60 minutes.

[0090] G. Acrylic Dispersion 7 Sodium carbonate (0.01% BOM, 0.55 g) was added as a buffer to a 96°C kettle charge of nitrogen-swept water (518 g) equipped with an overhead stirrer, thermometer, and reflux condenser. This was followed by the addition of ammonium persulfate (0.217% BOM, 5.9 g) as initiator and a preform seed charge (100 nm starting particle size, 1.251% BOM, 70.79 g) to set the initial particle size. The monomer emulsion feed and co-feed were started. The monomer emulsion consisted of sodium carbonate (0.02% BOM, 1.4 g), itaconic acid (0.2%, 5.1 g), acrylic acid (0.8% BOM, 20.4 g), disodium ethoxylated alcohol half ester of sulfosuccinic acid (0.17%, 14.3 g), sodium dodecylbenzenesulfonate (0.21% BOM, 24.2 g), butyl acrylate (71.1% BOM, 1818 g), methyl methacrylate (6.0% BOM, 152.8 g), styrene (1.6% BOM, 40.8 g), and water (16.8% of total monomer emulsion, 411 g) and was fed over 75 min. A co-feed of ammonium persulfate (0.173% BOM, 4.6 g) was fed over 75 min. The temperature of the reaction was controlled at 88-90 °C. Halfway through the monomer emulsion feed, a portion of sodium dodecylbenzenesulfonate (0.235% BOM, 26.5 g) was added to the kettle. Once the monomer emulsion addition was complete, the temperature was held. After 15 minutes, the kettle was cooled to 75°C, and dilute ferrous sulfate (0.001% BOM, 0.03 g) and tetrasodium ethylenediaminetetraacetate (0.001% BOM, 0.03 g) were added to the kettle. The monomer emulsion feed and co-feed were then started. The monomer emulsion consisted of tetrasodium 1,1-diphosphonatoethanol (0.002%, 0.1 g), acetic acid (0.03% BOM, 0.6 g), sodium dodecylbenzenesulfonate (0.05% BOM, 5.3 g), butyl acrylate (5% BOM, 127.8 g), butyl methacrylate (15% BOM, 353.3 g), 3-methylmercaptopropionate (0.38% BOM, 9.8 g), and water (105.7 g) for 20 minutes. One cofeed consisted of t-butyl hydroperoxide (0.4% BOM, 15.1 g) for 50 minutes.The other co-feed consisted of sodium hydroxymethanesulfonate (0.24% BOM, 8.1 g) and was fed over 50 minutes. The temperature was controlled at 74-76°C during the monomer emulsion feed. Once the monomer emulsion was complete, the batch was cooled to 65°C. The dispersion was then neutralized with ammonium hydroxide to a pH of 7. After neutralization, the batch was cooled to below 35°C.

[0091] Table 2 below summarizes the properties for Acrylic Dispersions 1-7, with component amounts listed as weight percent based on the dry weight of the acrylic dispersion.

[0092] [Table 4] Wt% based on dry weight of acrylic dispersion

[0093] 2. Preparation of EVA Dispersion Aqueous EVA dispersions were prepared using a Bersdorf ZE25 48 L / D 25 mm twin-screw extruder (Kraus-Maffei Corporation, Florence, Kentucky, USA) rotating at 450 rpm according to the following procedure. EVA copolymer resin (EVA Feed 1 in Table 3 below) was fed into the extruder feed throat via a Schenck Mechatron loss-in-weight feeder and a K-tron loss-in-weight feeder to control the blend composition. The EVA resin was melt-blended and then emulsified in the presence of an initial water flow (IA) and oleic acid (dispersant), neutralized with potassium hydroxide (KOH), both injected using an ISCO dual syringe pump (Teledyne Isco, Inc., Lincoln, Nebraska, USA). The dispersed liquid phase was then conveyed to the extruder dilution and cooling zone, where additional dilution water was added via the ISCO dual syringe pump to form an aqueous dispersion with a solids level content of less than 70 weight percent. The barrel temperature of the extruder was set at 140-150° C. After the EVA dispersion exited the extruder, it was further cooled and filtered through a bag filter with a mesh size of 200 μm.

[0094] Specific feed rates and results are shown in Table 3 below.

[0095] [Table 5]

[0096] 3. Preparation of Pressure-Sensitive Adhesive Composition Aqueous pressure-sensitive adhesive compositions were formulated as follows: All samples, unless otherwise noted, were formulated with 0.3% (wet / wet) SURFYNOL 440 wetting agent ("440"), based on the total dispersion, from Evonik to improve wetting for laboratory drawdowns. The viscosity was then adjusted to approximately 600 cps (600 mPa s) using ACRYSOL™ DR-5500 ("DR-5500") thickener, available from The Dow Chemical Company, Midland, Michigan (Brookfield, RVDV, 30 rpm, 63#), and the final pH was adjusted to 7.0-7.5 using ammonium hydroxide.

[0097] The acrylic dispersions were blended with the EVA dispersions according to the dosage levels (wet or dry weight based on the total weight of the acrylic dispersion) shown in the respective tables under adequate agitation.

[0098] 4. Preparation of PSA Articles Lab Drawdown:

[0099] Polypropylene ("PP") film (60 microns thick) was pretreated by corona treatment before lamination. A sample of the water-based PSA composition was coated onto release paper and dried at 80°C for 5 minutes. The PP film was laminated with a release liner coated with a water-based pressure-sensitive adhesive ("adhesive laminate").

[0100] The adhesive laminates were conditioned in a controlled environment (22.2-23.3°C (72-74°F) and 50% relative humidity) for at least 1 day (24 hours) before performance testing.

[0101] High-density polyethylene (HDPE) panels purchased from Cheminstruments (510 Commercial Dr., West Chester Township, OH 45014) are cleaned and conditioned before use for adhesive testing. Wipe the panels with a lint-free, non-abrasive cloth soaked in isopropanol to remove any adhesive residue from the previous test. Be careful not to scratch the surface. Once the panel surface appears clean, perform an additional wipe 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 not more than 24 hours.

[0102] 5.PSA application test Performance testing was performed after the aqueous PSA compositions in the adhesive laminates had been thoroughly dried and conditioned in a controlled environment (22.2–23.3°C, 50% relative humidity) in a laboratory at least overnight, and in some cases after as long as 120 hours under a 12 kg weight.

[0103] Peel adhesion, loop tack, and shear data for adhesive laminates having dried PSA compositions comprised of (i) Acrylic Dispersion 1 and (ii) either COHESA 3050 or EVA dispersion are provided in Table 4 below.

[0104] [Table 6] CS = Comparative Sample, IE = Inventive Example

[0105] The 90° HDPE peel adhesion (24 hr) observed for PSA articles (laminates) prepared from blends of Acrylic Dispersion 1 and Ethylene Copolymer Dispersion unexpectedly increases with decreasing MI. CS1 at >500 MI exhibits a 90° HDPE peel adhesion (24 hr) of 3.4 N / in compared to an IE3 of 43 MI and a 90° HDPE peel adhesion of 4.7 N / in.

[0106] Based on prior art laminates utilizing high MI (>500 MI) and anionic, highly polar, low molecular weight copolymer additives, it is expected that low MI (<500 MI) nonionic and nonpolar EVA additives will have poor compatibility with polyolefin substrates and acrylic copolymers, and therefore such formulations will have poor adhesion. Applicants unexpectedly discovered that the opposite was also true. The low molecular weight formulation (Cohesa 3050 ethylene acrylic acid dispersion (CS1)) had poorer adhesion to HDPE (lower 90° HDPE peel adhesion, 3.4 N / in.) than inventive Examples IE1 (3.8 N / in.), IE2 (4.2 N / in.), and IE3 (4.7 N / in.).

[0107] The peel adhesion and loop tack of adhesive laminates having dried PSA compositions comprised of (i) Acrylic Dispersion 2 and (ii) EVA Dispersion are provided in Table 5 below.

[0108] [Table 7] CS = Comparative Sample, IE = Inventive Example

[0109] The 90° HDPE peel adhesion (24 h) observed for PSA article (laminate) formulations of Acrylic Dispersion 2 and ethylene copolymer dispersions is higher than that of laminates prepared from Acrylic Dispersion 2 alone. Based on prior art utilizing high-MI and low-molecular-weight ethylene copolymer additives that are anionic and highly polar, low-melt index additives such as nonionic, low-polarity EVA are expected to be incompatible with acrylic polymers, such that these formulations exhibit poor adhesion. Instead, these formulations improve adhesion to HDPE regardless of the level of VA in the EVA. The relative increase in 90° HDPE peel adhesion (24 h) as the EVA dispersion concentration is increased from 0 (CS2) to 0.4, 2.0, and 4.0 parts (IE4 to IE18) is not linear. In some cases, such as IE10-IE12 and IE16-IE18, a significant improvement in 90° HDPE peel adhesion is shown with the addition of 0.4 phe solids, but the increase levels off thereafter. In other cases, such as IE4-IE6, IE7-9, and IE13-15, the 90° HDPE peel adhesion gradually increases as more EVA dispersion is added.

[0110] 6. Preparation of Pressure-Sensitive Adhesive Compositions Containing Tackifiers Aqueous pressure-sensitive adhesive compositions containing tackifiers were formulated as follows: Unless otherwise noted, all samples were formulated with 0.3% (wet / wet) Aerosol OT-75 and 0.1% (wet / wet) Surfynol 440 wetting agents, obtained from Solvay, based on the total dispersion, to improve wetting for laboratory drawdowns. For samples containing tackifier, the tackifier was added at a level of 10% (dry weight of tackifier / dry weight of total formulation). Tackifiers used were Snowtack SE782G and Snowtack SE784G from Lawter, and Dermulsene RE 1513 from DRT. EVA3 was added to selected samples at a level of 1% (wet / wet) based on the total dispersion. The final pH was adjusted to 7.0-8.0 using ammonium hydroxide.

[0111] A sample of the aqueous PSA composition containing the tackifier was coated onto release paper and dried at 105°C for 2 minutes. Wood-free vellum paper (70 g / m 2 ) was laminated with a release liner coated with a pressure-sensitive adhesive ("adhesive laminate"). The dry coating weight of the adhesive was 18 g / m 2 It was.

[0112] The adhesive laminates were conditioned in a controlled environment (22.2-23.3°C (72-74°F), 50% relative humidity) for at least 4 hours before performance testing.

[0113] Table 6: Peel adhesion and loop tack data for adhesive laminates with dried PSA compositions containing tackifier.

[0114] [Table 8]

[0115] Tackifiers act to increase the adhesive properties of PSAs due to their low molecular weight and high glass transition temperature. In the prior art, low molecular weight, anionic, and highly polar ethylene copolymers, such as ethylene acrylic acid copolymers or oxidized polyethylene, have shown effectiveness in increasing the adhesion of tackified PSA formulations. Therefore, it is surprising that non-oxidized, nonionic, less polar EVA with a lower melt index increases the adhesive properties of tackified PSA formulations.

[0116] 7. Formulation of acrylic dispersions containing EVA3 The acrylic dispersions were blended and mixed with the EVA dispersions according to the dosage levels (wet weight based on the total weight of the acrylic dispersion) shown in the respective tables under adequate agitation.

[0117] [Table 9]

[0118] 8. Formulation of acrylic dispersions containing EVA6 In another experiment, EVA 6 was blended with Acrylic Dispersion 2 and PSA application tests were performed according to the method described above. The peel adhesion and loop tack of adhesive laminates having dried PSA compositions comprised of (i) Acrylic Dispersion 2 and (ii) EVA Dispersion 6 are provided in Table 8 below.

[0119] [Table 10] CS = Comparative Sample, IE = Inventive Example

[0120] The 90° HDPE peel adhesion (20 minutes and 24 hours) observed for PSA article (laminate) formulations of Acrylic Dispersion 2 and Ethylene Copolymer Dispersion EVA6 is higher than that of laminates prepared from Acrylic Dispersion 2 alone. Based on prior art utilizing high MI and low molecular weight ethylene copolymer additives that are anionic and highly polar, low melt index additives such as EVA, which are nonionic and low polar, would be expected to be poorly compatible with acrylic polymers such that these formulations would have poor adhesion. Instead, these formulations improve adhesion to HDPE.

[0121] 9. Formulation of acrylic dispersions containing EVA7, EVA8, EVA9, EVA10, and EVA11 In separate experiments, EVAs 7-11 were blended with Acrylic Dispersion 2 and PSA application tests were performed according to the method described above. The peel adhesion and loop tack of adhesive laminates having dried PSA compositions comprised of (i) Acrylic Dispersion 2 and (ii) EVA Dispersions 7-11 are provided below in Table 9.

[0122] [Table 11] CS = Comparative Sample, IE = Inventive Example

[0123] The 90° HDPE peel adhesion (20 minutes and 24 hours) observed for PSA article (laminate) formulations of Acrylic Dispersion 2 and ethylene copolymer dispersions EVA7-11 is higher than that of laminates prepared from Acrylic Dispersion 2 alone. Based on prior art utilizing high-melt index and low-molecular-weight ethylene copolymer additives that are anionic and highly polar, low-melt index additives such as EVA, which are nonionic and low-polar, are expected to be incompatible with acrylic polymers, such that these formulations exhibit poor adhesion. Instead, these formulations improve adhesion to HDPE. In the case of IE31, the HDPE adhesion at 20 minutes is not higher than that of CS2, but over time, the adhesion of the formulation containing EVA9 improves, such that the HDPE adhesion exceeds that of CS2 at 24 hours.

[0124] Formulation of acrylic dispersions containing EVA12 and EVA13 In a separate experiment, EVA 12-13 were blended with Acrylic Dispersion 2 and PSA application tests were performed according to the method described above. The peel adhesion and loop tack of adhesive laminates having dried PSA compositions comprised of (i) Acrylic Dispersion 2 and (ii) EVA Dispersions 12-13 are provided in Table 10 below.

[0125] [Table 12]

[0126] The 90° HDPE peel adhesion (20 minutes and 24 hours) observed for PSA article (laminate) formulations of Acrylic Dispersion 2 with ethylene copolymer dispersions EVA12-13 is higher than that of laminates prepared from Acrylic Dispersion 2 alone. Based on prior art utilizing high MI and low molecular weight ethylene copolymer additives that are anionic and highly polar, low melt index additives such as the less polar EVA12 and EVA13 would be expected to have poor compatibility with acrylic polymers such that these formulations would have poor adhesion. Instead, these formulations improve adhesion to HDPE.

[0127] 11. Formulation of acrylic dispersions containing EVA14 In another experiment, EVA 14 was blended with Acrylic Dispersion 2 and PSA application tests were performed according to the method described above. The peel adhesion and loop tack of adhesive laminates having dried PSA compositions comprised of (i) Acrylic Dispersion 2 and (ii) EVA Dispersion 14 are provided in Table 11 below.

[0128] [Table 13]

[0129] The 90° HDPE peel adhesion (20 minutes and 24 hours) observed for PSA article (laminate) formulations of Acrylic Dispersion 2 and Ethylene Copolymer Dispersion EVA14 is higher than that of laminates prepared from Acrylic Dispersion 2 alone. Based on prior art utilizing high MI and low molecular weight ethylene copolymer additives that are anionic and highly polar, low melt index additives such as EVA, which are nonionic and low polar, would be expected to have poor compatibility with acrylic polymers such that these formulations would have poor adhesion. Instead, these formulations improve adhesion to HDPE.

[0130] The present disclosure is not limited to the embodiments and examples contained herein, but is expressly intended to include portions of the 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. The inventions described in the original claims of this application are set forth below. [1] An aqueous pressure-sensitive adhesive composition comprising: (A) (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than -20°C; and (ii) an acrylic dispersion containing a surfactant; (B) (i) particles of ethylene vinyl acetate copolymer having from 10% by weight to less than 50% by weight of vinyl acetate comonomer; and (ii) an ethylene vinyl acetate (EVA) dispersion containing a dispersant; 1. An aqueous pressure-sensitive adhesive composition comprising: [2] The acrylic polymer is selected from the group consisting of acrylic acid (AA), butyl acrylate (BA), ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), butyl methacrylate (BMA), 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, C12 ~C 18 [1] The aqueous pressure-sensitive adhesive composition according to [1], comprising one or more acrylic monomers selected from the group consisting of alkyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and combinations thereof. [3] The water-based pressure-sensitive adhesive according to [2], wherein the acrylic polymer contains a monomer selected from the group consisting of styrene, vinyl ester, and combinations thereof. [4] The aqueous pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the acrylic polymer has a Tg of -80°C to -20°C. [5] The aqueous pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the particles of the EVA copolymer have a volume average particle size of 0.1 microns to 2.0 microns. [6] The aqueous pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the EVA copolymer has a melt index of 1 g / 10 min to 600 g / 10 min. [7] The ethylene vinyl acetate copolymer With a density of 0.920g / cc~0.970g / cc, A melting point (Tm) of 40°C to 75°C, The aqueous pressure-sensitive adhesive composition according to any one of [1] to [6], which has a Vicat softening point of 20°C to 65°C. [8] The aqueous pressure-sensitive adhesive composition according to any one of [1] to [7], wherein the dispersant is selected from the group consisting of long-chain fatty acids having 14 to 40 carbon atoms, anionic surfactants, cationic surfactants, nonionic surfactants, acid-functional polyethylene, acid-functional polypropylene, and combinations thereof. [9] The aqueous pressure-sensitive adhesive composition according to any one of [1] to [8], wherein the dispersant is a long-chain fatty acid having 14 to 40 carbon atoms.

[10] (A) 40% by weight to 99.8% by weight of the acrylic dispersion; (B) 10% by weight to 0.2% by weight of the EVA dispersion; (C) 0 wt% to 50 wt% of a tackifier, [1] to [9], the aqueous pressure-sensitive adhesive composition according to any one of [1] to [9], wherein the weight percentage is based on the total dry weight of the aqueous pressure-sensitive adhesive composition.

[11] An article, a first substrate; a layer of an aqueous pressure-sensitive adhesive composition on the first substrate, wherein the aqueous pressure-sensitive adhesive composition comprises: (A) (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than -20°C; and (ii) an acrylic dispersion containing a surfactant; (B) (i) particles of ethylene vinyl acetate copolymer having from 10% by weight to less than 50% by weight of vinyl acetate comonomer; and (ii) an ethylene vinyl acetate (EVA) dispersion comprising a dispersing agent.

[12] The article of

[11] , wherein the first substrate is selected from the group consisting of a film, a cellulosic material, a fabric, a tape, and a release liner.

Claims

1. (A) (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than −20° C.; and (ii) surfactant an acrylic dispersion comprising (B) 0.2 to 7 weight percent, based on the total dry weight of the aqueous pressure-sensitive adhesive composition, of an ethylene vinyl acetate (EVA) dispersion; 1. An aqueous pressure-sensitive adhesive composition comprising: the aqueous pressure-sensitive adhesive composition is a mixture of (A) an acrylic dispersion and (B) an ethylene vinyl acetate (EVA) dispersion; The (B) ethylene vinyl acetate (EVA) dispersion is (i) particles of ethylene vinyl acetate copolymer having from 10% to less than 50% by weight of vinyl acetate comonomer; and (ii) Dispersant 1. An aqueous pressure-sensitive adhesive composition comprising:

2. The acrylic polymer may be selected from the group consisting of acrylic acid (AA), butyl acrylate (BA), ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), methyl acrylate (MA), butyl methacrylate (BMA), 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 10. The aqueous pressure-sensitive adhesive composition of claim 1, comprising one or more acrylic monomers selected from the group consisting of alkyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and combinations thereof.

3. 3. The water-based pressure-sensitive adhesive of claim 2, wherein the acrylic polymer comprises a monomer selected from the group consisting of styrene, vinyl esters, and combinations thereof.

4. 4. The aqueous pressure-sensitive adhesive composition of claim 1, wherein the acrylic polymer has a Tg of from -80°C to -20°C.

5. 5. The aqueous pressure-sensitive adhesive composition of claim 1, wherein the particles of the EVA copolymer have a volume average particle size of from 0.1 microns to 2.0 microns.

6. 6. The aqueous pressure-sensitive adhesive composition according to claim 1, wherein the EVA copolymer has a melt index (measured according to ASTM D1238 (190°C / 2.16 kg)) of from 1 g / 10 min to 600 g / 10 min.

7. The ethylene vinyl acetate copolymer is a density of 0.920 g / cc to 0.970 g / cc; a melting point (Tm) of 40°C to 75°C; 7. The aqueous pressure-sensitive adhesive composition of claim 1, having a Vicat softening point of from 20°C to 65°C.

8. 8. The aqueous pressure-sensitive adhesive composition of claim 1, wherein the dispersing agent is selected from the group consisting of long chain fatty acids having from 14 to 40 carbon atoms, anionic surfactants, cationic surfactants, nonionic surfactants, acid-functionalized polyethylene, acid-functionalized polypropylene, and combinations thereof.

9. 9. The aqueous pressure-sensitive adhesive composition of claim 1, wherein the dispersing agent is a long-chain fatty acid having from 14 to 40 carbon atoms.

10. (A) 40% to 99.8% by weight of the acrylic dispersion; (B) 10% by weight to 0.2% by weight of the EVA dispersion; (C) 0 wt% to 50 wt% of a tackifier; 10. The aqueous pressure-sensitive adhesive composition of claim 1, wherein the weight percentages are based on the total dry weight of the aqueous pressure-sensitive adhesive composition.

11. a first substrate; a layer of an aqueous pressure-sensitive adhesive composition on the first substrate; An article comprising: The aqueous pressure-sensitive adhesive composition comprises (A) (i) particles of an acrylic polymer having a glass transition temperature (Tg) of less than −20° C.; and (ii) surfactant an acrylic dispersion comprising (B) 0.2 to 7 weight percent, based on the total dry weight of the aqueous pressure-sensitive adhesive composition, of an ethylene vinyl acetate (EVA) dispersion; Including, the aqueous pressure-sensitive adhesive composition is a mixture of (A) an acrylic dispersion and (B) an ethylene vinyl acetate (EVA) dispersion; The (B) ethylene vinyl acetate (EVA) dispersion is (i) particles of ethylene vinyl acetate copolymer having from 10% to less than 50% by weight of vinyl acetate comonomer; and (ii) Dispersant Including, goods.

12. 12. The article of claim 11, wherein the first substrate is selected from the group consisting of a film, a cellulosic material, a fabric, a tape, and a release liner.

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