Wash-off pressure sensitive adhesive

Abstract

A pressure sensitive adhesive (PSA) that washes off from a variety of substrates is disclosed. The PSA comprises at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizer, at least one surfactant and at least one special hydrophilic monomer. Also disclosed is a label having a substrate layer and a PSA layer consisting of at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizing agent, at least one surfactant, and at least one specialty hydrophilic monomer. Suitable special hydrophilic monomers include, but are not limited to, poly (ethylene glycol) methacrylate (PEGMA) and derivatives thereof, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) or AMPS-sodium salt and derivatives thereof.

Description

Technical Field

[0001] The present disclosure relates to pressure sensitive adhesives (PSAs) that are washed off from a variety of substrates. More specifically, the present disclosure relates to a pressure sensitive adhesive layer comprising at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizing agent, at least one surfactant, and at least one specialty hydrophilic monomer. Background Art

[0002] Adhesive compositions can be used for a wide variety of purposes. A particularly useful subset of adhesive compositions is water-based pressure sensitive adhesives. The use of water-based pressure sensitive adhesives in different end-use applications is generally known. For example, water-based pressure sensitive adhesives can be used with labels, notepads, tapes, decals, bandages, decorative and protective sheets, and many other products.

[0003] As used in the art, the term "pressure-sensitive adhesive" refers to a material comprising one or more polymer compositions that, when dry, is strongly tacky and permanently tacky at various temperatures. Further, the term "water-based" means that the pressure-sensitive adhesive is made with an aqueous carrier. Typical water-based pressure-sensitive adhesives will adhere firmly to a variety of different surfaces upon mere contact, without requiring more pressure from fingers or hands.

[0004] Pressure sensitive adhesives are commonly used to adhere paper or film labels to PET. PET is often recyclable, but usually only if the attached items, such as labels, can be easily removed. Crushing a PET container with a PSA label still attached can cause processing challenges and contamination. Labels and adhesives that can be cleanly removed without excessive heating and additional processing steps would allow the container to be reused with minimal post-processing. Therefore, PSA labels that can be easily washed off from a variety of substrates are desirable. DETAILED DESCRIPTION

[0005] The present disclosure relates to pressure sensitive adhesives (PSAs) that are washed off from a plurality of substrates. More specifically, the PSA comprises at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizing agent, at least one surfactant, and at least one specialty hydrophilic monomer. A label having a substrate layer and a PSA layer is currently disclosed, wherein the PSA layer is composed of at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizing agent, at least one surfactant, and at least one specialty hydrophilic monomer. According to the current disclosure, the PSA layer can be removed using a constant stirring bath having a temperature below 85 degrees Celsius and a pH between 7 and 14, ideally a pH of about 13.

[0006] Basal layer

[0007] The presently disclosed substrate layer for forming a wash-off label may comprise a single layer of substrate material or may be formed of a multilayer construction. The properties of the material used to form the substrate layer as well as the intended use and desired performance properties of the label may determine the selection of appropriate materials and constructions to use. In the case of a multilayer substrate, an important consideration is the nature of the outer layer in contact with the PSA layer.

[0008] In a multilayer substrate, it may be advantageous for one or more of the layers other than the layers in contact with the PSA to be a stressed substrate, such as uniaxially or biaxially stretched polyvinyl chloride or other stretchable substrate which, when subjected to appropriate wash-off conditions, will curl and aid in pulling the label away from the glass or plastic substrate.

[0009] A variety of materials can be used to form the substrate layer, including paper and polymer compositions. The material can be primed or unprimed. The material can be shrinkable / expandable or non-shrinkable. The material can be surface treated by, for example, corona discharge, flame, plasma, etc., to provide a surface with desired properties, such as increased adhesion to subsequently applied layers. The procedures for corona treatment and flame treatment of polymer substrates are well known to those skilled in the art.

[0010] The substrate layer can be a single layer substrate or a multilayer substrate. A multilayer substrate can contain more than 2 layers. The substrate layer can be oriented or non-oriented. The substrate layer can be transparent or opaque.

[0011] Suitable polymers for preparing the substrate layer may include, for example, polymers and copolymers of one or more of the following: polyolefins, polyacrylates, polystyrenes, polyamides, polyvinyl alcohols, poly(alkylene acrylates), poly(ethylene vinyl alcohols), poly(alkylene vinyl acetates), polyurethanes, polyacrylonitrile, polyesters, polyester copolymers, fluoropolymers, polysulfones, polycarbonates, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, ionomers based on sodium or zinc salts of ethylene methacrylic acid, polyacrylonitrile, alkylene-vinyl acetate copolymers, or so-called "biopolymers", or mixtures of two or more of the above. The substrate layer may include a polyamide film, such as polyamide 6, polyamide 11, and polyamide 12.

[0012] Biopolymers that can be used to form the labels of the present disclosure can be obtained from biological sources and can be selected from carbohydrates; polysaccharides (such as starch, cellulose, glycogen, hemicellulose, chitin, fructan inulin); lignin and / or pectic substances); gums; proteins, optionally cereal, vegetable and / or animal proteins (such as gluten (e.g. from wheat), whey protein and / or gelatin); colloids (such as hydrocolloids, e.g. natural hydrocolloids, e.g. gums); effective mixtures of other polyorganic acids thereof (such as polylactic acid and / or polygalactonic acid); and / or effective modified derivatives thereof.

[0013] As currently disclosed, biopolymer membranes are biopolymer membranes formed from biopolymers selected from cellulose, cellulose derivatives (such as cellulose acetate) or polylactic acid. The substrate layer can be based on a substrate comprising cellulose, which is substantially continuous in structure, preferably non-woven and / or entangled. The substrate layer of the present disclosure can include non-microbial cellulose, such as cellulose regenerated from a cellulose dispersion in a non-solvated fluid (such as, but not limited to, a mixture of N-methylmorpholine-N-oxide (NMMO) and LiCl and dimethyl phthalate (DMP)). A specific example is "viscosity", which is cellulose sodium xanthate in caustic soda. The cellulose from the dispersion can be cast into a film by in-situ regeneration of the cellulose by suitable treatment (e.g., adding a suitable reagent, which can be dilute sulfuric acid for viscose) and optionally extruding the cellulose thus formed. Such cellulose is referred to as regenerated cellulose in this article. A suitable cellulose-based film is NatureFlex TM Regenerated cellulose film (Innovia Films).

[0014] As presently disclosed, the plastic substrate of the base layer can be unstressed (i.e., unstretched), or stretched in at least one direction. In a multilayer substrate, only one layer or less than all of the layers can be stretched uniaxially or biaxially. In the case of a multilayer substrate in which more than one layer is stretched, the layers can all be stretched in substantially the same orientation, or different layers can be stretched in different orientations relative to each other.

[0015] As currently disclosed, the substrate layer or at least the layer of the multilayer substrate with the adhesive layer can be treated before applying the adhesive layer, for example by corona treatment, flame pretreatment, plasma pretreatment or chemical grafting, or with the help of an adhesion-promoting intermediate layer containing, for example, chlorinated polyolefins, chlorinated rubbers, ethylene / vinyl acetate (EVA) copolymers, chlorinated polypropylene or polymerized ethylene / acrylamide comonomers.

[0016] PSA layer

[0017] A PSA layer formed by drying an aqueous polymer dispersion is disclosed. The polymer of the dispersion comprises at least one hydrophilic monomer and at least one hydrophobic monomer. The PSA also comprises at least one neutralizing agent, at least one surfactant, and at least one specialty hydrophilic monomer. The PSA may have 50%-90% hydrophobic monomers, 50%-80% hydrophobic monomers, 50%-70% hydrophobic monomers, or 50%-60% hydrophobic monomers. Examples of acceptable hydrophobic monomers include, but are not limited to, butyl acrylate, ethylhexyl acrylate, octyl acrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, pentadecyl methacrylate, stearyl methacrylate, and C methacrylate. 12 To C 18 All weight percentages are based on the total weight of the adhesive composition.

[0018] The PSA may have 10%-35% hydrophilic monomers. The PSA may have 15%-35% hydrophilic monomers. The PSA may have 20% to 35% hydrophilic monomers. Examples of acceptable hydrophilic monomers include, but are not limited to, alkyl acrylates such as ethyl acrylate, methyl acrylate, and propyl acrylate, as well as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0019] The PSA may have 0.5% to 5% of a specialty hydrophilic monomer. The PSA may have 0.5% to 1% of a specialty hydrophilic monomer. The PSA may have 1% to 3% of a specialty hydrophilic monomer. The PSA may have 1% to 2% of a specialty hydrophilic monomer. The PSA may have 2% to 5% of a specialty hydrophilic monomer. The specialty hydrophilic monomer may have a number average molecular weight greater than 150. Suitable specialty hydrophilic monomers include, but are not limited to, poly(ethylene glycol) methacrylate (PEGMA) and derivatives thereof, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) or AMPS-sodium salt and derivatives thereof, shown in Structures 1 and 2, respectively.

[0020]

[0021] The preparation of aqueous dispersions of water-insoluble latex polymers by emulsion polymerization is well known in the art. The practice of emulsion polymerization is described in D. C. Blackley, Emulsion Polymerization ) (Wiley, 1975) and in H.Warson, The Applications of Synthetic Resin Emulsio ns)》, Chapter 2 (Ernest Benn Ltd., London 1972). Polymerization methods and useful polymerization aids, such as dispersants, initiators, chain transfer agents, etc. are well known and described, for example, in published U.S. patent application US2008 / 0176996.

[0022] The PSA can be formed in a multi-stage process, wherein after preparation of a first stage polymer, one or more subsequent stages of polymerization are performed, wherein the monomers comprise at least one hydrophilic monomer and at least one hydrophobic monomer. The PSA can contain a monomer emulsion buffer that maintains a pH of less than 7 during polymerization. The monomer emulsion buffer can be an inorganic base, ammonia, or an organic amine.

[0023] After polymerization, the emulsion polymer dispersed throughout the aqueous medium may be stabilized by a sodium salt of a fatty alcohol ether sulfate surfactant post-additive. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise at least 0.5% of the composition. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise 0.5% to 3% of the composition. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise 1.0% to 1.3% of the composition. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise 1.0% to 3% of the composition. Examples of suitable sodium salts of fatty alcohol ether sulfate surfactants include, but are not limited to FES 77, FES 32, FES 993 and FES 61, all available from BASF.

[0024] The initiator can then be introduced into the water kettle into which the emulsified monomer mixture is fed. The initiator can be configured to react with at least one monomer to form an emulsion polymer comprising monomer subunits. The initiator can react with the monomers dispersed throughout the aqueous medium until all or substantially all of the monomers are polymerized. The end result can be a dispersion of polymer particles in an aqueous medium comprising monomer subunits. Such dispersions are commonly referred to as emulsion polymers. After all monomers are fed into the emulsion polymer, additional redox initiators can be introduced into the emulsion polymer to reduce the level of residual monomers.

[0025] Reduction-oxidation (redox) initiator systems consisting of at least one, usually inorganic, reducing agent and an inorganic or organic oxidizing agent are particularly suitable. The oxidizing component may include, for example, ammonium and alkali metal salts of peroxodisulfuric acid, for example sodium peroxodisulfate, hydrogen peroxide or organic peroxides, for example tert-butyl hydroperoxide, tert-amyl hydroperoxide. The reducing component may include, for example, alkali metal salts of sulfites, such as sodium sulfite, sodium bisulfite; alkali metal salts of disulfites, such as sodium disulfite; addition compounds of bisulfites with aliphatic aldehydes and ketones, such as acetone bisulfite; or reducing agents, such as hydroxymethanesulfinic acid and its salts, FF6 or isoascorbic acid. Redox initiator systems can be used with soluble metal compounds having a metal component that can exist in multiple valence states.

[0026] Examples of commonly used redox initiator systems are tert-butyl hydroperoxide / sodium bisulfite, tert-butyl hydroperoxide / isoascorbic acid and tert-butyl hydroperoxide / sodium hydroxymethanesulfinate. Individual components, such as the reducing component, can also be mixtures, such as a mixture of hydroxymethanesulfinic acid sodium salt and sodium disulfite.

[0027] The amount of initiator is generally 0.1% to 15% by weight, preferably 0.5% to 10% by weight, based on the monomers to be polymerized. It is also possible to use a plurality of different initiators during the emulsion polymerization.

[0028] After polymerization, the emulsion polymer dispersed throughout the aqueous medium may be stabilized by a sodium salt of a fatty alcohol ether sulfate surfactant post-additive. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise at least 0.5% of the composition. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise 0.5% to 3% of the composition. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise 1.0% to 1.3% of the composition. The sodium salt of the fatty alcohol ether sulfate surfactant may comprise 1.0% to 3% of the composition. Examples of suitable sodium salts of fatty alcohol ether sulfate surfactants include, but are not limited to FES 77, FES 32, FES 993 and FES 61, all available from BASF.

[0029] Dioctyl sodium sulfosuccinate ( OT-75) and acetylene glycol ethylene oxide / propylene oxide adduct surfactants can also be added to the composition. Dioctyl sodium sulfosuccinate can account for 0.1% to 3.0% of the composition. Dioctyl sodium sulfosuccinate can account for 0.2% to 0.5% of the composition. Dioctyl sodium sulfosuccinate can account for 0.2% to 1.5% of the composition. Alkyne glycol ethylene oxide / propylene oxide adduct surfactants can account for 0.05% to 1.5% of the composition. Alkyne glycol ethylene oxide / propylene oxide adduct surfactants can account for 0.1% to 0.5% of the composition. Acceptable acetylene glycol ethylene oxide / propylene oxide adduct surfactants include but are not limited to 440, 104. 420, 450, 465 and 485. OT-75 is available from Solvay, and Surfactants are available from Evonik. The acetylenic diol ethylene oxide / propylene oxide adduct surfactants may be replaced or combined with nonionic branched secondary alcohol ethoxylate surfactants.

[0030] Optionally, water-soluble additives can be used in combination with the polymer backbone to improve wash-off performance. The example of suitable water-soluble additives includes but is not limited to synthetic water-soluble polymers such as polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), poly (vinyl alcohol) (PVOH), polyacrylic acid (PAA), polyacrylamide, N-(2-hydroxypropyl) methacrylamide (HPMA), divinyl ether-maleic anhydride (DIVEMA), polyoxazoline, polyphosphate, polyphosphazene, natural water-soluble polymers such as xanthan gum, pectin, chitosan derivatives, dextran, carrageenan, guar gum, cellulose ether, hyaluronic acid (HA), albumin, starch or based on starch derivatives or their combination. The water solubility and hydrophilicity of additives as above make adhesive contact with washing solution relatively quickly and comprehensively, which helps washing solution to penetrate into the back of the label, and improves the removability of the label. Examples of water-soluble additives include PEG 400, PEG 600, PEG 1000, PEG 1450, PEG 3350, PEG 8000, PVP K60, PVP K90 with different molecular weights. The concentration and molecular weight of the water-soluble additive need to balance the wash-off performance, adhesive (PSA) properties, viscosity, clarity of the dry adhesive, stability of the emulsion, solids %, rheology and coatability of the final product formulation. For example, the concentration of the active water-soluble additive can range from 0.05% to 20%. Preferably 0.25%-10%.

[0031] Acid-containing cross-linked acrylic emulsion copolymers, such as alkali swellable acrylic emulsions (ASE), may be added to aid in the rheology and wash-off properties of the polymer. Acceptable additives include, but are not limited to, ACRYSOL TM ASE-60. In addition, rheology modifiers such as hydrophobically modified alkali swellable (HASE) associative thickeners may be added to aid in the rheology and wash-off properties of the polymer. Acceptable additives include, but are not limited to, ACRYSOL TM RM-7 and ACRYSOL TM RM-55.

[0032] The presently disclosed PSAs do not contain effective amounts of tackifiers, vinyl acetate, or vinyl acetate derivatives. The presently disclosed PSAs do not contain effective amounts of adipic acid dihydrazide (ADH) or waxes. The presently disclosed PSAs do not contain effective amounts of polyhydroxy functional amines. The presently disclosed PSAs do not contain effective amounts of photocrosslinkable monomers.

[0033] Presently disclosed is a label comprising a substrate layer and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises at least one hydrophilic monomer, at least one hydrophobic monomer, at least one specialty hydrophilic monomer, at least one neutralizing agent, and at least one surfactant.

[0034] The PSA adhesive and any attached labels can be removed by peeling off the PSA coated substrate and immersing the sheet in a sodium hydroxide solution having a pH of 12-14 and maintained at a temperature below 85°C and stirred at a speed of at least 100 rpm. After the label is separated from the substrate, the floating label portion and the settled substrate portion can be separated by filtration.

[0035] Example

[0036] A four-liter, five-necked reactor equipped with a condenser, mechanical stirrer, temperature-controlled thermocouple, and inlets for initiator, monomer, and redox chaser activator was charged with 740 g of deionized water and heated to 89°C-91°C under a gentle nitrogen flow. In a separate container, 340 g of DI water, 15.1 g of A-102, 29.76g A monomer emulsion (ME) was prepared by adding DS-4, 3.2 g of sodium carbonate, and 2136.5 g of a monomer mixture consisting of 85 wt.% 2-ethylhexyl acrylate (2-EHA), 10 wt.% ethyl acrylate (EA), 1 wt.% styrene (STY), 2 wt.% acrylic acid (AA), and 2 wt.% polyethylene glycol methacrylate (PEGMA). A buffer solution of 1.376 g of sodium carbonate in 32 g of water was charged to the reactor, followed by a charge of 80.0 g (3.17%) of the monomer emulsion (ME). With the reactor temperature at 79°C-82°C, a charge of 56 g of DI water containing 8.8 g of ammonium persulfate (APS) initiator was added to the reactor. An exotherm occurred within 1 minute. The reaction temperature rose to about 7°C. After the exotherm peaked and the reactor temperature was 82°C-90°C, the remaining monomer emulsion was fed to the reactor along with a co-feed solution of 1.4 g ammonium persulfate (APS) in 44 g DI water as a co-feed initiator. The ME and co-feeds were fed for 80 minutes with the reaction temperature maintained at 88°C-90°C by external cooling. Within thirty-five minutes of the 80 minute ME feed, a solution of 24.17 g Siponate DS-4 in 40 grams of water was added to the reactor to start the second smaller particle size mode. After the monomer emulsion and co-feed initiator additions were complete, a redox chaser accelerator solution was added to the reactor containing 0.032 g ferrous sulfate heptahydrate and 0.032 g VERSENE TM Then add tert-butyl hydroperoxide solution (70%) (t-BHP) (0.89 g in 8 g DI water) and FF6 M solution (0.76 g in 8 g DI water). The reaction was then cooled to 60°C. At 60°C, a solution of 0.78 g actrene in 8 g water was added to the reactor as a polymer inhibitor, followed by a charge of 40.6 g 1,3 butanediol dimethacrylate (BGDMA) monomer and a rinse of 16 grams of DI water. Five minutes after the addition of BGDMA, a 70% active t-BHP solution (5.6 g in 24 g DI water) was charged to the reactor, followed by FF6M solution (4.06 g in 28 g DI water) was added to initiate polymerization of BGDMA. An exotherm of 2°C-3°C was observed within 60 seconds. The batch was held at 56°C-62°C for 5 minutes. After the hold, a chaser solution of 70% active t-BHP (11.7 g in 56 g DI water) was added over a 30 minute period. A chaser solution of FF6 M (8.64 g in 52 g DI water) was fed into the reactor together to reduce the residual monomer level. A temperature range of 55°C-60°C was maintained throughout the chaser feed. At the end of the chaser feed, cooling to 55°C was begun and the reaction was diluted with 51 g DI water. At 55°C, 23.04 g ammonia (28%) was added to neutralize the batch to a pH of ~6.75. The reaction was stopped at this point. The acrylic dispersion obtained contained an acrylic-based polymer consisting of 85 wt.% 2-EHA, 10 wt.% EA, 1 wt.% STY, 2 wt.% AA and 2 wt.% PEGMA. The above polymers were further formulated before performance and wash-off testing.

[0037] Inventive polymer 2 :

[0038] To about 100 g of the above polymer, 0.2 g OT-75 and 1.04g Acrysol TM ASE-60. The mixture was stirred for 10 minutes to ensure proper incorporation of the components. The pH of the mixture was adjusted to pH: ~6.5 with ammonia (28%) if necessary. The composition of the monomers was 85 wt.% 2-EHA, 10 wt.% EA, 1 wt.% STY, 2 wt.% AA and 2 wt.% PEGMA.

[0039] Inventive polymer 1 :

[0040] Inventive polymer 1 was prepared in a similar manner except that the backbone composition had 1% 2-acrylamido-2-methylpropanesulfonic acid (AMPS) sodium salt instead of PEGMA monomer. To approximately 100 g of the above polymer was added 0.2 g OT-75 and 1.04g Acrysol TM ASE-60. The mixture was stirred for 10 minutes to ensure proper incorporation of the components. The pH of the mixture was adjusted to pH: ~6.5 with ammonia (28%) if necessary. The composition of the monomers was 86 wt.% 2-EHA, 10 wt.% EA, 1 wt.% STY, 2 wt.% AA and 1 wt.% AMPS.

[0041] Sample conditioning and label lamination

[0042] The prepared, fully formulated wet samples were conditioned for at least 24 hours prior to testing to ensure that no air bubbles were trapped and that the product had time to reach equilibrium. After 24 hours, the wet adhesive sample was applied to siliconized paper (or film) by pipette and coated using a knife coating technique at 18 g / m 2The dry adhesive coating weight was applied. The coated adhesive samples were dried in a convection oven at 105°C for two minutes and then conditioned at 50% + / - 5% humidity and 21°C + / - 2°C for approximately four hours. After this conditioning period, the dry adhesive on siliconized paper was laminated to a pre-treated biaxially oriented polypropylene substrate (BOPP) using a hot roll laminator at 40°C and 40atm of pressure. A 12kg weight was then placed on the fully assembled laminate for four days.

[0043] PSA Characterization Test Procedure

[0044] The peel adhesion of PSA was determined using the International Federation of Adhesive and Thermocollants Manufacturers and Processors (FINAT) TM ”) Test Method Test No. 2. The backing material is removed from a longitudinal strip 25 mm wide and at least 175 mm long, and the adhesive coated facing material is secured to the test panel. The test panel is secured in a horizontal support that is secured to the bottom jaws of the tester. The machine is set to a jaw separation rate of 300 mm per minute, and the machine load averaging function is set to average the data.

[0045] Using FINAT TM Test Method No. 8 Shear resistance testing of standard glass or stainless steel surfaces is performed. A 25.4 x 25.4 mm sample strip is attached to a glass or stainless steel (SS) plate at a 2° vertical tilt. The time taken for a 1 kg weight to break the adhesive film inside of the strip is measured.

[0046] Wash-off test procedure

[0047] Using the European PET Bottle Platform (EPBP TM ) The washability of the labels is tested using the Quick Test (QT) 508 procedure. This procedure is a small-scale simulation of the current industrial procedure used by plastic recycling companies. The sample is immersed in a 1% NaOH solution at 80°C and stirred at 350 rpm by a magnetic stirrer. The plastic flakes are washed for less than 15 minutes. Optionally, a 0.5% solution of a nonionic surfactant secondary alcohol ethoxylate is added to better disperse the adhesive particles in the liquid and to enable better filtration of the plastic flakes.

[0048] As can be seen from Table 2, the samples of the present invention have a wash-off percentage of at least 60%, while the maximum wash-off percentage achieved by the comparative examples is 30%. The samples of the present invention achieve a wash-off percentage of greater than 70%.

[0049] Table 1

[0050]

[0051] Table 2 - Wash-off and performance data at 80°C / bath wash conditions

[0052]

Claims

1. A pressure-sensitive adhesive layer comprising at least one hydrophilic monomer, at least one hydrophobic monomer, at least one special hydrophilic monomer, at least one neutralizing agent and at least one surfactant.

2. The pressure sensitive adhesive of claim 1, wherein the at least one hydrophilic monomer comprises at least 10% of the composition and the at least one hydrophobic monomer comprises at least 50% of the composition.

3. The pressure sensitive adhesive according to any one of the preceding claims, wherein the at least one surfactant comprises at least 0.5% of the composition.

4. The pressure sensitive adhesive of any one of the preceding claims, wherein the at least one specialty hydrophilic monomer comprises at least 1% of the composition.

5. The pressure-sensitive adhesive according to any one of the preceding claims, wherein the at least one hydrophilic monomer is one or more of the group consisting of ethyl (meth)acrylate or (meth)acrylic acid.

6. The pressure-sensitive adhesive according to any one of the preceding claims, wherein the at least one hydrophobic monomer is an alkyl acrylate.

7. The pressure sensitive adhesive according to any one of the preceding claims, wherein the at least one neutralizing agent is one or more of the group consisting of NaOH, ammonia or an organic amine.

8. The pressure-sensitive adhesive according to any one of the preceding claims, wherein the at least one surfactant is a sodium salt of a fatty alcohol ether sulfate.

9. The pressure sensitive adhesive according to any one of the preceding claims, wherein the at least one specialty hydrophilic monomer is one or more of the group consisting of 2-acrylamido-2-methylpropanesulfonic acid, the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid, or poly(ethylene glycol) methacrylate.

10. The pressure sensitive adhesive layer of claim 1 further comprising at least 0.03% of a rheology modifier.

11. A pressure sensitive adhesive according to any preceding claim further comprising at least 0.3% of an emulsifier.

12. The pressure sensitive adhesive of any preceding claim, further excluding an effective amount of vinyl acetate or a vinyl acetate derivative.

13. A label comprising a base layer and a pressure-sensitive adhesive layer; the pressure-sensitive adhesive layer further comprises at least one hydrophilic monomer, at least one hydrophobic monomer, at least one special hydrophilic monomer and at least one neutralizing agent, at least one surfactant.

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