Release coatings comprising aqueous latex polymers containing polymerized surfactants

Abstract

A release coating composition comprising aqueous latex polymer particles comprising the polymerization reaction product of: i) a first monomer having an alkyl group containing 12 to 24 carbon atoms, a nitrogen-containing or ester linking group, and a free-radically polymerizable (meth)acryloyl group; ii) a second free-radically polymerizable monomer having fewer than 12 carbon atoms; and iii) a free-radically polymerizable surfactant; and an aqueous carrier liquid. Also described are methods for preparing articles having a release coating and articles.

Description

Summary of the Invention

[0001] A release composition comprising aqueous latex polymer particles comprising the polymerization reaction product of: i) a first monomer having an alkyl group containing 12 to 24 carbon atoms, a nitrogen-containing or ester linking group, and a free-radically polymerizable (meth)acryloyl group; ii) a second free-radically polymerizable monomer having fewer than 12 carbon atoms; and iii) a free-radically polymerizable surfactant; and an aqueous carrier liquid. In some embodiments, the first monomer has the formula:

[0002] C n H 2n+1 -YC m H 2m -X-CR 1 =CH2

[0003] Where n ranges from 12 to 24;

[0004] Y is a nitrogen-containing or ester linking group;

[0005] R 1 is hydrogen or methyl;

[0006] m ranges from 2 to 10, and

[0007] X is a divalent linking group selected from ester or amide.

[0008] In typical embodiments, the polymerizable surfactant comprises an (e.g., sulfur-containing or phosphorus-containing) anion. The polymerizable surfactant also typically comprises ethylene oxide repeating units. In advantageous embodiments, the release composition comprises less than 100 ppm of unpolymerized surfactant.

[0009] A method of making a release-coated article and the article are also described. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a side view of an article comprising a backing, a release coating on a major surface of the backing, and a pressure-sensitive adhesive on an opposite major surface of the backing;

[0011] Figure 2 is a side view of another article comprising a release coated backing and a separate pressure sensitive adhesive coated substrate;

[0012] Figure 3 is a side view of another article comprising a backing having a release coating on both major surfaces and a pressure-sensitive adhesive between the release coating surfaces; DETAILED DESCRIPTION

[0013] Aqueous latex polymer compositions are described which are suitable for use as low adhesion backsizes (LABs) and release coatings for pressure-sensitive adhesive-coated articles.

[0014] The latex polymer comprises the reaction product of a first monomer having an alkyl group containing from 12 to 24 carbon atoms, a nitrogen-containing or ester linking group, and a free radical polymerizable group. This first free radical polymerizable monomer can be characterized as a "long chain" monomer.

[0015] Long-chain monomers typically have the following general formula:

[0016] C n H 2n+1 -YC m H 2m -X-CR 1 =CH2

[0017] Where n ranges from 12 to 24;

[0018] Y is a divalent polar linking group;

[0019] R 1 is hydrogen or methyl;

[0020] m ranges from 2 to 10, and

[0021] X is a divalent linking group selected from esters or amides.

[0022] In typical embodiments, Y is an ester group or a nitrogen-containing group such as a carbamate or amide. Representative Y groups include, for example

[0023]

[0024] In typical embodiments, the alkyl group, C n H 2n+1 - has a chain length sufficient to allow the monomer or polymerized monomer to crystallize at room temperature. In typical embodiments, n is at least 12, 13, 14, 15, 16, 17 or 18.

[0025] In some embodiments, m is at least 2 or 4, and typically no greater than 3 or 4.

[0026] In some advantageous embodiments, Y is a nitrogen-containing group. In some advantageous embodiments, Y is a carbamate group. A representative long-chain monomer is octadecylcarbamoylethyl acrylate (ODCEA) as shown below:

[0027]

[0028] Other long chain monomers include, for example, octadecanoyl ethyl acrylate (ODEA) and hexadecylcarbamoyl ethyl acrylate (HDCEA) as shown below:

[0029]

[0030] Other examples of long chain monomers are described in US 5,225,480; which is incorporated herein by reference.

[0031] In some embodiments, a combination of at least two long-chain monomers of different types (eg, different Y and / or different X groups) or of the same type but different alkyl chain lengths may be used.

[0032] The long chain monomer is polymerized with one or more suitable second free radical polymerizable monomers. The second monomer does not contain an alkyl group having at least 12 carbon atoms. In a typical embodiment, the second monomer typically contains an alkyl group having less than about 12 carbon atoms. Examples of the second free radical polymerizable monomer include, but are not limited to, the following: vinyl halides such as vinylidene chloride, etc.; vinyl ethers such as vinyl propyl ether, vinyl butyl ether, etc.; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc.; acrylates such as methyl acrylate, ethyl acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, hydroxyethyl acrylate, glycidyl acrylate, etc.; methacrylates such as ethyl methacrylate, butyl methacrylate, hexyl methacrylate, tetrahydrofurfuryl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, etc.; acids such as acrylic acid, methacrylic acid, etc.; amides such as acrylamide, methacrylamide, etc.; aromatic vinyl compounds such as styrene, vinyltoluene, etc.; heterocyclic vinyl monomers such as vinyl pyrrolidone, vinyl pyridine, etc.; vinyl nitriles such as acrylonitrile, methacrylonitrile, etc.; allyl compounds such as allyl glycidyl ether, etc.; esters and half esters of diacids such as diethyl maleate, monomethyl itaconate, monobutyl itaconate, etc.; and mixtures thereof.

[0033] The second monomer more typically comprises an alkyl or alkylene group having 2 to 4 carbon atoms, such as vinyl acetate, vinyl propionate, methyl acrylate, butyl methacrylate, hydroxyethyl acrylate, methacrylic acid, glycidyl methacrylate, and mixtures thereof. Preferably, the second monomer is vinyl acetate, vinyl propionate, and mixtures thereof.

[0034] The weight ratio of the long-chain monomer to the second monomer can range from about 10:90 to about 90:10, depending on the type of PSA used in conjunction with the waterborne LAB or release coating and the desired release tightness. In some embodiments, the weight ratio of the long-chain hydrocarbon monomer to the second monomer is at least 15:85, 20:80, 25:75, 30:70, 35:65, or 40:60. In some embodiments, the weight ratio of the long-chain hydrocarbon monomer to the second monomer is no greater than 85:15, 80:20, 75:25, 70:30, 65:35, or 60:40.

[0035] The long chain monomers are polymerized with one or more suitable second free radical polymerizable monomers and a polymerizable surfactant.Polymerizable surfactants are also described as polymerizable emulsifiers.

[0036] Surfactants useful in conventional emulsion polymerization can be classified as anionic, nonionic, amphoteric, and cationic.

[0037] The hydrophilic-lipophilic balance (HLB) of a surfactant is an expression of the balance of the size and strength of the hydrophilic and lipophilic groups of a surfactant. HLB refers to the value obtained by the Griffin method (see Griffin WC: "Calculation of HLB values of non-ionic surfactants," Journal of the Society of Cosmetic Chemists 5 (1954): 259). Calculations were performed using the software program Molecular Modeling Pro Plus, available from Norgwyn Montgomery Software, Inc., North Wales, PA.

[0038] According to the Griffin method:

[0039] HLB=20*Mh / M

[0040] Where Mh is the molecular mass of the hydrophilic portion of the molecule, and M is the molecular mass of the entire molecule. This calculation provides a numerical result on a scale of 0 to 20, with "0" being highly lipophilic. Generally, emulsifiers / surfactants with an HLB value greater than 8 are suitable for preparing the emulsions described herein.

[0041] Suitable anionic surfactants include, but are not limited to, sulfosuccinates and derivatives, alkylaryl sulfonates, olefin sulfonates, phosphate esters, sulfates and sulfonates of ethoxylated alkylphenols, sulfates and sulfonates of ethoxylated fatty alcohols, sulfates of fatty acid esters, and mixtures thereof.

[0042] Useful nonionic surfactants include, but are not limited to, ethoxylated fatty alcohols, ethoxylated fatty acid esters, ethoxylated fatty acids, ethoxylated alkylphenols, ethylene oxide-propylene oxide block copolymers, and mixtures thereof.

[0043] Useful cationic surfactants include, but are not limited to, long chain amines and their salts, quaternary ammonium salts, and mixtures thereof.

[0044] Useful amphoteric surfactants include, but are not limited to, betaine derivatives, sulfobetaine derivatives, and mixtures thereof.

[0045] Surfactants used herein also include free radical polymerizable groups, such as vinyl or (meth) acrylate groups. Therefore, surfactants are copolymerized into the polymer chain of the latex polymer. Polymerizable surfactants can be aromatic or aliphatic. Polymerizable surfactants are typically anionic surfactants that include sulfur-containing or phosphorus-containing anions. Polymerizable surfactants also typically include ethylene oxide (e.g., EO) repeating units. A representative class of such surfactants are sulfates and sulfonates of ethoxylated alkylphenols and alkylphenyls. Some representative structures are as follows, where m and n are the number of repeating units:

[0046]

[0047] Another representative class of surfactants of this type are sulfates and sulfonates of ethoxylated alkyl ethers. A representative structure is as follows:

[0048]

[0049] Each of these structures may have other anionic groups, such as phosphate. Each of the structures may have a different number of ethylene oxide repeating units (i.e., n in the first two structures and m in the third structure). Typically, the number of ethylene oxide units is at least 5 or 10 and not more than 50, 45, 40, 35, or 30. In some embodiments, the number of ethylene oxide units is less than 25, 20, or 15. In some embodiments, the number of hydrophobic units (e.g., m in the first structure and n in the third structure) is such that the HLB is typically at least 8, 9, 10, 11, or 12, 13, 14, or 15.

[0050] The polymerizable surfactants are commercially available from DKS Japan under the trade names HITENOL AR 1025, HITENOL AR 2025, HITENOL AR3025, HITENOL BC-1025 and HITENOL KH-1025. Anionic copolymerizable surfactants are also commercially available under the trade name Maxemul TM 6106-LQ-(MH)Maxemul TM 6112-SO(MH) was purchased from Croda Inc., Newark, NJ.

[0051] The amount of polymerizable surfactant is typically at least 1, 2, 3, 4, or 5 weight percent solids, based on the total weight of solids of the dry aqueous latex emulsion. In some embodiments, the amount of polymerizable surfactant is no greater than 15, 14, 13, 12, 11, 10, 9, 8, or 7 weight percent solids, based on the total weight of solids of the dry aqueous latex emulsion.

[0052] Mixtures of polymerizable surfactants can be used. In typical embodiments, little or no conventional non-polymerizable surfactant is used in the compositions described herein. In typical embodiments, the final aqueous polymer emulsion contains little or no "free" surfactant, i.e., surfactant that is not covalently bonded to the polymer chains of the latex polymer. The amount of surfactant that is not covalently bonded to the polymer chains of the latex polymer is typically less than 500, 400, 300, 200, or 100 ppm (0.1 wt. % solids of the dry latex).

[0053] As known to those skilled in the art, initiators are generally used in emulsion polymerization. Preferably, the initiator used is a water-soluble initiator, such as a dissociation initiator and a redox initiator. Dissociation initiators are those that act by simply dissociating a molecule or ion into two free radical species, from which species initiation can then occur. Redox initiators are initiator systems comprising two or more substances, the interaction of which produces free radicals capable of initiating polymerization.

[0054] The dissociation initiator is typically an inorganic salt of persulfate, such as potassium persulfate, sodium persulfate, and ammonium persulfate. Other useful dissociation initiators include, but are not limited to, aromatic diazoamino compounds, aromatic diazothioethers, alkali metal aryldiazoates, water-soluble analogs of azobisisobutyronitrile such as 4,4'-azobis-(4-cyanovaleric acid) and its alkali metal salts, 2,2'-azobis-(2-cyanopropane-1-sulfonate), 2,2'-azobis-(2-amidinopropane) dihydrochloride, α,α'-azobis-butylamidine hydrochloride, and azobis-(N,N'-dimethylideneisobutylamidine) and its salts with strong acids.

[0055] Useful redox initiator systems include, but are not limited to, persulfate-thiol systems, persulfate-sulfite systems, chlorate-bisulfite systems, hydrogen peroxide-ferric systems, hydroperoxide-ferric systems, dibenzoyl peroxide-ferric pyrophosphate systems, and hydroperoxide-polyamine systems.

[0056] Latex polymer emulsions are prepared by methods known in the art, such as described in previously cited US 5225480. Long-chain monomers can be placed in suitable containers and melted at a temperature higher than their melting point. A second monomer can be gradually added to the container containing the molten long-chain monomer to form a mixture, during which the mixture remains molten. Preferably, before melting, the solid long-chain monomer is placed in a suitable container together with the solid or liquid second monomer. When the second monomer has a relatively low boiling point, a container equipped with a reflux condenser can be used. The melting and mixing of monomers can also be carried out in a container maintained under pressure. The remainder of the emulsion polymerization components (including an aqueous phase (preferably deionized water, optionally in combination with a cosolvent such as hexadecane, hexadecanol, amyl alcohol, hexadecyl alcohol and myristyl alcohol), a polymerizable surfactant, and an optional pH buffer) are typically mixed in a separate container to form an aqueous solution, which is then heated to a temperature equal to or higher than the temperature of the monomer mixture. The monomer mixture is then typically added to the aqueous solution, and the resulting mixture is subsequently homogenized.

[0057] Alternatively, the long-chain monomers can be added in solid form in any order, and the optional second monomer can be added in solid or liquid form to a container already containing an aqueous solution, which is then heated to melt the monomers. The resulting mixture is then homogenized. In either method, gentle stirring can be applied during heating to facilitate the melting process.

[0058] Homogenization can be accomplished using conventional homogenizers known in the art, such as those available from Microfluidizer Inc. The emulsion thus obtained is a stable emulsion comprising droplets of monomer or monomer mixture having a diameter on the order of about 0.1 to about 0.5 micrometers dispersed in an aqueous phase.

[0059] The emulsion is typically loaded into a suitable reactor and then the initiator is added. To avoid inhibition by oxygen, the reactor is typically purged with an inert gas such as nitrogen before and after the emulsion is loaded into the reactor. For emulsion polymerization, a conventional polymerization reactor equipped with an agitator and condenser can be used. In the laboratory, resin flasks and bottles heated in a water bath with appropriate stirring can also be used for this purpose.

[0060] Polymerization is then initiated by subjecting the emulsion to an initiation means, typically by application of heat. Suitable polymerization temperatures typically fall within the range of about 50°C to about 90°C, depending on the type of initiator system and monomer composition used. It is desirable to maintain the polymerization temperature above the melting point or points of the long-chain monomers used, thereby obtaining a more uniform polymer composition. A polymerization time of about 2 to about 20 hours is generally sufficient, depending on the initiator used, the monomer composition, and the polymerization temperature. The latex thus obtained comprises polymer particles having a diameter on the order of about 0.1 to about 0.5 microns, which are stabilized by an emulsifier in the aqueous phase. The latex polymer thus obtained typically has one or more melting points above about 30°C, with at least one melting point in the range of about 50°C to about 100°C, due to the presence of long-chain alkyl groups.

[0061] The latex release coating may optionally include various additives known in the art, such as pH regulators, coalescents, rheology modifiers, and defoamers. Depending on the selected monomer composition, the type of emulsifier, and the type of initiator, it is desirable to maintain the pH of the emulsion polymerization system within a certain range. For example, when using persulfate initiators and anionic emulsifiers, a pH greater than about 5 is required for better colloidal stability. Examples of available pH buffers include sodium bicarbonate, sodium hydrogen phosphate, ammonium hydroxide, sodium hydroxide, and the like. Coagulants can be mixed with the latex to ensure sufficient coverage of its coating on the substrate. Available coalescents include, but are not limited to, NMP, toluene, xylene, ethyl acetate, methyl ethyl ketone, alcohols (e.g., isopropyl alcohol), and mixtures thereof. Available rheology modifiers include, but are not limited to, hydroxyethyl cellulose, poly(ethylene glycol), and mixtures thereof. When present, the total amount of such additives is typically no greater than 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% by weight based on the total dry release coating. In typical embodiments, the release coating may be silicone-free.

[0062] The desired concentration of latex polymer in the aqueous carrier liquid of the emulsion depends on the coating method and the desired coating thickness. The aqueous carrier liquid comprises at least 75, 80, 85 or 90 % by weight of water, optionally in combination with an organic solvent (e.g., coalescing agent), as previously described. In some embodiments, the polymer latex of the higher percentage solid content obtained from the emulsion polymerization process can be diluted with water to a lower concentration. In some embodiments, the solid weight percent of the latex polymer is at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 % by weight solid. In some embodiments, the solid weight percent of the latex polymer is not more than 35, 30, 25 or 20 % by weight solid. By changing the solid percentage of the coating solution from 5% to 30%, and changing the wet coating thickness from 5 μm to 30 μm, a certain range of coating weights can be prepared if necessary. The thickness of the coating can be further reduced by stretching the coated substrate. In some embodiments, the thickness of the dry release coating is at least 25, 30, 35, 40 or 50 nm. The thickness of the dry release coating is typically less than 100, 75, 50 or 25 microns.

[0063] The latex coating composition can be applied to a suitable substrate using conventional coating techniques, such as wire-wound rod, direct gravure, gravure, reverse roll, air knife coating, and drag knife coating. Typically, the coating is dried at a temperature of at least about 5°C above the highest melting point of the latex polymer to obtain a coating with good release properties.

[0064] In some embodiments, a release coating may be applied during manufacture of the film substrate.

[0065] Thermoplastic (e.g. polyester) films can be manufactured by extrusion processes. First, (e.g. polyester) resin is heated to a molten state and then extruded in the form of an amorphous sheet through a wide slit die. The sheet extrudate is rapidly cooled to form a cast polyester sheet by extruding an amorphous sheet around a polished, rotating cooling casting drum. The cast polyester sheet can then be stretched in at least one direction while being heated to a temperature of at least 80°C, 90°C, 100°C, or 160°C. Other thermoplastic materials are extruded at different temperature ranges, as known in the art. For example, a polypropylene film can be stretched at approximately 150°C. The degree of stretching can be approximately three to five times the unit size of the original cast sheet, preferably approximately three to four times the unit size of the original cast sheet. In some embodiments, the polyester film is biaxially oriented rather than uniaxially oriented.

[0066] Prior to coating the film surface with the aqueous coating composition of the present invention, the film may be surface treated in a conventional manner by exposing the surface to a corona discharge. Alternatively, a primer may be applied to the film surface as is known in the art.

[0067] In some embodiments, the coating may be applied and dried prior to stretching. In other embodiments, the heat applied to the film during the subsequent preheating, stretching, and / or heat setting stages is typically sufficient to evaporate water and cure and bond the coating to the polyester film. Oriented (e.g., polyester) films are typically heat set at a temperature of at least 190° C., 200° C., or 210° C., and typically no greater than 235° C. or 240° C.

[0068] Suitable substrates include paper, metal sheets and foils, nonwoven fabrics, and films of thermoplastic resins, such as polyesters such as polyethylene terephthalate (PET), polylactic acid (PLA), and polyethylene naphthalate (PEN), polyamides, polyolefins such as polyethylene and polypropylene (e.g., biaxially oriented polypropylene BOPP), polycarbonate, polyvinyl chloride, and the like, but any surface requiring release from the adhesive may be used. In some embodiments, the thickness of the substrate is at least 0.5 mil, 1 mil, or 2 mils, and typically no greater than 5 mils, 10 mils, or 15 mils.

[0069] One or both major surfaces of the substrate (eg, backing) may also include a primer or be surface treated (eg, corona treated) as is known in the art to promote adhesion of a release coating, adhesive, or both.

[0070] The resulting PSA article can be a tape, label or wound dressing. The adhesive article can be in the form of a sheet, a multilayer sheet or a stack of sheets (e.g., a note pad, an easel pad, a label pad, a stack of tapes), or in the form of a roll, such as a roll of tape.

[0071] Figure 1 An illustrative PSA article 100 is shown in FIG. This embodiment (eg, tape) article includes a release coating 110 disposed on a major surface of a substrate (eg, backing) 120 and a pressure-sensitive adhesive 130 disposed on an opposing major surface of 120 .

[0072] Figure 2 Another PSA article 200 is depicted. The article of this embodiment includes a release coating 210 disposed on a major surface of a substrate (eg, backing) 220. A pressure sensitive adhesive 230 is releasably bonded to the release coating 210. The pressure sensitive adhesive is disposed on a major surface of a second substrate 221.

[0073] Figure 3 Another PSA article 300 is depicted. This embodiment (e.g., tape) article includes release coatings 310 and 311 disposed on both major surfaces of a substrate (e.g., backing) 320 and a pressure-sensitive adhesive 330 releasably bonded to the release coating 311. One or both of the release coatings 310 and 311 are release coatings as described herein.

[0074] The release coatings described herein are suitable for use with a variety of pressure-sensitive adhesive compositions. Suitable (e.g., pressure-sensitive) adhesives include natural or synthetic rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, vinyl alkyl ether pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, polyamide pressure-sensitive adhesives, poly-α-olefins, polyurethane pressure-sensitive adhesives, and pressure-sensitive adhesives based on styrene block copolymers. Pressure-sensitive adhesives typically have a dynamic mechanical analysis at a frequency of 1 Hz measured at room temperature (25° C.) of less than 3×10 6 Storage modulus (E') in dynes / cm.

[0075] The pressure sensitive adhesive can be organic solvent based, water based emulsion, hot melt (eg, such as described in US 6,294,249), heat activatable, and actinic radiation (eg, electron beam, UV) curable pressure sensitive adhesives.

[0076] The pressure-sensitive adhesive may further comprise one or more suitable additives. Examples of suitable additives are crosslinking agents (e.g., multifunctional (meth)acrylate crosslinking agents (e.g., TMPTA), epoxy crosslinking agents, isocyanate crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, etc.), tackifiers (e.g., phenol-modified terpenes and rosin esters, such as glycerol esters of rosin and pentaerythritol esters of rosin, and C5 and C9 hydrocarbon tackifiers), thickeners, plasticizers, fillers, antioxidants, UV absorbers, antistatic agents, surfactants, leveling agents, colorants, flame retardants, and silane coupling agents.

[0077] It will be appreciated that for different pressure sensitive adhesive compositions, different release compositions are preferred. It will also be appreciated that different types of adhesive articles have different preferred release characteristics.

[0078] The peel and readhesion properties can be measured according to the test methods in the Examples.

[0079] The release coating may typically have an average peel force in the range of 1 oz / in to 15 oz / in at a peel rate of 90 inches (228.6 cm) / minute. In some embodiments, the average peel is no greater than 45, 40, 35, 30, 25, 20, 15, 10, or 5 oz / in at a peel rate of 90 inches (228.6 cm) / minute.

[0080] In some embodiments, at a peel rate of 90 inches (228.6 cm) per minute, the average peel force is at least 2 oz / inch, 3 oz / inch, 4 oz / inch, 5 oz / inch, 6 oz / inch, or 7 oz / inch (22.3 g / cm, 33.5 g / cm, 44.6 g / cm, 55.8 g / cm, 78.1 g / cm). In some embodiments, a higher average initial peel force at a lower peel rate may be preferred to prevent the tape roll from unwinding itself or to provide greater holding force when over-taping occurs, such as for packaging tape.

[0081] The release coating typically has a readhesion force of no greater than 50, 45, 40, 35, 30, 25, 20, or 15 ounces per inch at a peel rate of 90 inches (228.6 cm) per minute.

[0082] In some embodiments, the difference in peel force and / or readhesion between 23°C and 50% humidity or 7 days at 50°C is no more than 25%, 20%, 15%, or 10% of the average CTH value.

[0083] In some embodiments, the release compositions described herein provide lower initial peel values than the same compositions comprising octadecyl acrylate (lacking an ester or nitrogen-containing linking group). In some embodiments, the release compositions described herein provide higher re-adhesion than the same compositions comprising octadecyl acrylate. Additionally, free radical polymerizable surfactants can provide lower peel and re-adhesion values than non-polymerizable surfactants.

[0084] Example

[0085] Unless otherwise indicated or readily apparent from the context, all parts, percentages, ratios, etc. in the examples and the remainder of the specification are by weight.

[0086] Table 1. Materials used in the examples

[0087]

[0088]

[0089]

[0090] Prepared by hot melt continuous coating of an approximately 25 μm thick synthetic rubber-based adhesive mixture onto a 50 μm thick corona-treated 1.3 mil (0.03 mm) biaxially oriented polypropylene film (obtained from 3M Co., Maplewood, MN.) Test tape 1The mixture comprises 100 parts of a SIS block copolymer having a styrene content of 14.3%, a coupling efficiency of 88%, and a melt index of 9 g / 10 min (Condition G), obtained from Zeon Corporation of Tokyo, Japan under the trade name QUINTAC 3620; 85 parts of a C9 modified C5 tackifying resin having a Ring and Ball softening point of 87°C (available under the trade name "WINGTACK TM 86" was obtained from Cray Valley, Exton, PA) and 2 parts antioxidant. The opposite side of the BOPP film was then coated with a solvent-based comparative release coating and dried.

[0091] Test Method

[0092] Preparation of Laminates for Release and Readhesion Testing. Four test tapes (3M845, 850, 3750, and 232) were used to evaluate the release properties of the prepared coatings on film backings. Coated film strips (PET or PP, 1 inch x 8 inches) were adhered to a glass plate using double-sided tape so that the coated side (LAB) faced upward (outward). Test tape strips (1 inch x 9 inches) were then cut and their adhesive laminated to the test LAB using 2 kg. A rubber roller was rolled back and forth over the strips twice. Unless otherwise stated, the laminated tape strips were aged for 7 days under different conditions (as shown in the table): (1) 23°C, 50% relative humidity (CTH); (2) 50°C; and (3) 90°F (32°C), 90% RH. Once the samples were aged, the test tape was peeled from the LAB film using a peel tester (Model IMASS SP-2000 Slip / Peel Tester, available from IMASS, Incorporated, Accord, MA) at an angle of 180° and a rate of 90 in / min, with a data averaging time of 5 seconds. The average of three peel tests is reported in the table below.

[0093] After the peel test, the tape was laminated to a clean glass surface using a rubber mallet as described above. The glass plate was cleaned by wiping with hexane, isopropyl alcohol, and methyl ethyl ketone using a solvent-moistened KIMWIPE (Kimberly-Clark Corporation, Neenah, WI). Once the tape was laminated to the glass surface, a 5-pound roller was passed back and forth over the tape strip once before measuring the re-adhesion force. The peel force data were collected in the same manner as described above and the average of the three measurements was reported in the table below as the re-adhesion force.

[0094] The percent solids of the latex solutions were determined gravimetrically by standard methods. pH was measured using a handheld meter. Particle size was determined by dynamic light scattering (Brookhaven NanoBrook 90 Plus PALS, Holtsville, NY).

[0095] Example

[0096] Synthesis of Octadecylcarbamoylethylacrylate (ODCEA)

[0097] One equivalent of octadecyl isocyanate was charged into a 500 ml flask containing a solution containing 1.01 equivalents of hydroxyethyl acrylate, a trace amount of dibutyltin dilaurate catalyst, and the desired amount of ethyl acetate to prepare a 30% solids solution. The mixture was stirred and allowed to react overnight. Upon cooling, the resulting precipitate was isolated by filtration, recrystallized from ethyl acetate, and dried in vacuo at 40° C. for 48 hours to provide the ODCEA monomer. The solid monomer was analyzed using NMR and IR to monitor conversion and the purity of the ODCEA monomer.

[0098] General Synthesis of Acrylic Latex

[0099] In a clean reactor equipped with a mechanical stirrer, thermocouple and nitrogen inlet / outlet, the monomers (total 100 parts by weight) were added in the desired ratios, a copolymerizable emulsifier (6 parts by weight relative to the monomers), sodium bicarbonate (2.5 parts by weight relative to the monomers) and water (amount determined as solid %) were added. The reaction mixture was heated to 75° C. and then passed through a high pressure homogenizer from Microfluidics (available from Microfluidics, Westwood, Massachusetts) preheated at 75° C. for two passes. After homogenization, the reaction mixture was added back to the reactor and sealed. The reaction mixture was purged with nitrogen and then ammonium persulfate (2.5 parts by weight relative to monomer) was added. The reaction mixture was held at 75° C. for 12 hours and then cooled to room temperature, filtered through a 5 μm filter, and checked for coagulum. The resulting latex was analyzed by dynamic light scattering (Brookhaven NanoBrook 90 Plus PALS) for % solids (by weight), pH, and particle size. The latex solution was diluted to 5%-30% solids with additional DI water before use.

[0100] The synthesis of copolymer latexes P1A and P2 and P3 was carried out using the above procedure with various free radical polymerizable surfactants and comparative emulsifiers identified in the table below.

[0101] Preparation of coated and stretched PET films.The following procedure is representative of coated PET film. A 5% solids solution of P1A was coated onto 20 mil cast PET using a Meyer rod #12. The coating was dried in an oven at 80°C for 2 minutes. The coated sample was cut into 5 inch x 5 inch pieces and stretched in a KARO IV laboratory stretcher (Brückner) using the following procedure: (i) preheat in a first oven at 100°C for 45 seconds (ii) stretch simultaneously in the cross-web and longitudinal directions to 3.1 x 3.1 at a continuous rate of 40% (iii) move to a second oven set at 225°C and stretch similarly to 3.2 x 3.2 (iv) anneal at 225°C for 20 seconds. The final thickness of the PET film was approximately 2 mils, and the calculated thickness of the stretched coating was approximately 130 nm.

[0102] Preparation of coated and stretched PP films

[0103] A 10% (aqueous) coating solution was prepared by sequentially mixing P1A (27% solids in water, 33.3 g), deionized water (63.0 g), DYNOL 607 (0.100 g), and ADVABOND 7419 (3.6 g) and stirring the mixture for 10 minutes. This solution was coated onto a cast polypropylene substrate (54 mils thick) using a #6 or #12 Meyer rod and the film was dried at 75°C for 2 minutes. The coated cast film was converted into a sheet, loaded into a KARO IV laboratory stretcher (Brückner), and stretched 5 inches by 7 inches at 152°C. The calculated coating thickness on the stretched film was 40 nm (Meyer rod #6) and 80 nm (Meyer rod #12).

[0104] Preparation Examples 1-S to 4-S

[0105] PET cast film was coated with the P1A solution and stretched as described above. Laminates were prepared using the test tape as described above. Peel and readhesion data are listed in Table 2.

[0106] Preparation of Unstretched Examples 1-U to 4-U

[0107] 2 mil ready-made primed PET film obtained from Mitsubishi Film (3SAB) was coated with P1A and dried at 80°C for 2 minutes. Laminates were prepared using the test tape as described above. Peel and readhesion data are listed in Table 2.

[0108] Table 2. Peeling and re-adhesion results of different test tapes

[0109]

[0110] Preparation of Examples 5 to 12 and Comparative Examples 5 to 9

[0111] Samples were prepared in the same manner as described for Comparative Examples 1 to 4 using the latex polymers shown in Table 3. Examples 5 to 12 were prepared using a polymerizable emulsifier. Comparative Examples 5 to 9 were prepared using a non-polymerizable emulsifier.

[0112] Table 3. Stripping and re-adhesion results of polymer latex prepared with various emulsifiers, coating On unstretched primed PET and tested with 3M 232 tape.

[0113]

[0114] Table 4. Peeling and re-adhesion of polymer latexes prepared using ODCEA and ODA monomers The results were coated onto primed unstretched PET and tested with 3M 232 tape.

[0115]

[0116] Table 5. Polymer latex with 3M 850 and 845 tapes on the tensile PP peel and Re-adhesion results

[0117]

[0118] Table 6. Polymer latex with 3M Peeling on stretched PP of 232 and 3850 tapes and re-adhesion results

[0119]

[0120] Table 7. Use of 3M TM Adhesive Transfer Tape 467MP (Acrylic Adhesive) for lining applications on PET latex Test data of the compound

[0121]

Claims

1. A release composition comprising aqueous latex polymer particles comprising the polymerization reaction product of: i) a first monomer having the formula C n H 2n+1 -Y-C m H 2m -X-CR 1 =CH2 Where n ranges from 12 to 24; Y is a nitrogen-containing or ester linking group; R 1 is hydrogen or methyl; m ranges from 2 to 10, and X is a divalent linking group selected from esters or amides; ii) a second free radical polymerizable monomer, said second free radical polymerizable monomer having less than 12 carbon atoms; iii) 1 to 15% by weight of a free-radically polymerizable surfactant, based on the total amount of i), ii) and iii); An aqueous carrier liquid wherein the release composition contains no or less than 500 ppm of unpolymerized surfactant, based on the weight of latex polymer solids.

2. The release composition of claim 1, wherein the first monomer has an alkyl group having at least 16, 17, or 18 carbon atoms.

3. The release composition of claim 1, wherein the first monomer comprises a urethane linking group.

4. The release composition according to claim 1, wherein the free radical polymerizable (meth)acryloyl group is (meth)acrylate or (meth)acrylamide.

5. The release composition of claim 1, wherein the second free radical polymerizable monomer comprises an alkyl or alkylene group having 2 to 4 carbon atoms.

6. The release composition of claim 1, wherein the free radical polymerizable surfactant comprises an anionic group.

7. The release composition according to claim 6, wherein the anionic group is a sulfur-containing or phosphorus-containing anion.

8. The release composition of claim 1, wherein the free radical polymerizable surfactant comprises ethylene oxide repeating units.

9. The release composition of claim 1, wherein the release composition comprises less than 100 ppm of unpolymerized surfactant.

10. A method for producing an article with a release coating, the method comprising: providing a substrate; applying the release composition according to claim 1 to the substrate; as well as The aqueous carrier liquid is removed. The method according to claim 10 , wherein the substrate is a film.

12. The method of claim 11, wherein the film comprises a thermoplastic material.

13. The method of claim 11, further comprising stretching the release-coated film.

14. An article comprising a substrate and a release coating, wherein the release coating comprises: i) polymerized units of a first monomer having the formula C n H 2n+1 -Y-C m H 2m -X-CR 1 =CH2 Where n ranges from 12 to 24; Y is a nitrogen-containing or ester linking group; R 1 is hydrogen or methyl; m ranges from 2 to 10, and X is a divalent linking group selected from esters or amides; ii) polymerized units of a second free radically polymerizable monomer having less than 12 carbon atoms; iii) 1 to 15% by weight, based on the total amount of i), ii) and iii), of polymerized units of a free-radically polymerizable surfactant, wherein the release coating contains no or less than 500 ppm of unpolymerized surfactant, based on the weight of latex polymer solids.

15. The article of claim 14, wherein the first monomer has an alkyl group containing at least 16, 17, or 18 carbon atoms.

16. The article of claim 14, wherein the first monomer comprises a urethane linking group.

17. The article of claim 14, wherein the free radically polymerizable (meth)acryloyl group is a (meth)acrylate or a (meth)acrylamide.

18. The article of claim 14, wherein the second free radical polymerizable monomer comprises an alkyl or alkylene group having 2 to 4 carbon atoms.

19. The article of claim 14, wherein the free radical polymerizable surfactant comprises an anionic group.

20. The article of claim 19, wherein the anionic group is a sulfur-containing or phosphorus-containing anion.

21. The article of claim 14, wherein the free radical polymerizable surfactant comprises ethylene oxide repeating units.

22. The article of claim 14, wherein the release coating comprises less than 100 ppm of unpolymerized surfactant.

23. The article of claim 14, wherein the substrate is a film.

24. The article of claim 23, wherein the film comprises a thermoplastic material.

25. The article of claim 14, wherein the article comprises a uniaxially oriented or biaxially oriented film.

26. The article of claim 14, further comprising a pressure sensitive adhesive in contact with the release coating.

27. The article of claim 26, wherein the article is an adhesive tape.

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