Compositions and Methods for Providing Release Coatings

Abstract

An aqueous composition that can be used to impart release properties to an adhesive tape substrate and that can be applied at a coating weight far less than that required for previously available compositions containing the same or similar release polymers. The inclusion of a small amount of superwetting agent results in improved coatability and a reduction in the amount of sound generated during the peeling of the adhesive tape from its roll.

Description

BACKGROUND OF THE INVENTION

[0001] Adhesive tapes, which are typically provided in the form of rolls, are highly engineered articles that include a substrate as a primary element, as well as an adhesive and a low-adhesion backsheet (LAB) provided on opposite primary surfaces of the substrate. Although the adhesive layer carried on one layer of the substrate is adjacent to the other layer of the substrate, the low-adhesion backsheet (LAB) improves handling characteristics, providing reversible adhesion or the ability to unwind the roll product. For more information on the composition and common physical forms of LAB, the interested reader may refer to Chapter 26 of D. Satas, "Release Coatings," Handbook of Pressure Sensitive Adhesive Technology, 3rd Edition (1999).

[0002] The main types of substrates used in the manufacture of adhesive tapes are fiber-based (e.g., paper) films and polymer films. Each presents its own set of challenges in providing a quality LAB.

[0003] In the case of polymer film backings, providing LAB involves so-called release agents. Examples of release agents include nonionic surfactants, long-chain alkyl carboxylic acids and esters, (meth)acrylates with long-chain side groups, polyurethanes, silicone polymers (especially polydialkylsiloxane homopolymers and copolymers), and fluorinated polymers and waxes; for more information on release agents, the interested reader may refer to various texts and overviews, such as Chapter 12 of Kenning and Schneider, "Release Coatings for Pressure Sensitive Adhesives," Adhesion Science and Engineering - Surfaces, Chemistry, and Applications, pp. 535-71 (2002). Coating techniques include (1) applying a liquid composition (e.g., an emulsion, suspension, or dispersion) containing a film-forming polymer and one or more release agents, followed by drying, which results in a release film with the release agent entrained in the polymer network, and (2) extruding the LAB composition, which includes one or more release agents mixed with an extrudable polymer (e.g., a polyolefin).

[0004] Silicone-based compounds (i.e., polysiloxanes), alone or mixed with hydrocarbon polymers, can be very effective release agents. However, small amounts of silicone compounds often transfer to the adhesive, which can cause "craters" or "fisheyes".

[0005] Certain types of adhesive articles use non-silicone polymers to provide release properties, such as vinyl acetate, acrylate, or urethane, such as PVODC or the types described in U.S. Patent No. 10,889,736.

[0006] When applying a silicone-free release polymer to provide a release coating to an adhesive tape, a polymer with a solids content of ~3% (w / w) can be used when an organic liquid is used as the carrier liquid. The organic liquid provides a uniform and continuous coating on the polymer film.

[0007] However, for coatings based on these same silicone-free release polymers, when the carrier liquid is changed to water (which provides regulatory advantages due to reduced VOCs), a polymer with a solids content of approximately 20% (w / w) is required to ensure coverage of the film substrate. This increases the weight of the resulting tape and puts the water-based release coating compositions at a significant cost disadvantage relative to their higher-VOC organic liquid counterparts.

[0008] There is still a need for water-based release coating compositions for polymer film tape substrates that can be applied at a coating weight approaching the 3% (w / w) amount achievable with organic liquid release coating compositions and that provide a release coating of a silicone-free release polymer. SUMMARY OF THE INVENTION

[0009] Provided herein are water-based compositions useful for providing release properties to adhesive tape substrates. These compositions can be provided in a VOC-free form and can provide a surface or coating that exhibits excellent release even after aging at high humidity. Advantageously, these compositions can be applied at a coating weight far less than that required in previously available compositions containing the same release polymer.

[0010] In addition to water and one or more types of non-silicone release polymers, these compositions also contain low levels of superwetters, e.g., greater than zero to 2% (w / w, relative to the total composition). Even when the solids in the composition are far lower than those previously required in practice, this type of composition can still provide uniform coating of the release composition.

[0011] The adhesive tape substrate can be coated with a composition containing no more than 14%, no more than 12%, no more than 10%, or even no more than 8% solids (both w / w). This results in a 30% - 60% reduction in the solids content compared to previously available compositions containing the same release polymer.

[0012] Upon application and even after aging at high humidity and / or at low or high temperatures, the release polymers in the coating compositions exhibit good adhesion to the types of substrates most commonly used in articles such as label liners and wound tapes. In addition, they provide good release from a wide variety of adhesives, including but not limited to natural rubber, acrylic resins, and hot melt adhesives.

[0013] Accordingly, in another aspect, there are also provided articles that include a surface bearing an adhesive layer and a surface in contact with the adhesive layer and bearing a release layer provided by such a composition. In a tape article, the adhesive layer and the release layer can be on opposite sides of the same substrate. In a label article, the adhesive layer can be applied to one substrate and the release layer to another substrate, arranging the two substrates so that the adhesive layer and the release layer are in direct contact.

[0014] There is also provided a method for making such articles.

[0015] Other aspects of the present invention will become clear to those of ordinary skill in the art from the following detailed description. To assist in understanding the description, some definitions are provided immediately below, which are intended to apply throughout the text unless the surrounding text clearly indicates the contrary intention:

[0016] "Comprising" means including but not limited to the listed components;

[0017] "Consisting of" means including only the listed components and a small amount of inactive additives or adjuvants;

[0018] "Consisting essentially of" means including only the listed components, a small amount (less than 5%, 4%, 3%, 2%, 1%, 0.5%, 0.25%, or 0.1% w / v) of other components, and / or inactive additives or adjuvants, where the other components supplement the release performance of the polymer, coating, or LAB and / or provide a secondary effect desired for the intended end use (e.g., antioxidant);

[0019] "Polymer" means a polymerization product of one or more monomers, including homopolymers, copolymers, terpolymers, quaterpolymers, etc.;

[0020] "Copolymer" means a polymer comprising monomer units derived from two reactants (usually monomers), including random, block, segmented, graft, etc. copolymers;

[0021] "Interpolymer" means a polymer comprising monomer units derived from at least two reactants (usually monomers), including copolymers, terpolymers, quaterpolymers, etc.;

[0022] "Monomer unit ('mer' or'mer unit')" means the portion of a polymer derived from a single reactant molecule (e.g., an ethylene monomer unit has the general formula -CH 2 CH 2 -);

[0023] "Substituted" means that a compound contains a heteroatom or functional group (e.g., a hydrocarbyl group) that does not interfere with the intended purpose of the group being discussed;

[0024] "Polyene" means a molecule having at least two double bonds in its longest portion or chain, usually a monomer, and specifically includes dienes, trienes, etc.;

[0025] "Polydiene" means a polymer containing monomer units from one or more dienes;

[0026] "Release agent" means a compound or mixture of compounds that is designed or intended to allow an adhesive to be smoothly and controllably peeled from the surface to which the compound is applied without transferring to the adhesive during the peeling process;

[0027] "Release polymer" means a polymeric release agent;

[0028] "Low adhesion backsize" or "LAB" means a composition comprising at least a coating polymer and a release agent, usually in combination with a component comprising one or more surfactants;

[0029] "VOC-free" means that when subjected to standard analytical test procedures, it shows generally less than 0.5 ppm, usually less than 0.25 ppm, typically less than 0.1 ppm, and preferably less than 0.05 ppm of volatile organic chemicals;

[0030] The morphological element "(thio)" is intended to include S-containing analogs of the compounds or groups used in association with this morphological element;

[0031] “Iso(thio)cyanate” means a group of the general formula -N=C=O or -N=C=S or a compound containing such a group;

[0032] “(Meth)acrylate” means a methacrylate or an acrylate;

[0033] “Active hydrogen” is an H atom that causes methane production when a compound containing the H atom is subjected to the Zerewitinoff determination test;

[0034] “Lower alkyl” means an alkyl group containing no more than 6 C atoms;

[0035] “Long-chain alkyl” means an alkyl group containing at least 12 C atoms;

[0036] “Super wetting agent” (also referred to as “super-spreader”) means a type of surface-active reagent (surfactant) that will spontaneously spread when a drop of it is placed on the surface of paraffin at room temperature; and

[0037] “Radical” means a part of a molecule that remains after reacting with another molecule, whether or not any atoms are gained or lost as a result of the reaction. Detailed Description of the Invention

[0038] As indicated in the “Summary of the Invention” section above, the composition can contain as few as three components: water, a non-silicone release polymer, and up to 2% (w / w) of a super wetting agent.

[0039] Release polymers useful in the composition include those polymers containing at least 50%, preferably at least 60%, more preferably at least 70%, still more preferably at least 80%, even still more preferably at least 90%, and most preferably at least 99% of vinyl acetate or acrylate monomer units. (Each of the above is mol%).

[0040] The polymers described in U.S. Patent No. 10,889,736 are a preferred group of release polymers including acrylate monomer units because they can provide compositions with very low VOC, including VOC-free compositions, which do not produce formaldehyde during processing (e.g., drying) under normal manufacturing conditions. For ease of reference, a brief description of these polymers is provided herein.

[0041] The polymers in this preferred group contain monomer units having side groups including at least two (thio)carbonyl groups and a plurality of additional heteroatoms.

[0042] In some embodiments, the C atom of one (thio)carbonyl moiety of the side group is linked to two additional heteroatoms, one of which is N and the other is selected from O, S, and N.

[0043] In some of these embodiments, the side group can be represented by the following general formula,

[0044]

[0045] wherein X represents O or S, E represents an O or S atom or an NR' group, wherein R' is H or C 1 -C 6 alkyl group, and R 2 represents a lower alkyl, aryl, alkaryl, or aralkyl group (optionally containing a heteroatom (such as O), provided that no active hydrogen atoms are present), Z represents a group containing a divalent (thio)carbonyl group, which further contains two additional heteroatoms linked to the C atom of the (thio)carbonyl moiety, and R 3 represents a long-chain alkyl group or a larger functional group containing a long-chain alkyl group. Examples of the additional heteroatoms that can be linked to the C atom of the carbonyl moiety in Z include O, S, and N; at least one of the additional heteroatoms is usually N. (The main form of Z depends on the specific characteristics of E and X and, to some extent, also on the conditions under which the reaction proceeds.)

[0046] Preferred polymers containing side groups of the type of general formula (I) can be provided by monomers represented by the following general formula, where each of R 2 , R 3 , E, and X is as defined above, and R 1 is H or a methyl group:

[0047]

[0048] In other embodiments, the side group can be represented by the following general formula,

[0049]

[0050] wherein R 3 , X, and E are as defined above, n is 0 or 1, R 4 is a moiety of a hydrocarbon having two isocyanate (thio) groups with different reactivities, and R 6 is a linking group, such as a carbonyl, ether, amine, or other group. The side group of general formula (II) is similar to the side group defined by general formula (I), except that Z and R 3 (from general formula (I)) are not directly linked, but are separated by an additional linking group.

[0051] Polymers containing side group radicals of the general formula (II) can be provided by monomers represented by the following general formula, R 3 、R 4 、E and X are each as defined above, R 5 is a polymerizable group, optionally but typically linked to the adjacent E atom via a linear or cyclic linking group (such as -R 2 XC(X)-group):

[0052]

[0053] Associated with the polymers defined by general formula (II-a) are polymers produced by a two-step reaction scheme. Diisothiocyanates having isothiocyanate groups of different reactivities (such as isophorone diisocyanate (IPDI), 2,4-toluene diisocyanate (2,4-TDI), etc., and their sulfur analogs) are reacted with two compounds containing an EH group (provided that if E = NR', then R' is preferably not H to prevent interference with the reaction). One of the EH groups includes a polymerizable functional group and the other includes a long-chain alkyl group (or a larger functional group containing a long-chain alkyl group), specifically for example C 15 -C 25 、preferably C 16 -C 20 、more preferably C 17 -C 18 , substituted or unsubstituted alkyl groups.

[0054] Non-limiting examples of the first type of compound containing an EH group include compounds represented by the following general formula,

[0055]

[0056] wherein, R 1 、R 2 、n、E and X are as defined above, R 7 is a phenyl or C 1 -C 6 alkyl group. (In certain embodiments, R 2 is preferably a C 1 -C 6 alkyl group.)

[0057] A subset of the general formula (III-b) compounds where n is 0 are substituted styrenes, including compounds where R 7 is a phenyl group, defined by the following general formula,

[0058]

[0059] wherein E is as defined above. Variations of this general formula are also possible; for example, α-methylstyrene analogs of compounds of general formula (III-b-1) are expected to be useful, as are compounds in which the EH group is indirectly linked to the styrene ring (e.g., via a hydrocarbon linking group).

[0060] Another subset of compounds of the general formula (III-b) in which n is 0 are vinyl alcohol / ethers, i.e., compounds of general formula (III-b) in which R 7 is a lower alkyl group, preferably C 1 -C 3 alkylene group, more preferably C 1 -C 2 alkylene group. Also contemplated are sulfur and amine analogs of these compounds, i.e., embodiments in which E = S or NR'.

[0061] One subset of compounds of the general formula (III-b) in which n is 1 are diol vinyl ethers, i.e., compounds of general formula (III-b) in which X is an O atom and R 7 is a lower alkylene group, preferably C 1 -C 4 alkylene group. Also contemplated are sulfur and amine analogs of these compounds, i.e., embodiments in which E = S or NR', and those analogs in which X = S.

[0062] Non-limiting examples of a second class of compounds containing an EH group include compounds defined by R 3 -EH, wherein R 3 and E are as defined above.

[0063] Other preferred polymers contain monomer units having side groups represented by the following general formula,

[0064] -(X) n -R 7 -Z-R 3 (IV),

[0065] wherein X, n, Z, R 3 and R 7 are as defined above.

[0066] Polymers containing side groups of the general formula (IV) can be provided by monomers represented by the following general formula, all variations of which are as defined above:

[0067]

[0068] The predominant form of Z depends on the specific characteristics of E and X and to some extent on the conditions under which the reaction is carried out. The polymer produced by polymerization of compounds of formula (IV) has a hydrocarbon backbone containing a plurality of pendant groups defined by formula (IV).

[0069] As a specific non-limiting example, the compound of formula (III-b-1) can be combined with R 3 -NCX compounds (R 3 and X are defined above) to provide a monomer represented by the following general formula,

[0070]

[0071] E, X, and R 3 As defined above. 3 Reaction products of NCX compounds with various other compounds of the general formula (III-b) are also possible.

[0072] In certain embodiments, each X in each of the above formulae may be an oxygen atom.

[0073] The preparation of each of these types of polymers is described in previously cited U.S. Patent No. 10,889,736. The polymerization may be a homopolymerization, may involve two or more such compounds, or may involve one or more comonomers that can participate in emulsion polymerization and can be free radical initiated, for example, polyolefins, particularly conjugated dienes, and vinyl compounds, particularly (meth)acrylates and their derivatives. It is preferred that the long chain alkyl side groups be included and / or that the glass transition temperature (T) of the resulting interpolymer be increased or not substantially decreased. g ) and / or melting temperature (T m ) comonomer.

[0074] The numerical (molar) percentage of monomer units derived from one or more of the aforementioned pendant groups containing carbamate moieties is at least 33%, generally at least 50%, 55%, 60% or 65%, usually at least 67% or 70%, and typically at least 75% or more. The numerical (molar) percentage of monomer units derived from the release polymer of the present invention is generally at least 80%, 85%, 90% or even 95%.

[0075] The VOC content of such polymers is generally less than 5 ppm, usually less than 3 ppm, more usually less than 2 ppm, and typically less than 1 ppm.In many embodiments, the polymer is free of VOCs.

[0076] Regardless of the specific monomers used to prepare the release polymer, the result of the emulsion polymerization is generally an aqueous dispersion of a polymer having a weight average molecular weight (M). w) is about 125 ± 75 kg / mol, typically 125 ± 50 kg / mol, and typically 125 ± 25 kg / mol.

[0077] The emulsion polymerization of the release polymer can generally have a solids content of from about 15% to about 75% (w / w), preferably from about 20% to about 70% (w / w), and more preferably from about 25% to 65% (w / w). Maximizing the solids content is generally desirable, and this property can be facilitated by a polymodal particle size distribution. A second or subsequent particle size can be generated by introducing a seed polymer, by adding an excess of emulsifier, or by adding a mini-emulsion.

[0078] The release polymer can be used in the form of its aqueous dispersion, or it can be recovered and further processed. Before such further processing, it is not necessary to remove surfactants, initiators, chain transfer agents, etc.

[0079] As described above, the compositions of the present invention contain ≤ 14%, ≤ 12%, ≤ 10%, or even ≤ 8% solids (all w / w), and thus the products of typical emulsion polymerizations can be diluted with water to achieve the desired solids content.

[0080] In addition to water and one or more non-silicone release polymers, the compositions of the present invention further contain from greater than 0 to 2% (w / w) of one or more superwetting agents.

[0081] In certain embodiments, the amount of superwetting agent can be at least 0.25% (w / w). Preferred amounts include from 0.1% to 1.5%, from 0.5% to 1.5%, and especially from 0.75% to 1.25% (all w / w, based on the weight of the total composition).

[0082] The values and ranges of the immediately preceding paragraphs apply to superwetting agents having a molecular weight similar to that of dioctylsulfosuccinate (DOSS) (i.e., MW ≈ 450 g / mol ± 20%). For those superwetting agents having a larger molecular weight (e.g., polyoxyethylene (20) sorbitan monooleate, MW ≈ 1300 g / mol) or a smaller molecular weight (e.g., myristyl dimethylamine oxide, MW ≈ 250 g / mol; lauryl dimethylamine oxide, MW ≈ 230 g / mol; and 1-octyl-2-pyrrolidone, MW ≈ 200 g / mol), the weight percentage values and ranges can be adjusted appropriately to provide approximately equimolar amounts of superwetting agent to the composition.

[0083] It has been found that including the above amounts of superwetting agents in the composition improves the appearance and peelability of the coatings provided thereby. For example, a composition having a solids content of 10% (w / w) but without a superwetting agent will exhibit significant de-wetting during application, while the same composition containing a small amount (e.g., 0.5% (w / w)) of a superwetting agent exhibits little or no de-wetting. Additionally, surprisingly, the sound emitted during the peeling of an adhesive tape from its roll can be significantly reduced from a zippy sound (which, in an industrial environment, can cause workers to require ear protection) to a much lower volume.

[0084] Without wishing to be bound by theory, it is believed that including a superwetting agent in an aqueous composition reduces the number and / or size of the portions of the substrate that are not covered by the peeled coating (after evaporation and coalescence of the water in the coating). It is believed that the bare substrate gives rise to a slip-stick phenomenon that generates noise during peeling (i.e., during the unwinding of the PSA roll).

[0085] Even at low concentrations, superwetting agents greatly reduce the surface tension of aqueous compositions, promote their dispersion on hydrophobic surfaces, and in some cases, reduce the amount of time required to achieve such dispersion and / or render the surface superhydrophilic. It is believed that this ability is based on their ability to very effectively wrap around the surface.

[0086] Non-limiting examples of compounds that can serve as superwetting agents include silicone polyether copolymers (of different molecular weights and structures), gemini silicone surfactants, alkynediols, certain fluorosurfactants, organosilicones, trisiloxane-based surfactants, carbosilanes, fluoroorganic surfactants, alkoxylated alkynediols, hydroxy sulfides, etc.; see also U.S. Patent Nos. 10,552,557, 10,485,739, 10,456,766, 10,415,000, 9,834,699, 8,648,211, 7,264,885, 7,160,373, 6,926,766, 6,645,392, 6,566,322, 6,495,058, 6,475,953, and 6,407,042.

[0087] Of particular interest are those superwetting agents that are neither silicone-based (i.e., polymers containing siloxane groups) nor fluorine-based (i.e., polymers containing F atoms) in relation to the peel polymers specifically described above.

[0088] Superwetting agents are commercially available, for example, under the brand name Silwet TM(Momentive; Waterford, New York), Dowsil TM (Dow; Midland, Michigan), Surfynol TM and Dynol TM (Evonik; Essen, Germany), Ammonyx TM (Stepan; Northfield, Illinois), Tween TM (Croda Intl.; East Yorkshire, UK), Easy-Wet TM (Ashland; Wilmington, Delaware), etc.

[0089] Specific improvements in coatability and sound-upon-release have been observed with sulfosuccinates (e.g., DOSS), C 12 -C 16 alkylamine oxides (including myristyl dimethylamine oxide), polysorbates, and mixtures of 1-undecanol, sodium lauryl sulfate, 1-octyl-2-pyrrolidone, and ethoxylated undecanol.

[0090] Particularly interesting coating compositions include those described in the "Examples" section below. Specific superwetting agents used therein include DOSS, polysorbates (which are of particular interest for end-use applications involving food contact, packaging, etc. because they are considered non-toxic and are actually edible), amine oxides (optionally with additives such as antioxidants to inhibit potential yellowing of the superwetting agent), and 1-alkyl-2-pyrrolidone.

[0091] Advantageously, the aqueous compositions of the present invention for providing release properties to an adhesive tape substrate can be processed and used similarly to other compositions based on aqueous deliverable release polymers. Various substrates (including various papers, foils, and polymer films) can be coated using standard commercial conditions, coating thicknesses, coating speeds, etc.

[0092] The release coating provided by the present composition can be used in conjunction with various adhesives, which are typically pressure-sensitive adhesives (PSA), including one or more polymers such as natural rubber, butyl rubber, vinyl ether, any of various acrylates, polymers (including polyene monomer units, especially polydienes such as 1,3-butadiene, isoprene, etc.), block copolymers (such as SBS, SIS, etc.), random copolymers (such as SBR), silicone rubber, etc. The foregoing should be considered exemplary and not restrictive, and it has been found that the release polymers of the present invention cooperate well with many types of adhesives.

[0093] Although various embodiments of the present invention have been provided, they are presented in an exemplary rather than restrictive manner. To the extent possible, the features and embodiments described separately above can be combined with other features and embodiments as long as they do not interfere with each other or are not mutually exclusive.

[0094] The relevant portions of any document specifically cited in the foregoing text or in the following examples are incorporated herein by reference.

[0095] The following non-limiting illustrative examples provide the reader with detailed conditions and materials useful in the practice of the present invention.

[0096] Examples

[0097] Unless otherwise specified as to the specific source, all chemicals used in the following examples are available from general chemical suppliers (e.g., Sigma-Aldrich Co. (St. Louis, Missouri)).

[0098] From Suncryl TM A series of aqueous coating compositions with 10% (w / w) solids were prepared from HP 114 acrylate polymer emulsion (OMNOVA Solutions Inc.; Beachwood, Ohio). Different amounts (0.1 wt% to 1.0 wt%) of DOSS superwetting agent were added to them.

[0099] Aliquots of these compositions were applied to a PET film with a thickness of 0.051 mm (2 mil) using a #0 bar, and then dried at ~116 °C (240 °F) for ~120 seconds.

[0100] Then, these coated films were laminated to the adhesive side of a film tape (tesa TM 7475 acrylic adhesive tape (tesatape inc.; Charlotte, North Carolina)).

[0101] Age the coated test film (tape laminate) at a constant temperature of 65 °C and 60% relative humidity (under heating conditions) for ~16 hours.

[0102] Without heating, laminate strips of a self-wrapping tape product cut to ~2.54 cm (1 in.) wide and ~12 cm (5 in.) long using a 2.54 cm wide double-coated adhesive paper tape applied to the release side of the test strip. Roll the attached test strip twice on the working platen using a 2 kg rubber roller moving at a rate of ~0.005 m / sec (1 ft. / min).

[0103] Evaluate each test film using the Pressure Sensitive Tape Council’s Peel Adhesion of Pressure Sensitive Tape method (PSTC-101, rev. 05-2007, Test Method A (180° peel) and F (90° peel)). The resulting peel test values are quantitative measurements of the force required to remove a flexible adhesive tape from the coating of a given release material at a specific angle and removal rate.

[0104] In the test labeled 101-A below, pull the adhesive tape strip at an angle of 180° and a rate of 0.005 m / sec (1 ft. / min.) from the release-coated material. Measure the force required to remove the adhesive from the release coating during a 5-second data acquisition time.

[0105] In the test labeled 101-F below, pull the adhesive tape strip at an angle of 90° and a rate of 0.255 m / sec (50 ft. / min.) from the release-coated material. Measure the force required to remove the adhesive from the release coating during a 5-second data acquisition time.

[0106] In the test labeled 101-E below, perform a so-called subsequent adhesion evaluation using PSTC-101, Method E.

[0107] The test results are listed in Table 1, where the letters represent the following samples (the numbers in parentheses represent the weight % of DOSS contained):

[0108] A (1%) - Very good, clear coating, with slight edge crawl

[0109] B (0.75%) - Good, clear coating, with slightly more edge crawl than A

[0110] C (0.5%) - The coating is clear, with more edge wrinkling and some warbling near the edge ("orange peel") than B.

[0111] D (0.25%) - Obvious edge wrinkling and many small dew point areas during the entire draw down process.

[0112] E (0.1%) - The edge wrinkling is similar to D, but there are more dew point areas.

[0113] The column marked "Sound" is subjectively determined:

[0114] Z (sharp sound) - The sound of tearing.

[0115] SZ (slightly sharp sound) - The sound of a controlled tear.

[0116] VSZ (very slightly sharp sound) - Some audible tearing sounds.

[0117] SS (slight sound) - No tearing sound, but audible in the distance.

[0118] VSS (very slight sound) - Audible nearby.

[0119] Table 1: Suncryl TM HP 114 Peel Performance

[0120]

[0121] Repeated the aforementioned tests with different peel coatings (Suncryl TM CL 223B (OMNOVA Solutions)) and different total solid contents (20%, instead of 10%).

[0122] The results of these tests are listed in Table 2, where the letters represent the following samples:

[0123] F - 0% superwetting agent

[0124] G - 0.25% superwetting agent

[0125] H - 0.5% superwetting agent

[0126] I - 0.75% superwetting agent

[0127] Table 2: Suncryl TM Peel Performance of CL 223B

[0128]

[0129] *Control

[0130] As can be seen from the above, even a small amount of superwetting agent included in the aqueous coating composition can provide improved peelability for the release coating and reduce the amount of sound emitted during the process of peeling an adhesive tape from its roll.

[0131] Using DOSS as the superwetting agent in the above two sets of tests enabled a head-to-head comparison of two types of release coating compositions. However, this should not be considered restrictive: other types of superwetting agents are expected to exhibit similar trends at similar loading levels.

[0132] From Suncryl TM HP 114 acrylate polymer emulsion, another series of aqueous coating compositions were prepared with respective solids of 10% (w / w). A control sample (J, 32.70%) without superwetting agent and four samples with 1% (w / w) superwetting agent were prepared, namely

[0133] K-Surfynol TM AS 5120 wetting agent (33.60%),

[0134] L-Tween TM 80 polysorbate (33.24%),

[0135] M-Easy-Wet TM 20 l-octyl-2-pyrrolidone (32.52%), and

[0136] N-Ammonyx TM LO laurylamine oxide (33.45%).

[0137] (The numbers in parentheses represent the total solids content of the coating composition.)

[0138] Using a #3 rod, aliquots of these compositions were applied to a PET film with a thickness of 0.051 mm (2 mil). The drawdowns of sample K and sample M were well-coated with small edge wrinkling; the drawdowns of sample L and sample N were well-coated with very small edge wrinkling; while the drawdown of the control sample J was clearly coated with a dewetting area of 0.5 cm in size throughout. Each sample was dried at ~116 °C (240 °F) for ~120 seconds.

[0139] Then, these coated films were laminated to the adhesive side of a film tape (tesa TM 7475 acrylic adhesive tape).

[0140] Age the coated test film (tape laminate) at a constant temperature of ~49 °C (120 °F) and 50% relative humidity for ~16 hours (under heating conditions).

[0141] Each test was performed three times on each sample, and the average values and standard deviations of these tests are listed in Tables 3a and 3b.

[0142] Table 3a: Peel performance of Suncryl TM HP 114 with 1% (w / w) super wetting agent, initial values

[0143]

[0144] * Control

[0145] Table 3b: Peel performance of Suncryl TM HP 114 with 1% (w / w) super wetting agent, after thermal aging

[0146]

[0147] * Control

[0148] In the relevant adhesion tests, the super wetting agent at 1% (w / w) for each test provided a significant improvement. However, during the process of peeling the adhesive tape from its roll, none of them could provide the same degree of improvement as DOSS in terms of sound emission.

Claims

1. A release coating without silicone release polymers, the release coating comprising (a) at least one superwetting agent that does not contain siloxane groups and F atoms, and (b) at least one release polymer that comprises at least 50 mol% acrylate or vinyl acetate monomer units and has a weight-average molecular weight of 125 ± 75 kg / mol, the release coating being provided by a composition comprising 0.5 - 1.0 wt% of the at least one superwetting agent, wherein, the composition is an aqueous composition and has a total solids content of no more than 10 wt%; and wherein the superwetting agent is dioctyl sulfosuccinate.

2. The release coating according to claim 1, wherein, the total solids content is no more than 8 wt%.

3. The release coating according to any one of claims 1 or 2, wherein, the at least one release polymer comprises a polymer having at least 50 mol% acrylate monomer units.

4. The release coating according to any one of claims 1 or 2, wherein, the at least one release polymer comprises a polymer having at least 50 mol% vinyl acetate monomer units.

5. The release coating according to any one of claims 1 or 2, wherein, the composition comprises 0.75 wt% to 1.0 wt% of the at least one superwetting agent relative to the composition.

6. The release coating according to any one of claims 1 or 2, wherein, the at least one release polymer comprises at least 50 mol% acrylate monomer units, at least some of the acrylate monomer units comprising side groups that include at least two (thio)carbonyl groups and a plurality of additional heteroatoms, and wherein the total solids content of the composition is no more than 10 wt%.

7. An article comprising a substrate bearing the release coating according to any one of claims 1 - 6.

8. The article according to claim 7, the article further comprising an adhesive layer.

Images