Medical pressure-sensitive adhesives without polar groups

Abstract

The crosslinked (meth)acrylate-based pressure-sensitive adhesive is capable of adhering to mammalian skin for at least 10 days. The crosslinked adhesive composition comprises a crosslinked (meth)acrylate-based copolymer without polar groups and a hydrogenated hydrocarbon tackifying resin. The crosslinked adhesive composition is prepared by photocrosslinking a hot-melt processable blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifying resin. The (meth)acrylate copolymer is the reaction product of an alkyl (meth)acrylate monomer, having an alkyl group containing 4 to 22 carbon atoms and without polar groups, with a copolymerizable photocrosslinker.

Description

Technical Field

[0001] The present disclosure relates to (meth)acrylate-based pressure-sensitive adhesives that can be used to form adhesive articles such as tapes and other medical articles useful for medical applications.

Background Art

[0002] A wide range of adhesive articles are used in medical applications. These adhesive articles include gels used to attach electrodes and other sensing devices to a patient's skin, a wide range of tapes for fixing medical devices to patients, and adhesive dressings used to cover and protect wounds.

[0003] Many of the adhesive articles use pressure-sensitive adhesives. It is well known to those skilled in the art that pressure-sensitive adhesives have certain properties at room temperature, including (1) strong and persistent adhesive force, (2) adhesion by pressure below finger pressure, (3) sufficient ability to adhere to the adherend, and (4) sufficient cohesive force to be cleanly removed from the adherend. Materials that have been found to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit the viscoelastic properties necessary to provide the desired balance of adhesive force, peel adhesion, and shear strength. The polymers most commonly used in the preparation of pressure-sensitive adhesives are natural rubber, synthetic rubber (e.g., styrene / butadiene copolymer (SBR) and styrene / isoprene / styrene (SIS) block copolymer), various (meth)acrylate (e.g., acrylate and methacrylate) copolymers, and silicone.

Summary of the Invention

[0004] This specification discloses crosslinked (meth)acrylate pressure-sensitive adhesives that can be used to form adhesive articles such as tapes and other medical articles useful for medical applications. In some embodiments, the crosslinked adhesive composition comprises a crosslinked (meth)acrylate copolymer without polar groups and a hydrogenated hydrocarbon tackifier. The crosslinked adhesive composition is the product of a hot-meltable blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier. The (meth)acrylate copolymer is the reaction product of a reaction mixture comprising at least one alkyl (meth)acrylate monomer having 4 to 22 carbon atoms and an alkyl group without polar groups, and a copolymerizable photocrosslinking agent. The hot-melt blend is photocrosslinked.

[0005] Furthermore, an adhesive article is disclosed, comprising a substrate having a first main surface and a second main surface, and a crosslinked adhesive layer having a first main surface and a second main surface, wherein the first main surface of the adhesive layer is at least partially located on the second main surface of the substrate. The crosslinked adhesive layer comprises a crosslinked adhesive composition as described above. The crosslinked adhesive composition comprises a crosslinked (meth)acrylate copolymer without polar groups and a hydrogenated hydrocarbon tackifier. The crosslinked adhesive composition is the product of a hot-meltable blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier. The (meth)acrylate copolymer is the reaction product of a reaction mixture comprising at least one alkyl (meth)acrylate monomer having 4 to 22 carbon atoms and an alkyl group without polar groups, and a copolymerizable photocrosslinking agent. The hot-melt processed blend is photocrosslinked. The adhesive article can adhere to mammalian skin for at least 10 days. [Modes for carrying out the invention]

[0006] The use of adhesive products in the medical industry has been widespread and increasing for many years. However, while adhesives and adhesive articles have shown to be very useful in medical applications, there are also problems in their use. In particular, the desired properties of adhesives are often contradictory. For example, it is desirable that adhesives have high adhesion to arrays of surfaces, including human skin, and yet be removable, preferably without damaging the skin. Furthermore, medical articles are now used for longer periods and need to remain adhered, yet be removable without damaging the skin or leaving residue.

[0007] Medical adhesive-related skin injury (MARSI) poses a significant risk to patient safety. Skin injuries associated with the use of medical adhesives are a widespread but often overlooked complication that occurs across all care settings and age groups. Furthermore, treating skin injuries is costly in terms of service delivery, time, and additional treatment and supplies.

[0008] Skin damage occurs when the surface layer of the skin is removed along with the medical adhesive product. This not only affects the integrity of the skin but also causes pain and an increased risk of infection, can enlarge the wound, and can delay healing, all of which reduce the patient's quality of life.

[0009] Medical adhesive tapes can simply be defined as pressure-sensitive adhesives and backings that function as carriers for the adhesives. The U.S. Food and Drug Administration more specifically defines medical adhesive tapes or bandages as "devices intended for medical purposes consisting of a piece of fabric material or plastic, which is coated on one side with adhesive, and which may include non-disinfectant surgical dressing pads. These devices are used to cover and protect wounds, to hold together the skin edges of a wound, to support an injured part of the body, or to fasten an object to the skin."

[0010] The pathophysiology of MARSI is only partially understood. Skin damage occurs when the adhesion of the adhesive to the skin is stronger than the adhesion of skin cells to other skin cells. When the adhesive strength exceeds the strength of the skin cell interactions, aggregation breakdown occurs within the skin cell layer.

[0011] Next, the inherent properties of all components of the adhesive product must be considered in order to address these factors that may lead to MARSI. The properties of the adhesive to be considered include cohesiveness over time and corresponding adhesive strength, while the properties of the tape / backing / dressing material include breathability, stretchability, adaptability, flexibility, and strength.

[0012] The widespread use of adhesives in medical applications has led to the development of skin-friendly adhesives and adhesive articles. Some of these adhesives are pressure-sensitive adhesives. The application of pressure-sensitive adhesives, including acrylate-based and silicone-based pressure-sensitive adhesives for adhesion to skin, is well known in the art, and many examples are commercially available.

[0013] Among the widely used adhesive materials for pressure-sensitive adhesives are (meth)acrylate-based pressure-sensitive adhesives. These materials often possess many desirable properties, being inherently tacky and therefore not requiring the use of added tackifiers. They are typically formed with high reaction rates by free radical polymerization, which leaves little to no unpolymerized monomers in the formed pressure-sensitive adhesive, meaning that a wide range of monomers can be used to form (meth)acrylate copolymers and adjust the desired properties of the pressure-sensitive adhesive. Often, (meth)acrylate-based pressure-sensitive adhesives are prepared from reaction mixtures containing polar groups, such as acidic and basic groups. Acidic and basic monomers tend to increase the cohesive force of (meth)acrylate-based pressure-sensitive adhesives and are therefore often classified as reinforcing monomers in the adhesive field. Thus, preparing (meth)acrylate-based pressure-sensitive adhesives that retain useful cohesive force for medical applications without containing these polar reinforcing monomers is a challenging task.

[0014] Another reason for including acidic, basic, or other polar groups in medical adhesives is to make the adhesive more hydrophilic, thereby improving its moisture vapor transmission rate (MVTR) for long-term wear. Furthermore, a wide variety of medical articles and devices are intended to remain adhered to the skin for extended periods. Current adhesive systems are difficult to retain on the skin for long periods because the adhesive suffers from moisture loading, i.e., moisture trapped between the skin and the adhesive layer, due to an inadequate MVTR that causes the adhesive system to "lift." MVTR is a measure of how easily water vapor passes through a substance or barrier. Because sweating occurs naturally on the skin, a low MVTR in a material or adhesive system can lead to moisture buildup between the skin and the adhesive, potentially causing the adhesive to "lift" or peel, or promoting other harmful effects such as bacterial growth and skin irritation. Therefore, much effort has focused on developing adhesive systems with high MVTRs. Typically, adhesives are designed to be hydrophilic so that moisture from the skin passes through the adhesive layer and does not accumulate at the skin / adhesive interface. Adhesives are typically hydrocarbon-rich and therefore nonpolar and hydrophobic; thus, they typically contain acidic groups, basic groups, or polar groups such as hydroxyl groups. Therefore, hydrocarbon-rich adhesives without polar groups are expected to have insufficient MVTR and thus low long-term durability.

[0015] Another trend in adhesive technology is the preparation of adhesives without the use of solvents. While there are various environmental and other reasons for eliminating solvents in the preparation of adhesive articles, manufacturing adhesives such as (meth)acrylate adhesives without solvents can be problematic. Among the methods developed for preparing and coating adhesive systems are 100% solid systems, such as hot-melt pressure-sensitive adhesives. Difficulties arise when solvent processing is replaced by hot-melt processing. In many cases, it is difficult to replicate the properties of solvent-delivered adhesive layers in a hot-melt delivery system.

[0016] Therefore, desirable, often contradictory, features for medical adhesives include: high adhesion sufficient to adhere to the skin without causing skin damage upon removal; being acidic, basic, or free of polar groups such as hydroxyl groups, yet possessing sufficiently high cohesive force to be useful; having long-term durability; and being hot-melt processable so as to eliminate the need for solvents.

[0017] This specification discloses adhesive compositions and adhesive articles having the desirable characteristics described above. The adhesives disclosed herein do not have polar groups. One might expect that the absence of polar groups would result in insufficient MVTR and therefore low long-term durability, but surprisingly, this has been found not to be the case. As mentioned above, the absence of polar groups reduces the cohesive force of the adhesive matrix and also results in a very tacky adhesive matrix. Current adhesives compensate for the lack of cohesive force and high tackiness through the use of branched and crosslinked matrices and high tackifier filler, but this actually reduces the tackiness of the matrix. However, the nonpolarity of the adhesive matrix reduces compatibility with many tackifiers that are relatively polar and can form blends with phase separation problems. Therefore, relatively nonpolar tackifiers, such as hydrogenated hydrocarbon tackifiers, are used. The use of these nonpolar tackifiers allows for relatively high filler amounts of tackifiers without phase separation. These hydrogenated hydrocarbon tackifiers are generally not very compatible with more polar adhesive matrices and are therefore not useful at high filler levels.

[0018] This specification discloses a crosslinked adhesive composition comprising a crosslinked (meth)acrylate copolymer without polar groups and a hydrogenated hydrocarbon tackifier. The crosslinked adhesive composition is the product of a hot-meltable blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier. The (meth)acrylate copolymer is the reaction product of a reaction mixture comprising at least one alkyl (meth)acrylate monomer having 4 to 22 carbon atoms and an alkyl group without polar groups, and a copolymerizable photocrosslinking agent. The hot-melt-processed blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier is photocrosslinked to form a crosslinked adhesive composition. Adhesive articles can be prepared by placing this crosslinked adhesive composition on the surface of a substrate. The crosslinked adhesive composition is a hydrocarbon-enriched and hydrophobic composition, and moreover, the adhesive provides good long-term durability.

[0019] Unless otherwise indicated, all numbers used in this specification and the claims to represent feature dimensions, quantities, and physical properties shall be understood in all cases to be modified by the term “approximately.” Therefore, unless otherwise indicated, the numerical parameters described in the above specification and the appended claims are approximations that may vary depending on the desired properties to be obtained by a person skilled in the art using the teachings disclosed herein. Numerical ranges described by endpoints include all numbers encompassed within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0020] As used herein and in the appended claims, the singular forms "a," "an," and "the" encompass embodiments having multiple references unless otherwise specified. For example, a reference to "layer" encompasses embodiments having one, two, or more layers. As used herein and in the appended claims, the term "or" generally means "and / or" unless otherwise specified.

[0021] As used herein, the term "adhesive" refers to a polymeric composition useful for bonding two adherends together. An example of an adhesive is a pressure-sensitive adhesive.

[0022] It is well known to those skilled in the art that pressure-sensitive adhesive compositions possess properties including: (1) strong tack and persistent adhesiveness, (2) adhesion under pressure below finger pressure, (3) sufficient ability to hold the adherend in place, and (4) sufficient cohesive strength to cleanly remove from the adherend. Materials known to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit the viscoelastic properties necessary to provide the desired balance of adhesive force, peel adhesion, and shear holding power. Obtaining the proper balance of properties is not a simple process.

[0023] The term "(meth)acrylate" refers to esters of alcohols with monomeric acrylic or methacrylic acids. Acrylate and methacrylate monomers or oligomers are collectively referred to herein as "(meth)acrylates". A material referred to as having "(meth)acrylate functionality" is a material containing one or more (meth)acrylate groups. A polymer described as "(meth)acrylate-based" contains at least a majority of (meth)acrylate monomers and may contain other copolymerizable ethylenically unsaturated monomers.

[0024] The term "polar group" is used herein in accordance with its general chemical usage. Suitable polar groups in the adhesive composition include acidic groups, basic groups, and hydroxyl groups.

[0025] The terms "room temperature" and "ambient temperature" are used interchangeably and mean a temperature in the range of 20°C to 25°C.

[0026] When referring to two layers, as used herein, the term "adjacent" means that the two layers are in close proximity to each other and there is no intervening open space between them. These may be in direct contact with each other (e.g., laminated together) or there may be intervening layers.

[0027] As used herein, the term "polymer" is used in accordance with its ordinary meaning in the chemical arts. A polymer is composed of many repeating subunits, which may be the same (a homopolymer) or they may be different (a copolymer). The term "polymer" is used to describe a material obtained by a polymerization reaction.

[0028] The term "phr" refers to the amount of a component per 100 parts of resin, a measure used in the rubber industry (usually described as the amount per 100 parts of rubber), and particularly represents the amount of a specific component required before vulcanization. The term phr and parts per 100 parts by weight of all monomers present in the reaction mixture are used interchangeably.

[0029] The term "alkyl" means a monovalent group that is a group of an alkane, which is a saturated hydrocarbon. Alkyl may be linear, branched, cyclic, or a combination thereof, and typically has from 1 to 20 carbon atoms. In some embodiments, an alkyl group contains from 1 to 18, from 1 to 12, from 1 to 10, from 1 to 8, from 1 to 6, or from 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

[0030] The terms "free-radical polymerizable" and "ethylenically unsaturated" are used interchangeably and refer to a reactive group containing a carbon-carbon double bond that can be polymerized via a free-radical polymerization mechanism.

[0031] As used herein, the term "long-term durability" refers to the property of an adhesive article that adheres to mammalian skin and can remain adhered for a long period of time. Long periods of time include 10 days, 20 days, 30 days, and more than 30 days. A long-term durability article is also removable from mammalian skin after a long period of time.

[0032] As used herein, the term “microstructure” means the configuration of a feature part in which at least two dimensions are microscopic. Local and / or cross-sectional views of this feature part must be microscopic.

[0033] As used herein, the term “microscopic” refers to a feature element that is small enough that visual assistance is required to determine its shape when viewed from any plane of the field of view. One criterion is found in *Modern Optic Engineering* by W.S. Smith, McGraw-Hill, 1966, pages 104–105, which states that “...is defined and measured in terms of the visual angle of the smallest identifiable character.” Normal visual acuity is considered to be when the smallest identifiable character corresponds to a height of 5 / 5 arc on the retina. At a typical working distance of 250 mm (10 inches), this results in a lateral dimension of 0.36 mm (0.0145 inches) for this object.

[0034] This specification discloses a crosslinked adhesive composition comprising a non-polar crosslinked (meth)acrylate copolymer and a hydrogenated hydrocarbon tackifier. The crosslinked adhesive composition is the product of a hot-meltable blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier. The (meth)acrylate copolymer is the reaction product of a reaction mixture comprising at least one alkyl (meth)acrylate monomer having 4 to 22 carbon atoms and an alkyl group that does not have polar groups, and a copolymerizable photocrosslinking agent. The hot-melt-processed blend of the (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier is photocrosslinked to form a crosslinked adhesive composition.

[0035] The crosslinked adhesive composition is prepared by hot-melt blending a crosslinkable (meth)acrylate copolymer and a hydrogenated hydrocarbon tackifier, and photocrosslinking the (meth)acrylate copolymer. The crosslinkable (meth)acrylate copolymer is acidic, basic, or does not have polar groups such as hydroxyl groups. The crosslinkable (meth)acrylate copolymer is prepared from the reaction product of a reaction mixture comprising at least one alkyl (meth)acrylate monomer having 4 to 22 carbon atoms and an alkyl group that does not have polar groups, and a copolymerizable photocrosslinking agent. The reaction mixture also contains a free radical initiator. In some embodiments, the reaction mixture may contain additional (meth)acrylate monomers or other free radical polymerizable monomers, and may contain additional components, such as polyfunctional (meth)acrylates and chain transfer agents. The reaction mixture typically contains at least one (meth)acrylate monomer and a copolymerizable photocrosslinking agent as polymerizable components. Each of these components is described in more detail below.

[0036] The reaction mixture is based on general formula I: [ka] (In the formula, R 1 R is a hydrogen or methyl group, 2 It comprises at least one (meth)acrylate monomer (which is an alkyl having 4 to 22 carbon atoms).

[0037] Suitable alkyl (meth)acrylate monomers include, but are not limited to, non-tertiary alkyl alcohols such as 1-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 1-methyl-1-butanol, 1-methyl-1-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 2-ethyl-1-hexanol, 3,5,5-trimethyl-1-hexanol, 3-heptanol, 2-octanol, 1-decanol, 1-dodecanol, and mixtures thereof, selected from the group consisting of esters of acrylic acid or methacrylic acid. Such monomeric acrylics or methacrylic esters are known and commercially available in the art.

[0038] In some embodiments, alkyl (meth)acrylate monomers having an alkyl group contain 8 to 18 carbon atoms. Particularly preferred examples of alkyl acrylate monomers are isooctyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate (also called octadecyl acrylate), dodecyl acrylate, and mixtures thereof.

[0039] The reaction mixture forming the (meth)acrylate copolymer also contains a copolymerizable photocrosslinker. The copolymerizable photocrosslinker is a substance containing free radical polymerizable groups that copolymerize with the monomers described above. The copolymerizable photocrosslinker also contains photosensitive groups, which, when exposed to wavelengths on the right side of light, typically high-intensity ultraviolet (UV) rays, form free radicals that can form crosslinks in the polymer. When the (meth)acrylate polymer is formed using a photoinitiator, the photocrosslinker is not activated by light of the same wavelength as the photoinitiator. In this way, the copolymerizable photocrosslinker is incorporated into the polymer and can be thermally processed because the crosslinker is thermally stable and remains intact until activated by the appropriate wavelength of light. This allows the copolymerizable photocrosslinker to be activated after the polymer has been hot-melt coated. The coated crosslinkable pressure-sensitive adhesive layer is exposed to a high-intensity UV lamp to bring about crosslinking. Examples of suitable UV lamps include medium-pressure mercury lamps or UV blacklights.

[0040] Suitable photocrosslinking agents are monoethylenically unsaturated aromatic ketone comonomers that do not have ortho-aromatic hydroxyl groups, such as those described in U.S. Patent No. 4,737,559 (Kellen et al.). Specific examples include para-acryloxybenzophenone (ABP), para-acryloxyethoxybenzophenone, para-N-(methylacryloxyethyl)-carbamoylethoxybenzophenone, para-acryloxyacetophenone, ortho-acrylamidoacetophenone, and acrylated anthraquinones. ABP-para-acryloxybenzophenone, also known as 4-acryloxybenzophenone, is particularly preferred.

[0041] Typically, such photocrosslinkers are used in amounts of about 0.05 phr to 0.50 phr. The term "phr" refers to the amount added per 100 parts of resin, a unit of measurement used in the rubber industry (usually expressed as the amount added per 100 parts of rubber), and specifically represents the amount of a particular component required before vulcanization. In this case, the term phr refers to parts by weight of the photocrosslinker per 100 parts by weight of all monomers present in the reaction mixture. In some embodiments, the photocrosslinker is present in an amount of about 0.10 parts by weight per 100 parts by weight of all monomers present in the reaction mixture.

[0042] The reaction mixture that forms a crosslinkable (meth)acrylate copolymer may also contain at least one difunctional (meth)acrylate monomer. Difunctional (meth)acrylates are well known as crosslinking agents for (meth)acrylate copolymers, but in the reaction mixture, the amount of difunctional (meth)acrylate is kept low so as not to form a highly crosslinked network, but to increase the molecular weight and possibly increase branching. Typically, the difunctional (meth)acrylate monomer is present in the reaction mixture in an amount of 0.01 phr to 1.00 phr. One particularly preferred difunctional (meth)acrylate is HDDA (hexanediol diacrylate).

[0043] The reaction mixtures that form crosslinkable (meth)acrylate copolymers may also contain free radical chain transfer agents, often simply referred to as chain transfer agents. Examples of useful chain transfer agents include, but are not limited to, those selected from the group consisting of carbon tetrabromide, mercaptans, alcohols, and mixtures thereof. A particularly preferred chain transfer agent is IOTG (isooctyl thioglycolate). Chain transfer agents and their use are well understood in the field of adhesives. Typically, the chain transfer agent is present in the reaction mixture in an amount of 0.05 phr to 0.50 phr.

[0044] One way to increase molecular weight is to incorporate polymer branching by adding both a bifunctional (meth)acrylate comonomer (e.g., 1,6-hexanediol diacrylate, or HDDA) and a free radical chain transfer agent (e.g., isooctyl thioglycolate, or IOTG).

[0045] The reaction mixture also contains at least one initiator. Typically, the initiator is a photoinitiator, meaning that the initiator is activated by light, typically ultraviolet (UV) light. Photoinitiators are well understood by those skilled in the art of (meth)acrylate polymerization. Examples of suitable free radical photoinitiators include DAROCURE 1173, DAROCURE 4265, IRGACURE 184, IRGACURE 651, IRGACURE 1173, IRGACURE 819, LUCIRIN TPO, and LUCIRIN TPO-L, all commercially available from BASF, Charlotte, NC. The photoinitiator DAROCURE 1173 is particularly preferred.

[0046] Generally, the photoinitiator is used in an amount of 0.01 to 2 parts by weight, more typically 0.1 to 0.5 parts by weight, per 100 parts by weight of the total reactive components.

[0047] Crosslinkable (meth)acrylate copolymers can be prepared by a variety of polymerization methods. Polymerization techniques include solvent polymerization, aqueous polymerization, or 100% solid polymerization. 100% solid polymerization methods include bulk polymerization and polymerization in a package. All of these methods are well known in the field of polymer technology.

[0048] In some embodiments, the crosslinkable (meth)acrylate copolymer is prepared within a thermoplastic package. This method is particularly suitable for hot-melt processing because the package is fed into a hot-melt processing apparatus such as an extruder and can be hot-melt blended. A method for preparing a hot-meltable packaging adhesive composition is described in U.S. Patent No. 5,804,610 (Hamer et al.). The hot-meltable packaging adhesive composition of the present disclosure comprises a hot-meltable adhesive comprising a crosslinkable (meth)acrylate copolymer formed from a polymerizable pre-adhesive reaction mixture, and a package material. These pre-adhesive reaction mixtures are substantially free of polar monomers and are described above. The pre-adhesive reaction mixtures typically comprise at least one alkyl (meth)acrylate monomer, a copolymerizable photocrosslinker, and at least one initiator. In some embodiments, the pre-adhesive composition contains other components such as a chain transfer agent and / or a bifunctional (meth)acrylate. Each of these components is described in more detail above.

[0049] As described above, the crosslinked pressure-sensitive adhesive comprises the above-mentioned crosslinked (meth)acrylate copolymer and further comprises at least one hydrogenated hydrocarbon tackifier. The hydrogenated hydrocarbon tackifier is substantially free of unsaturated groups and also free of polar groups. A wide range of hydrogenated hydrocarbon tackifiers are preferred. Suitable resins include those available from Aquent Impex under the trade names ES300, ES320, ES340, ES380, ES600, and ES615, as well as those available from Arakawa Chemical under the trade name ARKON, such as ARKON M-100, ARKON M-115, ARKON M-135, ARKON M-90, ARKON P-100, ARKON P-115, ARKON P-125, ARKON P-140, ARKON P-90, and ARKON P-70. Similarly, resins manufactured by Eastman Chemical under the trade names REGALREZ and REGALITE, such as REGALREZ 1085, REGALREZ 1094, REGALREZ 3102, REGALREZ 1126, REGALREZ 1139, REGALREZ 6108, REGALITE S1100, REGALITE S5100, REGALITE R7100, REGALITE R9010, and REGALITE R9100, are preferred.

[0050] A hydrogenated hydrocarbon tackifier is hot-melt blended with a crosslinkable (meth)acrylate copolymer and placed on the surface to form an adhesive layer. The adhesive layer is then crosslinked by exposure to UV light to form a crosslinked pressure-sensitive adhesive layer. Typically, the crosslinked pressure-sensitive adhesive layer contains less than 50% by weight of the hydrogenated hydrocarbon tackifier. In some embodiments, the crosslinked adhesive composition contains 10% to 40% by weight of the hydrogenated hydrocarbon tackifier.

[0051] Since the tackifying resin is hydrocarbon-based, such as a crosslinked (meth)acrylate copolymer, and does not have polar groups, the crosslinked pressure-sensitive adhesive layer is highly hydrophobic, and therefore, according to conventional logic for medical adhesives, it is expected to have a very low MVTR and thus low long-term durability. However, as will be discussed below, the crosslinked pressure-sensitive adhesive layer of this disclosure has good long-term durability.

[0052] The crosslinked pressure-sensitive adhesive layer may have any suitable thickness depending on the desired application. In some embodiments, the thickness is at least 10 micrometers and up to 2 millimeters, and in some embodiments, the thickness is at least 20 micrometers and up to 1 millimeter. A wide range of intermediate thicknesses, such as 25 to 500 micrometers and 200 to 400 micrometers, are also suitable.

[0053] In addition to the crosslinked (meth)acrylate copolymer and the hydrogenated hydrocarbon tackifier, the crosslinked pressure-sensitive adhesive layer may further contain one or more additives. A wide variety of additives are suitable, as long as they do not impair the usefulness of the pressure-sensitive adhesive layer in medical articles. Additives can be added to the reaction mixture as long as they do not interfere with the polymerization reaction. In addition, additives can be added to the (meth)acrylate copolymer during the hot-melt process.

[0054] As described above, in embodiments in which the (meth)acrylate copolymer is polymerized within the package, the package containing the crosslinkable (meth)acrylate copolymer is placed in a hot-melt extruder, crushed, mixed with a hydrogenated hydrocarbon tackifier, coated onto a substrate, and crosslinked to form a crosslinked pressure-sensitive adhesive layer. One artifact of this process is that the hot-melt processing of the packaged (meth)acrylate copolymer generates particles of the package material within the crosslinked pressure-sensitive adhesive layer. Therefore, in many embodiments, the crosslinked pressure-sensitive adhesive further comprises particles formed from the package material, which is a thermoplastic polymer. A wide variety of thermoplastic polymers are suitable. Examples of suitable thermoplastic polymers include polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene acrylic acid ionomer, polypropylene, acrylic polymer, polyphenylene ether, polyphenylene sulfide, acrylonitrile-butadiene-styrene copolymer, polyurethane, and mixtures and blends thereof.

[0055] Other suitable optional additives that may be included in the crosslinked pressure-sensitive adhesive layer include plasticizers, antioxidants, fillers, leveling agents, UV absorbers, hindered amine light stabilizers (HALS), oxygen inhibitors, wetting agents, rheology modifiers, defoamers, biocides, dyes, pigments, and the like. All of these additives and their uses are well known in the art. It should be understood that any of these compounds can be used as long as they do not adversely affect the adhesive properties.

[0056] Adhesive articles are also disclosed herein. Adhesive articles have long-lasting adhesion. In this case, long-lasting adhesion means that the adhesive article can adhere to mammalian skin for at least 10 days. In some embodiments, the adhesive article can adhere to mammalian skin for at least 20 days, 30 days, or longer. The adhesive article comprises a substrate having a first principal surface and a second principal surface, and a crosslinked adhesive layer having a first principal surface and a second principal surface, wherein the first principal surface of the adhesive layer is at least partially located on the second principal surface of the substrate. The crosslinked adhesive layer is as described above. Typically, the crosslinked adhesive layer comprises a crosslinked adhesive composition comprising a crosslinkable (meth)acrylate copolymer and a hydrogenated hydrocarbon tackifier. As described above, the crosslinked adhesive composition is a product of a hot-meltable blend of a crosslinkable (meth)acrylate copolymer and a hydrogenated hydrocarbon tackifier. Crosslinkable (meth)acrylate copolymers are reaction products of a reaction mixture comprising at least one alkyl (meth)acrylate monomer having 4 to 22 carbon atoms and an alkyl group that does not have polar groups, and a copolymerizable photocrosslinking agent. Typically, the reaction mixture also comprises a photoinitiator and may include, as described above, a bifunctional (meth)acrylate comonomer (e.g., 1,6-hexanediol diacrylate, or HDDA) and / or a free radical chain transfer agent (e.g., iso-octyl thioglycolate, or IOTG).

[0057] As described above, in some embodiments, the crosslinkable (meth)acrylate copolymer is prepared in a thermoplastic package, the packaged copolymer is hot-melt blended with a hydrogenated hydrocarbon tackifier, the hot-melt blend is placed on the substrate surface to form an adhesive layer, and the adhesive layer is crosslinked to form a crosslinked (meth)acrylate-based pressure-sensitive adhesive layer.

[0058] In some embodiments, the second main surface of the crosslinked adhesive layer includes a structured surface, typically a microstructured surface.

[0059] Microstructures can be imparted to adhesive layers in various different ways. Typically, an adhesive composition is applied to a microstructured surface to form a microstructured adhesive layer. The substrate can then be brought into contact with this microstructured adhesive layer to form an adhesive article. Another method for imparting a microstructured adhesive layer is to form an adhesive layer by bringing the adhesive composition into contact with the substrate surface, and then bringing this adhesive layer into contact with the microstructured surface. Each method has its advantages and disadvantages. In the case of a crosslinked microstructured adhesive layer, it is typically desirable to induce crosslinking of the adhesive while it is in contact with the microstructured surface so that the adhesive is crosslinked in a microstructured state. In this way, the microstructure becomes substantially permanent. When a crosslinked pressure-sensitive adhesive is in contact with a microstructured surface, the microstructure is not permanent upon removal of the microstructured surface.

[0060] The adhesive composition can be applied to a microstructured surface, such as a microstructured release liner or microstructured tool, by any conventional application method, including but not limited to extrusion coating, gravure coating, curtain coating, slot coating, spin coating, screen coating, transfer coating, brush or roller coating, etc. The adhesive composition can be applied to the microstructured surface as a hot melt composition, a solvent-based composition, or a 100% solid composition. The adhesive layer coating can be further processed to produce an adhesive layer. This processing may include drying the adhesive layer coating in the case of a solvent-based composition, cooling the adhesive layer coating in the case of a hot melt coating, or crosslinking the adhesive layer. If desired, crosslinking can be performed by applying heat or radiation, or a combination thereof. Typically, the thickness of the coated adhesive layer in liquid form depends in part on the properties of the material used and the specific properties to be desired, but these properties and the relationship between thickness and properties are well understood in the art. An exemplary thickness of the adhesive layer may range from about 0.05 micrometers to about 100 micrometers.

[0061] Typically, microstructured release liners are used to impart a microstructured pattern within the adhesive layer, because the release liner remains with the adhesive layer during transport and processing and is removed only when the adhesive article is used. In this way, the adhesive layer is protected until the article is used. A wide range of microstructured release liners are preferred. Typically, microstructured release liners are manufactured by embossing. This means that the release liner has an embossable surface that, upon application of pressure and / or heat, comes into contact with a structured tool to form an embossed surface. This embossed surface is a structured surface. The structure on the embossed surface is an inversion of the structure on the tool surface; that is, protrusions on the tool surface form recesses on the embossed surface, and recesses on the tool surface form protrusions on the embossed surface.

[0062] A wide variety of patterns and shapes can exist on the microstructured surface of a release liner. The shape or pattern of the structure is not critical if the pattern is pre-embossed onto the release liner before contact with the adhesive layer, or if the structure is imparted to the release liner surface by embossing through the release liner when it contacts the adhesive layer. Structures can have a wide range of shapes and sizes. Generally, a structure is a microstructure, meaning a microstructure feature having at least two microscopic dimensions. Microstructure features can take on various shapes. Typical examples include hemispheres, prisms (square prisms, rectangular prisms, cylindrical prisms, and other similar polygonal features), pyramids, ellipses, grooves (e.g., V-grooves), channels, etc. Generally, it is desirable to include topographic features that facilitate air evacuation at the bonding interface when the adhesive layer is laminated onto the substrate. In this regard, V-grooves and channels extending to the edges of the article are particularly useful. The specific dimensions and patterns characterizing the microstructure features are selected based on the specific application for which the article is intended.

[0063] A wide range of substrates are suitable for use in the adhesive articles of this disclosure. The substrate may be monolithic or multilayer in structure, as described below. In a multilayer structure, the substrate may have various coatings or layers, either adjacent to the substrate or as a first or second surface of the substrate.

[0064] A wide range of substrates are preferred, including release liners and medical substrates. The release liner is a sheet material having a low-adhesion coating on at least one surface. The hot-meltable pressure-sensitive adhesive of this disclosure can be placed on a release liner to produce an article containing a layer of pressure-sensitive adhesive on the release liner. Using this adhesive / release liner article, other adhesive / substrate articles can be produced by laminating the adhesive layer onto a different substrate and then removing the release liner. This makes it possible to place the adhesive on substrates where it is difficult to directly place a hot-meltable pressure-sensitive adhesive, such as heat-sensitive substrates. The adhesive / release liner article may also be used to apply the pressure-sensitive adhesive layer to articles such as electrodes and fistula-forming devices.

[0065] Exemplary medical substrates include polymer materials, plastics, natural polymer materials (e.g., collagen, wood, cork, silk, and leather), paper, cloth, fabrics, nonwovens, metals, glass, ceramics, composites, and combinations thereof. The medical substrate may also be a tape backing. A suitable example of a tape backing is a breathable, adaptable backing on which an adhesive is placed. A wide range of breathable, adaptable backings are suitable for use in the articles of this disclosure. Typically, breathable, adaptable backings include woven or knitted fabrics, nonwovens, or plastics.

[0066] In some embodiments, the breathable adaptive backing includes a highly water vapor permeable film backing. Examples of such backings, methods for manufacturing such films, and methods for testing their permeability are described, for example, in U.S. Patents 3,645,835 and 4,595,001. Typically, such backings are porous materials.

[0067] Generally, backings are conformable to anatomical surfaces. Therefore, when applied to an anatomical surface, the backing conforms to that surface even if the surface moves. Generally, backings are also conformable to the anatomical joints of animals. When a joint is flexed and then returned to its unflexed position, the backing stretches to adapt to the flexion, but it retains sufficient elasticity to continue conforming to the joint when it returns to its unflexed position.

[0068] Particularly suitable backings can be found in U.S. Patents No. 5,088,483 and No. 5,160,315, and include elastomer polyurethane, polyester, or polyether block amide films. These films have a desirable combination of properties, including elasticity, high water vapor permeability, and transparency.

[0069] The article may include additional optional layers. In some embodiments, it may be desirable to have a primer layer between the substrate surface and the pressure-sensitive adhesive layer. Generally, the primer layer comprises a material commonly referred to as a “primer” or “adhesion promoter.” Primers and adhesion promoters are materials applied as a thin coating on a surface, which adheres strongly to the surface and provides a modification of the interfacial chemistry on the surface. Examples of suitable coating materials include polyamides, poly(meth)acrylates, chlorinated polyolefins, rubbers, chlorinated rubbers, polyurethanes, siloxanes, silanes, polyesters, epoxys, polycarbodiimides, phenolic resins, and combinations thereof. Typically, the articles of this disclosure do not require a primer layer, as the hot-meltable pressure-sensitive adhesive placed on the substrate surface tends to form a strong interaction with a wide range of substrate surfaces, making a primer unnecessary.

[0070] In some embodiments, it may be desirable for the first main surface of the substrate, i.e., the surface not coated with the adhesive structure, to have a low-adhesion coating. This is especially true when the adhesive article is supplied in tape form. Many tapes are supplied as rolls, and the adhesive layer comes into contact with the non-adhesive "back" side of the backing when wound up. Often, this non-adhesive surface of the backing has a low-adhesion or release coating on it so that the roll can be unwound. These low-adhesion coatings are often called "low-adhesion backsizing" or LAB. Whether a LAB coating is necessary or desirable is controlled by many factors, including the properties of the adhesive, the composition and topography of the backing, and the desired application of the tape article. [Examples]

[0071] These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. All parts, percentages, ratios, etc., in the examples and elsewhere in this specification are by weight unless otherwise indicated. The solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company; Milwaukee, Wisconsin unless otherwise noted. The following abbreviations are used: cm = centimeter, mm = millimeter, RPM = revolutions per minute, mW = milliwatt, mJ = millijoule, FPM = feet / min, MPM = meters per minute. The term "phr" refers to parts by weight per 100 parts by weight of (meth)acrylate monomer.

[0072] [Table 1]

[0073] Procedures and Test Methods Bulk photopolymerization: The acrylate polymer formulations were prepared according to the method described in U.S. Patent No. 6,294,249 (Hamer et al.).

[0074] Hot melt coating process: The packaged acrylate polymer was blended with a tackifier in a twin-screw extruder at a temperature in the range of 145°C to 180°C and a screw speed of 300 rpm. The blended adhesive mixture was coated onto a paper release liner through a contact die to a desired film thickness in the range of 25 micrometers to 150 micrometers.

[0075] UV curing process: The coated adhesive film was cured either in-line or (b) offline UV crosslinking. For (a) in-line curing, the coated adhesive film was annealed in an in-line oven at 200°F (93°C) at a line speed of 3 fpm (0.9 mpm) for 20 seconds, with a curing rate of 50 mJ / cm². 2The film was cured in an inline UV station with the specified UVC dose. b) For offline curing, the coated adhesive film was annealed in a bench oven at 200°F (93°C) for 10 minutes at 50 mJ / cm². 2 It was cured using an offline UV station with the specified UVC dosage.

[0076] Wearability Test Method Test sample dressings were prepared by hand laminating UV-curing adhesive onto meltblown nonwoven polyurethane medical tape backing (CoTran 9700, 3M Company, St. Paul, MN) of the desired thickness, as listed in Table 2. The laminates were die-cut into 33 mm square patches with rounded corners. A 29 mm square acrylic plate, 1.6 mm thick and with rounded corners, was bonded to the center of the patch using 3M Medical Tape 9889 (3M Company, St. Paul, MN), die-cut to the same dimensions as the plate.

[0077] The wearability study involved two male volunteers who had the sample attached to the underside of their arms. The only restriction on activity was that swimming or any other prolonged immersion of the sample in water was prohibited. No precautions were taken to keep the sample dry during exercise or showering. The endurance time reported in Table 2 is the day the sample detached. If the sample remained attached 45 days after application, it was removed on that day.

[0078] Most samples were attached to both the right and left arms by a single volunteer. The large variation in the attachment time of comparable samples (15 and 26 days in Examples 3 and 4) was associated with insufficient placement of the samples on the arms, resulting in premature failure of one of the two samples.

[0079] Examples Example 1 Using the bulk photopolymerization procedure provided above, the base polymer was formulated with 100 parts DAIB, 0.2 parts / resin (phr) of photoinitiator, 0.065 phr of ABP, 0.04 phr of IOTG, 0.03 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared base polymer was blended with TACK-1 in a mass ratio of 85-15, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured in-line. The cured adhesive was then tested according to the adhesion test method described above.

[0080] Example 2 The base polymer was formulated using the bulk photopolymerization procedure provided above with 100 parts DAIB, 0.2 phr of photoinitiator, 0.065 phr of ABP, 0.04 phr of IOTG, 0.03 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 80-20, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0081] Example 3 The base polymer was formulated using the bulk photopolymerization procedure provided above with 100 parts DAIB, 0.2 phr of photoinitiator, 0.065 phr of ABP, 0.04 phr of IOTG, 0.03 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 70-30, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0082] Example 4 The base polymer was formulated using the bulk photopolymerization procedure provided above with 100 parts DAIB, 0.2 phr of photoinitiator, 0.065 phr of ABP, 0.04 phr of IOTG, 0.03 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 65-35, and this blend was extruded onto a paper release liner using the hot-melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0083] Example 5 The base polymer was formulated using the bulk photopolymerization procedure provided above with 100 parts DAIB, 0.2 phr of photoinitiator, 0.065 phr of ABP, 0.05 phr of IOTG, 0.032 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 65-35, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0084] Example 6 The base polymer was formulated using the bulk photopolymerization procedure provided above with 100 parts DAIB, 0.2 phr of photoinitiator, 0.065 phr of ABP, 0.05 phr of IOTG, 0.032 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-2 in a mass ratio of 65-35, and this blend was extruded onto a paper release liner using the hot-melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0085] Comparative Example 1 Using the bulk photopolymerization procedure provided above, the base polymer was formulated with 98 parts DAIB, 2 parts AA, 0.2 phr of photoinitiator, 0.05 phr of ABP, 0.06 phr of IOTG, 0.045 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was extruded onto a paper release liner using the hot-melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0086] Comparative Example 2 Using the bulk photopolymerization procedure provided above, the base polymer was formulated with 98 parts DAIB, 2 parts AA, 0.2 phr of photoinitiator, 0.05 phr of ABP, 0.06 phr of IOTG, 0.045 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 80-20, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0087] Comparative Example 3 Using the bulk photopolymerization procedure provided above, the base polymer was formulated with 98 parts DAIB, 2 parts AA, 0.2 phr of photoinitiator, 0.05 phr of ABP, 0.06 phr of IOTG, 0.054 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 90-10, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0088] Comparative Example 4 Using the bulk photopolymerization procedure provided above, the base polymer was formulated with 98 parts DAIB, 2 parts AA, 0.2 phr of photoinitiator, 0.05 phr of ABP, 0.06 phr of IOTG, 0.054 phr of HDDA, and 0.4 phr of antioxidant. The as-prepared polymer was blended with TACK-1 in a mass ratio of 90-10, and this blend was extruded onto a paper release liner using the hot melt coating process described above. The extruded adhesive film was then UV-cured offline. The cured adhesive was then tested according to the adhesion test method described above.

[0089] [Table 2]

[0090] [Table 3]

Claims

1. A crosslinked (meth)acrylate copolymer having no polar group, a hydrogenated hydrocarbon tackifier resin, and a crosslinked adhesive composition comprising: at least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 22 carbon atoms and having no polar group, a copolymerizable photo-crosslinking agent and a (meth)acrylate copolymer containing a reaction product of a reaction mixture, and a hydrogenated hydrocarbon tackifier resin is a product of a hot-melt processable blend of the hot-melt processed blend is photo-crosslinked, a crosslinked adhesive composition.

2. The crosslinked adhesive composition according to claim 1, wherein the crosslinked adhesive composition contains less than 50% by weight of a hydrogenated hydrocarbon tackifier resin.

3. The crosslinked adhesive composition according to claim 1, wherein the crosslinked adhesive composition contains 10% to 40% by weight of a hydrogenated hydrocarbon tackifier resin.

4. The crosslinked adhesive composition according to claim 1, wherein at least one alkyl (meth)acrylate monomer having an alkyl group contains 8 to 18 carbon atoms.

5. The crosslinked adhesive composition according to claim 1, wherein the reaction mixture further contains at least one difunctional (meth)acrylate monomer.

6. The crosslinked adhesive composition according to claim 5, wherein the difunctional (meth)acrylate monomer constitutes 0.01 phr to 1.00 phr of the reaction mixture.

7. The crosslinked adhesive composition according to claim 1, wherein the reaction mixture contains 0.05 phr to 0.50 phr of a photo-crosslinking agent.

8. The crosslinked adhesive composition according to claim 1, wherein the crosslinked adhesive composition further contains particles of a thermoplastic polymer.

9. The crosslinked adhesive composition according to claim 8, wherein the hot-melt processable blend contains a packaged composition including a thermoplastic package surrounding the reaction mixture, and the particles of the thermoplastic polymer contain residues of the package material.

10. An adhesive article comprising a substrate including a first major surface and a second major surface, and a crosslinked adhesive layer having a first major surface and a second major surface, wherein the first major surface of the adhesive layer is at least partially disposed on the second major surface of the substrate, and the crosslinked adhesive layer is a crosslinked (meth)acrylate copolymer having no polar group, a hydrogenated hydrocarbon tackifier resin ​ A crosslinkable adhesive composition, the crosslinkable adhesive composition comprising at least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 22 carbon atoms and having no polar group, a copolymerizable photo-crosslinking agent a (meth)acrylate copolymer comprising a reaction product of a reaction mixture containing a hydrogenated hydrocarbon tackifier resin a hot-melt processable blend product, the hot-melt processed blend being photo-crosslinked, the adhesive article being capable of adhering to mammalian skin for at least 10 days, an adhesive article.

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