Radiation-stable pressure-sensitive adhesive

Abstract

A radiation-stable adhesive article comprises a substrate and a layer of adhesive composition. The adhesive composition is an acrylate-methacrylate copolymer prepared from a reaction mixture comprising at least one alkyl acrylate having an alkyl group having at least four carbon atoms and at least one alkyl methacrylate having an alkyl group having at least four carbon atoms. The adhesive composition is a pressure-sensitive adhesive and is radiation-stable, meaning that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and after exposure to electron beam radiation, gamma-ray radiation, X-ray radiation, or a combination thereof, the peel adhesion is at least 80% of the peel adhesion of the same composition not exposed to electron beam radiation, gamma-ray radiation, X-ray radiation, or a combination thereof.

Description

[Technical Field]

[0001] This specification discloses adhesive compositions and adhesive articles that are radiation-stable. In some embodiments, the adhesive composition comprises an acrylate-methacrylate copolymer prepared from a reaction mixture comprising at least one alkyl acrylate having an alkyl group containing at least four carbon atoms and at least one alkyl methacrylate having an alkyl group containing at least four carbon atoms. The adhesive composition is a pressure-sensitive adhesive and is radiation-stable, where radiation-stable means that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and after exposure to electron beam radiation of 30 KGy to 60 KGy, gamma ray radiation of 30 KGy to 60 KGy, X-ray radiation of at least 25 KGy, or a combination thereof, the peel adhesion to protein leather is at least 80% of the peel adhesion to protein leather of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof.

[0002] Also disclosed is an adhesive article comprising a first substrate having a first main surface and a second main surface, and a first pressure-sensitive adhesive layer disposed on the second main surface of the first substrate, wherein the first pressure-sensitive adhesive layer is a layer of the adhesive composition described above. [Modes for carrying out the invention]

[0003] The use of adhesive products in the medical industry has long been widespread and is increasing. However, while adhesives and adhesive articles have shown to be very useful for medical applications, there are also problems with their use. In particular, the desired properties of adhesives are often contradictory. For example, it is desirable for adhesives to have high adhesion to many surfaces, including human skin, but it is also desirable for adhesives to be removable without damaging the skin. In addition, the lifespan of medical articles is becoming longer, and medical articles need to remain adhered and be removable without damaging the skin or leaving any residue.

[0004] Medical adhesive-related skin injury (MARSI) poses a significant threat to patient safety. Skin injuries associated with the use of medical adhesives are a common but often overlooked complication that can occur in any care setting and at any age. Furthermore, treating skin injuries incurs costs in terms of service provision, time, and additional treatments and supplies.

[0005] Skin damage occurs when the surface layer of the skin is removed along with medical adhesive products. This not only affects the integrity of the skin but also increases the risk of pain and infection, can enlarge the wound, and can delay healing, all of which reduce the patient's quality of life.

[0006] However, the pathophysiology of MARSI is only partially understood. Skin damage occurs when the adhesion between the skin and the adhesive is stronger than the adhesion between skin cells. When the adhesive strength exceeds the strength of the interaction between skin cells, aggregate breakdown occurs within the skin cell layer.

[0007] A typical medical adhesive article comprises an adhesive layer and a base layer, the base layer of which may be, for example, a tape backing. Other medical adhesive articles may have other base layers and may include multiple layers, devices, etc. In this case, the inherent properties of all components of the adhesive article must be considered in order to address these factors that may cause MARSI. The properties of the adhesive to be considered include cohesiveness over time and the corresponding adhesive strength, while the properties of the tape / backing / dressing material to be considered include breathability, elasticity, fit, flexibility, and strength.

[0008] A class of adhesive materials widely used as pressure-sensitive adhesives includes (meth)acrylate-based pressure-sensitive adhesives. These materials often possess many desirable properties, such as not requiring the use of tackifying agents because they are often inherently tacky, and are typically formed with high conversion rates by free-radical polymerization (meaning little to no unpolymerized monomers remain in the formed pressure-sensitive adhesive). A wide range of monomers can be used to form (meth)acrylate copolymers, allowing for the modification of desired properties in the pressure-sensitive adhesive.

[0009] The evolving use of adhesives and adhesive articles extends beyond their traditional application to wound sites. A wide range of medical articles, such as tapes and drapes, are not applied to the wound site itself, but rather play a supporting role in treatment, such as holding absorbable materials or medical devices in place on the skin. Examples of medical devices held in place with tape include tubes, catheters, ostomy devices, and sensors.

[0010] However, while adhesives and adhesive articles have shown to be very useful in medical applications, there are also problems with their use. One growing problem is that many medical adhesive articles are sterilized using radiation such as gamma rays, electron beams (E-beams), or X-rays. Each of these sterilization techniques has its advantages and disadvantages, which are summarized below.

[0011] Gamma-ray radiation consists of photons produced by the decay of radioactive atomic nuclei (e.g., cobalt-60), and therefore, the dose rate depends on the decay. Photons have no mass and can penetrate deep into matter, but they cannot cause changes that affect the energy spectrum. As a result, medium to high-density materials are ideal for gamma-ray treatment.

[0012] E-beam radiation refers to high-energy electrons generated by a machine. Since electrons have mass, their penetration is limited by their energy. This makes electron beam technology highly useful for low-to-medium density products and more preferable for processing boxes compared to whole pallets. Furthermore, considering the nature of the technology, e-beams are very suitable for sensitive products because they can deliver doses significantly faster than gamma rays or X-rays—in seconds or minutes, rather than hours. In this case, the reaction lifetime is orders of magnitude shorter, thus reducing harmful effects.

[0013] Industrial X-rays are generated using an electron beam accelerator coupled to a metal target. When electrons collide with the metal target, X-rays are produced. X-rays are also composed of photons (but have different energies than gamma rays), and therefore, X-rays are also potentially well-suited for medium to high-density products. The dose rate is also higher than that of gamma rays, but because they are mechanical, they are limited or slower compared to e-beams. For example, to deliver a standard sterilization dose of 25 kGy, it takes about 2.5 hours or more using gamma ray emission, 45 minutes to 1 hour using X-rays, and a few seconds to a few minutes using e-beam technology.

[0014] Exposure of adhesive articles, particularly (meth)acrylate adhesive articles, to such radiation can have harmful side effects. E-beams, gamma rays, and X-ray radiation are known to induce the formation of free radicals in such polymer matrices, and these free radicals form crosslinks within the polymer matrix. In many cases, this crosslinking adversely affects the adhesive properties of the adhesive article.

[0015] One technique used to counteract crosslinking of adhesive articles when exposed to sterile E-beam, gamma, or X-ray radiation is to include additives in the polymer matrix, such as materials used as tackifiers, to prevent crosslinking from occurring. Examples of such materials include hydrogenated rosin, hydrogenated rosin esters, hydrogenated terpene resins, and aliphatic petroleum resins. However, these additives can cause skin irritation and other problems, which can be problematic in adhesive layers that adhere to mammalian skin.

[0016] This specification discloses a methodology for maintaining the adhesive properties of an adhesive layer upon exposure to sterile E-beam, gamma-ray, or X-ray radiation by constructing an adhesive matrix designed to compensate for crosslinking associated with radiation exposure.

[0017] It has been discovered that the use of a mixture of acrylate-functional monomers and methacrylate-functional monomers generates a matrix in which not only crosslinking but also chain breakage occurs upon exposure to sterile E-beam, gamma ray, or X-ray radiation. In this way, the formation of chemical bonds by crosslinking is balanced by the breaking of chemical bonds within the matrix. As a result of this balance, upon exposure to sterile E-beam, gamma ray, or X-ray radiation, the matrix does not form a highly crosslinked adhesive matrix, and therefore does not form a matrix with reduced adhesive properties or a non-adhesive matrix, but rather the matrix retains its adhesive properties.

[0018] This specification discloses adhesive compositions comprising an acrylate-methacrylate copolymer prepared from a reaction mixture containing at least one alkyl acrylate and at least one alkyl methacrylate. The adhesive compositions are pressure-sensitive adhesives and are radiation-stable. Radiation stability means that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and that after exposure to electron beam radiation of 30 KGy to 60 KGy, gamma ray radiation of 30 KGy to 60 KGy, X-ray radiation of at least 25 KGy, or a combination thereof, the peel adhesion to protein leather is at least 80% of the peel adhesion to protein leather of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof. Adhesive articles containing these adhesive compositions are also disclosed.

[0019] As used herein, the term “adhesive” refers to a polymer composition useful for bonding two adherends together. An example of an adhesive is a pressure-sensitive adhesive.

[0020] It is well known to those skilled in the art that pressure-sensitive adhesive compositions possess the following properties: (1) strong and permanent tackiness, (2) adhesion under pressure less than finger pressure, (3) sufficient ability to be retained on a substrate, and (4) sufficient cohesive force to be easily removed from the substrate. Materials found to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit the viscoelastic properties necessary to provide a desirable balance of tackiness, peel adhesion, and shear retention. Achieving the right balance of properties is not an easy process.

[0021] The term "(meth)acrylate" refers to an ester of an alcohol of monomeric acrylic acid or methacrylic acid. Acrylates and methacrylate monomers or oligomers are collectively referred to as "(meth)acrylate" in this specification. A material referred to as "(meth)acrylate functional" is a material containing one or more (meth)acrylate groups.

[0022] The terms "room temperature" and "ambient temperature" are used interchangeably to mean a temperature in the range of 20°C to 25°C.

[0023] The terms "Tg" and "glass transition temperature" are used interchangeably. When measuring, the Tg value is determined by DMA (dynamic viscoelastic analysis) at 1 Hz unless otherwise indicated. Often, the Tg value of a copolymer is not measured, but as understood by those skilled in the art, it is calculated using the well-known Fox equation using the Tg value of the homopolymer of that monomer provided by the monomer supplier.

[0024] The term "adjacent" as used herein when referring to two layers means that the two layers are in close proximity to each other without an intervening open space therebetween. They may be in direct contact with each other (e.g., laminated together), or there may be intervening layers.

[0025] The terms "polymer" and "macromolecule" are used herein in accordance with their general usage in chemistry. Polymers and macromolecules are composed of many repeating subunits. As used herein, the term "macromolecule" is used to describe a group bonded to a monomer having a plurality of repeating units. The term "polymer" is used to describe the resulting material formed from a polymerization reaction. [[ID=?]] [[ID=?]]

[0026] [[ID=?]] The term "alkyl" refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. Alkyl can be linear, branched, cyclic, or a combination thereof, and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 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.

[0027] The term "aryl" refers to a monovalent group that is aromatic and has a carbocyclic structure. An aryl group may have one to five rings bonded to or fused to an aromatic ring. Other ring structures may be aromatic, non-aromatic, or a combination thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perilenyl, and fluorenyl.

[0028] The term "alkylene" refers to the divalent radical of an alkane. Alkylenes can be straight-chained, branched, cyclic, or a combination of these. Alkylenes often have 1 to 20 carbon atoms. In some embodiments, alkylenes contain 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The radical center of an alkylene may be on the same carbon atom (i.e., alkylidene) or on different carbon atoms.

[0029] The term "arylene" refers to a carbocyclic, aromatic, divalent group. This group has 1 to 5 rings that are linked, condensed, or a combination thereof. The other rings may be aromatic, non-aromatic, or a combination thereof. In some embodiments, the arylene group has up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or 1 aromatic ring. For example, the arylene group may be phenylene.

[0030] The term "heteroalkylene" refers to a divalent group containing at least two alkylene groups linked by thio, oxy, or -NR- (where R is alkyl). Heteroalkylenes can be linear, branched, cyclic, or a combination thereof, substituted with alkyl groups. Some heteroalkylenes are polyoxyalkylenes, where the heteroatom is oxygen, e.g., -CH2CH2(OCH2CH2) n OCH2CH2- That is the case.

[0031] The terms "free radical polymerizable" and "ethylenically unsaturated" are used interchangeably and refer to reactive groups containing carbon-carbon double bonds that can be polymerized via free radical polymerization mechanisms.

[0032] As used herein with respect to adhesives, the terms “radiation-stable” and “radiation stability” mean that the adhesive retains at least one adhesive property upon exposure to E-beam radiation, gamma-ray radiation, X-ray radiation, or a combination thereof. In many embodiments, the retained adhesive property described is the peel adhesion to protein leather, and retention of this property means that, after exposure to radiation, the adhesive maintains at least 80% of the peel adhesion to protein leather compared to the same composition that has not been exposed to radiation. Other measurement techniques may also be used to determine radiation stability.

[0033] This specification discloses adhesive compositions. Many of these adhesive compositions are suitable for medical applications, particularly for use in medical articles. The adhesive compositions comprise an acrylate-methacrylate copolymer prepared from a reaction mixture containing at least one alkyl acrylate and at least one alkyl methacrylate. The adhesive compositions are pressure-sensitive adhesives and are radiation-stable. Radiation-stable means that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and that after exposure to electron beam radiation of 30 KGy to 60 KGy, gamma ray radiation of 30 KGy to 60 KGy, X-ray radiation of at least 25 KGy, or a combination thereof, the peel adhesion to protein leather is at least 80% of the peel adhesion to protein leather of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof.

[0034] The acrylate-methacrylate copolymer has the formula 1: CH2=CR 1 -(CO)-OR 2 Formula 1 (wherein R 1 is hydrogen, -(CO)- is a carbonyl group C=O, and R 2 is an alkyl group containing at least 4 carbon atoms) and at least one alkyl acrylate of formula 2: CH2=CR 3 -(CO)-OR 4 Formula 2 (wherein R 3 is a methyl group, -(CO)- is a carbonyl group C=O, and R 4 is an alkyl group containing at least 4 carbon atoms) and at least one alkyl methacrylate, and is prepared from a reaction mixture containing the same.

[0035] A wide range of acrylates are suitable as at least one alkyl acrylate of formula 1. Typically, the alkyl acrylate has an alkyl group having at least 4 carbon atoms. Mixtures of alkyl acrylates are also suitable. Examples of suitable alkyl acrylates include butyl acrylate, isobutyl acrylate, pentyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, isononyl acrylate, n-nonyl acrylate, isoamyl acrylate, n-decyl (meth) acrylate, isodecyl acrylate, dodecyl acrylate, isobornyl acrylate, cyclohexyl acrylate, isostearyl acrylate, 2-methylbutyl acrylate, and combinations thereof.

[0036] In some embodiments, at least one alkyl acrylate of formula 1 is R 2The composition comprises at least one alkyl acrylate of formula 1, wherein the alkyl group has at least eight carbon atoms. The composition may also contain other alkyl acrylates.

[0037] In some embodiments, at least one alkyl acrylate of formula 1 is R 2 The composition comprises at least one alkyl acrylate of formula 1, wherein the alkyl group has at least 12 carbon atoms. The composition may also contain other alkyl acrylates.

[0038] A wide range of methacrylates are suitable as at least one alkyl methacrylate of formula 2. In some embodiments, the at least one methacrylate monomer includes n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, n-stearyl methacrylate, isostearyl methacrylate, isodecyl methacrylate, or a combination thereof.

[0039] In some embodiments, it may be desirable to select methacrylate monomers having a relatively low Tg. In this context, a relatively low Tg means a monomer selected to give the formed copolymer a Tg below 0°C. In some embodiments, the Tg of the copolymer may be below -10°C, or even below -15°C. Having methacrylate monomers with a relatively low Tg helps the adhesive composition adhere quickly and strongly to substrates such as mammalian skin.

[0040] In some embodiments, the at least one alkyl methacrylate monomer comprises a mixture of methacrylate monomers, the mixture comprising up to 30% by weight of tert-butyl methacrylate and at least one additional methacrylate monomer of formula 2.

[0041] As described above, the application of radiation to the adhesive composition induces the formation of chemical bonds through crosslinking, which is balanced by the disruption of chemical bonds within the matrix. This balance is achieved by a reaction mixture containing both acrylate monomers and methacrylate monomers. The reaction mixture can include a wide range of compositions. In some embodiments, the reaction mixture contains at least 10 mol% of methacrylate monomer. In other embodiments, the reaction mixture contains at least 20 mol% of methacrylate monomer. In yet another embodiment, the reaction mixture contains at least 40 mol% of methacrylate monomer.

[0042] The adhesive composition may optionally contain one or more additional components. In some embodiments, the reaction mixture further comprises at least one copolymerizable monomer. In some embodiments, the copolymerizable monomer may be a crosslinkable monomer. A photocrosslinker is particularly preferred. The photocrosslinker has free radical polymerizable groups for copolymerizing with the above monomers and also contains photosensitive groups. When exposed to light of the appropriate wavelength, typically high-intensity ultraviolet (UV) radiation, the photosensitive groups can form free radicals, which can form crosslinks in the polymer.

[0043] A suitable photocrosslinking agent for monoethylenically unsaturated aromatic ketone comonomers that do not contain ortho-aromatic hydroxyl groups, such as those described in U.S. Patent No. 4,737,559 (Kellen et al.). Specific examples include para-acrylooxybenzophenone (ABP), para-acrylooxyethoxybenzophenone, para-N-(methylacrylooxyethyl)-carbamoylethoxybenzophenone, para-acrylooxyacetophenone, ortho-acrylamidoacetophenone, and acrylic anthraquinone. ABP para-acrylooxybenzophenone and AeBP acrylooxyethylbenzophenone are particularly preferred.

[0044] The radiation stability of the adhesive compositions of this disclosure can be determined by various methods. As described above, the stability of the peel adhesion to protein leather is one indicator that the adhesive composition has radiation stability. In some embodiments, radiation stability can be measured by DMA (dynamic viscoelastic analysis). Some embodiments of the adhesive composition have a stable tanδ value at a temperature 160°C higher than the Tg of the adhesive composition. Stability means that the tanδ value after exposure to electron beam radiation of 30 KGy to 60 KGy, gamma ray radiation of 30 KGy to 60 KGy, X-ray radiation of at least 25 KGy, or a combination thereof, is at least 80% of the tanδ value of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof. tanδ is the ratio of the storage modulus (G”) to the loss modulus (G'), measured by DMA, and Tg is similarly measured by DMA at 1 Hz. A wide range of embodiments, particularly those containing at least 40 mol% of methacrylate monomer, have this tanδ property.

[0045] The adhesive composition may also contain non-reactive additives to modify the properties of the adhesive composition, provided that these additives do not adversely affect the adhesive properties or radiation stability properties of the adhesive composition. In some embodiments, the adhesive composition further includes at least one additive selected from plasticizers or liquid resins. Examples of suitable plasticizers include IOP (isooctyl palmitate) from Nikko, RHEODOL MO-60 (glycerol monooleate) from Kao Chemical, and KEYDOL (liquid paraffin) from Sonneborn. Examples of suitable liquid resins include Ester Gum HT (hydrogenated rosin ester) from Arakawa Chemical, Ester Gum AT (rosin ester) from Arakawa Chemical, YS RESIN CP (hydrogenated rosin ester) from Yasuhara Chemical, and DIMERONE (mixture of terpene polymer and petroleum hydrocarbon) from Yasuhara Chemical. Polyols, particularly polyester polyols available from Croda under the trade name PRIPLAST, may also be suitable.

[0046] Adhesive articles are also disclosed herein. In some embodiments, the adhesive article comprises a first substrate having a first main surface and a second main surface, and a first pressure-sensitive adhesive layer disposed on the second main surface of the first substrate. The first pressure-sensitive adhesive layer comprises an adhesive composition prepared from the above reaction mixture. In some embodiments, the reaction mixture is Formula 1: CH2=CR 1 -(CO)-OR 2 formula 1 (In the formula, R 1 is hydrogen, -(CO)- is a carbonyl group C=O, and R 2 (where is an alkyl group containing at least 4 carbon atoms) and at least one alkyl acrylate of formula 2: CH2=CR 3 -(CO)-OR 4 formula 2 (In the formula, R 3 is a methyl group, -(CO)- is a carbonyl group C=O, and R 4 The adhesive composition comprises at least one alkyl methacrylate (where is an alkyl group containing at least four carbon atoms). As described above, the adhesive composition is a pressure-sensitive adhesive and is radiation-stable, where radiation-stable means that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and after exposure to electron beam radiation of 30 KGy to 60 KGy, gamma ray radiation of 30 KGy to 60 KGy, X-ray radiation of at least 25 KGy, or a combination thereof, the peel adhesion to protein leather is at least 80% of the peel adhesion to protein leather of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof.

[0047] A wide variety of substrates are suitable. In some embodiments, the substrate comprises a release liner or tape backing. The release liner is well known in the field of adhesives and is a film that allows for easy removal of adhesive compositions or coatings. Exemplary release liners are those prepared from paper (e.g., kraft paper) or polymer materials (e.g., polyolefins such as polyethylene or polypropylene, ethylene vinyl acetate, polyurethane, polyesters such as polyethylene terephthalate, and combinations thereof). At least some release liners are coated with a layer of release agent, such as a fluorosilicone-containing material or a fluorocarbon-containing material.

[0048] In some embodiments, the release liner may be a microstructured release liner. Microstructured release liners are well known in the field of adhesives. Typically, a microstructured release liner is prepared by embossing a release liner having an embossable surface with a structuring tool to impart a structured surface to the release liner. The microstructured release liner imparts a microstructured surface to the adhesive layer in which it is placed.

[0049] Suitable tape backing materials include polymer films, foils, cloths, nonwovens, foams, paper, meshes, or combinations thereof. In many embodiments, the backing material conforms to uneven surfaces. Therefore, when the backing material is applied to an uneven surface, it conforms to the surface even if the surface moves. Examples of such backing materials can be found in U.S. Patents No. 5,088,483 and No. 5,160,315, and include elastomer polyurethanes, polyesters, or polyether block amide films. These films have a desirable combination of properties, including resilience, high water vapor permeability, and transparency.

[0050] In some embodiments, the tape backing material is optically transparent and includes polyester, polycarbonate, PS (polystyrene), CBC (cyclic block copolymer), polyolefin (including, but not limited to, BOPP (biaxially oriented polypropylene), COP (cyclic olefin polymer), COC (cyclic olefin copolymer), polypentene), or a combination thereof.

[0051] In some embodiments, the adhesive article further comprises a second pressure-sensitive adhesive layer disposed on a first main surface of a first substrate, wherein the second pressure-sensitive adhesive layer is the same as or different from the first pressure-sensitive adhesive layer. Such an article is a double-sided tape.

[0052] Suitable reaction mixtures, pressure-sensitive adhesive compositions, and components of the reaction mixture for forming a pressure-sensitive adhesive layer are described in detail above.

[0053] The pressure-sensitive adhesive layer can have a wide range of thicknesses. Generally, the pressure-sensitive adhesive layer has a thickness of 10 micrometers to 1 millimeter. [Examples]

[0054] 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 the remainder of the specification are in weight unless otherwise specified. The following abbreviations are used: cm = centimeter, mm = millimeter, in = inch, RPM = revolutions per minute, kg = kilogram, kGy = kilogray, keV = kiloelectronvolt, Hz = hertz, sec = second, min = minute, hrs = hour. The terms "weight %", "weight % (% by weight)", and "weight % (wt%)" are used interchangeably.

[0055] [Table 1]

[0056] Test method Rheology Test tanδ retention rate PSA samples with a diameter of 8 mm and a thickness of 1 mm were prepared, and rheological data before and after E-beam or gamma-ray treatment were measured using a rheometer MCR302 (Anton Parr) or ARES-G2 (TA Instrument). For vibrational shear (frequency = 1 Hz), a temperature gradient test method (-50°C to 180°C) was used for tanδ at a temperature 160°C higher than Tg (peak temperature of the tanδ curve).

[0057] Calculation formula: tanδ retention rate = (tanδ at a temperature 160°C higher than the post-treatment Tg / tanδ at a temperature 160°C higher than the pre-treatment Tg) × 100%

[0058] Adhesive Test Adhesion retention rate Tape samples measuring 25 mm x 75 mm were laminated onto a 30 mm x 100 mm protein leather using a 2 kg roller. The applied tape was removed by T-peel at a test speed of 90 inches / min (230 cm / min) using an SP-2100 (IMASS). The average peel force before and after E-beam or gamma ray treatment was measured. The formula for calculating the adhesive strength retention rate is as follows.

[0059] Calculation formula: Adhesion retention rate = (Adhesion after treatment / Adhesion before treatment) × 100%

[0060] Electron beam processing The samples were processed with an E-beam having an acceleration voltage of 200 keV and a dose of 60 kGy.

[0061] Gamma ray treatment The samples were treated with gamma-ray radiation at doses of 30 kGy or 60 kGy.

[0062] Example 1 of the study Examples 1-3 A radiation-stable adhesive layer was prepared according to the composition description below, tested according to the procedure described above, and the data is shown in the table below.

[0063] Polymer formation The adhesive compositions were prepared by preparing the reaction mixtures shown in Table 1 below, and were named Compositions 1 to 3. The reactive components and 119 parts by weight of water were placed in a bottle and homogenized at 15,000 rpm for 15 minutes. This dispersion and 0.2 parts of initiator-1 were placed in a glass jar. After purging with nitrogen for 10 minutes, polymerization was carried out at 65°C for 20 hours to prepare a copolymer emulsion with a solids content of 45%.

[0064] A thickening agent was added to the copolymer emulsion, and the pH was adjusted to 7-8 with NH3aq to obtain a viscous emulsion.

[0065] This viscous emulsion was coated onto the TSC surface of liner-1. After drying in an oven (7 minutes at 60°C and 2 minutes at 120°C), the formed PSA layer, which had a thickness of 3 mil (76 micrometers), was covered with liner-2.

[0066] [Table 2]

[0067] Adhesive tape is formed Adhesive tape samples were prepared by removing liner-2, corona-treating the adhesive surface, and then laminating backing material-1 using a thermal laminator.

[0068] Adhesive samples were tested using the rheological testing method described above, and tape samples were tested using the adhesive strength testing method described above. The adhesive and tape samples were exposed to E-beam radiation according to the processing procedure described above and tested according to the method described above. The data are shown in Tables 2 and 3. The example numbers correspond to the composition numbers in Table 1.

[0069] [Table 3]

[0070] [Table 4]

[0071] Example 2 of the study Examples 4-26 A radiation-stable adhesive layer was prepared according to the composition description below, tested according to the procedure described above, and the data is shown in the table below.

[0072] Polymer formation The adhesive compositions were prepared by preparing the reaction mixtures shown in Tables 4-7 below, and were named Compositions 4-26. The reaction components were placed in bottles. The solvent was 100 parts by weight of toluene for Compositions 4-17, and 100 parts by weight of EtOAC for the remaining compositions. After purging the solutions with nitrogen for 2 minutes, polymerization was carried out at 70°C for 20 hours to prepare viscous polymer solutions. Additives were mixed according to the formulation to obtain viscous coating solutions.

[0073] A viscous coating solution was coated onto the TSC surface of liner-1. After drying in an oven (60°C for 2 minutes, then 120°C for 2 minutes), a polymer layer with a thickness of 80 micrometers was prepared. The polymer layer was exposed to 200 mJ / cm2 of UV-C, and then the polymer layer was covered with liner-2.

[0074] [Table 5]

[0075] [Table 6]

[0076] [Table 7]

[0077] [Table 8]

[0078] Adhesive tape is formed Adhesive tape samples were prepared by removing liner-2, corona-treating the adhesive surface, and then laminating backing material-1 using a thermal laminator.

[0079] Adhesive samples were tested using the rheological testing method described above, and tape samples were tested using the adhesive strength testing method described above. The adhesive and tape samples were exposed to E-beam or gamma-ray radiation according to the processing procedure described above and tested according to the method described above. The data are shown in Tables 8-12. The example numbers correspond to the composition numbers in Tables 4-7.

[0080] [Table 9]

[0081] [Table 10]

[0082] [Table 11]

[0083] [Table 12]

[0084] [Table 13]

Claims

1. Formula 1 CH ２ =CR １ -(CO)-OR ２ Formula 1 (In the formula, R １ It is hydrogen, -(CO)- is a carbonyl group C=O, R ２ (It is an alkyl group containing at least four carbon atoms.) at least one alkyl acrylate, Formula 2 CH ２ =CR ３ -(CO)-OR ４ Formula 2 (wherein, R ３ is a methyl group, -(CO)- is a carbonyl group C=O, R ４ (It is an alkyl group containing at least four carbon atoms.) at least one alkyl methacrylate, Acrylate-methacrylate copolymer prepared from a reaction mixture containing An adhesive composition comprising, The adhesive composition is a pressure-sensitive adhesive and is stable to radiation, where stable to radiation means that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and after exposure to electron beam radiation of 30 kGy to 60 kGy, gamma ray radiation of 30 kGy to 60 kGy, X-ray radiation of at least 25 kGy, or a combination thereof, the peel adhesion to protein leather is at least 80% of the peel adhesion to protein leather of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof.

2. The adhesive composition according to claim 1, wherein the at least one alkyl acrylate includes butyl acrylate, isobutyl acrylate, pentyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, isononyl acrylate, n-nonyl acrylate, isoamyl acrylate, n-decyl (meth) acrylate, isodecyl acrylate, dodecyl acrylate, isobornyl acrylate, cyclohexyl acrylate, isostearyl acrylate, 2-methylbutyl acrylate, isodecyl acrylate, and combinations thereof.

3. The at least one alkyl acrylate is a compound of formula 1 (wherein R ２ The adhesive composition according to claim 1, comprising at least one alkyl acrylate monomer (where is an alkyl group having at least eight carbon atoms).

4. The adhesive composition according to claim 1, wherein the reaction mixture contains at least 10 mol% of the at least one methacrylate monomer.

5. The adhesive composition according to claim 1, wherein the reaction mixture contains at least 20 mol% of the at least one methacrylate monomer.

6. The adhesive composition according to claim 1, wherein the reaction mixture further comprises at least one copolymerizable monomer.

7. The adhesive composition according to claim 1, wherein stability to radiation means that the tanδ value, which is the ratio of the storage modulus (G'') to the loss modulus (G') measured by DMA (dynamic viscoelastic analysis) at a temperature 160°C higher than the Tg of the adhesive composition, is at least 80% of the tanδ value of the same composition not exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof, and Tg is measured by DMA at 1 Hz after exposure to electron beam radiation of 30 kGy to 60 kGy, gamma ray radiation of 30 kGy to 60 kGy, X-ray radiation of at least 25 kGy, or a combination thereof.

8. The adhesive composition according to claim 7, wherein the reaction mixture contains at least 40 mol% of the at least one methacrylate monomer.

9. The adhesive composition according to claim 1, wherein the at least one methacrylate monomer comprises n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, n-stearyl methacrylate, isostearyl methacrylate, or a combination thereof.

10. The at least one methacrylate monomer comprises a mixture of methacrylate monomers, the mixture comprising up to 30% by weight of tert-butyl methacrylate and formula 2: CH ２ =CR ３ -(CO)-OR ４ Formula 2 (In the formula, R ３ It is a methyl group, -(CO)- is a carbonyl group C=O, R ４ (It is an alkyl group containing 8 to 12 carbon atoms.) The adhesive composition according to claim 8, comprising at least one additional methacrylate monomer.

11. The adhesive composition according to claim 1, further comprising at least one additive selected from plasticizers or liquid resins.

12. A first substrate having a first main surface and a second main surface, Displaced on the second main surface of the first substrate, Formula 1 CH ２ =CR １ -(CO)-OR ２ Formula 1 (In the formula, R １ It is hydrogen, -(CO)- is a carbonyl group C=O, R ２ (It is an alkyl group containing at least four carbon atoms.) At least one alkyl acrylate, and Formula 2 CH ２ =CR ３ -(CO)-OR ４ Formula 2 (In the formula, R ３ It is a methyl group, -(CO)- is a carbonyl group C=O, R ４ at least one alkyl methacrylate (where is an alkyl group containing at least four carbon atoms) A first pressure-sensitive adhesive layer comprising an adhesive composition prepared from a reaction mixture containing, Adhesive articles including, Adhesive article wherein the adhesive composition is a pressure-sensitive adhesive and is radiation-stable, where radiation-stable means that the peel adhesion to protein leather is at least 0.5 Newtons / 25 mm, and after exposure to electron beam radiation of 30 kGy to 60 kGy, gamma ray radiation of 30 kGy to 60 kGy, X-ray radiation of at least 25 kGy, or a combination thereof, the peel adhesion to protein leather is at least 80% of the peel adhesion to protein leather of the same composition that has not been exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof.

13. The adhesive article according to claim 12, wherein the substrate comprises a release liner or a tape backing material.

14. The adhesive article according to claim 12, further comprising a second pressure-sensitive adhesive layer disposed on the first main surface of the first substrate, wherein the second pressure-sensitive adhesive layer is the same as or different from the first pressure-sensitive adhesive layer.

15. The adhesive article according to claim 12, wherein the reaction mixture contains at least 10 mol% of the at least one methacrylate monomer.

16. The adhesive article according to claim 12, wherein the reaction mixture further comprises at least one copolymerizable monomer.

17. The adhesive article according to claim 12, wherein stability to radiation means that the tanδ value, which is the ratio of the storage modulus (G'') to the loss modulus (G') measured by DMA (dynamic viscoelastic analysis) at a temperature 160°C higher than the Tg of the adhesive composition, is at least 80% of the tanδ value of the same composition not exposed to electron beam radiation, gamma ray radiation, X-ray radiation, or a combination thereof, and Tg is measured by DMA at 1 Hz after exposure to electron beam radiation of 30 kGy to 60 kGy, gamma ray radiation of 30 kGy to 60 kGy, X-ray radiation of at least 25 kGy, or a combination thereof.

18. The adhesive article according to claim 12, wherein the reaction mixture contains at least 40 mol% of the at least one methacrylate monomer.

19. The adhesive article according to claim 17, wherein the at least one methacrylate monomer includes n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, n-stearyl methacrylate, isostearyl methacrylate, or a combination thereof.

20. The at least one methacrylate monomer comprises a mixture of methacrylate monomers, the mixture comprising up to 30% by weight of tert-butyl methacrylate and formula 2: CH ２ =CR ３ -(CO)-OR ４ Formula 2 (In the formula, R ３ It is a methyl group, -(CO)- is a carbonyl group C=O, R ４ (It is an alkyl group containing 8 to 12 carbon atoms.) The adhesive article according to claim 19, comprising at least one additional methacrylate monomer.

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