Acrylate-based pressure-sensitive adhesive containing hydrophobic oil

Abstract

A radiation-crosslinkable pressure-sensitive adhesive precursor comprising 50% to 90% by weight of an acrylic ester copolymer (the acrylic ester copolymer contains C4 to C16 acrylic monomers) and 10% to 50% by weight of a hydrophobic oil. The mixture of the pressure-sensitive adhesive precursor is crosslinked using electron beam radiation to provide an adhesive composition having a modified gel content of more than 50%, clean removal from stainless steel, immediate wettability to smooth and structured surfaces, controlled adhesiveness, and low adhesion enhancement. A method for preparing an adhesive comprising such a radiation-crosslinkable pressure-sensitive adhesive precursor and its crosslinked form, and an article comprising these adhesives are provided.

Description

Technical Field

[0001] The present disclosure generally relates to the field of adhesives, and more specifically to the field of radiation-curable pressure-sensitive adhesives containing acrylate copolymers and hydrophobic oils.

Background Art

[0002] Adhesives are used in a variety of applications such as marking, holding, protecting, sealing, and masking. Adhesive tapes generally include a backing or substrate and an adhesive. One type of adhesive, pressure-sensitive adhesive, is particularly preferred in many applications. Pressure-sensitive adhesives ("PSA") are widely known to those of ordinary skill in the art as having the following properties at room temperature: (1) strong and permanent adhesiveness, (2) adhering with a pressure of finger pressing, (3) having sufficient holding power to the adherend, and (4) having sufficient cohesive strength.

[0003] Materials that have been confirmed to function well as pressure-sensitive adhesives are polymers designed and prepared to exhibit the viscoelastic properties necessary to achieve the desired balance of adhesiveness, peel adhesion, and shear strength.

Summary of the Invention

[0004] In one aspect of the present disclosure, a radiation-curable pressure-sensitive adhesive precursor is provided, which contains 50 wt% to 90 wt% of an acrylate copolymer, the acrylate copolymer contains C4-C16 acrylic monomers, and 10 wt% to 50 wt% of a hydrophobic oil. The mixture of the pressure-sensitive adhesive precursor can be crosslinked using electron beam radiation, thereby having a modified gel content of more than 50%, enabling clean removal from stainless steel, exhibiting immediate wet-out on both smooth and structured surfaces, and obtaining an adhesive composition with controlled adhesiveness and low adhesive enhancement.

[0005] As another aspect of the present disclosure, a method for preparing an adhesive including the above radiation-crosslinkable pressure-sensitive adhesive precursor and a crosslinked form of the radiation-crosslinkable pressure-sensitive adhesive precursor is provided.

[0006] As another aspect of the present disclosure, articles including these adhesives are also provided in the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[0007] In the present disclosure, singular forms such as "a", "an", and "the" are often used for convenience, but it should be understood that the singular forms include the plural forms unless the singular form is specifically required or the context clearly indicates otherwise.

[0008] Polymers most commonly used in the preparation of pressure-sensitive adhesives ("PSA") include natural rubber, synthetic rubbers (e.g., styrene / butadiene copolymers ("SBR") and styrene / isoprene / styrene ("SIS") block copolymers), various (meth)acrylate (e.g., acrylate and methacrylate) copolymers, and silicones.

[0009] There is a need for an acrylate-based PSA that has at least the advantages of silicone gel-based PSA and can be cleanly and easily removed (e.g., gentle on the skin). Silicone gel is softer than silicone-based PSA and has characteristics such as low lift, low residue, the ability to adjust from "gentle on the skin" to "strong" skin adhesion by formulation change, adhesion performance at low temperatures, masking and rough surface tape applications, and adhesion to oily surfaces. Similarly, acrylate-based PSA also tends to form strong and positive bonds on smooth surfaces such as skin and stainless steel. Acrylate-based PSA is used in medical skin patches, but requires a balance of cohesive strength, removability without peeling the skin, and sufficient conformability to stay adhered to the skin for more than 24 hours without the edges lifting. Acrylate-based PSA is not usually modified with high concentrations of hydrophobic oil because of its original incompatibility and loss of cohesive strength. The combination of adding hydrophobic oil and electron beam crosslinking provides a gel that is softer than conventional acrylates, suppresses long-term adhesion enhancement, and reduces the force during removal.

[0010] The composition and performance of an adhesive depend on the use of the adhesive. In some applications, a tape with gentle adhesion is required, while in other applications, a strong tape is needed. When an adhesive is applied to a sensitive area of the body, generally a tape with gentle adhesion is used. However, when it is important for the adhesive to remain attached for a long time or when it is applied to a very mobile area, a stronger tape is used. The term "gentle adhesive" refers to an adhesive whose adhesive strength does not increase significantly over time. The term "strong adhesive" refers to an adhesive that has high resistance to lifting and peeling.

[0011] Medical adhesives are commonly used in wound dressings, surgical drapes, bandages, and tapes. These items typically consist of a backing material to which the adhesive is applied. A liner may or may not be used to protect the adhesive. The performance of the adhesive depends in part on the occlusivity of the backing material. The backing material is classified as either a non-occlusive or occlusive backing depending on its porosity. When a non-occlusive backing material is used in medical applications such as bandages, the resulting bandage typically does not adhere well to the skin over an extended period of time. Without being bound by a particular theory, this is presumably because the bandage cannot release water vapor, moisture is retained, and this causes the adhesive to lift from the skin.

[0012] Compliance and cohesion are two inversely correlated properties to consider when formulating or selecting a medical adhesive. It is desirable for a medical adhesive to conform to the shape of the skin of the application site as this can enhance the comfort of the wearer, and also because the adhesive can flow into the irregularities of the skin, potentially improving the initial adhesion to the skin. However, if the adhesive is too compliant, there may be insufficient cohesion required to remove the dressing cleanly from the skin. If the adhesive lacks cohesive strength, attempting to remove a bandage can result in the bandage adhesive splitting and leaving some residue of the adhesive adhered to the skin, while some of the adhesive peels off with the backing of the bandage. This property is unacceptable to most medical professionals and patients.

[0013] To address at least some of the above problems, the present disclosure provides a tacky, hydrophobic oil gel acrylic ester pressure sensitive adhesive (「PSA」) that is softer than common acrylic PSA by the addition of hydrophobic oil. The addition of hydrophobic oil results in an adhesive that may be useful for adhesion to smooth surfaces, rough surfaces, and skin surfaces. These PSAs can have properties such as, for example, a high oil loading (i.e., 10 - 50 wt%), a high modified gel content (i.e., greater than 50 wt%), no oily residue, and immediate wettability due to a low glass transition temperature (「Tg」) at 1 Hz frequency, for example in the range of -60 °C < Tg < -20 °C.

[0014] In some embodiments, the present disclosure provides a radiation curable pressure sensitive adhesive precursor comprising 40 wt% - 90 wt%, optionally 40 wt% - 80 wt%, optionally 50 wt% - 90 wt%, or optionally 50 wt% - 80 wt% of an acrylic ester copolymer and 10 wt% - 50 wt%, optionally 20 wt% - 40 wt% of a hydrophobic oil.

[0015] Acrylic ester copolymer Acrylic ester copolymers useful in embodiments of the present disclosure are known in the art and are described, for example, in U.S. Patent No. 9,102,774 (Clapper et al.), U.S. Reissue Patent No. 24,906 (Ulrich), and U.S. Patent No. 5,804,610 (Hamer et al.). Such acrylic acid ester copolymers can be prepared from C4 - C16 acrylic monomers by methods known to those of ordinary skill in the art.

[0016] In some preferred embodiments, the C4-C16 acrylic monomer contains 10 wt% to 100 wt%, optionally 20 wt% to 80 wt%, or optionally 30 wt% to 70 wt% of a C10-C16 acrylic monomer. The C10-C16 acrylic monomers useful in the embodiments of the present disclosure include those selected from primary (“1°”) acrylic monomers, secondary (“2°”) acrylic monomers, and combinations thereof. Examples of such C10-C16 acrylic monomers include, but are not limited to, decyl acrylate, isononyl acrylate, dodecyl acrylate, 2-propylheptyl acrylate, isodecyl acrylate, tridecyl acrylate, 2-decyl acrylate, 2-dodecyl acrylate, 2-tetradecyl acrylate, and combinations thereof.

[0017] In some preferred embodiments, the C4-C16 acrylic monomer contains 10 wt% to 100 wt%, optionally 20 wt% to 80 wt%, or optionally 30 wt% to 50 wt% of a C4-C8 acrylic monomer. Examples of such C4-C8 acrylic monomers include, but are not limited to, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, isooctyl acrylate, and combinations thereof. In some preferred embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor of the present disclosure comprises an acrylic ester copolymer that does not contain an insoluble gel as measured by a modified gel test. In some preferred embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor of the present disclosure comprises an acrylic ester copolymer that does not contain a polyfunctional acrylate such as, for example, hexanediol diacrylate, trimethylolpropane triacrylate. In some preferred embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can have a weight average molecular weight (“Mw”) measured by gel permeation chromatography (“GPC”) of 500,000 g / mol to 1,500,000 g / mol, optionally 750,000 g / mol to 1,000,000 g / mol.

[0018] Hydrophobic oil The hydrophobic oils useful in the embodiments of the present disclosure are typically oils with low solubility in water (i.e., less than 1 wt%). Commercial examples of such hydrophobic oils include paraffin oils such as KAYDOL USP grade oil from Sonneborn, Inc., and CALSO 9 series available from Calumet Specialty Products Partners, L.P. (Indianapolis, Indiana), naphthenic oils such as CALSOL 5 series available from Calumet Specialty Products Partners, L.P. (Indianapolis, Indiana) with a molecular weight range of 350 - 1000 grams / mol, and polypropylene glycols with a molecular weight range of 400 - 2000 grams / mol such as Polyglycol P - 1000E and P - 2000E available from Dow Chemical Company (Midland, Michigan).

[0019] As another classification of hydrophobic oils that may be useful, for example, polybutenes having terminal unsaturated groups such as INDOPOL L and H series from Ineos Oligomers (League City, Texas), and hydrogenated polybutenes such as PANALANE L and H series available from Vantage Specialty Chemicals (Deerfield, Illinois) can be mentioned. Useful polybutenes generally have a molecular weight range of 350 - 1500 grams / mol.

[0020] The presence of aromatic components has been observed to potentially reduce the electron beam curing efficiency. The hydrophobic oils compatible with the embodiments of the present disclosure have minimal interference with the electron beam curing process.

[0021] Additional additives The radiation - curable pressure - sensitive adhesive precursors of the present disclosure can include additional additives depending on the properties required for the final cross - linked pressure - sensitive adhesive.

[0022] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can further include up to 5 wt%, optionally up to 4 wt%, or optionally up to 2 wt% of a polar acrylic monomer. Examples of polar acrylic monomers useful in embodiments of the present disclosure include, but are not limited to, acrylic acid, N,N-dimethylacrylamide, and combinations thereof.

[0023] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include up to 10 wt%, up to 5 wt%, up to 4 wt%, or up to 2 wt% of a high-Tg acrylate monomer. Examples of high-Tg acrylate monomers useful in embodiments of the present disclosure include, but are not limited to, isobornyl acrylate, polystyrene macromonomer, and combinations thereof.

[0024] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include additives selected from photoinitiators, chain transfer agents, antioxidants, tackifying resins, and combinations thereof.

[0025] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include a predetermined amount of a photoinitiator in parts per hundred parts by weight of acrylic monomer (``pphm''). In some preferred embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include up to 0.1 pphm, up to 0.5 pphm, or up to 1 pphm of a photoinitiator. Examples of photoinitiators useful in embodiments of the present disclosure include, but are not limited to, 2,2-dimethoxy-1,2-diphenylethan-1-one (OMNIRAD 651, formerly IRGACURE 651), 2-hydroxy-2-methyl-1-phenylpropan-1-one (OMNIRAD 1173), 1-hydroxy-cyclohexyl-phenyl-ketone (OMNIRAD 184), and combinations thereof, commercially available from IGM Resins USA Inc. (Charlotte, North Carolina).

[0026] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include a predetermined amount of a chain transfer agent in parts per hundred parts by weight (``pphm'') per 100 parts by weight of the acrylic monomer. In some preferred embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include up to 0.001 pphm, up to 0.005 pphm, or up to 0.01 pphm of the chain transfer agent. Examples of chain transfer agents useful in embodiments of the present disclosure include, but are not limited to, isooctyl thioglycolate (``IOTG''), carbon tetrabromide (``CBr4''), and combinations thereof.

[0027] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include a predetermined amount of an antioxidant in parts per hundred parts by weight (``pphm'') per 100 parts by weight of the acrylic monomer. In some preferred embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can include up to 0.1 pphm, up to 0.2 pphm, up to 0.5 pphm, or up to 1 pphm of the antioxidant. Examples of antioxidants useful in embodiments of the present disclosure include bulky phenolic compounds that are primary antioxidants, including IRGANOX 1076 (octadecyl-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and IRGANOX 1010 (pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate]) antioxidants available from BASF Corporation, and combinations thereof, but are not limited thereto.

[0028] In some embodiments, the radiation-crosslinkable pressure-sensitive adhesive precursor can contain up to 20 wt%, up to 10 wt%, up to 5 wt%, or up to 1 wt% of a tackifying resin. Solid tackifying resins useful in embodiments of the present disclosure typically impart tack to adhesives containing the radiation-crosslinkable pressure-sensitive adhesive precursor and have a softening point (“SP”) of less than 120°C. Examples of commercially available useful solid resins include resins derived from C5 aliphatic hydrocarbons, such as the ESCOREZ 1000 series from ExxonMobil Chemical Company (Irving, Texas), the WINGTACK series from Kraton Corporation (Exton, Pennsylvania), the PICCOTAC series from Eastman Chemical Company (Kingsport, Pennsylvania), the QUINTONE series from Zeon Corporation (Tokyo, Japan), and the like. Other useful resins include cycloaliphatic C9 hydrocarbon resins, such as the ARKON P series (fully hydrogenated) and ARKON M series (partially hydrogenated) available from Arakawa Chemical Industries, Ltd. (Chicago, Illinois); cycloaliphatic C10 hydrocarbons, such as the ESCOREZ 5000 series from ExxonMobil Chemical Company; hydrogenated pure monomer resins, such as the REGALREZ series from Eastman Chemical Company; gum rosin esters, such as the FORAL series and STAYBELITE A and E series from Pinova Inc. (Brunswick, Georgia); tall oil rosin esters, such as the SYLVATAC and SYLVALITE series from Clayton Polymer Company (Houston, Texas), the WESTREZ 5000 series from MeadWestvaco Corporation (Richmond, Virginia), the PERMALYN series from Eastman Chemical Company; polyterpenes such as the PICCOLYTE A, F, C, and S series from Pinova Inc.; and terpene resins (turpentine) such as SYLVARES TP2019 from Clayton Polymer Company.Examples of useful liquid resins available commercially include polyterpenes derived from α-pinene available from Pinova under the trade name PICCOLYTE A25, polyterpenes derived from β-pinene available from Pinova under the trade name PICCOLYTE S25, aliphatic resins derived from hydrogenated C9 available from Eastman Chemical under the trade name REGALREZ 1018, the same resin available from Kremer Pigments under the trade name WINGTACK 10, and tall oil-based liquid rosin esters available from Clayton Polymers under the trade name SYLVALITE RE10L. The compatible tackifying resin should be a mixture of solid and liquid and should have minimal interference with the electron beam curing process. The presence of aromatic components may reduce the electron beam curing efficiency.

[0029] Preparation of a radiation-crosslinkable pressure-sensitive adhesive precursor and an adhesive, and an article containing the same The radiation-crosslinkable pressure-sensitive adhesive precursor of the present disclosure is known to those of ordinary skill in the art and is described in International Publication WO2016 / 106003 (D’Haese et al.) and can be easily prepared and processed via hot melt and solvent mixing and coating processes. The radiation-crosslinkable pressure-sensitive adhesive precursor mixture may be exposed to electron beam (EB) radiation to induce crosslinking of the radiation-crosslinkable pressure-sensitive adhesive precursor to obtain an adhesive composition. The EB dose suitable for embodiments of the present disclosure is typically from 4 megarads (MR) to 10 MR. Sufficient gel content and crosslinking are achieved, for example, at an acceleration energy of 6 MR and 175 kilovolts (kV) with a coating thickness of from 0.001 inches to 0.004 inches (0.00254 cm to 0.01016 cm). The final composition preferably has a modified gel content of greater than 50%. This corresponds to a crosslinking amount that enables flow initiation (i.e., no cross-over temperature of G’ / G’’) and clean removal without oily residue at a frequency of 1 Hz in a temperature range from room temperature (e.g., 22 °C) to above 150 °C. G’ represents the storage modulus and G’’ represents the loss modulus. The corresponding tangent delta (δ) is in the range of 0.4 to 0.6 at temperatures above 22 °C at a frequency of 1 Hz, providing a pressure-sensitive adhesive useful for clean removal from stainless steel. The coating composition can be mixed with a polymer component that is compatible prior to EB crosslinking and / or can be foamed.

[0030] The radiation-crosslinkable pressure-sensitive adhesives of the present disclosure and their radiation-crosslinkable pressure-sensitive adhesive precursors, particularly hot-melt and solution-processable adhesives and precursors, can be advantageously used in the manufacture of various adhesive tapes and articles. Many of these tapes and articles include a backing or other substrate for supporting the adhesive layer. On the other hand, there are also adhesive tapes and articles that do not include a backing or substrate layer and exist as independent adhesive layers. Double-sided tapes are an example of such adhesive articles. A double-sided tape (also called a "transfer tape") is a tape having adhesives on both exposed surfaces. In some transfer tapes, the exposed surfaces are the two sides of a single adhesive layer. Other transfer tapes are multi-layer transfer tapes having at least two adhesive layers, and these adhesive layers may be the same or different and may optionally include intermediate layers other than the adhesive layers. For example, a multi-layer transfer tape may have a three-layer structure of an adhesive layer, a film layer, and another adhesive layer. The film layer can provide handleability and / or tear strength, or other desirable properties. In the present disclosure, double-sided adhesives having a layer of a single self-supporting pressure-sensitive adhesive are manufactured. Since these double-sided adhesives are self-supporting, they need to have sufficient strength to be handled without a support layer.

[0031] The adhesives of the present disclosure are useful in the manufacture of medical supplies containing adhesives, such as surgical tapes, surgical drapes, bandages, athletic tapes, wound dressings, and the like. The adhesives disclosed herein can be applied to any backing material suitable for medical use, such as occlusive (virtually non-breathable) backing materials and non-occlusive (breathable) backing materials, using a solvent method or a hot melt method. Occlusive backing materials are also known as low-porosity backing materials. Examples of occlusive backing materials include, but are not limited to, films, foams, and laminates thereof. Examples of non-occlusive backing materials include, but are not limited to, woven backing materials, non-woven backing materials such as hydroentangled materials and meltblown webs, foams, and thermally embossed non-woven backing materials. The adhesives of the present invention can be applied continuously (knife or contact rod), discontinuously (e.g., stripe coating), or in a pattern, and can form spatially different (e.g., dots, triangles, squares) or differently thick regions on the backing material.

[0032] The objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, but the specific materials and their amounts, as well as other conditions and details described in these examples, should not be construed as unduly limiting the present disclosure.

Examples

[0033] Unless otherwise specified or not apparent from the context, all parts, percentages, ratios, etc. in the examples and other specifications are on a weight basis. Unless otherwise indicated, the materials used in the examples were obtained from commercial suppliers (e.g., Aldrich Chemical Co., Milwaukee, Wisconsin) and / or were prepared by known methods. The abbreviations used in the Examples section are as follows: pphm = parts per 100 parts by weight of acrylic monomer, EB = electron beam, rpm = revolutions per minute, in = inch, mil = thousandth of an inch, °F = Fahrenheit, °C = Celsius, min = minute, mW = milliwatt, cm 2 = square centimeter, oz = ounce, Hz = hertz.

Table 1

[0034] Test method Test method for gel content The samples were scraped from polyethylene terephthalate (PET) films after EB crosslinking. Approximately 0.5 grams of the adhesive component were weighed from each sample. In the following formula, this weight was taken as the sample weight. The weighed predetermined amount of sample was added to 50 grams of a 50 / 50 toluene / ethyl acetate solution in a glass bottle and placed on a rotator at room temperature for 1 - 2 days. This mixture was filtered through a 200 - mesh screen. The screen and the insoluble substances were dried at 220°F (104°C) for 1 - 2 hours. The weight of the insoluble component was measured and in the following formula, this was taken as the insoluble weight. The modified gel content was calculated based on the following formula.

Number

[0035] Adhesion test method to stainless steel Samples coated on PET films and EB crosslinked were tested for adhesion to stainless steel (ATSS) under controlled temperature and humidity (CTH) conditions. ATSS was measured at a peel angle of 180 degrees at a speed of 12 inches per minute (ipm) (4.7 cm / min). A tape 6 inches (3 cm) long and 1 inch (0.4 cm) wide was used, and the test was conducted within 5 minutes after the tape was attached to a cleaned steel panel. For this test, a 3M90 slip / peel tester available under the trade name of T65871 from Instrumentors, inc. (Strongsville, Ohio) was used. The tape was attached by passing it 4 times over a 4.5 - pound roller. The averaging time was 2 seconds at 12 ipm. The obtained peel force was recorded as ATSS, and the cleanliness of the steel surface was evaluated as the failure mode and recorded in Table 4.

[0036] Dynamic Mechanical Analysis (DMA) Test Method The tests were performed using an ARES-G2 rheometer available from TA Instruments (New Castle, Delaware) with 8 mm disposable parallel plates made of aluminum attached to the upper and lower fixtures. Using the "Low Temperature and High Temperature Ramp" test method, the temperature dependencies of tangent delta (Tanδ) and loss modulus / storage modulus (G'' and G', respectively) were measured at a frequency of 1 Hz. After EB crosslinking, the samples were scraped from the PET film using a dental pick, compacted to a thickness of 1 - 2 mm, and then thermally relaxed. After holding at 30 °C for 180 seconds, the first ramp of the DMA test was started at 30 °C, and the temperature was decreased at 3 °C / min until the defined Tanδ peak (glass transition temperature / Tg) was reached. In the second ramp of the DMA test, the temperature was increased from 30 °C to 150 °C at 3 °C / min. The Tanδ values were determined by combining the results of both ramps. To ensure that the material was within the linear viscoelastic region (LVR) during all temperature ramps, automatic strain adjustment was enabled.

[0037] Preparation Examples (PE-1 and PE-2) For each preparation example, the acrylic ester copolymer was prepared as follows. The acrylic monomers, IOTG, photoinitiator, and antioxidant A were placed in a flask in the amounts shown in Table 2 to prepare a monomer mixture. A magnetic stir bar was added to this mixture, and it was placed on a stirring plate to form a curable composition. An EVA film was heat-sealed to create an open-ended container measuring 18 cm × 5 cm. Each container was filled with approximately 24 grams of the curable composition. Air was evacuated from the open end, and then the ends were sealed using a heat sealer sold under the trade name "MIDWEST PACIFIC IMPULSE SEALER" available from J.J. Elemer Corp. (St. Louis, Missouri). The sealed EVA film container enclosing the curable composition was immersed in a constant temperature water bath at 16 °C, and ultraviolet light (365 nm, 4.5 mW / cm 2) was irradiated on both sides for 9 minutes each to polymerize the curable composition. The curable composition in the container was placed in a melt mixer for use in the examples and comparative examples described below.

Table 2

[0038] Examples (EX-1 to EX-6) and Comparative Examples (CE-1 and CE-2) Each sample (PE-1 or PE-2) was mixed with antioxidant B and KAYDOL in the amounts shown in Table 3 using a melt mixer (a twin-screw extruder with a diameter of 30 mm). For each sample, 140 grams of the mixture was charged into the mixer and mixed for 3 minutes at a screw speed of 150 rpm. The mixture was discharged through a heated gear pump operating at 200 rpm. The samples were coated onto a 1.2-mil-thick PET film or crepe paper, approximately 4 inches wide, at a coating weight of 18 grains / 24 square inches (thickness 0.003 inches - 75 grams per square meter (GSM)) using a contact die as shown in Table 3. A release-coated PET liner was laminated to the sample surface on the opposite side of the PET film or crepe paper. The samples were exposed to radiation from an electron beam source using an electron beam generator Model CB-300 manufactured by Energy Sciences, Inc. (Wilmington, Massachusetts). The uncured material was EB irradiated through the release liner. The composition of the samples, the EB dose after the release liner, and the coating weight are shown in Table 3. The property evaluation of the samples after EB irradiation is shown in Table 4.

Table 3

Table 4

[0039] All documents, patents, and patent applications cited in this patent application are hereby incorporated by reference in their entirety in a consistent manner. In the event of any inconsistency or conflict between the incorporated portions of the documents and this application, the description in the foregoing specification shall prevail. The foregoing description of the specification is provided to enable those skilled in the art to practice the claimed subject matter of the present disclosure and should not be construed as limiting the scope of the present disclosure.

Claims

1. A radiation-crosslinkable pressure-sensitive adhesive precursor, comprising: 40% to 90% by weight of an acrylate copolymer containing a C4-C16 acrylic monomer; and 10% to 50% by weight of a hydrophobic oil A radiation-crosslinkable pressure-sensitive adhesive precursor containing the same.

2. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, comprising 40% to 80% by weight, optionally 50% to 90% by weight, or optionally 50% to 80% by weight of the acrylate copolymer.

3. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the C4-C16 acrylic monomer contains 10% to 100% by weight, optionally 20% to 80% by weight, or optionally 30% to 70% by weight of a C10-C16 acrylic monomer.

4. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 3, wherein the C10-C16 acrylic monomer is selected from the group consisting of primary acrylic monomers, secondary acrylic monomers, and combinations thereof.

5. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 4, wherein the C10-C16 acrylic monomer is selected from the group consisting of decyl acrylate, isononyl acrylate, 2-dodecyl acrylate, 2-propylheptyl acrylate, isodecyl acrylate, tridecyl acrylate, 2-decyl acrylate, 2-tetradecyl acrylate, and combinations thereof.

6. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the C4-C16 acrylic monomer contains 10% to 100% by weight, optionally 20% to 80% by weight, or optionally 30% to 50% by weight of a C4-C8 acrylic monomer.

7. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 6, wherein the C4-C8 acrylic monomer is selected from the group consisting of butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, isooctyl acrylate, and combinations thereof.

8. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, comprising 10% to 50% by weight, optionally 20% to 40% by weight, of the hydrophobic oil.

9. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the hydrophobic oil is selected from the group consisting of paraffin oil, naphthenic oil, polypropylene glycol having a molecular weight range of 400 to 2000 g / mol, polybutene having a molecular weight range of 350 to 1500 g / mol, and combinations thereof.

10. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, further comprising 0.01% to 5% by weight, optionally 0.01% to 4% by weight, or optionally 0.01% to 2% by weight of a polar acrylic monomer.

11. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 10, wherein the polar acrylic monomer is selected from the group consisting of acrylic acid, N,N-dimethylacrylamide, and combinations thereof.

12. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, further comprising 0.1% to 10% by weight, optionally 0.1% to 5% by weight, or optionally 2% to 5% by weight of a high-Tg acrylic monomer.

13. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the high-Tg acrylic monomer is selected from the group consisting of isobornyl acrylate, polystyrene macromonomer, and combinations thereof.

14. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, further comprising an additive selected from the group consisting of a photoinitiator, a chain transfer agent, an antioxidant, an adhesion-imparting resin, and combinations thereof.

15. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the weight-average molecular weight (Mw) measured by gel permeation chromatography is from 500,000 g / mol to 1,500,000 g / mol, optionally from 750,000 g / mol to 1,000,000 g / mol.

16. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the acrylic ester copolymer does not contain an insoluble gel as measured by a modified gel test.

17. The radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1, wherein the acrylic ester copolymer does not contain a polyfunctional acrylate.

18. An adhesive comprising the crosslinked form of the radiation-crosslinkable pressure-sensitive adhesive precursor according to claim 1.

19. The adhesive according to claim 18, wherein the crosslinked form of the radiation-crosslinkable pressure-sensitive adhesive precursor is formed by exposing the radiation-crosslinkable pressure-sensitive adhesive precursor to electron beam radiation.

20. The adhesive according to claim 18, wherein the modified gel content is from 50% by weight to 90% by weight, optionally from 50% by weight to 80% by weight, or optionally from 50% by weight to 70% by weight.

21. An article comprising the precursor according to claim 1.

22. An article comprising the adhesive according to claim 18.

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