Flame-retardant pressure-sensitive adhesive

Abstract

To provide an adhesive article that is optically transparent and flame-retardant. [Solution] The flame-retardant pressure-sensitive adhesive and tape comprises a base layer and a layer of pressure-sensitive adhesive disposed on the base layer. The pressure-sensitive adhesive is a UV-curable composition of a curable composition. The curable composition comprises a polymerizable (meth)acrylate mixture, a polymerizable aromatic (meth)acrylate oligomer, a liquid flame retardant, and at least one UV initiator. The UV-curable composition is a flame-retardant, optically transparent pressure-sensitive adhesive.

Description

[Technical Field]

[0001] This disclosure generally relates to the field of adhesives and tapes, and more specifically to flame-retardant pressure-sensitive adhesives and tapes. [Background technology]

[0002] Adhesives are used for a variety of marking, retention, protection, sealing, and shielding purposes. Adhesive tapes generally consist of a backing or substrate and an adhesive. Pressure-sensitive adhesives, a type of adhesive, are particularly useful in many applications.

[0003] 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 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 known to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit the viscoelastic properties necessary to provide a desired balance of tackiness, peel strength, 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 silicones. Each of these categories of materials has its own advantages and disadvantages. [Overview of the Initiative]

[0004] This disclosure generally relates to the field of adhesives and tapes, more specifically to flame-retardant pressure-sensitive adhesives and tapes. In some embodiments, an adhesive article includes a substrate layer having a first main surface and a second main surface, and a layer of pressure-sensitive adhesive disposed on at least a portion of the first main surface of the substrate layer. The pressure-sensitive adhesive includes a UV-curable composition of a curable composition, the curable composition including a polymerizable (meth)acrylate mixture, a polymerizable aromatic (meth)acrylate oligomer, a liquid flame retardant, and at least one UV initiator. The UV-curable composition is an optically transparent pressure-sensitive adhesive that has improved flame retardancy compared to the same adhesive article in which a comparative pressure-sensitive adhesive includes a UV-curable composition comprising a polymerizable (meth)acrylate mixture and at least one UV initiator.

[0005] Adhesive structures are also disclosed. In some embodiments, the adhesive structure includes a substrate having a first main surface and a second main surface, and an adhesive article in contact with the second main surface of the substrate. The adhesive article is the optically transparent, flame-retardant, pressure-sensitive adhesive article described above. [Modes for carrying out the invention]

[0006] The use of adhesives, particularly pressure-sensitive adhesives, is increasing. Areas where adhesive use is growing include the medical, electronics, and optical industries, as well as consumer goods and public transportation. These industries require adhesives with specialized functions. For example, there is a need for pressure-sensitive adhesives that offer additional functions beyond the conventional properties of tackiness, peel strength, and shear strength. Newer classes of materials are desirable to meet increasingly stringent performance requirements for pressure-sensitive adhesives. These performance requirements include optical clarity and flame retardancy. Optical clarity is often required because the adhesive layer is frequently a component of optical articles or devices, while flame retardancy is required to prevent or reduce the spread of fire to protect lives and property.

[0007] Flame-retardant adhesives can be prepared using various techniques. Often, flame-retardant additives are added to the adhesive to impart flame retardancy. Flame retardants are widely used in industry to reduce the flammability of plastic materials. These additives help make ignition of plastics more difficult, inhibit the combustion process, and limit heat generation. Adding flame-retardant additives to pressure-sensitive adhesives presents several challenges. Many commonly used flame-retardant additives are halogen-containing, such as polychlorinated biphenyls and polybrominated diphenyl ethers. However, halogen-containing materials are increasingly viewed as environmentally undesirable, and their use in adhesives is becoming increasingly restricted. While various non-halogenated flame-retardant additives have been developed, many may pose problems as additives to pressure-sensitive adhesives. In some cases, the additives are liquids, and these liquids act as plasticizers in the adhesive matrix. This plasticization of the pressure-sensitive adhesive affects the cohesive force of the matrix, which is problematic. One technique available to overcome this plasticization is to crosslink the pressure-sensitive adhesive or add high-Tg monomers to the pressure-sensitive adhesive matrix to increase the cohesive force and rigidity of the pressure-sensitive adhesive matrix. However, this technique has the problem that crosslinking or increasing the cohesive force of the pressure-sensitive adhesive matrix makes the pressure-sensitive adhesive too rigid, thus negatively affecting its adhesive properties.

[0008] Other flame retardant additives are solid and therefore do not plasticize the matrix; however, the presence of solid additives can still be problematic because it can adversely affect the optical properties of pressure-sensitive adhesives. In some cases, the presence of solid flame retardant additives can make the pressure-sensitive adhesive layer opaque.

[0009] Pressure-sensitive adhesives having various desirable properties in addition to the usual desirable properties of adhesives (peel strength, shear holding power, and tackiness) are disclosed herein. The adhesives are flame-retardant and optically transparent. This flame retardancy is achieved in some embodiments using halogen-containing flame retardant additives, and in other embodiments without halogen-containing flame retardant additives. The combination of flame retardancy and optical transparency is achieved by a combination of a flame retardant and a (meth)acrylate polymer matrix that has a balanced property of rigidity and flexibility.

[0010] This specification discloses optically transparent and flame-retardant adhesive articles and adhesive structures. In some embodiments, the adhesive article comprises a substrate and a layer of pressure-sensitive adhesive disposed on the substrate layer, the pressure-sensitive adhesive comprising a UV-curable composition of a curable composition comprising a polymerizable (meth)acrylate mixture, a polymerizable aromatic (meth)acrylate oligomer, a liquid flame retardant, and at least one UV initiator.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] It is well known to those skilled in the art that pressure-sensitive adhesive compositions possess the following properties: (1) strong and persistent tackiness, (2) adhesion under pressure less than finger pressure, (3) sufficient ability to bond adherends, and (4) sufficient cohesive force to remove cleanly from adherends. Materials known to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit the viscoelastic properties necessary to provide a desired balance of tackiness, peel adhesion, and shear retention. Achieving the right balance of properties is not a simple process.

[0015] The terms "halogen-containing" or "halogen-free" apply to materials, particularly additives for adhesives. Additives that are halogen-free essentially do not contain halogen atoms such as fluorine, chlorine, bromine, and iodine atoms. Additives that are halogen-containing have at least some hydrogen atoms substituted with halogen atoms.

[0016] Unless otherwise specified, "optically transparent" refers to an article, film, or adhesive that has high light transmittance over at least a portion of the visible light spectrum (approximately 400 to 700 nm). Typically, an optically transparent article has a luminous transmission of at least 80% of the visible light spectrum. The term "transparent film" refers to a film having a certain thickness. A film is used, and when the film is placed on a substrate, the image (placed on or adjacent to the substrate) is visible through the thickness of the transparent film. In many embodiments, the transparent film makes it possible to view the image through the thickness of the film without substantially losing the transparency of the image. In some embodiments, the transparent film has a matte or glossy finish.

[0017] Unless otherwise specified, "optically transparent" refers to an adhesive or article that has high light transmittance over at least a portion of the visible light spectrum (approximately 400 to 700 nm) and exhibits low haze. Typically, an optically transparent article has a light transmittance of at least 90%, often at least 95%, and a haze of less than 10%, often less than 5%, or even less than 2%.

[0018] The term "(meth)acrylate" refers to an ester of an alcohol, monomer acrylic, or methacrylic. Acrylates and methacrylate monomers or oligomers are collectively referred to as "(meth)acrylate" in this specification. The term "(meth)acrylate system," when used to describe polymers such as block copolymers, refers to polymers prepared from (meth)acrylate monomers. These polymers may contain only (meth)acrylate monomers, or they may contain monomers that are co-reactive with (meth)acrylate.

[0019] As used herein, the term "polymer" refers to a polymer material that is a homopolymer or copolymer. As used herein, the term "homopolymer" refers to a polymer material that is a reaction product of one monomer. As used herein, the term "copolymer" refers to a polymer material that is a reaction product of at least two different monomers.

[0020] The terms "tackifying resin," "tackifier," and "tackifying agent" are used interchangeably in this specification.

[0021] The terms "plasticizing resin", "plasticizing agent", and "plasticizer" are used interchangeably in this specification.

[0022] 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 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, ethylhexyl, n-lauryl, isodecyl, tridecyl, tetradecyl, hexadecyl, and octadecyl.

[0023] The term "aryl" refers to a monovalent group that is aromatic and a carbocyclic ring. Aryl may have 1 to 5 rings connected or fused to the 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, perylenyl, and fluorenyl.

[0024] The term "alkylene" refers to a divalent group that is a group of an alkane. Alkylene may be linear, branched, cyclic, or a combination thereof. Alkylene often has 1 to 20 carbon atoms. In some embodiments, alkylene contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The center of the alkylene group may be on the same carbon atom (i.e., alkylidene) or on different carbon atoms.

[0025] The term "heteroalkyl" refers to a monovalent group containing at least two alkylene groups linked by thio, oxy, or -NR- (where R is alkyl). Heteroalkyls may be linear, branched, cyclic, substituted with alkyl groups, or a combination thereof. Some heteroalkyls are, for example, CH3CH2(OCH2CH2) n These are polyoxyalkylenes, such as OCH2CH2-, where the heteroatom is oxygen.

[0026] The term "arylene" refers to a divalent group that is both a carbon ring and aromatic. This group has one to five rings that are linked, fused, or a combination thereof. The other rings may be aromatic, non-aromatic, or a combination thereof. In some embodiments, the arylene group may have up to five rings, up to four rings, up to three rings, up to two rings, or one aromatic ring. For example, the arylene group may be phenylene.

[0027] The term "heteroarylene" refers to a divalent group that is a carbon ring, aromatic, and contains heteroatoms such as sulfur, oxygen, nitrogen, or halogens such as fluorine, chlorine, bromine, or iodine.

[0028] The term "aralkill" is derived from the formula, -R a -Ar a [In the formula, R a It is alkylene, Ar a This refers to a monovalent group that is aryl (i.e., an alkylene bonded to an aryl group).

[0029] The terms "free radical polymerizability" and "ethylenically unsaturated" are used interchangeably and refer to reactive groups containing carbon-carbon double bonds that can be polymerized via the free radical polymerization mechanism.

[0030] This specification discloses adhesive articles that are optically transparent and flame-retardant. In some embodiments, the adhesive article comprises a substrate having a first main surface and a second main surface, and a layer of pressure-sensitive adhesive disposed on at least a portion of the first main surface of the substrate layer. The pressure-sensitive adhesive comprises a UV-curable composition of a curable composition comprising a polymerizable (meth)acrylate mixture, a polymerizable aromatic (meth)acrylate oligomer, a liquid flame retardant, and at least one UV initiator. The UV-curable composition is an optically transparent pressure-sensitive adhesive and has improved flame retardancy compared to the same adhesive article comprising a UV-curable composition comprising a polymerizable (meth)acrylate mixture and at least one UV initiator.

[0031] The adhesive article retains desirable peel-bonding properties in addition to having desirable optical clarity and flame retardancy. In some embodiments, the adhesive article has a pressure-sensitive adhesive layer with a peel-bonding strength of at least 40%, more typically at least 60%, of the same adhesive article containing a UV-curable composition comprising a (meth)acrylate mixture and at least one UV initiator. In some embodiments, the adhesive article has a peel-bonding strength of at least 65%, at least 70%, or even at least 80%, of the same adhesive article containing a pressure-sensitive adhesive layer with a UV-curable composition comprising a (meth)acrylate mixture and at least one UV initiator. Thus, the adhesive retains the desirable properties of a pressure-sensitive adhesive, with added optical clarity and flame retardancy.

[0032] A wide variety of substrates are suitable as the substrate layer of the adhesive article. The substrate may be, for example, a tape backing, the surface of the article, or a release liner. Examples of suitable tape backings include, for example, paper and polymer films. Examples of paper include clay-coated paper and polyethylene-coated paper. Examples of polymer films include films containing one or more polymers such as cellulose acetate butyrate; cellulose acetate propionate; cellulose triacetate; poly(meth)acrylates such as polymethyl methacrylate; polyesters such as polyethylene terephthalate and polyethylene naphthalate; naphthalenedicarboxylic acid copolymers or blends; polyethersulfone; polyurethane; polycarbonate; polyvinyl chloride; syndiotactic polystyrene; cyclic olefin copolymers; and polyolefins including polyethylene and polypropylene such as cast and biaxially oriented polypropylene, as well as fluorothermoplastic polymers. The substrate may be a single layer or a multilayer such as polyethylene-coated polyethylene terephthalate. The substrate may be primed or treated to impart some desired properties to one or more of its surfaces. Examples of such treatments include corona treatment, flame treatment, plasma treatment, and chemical treatment. Particularly suitable tape backings are prepared from polyethylene terephthalate (PET), polyurethane, or fluorothermoplastic polymers. Particularly suitable materials for polymer film substrates include polyester, vinyl, polyolefin, polyurethane, or combinations thereof.

[0033] In other embodiments, the substrate is the surface of an article. A wide variety of article surfaces are suitable, whether rigid (e.g., metal plates, glass plates, etc.) or flexible (e.g., cloth, woven fabrics, and non-woven fabrics). This could be woven web, foam, carpet, metal foil, etc.

[0034] The substrate may be a release liner. Any suitable release liner can be used. Exemplary release liners include those prepared from paper (e.g., kraft paper) or polymer materials (e.g., polyolefins such as polyethylene or polypropylene, ethylene vinyl acetate, polyurethane, and polyesters such as polyethylene terephthalate). At least some release liners are coated with a layer of release agent, such as a silicone-containing material or a fluorocarbon-containing material. Exemplary release liners include, but are not limited to, liners commercially available from CP Film (Martinsville, Va.) under the trade names "T-30" and "T-10," which have a silicone release coating on a polyethylene terephthalate film. The liner may have a microstructure on its surface, which is imparted to the adhesive to form a microstructure on the surface of the adhesive layer. The liner can then be removed to expose the adhesive layer having the microstructured surface.

[0035] In some embodiments, since the adhesive is optically transparent or optically transparent, the resulting article may be an optical element or may be used to prepare an optical element. As used herein, the term “optical element” refers to an article having an optical effect or optical application. Optical elements can be used, for example, in electronic displays, architectural applications, transportation applications, projection applications, optical communication applications and graphic applications. Suitable optical elements include, but are not limited to, screens or displays, cathode ray tubes, polarizers, and reflectors.

[0036] Any suitable optical film may be used in this article. As used herein, the term “optical film” refers to a film that can be used to produce an optical effect. Optical films are typically polymer-containing films, which may be single-layer or multi-layer. Optical films are flexible and may be of any suitable thickness. Optical films are often at least partially transparent, reflective, anti-reflective, polarizing, optically transparent, or diffusive to certain wavelengths of the electromagnetic spectrum (e.g., wavelengths in the visible, ultraviolet, or infrared regions of the electromagnetic spectrum). Exemplary optical films include, but are not limited to, visible light specular films, colored specular films, sunlight reflective films, infrared reflective films, ultraviolet reflective films, reflective polarizing films (such as brightness-enhancing films and dual brightness-enhancing films), absorptive polarizing films, optically transparent films, colored films, and anti-reflective films.

[0037] In some embodiments, the optical film has a coating. Generally, coatings can be used to enhance the functionality of the film or to provide additional functionality to the film. Examples of coatings include, for example, hard coats, anti-fog coatings, scratch-resistant coatings, privacy coatings, or combinations thereof. Highly durable coatings such as hard coats, anti-fog coatings, and scratch-resistant coatings are desirable in applications such as touchscreen sensors, display screens, and graphic applications. Examples of privacy coatings include, for example, obscuring or frosted coatings to obscure the view, or louvered films to limit the viewing angle.

[0038] Some optical films have multiple layers, such as multiple layers of polymer-containing materials (e.g., polymers containing or not containing dyes), or multiple layers of metal-containing materials and polymer materials. Some optical films have alternating layers of polymer materials with different refractive indices. Other optical films have alternating polymer layers and metal-containing layers. Exemplary optical films are described in the following patents: U.S. Patent No. 6,049,419 (Wheatley et al.); U.S. Patent No. 5,223,465 (Wheatley et al.); U.S. Patent No. 5,882,774 (Jonza et al.); U.S. Patent No. 6,049,419 (Wheatley et al.); U.S. Reissue Patent No. 34,605 ​​(Schrenk et al.); U.S. Patent No. 5,579,162 (Bjornard et al.); and U.S. Patent No. 5,360,659 (Arends et al.).

[0039] The adhesive article further includes a layer of pressure-sensitive adhesive disposed on at least a portion of the first main surface of the substrate layer. The layer of pressure-sensitive adhesive is a UV-cured layer of a UV-curable composition. The UV-curable composition comprises a polymerizable (meth)acrylate mixture, a polymerizable aromatic (meth)acrylate oligomer, a liquid flame retardant, and at least one UV initiator.

[0040] In some embodiments, the UV-curable composition comprises 61-75% by weight of a polymerizable (meth)acrylate mixture, 4-13% by weight of a polymerizable aromatic (meth)acrylate oligomer, 18-29% by weight of a liquid flame retardant, and at least one UV initiator, where the weight percentages are based on the total weight obtained by subtracting the UV initiator from the curable composition. Each of these elements is described in detail below.

[0041] The thickness of the pressure-sensitive adhesive layer depends on various factors, including the desired use of the adhesive article. Typically, the thickness of the adhesive layer tends to be greater than about 5 micrometers, greater than about 10 micrometers, greater than about 15 micrometers, or even greater than about 20 micrometers. The thickness is often less than about 1000 micrometers, less than about 250 micrometers, less than about 200 micrometers, or even less than about 175 micrometers. For example, the thickness may be about 5 to about 1000 micrometers, about 10 to about 500 micrometers, about 25 to about 250 micrometers, or about 50 to about 175 micrometers.

[0042] Polymerizable (meth)acrylate mixtures include coatable syrups which are partially polymerized mixtures of (meth)acrylate monomers. Coatable syrups which are partially polymerized mixtures of (meth)acrylate monomers have been used to prepare adhesive articles by coating and curing techniques. In this technique, the coatable mixture is coated onto a web and then photochemically cured overall. The web may be a backing, substrate, release liner, etc. It has been found that when the coatable mixture contains only monomers, the viscosity cannot be high enough to be easily coatable. Coatable syrups can be obtained by partially prepolymerizing the monomer mixture, for example, as described in U.S. Patent No. 6,339,111 (Moon et al.).

[0043] Current polymerizable (meth)acrylate mixtures are mixtures of at least one alkyl (meth)acrylate monomer and at least one reinforcing monomer. The material contains a wide variety of monomers suitable for use as alkyl (meth)acrylate monomers and reinforcing monomers. Generally, when polymerizable (meth)acrylate mixtures polymerize, they form a pressure-sensitive adhesive. The pressure-sensitive adhesive thus formed is used as a comparative adhesive to the adhesives of this disclosure.

[0044] Suitable alkyl (meth)acrylate monomers include those having a Tg of less than approximately 0°C as homopolymers. Examples of such alkyl (meth)acrylate monomers include, but are not limited to, those in which the alkyl group contains approximately 2 to 20 carbon atoms, such as n-butyl acrylate, 2-methylbutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof. Optionally, other vinyl monomers and alkyl (meth)acrylate monomers having a Tg greater than 0°C, such as methyl acrylate, methyl methacrylate, isobornyl acrylate, vinyl acetate, etc., can be used together with one or more alkyl (meth)acrylate monomers as homopolymers.

[0045] A polymerizable (meth)acrylate mixture also contains at least one reinforcing monomer. Typically, the reinforcing monomer is an acidic or basic monomer copolymerizable with the alkyl (meth)acrylate monomer, or a high Tg copolymerizable monomer such as styrene. A wide variety of copolymerizable acidic and basic monomers are preferred.

[0046] Useful acidic monomers include, but are not limited to, ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated phosphonic acids, and mixtures thereof. Examples of such compounds include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, oleic acid, beta-carboxyethyl acrylate, 2-sulfoethyl methacrylate, styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylphosphonic acid, and mixtures thereof. Due to their availability, ethylenically unsaturated carboxylic acids are typically used, and acrylic acid is a particularly preferred acidic monomer.

[0047] Examples of basic monomers include N,N-dimethylaminopropyl methacrylamide (DMAPMAm); N,N-diethylaminopropyl methacrylamide (DEAPMAm); N,N-dimethylaminoethyl acrylate (DMAEA); N,N-diethylaminoethyl acrylate (DEAEA); N,N-dimethylaminopropyl acrylate (DMAPA); N,N-diethylaminopropyl acrylate (DEAPA); N,N-dimethylaminoethyl methacrylate (DMAEMA); N,N-diethylaminoethyl methacrylate (DEAEMA); N,N-dimethylaminoethylacrylamide (DMAEAm); N,N-dimethylaminoethyl methacrylamide (DMAEMAm); N,N-diethylaminoethylacrylamide (DEAEAm); N,N-diethylaminoethyl methacrylamide (DEAEMAm); N,N-dimethylaminoethyl vinyl ether (DMAEVE); N,N-diethylaminoethyl vinyl ether (DEAEVE); and mixtures thereof. Other useful basic monomers include vinylpyridine, vinylimidazole, tertiary amino-functionalized styrenes (e.g., 4-(N,N-dimethylamino)-styrene (DMAS), 4-(N,N-diethylamino)-styrene (DEAS)), N-vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile, N-vinylformamide, (meth)acrylamide, and mixtures thereof. (Meth)acrylamide is a particularly preferred basic monomer because it is commercially available.

[0048] Typically, alkyl (meth)acrylate monomers constitute the majority of the polymerizable (meth)acrylate mixture, meaning that alkyl (meth)acrylate or a mixture of alkyl (meth)acrylates constitute more than 50% by weight, typically more than 70% by weight, of the curable mixture. Typically, reinforcing monomers are present in amounts of 1–30% by weight, more typically 2–20%, or even 2–10% by weight of the reaction mixture.

[0049] In some embodiments of the adhesive article, the pressure-sensitive adhesive layer is halogen-free. Halogen-free means that the monomers and liquid flame retardants essentially do not contain halogen atoms. In other embodiments described below, the polymerizable aromatic (meth)acrylate oligomer contains halogen atoms.

[0050] In a halogen-free pressure-sensitive adhesive layer, typically, the polymerizable aromatic (meth)acrylate oligomer includes at least one phosphorus-modified (meth)acrylate oligomer or monomer. Examples of phosphorus-modified (meth)acrylate oligomers include the bifunctional acrylated phosphorus-containing oligomer RAYLOK 1722 commercially available from ALLNEX, and the trifunctional acrylated phosphorus-containing monomer VISCOAT 3PA manufactured by Kowa Company.

[0051] In a halogen-free pressure-sensitive adhesive layer, the liquid flame retardant is also halogen-free. In some embodiments, the liquid flame retardant includes aryl phosphate. For example, various aryl phosphates such as the isopropylphenyl phosphate mixture commercially available as PHOSFLEX 31L from ICL Industrial Products are suitable.

[0052] In other embodiments of the adhesive article of the present disclosure, the pressure-sensitive adhesive layer is halogen-containing. In these embodiments, one or more elements in the UV-curable mixture that forms the pressure-sensitive adhesive layer upon curing are halogen-containing. In some embodiments, the polymerizable aromatic (meth)acrylate oligomer includes a halogen-modified polymerizable aromatic (meth)acrylate oligomer. The halogen-modified polymerizable aromatic (meth)acrylate oligomer has the general formula 1: Ar hal -O-(CO)-CR 1 =CH2 Formula 1 [where R 1 is H or a methyl group, (CO) is a carbonyl group C=O, and Ar halThe compounds include an aromatic group selected from phenyl, substituted phenyl, or condensed aromatic groups, wherein at least one hydrogen atom is substituted with a halogen atom.

[0053] A wide variety of compounds according to Formula 1 are suitable. In some particularly suitable embodiments, the compound of Formula 1 is R 1 H is and Ar hal This is a per-bromophenyl (C6Br5) group. This compound is commercially available from Sartomer as CN2601. Another compound is a material commercially available from ICL Industrial Products as FR-1025.

[0054] In halogen-containing embodiments, the liquid flame retardant may be halogenated or non-halogenated. Non-halogenated flame retardants are as described above. A wide variety of halogenated liquid flame retardants are preferred, such as halogenated trialkyl phosphate esters, including tris(2-chloroisopropyl) phosphate-based alkyl phosphate flame retardants commercially available from ICL Industrial Products as FYROL PCF.

[0055] In some embodiments, the polymerizable aromatic (meth)acrylate oligomer comprises a halogen-modified polymerizable aromatic (meth)acrylate oligomer, and the liquid flame retardant comprises a halogenated trialkyl phosphate ester.

[0056] UV-curable compositions also contain at least one photoinitiator, meaning that the initiator is activated by light, typically ultraviolet (UV) light. Examples of suitable free radical photoinitiators include DAROCURE 4265, IRGACURE 651, IRGACURE 184, IRGACURE 1173, IRGACURE 819, LUCIRIN TPO, and LUCIRIN TPO-L, all commercially available from BASF, Charlotte, and NC.

[0057] To carry out polymerization at the desired temperature and conversion rate, a sufficient amount of initiator is typically used. The total amount of initiator used is typically in the range of about 0.01% to about 5.0% by weight, based on the total monomer content.

[0058] The adhesive article may contain additional elements. These additional elements may be part of the substrate, i.e., the substrate may be a multilayer article or may contain additional layers or coatings. The additional elements may be part of the pressure-sensitive adhesive layer. Any suitable additive may be used, insofar as it does not interfere with the curing of the reactive components or adversely affect the properties of the cured pressure-sensitive adhesive layer, such as flame retardancy or optical properties. Examples of suitable non-reactive additives include plasticizers, tackifiers, nanoparticle fillers, bead fillers, antioxidants, viscosity-controlling additives, refractive index modifiers, or combinations thereof. In some embodiments, the additional elements may be a release liner in contact with the pressure-sensitive adhesive layer. The release liner can protect the pressure-sensitive adhesive layer until the adhesive layer adheres to the surface and forms a structure, as described below. Any suitable release liner may be used. Exemplary release liners may be prepared from paper (e.g., kraft paper) or polymer materials (e.g., polyolefins such as polyethylene or polypropylene, ethylene vinyl acetate, polyurethane, and polyesters such as polyethylene terephthalate). At least some release liners are coated with a layer of release agent, such as a silicone-containing material or a fluorocarbon-containing material. Exemplary release liners include, but are not limited to, those commercially available from CP Film (Martinsville, Va.) under trade names "T-30" and "T-10," which have a silicone release coating on a polyethylene terephthalate film. The liner may have a microstructure on its surface, which is imparted to the adhesive to form a microstructure on the surface of the adhesive layer. The liner can then be removed to expose the adhesive layer with the microstructured surface.

[0059] Adhesive structures are also disclosed. The adhesive structure includes a second substrate having a first main surface and a second main surface, and an adhesive article in contact with the second main surface of the second substrate. Adhesive articles have been described above, including an adhesive article comprising a first substrate layer having a first main surface and a second main surface, and a layer of pressure-sensitive adhesive disposed on at least a portion of the first main surface of the substrate layer, wherein the pressure-sensitive adhesive has a first main surface and a second main surface, at least a portion of the second main surface of the pressure-sensitive adhesive layer is in contact with the first main surface of the substrate layer, and the first main surface of the pressure-sensitive adhesive layer is in contact with the second main surface of the substrate, and the pressure-sensitive adhesive comprises a UV-curing composition of a curable composition comprising a polymerizable (meth)acrylate mixture, a polymerizable (meth)acrylate mixture, a polymerizable aromatic (meth)acrylate oligomer, a liquid flame retardant, and at least one UV initiator. Each of these elements is described in detail above.

[0060] A wide variety of second substrates are suitable. The second substrate may be the same as or different from the first substrate. In some embodiments, the second substrate includes the outer surface of a device or vehicle. In some embodiments, the second substrate includes a treatment surface. The surface includes film-coated surfaces, painted surfaces, or coated surfaces. Examples of surfaces to which the adhesive articles of this disclosure may be attached include transport vehicles such as automobiles, trains, buses, subway cars, and airplanes. Preferred surfaces include glass surfaces such as windows. [Examples]

[0061] Flame-retardant pressure-sensitive adhesive compositions and films coated with the adhesive were prepared, and their material properties were evaluated. 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 (St. Louis, Missouri) unless otherwise indicated. The following abbreviations are used herein: °C = degrees Celsius, h = hours, min = minutes, mg = milligrams, kPa = kilopascals, N / m = Newtons / meter, ΔE * =Color difference, K / sec = Kelvin degrees / second, J / gK = Joules / gram Kelvin degrees, K = Kelvin degrees, kJ / g = Kilojoules / gram, mJ / cm 2 = millijoules / square centimeter.

[0062] [Table 1]

[0063] Test method Haze, clarity, and transmittance Light haze, clarity, and transmittance were measured according to ASTM D1003-13 using the BYK Haze-Gard Plus model AT-4725 (available from BYK-Gardner (Columbia, MD)). The adhesive was coated directly onto the polyester film for measurement.

[0064] color The color difference of the adhesive is due to the X-RITE spectrophotometer model Ci62 (X-Rite (Grand The color shift (ΔE) of film-backed adhesive samples laminated on white vinyl film (available from 3M (St. Paul, MN) as 3M CONTROLTAC IJ180MC-10) was measured according to ASTM D2244-16 using a D65 / 10° light source / observer. * The values ​​were calculated from CIELAB color space values ​​measured according to the following formula, using an unadded adhesive as a reference.

number

[0065] Peel adhesive strength Peel adhesion was measured using an INSTRON Model 5965 (available from Instron (Norwood, MA)) according to ASTM D330-04. Film backing adhesive samples were cut into 25.4 mm wide strips and applied by hand using a squeegee to Q-Panel aluminum panels (available from Q-Lab (Westlake, OH) as 6061T6 SP-104177) or aluminum panels covered with vinyl film (available from 3M (St. Paul, MN) as 3M CONTROLTAC IJ180MC-10). The samples were conditioned for a specified dwell period in an oven set to constant temperature and humidity (23°C and 50% relative humidity) or 65°C. After the specified conditioning, peel adhesion was measured by peeling the sample from the substrate at a removal rate of 30.5 cm / min and an angle of 180 degrees. The peel strength was measured in feet-pounds per inch and converted to Newtons per meter (N / m).

[0066] Micro-combustion calorimetry (MCC) The flammability of the adhesive was measured using a microscale calorimeter model MCC-2 (available from Govmark (Farmingdale, NY)) according to ASTM D7309-13 Method A. 2-3 mg samples of cured adhesive were heated at a rate of 1 K / s in a nitrogen environment. The decomposition products were completely oxidized in a combustion chamber maintained at 900°C in an environment of 20% oxygen and 80% nitrogen. The exothermic reaction of the decomposition gas was determined by the mass of oxygen used to completely combust the sample. The following parameters were calculated from the data: Heat generation capacity η c (J / gK) is calculated by dividing the maximum specific heat generation rate by the heating rate.

[0067] Specific heat generation h c (kJ / g), this represents the net exothermic reaction over the entire temperature range.

[0068] Pyrolysis residue Yp (%): This is the percentage of the sample mass remaining after the test.

[0069] Examples Examples 1-8 (EX1-EX8) The halogen-containing flame-retardant adhesive solution was prepared by mixing ADH1, LFR1 or LFR2, PFR1, PI1, and PI2 in the weight ratios shown in Table 1 in an amber bottle, and diluting with ethyl acetate to a 35% solids content. The solution was coated onto L1 with a 203 micrometer gap using a knife coater and dried in an oven set to 65°C for 10 minutes. The dried coating was then passed through a Honle JetCURE UV curing unit (available from Honle UV America, Inc. (Marlboro, MA)) under a nitrogen flow at 60 mJ / cm². 2 The material was irradiated with UVC light at a dose of 0.5°C. The release liner coated with the cured adhesive was laminated onto the film substrate using a laminator at a nip pressure of 276 kPa and a speed of 0.9 to 1.5 meters per minute.

[0070] [Table 2]

[0071] Examples 9-16 (EX9-EX16) Halogen-free flame-retardant adhesive solutions were prepared by mixing ADH1, LFR3, PFR2 or PFR3, PI1, and PI2 in an amber bottle according to the ratios shown in Table 2, and diluting with ethyl acetate to a 35% solids content. The solutions were similarly coated and laminated onto film substrates as described in Examples 1-8.

[0072] [Table 3]

[0073] Comparative examples 1~2 (C1~C2) A comparative adhesive solution free of any flame retardant additives was prepared by diluting ADH1 with ethyl acetate to a 35% solids content and treating it in the same manner as in Examples 1-16.

[0074] Comparative examples 3~5 (C3~C5) Comparative adhesive solutions using liquid flame retardant additives and non-flammable polymerizable additives were prepared by mixing ADH1, LFR1, PM1, PI1, and PI2 in amber bottles in the weight ratios shown in Table 3, and diluting with methyl ethyl ketone to a 35% solids content. The solutions were similarly coated and laminated onto film substrates as described in Examples 1 to 16.

[0075] [Table 4]

[0076] result The examples were tested using the test method described above. The results are shown in Tables 4-6.

[0077] [Table 5]

[0078] Table 6

[0079] Table 7

Claims

1. Adhesive articles, A substrate layer having a first main surface and a second main surface, The substrate layer comprises a layer of pressure-sensitive adhesive disposed on at least a portion of the first main surface of the substrate layer, The pressure-sensitive adhesive is Polymerizable (meth)acrylate mixture, Polymerizable aromatic (meth)acrylate oligomers, Liquid flame retardant and At least one UV initiator, A UV curing composition comprising a curable composition containing, The aforementioned UV-curing composition is an optically transparent pressure-sensitive adhesive, and it is, Pressure-sensitive adhesive, The polymerizable (meth)acrylate mixture, At least one UV initiator, An adhesive article having improved flame retardancy compared to the same adhesive article containing a UV-curing composition containing [the specified substance].

2. The adhesive article according to claim 1, wherein the base layer comprises a polymer film containing polyester, vinyl, polyolefin, polyurethane, or a combination thereof.

3. The adhesive article according to claim 1, wherein the polymerizable (meth)acrylate mixture comprises a coatable syrup containing a partially polymerized mixture of (meth)acrylate monomers.

4. The adhesive article according to claim 3, wherein the mixture of (meth)acrylate monomers comprises at least one alkyl (meth)acrylate monomer having 2 to 20 carbon atoms and at least one reinforcing monomer.

5. The adhesive article according to claim 4, wherein the at least one reinforcing monomer is selected from (meth)acrylic acid, (meth)acrylamide, and styrene.

6. The adhesive article according to claim 1, wherein the pressure-sensitive adhesive layer is halogen-free.

7. The adhesive article according to claim 6, wherein the polymerizable aromatic (meth)acrylate oligomer comprises one or more phosphorus-modified (meth)acrylate oligomers, and the liquid flame retardant comprises an aryl phosphate.

8. The adhesive article according to claim 1, wherein the polymerizable aromatic (meth)acrylate oligomer comprises a halogen-modified polymerizable aromatic (meth)acrylate oligomer, and the liquid flame retardant comprises a halogenated trialkyl phosphate ester.

9. The halogen-modified polymerizable aromatic (meth)acrylate oligomer is defined by general formula 1: Ar ｈａｌ -O-(CO)-CR １ =CH ２ Formula 1 [In the formula, R １ (H) is an H or methyl group, (CO) is a carbonyl group C=O, and Ar ｈａｌ The adhesive article according to claim 8, comprising a compound of an aromatic group selected from phenyl, substituted phenyl, or condensed aromatic groups, wherein at least one hydrogen atom is substituted with a halogen atom.

10. The halogen-modified polymerizable aromatic (meth)acrylate oligomer is defined by general formula 1: Ar ｈａｌ -O-(CO)-CR １ =CH ２ Formula 1 [Wherein, R １ is H, (CO) is a carbonyl group C=O, and Ar ｈａｌ is a per-bromophenyl (C ６ Br ５ ) group], the adhesive article according to claim 8, comprising a compound of

11. The adhesive article, The pressure-sensitive adhesive layer The (meth)acrylate mixture mentioned above, At least one UV initiator, The adhesive article according to claim 1, having a peel adhesion strength of at least 60% of the peel adhesion strength of the same adhesive article comprising a UV curing composition comprising the above.

12. The adhesive article according to claim 1, further comprising a release liner in contact with the pressure-sensitive adhesive layer.

13. The pressure-sensitive adhesive, A polymerizable (meth)acrylate mixture in an amount of 61-75% by weight, 4-13% by weight of polymerizable aromatic (meth)acrylate oligomers, 18-29% by weight of liquid flame retardant, At least one UV initiator, A UV curing composition comprising a curable composition containing, The adhesive article according to claim 1, wherein the weight percentage is based on the total weight obtained by subtracting the UV initiator from the curable composition.

14. An adhesive structure, A substrate having a first main surface and a second main surface, The adhesive article in contact with the second main surface of the substrate, The adhesive article is A substrate layer having a first main surface and a second main surface, The substrate layer comprises a layer of pressure-sensitive adhesive disposed on at least a portion of the first main surface of the substrate layer, The pressure-sensitive adhesive is It has a first main surface and a second main surface, At least a portion of the second main surface of the pressure-sensitive adhesive layer is in contact with the first main surface of the substrate layer. The first main surface of the pressure-sensitive adhesive layer is in contact with the second main surface of the substrate. The pressure-sensitive adhesive is Polymerizable (meth)acrylate mixture, Polymerizable (meth)acrylate mixture, Polymerizable aromatic (meth)acrylate oligomers, Liquid flame retardant and At least one UV initiator, A UV curing composition comprising a curable composition containing, The UV-curing composition is an adhesive structure that is a flame-retardant, optically transparent, pressure-sensitive adhesive.

15. The adhesive structure according to claim 14, wherein the substrate includes the outer surface of a device or vehicle.

16. The adhesive structure according to claim 14, wherein the substrate includes a treated surface, and the treated surface includes a film-coated surface, a painted surface, or a coated surface.

17. The adhesive structure according to claim 14, wherein the polymerizable (meth)acrylate mixture comprises a coatable syrup containing a partially polymerized mixture of (meth)acrylate monomers.

18. The adhesive structure according to claim 17, wherein the mixture of (meth)acrylate monomers comprises at least one alkyl (meth)acrylate monomer having 2 to 20 carbon atoms and at least one reinforcing monomer.

19. The adhesive structure according to claim 14, wherein the polymerizable aromatic (meth)acrylate oligomer comprises a phosphorus-modified (meth)acrylate oligomer, and the liquid flame retardant comprises an aryl phosphate.

20. The polymerizable aromatic (meth)acrylate oligomer is defined by general formula 1: Ar ｈａｌ -O-(CO)-CR １ =CH ２ Formula 1 [In the formula, R １ (H) is an H or methyl group, (CO) is a carbonyl group C=O, and Ar ｈａｌ The adhesive structure according to claim 14, comprising a halogen-modified polymerizable aromatic (meth)acrylate oligomer of an aromatic group selected from phenyl, substituted phenyl, or condensed aromatic groups, wherein at least one hydrogen atom is substituted with a halogen atom.

21. The pressure-sensitive adhesive, A polymerizable (meth)acrylate mixture in an amount of 61-75% by weight, 4-13% by weight of polymerizable aromatic (meth)acrylate oligomers, 18-29% by weight of liquid flame retardant, At least one UV initiator, A UV curing composition comprising a curable composition containing, The adhesive structure according to claim 14, wherein the weight percentage is based on the total weight obtained by subtracting the UV initiator from the curable composition.

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