Improved tack-free properties of photocurable compositions

Abstract

Viscosity reducing components and methods of using the same are disclosed. The visbreaking component provides a wide range of radiation curable compositions having a cured surface with reduced tack. The viscosity depressant is used at very low levels in a radiation curable composition and comprises an acrylate-functionalized polydimethylsiloxane, optionally in a diacrylate monomer, or a non-acrylate-functionalized polydimethylsiloxane, optionally in a diacrylate monomer.

Description

Technical Field

[0001] The present invention relates generally to radiation curable compositions and, more particularly, to radiation curable compositions having little or no tack after radiation curing. Background Art

[0002] Radiation-curable compositions are well known for use as adhesives, sealants and coatings. These compositions typically comprise an oligomer or polymer having (meth)acrylate functionality; a diluent; one or more photoinitiators optionally present and other optional additives. Depending on the formulation, the uncured composition can be a liquid to a viscous liquid. These compositions are cured by exposure to actinic radiation after application to a substrate. Depending on the formulation, the cured composition can range from a desired tacky or viscous pressure-sensitive adhesive to a desired non-tacky hard structural composition, such as an adhesive, sealant or coating.

[0003] Improving the tack-free properties of a curable composition can be highly desirable because it leads to greater user acceptance in applications where the tack of the curing composition may slow or prevent the movement of a part / assembly to the next operation or storage. In addition, users often perceive the tack of a curing composition as an indication of a lack of cure or undercure of the radiation-curable composition in an application. This is particularly important for exposed adhesive layers, such as where an undercured adhesive may come into critical contact with a fluid such as a saline solution.

[0004] However, it is challenging to achieve non-tack properties with radiation curable compositions. Formulations of various acrylate monomers and acrylate functional resins in combination with photoinitiator levels and systems tend to impart desired curable composition properties such as strength or hardness, which can promote the curable composition to tend to produce a viscous cured surface. In addition, moving to an LED radiation source to cure the composition can make the cured composition sticky. LED radiation sources emit in a narrow range centered at a higher wavelength (e.g., 365nm, 385nm, or 405nm), while older mercury vapor and metal halide sources emit in a wider range of ultraviolet wavelengths, including higher energy shorter wavelengths, with multiple emission peak wavelengths. For some radiation curable compositions, a broad spectrum source provides better (less or no) tack properties compared to a narrow spectrum LED source.

[0005] There remains a need for radiation curable compositions that achieve a low tack or tack-free state. This is particularly important where the composition is an adhesive or coating that also requires a "tack-free" coating-like property. This is also important when the radiation exposure time is very short. Radiation curable adhesives are typically heated at about 1,000 mW / cm 2 (About 5,000 to 20,000 mJ / cm 2) is exposed to the radiation for about 5 to 20 seconds to ensure the desired curing level. When the radiation exposure time is very short, such as 1 second or less, it is very difficult to achieve low or no tack. There is also a need for additives that can improve the appearance by reducing the surface tack of existing compounds.

[0006] The properties of the uncured radiation curable composition are also important. The uncured composition must have a viscosity suitable for its intended application. In some applications, it is suitable and even preferred to use pressurized distribution of viscous materials. In other applications or dripping applications using wicking, low viscosity compositions are needed.

[0007] The properties of the cured composition are further important and must be matched to the application. Cured adhesives bonding rigid materials require little flexibility, while cured adhesives bonding flexible materials must have considerable flexibility to avoid cracking in use. Generally, it is desirable for the adhesive to have a high bond strength to the parts being bonded, and it is generally desirable for the parts being bonded to fail before the adhesive bonds. Summary of the invention

[0008] One aspect of the present disclosure provides a radiation curable composition that cures to a low tack or tack-free state.

[0009] One aspect of the present disclosure provides a radiation curable composition that cures to a low-tack or tack-free state even after very short radiation exposure.

[0010] Another aspect of the present disclosure provides one or more components that can be added to the radiation curable composition at very low levels to reduce the viscosity of the cured composition.

[0011] Another aspect of the present disclosure provides the use of very low levels of acrylate functionalized polydimethylsiloxane copolymer components or non-acrylate functionalized polydimethylsiloxane copolymer components, which can be added to radiation curable compositions at very low levels to reduce the viscosity of the cured composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Referring now to the drawings, wherein like elements are numbered alike throughout the several views:

[0013] Figure 1 is a graph of the viscosity ratings of different compositions with and without a viscosity reducing agent.

[0014] Figure 2 is a graph of the viscosity ratings of different compositions with and without a viscosity reducing agent.

[0015] Figure 3 is a graph of the viscosity ratings of different compositions with and without a viscosity reducing agent.

[0016] Figure 4 is a graph of the viscosity ratings of different compositions with and without a viscosity reducing agent.

[0017] Figure 5 is a graph of the viscosity ratings of different commercial compositions with and without viscosity reducing agents.

[0018] Figure 6 is a graph of the viscosity ratings of different commercial compositions with and without viscosity reducing agents.

[0019] Figure 7 The tack test criteria for actinically cured samples of the disclosed compositions are shown. DETAILED DESCRIPTION

[0020] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0021] As used herein, about or "approximately" with respect to a numerical value refers to the numerical value ±10%, preferably ±5%, more preferably ±1% or less.

[0022] As used herein, the term "comprising" is synonymous with "including" or "containing" and is inclusive or open-ended and does not exclude additional, unrecited members, elements, or method steps.

[0023] When amounts, concentrations, sizes and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits or preferred upper and lower limits, it should be understood that any range obtainable by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the obtained range is clearly mentioned in the context.

[0024] Preferred and preferably are often used herein to refer to embodiments of the present disclosure that may provide specific benefits in certain circumstances. However, the recitation of one or more preferred embodiments does not mean that other embodiments are not useful, and is not intended to exclude those other embodiments from the scope of the present disclosure.

[0025] Unless otherwise specified, the molecular weights given herein refer to the number average molecular weight (Mn). Unless otherwise specified, molecular weight data can be obtained by gel permeation chromatography (GPC) according to DIN 55672-1: 2007-08 at 35°C calibrated against polystyrene standards. w It can be determined by GPC, such as M n "Polydispersity index" refers to a measure of the molecular weight distribution in a given polymer sample. The polydispersity index is calculated by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn).

[0026] As used herein, a curable one-component (1K) composition is a single formulation that has sufficient commercial stability to prepare, store and transport to an end user. The 1K composition can be used without adding any additional components and will crosslink or cure when exposed to suitable conditions. As used herein, a two-component (2K) composition has two or more components. Each component is prepared, stored and transported separately from the other components. The components are mixed immediately before use. The mixing of the components causes a curing reaction, so commercial storage after mixing is not possible.

[0027] (Meth)acrylate refers to at least one of acrylate and methacrylate. "Vinyl" refers to (CH2=CH-). "(Meth)acryloyl" refers to at least one of acryloyl and methacryloyl. "Acryloyl" refers to (CH2=CHCO)-. "Methacryloyl" refers to (CH2=C(CH3)CO-).

[0028] "Acyl" refers to the general formula -C(O)alkyl.

[0029] "Aliphatic" refers to a saturated or unsaturated straight chain, branched chain or cyclic hydrocarbon group.

[0030] "Alkenyl" or "lower alkenyl" refers to a straight, branched or cyclic carbon chain having 1 to about 16 carbon atoms, advantageously about 1 to about 6 carbon atoms, and at least one double bond between carbon atoms in the chain. Examples include, for example, ethylene, propadiene, butylene, butadiene, hexene, hexadiene, 5,5-dimethyl-1-hexene and cyclohexene. Unless otherwise specifically limited, alkenyl can be unsubstituted, monosubstituted or polysubstituted, with substituents at any possible position.

[0031] "Alkoxy" refers to a radical of the formula -O-alkyl.

[0032] "Alkyl" refers to a straight chain, branched or cyclic alkyl group having 1 to about 9 carbon atoms, including, for example, methyl, ethyl, propyl, butyl, hexyl, octyl, isopropyl, isobutyl, tert-butyl, cyclopropyl, cyclohexyl, cyclooctyl, vinyl and allyl. Unless otherwise specifically defined, an alkyl group may be saturated or unsaturated and substituted or unsubstituted. Unless otherwise specifically limited, a cycloalkyl group includes monocyclic, bicyclic and polycyclic rings, such as norbornyl, adamantyl and related terpenes.

[0033] "Alkylamino" refers to a radical of the formula -(NH)-alkyl.

[0034] "Dialkylamino" refers to a group of the general formula -N-(alkyl) 2. Unless otherwise specifically limited, dialkylamino includes cyclic amine compounds such as piperidine and morpholine.

[0035] The term "aromatic" or "aryl" refers to a cyclic conjugated hydrocarbon structure (C1-12 ).

[0036] "Aroyl" refers to a radical of the formula -C(=O)-aryl.

[0037] As used herein, free or substantially free means less than 10%, preferably less than 5%, more preferably less than 1%, and even more preferably no more than trace or impurity amounts or 0% are present.

[0038] "Halogen" or "halo" when used alone or as part of another group refers to chlorine, fluorine, bromine or iodine.

[0039] Room temperature refers to a temperature of about 25°C.

[0040] "Radiation" refers to actinic radiation, including electron beam radiation and radiation in the ultraviolet (UV-A, UV-B and UV-C), visible and infrared wavelengths.

[0041] The term substitution refers to substitution by at least one of the following substituents at any possible one or more positions. The substituents that can be used for the above-mentioned parts of the disclosed compounds are those groups that do not significantly reduce the biological activity of the disclosed compounds. Substituents that do not significantly reduce the required activity of the disclosed compounds include, for example, H, halogen, N3, NCS, CN, NO2, NX1X2, OX4, C(X4)3, OAc, O-acyl, O-aroyl, NH-acyl, NH-aroyl, NHCOalkyl, CHO, C(halogen)3, COOX4, SO3H, PO3H2, SO2NX1X2, CONX1X2, C(O)CF3, alkyl(C 1-8 ), alkoxy, alkylthiol, alkylamino, dialkylamino, aryl, alkaryl, sulfonamide or thioalkoxy, wherein X1 and X2 each independently include H or alkyl, or X1 and X2 together form part of a heterocyclic ring having about 4 to about 7 ring members and optionally one additional heteroatom selected from O, N or S, or X1 and X2 together form part of an imide ring having about 5 to about 6 ring members, and X4 includes H, alkyl, lower alkylhydroxy or alkyl-NX1X2. Unless otherwise specifically limited, the substituents may be in any possible single position or, if polysubstituted, any possible multiple positions.

[0042] The term "oligomer" refers to a certain small number of repeating monomer units, such as 10-5,000 units, ideally 10-100 units, polymerized to form a molecule, which is a type of the term polymer. The term "resin" also describes a molecule with multiple repeating monomer units and is a type of the term polymer. The term "polymer" refers to any polymerization product, including oligomers, polymers and resins.

[0043] As used herein, "one or more" refers to at least one and includes 1, 2, 3, 4, 5, 6, 7, 8, 9 or more of the substances mentioned. Similarly, "at least one" refers to one or more, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9 or more. As used herein, "at least one" refers to the number of chemically different molecules, i.e., the number of different types of the substances mentioned, but not the total number of molecules. For example, "at least one polyol" refers to the use of at least one type of molecule belonging to the definition of polyol, but there may also be two or more different polyol types belonging to the definition, but it does not mean that only one type of the polyol must be present. When a range of numerical values ​​is provided, the range includes all values ​​within the range.

[0044] The disclosed compounds include any and all isomers and stereoisomers. Generally, unless otherwise expressly stated, the disclosed materials and methods can be formulated to include, consist of, or consist essentially of any suitable component, part, or step disclosed herein. The disclosed materials and methods can additionally or alternatively be formulated to be free of or substantially free of any component, material, ingredient, adjuvant, part, substance, and step used in prior art compositions or not necessary to achieve the functions and / or purposes of the present disclosure.

[0045] Unless expressly stated otherwise, all percentages cited in connection with the compositions described herein refer to weight percentages (wt. %) relative to the final composition having all components, unless otherwise stated.

[0046] The radiation curable composition generally comprises one or more polymers having (meth)acrylate functional groups; one or more diluents; one or more viscosity reducing additives; one or more photoinitiators optionally present and one or more additives optionally present. In a preferred embodiment, the radiation curable composition comprises a plurality of different polymers having (meth)acrylate functional groups; a plurality of different reactive diluents, each having a different number of (meth)acrylate functional groups; one or more viscosity reducing additives; one or more photoinitiators optionally present and one or more additives optionally present.

[0047] Polymers having (meth)acrylate functional groups

[0048] In one embodiment, the backbone of the (meth)acrylate polymer is formed from various monofunctional (meth)acrylate monomers, such as monofunctional (meth)acrylate C 1-10 Homopolymers of alkyl esters and monofunctional (meth)acrylates C 1-10Copolymers of alkyl esters. Particularly useful monomers include ethyl acrylate, methoxyethyl acrylate, n-butyl acrylate, and homopolymers and copolymers thereof. Other examples of useful monomers include (meth)acrylic acid monomers, such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, toluene (meth)acrylate. esters, benzyl (meth)acrylate, carboxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, γ-(methacryloyloxypropyl)trimethoxysilane, (meth)acrylic acid-ethylene oxide adduct, trifluoromethyl methyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate 2-perfluoroethyl ester, perfluoromethyl (meth)acrylate, diperfluoromethyl methyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethyl methyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, 2-perfluorohexadecylethyl (meth)acrylate, etc.; styrene monomers such as styrene, vinyl toluene, α-methylstyrene, chlorostyrene, styrene sulfonic acid and its salts; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, vinylidene fluoride, etc.; silicon-containing vinyl monomers such as vinyl trimethoxysilane, vinyl triethoxysilane, etc.; maleic anhydride, maleic acid, monoalkyl esters and dialkyl esters of maleic acid; fumaric acid and monoalkyl fumaric acid esters and dialkyl esters; maleimide monomers such as maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, phenylmaleimide, cyclohexylmaleimide, etc.; nitrile-containing vinyl monomers such as acrylonitrile, methacrylonitrile, etc.; amide-containing vinyl monomers such as acrylamide, methacrylamide, etc.; vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, vinyl cinnamate, etc.; olefins such as ethylene, propylene, etc.; conjugated dienes such as butadiene, isoprene, etc.; vinyl chloride, vinylidene chloride, allyl chloride and allyl alcohol.These monomers may be used alone or plural of them may be copolymerized.

[0049] In another embodiment, the main chain of the (meth) acrylate oligomer can be formed by or include one or more polymer segments or units. Such segments include one or more of carbamate, styrene, polyolefin, isoprene, butadiene, polyisobutylene, acrylamide, nylon, (meth) acrylonitrile and / or substituted (meth) acrylonitrile. Useful (meth) acrylate functionalized carbamates include tetramethylene glycol carbamate acrylate oligomers and propylene glycol carbamate acrylate oligomers. Other (meth) acrylate functionalized carbamates are carbamate (meth) acrylate polymers based on polyethers or polyesters, which react with aromatic, aliphatic or alicyclic diisocyanates and end-block with acrylates. Some useful examples include difunctional urethane acrylate oligomers such as polyesters of adipic acid and diethylene glycol terminated with isophorone diisocyanate and end-blocked with 2-hydroxyethyl acrylate; polypropylene glycol terminated with toluene-2,6-diisocyanate and end-blocked with 2-hydroxyethyl acrylate; polyesters of adipic acid and diethylene glycol terminated with 4,4'-methylenebis(cyclohexyl isocyanate) and end-blocked with 2-hydroxyethyl acrylate; Polyesters of adipic acid, 1,2-ethylene glycol and 1,2-propylene glycol, terminated with toluene-2,4-diisocyanate, end-blocked with 2-hydroxyethyl acrylate; polyesters of adipic acid, 1,2-ethylene glycol and 1,2-propylene glycol, terminated with 4,4'-methylenebis(cyclohexylisocyanate), end-blocked with 2-hydroxyethyl acrylate; and polytetrahydrofuran, terminated with 4,4'-methylenebis(cyclohexylisocyanate), end-blocked with 2-hydroxyethyl acrylate. Other (meth)acrylate functionalized urethanes are monofunctional urethane acrylate oligomers, such as polypropylene terminated with 4,4'-methylenebis(cyclohexylisocyanate), end-blocked with 2-hydroxyethyl acrylate and 1-dodosanol. (Meth)acrylate functionalized urethanes also include difunctional urethane methacrylate oligomers such as polytetrahydrofuran, which is terminated with toluene-2,4-diisocyanate and end-blocked with 2-hydroxyethyl methacrylate; polytetrahydrofuran, which is terminated with isophorone diisocyanate and end-blocked with 2-hydroxyethyl methacrylate; polytetrahydrofuran, which is terminated with 4,4'-methylenebis(cyclohexyl isocyanate) and end-blocked with 2-hydroxyethyl methacrylate; and polypropylene glycol, which is terminated with toluene-2,4-diisocyanate and end-blocked with 2-hydroxyethyl methacrylate.

[0050] In one embodiment, the (meth)acrylate oligomer or polymer has a polyisobutylene backbone and is represented by the general formula (1):

[0051]

[0052] Where R 1 represents a monovalent or polyvalent aromatic hydrocarbon group or a monovalent or polyvalent aliphatic hydrocarbon group, preferably a divalent phenylene group, PIB represents a polyisobutylene main chain containing multiple repeating -[CH2C(CH3)2]- units, R 2 and R 3 Each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, R 4 represents a divalent hydrocarbon group having 2 to 6, preferably 3 or 4, carbon atoms and optionally containing an oxygen atom, R 5 represents a hydrogen atom, a methyl group, an ethyl group or a propyl group, and n is any integer from 1 to 6, preferably 2 or 3.

[0053] The number average molecular weight (Mn) of the (meth)acrylate oligomer may be 1000 to 100,000, more desirably 2000 to 50,000.

[0054] (Meth)acrylate oligomers or polymers can be prepared using standard techniques known in the art, or can be obtained from suitable commercial sources. Preparation techniques include controlled radical polymerization methods, including single electron transfer living radical polymerization (SET-LRP), by stable radical polymerization (SFRP), such as by coupling or by reversible deactivation of degenerate chain transfer (DT). Once polymerization is complete, the method may include further reacting the resulting polymer to form functional end groups on the polymer. Forming functional ends on the polymer can be carried out, for example, by performing end-capping reactions or substitution reactions.

[0055] Combinations of two or more acrylate-functional oligomers and / or acrylate-functional polymers can be used to adjust the uncured and cured properties of the composition.

[0056] Thinner

[0057] The curable composition may optionally include at least one diluent and / or reactive diluent. Available reactive diluents may include compounds having one or more (meth)acrylate functional groups. Illustrative examples of available (meth)acrylates include alkyl (meth)acrylates, cycloalkyl (meth)acrylates, alkenyl (meth)acrylates, heterocycloalkyl (meth)acrylates, heteroalkyl methacrylates, alkoxy polyether mono(meth)acrylates, and amide-containing vinyl monomers such as (meth)acrylamide and di(meth)acrylamide.

[0058] The alkyl group on the (meth)acrylate may desirably be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, desirably 1 to 10 carbon atoms, optionally having at least one substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 1 to 20 carbon atoms, desirably 1 to 10 carbon atoms, a substituted or unsubstituted bicyclic or tricyclic alkyl group having 1 to 20 carbon atoms, desirably 1 to 15 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms.

[0059] The alkenyl group on the (meth)acrylate may desirably be a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, desirably 2 to 10 carbon atoms, optionally having at least one substituent selected from an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an epoxy group having 2 to 10 carbon atoms, a hydroxyl group, and the like.

[0060] The heterocyclic group on the (meth)acrylate may desirably be a substituted or unsubstituted heterocyclic group having 2 to 20 carbon atoms, desirably 2 to 10 carbon atoms, containing at least one heteroatom selected from N and O, and optionally having at least one substituent selected from an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or an epoxy group having 2 to 10 carbon atoms.

[0061] The alkoxy polyether mono(meth)acrylate may be substituted with an alkoxy group having 1 to 10 carbons, and the polyether may have 1 to 10 repeating units.

[0062] Some exemplary (meth)acrylate monomers include, but are not limited to, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, isobornyl (meth)acrylate; tetrahydrofurfuryl acrylate; benzyl (meth)acrylate, carboxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, γ-(methacryloxypropyl)trimethoxysilane, (meth)acrylic acid-ethylene oxide adduct, trifluoromethyl methyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethyl methyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethyl methyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate and 2-perfluorohexadecylethyl (meth)acrylate. In one aspect of the invention, the (meth)acrylate monomer is polyethylene glycol diacrylate, such as SR 259 (polyethylene glycol (200) diacrylate from Sartomer). Some useful multifunctional (meth)acrylates include, for example, polyethylene glycol di(meth)acrylates, desirably triethylene glycol di(meth)acrylate, hydroxypropyl (meth)acrylate, bisphenol-A di(meth)acrylates such as ethoxylated bisphenol-A (meth)acrylate ("EBIPA" or "EBIPMA"), and tetrahydrofuran (meth)acrylate and di(meth)acrylate, citronellyl acrylate and methacrylate, hexanediol di(meth)acrylate ("HDDA" or "HDDMA"), trimethylolpropane tri(meth)acrylate, tetrahydrodicyclopentadienyl (meth)acrylate, ethoxylated trimethylolpropane triacrylate ("ETTA"), triethylene glycol diacrylate, pentaerythritol tetraacrylate, and triethylene glycol dimethacrylate ("TRIEGMA").

[0063] Viscosity reducing component

[0064] The viscosity-reducing component reduces the surface tack or adhesion of the cured or even partially cured radiation-curable composition. Typical viscosity-reducing agents may include a polysiloxane portion. However, polysiloxane homopolymers have poor solubility or poor dispersibility in radiation-curable compositions. Preferably, the viscosity-reducing component does not contain or is substantially free of polysiloxane homopolymers. Preferably, the viscosity-reducing component comprises a copolymer of polysiloxane and other polymer segments such as polyester and / or polyether in the main chain of the molecule. The viscosity-reducing component may include one or preferably multiple acrylate functional groups on the molecule. The acrylate functional group may be a side group or terminal on the molecule. In other embodiments, the viscosity-reducing component may not contain or is substantially free of acrylate functional groups on the molecule. The viscosity-reducing component may be used as a mixture with a (meth)acrylate diluent for ease of handling.

[0065] One useful viscosity reducing component is BYK-3505 available from BYK-Chemie GmbH, Germany. BYK-3505 is described as a multi-acrylate functional modified polydimethylsiloxane macromonomer having an AB molecular structure functionalized only at one end of the molecule. The AB structure is a combination of a polyether / polyester and a high content of polysiloxane. BYK-3505 is provided as a diacrylate monomer (TPGDA). Another useful viscosity reducing agent is BYK-3510, also available from BYK-Chemie GmbH. BYK-3510 is described as a polyether modified polydimethylsiloxane without reactive moieties. BYK-3510 is provided as a diacrylate monomer (TPGDA). Of course, combinations of different viscosity reducing components can be used in the radiation curable composition.

[0066] Photoinitiator

[0067] The curable composition includes at least one photoinitiator to help initiate and induce curing when the composition is exposed to radiation. Typical photoinitiators will induce curing when the composition is exposed to ultraviolet (UV) or visible wavelength radiation. Naturally, the photoinitiator should be selected to be active at the UV wavelength used for curing.

[0068] Useful polymeric thioxanthone derivative photoinitiators include Genopol TX available from Rahn; OMNIPOL TX (formula below) available from IGM; and SPEEDCURE 7010-L available from Lambson. Other photoinitiators are described in U.S. Patent Application Nos. 9,278,949, 8,883,873, 7,354,957, and International Patent Publication No. WO2009060235, the contents of each of which are incorporated herein by reference.

[0069] Other useful photoinitiators that respond to radiation to initiate and induce curing of the curable composition include, but are not limited to, low wavelength photoinitiators such as hydroxycyclohexyl phenyl ketone available as Tinocure 184; aromatic tertiary amines such as ethyl-4-dimethylaminobenzoate Genocure EPD, ethyl-4-dimethylaminobenzoate, polymeric aminobenzoate derivatives such as Genopol AB-2, Omnipol ASA, aminoacrylates such as Genomer 5142, 5161, 5271, 6275, Photomer 4250, 4771, 4775, 4780, 4967, 5006 and phosphine oxide photoinitiators such as trimethylbenzoyl diphenylphosphine oxide. A useful co-photoinitiator is Genopol AB-2 available from Rahn.

[0070] One photoinitiator or a combination of different photoinitiators can be used. The photoinitiator can be used in an amount of about 0.1% to about 10% by weight of the total composition. More desirably, the photoinitiator is present in an amount of about 0.5% to about 5% by weight of the total composition.

[0071] additive

[0072] The curable composition may optionally include one or more additives. Optional additives include, for example, stabilizers, inhibitors, oxygen scavengers, dyes, colorants, pigments, fillers, adhesion promoters, plasticizers, tougheners, reinforcing agents, fluorescent agents, wetting agents, antioxidants, rheology modifiers, thermoplastic polymers, tackifiers and combinations thereof. The curable composition may also be free of any or all of these additives.

[0073] The curable composition may optionally include at least one type of filler. Suitable fillers may be organic or inorganic. Some useful fillers include, for example, organic fillers such as polymer powders, fibers and microspheres; lithopone; zirconium silicate; diatomaceous earth; clay; hydroxides such as hydroxides of calcium, aluminum, magnesium, iron, etc.; carbonates such as carbonates of sodium, potassium, calcium, magnesium, etc.; metal oxides such as metal oxides of calcium, zinc, magnesium, chromium, zirconium, aluminum, titanium, iron and silicon; silicon dioxide; fumed silica, which may be untreated, such as AEROSIL R 8200 purchased from Degussa, or treated with an adjuvant, such as HDK2000 purchased from Wacker-Chemie. Combinations of different fillers may also be used. The filler may be used in an amount of about 5.0% by weight to about 50% by weight of the total composition. More desirably, the filler is present in an amount of 15.0% by weight to about 40% by weight of the total composition.

[0074] In some embodiments, the radiation curable composition has a formulation falling within one or more of the following ranges.

[0075]

[0076] In some embodiments, the radiation curable composition has a formulation falling within one or more of the following ranges.

[0077]

[0078] In some embodiments, the polymer may be a ratio of 3.5-4.5 parts of a first polymer having (meth)acrylate functionality and a viscosity >20,000 cP at 60° C.: 1.5-2.5 parts of a second polymer having (meth)acrylate functionality and a viscosity <20,000 cP at 60° C.: 0.5 to 1.5 parts of a third polymer having (meth)acrylate functionality and a viscosity <6,000 cP at 60° C. The parts are parts by weight of the total polymer content in the composition.

[0079] In some embodiments, the reactive diluent may be in a ratio of 4.5-7.5 parts monoacrylate functional reactive diluent: 0.5-1.5 parts triacrylate functional reactive diluent: 0.5-1.5 parts tetraacrylate functional reactive diluent. Parts are by weight of the total reactive diluent content in the composition.

[0080] In some embodiments, the reactive diluent may be in a ratio of 1-2 parts isobornyl acrylate: 2.5 to 3.5 parts N,N-dimethylacrylamide: 1 to 2 parts tetrahydrofurfuryl acrylate. Parts are by weight of the total reactive diluent content in the composition.

[0081] In some embodiments, the reactive diluent may be in a ratio of 1-2 parts isobornyl acrylate: 2.5 to 3.5 parts N,N-dimethylacrylamide: 1 to 2 parts tetrahydrofurfuryl acrylate: 0.5-1.5 parts triacrylate functional reactive diluent: 0.5-1.5 parts tetraacrylate functional reactive diluent. Parts are parts by weight of the total reactive diluent content in the composition.

[0082] The combined balanced addition of small amounts of multifunctional diluents (tri- and tetra-) and a viscosity reducing component (TLC) relative to monofunctional and difunctional resins in the above ratios allows for faster gel formation on the curing surface, particularly under very short light conditions. Thus, with this combination, faster gel formation on the curing surface under very short light conditions provides improved surface tack characteristics without compromising the desired physical properties of adhesive strength or flexibility.

[0083] In some embodiments, the viscosity of the uncured composition is about 100 to 25,000 cP at 25° C. In some embodiments where it is desired that the composition flow, a viscosity of about 1,000 to 2,200 cP at 25° C. A viscosity within this range can allow for more precision in applications where small amounts of adhesive are applied to a part.

[0084] In some embodiments, the composition will have a viscosity rating of 2 or less, more preferably 0-1, after very short exposure to actinic radiation. Very short exposure refers to exposure of the composition to 400 mW / cm2 of UV or 405 nm wavelength. 2 The actinic radiation is applied for a period of less than 5 seconds. In preferred embodiments, the exposure time is less than 2 seconds, or less than 1 second, or less than 0.5 seconds, or less than 0.2 seconds, or less than 0.1 seconds. The irradiance is less than that conventionally used, and the exposure time is an order of magnitude less than that conventionally used. It is surprising and desirable to be able to provide a tack-free surface after these irradiation arrangements.

[0085] In some embodiments, the cured composition will have an elongation of about 100% or greater, preferably about 150% or greater, and more preferably about 200% or greater. Elongation within this range provides flexibility to the cured adhesive, thereby allowing the cured adhesive to bend with the bonded flexible component without breaking the bond. Flexible parts or components are typically those that can be easily flexed or bent or folded by the user by hand without the use of tools. Some flexible substrates include polymers, such as acrylics and polyurethanes; thin metals, such as foils and wires; and rubber. In some embodiments, the cured composition will have an elongation of less than about 150%. These cured compositions will be relatively rigid, which is more suitable for bonding non-flexible substrates such as ceramics; and thick rigid polymer products or thick rigid metal products.

[0086] In some embodiments, the cured adhesive will have a strength of about 500 to 1,600 psi. In these embodiments, the low bond strength desirably allows the bond to fail within the adhesive or at the part surface and adhesive interface, thereby leaving the part surface substantially intact.

[0087] Typically, the article includes a plurality of components, some of which will be bonded together by an adhesive. Each component can be independently composed of a material or a plurality of materials arranged in a desired manner. The components to be bonded have a bonding surface. A certain amount of uncured composition is arranged at discrete points on some portions of the bonding surface or all of the bonding surface of the first component. The second component is positioned so that the second component bonding surface is adjacent to the first component bonding surface and contacts the arranged composition. The composition arranged between the first and second components is cured by exposure to radiation so that the cured reaction product of the arranged composition adhesively fixes the first component to the second component.

[0088] In some embodiments, two or more flexible parts in the composition bonding article of solidification.In other embodiments, the adhesive bonding strength of solidification is low enough to allow the bonding surface to separate without damaging the bonding surface substantially.Separation can be completed manually by the user with or without the use of a tool.

[0089] The following examples are included for illustrative purposes so that the present disclosure may be more easily understood, and are in no way intended to limit the scope of the present disclosure unless otherwise specifically stated.

[0090] Viscosity test

[0091] Use with 50mm cone and 50s -1 Physica MCR301 viscometer for shear rate testing of uncured samples. Testing at 25°C.

[0092] Preparation of viscosity test samples

[0093] A clean glass slide with a thickness of about 0.038 inches was used. A rectangular polymer spacer with approximately the outer dimensions of the glass slide, a rectangular interior space, and a height of about 0.038 was placed on the surface of one glass slide. Six drops of the test composition were placed in the center of the open spacer. The sample was pulled to the height of the spacer using another glass slide. The material thickness was checked after curing.

[0094] Adhesive test sample curing

[0095] The samples on microscope slides were cured using a Loctite LED 405nm flood light system. The samples were cured for either 5 seconds or 30 seconds. The 5 and 30 second exposures only differentiated any possibility of the effect of longer cures on surface tack. The curing light intensity is shown in the table below. The intensity was measured using a UV V radiometer.

[0096] Curing Radiation Peak radiation wavelength <![CDATA[Radiation intensity mW / cm 2 > LED 405nm 405nm 400

[0097] Cured sample viscosity test

[0098] Sprinkle 80 mesh silicon carbide powder over the cured surface of the sample on the microscope slide until the entire sample surface is covered. Provide a 1 inch (25.4 mm) wide paint brush (Loew-Cornell 257 or equivalent). Using only the weight of the paint brush, remove loose silicon carbide grit from the sample surface by brushing four times over the length of the cured surface and another four times over the width of the cured surface. Evaluate the brushed sample using the following scale. Note that silicon carbide grit present only at some or all of the extreme edges of the sample should be considered tack-free. See Figure 7 Make a comparison.

[0099] 0Almost no grit, very little stickiness on the surface. This is the least sticky result.

[0100] 1 A small amount of sand

[0101] 2 medium grits

[0102] 3More sand

[0103] 4. Large amount of grit, full surface coverage, very sticky surface. This is the stickiest result.

[0104] Elongation test

[0105] The uncured composition was placed on a glass slide and cured as before to produce a 150 mm x 6 mm x 1 mm thick sample. Using ASTM method D882-09 (January 1, 2009), the sample was placed in a tensile test apparatus and the elongation at sample break was recorded.

[0106] Block shear strength test

[0107] The following is from ASTM D4501-01 (3 / 10 / 2001). An uncured composition was placed on the large face of a 76.2 mm x 76.2 mm x 12.7 mm thick polycarbonate sample so that a 12.7 mm (0.5 inch) wide band adjacent to the edge of the first sample was completely covered. A second sample was placed over the applied composition so that the large face of the second sample partially overlapped the large face of the adhesive and the first block and a 12.7 mm (0.5 inch) wide bond area existed between the blocks. The sample and uncured composition were exposed to 1,000 mW / cm 2 The cured samples were placed in a tensile test apparatus and the force required to separate the bonded parts was recorded, typically in accordance with ASTM D882-09 (01 / 01 / 2009).

[0108] Example 1

[0109] Two base formulations with different viscosities were prepared as shown in the table below. The components were added and mixed until uniform. The viscosity of formulation A on the main pipe was lower than that of formulation B. Neither formulation contained a viscosity reducing component. All amounts are by weight of the composition.

[0110] Material A B <![CDATA[Diluent 1 > 70.95 65.95 <![CDATA[Fluorescent brightening agent 2 > 0.05 0.05 <![CDATA[Photoinitiator 3 > 4.00 4.00 <![CDATA[Adhesion promoter 4 > 1.00 1.00 <![CDATA[Oligomer 5 > 23.00 28.00 Viscosity reducing component 0 0

[0111] 1-Isobornyl acrylate

[0112] 2 Tinopal OB CO No. 5 available from BASF

[0113] 3Omnirad TPO-L, purchased from IGM Resins USA Inc.

[0114] 4γ-Glycidyloxypropyltrimethoxysilane (GLYMO g-GPTMS), purchased from Momentive Performance Materials as Silquest A-187

[0115] 5Epion EP400V, purchased from Kaneka Corporation.

[0116] Base Formulation A was used to prepare radiation curable compositions containing the viscosity reducing components shown in the following table. All amounts are in parts by weight.

[0117] Material A 1 2 3 4 preparation 100 99.0 99.0 99.0 99.0 <![CDATA[Visbreaking component 1 > 0 1.0 0 0 0 <![CDATA[Visbreaking component 2 > 0 0 1.0 0 0.5 <![CDATA[Functional diluent 3 > 0 0 0 1.0 0.5

[0118] 1BYK UV-3505 purchased from BYK-Chemie GmbH

[0119] 2BYK-UV-3510 purchased from BYK-Chemie GmbH

[0120] 3 Tripropylene glycol diacrylate (TPGDA) available from IGM Resins USA Inc. as Photomer 4061.

[0121] Material B 5 6 7 8 Preparation B 100 99.0 99.0 99.0 99.0 <![CDATA[Visbreaking component 1 > 0 1.0 0 0 0 <![CDATA[Visbreaking component 2 > 0 0 1.0 0 0.5 <![CDATA[Diluent 3 > 0 0 0 1.0 0.5

[0122] 1BYK UV-3505 purchased from BYK-Chemie GmbH

[0123] 2BY-UV-3510 purchased from BYK-Chemie GmbH

[0124] 3 Tripropylene glycol diacrylate (TPGDA) available as Photomer 4061 from IGM Resins USA Inc.

[0125] Multiple samples of each composition were placed on a microscope slide. Three samples of each composition were cured with (exposed to) light for 5 seconds or 30 seconds and then tested for tack-free properties using the previously described cured sample tack test; the results were averaged and the average was rounded. The results are shown in the following table and Figures 1 to 4 In each table: M.Film Thickness is the measured thickness of the sample in inches; C.Film Thickness is the film thickness calculated from the measured film thickness in mm; and EXP.Time is the time the sample was exposed to radiation in seconds. 4 is the worst result and 0 is the best result.

[0126] sample M. Film thickness (in) C. Film thickness (mm) Exp. Time (seconds) Rating A 0.018 0.46 5 4 A 0.021 0.53 5 4 A 0.021 0.53 5 4 average value 0.02 0.51 4 1 0.016 0.41 5 1 1 0.024 0.61 5 0 1 0.026 0.66 5 0 average value 0.02 0.51 0 2 0.015 0.38 5 2 2 0.022 0.56 5 2 2 0.016 0.41 5 2 average value 0.018 0.45 2 3 0.022 0.56 5 4 3 0.018 0.46 5 4 3 0.021 0.53 5 4 average value 0.020 0.52 4 4 0.024 0.61 5 0 4 0.016 0.41 5 1 4 0.019 0.48 5 1 average value 0.020 0.50 1

[0127] The results of the above table are shown in Figure 1 middle.

[0128] sample Film thickness (in) Film thickness(mm) Exp. Time (seconds) Rating A 0.015 0.38 30 4 A 0.018 0.46 30 4 A 0.02 0.51 30 4 average value 0.02 0.45 4 1 0.013 0.33 30 1 1 0.02 0.51 30 0 1 0.022 0.56 30 0 average value 0.02 0.47 0 2 0.016 0.41 30 2 2 0.016 0.41 30 2 2 0.019 0.48 30 1 average value 0.02 0.43 2 3 0.017 0.43 30 4 3 0.02 0.51 30 4 3 0.019 0.48 30 4 average value 0.02 0.47 4 4 0.024 0.61 30 1 4 0.02 0.51 30 0 4 0.024 0.61 30 0 average value 0.02 0.58 0

[0129] The results of the above table are shown in Figure 2 middle.

[0130] sample Film thickness (in) Film thickness(mm) Exp. Time (seconds) Rating B 0.024 0.61 5 4 B 0.025 0.64 5 4 B 0.024 0.61 5 4 average value 0.02 0.61 4 5 0.026 0.66 5 0 5 0.027 0.69 5 1 5 0.02 0.51 5 1 average value 0.02 0.61 1 6 0.025 0.64 5 2 6 0.021 0.53 5 2 6 0.025 0.64 5 2 average value 0.02 0.60 2 7 0.027 0.69 5 2 7 0.021 0.53 5 3 7 0.027 0.69 5 3 average value 0.02 0.63 3 8 0.014 0.36 5 1 8 0.024 0.61 5 1 8 0.019 0.48 5 0 average value 0.02 0.48 1

[0131] The results of the above table are shown in Figure 3 middle.

[0132] sample Film thickness (in) Film thickness(mm) Exp. Time (seconds) Rating B 0.02 0.51 30 4 B 0.02 0.51 30 4 B 0.023 0.58 30 4 average value 0.02 0.53 4 5 0.022 0.56 30 1 5 0.027 0.69 30 0 5 0.021 0.53 30 1 average value 0.02 0.59 1 6 0.015 0.38 30 2 6 0.015 0.38 30 1 6 0.024 0.61 30 1 average value 0.02 0.46 1 7 0.025 0.64 30 2 7 0.022 0.56 30 1 7 0.019 0.48 30 2 average value 0.02 0.56 2 8 0.021 0.53 30 1 8 0.026 0.66 30 0 8 0.024 0.61 30 1 average value 0.02 0.60 1

[0133] The results of the above table are shown in Figure 4 middle.

[0134] In each of the above tables, Test Formulation A provided the worst result of 4 (most tack). Adding viscosity reducing component 1 changed the formulation from most tack to least tack. Adding TPGDA did not change the viscosity result of Formulation A for most tack. Adding TPGDA and Viscosity Reducer 2 significantly reduced the viscosity of Formulation A (1 very low viscosity).

[0135] Example 2

[0136] Different viscosity reducing components were added to commercially available radiation curable compositions C, D, E and F. The sample formulations are shown in the table below. All parts are by weight.

[0137] Material 9 10 11 12 13 14 15 16 <![CDATA[C 1 ]]> 99.0 99.0 0 0 0 0 0 0 <![CDATA[D 2 ]]> 0 0 99.0 99.0 0 0 0 0 <![CDATA[E 3 ]]> 0 0 0 0 99.0 99.0 0 0 <![CDATA[F 4 ]]> 0 0 0 0 0 0 99.0 99.0 <![CDATA[TLC1 5 ]]> 1 0 1 0 1 0 1 0 <![CDATA[TLC2 6 ]]> 0 0.5 0 0.5 0 0.5 0 0.5 <![CDATA[Diluent 7 > 0 0.5 0 0.5 0 0.5 0 0.5

[0138] 1 Loctite 3341, a radiation curable composition, available from Henkel Corporation, US.

[0139] 2 Loctite 3921, a radiation curable composition, available from Henkel Corporation, US.

[0140] 3 Loctite 3951, a radiation curable composition, available from Henkel Corporation, US.

[0141] 4 Loctite 3961, a radiation curable composition, available from Henkel Corporation, US.

[0142] 5 Viscosity reducing component 1; BYK UV-3505

[0143] 6 Viscosity reducing component 2; BYK UV-3510

[0144] 7 Tripropylene glycol diacrylate (TPGDA) available from IGM Resins USA Inc. as Photomer 4061.

[0145] Cured samples were prepared as described above and tested using the Cured Sample Tack Test described above. The results are shown in the following table. In each table: M. Film Thickness is the measured thickness of the sample in inches; C. Film Thickness is the film thickness calculated from the measured film thickness in mm; and EXP. Time is the time the sample was exposed to radiation in seconds. 4 is the worst result and 0 is the best result.

[0146] sample M. Film thickness (in) C. Film thickness (mm) Exp. Time (seconds) Rating C 0.062 1.57 5 2 C 0.061 1.55 5 2 C 0.064 1.63 5 2 average value 0.061 1.55 2 9 0.064 1.63 5 1 9 0.062 1.57 5 1.5 9 0.065 1.65 5 1 average value 0.062 1.58 1 10 0.063 1.60 5 1 10 0.063 1.60 5 1 10 0.062 1.57 5 1 average value 0.063 1.59 1

[0147] The results of the above table are shown in Figure 5 middle.

[0148]

[0149]

[0150] The results of the above table are shown in Figure 5 middle.

[0151] sample M. Film thickness (in) C. Film thickness (mm) Exp. Time (seconds) Rating E. 0.065 1.65 5 3.5 E. 0.064 1.63 5 3.5 E. 0.068 1.73 5 3.5 average value 0.07 1.67 3.5 13 0.058 1.47 5 1.5 13 0.058 1.47 5 1 13 0.057 1.45 5 1.5 average value 0.06 1.46 1.5 14 0.058 1.47 5 1 14 0.058 1.47 5 1 14 0.059 1.50 5 1.5 average value 0.06 1.48 1

[0152] The results of the above table are shown in Figure 5 middle.

[0153]

[0154]

[0155] The results of the above table are shown in Figure 5 middle.

[0156] sample M. Film thickness (in) C. Film thickness (mm) Exp. Time (seconds) Rating C 0.066 1.68 30 2 C 0.064 1.63 30 2 C 0.063 1.60 30 2 average value 0.06 1.53 2 9 0.061 1.55 30 1 9 0.06 1.52 30 1.5 9 0.062 1.57 30 1 average value 0.06 1.54 1 10 0.06 1.52 30 1 10 0.061 1.55 30 1 10 0.064 1.63 30 0.5 average value 0.06 1.57 1

[0157] The results of the above table are shown in Figure 6 middle.

[0158] sample M. Film thickness (in) C. Film thickness (mm) Exp. Time (seconds) Rating D 0.056 1.42 30 4 D 0.058 1.47 30 4 D 0.056 1.42 30 4 average value 0.06 1.44 4 11 0.05 1.27 30 1.5 11 0.057 1.45 30 1 11 0.058 1.47 30 2 average value 0.06 1.40 1.5 12 0.059 1.50 30 1.5 12 0.064 1.63 30 1 12 0.056 1.42 30 1.5 average value 0.06 1.51 1.5

[0159] The results of the above table are shown in Figure 6 middle.

[0160]

[0161]

[0162] The results of the above table are shown in Figure 6 middle.

[0163] sample M. Film thickness (in) C. Film thickness (mm) Exp. Time (seconds) Rating F 0.062 1.57 30 1 F 0.059 1.50 30 2 F 0.062 1.57 30 1.5 average value 0.06 1.55 1.5 15 0.06 1.52 30 0.25 15 0.058 1.47 30 0.25 15 0.058 1.47 30 0.25 average value 0.06 1.49 0 16 0.062 1.57 30 0.25 16 0.059 1.50 30 0.25 16 0.06 1.52 30 0.25 average value 0.06 1.52 0

[0164] The results of the above table are shown in Figure 6 middle.

[0165] The cured tack ratings for the commercial samples after 5 seconds of radiation exposure were 2 for Sample C, 4 for Sample D, 3.5 for Sample E, and 1 for Sample F. The cured tack ratings after 30 seconds of radiation exposure were essentially the same; 2 for Sample C, 4 for Sample D, 3.5 for Sample E, and 1.5 for Sample F.

[0166] In almost every formulation, the addition of Viscosity Reducing Component 1 reduced the cured viscosity by about half. Adding TPGDA and Viscosity Reducing Agent 2 reduced the cured viscosity by about the same amount as Viscosity Reducing Agent 1, by about half.

[0167] The data show that, in a range of radiation curable formulations, the viscosity reducing component can surprisingly reduce the viscosity of the cured composition. Viscosity reducing agent 1 having (meth)acrylate functional groups significantly reduces the viscosity of the cured surface. Viscosity reducing component 2, a surface wetting agent without (meth)acrylate functional groups, can also surprisingly reduce the viscosity of the cured surface. The use of a multi-(meth)acrylate functional diluent does not reduce the viscosity of the cured surface. However, the use of a combination of viscosity reducing component 2 and a multi-(meth)acrylate functional diluent can synergistically reduce the viscosity of the cured surface compared to the use of viscosity reducing agent 2 alone.

[0168] Example 3

[0169] Additional radiation curable compositions were prepared using the formulations in the following table. All amounts are in wt. % of the composition.

[0170] Material 17 18 19 <![CDATA[Carbamate acrylate polymer 1 > 30 30 30 <![CDATA[urethane acrylate polymer 2 > 15 15 15 <![CDATA[urethane acrylate polymer 3 > 8 8 7 <![CDATA[Diluent 4 > 8 8 7 <![CDATA[Diluent 5 > 17.5 16.5 15.5 <![CDATA[Diluent 6 > 7 7 6 <![CDATA[Diluent 7 > 5 5 5 <![CDATA[Diluent 8 > 3.5 3.5 3.5 <![CDATA[Diluent 9 > 0 1 5 <![CDATA[Visbreaking component 10 > 1 1 1 <![CDATA[Photoinitiator 11 > 1.5 1.5 1.5 <![CDATA[Photoinitiator 12 > 2.5 2.5 2.5 <![CDATA[Additive 13 > >0.1 >0.1 >0.1 <![CDATA[Additive 14 > 1 1 1

[0171] 1 Polyether urethane acrylate oligomer with a viscosity of 26,000 cP at 60°C and an acrylate functionality of about 2, available from Dymax.

[0172] 2 Polyether urethane acrylate oligomer with a viscosity of 13,000 cP at 60°C and an acrylate functionality of about 2, available from Dymax.

[0173] 3 Aliphatic urethane acrylate oligomer having a molecular weight of about 1,500 g / mol, a viscosity of 2,500-4,000 cP at 60°C, and an acrylate functionality of about 2, available from IGM Resins.

[0174] 4-Isobornyl acrylate

[0175] 5-Dimethylacrylamide

[0176] 6-Tetrahydrofurfuryl acrylate

[0177] 7 Trimethylolpropane triacrylate

[0178] 8 Sipomer b-CEA available from Solvay

[0179] 9 Pentaerythritol tetraacrylate

[0180] 10BYK UV 3505

[0181] 11-Hydroxycyclohexylphenylketone 184

[0182] 12-Trimethylbenzoyldiphenylphosphine oxide

[0183] 13 Fluorescent brightener, Tinopal OB CO available from BASF.

[0184] 14γ-Glycidyloxypropyltrimethoxysilane (GLYMO g-GPTMS), purchased from Momentive Performance Materials as Silquest A-187.

[0185] Multiple samples of each composition were placed on a microscope slide. Samples of each composition were cured by exposure to radiation as listed in the table below, and then tested for tack-free properties using the Cured Sample Tack Test described previously; the results were averaged and the averages were rounded. The results are shown in the table below.

[0186]

[0187]

[0188] 1 Loctite 3341, a radiation curable composition, available from Henkel Corporation, US. This sample did not include a viscosity reducing component.

[0189] 2Transparent to turbid liquid

[0190] 3 Transparent to light yellow liquid

[0191] 4 Not tested but assumed to be greater than 100%

[0192] 5 Edge cured, the polycarbonate specimen remained bonded by the cured composition after exposure to radiation, but the bond strength was too low for repeatable measurements on a tensile test apparatus.

[0193] 6 Uncured, the polycarbonate sample did not bond through the composition after exposure to radiation.

[0194] 7 Not tested

[0195] Samples 17-19 again illustrate the surprising benefit of adding a viscosity reducing compound even when the radiation curable composition is exposed to actinic radiation for a very short period of time.

[0196] Samples 17-19 used a combination of different oligomers and combinations of monomers with different acrylate functionalities. Using these combinations provided low viscosity given the high viscosity oligomers in the composition; good bond strength even at a very short exposure time of 0.1 seconds, and low tack even at a very short exposure time of 0.25 seconds. The cured samples were subjectively flexible and were expected to have an elongation of over 100%.

[0197] The flexibility of the cured samples is surprising because the composition includes trifunctional trimethylolpropane triacrylate and tetrafunctional pentaerythritol tetraacrylate. High functionality diluents are expected to crosslink at each acrylate functional group, resulting in a highly crosslinked product with little flexibility. For this reason, high functionality acrylate monomers would not be selected for use in compositions that must be cured to a flexible condition. Without being bound by any theory, the inventors speculate that the multifunctional acrylate monomers contribute to the rapid curing of the composition under the short irradiation time used, without fully reacting, thereby allowing the cured composition to remain flexible.

Claims

1. A radiation curable composition comprising a polymer having (meth)acrylate functional groups; a diluent having one or more (meth)acrylate functional groups; a viscosity reducing component; optionally one or more photoinitiators and optionally additives.

2. The composition of claim 1, wherein the viscosity reducing component comprises an acrylate functionalized polydimethylsiloxane, a non-acrylate functionalized polydimethylsiloxane, or both.

3. The composition according to claim 1 or 2, wherein the polymer having a (meth)acrylate functional group has a polyisobutylene backbone and is represented by the general formula (1): Where R 1 represents a monovalent or polyvalent aromatic hydrocarbon group or a monovalent or polyvalent aliphatic hydrocarbon group, PIB represents a polyisobutylene main chain containing multiple repeating -[CH2C(CH3)2]- units, R 2 and R 3 Each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, R 4 represents a divalent hydrocarbon group having 2 to 6 carbon atoms and optionally containing an oxygen atom, R 5 represents a hydrogen atom, a methyl group, an ethyl group or a propyl group, and n is any integer from 1 to 6.

4. The composition according to claim 1 or 2, wherein the polymer having a (meth)acrylate functional group has a polyisobutylene backbone and is represented by the general formula (1): Where R 1 Contains divalent phenylene, PIB represents a polyisobutylene backbone containing multiple repeating -[CH2C(CH3)2]- units, R 2 and R 3 are each independently a hydrogen atom, a methyl group or an ethyl group, R 4 is a divalent hydrocarbon group having 3 or 4 carbon atoms and optionally containing an oxygen atom, R 5 represents a hydrogen atom or a methyl group, and n is any integer from 1 to 6.

5. The composition of claim 1 or 2, wherein the polymer comprises a first polyether urethane acrylate oligomer having a viscosity greater than 20,000 cP at 60°C and a second polyether urethane acrylate oligomer having a viscosity less than 20,000 cP at 60°C.

6. The composition according to claim 1 or 2, wherein the diluent having one or more (meth)acrylate functional groups comprises 0 to 45 wt.% of a first diluent having a single acrylate functional group; 0 to 20 wt.% of a second diluent having two acrylate functional groups; 0 to 20 wt.% of a third diluent having three acrylate functional groups; and 0 to 20 wt. % of a fourth diluent having four or more acrylate functional groups.

7. The composition of claim 1 or 2, wherein the polymer comprises a first urethane acrylate polymer having a viscosity greater than 20,000 cP at 60°C, a second urethane acrylate polymer having a viscosity less than 20,000 cP at 60°C, and a third urethane acrylate polymer having a viscosity less than 6,000 cP at 60°C, and the polymers are present in a ratio of 3.5-4.5 parts of the first polymer: 1.5-2.5 parts of the second polymer: 0.5-1.5 parts of the third polymer, the parts being calculated by weight of the total polymer content in the composition.

8. The composition of claim 1 or 2, wherein the diluent comprises a monoacrylate functional reactive diluent, a triacrylate functional reactive diluent, and a tetraacrylate functional reactive diluent, and the reactive diluent is in a ratio of 4.5-7.5 parts monoacrylate functional reactive diluent: 0.5-1.5 parts triacrylate functional reactive diluent: 0.5-1.5 parts tetraacrylate functional reactive diluent, the parts being parts by weight of the total reactive diluent content in the composition.

9. The composition according to claim 1 or 2, wherein the diluent comprises isobornyl acrylate, dimethylacrylamide and tetrahydrofurfuryl acrylate as reactive diluents, and the diluent is present in a ratio of 1-2 parts of isobornyl acrylate: 2.5 to 3.5 parts of dimethylacrylamide: 1 to 2 parts of tetrahydrofurfuryl acrylate, the parts being parts by weight of the total reactive diluent content in the composition.

10. The composition according to claim 1 or 2, wherein the diluent comprises isobornyl acrylate, dimethylacrylamide, tetrahydrofurfuryl acrylate, a triacrylate-functional reactive diluent and a tetraacrylate-functional reactive diluent as reactive diluents, and the reactive diluents are present in a ratio of 1-2 parts of isobornyl acrylate: 2.5 to 3.5 parts of dimethylacrylamide: 1 to 2 parts of tetrahydrofurfuryl acrylate: 0.5-1.5 parts of triacrylate-functional reactive diluent: 0.5-1.5 parts of tetraacrylate-functional reactive diluent, the parts being parts by weight of the total reactive diluent content in the composition.

11. An article comprising the composition of claim 1 or 2 disposed between a first component bonding surface and a second component bonding surface.

12. The article of claim 11, wherein the composition cures after exposure to radiation such that a cured reaction product of the composition bonds the first component bonding surface to the second component bonding surface.

13. The article of claim 11, wherein the first component and the second component are each flexible.

14. The article of claim 11, wherein the first component and the second component are each flexible, and the first component bonding surface and the second component bonding surface are independently selected from acrylic polymers, urethane polymers, metal foils, metal wires, and rubbers.

15. The article of claim 11, wherein the first component and the second component are bonded at discrete points on the first bonding surface and the second bonding surface, the remainder of the first bonding surface and the second bonding surface remaining substantially free of cured reaction product.

16. A method of reducing the viscosity of an at least partially cured polymer composition, comprising: Providing a radiation curable formulation comprising a (meth)acrylate functional polymer; providing a viscosity reducing component comprising an acrylate-functionalized polydimethylsiloxane, a non-acrylate-functionalized polydimethylsiloxane, or both; combining the radiation curable formulation and the viscosity reducing component to form a radiation curable composition; and The radiation curable composition is exposed to radiation to cure the composition, wherein a cured reaction product of the composition has a lower viscosity rating than a cured reaction product of the radiation curable formulation.

17. The method of claim 16, wherein the viscosity reducing component comprises a combination of acrylate functionalized polydimethylsiloxane and TPGDA, a combination of non-acrylate functionalized polydimethylsiloxane and TPGDA, or a combination of acrylate functionalized polydimethylsiloxane, non-acrylate functionalized polydimethylsiloxane, and TPGDA.

18. Use of a viscosity reducing component for reducing the viscosity of a cured reaction product of a radiation curable formulation.

19. The use according to claim 18, wherein the viscosity reducing component comprises a non-acrylate functionalized polydimethylsiloxane and a multi-(meth)acrylate functional diluent having 1 to 20 carbon atoms.

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