Uv curable resin-linear polysiloxane hot melt composition

Abstract

A hot melt composition containing: (a) based on T Ar a resin-linear block copolymer of the type -D, wherein the block of TAr siloxane units is linked to the block of D-type siloxane units by a bond comprising in at least some cases an alkenyl group, with the proviso that the concentration of such alkenyl groups is in the range of 0.5 to 3.0 mol-% relative to the total number of moles of silicon atoms in the resin-linear block copolymer; (b) a crosslinker containing on average at least two (meth)acryloyloxy groups per molecule; (c) a free-radical photoinitiator; and optionally (d) an ultraviolet light stabilizer; and optionally (e) an adhesion promoter.

Description

Technical Field

[0001] This invention relates to UV-curable polysiloxane hot melt compositions, methods for curing such compositions, and articles comprising such compositions. Background Technology

[0002] The market for miniature and micro-sized light-emitting diodes (LEDs) is growing rapidly, partly due to their use in displays and automotive applications. Miniature LED arrays are used as backlight panels for standard LCD displays, improving brightness, contrast, and black levels. Micro-sized LEDs refer to tiny LEDs used directly as pixels in a display, specifically combinations of red, green, and blue LED dots. Both technologies require sealants to protect the fragile LEDs and improve light extraction by replacing air with silicone interlayers.

[0003] Historically, encapsulation compositions have been applied to LED components via liquid injection methods. Recently, hot melt systems have become more popular due to their advantages over liquid injection systems. These advantages include ease of covering large areas, process simplicity, and reprocessability.

[0004] One form of sealant technology involves using silicone sealants that are cured via hydrogen silanization after application to LED components. Hydrogen silanization typically requires elevated temperatures, often exceeding 60 degrees Celsius (°C) and / or curing times of one hour or longer. Unfortunately, some display designs incorporate temperature-sensitive materials that cannot be exposed to high temperatures without compromising their functionality. Therefore, to protect temperature-sensitive materials and improve manufacturing efficiency to meet the growing demand for miniature and micro-LED devices, it is desirable to identify a hot melt encapsulation technology that does not require the temperature or time of a hydrogen silanization curing system.

[0005] WO2017068762 discloses a hot-melt UV (UV) curable system using thiol-olefin chemical curing. While this system can cure at lower temperatures than hydrogen silane curing systems, these hydrogen silane curing systems use thiol-based reactants, which may produce undesirable odors and potentially cause yellowing.

[0006] It will advance the field of LED sealants by identifying a hot melt sealant composition that cures at a temperature below 60°C and / or for a curing time of one hour or less, or even 30 minutes or less, and does not use thiol-based reactants. Summary of the Invention

[0007] The present invention provides a hot melt sealant composition that is cured at a temperature below 60°C and / or for a curing time of one hour or less, or even 30 minutes or less, and does not use thiol-based reactants.

[0008] This invention stems from the discovery of a resin-linear technology that can withstand acrylate-olefin UV curing and can be a suitable hot-melt sealant composition without requiring unbound nanophase particles of MQ resin. This invention utilizes T-based resins with alkenyl functional groups... Ar -D resin-linear block copolymers combined with crosslinking agents having multiple (meth)acryloyloxy groups per molecule provide hot melt compositions that can be UV-cured in just a few minutes, or even less than a minute, at temperatures below 60°C, or even 40°C or lower, 30°C or lower, or even 25°C or lower, without requiring any thiol components.

[0009] In a first aspect, the present invention is a hot melt composition comprising: (a) 80 to 99 parts by weight of at least one T-based... Ar -D resin-linear block copolymers, at least one of which is based on T Ar -D resin-linear block copolymers contain T Ar Type T siloxane unit blocks and D-type siloxane unit blocks, wherein: (i)T Ar The type-I siloxane block is linked to the D-type siloxane unit block by bonds selected from those having the following structure (I):

[0010]

[0011] Where Ar is C6-C 20 Aryl; R 1 Selected from C1-C 20 alkyl groups and C2-C 20 Alkenyl groups, provided that the number of alkenyl groups is relative to the total number of silicon atoms, based on T. Ar -D resin-linear block copolymer alkenyl R 1 The average concentration of the groups is in the range of 0.5 mol% to 3.0 mol%; and R 2 and R 3 Independently, it is C1-C 20 Hydrocarbon groups, each dashed line corresponding to a valence bond with silicon, hydrogen, or a hydrocarbon group; and wherein: (ii) T ArThe molar ratio of type-3 siloxane unit blocks to type-4 siloxane unit blocks is at least 2; (iii) the resin-linear block copolymer contains 8 mol% to 35 mol% Si-OR' bonds relative to the molar number of silicone atoms, wherein R' is an H or C1-C8 hydrocarbon group; (iv) each type-4 siloxane unit block contains an average of 20 to 200 type-4 siloxane units; and (v) each T Ar The siloxane unit block has a weight-average molecular weight in the range of 500 g / mol to 10,000 g / mol; (b) 0.5 parts by mass to 20 parts by mass of a crosslinking agent, which contains an average of at least two (meth)acryloyloxy groups per molecule; (c) 0.1 parts by mass to 10 parts by mass of a free radical photoinitiator; (d) 0 parts by mass to 2.0 parts by mass of a UV stabilizer; and (e) 0 parts by mass to 2.0 parts by mass of an adhesion promoter.

[0012] In a second aspect, the invention is a method comprising the steps of: heating a hot melt composition of the first aspect to soften the hot melt composition, and then applying the softened hot melt composition over at least a portion of a substrate to form a coating of the hot melt composition over at least a portion of the surface of the substrate.

[0013] In a third aspect, the present invention is an article comprising a hot melt composition of at least a portion of the coating substrate surface of the first aspect.

[0014] The compositions of this invention can be used as LED sealants. Detailed Implementation

[0015] When a test method number is not used to indicate a date, the test method refers to the most recent test method as of the priority date of this document. References to test methods include references to both the testing association and the test method number. The following test method abbreviations and identifiers apply to this document: ASTM refers to the American Society for Testing and Materials; EN refers to European Standards; DIN refers to the German Institute for Standardization; JIS refers to Japanese Industrial Standards; and ISO refers to the International Organization for Standardization.

[0016] Products identified by their trade names refer to compositions available under those trade names as of the priority date of this document.

[0017] "Multiple" means two or more. "And / or" means "and, or as an alternative." Unless otherwise specified, all scopes include the endpoints. Material identified by a trademark or trade name means that the material has components sold under that trademark or trade name as of the priority date of this document.

[0018] "Parts by mass" refers to the mass of a component in a composition, measured in the same unit of measurement as the parts by mass of other components, to provide a mass indication of each component in the composition relative to the other components. For example, a composition containing 5 grams of component A and 10 grams of component B will have one part by mass of component A and 2 parts by mass of component B, or, alternatively, 5 parts by mass of component A and 10 parts by mass of component B. In this document, parts by mass refers to the concentration of a component in a hot melt composition relative to the mass of other components in the hot melt composition—meaning all parts by mass are based on the same unit of mass for the components of the hot melt composition.

[0019] General term "C" x-y “C” x -C y "Cx to Cy" and "Cx-Cy" are interchangeable in the context of chemical structure and refer to a chemical structure having x to y carbon atoms.

[0020] The number-average molecular weight (Mn), weight-average molecular weight (Mw), polydispersity index (PDI), and free resin percentage of the materials were determined by gel permeation chromatography (GPC) using the following method: Sample preparation: Samples were prepared in toluene eluent at a concentration of 20 mg / mL polymer. The solution was shaken on a plate shaker at ambient temperature for approximately 2 hours. The solution was filtered through a 0.45 μm PTFE syringe filter prior to injection. GPC was performed on a Viscotek GPC Max pump and autosampler. The flow rate was set to 1 mL / min, and the injection volume of standards was set to 100 μL, while the injection volume of the study sample was set to 200 μL. Each sample was injected in duplicate. Separation was performed on two Agilent Plgel Mixed-B columns maintained at 35 °C. The detectors were Viscotek TDA 305 triple detector arrays maintained at 35 °C. The triple detectors included RI, UV, LALS, RALS, and DP. Software and Data Processing: Malvern OMNISEC 5.02 was used for data collection, and Malvern OMNISEC 5.12 was used for data reduction. Routine molecular weight calibration was performed using a total of 17 linear narrow molecular weight PS standards with Mp values ​​ranging from 4,000 kg / mol to 0.58 kg / mol from Agilent. Calibration curve fitting was performed using a third-order polynomial. Therefore, all molecular weight averages, distributions, and molecular weight references provided in this report are polystyrene (PS) equivalents, and only RIs are used for molecular weight calculations.

[0021] On one hand, the present invention is a hot-melt composition. A "hot-melt" composition is characterized by a softening point of 50 degrees Celsius (°C) or higher, and typically 150°C or lower. The hot-melt compositions of the present invention desirably have a softening point of 50°C or higher, preferably 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, and may be 100°C or higher, while desirably 150°C or lower, preferably 125°C or lower, and even 100°C or lower. The softening point of the composition is determined by the ring and ball method of JIS K6863-1994. The softening of the hot-melt composition is reversible, meaning that the hot-melt composition can be repeatedly heated above its softening point and cooled below its softening point while maintaining its hot-melt behavior.

[0022] Ideally, the hot melt composition of the present invention has a storage modulus greater than 0.01 MPa at 25°C and a tanδ of less than 2.0 or preferably 1.5 or less at 25°C, which means that the hot melt composition is non-flowable at 25°C. It is also desirable that the hot melt composition of the present invention have any combination of one or more of the following additional properties that make it particularly suitable as an LED sealant: (i) a ratio of viscosity at 25°C to viscosity at 100°C (measured in kPa) of 20 or greater, preferably 100 or greater, while typically 10,000 or less, and may be 5,000 or less, 4,000 or less, or even 3,800 or less; (ii) a storage modulus at 25°C preferably greater than 0.1 MPa, while typically 100 MPa or less, or even 50 MPa or less, 25 MPa or less, 10 MPa or less, or even 8.5 MPa or less, or 8 MPa or less; and (iii) a Tanδ value at 25°C preferably 2.0 or less, while typically 0.01 or greater, and may be 0.05 or greater, 0.10 or greater, or even 0.12 or greater. The viscosity, storage modulus, and Tanδ of the composition were determined by rotational rheology using an ARES-G2 apparatus equipped with a TA instrument featuring a 25 mm parallel plate and a 1 mm sample thickness. The sample in the test apparatus was equilibrated at 20 °C for 5 minutes, and then the temperature was increased to 120 °C at a rate of 3 °C / min, with data collected every 9 seconds.

[0023] The hot melt composition comprises: (a) based on T Ar (a) a resin-linear block copolymer of -D; (b) a crosslinking agent; (c) a free radical photoinitiator; optionally (d) a UV stabilizer; and optionally (e) an adhesion promoter. The hot melt composition may and desirably be free of mercapto-functionalized siloxanes. The hot melt composition is even more desirably free of any mercapto-functionalized components. The hot melt may additionally or alternatively be free of unbound Q-based resin particles. "Unbound" means free of T-based... Ar-D refers to the covalent bonds of the resin-linear block copolymer or crosslinker. "Q-based resin particles" refers to particles containing more than 40 mol% SiO₂, typically more than 50 mol% SiO₂, relative to all siloxane units in a polysiloxane molecule. 42 Polysiloxane particles composed of siloxane units, wherein O 4 / 2 It refers to four oxygen atoms, each of which combines with a silicon atom and shares with another silicon atom to form a siloxane bond.

[0024] "Resin-linear block copolymer" refers to a block copolymer comprising one or more linear polymer blocks bonded to one or more resin polymer blocks. "Block" refers to a repeating segment of multiple units of the same basic type. Based on T Ar -D resin-linear block copolymers include T Ar Type-3 siloxane unit blocks and D-type siloxane unit blocks, these T Ar The D-type siloxane unit blocks are resin polymer blocks, and these D-type siloxane unit blocks are block or linear polymers.

[0025] T Ar The type of siloxane unit has the chemical formula:

[0026] ArSi(OR') t O (3-t) / 2

[0027] in:

[0028] Ar refers to an aryl group having 6 or more, and may have 7 or more, 8 or more, 9 or more, 10 or more, 12 or more, 14 or more, 16 or more, or even 18 or more, while usually having 20 or fewer, and may have 18 or fewer, 16 or fewer, 14 or fewer, 12 or fewer, 10 or fewer, or 8 or fewer carbon atoms, while preferably the aryl group is a phenyl group;

[0029] R' is independently selected from hydrogen and hydrocarbon groups each time it appears, wherein these hydrocarbon groups preferably have one or more, and may have 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, or even 7 or more, while usually having 8 or fewer, and may have 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, or even 2 or fewer carbon atoms;

[0030] The subscript t represents the number of (OR') groups bonded to the silicon atom, and typically has a value in the range of zero to 2; and

[0031] O (3-t) / 2It refers to the (3-t) oxygen atom that combines with a silicon atom and shares with another silicon atom to form a siloxane bond.

[0032] T Ar The blocks of the type siloxane unit contain multiple T-type siloxane units linked together by shared siloxane bonds. Ar Type siloxane unit.

[0033] D-type siloxane units have the general chemical formula: R₂SiO₂ 2 / 2 ; where O 2 / 2 A siloxane group refers to two oxygen atoms bonded to a silicon atom and shared with another silicon atom to form a siloxane bond; and each R is independently selected from hydrocarbon groups having one or more, and may have 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, even 7 or more, 8 or more, 10 or more, 12 or more, 14 or more, 16 or more, even 18 or more, while typically having 20 or fewer, 18 or fewer, 16 or fewer, 14 or fewer, 12 or fewer, 10 or fewer, 8 or fewer, and may have 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, even 2 or fewer carbon atoms. Typically, each R group is methyl. A block of a D-type siloxane unit comprises multiple D-type siloxane units linked together by shared siloxane bonds.

[0034] Based on T Ar The resin-linear block copolymer of -D is also characterized by the following properties:

[0035] (i)T Ar The type-I siloxane block binds to D-type silicon via bonds selected from those having the following structure (I).

[0036] Oxyalkane unit block linkage:

[0037]

[0038] Where: Ar is as described above; R 1 Selected from C1-C 20 alkyl groups and C2-C 20 Alkenyl groups (preferably vinyl groups), conditions based on T Ar -D resin-linear block copolymer R 1The average concentration of the alkenyl group is in the range of 0.5 mol% to 3.0 mol%, and can be 0.5 mol% or more, 0.75 mol% or more, 1.0 mol% or more, 1.5 mol% or more, 2.0 mol% or more, or even 2.5 mol% or more, while being 3.0 mol% or less, and relative to the total number of moles of silicon atoms, can be 2.5 mol% or less, 2.0 mol% or less, 1.5 mol% or less, or even 1.0 mol% or less; and R 2 and R 3 The R group is independently selected from those described above, and preferably from methyl and ethyl groups; and each dashed line corresponds to a valence bond with a silicon, hydrogen, or hydrocarbon group;

[0039] (ii)T Ar The molar ratio of type D siloxane unit blocks to type D siloxane unit blocks is 2 or greater, and preferably each type D siloxane unit is marked with a T at either end. Ar Type siloxane unit block end capping;

[0040] (iii) Compared to T-based Ar The total molar number of silicone atoms in the -D resin-linear block copolymer, based on T Ar -D resin-linear block copolymers have sufficient OR' groups to provide 8 or more, and possibly 9 or more, 10 or more, 11 or more, 12 or more, 14 or more, 16 or more, 18 or more, 20 or more, 22 or more, 24 or more, 26 or more, or even 28 or more, while 35 or less, and possibly 30 or less, 25 or less, 20 or less, 15 or less, or even 10 or less molar percentage (mol%) Si-OR' bonds; and

[0041] (iv) Each D-type siloxane unit block contains an average of 10 to 200 D-type siloxane units, and may contain an average of 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 120 or more, 140 or more, 160 or more, or even 180 or more, while typically containing 200 or fewer, 180 or fewer, 160 or fewer, 140 or fewer, 120 or fewer, 100 or fewer, 90 or fewer, 80 or fewer, 70 or fewer, 60 or fewer, 50 or fewer, 40 or fewer, 30 or fewer, or even 20 or fewer D-type siloxane units; and

[0042] (v) Each T Ar The type siloxane unit block has a weight-average molecular weight (Mw) in the range of 500 g / mol to 10,000 g / mol, and can have 500 or greater, 750 or greater, 1000 or greater, 2500 or greater, 5000 or greater, or even 7500 or greater, while typically 10,000 or less, 7500 or less, 5000 or less, 2500 or less, and can be 1000 or less, or even 750 or less Mw.

[0043] pass 29 Si NMR spectroscopy determination based on T Ar The average number of D-type siloxane units in the -D resin-linear block copolymer. Using the above procedure, the number of D-type siloxane units was determined based on T by gel permeation chromatography (GPC). Ar -D resin-linear block copolymers in T Ar The average Mw of the type siloxane unit block.

[0044] Based on T Ar -D resin-linear block copolymers may be free of (meth)acryloyloxy groups. In fact, the entire composition may be free of (meth)acryloyloxy-functionalized polysiloxanes.

[0045] The hot melt composition comprises 80 parts by weight or more, and may comprise 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, or even 97 parts by weight or more, while typically comprising 99 parts by weight or less, and may comprise 98 parts by weight or less, 95 parts by weight or less, 90 parts by weight or less, or even 85 parts by weight or less, at least one of T-based components. Ar -D resin-linear block copolymer.

[0046] Based on T Ar -D resin-linear block copolymers may be free of alkenyl functionalized R”3SiO 1 / 2 A siloxane unit, wherein R” is a hydrocarbon group and O 1 / 2 It refers to oxygen that is bonded to a silicon atom and shared with another silicon atom in a siloxane bond.

[0047] Crosslinking agents are molecules that contain an average of two or more (meth)acryloyloxy groups per molecule, and may contain three or more, or even four or more, while typically containing eight or fewer, seven or fewer, six or fewer, five or fewer, four or fewer, or even three or fewer (meth)acryloyloxy groups per molecule.

[0048] To avoid loss of composition components during heating (i.e., to obtain stable curability), it is desirable for the crosslinking agent and / or free radical photoinitiator to have a temperature above 100°C, preferably 150°C or higher, more preferably 200°C or higher, while typically 400°C or lower, and may have a boiling point of 350°C or lower, 300°C or lower, 250°C or lower, or even 200°C or lower.

[0049] The crosslinking agent may be one or more compounds selected from those having average chemical structures (III) and (IV):

[0050] R' m CX (4-m) (III)

[0051] XR”-X (IV)

[0052] in:

[0053] Each R' is independently selected each time it appears from alkyl groups having one to 20 carbon atoms, and may have one or more, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, ten or more, twelve or more, fourteen or more, sixteen or more, or even eighteen or more, while usually having 20 or fewer, eighteen or fewer, sixteen or fewer, fourteen or fewer, twelve or fewer, ten or fewer, eight or fewer, six or fewer, four or fewer, or even two or fewer carbon atoms;

[0054] Each X is independently selected from the -CH2OC(O)CH=CH2 and -CH2OC(O)C(CH3)=CH2 groups, and

[0055] "R" is an alkylene group having one to 20 carbon atoms, and may have one or more, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, eleven or more, twelve or more, fourteen or more, sixteen or more, or even eighteen or more, while having 20 or fewer, eighteen or fewer, sixteen or fewer, fourteen or fewer, twelve or fewer, ten or fewer, eight or fewer, six or fewer, four or fewer, or even two or fewer carbon atoms.

[0056] Examples of suitable crosslinking agents include trimethylpropane triacrylate, pentaerythritol tetraacrylate, and 1,12-dodecanediol dimethacrylate.

[0057] The concentration of the crosslinking agent in the hot melt composition is typically in the range of 0.5 parts by mass to 20 parts by mass, and can be present at concentrations of 0.5 or higher, 1.0 or higher, 2.0 or higher, 4.0 or higher, 6.0 or higher, 8.0 or higher, 10.0 or higher, 12.0 or higher, 14.0 or higher, 16.0 or higher, or even 18.0 or higher, while typically present at concentrations of 20.0 or lower, 18.0 or lower, 16.0 or lower, 14.0 or lower, 12.0 or lower, 10.0 or lower, 8.0 or lower, 5.0 or lower, 4.0 or lower, 3.0 or lower, 2.0 or lower, or even 1.0 or lower parts by mass.

[0058] The hot-melt composition contains a free radical photoinitiator at concentrations of 0.1 parts by weight or higher, 0.5 parts by weight or higher, 1.0 parts by weight or higher, 2.0 parts by weight or higher, 3.0 parts by weight or higher, 4.0 parts by weight or higher, 5.0 parts by weight or higher, 6.0 parts by weight or higher, 7.0 parts by weight or higher, 8.0 parts by weight or higher, or even 9.0 parts by weight or higher, while simultaneously containing 10 parts by weight or lower, 9.0 parts by weight or lower, 8.0 parts by weight or lower, 7.0 parts by weight or lower, 6.0 parts by weight or lower, 5.0 parts by weight or lower, 4.0 parts by weight or lower, 3.0 parts by weight or lower, 2.0 parts by weight or lower, or even 1.0 parts by weight or lower.

[0059] Free radical photoinitiators can be, for example, combinations of any one or more components selected from the group consisting of: benzophenone and benzophenone derivatives, acetophenone and acetophenone derivatives, benzoin and its alkyl esters, phosphine oxide derivatives, xanthonesone derivatives, oxime ester derivatives, and camphorquinone. Suitable commercially available photoinitiators include any combination of any one or more of the following: 2,6-bis(4-azidobenzyl)cyclohexanone; 2,6-bis(4-azidobenzyl)-4-methylcyclohexanone; 1-hydroxy-cyclohexyl-phenyl-one (under the name OMNIRAD). TM184); 2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropane-1-one (obtained under the name OMNIRAD 907); 2-hydroxy-2-methyl-1-phenyl-propane-1-one (obtained under the name OMNIRAD 1173); 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (obtained under the name OMNIRAD 2959); methyl benzoylformate (obtained under the name OMNIRAD MBF); α,α-dimethoxy-α-phenylacetophenone (obtained under the name OMNIRAD 651); 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone (obtained under the name OMNIRAD 907); 369); diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (obtained under the name OMNIRADTPO); ethyl (2,4,6-trimethylbenzoyl)phenylphosphine sulfate (obtained under the name OMNIRAD TPO-L); oxime ester compounds (obtained as products N-1919, NCI-831, NCI-930, NCI-730 and NCI-100 from Adeka Corporation); 12-thioxanth-9-one; 10-methylphenothiazine; isopropyl-9H-thioxanth-9-one; 2,4-diethyl-9H-thioxanth-9-one; 2-chlorothioxanth-9-one; and 1-chloro-4-propoxy-9H-thioxanth-9-one. OMNIRAD is a trademark of IGM Group BV. One particularly desirable free radical photoinitiator is 2,4,6-trimethylbenzoyl-phenylphosphine ester.

[0060] Optionally, the hot melt composition may contain a UV stabilizer. UV stabilizers are free radical scavengers, and these UV stabilizers can extend the storage stability of the hot melt composition by inhibiting curing until the hot melt composition is intentionally exposed to UV light. UV stabilizers include phenolic compounds, such as any one or more of the following in any combination: 4-methoxyphenol (MEHQ, methyl ether of hydroquinone), hydroquinone, 2-methylhydroquinone, 2-tert-butylhydroquinone, tert-butylcatechol, butylated hydroxytoluene, and butylated hydroxyanisole. Other types of UV stabilizers include phenothiazines and anaerobic inhibitors, such as NPAL-type inhibitors (tris(N-nitroso-N-phenylhydroxylamine) aluminum salt) available from Albemarle Corporation.

[0061] The concentration of UV stabilizers is typically zero parts by mass or higher, but can be 0.1 parts by mass or higher, 0.5 parts by mass or higher, 1.0 parts by mass or higher, or even 1.5 parts by mass or higher, while typically 2.0 parts by mass or lower, 1.5 parts by mass or lower, 1.0 parts by mass or lower, or even 0.5 parts by mass or lower.

[0062] Optionally, the hot melt composition may contain an adhesion promoter. Suitable adhesion promoters include organosilicon compounds having at least one alkoxy group bonded to silicon in the molecule. Examples of the alkoxy group are methoxy, ethoxy, propoxy, butoxy, and methoxyethoxy groups, with the methoxy group being particularly preferred. Furthermore, examples of silicon-bonded groups in organosilicon compounds, other than alkoxy groups, include halogenated or unsubstituted monovalent hydrocarbon groups, such as alkyl groups, alkenyl groups, aryl groups, aralkyl groups, haloalkyl groups, haloaryl groups, and haloaralkyl groups; glycidyloxyalkyl groups, such as 3-glycidyloxypropyl groups and 4-glycidyloxybutyl groups; epoxycyclohexylalkyl groups, such as 2-(3,4-epoxycyclohexyl)ethyl groups and 3-(3,4-epoxycyclohexyl)propyl groups; epoxyalkyl groups, such as 3,4-epoxybutyl groups and 7,8-epoxyoctyl groups; monovalent organic groups containing acrylic groups, such as 3-methacryloyloxypropyl groups; and hydrogen atoms. Adhesion promoters preferably contain groups that can react with alkenyl groups or silicon-bonded hydrogen atoms. Specifically, adhesion promoters preferably contain silicon-bonded hydrogen atoms or alkenyl groups. Furthermore, adhesion promoters preferably possess at least one monovalent organic group containing an epoxy group in their molecule, as they can impart good adhesion to various types of substrates. Examples of this type of adhesion promoter are organosilane compounds, organosiloxane oligomers, and alkyl silicate esters. Examples of molecular structures for organosiloxane oligomers or alkyl silicate esters include straight-chain, partially branched straight-chain, branched, cyclic, and network structures. Straight-chain, branched, and network structures are particularly preferred. Examples of adhesion promoters are silane compounds, such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane; siloxane compounds having at least one silicon-bonded alkenyl group or each of a silicon-bonded hydrogen atom and a silicon-bonded alkoxy group in the molecule; mixtures of silane compounds having at least one silicon-bonded alkoxy group and siloxane compounds having at least one silicon-bonded hydroxyl group and at least one silicon-bonded alkenyl group in the molecule; and methyl polysilicates, ethyl polysilicates, and ethyl polysilicates containing epoxy groups. The adhesion promoter is preferably a low-viscosity liquid, and the viscosity of the adhesion promoter is not particularly limited, but is preferably 1 mPa to 500 millipascals (mPa) at 25°C.

[0063] The concentration of adhesion promoters is typically zero parts by mass or higher, but can be 0.1 parts by mass or higher, 0.5 parts by mass or higher, 1.0 parts by mass or higher, or even 1.5 parts by mass or higher, while typically 2.0 parts by mass or lower, 1.5 parts by mass or lower, 1.0 parts by mass or lower, or even 0.5 parts by mass or lower.

[0064] It is worth noting that the hot-melt composition of the present invention may be free of hydrogenation silylation catalysts, such as platinum catalysts. Therefore, the hot-melt composition may be platinum-free, which is desirable for avoiding yellowing of the composition and maintaining a lower cost than systems requiring platinum catalysts.

[0065] On the other hand, the present invention is a method for using the hot melt composition of the present invention as a curable coating on a substrate. The method includes the steps of: heating the hot melt composition according to the present invention to soften the hot melt composition, and then applying the softened hot melt composition over at least a portion of a substrate to form a coating of the hot melt composition over at least a portion of the surface of the substrate. The method further includes exposing the coating of the hot melt composition to ultraviolet light to induce crosslinking of the composition coating. When the (meth)acryloyloxy group of the crosslinking agent reacts with T... Ar Crosslinking occurs when the alkenyl groups of the -D resin-linear block copolymer react.

[0066] In particularly desirable applications, the hot-melt composition of the present invention is a sealant for light-emitting diodes (LEDs). In such applications, the method is as described above, and the substrate on which the hot-melt composition is coated comprises an LED. The coating covers the LED, thereby encapsulating the LED, and is then cured by exposure to UV light.

[0067] In another aspect, the present invention is an article comprising a hot-melt composition coated on at least a portion of the surface of a substrate. Desiredly, and most preferably, the substrate portion coated with the hot-melt composition includes a light-emitting diode.

[0068] Example

[0069] Synthesis of silanol-terminated polydimethylsiloxane (PDMS)

[0070] The silanol-terminated PDMS material used in the following examples was prepared by reacting shorter-chain silanol-terminated PDMS with a potassium hydroxide (KOH) catalyst solution to produce longer-chain silanol-terminated PDMS, while purging the reaction with nitrogen during the reaction to remove water. Chain length was monitored by observing changes in the OH band concentration in Fourier transform infrared (FT-IR) spectroscopy. Different chain lengths could be prepared by starting with silanol-terminated PDMS of different chain lengths, using different catalyst concentrations, and by conducting the reaction for different times. Once the reaction was complete, the chain length was monitored by... 29 The degree of polymerization (DP) was confirmed by Si NMR. The silanol-terminated PDMS materials of the following examples are characterized in Table 1.

[0071] Table 1

[0072]

[0073] The following are the procedures for the longest and shortest silanol-terminated PDMS used in the examples. Those skilled in the art should be able to prepare silanol-terminated PDMS materials in the medium range based on these procedures. This method uses starting silanol-terminated PDMS with a viscosity in the range of 50 centistokes to 120 centistokes (available from The Dow Chemical Company under the name XIAMETER). TM PMX-0156 was purchased commercially. XIAMETER is a trademark of Dow Silicones Corporation. DOWSIL is a trademark of The Dow Chemical Company.

[0074] Silanol-terminated PDMS1: Degree of polymerization (DP) = 54

[0075] 500.0 g of starting silanol-terminated PDMS was added to a 1-liter, 3-necked round-bottom flask equipped with a PTFE stirrer and thermocouple, with one neck kept open, while purging with nitrogen at a flow rate of 1.5 standard cubic feet per hour. 0.17 g of a 3 wt% potassium hydroxide solution was added to the flask at 90°C. After 3 hours at 90°C, 0.53 g of a 2.5 wt% aqueous phosphoric acid solution was added. The solution was cooled to 25°C. It was purged with nitrogen overnight to remove water. The solution was filtered through a nylon filter to obtain PDMS1. 29 Si NMR confirmed that PDMS1 has a DP of 54.

[0076] Silanol-terminated PDMS2: DP = 98

[0077] 1255.6 g of silanol-terminated PDMS was added to a 1-liter, three-necked round-bottom flask equipped with a PTFE stirrer and thermocouple, with one neck kept open, while purging with nitrogen at a flow rate of 1.5 standard cubic feet per hour. 0.42 g of a 3 wt% potassium hydroxide solution was added to the flask at 90 °C. The mixture was incubated at 90 °C for 3 hours and... 1 Two hours later, add 1.32 g of a 2.5 wt% aqueous phosphoric acid solution. Cool the solution to 25°C. Purge with nitrogen overnight to remove water. Filter through a nylon filter to obtain PDMS2. 29 Si NMR confirmed that PDMS2 has a DP of 98.

[0078] Based on T Ar Synthesis of -D resin-linear block copolymers RL1-RL6

[0079] In addition to PDMS1-4, Table 2 lists the components used together with silanol-terminated PDMS to prepare RL1-RL6.

[0080] Table 2

[0081]

[0082] DOWSIL is a trademark of The Dow Chemical Company.

[0083] RL1: 45wt% resin / 55wt% silanol-terminated PDMS1 and vinyl functionalized

[0084] 90.0 g of resin and 185.5 g of toluene were loaded into a 1-liter (1 L) four-necked round-bottom flask equipped with a thermocouple, a PTFE stirrer, and a Dean Stark apparatus connected to a water-cooled condenser. Sufficient additional toluene equal to the volume of the Dean Stark apparatus was added. An inert gas smothering was applied, and the mixture was refluxed for 30 minutes to remove water.

[0085] Diacetyloxysilane-terminated PDMS was prepared by adding 8.50 g VTA and 5.4 g acetyloxysilane to a mixture of 59.2 g toluene and 110.0 g silanol-terminated PDMS 1 in a 500 mL round-bottom flask. The mixture was stirred for one hour. The resulting diacetyloxysilane-terminated PDMS was rapidly added to a resin-containing flask at 106 °C to form a reaction mixture. The mixture was refluxed for 2 hours. The reaction mixture was cooled to 90 °C and 21.9 g deionized water was added. Water and acetic acid byproducts were removed by azeotropic distillation. Water was added and removed again. 81.0 g of volatiles were removed by distillation to obtain a concentrated solution. The addition and removal of water were repeated three times. The resulting solution was filtered through a 5 μm nylon filter. Volatiles were reduced using a rotary evaporator to increase the solids content. Based on the solution mass, a translucent solution of RL1 in toluene retained an active concentration of 79.6% by mass of RL1.

[0086] RL2: 35wt% resin / 65wt% silanol-terminated PDMS2 and vinyl functionalization

[0087] 70.0 g of resin and 230.0 g of toluene were loaded into a 1-liter (1L) four-necked round-bottom flask equipped with a thermocouple, a PTFE stirrer, and a Dean Stark apparatus connected to a water-cooled condenser. Sufficient additional toluene equal to the volume of the Dean Stark apparatus was added. An inert gas smothering was applied, and the mixture was refluxed for 30 minutes to remove water.

[0088] Diacetyloxysilane-terminated PDMS was prepared by adding 8.50 g VTA and 0.56 g acetyloxysilane to a mixture of 70.0 g toluene and 130.0 g silanol-terminated PDMS 2 in a 500 mL round-bottom flask. The mixture was stirred for one hour. At 106 °C, the resulting diacetyloxysilane-terminated PDMS was rapidly added to a resin-containing flask to form a reaction mixture. The mixture was refluxed for 2 hours. The reaction mixture was cooled to 106 °C and 1.75 g acetyloxysilane was added. The mixture was refluxed for one hour. The mixture was cooled to 25 °C and 16.9 g deionized water was added. Water and acetic acid byproducts were removed by azeotropic distillation. Water was added and removed again. Volatile matter was removed by distillation to obtain a concentrated solution. The addition and removal of water were repeated three times. The resulting solution was filtered through a 5 μm nylon filter. Volatile matter was reduced using a rotary evaporator to increase the solids content. Based on solution mass, a semi-transparent solution of RL2 in toluene retains 72.9% by mass of RL2 active in toluene.

[0089] RL3: 45wt% resin / 55wt% silanol-terminated PDMS4 and vinyl functionalized

[0090] 270.0 g of resin and 722.3 g of toluene were loaded into a 3-liter (3L) four-necked round-bottom flask equipped with a thermocouple, a PTFE stirrer, and a Dean Stark apparatus connected to a water-cooled condenser. Sufficient additional toluene equal to the volume of the Dean Stark apparatus was added. An inert gas smothering was applied, and the mixture was refluxed for 30 minutes to remove water.

[0091] Diacetyloxysilane-terminated PDMS was prepared by adding 25.50 g VTA and 10.36 g acetyloxysilane to a mixture of 177.7 g toluene and 330.0 g silanol-terminated PDMS 4 in a 500 mL round-bottom flask. The mixture was stirred for one hour. At 106 °C, the resulting diacetyloxysilane-terminated PDMS was rapidly added to a resin-containing flask to form a reaction mixture. The mixture was refluxed for 2 hours. The mixture was cooled to 90 °C and 56.0 g deionized water was added. Water and acetic acid byproducts were removed by azeotropic distillation. Water was added and removed again. 300.0 g of volatiles were removed by distillation to obtain a concentrated solution. The addition and removal of water were repeated three times. The resulting solution was filtered through a 5 μm nylon filter. Volatiles were reduced using a rotary evaporator to increase the solids content. Based on the solution mass, a translucent solution of RL3 in toluene retained 78.7% by mass of active RL3.

[0092] RL4: 45wt% resin / 55wt% silanol-terminated PDMS2 and vinyl functionalization

[0093] 90.0 g of resin and 230.0 g of toluene were loaded into a 1-liter (1 L) four-necked round-bottom flask equipped with a thermocouple, a PTFE stirrer, and a Dean Stark apparatus connected to a water-cooled condenser. Sufficient additional toluene equal to the volume of the Dean Stark apparatus was added. An inert gas smothering was applied, and the mixture was refluxed for 30 minutes to remove water.

[0094] Diacetyloxysilane-terminated PDMS was prepared by adding 7.71 g VTA to a mixture of 70.0 g toluene and 110.0 g silanol-terminated PDMS 2 in a 500 mL round-bottom flask. The mixture was stirred for one hour. The resulting diacetyloxysilane-terminated PDMS was rapidly added to a resin-containing flask at 106 °C to form a reaction mixture. The mixture was refluxed for 2 hours. The reaction mixture was cooled to 106 °C and 0.79 g VTA and 6.72 g acetyloxysilane were added. The mixture was refluxed for one hour. The mixture was cooled to 90 °C and 23.8 g deionized water was added. Water and acetic acid byproducts were removed by azeotropic distillation. Water was added and removed again. Volatile matter was removed by distillation to obtain a concentrated solution. The addition and removal of water were repeated three times. The resulting solution was filtered through a 5 μm nylon filter. Volatile matter was reduced using a rotary evaporator to increase the solids content. Based on the solution mass, a translucent solution of RL4 in toluene retained 71.1% by mass of active RL4.

[0095] RL5: 45wt% resin / 55wt% silanol-terminated PDMS 3 and vinyl functionalized

[0096] 90.0 g of resin and 240.8 g of toluene were loaded into a 1-liter (1 L) four-necked round-bottom flask equipped with a thermocouple, a PTFE stirrer, and a Dean Stark apparatus connected to a water-cooled condenser. Sufficient additional toluene equal to the volume of the Dean Stark apparatus was added. An inert gas liner was applied, and the mixture was refluxed for 30 minutes to remove water.

[0097] Diacetyloxysilane-terminated PDMS was prepared by adding 8.50 g VTA to a mixture of 59.2 g toluene and 110.0 g silanol-terminated PDMS 3 in a 500 mL round-bottom flask. The mixture was stirred at 25 °C for one hour. At 106 °C, the resulting diacetyloxysilane-terminated PDMS was rapidly added to a resin-containing flask to form a reaction mixture. The mixture was refluxed for 2 hours. The reaction mixture was cooled to 106 °C and 7.49 g acetyloxysilane was added. The mixture was refluxed for one hour. The mixture was cooled to 90 °C and 25.1 g deionized water was added. Water and acetic acid byproducts were removed by azeotropic distillation. Water was added and removed again. 100 g of volatiles were removed by distillation to obtain a concentrated solution. The addition and removal of water were repeated three times. The resulting solution was filtered through a 5 μm nylon filter. Volatiles were reduced using a rotary evaporator to increase the solids content. Based on the solution mass, a translucent solution of RL5 in toluene retained 78.7% by mass of active RL5.

[0098] RL6: 45wt% resin / 55wt% silanol-terminated PDMS 4 without alkenyl functionalization

[0099] 90.0 g of resin and 240.8 g of toluene were loaded into a 1-liter (1 L) four-necked round-bottom flask equipped with a thermocouple, a PTFE stirrer, and a Dean Stark apparatus connected to a water-cooled condenser. Sufficient additional toluene equal to the volume of the Dean Stark apparatus was added. An inert gas liner was applied, and the mixture was refluxed for 30 minutes to remove water.

[0100] Diacetyloxysilane-terminated PDMS was prepared by adding 11.78 g of acetyloxysilane to a mixture of 59.3 g toluene and 110.0 g of silanol-terminated PDMS 4 in a 500 mL round-bottom flask. The mixture was stirred for one hour. At 106 °C, the resulting diacetyloxysilane-terminated PDMS was rapidly added to a resin-containing flask to form a reaction mixture. The mixture was refluxed for 2 hours. The solution was cooled to 25 °C and 18.7 g of deionized water was added. Water and acetic acid byproducts were removed by azeotropic distillation. Water was added and removed again. Volatile matter was removed by distillation to obtain a concentrated solution. The addition and removal of water were repeated three times. The resulting solution was filtered through a 5 μm nylon filter. Volatile matter was reduced using a rotary evaporator to increase the solids content. A translucent solution of RL6 in toluene retained 73.1% by mass of active RL6 relative to the solution mass.

[0101] Table 3 presents the results based on T. Ar Summary of the properties of -D resin-linear block copolymers RL1-RL6.

[0102] Table 3

[0103]

[0104] Sample composition

[0105] The following sample compositions were prepared using RL1-RL6 and components from Table 4.

[0106] Table 4

[0107]

[0108]

[0109] Samples were prepared by uniformly mixing the mass fractions of each component specified in Table 5 in toluene. A solution of the prepared resin-linear component in toluene was used for the resin-linear component in an amount corresponding to the mass fractions of the active material described in Table 5 (i.e., the mass fractions of the resin-linear block copolymer). The components were mixed in a dental cup and uniformly mixed using a dental mixer. The formulation was coated onto an ethylene tetrafluoroethylene (ETFE) film and dried at 70°C for one hour prior to characterization.

[0110] The dried samples were characterized to determine whether they met the requirements for a “hot melt” composition, as described above, by means of JIS K6863-1994, having a softening point in the range of 50°C–150°C, a storage modulus greater than 0.01 MPa at 25°C, a Tanδ value less than 5.0 at 25°C, and a viscosity ratio greater than 20 at 25°C to viscosity at 100°C. The “curability” of the samples was also characterized. For suitable UV curability, the samples must pass the following UV-curability test. For suitability as optical sealants, such as LED sealants, the composition should cure to a percentage (%T) of visible light transmittance greater than 90%. %T was determined using the following procedure. [Ac] / [Vi] is the molar ratio of (meth)acryloyloxy groups to vinyl groups in the composition. The characterization results for various samples are summarized in Table 5.

[0111] UV-curability test

[0112] The sample was coated onto an ethylene tetrafluoroethylene (ETFE) membrane and allowed to dry at 70°C to form a 200 μm thick sample membrane. The sample membrane was then covered with another ETFE membrane to sandwich the sample membrane between the ETFE membranes. The sandwiched sample was placed in a UVitron SkyRAY with Raven variation and exposed to 365 nm UV radiation (250 mW) for 16 seconds. The sample was flipped and the exposure was repeated. The total UV dose was 8 joules / cm² of UV radiation (4 joules / cm² on each side).

[0113] Gel percentage

[0114] The starting sample mass is obtained by weighing a sample of the cured hot-melt composition (approximately 1.0 g) and placing it in a 40 mL dental cup. 15.0 g of toluene is added to the cup and the mixture is shaken for one hour. The toluene solution is decanted, leaving undissolved cured hot-melt material, and the gel percentage (gel %) is determined. The undissolved cured hot-melt material is transferred to a balance plate and dried at 120°C for 2 hours, then weighed to determine the mass of the undissolved cured hot-melt material. Gel % = 100% × (mass of undissolved cured hot-melt material) / (starting sample mass).

[0115] If a UV-curable sample has a gel content greater than 50%, then the UV-curable sample is considered suitable for curing.

[0116] Optical transmittance

[0117] The %T of the cured composition was determined using a 200-micron thick film of the cured composition and the Haze-Guard Plus (BYK Gardner) of ASTM D1003.

[0118]

Claims

1. A hot-melt composition, said hot-melt composition comprising: (a) at least one T-based compound, ranging from 80 to 99 parts by weight Ar -D resin-linear block copolymers, wherein at least one is based on T Ar -D resin-linear block copolymers contain T Ar Type I siloxane unit blocks and D-type siloxane unit blocks, wherein: (i)T Ar The type-I siloxane block is linked to the D-type siloxane unit block by bonds selected from those having the following structure (I): (I) Where Ar is C6-C 20 Aryl; R 1 Selected from C1-C 20 alkyl groups and C2-C 20 Alkenyl groups, provided that the condition is relative to the total molar number of silicon atoms, as described by T Ar -D resin-linear block copolymer alkenyl R 1 The average concentration of the functional groups ranges from 0.5 mol% to 3.0 mol%; and R 2 and R 3 Independently, it is C1-C 20 Hydrocarbon groups, each dashed line corresponds to a valence bond with silicon, hydrogen, or a hydrocarbon group; And among them: (ii)T Ar The molar ratio of type-3 siloxane unit blocks to type-D siloxane unit blocks is at least 2; (iii) The resin-linear block copolymer contains 8 mol% to 35 mol% of Si-OR' bonds relative to the number of silicone atoms, wherein R' is an H or C1-C8 hydrocarbon group; (iv) Each D-type siloxane unit block contains an average of 20 to 200 D-type siloxane units; and (v) Each T Ar The type siloxane unit blocks have a weight-average molecular weight in the range of 500 g / mol to 10,000 g / mol; (b) 0.5 to 20 parts by weight of a crosslinking agent, wherein each molecule of the crosslinking agent contains an average of at least two (meth)acryloyloxy groups; (c) 0.1 to 10 parts by weight of a free radical photoinitiator; (d) Zero to 2.0 parts by weight of UV stabilizer; and (e) Zero to 2.0 parts by weight of adhesion promoter.

2. The hot-melt composition according to claim 1, wherein the resin-linear block copolymer is free of (meth)acryloyloxy groups.

3. The hot-melt composition according to claim 1 or 2, wherein Ar is phenyl, and R... 1 It is vinyl, and R 2 and R 3 It is independently selected from methyl and ethyl groups.

4. The hot melt composition according to claim 1 or 2, wherein the composition does not contain unbound Q-based resin particles.

5. The hot-melt composition according to claim 1 or 2, wherein the crosslinking agent is one or more compounds selected from those having average chemical structures (III) and (IV): R' m CX (4-m) (III) X-R''-X(IV) Each R' is independently selected from an alkyl group having one to 20 carbon atoms each time it appears, each X is independently selected from -OC(O)CH=CH2 and -OC(O)C(CH3)=CH2 groups, m is a value that makes each molecule of the crosslinking agent contain an average of 2-4 X groups, and R'' is an alkylene group having one to 20 carbon atoms.

6. A method for using the hot-melt composition of any of the preceding claims as a curable coating on a substrate, the method comprising the steps of: The hot melt composition is heated to soften it, and then the softened hot melt composition is applied over at least a portion of a substrate to form a coating of the hot melt composition over at least a portion of the substrate surface.

7. The method of claim 6, wherein the method further comprises exposing the coating of the hot melt composition to ultraviolet light to induce crosslinking of the composition coating.

8. An article comprising the hot-melt composition according to any one of claims 1 to 5, wherein, The hot melt composition is coated on at least a portion of the substrate surface.

9. The article of claim 8, wherein the substrate comprises a light-emitting diode.

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