Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/44—Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/26—Esters containing oxygen in addition to the carboxy oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
  • C08F283/02—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polycarbonates or saturated polyesters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/62—Polymers of compounds having carbon-to-carbon double bonds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/72—Polyisocyanates or polyisothiocyanates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
  • C09D175/04—Polyurethanes
  • C09D175/06—Polyurethanes from polyesters

Definitions

• the present invention relates to a curable resin composition, a paint, and an article having a cured coating film of the paint, which is excellent in pot life and curability.
• Solvent-type high-solid resins designed to have a low molecular weight have been proposed in order to achieve operable viscosity even with a small amount of VOCs (see, for example, Patent Document 1).
• the coating composition described in Patent Document 1 contains an acrylic polyol obtained from isobornyl (meth)acrylate, a hydroxyl group-containing ethylenically unsaturated monomer, and a carboxyl group-containing ethylenically unsaturated monomer, and an isocyanate curing agent. Although the viscosity is kept low, there is a problem that the drying property of the coating film is insufficient.
• the problem to be solved by the present invention is a curable resin composition, a paint, and a cured coating film of the paint that has a high non-volatile content and a low viscosity, and the resulting coating film has excellent drying properties, appearance, hardness, and chemical resistance. It is to provide an article having
• a curable resin composition containing a specific copolymer and a polyester polyol and having a specific non-volatile content has a high non-volatile content and a low viscosity.
• the inventors have found that a cured coating film having excellent drying property, appearance, hardness and chemical resistance can be obtained, and completed the present invention.
• the present invention contains a copolymer (A) having a hydroxyl group and a polyester polyol (B) having 3 or more hydroxyl groups, and has a non-volatile content of 65 to 85% by mass.
• a curable resin characterized in that Regarding the composition.
• the curable resin composition of the present invention has a high non-volatile content and low viscosity, and can obtain a cured coating film having excellent drying properties, appearance, hardness, and chemical resistance. , industrial machinery, building materials, and wooden floors.
• the curable resin composition of the present invention contains a copolymer (A) having hydroxyl groups and a polyester polyol (B) having 3 or more hydroxyl groups, and has a nonvolatile content of 65 to 85% by mass.
• This copolymer (A) is obtained, for example, by copolymerizing a monomer (a1) having a hydroxyl group and another monomer (a2).
• Examples of the monomer (a1) having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxy-n-butyl (meth)acrylate, 2-hydroxypropyl ( meth) acrylate, 2-hydroxy-n-butyl (meth) acrylate, 3-hydroxy-n-butyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, glycerin mono (meth) acrylate, polyoxy Ethylene mono (meth) acrylate, polyoxypropylene mono (meth) acrylate, polyoxybutylene mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-(meth) acryloyloxyethyl-2-hydroxy Ethyl phthalate, polycaprolactone-modified hydroxyethyl mono(meth)acrylate, and the like.
• Examples of the other monomer (a2) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl ( meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acryl
• (meth)acrylic acid refers to one or both of methacrylic acid and acrylic acid
• (meth)acrylate refers to one or both of methacrylate and acrylate
• (meth) ) acryloyl refers to one or both of methacryloyl and acryloyl
• glass transition temperature (Tg) of the homopolymer is described in Polymer Handbook (4th Edition) J. Mol. Brandrup, E. H. Immergut, E.; A. The values described by Grulke (Wiley Interscience) and the like can be used.
• the amount of the monomer (a1) having a hydroxyl group used is 1 by mass ratio in the monomer component which is the raw material of the copolymer (A), since the physical properties of the resulting coating film are further improved.
• the range of ⁇ 70% by mass is preferable, the range of 5 to 60% by mass is more preferable, and the range of 10 to 50% by mass is even more preferable.
• the amount of the other monomer (a2) used is from 30 to 30 in mass ratio in the monomer component which is the raw material of the copolymer (A), since the physical properties of the resulting coating film are further improved.
• a range of 99% by mass is preferable, a range of 40 to 95% by mass is more preferable, and a range of 50 to 90% by mass is even more preferable.
• the copolymer (A) can be produced by a known polymerization method using the monomer (a1) having a hydroxyl group and the other monomer (a2) as raw materials. It is preferable because the polymerization method is simple.
• each monomer as a raw material is dissolved in a solvent and/or the polyester polyol (B), and polymerized in the presence of a polymerization initiator.
• a method of carrying out a reaction can be mentioned, but it is preferable to carry out the polymerization reaction in the presence of the polyester polyol (B) because the drying properties, acid resistance, and alkali resistance are more excellent.
• the solvent examples include hydrocarbon solvents such as toluene, xylene, cyclohexane, n-hexane, octane; methanol, ethanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, ethylene glycol monomethyl ether, alcohol solvents; ester solvents such as methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate and amyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. These solvents can be used alone or in combination of two or more.
• polymerization initiator examples include 2,2′-azobis(isobutyronitrile), 2,2′-azobis(2-methylbutyronitrile), azo compounds such as azobiscyanovaleric acid; tert-butyl peroxy organic peroxides such as pivalate, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, tert-butyl hydroperoxide; Oxides; inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium persulfate; These polymer initiators can be used alone or in combination of two or more. Further, the polymerization initiator is preferably used within a range of 0.1 to 10% by mass with respect to the total amount of monomers that are raw materials of the copolymer (A).
• chain transfer agents such as lauryl mercaptan, octyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid, and ⁇ -methylstyrene dimer can also be used. can.
• the hydroxyl value of the copolymer (A) is preferably 50 to 250 mgKOH/g, more preferably 100 to 200 mgKOH/g, because the coating film hardness, acid resistance, and alkali resistance are further improved.
• the hydroxyl value of the copolymer in the present invention is a value calculated based on the raw materials used.
• the weight average molecular weight (Mw) of the copolymer (A) is preferably 1,000 to 30,000, more preferably 2,000 to 15,000.
• the weight average molecular weight (Mw) is a value converted to polystyrene based on gel permeation chromatography (hereinafter abbreviated as "GPC") measurement.
• the polyester polyol (B) has 3 or more hydroxyl groups.
• examples include polylactone polyols obtained by ring-opening polymerization of cyclic ester compounds such as caprolactone, and copolymerized polyesters thereof. Among these, polylactone polyols are preferable, and polycaprolactone polyols are more preferable, since curability and resin compatibility are further improved.
• the number average molecular weight of the polyester polyol (B) is preferably 100 to 4,000, more preferably 100 to 2,000, since the effect of reducing the paint viscosity is further improved.
• the hydroxyl value of the polyester polyol (B) is preferably from 50 to 600, more preferably from 70 to 600, because the drying property, acid resistance, and alkali resistance are further improved.
• the non-volatile content of the curable resin composition of the present invention is 65 to 85% by mass, and preferably 70 to 85% by mass because the emission of VOCs can be further reduced.
• the non-volatile matter is defined by weighing about 1.0 g of a sample in a metal petri dish, adding 5 ml of a solvent in which toluene and methanol are mixed at a ratio of 7:3 (volume ratio), and dissolving the mixture uniformly. Dry for 1 hour in a hot air circulating dryer adjusted to 5 ⁇ 2.5° C., and obtain the value obtained by post-drying mass/pre-drying mass ⁇ 100 (percentage).
• the mass ratio (A/B) of the copolymer (A) and the polyester polyol (B) in the curable resin composition of the present invention is 97/3 to 75 from the balance of low VOC properties and drying properties. /25 is preferred, and 95/5 to 80/20 are more preferred.
• the molar ratio (A/B) of the hydroxyl groups derived from the copolymer (A) and the hydroxyl groups derived from the polyester polyol (B) in the curable resin composition of the present invention is , preferably 13/1 to 3/5, more preferably 8/1 to 5/3.
• the curable resin composition of the present invention may contain an organic solvent, and the organic solvent in the curable resin composition is preferably 15 to 35% by mass from the viewpoint of the balance between low VOC properties and workability.
• the organic solvent it is preferable to directly use the solvent used in the production of the copolymer (A) because it is convenient. These organic solvents can be used alone or in combination of two or more.
• the paint of the present invention contains the curable resin composition of the present invention, and other ingredients such as inorganic pigments, organic pigments, extender pigments, colored pigments, brightening pigments, cellulose derivatives, waxes, surfactants, agents, stabilizers, flow modifiers, dyes, leveling agents, rheology control agents, UV absorbers, antioxidants, plasticizers, antistatic agents, antifoaming agents, viscosity modifiers, light stabilizers, weather stabilizers, heat resistance Stabilizers, pigment dispersants, hardeners and the like can be used.
• other ingredients such as inorganic pigments, organic pigments, extender pigments, colored pigments, brightening pigments, cellulose derivatives, waxes, surfactants, agents, stabilizers, flow modifiers, dyes, leveling agents, rheology control agents, UV absorbers, antioxidants, plasticizers, antistatic agents, antifoaming agents, viscosity modifiers, light stabilizers, weather stabilizers, heat resistance
• the physical properties of the coating film can be further improved.
• the polyisocyanate compound (C) include aromatic diisocyanate compounds such as tolylene diisocyanate, diphenylmethane diisocyanate, m-xylylene diisocyanate, m-phenylenebis(dimethylmethylene) diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, 1, Fats such as 3-bis(isocyanatomethyl)cyclohexane, 2-methyl-1,3-diisocyanatocyclohexane, 2-methyl-1,5-diisocyanatocyclohexane, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate group or alicyclic diisocyanate compounds.
• polyisocyanate compound a prepolymer having an isocyanate group obtained by subjecting the above diisocyanate compound to an addition reaction with a polyhydric alcohol; a compound having an isocyanurate ring obtained by cyclotrimerizing the above diisocyanate compound; Polyisocyanate compounds having urea bonds and burette bonds obtained by reacting the above diisocyanate compounds with water; 2-isocyanatoethyl (meth)acrylate, 3-isopropenyl- ⁇ , ⁇ -dimethylbenzyl isocyanate, (meth)acryloyl Homopolymers of acrylic monomers having an isocyanate group such as isocyanate; the acrylic monomers having the isocyanate group, other acrylic monomers, vinyl ester compounds, vinyl ether compounds, aromatic vinyl monomers, fluoroolefins
• a copolymer having an isocyanate group obtained by copolymerizing with a monomer such as a copolymer can also be used
• the above polyisocyanate compound (C) can be used alone or in combination of two or more.
• the equivalent ratio (NCO/OH) between the isocyanate group (NCO) of the polyisocyanate compound (C) and the hydroxyl group (OH) of the curable resin composition is , preferably 0.2 to 2, more preferably 0.5 to 1.5.
• the coating method of the paint of the present invention varies depending on the article to be coated. Methods such as screen printing, spraying, applicator, bar coater, and brush can be used.
• the paint of the present invention can be diluted with an organic solvent in order to adjust the viscosity to suit the above coating method.
• organic solvent include aromatic hydrocarbon solvents such as toluene and xylene; methanol, ethanol, isopropanol, t-butanol, propylene glycol monomethyl ether, propylene glycol normal propyl ether, ethylene glycol monobutyl ether, diacetone alcohol, alcohol solvents; ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate, normal propyl acetate, propylene glycol monomethyl ether acetate and ethyl 3-ethoxypropionate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexanone. be done. These solvents can be used alone or in combination of two or more.
• the paint of the present invention can provide a cured coating film with excellent appearance and various coating film physical properties on the surface of various articles.
• the paint of the present invention may be applied directly to the article to be painted, or may be applied with a primer coating material suitable for the article to be painted, and then the coating composition of the present invention may be applied.
• Materials of articles to be coated include various metals such as iron, copper, zinc, aluminum, magnesium, and alloys thereof; polycarbonate, acrylonitrile-butadiene-styrene copolymer, PC-ABS polymer alloy, polymethyl methacrylate. , polyethylene terephthalate, polyamide, polypropylene, and other plastics, and fiber-reinforced plastics obtained by adding fillers such as glass fibers to these plastics; and wood.
• Examples of articles having a cured coating film formed using the coating material of the present invention include interior and exterior materials for various vehicles such as automobiles and railroad vehicles; industrial machinery, exterior walls, roofs, glass, veneers, wooden floors, Interior and exterior materials for buildings; Civil engineering materials such as soundproof walls and drains; Housings for home appliances such as televisions, refrigerators, washing machines, and air conditioners; Electronic devices such as personal computers, smartphones, mobile phones, digital cameras, and game consoles Housing: housings of OA equipment such as printers and facsimiles.
• weight average molecular weight (Mw) is measured under the following GPC measurement conditions.
• Measuring device high-speed GPC device ("HLC-8220GPC” manufactured by Tosoh Corporation) Column: The following columns manufactured by Tosoh Corporation were connected in series and used. "TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000” (7.8mm I.D. x 30cm) x 1 "TSKgel G3000” (7.8mm I.D. x 30cm) x 1 Book “TSKgel G2000" (7.8 mm I.D.
• Example 1 Production of curable resin composition (1)
• 20 parts by mass of butyl acetate, polycaprolactone triol manufactured by Daicel Co., Ltd. "PLAXEL 305", molecular weight 550; hereinafter referred to as "PLAXEL 305”
• PVAXEL 305" molecular weight 550; hereinafter referred to as "PLAXEL 305”
• styrene (hereinafter abbreviated as “St") 40 parts by mass, methyl methacrylate (hereinafter abbreviated as “MMA”) 20 parts by mass, 2-hydroxyethyl methacrylate (hereinafter abbreviated as “2-HEMA”) ) and 5 parts by mass of di-tert-butyl peroxide (hereinafter abbreviated as “PD”) was added dropwise over 4 hours, and reacted at 160° C. for an additional 2.5 hours. Then, butyl acetate was added to adjust the nonvolatile content to obtain a curable resin composition (1) having a nonvolatile content of 80% by mass.
• the weight average molecular weight of the copolymer was 5,000.
• Example 2 Production of curable resin composition (2)
• 20 parts by mass of butyl acetate was charged into a pressure-resistant reactor equipped with a stirrer, a thermometer, a dropping pump, a cooling tube and a nitrogen gas inlet, and nitrogen was added to the liquid for the purpose of removing dissolved oxygen.
• the temperature was raised to 160° C. while stirring.
• a mixture of 40 parts by mass of St, 20 parts by mass of MMA, 30 parts by mass of 2-HEMA, and 5 parts by mass of PD was added dropwise over 4 hours, reacted at 160°C for an additional 2.5 hours, and then heated to 100°C.
• the temperature was cooled and the pressure was released.
• Example 3 Production of curable resin composition (3)
• 20 parts by mass of butyl acetate and 10 parts by mass of Plaxel 305 were charged into a pressure-resistant reaction vessel equipped with a stirrer, thermometer, dropping pump, cooling tube, and nitrogen gas inlet, and the liquid was stirred for the purpose of removing dissolved oxygen.
• the temperature was raised to 160° C. while stirring in a nitrogen atmosphere.
• a mixture of 40 parts by mass of St, 10 parts by mass of MMA, 10 parts by mass of isobornyl methacrylate (hereinafter abbreviated as "IBOMA"), 30 parts by mass of 2-HEMA, and 5 parts by mass of PD was added for 4 hours. After the mixture was added dropwise over 160° C.
• IBOMA isobornyl methacrylate
• Example 4 Production of curable resin composition (4)
• 20 parts by mass of butyl acetate was charged into a pressure-resistant reactor equipped with a stirrer, a thermometer, a dropping pump, a cooling tube and a nitrogen gas inlet, and nitrogen was added to the liquid for the purpose of removing dissolved oxygen.
• the temperature was raised to 160° C. while stirring.
• a mixture of 36 parts by mass of St, 18 parts by mass of MMA, 30 parts by mass of 2-HEMA, 10 parts by mass of IBOMA and 5 parts by mass of PD was added dropwise over 4 hours, and reacted at 160° C. for an additional 2.5 hours. After that, the temperature was lowered to 100° C. and the pressure was released.
• a tin plate of A4 size was prepared, and the paint was applied by an arbitrary spray so that the dry film thickness was 50 ⁇ m to prepare a coated plate. Place a pinch of absorbent cotton on the coated plate, measure the time until the absorbent cotton is removed using a rubber instrument (Jumbo Hurricane manufactured by NU Co., Ltd.) that blows away dust and dirt, and dry it. time.
• a rubber instrument Jumbo Hurricane manufactured by NU Co., Ltd.
• Table 1 shows the compositions and evaluation results of the curable resin compositions (1) to (4) and (R1) to (R2) obtained above.
• A was polymerized in the presence of polyester polyol, and B was otherwise.
• the curable resin compositions of the present invention of Examples 1 to 4 have a high non-volatile content and low viscosity, the resulting paint has a low VOC content, and the coating film has excellent drying properties, appearance, hardness, acid resistance, and It was confirmed that the alkali resistance is excellent.
• Comparative Examples 1 and 2 are examples that do not contain polyester polyol (B), which is an essential component of the present invention, but have high viscosity, the resulting paint has a high VOC content, and the coating film is dried was found to be inadequate.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Paints Or Removers (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=84425202

Family Applications (1)

Country Status (2)

Citations (4)

Family Cites Families (3)

• 2022
  • 2022-03-31 JP JP2023527539A patent/JPWO2022259740A1/ja active Pending
  • 2022-03-31 WO PCT/JP2022/016452 patent/WO2022259740A1/ja not_active Ceased

Patent Citations (4)

Also Published As

Similar Documents

Legal Events