Blocked isocyanate prepolymer system, method for preparing the same, and application thereof

Abstract

2023PF30086-Foreign Countries - 23 - BLOCKED ISOCYANATE PREPOLYMER SYSTEM, METHOD FOR PREPARING THE SAME, AND APPLICATION THEREOF A b s t r a c t The present application relates to a blocked isocyanate prepolymer system, a method for preparing the same, and an application thereof. The blocked isocyanate prepolymer system is prepared by reacting an isocyanate comprising two or more isocyanate groups first with a blocking agent and then with a polyhydroxyl compound. The blocked isocyanate prepolymer system of the present invention can be processed into various products for a wide range of applications. In addition, the blocked isocyanate prepolymer system of the present invention remains low in viscosity even if it is not diluted by a solvent, and therefore is conducive for subsequent use.

Description

[0001] BLOCKED ISOCYANATE PREPOLYMER SYSTEM, METHOD FOR PREPARING THE SAME, AND APPLICATION THEREOF

[0002] TECHNICAL FIELD

[0003] The present invention relates to the technical field of isocyanate. In particular, the present invention relates to a blocked isocyanate prepolymer system, a method for preparing the same, and an application thereof.

[0004] BACKGROUND ART

[0005] Epoxy resins are widely used in machinery, home appliances, transportation, and construction fields and the like, due to their good thermal stability, excellent adhesiveness and adhesion, and chemical resistance. However, epoxy systems are brittle, especially the case under low temperatures. To improve and enhance their flexibility, polyurethane may be incorporated to achieve desirable and long-lasting el astifi cation of epoxy resins.

[0006] DE2338256A1 discloses production of a high molecular weight amine terminated polyetherurethane-urea by reacting a prepolymer comprising free isocyanate groups with an amine in a highly diluted solution, followed by curing with epoxy resins. However, the use of a solvent necessary for the above reaction is unfavorable from both technical and physiological perspectives. Conversely, the solvent-free reaction product as prepared would have a viscosity too high for practical application.

[0007] DE2152606A1 discloses reactive systems based on alkylphenol -blocked polyisocyanates and polyamines that can optionally be cured in combination with epoxy resins. These reactive systems are also associated with some application- oriented disadvantages. For example, the reactive system has a relatively high viscosity, and the blocking agent which is released has a comparatively low molecular weight, so that it can migrate out of the coating over time, which can lead to poor adhesion between the coating and the substrate.

[0008] US6060574A discloses a reactive composition consisting of reversibly blocked organic polyisocyanate and at least one polyamine having at least two primary amino groups, and optionally a compound containing oxirane groups. The blocking agent serving as the organic poly isocyanate is a hydrocarbon resin containing phenolic OH groups. Such blocked polyisocyanates, when compared with alkylphenol-blocked polyisocyanates, have a greatly reduced reactivity towards polyamines. The organic polyisocyanate used can be a prepolymer obtained by the reaction of polyhydroxyl compounds with excess amounts of diisocyanates or polyisocyanates. However, the blocked polyisocyanates generally prepared by reacting the formed polyisocyanate prepolymers with blocking agent, such as disclosed in US7057003B2, have a high viscosity due to the formation of higher oligomers during the prepolymerization of diisocyanates with multifunctional polyhydroxyl compounds, and sometimes even require dilution with organic solvents.

[0009] This constitutes a significant drawback for processing corresponding reactive systems comprising polyamines and optional epoxides. Due to the high viscosity of these systems, they commonly cannot be applied for spray coating.

[0010] Therefore, there is a need for a blocked isocyanate prepolymer system with a low viscosity in the art.

[0011] SUMMARY OF THE INVENTION

[0012] One objective of the present invention is to provide a blocked isocyanate prepolymer system with a low viscosity.

[0013] Another objective of the present invention is to provide a method for preparing a blocked isocyanate prepolymer system with a low viscosity.

[0014] Therefore, according to a first aspect of the present invention, there is provided a blocked isocyanate prepolymer system, characterized in that: it is prepared by reacting an isocyanate comprising two or more isocyanate groups first with a blocking agent and then with a polyhydroxyl compound, wherein: the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.8 to 1 : 2.5, and the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.8 to 1 : 1.2.

[0015] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned blocked isocyanate prepolymer system, comprising the steps of:

[0016] A. reacting an isocyanate comprising two or more isocyanate groups with a blocking agent, wherein the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.8 to 1 : 2.5; and B. further reacting the remaining isocyanate groups with a polyhydroxyl compound until the amount of free isocyanate groups is less than 0.5% by weight relative to the total weight of the entire reaction system, wherein the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.8 to 1 : 1.2.

[0017] According a third aspect of the present invention, there is provided use of the above-mentioned blocked isocyanate prepolymer system for preparing polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials.

[0018] According a fourth aspect of the present invention, there are provided polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials comprising the above-mentioned blocked isocyanate prepolymer system.

[0019] The blocked isocyanate prepolymer system of the present invention can be processed into various products for a wide range of applications. In addition, the blocked isocyanate prepolymer system of the present invention remains low in viscosity even if it is not diluted by a solvent, and therefore is conducive for subsequent use.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] Some specific embodiments of the present invention will be described below for the purpose of illustration rather than limitation.

[0022] Blocked Isocyanate Prepolymer System

[0023] According to a first aspect of the present invention, there is provided a blocked isocyanate prepolymer system, characterized in that: it is prepared by reacting an isocyanate comprising two or more isocyanate groups first with a blocking agent and then with a polyhydroxyl compound, wherein: the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.8 to 1 : 2.5, and the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.8 to 1 : 1.2. The blocked isocyanate prepolymer of the present invention has a low viscosity, typically below 24,000 mPas as measured at 23 °C according to DIN EN ISO 3219: 1994-10, and remains low in viscosity even if it is not diluted by a solvent, which is conducive for subsequent use.

[0024] Preferably, the blocked isocyanate prepolymer of the present invention has a viscosity of not more than 20,000 mPas as measured at 23°C according to DIN EN ISO 3219: 1994-10.

[0025] The system not only comprises a blocked isocyanate prepolymer prepared from a partially blocked isocyanate and a polyhydroxyl compound, but also comprises a fully blocked isocyanate.

[0026] The term “fully blocked isocyanate” as used herein refers to a product formed by reaction of all isocyanate groups contained in isocyanate molecules with a blocking agent.

[0027] Preferably, the fully blocked isocyanate has a weight-average molecular weight in the range of 380 to 1,400 g / mol.

[0028] Preferably, the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.9 to 1 : 2.5, more preferably from 1 : 1.95 to 1 : 2.5, most preferably from 1 : 2.0 to 1 : 2.5.

[0029] Preferably, the fully blocked isocyanate accounts for 1% to 30% by weight, more preferably from 5% to 22%, even more preferably from 8% to 15%, relative to the total weight of the blocked isocyanate prepolymer system. This value can be determined using a GPC test, based on the proportion of the peak area of the corresponding component.

[0030] Preferably, the blocked isocyanate prepolymer system is solvent-free.

[0031] Isocyanate

[0032] The isocyanate used in the present invention can be any diisocyanate and / or polyisocyanate having isocyanate groups with aliphatic, alicyclic, aromatic-aliphatic and / or aromatic linkage.

[0033] As used herein, the term “polyisocyanate” refers to an isocyanate having an isocyanate group functionality of greater than 2.

[0034] Suitable diisocyanates include any diisocyanate that can be obtained by various ways (e.g., by phosgenation in the liquid or gas phase, or by a phosgene-free route such as thermal cleavage of carbamate compounds). Preferred diisocyanates are those having isocyanate groups with aliphatic, alicyclic, aromatic-aliphatic and / or aromatic linkage and having a molecular weight in the range of 140 to 400 g / mol. Examples of such diioscyanates include 1,4-butane diisocyanate, 1,5-pentane diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), 2- methyl-l,5-pentane diisocyanate, l,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or

[0035] 2.4.4-trimethyl-l,6-hexane diisocyanate, 1,10-decane diisocyanate, 1,3- and 1,4- cyclohexane diisocyanate, 1,3- and l,4-bis(isocyanatomethyl)cyclohexane, 1- isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4,4'-dicyclohexylmethane diisocyanate, 1-isocyanato-l-methyl- 4(3)isocyanatomethylcyclohexane, bis(isocyanatomethyl)norbornane, 1,3- and 1,4- bis(2-isocyanatopropan-2-yl)benzene (TMXDI), toluene diisocyanate (toluene 2,4- and 2,6-diisocyanate, TDI), 2,4'- and 4,4'-diphenylmethane diisocyanate (MDI), 1,5- naphthalene diisocyanate (NDI), norbomane diisocyanate (NBDI) or any mixture of these diisocyanates.

[0036] More preferred diisocyanates are those having isocyanate groups with different reactivity, such as 2-methyl-l,5-pentane diisocyanate, l,5-diisocyanato-2,2- dimethylpentane, 2,2,4- or 2,4,4-trimethyl-l,6-hexane diisocyanate, 1-isocyanato-

[0037] 3.3.5-trimethyl-5-isocyanato-methylcyclohexane (isophorone diisocyanate, IPDI), 1- isocyanato-1 -methyl -4(3 )isocyanato-methylcyclohexane, toluene diisocyanate (toluene 2,4- and 2,6-diisocyanate, TDI), 2,4'-diphenylmethane diisocyanate (MDI) or any mixture of these diisocyanates.

[0038] Particularly suitable diisocyanates are l-isocyanato-3,3,5-trimethyl-5-isocyanato- methylcyclohexane (isophorone diisocyanate, IPDI), toluene diisocyanate (toluene 2,4- and 2,6-diisocyanate, TDI), 2,4'-diphenylmethane diisocyanate (MDI) or any mixture of these diisocyanates. Among them, toluene diisocyanate (toluene 2,4- and 2,6-diisocyanate, TDI), in particular, the 2,4- and 2,6- isomers and a technical mixture of these two isomers, are preferred.

[0039] Especially suitable aromatic diisocyanates are toluene 2,4-diisocyanate and a technical mixture thereof comprising 70 to 90% of toluene 2,4-diisocyanate and 30 to 10% of toluene 2,6-diisocyanate. Suitable isocyanates may also include any polyisocyanate having a uretdi one, isocyanurate, allophanate, biuret, imino-oxadiazine dione and / or oxadiazinetrione structure, prepared by modification of simple aliphatic, alicyclic, aromatic-aliphatic and / or aromatic diisocyanates and / or polysiocyanates, such as those of the types mentioned above, as described for example in J. Prakt. Chem. 336 (1994) 185-200, DE-A 1 670 666, DE-A 1 954093, DE-A 2414 413, DE-A 2452 532, DE-A 2 641 380, DE-A 3 700209, DE-A 3 900 053 and DE-A 3 928 503 orEP-A 0 336 205, EP-A 0 339 396 and EP-A 0 798 299, or any mixture of these isocyanates. Blocking Agent

[0040] The blocking agent suitable for use in the present invention includes, for example, pyrazole, alcohol, oxime, lactam, P-dicarbonyl compounds and phenolic compounds.

[0041] As an example of the pyrazole compound, mention may be made of 3,5- dimethylpyrazole.

[0042] As examples of the alcohol compound, mention may be made of methanol, ethanol, 2 -propanol, n-butanol, sec-butanol, 2-ethyl-l -hexanol, 2-m ethoxy ethanol, 2- ethoxy ethanol and 2 -butoxy ethanol.

[0043] As examples of the oxime compound, mention may be made of butanone oxime, acetone oxime, formaldehyde oxime, acetaldehyde oxime and cyclohexanone oxime.

[0044] As examples of the lactam compound, mention may be made of s-caprolactam, 5- valerolactam and y-butyrolactam.

[0045] As examples of the P-dicarbonyl compound, mention may be made of dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, di-n-propyl malonate, di-isopropyl malonate, di-n-butyl malonate and di-isobutyl malonate.

[0046] As examples of the phenolic compound, mention may be made of phenol, nonylphenol, cardanol, bisphenol A and bisphenol F.

[0047] Preferably, the blocking agent is selected from phenolic compounds. More preferably, the blocking agent is selected from phenolic compounds with an OH value of 184 to 206 mg KOH / g, preferably 184 to 200 mg KOH / g, more preferably 186 to 192 mg KOH / g.

[0048] Even more preferably, the blocking agent is selected from nonylphenol, cardanol, or a mixture of them, with a further preference for cardanol.

[0049] The cardanol has the following structure: wherein R represents CisHn-n, in which n=0, 2, 4 and 6.

[0050] Polyhydroxyl Compound

[0051] The polyhydroxyl compound suitable for use in the present invention can be any polyols, for example, polymer polyols known in polyurethane chemistry, such as polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, and / or polyacrylate polyols.

[0052] Polyols typically have an average functionality of 1.8 to 6.0, preferably 1.8 to 4.0, more preferably 1.9 to 2.2. These polyols typically have a number average molecular weight (determined according to DIN 55672-1:2016-03) in the range of 1,000 to 10,000 g / mol, preferably 1,000 to 4,000 g / mol, more preferably 2,000 to 4,000 g / mol. Any mixture of these polyols may be used as well.

[0053] Preferably, the polyhydroxyl compound is poly ether polyols or a mixture of polymer polyols comprising at least one polyether polyol.

[0054] More preferably, the polyhydroxyl compound is selected from polyether polyols, such as those of the types mentioned in DE2622951B (see column 6, line 65 to column 7, line 26), EP-A0978523 (see page 4, line 45 to page 5, line 14), or WO2011 / 069966 (see page 4, line 20 to page 5, line 23), insofar as they meet the requirements of the above-mentioned functionality and molecular weight.

[0055] Particularly preferred polyether polyols are addition products of ethylene oxide and / or propylene oxide on 1,2-propanediol, 1,3-propanediol, dipropylene glycol, diethylene glycol, glycerol, trimethylolpropane, triethanolamine, ethylenediamine and / or pentaerythritol, or polytetramethylene ether glycol with the molecular weight falling within the above range, for example, obtainable by polymerization of tetrahydrofuran according to Angew. Chem. 72, 927 (1960).

[0056] Especially preferred are addition products of ethylene oxide and / or propylene oxide under 1,2-propanediol, 1,3-propanediol, dipropylene glycol and / or diethylene glycol initiated polymerization. Even more particularly preferred are addition products of ethylene oxide and / or propylene oxide under 1,2-propanediol initiated polymerization, said poly ether polyols comprising 80 wt.% of 1,2-propanediol, more preferably 90 wt.% of 1,2-propanediol, most preferably 100 wt.% of 1,2-propanediol.

[0057] Method for Preparing a Blocked Isocyanate Prepolymer System

[0058] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned blocked isocyanate prepolymer system, comprising the steps of:

[0059] A. reacting an isocyanate comprising two or more isocyanate groups with a blocking agent, wherein the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.8 to 1 : 2.5; and B. further reacting the remaining isocyanate groups with a polyhydroxyl compound until the amount of free isocyanate groups is less than 0.5% by weight relative to the total weight of the entire reaction system, wherein the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.8 to 1 : 1.2.

[0060] The isocyanate, blocking agent and polyhydroxyl compound are as previously defined in the first aspect of the present invention.

[0061] Preferably, the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.9 to 1 : 2.5, more preferably from 1 : 1.95 to 1 : 2.5, most preferably from 1 : 2.0 to 1 : 2.5.

[0062] Preferably, the reaction of the isocyanate with the blocking agent in step A is carried out at a temperature of 0 to 150°C, preferably 20 to 140°C, more preferably 40 to 100°C.

[0063] Preferably, in step A predominantly mono-blocked isocyanate is formed. Predominantly means that more than 50 wt%, preferably more than 55 wt%, more preferably more than 60 wt%, even more preferably more than 65 wt%, most preferably more than 67 wt% of the isocyanate is mono-blocked isocyanate, wherein the weight % (wt%) is based on the total weight of isocyanate and blocking agent present in the reaction mixture. The weight percentages of the mono-blocked isocyanate can be determined by Gel Permeation Chromatography (GPC). Formation of mono-blocked isocyanate can be stimulated by careful controlling the reaction conditions. For example reaction temperature and the way of adding the reactants, slow dosing of the mono-functional blocking agent into multi-functional isocyanate is helpful to promote mono-blocked isocyanate.

[0064] Preferably, step B is performed when the remaining isocyanate (NCO) content falls within the range of the theoretically calculated amount NCO±0.5%.

[0065] The reaction of the isocyanate with the blocking agent can be carried out in the presence of a catalyst to expedite the reaction, thereby shortening the reaction time.

[0066] Suitable catalysts can be those known in polyurethane chemistry, for example, metal-organic compounds such as tin(II) octanoate, dibutyltin(II) diacetate, dibutyltin(II) laurate, 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, diazabicyclooctane, l,8-diazabicyclo[5.4.0]undec-7-ene, and a mixture comprising two or more of the above compounds.

[0067] The amount of suitable catalysts is in the range of 0.01% to 0.5%, preferably 0.02% to 0.3%, more preferably 0.02% to 0.2%. Preferably, the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.9 to 1 : 1.1.

[0068] The reaction of the isocyanate groups with the polyhydroxyl compound can be carried out under conditions well known in the polyurethane field.

[0069] For example, the reaction of the isocyanate groups with the polyhydroxyl compound in step B can be carried out at a temperature of 0 to 250°C, preferably 20 to 140°C, more preferably 40 to 100°C.

[0070] Preferably, step B ends when the amount of free isocyanate groups is less than 0.2% by weight.

[0071] More preferably, step B ends when the amount of free isocyanate groups is less than 0.1% by weight.

[0072] The reaction of the isocyanate groups with the polyhydroxyl compound can be carried out in the presence of a catalyst to expedite the reaction, thereby shortening the reaction time.

[0073] Suitable catalysts can be selected from those known in polyurethane chemistry, identical to or different from the catalyst for the reaction of the isocyanate with the blocking agent, in particular the compounds or a mixture thereof as exemplified in the above reaction of the isocyanate with the blocking agent, preferably the same catalysts as those for the reaction of the isocyanate with the blocking agent. The amount of suitable catalysts is in the range of 0.01% to 0.5%, preferably 0.02% to 0.3%, more preferably 0.02% to 0.2%.

[0074] The reactions in steps A and B can also be carried out in a solvent that is inert to the reactive groups of the starting components.

[0075] Examples of suitable solvents include, but are not limited to, ethyl acetate, butyl acetate, ethylene glycol monomethyl ether or monoethyl ether acetate, 1 -methoxy -2- propyl acetate (MPA), 3 -m ethoxy -n-butyl acetate, acetone, 2-butanone, 4-methyl-2- pentanone, cyclohexanone, toluene, xylene, chlorobenzene, white spirit, more highly substituted aromatic hydrocarbons, such as those types sold under the names Solvent naphtha, Solvesso, Isopar, Nappar (ExxonMobil Chemical Central Europe GmbH, Cologne, Germany) and Shellsol (Shell Deutschland Oil GmbH, Hamburg, Germany), and solvents such as propylene glycol diacetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl ether and butyl ether acetate, N-methyl pyrrolidone and N-methyl caprolactam, or any mixture of these solvents.

[0076] Preferably, steps A and B are performed in the absence of a solvent to obtain a solvent-free blocked isocyanate prepolymer. Use of Blocked Isocyanate Prepolymer System and Product Comprising the Same

[0077] According a third aspect of the present invention, there is provided use of the above-mentioned blocked isocyanate prepolymer system for preparing polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials.

[0078] The blocked isocyanate prepolymer system of the present invention can be processed into various products such as polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials. The application fields include, but not limited to, hydraulic engineering, shipbuilding (e.g., ballast tanks), transportation, green energy, piping and flooring etc.

[0079] Therefore, according to a fourth aspect of the present invention, there are provided polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials comprising the above-mentioned blocked isocyanate prepolymer system.

[0080] In some embodiments, there is provided a solvent-free reactive system, comprising the above-mentioned blocked isocyanate prepolymer system, polyamines and optional epoxides.

[0081] Preferably, the polyamines are those having at least two primary amino groups per molecule and optionally also secondary amino groups and preferably having an average molecular weight of 60 to 500 g / mol. As examples of such polyamines, mention may be made of ethylenediamine, 1,2- and 1,3-diaminopropane, 1,4- diaminobutane, 2,2,4- and / or 2,4,4-trimethylhexanediamine, isomeric dimethylbenzenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, 1,4- diaminocyclohexane, 4, 4'-diaminodi cyclohexylmethane, 1,3-diaminocyclopentane, 4,4'-diaminodicyclohexyl sulfone, 4,4'-diaminodicyclohexylpropane-l,3-, or -4,4'- diaminodicyclohexylpropane-2,2-, or -3,3'-dimethyl-4,4'- diaminodi cyclohexylmethane, 3-aminomethyl-3,3,5-trimethylcyclohexylamine

[0082] (isophorone diamine), 3 (4)-aminom ethyl- 1 -methylcyclohexylamine, technical grade bis(aminomethyl)tri cyclodecane, octahydro-4, 7-methyleneindene-l,5-dimethylamine, and phenolic amine curing agents synthesized from phenol-formaldehyde resins and amine compounds, or polyamines having a secondary amine in addition to at least two primary amines, such as diethylene-triamine or diethylene-tetraamine.

[0083] Particularly preferred are polyamines, especially diamines containing one or more alicyclic rings with the molecular weight falling within the range described above. Examples of such polyamines include 1,4-diaminocyclohexane, 4,4'- diaminodicyclohexylmethane, 1,3-diaminocyclopentane, 4,4'- diaminodicyclohexylsulfone, 4,4'-diaminodicyclohexyl propane-1,3-, or -4,4'- diaminodicyclohexylpropane-2,2-, or -3,3'-dimethyl-4,4'- diaminodi cyclohexylmethane, 3-aminomethyl-3,3,5-trimethylcyclohexylamine (isophorone diamine), 3- and 4-aminom ethyl- 1 -methylcyclohexylamine or technical grade bis(aminomethyl)tricyclodecane.

[0084] It is also possible to use the adducts prepared by reacting an excess of said poly amines with epoxy resins of the types described below as ingredients of the amine component.

[0085] The polyamines may also include polyetheramines prepared by reacting polyether polyols with ammonia, and sold, for example, under the trade name Jeffamine ® by Huntsman.

[0086] The epoxides are compounds having epoxy groups. Suitable compounds having epoxy groups are epoxy resins containing, on average, no less than one epoxy group per molecule. Examples of suitable epoxy resins include glycidyl ethers of polyols such as butylene glycol, hexylene glycol, glycerol, hydrogenated diphenolylpropane, or polyphenols such as resorcinol, diphenolylpropane-2,2 (bisphenol A), diphenolylmethane (bisphenol F), or phenolic aldehyde condensates. Glycidyl esters of polycarboxylic acids such as hexahydrophthalic acid or dimerized fatty acid may be used.

[0087] Particularly preferred are liquid epoxy resins based on epichlorohydrin and diphenylpropane-2,2 (bisphenol A) or diphenylmethane (bisphenol F) or a mixture thereof. If desired, the viscosity of the mixture can be reduced with monofunctional epoxy compounds, to improve processing. Examples of such liquid epoxy resins include aliphatic and aromatic glycidyl ethers such as butyl glycidyl ether, phenyl glycidyl ether, or glycidyl esters such as tertiary carbonate glycidyl ester, or epoxides such as styrene oxide or 1,2-epoxy decane.

[0088] The solvent-free reactive system can be cured at room temperature, for use as coating materials. The coatings made from the reactive system have superior impact resistance and shock resistance, while exhibiting flexibility and elasticity.

[0089] The descriptions of various features in the present application may be combined with each other where there is no contradiction, and all fall within the protection scope of the present application.

[0090] As used in the present application, “and / or” refers to one or all of the elements mentioned. All percentages in the present application are percentages by weight, unless otherwise specified.

[0091] The analytical measurements described in the present application were all carried out at 23 °C, unless otherwise specified.

[0092] The weight average molecular weight and the number average molecular weight of the isocyanate (including the fully blocked isocyanate) described in the present application were determined by Gel Permeation Chromatography (GPC) according to DIN 55672-1 :2016-03 with a HLC-8320 EcoSEC-type gel chromatograph from TOSOH, using polystyrene standards, a high-performance universal chromatographic 4x column set (TSKgel G2000HXL, TSKgel G2500HXL, TSKgel G3000HXL and TSKgel G4000HXL, the chromatographic columns packing material is styrene- divinylbenzene copolymer) and a differential refraction detector, using tetrahydrofuran as eluent, a flow rate of 1.0 ml / min, a pressure of 6.4 MPa and the column temperature of 40°C. The content of fully blocked isocyanate component was determined by the area percentage of the GPC peak of the fully blocked isocyanate.

[0093] The content of isocyanate groups (NCO) was determined titrimetrically according to DIN-EN ISO 11909:2007-05, and the data measured include the content of free and potentially free isocyanate groups.

[0094] The potentially free isocyanate groups may convert into free isocyanate groups under such conditions as heating.

[0095] The viscosity was measured by using a HAAKE VT550 Viscometer according to DIN EN ISO 3219: 1994-10.

[0096] The impact resistance was measured according to ASTM 2794-1993 as follows: a 120 pm wet film was applied onto a tinplate substrate, and after sufficient curing and maintenance, a reverse impact test was performed with the paint film facing downward. The test data was characterized as the maximum drop height (cm) that the paint film could withstand without rupture.

[0097] The stress at break and elongation at break were determined according to DIN EN ISO 527-2:2012-06 as follows: a 250 pm wet film is scrape coated onto a glass plate coated with a release agent, and after sufficient curing and maintenance, the dry film was peeled off and cut into a dumbbell II shape, and the stress at break and elongation at break was measured with a tensile tester at room temperature.

[0098] Shore hardness D was measured according to DIN 53505:2000-08 as follows: a film with desired thickness was prepared according to the standard, and after sufficient curing and maintenance, a test was performed on a Shore hardness tester to get the result. The pendulum hardness test method was carried out according to DIN EN ISO 1522-2007 as follows: a 120 pm wet film was applied onto a glass plate substrate, and after sufficient curing and maintenance, the pendulum swing time (in seconds) was measured on a pendulum tester. The pendulum swing time in the pendulum test result can represent hardness of the paint film. The longer the pendulum swing time, the higher the hardness of the paint film.

[0099] The terms “comprising” and “including” described in the present application cover the circumstances which further comprise or include other elements not specifically mentioned and the circumstances consisting of the elements mentioned.

[0100] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the field the present invention belongs to. When the definition of a term in the present description conflicts with the meaning as commonly understood by a person skilled in the field the present invention belongs to, the definition described herein shall apply.

[0101] Unless otherwise specified, all numerical values expressing the amount of ingredients, reaction conditions and the like used in the description and claims are to be understood as being modified by the term “about”. Accordingly, unless indicated to the contrary, the numerical values and parameters described herein are approximate values which are subject to change according to the performance as required.

[0102] Examples

[0103] The conception, specific structures and technical effects of the present invention will be further described below in conjunction with the Examples, so that a person skilled in the art can fully understand the objectives, features and effects of the present invention. It will be easily appreciated by a person skilled in the art that the Examples are for illustrative purposes only and the scope of the present invention is not limited thereto.

[0104] Main Materials

[0105] The main materials used in the following examples are as follows:

[0106] DESMODUR® T 80: comprising about 80 wt.% of toluene 2,4-diisocyanate and 20 wt.% of toluene 2,6-diisocyanate, available from Covestro Polymers (China) Co., Ltd.

[0107] DESMODUR® IPDI: Isophorone Diisocyanate, available from Covestro Polymers (China) Co., Ltd. NX 2026: Cardanol, available from the company Cardolite Specialty Chemicals Europe N. V.

[0108] DP 2000E: Poly ether diol with an OH value of 54 to 58 mg KOH / g, available from Kukdo Chemical Co., Ltd.

[0109] EG 1000: Polyether diol with an OH value of 110 to 114 mg KOH / g, available from Shandong Bluestar Dongda Co., Ltd.

[0110] DP 4000E: Poly ether diol with an OH value of 26 to 30 mg KOH / g, available from Kukdo Chemical Co., Ltd.

[0111] Arcol Polyol 1026: Poly ether diol with an OH value of 28 mg KOH / g, available from Covestro Polymers (China) Co., Ltd.

[0112] Zirconium 18: Catalyst zirconium isooctanoate, available from Borchers OM Group.

[0113] Stannous octanoate (II): Catalyst, available from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0114] DER 331 : Bisphenol A epoxy resin with an epoxy equivalent of 180 to 200 g / mol, available from Dow Chemical Company.

[0115] Desmocap 14CNB: Blocked isocyanate with a viscosity of 30,200 mPas, available from Covestro Polymers (China) Co., Ltd.

[0116] IPDA: Isophorone diamine with an amine value of 550 to 580 mg KOH / g, available from Covestro Polymers (China) Co., Ltd.

[0117] Inventive Example 1

[0118] 420.0 g of toluene diisocyanate (DESMODUR® T 80) was added into a reaction flask and heated while stirring to 90°C. Then, 766.8 g of cardanol (NX 2026) was slowly added dropwise to the reaction solution through a dropping funnel over a period of about 4 hours. After the addition was completed, the reaction continued with stirring at 90°C and cooled down when the NCO content reached 8.6% (the theoretically calculated amount of NCO being about 8.1%), to produce a cardanol-blocked toluene diisocyanate.

[0119] 200.0 g of the above prepared cardanol-blocked toluene diisocyanate was placed into a reaction flask and heated while stirring to 80°C. Then, 435.4 g of polyether diol (DP 2000E) was slowly added dropwise through a dropping funnel. After the addition was completed, the reaction continued at 80°C until the NCO% was <0.4%. Upon cooling, a blocked isocyanate prepolymer 1 was obtained, with a measured viscosity of 17,200 mPas and a fully blocked isocyanate content of 14.9%.

[0120] Comparative Example 1

[0121] 172.4 g of polyether diol (DP 2000E) was prepolymerized with 30.0 g of toluene diisocyanate (DESMODUR® T 80) at 90°C for about 3 hours, until a theoretical NCO content of 3.7% was reached.

[0122] Then, 61.5 g of cardanol (NX 2026) and 0.2 g of catalyst tin(II) octanoate were added, and stirred at 65 °C until the NCO content was below 0.4%. Next, 0.26 g of benzoyl chloride was added and stirred for an additional 30 minutes. Upon cooling, a blocked isocyanate prepolymer 2 was obtained, with a viscosity of 173,300 mPas and a fully blocked isocyanate content of 0%.

[0123] Inventive Example 2

[0124] 500.0 g of polyether diol (EG 1000) was placed into a reaction flask, and heated while stirring to 60°C. Then, 495.6 g of the cardanol -blocked toluene diisocyanate obtained in Inventive Example 1 was slowly added dropwise through a dropping funnel into the reaction flask. After the addition was completed, the reaction continued at 60°C until the NCO% was <0.5%. Upon cooling, a blocked isocyanate prepolymer 3 was obtained, with a measured viscosity of 23,900 mPas and a fully blocked isocyanate content of 14.7%.

[0125] Inventive Example 3

[0126] 600.0 g of polyether diol (DP 4000E) was placed into a reaction flask, and heated while stirring to 70°C, and 0.4 g of catalyst zirconium isooctanoate (Zirconium 18) was added. Then, 140.0 g of the cardanol-blocked toluene diisocyanate obtained in Inventive Example 1 was slowly added dropwise through a dropping funnel into the reaction flask. After the addition was completed, the reaction continued at 70°C until the NCO% was <0.3%. Upon cooling, a blocked isocyanate prepolymer 4 was obtained, with a measured viscosity of 9,900 mPas and a fully blocked isocyanate content of 8.8%.

[0127] Inventive Example 4 120.0 g of isophorone diisocyanate (IPDI) was added into a reaction flask, and heated while stirring to 80°C. Then, 0.3 g of catalyst tin(II) octanoate was added, and

[0128] 171.6 g of a phenolic blocking agent (NX 2026) was added slowly dropwise through a dropping funnel to the reaction solution over a period of 3 hours. After the addition was completed, the reaction continued with stirring at 80°C and cooled down when the NCO content reached 7.2%, to produce a cardanol-blocked isophorone diisocyanate.

[0129] 290.0 g of polyether diol (DP 4000E) was placed into a reaction flask, and heated while stirring to 60°C. Then, 80.0 g of the cardanol-blocked isophorone diisocyanate was added dropwise through a dropping funnel into the reaction flask. After the addition was completed, the reaction continued at 60°C until the NCO% was <0.4%. Upon cooling, a blocked isocyanate prepolymer 5 was obtained, with a measured viscosity of 14,400 mPas and a fully blocked isocyanate content of 12.2%.

[0130] Inventive Example 5

[0131] 100.0 g of poly ether diol (Arcol Polyol 1026) was placed into a reaction flask, and heated while stirring to 90°C. Then, 0.5 g of catalyst tin(II) octanoate was added, and 24.0 g of the cardanol-blocked toluene diisocyanate obtained in Inventive Example 1 was added slowly dropwise through a dropping funnel into the reaction flask. After the addition was completed, the reaction continued at 90°C until the NCO% < 0.3%. Next, 0.7 g of benzoyl chloride was added and stirred for an additional 30 minutes. Upon cooling, a blocked isocyanate prepolymer 6 was obtained, with a measured viscosity of 13,900 mPas and a fully blocked isocyanate content of 9.2%.

[0132] Inventive Example 6

[0133] 30.0 g of isophorone diisocyanate (IPDI) was added into a reaction flask, and heated while stirring to 65°C. Then, 0.1 g of catalyst tin(II) octanoate was added, and

[0134] 48.6 g of a phenolic blocking agent (NX 2026) was added slowly dropwise through a dropping funnel to the reaction solution over a period of 1 hour. After the addition was completed, reaction continued with stirring at 65°C for about 1 hour. Next, 135.2 g of polyether diol (DP 2000E) was added. After the addition was completed, the reaction continued at 65°C for about 1 hour until the NCO% < 0.4%. Upon cooling, a blocked isocyanate prepolymer 7 was obtained, with a measured viscosity of 8,832 mPas and a fully blocked isocyanate content of 21.3%.

[0135] Comparative Example 2 287.4 g of polyether diol (Arcol Polyol 1026) was prepolymerized with 25.0 g of toluene diisocyanate (DESMODUR® T 80) at 90 °C for 3 hours, until a theoretical NCO content of 1.9% was reached. Then, 43.0 g of cardanol (NX 2026) and 1.6 g of catalyst tin(II) octanoate were added, and stirred at 65°C until the NCO content was below 0.4%. Next, 2.1 g of benzoyl chloride was added and stirred for an additional 30 minutes. Upon cooling, a blocked isocyanate prepolymer 8 was obtained, with a high viscosity unmeasurable and the fully blocked isocyanate content of 0%.

[0136] Comparative Example 3

[0137] 216.0 g of toluene diisocyanate (DESMODUR® T 80) was added into a reaction flask, and heated while stirring to 70°C. Then, 413.5 g of polyether diol (Arcol Polyol 1026) was slowly added dropwise to the reaction solution through a dropping funnel over a period of 3 hours. After the addition was completed, reaction continued with stirring at 70°C, and cooled down when the NCO content reached 14.1%. Next, excessive toluene diisocyanate was removed by two-stage film evaporation (the temperatures of the first and second stage evaporators were 145°C and 140°C, respectively, and the vacuum degree was 0.2 mbar) to obtain 449 g of a toluene diisocyanate prepolymer. The prepolymer has an NCO% of about 3.3% and a viscosity of 5,300 mPas.

[0138] 280.0 g of the toluene diisocyanate prepolymer obtained from the above steps was placed into a reaction flask, and heated while stirring to 60°C, and 0.08 g of the catalyst tin(II) octanoate was added. Then, 68.3 g of cardanol (NX 2026) was added slowly dropwise through a dropping funnel. After the addition was completed, the reaction continued at 60°C until the NCO% was <0.5%. Upon cooling, a blocked isocyanate prepolymer 9 was obtained, with a measured viscosity of 26,500 mPas and a fully blocked isocyanate content of 0%.

[0139] The isocyanates and the polyhydroxyl compounds used, the viscosity of the resulting prepolymer system at room temperature, and the fully blocked isocyanate content in the above Inventive Examples and Comparative Examples are summarized in Table 1.

[0140] Table 1 instrument.

[0141] Inventive Example 7

[0142] To 56.92 g bisphenol A epoxy resin DER 331 was added 28.46 g of the blocked isocyanate prepolymer 1 from Inventive Example 1, and stirred to a homogenous mixture. Then, 14.63 g of IPDA (isophorone diamine) was added and mixed by stirring again until homogenous. The mixture was used to prepare films, the individual properties of which were tested after curing for 7 days at room temperature. The test results are summarized in Table 2.

[0143] Comparative Example 4

[0144] To 81.5 g of bisphenol A epoxy resin DER 331 was added 18.5 g of IPDA (isophorone diamine), and mixed by stirring until homogenous. The mixture was used to prepare films, the individual properties of which were tested after curing for 7 days at room temperature. The test results are summarized in Table 2.

[0145] Comparative Example 5

[0146] To 57.11 g of bisphenol A epoxy resin DER 331 was added 28.56 g ofDesmocap 14CNB, and stirred to a homogeneous mixture. Then, 14.33 g of IPDA (isophorone diamine) was added and mixed by stirring again until homogenous. The mixture was used to prepare films, the individual properties of which were tested after curing for 7 days at room temperature. The test results are summarized in Table 2.

[0147] Table 2

[0148] As can be seen from Table 2, as compared with Comparative Example 4 which did not incorporate a blocked isocyanate prepolymer, Inventive Example 7 yielded a transparent, tough material with high elasticity. As compared with Comparative Example 5 (the currently available product Desmocap 14CNB), the product obtained from Inventive Example 7 had the advantages of low viscosity while improving and enhancing the elasticity and flexibility of epoxy systems.

[0149] The above disclosure merely describes exemplary embodiments or Examples of the present invention, and is not intended to limit the present invention. For a person skilled in the art, the present invention may be modified or changed in various ways. Any amendment, equivalent substitution, improvement and the like without departing from the spirit and principles of the present invention all fall within the scope of the claims of the present application.

Claims

Claims:

1. A blocked isocyanate prepolymer system, characterized in that: it is prepared by reacting an isocyanate comprising two or more isocyanate groups first with a blocking agent and then with a polyhydroxyl compound, wherein: the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.8 to 1 : 2.5, and the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.8 to 1 : 1.2, wherein the blocking agent is selected from phenolic compounds.

2. The blocked isocyanate prepolymer system of claim 1, characterized in that the blocked isocyanate prepolymer has a viscosity of not more than 24,000 mPas, preferably not more than 20,000 mPas, as measured at 23 °C according to DIN EN ISO 3219: 1994-10.

3. The blocked isocyanate prepolymer system of claim 1 or 2, further comprising a fully blocked isocyanate, preferably, the fully blocked isocyanate has a weightaverage molecular weight in the range of 380 to 1,400 g / mol; more preferably, the fully blocked isocyanate accounts for 1% to 30% by weight, preferably from 5% to 22%, more preferably from 8% to 15%, relative to the total weight of the blocked isocyanate prepolymer system.

4. The blocked isocyanate prepolymer system of any one of claims 1 to 3, characterized in that the isocyanate is selected from diisocyanates and / or polyisocyanates having isocyanate groups with aliphatic, alicyclic, aromatic-aliphatic and / or aromatic linkage; preferably, the isocyanate is selected from diisocyanates having isocyanate groups with aliphatic, alicyclic, aromatic-aliphatic and / or aromatic linkage, more preferably selected from diisocyanate having isocyanate groups with different reactivity, such as 2-methyl-l,5-pentane diisocyanate, l,5-diisocyanato-2,2- dimethylpentane, 2,2,4- or 2,4,4-trimethyl-l,6-hexane diisocyanate, 1-isocyanato- 3,3,5-trimethyl-5-isocyanato-methylcyclohexane, 1 -isocyanato-1 -methyl -4(3)isocyanato-methylcyclohexane, toluene diisocyanate (toluene 2,4- and 2,6- diisocyanate, TDI), 2,4'-diphenylmethane diisocyanate (MDI) or any mixture of these diisocyanates.

5. The blocked isocyanate prepolymer system of any one of claims 1 to 4, characterized in that the blocking agent is selected from phenolic compounds with an OH value of 184 to 206 mg KOH / g, preferably 184 to 200 mg KOH / g, more preferably 186 to 192 mg KOH / g; more preferably, the blocking agent is selected from phenol, nonylphenol, cardanol, bisphenol A and bisphenol F; still more preferably, the blocking agent is selected from nonylphenol and cardanol.

6. The blocked isocyanate prepolymer system of any one of claims 1 to 5, characterized in that the polyhydroxyl compound is selected from polyols having an average functionality of 1.8 to 6.0, preferably 1.8 to 4.0, more preferably 1.9 to 2.2, and a number average molecular weight of 1,000 to 10,000 g / mol, preferably 1,000 to 4,000 g / mol, more preferably 2,000 to 4,000 g / mol; preferably, the polyhydroxyl compound is polyether polyols or a mixture of polymer polyols comprising at least one polyether polyol; more preferably, the polyether polyols are selected from addition products of ethylene oxide and / or propylene oxide on 1,2-propanediol, 1,3- propanediol, dipropylene glycol, diethylene glycol, glycerol, trimethylolpropane, triethanolamine, ethylenediamine and / or pentaerythritol; further preferably, the polyether polyols are selected from addition products of ethylene oxide and / or propylene oxide on 1,2-propanediol, 1,3-propanediol, dipropylene glycol and / or diethylene glycol; most preferably, the polyether polyols are selected from addition products of ethylene oxide and / or propylene oxide on 1,2-propanediol.

7. The blocked isocyanate prepolymer system of any one of claims 1 to 6, characterized in that the blocked isocyanate prepolymer system is solvent-free.

8. A method for preparing the blocked isocyanate prepolymer system of any one of claims 1 to 7, comprising the steps of:A. reacting an isocyanate comprising two or more isocyanate groups with a blocking agent, wherein the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.8 to 1 : 2.5; andB. further reacting the remaining isocyanate groups with a polyhydroxyl compound until the amount of free isocyanate groups is less than 0.5% by weight relative to the total weight of the entire reaction system, wherein the molar ratio of theOH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.8 to 1 : 1.2.

9. The method of claim 8, characterized in that the reaction of the isocyanate with the blocking agent in step A is carried out at a temperature of 0 to 150°C, preferably 20 to 140°C, more preferably 40 to 100°C.

10. The method of claim 8 or 9, characterized in that step B is performed when the remaining isocyanate (NCO) content falls within the range of the theoretically calculated amount NCO±0.5%.

11. The method of any one of claims 8 to 10, characterized in that the molar ratio of the active groups of the blocking agent that can react with the isocyanate to all isocyanate groups of the isocyanate is from 1 : 1.9 to 1 : 2.5, more preferably from 1 : 1.95 to 1 : 2.5, most preferably from 1 : 2.0 to 1 : 2.5.

12. The method of any one of claims 8 to 11, characterized in that the molar ratio of the OH groups of the polyhydroxyl compound to the remaining isocyanate groups after the blocking reaction is from 1 : 0.9 to 1 : 1.1, more preferably from 1 : 0.95 to 1 : 1.05.

13. The method of any one of claims 8 to 12, characterized in that the reaction of the isocyanate groups with the polyhydroxyl compound in step B is carried out at a temperature of 0 to 250°C, preferably 20 to 140°C, more preferably 40 to 100°C.

14. Use of the blocked isocyanate prepolymer of any one of claims 1 to 7 for preparing polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials.

15. Polyurethane plastics, adhesives, sealing materials, encapsulating materials, fiber sizing materials or coating materials comprising the blocked isocyanate prepolymer of any one of claims 1 to 7.

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