Urethane prepolymer and cured urethane product using the same

Abstract

To provide: a highly transparent urethane prepolymer having excellent curability and contributing to formation of polyurethanes having high strength; and a cured urethane which is highly transparent and has high strength and little surface tack.SOLUTION: The present invention discloses a urethane prepolymer (E) terminated by an active-hydrogen group, the urethane polymer (E) having a C3 or higher, alkylene oxide residue, an aromatic amine residue, and a polyisocyanate residue and having a polyol structure locally having an aromatic amine residue at a molecular end.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to urethane prepolymers. [Background technology]

[0002] Polyalkylene oxides containing a large amount of by-produced monools having an unsaturated group at one end (hereinafter referred to as unsaturated monools) are used as raw materials for polyurethanes. However, when attempting to obtain polyurethanes using these polyalkylene oxides, there is a problem that the curing (solidification) associated with the reaction with an isocyanate compound takes time, resulting in a loss of productivity.

[0003] Furthermore, polyurethanes obtained from polyalkylene oxides containing a large amount of such unsaturated monools are unlikely to have a high molecular weight, and have low tensile break elongation and low tensile break strength. In contrast, even polyalkylene oxides containing a large amount of unsaturated monools can be reacted with an isocyanate compound having a large average number of isocyanate groups to obtain high molecular weight polyurethanes. However, in this case, the polyurethane does not become linear and highly molecular weight, but becomes a crosslinked product having a dense crosslinked structure, resulting in low tensile break elongation and low tensile break strength.

[0004] On the other hand, since unsaturated monools have a relatively low molecular weight, compositions containing conventional polyalkylene oxides containing a large amount of unsaturated monools have a low viscosity, and when these compositions are coated with a coating machine or the like to obtain polyurethanes, they have the advantage of being easy to coat.

[0005] Here, Patent Document 1 discloses that by using a urethane-forming composition containing a polyalkylene oxide with a small amount of unsaturated monool, a polyalkylene oxide having an aromatic amine residue, and a polyalkylene oxide having one hydroxyl group and an ethylene oxide residue, and a urethane-forming composition containing a urethane prepolymer using the same, a polyurethane with good coatability and productivity and high tensile strength can be obtained.

[0006] However, these polyurethane-forming compositions described in Patent Document 1 and urethane prepolymers using them contain, as essential components, polyalkylene oxides with little low-molecular-weight unsaturated monools that act easily as compatibilizers, and use rigid aromatic amine polyols with catalytic activity. Therefore, due to factors such as poor compatibility with polyalkylene oxides with little unsaturated monools, transparency is likely to deteriorate depending on reaction conditions such as stirring conditions, reactor, and solvent amount, and adhesion of particulate precipitates or gel-like substances may occur, and the resulting urethane cured product may also become hard, making it difficult to wet and therefore poor in handleability.

[0007] Therefore, there has been a demand for a urethane prepolymer that has good coatability and productivity regardless of whether or not a polyalkylene oxide with a low unsaturated monool content is used, that contains a rigid aromatic amine polyol structure, and that contributes to the formation of a strong, highly transparent polyurethane, that is stable and free of precipitates or gel-like matter regardless of conditions such as the amount of solvent, and that has good curability and transparency, as well as a polyurethane that is highly transparent, has high strength, and has little surface tackiness, which can be obtained using the same. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-158551 Summary of the Invention [Problem to be solved by the invention]

[0009] To provide a highly transparent urethane prepolymer that contributes to the formation of polyurethane with excellent curability and high strength, and a highly transparent, high-strength, cured urethane product with little surface tack. [Means for solving the problem]

[0010] The embodiments of the present invention are as follows [1] to

[11] . [1] A urethane prepolymer (E) having an alkylene oxide residue having 3 or more carbon atoms, an aromatic amine residue, and a polyisocyanate residue, and having a polyalkylene oxide structure with aromatic amine residues locally present at the molecular terminals, and having an active hydrogen group terminal. [2] The urethane prepolymer (E) according to [1], which is a reaction product of an NCO-terminated prepolymer (D), which is a reaction product of a polyalkylene oxide (A) and a polyisocyanate (C), and a polyalkylene oxide (B) having an aromatic amine residue and two or more hydroxyl groups. [3] The urethane prepolymer (E) according to [1] or [2], which contains 5 to 70% by weight of a polyalkylene oxide structure having an aromatic amine residue or a residue thereof. [4] The urethane prepolymer (E) according to any one of [1] to [3], which contains, as an aromatic amine residue, one or more residues selected from the group consisting of 4,4'-diphenylmethanediamine residues, 2,4-tolylenediamine residues, and 2,6-tolylenediamine residues. [5] The urethane prepolymer (E) according to any one of [1] to [4], characterized in that the polyisocyanate residue comprises an aliphatic isocyanate residue, an alicyclic isocyanate residue, or a modified residue thereof, or two or more types of residues thereof. [6] The urethane prepolymer (E) according to any one of [1] to [5], wherein the polyalkylene oxide structure having an aromatic amine residue locally present at the molecular terminal contains one or more residues selected from the group consisting of polypropylene oxide residues, polypropylene-ethylene oxide residues, and polyethylene oxide residues. [7] A urethane prepolymer composition solution comprising the urethane prepolymer (E) according to any one of [1] to [6], an organic solvent, and an additive, The urethane prepolymer composition solution has a urethane prepolymer concentration of 60% by weight or more and 99% by weight or less. [8] A urethane-forming composition comprising the urethane prepolymer (E) according to any one of [1] to [6] and an isocyanate compound (F). [9] A urethane-forming composition solution comprising the urethane prepolymer composition solution according to [7] and an isocyanate compound (F).

[10] A urethane-cured product comprising a reaction product of the urethane-forming composition according to [8] or the urethane-forming composition in the urethane-forming composition solution according to [9].

[11] A polyurethane sheet comprising the urethane cured product according to

[10] . [Effects of the Invention]

[0011] The urethane prepolymer of one embodiment of the present invention is free from precipitates or gel-like matter, has excellent storage stability, and exhibits good compatibility, transparency, and curability, regardless of whether a polyalkylene oxide with a low unsaturated monool content is used, reaction conditions, solvent amount, etc., even when a rigid aromatic amine polyol necessary for achieving high strength is used. It is also possible to provide a urethane prepolymer that is free from precipitates or gel-like matter and has excellent storage stability, compatibility, transparency, and curability, and a highly transparent, high-strength urethane cured product using the same. DETAILED DESCRIPTION OF THE INVENTION

[0012] Exemplary embodiments for carrying out the present invention are described in detail below.

[0013] A urethane prepolymer according to one embodiment of the present invention is an active hydrogen group-terminated urethane prepolymer (E) having an alkylene oxide residue having 3 or more carbon atoms, an aromatic amine residue, and a polyisocyanate residue, and having a polyol structure having an aromatic amine residue locally located at the molecular terminal. <Urethane prepolymer (E)> The urethane prepolymer (E) of one embodiment of the present invention is an active hydrogen group-terminated urethane prepolymer having an alkylene oxide residue having 3 or more carbon atoms, an aromatic amine residue, and a polyisocyanate residue, and having a polyalkylene oxide structure with aromatic amine residues locally located at the molecular terminals.

[0014] Urethane prepolymer (E) contains an alkylene oxide residue having 3 or more carbon atoms as an essential component. If it does not contain an alkylene oxide residue having 3 or more carbon atoms, the strength of the resulting cured urethane product is likely to increase, but flexibility is significantly reduced, resulting in poor storage stability and handleability, making it difficult to use. Furthermore, if it contains only alkylene oxide residues having 2 carbon atoms but no alkylene oxide residues having 3 or more carbon atoms, crystallinity increases, resulting in poor transparency of the urethane prepolymer (E) and the resulting cured urethane product, as well as poor storage stability and handleability of the urethane prepolymer (E), making it difficult to use.

[0015] The alkylene oxide residue having 3 or more carbon atoms is not particularly limited, and examples thereof include alkylene oxide residues having 3 to 20 carbon atoms. Specific examples include propylene oxide residue, 1,2-butylene oxide residue, 2,3-butylene oxide residue, isobutylene oxide residue, butadiene monoxide residue, pentene oxide residue, styrene oxide residue, cyclohexene oxide residue, etc. Among these alkylene oxide residues, propylene oxide residue is preferred because the raw material polyalkylene oxide is easily available, and a liquid urethane prepolymer (E) having low crystallinity and appropriate viscosity can be easily produced, making it highly industrially valuable.

[0016] The alkylene oxide residue having 3 or more carbon atoms may contain only a single alkylene oxide residue, or may contain two or more types of alkylene oxide residues. When two or more types of alkylene oxide residues are contained, for example, one type of alkylene oxide residue may be linked in a chain to another alkylene oxide residue, or two or more types of alkylene oxide residues may be linked randomly. Furthermore, it is sufficient that the alkylene oxide residue has 3 or more carbon atoms, and in addition to this, an ethylene oxide residue having 2 carbon atoms may be contained. When an ethylene oxide residue having two carbon atoms is contained, its content is not particularly limited, but in order to easily achieve excellent fluidity and high coatability, the weight ratio of alkylene oxide residues having three or more carbon atoms to ethylene oxide residues having two carbon atoms (alkylene oxide residues having three or more carbon atoms / ethylene oxide residues having two carbon atoms) is preferably in the range of 10 / 90 to 99.9 / 0.1, more preferably in the range of 30 / 70 to 99.7 / 0.3, and most preferably in the range of 50 / 50 to 99.5 / 0.5. When an ethylene oxide residue having two carbon atoms is contained, it is not particularly limited, but in order to easily achieve excellent coatability, it is preferable that the composition has a chain structure of ethylene oxide residues having two carbon atoms, such as a polyoxyethylene glycol monoalkyl ether residue.

[0017] The content of alkylene oxide residues having 3 or more carbon atoms contained in the urethane prepolymer (E) is not particularly limited, but is preferably 30% by weight to 99% by weight to facilitate the development of good coating properties and high transparency, more preferably 50% by weight to 95% by weight to facilitate the realization of both higher transparency and high strength, and most preferably 70% by weight to 90% by weight. The content can be calculated by analysis using NMR or Corisch decomposition, or if the raw materials are known, it may be calculated from the amounts added.

[0018] The urethane prepolymer (E) contains an aromatic amine residue as an essential component. Without an aromatic amine residue, the transparency of the urethane prepolymer (E) and the resulting cured urethane product is likely to be improved, but the strength of the cured urethane product is insufficient, and strength-related physical properties such as easy peelability and durability are significantly impaired, making it difficult to use. The curability of the urethane prepolymer is also insufficient, resulting in poor productivity and making it difficult to use. In other words, the presence of an aromatic amine residue with a rigid skeleton and moderate catalytic activity improves the curability of the urethane prepolymer and the strength of the resulting cured urethane product.

[0019] Among these, the urethane prepolymer (E) is characterized by having a polyalkylene oxide structure (hereinafter referred to as an aromatic amine polyol structure) having aromatic amine residues locally located at the molecular terminal. Localized in this specification means "being in a limited location, being in a biased location" (see Selected Edition of the Japanese Language Dictionary, Shogakukan Publishing). It is sufficient that the aromatic amine polyol structure is contained in excess around the molecular terminal compared to the interior of the molecule, and is biased, and it may also be contained inside the molecule.

[0020] There are no particular limitations as long as the aromatic amine polyol structure is contained locally around the molecular terminal, but it is preferable that the content ratio of the aromatic amine polyol structure at the molecular terminal is high relative to the content of the aromatic amine polyol structure in the entire polyol, that is, it is preferable that the molar ratio of the aromatic amine polyol structure at the molecular terminal is high relative to the molar ratio of the aromatic amine polyol structure in the entire polyol constituting the urethane prepolymer (E).

[0021] Aromatic amine residues generally have catalytic activity for urethanization and often have a similar structure to crosslinkers. Therefore, if the aromatic amine polyol structure is not present at the molecular end in excess of that present within the molecule, compatibility with the crosslinker deteriorates and reactivity decreases, making it difficult to consistently form highly transparent, high-strength cured urethane products, regardless of whether a polyalkylene oxide with a low unsaturated monool content is used, reaction conditions, solvent amount, etc. Furthermore, depending on the reaction conditions, the urethane prepolymer (E) may exhibit poor transparency or produce particulate precipitates or gel-like materials, which also reduces the transparency of the resulting cured urethane product, making it difficult to use. In other words, the presence of an excess of polyol structures with aromatic amine residues at the molecular end improves compatibility and curing properties, resulting in a highly transparent and curable urethane prepolymer (E), and the resulting cured urethane products are consistently highly transparent and strong.

[0022] The content ratio of aromatic amine polyol structures at molecular terminals to the content of aromatic amine polyol structures in the entire polyol (molar ratio of aromatic amine polyol at molecular terminals / molar ratio of aromatic amine polyol in the entire polyol) is preferably greater than 1.0, but is not particularly limited. In particular, since significantly higher transparency is likely to be achieved regardless of reaction conditions, solid content, etc., it is preferably greater than 1.01 and less than 10, more preferably greater than 1.03 and less than 2.5, and most preferably greater than 1.10 and less than 1.7.

[0023] Urethane prepolymer (E) is obtained by adding aromatic amine polyol to the terminals. In this case, other polyols (BC) can be used in combination, and the proportion of aromatic amine polyol structural residues contained at the molecular terminals may decrease depending on the amount added. For example, if 90 mol% of a polyol containing aromatic amine residues and 10 mol% of another polyol without aromatic amine residues are added to the terminals in combination and there is no difference in reactivity, the proportion of aromatic amine polyol structures contained at the molecular terminals will be approximately 90%. Monools are often used to cap the molecular terminals regardless of the reaction timing, but because they do not have reactive hydroxyl groups after the reaction, they are not included in the polyol structural residues at the molecular terminals.

[0024] The proportion of aromatic amine polyol structures contained in the molecular terminals is not particularly limited, but a low proportion of aromatic amine polyol structures contained in the molecular terminals may result in poor compatibility with the crosslinking agent or reduced reactivity, and a molecular terminal aromatic amine polyol structure proportion of 30% or more is preferred because this facilitates the formation of a highly transparent and high-strength urethane cured product regardless of the use of a polyalkylene oxide with a low unsaturated monool content, the reaction conditions, the amount of solvent, etc. In particular, a molecular terminal aromatic amine polyol structure proportion of 60% or more is preferred, more preferably the urethane prepolymer (E) contains 20% by weight or more of aromatic amine polyol structures and the molecular terminal aromatic amine polyol structure proportion is 80% to 100%, and most preferably the molecular terminal aromatic amine polyol structure proportion is 90% to 99.99%.

[0025] For example, normally, a polyol having a molecular weight of less than 2000 and an aromatic amine residue exhibits significantly higher reactivity than a polyol having a molecular weight of more than 2000 and not having an aromatic amine residue, so although it varies somewhat depending on the raw material ratio and molecular weight used, when a polyol having a molecular weight of more than 2000 and not having an aromatic amine residue and a polyol having a molecular weight of less than 2000 are used in the same molar ratio (1:1) by conventional methods, the aromatic amine polyol structure ratio at the molecular end is less than 50%, and when a polyol having a molecular weight of more than 2000 and not having an aromatic amine residue and a polyol having a molecular weight of less than 2000 and an aromatic amine residue are used in a molar ratio of 1:9, the aromatic amine polyol structure ratio at the molecular end is less than 90%. Therefore, the content ratio of the aromatic amine polyol structure at the molecular end is lower than the content ratio of the overall aromatic amine polyol structure.

[0026] The polyol structure ratio at the molecular end can be determined by analyzing the primary ratio of terminal hydroxyl groups, residues of alkylene oxides adjacent to hydroxyl groups, and various decomposition products. Furthermore, if an isocyanate-terminated prepolymer is formed and only polyols with aromatic amine residues at the end are added until the NCO groups disappear, theoretically the molecular end will be almost entirely an aromatic amine polyol structure, and the aromatic amine polyol structure ratio at the molecular end will be determined to be 100%.

[0027] When a polyol having an aromatic amine residue and another polyol not having an aromatic amine residue are used in combination and added to the terminal, if they have the same or higher molecular weight and the same alkylene oxide residue at the terminal, the polyol having the aromatic amine residue usually has higher reactivity. Furthermore, since the structural ratio of the terminal correlates with the ratio of the used in combination, the amount of the other polyol used in combination was calculated as the lower limit, taking into account the effects of reactivity, number of functional groups, impurities, etc., and when 90 mol % of a polyol having an aromatic amine residue and 10 mol % of another polyol not having an aromatic amine residue are used in combination and added to the terminal, the aromatic amine polyol structural ratio of the molecular terminal is determined to be 90% or more.

[0028] The aromatic amine polyol structure at the molecular end is not particularly limited. However, since this tends to result in higher compatibility and transparency, it is more preferable for the polyalkylene oxide residue to contain one or more residues selected from the group consisting of polypropylene oxide residues, polypropylene oxide-polyethylene oxide residues, and polyethylene oxide residues, including block structures, random structures, gradient structures, etc. Among these, it is preferable for the alkylene oxide residue to contain propylene oxide residues, since this tends to be less likely to crystallize from low to high temperatures and to have particularly excellent fluidity. Most preferably, 40 wt% or more of the alkylene oxide residues are propylene oxide residues. The content can be calculated by NMR or Corisch degradation analysis, but if the raw materials are known, it can also be calculated from the raw material structure.

[0029] The structure of the aromatic amine residue contained in the urethane prepolymer (E) is not particularly limited, but is preferably an aromatic amine residue having 1 to 20 aromatic rings per molecule, and more preferably an aromatic amine residue having 1 to 3 aromatic rings per molecule.

[0030] The content of aromatic amine residues contained in the urethane prepolymer (E) is not particularly limited, but is preferably 0.5% by weight or more and 25% by weight or less because this tends to produce high strength, more preferably 1% by weight or more and 15% by weight or less because this tends to achieve both higher strength and handleability of the cured product, and most preferably 3% by weight or more and 10% by weight or less. The content can be calculated by analysis such as NMR or Colish degradation, but if the raw materials are known, it may also be calculated from the molecular weight of the polyalkylene oxide calculated from the hydroxyl value, the nominal initiator structure, and the amount added.

[0031] Examples of such aromatic amine residues include aniline residues, 2,4-tolylenediamine residues, 2,6-tolylenediamine residues, 2,2'-diphenylmethanediamine residues, 2,4'-diphenylmethanediamine residues, 4,4'-diphenylmethanediamine residues, polyphenylenepolyamine residues, 1,5-naphthalenediamine residues, tolidinediamine residues, xylylenediamine residues, 1,3-phenylenediamine residues, 1,4-phenylenediamine residues, and residues of two or more of these.Preferred are 2,4-tolylenediamine residues, 2,6-tolylenediamine residues, and residues of two or more of these, which are readily available as raw materials and tend to exhibit good curability and high strength.The structure of the aromatic amine residue can be analyzed by MALDI-TOF-MS or the like.

[0032] The aromatic amine residues contained in the urethane prepolymer (E) are usually obtained by adding aromatic amines or aromatic amine polyols to the terminals or the interior of the molecule, but it is preferable to contain a polyol structure having an aromatic amine residue or a residue thereof, as this tends to result in excellent compatibility and higher transparency. The content of the polyol structure having an aromatic amine residue or a residue thereof is preferably 5 to 70 wt %, more preferably 10 to 55 wt %, and most preferably 20 to 50 wt %, as this tends to result in significantly higher strength and improved coatability. The content of the polyol structure having an aromatic amine residue or a residue thereof can be calculated by analysis such as alkaline decomposition or Corisch decomposition, but if the raw materials are known, it may also be calculated from the added amounts.

[0033] The urethane prepolymer (E) contains a polyisocyanate residue as an essential component. If the urethane prepolymer (E) does not contain a polyisocyanate residue, it will lack urethane groups with cohesive strength, resulting in reduced curing properties and making it difficult to use. The resulting cured urethane product will have reduced strength and poor substrate wettability, making it difficult to use. Furthermore, it will be difficult to form a polyol structure selectively having aromatic amine residues at its terminals.

[0034] The polyisocyanate residue contained in the urethane prepolymer (E) is not particularly limited as long as the average number of functional groups in the isocyanate residue is 2.0 or more.

[0035] The structure of the polyisocyanate residue is not particularly limited, but examples thereof include residues of the following polyisocyanates (C): 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, 1,6-hexamethylene diisocyanate, Examples of the isocyanate include residues of isocyanates, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, norbornane diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, and modified isocyanates obtained by reacting these with polyalkylene oxides, as well as residues of mixtures of two or more of these. Further examples include modified products of these isocyanates containing a urethane group, a carbodiimide group, an allophanate group, a urea group, a biuret group, an isocyanurate group, an amide group, an imide group, a uretonimine group, a uretdione group, or an oxazolidone group, and residues of condensates such as polymethylene polyphenylene polyisocyanate (polymeric MDI).

[0036] Among these, it is preferable that the polyisocyanate residue contains one or more residues selected from the group consisting of aliphatic isocyanate residues, alicyclic isocyanate residues, and modified residues thereof, in order to facilitate the production of a urethane-forming composition that is highly transparent and less colored.

[0037] The residue of such polyisocyanate (C) is not particularly limited, but examples include the residues of the polyisocyanate (C) exemplified below, and more preferred are residues of 1,6-hexamethylene diisocyanate, isophorone diisocyanate, aliphatic isocyanate-containing prepolymers, alicyclic isocyanate-containing prepolymers, or modified products of these isocyanates containing urethane groups, carbodiimide groups, allophanate groups, urea groups, biuret groups, isocyanurate groups, amide groups, imide groups, uretonimine groups, uretdione groups, or oxazolidone groups. The residues of these isocyanates may contain one type alone or two or more types.

[0038] Among these, it is preferable to contain residues of 1,6-hexamethylene diisocyanate or modified products thereof, because the viscosity of the urethane prepolymer increases little over time and the storage stability is excellent. It is also preferable to contain residues of isophorone diisocyanate, because these have primary and secondary NCO groups with different reactivities, which makes it easy to suppress high molecular weight due to chain reactions, thereby easily preventing deterioration of coatability and high viscosity, and tends to significantly improve the transparency of the urethane prepolymer and the urethane cured product obtained using the same. Therefore, it is preferable to contain residues of one or more types selected from 1,6-hexamethylene diisocyanate, modified products thereof, and isophorone diisocyanate.

[0039] The content of polyisocyanate residues contained in the urethane prepolymer (E) is not particularly limited, but is preferably 0.5% by weight or more and 30% by weight or less, as this tends to provide high strength, more preferably 2% by weight or more and 20% by weight or less, as this tends to provide both higher transparency and high strength, and most preferably 4% by weight or more and 12% by weight or less.

[0040] The content can be calculated by analysis using the NMR method or Colisch decomposition, but if the raw material is known, it may also be calculated from the amount added.

[0041] The urethane prepolymer (E) may contain other residues in addition to the alkylene oxide residues having 3 or more carbon atoms, aromatic amine residues, polyisocyanate residues, and the exemplified ethylene oxide residues having 2 carbon atoms, which are contained as essential components. Examples of residues that can be suitably contained include, but are not limited to, carbonate residues, oxytetramethylene residues, sugar residues, ester residues, oxetane residues, caprolactone residues, isobutylene residues, butadiene residues, alkyl ether residues, Mannich polyol residues, acrylic residues, silicone residues, fluorine residues, phosphate ester residues, aliphatic amine residues, imine residues, quaternary ammonium residues, and isocyanurate residues. Among these, the urethane prepolymer (E) preferably contains oxytetramethylene residues, sugar residues, alkyl ether residues, ester residues, carbonate residues, and aliphatic amine residues, as these residues exhibit higher curability and coatability, making it easier to obtain a high-strength urethane cured product. When the exemplified residues are contained, their content is not particularly limited, but is preferably in the range of 0.01% by weight to 70% by weight, more preferably in the range of 0.1% by weight to 50% by weight, and most preferably in the range of 0.5% by weight to 20% by weight, since this makes it easier to achieve both high curability and coatability.

[0042] Furthermore, the urethane prepolymer (E) may contain a monool structure having an unsaturated group in the polyalkylene oxide used, and may contain an unsaturated group that is the residue thereof.

[0043] Since the urethane prepolymer (E) exhibits high curability regardless of whether or not a polyalkylene oxide with a low unsaturated monool content is used, the unsaturated group content is not particularly limited and varies depending on the raw materials used, but since it tends to exhibit higher curability, it is preferable that the unsaturated group content be in the range of 0.0001 meq / g to 100 meq / g. When it does not substantially contain highly reactive unsaturated groups such as urethane acrylate groups or urethane methacrylate groups that can act as reactive groups, it tends to exhibit higher curability, so the unsaturated group content is preferably in the range of 0.0003 meq / g to 0.050 meq / g, more preferably in the range of 0.0005 meq / g to 0.010 meq / g, and most preferably in the range of 0.0007 meq / g to 0.002 meq / g. The unsaturated group content can be analyzed by various analytical methods such as NMR.

[0044] The ratio of primary hydroxyl groups in the urethane prepolymer (E) varies depending on the ratio of primary hydroxyl groups in each raw material polyol and is not particularly limited, but if it is too high, the coatability tends to deteriorate, so it is preferably 85% or less. The ratio of primary hydroxyl groups in the urethane prepolymer (E) can be calculated by reacting the hydroxyl groups with trifluoroacetic anhydride and calculating it from the peak shift in HNMR, similar to the calculation of the ratio of primary hydroxyl groups in polyalkylene oxide, or by reacting the hydroxyl groups with tetrafluorophthalic anhydride and calculating it from the peak shift in HNMR. In the present invention, the above methods were applied to calculate the approximate ratio.

[0045] It is preferable that the residual amount of aromatic amine polyol and polyol used in combination in the urethane prepolymer (E) is small. Although not particularly limited, it is within 20% by weight, more preferably 10% by weight or less, because it is likely to exhibit significantly high transparency. In particular, the residual amount of polyalkylene oxide not having aromatic amine polyol residues is preferably within 5% by weight, more preferably 2% by weight or less, because it is likely to exhibit even higher transparency. The residual amount of aromatic amine polyol and polyol used in combination in the urethane prepolymer (E) may be determined by the peak integral ratio (aromatic amine polyol and polyol used in combination peak / main peak × 100) by GPC method or the like.

[0046] The urethane prepolymer (E) is not particularly limited, but preferably has a viscosity of 1 to 100 Pa·s at 25°C and a transparent liquid appearance (haze of 15% or less at a thickness of 1 cm), and such a urethane prepolymer (E) can be produced efficiently and easily.

[0047] Among these, a preferred property is a viscosity in the range of 3 to 50 Pa s at 25°C, more preferably 5 to 30 Pa s, because this facilitates mixing of additives in later processes, provides excellent handling during mixing of crosslinking agents and coating, and tends to produce a stably highly transparent cured urethane product. If the viscosity is high, it can be reduced or adjusted by adding a solvent or additive, and if the viscosity is low, it can be increased or adjusted by concentration, etc.

[0048] The transparency of the urethane prepolymer (E) is not particularly limited, but it is preferably visually transparent since this tends to improve visibility, and it is more preferable that the haze at a thickness of 1 cm is 15% or less, and most preferably 5% or less.

[0049] The molecular weight of the urethane prepolymer (E) is not particularly limited, but the weight average molecular weight measured by gel permeation chromatography is preferably in the range of 2,500 or more and 500,000 or less, more preferably in the range of 5,000 or more and 200,000 or less, and more preferably in the range of 10,000 or more and 100,000 or less, because this tends to improve handleability.

[0050] The active hydrogen group-terminated urethane prepolymer (E) is characterized by containing a polyol structure having an aromatic amine residue locally present around the molecular end, and the production method is not particularly limited as long as an excess of the polyol having an aromatic amine residue can be introduced into the molecular end. For example, although not particularly limited, there are preferably used methods such as a method of adding the polyol having an aromatic amine residue at the end or at the end of a process to add it to the end, and a method of adjusting the reactivity of the raw materials used to add the polyol having an aromatic amine residue at the end or at the end to introduce it to the end.

[0051] Examples of adjusting the reactivity of the raw materials used include reducing the reactivity of the polyol having aromatic amine residues and / or improving the reactivity of the polyol used in combination, and forming a block structure by protecting the reactive groups. For example, when the solids content is 70% or more, reducing the reactivity of the polyol having aromatic amine residues can be done by increasing the molecular weight of the polyol having aromatic amine residues (for example, 500 or more), introducing secondary hydroxyl groups, or adding an acid compound. Examples of improving the reactivity of the polyol used in combination include reducing the molecular weight of the polyol used in combination (for example, 6000 or less), or using a polyol with a high primary content in which a large amount of ethylene oxide residues, tetrahydrofuran residues, propylene oxide residues having primary hydroxyl groups, etc. have been introduced at the terminals (for example, ethylene oxide residues of 16% by weight or more, primary content of 75% or more). However, these methods are not particularly limited, as the reactivity of each polyol differs depending on the structure of the polyol used in combination, the structure of the aromatic amine polyol, the solids content, etc., and the terminal structure ratio changes accordingly.

[0052] The most preferred method for producing the active hydrogen group-terminated urethane prepolymer (E) is, but is not particularly limited to, forming an NCO-terminated prepolymer having an alkylene oxide residue and an isocyanate residue, followed by addition of a polyalkylene oxide having an aromatic amine residue and two or more hydroxyl groups, which is preferred because it allows for the stable formation of a polyol structure having an aromatic amine residue at the end regardless of the reactivity of the raw materials, and it consistently exhibits remarkably high transparency regardless of the reaction conditions, etc. That is, it is preferred that the NCO-terminated urethane prepolymer (D), which is a reaction product of at least a polyalkylene oxide (A) and a polyisocyanate (C), is a reaction product of a polyalkylene oxide (B) having an aromatic amine residue and two or more hydroxyl groups. <Polyalkylene oxide (A)> The number average molecular weight of the polyalkylene oxide (A), which is preferably used in the urethane prepolymer (E) and the NCO-terminated urethane prepolymer (D), is not particularly limited, but is preferably 2000 or more because it has a moderate viscosity, excellent handleability, and tends to provide good coatability and wettability. Among these, the number average molecular weight of the polyalkylene oxide (A) is preferably 2500 or more and less than 30000, more preferably 3000 or more and less than 13000, and most preferably 3500 or more and less than 9000. The number average molecular weight of the polyalkylene oxide (A) can be calculated from the hydroxyl value of the polyalkylene oxide (A) calculated by the method described in JIS K-1557-1 and the number of hydroxyl groups in one molecule of the polyalkylene oxide (A). The hydroxyl value (mgKOH / g) of the polyalkylene oxide (A) is not particularly limited, but is preferably 3 or more and 250 or less, more preferably 5 or more and 180 or less, and most preferably 8 or more and 70 or less.

[0053] The viscosity of the polyalkylene oxide (A) at 25°C is not particularly limited and can be selected appropriately depending on the application. However, it is preferably 100 mPa·s or more and 200,000 mPa·s or less, and more preferably 200 mPa·s or more and 10,000 mPa·s or less. A viscosity of 100 mPa·s or more and 200,000 mPa·s or less at 25°C is preferred because it facilitates coating when applied using a coating machine or the like to obtain a polyurethane product. Here, the "viscosity" at 25°C is the value measured using a cone-plate rotational viscometer at a shear rate of 0.1 (1 / s) in accordance with JIS K1557-5, Section 6.2.3.

[0054] The polyalkylene oxide (A) preferably contains an alkylene oxide residue having 3 or more carbon atoms because it has excellent fluidity from low to high temperatures. The alkylene oxide residue having 3 or more carbon atoms is not particularly limited, and examples thereof include alkylene oxide residues having 3 to 20 carbon atoms. Specific examples include propylene oxide residue, 1,2-butylene oxide residue, 2,3-butylene oxide residue, isobutylene oxide residue, butadiene monoxide residue, pentene oxide residue, styrene oxide residue, and cyclohexene oxide residue. Among these alkylene oxide residues, propylene oxide residue is preferred because the raw materials for obtaining the polyalkylene oxide (A) are easily available and the resulting polyalkylene oxide (A) has high industrial value.

[0055] Furthermore, the polyalkylene oxide (A) may contain only a single alkylene oxide residue as the alkylene oxide residue having 3 or more carbon atoms, or may contain two or more types of alkylene oxide residues. When two or more types of alkylene oxide residues are contained, for example, one type of alkylene oxide residue may be linked in a chain to another alkylene oxide residue, or two or more types of alkylene oxide residues may be linked randomly. Furthermore, the polyalkylene oxide (A) may contain an ethylene oxide residue having 2 carbon atoms in addition to the alkylene oxide residue having 3 or more carbon atoms.

[0056] The number of hydroxyl groups in the polyalkylene oxide (A) is not particularly limited, but preferably has two or more hydroxyl groups per molecule, more preferably 2 to 6, and most preferably 2 to 3. When the number of hydroxyl groups per molecule of the polyalkylene oxide (A) is 6 or less, the crosslinked structure of the resulting urethane cured product is less likely to become dense, and the tensile elongation at break and strength are further increased, which is preferable.

[0057] The primary hydroxyl group ratio of the polyalkylene oxide (A) is not particularly limited, but is preferably in the range of 0 to 90%. When synthesis is carried out using a cationic polymerization system such as trifluoroborane or trispentafluorophenylborane as a catalyst, the primary ratio tends to be high even when propylene oxide or the like is used as the alkylene oxide other than ethylene oxide, and when a base catalyst such as potassium hydroxide or a metal catalyst such as a double metal cyanide (DMC) catalyst is used, the primary ratio tends to be low, but is not particularly limited, including the terminal structure, and either can be suitably used.

[0058] In addition, the polyalkylene oxide (A) is preferably liquid at room temperature, since this facilitates the production of the urethane prepolymer. The degree of unsaturation of the polyalkylene oxide (A) is not particularly limited because it is easy to achieve high transparency in prepolymers and urethane cured products regardless of whether or not a polyalkylene oxide with a low unsaturated monool is used, but because an increase in the amount of a multifunctional polyol such as a polyalkylene oxide (B) having an aromatic amine residue or a large amount of a bifunctional polyol having a more rigid skeleton than polypropylene oxide is likely to be required, the degree of unsaturation is preferably 0.010 meq / g or less, more preferably 0.007 meq / g or less, and most preferably 0.004 meq / g or less. Such a polyalkylene oxide (A) with a low degree of unsaturation is not particularly limited, but can be produced by adding an alkylene oxide to an active hydrogen compound using an iminophosphazenium salt and a Lewis acid catalyst. The molecular weight distribution (Mw / Mn) of the polyalkylene oxide (A) is not particularly limited because it is easy to achieve high transparency in prepolymers and urethane cured products regardless of whether or not a polyalkylene oxide with a narrow molecular weight distribution is used. However, since the molecular weight distribution of the prepolymer tends to narrow and handleability tends to be excellent, it is preferably 1.059 or less, more preferably 1.039 or less, and most preferably 1.004 to 1.029. The polyalkylene oxide (A) preferably has a water content of 2000 ppm or less, but since dehydration procedures and the like can be complicated, the water content can be selected depending on the intended use.

[0059] <Polyisocyanate (C)> The polyisocyanate (C) preferably used in the urethane prepolymer (E) and the NCO-terminated urethane prepolymer (D) preferably has an average functionality of 2.0 or more of the isocyanate group, but is not particularly limited thereto. Examples of the polyisocyanate (C) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexyl methyl acrylate, ... Examples of the isocyanate include xylmethane diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, norbornane diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, modified isocyanates obtained by reacting these with polyalkylene oxides, and mixtures of two or more of these. Further examples include modified products of these isocyanates containing a urethane group, a carbodiimide group, an allophanate group, a urea group, a biuret group, an isocyanurate group, an amide group, an imide group, a uretonimine group, a uretdione group, or an oxazolidone group, and condensates such as polymethylene polyphenylene polyisocyanate (polymeric MDI).

[0060] Among these, aliphatic isocyanates, alicyclic isocyanates, or modified products thereof are preferred because they are highly productive and allow for the easy production of a highly transparent and minimally colored urethane prepolymer (E) and a highly transparent and minimally colored urethane cured product using the same. 1,6-hexamethylene diisocyanate, isophorone diisocyanate, aliphatic isocyanate-containing prepolymers, alicyclic isocyanate-containing prepolymers, and modified products of these isocyanates containing urethane groups, carbodiimide groups, allophanate groups, urea groups, biuret groups, isocyanurate groups, amide groups, imide groups, uretonimine groups, uretdione groups, or oxazolidone groups are more preferred. These isocyanates may be used alone or in combination of two or more.

[0061] Among these, 1,6-hexamethylene diisocyanate and its modified products are preferred because they have high reactivity, good productivity, and excellent storage stability with little increase in viscosity of the urethane prepolymer (E) over time. Isophorone diisocyanate is also preferred because it contains primary and secondary NCO groups with different reactivities, which helps to suppress polymerization due to chain reactions, provides excellent coatability and viscosity, and significantly improves the transparency of the urethane prepolymer and the urethane cured product obtained using it. Therefore, it is preferred to use at least one selected from 1,6-hexamethylene diisocyanate, its modified products, and isophorone diisocyanate. <Polyalkylene oxide (B)> The polyalkylene oxide (B) preferably used in the urethane prepolymer (E) is a polyol having an aromatic amine residue. The presence of an aromatic amine residue in the polyalkylene oxide (B) tends to significantly increase the hardness and tensile strength of the resulting polyurethane. Among these, a polyol having an alkylene oxide residue of 2 to 10 carbon atoms and two or more active hydrogen groups per molecule is preferred, as it tends to exhibit good fluidity and excellent moldability, and also tends to achieve high hardness and tensile strength, resulting in excellent urethane physical properties. This may be a polyol in which one type of alkylene oxide is linked in a chain to an aromatic amine, or a polyol in which multiple alkylene oxides are linked in a chain or randomly to an aromatic amine.

[0062] Among these, alkylene oxides are preferably those in which only propylene oxide is linked in a chain to an aromatic amine, those in which only ethylene oxide is linked in a chain to an aromatic amine, or those in which propylene oxide and ethylene oxide are linked in a chain or randomly to an aromatic amine, because alkylene oxides are easily available industrially and synthesis is easy. More preferably, they contain propylene oxide residues because they are less likely to crystallize from low to high temperatures and tend to have particularly excellent fluidity, and most preferably, 40% by weight or more of the alkylene oxide residues contained in the polyalkylene oxide (B) are propylene oxide residues.

[0063] The polyalkylene oxide (B) preferably has two or more hydroxyl groups in one molecule, more preferably 3 or more but less than 15 hydroxyl groups in one molecule, and most preferably 4 or more but less than 6 hydroxyl groups in one molecule.

[0064] When the number of hydroxyl groups in one molecule of the polyalkylene oxide (B) containing an aromatic amine residue in one molecule is 3 or more but less than 15, the crosslinked structure of the resulting urethane cured product tends to be uniform, and the tensile strength at break is further increased, which is preferable.

[0065] The number-average molecular weight of the polyalkylene oxide (B) is preferably less than 2000. If the number-average molecular weight is less than 2000, the content of aromatic amine residues is likely to be high, the strength is likely to be further improved, and the reactivity is improved, making it difficult for a large amount of unreacted polyalkylene oxide (B) to remain, so that high transparency is likely to be more stably achieved.

[0066] Among these, there are no particular limitations and the molecular weight is appropriately selected depending on the application, but the molecular weight is preferably 200 or more and less than 1800, more preferably 400 or more and less than 1300, and most preferably 450 or more and less than 1000, because this makes it less likely for the composition to become unstable due to evaporation or the like, and the content of aromatic amine residues is high and it is easy to exhibit stable high strength.

[0067] The number average molecular weight of the polyalkylene oxide (B) can be calculated from the hydroxyl value of the polyalkylene oxide (B) calculated by the method described in JIS K-1557-1 and the number of hydroxyl groups in one molecule of the polyol (A2). In the case of commercially available products, the nominal number of functional groups and hydroxyl value can be used.

[0068] The structure of the aromatic amine residue in the polyalkylene oxide (B) is not particularly limited, but is preferably an aromatic amine residue having 1 to 20 aromatic rings per molecule, and more preferably an aromatic amine residue having 1 to 3 aromatic rings. If the polyalkylene oxide (B) does not contain an aromatic amine residue, the tensile strength at break is likely to be insufficient, and to improve the strength, an aromatic amine itself is used, or a polyol relatively more rigid than the polyalkylene oxide (A), such as a polyol containing a cyclic sugar residue having 6 or more carbon atoms, a polyester polyol, or polyoxytetramethylene glycol, is required. However, these make it difficult to prevent deterioration of coatability and cloudiness, and the resulting urethane cured product is likely to be brittle and highly tacky.

[0069] The content of aromatic amine residues in polyalkylene oxide (B) is not particularly limited, but is preferably 7% by weight or more to facilitate the development of high strength, more preferably 10% by weight to 50% by weight to facilitate the realization of both higher transparency and high strength, and most preferably 13% by weight to 30% by weight. The content can be calculated by analysis such as NMR or Colish decomposition, but may also be calculated from the molecular weight of the polyalkylene oxide calculated from the hydroxyl value and the nominal initiator structure.

[0070] Examples of such aromatic amine residues include aniline residues, 2,4-tolylenediamine residues, 2,6-tolylenediamine residues, 2,2'-diphenylmethanediamine residues, 2,4'-diphenylmethanediamine residues, 4,4'-diphenylmethanediamine residues, polyphenylenepolyamine residues, 1,5-naphthalenediamine residues, tolidinediamine residues, xylylenediamine residues, 1,3-phenylenediamine residues, 1,4-phenylenediamine residues, and residues of two or more of these. Preferred are one or more residues selected from the group consisting of 4,4'-diphenylmethanediamine residues, 2,4-tolylenediamine residues, and 2,6-tolylenediamine residues, which are readily available as raw materials and tend to exhibit good curability and tensile strength at break.

[0071] The polyalkylene oxide (B) is generally obtained by ring-opening polymerization of an alkylene oxide using an aromatic amine such as tolylenediamine or diphenylmethanediamine as an initiator. However, it may also be synthesized by using a low-viscosity active hydrogen compound that does not contain an aromatic amine residue, such as ethylenediamine, diethylenetriamine, triethanolamine, diethylene glycol, glycerin, or propylene glycol, in combination with the initiator, and may contain a component having the above residue.

[0072] For example, typically, a tolylenediamine-initiated polyol has four hydroxyl groups, and an aniline-initiated polyol has two hydroxyl groups. However, the number of hydroxyl groups may decrease due to the combined use of an initiator that does not contain a tolylenediamine residue or an aniline residue, or due to the presence of residual amino groups to which no alkylene oxide has been added.

[0073] Commercially available polyalkylene oxides (B) containing aromatic amine residues include JEFFOLAD-310 (nominal functionality 3.2, hydroxyl value 310) and JEFFOLAD-500 (nominal functionality 3.2, hydroxyl value 360) manufactured by Huntsman, TOHO POLYOL AB-250 (nominal functionality 2.0, hydroxyl value 440) manufactured by Toho Chemical Industry Co., Ltd., AR-2589 (nominal functionality 4.0, hydroxyl value 360) manufactured by Toho Chemical Industry Co., Ltd., and AR-750 (nominal functionality 4.0, hydroxyl value 300) manufactured by Toho Chemical Industry Co., Ltd., and these can be suitably used.

[0074] In addition to the polyalkylene oxide (B), two or more other rigid polyols may be used in combination, and are not particularly limited. For example, a combination of a polyol containing a sugar residue having 6 or more carbon atoms and a polyol having an aromatic amine residue may be used. The polyalkylene oxide (B) preferably has a water content of 2000 ppm or less, but since dehydration procedures and the like can be complicated, the water content can be selected depending on the intended use. <Other polyols and monools> The urethane prepolymer (E) and the NCO-terminated urethane prepolymer (D) that is preferably used are not particularly limited, but in addition to the polyalkylene oxides (A), polyalkylene oxides (B), and polyisocyanates (C) exemplified above, other polyols and monools (AC) may be used to improve the curability and coatability of the urethane prepolymer (E), improve the desired properties of the resulting urethane cured product, and adjust the ratio of NCO groups in the polyisocyanate (C) to the total amount of active hydrogen groups in the polyol.

[0075] As other polyols and monoalcohols (AC), those that do not impair the transparency and various physical properties of the prepolymer can be appropriately selected and are not particularly limited. For example, commercially available polyols such as polycarbonate polyol, polytetramethylene glycol, polyolefin polyol, acrylic polyol, polyester polyol, Mannich polyol, sucrose polyol, aliphatic diamine polyol, polyethylene glycol, polycaprolactone polyol, fluorinated polyol, silicone-containing polyol, phosphorus-based polyol, etc., monoalcohols such as polyoxyalkylene glycol monoalkyl ether, polyoxyalkylene glycol monoalkenyl ether, polyoxyalkylene glycol monophenyl ether, silicone-containing monoalcohol, and low-molecular-weight organic compounds such as cyclohexanedimethanol, tetraethylene glycol, tripropylene glycol, tripropylene glycol monobutyl ether, etc. can be mentioned.

[0076] Among them, in order to have particularly excellent coating properties when coating with a coating machine or the like, it is preferably one or more selected from the group consisting of polyoxyalkylene glycol monoalkyl ether, polyoxyalkylene glycol monoalkenyl ether, and polyoxyalkylene glycol monophenyl ether. Among them, it is easy to have excellent coating properties, maintain high transparency, and the resulting urethane has low contamination and low tackiness. Therefore, it is preferable to add polyoxyethylene glycol monomethyl ether with a molecular weight of 250 or more and 1300 or less.

[0077] It is preferable not to use a silicone component (monoalcohol, polyol, polyamine) having a reactive group or a fluorine component having a reactive group. When used, it is preferably used in the formation of the NCO-terminal urethane prepolymer (D) of the intermediate because it is easily incorporated into the molecular chain and the deterioration of contamination is likely to be reduced. <NCO-terminal urethane prepolymer (D)> The active hydrogen group-terminated urethane prepolymer (E) is not particularly limited, but it is preferable to use an NCO-terminated urethane prepolymer (D) comprising at least a polyalkylene oxide (A) and a polyisocyanate (C).

[0078] The NCO-terminated urethane prepolymer (D) is preferably mixed in such a ratio that the ratio of NCO groups in the polyisocyanate (C) to the total amount of active hydrogen groups in the polyol containing the polyalkylene oxide (A) (NCO / OH ratio) is 1.30 to 5.00. By mixing in such a ratio that the NCO / OH ratio is 1.30 to 5.00, the mixture has an appropriate viscosity and is easy to handle, and the transparency of the urethane prepolymer (D) and the resulting cured urethane product is likely to be improved.

[0079] Among these, the ratio of NCO groups in the polyisocyanate (C) to the total amount of active hydrogen groups in the polyol containing the polyalkylene oxide (A) (NCO / OH ratio) is preferably in the range of 1.60 to 4.40, more preferably 1.90 to 3.60, because the NCO-terminated urethane prepolymer (D) is mainly composed of a structure in which the polyalkylene oxide (A) and the polyisocyanate (C) are reacted in a molar ratio of 1:2, and is less likely to contain high molecular weight compounds resulting from chain reactions or free (unreacted) polyisocyanate (C), and the transparency of the urethane prepolymer (E) and its cured urethane product is likely to be significantly improved even when a polyalkylene oxide (B) having a polyfunctional aromatic amine residue is used.

[0080] Among these, when a polyisocyanate (C) having no difference in the reactivity of the NCO group, such as hexamethylene diisocyanate or a derivative thereof, is used as the polyisocyanate (C), it is most preferable to form the urethane prepolymer (D) with an NCO / OH ratio in the range of 2.20 to 3.60, and when isophorone diisocyanate is used as the polyisocyanate (C), it is most preferable to form the urethane prepolymer (D) with an NCO / OH ratio in the range of 2.00 to 3.10, because this tends to result in good transparency while suppressing gelation and high viscosity.

[0081] Furthermore, by using a small amount of polyalkylene oxide (B), the amount of free (unreacted) polyisocyanate (C) can be reduced, which makes it easier to suppress a chain reaction between the polyalkylene oxide (B) and the polyisocyanate (C) when forming the urethane prepolymer (E), thereby improving the coatability of the resulting urethane prepolymer (E) and making it easier for the cured urethane to exhibit high transparency, which is preferable.

[0082] Furthermore, in order to obtain particularly excellent coatability when applied using a coating machine or the like, it is preferable to form the urethane prepolymer (D) by adding one or more members selected from the group consisting of polyoxyalkylene glycol monoalkyl ethers, polyoxyalkylene glycol monoalkenyl ethers, and polyoxyalkylene glycol monophenyl ethers. Of these, it is preferable to add polyoxyethylene glycol monomethyl ether having a molecular weight of 250 or more and 1300 or less, as this tends to provide excellent coatability, maintain high transparency, and result in a urethane with low contamination and low tackiness.

[0083] It is preferable not to use silicone components (monols, polyols, polyamines) having reactive groups or fluorine components having reactive groups, but if used, they are preferably used in the formation of the intermediate NCO-terminated urethane prepolymer (D) because they are easily incorporated into the molecular chain and thus tend to reduce deterioration of contamination.

[0084] When polyalkylene oxide (B) and other polyols and monools (AC) are added in addition to polyalkylene oxide (A) to form urethane prepolymer (D), if the amount is too large, the amount of hydroxyl groups in the system increases, the NCO / OH ratio becomes too low, making it difficult to form an NCO-terminated prepolymer, or gelation and thickening may occur, resulting in poor moldability and poor transparency of the resulting prepolymer and cured urethane. Therefore, it is preferable to add polyalkylene oxide (B) and other polyols and monools (AC) in a total amount of 30 parts by weight or less per 100 parts by weight of polyalkylene oxide (A). Among these, an addition amount of 0.1 to 20 parts by weight or less is preferred, and an addition amount of 0.5 to 15 parts by weight is most preferred, because this provides good handleability, is likely to exhibit higher transparency, and is likely to exhibit higher strength.

[0085] In addition, a urethane catalyst, a solvent, a plasticizer, a leveling agent, and other additives may be added as needed to form the urethane prepolymer (D). Among these, the urethane catalyst containing a metal component is preferably contained in an amount of 0.001 to 0.2% by weight, more preferably 0.003 to 0.1% by weight, and most preferably 0.005 to 0.05% by weight, based on the total amount of the polyol containing the polyalkylene oxide (A) and the polyisocyanate (C), and the polyisocyanate, because this facilitates efficient formation of an NCO-terminated urethane prepolymer, minimizes side reactions, and facilitates the production of a more transparent urethane prepolymer and cured urethane product.

[0086] The urethanization catalyst containing a metal component is not particularly limited as long as it is a compound that contains a metal component and exhibits urethanization activity, but is preferably an organometallic compound containing one or more of the metals Fe, Sn, Zr, Ti, and Al. Among these, Sn catalysts, which are easily available and have low temperature dependency of catalytic activity, and one or more metal chelate catalysts such as Fe chelate catalysts, Zr chelate catalysts, Ti chelate catalysts, and Al chelate catalysts, whose reactivity is easy to adjust, are more preferred because they facilitate efficient formation of NCO-terminated urethane prepolymers, and it is most preferred to use an Fe chelate catalyst alone.

[0087] The Sn catalyst is not particularly limited, but examples thereof include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diversatate, and dibutyltin bis(acetylacetonate).

[0088] The Fe chelate catalyst is not particularly limited, but examples thereof include iron trisacetylacetonate, etc.; Zr chelate catalysts include zirconium tetraacetylacetonate and zirconium ethylacetoacetate, etc.; Ti chelate catalysts include titanium acetylacetonate and titanium ethylacetoacetate, etc.; and Al chelate catalysts include aluminum trisacetylacetonate, etc.

[0089] When the urethane prepolymer (D) is formed in advance, although there are no particular limitations, it is preferable to mix the organic solvent in an amount that results in a solids concentration in the range of 60 to 99% by weight, more preferably in the range of 70 to 97% by weight, and most preferably in the range of 85 to 95% by weight.

[0090] Examples of solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone, benzene, dioxane, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, glycol ether solvents, etc. Among these, glycol ether solvents, ethyl acetate, toluene, methyl ethyl ketone, or mixed solvents thereof are preferred because they are easy to handle, such as in terms of solubility and the boiling point of the organic solvent, and also because the resulting urethane cured product tends to exhibit higher transparency.

[0091] Among these, glycol ether solvents having an sp value of 8.0 or more are preferred because they remain in the system during drying and curing for a longer period of time, maintaining compatibility, and stably suppressing cure shrinkage that tends to occur during reaction curing, making it easier to form urethane with good moldability and a wrinkle-free, good appearance. Examples of glycol ether solvents include diethylene glycol diethyl ether (sp value 8.2, boiling point 189°C), triethylene glycol dimethyl ether (sp value 8.4, boiling point 216°C), diethylene glycol ethyl methyl ether (sp value 8.1, boiling point 176°C), diethylene glycol dimethyl ether (sp value 8.1, boiling point 162°C), tetraethylene glycol dimethyl ether (sp value 8.5, boiling point 275°C), and propanediol. Examples include pyrene glycol monomethyl ether acetate (sp value 8.7, boiling point 146 ° C), ethylene glycol monomethyl ether acetate (sp value 9.0, boiling point 145 ° C), ethylene glycol monobutyl ether acetate (sp value 8.9, boiling point 188 ° C), methoxybutyl acetate (sp value 8.7, boiling point 171 ° C), triacetin (sp value 10.2, boiling point 260 ° C), and the like. Among these, diethylene glycol diethyl ether (sp value 8.2, boiling point 189 ° C), triethylene glycol dimethyl ether (sp value 8.4, boiling point 216 ° C), and ethylene glycol monobutyl ether acetate (sp value 8.9, boiling point 188 ° C) are most preferred. Furthermore, the use of ethyl acetate, toluene, and methyl ethyl ketone in combination makes it easy to adjust the moldability.

[0092] The preparation of the urethane prepolymer (D) is not particularly limited as long as it is a method that can uniformly disperse and react the raw materials, and various conventionally known stirring methods can be used, such as a method of stirring using a stirrer, such as a general-purpose stirrer, a planetary mix ...

[0093] The molecular weight of the NCO-terminated urethane prepolymer (D) is not particularly limited, but in order to facilitate better handling, the weight-average molecular weight measured by gel permeation chromatography is preferably in the range of 2,500 or more and 500,000 or less, more preferably in the range of 5,000 or more and 200,000 or less, and more preferably in the range of 10,000 or more and 100,000 or less. <Method for producing urethane prepolymer (E)> The active hydrogen group-terminated urethane prepolymer (E), which is one embodiment of the present invention, is not particularly limited, but is preferably a reaction product of an NCO-terminated urethane prepolymer (D) and a polyalkylene oxide (B), and the urethane prepolymer (D) preferably comprises at least a polyalkylene oxide (A) and a polyisocyanate (C).

[0094] Although the method for producing the urethane prepolymer (E) is not particularly limited, it is preferable to produce an active hydrogen group-terminated urethane prepolymer (E) by mixing the polyalkylene oxide (A) and the polyalkylene oxide (B) in a quantity ratio such that the molar ratio (NCO / OH molar ratio) of the total amount of NCO groups in the polyisocyanate (C) to the total amount of active hydrogen groups in the polyalkylene oxide (A) and the polyalkylene oxide (B) is 0.10 to 0.70. That is, it is preferable to mix the raw materials including the polyalkylene oxide (B) so that the molar ratio (total NCO / total OH molar ratio) of the total amount of polyisocyanate groups in all raw materials to the total amount of active hydrogen groups in all raw materials including the raw materials for the urethane prepolymer (D) is 0.10 to 0.70.

[0095] By mixing the raw materials in a quantity ratio that results in an NCO / OH ratio of 0.10 to 0.70, the hydroxyl groups become terminal and the urethane prepolymer (E) has a moderate viscosity and good coatability, and it is easy to stably form a urethane cured product with higher transparency.

[0096] Among these, it is preferable to mix them in an amount that results in a final NCO / OH ratio of 0.15 to 0.60, and more preferably in the range of 0.20 to 0.50, because this provides a moderate viscosity, reduces the amount of unreacted polyalkylene oxide (B) remaining in the urethane prepolymer (E), making the urethane prepolymer (E) and the cured urethane product more transparent, and makes it possible to introduce a large amount of polyalkylene oxide (B), making it easier to more significantly exhibit strength and low tackiness.

[0097] Among these, when a polyisocyanate (C) having no difference in the reactivity of the NCO group, such as hexamethylene diisocyanate or a derivative thereof, is used as the polyisocyanate (C), it is most preferable that the final NCO / OH ratio is in the range of 0.20 to 0.40, and when isophorone diisocyanate is used as the polyisocyanate (C), it is most preferable that the final NCO / OH ratio is in the range of 0.20 to 0.49, because this tends to achieve good transparency while suppressing gelation and high viscosity.

[0098] The weight ratio of polyalkylene oxide (A) to all raw material polyalkylene oxide (B) (polyalkylene oxide (A) / polyalkylene oxide (B)) is preferably in the range of 10 / 90 to 90 / 10, more preferably in the range of 25 / 75 to 80 / 20, which tends to result in higher strength while stably exhibiting transparency, and most preferably in the range of 40 / 60 to 75 / 25.

[0099] The average functionality of the polyol, which is a combination of polyalkylene oxide (A), polyalkylene oxide (B), other polyols, and monools (AC), is not particularly limited, but is preferably in the range of 2.5 to 4.5 functionality, more preferably in the range of 2.8 to 3.9 functionality, and most preferably in the range of 3.1 to 3.8 functionality, in order to easily achieve higher transparency and strength. The average functionality of the polyol refers to a value calculated from the mole fraction and content of each raw material.

[0100] When polyalkylene oxide (B) is used to form urethane prepolymer (D), the weight ratio of polyalkylene oxide (B) used to form active hydrogen group-terminated urethane prepolymer (E) to the amount of polyalkylene oxide (B) used to form NCO-terminated urethane prepolymer (D) (polyalkylene oxide (B) for forming (E) / polyalkylene oxide (B) for forming (D)) is preferably in the range of 70 / 30 to 99.9 / 0.1, more preferably in the range of 80 / 10 to 99 / 1, and most preferably in the range of 90 / 10 to 97 / 3.

[0101] When forming the urethane prepolymer (E), other additives such as polyols, monools, urethanization catalysts, solvents, plasticizers, leveling agents, reaction retarders, etc. may be added as needed. When forming the urethane prepolymer (D), the additives added may remain.

[0102] Other raw materials that are preferably included when forming the urethane prepolymer (E) are not particularly limited, but include the same raw materials and amounts as those of the other raw materials that are preferably included when forming the urethane prepolymer (D), and these can be suitably applied.

[0103] Among these, a urethane catalyst or a solvent may be added, and is preferred, because it is easy to suppress an increase in viscosity of the urethane prepolymer (E) over time, it has excellent storage stability, and it is easy to adjust the viscosity to an appropriate level while improving the handleability and curability.

[0104] When an organic solvent is used, the solids concentration of the urethane prepolymer (E) is not particularly limited, but is preferably contained in an amount ranging from 60 to 99% by weight, more preferably from 80 to 97% by weight, and most preferably from 85 to 95% by weight, to facilitate the development of good viscosity and good handleability. The urethane catalyst containing a metal component is preferably contained in the urethane prepolymer (E) in an amount ranging from 0.001 to 0.2% by weight, more preferably from 0.003 to 0.1% by weight, and most preferably from 0.005 to 0.05% by weight.

[0105] The preparation of the urethane prepolymer (E) is not particularly limited as long as the method can uniformly disperse and react the raw materials, and the same reaction conditions as those used in the preparation of the urethane prepolymer (D), such as the preferred stirring method, can be suitably employed.

[0106] When preparing the urethane prepolymer (E), a small amount of other polyol or monool (BC) may be added in addition to the urethane prepolymer (D) and the polyalkylene oxide (B), although this is not particularly limited, in order to adjust the ratio of NCO groups in the polyisocyanate (C) to the total amount of active hydrogen groups in the final polyol, or to adjust the composition to obtain the desired tensile strength, coatability, or solution viscosity.

[0107] When other polyols or monools (BC) are added in addition to polyalkylene oxide (B) to prepare urethane prepolymer (E), if the amount is too large, the amount of unreacted components remaining increases, which can deteriorate moldability and contamination resistance and can also deteriorate the transparency of the resulting prepolymer or cured urethane product. Therefore, it is preferable to add the other polyols or monools in a total amount of 15 parts by weight or less per 100 parts by weight of polyalkylene oxide (B). It is preferable that the molecular weight be less than 2000, because higher molecular weights tend to result in poor compatibility and further deterioration of transparency.

[0108] Other polyols and monools (BC) can be appropriately selected from those that do not impair the transparency and various physical properties of the prepolymer, and are not particularly limited. Examples include commercially available polyols such as polycarbonate polyol, polytetramethylene glycol, polyolefin polyol, acrylic polyol, polyester polyol, Mannich polyol, sucrose polyol, aliphatic diamine polyol, polyethylene glycol, polycaprolactone polyol, fluorinated polyol, silicone-containing polyol, and phosphorus-based polyol; monools such as polyoxyalkylene glycol monoalkyl ether, polyoxyalkylene glycol monoalkenyl ether, polyoxyalkylene glycol monophenyl ether, and silicone-containing monool; and low-molecular-weight organic compounds such as cyclohexanedimethanol, tetraethylene glycol, tripropylene glycol, and tripropylene glycol monomethyl ether.

[0109] Among these, when added, sucrose polyol or polytetramethylene glycol is preferred because it has relatively good compatibility, is likely to exhibit high transparency, and is likely to increase strength. In this case, it is preferred to add it in a range of 0.1 to 13 parts by weight or less, more preferably 0.5 to 10 parts by weight, because it is unlikely to increase viscosity and is excellent in handleability. Most preferably, sucrose polyol is added in a range of 1 to 10 parts by weight, because it is likely to exhibit higher strength.

[0110] Furthermore, it is preferable not to use silicone components (monols, polyols, polyamines) having reactive groups or fluorine components having reactive groups, as they tend to remain and cause contamination, but there are no particular limitations. <Urethane prepolymer (E) composition> The urethane prepolymer (E) is not particularly limited, but may be concentrated or the viscosity may be adjusted by adding a solvent as needed, and a chain extender, antistatic agent, plasticizer, reaction retarder, leveling agent, or other additives may be added and mixed to prepare a urethane prepolymer composition.

[0111] The chain extender is not particularly limited, and examples thereof include glycols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, pentaerythritol, and low-molecular-weight polyalkylene glycols having a molecular weight of 1,000 or less; and polyvalent amines such as ethylenediamine, N-aminoethylethanolamine, piperazine, isophoronediamine, and xylylenediamine. Among these, polyvalent amines are preferred because they form urethane urea and make it easy to obtain urethane with good physical properties.

[0112] The antistatic agent is not particularly limited, but examples thereof include alkali metal salts and ionic liquids, such as lithium salts such as lithium bis(trifluoromethanesulfonylimide), quaternary ammonium salts, imidazolium salts, phosphonium salts, and pyridinium salts.

[0113] The plasticizer is not particularly limited, but examples thereof include fatty acid esters, alicyclic esters, polyether esters, and the like, such as epoxidized fatty acid esters, myristate esters, and terminal ester-modified compounds of polyalkylene glycols.

[0114] The reaction retarder is not particularly limited, and various retarders can be used, such as additives that have the effect of suppressing the activity of the urethanization catalyst (acid retarders, chelating compounds, etc.), additives that prevent the molecular weight of the main component from increasing during the reaction (thickening inhibitors, etc.), and additives that reduce the reactivity of isocyanates or polyol prepolymers (acid retarders, stabilizers, etc.), and it is preferable to use a combination of such retarders.

[0115] Among them, it is preferable to use one or more of acid retarders, chelating compounds, thickening inhibitors, and stabilizers as the reaction retarder, more preferably two to four of acid retarders, chelating compounds, thickening inhibitors, and stabilizers in combination, and most preferably three to four of acid retarders, chelating compounds, and thickening inhibitors, each including one or more.Furthermore, the acid retarders, chelating compounds, and thickening inhibitors are not limited to one type each, and two or more types can be used in combination, which is preferable.

[0116] Among these, it is preferable to contain an acid retarder, because it makes it easier to suppress the catalytic activity derived from the amine structure of the polyalkylene oxide (B), extends the usable life, makes it easier to suppress sudden gelation during drying, aging, and coating, and stably suppresses wrinkles, thereby improving moldability.Although not particularly limited, it is preferable to contain an acid having a pKa of 5.0 or less.

[0117] Examples of such acids with a pKa of 5.0 or less include hydrochloric acid, nitric acid, phosphoric acid, and phosphorus-based acid retarders such as acidic phosphate esters having 2 to 20 carbon atoms, such as ethyl acid phosphate and 2-ethylhexyl acid phosphate. Among these, phosphorus-based acid retarders are preferred because they tend to provide a good balance between reactivity and physical properties. When an acid retarder is used, its content is preferably in the range of 0.001 to 1 part by weight, more preferably 0.005 to 0.1 part by weight, per 100 parts by weight of prepolymer (E). Furthermore, when an acid retarder is used, the pH of the urethane prepolymer (E) is preferably in the range of 4 to 9, since this tends to increase curability and result in a liquid with good low corrosiveness. The pH of the urethane prepolymer (E) is measured using a pH meter after dispersing the urethane prepolymer (E) at a solids content of 7% by weight in a mixture of water and IPA at a weight ratio of 5:3.

[0118] The chelating compound preferably contains one or more of a keto-enol tautomer compound and a triazole derivative, because it is easy to adjust the catalytic activity and suppress thickening after mixing with a crosslinking agent, and also easy to improve moldability. It is more preferable to use one or more of each of a keto-enol tautomer compound and a triazole derivative (two or more in total) as the chelating compound.

[0119] The keto-enol tautomeric compound is not particularly limited, but is preferably one or more of ethyl acetoacetate or acetylacetone, which can more easily adjust the catalytic activity and improve moldability. When such a keto-enol tautomeric compound is contained, the molar ratio (keto-enol tautomeric compound / metal catalyst) relative to the urethanization catalyst containing a metal component is preferably 10 times or more, more preferably 50 to 5,000 times, in order to more easily improve moldability, and is preferably 0.01 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the urethane prepolymer (E).

[0120] The triazole derivative is not particularly limited, but is preferably a benzotriazole derivative having a phenolic hydroxyl group, as it has a high effect of suppressing cure shrinkage and is easy to form a urethane with good coating film appearance. More preferably, it is a benzotriazole derivative having a phenolic hydroxyl group, which is liquid at room temperature, has a molecular weight in the range of 300 to 700, and has an aryl group having a phenolic hydroxyl group directly bonded to the benzotriazole, as it tends to increase the transparency of the urethane. Examples of the above compound include, but are not limited to, 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN 571 manufactured by BASF), and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-benzenepropionic acid (C7-9 alkyl ester) (TINUVIN 99-2, TINUVIN 384-2 manufactured by BASF). When a triazole derivative is used, the content is preferably in the range of 0.1 to 3 parts by weight relative to 100 parts by weight of the urethane prepolymer (E), more preferably in the range of 0.2 to 2 parts by weight, and most preferably in the range of 0.3 to 1.5 parts by weight, since this makes it easier to form a coating film with higher transparency and better appearance.

[0121] When a keto-enol tautomeric compound and a triazole derivative are used in combination as chelate compounds, the weight ratio of the keto-enol tautomeric compound to the triazole derivative (keto-enol tautomeric compound / triazole derivative) is preferably 0.5 or more and 50 or less, and more preferably 2 or more and 20 or less, because this tends to suppress wrinkles in the resulting urethane and improve moldability.

[0122] Examples of thickening inhibitors include, but are not limited to, compounds that delay the increase in molecular weight or crosslinking degree that is related to thickening during the reaction, and compounds that suppress thickening even when the molecular weight increases due to the reaction.

[0123] For example, compounds that are reactive with an isocyanate crosslinking agent and whose reaction proceeds in parallel with or prior to the reaction between the main prepolymer (E) and the isocyanate crosslinking agent (F) thereby delaying the increase in molecular weight, and compounds that suppress or reduce the increase in viscosity of the system by improving affinity or changing structure due to the increase in molecular weight, etc., can be mentioned.

[0124] In particular, the thickening inhibitor is preferably a compound having a lower molecular weight than the prepolymer (E) and having an active hydrogen group that is reactive with the isocyanate crosslinking agent (F). By including such a thickening inhibitor, the reaction proceeds in parallel with or prior to the reaction between the main prepolymer (E) and the isocyanate crosslinking agent (F), making it easier to suppress crosslinking between the prepolymers and thereby suppress thickening.

[0125] Such thickening inhibitors are preferably compounds with a molecular weight of 1000 or less, which tend to have high active hydrogen group reactivity, because they react more readily than the base compound and inhibit crosslinking between prepolymers, thereby inhibiting thickening. In particular, if the molecular weight is too low, the reactivity of the active hydrogen groups may become too high, resulting in premature reaction and consumption, shortening the period during which thickening can be inhibited, reducing the reaction delay effect, or they may be partially or completely removed during the drying process, resulting in unstable physical properties. If the molecular weight is too high, thickening may occur during the reaction, and the reactivity of the active hydrogen groups may decrease, facilitating reaction between base compounds and reducing the thickening inhibition effect. Therefore, the molecular weight is preferably in the range of 60 to 700, more preferably in the range of 90 to 300, and most preferably in the range of 100 to 160. Furthermore, it is preferable for such thickening inhibitors to have 2 to 8 active hydrogen groups, such as hydroxyl groups, amino groups, or thiol groups, per molecule, because this reduces the degree of crosslinking during the reaction and the tensile strength. In particular, since too many active hydrogen groups tend to increase the degree of crosslinking during the reaction between the thickening inhibitor and the isocyanate crosslinking agent, and the thickening inhibitory effect tends to be reduced, it is preferable for the thickening inhibitor to have 2 to 4 active hydrogen groups such as hydroxyl groups, amino groups, or thiol groups per molecule, more preferably 2 to 3 hydroxyl groups per molecule, and most preferably a diol having two primary hydroxyl groups per molecule, as this has moderate reactivity and tends to significantly increase the thickening inhibitory effect.When a thickening inhibitor is used, its content is preferably in the range of 0.1 to 3 parts by weight per 100 parts by weight of the urethane prepolymer (E), more preferably 0.2 to 2 parts by weight per 100 parts by weight of the urethane prepolymer (E), and most preferably 0.3 to 1.5 parts by weight per 100 parts by weight of the urethane prepolymer (E), as this tends to form a urethane with higher transparency and better physical properties. Furthermore, when the thickening inhibitor has an active hydrogen group, the thickening inhibitor is likely to have a high thickening inhibitory effect while maintaining the urethane physical properties, so it is preferable to add the thickening inhibitor in an amount ranging from 3 to 30 mol % relative to 100 mol % of the active hydrogen groups in the urethane prepolymer (E), and more preferably in an amount ranging from 5 to 20 mol %.

[0126] The stabilizer is not particularly limited, but examples include compounds that suppress the reactivity of isocyanates and polyol prepolymers, such as phenolic antioxidants. Furthermore, in this embodiment, triazole derivatives are not included as stabilizers. Using such antioxidants in an increased amount of 1,000 ppm or more, preferably 3,000 ppm or more, and most preferably in the range of 5,000 ppm to 20,000 ppm, stabilizes the isocyanates and polyol prepolymers, reduces their reactivity, and inhibits thickening. Among these, BHT and hindered phenolic antioxidants with molecular weights of 1,000 or less (such as the Irganox series), which are readily available and have good compatibility with urethanes, are preferred. Room-temperature liquids such as Irganox 1135 and Irganox 1726 are preferred because they tend to increase the transparency of the resulting urethane. However, highly compatible structures such as BHT, Irganox 1076, and Irganox 1010 are also suitable because they are uniformly dispersed in the prepolymer and do not impair transparency during urethane formation.

[0127] When a stabilizer is used, its content is preferably in the range of 0.1 to 3 parts by weight per 100 parts by weight of the urethane prepolymer (E). In particular, the content of the stabilizer is more preferably in the range of 0.2 to 2.5 parts by weight, and most preferably in the range of 0.5 to 2 parts by weight, since this makes it easier to form a urethane with higher transparency and better physical properties.

[0128] The mixing process of these additives may be carried out at room temperature because weight loss due to volatilization is minimal, or may be carried out under heating to improve solubility and mixing. The mixing method is also not particularly limited. The concentration process, which is carried out as needed, may be carried out by bubbling with nitrogen or the like, heating, reducing pressure, or any other method that can adjust the concentration to the desired level.

[0129] The urethane prepolymer composition solution containing the urethane prepolymer (E) of one embodiment of the present invention, an organic solvent, and additives is preferably mixed in an amount ratio that results in a solids concentration in the range of 60 to 99 wt %, more preferably 70 to 97 wt %, and most preferably 85 to 95 wt %, because this improves handleability. Furthermore, the viscosity at 25°C is preferably in the range of 3 to 50 Pa·s, more preferably 5 to 30 Pa·s, because this improves handleability during mixing with a crosslinking agent and coating, and tends to produce a stably highly transparent cured urethane product.

[0130] The transparency of the urethane prepolymer composition solution is not particularly limited, but transparency is preferred, and the inclusion of the urethane prepolymer (E) of the present invention makes it easy to obtain such properties. In particular, the haze at a thickness of 1 cm is preferably 15% or less, and more preferably 5% or less. <Method of manufacturing urethane cured products and urethane coating films> The urethane prepolymer (E) and the urethane prepolymer composition using it can be reacted and cured (solidified) by various methods to produce a cured urethane product. The method for producing the cured urethane product is not particularly limited, but for example, the urethane prepolymer (E) or a composition containing the urethane prepolymer (E) can be subjected to a urethane reaction and a urea reaction at room temperature or a high temperature of 150°C or less in the presence of a urethane catalyst, a solvent, an antioxidant, a light stabilizer, a chain extender, a crosslinking agent, and other additives, as necessary, and then dried, to produce the cured urethane product.

[0131] Among these, it is preferable to contain an isocyanate compound (F) as a crosslinking agent, as this tends to more stably exhibit high curability and high transparency, and it is preferable to contain a urethane-forming composition containing a urethane prepolymer (E) and an isocyanate compound (F), or a urethane-forming composition solution containing the above-mentioned urethane prepolymer composition solution and an isocyanate compound (F).

[0132] The isocyanate compound (F) used as the crosslinking agent is not particularly limited, but examples thereof include polyisocyanates similar to the above-mentioned polyisocyanate (C), which can be suitably used. The isocyanate compound (F) and the isocyanate compound (C) may be the same or different.

[0133] The content of the isocyanate compound (F) in the urethane-forming composition and the urethane-forming composition solution is not particularly limited. However, in order to achieve better curability and higher transparency, it is preferable to use a urethane prepolymer (E) containing a total amount of hydroxyl groups derived from other active hydrogen compounds (M OH ) the amount of isocyanate groups derived from the isocyanate compound (F) relative to NCO ) ratio (M NCO / M OH ) is preferably a molar ratio of 0.5 or more and less than 4.0, and more preferably a molar ratio of 0.7 or more and less than 2.5. The weight ratio of the urethane prepolymer (E) to the isocyanate compound (F) (weight of (E) / weight of (F)) is preferably in the range of 99 / 1 to 50 / 50, and more preferably in the range of 90 / 10 to 70 / 30, in order to easily achieve higher transparency, high curability, and high strength.

[0134] The viscosity of the urethane-forming composition or urethane-forming composition solution at 25°C is not particularly limited, but is typically from 0.001 Pa·s to 100 Pa·s, preferably from 0.2 Pa·s to 30 Pa·s, and even more preferably from 0.5 Pa·s to 10 Pa·s, since this provides significantly better coatability. Forming and curing a coating film is preferred, but is not particularly limited, since this provides significantly better coatability when applied using a coating machine or the like, allowing for the production of a urethane coating film of uniform thickness. Alternatively, a polyurethane sheet having the urethane coating film on a substrate can be formed by forming a coating film of the cured urethane product on a base substrate such as a PET film or a COP film using various methods, and then laminating or molding the resulting film with another substrate such as release PET or release paper, as needed.

[0135] Among these, a highly transparent, low-tack urethane coating film can be produced with high productivity by going through the steps of mixing the urethane prepolymer (E) obtained by the present invention with additives and an isocyanate crosslinking agent (F), applying the coating to a substrate at a thickness of 10 to 500 μm, and drying and curing at 70 to 160° C. for 30 seconds to 10 minutes. More preferably, the process includes a step of applying the coating to a thickness of 30 μm or more, and more preferably a step of applying the coating to a thickness in the range of 30 to 200 μm, since this has excellent curing properties and makes it easy to obtain a highly transparent coating film with a uniform thickness ranging from thin to thick.

[0136] Furthermore, since the urethane prepolymer (E) has aromatic amine residues near the molecular ends, it has significantly high initial curing properties, is resistant to flow even at high temperatures, and cures quickly with little thickness unevenness. Therefore, it is preferably dried and cured at 100 to 150°C for 1 to 8 minutes, and even more preferably at 120 to 145°C for 2 to 6 minutes, as this provides superior productivity for urethane coating films.

[0137] The uses of the cured urethane products and urethane coatings are not particularly limited and can be used in any application where ordinary polyurethanes are used, but they are particularly suitable for applications requiring mechanical properties and tackiness / adhesion characteristics, etc. Specific examples of suitable uses include sealing materials for construction and civil engineering, adhesives such as elastic adhesives for construction, gummed tapes and surface protection films, various pressure-sensitive adhesives, including optical pressure-sensitive adhesives, paints, elastomers, waterproof coating materials, flooring materials, plasticizers, flexible polyurethane foams, semi-rigid polyurethane foams, and rigid polyurethane foams.

[0138] Among these, polyurethanes are particularly preferred for use as sealants, paints, pressure sensitive adhesives and adhesives, as they are required to have strong mechanical properties and adhesive properties, and are also required to have good workability and coatability. [Example]

[0139] The present invention will be explained in more detail below with reference to examples, but the present invention should not be construed as being limited to the following examples as long as the gist of the invention is not exceeded. The raw materials and evaluation methods used in the following examples and comparative examples are as follows. (Raw Material 1) Polyalkylene oxide (A) or other polyol or monool (AC) used in the Examples and Comparative Examples The properties of the polyalkylene oxides or other polyols and monools (AC) used in the examples and comparative examples were determined by the following methods. <Degree of unsaturation of polyalkylene oxide> The degree of unsaturation of the polyalkylene oxide was measured by the NMR method described in Kobunshi Ronbunshu 1993, 50, 2, 121-126, with 800 scans. NMR measurements were carried out using deuterated chloroform as the heavy solvent and a JEOL 400 MHz NMR ECZS as the measuring device. <Hydroxyl value and number average molecular weight of polyalkylene oxide> The hydroxyl value of the polyalkylene oxide was measured in accordance with the method described in JIS-K1557-1. The number average molecular weight of the polyalkylene oxide was calculated from the hydroxyl value of the polyalkylene oxide and the number of hydroxyl groups in one molecule of the polyalkylene oxide. <Molecular weight distribution of polyalkylene oxide (Mw / Mn)> The molecular weight distribution (Mw / Mn) of the polyalkylene oxide was measured by gel permeation chromatography (GPC) according to the following procedure.

[0140] 10 mg of polyalkylene oxide and 10 ml of tetrahydrofuran (THF) were placed in a sample bottle, left to stand for one day to dissolve the polyalkylene oxide in the THF, and filtered through a PTFE cartridge filter (0.5 μm) to prepare a sample for GPC measurement.

[0141] The GPC measurements were performed using THF as the developing solvent at a column temperature of 40°C, and the molecular weight distribution (Mw / Mn) was analyzed using a calibration curve based on a cubic approximation curve of eight standard polystyrenes manufactured by Tosoh Corporation with known molecular weights. The measurement equipment used was a Tosoh HLC-8320GPC, and the analysis was performed using a Tosoh HLC-8320GPC-ECOSEC-WorkStation. <Viscosity of Polyalkylene Oxide> The viscosity of the polyalkylene oxide was determined according to the method described in JIS K-1557-5, using a cone-plate rotational viscometer at a temperature of 25°C and a shear rate of 0.1 (1 / s), using an Anton-Paar MCR-300 measuring device. (Raw Material 1-1) Polyalkylene Oxide (A) Used in Examples and Comparative Examples Polyalkylene oxide (A1) was obtained by using an imino group-containing phosphazenium salt (hereinafter referred to as IPZ catalyst) in combination with triisopropoxyaluminum, thoroughly dehydrating and removing the solvent, and then adding thoroughly dehydrated propylene oxide to a bifunctional polyoxypropylene glycol with a molecular weight of 400. (A1) is a polyoxypropylene glycol (diol) that has only propylene oxide groups as alkylene oxide groups and has two hydroxyl groups per molecule.

[0142] Polyalkylene oxide (A2) is prepared in the same manner as (A1), using an IPZ catalyst and triisopropoxyaluminum in combination to add propylene oxide groups as alkylene oxide groups, and then removing the propylene oxide remaining in the system, followed by block-wise addition of ethylene oxide; it is a diol containing a primary hydroxyl group and having a low degree of unsaturation.

[0143] Polyalkylene oxide (A4) is prepared by using a trifunctional polyoxypropylene triol with a molecular weight of 600 as an initiator, and using an IPZ catalyst and triisopropoxyaluminum in combination as in (A2). Propylene oxide groups are added as alkylene oxide groups, and after removing the propylene oxide remaining in the system, ethylene oxide is added in blocks. This polyalkylene oxide is a triol containing primary hydroxyl groups and having a low degree of unsaturation.

[0144] As the polyalkylene oxide (A3), Sannix PP-3000 manufactured by Sanyo Chemical Industries, Ltd., which is a polypropylene glycol synthesized by adding only propylene oxide in a conventional manner, was used.

[0145] The properties of (A1) to (A4) are shown in Table 1. (A1), (A2), and (A4) have an extremely low amount of unsaturated monool (extremely low degree of unsaturation) and a narrow molecular weight distribution, while (A3) is a polyalkylene oxide with a general degree of unsaturation and molecular weight distribution. The polyalkylene oxides (A1) to (A4) used in the examples were all heated and vacuum dehydrated before use. In addition, the polyalkylene oxides produced using the IPZ catalyst were used after removing the catalyst, including aluminum. (Raw Material 1-2) Other polyols and monools (AC) used in the examples and comparative examples The monool (AC1) is a bifunctional polyoxytetramethylene glycol having a molecular weight of 2100, and is a polyol having a molecular weight of 2000 or more and having no alkylene oxide residue.

[0146] [Table 1]

[0147] (Raw Material 2) Polyalkylene Oxide (B) (Raw Material 2-1) Polyalkylene oxides (B1), (B2), and (B3) used in the examples The polyalkylene oxide (B1) is a commercially available tolylenediamine-based polypropylene glycol, manufactured by Toho Chemical Industry Co., Ltd., called Toho Polyol AR-2589. It has a nominal functionality of 4.0, a hydroxyl value of 356 mg KOH / g, and a viscosity of 9,500 mPa·s at 25°C. The molecular weight calculated from its properties is 630, and the aromatic amine residue content is 19%.

[0148] The polyalkylene oxide (B2) used was Sannix HM-551, a commercially available tolylenediamine-based polypropylene glycol / polyethylene glycol copolymer manufactured by Sanyo Chemical Industries, Ltd., with a nominal functionality of 4.0, a hydroxyl value of 413 mg KOH / g, and a viscosity of 15,000 mPa·s at 25°C. The molecular weight calculated from this property is 540, and the aromatic amine residue content is 22%.

[0149] The polyalkylene oxide (B3) used was a commercially available tolylenediamine / glycol co-initiated polyalkylene oxide, JEFFOLAD-310 manufactured by Huntsman, with a nominal functionality of 3.2, a hydroxyl value of 310 mgKOH / g, and a viscosity of 2200 mPa·s at 25°C. Based on the properties, the initiator molar ratio was calculated to be aromatic amine / glycol = 6 / 4, the molecular weight was 580, and the aromatic amine residue content was 12%. (Raw Material 2-1) Active hydrogen compounds (BC1), (BC2), and (BC3) used in the examples and comparative examples As the active hydrogen compound (BC1), Sannix GP600 manufactured by Sanyo Chemical Industries, Ltd., which is a commercially available trifunctional polypropylene triol having a molecular weight of 600, was used. The active hydrogen compound (BC2) used was O-855W manufactured by Toho Chemical Industry Co., Ltd., which is a sucrose-based polyol having a nominal functionality of 8.0 and a molecular weight of 1190. The active hydrogen compound (BC3) used was 2,4-tolylenediamine, an aromatic amine with four functional groups.

[0150] Active hydrogen compound (BC1) is a polyalkylene oxide having the same molecular weight as polyalkylene oxide (B1) having aromatic amine residues but not having aromatic amine residues. Active hydrogen compound (BC2) is a polyalkylene oxide having no aromatic amine residues but containing sucrose residues with a high functionality and a rigid cyclic sugar structure. Active hydrogen compound (BC3) is a compound consisting only of aromatic amines and not having a polyalkylene oxide structure or hydroxyl groups. (Raw Material 3) Isocyanate Compounds (C) and (F) Used in Examples and Comparative Examples In the examples and comparative examples, the following three types of isocyanate compounds (C) and (F) were used.

[0151] Isocyanate compound (C1): isophorone diisocyanate (IPDI). (C1) is a diisocyanate having a primary NCO group and a secondary NCO group as isocyanate groups.

[0152] Isocyanate compound (C2): 1,6-hexamethylene diisocyanate (HDI). (C2) is a diisocyanate having only primary NCO groups as isocyanate groups.

[0153] Isocyanate compound (F1): Coronate HXLV manufactured by Tosoh Corporation, which is a 1,6-hexamethylene diisocyanate (HDI) modified isocyanate, and the average functionality of the isocyanate groups in (F1) is 3.2. (Raw material 4) Urethane catalyst In the examples and comparative examples, a urethane catalyst was added as an additive. The urethane catalyst used was trisacetylacetonatoiron (abbreviated as Fe(acac)3), manufactured by Nippon Chemical Industries, Ltd., called Nacem Iron. This catalyst was added as a masterbatch of a 5% solution to improve workability. The amounts added in the tables do not include the solvent. (Raw material 5) Solvent In the examples and comparative examples, methyl ethyl ketone (abbreviated as MEK) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. and triethylene glycol dimethyl ether (abbreviated as TEGDM) manufactured by Toho Chemical Industry Co., Ltd. were used as solvents. (Production examples of urethane prepolymer (D) and urethane prepolymer (E)) Polyalkylene oxide (A), which is the raw material for urethane prepolymer (D), and polyalkylene oxide (B) and monool (AC), which are added as needed, were placed in a four-necked recovery flask, and the mixture was subjected to vacuum dehydration at 100°C for at least 1 hour to remove water. The mixture was then cooled to below 50°C, and for systems using a solvent, the solvent, isocyanate, and catalyst masterbatch were added, followed by heating to the specified temperature. The reaction began when the specified temperature was reached. After 3 hours of reaction, FT-IR confirmed that NCO groups remained and that there was no change in the liquid properties or the amount of NCO groups, yielding an NCO-terminated urethane prepolymer (D).

[0154] After cooling to below 60°C, a predetermined amount of polyalkylene oxide (B) was added to the urethane prepolymer (D). After visually confirming uniform stirring and no significant heat generation, the mixture was heated to the predetermined temperature to initiate the reaction. After 3 hours of reaction, FT-IR confirmed that the NCO groups had disappeared and that no changes in the liquid properties were observed, yielding an active hydrogen-terminated urethane prepolymer (E). If necessary, the mixture was concentrated to adjust the viscosity. The internal temperature was cooled to 50° C. or below, various additives were mixed and uniformly dispersed as necessary, and the contents were passed through a SUS wire mesh to remove insoluble matter, thereby obtaining a urethane prepolymer (E) composition. (Evaluation items for urethane prepolymer) <Liquid transparency> The transparency of the urethane prepolymer was evaluated according to the following criteria.

[0155] ◎ (Pass): When the liquid is visually transparent (haze of the liquid is 5% or less) ○ (Pass): Slight turbidity is visible to the naked eye, but the haze of the liquid is 15% or less (almost transparent).

[0156] × (Fail): When obvious strong turbidity is visible to the naked eye or when the haze of the liquid is more than 15%. <Curability> 1.1 equivalents of the HDI isocyanurate crosslinker Coronate HXLV was added to the hydroxyl groups of the urethane prepolymer at the active hydrogen end, and the mixture was applied to a PET substrate at a thickness of 80 μm or less. The cured urethane was then dried at 130°C for 5 minutes and evaluated by touch using the following criteria.

[0157] ◎ (Pass): Tack has disappeared, and significantly higher strength and easy peelability can be expected.

[0158] ○ (Pass): When slight tackiness is observed, and significantly high strength and easy peelability can be expected.

[0159] × (Fail): When the tack is large and the hardening is insufficient, and significantly high strength and easy peelability cannot be expected.

[0160] Furthermore, a 20 cm x 20 cm release PET Purex A31 sheet was attached to the cured urethane product obtained in the above curing property evaluation, and the handleability of the cured urethane product was evaluated according to the following criteria. <Handling> ◎: When there is no lifting, peeling or cracking when bent within approximately 30°.

[0161] ○: When bent within approximately 30°, some lifting was observed, but there was no cracking or peeling.

[0162] △: When peeling or cracking occurs when bent within approximately 30°, it is judged to be prone to misalignment during winding or lamination, or brittle fracture.

[0163] Those that met both the transparency and curability criteria were judged to be acceptable, being urethane prepolymers with active hydrogen groups at the end that are highly transparent, have little tack, and are expected to have significantly high strength and easy releasability. Furthermore, those that met the criteria of ⊚ and ○ for the handleability of the cured urethane product were judged to have excellent handleability of the cured urethane product. <Example> Example 1 According to the composition ratios shown in Production Example 1 of urethane prepolymer (D) and urethane prepolymer (E) and Synthesis Example 1 in Table 2, 60 parts by weight of polyalkylene oxide (A1) was added and dehydrated, and then an isocyanate compound (C1) and 0.02 parts by weight of iron trisacetylacetonate as a urethanization catalyst were added to the mixture, and the amount of hydroxyl groups derived from (A1) (M OH ) and the amount of isocyanate groups derived from (C1) (M NCO ) is the molar ratio, and M of (C1) NCO / (A1) M OH The mixture was charged to a mixing ratio of MNCO / (A1) = 1.86, and reacted for 3 hours at a constant temperature of 70°C to obtain an NCO-terminated urethane prepolymer (D). After cooling, 40 parts by weight of polyalkylene oxide (B1) was added to the urethane prepolymer (D), and the reaction was completed under the same reaction conditions as for the production of the urethane prepolymer (D), yielding an active hydrogen-terminated urethane prepolymer (E1) in which the final isocyanate compound (C) had an MOH of MNCO / (A1) and (B1) of 0.15.

[0164] The active hydrogen-terminated urethane prepolymer (E1) is synthesized from the NCO-terminated urethane prepolymer (D), and then only aromatic amine polyol is added. Therefore, theoretically, 100% of the molecular ends having active hydrogen groups are aromatic amine polyol structures, and the aromatic amine polyol content in all polyols is higher than 85.1 mol%. Table 3 shows the results of Example 1. The urethane prepolymer (E1) was highly transparent with no gel-like matter or precipitates, had remarkably good initial curing properties, and was expected to have even greater strength. The cured urethane also had good wettability and flexibility, was easy to handle, and was highly transparent. Examples 2 to 13 In comparison with Example 1, these were produced by using various solvents according to the composition ratios shown in Synthesis Examples 2 to 13 in Table 2, and by changing the types and ratios of the charged amounts of polyalkylene oxides (A) and (B). As in Example 1, an NCO-terminated urethane prepolymer (D) was produced, and mixed with polyalkylene oxide (B) having an aromatic amine residue to complete the reaction, producing an active hydrogen-terminated urethane prepolymer (E). Therefore, theoretically, 100% of the molecular ends having active hydrogen groups are aromatic amine polyol structures, and both are higher than the aromatic amine polyol content ratio in all polyols.

[0165] The results of Examples 2 to 13 are shown in Table 3. In Examples 5 and 13, the content and content ratio of the polyol structure having a rigid aromatic amine residue were high, and the urethane prepolymer (E) was slightly cloudy and had somewhat low wettability, while in Example 8, the content and content ratio of the polyol structure having a rigid aromatic amine residue was low, and slight tackiness was observed, but all were highly transparent with no gel-like matter or precipitates, had significantly good initial curing properties, and were expected to have significantly higher strength, and the cured urethane products were all highly transparent.

[0166] [Table 2]

[0167] [Table 3]

[0168] (Examples 14 to 16) Following the synthesis of NCO-terminated urethane prepolymer (D) according to Synthesis Examples 14 to 16 in Table 4, a glycol-containing polyalkylene oxide (B3) was added as a polyol having an aromatic amine residue. The molar ratio of tetrafunctional aromatic amine to difunctional glycol was 6 / 4. The polyol having a tetrafunctional aromatic amine residue has a higher functionality, and it is presumed to have an amine structure with catalytic activity and equal or greater reactivity. Therefore, 60% or more of the molecular ends having active hydrogen groups are aromatic amine polyol structures, and both are higher than the aromatic amine polyol content in the total polyol. Table 5 shows the results of Examples 14 to 16. The urethane prepolymer (E) was highly transparent, free of gel-like matter or precipitates, exhibited remarkably good initial curing properties, and was expected to have significantly higher strength. The cured urethane also had good wettability, flexibility, and handling properties, and was highly transparent. (Examples 17 to 22) After synthesizing NCO-terminated urethane prepolymer (D) according to Synthesis Examples 17 to 22 listed in Table 4, a small amount of a polyol without aromatic amine residues was added to a polyol with aromatic amine residues. None of the polyols used in combination had an amine structure with catalytic activity, and although their molecular weights were equal to or greater than the original, they were presumed to have low reactivity. Most of the molecular ends with active hydrogen groups were aromatic amine polyol structures, and the aromatic amine polyol content in each of these structures was higher than the total polyol content. Table 5 shows the results of Examples 17 to 22. Urethane prepolymer (E) was highly transparent, free of gel-like matter or precipitates, had remarkably good initial curing properties, and was expected to have even higher strength. The cured urethane also had good wettability and flexibility, was easy to handle, and was highly transparent. Example 23 Urethane prepolymer (E) was produced according to Synthesis Example 23 in Table 4, using polyalkylene oxide (A3) with a typical degree of unsaturation and molecular weight distribution instead of polyalkylene oxide (A1) with a low degree of unsaturation. The results are shown in Table 5. Even though polyalkylene oxide (A3) with a typical degree of unsaturation and molecular weight distribution was used, urethane prepolymer (E) had many polyalkylene oxide structures with aromatic amine residues at the molecular terminals, resulting in a high transparency without gel-like substances or precipitates, high curability, and the expected strength of the urethane cured product. The urethane cured product also had good wettability and flexibility, excellent handleability, and high transparency. Example 24 According to Synthesis Example 24 listed in Table 4, in addition to the polyalkyne oxide (B) having a rigid aromatic amine residue, a small amount of polyalkylene oxide (BC1) having a high functionality and a rigid cyclic sucrose structure was used in addition to the polyalkyne oxide (B) having a rigid aromatic amine residue, thereby obtaining a urethane prepolymer (E) that maintains high transparency while exhibiting higher curability and is expected to produce a urethane cured product with even higher strength. Example 25 According to Synthesis Example 25 in Table 4, urethane prepolymer (E25) was synthesized by synthesizing NCO-terminated urethane prepolymer (D) using polyalkyleoxide (A2) having ethylene oxide residues at the molecular terminals and a high proportion of primary hydroxyl groups, and then adding only polyalkyleoxide (B1) having only propylene oxide residues and aromatic amine residues with almost no primary hydroxyl groups.

[0169] Since the urethane prepolymer (E25) has almost no primary hydroxyl groups derived from the polyalkylene oxide (A2), it was shown that the polyalkylene oxide (B1) having aromatic amine residues is concentrated at the molecular terminals, and that the content of aromatic amine polyol is higher than the total content of the polyol. Table 5 shows the results of Example 25. The urethane prepolymer (E25) was highly transparent with no gel-like matter or precipitates, had significantly good initial curing properties, and was expected to have significantly higher strength. The cured urethane also had good wettability and flexibility, was easy to handle, and was highly transparent.

[0170] The urethane prepolymers (E) obtained in this example were all highly transparent, regardless of reaction conditions such as the amount of solvent, with almost no gel-like material, adhesion to the flask wall, or sedimentation. All had viscosities in the range of 1 to 100 Pa s and exhibited good fluidity. Furthermore, in a curing evaluation, the cured urethane products obtained all had no shrinkage, were highly transparent to the naked eye, and had a haze of 5% or less.

[0171] From the above, it was shown that localization and uneven distribution of aromatic amine polyol around the molecular terminals results in high transparency and significantly better initial curing properties for the urethane prepolymer (E), and that the cured urethane product can be expected to have high transparency, good appearance, and significantly higher strength.

[0172] [Table 4]

[0173] [Table 5]

[0174] <Comparative Example> (Comparative Example 1) This urethane prepolymer (EC1) was synthesized by a conventional method according to the composition ratio shown in Synthesis Example 26 in Table 6. It does not have a polyalkylene oxide structure with aromatic amine residues unevenly distributed at the molecular terminals. Although a polyalkylene oxide (B2) with ethylene oxide residues was used to form the urethane prepolymer (EC1), almost no primary hydroxyl groups were observed, and most of the urethane prepolymer had secondary hydroxyl groups. This indicates that most of the molecular terminals are polyol structures derived from the polyalkylene oxide (A1) with no aromatic amine residues. The content of polyalkylene oxide structures with aromatic amine residues at the molecular terminals was lower than the content of polyalkylene oxide structures with aromatic amine residues in the overall product. Table 7 shows the results of Comparative Example 1. The composition ratio and solid content of Synthesis Example 26 exhibited significant cloudiness due to poor compatibility. The urethane prepolymer was opaque and difficult to use due to the active hydrogen group-terminated urethane prepolymer, and it was difficult to consistently produce highly transparent cured urethane products from it. (Comparative Example 2) According to the composition ratios shown in Synthesis Example 27 in Table 6, an NCO-terminated urethane prepolymer (DC2) was synthesized, and then only an active hydrogen compound (BC1) with the same molecular weight but no aromatic amine residues was added to the end to obtain a urethane prepolymer (EC2) with no aromatic amine residues. Table 7 shows the results of Comparative Example 2. Because it did not contain rigid aromatic amine residues, it had poor curability and was difficult to use, and the strength of the resulting cured urethane was not as expected. (Comparative Example 3) According to the composition ratios shown in Synthesis Example 28 in Table 6, an NCO-terminated urethane prepolymer (DC3) was synthesized, and then only an active hydrogen compound (BC2) having a rigid cyclic sucrose residue without aromatic amine residues was added to the end to obtain a urethane prepolymer (EC3) without aromatic amine residues. Table 7 shows the results of Comparative Example 3. Because it had many rigid sucrose residues without aromatic amine residues, it had poor transparency, making it difficult to use, and the transparency of the resulting cured urethane was not as expected. Comparative Example 4 According to the composition ratios shown in Synthesis Example 29 in Table 6, an NCO-terminated urethane prepolymer (DC4) was synthesized using polytetramethylene glycol that had no alkylene oxide residues containing 3 or more carbon atoms, and then an active hydrogen compound (BC3), which was an aromatic amine that had no alkylene oxide residues containing 3 or more carbon atoms, was added to the end to obtain a urethane prepolymer (EC4) that had no alkylene oxide residues containing 3 or more carbon atoms and had an aromatic amine residue at the molecular terminal and had no polyalkylene oxide structure. Table 7 shows the results of Comparative Example 4. Because it did not contain alkylene oxide residues containing 3 or more carbon atoms and the aromatic amine had no alkylene oxide residues, it was poorly compatible, opaque, and difficult to use, and the resulting cured urethane product did not have the transparency expected. (Comparative Example 5) According to the composition ratios shown in Synthesis Example 30 in Table 6, an NCO-terminated urethane prepolymer (DC5) was synthesized, and then an active hydrogen compound (BC3), which is an aromatic amine having no alkylene oxide residue and 3 or more carbon atoms, was added to the end to obtain a urethane prepolymer (EC5) having an aromatic amine residue at the molecular end but no polyalkylene oxide structure. Table 7 shows the results of Comparative Example 5. Because it did not have a polyalkylene oxide structure at the molecular end, it was opaque and difficult to use due to poor compatibility, and the resulting cured urethane product did not have the transparency expected. (Comparative Example 6) According to the composition ratios shown in Synthesis Example 31 in Table 6, an NCO-terminated urethane prepolymer (DC6) having a polyalkylene oxide structure with aromatic amine residues was synthesized, and then only an active hydrogen compound (BC1) without aromatic amine residues was added to the end to obtain a urethane prepolymer (EC6) having a polyalkylene oxide structure with aromatic amine residues only in the interior of the molecule and not at the molecular terminals. Table 7 shows the results of Comparative Example 6. Because it did not have a polyalkylene oxide structure with aromatic amine residues at the molecular terminals, it had poor curability and poor compatibility, making it opaque and difficult to use, and the resulting cured urethane product did not have the transparency expected. (Comparative Example 7) According to the composition ratios shown in Synthesis Example 32 in Table 6, an NCO-terminated urethane prepolymer (DC7) having a polyalkylene oxide structure with aromatic amine residues was synthesized, and then only an active hydrogen compound (BC2) without aromatic amine residues was added to the end to obtain a urethane prepolymer (EC7) having a polyalkylene oxide structure with aromatic amine residues only in the interior of the molecule, not at the molecular terminals. Table 7 shows the results of Comparative Example 7. Because it did not have a polyalkylene oxide structure with aromatic amine residues at the molecular terminals, it had significantly poor compatibility, was opaque, and difficult to use, and the resulting cured urethane product did not have the transparency expected. (Comparative Example 8) According to the composition ratios shown in Synthesis Example 33 in Table 6, an NCO-terminated urethane prepolymer (DC8) having a polyalkylene oxide structure with aromatic amine residues was synthesized, and then only an active hydrogen compound (BC3) without polyalkylene oxide residues was added to the end to obtain a urethane prepolymer (EC8) having a polyalkylene oxide structure with aromatic amine residues only in the interior of the molecule and not at the molecular terminals. Table 7 shows the results of Comparative Example 8. Because it did not have a polyalkylene oxide structure at the molecular terminals, it had significantly poor compatibility, was opaque, and difficult to use, and the resulting cured urethane product did not have the transparency expected. (Comparative Examples 9 to 11) According to the composition ratios shown in Synthesis Examples 34 to 36 in Table 6, an NCO-terminated urethane prepolymer (DC) having a polyalkylene oxide structure with aromatic amine residues was synthesized, followed by the addition of a small amount of a polyol having aromatic amine residues and an excess of a polyol (BC1) without aromatic amine residues, resulting in a polyol structure without aromatic amine residues at most of the molecular terminals. Table 7 shows the results of Comparative Examples 9 to 11. Even if the content of the polyol structure with aromatic amine residues was slightly changed, most of the molecular terminals were polyol structures without aromatic amine residues, resulting in insufficient curability and difficulty in use, and the strength of the resulting cured urethane was not as expected. (Comparative Example 12) According to the composition ratios shown in Synthesis Example 37 in Table 6, an NCO-terminated urethane prepolymer (DC12) having a polyalkylene oxide structure with aromatic amine residues was synthesized, followed by addition of a polyol containing a small amount of aromatic amine residues and an excess polyol (BC2) containing sucrose residues but no aromatic amine residues, resulting in a polyol structure containing sucrose residues at most of the molecular ends. Table 7 shows the results of Comparative Example 12. Because most of the molecular ends were rigid polyol structures containing sucrose residues and no aromatic amine residues, the compatibility was significantly poor, the polymer was opaque, and difficult to use, and the resulting cured urethane product did not have the transparency expected.

[0175] As shown above in the comparative examples, when the composition does not contain a polyol structure having aromatic amine residues localized or unevenly distributed around the molecular terminals, it is difficult to stably express transparency and curability due to the influence of the amount of solvent and reaction conditions, making it difficult to use and to stably form a highly transparent, high-strength cured urethane product.

[0176] [Table 6]

[0177] [Table 7]

[0178] <Example of manufacturing a cured urethane product> For 100 parts by weight of the solids content of the urethane prepolymer (E) of Examples 2, 12, 18, and 25, 5 parts by weight of acetylacetone and 600 ppm of acidic phosphate ester (JP508 manufactured by Johoku Chemical Industry Co., Ltd.) as reaction retarders, 0.8 parts by weight of the triazole stabilizer Tinuvin 99-2, 0.2 parts by weight of diethylene glycol, 10 parts by weight of hexadecyl 2-ethylhexanoate as a plasticizer, 1.5 parts by weight of 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide as an antistatic agent, and 0.05 parts by weight of F-571 manufactured by DIC as a leveling agent were mixed and dispersed, and 1.1 equivalents of Coronate HXLV, an isocyanate compound (F1), were added as a crosslinking agent, and the mixture was applied to a PET substrate to a thickness of 80 μm or less and dried at 130 °C for 5 minutes to produce a urethane coating film. The viscosity of the compositions containing urethane prepolymer (E) in each example was in the range of 1 to 100 Pa s, and the residual liquid of the composition after sheet preparation showed good fluidity even after 24 hours. The resulting cured urethane products had good wettability, high strength, and high transparency, making them suitable for use in sealants, paints, pressure-sensitive adhesives, adhesives, etc.

[0179] As shown above in the examples, the urethane prepolymer (E) of the present invention is a highly transparent urethane prepolymer that is free from gel-like substances and precipitates and has excellent curing properties. By using the urethane prepolymer (E), it is possible to stably form a highly transparent, strong, and easily peelable urethane coating film with little surface tack.

[0180] By utilizing this characteristic, it has been shown that polyurethanes obtained using the urethane prepolymer (E) can be suitably used for sealants, paints, pressure sensitive adhesives, adhesives, etc.

Claims

1. a polyalkylene oxide structure having an alkylene oxide residue having 3 or more carbon atoms, an aromatic amine residue, and a polyisocyanate residue, and having an aromatic amine residue locally located at a molecular terminal; The present invention provides an active hydrogen group-terminated urethane prepolymer (E) which is a reaction product of an NCO-terminated prepolymer (D) which is a reaction product of a polyalkylene oxide (A) and a polyisocyanate (C), and a polyalkylene oxide (B) which has an aromatic amine residue and two or more hydroxyl groups.

2. 2. The urethane prepolymer (E) according to claim 1, which contains 5 to 70% by weight of a polyol structure having an aromatic amine residue or a residue thereof.

3. The urethane prepolymer (E) according to claim 1 or claim 2, which contains, as an aromatic amine residue, one or more types of residues selected from the group consisting of 4,4'-diphenylmethanediamine residues, 2,4-tolylenediamine residues, and 2,6-tolylenediamine residues.

4. The urethane prepolymer (E) according to any one of claims 1 to 3, wherein the polyisocyanate residue comprises one or more residues selected from the group consisting of aliphatic isocyanate residues, alicyclic isocyanate residues, and modified residues thereof.

5. 5. The urethane prepolymer (E) according to claim 1, wherein the polyol structure having an aromatic amine residue at a molecular terminal contains a polyalkylene oxide residue, and the polyalkylene oxide residue contains one or more residues selected from the group consisting of polypropylene oxide residues, polypropylene-ethylene oxide residues, and polyethylene oxide residues.

6. A urethane prepolymer composition solution comprising the urethane prepolymer (E) according to any one of claims 1 to 5, an organic solvent, and an additive, The urethane prepolymer composition solution has a concentration of the urethane prepolymer (E) in the urethane prepolymer composition solution of 60% by weight or more and 99% by weight or less.

7. A urethane-forming composition comprising the urethane prepolymer (E) according to any one of claims 1 to 5 and an isocyanate compound (F).

8. A urethane-forming composition solution comprising the urethane prepolymer composition solution according to claim 6 and an isocyanate compound (F).

9. A cured urethane product comprising a reaction product of the urethane-forming composition according to claim 7 or the urethane-forming composition in the urethane-forming composition solution according to claim 8.

10. A polyurethane sheet comprising the cured urethane product according to claim 9.

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