Method for producing a urethane prepolymer

Abstract

To provide a method for stably producing an urethane prepolymer which is excellent in storage stability and handling property and curability, and has high transparency, and a method for producing an urethane coated film which has high transparency, has high strength and is reduced in surface tack.SOLUTION: There is provided a method for producing an urethane prepolymer (E) which includes the following step (X) and step (Y). Step (X): a step of mixing polyol containing a polyalkylene oxide (A) having a number average molecular weight of 2,000 or more with polyisocyanate (C) in a quantitative ratio such that a ratio (NCO / OH ratio) of an NCO group of the polyisocyanate (C) to the total amount of an active hydrogen group of the polyol is 1.30 to 5.00, and producing an urethane polymer (D) terminated with the NCO group. Step (Y): a step of mixing polyol containing a polyalkylene oxide (B) having an aromatic amine residue and a number average molecular weight of less than 2,000 with the urethane prepolymer (D) produced by the step (X) in the step (X) and the step (Y) in a quantitative ratio such that a total amount (NCO / OH ratio) of the NCO group of the polyisocyanate (C) to the total amount of the active hydrogen group of the polyol mixed in the step (X) and the step (Y) is 0.10 to 0.70, and producing the urethane prepolymer (E) terminated with an active hydrogen group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for producing a urethane prepolymer.

Background Art

[0002] A polyalkylene oxide containing a large amount of a by-product monool having an unsaturated group at one end (hereinafter referred to as an unsaturated monool) is used as a raw material for polyurethane. However, when attempting to obtain polyurethane using this polyalkylene oxide, a problem occurs in that the curing (solidification) accompanying the reaction with the isocyanate compound requires time and the productivity is impaired.

[0003] Furthermore, the polyurethane obtained from a polyalkylene oxide containing a large amount of such an unsaturated monool is difficult to have a high molecular weight, has a small elongation at break, and a small tensile break strength. On the other hand, even with a polyalkylene oxide containing a large amount of an unsaturated monool, a high molecular weight polyurethane can be obtained by reacting it with an isocyanate compound having a large average functionality of isocyanate groups. However, in this case, the polyurethane does not have a high molecular weight in a linear form but becomes a cross-linked product having a dense cross-linked structure, so that the obtained polyurethane has a small elongation at break and a small tensile break strength.

[0004] On the other hand, since the unsaturated monool has a relatively low molecular weight, a composition containing a conventional polyalkylene oxide containing a large amount of the unsaturated monool has a low viscosity, and when coating with a coating machine or the like to obtain polyurethane from these compositions, there is an advantage that it is 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 prepolymer using the same, a polyurethane with good coatability and productivity and high tensile strength can be obtained.

[0006] However, these urethane-forming compositions described in Patent Document 1 and the urethane prepolymers using the same essentially contain a polyalkylene oxide with a small amount of low-molecular-weight unsaturated monool that easily acts as a compatibilizer, and use a rigid aromatic amine polyol having catalytic activity. Therefore, especially due to the deterioration of compatibility with a polyalkylene oxide with a small amount of unsaturated monool, the transparency is likely to deteriorate depending on reaction conditions such as the amount of solvent, and there may be problems such as the generation of particulate precipitates or the adhesion of gel-like substances, resulting in insufficient production stability and storage stability.

[0007] Therefore, there has been a demand for a method for producing a urethane prepolymer that is good in coatability and productivity, contributes to the formation of a highly transparent polyurethane using a rigid aromatic amine polyol with high strength, and can stably produce a urethane prepolymer without precipitates or gel-like substances regardless of the presence or absence of a polyalkylene oxide with a small amount of unsaturated monool and reaction conditions such as stirring and the amount of solvent, and has excellent storage stability and handleability, as well as a method for producing a polyurethane that is stably highly transparent, has high strength, and has little surface tack.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Provided are a production method for stably producing a highly transparent urethane prepolymer excellent in storage stability, handleability, and curability, and a production method for a urethane coating film that is highly transparent, has high strength, and has little surface tack.

Means for Solving the Problems

[0010] Each aspect of the present invention is as shown in [1] to

[10] below. [1] A method for producing a urethane prepolymer (E) including at least the following steps (X) and (Y).

[0011] (X) step: A polyol containing a polyalkylene oxide (A) having a number average molecular weight of 2000 or more and a polyisocyanate (C) are mixed in an amount ratio such that the ratio (NCO / OH ratio) of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol is 1.30 to 5.00, and a urethane prepolymer (D) having an NCO group terminal is produced.

[0012] (Y) step: A polyol containing a polyalkylene oxide (B) having an aromatic amine residue and having a number average molecular weight of less than 2000 and the urethane prepolymer (D) produced in the (X) step are mixed in an amount ratio such that the ratio (NCO / OH ratio) of the total amount of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol mixed in the (X) step and the (Y) step is 0.10 to 0.70, and a urethane prepolymer (E) having an active hydrogen group terminal is produced. [2] The method for producing a urethane prepolymer (E) according to [1], wherein the polyalkylene oxide (B) in the (Y) step has an alkylene oxide residue having 2 to 10 carbon atoms and has two or more active hydrogen groups in one molecule. [3] The method for producing a urethane prepolymer (E) according to [1] or [2], wherein the polyalkylene oxide (B) in the (Y) step contains one or more residues selected from the group consisting of 4,4'-diphenylmethanediamine residues, 2,4-tolylenediamine residues, and 2,6-tolylenediamine residues. The method for producing the urethane prepolymer (E) according to any one of [1] to [3], wherein the polyisocyanate (C) in the [4] (X) step contains one or more selected from the group consisting of aliphatic isocyanates, alicyclic isocyanates, and modified products thereof. The method for producing the urethane prepolymer (E) according to any one of [1] to [4], wherein in the [5] (X) step, 0.001 to 0.2 parts by weight of a urethanization catalyst containing a metal component is brought into contact with 100 parts by weight of the total amount of the polyol and the polyisocyanate (C). The method for producing the urethane prepolymer (E) according to any one of [1] to [5], wherein the urethane prepolymer (E) has a viscosity of 1 to 100 Pa·s and a Haze of 15% or less at a thickness of 1 cm under the condition of 25°C. The method for producing the urethane prepolymer (E) according to any one of [1] to [6], wherein in the [7] (X) step, an organic solvent containing one or more selected from the group consisting of glycol ether solvents, ethyl acetate, toluene, and methyl ethyl ketone is mixed in a ratio such that the solid content concentration is in the range of 60 to 99% by weight.

Advantages of the Invention

[0013] According to the present invention, even when using a rigid aromatic amine polyol necessary for exhibiting high strength, there are no precipitates or gel-like substances stably regardless of the presence or absence of the use of a polyalkylene oxide having a small amount of unsaturated monool, reaction conditions, and the amount of solvent, and a method for producing a urethane prepolymer having good compatibility and transparency can be provided.

Embodiments for Carrying Out the Invention

[0014] Exemplary embodiments for carrying out the present invention will be described in detail below. The method for producing a urethane prepolymer according to one embodiment of the present invention is a method for producing a urethane prepolymer (E) including at least the following (X) step and (Y) step.

[0015] (X) Process: A polyol containing a polyalkylene oxide (A) with a number average molecular weight of 2000 or more and a polyisocyanate (C) are mixed in an amount ratio such that the ratio of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol (NCO / OH ratio) is 1.30 to 5.00 to produce an NCO group-terminated urethane prepolymer (D).

[0016] (Y) Process: A polyol containing a polyalkylene oxide (B) with an aromatic amine residue and a number average molecular weight of less than 2000 and the urethane prepolymer (D) produced in the (X) process are mixed in an amount ratio such that the ratio of the total amount of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol mixed in the (X) process and the (Y) process (NCO / OH ratio) is 0.10 to 0.70 to produce an active hydrogen group-terminated urethane prepolymer (E). <(X) Process> (X) process is a process of mixing a polyol containing a polyalkylene oxide (A) with a number average molecular weight of 2000 or more and a polyisocyanate (C), and mixing them in an amount ratio such that the ratio of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol containing the polyalkylene oxide (A) (NCO / OH ratio) is 1.30 to 5.00 to produce an NCO group-terminated urethane prepolymer (D).

[0017] Although not particularly limited, other polyols, monools, urethanization catalysts, solvents, plasticizers, other additives, etc. may be added for production as needed. Further, in order to stabilize the properties of the obtained urethane prepolymer, a dehydration process or a humidity conditioning process of the raw materials, etc. may be provided as a pre-process of the (X) process and set to an arbitrary moisture value. The moisture value is not particularly limited, but it is preferably 2000 ppm or less. (X) In the production of the urethane prepolymer (D) for the project, there is no particular limitation as long as it is a method capable of uniformly dispersing and reacting the raw materials, and various conventionally known stirring methods can be used. For example, a method of stirring using a stirrer can be mentioned. Examples of the stirrer include general-purpose stirrers, revolving and orbiting mixers, dispersers, dissolvers, kneaders, mixers, lab plast mills, planetary mixers, etc. The shape of the stirring blade is not particularly limited, but it is preferably any one of a turbine blade, paddle blade, Faudler blade, anchor blade, full zone blade, etc. Among them, since it has high versatility and stirring efficiency, it is more economically easy to prepare uniformly, and it is difficult to generate high molecular weight components of the urethane prepolymer regardless of reaction conditions such as the amount of solvent. Therefore, an anchor blade is preferred. The presence or absence of baffles is not particularly limited, but since it can be uniformly dispersed and gelation is easily suppressed, it is preferable to have one or more selected from baffle plates, rod-shaped objects, internal coils, etc. that act as baffles.

[0018] The reaction temperature is not particularly limited, but it is preferably in the range of 20 to 130 °C. Since the reaction proceeds efficiently, reaction control is easy, and it is more likely to become highly transparent, it is more preferably in the range of 40 to 90 °C, and most preferably in the range of 60 to 80 °C. Also, since heat removal is easy and reaction control is easy, the temperature can be gradually increased, or after reacting at a relatively low temperature of 20 to 60 °C for a certain period of time, the temperature can be increased to a predetermined temperature, or a catalyst can be added in the latter half of the reaction. In order to reduce the influence of moisture in the outside air, it is preferable to carry out the reaction under an inert gas such as nitrogen.

[0019] The reaction time varies depending on the amount of catalyst and reaction conditions, so it is not particularly limited. However, since cloudiness due to side reactions with outside air moisture, etc. is unlikely to occur and the end point of the reaction is easy to determine, it is preferably within 10 minutes to 24 hours, more preferably within 30 minutes to 12 hours, and most preferably within 1 hour to 6 hours. Among them, since the properties are likely to be stable, it is preferable to track the attenuation of the NCO group using FT-IR or titration method and react until the attenuation stops.

[0020] The addition method is not particularly limited. However, since it is easy to suppress clouding and gelation due to local reactions regardless of the reaction conditions, it is preferable to add and mix polyisocyanate (C) to the polyol containing polyalkylene oxide (A). The polyisocyanate (C) may be added in its entirety at once or added in portions for heat removal or the like. When using a catalyst, it is preferably added after the polyisocyanate (C) in order to uniformly disperse the polyisocyanate (C) before the reaction. However, it may also be added and mixed prior to the polyisocyanate (C) in order to uniformly disperse the catalyst. <Polyol containing polyalkylene oxide (A)> (X) The polyalkylene oxide (A) contained in the polyol used in the step is characterized by having a number average molecular weight of 2000 or more. When the number average molecular weight is less than 2000, even when using a rigid aromatic amine polyol, in both the production method of the present invention and any production method of conventional methods, it is difficult to precipitate regardless of the stirring conditions, reaction conditions, and amount of solvent, and the compatibility and transparency tend to be good. However, the resulting polyurethane becomes too hard and has poor tensile strength, making it difficult to use. The preferable number average molecular weight of the polyalkylene oxide (A) in the (X) step is 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.

[0021] The viscosity of the polyalkylene oxide (A) at 25°C is not particularly limited and is appropriately selected according to the application. Preferably, it is 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. When the viscosity of the polyalkylene oxide (A) at 25°C is 100 mPa·s or more and 200,000 mPa·s or less, it is preferable because it is easy to apply when applying with a coating machine or the like to obtain a polyurethane product. Here, the "viscosity" at 25°C is a value measured at a shear rate of 0.1 (1 / s) using a cone-plate rotational viscometer in accordance with Paragraph 6.2.3 of JIS K1557-5.

[0022] The polyalkylene oxide (A) preferably contains an alkylene oxide residue having 3 or more carbon atoms. It is not particularly limited as the alkylene oxide residue having 3 or more carbon atoms, and examples thereof include alkylene oxide residues having 3 to 20 carbon atoms. Specifically, propylene oxide residue, 1,2-butylene oxide residue, 2,3-butylene oxide residue, isobutylene oxide residue, butadiene monooxide residue, pentene oxide residue, styrene oxide residue, cyclohexene oxide residue, etc. can be mentioned. Among these alkylene oxide residues, the propylene oxide residue is preferable because the raw material for obtaining the polyalkylene oxide (A) is easily available and the industrial value of the obtained polyalkylene oxide (A) is high.

[0023] In addition, the polyalkylene oxide (A) may contain only a single alkylene oxide residue or two or more types of alkylene oxide residues as the alkylene oxide residue having 3 or more carbon atoms. When two or more types of alkylene oxide residues are contained, for example, it may be a chain of one type of alkylene oxide residue connected to a chain of other alkylene oxide residues, or a random connection of two or more types of alkylene oxide residues. Furthermore, the polyalkylene oxide (A) only needs to contain an alkylene oxide residue having 3 or more carbon atoms, and in addition to this, it may contain an ethylene oxide residue having 2 carbon atoms.

[0024] Further, it is preferable that the polyalkylene oxide (A) has two or more hydroxyl groups in one molecule. As long as the polyalkylene oxide (A) has two or more hydroxyl groups in one molecule, the number of hydroxyl groups is not particularly limited, but the number of hydroxyl groups in one molecule is preferably 6 or less, and more preferably 3 or less. When the number of hydroxyl groups in one 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 the tensile strength at break are further increased, which is preferable.

[0025] The primary ratio of the hydroxyl groups of the polyalkylene oxide (A) is not particularly limited, but is preferably in the range of 0 to 90%. When synthesizing with a cationic polymerization system such as trifluoroborane or tris(pentafluorophenyl)borane as a catalyst, even when using propylene oxide or the like other than ethylene oxide as the alkylene oxide, the primary ratio tends to be high. When using a basic catalyst such as potassium hydroxide or a metal-based catalyst such as a DMC catalyst, the primary ratio tends to be low, but it is not particularly limited including the terminal structure, and any of them can be preferably used.

[0026] Further, since the production of the urethane prepolymer becomes easy, the polyalkylene oxide (A) is preferably liquid at room temperature.

[0027] The degree of unsaturation of the polyalkylene oxide (A) is not particularly limited because it is easy to make prepolymers and urethane cured products highly transparent regardless of the use of polyalkylene oxides with few unsaturated monools. However, since an increase in the amount of polyfunctional polyols such as polyalkylene oxides (B) having aromatic amine residues or a large amount of polyols having a more rigid skeleton than polypropylene oxide even with bifunctionality is likely to be required, it 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.

[0028] The molecular weight distribution (Mw / Mn) of the polyalkylene oxide (A) is not particularly limited because it is easy to make prepolymers and urethane cured products highly transparent regardless of the use of polyalkylene oxides with a narrow molecular weight distribution. However, since the molecular weight distribution of the prepolymer is likely to be narrow and the handleability is more excellent, it is preferably 1.059 or less, more preferably 1.039 or less, and most preferably 1.004 to 1.029.

[0029] (X) In the process, in order to adjust the ratio of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol, in addition to the polyalkylene oxide (A), the polyalkylene oxide (B) described later, other polyols, and monools (AC) may be added. Among them, adding a small amount of the polyalkylene oxide (B) in the (X) process can reduce the free (unreacted) polyisocyanate (C), easily suppress the chain reaction between the polyalkylene oxide (B) and the polyisocyanate (C) in the (Y) process, improve the coatability of the resulting urethane prepolymer (E), and make it easy for the urethane cured product to exhibit high transparency, which is preferable.

[0030] In the (X) process, when adding polyalkylene oxide (B), other polyols, and monoalcohol (AC) in addition to polyalkylene oxide (A) to the polyol, if the amount is too large, the amount of hydroxyl groups in the system will increase and the NCO / OH ratio will become too low. When the NCO / OH ratio is less than 1.30, it becomes difficult to form an NCO-terminated prepolymer, or gelation and thickening may easily occur, resulting in deterioration of moldability and transparency of the obtained prepolymer and urethane cured product. Therefore, it is preferable to add the total amount of polyalkylene oxide (B), other polyols, and monoalcohol (AC) in the range of 30 parts by weight or less with respect to 100 parts by weight of polyalkylene oxide (A). Among them, in order to have good handleability, be more likely to exhibit higher transparency, and be more likely to exhibit higher strength, it is preferably added in the range of 0.1 to 20 parts by weight or less, and most preferably added in the range of 0.5 to 15 parts by weight.

[0031] As other polyols and monoalcohol (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, etc., and low-molecular-weight organic compounds such as cyclohexanedimethanol, tetraethylene glycol, tripropylene glycol, tripropylene glycol monobutyl ether, etc. can be mentioned.

[0032] Among them, in order to have particularly excellent coating properties when coating with a coating machine or the like, it is preferably at least one selected from the group consisting of polyoxyalkylene glycol monoalkyl ethers, polyoxyalkylene glycol monoalkenyl ethers, and polyoxyalkylene glycol monophenyl ethers. 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 having a number average molecular weight of 250 or more and 1300 or less.

[0033] It is preferable not to use a silicone component having a reactive group (monool, polyol, polyamine), a fluorine component having a reactive group, etc. When using, it is preferably added in the (X) step because it is easily incorporated into the molecular chain and the deterioration of contamination is likely to be small.

[0034] <Polyisocyanate (C)> (X) The polyisocyanate (C) used in the project preferably has an average functionality of isocyanate groups of 2.0 or more, but is not particularly limited. 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, tetramethylxylylene diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, norbornane diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatemethyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, and modified isocyanates obtained by reacting these with polyalkylene oxides, and mixtures of two or more of these. Further, modified products containing urethane groups, carbodiimide groups, allophanate groups, urea groups, biuret groups, isocyanurate groups, amide groups, imide groups, uretonimine groups, uretdione groups or oxazolidone groups in these isocyanates, and condensates such as polymethylene polyphenylene polyisocyanate (polymeric MDI) are included. These isocyanates may be used alone or in combination of two or more.

[0035] Among these, in order to easily obtain a urethane-forming composition having excellent productivity, high transparency, and little coloring, it is preferable to use one or more selected from the group consisting of aliphatic isocyanates, alicyclic isocyanates, and modified products thereof. More preferably, it is 1,6-hexamethylene diisocyanate, isophorone diisocyanate, a prepolymer containing an aliphatic isocyanate, a prepolymer containing an alicyclic isocyanate, or a modified product 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 of these isocyanates.

[0036] Among them, since it has high reactivity, good productivity, little increase in the viscosity of the urethane prepolymer over time, and excellent storage stability, it is preferable to contain 1,6-hexamethylene diisocyanate or modified products thereof. In addition, it has a primary NCO group and a secondary NCO group with different reactivities, is easy to suppress the increase in molecular weight by a chain reaction, is easy to suppress the deterioration of coatability and the increase in high viscosity, is easy to set the NCO / OH ratio to 2.50 or less, and the transparency of the urethane prepolymer and the urethane cured product obtained using it is more likely to be significantly better. Therefore, it is also preferable to contain any one or more selected from 1,6-hexamethylene diisocyanate or modified products thereof and isophorone diisocyanate. <(Mixing ratio of raw materials in step (X))> In the step (X), the polyisocyanate (C) is mixed with the total amount of the active hydrogen groups of the polyol containing the polyalkylene oxide (A) at a ratio (NCO / OH ratio) of 1.30 to 5.00.

[0037] When the ratio of the NCO groups of the polyisocyanate (C) to the total amount of active hydrogen groups of the polyol containing the polyalkylene oxide (A) (NCO / OH ratio) is less than 1.30, if the NCO / OH ratio approaches 1.00 and the molecular weight increases, the coating property becomes poor and it is difficult to suppress gelation and high viscosity, or if the NCO / OH ratio is less than 1.00 and it becomes a hydroxyl-terminated group, it does not react with the polyalkylene oxide (B) in the (Y) step and the unreacted polyalkylene oxide (A) remains, deteriorating the compatibility, and a prepolymer and a urethane cured product with stable and high transparency cannot be obtained.

[0038] Also, when the NCO / OH ratio exceeds 5.00, the amount of free (unreacted) polyisocyanate (C) increases in the intermediate obtained in the (X) step. Therefore, it is likely to react chainwise with the polyalkylene oxide (B) added in the (Y) step to form and precipitate insoluble components and gel components, making it difficult to use stably, and the transparency of the obtained urethane cured product is also likely to deteriorate.

[0039] Therefore, in the (X) step, by mixing at a ratio such that the NCO / OH ratio is 1.30 to 5.00, it is possible to suppress the deterioration of the coating property and the deterioration of the transparency of the prepolymer and the obtained urethane cured product.

[0040] Among them, it is easy to mainly generate a structure in which the polyalkylene oxide (A) and the polyisocyanate (C) react in a molar ratio of 1:2, and it is difficult to contain a high molecular weight intermediate that reacts chainwise and free (unreacted) polyisocyanate (C). Even when using a polyalkylene oxide (B) having a low compatibility and a polyfunctional aromatic amine residue in the subsequent (Y) step, the transparency of the obtained prepolymer and urethane cured product is likely to be significantly improved. Therefore, in the (X) step, it is preferable to mix at a ratio such that the NCO / OH ratio is 1.60 to 4.40, and more preferably in the range of 1.90 to 3.60.

[0041] Among them, when using a polyisocyanate (C) with no difference in the reactivity of NCO groups such as hexamethylene diisocyanate or its derivatives as the polyisocyanate (C), when the NCO / OH ratio in the (X) step is in the range of 2.20 to 3.60, and when using isophorone diisocyanate as the polyisocyanate (C), it is most preferable that the NCO / OH ratio in the (X) step is in the range of 2.00 to 3.10 because gelation and high viscosity can be suppressed and transparency is likely to be good. <Other raw materials in the (X) step> (X) In the step, a urethanization catalyst, a solvent, a plasticizer, a leveling agent, and other additives may be added as necessary. Among them, since it is easy to efficiently form an NCO-terminated urethane prepolymer, has few side reactions, and it is easy to obtain a more highly transparent urethane prepolymer and a urethane cured product, it is preferable to produce the NCO-terminated urethane prepolymer (E) by contacting 0.001 to 0.2 parts by weight of a urethanization catalyst containing a metal component with respect to 100 parts by weight of the total amount of the polyol and the polyisocyanate. More preferably, the urethanization catalyst containing a metal component is 0.003 to 0.1 parts by weight, and most preferably, it is in the range of 0.005 to 0.05 parts by weight.

[0042] The urethanization catalyst containing a metal component is not particularly limited as long as it is a compound containing a metal component and showing urethanization activity, but it is preferably an organometallic compound containing one or more of the metals Fe, Sn, Zr, Ti, and Al. Among them, it is more preferable that it is one or more of an Sn catalyst that is easy to obtain and has low temperature dependence of catalyst activity, and metal chelate catalysts such as an Fe chelate catalyst, a Zr chelate catalyst, a Ti chelate catalyst, and an Al chelate catalyst that are easy to adjust reactivity, and most preferably, it is to use an Fe chelate catalyst alone.

[0043] The Sn catalyst is not particularly limited, and examples thereof include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dibutyrate, dibutyltin bis(acetylacetonate), and the like.

[0044] The Fe chelate catalyst is not particularly limited. For example, iron trisacetylacetonate, etc. The Zr chelate catalyst includes zirconium tetraacetylacetonate, zirconium ethylacetoacetate, etc. The Ti chelate catalyst includes titanium acetylacetonate, titanium ethylacetoacetate, etc. The Al chelate catalyst includes aluminum trisacetylacetonate, etc.

[0045] (X) In the process, although not particularly limited, it is preferable to mix an organic solvent in a quantitative ratio such that the solid content concentration is 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.

[0046] Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone, benzene, dioxane, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, glycol ether solvents, etc. From the viewpoints of solubility, boiling point of the organic solvent, etc., an organic solvent containing one or more selected from the group consisting of glycol ether solvents, ethyl acetate, toluene, and methyl ethyl ketone is preferable.

[0047] Among them, since the period during which it remains in the system and retains compatibility during drying and curing is long, it is easy to stably suppress the curing shrinkage that easily occurs during reaction curing and form a urethane with good moldability and a good appearance without wrinkles. Therefore, it is preferable to contain a glycol ether solvent having an sp value of 8.0 or more. For example, 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), propylene 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), etc. can be mentioned. Among them, it is most preferable to contain any one or more of 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). <(Y) step> (Y) step is a step of mixing a polyol containing a polyalkylene oxide (B) having an aromatic amine residue and a number average molecular weight of less than 2000 with a urethane prepolymer (D) produced in the (X) step in an amount ratio such that the total amount of NCO groups of the polyisocyanate (C) relative to the total amount of active hydrogen groups of the polyol mixed in the (X) step and the (Y) step (NCO / OH ratio) is 0.10 to 0.70, to produce a urethane prepolymer (E) having an active hydrogen group at the end.

[0048] Although not particularly limited, other polyols, monools, urethanization catalysts, solvents, plasticizers, leveling agents, and other additives may be added as necessary for production. Also, additives and the like added in the (X) step may remain as they are and be included. Further, in order to stabilize the properties such as the viscosity and transparency of the resulting urethane prepolymer, a dehydration step or a moisture conditioning step of raw materials such as polyalkylene oxide (B) used in the (Y) step may be provided, and it may be set to an arbitrary moisture value. Although it is preferable that the moisture value is 2000 ppm or less, since the operation becomes complicated, it can be selected according to the use and the like.

[0049] The preparation of the urethane prepolymer (E) in the (Y) step is not particularly limited as long as it is a method capable of uniformly dispersing and reacting the raw materials. The same preferable stirring method, stirrer, stirring blade, baffle shape, reaction temperature, reaction atmosphere such as nitrogen, and reaction conditions as those for the preparation of the urethane prepolymer (D) in the (X) step can be preferably adopted. The mixing method of the polyalkylene oxide (B) in the (Y) step is not particularly limited. However, since a rapid reaction is likely to occur due to the catalytic activity derived from the aromatic amine structure contained in the polyalkylene oxide (B), it is preferable to add the polyalkylene oxide (B) to the reaction vessel of the urethane prepolymer (D) produced in the (X) step. Among them, since it is difficult to generate a gel-like substance due to local reaction in the (Y) step regardless of reaction conditions such as the amount of solvent, and it is easy to obtain a urethane prepolymer (E) with high transparency and few gel-like substances stably, it is preferable to cool the urethane prepolymer (D) produced in the (X) step to 35°C or higher and 70°C or lower and add it, and more preferably to cool it to 55°C or lower and add it.

[0050] Also, since the viscosity of the polyalkylene oxide (B) is reduced, it is quickly added easily, and local reaction is easily suppressed. Therefore, the polyalkylene oxide (B) is preferably pre-heated to 30°C or higher, more preferably heated to 45°C or higher and added, and it is preferable to add it while stirring.

[0051] Further, although not particularly limited, since it is possible to suppress the formation of cloudiness or gel-like substances due to the reaction with moisture in the outside air over time, and it is easier to stably produce a highly transparent urethane prepolymer, it is preferable to proceed to step (Y) within 48 hours after the completion of step (X), and more preferably within 24 hours.

[0052] The reaction time varies depending on reaction conditions such as the amount of catalyst, reaction temperature, and stirring conditions, and is not particularly limited. However, since the viscosity increase of the resulting urethane prepolymer (E) over time is less likely to occur and it is likely to have excellent storage stability, it is preferable to confirm the disappearance of the NCO group using FT-IR or titration method and then continue the reaction for 30 minutes or more. In particular, when using a polyisocyanate (C) having a secondary NCO group, since the viscosity increase over time is likely to occur, it is preferable to confirm the disappearance of the NCO group and then continue the reaction for 1 hour or more.

[0053] Such a reaction time is 1 hour or more and 24 hours or less, preferably 1.5 hours or more and 12 hours or less, and most preferably 2 hours or more and 8 hours or less. <Polyol containing polyalkylene oxide (B)> The polyalkylene oxide (B) contained in the polyol used in step (Y) is a polyol having an aromatic amine residue. When the polyalkylene oxide (B) does not have an aromatic amine residue, the hardness and tensile strength of the resulting polyurethane are low and it is difficult to use. Among them, a polyol having an alkylene oxide residue with 2 to 10 carbon atoms and having two or more active hydrogen groups in one molecule is preferable because it exhibits good fluidity and is likely to have excellent moldability, and also has high hardness and tensile strength and is likely to have excellent urethane physical properties. It may be any of those in which one kind of alkylene oxide is chain-linked to an aromatic amine, those in which a plurality of alkylene oxides are chain-linked to an aromatic amine, or those linked randomly.

[0054] Among them, since alkylene oxide is industrially easily available and the synthesis is likely to be simple, those in which only propylene oxide is linked in series to an aromatic amine, those in which only ethylene oxide is linked in series to an aromatic amine, those in which propylene oxide and ethylene oxide are linked in series or randomly linked to an aromatic amine are preferred. More preferably, since it is difficult to crystallize from low temperature to high temperature and is particularly likely to have excellent fluidity, it preferably has a propylene oxide residue which is an alkylene oxide residue having 3 carbon atoms. Most preferably, 40% by weight or more of the alkylene oxide residues contained in the polyalkylene oxide (B) are propylene oxide residues.

[0055] The polyalkylene oxide (B) preferably has two or more hydroxyl groups in one molecule. More preferably, the number of hydroxyl groups in one molecule is 3 or more and less than 15, and most preferably 4 or more and less than 6.

[0056] 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 and less than 15, the crosslinked structure of the resulting urethane cured product is likely to be uniform and the tensile breaking strength is further increased, which is preferable.

[0057] The number average molecular weight of the polyalkylene oxide (B) used in the (Y) step is characterized by being less than 2000. When the number average molecular weight is 2000 or more, it is difficult to use because the content of the aromatic amine residue is likely to decrease and the strength decreases, and since the reactivity decreases and a large amount of unreacted polyalkylene oxide (B) tends to remain, it is difficult to stably exhibit high transparency.

[0058] Among them, it is not particularly limited and is appropriately selected according to the use. However, since the composition is less likely to be destabilized by volatilization during other steps or the curing reaction, etc., and the content of the aromatic amine residue is high and it is likely to stably exhibit high strength, it 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.

[0059] Incidentally, 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 functional group number and hydroxyl value can be used.

[0060] The structure of the aromatic amine residue of the polyalkylene oxide (B) is not particularly limited, but is preferably an aromatic amine residue having 1 to 20 aromatic rings in one molecule, and more preferably an aromatic amine residue having 1 to 3 aromatic rings. When the polyalkylene oxide (B) does not contain an aromatic amine residue, the tensile breaking strength is likely to be insufficient, and a polyol that is relatively rigid compared to 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 for improving the strength. However, these are difficult to use because they are likely to deteriorate the coating property and suppress cloudiness, and the resulting urethane cured product has high brittleness and tack.

[0061] The content of the aromatic amine residue in the polyalkylene oxide (B) is not particularly limited, but is preferably 7% by weight or more because high strength is easily exhibited. More preferably, in order to easily achieve both higher transparency and higher strength, it is in the range of 10% by weight or more and 50% by weight or less, and most preferably in the range of 13% by weight or more and 30% by weight or less. The content can be calculated by NMR method or analysis by Kolisch decomposition of the obtained urethane, etc., but it may also be calculated from the molecular weight of the polyalkylene oxide calculated from the hydroxyl value and the nominal initiator structure.

[0062] 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, polyphenylene polyamine residues, 1,5-naphthalenediamine residues, tolidine diamine residues, xylylene diamine residues, 1,3-phenylenediamine residues, 1,4-phenylenediamine residues, and mixed residues of two or more of these. Preferably, the residues 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 easily available as raw materials and are likely to exhibit good curability and tensile breaking strength.

[0063] 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, but may be synthesized by using in combination a low-viscosity active hydrogen compound containing no aromatic amine residue such as ethylenediamine, diethylenetriamine, triethanolamine, diethylene glycol, glycerin, or propylene glycol as an initiator, and may contain a component having the above residue.

[0064] For example, usually, the number of hydroxyl groups in a tolylenediamine-initiated polyol is 4, and the number of hydroxyl groups in an aniline-initiated polyol is 2, but the number of hydroxyl groups may decrease due to the combined use of an initiator containing no tolylenediamine residue or aniline residue or the remaining amino groups to which no alkylene oxide has been added.

[0065] Examples of the commercially available polyalkylene oxide (B) containing an aromatic amine residue include Huntsman's JEFFOLAD-310 (nominal functionality 3.2, hydroxyl value 310), JEFFOLAD-500 (nominal functionality 3.2, hydroxyl value 360), 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., AR-750 (nominal functionality 4.0, hydroxyl value 300) manufactured by Toho Chemical Industry Co., Ltd., etc., and they can be preferably used.

[0066] In addition to the polyalkylene oxide (B), two or more other rigid polyols may be combined and used, and there is no particular limitation. 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 can be mentioned.

[0067] In the (Y) step, in order to adjust the ratio of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the final polyol, or to adjust the composition for obtaining a desired tensile strength, coatability, and solution viscosity, a small amount of other polyols and monools may be added in addition to the polyalkylene oxide (B).

[0068] When other polyols and monools (BC) are added to the polyalkylene oxide (B) in the (Y) step, the remaining amount of unreacted components is reduced, and it is easier to exhibit better moldability and stain resistance, and the transparency of the obtained prepolymer and urethane cured product is also more likely to be better. Therefore, it is preferable to add the other polyols and monools in a total amount of 15 parts by weight or less with respect to 100 parts by weight of the polyalkylene oxide (B). Since the compatibility deteriorates and the transparency is more likely to deteriorate when the number average molecular weight is high, the number average molecular weight is preferably less than 2000.

[0069] As other polyols and monoalcohols (BC), 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, sorbitol polyol, aliphatic amine 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 monomethyl ether, etc. can be mentioned.

[0070] When adding other polyols and monoalcohols (BC) in addition to the polyalkylene oxide (B), since the compatibility is relatively good and it is easy to exhibit high transparency and the strength is likely to be high, it is preferably included sucrose polyol or polytetramethylene glycol. In that case, since it is difficult to increase the viscosity and it has excellent handleability, it is preferably added in the range of 0.1 to 20 parts by weight or less. Among them, in order to more easily exhibit higher strength, it is more preferably added sucrose polyol in the range of 0.5 to 15 parts by weight, and most preferably added in the range of 1 to 10 parts by weight.

[0071] Also, since silicone components (monoalcohols, polyols, polyamines) having reactive groups and fluorine components having reactive groups are likely to remain and cause contamination, it is preferably not used, but it is not particularly limited. <Raw material mixing ratio of step (Y)> In the (Y) step, the total amount of NCO groups of the polyisocyanate (C) is mixed with respect to the total amount of active hydrogen groups containing the polyalkylene oxide (A) and the polyalkylene oxide (B) at a ratio such that the NCO / OH ratio is 0.10 to 0.70, and a urethane prepolymer (E) having an active hydrogen group at the terminal is produced.

[0072] That is, after forming an NCO-terminated prepolymer with an NCO group ratio (NCO / OH ratio) of 1.30 to 5.00 for the polyol and the isocyanate (C) in the (X) step, each raw material containing the polyalkylene oxide (B) is mixed so that the total amount of polyisocyanate groups in all steps with respect to the total amount of active hydrogen groups of the raw materials used in all steps including the (X) step (total NCO / total OH ratio) is in the ratio of 0.10 to 0.70.

[0073] When the ratio of the NCO groups of the polyisocyanate (C) to the total amount of active hydrogen groups of the polyol in all steps (total NCO / total OH ratio) exceeds 0.70, the NCO / OH ratio approaches 1.00 and the molecular weight increases, resulting in poor coating properties and difficulty in suppressing gelation and high viscosity. Or, when the NCO / OH ratio exceeds 1.00 and becomes an NCO group terminal, the storage stability deteriorates and it is difficult to use.

[0074] Also, when the NCO / OH ratio is less than 0.10, the molecular weight of the resulting urethane prepolymer (E) is low, the viscosity decreases, the coating properties are poor, and a large amount of unreacted polyalkylene oxide (B) remains. Therefore, it is difficult to stably produce a highly transparent urethane prepolymer (E) or a highly transparent urethane cured product obtained using the same.

[0075] Therefore, in the (Y) step, by mixing the raw materials added in all steps at a ratio such that the NCO / OH ratio is 0.10 to 0.70, it is possible to suppress the deterioration of coating properties and the deterioration of the transparency of the prepolymer and the resulting urethane cured product.

[0076] Among them, a prepolymer and a urethane cured product having an appropriate viscosity and obtained with a reduced residual amount of unreacted polyalkylene oxide (B) can be produced with higher transparency, and a large amount of polyalkylene oxide (B) can be introduced to more significantly exhibit strength and low tackiness. Therefore, in the (Y) step, it is preferable to mix at a molar ratio such that the final NCO / OH ratio is in the range of 0.15 to 0.60, and more preferably in the range of 0.20 to 0.50.

[0077] Among them, when using a polyisocyanate (C) with no difference in the reactivity of the NCO group such as hexamethylene diisocyanate or its derivative as the polyisocyanate (C), the final NCO / OH ratio in the (Y) step is in the range of 0.20 to 0.40, and when using isophorone diisocyanate as the polyisocyanate (C), the final NCO / OH ratio in the (Y) step is in the range of 0.20 to 0.49. This is most preferable because it is easy to obtain good transparency while suppressing gelation and high viscosity.

[0078] The weight ratio of polyalkylene oxide (A) to polyalkylene oxide (B) used in the (X) step (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 because it is easier to achieve higher strength while stably exhibiting transparency, and most preferably in the range of 40 / 60 to 75 / 25.

[0079] When adding polyalkylene oxide (B) in the (X) step, the weight ratio of the amount of polyalkylene oxide (B) added in the (Y) step to the polyalkylene oxide (B) added in the (X) step ((polyalkylene oxide (B) added in the (Y) step) / (polyalkylene oxide (B) added in the (X) step)) 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. <Other raw materials in the (Y) step> In the (Y) step, other polyols, monools, urethanization catalysts, solvents, plasticizers, leveling agents, reaction retardants, other additives, etc. may be added as necessary for production. Also, additives, etc. added in the (X) step may remain as they are and be included.

[0080] Other raw materials preferably included in the (Y) step are not particularly limited, but examples include the same raw materials and usage amounts as the other raw materials preferably included in the (X) step, and they can be preferably applied.

[0081] Among them, although it may be added in advance in the (X) step and is not particularly limited, it is preferable to add a urethanization catalyst and a solvent in the (Y) step because it is easy to suppress the increase in viscosity of the urethane prepolymer (E) over time, has excellent storage stability, and is easy to improve handleability and curability while adjusting to an appropriate viscosity.

[0082] In the (Y) step, it is preferable to mix an organic solvent in a ratio such that the solid content concentration is in the range of 70 to 99% by weight, more preferably in the range of 80 to 97% by weight, and most preferably in the range of 85 to 95% by weight. For the urethanization catalyst containing a metal component, it is preferable to produce the urethane prepolymer (E) having active hydrogen group terminals by contacting 0.001 to 0.2 parts by weight with respect to 100 parts by weight of the urethane prepolymer (D). More preferably, the urethanization catalyst containing a metal component is 0.003 to 0.1 part by weight, and most preferably in the range of 0.005 to 0.05 part by weight. <Urethane prepolymer (E)> The urethane prepolymer (E) obtained by the present production method including at least the (X) step and the (Y) step is not particularly limited because it is difficult to generate gel-like substances, become highly viscous, or become cloudy. However, at 25°C, the viscosity is preferably 1 to 100 Pa·s, and the external appearance of the liquid is preferably transparent (Haze at 1 cm thickness is 15% or less). Such a urethane prepolymer (E) can be efficiently and easily produced.

[0083] Among them, the preferable properties of the urethane prepolymer (E) obtained by this production method are that it is easy to mix additives in the subsequent process, has excellent handleability such as mixing of a crosslinking agent and coating, and the urethane cured product is likely to be stably highly transparent. Therefore, at 25 °C, the viscosity is in the range of 3 to 50 Pa·s, and more preferably in the range of 5 to 30 Pa·s. When the viscosity is high, the viscosity may be reduced and adjusted by adding a solvent or an additive. When the viscosity is low, the viscosity may be increased and adjusted by concentration or the like.

[0084] The transparency of the urethane prepolymer (E) obtained by this production method is not particularly limited, but it is preferably transparent, and such properties are likely to be obtained by this production method. Among them, the Haze at a thickness of 1 cm is preferably 15% or less, and more preferably 5% or less.

[0085] The molecular weight of the urethane prepolymer (E) obtained by this production method is not particularly limited, but since the handleability is likely to be better, 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 preferably in the range of 10,000 or more and 100,000 or less. <Subsequent process> In the step (Y), after forming the urethane prepolymer (E), a subsequent process may be added as necessary. The subsequent process is not particularly limited, but the viscosity may be adjusted by concentration or solvent addition as necessary, and a chain extender, an antistatic agent, a plasticizer, a reaction retarder, a leveling agent, and other additives may be added and mixed. Further, it is preferable to pass through a filtration step.

[0086] The chain extender is not particularly limited. For example, glycols such as ethylene glycol, 1,4 - butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, pentaerythritol, and low - molecular - weight polyalkylene glycols with a molecular weight of 1000 or less; polyvalent amines such as ethylenediamine, N - aminoethylethanolamine, piperazine, isophoronediamine, and xylylenediamine can be mentioned. Among them, polyvalent amines are preferred because they form urethane - urea and it is easy to obtain urethanes with good physical properties.

[0087] The antistatic agent is not particularly limited, and examples include alkali metal salts and ionic liquids. For example, lithium salts such as lithium bis(trifluoromethanesulfonylimide), quaternary ammonium salts, imidazolium salts, phosphonium salts, pyridinium salts, etc. can be mentioned.

[0088] The plasticizer is not particularly limited, and examples include fatty acid esters, alicyclic esters, polyether esters, etc. For example, epoxidized fatty acid esters, myristic acid esters, terminal ester - modified compounds of polyalkylene glycols, etc. can be mentioned.

[0089] The reaction retarder is not particularly limited. For example, additives that have the effect of suppressing the activity of urethanization catalysts (acid retarders, chelate compounds, etc.), additives that make it difficult for the main agent molecular weight to increase during the reaction (thickening inhibitors, etc.), additives that reduce the reactivity of isocyanates and polyol prepolymers (acid retarders, stabilizers, etc.) and various other retarders can be used. It is preferable to use such retarders in combination.

[0090] Among them, it is preferable to use any one or two or more of an acid retarder, a chelate compound, a thickening inhibitor, and a stabilizer as the reaction retarder. More preferably, it is preferable to use any 2 to 4 of an acid retarder, a chelate compound, a thickening inhibitor, and a stabilizer in combination. Most preferably, it is to use all 3 to 4 kinds including at least one of an acid retarder, a chelate compound, and a thickening inhibitor in combination. In addition, each of the above acid retarder, chelate compound, and thickening inhibitor is not limited to one kind, and it is possible and preferable to use two or more kinds in combination.

[0091] Among them, it is preferable to contain an acid retarder because it becomes easier to suppress the catalytic activity derived from the amine structure of the polyalkylene oxide (B), the pot life is extended, and it becomes easier to suppress the rapid gelation during drying, aging, and coating, and it is easy to stably suppress wrinkles and improve the moldability. Although not particularly limited, it is preferable to contain an acid having a pKa of 5.0 or less.

[0092] Examples of such acids having a pKa of 5.0 or less include phosphoric acid-based acid retarders such as hydrochloric acid, nitric acid, phosphoric acid, ethyl acid phosphate, and 2-ethylhexyl acid phosphate, which are acidic phosphate esters having 2 to 20 carbon atoms. Among them, it is preferable to use a phosphoric acid-based acid retarder because the balance between reactivity and physical properties is likely to be good. The content when using an acid retarder is preferably in the range of 0.001 to 1 part by weight with respect to 100 parts by weight of the prepolymer (E), and more preferably in the range of 0.005 to 0.1 part by weight. In addition, the pH of the urethane prepolymer (E) when using an acid retarder is preferably an amount in the range of pH 4 to 9 because the curability is likely to be high and the liquid property with low corrosivity is likely to be good. The pH of the urethane prepolymer (E) refers to the value measured with a pH meter after dispersing in a liquid obtained by mixing water and IPA at a weight ratio of 5:3 with a solid content of 7% by mass.

[0093] As the chelate compound, it is preferable to contain one or more kinds of keto-enol tautomeric compounds and triazole derivatives because it is easy to adjust the catalytic activity to suppress thickening after mixing the crosslinking agent and the moldability is also likely to be good. More preferably, as the chelate compound, it is preferable to use one or more kinds (a total of two or more kinds) of each of the keto-enol tautomeric compound and the triazole derivative.

[0094] The keto-enol tautomeric compound is not particularly limited, but in order to more easily adjust the catalytic activity and improve the moldability, it is preferably one or more of ethyl acetoacetate or acetylacetone. When such a keto-enol tautomeric compound is contained, the content is preferably such that the molar ratio (keto-enol tautomeric compound / metal catalyst) to the urethanization catalyst containing a metal component is 10 times or more in order to more easily improve the moldability. More preferably, it is in the range of 50 to 5000 times, and preferably in the range of 0.01 to 20 parts by weight, more preferably in the range of 0.5 to 10 parts by weight, based on 100 parts by weight of the urethane prepolymer (E).

[0095] The triazole derivative is not particularly limited, but it is preferably a benzotriazole derivative having a phenolic hydroxyl group because it has a high effect of suppressing curing shrinkage and easily forms a urethane with a good coating film appearance. More preferably, since the transparency of the urethane tends to be high, it is a benzotriazole derivative having a phenolic hydroxyl group in which an aryl group containing a phenolic hydroxyl group is directly bonded to benzotriazole and is in the range of 300 to 700 in molecular weight and liquid at room temperature. The above compounds are not particularly limited, but examples include 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (Tinuvin 571 manufactured by BASF), 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-benzenepropionic acid alkyl ester having 7 to 9 carbon atoms) (Tinuvin 99-2, Tinuvin 384-2 manufactured by BASF), etc. When using a triazole derivative, the content is preferably in the range of 0.1 to 3 parts by weight with respect to 100 parts by weight of the urethane prepolymer (E). Among them, since it is easier to form a more transparent and good coating film appearance, it is 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.

[0096] As for the chelate compound, when a keto-enol tautomeric compound and a triazole derivative are used in combination, the mixing weight ratio is preferably such that the weight ratio of the keto-enol tautomeric compound to the triazole derivative (keto-enol tautomeric compound / triazole derivative) is 0.5 or more and 50 or less in order to suppress wrinkles of the resulting urethane and make the moldability good, and more preferably 2 or more and 20 or less.

[0097] The thickening inhibitor is not particularly limited, and examples include compounds that delay the increase in molecular weight and crosslinking degree related to thickening during the reaction and compounds that suppress thickening even when the molecular weight increases during the reaction.

[0098] For example, a compound that has reactivity with an isocyanate crosslinking agent and delays the increase in molecular weight by reacting concurrently with and / or preferentially to the reaction between the main agent prepolymer (E) and the isocyanate crosslinking agent (I), a compound that suppresses or reduces the degree of increase in the viscosity of the system due to an improvement in affinity or a structural change accompanying an increase in molecular weight, etc. may be mentioned.

[0099] Among them, the thickening inhibitor preferably has a lower molecular weight than the prepolymer (E) and is a compound having an active hydrogen group that has reactivity with the isocyanate crosslinking agent (I). By including such a thickening inhibitor, the reaction proceeds concurrently with and / or preferentially to the reaction between the main agent prepolymer (E) and the isocyanate crosslinking agent (I), suppressing the crosslinking between the prepolymers and making it easy to suppress thickening.

[0100] As such a thickening inhibitor, it is preferably a compound with a molecular weight of 1000 or less that easily undergoes reaction prior to the main agent and easily suppresses crosslinking between prepolymers to suppress thickening, because the reactivity of the active hydrogen group is likely to increase. Among them, if the molecular weight is too low, the reactivity of the active hydrogen group becomes too high, resulting in early reaction consumption and a short period during which thickening can be suppressed, leading to a low reaction delay effect, or partial or complete removal during the drying process and unstable physical properties. If the molecular weight is too high, thickening is likely to occur during the reaction, the reactivity of the active hydrogen group also decreases, and the reaction between the main agents becomes easier, resulting in a small thickening suppression 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. Also, as such a thickening inhibitor, it preferably has 2 to 8 active hydrogen groups such as hydroxyl groups, amino groups, and thiol groups in one molecule because the degree of crosslinking is not easily reduced and the tensile strength is not easily reduced during the reaction. Among them, if there are too many active hydrogen groups, the degree of crosslinking is likely to increase during the reaction between the thickening inhibitor and the isocyanate crosslinking agent, and the thickening suppression effect is likely to become small. Therefore, it preferably has 2 to 4 active hydrogen groups such as hydroxyl groups, amino groups, and thiol groups in one molecule, more preferably has 2 to 3 hydroxyl groups in one molecule, and most preferably is a diol having 2 primary hydroxyl groups in one molecule because it has appropriate reactivity and the thickening suppression effect is significantly likely to be high. The content when using the thickening inhibitor is preferably in the range of 0.1 to 3 parts by weight with respect to 100 parts by weight of the urethane prepolymer (E). Among them, because it is easier to form a urethane with higher transparency and good physical properties, it is more preferably in the range of 0.2 to 2 parts by weight with respect to 100 parts by weight of the urethane prepolymer (E), and most preferably in the range of 0.3 to 1.5 parts by weight. Also, when the thickening inhibitor has an active hydrogen group, it is preferable to add a thickening inhibitor in the range of 3 to 30 mol% with respect to 100 mol% of the active hydrogen groups of the urethane prepolymer (E) because the thickening suppression effect is likely to be high while maintaining the urethane physical properties, and it is more preferably added in the range of 5 to 20 mol%.

[0101] The stabilizer is not particularly limited, but examples include compounds that suppress the reactivity of isocyanates and polyol prepolymers, such as phenolic antioxidants. In this embodiment, triazole derivatives are not included as stabilizers. By increasing the amount of such an antioxidant to 1000 ppm or more, preferably 3000 ppm or more, and most preferably in the range of 5000 ppm to 20000 ppm, it is preferable because it stabilizes isocyanates and polyol prepolymers, reduces reactivity, and easily suppresses thickening. Among them, it is preferable to use BHT, which is easily available and has good compatibility with urethane, and hindered phenolic antioxidants (such as Irganox series) with a molecular weight of 1000 or less. Also, Irganox 1135, Irganox 1726, etc. are preferable because the transparency of the resulting urethane is likely to be high if it is liquid at room temperature. However, if it has a highly compatible structure such as BHT, Irganox 1076, or Irganox 1010, it can be preferably used because it can be uniformly dispersed in the prepolymer and is less likely to deteriorate the transparency during urethane formation.

[0102] When using a stabilizer, the content is preferably in the range of 0.1 to 3 parts by weight with respect to 100 parts by weight of the urethane prepolymer (E). Among them, in order to more easily form a urethane with higher transparency and good physical properties, 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. The mixing step of these additives may be carried out at room temperature because the weight increase or decrease due to volatilization is small, or it may be carried out by heating to enhance solubility and miscibility. Also, the mixing method is not particularly limited. In the concentration step, which is carried out as necessary, it is not particularly limited as long as it can be adjusted to a predetermined concentration, such as bubbling with nitrogen or heating and reducing pressure.

[0103] As a filtration step preferably included as a post - process, since it is easy to balance high productivity and storage stability and is likely to achieve high transparency, it is preferably a step of filtering and extracting through a mesh. By going through the step of filtering and extracting through a mesh, it becomes possible to remove foreign matters and extract simultaneously, and it can be manufactured with high productivity. Among them, since it is easy to stably exhibit high productivity and high transparency, it is preferably a step of filtering and extracting through a metal mesh with an aperture of 150 - 1000 μm, and more preferably it is carried out under a pressure of gauge pressure 0.01 - 3 MPa. Also, a step of packing into a predetermined container simultaneously with extraction may be added, which is preferable because of high productivity.

[0104] When performing the post - process, the composition containing the urethane prepolymer (E) obtained is likely to have excellent handleability. Therefore, it is preferably mixed in a ratio such that the solid content concentration is in the range of 60 - 99% by weight, more preferably in the range of 70 - 97% by weight, and most preferably in the range of 85 - 95% by weight. Also, due to excellent handleability such as mixing of cross - linking agents and coating, the urethane cured product is likely to be stably highly transparent. At 25°C, the viscosity is in the range of 3 - 50 Pa·s, and more preferably in the range of 5 - 30 Pa·s.

[0105] The transparency of the composition containing the urethane prepolymer (E) obtained by this manufacturing method is not particularly limited, but it is preferably transparent, and such properties are likely to be obtained by this manufacturing method. Among them, it is preferably that the Haze at a thickness of 1 cm is 15% or less, and more preferably 5% or less. <Method for manufacturing urethane cured product, urethane coating film> The urethane prepolymer (E) obtained by this production method can be reacted by various methods and cured (solidified) to produce a urethane cured product. The production method of the urethane cured product is not particularly limited. For example, the urethane prepolymer (E) or a composition containing the urethane prepolymer (E) can be subjected to a urethanization reaction, a urea formation reaction, and, if necessary, drying at room temperature or a high temperature of 150 °C or lower in the presence of a urethanization catalyst, a solvent, an antioxidant, a light stabilizer, a chain extender, a crosslinking agent, and other additives.

[0106] Here, since the coatability during coating with a coating machine or the like is remarkably excellent, a urethane coating film with a uniform thickness can be obtained. Although not particularly limited, it is preferable to form and cure the coating film. Further, the coating film of the urethane cured product can be formed on a base substrate such as a PET film or a COP film by various methods, and if necessary, a polyurethane sheet having the urethane coating film on the substrate can be formed by laminating or molding with another base material such as a release PET or release paper.

[0107] Among them, by passing through the steps of mixing the urethane prepolymer (E) obtained by this production method with an additive and an isocyanate crosslinking agent, coating the substrate with a thickness of 10 to 500 μm, and drying and curing at 70 to 160 °C for 30 seconds to 10 minutes, a highly transparent urethane coating film with little tack can be produced with high productivity, which is preferable. More preferably, since it has excellent curability and a highly transparent coating film with a uniform thickness can be easily obtained from a thin film to a high thickness, it preferably includes a step of coating with a thickness of 30 μm or more, and more preferably includes a step of coating in the range of 30 to 200 μm.

[0108] In addition, since the urethane prepolymer (E) obtained by this production method has an aromatic amine residue at the terminal, it has remarkably high initial curability, is difficult to flow even at a high temperature, has little thickness unevenness, and cures rapidly. Therefore, it is preferably dried and cured in the range of 100 to 150 °C for 1 to 8 minutes, and more preferably dried and cured in the range of 120 to 145 °C for 2 to 6 minutes because it is more likely to be excellent in the productivity of the urethane coating film.

[0109] The uses of the cured urethane and urethane coating film are not particularly limited and can be used in any application where ordinary polyurethane is used. However, they can be particularly preferably used in applications where mechanical properties, viscosity and adhesion properties are required. Specifically, examples of the uses include sealing materials for construction and civil engineering, adhesives such as elastic adhesives for construction, gum tapes, surface protection films, various adhesives typified by those for optical use, paints, elastomers, waterproof coating films, floor materials, plasticizers, flexible polyurethane foams, semi-rigid polyurethane foams, rigid polyurethane foams, etc., and they can be preferably used.

[0110] Among them, since the requirements for mechanical properties, viscosity and adhesion properties are strong for polyurethane, and workability and coating properties are required, it is particularly preferable to use them as sealing materials, paints, adhesives, and adhesives.

Examples

[0111] Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not construed as being limited by the following examples as long as the gist thereof is not exceeded. The raw materials and evaluation methods used in the following examples and comparative examples are as shown below. (Raw material 1) Polyalkylene oxide (A) used in the examples and comparative examples, or other polyols, monoalcohols (AC) The properties of the polyalkylene oxide, or other polyols, monoalcohols (AC) used in the examples and comparative examples were determined by the following method. <Unsaturation degree of polyalkylene oxide> The unsaturation degree of the polyalkylene oxide was measured at 800 scan times in accordance with the NMR method described in Polymer Journal 1993, 50, 2, 121-126.

[0112] For the NMR measurement, deuterated chloroform was used, and the measurement apparatus was JEOL400MHz NMR ECZS. <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. Further, 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 (Mw / Mn) of polyalkylene oxide> Regarding the molecular weight distribution (Mw / Mn) of the polyalkylene oxide, it was measured by the following procedure using gel permeation chromatography (GPC) method.

[0113] 10 mg of polyalkylene oxide and 10 ml of tetrahydrofuran (THF) were placed in a sample bottle, and the polyalkylene oxide was dissolved in THF by standing for one day, and then filtered through a PTFE cartridge filter (0.5 μm) to prepare a sample for GPC measurement.

[0114] For GPC measurement, THF was used as the eluent, the measurement was carried out at a column temperature of 40 °C, and the molecular weight distribution (Mw / Mn) was analyzed using a third-order approximation curve of 8 standard polystyrenes manufactured by Tosoh Corporation with known molecular weights as the calibration curve. For the measuring device, HLC-8320GPC manufactured by Tosoh was used, and for the analysis, HLC-8320GPC-ECOSEC-WorkStation manufactured by Tosoh was used. <Viscosity of polyalkylene oxide> The viscosity of the polyalkylene oxide was determined in accordance with the method described in JIS K-1557-5. Specifically, it was measured using a cone-plate rotational viscometer at a temperature of 25 °C and a shear rate of 0.1 (1 / s), and Anton-Paar's MCR-300 was used as the measuring device. (Raw material 1-1) Polyalkylene oxide (A) used in Examples and Comparative Examples Polyalkylene oxide (A1) was obtained by adding propylene oxide that had been sufficiently dehydrated to polyoxypropylene glycol with two functional groups and a molecular weight of 400, while using an imino group-containing phosphazenium salt (hereinafter referred to as IPZ catalyst) and triisopropoxyaluminum in combination and performing sufficient dehydration and solvent removal. (A1) is a polyoxypropylene glycol (diol) that has only propylene oxide groups as alkylene oxide groups and has two hydroxyl groups in one molecule.

[0115] Polyalkylene oxide (A2) was obtained by adding ethylene oxide in a block manner after removing the remaining propylene oxide in the system, after adding a propylene oxide group as an alkylene oxide group, while using an IPZ catalyst and triisopropoxyaluminum in combination in the same manner as (A1). It is a diol with a low degree of unsaturation containing primary hydroxyl groups.

[0116] Polyalkylene oxide (A4) was obtained by adding ethylene oxide in a block manner after removing the remaining propylene oxide in the system, after adding a propylene oxide group as an alkylene oxide group, while using an IPZ catalyst and triisopropoxyaluminum in combination in the same manner as (A2), using polyoxypropylene triol with three functional groups and a molecular weight of 600 as an initiator. It is a polyoxyalkylene triol with a low degree of unsaturation containing primary hydroxyl groups.

[0117] Polyalkylene oxide (A3) is polypropylene glycol synthesized by adding only propylene oxide by a conventional method, and Sunnex PP-3000 manufactured by Sanyo Chemical Industries, Ltd. was used.

[0118] Table 1 shows the properties of (A1) to (A4). (A1), (A2), and (A4) have an extremely small amount of unsaturated monool (extremely low degree of unsaturation) and a narrow molecular weight distribution, and (A3) is a polyalkylene oxide with a general degree of unsaturation and molecular weight distribution.

[0119] Note that all of the polyalkylene oxides (A1) to (A4) used in the examples were used after being heated and dehydrated under vacuum. For the polyalkylene oxides prepared using the IPZ catalyst, the catalyst was removed including aluminum before use. (Raw material 1-2) Other polyols and monools (AC) used in the examples and comparative examples The monool (AC1) is polyethylene glycol monomethyl ether, a monool having a methyl group at one end and consisting of one hydroxyl group and ethylene oxide group in one molecule.

[0120] The polyol (AC2) is a bifunctional polypropylene glycol with a molecular weight of 1000, which has a lower molecular weight than the polyalkylene oxide (A) with a molecular weight of 2000 or more.

[0121] The polyol (AC3) is a bifunctional polyoxytetramethylene glycol with a molecular weight of 2100, which is a polyol with a molecular weight of 2000 or more having no alkylene oxide residue.

[0122] [Table 1]

[0123] (Raw material 2) Polyalkylene oxide (B), polyol (BC) (Raw material 2-1) Polyalkylene oxides (B1), (B2), (B3) used in the examples The polyalkylene oxide (B1) is a commercially available tolylene diamine-based polypropylene glycol. The nominal functionality is 4.0, the hydroxyl value is 356 mgKOH / g, and the viscosity at 25°C is 9500 mPa·s. Tohopu Polyol AR-2589 manufactured by Toho Chemical Industry Co., Ltd. was used. The molecular weight calculated from these properties is 630, and the aromatic amine residue content is 19%.

[0124] The polyalkylene oxide (B2) is a commercially available tolylene diamine-based polypropylene glycol / polyethylene glycol copolymer. Sannix HM-551 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 was used. The molecular weight calculated from these properties is 540, and the aromatic amine residue content is 22%.

[0125] The polyalkylene oxide (B3) is a commercially available polyalkylene oxide using a combined tolylene diamine / glycol initiation system. Jeffol AD-310 manufactured by Huntsman with a nominal functionality of 3.2, a hydroxyl value of 310 mg KOH / g, and a viscosity of 2,200 mPa·s at 25°C was used. The initiator molar ratio calculated from these properties is aromatic amine / glycol = 6 / 4, the molecular weight is 580, and the aromatic amine residue content is 12%. (Raw material 2-1) Polyols (BC1), (BC2), (BC3) used in the examples and comparative examples The polyol (BC1) is a commercially available trifunctional polypropylene triol with a molecular weight of 600. Sannix GP600 manufactured by Sanyo Chemical Industries, Ltd. was used.

[0126] The polyol (BC2) is a commercially available difunctional polyoxytetramethylene glycol with a molecular weight of 1,000. PTG1000SN manufactured by Hodogaya Chemical Co., Ltd. was used.

[0127] The polyol (BC3) is a sucrose-based polyol with a nominal functionality of 8.0 and a molecular weight of 1,190. O-855W manufactured by Toho Chemical Industry Co., Ltd. was used.

[0128] The polyol (BC1) is a polyalkylene oxide having an equivalent molecular weight to the polyalkylene oxide (B1) having an aromatic amine residue and having no aromatic amine residue. The polyol (BC2) is a polyol having a relatively rigid polyoxytetramethylene residue without an alkylene oxide residue. The polyol (BC3) is a polyalkylene oxide containing a sucrose residue having a rigid and high functional group number cyclic sugar structure instead of a rigid aromatic amine residue. (Raw material 3) Isocyanate compounds (C) and (F) used in Examples and Comparative Examples In Examples and Comparative Examples, the following three types were used as the isocyanate compounds (C) and (F).

[0129] Isocyanate compound (C1): Isophorone diisocyanate (IPDI). (C1) is a diisocyanate having a primary NCO group and a secondary NCO group as isocyanate groups.

[0130] Isocyanate compound (C2): 1,6-Hexamethylene diisocyanate (HDI). (C2) is a diisocyanate having only a primary NCO group as an isocyanate group.

[0131] Isocyanate compound (F1): Coronate HXLV manufactured by Tosoh Corporation, which is a modified isocyanate of 1,6-hexamethylene diisocyanate (HDI) type. The average functional group number of the isocyanate groups in (F1) is 3.2. (Raw material 4) Urethane-forming catalyst In Examples and Comparative Examples, a urethane-forming catalyst was added as an additive. The urethane-forming catalyst is trisacetylacetonatoiron (abbreviation: Fe(acac)3), and Narsem iron manufactured by Nippon Chemical Industry Co., Ltd. was used. This catalyst was added as a 5% solution masterbatch to improve workability. The addition amount without solvent is described in the table. (Raw material 5) Solvent In the examples and comparative examples, as the solvent, ethyl acetate (abbreviated as EtOAc) manufactured by FUJIFILM Wako Pure Chemical Corporation, or methyl ethyl ketone (abbreviated as MEK) manufactured by FUJIFILM Wako Pure Chemical Corporation, or triethylene glycol dimethyl ether (abbreviated as TEGDM) manufactured by Toho Chemical Industry Co., Ltd. was used. (Method for producing urethane prepolymer (D) and urethane prepolymer (E)) Into a 1 L four-necked eggplant flask, polyalkylene oxide (A) which is a raw material of urethane prepolymer (D), polyalkylene oxide (B) and monoalcohol (AC) added as necessary were charged. Two glass ground three-way cocks were inserted, a thermocouple thermometer acting as a baffle was inserted, and a stirring rod equipped with an anchor blade with a blade diameter of 9 cm was set on a mechanical stirrer equipped with a vacuum stirring device at the central port. Then, vacuum dehydration was carried out at 210 rpm and 100 °C for 2 hours to remove moisture, perform nitrogen substitution, and cool to room temperature to 50 °C (dehydration step). Then, while stirring at 210 rpm under nitrogen, in the system using a solvent, the solvent, isocyanate, and catalyst masterbatch were added in this order, and then the stirring speed was increased to 310 rpm. In order to control the heat generation by controlling the reaction rate and suppress the generation of gel-like substances, if necessary, the internal temperature was maintained at 30 °C for 30 minutes and then heated to a predetermined temperature, and the reaction was started when the predetermined temperature was reached.

[0132] After reacting for a predetermined time, it was confirmed by FT-IR that the NCO groups remained and the liquid properties did not change or the amount did not change. After 30 minutes had passed, the (X) step was terminated to obtain urethane prepolymer (D) with NCO group terminals.

[0133] In the (Y) process, in order to suppress the formation of a gel-like substance and deposits adhering to the flask due to the catalytic activity derived from the amine structure and the chain reaction of the polyalkylene oxide (B) having a rigid aromatic amine residue, a 1-L four-necked eggplant flask containing the urethane prepolymer (D) was cooled from the outside by air cooling until the internal temperature reached 55°C or lower, and while gently flowing nitrogen and stirring at 310 rpm, the raw materials to be added in the (Y) process, such as the polyalkylene oxide (B) heated to 35°C or higher, were added all at once in a predetermined amount (within 10 minutes on a 1-L scale). The flask wall was kept warm so that the deposits on the wall became uniform in flow, and after confirming that it could be visually stirred uniformly and there was no significant heat generation, the temperature was raised to a predetermined temperature, and the reaction in the (Y) process was started.

[0134] After reacting for a predetermined time, it was confirmed by FT-IR that the NCO groups disappeared and there was no change in the liquid properties. After 30 minutes had elapsed, the (Y) process was terminated, and a urethane prepolymer (E) with a terminal active hydrogen group was obtained. Concentration was carried out as necessary to adjust the viscosity.

[0135] The internal temperature was cooled to 55°C or lower, various additives were mixed and uniformly dispersed as necessary, and while slightly pressurizing and filtering with nitrogen through a 200-mesh SUS wire mesh, it was withdrawn into a transparent glass container and packed to obtain a urethane prepolymer (E) composition (additive mixing process, filtration and withdrawal process). In addition, according to the charging composition ratio, the charging was carried out at a weight ratio such that the final can efficiency was 50% or more. (Evaluation items of urethane prepolymer) <Liquid properties> The liquid properties of the urethane prepolymer were evaluated according to the following criteria. The flask after withdrawal was gently washed with 100 ml of acetone, and the presence or absence of deposits with low solubility on the flask wall and gel-like substances was confirmed.

[0136] ◎ (Pass): Good, especially excellent in handling properties ○ (Pass): Slightly high viscosity, but no problem in the withdrawal process, etc.

[0137] × (Failed): When there are problems in the extraction process due to gelation, formation of gel-like substances, or high-viscosity substances. <Transparency of the liquid> The transparency of the urethane prepolymer was evaluated according to the following criteria.

[0138] ◎ (Passed): When it is visually transparent (liquid Haze is 5% or less).

[0139] ○ (Passed): When there is a slight turbidity visible visually, but the liquid Haze is 15% or less (almost transparent).

[0140] × (Failed): When there is a clearly visible strong turbidity visually, or when the liquid Haze exceeds 15%. <Curing property> To 1 equivalent of hydroxyl groups of the obtained urethane prepolymer with active hydrogen group terminals, 1.1 equivalents of HDI isocyanurate crosslinking agent Coronate HXLV was added, coated on a PET substrate at 80 μm or less, and the urethane cured product immediately after drying at 130 °C for 5 minutes was evaluated by touch according to the following criteria.

[0141] ◎ (Passed): When the tack has disappeared and higher strength and easy peelability can be expected more significantly.

[0142] ○ (Passed): When the tack is slight and higher strength and easy peelability can be expected significantly.

[0143] × (Failed): When the tack is large and the curing is insufficient, and higher strength and easy peelability cannot be expected.

[0144] Also, the urethane cured product obtained by the above evaluation of the curing property was evaluated visually, and the sheet appearance (transparency, presence or absence of shrinkage) was evaluated.

[0145] A production method in which the urethane prepolymer (E) passes all of the above evaluations in terms of the liquid properties, transparency, and curability of the liquid, and a sheet with good visual appearance (transparent and no shrinkage) is obtained in the curability evaluation is determined to be a production method of a urethane prepolymer that contributes to the formation of a highly transparent polyurethane with high tensile strength by using a rigid aromatic amine polyol and having good coatability, transparency, and productivity. <Examples, Comparative Examples> (Example 1) According to the production method of the urethane prepolymer (D), 65 parts by weight of polyalkylene oxide (A1) was added and dehydrated, and 0.03 part by weight of iron trisacetylacetonate as an isocyanate compound (C1) and a urethanization catalyst was added. The amount of hydroxyl groups (M OH ) derived from (A1) and the amount of isocyanate groups (M NCO ) derived from (C1) were charged in a molar ratio such that M NCO of (C1) / M OH of (A1) = 2.30, and the reaction was carried out at 70°C for 3 hours to produce an NCO group-terminated urethane prepolymer (D) ((X) step). According to the production method of the urethane prepolymer (E), after passing through a cooling step to 55°C or lower, 35 parts by weight of polyalkylene oxide (B1) was added to the urethane prepolymer (D) produced in the (X) step, and the reaction was carried out under the same reaction conditions as the production of the urethane prepolymer (D) to produce an active hydrogen group-terminated urethane prepolymer (E1) with MNCO / (A1) and MOH of (B1) being 0.20 ((Y) step). Filtration and extraction were carried out under slightly increased pressure and packed in a transparent glass container (slightly increased pressure filtration and extraction step).

[0146] The results of Example 1 are shown in Table 2. Both the intermediate urethane prepolymers (D1) and urethane prepolymers (E1) are highly transparent, and there are no deposits or gel-like substances on the flask walls or mesh, showing good liquid properties, moderate viscosity, and good handling properties, and can be expected to have good coating properties and high productivity. Also, the urethane prepolymer (E1) obtained by the production method of this example has significantly good initial curability and can be expected to have significantly higher strength, and the urethane cured product is also significantly transparent. (Examples 2 - 6) These were produced by using a solvent in the (X) step and changing the ratio of the charged amounts and the reaction conditions compared to Example 1. Similar to Example 1, an active hydrogen compound containing polyalkylene oxide (A1) and isocyanate (C1) were added in the (X) step to produce an NCO group-terminated urethane prepolymer (D), and then mixed and reacted with polyalkylene oxide (B) having an aromatic amine residue in the (Y) step to produce an active hydrogen group-terminated urethane prepolymer (E1). The results of Examples 2 - 6 are shown in Table 2. Both the intermediate urethane prepolymers (D) and urethane prepolymers (E) are significantly highly transparent, and there are no deposits or gel-like substances on the flask walls or mesh, showing good liquid properties, moderate viscosity, and good handling properties, and can be expected to have good coating properties and high productivity. Also, the urethane prepolymer (E) obtained by the production method of this example has significantly good initial curability and can be expected to have significantly higher strength, and the urethane cured product is also significantly transparent. (Examples 7, Example 8) Example 7 is a manufacturing method in which the molar ratio of the isocyanate compound in the (X) step is relatively high at 4.31 compared to Example 1, and more free isocyanate is generated. Example 8 is a manufacturing method in which the molar ratio of the final isocyanate compound in the (Y) step is 0.12 and polyalkylene oxide (B) tends to remain relatively more compared to Example 1. The results of Examples 7 to 8 are shown in Table 2. In both cases, at a thickness exceeding 1 cm, although there is slight turbidity, they are almost transparent and have high transparency. There are no deposits or gel-like substances on the flask wall or mesh, and they have good liquid properties, showing appropriate viscosity and good handleability, and can be expected to have good coating properties and high productivity. Also, the urethane prepolymer (E) obtained by the manufacturing method of this example has significantly good initial curability and can be expected to have significantly higher strength. The urethane cured product is also highly transparent. (Example 9) Compared to Example 1, it was manufactured with a large amount of 90 parts by weight of polyalkylene oxide (A) in the (X) step and a relatively small ratio of 10 parts by weight of the rigid polyalkylene oxide (B) added in the (Y) step. The results of Example 9 are shown in Table 2. Both the intermediate urethane prepolymer (D) and the urethane prepolymer (E) are significantly highly transparent, and there are no deposits or gel-like substances on the flask wall or mesh, and they have good liquid properties, showing appropriate viscosity and good handleability, and can be expected to have good coating properties and high productivity. Also, the urethane prepolymer (E) obtained by the manufacturing method of this example has good initial curability although it is slightly tacky immediately after curing and can be expected to have significantly higher strength. The urethane cured product is also significantly transparent. (Example 10) In Example 4, since a large amount of polyalkylene oxide (B) with a high functional group number is added in the (X) step, and the molar ratio of the isocyanate compound in the (X) step is as low as 1.90, and the molar ratio of the isocyanate compound in the (Y) step is as high as 0.57, it is a production method in which the urethane prepolymers (D) and urethane prepolymers (E) are slightly more likely to have a higher molecular weight and a higher functional group number. Table 2 shows the results of Example 10. The intermediate urethane prepolymers (D10) and urethane prepolymers (E10) both had a relatively high viscosity, but showed good handleability and could be expected to have good coating properties and high productivity. They had a high transparency and no deposits or gel-like substances were observed on the flask walls or mesh, and they had good liquid properties. Also, the urethane prepolymer (E10) obtained by the production method of this example had significantly good initial curability and could be expected to have a significantly higher strength, and the urethane cured product was also significantly transparent. (Example 11) In Example 6, since a large amount of polyalkylene oxide (B) with a high functional group number is added in the (X) step, it is a production method in which the urethane prepolymers (D) and urethane prepolymers (E) are slightly more likely to have a higher molecular weight and a higher functional group number. Table 2 shows the results of Example 11. The intermediate urethane prepolymers (D11) and urethane prepolymers (E11) both had a relatively high viscosity, but showed good handleability and could be expected to have good coating properties and high productivity. They had a high transparency and no deposits or gel-like substances were observed on the flask walls or mesh, and they had good liquid properties. Also, the urethane prepolymer (E11) obtained by the production method of this example had significantly good initial curability and could be expected to have a significantly higher strength, and the urethane cured product was also significantly transparent. (Examples 12 to 14) For Examples 1 to 11, hexamethylene diisocyanate having only primary NCO groups was used as the polyisocyanate (C), and it was produced by changing the composition ratio and the like. For Examples 1 to 11, it was necessary to set a higher polyisocyanate ratio to make it easier to gel by chain reaction in the (X) step, but it had higher reactivity and better productivity. Table 2 shows the results of Examples 12 to 14. Both the intermediate urethane prepolymer (D) and the urethane prepolymer (E) were highly transparent, and there were no deposits or gels on the flask wall or the mesh, showing good liquid properties, moderate viscosity, and good handling properties, and could be expected to have good coating properties and high productivity. Also, the urethane prepolymer (E) obtained by the production method of Examples 12 to 14 had significantly good initial curability and could be expected to have significantly higher strength, and the urethane cured product was also significantly transparent. (Example 15) For Example 12, it is a production method in which the molar ratio of the isocyanate compound in the (X) step is relatively high at 4.56, generating a large amount of free isocyanate. Table 2 shows the results of Example 15. Although there is slight turbidity at a thickness exceeding 1 cm, they are almost transparent and have high transparency, and there are no deposits or gels on the flask wall or the mesh, showing good liquid properties, moderate viscosity, and good handling properties, and could be expected to have good coating properties and high productivity. Also, the urethane prepolymer (E) obtained by the production method of this example had significantly good initial curability and could be expected to have significantly higher strength, and the urethane cured product was also highly transparent.

[0147]

Table 2

[0148] (Comparative Example 1) This is produced without adding polyalkylene oxide (B) having a rigid aromatic amine residue to Example 1, and is a production method that does not include the (Y) step to produce a urethane prepolymer (DC1) with an active hydrogen group at the terminal. The results are shown in Table 3. Since it is produced without adding polyalkylene oxide (B) having an aromatic amine residue, although the liquid properties and transparency are good, the curability of the urethane prepolymer (E) is low and the tack is large, and it is a production method of a urethane prepolymer (E) in which a high strength of the urethane cured product cannot be expected and is difficult to use. (Comparative Example 2) This is produced by adding a large amount of polyalkylene oxide (B) having a rigid aromatic amine residue in the (X) step to Example 1, and is a production method that does not include the (Y) step to produce a urethane prepolymer (DC2) with an active hydrogen group at the terminal. The results are shown in Table 3. Since it is produced by adding polyalkylene oxide (B) in the (X) step and does not go through the (Y) step, the compatibility of the raw materials in the (X) step is poor, and turbidity is observed under the solid content and reaction conditions of this production example. It is a production method in which it is difficult to stably produce a highly transparent urethane prepolymer with an active hydrogen group at the terminal and it is also difficult to stably produce a highly transparent urethane cured product. (Comparative Example 3) This is a production method in which, compared to Comparative Example 2, after reducing the amount of polyalkylene oxide (B) in the (X) step to form a urethane prepolymer with a hydroxyl group at the terminal, a small amount of polyalkylene oxide (B) is added in the (Y) step, and the production method does not produce the NCO-terminal urethane prepolymer (D) in the (X) step. The results are shown in Table 3. Since it is a production method that does not produce the NCO-group-terminal urethane prepolymer (D) in the (X) step, the compatibility of the raw materials in the (X) step is poor and the reactivity is also different. Therefore, turbidity is observed under the solid content and reaction conditions of this production example. It is a production method in which it is difficult to stably produce a highly transparent urethane prepolymer (E) and it is also difficult to stably produce a highly transparent urethane cured product. (Comparative Example 4) A production method in which, compared with Comparative Example 3, the amount of polyalkylene oxide (B) in the (X) step is further reduced to form a urethane prepolymer having an NCO group terminal, and then a large amount of polyalkylene oxide (B) is added in the (Y) step. The molar ratio of the isocyanate compound in the (X) step is as low as 1.09, and it is a production method that is easy to increase the molecular weight and crosslink. The results are shown in Table 3. Since the molar ratio of the isocyanate compound in the (X) step is lower than 1.30, the urethane prepolymer (D) gels in the (X) step, and it is difficult to separate from the polyalkylene oxide (B) added in the (Y) step to form a uniform composition. It was a production method that was difficult to use because it gelled and had no fluidity. (Comparative Example 5) (X) A production method in which, after forming a urethane prepolymer having an NCO group terminal in the step, a large amount of polyalkylene oxide (B) is added in the (Y) step. The molar ratio of the isocyanate compound in the (X) step is as high as 6.76, and a large amount of free isocyanate remains in the (Y) step. The results are shown in Table 3. Since the molar ratio of the isocyanate compound in the (X) step is higher than 5.00, it is considered that a strong turbidity occurred due to the chain reaction between the polyalkylene oxide (B) having a rigid aromatic amine residue added in the (Y) step and the free polyisocyanate. The urethane prepolymer (E) was inferior in transparency, and it was a production method that made it difficult to form a urethane cured product with high transparency. (Comparative Example 6) (X) A production method in which, after forming a urethane prepolymer having an NCO group terminal in the step, a large amount of polyalkylene oxide (B) is added in the (Y) step, and the polyalkylene oxide (A) having a molecular weight of 2000 or more is not added in the (X) step. The results are shown in Table 3. Since the relatively flexible polyalkylene oxide (A) having a molecular weight of 2000 or more was not added, and a large amount of polyalkylene oxide (B) having a rigid aromatic amine residue with catalytic activity and a high functional group number was used, the urethane prepolymer (E) was inferior in transparency, and it was a production method that made it difficult to form a urethane cured product with high transparency. (Comparative Example 7) In order to suppress gelation in the (X) step for Comparative Example 4, a production method was used in which the addition amount of the isocyanate compound in the (X) step was increased to increase the molar ratio. The results are shown in Table 3. Since the addition amount of the isocyanate compound in the (X) step was increased, the urethane prepolymer (D) obtained in the (X) step was transparent and had good liquid properties. However, since the molar ratio of the isocyanate compound in the (Y) step was as high as 0.85, gelation occurred in the (Y) step, making it a production method that was difficult to use. (Comparative Example 8) For Comparative Example 2, hexamethylene diisocyanate having only primary NCO groups was used as the polyisocyanate (C), and it was produced by changing the composition ratio, etc. Similar to Comparative Example 2, a urethane prepolymer (EC8) with an active hydrogen group terminal was produced without going through the (Y) step. The results are shown in Table 3. Since an aromatic amine residue-containing polyalkylene oxide (B) was added in the (X) step and the production method did not go through the (Y) step, the compatibility of the raw materials in the (X) step was poor. At the solid content and reaction conditions of this production example, turbidity was observed, making it difficult to stably produce a highly transparent urethane prepolymer with an active hydrogen group terminal and also difficult to stably produce a highly transparent urethane cured product. (Comparative Example 9) For Comparative Example 8, a production method was used in which the polyalkylene oxide (B) in the (X) step was reduced in amount to form an NCO group terminal urethane prepolymer, and then the polyalkylene oxide (B) was added in the (Y) step. The molar ratio of the isocyanate compound in the (X) step was as low as 1.09, making it a production method that is prone to high molecular weight and high crosslinking. The results are shown in Table 3. Since the molar ratio of the isocyanate compound in the (X) step was lower than 1.30, the urethane prepolymer (D) gelled in the (X) step and was also separated from the polyalkylene oxide (B) added in the (Y) step, making it difficult to form a uniform composition. It was a production method that was difficult to use because of gelation and lack of fluidity. (Comparative Example 10) A production method in which after forming a urethane prepolymer having an NCO group terminal in step (X), a significantly larger amount of polyalkylene oxide (B) is added in step (Y), and the molar ratio of the isocyanate compound in step (Y) is significantly low at 0.029. The results are shown in Table 3. Since a large amount of polyalkylene oxide (B) having a rigid aromatic amine residue with low compatibility remains due to a large amount of polyalkylene oxide (B) added in step (Y) and the molar ratio of the isocyanate compound in step (Y) being less than 0.10, turbidity occurs, which is considered to be the influence of the remaining polyalkylene oxide (B). The urethane prepolymer (E) was inferior in transparency, and it was a production method in which it was difficult to form a urethane cured product with high transparency.

[0149]

Table 3

[0150] (Examples 16 to 21) With respect to Example 1, the types and ratios of polyalkylene oxide (A) used in step (X) and polyalkylene oxide (B) used in step (Y) were changed. Also, from Example 16 onwards and from Comparative Example 11 onwards, the reactions in steps (X) and (Y) were carried out under the conditions of a reaction time of 3 hours and a constant temperature of 70°C, and in all examples, the completion of the reaction in each step was confirmed.

[0151] The results are shown in Table 4. Even when the molecular weight and the number of functional groups of the polyalkylene oxide (A) and the molecular weight and the alkylene oxide residues contained in the polyalkylene oxide (B) are changed, both the intermediate urethane prepolymer (D) and the urethane prepolymer (E) are highly transparent. In Example 20, cooling was insufficient in the cooling step after the (X) step, and a small amount of deposits were formed on the flask wall, but it was still within a usable range. In other examples, no deposits or gels were observed on the flask wall or the mesh, and the liquid properties were good. All of them showed appropriate viscosities and good handleability, and were expected to have good coating properties and high productivity. Further, the urethane prepolymer (E) obtained by the production method of this example had significantly good initial curability and was expected to have significantly higher strength. The urethane cured product was also significantly transparent. (Comparative Example 11) Instead of the polyalkylene oxide (A) with a molecular weight of 2000 or more, polyalkylene oxide (AC2) with a molecular weight of 1000 was used. The results are shown in Table 4. Since the polyalkylene oxide (AC2) has a low molecular weight and many hydroxyl groups, when the molar ratio of the polyisocyanate (C) in the (X) step is set to 2.50, the total amount of the polyisocyanate (C) increases, and it becomes difficult to lower the molar ratio of the polyisocyanate (C) even when the polyalkylene oxide (B) is added in the (Y) step, resulting in gelation in the (Y) step, making it a difficult-to-use production method. (Comparative Example 12) In order to reduce the molar ratio of the polyisocyanate (C) in the (Y) step and suppress gelation in the (Y) step compared to Comparative Example 11, the polyalkylene oxide (AC2) in the (X) step was reduced to 30 parts by weight, and the polyalkylene oxide (B) in the (Y) step was increased for production. The results are shown in Table 4. Since a large amount of the polyalkylene oxide (B) having a rigid aromatic amine residue with catalytic activity and a high number of functional groups is required, the urethane prepolymer (E) is inferior in transparency, making it a production method difficult to form a highly transparent urethane cured product. (Comparative Example 13) It was produced using polyoxytetramethylene glycol that does not have an alkylene oxide residue instead of polyalkylene oxide (A). The results are shown in Table 4. Polyoxytetramethylene glycol does not have an alkylene oxide residue and has low compatibility with polyalkylene oxide (B), so it is inferior in transparency to urethane prepolymer (E) and cannot be expected to have transparency in the urethane cured product. Since it has higher crystallinity than polyalkylene oxide (A), urethane prepolymer (D) and urethane prepolymer (E) are likely to thicken, and it was a manufacturing method that could not be expected to have coatability and handleability and was difficult to use. (Comparative Examples 14 to 17) Instead of polyalkylene oxide (B) having an aromatic amine residue, Comparative Example 14 uses polyalkylene oxide (BC1) having the same molecular weight and no aromatic amine residue, Comparative Example 15 uses a polyol (BC2) having no alkylene oxide residue and a relatively rigid polyoxytetramethylene residue, and Comparative Examples 16 and 17 use polyalkylene oxide (BC3) containing a sucrose residue having a rigid and high functional group number and a cyclic sugar structure instead of a rigid aromatic amine residue.

[0152] Comparative Example 14 is a urethane prepolymer that cannot be expected to have the strength of the urethane cured product because it does not have a rigid structure, and also has low reactivity, so turbidity considered to be the remaining influence in step (Y) occurs and it is inferior in transparency and difficult to use.

[0153] In Comparative Example 15, since it does not have an alkylene oxide residue, it had only a slight turbidity within the usable range with low compatibility with urethane prepolymer (D), but urethane prepolymer (E) became highly viscous and could not be expected to have coatability and handleability. Also, there was a lack of curability, presumably due to the inferior rigidity of the polyoxytetramethylene residue compared to the aromatic amine residue, and it could not be expected to have strength and was difficult to use. Comparative Example 16 had a high functional group number, had a cyclic sugar structure, and contained a large amount of sucrose residues with poor compatibility. Therefore, the transparency of the urethane prepolymer (E) deteriorated, and it was a manufacturing method in which it was difficult to form a highly transparent urethane cured product.

[0154] In Comparative Example 17, the compatibility was improved by reducing the sucrose polyol with poor compatibility to 10 parts by weight or less, and high transparency was exhibited. However, the viscosity was high, and compared with the polyalkylene oxide (B) having an aromatic amine residue, it did not have catalytic activity, and at 10 parts by weight, the initial curability was insufficient, so it was a manufacturing method in which it was difficult to expect the development of strength.

[0155]

Table 4

[0156] (Examples 22, 23, 25) For Examples 1 to 21, a urethane prepolymer (E) was produced using a polyalkylene oxide (A3) with a general degree of unsaturation and molecular weight distribution instead of the polyalkylene oxide (A) with a low degree of unsaturation in the (X) step. The results are shown in Table 5. Even when using a polyalkylene oxide (A3) with a general degree of unsaturation and molecular weight distribution, by applying this manufacturing method, in the (Y) step, while maintaining transparency, a large amount of polyalkyne oxide (B) having a rigid aromatic amine residue can be added, and it was a manufacturing method of a urethane prepolymer (E) that could be expected to have high curability and the strength of the urethane cured product. (Examples 24, 26) For Examples 23 and 25, in addition to the polyalkyne oxide (B) having a rigid aromatic amine residue, a polyalkylene oxide (BC3) having a higher functional group number and a rigid cyclic sucrose structure was used, so that while maintaining high transparency, it had higher curability, and it was a manufacturing method of a urethane prepolymer (E) in which a urethane cured product could be expected to have even higher strength. (Comparative Examples 18, 19) Using a polyalkylene oxide (A3) with a general degree of unsaturation and molecular weight distribution, a large amount of a polyalkylene oxide (B) having a rigid aromatic amine residue was added in the (X) step, and urethane prepolymers (DC18) and (DC19) with active hydrogen group terminals were produced by a production method that does not include the (Y) step. The results are shown in Table 5. Since it is a production method in which the polyalkylene oxide (B) having an aromatic amine residue is added in the (X) step and does not go through the (Y) step, even when using a polyalkylene oxide (A3) containing a monool, the compatibility of the raw materials in the (X) step is poor, turbidity is observed under the solid content and reaction conditions of this production example, and it is difficult to stably produce a highly transparent urethane prepolymer with an active hydrogen group terminal, and it is also difficult to stably produce a highly transparent urethane cured product.

[0157] That is, according to Examples 22 to 26 and Comparative Examples 18 and 19, regardless of the use or non-use of polyalkylene oxides (A1), (A2), and (A4) with a low degree of unsaturation, even when using a polyalkylene oxide (A3) with a general degree of unsaturation and molecular weight distribution, by applying this production method in which a polyalkylene oxide (B) having an aromatic amine residue is added in the (Y) step, it is shown that a urethane prepolymer (E) with high transparency can be maintained, high curability can be exhibited, and high strength and low tack (easy peelability) can be expected.

[0158]

Table 5

[0159] All of the urethane prepolymers (E) obtained in this example were highly transparent regardless of reaction conditions such as the amount of solvent, and almost no gel-like substances, deposits on the flask wall, sediment components, etc. were observed. All viscosities were in the range of 1 to 100 Pa·s and showed good fluidity. In addition, all of the urethane cured products obtained by the curability evaluation had no shrinkage and visually high transparency, and the Haze was 5% or less. <Production Example of Urethane Cured Product> To 100 parts by weight of the solid content of the urethane prepolymer (E) obtained in Examples 3, 12, 17, and 23, 5 parts by weight of acetylacetone as a reaction retarder, 600 ppm of acidic phosphate ester (JP508 manufactured by Johoku Chemical Industry Co., Ltd.), 0.8 parts by weight of 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 DIC F-571 as a leveling agent were mixed and dispersed. As a crosslinking agent, Coronate HXLV was mixed in an amount of 1.1 equivalents based on the hydroxyl group and coated on a PET substrate at 80 μm or less, and dried at 130 °C for 5 minutes to produce a urethane sheet containing a urethane coating film. The viscosity of the composition containing the urethane prepolymer (E) produced by the production method of any of the examples was in the range of 1 to 100 Pa·s, and the remaining liquid of the composition after sheet formation showed good fluidity even after 24 hours. The obtained urethane cured product had good wettability, high strength, and high transparency, and was suitably used for sealing materials, paints, adhesives, and adhesives.

[0160] As described above in the examples, the method for producing a urethane prepolymer in the present invention can stably produce a highly transparent urethane prepolymer excellent in storage stability, handleability, and curability. By using the urethane prepolymer obtained by this production method, a stable production method for a urethane coating film with high transparency, high strength, low surface tack, and easy peelability can be provided. By taking advantage of its characteristics, it has been shown that the polyurethane obtained by this production method can be suitably used for sealing materials, paints, adhesives, adhesives, and the like.

Claims

1. A method for producing a urethane prepolymer (E), comprising at least the following steps (X) and (Y). Step (X); A polyol containing a polyalkylene oxide (A) having a number average molecular weight of 2000 or more and a polyisocyanate (C) are mixed in an amount ratio such that the ratio of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol (NCO / OH ratio) is 1.30 to 5.00, and a urethane prepolymer (D) having an NCO group terminal is produced. This is a step, The polyalkylene oxide (A) contains an alkylene oxide residue having 3 or more carbon atoms, and the alkylene oxide residue having 3 or more carbon atoms is a propylene oxide residue, a 1,2-butylene oxide residue, a 2,3-butylene oxide residue, an isobutylene oxide residue, a butadiene monooxide residue, a pentene oxide residue, a styrene oxide residue, or a cyclohexene oxide residue. It is only one or two or more selected from the group consisting of residues. Step (Y); A polyol containing a polyalkylene oxide (B) having an aromatic amine residue and a number average molecular weight of less than 2000 and the urethane prepolymer (D) produced in step (X) are mixed in an amount ratio such that the total amount of the NCO groups of the polyisocyanate (C) to the total amount of the active hydrogen groups of the polyol mixed in steps (X) and (Y) (NCO / OH ratio) is 0.10 to 0.70, and a urethane prepolymer (E) having an active hydrogen group terminal is produced. This is a step, The polyalkylene oxide (B) is one in which only propylene oxide is chain-linked to an aromatic amine, one in which only ethylene oxide is chain-linked to an aromatic amine, one in which propylene oxide and ethylene oxide are chain-linked to an aromatic amine, or one in which propylene oxide and ethylene oxide are randomly linked to an aromatic amine.

2. The method for producing a urethane prepolymer (E) according to claim 1, wherein the polyalkylene oxide (B) in step (Y) contains one or more residues selected from the group consisting of 4,4'-diphenylmethanediamine residues, 2,4-tolylenediamine residues, and 2,6-tolylenediamine residues.

3. The method for producing a urethane prepolymer (E) according to claim 1 or claim 2, wherein the polyisocyanate (C) in step (X) contains one or more selected from the group consisting of aliphatic isocyanates, alicyclic isocyanates, and modified products thereof.

4. In the (X) step, a urethanization catalyst containing a metal component is contacted in an amount of 0.001 to 0.2 parts by weight with respect to 100 parts by weight of the total amount of the polyol and the polyisocyanate (C). The method for producing the urethane prepolymer (E) according to any one of claims 1 to 3.

5. The method for producing the urethane prepolymer (E) according to any one of claims 1 to 4, wherein the urethane prepolymer (E) has a viscosity of 1 to 100 Pa·s and a haze of 15% or less at a thickness of 1 cm under the condition of 25°C.

6. In the (X) step, an organic solvent containing one or more selected from the group consisting of glycol ether solvents, ethyl acetate, toluene, and methyl ethyl ketone is mixed in a ratio such that the solid content concentration is in the range of 60 to 99% by weight. The method for producing the urethane prepolymer (E) according to any one of claims 1 to 5.

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