Method for producing hydrazide compounds, urethane resin, and moisture-curing hot-melt adhesive

Abstract

One aspect of the present invention aims to provide a moisture-curing hot-melt adhesive whose peel strength is easily reduced by an oxidizing agent. Another aspect of the present invention aims to provide a urethane resin suitably used in the adhesive, and a novel method for producing a hydrazide compound suitably used as a raw material for the urethane resin. [Solution] The following formula (1): [Formula 1] TIFF2026521010000013.tif35103 (in the formula, R 1 and R 2 (Each of these independently represents an alkylene group, and m and n independently represent integers greater than or equal to 2.) A method for producing a hydrazide compound represented by formula (1), comprising the step of obtaining the hydrazide compound represented by formula (1) by causing a ring-opening reaction between hydrazine and lactone.

Description

[Technical Field]

[0001] This disclosure relates to a method for producing hydrazide compounds, urethane resins, and moisture-curing hot-melt adhesives. [Background technology]

[0002] In automobiles, building materials, textile products, and other applications, moisture-curing hot-melt adhesives containing urethane resin are often used to bond materials together. In recent years, from an environmental protection standpoint, there has been a demand for the recycling and reuse of materials, but recycling and reuse require the disassembly of materials bonded together. In this case, there is a need for an adhesive that can be easily separated from materials by applying an external stimulus to the adhesive to reduce its peel strength. For example, Patent Document 1 discloses that a coating film containing urethane resin obtained using a compound having a diacylhydrazine bond decomposes when it comes into contact with an oxidizing agent, as the diacylhydrazine bond cleaves. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-1692 [Overview of the project] [Problems that the invention aims to solve]

[0004] One aspect of the present invention aims to provide a moisture-curing hot-melt adhesive whose peel strength is easily reduced by an oxidizing agent. Another aspect of the present invention aims to provide a urethane resin suitably used in the adhesive, and a novel method for producing a hydrazide compound suitably used as a raw material for the urethane resin. [Means for solving the problem]

[0005] As a result of our investigations, we found that a hydrazide compound obtained by ring-opening a hydrazine and a lactone is suitably used as a raw material for urethane resin, and that moisture-curing hot-melt adhesives containing urethane resin obtained using this hydrazide compound are prone to having their peel strength reduced by oxidizing agents.

[0006] The present invention includes the following aspects. [1] The following formula (1): [ka] (In the formula, R 1 and R 2 (Each of these independently represents an alkylene group, and m and n independently represent integers greater than or equal to 2.) A method for producing a hydrazide compound represented by, A manufacturing method comprising the step of obtaining a hydrazide compound represented by formula (1) by causing a ring-opening reaction between hydrazine and lactone. [2] A urethane resin which is a reaction product of a polyol and a polyisocyanate, Formula (1): [ka] (In the formula, R 1 and R 2 (Each of these independently represents an alkylene group, and m and n independently represent integers greater than or equal to 2.) A urethane resin containing a structure derived from a hydrazide compound represented by [formula]. A moisture-curing hot-melt adhesive containing the urethane resin described in [3] [2]. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a moisture-curing hot-melt adhesive whose peel strength is easily reduced by an oxidizing agent. Furthermore, according to another aspect of the present invention, it is possible to provide a urethane resin suitably used in the adhesive, and a novel method for producing a hydrazide compound suitably used as a raw material for the urethane resin.

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is a method for producing a hydrazide compound represented by the following formula (1).

Chemical Formula

[0009] R 1 and R 2 The alkylene group represented by may be linear or branched. The number of carbon atoms of the alkylene group may be 1 or more, 2 or more, 3 or more, or 4 or more, may be 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less, and may be 5. R 1 and R 2 may be the same as or different from each other, and preferably may be the same as each other.

[0010] m and n may be 3 or more, may be 6 or less, 5 or less, or 4 or less. m and n may be the same as or different from each other. The hydrazide compound represented by formula (1) may contain a mixture of a plurality of types of compounds in which m and n are different from each other. For example, the hydrazide compound represented by formula (1) may contain a mixture of compounds in which m and n are each 2 to 4, and may also contain a mixture of compounds in which m and n are each 2 to 5.

[0011] The above production method includes a step (reaction step) of obtaining a hydrazide compound represented by formula (1) by subjecting hydrazine and lactone to a ring-opening reaction. Hydrazine is a compound represented by H2N-NH2. The hydrazine used in the reaction step may be in a hydrated state.

[0012] Lactone is a cyclic ester represented by the following formula (2). [ka] In the formula, R 3 represents an alkylene group.

[0013] R 3 The alkylene group represented by may be linear or branched. The number of carbon atoms in the alkylene group may be 1 or more, 2 or more, 3 or more, or 4 or more, and may be 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less.

[0014] Examples of lactones include α-acetolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, γ-caprolactone, and γ-pentolactone. The lactone is preferably ε-caprolactone. One of these lactones may be used in the reaction step, or two or more may be used.

[0015] The amount of lactone in the reaction step may be 2 moles or more per mole of hydrazine. The greater the amount of lactone, the larger m and n in equation (1) tend to be. The amount of lactone may be 2.1 moles or more, 2.2 moles or more, 2.3 moles or more, 3 moles or more, or 4 moles or more per mole of hydrazine, and may be 6 moles or less, 5 moles or less, or 4.8 moles or less.

[0016] The reaction temperature in the reaction step may be 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher, and may be 180°C or lower, 170°C or lower, or 160°C or lower. The reaction time in the reaction step may be 6 hours or higher, 7 hours or higher, or 8 hours or higher, and may be 12 hours or lower, 11 hours or lower, or 10 hours or lower.

[0017] In the reaction step, the ring-opening reaction between hydrazine and lactone may be carried out in the presence of a catalyst. Examples of catalysts include p-toluenesulfonic acid, titanium tetraisopropoxide, titanium tetrabutoxide, and dibutyltin oxide. The amount of catalyst may be 0.1 mmol or more, 0.5 mmol or more, 1 mmol or more, 2 mmol or more, or 3 mmol or more, and may be 10 mmol or less, 7 mmol or less, or 5 mmol or less, per 1 mole of hydrazine.

[0018] In the above manufacturing method, the hydrazide compound represented by formula (1) can be obtained in a single step by the ring-opening reaction of hydrazine and lactone, and by-products are less likely to be generated. Therefore, this manufacturing method is more efficient than conventional methods.

[0019] The number-average molecular weight of the hydrazide compound represented by formula (1) may be 250 or more, 300 or more, 400 or more, 500 or more, 600 or more, or 700 or more, and preferably 750 or more, 800 or more, or 850 or more, and more preferably 900 or more, 950 or more, or 1000 or more, from the viewpoint of further reducing the peel strength of the adhesive by the oxidizing agent. The number-average molecular weight of the hydrazide compound represented by formula (1) may be 2000 or less, 1900 or less, 1800 or less, 1700 or less, 1600 or less, 1500 or less, 1400 or less, 1300 or less, 1200 or less, or 1100 or less. In this disclosure, the number-average molecular weight means the value calculated based on the hydroxyl value measured in accordance with JIS K1557-1 (Method A).

[0020] The hydrazide compound represented by formula (1) is suitably used as a raw material for urethane resins. That is, another embodiment of the present invention is a urethane resin which is a reaction product of a polyol (A) and a polyisocyanate (B). This urethane resin contains a structure derived from the hydrazide compound represented by formula (1). The structure derived from the hydrazide compound represented by formula (1) may be, for example, the structure represented by the following formula (1a).

[0021] R in formula (1a) of TIFF2026521010000006.tif36114 1 , R 2 , m and n are R in equation (1) 1 , R 2 These are synonymous with m and n, respectively.

[0022] The hydrazide compound represented by formula (1) has a -CO-NH-NH-CO- bond, and therefore this bond can be cleaved by an oxidizing agent (a chemical with oxidizing properties). Consequently, the peel strength of urethane resin obtained using the hydrazide compound represented by formula (1) as a raw material (urethane resin containing a structure derived from the hydrazide compound represented by formula (1)) and adhesives containing said urethane resin decreases with the use of an oxidizing agent. Also, in formula (1), R 1 and R 2 Because it is an alkylene group, aggregation caused by hydrogen bonding is less likely to occur, and the fluidity required for adhesives can be maintained.

[0023] In one embodiment, polyol (A) comprises a hydrazide compound represented by formula (1). Polyol (A) may further contain polyols other than the hydrazide compound represented by formula (1). Examples of polyols other than the hydrazide compound represented by formula (1) include polyether polyols, polyester polyols, polyether ester polyols, polycarbonate diols, and polyols with a carbon-carbon bond in the main chain. Other polyols may be used alone or in combination of two or more.

[0024] Polyol (A) may further contain polyester polyols as polyols other than the hydrazide compound represented by formula (1), and the polyester polyol content in polyol (A) may be the highest. Examples of polyester polyols include aliphatic polyester polyol (a1) and aromatic polyester polyol (a2). Polyol (A) may contain one type of polyester polyol (aliphatic polyester polyol (a1) or aromatic polyester polyol (a2)), or two types of polyester polyols (aliphatic polyester polyol (a1) and aromatic polyester polyol (a2)). Furthermore, polyol (A) may contain aliphatic polyester polyol (a1) and / or aromatic polyester polyol (a2) and other polyols other than polyester polyols (a3).

[0025] The aliphatic polyester polyol (a1) is a polyester polyol produced by known and conventional methods, mainly composed of aliphatic polycarboxylic acid and aliphatic polyol, and the method of production is not particularly limited.

[0026] As the aliphatic polycarboxylic acid used in the synthesis of the aliphatic polyester polyol (a1), aliphatic polycarboxylic acids having 4 to 12 carbon atoms are preferred, such as succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decandioic acid, dodecandioic acid, eicosanioic acid, citraconic acid, itaconic acid, citraconic anhydride, and itaconic anhydride.

[0027] The aliphatic polycarboxylic acid may be, for example, a lower alkyl ester derivative such as a methyl ester; or a corresponding acid derivative such as an acid anhydride or an acid halide.

[0028] The aliphatic polyol used in the synthesis of the aliphatic polyester polyol (a1) is preferably an aliphatic polyol having at least two hydroxyl groups in its molecule and having 2 to 12 carbon atoms. (a1) may have a linear, branched, or cyclic structure.

[0029] Examples of the aliphatic polyols include linear aliphatic polyols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, triethylene glycol, and tetraethylene glycol, or neopentyl glycol, 1,3-butanediol, and 2,2-diethyl-1,3-propanediol. Examples include branched aliphatic polyols such as 2,2-diethylpropanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,4-diethyl-1,5-pentanediol, trimethylolethane, trimethylolpropane, and pentaerythritol, or alicyclic polyols such as cyclopentanediol, cyclohexanediol, and cyclohexanedimethanol. Among these, ethylene glycol, 1,6-hexanediol, and neopentyl glycol are preferred.

[0030] Furthermore, adducts obtained by adding various alkylene oxides to hydrogenated bisphenol A, hydrogenated bisphenol F, etc., can also be used. Polymers obtained by ring-opening polymerization of γ-butyrolactone, ε-caprolactone, etc., using a low molecular weight polyol as an initiator can also be used. These may be used individually or in combination of two or more.

[0031] Among the combinations of aliphatic polycarboxylic acids and aliphatic polyols, it is preferable to include an aliphatic polyester polyol (a1) produced by a combination of aliphatic polycarboxylic acid having 4 to 12 carbon atoms and aliphatic polyol having 2 to 12 carbon atoms in polyol (A), as this further improves the viscosity stability during molding of the hot melt urethane resin adhesive and exhibits an excellent effect in preventing a decrease in melt viscosity.

[0032] Furthermore, the aromatic polyester polyol (a2) is a polyester polyol produced by known and conventional methods, mainly consisting of an aromatic polycarboxylic acid and an aliphatic polyol, or an aliphatic polycarboxylic acid and an aromatic polyol, and the method of production is not particularly limited.

[0033] The aforementioned aromatic polycarboxylic acid is a carboxylic acid in which at least two carboxyl groups are bonded to an aromatic ring, preferably an aromatic polycarboxylic acid having 8 to 24 carbon atoms, such as orthophthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, biphenyldicarboxylic acid, and naphthalenedicarboxylic acid. These may be used individually or in combination of two or more.

[0034] Furthermore, the aromatic polycarboxylic acid may be, for example, a lower alkyl ester derivative such as a methyl ester; or a corresponding acid derivative such as an acid anhydride or acid halide.

[0035] Examples of the aliphatic polyol include those similar to the aliphatic polyols that can be used in the synthesis of the aliphatic polyester polyol (a1).

[0036] Furthermore, the aliphatic polyols that can be used in the synthesis of the aromatic polyester polyol (a2) and the aliphatic polyester polyol (a1) may include, for example, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-bis(β-hydroxyethoxy)benzene, in which some of the carbon atoms are substituted with oxygen atoms or aromatic rings. These aliphatic polyols may also be used individually or in combination of two or more.

[0037] Furthermore, the aromatic polyester polyol (a2) may be a mixture of polyester polyols obtained from these aromatic polycarboxylic acids and aliphatic polyols.

[0038] Aliphatic polycarboxylic acids that can be used in the synthesis of the aromatic polyester polyol (a2) include aliphatic polycarboxylic acids having 4 to 12 carbon atoms, similar to those that can be used in the synthesis of the aliphatic polyester polyol (a1).

[0039] The aforementioned aromatic polyols are not particularly limited, but examples include aliphatic polyols such as ethylene glycol and neopentyl glycol, and aromatic polyols obtained from aromatic polycarboxylic acids such as orthophthalic acid and terephthalic acid.

[0040] Furthermore, as the aromatic polyol, adducts obtained by adding alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide to bisphenol A, bisphenol F, etc., can also be used.

[0041] The equivalent ratio (i.e., [OH / COOH equivalent ratio]) of the hydroxyl groups of the aliphatic polyol and aromatic polyol to the carboxyl groups of the aliphatic polycarboxylic acid and aromatic polycarboxylic acid during the synthesis of the aliphatic polyester polyol (a1) and aromatic polyester polyol (a2) is preferably in the range of 1.03 to 1.50, and more preferably in the range of 1.05 to 1.30. A [OH / COOH equivalent ratio] within this range is preferable because it allows for the generation of more polyols with hydroxyl groups at the hydroxyl terminals, thereby facilitating the urethane reaction with polyisocyanate (B).

[0042] The polycondensation conditions for the synthesis of the aliphatic polyester polyol (a1) and aromatic polyester polyol (a2) are not particularly limited, as long as no abnormal reactions occur and normal products can be obtained. Typically, a predetermined amount of aliphatic polycarboxylic acid and aliphatic polyol, or aromatic polycarboxylic acid and aliphatic polyol, can be subjected to an esterification or transesterification reaction at an internal temperature of 150-250°C for 5-50 hours, with or without a catalyst, followed by a polycondensation reaction.

[0043] Polycondensation reactions are preferable to carry out in the presence of a catalyst, as this facilitates the reaction. The catalyst is not particularly limited, but examples include titanium-based catalysts such as titanium tetrabutoxide and tin-based catalysts such as dibutyltin oxide.

[0044] The catalyst may be charged together with an aliphatic polyol and an aliphatic polycarboxylic acid, or with an aliphatic polyol and an aromatic polycarboxylic acid, or it may be added after prepolymerization without a catalyst.

[0045] In the production of the aliphatic polyester polyol (a1) and aromatic polyester polyol (a2), it is desirable that both ends of each polyol be almost entirely hydroxyl groups, with as few carboxyl group ends remaining as possible. For this purpose, it is effective and preferable to add the catalyst after prepolymerization.

[0046] The number-average molecular weight (Mn) of the aliphatic polyester polyol (a1) and aromatic polyester polyol (a2) is preferably in the range of 500 to 6000, more preferably in the range of 1000 to 5000, and particularly preferably in the range of 2000 to 4000. If the Mn of (a1) and (a2) is within this range, a balance of physical properties such as strength and elongation can be obtained according to the application, which is preferable.

[0047] Examples of the other polyols (a3) ​​include polycarbonate polyols, polylactone polyols, and polyether polyols. Examples of the polycarbonate polyols include polycarbonate polyols obtained using the linear aliphatic polyols such as 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Examples of the polylactone polyols include polycaprolactone polyols obtained by ring-opening polymerization of caprolactone monomers. Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0048] The content ratio of the aliphatic polyester polyol (a1), the aromatic polyester polyol (a2), and the other polyol (a3) ​​may be 20-60 parts by mass / 10-50 parts by mass / 0-50 parts by mass per 100 parts by mass of polyol (A), preferably 30-50 parts by mass / 20-40 parts by mass / 10-20 parts by mass. Within this range of content ratio, the melt viscosity of polyol (A) can be adjusted to an appropriate range, resulting in a moisture-curable hot-melt urethane resin adhesive that exhibits excellent workability and miscibility, and furthermore, excellent solidification properties.

[0049] The content of the hydrazide compound represented by formula (1) in polyol (A) may be 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, or 6 parts by mass or more per 100 parts by mass of polyol (A), and may be 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, 9 parts by mass or less, 8 parts by mass or less, or 7 parts by mass or less.

[0050] In another embodiment, polyol (A) may be a polyol obtained by reaction of a hydrazide compound represented by formula (1) with other compounds. Examples of such other compounds include the aliphatic polycarboxylic acids described above. The other compounds may further include the aliphatic polyol described above in addition to the aliphatic polycarboxylic acids described above. In this embodiment, the amount of the hydrazide compound represented by formula (1) may be 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, or 6 parts by mass or more, and may be 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, 9 parts by mass or less, 8 parts by mass or less, or 7 parts by mass or less, based on 100 parts by mass of the total amount of the hydrazide compound represented by formula (1) and other compounds.

[0051] The polyisocyanate (B) can be any known or commonly used aliphatic, aromatic, or alicyclic polyisocyanate, such as diphenylmethane diisocyanate (MDI; its 4,4', 2,4', or 2,2' isomer, or mixtures thereof, crude MDI), carbodiimide-modified MDI (modified MDI), polymethylene polyphenyl polyisocyanate, carbodiimide-modified diphenylmethane polyisocyanate, xylene diisocyanate, tolylene diisocyanate (TDI; its 2,4, or 2,6 isomer, or mixtures thereof), xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate (NDI), tetramethylxylene diisocyanate, phenylene diisocyanate Examples include aromatic diisocyanates such as annetes, or aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), dimer acid diisocyanate, norbornene diisocyanate, lysine diisocyanate, and tetramethylxylylene diisocyanate, or alicyclic diisocyanates such as isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate. Among these, MDI and XDI are preferred because they react quickly with the polyol (A) and moisture (water) and offer excellent workability. These may be used individually or in combination of two or more.

[0052] The ratio in which the polyol (A) and the polyisocyanate (B) are reacted should be within a range that does not adversely affect the reaction behavior or product quality. Typically, the equivalent ratio (hereinafter referred to as [NCO / OH equivalent ratio]) of the isocyanate groups of the polyisocyanate (B) to the hydroxyl groups of the polyol (A) is preferably in the range of 1.2 to 4.0, and more preferably in the range of 1.5 to 3.0. When the [NCO / OH equivalent ratio] is within this range, the melt viscosity of the target moisture-curable hot-melt urethane resin composition will be within an appropriate range, and it will exhibit excellent workability, film properties, and even better solidification properties.

[0053] The reaction conditions should be set within a range that does not adversely affect the reaction behavior or product quality, and are not particularly limited, but it is generally preferable to carry out the reaction at a reaction temperature of 80 to 130°C for 1 to 10 hours.

[0054] The reaction method can be selected from known methods, such as batch reactions, semi-continuous reactions, or continuous reactions. Furthermore, the reaction can be carried out in or without a solvent. However, when carrying out the reaction in a solvent, it is preferable to remove the solvent during or after the reaction to ultimately obtain a solvent-free solution. The method of solvent removal is not particularly limited.

[0055] The above-mentioned urethane resin is suitably used in moisture-curing hot-melt adhesives. That is, another embodiment of the present invention is a moisture-curing hot-melt adhesive containing the above-mentioned urethane resin.

[0056] The urethane resin content may be 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, or 90% or more by mass, based on the total amount of the moisture-curing hot melt adhesive. The moisture-curing hot melt adhesive may consist only of urethane resin, or it may further contain other components besides urethane resin.

[0057] Other components may be resins other than urethane resin, and may also be additives. Examples of additives include tackifiers, antioxidants, curing catalysts, fillers, foam stabilizers, defoaming agents, UV absorbers, abrasives, pigments, dyes, colorants, thickeners, surfactants, flame retardants, plasticizers, lubricants, antistatic agents, heat stabilizers, stabilizers, fluorescent whitening agents, silane coupling agents, and waxes. [Examples]

[0058] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0059] [Example 1-1] 228.3 parts by mass (2.0 mol) of ε-caprolactone was added to a 1-liter flask, and 213.6 parts by mass (1.0 mol) of 85% hydrazine monohydrate was added dropwise over 1 hour while stirring the flask at room temperature. The temperature was raised to 90°C, and the ring-opening reaction was carried out over 10 hours to form hydrazide compound 1 (R in formula (1)) with a number average molecular weight of 774. 1 and R 2 We obtained compounds in which the linear pentylene group is present and m and n are 2 to 4.

[0060] [Examples 1-2] 273.9 parts by mass (2.4 mol) of ε-caprolactone were added to a 1-liter flask, and 213.6 parts by mass (1.0 mol) of 85% hydrazine monohydrate were added dropwise over 1 hour while stirring the flask at room temperature. The temperature was raised to 150°C, and the ring-opening reaction was carried out over 10 hours to form hydrazide compound 2 (R in formula (1)) with a number average molecular weight of 888. 1 and R 2 We obtained compounds in which the linear pentylene group is present and m and n are 2 to 4.

[0061] [Examples 1-3] 536.5 parts by mass (4.7 mol) of ε-caprolactone was added to a 1-liter flask, and 213.6 parts by mass (1.0 mol) of 85% hydrazine monohydrate was added dropwise over 1 hour while stirring the flask at room temperature. After adding 0.57 parts by mass (3.3 mmol) of p-toluenesulfonic acid, the temperature was raised to 125°C and the ring-opening reaction was carried out over 10 hours to obtain hydrazide compound 3 (R in formula (1)) with a number average molecular weight of 1098. 1 and R 2 A compound was obtained in which the group is a linear pentylene group and m and n are 2 to 5.

[0062] [Comparative Example 1-1] 228.3 parts by mass (2.0 mol) of ε-caprolactone and 174.2 parts by mass (1.0 mol) of adipic acid dihydrazide were added to a 1-liter flask, the temperature was raised to 180°C, and the reaction was carried out for 10 hours to obtain hydrazide compound 4 with a number average molecular weight of 1317.

[0063] [Example 2-1] In a 1-liter flask, 37 parts by mass of polypropylene glycol (Mn=1000), 36 parts by mass of aliphatic polyester polyol (Mn=3500) obtained by reacting 1,6-hexanediol (HD) and adipic acid (AA) in an HD / AA = 46 / 54 mass ratio, and 5 parts by mass of hydrazide compound 1 obtained in Example 1-1 were mixed and melted to prepare polyol (A). Next, the polyol (A) was heated to 110°C and dehydrated under reduced pressure until the moisture content was 0.05% by mass. Then, it was cooled to 70°C, and 22 parts by mass of 4,4-diphenylmethane diisocyanate were added. The mixture was reacted at 90°C for 3 hours until the NCO content (%) became constant. This yielded a urethane resin.

[0064] [Example 2-2] In Example 2-1, the same procedure was followed except that hydrazide compound 1 was replaced with hydrazide compound 2 obtained in Example 1-2, to obtain a urethane resin.

[0065] [Examples 2-3] In Example 2-1, the same procedure was followed except that hydrazide compound 1 was replaced with hydrazide compound 3 obtained in Example 1-3, to obtain a urethane resin.

[0066] [Comparative Example 2-1] In Example 2-1, the same procedure was followed except that polyol (A) containing hydrazide compound 1 was replaced with polyol (a) that does not contain hydrazide compound, to obtain a urethane resin. Polyol (a) was prepared by mixing 39 parts by mass of polypropylene glycol (Mn=1000) and 39 parts by mass of aliphatic polyester polyol (Mn=3500) obtained by reacting 1,6-hexanediol (HD) and adipic acid (AA) in an HD / AA = 46 / 54 mass ratio in a 1-liter flask and melting the mixture.

[0067] [Comparative Example 2-2] In a 1-liter flask, 39 parts by mass of polypropylene glycol (Mn=1000), 34 parts by mass of aliphatic polyester polyol (Mn=3500) obtained by reacting 1,6-hexanediol (HD) and adipic acid (AA) in an HD / AA = 46 / 54 mass ratio, and 5 parts by mass of hydrazide compound 4 obtained in Comparative Example 1-1 were mixed and melted to prepare polyol (b).

[0068] Next, the polyol (b) was heated to 110°C and dehydrated under reduced pressure until the moisture content reached 0.05% by mass. Afterward, it was cooled to 70°C, and 22 parts by mass of 4,4-diphenylmethane diisocyanate were added and reacted at 90°C. However, aggregates that were difficult to dissolve were obtained. Therefore, further evaluation could not be performed.

[0069] [Evaluation of peel strength (1)] The urethane resins obtained in Examples 2-1 to 2-3 and Comparative Example 2-1 were used as moisture-curing hot-melt adhesives. The adhesives were heated to a melted state at 120°C, and a 50 μm thick layer of the adhesive was placed between a polyester-based thin-film type TPU (thermoplastic polyurethane elastomer) film (thickness 0.23 mm) and a PET (polyethylene terephthalate) fabric (thickness 0.20 mm) using a lab coater. The resulting adhesive was left to stand for 48 hours or more under conditions of 23°C and 50% RH humidity to complete the moisture curing reaction of the adhesive. Subsequently, the adhesive was immersed in a 5% sodium hypochlorite aqueous solution at 23°C for 24 hours, then washed with water and dried. Before and after immersion in a sodium hypochlorite aqueous solution, a 180° peel test was performed on the adhesive in accordance with JIS K6854-2:1999, and the peel strength (N) per inch of width of the adhesive was measured both before and after immersion. The peeling speed was set to 200 mm per minute. From the measured peel strength, the strength reduction rate defined by the following formula was calculated. Strength reduction rate (%) = 100 × (Peel strength before immersion (N) - Peel strength after immersion (N)) / Peel strength before immersion (N) The results are shown in Table 1.

[0070] [Table 1]

[0071] As can be seen from Table 1, adhesives containing urethane resin obtained using the hydrazide compound represented by formula (1) (Examples 2-1 to 2-3) decompose when exposed to an oxidizing agent (5% sodium hypochlorite aqueous solution), resulting in a significant decrease in the peel strength of the adhesive. In contrast, adhesives containing urethane resin obtained without using the hydrazide compound represented by formula (1) (Comparative Example 2-1) show less decrease in peel strength compared to the examples. This difference in the decrease in peel strength between the examples and comparative examples was similarly observed even when the types of film and fabric were changed, as shown below. Furthermore, in Comparative Example 2-2, which used hydrazide compound 4 synthesized from adipic acid dihydrazide, aggregation occurred as described above, making it impossible to evaluate its properties as an adhesive.

[0072] [Evaluation of peel strength (2)] Except for using a polyether-based thin-film TPU film (thickness 0.31 mm) instead of a polyester-based thin-film TPU film (thickness 0.23 mm), the rate of strength reduction for each adhesive was determined in the same manner as in the peel strength evaluation (1). The results are shown in Table 2.

[0073] [Table 2]

[0074] [Evaluation of peel strength (3)] Except for using a polyether-based thick-film TPU film (0.48 mm thick) instead of a polyester-based thin-film TPU film (0.23 mm thick) and canvas (1.60 mm thick) instead of PET fabric, the strength reduction rate of each adhesive was determined in the same manner as in the peel strength evaluation (1). The results are shown in Table 3.

[0075] [Table 3]

[0076] [Evaluation of peel strength (4)] Except for using a polyester-based thick-film TPU film (thickness 0.46 mm) instead of a polyether-based thick-film TPU film (thickness 0.48 mm), the rate of strength reduction for each adhesive was determined in the same manner as in the peel strength evaluation (3). The results are shown in Table 4.

[0077] [Table 4]

Claims

1. The following formula (1): 【Chemistry 1】 (In the formula, R １ and R ２ (Each of these independently represents an alkylene group, and m and n independently represent integers greater than or equal to 2.) A method for producing a hydrazide compound represented by, A method for producing a hydrazide compound represented by formula (1) by causing a ring-opening reaction between hydrazine and lactone.

2. A urethane resin which is a reaction product of a polyol and a polyisocyanate, The following formula (1): 【Chemistry 2】 (In the formula, R １ and R ２ (Each of these independently represents an alkylene group, and m and n independently represent integers greater than or equal to 2.) A urethane resin containing a structure derived from a hydrazide compound represented by [formula].

3. A moisture-curing hot-melt adhesive containing the urethane resin described in claim 2.

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