JP6836713B2 - Moisture curable polyurethane hot melt composition - Google Patents

Description

The present invention relates to a moisture curable polyurethane hot melt composition.

For materials with curved or uneven surfaces used for building materials such as kitchen doors, closet doors, window frames, and furniture such as counter tables, olefin sheets with wood grain printing are used to improve the design. Wrapping processing is widely performed in which synthetic resin decorative sheets such as PET (polyethylene terephthalate) sheets, resin-processed paper, and surface covering sheets such as attached boards are continuously wrapped and attached using an adhesive.

When performing the lapping process, a strong initial strength and a durable adhesive such as hydrolysis resistance and heat resistance are required for the material having a curved surface or unevenness on the surface.

As an adhesive that can be used in the wrapping process, for example, a urethane prepolymer having an isocyanate group obtained by reacting a polyol containing an alicyclic polyester polyol and an aliphatic polyester polyol with 4,4'-diphenylmethane diisocyanate is used. Moisture curable polyurethane hot melt adhesives containing are known (see, for example, Patent Document 1).

Although the moisture-curable polyurethane hot-melt adhesive has excellent initial adhesiveness, improvements in hydrolysis resistance and thermal stability have been required.

Japanese Unexamined Patent Publication No. 2013-87150

An object to be solved by the present invention is to provide a moisture-curable polyurethane hot melt composition having excellent initial strength, hydrolysis resistance, and thermal stability.

The present invention is a urethane prepolymer (i) having an isocyanate group and having a structure derived from a polyol (A) containing a polyester polyol (A-1) represented by the following formula (1), and a polyfunctional isocyanate (ii). The present invention relates to a moisture-curable polyurethane hot melt composition containing.

（式（１）中、Ｒ^１及びＲ^２は、それぞれ独立して炭素原子数が偶数である直鎖のアルキレン基を示し、Ｒ^１及びＲ^２の有する炭素原子数の合計は１２以上であり、ｎは３〜４０の整数を示す。）

(In the formula (1), R ¹ and R ² each independently represent a linear alkylene group having an even number of carbon atoms, and the total number of carbon atoms of ^{R 1} and R ^{2 is 12 or more.} , N represents an even number from 3 to 40.)

The moisture-curable urethane hot-melt composition of the present invention is excellent in initial strength, hydrolysis resistance, and thermal stability. Therefore, the moisture-curable urethane hot melt composition of the present invention can be used for building interior materials such as lower leg doors, closet doors, kitchen doors, frame materials, frame materials, peripheral edges, skirting boards, counter tables, furniture top plates, etc. It can be particularly preferably used as an adhesive used for wrapping furniture.

The moisture-curable urethane hot-melt composition of the present invention has an isocyanate group-containing urethane prepolymer (i) having a structure derived from the polyol (A) containing the polyester polyol (A-1) represented by the following formula (1). , And polyfunctional isocyanate (ii).

（式（１）中、Ｒ^１及びＲ^２は、それぞれ独立して炭素原子数が偶数である直鎖のアルキレン基を示し、Ｒ^１及びＲ^２の有する炭素原子数の合計は１２以上であり、ｎは３〜４０整数を示す。）

(In the formula (1), R ¹ and R ² each independently represent a linear alkylene group having an even number of carbon atoms, and the total number of carbon atoms of ^{R 1} and R ^{2 is 12 or more.} , N represents an even number of 3 to 40.)

It is essential to use the polyester polyol (A-1) represented by the formula (1) in order to obtain excellent initial strength.

^{R 1} in the formula (1) is a linear alkylene group having an even number of carbon atoms, and can be appropriately selected within a range in which the total number of carbon atoms of ^{R 1} and R ^{2 is 12 or more.} it can. Among them, a linear alkylene group having an even number of carbon atoms of 4 or more, more preferably 4 to 12, and even more preferably 4 to 8 is preferable from the viewpoint of obtaining more excellent initial strength.

R ² in the formula (1), the a linear alkylene group having the number of carbon atoms independently is an even number and R ^1, the total number of carbon atoms possessed by R ¹ and R ² is 12 or greater It can be selected as appropriate within the above range. Among them, a linear alkylene group having an even number of carbon atoms of 4 or more, more preferably 6 to 12, is preferable from the viewpoint of obtaining more excellent initial strength.

N in the formula (1) represents an integer of 3 to 40. Among them, 5 to 25 is preferable, and 9 to 15 is more preferable, from the viewpoint of obtaining more excellent initial strength.

As a specific example of the polyester polyol (A-1), for example, a condensation reaction product of a linear diol having an even number of carbon atoms and a polybasic acid having an even number of carbon atoms can be used.

As the linear diol having an even number of carbon atoms, for example, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol and the like are used. Can be done. These diols may be used alone or in combination of two or more. Among these, one or more diols selected from the group consisting of 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol should be used from the viewpoint of obtaining more excellent initial strength. Is preferable.

As the polybasic acid having an even number of carbon atoms, for example, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dodecamethylenedicarboxylic acid and the like can be used. These tabasic acids may be used alone or in combination of two or more. Among these, it is preferable to use one or more polybasic acids selected from the group consisting of adipic acid, sebacic acid, and dodecanedioic acid from the viewpoint of obtaining more excellent initial strength, and sebacic acid and / or dodecanniic acid is preferable. It is more preferable to use an acid.

The number average molecular weight of the polyester polyol (A-1) is preferably in the range of 500 to 10,000, more preferably in the range of 700 to 8,000, from the viewpoint of obtaining more excellent initial strength. The range of 800 to 5,000 is more preferable. The number average molecular weight of the polyester polyol (A-1) is a value measured under the following conditions by a gel permeation chromatography (GPC) method.

Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 This "TSKgel G2000" (7.8 mm ID x 30 cm) x 1 Detector: RI (Differential Refractometer)
Column temperature: 40 ° C
Eluent: tetrahydrofuran (THF)
Flow velocity: 1.0 mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

The content of the polyester polyol (A-1) is preferably in the range of 10 to 85% by mass, preferably in the range of 20 to 70% by mass, from the viewpoint of obtaining more excellent initial strength. Is more preferable.

Examples of the polyol (A) include polyether polyols such as polyethylene glycol, polypropylene glycol, and polyether polyols in addition to the polyester polyol (A-1); aliphatic polyester oars other than the polyester polyol (A-1), and fragrance. Polyester polyols such as group polyester polyols; polyols such as polycarbonate polyols, acrylic polyols, and dimerdiols can be used. These polyols may be used alone or in combination of two or more. Among these, it is preferable to use one or more polyols selected from the group consisting of polyether polyols, polycarbonate polyols, and aromatic polyester polyols from the viewpoint of obtaining more excellent melt viscosity and hydrolysis resistance. , Polypropylene glycol, polycarbonate polyol, and aromatic polyester polyol are more preferred.

The number average molecular weight of the polyol other than the polyester polyol (A-1) is in the range of 500 to 20,000 from the viewpoint of obtaining more excellent mechanical strength of the coating film and hydrolysis resistance. Is preferable, and the range of 700 to 8,000 is more preferable. The number average molecular weight of these polyols shows the values obtained by measurement in the same manner as the polyester polyol (A-1).

As the urethane prepolymer (i), for example, a reaction product of the polyol (A) and the polyisocyanate (B) can be used.

As the polyisocyanate (B), for example, diisocyanate (B-1), polyfunctional isocyanate (B-2) other than diisocyanate, or the like can be used.

Examples of the diisocyanate (B-1) include aromatic polyisocyanates such as diphenylmethane diisocyanate, phenylenediocyanate, tolylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and xylylene diisocyanate. Diisocyanates such as aliphatic or alicyclic polyisocyanates such as isocyanate and tetramethylxylylene diisocyanate can be used. These diisocyanates may be used alone or in combination of two or more.

Examples of the polyfunctional isocyanate (B-2) other than the diisocyanate include the isocyanurate compound (B-2-1) of the diisocyanate (B-1); the adduct compound; the bullet compound; the allophanate compound; the polymethylene polyphenyl polyisocyanate. A polyfunctional polyisocyanate such as (B-2-2) can be used. These polyfunctional isocyanates may be used alone or in combination of two or more. In the present invention, the "polyfunctional" of the "polyfunctional isocyanate (B-2)" means that it has three or more isocyanate groups.

The polyisocyanate (B) preferably contains a diisocyanate (B-1) from the viewpoint of obtaining even more excellent hydrolysis resistance, and the diisocyanate (B-1) and the isocyanurate compound (B-1) are preferably contained. It is more preferable to contain -2-1) and / or the polymethylene polyphenyl polyisocyanate (B-2-2). Further, it is preferable to use diphenylmethane diisocyanate as the diisocyanate (B-1), and it is preferable to use an aliphatic isocyanurate compound as the isocyanurate compound (B-2-1).

When the diisocyanate (B-1) is used, the content is preferably in the range of 10 to 90% by mass in the polyisocyanate (B) from the viewpoint of obtaining even more excellent hydrolysis resistance and adhesiveness. The range of ~ 80% by mass is more preferable.

When the isocyanurate compound (B-2-1) is used, the content is in the range of 0.1 to 30% by mass in the polyisocyanate (B) from the viewpoint of obtaining more excellent hydrolysis resistance. It is preferably in the range of 5 to 25% by mass, more preferably in the range of 10 to 20% by mass.

When the polymethylene polyphenyl polyisocyanate (B-2-2) is used, the content is 0.1 to 30% by mass in the polyisocyanate (B) from the viewpoint of obtaining more excellent hydrolysis resistance. The range of 5 to 25% by mass is more preferable, and the range of 10 to 20% by mass is further preferable.

The polymethylene polyphenyl polyisocyanate (B-2-2) is specifically represented by the following formula (2), and preferably represents an integer in which n is 1 to 5 in the formula (2). It is a thing.

（式（２）中、ｎは１以上の整数である。）

(In equation (2), n is an integer of 1 or more.)

Examples of the polymethylene polyphenyl polyisocyanate (B-2-2) include "Millionate MR-100" and "Millionate MR-200" manufactured by Tosoh Corporation, and "WANATE PM-200" manufactured by Manka Japan Co., Ltd. "WANNAME PM-400", "Cosmonate M-1500" manufactured by Mitsui Chemicals, Inc., "Boranate M-595" manufactured by Dow Chemicals Co., Ltd., etc. can be obtained as commercial products.

The urethane prepolymer (i) having an isocyanate group is obtained by reacting the polyol (A) with the polyisocyanate (B), and is used in the air or on a housing or a cover to which the urethane prepolymer is applied. It has an isocyanate group at the end of the polymer or in the molecule that can react with the water present in the polymer to form a crosslinked structure.

As a method for producing the urethane prepolymer (i), for example, the polyisocyanate (B) is dropped into a reaction vessel containing the polyol (A) and then heated to have an isocyanate group contained in the polyisocyanate (B). However, it can be produced by reacting with the hydroxyl group of the polyol (A) under conditions that are excessive.

When the urethane prepolymer (i) is produced, the equivalent ratio of the isocyanate group of the polyisocyanate (B) to the hydroxyl group of the polyol (A) ([isocyanate group / hydroxyl group]) is higher than the initial strength. The range is preferably in the range of 1.1 to 5, and more preferably in the range of 1.5 to 3 from the viewpoint of further improvement and obtaining an appropriate melt viscosity.

When producing the urethane prepolymer (i), a urethanization catalyst can be used if necessary. The urethanization catalyst can be added as appropriate at any stage of the reaction.

As the urethanization catalyst, for example, a nitrogen-containing compound such as triethylamine, triethylenediamine, N-methylmorpholine; a metal salt such as potassium acetate, zinc stearate, tin octylate; an organic metal compound such as dibutyltin dilaurate is used. be able to. These catalysts may be used alone or in combination of two or more.

The isocyanate group content of the urethane prepolymer (i) obtained by the above method (hereinafter, abbreviated as "NCO%") is in the range of 0.5 to 10% from the viewpoint of initial strength. Preferably, the range of 1.7 to 5% is more preferable. The NCO% of the urethane prepolymer is a value measured by the potentiometric titration method in accordance with JISK1603-1: 2007.

The melt viscosity of the urethane prepolymer (i) is preferably in the range of 1,000 to 20,000 mPa · s at 120 ° C. from the viewpoint of further improving workability and initial strength. More preferably, it is in the range of 000 to 13,000 mPa · s. The melt viscosity at 120 ° C. indicates a value measured by a cone plate viscometer (manufactured by ICI).

The polyfunctional isocyanate (ii) is an essential component for obtaining excellent thermal stability.

As the polyfunctional isocyanate (ii), the same one as the polyfunctional isocyanate (B-2) used as a raw material for the urethane prepolymer (i) can be used. Among these, diisocyanate (ii-1), isocyanurate compound of diisocyanate (ii-2), adduct compound of diisocyanate (ii-3), and bullet compound of diisocyanate (iii-3), from the viewpoint of obtaining even more excellent thermal stability. It is preferable to use one or more compounds selected from the group consisting of ii-4) and polymethylene polyphenyl polyisocyanate (ii-5), and isocyanurate compound (ii-2) and / or polymethylene polyphenyl. Polyisocyanate (ii-5) is more preferred.

The blending amount of the polyfunctional isocyanate (ii) is in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the urethane prepolymer (i) from the viewpoint of obtaining even more excellent thermal stability. It is preferably in the range of 0.5 to 10 parts by mass, and more preferably.

The moisture-curable polyurethane hot-melt composition of the present invention may be composed only of the urethane prepolymer (i) and the polyfunctional isocyanate (ii), but may contain other additives as necessary. May be.

As the other additives, for example, antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent whitening agents, silane coupling agents, waxes, thermoplastic resins and the like are used. Can be done. These additives may be used alone or in combination of two or more. Among these, it is preferable to use a silane coupling agent from the viewpoint of obtaining even more excellent initial strength, hydrolysis resistance, and thermal stability.

Examples of the silane coupling agent include silane coupling agents having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; 2- (3,4-epylcyclohexyl) ethyltrimethoxysilane and 3-glycidoxy. A silane coupling agent having an epoxy group such as propylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane; p-styryltri Silane coupling agent having a styryl group such as methoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, etc. Silane coupling agent having a methacryloyl group; silane coupling agent having an acryloyl group such as 3-acryloxypropyltrimethoxysilane; N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (Aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N -(Vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride or other amino group-bearing silane coupling agent; 3-willedpropyltrialkoxysilane or other Willed group-bearing silane coupling agent A silane coupling agent having a mercapto group such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; a silane coupling agent having a sulfide group such as bis (triethoxysilylpropyl) tetrasulfide; A silane coupling agent having an isocyanurate skeleton such as trimethoxysilylpropyl) isocyanurate; a silane coupling agent having an isocyanate group such as 3-isocyanuppropyltriethoxysilane can be used. These silane coupling agents may be used alone or in combination of two or more.

When the silane coupling agent is used, the blending amount is, for example, in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the urethane prepolymer (i).

The moisture-curable urethane hot-melt composition of the present invention obtained by the above method is excellent in initial strength, hydrolysis resistance, and thermal stability. Therefore, the moisture-curable urethane hot melt composition of the present invention can be used for building interior materials such as lower leg doors, closet doors, kitchen doors, frame materials, frame materials, peripheral edges, skirting boards, counter tables, furniture top plates, etc. It can be particularly preferably used as an adhesive used for wrapping furniture.

As a method of wrapping using the moisture-curable polyurethane hot-melt composition of the present invention, for example, the moisture-curable polyurethane hot-melt composition is melted at a temperature of 100 to 120 ° C., and then melted on a substrate. Examples thereof include a method in which the moisture-curable polyurethane hot melt composition is applied and then the sheet or film is pressure-bonded by a known wrapping device.

Examples of the method for applying the melted moisture-curable polyurethane hot melt composition include a method using a knife coater, a head coater, a slit coater, a T-die coater, a roll coater, and the like.

The thickness of the coating material of the moisture-curable polyurethane hot-melt composition is appropriately determined depending on the intended use, and is, for example, in the range of 1 to 200 μm.

As the base material, for example, natural wood, plywood, MDF (medium density fiberboard), wood base material such as particle board; metal base material such as iron; plastic board, aluminum and the like can be used. The base material may have a portion having a complicated shape such as a groove portion, an R portion, and an inverted R portion.

As the sheet or film, for example, a sheet or film obtained by using a resin such as polyester, polyamide, polystyrene, polycarbonate, vinyl chloride, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyethylene, polypropylene; paper; metal. Foil; a protruding plate or the like can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Example 1]
In a four-necked flask equipped with a thermometer, a stirrer, and an inert gas inlet, a polyester polyol (reactant of 1,6-hexanediol and dodecanedioic acid, number average molecular weight: 3,500, hereinafter "HG / DDA" (Abbreviated as "PPG") is charged in 33 parts by mass and polypropylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as "PPG") is charged in 48 parts by mass and heated under reduced pressure at 100 ° C. to increase the water content in the flask. Was dehydrated to 0.05% by mass or less.
Next, the inside of the flask was cooled to 70 ° C., and 13 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI") melted at 70 ° C., polymethylene polyphenyl polyisocyanate (manufactured by Tosoh Corporation, """MillionateMR-200", hereinafter abbreviated as "Polymeric MDI") 3 parts by mass and 3 parts by mass of an isocyanurate compound of hexamethylene diisocyanate (hereinafter, abbreviated as "HDI nurate") are added, and NCO is added under a nitrogen atmosphere. A urethane prepolymer was obtained by reacting at 100 ° C. for about 3 hours until the% became constant.
A moisture-curable polyurethane hot melt composition was obtained by blending 3 parts by mass of polypeptide MDI with respect to 100 parts by mass of this urethane prepolymer.

[Examples 2 to 5 and Comparative Example 1]
A urethane prepolymer was obtained in the same manner as in Example 1 except that the types and amounts of the polyol (A), polyisocyanate (B), and polyfunctional isocyanate (ii) used were changed as shown in Table 1, and the moisture-curable polyurethane was obtained. A hot melt composition was obtained.

[Evaluation method of initial strength]
The moisture-curable polyurethane hot-melt compositions obtained in Examples and Comparative Examples were each melted at a temperature of 120 ° C. for 1 hour. The adhesive was applied onto a polyethylene terephthalate sheet using an applicator so as to have a thickness of 50 μm. MDF (medium density fiberboard) was laminated on the coating layer and crimped with a crimping roller. After 5 minutes from crimping, a load of 75 g was applied to a 25 mm wide test piece in the 90 ° direction, and the peeling length (mm) of the polyethylene terephthalate sheet after 15 minutes was measured. evaluated.
"○": Peeling length is less than 5 mm "×": Peeling length is 5 mm or more

[Evaluation method of hydrolysis resistance]
The moisture-curable polyurethane hot-melt compositions obtained in Examples and Comparative Examples were each melted at a temperature of 120 ° C. for 1 hour. The adhesive was applied onto a polyliethylene terephthalate sheet using an applicator so as to have a thickness of 50 μm. MDF was laminated on the coating layer and crimped with a crimping roller. The obtained test piece was cured under the conditions of 23 ° C. and 50% humidity for 5 days, and then polyethylene was applied to a width of 25 mm and a load of 70 g in the 90 ° direction under an atmosphere of 85 ° C. and 85% humidity. The number of days until the terephthalate sheet was peeled off by 40 mm or more was measured and evaluated as follows.
"○": 20 days or more "×": less than 20 days

[Evaluation method of thermal stability]
The moisture-curable polyurethane hot-melt compositions obtained in Examples and Comparative Examples were continuously heated at 120 ° C. for 24 hours under nitrogen encapsulation, and the rate of change in melt viscosity before and after that ([melt viscosity after continuous heating]). / [Melting viscosity before continuous heating]) was measured and evaluated as follows. As for the melt viscosity of the moisture-curable polyurethane hot-melt composition, 1 ml of the moisture-curable polyurethane hot-melt composition was sampled, and the melt viscosity was measured with a cone plate viscometer (40P cone, rotor rotation speed; 50 rpm). ..
"○": Change rate is less than 2 "×": Change rate is 2 or more

The abbreviations in Table 1 indicate the following.
"HG / SEBA": Reactant of 1,6-hexanediol and sebacic acid, number average molecular weight: 3,500
"HG / AA": Reactant of 1,6-hexanediol and adipic acid, number average molecular weight: 3,500
-"PEs2": Reactants of ethylene glycol, neopentyl glycol, isophthalic acid, and terephthalic acid, number average molecular weight: 2,600

It was found that Examples 1 to 5 of the moisture-curable polyurethane hot-melt composition of the present invention were excellent in initial strength, hydrolysis resistance, and thermal stability.

On the other hand, No. 1 is an embodiment in which another polyester polyol is used instead of the polyester polyol (A-1), but the initial strength and thermal stability are poor.

Claims (1)

It contains a urethane prepolymer (i) having an isocyanate group and a structure derived from the polyol (A) containing the polyester polyol (A-1) represented by the following formula (1), and a polyfunctional isocyanate (ii) .
The polyfunctional isocyanate (ii) is an isocyanurate compound of diisocyanate (ii-2), an adduct compound of diisocyanate (ii-3), a bullet compound of diisocyanate (ii-4), and a polymethylene polyphenyl polyisocyanate (ii). moisture-curable polyurethane hot melt composition comprising one or more compounds der Rukoto selected from the group consisting of -5).

(In the formula (1), R ¹ and R ² each independently represent a linear alkylene group having an even number of carbon atoms, and the total number of carbon atoms of ^{R 1} and R ² is 10 or more. , N represents an even number from 3 to 40.)