JP2002046244A - Structure having moisture curable resin layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure having an upper layer and a lower layer excellent in water resistance and the adhesiveness to the upper layer and effective for a waterproof material of a parking zone or a factory floor on which a heavy article such as a forkleft or the like passes. SOLUTION: The structure comprises at least two layers, that is, the lower layer, which is obtained from a moisture curable composition containing (A) a polyisocyanate compound and (B) a compound dissociated by moisture to generate active hydrogen, and the upper layer comprising (C) a resin with a JIS-A hardness of 70 or more or a resin with a Shore D hardness of 50 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure in which a lower layer has excellent workability and water resistance and an excellent adhesion to an upper layer. This structure is effective for floors and the like.

[0002]

2. Description of the Related Art A conventional combination of a urethane-based intermediate coating material and a urethane-based upper coating material, or a combination of a urethane-based intermediate coating material and FRP is used for a conventional parking lot or for a floor of a factory where a forklift or the like passes.
Combinations with a system overcoating material have been proposed, but in all cases, urethanes are of two-part mixing type and require weighing and mixing of the materials. In addition, an interlayer primer is required between the middle coat layer and the top coat layer, which requires a lot of work. Furthermore, there is a problem that peeling is likely to occur between the intermediate coating layer and the overcoat layer over time, and a solution is required. Among these, as a moisture-curable urethane composition, Japanese Patent Application Laid-Open No. 57-94056 is known. However, the coating film often swells due to carbon dioxide gas generated when moisture reacts with isocyanate groups during curing. There is a problem that occurs. Moisture dissociation type cross-linking agents such as ketimine and enamine have been proposed in order to suppress the generation of carbon dioxide which causes swelling.
Compositions using an oxazolidine compound proposed in JP-A-93821, JP-A-7-33852, JP-A-7-10949 and the like are materials which do not generate carbon dioxide gas and have a relatively well-balanced performance.

[0003]

SUMMARY OF THE INVENTION The present invention provides a structure having a moisture-curable urethane resin layer as a lower layer and having excellent durability and adhesion to an upper layer.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the lower layer is a polyisocyanate compound, particularly a prepolymer (A) having two or more isocyanate groups at the terminal, and active hydrogen is generated by dissociation with moisture. Obtained from a moisture-curable composition containing a compound (B) having an oxazolidine group at a terminal capable of dissociating in moisture to generate active hydrogen, and wherein the upper layer has a JIS-A hardness of 70 or more or Shore. A structure comprising a resin having a D hardness of 50 or more, particularly a polyurethane resin (C) comprising an isocyanate component containing polyphenylmethane polyisocyanate as a main component and a natural oil and / or a derivative thereof and / or an active hydrogen-containing bisphenol derivative. Provide body.
Hereinafter, the present invention will be further described.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION (B) Used in the lower layer of the present invention
As a compound which dissociates by moisture to generate an active hydrogen compound, active hydrogen is masked by various methods, and N is absorbed by moisture.
Compounds that generate active hydrogen such as H, NH ₂ , OH and the like, for example, ketimine, enamine, aldimine, oxozaridine, compounds having a silanol bond by de-alcoholization with water, among which compounds having an oxazolidine group Is preferably used.

The compound having an oxazolidine group preferably used in the present invention includes (b1) a polyisocyanate compound having two or more isocyanate groups at its terminal and (b1)
2) It is obtained by reacting with N-2-hydroxyalkyloxazolidine. Both (A) a polyisocyanate compound having two or more isocyanate groups at the terminal and (b1) a polyisocyanate compound having two or more isocyanate groups at the terminal have two isocyanate groups.
And a urethane prepolymer prepared by an ordinary method in the presence of an excess of polyisocyanate alone and / or an organic polyisocyanate.

The organic polyisocyanate includes tolylene diisocyanate, diphenylmethane diisocyanate, partially carbodiimidated diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolylene diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, One or a mixture of two or more aromatic diisocyanates, such as xylylene diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and cyclohexane diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate.

The polyols include polyether polyols, polyester polyols, other polyols, and mixed polyols thereof. For example, a polyol produced using a double metal cyanide complex as a catalyst is also included.

Examples of the polyether polyol include one or more polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, trimethylolpropane, glucose, sorbitol, and sucrose, and the like. Oxide, oxide,
Examples thereof include polyols and polyoxytetramethylene polyols obtained by adding one or more kinds of styrene oxide and the like.

Examples of the polyester polyol include one or two of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, trimethylolpropane, and other low-molecular polyols.
Or more and one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, hydrogenated dimer acid or other low molecular dicarboxylic acid or oligomeric acid Examples include condensation polymers and ring-opening polymers such as propiolactone, caprolactone, and valerolactone.

Other polyols include, for example, polycarbonate polyols, polybutadiene polyols,
Examples include hydrogenated polybutadiene polyol and acrylic polyol. Also, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol,
Low molecular polyols such as hexanediol, cyclohexanedimethanol glycerin, trimethylolpropane, glucose, sorbitol, and sucrose are also included.

The polyol is preferably a polyoxyalkylene polyol having a number average molecular weight of 500 to 16000, and 5 to 80% by weight of a butylene ether bond and 0 to 10% by weight of an ethylene ether bond in the polyoxyalkylene polyol. It is preferable to contain the propylene ether bond in the range of 10 to 95% by weight from the viewpoint of curability and water resistance.

The number of terminal isocyanate groups of the polyisocyanate compound is preferably 2 or more, more preferably 2 to 3. Further, the NCO / OH ratio between the isocyanate and the polyol is preferably 1.4 or more, and more preferably 1.4 to 5.0. The residual NCO% is preferably 1 to 20% by weight.

(A) Polyisocyanate compound and (B)
The compounding ratio of the compound that dissociates in moisture to generate an active hydrogen compound is such that the ratio of (A) the NCO group of the polyisocyanate compound to (B) the active hydrogen group of the active hydrogen compound generated by ring opening with moisture is: A range from 0.4 to 4.0 is preferred. With that ratio, the generation of carbon dioxide is small and the storage stability is good.

The polyisocyanate compound preferably has a number average molecular weight of 500 to 8,000. With that molecular weight, the base followability and the curing speed are good. Further, the average number of NCO groups at the terminal of the polyisocyanate compound is preferably from 2.0 to 2.6. If the number is such, the curability and the base followability are good. Further, the NCO / OH ratio between the isocyanate and the polyol is preferably 1.6 or more,
More preferably, it is 1.8 to 4.0. Residual NCO%
Is preferably 1 to 15% by weight.

The reaction ratio between the organic polyisocyanate and N-2-hydroxyalkyloxazolidine is NCO
/OH=0.95 to 3.0 is preferred. With such a reaction ratio, N-2-hydroxyalkyloxazolidine is sufficiently reacted, and storage stability, curing speed, and viscosity are good.

N-2-hydroxyalkyloxazolidine (b2) includes, for example, formaldehyde, acetaldehyde, propylaldehyde, butyraldehyde,
It is a compound obtained by a known condensation reaction between an aldehyde such as benzaldehyde and a dihydroxyalkylamine such as diethanolamine and dipropanolamine.

The number of terminal oxazolidine groups of the urethane oxazolidine prepolymer is preferably 1 to 3. With that number, the extensibility after curing is good. Needless to say, if at least one oxazolidine group is present at the terminal of the urethane oxazolidine prepolymer, the other terminal may be an isocyanate group.

In the composition constituting the lower layer of the present invention, an acid as an oxazolidine dissociation catalyst, an organic solvent, an inorganic filler, a process oil, a plasticizer, a thixotropy It may contain various additives such as an agent, an extender, an ultraviolet inhibitor for maintaining and improving weather resistance, and a stabilizer. These mixtures can be uniformly mixed and can be manufactured by a mixing and kneading apparatus sufficient to ensure the preservability.

Examples of the acid used as the dissociation catalyst include known acids such as salicylic acid, orthophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, melitic acid and anhydrides thereof, and particularly preferred is terephthalic acid. Acids and salicylic acids are used.

As the solvents, usual urethane solvents such as toluene, xylene, terpene and ethyl acetate can be used.

Examples of the thixotropic agent include surface-treated calcium carbonate, polyvinyl chloride powder, finely divided silica, bentonite and the like. In addition, the composition of the present invention may be mixed with a petroleum-based high-boiling aromatic fraction, a petroleum resin and the like.

Examples of the plasticizer include dibutyl phthalate, dioctyl phthalate, diundecyl phthalate,
Examples include ester plasticizers such as dilauryl phthalate, butylbenzyl phthalate, diisodecyl phthalate, dibutyl adipate, dioctyl adipate, diisononyl adipate, dioctyl azelate, and dioctyl sebacate, and phosphate plasticizers such as trioctyl phosphate and triphenyl phosphate. Can be

Examples of the stabilizer include an antioxidant and an ultraviolet absorber. As the inorganic filler, for example, calcium carbonate, calcium oxide, clay, talc,
Titanium oxide, aluminum sulfate, kaolin, diatomaceous earth,
Examples thereof include powders of inorganic compounds such as glass balloons.
The amount added is preferably 5 to 70, more preferably 10 to 60% by weight in the composition.

The upper layer of the structure of the present invention has a hardness of J
Resin (C) having an IS-A hardness of 70 or more, preferably 70 to 100 or more, or a Shore D hardness of 50 or more,
Preferably, it is composed of 50 to 90 or more resins (C). (C) The resin whose hardness is JIS-A hardness 70 or more is
A relatively soft to hard resin or resin composition. The resin having a Shore D hardness of 50 or more is a relatively hard resin or a resin composition. For example, known resin compositions such as urethane-based and unsaturated polyesters such as FRP and acrylic resin can be used. Preferably, isocyanate (c1) containing polyphenylmethane polyisocyanate as a main component and natural oil and / or An active hydrogen compound (c2) of the derivative and / or an active hydrogen-containing bisphenol derivative is mixed and cured, and a resin composition having a hardness of 50 or more measured by a Shore D hardness meter is used.

The JIS-A hardness in the present invention is determined by setting a hardness meter to a rubber hardness meter constant pressure loader (for example, CL-150M, manufactured by Kobunshi Keiki Co., Ltd.). Measure. For Shore D hardness, a rubber hardness meter constant pressure loader (for example, CL-150M,
Set a hardness tester on a polymer meter
The highest value of the hardness is measured at 0 g.

The isocyanate (c1) containing polyphenylmethane polyisocyanate as a main component is MR
Known polyphenylmethane polyisocyanates such as -100, MR-200 (manufactured by Nippon Polyurethane), Cosmonate M-50, and Cosmonate CX-200, and modified products thereof are used.

The active hydrogen compound (c2) is a natural oil and / or a derivative thereof (a natural oil derivative containing active hydrogen) and / or an active hydrogen-containing bisphenol derivative. Is a natural oil such as castor oil, soybean oil, and coconut oil, and / or derivatives thereof. Among them, castor oil having a secondary hydroxyl group and its derivatives are preferably used. Examples of the derivative of the natural oil mentioned here include a transesterification product of the natural oil and a polyhydric alcohol, a polymer of the natural oil, a dicyclopentadiene adduct of the natural oil, and the like.

The bisphenol derivative has an active hydrogen, and examples thereof include an alkylene oxide adduct of a bisphenol epoxy and a reaction product of a bisphenol epoxy with a higher fatty acid. In addition, known polyols, activated alumina powder for preventing foaming, synthetic zeolite powder, and the like, plasticizers, fillers, catalysts, additives for improving weather resistance, and the like can be contained. The product is Praiadec HF-3 manufactured by Dainippon Ink and Chemicals.
000 main agent / curing agent (Shore D hardness 65-75), Priadec HF-3500 main agent / curing agent (Shore D hardness)
Hardness of 70 to 80) is preferably used.

As the active hydrogen compound (c2), the above compounds are preferable, but other compounds may be used as long as the effects of the present invention can be achieved.

The present invention uses (A) a polyisocyanate compound having two or more isocyanate groups at the terminal in the lower layer and (B) a moisture-curable urethane containing an active hydrogen compound dissociated by moisture, and (C) a top coat. By using a resin composition having a cured film hardness of 70 or more according to a JIS-A hardness tester as a layer (upper layer), the finish and workability of the intermediate coating material (lower layer) are excellent, and the intermediate coating material and the upper coating are further applied. Due to the excellent adhesiveness of the material, there is a feature that delamination hardly occurs even when used under severe conditions. Preferably, the compound which dissociates in moisture to generate an active hydrogen compound is an oxazolidine-based compound, and more preferably an isocyanate component containing polyphenylmethane polyisocyanate as a main component and a natural oil and / or a derivative thereof and / or a bisphenol derivative in the overcoat material. The effect can be further enhanced by mixing and curing an active hydrogen component containing a resin composition, and using a resin composition having a cured film hardness of 40 or more measured by a Shore D hardness meter.

The preferred thickness of each layer in the structure of the present invention the lower layer is 0.05~3.0mm / m ^2, the upper layer is 0.05~5.0mm / m ^2. Within this range, durability such as favorable base followability can be obtained. Although such a structure has at least upper and lower layers, a finishing layer or a top coat layer may be laminated on the upper layer depending on the purpose of use, or a substrate may be formed on the lower layer.

The structure of the present invention is used, for example, for parking lots, factory floors and the like. In particular, when applied to waterproofing construction of a parking lot, an undercoat primer is laminated on a base such as concrete, then the structure of the present invention is laminated, and a finishing layer and, if necessary, a top coat layer are further laminated thereon. It is laminated. Of course, an interlayer primer such as a known moisture-curable urethane primer or epoxy primer may be used to enhance the adhesiveness of the upper and lower layers of the structure of the present invention. In addition, in waterproofing construction of a parking lot, it is preferable to apply a urethane-based or epoxy-based primer in advance before applying the intermediate coating material (the lower layer constituent material of the present invention) to the base such as concrete. Before applying the material (the upper layer constituent material of the present invention), the same primer as described above may be applied on the intermediate coating layer in advance. In addition, various kinds of specifications can be set according to the required specifications of finish, such as spraying silica sand or the like on the overcoat layer, or blending it with the overcoat layer to provide a non-slip finish. Further, an acrylic urethane-based, fluorine-based, acrylic-silicon-based top coat may be applied on the overcoat layer for the purpose of improving the weather resistance.

The structure of the present invention is characterized in that the intermediate coating material is excellent in workability and water resistance, and further excellent in adhesion to the top coating material, so that delamination hardly occurs even when used under severe conditions. Further, as a preferred overcoat material, an isocyanate component containing polyphenylmethane polyisocyanate as a main component and an active hydrogen component containing natural oil and / or a derivative thereof and / or a bisphenol derivative are mixed and cured, and the coating film hardness is Shore D hardness meter. The use of a resin composition of 50 or more provides a structure with even more excellent durability.

[0035]

Next, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following, all parts and percentages are by weight unless otherwise specified.

<Synthesis of Component (A)> (Preparation Example 1 of Polyisocyanate Compound) 600 g of polybutylene ether diol having a number average molecular weight of 2,000
(0.3 mol), 400 g (0.13 mol) of polypropylene ether triol having a number average molecular weight of 3000,
191.4 g (1.1 mol) of 4-tolylene diisocyanate, that is, an NCO / OH equivalent ratio of 2.2 was reacted in a flask with stirring at 80 ° C. for 15 hours under a nitrogen stream to give an NCO% of 4. 26% of a BO component-containing polyisocyanate compound (A-1) was obtained.

(Preparation Example 2 of Polyisocyanate Compound)
Preparation Example 1 of Polyisocyanate Compound: Polypropylene ether triol 30 having a number average molecular weight of 3000
Number average molecular weight 3000 instead of 0 g (0.1 mol),
Synthesized in the same manner except that 300 g (0.1 mol) of polyethylene propylene ether triol having an oxyethylene chain content of 8% was used, and the NCO% was 4.22%.
The BO component-containing polyisocyanate compound (A-2) was obtained.

<Synthesis of Component (B)> (Preparation Example 1 of Oxazolidine-Containing Urethane Compound) 500 g of polyethylene propylene ether triol having a number average molecular weight of 4,800 and an oxyethylene chain content of 14%
(0.104 mol) and 500 g (0.25 mol) of a polypropylene ether diol having a number average molecular weight of 2000 were mixed to obtain an oxyethylene chain having an average content of 7.5%, an average number of functional groups of 2.29 and a number average molecular weight of 2820. A polyol was obtained. Further, hexamethylene diisocyanate 143.
3 g (0.853 mol), that is, an NCO / OH equivalent ratio of 2.1 was reacted under stirring in a flask at 80 ° C. for 48 hours under a nitrogen stream to give an NCO% of 3.29% and a molecular weight per molecule. A polyisocyanate compound (b1-1) having a terminal NCO group number of 2.29 was obtained.

Polyisocyanate compound (b1-1) 1
40.8 g and 15.9 g of 2-isopropyl-3 (2-hydroxyethyl) 1,3 oxazolidine, ie NCO
/ OH at 60 ° C. under a nitrogen stream at an equivalent ratio of 1.1
The reaction was carried out while stirring in a flask for a time to obtain an oxazolidine-containing urethane compound (OXZ-1). As a result of measuring the GPC of this composition, it was confirmed that the content of the remaining 2-isopropyl-3 (2-hydroxyethyl) 1,3 oxazolidine was 1% or less.

(Preparation Example 2 of Oxazolidine-Containing Urethane Compound) 20 g (0.033 mol) of polyethylene propylene ether triol having a number average molecular weight of 600 and an oxyethylene chain content of 30% and 270 g of polypropylene ether diol having a number average molecular weight of 600 (0 .45 mol)
Was mixed to obtain a polyol having an average oxyethylene chain content of 2.1%, an average number of functional groups of 2.07, and a number average molecular weight of 600. Furthermore, 174 2,4 tolylene diisocyanate
g (1.0 mol), ie NCO / OH equivalent ratio 2.
The mixture was reacted while stirring in a flask at 60 ° C. for 48 hours under a nitrogen stream at 0 to obtain a polyisocyanate compound (b1-2) having an NCO% of 9.07% and a terminal NCO group number of 2.07 per molecule. Was.

Polyisocyanate compound (b1-2))
48.7 g and 15.9 g of 2-isopropyl-3 (2-hydroxyethyl) 1,3 oxazolidine, ie NCO
/ OH at 60 ° C under a nitrogen stream at an equivalent ratio of 1.05.
The reaction was carried out for 8 hours while stirring in a flask to obtain an oxazolidine-containing urethane compound (OXZ-2). As a result of measuring the GPC of this composition, it was confirmed that the content of the remaining 2-isopropyl-3 (2-hydroxyethyl) 1,3 oxazolidine was 1% or less.

<Compounding compound> Intermediate material (lower layer)
120 in a closed planetary mixer to produce
Calcium carbonate (NS-200, manufactured by Nitto Powder Co., Ltd.) 320 which was dried under reduced pressure at 5 ° C. for 5 hours to adjust the water content to 0.05% or less.
Parts, dried under reduced pressure at 120 ° C. for 5 hours, and 30 parts of fatty acid-treated calcium carbonate (Hakuenka CCR made of Shiraishi calcium) whose water content was adjusted to 0.1% or less, 80 parts of xylene, 90 parts of dioctyl phthalate (hereinafter abbreviated as DOP), 10 parts of a paste in which terephthalic acid and DOP were premixed at a weight ratio of 1: 1 using a roll mixer, 0.6 part of salicylic acid, a polyisocyanate compound (A) and an oxazolidine-containing urethane compound (B) shown in the following table, respectively. After adding a predetermined amount and mixing uniformly, the mixture was defoamed under a reduced pressure of 60 Torr to obtain a moisture-curable urethane compound.

(Examples 1-3, Comparative Examples 1-3) 30 × 3
After applying 200 g / m ^{2 of} Priadec T-120-35 (manufactured by Dainippon Ink and Chemicals) as a primer on the surface of a 0 cm concrete pavement plate in advance, the intermediate coating material (lower layer) shown in Tables 1 and 2 below Is applied at ² kg / m ² and left at room temperature for 7 days. Out topcoat material shown in Table 1 and 2 (upper layer) 1.5 kg / m ² was coated on the rear thereon, foundation structure consisting of upper and lower layers are stacked to stand at room temperature for 7 days (concrete pavement plate)
Get. [Test Method] (Durability test) The above laminate is immersed in warm water at 60 ° C for 28 days. After taking out the sample and leaving it at room temperature for 3 hrs, a stationary test was carried out with a stationary tester NKA-187 (manufactured by Nikken Co., Ltd.) under the condition of an installation pressure of 40 kg / cm2, and between the overcoat layer and the intermediate coat layer. The number of times of installation until an abnormality such as peeling occurred was measured. In addition, when abnormality such as peeling did not occur even when the number of times of deferment was 3000, it was determined that there was no abnormality. (Curability of intermediate coating material) The intermediate coating material is flowed at a ratio of 1.5 mm on a glass plate (30 x 30 cm) on which mold paper is attached around all sides with a frame, and the conditions are set at 25 ° C x 50%. The film was left standing, touched with a finger, and the time until the movement of the coating film disappeared was measured.

(Non-foaming test of intermediate coating material) An intermediate coating material was flowed at a ratio of 2 mm on a slate plate (30 × 30 cm) surrounded by a frame on all sides, and cured at 50 ° C. × 90%. After that, the surface of the coating film was observed for blisters and pinholes. A sample without blisters and pinholes was rated as "O", and a sample with blisters and pinholes was rated as "x".

[Blending conditions and test results]

[Table 1] PF570 / E570: Hardness of cured coating JIS-A 92 (manufactured by Dainippon Ink and Chemicals) HF3500: Hardness of cured coating Shore D 75 (manufactured by Dainippon Ink and Chemicals)

[Formulation conditions and test results]

[Table 2] In Comparative Example 3, a two-component curable urethane, Sansilal N (manufactured by Mitsui Toatsu Chemicals, Inc.) was used as an intermediate coating material.

When the composition (B) containing no compound capable of dissociating in moisture to generate an active hydrogen compound was used as the intermediate coating material in Comparative Examples 1 and 2, the curability, non-foaming property and durability were poor. Met. When the two-component curable urethane was used instead of the moisture-curable urethane of Comparative Example 3, the curability and durability were poor.

[0048]

The structure of the present invention is characterized in that the lower layer is excellent in water resistance and the adhesiveness to the upper layer is excellent, so that delamination hardly occurs even when used under severe conditions.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F100 AK01B AK01C AK41A AR00A BA02 BA03 BA06 BA07 GB01 JB07 JB20A JK06 JK12B JK12C JL11 YY00A YY00B YY00C

Claims (6)

[Claims] 1. A polyisocyanate compound (A) having a lower layer
And a moisture-curable composition containing a compound (B) that dissociates in moisture to generate active hydrogen, and the upper layer is a resin (C) having a JIS-A hardness of 70 or more.
A structure consisting of at least two layers. 2. The method according to claim 1, wherein the lower layer is a polyisocyanate compound (A).
And a compound (B) containing a compound (B) capable of dissociating in moisture to generate active hydrogen, and a resin (C) having an upper layer having a Shore D hardness of 50 or more.
A structure consisting of at least two layers. 3. The structure according to claim 1, wherein the compound that dissociates in moisture to generate active hydrogen is a compound having an oxazolidine group at a terminal. 4. A resin (C) obtained by reacting (c1) an isocyanate component mainly composed of polyphenylmethane polyisocyanate with (c2) a natural oil and / or a derivative thereof and / or an active hydrogen-containing bisphenol derivative. The structure according to claim 2 or 3, wherein the structure is a polyurethane resin having a Shore D hardness of 50 or more. 5. A compound having an oxazolidine group at a terminal is obtained by reacting (b1) a polyisocyanate compound having two or more isocyanate groups at a terminal with (b2) an N-2-hydroxyalkyloxazolidine. The structure according to claim 3 or 4, which is a urethane oxazolidine prepolymer having the following formula: 6. The polyisocyanate compound (A) is a prepolymer having two or more isocyanate groups at the terminal obtained by reacting a polyisocyanate compound with a polyoxyalkylene polyol, and having a butylene ether bond in the polyoxyalkylene polyol. 5 to 80% by weight, 0 to 10% by weight of an ethylene ether bond and 10 to 95% by weight of a propylene ether bond.