WO2011081409A2

WO2011081409A2 - Substituted aminosilane having hydroxy group and silane-modified polyurethane prepolymer prepared using same

Info

Publication number: WO2011081409A2
Application number: PCT/KR2010/009424
Authority: WO
Inventors: Sang Hyun Lee; Ju Ai Jung; In Ha Park; Joon Mo Lee
Original assignee: SKC Co Ltd
Current assignee: SKC Co Ltd
Priority date: 2009-12-30
Filing date: 2010-12-28
Publication date: 2011-07-07
Anticipated expiration: 2012-06-30
Also published as: WO2011081409A3

Abstract

A silane-modified polyurethane prepolymer which is prepared by reacting an isocyanate-terminated polyurethane prepolymer with an end-capping agent comprising an substituted aminosilane having a hydroxy group or a mixture thereof with two or more hydroxyl substituted aminosilanes, has an improved viscosity, superior hardness, and enhanced durability. Accordingly the silane-modified polyurethane prepolymer is useful for preparing a polyurethane for sealing, coating, or bonding materials.

Description

SUBSTITUTED AMINOSILANE HAVING HYDROXY GROUP AND

SILANE-MODIFIED POLYURETHANE PREPOLYMER PREPARED USING SAME

FIELD OF THE INVENTION

The present invention relates to a novel aminosilane having a hydroxy substituent and a silane-modified polyurethane prepolymer prepared using the same.

BACKGROUND OF THE INVENTION

Silane-modified polyurethane prepolymers such as silylated polyurethane and silane- terminated polyurethane have been used for sealing, coating, or bonding articles.

Various methods for preparing such silane-modified polyurethane prepolymers have been developed. For example, US Patent No. 5,990,257 discloses a method for preparing a silane-modified polyurethane prepolymer comprising the steps of subjecting a polyether polyol to a reaction with a diisocyanate to obtain a hydroxy-terminated polyurethane prepolymer, and conducting a reaction of the prepolymer with isocyanate silane-containing isocyanate.

Further, US Patent Nos. 6,989,429, 3,979,344, and 4,645,816 disclose a method for preparing silane-modified polyurethane prepolymer by end-capping a isocyanate-terminated polyurethane prepolymer prepared by treating a polyether polyol with diisocyanate with a primary aminosilane, and EP Patent No. 0831 108 and US Patent No. 6,545,087 disclose a method for preparing silane-modified polyurethane prepolymer by treating an isocyanate- terminated polyurethane prepolymer prepared by the same method as above with an aspartate- functional silane having a secondary amino group.

However, the reaction of the amino group with the isocyanate group in the above method also generates urea bonds, causing the prepolymer to become undesirably viscouse.

In order to resolve the above problems, US Patent No. 6,762,270 discloses a method comprising the step of end-capping an isocyanate-terminated polyurethane prepolymer with secondary aminosilanes together with mono-ols.

However, there has been a need for developing a polyurethane prepolymer which is useful for preparing a polyurethane having an improved viscosity, superior hardness, and enhanced durability.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a novel aminosilane derivative useful for a preparation of a silane-modified polyurethane having an improved viscosity, superior hardness, and enhanced durability.

It is another object of the present invention to provide a silane-modified polyurethane prepolymer having an improved viscosity, superior hardness, and enhanced durability, which is prepared by using the aminosilane or a mixture thereof with two or more hydroxyl- substituted aminosilanes.

In accordance with an aspect of the present invention, there is provided a substituted aminosilane having a hydroxy. group of formula (I):

X

HO— R¹— N— R²-Si Y

A Z (I)

wherein,

A is H or -R³OH;

R to R^J are each independently C_1-5 alkylene;

alkyl or C_1-4 alkoxy; and

each independently C_1-4 alkoxy. In accordance with a further aspect of the present invention, there is provided an end- capping agent for preparing a silane-modified polyurethane prepolymer, which comprises the substituted arninosilane having a hydroxy group of formula (I) or a mixture thereof with two or more hydroxyl substituted aminosilanes.

In accordance with another aspect of the present invention, there is provided a method for preparing the substituted arninosilane having a hydroxy group or the mixture thereof with two or more hydroxyl substituted aminosilanes which comprises subjecting an arninosilane of formula (II) to a reaction with C_2-5 alkylene oxide:

wherein,

R² is C_1-5 alkylene;

X is C_1-4 alkyl or C_1-4 alkoxy; and

Y and Z are each independently C_1-4 alkoxy.

In accordance with still further aspect of the present invention, there is provided a silane-modified polyurethane prepolymer having a terminal alkoxysilane group, which is prepared by treating an isocyanate-terminated polyurethane prepolymer with the end-capping agent. BRIEF DESCRIPTION OF DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of the invention taken in conjunction with the following accompanying drawings, which respectively show:

FIG. 1 : an infrared (IR) spectrum of aminopropyltriethoxysilane, a source material; FIG. 2 : a gel permeation chromatography (GPC) scan of the aminopropyltriethoxysilane;

FIG. 3 : an infrared spectrum of the compound obtained in Example 1 ;

FIG. 4 : a gel permeation chromatography scan of the compound obtained in Example 1 ;

FIG. 5 : a gel permeation chromatography scan of the compound obtained in Example

3; and

FIG. 6 : an infrared spectrum of the compound obtained in Example 4. DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a detailed description of the present invention is given.

The present invention is characterized in that a substituted aminosilane having a hydroxy group or a mixture thereof with two or more hydroxyl substituted aminosilanes is prepared by subjecting a primary aminosilane to an addition reaction with an alkylene oxide to remove an active hydrogen boned to nitrogen atom of the aminosilane and to introduce a substituted alkylene group having a hydroxy functioal group.

Accordingly, the substituted aminosilane having a hydroxy group of the present invention has a structure of formula (I):

X

HO— R¹— N— R²-Si Y

A Z (I)

wherein,

A is H or -R³OH;

R¹ to R³ are each independently C_\

X is C_1-4 alkyl or C_1-4 alkoxy; and Y and Z are each independently C_1-4 alkoxy.

Preferably, R to R are each independently ethylene, propylene, isopropylene, butylenes, or isobutylene, X is methyl, methoxy, or ethoxy, and Y and Z are each independently methoxy or ethoxy.

The molecular weight of the substituted aminosilane having a hydroxy group is in the range of 250 to 500.

Examples for the substituted aminosilane having a hydroxy group include (hydroxyethyl)aminopropyltriethoxysilane, (hydroxyisopropyl)aminopropyltriethoxysilane, bis-(hydroxyethyl)aminopropyltriethoxysilane, and bis- (hydroxyisopropyl)aminopropyltriethoxysilane.

The substituted aminosilane having a hydroxy group or the mixture thereof with two or more hydroxyl substituted aminosilanes is prepared by a method which comprises subjecting the aminosilane of formula (II) to a reaction with C_2-5 alkylene oxide:

wherein, R is Ci_-5 alkylene, X is C_1-4 alkyl or C alkoxy, and Y and Z are each independently CM alkoxy.

Examples for the C_2-5 alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and a mixture thereof, and the C_2-5 alkylene oxide is used in an amount corresponding to 1 to 5 equivalents based on the aminosilane of formula (II).

The reaction of the aminosilane with the C_2-5 alkylene oxide is conducted at the temperature ranging from 50 ^°C to 140 ^°C , preferably from 60 °C to 80 °C , and a reaction pressure is about 5kgf under vacuum.

Further, a catalyst such as lithium nitrate and calcium nitrate may be used in the reaction. The substituted aminosilane having a hydroxy group or the mixture thereof with two or more hydroxyl substituted aminosilanes prepared according to the preparation method, are useful for preparing a silane-modified polyurethane prepolymer as an end-capping agent.

Therefore, the present invention provides an end-capping agent for preparing a silane- modified polyurethane prepolymer, which comprises the substituted aminosilane having a hydroxy group of formula (I) or the mixture thereof with two or more hydroxyl substituted aminosilanes.

Preferably, the end-capping agent composed of a mixture of the compound of the formula (I) in which A is H, and the compound of the formula (I) in which A is -R³OH in a weight ratio of 1 : 1 to 1 :3.

The present invention provides a silane-modified polyurethane prepolymer which is prepared by using the end-capping agent.

Particularly, the silane-modified polyurethane prepolymer is prepared by a method comprising the steps of: preparing an isocyanate-terminated polyurethane prepolymer; and treating the isocyanate-terminated polyurethane prepolymer with the end-capping agent.

Preferably, the amount of the isocyanate terminal group is of 0.2 to 1.0 mol% based on the isocyanate-terminated polyurethane prepolymer. The number average molecular weight of the isocyanate-terminated polyurethane prepolymer is in the range of 8,000 to 60,000, preferably 18,000 to 35,000.

The polyurethane prepolymer may be prepared by a method which comprises subjecting aromatic, aliphatic, or cycloaliphatic isocyanates to a polymerization with polyether diols or polyether triols.

The aromatic, aliphatic, or cycloaliphatic isocyanates contains the isocyanate group in an amount of 20 to 40 mol%. Examples for the aromatic, aliphatic, or cycloaliphatic isocyanates include toluene 2,4-diisocyanate(TDI), methylene diphenyldiisocyanate(MDI), isophorone diisocyanate(IPDI), dicyclomethane-4,4'-diisocyanate(H12MDI), hexamethylene diisocyanate(HDI), and a mixture thereof.

The polyether diol and polyether triol has a number average molecular weight of 400 to 20,000, and examples for the polyether diol and polyether triol include polypropylene glycol (PPG) and poly(tetramethylene ether) glycol (PTMEG).

The aromatic, aliphatic, or cycloaliphatic isocyanates are used with the polyether diol or polyether triol in an amount corresponding to an equivalent ratio of isocyanate group to hydroxy group of 1 :0.55 to 1 : 1.

The step for preparing the isocyanate-terminated polyurethane prepolymer is preferably conducted until the amount of the isocyanate group is ranging from 0.2 to 1.0 mol% based on the isocyanate-terminated polyurethane prepolymer.

Further, the isocyanate-terminated polyurethane prepolymer and the end-capping agent are used in a weight ratio of 49: 1 to 4: 1.

The silane-modified polyurethane prepolymer prepared according to the preparation method comprises a terminal alkoxysilane group, and have a number average molecular weight ranging from 10,000 to 100,000 and a viscosity ranging from 7,000 to 50,000 cPs.

The silane-modified polyurethane prepolymer is useful for preparing a polyurethane polymer for sealing, coating, or bonding articles.

For example, the polyurethane polymer for sealing may prepared by a method comprising the step of : mixing the silane-modified polyurethane prepolymer with a plasticizer, a moisture scavenger, calcium carbonate, a light stability, fumed silica, and a colorant, for 10 to 30 min, preferably 20 min to obtain a suspension; and adding N-aminoethyl-3-aminopropyl- methyldimethoxysilane and dibutyltin bis(acetylacetonate) to the suspension .

A sealant comprising the polyurethane polymer has a viscosity of 25,000 to 60,000 cPs.

The following Examples are intended to further illustrate the present invention without limiting its scope.

Example 1: Preparation of a substituted aminosilane having a hydroxy group

552 g of aminopropyltriethoxysilane (APTES) was placed in 1L of a reactor and the reactor was depressurized to vacuum. The reactor was heated to 80 ^°C with stirring and 1 10 g of ethylene oxide (EO) was added thereto at a rate of 2 g/min. For aging of ethylene oxide, the reactor was stirred while maintaining the temperature at 80 ^°C until the pressure of the reactor is less than 1 kg/cm . The mixture thus obtained was concentrated under a reduced pressure to remove unreacted ethylene oxide to obtain a mixture of (hydroxyethyl)aminopropyltriethoxysilane and bis-(hydroxyethyl)aminopropyltriethoxysilane in a weight ratio of 7.5:12.7 (542 g).

Example 2: Preparation of a substituted aminosilane having a hydroxy group

331 g of aminopropyltriethoxysilane was placed in 1L of a reactor and the reactor was depressurized to vacuum. The reactor was heated to. 80 ^°C with stirring and 330 g of ethylene oxide was added thereto at a rate of 2 g/min. For aging of ethylene oxide, the reactor was stirred while maintaining the temperature at 80 ^°C until the pressure of the reactor is less than 1 kg/cm². The mixture thus obtained was concentrated under a reduced pressure to remove unreacted ethylene oxide to obtain a mixture of (hydroxyethyl)aminopropyltriethoxysilane and bis-(hydroxyethyl)aminopropyltriethoxysilane in a weight ratio of 19.7:32.1 (575 g).

Example 3: Preparation of a substituted aminosilane having a hydroxy group

552 g of aminopropyltriethoxysilane was placed in 1L of a reactor and the reactor was depressurized to vacuum. The reactor was heated to 80 ^°C with stirring and 145 g of propylene oxide was added thereto at a rate of 2 g/min. For aging of propylene oxide, the reactor was stirred while maintaining the temperature at 80 ^°C until the pressure of the reactor is less than 1 kg/cm². The mixture thus obtained was concentrated under a reduced pressure to remove unreacted propylene oxide to obtain a mixture of (hydroxyisopropyl)aminopropyltriethoxysilane and bis-

(hydroxyisopropyl)aminopropyltriethoxysilane in a weight ratio of 6.9:13.4 (404 g).

Example 4: Preparation of a substituted aminosilane having a hydroxy group 331 g of aminopropyltriethoxysilane was placed in 1L of a reactor and the reactor was depressurized to vacuum. The reactor was heated to 80 ^°C with stirring and 435 g of propylene oxide was added thereto at a rate of 2 g/min. For aging of propylene oxide, the reactor was stirred while maintaining the temperature at 80 ^°C until the pressure of the reactor is less than 1 kg/cm². The mixture thus obtained was concentrated under a reduced pressure to remove unreacted propylene oxide to obtain a mixture of (hydroxyisopropyl)aminopropyltriethoxysilane and bis-

(hydroxyisopropyl)aminopropyltriethoxysilane in a weight ratio of 20.4:31.9 (628 g). Example 5: Preparation of a substituted aminosilane having a hydroxy group

552 g of aminopropyltriethoxysilane was placed in 1L of a reactor and the reactor was depressurized to vacuum. The reactor was heated to 80 ^°C with stirring and 127 g of a mixture of ethylene oxide and propylene oxide (a weight ratio of 50:50) was added thereto at a rate of 2 g/min. For aging of the mixture, the reactor was stirred while maintaining the temperature at 80 ^°C until the pressure of the reactor is less than 1 kg/cm². The mixture thus obtained was concentrated under a reduced pressure to remove unreacted ethylene oxide and propylene oxide to obtain a mixture of (hydroxyethyl)aminopropyltriethoxysilane, (hydroxyisopropyl)aminopropyltriethoxysilane, bis-(hydroxyethyl)aminopropyltriethoxysilane, and bis-(hydroxyisopropyl)aminopropyltriethoxysilane in a weight ratio of 19.9:13.0:11.2:8.0 (482 g).

Example 6: Preparation of a substituted aminosilane having a hydroxy group

331 g of aminopropyltriethoxysilane was placed in 1L of a reactor and the reactor was depressurized to vacuum. The reactor was heated to 80 ^°C with stirring and 382 g of a mixture of ethylene oxide and propylene oxide (a weight ratio of 50:50) was added thereto at a rate of 2 g/min. For aging of the mixture, the reactor was stirred while maintaining the temperature at 80 ^°C until the pressure of the reactor is less than 1 kg/cm². The mixture thus obtained was concentrated under a reduced pressure to remove unreacted ethylene oxide and propylene oxide to obtain a mixture of (hydroxyethyl)aminopropyltriethoxysilane, (hydroxyisopropyl)aminopropyltriethoxysilane, bis-(hydroxyethyl)aminopropyltriethoxysilane, and bis-(hydroxyisopropyl)aminopropyltriethoxysilane in a weight ratio of 19.9:13.0:11.2:8.0 (577 g).

Example 7: Preparation of a silane-modified polyurethane prepolymer

A mixture of 2,400 g of polypropyleneglycol having OH value of 14 mgKOH/g (DF- 8000, SKC Co. Ltd.) and 600 g of polypropyleneglycol having OH value of 112 mgKOH/g (DF-1000, SKC Co. Ltd.) was mixed with 209 g of toluene 2,4-diisocyanate and conducted a polymerization at 80 ^°C until a stoichiometric amount of NCO group is 0.8 mol%. 186 g of the compound obtained in Example 1, an end-capping agent, was added thereto and carried out polymerization until an absorption band of isocyanate is not detected in the infrared spectrum, to obtain the polyurethane prepolymer. Example 8: Preparation of a silane-modified polyurethane prepolymer

A mixture of 3,200 g of Polypropyleneglycol having OH value of 14 mgKOH/g (DF- 8000, SKC Co. Ltd.) and 36 g of 1,3-butanediol having OH value of 1,245 mgKOH/g (DF- 1000, SKC Co. Ltd.) was mixed with 174 g of toluene 2,4-diisocyanate and conducted a polymerization at 80 ^°C until a stoichiometric amount of NCO group is 0.5 mol%. 124 g of the compound obtained in Example 1 , an end-capping agent, was added thereto and carried out polymerization until an absorption band of isocyanate is not detected in the infrared spectrum to obtain the polyurethane prepolymer.

Example 9: Preparation of a silane-modified polyurethane prepolymer

A mixture of 500 g of polypropyleneglycol having OH value of 33.6 mgKOH/g (TF-

5000, SKC Co. Ltd.) and 4,000 g of polypropyleneglycol having OH value of 14 mgKOH/g (DF-1000, SKC Co. Ltd.) was mixed with 139 g of toluene 2,4-diisocyanate and conducted a polymerization at 80 ^°C until a stoichiometric amount of NCO group is 0.7 mol%. 186 g of the compound obtained in Example 1, an end-capping agent, was added thereto and carried out polymerization until an absorption band of isocyanate is not detected in the infrared spectrum to obtain the polyurethane prepolymer. Example 10: Preparation of a silane-modified polyurethane prepolymer

A mixture of 1,200 g of polypropyleneglycol having OH value of 56 mgKOH/g (DF- 2000, SKC Co. Ltd.) and 2,400 g of polypropyleneglycol having OH value of 14 mgKOH/g (DF-1000, SKC Co. Ltd.) was mixed with 208 g of toluene 2,4-diisocyanate and conducted a polymerization at 80 ^°C until a stoichiometric amount of NCO group is 0.4 mol%. 186 g of the compound obtained in Example 1 , an end-capping agent, was added thereto and carried out polymerization until an absorption band of isocyanate is not detected in the infrared spectrum to obtain the polyurethane prepolymer.

Example 11: Preparation of a silane-modified polyurethane prepolymer

A mixture of 2,000 g of polypropyleneglycol having OH value of 33.6 mgKOH/g

(TF-5000, SKC Co. Ltd.) and 4,800 g of polypropyleneglycol having OH value of 14 mgKOH/g (DF-8000, SKC Co. Ltd.) was mixed with 261 g of toluene 2,4-diisocyanate and conducted a polymerization at 80 ^°C until a stoichiometric amount of NCO group is 0.4 mol%. 186 g of the compound obtained in Example 1 , an end-capping agent, was added thereto and carried out polymerization until an absorption band of isocyanate is not detected in the infrared spectrum to obtain the polyurethane prepolymer.

Comparative Example 1: Preparation of a silane-modified polyurethane prepolymer

A mixture of 1,200 g of Polypropyleneglycol having OH value of 56 mgKOH g (DF-

2000, SKC Co. Ltd.) and 2,400 g of polypropyleneglycol having OH value of 14 mgKOH/g (DF-8000, SKC Co. Ltd.) was mixed with 208 g of toluene 2,4-diisocyanate and conducted a polymerization at 80 ^°C until a stoichiometric amount of NCO group is 0.4 mol%. I l l g of aminopropyltriethoxysilane (APTES), an end-capping agent, was added thereto and carried out polymerization until an absorption band of isocyanate is not detected in the infrared spectrum to obtain the polyurethane prepolymer.

Experimental Example 1

IR spectrum and GPC scan of the compounds obtained in Examples were measured and the results were showed in Figs. 3 to 6. For reference, IR spectrum and GPC scan of aminopropyltriethoxysilane are provided in Fig. 1 and 2.

Figs. 3 and 6 are IR spectrums of the compounds obtained in Examples 1 and 4 respectively.

As shown in Figs 3 and 6, a strong and broad absorption peak of OH group which did not detected in Fig. 1 was shown in the range of 3200 to 3700 nm.

Experimental Example 2

The properties of the compounds obtained in Examples 1 to 6 were measured and the results were showed in table 1.

(1) OH value : ASTM D-4247 was used to measure the OH value of the compound.

(2) Amine value : ASTM D-2073 was used to measure the amine value of the compound.

Table 1

Experimental Example 3 : Measurement of the property of the silane-modified polyurethane prepolymer

(1) OH value (OHV) of the silane-modified polyurethane prepolymers which are obtained in Examples 7 to 1 1 and Comparative Example, was measured and an average molecular was calculated by using the OH value in accordance with the following equation. The results were shown in Table 2.

Equation 1

OH value =56100 x 2 / OHV

(2) A viscosity of the silane-modified polyurethane prepolymers obtained in Examples was measured using the RV-DVII Cone-plate type viscometer (Brookfield Co.) in the condition of CPE 41 , 25 ^°C , and 0.3rpm and the results were showed in Table 2.

Experimental Example 4 : Property Measurement of a sealant prepared by using the silane-modified polyurethane prepolymer

Each of the silane-modified polyurethane prepolymer obtained in Examples 7 to 11 and Comparative Example (38 weight part) was mixed with 38 weight part of plasticizer (diisoundecyl phthalate), 0.34 weight part of moisture scavenger, 40 weight part of calcium carbonate, 0.46 weight part of light stability, 1.115 weight part of fumed silica, and 1.15 weight part of colorant and stirred for 20 min to obtain a suspension. At that time, the temperature of the suspension was 60 ^°C . 0.57 weight part of N-aminoethyl-3-aminopropyl- methyldimethoxysilane and 0.03 weight part of dibutyltin bis(acetylacetonate) were added to the suspension and stirred for 10 min to obtain a polyurethane-based sealant having no isocyanate.

The polyurethane-based sealant was hardened in a thermo-hygrostat (20 ^°C , humidity: 50 %) for 1 week. The properties of the sealant were measured in accordance with the following method and shown in the Table 2.

(1) Hardness: KS B 0807 was used to measure hardness of the sealant.

(2) Tensile strength: ASTM D 412 was used to measure tensile strength of the sealant.

(3) Elongation: ASTM D 412 was used to measure Elongationof the sealant.

(4) Durability: Durability of the sealants was calculated by multiplying Tensile strength by Elongation.

Table 2

As shown in Table 2, the silane-modified polyurethane prepolymers prepared by using the substituted aminosilanes having a hydroxy group in Examples, especially Example 10, showed lower viscosity compared to that of Comparative Example. Accordingly, the sealant prepared by hardening the silane-modified polyurethane prepolymer obtained in Examples showed enhanced durability.

While the invention has been described with respect to the above specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art which also fall within the scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A substituted aminosilane having a hydroxy group of formula (I):

X

HO— R¹— N— R²-Si Y

A Z (I) wherein,

A is H or -R³OH;

R¹ to R³ are each independently C_1-5 alkylene;

X is C_1-4 alkyl or Ci_-4 alkoxy; and

Y and Z are each independently C_1-4 alkoxy.

1 3

2. The substituted aminosilane of claim 1 , wherein R to R are each independently ethylene, propylene, isopropylene, butylene, or isobutylene.

3. The substituted aminosilane of claim 1, wherein X is methyl, methoxy, or ethoxy.

4. The substituted aminosilane of claim 1, wherein Y and Z are each independently methoxy or ethoxy.

5 . The substituted aminosilane of claim 1 , which has a molecular weight of 250 to 500.

6 . The substituted aminosilane of claim 1 , which is selected from the group consisting of (hydroxyethyl)aminopropyltriethoxysilane, (hydroxyisopropyl)aminopropyltriethoxysilane, bis-(hydroxyethyl)aminopropyltriethoxysilane, and bis- (hydroxyisopropyl)aminopropyltriethoxysilane.

7. An end-capping agent comprising the substituted aminosilane of claim 1 or a mixture thereof with two or more hydroxyl substituted aminosilanes.

8. The end-capping agent of claim 7, which is composed of a mixture of the compound of formula (I) in which A is H, and the compound of formula (I), in which A is -R OH in a weight ratio of 1 : 1 to 1 :3.

9. A method for preparing the substituted aminosilane having a hydroxy group of claim 1 or a mixture thereof with two or more hydroxyl substituted aminosilanes, which comprises subjecting an aminosilane of formula (II) to a reaction with C₂.₅ alkylene oxide:

wherein,

R² is d-5 alkylene, X is Ci_-4 alkyl or CM alkoxy, and Y and Z are each independently C_1-4 alkoxy.

10. The method of claim 9, wherein the C_2-5 alkylene oxide is used in an amount corresponding to 1 to 5 equivalents based on the aminosilane.

11. The method of claim 9, wherein the C_2-5 alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and a mixture thereof.

12. A silane-modified polyurethane prepolymer having a terminal alkoxysilane group, which is prepared by treating an isocyanate-terminated polyurethane prepolymer with the end- capping agent of claim 7.

13. The silane-modified polyurethane prepolymer of claim 12, which has a viscosity of 7,000 to 50,000 cPs.

14. The silane-modified polyurethane prepolymer of claim 12, which has a number average molecular weight of 10,000 to 100,000.

15. The silane-modified polyurethane prepolymer of claim 12, wherein the number average molecular weight of the isocyanate-terminated polyurethane prepolymer is in the range of 8,000 to 60,000.

16. The silane-modified polyurethane prepolymer of claim 12, wherein the amount of the isocyanate terminal group is of 0.2 to 1.0 mol% based on the isocyanate-terminated polyurethane prepolymer.

17. The silane-modified polyurethane prepolymer of claim 12, wherein the polyurethane prepolymer is prepared by subjecting aromatic, aliphatic, or cycloaliphatic isocyanates to a polymerization with polyether diols or polyether triols.

18. The silane-modified polyurethane prepolymer of claim 17, wherein the aromatic, aliphatic, or cycloaliphatic isocyanate contains the isocyanate group in an amount of 20 to 40 mol%

19. The silane-modified polyurethane prepolymer of claim 17, wherein the aromatic, aliphatic, or cycloaliphatic isocyanate is selected from the group consisting, of toluene 2,4- diisocyanate, methylene diphenyldiisocyanate, isophorone diisocyanate, dicyclomethane-4,4'- diisocyanate, hexamethylene diisocyanate, and a mixture thereof.

20^'. The silane-modified polyurethane prepolymer of claim 17, wherein the polyether diol or polyether triol has a number average molecular weight of 400 to 20,000.

21. The silane-modified polyurethane prepolymer of claim 17, wherein the polyether diol or polyether triol is polypropylene glycol or poly(tetramethylene ether) glycol.

22. The silane-modified polyurethane prepolymer of claim 17, wherein the aromatic, aliphatic, or cycloaliphatic isocyanate are used with the polyether diol or polyether triol in an amount corresponding to an equivalent ratio of isocyanate group to hydroxy group of 1 :0.55 to 1 :1.

23. The silane-modified polyurethane prepolymer of claim 12, the isocyanate-terminated polyurethane prepolymer and the end-capping agent are used in a weight ratio of 49: 1 to 4: 1.