Silylated Polyurethanes, Their Preparation and Use

Abstract

A silylated polyurethane obtainable by a process comprising the following steps: (a) reacting at least one polyol with at least one triisocyanate to form a hydroxyl-terminated polyurethane prepolymer, and (b) reacting said polyurethane prepolymer with at least one isocyanatosilane of the formula (1): OCN—R—Si—(X).sub.m(R.sup.1).sub.3-m, wherein m is 0, 1 or 2, each R.sup.1 is independently from each other a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or —OCH(R.sup.2)COOR.sup.3, wherein R.sup.2 is hydrogen or an alkyl group having 1 to 4 carbon atoms and R.sup.3 is a straight-chain or branched alkyl group having 1 to 8 carbon atoms, each X is independently from each other and optionally substituted hydrocarbon group having 1 to 10 carbon atoms, which can be interrupted by at least one heteroatom, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanatosilane. The silylated polyurethanes are suitable for use in a preparation as an adhesive, sealant, or coating agent.

Claims

1. A silylated polyurethane obtained by a process comprising the following steps: (a) reacting at least one polyol with at least one triisocyanate to form a hydroxyl-terminated polyurethane prepolymer; and (b) reacting the hydroxyl-terminated polyurethane prepolymer with at least one isocyanatosilane of formula (1) to endcap the hydroxyl groups on the hydroxyl-terminated polyurethane prepolymer with the isocyanatosilane,
OCN—R—Si—(X).sub.m(R.sup.1).sub.3-m  (1) wherein m is 0, 1 or 2, each R.sup.1 is independently from each other a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or —OCH(R.sup.2)COOR.sup.3, wherein R.sup.2 is hydrogen or an alkyl group having 1 to 4 carbon atoms and R.sup.3 is a straight-chain or branched alkyl group having 1 to 8 carbon atoms, each X is independently from each other an optionally substituted hydrocarbon group having 1 to 10 carbon atoms, which can be interrupted by at least one heteroatom, and R is a difunctional organic group.

2. The silylated polyurethane according to claim 1, wherein a molar ratio of the NCO groups of the triisocyanate to hydroxyl groups of the polyol is from 0.05 to 0.45.

3. The silylated polyurethane according to claim 1, wherein said polyol is a polyether polyol.

4. The silylated polyurethane according to claim 1, wherein said polyol has a number average molecular weight of from 500 to 20,000 g/mol.

5. The silylated polyurethane according to claim 1, wherein said triisocyanate is derived from HDI, TDI, MDI, PDI, IPDI, or mixtures thereof.

6. The silylated polyurethane according to claim 1, wherein said isocyanatosilane is selected from the group consisting of 3-isocyanatopropyltrimethoxysilane, 2-isocyanatoisopropyltrimethoxysilane, 4-isocyanato-n-butyltrimethoxysilane, 2-isocyanato-1,1-dimethylethyltrimethoxysilane, 1-isocyanatomethyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 2-isocyanato-2-methylethyltriethoxysilane, 4-isocyanatobutyltriethoxysilane, 2-isocyanato-1,1-dimethylethyltriethoxysilane, 1-isocyanatomethyltriethoxysilane, 3-isocyanatopropyl)methyldimethoxysilane, 3-isocyanatopropyldimethylmethoxysilane, 3-isocyanatopropylphenylmethylmethoxysilane, 1-isocyanatomethylmethyldimethoxysilane, 3-isocyanatopropylethyldiethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, 1-isocyanatomethylmethyldiethoxysilane, and mixtures thereof.

7. The silylated polyurethane according to claim 1, wherein said process comprises further step of adding a catalyst.

8. A process for preparing a silylated polyurethane comprising the following steps: (a) reacting at least one polyol with at least one triisocyanate to form a hydroxyl-terminated polyurethane prepolymer; and (b) reacting the hydroxyl-terminated polyurethane prepolymer with at least one isocyanatosilane of formula (1) to endcap the hydroxyl groups on the hydroxyl-terminated polyurethane prepolymer with the isocyanatosilane,
OCN—R—Si—(X).sub.m(R.sup.1).sub.3-m  (1) wherein m is 0, 1 or 2, each R.sup.1 is independently from each other a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or —OCH(R.sup.2)COOR.sup.3, wherein R.sup.2 is hydrogen or an alkyl group having 1 to 4 carbon atoms and R.sup.3 is a straight-chain or branched alkyl group having 1 to 8 carbon atoms, each X is independently from each other an optionally substituted hydrocarbon group having 1 to 10 carbon atoms, which can be interrupted by at least one heteroatom, and R is a difunctional organic group.

9. An adhesive, sealant, or coating composition comprising the silylated polyurethane according to claim 1.

10. A silylated polyurethane that is the reaction product of a mixture comprising: (a) the hydroxyl terminated polyurethane prepolymer reaction product of a mixture comprising at least one polyol and at least one triisocyanate; and (b) at least one isocyanatosilane of formula (1)
OCN—R—Si—(X).sub.m(R.sup.1).sub.3-m  (1) wherein m is 0, 1 or 2, each R.sup.1 is independently from each other a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, or —OCH(R.sup.2)COOR.sup.3, wherein R.sup.2 is hydrogen or an alkyl group having 1 to 4 carbon atoms and R.sup.3 is a straight-chain or branched alkyl group having 1 to 8 carbon atoms, each X is independently from each other an optionally substituted hydrocarbon group having 1 to 10 carbon atoms, which can be interrupted by at least one heteroatom, and R is a difunctional organic group.

Description

EXAMPLES

Example 1 (Ex 1)

[0084] Manufacture of a Silylated Polyurethane (Use of Triisocyanate):

[0085] 384.02 g (33.88 mmol) of polypropylene ether polyol (Acclaim 12200, hydroxyl value=9.90) were dried in a 500 ml three-necked flask at 80-90° C. under vacuum. Under a nitrogen atmosphere, 0.28 g of bismuth neodecanoate (Borchi Kat 315) were added with stirring. Then, 2.52 g (4.52 mmol) of triisocyanate (Tolonate HDT-LV) were added (NCO/OH ratio=0.2) with stirring. The mixture was left for one hour at 80-95° C. The conversion was accomplished with NCO monitoring, and as soon as the theoretical NCO value of the prepolymer had been reached titrimetrically (% NCO=0), 13.18 g (62.69 mmol) of 3-isocyanatopropyltrimethoxysilane (Geniosil GF 40) were added with stirring and the mixture was left for a further hour at 80-95° C. (% NCO=0.00 to 0.09). A star-shaped polymer was obtained. The resulting polymer was stored in a moisture-proof glass vessel under a nitrogen atmosphere before being processed further into a curable composition. The viscosity was 41,200 mPas.

Comparative Example 1 (Comp 1)

[0086] Manufacture of a Silylated Polyurethane (Use of Diisocyanate):

[0087] A similar procedure to Example 1 was carried out except that HDI was used instead of triisocyanate. The viscosity was 28,200 mPas. Details are summarized in Table 1.

Example 2 (Ex 2)

[0088] Manufacture of a Silylated Polyurethane (Use of Triisocyanate):

[0089] A similar procedure to Example 1 was carried out except that NCO/OH ratio=0.4 and Acclaim 4200 (hydroxyl value=29.50) was used instead of Acclaim 12200. The viscosity was 78,600 mPas. Details are summarized in Table 1.

Comparative Example 2 (Comp 2)

[0090] Manufacture of a Silylated Polyurethane (Use of Diisocyanate):

[0091] A similar procedure to Example 2 was carried out except that HDI was used instead of triisocyanate. The viscosity was 10,600 mPas. Details are summarized in Table 1.

TABLE-US-00001 TABLE 1 Ex 1 Comp 1 Ex 2 Comp 2 Acclaim 384.02 g 385.33 g 12200 (33.88 mmol) (34.00 mmol) Acclaim 4200 357.13 g 364.02 g (93.90 mmol) (95.71 mmol) Borchi Kat 0.28 g 0.28 g 0.28 g 0.28 g 315 Tolonate 2.52 g 13.95 g HDT-LV (4.52 mmol) (25.04 mmol) HDI 1.16 g 6.52 g (6.80 mmol) (38.28 mmol) NCO/OH ratio 0.2 0.2 0.4 0.4 Geniosil GF 13.18 g 13.23 g 28.64 g 29.18 g 40 (62.69 mmol) (62.90 mmol) (136.15 mmol) (138.78 mmol) % NCO 0.00-0.09 0.00-0.09 0.00-0.25 0.00-0.25 after adding Geniosil GF 40 Viscosity 41,200 mPas 28,200 mPas 78,600 mPas 10,600 mPas

Determination of the Viscosity of the Polymer:

[0092] The viscosity values were determined using Brookfield viscometer (DV-II+ Pro), spindle 7, 20 rpm, at 23° C.

Examples A-F

[0093] Manufacture of Compositions Comprising a Silylated Polyurethane:

[0094] Each prepared silylated polyurethane according to above examples was heated for 24 hours at 23° C. and then 0.35 g of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (Geniosil GF 91) and 0.14 g of DOTL or DBU were added to 34.51 g of each of the prepared polymer. This mixture was homogenized twice for 60 seconds at 2700 rpm in a SpeedMixer (DAC 150 FC).

[0095] The time to form a skin (skin over time/SOT) and mechanical strength (tensil strength and elongation) were determined for the abovementioned mixtures. The results are summarized in Table 2 below. DOTL was used in preparing Examples A to D and DBU was used as a tin-free catalyst in preparing Examples E to F.

TABLE-US-00002 TABLE 2 A B C D E F Silylated Ex 1 Comp 1 Ex 2 Comp 2 Ex 1 Comp 1 Polyurethane SOT 14 min 16 min 22 min 1 h 33 min 44 min 21 min Tensil Strength 0.88 0.85 1.10 0.89 0.80 0.76 (N/mm.sup.2) Elongation (%) 57.98 61.75 43.28 39.38 55.53 53.88

Determination of the Skin-Over Time (SOT) and Mechanical Strength (Tensil Strength and Elongation):

[0096] The aforementioned mixtures were homogenized and applied in a frame (50×130×2 mm). Each mixture was evenly distributed so that the frame can be completely filled. A thin polymer film was thereby obtained. The time to form a skin (skin-over time/SOT) was determined for these compositions using a tool which has a rounded spatula at the tip (150×5 mm). The tip of the spatula was gently contacted with the surface of the polymer film every 1 to 5 minutes and removed carefully. The SOT was measured once no more residue of the formulation remains on the spatula when removing it from the surface of the polymer film. Then, the resulting string must be removed from the spatula without residue. The polymer film returned to its original shape. In examining the SOT a different part of the surface of the polymer film must be used every time. The test was performed at 23° C. and 50% relative humidity.

[0097] After being stored for 7 days (23° C., 50% relative humidity), four specimens were prepared from the polymer film and punched using a Mader press (APK T3-5-40) and a punching tool unit according to DIN 53504-S3A. The mechanical data were determined by reference to DIN 53504:2009-10. Each specimen was set to the initial test position using a pre-load of 0.05 MPa and a speed rate of 40 mm/min. Actual measurement was done using a speed rate of 50 mm/min.

[0098] The examples show that the mixtures A, C, and E containing a silylated polyurethane according the present invention (Examples 1 to 2), show reasonable viscosity, exhibit significantly shorter SOT than mixtures comprising a silylated polyurethane according to the Comparative Examples 1 to 2, while having good mechanical strength (tensil strength and elongation). In addition, comparison of Examples E and F shows that even in case of using non-tin catalyst the mixture containing a silylated polyurethane according the present invention also exhibits short SOT and good mechanical properties.