CH640248A5 - Process for the preparation of moisture-crosslinkable polyurethane prepolymers containing terminal alkoxysilyl groups, and the use thereof for the preparation of elastic compositions - Google Patents

Description

• u-ï'O1> * 8

1. A process for the preparation of moisture-crosslinkable polyurethane prepolymers containing terminal alkoxysilyl groups, characterized in that a diisocyanate prepolymer of the general formula 3

O

0CN-R '"- NH-C-0 / iQ'

can still carry aliphatic side chains with 1 to 4 carbon atoms, and

Y = O, S, NH or NR and a = 0.1.2 mean, first of all to a polyurethane prepolymer of the general formula 5 which has only one alkoxysilyl group and one terminal isocyanate group

(3)

10th

wherein R '"is a divalent alkyl radical having 4 to 20 carbon atoms, a divalent O-Cu-cycloalky] -, Cä-Cw-aryl, C - Cv, -aralkyl or O-C30 alkaryl radical and Q' a divalent by withdrawing two Hydroxyl group-derived radical of a polyoxyalkylene glycol with a molecular weight of 200-20,000 mean with an alkoxysilane compound or a mixture of such compounds of the general formula 4

QC

O

, 0-C-NH-R "'- NC0 (R') a

I.

-O-C-NH-R '"- NH-C-Y-R"' -Si (OR> -a

II II

o o

(5)

15

(R ') a

I.

(RO) 3 -., Si-R "-YH

(4)

wherein

R is a Ci-Ci2-alkyl, a Cs-Cu-cycloalkyl, a Có-Cw-aryl, 2s aralkyl or alkaryl radical and

R 'is a Ci-Ci2-alkyl-, a Cs-Cn-cycloalkyl-, a C6-C14-

Aryl, aralkyl or alkaryl radical and

R "is a divalent C2-C10-alkyl radical, which optionally reacts in the presence of a solvent at temperatures of 30-150 ° C., and this prepolymer in turn with a polyoxyalkylene polyol of the general formula 6

Q (OH) b (6)

where b = 2-6 and

Q is a b-valent radical of a polyoxyalkylene polyol with a molecular weight of 200-20,000 derived from the withdrawal of b hydroxyl groups, via the free NCO group to a prepolymer of the general formula 2 which has at least two terminal alkoxysilyl groups

(R ') a O OOO

I II II II H,

(R0) 3-aSi-R "-Y-C-NH-R" '- NH-C-0-Q'-0-CNH-R "' - NH-C-0- / bQ (2)

implements.

2. Use of polyurethane prepolymers, produced by the process according to claim 1, for the production of elastic masses.

the general formula

40

(R ') a

O

O

(R0) 3-aSi-R "-y-C-NH-R" '- NH-C-0

bQ

Processes for the preparation of crosslinkable polyurethane prepolymers with terminal alkoxysilyl groups, which are vulcanized under the action of moisture at room temperature, are known per se and are e.g. in the American patent 3,632,557 and in the German laid-open publications 1 812 562.2 155 258 and 2 155 259. However, it has been shown that the prepolymers prepared according to the patent specifications mentioned, in which the substituents are defined in claim 1, have inadequate mechanical properties for the production of highly elastic products; e.g. 45 tear resistance, tear resistance and the often low elongation at break need improvement.

We have now found that the introduction of an additional polyether group Q 'as a chain-extending segment in the prepolymer molecule results in a substantial improvement in the mechanical properties mentioned. According to the present invention, oalkoxysilyl-substituted polyurethane prepolymers of the general formula

(R ') a O OO O

I II II II II

(RO) 3-aSi-R "-y-C-NH-R '" -NH-C-O-Q' -O-C-NH-R '"-NH-C-O

bQ

produced.

The symbols have the following meaning:

R is a Ci-Cn-alkyl or C5-C12 cycloalkyl or a C6-Ci4-aryl, aralkyl or alkaryl radical

R 'is a Ci-Cn-alkyl or C5-C12 cycloalkyl radical or a Cs-C 14 aryl, aralkyl or alkaryl radical

R "is a divalent C2-C10-alkyl radical which can optionally still carry aliphatic side chains with 1 to 4 carbon atoms,

R '"is a divalent alkyl radical having 4 to 20 carbon atoms, a divalent C4-C14 cycloalkyl, C" -Cw aryl, C7-C30 aralkyl or C7-C30 alkaryl radical,

65 Q 'is a divalent radical of a polyoxyalkylene diol having a molecular weight of 200-20,000, derived from two hydroxyl groups, but preferably 200 to 6000

Q is a b-value polyurethane prepolymer carrying b hydroxyl group isocyanate group and the derived residue of a polyoxyalkylene polyol of the molecular formula lar weight 200-20,000, but preferably 200 to 3000

Y = O, S, NH, NR a = 0.1.2

b = 2 to 6, preferably 2 or 3

In the process according to the invention, a polyisocyanato-polyurethane prepolymer of the formula is first used

O

0CN-R '"- NH-C-0

: Q '

with an alkoxysilane compound or a mixture of such compounds of the general formula

(R ') a

I.

(RO) 3-aSi-R "-YH

QC

to only one alkoxysilyl group and a terminal mer of the formula

O

II

"0-C-NH-R" '- NC0

O (R ') a

II I

io ^ O-C-NH-R '"-NH-C-Y-R" -Si (OR) 3-a

II

O

implemented in the presence of a solvent at temperatures of 30-150 ° C. This prepolymer in turn is now made with a polyoxyalkylene polyol

20 Q (OH) b 6

via the isocyanate group to a polyurethane prepoly having at least two terminal alkoxysilyl groups

(R ') a O OO O

I II II II II

(RO) 3-aSi-R "-y-C-NH-R '" -NH-C-O-Q' O-C-NH-R '"-NH-C-0

bQ

preferably in the presence of a solvent, and in particular at temperatures of 20 to 150 ° C.

Starting compounds for the preparation of the prepolymers 2 which can be prepared according to the invention are diisocyanate 35 nato prepolymers of the general formula

O

II

OCN-R '"- NH-C-0

2Q '

40

in which R '"and Q' have the meaning already given.

Type 3 prepolymers can be prepared in a known manner by using one or more polyoxyalkylene derivatives of the general formula 4s

Q '(OH) 2

with diisocyanates of the general formula R '"(NCO) 2

or 2,6-tolylene diisocyanate and mixtures of these isomers, diphenylmethane -4,4'-diisocyanate and isophorondii socyanate.

Alkoxysilane compounds of the general formula are used to produce the silyl-substituted prepolymers of type 2 which can be prepared according to the invention

(RO) 3-aSi-R "-YH 4

I.

R ') a used in which the symbols R, R ", y a, have the meaning already mentioned.

As preferred silane compounds in the process according to the invention, e.g. the following compounds or any mixtures of these compounds are used:

50

(CH30) 3Si-CH2-CH2-NH (CHjO) 3 SÌ-CH2-CH2-CH2-NH2

to react. The diiso- (CH30) 2 SÌ-CH2-CH2-NH2 cyanate 8 is normally used in excess, so that the number of NCO- |

Groups in the initial reaction mixture double 55 CH3

the number of OH groups.

Examples of the diisocyanates of type 8 are the (CH30) 2 SÌ-CH2-CH2-CH2-NH2 known aromatic, aliphatic, cycloaliphatic |

tables and araliphatic diisocyanates used, at- CH3

for example 2,4- and 2,6-tolylene diisocyanate and any 60

Mixtures of these isocyanates, diphenylmethane-4,4'-diiso- (C2H5OJ3 SÌ-CH2-CH2-NH2 cyanate, 1,3- and 1,4-phenylene diisocyanate, naphthylene -1,5-diisocyanate, 1,4-tetramethylene diisocyanate, 1 , 6-hexamethyl

lene diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate, 1-iso- (C2HsO) 3 SÌ-CH2-CH2-CH2-NH2 cyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (iso- 65

phorone diisocyanate), 4,4'-diisocyanato-dicyclohexylmethane. (C2H50> SÌ-CH2-CH2-NH2

Particularly preferred diisocyanates of the formula 8 are the

technically easily accessible connections such as the 2,4-CH3

9

10th

11

12

13

14

15

640248

4th

(C2HsO) 2 SÌ-CH2-CH2-CH2-NH2 16

I.

CHj

Mixtures of a trimethoxy or ethoxysilane with a dimethoxy or ethoxysilane in a molar ratio of 1: 1 are preferably used.

In contrast to the processes described in the cited patents, in the process according to the invention the silane compounds are reacted with the diisocyanate prepolymer 3 in such a way that the resulting prepolymer still has a free NCO group.

O

q;

-C-NH-R '"- NCO

O (R ') a

II I

O-C-NH-R '"- NH-C-Y-R'" -Si (OR> -a

O

This makes it possible to couple two or more of these type 5 prepolymers via the isocyanate groups by reacting a polyhydroxy compound. The polyhydroxy compounds used in the process according to the invention are usually the known, easily accessible polyoxyalkylene polyols. The polyols preferably used in the process according to the invention are e.g. Polyoxypropylene glycols (medium MG 150-4000), polyoxypropylene-polyoxyethylene glycols (medium MG 1000-3700), polyoxypropylene adducts of glycerol (MG 409-5000) and polyoxypropylene-polyoxyethylene adducts of trimethylolpropane.

The reaction components mentioned are generally reacted with the exclusion of moisture, in the presence of a solvent such as e.g. Toluene, xylene, benzene, cyclohexane, dimethylformamide, N-methylpyrrolidone and others Toluene or xylo] are used as preferred solvents. The reaction temperatures are between 30 ° and 150 ° C. The preferred temperature range of this stage of the process according to the invention is 60-130 ° C.

The described prepolymers of formula 2 are crosslinked in a known manner under the action of moisture, a hydrolyzable alkoxy group being substituted by a hydroxyl group, with the corresponding alcohol being split off, and then in each case one hydroxysilyl group with one alkoxysilyl group or two hydroxysilyl groups forming a siloxane bond.

-Si-OH + -Si-OR - -Si-O-Si- + ROH

I I II I I II

-Si-OH + -Si-OH - -Si-O-Si- + H2O

I I II

In the previously known processes for the production of polyurethane prepolymers with siloxane bridges, the crosslinking density could only be influenced to a small extent. We have now found that by means of the prepolymers of formula 2 produced by the process according to the invention, there is a possibility of producing polyurethane polymers with siloxane bridges, the crosslinking density and other physical properties of which are controlled in a wide range and thereby the desired

Usage properties of a product can be adjusted.

example 1

5 600 g of polypropylene glycol with an average molecular weight of 2000 (Niac PPG 2025; OHZ = 56.1), 70 g of tolylene diisocyanate, 134 g of xylene and 0.4 g of dibutyltin dilaurate are placed in an 11-round flask and stirred with the reaction temperature to 80 ° heated. The reaction is checked by periodic analysis of the free NCO content. The desired NCO content of 1.2% is reached after 3 hours. Now 0.6% of the free NCO is capped by adding 15.6 g of y-aminopropylmethyldimethoxysilane. The temperature is kept at 80 °. After 5 ls minutes, the remaining 0.6% of the free NCO are reacted by adding 20.7 g of a polypropylene glycol with an average molecular weight of 400 (Niax PPG 425: OHZ = 259). After 1-2 hours no; free NCO can be detected more.

20th

Example 2

The procedure is the same as in Example 1, but instead of the y-aminopropylmethyldimethoxysilane, 17.1 g of the 25 trifunctional y-aminopropyltrimethoxysilane are used for the capping of 0.6% free NCO.

Example 3

30 Instead of a bifunctional or trifunctional silane according to Examples 1 and 2, a mixture of these silanes is used. For the capping of 0.6% free NCO, 8.6 g of y-aminopropyltrimethoxysilane and 7.8 g of y-aminopropylmethyldi-methoxysilane are used. The reaction procedure is the same as in Example No. 1.

Example 4

In an 11-round flask, 200 g of polypropylene-40 glycol with an average molecular weight of 2000 (Niax PPG 2025; OHZ = 56.1), 184 g of polypropylene glycol with an average molecular weight of 400 (Niax PPG 425; OHZ = 259), 104 , 9 g of tolylene diisocyanate, 288 g of xylene and 0.3 g of dibutyltin dilaurate and heated to the reaction temperature of 80 ° with stirring. The reaction is checked by periodic analysis of the free NCO content. The desired NCO content of 1.2% is reached after 3 hours. Now 0.6% of the free NCO is capped by adding 14.1 g of y-aminopropylmethyldimethoxysilane 50. The reaction temperature of 80 ° C is maintained.

After about 5 minutes, the remaining 0.6% of the free NCO is reacted by adding 15 g of a polypropylene glycol with an average molecular weight of 400 (Niax 55 PPG 4025; OHZ = 259). Free NCO can no longer be detected after approx. 1-2 hours.

Example 5

60 Instead of the bifunctional silane according to Example 4, a mixture of bifunctional and trifunctional silanes is used. 5.7 g of yamino-nopropylmethyldimethoxysilane and 6.3 g of yamino-propyltrimethoxysilane are used to mask 0.6% NCO. The reaction procedure is the same 65 as in Example 4.

Mechanical properties of approximately 1 mm thick crosslinked films of the prepolymers prepared according to Example 1-5.

Example No. tensile strength kp cm; Elongation at break ".1 Tear strength

according to DIN 53.504 according to DIN 53.504 kg / cm according to DIN

53,515

1 5.5 300 1.5

2 6.0 190 1.5

3 5.5 250 1.5

4 19.0 420 3.0

5 10.0 280 3.1