GUANIDINE CATALYST FOR CURABLE COMPOSITIONS

Abstract

A guanidine of the formula (I) and to the use thereof as catalyst for the crosslinking of a functional compound, especially a polymer having silane groups. The guanidine of the formula (I) described is preparable in a simple method via a polyfunctional carbodiimide adduct from the readily available raw materials, and is largely odorless at room temperature and of low toxicity. In spite of its comparatively high molecular weight, it accelerates the crosslinking of functional compounds surprisingly well, and such compositions do not have a tendency to migration-related defects such as separation, exudation or substrate soiling.

Claims

1. A guanidine of the formula (I) ##STR00007## where n is an integer from 1 to 20, A is an alkyl, cycloalkyl or aralkyl radical which has 1 to 100 carbon atoms and optionally has one or more heteroatoms, or together with R.sup.1 is an alkylene radical which has 2 to 6 carbon atoms and optionally contains ether oxygen or amine nitrogen and is optionally substituted, R.sup.1 is a hydrogen radical or is an alkyl radical which has 1 to 8 carbon atoms and optionally contains ether oxygen, or together with A is an alkylene radical which has 2 to 6 carbon atoms and optionally contains ether oxygen or amine nitrogen and is optionally substituted, D is a divalent aliphatic or cycloaliphatic or arylaliphatic radical having 6 to carbon atoms, B is a monovalent organic radical which has an average molecular weight in the range from 150 to 5,000 g/mol and is free of hydroxyl groups, primary and secondary amino groups and mercapto groups, and X is O or S or NR.sup.2 where R.sup.2 is a hydrogen radical or is an alkyl radical which has 1 to 8 carbon atoms and optionally contains ether oxygen or tertiary amine nitrogen.

2. A guanidine as claimed in claim 1, wherein A is selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl, n-octyl, 2-ethylhexyl, n-decyl, lauryl, cocoalkyl, oleyl, cyclohexyl, benzyl, 2-methoxyethyl, 3-methoxypropyl, 3-(2-ethylhexyloxy)propyl, 3-(N,N-dimethylamino)propyl and -(alkyloxy)poly(oxyalkylene)alkyl having 1,2-oxyethylene and 1,2-oxypropylene units and a molecular weight in the range from 180 to 600 g/mol.

3. A guanidine as claimed in claim 1, wherein D is selected from the group consisting of 2-methyl-1,5-pentylene, 1,6-hexylene, 2,2(4),4-trimethyl-1,6-hexamethylene, (1,5,5-trimethylcyclohexan-1-yl)methane-1,3, 1,3-cyclohexylenebis(methylene), 1,4-cyclohexylenebis(methylene), 1,3-phenylenebis(methylene) and (methylenedicyclohexyl)-4,4.

4. A guanidine as claimed in claim 1, wherein X is O and B is 2-(-(alkyloxy)poly(oxyethylene))ethyl, 2-(-(alkyloxy)poly(oxyethyleneoxypropylene))ethyl, 2-(-(alkyloxy)poly(oxyethyleneoxypropylene))propyl or 2-(-(alkyloxy)poly(oxypropylene))propyl, where alkyl is methyl, ethyl, butyl, 2-ethylhexyl, lauryl, cocoalkyl or oleyl and these radicals have a molecular weight in the range from 150 to 2,000 g/mol.

5. A guanidine as claimed in claim 1, wherein it has an average value of n in the range from 1.1 to 6.

6. A process for preparing a guanidine as claimed in any of claim 1 wherein a carbodiimide adduct of the formula (II) is reacted with at least one amine of the formula (III). ##STR00008##

7. The process as claimed in claim 6, wherein first at least one diisocyanate of the formula D-(NCO).sub.2 is converted in the presence of a carbodiimidization catalyst while heating and with release of CO.sub.2, then the resultant carbodiimide of the formula (IV) is reacted with at least one compound of the formula (V), ##STR00009## and finally the resultant carbodiimide adduct of the formula (II) is reacted with at least one amine of the formula (III).

8. A method comprising a step of catalyzing the crosslinking of a functional compound with the guanidine of claim 1.

9. The method as claimed in claim 8, wherein the functional compound is a silane, a polymer having silane groups, a polyisocyanate or a polyurethane polymer having isocyanate groups.

10. The method as claimed in claim 8, wherein the functional compound is a polyether having silane groups.

11. A curable composition comprising at least one guanidine as claimed in claim 1.

12. The curable composition as claimed in claim 11, wherein it contains silane groups and/or isocyanate groups.

13. The curable composition as claimed in claim 11, wherein it comprises at least one polymer having silane groups.

14. The curable composition as claimed in claim 11, wherein it is an adhesive or a sealant or a coating.

15. A cured composition obtained from the curable composition as claimed in claim 11.

Description

EXAMPLES

[0247] Working examples are adduced hereinafter, which are intended to elucidate the invention described in detail. It will be appreciated that the invention is not restricted to these described working examples.

[0248] Standard climatic conditions refer to a temperature of 231 C. and a relative air humidity of 505%.

[0249] Infrared spectra (FT-IR) were measured on a Nicolet iS5 FT-IR instrument from Thermo Scientific equipped with a horizontal ATR measurement unit with a diamond crystal. Liquid samples were applied undiluted as films; solid samples were dissolved in CH.sub.2Cl.sub.2.

[0250] The skin time (HBZ) was determined by applying a few grams of the composition to cardboard in a film thickness of about 2 mm and measuring under standard climatic conditions the time until, upon gentle tapping of the surface of the composition using an LDPE pipette, no residue remained on the pipette for the first time.

[0251] The characteristics of the surface were tested by touch.

[0252] The mechanical properties of tensile strength, elongation at break and modulus of elasticity (at 0-25% or at 0-5% and 0-50% elongation) were measured in accordance with DIN EN 53504 at a pulling speed of 200 mm/min. Viscosity was measured on a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1, cone tip-plate distance 0.05 mm, shear rate 10 rpm).

Carbodiimide Adducts of the Formula (II) Used:

Carbodiimide Adduct A1:

[0253] Commercial carbodiimide adduct having a carbodiimide equivalent weight of about 700 g/mol (Picassian XL-725 from Stahl Polymers).

Carbodiimide Adduct A2:

[0254] In a round-bottom flask, 100.00 g of dicyclohexylmethane 4,4-diisocyanate (Desmodur W, from Covestro) and 0.07 g of 1-oxo-3-methyl-1-phenyl-2-phosphylene were mixed and heated under a nitrogen atmosphere. The mixture was stirred first at 180 C. for 2 h, then at 200 C. for 22 h, drawing vacuum (500 mbar) for 3 min every full hour. Thereafter, the content of free isocyanate groups determined by titrimetry was 11.4% by weight. 119.06 g of UCON OSP-18 (polyalkylene glycol monool having an average molecular weight of 500 g/mol, from Dow) were added and the mixture was stirred at 140 C. After 16 h, no free isocyanate was detectable any longer by means of FT-IR spectroscopy. The polycarbodiimide adduct obtained was cooled down to room temperature and stored with exclusion of moisture. What was obtained was a yellowish, clear liquid having a calculated carbodiimide equivalent weight of 748 g/mol.

Carbodiimide Adduct A3:

[0255] In a round-bottom flask, 50.00 g of dicyclohexylmethane 4,4-diisocyanate (Desmodur W, from Covestro), 50.00 g of hexamethylene 1,6-diisocyanate (Desmodur H, from Covestro) and 0.08 g of 1-oxo-3-methyl-1-phenyl-2-phosphylene were mixed and heated under a nitrogen atmosphere. The mixture was stirred first at 180 C. for 2 h, then at 200 C. for 6 h, drawing vacuum (500 mbar) for 3 min every full hour. Thereafter, the content of free isocyanate groups determined by titrimetry was 14.5% by weight. 75.84 g of UCON OSP-18 (polyalkylene glycol monool having an average molecular weight of 500 g/mol, from Dow) were added in order to convert half the isocyanate groups present and to lower the viscosity of the mixture. Ultimately, the mixture was stirred at 160 C. for a further 5 h, after which the content of free isocyanate groups was 4.3% by weight. A further 85.55 g of UCON OSP-18 were added and the mixture was stirred at 140 C. After 18 h, no free isocyanate was detectable any longer by means of FT-IR spectroscopy. The polycarbodiimide adduct obtained was cooled down to room temperature and stored with exclusion of moisture. What was obtained was a yellowish, clear liquid of high viscosity having a calculated carbodiimide equivalent weight of 716 g/mol.

Preparation of guanidines of the formula (I):

Guanidine G1:

[0256] In a round-bottom flask, 7.00 g of carbodiimide adduct A1 and 2.02 g of hexylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 100 C. for 24 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. 0.09 g of vinyltriethoxysilane was added and the mixture was cooled down to room temperature. What was obtained was a brownish, clear, odorless solid.

Guanidine G2:

[0257] In a round-bottom flask, 7.00 g of carbodiimide adduct A1 and 1.42 g of 2-ethylhexylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 80 C. for 24 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. 0.09 g of vinyltriethoxysilane was added and the mixture was cooled down to room temperature. What was obtained was an odorless, brownish, clear liquid.

Guanidine G3:

[0258] In a round-bottom flask, 10.00 g of carbodiimide adduct A2 and 1.90 g of 2-ethylhexylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 120 C. for 48 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. 0.12 g of vinyltriethoxysilane was added and the mixture was cooled down to room temperature. What was obtained was an odorless, yellow, clear liquid of high viscosity.

Guanidine G4:

[0259] In a round-bottom flask, 10.00 g of carbodiimide adduct A3 and 1.97 g of 2-ethylhexylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 120 C. for 48 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. 0.10 g of vinyltriethoxysilane was added and the mixture was cooled down to room temperature. What was obtained was an odorless, yellow, clear liquid.

Guanidine G5:

[0260] In a round-bottom flask, 7.00 g of carbodiimide adduct A1 and 2.02 g of 3-(2-ethylhexyloxy)propylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 100 C. for 48 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. What was obtained was a brownish, clear, odorless solid.

Guanidine G6:

[0261] In a round-bottom flask, 10.00 g of carbodiimide adduct A2 and 2.77 g of 3-(2-ethylhexyloxy)propylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 120 C. for 48 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. What was obtained was an odorless, yellow, clear liquid.

Guanidine G7:

[0262] In a round-bottom flask, 10.00 g of carbodiimide adduct A3 and 2.89 g of 3-(2-ethylhexyloxy)propylamine were mixed under a nitrogen atmosphere and the mixture was stirred at 120 C. for 48 h. Then the carbodiimide band in the FT-IR at about 2120 cm.sup.1 had completely disappeared. What was obtained was an odorless, yellow, clear liquid.

Preparation of Polyethers Having Silane Groups:

Polymer STP-1:

[0263] With exclusion of moisture, 1000 g of Acclaim 12200 polyol (polyoxypropylenediol having a low level of unsaturation, from Covestro; OH number 11.0 mg KOH/g), 43.6 g of isophorone diisocyanate (IPDI; Vestanat IPDI, from Evonik), 126.4 g of diisononyl cyclohexane-1,2-dicarboxylate (DINCH) and 0.1 g of bismuth tris(neodecanoate) (10% by weight in DINCH) were heated up to 90 C. while stirring constantly and left at this temperature until the content of free isocyanate groups determined by titrimetry had reached a stable value of 0.63% by weight. Subsequently, 63.0 g of diethyl N-(3-trimethoxysilylpropyl)aminosuccinate (adduct of 3-aminopropyltrimethoxysilane and diethyl maleate; prepared as per U.S. Pat. No. 5,364,955) were mixed in and the mixture was stirred at 90 C. until it was no longer possible to detect any free isocyanate by FT-IR spectroscopy. The polyether having trimethoxysilane groups obtained in this way was cooled down to room temperature and stored with exclusion of moisture.

Polymer STP-2:

[0264] With exclusion of moisture, 1000 g of Acclaim 12200 polyol (polyoxypropylenediol having a low level of unsaturation, from Covestro; OH number 11.0 mg KOH/g), 43.6 g of isophorone diisocyanate (IPDI; Vestanat IPDI, from Evonik), 126.4 g of diisononyl cyclohexane-1,2-dicarboxylate (DINCH) and 0.1 g of bismuth tris(neodecanoate) (10% by weight in DINCH) were heated up to 90 C. while stirring constantly and left at this temperature until the content of free isocyanate groups determined by titrimetry had reached a stable value of 0.64% by weight. Subsequently, 70.6 g of diethyl N-(3-triethoxysilylpropyl)-aminosuccinate (adduct formed from 3-aminopropyltriethoxysilane and diethyl maleate) were mixed in and the mixture was stirred at 90 C. until it was no longer possible to detect any free isocyanate by means of FT-IR spectroscopy. The polyether having triethoxysilane groups obtained in this way was cooled down to room temperature and stored with exclusion of moisture.

Commercial Catalysts Used:

[0265] DBU 1,8-diazabicyclo[5.4.0]undec-7-ene (Lupragen N 700, from BASF) TMG 1,1,3,3-tetramethylguanidine (from Sigma-Aldrich)

Compositions Based on Polymers Having Silane Groups:

[0266] Comparative examples in tables 1 to 4 are indicated by (Ref).

Compositions Z1 to Z9:

[0267] A composition composed of 97.6 g of polymer STP-1, 2.0 g of vinyltrimethoxysilane and 0.4 g of 3-aminopropyltrimethoxysilane was blended with various catalysts in the amount specified according to table 1, and the mixture was tested for viscosity at 25 C. and skin time (HBZ) under standard climatic conditions, before and after storage. Skin time serves as a measure of the activity of the catalyst in relation to the crosslinking reaction of the silane groups, i.e. of the crosslinking rate; the change in viscosity and the skin time after storage are a measure of storage stability of the composition. In addition, the mixture applied, after 24 h under standard climatic conditions, was tested as to whether the surface was dry as desired or whether a greasy film had formed, which is a sign of the exudation of the catalyst owing to poor compatibility with the cured polymer, and/or whether the surface was tacky, which is a sign of incomplete curing. In addition, the mixture was used to produce a film of thickness 2 mm, which was cured under standard climatic conditions for 7 days and tested for mechanical properties.

[0268] For the preparation of compounds Z1 and Z5, the guanidine G1 and G5, respectively, was liquefied beforehand at 60 C.

[0269] The results are shown in tables 1 and 2.

TABLE-US-00001 TABLE 1 Viscosity Compo- Concen- [Pa .Math. s] HBZ sition Catalyst Amount tration.sup.1 fresh stored.sup.2 fresh stored.sup.2 Z1 Guanidine 1.69 g 1.9 42.7 53.1 11 9 G1 Z2 Guanidine 1.57 g 1.9 41.7 54.8 22 14 G2 Z3 Guanidine 1.66 g 1.9 50.0 40.2 14 21 G3 Z4 Guanidine 1.72 g 1.9 30.2 27.5 24 27 G4 Z5 Guanidine 1.67 g 1.9 46.1 58.0 22 33 G5 Z6 Guanidine 1.77 g 1.9 32.2 30.4 23 15 G6 Z7 Guanidine 1.84 g 1.9 31.1 22.9 21 21 G7 Z8 DBU 0.30 g 26.3 31.0 29 31 (Ref) Z9 TMG 0.22 g 1.9 22.3 24.6 65 75 (Ref) .sup.1mmol of guanidine groups per 100 g of polyether having silane groups. .sup.2for 7 days at 70 C. in a closed container.

TABLE-US-00002 TABLE 2 Surface Tensile Elongation Modulus of elasticity Composition after 24 h strength at break 0-5% 0-50% Z1 dry 0.75 MPa 101% 1.1 MPa 0.8 MPa Z2 dry 0.76 MPa 101% 1.1 MPa 0.8 MPa Z3 dry 0.78 MPa 111% 1.1 MPa 0.8 MPa Z4 dry 0.83 MPa 123% 1.1 MPa 0.8 MPa Z5 dry 0.89 MPa 136% 1.1 MPa 0.8 MPa Z6 dry 0.83 MPa 126% 1.2 MPa 0.8 MPa Z7 dry 0.78 MPa 114% 1.2 MPa 0.8 MPa Z8 (Ref) greasy 0.70 MPa 95% 1.0 MPa 0.8 MPa Z9 (Ref) tacky 0.62 MPa 90% 1.2 MPa 0.8 MPa

Compositions Z10 to Z14:

[0270] In a planetary mixer, 36.2 g of polymer STP-2, 60.2 g of ground chalk (Omyacarb 5 GU, from Omya), 1.2 g of thixotropic paste, the preparation of which is described hereinafter, 1.2 g of vinyltriethoxysilane, 1.2 g of 3-aminopropyltriethoxysilane and various catalysts in the amount specified according to table 3 were blended, and the mixture was tested as described for composition Z1 for viscosity, skin time (HBZ), surface characteristics and mechanical properties. The results are shown in tables 3 and 4.

[0271] The thixotropic paste was prepared by gently heating an initial charge of 300 g of diisodecyl phthalate (Palatinol Z, from BASF) and 48 g of 4,4-methylene diphenyl diisocyanate (Desmodur 44 MC L, from Covestro) in a vacuum mixer and then slowly adding 27 g of n-butylamine dropwise while stirring vigorously.

[0272] The resultant paste was stirred for a further hour under reduced pressure while cooling.

TABLE-US-00003 TABLE 3 Viscosity Compo- Concen- [Pa .Math. s] HBZ sition Catalyst Amount tration.sup.1 fresh stored.sup.2 fresh stored.sup.2 Z10 Guanidine 2.33 g 2.6 174 145 3 h 3 h G3 2 32 Z11 Guanidine 2.41 g 2.6 162 140 3 h 2 h G4 19 49 Z12 Guanidine 2.48 g 2.6 167 143 1 h 2 h G6 44 11 Z13 Guanidine 2.58 g 2.6 165 133 2 h 2 h G7 30 41 Z14 DBU 0.40 g n.d. n.d. 1 h n.d. (Ref) 23 .sup.1mmol of guanidine groups per 100 g of composition. .sup.2for 7 days at 70 C. in a closed container.

TABLE-US-00004 TABLE 4 Surface Tensile Elongation Modulus of elasticity Composition after 24 h strength at break 0-5% 0-50% Z10 dry 3.1 MPa 145% 4.0 MPa 2.6 MPa Z11 dry 2.8 MPa 137% 5.1 MPa 2.8 MPa Z12 dry 2.9 MPa 142% 4.7 MPa 2.8 MPa Z13 dry 2.7 MPa 123% 4.5 MPa 2.7 MPa Z14 (Ref) greasy 2.5 MPa 155% 4.0 MPa 2.0 MPa