Tin- and phthalate-free sealant based on silane terminated polymers

Abstract

The present invention provides a moisture-curing sealant comprising a) at least one silane-functional polymer and b) at least one catalyst for the crosslinking of the silane-functional polymer, said sealant being free of organotin compounds and having, in the cured state, a secant modulus at 100% elongation and 23 C., determined to ISO 8339, of less than 0.4 MPa and a resilience at 100% elongation, determined to ISO 7389, of greater than 70%. The sealant is especially suitable as a construction sealant of the 25LM class according to DIN EN ISO 11600, especially as a facade sealant, or as a sealant according to ASTM C719 Class 50.

Claims

1. A moisture-curing sealant comprising a) at least one silane-functional polymer P; b) at least one catalyst for the crosslinking of the silane-functional polymer P, and c) at least 10 wt % of at least one plasticizer based on renewable raw materials, wherein the sealant is free from organotin compounds and in the cured state has a secant modulus at 100% elongation and 23 C., determined to DIN EN ISO 8339, of less than 0.4 MPa and an elastic recovery at 100% elongation, determined to DIN EN ISO 7389, of 70%.

2. The sealant as claimed in claim 1, wherein the sealant is free from phthalate-containing compounds.

3. The sealant as claimed in claim 1, wherein the silane-functional polymer P does not eliminate methanol on curing.

4. The sealant as claimed in claim 1, wherein the sealant has an extrusion force at 23 C. of less than 800 N.

5. The sealant as claimed in claim 1, wherein the sealant a) is free from phthalate compounds, b) is free from tin, c) eliminates no methanol on curing, and d) comprises renewable raw materials.

6. The sealant as claimed in claim 1, wherein the sealant is a construction sealant of class 25LM according to ISO 11600.

7. The sealant as claimed in claim 1, wherein the sealant further comprises: c) the at least one plasticizer comprising diisononyl 1,2-cyclohexanedicarboxylate, an alkylsulfonic ester of phenol, rapeseed oil methyl ester, and mixtures thereof, and/or d) at least one filler, the at least one filler being present in the sealant in an amount of 10 wt % to 80 wt %.

8. The sealant as claimed in claim 1, wherein the plasticizer is a rapeseed oil methyl ester.

9. The sealant as claimed in claim 1, wherein the catalyst for the crosslinking of the silane-functional polymer P comprises a compound which has at least one amidino group.

10. The sealant as claimed in claim 1, wherein the silane-functional polymer P is a -silane-terminated polymer.

11. The sealant as claimed in claim 1, wherein the sealant comprises: a) 20 wt % to 30 wt % of at least one silane-functional polymer P, optionally of a -silane-terminated polymer, the silane-functional polymer P optionally being a silane-functional polymer P which eliminates no methanol on curing, b) 0.01 wt % to 2 wt % of at least one catalyst for the crosslinking of the silane-functional polymer P, optionally a compound which has at least one amidino group, or a bicyclic amidine, and/or organotitanate, optionally a combination of a compound which has at least one amidino group, optionally a bicyclic amidine, and an organotitanate, c1) at least 10% of at least one plasticizer based on a renewable raw material, c2) 0 wt % to 50 wt % of at least one other plasticizer not based on renewable raw materials, optionally a mineral oil, an alkylsulfonic ester of phenol or a fatty acid alkyl ester or a combination thereof, and d) 10 to 60 wt % of at least one filler, and wherein the sealant does not release methanol on curing.

12. The sealant as claimed in claim 1, wherein the sealant in the cured state meets at least one of the following conditions: a) an elongation at break, determined to DIN 53504, of more than 300%, b) a Shore A hardness, determined to DIN 53505, of 10 to 40, c) a skin-over time of 20 min to 360 min.

13. The sealant as claimed in claim 1, wherein the silane-functional polymer P is selected from: a silane-functional polyurethane polymer P1, obtained by the reaction of a silane having at least one group that is reactive toward isocyanate groups with a polyurethane polymer comprising isocyanate groups, a silane-functional polyurethane polymer P2, obtained by the reaction of an isocyanatosilane with a polymer which has functional end groups that are reactive toward isocyanate groups, or a silane-functional polymer P3, obtained by a hydrosilylation reaction of polymers having terminal double bonds.

14. The sealant as claimed in claim 1, wherein the sealant comprises an organically modified castor oil as thixotropic agent and precipitated coated calcium carbonate as filler.

15. The sealant as claimed in claim 1, wherein the sealant meets the requirements according to ASTM C719 class 50 or the requirements according to ASTM C719 class 50.

16. A construction sealant obtained from the sealant as claimed in claim 1.

17. A cured sealant obtained from the sealant as claimed in claim 1 after curing thereof with water.

18. The sealant as claimed in claim 1, wherein the at least one plasticizer comprises diisononyl 1,2-cyclohexanedicarboxylate, an alkylsufonic ester of phenol, rapeseed oil methyl ester, or combination thereof.

19. The sealant as claimed in claim 1, wherein the catalyst for crosslinking of the silane-functional polymer P comprises a bicyclic amidine, a guanidine, a organotitanate, or a combination thereof.

20. The sealant as claimed in claim 1, wherein the catalyst for crosslinking of the silane-functional polymer P comprises a bicyclic amidine, a guanidine, and a organotitanate.

Description

EXAMPLES

(1) Set out below are working examples which are intended to elucidate the invention described in more detail. The invention is of course not confined to these working examples described. Unless otherwise stated, quantities and percentages are by weight.

(2) Test Methods

(3) The secant modulus is determined at 100% elongation and 23 C. in accordance with DIN EN ISO 8339.

(4) The elastic recovery is determined at 100% elongation in accordance with ISO 7389 (DIN concrete slabs, storage for curing: 28 days at 23 C., 50% relative humidity). For this purpose, two concrete slabs are arranged with the aid of two Teflon spacers on a polyethylene sheet to give a space in between (121250 mm), into which the sealant under test is filled. The sealant is cured under the conditions stated above. The sample is subsequently subjected to elongation by 100% using a tensile strength testing machine according to DIN 51221, part 2, class 1 (elongation distance from 12 to 24 mm), and metal spacers with a width of 24 mm are inserted. The sample is taken from the testing machine and held in the elongated position for 24 hours. The spacers are then removed and the sample is placed on a glass plate treated with talcum powder. After 1 hour, the distance is measured and is used to calculate the elastic recovery in accordance with the formula in ISO 7389.

(5) The tensile strength, the elongation at break, and the modulus of elasticity at 0-100% elongation were determined according to DIN 53504 (tensile speed: 200 mm/min) on films with a layer thickness of 2 mm, cured for 14 days at 23 C. and 50% relative humidity.

(6) The tear resistance was determined according to DIN 53515, on films with a layer thickness of 2 mm, cured for 7 days at 23 C. and 50% relative humidity.

(7) The skin-over time (time until freedom from tack, tack-free time) was determined at 23 C. and 50% relative humidity. For the determination of the skin-over time, a small part of the adhesive at room temperature was applied in a layer thickness of about 2 mm to paper board, and a record was made of the time which elapsed until for the first time, when the surface of the adhesive was gently touched with an LDPE pipette, there were no longer any residues left on the pipette.

(8) For the determination of the extrusion force, the compositions were introduced into internally coated aluminum cartridges (outer diameter 46.9 mm, inner diameter 46.2 mm, length 215 mm, aperture 15-M) and given an airtight seal with a polyethylene stopper (diameter 46.1 mm) from Novelis Deutschland GmbH. After conditioning at 23 C. for 24 hours, the cartridges were opened and the contents extruded using an extrusion device. For this device, a nozzle with a 3 mm inside diameter opening was screwed onto the cartridge thread. Using an extrusion device (Zwick/Roell Z005), a determination was made of the force needed to extrude the composition at an extrusion rate of 60 mm/min. The figure reported is an average value of the forces measured after an extrusion distance of 22 mm, 24 mm, 26 mm, and 28 mm. After an extrusion distance of 30 mm, measurement was halted.

(9) The cure rate is determined by means of through-curing in a wedge. This is done using a Teflon wedge mold (wedge length (L) 300 mm, maximum wedge depth (d) 10 mm, wedge width 10 mm). The sealant is introduced, without bubbles and in excess, starting from the lowest point of the wedge up to the end of the wedge. The protruding sealant is pressed into the holes still present at the edges of the mold, using a wooden spatula, and the remainder is taken off with the spatula. The wedge is stored at 23 C. and 50% relative humidity, and the through-curing is determined after 1, 2, 3, 4, and 7 days. For this purpose, starting from the thin end of the now cured wedge, the sealant is pulled out of the mold until uncured sealant is found on the Teflon mold. The length of the sealant which has already cured is ascertained in mm (l). The sealant is subsequently replaced in the mold and gently pressed down. The through-curing is determined by the following formula (all figures in mm): D=(l.Math.d)/L, where D is through-curing, l is length of sealant already cured, L is wedge length, and d is maximum wedge depth.

(10) The Shore A hardness was determined according to DIN 53505 on samples with a layer thickness of 6 mm, cured for 14 days at 23 C. and 50% relative humidity.

(11) For example 4 and the commercial product Sonolastic, testing took place to determine whether they meet the requirements of ASTM C719 class 50.

(12) Production of the Silane-Functional Polyurethane Polymer with Ethoxy end Groups P-EtO

(13) Under a nitrogen atmosphere, 700 g of Acclaim 12200 polyol (Bayer MaterialScience AG, Germany; low monol polyoxypropylene diol; OH number 11.0 mg KOH/g; water content about 0.02 wt %), 32.1 g of isophorone diisocyanate (Vestanat IPDI, Evonik Degussa GmbH, Germany), 85.4 g of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (Eastman TXIB; Eastman Chemical Company, USA), and 0.1 g of bismuth tris(neodecanoate) (10 wt % in Hexamoll DINCH, BASF SE, Germany) were heated to 90 C. with continual stirring and left at this temperature. After a reaction time of an hour, titration found a free isocyanate group content of 0.7 wt %. Then 0.14 mol (corresponding to a stochiometric reaction of the NCO groups with silane) of reactive silane (Int-EtO) was added, and stirring was continued at 90 C. for 2 to 3 hours more. The reaction was discontinued as soon as free isocyanate was no longer detectable by IR spectroscopy (2275-2230 cm.sup.1). The product was cooled to room temperature (23 C.) and stored in the absence of moisture (theoretical polymer content=90%).

(14) The reactive silane Int-EtO (diethyl N-(3-triethoxysilylpropyl)aminosuccinate) was prepared as follows: 100 g of 3-aminopropyltriethoxysilane (Dynasylan AMEO from Evonik Degussa GmbH, Germany) were introduced. Added slowly with thorough stirring at room temperature were 77.8 g of diethyl maleate (Fluka Chemie GmbH, Switzerland) and the mixture was stirred at 60 C. for 12 hours.

(15) Production of the Silane-Functional Polyurethane Polymer with Methoxy End Groups P-MeO

(16) The silane-functional polyurethane polymer with methoxy end groups P-MeO was produced in the same way as the silane-functional polyurethane polymer with ethoxy end groups P-EtO, except that instead of the reactive silane Int-EtO the reactive silane Int-MeO (diethyl N-(3-trimethoxysilylpropyl)aminosuccinate) was used. The reactive silane Int-MeO was prepared in the same way as the reactive silane Int-EtO, but using 3-aminopropyltrimethoxysilane rather than 3-aminopropyltriethoxysilane.

(17) Production of the Thixotropic Agent TM

(18) A vacuum mixer was charged with 1000 g of diisononyl 1,2-cyclohexanedicarboxylate (DINCH, Hexamoll DINCH) and 160 g of 4,4-diphenylmethane diisocyanate (Desmodur44 MC L, Bayer MaterialScience AG, Germany) and this initial charge was slightly warmed. Then 90 g of monobutylamine were added dropwise slowly with vigorous stirring. The white paste formed was stirred further for an hour under reduced pressure and with cooling. The thixotropic agent TM contains 20 wt % of thixotropic agent in 80 wt % of DINCH.

(19) Production of the Sealants

(20) In a vacuum mixer, in accordance with the parts by weight indicated in table 1, the silane-functional polymer (P-MeO or P-EtO), plasticizers (Hexamoll DINCH and/or rapeseed oil methyl ester), thixotropic agents (TM or Thixatrol ST) and vinyltrimethoxy- and/or -triethoxysilane (Dynasylan VTMO and/or VTEO from Evonik Degussa GmbH, Germany) were mixed thoroughly for 5 minutes. Subsequently the fillers (Socal U1S2, Solvay SA, Belgium and Omyacarb 5-GU, Omya AG, Switzerland) were incorporated with kneading at 60 C. for 15 minutes. With the heating switched off, the remaining constituents (catalysts, silanes) were subsequently added and were processed to a homogeneous paste under reduced pressure for 10 minutes. This paste was then dispensed into internally coated aluminum gun-application cartridges.

(21) TABLE-US-00001 TABLE 1 Composition of the sealants in parts by weight Ex.1 Ex.2 Ex.3 Ex.4 P-MeO 25 25 25 P-EtO 27 Thixotropic agent TM 17 Thixatrol ST 8 8 8 Dynasylan VTEO 2 Dynasylan VTMO 1.4 1 1.0 Hexamoll DINCH 10 6 7 12.5 Rapeseed oil methyl ester 15 15 15 Hydroseal G400H 5 Omyacarb 5 GU 20 24 20 Socal U1S2 20 15 25 38 Tyzor IBAY 0.5 Tytan TAA 0.57 Lupragen N 700 (DBU) 0.03 0.03 0.5 0.03 Silquest A-1891 1 Silquest A-1110 0.57 0.4 0.47

(22) Testing of the Sealant Formulations

(23) The formulations produced were tested using the test methods reported above. For comparison, the following commercial products, likewise based on silane-functional polymers, were tested in the same way:

(24) TABLE-US-00002 Sikaflex Sikaflex AT-Connection from Sika Danalim Danalim MS Byggefuge 552 Ljungdahl Ljungdahl MS 20 Polymeric Modehvid Sonolastic Sonolastic 150 with VLM Technology from BASF

(25) The results are set out in table 2 below. Also included in table 2 is information on the presence of organotin catalysts and phthalate plasticizers in the respective formulations or commercial products, and also on the release of methanol on curing.

(26) TABLE-US-00003 TABLE 2 Secant modulus (23 C.) at 100% Elastic Methanol elongation recovery Organotin Phthalate released on [MPa] [%] cat. plasticizer curing Sikaflex 0.35 75 yes yes yes Danalim 0.45 20 yes yes yes Ljungdahl 0.47 35 yes no yes Sonolastic* 0.25 32 yes yes yes Ex.1 0.17 70 no no yes Ex.2 0.25 75 no no yes Ex.3 0.32 72 no no no Ex.4* 0.20 73 no no yes *comply with ASTM C719 class 50

(27) The properties of the sealants produced were investigated. The results are shown in table 3.

(28) TABLE-US-00004 TABLE 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Tensile strength [MPa] 14 d RT 0.7 1.0 1.5 0.9 Elongation at break 14 d RT 500 770 420 600 [%] Secant modulus [MPa] 28 d RT 0.17 0.25 0.32 0.20 Stress 24 h (100%) OK OK OK OK OK/coh./adh. Tear resistance 7 dRT 3.6 4.0 5.1 3.8 [N/mm] Elasticity modulus 0- 14 d RT 0.2 0.2 0.4 0.2 100% [MPa] Skin-over time [min] 1 d RT 120 50 40 110 Extrusion force [N] 1 d RT 230 286 650 245 Through-curing [mm] 1 d RT 2.8 3.6 2.7 3.0 2 d RT 5.5 5.5 4.2 5.4 3 d RT 6.8 6.9 5.1 6.7 4 d RT 8.1 8.0 7.8 8.2 7 d RT 9.2 9.8 8.9 9.3 Shore A 14 d RT 10 15 30 10 Elastic recovery 70 75 72 73