Thixotropic agent for curable compositions

Abstract

A thixotropic agent for increasing the yield point of a curable composition, wherein the thixotropic agent includes (i) at least one urea compound from the reaction of at least one isocyanate with at least one amine and (ii) at least one polyether having blocked hydroxyl groups. The thixotropic agent is preparable in a simple manner and forms a spreadable paste which is firm at room temperature. It is particularly suitable as a constituent of moisture-curing polyurethane or SMP compositions, giving a good increase in the yield point thereof, without adversely affecting storage stability or migration characteristics. It enables phthalate-free adhesives, sealants or coatings that have surprisingly good conveyability coupled with a high yield point, and do not cause any problems with odor or fogging.

Claims

1. A thixotropic agent for increasing the yield point of a curable composition, wherein the thixotropic agent comprises (i) at least one urea compound from the reaction of at least one isocyanate with at least one amine and (ii) at least one polyether having blocked hydroxyl groups which is free of urethane groups.

2. The thixotropic agent as claimed in claim 1, wherein the at least one urea compound has the formula (I) ##STR00004## where E is an alkyl or cycloalkyl radical having 1 to 12 carbon atoms, and Q is a divalent hydrocarbyl radical having 6 to 15 carbon atoms.

3. The thixotropic agent as claimed in claim 1, wherein the thixotropic agent takes the form of a spreadable paste which is firm at room temperature.

4. The thixotropic agent as claimed in claim 1, wherein 5% to 25% by weight of urea compounds and 50% to 95% by weight of polyethers having blocked hydroxyl groups are present.

5. The thixotropic agent as claimed in claim 1, wherein the at least one polyether having blocked hydroxyl groups has a viscosity at 20 C. in the range from 30 to 500 mPa.Math.s, where the viscosity is determined with a cone-plate viscometer having cone diameter 25 mm, cone angle 1, cone tip-plate distance of 0.05 mm, at a shear rate of 10 s.sup.1.

6. The thixotropic agent as claimed in claim 1, wherein the at least one polyether having blocked hydroxyl groups has an average of 1 to 3 blocked hydroxyl groups per molecule.

7. The thixotropic agent as claimed in claim 1, wherein the blocked hydroxyl groups are selected from the group consisting of acetal, ester, aceto ester and carbonate groups.

8. The thixotropic agent as claimed in claim 1, wherein 70% to 100% by weight of the repeat units in the at least one polyether having blocked hydroxyl groups consist of 1,2-propyleneoxy groups, and 0% to 30% by weight of the repeat units in the at least one polyether having blocked hydroxyl groups consists of 1,2-ethyleneoxy groups.

9. The thixotropic agent as claimed in claim 1, wherein the at least one polyether having blocked hydroxyl groups has an average molecular weight M.sub.n in the range from 600 to 2,500 g/mol, determined by means of gel permeation chromatography versus polystyrene as standard with tetrahydrofuran as mobile phase, refractive index detector and evaluation from 200 g/mol.

10. The thixotropic agent as claimed in claim 1, wherein the at least one polyether having blocked hydroxyl groups is derived from at least one hydroxy-functional polyether selected from the group consisting of alcohol-started, polyoxypropylene monools having an OH number in the range from 25 to 90 mg KOH/g, polyoxypropylene diols having an OH number in the range from 45 to 155 mg KOH/g and trimethylolpropane-started, optionally ethylene oxide terminated, polyoxypropylene triols having an average OH functionality in the range from 2.2 to 3 and an OH number in the range from 90 to 230 mg KOH/g.

11. A preparation of the thixotropic agent as claimed in claim 1, wherein the reaction between the at least one isocyanate and the at least one amine is performed in the at least one polyether having blocked hydroxyl groups.

12. A method comprising applying the thixotropic agent as claimed in claim 1 in a curable composition for increasing the yield point of the curable composition.

13. A curable composition comprising the thixotropic agent as claimed in claim 1 and at least one polymer containing isocyanate and/or silane groups.

14. The curable composition as claimed in claim 13, wherein it is a one-component moisture-curing composition.

15. An article bonded or sealed or coated with the curable composition as claimed in claim 13.

Description

EXAMPLES

(1) Working examples are adduced hereinafter, which are intended to elucidate the invention described in more detail. The invention is of course not limited to these described working examples.

(2) Standard climatic conditions (SCC) refer to a temperature of 231 C. and a relative air humidity of 505%.

(3) Unless otherwise stated, the chemicals used were from Sigma-Aldrich Chemie GmbH.

(4) Preparation of Polyethers Having Blocked Hydroxyl Groups:

(5) Viscosity was measured with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 25 mm, cone angle 1, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.1).

(6) Infrared spectra (FT-IR) were measured as undiluted films on a Nicolet iS5 FT-IR instrument from Thermo Scientific equipped with a horizontal ATR measurement unit with a diamond crystal. The absorption bands are reported in wavenumbers (cm.sup.1).

(7) .sup.1H NMR spectra were measured on a spectrometer of the Bruker Ascend 400 type at 400.14 MHz; the chemical shifts are reported in ppm relative to tetramethylsilane (TMS). No distinction was made between true coupling and pseudo-coupling patterns.

(8) Polyether-1: n-butanol-started acetylated PPG monool with average molecular weight about 800 g/mol

(9) 120.00 g of n-butanol-started polyoxypropylene monool (Synalox 100-20B, average molecular weight about 750 g/mol; from DowDuPont Inc.) and 18.74 g of acetic anhydride were initially charged in a round-bottom flask with distillation attachment under a nitrogen atmosphere. Then the reaction mixture was stirred under a gentle nitrogen stream at 130 C., with collection of acetic acid as distillate. Subsequently, the volatile constituents were removed from the reaction mixture at 80 C. and a reduced pressure of 10 mbar. A clear, colorless liquid having a viscosity of 75 mPa.Math.s at 20 C. was obtained.

(10) FT-IR: 2970, 2931, 2867, 1738, 1454, 1372, 1345, 1296, 1241, 1098, 1014, 959, 925, 866, 827.

(11) .sup.1H NMR (CDCl.sub.3): 5.02 (hept., 1 H, CH.sub.2(CH.sub.3)CHOAc), 3.75-3.34 (2m, about 39 H, OCH.sub.2CH(CH.sub.3)O), 3.33-3.28 (m, 2H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O), 2.04 (s, 3H, O(CO)CH.sub.3), 1.55 (quint., 2 H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O), 1.36 (sext., 2 H,

(12) CH.sub.3CH.sub.2CH.sub.2CH.sub.2O), 1.22 (d, 3H, CH.sub.2(CH.sub.3)CHOAc), 1.17-1.10 (m, about 36 H, OCH.sub.2CH(CH.sub.3)O), 0.91 (t, 3H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O).

(13) Polyether-2: n-butanol-started polypropylene glycol with 1-(isobutoxy)ethoxy end group and average molecular weight of about 1,200 g/mol 300.00 g of n-butanol-started polyoxypropylene monool with average molecular weight 1,100 g/mol (Synalox 100-40B, from DowDuPont Inc.) and 0.17 g of methanesulfonic acid (anhydrous) were initially charged in a round-bottom flask under nitrogen atmosphere. Then 28.16 g of isobutyl vinyl ether (stabilized with 0.1% potassium hydroxide) was slowly added dropwise while stirring, such that the temperature of the reaction mixture did not rise above 70 C., and then the mixture was stirred at 70 C. under a nitrogen atmosphere until no hydroxyl groups were detectable any longer by means of IR and GC spectrometry. Subsequently, 0.07 g of sodium methoxide was added and stirred in, followed by 0.06 g of acetic acid. Then the volatile constituents were removed from the reaction mixture, first at 80 C. and a reduced pressure of 5 mbar and then at 100 C. and 2 mbar. A clear, yellowish liquid having a viscosity of 205 mPa.Math.s at 20 C. was obtained.

(14) FT-IR: 2969, 2931, 2868, 1455, 1372, 1344, 1296, 1257, 1099, 1012, 924, 906, 867, 831.

(15) Polyether-3: Diacetylated PPG diol with average molecular weight about 1,100 g/mol

(16) 80.00 g of polyoxypropylene diol (Voranol P 1010, OH number 110 mg KOH/g; from DowDuPont Inc.) and 18.74 g of acetic anhydride were converted as described for polyether-1. A clear, colorless liquid having a viscosity of 145 mPa.Math.s at 20 C. was obtained.

(17) Preparation of Thixotropic Agents:

(18) Thixotropic Agent T-1 (Inventive):

(19) A vacuum mixer was initially charged with 300 g of polyether-1 and 48 g of methylene diphenyl 4,4-diisocyanate (Desmodur 44 MC L, from Covestro AG) and heated up slightly, and then 27 g of n-butylamine was slowly added dropwise with vigorous stirring. The resultant paste was stirred for a further hour under reduced pressure while cooling. A white, finely divided, homogeneous, spreadable paste was obtained.

(20) Thixotropic Agent T-2 (Inventive):

(21) Prepared as described for thixotropic agent T-1, except that 300 g of polyether-2 was used in place of polyether-1. A yellowish, finely divided, homogeneous, spreadable paste was obtained.

(22) Thixotropic Agent T-3 (Inventive):

(23) Prepared as described for thixotropic agent T-1, except that 300 g of polyether-3 was used in place of polyether-1. A white, finely divided, homogeneous, spreadable paste was obtained.

(24) Thixotropic Agent T-4 (Comparative Example):

(25) Prepared as described for thixotropic agent T-1, except that 300 g of diisodecyl phthalate (Palatinol 10-P, from BASF SE) was used in place of polyether-1. A white, finely divided, homogeneous, spreadable paste was obtained.

(26) Thixotropic Agent T-5 (Comparative Example):

(27) Prepared as described for thixotropic agent T-1, except that 300 g of diisononyl cyclohexane-1,2-dicarboxylate (Hexamoll DINCH, from BASF SE) was used in place of polyether-1. A white, finely divided, homogeneous, spreadable paste was obtained.

(28) Thixotropic Agent T-6 (Comparative Example):

(29) Prepared as described for thixotropic agent T-1, except that 300 g of di(2-ethylhexyl) adipate (Plastomoll DOA, from BASF SE) was used in place of polyether-1. A white, finely divided, homogeneous, spreadable paste was obtained.

(30) Some thixotropic agents were tested as follows for sag resistance and expression force:

(31) Sag resistance was determined by applying about 8 ml of the paste under standard climatic conditions by means of a cartridge tip with internal diameter 10 mm onto a vertical corrugated cardboard surface so as to result in a nose protruding horizontally for about 50 mm and having a diameter of about 20 mm. After 3 hours, the extent to which the nose had sagged from the horizontal position, measured at the tip, was determined. A sag of less than 2 mm was rated as good, 2 to 5 mm as average, and more than 5 mm as poor.

(32) Expression force (5 mm; 3 mm; 2 mm) was determined by introducing the paste into a standard aluminum cartridge, then screwing on a nozzle having internal diameter 5 mm or 3 mm or 2 mm and using an expression device (Zwick/Roell Z005) to measure the force expended in order to express the thixotropic agent through the respective nozzle at an expression rate of 60 mm/min. The value reported is an average of the forces that were measured after an expression distance of 22 mm, 24 mm, 26 mm and 28 mm.

(33) The results are shown in table 1.

(34) TABLE-US-00001 TABLE 1 Properties of thixotropic agents T-1 and T-4. T-1 T-4 Thixotropic agent (inventive) (comparative example) Sag resistance good good Expression force [N] 5 mm 518 566 3 mm 696 760 2 mm 854 951
Production of Curable (One-Component) Compositions:
Polymer P1:

(35) 590 g of polyoxypropylene diol (Acclaim 4200, from Covestro AG; OH number 28.5 mg KOH/g), 1180 g of polyoxypropylenepolyoxyethylene triol (Caradol MD34-02, from Shell Chemicals Co.; OH number 35.0 mg KOH/g) and 230 g of isophorone diisocyanate (Vestanat IPDI, from Evonik Industries AG) were reacted by a known method at 80 C. to give a polymer containing isocyanate groups which is liquid at room temperature and has a content of free isocyanate groups of 2.1% by weight.

(36) Polymer P2:

(37) 400 g of polyoxypropylene diol (Acclaim 4200, from Covestro AG; OH number 28.5 mg KOH/g) and 52 g of diphenylmethane 4,4-diisocyanate (Desmodur 44 MC L, from Covestro AG) were reacted by a known process at 80 C. to give an NCO-terminated polymer which is liquid at room temperature and has a content of free isocyanate groups of 1.85% by weight.

(38) Polymer P3:

(39) 3080 g of polyoxypropylene diol (Acclaim 4200, from Covestro AG; OH number 28.5 mg KOH/g), 1540 g of polyoxypropylenepolyoxyethylene triol (Caradol MD34-02, from Shell Chemicals Co.; OH number 35.0 mg KOH/g) and 385 g of tolylene diisocyanate (Desmodur T 80 P, Covestro AG) were reacted at 80 C. by a known method to give an NCO-terminated polyurethane polymer which is liquid at room temperature and has a content of free isocyanate groups of 1.5% by weight.

(40) Aldimine-1: N,N-Bis(2,2-dimethyl-3-lauroyloxypropylidene)-3-aminomethyl-3,5,5-trimethylcyclohexylamine

(41) 598 g (2.1 mol) of 2,2-dimethyl-3-lauroyloxypropanal was initially charged in a round-bottom flask under a nitrogen atmosphere. Then 170.3 g (1 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (Vestamin IPD, from Evonik Industries AG) was added with good stirring, and then the volatile constituents were removed at 80 C. and a reduced pressure of 10 mbar. 732 g of a colorless liquid having an amine content of 2.73 mmol N/g was obtained, corresponding to a calculated aldimine equivalent weight of 367 g/mol.

(42) Compositions Z1 and Z2

(43) For each composition, the ingredients specified in table 2 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute.

(44) Sag resistance of each composition was determined by applying about 8 ml of the composition under standard climatic conditions by means of a cartridge tip with internal diameter 10 mm onto a vertical corrugated cardboard surface so as to result in a nose protruding horizontally for about 50 mm and having a diameter of about 20 mm. After curing under standard climatic conditions, the extent to which the nose had sagged from the horizontal position, measured at the tip, was determined. A sag of less than 15 mm was rated as good, 15 to 30 mm as average, and more than 30 mm as poor.

(45) The results are reported in table 2.

(46) Compositions labeled (Ref.) are comparative examples.

(47) TABLE-US-00002 TABLE 2 Composition (in parts by weight) and properties of Z1 and Z2. Z2 Composition Z1 (Ref.) Polymer P1 200.0 200.0 Thixotropic agent T-1 T-4 200.0 200.0 Sag resistance good good
Compositions Z3 to Z6

(48) For each composition, the ingredients specified in table 3 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute.

(49) For each composition, formation of specks on cardboard was determined as a measure of plasticizer migration. For this purpose, each composition was applied to a piece of cardboard such that it had a round base area of diameter 15 mm and a height of 4 mm, and was stored under standard climatic conditions for 7 days. Around each composition, thereafter, a dark oval stain had formed on the cardboard. The dimensions thereof (height and width) were measured and reported in table 3 as Migration.

(50) Compositions labeled (Ref.) are comparative examples.

(51) TABLE-US-00003 TABLE 3 Composition (in parts by weight) and properties of Z3 to Z6. Z4 Z5 Z6 Composition Z3 (Ref.) (Ref.) (Ref.) Polymer P2 80.00 80.00 80.00 80.00 Chalk.sup.1 80.00 80.00 80.00 80.00 Thixotropic agent T-1 T-4 T-5 T-6 115.9 115.9 115.9 115.9 2,2-Dimorpholinodiethylether 0.26 0.26 0.26 0.26 Migration Height 0.5 0.5 1 3 (7 d) mm Width 1 1 2 4 .sup.1Omyacarb 5 GU (from Omya AG)
Compositions Z7 to Z9

(52) For each composition, the ingredients specified in table 4 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute and stored with exclusion of moisture.

(53) Each composition was tested as follows:

(54) Sag resistance was determined as described for composition Z1. An assessment was additionally made as to whether a long thread was drawn when the application tool was pulled away after the application of the nose. If no thread formed, but rather a short tip of less than 10 mm, threading was assessed as no.

(55) As a measure of the open time, skin time (ST) was determined. For this purpose, a few grams of the composition was applied to cardboard in a layer thickness of about 2 mm and, under standard climatic conditions, the first period of time after which no residues remained any longer on an LDPE pipette used to gently tap the surface of the composition was determined.

(56) Shore A hardness was determined to DIN 53505 on test specimens cured under standard climatic conditions for 14 days.

(57) To determine the mechanical properties, the composition was applied to a PTFE-coated film to give a film of thickness 2 mm, the film was stored under standard climatic conditions for 14 days, and a few dumbbells having a length of 75 mm with a bar length of 30 mm and a bar width of 4 mm were punched out of the film and these were tested in accordance with DIN EN 53504 at a strain rate of 200 mm/min for Tensile strength (breaking force), Elongation at break, Modulus of elasticity 5% (at 0.5%-5% elongation) and Modulus of elasticity 25% (at 0.5%-25% elongation).

(58) Appearance was assessed visually on the films produced. Nice was used to describe a nontacky film without blisters.

(59) Odor was assessed by smelling by nose at a distance of 2 cm from the freshly produced films. No means that no odor was perceptible.

(60) The results are reported in table 4.

(61) TABLE-US-00004 TABLE 4 Composition (in parts by weight) and properties of Z7 to Z9. Composition Z7 Z8 Z9 Polymer P3 28.00 28.00 28.00 Aldimine-1 2.58 2.58 2.58 Polyether-1 14.00 Polyether-2 14.00 Polyether-3 14.00 Thixotropic agent T-1 T-2 T-3 20.00 20.00 20.00 Chalk .sup.1 33.89 33.89 33.89 Salicylic acid solution .sup.2 1.50 1.50 1.50 Dibutyltin dilaurate 0.03 0.03 0.03 Sag resistance good good good Threading no no no ST [min] 25 25 25 Shore A 10 9 16 Tensile strength [MPa] 1.14 1.22 1.37 Elongation at break [%] 809 776 784 Modulus of elasticity 5% 0.52 0.44 0.54 [MPa] Modulus of elasticity 25% 0.26 0.26 0.45 [MPa] Appearance nice nice nice Odor no no no .sup.1 Omyacarb 5-GU (from Omya AG) .sup.2 5% by weight in di(2-ethylhexyl) adipate