Thixotropic composition that can be used as an anti-running agent for mastics

Abstract

An adhesive sealant composition of at least one moisture-crosslinkable prepolymer and an anti-sagging agent of 5% to 30% by weight of a thixotropic composition of 10% to 40% by weight of a bisurea a) obtained by reaction of a primary aliphatic amine a1) with a diisocyanate a2) having a molar mass of less than 500 g/mol, and 60% to 90% by weight of an ester b) of formula (I): ##STR00001##
in which R.sup.1, R.sup.2 and R.sup.3 are an oxycarbonylalkyl radical having from 4 to 20 carbon atoms, R.sup.4 is hydrogen, methyl or ethyl or —CH.sub.2—R.sup.5 in which R.sup.5 is oxycarbonylalkyl having from 4 to 20 carbon atoms, in the form of a suspension of solid particles of bisurea a) in a continuous phase formed by ester b).

Claims

1. An adhesive sealant composition comprising at least one moisture-crosslinkable prepolymer and, as anti-sagging agent, from 5% to 30% by weight, on the basis of the total weight of said adhesive sealant composition, of a thixotropic composition comprising 10% to 40% by weight of a bisurea a) obtained by reaction of a primary aliphatic amine a1) with a diisocyanate a2), said diisocyanate a2) having a molar mass of less than 500 g/mol, and from 60% to 90% by weight of an ester b) of formula (I): ##STR00015## in which: R.sup.1, R.sup.2 and R.sup.3, which are identical or different, each represent an oxycarbonylalkyl radical having from 4 to 20 carbon atoms; R.sup.4 represents a hydrogen atom, a methyl or ethyl radical or a radical: —CH.sub.2—R.sup.5 in which R.sup.5 represents an oxycarbonylalkyl radical having from 4 to 20 carbon atoms; said thixotropic composition being in the form of a suspension of solid particles of bisurea a) in a continuous phase formed by the ester b).

2. The adhesive sealant composition according to claim 1, wherein the amine a1) is an n-alkylamine having 1 to 22 carbon atoms.

3. The adhesive sealant composition according to claim 1, wherein the amine a1) is n-butylamine.

4. The adhesive sealant composition according to claim 1, wherein the diisocyanate a2) has the formula (II):
NCO—R.sup.6—NCO  (II) in which R.sup.6 is one of the following divalent radicals, the formulae of which show 2 free valencies: a) the divalent radical derived from isophorone: ##STR00016## b) the divalent radical 4,4′-methylene-bis(cyclohexyl) ##STR00017## c) the divalent radical derived from toluene 2,4-diisocyanate (or 2,4-TDI) or from toluene 2,6-diisocyanate (or 2,6-TDI) of respective formulae: ##STR00018## d) the divalent radical derived from 4,2′-diphenylmethylene diisocyanate (or 4,2′-MDI) or from 4,4′-diphenylmethylene diisocyanate (or 4,4′-MDI), of formulae: ##STR00019## e) —(CH.sub.2).sub.6— (or hexamethylene radical); f) ##STR00020## or g) ##STR00021##

5. The adhesive sealant composition according to claim 1, wherein the diisocyanate a2) is 4,4′-diphenylmethylene diisocyanate.

6. The adhesive sealant composition according to claim 1, wherein the ester b) has the formula (I), in which R.sup.4 represents a radical: —CH.sub.2—R.sup.5.

7. The adhesive sealant composition according to claim 1, wherein the ester b) has the formula (I), in which: R.sup.1, R.sup.2 and R.sup.3 are identical and each represent an oxycarbonylalkyl radical having 4 or 5 carbon atoms; and R.sup.4 represents a radical: —CH.sub.2—R.sup.5 in which R.sup.5 is identical to R.sup.1, R.sup.2 and R.sup.3.

8. The adhesive sealant composition according to claim 1, wherein the ester b) is pentaerythritol tetravalerate.

9. The adhesive sealant composition according to claim 1, comprising: from 10% to 30% by weight of at least one moisture-crosslinkable prepolymer, from 20% to 70% by weight of at least one filler, from 5% to 25% by weight of the thixotropic composition, and from 0.01% to 1% by weight of at least one crosslinking catalyst, the percentages by weight being expressed with respect to the total weight of said adhesive composition.

10. The adhesive sealant composition according to claim 1, wherein the moisture-crosslinkable prepolymer is a polyurethane comprising —NCO end groups.

11. The adhesive sealant composition according to claim 1, comprising 5 to 35% by weight, on the basis of the weight of said adhesive sealant composition, of a plasticizer other than ester b).

12. A ready-to-use article comprising the adhesive sealant composition as defined in claim 1, in a hermetic packaging protected from air.

Description

(1) Example A (reference): thixotropic composition consisting of a 23.3% weight/weight suspension of bisurea in DIDP

(2) Prepared firstly are: a solution A of n-butylamine in DIDP, consisting of 17.17% weight/weight of n-butylamine and of 82.83% weight/weight of DIDP, then a solution B of 4,4′-MDI in DIDP, consisting of 29.46% weight/weight of 4,4′-MDI and of 70.34% weight/weight of DIDP.

(3) The two solutions A and B are heated to 100° C. and then introduced, each under a pressure of 100 bar, into a reactor, in which they are sprayed continuously over one another in a ratio A/B=50.1/49.9 by weight, corresponding to an n-butylamine/MDI molar ratio equal to 2. The reaction is immediate and the temperature of the reactor reaches 140° C. at the end of manufacture.

(4) At the reactor outlet, a stable 23.3% weight/weight dispersion of a bisurea in DIDP is obtained, the bisurea being of formula:

(5) ##STR00014##

(6) The Brookfield viscosity of the suspension, measured at 23° C., is 15 Pa.Math.s.

(7) Example B (reference): adhesive sealant composition based on polyurethane prepolymer comprising —NCO end groups comprising the thixotropic composition of Example A

(8) The following sealant composition, in which the percentages are weight/weight percentages, is prepared by simple mixing of the ingredients: 17% of polyurethane comprising —NCO end groups obtained by reaction of a mixture of 80% by weight of tolylene 2,4-diisocyanate and 20% by weight of tolylene 2,6-diisocyanate with a mixture of a polyether diol with a molar mass of 2000 g/mol and of polyether triol with a molar mass of 4200 g/mol, 25% of carbonate filler, 20% by weight of PVC, 15% by weight of the thixotropic composition of Example A, 10% by weight of DIDP as plasticizer, 8% by weight of xylene, 5% by weight of other additives, including the crosslinking catalyst.

(9) The polyurethane was introduced into the composition in the form of a solution in xylene.

(10) The sealant composition obtained is packaged in an aluminium cartridge, provided with a nozzle, for the purpose of its application by means of a gun for the tests described below.

(11) B.1. Test on the Migration of the Plasticizer:

(12) This test is a good indicator of the migration of the plasticizer out of the crosslinked sealant.

(13) A mass of 1 g of sealant, in the approximate shape of a sphere, is deposited, by means of the cartridge containing the composition of Example B, at the centre of a 1.sup.st square glass sheet with a side length of 5 cm, which was placed horizontally beforehand.

(14) A 2.sup.nd glass sheet identical to the 1.sup.st is subsequently strongly applied to said mass of sealant and by means of a manual pressure, so as to superimpose the two sheets and to thus spread the sealant in the approximate shape of a disc with a diameter of approximately 4.5 cm.

(15) There is then observed, through the upper glass sheet, the appearance of a transparent liquid exuded by the compressed disc of sealant, in the form of a ring surrounding said disc, with an annular radius of between 1 and 2 mm.

(16) B.2. Test on the Flow of the Non-Crosslinked Sealant after Extrusion:

(17) The aim of this test is to assess the extrudability, through the nozzle, of the cartridge-packaged sealant, under the effect of the pressure exerted by the piston, which is integral with the trigger of the gun actuated by the operator.

(18) With this aim, the sealant is extruded under air pressure through a calibrated nozzle and the weight discharged over one minute is measured.

(19) The sealant to be tested is placed in a cylinder-shaped cup (diameter of 24 mm) terminated by an extrusion nozzle with a diameter of 4 mm and a length of 22.5 mm, and a pressure of 3 bar is exerted on the sealant by means of a suitable appliance, the operation being carried out in a climate-controlled chamber at ambient temperature (23° C.).

(20) The flow rate measured is shown in g/minute in the Table below and corresponds to a perfectly compliant sealant behaviour.

(21) B.3. Test On the Tensile Strength Properties of an Adhesive Joint Formed by the Crosslinked Sealant and Uniting Two Substrates

(22) This test is carried out for an adhesive joint uniting two concrete substrates and also for an adhesive joint uniting two aluminium substrates.

(23) The two concrete substrates intended to be jointed are two identical substrates of parallelepipedal shape, having a length of 75 mm, a width of 12 mm and a height of 6 mm, the rectangular face of each substrate intended to be in contact with the joint having a length of 75 mm and a height of 12 mm.

(24) The two aluminium substrates intended to be jointed are two identical substrates of parallelepipedal shape, having a length of 75 mm, a width of 25 mm and a height of 12 mm, the two rectangular faces intended to be in contact with the joint having a length of 75 mm and a height of 12 mm.

(25) B.3.1 Preparation of the Specimens of Joints to be Tested:

(26) The concrete (or aluminium) joints to be tested are prepared using the sealant of Example B, so that the crosslinked sealant joint which bonds the two substrates is centred on the corresponding rectangular faces, and has a parallelepipedal shape with a length of 50 mm, a width of 12 mm and a height of 12 mm.

(27) The details relating to the shape of the adhesive joint specimens and their preparation are given in European Standard EN 8339 (cf. § 6 and 7). In particular, the sealant of Example 2 is crosslinked by a residence of 28 days in an oven at 23° C. and 50% relative humidity (according to Method A shown in the standard), followed by an alternating cycle of residences in an oven at 70° C. and residences in water at 23° C. (according to Method B shown in the standard).

(28) B.3.2 Tensile Tests on the Joints:

(29) The specimens of joints prepared according to B.3.1. are drawn in a tensile tensing device, the movable jaw of which moves at a constant rate equal to 5.5 mm/minute. The stress applied and the elongation of the test specimen (expressed as %) during the drawing thereof are recorded.

(30) The 100% modulus, corresponding to the stress (in MPa) recorded for an elongation of the joint of 100%, and also the elongation (as %) measured at the breaking of the joint are shown in the table below, for each type of substrate: concrete or aluminium.

(31) B.4 Slump Test:

(32) The degree of slump (or sagging) of a sealant employed in a vertical joint is measured according to standard ASTM D 2202.

(33) An absence of slump of the sealant, i.e. a distance measured on the graduated scale of the appliance of less than 2.5 mm, is observed.

(34) Example 1 (according to the invention): thixotropic composition consisting of a 23.3% weight/weight suspension of bisurea in pentaerythritol tetravalerate

(35) Example A is repeated, the DIDP being replaced with pentaerythritol tetravalerate.

(36) A stable 23.3% weight/weight dispersion of the same bisurea is obtained, the Brookfield viscosity of which, measured at 23° C., is 16.7 Pa.Math.s.

(37) Example 2 (according to the invention): adhesive sealant composition based on polyurethane prepolymer comprising —NCO end groups comprising the thixotropic composition of Example 1

(38) Example B is repeated, replacing, during the preparation of the sealant: the thixotropic composition of Example A with that of Example 1, and the 10% of DIDP with 10% of pentaerythritol tetravalerate.

(39) The results of the tests are shown in the table.

(40) TABLE-US-00001 Example B Example 2 Migration of the plasticizer between 1 and 2 <0.5 Annular radius (in mm) Flow after extrusion 69 69 (in g/minute) 100% modulus (in MPa) 0.44 0.48 concrete substrate Elongation at break 480 563 (in %) concrete substrate 100% modulus (in MPa) 0.41 0.46 aluminium substrate Elongation at break 213 387 (in %) aluminium substrate Slump distance (in mm) <2.5 <2.5 according to ASTM D 2202

(41) These results reveal, for the sealant of Example 2, a behaviour in the extrusion during the cartridge application which is identical to that of Example B.

(42) The 100% modulus (which indicates the cohesion of the adhesive joint) and the elongation at break (which corresponds to the elasticity of the adhesive joint) are each improved for Example 2 according to the invention in comparison with the reference Example B, both for concrete substrates and for aluminium substrates.