SELF-BLOWING ISOCYANATE-FREE POLYURETHANE FOAMS

Abstract

The present invention relates to a curable isocyanate-free formulation for preparing a polyurethane self-blowing foam comprising at least one multifunctional cyclic carbonate having at least two cyclic carbonate groups at the end of the chain (compound A), at least one multifunctional amine (compound B), at least one masked thiol precursor (compound C) and optionally at least one catalyst (compound D), to a process for preparing said foams, to the thus obtained foams and to the recycling of said foams.

Claims

1. A curable isocyanate-free formulation for preparing a polyurethane self-blowing foam comprising at least one multifunctional cyclic carbonate having at least two cyclic carbonate groups at the end of the chain (compound A), at least one multifunctional amine (compound B), at least one masked thiol precursor (compound C) and optionally at least one catalyst (compound D).

2. The formulation according to claim 1 wherein compound A corresponds to formula I ##STR00028## wherein i is an integer higher than or equal to 2, in particular from 2 to 10, more particularly 2 or 3, R.sup.1 is a carbon bond between the cyclic carbonate rings or is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl, a heterocycle, an aryl or a heteroaryl, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 3 to 60 carbon atoms.

3. The formulation according to claim 1 wherein compound B corresponds to formula II
R.sup.2(NHR)jFormula (II) wherein j is an integer higher than or equal to 2, in particular from 2 to 6, R.sup.2 is an aryl or heteroaryl, each of which may be unsubstituted or substituted, or a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, and wherein R each independently may be hydrogen, an alkyl or a cycloalkyl.

4. The formulation according to claim 1 wherein compound C corresponds to formula III, IV, V or VI ##STR00029## wherein k is an integer higher than or equal to 2, in particular from 2 to 6, l is an integer higher than or equal to 2, in particular from 2 to 1000, X is O or S, Y is O, S, NR.sup.4, CR.sup.5R.sup.6, R.sup.3 is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by an aryl, a heteroatom, a ketone, an amide, an amine, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, said hydrocarbon chain including carbon and hydrogen atoms wherein the carbon groups are linked through single or double bonds, R.sup.4 is hydrogen or a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by an aryl, a heteroatom, a ketone, an amide, an amine, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, R.sup.5 and R.sup.6 are identical or different and are hydrogen or a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by an aryl, a heteroatom, a ketone, an amide, an amine, a cycloalkyl or an heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, R.sup.5 and R.sup.6 together may form a cyclic structure, R.sup.7 is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by an aryl, a heteroatom, a ketone, an amide, an amine, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, R.sup.8 is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, an amide, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, or R.sup.8 is a linear or branched polymeric group, R.sup.9 and R.sup.10 are identical or different, and are a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, an amide, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, or R.sup.9 or/and R.sup.10 is/are a linear or branched polymeric group, R.sup.11 and R.sup.12 are identical or different, and are a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, an amide, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms.

5. The formulation according to claim 1 wherein compound C is selected from the group consisting of thiolactones, xanthates, thioesters, thiocarbonates and thiocarbamates.

6. The formulation according to claim 1 wherein compound D is selected from the group consisting of an amine catalyst, an ionic salt or ionic liquid composed of a combination of a cation and an anion, organometallic catalyst and a phosphine-based catalyst and is preferably 1,8-diazabicyclo[5.4.0]undec-7-ene, tetrabutylammonium phenolate, potassium carbonate, cesium carbonate or potassium phosphate or hydrogenophosphate.

7. The formulation according to claim 1 wherein compound A is present in an amount of from 18 to 80 wt %, in particular from 40 to 70 wt %, more in particular from 40 to 60 wt %, the percentage being expressed relative to the total weight of the formulation.

8. The formulation according to claim 1 wherein compound B is present in an amount of from 10 to 80 wt %, in particular from 10 to 70 wt %, more in particular from 10 to 50 wt %, the percentage being expressed relative to the total weight of the formulation.

9. The formulation according to claim 1 wherein compound C is present in an amount of from 1 to 60 wt %, in particular from 2 to 40 wt %, more in particular from 5 to 20 wt %, the percentage being expressed relative to the total weight of the formulation.

10. The formulation according to claim 1 wherein compound D is present in an amount of from 0.1 to 15 wt %, in particular from 0.5 to 7 wt %, the percentage being expressed relative to the total weight of the formulation.

11. The formulation according to claim 1 further comprising a monofunctional cyclic carbonate (compound E), preferably in an amount of from 1 to 50 wt %, in particular from 5 to 10 wt %, the percentage being expressed relative to the total weight of the formulation, said monofunctional cyclic carbonate preferably corresponding to formula VII ##STR00030## wherein R.sup.13 is hydrogen or a linear or branched hydrocarbon chain, which may be unsubstituted or substituted e.g. with a functional group such as an alcohol, a secondary or tertiary amine, a carboxylic acid, an alkene, an ester, etc. and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 1 carbon atom, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms,

12. The formulation according to claim 1 further comprising a multifunctional cyclic carbonate having at least two cyclic carbonate groups within the chain (compound F), preferably in an amount of from 1 to 50 wt %, in particular from 2 to 20 wt %, the percentage being expressed relative to the total weight of the formulation.

13. The formulation according to claim 1 further comprising a monofunctional thiol (compound G), preferably in an amount of from 1 to 50 wt %, in particular from 2 to 10 wt %, the percentage being expressed relative to the total weight of the formulation, said monofunctional thiol preferably corresponding to formula XI
R.sup.25SHFormula (XI) wherein: R.sup.25 is an aryl group which may be unsubstituted or substituted or a linear of branched polymeric group or a linear or branched hydrocarbon chain which may be unsubstituted or substituted e.g. with a functional group such as alcohol, primary, secondary or tertiary amine, carboxylic acid, ester, etc., and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced with a heteroatom, a ketone, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms.

14. The formulation according to claim 1 further comprising a multifunctional thiol (compound H), preferably in an amount of from 1 to 50 wt %, in particular from 2 to 10 wt %, the percentage being expressed relative to the total weight of the formulation, said multifunctional thiol preferably corresponding to formula XII
R.sup.26(SH).sub.rFormula (XII) wherein r is an integer higher than or equal to 2, in particular from 2 to 6, R.sup.26 is a linear or branched hydrocarbon chain, which may be unsubstituted or substituted, and wherein one or several hydrocarbon groups of said hydrocarbon chain may be replaced by a heteroatom, a ketone, a cycloalkyl or a heterocycle, each of which may be unsubstituted or substituted, said hydrocarbon chain having at least 2 carbon atoms, in particular from 2 to 60 carbon atoms, more particularly from 2 to 20 carbon atoms, even more particularly from 2 to 15 carbon atoms, or R.sup.26 is a linear or branched polymeric group.

15. The formulation according to claim 1 further comprising a polyepoxide (compound I), preferably in an amount of from 0.1 to 50 wt %, in particular from 0.5 to 20 wt %, the percentage being expressed relative to the total weight of the formulation.

16. A process for preparing a polyurethane self-blowing foam comprising the steps of providing a formulation as defined in claim 1 and curing said formulation preferably at a temperature between 25 C. and 200 C., more preferably between 40 and 150 C. and most preferably between 60 and 120 C. so as to promote the formation of CO.sub.2 and form a non-isocyanate polyurethane foam.

17. A process for preparing a polyurethane foam comprising the steps of (i) mixing compounds A and B, and optionally any one, some or all of compounds E, F, G, H and I, optionally in the presence of compound D so as to form a viscous mixture, (ii) partially curing said mixture so as to form a non-isocyanate polyurethane viscous prepolymer, (iii) adding compound C, and optionally, any one, some or all of compounds E, F, G, H and I to said prepolymer, (iv) curing said mixture obtained in step (iii) so as to form a non-isocyanate polyurethane foam, wherein compounds A, B, C, D, E, F, G, H and I are as defined in claim 1.

18. A process for preparing a polyurethane foam comprising the steps of (i) mixing compounds A and B, and optionally any one, some or all of compounds E, F, G, H and I, in the presence of compound C so as to form a viscous mixture, (ii) partially curing said mixture so as to form a viscous prepolymer, (iii) adding compound D to said prepolymer, (iv) curing said mixture obtained in step (iii) so as to promote the formation of CO.sub.2 and form a non-isocyanate polyurethane foam, wherein compounds A, B, C, D, E, F, G, H and I are as defined in claim 1.

19. A polyurethane foam obtainable by the process as defined in claim 16.

20. A process for recycling a polyurethane foam as defined in claim 19 by compression molding or extrusion.

21. A recycled polyurethane foam obtainable by the process as defined in claim 20 processed as a film, coating, adhesive, fibre or as bulk material.

Description

LIST OF FIGURES

[0163] FIG. 1 shows a picture of the foams as obtained in Example 1A, 1B and 1C, respectively

[0164] FIG. 2 shows SEM images of the foams as obtained in Example 1A, 1B and 1C, respectively

[0165] FIG. 3 shows a picture of the foam obtained in Example 2

[0166] FIG. 4 shows a picture of the foam obtained in Example 3

[0167] FIG. 5 shows a picture of the foam obtained in Example 4

[0168] FIG. 6 show SEM images of the foams obtained in Example 5

[0169] FIG. 7 shows SEM images of NIPU foams recycled as films in Example 5

[0170] FIG. 8 shows SEM images of NIPU foams recycled as coated fabric in Example 6.

EXAMPLES

[0171] In the following examples foams were produced using the following compounds:

##STR00027##

[0172] The average density of the foams is evaluated by weighting three foamed cubic samples with dimension of 101010 mm.

[0173] Example 1: Comparison of foams produced with a masked thiol precursor according to the invention and with thiol of the prior art.

[0174] Example 1A: Foaming with a masked thiol precursor in the absence of a thiol. A mixture of compound A (TMPTC), compound B (DiA), compound C (NAHcT) and compound D (DBU) was placed in a polypropylene beaker and stirred at room temperature for 2 minutes. Then the reactive mixture was poured in a silicon mold and placed in an oven at 80 C. After 5 minutes at 80 C., the mixture was stirred a last time for 2 minutes and then placed again in the oven at 80 C. After 2 h at 80 C., 30 minutes of temperature increase until 100 C. and 1 h at 100 C., a foam was obtained with an average density of 2214 Kg/m.sup.3.

TABLE-US-00001 Compound Structure Content Weight % A TMPTC 5 g 54.4 B DiA 2.559 g 27.8 C NAHcT 1.374 g 14.9 D DBU 0.258 g 2.8

[0175] Example 1B: Foaming with a masked thiol precursor in the presence of a thiol. A mixture of compound A (TMPTC), compound B (DiA), compound C (NAHcT), compound H (DiTh) and compound D (DBU) was placed in a polypropylene beaker and stirred at room temperature for 2 minutes. Then the reactive mixture was poured in a silicon mold and placed in an oven at 80 C. After 5 minutes at 80 C., the mixture was stirred a last time for 2 minutes. After 2 h at 80 C., 30 minutes of temperature increase until 100 C. and 1 h at 100 C., a foam was obtained with an average density of 2557 Kg/m.sup.3.

TABLE-US-00002 Compound Structure Content Weight % A TMPTC 5 g 58.3 B DiA 2.239 g 26.1 C NAHcT 0.687 g 4.6 H DiTh 0.394 g 8 D DBU 0.258 g 3

[0176] Example 1C: Foaming using a thiol of the prior art in the absence of a masked thiol precursor. A mixture of compound A (TMPTC), compound B (DiA), compound H (DiTh) and compound D (DBU) was placed in a polypropylene beaker and stirred at room temperature for 2 minutes. Then the reactive mixture was poured in a silicon mold and placed in an oven at 80 C. After 5 minutes at 80 C., the mixture was stirred a last time for 2 minutes. After 2 h at 80 C., 30 minutes of temperature increase until 100 C. and 1 h at 100 C., a well-formed foam was obtained with an average density of 60354 Kg/m.sup.3.

TABLE-US-00003 Compound Structure Content Weight % A TMPTC 5 g 62.8 B DiA 1.919 g 24.1 H DiTh 0.787 g 9.9 D DBU 0.258 g 3.2

[0177] FIG. 1 shows the different foams obtained in example 1: example 1C on the left, example 1B in the middle, example 1A on the right. It can be seen that the sample obtained in example 1C (in the absence of masked thiol precursor) is poorly foamed, whereas the samples obtained in examples 1A and 1B (with masked thiol precursor) are highly foamed. Therefore, the comparison of examples 1A, 1B and 1C demonstrates the importance of adding a masked thiol precursor (compound C), alone or in combination with a thiol (compound H) as illustrated in FIG. 1. Without the masked thiol precursor of the present invention (example 1C), some foaming is observed however, the foam is not homogeneous and is poorly expanded when the formulation is directly heated at the foaming temperature. In the presence of the masked thiol precursor (examples 1A and 1B), homogeneous and more expanded foams are formed as the result of the rapid viscosity increase of the formulation when heated at the foaming temperature. FIG. 2 shows SEM (Scanning Electron Micrography) micrographs of the different foams obtained in example 1: example 1C on the left, example 1B in the middle, example 1A on the right.

[0178] Example 2: Foaming with a masked thiol precursor in the absence of a thiol and in the absence of a catalyst. A mixture of compound A (TMPTC), compound B (DiA) and compound C (NAHcT) was placed in a beaker and stirred at room temperature for 2 minutes. Then the reactive mixture was poured in a silicon mold and placed in an oven at 100 C. After 5 minutes at 100 C., the mixture was stirred a last time for 2 minutes and then placed again in the oven at 100 C. After 3 h at 100 C., a foam was obtained with an average density of 31435 Kg/m.sup.3.

TABLE-US-00004 Compound Structure Content Weight % A TMPTC 5 g 56 B DiA 2.559 g 28.6 C NAHcT 1.374 g 15.4

[0179] FIG. 3 shows the foam obtained in example 2, without any catalyst. The sample was correctly foamed indicating that the foaming process occurs even in the absence of a catalyst.

[0180] Example 3: Foaming with a masked thiol precursor in the absence of a thiol and with an inorganic catalyst (compound D). A mixture of compound A (TMPTC), compound B (DiA), compound C (NAHcT) and compound D (K.sub.3PO.sub.4) was placed in a beaker and stirred at room temperature for 2 minutes. Then the reactive mixture was poured in a silicon mold and placed in an oven at 100 C. After 5 minutes at 100 C., the mixture was stirred a last time for 2 minutes and then placed again in the oven at 100 C. After 3 h at 100 C., a foam was obtained with an average density of 30516 Kg/m.sup.3.

TABLE-US-00005 Compound Structure Content Weight % A TMPTC 5 g 53.8 B DiA 2.559 g 27.5 C NAHcT 1.374 g 14.8 D K.sub.3PO.sub.4 0.3665 g 3.9

[0181] FIG. 4 shows the foam obtained in example 3, with an inorganic catalyst. The sample was highly foamed, indicating that such a catalyst is efficient to promote the reaction process.

[0182] Example 4: Foaming with a masked thiol precursor in the absence of a thiol with another diamine. A mixture of compound A (TMPTC), compound B (m-x Dia), compound C (NAHcT) and compound D (DBU) was placed in a beaker and stirred at room temperature for 2 minutes. Then the reactive mixture was poured in a silicon mold and placed in an oven at 80 C. After 5 minutes at 80 C., the mixture was stirred a last time for 2 minutes and then placed again in the oven at 80 C. After 2 h at 80 C., 30 minutes of temperature increase until 100 C. and 1 h at 100 C., a rigid foam was obtained with an average density of 10911 Kg/m.sup.3.

TABLE-US-00006 Compound Structure Content Weight % A TMPTC 5 g 55.6 B m-x DiA 2.353 g 26.2 C NAHcT 1.374 g 15.3 D DBU 0.263 g 2.9

[0183] A viscosity measurement was performed on the mixture TMPTC as compound A, m-x DiA as compound B and DBU as compound D, without the compound C. The initial viscosity as measured by rheology was 10 Pa.Math.s and it increased to 10 000 Pa.Math.s after 2 hours in the oven at 80 C. We therefore noticed an increase of viscosity of a factor 1000. Rheology was performed on an ARES Rheometric scientific rheometer, equipped with two parallel plate geometries at a frequency of 1.6 Hz, a strain of 1%.

[0184] FIG. 5 shows the foam obtained in example 4, with compound B being m-x Dia. The sample is highly foamed, indicating that such formulation is also efficient to obtain rigid polyurethane foams.

[0185] Example 5: Process for recycling a NIPU foam made from masked thiol precursor. A NIPU foam was prepared according to example 1A, with the same compounds, in same quantities. The sample was cured 5 hours at 80 C. and then allowed to cool down to room temperature before demolding. Characterizations were performed at least after 24 hours of equilibration under ambient atmosphere. The obtained sample is referred to as NIPUF1. The obtained density is 167 Kg.Math.m.sup.3.

[0186] A second NIPU foam was prepared with the compounds of example 4, in same quantities. The curing was performed for 5 hours at 80 C. The obtained sample is referred to as NIPUF2. The obtained density is 185 Kg.Math.m.sup.3. FIG. 6 shows SEM images of the foams NIPUF1 and NIPUF2. These two foams were then reprocessed by compression molding as follows: a foam slice (NIPUF1 or NIPUF2) about 0.5 cm thick (about 2 g) was placed between Teflon sheets and pressed for 2 h at 160 C. under a 1 tonne force. 3 cycles of applying-releasing the pressure were performed in the beginning to allow volatiles draining in order to give well-formed, cracks-free and homogeneous NIPU films.

[0187] NIPU films of mixed composition were also prepared by grinding NIPUF1 (1 g) and NIPUF2 (1 g) together in liquid nitrogen in order to give a homogeneous fine powder. This powder was briefly dried for 15 minutes in an oven at 60 C. before being placed between Teflon sheets and reprocessed as previously described to provide a NIPU film.

[0188] The obtained films were characterized by SEM, showing no cracks as can be seen in FIG. 7. The samples were further characterized by Dynamic Mechanical Analysis (DMA) and Differential Scanning Calorimetry (DSC). Therefore, pieces of about 256 mm were cut out of NIPU films. Thickness was in the range of 0.2 to 0.5 mm. Samples were analyzed on a DMA Q800 (TA) with a preload force of 0.01N and an oscillating amplitude of 5 m between 80 and 160 C. at a heating rate of 3 C./min. Ta was determined as a maximum of the tan delta curve. Analysis by DSC was performed on a TA DSC250 apparatus. About 4 mg of samples were sealed in the pan for analysis between 80 and 80 C. under N.sub.2 flow at a rate of 10 C./min.

TABLE-US-00007 Mix of NIPUF Reprocessed 1 and 2 Reprocessed Properties NIPUF1 reprocessed NIPUF2 T.sub.g ( C.) (DSC) 22 19/8 18 T.sub. ( C.) (DMA) 11 8/18 23

[0189] NIPU films were also analyzed on an Instron device. Samples of 505 mm were studied in traction mode at a rate of 2 mm/min.

TABLE-US-00008 Mix of NIPUF Reprocessed 1 and 2 Reprocessed Properties NIPUF1 reprocessed NIPUF2 Young 0.00848 0.00076 0.0111 0.00082 0.373 0.191 modulus (MPa) Deformat. at 87 10 100 6 258 35 break (%)

[0190] Example 6: Process for recycling a NIPU foam obtained from masked thiol precursor as coated fabric. NIPU films were prepared according to the process described in Example 5. The as-prepared films were pressed on CORDURA nylon fabrics with a linear density of 330 den and a surface density of 185 g/m.sup.2. Both films were pressed for 2 h at 160 C. under a 4 tonne pressure on the fabric, between Teflon sheets, to give coated fabrics. SEM pictures (FIG. 8) of the composite suggest a good impregnation between the NIPU film and the fabric.

[0191] Example 7: Process for recycling a NIPU foam obtained from masked thiol precursor as adhesive. The NIPU coated fabric composite as prepared from NIPUF1 foam was cut as slices of about 6 mm wide and 30 mm long and superimposed over about 5 mm before being pressed at 160 C. for 10 minute under minimal pressure to ensure good contact between the NIPU layers. At least 3 samples were tested for lap-shear test in traction at 2 mm/min with a preload of 0.1N.

TABLE-US-00009 Properties NIPUF1 composite lap-shear sample Stress at break (MPa) 2 0.4 Strain at break (%) 20.5 4.1