Titanium-based catalyst for vitrimer resins of epoxy/anhydride type

Abstract

The present invention relates to a composition containing, besides a thermosetting resin of epoxy type and a hardener of anhydride type, at least one catalyst comprising an organometallic titanium complex. This composition enables the manufacture of vitrimer resins, that is to say resins that can be deformed in the thermoset state. It also relates to a kit for manufacturing this composition, an object obtained from this composition and a kit for manufacturing this object. Another subject of the invention relates to an organometallic titanium complex corresponding to the structure titanium bis(3-phenoxy-1,2-propane dioxide) (Ti(PPD).sub.2), and the use thereof as vitrimer effect catalyst in systems based on epoxy resin and on hardener of anhydride type.

Claims

1. A composition comprising at least: a catalyst comprising titanium bis(3-phenoxy-1,2-propane dioxide) (Ti(PPD).sub.2), a thermosetting resin comprising at least one epoxide function and optionally at least one free hydroxyl and/or ester function, and a thermosetting-resin curing agent selected from carboxylic acid anhydrides, wherein the thermosetting resin is selected from the group consisting of glycidyl esters, glycidyl ethers, glycidyl amines and glycidyl isocyanurates, comprising at least two glycidyl groups per molecule, and epoxidized olefin compounds which are linear, branched or cyclic comprising more than six members.

2. The composition as claimed in claim 1, wherein the catalyst further comprises titanium isopropoxide.

3. The composition as claimed in claim 1, wherein the thermosetting resin is selected from the group consisting of glycidyl esters, glycidyl ethers, glycidyl amines and glycidyl isocyanurates, comprising at least two glycidyl groups per molecule, and mixtures thereof.

4. The composition as claimed in claim 1, wherein the thermosetting resin is selected from the group consisting of epoxidized olefin compounds which are linear, branched or cyclic comprising more than six members, and mixtures thereof.

5. The composition as claimed in claim 1, wherein the thermosetting resin is selected from the group consisting of: bisphenol A diglycidyl ether (DGEBA), tetraglycidyl methylene dianiline (TGMDA), bisphenol F diglycidyl ether, Novolac resins, trimethylol triglycidyl ether (TMPTGE), the diglycidyl ester of phthalic, isophthalic or terephthalic acid, tetrabromo bisphenol A diglycidyl ether, 1,4-butanediol diglycidyl ether, the epoxidized cycloaliphatic resin represented by formula (II), triglycidyl isocyanurate (TGIC), poly(glycidyl methacrylate), and mixtures thereof ##STR00008##

6. The composition as claimed in claim 1, wherein the thermosetting resin is selected from the group consisting of bisphenol A diglycidyl ether (DGEBA), tetraglycidyl methylene dianiline (TGMDA), Novolac resins and glycidyl methacrylate.

7. The composition as claimed in claim 1, wherein the amount of curing agent is such that the number of moles of epoxide functions of the thermosetting resin ranges from 50% to 300%, relative to the number of moles of anhydride functions of the curing agent.

8. The composition as claimed in claim 1, wherein the content of thermosetting resin and of curing agent ranges from 10% to 90% by weight, relative to the total weight of the composition, the remainder to 100% being provided by the catalyst and optionally by one or more additional compounds selected from the group consisting of: polymers, pigments, dyes, fillers, plasticizers, long or short fibers, woven or nonwoven fibers, flame retardants, antioxidants, lubricants, wood, glass, metals, and mixtures thereof.

9. The composition as claimed in claim 1, further comprising at least one epoxide-opening additional catalyst.

10. The composition as claimed in claim 1, further comprising at least one polyol.

11. The composition as claimed in claim 10, wherein the polyol is glycerol, trimethylolpropane or pentaerythritol.

12. The composition as claimed in claim 1, comprising at least one thermosetting resin selected from the group consisting of bisphenol A diglycidyl ether (DGEBA), tetraglycidyl methylene dianiline (TGMDA), Novolac resins, and glycidyl methacrylate, and at least one carboxylic acid anhydride.

13. A kit for producing a composition as claimed in claim 1, comprising at least: a first composition comprising the catalyst; a second composition comprising the curing agent; and a third composition comprising the thermosetting resin.

14. A method for producing an object made of thermoset resin that is hot-deformable, comprising using the composition as claimed in claim 1.

15. An object comprising a thermoset resin obtained from a composition as defined in claim 1.

16. A process for deforming an object, comprising applying to an object in accordance with claim 15 a mechanical stress at a temperature (T) above the glass transition temperature Tg of the thermoset resin.

17. The composition as claimed in claim 1, wherein the thermosetting resin is a glycidyl ether.

18. A kit for producing a composition as claimed in claim 1, comprising: a first composition comprising the catalyst and the curing agent; and a second composition comprising the thermosetting resin.

19. A kit for producing a composition as claimed in claim 1, comprising: a first composition comprising the catalyst and the thermosetting resin; and a second composition comprising the curing agent.

20. A method of producing a composition as claimed in claim 1, comprising combining the catalyst, the thermosetting resin, and the curing agent.

21. An organometallic titanium complex corresponding to the structure titanium bis(3-phenoxy-1,2-propane dioxide) (Ti(PPD).sub.2).

22. A method comprising using the organometallic titanium complex as claimed in claim 21 as a vitrimer effect catalyst in a system based on an epoxy resin and on a curing agent of anhydride type.

Description

FIGURES

(1) FIG. 1 represents the superimposition of the .sup.1H NMR spectra (CDCl.sub.3, 400 MHz) of various vitrimer effect catalysts.

(2) FIG. 2 represents the superimposition of the TGA curves of the Zn(acac).sub.2 catalyst and of the Ti(PPD).sub.2 catalyst.

(3) FIG. 3 illustrates the superimposition of the stress relaxations (at 260 C.) of the vitrimers catalyzed by 5 mol % of Ti(iPr).sub.4, and by 5 mol % of Ti(PPD).sub.2 and by 5 mol % of Zn(acac).sub.2. The static force is represented as a function of time.

(4) FIG. 4 illustrates the variation in the relaxation time for a DGEBA/glutaric anhydride network catalyzed by 5 mol % of Ti(PPD).sub.2 as a function of the inverse of the temperature.

(5) FIG. 5 illustrates the DMA curves of a 1:0.5 DGEBA/glutaric anhydride system with 5 mol % of Ti(PPD).sub.2.

EXAMPLES

(6) The following examples illustrate the invention without limiting it.

(7) Characterization Methods

(8) Nuclear magnetic resonance analysis: All the nuclear magnetic resonance (NMR) analyses were carried out on an apparatus with a resonant frequency at 400 MHz, with chloroform as deuterated solvent and at concentrations of 8 mg/ml.

(9) Thermal analysis: the Tg of the samples of examples 2 to 4 was characterized by differential scanning calorimetry (DSC) analysis. The following protocol was applied: first heating at 10 C./min from 70 C. to 170 C., isotherm of 5 min at 170 C., cooling at 10 C./min down to 70 C., isotherm at 70 C. for 5 min, then second heating up to 170 C. at 10 C./min.

(10) Mechanical analysis: the storage moduli (G) of the samples of examples 2 to 4 were measured by dynamic mechanical analysis (DMA) in 3-point flexural geometry. The following protocol was applied: Oscillation amplitude of 25 m, frequency 1 Hz, starting temperature at 25 C., final temperature at 200 C., heating at 3 C./min. The tests were carried out on samples 30 mm13 mm1.5 mm in size.

(11) The samples of examples 5 to 8 were also subjected to a DMA analysis, under slightly different conditions. Specifically, a bar 10303 mm in size was fixed between two clamps and subjected to a rectangular torsion (imposed deformation of 0.05%) in an RDA3 apparatus from Rheometric Scientific, with a frequency of 1 Hz, by carrying out a temperature sweep from 25 to 250 C. with a temperature ramp of 3 C./min. The value of Ta was determined at the top of the peak of the tan curve, and is considered hereinafter to be the Tg of the sample, while the storage modulus G was determined on the rubbery plateau at 200 C.

Example 1

Preparation of a Catalyst According to the Invention, and Characterization Thereof

(12) This example illustrates the synthesis of an organometallic titanium complex, used as catalyst according to the invention.

(13) The reaction scheme is represented below:

(14) ##STR00007##

(15) The phenoxypropanediol (10 g, 0.06 mol) was placed in a single-necked round-bottomed flask with a volume of 100 ml, then the round-bottomed flask was heated until the reagent was liquid (80 C.) and left to stir for 15 min. Still at 80 C., the titanium isopropoxide (5.63 g, 0.02 mol) was added dropwise, very slowly. The mixture was left to stir for 4 h under an inert atmosphere and then the medium was gradually placed under a dynamic vacuum at 80 C., where it was left for 15 h in order to eliminate the isopropanol. The ligand exchange reaction was virtually instantaneous. During the addition of the titanium isopropoxide, the product precipitated and the reaction medium became white. In order to eliminate the excess ligand, the product at the end of the reaction (in solid form) was placed in an Erlenmeyer flask with 100 ml of chloroform and the mixture was left to stir overnight (phenoxypropanediol is very soluble in chloroform). The product was recovered by filtration and then drying under a dynamic vacuum at 50 C. for 15 h. The final product was characterized by proton NMR (see FIG. 1). It will subsequently be referred to as Ti(PPD).sub.2.

(16) The solubility of the Ti(PPD).sub.2 compound in a DGEBA epoxy resin and in a DGEBA/anhydride system was tested as follows:

(17) Test of Solubility in DGEBA

(18) The DGEBA (DER 330-2.1 g, 12.1 mmol) and Ti(PPD).sub.2 (0.232 g, 0.6 mmol; 5 mol %) are added to a Schlenk tube. The mixture is placed, with stirring, in an oil bath at 130 C. The mixture remains cloudy, since the catalyst is only dispersed and not dissolved.

(19) After 60 min, a sample is taken and analyzed by infrared spectroscopy in order to verify the state of the DGEBA. It is noted that the absorption band corresponding to the epoxide function is still more than 95% intact, indicating that the anionic homopolymerization of the DGEBA is not initiated by the presence of the titanium compound Ti(PPD).sub.2 in the medium at 130 C.

(20) Test of Solubility in the DGEBA+Glutaric Anhydride Reactive Mixture

(21) Glutaric anhydride (0.689 g, 6 mmol; 50 mol %) is added to the above mixture, still with stirring at 130 C. The amount is adjusted such that there are as many epoxide functions as acid functions in the medium (same conditions as during synthesis of a vitrimer plate). The effect is virtually instantaneous, with the total disappearance of catalyst in solid form in the mixture. Said mixture becomes colored and translucent.

(22) The reaction was monitored by infrared spectroscopy showing the drop in the intensity of the absorption band corresponding to the epoxide function (916 cm.sup.1), illustrating the progression of the reaction.

Example 2

Synthesis of an Epoxy-anhydride Network in the Presence of 5% of Ti(PPD)2

(23) The following were added to a Teflon beaker: 19 g of epoxy resin of DGEBA type (DER332) in liquid form (DOW, Mass Epoxy Equivalent: 174 g/eq) and 2.1 g of Ti(PPD).sub.2 prepared in example 1 (MW=383.87 g/mol), which corresponded to 0.05 gram atom of titanium per epoxy function. The reagents were mixed while at the same time heating using a hot air gun (T60 C.) for 2 mm. The mixture became white, non-translucent. 6.23 g of glutaric anhydride (CAS 108-55-4, MW=114.1 g/mol) in solid form were then added thereto, while heating using a hot air gun (T150 C.) until complete dissolution. The mixture was no longer white and became translucent. At that time, it was cast in a mold 1001001.4 mm in size (preheated to 140 C.) between two sheets of non-stick siliconized paper, and then fired under a press at 140 C. for 8 h. An infrared spectrum measurement carried out on the material at the end of the reaction demonstrated the complete disappearance of the anhydride (1810 cm.sup.1) and epoxy (915 cm.sup.1) signals. The band characteristic of ester functions at 1735 cm.sup.1 and a broad unresolved absorption peak at 3200-3600 cm.sup.1, characteristic of hydroxyl groups, were recorded on the sample after polymerization.

(24) The material exhibited by DMA a Tg of about 70 C., and a storage modulus of 2.2 GPa at 25 C. and of 25 MPa at 150 C.

(25) Its DMA curve is shown in FIG. 5. As emerges from this figure, the material exhibits a storage modulus at 25 C. and at 150 C. of 2.2 GPa and of 25 MPa, respectively. The T value is 74 C. and the narrowness of the tan delta peak shows that the material is homogeneous.

(26) In addition, FIG. 4 shows the variation in the relaxation time of this material as a function of the inverse of the temperature. As emerges from this figure, the relaxation time follows an Arrhenius law of the type:

(27) $\frac{1}{}=\frac{1}{{}_0}{e}^{-\frac{E_a}{\mathrm{RT}}}$
where .sub.0 the normalization constant is a time (s), E.sub.a is the activation energy (J.Math.mol.sup.1.Math.K.sup.1), R the universal constant of perfect gases (J.Math.mol.sup.1), and T the temperature (K). The activation energy, determined from the slope (E.sub.a/R), is approximately 80 kJ.Math.mol.sup.1.Math.K.sup.1.

Comparative Example 3

Synthesis of an Epoxy-anhydride network in the Presence of 5% of Zinc Acetylacetonate

(28) A comparative sample was prepared using the same protocol as in example 2, but using zinc acetylacetonate as catalyst at the same concentration, in other words at 0.05 gram atom of titanium per epoxy function.

(29) The material exhibited by DMA a Tg of about 70 C., and a storage modulus of 2 GPa at 25 C. and of 19 MPa at 150 C.

Example 4

Synthesis of an Epoxy-anhydride Network in the Presence of 5% of Titanium Isopropoxide

(30) A sample was prepared using the same protocol as in example 2, but using titanium isopropoxide (CAS 546-68-9, MW=284.22 g/mol) as catalyst at the same concentration, in other words at 0.05 gram atom of titanium per epoxy function.

(31) The material exhibited by DMA a Tg of about 67 C., and a storage modulus of 2.4 GPa at 25 C. and of 8.5 MPa at 150 C.

Example 5

Synthesis of an Epoxy-anhydride Network in the Presence of 10% of Titanium Isopropoxide

(32) Three samples of vitrimer material (respectively 5a, 5b and 5c) were prepared according to the following method.

(33) Added to a beaker were an epoxy resin of DGEBA type (DER332) in liquid form (DOW, Mass Epoxy Equivalent: 174 g/eq), methyltetrahydrophthalic anhydride (MTHPA) (MW=166.18 g/mol) and titanium isopropoxide (supplied by Dorf Ketal), in a proportion of 0.1 gram atom of titanium per epoxy function. The reagents were mixed and then homogenized in a thermostated oil bath at 100 C. for approximately 10 minutes. The mixture was then cast in a lightly siliconized 701403 mm hollow metal mold. The mold was interlocked, by means of a silicone seal, with a metal plate covered with a Teflon coating, then the assembly was introduced into a heated press preset to a temperature of 140 C. and firing was begun at a pressure of 10 bar. The firing was carried out for 17 hours.

(34) A molar ratio of epoxide functions of the resin to anhydride functions of the curing agent respectively equal to 1/0.8; 1/1 and 1/1.2 was used to produce these samples.

(35) The Tg of the resulting materials was measured by DMA along with the storage modulus of said resulting materials.

(36) These materials exhibited respectively a Tg of 118 C., 116 C. and 102 C. and a storage modulus at 200 C. of 17 MPa, 12.6 MPa and 11.6 MPa.

Comparative Example 6

Synthesis of an Epoxy-anhydride Network in the Presence of 10% of Zinc Acetylacetonate

(37) Three samples of material (respectively 6a, 6b and 6c ) were prepared in a manner identical to example 5, except that the catalyst was replaced with zinc acetylacetonate or Zn(acac).sub.2. These materials exhibited respectively a Tg of 138 C., 130 C. and 112 C. and a storage modulus at 200 C. of 16 MPa, 13.5 MPa and 10.2 MPa.

Example 7

Synthesis of an Epoxy-anhydride Network in the Presence of 10% of Titanium Acetylacetonate

(38) A sample of material was prepared in a manner identical to example 5 using a molar ratio of epoxide functions of the resin to anhydride functions of the curing agent equal to 1/0.8, except that the catalyst was replaced with titanium acetylacetonate or Ti(acac).sub.2.

(39) This material exhibited a Tg of 112 C. and a storage modulus at 200 C. of 8.0 MPa.

Example 8

Synthesis of an Epoxy-anhydride Network in the Presence of Titanium Isopropoxide and of an Additional Catalyst of Amine Type

(40) Two samples of vitrimer material were prepared according to a process similar to that described in example 5, the operating conditions of which were modified as described in table 1 below. Additional samples were prepared by adding a variable amount of additional catalyst of amine type, namely either 2-methylimidazole (hereinafter 2-MIA) or 2,4,6-tri(dimethylaminomethyl)phenol (hereinafter Anc for Ancamine K54 from Air Products), to the system before curing.

(41) TABLE-US-00001 TABLE 1 Sample 8a 8b 8c 8d 8e 8f Epoxide DER332 DER332 DER332 DER332 DER332 DER332 Curing agent MTHPA MTHPA MTHPA MTHPA MTHPA MTHPA Additive 2-MIA 2-MIA Anc Anc Catalyst Ti(iPr).sub.4 Ti(iPr).sub.4 Ti(iPr).sub.4 Ti(iPr).sub.4 Ti(iPr).sub.4 Ti(iPr).sub.4 mol % 0.5% 2.5% 1% 2% amine/epoxy mol % 5% 5% 5% 10% 10% 10% catalyst/epoxy Tg ( C.) 136 122 120 118 108 114 G (MPa) 17 12 12 17 13 17

Example 9

Study of the Relaxation and Deformation Properties of Various Vitrimer Materials

(42) a) The samples of examples 2, 3 and 4 were subjected to a stress relaxation experiment: the stress relaxation times were measured by means of a DMA (or DMTA for Dynamic Mechanical Thermal Analysis) in 3-point flexural geometry. The following protocol was applied: heating up to test temperature, isotherm of 20 min, then application of a 1% deformation. The tests were carried out on samples 30 mm13 mm1.4 mm in size.

(43) The results are collated in the appended FIG. 3. As this figure shows, the samples obtained using the catalysts according to the invention exhibit similar performance levels that are much higher than those of the material obtained using zinc acetylacetonate, insofar as their stresses are more completely and more rapidly relaxed.

(44) b) in parallel, each of the samples prepared according to examples 5 to 8 was subjected to an experiment consisting in imposing, on a test specimen of material of 40202 mm, a 3-point flexural deformation under a nitrogen stream, using a Metravib apparatus of DMA50N type, after the sample had been brought to a temperature equal to T+100 C. and stabilized for 5 min at this temperature. The change in the stresses induced in the material in order to keep the deformation constant is monitored for 5000 seconds and measured using a sensor. A force equal to zero is then imposed on the sample and the deformation (recovery) of the sample is measured for a further 5000 seconds. When the material retains the deformation that was imposed on it, it is considered that all the stresses have been relaxed. The normalized stress (/o) is then plotted as a function of time and, for each test, the relaxation time required to obtain a normalized stress value equal to 1/e, and also the percentage of stresses relaxed at 5000 seconds, hereinafter denoted .sub.5000s, are recorded.

(45) The results obtained are collated in table 2 below.

(46) TABLE-US-00002 TABLE 2 Sample 6a 6b 6c 5a 5b 5c comp comp comp 7 (s) 75 510 370 1105 1565 3630 555 .sub.5000 s (%) 100 100 100 100 84 69 100 Sample 8a 8b 8c 8d 8e 8f (s) 2430 1060 735 75 45 23 .sub.5000 s (%) 75 85 100 100 100 100

(47) As emerges from this table, the catalysts according to the invention (samples 5a to 5c and 7) make it possible to obtain materials capable of relaxing their stresses more completely and more rapidly than the materials obtained using the same amount of zinc acetylacetonate-based catalyst (samples 6a to 6c). Moreover, these performance levels are not obtained to the detriment of the mechanical properties of the material. In addition, these performance levels of the catalysts according to the invention are further improved in the presence of an additional catalyst of amine type, as shown by the comparison of samples 8b and 8c with sample 8a and of samples 8e and 8f with sample 8d.

Example 10

Study of the Thermal Stability of Various Vitrimer Materials

(48) a) The samples of examples 2, 3 and 4 were subjected to a thermogravimetric analysis (TGA). 10 mg of product (catalyst or resin) were placed in an alumina capsule. The gravimetric measurements were carried out from 25 C. to 900 C., at 10 C./min.

(49) The samples obtained using the catalysts according to the invention are more stable than those using zinc acetylacetonate, in a range of temperatures suitable for their industrial transformation, i.e. up to a temperature of approximately 200 C. The Ti(PPD).sub.2-based catalyst is even stable above this temperature and does not substantially degrade up to 300 C.

(50) In particular, it was observed that the material of example 2 showed a loss of mass of only 0.07% at 260 C., whereas the material of comparative example 3 showed a loss of mass of 1.68% at the same temperature.

(51) b) The appended FIG. 2 shows that the Zn(acac).sub.2 catalyst is less thermally stable than the Ti(PPD).sub.2 catalyst since it degrades starting from 200 C., whereas the latter undergoes only a small loss of mass up to 300 C.

(52) c) The thermal stability of the materials of examples 5a and 6a and also of example 2 were moreover evaluated by TGA on a Perkin Elmer apparatus of type TGA7, while performing a temperature scan from 25 C. to 500 C. according to a ramp of 10 C./min. The temperature resulting in a loss of material of 1% was 176 C. in the case of the material of comparative example 6a and 235 C. in the case of the material of example 5a, thereby confirming the better thermal resistance of the materials according to the invention at the re-forming and recycling temperatures.

(53) The temperature resulting in a loss of material of 1% was 254 C. in the case of the material of example 2 prepared with Ti(PPD).sub.2.