USE OF A COMPOSITION OF LOW-VISCOSITY BIS-ANHYDROHEXITOL ETHERS AS A REACTIVE DILUENT FOR CROSSLINKABLE RESIN, ADHESIVE, COATING AND MATRIX COMPOSITIONS FOR COMPOSITES

Abstract

The present invention relates to the use of bis-anhydrohexitol ethers as reactive diluents in a crosslinkable resin, adhesive, coating or composite matrix composition. Not only do these products make it possible to advantageously reduce the viscosity of the mixtures obtained, but they also lead to a very small reduction in the glass transition temperature of the crosslinked mixtures, compared to other reactive diluents, while spectacularly improving the mechanical properties of the latter such as the Young's modulus, the tensile strength, the elongation at break and the toughness.

Claims

1. The use, as reactive diluent for the preparation of a polymerizable and/or crosslinkable resin, adhesive, coating or composite matrix composition, of at least one bis-anhydrohexitol ether of formula (I): ##STR00007## and having a Brookfield viscosity, measured at 20 C., of less than 500 mPa.Math.s, said polymerizable and/or crosslinkable composition being based on a polymerizable organic matrix of epoxy type.

2. The use as claimed in claim 1, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C., of less than 400 mPa.Math.s.

3. The use as claimed in claim 1, characterized in that the compound of formula (I) has an epoxy equivalent weight of between 129 and 145 g/eq.

4. The use as claimed in claim 1, characterized in that the compound of formula (I) has a weight content of chlorine of less than 0.5%.

5. A polymerizable and/or crosslinkable resin, adhesive, coating or composite matrix composition, said composition comprising: an epoxy resin as polymerizable and/or crosslinkable organic matrix; at least one bis-anhydrohexitol ether of formula (I): ##STR00008## and having a Brookfield viscosity, measured at 20 C., of less than 500 mPa.Math.s.

6. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C., of less than 400 mPa.Math.s.

7. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has an epoxy equivalent weight of between 129 and 145 g/eq.

8. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has a weight content of chlorine of less than 0.5%.

9. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that it additionally contains at least one accelerator and/or hardener.

10. A crosslinked composition obtained from the composition as claimed in claim 5.

11. The use as claimed in claim 1, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C., of less than 300 mPa.Math.s.

12. The use as claimed in claim 1, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C. of between 50 and 300 mPa.Math.s.

13. The use as claimed in claim 1, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C. of between 100 and 300 mPa.Math.s.

14. The use as claimed in claim 1, characterized in that the compound of formula (I) has an epoxy equivalent weight of between 129 and 136 g/eq.

15. The use as claimed in claim 1, characterized in that the compound of formula (I) has a weight content of chlorine of less than 0.3%.

16. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C., of less than 300 mPa.Math.s.

17. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C., of between 50 and 300 mPa.Math.s.

18. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has a Brookfield viscosity, measured at 20 C., of between 100 and 300 mPa.Math.s.

19. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has an epoxy equivalent weight of between 129 and 136 g/eq.

20. The polymerizable and/or crosslinkable composition as claimed in claim 5, characterized in that the compound of formula (I) has a weight content of chlorine of less than 0.3%.

Description

EXAMPLES

[0082] The following examples relate to the use of various reactive diluents according to the invention (isosorbide diglycidyl ether) or according to the prior art (commercial products) in a crosslinkable composition based on a polymerizable organic matrix of epoxy type or based on epoxy resin.

[0083] Preparation of the Isosorbide Diglycidyl Ether:

[0084] 125 g of isosorbide (0.86 mol, 1 molar equivalent), 395.6 g of epichlorohydrin (4.27 mol, 5 molar equivalents) and then 1.25 g of triethylammonium bromide (1 wt % relative to the isosorbide) are introduced into a 1-liter jacketed reactor, heated by a thermostatic heat-transfer fluid bath, equipped with a mechanical blade stirring system, with a system for controlling the temperature of the reaction medium and with a reverse Dean-Stark apparatus surmounted by a condenser.

[0085] The system is brought to a pressure of 275 mbar relative. The reaction mixture is heated to 80 C. (boiling point=80 C. at 275 mbar) before beginning the controlled addition of 136.9 g of a 50% aqueous sodium hydroxide solution (1.71 mol, 2 molar equivalents). The addition lasts for a total of 2 h 50 min. The water is then continuously eliminated by azeotropic distillation.

[0086] The reaction medium is filtered under vacuum in order to eliminate therefrom the sodium chloride formed over time and the catalyst. The salts are washed with epichlorohydrin which is then eliminated by evaporation under reduced pressure in a rotary evaporator. A step of purification by distillation under reduced pressure (<1 mbar) is carried out. The distillate obtained then corresponds to the isosorbide diglycidyl ether in the form of a clear and colorless liquid (Brookfield viscosity at 20 C. of 218 mPa.Math.s) having an epoxy equivalent of 132 g/equivalent, and having a weight content of chlorine of 0.1% measured according to the ISO 21627-3 standard.

[0087] Characteristics of the Various Compounds Tested:

[0088] The main characteristics of the epoxy resin and of the various reactive diluents tested are found in table 1 (EE denoting the epoxy equivalent weight which is measured according to the ISO 3001 or ASTM D1652 standard).

TABLE-US-00001 TABLE 1 Diluent 1 Diluent 2 Diluent 3 Diluent 4 Epoxy resin Chemical Isosorbide Trimethylolpropane 1,4- C12-C14 Bisphenol A name diglycidyl triglycidyl butanediol alcohol diglycidyl ether ether diglycidyl monoglycidyl ether ether ether (DGEBA) Commercial Araldite DY-T Eposir 7107 Polypox Epotec name Araldite DY-D R24 YD128 Araldite DY-E EE (g/eq) 132 136 101 291.5 186 Viscosity at 218 168 14 8.3 14445 20 C. (mPa .Math. s)

Example 1

[0089] This example relates to the manufacture of compositions between the bisphenol A diglycidyl ether (DGEBA) epoxy resin and various reactive diluents in varied proportions, and to the determination of the Brookfield viscosity at 20 C. of said compositions.

[0090] In order to do this, 100 g of DGEBA epoxy resin are mixed at ambient temperature with 11.1 g of reactive diluent. The mixture is brought to 20 C. and the viscosity is measured using a Brookfield rotational viscometer, of DV-II+ type. The measurement is carried out after stabilization of the medium maintained at 20 C. using a thermostatic water bath. The viscosity measurements are obtained with a torque, as % of the maximum torque, of between 10% and 100%.

[0091] Throughout the present application, the speed at which the Brookfield viscosity is determined is not indicated. This is because a person skilled in the art knows how to adapt it relative to the choice of the rotor and so as to be positioned at a percentage of the torque of between 10% and 100%.

[0092] Each composition is produced in the same way by increasing the amount of diluent so as to obtain compositions that comprise between 0 and 40% by weight of reactive diluent. For the commercial diluents, the % is understood to be the % as they are. Each composition is perfectly homogeneous and the viscosities at 20 C. are given in table 2.

TABLE-US-00002 TABLE 2 % diluent by weight diluent 1 diluent 2 diluent 3 diluent 4 0 14 445 14 445 14 445 14 445 10 6575 5543 2160 1968 20 4343 3287 1032 744 30 3120 2016 431 234 40 1632 1296 211 126

[0093] Table 2 demonstrates that the introduction of 10% by weight of the reactive diluent according to the invention makes it possible to halve the viscosity of the mixture. Moreover, the viscosity levels comparable to those obtained with the products from the prior art are attained.

Example 2

[0094] This example relates to the crosslinking of the compositions obtained above, and to the determination of the glass transition temperatures of the thus crosslinked compositions.

[0095] The crosslinking of the crosslinkable compositions of epoxy resins is carried out in the presence of an amine hardener: isophorone diamine. The amount of isophorone diamine introduced is calculated so that the ratio of the number of NH groups to the number of epoxy groups is equal to 1. Isophorone diamine is available under the brand name Vestamid IPD from Evonik. The NH group weight equivalent is 42.5 g/eq. The formula used to calculate the amounts of diamine to be used is the following:

[00001]$m\left(\mathrm{isophorone}.Math..Math.\mathrm{diamine}\right)=\frac{\mathrm{mepoxy}.Math..Math.\mathrm{resin}42.5}{\mathrm{EE}.Math..Math.\mathrm{epoxy}.Math..Math.\mathrm{resin}}+\frac{\mathrm{mreactif}.Math..Math.\mathrm{diluent}42.5}{\mathrm{EEreactive}.Math..Math.\mathrm{diluent}}$

[0096] By way of example, the process for the crosslinking of the mixture between the resin and 10% by weight of the reactive diluent according to the invention was as below, the other tests having been carried out according to the same protocol while adapting the amounts of products.

[0097] 90 g of epoxy resin are mixed at ambient temperature with 10 g of reactive diluent 1. Next, x=23.7 g of isophorone diamine, (x being calculated using the above equation and depends on the EE of the chosen reactive diluent) are added and the mixture is stirred for 1 minute. The mixture, which is homogeneous and flows at ambient temperature, is placed in a silicone mould (L=43 mm, W=20 mm). The crosslinking is carried out for 1 day at ambient temperature followed by 1 day at 90 C. and 3 days at 130 C. in an oven. A material which is solid at ambient temperature and which has a glass transition temperature (Tg) of 149 C. is then obtained. The glass transition temperature is measured by differential scanning calorimetry (DSC) at the second pass of a temperature ramp from 100 to 200 C. at 10 C./min. The Tg values are reported in table 3.

TABLE-US-00003 TABLE 3 % diluent by weight diluent 1 diluent 2 diluent 3 diluent 4 0 150 150 150 150 10 149 145 123 112 20 146 138 98 88 30 145 131 84 58 40 138 126 33 45

[0098] Surprisingly, the glass transition temperatures are much higher with the use of the reactive diluent according to the invention. These results are particular advantageous in view of an application of the crosslinked compositions or crosslinked resins for the manufacture of an object, of composites, coatings, adhesives, paints, inks, etc. likely to be exposed to high temperatures, above 120 C., without loss of properties during their use.

[0099] FIG. 1 represents, for each reactive diluent, the change in the glass transition temperature (Tg in C.) of the crosslinked resin or crosslinked composition measured in example 2, as a function of the Brookfield viscosity of the composition before crosslinking (in mPa.Math.s, measured at 20 rpm and at 20 C.) measured in example 1.

[0100] FIG. 1 very clearly illustrates that the reactive diluent 1 according to the invention offers the best compromise between the viscosity of the mixture and the glass transition temperature of the crosslinked mixture.

Example 3

[0101] This example relates to the determination of a certain number of mechanical properties on test specimens obtained with the use of: [0102] no reactive diluent (test no. 1 according to the prior art) [0103] 40% by weight of reactive diluent 1 (test no. 2 according to the invention) [0104] 40% by weight of reactive diluent 2 (test no. 3 according to the prior art).

[0105] The mechanical properties are determined by a tensile test on flat test specimens: [0106] Young's modulus or modulus of elasticity (MPa): corresponds to the mechanical stress that an elongation of 100% of the initial length of the test specimen would generate (determined according to the method described in the ASTM D638 standard) [0107] tensile strength (MPa): corresponds to the mechanical tensile stress exerted on a test specimen until it breaks (determined according to the method described in the ASTM D638 standard) [0108] elongation at break: defines the capacity of a material to be stretched before breaking (determined according to the method described in the ASTM D638 standard) [0109] toughness (K.sub.IC): characterizes the property of a material to resist fracture when a crack is present. The higher the value of K.sub.IC, the more energy the material can absorb before breaking (determined according to the method described in the ASTM D5045 standard).

[0110] The results are given in table 4. The numbers of the tests refer to the compositions indicated at the start of example 3.

TABLE-US-00004 TABLE 4 Young's Tensile Elongation Toughness Test Tg modulus strength at break K.sub.IC No. ( C.) (MPa) (MPa) (%) (MPa .Math. m.sup.1/2) 1 150 1744 49.7 3.5 0.79 2 138 1710 57.7 4.4 1.07 3 126 1630 54.5 4.4 0.79

[0111] The incorporation of isosorbide diglycidyl ether makes it possible to dramatically improve the mechanical and impact strength properties.

[0112] The reactive diluent according to the invention therefore has many advantages: [0113] it offers the best compromise between the viscosity of the mixture and the glass transition temperature of the crosslinked mixture; [0114] it results in excellent mechanical properties; [0115] it significantly increases the toughness of the epoxy network, at least as much as 20% for a liquid elastomer of CTBN type, while retaining a very low initial viscosity and without having to the deal with the problem of phase separation induced by the polymerization (the network is homogeneous from a thermodynamic point of view) which is the lot of all additives of liquid elastomer type.