Compositions of thermoplastic epoxy resins - block copolymers

Abstract

The invention relates to compositions of block copolymers and thermoplastic epoxy resins, their use in the mechanical reinforcement of filled or unfilled thermosetting epoxy formulations, and the resulting filled or unfilled thermosetting epoxy formulations. The invention also relates to a method for preparing these compositions of block copolymers and thermoplastic epoxy resins.

Description

Title of the invention: Thermoplastic epoxy resin compositions - block copolymers

[0001] The invention relates to compositions of block copolymers and thermoplastic epoxy resins, their use in the mechanical reinforcement of filled or unfilled thermosetting epoxy formulations, as well as the filled or unfilled thermosetting epoxy formulations obtained. The invention also relates to a method for preparing these compositions of block copolymers and thermoplastic epoxy resins.

[0002] Epoxy resins are used in a wide variety of fields, ranging from the manufacture of objects for the automotive, aeronautical, and sporting goods sectors. They find applications in structural adhesives, as matrices for composite materials, and in applications for the protection of electronic components.

[0003] Epoxy objects or materials are obtained by reacting functional epoxy resins with a functional hardener. When more than two functionalities are used on the epoxy resins and / or the hardener, a thermosetting material is obtained, i.e., one with a certain crosslinking density. The crosslinking density allows for adjusting the properties, as do the nature of the epoxy resins and the nature of the hardener(s). Thermosetting epoxy materials generally have a high crosslinking density to ensure a high glass transition temperature (Tg), so that the final material exhibits good thermomechanical properties.

[0004] However, the stresses experienced by mechanical parts under high stress, such as for example in the aeronautical field, have required the development of improvements to certain properties such as impact resistance and the limitation of crack propagation, for example.

[0005] Solutions have been found by combining these formulations with core-shell particles or block copolymers containing flexible sequences with a low glass transition temperature (Tg). In the case of block copolymers, this is described in EPI290088. In FR2880895, a further improvement is provided by the presence of a functional monomer in the block copolymers.

[0006] This type of block copolymers and in particular those in which at least one of the blocks has a polar and / or hydrophilic functionality are the best candidates known to date for improving the mechanical properties of epoxy resins.

[0007] A technical problem remains when one wishes to correctly formulate the block copolymer with the epoxy resin(s). The mechanical properties of the final material are maximal when the block copolymers are in a so-called The "nanostructured" structure can only be achieved through thermodynamic processes that are not always fully controlled. Block copolymers, useful for strengthening epoxy resins, are available in granular form at room temperature. Epoxy resins are liquid or solid at room temperature, and mixing them with block copolymers requires specific stirring, time, and temperature conditions that are challenging for the formulator. One solution involves grinding the block copolymer granules to facilitate dilution, but this adds an extra step. Using a liquid epoxy resin with a solid epoxy resin facilitates the dissolution of block copolymers in powder or granular form, but this requires heating and vigorous stirring for an extended period.This leads to the presence of foaming and bubbles which cannot be completely eliminated even with additional degassing, thus weakening the final material.

[0008] Another solution has been used by pre-diluting the block copolymer in a liquid epoxy resin as a masterbatch, which is then diluted in the epoxy resin(s) of the final formulation. This solution does not eliminate the step of mixing the block copolymer in a liquid epoxy resin at levels up to 25%, rendering this academic approach unusable in industry because the aforementioned drawbacks (foaming, bubbling, time) are exacerbated by the significant proportions of block copolymers in these block copolymer mixtures in solid form in liquid epoxies (up to 25%). Such an approach is described, for example, in Andreas Peter Klingler's thesis on page 40 under ISBN 978-3-944440-44-6.

[0009] To avoid the drawbacks associated with the dissolution of block copolymers in epoxy resins, the applicant has developed a composition that facilitates the dispersion of block copolymers in epoxy resins. This composition is presented as granules with a high block copolymer content in a solid thermoplastic epoxy resin. These granules are obtained using a mixing tool such as a mixer or extruder. These granules mix much more easily, avoiding problems related to mixing time, bubbling, or foaming that are generated during formulation.

[0010] Moreover, the compositions obtained allow a balance of final properties at identical block copolymer ratio superior to those obtained in the prior art.

[0011] Summary of the invention.

[0012] The invention relates to a mass composition consisting of the following mixture M:

[0013] -at least one thermoplastic epoxy resin (1) whose glass transition temperature(s) measured by DSC are greater than 25°C,

[0014] -at least one block copolymer (2) in mass proportions between 25 and 70% of the total (1) + (2), wherein at least one block copolymer has at least one block A having a glass transition temperature Tg greater than 25°C measured by DMA and at least one block B having a transition temperature Tg less than 0°C measured by DMA and having at least one polar and / or hydrophilic functional monomer in at least one of the blocks, said polar and / or hydrophilic functional monomer being present in mass proportions relative to the block considered of between 5 and 50%, said composition being in solid form at a temperature less than 50°C. Description of the implementation methods

[0015] The thermoplastic epoxy resin(s) present in the compositions of the invention have Tg values ​​greater than 25 °C, preferably greater than 30 °C and even more preferably greater than 50 °C measured by DSC (differential scanning calorimetry).

[0016] These are compounds of the pure epoxy, polyester epoxy, novolac, or acrylate epoxy type. Examples include bisphenol-A diglycidyl ethers, bisphenol F, aromatic glycidyl amines, and cycloaliphatic epoxies, these compounds having an oxirane functionality greater than or equal to two. They may be fluorinated, phosphoric, or silylated. They may be of renewable origin, based on natural oils (soybean, linseed, castor, etc.), isosorbide-based, epoxy-coated natural rubber, epoxy lignin derivatives, or rosin.

[0017] The block copolymers useful within the scope of the present invention are multi-block copolymers, preferably not containing butadiene. They consist of blocks A (called hard blocks) having a glass transition temperature Tg above 25°C, preferably above 50°C and even more preferably above 70°C, and blocks B (called soft blocks) having a Tg below 0°C, preferably below -25°C, linear or star-shaped with the formula (A)nB or (B)nA, and preferably (A)nB, with n taking values ​​from 2 to 8, preferably 2 to 6, preferably 2 to 4 and even more preferably 2 to 3, that is to say, diblock or triblock copolymers, and preferably triblock, linear or star-shaped. A combination of these copolymers constitutes a variant of the invention.At least one of blocks A or B comprises at least one polar and / or hydrophilic monomer in mass proportions of polar and / or hydrophilic monomers between 5 and 50% of the block in question.

[0018] The term "glass transition temperature" or "Tg" refers to the temperature at which the polymer material transitions from a glassy state to a non-glassy state corresponding to a certain mobility of the polymer chains relative to each other. The glass transition temperature of block copolymers is determined by analysis Dynamical mechanical analysis (DMA).

[0019] The expression "block copolymer" refers to a copolymer having a plurality of different polymer segments, each segment, also referred to as a "block," being made up of a chain of monomers that may be identical or different. Thus, each segment or block may be a homopolymer or a copolymer.

[0020] Preferably, the blocks A comprise a chain of monomers selected from linear or branched alkyl (meth)acrylates, from C1 to encyclic or non-encyclic, and in particular methyl methacrylate, possibly obtained from a depolymerization recycling process, styrene and substituted styrenes, isobornyl (meth)acrylates, and acrylates or methacrylates substituted with polar and / or hydrophilic functional groups, whether combined or not. Polar and / or hydrophilic means groups such as carboxylic (-COOH), hydroxyl (-OH), amide (-CONH), or ethylene glycol or polyethylene glycol groups, whether or not their terminal function is substituted with alkyl, phosphate, phosphonate, or sulfonate groups. In particular, we will mention (meth)acrylic acids as well as alkyl acrylamides, in particular dimethyl acrylamide, diethyl acrylamide or isopropyl acrylamide.

[0021] Preferably, the blocks B will preferably be made up of a chain of monomers selected from butyl acrylate, acrylate 2- Ethylhexyl, octyl, nonyl, and lauryl acrylates and their mixtures, possibly in mixtures with styrene, acrylates or methacrylates substituted with polar and / or hydrophilic functions. Particular mention should be made of (meth)acrylic acid and alkyl acrylamides, especially dimethyl acrylamide, diethyl acrylamide, and isopropyl acrylamide.

[0022] More preferably, the blocks B are made up of a chain of butyl acrylate monomers with or without a polar and / or hydrophilic functional monomer.

[0023] Preferably, at least one of the blocks A or B comprises at least one polar and / or hydrophilic functional monomer in mass proportions of polar and / or hydrophilic functional monomers of between 5 and 50% by mass, preferably between 5 and 30%, preferably between 5 and 20% when at least one polar and / or hydrophilic functional monomer is present in the soft block B with preferably between 5 and 12%, and when at least one polar and / or hydrophilic functional monomer is present in the hard block A preferably between 5 and 12%.

[0024] Preferably, and when at least one polar and / or hydrophilic functional monomer is present, the polar and / or hydrophilic functional monomer is present in the hard block A.

[0025] We can thus cite the following tri-block, di-block and tri-star-block copolymers of non-limiting manner useable within the scope of the invention, alone or in mixture:

[0026] p(MMAcoMAA)-pBuA-p(MMAcoMAA), p(MMAcoAA)-pBuA-p(MMAcoAA), pMMA-p(BuAcoAA)-pMMA, p(MMAcoDMA)-p(MMACoA), p(MMACoDMA) IPA)-pBuA- p(MMAco IPA) and preferably p(MMAco DMA)-pBuA- p(MMAco DMA), p(MMAco IPA)-pBuA- p(MMAco IPA), p(MMAco DEA)-pBuA- p(MMAco DEA),

[0027] p(MMAcoMAA)-pBuA, p(MMAcoAA)-pBuA, p(MMAcoMAA)-p(BuAcoSty), pMMA-p(BuAcoAA), p(MMAco DMA)-pBuA-, p(MMAco IPA)-pBuA, p(MMAco DEA)-pBuA and p(MMAco DEA)-pBuA DMA)-pBuA, p(MMAco IPA)-pBuA and p(MMAco DEA)-pBuA.

[0028] pBuA-(p(MMAcoMAA))3, pBuA-(p(MMAcoAA))3, p(BuAcoAA)-(pMMA)3, pBuA- (p(MMAco DMA))3, pBuA- (p(MMAco IPA))3, pBuA- (p(MMAco DEA)) pBuA-(p(MMAco DMA))3, pBuA- (p(MMAco IPA))3, p(BuAcoSty)-(p(MMAcoMAA))3 And pBuA- (p(MMAco DEA))3.

[0029] In all of these block copolymers, MMA can be substituted in whole or in part by IBOA and / or IBOMA.

[0030] With MMA: methyl methacrylate, MAA: methacrylic acid, AA: acrylic acid, BuA: butyl acrylate, Sty: styrene, DMA: dimethylacrylamide, IPA: isopropylacrylamide, DEA: diethyl acrylamide, IBOA: isobornyl acrylate, IBOMA: isobornyl methacrylate

[0031] The useful block copolymers within the framework of the present invention typically have a molecular weight measured by SEC (size exclusion chromatography) with a polystyrene calibration of between 10000 and 200000 g / mol and preferably between 30000 and 150000 g / mol, and even more preferably between 30000 and 100000 g / mol with a hard block / soft block mass ratio of between 20 / 80 and 80 / 20.

[0032] The block copolymers useful within the scope of the present invention are preferably prepared by controlled radical polymerization, without excluding other preparation methods. Controlled radical polymerizations allow the block copolymers to be obtained in sequential steps within the same process operation. For example, block copolymers can be prepared by RAFT (Radical Addition Fragmentation Transfer) polymerization or by nitroxide-mediated polymerization, also known as NMP (Nitroxide Mediated Polymerization). Preferably, block copolymers are prepared by NMP, in particular by NMP using the counter radical N-tert-butyl-1-diethyl-phosphono-2,2-dimethyl-propyl nitroxide. The synthesis of block copolymers using this counter radical is described in particular in EP1526138.

[0033] The compositions of the invention consist of one or more epoxy resins of Tg > 25°C measured by DSC and at least one block copolymer in mass proportions of block copolymer between 25 and 70% of the total mass of epoxy resin and block copolymers and preferably between 27 and 55%.

[0034] It has indeed been shown that at concentrations below 25%, the associated rheologies do not allow for properly extruded granules, nor do they provide any additional effect of the properties observed when using these masterbatches. Above 70%, the advantages conferred by diluting the resin with block copolymers are no longer significant compared to using block copolymer alone when the aim is to mix the compositions of the invention with the final formulation of a ready-to-use epoxy resin composition.

[0035] The compositions of the invention have a viscosity greater than 50 Pa.s for a shear gradient between 0.1 and 100 s-1, in a temperature range between 120°C and 210°C, and preferably between 140 and 190°C.

[0036] The compositions of the invention are prepared using a mixing tool of the single-screw or twin-screw extruder type, preferably twin-screw, or a mixer, at temperatures between 120 and 210°C. A degassing well, preferably of the invention, may be present with a vacuum system, completely eliminating bubbling phenomena within the granules obtained.

[0037] Thus, the present invention also relates to a method for preparing the compositions of the invention comprising the following steps: - Extrusion of a mixture of at least one epoxy resin whose Tg(s) measured by DSC are greater than 25°C and block copolymers with a mass proportion of block copolymers between 25 and 70% and preferably between 27 and 55%. - -possible degassing using a vent. - Granulation of the extrudate obtained in the form of granules.

[0038] The invention also relates to the use of the compositions of the invention in the formulation of ready-to-use epoxy resins, that is, resins that form part of the composition of objects once polymerized. These so-called ready-to-use epoxy resin formulations are formulations using the compositions of the invention combined with at least one other epoxy resin and at least one crosslinking agent, also called a hardener. Preferably, the compositions of the invention will be combined with at least one liquid epoxy resin at room temperature (25°C) and at least one solid epoxy resin at room temperature, with a Tg measured by DSC above 25°C and preferably above 50°C.

[0039] Among the hardeners used are compounds that can react within temperature ranges of 15 to 200°C. They can be acidic or basic. They can be anhydride-type compounds, amine compounds, etc. phatic with functionalities greater than or equal to two.

[0040] The present invention also relates to thermosetting epoxy compositions formulated with the compositions of the invention by combining the compositions of the invention, at least one epoxy resin (3), and at least one hardener suitable for their polymerization, with or without fillers such as woven or non-woven carbon, glass, aramid, boron, or silica fibers, and possibly with other additives such as solvents, reactive diluents such as glycidyl ethers and esters, pigments and dyes, plasticizers, and flame retardants, without limitation. The term "formulated" refers to the homogenized mixture of the compositions of the invention consisting of a thermoplastic epoxy resin and a block copolymer, at least one second epoxy resin, and at least one hardener.

[0041] The present invention also relates to composite materials obtained using the compositions of the invention, whether in the form of prepregs (called "prepreg" in Anglo-Saxon terminology) or thermo-cured composite objects.

[0042] Example 1: preparation of the compositions of the invention.

[0043] Raw materials used:

[0044] The block copolymer, designated BCP, has one block with a Tg below 0°C and one block with a Tg above 25°C. The block copolymer exhibits acrylamide functionality. This type of copolymer is available under the trade name Nanostrength® from Arkema.

[0045] The epoxy resin used, CAS No. 25036-25-3, has a Tg of 31°C measured by DSC (differential scanning calorimetry) and is available under the trade name EPON™ Resin 1001F (Hexion).

[0046] In a Labtech LTE 26-40 twin-screw pilot extruder, screw diameter 26 mm, L / D ratio 40, the extrusion of compositions M at different mass percentages of BCP and epoxy resin is carried out according to Table 1 under the following conditions:

[0047] - Temperature profile: 70-100-130-160-180-180-180-180-180-180°C.

[0048] - Screw speed: 350 rpm, flow rate: 8kg / h, water-cooled rod.

[0049] The different constituents are dosed using two gravimetric dosers.

[0050] The first doser is used for dosing the polymer, which is introduced at the level of the main hopper.

[0051] The second dispenser is used to dose the epoxy flakes.

[0052] The products are introduced into the Textrudeuse at the main hopper. The mass compositions are given in Table 1:

[0053] [Tables] Table 1 BCP % epoxy resin % Ml 5 95 M2 25 75 M3 35 65 M4 50 50

[0054] MO being 100% epoxy resin and M5 being 100% BCP.

[0055] Example 2: Rheology of M compositions.

[0056] The resin used, EPON™ Resin 1001F, represents the most unfavorable case because its Tg is 31°C, with a low molecular weight. Any other resin with a Tg above 31°C will exhibit rheological behavior that will be more favorable for manufacturing the compositions of the invention by extrusion, with the possibility of obtaining granules.

[0057] The viscosity of the formulations is determined on a rheometer with imposed constraints type MCR301 from ANTON PAAR.

[0058] The measurement is performed by stress scanning in flow at the desired measurement temperature. The geometry used is of the duvet or plane-plane type.

[0059] The flow curves of viscosity as a function of the shear gradient can then be obtained:

[0060] [Fig.1]: 140°C,

[0061] [Fig.2]: 160°C,

[0062] [Fig.3]: 175°C,

[0063] [Fig.4]: 190°C.

[0064] The compositions of the invention have a viscosity greater than 50 Pa.s for a shear gradient between 0.1 and 100 s-1, in a temperature range between 120°C and 210°C, and preferably between 140 and 190°C.

[0065] Table 2 gives EtaO viscosities on the Newtonian plateau for different temperatures of compositions MO to M5. Granulation is possible when the compositions have an EtaO viscosity greater than 50 Pa.s.

[0066] [Tables2] i abieau 2 T (X) EteO (Pa.s) granu ation MO 90 138 POSSÏ bfe 100 39 9 Possible 110 144 Possible 130 2.99 Not possible 150 0.9 Not possible 160 0.38 Not possible 175 0.14 Not possible 190 0.056 Not possible Ml 90 323 Possible 100 111 Possi oie 110 39.3 Not possible 130 9 Not possible 150 3 Not possible 160 1.68 Not possible 175 0.71 Not possible 190 0.38 Not possible M2 140 2580 Possi 160 482 Possi be 175 160 Possi be 190 40 Not possible M3 140 3796 Possi ce 160 CM CO Possi be 175 286 Possi be 190 94 Possi oe M4 140 261E+04 Possi ble 160 3837 Possi be 175 1655 Possi be 190 324 Possi be M5 190 637.5 Possi be

[0067] Example 3: Thermoset compositions and mechanical evaluations.

[0068] In this example, we compare the performance of thermoset compositions in the presence of block copolymer with the introduction of the block copolymer according to the invention or according to the prior art.

[0069] Raw materials used:

[0070] -Bisphenlol type epoxy resin A: available under the name Araldite® LY556 from Huntsman.

[0071] - EPON™ Resin 1001F.

[0072] -Epikote™ 828.

[0073] - BCP copolymer available under the trade name Nanostrength®, supplier Arkema.

[0074] Dicyandiamine (DICY) CAS 461-58-3 DyhardlOOSF (supplier Alzchem)

[0075] TDI: TDI catalyst 1,1 dimethyl-3-phenylurea CAS: 101-42-8 TDI UR300 (supplier Degussa). BYK®-P 9920: antifoaming agent (supplier BYK). 1. The following formulations are carried out according to Table 3:

[0076] The LY556 epoxy resin is weighed in the tank of a glass reactor equipped with a flat toothed disc dispersion turbine at 95 °C at an agitation of 200 rpm.

[0077] At 95°C, the quantity of Master batch M52N+1001F is introduced through a funnel with stirring at 400 rpm for 3 or 4 hours. The defoaming agent BYK P9920 is then added, and the mixture is degassed. The mixture is then cooled to 80°C. After breaking the vacuum, the hardener / accelerator combination is introduced using a funnel. It is allowed to dissolve for 15 minutes, and the vacuum is re-established for 35 minutes. The still-liquid solution (80°C) is poured into stainless steel molds (previously placed in an oven at 160°C) with a thickness of 6 mm for K1C and GIC tests, and 2 mm for tensile test specimens.

[0078] [Tables3] Table 3: Mass % EPON™ 1001F Araldite® LY556 BCP M4 DICY TDI BYK-P 9920 Control 1 82.8 9.8 5.8 0.2 1.4 Control 2 9.8 73 9.8 5.8 0.2 1.4 Invention 1 73 19.6 5.8 0.2 1.4 1. Evaluation of mechanical properties:

[0079] All test tubes are cut using the Charly robot (milling cutter)

[0080] TESTS: K1C GIC according to ISO 13586:2000

[0081] Traction standard according to ISO 527-2:2012

[0082] Table 4 sets together the values ​​obtained demonstrating the superiority of the formulations obtained using the compositions of the invention.

[0083] [Tables4] Table 4 Kl c max (MPa.Am) GIc (J / m2) E (Gpa) Control 1 1.46 + / - 0.04 901 + / - 49 2.37 + / - 0.06 Control 2 2.22 + / - 0.11 2066 + / - 208 2.38 + / - 0.06 Invention 1 2.45 + / - 0.25 1800 + / - 290 3.44 + / - 0.06

[0084] Example 4: Dissolving formulations:

[0085] The masterbatch is dissolved at 10% in an Epikote 828 type resin at temperature ambient temperature, in a beaker, using a magnetic stir bar. In the control solution, 5% of block copolymers and 5% of Epon 1001F are introduced into an Epikote 828 type resin.

[0086] After 3 hours, the solution containing the master mixture (invention 2) is completely homogeneous, while the control solution 3 still contains undissolved granules and exhibits bubbling, Table 5:

[0087] [Tables5] Table 5 Epikote™ 828 EPON™ 1001F BCP M4 Mixing time (h) Bubbles Control 3 90 5 5 0 4 Yes Invention 2 90 10 3 No

[0088] The compositions of the invention therefore make it possible to obtain better mechanical properties on formulations with epoxy resins and are easier to implement.

Claims

Claims

1. Mass composition consisting of the following mixture M: - at least one thermoplastic epoxy resin (1) whose glass transition temperature(s) measured by DSC are greater than 25°C, - at least one block copolymer (2) in mass proportions of between 25 and 70% of the total (1) + (2), in which at least one block copolymer has at least one block A having a glass transition temperature Tg greater than 25°C measured by DMA and at least one block B having a transition temperature Tg less than 0°C measured by DMA and having at least one polar and / or hydrophilic functional monomer in at least one of the blocks, said polar and / or hydrophilic functional monomer being present in mass proportions relative to the block in question of between 5 and 50%, said composition being in solid form at a temperature less than 50°C.

2. A composition comprising a homogenized mixture of a composition according to claim 1, at least one second epoxy resin (3) and at least one hardener.

3. Composition according to claim 2 further comprising at least one woven or non-woven fiber.

4.

5. Prepreg comprising a composition according to claim 3. Composite material obtained using one of the compositions according to one of claims 3 or 4.

6. Process for preparing a composition according to claim 1 comprising the following steps: - Extrusion at a temperature between 120 and 200°C of a mixture of at least one epoxy resin whose Tg(s) measured by DSC are greater than 25°C and of block copolymers with a mass proportion of block copolymers between 25 and 70%, - -optional degassing using a vent, - Granulation of the extrudate obtained in the form of granules.

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