Block copolymer / thermoplastic epoxy resin compositions

Abstract

The invention relates to compositions of block copolymers and thermoplastic epoxy resins, to the use thereof in the mechanical reinforcement of filled or non-filled thermo-set epoxy formulations and to the resulting filled or non-filled thermo-set epoxy formulations. The invention also relates to a method for producing said block copolymer / thermoplastic epoxy resin compositions.

Description

[0001] DESCRIPTION

[0002] TITLE: Thermoplastic epoxy resin compositions - block copolymers

[0003] The invention relates to compositions of block copolymers and thermoplastic epoxy resins, their use in the mechanical reinforcement of filled or unfilled thermoset epoxy formulations, as well as the filled or unfilled thermoset epoxy formulations obtained. The invention also relates to a process for preparing these compositions of block copolymers and thermoplastic epoxy resins.

[0004] Epoxy resins are used in a wide variety of fields, ranging from the manufacturing of objects intended for the automotive, aeronautical, and sports sectors. They find applications in structural adhesives, as a matrix for composite materials, and in electronic component protection applications.

[0005] Epoxy objects or materials are obtained by reacting functional epoxy resins with a functional hardener. When more than 2 functionalities on the epoxy resins and / or on the hardener are used, a thermo-hard material is obtained, i.e. one with a certain crosslinking density. The crosslinking density allows the properties to be adjusted, as do the nature of the epoxy resins and the nature of the hardener(s). Thermo-cured epoxy materials generally have a high crosslinking density, this to ensure a high glass transition temperature (Tg), so that the final material has good thermomechanical properties.

[0006] However, the constraints experienced by mechanical parts under high stress, such as in the aeronautics sector, have required the development of improvements to certain properties such as impact resistance and limiting the propagation of cracking, for example.

[0007] Solutions have been provided by combining these formulations with core-shell particles or block copolymers containing soft blocks of low Tg (glass transition temperature). In the case of block copolymers, this is described in EP1290088. In FR2880895, a further improvement is provided by the presence of functional monomer in the block copolymers.

[0008] 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.

[0009] 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 "nanostructured" state, which can only be obtained with thermodynamic steps that are not always controlled. The block copolymers useful in reinforcing epoxy resins are available at room temperature in the form of granules. Epoxy resins are available in liquid or solid form at room temperature, and mixing with the block copolymers requires conditions of agitation, time, and temperature that are restrictive for the formulator. One solution used is to grind the block copolymer granules to facilitate their dilution, but this adds an additional step.Using liquid epoxy resin with solid epoxy resin makes it easier to dissolve block copolymers in powder or granular form, but requires prolonged heating and vigorous stirring. This leads to the presence of foaming and bubbles, which cannot be completely eliminated even with additional degassing, which weakens the final material.

[0010] Another solution has been used by pre-diluting the block copolymer in a liquid epoxy resin in the form of a masterbatch subsequently 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 rates up to 25%, making this academic approach unusable in industry because the aforementioned disadvantages (foaming, bubbling, time) are exacerbated by the high proportions of block copolymers in these block copolymer blends in solid form in liquid epoxies (up to 25%). Such an approach is for example described in the thesis of Andreas Peter Klingler on page 40 under the registration number ISBN: 978-3-944440-44-6.

[0011] To avoid the disadvantages associated with the dissolution of the block copolymer in epoxy resins, the applicant has developed a composition which facilitates the dispersion of the block copolymers in epoxy resins in the form of granules with a high content of block copolymer in a solid thermoplastic epoxy resin. These granules are obtained in a mixing tool of the mixer or extruder type. These granules mix much more easily, avoiding the problems associated with mixing time, bubbling or foaming which are generated during formulation.

[0012] In addition, the compositions obtained allow a balance of final properties at identical block copolymer levels superior to those obtained in the prior art.

[0013] Summary of the invention.

[0014] The invention relates to a mass composition consisting of the following mixture M:

[0015] - at least one thermoplastic epoxy resin (1) whose glass transition temperature(s) measured by DSC are greater than 25°C,

[0016] -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.

[0017] Detailed description:

[0018] The thermoplastic epoxy resin(s) present in the compositions of the invention have Tgs greater than 25°C, preferably greater than 30°C and more preferably greater than 50°C measured by DSC (differential scanning calorimetry).

[0019] These are compounds of the pure epoxy, polyester epoxy, novolac or acrylate epoxy type. Examples include diglycidyl ether types of bisphenol-A, bisphenol F, aromatic glycidyl amines, cycloaliphatic epoxies, these compounds having an oxirane functionality greater than or equal to two. They can be fluorinated, phosphorous or silylated. They can be of renewable origin, based on natural oils (soybean, linseed, castor oil, etc.), based on isosorbide, epoxidized natural rubber, epoxy lignin derivatives or even rosin.

[0020] The block copolymers useful in the context 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 greater than 25°C, preferably greater than 50°C and more preferably greater than 70°C, and of blocks B (called soft blocks) having a Tg less than 0°C, preferably less than -25°C, linear or star-shaped of formula (A) n B or (B) n A, and preferably (A) nB, with n taking the values ​​from 2 to 8, preferably 2 to 6, preferably 2 to 4 and more preferably 2-3, that is to say di-block or tri-block copolymers and preferably tri-block, linear or star. A combination of these copolymers constitutes a variant of the invention. At least one of the blocks A or B comprises at least one polar and / or hydrophilic monomer in mass proportions of polar and / or hydrophilic monomers of between 5 and 50% of the block considered. The term "glass transition temperature" or "Tg" designates the temperature at which the polymer material passes from the glassy state to a non-glassy state corresponding to a certain mobility of the polymer chains between them. The glass transition temperature of the block copolymers is determined by dynamic mechanical analysis DMA (dynamical mechanical analysis).

[0021] The term "block copolymer" means 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 which may be identical or different. Thus, each segment or block may be a homopolymer or a copolymer.

[0022] Preferably, the blocks A comprise the chain of monomers chosen from linear or branched alkyl (meth)acrylates from C 1 to C 18 cyclic or not, and in particular methyl methacrylate, optionally resulting from a recycling process by depolymerization, styrene and substituted styrenes, isobornyl (meth)acrylates, acrylates or methacrylates substituted by polar and / or hydrophilic functions in a combined manner or not. By polar and / or hydrophilic, we mean groups such as carboxylic (-COOH), hydroxyl (-OH), amide (-CONH) groups, or ethylene glycol or polyethylene glycol substituted or not on their terminal function by alkyl, phosphate, phosphonate or sulfonate groups. In particular, mention will be made of (meth)acrylic acids as well as alkyl acrylamides, in particular dimethyl acrylamide, diethyl acrylamide or isopropyl acrylamide.

[0023] Preferably, the B blocks will preferably consist of a chain of monomers chosen from butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, nonyl acrylate, lauryl acrylate and mixtures thereof, optionally mixed with styrene, acrylates or methacrylates substituted by polar and / or hydrophilic functions. Mention will be made in particular of (meth)acrylic acids as well as alkyl acrylamides, in particular dimethyl acrylamide, diethyl acrylamide or isopropyl acrylamide. More preferably, the B blocks consist of a chain of butyl acrylate monomers with or without a polar and / or hydrophilic functional monomer.

[0024] 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, 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%.

[0025] More 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.

[0026] The following non-limiting tri block, di block and tri block copolymers can be used within the scope of the invention, alone or in mixtures: p(MMAcoMAA)-pBuA-p(MMAcoMAA), p(MMAcoAA)-pMABuA-p(MMcoAA), pMMA-p(BuAcoAA)-pMMA, p(MMAco DMA)-pBuA- p(MMAcoDMA), p(MMAco IPA)-pBuA- p(MMAco IPA) and preferably p(MMAco DMA)- pBuA- p(MMAco DMA), p(MMAco IPA)-p(MMAco IPA), p(MMAco IPA), p(MMAco IPA) DEA)-pBuA- p(MMAco DEA), p(MMAcoMAA)-pBuA, p(MMAcoMAA)-pBuA, p(MMAcoMAA)-p(BuAcoSty), pMMA-p(BuAcoAA), p(MMAco DMA)-pBuA-, p(MMAco IPA)-pMABuA, p(MMAco DEA) p(MMAco DMA)-pBuA, p(MMAco IPA)-pBuA and p(MMAco DEA)-pBuA. pBuA-(p(MMAcoMAA))s, pBuA-(p(MMAcoAA))s, p(BuAcoAA)-(pMMA)s, pBuA- (p(MMAco DMA))3, pBuA- (p(MMAco DEA))3, pBuA- (p(MMAco DEA))3 and respectively p(MMAco-(MMAco)) DMA))s, pBuA- (p(MMAco IPA))s, p(BuAcoSty)-(p(MMAcoMAA))s And pBuA- (p(MMAco DEA))s.

[0027] In all these block copolymers, MMA may be substituted in whole or in part by IBOA and / or IBOMA.

[0028] 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

[0029] The block copolymers useful in the context of the present invention typically have a molecular mass by weight measured by SEC (size exclusion chromatography) with a polystyrene calibration of between 10,000 and 200,000 g / mol and preferably between 30,000 and 150,000 g / mol, and more preferably between 30,000 and 100,000 g / mol with a hard block / soft block mass ratio of between 20 / 80 and 80 / 20.

[0030] The block copolymers useful in the context of the present invention are preferably prepared by controlled radical polymerization, without excluding other methods of preparation. Controlled radical polymerizations make it possible to obtain block copolymers in sequential steps within the same process operation. For example, the block copolymers can be prepared by "RAFT" (Radical Addition Fragmentation Transfer) polymerization or by nitroxide-controlled polymerization, also called "NMP" (Nitroxide Mediated Polymerization). Preferably, the 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.

[0031] The compositions of the invention consist of one or more epoxy resins with a Tg > 25°C measured by DSC and at least one block copolymer in mass proportions of block copolymer of between 25 and 70% of the total mass of epoxy resin and block copolymers and preferably between 27 and 55%.

[0032] It has indeed been shown that at rates lower than 25%, the associated rheologies do not allow for correctly extruded granules to be obtained, nor for any additional effect of the properties observed when using these masterbatches. Beyond 70%, the advantages provided by diluting the resin with block copolymers are no longer significant compared to the use of block copolymer alone when seeking to mix the compositions of the invention with the final formulation of a ready-to-use epoxy resin composition.

[0033] The compositions of the invention have a viscosity greater than 50 Pa.s for a shear gradient of between 0.1 and 100 s-1, in a temperature range of between 120°C and 210°C, and (preferably) between 140 and 190°C.

[0034] 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, completely eliminating the bubbling phenomena within the granules obtained.

[0035] Thus, the present invention also relates to a process for preparing the compositions of the invention comprising the following steps:

[0036] - 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 of between 25 and 70% and preferably between 27 and 55%.

[0037] - -possible degassing using a vent.

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

[0039] Among the hardeners used, these are compounds that can react in temperature ranges between 15 and 200 °C. They can be acidic or basic. They can be anhydride-type compounds, amino compounds, aliphatic compounds with functionalities greater than or equal to two.

[0040] The present invention also relates to thermoset epoxy-type 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 in the presence or absence of fillers such as woven or non-woven fibers of carbon, glass, aramid, boron or silica fibers and optionally in the presence of other adjuvants such as solvents, reactive diluents such as glycidyl ethers and esters, pigments and dyes, plasticizers, flame retardants, in a non-limiting manner. By formulated is meant 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 the composite materials obtained using the compositions of the invention, whether in the form of pre-impregnated materials (known as "prepregs" in English terminology) or thermo-cured composite objects.

[0042] Example 1: Preparation of the compositions of the invention. Raw materials used:

[0043] The block copolymer denoted BCP has one block whose Tg is less than 0°C and one block whose Tg is greater than 25°C. The block copolymer has an acrylamide functionality. This type of copolymer is available under the trade name Nanostrength® from Arkema.

[0044] The epoxy resin used with 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 1001 F (Hexion).

[0045] 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 according to table 1 is carried out under the following conditions:

[0046] - Temperature profile: 70-100-130-160-180-180-180-180-180-180°C.

[0047] - Screw speed: 350 rpm, flow rate: 8kg / h, water cooling of the rod.

[0048] The various constituents are dosed using two gravimetric dosers.

[0049] The first doser is used for dosing the polymer, which is introduced at the main hopper.

[0050] The second dispenser is used to dose the epoxy flakes.

[0051] The products are introduced into the extruder at the main hopper. The mass compositions are given in Table 1:

[0052] [Table 1]

[0053] MO being 100% epoxy resin and M5 being 100% BCP.

[0054] Example 2: Rheology of compositions M. The resin used EPON™ Resin 1001 F is the most unfavorable case because its Tg is 31 °C, with a low molecular weight. Any other resin with a Tg higher than 31 °C will exhibit rheological behavior that will be more favorable for the manufacture of the compositions of the invention by extrusion with the possibility of obtaining granules.

[0055] The viscosity of the formulations is determined on an imposed stress rheometer type MCR301 from ANTON PAAR.

[0056] The measurement is carried out by flow stress scanning at the desired measurement temperature. The geometry used is of the quilt or plane-plane type.

[0057] The flow curves of viscosity as a function of shear gradient can then be obtained:

[0058] Figure 1: 140°C,

[0059] Figure 2: 160°C,

[0060] Figure 3: 175°C, Figure 4: 190°C.

[0061] The compositions of the invention have a viscosity greater than 50 Pa.s for a shear gradient of between 0.1 and 100 s-1, in a temperature range of between 120°C and 210°C, and (preferably) between 140 and 190°C.

[0062] 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. [Table 2]

[0063] Example 3: Thermoset compositions and mechanical evaluations. In this example, the performance of thermoset compositions in the presence of block copolymer is compared with the introduction of the block copolymer according to the invention or according to the state of the art.

[0064] Raw materials used:

[0065] -Bisphenol A epoxy resin: available under the name Araldite® LY556 from Huntsman.

[0066] - EPON™ Resin 1001 F. -Epikote™ 828.

[0067] -BCP copolymer available under the trade name Nanostrength®, supplier Arkema.

[0068] Dicyandiamine (DICY) CAS 461-58-3 Dyhardl OOSF (supplier Alzchem) TDI: TDI catalyst 1,1-dimethyl-3-phenylurea CAS: 101-42-8 TDI UR300 (supplier Degussa).

[0069] BYK®-P 9920: anti-foaming agent (BYK supplier).

[0070] 1) The following formulations are produced according to Table 3:

[0071] The LY556 epoxy resin is weighed into the tank of a glass reactor equipped with a flat toothed disc dispersion turbine at 95 °C with stirring at 200 rpm. At 95 °C, the quantity of Master batch M52N + 1001 F is introduced through the funnel with stirring at 400 rpm for 3 or 4 hours. The defoaming agent BYK P9920 is then introduced and the mixture is degassed. The mixture is then cooled to 80 °C. After breaking the vacuum, the hardener / accelerator pair is introduced using a funnel. It is left 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 the K1 C and G1 C tests and a thickness of 2 mm for the tensile test pieces.

[0072] [Table 3]

[0073] 2) Evaluation of mechanical properties:

[0074] All the test pieces are cut with the Charly robot (milling cutter)

[0075] TESTS: K1 C G1 C according to ISO 13586:2000 standard

[0076] Traction standard according to ISO 527-2:2012

[0077] Table 4 brings together the values ​​obtained demonstrating the superiority of the formulations obtained using the compositions of the invention. [Table 4]

[0078] Example 4: dissolution of formulations:

[0079] The masterbatch is dissolved at 10% in an Epikote 828 type resin at room temperature, in a beaker, using a magnetic bar. In the control solution, 5% of block copolymers and 5% of Epon 1001 F are introduced into an Epikote 828 type resin.

[0080] After 3 hours, the solution containing master mix (invention 2) is completely homogeneous, while control solution 3 still contains undissolved granules and shows bubbles, table 5:

[0081] [Table 5]

[0082] 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 below 50°C. 2 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 Pre-impregnated comprising a composition according to claim 3. 5 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%, - -possible degassing using a vent, - Granulation of the extrudate obtained in the form of granules.

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