Suspension Polymerization of Alkoxyamines Using Styrenic and (Meth)Acrylic Monomers

Abstract

The present invention relates to a process for the suspension polymerization of alkoxyamines with styrenic and (meth)acrylic monomers, to the beads and compositions thus obtained, and to the use of these beads and compositions.

Description

Technical Field

[0001] The present invention relates to a method for suspension polymerization of alkoxyamines with styrenic and (meth)acrylic monomers, beads and compositions thus obtained, and the use of these beads and compositions.

Background Art

[0002] In order to improve some of their properties, there is a need to explore methods that result in more efficient materials.

[0003] Block copolymers are polymers that are difficult to manufacture but have advantages due to their block structures that enable the establishment and adjustment of morphology at the nanometer scale. Their physical behavior, such as mechanical behavior, optical behavior, and chemical behavior such as resistance to chemical agents, is superior to that of homopolymers or random copolymers.

[0004] Some synthetic methods can target or cancel out combinations of these physical and chemical behaviors to target properties.

[0005] The chemistries and synthetic methods used to produce them can be ionic, controlled radical, and condensation polymerizations operating in bulk, solution, emulsion, and suspension. Optionally, the dispersity of the resulting block copolymer can approach 1. In the context of the present invention, the applicant is interested in compositions of (meth)acrylic and / or styrenic block copolymers prepared by controlled radical polymerization of nitroxides (nitroxide-mediated polymerization, NMP) containing alkoxyamines, and more particularly, block copolymers having at least one soft block within the block copolymer, i.e., a Tg measured by DSC of less than 0°C, and block copolymer compositions having at least one hard block within the block copolymer, i.e., a Tg measured by DSC of greater than 20°C.

[0006] In NMP, alkoxyamines are used that enable the control of block polymerization by balancing radicals with nitroxides released at a specific temperature. This technique is described, for example, in the paper by Nicolas J. et al., Progress in Polymer Science 38 (2013) 63 - 235. In alkoxyamine chemistry, the dispersity of block copolymers can vary from 1.2 to 2 depending on the conversion at which the polymerization is carried out.

[0007] In order to avoid excessive drift in the dispersity of the resulting block copolymer, it may be necessary to limit the conversion. This results in unreacted monomers that must be removed.

[0008] For example, to prepare a diblock copolymer, a monofunctional alkoxyamine is reacted in a reactor in the presence of a first monomer or monomer group M1 in a solvent, or up to about 70% conversion, and then the remaining monomer M1 is generally removed by evaporation. The resulting macroalkoxyamine is then placed in the presence of a second monomer or monomer group M2 to form the second block, following the same method of conversion / removal of M2. A PolyM1 - PolyM2 diblock copolymer is then obtained.

[0009] This method enables the production of products with the desired properties, but the conditions of the method cannot make a connection between the impurities or the exact nature of the block copolymers produced in this way, imposing a disadvantage on some of these properties such as optical or thermal properties.

[0010] A second method called emulsion has been attempted, but the transition to industrial scale is complex (product synthesis, recovery).

[0011] The third so-called suspension method seems to have advantages with respect to obtaining a copolymer composition that allows maximizing certain properties such as mechanical, thermal or optical properties. The composition obtained by this suspension method is different because part of the monomers are obtained in the form of a homopolymer or a random copolymer and not in the form of a block copolymer.

[0012] Suspension polymerization involves polymerizing the reaction mixture within droplets dispersed in water. For this purpose, effective stirring in the reactor and a "suspending" agent are used, enabling the preparation of beads or balls that can vary or be adjusted in diameter from a few microns to several hundred microns.

[0013] Unlike the bulk or solvent methods, no solvent is present, and the presence of water during the suspension method allows the production of materials with much higher optical quality. The use of these compositions is possible in applications where optical quality is required when this is not possible with products obtained from polymerization in bulk or in a solvent. Furthermore, the products resulting from this method have been found to be more thermally stable in the context of the present invention.

[0014] Unlike the bulk or solvent methods, it is not possible to stop the conversion to limit the dispersity drift, or the implementation in the suspension method is complex.

[0015] During the synthesis of the first poly-M1 block, the conversion is maximized even if there is a drift in the dispersity of the obtained block.

[0016] In the second conversion step of the second monomer or group of monomers, it is appropriate to select various chemical agents that enable effective conversion of the monomer group M2 into a polymer block by attempting to minimize the defects that may appear at the chain ends of the resulting copolymer.

[0017] In Chemical Engineering Journal 316(2017)655-662, Ballard et al. described the suspension polymerization of methacrylic monomers in the presence of alkoxyamines.

[0018] This suspension method uses, as the alkoxyamine, 3-(((2-cyanopropan-2-yl)oxy)(cyclohexyl)amino)-2,2-dimethyl-3-phenylpropanenitrile of structure.

[0019] This enables the controlled radical polymerization of methacrylates, but for acrylates, less than 50% conversion is observed because acrylates cause side reactions (Simula A. et al., European Polymer Journal 110(2019)319-329). However, the introduction of acrylates into block copolymers, unlike methacrylates, enables the use of monomers that result in blocks with very low Tg, which is interesting. Thus, for butyl acrylate or 2-ethylhexyl acrylate, a Tg much lower than -20 °C is observed. This allows for obtaining materials with good impact resistance.

[0020] In the present invention, the applicant is interested in different families of alkoxyamines that enable the polymerization of acrylates and / or styrene-based systems in a controlled manner. In the context of the present invention, the first block is prepared using acrylate and / or styrene-based monomers, and the other blocks are composed of blocks composed of methacrylate and / or styrene-based entities.

[0021] During this second step, which is not a controlled method with this family of alkoxyamines, the applicant sought conditions that would enable effective conversion of methacrylates while minimizing the so-called disproportionation reactions specific to them.

[0022] Thus, if the first step follows the conventional method of conversion of the first block by a controlled method, the second step, which is mainly carried out with methacrylate, is carried out in an uncontrolled manner because of the characteristics of this family of alkoxyamines used in the context of the present invention.

[0023] Unexpectedly, the presence of mercaptan from the start of this second step does not interfere with the polymerization method from the poly M1 block, and the synthesis of the block copolymer takes place, with random entities being synthesized together. Compared with the product obtained in the absence of mercaptan, the conversion is accelerated (Figure 1). The product obtained in the presence of mercaptan during the second step is even more thermally stable, as can be verified by thermogravimetric analysis.

[0024] In the present invention, the Applicant shows that it is possible to convert up to 90%, and even up to 95%, of the monomers within the process resulting from the synthesis of the various blocks.

[0025] The small amount of unconverted monomer is polymerized using a water-soluble initiator at the end of the second step. A surfactant can be added from the first step. Thus, the Applicant has verified that the polymers resulting from these low percentages of monomers, which are a problem encountered in the absence of a water-soluble initiator, agglomerate on the surface of the beads produced, form a shell, and facilitate the downstream processing of separation and drying.

[0026] When using a bulk or solvent method, another difficulty arises. The copolymer obtained has a high viscosity, for example in an extruder or an injection molding machine, and the deformation process becomes complicated. At the same molecular weight, the composition of the present invention shows better fluidity than the product obtained by the bulk method.

[0027] Thus, by the method of the present invention, a composition of block copolymers and polymers obtained from a radical method related to the presence of mercaptans is obtained. This composition has the characteristics of the monomers or the central sequence of the copolymer different from those obtained using other methods because the reactivity ratios of the monomers in the suspension method are different (see in particular P.J. Dowding, B. Vincent: Colloids and Surfaces A: Physicochem. Eng. Aspects 161 (2000) 263 - 264). These compositions are not as clearly defined in structure as the block copolymers obtained from the bulk method and are therefore novel. Nevertheless, they have been found to be effective by exhibiting excellent optical properties and better thermal stability.

[0028] These novel compositions of the copolymers obtained using the method of the present invention enable use in applications requiring optical quality, heat resistance, easy deformation conditions or optimal mechanical performance. They can be used for three-dimensional printing by sintering of beads.

Summary of the Invention

[0029] The present invention relates to a method for suspension polymerization of (meth)acrylic and / or styrenic monomers for obtaining beads of a composition comprising at least one block copolymer, the method comprising the following two consecutive synthesis steps. Step 1: In a stirred reactor containing water, 0.5 - 4% by mass of a suspending agent constituting the aqueous phase, and 0 - 10000 ppm of a surfactant, an organic phase consisting of at least one alkoxyamine and at least one acrylic and / or styrenic monomer having a molar ratio of nitroxide / monomer of 1 / 50 - 1 / 1000 and a mass ratio of aqueous phase / organic phase of 3 - 10 is introduced, the alkoxyamine having the following formula: [Chemical formula 1] TIFF0007713131000001.tif29170(R a and R brepresents the same or different alkyl groups having 1 to 40 carbon atoms, which are optionally linked together to form a ring and may be substituted with hydroxyl, alkoxy or amino groups, R L represents a monovalent group having a molar mass greater than 15.42 g / mol, and R a and R b represent the same or different alkyl groups having 1 to 40 carbon atoms, which are optionally linked together to form a ring and may be optionally substituted with hydroxyl, alkoxy or amino groups, R L has at least one nitroxide corresponding to (represents a monovalent group having a molar mass greater than 15.42 g / mol), polymerization of monomers in suspension at a temperature of 15 °C to 140 °C up to a minimum mass conversion rate of 80%, Step 2: · Introduction of at least one methacrylic and / or styrenic monomer and at least one mercaptan into the previous polymerization suspension, which is a molar ratio of mercaptan / nitroxide of 2 / 1000 to 8 / 1000 and a mass ratio of monomer (acrylic and / or styrenic) / methacrylic and / or styrenic monomer of 25 / 75 to 70 / 30, · Polymerization of monomers with stirring at a temperature of 15 °C to 140 °C up to a minimum conversion rate of 95%, · Introduction of an initiator soluble in the aqueous phase at a rate of 0.1 to 2% based on the mass of the total organic phase to complete the polymerization up to a minimum mass conversion rate of 99%, · Filtration, washing and then drying of the beads.

[0030] Detailed Description The present invention relates to the suspension polymerization of monomers and alkoxyamines carrying nitroxides of general formula (1) as follows. [Chemical formula 2] TIFF0007713131000002.tif34170(R a and R brepresents the same or different alkyl groups having 1 to 40 carbon atoms, which may optionally be joined together to form a ring and may be substituted with a hydroxyl, alkoxy or amino group, R L represents a monovalent group having a molar mass greater than 15.42 g / mol, preferably greater than 30 g / mol.) Group R L can have, for example, a molar mass of 40 to 450 g / mol. Preferably, it is a phosphorus group of the following general formula. [Chemical formula 3] TIFF0007713131000003.tif19170(wherein X and Y, which may be the same or different, may be selected from alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy, perfluoroalkyl and aralkyl groups and may contain 1 to 20 carbon atoms. X and / or Y may be a halogen atom such as a chlorine, bromine or fluorine atom.)

[0031] Advantageously, R L is a phosphonate group of the following formula. [Chemical formula 4] TIFF0007713131000004.tif22170(wherein R c and R d are two identical or different alkyl groups which may optionally be joined together to form a ring and which contain 1 to 40 optionally substituted carbon atoms or optionally unsubstituted carbon atoms.)

[0032] Group R L may also contain at least one aromatic ring such as a phenyl radical or a naphthyl radical, which is substituted, for example, by one or more alkyl radicals containing 1 to 10 carbon atoms.

[0033] As taught in International Publication No. 03 / 062293, the nitroxide of formula 1 is preferred because it enables effective control of the radical polymerization of (meth)acrylic monomers. Accordingly, the following alkoxyamine (2) having the nitroxide of formula (1) is preferred. [Chemical Formula 5] TIFF0007713131000005.tif30170(wherein, Z represents a polyvalent group. Examples of the nitroxide of formula (1) that can be supported by the alkoxyamine (2) include the following. · N-tert-butyl-1-phenyl-2-methylpropyl nitroxide, · N-(2-hydroxymethylpropyl)-1-phenyl-2-methylpropyl nitroxide, · N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide · N-tert-butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl nitroxide, · N-tert-butyl[(1-diethylphosphono)-2-methylpropyl] nitroxide, · N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono) nitroxide, · N-(1-phenylbenzyl)-[(1-diethylphosphono)-1-methylethyl] nitroxide, · N-phenyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide, · N-phenyl-1-diethylphosphono-1-methylethyl nitroxide, · N-(1-phenyl 2-methylpropyl)-1-diethylphosphonomethylethyl nitroxide, · Or alternatively, a nitroxide of the following formula [Chemical Formula 6] TIFF0007713131000006.tif25170 · The nitroxide of formula (3) is particularly preferred. [Chemical Formula 7] TIFF0007713131000007.tif34170

[0034] This is N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide.

[0035] Preferred alkoxyamines having these nitroxides are derived from the following monoalkoxyamine (4). [Chemical Formula 8] TIFF0007713131000008.tif24170

[0036] This is 2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2-methylpropionic acid.

[0037] This alkoxyamine (4) is monofunctional with respect to the alkoxyamine and thus the nitroxide. It results in a composition of diblock copolymers in the context of the present invention, which constitutes one of the preferred embodiments of the present invention.

[0038] By adding this alkoxyamine (4) to a bifunctional, trifunctional or polyfunctional monomer, an alkoxyamine that is polyfunctional with respect to the alkoxyamine and thus the nitroxide can be obtained. Such polyfunctional alkoxyamines are described in European Patent No. 1526138. These polyfunctional alkoxyamines (5) are preferably dialkoxyamines (6) and constitute the second preferred embodiment of the present invention.

[0039] Diacrylate diol C2-C 10 Using alkyl, dialkoxyamines typical of the present invention can be obtained. These make it possible to prepare compositions of triblock copolymers. Preferably C2-C6, more preferably C2-C4 alkyl (ethanediol diacrylate, propanediol diacrylate, butanediol diacrylate) is preferred. The addition product of alkoxyamine (4) to butanediol diacrylate is particularly preferred, resulting in dialkoxyamine (7).

[0040] Using other bifunctional or polyfunctional compounds, dialkoxyamines, trialkoxyamines or polyalkoxyamines that can be used in the context of the present invention can be prepared, whether acrylic or styrenic.

[0041] The monomers used in the preparation of the block copolymer composition of the present invention are selected from the following list.

[0042] (Meth)acrylic monomers and vinyl aromatic monomers such as styrene or substituted styrene, especially α-methylstyrene, silylated styrene, acrylic monomers such as acrylic acid or its salts, cycloalkyl or aryl acrylates such as alkyl, methyl, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate or phenyl acrylate, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, alkyl ether acrylates such as 2-methoxyethyl acrylate, alkoxy or aryloxy polyalkylene glycol acrylates such as methoxypolyethylene glycol acrylate, ethoxypolyethylene glycol acrylate, methoxypolypropylene glycol acrylate, methoxy-polyethylene glycol-polypropylene glycol acrylate or mixtures thereof, aminoalkyl acrylates such as 2-(dimethylamino)ethyl acrylate (ADAME), fluorinated acrylates, isobornyl acrylate, tert-butylcyclohexyl acrylate, silylated acrylate, phosphorus-containing acrylates such as alkylene glycol phosphate acrylate, glycidyl acrylate, dicyclopentenyl oxyethyl acrylate, methacrylic monomers such as methacrylic acid or its salts, alkenyl or aryl methacrylates such as alkyl, cycloalkyl, methyl methacrylate (MAM), lauryl methacrylate, cyclohexyl methacrylate, allyl methacrylate, phenyl methacrylate or naphthyl methacrylate, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, alkyl ether methacrylates such as 2-ethoxyethyl methacrylate, alkoxy or aryloxy polyalkylene glycol methacrylates such as methoxypolyethylene glycol methacrylate, ethoxypolyethylene glycol methacrylate, methoxypolypropylene glycol methacrylate, methoxy-polyethylene glycol-polypropylene glycol methacrylate or mixtures thereof, aminoalkyl methacrylates such as 2-(dimethylamino)ethyl methacrylate (MADAME), 2,2,Fluorinated methacrylates such as 2-trifluoroethyl methacrylate, silylated methacrylates such as 3-methacryloylpropyltrimethylsilane, phosphorus-containing methacrylates such as alkylene glycol phosphate methacrylate, hydroxyethylimidazolidone methacrylate, hydroxyethylimidazolidinone methacrylate, 2-(2-oxo-1-imidazolidinyl)ethyl methacrylate, acrylonitrile, acrylamide or substituted acrylamide, 4-acryloylmorpholine, N-methylolacrylamide, methacrylamide or substituted methacrylamide, N-methylolmethacrylamide, methacrylamidopropyltrimethylammonium chloride (MAPTAC), glycidyl or dicyclopentenyl oxyethyl methacrylate, itaconic acid, maleic acid or its salt, maleic anhydride, alkyl or alkoxy- or aryloxy-polyalkylene glycol maleate or hemimaleate, vinylpyridine, vinylpyrrolidone, (alkoxy-)poly(alkylene glycol) vinyl ether or divinyl ether compound, methoxypoly(ethylene glycol) vinyl ether, etc., poly(ethylene glycol) divinyl ether, alone or as a mixture of at least two of the aforementioned monomers.,

[0043] Preferably, these are alkyl acrylates and methacrylates, butyl acrylate, especially 2-ethylhexyl acrylate, isobornyl acrylate and methacrylate, 4tert-butylcyclohexyl acrylate, methyl methacrylate, acrylic acid and methacrylic acid, even more preferably butyl acrylate, styrene, methacrylic acid and methyl methacrylate.,

[0044] Acrylic and styrene monomers are used in the synthesis of step 1 in the context of the method of the present invention. Methacrylic and styrene monomers are used in the synthesis of step 2 in the context of the method of the present invention.,

[0045] The monomers in Step 1 are preferably selected from butyl acrylate, 2-ethylhexyl acrylate, and styrene, either alone or in combination, and the monomers in Step 2 are selected from methyl methacrylate, methacrylic acid, and styrene, either alone or in combination.

[0046] In Step 1 of the method of the present invention, the molar ratio of nitroxide / monomer is 1 / 50 to 1 / 1000.

[0047] Regarding the mercaptans used in Step 2 of the method of the present invention, these are any type of mercaptan called R-SH, where R is an alkyl group that is linear or non-functionalized or not, and has 3 to 12 carbons, preferably 4 to 8 carbons. In particular, mercaptoethanol, mercaptopropanol, mercaptobutanol, mercaptoacetic acid, mercaptopropionic acid, butyl, octyl, and n-dodecyl mercaptan can be listed alone or in combination. Butyl or octyl mercaptan is preferably alone or in a mixture.

[0048] The suspending agent used in the context of the present invention is a typical suspending agent known to those skilled in the art. This can be polyvinyl alcohol, polyvinylpyrrolidone, a copolymer of (meth)acrylic acid, or a copolymer of 2-acrylamido-2-methylpropanesulfonic acid, preferably polyvinyl alcohol or a copolymer of 2-acrylamido-2-methylpropanesulfonic acid, more preferably a copolymer of 2-acrylamido-2-methylpropanesulfonic acid. This suspending agent is described in European Patent No. 0683182 in Example 1.

[0049] The suspending agent is present in an amount of 0.5 to 4% by mass based on the aqueous phase.

[0050] Optionally, inorganic particles can be added to improve the stability of the suspension.

[0051] The surfactant can be added to the aqueous phase in an amount of 0 to 10,000 ppm, preferably 0 to 5,000 ppm, more preferably 0 to 400 ppm, relative to the aqueous phase. It can be any type of ionic or non-ionic surfactant.

[0052] The water-soluble initiator can be selected from, for example, persulfates and in particular potassium persulfate, and added in an amount that can vary from 0.1% to 2%, preferably from 0.1% to 1% by mass, relative to the total organic phase, at the end of the polymerization when the suspension to be polymerized has reached a conversion of more than 95%.

[0053] The water-soluble initiator makes it possible, at the end of the synthesis, to convert the last small percentage of monomers into a shell that adheres to the beads obtained by the method of the invention.

[0054] According to one aspect that is the subject of the present invention, an additional amount of the monomer of step 2, which is from 1% to 10% by mass, preferably from 3% to 7% by mass, relative to the amount of monomers of steps 1 and 2, can be added together with the water-soluble initiator.

[0055] The mass ratio of the aqueous phase to the organic phase in step 1 of the method of the present invention is from 3 to 10, preferably from 4 to 8.

[0056] During step 2 of the method of the present invention, the molar ratio of the monomer (acrylic and / or styrenic) / methacrylic monomer is from 25 / 45 to 70 / 30, preferably from 25 / 75 to 55 / 45.

[0057] During this step 2, the mercaptan is introduced with a molar ratio of mercaptan / nitroxide of 0.2 to 0.8, preferably 0.4 to 0.6.

[0058] Stirring depends on the reactor used. For example, in the case of a 20-liter reactor equipped with an impeller-type stirring element, it is several hundred revolutions per minute. In a 5000-liter reactor, still using an impeller-type stirring element, it is from 100 to 250 revolutions per minute. In the context of the present invention, other types of stirring can be used.

[0059] The overlapping temperature is 15 to 150 °C, preferably 100 to 135 °C, more preferably 125 to 135 °C.

[0060] The weight average molecular weight of the composition obtained by the method of the present invention is 5000 to 300000 g / mol, preferably 10000 to 200000 g / mol, and the dispersion index is 2 to 4, preferably 2.5 to 3.3. According to one aspect of the present invention, the composition is preferably a composition of a diblock copolymer and a random copolymer derived from a monoalkoxyamine.

[0061] According to another aspect of the present invention, the composition is preferably a composition of a triblock copolymer and a random copolymer derived from a dialkoxyamine.

[0062] The present invention relates to beads obtained using the method of the present invention. They are in the form of spheres having a weight average diameter of 5 to 600 μm, preferably 50 to 400 μm, more preferably 50 to 250 μm, as measured by laser diffraction in a dry method using equipment manufactured by Malvern. The beads are composed of a nanostructured material consisting of a matrix of one block and a dispersed phase of the other block, and a continuous shell of a hard phase with Tg > 20 °C, and the shell has a thickness varying from 30 to 150 nm.

[0063] Beads having a continuous shell are a preferred embodiment of the beads obtained using the method of the present invention.

[0064] The present invention also relates to the compositions obtained using the method of the present invention, because both their analytical aspects and their properties are different from those obtained by other methods (solvent, bulk, emulsion).

[0065] The present invention also relates to the use of the compositions or the beads of the present invention for manufacturing objects by molding, injection, compression or extrusion.

[0066] The present invention also relates to the use of beads obtained by the method of the present invention in the field of three-dimensional printing called laser sintering for forming objects.

[0067] Laser beam powder sintering technology is used to manufacture three-dimensional objects such as prototypes or models, but is also used in particular to manufacture functional parts in the fields of automotive, marine, aviation, aerospace, medical (prostheses, auditory systems, cell tissues, etc.), textiles, clothing, fashion, decoration, electronic casings, telephones, home automation, computing or lighting.

[0068] In laser sintering technology, a thin layer of powder is deposited on a horizontal plate held in a chamber heated to a certain temperature. The laser contributes the energy necessary to sinter the powder particles at different points of the powder layer according to the geometric shape corresponding to the object, for example using a computer having the shape of the object in its memory and reproducing this shape in the form of slices. Subsequently, the horizontal plate is lowered by a value corresponding to the thickness of the powder layer (for example, 0.05 to 2 mm, generally about 0.1 mm), then a new powder layer is deposited and the laser contributes the energy necessary to sinter the powder particles according to the geometric shape corresponding to this new slice of the object, etc. This procedure is repeated until the entire object is manufactured. Inside the chamber, an object surrounded by unsintered powder is obtained. Thus, the unsintered parts remain in powder form. After being completely cooled, the object is separated from the powder, which can be reused in another operation.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0070] Explanation of the measurement method: · Atomic force microscope. By using this microscopy method, it becomes possible to visualize the soft and hard regions of the sample, here the planar cross-section of the beads coated with epoxy resin. The sample is observed in the "tapping" mode. · Liquid adsorption chromatography (LAC) is a chromatography method.

[0071] Adsorption liquid chromatography is a technique for separating complex mixtures of polymers, and each of its components can be eluted according to its chemical composition and thus independently of its molar mass.

[0072] The sample is injected into a WATERS ALLIANCE 2695 HPLC apparatus.

[0073] The eluent is a gradient (hexane / THF) acidified with 5% acetic acid and stabilized with BHT.

[0074] The polar column used is a SunFire Prep Silica 5μm 4.6*250mm column (CAP-Sunfire-02).

[0075] The flow rate is 1 ml / min and the volume of the sample to be injected is 30 μl.

[0076] The detectors used were an Agilent ELSD (Evaporative Light Scattering Detector) 380 and a Waters 2487 Dual UV 254 nm.

[0077] For liquid adsorption chromatography, the polymer sample was prepared at 2 g / l in THF. The PMMA and PABu samples will function as standards so that they can be identified at the end of the analysis of the PMMA-PABu / PMMA triblock. Inject a volume of 30 μL.

[0078] Yellowness index: Measured according to the YIE313 standard (NF ISO 7724-3 1988). The yellowness index (YI) is measured with a Colorquest HunterLab (conditions: light emission: D65, observation angle: 10°, observation mode: transmission).

[0079] Molecular weight. They are measured by SEC using polystyrene standards.

Example

[0080] Example 1 (of the present invention): Synthesis of the composition by the method of the present invention: The starting alkoxyamine used is N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyprop-2-yl)hydroxylamine, and its expanded formula is as follows. [Chemical formula 9] TIFF0007713131000009.tif38170 This is available from Arkema under the name Blocbuilder® MA.

[0081] The following steps are carried out. 1: Add Blocbuilder® MA to butanediol diacrylate to form a dialkoxyamine (7) called a diamine which is the starting point of the triblock copolymer. 2: Synthesis of dialkoxyamine polybutyl acrylate (PABu) by reaction of butyl acrylate with dialkoxyamine. 3: Synthesis in suspension of PMMA-PAbu-PMMA triblock copolymer composition.

[0082] 1 / Synthesis of diamine: The diamine is prepared in ethanol and butanediol diacrylate (BDMA) from Blocbuilder MA® (Arkema). A 1 L reactor is inerted with nitrogen. 114 g of ethanol, 60 g of Blocbuilder MA® and 15.7 g of BDMA are introduced into the reactor. The reactor is stirred at 100 rpm and heated to 80 °C (1 bar) for 4 hours. The solids content is 35%. The temperature is lowered to 25 °C. After evaporation of the ethanol, the diamine can be recovered and used as is.

[0083] 2 / Synthesis of the poly(butyl acrylate) block in step 1 of the process of the invention: A 5 L reactor is used. The aqueous phase is prepared directly in the reactor and stirred at 500 rpm for 30 minutes. Aqueous phase: · Demineralized water: 1800 g · Suspending agent: copolymer of 2-acrylamido-2-methylpropanesulfonic acid: 15.3 g (305.8 g in 5% solution) · Surfactant: polyethoxylated C12-C14 alcohol (50 ethoxylation units) is used, available for example from Cognis, Disponil® LS500: 0.5 g The organic phase is prepared in a separate container: · Diamine: 16.1 g · Butyl acrylate: 350 g After alternating vacuum and nitrogen cycles in the reactor, the organic phase is added. Then the suspension is heated in the following cycle: Segment 1 Initial temperature 20 Final temperature 130 Time 90 Segment 2 Initial temperature 130 Final temperature: 130 Time: 50 Initial temperature of segment 3: 130 Final temperature: 20 Time: 45

[0084] Synthesis of 3 / polymethyl methacrylate - poly(butyl acrylate) - polymethyl methacrylate copolymer composition, Step 2 of the method of the present invention: The organic phase is prepared from methyl methacrylate and mercaptan. · Methyl methacrylate: 397.5 g · Octyl mercaptan and butyl mercaptan (50 / 50): 1.6 g The organic phase is introduced into the reactor under reduced pressure. The mixture is heated according to the cycle. Initial temperature: 20°C Final temperature: 130°C Time: 90 minutes Initial temperature of segment 1: 130°C Final temperature: 130°C Time: 90 minutes Initial temperature of segment 2: 130°C Final temperature: 20°C Time: 60 minutes

[0085] 4 / Synthesis of the shell: The shell is formed according to the following recipe. · Demineralized water: 92 g · Potassium persulfate: 0.73 g

[0086] The polymerization is carried out at 85°C for 1 hour and 30 minutes.

[0087] Then, the suspension is recovered. The beads are filtered, washed twice with water, and dried in an oven at 50°C.

[0088] The product has the following properties: · Peak molar mass: Mp = 110000 g / mol · Number-average molar mass: Mn = 55000 g / mol · Weight-average molar mass: Mw = 160000 g / mol · Polydispersity: Ip = 2.9 · The mass composition determined by NMR is 45% PABu and 55% PMMA.

[0089] Example 2 (comparative): Repeat Example 1, but do not add mercaptan in step 3.

[0090] The method of the present invention makes it possible to improve the kinetics (Figure 1) and results in better stability of the resulting composition (Figures 2 and 3). The presence of mercaptan during step 3 is crucial for the stability of the resulting composition.

[0091] Example 3: Bulk synthesis method. A comparative composition of a triblock copolymer prepared by the bulk method was carried out.

[0092] Into a 1L reactor equipped with a double jacket, 320 g of butyl acrylate (i.e., 2.5 mol) and 6.8 g of polyalkoxyamine (i.e., 7.1 mmol) prepared in step 1 of Example 1 are introduced at room temperature. After degassing several times with nitrogen, the reaction medium is brought to 115 °C and this temperature is maintained for 5 hours by thermal regulation. Samples are taken throughout the reaction to determine the kinetics of the polymerization by gravimetry (measurement of dry extract) and to follow the change in molecular weight according to the conversion.

[0093] When 80% conversion is reached, the reaction medium is cooled to 60 °C and the residual butyl acrylate is removed by evaporation under reduced pressure.

[0094] Then, at 60 °C, 391 g (i.e., 3.7 mol) of methyl methacrylate and 78 g of toluene are added. Then, the reaction medium is heated at 95 °C for 2 hours (conversion = 50%). After returning to 60 °C and diluting with 78 g of toluene, the PMMA-PAbu-PMMA copolymer is taken out of the reactor and the residual monomers and solvent are removed by evaporation under reduced pressure.

[0095] The resulting copolymer has a peak molecular mass (Mp) of 100,000 g / mol.

[0096] Example 4: Evaluation of the yellowness index for a 50 / 50 mass mixture of PMMA and the composition of the present invention from Example 1 and the composition obtained according to Example 3. These mixtures are obtained by extrusion molding followed by injection of specimens at 240 °C. The yellowness index (YI) is measured with a Colorquest HunterLab (conditions: luminous flux: D65, observation angle: 10°, observation mode: transmission).

[0097] The results of the yellowness index in Table 1 show a much higher quality for the samples of the mixtures using the composition of the present invention. A low yellowness index is always desirable in optical applications. [Table 1] TIFF0007713131000010.tif32170

[0098] Example 5 / The applicant compared the rheology of the compositions obtained according to Examples 1 and 3 of the present invention by measuring the melt index (MFI, melt flow index).

[0099] The results are shown in Table 2. They demonstrate that the compositions have different properties. At a similar weight average molecular weight, the compositions of the present invention are more fluid and advantageous for processing. [Table 2] TIFF0007713131000011.tif63170

[0100] Example 6 Stability in mixing with polyoxymethylene (POM): · Mixtures of POM / block copolymer or the composition of the present invention:

[0101] Block copolymers are used to improve the impact properties of general-purpose polymers. Block copolymers have blocks with a low glass transition temperature (below 0 °C, such as butyl acrylate) and blocks with a high glass transition temperature (above 90 °C, like PMMA). They make it possible to improve the impact resistance of many materials such as polyoxymethylene. A few percent of the copolymer is added to the polymer to obtain a material with improved impact properties. However, block copolymers synthesized by the solvent route can decompose polyoxymethylene and lead to the formation of formaldehyde during the use of the material (mixture formed at temperature). The synthesis by the aqueous route according to the method of the present invention allows the obtained composition to limit the decomposition of POM during the mixing step and to obtain a material with improved properties.

[0102] Mixtures containing 100%, then 98% POM and 2% of the composition of Example 1 of the present invention and 2% of the copolymer of Example 3 were prepared at 200 °C. Formaldehyde formation was measured by UHPLC / UV (acetonitrile / H2O mobile phase, 50 / 50 isocratic mode). This method involves the aqueous extraction of formaldehyde from the compounded POM and derivatization with 2,4-dinitrophenylhydrazine (DNPH) to quantify the compound using a UV detector (Table 3). The addition of the composition of the present invention does not affect the stability of POM (no decomposition observed by the formation of formaldehyde during mixing at 200 °C); Table 3. [Table 3] TIFF0007713131000012.tif42170

Claims

1. A method for suspension polymerization of (meth)acrylic and / or styrenic monomers to obtain beads of a composition comprising at least one block copolymer, comprising the following two consecutive synthesis steps: Step 1: In a stirred reactor containing water and 0.5 to 4% by mass of a suspending agent constituting an aqueous phase, An organic phase consisting of at least one alkoxyamine and at least one acrylic and / or styrenic monomer having a molar ratio of nitroxide / monomer of 1 / 50 to 1 / 1000 and a mass ratio of aqueous phase / organic phase of 3 to 10 is introduced, and the alkoxyamine has the following formula: [Chemical Formula 10] (R Ｌ represents a monovalent group having a molar mass greater than 15.42 g / mol, and R ａ and R ｂ are optionally linked together to form a ring and represent the same or different alkyl groups having 1 to 40 carbon atoms, which may be substituted with hydroxyl, alkoxy or amino groups), having at least one nitroxide corresponding thereto, Polymerization of the monomer in the suspension at a temperature of 15°C to 140°C up to a minimum mass conversion rate of 80%, Step 2: - Introduction of at least one methacrylic monomer and / or styrenic monomer and at least one mercaptan into the previous polymerization suspension at a molar ratio of mercaptan / nitroxide of 2 / 1000 to 8 / 1000 and a mass ratio of monomer (acrylic and / or styrenic from Step 1) / (methacrylic monomer and / or styrenic monomer from Step 2) of 25 / 75 to 70 / 30, - Polymerization of the monomer with stirring at a temperature of 15°C to 140°C up to a minimum conversion rate of 95%, - Introduction of an initiator soluble in the aqueous phase in an amount of 0.1 to 2% by mass based on the mass of the total organic phase to complete the polymerization up to a minimum mass conversion rate of 99%, - Filtration, washing, and then drying of the beads, A method comprising.

2. The method according to claim 1, wherein the surfactant is added to the aqueous phase during Step 1 at a rate varying from 1 to 10000 ppm.

3. The method according to claim 1 or 2, wherein the mercaptan is named R-SH having an R as a linear or non-functionalized or not alkyl group having 3 to 12 carbons.

4. The method according to any one of claims 1 to 3, wherein the monomer in Step 1 is selected alone or in combination from butyl acrylate, 2-ethylhexyl acrylate, and styrene, and the monomer in Step 2 is selected alone or in combination from methyl methacrylate, methacrylic acid, and styrene.

5. The method according to any one of claims 1 to 4, wherein the nitroxide is N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide.

6. The method according to any one of claims 1 to 5, wherein the alkoxyamine is 2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2-methylpropionic acid.

7. The method according to any one of claims 1 to 5, wherein the alkoxyamine is an addition product of 2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2-methylpropionic acid and butanediol diacrylate.

8. The method according to any one of claims 1 to 7, wherein the beads have a polydispersity index of 2 to 4 and a weight average molecular weight of 10,000 to 200,000 g / mol.

9. Use of the beads obtained by the method according to any one of claims 1 to 8 as an additive for polymers in three-dimensional printing or for the production of objects by molding, injection, compression or extrusion.

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