Suspension polymerization of alkoxyamines with styrene and (meth)acrylic acid monomers

Abstract

This invention relates to a suspension polymerization method for polymerizing alkoxyamines with styrene and (meth)acrylic acid monomers, to beads and compositions thus obtained, and to uses of such beads and compositions.

Description

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

[0002] To improve some of the properties of materials, it is necessary to find ways to produce more efficient materials.

[0003] Block copolymers are difficult polymers to manufacture, but they have advantages due to their block structure (which allows for the creation and tuning of morphologies at the nanoscale). Their physical behaviors (such as mechanical and optical behavior) and chemical behaviors (such as their resistance to chemical reagents) are superior to those of homopolymers or random copolymers.

[0004] Some synthetic methods allow or deny the combination of these physical and chemical behaviors into the desired properties.

[0005] The chemical and synthetic methods used to manufacture them can be ionic polymerization, controlled radical polymerization, and polycondensation operated in bulk, solvent, emulsion, and suspension. Depending on the circumstances, the dispersibility of the resulting block copolymers can be close to 1. In the context of this invention, the applicant is interested in compositions of (meth)acrylic and / or styrene block copolymers prepared by controlled radical polymerization (nitroxide-mediated polymerization, NMP) of nitroxide radicals (nitrooxygens) including alkoxyamines, and more particularly block copolymer compositions having at least one soft block (i.e., having a Tg less than 0°C as measured by DSC) and at least one hard block (i.e., having a Tg greater than 20°C as measured by DSC) within the block copolymer.

[0006] In NMP, alkoxyamines are used, which balance free radicals by releasing nitroxide radicals at a specific temperature, allowing for controlled block polymerization. This technique is described, for example, by Nicolas J et al. in Progress in PolymerScience 38 (2013) 63–235. For alkoxyamine chemistry, the dispersibility of block copolymers can vary between 1.2 and 2, depending on the conversion rate at which polymerization is carried out.

[0007] To avoid excessive drift in the dispersion of the obtained block copolymer, it is sometimes necessary to limit the conversion rate. This results in the removal of unconverted monomers.

[0008] For example, to prepare a diblock copolymer, a monofunctional alkoxyamine is reacted in a reactor in a solvent in the presence of a first monomer or monomer group M1, or until a conversion of about 70% is achieved. The residual monomer M1 is then typically removed by evaporation. The obtained macromolecular alkoxyamine is then placed in the presence of a second monomer or monomer group M2 to form a second block, following the same conversion / removal process as M2. The PolyM1-PolyM2 diblock copolymer is then obtained.

[0009] This method allows for the production of products with the desired properties, but the conditions of the method penalize some of these properties (such as optical or thermal properties) and cannot establish a link between impurities or the exact properties of the block copolymers thus produced.

[0010] A second method, known as emulsion, has been tried, but scaling it up to industrial scale is complicated (product synthesis, harvesting).

[0011] When it comes to obtaining copolymer compositions, a third method, the so-called suspension method, appears to have advantages, as it allows for the maximization of certain properties, such as mechanical, thermal, or optical properties. Compositions obtained through this suspension method differ because a portion of the monomers is obtained as homopolymers or random copolymers rather than block copolymers.

[0012] Suspension polymerization involves polymerizing a reaction mixture within droplets dispersed in water. For this purpose, effective stirring and a "suspending" agent in the reactor are used, allowing the preparation of beads or spheres whose diameters can vary from a few micrometers to hundreds of micrometers, or even be adjusted.

[0013] Unlike bulk or solvent-based methods, the absence of a solvent and the presence of water in the suspension process allow for the production of materials with significantly higher optical quality. The use of these compositions is possible in applications seeking optical quality when products obtained from bulk or solvent polymerization cannot provide this possibility. Furthermore, in the context of this invention, the products obtained by this method have proven to be more thermally stable.

[0014] Unlike bulk or solvent methods, stopping the conversion to limit dispersive drift is either impossible or complex to implement in suspension methods.

[0015] During the synthesis of the first Poly M1 block, the conversion rate is maximized, even if it means that the dispersion of the obtained blocks is drifted.

[0016] In the second conversion step of the second monomer or monomer group, it is appropriate to select various chemical agents that allow monomer M2 to be efficiently converted into polymer blocks in order to minimize defects that may appear at the chain ends of the obtained copolymer.

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

[0018] This suspension method uses the structure 3-(((2-cyanoprop-2-yl)oxy)(cyclohexyl)amino)-2,2-dimethyl-3-phenylpropionitrile as an alkoxyamine.

[0019] It allows for controlled radical polymerization of methacrylates, but with respect to acrylates, a conversion rate of less than 50% is observed due to the side reactions that occur with acrylates (Simula A. et al., European Polymer Journal 110(2019)319-329). However, the introduction of acrylates into block copolymers is of interest because, unlike methacrylates, it allows the use of monomers that result in very low Tg in the blocks. Thus, using butyl acrylate or 2-ethylhexyl acrylate, Tgs well below -20°C have been observed. This allows for the acquisition of materials with good impact resistance.

[0020] In this invention, the applicant is interested in different alkoxyamine families that enable the controlled polymerization of acrylates and / or styrene-based monomers. In the context of this invention, a first block is prepared using acrylate and / or styrene-based monomers, and other blocks consist of blocks comprising (composed of) methacrylates and / or styrene-based entities.

[0021] During this second step (which is not a controlled process using the alkoxyamine family), the applicant seeks to allow for efficient conversion of methacrylates while minimizing the conditions of their so-called disproportionation reactions.

[0022] Therefore, if the first step follows the conventional method of converting the first block according to the controlled method, the second step, which is mainly carried out with methacrylate, is carried out in an uncontrolled manner because it is characteristic of the alkoxyamine family used in the context of this invention.

[0023] Surprisingly, the presence of thiols from this second step onwards did not hinder the polymerization process from the Poly M1 blocks; the synthesis of the block copolymer did indeed occur, and the random entity was co-synthesized. The conversion rate was faster compared to the product obtained in the absence of thiols. Figure 1 The product obtained in the second step in the presence of thiols has much higher thermal stability, as can be verified by thermogravimetric analysis.

[0024] In this invention, the applicant demonstrates that up to 90% or even 95% of the monomers can be converted during the synthesis of various blocks.

[0025] At the end of the second step, a small proportion of unconverted monomers is polymerized using a water-soluble initiator. Surfactants can be added from the first step. Therefore, the applicant was able to verify that the polymers generated from these low proportions of monomers aggregate on the surface of the produced beads, forming a shell that facilitates downstream processing such as separation and drying—a problem encountered when a water-soluble initiator is unavailable.

[0026] Another challenge arises when using bulk or solvent-based methods. The resulting copolymers have high viscosity, which complicates the conversion steps, for example, in extruders or injection molding machines. At equivalent molecular weights, the compositions of the present invention exhibit better flowability than products obtained by bulk methods.

[0027] The method of this invention thus yields compositions of block copolymers and polymers obtained by radical methods related to the presence of thiols. These compositions possess monomer sequences or copolymer hearts that differ from those obtained using other methods due to the different monomer reactivity rates in the suspension process (see, in particular, PJ Dowding, B. Vincent: Colloids and Surfaces A: Physicochem. Eng. Aspects 161 (2000) 263–264). Therefore, these compositions, structurally less well-defined than block copolymers obtained by bulk methods, are novel. However, they prove effective by exhibiting excellent optical properties and better thermal stability.

[0028] These novel copolymer compositions obtained using the methods of this invention enable their use in applications requiring optical quality, heat resistance, easy conversion conditions, or optimal mechanical properties. They can be used for 3D printing by sintering beads. Summary of the Invention:

[0029] This invention relates to a method for suspension polymerization of (meth)acrylic monomers and / or styrene monomers to obtain beads comprising a composition containing at least one block copolymer, the method comprising the following two successive synthetic steps:

[0030] Step 1:

[0031] In a stirred reactor containing water constituting the aqueous phase, 0.5 to 4% by mass of a suspending agent, and 0 to 10,000 ppm of a surfactant,

[0032] An organic phase is introduced, the organic phase comprising at least one alkoxyamine and at least one acrylic and / or styrene monomer, wherein the molar ratio of nitroxide radical to monomer is between 1 / 50 and 1 / 1000 and the mass ratio of aqueous phase to organic phase is between 3 and 10, wherein the alkoxyamine carries at least one nitroxide radical corresponding to the following formula:

[0033] [Chemical Structure 1]

[0034]

[0035] R a and R b This refers to the same or different alkyl groups having 1 to 40 carbon atoms, wherein the carbon atoms are optionally linked together to form a ring and optionally substituted with hydroxyl, alkoxy, or amino groups.

[0036] R L R represents a monovalent group with a molar mass greater than 15.42 g / mol. a and R b This refers to the same or different alkyl groups having 1 to 40 carbon atoms, wherein the carbon atoms are optionally linked together to form a ring and optionally substituted with hydroxyl, alkoxy, or amino groups.

[0037] R L This indicates a monovalent group with a molar mass greater than 15.42 g / mol.

[0038] The monomers in the suspension are polymerized at temperatures ranging from 15°C to 140°C until a minimum mass conversion rate of 80% is achieved.

[0039] Phase 2:

[0040] - At least one methacrylic acid monomer and / or styrene monomer and at least one thiol are introduced into a previously polymerized suspension with a thiol / nitrogen oxide molar ratio between 2 / 1000 and 8 / 1000 and a monomer (acrylic and / or styrene) / methacrylic acid and / or styrene monomer molar ratio between 25 / 75 and 70 / 30.

[0041] - Polymerize monomers at temperatures ranging from 15°C to 140°C with stirring until a minimum conversion rate of 95% is achieved.

[0042] - Introduce an initiator soluble in the aqueous phase at a ratio of 0.1% to 2% of the total organic phase mass to complete the polymerization up to a minimum mass conversion of 99%.

[0043] - Filter, wash, and then dry the beads. Detailed implementation method:

[0044] This invention relates to the suspension polymerization of monomers and alkoxyamines with nitroxide radicals, the general formula of which (1) is as follows:

[0045] [Chemical Structure 2]

[0046]

[0047] R a and R b R represents the same or different alkyl groups having 1 to 40 carbon atoms, said carbon atoms optionally linked together to form a ring and optionally substituted with hydroxyl, alkoxy or amino groups. L A monovalent group indicating a molar mass greater than 15.42 g / mol, preferably greater than 30 g / mol. Group R L It can have a molar mass, for example, between 40 and 450 g / mol. It is preferably a phosphorus group having the following general formula:

[0048] [Chemical Structure 3]

[0049]

[0050] X and Y can be the same or different, and can be selected from alkyl, cycloalkyl, alkoxy, aryloxy, aryl, aralkyloxy, perfluoroalkyl and aralkyl, and can contain 1 to 20 carbon atoms; X and / or Y can also be halogen atoms such as chlorine, bromine or fluorine atoms.

[0051] Advantageously, R L Phosphate groups of the following formula:

[0052] [Chemical Structure 4]

[0053]

[0054] Where R c and R d It is two identical or different alkyl groups, which are optionally linked to form a ring containing 1 to 40 optionally substituted or unsubstituted carbon atoms.

[0055] Group R L It may also contain at least one aromatic ring, such as phenyl or naphthyl, which is substituted by, for example, one or more alkyl groups containing 1 to 10 carbon atoms.

[0056] Nitrogen oxide radicals of Formula (1) are preferred because they allow for effective control over the radical polymerization of (meth)acrylic acid monomers, as taught in WO 03 / 062293. Therefore, alkoxyamines (2) of the following formula having a nitroxide radical of Formula (1) are preferred:

[0057] [Chemical Structure 5]

[0058]

[0059] in:

[0060] Z represents a multivalent group;

[0061] As an example of a nitroxide radical of formula (1) that can be carried by an alkoxyamine (2), the following can be mentioned:

[0062] -N-tert-butyl-1-phenyl-2-methylpropyl nitroxide radical,

[0063] -N-(2-hydroxymethylpropyl)-1-phenyl-2-methylpropyl nitroxide radical,

[0064] -N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide radical

[0065] -N-tert-butyl-1-bis(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl nitroxide radical,

[0066] -N-tert-butyl[(1-diethylphosphono)-2-methylpropyl] nitroxide radical,

[0067] -N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitroxide radical,

[0068] -N-(1-Phenylenyl)-[(1-Diethylphosphono)-1-Methylethyl]nitroxide radical,

[0069] -N-phenyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide radical

[0070] -N-phenyl-1-diethylphosphono-1-methylethyl nitroxide radical,

[0071] -N-(1-Phenyl-2-methylpropyl)-1-diethylphosphonomethylethyl nitroxide radical,

[0072] -or an alternative to underground nitrogen oxide free radicals

[0073] [Chemical Structure 6]

[0074]

[0075] - The nitroxide radicals of the following formula (3) are particularly preferred:

[0076] [Chemical Structure 7]

[0077]

[0078] This is an N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide radical.

[0079] Preferred alkoxyamines with these nitroxide radicals are derived from the following monoalkoxyamines (4):

[0080] [Chemical Structure 8]

[0081]

[0082] This is 2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2-methylpropionic acid.

[0083] The alkoxyamine (4) is monofunctional in terms of alkoxyamines and therefore in terms of nitroxide radicals; it results in the composition of the diblock copolymer in the context of the present invention constituting one of the preferred forms of the present invention.

[0084] The alkoxyamine (4) can be added to a di-, tri-, or polyfunctional monomer to result in an alkoxyamine that is polyfunctional in terms of alkoxyamines and therefore in terms of nitroxide radicals. Such polyfunctional alkoxyamines are described in EP1526138. These polyfunctional alkoxyamines (5) constitute a second preference of the invention, wherein dialkoxyamines (6) are preferred.

[0085] diacrylate diol C2-C 10 Alkyl groups yield the dialkoxyamines typical of this invention; these enable the preparation of triblock copolymer compositions. C2-C6 alkyl groups are preferred, and C2-C4 alkyl groups (ethylene glycol diacrylate, propylene glycol diacrylate, and butanediol diacrylate) are more preferred. The addition product of the alkoxyamine (4) and butanediol diacrylate is particularly preferred and results in the dialkoxyamine (7).

[0086] Other di- or polyfunctional compounds can be used to prepare di-, tri-, or polyalkoxyamines that are applicable in the context of this invention, whether they are acrylic or styrene types.

[0087] The monomers used to prepare the block copolymer compositions of the present invention are selected from the following list:

[0088] (Meth)acrylic acid type 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; alkyl acrylates, cycloalkyl acrylates or aryl acrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate, 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 methoxy polyethylene glycol acrylate, ethoxy polyethylene glycol acrylate, methoxy polypropylene glycol acrylate, methoxy-polyethylene glycol-polypropylene glycol acrylate or its derivatives. Mixtures; aminoalkyl acrylates, such as 2-(dimethylamino)ethyl acrylate (ADAME); fluorinated acrylates; isobornyl acrylate; 4-tert-butylcyclohexyl acrylate; silylated acrylates; phosphorus-containing acrylates, such as alkylene glycol phosphate acrylates; glycidyl acrylates; dicyclopentenyloxyethyl acrylates; methacrylic acid monomers, such as methacrylic acid or its salts; alkyl methacrylates, cycloalkyl methacrylates, alkenyl methacrylates or aryl methacrylates, such as methyl methacrylate (MAM), lauryl methacrylate, cyclohexyl methacrylate, allyl methacrylate, phenyl methacrylate or naphthyl methacrylate; hydroxyalkyl methacrylates Alkyl esters, such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate; alkyl ether methacrylates, such as 2-ethoxyethyl methacrylate; alkoxy or aryloxy polyalkylene glycol acrylates, such as methoxy polyethylene glycol methacrylate, ethoxy polyethylene glycol methacrylate, methoxy polypropylene glycol methacrylate, methoxy-polyethylene glycol-polypropylene glycol methacrylate, or mixtures thereof; aminoalkyl methacrylates, such as 2-(dimethylamino)ethyl methacrylate (MADAME); fluorinated methacrylates, such as 2,2,2-trifluoroethyl methacrylate; silylated methacrylates, such as 3-methacryloylpropyltrimethylsilane; phosphorus-containing methacrylates. Such as alkylene glycol phosphate methacrylates; hydroxyethyl imidazolium methacrylates; hydroxyethyl imidazolium methacrylates; 2-(2-oxo-1-imidazolyl)ethyl methacrylates; acrylonitrile; acrylamide or substituted acrylamide; 4-acryloylmorpholine; N-hydroxymethylacrylamide; methacrylamide or substituted methacrylamide; N-hydroxymethylmethacrylamide; methacrylamide propyltrimethylammonium chloride (MAPTAC); glycidyl methacrylates or dicyclopentenyloxyethyl methacrylates; itaconic acid, maleic acid or its salts, maleic anhydride; alkyl or alkoxy or aryloxy polyalkylene glycol maleates or hemimaleates; vinylpyridine; vinylpyridinone;(alkoxy-)poly(alkylene glycol) vinyl ethers or divinyl ether compounds, such as methoxy-poly(ethylene glycol) vinyl ethers, poly(ethylene glycol) divinyl ethers, are available alone or in mixtures of at least two of the aforementioned monomers.

[0089] Preferably, these are alkyl acrylates and alkyl methacrylates, particularly butyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate and isobornyl methacrylate, 4-tert-butylcyclohexyl acrylate, methyl methacrylate, acrylic acid and methacrylic acid, and even more preferably butyl acrylate, styrene, methacrylic acid and methyl methacrylate.

[0090] In the context of the method of the present invention, 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.

[0091] 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.

[0092] In step 1 of the method of the present invention, the molar ratio of nitroxide radicals to monomers is between 1 / 50 and 1 / 1000.

[0093] Regarding the thiols used in step 2 of the method of the present invention, these are any type of thiols named R-SH, wherein R is an alkyl group having 3 to 12 carbons, preferably 4 to 8 carbons, which is either straight-chain or unfunctionalized or not straight-chain or unfunctionalized. In particular, references may be made to mercaptoethanol, mercaptopropanol, mercaptobutanol, mercaptoacetic acid, mercaptopropionic acid, butyl mercaptothiol, octyl mercaptothiol, and n-dodecyl mercaptothiol, either alone or in combination. Butyl mercaptothiol or octyl mercaptothiol are preferred, either alone or in mixtures.

[0094] The suspending agents used in the context of this invention are typical suspending agents known to those skilled in the art. These may be copolymers of polyvinyl alcohol, polyvinylpyrrolidone, (meth)acrylic acid, or 2-acrylamido-2-methylpropanesulfonic acid, preferably polyvinyl alcohol or copolymers of 2-acrylamido-2-methylpropanesulfonic acid, and more preferably copolymers of 2-acrylamido-2-methylpropanesulfonic acid. Such a suspending agent is described in Example 1 of EP0683182.

[0095] The suspending agent is present in an amount between 0.5 and 4% by mass relative to the aqueous phase.

[0096] Optionally, inorganic particles may be added to improve the stability of the suspension.

[0097] The surfactant can be added to the aqueous phase in an amount between 0 and 10,000 ppm, preferably between 0 and 5,000 ppm, more preferably between 0 and 400 ppm relative to the aqueous phase. It can be any type of ionic or nonionic surfactant.

[0098] At the end of polymerization, when the suspension to be polymerized reaches a conversion rate of more than 95%, a water-soluble initiator is added, selected from, for example, persulfates, and especially potassium persulfate, in an amount that can be 0.1 to 2% by mass relative to the total organic phase, and preferably 0.1 to 1% by mass.

[0099] The water-soluble initiator allows the final small percentage of monomers to be converted into a shell attached to the beads obtained by the method of the present invention at the end of the synthesis.

[0100] According to one aspect of the subject matter of the invention, an additional amount of the monomer in step 2, between 1 and 10% by mass, preferably between 3 and 7% by mass, relative to the amount of monomer in steps 1 and 2, may be added together with the water-soluble initiator.

[0101] In step 1 of the method of the present invention, the mass ratio of aqueous phase to organic phase is between 3 and 10, and preferably between 4 and 8.

[0102] During step 2 of the method of the present invention, the molar ratio of monomer (acrylic and / or styrene) to methacrylic monomer is between 25 / 45 and 70 / 30, and preferably between 25 / 75 and 55 / 45.

[0103] During step 2, thiols are introduced at a thiol / nitrogen radical molar ratio between 0.2 and 0.8, and preferably between 0.4 and 0.6.

[0104] The stirring speed depends on the reactor used. For example, for a 20-liter reactor with an impeller-type stirring element, it is several hundred revolutions per minute. For a 5000-liter reactor, still with an impeller-type stirring element, it is between 100 and 250 revolutions per minute. Other types of stirring can be used within the context of this invention.

[0105] The polymerization temperature is between 15 and 150°C, preferably between 100 and 135°C, and more preferably between 125 and 135°C.

[0106] The composition obtained by the method of the present invention has a weight-average molecular weight between 5,000 and 300,000 g / mol, and preferably between 10,000 and 200,000 g / mol, wherein the dispersion index is between 2 and 4, and preferably between 2.5 and 3.3. According to one aspect of the invention, the composition is preferably a composition derived from a diblock copolymer and a random copolymer of monoalkoxyamines.

[0107] According to another aspect of the invention, the composition is preferably a combination of triblock copolymers and random copolymers derived from dialkoxyamines.

[0108] This invention relates to beads obtained using the method of the invention. They are in spherical form with an average weight diameter between 5 and 600 μm, preferably between 50 and 400 μm, and more preferably between 50 and 250 μm, which is measured by laser diffraction during the drying process using an instrument from company Malvern. The beads consist of a continuous shell of nanostructured material and a hard phase with a Tg > 20 °C, the nanostructured material consisting of a block matrix and a dispersed phase of another block, the shell having a thickness of 30 to 150 nm.

[0109] Beads having a continuous shell are a preferred aspect of beads obtained using the method of the present invention.

[0110] The present invention also relates to compositions obtained using the methods of the present invention, as they differ from compositions obtained by other methods (solvents, bulk, emulsions) in both their analytical properties and their characteristics.

[0111] The present invention also relates to the use of the compositions of the present invention or the beads of the present invention for manufacturing objects by molding, injection, compression or extrusion.

[0112] The present invention also relates to the use of beads obtained by the method of the present invention in forming objects in the field of three-dimensional printing known as laser sintering.

[0113] Laser beam powder sintering technology is used to manufacture three-dimensional objects, such as prototypes or models, but it is also used to manufacture functional components, particularly in the fields of motor vehicles, marine, aviation, aerospace, medical (prosthetics, hearing systems, cell tissues, etc.), textiles, clothing, fashion, decoration, electronic housings, telephones, home automation, computing, or lighting.

[0114] In laser sintering, thin layers of powder are deposited onto a horizontal plate, which is fixed in a chamber heated to a specific temperature. Depending on the geometry corresponding to the object, for example using a computer that stores the object's shape in memory and reproduces it in slices, a laser contributes the energy required to sinter the powder particles at different points in the powder layer. The horizontal plate is then lowered by a value corresponding to the thickness of the powder layer (e.g., between 0.05 and 2 mm, and typically about 0.1 mm), and a new powder layer is deposited. The laser then contributes the energy required to sinter the powder particles according to the geometry corresponding to this new slice of the object, and so on. This process is repeated until the entire object is fabricated. Inside the chamber, an object surrounded by unsintered powder is obtained. Thus, the unsintered portions remain in a powder state. After complete cooling, the object is separated from the powder, which can be reused in another operation. Attached image description:

[0115] [ Figure 1 ]:

[0116] Figure 1 This refers to the conversion rate of methyl methacrylate during step 2 of the method of the present invention. Curves with hollow circles represent the conversion rate in the presence of thiols, such as in Example 1 of the present invention, while curves with filled circles represent the conversion rate during the same step in the absence of thiols, such as in Comparative Example 2.

[0117] [ Figure 2 ]:

[0118] Figure 2 This is the degradation curve of the product obtained in the presence of thiols as a function of temperature (TGA). The temperature at the degradation peak is 314℃.

[0119] [ Figure 3 ]:

[0120] Figure 3 The degradation curves of the product obtained in the absence of thiols are as a function of temperature (TGA), showing that the degradation curves are more pronounced than those in the presence of thiols. It can be noted that more degradation occurs, and this degradation happens at lower temperatures (282°C, 290°C, 300°C).

[0121] [ Figure 4 ]:

[0122] Figure 4This is an atomic force microscopy (AFM) image of the cross-section of beads obtained using a water-soluble initiator (potassium persulfate) according to the method of the present invention. The beads have a transparent crown (PMMA) on the outside. The interior of the beads consists of a transparent dispersed phase (PMMA) and a dark continuous phase (polybutyl acrylate). Such beads result in a manageable, non-sticky powder.

[0123] [ Figure 5 ]:

[0124] Figure 5 This is an atomic force microscopy (AFM) image of the cross-section of beads obtained according to the method of the present invention without a water-soluble initiator. There are poorly defined diffusion zones on the outer side of the beads. The interior of the beads consists of a transparent dispersed phase (PMMA) and a dark continuous phase (polybutyl acrylate). Such beads result in a difficult-to-manage sticky powder.

[0125] [ Figure 6 ]:

[0126] Figure 6 The normalized curve of the LAC chromatogram corresponding to the PAbu block. This polybutyl acrylate corresponds to the block prepared at the end of the first step of the method of the present invention. Therefore, it can be reactivated for use in the second step of the method of the present invention. It is obtained in step 2 of Example 1.

[0127] [ Figure 7 ]:

[0128] Figure 7 Normalized curves of the LAC chromatograms corresponding to the compositions of the present invention. Individual PAbu almost disappeared (elution at 16 minutes), while a peak at 35 minutes, attributable to the triblock copolymer, appeared. A peak appeared at 32 minutes, attributable to the PMMA-rich statistical composition, originating from the interior and shell of the beads.

[0129] [ Figure 8 ]:

[0130] Figure 8 The normalized curve corresponding to the LAC chromatogram of the composition obtained by the bulk method as prepared in Example 3.

[0131] It includes a non-negligible proportion of PAbu that has not been converted to triblock. The composition is triblock-rich (peaking at 34 minutes). Traces of the PMMA-rich composition are visible, peaking at 38 minutes.

[0132] [ Figure 9 ]:

[0133] Figure 9Normalized curves corresponding to the LAC chromatogram of the PMMA composition. Peaks visible at the start of elution (10 minutes prior) are from impurities, which are attributed to trace amounts of solvents and other additives present in the commercial grade used for analysis and should not be taken into account.

[0134] Measurement method description:

[0135] - Atomic force microscopy. This microscope allows visualization of both soft and hard regions of a sample (in this case, a cross-section of beads encased in epoxy resin). Observe the sample in "tapping" mode.

[0136] Liquid phase adsorption chromatography (LAC) is a chromatographic method.

[0137] Liquid phase adsorption chromatography is a technique for separating complex polymer mixtures in which each component can be eluted based on its chemical composition, and therefore regardless of its molar mass.

[0138] The sample was injected into the WATERS ALLIANCE 2695 HPLC system.

[0139] The eluent was a gradient (hexane / THF) acidified with 5% acetic acid and stabilized with BHT.

[0140] The polar column used was a SunFire Prep Silica 5μm 4.6*250mm column (CAP-Sunfre-02).

[0141] The flow rate was 1 ml / min, and the injected sample volume was 30 μl.

[0142] The detectors used were the Agilent ELSD (evaporative light scattering detector) 380 and the Waters 2487 Dual UV 254nm.

[0143] For liquid phase adsorption chromatography, polymer samples were prepared in THF at a concentration of 2 g / L. PMMA and PABu samples were used as standards to ensure their identification at the end of the PMMA-PABu / PMMA triblock analysis. A 30 μL volume was injected.

[0144] Yellowness index: Measured according to YIE313 standard (NF ISO 7724-3 1988). Yellowness index (YI) was measured on ColorquestHunterLab (conditions: light source: D65, viewing angle: 10°, viewing mode: transmission).

[0145] Molecular weight. These are measured by the SEC using polystyrene standards.

[0146] Example:

[0147] Example 1 (Invention): Synthesis of the composition according to the method of the invention:

[0148] The starting alkoxyamine used was N-(2-methylpropyl)-N-(1-dimethylphosphono-2,2-dimethylpropyl)-O-(2-carboxypropyl-2-yl)hydroxylamine, whose expanded formula is as follows:

[0149] [Chemical Structure 9]

[0150]

[0151] Its name MA is obtained from Arkema.

[0152] Perform the following steps:

[0153] 1: Use Blocbuilder It is added to butanediol diacrylate to form a dialkoxyamine called a diamine (7), which is the starting point of the triblock copolymer.

[0154] 2: Dialkoxyamine polybutyl acrylate (PABu) is synthesized by reacting butyl acrylate with dialkoxyamine.

[0155] 3: Synthesize PMMA-PAbu-PMMA triblock copolymer compositions in suspension.

[0156] Synthesis of 1 / diamine:

[0157] Diamine by Blocbuilder Arkema and butanediol diacrylate (BDMA) were prepared in ethanol. A 1L reactor was inert with nitrogen. 114g of ethanol and 60g of Blocbuilder were added. 15.7 g of BDMA was introduced into the reactor. The reactor was stirred at 100 rpm and heated to 80 °C (1 bar) for 4 hours. The solids content was 35%. The temperature was then lowered to 25 °C. After ethanol evaporation, the diamine was collected and could be used as is.

[0158] 2 / Synthesis of poly(butyl acrylate) blocks, step 1 of the method of the present invention:

[0159] Use a 5L reactor.

[0160] The aqueous phase was prepared directly in the reactor and stirred at 500 rpm for 30 minutes.

[0161] Aqueous phase:

[0162] - Softened water: 1800g

[0163] -Suspension agent: Copolymer of 2-acrylamido-2-methylpropanesulfonic acid: 15.3g (305.8g for a 5% solution)

[0164] - Surfactant: Use polyethoxylated C12-C14 alcohol (50 ethoxylation units), for example, available from Cognis. LS500: 0.5g

[0165] Prepare the organic phase in another container:

[0166] -Diamine: 16.1g

[0167] -Butyl acrylate: 350g

[0168] The organic phase is added after alternating vacuum and nitrogen circulation in the reactor. The suspension is then heated by the following cycle:

[0169] Initial temperature of segment 1: 20

[0170] Final temperature: 130

[0171] Time: 90

[0172] Initial temperature of segment 2: 130

[0173] Final temperature: 130

[0174] Time: 50

[0175] Initial temperature of segment 3: 130

[0176] Final temperature: 20

[0177] Time: 45

[0178] 3 / Synthesis of the polymethyl methacrylate-poly(butyl acrylate)-polymethyl methacrylate copolymer composition, step 2 of the method of the present invention:

[0179] The organic phase is prepared from methyl methacrylate and thiols.

[0180] -Methyl methacrylate: 397.5g

[0181] - Octylthiol and butylthiol (50 / 50): 1.6g

[0182] The organic phase is introduced into the reactor by reducing the pressure.

[0183] The mixture is heated according to the following cycle:

[0184] Initial temperature: 20°C

[0185] Final temperature: 130°C

[0186] Time: 90 minutes

[0187] Initial temperature of segment 1: 130°C

[0188] Final temperature: 130°C

[0189] Time: 90 minutes

[0190] Initial temperature of segment 2: 130°C

[0191] Final temperature: 20°C

[0192] Time: 60 minutes

[0193] 4 / Synthesis of the shell:

[0194] The shell is formed according to the following formula:

[0195] - Softened water: 92g

[0196] - Potassium persulfate: 0.73g

[0197] The polymerization reaction was carried out at 85°C for 1 hour and 30 minutes.

[0198] The suspension was then collected. The beads were filtered and washed twice with water, and then dried in an oven at 50°C.

[0199] This product has the following properties:

[0200] Peak molar mass: Mp = 110,000 g / mol

[0201] - Number-average molar mass: Mn = 55,000 g / mol

[0202] - Average molar mass: Mw = 160,000 g / mol

[0203] - Polydispersity: Ip = 2.9

[0204] -The mass composition determined by NMR is 45% PABu and 55% PMMA.

[0205] Example 2 (Comparative):

[0206] Repeat Example 1, but do not add thiols in step 3.

[0207] The method of the present invention enables the improvement of dynamics. Figure 1 This leads to better stability of the resulting composition. Figure 2 and 3 The presence of thiols during step 3 is crucial to the stability of the resulting composition.

[0208] Example 3: Ontology synthesis method.

[0209] Comparative compositions of triblock copolymers prepared by bulk method were developed.

[0210] In a 1L reactor equipped with a double jacket, 320 g (i.e., 2.5 mol) of butyl acrylate and 6.8 g (i.e., 7.1 mmol) of the polyalkoxyamine prepared in step 1 of Example 1 were introduced at room temperature. After several degassing processes with nitrogen, the reaction medium was brought to 115°C and maintained at this temperature for 5 hours by thermal conditioning. Samples were taken throughout the reaction to determine polymerization kinetics by gravimetric analysis (measuring the dry extract) and to track the evolution of molecular weight according to conversion.

[0211] When the conversion rate reaches 80%, the reaction medium is cooled to 60°C, and the residual butyl acrylate is removed by evaporation under vacuum.

[0212] At 60°C, 391 g (3.7 mol) of methyl methacrylate and 78 g of toluene were added. The reaction medium was then 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 was removed from the reactor, and residual monomers and solvents were removed by evaporation under vacuum.

[0213] The obtained copolymer has a peak molecular weight (Mp) of 100,000 g / mol.

[0214] Example 4: Evaluation of the yellow index of 50 / 50 mixtures by weight of PMMA with the composition of the present invention from Example 1 and the composition obtained according to Example 3. These mixtures were obtained by extrusion and then injection of samples at 240°C. The yellow index (YI) was measured on a Colorquest HunterLab (conditions: light source: D65, viewing angle: 10°, viewing mode: transmission).

[0215] The yellow index results in Table 1 show that the mixture samples using the compositions of the present invention are of much higher quality. A low yellow index is always required in optical applications.

[0216] [Table 1]

[0217]

[0218]

[0219] Example 5 / The applicant compared the rheological properties of the compositions obtained according to Example 1 and Example 3 according to the present invention by measuring the melt flow index (MFI).

[0220] The results are shown in Table 2. They demonstrated that the compositions exhibit different characteristics. At similar weight-average molecular weights, the compositions of the present invention exhibit greater flowability, which provides processing advantages.

[0221] [Table 2]

[0222]

[0223] Example 6

[0224] Stability when mixed with polyoxymethylene (POM):

[0225] - A mixture of POM / block copolymers or the compositions of the present invention:

[0226] Block copolymers are used to improve the impact properties of commercial polymers. Block copolymers have blocks with low glass transition temperatures (<0°C, e.g., butyl acrylate) and blocks with high glass transition temperatures (>90°C, e.g., PMMA). They allow for improved impact resistance in many materials, such as polyoxymethylene (POM). Adding a few percentages of the copolymer to the polymer yields a material with improved impact properties. However, block copolymers synthesized via solvent routes can degrade POM and result in the formation of formaldehyde (a mixture formed at temperature) during material use. The method according to the invention, synthesized via an aqueous route, allows the resulting composition to limit POM degradation during the mixing step and yields a material with improved properties.

[0227] A mixture containing 100% POM was prepared at 200°C, followed by a mixture containing 98% POM, 2% of the composition of Example 1 of the present invention, and 2% of the copolymer of Example 3. Formaldehyde formation was measured by UHPLC / UV (acetonitrile / H2O mobile phase, 50 / 50 isocratic mode). The method involved aqueous extraction of formaldehyde from the formulated POM and derivatization with 2,4-dinitrophenylhydrazine (DNPH) for quantification of the compound using a UV detector (Table 3). The addition of the composition of the present invention did not affect the stability of POM (no degradation was observed during mixing at 200°C via formaldehyde formation); Table 3.

[0228] [Table 3]

[0229] Table 3 Formaldehyde formation (mg / g) POM 0.02 POM + 2% of the triblock from Example 3 13.5 The composition of Example 1 of the present invention with POM + 2% 0.05

Claims

1. A method for suspension polymerization of (meth)acrylic and / or styrene monomers to obtain beads comprising a composition containing at least one block copolymer, said method comprising the following two successive synthetic steps: Step 1: In a stirred reactor containing water constituting the aqueous phase and 0.5 to 4% by mass of a suspending agent, An organic phase is introduced, the organic phase comprising at least one alkoxyamine and at least one acrylic and / or styrene monomer, wherein the molar ratio of nitroxide radical to monomer is between 1 / 50 and 1 / 1000 and the mass ratio of aqueous phase to organic phase is between 3 and 10, wherein the alkoxyamine carries at least one nitroxide radical corresponding to the following formula: [Chemical Structure 10] R L This indicates a monovalent group with a molar mass greater than 15.42 g / mol, and R a and R b This refers to the same or different alkyl groups having 1 to 40 carbon atoms, wherein the carbon atoms are optionally linked together to form a ring and optionally substituted with hydroxyl, alkoxy, or amino groups. The monomers in the suspension are polymerized at temperatures ranging from 15°C to 140°C until a minimum mass conversion rate of 80% is achieved. Step 2: - At least one methacrylic acid and / or styrene monomer and at least one thiol are introduced into the previously polymerized suspension at a thiol / nitroxide radical molar ratio between 2 / 1000 and 8 / 1000 and a monomer (acrylic and / or styrene monomer from step 1) / (methacrylic acid and / or styrene monomer from step 2) mass ratio between 25 / 75 and 70 / 30. - Polymerize monomers at temperatures ranging from 15°C to 140°C with stirring until a minimum conversion rate of 95% is achieved. - An initiator soluble in the aqueous phase is introduced at a ratio of 0.1% to 2% of the total organic phase mass to complete the polymerization up to a minimum mass conversion of 99%. - Filter, wash, and then dry the beads.

2. The method of claim 1, wherein the surfactant is added to the aqueous phase at a ratio of 1 to 10,000 ppm during step 1.

3. The method according to claim 1 or 2, wherein the thiol is named R-SH, wherein R is an alkyl group having 3 to 12 carbons, and the alkyl group is straight-chain or non-functionalized.

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

5. The method according to claim 1 or 2, wherein the monomer in step 1 is selected from butyl acrylate, 2-ethylhexyl acrylate and styrene alone or in combination, and the monomer in step 2 is selected from methyl methacrylate, methacrylic acid and styrene alone or in combination.

6. The method according to claim 1 or 2, wherein the nitroxide radical is an N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide radical.

7. The method according to claim 1 or 2, wherein the alkoxyamine is 2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2-methylpropionic acid.

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

9. The composition obtained by the method according to claim 1.

10. The composition according to claim 9, wherein the weight-average molecular weight is between 10,000 and 200,000 g / mol, and the dispersion index is between 2 and 4.

11. Beads obtained using the method according to any one of claims 1 to 8.

12. The beads of claim 11 as an additive to a polymer in 3D printing, or used on their own for manufacturing objects by molding, injection, compression or extrusion.

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