Block copolymers

0001The present invention relates to block copolymers (block copolymers) and more specifically to thermoplastic elastomer block copolymers.

0002Thermoplastic elastomers are known. These polymers have interesting mechanical properties (elastomers), associated with interesting handling and forming properties (thermoplastics). While conventional elastomers usually need a chemical crosslinking step, usually non-reversible, before or after being formed or applied to a support, the thermoplastic elastomers are crosslinked according to a physical phenomenon which is reversible by heating. This property makes it possible to obtain elastomeric compounds without a chemical crosslinking step which may be difficult to carry out on certain supports, or which would require complex formations (bicomponent or multicomponent formulations, or formulations comprising an active catalyst only under specific conditions such as drought ). Thermoplastic elastomers can be formed (by extrusion, injection, etc.) or applied to a support in a molten form. They are used for a variety of purposes, including soft-touch plastics for consumer goods or the interior of automobiles, structural or mechanical items, adhesives. They can also be used as additives in thermoplastics or in compositions used in the building industry to modify the mechanical properties of said thermoplastics or compositions.

0003Triblock copolymers comprising two rigid lateral styrene blocks and a flexible central block comprising units derived from diene monomers have been known and used for many years. By way of example, there may be mentioned block copolymers of styrene / butadiene / styrene (SBS), block copolymers of styrene / (ethylene butadiene) / styrene (SEBS) and hydrogenated. The styrene blocks are rigid blocks forming a rigid phase dispersed in a flexible phase of the central block (microphase separation). Without wishing to be linked to a particular theory, and by simplifying, it is believed that the dispersion of the rigid phase brings cohesion between the polymer chains and the other phase having elastomeric properties. This phenomenon can be called crosslinking according to a physical phenomenon. Therefore, it is believed that the separation of microphase from the blocks is a key factor. When heated, the rigid phase melts and the copolymers can be handled in a liquid form. Explanations regarding microphase separation of block copolymers are given in<nplcit id="ncit0001" npl-type="s"><text>Frank S. Bates and Glenn H. Fredrickson, Physics Today, publication February 1999; pages 32-38</text></nplcit>.

0004The abovementioned triblock copolymers have certain drawbacks. First, the central block sometimes turns yellow with age. Secondly, for certain uses, for example as adhesives or uses in which compatibility with other compounds is necessary, other functions must be added such as anhydride, carboxylic acid, ester and epoxide functions by copolymerizing the additional comonomers . To avoid yellowing and to meet certain needs for certain uses, blocks derived from esters of acrylic acid or methacrylic acid could constitute a solution.

0005In addition, the abovementioned triblock copolymers are usually prepared by an anionic polymerization process with optionally a hydrogenation step. Anionic polymerization processes are usually considered expensive compared to free radical polymerization processes. Therefore, there is a need for block copolymers which can be prepared by polymerization of free radicals and allow the phase separation of the blocks as explained above or more simply, which have elastomeric properties. On the other hand, obtaining block copolymer polymers having a high and controlled molecular weight is easier with an anionic polymerization process than with a free radical polymerization process: it can be difficult to obtain block copolymers with weight high molecular weight with a controlled structure and with molecular weights controlled by a free radical polymerization process. Currently, no solution has been found to the problem of proposing a block copolymer comprising a flexible block derived mainly from esters of acrylic acid or methacrylic acid, at moderate costs. Furthermore, it is known that the higher the molecular weight of the blocks, the easier the phase separation.

0006The Applicant has found new block copolymers which solve some of the aforementioned needs or problems. These block copolymers comprise a flexible block comprising esters of acrylic acid or of methacrylic acid which prevents delayed yellowing and leads to block copolymers having advantageous adhesion and compatibilization properties. The block copolymer discovered by the Applicant can be prepared by a free radical polymerization process. From there, the invention also relates to a process for manufacturing the block copolymer.

0007The invention relates to a block copolymer (block copolymer), which is a diblock copolymer (block A) - (block B), a triblock copolymer (block A) - (block B) - (block A) or triblock (block A) - (block B) - (block C),<ul id="ul0001" list-style="dash" compact="compact"><li>block A being a rigid block, comprising at least 55% of repeating units derived from a rigid monomer chosen from the group consisting of styrene, isobornyl acrylate and isobornyl methacrylate,</li><li>block B being a flexible block comprising at least 55% of recurring units derived from a flexible monomer chosen from the group consisting of acrylic acid esters, methacrylic acid esters and mixtures of these esters,</li><li>block C being a rigid block, comprising repeating units derived from a rigid monomer chosen from the group consisting of styrene, isobornyl acrylate and isobornyl methacrylate,</li></ul>in which :<ul id="ul0002" list-style="dash" compact="compact"><li>block A comprises more than 10% by weight of units derived from a block A segregation monomer chosen from the group consisting of acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, 2-vinylpyridine and 4-vinylpyridine or</li><li>block B comprises at least 6% by weight of units derived from a block B segregation monomer chosen from the group consisting of acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile and vinylpyrrolidones and</li><li>the block copolymer has a molecular weight of more than 10,000 g / mol.</li></ul>

0008The block copolymers according to the invention can be in solid or dried form. They can be dissolved in an organic solvent. They can be in the form of a latex dispersion in an aqueous medium. These dispersions or solutions are usually intended to be applied to a surface, and then dried, to make a film or a coating. In a dried form, the block copolymer according to the invention has elastomeric properties. It also has thermoplastic properties.

0009According to a second aspect, the invention relates to a method for manufacturing the above-mentioned block copolymer, said method being a method of polymerization of free radicals, living block (and controlled), preferably involving the use of a transfer agent comprising a group of formulas - SC (S) -X-, -SC (S) -S- or -SP (S) -X- or -SP (S) -S- in which X is an atom different from sulfur.

0010According to a third aspect, the invention relates to the use of the block copolymer defined above as an adhesive, its use in an adhesive composition and adhesive compositions or adhesive products comprising it.

0011The block copolymer comprises at least two different blocks: block A and block B. It is chosen from the group consisting of diblock copolymers (block A) - (block B), triblock copolymers (block A) - (block B) - (block A) or triblocks (block A) - (block B) - (block C). The block copolymer is a linear block copolymer. By linear, it is meant that the arrangement of the blocks is linear. However, a block may include patterns comprising a side chain macromolecular group.

0012A block is usually defined by the recurring patterns it includes. A block can be defined by naming a polymer or by naming the monomers from which it is derived. In the present description, a “unit derived from a monomer” is understood to be a unit which can be obtained directly from said monomer by polymerization. Thus, a “unit derived from an ester of acrylic acid or methacrylic acid” does not include a unit of formula -CH-CH (COOH) - or -CH-C (CH₃) (COOH) - obtained for example by polymerization of an ester of acrylic acid or methacrylic acid and then by hydrolysis. However, a “unit derived from acrylic acid or methacrylic acid” includes, for example, a unit obtained by polymerization of a monomer and reaction to obtain units of formula -CH-CH (COOH) - or -CH-C ( CH₃) (COOH) -.

0013At least one of the blocks, block A or block B, is a copolymer, comprising at least two different repeating units derived from at least two different monomers. Block A, block B and block C are separate polymers, derived from different monomers, but they may include some common recurring units. Preferably, block A and block B do not comprise more than 50% of a common recurring unit (derived from the same monomer). Block C and block B preferably do not comprise more than 50% of a common recurring unit (derived from the same monomer). Block A and Block C can comprise up to 94% by weight of a common recurring motif.

0014It should also be noted that in the triblock copolymers (block A) - (block B) - (block A), the two blocks A can have an identical or different molecular weight. They may include units derived from an identical or different block A segregation monomer. They can comprise an identical or different amount (more than 10% by weight) of units derived from said segregation monomer. Block C is a block which does not comprise units derived from a block A segregation monomer or which does not comprise more than 6% by weight of units derived from a block A segregation monomer

0015Block A and block C are called rigid blocks. Block B is called a flexible block. In the present description, the words “rigid” and “flexible” designate the property that a block would have without the other block (s) which is the property of a polymer composed of the same recurring units as said block preferably having the same molecular weight. A polymer or rigid block usually has a glass transition temperature of more than 50 ° C. and preferably greater than 100 ° C. A flexible polymer or block usually has a glass transition temperature of less than 20 ° C, more preferably less than 0 ° C.

0016In the present description, the expression “rigid monomers” designates monomers whose derivative polymer is rigid. In the present description, the expression “flexible monomers” designates monomers whose derivative polymer is flexible.

0017In the present description, the molecular weight of a block copolymer denotes the weighted average molecular weight of the block copolymer. The weighted average molecular weight of the polymer can be measured by gel permeation chromatography (GPC). In the present description, the molecular weight of a block designates the molecular weight calculated from the amounts of monomers, polymers (for example other block), initiators and / or transfer agents used to manufacture the block. Those skilled in the art know how to calculate these molecular weights. The weight ratios between the blocks denote the ratios between the quantities of compounds used to manufacture said blocks, taking into account extensive polymerization.

0018Typically, the molecular weight M of a block is calculated according to the following formula: <maths id="math0001" num=""><math display="block"><mi>M</mi><mo>=</mo><mstyle displaystyle="false"><mstyle displaystyle="true"><munder><mo>∑</mo><mi>i</mi></munder></mstyle><msub><mi>M</mi><mi>i</mi></msub><mo>*</mo><mfrac><msub><mi>not</mi><mi>i</mi></msub><msub><mi>not</mi><mi>precursor</mi></msub></mfrac></mstyle><mo>,</mo></math><img file="EP1516002B1_D0001.tif" /></maths>in which M_i is the molecular weight of a monomer i, ni is the number of moles of a monomer i and n_precursor is the number of moles of a compound to which the macromolecular chain of the block will be linked. Said compound can be a transfer agent or a transfer group or a preceding block. If it is a previous block, the number of moles can be considered as the number of moles of a compound to which the macromolecular chain of said previous block has been linked, for example a transfer agent or a transfer group. It can also be obtained by calculation from a measured value of the molecular weight of said previous block. If the two blocks are simultaneously cultivated from a previous block, at the two ends, the molecular weight calculated according to the preceding formula must be divided by two.

0019According to a first embodiment:<ul id="ul0003" list-style="dash" compact="compact"><li>block A comprises at least 55% by weight of units derived from the rigid monomers detailed below,</li><li>block A comprises more than 10%, preferably at least 15% by weight of units derived from the segregation monomers of block A detailed below,</li><li>block B comprises at least 55% by weight of units derived from the flexible monomers detailed below,</li><li>block B does not include any unit derived from the block B segregation monomers detailed below or does not include more than 6% of any unit derived from the block B segregation monomers detailed below.</li></ul>

0020According to a second embodiment:<ul id="ul0004" list-style="dash" compact="compact"><li>block A comprises at least 55% by weight of units derived from the rigid monomers detailed below,</li><li>block A does not include any unit derived from the block A segregation monomers detailed below or does not include more than 6% of any unit derived from the block A segregation monomers detailed below.</li><li>block B comprises at least 55% by weight of units derived from the flexible monomers detailed below,</li><li>block B comprises at least 6%, preferably at least 10%, even more preferably at least 15% by weight of units derived from the segregation monomers of block B detailed below.</li></ul>

0021According to a third embodiment:<ul id="ul0005" list-style="dash" compact="compact"><li>block A comprises at least 55% by weight of units derived from the rigid monomers detailed below,</li><li>block A comprises more than 10%, preferably at least 15% by weight of units derived from the segregation monomers of block A detailed below,</li><li>block B comprises at least 55% by weight of units derived from the flexible monomers detailed below,</li><li>block B comprises at least 6%, preferably at least 10%, even more preferably at least 15% by weight of units derived from the segregation monomers of block B detailed below.</li><li>the block B segregation monomers are different from the block A segregation monomers</li></ul>

0022The block copolymers according to the three preceding embodiments can also comprise a block C, comprising units derived from the rigid monomers detailed below. Block C does not include any unit derived from the block A segregation monomers detailed below or does not include more than 6% of any unit derived from the block A segregation monomers detailed below. Preferably, block C comprises at least 80% by weight, preferably at least 94% by weight of units derived from rigid monomers.

0023Block A and block B may include certain units which are different from the units derived from rigid monomers and from segregation monomers (block A or block B segregation monomers) detailed below. If this is not the case, the quantity by weight of units derived from the rigid, respectively flexible, monomers is equal to 100% minus the quantity of the block A segregation monomers, respectively block B.

0024The aforementioned rigid monomers are chosen from the group consisting of styrene, isobornyl acrylate and isobornyl methacrylate.

0025The abovementioned block A segregation monomers are chosen from the group consisting of acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, 2-vinylpyridine and 4-vinylpyridine.

0026The aforementioned flexible monomers are chosen from the group consisting of acrylic acid esters and methacrylic acid esters, such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, ethyl acrylate, methacrylate ethyl, butyl acrylate and butyl methacrylate. Mixtures of these monomers can be used to obtain a block comprising units derived therefrom, the block therefore being a random copolymer. Using mixtures makes it possible to control the glass transition temperature of the flexible block. For example, mixtures of hexyl acrylate or hexyl methacrylate and butyl acrylate or butyl methacrylate can be used. These monomers, their derived units and the block or polymer comprising said units are usually considered to be hydrophobic.

0027The abovementioned block B segregation monomers are chosen from the group consisting of acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile and vinylpyrrolidones.

0028Without wishing to be bound to a particular theory, it is believed that the monomers designated as segregation monomers reinforce the incompatibility of one block with another and therefore allow phase segregation, a rigid phase being dispersed is a continuous flexible phase. The block A segregation monomers would strengthen the incompatibility of block A with respect to block B. The block segregation monomers would reinforce the incompatibility of block B with respect to block A. Certain monomers could as well reinforce the incompatibility of block A with respect to block B as the incompatibility of block B with respect to block A. Therefore, certain monomers are considered as monomers for segregation of block A and / or monomers for segregation of block B. However, it is preferred that the two blocks A and B comprise more than 6% by weight of segregation monomers, that the segregation monomer of block A is different from the segregation monomer of block B or that the amount (% by weight) of block A segregation monomers in block A is different from the quantity (% by weight) of block B segregation monomers in block B.

0029The block copolymer of the invention has a molecular weight of at least 10,000 g / mol, preferably at least 25,000 g / mol and even more preferably at least 50,000 g / mol. The molecular weight is usually less than 200,000 g / mol. It can be less than 150,000 g / mol and even less than 100,000 g / mol. Obtaining the properties of a thermoplastic elastomer having a rigid phase dispersed in a continuous elastomer phase, at these low molecular weights, is one of the benefits and advantages of the invention.

0030Preferably, block A has a molecular weight between 1,000 and 30,000 and more preferably between 3,000 and 15,000 g / mol. Preferably, block B has a molecular weight between 6,000 and 12,000 and more preferably between 6,000 and 97,000 g / mol. More preferably, block B has a molecular weight of between 20,000 and 80,000 g / mol.

0031The ratio between the molecular weight of the block (s) A and the molecular weight of the block B is preferably between 0.45 and 0.5, more preferably between 0.05 and 0.3.

0032Preferably, block A comes mainly from styrene and block B comes mainly from ethyl acrylate or butyl acrylate, for example as follows:<ul id="ul0006" list-style="dash" compact="compact"><li>block A comprises from 75% to 90% by weight of units derived from styrene and from 10% to 25% by weight of units derived from acrylic acid or methacrylic acid and</li><li>block B comprises at least 75% by weight of units derived from ethyl acrylate, butyl acrylate or mixtures thereof.</li></ul>

0033According to a first preferred embodiment, the block copolymer is a diblock copolymer (block A) - (block B) where the block A comprises units derived from styrene and units derived from methacrylic acid and the block B comprises units derived from ethyl acrylate and where:<ul id="ul0007" list-style="dash" compact="compact"><li>block A comprises from 75% to 90% by weight of units derived from styrene and from 10% to 25% by weight of units derived from methacrylic acid and</li><li>block B comprises at least 75% by weight of units derived from ethyl acrylate or a mixture of ethyl acrylate and butyl acrylate.</li></ul>

0034According to a second preferred embodiment, the block copolymer is a triblock copolymer (block A) - (block B) - (block A) where the block A comprises units derived from styrene and units derived from methacrylic acid and the block B comprises units derived from ethyl acrylate and where:<ul id="ul0008" list-style="dash" compact="compact"><li>block A comprises from 75% to 90% by weight of units derived from styrene and from 10% to 25% by weight of units derived from methacrylic acid and</li><li>block B comprises at least 75% by weight of units derived from ethyl acrylate or a mixture of ethyl acrylate and butyl acrylate.</li></ul>

0035According to a third preferred embodiment, the block copolymer is a triblock copolymer (block A) - (block B) - (block A), where the block A comprises units derived from styrene and units derived from methacrylic acid and block B comprises units derived from butyl acrylate and where:<ul id="ul0009" list-style="dash" compact="compact"><li>block A comprises from 75% to 90% by weight of units derived from styrene and from 10% to 25% by weight of units derived from acrylic acid or methacrylic acid and</li><li>block B comprises at least 75% by weight of units derived from butyl acrylate.</li></ul>

0036According to a fourth preferred embodiment, the block copolymer is a triblock copolymer (block A) - (block B) - (block A) where the block A comprises units derived from styrene and units derived from methacrylic acid and the block B comprises units derived from 2-ethylhexyl acrylate and where:<ul id="ul0010" list-style="dash" compact="compact"><li>block A comprises from 75% to 90% by weight of units derived from styrene and from 10% to 25% by weight of units derived from methacrylic acid and</li><li>block B comprises at least 75% by weight of units derived from 2-ethylhexyl acrylate or a mixture of 2-ethylhexyl acrylate and ethyl acrylate and / or butyl acrylate.</li></ul>

0037According to a fifth preferred embodiment, the block copolymer is a triblock copolymer (block A) - (block B) - (block C) where the block A comprises units derived from styrene and units derived from methacrylic acid, the block B comprises units derived from 2-ethylhexyl acrylate, butyl acrylate or ethyl acrylate and block C comprises units derived from styrene and where:<ul id="ul0011" list-style="dash" compact="compact"><li>block A comprises from 75% to 90% by weight of units derived from styrene and from 10% to 25% by weight of units derived from methacrylic acid and</li><li>block B comprises at least 75% by weight of units derived from 2-ethylhexyl acrylate, butyl acrylate and / or ethyl acrylate or mixtures thereof and</li><li>block C comprises at least 94% by weight of styrene units.</li></ul>

0038The block copolymers according to the invention can be obtained by different methods. Examples of methods include "living" or "controlled" free radical polymerization methods. These methods involve the use of a specific transfer agent to achieve this effect.

0039In general, the block copolymers can be obtained by any “living” or “controlled” polymerization process, for example:<ul id="ul0012" list-style="dash" compact="compact"><li>the polymerization of free radicals controlled by xanthates according to the teaching of the request <patcit id="pcit0001" dnum="WO9858974A"><text>WO 98/58974</text></patcit> and the patent <patcit id="pcit0002" dnum="US6153705A"><text>US 6,153,705</text></patcit>,</li><li>polymerization of free radicals controlled by dithioesters according to the teaching of demand <patcit id="pcit0003" dnum="WO9801478A"><text>WO 98/01478</text></patcit>,</li><li>polymerization of free radicals controlled by dithioesters according to the teaching of demand <patcit id="pcit0004" dnum="WO9935178A"><text>WO 99/35178</text></patcit>,</li><li>free radical polymerization controlled by dithiocarbamates according to demand teaching <patcit id="pcit0005" dnum="WO9935177A"><text>WO 99/35177</text></patcit>,</li><li>polymerization of free radicals using nitroxide precursors according to the teaching of the application <patcit id="pcit0006" dnum="WO9903894A"><text>WO 99/03894</text></patcit>,</li><li>free radical polymerization controlled by dithiocarbamates according to demand teaching <patcit id="pcit0007" dnum="WO9931144A"><text>WO 99/31144</text></patcit>,</li><li>polymerization of free radicals controlled by dithiocarbazates according to the teaching of demand <patcit id="pcit0008" dnum="WO0226836A"><text>WO 02/26836</text></patcit>,</li><li>free radical polymerization controlled by halogenated xanthates according to demand teaching <patcit id="pcit0009" dnum="WO0075207A"><text>WO 00/75207</text></patcit> and demand <patcit id="pcit0010" dnum="US09980387B"><text>US 09/980 387</text></patcit>,</li><li>the polymerization of free radicals controlled by the dithiophosphoroesters according to the teaching of the request <patcit id="pcit0011" dnum="WO0210223A"><text>WO 02/10223</text></patcit>,</li><li>polymerization of free radicals controlled by a transfer agent in the presence of a disulfurized compound according to the teaching of the application <patcit id="pcit0012" dnum="WO0222688A"><text>WO 02/22688</text></patcit>,</li><li>radical polymerization controlled by atom transfer (ATRP) according to the teaching of the request <patcit id="pcit0013" dnum="WO9630421A"><text>WO 96/30421</text></patcit>,</li><li>radical polymerization controlled by iniferters according to the teaching of <nplcit id="ncit0002" npl-type="s"><text>Otu et al., Makromol. Chem. Rapid. Commun., 3.127 (1982</text></nplcit>),</li><li>radical polymerization controlled by degenerative transfer of iodine according to the teaching of <nplcit id="ncit0003" npl-type="b"><text>Tatemoto et al., Jap. 50, 127, 991 (1975), Daikin Kogyo Co Ltd Japan</text></nplcit> and <nplcit id="ncit0004" npl-type="s"><text>Matyjaszewski et al., Macromolecules, 28, 2093 (1995</text></nplcit>),</li><li>group transfer polymerization according to the teaching of <nplcit id="ncit0005" npl-type="s"><text>Webster OW, "Group Transfer Polymerization", p. 580-588</text></nplcit>, in "<nplcit id="ncit0006" npl-type="b"><text>Encyclopedia of Polymer Science and Engineering ", vol. 7, edited by HF Mark, NM Bikales, CG Overberger and G. Menges, Wiley Interscience, New York, 1987</text></nplcit>,</li><li>radical polymerization controlled by tetraphenylethane derivatives (<nplcit id="ncit0007" npl-type="s"><text>D. Braun et al., Macromol. Symp., 111, 63 (1996</text></nplcit>)),</li><li>radical polymerization controlled by organocobalt complexes (<nplcit id="ncit0008" npl-type="s"><text>Wayland et al., J. Am. Chem. Soc., 116, 7973 (1994</text></nplcit>)).</li></ul>

0040The preferred methods are the sequenced living free radical polymerization methods involving the use of a transfer agent. Preferred transfer agents are agents comprising a group of formulas -SC (S) -Y-, -SC (S) -S- or -SP (S) -Y or -SP (S) -S- in which Y is a different atom from sulfur such as an oxygen atom, a nitrogen atom and a carbon atom. They include dithioester groups, thioetherthione groups, dithiocarbamate groups, dithiophosphoroesters, dithiocarbazates and xanthate groups. Examples of groups contained in the preferred transfer agents include groups of the formulas -SC (S) -NR-NR '₂, -SC (S) -NR-N = CR '₂, -SC (S) -OR, -SC (S) -X in which R and R 'are identical or different hydrogen atoms or organic groups such as hydrocarbyl groups, optionally substituted, optionally comprising heteroatoms and X is a halogen atom. A preferred polymerization process is a living radical polymerization using xanthates.

0041A “living” or “controlled” polymerization process for free radicals used to manufacture block copolymers comprises for example the steps consisting in:<ol id="ol0001" compact="compact" ol-style=""><li>a) reacting monomers or a mixture of monomers, at least one free radical source compound and a transfer agent to obtain a first block (preferably a block A), the transfer agent being linked to the first said block ,</li><li>b) reacting the first block, the monomers and a mixture of monomers and optionally at least one radical source compound to obtain a diblock copolymer (preferably (block A) - (block B)),</li><li>c) optionally reacting the diblock copolymer, the monomers or a mixture of monomers and optionally at least one radical source compound to obtain a triblock copolymer (preferably (block A) - (block B) - (block A) or (block A) - (block B) - (block C)), then</li><li>d) possibly reacting the transfer agent with means to make it inactive or to eliminate it.</li></ol>

0042During step a), a first block of the block copolymer polymer is prepared, preferably block A, preferentially using rigid monomers and optionally segregation monomers from block A. During step b) , a second block is obtained, preferably a block B, connected to the first block to obtain a diblock copolymer, preferably block B, using flexible monomers and optionally block segregation monomers B. During the optional step c), a third block is obtained, connected to the second block, preferably a block A or block C to obtain a triblock copolymer, using rigid monomers and possibly monomers for segregation of block A. Au during step d), the transfer agent is reacted to make it inactive, or to avoid odor or yellowing.

0043The examples of transfer agents are transfer agents of the following formula (I):<chemistry id="chem0001" num="0001"><img file="EP1516002B1_D0002.tif" /></chemistry>in which :<ul id="ul0013" list-style="dash" compact="compact"><li>R represents a group R²GOLD²R '²N- or R³-, R² and R '² which are identical or different, representing (i) an allcyl, acyl, aryl, alkene or alkyne group or (ii) a saturated or unsaturated, optionally aromatic, carbon nucleus or (iii) a saturated or unsaturated heterocycle, these groups and nuclei ( i), (ii) and (iii) can be substituted, R³ representing H, Cl, an alkyl, aryl, alkene or alkyne group, a saturated or unsaturated (hetero) ring, optionally substituted, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxyl, acyloxy, carbamoyl, cyano, dialkylphosphonato or diarylphosphonato group or a dialkylphosphin group or diarylphosphinato or a polymer chain,</li><li>R¹ represents (i) an optionally substituted alkyl, acyl, aryl, alkene or alkyne group or (ii) a carbon nucleus which is saturated or unsaturated and which is optionally substituted or aromatic or (iii) a saturated or unsaturated heterocycle, optionally substituted, or a polymer chain, and</li></ul>R groups¹, R², R '² and R³ may be substituted by phenyl or substituted alkyl groups, substituted aromatic groups or the following groups: oxo, alkoxycarbonyl or aryloxycarbonyl (-COOR), carboxyl (-COOH), acyloxy (-O₂CR), carbamoyl (-CONR₂), cyano (-CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylallcylcarbonyl, isocyanato, phthalimido, maleimido, succinimido, amidino, guanidino, hydroxyl (-OH), amino (-NR)₂), halogen, allyl, epoxy, alkoxy (-OR), S-alkyl, S-aryl or silyl, groups having a hydrophilic or ionic nature, such as the alkali salts of carboxylic acids or alkali salts of sulfonic acid, poly (alkylene oxide) chains (PEO, PPO) or cationic substituents (quaternary ammonium salts), R representing an alkyl or aryl group.

0044Preferably, the transfer agent of formula (I) is a dithiocarbonate chosen from the compounds of the following formulas (IA), (IB) and (IC):<chemistry id="chem0002" num="0002"><img file="EP1516002B1_D0003.tif" /></chemistry><chemistry id="chem0003" num="0003"><img file="EP1516002B1_D0004.tif" /></chemistry><chemistry id="chem0004" num="0004"><img file="EP1516002B1_D0005.tif" /></chemistry>in which :<ul id="ul0014" list-style="dash" compact="compact"><li>R² and R²'represent (i) an alkyl, acyl, aryl, alkene or alkyne group or (ii) a saturated or unsaturated, optionally aromatic, carbon nucleus or (iii) a saturated or unsaturated heterocycle, the groups and nuclei (i), (ii ) and (iii) can be substituted,</li><li>R¹ and R^1, represent (i) an alkyl, acyl, aryl, alkene or alkyne group or (ii) a carbon nucleus which is saturated or unsaturated and which is optionally substituted or aromatic or (iii) a saturated or unsaturated heterocycle, optionally substituted or a polymer chain , and</li><li>p is a number between 2 and 10.</li></ul>

0045Other examples of transfer agents are transfer agents of the following formulas (II) and (III):<chemistry id="chem0005" num="0005"><img file="EP1516002B1_D0006.tif" /></chemistry><chemistry id="chem0006" num="0006"><img file="EP1516002B1_D0007.tif" /></chemistry>wherein<ul id="ul0015" list-style="dash" compact="compact"><li>R¹ is an organic group, for example an R group¹ as defined above for the transfer agents of formulas (I), (IA), (IB) and (IC),</li><li>R², R³, R⁴, R⁷ and R⁸ which are the same or different are hydrogen atoms or organic groups, possibly forming nuclei. Examples of organic groups R², R³, R⁴, R⁷ and R⁸ include hydrocarbyls, substituted hydrocarbyls, hydrocarbyls containing a heteroatom and hydrocarbyls containing a substituted heteroatom.</li></ul>

0046According to the aforementioned process, if all the successive polymerizations are carried out in the same reactor, it is generally preferable that all the monomers used during a stage have been consumed before the polymerization of the following stage begins, therefore before the new ones monomers are not introduced. However, it may happen that certain monomers from the previous step are always present in the reactor during the polymerization of the next block. In this case, these monomers do not generally represent more than 5 mol% of all the monomers and they participate in the following polymerization by contributing to the introduction of other units in the following block.

0047The polymerization can be carried out in an aqueous and / or organic solvent medium. The polymerization can also be carried out in an essentially pure molten form (bulk polymerization) or according to the latex type process in an aqueous medium.

0048The block copolymer can be in solid form and / or dried. It can also be in solution in an organic solvent. It can also be in the form of a dispersion in an aqueous medium in a latex form. It usually depends on the process used for its preparation. If it is not in solid and / or dried form, the solvent or the aqueous medium is usually intended to be removed in order to obtain the block copolymer in solid and / or dried form. For example, the solvent or the aqueous medium can be removed by evaporation or drying, once the latex solution or dispersion has been applied to a surface to obtain a film or a coating, in solid and / or dried form.

0049If in solid form, the block copolymer according to the invention can be melted, be formed, or applied to a surface. Then it can be cooled to obtain a solid article, film or coating.

0050It is believed that when it is in solid or dried form, the flexible block of the block copolymer according to the invention forms a continuous flexible phase and the rigid block or blocks form a rigid phase, the rigid phase being dispersed in the flexible phase. As explained above and without wishing to be linked to any theory, it is believed that phase separation provides cohesion by crosslinking according to a physical phenomenon.

0051When in solid or dried form, the block copolymer of the invention has an elastomeric property and a thermoplastic property. It can be designated a thermoplastic elastomer.

0052Thus, the block copolymer according to the invention has, in solid or dried form, an elongation at break of at least 500% and a tensile strength of at least 1.5 MPa. Preferably, the elongation at break is at least 750% and the tensile strength is at least 2.0 MPa. These properties are considered to be the properties of an elastomeric compound.

0053The block copolymers of the invention find use in many fields. They can be used for example for manufacturing articles. The block copolymers according to the invention are for example in the form of powders, pellets, solid granules, optionally compounded with other ingredients, to be melted, introduced into a mold in a liquid form, then cooled to obtain an article in a form solid. The articles obtained from block copolymers usually have an interesting feel, which can be called flexible or sticky (compared to the other thermoplastics) ... The articles obtained from block copolymers according to the invention also have elastomeric properties which can be required. The thermoplastic properties make it possible to manufacture articles having elastomeric properties with shapes which would be difficult to obtain with a polymer or a composition which would require chemical crosslinking. They can simplify the process for manufacturing elastomeric articles or simplify the compositions used to manufacture these articles.

0054It should be noted that to manufacture articles, the block copolymer can be used alone or with certain other ingredients, in the form of a compound in a plastic engineering formulation. Depending on the quantity of the different ingredients, the block copolymer can be considered as an additive to modify the properties of other polymers or as a polymer having properties modified by other ingredients. It is further mentioned that the copolymer may comprise units which enhance the compatibility with other compounds of a composition such as units comprising an epoxy group or a maleic anhydride group. Useful groups are known to those skilled in the art of thermoplastic formulations.

0055Certain block copolymers according to the invention can be used as adhesive compounds. They can be used as a compound in an adhesive composition. Block copolymers in which the flexible monomer is butyl acrylate or butyl methacrylate are specifically preferred for use as an adhesive compound. It is further mentioned that the copolymer may comprise units which enhance the adhesive properties or the compatibility with other compounds such as the units comprising an epoxy group or a maleic anhydride group. Useful groups are known to those skilled in the art of adhesive compositions.

0056For example, the block copolymers according to the invention or the compositions comprising said block copolymers, preferably the block copolymers in which the flexible monomer is butyl acrylate or butyl methacrylate, can be deposited on a surface in a molten form , in the form of a solution or in the form of a latex dispersion in an aqueous medium to obtain an adhesive layer. The surface is for example a base layer, forming an adhesive tape, together with an adhesive layer. Therefore, the surface on which the composition is deposited may for example be a plastic film or a paper-type product.

0057The block copolymer according to the invention can be included in the formulations intended to be applied to a surface, used in the construction of the building or in the decoration of the house, for example paint formulations (industrial paints, household paints or decorative). The block copolymer can also be included in a putty, a cement or a filler formulation. Formulations in which the block copolymer is in the form of a latex dispersion are particularly preferred. While the dispersion is not very viscous in paints, the viscosity of the putty, cement or filler formulation is usually quite high. The block copolymer can give a coating or a layer of paint having certain specific properties in relation to elasticity such as crack resistance, impact resistance, resistance to marks, resistance to the deposit of dirt, etc. cements or fillers comprising the block copolymer according to the invention have improved properties compared to sealants, cements or fillers comprising polymers based on (meth) acrylic acid ester. What is called crosslinking by an aforementioned physical phenomenon makes the use of block copolymers particularly useful since there is no need to carry out a crosslinking step once the formulation has been applied to a surface or '' use complex formulations, very sensitive or harmful to the environment or health (two-pack formulations, formulation comprising a catalyst which is inhibited in the presence of water ...). What is called crosslinking by a physical phenomenon also makes it possible to control the flow and adhesion properties.

0058Some examples are given below for a better understanding of the invention.

Example 1: Diblock copolymer of poly (styrene / methacrylic acid) -block-poly (ethyl acrylate / methacrylic acid) (St / MMA) -b- (EtA / MMA) where St / MMA = 80/20 and EtA / MMA = 95/5

Step 1: Synthesis of a statistical block (St / MMA) of styrene (St) and methacrylic acid (MMA) with a weight ratio of St / MAA = 80/20.

0059Polymerization is carried out under emulsion conditions in a jacketed reactor equipped with a three-blade stainless steel stirrer. 300 g of water, 7.46 g of sodium dodecyl sulfate (Aldrich) and 1.87 g of sodium carbonate Na₂CO₃ are introduced at ambient temperature in the form of a starting mixture. The mixture obtained is stirred for 30 minutes (190 revolutions / min) during this time, the temperature is brought to 75 ° C. Next, a mixture comprising 3.00 g of styrene, 1.56 g of methyl α- (o-ethylxanthyl) propionate (CH₃CHCO₂Me) SCSOEt and 0.75 g of methacrylic acid is incorporated. The temperature is subsequently brought to 85 ° C. and 0.31 g of ammonium persulfate (NH₄)₂S₂O₈ has been added. After five minutes, the addition is continued with 27.0 g of styrene, 6.75 g of methacrylic acid for one hour. Once the addition is complete, a copolymer emulsion (latex) is obtained which is maintained at 85 ° C. for one hour.

Step 2: Synthesis of a statistical block (EtA / MMA) of ethyl acrylate (EtA) and methacrylic acid (MMA) with a weight ratio: EtA / MAA = 95/5 to obtain a diblock copolymer.

006058.12 g of the copolymer emulsion obtained previously are removed from the reactor. 0.13 g ammonium persulfate (NH₄)₂S₂O₈ and 5.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0016" list-style="dash" compact="compact"><li>363.78 g of ethyl acrylate (EtA) and</li><li>19.15 g methacrylic acid (MAA)</li></ul>and simultaneously of another mixture comprising:<ul id="ul0017" list-style="dash" compact="compact"><li>385 g of water and</li><li>1.06 g Na₂CO₃.</li></ul>

0061The addition lasts 1 hour. The system is kept at this temperature for an additional three hours.

0062The calculated molecular weight of the block of (St / MMA) is 5000 g / mol and the calculated molecular weight of the block of (EtA / MMA) is 62 500 g / mol.

Example 2: poly (styrene / methacrylic acid) triblock -poly-block (ethyl acrylate / methacrylic acid) -poly (styrene / methacrylic acid) block (St / MMA) -b- (EtA) -b- (St / MMA) where St / MMA = 80/20 in the first block, St / MMA = 98/2 in the third block and EtA / MMA = 95/5

Step 1: Synthesis of a first statistical block (St / MMA) of styrene (St) and methacrylic acid (MAA) with a weight ratio of St / MAA = 80/20.

0063Polymerization is carried out under emulsion conditions in a jacketed reactor equipped with a three-blade stainless steel stirrer. 300 g of water, 7.46 g of sodium dodecyl sulfate (Aldrich) and 1.87 g of sodium carbonate Na₂CO₃ are introduced at ambient temperature in the form of a starting mixture. The mixture obtained is stirred for 30 minutes (190 revolutions / min) during this time, the temperature is brought to 75 ° C. Next, a mixture comprising 3.00 g of styrene, 1.56 g of methyl α- (o-ethylxanthyl) propionate (CH₃CHCO₂Me) SCSOEt and 0.75 g of methacrylic acid is incorporated. The temperature is subsequently brought to 85 ° C. and 0.31 g of ammonium persulfate (NH₄)₂S₂O₈ has been added. After five minutes, the addition is continued with 27.0 g of styrene, 6.75 g of methacrylic acid for one hour. Once the addition is complete, a copolymer emulsion (latex) is obtained which is maintained at 85 ° C. for one hour.

Step 2: Synthesis of a second statistical block (EtA / MMA) of ethyl acrylate (EtA) and methacrylic acid (MMA) with a weight ratio: EtA / MAA = 95/5 to obtain a diblock copolymer .

006458.12 g of the copolymer emulsion obtained previously are removed from the reactor. 0.13 g ammonium persulfate (NH₄)₂S₂O₈ and 5.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0018" list-style="dash" compact="compact"><li>363.78 g of ethyl acrylate (EtA) and</li><li>19.15 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0019" list-style="dash" compact="compact"><li>385 g of water and</li><li>1.06 g Na₂CO₃.</li></ul>

0065The addition lasts 1 hour. The system is kept at this temperature for an additional three hours. A copolymer (latex) emulsion is obtained.

Step 3: Synthesis of a third statistical block (St / MMA) of styrene (St) and methacrylic acid (MMA) with a weight ratio: St / MAA = 98/2 to obtain a triblock copolymer.

0066212.94 g of the copolymer emulsion obtained previously are removed from the reactor. 0.05 g ammonium persulfate (NH₄)₂S₂O₈ and 4.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0020" list-style="dash" compact="compact"><li>24.02 g of styrene (St) and</li><li>0.49 g methacrylic acid (MAA)</li></ul>and simultaneously of another mixture comprising:<ul id="ul0021" list-style="dash" compact="compact"><li>32.0 g of water and</li><li>0.03 g Na₂CO₃.</li></ul>

0067The addition lasts 1 hour. The system is kept at this temperature for an additional three hours. A copolymer (latex) emulsion is obtained.

0068The calculated molecular weight of the first block of (St / MMA) is 5000 g / mol, the calculated molecular weight of the second block of (EtA / MMA) is 62 500 g / mol and the calculated molecular weight of the third block of ( St / MMA) is 500 g / mol.

Example 3 (comparative): diblock of poly (styrene / methacrylic acid) -block-poly (ethyl acrylate / methacrylic acid) (St / MMA) -b- (EtA / MMA) where St / MMA = 96/4 and EtA / MMA = 95/5

Step 1: Synthesis of a statistical block (St / MMA) of styrene (St) and methacrylic acid (MAA) with a weight ratio of St / MAA = 96/4.

0069Polymerization is carried out under emulsion conditions in a jacketed reactor equipped with a three-blade stainless steel stirrer. 450 g of water, 9.32 g of dodecyl sodium sulfate (Aldrich) and 0.38 g of sodium carbonate Na₂CO₃ are introduced at ambient temperature in the form of a starting mixture. The mixture obtained is stirred for 30 minutes (190 revolutions / min) during this time, the temperature is brought to 75 ° C. Then, a mixture comprising 4.50 g of styrene, 1.95 g of methyl α- (o-ethylxanthyl) propionate (CH₃CHCO₂Me) SCSOEt and 0.19 g of methacrylic acid is incorporated. The temperature is subsequently brought to 85 ° C. and 2.28 g of ammonium persulfate (NH₄)₂S₂O₈ have been added. After five minutes, the addition is continued with 40.5 g of styrene, 1.69 g of methacrylic acid for one hour. Once the addition is complete, a copolymer (latex) emulsion is obtained which is maintained at 85 ° C. for one hour.

Step 2: Synthesis of a statistical block (EtA / MMA) of ethyl acrylate (EtA) and methacrylic acid (MMA) with a weight ratio: EtA / MAA = 95/5 to obtain a diblock copolymer.

0070113.51 g of the copolymer emulsion obtained previously are removed from the reactor. 0.17 g ammonium persulfate (NH₄)₂S₂O₈ and 7.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0022" list-style="dash" compact="compact"><li>424.41 g of ethyl acrylate (EtA) and</li><li>22.34 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0023" list-style="dash" compact="compact"><li>385 g of water and</li><li>1.06 g Na₂CO₃.</li></ul>

0071The addition lasts 1 hour. The system is kept at this temperature for an additional three hours.

0072The calculated molecular weight of the block of (St / MMA) is 5000 g / mol and the calculated molecular weight of the block of (EtA / MMA) is 62 500 g / mol.

Example 4 (comparative): triblock of poly (styrene / methacrylic acid) -block-poly (ethyl acrylate / methacrylic acid) -block-poly (styrene / methacrylic acid) (St / MMA) -b- (EtA / MMA ) -b- (St / MMA) where St / MMA = 80/20 in the first block, St / MMA = 95/5 in the third block and EtA / MMA = 95/5

Step 1: Synthesis of a statistical block (St / MMA) of styrene (St) and methacrylic acid (MAA) with a weight ratio of St / MAA = 96/4.

0073Polymerization is carried out under emulsion conditions in a jacketed reactor equipped with a three-blade stainless steel stirrer. 450 g of water, 9.32 g of dodecyl sodium sulfate (Aldrich) and 0.38 g of sodium carbonate Na₂CO₃ are introduced at ambient temperature in the form of a starting mixture. The mixture obtained is stirred for 30 minutes (190 revolutions / min) during this time, the temperature is brought to 75 ° C. Then, a mixture comprising 4.50 g of styrene, 1.95 g of methyl α- (o-ethylxanthyl) propionate (CH₃CHCO₂Me) SCSOEt and 0.19 g of methacrylic acid is incorporated. The temperature is subsequently brought to 85 ° C. and 2.28 g of ammonium persulfate (NH₄)₂S₂O₈ have been added. After five minutes, the addition is continued with 40.5 g of styrene, 1.69 g of methacrylic acid for one hour. Once the addition is complete, a copolymer (latex) emulsion is obtained which is maintained at 85 ° C. for one hour.

Step 2: Synthesis of a statistical block (EtA / MMA) of ethyl acrylate (EtA) and methacrylic acid (MMA) with a weight ratio: EtA / MAA = 95/5 to obtain a diblock copolymer.

0074113.51 g of the copolymer emulsion obtained previously are removed from the reactor. 0.17 g ammonium persulfate (NH₄)₂S₂O₈ and 7.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0024" list-style="dash" compact="compact"><li>424.41 g of ethyl acrylate (EtA) and</li><li>22.34 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0025" list-style="dash" compact="compact"><li>385 g of water and</li><li>1.24 g Na₂CO₃.</li></ul>

0075The addition lasts 1 hour. The system is kept at this temperature for an additional three hours. A copolymer (latex) emulsion is obtained.

Step 3: Synthesis of a third statistical block (St / MMA) of styrene (St) and methacrylic acid (MMA) with a weight ratio: St / MAA = 95/5 to obtain a triblock copolymer.

0076353.55 g of the copolymer emulsion obtained previously are removed from the reactor. 0.07 g ammonium persulfate (NH₄)₂S₂O₈ and 5.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0026" list-style="dash" compact="compact"><li>24.25 g of styrene (St) and</li><li>1.28 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0027" list-style="dash" compact="compact"><li>32.5 g of water and</li><li>0.07 g Na₂CO₃.</li></ul>

0077The addition lasts 1 hour. The system is kept at this temperature for an additional three hours.

0078The calculated molecular weight of the first block of (St / MMA) is 5000 g / mol, the calculated molecular weight of the second block of (EtA / MMA) is 62 500 g / mol and the calculated molecular weight of the third block of ( St / MMA) is 500 g / mol.

Example 5 triblock of poly (styrene / methacrylic acid) -block-poly (ethyl acrylate / methacrylic acid) -block-poly (styrene / methacrylic acid) (St / MMA) -b- (EtA / MMA) -b - (St / MMA) where St / MMA = 80/20 in the first block, St / MMA = 98/2 in the third block and EtA / MMA = 95/5

Step 1: Synthesis of a first statistical block (St / MMA) of styrene (St) and methacrylic acid (MAA) with a weight ratio of St / MAA = 80/20.

0079Polymerization is carried out under emulsion conditions in a jacketed reactor equipped with a three-blade stainless steel stirrer. 555 g of water, 12.05 g of sodium dodecyl sulfate (Aldrich) and 1.50 g of sodium carbonate Na₂CO₃ are introduced at ambient temperature in the form of a starting mixture. The mixture obtained is stirred for 30 minutes (190 revolutions / min) during this time, the temperature is brought to 75 ° C. Then, a mixture comprising 3.00 g of styrene, 2.60 g of methyl α- (o-ethylxanthyl) propionate (CH₃CHCO₂Me) SCSOEt and 0.75 g of methacrylic acid is incorporated. The temperature is subsequently brought to 85 ° C. and 0.52 g of ammonium persulfate (NH₄)₂S₂O₈ has been added. After five minutes, the addition is continued with 27.0 g of styrene, 6.75 g of methacrylic acid for one hour. Once the addition is complete, a copolymer emulsion (latex) is obtained which is maintained at 85 ° C. for one hour.

Step 2: Synthesis of a second random block (EtA / MMA) of ethyl acrylate (EtA) and methacrylic acid (MMA) with a weight ratio: EtA / MAA = 95/5 to obtain a diblock copolymer .

0080101.53 g of the copolymer emulsion obtained previously are removed from the reactor. 0.22 g ammonium persulfate (NH₄)₂S₂O₈ and 5.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0028" list-style="dash" compact="compact"><li>606.3 g of ethyl acrylate (EtA) and</li><li>31.91 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0029" list-style="dash" compact="compact"><li>512.5 g of water and</li><li>1.77 g Na₂CO₃.</li></ul>

0081The addition lasts 1 hour. The system is kept at this temperature for an additional three hours. A copolymer (latex) emulsion is obtained.

Step 3: Synthesis of a third statistical block (St / MMA) of styrene (St) and methacrylic acid (MMA) with a weight ratio: St / MAA = 98/2 to obtain a triblock copolymer.

0082333.07 g of the copolymer emulsion obtained previously are removed from the reactor. 0.09 g ammonium persulfate (NH₄)₂S₂O₈ and 4.0 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0030" list-style="dash" compact="compact"><li>4.0 g of styrene (St) and</li><li>0.08 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0031" list-style="dash" compact="compact"><li>40.0 g of water and</li><li>0.005 g Na₂CO₃.</li></ul>

0083The addition lasts 1 hour. The system is kept at this temperature for an additional three hours.

0084The calculated molecular weight of the first block of (St / MMA) is 3000 g / mol, the calculated molecular weight of the second block of (EtA / MMA) is 62 500 g / mol and the calculated molecular weight of the third block of ( St / MMA) is 500 g / mol.

Example 6 (comparative): triblock of poly (styrene / methacrylic acid) -block-poly (ethyl acrylate / methacrylic acid) -block-poly (styrene / methacrylic acid) (St / MMA) -b- (EtA / MMA ) -b- (St / MMA) where St / MMA = 98/2 in the first block, St / MMA = 98/2 in the third block and EtA / MMA = 95/5

Step 1: Synthesis of a first statistical block (St / MMA) of styrene (St) and methacrylic acid (MAA) with a weight ratio of St / MAA = 98/2.

0085Polymerization is carried out under emulsion conditions in a jacketed reactor equipped with a three-blade stainless steel stirrer. 660 g of water, 7.54 g of sodium dodecyl sulfate (Aldrich) and 0.31 g of sodium carbonate Na₂CO₃ are introduced at ambient temperature in the form of a starting mixture. The mixture obtained is stirred for 30 minutes (190 revolutions / min) during this time, the temperature is brought to 75 ° C. Then, a mixture comprising 6.82 g of styrene, 4.65 g of methyl α- (o-ethylxanthyl) propionate (CH₃CHCO₂Me) SCSOEt and 0.17 g of methacrylic acid is incorporated. The temperature is subsequently brought to 85 ° C. and 1.39 g of ammonium persulfate (NH₄)₂S₂O₈ has been added. After five minutes, the addition is continued with 58.8 g of styrene, 1.57 g of methacrylic acid for one hour. Once the addition is complete, a copolymer (latex) emulsion is obtained which is maintained at 85 ° C. for one hour.

Step 2: Synthesis of a second statistical block (EtA / MMA) of ethyl acrylate (EtA) and methacrylic acid (MMA) with a weight ratio: EttA / MAA = 95/5 to obtain a diblock copolymer .

008667.66 g of the copolymer emulsion obtained previously are removed from the reactor. 0.46 g ammonium persulfate (NH₄)₂S₂O₈ and 12 g of water are added to the emulsion remaining in the reactor at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0032" list-style="dash" compact="compact"><li>387.96 g of ethyl acrylate (EtA) and</li><li>7.91 g methacrylic acid (MAA) and simultaneously of another mixture comprising:</li></ul><ul id="ul0033" list-style="dash" compact="compact"><li>96 g of water and</li><li>0.44 g Na₂CO₃.</li></ul>

0087The addition lasts 1 hour. The system is kept at this temperature for an additional three hours. A copolymer (latex) emulsion is obtained.

Step 3: Synthesis of a third statistical block (St / MMA) of styrene (St) and methacrylic acid (MMA) with a weight ratio: St / MAA = 98/2 to obtain a triblock copolymer.

0088392.67 g of the copolymer emulsion obtained previously are removed from the reactor. 0.05 g of Na2CO3 in 5 g of water is added to the emulsion remaining in the reactor. 0.29 g ammonium persulfate (NH₄)₂S₂O₈ and 10.0 g of water are added thereto at 85 ° C. After five minutes, the addition of the following mixture, comprising:<ul id="ul0034" list-style="dash" compact="compact"><li>7.33 g of styrene (St) and</li><li>0.15 g methacrylic acid (MAA).</li></ul>

0089The addition lasts 1 hour. The system is kept at this temperature for an additional three hours.

0090The calculated molecular weight of the first block of (St / MMA) is 3000 g / mol, the calculated molecular weight of the second block of (EtA / MMA) is 19 500 g / mol and the calculated molecular weight of the third block of ( St / MMA) is 500 g / mol.

0091Certain characteristics of the block copolymers of the examples are given in Table 1.<tables id="tabl0001" num="0001"><table frame="all"><title><u style="single">Table 1</u></title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="27mm" /><colspec colnum="4" colname="col4" colwidth="25mm" /><thead><row><entry valign="top">Example</entry><entry valign="top">Block A</entry><entry valign="top">Block B</entry><entry valign="top">Block C</entry></row></thead><tbody><row rowsep="0"><entry>1</entry><entry>St / MMA: 80/20</entry><entry>EtA / MMA: 95/5</entry><entry>/</entry></row><row><entry /><entry>5000 g / mol</entry><entry>62 500 g / mol</entry><entry /></row><row rowsep="0"><entry>2</entry><entry>St / MMA: 80/20</entry><entry>EtA / MMA: 95/5</entry><entry>St / MMA: 98/2</entry></row><row><entry /><entry>5000 g / mol</entry><entry>62 500 g / mol</entry><entry>500 g / mol</entry></row><row rowsep="0"><entry>3 (comparative)</entry><entry>St / MMA: 96/4</entry><entry>EtA / MMA: 95/5</entry><entry>/</entry></row><row><entry /><entry>5000 g / mol</entry><entry>62 500 g / mol</entry><entry /></row><row rowsep="0"><entry>4 (comparative)</entry><entry>St / MMA: 96/4</entry><entry>EtA / MMA: 95/5</entry><entry>St / MMA: 95/5</entry></row><row><entry /><entry>5000 g / mol</entry><entry>62 500 g / mol</entry><entry>500 g / mol</entry></row><row rowsep="0"><entry>5</entry><entry>St / MMA: 80/20</entry><entry>EtA / MMA: 95/5</entry><entry>St / MMA: 98/2</entry></row><row><entry /><entry>5000 g / mol</entry><entry>62 500 g / mol</entry><entry>500 g / mol</entry></row><row rowsep="0"><entry>6 (comparative)</entry><entry>St / MMA: 96/4</entry><entry>EtA / MMA: 95/5</entry><entry>St / MMA: 98/2</entry></row><row><entry /><entry>3000 g / mol</entry><entry>62 500 g / mol</entry><entry>500 g / mol</entry></row></tbody></tgroup></table></tables>

Example 7: Stretch / stress tests

0092The films of the block copolymers of the previous examples are cast and dried in a silicon matrix at room temperature for two days, then cured in an oven at 50 ° C for 24 hours and finally at 75 ° C for 2 hours. The film obtained is approximately 1 mm thick. The 4 cm long and 2 cm wide strips are cut to form films in order to carry out the mechanical tests.

0093A stretching / stressing experiment is carried out with an INSTRON 5543. A constant stress rate is applied with a fixed extension speed of 2 mm / s. The stretch is measured on the elongation (stretch / stress curve). The maximum possible extension with this device is 3000%.

0094The following different behaviors are reported:<ul id="ul0035" list-style="none" compact="compact"><li>Elastic behavior: constant increase in stretching then sudden rupture at a critical stretch. Stretching (in megapascals: MPa) and elongation (in%) at break are reported.</li><li>Plastic behavior: no rupture below 3000% deformation, maximum stress observed at a low stretch value in the stretch / stress curve, then flow behavior with a stress decreasing with an increase in deformation. There is no break, the sample flows. Only the maximum of the stretch / stress curve in (megapascals: MPa) is reported.</li></ul>

0095The results are shown in Table 2.<tables id="tabl0002" num="0002"><table frame="all"><title><u style="single">Table 2</u></title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="38mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="28mm" /><colspec colnum="4" colname="col4" colwidth="44mm" /><thead><row><entry valign="top">Example polymer:</entry><entry align="center" valign="top">behaviour</entry><entry align="center" valign="top">Stretch (MPa)</entry><entry align="center" valign="top">Elongation at break</entry></row></thead><tbody><row><entry>1</entry><entry align="center">elastic</entry><entry align="center">3.05 (break)</entry><entry align="center">1000</entry></row><row><entry>2</entry><entry align="center">elastic</entry><entry align="center">2.75 (break)</entry><entry align="center">1150</entry></row><row><entry>3 (comparative)</entry><entry align="center">plastic</entry><entry align="center">0.9 (maximum)</entry><entry align="center">Not applicable</entry></row><row><entry>4 (comparative)</entry><entry align="center">plastic</entry><entry align="center">1.0 (maximum)</entry><entry align="center">Not applicable</entry></row><row><entry>5</entry><entry align="center">elastic</entry><entry align="center">1,4</entry><entry align="center">1600</entry></row><row><entry>6 (comparative)</entry><entry align="center">plastic</entry><entry align="center">0.2 (maximum)</entry><entry align="center">Not applicable</entry></row></tbody></tgroup></table></tables>

Example 8: Dynamic Mechanical Analysis (DMA) Tests

0096Dynamic mechanical analyzes were carried out on the block copolymer films. The glass transition of the flexible block, the elastic modulus of the elastic plate and the fusion of the rigid block (high Tg) were measured. The complex modules (in Pa) of the block polymers are measured at different temperatures (the temperature increases) at a constant frequency of 1 Hz. The device used is a Universal V3. 1B TA Instruments, using a unique temperature / frequency rise method. The geometry is either sheared or extensional. A first decrease in the complex modulus as the temperature increases, typically by 10⁹ Pa to 10⁶ Pa, is considered to correspond to the Tg of the flexible block. Then, the modulus is constant when the temperature increases (elastic plateau). The constant module is reported as the module of the elastic plate. Then, it decreases sharply again when it reaches the temperature considered to correspond to the high Tg of the polymer. This higher temperature is considered to correspond to the melting of the polymer (thermoplastic property). The results are shown in Table 3.<tables id="tabl0003" num="0003"><table frame="all"><title><u style="single">Table 3</u></title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="36mm" /><colspec colnum="2" colname="col2" colwidth="50mm" /><colspec colnum="3" colname="col3" colwidth="43mm" /><thead><row><entry valign="top">Example polymer</entry><entry align="center" valign="top">Module of the elastic plate (Pa)</entry><entry align="center" valign="top">Melting temperature (° C)</entry></row></thead><tbody><row><entry>1</entry><entry align="center">10⁶</entry><entry align="center">45</entry></row><row><entry>2</entry><entry align="center">10⁶</entry><entry align="center">45</entry></row><row><entry>3 (comparative)</entry><entry align="center">10⁶</entry><entry align="center">30</entry></row><row><entry>4 (comparative)</entry><entry align="center">10⁶</entry><entry align="center">30</entry></row><row><entry>5</entry><entry align="center">10⁶</entry><entry align="center">45</entry></row><row><entry>6 (comparative)</entry><entry align="center">No elastic plateau observed</entry><entry align="center">10</entry></row></tbody></tgroup></table></tables>

0097The polymers of Comparative Examples 3, 4 and 6 do not exhibit elastomeric behavior. The cohesion of the polymer is weak. The polymers flow. They exhibit poor thermoplastic behavior. The polymers of Examples 1, 2 and 5 exhibit strong elastomeric behavior and thermoplastic behavior. The elastomeric properties are good even if the molecular weight of the rigid block is low (5000 g / mol for the polymers according to Examples 1 and 2) and even very low (3000 g / mol for the polymers according to Example 5).