WO2021074507A1

WO2021074507A1 - Method for preparing an epoxidised diene elastomer

Info

Publication number: WO2021074507A1
Application number: PCT/FR2020/051777
Authority: WO
Inventors: Kevin Roos; Pedro MAXIMIANO-RAIMUNDO; Véronique BOUNOR-LEGARE; Noellie YLLA; Emmanuel BEYOU; Philippe Cassagnau
Original assignee: Compagnie Generale Des Etablissements Michelin; Centre National De La Recherche Scientifique; Institut National Des Sciences Appliquees De Lyon; Universite Claude Bernard Lyon 1; Universite Jean Monnet Saint-Etienne
Priority date: 2019-10-14
Filing date: 2020-10-08
Publication date: 2021-04-22
Also published as: FR3101876A1; FR3101876B1

Abstract

The invention relates to a method for bulk preparation of an epoxidised diene polymer in a tool for processing rubber, which method comprises at least two separate additions of a solid epoxidation agent. The method of the invention makes it possible to achieve an epoxidation rate that is comparable to the epoxidation rates achieved in a method where the diene polymer is epoxidised in solution, with a yield greater than or equal to 85%.

Description

A process for preparing an epoxidized diene elastomer.

Technical area

The field of the present invention is that of the mass preparation of an epoxidized diene elastomer.

Prior art

Elastomers based on conjugated diene monomers are widely described in the literature and used daily for their many applications, mainly for their elasticity property.

Epoxidized diene polymers have come to expand the offer of these diene polymers by proposing to widen the possible applications due to the presence of epoxy functional groups in the polymer chain. Thus, for example, the epoxidation of diene polymers makes it possible to envisage an alternative crosslinking to that usual by means of sulfur-based vulcanization systems. The epoxy functions of the epoxidized polymers can also be used to graft these polymers with molecules bearing a reactive part with respect to these epoxy functions. It is thus possible, for example, to envisage functionalizing a polymer along its chain by grafting appropriate functions.

Epoxidized diene polymers and their methods of obtaining are well known to those skilled in the art. Conventionally, epoxidation can be carried out using an epoxidizing agent such as a peracid or hydrogen peroxide in the presence of a carboxylic acid, with or without a catalyst. The epoxidation processes of diene polymers described in the literature can be classified into 2 types, namely the “solution” processes when the diene polymer is redissolved in an organic solvent and the “bulk” processes when the diene polymer. remains in the solid state.

The epoxidation rate is the molar ratio of the number of epoxy functions in the polymer to the number of carbon-carbon double bonds in the polymer. The epoxidation rates described in the literature depend on the type of epoxidation process used. With “solution” epoxidation processes, it is possible to achieve levels above 10%.

With “bulk” processes, the rate of epoxidation is generally described as not going beyond 6% to 8%. Whatever the type of epoxidation process, the reaction time is generally long and can be counted in several hours, often incompatible with an economically profitable industrial implementation.

As a “solution” process, mention may be made of EP 2530094 A1 which describes a solution process aimed at dissolving a diene polymer in an organic solvent and at epoxidizing it by reaction with metachloroperbenzoic acid (mCPBA) as part of the process. epoxidizing agent for about two hours at room temperature, in the presence of a catalyst. It is thus possible to achieve epoxidation rates of the order of 12% with yields greater than 90%.

Bulk processes also react diene polymers with a peracid which can be produced in-situ or ex-situ. The "bulk" processes can be carried out in two different ways: the polymer, which always remains in the solid state, can react in bulk or reduced to the state of granules or powder. If the polymer is transformed into granules or powder, the epoxidation reaction is carried out in a stirred reactor to generate a suspension of the polymer in a solution of the peracid. The reaction can also be carried out in an extruder fed with granules. Otherwise, when the diene polymer is in bulk, the reaction can be carried out in a kneader or else an extruder.

Thus, EP 0810237 A1 describes a bulk epoxidation process according to which the diene polymer is in the form of powder or granules. The polymer is suspended in an organic solvent which should not dissolve the polymer, for example ethyl acetate. Peracetic acid or performic acid, formed in situ, is used as an epoxidizing agent and reacts for several hours. An epoxidation rate of 0.2% to 4% is obtained. Similarly, EP 1403 287 A1 describes solid phase epoxidation with peracetic acid. A diene polymer is suspended in water with talc and is heated above 30 ° C. A solution of peracetic acid in ethyl acetate is gradually added and the reaction takes place over several hours. The examples show that epoxidation rates of 1.5% to 3.0% are achieved.

The process described in RU 2509780 C1 was developed for the epoxidation of polybutadiene fibers formed by electrospinning. The fibers are suspended in a stirred reactor in a mixture of a carboxylic acid and hydrogen peroxide in the presence of a catalyst. The various epoxidizing agents are formed in situ. The epoxidation time varies from one to four hours and the temperature from 10 ° C to 30 ° C. Following the reaction, the fibers are washed with distilled water and dried under vacuum. Variable epoxidation rates are obtained depending on the reaction conditions and are between 1 and 8% with low yields of less than 30%.

Document CN 1113906 C, which deals with the bulk epoxidation of 1,4-trans polyisoprene, describes epoxidation rates greater than 20% in a time reduced to one hour. However, it should be noted that the rate of epoxidation was measured indirectly by the consumption of the epoxidizing agent. However, this consumption can be linked to side reactions and not only to epoxidation. Also, the effective epoxidation rates given in this document are uncertain.

The documents JP5598365 B2 and JP5541125 B2 describe processes for the bulk epoxidation of diene polymers used in bulk without prior shaping. In the examples, the diene polymer is contacted first with stearic acid on heated rollers and, after a number of passes, with hydrogen peroxide. Different epoxidation rates are obtained varying from 0.8% to less than 3% depending on the temperature used in the mixer set at 50 ° C or 60 ° C.

Document CN 1263902 A describes an epoxidation process according to which the diene polymer can be loaded in bulk into an internal mixer of the Banbury type or an extruder, in the absence of any solvent. A solid peracid in the presence of a dispersion additive is also introduced into the mixer or the extruder. By way of example, polybutadienes are epoxidized in small internal laboratory mixers with solid phthalic monoperacid in the presence of talc for a period of 15 minutes at temperatures of 20 ° C, 25 ° C and 30 ° C. The epoxidation rates measured are between 5 mol% and 8 mol%, however without specifying the measurement protocol. Assuming that it is the epoxy groups which are assayed for this measurement, the epoxidation yields are between 50% and 70%. It emerges from the study of the prior art that it is not easy, with a mass epoxidation process, to achieve epoxidation rates as high as those obtained during the “solution” process and this in times compatible with an implementation on an industrial scale. It also emerges from the study of the state of the art that when satisfactory epoxidation rates can be obtained in bulk, they are obtained with an insufficient yield for a productive, economically profitable process.

The problem which the invention proposes to solve is therefore to provide a process for the mass epoxidation of diene polymers making it possible to obtain epoxidation rates of the same order as those obtained “in solution” in an acceptable time for a setting. implemented on an industrial scale.

The object of the invention is also to provide a process for the mass epoxidation of diene polymers which is productive and compatible with an economically profitable industrial application exhibiting a satisfactory yield.

From this point of view, the object of the invention is also to provide an epoxidation process that is simple to implement.

Disclosure of the invention

The inventors have developed a process for the mass preparation of an epoxidized diene polymer of simple and productive production, compatible with deployment on an industrial scale which makes it possible to achieve epoxidation rates of the order of those obtained. “In solution” with a high yield, for example greater than 80%, and this in a short time.

Thus, a first object of the invention is a process for the mass preparation of an epoxidized diene polymer which comprises, in a tool for processing rubber, bringing a diene elastomer into contact with a diene agent. A peracid type epoxidation in solid form, which epoxidizing agent is introduced in at least two times. The epoxidation reaction according to this process can take place at room temperature and for a short time, which in some cases can be less than one hour.

The process for the mass preparation of an epoxidized diene polymer according to the invention comprises

- loading a diene polymer into a rubber processing tool,

- the addition, at least twice, of an epoxidizing agent chosen from solid peracids,

- mixing after each addition of epoxidizing agent in the processing tool.

Preferably, according to the process of the invention, the diene polymer is a diene elastomer chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene-styrene copolymers (SBR), butadiene-ethylene copolymers, butadiene-ethylene-styrene copolymers, isobutene-isoprene copolymers, isoprene-styrene copolymers (SIR), isoprene-butadiene copolymers (BIR) and isoprene-butadiene-styrene (SBIR) copolymers.

Preferably, according to the process of the invention, the tool for processing the rubber is a roller mixer. Preferably then, the process comprises, after loading the diene polymer, a step of repeatedly passing the diene polymer over the rollers in order to uniformly cover said rolls with a continuous layer of polymer.

Preferably, according to the method of the invention, the mixer is equipped with a temperature regulation device.

Preferably, according to the process of the invention, the epoxidizing agent is solid in the form of powder, granules or any other similar form.

Preferably, according to the process of the invention, the epoxidizing agent is chosen from aromatic peracids, preferably from perbenzoic acid and its derivatives and monoperphthalic acid and its derivatives, more preferably from halogenated perbenzoic acids. Most notably, the epoxidizing agent is metachloroperbenzoic acid.

Preferably, according to the process of the invention, the total amount of epoxidizing agent added is at most 100 mol% and greater than 0 mol%, more preferably it is at least 5 mol%. Preferably, according to the process of the invention, the amounts of epoxidizing agent introduced at each addition are less than or equal to a quantity Qm ± 1 mol% of epoxidizing agent making it possible to achieve a stabilized epoxidation yield. at least 85%, preferably at least 90%, more preferably 100%, in a single addition.

Preferably, according to the process of the invention, the number of additions or stages of addition of the epoxidizing agent is greater than or equal to the whole part of the ratio of the total amount of epoxidizing agent to an amount Qm, Qm being an amount of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, in a single addition.

Preferably, according to the process of the invention, the mixing time after each addition of epoxidizing agent is at least equal to the time tm necessary to achieve the stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, for a given quantity Qm of epoxidizing agent added all at once, Qm being a quantity of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, in a single addition.

Preferably, according to the process of the invention, the quantity of epoxidizing agent introduced at each addition is less than or equal to a quantity denoted Qm ± 1 mol% of epoxidizing agent, the number of addition steps of the epoxidizing agent is greater than or equal to the whole part of the ratio of the total amount of epoxidizing agent to the amount Qm and the mixing time after each addition of epoxidizing agent is preferably at least equal to the time tm, Qm being an amount of epoxidizing agent making it possible to achieve this stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, in a single addition and tm is the time required to achieve this stabilized epoxidation yield.

Preferably, according to the process of the invention, the amount of epoxidizing agent introduced at each addition is at least 1.5 mol% and less than 8 mol%. Preferably, according to the process of the invention, the number of epoxidizing agent additions is greater than or equal to 2 and less than or equal to 10.

Preferably, according to the process of the invention, the mixing time after each addition of epoxidizing agent is less than or equal to 20 minutes,

Preferably, according to the process of the invention, one of the following characteristics is observed, preferably two, preferably three, preferably four, preferably five, preferably all: the diene polymer is a polymer of butadiene, preferably a polybutadiene , the tool for processing the rubber is a roller mixer, the epoxidizing agent is a perbenzoic acid or a derivative thereof, preferably metachloroperbenzoic acid, the amount of epoxidizing agent added to each addition step is less than or equal to a quantity Qm, Qm being a quantity of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably of 100%, in a single addition, preferably Qm being at least 1.5 mol% and less than 8 mol%, more preferably at most 5 mol%, the number of additions of epoxidizing agent is greater than or equal to the integer part of the the total amount of epoxidizing agent at the amount Qm, the number of additions preferably being less than or equal to 5, more preferably less than or equal to 4, the mixing time after each addition of epoxidizing agent is greater than or equal to a time tm, tm being the time necessary to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, for a quantity Qm of agent of epoxidation added all at once, preferably tm being at least 3 minutes.

Description of figures

Figure 1 is a graph illustrating the evolution of the yield as a function of time of an epoxidation reaction of a polybutadiene in a roller mixer by adding an epoxidizing agent all at once.

Figure 2 is a graph illustrating the evolution of the yield and the evolution of the epoxidation rate as a function of time of an epoxidation reaction of a polybutadiene in a roller mixer by successive addition of an epoxidizing agent according to the invention.

detailed description

In the present description, any interval of values designated by the expression “between a and b” represents the range of values greater than “a” and less than “b” (that is to say limits a and b excluded) while any range of values designated by the expression "from a to b" signifies the range of values going from "a" to "b" (that is to say including the strict limits a and b).

In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are molar percentages (%). In the present description, the term “mass process” is understood to mean a process carried out in a reaction medium not comprising a solvent.

The diene polymers and other compounds mentioned in the description can be of fossil origin or biobased. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass.

Thus, the invention relates to a process for the bulk preparation of an epoxidized diene polymer which comprises

- loading a diene polymer into a rubber processing tool,

- the addition, in at least twice, of an epoxidizing agent chosen from solid peracids soluble in the diene polymer,

- mixing after each addition of epoxidizing agent.

By diene polymer is meant according to the invention, any type of polymer derived at least in part (i.e. a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).

The diene polymer can be chosen from the group consisting of thermoplastic diene polymers, thermoplastic elastomers, diene elastomers and mixtures thereof. Preferably, the diene polymer is chosen from diene elastomers.

Among the diene elastomers, mention may be made of elastomers comprising units of a 1,3-diene monomer. The term “1,3-diene monomer unit” is understood to mean a unit which results from the insertion of a 1,3-diene monomer into a growing polymer chain. In a known manner, the units of a 1,3-diene monomer can result from a 1,2 or 1,4 insertion of the 1,3-diene monomer in the polymer chain. In the case of a 1,4 insertion, they can be in the cis or trans configuration.

Mention may be made, by way of 1,3-diene monomer, of those having 4 to 8 carbon atoms, such as, for example, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, isoprene, piperylene. Also suitable are their halogenated derivatives, such as, for example, chloroprene. The 1,3-diene monomer can also consist of a mixture of these monomers, in which the 1,3-diene monomer units consist of the monomer units of each of the monomers making up the mixture. Preferably, the 1,3-diene is 1,3-butadiene, isoprene or a mixture thereof.

In particular, the diene elastomer is advantageously a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), polybutadienes (BR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene (SBR) copolymers, ethylene-butadiene copolymers, ethylene-butadiene-styrene copolymers, isoprene-butadiene (BIR) copolymers. , isoprene-styrene (SIR) copolymers, isoprene-butadiene-styrene (SBIR) copolymers and mixtures of such copolymers.

The above diene elastomers can be, for example, block, random, sequenced or microsequenced. They can be modified in particular by coupling or starring. The term “rubber processing tool” is understood to mean a mixer suitable for mixing reaction media of high viscosity such as that of bulk diene elastomers of the type of those described above.

Thus, the mixer can be a roller mixer, an extruder, a mixer equipped with a stirring system such as those described in the book David B. Todd, Mixing of Highly Viscous Fluids, Polymers, and Pastes, in Handbook of Industrial Mixing: Science and Practice, EL Paul, VA Atiemo-Obeng, and SM Kresta, Editors. 2004, John Wiley and Sons. Page 998, Page 1021, more particularly a double Z-arm mixer, an internal mixer with meshing rotors, other internal mixers ....

By roller mixer is understood in the sense known to those skilled in the art any type of external mixer having two horizontal parallel rollers, which can be cooled or heated, rotating in the opposite direction, usually at different speeds, their spacing being adjustable, and allowing chewing and mass mixing of a polymer or a polymer composition.

By extruder in the context of the invention, is meant an extruder or co-extruder provided with at least two injection points along its mixing cavity in order to be able to add the epoxidizing agent in at least twice the amount. along the progressive path of the polymer in said cavity. In order to control the heat of the epoxidation reaction, the extruder can also be fitted with a cooling system over all or part of the length of the mixing cavity and have a specific profile allowing self-heating to be minimized.

By double Z-arm mixer (or sigma) in the context of the invention is meant, for example, Z or sigma paddle mixers equipped with a discharge screw such as "sigma blades mixer-discharge screw type" marketed by the company Battaggion SPA, “extrusion-kneader” marketed by the company Aachener Misch- und Knetmaschinenfabrik Peter Küpper GmbH & Co. KG, “double-z-kneader with extrusion screw” marketed by the company Hermann Linden Maschinenfabrik GmbH & Co. KG. , “Mixer extruders”, marketed by Aaron Process Equipment Company.

In the context of the invention, the term “internal mixer with intermeshing rotors” means for example a mixer as described in document US Pat. No. 4,775,240 and sold under the name “VIC” (Variable Intermeshing Clearance, that is to say internal mixer with intermeshing rotors and variable clearance).

Other internal mixers include, for example, instrumented laboratory mixers of the Measuring Mixer 350 type marketed by the company Brabender.

According to a preferred embodiment of the invention, the tool for processing the rubber is a roller mixer. The choice of such a mixer makes it possible to better control the heat of the reaction, the mixer being open.

Preferably, after loading the bulk diene polymer into the rubber processing tool, the latter is kneaded for a few minutes. The purpose of this step is to relax the polymer for better incorporation of the epoxidizing agent. According to the embodiment of the invention according to which the mixer is a roller mixer, the kneading step is carried out by repeatedly passing the diene polymer over the rollers until the rolls are uniformly covered with a continuous layer of polymer. .

Thus, preferably according to this embodiment, the polymer is kneaded by repeated passage over the rollers until a continuous sheet is formed uniformly covering the rolls (also called sleeving). This mixing or sleeving step can last several minutes. Its duration depends in particular on the nature of the diene polymer and on the temperature. By way of illustration, this step can last up to 20 minutes, preferably up to 10 minutes.

At the end of this mixing time, the epoxidizing agent is added in at least twice.

The epoxidizing agent is introduced into the rubber processing tool in the solid state in the form of powder, granules or other similar form.

The epoxidizing agent is advantageously a compound with strong oxidizing power. Preferably, the epoxidizing agent is an organic peracid. By way of organic peracids, mention may be made of aliphatic percarboxylic acids and aromatic percarboxylic acids.

Preferably, the epoxidizing agent is an aromatic percarboxylic acid. More preferably then, the epoxidizing agent is chosen from perbenzoic acid and its derivatives and monoperphthalic acid and its derivatives. Mention may be made, as derivatives of perbenzoic acid, of halogenated perbenzoic acids and nitrated perbenzoic acids. Among these derivatives of perbenzoic acid, most particularly preferred is metachloroperbenzoic acid as an epoxidizing agent.

The epoxidizing agent is added sequentially at least twice to the mixer in order to maintain a satisfactory epoxidation yield. This addition in several stages makes it possible to achieve a yield greater than or equal to 85%, preferably greater than or equal to 90%. This increases the productivity of the process according to the invention compared to the bulk processes of the prior art.

The total amount of epoxidizing agent used in the process according to the invention is not limited and depends on the desired epoxidation rate. The total amount of epoxidizing agent added is greater than 0 mol% expressed relative to the total number of moles of carbon-carbon double bonds of the diene polymer. However, advantageously, the total amount of epoxidizing agent is at least 5 mol%. Although not having an upper limit, the total amount of epoxidizing agent added is preferably at most 100 mol%. According to certain variants of the process, the total amount of epoxidizing agent added is at most 50 mol%. According to other variants of the process, the total amount of epoxidizing agent is at most 25 mol%, preferably at most 15 mol%. Thus, advantageously, the total amount of epoxidizing agent is at least 5 mol% and at most 15 mol%.

Those skilled in the art will know how to determine the total amount of epoxidizing agent necessary to obtain the desired rate of epoxidation of the diene polymer, in particular the total amount of epoxidizing agent may correspond to the desired rate of epoxidation. The total amount of epoxidizing agent is the sum of the amounts of epoxidizing agent introduced at each addition. Advantageously, according to one implementation of the invention, the quantity of epoxidizing agent introduced at each addition is less than or equal to a quantity denoted Qm of epoxidizing agent. This quantity Qm is a quantity of epoxidizing agent making it possible to achieve, in a single addition, a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, for a diene polymer given in the same rubber processing tool.

According to the invention, the amount of epoxidizing agent added at each addition step has no minimum limit. It is preferable to distribute the amounts of epoxidizing agent as evenly as possible at each addition step.

It is up to a person skilled in the art to define the value of Qm allowing him to achieve a stabilized epoxidation yield of at least 85% depending on the epoxidizing agent or the elastomeric matrix to be epoxidized. This value Qm can be determined experimentally in a simple manner within the reach of those skilled in the art. A method for determining a value Qm is described below and in the examples which follow.

The number of additions or stages of addition of the epoxidizing agent, according to an advantageous implementation of the invention, is an integer greater than or equal to the ratio of the total amount of epoxidizing agent to the quantity Qm.

According to the invention, the number of additions of epoxidizing agent is at least 2. The maximum number of additions is not limited per se. However, for reasons of industrial reality and in order to limit the steps of the process, this number is preferably less than or equal to 10.

According to an advantageous implementation of the invention, the mixing time after each addition of epoxidizing agent is preferably at least equal to the time tm necessary to achieve the stabilized epoxidation yield of at least 85%, of preferably at least 90%, more preferably 100%, for a quantity Qm of epoxidizing agent added all at once in a tool for processing the rubber. The time tm is measured from the addition of the epoxidizing agent.

It is up to a person skilled in the art to define the value of tm allowing him to achieve a stabilized epoxidation yield of at least 85% depending on the epoxidizing agent or the elastomeric matrix to be epoxidized. The time tm can be determined experimentally in a simple manner within the reach of those skilled in the art. A method for determining tm is described below and in the examples which follow.

Although there is no maximum limit on the mixing time after each addition, too long a mixing time could result in a decrease in the productivity of the process.

The mixing time after each addition of epoxidizing agent is preferably less than or equal to 20 minutes.

According to a particularly advantageous implementation of the invention, the amount of epoxidizing agent introduced at each addition is less than or equal to a quantity denoted Qm of epoxidizing agent, the number of addition steps of l 'epoxidizing agent is an integer greater than or equal to the ratio of the total amount of epoxidizing agent to the amount Qm and the mixing time after each addition of epoxidizing agent is preferably at least equal to the time tm. According to this implementation, it is possible to further optimize the epoxidation yield of the process according to the invention for high epoxidation rates.

Those skilled in the art will understand that the values tm and Qm depend essentially on the nature of the diene polymer, more particularly on the ability of its carbon-carbon double bonds to be epoxidized, on the nature of the epoxidizing agent, operating conditions ...

An amount Qm and a time tm can be determined experimentally in a simple manner within the abilities of those skilled in the art. Qm and tm can be determined by carrying out, in the same rubber processing tool and under the same operating conditions, in particular of set temperature, of mixing time, as well as of the operating parameter of the mixer, the epoxidation of a same diene polymer with Qi quantity of the same epoxidizing agent added at one time. Several Qi amounts of the epoxidizing agent can be tested. The evolution as a function of time of the yield of the epoxidation reaction is studied for a quantity Qi of epoxidizing agent introduced at one time. The yield of the reaction is determined according to the method described later. The evolution of this function forms an asymptotic type curve whose asymptote is horizontal (see Figure 1 for example). The term “stabilized epoxidation yield” is then understood to mean the value on the ordinate of the horizontal asymptote to this curve. A quantity Qi = Qm corresponds to a quantity of a given epoxidizing agent for which the value on the ordinate of the asymptote is greater than or equal to 85%, preferably at least 90%, more preferably 100%. The time tm corresponds to the time necessary, from the addition of the epoxidizing agent, for a determined quantity Qm of agent, to arrive at the asymptote, that is to say to achieve a yield d epoxidation stabilized by at least 85%, preferably at least 90%, more preferably 100%.

By way of illustration and with reference to FIG. 1, two epoxidation tests of a polybutadiene were carried out in the same roller mixer and under the same operating conditions (in particular of the tool for processing the rubber, of set temperature, sleeving time, as well as the speed and spacing of the tool rollers). For each of these tests, a certain quantity Qi of epoxidizing agent (metachloroperbenzoic acid or m-CPBA) is introduced all at once into the mixer.

A first test consists of adding Qi = 8 mol% of m-CPBA all at once. The change in yield as a function of time, illustrated by the graph in FIG. 1, forms an asymptotic-type curve whose asymptote is horizontal and has a value on the ordinate of the order of 60%. Thus, the value Qi = 8 mol% is not a quantity Qm according to the invention, since the value on the ordinate of the asymptote is not greater than or equal to 85%.

The second test consists of adding 3.2 mol% of m-CPBA all at once. The change in efficiency as a function of time, illustrated by the graph in FIG. 1, forms an asymptotic-type curve whose asymptote is horizontal and has a value on the ordinate of the order of 90%. Thus, the value Qi = 3.2 mol% is a quantity Qm according to the invention, since the value on the ordinate of the asymptote is greater than or equal to 85.

The value of tm can be determined graphically for this quantity Qm = 3.2 mol%. The epoxidation yield of 90% is reached after 4 minutes from the addition of m-CPBA. So tm is 4 minutes. According to a variant of the invention, it is possible to use a compound for aid in the dispersion of the epoxidizing agent in the polymer. As dispersion aid compounds, mention may be made of inorganic powders such as talc, kaolin, silica and other similar compounds, as well as their mixtures. When such a compound is used, the epoxidizing agent and the dispersion aid compound are advantageously mixed prior to their use in the process of the invention.

According to the invention, the bulk epoxidation process can make it possible to achieve high epoxidation rates with high yields at set temperatures around the ambient. Thus, preferably the set point temperature of the epoxidation process according to the invention varies from 20 ° C to 30 ° C, preferably from 23 ° C to 27 ° C and is advantageously room temperature, ie of the order of 25 ° C, at normal pressure. Too high a temperature would have the drawback of possibly initiating the degradation of the epoxy groups formed or of possibly initiating the decomposition of the peracid by thermal means, thus reducing the yield of the process.

Since the epoxidation reaction is exothermic, the temperature can be maintained within these ranges if necessary by cooling the reaction system by means of cooling devices which may be fitted to the rubber processing tool. For example, for a roller mixer, the inside of the rollers may be hollow, thus allowing the circulation of liquids which serve to control the set temperature and to minimize local self-heating.

The use of a roller mixer as a rubber processing tool has the advantage, since it is open, of better controlling the thermal of the epoxidation process.

According to a particular implementation of the invention, the process has at least one of the following characteristics, preferably two, preferably three, preferably four, preferably five, preferably all: the diene polymer is a butadiene polymer, preferably a polybutadiene, the tool for processing the rubber is a roller mixer, the epoxidizing agent is a perbenzoic acid or a derivative thereof, preferably metachloroperbenzoic acid, the amount of agent of epoxidation added at each addition step is less than or equal to an amount Qm,, Qm being an amount of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90 %, more preferably 100%, in a single addition, which quantity Qm is preferably at least 1.5 mol% and less than 8 mol%, the number of additions of epoxidizing agent is a number integer greater than or equal to the ratio of the quantity tot ale of epoxidizing agent in the quantity Qm, preferably less than or equal to 5, more preferably less than or equal to 4, the mixing time after each addition of epoxidizing agent is greater than or equal to a time tm, tm being the time required to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, for a quantity Qm of epoxidizing agent added all at once, which tm is preferably at least 3 minutes.

According to this particular implementation of the invention, the process has at least one of the following characteristics, preferably two, preferably three, preferably four, preferably five, preferably all: the diene polymer is a polybutadiene, the tool for processing the rubber is a roller mixer, the epoxidizing agent is metachloroperbenzoic acid, the amount of epoxidizing agent added at each addition step is at least 1.5 mol% and less than 8 mol%, the number of epoxidizing agent additions is less than or equal to 5, more preferably less than or equal to 4, the mixing time after each addition of epoxidizing agent is greater or equal to a time tm is at least 3 minutes.

At the end of the epoxidation reaction, a bulk epoxidized diene polymer is recovered.

Advantageously, according to the process of the invention, it is possible to prepare an epoxidized diene polymer exhibiting a high epoxidation rate in view of the epoxidation rates attainable by the mass processes of the state of the art, with a yield of at least 85%, preferably at least 90%, in a short time.

The epoxidized diene polymer obtained at the end of the process according to the invention can be used in various applications known to those skilled in the art depending on its nature.

Examples

I. Measurement methods used

La. Determination of the epoxy groups in the epoxidized diene polymer:

The spectral characterization and measurements of the epoxidized BR polymer microstructure are carried out by liquid phase Nuclear Magnetic Resonance (NMR) spectroscopy.

For these measurements, a Bruker Avance III HD 400 MHz spectrometer is used, equipped with a Bruker cryo-BBFO z-grad 5 mm probe.

The ^X H experiments are recorded using a radiofrequency pulse with a tilting angle of 30 °, the number of repetitions is 64 with a recycling delay of 5 seconds.

The experiments are carried out at 25 ° C.

25 mg of sample are dissolved in 1 mL deuterated chloroform (CDCI ₃ ).

Structure of an epoxidized polybutadiene

The axis of the chemical shifts ¹ H is calibrated with respect to the signal of the protonated impurity of the solvent (CHCl 3) at d ¹ H = 7.2 ppm.

The chemical shifts of the signals characteristic of this matrix are presented in Table 1 of assignment of the ¹ H signals of epoxidized polybutadiene in CDCl3.

Table 1 d ¹ H (ppm) Assignments

-CH = (BR1-2)

6.00 - 5.00 CH = CH- (BR1-4)

5.00 - 4.60 = CH ₂ (BR1-2)

3.20 - 2.55 CH-CH- Epoxy

The quantifications were carried out from the integration of the 1D ¹ H NMR spectra using the Topspin software.

The integrated signals for the quantization of the different patterns are:

11 = between 6.0 and 5.00 ppm: 1H -CH = ethylenic of BR1-2 + 2H -CH = CH- ethylenic of BR1-4

12 = between 5.00 and 4.60 ppm: 2H = ethylenic CH2 of the BR1-2 units

13 = between 3.20 and 2.55 ppm: 2H -CH-CH- of the epoxy units.

They are then normalized as follows:

1H BR1-4 = (ll-l2) / 2 = A 1H BRl-2 = 12/2 = B 1H Epoxy = 13/2 = C

The quantification of the microstructure is carried out in molar percentage (mol%) as follows: mol% BR1-4 / BRepoxidated = A / (A + B + C)

mol% BR1-2 / Bepoxidized = B / (A + B + C)

Molar% Epoxy / Bepoxidized = C / (A + B + C) Epoxidation rate

The epoxidation rate measured is therefore the molar percentage ratio of epoxy group to the sum of the molar percentages of epoxy groups and of carbon-carbon double bonds (BR1-4 and BR1-2)

So :

Epoxidation rate measured (%) = (C / (A + B + C)) x 100

I.b. Yield

The yield is calculated as being the epoxidation rate ratio measured to the target epoxidation rate.

So :

Yield (%) = (Measured epoxidation rate / Targeted epoxidation rate) x 100 With

• target epoxidation rate = nb of mole of m-CPBA / nb of mole of carbon-carbon double bonds

• Nb of moles of C = C double bonds = Nb of moles of the diene part, ie the number of moles of BR in the examples.

• Nb of moles of the diene part = mass of the diene part (g) / molar mass of the diene unit,

Either in the examples

Nb of mole of BR = mass of BR (g) / molar mass of a polybutadiene unit (54 g / mol)

II. Examples 1

II. at. Reagents:

BR: mass microstructure (0.5% unit 1.2, 97% unit 1.4 cis, 2.5% unit 1.4 trans) m-CPBA: metachloroperbenzoic acid at 172.57 g / mol m-CBA = metachlorobenzoic acid at 156.57g / mol m-CPBA used in the examples is pure at 77% by mass, the remainder being m-CBA

The epoxidation of BR by a peracid was studied in a Scamex 0 100 roller mixer with oil circulation.

II. b. Method of epoxidation of a BR with the addition at once of 8 mol% of m-CPBA 200g (3.70mol) of BR is injected into the roller mixer. As a result of the passage between the rollers, a BR film is obtained around the front roller and a bead is formed induced by the air gap and the difference between the speed of the front and rear roller. The air gap is the distance between the two rollers. It is set at 1mm and is kept constant throughout the mixing time.

The speed of the rear roller corresponds to 80% of the speed of the front roller which is fixed at 5 rpm and kept constant throughout the duration of the mixing. The setpoint temperature is set at 25 ° C.

- After 10 minutes a continuous film of gum is obtained.

- 66.40g of 77% pure m-CPBA is then injected (0.296 mol, i.e. 8 mol% of 3.70 mol of BR) in the bead and the epoxidation reaction begins.

- a rubber sample is taken from the rollers every minute for up to 5 minutes, then at 7, 10, 15 and 20 minutes, to measure the rate of epoxidation and the yield

NB: m-CPBA being pure 77% by mass, this represents 66.40g (i.e. 51.13 of m-CPBA and 15.27g of m-CBA)

II. b. BR epoxidation process with the addition of 3.2 mol% m-CPBA all at once

- 200g (3.70mol) of BR is injected first. As a result of the passage between the rollers, a BR film is obtained around the front roller and a bead is formed induced by the air gap and the difference between the speed of the front and rear roller. The air gap is the distance between the two rollers.

It is set at 1mm and is kept constant throughout the mixing time. The speed of the rear roller corresponds to 80% of the speed of the front roller which is fixed at 5 rpm and kept constant throughout the duration of the mixing. The setpoint temperature is set at 25 ° C.

- after 10 minutes a continuous film of gum is obtained

- 26.43 g of 77% pure m-CPBA is then injected (0.118 mol, or 3.2 mol% of 3.70 mol of BR) into the bead and the epoxidation reaction begins.

- A sample of gum from the rollers is taken every 5 minutes up to 30 minutes, then every 10 minutes up to 60 minutes, to measure the rate of epoxidation and the yield.

NB: m-CPBA being pure 77% by mass, this represents 26.43g (i.e. 20.35 of m-CPBA and 6.08g of m-CBA)

FIG. 1 illustrates the change in the yield as a function of time of the epoxidation reaction of polybutadiene in a roller mixer by adding an epoxidizing agent all at once. The two curves shown in the graph illustrate, for one, the addition at once of 8 mol% of m-CPBA and for the other the addition of 3.2 mol% of m-CPBA at once.

FIG. 1 shows that the introduction at once of an amount of 8 mol% of m-CPBA does not make it possible to achieve a yield greater than 75%, even while prolonging the reaction time. The change in yield as a function of time describes an asymptotic curve whose asymptote, reached after about 7 minutes, is horizontal with a value on the ordinate of the order of 60%, i.e. an epoxidation rate 4.8%.

FIG. 1 also shows that the introduction at one time of an amount of 3.2 mol% of m-CPBA makes it possible to achieve a yield greater than 85%. The change in yield as a function of time describes an asymptotic curve which reaches its asymptote after 4 minutes from the addition of the epoxidizing agent. The asymptote is horizontal with a value on the ordinate of the order of 90%. However, only a low epoxidation rate of 2.9% is achieved with such a high yield.

Examples 2

III. at. BR epoxidation process with sequenced addition of 8 total mol% of m-CPBA according to the invention. The operating conditions are identical with regard to the roller mixer used, the nature of the BR, the set temperature, etc. as for the two preceding processes.

Determination of Qm, tm and N

The curve in FIG. 1 is used, which illustrates the change in the yield as a function of time of the epoxidation reaction of polybutadiene in a roller mixer by adding an epoxidizing agent all at once. It is noted that the introduction at once of an amount of 3.2 mol% of m-CPBA makes it possible to achieve a yield of the order of 90%. The value of Qm is then fixed at 3.2 mol%. Thus, to achieve an epoxidation yield greater than 85%, the amount of m-CPBA to be added at each addition step is less than or equal to 3.2 mol%.

The asymptote of the curve is reached after 4 minutes from the addition of the epoxidizing agent tm is therefore 4 minutes. Thus the mixing time D after each addition is at least 4 minutes.

It is desired to epoxy a BR with 8 total mol% of m-CPBA. The number of addition N is at least 3 (integer greater than or equal to 8 / 3.2).

We set N = 3 and D = 10 minutes. The amount of m-CPBA to be added at each addition step is less than or equal to 3.2% (Qm), the sum of the amounts added being equal to 8 mol%.

Epoxidation process

200g (3.70mol) of BR is injected into the roller mixer. As a result of the passage between the rollers, a BR film is obtained around the front roller and a bead is formed induced by the air gap and the difference between the speed of the front and rear roller. The air gap is the distance between the two rollers. It is set at 1mm and is kept constant throughout the mixing time.

The rear roller speed corresponds to 80% of the front roller speed which is set at 5 rpm and kept constant during the process. The setpoint temperature is set at 25 ° C.

After 10 minutes a continuous film of gum is obtained, a first part (0.118 mol or 3.2 mol%) of the total peracid (m-CPBA) (0.296 mol) is injected into the bead and the epoxidation reaction begins at this instant denoted t0.

At tl = t0 + 10 minutes approximately a second part of the total peracid is injected (0.089mol or 2.4 mol%)

At t2 = t0 + 20 minutes the third and last part of the total peracid is injected (0.089mol or 2.4 mol%) a sample of gum is taken before each new addition of m-CPBA to measure the rate of epoxidation and the reaction yield.

FIG. 2 illustrates the evolution of the yield and of the epoxidation rate as a function of the time of the epoxidation reaction of polybutadiene in a roller mixer by addition in three stages of an epoxidizing agent, according to the invention. The two curves shown on the graph illustrate for one the evolution of the yield of the epoxidation reaction as a function of time and for the other the evolution of the epoxidation rate as a function of time when the addition of 8 mol% of m-CPBA is carried out in three times respectively of a first amount of 3.2 mol% and twice of 2.4 mol%. FIG. 2 shows that the introduction in several times of a total quantity of 8 mol% of m-CPBA makes it possible to achieve a yield of the order of 95% after 30 minutes of reaction. Figure 2 shows that the introduction in 3 times with mixing for 10 minutes at the end of each addition, of a total amount of 8 mol% of m-CPBA makes it possible to achieve a yield of the order of 95 % after 30 minutes of reaction. The evolution of the epoxidation rate shows that an epoxidation rate of 7.6% is reached.

It emerges from these tests that the process according to the invention, sequencing the addition of an epoxidizing agent, makes it possible to mass prepare an epoxidized diene polymer exhibiting a high epoxidation rate, of the same order as the epoxidation rates. obtained with epoxidation processes in solution, with a high yield which can reach values greater than or equal to 80%.

In fact, it is possible, for example, to envisage targeting BR epoxidation rates that are much higher than that of this test, in particular greater than 10%, by adding the epoxidizing agent m-CPBA in fractions of at most 3, 2 mol% until the target level is reached. Thus, it will be possible to obtain a high yield greater than or equal to 80% and an epoxidation rate close to the targeted epoxidation rate.

The process according to the invention is more productive than the bulk processes of the prior art and limits the stages of treatment of the polymer to be epoxidized and of recovery of the epoxidized polymer. The process according to the invention makes it possible to achieve higher mass polymer epoxidation rates than the mass processes of the prior art.

Claims

1. A process for the bulk preparation of an epoxidized diene polymer which comprises

- loading a diene polymer into a rubber processing tool,

- the addition, at least twice, of a solid epoxidizing agent,

- Mixing the diene polymer with the epoxidizing agent, after each addition of the epoxidizing agent in the tool for processing the rubber.

2. Method according to claim 1, characterized in that the diene polymer is a diene elastomer chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), copolymers of butadiene-styrene (SBR), butadiene-ethylene copolymer, isobutene-isoprene copolymers, isoprene-styrene copolymer (SIR), isoprene-butadiene copolymer (BIR) and isoprene-copolymer butadiene-styrene (SBIR).

3. Method according to any one of the preceding claims, characterized in that the implementation tool is a roller mixer.

4. Method according to the preceding claim, characterized in that the loading of the polymer into the roller mixer is followed by a step of repeated passage of the diene polymer in order to uniformly cover the rolls with a continuous layer of polymer.

5. Method according to any one of the preceding claims, characterized in that the epoxidizing agent is solid in the form of powder, granules or any other similar form.

6. Method according to any one of the preceding claims, characterized in that the epoxidizing agent is chosen from aromatic peracids, preferably from perbenzoic acid and its derivatives and monoperphthalic acid and its derivatives, more preferably. among halogenated perbenzoic acids, most particularly the epoxidizing agent is metachloroperbenzoic acid.

7. Method according to any one of the preceding claims, characterized in that the total amount of epoxidizing agent added is at most 100 mol% and greater than 0 mol%, more preferably it is at least 5 mol%. , which amount is expressed relative to the number of moles of carbon-carbon double bond of the diene polymer.

8. Method according to any one of the preceding claims, characterized in that the quantity of epoxidizing agent introduced at each addition is less than or equal to a quantity Qm of epoxidizing agent making it possible to achieve a yield of. epoxidation stabilized by at least 85%, preferably at least 90%, more preferably 100%, in a single addition.

9. Method according to any one of the preceding claims, characterized in that the number of additions or stages of addition of the epoxidizing agent is an integer greater than or equal to the ratio of the total amount of epoxidizing agent in an amount Qm of epoxidizing agent, Qm being an amount of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, plus preferably 100%, in a single addition.

10. Method according to any one of the preceding claims, characterized in that the mixing time after each addition of epoxidizing agent is at least equal to the time tm necessary to achieve the stabilized epoxidation yield of at least 85. %, preferably at least 90%, more preferably 100%, for a quantity Qm of epoxidizing agent added all at once, Qm being a quantity of epoxidizing agent making it possible to achieve this epoxidation yield stabilized by at least 85%, preferably at least 90%, more preferably 100%, in a single addition.

11. Method according to any one of the preceding claims, characterized in that the quantity of epoxidizing agent introduced at each addition is less than or equal to a quantity denoted Qm of epoxidizing agent, the number of steps d the addition of the epoxidizing agent is an integer greater than or equal to the ratio of the total amount of epoxidizing agent to the amount Qm and the mixing time after each addition of epoxidizing agent is preferably at less equal to the time tm, which Qm is an amount of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, in a single addition and which tm is the time required to achieve this stabilized epoxidation yield.

12. Method according to any one of the preceding claims, characterized in that the amount of epoxidizing agent introduced at each addition is at least 1.5 mol% and less than 8 mol%, which amount is expressed. relative to the number of moles of carbon-carbon double bond of the diene polymer.

13. Method according to any one of the preceding claims, characterized in that the number of additions of epoxidizing agent is greater than or equal to 2 and less than or equal to 10.

14. Method according to any one of the preceding claims, characterized in that the mixing time after each addition of epoxidizing agent is less than or equal to 20 minutes.

15. Method according to any one of the preceding claims, characterized in that it has at least one of the following characteristics, preferably two, preferably three, preferably four, preferably five, preferably all: the diene polymer is a polymer of butadiene, preferably a polybutadiene, the mixer is a roller mixer, the epoxidizing agent is a perbenzoic acid or a derivative thereof, preferably metachloroperbenzoic acid, the amount of epoxidizing agent added at each addition step is less than or equal in an amount Qm, Qm being an amount of epoxidizing agent making it possible to achieve a stabilized epoxidation yield of at least 85%, preferably at least 90%, more preferably 100%, in a single addition, which Qm is preferably at least 1.5 mol% and less than 8 mol% the number of additions of epoxidizing agent is an integer greater than or equal to the ratio of the total amount of agent d epoxidation at a quantity Qm of epoxidizing agent, the number of additions preferably being less than or equal to 5, more preferably less than or equal to 4, the mixing time after each addition of epoxidizing agent is greater or equal to a time tm, tm being the time necessary to achieve an epoxidation yield s tabilised at least 85%, at least 90%, more preferably 100%, for a quantity Qm of epoxidizing agent added all at once, tm preferably being at least 3 minutes.