Field of the invention

The invention relates to the field of modified diene-containing (co)polymers, in particular a modified butadiene-styrene copolymer that can be used as a flame retardant for polymer compositions based on expandable polystyrene. In particular, the invention relates to a modified diene-containing (co)polymer, a method for preparing thereof and the use of the same as a flame retardant for polystyrene, including expandable polystyrene.

Background

Flame retardants are widely used in products made of various polymers and polymer compositions, for example in products made of expandable polystyrene, to provide them with flame retardant properties [Stockholm Convention on Persistent Organic Pollutants, UNEP/POPS/POPRC.6/10, 15.10.2010] Such polymer compositions usually contain various low molecular weight brominated compounds, for example hexabromocyclododecane (HBCD), used as flame retardants. However, the results of many studies have shown that HBCD has tendency to bioaccumulation and is highly toxic and resistant to environmental factors [Stockholm Convention on Persistent Organic Pollutants, UNEP/POPS/POPRC.6/10, 15.10.2010, Article 4]. This has led to limited use of HBCD as flame retardant in order to reduce ecological risks.

Processing temperatures for some polymer compositions, for example based on expandable polystyrene [Stockholm Convention on Persistent Organic Pollutants, UNEP/POPS/POPRC.6/10, 15.10.2010, Article 74], are often very high and can result in the degradation of a flame retardant during processing a polymer composition. In such a case, polymer compositions lose their flame retardant properties, and decomposition products, such as HBr, are formed. Therefore, it is important that a flame retardant was thermally stable at processing temperatures of polymer materials and met the requirements of non-toxicity and environmental compatibility.

As an alternative of HBCD, more ecologically friendly flame retardants, as compared to HBCD, are known, which are prepared on the basis of diene-containing (co)polymers, in particular, butadiene-styrene copolymers. Examples of such flame retardant are brominated butadiene-styrene copolymers disclosed in application W02008021417 and patent RU2414479.

Thus, patent RU2414479 provides a heat-resistant brominated butadiene-styrene copolymer that can be used as a flame retardant in expandable and non-expandable polymer materials. Said brominated butadiene-styrene copolymer is characterized by a content of non-brominated non-aromatic double bonds of less than or equal to 15% based on the content of non-aromatic double bonds in the copolymer before bromination, as determined by 'H NMR spectroscopy and a 5% weight loss temperature of at least 200°C, as determined by thermogravimetric analysis (TGA).

The invention of patent RU2414479 also relates to a method for preparing the above-mentioned heat-resistant brominated copolymer, the method comprises:

a) providing a homogeneous reaction solution of copolymer, a brominating agent, in particular tetraalkylammonium tribromide, and a solvent;

b) aging the reaction solution under reaction conditions for a time sufficient for bromination of at least 85% of non-aromatic double bonds comprised in the copolymer; c) isolating the brominated copolymer by passing a filtrate through silica gel or an ion-exchange resin layer;

d) washing the filtrate with an aqueous solution of sodium hydrogen sulfite to neutralize a non-reacted brominating agent; and

e) isolating the brominated copolymer by precipitation in methanol.

In addition, the invention of patent RU2414479 provides a polymer mixture comprising said heat-resistant brominated butadiene-styrene copolymer and a molded article comprising said polymer mixture.

This flame retardant possesses low thermal stability at high processing temperatures of expandable polystyrene and a limited compatibility of highly brominated butadiene-styrene copolymers, which can make it difficult to obtain a homogeneous structure of expanded polystyrene in large-thickness products made thereof.

In addition, from the prior art (patent RU2530021) it is known that brominated and epoxidized butadiene-styrene copolymer can be used as a flame retardant for expandable polystyrene. According to this invention, the flame retardant is prepared by a method comprising:

a) epoxidizing a starting butadiene-styrene copolymer having a molecular weight of at least 700 g/mol such that at least a part of non-conjugated carbon-carbon double bonds is epoxidized; and

b) brominating at least a part of the remaining non-conjugated carbon-carbon double bonds by contacting the butadiene-styrene copolymer epoxidized in step (a) with quaternary ammonium tribromide to obtain a brominated and epoxidized butadiene- styrene copolymer.

The flame retardant obtained according to said invention is characterized by a molecular weight of at least 1500 g/mol, a bromine content of at least 35 wt.%, and a 5% weight loss temperature of at least 180°C.

However, despite the fact that said flame retardant contains epoxy groups capable of absorbing HBr released at high processing temperatures of polymer compositions based on expandable polystyrene, it has been found that such flame retardant affects the polymerization process and the yield of polystyrene granules, which is confirmed by comparative experiments provided below.

In addition, an example of polymer flame retardant for expandable polystyrene is hydroxybrominated butadiene-styrene copolymers disclosed, for example, in application WO2016123263.

The flame retardant according to application WO2016123263 is prepared by reacting butadiene-styrene copolymer with quaternary ammonium tribromide to brominate from 50 to 98% of repeating butadiene units in the starting copolymer, thus obtaining a partially brominated copolymer, and then by reacting the partially brominated copolymer with N-haloimide, for example N-chlorosuccinimide or N- bromosuccinimide, in the presence of water and a water-miscible solvent to halohydrate a part of repeating butadiene units, thus obtaining hydroxybrominated butadiene-styrene copolymer. The resulting hydroxybrominated butadiene-styrene copolymer comprises from 2 to 50 wt.% of butadiene units, which are hydroxybrominated, and from 50 to 98 wt.% of butadiene units, which are brominated, and has a 5% weight loss temperature of at least 250°C. This flame retardant has a high content of hydroxyl groups, which leads to a significant increase in the polarity of the flame retardant molecule, which, in turn, deteriorates the stability of the system during the preparation of polystyrene, thereby worsening the polystyrene particle size distribution, which is confirmed by the experiments provided below.

In addition, the method for preparing a flame retardant according to said invention is characterized by large amount of time spent in the step of preparing a hydroxybrominated butadiene-styrene copolymer, and inthe step of its isolation from the reaction mass, and the need to use expensive reagents, in particular, N-haloimide.

Thus, the prior art flame retardants based on diene-containing (co)polymer and methods for preparing thereof are not efficient enough and also require large economic and time costs.

In this connection, one of the prospective directions is the development of a flame retardant based on diene-containing (co)polymer that would be heat resistant, would meet requirements of environmental friendliness, and would provide polystyrene, including expandable polystyrene, with excellent flame retardant properties.

Summary of the invention

The objective of the present invention is to develop a modified diene- containing (co)polymer that can be used as a flame retardant for expandable polystyrene and a method for preparing thereof.

The prepared modified diene-containing (co)polymers are characterized by high heat resistance, in particular, a 5% weight loss temperature of at least 180°C; a molecular weight of at least 1500 g/mol and a halogen content of at least 35 wt.% based on the total weight of the (co)polymer, wherein said (co)polymers do not affect the process of polymerization and the process of the formation of polystyrene granules, and are highly compatible with polystyrene.

An additional technical result is that the flame retardant according to the claimed invention provides expandable polystyrene with flame retardant properties, which allows the expandable polystyrene comprising the flame retardant according to the claimed invention to be classified to moderately flammable materials of inflammability class B2 (according to Item 7 of Article 13 of "Technical regulations of fire safety requirements" (Federal Act of 22.07.2008, No. 123, in the edition of 29.07.2017).

This technical objective is addressed and the technical result is achieved by a modified diene-containing (co)polymer containing hydroxyhalogenated diene units in an amount of from 0.05 to 5 wt.% and halogen atoms in an amount of at least 35 wt.% based on the total weight of the (co)polymer.

In addition, the inventors have found that said modified diene-containing (co)polymer can be prepared by using, as a modified system, a mixture of halogen and water in the presence of an aliphatic alcohol. The modifying system enables hydroxyl groups and halogen atoms to be introduced into the structure of a starting (co)polymer.

The inventors have found that a modified diene-containing (co)polymer comprising a relatively low amount of hydroxyhalogenated diene units (units that contain a halogen atom and a hydroxyl group), in particular in an amount of from 0.05 to 5 wt.%, and comprising halogen atoms in an amount of at least 35 wt.% based on the total weight of the (co)polymer is heat resistant, does not affect the process of polymerization and the process of the formation of polystyrene granules, is well compatible with polystyrene, and provides expandable polystyrene with high flame retardant properties.

It is suggested that it is a low content of hydroxyhalogenated diene units that enable a balance between hydrophilic and hydrophobic properties in the molecule of a modified diene-containing (co)polymer, thus providing stability of the entire system during the process of preparing polystyrene, while not affecting the process of the formation of polystyrene granules and providing the polystyrene with high flame retardant properties.

The present invention provides a modified diene-containing (co)polymer comprising hydroxyhalogenated diene units and halogen atoms, wherein the (co)polymer can be used as a flame retardant in various polymer compositions, for example based on polystyrene, including expandable polystyrene.

Description of drawings

Figures 1-5 are intended to clarify the technical solutions disclosing the essence of the present invention. Fig.1 is a flowchart that shows the sequence of steps for preparing the modified diene-containing (co)polymer according to the present invention, through the step of epoxidation.

Fig.2 is a flowchart that shows the sequence of steps for preparing the modified diene-containing (co)polymer according to the present invention, by using a modifying system.

Fig.3 is the 'H NMR spectrum of the resulting styrene-butadiene copolymer containing hydroxyl groups and bromine atoms.

Fig.4 shows the distribution of bromine in polystyrene samples containing the modified diene-containing (co)polymer according to the present invention, as measured by X-ray fluorescence analysis (XRFA).

Fig.5 shows the distribution of the modified diene-containing (co)polymer according to the present invention in polystyrene, as measured by the method of scanning electron microscopy (SEM).

Detailed description of the invention

A detailed description of various aspects of embodiments of the present invention is provided below.

According to the present invention, the prepared modified diene-containing (co)polymer is a heat resistant modified diene-containing (co)polymer that is characterized by a weight-average molecular weight of at least 1500 g/mol, preferably from 2000 to 280000 g/mol, more preferably from 10000 to 150000 g/mol, most preferably from 60000 to 100000 g/mol, and by multiple non-conjugated carbon-carbon double bonds, wherein at least one of them (but less than all non-conjugated carbon- carbon double bonds) is subjected to modification, and wherein the modified diene- containing (co)polymer comprises at least 35 wt.%, preferably at least 60 wt.%, and more preferably at least 75 wt.% of halogen based on the total weight of the polymer, and at least one hydroxyhalogenated non-conjugated carbon-carbon double bond.

The term "heat resistance" as used herein means a 5% weight loss temperature of the modified diene-containing (co)polymer, as measured by thermogravimetric analysis (TGA) described below.

The prepared heat resistant modified diene-containing (co)polymer comprises hydroxyhalogenated diene units in an amount of from 0.05 to 5 wt.%, preferably from 0.1 to 3 wt.%, and more preferably from 0.15 to 2 wt.% based on the total weight of the (co)polymer.

Hydroxyhalogenated diene units in the modified diene-containing (co)polymer in an amount of from 0.05 to 5 wt.% and halogen atoms in said (co)polymer in an 5 amount of 35 wt.% based on the total weight of the (co)polymer ensure polystyrene granules having desired physicomechanical characteristics, increased compatibility of the (co)polymer flame retardant with polystyrene, and provides expandable polystyrene with high flame retardant properties.

Accordingly, a 5% weight loss temperature of the modified diene-containing 10 (co)polymer is at least 180°C, preferably at least 200°C, more preferably at least 220°C.

An example of the modified diene-containing (co)polymer prepared according to the present invention is, but is not limited to, a modified diene-containing (co)polymer of the general formula (1):

_, 15 wherein Ri to R3 are the same or different and can be hydrogen or a hydrocarbon group comprising 1 to 6 carbon atoms, for example an alkyl group; Hal is halogen; m, 1, and p can be the same or different and preferably l<m<37, 2<(l+p)<3680, more preferably 6<m<12, 610<(l+p)<1225, and most preferably 7<m<10, 735<(l+p)<985, n is the number of polymer units in a chain, preferably 50<n<450, more preferably 20 100<n<350, and most preferably 140<n<250.

According to the present invention, the modified diene-containing (co)polymer can be prepared by any method known from the prior art enabling introduction of hydroxyl groups and halogen atoms into the structure of a starting diene-containing (co)polymer.

25 The starting diene-containing (co)polymer for preparing a modified diene- containing (co)polymer can be conjugated diene polymers or copolymers. Suitable conjugated dienes are conjugated dienes comprising 4 to 12 carbon atoms, for example, 1,3 -butadiene, 2-methyl- 1,3 -butadiene (isoprene), 2-ethyl- 1,3- butadiene, 2, 3 -di(Ci-C5alkyl)- 1,3 -butadienes, such as 2, 3-dimethyl-l, 3-butadiene, 2,3- diethyl- 1 ,3 -butadiene, 2-methyl-3 -ethyl- 1 ,3 -butadiene, 2-methyl-3 -isopropyl- 1 ,3- butadiene, phenyl- 1,3 -butadiene, 1,3-pentadiene, 2,4-hexadiene, 2-methyl-pentadiene, 4-methyl-pentadiene, or mixtures thereof, and the like. 1,3-Butadiene or isoprene are preferable.

Suitable comonomers in the starting diene-containing (co)polymer are vinyl aromatic compounds, such as styrene, a-methyl styrene, ortho-, meta- and para-methyl styrene, 3 -vinyl toluene, ethylvinyl benzene, 4-cyclohexyl styrene, para-tert-butyl styrene, methoxystyrenes, vinyl mesitylene, divinyl benzene, 1 -vinyl naphthalene, 2,4,6-trimethyl styrene, and the like, or mixtures thereof. Styrene or a-methyl styrene are preferable.

Suitable conjugated diene polymers and copolymers comprise at least 30 wt.%, preferably at least 50 wt.%, and more preferably 70 wt.% of polymerized conjugated diene units.

Preferable (co)polymers used as the starting diene-containing (co)polymer are, for example, butadiene, butadiene-styrene, and butadiene-styrene-isoprene copolymers, wherein a butadiene-styrene copolymer, which can be a di- or triblock copolymer of styrene and butadiene, is most preferable.

Examples of commercially available diene-containing (co)polymers include, but are not limited to, butadiene polymers known under the trade names BR-1243 Nd, grade B (LP), BR-1243 Nd, grade B, and BR-1243 ND HV; butadiene-styrene block copolymers known under the trade names DST R 30-00, SBS L 30-01A, SBS R 30- 00A, DST L 30-01, and DST L 30-01 (SR); and a butadiene-styrene copolymer prepared by the method of solution polymerization, known under the trade names: DSSK-2560-M27 (grade AA), DSSK-2560-M27 BB (grade A), DSSK-4040-M27 (grade A), produced by PJC "SIBUR-Holding".

Suitable starting diene-containing (co)polymers have a weight-average molecular weight of at least 700 g/mol, preferably from 1000 to 400000 g/mol, more preferably from 2000 to 300000 g/mol, more preferably from 5000 to 200000 g/mol, more preferably from 20000 to 120000 g/mol, and most preferably from 20000 to 50000 g/mol, with a polydispersity index of from 0.8 to 3, more preferably from 1 to 1.8, and most preferably from 1.1 to 1.5, with the number of 1,2-units of at least from 10 to 100 wt.%, preferably at least from 50 to 99 wt.%, and more preferably from 60 to 80 wt.% per polydiene part of the (co)polymer.

According to the present invention, the modified diene-containing (co)polymer can be prepared by a method comprising the steps of:

a) dissolution: dissolving an optionally pre-ground starting diene-containing (co)polymer in an organic solvent;

b) epoxidation: adding an epoxidizing agent to the solution of the starting diene- containing (co)polymer in the organic solvent, prepared in step (a);

c) neutralization and separation: adding an aqueous solution of a neutralizing agent to the reaction mass obtained in step (b), and separating an aqueous layer and an organic layer;

d) halogenation: adding a halogenating agent, water and optionally an aliphatic alcohol to the organic layer obtained in step (c);

e) neutralization and separation: adding an aqueous solution of a neutralizing agent to the reaction mass obtained in step (d), and separating an aqueous layer and an organic layer;

f) precipitation: precipitating the modified diene-containing (co)polymer by adding an excess of an alcohol-precipitant to the organic layer obtained in step (e); and g) isolation: filtrating and then drying the precipitated modified diene-containing (co)polymer.

Dissolution step (a):

At this step, an optionally pre-ground starting diene-containing (co)polymer is dissolved in an organic solvent with stirring.

The starting diene-containing (co)polymer is optionally ground by any method known from the prior art, for example, using (knife, hummer, or rotor) grinders, (fluid or screw) millers, etc.

The starting diene-containing (co)polymer when dissolved is stirred by any method known from the prior art, for example, using a device equipped with a mixer or a static mixer at a temperature of from 10 to 50°C, preferably from 15 to 40°C, and more preferably from 20 to 30°C. Suitable solvents are, but are not limited to, organic solvents that preferably have a purity of 99% and more and are ethers, for example, tetrahydrofuran; halogenated saturated aliphatic hydrocarbons, for example, carbon tetrachloride, chloroform, dibromomethane, dichloromethane, 1,2-dichloroethane; cycloaliphatic hydrocarbons, for example, cyclohexane; aromatic hydrocarbons, for example, toluene; halogenated aromatic hydrocarbons, for example, bromobenzene, chlorobenzene, and dichlorobenzene. Preferable organic solvents are solvents which are liquid under conditions of the modification of the starting diene-containing (co)polymer and do not react with the modifying system or the starting (co)polymer. Tetrahydrofuran, chloroform, dichloromethane, dichloroethane, cyclohexane, and toluene are preferred as the solvent, wherein tetrahydrofuran, chloroform, and dichloromethane are most preferable.

The weight ratio of the organic solvent to the starting diene-containing (co)polymer is from 5:1 to 30:1, preferably from 8:1 to 20:1, and more preferably from 10:1 to 15:1.

The time of the dissolution process is at most 60 min, at most 50 min, at most 40 min, at most 30 min, at most 25 min, at most 20 min, at most 15 min, at most 13 min, at most 11 min, at most 9 min, at most 7 min, or at most 5 min.

The mass obtained in the dissolution step is a solution of the starting diene- containing (co)polymer in the organic solvent.

Epoxidation step (b):

In step (b), the epoxidation is carried out by adding an epoxidizing agent to the solution of the starting diene-containing (co)polymer obtained in step (a), thereby oxidizing non-conjugated carbon-carbon double bonds with the formation of epoxide groups.

According to the present invention, the epoxidizing agent is a pure compound comprising active oxygen, and a solution of such a compound in an organic solvent in which the amount of the epoxidizing agent is from 10 to 50 wt.%, preferably from 15 to 30 wt.%, and more preferably from 20 to 25 wt.%.

Suitable epoxidizing agents are, but are not limited to, peracids, for example, performic acid, peracetic acid, meta-chloroperbenzoic acid; and peroxides, for example, hydrogen peroxide; or mixtures thereof, including in the presence of a catalyst, for example, a molybdenum or tungsten derivative.

The epoxidizing agent can be dissolved in an organic solvent or a mixture of organic solvents that preferably have a purity of 99% and more and are ethers, for example tetrahydrofuran; halogenated saturated aliphatic hydrocarbons, for example chloroform, dibromomethane, dichloromethane, or 1 ,2-dichloroethane; cycloaliphatic hydrocarbons, for example cyclohexane; aromatic hydrocarbons, for example toluene; or halogenated aromatic hydrocarbons, for example bromobenzene, chlorobenzene, or dichlorobenzene. It is preferable to add the epoxidizing agent in the form of its solution in the same solvent that was used in step (a) to dissolve the starting diene-containing (co)polymer.

The epoxidizing agent is used in an amount sufficient for epoxidixing at most 6 mol.% of non-aromatic double bonds, preferably at most 2.5 mol.% non-aromatic double bonds, and more preferably at most 0.5 mol.% non-aromatic double bonds.

In the epoxidation step, the epoxidizing agent or a solution thereof is preferably dosed at a rate of 0.80 to 50 ml/min, preferably from 1 to 10 ml/min, and more preferably from 1.5 to 5 ml/min. A very high dosing rate leads to crosslinking of the polymer in the reaction mass, whereas a low dosing rate significantly increases the time of synthesis.

The epoxidation step is carried out in any known from the prior art batch or continuous process equipment. Suitable equipment is, but is not limited to, a continuous stirred tank reactor, a batch stirred tank reactor, and an autoclave equipped a mixer.

The epoxidation step is carried out at a temperature of from (-20) to 100°C, preferably from (-10) to 50°C, and more preferably from 0 to 20°C, under atmospheric pressure.

The epoxidation step can be carried out for any time sufficient to achieve a desired epoxidation level of the starting diene-containing (co)polymer described above. The time of the epoxidation step is preferably at least 15 min, at least 20 min, at least 25 min, at least 30 min, at least 45 min, at least 60 min, or at least 120 min.

The epoxidized reaction mass obtained in step (b) comprises a partially epoxidized diene-containing (co)polymer.

Neutralization and separation step (c): This step comprises neutralization of the reaction mass obtained in step (b), which comprises a partially epoxidized diene-containing (co)polymer, by adding a solution of a neutralizing agent, followed by washing the neutralized reaction mass with water and separating the aqueous layer and the organic layer comprising the partially epoxidized diene-containing (co)polymer.

The neutralizing agent can be, but is not limited to, an aqueous solution of a base known from the prior art, for example, sodium hydroxide, sodium thiosulfate, sodium bisulfite, sodium carbonate, etc.

The molar ratio of the neutralizing agent to the added epoxidizing agent is usually from 1 :1 to 3 : 1 , preferably from 1 :1 to 2 : 1 , and more preferably 1 : 1.

The neutralization step is preferably carried out at a temperature of from 15 to 50°C, preferably from 20 to 40°C, and more preferably from 25 to 30°C, under atmospheric pressure.

The washing with water is carried out with at least one-fold, preferably two-fold, and more preferably three-fold volume excess of water relative to the volume of the reaction mass subjected to neutralization, thereby separating the reaction mass into two layers: the organic layer comprising a partially epoxidized diene-containing (co)polymer and the aqueous layer.

The organic and aqueous layers are separated by any prior art method, for example, using a funnel, a separator, or a gravity tank.

Halogenation step (d):

In halogenation step (d), a halogenating agent, water, and optionally an aliphatic alcohol are added to the organic layer obtained in step (c), which comprises a partially epoxidized diene-containing (co)polymer.

Halogen in the halogenating agent is chlorine, bromine, or iodine used as an elemental compound as such or in the form of a solution in an organic solvent.

The halogenating agent is preferably elemental bromine (Br2) as such or its solution in an organic solvent with a bromine amount of at most 70 wt.%, more preferably at most 60 wt.%, and most preferably at most 50 wt.%. Suitable halogenating agents are also, but are not limited to, quaternary ammounium bromides, for example, phenyl triethylammonium bromide, benzyl trimethylammonium bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetra-n-butylammonium bromide, and quaternary phosphonium bromides, for example, tetramethylphosphonium bromide, tetraethylphosphonium bromide, tetrapropylphosphonium bromide, tetra-n-butyl-phosphonium tribromide, or a mixture thereof.

It is preferable to use, as the halogenating agent, elemental bromine (Efo) together with quaternary ammonium bromides or quaternary phosphonium bromides. In this case, the elemental bromine reacts with epoxy groups in the presence of water, which leads to the opening of epoxy rings and to the formation of hydroxybrominated diene units, and the use of a quaternary ammonium bromide or quaternary phosphonium bromide allows avoiding significant substitution of hydrogen for bromine in tertiary or allylic carbon atoms, which, in turn, has an effect on the heat resistance of the resulting modified diene-containing (co)polymer.

In the context of the present invention, water is, but is not limited to, distilled, deionized, demineralized, osmotic, or bidistilled water and is used in an equimolar amount relative to epoxy groups.

The used aliphatic alcohol can be, but is not limited to, an alcohol containing 1 to 6 carbon atoms, such as, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, or hexanol. Propanol, butanol, isobutanol, and pentanol are preferred as the aliphatic alcohol, wherein butanol, isobutanol, and pentanol are more preferable.

The molar ratio of the starting diene-containing (co)polymer to the halogenating agent and the aliphatic alcohol is from 1 :1.5:3 to 1 :5:3, more preferably from 1 :2:3 to 1 :4:3, and most preferably from 1 :2.5:3 to 1 :3:3. In addition, when elemental bromine is used together with quaternary ammonium bromide or quaternary phosphonium bromide as the halogenating agent, the molar ratio of elemental bromine to bromine atoms in quaternary ammonium bromide or quaternary phosphonium bromide is from 1 :1 to 1 :4, more preferably from 1 :2 to 1 :3, and most preferably from 1 :1 to 1 :1.5.

The halogenating agent, water, and the aliphatic alcohol can be added to the partially epoxidized diene-containing (co)polymer obtained in step (c) in any order. It is preferable to add first the aliphatic alcohol to the partially epoxidized diene-containing (co)polymer obtained in step (c), and then to add water and the halogenating agent. When a quaternary ammonium bromide or quaternary phosphonium bromide and elemental bromide are used together as the halogenating agent, the entire volume of quaternary ammonium bromide or quaternary phosphonium bromide in the form of its solution in an organicsolvent is at once added to the reaction mass.

The elemental bromine is preferably added in the form of its solution in an organicsolvent by dosing the solution to the reaction mass at a rate of from 0.80 to 50 ml/min, preferably from 1 to 10 ml/min, and more preferably from 1.5 to 5 ml/min. A very high dosing rate leads to local overheating of the reaction mass, an increase in its viscosity, which, in turn, can lead to a modified diene-containing (co)polymer with a low content (less than 35 wt.%) of halogen atoms.

The addition of the entire volume of the elemental bromine (B^) solution to the partially epoxidized diene-containing (co)polymer obtained in step (c) can lead to its crosslinking, local overheating of the reaction mass, and an increase in the viscosity of the reaction mass, which can also result in a modified diene-containing (co)polymer with a low content (less than 35 wt.%) of halogen atoms.

The halogenating agent can be dissolved in an organic solvent or a mixture of organic solvents that preferably have a purity of 99% and more and are ethers, for example, tetrahydrofuran; halogenated saturated aliphatic hydrocarbons, for example, chloroform, dibromomethane, dichloromethane, or 1 ,2-dichloroethane; cycloaliphatic hydrocarbons, for example, cyclohexane; aromatic hydrocarbons, for example, toluene; halogenated aromatic hydrocarbons, for example, bromobenzene, chlorobenzene, or dichlorobenzene. It is preferable to add the halogenating agent in the form of its solution in the same solvent that was used in step (a) to dissolve the starting diene-containing (co)polymer.

The halogenation step is carried out in any known from the prior art batch or continuous process equipment. Suitable equipment is, but is not limited to, a continuous stirred tank reactor, a batch stirred tank reactor, and autoclave equipped with a mixer, which are designed to work with highly corrosive environments.

The halogenation step of the partially epoxidized diene-containing (co)polymer obtained in step (c) is preferably carried out without exposure to light, for example, the halogenation process is carried out in dark glass vessels, in a foil-wrapped reactor, or in a metal reactor, in order to reduce the possibility of non-selective photocatalytic halogenation reactions. The halogenation step is carried out at a temperature of from 0 to 50°C, preferably from 20 to 45°C, and more preferably from 30 to 40°C, under atmospheric pressure.

The rate of stirring of the reaction mass after addition of the halogenating agent is from 50 to 600 rpm, preferably from 100 to 500 rpm, and more preferably from 200 to 300 rpm.

The halogenation step can be carried out for any time sufficient to achieve a desired halogenation level of the partially epoxidized diene-containing (co)polymer disclosed above. The time of the halogenation step is preferably at least 15 min, at least 20 min, at least 25 min, at least 30 min, at least 45 min, at least 60 min, or at least 120 min.

The reaction mass obtained after the halogenation step (d) comprises a target product, which is a modified diene-containing (co)polymer comprising hydroxyl groups and halogen atoms.

Neutralization and separation step (e):

This step comprises neutralization of the reaction mass obtained in step (d), which comprises a modified diene-containing (co)polymer, by adding a solution of a neutralizing agent, followed by washing the neutralized reaction mass with water and separating an aqueous layer and an organic layer comprising the modified diene- containing (co)polymer.

The neutralizing agent can be, but is not limited to, an aqueous solution of a base known from the prior art, for example, sodium hydroxide, sodium thiosulfate, sodium bisulfite, sodium carbonate, etc.

The molar ratio of the neutralizing agent to the added halogen is usually from 1 : 1 to 3 : 1 , preferably from 1 : 1 to 2: 1 , and more preferably 1 :1.

The neutralization step is preferably carried out at a temperature of from 15 to 50°C, preferably from 20 to 40°C, and more preferably from 25 to 30°C, under atmospheric pressure.

The washing with water is carried out with at least one-fold, preferably two-fold, more preferably three-fold volume excess of water relative to the volume of the reaction mass subjected to neutralization, thereby separating the reaction mass into two layers: the organic layer comprising a modified diene-containing (co)polymer and the aqueous layer.

The organic and aqueous layers are separated by any method known from the prior art, for example, using a funnel, a separator, or a gravity tank.

Precipitation step (f):

The modified diene-containing (co)polymer obtained in step (e) is precipitated by adding an alcohol-precipitant to the organic layer obtained in step (e) in a weight ratio of the alcohol-precipitant to the modified (co)polymer of from 1 :1 to 15:1, preferably from 3:1 to 10:1, and more preferably from 4:1 to 5:1.

Suitable alcohol-precipitants are, but are not limited to, aliphatic alcohols containing from 1 to 4 carbon atoms. Examples of such alcohols are, but are not limited to, methanol, ethanol, propanol, isopropanol, butanol, and isobutanol. Methanol and ethanol are preferred as the alcohol-precipitant.

Isolation step (g):

In isolation step (g), the modified diene-containing (co)polymer is purified from the residues of the solvent and alcohol-precipitant by filtration in any devices known from the prior art, for example, porous membrane filters, nutch filters, etc.

The filtration of the modified diene-containing (co)polymer is carried out at a temperature of from 20 to 40°C, inclusive.

Water and/or water vapor and the solvent and/or its vapor are removed from the modified diene-containing (co)polymer by drying said (co)polymer. The process of drying of the modified diene-containing (co)polymer may be carried out by physical methods usually used for separation and purification of organic compounds (removal a solvent under reduced pressure, vacuum drying, etc.) and by using drying agents that remove moisture by adsorption, formation of hydrates or chemical reactions with water and solvents.

The drying is preferably performed at a temperature of from 50 to 105°C and under a pressure of from 1 to 20 kPa.

In accordance with another embodiment of the invention, a modified diene- containing (co)polymer can be prepared by a method that comprises the steps of:

a) dissolution: dissolving an optionally pre-ground starting diene-containing (co)polymer in an organic solvent; b) modification: adding the components of a modifying system to the solution of the starting diene-containing (co)polymer in the organic solvent, obtained in step (a); c) neutralization and separation: adding an aqueous solution of a neutralizing agent to the reaction mass obtained in step (b) and separating an aqueous layer and an organic layer;

d) precipitation: precipitating the modified diene-containing (co)polymer by adding an excess of an alcohol-precipitant to the organic layer; and

e) isolation: filtrating and then drying the precipitated modified diene-containing (co)polymer,

wherein the method is characterized in that in modification step (b), the modifying system is a mixture of halogen and water at a molar ratio of halogen to water of from 1 :0.01 to 1 :1, preferably from 1 :0.5 to 1 :0.7 , and more preferably from 1 :0.25 to 1 :0.7 based on the total number of double bonds.

Dissolution step (a):

In this step, an optionally pre-ground starting diene-containing (co)polymer is dissolved in an organic solvent with stirring.

The starting diene-containing (co)polymer is optionally ground by any method known from the prior art, for example, using (knife, hummer, and rotor) grinders, (fluid and screw) millers, etc.

The starting diene-containing (co)polymer when dissolved is stirred by any method known from the prior art, for example, using a device equipped with a mixer or a static mixer at a temperature of from 10 to 50°C, preferably from 15 to 40°C, and more preferably from 20 to 30°C.

Suitable solvents are, but are not limited to, organic solvents that preferably have a purity of 99% and more and are ethers, for example, tetrahydrofuran; halogenated saturated aliphatic hydrocarbons, for example, carbon tetrachloride, chloroform, dibromomethane, dichloromethane, 1,2-dichloroethane; cycloaliphatic hydrocarbons, for example, cyclohexane; aromatic hydrocarbons, for example, toluene; halogenated aromatic hydrocarbons, for example, bromobenzene, chlorobenzene, and dichlorobenzene. Preferable hydrocarbon solvents are solvents which are liquid under conditions of the modification of the starting diene-containing (co)polymer and do not undesirably react with the modifying system or the starting (co)polymer. Tetrahydrofuran, chloroform, dichloromethane, dichloroethane, cyclohexane, and toluene are preferred as the solvent, wherein tetrahydrofuran, chloroform, and dichloromethane are most preferable.

The weight ratio of the organic solvent to the starting diene-containing (co)polymer is from 5:1 to 30:1, preferably from 8:1 to 20:1, and more preferably from 10:1 to 15:1.

The time of the dissolution process is at most 60 min, at most 50 min, at most 40 min, at most 30 min, at most 25 min, at most 20 min, at most 15 min, at most 13 min, at most 11 min, at most 9 min, at most 7 min, or at most 5 min.

The mass obtained in the above-mentioned dissolution step is a solution of the starting diene-containing (co)polymer in an organic solvent.

Modification step b):

In modification step (b), the components of a modifying system are added to the solution of the starting diene-containing (co)polymer obtained in step (a).

According to the present invention, the modifying system consists of halogen and water in the presence of an aliphatic alcohol at a mass ratio of halogen to water of from 1 :0.01 to 1 :1, preferably from 1 :0.5 to 1 :0.7 , and more preferably from 1:0.25 to 1 :0.7 based on the total number of double bonds.

The halogen is chlorine, bromine, or iodine in the form of an elemental compound as such or in the form of a solution in an organic solvent.

The halogen is preferably elemental bromine (Ete) as such or its solution in an organic solvent with a bromine amount of at most 70 wt.%, more preferably at most 60 wt.%, and most preferably at most 50 wt.%.

In the context of the present invention, water is, but is not limited to, distilled, deionized, demineralized, osmotic, or bidistilled water.

The used aliphatic alcohol can be, but is not limited to an alcohol containing 1 to 6 carbon atoms, such as, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, or hexanol. Propanol, butanol, isobutanol, and pentanol are preferred as the aliphatic alcohol, wherein butanol, isobutanol, and pentanol are more preferable.

The molar ratio of the starting diene-containing (co)polymer to the modifying system and the aliphatic alcohol is from 1 :1.5:3 to 1 :5:3, more preferably from 1 :2:3 to 1 :4:3, and most preferably from 1 :2.5:3 to 1 :3:3. The components of the modifying system and the aliphatic alcohol are added to the solution of the starting diene-containing (co)polymer in any order. It is preferably to add first the aliphatic alcohol to the solution of the starting diene-containing (co)polymer, and then to add water and halogen or its solution, or vice versa.

Halogen is preferably added in the form of its solution in an organic solvent by dosing the solution to the reaction mass. Halogen can be dissolved in the organic solvent or a mixture of organic solvents that preferably have a purity of 99% and more and are ethers, for example, tetrahydrofuran; halogenated saturated aliphatic hydrocarbons, for example, chloroform, dibromomethane, dichloromethane, or 1,2- dichloroethane; cycloaliphatic hydrocarbons, for example, cyclohexane; aromatic hydrocarbons, for example, toluene; halogenated aromatic hydrocarbons, for example, bromobenzene, chlorobenzene, or dichlorobenzene. Halogen is preferably dosed in the form of a solution in the same solvent that was used in step (a) to dissolve the starting diene-containing (co)polymer.

The halogen also can be dosed to the reaction mass in the form of a solution in the organic solvent defined above after premixing such a solution with water.

The rate of dosing the halogen solution or a mixture of the halogen solution with water is from 0.80 to 50 ml/min, preferably from 1 to 10 ml/min, and more preferably from 1.5 to 5 ml/min. A very high dosing rate leads to local overheating of the reaction mass, an increase in its viscosity, which in turn can result in a modified diene- containing (co)polymer with a low content (less than 35 wt.%) of halogen atoms.

The addition of the whole volume of the halogen solution to a solution of the starting diene-containing (co)polymer can lead to its crosslinking, local overheating of the reaction mass, and an increase in the viscosity of the reaction mass, which can also result in a modified diene-containing (co)polymer with a low content (less than 35 wt.%) of halogen atoms.

The modification step is carried out in any known from the prior art batch or continuous process equipment. Suitable equipment is, but is not limited to, a continuous stirred tank reactor, a batch stirred tank reactor, and autoclave with a mixer, which are designed to work with highly corrosive environments.

The modification step of the starting diene-containing (co)polymer is preferably carried out without exposure to light, for example, the modification process is carried out in dark glass vessels, in a foil-wrapped reactor, or in a metal reactor, in order to reduce the possibility of non-selective photocatalytic halogenation reactions.

The modification step is carried out at a temperature of from 0 to 50°C, preferably from 20 to 45°C, and more preferably from 30 to 40°C, under atmospheric pressure.

The rate of stirring of the reaction mass after addition of the modifying system is from 50 to 600 rpm, preferably from 100 to 500 rpm, more preferably from 200 to 300 rpm.

The modification step can be carried out for any time sufficient to achieve a desired modification level of the starting diene-containing (co)polymer disclosed above. The time of the modification step is preferably at least 15 min, at least 20 min, at least 25 min, at least 30 min, at least 45 min, at least 60 min, or at least 120 min.

The reaction mass obtained after modification step (b) comprises the target product, which is a modified diene-containing (co)polymer.

Neutralization and separation step (c):

This step comprises neutralization of the reaction mass obtained in step (b), which comprises a modified diene-containing (co)polymer, by adding a solution of a neutralizing agent, followed by washing the neutralized reaction mass with water and separating the aqueous layer and the organic layer comprising the modified diene- containing (co)polymer.

The neutralizing agent can be, but is not limited to, an aqueous non-alkaline solution known from the prior art, for example, sodium thiosulfate, sodium bisulfite, sodium carbonate or the like.

The molar ratio of the neutralizing agent to the added halogen is usually from 1:1 to 3:1, preferably from 1 :1 to 2: 1 , and more preferably 1 :1.

The neutralization step is preferably carried out at a temperature of from 15 to 50°C, preferably from 20 to 40°C, and more preferably from 25 to 30°C, under atmospheric pressure.

The washing with water is carried out with at least one-fold, preferably two-fold, and more preferably three-fold volume excess of water relative to the volume of the reaction mass subjected to neutralization, resulting in the separation of the reaction mass into two layers: an organic layer comprising a modified diene-containing (co)polymer and an aqueous layer.

The organic and aqueous layers are separated by any method known from the prior art, for example, using a funnel, a separator, or a gravity tank.

Precipitation step (d):

The modified diene-containing (co)polymer obtained in step (b) is precipitated by adding an alcohol-precipitant to the organic layer obtained in step (c), containing the modified diene-containing (co)polymer. The weight ratio of the alcohol-precipitant to the modified diene-containing (co)polymer is from 15:1 to 1 :1, preferably from 10:1 to 3:1, and more preferably from 5:1 to 4: 1.

Suitable alcohol-precipitants are, but are not limited to, aliphatic alcohols containing from 1 to 4 carbon atoms. Examples of such alcohols are, but are not limited to, methanol, ethanol, propanol, isopropanol, butanol, and isobutanol. Methanol and ethanol are preferred as the alcohol-precipitant.

Isolation step (e):

In isolation step (e), the modified diene-containing (co)polymer is purified from the residues of the solvent and alcohol-precipitant by filtration in any prior art devices, for example, in porous membrane filters, nutch filters, etc.

The filtration of the modified diene-containing (co)polymer is carried out at a temperature of from 20 to 40°C, inclusive.

Water and/or water vapor and a solvent and/or solvent vapor are removed from the modified diene-containing (co)polymer by drying said (co)polymer. The drying process of the modified diene-containing (co)polymer may be carried out by physical methods usually used for separation and purification of organic compounds (removal a solvent under reduced pressure, vacuum drying, etc.) and by using drying agents that remove moisture by adsorption, formation of hydrates or chemical reactions with water and solvents.

The drying is preferably carried out at a temperature of from 50 to 105°C and under a pressure of from 1 to 20 kPa.

The invention is clarified in Fig.l that shows a flowchart of preparing a modified diene-containing (co)polymer through the step of epoxidation, wherein 101 is a unit for the dissolution of a starting diene-containing (co)polymer, 102 is a unit for the epoxidation of the starting diene-containing (co)polymer, 103 is a unit for neutralization and separation, 104 is a unit for halogenation, 105 is a unit for neutralization and separation, 106 is a unit for precipitation, 107 is a unit for filtration, and 108 is a unit for drying.

According to the presented method, an optionally ground starting diene- containing (co)polymer (1) is delivered to dissolution unit 101 where it is mixed with an organic solvent (2) to obtain a solution of the starting diene-containing (co)polymer (3). Further, said (co)polymer solution (3) is delivered to epoxidation unit 102 that is also charged with an epoxidizing agent (4). After that, the partially epoxidized diene- containing (co)polymer (5) obtained in unit 102 is delivered to neutralization unit 103 that is charged with a neutralizing agent (6) and then with water (7) for washing the neutralized reaction mass, followed by separating an organic layer (9) comprising the partially epoxidized diene-containing (co)polymer and an aqueous layer (8). Then, the organic layer (9) comprising the partially epoxidized diene-containing (co)polymer is delivered to halogenation unit 104 that is also charged with water (10), an aliphatic alcohol (11), and a halogenating agent (12), thereby obtaining a reaction mass comprising a modified diene-containing (co)polymer that comprises hydroxyl groups and halogen atoms. After that, the obtained reaction mass (13) comprising the modified diene-containing (co)polymer is delivered to neutralization and separation unit 105 that is charged with a neutralizing agent (14) and then with water (15) for washing the neutralized reaction mass, followed by separating an organic layer (17) comprising the modified diene-containing (co)polymer and an aqueous layer (16). Then the organic layer (17) comprising the modified diene-containing (co)polymer is delivered to precipitation unit 106 that is also charged with an alcohol-precipitant (18) to precipitate the modified diene-containing (co)polymer. Further, the precipitated modified diene- containing (co)polymer (19) is sequentially delivered to filtration unit 107 and (20) to drying unit 108 to obtain the resulting product, which is a modified diene-containing (co)polymer (21). The method for preparing a modified diene-containing (co)polymer can comprise a unit of regeneration of the organic solvent that is further recycled to unit 101 of dissolving the starting diene-containing (co)polymer (not shown in Fig. 1).

The invention is disclosed in detail in Fig.2 that shows a flowchart of preparing a modified diene-containing (co)polymer by using a modifying system, wherein 201 is a unit of the dissolution of a starting diene-containing (co)polymer, 202 is a unit of the modification of the starting diene-containing (co)polymer, 203 is a unit of neutralization and separation, 204 is a unit of precipitation, 205 is a unit of filtration, and 206 is a unit of drying.

According to the presented method, an optionally ground starting diene- containing (co)polymer (1) is delivered to dissolution unit 201 where it is mixed with an organic solvent (2) to obtain a solution of the starting diene-containing (co)polymer (3). Further, said (co)polymer solution (3) is delivered to modification unit 202 that is also charged with a modifying system (4) and an aliphatic alcohol (5). After that, the modified diene-containing (co)polymer (6) obtained in unit 202 is delivered to neutralization unit 203 that is charged with a neutralizing agent (7) and then with water (8) for washing the neutralized reaction mass, followed by separating an organic layer (10) comprising a modified diene-containing (co)polymer and an aqueous layer (9). Then the organic layer (10) comprising the modified diene-containing (co)polymer is delivered to precipitation unit 204 that is also charged with an alcohol-precipitant (11) to precipitate the modified diene-containing (co)polymer. Further, the precipitated modified diene-containing (co)polymer (12) is sequentially delivered to filtration unit 205 and (13) to drying unit 206 to obtain the resulting product, which is a modified diene-containing (co)polymer (14). The method for preparing a modified diene- containing (co)polymer can comprise a unit of regeneration of the organic solvent that is further recycled to unit 201 of dissolving the starting diene-containing (co)polymer (not shown in Fig. 2).

The flowcharts in Figs 1 and 2 are only examples of the present invention and are not intended to limit the scope of the said invention.

The modified diene-containing (co)polymers prepared according to the present invention can be used as flame retardants in various polymers and polymer compositions, for example based on expandable polystyrene, to provide them with flame retardant properties. In addition, flame retardant should be compatible with polymer or a polymer composition.

According to the present invention, the modified diene-containing (co)polymer is added to expandable polystyrene in the step of preparing thereof by a method comprising preparing polystyrene by polymerizing styrene in the presence of a polymerization initiator, a polymerization stabilizer, etc., followed by expanding the prepared polystyrene (see, for example, US5086078).

In this case, the content of the modified diene-containing (co)polymer used as a flame retardant should not be lower than 0.5 weight parts, preferably not lower than 0.7 weight parts, and more preferably not lower than 1 weight part, otherwise, the efficiency of improving the flame retardant characteristics of the prepared expandable polystyrene is reduced.

In addition, compositions based on expandable polystyrene according to the invention can also include usual additives ensuring a desired complex of technological, physicomechanical, and operational characteristics, for example, antistatics, stabilizers, dyes, lubricants, fillers, adhesion reducing agents, etc.

According to the present invention, compositions based on expandable polystyrene can be used for the production of a large variety of products, such as constructive heat- and sound-insulators, in particular, heat- and sound insulation boards, permanent forms, car components, floatable articles, as well as raw materials for polystyrene foam blocks used in the construction of roads and bridges, and packing domestic appliances.

The modified diene-containing (co)polymer prepared according to the present invention can be used as a flame retardant in expandable polystyrene since this (co)polymer is characterized by a high heat resistance, in particular, a 5% weight loss temperature of at least 180°C measured by thermogravimetric analysis, does not affect the process of polymerization and the process of the formation of polystyrene granules, which is confirmed by the particle size distribution of the prepared polystyrene, and has a high compatibility with expandable polystyrene. In addition, the flame retardant prepared according to the present invention provides expandable polystyrene with flame retardant properties, which allows the expandable polystyrene comprising the flame retardant according to the claimed invention to be classified to moderately flammable materials of the inflammability class B2 (according to Item 7 of Article 13 of "Technical regulations of fire safety requirements" (Federal Act of 22.07.2008, No. 123, in the edition of 29.07.2017). The present invention is described in detail in the examples below. These examples are given only as an illustration of the present invention and are not intended to limit the scope of the present invention.

Embodiments of the invention

Methods of testing a modified ymer

Thermogravimetric analysis

A 5% weight loss temperature of a modified diene-containing (co)polymer was measured to determine its heat resistance by studying the thermal behavior of a sample(s) of the polymer by a method of simultaneous thermal analysis (STA) (combined methods of differential scanning calorimetry (DSC) and thermogravimetry (TG)) according to ISOl 1358 by using a STA 449 Jupiter NETZSCH device.

Experimental conditions: inert atmosphere (argon) at a temperature in the range of from 30°C to 600°C, a heating rate of 10°C/min.

Nuclear magnetic resonance method (NMR)

The polymer chain microstructure of a modified diene-containing (co)polymer was determined by NMR spectroscopy on hydrogen nuclei ('H) using a Bruker Avance III device (400 MHz). A solution was prepared by dissolving a 30 mg sample in 0.6 ml of deuterated chloroform. The number of scans on 'H nuclei was equal to 32.

Gel permeation chromatography (GPC)

Molecular-weight characteristics of the samples of a starting diene-containing (co)polymer and modified diene-containing (co)polymer were measured by low- temperature GPC according to ISO 16014-3 in Agilent 1200 liquid chromatography system with a refractometric detector.

Analysis conditions: eluent - tetrahydrofuran; temperature of dissolution and measurement - 40°C; eluent flow rate: 1.0 ml/min; column: PLgel Mixed-C (2-3 items). The calculation was made according to relative calibration of polystyrene standards (EasiVial PS-H 4ml, Agilent Technologies) using the Mark-Houwink constants for the (co)polymer, K = 0.000374, a = 0.699

Particle-size distribution of polystyrene

The particle-size distribution of polystyrene powder was measured using a test sieve shaker HAVER EML digital plus. The used test sieves had diameters of: 2.0; 1.6; 1.0; 0.70; 0.40; and 0.20 mm. The time of sieving was 15 min. The weight of powder on sieves was measured by the gravimetric method.

Compression of polystyrene samples

Samples were compressed in a hydraulic Collin press at a strength of 300 kN. A sample was previously kept in a drier at 50°C. Samples were compressed for 18 min with gradual heating to 190°C for 5 min under 50 bar; the sample was kept under a pressure of 50 bar at 190°C for 3 min. Then, the sample was cooled to 40°C under 50 bar for 10 min.

X-ray fluorescence analysis (XFRA)

The distribution of modified diene-containing (co)polymers in polystyrene was determined by measuring the intensity of the distribution of bromine atoms in a layer of a polystyrene sample.

The study was performed in a wavelength-dispersive X-ray fluorescence spectrometer SHIMADZU XRF-1800 with mapping function. A pretreated compressed polystyrene sample in the form of a plate with a thickness of 1 mm was placed in a special holder for local analysis with a mask diameter of 30 mm. Measurement parameters: measurement interval: 0.5 mm; voltage and current intensity of X-ray tube (Rh-anode): 40 kV, 95 mA; angle: 29.97° The bromine intensity was measured in each point, and histograms of the bromine distribution in the samples were generated according to these data.

Scanning electron microscopy (SEM)

The compatibility of a modified diene-containing (co)polymer prepared according to the present invention, comprising hydroxyl groups and bromine atoms, with polystyrene was determined by measuring the intensity of the distribution of bromine atoms in a layer of a polystyrene sample.

The study was performed using a FEI Quanta 3D scanning electron microscope at an accelerating voltage of 30 kV and DualBSD (back-scattering detector) at a low vacuum.

Flame-resistance test

Flame resistance of the samples of expandable polystyrene comprising a flame retardant was determined according to TT 2214-019-53505711-2010. Preparation of a sample: 40 mm were cut from a molded item and discarded. Then, 5 samples were cut with dimensions (190±l)*(90±0.5)x(20.0±0.5) mm so that a technological film, cracks, chips, and open bubbles didn’t form during the block formation,. The bottom face of the samples should be cut smoothly with sharp edges and should form right angles with side faces.

The method is based on the determination of the flame height of a burning sample for 20 seconds after the removal of the source of fire.

Preparation for testing:

The device was prepared and set into the operational mode. The ventilation in a chamber was turned off. The air velocity was measured with a thermal anemometer in the exhaust tube of the test chamber. The required value was from 0.5 to 0.8 m/s.

Before testing, the samples were conditioned for at least 14 days at a temperature of (23±5)°C and a relative air humidity of (50±20)% to constant weight.

Further, a mark was placed on the sample at a distance of 150 mm from the lower edge on the front and back faces. Then the samples were vertically hooked in the burning chamber to keep the measuring mark upward, and the bottom face was positioned in the same plane with the mark of the rack holder. Then the holder with the sample was vertically moved so that the stabilizer nozzle for flame exposure touched along the bottom face of the sample.

Then the burner was ignited, and the flame was adjusted using a template held from the side so that the height of the flame with a yellow glow was (20±1) mm. The height of the flame was checked before each exposure of the flame to the sample.

At the bottom of the test chamber, filter paper was placed under the sample in a wire box in 2 layers.

Testing:

The burning chamber was closed. A flaming burner turned at an angle of 45° was drawn sideways to the center of the free end (face) of the sample, after which a stopwatch was started. The sample was exposed to flame for 15 seconds, and then the burner was removed, and burning of the sample was observed. At the same time, the time from the beginning of the flame exposure to the moment when the top of the flame of the burning sample reached the measuring mark of 150 mm was measured, if before this the flame did not extinguish by itself. The tests were interrupted after 20 seconds (from the beginning of the process of treating the sample with a flame), and the maximum flame height and dripping (falling out of burning fragments) were estimated.

The test was considered completed if for each of 5 tested samples, the flame tip of a burning sample does not exceed the measuring mark before the 20 ^th second expires and if burning drops when fallen (falling out of burning fragments) bum on the filter paper no more than 2 seconds without burning the filter paper.

Example 1. Preparation of a modified butadiene-styrene copolymer comprising 0.05 wt.% of hydroxybrominated butadiene units

A solution of a starting butadiene-styrene copolymer (20g in 200 g of dichloromethane) was cooled to 0 to 5°C with stirring. 0.4 g of a 10 wt.% solution of m- chloroperbenzoic acid in dichloromethane (1 mol acid per 1 mol diene units to be epoxidized) was dosed to the cooled solution of copolymer. The temperature of the cooling bath was maintained at 0 to 5°C. After adding the entire volume of acid, the reaction mass was stirred at a given temperature for additional 30 minutes, then for 1 hour at 25°C, and for 1 hour at 50°C. After the epoxidation, the residues of m- chloroperbenzoic acid were neutralized with a solution of sodium hydroxide, and the reaction mass was washed with a three-fold volume excess of water, followed by separating the aqueous and organic layers.

Further, the organic layer was placed in a dark glass flask, 60 g of butanol and 5 g of water were added thereto, and a solution of bromine in dichloromethane (39.4 g of bromine per 50 ml of dichloromethane) was dosed for 10-20 minutes. After addition of the entire solution of bromine in dichloromethane, the stirring was continued for 30 minutes, then a 10% solution of sodium thiosulfate was added, and the bromine was neutralized for 60 minutes. After that, the inorganic layer was discharged, and the organic layer was washed with a three-fold volume excess of distilled water. Then, the modified butadiene-styrene (co)polymer containing hydroxyl groups and bromine atoms was precipitated in a five-fold volume excess of an alcohol, separated and dried by distilling off the solvent at 91°C and under a pressure of 10 kPa, followed by drying in a vacuum oven at 70°C and under 0.5 kPa.

The characteristics of the product prepared in Example 1 are shown in Table 1.

Example 2. Preparation of a modified butadiene-styrene copolymer comprising 0.15 wt.% of hydroxybrominated butadiene units The process was carried as disclosed in Example 1 , except for addition of 1.08 g of a 10 wt.% solution of m-chloroperbenzoic acid in dichloromethane.

The characteristics of the product prepared in Example 2 are shown in Table 1.

'H NMR spectrum of the prepared modified butadiene-styrene copolymer is shown in Fig.3.

‘H NMR spectrum (CDCb, d, ppm): 6.6-7.1 (styrene); 5.6 (1,4-butadiene); 5.1 (1,2-butadiene); 3.8-4.2 (brominated butadiene); 3.6 (hydroxyl groups).

Example 3. Preparation of a modified butadiene-styrene copolymer comprising 1.25 wt.% of hydroxybrominated butadiene units

The process was carried as disclosed in Example 1 , except for addition of 9 g of a 10 wt.% solution of m-chloroperbenzoic acid in dichloromethane to the reaction mass in the epoxidation step.

The characteristics of the product prepared in Example 3 are shown in Table 1.

Example 4. Preparation of a modified butadiene-styrene copolymer comprising 1.9 wt.% of hydroxybrominated butadiene units

The process was carried as disclosed in Example 1, except for addition of 13.7 g of a 10 wt.% solution of m-chloroperbenzoic acid in dichloromethane to the reaction mass in the epoxidation step.

The characteristics of the product prepared in Example 4 are shown in Table 1.

Example 5. Preparation of a modified butadiene-styrene copolymer comprising 5.5 wt.% of hydroxybrominated butadiene units (comparative)

The process was carried as disclosed in Example 1, except for addition of 35.99 g of a 10 wt.% solution of m-chloroperbenzoic acid in dichloromethane to the reaction mass in the epoxidation step.

The characteristics of the product prepared in Example 5 are shown in Table 1.

It should be noted that in the process of compressing the polystyrene plates to determine the compatibility of the flame retardant according to the present invention with polystyrene by the XRFA and SEM methods under a pressure of 50 bar, a shortterm change in the pressure to 58 bar was observed for the polystyrene samples containing the flame retarder according to Example 3 due to a low density of the polystyrene granules, which led to the adhesion of polystyrene granules, which, in turn, led to the impossibility of testing the expandable polystyrene on fire resistance. Example 6. Preparation of a brominated butadiene-styrene copolymer

A solution of a starting styrene-butadiene copolymer in dichloromethane (10 g copolymer per 150 g dichloromethane) was added to a 250 ml dark glass flask. Then, 30 g of butanol were added to the flask, after which a solution of 19.66 g of bromine in 20 ml of dichloromethane were dosed. The bromination reaction was conducted for 30 to 40 minutes. After the reaction was complete, a solution of sodium hydroxide (NaOH) was added to the flask, and neutralization was carried out for 1 hour. Then, the reaction mass comprising a brominated butadiene-styrene copolymer was washed with a threefold volume excess of water.

The resulting brominated butadiene-styrene copolymer was further filtered, then precipitated in isopropanol, dried by distilling off the solvent at a temperature of 30 to 95°C under 3 kPa, and further dried in a vacuum oven at 70°C under 0.5 kPa.

The characteristics of the brominated butadiene-styrene copolymer prepared according to Example 6 are shown in Table 1.

Example 7. Preparation of a modified butadiene-styrene copolymer comprising 0.15 wt.% of hydroxybrominated butadiene units by using a modifying system

A solution of a starting styrene-butadiene copolymer in dichloromethane (10 g of copolymer per 150 g of dichloromethane) was added to a 250 ml dark glass flask. Then, 30 g of butanol and 10 g of water were added to the flask, after which a solution of 19.7 g of bromine of in 20 ml of dichloromethane was dosed. The modification reaction was conducted for 30 to 40 minutes. After the reaction, a 20% solution of sodium metabisulfite was added to the flask, and neutralization was carried out for one hour. Then, the reaction mass comprising a modified diene-containing copolymer was washed with a three-fold volume excess of water.

After that, the resulting modified diene-containing copolymer was filtered, then precipitated in isopropanol, dried by distilling off the solvent at a temperature of 30 to 95°C under 3 kPa, and further dried in a vacuum oven at 70°C under 0.5 kPa.

The characteristics of the product prepared in Example 7 are shown in Table 1.

Table 1. Comparative table of the results of experiments on the preparation of modified diene-containing (co)polymers

Example 8. Preparation of expandable po ystyrene

87 parts of water and 0.43 parts of a polymerization stabilizer (a mixture of sodium pyrophosphate and magnesium sulfate) were mixed in a flask at a temperature of 25°C. A mixture of 100 parts of styrene, 0.46 parts of a mixture of polymerization initiators (benzoylperoxide and tert-butyl perbenzoate), 0.62 parts of a flame retardant prepared according to examples 1 to 5, and 0.21 parts of a flame retardant synergist (dicumyl peroxide) were added to this mixture with stirring. The mixture was stirred for 2 hours at a temperature of up to 85°C and then heated to 115°C for 4.5 hours. 70 minutes after the temperature in the flask reached 80°C, a 10% aqueous solution of polyvinylpyrrolidone was added to the reaction mixture. After additional 100-120 minutes, a solution of 0.10 parts of a chain transfer agent in 4.7 parts of a foaming reagent (n-heptane) was added to the reaction mass— a step of expanding polystyrene. After reaching 115°C, the flask was kept at a constant temperature for 3 hours, after that the mixture was cooled to a temperature of 25 °C for 3 hours.

Then, the particle size distribution of the polystyrene obtained before the step of its expanding was determined. The results of the measurements of particle-size distribution are given in Table 2.

Table 2. Particle-size distribution of polystyrene comprising a flame retardant

have a total yield of fractions (1.60 + 1.00 + 0.70) (target fractions) of more than 85%.

Comparison of particle size distributions of the samples of polystyrene containing the flame retardants according to Examples 1 to 4 (Table 2) shows that the introduction of hydroxyl groups into the (co)polymer structure in a small amount (from 0.05 to 1.90 wt.% of hydroxybrominated diene units) does not adversely affect the stability of the suspension in the synthesis of polystyrene and does not affect its particle size distribution. An increase in the content of hydroxybrominated diene units in the structure of the flame retardant (Example 5) up to 5.5 wt.% leads to a decrease in the yield of the target polystyrene fractions due to a high polarity of the flame retardant molecule, resulting in a shift of the particle size distribution towards larger factions. In this case, such granules have a tendency to adhere to each other.

Polystyrene plates were tested by the XRFA and SEM methods described above in order to assess the compatibility of the flame retardant prepared according to the invention with polystyrene.

Fig.4 shows the distribution of bromine in the samples of polystyrene comprising one of the following flame retardants: (a) HBCD, (b) a brominated styrene- butadiene copolymer, (c) a modified styrene-butadiene copolymer containing 0.15 wt.% hydroxybrominated butadiene units, and (d) a modified styrene-butadiene copolymer containing 5.5 wt.% hydroxybrominated butadiene units. The darkest areas in FIG. 4 correspond to the highest concentration of bromine atoms, and the lightest areas correspond to the lowest concentration of bromine atoms, respectively.

As can be seen from the data in FIG. 4, sample (a) of polystyrene containing

HBCD as a flame retardant has a highly uniform concentration of bromine in the entire studied volume. Sample (b) of polystyrene containing brominated butadiene-styrene copolymer as a flame retardant has a smaller area of the dark region, which indicates a low bromine concentration in the sample.

The presented data demonstrate that polystyrene containing modified styrene- butadiene copolymer containing 0.15 wt.% of hydroxybrominated butadiene units has a high concentration of bromine in its composition, wherein the distribution of bromine in the polystyrene is similar to the distribution of bromine in polystyrene containing HBCD. Therefore, said modified styrene-butadiene copolymer provides expandable polystyrene with flame retardant properties comparable to those provided by HBCD, which is also confirmed by the flame resistance tests, which allowed the expandable polystyrene containing the flame retardant according to the present invention to be classified to moderately flammable materials of the inflammability class B2 (according to Item 7 of Article 13 of "Technical regulations of fire safety requirements" (Federal Act of 22.07.2008, No. 123, in the edition of 29.07.2017)).

The concentration of bromine in polystyrene containing a modified styrene- butadiene copolymer containing 5.5 wt.% of hydroxybrominated butadiene units is lower than in polystyrene containing HBCD and similar to the distribution of bromine in the polystyrene containing a brominated styrene-butadiene copolymer. This can be explained by the fact that, a high content of hydroxybrominated butadiene units in the flame retardant molecule results in a decrease in the total number of brominated butadiene units, which, in turn, does not allow this modified styrene-butadiene copolymer to provide expandable polystyrene with desired flame retardant properties.

Figure 5 shows photographs of the samples of polystyrene containing one of the following flame retardant: (a) HBCD, (b) a brominated styrene-butadiene copolymer, (c) a modified styrene-butadiene copolymer containing 0.15 wt.% of hydroxybrominated butadiene units, and (d) a modified styrene-butadiene copolymer containing 5.5 wt.% of hydroxybrominated butadiene units, as determined by the SEM method.

As can be seen from the obtained data, the formed domains (light areas) containing bromine became lighter in all the samples, except for the sample (a) with HBCD, which is homogeneously distributed in polystyrene, because the sample of flame retardant is insufficiently homogeneously distributed in polystyrene. It should be noted that for polystyrene samples containing the modified styrene-butadiene copolymers (with a content of hydroxybrominated butadiene units of 0.15 wt.% and 5.5 wt.%), the number of domains is small, which also indicates a more homogeneous distribution of the flame retardant in polystyrene samples compared with the sample of polystyrene containing the brominated styrene-butadiene copolymer as a flame retardant.

Thus, the results of the experiments showed that a modified styrene-butadiene copolymer containing hydroxyl groups and bromine atoms in its structure, used as a flame retardant, is homogeneously distributed in polystyrene, which provides expandable polystyrene with flame retardant properties comparable to those provided by HBCD.