Abstract: A process for the preparation of expandable polystyrene including the following steps: i°) heating an aqueous suspension including styrene monomer and at least one organic peroxide initiator of formula (I) 1-alkoxy-1-t-alkylperoxycyclohexane in which the alkoxy group contains 1 to 4 carbon atoms, the t-alkyl group contains 4 to 12 carbon atoms, and the cyclohexane ring may optionally be substituted with 1 to 3 alkyl groups each, independently having 1 to 3 carbon atoms, at a temperature ranging from 100° C. to 120° C.), ii°) adding a blowing agent selected from the group of alkanes having from 4 to 6 carbon atoms and mixtures thereof. Also, an expandable polystyrene obtainable according to such a process and to insulation parts and packaging including such an expandable polystyrene.

Abstract: A method for manufacturing polyethylene or an ethylene copolymer, including a step of free radical polymerization or copolymerization of the ethylene at an initiation temperature varying from 150° C. to 200° C., at a pressure varying from 500 to 3000 bar, in the presence of a peroxidic polymerization initiator selected from among the peroxide compounds of formula (I) in which R1 and R8 are, separately, a C2-C6 alkyl group; R2, R3, R6 and R7 are, separately, a C1-C5 alkyl group; and R4 and R5 are, separately, a C1-C6 alkyl group.

Abstract: A process for the preparation of expandable polystyrene including the following steps: i°) heating an aqueous suspension including styrene monomer and at least one organic peroxide initiator of formula (I) 1-alkoxy-1-t-alkylperoxycyclohexane in which the alkoxy group contains 1 to 4 carbon atoms, the t-alkyl group contains 4 to 12 carbon atoms, and the cyclohexane ring may optionally be substituted with 1 to 3 alkyl groups each, independently having 1 to 3 carbon atoms, at a temperature ranging from 100° C. to 120° C., ii°) adding a blowing agent selected from the group of alkanes having from 4 to 6 carbon atoms and mixtures thereof. Also, an expandable polystyrene obtainable according to such a process and to insulation parts and packaging including such an expandable polystyrene.

Abstract: A method for manufacturing polyethylene or an ethylene copolymer, including a step of free radical polymerisation or copolymerisation of the ethylene at an initiation temperature varying from 150° C. to 200° C., at a pressure varying from 500 to 3000 bar, in the presence of a peroxidic polymerisation initiator selected from among the peroxide compounds of formula (I) in which R1 and R8 are, separately, a C2-C6 alkyl group; R2, R3, R6 and R7 are, separately, a C1-C5 alkyl group; and R4 and R5 are, separately, a C1-C6 alkyl group.

Abstract: A process for the preparation of expandable polystyrene including the following steps: i°) heating an aqueous suspension including styrene monomer and at least one organic peroxide initiator of formula (I) 1-alkoxy-1-t-alkylperoxycyclohexane in which the alkoxy group contains 1 to 4 carbon atoms, the t-alkyl group contains 4 to 12 carbon atoms, and the cyclohexane ring may optionally be substituted with 1 to 3 alkyl groups each, independently having 1 to 3 carbon atoms, at a temperature ranging from 100° C. to 120° C.), ii°) adding a blowing agent selected from the group of alkanes having from 4 to 6 carbon atoms and mixtures thereof. Also, an expandable polystyrene obtainable according to such a process and to insulation parts and packaging including such an expandable polystyrene.

Abstract: The present invention relates to a process for the preparation of expandable polystyrene comprising the following steps: io) heating an aqueous suspension comprising styrene monomer and at least one organic peroxide initiator of formula (I) 1-alkoxy-1-t-alkylperoxycyclohexane in which the alkoxy group contains 1 to 4 carbon atoms, the t-alkyl group contains 4 to 12 carbon atoms, and the cyclohexane ring may optionally be substituted with 1 to 3 alkyl groups each, independently having 1 to 3 carbon atoms, at a temperature ranging from 100° C. to 120° C., iio) adding a blowing agent selected from the group consisting of alkanes having from 4 to 6 carbon atoms and mixtures thereof. The invention also relates to an expandable polystyrene obtainable according to such a process and to insulation parts and packaging comprising such an expandable polystyrene.

Abstract: The invention relates to a process comprising a stage of polymerization or copolymerization of at least one polymerizable or copolymerizable monomer by a radical mechanism in the presence of a stable free radical and of an initiator of formula: R1—O—O—R2 wherein R1 and R2, which can be identical or different, represent an alkyl, aryl, alkylaryl or aralkyl radical comprising, for example, from 1 to 20 carbon atoms. The process is fast, allows the initiator to act more efficiently and results in polymers or copolymers exhibiting a low yellowing index.

Abstract: The present invention relates to a process for the manufacture of a composition comprising a vinylaromatic polymer and a rubber, wherein the polymerization stage is carried out in the presence of a stable free radical in a polymerization mixture. The presence of the stable free radical in the polymerization mixture makes its possible to increase the melt index and to influence the size of the rubber nodules in the final composition by generally increasing the fraction, by volume, of the rubbery phase and by widening the distribution of the size of these nodules. This is reflected by an improvement both in the melt index and in the impact strength of the final composition, which makes the latter an ideal composition for injection molding.

Abstract: The invention relates to a process for the polymerization or copolymerization of at least one monomer which is polymerizable by the radical route in the presence of a stable free radical from the nitroxide family. The stable free radical is &bgr;-substituted and provides excellent control of polydispersity while ensuring a better rate of polymerization or copolymerization, if they are compared with the stable free radicals used in the prior art.

Abstract: The invention relates to a process for the polymerization or copolymerization of at least one monomer which can be polymerized or copolymerized by the radical route in the presence of a stable free radical and of an iniferter. The presence of the stable free radical greatly modifies the behavior of the iniferter during the polymerization or copolymerization, so that undesirable reactions are much reduced. It is possible, rapidly and with a high yield, to polymerize or copolymerize in the presence of an iniferter in order to result in a polymer or copolymer with a reduced polydispersity and with a monomodal molecular mass distribution.

Abstract: The invention relates to a process for the polymerization or copolymerization of at least one monomer which can be polymerized or copolymerized by the radical route in the presence of a stable free radical and of an iniferter.

Abstract: The present invention relates to the stabilization of a polymer by a stable free radical and in particular to the use of a stable free radical for inhibiting the degradation of a polymer by a mechanism which does not involve oxygen. This use can be carried out when the polymer is in the presence or in the absence of oxygen. The degradation which can be inhibited can be a depolymerization or a crosslinking.

Abstract: A process is provided for the preparation of a bitumen-polymer composition which comprises(a) producing at a temperature of between 100.degree. C. and 230.degree. C., a mixture of(i) a bitumen(ii) a linear block copolymer of styrene and a conjugated diene, the block copolymer being used in a quantity of from 0.5% to 25% by weight of bitumen and having a weight-average molecular weight of between 170,000 and 250,000 and a structure of A-B-A with A denoting a polymer block consisting of a polystyrene block which may be extended on the B side by a random copolymer of styrene and of the conjugated diene and B denoting a polymer block consisting of conjugated diene units, and(iii) a coupling agent containing at least one sulphur-donor compound and used in an amount to provide a quantity of sulphur representing, by weight, 0.1% to 10% of the weight of the linear block copolymer of styrene and conjugated diene; and(b) keeping the mixture thus produced at a temperature of between 100.degree. C. and 230.degree. C.

Abstract: The process for the controlled radical (co)polymerization of (meth)acrylic and/or vinyl monomers is characterized in that the bulk, solution, emulsion or suspension polymerization or copolymerization is carried out, at a temperature at which can fall to 0.degree. C., of at least one of the said monomers in the presence of an initiating system comprising a radical-generating compound and at least one catalyst composed of a metal complex containing a ligand of the type?4-R.sup.3 -2,6-(CH.sub.2 NR.sup.1 R.sup.2).sub.2 C.sub.6 H.sub.2 !--(I)in which: R.sup.1 and R.sup.2, which are identical or different, represent a branched or unbranched C.sub.1 -C.sub.4 alkyl group or a phenyl group or alternatively R.sup.1 and R.sup.2 form, with the nitrogen atom to which they are connected, a cyclic amine or alternatively the two R.sup.2 groups, taken together, form a polymethylene bridge and R.sup.3 represents a hydrogen atom, an alkyl or benzyl group or an electron-donating or electron-withdrawing functional group.

Abstract: A multifunctional anionic polymerization initiator which is in the form of a star-shaped polymer, and which is soluble in a nonpolar medium and is substantially free of residual double bonds. The initiator is denoted by the general formula (PA).sub.a N.sup.n- nLi.sup.+. PA is a polymer block of a vinylaromatic or diene monomer A. The variable "a" is the number of branches in the block PA. N is a crosslinked core comprising no or practically no residual double bonds and has the formula (PMc)(RLi).sub.p. Mc is a monomer containing at least two polymerizable double bonds per molecule. PMc is a crosslinked core of at least one polymerized monomer Mc, containing 3 to 30% of residual double bonds in relation to the initial double bonds originating from the monomer Mc. R is an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl, or alkenyl. The variable "p" is the number of residual double bonds in PMc which are neutralized by RLi. The variable "n" is the number of anionic sites present in the crosslinked core N.

Abstract: A functionalized elastomer is provided which is of the type containing a substrate elastomer, having a weight-average molecular mass (Mw).sub.0 of between 10,000 and 600,000 daltons and a polydispersity index of less than 5, onto which are grafted, in an amount representing 0.1 to 10% by weight of the substrate, sequences carrying carboxyl or ester functional groups, wherein its weight-average molecular Mw is such that the ratio ##EQU1## is less than 20% and the sequences grafted onto the substrate correspond to the formula ##STR1## in which R.sub.1 denotes an (x+z+1)-valent C.sub.1 to C.sub.12 hydrocarbon radical, X represents H or a monovalent C.sub.1 to C.sub.12 hydrocarbon radical R, z is equal to zero or 1 and x is an integer having a value ranging from 1 to 3 with x+z .ltoreq.3. Bitumen/EF compositions useful for making surfacings may be produced by incorporating the EF into a bituminous component.

Abstract: A multifunctional anionic polymerization initiator which is in the form of a star-shaped polymer, and which is soluble in a nonpolar medium and is substantially free of residual double bonds. The initiator is denoted by the general formula (PA).sub.a N.sup.n- nLi.sup.+. PA is a polymer block of a vinylaromatic or diene monomer A. The variable "a" is the number of branches in the block PA. N is a crosslinked core comprising no or practically no residual double bonds and has the formula (PMc)(RLi).sub.p. Mc is a monomer containing at least two polymerizable double bonds per molecule. PMc is a crosslinked core of at least one polymerized monomer Mc, containing 3 to 30% of residual double bonds in relation to the initial double bonds originating from the monomer Mc. R is an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl, or alkenyl. The variable "p" is the number of residual double bonds in PMc which are neutralized by RLi. The variable "n" is the number of anionic sites present in the crosslinked core N.

Abstract: The invention relates to a star block copolymer of the formula [S.sub.1 -S.sub.2 -(B.sub.1 /S.sub.3)-B.sub.2 ].sub.m -X-[B.sub.2 (B.sub.1 /S.sub.3)-S.sub.2 ].sub.n in which X represents a polyfunctional radical resulting from a coupling agent, m and n represent non-zero integers such that m+n is equal to 3 or 4, S.sub.1 and S.sub.2 each represent a block of a polymer containing at least one vinylaromatic monomer, B.sub.2 represents a block of a polymer containing at least one conjugated diene, (B.sub.1 /S.sub.3) represents a block of a statistical copolymer containing at least one vinylaromatic monomer and at least one conjugated diene, 40 to 75% by weight of (B.sub.1 /S.sub.3) consisting of resulting from vinylaromatic monomer, characterized in that the sum of the mass of the blocks B.sub.2 contains more than 40% by weight and less than 90% by weight of the total mass of the conjugated diene contained in the said star block copolymer. The invention also relates to the process for obtaining this copolymer.

Abstract: A multifunctional anionic polymerization initiator which is in the form of a star-shaped polymer soluble in an apolar medium and substantially free of residual double bonds. The initiator is denoted by the general formula (PA).sub.a N.sup.n- nLi.sup.+. PA is a polymer block of a vinylaromatic or diene monomer A. The variable "a" is the number of branches in the block PA. N is a crosslinked core comprising no or practically no residual double bonds and has the formula (PMc)(RLi).sub.p. Mc is a monomer containing at least two polymerizable double bonds per molecule. PMc is a crosslinked core of at least one polymerized monomer Mc, containing 3 to 30% of residual double bonds in relation to the initial double bonds originating from the monomer Mc. R is an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl, or alkenyl. The variable "p" is the number of residual double bonds in PMc which are neutralized by RLi. The variable "n" is the number of anionic sites present in the crosslinked core N.

Abstract: A process is provided for the preparation of a bitumen-polymer composition which comprises(a) producing at a temperature of between 100.degree. C. and 230.degree. C., a mixture of(i) a bitumen;(ii) a linear block copolymer of styrene and a conjugated diene, the block copolymer being used in a quantity of from 0.5% to 25% by weight of bitumen and having a weight-average molecular weight of between 170,00 and 250,000 and a structure of A-B with A denoting a polymer block consisting of a polystyrene block which may be extended on the B side by a random copolymer of styrene and of the conjugated. diene and B denoting a polymer block consisting of conjugated diene units, and(iii) a coupling agent containing at least one sulphur-donor compound and used in an amount to provide a quantity of sulphur representing, by weight, 0.1% to 10% of the weight of the liner block copolymer of styrene and conjugated diene; and(b) keeping the mixture thus produced at a temperature of between 100.degree. C. and 230.degree. C.