Abstract: High transparency polymeric composition essentially consisting of: (1) from 30 to 95% of polystyrene; (2) from 70% to 5% of a composition of vinylarene-conjugated diene block copolymers; the percentage sum of (1) and (2) being equal to 100; the composition (2) consisting of: (2a) from 30 to 60% by weight of copolymers with a linear structure (2b) from 70% to 40% by weight of copolymers with a branched structure; the weight average molecular weight of the above composition (2) ranging from 30,000 to 400,000, preferably from 50,000 to 200,000.

Abstract: High transparency polymeric composition essentially consisting of:

Abstract: Composition of vinylarene/hydrogenated diene block copolymers, the latter being selected from ethylene-butene and ethylene-propylene, characterized in that it comprises: a) copolymers having linear structures from 30% to 60% by weight, preferably from 35% to 50%; b) copolymers having branched structures from 70% to 40% by weight, preferably from 65% to 50%; the sum of components (a) and (b) being equal to 100; the weight average molecular weight of the above composition ranging from 30,000 to 400,000, preferably from 50,000 to 200,000.

Abstract: A description follows of epoxydated block copolymers, either linear or branched, which can be defined with the following formulae:1) [A--(E--B--EPOX)].sub.n X2) A.sub.1 --(E.sub.1 --B.sub.1 --EPOX.sub.1)--A--HT--(E.sub.2 --B.sub.2 --EPOX.sub.2)3) [(E.sub.1 --B.sub.1 --EPOX.sub.1)--HT--A(E.sub.2 --B.sub.2 --EPOX.sub.2)].sub.x Xwhere A is a polyvinylaromatic block in a percentage ranging from 10 to 50% by weight, E--B--EPOX is a block composed of ethylene units, epoxydated butene and diene units in which the percentage by weight of the epoxy group ranges from 1% to 40%, HT is a tapered copolymer segment made up of hydrogenated and epoxydated diene monomeric units and vinylaromatic units whose content ranges from 0 to 20%, x is a radical having a valence ranging from 1 to 20.The block copolymers have an average molecular weight ranging from 30,000 to 400,000, a content of polyvinylaromatic blocks of between 10 and 50% by weight and a content of (E.sub.1 --B.sub.1 --EPOX.sub.1)+(E.sub.2 --B.sub.2 --EPOX.sub.

Abstract: A description follows of epoxydated block copolymers, either linear or branched, which can be defined with the following formulae:1) [A-(E-B-EPOX)].sub.n X2) A.sub.1 -(E.sub.1 -B.sub.1 -EPOX.sub.1)-A-HT-(E.sub.2 -B.sub.2 -EPOX.sub.2)3) [(E.sub.1 -B.sub.1 -EPOX.sub.1)-HT-A(E.sub.2 -B.sub.2 -EPOX.sub.2)].sub.n Xwhere A is a polyvinylaromatic block in a percentage ranging from 10 to 50% by weight, E-B-EPOX is a block composed of ethylene units, epoxydated butene and diene units in which the percentage by weight of the epoxy group ranges from 1% to 40%, HT is a tapered copolymer segment made up of hydrogenated and epoxydated diene monomeric units and vinylaromatic units whose content ranges from 0 to 20%, x is a radical having a valence ranging from 1 to 20.The block copolymers have an average molecular weight ranging from 30,000 to 400,000, a content of polyvinylaromatic blocks of between 10 and 50% by weight and a content of (E.sub.1 -B.sub.1 -EPOX.sub.1)+(E.sub.2 -B.sub.2 -EPOX.sub.

Abstract: A branched block copolymer is described, which can be defined by the formula (B.sub.1 -T-A-B.sub.2).sub.n X, where B.sub.1, and B.sub.2 are polydiene blocks, A is an aromatic polyvinyl block, T is a random copolymer segment made up of dienic monomeric and aromatic vinyl units, X is a coupling radical having a valence equal to n, and n is a whole number ranging from 3 to 20. This kind of block copolymer is used in formulations of adhesives having an excellent balance of adhesive, cohesive, rheological characteristics, as well as resistance to heat oxidation, and in compositions together with thermoplastic polymers capable of giving products with improved shock resistance and transparency.

Abstract: A branched block copolymer is described, which can be defined by the formula (B.sub.1 --T--A--B.sub.2).sub.n X, where B.sub.1 and B.sub.2 are polydiene blocks, A is an aromatic polyvinyl block, T is a random copolymer segment made up of dienic monomeric and aromatic vinyl units, X is a coupling radical having a valence equal to n, and n is a whole number ranging from 3 to 20.This kind of block copolymer is used in formulations of adhesives having an excellent balance of adhesive, cohesive, rheological characteristics, as well as resistance to heat oxidation, and in compositions together with thermoplastic polymers capable of giving products with improved shock resistance and transparency.

Abstract: New polymeric compositions comprising:(a) a linear copolymer constituted by four alternating blocks, which can be represented by the formula (I) or (II)B.sub.1 -T-A.sub.1 -B.sub.2 -A.sub.2 (I)orB.sub.1 -A.sub.1 -B.sub.2 -T-A.sub.2 (II)wherein:B.sub.1 and B.sub.2 are polydienic blocks, preferably polybutadienic blocks;A.sub.1 and A.sub.2 are polyvinylaromatic blocks and preferably polystyrenic blocks;T is a portion of random copolymer formed by dienic and vinylaromatic monomer units;(b) a linear copolymer constituted by two blocks, which can be represented by the formulae (III) or (IV)B.sub.3 -T-A.sub.3 (III)orB.sub.3 -A.sub.3 (IV)wherein:B.sub.3 is a polydienic block;A.sub.3 is a polyvinylaromatic block; andT has the above seen meaning.The polymeric composition, which can be blended with polystyrene, can be obtained both by blending the individual components, and by means of novel and original synthesis processes which make it possible both (A) and (B) components to be obtained simultaneously.

Abstract: A branched and hydrogenated block copolymer can be defined by the formula [(EB).sub.1 --HT--A--(EB).sub.2 ].sub.n X, where (EB).sub.1 and (EB).sub.2 are hydrogenated polydiene blocks, A is a polyvinylaromatic block, HT is a random copolymer segment made up of hydrogenated dienic monomeric and vinylaromatic units, X is a coupling radical having a valence equal to n, and n is a whole number ranging from 3 to 20.This kind of block copolymer shows excellent mechanical characteristics and resistance to atmospheric agents, even when used in combination with other resins.

Abstract: New polymeric compositions comprising:(a) a linear copolymer constituted by four alternating blocks, which can be represented by the formula (I) or (II)B.sub.1 --T--A.sub.1 --B.sub.2 --A.sub.2 (I)orB.sub.1 --A.sub.1 --B.sub.2 --T--A.sub.2 (II)wherein:B.sub.1 and B.sub.2 are polydienic blocks, preferably polybutadienic blocks;A.sub.1 and A.sub.2 are polyvinylaromatic blocks and preferably polystyrenic blocks;T is a portion of random copolymer formed by dienic and vinylaromatic monomer units;(b) a linear copolymer constituted by two blocks, which can be represented by the formulae (III) or (IV)B.sub.3 --T--A.sub.3 (III)orB.sub.3 --A.sub.3 (IV)wherein:B.sub.3 is a polydienic block;A.sub.3 is a polyvinylaromatic block; andT has the above seen meaning.The polymeric composition, which can be blended with polystyrene, can be obtained both by blending the individual components, and by means of novel and original synthesis processes which make it possible both (A) and (B) components to be obtained simultaneously.

Abstract: Radial and branched block copolymers show a structure: ##STR1## wherein: Z is a radical deriving from a tetrafunctional coupling agent;A is a polystyrene block;B is a polybutadiene blockm, n, p, q are either 1 or zero, with the condition that their sum is comprised within the range of from 1 to 4.Compositions of block copolymers comprise the hereinabove disclosed radial and branched block copolymers, blended with a two-block copolymer B-A, and an "A" homopolymer.The process for the preparation of said radial and branched block copolymers and of the related compositions is disclosed, and furthermore their use is disclosed in bituminous compositions, in order to improve the general characteristics of the bitumens.

Abstract: Linear copolymers with four alternating blocks, represented by the following formula:B.sub.1 -T-A.sub.1 -B.sub.2 -A.sub.2where: A.sub.1 and A.sub.2 are polyvinylaromatic blocks, B.sub.1 and B.sub.2 are blocks consisting of ethylene-butene-1 or ethylene-propylene copolymers, and T is a statistical terpolymer segment formed from ethylene-propylene-vinylarene or ethylene-butene-1-vinylarene monomer units.The copolymers are characterized by a weight-average molecular weight of between 20,000 and 300,000 and a total content of vinylaromatic units of between 10 and 60% by weight. The ratio of the weight-average molecular weight of block A.sub.1 to that of block A.sub.2 is a number between 0.25 and 2.0, and the ratio of the weight-average molecular weight of block B.sub.1 to that of block B.sub.2 is a number between 0.05 and 0.5.

Abstract: A linear copolymer constituted by four alternating blocks:B1-A1-B2-A2wherein:B1 and B2 are polydienic blocks, and preferably polybutadiene blocks, andA1 and A2 are polyvinylaromatic, and preferably polystyrene blocks;which polymer has a weight average molecular weight of from 30,000 to 250,000, and a global content of monomer dienic units of from 40 to 80% by weight, wherein the weight average molecular weight of B1 block is comprised within the range of from 0.1 to 0.5 times the weight average molecular weight of B2 block, and the weight average molecular weight of A1 block is comprised within the range of from 0.25 to 2.0 times the weight average molecular weight of A2 block, and which contains between B1 and A1 blocks a copolymeric moiety formed by randomly linked monomer dienic and vinylaromatic units; is endowed with a desired balance of mechanical characteristics, rheologic characterisatics and characteristics of thermooxidative resistance.The process to prepare such a block copolymer is disclosed.

Abstract: The terminal hydroxyl groups of an acetal polymer are esterified or etherified by reaction with an end-capping agent chosen from anhydrides of carboxylic acids, orthoesters and orthocarbonates, by forming an intimate mixture of polymer in powder form and liquid end-capping agent, the amount of said agent in the mixture being less than that which results in loss of the free-flowing characteristics of the powder, and reacting said mixture under stirring at 50.degree.-170.degree. C.

Abstract: The thermal and chemical stability of etherified acetal homopolymers is improved by heat-treating the latter in the molten state at a temperature of at least 180.degree. C., in the presence of a halide of an alkali or alkaline earth metal, until substantially complete degradation of the unstable polyoxymethylene chains.

Abstract: An etherified acetal homopolymer is stabilized by heat-treating said homopolymer suspended in a liquid diluent chosen from water or mixtures thereof with polar organic compounds, preferably in the presence of a basic compound, at a temperature of 100.degree.-160.degree. C and below the melting point of the homopolymer, thereby to substantially degrade the unstable fraction of said homopolymer.

Abstract: The unstable terminal hydroxyl groups of acetal polymers are etherified in a liquid reaction medium in the presence of organic additives.

Abstract: Process for the stabilization of polyacetal resins having terminal hydroxyl groups, which comprises reacting a reagent capable of etherifying the hydroxyl groups with the polyacetal resins suspended in a reaction medium that is liquid under the conditions used, the said reaction medium consisting of at least one substance that is a solvent for the polymer and at least one substance that is a non-solvent for the polymer, the said solvent and non-solvent substances being completely miscible at the reaction temperatures but immiscible or partly miscible at temperature substantially lower than the reaction temperatures, and carrying out the operation in the presence of catalytic quantities of one or more compounds selected from the groups consisting ofA. strong or medium-strong mineral acids whose acid dissociation constant or first acid dissociation constant is higher than 10.sup..sup.-7 ;B. strong or medium-strong oganic acids whose acid dissociation constant is higher than 10.sup..sup.-6 ;C.