MXPA97007988A - Material of molding termoplast - Google Patents

Abstract

Elastomeric block copolymers, comprising at least one hard block A, composed of styrene monomers, and at least one elastomeric block (B / A), composed of styrene and dienes monomers, the glass transition temperature, Tg, of the block A is greater than 25øC and that of the block (B / A) is less than 25øC, and the ratio of the phase volume from block A to block (B / A) is selected so that the proportion of the phase lasts in the total block copolymer is from 1 to 40% by volume, and the amount by weight of the diene is less than 50% by weight, and the relative proportion of links 1, 2 of the polydiene, based on the sum of the bonds 1 , 2- and 1,4-cis / trans, are below 15%, are prepared by the anionic polymerization, by means of a lithium-alkyl, in a non-polar solvent, in the presence of a soluble potassium salt, and used in the production of configured items

Description

MOLDING MATERIAL TERMOPLAST1CO Block copolymers of vinylaromatic compounds (for example styrene) and of dienes (for example butadiene) are copolymers of a plurality of molecular polymer segments (ie, blocks), which are arranged in series or linked together way and have a more or less uniform composition. Depending on the structure and the * content of diene monomers, they may have, in Generally speaking - at certain temperatures - elastomeric properties or non-elastomeric, rigid properties, ie as a whole they exhibit an elastomeric behavior similar to a polydiene and are important, for example, as the rubber of SB, or they behave as polymers of Styrene transparencies 15, resistant to impact. Similar to the definitions In the case of hardened polystyrene, it is usual to refer to those parts, which determine the elastomeric behavior, such as the soft phase, and the rigid parts (the pure polystyrene fraction), such as the hard phase. The SB rubbers should be vulcanized in the same way as the usual diene polymers for use, which greatly restricts their use and makes the process more expensive. The present invention relates to block copolymers, usually transparent, of aromatic vinyl compounds and dienes, these block copolymers can be processed by a purely thermoplastic method and have an elastomeric behavior and in particular improved mechanical and thermal properties. The following should thus be mentioned in this context: Anionic polymerization, which leads to active polymers and in which the growth of a chain molecule takes place at one chain end, which, in the absence of a spontaneous termination of the chain or transfer reaction, remains theoretically for an unlimited time (remains polymerizable), and the reaction of the active polymer with monofunctional or polyfunctional reagents is known to be a versatile possible method for synthesizing the block copolymers, although the selection of monomers is limited; in practice, only block copolymers of vinyl aromatic compounds, ie styrene and its derivatives, on the one hand, and dienes, essentially butadiene or isoprene, on the other, have become important. The block copolymers are obtained by carrying out, in each case, the polymerization until the monomer material is virtually depleted and then the monomer or monomers are changed. This process can be repeated several times. Linear block copolymers are described, for example in the patents of E. U. A., Nos. 3,507,934 and 4,122,134. Star block copolymers are described, for example, in the patents of U. U.A., Nos. 4,086,298, 4,167,545 and 3,639,517. The properties profile of these block copolymers is characterized essentially by the content of polymerized diene monomers, ie the length, arrangement and ratio of the polydiene and polystyrene blocks, Also, the type of transition between different blocks plays a role important. The influence of curled and tapered transitions (depending on whether the monomer change is abrupt or gradual) is explained in detail in DE-A1-44 20 952, so a further description is not necessary here. It is merely necessary to note that, in block copolymers having a tapered block transition, the sequence lengths do not mean randomly distributed, but rather the length of the sequence of the pure diene phase compared to the polystyrene phase and thus its volume ratio, move in favor of the diene phase. This has the disadvantage that the poor properties of the diene polymer are unnecessarily strong, evident in the behavior of the material during the process.

In particular, materials having a diene content greater than 35% by weight, which, due to their properties profile (hardness, transparency, gas permeability), will be suitable for medical applications, such as in infusion tubes , infusion drip chambers and stretched films can be processed by extrusion of the profile, injection molding or extrusion of the tubular film only with a very great difficulty; despite stabilization with antioxidants and radical acceptors free, they are very sensitive to heat and tend to become sticky, and thus need an expensive remedy with additives. The blocking (adhesion of the films and tubes to the roller) and the poor release properties of the mold, can make the injection molding process completely impossible. DE-A1-44 20 952 has thus proposed in this context the preparation of an elastomeric block copolymer, which consists of at least one block A, which has polymerized units of a vinylaromatic monomer and which forms a hard phase and / or a B block containing diene monomers and forming a first (soft) elastomeric phase and at least one elastomeric block (B / A) having polymerized units of a vinylaromatic monomer and a diene and forms a soft phase or a subsequent soft phase, the glass transition temperature, Tg, of block A is above 25se and that of block (B / A) is below 25ec and the phase volume ratio of the block A to block B (B / A) is selected so that the proportion of the phase lasts in the total block copolymer, from 1 to 40% by volume, and the amount of the diene is less than 50% by weight. These block copolymers are already a considerable advance over the previously known block copolymers, which have tapered block transitions. However, materials having a diene content of up to 35% also tend to form gels (entanglement by olefinically unsaturated chain elements) when subjected to prolonged thermal stresses and shear stresses, as occurs, in particular , during the extrusion. Particularly, in the production of films, the gel particles can be evident as troublesome mottles. The tendency to interlace is attributed, in particular, to short chain branches, present in polydienes, that is, the side chains that have the structure: \ CH-CH-CH2 / ^ BßB "" It is an object of the present invention to obtain, by suitable selection of the molecular structure, elastomeric block copolymers, which can be easily produced on a large industrial scale, have a hardness of maximum with a low diene content and can be processed in the same way as the thermoplastic products in extruders and injection molding machines, in a simple manner and, in particular, without the problem of gel formation. It has been found that this object is achieved, in general, according to the invention, if, in a vinylaromatic / diene block copolymer, comprising blocks that form a hard phase (block of type A) and those that form a phase soft, a block of pure polydiene (type B of block), as the soft phase, is replaced by a block (B / A) of diene and vinylaromatic units, which have a strictly random structure, the relative amount of the 1,2 bonds of the polydiene, based on the sum of the 1,2- and 1,4-cis / trans bonds, always being below approximately 12 to 15%. As a statistical average, the structure can be homogeneous or non-homogeneous, along the chain. The present invention relates directly to an elastomeric block copolymer, comprising at least one flPL-block A having polymerized units of a vinylaromatic monomer and forming a hard phase and at least one elastomeric block (B / A (having units polymerized from a vinylaromatic monomer and a diene and form a soft phase, the glass transition temperature Tg of block A being above 252C and that of block (B / A) being below 25se and the phase volume ratio from block A to block (B / A) being selected so that the proportion of the hard phase in the total block copolymer is from 1 to 40% by volume and the amount of the diene is less than 50% by weight. The relative amount of 1,2-bonds of the polydiene, based on the sum of the 1,2- and 1,4 cis / trans bonds, is less than about 12 to 25%. The vinylaromatic monomer is preferably selected from styrene, α-methylstyrene, vinyltoluene and 1,1-diphenylethylene, and the diene of butadiene and isoprene. This novel elastomeric block copolymer that has less interlacing tendency is obtained if, within the above parameters, the soft phase is formed from the random copolymer of a vinylaromatic monomer with a diene; The random copolymers of vinylaromatic monomers and dienes are obtained by the polymerization in the presence of a potassium salt soluble in non-polar solvents. The random copolymerization of styrene and R ^, butadiene in cyclohexane, in the presence of soluble potassium salts, is described by S. D. Smith, A. Ashra et al. , in Polymer Preprints 34 (2) (1993), 672 and 35 (2) (1994), 466. 2, 3-dimethyl-3-pentanolate potassium and 5 3-ethyl-3-pentanolate potassium are mentioned as soluble potassium salts. In principle, it is possible to produce random copolymers by adding polar coordinating solvents, as described in DE-A1-44 20 952, to the copolymers resulting, in a greater proportion of the links 1,2. The difference, according to the invention, of the method described here is that the ratio of the 1,2- to 1,4-diene bonds is not changed by adding the potassium salt. When the amount of the potassium salt required for the strictly random copolymerization of, for example, styrene and butadiene is added, the relative proportion of the 1,2-vinyl structure remains below 15%, in one case advantageous, below about 11 to 112%, based on the sum of the microstructure of 1,2-vinyl and 1,4-20 cis / trans. In the case of the polymerization initiated with the butyllithium in the cyclohexane, the molar ratio of lithium to potassium in this case is from about 10: 1 to 40: 1. If a gradient of the composition (ie a composition that changes more or less constantly within the scope of the invention, from butadiene to styrene), the Li / K ratios greater than 40 are desired throughout the random block: 1 should be chosen, and ratios smaller than 10: 1 in the case of a gradient of styrene to butadiene. A novel block copolymer can be represented, for example, by one of the general formulas 1 to 11: (I) (A- (B / A)) n; 10 (2) (A- (B / A)) n-A; (3) (B / A) - (A- (B / A)) n; (4) X - [(A- (B / A) n] m + l; (5) X - [((B / A) -A) n] m + l; (6) X - [(A- (B / A)) nA) m + l; 15 (7) X - [((B / A) -A) n- (B / A)] m + 1; (8) Y- [(A- (B / A)) n] m + l; (9) Y - [((B / A) -A) n] m + 1; -% > (10) Y - [(A- (B / A)) n-A] m + l; (II) Y - [((B / A) -A) n- (B / A)] m + l; Where A is a vinylaromatic block and (B / A) is the soft phase, that is, the block comprising random units of diene and vinylaromatic, X is a radical of an n-functional initiator, and is a radical of a m-functional coupling agent y and n are natural numbers from 1 to 10.

A preferred block copolymer is one of the general formulas A- (B / A) -A, X - [- (B / A) -A] 2 and Y- [- (B / A) -A] 2 (for the meanings of the abbreviations, see above) and a particularly preferred block copolymer is one whose soft phase is divided into blocks. (12) (B / A) r (B / A) 2; (13) (B / A) 1- (B / A) 2- (B / A) 1; (14) (B / A)! - (B / A) 2- (B / A) 3; Wherein the blocks have different compositions or their ratio of vinylaromatic monomers / diene in the individual blocks (B / A (changes such that a gradient of the composition (B / A) p ^ "(B / A) p2" ( B / A) p3 .... occurs in each segment (block part), the glass transition temperature Tg of each block part is less than 25 ^ C. Such block copolymers having within a block (B / A), for example, p repeated segments (block parts) with the changing monomer composition can be formed by the addition of p portions of the monomers, where p is an integer from 2 to 10 (see also the following examples). The addition of a few at a time may serve, for example, to control the thermal equilibrium in the reaction mixture.

A block copolymer, which has a plurality of blocks (B / A) and / or A, each with a different molecular weight per molecule, is similarly preferred. It is also possible for a block A, compound exclusively of vinylaromatic units being replaced by a block B, since it is important that an elastomeric block copolymer is formed. Such copolymers can have, for example, structures (15) to (18): (15) B- (B / A) (16) B / A) -B- (B / A) (17) (B / A) 1-B- (B / A) 2 (18) B [( B / A)! - (B / A)] 2.

Innovative block copolymers are very suitable for the production of elastomeric shaped articles by conventional methods for the thermoplastic process, for example as a film, foam, thermoformed molding, injection molding or extruded profile. For the purposes of the present invention, preferred vinylaromatic compounds are styrene and also a-methylstyrene and vinyltoluene and mixtures of these compounds. Preferred dienes are butadiene and isoprene and also piperylene, 1-phenylbutadiene and mixtures of these compounds.

A particularly preferred monomer combination comprises butadiene and styrene. All the weights and volumes indicated below are based on this combination; If the technical equivalents of styrene and butadiene are used, it may be necessary to convert the data appropriately. The block (B / A) consists of, for example, 75-40% by weight of styrene and 25-60% by weight of butadiene.

Particularly, preferably, a soft block has a butadiene content of 35 to 70% and a styrene content of 65 to 30%. In the phase of the combination of styrene / butadiene monomers, the amount by weight of the diene in the total block copolymer is from 1 to 65% by weight and that of the vinyl aromatic component is correspondingly from 85 to 35% by weight. The butadiene / styrene block copolymers, which have a monomer composition comprising from 25 to 60% by weight of diene and from 75 to 40% by weight of the vinylaromatic compound, are particularly preferred. The block polymers are prepared by anionic polymerization in a non-polar solvent, the initiation being carried out by means of organometallic compounds. Alkali metal compounds, in particular the "< s ** ~ f-lithium, are preferred. Examples of initiators are methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium, sec. -butillitio and tere. -butyl lithium. The organometallic compound is added as a solution in a chemically inert hydrocarbon. The dose depends on the intended molecular weight of the polymer, but is, as a rule, from 0.002 to 5%, based on the monomers. The solvents used are preferably aliphatic hydrocarbons, such as cyclohexane and • # methyl-cyclohexane. According to the invention, the random blocks of the block copolymers, these blocks simultaneously contain vinylaromatic and diene monomers, are prepared with the addition of a soluble potassium salt, in particular a potassium alcoholate. It is believed that potassium salt suffers a metal exchange with the pair of lithium-carbanion ions, potassium-carbanions being formed and # ^ preferably suffering an addition reaction with the styrene, while the lithium-carbanions preferably undergo an addition reaction with the butadiene. Because that the potassium-carbanions are substantially more reactive, a small fraction, ie from 1/10 to 1/40, is sufficient on average, together with the predominant lithium-carbanions, to make the incorporation of styrene and butadiene equally likely . Likewise, it is believed that < Hv- metal exchange occurs frequently between the active chains and between an active chain and the dissolved salt, during the polymerization process, so that the same chain preferably undergoes the addition with the styrene, for a part, and then with the butadiene, on the other. Consequently, the parameters of the copolymerization are then virtually the same for styrene and butadiene. Particularly suitable potassium salts are potassium alcoholates, in this case in particular the tertiary alcoholates of at least 7 carbon atoms. Typical corresponding alcohols are, for example, 3-ethyl-3-pentanol and 2,3-dimethyl-3-pentanoi. Tetrahydroalinalool (3,7-dimethyl-3-octanol) has proven to be particularly suitable. In addition to potassium alcoholates, other Potassium salts that are inert to metal alkyls are, in principle, also suitable. Examples of these are dialkyl potassium amides, alkylated diaryl potassium amides, alkyl thiolates and alkylated aryl thiolates. The moment when the potassium salt is added to the reaction medium is important. Usually, at least parts of the solvent and monomer for the first block are initially taken in the reaction vessel. It is not advisable to add the potassium salt at this time, since it is at least partially hydrolysed to KOH and alcohol by traces of protic impurities. The potassium ions are then irreversibly deactivated by the polymerization. The organic lithium must, therefore, be added first and mixed before adding the potassium salt. If the first block is a homopolymer, it is advisable to add the potassium salt only briefly before the polymerization of the randomized block. Potassium alcoholate can be prepared Easily from the corresponding alcohol, stirring a solution of cyclohexane in the presence of an excess of potassium-sodium alloy. After 24 hours at 252C, the evolution of hydrogen and thus the reaction are completed. However, the reaction can also be shortened to a few hours by Reflux to 802c. An alternative reaction involves adding a small excess of potassium methylate, potassium ethylate or potassium tert-butylate to the alcohol.1. in the presence of a high-boiling inert solvent, such as decalin or ethylbenzene, distill the alcohol low boiling point, in this case methanol, ethanol or tere. -butanol, dilute the residue with cyclohexane and filter and separate the solution from the excess of the sparingly soluble alcoholate.

As a result of the addition of the potassium compound, the proportion of the 1,2-bonds as a ratio of the sum of the 1,2 and 1,4 bonds of the diene comes, in general, from 11 to 9%. In comparison, when a Lewis base, 5 according to DE-A1-44 20 952 is used, the ratio of the 12 and 1.4 bonds of the diene units comes, for example, from 15 to 40% for the links 1,2 and 85 to 60% for the 1,4 links, with base, in each case, in the total amount of the polymerized diene units. The temperature of the polymerization can be from 0 to 1302C, preferably from 3Q to lOOsc. The volume quantity of the soft phase in the solid is of decisive importance for the mechanical properties. According to the invention, the amount in The volume of the soft phase composed of diene and vinylaromatic sequences is from 60 to 95%, preferably from 70 to 90%, particularly preferred from 80 to 90% by volume. The A blocks formed of the vinylaromatic monomers form the hard phase, the sanctity in corresponding volume sum of the to 40, preferably 10 to 30, particularly preferred 10 to 20% by volume. It should be noted that there is no strict concordance between the aforementioned ratios of the vinylaromatic compound and the diene. the aforementioned limits of the phase volumes and the composition, which result from the novel intervals of the glass transition temperature, since they are, in each case, numerical values rounded to full tens. Rather, any such relationship can be merely accidental. The volume quantity of the two phases can be measured by high contrast electron microscopy or nuclear magnetic resonance spectroscopy, NMR, solid state. The amount of vinylaromatic blocks can be determined by precipitation and weight, after the degradation of the osmium of the polydiene fraction. The ratio of the future phase of n polymer can also be calculated from the amounts of monomers used if complete polymerization is allowed in each case. For the purposes of the present invention, the block copolymer is unambiguously defined by the quotient of the volume fraction as a percentage of the soft phase formed of the blocks (B / A) and the fraction of the diene units in the soft phase, which is from 25 to 70% by weight for the styrene / butadiene combination. The glass transition temperature (Tg) is influenced by the incorporation of vinylaromatic compounds in the smooth block of the block copolymer and the use of potassium alcoholates during the polymerization. A glass transition temperature of -50 to +252C, preferably from -50 to + 52C is typical. In the case of novel catalyzed randomized potassium copolymers, the glass transition temperature is on average 2 to 5 times less than in the case of the corresponding products catalyzed by a Lewis base, because the latter has a higher proportion of 1,2-butadiene bonds. The 1,2-polybutadiene has a glass transition temperature, which is 70 to 902 greater than that of 1,4-polybutadiene. The molecular weight of block A is, in general, 1000 to 200,000, preferably from 3000 to 80,000 g / mol. Within a molecule, the A blocks may have different molecular weights. The molecular weight of the block (B / A) is usually from 2,000 to 250,000, preferably from 5,000 to 150,000 g / mol. As in the case of block A, a block (B / A) may also have different molecular weights within a molecule. The coupling center X is formed by the reaction of the active anionic chain ends with a bifunctional or polyfunctional coupling agent. Examples of such compounds are described in the patents of U. U.A., Nos. 3,985,830, 3,280,084, 3,637,554 and 4,091,053. For example, epoxidized glycerides, such as epoxidized flaxseed oil or soybean oil, are preferably used; Divinylbenzene is also adequate. Dichloro-dialkylsilanes, dialdehydes, such as terephthalic aldehyde and esters, such as ethyl formate or ethyl benzoate, are particularly suitable for dimerization. Preferred polymer structures are A- (B / A) -A; X - [- B / A) -A] 2 and Y- [- (B / A) -A] 2, where the block itself * random (B / A) can, in turn, be subdivided into blocks (B ^ /? -) - (B2 / A2) - (B3 / A3) -... The random block preferably consists of 2 to 15, particularly preferred 3 to 10, random partial blocks. The subdivision of the random block (B / A) into a very large number of partial blocks Bn / An has the decisive advantage that the block (B / A) as a total behaves like a virtually perfect random polymer, even in the case of a composition that continuously changes Jun gradient) within a partial block Bn / An, since it is difficult to avoid in anionic polymerization under practical conditions (see below). For the Therefore, it is useful to add less than the theoretical amount of potassium alcoholate. A greater or lesser proportion of the partial blocks can be provided, with a high content of diene. this results in the polymer retaining a hardness residue and not becoming completely brittle, yet ^^ - below the glass transition temperature of the predominant (B / A) blocks. The novel block copolymers have a spectrum of properties very similar to that of soft PVC, but they can be prepared completely free of low molecular weight plasticizers, capable of migration. Under the usual conditions of the process (180 to 2202C), they are stable to interweaving. The excellent stability of the novel polymers to the interlacing can be demonstrated clearly by means of the rheography. The experimental setting corresponds to that of the MVR measurement. At a constant melt flow rate, the increase in pressure as a function of time is recorded. The novel polymers show no increase in pressure, even after 20 minutes at 2502C and give a uniform melt extrudate, while under the same conditions, a comparative sample produced with j ^ 2? F THF, according to DE-AI 44 20 952, exhibited triple the pressure and its The extrudate has the appearance of a barbed wire, typical of entanglement. 20 The novel block copolymers are also distinguished by the high perception of oxygen P0 and the steam permeation of water Pw of more than 2000 [cm3-100 mm / m2, d-bar] and more than 10 [g 100 mm / m2 -d-bar], respectively, where P0 is the amount of oxygen in cm3 and Pw is the amount of water vapor in grams, which passes through 1 m2 of the film with a standard thickness of 100 mm per day and per partial pressure difference bar. A high strength of restoration in the deformation, as observed in the case of thermoplastic elastomers, high transparency (more than 90% at a layer thickness of 10 mm), a low welding temperature of less than 120QC and a wide range of welding (more than 52), in combination with a moderate tackiness make the novel block copolymers a starting material suitable for the production of stretched films. Infusion tubes and other extruded items, injection molded, thermoformed or blown finishing, which have a high transparency and hardness, particularly for medical applications. The polymerization is carried out in a plurality of stages and, in the case of monofunctional initiation, is initiated, for example, with the preparation of a hard A block. A part of the monomers is initially taken into the reactor and the polymerization is started by adding the initiator. In order to achieve a defined chain structure, which can be calculated from the monomer and initiator dose, it is advisable to carry out the process at high conversion (more than 99%) before the addition of the second monomer. Also, this is not absolutely essential.

The order of monomer addition depends on the chosen structure of the block. In the case of monofunctional initiation, for example, the vinylaromatic compound is either initially taken or directly dosed. A solution of cyclohexane of potassium alcoholate is then added. The diene and vinylaromatic monomers must then be added in the simultaneously possible form. The addition can be effected in a plurality of portions, for example, to facilitate the removal of heat. The random structure and the composition of the block (B / A) are determined by the ratio of the diene compound to the vinylaromatic, the concentration of the potassium salt and the temperature. According to the invention, the weight amount of the diene is from 25 to 70% relative to the total mass, which includes the vinylaromatic compound. Block A can then be polymerized by the addition of the vinylaromatic compound. Instead, the required polymer blocks can also be linked together by the coupling reaction. In the case of bifunctional initiation, the block (B / A) is synthesized first, followed by block A. Further processing is carried out by conventional methods. It is advisable to work in a stirred kettle and protonate the carbanions with an alcohol, such as isopropanol, to make the mixture weakly acidic, before further processing, in a conventional manner with C02 / water, to stabilize the polymer with an inhibitor of oxidation and a free radical acceptor (commercial products, such as trisnonylphenyl phosphite (TNPP) or 5 to alpha-tocopherol (vitamin E or products that can be obtained under the trade names Irganox 1076 or Irganox 3052)), to remove the solvent by conventional methods and carry out extrusion and granulation. The granules can be protected from adhesion, as in the other grades of rubber, with an anti-blocking agent, such as Acrawaz®, Besquare® or Aerosil®. Examples For each example, a stainless steel autoclave, with a capacity of 50 liters, that can be heated and The simultaneous cooling, which was equipped with a cross-arm stirrer, was prepared by flooding it with nitrogen, boiling a solution of secondary butyl-lithium and 1,1-diphenylethylene, in a molar ratio of 1: 1, into cyclohexane and drying. 20 22.8 liters of cyclohexane were then introduced in each case and the amounts of the initiator, monomers and potassium alcoholate, shown in Table 1, were added. The duration of the polymerization and the initial and final temperature, T and Tp, respectively, are also noted, the duration of the monomer charge always being small compared to the duration of the polymerization. The temperature of the reaction mixture was controlled by heating or cooling the reactor jacket. After the end of the reaction (consumption of the monomers), the titration was carried out with the ethanol in Examples 1-7 and the comparative experiment with the ethyl formate in Example 8 and with epoxidized linseed oil in the Example 9, until the color disappeared, or, in Examples 11 and 12, until A pale yellow color appeared and the mixture was acidified with a 1.5 fold excess of formic acid. Finally, 34 g of a commercial stabilizer (Irganox® 3052, Ciba-Geigy / Basilea) and 82 g of trisnonylphenyl phosphite were added. The solution was worked in a devolatilization extruder (three domes, devolatilization back and forth) to 2002C and the granulation was carried out. 10 g of Acrawax®, as an external lubricant, were added to the granules in a fluid mixer. For mechanical measurements, sheets were produced of 2 mm thick by compression molding (2002C, 3 minutes) and the standard test specimens were marked. fP- Table l; Polymerization and analysis of the linear block copolymers S-SB-S and a star block copolymer (Example 9; Table la)) Vl ~ ww * Table 1 (Continued) a), b), these 2 stages of transition to glass, which extend in each case over the indicated range and can presumably be signaled to the chemically different polymer regions. r ^ * ~ Table the Table the (Continuation S ^ P * " __TO a), b) see above c) Ethyl format; d) Edenol ® B 316, from Henkel.

Table 2: Mechanical Properties (all values in fN / mm2)) W- Table 2 (Continued) Table 3; Rheographic measurement (determination of thermal stability) at 25Qec The rheographic measurements were carried out in a Gottfrt MFl apparatus. The increase in pressure, which is a measure of the increased entanglement of the sample at the selected temperature, was monitored at a constant flow. Since the materials are also especially suitable for thin films, the extremely low gel content, ie, low tendency to interlace at the process temperature of, for example, 200 to 2202C, is important.

Claims (23)

1. CLAIMS 1. An elastomeric block copolymer, comprising at least one block A, having polymerized units of a vinylaromatic monomer and forming a hard phase and at least one elastomeric block (B / A), having polymerized units of a monomer vinylaromatic, and of a diene and forming a smooth phase, the glass transition temperature, Tg, of block A is above 252C and that of block (B / A) is below 252C, and the ratio of phase volume from block A to block (B / A) is selected so that the proportion of the hard phase in the total block copolymer is from 1 to 40% by volume, and the amount of the diene is less than 50% by weight, The relative amount of the 1,2-links of the polydiene, based on the sum of the 1,2- and 1,4-cis / trans bonds, is less than 15%.
2. 2. A block copolymer, as claimed in claim 1, wherein the amount of 1,2-bonds of the polydiene is less than 12%.
3. 3. A block copolymer, as claimed in claim 1, wherein the glass transition temperature of the hard phase is greater than 50SC and the glass transition temperature of the soft phase is less than 5se.
4. 4. A block copolymer, as claimed in claim 1, wherein the vinylaromatic monomer is selected from styrene, α-methylstyrene, vinyltoluene and 1,1-diphenylethylene, and the diene is derived from butadiene and isoprene.
5. 5. A block copolymer, as claimed in claim 1, wherein the B / A block has a weight Molecular weight of 2000 to 250,000 (g / mol) and block A has a molecular weight of 1000 to 200,000 (g / mol).
6. 6. A block copolymer, as claimed in claim 1, wherein the monomer composition £ comprises from 25 to 60% by weight of the diene and from 75 to 40% by weight of the vinylaromatic compound.
7. 7. A block copolymer, as claimed in claim 6, having a monomer composition of about 75 to 40% by weight of styrene and 25 to 60% by weight of butadiene.
8. 8. A block copolymer, as claimed in claim 1, wherein the soft block (B / A) has a butadiene content of 39 to 70% and a styrene content of 65 to 30%.
9. 9. A block copolymer, as claimed in claim 1, wherein the soft phase (B / A) is a random copolymer of vinylaromatic monomers and dienes. 10. A block copolymer, as claimed in claim 1, which is one of formulas 1 to 11: (1) (A- (B / A)) n; (2) (A- (B / A)) n-A; (3) (B / A) - (A- (B / A)) n; (4) X - [(A- (B / A) n] m + l; (5) X - [((B / A) -A) n] m + l; (6) X - [(A- (B / A)) nA) m + l; (7) X - [((B / A) -A) n- (B / A)] m + l; (8) Y - [(A- (B / A)) n] m + l; (9) Y - [((B / A) -A) n] m + l; (10) Y - [(A- (B / A)) n-A] m + 1; (11) Y-caB / AJ-AJn-ÍB / Apm + l; where A is a vinylaromatic block and (B / A) is the block comprising random units of diene and vinyl aromatics, X is a radical of an n-functional initiator, Y is a radical of an m-functional coupling agent and m and n are natural numbers from 1 to
10. 10.
11. 11. A block copolymer, as claimed in claim 1, which is one of the formulas: A- (B / A) -A, X - [- (B / A) -A] 2 and Y - [- (B / A) -A] 2.
12. 12. A block copolymer, as claimed in claim 1, wherein the soft phase (B / A) is subdivided into a plurality of blocks of formulas 12 to 14: (12) (B / A) 1- ( B / A) 2; (13) (B / A) 1- (B / A) 2- (B / A) 1; (14) (B / A)! - (B / A) 2- (B / A) 3; ML where the blocks have different compositions, within the ranges of claim 1.
13. 13. A block copolymer, as claimed in claim 1, wherein a plurality of 5 blocks (B / A) and the ratio of the vinyl-atomic / diene monomers is different in the individual blocks (B / A).
14. 14. A block copolymer, as claimed in claim 1, in which the repeated segments p (blocks 10 partial) with a changing monomer composition, are present within a block (B / A), as formed by the addition of the p portions of the monomers, where p is an integer from 2 to 10.
15. 15. A block copolymer, as claimed in claim 14, wherein the composition within a block changes within the limits of claim 1, so that a gradient of the composition (B / A) p ^ "( B / A) p « (B / A) p3 ..... occurs in each segment (partial block), the glass transition temperature Tg of each partial block 20 is less than 25ec.
16. 16. A block copolymer, as claimed in claim 1, wherein a plurality of blocks (B / A) or A, each with a different molecular weight per molecule, are present.
17. 17. A method for the preparation of a block copolymer, as claimed in claim 1, by the anionic polymerization by means of the alkyl lithium, in a non-polar solvent, where the polymerization is carried out from at least the soft phase ( B / A), in the presence of a soluble potassium salt.
18. 18. A method, as claimed in claim 17, in which the potassium salt used is a potassium alcoholate of a tertiary alcohol having at least 7 carbon atoms.
19. 19. A method, as claimed in claim 17, wherein the soluble potassium salt used is potassium 2,3-dimethyl-3-pentanolate, potassium 3,7-dimethyl-3-octanolate or 3-ethyl. -3-potassium pentanolate.
20. 20. A method, as claimed in claim 17, wherein the molar ratio of lithium to potassium is from 10: 1 to 40: 1.
21. 21. A method, as claimed in claim 17, wherein, in order to achieve a gradient of the composition along the block (B / A), the molar ratio of lithium to potassium is selected to be greater than 40: 1 or less than 10: 1.
22. 22. A method, as claimed in claim 17, in which the potassium salt is added only briefly 'M before the polymerization of the randomized block, if necessary (in addition) first the lithium organyl and then the salt is added. of potassium
23. 23. The use of a block copolymer, as 5 claims in claim 1, for the production of articles configured in the form of a film, foam, thermoformed article, injection molded article or extruded profile. go