DE2234703A1 - BLOCK COPOLYMERS WITH SILOXAN BLOCKS AND ORGANIC BLOCKS - Google Patents

Description

counselors

'■. DR. I. MAAS DR. F. VOITHENLEITNER 8 MUNICH 40

SCHLEISSHEIMER STR. 299 -TEL. 3592201I205

MS-P 274

Dow Corning Ltd., Whitehall, London / England (formerly Midland Silicones Limited)

Block copolymers with siloxane blocks and organic blocks

Addition to P 20 30 272.1

summary

A further development of the subject matter of P 20 30 272.1 is a process for the production of copolymers with siloxane blocks and organic blocks described in which the organic blocks predominantly consist of alpha-methylstyrene units exist.

According to this method, alpha-methyl styrene is polymerized anionic at a temperature below 20 ⁰ C, the product is a different anionically polymerizable monomer, for example styrene, and a cyclic organotrisiloxane is und.dann kept below 20 ⁰ C was added.

The block copolymers are advantageous as additives for modifying the surface properties of polymers or can be coupled to form thermoplastic elastomers.

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The invention aims to further develop or improve the subject matter of P 20 30 272.1 and relates to a process for the preparation of block copolymers with Siloxane blocks and organic blocks.

It is known. Copolymers with blocks of organosiloxane units and making blocks from organic units (e.g., styrene units). Copolymers this Type can be made by polymerizing an organic monomer using a carbanion-forming catalyst and then combining the polymerized monomer with a cyclic siloxane. One such The process is described in the main patent (P 20 30 272.1).

With styrene and other organic monomers that delivers Process according to the main patent, although useful results, when using alpha-methylstyrene as the organic Monomers, however, the formation of block copolymers takes place so slowly that the process is suitable for industrial use is not attractive.

It has now been found that block copolymers with organosiloxane blocks and blocks, which are predominantly made of poly (alpha-methylstyrene) exist, in considerably shortened reaction times and in improved yield through a modification of the process according to the main patent can be obtained. Furthermore, it was found that branched polymers with units, derived from alpha-methylstyrene can be produced, which are characterized by advantageous elastomers Characteristics distinguish.

The process according to the invention for the production of block copolymers with siloxane blocks and organic blocks,

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which consist predominantly of units of polymerized alpha-methylstyrene, is characterized in that (1) alpha-methylstyrene is anionically polymerized in the presence of a lithium-containing carbanion-forming polymerization initiator and an aprotic solvent at a temperature below 20 ° C, (2) the product of (1) maintained at a temperature below 20 ⁰ C and which is mixed in step (1) obtained polymerized älpha-methylstyrene with an anionically polymerizable organic monomers and with a cyclic organotrisiloxane, in which the substituents on the silicon atoms, hydrogen atoms ,, monovalent hydrocarbon radicals or ß-Perfluoroalkyläthylreste, but not more than 1 hydrogen atom is bonded directly to a silicon atom, and (3) the cyclic organotrisiloxane is polymerized in the presence of a polar aprotic organic solvent. .

According to step (1) of the process according to the invention alpha-methylstyrene in the presence of a lithium-containing one Polymerization initiator forming carbanions is anionically polymerized. Suitable lithium-containing initiators are the alkyl, aryl and alkenyl lithium compounds, for Example nH-butyllithium, sec-butyllithium, methyllithium, Phenyllithium, lithium anthracene and vinyl lithium. Further Lithium containing initiators are also useful, for example dilithiurastilbene and dilithium naphthalene. For cost reasons and because of easier accessibility however, the monolthium compounds, especially butyllithium, preferred"

As with known polymerization processes with carbanions as polymerization initiators, the amount of initiator used depends on the desired degree of polymerization

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of the polymeric alpha-methylstyrene. The ratio of. '

Initiator and alpha-methylstyrene, which for a polymer block j

- ■ ■ i

with a given molecular weight is required, can;

can be easily calculated and for example from 0.00001 mol <

Initiator per mole of alpha-methylstyrene for the production *

from high molecular weight polymer blocks to about 0.2 moles;

Initiator per mole of alpha-methylstyrene, if low molecular weight polymer blocks are desired, are sufficient.

The polymerization of alpha-methylstyrene according to stage (1) of the method according to the invention is also like in the case of known anionic polymerization methods, best in the absence of water or other impurities carried out the initiator or the generated anion could deactivate.

The polymerization of the alpha-methylstyrene is also carried out in the presence of an aprotic solvent, i.e. a organic solvent that is free of active protons, which is responsible for the formation and further growth of the carbanion polymerisation centers could affect. Examples of such aprotic solvents are benzene, toluene, xylene or hexane and polar solvents such as dioxane, tetrahydropyran, tetrahydrofuran, diethyl ether, Diethylene glycol dimethyl ether and dimethoxyethane. By using of polar aprotic solvents, the rate of polymerization of alpha-methylstyrene becomes considerable elevated. Therefore, the use of such solvents, either alone or in combination with non-polar aprotic solvents, for example toluene, are preferred.

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"While the polymerization step (1) the temperature of the reaction mixture is kept below 20 C. A particularly advantageous temperature range for the polymerization is a range of -40 to 0 ⁰ C. At such temperatures, the polymerization of alpha-methyl styrene in the presence aprotisehen a polar Solvent, for example tetrahydrofuran, run off quickly.

After Polyirierisation of alpha-methyl styrene, the polymeric product is kept at a temperature below 20 ⁰ C and mixed at a temperature below 20 ⁰ C with the cyclic organotrisiloxane and with an organic monomers that can be polymerized anionically and its anion with the organotrisiloxane reacted. Organic monomers that meet these conditions are styrene, alpha-vinylnaphthalene, butadiene, isoprene, 2- and 4-vinylpyridine, acrylonitrile, thiacyclobutane, methylthiacyclobutane, and propylene sulfide. Styrene is preferred. If desired, more than one of these organic monomers can be used to make block copolymers. The order of shuffling is not critical. The organic monomer and the organotrisiloxane are expediently introduced together into the polymerized alpha-methylstyrene. However, if desired, either the organotrisiloxane or the monomer can be mixed with the polymerized alpha-methylstyrene before the other is added.

The amount of anionically polymerizable organic monomer used depends on the desired ratio of Units of the monomer and the alpha-methylstyrene in the organic block of the block copolymer produced.

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Preferably the organic monomer is employed in an amount which averages at least one molecule of the monomer per molecule of polymerized alpha-methyl styrene results. If the presence of unreacted poly (alpha) pharaethylstyrene) in the block copolymer is allowable or desirable, a minor proportion of the organic monomer can be used can be applied. It is particularly preferred to use the organic monomer in an amount that is average 1 to 6 corresponding monomer units attached to each poly (alpha-methylstyrene) block. The amount of organotrisiloxane used also depends on the desired molecular weight of the siloxane blocks of the copolymer away. In the cyclic organotrisiloxane, the silicon-bonded substituents hydrogen atoms, monovalent Hydrocarbon residues or ß-perfluoroalkylethyl residues, for example methyl, ethyl, propyl, decyl, tetradecyl, octadecyl, phenyl, naphthyl, vinyl, allyl, chlorophenyl or 3,3,3-trifluoropropyl radicals. Not more than a hydrogen atom should be present as a substituent on every silicon atom. Cyclic ones are preferred Organotrisiloxanes, in which the silicon-bonded substituents are organic radicals with fewer than 7 carbon atoms, preferably methyl radicals with or without vinyl, phenyl or 3,3,3-trifluoropropyl radicals as one or more further leftovers are. Examples of the preferred organotrisiloxanes are hexamethylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane, 1,3,5-triethyl-1,3,5-trivinylcyclotrisiloxane and 1,3,5-trimethyl-1,3,5-tri (3,3,3-trifluoropropyl) -cyclotrisiloxane.

After introducing the organic monomer into the mixture, the alpha-methylstyryl anion is converted to an anion which ^/ more rapidly with the cyclic organotrisiloxane to form one

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Reacts "alive" silanolate anion. Polymerization of the cyclotrisiloxane then takes place starting from the silanolate anion. During this polymerization, units from the organic polymer are incorporated into the organic block. During this polymerization, units from the organic monomer are incorporated into the organic block and are present in the block copolymer produced. The polymerization of the cyclotrisiloxane can take place at temperatures below 20 ^° C., but in order to achieve higher polymerization rates, the use of higher temperatures is preferred. Normally, the polymerization proceeds the Organotrisiloxans at temperatures of 20 to 50 ⁰ C satisfactory, but if desired the reaction mixture can even higher temperatures, for example to the reflux temperature are employed.

It is usually unnecessary to use the polymerized alpha-methylstyrene before the copolymerization with the organic monomers and the cyclic organotrisiloxane from the to isolate organic solvents used as a carrier. For the sake of simplicity, therefore, the organic Solvent system used for the polymerization of alpha-methylstyrene, or a part of which are carried along and are present during the polymerization of the organotrisiloxane. The polymerization of the " Organotrisiloxane should expediently be carried out in the presence of a polar solvent, so that a industrially advantageous rate of polymerization is achieved. In cases where the solvent system is carried over from the first to the second polymerization stage a polar solvent should be added if it is not already contained in it. That The finished polymer can therefore contain several different solvents contain, including a polar solvent,

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a non-polar solvent, for example toluene, as a carrier for the cyclic organotrisiloxane and possibly another non-polar solvent, for example Hexane, as a carrier for the lithium-containing polymerization initiator.

The polymerization of the cyclic organotrisiloxane can carried out to the end and the copolymer can then be recovered as such or with an agent that active silanolation neutralized, treated. If desired, however, block copolymers with a narrower molecular weight distribution by terminating the polymerization of the organotrisiloxane at an earlier stage Section of the polymerization reaction can be obtained. For example, the polymerization can take place at a time be terminated in which less than 80% of the organotrisiloxane has polymerized. The appropriate duration the polymerization stage to achieve the desired conversion can easily be determined by analytical methods will.

Suitable neutralizing agents to terminate the siloxane polymerization are for example dilute acids, compounds containing active hydrogen, halosiloxanes and halosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane and dimethylphenylchlorosilane.

In this section, the block copolymer can be isolated by any suitable method. For example, can the solvent or solvents are removed by distillation and the product obtained by fractional precipitation. In general, however, it is preferred to have two or more

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of the block copolymers to couple together, for example to obtain a linear ABcBA copolymer or a branched copolymer in which several blocks AB with each other are linked, i.e. an (AB) c copolymer, in which A denotes the organic block and B denotes the siloxane block, χ has a value of 2 or more and c is the linking group. It has been found that the copolymers obtained as a result of the coupling of the blocks AB, tough elastomeric materials * are particularly preferred Because of their increased tensile strength, the branches are branched Copolymers in which χ has a value of 4 or more.

Any substance with at least two atoms or radicals / those with the active silanolate ions can be used as coupling agent in which block copolymer molecules are reactive can be used. The preferred substances are Organosilicon compounds with two or more reactive Positions, for example halogen atoms bonded to silicon. The organosilicon compounds can be of any kind be. For example, they can be silanes, polysilanes, cyclic siloxanes, disiloxanes / polysiloxanes, silalkylenes, Be silarylene and silalkylene siloxanes. The particularly preferred organosilicon compounds are silanes general formula

V ^iX 4-n,

Siloxanes with at least two units of the general formula

^Rl m ^Si0 4-m

and silethylene compounds of the general formula (R ' ₃ SiCH ₂ ) ₂ ,

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where in these general formulas R is a monovalent hydrocarbon radical or monovalent halogenated hydrocarbon radical and R 'denotes a monovalent hydrocarbon or halogenated hydrocarbon ^{radical or a halogen atom, at least two of the substituents R 1} in the siloxane and silethylene molecules are halogen atoms, X is a halogen atom, preferably chlorine, and η is 0, 1 or 2 and m is 1, 2 or 3.

Examples of the substituents R and R ¹ are methyl, ethyl, propyl, octyl, tetradecyl, vinyl, allyl, phenyl, tolyl, benzyl, chlorophenyl and 3,3,3-trifluoropropyl.

Examples of the preferred organosilicon compounds are (CH ₃ ) ₂ SiCl ₂ , C ₆ H ₅ SiCl ₃ , CH ₃ (CH ₂ = CH) SiBr ₂ , C ₃ H ₅ SiCl ₃ , CH ₃ SiCl ₃ , SiCl ₄ , 1.5 -Dichloro-1,1,2,2,5,5-hexamethyltrisiloxane and

The nature of the linking group depends on the type of coupling agent used. When the coupling agent is a silane or siloxane, the linking group c can consist of one or more siloxy units. These units can be identical to those of the siioxane block in the original block copolymer. In in this case c can be regarded as part of the B blocks.

The preferred copolymers obtainable by the process of the invention are those in which the alpha-methylstyrene units make up at least 80% of the total number of units in the organic blocks. Such copolymers are new and within the scope of the invention are block copolymers which contain at least one block of at least three siloxane units of the general formula R ₂ SiO, where R is a hydrogen atom, a monovalent hydrocarbon radical or a ß-perfluoroalkylethyl radical, but on each silicon atom

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no more than one hydrogen atom is directly bound, and contain at least one block of at least five alpha-methyl styrene units and in which the blocks with each other by a linking group of the general formula

are linked, in which M is the repeating unit of a polymer made from styrene, alpha-vinylnaphthalene, butadiene, isoprene, 2-vinylpyridine, 4-vinylpyridine, acrylonitrile, thiacyclobutane, methylthiacyclobutane or propylene. is sulfide and y has a value from 1 to a number which is 25% of the number of alpha-methylstyrene units. Each block particularly preferably contains at least alpha-methylstyrene units, y has a value from 1 to and M denotes the radical -CH ₀ CH (C ^ H ₁ -) -.

£. DO

In the siloxane blocks of the preferred copolymers, R any monovalent hydrocarbon radical or ß-perfluoroalkylethyl radical be as mentioned above in connection with the silicon-bonded substituents of the cyclotrisiloxane used as a reactant. The preferred substituents are, however, the methyl, ethyl, Phenyl, vinyl and 3,3,3-trifluoropropyl radical.

The block copolymers according to the invention have at least one of the defined siloxane blocks, those with the defined organic blocks are connected to. They can be of type AB or type ABA or any of them have other linear or branched configuration, for example (AB) c, where A, B, c and χ as before are defined, but c is preferably the radical that is bonded to silicon by removing 3 to 8 Halogen atoms are formed from a halogenated organosilicon compound.

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uie obtainable by the process according to the invention Block copolymers can be very different in terms of their physical nature. The properties of the copolymers depend mainly on their configuration, molecular weight and proportions Siloxane blocks and organic blocks. If that Copolymer of configuration (AB) c corresponds, in which χ is at least 2, and the organic blocks approximately Making up 5 to about 40% of the total weight of the copolymer, the products concerned are thermoplastic Elastomers. When the organic blocks make up about 40 to about 90% of the total weight of the copolymer, the products are thermoplastic. Molecular Weight Copolymers up to about 10,000 are available as additives for modifying the properties of organic polymers advantageous. For example, the introduction of small proportions of the copolymer, for example of 0.01 to 5 weight percent, in a hydrocarbon polymer such as poly (alpha-methylstyrene) or polystyrene die Effect that the polymer gets surface properties that are characteristic of the silox fraction, but more permanent are. The copolymers of relatively high molecular weight, especially those that are elastomers, are advantageous for the production of sealants, sealing bodies and other products.

The invention is further illustrated by the following examples explained. The physical properties of the copolymers mentioned in the examples are according to the standards of British Standard 903 Parts A2 and A8 measured using the Dunlop Tripsometer to measure the resistance became.

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example 1

A solution of 2.3 g-moles of butyllithium in 1000 g Ifexan is added dropwise to 310 ml of a solution of 100 g of alpha-methylstyrene in tetrahydrofuran at 40 ⁰ C. The measure serves to neutralize any impurities that are present, but no substantial polymerization of the alpha-methylstyrene takes place. The dropwise addition is continued until a persistent deep red color, derived from poly (alpha-methylstyryl) lithium, forms. At this time, the butyl lithium solution are added and a further 2.5 ml of the reaction mixture is rapidly cooled to 0 ⁰ C. Rapid polymerization occurs at this temperature, converting about 85 percent by weight of the alpha-methylstyrene to the polymer.

After equilibrium is established as determined by GLC analysis, it becomes a solution of 15 g of hexamethylcyclotrisiloxane in 15 ml of tetrahydrofuran and then a solution of 5 g of styrene in. 5 ml of tetrahydrofuran added. With the formation of the polysiloxanolate anion, the reaction mixture becomes colorless. Then another 200 g of hexamethylcyclotrisiloxane

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added as a solution in 300 ml of toluene and the solution is heated to about 40.degree. The polymerization of the cyclic siloxane, which occurs under these conditions, is allowed to proceed until 62% of the cyclic siloxane is converted to polysiloxane. In this section, 0.58 g / ClSi (CH ₃₎ JSO be ^{0 to} 9 ^{Beendi un} 9 added to ^the polymerisation and coupling of the block copolymer molecules having the configuration AB. The product, a copolymer with the configuration ABA, is recovered by precipitation with methanol and dried to constant weight in a vacuum oven. It has a number average molecular weight of 54,000 and contains 28 mole percent alpha-methylstyrene blocks, which are linked to the siloxane block by an average of two styrene units per block. A thick film of this copolymer, 1.27 mm (0.050 ") thick, is cast from a solution in cyclohexane. The material is elastomeric and has tensile strength at break

2
of 52.7 kg / cm (750 psi), an elongation at break of 500%, and a tenacity of 3.39 kg / cm (19 lbs./inch).

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Example 2

10/0 ml of a 2.03 molar solution of n-butyllithium in hexane at 1050 maintained at -10 ⁰ C ml of an anhydrous solution of 248 g of alpha-methylstyrene in 610 g toluene and 27 g of tetrahydrofuran. The plum red color of the alpha-methylstyryl anion forms instantly, and in 90 minutes at this temperature the polymerization reaction reaches equilibrium as shown by gas-liquid chromatography.

Then an anhydrous solution of 68 g of hexamethylcyclotrisiioxane (D ₃ ) and 38 g of styrene in 230 g of toluene is added. The temperature of the mixture is kept at -10 C until the silanolate ion has formed, which is indicated by the disappearance of the red color. At this time, a solution of 454 g of D _3, 1570 ml of toluene and 140 g of dimethylformamide is added and increases the temperature of the reaction mixture to 40 ⁰ G. After 3 hours, the GLC analysis shows that the D- has polymerized with a conversion of 100%. A small portion (1 ml) is removed from the solution and the active silanolate ion is _{neutralized by adding (CH 3} ) 'SiCl. 10.66 ml of an anhydrous solution of 12 g / Cl ₂ CH ₃ SiCH _2- Z ₂ in 88 ^ l of cyclohexane are then added to the remaining solution in order to produce a block copolymer of the type (AB) -c, where c is the remainder ■ .

CH_SiCH_CH _o SiCH 3/2 2 _N 3

designated.

The solution slowly doubles with good stirring Given excess methanol, whereby the (AB) ^ - copolymer

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is felled. The block copolymer is then used with other
500 ml of methanol and washed in 'a vacuum oven
60 ⁰ C and 1.0 mm Hg dried to constant weight.

When the copolymer is analyzed, it becomes 26.6 percent by weight
Si (calculated 25.8%) found.

Gel permeation chromatography gives molecular weight values of 42,000 for the AB copolymer and of 160,000 for the (AB) ₄ c copolymer. The calculated molecular weight of the AB copolymer is 36,400.

Are transparent films of the (AB) c ₄ copolymers having a thickness of about 1.65 mm (0.065 ")

(1) by pouring from solution with a solution of 30 g of the copolymer in 300 ml of cyclohexane and

(2) Compression molding of the copolymer crumbs for 20 minutes at 250 ^° C. and a pressure of 176 kg / cm (2500 psi) and
subsequent quenching to room temperature

made in 3 minutes.

The measurement of the physical properties provides the following results:

Sample (kg.cm)

^% permanent

_Elongation deformation rebound at break at break elasticity

(1) (2)

96.5

95.6

830
550

45 15

50 50

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Using the same procedure, a copolymer of the type AB produced, and the silanolate ion is neutralized with (CH -) ^ SlCl:. The copolymer is too weak to measure tensile strength and elongation.

Example 3

Using the amounts and following the procedure of Example 2, poly (alpha-ethylstyrene) is prepared. Then an anhydrous solution of 68 g D and 38 g styrene is added in 230 g of toluene while the solution is maintained at -10 ⁰ C until the red color of the solution disappears. ' Then a solution of 262 g of D, 100 g of dimethylformamide and 1140 ml of toluene is added and the temperature raised to 40 ⁰ C. After 3 hours, GLC analysis shows that all D has polymerized. A small portion of the solution (about 1 ml) is removed for molecular weight determination and the active silanolate ion is neutralized by treatment with solid carbon dioxide.

The remaining solution is then reacted with 10.66 ml of an anhydrous solution of 12 g of ^ Cl-CH ₃ SiCKL / - in 88 ml of cyclohexane to form a block copolymer of type (AB) .c. When the copolymer is isolated by the method described in Example 1, it is found by gel permeation chromatography to have a molecular weight of 100,000. It contains 23.6 percent silicon by weight. The molecular weight of the AB copolymer is 25,000.

The physical properties of the (AB) .c copolymer are measured on test films, which as in Example 2 by Casting from solution and compression molding can be made. It the following results are obtained:

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Tensile strength _{% elongation% rebound} - (kg.cm) elasticity at break

poured from solution 136 680 40

compression molded 118 230 40

Example 4

A type AB copolymer is prepared in the amounts and according to the procedure of Example 2. In the neutralization section, however, the AB copolymer is _{coupled by reaction with 14.3 ml of a solution of / Cl 2} CH ₃ Si (CH ₂ J ₂ CH ₃ SiO _- Z ₄ in toluene (144 g / l). The product produced is a Block copolymer of type (AB) “c and is isolated according to the procedure described in Example 2.

The copolymer contains 26 weight percent silicon and has a molecular weight of 400,000.

The physical properties of the copolymer are measured on a film that is cast from a solution of 30 g of copolymer is made in 300 ml of cyclohexane. The copolymer has a tensile strength of 94.2 kg. cm, one Elongation at break of 1170% and permanent deformation at break of 30%.

Example 5

15.0 ml of a 2.03 molar solution of n-butyllithium in hexane are added to a solution of 248 g of alpha-methylstyrene in 610 g toluene and 27 g of tetrahydrofuran at -10 ⁰ C. It immediately turns a plum red color and equilibrium is achieved in less than 90 minutes.

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Then an anhydrous solution of 68 g of D ₃ and 24 g of isoprene in 230 g of toluene is added. The color of the solution gradually disappears. A solution of 454 g of D ₃ in 1570 ml of toluene and 140 g of dimethylformamide is then added to the solution. The temperature of the mixture is then increased to 40 ^° C., whereupon the D is polymerized in less than 3 hours.

The AB copolymer thus produced is by treating the mixture with 16 _r 0 ml of an anhydrous solution of 12 g (Cl ₂ CH ₃ SiCH _{2) 2} in 88 ml of cyclohexane to a copolymer of the type (AB) coupled ₄ C. The copolymer isolated according to the procedure of Example 2 proved to be a similar elastomer.

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Claims (5)

Patent claims Process according to P 20 30 272.1 for the production of block copolymers with siloxane blocks and organic blocks which consist predominantly of alpha-methylstyrene units, characterized in that (1) alpha-methylstyrene in the presence of a lithium-containing carbanion-forming polymerization initiator and an aprotic solvent at a temperature below 20 C is anionically polymerized, (2) the product from (1) is kept at a temperature below 20 ^° C. and the alpha-methylstyrene polymerized in stage (1) is mixed with an anionically polymerizable organic monomer and with a cyclic organotrisiloxane, in which the Substituents on the silicon atoms are hydrogen atoms, monovalent hydrocarbon radicals or ß-perfluoroalkylethyl radicals, but no more than one hydrogen atom is bonded directly to a silicon atom, and (3) the cyclic organotrisiloxane is polymerized in the presence of a polar aprotic organic solvent. 2. The method according to claim 1, characterized in that the anionically polymerizable organic monomer Styrene is used. 3. The method according to claim 1 or 2, characterized in that the block copolymer produced with siloxane blocks and organic blocks are reacted with an organosilicon compound having at least two groups bonded to silicon which react with the active silanolate anions in the block copolymer. 209884/1279 4. The method according to claim 3, characterized in that that als.Organosiliconverbindungen a silane of the general formula ^R n ^SiX 4-n ' a siloxane with at least two units of the general formula ^Rl m ^Si0 4-m "'■ or a silethylene compound of the general formula is used, where in the general formulas R denotes a monovalent hydrocarbon radical or monovalent halogenated hydrocarbon radical and R ¹ denotes a monovalent hydrocarbon radical, a monovalent halogenated hydrocarbon radical or a halogen atom, at least two of the substituents R ¹ in the siloxane and silethylene molecules are halogen atoms, X is a Is halogen atom and η is 0, 1 or 2 and m is 1, 2 or 3. 5. Block copolymer with siloxane blocks and organic Blocks, characterized in that there is at least one block of at least three siloxane units of the general a formula R ₂ SiO, wherein R each represents a hydrogen atom, a monovalent one Hydrocarbon radical or a ß-perfluoroalkylethyl radical means but not more than one hydrogen atom '20 9 88 4/127 9 bonded directly to a silicon atom, and at least one organic block of at least five alpha-methylstyryl units contains and that the blocks are connected to one another via a divalent group of the formula are linked, wherein M is a divalent radical of such as organic monomers defined previously, and y is a Has a value from 1 to a number which is 25% of the number of alpha-methylstyrene units. 2 0 9884/1279