DK155369B - SHIPPING POLYMER MIXTURE, MAINLY CONSISTING OF THE POLYSTYR AND A BLOCK COPOLYMER OF THE STEERING AND A CONJUGATED DIES - Google Patents

Description

Π \ / a r r 7 / c P

Λ i ο c> ο υ / b

The invention relates to an impact-resistant polymer blend of the kind set forth in the preamble of claim 1, wherein the blend consists essentially of a polystyrene and a thermoplastic, star-shaped, branched and optionally hydrated block polymer of styrene and a conjugated diene which exhibits good transparency. and a good impact resistance.

Polystyrene is a hard, thermoplastic resin, which is particularly distinguished by its transparency. It is a disadvantage for 10 many applications that the material is brittle and exhibits poor toughness.

It is known that to improve the mechanical properties of polystyrene, especially its impact strength, polystyrene can be modified with rubbery substances, either mixing the rubber with the polystyrene or polymerizing the styrene in the presence of the rubber. As rubbery agents for modifying the impact strength, homo- and copolymers of conjugated dienes are used, in particular, polymers of butadiene or isoprene. Particularly advantageous products with respect to the mechanical properties are obtained when elastomeric block copolymers of styrene and a conjugated diene are obtained. These e-lastomeric block copolymers are made up of a predominant portion of the conjugated diene and a minor proportion of styrene and may have a linear or star-shaped branched structure.

However, with the incorporation of rubbery substances into the polystyrene, its transparency is lost, so that the styrene polymers so modified to become impact-resistant are unsuitable for many applications, e.g. packaging purposes.

35 2 DK 155369 8

Furthermore, it is known to produce impact-resistant styrene polymers with good mechanical properties when producing non-elastomeric block copolymers of styrene and a conjugated diene made up of a predominant proportion of styrene and an inferior proportion of the conjugating diene. Thus, in DE Publication No. 19 59 922, e.g. branched block copolymers with a star-shaped structure of a predominant proportion of styrene and an inferior proportion of a conjugated diene which combine impact strength, clarity, good processability and good resistance in a polymer. These branched block copolymers are obtained by coupling styrene-diene two-block copolymers in which the terminal polystyrene blocks have different block lengths. Admittedly, these products exhibit a satisfactory property image in many respects and are both impact-resistant and transparent; however, because of the cumbersome manufacturing method, they are relatively expensive.

It is therefore an object of the invention to more easily improve the mechanical properties of polystyrene while maintaining transparency in such a way as to produce, in particular, good impact strength products which are at the same time as glass-clear as possible and as easily processable as possible.

25

The object of the invention is fulfilled in that polystyrene is mixed with a non-elastomeric, star-shaped branched copolymer of styrene and a conjugated diene, whereby the non-elastomeric, star-shaped, branched copolymer possesses a specific, more specific structure.

The polymer blend according to the invention, which is of the kind specified in the preamble of claim 1, is thus property according to the characterizing part of claim 1.

Although polystyrene and non-elastomeric, star-shaped branched block copolymers with a predominant proportion of 5 styrene and an inferior proportion of a conjugated diene are alone transparent and transparent products, it was extremely surprising that transparency was maintained by mixing the two components. according to the present invention, because the refractive indices of the two components are distinctly different and the known mixtures of polystyrene with branched block copolymers of styrene and a conjugated diene having an elastomeric character clearly produce opaque to opaque products. It is believed that the transparency of the polymer blends of the invention depends on the compatibility of the two blend components very rarely observed with polymer blends.

It is admittedly known from French Publication 20,259,874 transparent mixtures of polystyrene and block copolymers of styrene and butadiene. However, the structure of the block copolymers used in the polymer blends of the invention differs substantially from the structure of the known block copolymers, according to the main requirement of this application, these known block copolymers being linear and exhibiting an elastomeric middle block and terminal polystyrene blocks, and in addition that the polymer blends of the invention exhibit better transparency and processing properties than the known polymer blends.

It is also known from US patent no.

3,637,554 mixtures of polystyrene and branched block copolymers. However, the known polymer blends contain 4

DK '53 * 9 B

These are monomodally-formed, branched block copolymers, while the block copolymers used in the polymer blends of the invention contain polymodally-branched block copolymers. The polymer blends of the invention surprisingly exhibit improved properties in both the impact strength and the notch impact strength relative to the known polymer blends.

As to the prior art most closely related to the invention, in particular CIS Patent No. 3,637,554, it can be stated that the polymer blends according to the invention exhibit properties which could not be foreseen by the expert. As evidence of this, the applicant has measured values for impact strength (an) and notch impact strength (a ^) of two mixtures a and b. These two mixtures a and b both consist of a polystyrene and a branched block copolymer in weight ratio 1: 2. The block copolymer is in composition a non-polymodally constructed, while in mixture b it is polymodally constructed. The weight proportions of styrene and butadiene in the two two block copolymers are the same. Surprisingly, it turns out that the polymer blends according to the invention, in comparison with the known polymer blends, exhibit improved properties in both impact strength and notch impact strength, as shown in the table below.

25 i 30 35 5

DK

Table

Mixture Weight ratio [kJ / m2] 1: 2 an ac 5 - a Polystyrene + branched block copolymer 5.6 0.75 b Polystyrene + branched, polymodal block copolymer 16.3 2.63

Polymer blend a thus represents the state of the art according to U.S. Patent No. 3,637,554.

The known polymer blend consists of polystyrene and mono-modally formed branched block copolymer. Polymer blend b represents the invention, wherein polymer blend b consists of blends of polystyrene and polymodally formed star-shaped, branched block copolymer. The gross composition of the block copolymers is the same 20 for a and b, namely 68 wt% styrene and 32 wt% butadiene.

The polystyrene to be used as component A of the polymer blend according to the invention can be prepared in known manner by polymerization of styrene in mass, solution or aqueous dispersion. Preferably, a polystyrene made by mass or solution polymerization is used. This is the usual amorphous polystyrene. The molecular weight (the average molecular weight is measured by the viscosity) of the polystyrene is generally in the range of 50,000 to 1,000,000, preferably in the range of 100,000 to 500,000. The polystyrene is present in the polymer blend in amounts between 10 and 70% by weight, calculated in terms of the sum of components A and B.

Component B of the polymer blend according to the invention, used in amounts between 90 and 30% by weight, calculated in proportion to the sum of A and B, is a non-elastomeric, star-shaped branched block copolymer of a predominant proportion of styrene and a minor proportion of a conjugated diene.

As conjugated dienes, those having 4 to 8 carbon atoms are generally used. Examples of conjugated dienes which alone or in admixture can be used to prepare the branched block copolymers are butadiene, isoprene and 2,3-dimethylbutadiene. Particularly preferred are then butadiene or isoprene, again butadiene being the most preferred.

The branched block copolymers of the polymer blend of the invention should contain, in a polymerized state, 60 to 95% by weight of styrene, in particular 70 to 90% by weight of styrene, and 40 to 5% by weight, preferably 30 to 10% by weight, of the conjugated diene, in each case calculated in relation to the total amount of monomers used. The molecular weight of the branched block copolymers is thus generally in the range of 100,000 to 1,000,000 and preferably amounts to between 150,000 and 500,000. These indications refer to the average molecular weight. by weight, as determined by viscosity measurements in 0.5% by weight of toluene solution at 25 ° C.

30

The star-branched block copolymers to be used in accordance with the invention consist in their branches of copolymeric blocks in which the styrene and the conjugated diene are embedded block-shaped to form single-stranded polymers.

DK 15 E

to polymer segments. These block-shaped, copolymerized blocks forming the branches are thereby chemically interconnected by a coupling agent. The star-branched block copolymers possess at least 5 3, generally 3 to 10, and preferably 3 or 4, such branches, whereby these branches must consist of at least two species of copolymer blocks having an average different structure. In addition, at least 50 wt%, preferably at least 10 60 wt%, of the total polymerized styrene polymerized in the star-branched block copolymer in one or more of the copolymer blocks of the branches as terminal homopolymer segment must be incorporated.

As component B of the polymer blend according to the invention, star-branched block copolymers are used which exhibit, on average, as the most probable structure, one of the following general formulas (I), (II) or (III):

(I) (A ° -B °) k-X

(II) (A ^ B1 ^ A2) nX- (A2-f- B1) ^ (III) (A3-A4-B2- * A5) nX- (A5 «- B2-A4) m 25 In these general formulas ( I) - (III) means: A °, A ^-A “non-elastomeric polymeric segments of styrene, whereby the polymeric segments A polymer of polymer isate (I) must exhibit a polymodal, preferably bimodal, molecular weight distribution, while the individual polymer segments A 1 -A 2 in the polymers (II) and (III) in each case exhibit a homogeneous molecular weight distribution, B °, B3 ·, B2 elastomeric polymer segments based on the conjugated diene, X the remainder of a polyfunctional coupling agent, through which the copolymer blocks forming the branches 5 are chemically interconnected, have a high number of at least 3, generally from 3 to 10 and preferably 1 or 4, and 10 m and n numbers, whereby m> n and the sum of m and n is at least 3, generally an integer ranging from 3 to 10 and preferably 3 or 4.

A polymodal (bimodal) molecular weight distribution is a molecular weight distribution with three or more peaks on the curve representing the percentage fraction of the polymerate (ordinate) plotted against the molecular weight (abscissa).

A homogeneous molecular weight distribution corresponds to a smooth curve with a single peak, recorded in the coordinate system just specified.

The symbol + in the general formulas (II) and (III) means that the transition between the polymer segments in question is not sharply separated, but takes place gradually.

25

Star-branched block copolymers of the general formula (A ° -B °) j-X (I) are already described in DE Publication No. 19 59 922. The non-elastomeric polymer segment AQ thus represents in particular a homopolystyrene segment. . Molecular weight and polymodality are preferably directed to the purpose of use to which the final product, ie the finished polymer blend according to the invention of components A and B, is to be used. The molecular weight is thereby determined, as later stated, 35 9

DK 1 55:, · B

of the amount of initiator used in the preparation per mole of the monomers; the polymodality depends on the frequency of the initiator addition of the polymerization cg is preferably 2 or 3 and especially 2. The elastomeric polymer segment B ° based on the conjugated dienes is preferably a homopolydiene segment, especially a homopolybutadiene or a homopolyisoprene segment. But it may also contain, in a polymerized form, amounts of approx. up to 30% by weight, preferably below 20% by weight, calculated 10 relative to the polymer segment B °, of other copolymerizable monomers, especially styrene.

In the star-branched block copolymers having, on average, as the most probable structure, one having the general formula (II) (Α1-Β1 ^ · Δ2) nX- (A2 «* 1) m (II), the non-elastomeric polymer segment contains A1, with advantage, 50 to 80% by weight, preferably 60 to 78% by weight, of the styrene used in the preparation of the branched block copolymer, in a polymerized form, thus representing a homopolystyrene segment. The molecular weight of A1 is mainly directed to the intended use for the final product (ie the finished polymer blend according to the invention of components A and B) and preferably ranges from 50,000 to 250,000. The elastomeric polymer segment B · * · is a copolymer block of essentially the conjugated diene 30 as well as a small proportion of monovinyl aromatic compound with wide statistical distribution of the monomers. The proportion of the monovinyl aromatic compound in the polymer segment B1 is generally below ca. 30% by weight and in particular less than approx. 20% by weight, calculated in relation to DK 1 hbZ <; 8 the amount of monovinyl aromatic compound of the branched block copolymer which is not incorporated in the polymer segment A3 ·. The transition between polymer segments A3 and B3 is thereby sharply separated, while the transition between polymer segments B1 and A2 is the result that, gradually, the proportion of the monovinyl aromatic compound in polymer segment B1 towards polymer segment A2 increases steadily. and that the proportion of the conjugated diene is similarly still reduced. The non-el10 elastomeric polymer segments A are like the polymer segment A1 homopolystyrene segments. The molecular weight of the polymer blocks (B3 - A2) is preferably 10,000 to 100,000.

In the star-branched block copolymers which, on average, have the most probable structure of one of the general formula (III) (A3-A4-B2 - * - A5) nX- (A5 '-B2-A4) m (III), 20 n advantageously, the non-elastomeric polymer segment AJ contains 50 to 80% by weight, preferably 60 to 75% by weight, of the styrene used in the preparation of the branched block copolymer in indolymerized form and thus represents a homopolystyrene segment. Its molecular weight is preferably in the range of 50,000 to 250,000. The polymer segments A4 correspond to the polymer segments A \ but they have a lower molecular weight, usually between 5000 and 50,000. They contain 1 to 30 wt.% 30 and preferably 5 to 25 wt.% Of the styrene in prepolymerized form, however, the sum of the styrene polymerized in polymer segments A3 and A4 should not, however, exceed 90 wt.% Of the total to produce the branched. block copolymers used amount of styrene. It e-35 11

DK 15 5 3 '' 1 J

lastomeric polymer segment B2 3 is a copolymer block of substantially the conjugated diene as well as a small proportion of monovinyl aromatic compound with wide statistical distribution of the monomers. The proportion of monovinyl aromatic compound in the polymer segment is generally less than ca. 30% by weight and in particular less than approx. 20% by weight, calculated in relation to the amount of monovinyl aromatic not incorporated in polymer segments A2 and A4. The transition 49 between the polymer segments A and B is thereby sharply separated, while the transition between the polymer segments B2 and A5 occurs gradually. The non-elastomeric polymer segments A 5, like the polymer segments A2 and A4, are homopolystyrene segments. The molecular weight of the polymer blocks (A2-A4-B2- * A2) is preferably in the range of 100,000 to 15,500,000, and of the polymer blocks (A4-B2- * A2) in the range of 10,000 to 100,000.

According to a preferred embodiment of the invention, as component B, non-elastomeric, star-shaped branched block copolymers whose content of 3 olefinic double bonds by selective hydration has been reduced to a residue of less than 5% is used as 4 component less. than 2%. If selectively hydrated derivatives of star-branched block polymers of the same general formula (I) are used in which the polymer segment B ° from the hydrogenation is a polybutadiene segment, care should be taken to ensure that this polybutadiene segment has a 1,2-vinyl content in the range of 10 to 50% by weight, and the polymer segment B ° after hydration has a crystallinity of less than 5%, preferably less than 2%, to produce products having the desired properties. The crystallinity of the hydrated polymer segments B ° is thereby determined differential calorimetrically with a Perkin-Elmer DSC calorimeter.

12 DK 15 53 6 9 d

The particular structure and structure of the star-branched block copolymers depends on the precursors selected for polymerization of the monomeric precursors and is determined by them. In general, the non-elastomeric star-branched block copolymers, which are suitable as component B of the polymer blend of the invention, are prepared by successive polymerization of the monomers in solution in the presence of a monolithium hydrocarbon as initiator under stepwise monomer and initiator addition and subsequent coupling of the resulting live linear block copolymers with a polyfunctional, reactive compound as coupling agent.

As the initiator, the known monolithium hydrocarbons of the general formula RLi serve, wherein R is an aliphatic, cycloaliphatic, aromatic or mixed aliphatic-aromatic hydrocarbon group. The hydrocarbon may contain from 1 to approx. 12 carbon atoms. Examples of suitable lithium hydrocarbon initiators should be cited: methyl lithium, ethyl lithium, (n-, sec-, tert.-) butyllithium, isopropyllithium, cyclohexyllithium; phenyllithium or p-tolyllithium. Preferably, the monolithium alkyl compounds having 2 to 6 carbon atoms are used in the alkyl group, with n-butyllithium and sec-butyllithium being particularly preferred.

The polymerization of the monomers is carried out in solution in an inert organic hydrocarbon solvent. Suitable hydrocarbon solvents are aliphatic, cycloaliphatic or aromatic hydrocarbons which are liquid under reaction conditions and preferably contain from 4 to 12 carbon atoms. As solvents, e.g. the following is considered: isobutane, n-pentane, iso-octane; cyclopentane, cyclohexane, cycloheptane; benzene, to-35

DK 155369E

13 hat and xylene. Mixtures of these solvents can also be used. It is also possible to carry out the polymerization in the presence of small amounts, generally 10 to 3% by weight, based on the total solvent, of ethers such as tetrahydrofuran, dimethoxyethane and phenylmethyl ether, may influence the rate of polymerization, the configuration of the diene polymerate segments, as well as the static transition between segments B1 and A2 or B2 and A ^ at the products of general formula (II) or (III). The concentration of the monomers in the reaction solution is not critical and can be adjusted in such a way that any desired apparatus can be used for the polymerization. Usually 10 to 30% solutions are polymerized, 15 calculated relative to the inert solvents.

The polymerization is carried out under the usual conditions of the anionic polymerization with lithium organic compounds, such as e.g. in inert gas atmosphere, the exclusion of air and humidity. The polymerization temperature may be between 0 and 120 ° C and preferably maintained between 40 and 80 ° C.

The polyfunctional coupling agent used for the coupling reaction in connection with the polymerization must be at least trifunctional, i.e. it must be able to react with at least three or more of the active linear block copolymer chains formed at their terminal lithium carbon bonds to form a chemical bond to form a single, coupled and thus branched block copolymer. The coupling of lithium-terminated live polymerisates with polyfunctional coupling agents is well known in the art. disclosed in GB-PS 985 614. Coupling agents suitable for the preparation of the star-shaped branched block copolymers to be used according to the invention are e.g. polyepoxides such as epoxidized flaxseed oil, polyisocyanates, e.g. benzo-1,2,4-triisocyanate, polyketones such as 1,3,6-hexanthrione or 1,4,9,10-anthracentetron, polyanhydrides such as e.g. the dianhydride of pyromellitic acid, or polyhalides. Also, dicarboxylic acid esters, e.g. diethyl adipate, as a coupling agent. A further preferred group of coupling agents are the silicon halides, especially silicon tetrachloride, silicon tetrabromide, trichloroethylsilane and 1,2-bis (methyldichloro silite) ethane. In addition, polyvinyl aromatics, especially divinylbenzene, e.g. as described in U.S. Patent No. 3,280,084. In this case, some divinylbenzene units are added during crosslinking to a branching center over which the preformed polymeric blocks are joined.

The nature of the polyfunctional coupling agents used is not critical as long as the desired properties of the final product, ie the finished blend according to the invention of components A and B, are not adversely affected in the harmful direction. Preferably, a tri- or tetra-functional coupling agent of the kind or di-vinylbenzene used is used. The polyfunctional coupling agent is thereby generally added to the reaction solution in amounts equivalent to the total amount of "living" polymer blocks, i.e. with the number of active lithium carbon bonds in the previously formed linear copolymer blocks. The reaction between the live linear block copolymers and the polyfunctional coupling agent preferably takes place under the same reaction conditions as the prior polymerization of the monomers.

35 15 DK 155369 8

The non-elastomeric, star-branched block copolymers to be used in the polymer blend of the invention are prepared in detail as follows: In a first process step, a substantial portion of the total amount of the styrene, generally between 50 and 80 weight, is first polymerized. -%, especially between 60 and 75% by weight, of the amount of styrene used in the manufacture of the star-shaped branched copolymer, by means of a relatively small amount of the monolithium hydrocarbon initiator until complete reaction of the styrene. The amount of initiator used in the first process step is above all to the desired molecular weight of the polymerate and is generally between 0.1 and 5 mmol per mole of the amount of styrene used in this first process step. Preferably, for the polymerization in the first process step, 0.4 to 2.5 mmol of initiator per mole of styrene is used. In this way, a solution of non-elastomeric living polymers of the styrene is obtained with active, terminal lithium-carbon bonds suitable for further application of the monomer. In a second process step, after the addition of an additional additional initiator amount, at least equal to or greater than the initial initiator amounts used in the first process step of the polymerization, this additional solution is added to the reaction solution. residual amount of monomeric styrene at one time or several successive stages and polymerize. Preferably, in the second process step 30, an amount of additional fresh initiator, in particular between 1 and 10 times the amount of additional fresh initiator, calculated relative to the initial amount of initiator added, is added. Especially advantageous are 1 to 5 times the size of supplemental ini-35 16

DK 15536? B

titer amounts, especially when using tri- or tetra-functional coupling agents in the subsequent coupling reaction. Preferably, the same initiator is used as in the first process step; It is advantageous to add the additional fresh initiator to the reaction solution before adding the remaining amount of the monomers.

By the nature of the conjugated diene added to the reaction solution in the first process step, the structure and structure of the resulting block copolymers can be determined and varied. The remaining proportion of the styrene and the conjugated diene can thereby e.g. added as an intermix in one step; but they can also be added in several steps in succession, e.g. separately, first the remaining portion of the styrene and then the conjugated diene or first a further subset of the styrene and then a mixture of the remaining portion of the styrene and the conjugated diene. After each renewed addition of monomers in the second process step, polymer is added to complete reaction of these monomers before a further monomer addition or final coupling agent is added. Optionally, in the second process step, several additional initiator quantities can also be used several times.

For the preparation of star-branched block copolymers of the general formula (I) (Α ° -Β °)] ζ-Χ, which exhibits a polymodal distribution with respect to the non-elastomers of the styrene-built polymer segments A °, goes one for example. further, by adding to the reaction solution prepared in the first process step the residual styrene, i.e. 20 to 50% by weight, preferably 25 to 40% by weight, of the total 35

DK 155369 B

17 for the preparation of the branched block copolymer used in one or more proportions, wherein each partial addition of the styrene is accompanied by the addition of an γ-additional initiator amount at least equal to or greater than the initial initiator amount used. during the first process step during polymerization. Although it is possible to add the remaining proportion of the styrene in the second process step to the reaction solution in as many proportions as desired, it is preferable to add the residual styrene of the second process step in 1 or 2 parts to the polymerization solution, thereby adding the residual styrene 1 share has proved particularly advantageous. The styrene 15 added in the second process step is thereby added to both the active, lithium-terminated chain units of the previously formed polymerisates, and new chains of living polymers are formed in the case of each additional fresh initiator in each case.

Thus, after outpolymerizing the remaining amount of styrene 20, there is a solution containing polymerisates of the styrene having on average different chain lengths, i.e. the resulting non-elastomeric polymer segments A ° from the styrene have a polymodal distribution, whereby the polymodality of the polymer segments A ° corresponds to 25 for the total number of initiator and monomer additions. Then, in a second step, the total amount of the conjugated diene is added and polymerized to complete reaction. Thereby, the conjugated diene camps to the active, lithium-terminated chain units of the previously formed polymodal, non-elastomeric polymer segments A ° to form the elastomeric polymer segments B °, so that the copolymer blocks (A ° -B °) forming the branches, in the reaction solution is provided with an active, reactive lithium-carbon bond at 18

Hk '' i r r v, · r>:; * Ut \ i l'j jo; u the free end of the elastomeric diene polymer segment B ° which is then coupled.

For the preparation of star-branched block polymerisates of the general formula (II) (A1 - 1 * 1 - »A2) nX - (A2 - * 1) m (II), the second process step of polymerization-10 is followed. one in such a way that after the addition of a further additional initiator amount to the out-polymerized reaction solution from the first process step, a mixture of the remaining amount of styrene and the total amount of the conjugated diene is added and polymerized. Thereby, the monomers added in the second process step are added to both the active, living chain ends of the previously formed polymer segments A A, and, as the new fresh initiator is added, new chains of living polymers are formed. Because of the different copolymerization parameters, the conjugated dienes thereby polymerize substantially faster than the styrene, so that after the addition of the monomer mixture in the second process step, there is only predominantly the polymerization of the conjugated dienes and only in a few cases of the styrene. Only towards the end of the diene polymerization, i.e. when almost all the amount of conjugated diene is polymerized, the polymerization of the styrene inserts appreciably to such an extent that the predominant proportion - usually more than 30, and preferably more than 80% by weight - of the styrene present in the monomer mixture first polymerizes after consumption. of the conjugated dienes. In this case, thus, in the second process step, first, the elastomeric polymer segment B1 is formed on the basis of the conjugated diene, which is a copolymeric segment of mainly the conjugated diene and low amounts of the styrene, upon which formation of the non-polymeric diene occurs. elastomeric polymer segment A, which is only made up of styrene. As the proportion of styrene towards the end of polymer segment B1 continues to increase and the proportion of the conjugated diene is still reduced, the transition between the thus-formed polymer segments B · * · and A2 is not sharp, but it is gradual; sometimes, therefore, 10 also speaks of a "sliding" transition between the segments. Thus, after outpolymerizing the monomer mixture in the second process step, there is in the reaction solution a mixture of branching, linear block copolymers of the types (A + - B1 - +2) and (B + + A2) with active reactive lithium-carbon bonds, in each case at the free end of polymer segments A2.

The ratio of the two types of block copolymers in the reaction solution thus corresponds to the initiator ratio in the first and second process steps. The mixture 20 of these two types of block copolymers is then coupled to the reaction solution by the addition of polyfunctional reactive compound as coupling agent.

For the preparation of star-branched block copolymers of the general formula (III) (A3-A4-B2 - A5) nX- (A5 + B2-A4) m (III), the second process step of polymerization-30 is followed. one further in that, after adding an additional additional initiator amount, to the out-polymerized reaction solution from the first process step, an additional 1 to 30% by weight, preferably 5 to 25% by weight of the total amount of it to 35 20

DK 15 b 3 6 9 B

the preparation of the branched block copolymers in all styrene used. However, the sum of the amount of styrene used in the first and second steps of the process shall not exceed 90% by weight of the total amount of styrene used in the manufacture of the branched block copolymers. The added amount of styrene is thereby added to form polymer segments A4 both to the active, lithium-terminated chain ends of the polymer segment A3 formed in the first process step, and, as the fresh fresh initiator, new chains of live polymers are formed by the styrene. Thus, after outpolymerizing the styrene added in the second process step, there is a solution containing live polymerisates of the styrene having an average of two different chain lengths, namely, the first active, live polymer segments of type (A3-A4) which has arisen from the addition of the styrene added in the second process step to the active 20 active polymer segments A3 formed in the first process step, and secondly to the active A4 living polymer segments formed by the polymerization of the the second process step first added styrene with the additional fresh initiator added. Therefore, the ratio in which these two types of styrene-based non-elastomeric polymer segments are present in the reaction solution corresponds to the i-initiator ratio in the first and second process steps. Both types of the polymer segments (A3-A4) and A4 have, by their one chain-active, reactive li-30-carbon bonds suitable for further monomers formation. To this reaction solution is then added a monomer mixture of the residual styrene and the total amount of the conjugated diene and polymerized to virtually complete reaction of 35

DK 155369B

21 the monomeric. As described above, in the polymerization of the monomer mixture of residual styrene and conjugated diene according to the various copolymerization parameters of the monomers, first the elastomeric polymer segment B2 is formed on the basis of the conjugated diene, which is a copolymer composed of mainly the conjugated diene and rings. quantities of the styrene network upon which a non-

C

elastomeric polymer segment A, constructed only by the styrene. As the styrene towards the end of the polymer Λ 10 segment ΒΔ becomes increasingly polymerized and the proportion of the conjugated diene similarly still decreases, the transition between the formed polymer segments B2 and A5 is not sharp, but takes place gradually. After outpolymerizing the monomer mixture of the remaining amount of styrene and the conjugated diene, there is in the reaction solution a mixture of the linear block copolymers of the types (A A-A4-B2 - »- A A) and (A4-B2 -> - A ) which form the branches and which have active, responsive lithium-carbon bonds, at least 20 at the free end of the polymer segment A5, which is then coupled to the star-branched block copolymer inserted.

The isolation of the resulting branched block copolymers of the reaction solution takes place in the usual manner, e.g. by precipitation and filtration of the polymerate from the reaction solution.

In addition, in connection with the coupling reaction and suitably prior to the isolation of the reaction product from the reaction solution, the olefinic double bonds of the resulting branched block copolymers may also be selectively hydrated. The selective hydration may be carried out in the usual manner by molecular hydrogen 22

Arrow / r r ν f η ο Ur \ [0000. Ο and catalysts based on metals or metal salts of the 8th group of the periodic system, such as e.g. is disclosed in U.S. Patent No. 3,113,986, U.S. Pat. No. 1,222,260, U.S. Patent No. 2,013,263, or U.S. Pat.

3 700 633. The selective hydration of the olefinic double bonds of the branched block copolymer, preferably in homogeneous phase, with catalysts based on salts, especially carboxylates, enolates or 10 alkoxides, of nickel, cobalt or iron is reduced. with metal alkyls, especially aluminum alkyls, at hydrogen pressures between 1 and 100 bar and temperatures between 25 and 150 ° C. The selective hydration is carried out to such an extent that the content of olefinic double bonds in the branched block copolymer has been reduced to a residual fraction of less than 5%, preferably below 2%. The residual olefinic double bonds are determined by titration by Wijs or by IR spectroscopic analysis. In particular, the alkenic double bonds are hydrated to substantially complete reduction thereof. Preferably, the hydrogenation is carried out such that the aromatic double bonds in the branched block copolymer are not attacked thereby.

The components A and B of the polymer blend according to the invention can be homogeneously blended in a conventional manner according to the known methods, e.g. in the melt by suitable mixing means, e.g. furnaces, internal mixers or extruders. The polymer blends may additionally contain the usual polystyrene additives such as antistatics and stabilizers.

Like the polystyrene itself, the polymer blends of the invention exhibit good transparency and clarity. A Goal 35 23

DK 1553 C · 9 B

for transparency and clarity is thereby the proportion of light that is scattered when passing through a foil or plate.

Compared to polystyrene, the polymer blend according to the invention possesses significantly improved mechanical properties, especially an improved impact strength and notch strength. Compared to the non-elastomeric star-branched block copolymers known from DE Publication No. 1,959,922, the costs associated with the preparation of the polymer blends according to the invention are less (because the block copolymers as special products are more expensive than the standard polystyrene, whereby the polymer blend according to the invention being cheaper than the known block copolymers), without having to consider a significant decrease in impact strength and 15 notch impact strength, even with a relatively large proportion of polystyrene in the mixture. The polymer blend according to the invention is readily processed according to the usual processing methods for thermoplastic materials, such as extrusion, deep drawing or injection molding, and it is particularly suitable for the manufacture of moldings, such as foils, films and sheets, and for packaging agents. .

The invention is explained by the following examples. The parts and percentages stated in the 25 examples - unless otherwise stated - refer to the weight. The viscosity number, measured in 0.5% solution in toluene at 25 ° C according to DIN 53724, or directly the viscosimetric weight average, is indicated as the measure of the molecular weight. Impact strength and notch impact strength a ^ were determined according to DIN No. 53,453 on sprayed mold bodies.

The transparency was visually determined on a 500 μπι thick film.

In all examples, a polystyrene made by mass polymerization having a molecular weight of approx. 200,000 (viscosity number VZ = 85 cm 2 / g where viscosity is measured according to DIN 53724), whose impact strength an = 4.4 kJ / m ^ and whose notch strength a ^ = 0.61 kJ / m.

EXAMPLE 1

As component B, a star-branched non-elastomeric block copolymer of the general formula (II) type having an average (most likely) structure [polystyrene-poly (butadiene / styrene) -> polystyrene] 2 ~ Si-15 was used. polystyrene - «- poly (styrene / butadiene)] 2

The styrene content of the block copolymer was 73% in total and the butadiene proportion was 27%. The terminal free polystyrene segment had thus polymerized 76% of the total styrene 20 used and had a viscosity number of 37.1 (cm 2 / g). The viscosity number of the star-branched block copolymer was 90 (cm 2 / g, viscosity measured according to DIN 53724). The star-branched block copolymer was prepared by successive polymerization of styrene and a mixture of butadiene and styrene with n-butyl lithium as a catalyst in toluene as solvent during stepwise initiator addition and subsequent coupling with silicon tetrachloride in an amount of 1 moles of silicon tetrachloride per 4 moles of n-butyl lithium.

The polystyrene (component A) and the star-branched block copolymer (component B) were mixed homogeneously on a extruder in the molten state in the ratio 1: 2. The mixture had a impact strength an = 16.3 kJ / m2 and a notch impact strength a ^ = 2.63 kJ / m2. One film made from this mixture was transparent.

EXAMPLE 2

As component B, a star-shaped branched non-elastomeric block copolymer of the general formula (I) having an average (most likely) structure (polystyrene I - polybutadiene) 2 "Si (polybutadiene polystyrene 11) 2 · 15 was used. The control proportion in the whole block copolymer was 75% and the butadiene proportion was 25%. The polystyrene I segment had an average molecular weight of 65,000 and the polystyrene II segment had an average molecular weight of 10,000.

The branched block copolymer was prepared by successive polymerization of styrene and butadiene with 1.5 mmol of n-butyllithium as a catalyst under a total of two times the initiator addition of the polymerization of styrene, whereby the added initiator amounts were equal. The coupling was performed with 0.38 mmol with silicon tetrachloride.

One blend made from the polystyrene (component A) and the star-branched block copolymer (component B) (blend ratio A: B = 1: 2) had an impact strength an = 16.3 kJ / m2 and a notch impact strength a 63 kJ / m2.

One of the films made from the mixture was transparent.

EXAMPLE 3

As component B, a star-shaped branched non-elastomeric block copolymer of styrene and butadiene 5 of the type having the general formula (I) whose olefinic double bonds were selectively hydrated was used. The star-branched block copolymer was prepared as follows: In a 6 liter pressure section, 2.7 kg of cyclohexane and 525 g of styrene were quenched with sec-butyl-lithium and polymerized with 0 33 g of sec-butyl lithium for 30 minutes. The temperature was first 54 ° C. To the active reaction solution was added at 71 ° C 0.22 kg cyclohexane, 0.9 g sec-butyl lithium and 225 g styrene and polymerized for one hour; then 10 g of tetrahydrofuran and 250 g of butadiene were polymerized for one hour at ca. 74 ° C. Finally coupled with 10 ml of Epoxyl 9-5 in 150 ml of toluene.

Epoxyl 9-5 is a commercial product which cannot be characterized by a chemical formula; Epoxyl 9-5 contains epoxidized plant oils, including soybeans, and can be obtained from Swift & Co. The viscosity was 91.9 cm 2, with the viscosity measured according to DIN 53724. Then the olefinic double bonds of the resulting star-branched block copolymer with 8.36 g of a Ni hydration catalyst were selectively hydrated until the residue of the olefinic double bonds in the block copolymer were less than 1%.

30

From the polystyrene (component A) and the selectively hydrated star-shaped block copolymer (component B), three mixtures with different mixing ratios between the two components were prepared. The properties of these mixtures-35 27

DK 15536 '·' S

are summarized in the following table. All mixtures gave rise to the formation of transparent foils.

TABLE

5

Mixing ratio A: B 1: 2 1: 1 2: 1

Impact Strength an (kJ / m 2) 14.1 12.0 11.2 Notch Strength a ^ (kJ / m 2) 1.53 1.36 0.91 iO - 15 20 25 30 35

Claims (2)

A impact-resistant polymer blend consisting essentially of A) 10 to 70% by weight of polystyrene and B) 90 to 30% by weight of a thermoplastic, star-shaped, branched and optionally selectively hydrated block copolymer of styrene and a conjugated diene , Characterized in that component B is made up of 60 to 95 wt% styrene and 40 to 5 wt% of a conjugated diene, and exhibits at least two species of branching copolymer blocks having a mutually differing structure, whereby at least 15% by weight of the polymerized styrene in the star-branched block copolymer is block-shaped as terminal polymer segments in one or more of the copolymer block in the branches, the component B representing branched block copolymers, which exhibits, on average, the most likely structure corresponding to the following general formulas (I), (II) or (III); (I) (A ° -B °) kX, (II) (A1-B1 - »'A2) nX- (A2 ^ B1) m, (III) (A3-A4-B2 ^ A5) nX- (A5 + B2-A4) m, whereby the symbols of the general formulas (I) - (III) have the following meanings: 30 A °, A ^ -A3 are non-elastomeric polymer segments of styrene, whereby the polymer segments A ° of the polymerate (I) must exhibit a polymodal, preferably bimodal molecular weight distribution, while the individual polymer segments A - ^ - A3 in the polymers (II) and (III) in each case exhibit a uniform molecular weight distribution, B °, B1, B2 are elastomeric polymer segments of base of the conjugated diene, 5. is the remainder of a polyfunctional coupling agent over which the copolymer blocks forming the branches are chemically interconnected, k is an integer at least 3, preferably between 3 and 10, especially 3 or 4, and 10 m, n are numbers whereby m is equal to or greater than n and the sum of m and n is at least 3, preferably an integer from 3 to 10, especially 3 or 4, and the symbol + indicates that the transition between the p the polymer segments in question are not sharp, but fluid. 15 Polymer blend according to claim 1, characterized in that the olefinic double bonds of the non-elastomeric, star-branched block copolymer, by selective hydration, are reduced to a residual proportion of less than 5% and that the selectively hydrated segments of the copolymer exhibits a crystallinity of less than 5%. 25 1 35