JPS6035922B2 - Method for producing segmented block copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a major proportion of monovinyl aromatic compounds and a smaller proportion of conjugated genes, and has high transparency and clarity as well as good mechanical properties, especially a high degree of impact resistance. The present invention relates to a method for producing a branched block copolymer having properties.

Block copolymers in which one or several non-elastomeric polymer blocks are combined with one or several elastomeric polymer blocks by polymerizing styrene and butadiene using a lithium hydrocarbon as an initiator. is known to be obtained.

Depending on the content of polymer blocks in the total polymer, the thermoplastic block copolymers exhibit non-elastomeric or elastomeric properties. By sequentially polymerizing the monomers, a block copolymer having a linear structure is produced. When linear block copolymers of this type are bonded to each other via a multifunctional reactive compound, a branched block copolymer having a star structure is obtained. Branched block copolymers of this type, described for example in GB 985,614, have a symmetrical structure and generally exhibit improved processability compared to bran-like block copolymers. . Styrene-butagesofloc copolymers with high styrene content are known to be clear, impact-resistant thermoplastic products.

Although this type of block copolymers developed and proposed so far have satisfactory properties in many respects,
These still do not satisfy many of the demands posed by practical applications. In particular, either their physical and mechanical properties are insufficient or the products do not have the transparency required for many applications. German Patent Application No. 959,922 discloses a branched block copolymer with a star structure consisting of a major proportion of styrene and a smaller proportion of conjugated genes, which has good impact resistance, clarity and A combination of excellent processability and extreme stability in one polymer is described.

This branched block copolymer is obtained by combining a styrogene-two block copolymer in which the terminal polystyrene flocs have different block lengths. Although this product exhibits greatly improved properties compared to symmetrical branched block copolymers, it does not completely meet the requirements with regard to its mechanical properties, in particular its impact resistance.

Asymmetric branched block copolymers are also described in DE 21 25 344 A1.

Advantages of this block copolymer having a homopolymer block in at least one branch include lower polymer viscosity in solution compared to symmetrical block copolymers. Regarding its mechanical properties (impact resistance), the polymer described in DE 21 25 344, if it consists of the main proportion of styrene, It is as unsatisfactory as the known product. The aim of the present invention was to improve the mechanical properties of styrene-butadiene floc copolymers consisting of a predominant proportion of styrene and, in particular, to provide a product with increased impact resistance.

Furthermore, the product should be transparent and as glassy clear as possible and should be easy to process. The inventors have unexpectedly discovered that a non-elastomeric branched block copolymer consisting of a monovinyl aromatic compound and a conjugated diene and having a completely specific block configuration and block structure in the branching is comparable to known block copolymers. It has been found that it exhibits improved properties compared to copolymers.

The present invention involves polymerizing 60 to 8% by weight of the total amount of monovinyl aromatic compound in the first reaction stage until virtually complete reaction in the presence of a relatively small amount of monolithium hydrocarbon; adding to the reaction solution in the reaction step an amount of additional initiator equal to or greater than the amount of initiator initially used, followed by addition of 1 to 3% by weight of the total amount of monovinyl aromatic compound; At this time, the first and second
The amount of monovinyl aromatic compound added in the second reaction step is at most 90% by weight of the total amount of monovinyl aromatic compound used to prepare the branched block copolymer; The monovinyl aromatic compound is likewise polymerized until practically completely reacted, then in a third reaction step a mixture of the remaining monovinyl aromatic compound and the total amount of conjugated diene is added to the reaction solution and polymerized, and finally the monovinyl aromatic compound is polymerized until practically completely reacted. After the polymers have reacted virtually completely, the resulting mixture of linear block copolymers with active terminal lithium-carbon bonds is combined with the addition of a multifunctional binder to form a branched block.

The monostars are sequentially combined in an inert solvent in the presence of a monolithium hydrocarbon as an initiator, characterized by the formation of block copolymers, followed by the resulting active twill block copolymers. Branched block copolymers from 60-95% by weight of monovinyl aromatic compounds and 40-5% by weight of conjugated genes having 4-8 carbon atoms by combining the polymers with a multifunctional binder. This is the manufacturing method. The branched block copolymer obtained by the method of the present invention has the general formula (AI-A2-B→A3) n-X-(A3
←B-A2)m (where AI, A2 and A3 are non-elastomeric polymer segments based on monovinyl aromatic compounds, and B is elastomeric polymer segments based on conjugated genes, and m and n are means a number satisfying the condition that m is equal to or greater than n, the sum of m and n is at least 3, and X is a residue of a multifunctional binder through which the branching The formed polymer block means that the polymer segments are chemically bonded to, where the polymer segment AI is 50 to 80% of the total monovinyl aromatic compounds of the branched block copolymer.
% by weight, polymer segment A2 is from 1 to 3% by weight, but polymer segments AI and A2 together contain up to 90% by weight, and the transition between polymer segments A and B is clearly demarcated. However, polymer segments B and A3
The transition between them occurs gradually).

Monovinyl aromatic compounds used in the construction of the branched block copolymers of the invention are, for example, styrene, side-chain alkylated styrols such as Q-methylstyrene and core-substituted styrols such as vinyltoluol or ethylvinylbenzole.

The monovinylaromatic compounds can be used alone or in mixtures with one another. However, preferably styrene is used alone. Examples of conjugated genes which can be used according to the invention alone or in mixtures with one another for the preparation of branched block copolymers are butadiene, isoprene and 2,3-dimethylbutadiene. Particular preference is given here to butadiene and isoprene, of which butadiene is preferred. The branched block copolymers according to the invention can contain a total of 60 to 95% by weight, in particular 70 to 9% by weight, based on the total monomers used in each case.
of monovinyl aromatics and 40-5% by weight of
, preferably from 30 to 1% by weight of the conjugated gene.

In this case, the molecular weight of the branched block copolymer is usually 1000.
00 to 1,000,000, and preferably 150,000 to 500,000. In this figure, the weight average of the molecular weight determined by the viscosity method at 2500 in toluene is used. The branched block copolymer of the present invention is obtained by sequentially polymerizing the monomers in solution while adding the monomers and the initiator stepwise in the presence of a mono-IJ-tum hydrocarbon as an initiator. Specifically, the active linear block copolymer is bonded using a multifunctional reactive compound as a binder, as follows.

In the first reaction, a non-elastomeric polymer segment AI is first produced, for which a substantial portion of the total amount of monovinyl aromatic compound is mixed with a relatively small amount of monolithium hydrocarbon initiator. Polymerization is carried out under conventional conditions in an inert solvent.

In this case, from 50 to 8% by weight, preferably from 60 to 75% by weight, of the total amount of monovinyl aromatic compound used to produce the branched block copolymer is used. The total amount of monovinyl aromatic compound for the production of the branched block copolymer is 60 to 60% of the total monomers used in the production of the polymer.
95% by weight, especially 70-9% by weight. The amount of initiator used in the first reaction stage is determined in particular by the desired molecular weight of the polymer and is generally in the range 0.1 to 10 mmol per mole of monovinyl aromatic compound used in this first reaction stage. It is in.

Preferably, for the polymerization in the first reaction stage, 0.000.
4 to 2.5 mmol of initiator is used. As the initiator, a known monolithium hydrocarbon represented by the general formula RLi, in which R means an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic hydrocarbon residue, is used. Hydrocarbon residues have 1 to about 12 carbon atoms. Examples of lithium hydrocarbon initiators used in the present invention include the following. methyllithium, ethyllithium,
(n-, secondary- or tertiary-)butyllithium, isopropyllithium, cyclohexyllithium, phenyllithium or p-tolyllithium. Monolithium alkyl compounds having 2 to 6 carbon atoms in the alkyl radical are preferably used, n-butyllithium and secondary butyllithium being particularly preferred. Polymerization of the monovinyl aromatic compound is carried out in solution in an inert organic hydrocarbon solvent. Suitable hydrocarbon solvents are liquid under the reaction conditions and are preferably aliphatic, cycloaliphatic or aromatic hydrocarbons having 4 to 12 carbon atoms. Examples of the solvent include isoptane, n-bentane, isooctane, cyclobentaso, cyclohexane, cycloheptane,
Benzol, toluol, xylol, etc. are used, and mixtures of these solvents can also be used. Furthermore, the polymerization can be carried out in the presence of small amounts, generally from 10-3 to 5% by weight of the total solvent, of ethers such as tetrahydrofuran, dimethoxyethane, phenylmethyl ether, etc., thereby increasing the polymerization rate as is known. , can influence the structure of the butadiene polymer polymer segment B as well as the statistical transition between polymer segments B and A3. However, it is preferable to operate without addition of ether.
The concentration of monomers in the reaction solution is not critical and can be adjusted to accommodate any desired equipment for polymerization. Usually 10 to 30 of inert solvent
% solution. The polymerization is carried out under the usual conditions for anionic polymerization using organolithium compounds, for example in an inert atmosphere with exclusion from air and moisture.

The polymerization temperature may be between 0 and 120°C and is preferably kept between 40° and 80°C. The polymerization in the first reaction stage is carried out until the monovinyl aromatic compound used has reacted practically completely.

Non-elastomeric activated polymers (polymer segments AI) from monovinyl aromatic compounds with active terminal lithium-carbon bonds to which thus further monomers can be added.
A solution of is obtained. In the second reaction step, an additional initiator and a branched block copolymer are added to a solution of a non-elastomeric active polymer based on this monovinyl aromatic compound and having a polymerization-active terminal IJ tium chain end. 1 to 1 of the total amount of monovinyl aromatic compound used in the production of
Add 3% by weight, preferably 5-25% by weight.

However, in this case, the sum of the amounts of monovinyl aromatic compounds used in the first and second reaction stages amounts to at most 9% by weight of the total amount of monovinyl aromatic compounds used in the preparation of the branched block copolymer. Should. The amount of fresh initiator additionally added to the reaction solution in the second reaction stage should be at least equal to or greater than the initial amount of initiator used in the first reaction stage of the polymerization. Preferably, in the second reaction stage, 1-1 times more, and especially 1-1 times more fresh initiator is added than the amount of initiator originally used. As described below, an additional amount of initiator of 1 to 5 times is particularly preferred, especially when a trifunctional or tetrafunctional binder is used in the subsequent coupling reaction. Monolithium hydrocarbons, which can also be used in the first reaction stage, are used as initiators; however, preference is given to using the same initiators as used in the first reaction stage. If additional fresh initiator is added to the reaction solution, it is preferred to do this before adding the additional monovinyl aromatic compound. In the second reaction stage the same polymerization conditions are maintained as in the first reaction stage, and in this case too polymerization is carried out until practically complete reaction of the monovinyl aromatic compound added again.

At this time, the monomer added in the second reaction step is the polymer segment A previously formed in the first reaction step.
In addition to adding to the active terminal lithium chain end of I,
Additional new initiator forms new active polymer chains. After the end of the polymerization of the monomers in the second reaction stage, there therefore exists a solution containing active polymers of monovinylaromatic compounds having on average two different chain lengths.

In the reaction solution there are on the one hand non-elastomeric polymer segments having an activity of the type (AI-A2)-Li;
This resulted from the addition of the monomer in the second reaction step to the active polymer segment AI-Li previously formed in the first reaction step, and on the other hand, the activity of the crab-Li type. There is a non-elastomeric polymer segment having a 100% elastomeric polymer segment, which was formed by polymerization of the polymer of the second reaction phase with the addition of new initiator. The ratio in which these two types of non-elastomeric polymer segments based on monovinyl aromatic compounds are present in the reaction solution therefore corresponds to the ratio of the initiators of the first and second reaction stages. Both types of polymer segments (AI-
A2) and A2 have an active, reactive lithium-carbon bond at the chain end, to which further monomers can be added. Then, in a third reaction step, both types of non-elastomeric monopolymer segments (AI-A2)
- Polymer segment B at the active chain end of Li and Per-Li
Then, a polymer segment is added to this to form a polymer block (AI-A2-B→Ko) and (Crab-
B→A3), which form the branches of the block copolymers of the invention.

For this purpose, the remaining monopynyl aromatic compound and the total amount of the monomeric polymer from the conjugated gene are added to the reaction solution after the polymerization of the second reaction stage. The amount of conjugated gene is in this case between 5 and 4% by weight, preferably between 10 and 3% by weight of the total monomers used for the preparation of the branched block copolymers of the invention.
It is. The monomer polymerization is again polymerized under the same conditions applied for the first two reaction steps until the monomers have reacted virtually completely. Due to the different copolymerization parameters, the conjugated diene here polymerizes essentially more quickly than the monovinyl aromatic compound, so that after the addition of the monomer mixture in the third reaction stage, initially mainly the conjugated diene is polymerized. , and polymerization of monovinyl aromatic compounds takes place only sparsely.

It is only towards the end of the gen polymerization, i.e. when almost all the conjugated gen has finished polymerizing, that the polymerization of the monovinyl aromatic compound begins to a significant extent and thus the monovinyl aromatic compound contained in the monomeric polymer. A major proportion, usually greater than 70% by weight, and often greater than 8% by weight, polymerizes only after the conjugated gene has been consumed. That is, in the third reaction stage, the non-elastomeric monopolymer segment (AI-A2) and A2 are first polymerized with an elastomeric polymer segment B based on a conjugated diene, which mainly contains a conjugated diene and a small amount of a monovinyl aromatic compound. This is followed by the formation of a non-elastomeric polymer segment A3 consisting solely of a monovinyl aromatic compound.

The proportion of monovinyl aromatics increases progressively and significantly closer to the end of the polymer segment B, and the proportion of conjugated compounds gradually decreases accordingly, so that the transition between the polymer segments B and B thus formed increases. occurs gradually rather than distinctly, so it is also now referred to as a "filled in" transition between segments. This fact is indicated by the symbol → in the general formula for the branched block copolymers of the invention. After the completion of the polymerization of the monomer mixture in the third reaction stage, each polymer segment A3 has an active reactive lithium-carbon bond at its free end, (AI-A2-B→4)- Li and (
There is a mixture of active linear block copolymers of the type A2-B→A3)-Li.

This mixture of linear block copolymers with both types of activity is reacted in the next reaction step with the addition of a multifunctionally reactive compound as a binder.

The multifunctional binder used must in this case have at least 0.3% strength. i.e. reacts with at least three or more active block copolymer chains at their terminal lithium-carbon bonds to form chemical bonds, forming a combined and therefore branched single block copolymer. It must be something that can be done. The attachment of activated polymers of terminal lithium by multifunctional binders is generally known and described, for example, in the first cited publications, in particular GB 985,614. Suitable binders for the preparation of the branched block copolymers of the invention are, for example, polyepoxides such as epoxidized linseed oil, polyisocyanates such as penzo-1,2,4-triisocyanate, polyketones such as 1,3,6-triisocyanate, etc. Hexanthrone or 1,4,9,10-isothracentetron, polyanhydrides such as the dianhydride or polyhalogenide of pyromellitic acid.

It is likewise possible to use dicarboxylic acid esters such as diethyl adipate or the like as binders.
Other preferred groups of binders include silicon halides, especially silicon tetrachloride, silicon tetrabromide, trichloroethylsilane or 1,2
-bis-(methyldichlorosilyl)-ethane. Furthermore, it is also possible to use polyvinyl aromatic compounds as binders, in particular divinylbenzole, as described for example in US Pat. No. 3,280,084. In this case, some divinylbenzole units are added under crosslinking to form branching centers, via which the preformed polymer blocks are bonded to one another. The type of multifunctional binder used is not critical as long as the desired properties of the desired product are not essentially compromised thereby.

Preferably, trifunctional or tetrafunctional binders of the type mentioned above or divinylbenzole are used. The multifunctional binder is added to the reaction solution in an amount that is generally equivalent to the total amount of "active" polymer blocks, i.e. the number of active lithium-carbon bonds in the previously formed linear copolymer block. is added in an amount that is equivalent to The reaction of the active linear block copolymer with the multifunctional binder is preferably carried out under the same reaction conditions as the previously carried out polymerization of the monomers. Isolation of the obtained branched block copolymer from the reaction solution is carried out according to conventional methods, for example, by precipitation of the polymer from the reaction solution and filtration. Following coupling and preferably before isolation of the product from the reaction solution, the branched block copolymer can be further hydrogenated if desired.

The hydrogenation can be carried out selectively or non-selectively and is carried out by conventional means using catalysts based on molecular hydrogen and metals or metal salts of groups of the periodic table. This is done using catalysts based on salts, especially cobalt, nickel or iron carboxylates, alkoxides or phenolates, reduced with metal alkyls, especially aluminum alkyls, in a homogeneous phase, for example in US Pat.
13986, German Patent Application Publication No. 12222
60 or German Patent Application No. 2013263. Under mild conditions, a hydrogen pressure of 1 to 100 bar and a hydrogen pressure of 25 to 150 bar are used.
The olefinic double bonds are hydrogenated at a temperature of .degree. Hydrogenation can also be carried out in a heterogeneous phase using metallic nickel or metallic platinum as a catalyst at a hydrogen pressure of 20 to 300 bar and a temperature of 40 to 300°C (for example as described in German Patent Application No. 1106961 or German Patent Application No. 1595345)). In this case, aromatic double bonds as well as olefinic double bonds are hydrogenated. If the hydrogenation is carried out in solution, it is preferably carried out in the same solvent as the polymerization carried out previously. The branched block copolymers can be partially or completely hydrogenated here. Preferably, when hydrogenated, the olefinic double bonds of the polymer are selectively hydrogenated, with the hydrogenated branched block copolymer preferably still comprising no more than 10%, and especially no more than 3%. It contains only olefinic double bonds. Branched block copolymers prepared in the presence of small amounts of ether during the polymerization are preferably used for the hydrogenation. The composition and structure of the branched block copolymer of the present invention are determined by the production method.

For example, a tetrafunctional binder is used, and in the reaction solution at the end of the polymerization of the third reaction stage, two types of polymer blocks forming branches (AI-A2-B→)-Li and ( If the ratio of Li-B→A3)-Li is, for example, 1:1 or 1:3, the resulting branched block copolymer has the formula (AI-A
2-B→A3) 2-X-(ga←B-crab)2 or (A
It has a structure represented by I-A2-B→A3), -X-(but←B-kō)3.

Sankikuma binder and both types of branching (AI-A2-B→A
3) At a 1:2 ratio of -Li and (A2-B→A3)-Li, the most likely average structure of the branched floc copolymer is the following formula (AI-A2-B→A3)-×- (A3
←B-#)2, where X means a residue of a multifunctional binding agent.

In general, the branched block copolymer produced according to the present invention has the following formula (A
It has a structure represented by I-A2-B→P)n-X-(A3''B-#)m, where m and n are integers, and the sum of n and m is the functional number of the binder. and is therefore at least 3, generally in the range from 3 to 10, and preferably 3 or 4.

In this case, m is at least equal to or greater than n. 50 to 8% by weight, preferably 6% by weight of the total monovinyl aromatic compounds used in the preparation of the branched block copolymer
The elastomeric polymer segments AI containing from 0 to 75% by weight preferably consist exclusively of monovinyl aromatic compounds and are especially styrene homopolymer segments. Its molecular weight is determined primarily by the intended use for the desired product and is preferably in the range from 50,000 to 250,000. The polymer segment is necessarily similar to polymer segment AI, but it is smaller, usually only having a molecular weight of 5,000 to 50,000. This ranges from 1 to 3% by weight of the total monopynyl aromatics, and preferably from 5 to 25% by weight.
Contains polymerized. The elastomer polymer segment B, as described above, is essentially a copolymer block of conjugated genes and a small proportion of monopynyl aromatic compounds, in which the olefinic double bonds can be selectively hydrogenated if desired. may be The proportion of monovinyl aromatics in polymer segment B is not more than about 3% by weight, and in particular about 2% by weight, based on the amount of monovinylaromatics not contained as a constituent in polymer segments AI and A2. It is as follows. The non-elastomeric polymer segment A3, like the polymer segments AI and #, is preferably composed only of monovinyl aromatic compounds,
In particular, it is a homopolymer of styrene. The molecular weight of the polymer block (AI-Par B→A3) is preferably 10
The molecular weight of the polymer block (A2-B→A3) is in the range of 10,000 to 10,000.
It is within the range of 0. The branched block copolymer of the present invention has high transparency and clarity as well as good mechanical properties,
In particular with respect to its impact resistance and stretching tension, it is superior to the known product described in German Patent Application No. 1959922.

This was unexpected, and according to DE 1959922 all non-elastomeric polymer segments must be terminal if sufficient mechanical properties are to be obtained. This was all the more unexpected since it is said that this is not the case. Hydrogenation improves, in particular, the aging stability of the product, although, of course, the clarity of the product is reduced somewhat if necessary. The branched block copolymers of the invention can be easily processed by the usual processing methods for thermoplastics, such as extrusion, deep drawing or injection molding, and are particularly suitable for the production of moldings and packaging articles. The invention will be explained in more detail by the following examples.

The viscosity number, measured at 2500 in a 0.5% solution in toluene, was used as a measure of molecular weight. The impact strength an and the notch impact strength ak were determined on compression molded bodies according to DIN 53453. Stretching tension Y,
The tear strength Z and the elongation D were determined according to DIN 53455 on compression-molded shoulder bars. Example 1 10 6 kg of toluene and 430 g of styrene were charged into the pressure-resistant container, and 1.5 kg of styrene was charged under an inert gas atmosphere.
% n-butyllithium solution until polymerization just begins.

This was followed by 7 mmol of n-phthyllithium (3
% solution) and allow to polymerize for about 1 hour until the monomers are virtually completely reacted at 50-60 oo. The polymer has a viscosity number of 34.7 (s/g). 7 mmol of n-butyllithium (as a 3% solution in hexane) are again added to the active reaction solution, followed by 80 g of styrene and the polymerization is completed at 50-6000 ml. The viscosity number is 33.1 (base/g). A mixture of 120 grams of styrene and 21 grams of Butadiene is then added and again polymerized at 50-6000 for about 2 hours until the monomers are virtually completely reacted. Then 3.5 mmol of silicon tetrachloride are added. The branched block copolymer formed is precipitated by addition of methanol and filtered. It has a viscosity number of 84.3 (base/g). The mechanical properties are shown in the table below. Example 2 Proceed as in Example 1, but in this case 450 g of styrene in toluene 6k9 are charged and after titration 500 g of styrene is added with 3.8 mmol of n-butyllithium.
When polymerized at 0, a viscosity number of 49.1 (s/g) is obtained.

Then 11.4 mmol of n-butyllithium are added again and 60 g of styrene are polymerized at 50-6000. At this time, the viscosity number is 46.3 (base/g). A mixture of 120 g of styrene and 210 g of butadiene is then added and polymerized again at about 6000 ml until virtually complete reaction of the monomers. Subsequently, they are combined using 3.8 mmol of silicon tetrachloride to form a branched block copolymer. The viscosity number is 79.3 (base/g). The mechanical properties are shown in the table below. Comparative Example (according to German Patent Application No. 1959922) 6 2.7 kg of cyclohexane and 52 kg of styrene were prepared in a pressure-resistant container under an inert gas atmosphere with moisture excluded.
5 g are titrated with sec-butyl lithium and polymerized for 30 minutes with 0.33 g of sec-butyl lithium.

Claims (1)

[Claims] 1. In a first reaction stage, 60 to 80% by weight of the total amount of monovinyl aromatic compound is polymerized in the presence of a relatively small amount of monolithium hydrocarbon until practically completely reacted;
Then, in a second reaction step, additional initiator is added to the reaction solution in an amount equal to or greater than the amount of initiator initially used, followed by an additional 1 to 30% by weight of the total amount of monovinyl aromatic compound. in such a way that the amount of monovinyl aromatic compound added in the first and second reaction stages is at most 90% by weight of the total amount of monovinyl aromatic compound used to produce the branched block copolymer. and the monovinyl aromatic compound added in the second reaction stage is likewise polymerized to virtually complete reaction, and then in the third reaction stage a mixture of the remaining monovinyl aromatic compound and the total amount of conjugated diene is added to the reaction solution. and finally, after virtually complete reaction of the monomers, the resulting mixture of linear block copolymers with active terminal lithium-carbon bonds is subjected to addition of a multifunctional binder. The monomers and the initiator are combined in an inert solvent in the presence of a monolithium hydrocarbon as an initiator, characterized in that they are combined together to form a branched block copolymer. monovinyl aromatic compounds 60 to 95 by sequential bonding under selective addition and subsequent bonding of the obtained active linear block copolymers using a multifunctional binder.
% by weight and 40 conjugated dienes with 4 to 8 carbon atoms
A method for producing a branched block copolymer from ~5% by weight.