DE1150205B - Process for the preparation of end-group modified butadiene polymers - Google Patents

Description

Process for the preparation of end-group-modified butadiene polymers The invention relates to a process for the preparation of end-group-modified Butadiene polymers by polymerizing butadiene with entering as end groups Starters and modifiers with bis-type structure.

The method is characterized in that for the production of liquid Butadiene polymers with a molecular weight of 500 to 15,000 as well as free Free radical initiators as well as modifiers such compounds with bis-type structure can be used which have terminal carboxyl groups.

The curable polymers produced according to the invention are addition polymers of medium molecular weight, with the molecules reactive at the ends Have groups. The properties of these polymers are essentially the same like those of long chain polymers, but allows the presence of more reactive ones End groups the further polymerisation of the polymers through curing reactions. The curable liquid polymers produced according to the invention are used for impregnation, spraying, pouring and other technical processes in which liquid polymers are to be used with advantage. For example, the Fabrics after impregnation or soaking or after pouring are slightly TOO firm, difficult-to-melt polymeric products of high molecular weight are cured.

The polymers obtained according to the invention with reactive, functional end groups essentially have the properties of butadiene polymers without functional terminal groups; but they also have others Characteristics that show their superiority over the previously known substances of this Kind of prove. In particular, the claimed polymerisation process leads to substances which have excellent characteristics at low temperatures.

The polymerization of the butadiene takes place according to the present invention by free radicals. The polymerization process according to the invention results an essentially linear polymer formed by 1,4-additives that only a small percentage of vinyl groups attached to the main polymer chain Has. For example, these polybutadienes contain only about 20% monomeric butadiene, which has been polymerized by 1,2-addition. In other procedures, e.g. B. the Sodium or ion polymerization of butadiene, 50 to 75% of monomeric butadiene occur with 1,2-addition in the polymer chain, whereby one has a correspondingly large Number of vinyl side groups obtained. It is believed to be the lack of attached groups in the finished polymeric compositions produced by the process according to the invention the excellent behavior of the polymers at low temperatures. For example, the polybutadienes produced according to the invention have a gjoooo (i.e., the temperature at which the torsional modulus of a 1 square inch rod Cross section is equal to around 700 kg / cm2) of around 760 C, which value is below the value which was found in the usual polybutadienes. When working under low temperatures and use of these polymers is such a lower Value of Gf - which is the brittleness point (Tg) or the cold resistance of the polymer approaching - of considerable importance. The polymers produced according to the invention namely retain their flexibility even at low temperatures and are therefore For uses where a low temperature prevails, especially he wishes.

The introduction of the terminal carboxyl groups into the polymers takes place by initiating the polymerization of butadiene using a dissociable starter reagent which contains carboxyl groups. By splitting up of the starter reagent, for example by thermal means, one obtains several free ones Radicals, each of the same with a carboxyl group. These radicals now initiate the polymerization of the monomer through a reaction with the same, wherein the core of a polymeric chain with a carboxyl group is formed.

The chain is lengthened through the reaction of this chain core with other molecules of the monomer. There is also a bifunctional in the mixture Modifier or chain length regulator.

The breaking of the polymer chain and the subsequent excretion Free radicals can occur through a number of different reactions.

For example, the polymer chain can by reacting with a other free radical end groups derived from the starter are terminated.

The resulting polymer then has two functional terminal positions Carboxyl groups derived from the free radical initiator. The Polymer chain but also with the modifier present in a chain termination reaction implemented. The modifier used also has carboxyl groups, and in this case then the polymer chain has end groups, which are both from derive from the starter as well as from the modifier.

The modifier selected here is one that is used for the Reaction with a free radical polymer chain generates a free radical, and the generated free radical fraction of the modifier can now the further polymerization initiate new polymer chains by forming the core. Both polymer chains can can also be terminated by reacting with one another. In each of these cases, with which the possibilities for a reaction are by no means exhausted, has what is formed in the process polymeric molecule has two functional, terminal carboxyl groups that are either from the existing starter or from the bifunctional modifier or chain length regulator derive. The end chains of the polymer therefore either only come from the starter or only from the modifier or from both at the same time.

Numerous free radical initiators can be used in the process according to the invention can be used, the only condition being that they be the required have functional carboxyl groups.

You must of course also have an adequate ability to be free Generate radicals. In a preferred embodiment of the invention Process is an o, w'-azobis (o> -cyanoalkanecarboxylic acid) as the starter substance and an o, co'-dithio-bis (alkanecarboxylic acid) used as a modifier.

4,4'-Azo-bis- (cyanvaleric acid) has proven particularly useful as a starter substance. and as a modifier dithiodibutyric acid.

The disulfides particularly suitable for the invention are accordingly Dithio compounds of the lower members of the aliphatic series co-subsuted functional groups of the type described.

Substances of this type are, for example, the lower dithioalkanoic acids, like the mentioned dithiodibutyric acid (DTDB) HOOC (CH2) 3SS (CH2) 3COOH, dithiodiproprionic acid HOOC (CH2) 2SS (CH2) 2COOH and the dithiodipropionic acid HOOC (CH2) sSS (CH2) 5COOH.

If, for example, 4,4'-azo-bis- (4-cyano-valeric acid) is used as the starter substance, dithiodibutyric acid as the modifier and butadiene as the monomer, the reactions for initiating the polymerization and for the progressive growth of the chains can be given by the following equations being represented: In reaction I, the azo starter decomposes with the formation of the free radical This reaction is the first to generate free radicals. The polymerization is thus initiated by the presence of a free radical, and the number of free radicals present determines the number of growing chains in the reaction. A small amount of starter results in relatively few free radicals and therefore a slower reaction. Conversely, a large amount of starter leads to a faster reaction. By using a modifier, other reactive free radicals can also be added in the course of the reaction. The number of growing chains can therefore be determined by the amount of starter substance used. However, the polymerization reaction can also be driven by the use of a modifier which continues the chain of free radicals, even after the polymerization has been terminated in a single chain. There is considerable freedom in choosing the ratio of the amount of initiator to the amount of modifier that can be used and, as a result, one has a means of controlling both the rate of the reaction and the length of the polymer chain. For example, a high concentration of the chain length regulator will result in substances of lower molecular weight.

Equation II shows the reaction of the free radical of the starter substance with the monomeric butadiene. You can see that the reaction is one of the double bonds of the butadiene is required to create the chain and that the other bond is generally shifted towards the middle carbon atoms. n is the Number which is the average of the basic butadiene building blocks that existed before the termination polymerize in the chain.

Equation III shows the reaction of the growing polymer chain with the modifier. In this reaction, the modifier becomes on the disulfide member cleaved to react with the free radical polymer, with both a polymeric molecule with a functional terminal group as well as a new one functional free radical capable of chain polymerization continue to be generated.

Equation IV shows the response between that from the modifier generated free radical and other basic building blocks of the monomeric butadiene, where a growing polymer chain containing the modifier end group, and a still growing polybutadiene radical can be generated. This radical can then die repeat the process steps already described.

The reactions given here are of course only illustrative. Instead of 4,4'-azo-bis- (4-cyano-valeric acid), other starter substances can also be used having an active terminal carboxyl group as indicated above was used will.

The end of the polymerization takes place, for example, as soon as a growing chain reacts with a modifier molecule. As has already been specified, the formation of a new chain is initiated, which continues to grow, so that the reaction, albeit the formation of a polymeric molecule is finished so that it has not yet been canceled. However, if two are free If radicals react with each other, then there will be no further free radicals to propagate the chain, and the reaction is terminated.

For example, the starter radical of reaction I and the polymer radical cause reaction II to terminate their reaction with one another by they create a molecule that has the same starter radicals at each end of the polymer chain Has. Reaction IV can likewise be carried out by the reaction with a free starter radical or terminated with a free radical of the modifier. Also two free ones Radically growing polymer chains of that described in Reactions II and IV Type can be coupled together to stop the polymerization cause. However, since the molecular weight range of the manufactured according to the invention Products is relatively narrow, this reaction apparently only occurs in limited scope to.

From a consideration of the possible termination reactions it is clear that three types of molecules - in relation to the end groups - can be generated, which are represented by the following formulas: As you can see from this, every compound has the same reactive end group, namely the carboxyl group, which is why all three types of molecules react in the same way.

The chains are also bifunctional with regard to the carboxyl group, and this bifunctionality is essential when followed by any subsequent Curing reactions higher polymers are to be generated. The presence of a ineffective end group in the molecule, as is usually the case in normal polymerization generated is sufficient to chain growth in the direction of the ineffective end group to avoid.

The curable polymeric products discussed here can pass through the following general formula can be represented: HOOC - R (CII. - CII CH R 'COOH In this formula, R and R 'are the non-functional parts of the end groups, which - as can be seen from the specific formulas - the same in the final molecule or can be different from one another; n is an integer which is the number of butadiene molecules in the chain. Although polybutadiene like it from this general formula, is a 1,4-reaction product, it has been recognized that this is not the only way in which polymerization of the Butadiene can go on. However, because of the reaction a predominantly linear one Polymer is produced and at the same about 75 to 80 80% of the monomeric butadiene are polymerized in a 1,4 reaction, the polymer here is in a form shown in which attached vinyl groups are missing. As mentioned earlier ion or sodium polymerization of butadiene predominantly leads to a polybutadiene with pendant vinyl groups or branch chains.

For the curing, which is not claimed here, of the products produced according to the invention Reactive polymers, isocyanates, ethylene oxides and imides are particularly suitable. Metal oxides, polyhydric alcohols, polyamines and the like are also useful Pollyfunctional connections.

The numerical value of n in the above formula must be so high that one a polymeric product having a molecular weight between about 500 and 15,000. Within this range, the average molecular weight of the polymer Product can be regulated by looking at the total amounts of starter and Modifier migrates and continues to change the amount of these substances in each The course of the reaction is present.

In order to bring about a sufficiently rapid reaction, one can, for example use relatively large amounts of the starter substance. However, it can also smaller amounts of the latter can be used if appropriate by the modifier larger amounts are represented. To have a reasonably high degree of conversion too received, the starter is usually added in portions and at intervals. The modifier is preferably one which has chain propagation reactions which roughly keep pace with the consumption of the monomer. The responsiveness the modifier and the monomer can nen are balanced to each other so that to obtain polymers with a molecular weight within the desired range and also achieved a fairly uniform molecular weight distribution. So can for example products with a large number of substances from very low Avoid molecular weight and, with a small residue, very high molecular weight substances. When the reactivity of the modifier is significantly different from that of the monomer is different, the molecular weight distribution can be adjusted by adjusting the The time measure for the additions of the modifier can be regulated.

Example 1 A carboxyl-terminated polybutadiene polymer was made from 1380 g butadiene, 100 g dithiodibutyric acid (DTDB) and 64 g 4,4'-azo-bis (4-cyano-valeric acid) (ACP) in the following manner: The entire DTDB modifier and a first part of the starter substance with a content of 16 g of ACP dissolved in a mixture of 80 g of methanol and 16 g of water placed in an autoclave with a content of 3.785 liters. One has with the same Other, non-alcoholic, organic solvents, e.g. B.

Acetone is used to dissolve the ACP and can do the possible Avoid the formation of esters.

The autoclave was then filled with the monomeric butadiene and closed and brought to a temperature of 85 ° C. After 6 hours of heating with this Temperature (corresponding to a pressure of 14 kg / cm2 in the autoclave used) was a second portion of the starter substance, as before in methanol and water dissolved, added under pressure, whereupon the reaction was continued.

Other aliquots of the starter substance were after the course of 12 and of 18 hours was added and the heating was continued for a total of 24 hours continued. (Although this example covers the paragraph-wise addition of the ACP, so there is also a method with continuous supply in which the ACP over a period of 12 hours is added; this procedure was Applied with particular success and even allows better regulation of the quantity of starter substance, which must be present during the entire reaction). After 24 hours, approximately 400/0 of the monomer originally present had been converted.

The unreacted butadiene and methanol were used up the reaction mixture was distilled off, and the remaining polymer was with methanol washed until the unreacted acids - DTDB and ACP - removed had been. The liquid polymer was finally dried in a vacuum with stirring, to remove all of the methanol. The product was a liquid with a Brookfield viscosity of 440 poise at 26.670 C and a carboxyl content of 0.041 Equivalents per 100 g. This equivalent corresponds to an average molecular weight from about 5000. To some extent the high viscosity of the product attributed to washing with methanol, because doing so the substances with low Molecular weight can be washed out and the viscosity of the polymer by fractionation is increased.

Example 2 Following the polymerization process described in Example 1 a liquid polymer was produced, but when the reaction ended, it was and after distilling off the butadiene and methanol which have not reacted from the reaction mixture the product washed several times with hot water until the all unreacted amounts of acid - DTDB and ACP - have been removed was. The polymer was then dried under vacuum. The Brookfield viscosity of the product was 210 poise at 26.670 C, the carboxyl content was 0.68 Equivalents per 100 g and the average molecular weight to 2940.

Example 3 A polymer of higher average molecular weight was prepared as in Example 2 and washed with water, except that instead of 100 g of the DTDB modifier in the reaction mixture as in Example 2 of which only 75 g were used. The polymer washed with water had a Brookfield viscosity of 315 poise at 26.670 C, a carboxyl content of 0.057 Equivalents per 100 g and a molecular weight of 3500.

Example 4 A carboxyl-terminated polymer was obtained prepared according to the procedure of Example 2.

The reaction took place at 850 C, the addition of the starter substance in 6 hour intervals and the yield was about 40%. For The following substances were used for the production: 1380 g butadiene, 100 g p-carboxy-methylphenol disulfide, dissolved in methanol, and 64 g of ACP, which are added in four equal portions became. The Brookfield viscosity was 300 poise at 26.670 ° C and the carboxyl equivalent to 0.05 per 100 g, corresponding to a molecular weight of about 3600.

The way in which the average molecular weight of reactive polymers by changing the temperature and the existing Amounts of modifier and starter substance can be modified, results from the examples below.

Example 5a Using a batch of 1380 g of butadiene, 300 g DTDB and 64 g ACP, polymerization at 85 C with about 400% conversion, using the method according to Example 2, a polymer is obtained with a average molecular weight of about 1000.

Example 5b Using the same amount of butadiene but of 100 g of DTDB and 25 g of ACP, a polymer was obtained with an average Molecular weight from 3,000 to 4,000. The yield here is also approximately between 35 and 40o. The experiment was carried out as in Example 2; H. Washing the polymer with water, but at a polymerization temperature of 950 C. The ACP is in four aliquots of about 6 g each are added, each aliquot before the addition was dissolved in about 6 g of water and 30 g of methanol.

Example 5c Using the same amount of butadiene as in Examples 5a and 5b, with only 25 g of DTDB and 64 g of ACP, a polymer is obtained having a molecular weight of 10,000 to 12,000. The reaction procedure was about the same as in Example 2, at a polymerization temperature of 853 C and a yield of 35 to 40%.

The curing of the curable polymers of the type described above is illustrated by the following experiments: Using the polymer from Example 1 above, a number of cured polymeric substances were prepared from the following reaction mixtures: A | BC Polymer from Example 1 .. -100 100 100 Finely divided coal (»Ther- Max") . . . 20 20 20 Difunctional epoxy or ethylene oxide hardener. 11.7 - - Tri- (dimethylaminomethyl) - phenol (amine catalyst for epoxies or sithylene oxides). . 1.2 - - Ethylene substituted methane with terminal imide group . . - 10.7 - Tris -2-methylaziridinophos- phinoxyd. 1 - ~ 4.7 In each case, after addition, these substances were mixed with one another in a paint mill in the order given in the table. Milling was continued until a smooth mixture was obtained.

The curing took place by heating at 770 C in a rotary kiln over the course of 20 hours, the tests with the cured polymers yielding the following results: A | B | C. Tensile strength, kg / cm2. 14.56 34.86 16.45 Elongation, o / o. 385 270 420 Shore hardness with durometer measured. . 46 68 32 Tear Strength, kg / cm. . 5.7 14.3 8.6 Example 6 A polymer with reactive terminal groups was prepared according to the procedure described in Example 1, except that 75 g of DTDB were used and that the reaction time was 48 hours at a reaction temperature of 750 ° C. instead of 850 ° C. at this temperature the pressure in the autoclave is 9.8 kg / cm2). The resulting polymer had a viscosity of 590 poise, a carboxyl equivalent of 0.44 per 100 grams, and a molecular weight of 4,500.

100 parts of this polymer were cured in the presence of 20 parts by weight of carbon black, using 10.7 parts by weight of an ethyleneimino-substituted Methane and using the method of Example 5. The resulting polymer had a tensile strength of 54.39 kg / cm2, an elongation of 463%, a Shore hardness A of 75 Duro and a tear strength of 28.6 kg / cm.

When curing the same polymer with the same hardener, the following physical properties were obtained with different proportions between the polymer with a terminal carboxyl group and the hardener, as can be seen from the table below: AB c Polymer. . 100 100 Harder as in the example Sc, Attempt B. .. 7.3 11.1 14.6 Tensile strength, kg / cm2. . 8.82 39.9 40.6 Elongation, ° / o. . . 75 380 367 Shore hardness A in Duro 50 70 72 Tear Strength, kg / cm. . 4.5 30 33.1 In general, when the curable polymers produced according to the invention are cured by means of the curing agents described, the curable polymers with higher viscosity also give higher tensile strengths, namely because of the high molecular weights involved. However, crosslinking, polarity and other characteristics of the polymer can have a profound effect on the final properties. After curing, the polymers produced according to the invention are of the same benefit as the high molecular weight polymers which are usually produced from the monomers contained therein. However, the products made according to the invention have the great advantage of easy handling and processing as long as the substances are in a form with a low molecular weight. For example, many rubbery, cured materials can be used to advantage in coatings of various types; however, they are difficult to apply unless by rolling onto roughened or corrugated sheets or plates. The reactive polymers of low molecular weight produced according to the invention, however, permit soaking, coating by dipping or even spraying of the liquid substances onto the surface to be coated. After application, the polymers can then be cured to give the finished rubber-like material. The low molecular weight polymers made in accordance with the present invention can similarly be cast into intricate shapes or used as binders in encapsulated devices. Curing the polymers gives coatings of high molecular weight, the properties of which are similar to those of the polymers produced by conventional polymerization technology, since the two types of polymers differ from one another only through the small proportion of connecting groups in the molecule of the cured one according to the invention different polymers produced.

The excellent properties at low temperatures of the A comparison shows polybutadienes produced by the process according to the invention with the polybutadienes produced by other methods. When using sodium polymerization and a temperature of 800 ° C., a polybutadiene is obtained at which 626 / o des Monomers are polymerized by 1,2-addition. Such a polymer has a cold resistance Tg of about -540 C. The cured polybutadienes according to the invention with terminal carboxyl group, the polymerization at a temperature of about 850 C going on showed G10, 000 values below 760 C leading to the point come close to the cold resistance (Tg).

Claims (3)

PATENT CLAIMS: 1. Process for the production of end-group modified Butadiene polymers by polymerizing butadiene in the presence of as end groups occurring starters and modifiers with bis-type structure, characterized in that that one for the production of liquid butadiene polymers having a molecular weight of 500 to 15,000 as both a free radical initiator and a modifier those compounds with bis-type structure are used which have terminal carboxyl groups exhibit. 2. The method according to claim 1, characterized in that as Starter substance o, w "azo-bis (w-cyanoalkanecarboxylic acids) and as a modifier a>, , cv'-dithio-bis- (alkanecarboxylic acids) are used. 3. The method according to claim 1 or 2, characterized in that the modifier is added after the initiator. References considered: J. Polym. Sci., Vol. 17, p. 221 to 246, 319 to 340; U.S. Patent Step No. 2,844,632.