DE2924598A1 - METHOD FOR ISOMERIZING INSULATED TO CONJUGATED DOUBLE BINDINGS IN HOMO AND / OR COPOLYMERS OF 1,3-DIENES - Google Patents

Description

Process for isomerization of isolated to

conjugated double bonds in homo- and / or copolymers of 1 , 3-dienes In the homopolymerization of 1,3-dienes and in their copolymerization with one another or with vinyl-substituted aromatics, polymers are obtained with isolated Double bonds.

However, it is known that low and high molecular weight compounds with conjugated double bonds the corresponding compounds with isolated Double bonds are superior in terms of reactivity and thus also in terms of attractiveness. the end For this reason, processes for the preparation of compounds with conjugated Double bonds developed. You can z. B. proceed so that one 1,3-dienes DJ copolymerizes with acetylene. Furukawa et al., Journ. Polym. Sci., Polym. Chem. Ed., Vol. 14, 1213-19 (1976 dz Another and more economical option is the isomerization of isolated to conjugated double bonds. To carry out A wide variety of catalyst systems were used for this isomerization.

For example, DE-AS 11 74 071 discloses a process for the isomerization of Butadiene polymers known, in which the butadiene polymers are in the presence small amounts of transition metals of VI. to VIII. group des Periodic Table of the Elements and / or of compounds in which these Metals are in the zero-valent state, at temperatures between 100 and 300 ° C heated.

The disadvantages of this process are that once the isomerization temperature is very high and gelation can occur in the process; on the other hand takes place with the relative expensive cis-trans isomerization catalysts take place, resulting in loss of reactive leads to cis-1,4 structures.

Furthermore, according to the method of DE-OS 23 42 885, the combination from an organic alkali metal compound and a special diamine as an isomerization catalyst can be used for low molecular weight homo- and copolymers of butadiene. The chelating one However, the effect of the diamines used requires a relatively high content of alkali metal ions in the polymer, which has a negative effect, for example, when it is used in the paint sector. In addition, the combination of polymerization and described as preferred results Isomerization does not match the drying properties of low molecular weight polybutadienes advantageous high content of cis-1,4 structures.

Finally, DE-PS 11 56 788 and DE-AS 11 56 789 process for the conversion of fatty acid esters of monohydric alcohols with isolated double bonds known in fatty acid esters with conjugated double bonds, in which as isomerization catalysts Alkali alcoholates are used.

The object of the invention was to provide a process for the isomerization of isolated to conjugated double bonds in homo- and / or copolymers of 1 3-dienes to develop, in which in general while maintaining application technology more valuable cis-1,4 structures no gelation occurs, and the products are low in content of alkali metal ions.

This object has been achieved by using the isomerization catalyst an alkali used and the isomerization at temperatures from +50 to +250 oO performs.

The raucllbarkeit of the alkali alcoholates is surprising insofar as because their use appeared to be limited to specific compounds. So is z. B. the isomerization described for fatty acid esters of monohydric alcohols not on classes of compounds that are so chemically related, such as fatty acid esters of polyhydric alcohols or fats, transferable (cf. DE-OS 21 55 727, page 2, paragraph 1).

Untel homo- and copolymers of 1,3-dienes are included in this Invention understood: homopolymers of z. B. butadiene- (1,3), isoprene, 2,3-dimethylbutadiene and Piperzrlen, copolymers of these 1,3-dienes with one another and copolymers this 1,3-dienes with vinyl-substituted aromatic compounds, such as. B styrene, α-methylstyrene, vinyltoluene and divinylbenzene.

The content of vinyl-substituted aromatic compounds: -n the Copolymers should not exceed 50 mol percent. Are preferred in the Process according to the invention polybutadienes with molecular weights (Mn) from 900 to 20,000, particularly 600 to 10,000 and very particularly 800 to 6,000 are used. the The microstructure of the dienes in the homo- or copolymers is generally not critical, however, it is advantageous if at least 20% of the double bonds have a cis-1,4 structure own.

Alkali metal compounds can be used as alkali metal alcoholates in the process according to the invention of all monovalent and polyvalent primary, secondary and tertiary alcohols puts will. The sodium and lithium alkoxides are preferred to be monovalent (cyclo) aliphatic Alcohols with up to 20 carbon atoms, preferably 3 to 8 carbon atoms.

Typical alcoholates that can be used are, for. B. Sodium and Potassium Isopropylate, Sodium and potassium tert-butoxide, sodium and potassium 2-ethyl hexoxide.

The alkali metal alcoholate is generally used in the polymer to be isomerized in an amount of 0.1 to 10, preferably 0.5 to 3, grams per 100 grams of polymer added.

The polymer to be isomerized can be either with or without a solvent can be used. The use of a solvent is appropriate or necessary, when the viscosity of the polymer is so high that the homogeneous distribution of the catalyst components is not guaranteed.

As a solvent that is free of bothersome impurities, such as. B. Water, should be, come z. B. aliphatic, cycloaliphatic and aromatic Hydrocarbons in question. Typical representatives from these groups are hexane, octane, Cyclohexane, toluene and xylene.

The process according to the invention is carried out at temperatures from +50 to +250 OC, preferably +80 to +150 00, carried out.

When carrying out the process according to the invention, one goes in generally so that the polymer to be isgmerized, optionally dissolved in a solvent with the alcoholate and set to the desired temperature warmed up. If the catalyst is poorly soluble, e.g. B. in the case of methylates, the polymer, possibly dissolved in a solvent, is treated with a solubilizer, such as hexamethylphosphorus sauretriamid, offset, The required reaction time depends on the type and amount of the catalyst the polymers to be isomerized and the temperature. The optimal response time can easily be determined by a few preliminary experiments. The reaction will z. 9. Finished by cooling to room temperature (25 OC). Up to this procedural step all operations are preferred under an inert gas atmosphere, such as. B. argon performed. Subsequently, the catalyst is washed by aqueous and / or adsorptive Treatment, e.g. B. with fuller's earth, largely removed.

The momo- and / or isomerized by the process according to the invention Copolymers of 1,3-dienes, which are preferred for the preparation of coating agents find up to 35, based on the total number of double bonds, conjugated Diene structures. In addition, there are also conjugated tri- and tetraene structures to a small extent on.

The process according to the invention is illustrated by the following examples explained in more detail.

The conjuene contents stated therein were determined by UV spectroscopy and in the case of polybutadienes are expressed as percentages by weight, calculated for C8Ha4 (conjugated Dienes), $ C8H12 (conjugated trienes) and C8H10 (conjugated tetraenes). Room temperature means 25 OC in all siles. The metal / chain ratio represents each represents the molar ratio of metal to polymer.

Unless otherwise stated, all percentages are percentages by weight.

The microstructures were determined and placed by IR spectroscopy represents the proportional values of the double bonds.

Example 1 2,000 g of a polybutadiene oil with 76 o / o cis-1.4 structure and a content of conjugated diene structures of <0.5 0/0 (Mn = 1,500) placed in a heated 4 l stirred flask flushed with argon. To that on Oil heated to 120 OC was added 3 times 1 percent by weight at intervals of 120 minutes each time Potassium tert-butoxide given, whereby samples were taken beforehand in each case which the isomerization was terminated by cooling to room temperature. At 120 ° C, the oil turns dark red in the presence of potassium tert-butoxide.

Working up took place via dilution with hexane and centrifugation of the then precipitated alcoholate. The development of microstructures and conjunctivities over time is given in Table 1. All reactions, including those of the following examples, took place under an argon atmosphere, since the presence especially at a higher temperature of oxygen can lead to gelation.

Table 1 Time dependency of the isomerization with potassium tertiary butoxide (KtBO) at 120 oC Preserves the microstructure of conjuene content n KtBO X7 [%] [% By weight] [h] trans-1.4 1.2 cis-1.4 diolef.triolef.tetraolef. 1 2 22 1 77 12.8 0 0 2 4 20 1 79 | 19 | 0.06 | 0 3 6 21 1 78 32 0.08 0 The reproduced microstructures represent the relative values (converted to 100%). The absolute contents are between 80 and 95%.

The product became a sheet with a wet film thickness of 50 μ brought and examined on the basis of DIN 53 150 with regard to the drying behavior. Dust and through-drying times of hours were found (comparison: starting product : Dust and thorough drying: 9 hours).

The same experiment was also carried out with freshly sublimed StBO of the commercially available. He got the same results.

It is also possible to use the entire amount of the catalyst at once admit. Somewhat lower conjuene contents (20 ffi conjugated diolefins after 6 hours).

Examples 2 to 6 The isomerization with KtBO as a catalyst was carried out on polybutadiene oils of different structures and different molecular weights. Copolymers with styrene and oils from other monomers were also used. the Table 2 contains the results. The microstructures remain almost as in Example 1 constant.

Table 2 Isomerization of oils with different monomers, different structure and higher molecular weights No. Oil type * KtBo T t Konjuen content [%] [% By weight] [° C] [h] diolefin 2 VPO 10 150 2 9.9 | 3 | PO130 2 120 5 7.5 t 4 PO 160 2- 120 5 4.6 5 | St / Bu | 5 | 150 | 3 | 7.8 $ 6 PIP 5 150 5 2.1 Oil types: VPO = vinyl poly oil (manufactured according to DE-OS 23 61 782) P0130 ~ commercial products from Chemische P0160 Werke Hüls AG St / Bu = copolymer oil styrene / butadiene (manufactured based on DE-PS 12 12 302) PIP = polyisoprene oil made with LiBu The catalyst was added all at once in the experiments.

Data of the starting oils (conjuene content <0.5%): Mn microstructure [%] trans-1.4 1.2 cis-1.4 styrene VPO 930 12 42 46 0 P0130 3,000 19 1 80 0 PO160 6 000 8 - 16 2 - 4 80 - 90 0 St / Bu 960 12 5 54 29 PIP 1 600 51 (3.4) 3 41 (1.4) 0 Examples 7 and 8 Based on the procedure of Example 1, sodium was used or potassium 2-ethylhexylate (Na or KOC8) isomerized. The results are in Table 3 included.

Table 3 Isomerization with Na and K alcoholates Example alcoholate [wt.%] T t conj. Diolefins No. [° C] [h] 7 NaOC8 5 150 5 6 8 K008 5 120 1 13.2 To produce the alcoholates, the alkali metals are finely atomized in xylene. They were then allowed to react with excess 2-ethylhexanol. To complete the reaction, the mixture was heated to 145 oC and excess alcohol and xylene were driven off.

Then the polybutadiene oil was added and the mixture to the desired one Temperature brought. However, it can also be isomerized with the excess alcohol will.

Examples 9-13 The procedure of Example 1 was repeated with others Repeated alcoholates, the catalyst being added all at once. There came Potassium or sodium alcoholates of methanol (9, 10), isopropanol (11), cyclohexanol (12), benzyl alcohol (14) and 1,2-propylene glycol (13), which are based on the in Examples 7 and 8 were prepared in the manner indicated. The results are there Table 4 again.

Table 4 Isomerization with various alcoholates Example alcoholate [wt.%] T t conj. Diolef. No. [° C] [h] [%] 9 NaOCH3 5 120 2 1.1 10 NaOCH3 / 10% HMPT * 5 120 5 3.4 11 KO i Prop 5 150 3 11.1 12 KO cyclohexyl 5 120 7 11.9 13 KOC3OH 5 150 3 11.5 14 KO Benzyl 7 150 7 18 Hexamethylphosphoric triamide A comparison of Examples 9 and 10 clearly shows that the addition of a solubilizer such as HMPT is useful in the case of poorly soluble alcoholates such as methylate. Examples 15 to 22 Based on the procedure described in Example 1, different concentrations of KtBO were used at different temperatures. The results are shown in Table 5.

Table 5 Isomerization with KtBO Example KtBO T t conj. Diolefins No. [wt.%] [° C] [h] [%] 15 0.1 150 1 1.1 16 0.5 120 3 7.1 17 1 120 3 14.0 18 5 150 0.5 16.7 19 10 | 120 5 17.6 20 5 120 3 17.1 21 | 5 | 80 | 5 | 6.3 22 5 50 5 1.1 Example 23 The procedure of Example 1 was repeated in xylene as the solvent. To this end, 200 g of polybutadiene oil in 40 g of xylene were admixed with 1 percent by weight of KbBO at room temperature and then heated to 135.degree.

After 1/2 hour, 14.2% conjugated diolefins were found by UV spectroscopy certainly.

Claims (2)

Claims: 1. Process for isomerization of isolated to conjugated double bonds in homo- and / or copolymers of 1,3-dienes with the help an isomerization catalyst and optionally in the presence of a solvent, characterized in that an alkali metal alcoholate is used as the isomerization catalyst begins and the isomerization is carried out at temperatures of +50 to +250 OC. 2. The method according to claim 1, characterized in that as Alkali alcoholate is the sodium and / or potassium salt of a monovalent (cyclo) aliphatic '' Uses alcohol with up to 20 carbon atoms.