JPS6212802B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for catalytically hydrogenating a copolymer of a conjugated diene and a vinyl-substituted aromatic hydrocarbon in order to impart thermal stability, weather resistance, and ozone resistance to the copolymer. Specifically, the reaction can be carried out at low temperature and low hydrogen pressure,
The conjugated diene moiety can be selectively hydrogenated,
Furthermore, the present invention relates to a catalytic hydrogenation method in which the catalyst can be separated by a physical method after the reaction. A copolymer of a conjugated diene and a vinyl-substituted aromatic hydrocarbon has a carbon-carbon double bond in the conjugated diene unit, and therefore has poor thermal stability, weather resistance, and ozone resistance. In particular, block copolymers of conjugated dienes and vinyl-substituted aromatic hydrocarbons are used without vulcanization as thermoplastic elastomers, transparent impact-resistant resins, or as modifiers for styrenic and olefin resins. This poses a problem in that it has poor thermal stability, weather resistance, and ozone resistance, which limits its uses. This is due to unsaturated bonds, and hydrogenation of the carbon-carbon double bonds in the diene portion of the polymer significantly improves these properties. The catalysts used in this hydrogenation reaction include (1) a so-called Ziegler type homogeneous catalyst obtained by reacting an organic acid salt or acetylacetone salt of nickel or cobalt with a reducing agent such as organoaluminum in a solvent; 2) Supported catalysts in which metals such as nickel, palladium, and ruthenium are generally supported on carriers such as carbon, alumina, silica, silica/alumina, and diatomaceous earth are known. The former Ziegler type homogeneous catalyst has the characteristic that the reaction proceeds at lower temperature and lower hydrogen pressure than the supported type, and it also selectively reacts with the conjugated diene moiety of the conjugated diene and vinyl-substituted aromatic hydrocarbon copolymer. It is possible to hydrogenate. However, the polymer solution after hydrogenation is apparently homogeneous, and it is impossible to separate the catalyst by physical methods such as filtration. It is necessary to perform a complex chemical reaction in which the catalyst is oxidized with an oxidizing agent such as hydrogen peroxide, then tartaric acid is added and reacted, and this is extracted with alcohol. If catalyst residue remains in the polymer, the weather resistance and heat resistance of the polymer will be extremely poor, so the above-mentioned catalyst removal operation is always necessary. On the other hand, supported catalysts generally have low activity, and the hydrogenation reaction conditions are severe, such as high temperature and high pressure. In particular, as the reaction progresses when the polymer comes into contact with the supported catalyst,
Compared to liquid low polymerization degree polymers, high molecular weight polymers suffer from greater steric hindrance and are difficult to hydrogenate. Therefore, in order to hydrogenate a highly polymerized polymer, a reaction particularly at high temperature and pressure is required, but in this case, decomposition and gelation of the polymer are likely to occur. Furthermore, supported catalysts generally do not have hydrogenation selectivity, and the conjugated diene portion and the aromatic nucleus portion are hydrogenated simultaneously. For example, JP-A-54-77689 discloses a method of hydrogenating a styrene-butadiene-styrene type block copolymer using a platinum catalyst supported on alumina.
When hydrogenation was carried out at Kg/cm ² and a temperature of 150° C., the hydrogen conversion rates of the butadiene portion and the styrene portion were almost the same, and no selectivity was observed. To improve heat resistance, weather resistance, and ozone resistance, it is sufficient to hydrogenate only the conjugated diene part, and there is no merit in hydrogenating the aromatic nucleus part in terms of physical properties, and it causes the disadvantage of increased hydrogen consumption. be. Additionally, supported catalysts are said to be easier to separate by physical methods after hydrogenation, but this applies to organic compounds and polymers with a low degree of polymerization; high polymers have high solution viscosity and Separation is not always easy because the polymer becomes insoluble in the solvent and the solution becomes pudding-like. In order to solve such problems, the present inventors have conducted intensive studies and have developed a method for catalytic hydrogenation of a copolymer of a conjugated diene and a vinyl-substituted aromatic hydrocarbon. The copolymer in which the sum (a+b) of the aromatic hydrocarbon polymer block content (a) and the vinyl bond content of the conjugated diene (b) is 30% by weight or more based on the total copolymer is treated with an inert solvent. Inside, rhodium metal supported on a carrier is used as a catalyst at 120℃.
By hydrogenating at the following temperature, the conjugated diene part is selectively hydrogenated to 70% or more and the vinyl-substituted aromatic hydrocarbon part to 30% or less, and after the reaction, the catalyst is removed from the solution by a physical method. We have discovered that it is possible to separate the two, and have arrived at the present invention. Furthermore, the catalyst separated and recovered by physical methods is
It can be used repeatedly as a catalyst and its activity remains virtually unchanged. Examples of the conjugated diene in the copolymer of a conjugated diene and a vinyl-substituted aromatic hydrocarbon used in the present invention include butadiene, isoprene, 1.3-
Pentadiene, 2,3-dimethylbutadiene, etc. are included, and vinyl-substituted aromatic hydrocarbons include, for example, styrene, t-butylstyrene, methylstyrene, divinylbenzene, 1,1-diphenylethylene, and the like. Preferred conjugated dienes are butadiene and isoprene, and preferred vinyl-substituted aromatic hydrocarbons are styrene. The vinyl-substituted aromatic hydrocarbon content in the copolymer is preferably from 5% to 95% by weight, and if it is outside this range, sufficient characteristics as a copolymer cannot be obtained. The copolymer of the present invention includes a random copolymer,
Gradually decreasing block copolymers and complete block copolymers are included, and the sum of the vinyl-substituted aromatic hydrocarbon polymer block content (a) and the vinyl bond content of the conjugated diene moiety (b) in the copolymer (a+b) must be at least 30% by weight of the total copolymer. 30% by weight
If it is less than 100%, the reaction solution after hydrogenation becomes extremely viscous, the polymer becomes insoluble, and the entire solution becomes pudding-like, making it extremely difficult to separate it from the catalyst.
Additionally, hydrogenated polymers often undergo crosslinking and gelation. Vinyl-substituted aromatic hydrocarbon polymer block content (a) was determined by LMKolthoff et al, J. Polymer Sci.
1 , 429 (1946), and the content (a) is expressed as the block polymer content in the total polymer. Vinyl bond content of conjugated diene moiety in polymer
(b) uses an infrared absorption spectrum, and the Hampton method [RRHampton Anal.Chem. 29 , 923
(1949)], the proportion of vinyl bonds in the conjugated diene moiety was calculated and converted to the weight proportion in the total polymer. In the case of SBR, the wavenumbers used were cis-1,4 (724 cm ^-1 ) of butadiene, trans-1,4 (967 cm ^-1 ), 1,2-vinyl (911 cm ^-1 ), and styrene (699 cm ^-1 ). From this, the concentration of each component can be determined. The copolymer of the present invention preferably has a vinyl-substituted aromatic hydrocarbon polymer block content of 10% or more and 90% or less. A block copolymer is a copolymer having at least one polymer block A mainly composed of a vinyl-substituted aromatic hydrocarbon and at least one polymer block B mainly composed of a conjugated diene, and has the following general formula: It is indicated by. Block A may contain a small amount of conjugated diene and block B may contain a small amount of vinyl substituted aromatic hydrocarbon. A(-B-A) _n B-A(-B-A) _o {(A-B) _p }- _q X {B(-A-B) _p }- _q X (where m=1 to 5, n=0-5, p=1-5,
q=2 to 10, and X represents carbon, silicon, tin, divinylbenzene, etc. ) Linear polymers represented by the general formulas A(-B-A) _n and B-A(-B-A) _o are produced by carbonization of conjugated diene monomers and vinyl-substituted aromatic compounds using organic alkali metal catalysts. It can be produced by sequentially adding hydrogen monomers and polymerizing them. Also, {(A-B) _p }- _q X and {B(-A-B) _p }
_−q
The branched, radial, or star-shaped block copolymer represented by It can be manufactured by coupling with a coupling agent. More preferably, the microstructure of the conjugated diene portion of the block copolymer used in the present invention is 30 to 70% vinyl bonds and 30 to 70% 1,4-bonds (cis bonds and trans bonds). Block copolymers in this range not only have high industrial value because the olefin portion has rubber elasticity after hydrogenation, but also have extremely low viscosity in the hydrogenated polymer solution, making them particularly advantageous for catalyst separation. It is. The molecular weight of the copolymer used in the present invention is preferably from 20,000 to 1,000,000, and preferably from 20,000 to 1,000,000, and when it is less than 20,000, the mechanical properties of the resulting hydrogenated polymer are poor, and when it is more than 1,000,000, the processability is poor. As the substance supporting rhodium metal used in the present invention, known carbon, alumina, silica/alumina, diatomaceous earth, etc. are used. Preferably, it is supported on carbon and alumina, and in particular, it is preferably supported on carbon because it can be easily separated from the hydrogenated polymer solution. The particle size of the carrier may be any known particle size, for example 0.1
~500μ range. Particularly preferably 10-200μ
is within the range of As the insoluble solvent used in the present invention, aliphatic and alicyclic saturated hydrocarbons such as cyclohexane, hexane, heptane, octane, tetrahydrofuran, chlorinated hydrocarbons or mixtures thereof are used. Since the hydrogenation copolymer used in the present invention is generally produced in an inert hydrocarbon solvent, it is advantageous to use its solution as is for hydrogenation. Since various alcohols and ethers have the function of activating the catalyst, they can be added to the solvent for use as long as they do not particularly reduce the solubility of the polymer. The hydrogenation temperature used in the present invention is below 120°C, preferably below 100°C. At temperatures above 120°C, hydrogenation selectivity between the conjugated diene moiety and the aromatic nucleus moiety cannot be obtained. The lower the hydrogenation temperature, the better the selectivity, but the lower the hydrogenation rate. The pressure of hydrogen used is normal pressure to 200Kg/
^cm2 . The hydrogenation reaction time is 1 minute to 20 hours. The hydrogenation reaction may be carried out by any method such as a fixed bed method or a suspension method. In the suspension method, for example, after adding a polymer solution and a catalyst, hydrogenation is performed at a predetermined temperature and under hydrogen pressure with stirring. The reaction may be carried out either batchwise or continuously. By tracking the progress of the reaction based on the hydrogen absorption amount, the hydrogenated copolymer of the present invention has a hydrogenation conversion rate of 70% or more in the diene portion and a hydrogenation conversion rate of 30% or less in the aromatic nucleus portion. be able to. If the hydrogenation conversion rate of the diene portion is less than 70%, the effect of improving heat resistance, ozone resistance, and weather resistance will not be sufficient. Further, even if the hydrogenation conversion rate of the aromatic nucleus portion is increased to 30% or more, no improvement in physical properties is observed, and rather the excellent moldability of the vinyl-substituted aromatic hydrocarbon polymer block is lost. Furthermore, hydrogenation of aromatic nuclei consumes a large amount of hydrogen and requires hydrogenation for a long time, resulting in increased costs. The above hydrogenation conversion rate was calculated from the ultraviolet absorption spectrum and the infrared absorption spectrum. That is, the hydrogenation conversion rate of the styrene portion was determined from the following equation by measuring the styrene content in the polymer from the absorption of the styrene portion at 250 mμ in the ultraviolet absorption spectrum. Hydrogenation conversion rate (%) of the styrene part = (1 - styrene content of the polymer after hydrogenation / styrene content of the polymer before hydrogenation) × 100 In addition, the hydrogenation conversion rate of the butadiene part is From the infrared absorption spectrum of the polymer, the ratio ν of the concentration of the unsaturated part, that is, the butadiene part (unhydrogenated) and the styrene part (unhydrogenated) in the polymer, and the styrene content before and after hydrogenation determined above. Calculated from. ν = Butadiene content of the polymer after hydrogenation (unhydrogenated diene content) / Styrene content of the polymer after hydrogenation (unhydrogenated styrene content) Hydrogenation rate of butadiene portion (%) = ( 1-Butadiene content of the polymer after hydrogenation/Butadiene content of the polymer before hydrogenation) x 100 = (1-a (Styrene content after hydrogenation)/(1-Styrene content before hydrogenation) Amount))×100 A polymer solution hydrogenated using the method of the present invention using the copolymer specified in the present invention can be subjected to decantation, filtration, pressure filtration, centrifugation, centrifugal sedimentation, etc. It is possible to separate and recover the catalyst using physical methods. Outside the copolymer and hydrogenation conditions specified in the present invention, the hydrogenated polymer solution becomes viscous, pudding-like, or slurry-like, and often gels, making separation of the catalyst extremely difficult. . Generally, the lower the hydrogenation temperature and the shorter the reaction time, the easier the separation and recovery of the catalyst. When the catalyst is separated well, the catalyst naturally settles and the filtrate becomes almost transparent. The recovered catalyst can be reused as it is or after being washed with a solvent. Since rhodium metal is expensive, it is essential to recover and reuse the catalyst, and the fact that this has become possible has great industrial significance. As described above, the present invention makes it possible to selectively reduce the conjugated diene moiety of a copolymer of a conjugated diene and a monovinyl-substituted aromatic hydrocarbon even if a supported catalyst is used, and It has become possible to collect and reuse. The hydrogenated copolymer obtained in the present invention is used as a thermoplastic elastomer or thermoplastic resin, or as a rubber with excellent weather resistance and heat resistance. It is also possible to add stabilizers, ultraviolet absorbers, oils, fillers, etc. to the hydrogenated copolymer. Hereinafter, some examples will be given to show specific embodiments of the present invention, but these are intended to explain the gist of the present invention more specifically, and are not intended to limit the present invention. Reference example 1 400g of cyclohexane, 15g of styrene monomer and 0.11g of n-butyllithium in an autoclave
was added and polymerized at 60°C for 3 hours, then 70g of butadiene monomer was added and polymerized at 60°C for 3 hours. Finally, add 15g of styrene monomer and heat at 60°C.
Styrene-butadiene, which is polymerized for hours and has a weight average molecular weight of approximately 60,000, with a bound styrene content of 30%, a blocked styrene content of 29.5%, and a 1,2-vinyl bond content of the butadiene portion of 13% (9% in terms of total polymer). A styrene type 3 block copolymer was obtained. Reference example 2 30g of styrene monomer in 500g of cyclohexane
and 0.45 g of n-butyllithium were added and polymerized at 60°C for 3 hours, then 70 g of butadiene monomer and tetrahydrofuran (THF) were added at a molar ratio of n-butyllithium/tetrahydrofuran = 20, and the polymerization was conducted at 40°C for 2 hours. After polymerization, a catalytic amount of 1/4 mole of silicon tetrachloride was added to perform coupling. The properties of the obtained polymer are shown in Table 1. Reference example 3 In a Bethel reactor with a volume of 1 and a height/diameter of 4 equipped with a stirrer, 1200 g/hr of cyclohexane, 210 g/hr of butadiene monomer, and 1.35 g/hr of n-butyrium were added.
Kg/hr, tetrahydrofuran (n-BuLi/THF
= 30 molar ratio) is continuously supplied from the bottom of the reactor,
In addition, 90g/hr of styrene monomer is added from the top of the reactor.
The polymer solution was continuously taken out from the reactor. The properties of the obtained polymer are shown in Table 1. Reference example 4 70 g of butadiene monomer in 400 g of cyclohexane
g, styrene monomer 20g, tetrahydrofuran
Add 0.9g and 0.05g of n-butyllithium,
After polymerizing for 2 hours at 40°C, 10% of the styrene monomer
g was added, and polymerization was further carried out at 60°C for 1 hour. The properties of the obtained polymer are shown in Table 1. Reference example 5 cyclohexane 400g, butadiene monomer 70
g, styrene monomer 30g, n-butyllithium
0.05g and 0.9g of THF were simultaneously added to the autoclave and polymerized at 40°C for 2 hours. The properties of the obtained polymer are shown in Table 1. Reference example 6 Add cyclohexane to autoclave (2)
400 g and 0.05 g of n-butyllithium were added, and then a monomer mixture of butadiene/styrene = 70/30 was fed in constant amounts over 3 hours using a metering pump, and the autoclave was kept at 90° C. for polymerization. The total amount of monomer fed is 100 g.
After the monomer supply was completed, the polymer solution was taken out from the autoclave. The properties of the obtained polymer are shown in Table 1. Reference example 7 The amount of styrene monomer was 40g each (total 80
g) A block copolymer with a high styrene content was synthesized in the same manner as in Reference Example 1, except that the amount of butadiene monomer was changed to 20 g. The properties of the obtained polymer are shown in Table 1. Reference Example 8 A styrene-isoprene-styrene type block copolymer was synthesized in the same manner as in Reference Example 1 except that isoprene was used instead of butadiene. The properties of the obtained polymer are shown in Table 1.

【table】

[Table] Examples 1 to 6 Samples of polymer solutions synthesized in Reference Examples 1 to 8
N0.1 to 8 were diluted with the same amount of cyclohexane to give a polymer concentration of 10% by weight and subjected to a hydrogenation reaction (these samples were named 1 to 8, respectively). In addition, liquid polybutadiene NISSO-PB, B-3000 (manufactured by Nippon Soda Co., Ltd.) and diene 35 (manufactured by Asahi Kasei) were dissolved in cyclohexane to 10% by weight and subjected to a hydrogenation reaction (sample names 9 and 10). The catalyst was Rhodium Carbon-Rh/C manufactured by Nippon Engelhard Co., Ltd. (Rhodium loading amount was 5%, and the carbon carrier was activated carbon powder with an average size of 20 to 40 microns.
The specific surface area was approximately 1100 m ² /g). Capacity 2
Add 1000 ml of each polymer solution to an autoclave with a stirrer.
(100 g of polymer) and 20 g of Rh/C catalyst (1 g as rhodium metal) were added, and after replacing the air in the autoclave with hydrogen, the autoclave was heated at a constant temperature (80 g).
After carrying out the hydrogenation reaction for 90 minutes with vigorous stirring at a constant hydrogen pressure (50 Kg/cm ² G), the reaction solution was heated to room temperature.
The pressure was returned to normal, the solution was taken out from the autoclave, the state of the solution was observed, and the catalyst was separated by filtration using a pressure filter. The cloth used in the pressure filter was No. 400 cloth, which had been pretreated with plain carbon. A large amount of methanol was added to the polymer solution from which the catalyst had been separated to precipitate the polymer. The hydrogenation rate of the obtained polymer, the state of the reaction solution, the ease of filtration, and the state of the hydrogenated polymer are summarized in Table 2.

【table】

[Table] As shown in Table 2, in Examples 1 to 6 and Comparative Example 3, the hydrogenation reaction liquid was a uniform low viscosity solution and was separated by pressure filtration. In particular, Examples 2, 3, and 4, which have a large number of 1,2-vinyl bonds, have a high hydrogenation rate and a low viscosity of the hydrogenated polymer solution, making separation easy. On the other hand, in Comparative Examples 1 and 2, the hydrogenated product became pudding-like, and in order to remove the catalyst from it, the solution was diluted until the polymer concentration was 1% by weight or less, and then
It was necessary to filter it while heating it to 70℃. The liquid polybutadiene of Comparative Example 3 can be filtered, but the high molecular weight polybutadiene of Comparative Example 4 becomes a pudding-like or slurry-like product that is insoluble in solvents and is difficult to separate. Furthermore, it can be seen that the hydrogenation conversion rate of the polymer is very high, and most of the hydrogen is consumed for hydrogenation of the diene moiety. Examples 7 to 9 The styrene-butadiene-styrene type 3 block copolymer solution of Sample 2 prepared in Reference Example 2 was diluted with an equal amount of cyclohexane to 10% by weight, and this was hydrogenated under the conditions shown in Table 3. did. The results are shown in Table 3.

[Table] As is clear from Table 3, when Rh/C is used, excellent selectivity is obtained at hydrogenation temperatures of 70°C, 80°C, and 100°C, and the selectivity is particularly good at lower temperatures. be. At 130°C, the hydrogenation conversion rate of the styrene portion is 40%, while the hydrogenation conversion rate of the diene portion is slightly over 70%, which is not preferable. Furthermore, if you try to increase the hydrogenation rate of the diene part to over 90% at 130℃, the hydrogenation rate of the styrene part will decrease.
It exceeds 60%. On the other hand, when using a catalyst in which ruthenium is supported on alumina (Ru/Al ₂ O ₃ ), hydrogenation does not substantially proceed at low temperatures, and although hydrogenation does proceed at high temperatures of 140°C, the rate is extremely slow. , and no selectivity is observed. Furthermore, when a catalyst in which palladium was supported on carbon (Pd/C) was used, the hydrogenation rate was faster than that of ruthenium, but there was still no selectivity at all. Example 10 The catalyst used in Example 2 was separated and recovered, and hydrogenation was carried out using it under the same conditions as in Example 2. As shown below, there was almost no difference in the hydrogenation results. Hydrogenation time: 90 minutes Hydrogenation conversion rate of butadiene portion: 95% Hydrogenation conversion rate of styrene portion: 11% Example 11 Hydrogenation was carried out under the same conditions as in Example 2 except for the catalyst. As the catalyst, alumina supported with rhodium was used. As a result, the hydrogenation results were almost the same. Hydrogenation time: 100 minutes Hydrogenation conversion rate of butadiene portion: 92% Hydrogenation conversion rate of styrene portion: 13% The catalyst was separated using a centrifugal separator, sedimented at 15,000 rpm, and separated by decantation.

Claims (1)

[Scope of Claims] 1. In a method of catalytically hydrogenating a copolymer of a conjugated diene and a vinyl-substituted aromatic hydrocarbon, the block content (a) of the vinyl-substituted aromatic hydrocarbon polymer in the copolymer and the conjugate The copolymer in which the sum (a+b) of the vinyl bond content (b) in the diene portion is 30% by weight or more of the total polymer is heated at 120°C in an inert solvent using rhodium metal supported on a carrier as a catalyst. A method for hydrogenating a polymer, which comprises hydrogenating at the following temperature and selectively hydrogenating a conjugated diene moiety. 2. The method according to claim 1, wherein after the hydrogenation reaction, the catalyst is separated and recovered from the polymer solution by a physical method and is reused in the hydrogenation reaction. 3 The hydrogenation rate of the conjugated diene moiety in the copolymer is 70
% or more, and selectively hydrogenating the aromatic nucleus portion to a hydrogenation rate of 30% or less. 4. The method according to claims 1 to 3, wherein the copolymer has a molecular weight of 20,000 or more and 1,000,000 or less. 5. The method according to any one of claims 1 to 4, wherein the copolymer is a block copolymer having a vinyl-substituted aromatic hydrocarbon polymer block content of 10% by weight or more and 90% by weight or less. 6. The method according to claims 1 to 5, wherein the microstructure of the conjugated diene moiety in the copolymer is 30 to 70% vinyl bonds and 30 to 70% 1,4-bonds.