JPH0579084B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for hydrogenating carbon-carbon double bonds in conjugated diene polymers, and more specifically, the present invention relates to a method for hydrogenating carbon-carbon double bonds in conjugated diene polymers. This invention relates to a method for hydrogenating a conjugated diene polymer used as a conjugated diene polymer. (Prior art) Conventionally, when unsaturated polymers are hydrogenated in solution, reduction metal catalysts in which metals from group 8 of the periodic table are supported on carriers such as activated carbon, alumina, and silica have been used. Due to the high viscosity of polymer solutions, obtaining sufficient hydrogenation efficiency using such heterogeneous catalysts requires a relatively large amount of catalyst, high reaction temperature of 150 °C or more, and high pressure of hydrogen. However, at such high temperatures, the main chain of the polymer is likely to be cleaved, side reactions occur, and selectivity is impaired. It was also extremely difficult to remove the catalyst from the obtained hydrogenated polymer. Various homogeneous catalysts have been proposed in an attempt to solve these drawbacks. For example, a diene-based polymer is produced using lithium hydrocarbyl as a polymerization catalyst, and then hydrogen is blown into the polymer solution.
An attempt was made to hydrogenate the compound using a hydrogenation catalyst (Japanese Patent Publication No. 45-39274), an attempt was made to use a reaction product of a hydrocarbyl metal compound with iron, cobalt, or nickel as a catalyst (Japanese Patent Publication No. 42-25304), Li,
Attempt to hydrogenate a solution of a diene polymer polymerized using an organometallic compound such as Al as a polymerization catalyst by adding an organic complex compound of nickel to the solution (Japanese Patent Publication No. 49-5756
), a proposal to use a nickel π-complex as a catalyst (Japanese Patent Publication No. 46-17130), a proposal to use a Wilkinson-type complex as a catalyst (US Patent No. 3700637, JP-A-52-1999)
No. 32095, JP-A-59-115303, JP-A-60-60106
No.) etc. These catalyst materials are unstable to air, water, and impurities in the polymer, and are not only difficult to handle, but also difficult to handle before hydrogenation, such as purification of the polymer to be hydrogenated and removal of water from the polymer solution. The treatment must be carried out thoroughly, and there is an advantage in sequentially carrying out solution polymerization and hydrogenation, but when hydrogenating a rubber obtained by emulsion polymerization in which various polymerization auxiliary materials remain is made into a solution. It cannot be said that it is necessarily suitable for (Problems to be Solved by the Invention) The present inventors have already discovered that a stable and easily handled palladium salt of carboxylic acid reduced with molecular hydrogen can be used as a homogeneous catalyst (particularly 117501). However, since this catalyst uses palladium, which is an expensive noble metal, it is necessary to achieve high hydrogenation with as little amount as possible from an economic point of view. An object of the present invention is to provide a method for hydrogenating a conjugated diene polymer in which high hydrogenation is achieved using a palladium salt of carboxylic acid as a hydrogenation catalyst. (Means for Solving the Problems) An object of the present invention is to catalytically hydrogenate carbon-carbon double bonds of a conjugated diene polymer in a solution.
This is achieved by using a hydrogenation process characterized in that a palladium salt of a carboxylic acid reduced with hydrazine is used as a catalyst. A feature of the present invention is that the palladium salt of a carboxylic acid is reduced with hydrazine, thereby obtaining a catalytic activity greater than that obtained by reduction with molecular hydrogen. In the present invention, a hydrate of hydrazine can also be used, and the amount of hydrazine is 1 mole of palladium in the palladium salt of the carboxylic acid used.
The range is ~5000 times, and if it is less than 1 times, only the same activity as in the case of reduction with molecular hydrogen is obtained, and
If the increase exceeds 5000 times, reduction of the palladium salt occurs, but surprisingly, hydrogenation activity is completely lost. Preferably 4 to 2000 times more preferably 5 to 2000 times
500 times the range. The palladium salts of carboxylic acids used in the present invention are soluble or partially soluble in solvents, such as formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, lauric acid, palmitic acid, stearic acid, oxalic acid, and malonic acid. Palladium salts of saturated aliphatic carboxylic acids such as , succinic acid, adipic acid, pimelic acid, sebacic acid, glycolic acid, lactic acid, methoxyacetic acid, glyoxylic acid, citric acid; acrylic acid, vinylacetic acid, putenoic acid, crotonic acid, methacrylic acid acids, palladium salts of unsaturated aliphatic carboxylic acids such as pentenoic acid, octenoic acid, oleic acid, octadecenoic acid, linoleic acid, linoleic acid, propiolic acid;
Examples include, but are not limited to, palladium salts of aromatic carboxylic acids such as benzoic acid, toluic acid, ethylbenzoic acid, trimethylbenzoic acid, phenyl acid, phthalic acid, isophthalic acid, terephthalic acid, and naphthoic acid. isn't it. All of these carboxylic acid salts are stable and easy to handle.
The amount of the above palladium salt of carboxylic acid used as a catalyst can be determined as appropriate based on the type of polymer to be hydrogenated and the target hydrogenation rate, but it may affect the various properties of the polymer after the reaction is completed. , 1500ppm or less of palladium per polymer due to economic efficiency, etc.
Preferably it is 1000 ppm or less. The conjugated diene polymer used in the present invention has conjugated diene monomers such as 1,3-butadiene, 2,3-
One or more monomers selected from dimethylbutadiene, isobrene, 1,3-pentadiene, etc., 10 to 100% by weight of the total monomers, and the ethylenically unsaturated monomer is an unsaturated nitrile such as acrylonitrile, methacrylonitrile, etc. monovinylidene aromatic hydrocarbons, such as styrene, alkylstyrenes (o-, m- and p-methylstyrene, ethylstyrene, etc.), unsaturated carboxylic acids or their esters, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid ,
maleic acid or one or more monomers selected from vinylpyridine and vinyl esters such as vinyl acetate, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, etc. It is a conjugated diene polymer composed of 0 to 90% by weight of monomers, and is produced by solution polymerization, emulsion polymerization, etc. Typical conjugated diene polymers include polybutadiene, polyisoprene, and butadiene.
Styrene (random and block) copolymers,
Examples include acrylonitrile-butadiene (random and alternating) copolymers, and the use of the catalyst of the present invention is particularly suitable for the hydrogenation of acrylonitrile-butadiene copolymers, without reducing the nitrile group. Hydrogenation is possible. The hydrogenation reaction is carried out in the form of a solution when using a polymer polymerized by solution polymerization, or in the form of a solution when a solid polymer is used. The concentration of the polymer solution is 1~
70% by weight, preferably 1-40% by weight. The solvent is preferably one that dissolves the catalyst and polymer, but it is acceptable even if the catalyst has some undissolved portion. The solvent is selected depending on the type of carboxylic acid palladium salt used and the type of polymer, but solvents include benzene, toluene, xylene, hexane,
Cyclohexane, cyclohexanone, acetone,
Examples include methyl ethyl ketone, diethyl ketone, tetrahydrofuran, and ethyl acetate. During the hydrogenation reaction, the palladium salt of the carboxylic acid is added to an inert solvent in advance, and after being reduced with hydrazine or its hydrate, a predetermined amount of the solution is introduced into the polymer solution and brought into contact with molecular hydrogen. Although the hydrogenation reaction can also be carried out by adding the palladium salt of the carboxylic acid directly to the polymer solution, adding hydrazine or its hydrate and reducing it in the presence of the polymer, followed by It is desirable to carry out a hydrogenation reaction using molecular hydrogen. The latter method has higher reaction activity and is easier to operate than the former. The reduction temperature of the catalyst is 5°C to 100°C, preferably 10°C to 90°C. The reduction time is less than 1 hour. The hydrogenation reaction temperature is 0 to 300°C, preferably 20 to 150°C. Temperatures above 150°C are acceptable, but side reactions occur, which is undesirable in terms of selective hydrogenation. For example, hydrogenation of the solvent or hydrogenation of ethylenically unsaturated monomer units in the polymer, such as the nitrile group of acrylonitrile or the benzene nucleus of styrene, occurs. The hydrogen pressure ranges from atmospheric pressure to 300 Kg/cm ² , preferably from 5 to 200 Kg/cm ² . Although high pressures of 300 kg/cm ² or higher are acceptable, there are major factors that hinder practical application, such as increased equipment costs and cumbersome handling. After the completion of the hydrogenation reaction, an ion exchange resin or the like may be added to the reaction solution to adsorb the catalyst, or the catalyst may be left as it is in the hydrogenated polymer without being removed. The method for separating the hydrogenated polymer from the reaction solution is
The method normally used to recover the polymer from a polymer solution can be used as is, such as the steam coagulation method in which the polymer solution is brought into direct contact with water vapor, or the polymer solution is dropped onto a heated rotating drum to evaporate the solvent. Examples include a drum drying method in which the polymer is dried, a method in which a poor solvent is added to the polymer solution to precipitate the polymer, and the like. By using such a polymer separation method, the hydrogenated polymer can be separated from the solution, drained,
It is recovered as a solid hydrogenated polymer through a drying process such as hot air drying, vacuum drying, or extrusion drying. The obtained hydrogenated conjugated diene polymer has excellent weather resistance, ozone resistance, heat resistance, cold resistance, etc., and can therefore be used in a wide range of fields. The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. The hydrogenation rate of carbon-carbon double bonds was measured by the iodine value method. Example 1 Palladium acetate as a catalyst was prepared as a 0.5% by weight acetone solution. Acrylonitrile-butadiene copolymer (hereinafter referred to as
Abbreviated as NBR; amount of bound acrylonitrile 39.4
Weight%, ML _{1+4 100} ℃=50), volume 100ml
A solution prepared by dissolving 7.5 g of NBR in 42.5 g of acetone was charged into an autoclave, and 0.4 ml of the above catalyst solution (PD was 1 x 10 ^-4 parts by weight per 1 part by weight of polymer) was charged. After replacing the inside of the system with nitrogen, the autoclave was heated at room temperature. Hydrazine (10% aqueous solution) was added and the temperature of the autoclave was raised to 50°C. Subsequently, hydrogenation was carried out for 5 hours at a hydrogen pressure of 50 kg/cm ² . The amount of hydrazine used for reduction was varied in molar ratio to PD: 5, 10, 100, 1000. For comparison, hydrogenation reactions were carried out without the addition of hydrazine and with 10,000 times more hydrazine. The results are shown in Table 1.

[Table] Example 2 The amount of hydrazine used was set to 100 in molar ratio with PD,
Example 1 was repeated under the same conditions but using the carboxylic acids listed in Table 2. The results are shown in Table 2.

[Table] Example 3 Polybutadiene (hereinafter abbreviated as BR; cis 1,4 content 98%,
ML _1+4,100 ℃=40), polyisoprene (hereinafter abbreviated as IR; ML _1+4,100 ℃=80), and styrene-butadiene copolymer (hereinafter abbreviated as SBR; styrene content 23.5% by weight, ML _{1+ 4,100} ℃=50),
A hydrogenation reaction was carried out under the same conditions as in Example 1, except that benzene was used as a solvent and the catalyst listed in Table 3 was used. The results are also listed in Table 3.

[Table] As shown in the three examples above, when using a palladium salt of carboxylic acid as a hydrogenation catalyst, by using a specific amount of hydrazine as a reducing agent,
It can be seen that the catalytic activity is significantly improved.

Claims (1)

[Claims] 1. Hydrogen of a conjugated diene polymer characterized in that a palladium salt of a carboxylic acid reduced with hydrazine is used as a catalyst in catalytically hydrogenating the carbon-carbon double bond of the conjugated diene polymer in a solution. method.