JPH0376706A - Production of hydrogenated styrenic resin - Google Patents

Abstract

PURPOSE:To carry out the hydrogenation of a styrenic resin mild conditions to thereby avoid the significant mol.wt. degradation by hydrogenating arom. rings of the styrenic resin in the presence of a palladium catalyst catalyst carried by a specific carrier. CONSTITUTION:A silica carrier having a specific surface area of 100-500m<2>/g and a mean pore diameter of 200-500Angstrom is impregnated with an aq. soln. of palladium salts, and then reduced to give a palladium catalyst carrying 0.001-30wt.% palladium. The resulting catalyst is added to a 5-50wt.% solvent soln. (e.g. a cycloheptane soln.) of a styrenic resin contg. at least 50wt.% styrene in an amt. of the catalyst of 1-100wt.% based on the styrenic resin. Then the soln. is reacted in hydrogen under an atmospheric pressure to 300kg/cm<2> at 0-300 deg.C to hydrogenate atom. rings of the styrenic resin, thus producing a hydrogenated styrenic resin wherein 70% or higher of the arom. rings are hydrogenated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a high molecular weight hydrogenated styrene resin. suitable.

[Prior Art] It is already known that styrenic resins are subjected to nuclear hydrogenation using a solvent in the presence of a hydrogenation catalyst.

Typical examples of catalysts used in hydrogenation reactions include metals from Group I of the periodic table, including nickel,
Examples include ruthenium, rhodium, palladium, platinum, and the like. In many cases, these metals are carbon, alumina,
It is used by being supported on a porous carrier such as silica, silica-aluminum, diatomaceous earth, etc.

For example, activated carbon-supported ruthenium catalyst (Japanese Patent Application Laid-Open No. 63-439
A method using a nickel catalyst supported on diatomaceous earth (Japanese Patent Application Laid-open No. 64-62307) is known.

However, although the hydrogenation reaction of styrenic resins using a ruthenium catalyst has the advantage of being able to use relatively mild reaction conditions, decomposition and hydrogenolysis of the resin occur during the hydrogenation reaction, resulting in the production of low molecular weight hydrogen. In addition to the problem that only styrene-based resins can be obtained, there is a problem that it is difficult to separate the catalyst from the highly viscous solution containing the polymer after the hydrogenation reaction is completed.

On the other hand, in the hydrogenation reaction using a nickel catalyst, there is relatively little resin decomposition and hydrogenolysis, but there is a problem in that harsh reaction conditions must be adopted in order to achieve the desired hydrogenation rate. .

[Problems to be Solved by the Invention] The present inventors have conducted extensive studies as a hydrogenation catalyst for the hydrogenation reaction of high-molecular-weight styrene-based resins, and found that using a palladium catalyst supported on a specific silica carrier reduces the hydrogenation of the polymer. We have discovered that this is a catalyst that causes less chemical decomposition, is easy to separate from a polymer-containing highly viscous solution after the hydrogenation reaction is completed, and exhibits high activity under mild conditions, leading to the present invention. Means for producing hydrogenated styrene resin according to the present invention has a specific surface area of 100 to 500 m'/g and an average pore diameter of 200 to 5.0 m'/g.
It is characterized by nuclear hydrogenation of styrenic resin using a palladium catalyst supported on a silica carrier having 00A.

In the present invention, the styrenic resin refers to a styrene homopolymer or one or more copolymers containing styrene in an amount of 50% by weight or more and an unsaturated monomer.

Examples of such unsaturated monomers include styrenes such as bromustyrene, chlorostyrene, paramethylstyrene, and α-methylstyrene, esters such as acrylic esters and methacrylic esters, acrylonitriles, and butadines. Ru.

The polymerization mode is not particularly limited, and examples thereof include random copolymers, block copolymers, graft copolymers, etc., and friend forms of these styrene resins including styrene homopolymers may also be used.

The nuclear hydrogenation rate of styrene resin is over 70%, especially 80%.
It is preferable that it is above. If it is less than 70%, the resin has a large birefringence and needs to be improved as an optical material, which is not preferable.

Any reaction solvent may be used as long as it dissolves the above styrene resin, specifically cycloheptane, cyclohexane, cyclooctane, methylcyclohexane,
Examples include hydrocarbons such as decalin and tetralin, ethers such as tetrahydrofuran, dioxane, and diethylene glycol dimethyl ether, esters such as methyl acetate and butyl acetate, lactones such as γ-butyrolactone, and amides such as dimethylformamide and dimethylacetamide. be done. Two or more of these solvents may be used as a mixed solvent.

The hydrogenation catalyst used in the present invention as a carrier has a specific surface area of 100 to 500 m2/g and an average pore diameter of 200 to 500 m2/g.
A palladium-supported silica catalyst with 500A is used. The physical properties of silica are preferably a specific surface area of 100 to 250 m2/g and an average pore diameter of 250 to 400.
People's stuff is better.

The value of specific surface area mentioned here is determined by measuring the amount of nitrogen adsorption, and
This is a value calculated using the formula, and the value of the average pore diameter is a value measured by mercury intrusion method.

If silica that does not meet the above conditions is used, the hydrogenation activity per catalyst will be greatly reduced or separation of the catalyst after the hydrogenation reaction will become difficult.

When carrying out hydrogenation using a supported catalyst, diatomaceous earth, silica-alumina, alumina, activated carbon, etc. have been used conventionally, but when diatomaceous earth, silica-alumina, alumina, etc. are used as a carrier, the hydrogenation activity is low. Although hydrogenation activity can be obtained with activated carbon, it is difficult to separate the catalyst by filtration after the reaction is completed. However, when the specific silica of the present invention is used, the above problems are solved, and it becomes possible to prepare a supported catalyst having high hydrogenation activity, low hydrogenolysis, and extremely good separability.

Palladium metal may be supported on a silica carrier by a conventional carrier-supporting method. For example, a silica-supported catalyst can be obtained by impregnating the silica carrier with an aqueous solution of various palladium salts, followed by reduction.

The amount of palladium metal supported on the silica carrier is usually 0.001 to 30% by weight per carrier, preferably 0.01% by weight.
~10% by weight.

The reaction may be carried out in a batch autoclave using a powdered catalyst or in a continuous fixed bed using a shaped catalyst.

A styrene resin is dissolved in the solvent at a concentration of 5 to 50% by weight, a catalyst is added to the resin at a concentration of 1 to 100%, and the reaction temperature is 0 to 300'C, preferably 20 to 200'C.
It is °C. The hydrogen pressure ranges from atmospheric pressure to 300 kg/cm2, preferably from 5 to 150 kg/cm''.

After the hydrogenation reaction is completed, the carrier-supported catalyst is separated from the hydrogenated styrene resin-containing solution by filtration or the like, and then the hydrogenated styrene resin is separated.

[Examples] The present invention will be explained in more detail by Examples below, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

In addition, calculation of the nuclear hydrogenation rate in Examples was performed by ultraviolet absorption spectrum analysis.

Example 1 Specific surface area as a carrier: 181 m2/g, pore volume: 1.35
A catalyst on which Pd was supported was prepared using silica (D-150-300A, manufactured by Dokai Kagaku Co., Ltd.) with me/g and average pore diameter of 320A so that the amount supported was 2% by weight.

After impregnating the carrier with an aqueous solution of PdCl2, it was calcined at 150°C for 2 hours under a nitrogen atmosphere, and then heated at 150°C under an atmosphere of water and Shiun.
The mixture was reduced at °C for 2 hours to obtain a 2% Pd/5iOJ medium.

Styrene resin (manufactured by Mitsubishi Monsanto Kakai Co., Ltd., trade name Dialex@HF-55; weight average molecular weight 260,000) 2
g was dissolved in 15 g of tetrahydrofuran, and 0.4 g of the catalyst prepared in the above method was charged into a 70 me spinner stirring autoclave, and a hydrogen pressure of 130 KG was applied at room temperature, and the reaction was carried out at 170 °C for 2.5 hours. Ta.

The hydrogenated polystyrene after reaction was taken out and the nuclear hydrogenation rate was measured and found to be 79%. The number average molecular weight after the hydrogenation reaction was 190,000.

Comparative Example 1 Specific surface area 420m27g, pore volume 1.25 as carrier
2% Pd/SiO2 was prepared in the same manner as in Example 1 using silica (D-150-120A manufactured by Dokai Kagaku Co., Ltd.) having an average pore diameter of 120A.

The reaction was carried out under the same conditions as in Example 1, and the hydrogenation rate was 30%, and the weight average molecular weight was 240,000.

Comparative Example 2 Silica with a specific surface area of 78 m2/g, average pore diameter of 615 A, and HJ pore capacity of 1.2 me/g (MV- manufactured by Fuji Davison)
A catalyst was prepared in the same manner as in Example 1 using 500).

When the catalyst activity test was conducted under the same reaction conditions as in Example 1,
The hydrogenation rate is 36%, and the weight average molecular weight after reaction is 18.
It was 10,000.

Example 2 Using the carrier used in Example 1, a catalyst was prepared in which Pd was supported so that the supported amount was 5% by weight.

After the carrier was impregnated with an aqueous solution of PdCl2, it was calcined at 150'C for 2 hours in an N2 atmosphere, and then reduced with N2 at 300'C for 12 hours to prepare 5% Pd/5i02.

30g of the same polystyrene as in Example 1 was dissolved in 75g of tetrahydrofuran and charged into a 200me induction stirring autoclave, 3g of the catalyst prepared in the above method was charged, and a constant pressure reaction was carried out at a stirring speed of 11,000 rpm, a hydrogen pressure of 100 KG, and a temperature of 170°C. for 6 hours. The reaction mixture containing hydrogenated polystyrene was diluted with 200% tetrahydrofuran.
The catalyst was removed by dilution with mff and filtration.

The reaction solution was poured into a large amount of methanol to recover hydrogenated polystyrene.

The hydrogenation rate of this product was 100%, and the weight average molecular weight was 180,000.

Example 3 Silica with a specific surface area of 110 m21 g, a pore volume of 1.05 me, and an average pore diameter of aooA (CARiA manufactured by Fuji Davison)
CT-30) in the same manner as in Example 2 to obtain 5% Pd.
/SiO2 catalyst was prepared.

The hydrogenation rate was 94 when the reaction was carried out under the same conditions as in Example 2.
% and the weight average molecular weight was 200,000.

Comparative Example 3 5% Pd/SiO2 activated carbon (manufactured by Tamoto Engelhard) 2 g
A hydrogenation reaction was carried out under the same reaction conditions as in Example 2 using as a catalyst.

The hydrogenation rate of the obtained polystyrene was 100%, and the weight average molecular weight was 190,000.

However, although attempts were made to recover the catalyst by separate furnaces after the reaction,
This was difficult and required filter aids to be added and the catalyst to be filtered out.

[Effects of the Invention] When the specific silica-supported palladium catalyst according to the present invention is used, a hydrogenated polystyrene resin with little decrease in molecular weight can be produced under relatively mild conditions.

Claims (1)

[Claims] (1) When hydrogenating using a palladium catalyst in which the aromatic ring of a styrene resin is supported on a carrier, the carrier has a specific surface area of 100 to 500 m^2/g and an average pore diameter of 20 m^2/g.
A method for producing a hydrogenated styrenic resin by nuclear hydrogenation of a styrenic resin, characterized by using silica having a thickness of 0 to 500 Å.