WO1999052953A1

WO1999052953A1 - Method for hydrogenating aromatic polymers in the presence of branched hydrocarbons

Info

Publication number: WO1999052953A1
Application number: PCT/EP1999/002138
Authority: WO
Inventors: Volker Wege; Johann Rechner
Original assignee: Bayer Aktiengesellschaft; Teijin Ltd.
Priority date: 1998-04-08
Filing date: 1999-03-29
Publication date: 1999-10-21
Also published as: DE19815737A1; AU3332899A; CN1296498A; EP1084157A1; AU747670B2; DE19980629D2; KR20010042533A; TW499452B; CA2327485A1; BR9909491A; ZA200004818B; JP2002511501A

Abstract

The invention relates to a method for hydrogenating polymers, optionally in the presence of catalysts, whereby branched hydrocarbons are used as solvents, possessing no more than one hydrogen atom at the branch point and having a boiling temperature above 45 °C and an ignition temperature (DIN 51794) of above 280 °C, or a mixture of such hydrocarbons with solvents that are suitable for hydrogenating reactions.

Description

Process for the hydrogenation of aromatic polymers in the presence of branched hydrocarbons

The present invention relates to a process for the hydrogenation of aromatic polymers, which is characterized in that branched saturated hydrocarbons are used as solvents which have a maximum of one hydrogen atom at the branching point, a boiling temperature greater than 45 ° C. and an ignition temperature (DIN 51794) have greater than or equal to 280 ° C and the polymers thus produced, or a mixture of solvents containing them

Hydrocarbons and the usual solvents for hydrogenation reactions.

The hydrogenation of aromatic polymers is already known. DE-AS 1 131 885 describes the hydrogenation of polystyrene in the presence of catalysts and solvents. Aliphatic and cycloaliphatic hydrocarbons, ethers, alcohols and aromatic hydrocarbons are generally mentioned as solvents. A mixture of cyclohexane and tetrahydrofuran is mentioned as preferred.

WO 96/34 896 (= US-A-5 612 422) describes, for example, a method for

Hydrogenation of aromatic polymers, in which hydrogenation is carried out in the presence of a metal supported by silicon dioxide as the hydrogenation catalyst with a specific pore size distribution of the silicon dioxide. Aliphatic or cycloaliphatic hydrocarbons are mentioned as solvents, and isopentane (2-methylbutane) is mentioned as branched saturated hydrocarbon. Diethylene glycol dimethyl ether and tetrahydrofuran are mentioned as ethers.

EP-A-322 731 describes the production of predominantly syndiotactic polymers based on vinylcyclohexane, a styrene-based polymer being hydrogenated in the presence of hydrogenation catalysts and solvents. Cycloaliphatic and aromatic hydrocarbons are mentioned as solvents. The specific solvents of the present invention are not mentioned.

The hydrocarbons described in the abovementioned documents, apart from isopentane, have ignition temperatures of less than or equal to 260 ° C. and are solvents which are not easy to handle for an industrial process. The solvents must have sufficiently high ignition temperatures (DIN 51 794) for a technical process, since during polymer processing there is contact with hot metal surfaces in the possible presence of air and the processing temperatures of a polymer solution of e.g. hydrogenated polystyrene in the presence of the solvent can reach or exceed 240 ° C. There is a possibility of ignition and explosion if there is not a sufficient temperature difference between processing temperature and ignition temperature.

Solvent exchange before the processing step for the production of granules is associated with considerable costs and technical effort.

Inerting measures of the entire polymer work-up step, which prevent a solvent / air contact from being made, are expensive and can hardly be implemented in practice for an industrial process, since e.g. the entire apparatus would have to be encapsulated under inert gas.

Without such or other complex and expensive precautions, the solvents known in the cited documents apart from isopentane (WO96 / 34896; US 5 612 422) can ignite and represent a considerable safety risk. However, isopentane is not a solvent for, for example, polystyrene, this solvent is therefore for the hydrogenation of this polymer is unsuitable. Isopentane as a solvent also has the disadvantage of boiling at 28 ° C., which on the one hand complicates the handling of the solutions and on the other hand leads to expensive and complex cooling and condensation apparatuses as a result of the cooling required in the work-up step. It is the task that the solvent used dissolves the starting polymer, the hydrogenation leads to a practically complete hydrogenation of the aromatic units, the reaction product is dissolved and this system is fed directly to the work-up step, a temperature difference of (at least 15% based on Celsius temperature scale) between the processing temperature and the ignition temperature of the solvent.

It has now been found that certain branched hydrocarbons have the required properties, thereby significantly simplifying an industrial process for the hydrogenation of aromatic polymers and their polymer workup. The process is characterized in that the hydrogenated polymer solution can be fed directly to the work-up step and no complex technical measures for excluding a solvent / air contact on a surface greater than or equal to the ignition temperature are necessary. Another advantage of using these special branched hydrocarbons is that the solvent can be separated from the polymer at higher temperatures, resulting in lower solvent residues and higher polymer throughputs.

The invention relates to a process for the hydrogenation of aromatic polymers, optionally in the presence of catalysts, using branched hydrocarbons as solvents which have at most one hydrogen atom at the branching point, a boiling temperature greater than 45 ° C. and an ignition temperature (DIN 51794) above 280 ° C, or a mixture of such hydrocarbons with solvents suitable for hydrogenation reactions.

The reaction is generally carried out at volume concentrations of the branched saturated hydrocarbons to the total solvent of 0.1% to 100%, preferably 1% to 80%, very particularly preferably 5 to 70%. - 4 -

The process according to the invention generally leads to a virtually complete hydrogenation of the aromatic units. As a rule, the degree of hydrogenation is> 80%, preferably> 90%, very particularly preferably> 99%, in particular 99.5 to 100%. The degree of hydrogenation can be determined, for example, by NMR or UV spectroscopy.

Aromatic polymers are used as starting materials, which are selected, for example, from polystyrene optionally substituted in the phenyl ring and / or on the vinyl group, or copolymers thereof with monomers selected from the group of olefins, (meth) acrylates or mixtures thereof. Other suitable polymers are aromatic polyethers, in particular polyphenylene oxide, aromatic polycarbonates, aromatic polyesters, aromatic polyamides, polyphenylenes, polyxylenes, polyphenylene vinylenes, polyphenylene ethylenes, polyphenylene sulfides, polyaryl ether ketones, aromatic polysulfones, aromatic polyether sulfones, aromatic polyimides and mixtures thereof, copolymers, optionally copolymers with aliphatic compounds.

As substituents in the phenyl ring come C 1 -C 4 -alkyl, such as methyl, ethyl, C 1 -C 4 -alkoxy, such as methoxy, ethoxy, fused aromatics which are connected to the phenyl ring via a carbon atom or two carbon atoms with phenyl,

Biphenyl, naphthyl in question.

Possible substituents on the vinyl group are C 1 -C 4 -alkyl, such as methyl, ethyl, n- or iso-propyl, in particular methyl in the α-position.

Suitable olefinic comonomers are ethylene, propylene, isoprene, isobutylene, butadiene, cyclohexadiene, cyclohexene, cyclopentadiene, optionally substituted norbornene, optionally substituted dicyclopentadiene, optionally substituted tetracyclododecenes, optionally substituted dihydrocyclopentadienes, Cl-Cg, preferably Cj-C4 alkyl esters of (meth) acrylic acid, preferably methyl and ethyl esters

Ci-Cg, preferably C 4 -C 4 alkyl ether of vinyl alcohol, preferably methyl and ethyl ether,

C ^ -Cg-, preferably Cι _ι-C4 alkyl esters of vinyl alcohol, vinyl acetate, preferably,

Derivatives of maleic acid, preferably maleic anhydride, derivatives of acrylonitrile, preferably acrylonitrile and methacrylonitrile.

The aromatic polymers generally have molecular weights Mw of 1,000 to 10,000,000, preferably 60,000 to 1,000,000, particularly preferably 70,000 to 600,000, determined by light scattering.

The polymers can have a linear chain structure as well as branching points due to co-units (e.g. graft copolymers). The branch centers include e.g. star-shaped polymers or other geometric shapes of the primary, secondary, tertiary, possibly quaternary polymer structure.

The copolymers can be either random, alternating or block copolymers.

Block copolymers include di-blocks, tri-blocks, multi-blocks and star-shaped

Block copolymers.

The starting polymers are generally known (for example WO 94/21 694). - 6 -

Preferred solvents are branched hydrocarbons of the formula (I) which have boiling temperatures greater than 45 ° C. and ignition temperatures (DIN 51 794) greater than or equal to 280 ° C.

R ¹ R ⁴ -C— R ² (I)

^RR

in which

the radicals R ¹ , R ² , R, ³ and R ^{4 represent} straight-chain or branched Ci-C _j r _j alkyl and at most one of the radicals R ¹ , R ² , R, ³ and R ^{4 can} also represent hydrogen,

The following are particularly preferred:

2,2,3-trimethylbutane; 2,2-dimethylbutane; 2,3-dimethylbutane; Methylcyclopentane; 2-methylpentane; 3-methylpentane; 3,3-diethylpentane; 2,4-dimethylpentane; 2,2-dimethylpentane; 2,3-dimethylpentane; 2,4-dimethyl-3-ethylpentane; 2,2,3-trimethylpentane; 2,3,3-trimethylpentane; 2,2,4-trimethylpentane (isooctane); 2,2,3,3-tetramethylpentane; 2,2,3,4-tetramethylpentane; 2,3,3,4-tetramethylpentane; 2-methylhexane; 3-methylhexane; 2-methyl-4-ethylhexane; tert-butylcyclohexane; 2-methylheptane; 2,5,5-trimethylheptane; 3,3-dimethylheptane; 2,2,5-trimethylheptane.

Very particularly preferred for the hydrogenation of polystyrene and its derivatives is methylcyclopentane, which is a good solvent compared to the hydrocarbons known in the hydrogenation, the publications mentioned above, has a boiling temperature of 72 ° C. and an ignition temperature of 315 ° C.

The amount of catalyst to be used is described, for example, in WO 96/34896. The amount of catalyst used depends on the process carried out, which can be carried out continuously, semi-continuously or batchwise.

In the continuous system, the response time is much shorter; it is from the

Dimensions of the reaction vessel affected. In the continuous mode of operation, the trickle system and the sump system, both with fixed catalysts, are possible, as is a system with a suspended and e.g. circulated catalyst. The fixed catalysts can be in tablet form or as extrudates.

The polymer concentrations, based on the total weight of solvent and polymer, are generally 80 to 1, preferably 50 to 10, in particular 40 to 15% by weight.

The hydrogenation of the starting polymers is carried out according to generally known methods (for example WO 94/21 694, WO 96/34 895, EP-A-322 731). A large number of known hydrogenation catalysts can be used as catalysts. Preferred metal catalysts are mentioned, for example, in WO 94/21 694 or WO 96/34 896. Any catalyst known for the hydrogenation reaction can be used as the catalyst. Catalysts with a large surface area (for example 100-600 m ² / g) and a small average pore diameter (for example 20-500 Å) are suitable. Furthermore, catalysts with a small surface area (for example> 10 m ² / g) and large average pore diameters are also suitable, which are characterized in that 98% of the pore volume has pores with pore diameters greater than 600 Å (for example approx.

1,000-4,000 Å) (see, for example, US-A 5,654,253, US-A 5,612,422, JP-A 03076706). In particular, Raney nickel, nickel on silicon dioxide or silicon dioxide / aluminum oxide, nickel on carbon as a support and / or noble metal catalysts, for example Pt, Ru, Rh, Pd, are used. The reaction is generally carried out at temperatures between 0 and 500 ° C, preferably between 20 and 250 ° C, in particular between 60 and 200 ° C.

The solvents which are customary for hydrogenation reactions are described, for example, in DE-AS 1 131 885 (see above).

The reaction is generally carried out at pressures from 1 bar to 1000 bar, preferably 20 to 300 bar, in particular 40 to 200 bar.

- 9 -

Examples:

Examples 1-2

A 1 liter autoclave is flushed with inert gas. The polymer solution and the catalyst are added (table). After sealing, the protective gas is then exposed to hydrogen several times. After depressurization, the respective hydrogen pressure is set and the batch is heated to the appropriate reaction temperature with stirring. The reaction pressure is kept constant after the onset of hydrogen absorption.

The reaction time is the time from heating the batch to complete hydrogenation of the polystyrene or, if the hydrogenation is incomplete, the time until the hydrogen uptake approaches its saturation value.

When the reaction has ended, the polymer solution is filtered. The product is precipitated in methanol and dried. The isolated product shows the physical properties listed in the table.

table

Hydrogenation of polystyrene depending on the solvent system

Example- polystyrene solution catalyst reaction- H2 pressure reaction hydrogenation solvent

No. Mass medium Mass Temperature time degree 1) Ignition temperature (DIN51794) g ml g ° C bar min% ° C

1 200 2300 13.5 ⁴ 150 875 (psig) 110 98.4 260

Comparison CYH

US-A-5 612 422

2 100.2 ^> 200 12.53 160 100 360 100 315 Invention MCP + 460 according to 100 MTBE

!) Determined by ^ H-NMR spectroscopy) Polystyrene type 158 k, Mw = 280,000 g / mol, BASF AG, Ludwigshafen, Germany o • v

3) Engelhard, De Meern, The Netherlands, Ni-5136 P, nickel on silicon dioxide / aluminum oxide H

Wo

⁴ ) US-A-5 612 422, 5% platinum / silica or the like

S '—O o

CYH = cyclohexane, MCP = methylcyclopentane, MTBE = methyl tert-butyl ether

00

- 11 -

The platinum catalyst (table) hydrogenates polystyrene in cyclohexane at 140 ° C (comparative example 1). Cyclohexane has an ignition temperature of 260 ° C and leads to problems when processing the product on an industrial scale because solvent / air contact on hot metal surfaces near the ignition temperature must be ruled out. The process according to the invention (Example 2) shows complete hydrogenation compared to Comparative Example 1, but all the solvents involved have ignition temperatures greater than 310 ° C.

Claims

- 12 patent claims

1. Process for the hydrogenation of aromatic polymers, optionally in the presence of catalysts, branched hydrocarbons being used as the solvent, at most one at the branching point

Have a hydrogen atom, a boiling temperature greater than 45 ° C and an ignition temperature (DIN 51794) above 280 ° C, or a mixture of such hydrocarbons with solvents suitable for hydrogenation reactions.

2. The method according to claim 1, wherein branched hydrocarbons of the formula (I)

R '

R ⁴ -C— R ² (I)

R °

in which

the radicals R ¹ , R ² , R, ³ and R ^{4 represent} straight-chain or branched Ci-C _j o-alkyl and at most one of the radicals R ¹ , R ² , R, ³ and R ^{4 can} also represent hydrogen,

be used.

J. The method of claims 1 and 2, wherein the solvent is selected from at least one of the following solvents: 2,2,3-trimethylbutane; 2,2-dimethylbutane; 2,3-dimethylbutane; Methylcyclopentane; 2-methylpentane; 3-methylpentane; 3,3-diethylpentane; 2,4-dimethylpentane; 2,2-dimethylpentane; 2,3-dimethylpentane; 2,4-dimethyl-3-ethylpentane; 2,2,3-trimethylpentane; 2,3,3-trimethylpentane; 2,2,4-trimethylpentane - 13 -

(Isooctane); 2,2,3,3-tetramethylpentane; 2,2,3,4-tetramethylpentane; 2,3,3,4-tetramethylpentane; 2-methylhexane; 3-methylhexane; 2-methyl-4-ethylhexane; tert-butylcyclohexane; 2-methylheptane; 2,5,5-trimethylheptane; 3,

3-dimethylheptane; 2,2,5-trimethylheptane.

4. The method according to one or more of the preceding claims, wherein a mixture of solvents containing at least one branched saturated hydrocarbon and at least one solvent which can be used for hydrogenation reactions is used.

5. The method according to one or more of the preceding claims, wherein the volume concentration of the saturated branched hydrocarbons to the total solvent is 0.1 to 100%.

6. The method according to one or more of the preceding claims, wherein the volume concentration of the saturated branched hydrocarbons is 1 to 80%.

7. The method according to one or more of the preceding claims, wherein the volume concentration of the saturated branched hydrocarbons is 5 to 70%.

8. The method according to one or more of the preceding claims, wherein the polymer concentration, based on the total weight of solvent and polymer, is 80 to 1% by weight.

9. The method according to one or more of the preceding claims, wherein the polymer concentration, based on the total weight of solvent and polymer is 50 to 10 wt .-%. - 14 -

10. The method according to one or more of the preceding claims, wherein the polymer concentration, based on the total weight of solvent and polymer is 40 to 15 wt .-%.

1 1. The method according to one or more of the preceding claims, wherein the aromatic polymers are selected from the group of the following polymers: in each case optionally substituted in the phenyl ring and / or polystyrene or copolymers thereof on the vinyl group, aromatic polyethers, aromatic polyesters, aromatic polyamides, Polyphenylenes, polyxylylene,

Polyphenylene vinylenes, polyphenylene ethylenes, polyphenylene sulfides, polyaryl ether ketones, aromatic polysulfones, aromatic polyether sulfones, aromatic polyimides and mixtures thereof, copolymers, optionally copolymers with aliphatic compounds.

12. The method according to claim 11, wherein the aromatic polymers are selected from the group of the following polymers: each optionally in the phenyl ring and / or on the vinyl group substituted polystyrene or copolymers thereof, with monomers selected from the group of olefins, (meth) acrylates or mixtures thereof.

13. The method according to claim 12, wherein the comonomers are selected from ethylene, propylene, isoprene, isobutylene, butadiene, cyclohexadiene, cyclohexene, cyclopentadiene, optionally substituted norbornene, optionally substituted dicyclopentadiene, optionally substituted tetracyclododecenes, optionally substituted dihydrocyclopentadienes,

Ci-Cg-alkyl esters of (meth) acrylic acid,

C _j -Cg alkyl ethers of vinyl alcohol, - 15 -

Ci-Cg-alkyl esters of vinyl alcohol,

Derivatives of maleic acid; Derivatives of acrylonitrile.

14. The method according to one or more of the preceding claims, wherein the aromatic polymers have molecular weights (weight average) from 1000 to 10,000,000.

15. The method according to one or more of the preceding claims, wherein the aromatic polymers have molecular weights (weight average) from 60,000 to 1,000,000.

16. Hydrogenated polymers obtainable by a process according to one or more of the preceding claims.