EP3004228A1

EP3004228A1 - Process to hydrogenate unsaturated bonds of a (co)polymer substrate using a titanium compound, composition of a titanium compound in a (co)polymer matrix and preparation thereof

Info

Publication number: EP3004228A1
Application number: EP14725458.5A
Authority: EP
Inventors: Richard Herman Woudenberg
Original assignee: Akzo Nobel Chemicals International BV
Current assignee: Nouryon Chemicals International BV
Priority date: 2013-05-24
Filing date: 2014-05-21
Publication date: 2016-04-13
Also published as: WO2014187861A1

Abstract

The present invention relates to a process to (partially) hydrogenate unsaturated bonds of a (co)polymer substrate comprising adding a titanium compound to the (co)polymer substrate, activating the titanium compound by adding an organometallic compound, and reacting said substrate with hydrogen in the presence of the activated titanium compound, wherein the titanium compound is added to the reaction mixture as a titanium compound-containing composition containing between 5 and 95 wt% on the total weight of the composition of the titanium compound and between 5 and 95 wt% on the total weight of the composition of at least one (co)polymer, wherein the titanium compound is distributed in the at least one (co)polymer,and relates to titanium compound-containing compositions that can be suitably used in the above process and their preparation.

Description

Process to hydrogenate unsaturated bonds of a (co)polymer substrate using a titanium compound, composition of a titanium compound in a (co)polymer matrix and preparation thereof The present invention relates to a process to hydrogenate unsaturated bonds of a (co)polymer substrate in which compositions of a titanium compound in a (co)polymer matrix are added, to compositions of a titanium compound in a (co)polymer matrix suitable for use in such a process, and to their preparation. Polymers of conjugated dienes such as 1 ,3-butadiene and isoprene and the copolymers of these dienes with vinylaromatic monomers, e.g. with styrene, are widely used in industry as elastomers. These (co)polymers contain double bonds in their chains, which permit their vulcanization. Some block copolymers of conjugated dienes and vinylaromatic hydrocarbons are used without vulcanization as thermoplastic elastomers, as transparent impact-resistant resins, or as modifiers or compatibilizers of polystyrene and polyolefin resins. However, these (co)polymers have a low resistance to ageing and oxidation by atmospheric oxygen and by ozone, due to the presence of double bonds in their chains. Hence, the use of these (co)polymers in applications requiring exposure to the external environment is limited. The resistance to oxidation by oxygen and ozone and, in general, the resistance to ageing may be considerably improved by (partially) hydrogenating these (co)polymers to obtain total or partial saturation of the double bonds. Numerous processes have been proposed for the (partial) hydrogenation of (co)polymers which contain olefinic double bonds. One process to (partially) hydrogenate the double bonds is using homogeneous catalysts of the organometallic titanium type. Because of the high activity of these catalysts the consumption of catalyst per unit weight of hydrogenated (co)polymer will be very low, which is reflected in a reduced cost of catalyst. On the other hand, at the low catalyst concentrations that are usually required in a process as that in accordance with the invention, it is not necessary to eliminate the catalyst residues from the (partially) hydrogenated (co)polymer, since they do not have an unfavourable influence on the properties of said (co)polymers. As indicated above, this fact is advantageous from the industrial point of view, particularly in the (partial) hydrogenation of polymers and copolymers of conjugated dienes, since it permits a substantial simplification of the process.

US 5,583,185 discloses a process of hydrogenation in solution of polymers of conjugated dienes in the presence of homogeneous catalysts that contain a titanium compound of the type Cp₂TiR₂. Titanium compounds are available as solid materials, but then they have the disadvantage that they give a significant dust formation and/or clump formation during handling. Because of the low solubility of a number of titanium compounds, in many applications the titanium compounds are converted to suspensions in a liquid medium, which suspensions can be dosed in the process in which the titanium compounds are used, such as a hydrogenation process. These suspensions suffer from several disadvantages. The most important disadvantage is that the solid titanium compound does not remain nicely distributed in the liquid medium but rapidly sinks to the bottom, which makes for a varied concentration of titanium compound over the suspension. Therefore, it is not possible to dose the titanium compound properly in the intended use, which often leads to overdosing. In addition, it is difficult to empty the containers holding the suspension, i.e. solid material may remain on the bottom of the containers. These phenomena lead to the use of higher amounts of titanium compounds than strictly necessary and so to higher costs. Moreover, incorrect dosing of titanium compounds when used as catalysts in polymer production leads understandably to poorer polymer quality. In addition, it leads to lower yields per unit catalyst in polymer production. For example, incorrect dosing of the titanium compound can give rise to polymers that have an undesirable colour. In addition, the uneven distribution of the titanium compound in a suspension with a high amount of solids in the bottom part or the dosing of solid titanium compounds that have a tendency to clump in some instances leads to plugging in reaction systems when used in the final application. To prevent the above disadvantages in the field sometimes the titanium compounds are chemically modified so that they become soluble in a liquid medium. However, these chemical modifications increase the price of the titanium compounds considerably. The present invention now provides a new process to (partially) hydrogenate unsaturated bonds of a (co)polymer substrate comprising the use of compositions containing a titanium compound in a (co)polymer matrix not having the above drawbacks. The process of the invention is a process to (partially) hydrogenate unsaturated bonds of a (co)polymer substrate comprising adding a titanium compound to the (co)polymer substrate, activating the titanium compound by adding an organometallic compound, and reacting said substrate with hydrogen in the presence of the activated titanium compound, wherein the titanium compound is added to the reaction mixture as a titanium compound-containing composition containing between 5 and 95 wt% on the total weight of the composition of the titanium compound and between 5 and 95 wt% on the total weight of the composition of at least one (co)polymer, and wherein the titanium compound is distributed in the at least one (co)polymer.

Though in the above it is said that the titanium compound is added to the (co)polymer substrate or the reaction mixture, it can also pre-dosed (i.e. inherently meaning that the copolymer substrate is added to the titanium compound). The addition can moreover be done in several ways, such as addition in one step, dosing in multiple steps over a period of time, or by continuous dosing. The process involves using compositions preferably containing between 10 and 70 wt%, more preferably between 20 and 60 wt%, most preferably between 30 and 50 wt%, on the total weight of the composition of a titanium compound and preferably between 30 and 90 wt%, more preferably between 40 and 80 wt%, most preferably between 50 and 70 wt%, on the total weight of the composition of at least one (co)polymer, wherein the titanium compound is distributed in the at least one (co)polymer.

The invention also provides some of the above titanium compound-containing compositions that can be suitably used in the process of the invention; namely compositions wherein the titanium compound is present in a quantity between 20 and 60 wt% on total composition and compositions wherein the titanium compound is a complex of the formula TiR1 R2R3R4 wherein at least one of the groups R1 to R4 is an anionic aromatic group that is directly linked to the titanium atom.

The invention in addition provides a process to make the titanium compound- containing compositions as suitably used in the process of the invention, wherein in a first step the titanium compound is mixed with the (co)polymer, preferably at a temperature higher than the Tg of the (co)polymer, and in a subsequent step the mixture of the titanium compound and the (co)polymer is particulated.

Tg is the glass transition temperature as measured by DSC (differential scanning calorimetry) wherein, typically, the sample is first cooled by 10°C/min and then heated with that same speed.

It should be noted that US 6,417,286 discloses a sulfur rubber containing a titanium compound with organic alkoxylate groups. The titanium compound is said to be present in an amount of up to 10%. It is said that the titanium compound and the rubber can be mixed in an extruder. However, this document describes a vulcanization process and not a hydrogenation process.

US 4,216,107 discloses the addition of an organic titanate to polyol compounds to reduce the viscosity of such polyol. Titanate means a titanium compound of the formula TiR1 R2R3R4 wherein each R group is linked to the titanium atom via an oxygen atom. The amount of titanate is 0.01 up to 20 wt% on polyol. US 6,376,603 discloses the addition of a titanium oxide in a high amount to a silicone rubber composition. In the Example the components are kneaded at elevated temperature but not particulated. The titanium oxide compound is used as a colorant of the silicone rubber and the document does not relate to a process of hydrogenating a (co)polymer composition. The titanium compound-containing compositions as used in the process of the invention were found to be less susceptible to dusting or clumping, which was found to be a huge benefit when they are applied in a process to (partially) hydrogenate a (co)polymer substrate. In this document (partially) hydrogenating in one embodiment means (partially) hydrogenating unsaturated (double) bonds, preferably unsaturated carbon-carbon bonds, to convert them to saturated bonds. In some documents such a process is also referred to as a selective hydrogenation process.

As indicated, the process to (partially) hydrogenate substrates involves activating the titanium compound in the composition of the invention by adding an organometallic compound, and reacting said substrate with hydrogen in the presence of the activated composition. The step wherein the titanium compound in the composition in the process of the present invention is activated, can take place before, during or after the composition of the invention is contacted with the substrate and before, during or after the addition of hydrogen.

In some embodiments the titanium compound-containing composition is (first) added to a liquid medium to give a suspension of the composition of the invention in the same liquid medium.

Another advantage of the present invention is that the particles containing the composition of the invention can be nicely and homogeneously suspended in (the above) inert solvents. Also the particles of the composition of the invention have no tendency to dust or clump when added to a liquid medium or to the reaction mixture. Because of the presence of the (co)polymer they have a higher viscosity than plain titanium compounds in a liquid and therefore do not sink so easily to the bottom of the suspension. It was established that the so-formed suspensions could be dosed to the hydrogenation process covered by the present invention without the drawbacks of the state of the art. In a more preferred embodiment, the amount of titanium compound in the compositions of the invention is between 20 and 60 wt%, even more preferably between 30 and 50 wt%, on total composition weight. The titanium compounds in the composition of the present invention in some embodiments are in the form of precursors for catalytically more active counterparts and in the process of the invention are activated by being reacted with organometallic compounds. Examples of organometallic compounds that can be used for increasing the activity and/or selectivity of the titanium compounds in the composition of the present invention - before or during the course of the reaction with a (co)polymer containing unsaturated groups - are organometallic compounds such as organolithium, organomagnesium or organoaluminium compounds. Examples of the aforementioned organolithium compounds are alkyl lithium compounds such as n-butyllithium, sec.-butyllithium, etc.; examples of the organomagnesium compounds are alkyl magnesium compounds such as dibutyl magnesium, butyloctyl magnesium, butylethyl magnesium, etc.; and examples of the organoaluminium compounds are alkyl aluminium compounds such as tri- isobutyl aluminium, triethyl aluminium, etc. The titanium compounds of the present invention are organometallic complexes of titanium of the formula Ti-R1 R2R3R4, wherein at least one, preferably two, of R1 to R4 is/are organic groups. The at least one or two organic groups can be alkoxylate, carboxylate, aliphatic or aromatic groups. Preferably, the titanium copounds are not titanates, i.e. not all R groups R1 to R4; more preferably, none of these R groups contain oxygen atoms that links them to the titanium atom. In further preferred embodiments at least one of R1 to R4 is an anionic aromatic group wherein the aromatic ring is directly linked to the titanium atom, such as a cyclopentadienyl, fluorenyl, indenyl group, and substituted derivatives thereof. Preferably, two of the ligands R1 to R4 are cyclopentadienyl groups. Examples of such titanium compounds useful within the invention include bis-(4- methoxyphenyl)-bis-(r|5-cyclopentadienyl) titanium, bis-(3-methoxyphenyl)-bis-(n5- cyclopentadienyl)titanium, bis-(4-ethoxyphenyl)-bis-(q5-cyclopentadienyl)titanium, bis-(3-ethoxyphenyl)-bis-(q5-cyclopentadienyl)titanium, and bis-

(diphenylphosphinomethylene)-bis-(q5-cyclopentadienyl)titanium.

Most preferably, the titanium compound in the composition of the present invention is a compound wherein one or two groups R1 to R4 are cyclopentadienyl groups and two or three groups are a halogenide, like fluoride, bromide, or chloride, preferably chloride (such compounds with two cyclopentadienyl groups are called titanocenes). The most preferred compound is titanocene dichloride (TDC):

The (co)polymer in which the titanium compound is distributed in the composition of the present invention, also referred to as the (co)polymer matrix, preferably is compatible with the (co)polymer (rubber) to be hydrogenated when the titanium compound-containing composition of the invention is applied in the production (hydrogenation) of a (co)polymer. In one much preferred embodiment, the (co)polymer matrix is the same as the (co)polymer to be (partially) hydrogenated or is the polymer after being (partially) hydrogenated. The (co)polymer can be a (non- hydrogenated, partially or fully hydrogenated) polymer of several dienes, possibly containing one or more (co)monomers. Suitable dienes are butadiene, pentadiene, and isoprene. Suitable (co)monomers are olefins like ethylene, propylene, butene, acrylonitrile, and styrene. One suitable example of the (co)polymer is a block polymer of 1 ,3-butadiene and styrene. In other embodiments the (co)polymer may be chosen from the group of aliphatic and aromatic olefins, esters of unsaturated carboxylic acids with an aliphatic or aromatic alkyl alcohol or a phenol, vinyl esters of aliphatic or aromatic acids, organic imines.

The (co)polymer in the matrix preferably has an average molecular weight of between approximately 500 and 1 ,000,000, and particularly is a copolymer of a conjugated diene such as 1 ,3-butadiene or isoprene with vinylaromatic compounds such as styrene or a-methylstyrene. These copolymers include the statistical copolymers, in which the comonomers are distributed at random along the polymer chain, the insertion copolymers, and the pure or gradual block copolymers. The block copolymers are especially interesting, since some of them are thermoplastic elastomers useful from the industrial point of view. Such block copolymers consist of a) at least one polymer block A formed by polymerization of an aromatic hydrocarbon with a vinylic substituent, such as styrene or a- methylstyrene, and b) at least one polymer block B formed by polymerization of conjugated dienes, such as 1 ,3-butadiene or isoprene.

In the process to (partially) hydrogenate, the polydiene blocks are converted into polyolefinic blocks in such a way that the copolymers behave like thermoplastic elastomers of great industrial value.

Preferred block copolymers are styrene-ethylene/butene-styrene block copolymers, or styrene-ethylene/butadiene-styrene block copolymers. As acknowledged by the skilled person, the compositions of the present invention can be made by any suitable method. In an embodiment, first, the titanium compound and the (co)polymer for the matrix are mixed, preferably at a temperature higher than the Tg (glass transition temperature) of the ( copolymer to make the mixture homogeneous. Next, the mixture is particulated, wherein particulating means any method to get particles, i.e. includes any method whereby the size of the material is decreased and is intended to include methods like breaking, crushing, pelletizing, or milling. A suitable method is extruding the (co)polymer containing the titanium compound in a kneader/mixer, operating above the Tg of the (co)polymer matrix, followed by a shaping operation. Most preferably, an extruder is used, followed by a chopper to make the extrudates.

In accordance with a preferred method within the framework of the present invention, the (partial) hydrogenation reaction of the unsaturated (co)polymer in the presence of the titanium compound-containing composition may be carried out in solution in an inert solvent. The term "inert solvent" signifies an organic solvent that does not react with any of the reactants participating in the reaction. Examples of inert solvents whose use is recommended within the framework of the invention are aliphatic and cycloaliphatic hydrocarbons such as n-hexane, n-octane, isooctane, cyclohexane, methylcyclopentane, methylcyclohexane, ethers such as tetrahydrofuran, aromatic hydrocarbons such as toluene, xylenes, etc., which are not hydrogenated under the reaction conditions selected, and mixtures of these compounds. The amount of activated titanium compound-containing composition to be used in the hydrogenation is not critical and may vary within broad limits; it can be comprised between 0.001 and 10 millimoles of titanium compound per 100 g of substance to be (partially) hydrogenated, and preferably between 0.01 and 5 mmoles of titanium compound per 100 g of substance to be (partially) hydrogenated.

To achieve the (partial) hydrogenation of the double bonds of the unsaturated (co)polymers, reaction temperatures of between approximately 20 and 150°C, preferably between 50 and 100°C, and hydrogen pressures of between approximately 1 and 70 kg/cm², preferably between 4 and 12 kg/cm², can be used.

The products of the (partial) hydrogenation may be readily separated from the solvent used by means of known processes such as distillation, precipitation, etc. In particular, the partially or completely hydrogenated polymers and copolymers may be separated from the solvent by various methods:

(1 ) By contacting the (partially) hydrogenated product/solution with a polar solvent such as acetone, methanol, and the like which, by being a poor solvent of the (co)polymer, causes the latter's precipitation and permits its physical separation.

(2) By contacting the (partially) hydrogenated product/solution with water and steam and eliminating the solvent by evaporation, separating the water, and drying the (co)polymer.

(3) By direct evaporation of the solvent.

EXAMPLE

400 grams of TDC (titanocene dichloride) were conveyed onto 600 grams of the desired polymer/rubber and shaken by hand. The premix was dosed to a Haake TW100 twin screw extruder fitted with intensive mixing screws. The extruder settings are temperature 160 (throat) - 175°C, 75 rpm. The extruded strand was fed through a water bath for cooling and cut by a granulator into pellets of 2 mm diameter and 2-3 mm length. 0.625 gram of the above titanocene dichloride extrudate (active material: 0.25 g, 0.001 mol) was added to 750 ml of an anhydrous solution of 100 grams (non- hydrogenated) butadiene polymer in heptane solvent under an argon atmosphere in an autoclave.

To this solution were added 1 .5 grams of butylethyl magnesium solution in heptane (0.003 mol) and the reaction mixture was stirred for 2 hours, to activate the titanium compound.

Then the autoclave is pressurized with 50 atm of hydrogen and brought to a temperature of 60°C by heating with a bath. The hydrogenation is carried out under these conditions for a duration of 120 minutes, with continuous feeding of hydrogen to keep the pressure value constant, which continuous feeding suggests the consumption of hydrogen gas and, hence, hydrogenation of the butadiene polymer. After the reaction, the pressure is released and the polymer isolated by precipitation in methanol.

Claims

Process to (partially) hydrogenate unsaturated bonds of a (co)polymer substrate comprising adding a titanium compound to the (co)polymer substrate, activating the titanium compound by adding an organometallic compound, and reacting said substrate with hydrogen in the presence of the activated titanium compound, wherein the titanium compound is added as a titanium compound-containing composition containing between 5 and 95 wt% on the total weight of the composition of the titanium compound and between 5 and 95 wt% on the total weight of the composition of at least one (co)polymer, and the titanium compound is distributed in the at least one (co)polymer.

Process of claim 1 , wherein the organometallic compound is selected from the group of organolithium, organomagnesium, and organoaluminium compounds.

Process of claim 2, wherein the organolithium, organomagnesium or organoaluminium compounds are selected from the group of n-butyllithium, sec.-butyllithium, dibutylmagnesium, butyloctyl magnesium, butylethyl magnesium, tri-isobutyl aluminium, and triethyl aluminium.

4. Process of any one of claims 1 to 3, wherein the amount of titanium compound is between 30 and 50 wt% on the total titanium compound- containing composition.

Process of any one of claims 1 to 4, wherein the titanium compound is a complex of the formula TiR1 R2R3R4 wherein at least one of the groups R1 to R4 is an organic group.

Process of any one of claims 1 to 5, wherein the titanium compound is titanocene dichloride.

Process of any one of claims 1 to 6, wherein the (co)polymer in the titanium compound-containing composition is the (co)polymer to be hydrogenated in the process or is such (co)polymer partially or completely hydrogenated.

Process of any one of claims 1 to 7, wherein the (co)polymer is a non- hydrogenated, partially or fully hydrogenated (co)polymer of a diene monomer.

Titanium compound-containing composition suitable for use in the process of any one of claims 1 to 8 wherein the composition contains between 5 and 95 wt% on the total weight of the composition of a titanium compound of the formula TiR1 R2R3R4 wherein at least one of the groups R1 to R4 is an anionic aromatic group directly linked to the titanium atom, and between 5 and 95 wt% on the total weight of the composition of at least one (co)polymer, and the titanium compound is distributed in the at least one (co)polymer

Titanium compound-containing composition suitable for use in the process of any one of claims 1 to 8 wherein the composition contains between 20 and 60 wt% on the total weight of the composition of a titanium compound of the formula TiR1 R2R3R4, and between 40 and 80 wt% on the total weight of the composition of at least one (co)polymer, and the titanium compound is distributed in the at least one (co)polymer.

1 1. Composition of claim 9 or 10, wherein the titanium compound is titanocene dichloride.

12. Composition of any one of claims 9 to 1 1 , wherein the (co)polymer is a non- hydrogenated, partially or fully hydrogenated (co)polymer of a diene monomer.

13. Process to prepare the composition of any one of claims 9 to 12, wherein in a first step the titanium compound is mixed with the (co)polymer and in a subsequent step the mixture of the titanium compound and the (co)polymer is particulated.

14. Process of claim 13, wherein the titanium compound is mixed with the (co)polymer at a temperature higher than the Tg of the (co)polymer.