GB2125419A - Reactive oligomers from vinyl aromatic hydrocarbons - Google Patents

Abstract

A reactive oligomer is produced by oligomerising a vinyl aromatic hydrocarbon, e.g. alpha methyl styrene, in a polar solvent using an alkali metal amalgam initiator. The reactive oligomer may then be reacted with a functional reagent, i.e. carbon dioxide to introduce carboxy groups, with alkylene oxide to introduce hydroxy groups or with carbon disulphide to introduce carbodithio groups into the oligomer, either by reacting a solution of the oligomer in an atomized state with the functional reagent in gaseous form or by reacting a solution of the oligomer with the functional reagent in liquid or liquefied form on a rotating disc.

Description

SPECIFICATION Process for production of reactive oligomers from vinyl aromatic hydrocarbons and for production of derivatives of the reactive oligomers The invention relates to a process for the production of reactive oligomers from vinyl aromatic hydrocarbons by oligomerization of the vinyl aromatic hydrocarbons with alkali metal initiators or mixed alkali metal initiators. The reactive oligomers may be reacted with a suitable functional reagent to form oligomer derivatives.

It is known that alpha methyl styrene and its nuclearly substituted derivatives can be caused to react with alkali metals or alkali metal mixtures in polar solvents to form oligomeric or polymeric substances.

The main alkali metals used for this purpose are lithium, sodium, potassium mixtures of two or more of the said metals. The alkali metals may be used in suspension, in the form of chips, wire or shreds. The polymeric or oligomeric vinyl aromatic hydrocarbons obtained with these initiators have reactive chain ends.

U.S. Patent Specifications 2 985 594 and 3 346 666 describe inter alia sodium dispersions for the production of tetrameric alpha methyl styrene oIigomers, paraffin oil and decalin being used as dispersion agents. Dispersion agents have a deleterious effect on the quality of functionalized alpha methyl styrene oligomers because when processed they remain in the oligomers and in addition to acting as softening agents reduce their functionality. Subsequent separation is a laborious and economically untenable process.

Alkali metal organic compounds, if use is made of butyl lithium (U.S. Specification 3 862 098) or sodium naphthalin (U.S. Specification 3 458 491), lead to non-functional or monofunctional alpha methyl styrene oligomers which have a limited sphere of use and are considerably more expensive than oligomers produced with alkali metal. The use of alkali metals in the form of powder, shreds or chips has hitherto only proved of use on a laboratory scale, because in the reaction to tetrameric alpha methyl styrene lumps are formed restricting the scope for the use of this method on an industrial scale.

The introduction of functional groups by means of suitable gaseous and liquid reagents into reactive oligomers and polymers is known, a variety of methods having so far been employed.

In Japanese Unexamined Specification 70 111 53, for instance, carboxylation is effected by introducing carbon dioxide as a suitable gaseous reagent and a reactive oligomer solution with a concentration of up to 16% solids into a rotating drum, on the inner wall of which a film of a thickness of up to 5 mm is formed.

The time taken by the carboxylation reaction in this process is over 0.5 second and usually 1 to 30 seconds before the reactive oligomer solution has undergone the required reaction with the carbon dioxide.

In German Specification 1 520 468 (Auslegeschrift) reactive oligomer solution and carbon dioxide are caused to react in a part of a Tshaped mixing battery where the two limbs of the latter lead in, and with the preferred reaction temperature of 273or the reaction time may amount to up to 5 seconds. The concentration of the reactive polymer solution is below 20% by weight, preferably amounting to 8 to 12% by weight. In this method carboxyl groups amounting to 1.1 to 1.57% by weight are incorporated into the polymers.

In a further process, described in U.S. Patent Specification 3 227 701, the carboxyl groups are introduced into reactive polymers by separating the polymer solution, by the aid of a rotating disc, and at about 277.50K into a vessel filled with carbon dioxide gas, while tetrahydrofuran and diethyl ether are used as solvents.

In a number of patent specifications (U.S.

Specifications 3 070 579 and 3 134 745), a description is given of the introduction of carboxyl, hydroxyl and carbodithio groups, the gaseous reagent being introduced into the reactive polymer solutions until the latter undergo discolouration, or a surplus being added all at once, while stirring vigorousiy in the case of liquid reagents.

The introduction of functional groups into reactive polymers with suitable reagents, particularly carbon cioxide, ethylene oxide, propylene oxide and carbon disulphide, has a number of typical characteristics and involves certain disadvantageous repercussions. Any reaction of reactive polymers leads to a certain increase in the viscosity of the reactant, as a result of the intensive interacting forces which act between the terminal functional groups of the polymer molecules of the reaction product and which are due to the saline nature of the said groups. The greater the content in saline functional groups, the greater the increase in viscosity. It is thus primarily the alkali metal salts of carboxylic acids that are formed by reaction with carbon dioxide. It may be very desirable to obtain these intermediate products.The incomplete reaction of the reactive polymers with carbon dioxide, ethylene dioxide, propylene oxide or carbon disulphide leads to subsidiary reactions which reduce the proportion of functional groups contained in the polymer and lead to an undesirable increase in the average molecular weight.

From J. Polym. Sci. Part A-Z (1964) 10, pp.

4545-4550, for example, it is known that in addition to the carboxylation reaction between reactive polymer molecules on the one hand and polymer molecules with terminal carboxyl groups on the other hand a coupling reaction takes place, accompanied by the formation of compounds of higher molecular weight (e.g. ketones, carbinols etc.). The effects of these coupling reactions manifest themselves in the reaction product by an increase in the molecular weight and a reduction of the carboxyl group content. On the same principie subsidiary reactions occur if the functional reagent used consists of carbon disulphide in place of carbon dioxide.

The use of ethylene oxide and propylene oxide as a functional reagent for reactive polymer solutions results in the formation of very solid gels. Reactive polymer solution is thus liable to be enclosed in the gel and thus no longer accessible for reaction with the alkylene oxide. This had the drawback of causing a lower degree of functionality. Owing to the typical characteristics explained at the beginning and the disadvantageous effects on the functionalization the latter cannot be ensured in all reactive chain ends by means of known processes. The complete suppression of undesirable subsidiary reactions, for instance, presupposes the intensive mixing of both reactants concerned in the reaction, this being essential in order to ensure that the functionalization reaction proceeds uniformly.

This intensive mixing, however, which is the equivalent of a continuous convective renewal of the reaction surfaces between the said two reagents, is opposed by the sudden increase in viscosity, leading to the formation of a gel.

Within the framework of the known processes attempts are made to combat the foregoing by limiting the proportion of reactive polymers in the solution to 8 to 12% and also diluting the reactive polymer solution down to a content of about 15% by weight with a polar solvent.

The purpose of the invention is to surmount the technological problems of the oligomerization of substituted and unsubstituted aromatic hydrocarbons, e.g. alpha methyl styrene and substituted alpha methyl styrene derivatives and to ensure as and when required high degrees of functionality in the oligomers in their reaction with substances forming terminal groups. The functionalization is to prove more economical than in the prior art inasmuch as products with higher functional properties are obtained with a reduced overall consumption of solvent.

According to this invention there is provided a process for the production of a reactive oligomer from a substituted or unsubstituted vinyl aromatic hydrocarbon by oligomerising the said hydrocarbon in a polar solvent using an alkali metal amalgam initiator. Preferably the initiator is obtained by treating an alkali metal or mixture of alkali metals with mercury in a polar solvent or mixture of polar solvents, the alkali metal(s) preferably being chosen from sodium, potassium and lithium.

The amalgamation of alkaline metal or mixed alkaline metal particles preferably measuring on an average 0.01 to 10 mm and preferably on an average 0.1 to 5 mm is preferably effected with 0.5 to 20 parts by weight of mercury, especially 2 to 5 parts by weight, based on 100 parts by weight of alkali metal or alkali metal mixture preferably in polar solvents at 2830 to 333"K, especially at 2930 to 3030K, usually with stirring and in the presence of an inert atmosphere. The oligomerization of alpha methyl styrene with a degree of polymerization of 2 to 8, preferably 4 to 5, may be carried out by the addition of alpha methyl styrene at 2630 to 3330K, preferably at 293" to 3030K, under anaerobic conditions.

In the invention the mercury used for amalgamation apparently plays no part in the oligomerization reaction and remains with surplus alkali metal in the reaction vessel, where it once again forms, with the added alkaline metal, a protective layer which prevents the formation of lumps at the time of initiation. Without the presence of the amalgam layer an alkali metal lump has a disadvantageous effect on the stirring process and reduces the reaction speed.

The preferred alkali metals are lithium, sodium and potassium or mixtures of two or more of the said alkali metals.

The derivatives of the alpha alkyl styrene which are substituted in the nucleus, such as o, p or malkyl alpha methyl styrene, may be oligomerized, alkyl preferably being methyl. The advantage of the process according to the invention for the production of oligomers of for instance alpha methyl styrene and its derivatives substituted in the nucleus are due to the fact that the oligomerization is carried out with the use of an alkali metal initiator which is amalgamated on the surface and which even with high concentrations of alkali metal does not form lumps in the oligomer formation phase, the mercury apparently not participating in the reaction. It is left as an amalgam in the surplus alkali metal used and can be combined with a further addition of alkali metal in the aforementioned concentration ranges, once again forminy the amalgam protective layer described.

The introduction of the functional terminal groups may be effected by reacting the reactive oligomer produced by the process with a functional reagent chosen from carbon dioxide to introduce carboxy groups into theoligomer, alkylene oxide, e.g. ethylene oxide or propylene oxide, to introduce hydroxy groups into the oligomer and carbon disulphide to introduce carbodithio groups into the oligomer.

Where the functional reagent is in gaseous form, e.g. gaseous carbon dioxide, this may be caused to flow at a rate of 0.5 to 20 m/sec., preferably 1 to 4 m/sec., around a central flow of an atomized solution of oligomer, e.g. a reactive methyl styrene oligomer solution, in a polar solvent containing 10 to 50% by weight of oligomer, e.g. 20 to 40% by weight of oligomer, in which the atomized particles have an average diameter of 1 to 100 ym, the preliminary pressure preferably being approximately 0.6 MPa for the oligomer solution and preferably being approximately 0.8 MPa for the gaseous reagent, and the ratio of the flow rate of the liquid to that of the gaseous constituent being within a ratio range of 1:20 to 1:600, preferably 1:50 to 1:300.

Where the functional reagent is in a liquid or liquefied form, e.g. alkylene oxides such as ethylene oxide or propylene oxide, or carbon disulphide, this may be caused to react with a solution of the reactive oligomer on a rotating disc, usually a horizontal disc rotating at high speed, whereby a thin film forms leading in a preferred form of the invention to the immediate formation of particles of gel or solid particles which as a result of centrifugal force occurring are flung against the wall of the reaction vessel as a colourless mass and then removed therefrom. The ratio of the flow rate of the oligomer solution to that of the functional reagent is usually within a ratio range of 1:0.01 to 1:10, preferably 1:0.1 to 1 :0.3, the preliminary pressures of the oligomer solution and the functional reagent preferably being approximately 0.6 MPa and approximately 0.8 MPa respectively.

With respect to the processes described in the previous two paragraphs the preferred temperature for the reaction is within a temperature range of 2930 to 2530K, e.g. 2730K, a temperature maintained preferably by the cooling of interacting currents.

As polar solvent there may be used appropriate cyclic ethers such as tetrahydrofuran or other ethers of hydrocarbons or suitable mixtures thereof.

Preferred forms of the invention will be explained below in greater detail with reference to the following examples.

Examples Production of initiator 4.5 litres of tetrahydrofuran, 146 g of sodium in pieces measuring about 5 mm and 2.2 g of mercury are introduced into a 6 litre 4-necked flask in an atmosphere of argon and equipped with a stirrer, internal thermometer and dropping funnel. Upon stirring mixture at 2980K the sodium particles acquire a silvery amalgam coating.

Example 1 1200 g of alpha methyl styrene is added in drops within one hour and at room temperature (2980K) to the initiator prepared above and in tetrahydrofuran as solvent. After 4 minutes the formation of reactive oligomer commences, accompanied by a dark red colouration.

After a reaction time of 4 hours reactive oligomer solution is drawn off under anaerobic conditions via a riser pipe with a filter from the surplus amalgamated sodium particles still present in the flask and reacted with ethylene oxide on a rotating disc by pressing alpha methyl styrene oligomer solution and liquefied ethylene oxide onto the disc via capillary tubes separate from each other, in the immediate vicinity of the rotating shaft, at pressures of 0.6 and 0.8 MPa respectively and flow rates of 10 and 2.5 litres per hour respectively, the reaction taking place on the disc at 2730K. The reaction temperature in the reaction zone is determined by suitably cooling the two currents of liquid.

The oligomeric alpha methyl styrene hydroxylated in accordance with the process occurs in the form of a firm gel. The alkaline metal compound is then converted, by the addition of water in a molar ratio of 3:1 based on the sodium, into the dihydroxy compound. This leads to the formation of 2 layers. The lower aqueous layer with caustic soda produced by the hydrolysis is separated from the oligomer solution. This latter is washed until almost neutral. The organic phase thus obtained is released from any sodium ions still present, except for a few ppm, by means of cation exchangers. The resulting solution is concentrated in a rotary evaporator, the diol then being dried in a vacuum at 3530K.

This produces 1280 g of a diol with the following characteristics: My: 680.

KOH number: 160.

Mercury content: 5 ppm.

Functionality: 1.94.

The sodium particles formed no lumps in the course of the oligomerization.

In an experiment performed on analogous lines without the addition of mercury sodium lumps formed in as early a phase as the initiation.

Example 2 20 tests were performed with the same formulation as in Example 1 and in one and the same reaction vessel without any further addition of mercury. The sodium consumed in the preceding test was simply replaced. The oligomerization was not accompanied by any formation of sodium lumps. The oligomer of the 20th test was processed as in Example 1 and analysed.

Quantity of oligomer diol: 1290 g.

My: 680.

KOH number: 164.

Mercury content: 3 ppm.

Functionality: 1.95.

Example 3 The same procedure was again adopted as in Example 1 except that a mixture of 50 parts each of tetrahydrofuran and methyl tert.butyl ether was used. No lumps were formed by the sodium particles. The oligomer was processed as described in Example 1 but with the difference that the reactive oligomer was reacted with carbon dioxide and the hydrolysis carried out with hydrochloric acid of 15% strength.

1210 g of oligomeric dicarboxylic acid with the following characteristics was obtained from the mixture: My: 620.

Acid number: 1 75 mg KOH/g.

Mercury content: 10 ppm.

Example 4 The procedure described in Example 1 was again adopted, except that in place of sodium a mixture of sodium and potassium was used in a ratio of 90/10 parts by weight. It was processed on similar lines to Example 1.

1320 g of a diol with the following characteristics was produced: My: 680.

KOH number: 161.

Mercury content: 5 ppm.

Functionality: 1.95.

Example 5 The procedure described in Example 1 was followed, with the difference that in place of alpha methyl styrene the derivative p-methyl alpha methyl styrene was employed. The reactive oligomer was separated from the surplus amalgamated sodium particles as in Example 1 and converted with 485 ml of isopropanol into a non-functional oligomer. After the addition of 200 ml of water, while gently stirring, with subsequent separation of the aqueous phase, the oligomer was isolated from the solution by means of a rotary evaporator. This produced 1150 g of oligomer with a molecular weight of 620.

Example 6 A reactive alpha methyl styrene oligomer solution was produced from the following: Alpha methyl styrene: 945 pts.

by weight.

Initiator described above: 88 pts.

by weight.

Tetrahydrofuran: 3100 pts.

by weight.

Temperature: 2980 K.

Time: 5 hours.

The tetrahydrofuran solvent which was cetyl purified was introduced into a sulphonation flask in an atmosphere of argon, after which the total quantity of initiator was added and the purified alpha methyl styrene uniformly added in drops over a period of 2 hours while stirring. After 5 hours the reactive oligomer, i.e. 25% strength alpha methyl styrene oligomer solution, was separated from the non-converted initiator in the presence or argon. The reactive oligomer was carboxylated by pressing the oligomer solution cooled in advance to 2630K through a vertically positioned circular aperture into a reaction vessel at a pressure of 0.6 MPa and at a flow rate of 10 litres/hour and at the same time adding the carbon dioxide at a pressure of 0.8 MPa and at a rate of 2500 litres/hour.The reactive oligomer of the alpha methyl styrene was present in the form of a viscous solution and was converted with an hydros hydrochloric acid, in a stoichiometric ratio to the sodium, into the dicarboxylic acid, sodium chloride being precipitated in the process.

By the addition of solid soda the solution was neutralized, after which the sodium chloride and the soda were separated by filtration. The carboxylated oligomer showed a molecular weight of 670 as determined by vapour pressure osmosis, with a carboxyl content of 13.19/0, this corresponding to a functionality of 1.95. An almost bifunctional oligomeric alpha methyl styrene was obtained. As shown by the molecular weight, no coupling reactions occurred in the course of the reaction with carbon dioxide.

Example 7 A 30%-strength tetrahydrofuran solution of a reactive alpha methyl styrene oligomer, produced in accordance with Example 6 (prior to reaction with carbon dioxide) and having a molecular weight of 600, was reacted as described in Example 1, not with ethylene oxide but with carbon disulphide as the reagent, at 2730K in the reaction zone.

The reactive oligomer solution was supplied to the rotating disc at a rate of 20 litres/hour, the carbon disulphide being supplied to it at 3 litres/hour. This produced a reddish and slightly viscous solution. By feeding it through a nozzle into five times the quantity of methanol, which had been acidified with aqueous hydrochloric acid, the alkaline salt was converted into the carbodithio acid. The alpha methyl styrene oligomer with carbodithio groups was present in the form of a light orange deposit. It was separated from the precipitating agent, washed and dried in a vacuum at 3050 K. The resulting alpha methyl styrene oligomer had the following properties: My: 760.

Carbodithio group content: 18.6% by weight.

Sulphur content: 16% by weight.

Functionality: 1.84.

Claims (23)

Claims

1. A process for the production of a reactive oligomer from a substituted or unsubstituted vinyl aromatic hydrocarbon by oligomerising the said hydrocarbon in a polar solvent using an alkali metal amalgam initiator.

2. A process according to Claim 1, wherein the initiator is obtained by treating an alkali metal or mixture of alkali metals with mercury in a polar solvent or mixture of polar solvents.

3. A process according to Claim 1 or Claim 2, wherein the alkali metal(s) is/are chosen from sodium, potassium and lithium.

4. A process according to any preceding claim, wherein the initiator is obtained by treating an alkali metal or mixture of alkali metals with mercury in a polar solvent or mixture of polar solvents at a temperature of 2830 to 3330K.

5. A process according to Claim 4, wherein the temperature is 2930 to 303 OK.

6. A process according to any preceding claim, wherein the initiator is obtained by treating alkali metal particles having an average particle size of 0.01 to 10 mm with mercury.

7. A process according to Claim 6, wherein the average particle size of the alkali metal particles is 0.1 to 5 mm.

8. A process according to any preceding claim, wherein the initiator is obtained by treating 100 parts by weight of alkali metal or alkali metal mixture with 0.5 to 20 parts by weight of mercury.

9. A process according to Claim 8, wherein 100 parts by weight of alkali metal or alkali metal mixture are treated with 2 to 5 parts by weight of mercury.

1 0. A process according to any preceding claim, wherein the initiator is obtained by treating an alkali metal or mixture of alkali metals in a polar solvent or mixture of polar solvents with mercury with stirring and in the presence of an inert atmosphere.

11. A process according to any preceding claim, wherein the vinyl aromatic hydrocarbon is alpha alkyl styrene or an ortho-, para- or metaalkyl alpha alkyl styrene.

1 2. A process according to any preceding claim, wherein the vinyl aromatic hydrocarbon is alpha methyl styrene or an ortho-, para- or metaalkyl alpha alkyl styrene.

1 3. A process according to any preceding claim, wherein the reactive oligomer produced by the process is reacted with a functional reagent chosen from carbon dioxide to introduce carboxy groups into the oligomer, alkylene oxide to introduce hydroxy groups into the oligomer and carbon disulphide to introduce carbodithio groups into the oligomer.

14. A process according to Claim 13, wherein the alkylene oxide is ethylene oxide or propylene oxide.

1 5. A process according to Claim 13 or Claim 14, wherein the functional reagent is reacted with the oligomer at a temperature of 253C to 2930K.

1 6. A process according to Claim 15, wherein the functional reagent is reacted with the oligomer at a temperature of 263 to 2730K.

1 7. A process according to any one of Claims 13 to 16, wherein the functional reagent is in gaseous form and this is caused to flow at a rate of 0.5 to 20 m/sec. around a central flow of an atomized solution of oligomer in a polar solvent containing 10 to 50% by weight of oligonnier in which the atomized particles have an average diameter of 1 to 100 m, the ratio of the flow rate of the liquid to that of the gaseous constituent being within a ratio range of 1:20 to 1:600.

18. A process according to Claim 17, wherein the preliminary pressure for the oligomer solution is approximately 0.6 MPa and the preliminary pressure for the gaseous reagent is approximately 0.8 MPa.

1 9. A process according to Claim 1 7 or Claim 18, wherein the atomized solution contains 20 to 40% by weight of oligomer.

20. A process according to any one of Claims 1 7 to 19, wherein the ratio of the flow rate of the liquid to that of the gaseous constituent is within a ratio range of 1:50 to 1:300.

21. A process according to any one of Claims 13 to 16, wherein a solution of the reactive oligomer is caused to react with the functional reagent in Iqiuid or liquefied form on a rotating disc, the ratio of the flow rate of the oligomer solution to that of the functional reagent being within a ratio range of 1:0.01 to 1:10.

22. A process according to Claim 21 , wherein the preliminary pressures of the oligomer solution and the functional reagent are approximately 0.6 MPa and approximately 0.8 MPa respectively.

23. A process according to Claim 21 or Claim 22, wherein the ratio of the flow rate of the oligomer solution to that of the functional reagent is within a ratio range of 1:0.1 to 1:0.3.