WO1993004100A1

WO1993004100A1 - Process for the living cationic polymerisation of electron-rich vinyl compounds

Info

Publication number: WO1993004100A1
Application number: PCT/NL1992/000146
Authority: WO
Inventors: Franciscus Johannes Marie Derks; Jacobus Antonius Loontjens; Gerry K. Noren
Original assignee: Dsm N.V.
Priority date: 1991-08-21
Filing date: 1992-08-20
Publication date: 1993-03-04
Also published as: NL9101413A; AU2586592A

Abstract

The invention relates to a process for the production of polymers by the living cationic polymerization of vinyl ethers, in which process the polymerization is terminated by the addition of a hydroxyl-containing component while adding an organic base. Polyvinyl ethers obtained by using a process according to the invention can be used for the production of block copolymers, or in other fields, such as telechelic polymers or macromonomers. Block copolymers obtained by applying a process according to the invention can be used in many fields in which boundary surfaces play a part. Examples are glass fiber-reinforced plastics, pigment dispersions in plastics or coatings, coating-substrate boundary surfaces, polymer blends, blends of polymers with fillers such as talcum, mica or chalk, etc.

Description

PROCESS FOR THE LIVING CATIONIC POLYMERIZATION OF ELECTRON-RICH VINYL COMPOUNDS

Field of the Invention

The invention relates to a process for the production of polymers by the living cationic polymerization of electron-rich vinyl compounds, in which process the polymerization is terminated by the addition of a hydroxyl- containing component.

Background of the Invention

Processes for the living cationic polymerization of electron-rich vinyl compounds are known from Oskar Nuyken and Hubertus Kroner, "Living cationic polymerization of isobutyl vinyl ether, 1, Initiation by hydrogen iodide/tetraalkylammonium salts", Makromol. Chem. , 191, No. 1, January 1990, which describes a living cationic polymerization process that is initiated by HI as initiator and is terminated by the addition of methanol, containing 5% (vol.) aqueous ammonia. The methanol is added in a large excess and is afterwards removed again by washing and by evaporation. If a smaller amount of methanol is used, all sorts of undesired by-products are formed, such as aldehydes and coupling products.

The disadvantage of such a process is that a large excess of methanol must be added and subsequently removed. This disadvantage is even greater if the hydroxyl-containing component is a less volatile compound.

The object of the invention is to provide a process that does not have said disadvantages, or only to a less degree. Summary of the Invention

The objects of the invention are achieved according to the process of the present invention in which the polymerization is terminated by the addition of a hydroxyl- containing component and an organic base.

It is preferred to add the organic base together with the hydroxyl-containing component at the moment of termination. Hence it is possible for only a small excess of the hydroxyl-containing component to be added. Preferably the hydroxyl-containing component is added in an amount of 1 to 10 times the number of initiator molecules present in the reaction medium.

Detailed Description of the Invention

As used herein, the phrase "electron-rich vinyl compounds" refers to vinyl compounds chosen from the group consisting of vinyl ethers and N-vinyl compounds. Examples of N-vinyl compounds are N-vinylpyrrolidone and N- vinylcarbazole. The vinyl compounds are preferably vinyl ethers.

Living cationic polymerization is a polymerization process under the influence of a cationic initiator, in which process the reaction is living, which means that the polymerization is characterized by little termination and few chain-transfer reactions. If, moreover, the initiation is rapid compared with the propagation reaction, polymers with a low polydispersity are obtained. A living cationic polymerization is eminently suited for the synthesis of block copolymers.

"Polydispersity D" is an indication of the molecular weight distribution. "D" is calculated by dividing the weight-average molecular weight M_w by the number-average molecular weight M_n .

Living cationic polymerization is further described by M. Miyamoto, M. Sawamoto and T. Higashimura, in Macromolecules, r7# 3, 265-268 (1984). There, too, neutralization takes place using ammonia-containing methanol. There is no question there of neutralizing the reaction by an organic base. A block copolymer is a copolymer consisting of polymer segments (blocks) built up from different monomers, with the various blocks having different properties.

A process for the production of block copolymers, notably AB block copolymers, by the living cationic polymerization of, inter alia, vinyl ethers is described in M. Minoda, M. Sawamoto and T. Higashimura, Macromolecules, (1987), 20.ι ⁹ _/ 2045-2049, the disclosure of which is incorporated herein. An AB block copolymer is a copolymer substantially consisting of 2 blocks A and B having a different composition. In most cases the blocks will have different properties such as, for instance, an apolar A and a polar B block.

An AB block copolymer can be obtained by living cationic polymerization by first polymerizing a particular monomer to form a block A and, after all monomers have been used, continuing the reaction by the addition of another type of monomer(s) and continuing the reaction until a block B has been obtained. The result is an AB block copolymer.

A second way of obtaining an AB block copolymer is the initiation of a living cationic polymerization process by a polymeric initiator.

A third way of obtaining an AB block copolymer is the coupling of two separately formed blocks A and B. Either block or both can be obtained by living cationic polymerization.

The invention further relates to the process in which the hydroxyl-containing component is an oligomer or polymer with a molecular weight of at least 100 and a boiling point of at least 100°C. The hydroxyl-containing component preferably consists of a polar oligomer or polymer suited for use as a B block in an AB block copolymer.

It has surprisingly been found possible in this process to terminate a living cationic polymerization with a relatively small amount of hydroxyl-containing component and consequently, in the process, at the same time to couple this component as a B block to the A block. According to the state of the art, this was not feasible, because the hydroxyl-containing component had to be added in a large excess and could not be properly removed afterwards.

The organic base must be non-aqueous and must not contain any unstable proton. It can be chosen from, for instance, the group consisting of tertiary aliphatic or non- aliphatic amines, such as triethylamine (TEA) and trimethylamine (TMA) and sterically hindered pyridines, such as 1,5-dimethylpyridine (DMP). The organic base is preferably chosen from the group consisting of TEA, TMA and DMP and is more preferably triethylamine.

The organic base can be used in an amount of 0.01 to 100 moles per mole initiator. It is preferred to use the organic base in an amount of 1 to 5 and more preferably about 2 moles per mole initiator. The organic base is preferably non-aqueous.

The hydroxyl-containing component can be chosen from the group consisting of glycols, such as monomethoxytriethylene glycol, monomethoxydiethylene glycol, polyethylene glycol monomethyl ether, polypropylene glycol, polytetrahydrofuran, etc.

It is preferred to choose the hydroxyl-containing component from the polyethylene glycols. The hydroxyl-containing component preferably has a molecular weight (M_w ) of about 30 to about 5000 and more preferably of about 100 to about 1000.

A vinyl ether is a compound containing a group according to formula I:

CH₂=CH-0-R (I)

The vinyl ethers may be chosen from, for example, methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and higher aliphatic vinyl ethers and mixtures of these.

The vinyl ethers are preferably chosen from the group consisting of ethyl vinyl ether, n-butyl vinyl ether and isobutyl vinyl ether.

Instead of regular vinyl ethers as described hereabove it is possible to use other vinyl ether group containing compounds such as propenyl ether. Such alternative compound can have a group according to formula II:

R¹-CH₂=CH-0-R (II)

in which R¹ can e.g. be methyl or ethyl.

The reaction can generally take place at a temperature of -100°C to +100°C and preferably takes place at a temperature of -80°C to 50°C. More preferably the reaction takes place at -50°C to 20°C.

The reaction can take place under normal pressure. If so desired, the reaction can take place under elevated or reduced pressure.

The reaction takes place in the presence of an initiator. The initiator can be chosen from, for example, the group consisting of HI, HC1, HBr, trimethylsilicon iodide, optionally together with dioxalane, (Me₃-Sil), and ethyl aluminum dichloride (EtAlCl₂). The initiator is preferably HI. The initiator can be added in an amount depending on the desired reaction rate and the desired molecular weights of the polymers formed.

Preferably a co-initiator is also added to the reaction mixture. The co-initiator can be chosen from, for instance, the group consisting of iodine, Znl₂ , ZnBr₂ , ZnCl₂ and tetraalkylammonium perchlorate.

The reaction preferably takes place in an inert solvent such as hexane, toluene, methylene chloride or chloroform.

Polyvinyl ethers obtained by applying a process according to the invention can be used for the production of block copolymers, or in other fields, such as telechelic polymers or macromonomers. Telechelic polymers are polymers with a functional end group at the α- and at the ω-site. Macromonomers are polymers which still have a certain reactivity, for instance by virtue of a double bond, which may yet undergo polymerization. A specially preferred embodiment of the invention is a process in which the hydroxyl-containing component comprises an ethylenically unsaturated group. Preferably this ethylenically unsaturated group is not or to a lesser extend susceptible to polymerization by cationic initation. Such a hydroxyl-containing component gives a macromonomer. The resultant macromonomer may be di- or even multi¬ functional if the original initiator system is di- or multi¬ functional. If the hydroxyl-containing component comprises more than one ethylenically unsaturated group, the resultant macromonomer will also be multi-functional. An example of such an initiator system would be DVE-3 (triehyleneglycol divinyl ether)/HI/ZnI₂. The ethylenically unsaturated group can e.g. be an acrylate or methacrylate group or a vinyl group such as a vinyl ester group or an allyl group or a group corresponding to an unsaturated dicarboxylic acid e.g. maleate, fumarate, itaconate. Formula III is an example of a. useful compound.

0 0 n It ROC-CH=CH-C-0-CH₂-CH-OH (III)

R¹

Further examples of useful hydroxyl containing components that comprise an ethylenically unsaturated group can be chosen, inter alia, from hydroxy alkyl (meth)- acrylates, unsaturated ester oligomers comprising a hydroxyl-group, hydroxy alkyl allyl ethers, etc.

A further preferred embodiment of the invention is a process in which the hydroxyl-containing component comprises a vinyl ether group. It may be necessary to enhance the nucleophility of the hydroxyl group to prevent this vinyl group from reacting cationically before the hydroxyl groups terminates the polymerization. This can e.g. be achieved by modifying the hydroxyl group to an ethanolate by adding of a metal salt.

Block copolymers obtained by applying a process according to the invention can be used in many fields in which boundary surfaces play a part. Examples are glass fiber-reinforced plastics, pigment dispersions in plastics or coatings, coating-substrate boundary surfaces, polymer blends, and blends of polymers with fillers such as talcum, mica or chalk, etc.

The invention will be elucidated by means of the following examples without being limited thereto.

In the following examples, the solvents were dried on a molecular sieve, 4A. Ethyl vinyl ether (Aldrich) was dried on sodium and distilled for use. HI was obtained from a 57% aqueous solution by dehydration with phosphorus pentoxide and stored as a hexane solution at -78°C. ZNI₂ (Aldrich, 99.99%) was used as obtained, dissolved in ether.

Gas chromatography (GC) was carried out using heptane as the internal standard.

The molecular weight distribution (molecular mass distribution MMD) was determined by gel permeation chromatography (GPC) in THF (tetrahydrofuran) with Ultrastyragel^R columns (1000, 500 and 100A, Waters). The M_n and M_w values were determined using a calibration curve based on polystyrene standards.

-*H-MNR spectra were recorded on CDC1₃ using a Bruker AC 200.

Example I

Termination with methanol/orqanic base

In a dry reactor vessel, 2 ml (0.02 mole) ethyl vinyl ether was introduced into 10 ml toluene in a dry nitrogen atmosphere at a temperature of 0°C. To the monomers, 2 ml HI solution in hexane (0.002 mole) was added for initiation purposes during stirring. After that, 0.064 g (0.0002 mole) ZNI₂ was added for the propagation of the reaction. The temperature was kept at 0°C. After more than 90% had been converted (checked with GC analysis), the reaction was terminated after about one hour by the addition of 0.128 g (0.004 mole) methanol and 0.404 g (0.004 mole) triethylamine (TEA). The methanol:HI ratio was 2 and the TEA:HI ratio was 2.

The reaction mixture was washed with 10% aqueous thiosulphate solution and with water and subsequently evaporated under reduced pressure till the product was dry. In the *-H-NMR spectrum the acetal end group was clearly to be found back, but there were no aldehyde peaks to be found, and the GPC spectrum showed that the polydispersity was low (D - 1.12). Hence it is evident that a good product has been formed with few or no side reactions.

Example II

Termination with MMTEGlycol/organic base - production of a block copolymer

The process of Example I was followed, the reaction being terminated with a mixture of 2 TEA equivalents and 10 monomethoxytriethylene glycol (MMTEG) equivalents instead of the methanol. The -*H-NMR spectrum did show an acetal, but not an aldehyde peak. The polydispersity D was narrow (D=1.10).

Comparative experiment A

Termination with an excess of methanol and ammonia

The process according to Example I was followed, the reaction being terminated with a large excess of a mixture of methanol and aqueous ammonia (5% vol., 25% wt) instead of said mixture. The methanol:HI ratio was about 500. The NH₄OH:HI ratio was 12.5. With --H-NMR it was clear that the polymer of the product had a methoxy end group. The polydispersity was 1.12. Comparative experiment B

The process of experiment A was followed using a methanol:HI ratio of 2:1. The NH₄OH:HI ratio was 2. The H₂0:HI ratio was 4. The **H-NMR spectrum showed an aldehyde peak, which aldehyde had probably been formed by an alcohol split-off from the polymer via the hemiacetal that can be formed by reaction with H₂0. The GPC curve showed a bimodal distribution of the molecular weight in which one of the tw peaks may be a dimer. The polydispersity was 1.32.

Comparative experiment C Termination with and without ammonia The process of experiment A was followed with a methanol:HI ratio of 10:1, with and without ammonia. The amount of aldehyde formed increased in the absence of ammonia, compared with the termination in the presence of ammonia. The GPC spectrum showed a broadening of the polydispersity D to 1.2.

Example III

Application of block copolymers in coatings

An amount of 0.5% (wt) of the block copolymer obtained according to Example II was incorporated in a coating resin. The resin consisted of a mixture of a Uralac SN805X7 acrylate resin of DSM Resins of Zwolle with a ϋramex MF 862B1X crosslinking agent, again of DSM Resins, and a pigment in a weight ratio of 63:32:5. A small iron plate of a thickness of 0.5 mm was coated with the mixture on one side and the coating was cured. The plate was exposed to the impact of a steel ball (diameter 5/8 inch, weight 2 lbs), which fell on the horizontally clamped plate from a height of 100 cm. The impact caused a dent of a depth of 3 mm. The coating remained intact when the ball fell on the coating and also when the ball fell on the plate at the back of the coating. Comparative experiment D Coatings without block copolymers

The process of Example III was followed without a block copolymer. In both cases the coating became detached on impact.

Claims

C L I M S

1. Process for the production of polymers by the living cationic polymerization of vinyl ethers, in which process the polymerization is terminated by the addition of a hydroxyl-containing component, characterized in that an organic base is added.

2. The process according to claim 1, wherein the organic base is added before or simultaneously with the hydroxyl-containing component.

3. The process according to any one of claims 1-2, wherein the organic base is chosen from the group consisting of tertiary amines and sterically hindered pyridines.

4. The process according to claim 3, wherein the organic base is triethylamine.

5. The process according to any one of claims 1-4, wherein the polymerization is initiated with an initiator and the organic base is added in an amount of -0.01 to 100 moles per mole initiator.

6. The process according to claim 5, wherein the organic base is added in an amount of 1 to 5 moles per mole initiator.

7. The process according to claim 6, wherein the organic base is added in an amount of about 2 moles per mole initiator.

8. The process according to any one of claims 1-7, wherein the polymerization is initiated by an initiator and hydroxyl-containing component is added in an amount of 1 to 10 times the number of initiator molecules.

9. The process according to any one of claims 1-8, wherein the hydroxyl-containing component is an oligomer or a polymer with a molecular weight of at least 100 and a boiling point of at least 100°C.

10. The process according to any one of claims 1-9, wherein the hydroxyl-containing component differs in polarity from the vinyl compounds.

11. The process according to any one of claims 1 to 10, wherein the hydroxyl-containing component has a molecular weight of 100 to 1000.

12. The process according to any one of claims 1-11, wherein the hydroxyl-containing component is a polyethylene glycol.

13. The process according to any of claims 1-12, wherein the hydroxyl-containing component comprises an ethylenically unsaturated group.

14. The process according to claim 13, wherein the ethylenically unsaturated group is chosen from the group consisting of acrylate or methacrylate groups, vinyl groups such as vinyl ester groups, allyl groups or groups corresponding to unsaturated dicarboxylic acids.

15. The process according to claim 14, wherein the ethylenically unsaturated component is chosen from the group consisting of hydroxy-functional maleate/fumarate esters.

16. The process according to claims 1-15, wherein the vinyl ethers are chosen from the group consisting of ethyl vinyl ether, n-butyl vinyl ether and isobutyl vinyl ether.

17. The process according to any one of claims 1-16, wherein the reaction takes place at a temperature of -50°C to 20°C.

18. The process according to any one of claims 1-17, wherein an initiator is present, said initiator being chosen from the group consisting of HI; HC1; HBr; trimethylsilicon iodide, optionally together with dioxalane; and ethyl aluminium dichloride.

19. The process according to any one of claims 1-18, wherein a co-initiator is present, said co-initiator being chosen from the group consisting of iodine, Znl₂ , ZnBr₂ , ZnCl₂ and tetraalkylammonium perchlorate.

20. Block copolymer obtained from the process according to any one of claims 1-19.

21. Application of a block copolymer according to claim 20 in plastics for the improvement of the compatibility with and/or adhesion to a substrate.

22. Application of a block copolymer in plastics for the purpose of improving the adhesion to a substrate.

23. Process and/or block copolymer as described in whole and/or in part in the specification and/or in the examples.