WO1993017050A1

WO1993017050A1 - Process for the production of a copolymer containing vinylaromatic units and maleimide units

Info

Publication number: WO1993017050A1
Application number: PCT/NL1993/000031
Authority: WO
Inventors: Gary Robert Gerard Fairley; Gerhard Van Vliet
Original assignee: Dsm N.V.
Priority date: 1992-02-19
Filing date: 1993-02-04
Publication date: 1993-09-02
Also published as: NL9200305A; AU3576393A

Abstract

The invention relates to a process for the production of a copolymer containing vinylaromatic units and maleimide units, the maleimide units being formed by imidating maleic anhydride units. The process according to the invention is characterized in that the imidation is effected with the aid of an ammonium salt. It has been found that the process according to the invention can be used in a simple manner and that the ammonium salt can be added in a simple manner.

Description

PROCESS FOR THE PRODUCTION OF A COPOLYMER CONTAINING

VINYLAROMATIC UNITS AND MALEIMIDE UNITS

The invention relates to a process for the production of a copolymer containing vinylaromatic units maleimide units, the maleimide units being formed by imidating maleic anhydride units.

Such a process is known from DE-C-3430802, which describes that a copolymer containing vinylaromatic units and maleimide units can be obtained because a copolymer containing vinylaromatic units and maleic anhydride units imidated with the aid of ammonia or a primary amine. To t end the ammonia or the primary amine is mixed, in gaseous dissolved condition, with the copolymer. If the reaction conditions, such as the reaction temperature, the average residence time and the pressure, are chosen well, a copolymer containing vinylaromatic and maleimide units ca be obtained.

The aforementioned process is suitable per se fo the production of a copolymer containing vinylaromatic un and maleimide units. However, use of the process accordin to DE-C-3430802 is significantly limited by the fact that the ammonia or the primary amine is added in gaseous or dissolved condition. The amount of ammonia or primary ami in the gas to be added or in the solution to be added is low that large amounts of gas or solution have to be adde to the copolymer to effect the imidation process. This is the case in particular when a copolymer with a high degre of imidation is desired. Of a copolymer with a high degre of imidation a large percentage of the maleic anhydride monomers is imidated.

In view of the large amounts of gas or solution that are to be added very high requirements are imposed w respect to the dosing unit of the gas or the solution. La amounts are to be dosed with the dosing unit, which is to suitable for use under high pressure. In addition, the dosing unit must meet stringent safety requirements. Because of this, major technological problems have to be solved whe ammonia or a primary amine in gaseous or dissolved conditio is used as an imidation reagent.

The aim of the present invention is to provide a process that does not present the above drawbacks.. The process according to the invention is characterised in that the imidation is effected with the aid of an ammonium salt. It has been found that the process according to the invention can be used in a simple manner without the aforementioned drawbacks arising with respect to the addition of the imidation reagent. The ammonium salt can be added in a simple manner.

As a starting polymer use can be made of a statistic, thermoplastically processable copolymer containing vinylaromatic units and maleic anhydride units. The vinylaromatic units can be chosen from for example the group comprising styrene, α-me hylstyrene, p-methylstyrene, ethylstyrene, p-tertiary butylstyrene, o-chlorostyrene and p-chlorostyrene. Preferably, use is made of styrene or α-methylstyrene. A general method for preparing copolymers of styrene and maleic anhydride is described in Chapters 9 and 10 of 'Maleic Anhydride', written by B.V. Trivedi and B.M. Culbertson, Plenum Press 1982, 1st edition.

In addition to vinylaromatic units and maleic anhydride units, the starting polymer may optionally also contain other units. These units are for example monomers from the group comprising acrylonitrile, methacrylonitrile, alkylesters with 1-8 carbon atoms of acrylic or methacrylic acid, such as methylmethacrylate and ethylmethacrylate, cycloalkyl esters with 5-10 carbon atoms of acrylic or methacrylic acid, for example cyclohexylmethacrylate, aryl esters with 6-14 carbon atoms of acrylic or methacrylic acid, for example benzylmethacrylate and phenylmethacrylate.

The ammonium salt that is used as an imidation reagent according to the present invention can be chosen from for example the group comprising ammonium hydrogen carbonate, ammonium hydrogen fluoride, ammonium carbamate, ammonium carbonate, ammonium fluoride, ammonium persulphat ammonium acetate, ammonium hydrogen sulphate, ammonium chloride, ammonium formiate, ammonium phosphate, ammonium benzoate, ammonium bromide, ammonium dichromate, ammonium nitrate and ammonium sulphamate. Optionally, a mixture of several of these salts may be used. Preferably, the ammoni salt used is chosen from the group comprising ammonium carbonate, ammonium phosphate and ammonium acetate.

The amount of ammonium salt used in the process according to the invention may vary within wide limits relative to the amount of maleic anhydride groups present. The final degree of imidation of the maleic anhydride grou present depends on this ratio. It has been found that virtually all the ammonium salt is consumed in the imidati process. If a certain degree of imidation is required a person skilled in the art can determine the required amoun of ammonium salt to be added in a simple manner. This amou is dependent on the amount of maleic anhydride groups to b imidated.

In a preferred embodiment of the process all male anhydride groups are imidated. To this end the ratio of th ammonium groups to the maleic anhydride groups must exceed 1.

The process according to the invention can be carried out in conventional mixing equipment, for example single- or twin-screw extruder, a static mixer, a Brabende kneader or a stirred vessel. The starting polymer can be mixed with the ammonium salt when it is in solid condition, for example a powder or a granulate, but, in order to enab fast mixing, it is preferable to already melt the starting polymer before mixing it with the ammonium salt. The imidation process preferably takes place in a single- or twin-screw extruder in view of the fact that a continuous process is possible with this equipment.

Optionally, additives may be added to the copolym containing vinylaromatic monomers and maleimide monomers thus obtained. Examples of such additives are stabilizers, antioxidants, lubricants, fillers, colourants, pigments, flame retardants, impact modifiers, reinforcing fibres and conductive fibres.

The invention is further elucidated with reference to the following examples without being limited thereto.

Example I

85 parts by weight powder of the styrene/maleic anhydride copolymer (SMA, M_w = 110000 g/mol, 28 wt.% maleic anhydride) and^*15 parts by weight ammonium carbonate powder ( .30 wt.% ammonia, Merck) were mixed and then fed to a ZSK- 30 twin-screw extruder via a hopper. The extruder was operated at a throughput of 6 kg/hour and a screw speed of 200 rpm. The temperatures in the six different temperature zones were set as follows:

Tl T2 T3 T4 T5 T6

20°C 20°C 220°C 250°C 250°C 250°C

No ammonia was observed above the hopper nor above the end product during the extrusion process. From this it was apparent that all of the ammonia present reacted with the copolymer during the extrusion process.

The following properties were determined of the reaction product thus obtained, a partially imidated styrene/maleic anhydride copolymer:

%N 0.9 degree of imidation of the anhydride groups 22% glass transition temperature, T_g 179°C Example II

Example I was repeated, only now 77.5 parts by weight powder of the styrene/maleic anhydride copolymer

(SMA, M_w = 110000 g/mol, 28 wt.% maleic anhydride) and 22. parts by weight ammonium carbonate powder (_>.30 wt.% ammonia, Merck) were added.

The temperatures in the six different temperature zones were set as follows:

Tl T2 T3 T4 T5 T6

90°C 95°C 220°C 250°C 250°C 250°C

No ammonia was observed above the hopper nor above the end product during the extrusion process. From this it was apparent that all of the ammonia present reacted with the copolymer during the extrusion process. The following properties were determined of the reaction product thus obtained, a partially imidated styrene/maleic anhydride copolymer:

%N 1.7 degree of imidation of the anhydride groups 42% glass transition temperature, T_g 183°C

Example III

Example I was repeated, only now 25 parts by weig powder of the styrene/maleic anhydride copolymer (SMA, M_w 110000 g/mol, 28 wt.% maleic anhydride) and 75 parts by weight ammonium carbonate powder (J> 30 wt.% ammonia, Merck) were added.

The temperatures of the six different temperature zones were set as follows:

Tl T2 T3 T4 T5 T6

80°C 100°C 220°C 250°C 250° 250°C _{Λ n}- ,. ,_{« ft} O 93/17050

- 6 -

No ammonia was observed above the hopper nor above the en product during the extrusion process. From this it was apparent that all of the ammonia present reacted with the copolymer during the extrusion process.

The following properties were determined of the reaction product thus obtained, a partially imidated styrene/maleic anhydride copolymers:

10

%N 3.8 degree of imidation of the anhydride groups 94% glass transition temperature, T_g 186°C

15 Example IV

Example I was repeated, only now 88 parts by wei powder of the styrene/maleic anhydride copolymer (SMA, M_w 110000 g/mol, 28 wt.% maleic anhydride) and 12 parts by weight ammonium phosphate were added. The temperatures of

20 the six different temperature zones of the extruder were as follows:

Tl T2 T3 T4 T5 T6

25 20°C 220°C 250°C 250°C 250°C 250°C

No ammonia was observed above the hopper nor above the en product during the extrusion process. From this it was apparent that all of the ammonia present reacted with the 30 copolymer during the extrusion process.

35 %N 1.2 degree of imidation of the anhydride groups 29% glass transition temperature, T_g 176°C Example V

Example I was repeated, only now 89 parts by we powder of the styrene/maleic anhydride copolymer (SMA, M 110000 g/mol, 28 wt.% maleic anhydride) and 11 parts by weight ammonium acetate were added. The temperatures in six different temperature zones of the extruder were set follows:

Tl T2 T3 T4 T5 T6

20°C 220°C 250°C 250°C 250°C 250°C

No ammonia was observed above the hopper nor above the e product during the extrusion process. From this it was apparent that all of the ammonia present reacted with th copolymer during the extrusion process.

%N 1.8 degree of imidation of the anhydride groups 44% glass transition temperature, T_g 178°C

The examples show that the process according to invention can be used in a simple manner without the aforementioned drawbacks arising with respect to the addition of the imidation reagent. The ammonium salt can added in a simple manner.

Claims

C L A I M S

1. Process for the production of a copolymer containing vinylaromatic units and maleimide units, the maleimide units being formed by imidating maleic anhydride, characterised in that the imidation is effected with th aid of an ammonium salt.

2. Process according to claim 1, characterised in that the molar ratio of the ammonium groups to the maleic anhydride groups is at least 1.

3. Process according to claim 1 or claim 2, characterised in that the ammonium salt used is chosen from the group comprising ammonium carbonate, ammonium phosphate and ammonium acetate.

4. Process according to any one of claims 1-3, characterised in that the imidation takes place in a single- or twin-screw extruder.

5. Process according to any one of claims 1-4, characterised in that the ammonium salt is mixed with the copolymer in molten condition.

6. Process according to any one of claims 1-5, characterised in that the vinylaromatic units are styrene and/or α-methylstyrene.

7. Process as substantially described and elucidated with reference to the examples.