WO1995026988A1

WO1995026988A1 - Method for the preparation of a macroporous polymeric sorbent

Info

Publication number: WO1995026988A1
Application number: PCT/EP1994/001074
Authority: WO
Inventors: Dominique Blondeau; Patrick Decock; Philippe Despres
Original assignee: Alltech France, S.A.R.L.
Priority date: 1994-04-05
Filing date: 1994-04-05
Publication date: 1995-10-12
Also published as: AU6565794A

Abstract

Method for the preparation of a macroporous polymeric sorbent, more particularly for chromatography, by copolymerisation of, on the one hand, a monomer containing (C1-C18) alkyl acrylate and/or (C1-C18) alkyl methacrylate, either or not substituted, with, on the other hand, a crosslinking agent from the group of alkylene diacrylate, alkylene dimethacrylate, polyglycol acrylate, polyglycol dimethylacrylate and/or dimethylbenzene, this copolymerisation being carried out in the presence of a suspension stabiliser and a polymerisation initiator, by forming an aqueous and an organic phase, wherein an aqueous phase with a reaction mixture of above-mentioned monomer, crosslinking agent and suspension stabiliser is preferably brought to its polymerisation temperature and the mixture is subjected to ultrasonic irradiation, more specifically at a frequency of 20 kHz or higher, and subsequently, after discontinuation of this irradiation, above-mentioned polymerisation initiator is added to this mixture, either with or without stirring, so that copolymerisation starts and a suspension of porous copolymer particles is obtained.

Description

Method for the preparation of a
macrooorous polymeric sorbent.

The invention relates to a method for preparing a macroporous polymeric sorbent, more particularly for chromatography, by copolymerisation of, on the one hand, a monomer containing (C1-C18) alkyl acrylate and/or (C1-C18) alkyl methacrylate, either or not substituted, with, on the other hand, a crosslinking agent from the group of alkylene diacrylate, alkylene dimethacrylate, polyglycol acrylate, polyglycol dimethylacrylate and divinylbenzene, this copolymerisation being carried out in the presence of a suspension stabiliser and a polymerisation initiator.

Such and similar sorbents have been described in following US-patents: 4,135,892; 4, 184,020; 3,991,018; 4, 111,859; 4,184,020; 4,111,859; 4,133,942; 4,101,461; 4,079,021; 4,076,691; 3,991,018; 3,925,267; 4,135,892; 4, 251, 634; 4, 281,233; 3,983,001; 4,097,420.

Gas and liquid chromatography are two of the easiest methods for the analysis of organic compounds.

Preparative chromatography is also an efficient means for purification of big quantities of organic compounds.

Generally, the commonly known methods for the preparation of such sorbents, e. g. those described in above mentioned patents, are based on suspension polymerisation and copolymerisation in an aqueous medium of acrylic monomer with diacrylic monomer as reticulant. Inert solvents are used to obtain a microreticular and macroporous structure.

However, sorbents produced with these methods show a large polydispersity as to the dimensions of the particles, so that only a relatively small volume with the required diameter for a specific use can be obtained.

Usually, the required diameter is between 1 and 10 pm for analytic LC columns and between 11 and 100 pm for preparative LC columns. GC packed columns require a particle size bigger than 100 ym. Particles smaller than 2 pm can be used in PLOT columns.

The invention aims primarily at introducing a new method for the preparation of such sorbents, which not only significantly reduces the above mentioned polydispersity, but also makes it possible to prepare a sorbent of which the size of the particles is adapted to fit the conditions of a particular use.

According to the invention, an aqueous phase with a reaction mixture, consisting of above mentioned monomer, crosslinking agent and suspension stabiliser, is preferably brought to the polymerisation temperature of this reaction mixture and subjected to ultrasonic irradiation, more specifically at a frequency of 20 kHz or higher. Subsequently, when the irradiation is discontinued, the polymerisation initiator is added to this mixture, either with or without stirring, so that copolymerisation starts and a suspension of porous copolymer particles is obtained which constitutes the required sorbent.

In this reaction mixture, the total volume of the aqueous phase lies more particularly between 0.1 and 3 times that of the organic phase.

In the preferred embodiment of the method according to the invention, the reaction mixture, after adding the polymerisation initiator, is stirred at 150 to 250 revolutions per minute, preferably at a speed of around 200 rpm.

Other particularities and advantages of the invention will become clear from the following description of some specific embodiments of the method according to the invention, which have been illustrated with concrete examples.

Figures 1 to 9, to which is referred in the following concrete examples of application, graphically represent the amount of polymer particles expressed in weight percentage in function of the diameter of the polymer particles expressed in micron.

According to the invention, the sorbent destined for the execution of separations and analyses with chromatography is produced by copolymerisation of a monomer consisting of (C1-C18) alkyl acrylate and/or (Cl-C18) alkyl methacrylate, either or not substituted, with a crosslinking agent consisting of alkylene diacrylate, alkylene dimethacrylate, polyglycol acrylate, polyglycol dimethacrylate and/or divinylbenzene. The process is, in particular, a binary or tertiary suspension copolymerisation executed in the presence of a suspension stabiliser and a polymerisation initiator.

Monomers and crosslinking agents of the type mentioned above, suited to this purpose, have been described among others in the patent literature cited above.

As to the monomer, the preference is for those belonging to the family of the hydroxylalkyl acrylates and hydroxyalkyl methacrylates, epoxyalkyl acrylates and epoxyalkyl methacrylates, the chloroalkyl acrylates and chloroalkyl methacrylates, the alkylaminoalkyl acrylates and dialkylaminoalkyl acrylates and the alkyl acrylates and alkyl methacrylates substituted by carboxyl, amino, amino alcohol, amide and aromatic groups, whereby in these compounds the alkyl group contains 1 to 18 carbon atoms.

Preferred crosslinking agents are chosen from the group of alkylene diacrylates and alkylene dimethacrylates, polyglycol acrylates and polyglycol dimethacrylates, and divinylbenzene.

The polymerisation is executed in an aqueous medium, whereby the total volume of the aqueous phase is between 0.1 and 3 times that of the organic phase, comprising the reaction components for the formation of the required copolymer. To these reagents are added suspension stabilisers which can consist of e. g. polyvinyl pyrrolidone, polyvinyl alcohol, partially hydrolysed polyvinyl acetate, starch, inorganic salts and organic compounds consisting of aliphatic and/or cyclo-aliphatic alcohols with 4 to 8 carbon atoms, as well as mixtures of these various compounds. Usually, the percentage of suspension stabilisers is 0,1 to 4% of the aqueous phase.

The polymerisation initiator is a free radical compound, soluble in the organic phase and substantially insoluble in the aqueous phase. Such compounds have been described in US-patent 4,135,892, column 2, lines 5 and 6 and elsewhere. In this way, such initiator can consist of aliphatic azobisnitriles, such as azosobutyronitrile and/or acylperoxydes, such as benzoylperoxyde. Relatively small amounts of these initiators are added, approximately 1 % (wt/wt) of the monomer.

The main characteristic of the invention lies in the fact that ultrasonic irradiation is applied to the reaction mixture containing above-mentioned monomer, crosslinking agent and suspension stabiliser, and this before adding the free radical polymerisation initiator.

Also, the reaction mixture is already brought to the temperature at which polymerisation will subsequently take place. The frequency of the ultrasonic irradiation is approximately 20 kHz or slightly higher, while the duration varies from 1 to 30 minutes with varying energy, as will become apparent from the following concrete application examples.

When the ultrasonic irradiation has stopped, the next step consists of adding the initiator and stirring the reaction mixture. In this way, a microsuspension is produced which is stable during a certain period, depending on the nature and the concentration of the suspension stabiliser used. If a weak stabiliser is chosen, or if the concentration of the stabiliser in the reaction mixture is relatively low, this will result in polymer particles with a relatively large diameter.

The choice and/or concentration of the suspension stabiliser will thus allow, with the same monomers and crosslinking agents, the production of copolymer particles of varying sizes but always with a low dispersity or spread.

In this description,"dispersity"is to be understood as the variation in diameter of the total amount of copolymer particles produced during the polymerisation reaction. The smaller or lower the. dispersity, the smaller the difference in size between the various particles and the higher the amount of particles with almost the same size.

Stirring tests have shown that, after 10 minutes, there is no change to the dispersity or to the size of the particles produced. This means that after a certain period, for a certain reaction mixture, in principle a suspension is produced of which the size of the particles has reached a certain minimum which remains stable. These particles will, moreover, always be spherical in shape, at least if the stirring speed during polymerisation is not too high.

The most favourable applied energy and frequency are established in an analogous experimental way.

However, these parameters are more dependent on the reactor's volume and the degree to which it can be filled and on the nature of the apparatus used for the production of the ultrasonic irradiation.

In any case, application of the invention produces spherical copolymer particles of greatly varying size but always with a highly limited polydispersity.

After the polymerisation initiator has been added, the mixture is usually stirred at a speed of 150 to 200 rpm, but preferably at around 200 rpm. This stirring speed is best kept as constant as possible during the complete process of polymerisation.

It was established that distortions of the copolymer particles occur when the stirring speed is too high, namely, the particles take on an ellipsoid shape.

This means that the stirring is not the most important factor in the formation and the maintenance of the suspension. In any case, the dimensions of the particles and their dispersity are not defined by the stirring speed.

After copolymerisation, the produced suspension of the copolymer particles is treated in the same way as with the existing methods, such as those described in the older US-patents cited above.

Depending on the use for which it is intended, the spherical sorbent particles can be modified to the production of specific materials.

Production of the relevant sorbent is considerably simplified with this invention, which is partly due to the automatic low polydispersity of the particle size.

This is because the fractioning of the particles can be done much faster than that of particles produced by existing methods. Besides, the loss of sorbents and loss of raw materials is considerably lower because the same amount of sorbent produces a larger percentage of particles suitable for use in chromatography.

Further, the physical properties of the sorbent can easily be modified without affecting the spherical shape of the particles.

Also, in most cases, by applying the method according to the invention, sorbents can be produced with a larger specific area than through applying the known standard methods.

Following are some specific application examples which further illustrate the method according to the invention. Naturally, these examples in no way limit the scope of the invention.

Example 1:
150 ml distilled water and 1,5 g polyvinyl alcohol were introduced into a reactor equipped with a
U-shaped mechanical stirrer and heated up to 70 C. Then a mixture of 8.5 g hydroxyethyl methacrylate. and 12.74 g ethyleneglycol dimethacrylate, 4.5 g dodecanol, 22.75 g cyclohexanol was added. Ultrasonic irradiation was applied for a period of 10 minutes with an energy of 60 W. 0.2 g of azoisobutyronitrile was added to the resulting microemulsion while the temperature was maintained at 70 C for 12 hours. The resulting copolymer was repeatedly decanted with water and methanol, then extracted for 24 hours with methanol, and finally dried. After drying, a polymer was obtained in spherical particles, the dimensions of which are represented in the annexed figure 1.

In order to demonstrate the validity of the method according to the invention, the test was repeated with the same ingredients, but ultrasonic irradiation was replaced by vigorous stirring at a speed of 700 to 1200 rpm. The copolymer obtained by this procedure showed a large dispersity and the size of the particles was larger than those produced using ultrasonic irradiation, as is demonstrated clearly in figure 1.

In both cases, the mechanical and chemical properties were similar, as well as the specific area, which was equal to 120 m2/g.

Example 2:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvents: 150 ml water, 0.75 g polyvinyl alcohol, 8.48 g hydroxyethyl methacrylate, 12.72 g ethyleneglycol dimethacrylate, 24 g dodecanol and 0.2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in figure 2. The specific area was equal to 20 m2/g.

Example 3:
The polymerisation was also carried out in the same way as in example 1, with the following amounts of reagents and solvent: 150 ml water, 0.75 g polyvinyl alcohol, 8.48 g hydroxyethyl methacrylate, 12.72 g ethyleneglycol dimethacrylate, 7.10 cyclohexanol, 18.67 g dodecanol and 0.2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in figure 3. The specific area was equal to 60 m2/g.

Example 4:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvent: 150 ml water, 0.75 g polyvinyl alcohol, 8.48 g hydroxyethyl methacrylate, 12.74 g ethyleneglycol dimethacrylate, 22.75 g cyclohexanol, 4.95 g dodecanol and 0.2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in figure 4. The specific area was equal to 130 m2/g.

Example 5:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvents: 150 ml water, 0.75 g polyvinyl alcohol, 4.23 g hydroxyethyl methacrylate, 16.9 g ethyleneglycol dimethacrylate, 21.31 g cyclohexanol, 6.22 g dodecanol and 0.2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in figure 5. The specific area was equal to 193 m2/g.

Example 6:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvents: 150 ml water, 0.75 g polyvinyl alcohol, 4.23 g hydroxyethyl methacrylate, 16.9 g ethyleneglycol dimethacrylate, 28.41 g cyclohexanol and 0.2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in figure 6. The specific area was equal to 250 m2/g.

Example 7:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvent : 150 ml water, 1,5 g polyvinyl alcohol, 9,6 g 2-hydroxy, 3- (2-methylcarboxylate, 4-hydroxy) azacyclopentyl] propyl methacrylate, 3,15 g methylmethacrylate, 12,72 g ethyleneglycol dimethacry-late, 22.72 g cyclohexanol, and 0.2 g azosobutyronitrile. The resulting polymer showed the dispersity presented in figure 7. The specific area was equal to 20 m2/g.]
Example 8:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvent: 150 ml water, 0.75 g polyvinyl pyrrolidone, 8.48 g hydroxyethyl methacrylate, 12.62 g ethyleneglycol dimethacrylate, 22.71 g cyclohexanol, 4.90 g dodecanol and
0.2 g azoisobutyronitrile. The resulting polymer had an average particle size of 200 pm.

The specific area was equal to 120 m2/g.

Example 9:
The polymerisation was carried out in the same way as in example 1, with the following amounts of reagents and solvent: 150 ml water, 1.5 g polyvinyl alcohol, 8.48 g hydroxyethyl methacrylate, 12.62 g ethyleneglycol dimethacrylate, 22.71 g cyclohexanol, 4.90 g dodecanol and 0.2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in figure 8. The specific area was equal to 120 m2/g.

Example 10:
The polymerisation was carried out in the same way as in example 1, with the following amounts of ragents and solvent : 150 ml water, 1,5 g polyvinylalcohol, 12,5 g paracarboxystyrene, 6,5 g divinylbenzene, 30 ml butane-1-ol and 0,2 g azoisobutyronitrile. The resulting polymer showed the dispersity presented in fig. 9. The specific area was equal to 5 m2/g.

Example 11:
300 ml distilled water and 0,9 g polyvinylpyrrolidone were introduced into a reactor equiped with a
U-shaped mechanical stirrer and heated up to 70 C. Then a mixture of 9,96 g dodecanol, 45,4 g cyclohexanol, 6,4 g methylmethacrylate, 9,5 g glycidylmethacrylate and 25,44 g ethyleneglycoldimethacrylate was added. Ultrasonic irradiation was applied for a period of 5 minutes with an energy of 25 W. 0,4 g of azoisobutyronitrile was added to the resulting microemulsion while the temperature was maintained at 70 C for 8 hours. The resulting copolymer was repeatedly decanted with water and methanol, then extracted for 4 hours with methanol and finally dried.

After drying, the polymer was screened by wet screening with water. 250-150 pm particles were washed with methanol and dried. 8 g of those particles were added to 30 ml diethylamin and the mixture was put under reflux for 2 hours. After cooling the polymer was carefully washed with methanol and dried.

The polymer was used as a packing for GC column to carry out separation of hydrocarbons (Cl to C6) and freons (R13, R23, R134a, R22, R142b, R21, R11, R113).

Example 12:
The polymerisation was carried out in the same way as in example 11, with 9,96 g dodecanol, 45,4 g cyclohexanol, 6,4 g methylmethacrylate, 9,5 g glycidylmethacrylate, 19,5 d divinylbenzene. The polymer was bonded with diethylamin and used as a packing for GC column. The column was used for separation of freons (R13,
R23, R13bl, R134a, R22, R12, R142b, R114, R21, R113).

The invention is naturally by no means limited to the application possibilities described above and within the framework of the invention several changes could be considered, e. g. concerning the choice and the relative amount of the reagents used for the formation of the sorbent, the frequency of the ultrasonic irradation, the stirring speed, etc.

Claims

CLAIMS 1. Method for the preparation of a macroporous polymeric sorbent, more particularly for chromatography, by copolymerisation of, on the one hand, a monomer containing (C1-C18) alkyl acrylate and/or (C1-C18) alkyl methacrylate, either or not substituted, with, on the other hand, a crosslinking agent from the group of alkylene diacrylate, alkylene dimethacrylate, polyglycol acrylate, polyglycol dimethylacrylate and/or dimethylbenzene, this copolymerisation being carried out in the presence of a suspension stabiliser and a polymerisation initiator, by forming an aqueous and an organic phase, characterised in that an aqueous phase with a reaction mixture of above mentioned monomer, crosslinking agent and suspension stabiliser is preferably brought to its polymerisation temperature and that the mixture is subjected to ultrasonic irradiation,

more specifically at a frequency of 20 kHz or higher, and that subsequently, after discontinuation of this irradiation, above mentioned polymerisation initiator is added to this mixture, either with or without stirring, so that copolymerisation starts and a suspension of porous copolymer particles is obtained.

2. Method according to claim 1, characterised in that, in the above mentioned reaction mixture, the total volume of the aqueous phase is between 0.1 and 3 times that of the organic phase.

3. Method according to claim 1 or 2, characterised in that an alkyl group with 3 to 18 carbon atoms of the alkyl acrylate and/or the alkyl methacrylate is substituted by one or more hydroxyl, epoxy, chloro, amino, alkylamino, dialkylamino, aminoalcohol, amide and/or aromatic groups.

4. Method according to claim 3, characterised in that the above mentioned monomer contains hydroxyalkyl acrylate and/or hydroxyalkyl methacrylate with in the hydroxylalkyl group 1 to 12 carbon atoms, and that the crosslinking contains alkylene diacrylate and/or dimethacrylate with in the alkylene group 1 to 12 carbon atoms.

5. Method according to anyone of the claims 1 to 4, characterised in that the suspension stabiliser contains, on the one hand, at least one of the following elements: polyvinyl pyrrolidone, polyvinyl alcohol, partially hydrolysed polyvinyl acetate, starch, and inorganic salts and, on the other hand, inert solvents consisting of aliphatc and/or cyclo aliphatic alcohols with 4 to 18 carbon atoms.

6. Method according to anyone of the claims 1 to 5, characterised in that the amount of suspension stabiliser is approximately 0,1 to 4 % of the aqueous phase.

7. Method according to anyone of the claims 1 to 6, characterised in that the polymerisation initiator is soluble in the organic phase and substantially insoluble in the aqueous phase and is chosen from the group of aliphatic azobisnitriles, such as azosobutyronitrile, and acylperoxydes, such as benzoylperoxyde.

8. Method according to anyone of the claims 1 to 7, characterised in that above mentioned reaction mixture contains 20 to 70 weight percentage of the total monomer mass and 30 to 80 weight percentage of the crosslinking agent.

9. Method according to anyone of the claims 1 to 7, characterised in that above mentioned reaction mixture is subjected to ultrasonic irradiation during 1 to 30 minutes.

10. Method according to anyone of the claims 1 to 9, characterised in that the reaction mixture, after having added the polymerisation initiator, is stirred at 150 to 250 rpm and preferably at a speed of approximately 200 rpm.