US20050046059A1

US20050046059A1 - Process for the preparation of non-microencapsulated monodisperse bead polymers

Info

Publication number: US20050046059A1
Application number: US10/924,616
Authority: US
Inventors: Lothar Feistel; Rudiger Seidel; Hubertus Mittag; Gerold Schade; Wolfgang Podszun; Claudia Schmid
Original assignee: Bayer Chemicals AG
Current assignee: Lanxess Deutschland GmbH
Priority date: 2003-08-26
Filing date: 2004-08-24
Publication date: 2005-03-03
Also published as: EP1512698A1; DE10339569A1; JP2005068421A; DE502004001457D1; EP1512698B1; CN1597707A

Abstract

Disclosed herein is the polymerization of monodisperse microencapsulated monomer droplets to produce monodisperse non-microencapsulated bead polymers through the addition strong alkalis or strong acids during the polymerization.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a process for the preparation of non-microencapsulated monodisperse bead polymers by polymerization of monodisperse microencapsulated monomer droplets.
2. Brief Description of the Prior Art
Recently, ion exchangers having a particle size as uniform as possible (referred to below as “monodisperse”) have become increasingly important because, in many applications, economic advantages can be achieved owing to the more favourable hydrodynamic properties of an exchanger bed comprising monodisperse ion exchangers. Monodisperse ion exchangers can be obtained by functionalizing monodisperse bead polymers. One of the processes for the preparation of monodisperse bead polymers consists of producing monodisperse monomer droplets by atomizing monomers into a continuous phase and then curing said droplets by polymerization. The formation of uniform droplet sizes can be promoted by excitation of vibrations. Thus, EP 0 051 210 B1 describes a process for the production of spherical monomer droplets having a uniform particle size by excitation of vibrations in a laminar monomer stream. If the monodispersity of the monomer droplets is to be retained during the polymerization, coalescence and the formation of new droplets must be prevented. A particularly effective method for preventing coalescence and the formation of new droplets consists of the microencapsulation of the droplets according to EP 0 046 535 B1. The microencapsulation of the monomer droplets has a plurality of advantages. As a result of this measure, the particle size and particle size distribution established are retained and the polymerization is very robust with regard to the stirring conditions and temperature programme. Furthermore, this process can be particularly readily used for the preparation of macroporous bead polymers.
The polymerization of microencapsulated monomer droplets leads to bead polymers which in turn are microencapsulated since the capsule wall is retained during the polymerization reaction. Microencapsulated bead polymers are suitable for many applications. Thus, for example, microencapsulated styrene/divinylbenzene bead polymers can be converted into strongly acidic cation exchangers by sulphonation. Seed-feed polymerization reactions are also possible in principle with microencapsulated seeds. Such a process is described, for example, in EP 0 826 704 B1.
The contents of EP 0 046 535 B1 and EP 0 826 704 B1 are fully incorporated in the present Application.
In the seed-feed process using microencapsulated seeds, it has, however, been found that the capsule wall represents a diffusion barrier, with the result that the swelling of the added feed into the seed is slowed down.
Moreover, there are fields of use, such as, for example, adsorber resins or carrier resins for active substances, in which a capsule wall is undesirable.
It was therefore an object of the present invention to provide a process for the preparation of monodisperse non-microencapsulated bead polymers from microencapsulated monomer droplets.

SUMMARY OF THE INVENTION

It has now been found that monodisperse non-microencapsulated bead polymers can be obtained in a simple manner if strong acids or strong alkalis are added in the course of the polymerization.
The present invention relates to a process for the preparation of non-microencapsulated monodisperse bead polymers by polymerization of monodisperse microencapsulated monomer droplets in aqueous dispersion, which is characterized in that strong acids or strong alkalis are added to the dispersion during polymerization.
The invention preferably relates to a process for the preparation of non-microencapsulated monodisperse bead polymers, characterized in that

- a) an aqueous suspension of
  - i) microencapsulated monodisperse monomer droplets containing monomer, crosslinking agent and free radical initiator and
  - ii) dispersant
  - is prepared,
- b) the polymerization is initiated by increasing the temperature to temperatures at which the free radical initiator is active,
- c) polymerization is effected to a polymerization conversion of 20 to 98%,
- d) strong acids or strong alkalis are added,
- e) the polymerization is completed and
- f) the resulting non-microencapsulated monodisperse bead polymer is isolated.

The invention furthermore relates to non-microencapsulated monodisperse bead polymers obtainable by

- a) preparing an aqueous suspension from
  - i) microencapsulated monodisperse monomer droplets containing monomer, crosslinking agent and free radical initiator and
  - ii) dispersant,
- b) initiating the polymerization by increasing the temperature to temperatures at which the free radical initiator is active,
- c) effecting polymerization to a polymerization conversion of 20 to 98%,
- d) adding strong acids or strong alkalis,
- e) completing the polymerization and
- f) isolating the resulting non-microencapsulated monodisperse bead polymer.

In the present invention, those bead polymers in which at least 90% by volume or by mass of the particles have a diameter which is in the range of ±10% of the most frequent diameter are referred to as monodisperse.
For example, in the case of a bead polymer having the most frequent diameter of 250 μm, at least 90% by volume or by mass are in a size range between 225 μm and 275 μm; in the case of a substance having the most frequent diameter of 300 μm, at least 90% by volume or by mass are in a size range between 330 μm and 270 μm.
The monodisperse bead polymers prepared according to the invention can be converted into ion exchangers directly or via the intermediate stage by a seed/feed process of enlarged polymer particles through functionalization.
There is effected destruction of the microencapsulation which can be characterized by the changed swelling behaviour. Furthermore, the effect in the feed behaviour becomes noticeable. While each microencapsulated styrene/divinylbenzene copolymer can be described by a characteristic feed behaviour, determined by the content of crosslinking agent, the non-microencapsulated bead polymer changes its properties in favour of a higher feed ratio. This behaviour has economic advantages in practice. A further advantage of the process according to the invention is the possibility of carrying out in situ feeding in the aqueous dispersion in which non-microencapsulated monodisperse bead polymers were prepared from the microencapsulated monodisperse monomer droplets. Such a step has considerable technical advantages. It is not possible without treatment with alkali. The invention therefore relates to the use of the non-microencapsulated monodisperse bead polymers prepared according to the invention for the preparation of ion exchangers by a seed/feed process or an in situ seed/feed process. A further advantage of the non-microencapsulated monodisperse polymers prepared according to the invention is that cation exchangers or anion exchangers can be prepared therefrom by functionalization, said anion exchangers surprisingly having exceptionally improved mixed-bed behaviour when used in a mixed bed.
The invention therefore also relates to the use of the non-microencapsulated monodisperse bead polymers prepared according to the invention for the preparation of cation or anion exchangers, in particular for monodisperse anion exchangers for mixed-bed applications.
If porogens are added in the preparation process, non-microencapsulated monodisperse bead polymers are obtained, which bead polymers, owing to the pore structure occurring because of the porogen, are outstandingly suitable as adsorbers. The present invention therefore also relates to the use of the non-microencapsulated monodisperse bead polymers, obtained by the novel process in combination with a porogen, as adsorbers.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, the microencapsulated monomer droplets contain monomers, crosslinking agents, free radical initiators and optionally porogens.
Monomers to be used according to the invention are compounds having a polymerizable C═C double bond. Monomers preferred according to the invention are, for example, styrene, vinyltoluene, ethylstyrene, α-methylstyrene, chlorostyrene, chloromethylstyrene, acrylic acid, methacrylic acid, acrylic esters, methacrylic esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide and mixtures of these compounds.
According to the invention, styrene or mixtures of styrene and the abovementioned monomers are particularly preferably used.
In the context of the present invention, crosslinking agents are compounds having at least 2, preferably 2 or 3, polymerizable C═C double bonds. In the context of the present Application, preferred crosslinking agents are, for example, divinylbenzene, divinyltoluene, trivinylbenzene, divinylnaphthalene, trivinylnaphthalene, diethylene glycol divinyl ether, 1,7-octadiene, 1,5-hexadiene, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, allyl methacrylate and methylene-N,N′-bisacrylamide. The type of crosslinking agents can be chosen with regard to the subsequent use of the polymer. Thus, for example, acrylate or methacrylate crosslinking agents are not very suitable if a cation exchanger is to be prepared from the polymer by sulphonation, since the ester bond is cleaved under the sulphonation conditions. Divinylbenzene is suitable in many cases, in particular for the preparation of strongly acidic cation exchangers. For most applications, commercial divinylbenzene qualities which, in addition to the isomers of divinylbenzene, also contain ethylvinylbenzene are adequate.
The crosslinking agents to be used according to the invention are generally used in amounts of 0.1 to 50% by weight, preferably 0.5 to 20% by weight, particularly preferably 1 to 15% by weight, based on the sum of monomer and crosslinking agent. The monomers should be substantially insoluble in the aqueous phase. Monomers which are partly soluble in water, such as acrylic acid, methacrylic acid and acrylonitrile, are therefore preferably used as a mixture with water-insoluble monomers. It is also possible to reduce the solubility of the monomers in the aqueous phase by salt addition.
Suitable free radical initiators to be used according to the invention are, for example, peroxy compounds, such as dibenzoyl peroxide, dilauryl peroxide, bis(p-chlorobenzoyl peroxide), dicyclohexyl peroxydicarbonate, tert-butyl peroctoate, 2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane or tert-amylperoxy-2-ethylhexane, and furthermore azo compounds, such as 2,2′-azobisisobutyronitrile or 2,2′-azobis(2-methylisobutyronitrile). Also suitable are aliphatic peroxyesters, such as, for example, tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyneodecanoate, tert-amyl peroxy-2-ethylhexanoate, tert-amyl peroxyneodecanoate, 2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, 2,5-dipivaloyl-2,5-dimethylhexane or 2,5-bis(2-neodecanoylperoxy)-2,5-dimethylhexane.
The free radical initiators are generally used in amounts of 0.01 to 2.5% by weight, preferably 0.1 to 1.5% by weight, based on the mixtures of monomer and crosslinking agent. Of course, mixtures of the abovementioned free radical initiators may also be used, for example mixtures of free radical initiators having different decomposition temperatures.
The microencapsulated monodisperse monomer droplets i) may contain so-called porogens, particularly when it is desired to obtain adsorbers. These porogens produce a macroporous structure in the non-microencapsulated monodisperse polymer. Organic solvents which do not permit swelling of the non-microencapsulated monodisperse polymer to be prepared according to the invention are primarily suitable for this purpose. Hexane, octane, isooctane, isododecane, methyl ethyl ketone, hexanol or octanol may be mentioned by way of example. However, it is also possible to use organic solvents which are good swelling agents, such as, for example, toluene. In this case, particularly fine pores can be produced. The amount of the porogen optionally to be used according to the invention is in general 20 to 100% by weight, preferably 40 to 90% by weight, based on the sum of monomer and crosslinking agent.
The preparation of the monomer droplets to be used according to the invention in process step a) is already known from the prior art, for example EP 0 046 535 B1, the content of which is incorporated in the present Application.
For the microencapsulation of monomer droplets, the materials known for this intended use are suitable, in particular polyesters, natural or synthetic polyamides, polyurethanes, polyureas. Gelatin, a natural polyamide, is particularly suitable. This is used in particular as a coacervate or complex coacervate. In the context of the present invention, gelatin-containing complex coacervates are understood as meaning especially combinations of gelatin and synthetic polyelectrolytes. Suitable synthetic polyelectrolytes are copolymers having incorporated units of, for example, maleic acid, acrylic acid, methacrylic acid, acrylamide or methacrylamide. Gelatin-containing capsules can be cured using customary curing agents, such as, for example, formaldehyde or glutaraldehyde. The encapsulation of monomer droplets, for example with gelatin, gelatin-containing coacervates or gelatin-containing complex coacervates, is described in detail, for example, in EP 0 046 535 B1. The methods of encapsulation with synthetic polymers are likewise known to a person skilled in the art. For example, phase boundary condensation, in which a reactive component (e.g. an isocyanate or an acid chloride) dissolved in the monomer droplet is reacted with a second reactive component (e.g. an amine) dissolved in the aqueous phase, is suitable. The microencapsulation with gelatin-containing complex coacervate is preferred.
The mean particle size of the encapsulated monomer droplets to be used in the process according to the invention is preferably 10 to 1 000 μm, in particular 100 to 800 μm.
The dispersants to be used in process step a) of the present invention, also referred to as protective colloids, are natural or synthetic water-soluble polymers, such as, for example, gelatin, starch, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid or copolymers of (meth)acrylic acid or (meth)acrylic esters. Cellulose derivatives, in particular cellulose esters and cellulose ethers, such as carboxymethylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose and hydroxyethylcellulose, are also very suitable. In the polymerization of monomer droplets encapsulated with gelatin or gelatin-containing complex coacervates, gelatin is also suitable as a protective colloid. The amount of the protective colloids used is in general 0.025 to 1.5% by weight, preferably 0.05 to 0.75% by weight, based on the aqueous phase.
The polymerization of the encapsulated monomer droplets to give the spherical non-microencapsulated polymer, which is to be carried out in the process steps b) and c), can optionally require the presence of a buffer system in the aqueous phase.
Buffer systems which set the pH of the aqueous phase to a value between 14 and 6, preferably between 12 and 8, at the beginning of the polymerization are preferred according to the invention. Under these conditions, the protective colloids having carboxyl groups are present completely or partly as salts. In this way, the effect of the protective colloids is advantageously influenced. Particularly suitable buffer systems contain phosphates or borates. In the context of the invention, the terms phosphate and borate also include the condensates of the ortho-forms of corresponding acids and salts. The concentration of phosphate or borate in the aqueous phase is 0.5 to 500 mmol/l, preferably 2.5 to 100 mmol/l.
The stirring speed in the polymerization in process step c) is not very critical and, in contrast to the conventional bead polymers, has no influence on the particle size. Low stirring speeds, which are sufficient for keeping the microcapsules in suspension and for promoting the removal of the heat of polymerization are used.
The volume ratio of encapsulated monomer droplets to aqueous phase is in general 1:0.75 to 1:20, preferably 1:1 to 1:6.
The polymerization temperature of the process steps b) and c) depends on the decomposition temperature of the free radical initiator used. It is in general 50 to 150° C., preferably 55 to 100° C. The polymerization takes 0.5 to a few hours. It has proved useful to use a temperature programme in which the polymerization is started at low temperature, e.g. 60° C., and the reaction temperature is increased as the polymerization conversion progresses. In this way, for example, the requirement for the safe reaction and high polymerization conversion can be very readily met.
During the polymerization itself, strong acids or strong alkalis are added to the aqueous suspension or dispersion. In the context of the present invention, suitable alkalis are primarily sodium hydroxide or potassium hydroxide, and suitable acids are hydrochloric acid or sulphuric acid. The alkalis or acids can be used as aqueous solutions, for example having a content of 5 to 50% by weight. The amount of alkalis or acids is chosen so that a concentration of alkali or acid of 0.1 to 5% by weight is reached in the aqueous phase.
The addition of the alkali or acid to the aqueous polymerization is effected, according to process step d), after the gel point has been reached. In this context, the gel point is defined as the conversion in the course of polymerization at which at least a part of the polymer formed forms a polymer network occupying the total capsule volume. The gel point depends, inter alia, on the content of crosslinking agent and, in a customary copolymerization of styrene and divinylbenzene, occurs at 3 to 15% conversion. According to the invention, the addition of the alkali or acid is effected at a polymerization conversion of 20 to 98%, preferably of 40 to 95%.
The polymerization conversion can be determined by sampling and analysis of the samples, for example by gas chromatography, during the polymerization reaction. It is also possible, and simpler for carrying out in practice, to determine the polymerization conversion by means of the heat flow.
After addition of the strong acids or strong alkalis, the polymerization is completed by further heating to 60-150° C., preferably 70-130° C., over a period of 0.5 to 5 h (process step e)).
After the polymerization, the polymer can be isolated by customary means, e.g. by filtration or decanting, and dried, optionally after one or more washes (process step f)).
The non-microencapsulated monodisperse bead polymers obtained have the same particle size distribution as the microencapsulated monodisperse monomer droplets. Surprisingly, there is no deterioration in the monodispersity.
The removal of the capsule wall by the process according to the invention during the polymerization has substantial advantages over subsequent removal after polymerization is complete. It is possible to achieve short cycle times since an additional operation is dispensed with. Surprisingly, it was found in the experimental work that the energy balance, too, is more advantageous since the heat of polymerization is utilized in the process according to the invention.
In addition, it was found that the removal of the shell is more complete compared with a removal of the capsule wall after polymerization is complete, since the shell fraction fixed to the polymer network by a grafting reaction is smaller.
It is to be regarded as surprising that the advantage of the microencapsulation, namely the preservation of the particle size distribution, is fully retained even when the capsule shell is removed during the polymerization.
The stated percentages of the following examples are based in each case on weight.
It will be understood that the specification and examples are illustrative but not limitative of the present invention and that other embodiments within the spirit and the scope of the invention will suggest themselves to those skilled in the art.

EXAMPLES

Example 1

Preparation of a Non-Microencapsulated Monodisperse Bead Polymer From Microencapsulated Monodisperse Monomer Droplets
In a 4 l vessel (l=litre) with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and temperature chart recorder, an initially introduced aqueous mixture of 440.4 g of demineralized water, 1.443 g of gelatin, 0.107 g of resorcinol and 0.721 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 500 g of microencapsulated monodisperse monomer droplets having a uniform particle size of 235 μm is added to this initially introduced mixture with stirring at 150 rpm (revolutions per minute), the microencapsulated monodisperse monomer droplets consisting of a capsule content of 99 parts by weight of styrene, 1 part by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as initiator (free radical initiator) and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating is then effected to 75° C. for 8 hours, a calorimetrically determined polymerization conversion of 88% being achieved. 128.55 g of 50% strength sodium hydroxide solution are then added via a dropping funnel in the course of 15 min. In order to complete the reaction, heating to 95° C. is effected and this temperature is maintained for two hours and then cooling is effected. The batch is washed over a 32 μm sieve and dried. 485 g of a non-microencapsulated monodisperse polymer having a uniform particle size of 230 μm are obtained.

Example 2

Preparation of a Non-Microencapsulated Monodisperse Bead Polymer From Microencapsulated Monodisperse Monomer Droplets
In a 4 l vessel with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and temperature chart recorder, an initially introduced aqueous mixture of 440.4 g of demineralized water, 1.443 g of gelatin, 0.107 g of resorcinol and 0.721 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 500 g of microencapsulated monodisperse monomer droplets having a uniform particle size of 235 μm is added to this initially introduced mixture with stirring at 150 rpm (revolutions per minute), the microencapsulated monodisperse monomer droplets consisting of a capsule content of 99 parts by weight of styrene, 1 part by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as initiator (free radical initiator) and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating is then effected to 75° C. for 6 hours, a polymerization conversion of 65% being achieved. 60.1 g of 50% strength sulphuric acid are then added via a dropping funnel in the course of 15 min. In order to complete the reaction, 75° C. is maintained for a further 2 hours, heating to 95° C. is then effected, 95° C. is maintained for a further 2 hours and cooling is effected. The batch is washed over a 32 μm sieve and dried. 488 g of a monodisperse polymer having a particle size of 230 μm are obtained.

Example 3

Preparation of a Non-Microencapsulated Monodisperse Bead Polymer From Microencapsulated Monodisperse Monomer Droplets
In a 4 l vessel with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and temperature chart recorder, an initially introduced aqueous mixture of 440.4 g of demineralized water, 1.443 g of gelatin, 0.107 g of resorcinol and 0.721 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 500 g of microencapsulated monodisperse monomer droplets having a uniform particle size of 330 μm is added to this initially introduced mixture with stirring at 150 rpm (revolutions per minute), the microencapsulated monodisperse monomer droplets consisting of a capsule content of 96 parts by weight of styrene, 4 parts by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as initiator (free radical initiator) and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating is then effected to 75° C. for 7 hours, a calorimetrically determined polymerization conversion of 90% being achieved. 85 g of 50% strength sodium hydroxide solution are then added via a dropping funnel in the course of 15 min. In order to complete the reaction, heating to 95° C. is effected and this temperature is maintained for two hours and cooling is then effected. The batch is washed over a 32 μm sieve and dried. 483 g of a monodisperse polymer having a particle size of 325 μm are obtained.

Example 4

Preparation of a Non-Microencapsulated Monodisperse Macroporous Bead Polymer From Microencapsulated Monodisperse Monomer Droplets
In a 4 l vessel with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and temperature chart recorder, an initially introduced aqueous mixture of 440.4 g of demineralized water, 1.443 g of gelatin, 0.107 g of resorcinol and 0.721 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 500 g of microencapsulated monodisperse monomer droplets having a uniform particle size of 380 μm is added to this initially introduced mixture with stirring at 150 rpm (revolutions per minute), the microencapsulated monodisperse monomer droplets consisting of a capsule content of 94 parts by weight of styrene, 6 parts by weight of divinylbenzene, 64 parts by weight of isododecane as a porogen and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as initiator (free radical initiator) and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating is then effected to 73° C. for 6 hours, a polymerization conversion of 85% being achieved. 60.17 g of 50% strength sodium hydroxide solution are then added via a dropping funnel in the course of 15 min. In order to complete the reaction, heating to 95° C. is effected and this temperature is maintained for two hours and cooling is then effected. The batch is washed over a 32 μm sieve and dried in vacuo at 80° C. for 24 hours. 290 g of a monodisperse, macroporous polymer are obtained.

Example 5 (Comparative Experiment)

Preparation of a Microencapsulated Monodisperse Bead Polymer From Microencapsulated Monodisperse Monomer Droplets
In a 4 l vessel with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and temperature chart recorder, an initially introduced aqueous mixture of 440.4 g of demineralized water, 1.443 g of gelatin, 0.107 g of resorcinol and 0.721 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 500 g of microencapsulated monodisperse monomer droplets having a uniform particle size of 235 μm is added to this initially introduced mixture with stirring at 150 rpm (revolutions per minute), the microencapsulated monodisperse monomer droplets consisting of a capsule content of 99 parts by weight of styrene, 1 part by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as initiator (free radical initiator) and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Thereafter, heating to 75° C. for 8 hours and heating to 95° C. for a further two hours and then cooling are effected. The batch is washed over a 32 μm sieve and dried. 488 g of a monodisperse polymer having a particle size of 230 μm are obtained.

Example 6

Checking of the Kinetics of Swelling
300 g of demineralized water, 1.2 g of boric acid and 0.3 g of sodium hydroxide are initially introduced into a 1 l stirred vessel and in each case 100 g of polymer from examples 1, 2 and 5 are added with stirring at 150 rpm. A monomer mixture of 238.3 g of styrene, 20 g of acrylonitrile and 41.7 g of divinylbenzene (80%) is then added dropwise at 25° C. over a period of 30 min. Immediately after the addition of the monomer mixture, and thereafter at intervals of 30 min, samples are taken and the amount of monomer mixture which has swollen into the polymer is determined from the increase in volume.

Amount of monomer mixture which has swollen in



	From	From	From
Polymer	example 1	example 2	example 5

After addition	96%	90%	22%
of the monomer
mixture
30 min swelling	100%	100%	48%
time
60 min swelling	100%	100%	70%
time
90 min swelling	100%	100%	86%
time
120 min swelling	100%	100%	92%
time
150 min swelling	100%	100%	96%
time

The experiment shows the considerably better kinetics of swelling of non-microencapsulated monodisperse bead polymers prepared according to the invention in comparison with a microencapsulated monodisperse bead polymer not prepared according to the invention.

Example 7

Checking of the Seed-Feed Polymerization
1 100 g of demineralized water, 3.6 g of boric acid and 1 g of sodium hydroxide are initially introduced into a 4 l vessel with a plane-ground joint, having a gate stirrer, a condenser, temperature sensor and thermostat and a temperature chart recorder, and in each case 300 g of bead polymer from examples 1, 2 and 4 are added with stirring at 340 rpm. A monomer mixture of 715 g of styrene, 60 g of acrylonitrile, 125 g of divinylbenzene (80%) and 7.2 g of dibenzoyl peroxide is then added dropwise at 25° C. over a period of 30 min. After the addition, stirring is effected at 25° C. for a further 30 min in the case of the bead polymers from examples 1 and 2 and for a further 2.5 hours in the case of example 4. Thereafter, a solution of 2.4 g of methylhydroxyethylcellulose in 120 g of demineralized water is added and the gas space is flushed with nitrogen. The batch is then heated to 63° C. for 10 hours and then to 95° C. for 2 hours. After cooling, the suspension obtained is washed over a 200 μm sieve and the product is dried at 80° C. overnight in a drying oven and weighed. For determining the yield, the weighed amount is reduced by the amount of seed polymer used and divided by the amount of monomer mixture.

From From From

Polymer example 1 example 2 example 5

Yield of the seed- 97% 96% 88%

feed polymerization
In the seed/feed process for the preparation of, for example, ion exchangers, the substantial superiority of non-microencapsulated monodisperse bead polymers is evident.

Example 8

Preparation of a Non-Microencapsulated Feed Polymer From Microencapsulated Monomer Droplets
In a 4 l vessel with a plane-ground joint, having a gate stirrer, a condenser, temperature sensor and thermostat and a temperature chart recorder, an initially introduced aqueous mixture of 880 g of demineralized water, 2.89 g of gelatin, 0.22 g of resorcinol and 1.44 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 380 g of microencapsulated monodisperse monomer droplets having a uniform particle size of 235 μm is added to this initially introduced mixture with stirring at 150 rpm, the microencapsulated monodisperse monomer droplets consisting of a capsule content of 99 parts by weight of styrene, 1 part by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as an initiator (free radical initiator) and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating is then effected to 75° C. for 8 hours, a calorimetrically determined polymerization conversion of 88% being achieved. 90 g of 50% strength sodium hydroxide solution are then added via a dropping funnel in the course of 15 min. For completing the reaction, heating to 95° C. is effected and this temperature is maintained for two hours and cooling is then effected. Neutralization is then effected with 127.7 g of hydrochloric acid (32%) in the course of 60 minutes. Thereafter, 912.8 g of feed phase consisting of 737.8 g of styrene, 119.8 g of divinylbenzene (80%), 48.3 g of acrylonitrile and 6.9 g of benzoyl peroxide (75%) are metered over a period of 30 min. Stirring is continued for 60 min at a speed of 210 rpm. 91 g of a 2% strength methylhydroxyethylcellulose solution are then metered. Heating to 63° C. is then effected in the course of 90 min, and stirring is effected at this temperature for 480 min. Thereafter, heating to 95° C. is effected in the course of 60 min and this temperature is maintained for 120 min and cooling is then effected.
The batch is washed and dried. 1 145 g of a monodisperse polymer having a particle size of 390 μm are obtained.

Example 9

Preparation of a Non-Microencapsulated Feed Polymer From Microencapsulated Monomer Droplets Having an Increased Feed Factor
In a 4 l vessel with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and a temperature chart recorder, an initially introduced aqueous mixture of 900 g of demineralized water, 2.96 g of gelatin, 0.22 g of resorcinol and 4.44 g of disodium hydrogen phosphate·12 water is produced. A mixture of 720 g of water and 1 016 g of microencapsulated monomer droplets having a uniform particle size of 400 μm is added to this initially introduced mixture with stirring at 150 rpm, the microencapsulated monomer droplets consisting of a capsule content of 95 parts by weight of styrene, 5 parts by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as an initiator and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating to 75° C. for 8 hours is then effected, a calorimetrically determined polymerization conversion of 92% being achieved. 99 g of 50% strength sodium hydroxide solution are then added via a dropping funnel in the course of 15 min during the heating. For completing the conversion, heating to 95° C. is effected, this temperature is maintained for two hours and cooling is then effected. The batch is washed over a 32 μm sieve and dried. 916 g of a monodisperse polymer having a particle size of 370 μm are obtained.
In the same polymerization apparatus, the feed polymerization is effected using a feed ratio which is not possible without the surface treatment.
An aqueous phase consisting of 550 g of demineralized water, 1.79 g of boric acid and 0.49 g of sodium hydroxide is initially introduced and stirred for 20 minutes. 290 g of seed of the first polymerization are dispersed in this solution at 220 rpm. A feed phase of 362.5 g (corresponds to a feed ratio of 1.25), consisting of 292.5 g of styrene, 43.9 g of 80% pure divinylbenzene, 26.1 g of acrylonitrile and 1.17 g of tert-butyl peroxy-2-ethylhexanoate is metered into this dispersion over a period of 30 min and stirring is carried out for a further 120 min. 65 ml of a 2% strength methylhydroxyethylcellulose solution are then added. Heating to 63° C. is effected in the course of 45 min and this temperature is maintained for 600 min. Heating to 95° C. is then effected in the course of 60 min and this temperature is maintained for 240 min and cooling is then effected.
The batch is washed and dried. 605 g of a monodisperse polymer having a particle size of 470 μm are obtained.

Example 10

Preparation of a Non-Microencapsulated Polymer From Microencapsulated Monomer Droplets
In a 4 litre vessel with a plane-ground joint, having a gate stirrer, condenser, temperature sensor and thermostat and a temperature chart recorder, an initially introduced aqueous mixture of 440.4 g of demineralised water, 1.3443 g of gelatin, 0.107 g of resorcinol and 0.721 g of anhydrous disodium hydrogen phosphate is produced. A mixture of 500 g of water and 500 g of microencapsulated monomer droplets having a uniform particle size of 430 μm is added to this initially introduced mixture with stirring at 150 rpm, the microencapsulated monomer droplets consisting of a capsule content of 95 parts by weight of styrene, 5 parts by weight of divinylbenzene and 0.5 part by weight of tert-butyl peroxy-2-ethylhexanoate as an initiator and a capsule wall of a complex coacervate cured with formaldehyde and comprising gelatin and an acrylamide/acrylic acid copolymer. Heating to 75° C. for 6.5 hours is then effected, a calorimetrically determined polymerization conversion of 89% being achieved. 128.55 g of 50% strength sodium hydroxide solution are then added via a dropping funnel in the course of 15 min. For completing the conversion, heating to 95° C. is effected and this temperature is maintained for two hours and cooling is then effected. The batch is washed over a 32 μm sieve and dried. 487 g of a monodisperse polymer having a particle size of 425 μm are obtained.

Example 11 (Comparative Experiment)

Preparation of a Microencapsulated Polymer From Microencapsulated Monomer Droplets
Example 10 was repeated, except that no sodium hydroxide solution is added. 482 g of a monodisperse polymer having a particle size of 425 μm are obtained.

Example 12

Preparation of Anion Exchangers and Checking of the Mixed-Bed Behaviour Thereof
Anion exchangers comprising 5% of crosslinked polymer, prepared according to examples 10 and 11, were tested.
Chloromethylation
250 ml of monochlorodimethyl ether having an iron (3) chloride content of 13.6 g/l are initially introduced into a four-necked flask equipped with stirrer, condenser, monitoring thermometer and bath heating. Thereafter, 50 g of polymer are metered with stirring and heating to 50° C. is effected in the course of 3 h and 53-55° C. is maintained for a further 6 h. After cooling to room temperature, the excess monochlorodimethyl ether is slowly decomposed with 250 ml of methanol. Thereafter, separation is effected over a frit and the product is washed with methylol and 3-4 methanol washes.
Results:

Yield Chlorine

Experiment Polymer in ml value in %

A from example 11 120 20.9

B from example 10 116 19.7
Animation:
600 ml of water, 150 ml of trimethylamine (50% strength) and 25 g of sodium chloride are initially introduced into a laboratory autoclave equipped with stirrer and jacket heating. The chloromethylated polymer filtered off with suction is transferred to the autoclave. Heating to 50° C. is effected in 1.5 h and this temperature is maintained for 10 h. After cooling, the mixture is transferred to an excess of 5% strength hydrochloric acid and washed with water to neutrality after 4 h.
The polymer used for comparison was chloromethylated and aminated by the same method.
Mixed-bed performance test:
The mixed-bed performance of the anion exchangers obtained was tested as follows:

100 ml of a mixture of 60% by volume of anion exchanger in the OH form, prepared according to the invention, and 40% by volume of Lexatit® Monoplus S 100 in the H form were thoroughly mixed for 14 hours on a vibrating table and then treated in an acid with deionate or dilute salt solutions at a loading of 200 BV/h in the following sequence (BV=bed volume).



	10 min deionate	(about 0.06 μS/cm)
	5 min sodium chloride solution	(1 ppm)
	5 min deionate
	5 min calcium chloride solution	(2.5 ppm)
	5 min deionate
	5 min sodium sulphate solution	(2.5 ppm)

The conductivity at the exit of the column was measured continuously, and the maximum conductivity value for the respective salt solutions was recorded and summed. The better the mixed-bed performance of the resin mixture, the lower is the total conductivity at the exit of the column (minimum 3×0.06 μS/cm deionate quality).
In the most unfavourable case of completely inert behaviour of the resin mixture, a conductivity of about 20 μS/cm at the column exit would result.
Results:

Sum of conductivity

peaks (μmS/cm)

Experiment Polymer (after 14 h)

A from example 11 0.39

B from example 10 0.18
While, in experiment B, the salt ions introduced were exchanged by the resin mixture for OH or H ions in the case of all salt solutions metered, and the conductivity therefore had optimum deionate quality at the exit of the column, in the case of experiment A not all salt ions were taken up by the resin mixture and a considerable residual conductivity was still observed at the column exit.

Claims

1. A process for the preparation of non-microencapsulated monodisperse bead polymers, comprising:

a) preparing an aqueous suspension of

i) microencapsulated monodisperse monomer droplets containing monomer, crosslinking agent and free radical initiator and

ii) dispersant

b) initiating polymerization by increasing the temperature of the suspension to temperatures at which the free radical initiator is active,

c) conducting the polymerization to a polymerization conversion of 20 to 98%,

d) adding strong acids or strong alkalis to c),

e) completing the polymerization and

f) isolating the resulting non-microencapsulated monodisperse bead polymer.

2. A process according to claim 1, wherein the monomer droplets are microencapsulated with a gelatin-containing capsule wall.

3. A process according to claim 1, wherein the addition of strong acids or strong alkalis is added at a polymerization conversion of 20 to 98%.

4. A process according to any of claim 1, wherein the strong alkali used is sodium hydroxide.

5. A process according to claim 4, wherein the sodium hydroxide is used in an amount to provide concentration of sodium hydroxide in the aqueous phase of 0.1 to 5% by weight.

6. A process according to claim 1, wherein the microencapsulated monomer droplets substantially comprise styrene and divinylbenzene.

7. A process according to claim 1, wherein the microencapsulated monodisperse monomer droplets additionally contain a porogen.

8. Non-microencapsulated monodisperse bead polymers obtained by

a) preparing an aqueous suspension from

ii) dispersant,

b) initiating the polymerization by increasing the temperature to temperatures at which the free radical initiator is active,

c) effecting polymerization to a polymerization conversion of 20 to 98%,

d) adding strong acids or strong alkalis,

e) completing the polymerization and

f) isolating the resulting non-microencapsulated monodisperse bead polymer.

9. A method of preparing ion exchangers or cation or anion exchangers, particularly for anion exchangers for use in a mixed bed comprising providing the non-microencapsulated monodisperse bead polymers according to claim 8 in seed/feed processes for the preparation thereof.

10. An adsorber obtained by a process according to claim 1, wherein the microencapsulated monodisperse monomer droplets additionally contain porogens.