Sulphonated polymer resin and preparation thereof

Details Sulphonated polymer resin and preparation thereof Sulphonated polymer resin and preparation thereof

2002-05-28

2003-12-16

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S344000

Reexamination Certificate

active

06664340

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to sulphonated polymer resins, particularly ion-exchange resins, and the preparation of such resins. The invention relates especially to polymer resins whose shell layer is sulphonated, and to the preparation thereof. The polymer material to be sulphonated is typically for example a cross-linked styrene-divinylbenzene copolymer (a styrene copolymer cross-linked with divinylbenzene). The obtained sulphonated polymer resins are useful for example as chromatographic resins, ion-exchange resins and catalyst resins, either in a spherical or pulverized form.
Polystyrene-based resins are conventionally sulphonated for example by concentrated sulphuric acid in a swelling agent (usually a chlorohydrocarbon). However, the use of chlorohydrocarbons has been reduced for example due to environmental reasons. Polystyrene-based resins have also been sulphonated directly by a gaseous sulphur trioxide. It has been noted, however, that the obtained products where polymer particles are fully sulphonated are not physically stable but they tend to break.
European Published Application 0,361,685 (Rohm & Haas Co.) describes partly functionalized, for example sulphonated, polymer resin particles and a process for producing them. The process provides polymer resin particles where 68 to 98% of the accessible functionalizable sites are functionalized (e.g. sulphonated). The unfunctionalized sites are situated in the inner core of the particles, whereas the functionalized groups are located in the shell layer of the particles. The depth of functionalization can be for example 0.32 to 0.75 times the average radius of the polymer particles. In this publication the sulphonation is carried out with concentrated sulphuric acid at a normal pressure at a high temperature, such as 120 to 140° C.
U.S. Pat. No. 3,252,921 (Dow Chemical Company) describes partial/heterogeneous sulphonation of alkenylaromatic polymer resins by first using a swelling agent (a chlorohydrocarbon) and by thereafter carrying out the actual sulphonation with chlorosulphonic acid or liquid sulphur trioxide. This provides polymer particles with a sulphonated shell layer.
Example 3 of German Offenlegungsschrift 2,627,877 (Sumitomo Chemical Co.) describes sulphonation of fibrous polyethylene with gaseous sulphur trioxide in a vacuum. According to claim
4
, the process is carried out at a low temperature (10 to 90° C.). The degree of sulphonation may vary within a broad range, such as 0.01 to 10 meq/g. The sulphonation reagent is said to have a concentration preferably in a range of from 10 to 80% by volume of SO
3
. If the SO
3
content of the sulphonation gas is higher, the sulphonation reaction does not proceed in a uniform manner.
French Patent 1,280,353 (Rohm & Haas Co.) describes the sulphonation of macroporous vinylaromatic polymers with gaseous sulphur trioxide (usually in a mixture with air) at a normal pressure. According to the examples, the temperature varies from 60 to 100° C. The publication does not disclose the preparation of partly sulphonated products.
Definitions
The extent to which resins are sulphonated is indicated by their degree of sulphonation, which is usually given in dry weight capacity. The theoretical dry weight capacity (one sulphone group per benzene ring) of a monosulphonated styrene-divinylbenzene copolymer resin varies between 4.8 and 5.4 meq/g.
One of the essential properties of ion-exchange resins is their capacity. The capacity of a sulphonated styrene-divinylbenzene copolymer resin indicates how many H
+
ions it can exchange per one mass and/or volumetric unit of resin. The capacity can be given as dry weight capacity or volume capacity. The dry weight capacity is indicated as milliequivalents per one gram of dry resin (meq/g) and the volume capacity is indicated as equivalents per one litre of fully swollen resin (eq/l).
When a resin is transferred from one medium to another, it may either swell or shrink. Great changes in the volume hinder the use of the resin in columns, wherefore the variation in volume should be minimal.
Resin particle size and the distribution thereof essentially affect the behaviour of an ion-exchange resin, such as kinetics of mass transfer, pressure drop over a backed bed, flow channelling and the degree of packing of the bed. The mean particle size of resin or the mean sphere size (resin particles are usually spherical) refers to an average based on the volume or mass proportion of different size fractions. The sharpness of the sphere size distribution is generally described by means of a uniformity coefficient (UC). This coefficient is calculated by forming a quotient between a mesh size that retains 40% of resin particles and a mesh size retaining 90% of resin particles. This ratio is given value 1 when all the particles are of equal size. For example, a typical resin intended for water treatment has a uniformity coefficient UC=1.7. The UC of industrial chromatographic separation resins varies between 1.05 and 1.25.
The degree of cross-linking of the sulphonated styrene-divinylbenzene copolymer resin is dependent on the amount of the divinylbenzene used as a cross-linking agent during the polymerization. A gel-type resin normally comprises 1 to 12% of divinylbenzene. The degree of cross-linking affects for example the mechanical strength, ion exchange capacity, water retention capacity, swelling, selectivity and chemical stability of the ion exchanger. Resins with a low degree of cross-linking are soft and mechanically unstable, whereas a high degree of cross-linking provides hardness, fragility and increased sensitivity to osmotic effects.
There are two main types of ion-exchange resins (e.g. sulphonated styrene-divinylbenzene copolymer resins): gel-type and macroporous resins. A macroporous ion-exchange resin is a resin where additional blowing agent has been added to the monomer mixture during polymerization and removed thereafter. This provides a structure with far greater pores than in the polymer network. A gel-type ion-exchange resin, in turn, refers to a resin where the porosity is only based on the porosity of the cross-linked polymer network.
Mechanical strength describes the resin's ability to resist wearing. In a physically advantageous ion-exchange resin the particles are spherical in shape, and the resin does not comprise cracks and is not fragile. Mechanical strength is examined for example by a cyclic test of watering and drying, where the resin strength is examined by subjecting the resin to repeated watering and drying operations. Physical hardness is measured by means of compression resistance. The resistance of a resin to osmotic forces is important in industrial applications. Several methods have been introduced to measure the resistance of a resin to osmotic shock.
Chemical stability of a resin refers to the resistance of active groups and the hydrocarbon backbone particularly to oxidation.
The primary factor restricting the use of a strongly acidic cation-exchange resin at high temperatures is desulphonation. A typical maximum operating temperature of such resins in long-term use is 120° C.
In the present invention the sulphonation of the shell layer means that the polymer particles are not fully sulphonated but the sulphonation is only effected beginning from the surface of the particles so that the core remains unsulphonated. There is a clearly defined interface between the sulphonated and unsulphonated regions. The sulphonation depth can vary.
Sulphonation with ‘substantially pure gaseous sulphur trioxide’ means in the present invention that the space where the sulphonation is carried out is substantially free of diluting gas components, such as air.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is to provide a process for preparing a sulphonated stable polymer resin so that the sulphonation can be carried out without a swelling agent, such as a chlorohydrocarbon. This problem has been solved in the invention such that the sulphonation of a polymer resin in a non-swo

Affiliated with

Also associated with

Rating

Sulphonated polymer resin and preparation thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Sulphonated polymer resin and preparation thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sulphonated polymer resin and preparation thereof will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3184228