GB1581671A - Porous acrylate resins - Google Patents

Description

(54) POROUS ACRYLATE RESINS (71) We, MONTEDISON S.p.A., a Body Corporate organised and existing under the laws of Italy, of 31 Foro Buonaparte, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to porous resins suitable as adsorbers for purifying and/or decol ourising aqueous solutions containing high molecular weight polar or apolar compounds coming from industrial processings.

The invention provides a porous resin having a mean pore radius of at least 5 A and a specific area of at least 5 m2/g, the resin being a homopolymer of a poly-functional acrylate containing at least three acrylic groups or a copolymer of such an acrylate with a monomer copolymerizable therewith.

Resins according to the invention are useful in purification and decolourising of industrial waste waters containing high molecular weight polar and ionic compounds, particularly waste waters from the preparation of dyes. They have good mechanical characteristics such as resistance to mechanical stresses occurring during the purification and decolourising opera tions, which stresses can cause flaking of the adsorbing product and consequent caking in the adsorption column with a resultant increase in the pressure drop. They also have good resistance to thermal degradation, in particular to pyrolysis, especially a considerable resis tance to elutions carried out at temperatures above 1200C or in gas chromatographic applications, in which the adsorbing product acting as a carrier may be subjected to tempera tures as high as 250"C to 3000C.

Resins according to the invention can be converted into ion exchange resins by introducing suitable exchange functions into the resin matrix. The resins are also useful as carriers for catalysis, as fillers in gel-permeation chromatography and in general as the stationary phase in gas chromatographic appliances.

The polymers constituting said resins preferably contain from 2 % to 100 % by weight pf the 'polyfunctional acrylate, which is preferably trimethylolpropane-triacrylate or pentaerythritol-tetraacrylate. In the case of the copolymers, the monomers copolymerizable with the acrylate may be aliphatic vinyl monomers such as allylacrylate, aromatic vinyl monomers such as divinylbenzene or difunctional methacrylates such as ethylene glycol dimethacrylate.

Resins according to the invention may be prepared by a process, also within the scope of the invention, which process comprises polymerizing in suspension the polyfunctional acry late, optionally with a monomer copolymerizable therewith. General details of the polymer ization include preparing an aqueous phase in which, besides deionized water, suspending, stabilizing products and buffering agents are present, such as polyvinyl alcohol, polymethac rylates, carboxymethylcellulose, sodium chloride and alkali, in variable ratios; and adding to the aqueous phase a monomer phase containing, besides the acrylic monomer or the mono mer mixture in a suitable ratio, for example from 2% upwards of the acrylate and up to 98 of the monomer copolymerizable therewith, suitably an aliphatic or aromatic vinyl monomer or a difunctional methacrylate monomer, one or more solvents for the monomer(s) which solvent(s) are non solvent(s) for the copolymer, the solvent being chosen and its amount being chosen according to the structural characteristics desired in the resin, and a radical polymerization initiator. Suitable solvents are benzene; toluene; xylene; aliphatic hydrocar bons such as hexane, heptane, octane and isooctane; and alcohols such as amyl, hexyl and decyl alcohols, preferably in admixture. Organic peroxides and azo-compounds, for example dibenzoylperoxide, lauroylperoxide and azo-bis-isobutyronitrile, are usually employed as initiators. The two phases may be mixed and heated, under stirring to temperatures of from 30"C to 1200C, preferably from 60"C to 90"C. The polymerization product may, after recovery, be freed from the solvent or from the solvent mixture by washing, and may then be dried.

The resins so obtained exhibit specific surfaces of at least 5 m2/g, generally of from 5 to 1000 m2/g, and a pore mean radius of at least 5 , generally of from 5 to 800 .

The following Examples, in which all parts and percentages are parts and percentages by weight, illustrate the invention.

The characteristics referred to in the Table appended to the Examples were determined as follows: Specific area in m2/g was determined according to the B.E.T. method described in Journal of the American Chemical Society, Vol. 60, page 309 (1938).

Effective density in g/cc was determined using a helium density bottle.

Porosity was calculated from the values of effective density determined as aforesaid and of apparent density in g/cc determined using a mercury density bottle, and is expressed as a percentage.

Mean pore radius was calculated from the values of specific area, of effective density and of apparent density, and is expressed in .

Adsorption capacity, a measurement of efficiency in purifying and decolourising, was deter- mined by percolating an industrial water, having a colour index of 6700 Hazen colour degrees (at 420 m,u ) and a C.O.D. of 110 g/litre, through a glass column of 20 mm diameter and 650 mm height, filled with the adsorbing resin for a useful height of 300 mm. Percolation was conducted at room temperature at a specific capacity of 2 volumes per volume of adsorbing resin per hour. Detections of Hazen colour degrees and of C.O.D. were effected on the effluent at intervals of 30, 60 and 90 minutes.

Hazen colour degrees measure the colour intensity and have been determined according to the method described in Sections 118 and 206 of "Standard Methods for the Examination of Water and Waste Water", 13th edition, 1971, published by A.P.H.A. and A.W.W. and W.P.C.F.

The C.O.D. represents the consumption of chemical oxygen, is a measure of the amount of organic and inorganic matters dissolved in water, and was determined according to the method described in Section 220 of the above-mentioned volume.

Resistance to mechanical stress has been determined (a) by grinding tests and (b) by abrasion tests, both carried out on beads, according to the following techniques: (a) 200 g of dry product having a particle size from 0.42 mm to 0.85 mm was introduced into a ceramic cylindrical jar having an internal capacity of 1.5 litres, an internal diameter of 125 mm, an external diameter of 160 mm and a useful height of 130 mm, containing thirty steatite spheres, of which ten have a diameter of 12 mm and a weight of 2.5 g, ten have a diameter of 28 mm and a weight of 32 g and ten have a diameter of 36 mm and a weight of 75 g. The whole was made to roll on itself, horizontally, for 60 minutes at 45 r.p.m. The product was then screened and the fraction having a particle size greater than 0.42 mm was weighed.

The resistance to grinding is the weight of this fraction expressed as a percentage of the weight of the total product. (b) 10 g of dry product having a particle size from 0.42 mm to 0.85 mm were introduced into a stainless steel cylinder having smooth inside walls, an internal diameter of 41 mm, an external diameter of 46 mm, a height of 232 mm, a weight of 1 kg and a threaded closure. The cylinder was subjected for 40 minutes to a rotational and translational motion of 235 oscillations/minute with an amplitude of 80 mm, by means of a horizontal traverse slide, the cylinder being arranged in a horizontal position perpendicular to the oscillation direction. At the conclusion of the test the product was screened and the fraction having a particle size greater than 0.42 mm was weighed. The resistance to abrasion is the weight of this fraction expressed as a percentage of the weight of the total product.

Resistance to thermal degradation was determined by using 10 mg samples introduced into a thermoanalyzer, mod. 900 Du Pont, equipped with a TGA module, mod. 950. The decomposition of the adsorbing products due to pyrolysis has been examined in the temperature range of from 100"C to 6000C, at a heating rate of 10 C/minute and under a nitrogen stream of 10 litres/hour.

In particular the temperature at which decomposition began and the temperatures at which 10% and 50% of the product had decomposed were recorded.

Example I There were introduced into a glass flask, equipped with heating, stirring and reagent feeding systems: deionized water 1600 parts polyvinyl alcohol 6.4 parts carboxymethylcellulose 4.8 parts sodium polymethacrylate 20 parts sodium chloride 48 parts NaOH to neutrality trimethylolpropane triacrylate (TMPTA) 200 parts toluene 400 parts laurylperoxide 1% on the monomer The reaction mixture was maintained under suitable stirring at a temperature of 70"C for 8 hours and then 80"C for 4 hours. The polymer so obtained was in the form of beads having a particle size of from 0.3 to 1.2 mm, whose characteristics are reported on Table 1. From Table 1 it appears evident that the polyfunctional acrylic homopolymer is effective in decolourising and in purifying the industrial waste waters, and exhibits good resistance to grinding, to abrasion and to thermal degradation.

Example 2 A copolymer of TMPTA with ethylene glycol dimethacylate (EGDMA) was prepared by operating as in Example 1, except that the 200 parts of TMPTA and 400 parts of toluene were replaced by 242 parts of TMPTA, 146 parts of EGDMA and 335 parts of toluene.

The characteristics of the copolymer are reported in the Table.

Example 3 A copolymer of TMPTA with allylacrylate (AA) was prepared by operating as in Example 1, except that the 200 parts of TMPTA and 400 parts of toluene were replaced by 242 parts of TMPTA, 121 parts of AA and 330 parts of toluene.

The characteristics of the copolymer are reported in the Table.

Example 4 A copolymer of TMPTA with divinylbenzene (DVB) was prepared by introducing into the apparatus described in Example 1 the following: deionized water 1460 parts sodium polymethlmethacrylate 47 parts complex silicates 7.5 parts sodium chloride 1.1 parts NaOH to neutrality commercial divinylbenzene at 60% of DVB 495 parts (TMPTA) ' 55 parts toluene 952 parts and by heating the whole as in Example 1. The characteristics of the copolymer are reported in the Table.

Example 5 A homopolymer of pentaerythritoltetraacrylate (PETA) was prepared by operating as in Example 1, except that the 200 parts of TMPTA and 400 parts of toluene were replaced by 304 parts of PETA and 396 parts of toluene. The characteristics of the resulting copolymer are reported in the Table.

TMPTA TMPTA/EGDMA TMPTA/AA TMPTA/DVB PETA homopolymer copolymer copolymer copolymer homopolymer PHYSICAL CHARACTERISTICS: Specific area in m2/g 350 375 265 620 455 Effective density in g/cc 1.29 1.33 1.28 1.13 1.25 Porosity (%) 54 44.3 37.5 44.3 64.8 Mean pore radius in 65 39 44 25 73 ADSORPTION CAPACITY: 1st sample at 30 minutes Hazen 0 127 3 132 0 C.O.D. in g/l 0.04 12.1 0.12 15 0.02 2nd sample at 60 minutes Hazen 57 400 427 415 32 C.O.D. in g/l 14 52.6 31.3 57.7 11 3rd sample at 90 minutes Hazen 310 1170 670 2200 196 C.O.D. in g/l 52 86.7 59.5 90.7 46 MECHANICAL RESISTANCE: Resistance to grinding (%) 84 94 94 91 92 Resistance to abrasion (%) 90 99 99 90 96 THERMAL RESISTANCE: decomposition starting temperature in C 325 300 300 250 250 10% decomposition temperature in C 420 405 410 425 425 50% decomposition temperature in C 475 465 475 468 466

Claims (13)

WHAT WE CLAIM IS:

1. A porous resin having a mean pore radius of at least 5 A and a specific area of at least 5 m2/g, the resin being a homopolymer of a polyfunctional acrylate containing at least three acrylic groups or a copolymer of such an acrylate with a monomer copolymerizable therewith.

2. A resin according to claim 1 in which the acrylate is present in an amount of from 2% to 100% by weight.

3. A resin according to claim 1 or claim 2 in which the acrylate is trimethylolpropane triacrylate or pentaerythritol tetraacrylate.

4. A resin according to any preceding claim being a copolymer of the acrylate with an aliphatic vinyl monomer.

5. A resin according to claim 4 in which the aliphatic vinyl monomer is allylacrylate.

6. A resin according to any of claims 1 to 3 being a copolymer of the acrylate with an aromatic vinyl monomer.

7. A resin according to claim 6 in which the aromatic vinyl monomer is divinylbenzene.

8. A resin according to any of claims 1 to 3 being a copolymer of the acrylate with a difunctional methacrylate.

9. A resin according to claim 8 in which the difunctional methacrylate is ethylene glycol dimethacrylate.

10. A process for the preparation of a porous resin having a mean pore radius of from 5 A to 800 A and a specific area of from 5 m2/g to 1000 m2/g, the process comprising polymerizing in suspension 2%to 100%by weight of a polyfunctional acrylate containing at least three acrylic groups with 0% to 98% by weight of an aliphatic or aromatic vinyl monomer or a difunctional methacrylate monomer, at a temperature of from 30"C to 1200C, in the presence of a solvent for the monomer which solvent is a non-solvent for the copolymer.

11. A porous resin substantially as described herein with reference to any one of the Examples.

12. A process for the preparation of porous resin the process being substantially as described herein with reference to any one of the Examples.

13. A porous resin prepared by a process according to claim 10 or claim 12.