JPS5915136B2 - Highly adsorptive macroporous polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to the condensation of melamine with improved adsorption properties and formaldehyde in the presence of an acid catalyst and an internal diluent to form a macroporous (Mac
OpOrOus).

It is well known to react amino-containing materials with aldehydes to form reactive monomers, which are then polycondensed to produce thermoset resins.

Perhaps the most common resin of this type is melamine resin, which results from the condensation of melamine and formaldehyde. These resins are widely used as molding compounds, adhesives, wet strength resins, and fabric coating compositions. Conventional amino resins do not exhibit useful sorption capacity and are relatively unstable under the conditions of use as adsorbents.

It is therefore desirable to produce multi-macroporous amino resins that have increased mechanical and osmotic stability while at the same time being permeable to fluids. Such permeability facilitates flow and diffusion through the resin in the liquid phase and enhances its utility as an absorption, adsorption, catalyst, etc. polyamino
It has been shown that highly adsorptive, multi-macroporous amino resins can be prepared by reacting triazine and formaldehyde in a molar ratio of about 1:2 to 1:7 in the presence of a miscible organic porogen and an acid catalyst. discovered.

The reaction mixture is stirred and heated to at least about 65° C. until gelation occurs. The resin is then cured to produce a material with high porosity and surface area on the order of 10 i/t or more. Resins produced by the method of the present invention have high mechanical and osmotic stability and greatly improved adsorption properties compared to conventional non-porous amino resins.

This multi-macroporous resin has been shown to have exceptional adsorption capacity for the removal of colorants and organic materials from solutions such as wood pulp bleaching wastewater, and has also been shown to have excellent adsorption capacity for the removal of colorants and organic substances from solutions such as wood pulp bleaching wastewater, as well as for supporting enzymes, catalysts, biocides, etc. Useful as a material. According to the present invention, melamine is reacted with formaldehyde to produce a basic resin.

The term formaldehyde refers not only to formaldehyde itself, but also to compounds that produce formaldehyde, such as:
Includes paraformaldehyde, etc. Formaldehyde is generally preferred for use as the aldehyde component, usually in the form of a 30-45% aqueous solution. This is because the production of resins is generally carried out in an aqueous medium. The molar ratio of melamine to formaldehyde is particularly critical and can range from about 2 to about 7 depending on the desired properties of the final product.

For the preferred system of melamine and formaldehyde,
A ratio of 3 to 5 moles of formaldehyde per mole of melamine has been found to be most suitable for the process of the invention. It has been determined that the condensation reaction of melamine and formaldehyde is significantly affected by pH, and the optimum pH range for macroporous resin precipitation is from about 2 to about 5.

Finally, the use of acids to catalyze the condensation in this process is recommended. Catalysts such as formic acid, sulfuric acid, hydrochloric acid and acetic acid can be used. Formic acid has been found to be the most effective in this process and is the preferred catalyst. The amount of acid catalyst can range from about 0.01 to about 0.10 mole per mole of melamine, with 0.04 to 0.06 mole being common concentrations. The use of effective miscible organic internal diluents is essential to the production of macroporous resins with the desired properties of high adsorption and large surface area. The internal diluent should be miscible with all of the reaction components. During condensation, the internal diluent acts to introduce the desired sponge-like macroporous structure into the final resin. Internal diluents can be selected from organic substances such as alcohols, thiols, amides, ethers, esters, or mixtures thereof. The preferred porogen for the process of the invention is n-propanol, which is miscible with all of the initial reaction components in the process and which allows final removal at normal drying temperatures above standard polymerization temperatures. A suitable boiling point (low enough to allow
97°C). The internal diluent can be present in the reaction mixture over a wide range of concentrations, usually from about 5% to about 30% of the total volume. Concentrations in the range of 16-20% by volume have been found to yield optimal adsorption to the product resin for the preferred melamine-formaldehyde system.

Other specific internal diluents useful in this method include ethoxyethanol and dimethylformamide. Since the production of the resin is carried out in an aqueous medium, the total amount of solids in the initial reaction mixture is not critical and usually ranges from 30 to 30% of the total mixture.
It is in the range of 55% by weight.

A solids content of about 45% was found to produce the most suitable resin, lower amounts produced a brittle resin, and higher amounts were found to reduce the porosity of the product.
The monomers, catalyst, and porogen are all fed into a suitably sized reactor, made of conventional glass or stainless steel, and equipped with conventional heating and agitation means.

The pH of the reaction mixture initially ranges from 2 to 5. The reaction mixture is gradually heated and stirred until dissolution of the initial reaction components is complete, then heating is continued until polymerization begins and a gel forms. This initial reaction is about 65°C to about 95°C.
, preferably at temperatures ranging from about 70<0>C to about 85<0>C. The initial reaction time depends on the temperature used and the rate of heat input into the reaction mixture. The average rate of temperature increase of the reaction mixture is maintained in the range 0.5-5°C 7/min until gelation. The reaction time increases with decreasing initial temperature. At 75°C the reaction continues for more than 30 minutes.

The reaction can be carried out under pressure, and pressure will affect the temperature and time mentioned above. After the initial reaction, the resin is cured for about 2-20 hours at ambient temperature to 100<0>C.

Cure time can be reduced by increasing the temperature to the upper end of the range. During the curing process, the condensation is completed and the degree of cross-linking increases. Completion of cure can be determined by measuring the stability of the resin to acidic hydrolysis. The product resin is then crushed, milled to the desired particle size, and washed. The resin has an ordinary physical appearance. The characteristic substance has a repeating unit of the following formula ＼ / N, and has a repeating unit of 10Tr1/f or more, about 1000
It will have a surface area of up to I/f (determined by B.E.T. nitrogen multipoint analysis) and a porosity (determined by heptane fraction) of 0.2 to 1.0 m1/y.

The oxidation resistance (measured by oxidation of H2O2) is 100% at ambient temperature for up to 5 hours. A typical resin is
It has an adsorption capacity of more than 200 kg/I as cobalt chloroplanate for "E" wastewater from a paper pulp mill, compared to 50 kg/I for conventional non-porous amino resins.
It has lower adsorption than M3. The final resin can be further processed by known methods, for example by reaction with epichlorohydrin and/or amination, to produce materials with different properties. The resins of the present invention have particular utility for the adsorption removal of organic substances from fluid media.

A typical application is the treatment of paper pulp mill effluents containing colored bodies of condensed guiacylpropane type structure with carbonyl and carboxyl groups and phenolic hydroxyl groups. Such substances are effectively removed by contact with the multi-macroporous resin of the present invention. The resin also has an average adsorption capacity for typical organic substances, i.e. 85-90% removal rate in 0.01 molar p-nitrophenol solution and 70% removal rate in munitions factory red wastewater. shows. The present invention will be further explained by the following example for determining σ.

Example 1 and Reference Example 1 (Application) 225f of melamine, 536ml of formaldehyde (
37%, aqueous solution), 240 ml of n-propanol and 12 ml of 88% formic acid were mixed in a jacketed resin pin with a stirrer, condenser and thermometer.

The mixture was stirred and heated to 80°C until gelation occurred (after about 20 minutes). After cooling, the product was removed from the bottle, ground and washed with water. The resin is an opaque solid with a pore volume of 0.6 m''/7, a surface area of 160 m''/7 and 280 kg as cobalt chloroplatinate.
/M2 of adsorption capacity for pulp mill wastewater. Example 2 and Reference Example 2 (Application) 765y melamine, 1608mZ formaldehyde (37%), 720ml n-propanol and 36
1 t1 of 88% formic acid was combined as in Example 1.

The mixture was stirred and heated to 75° C. until it gelled (approximately 30 minutes). Heating was continued at 80°C for an additional 12 hours. After cooling, milling and washing, the product resin is a white opaque solid with a pore volume of 0.74 m1/f, 1
It has a surface area of 80 TrI/7 and an adsorption capacity for paper mill wastewater of 360 kg/M3 as cobalt chloroplatinate. Example 3 and Reference Example 3 (Application) 44.3y of melamine, 63.2y of paraformaldehyde, 85mZ of water, 57w11f) n-propanol and 1.9ml of 95% sulfuric acid were combined as in Example 1. The mixture was stirred and heated to 78° C. until gelation occurred.

Heating was continued for an additional 16 hours at about 80°C, after which the material was cooled, ground, and washed. The product is then reduced to 100
Heated for a further 48 hours. The resulting resin was a white opaque solid with a pore volume of 0.35 m1/i and an adsorption capacity for paper valve mill effluent of 125 W9/i as cobalt chlorobratinate. Example 4 63V melamine, 150.5ml formaldehyde (37%), 25mZ ethoxyethanol, 75ml
of water and 3.35 ml of 88% formic acid were mixed as in Example 1.

The mixture was stirred and heated to 80° C. until gelling occurred. Heating was continued at 80°C for an additional 23 hours. The material was cooled, ground and washed. The resin was an opaque solid and had a surface area of 213 I/7. Example
565y melamine, 150.5ml formaldehyde (37%), 25mZ dimethylformamide, 75
WL1 of water and 3.35 ml of 88% formic acid were mixed and reacted as in Example 4.

The product of the resin is an opaque solid, 211TrI/f
It had a surface area of Example 6 and Reference Example 4 (Application) The giant porous resin of the present invention was produced on a large scale using a polymerization bottle with a capacity of 1901.

While stirring the reaction components, proceed in the following order: 104
．． 91 of formaldehyde (37%, aqueous, suppressed with methanol), 44.1 of melamine, 471 of n-propanol, and 2.351 of 88% formic acid were added in this order. The contents of the pin were gradually heated while stirring. The stirrer was removed when the mixture reached approximately 65°C and heating continued until gelation occurred. A mild exotherm then caused the temperature to rise to 80-85°C.
The bottle jacket temperature was then increased to approximately 85°C and maintained at this temperature for 4 hours. The resin product was then cooled, ground and washed. The reaction conditions and product properties for several batches are shown in the table below. The resin produced in Example 1 was used to decolorize tannin-containing surface water.

600APHA surface water flow to 1 inch (2.5
1 in a volume of 50 ml of resin in a column of 4 (V7!)
It passed at a speed of 1 ml/min.

A total of 12.51 waters were bleached to an average of 25 APHA units, with maximum color being 75 APHA units. Reference example 6 (
Application) The resin produced as in Example 1 was added to the N of bleached sulfate paper pulp mill liquor, referred to as "E" effluent.
It was used to decolorize the aOH extract.

The strength extract with a total color of 5355 APHA units was adjusted to PH4.

This solution was then poured into a 50 m glass column with a diameter of 2 cm.
of resin at a rate of 5 ml/min (6 bed volumes/hour). Column effluent was collected in aliquots, the pH was adjusted to 7.6, and compared to standards prepared from the feed solution to determine the percentage of colored material removed. The experiment was stopped at any point where the color removal rate decreased to 70%. For the resin of the invention, this resulted after treatment of a total of 350 kg/M3 of colored substances, expressed as cobalt chloroplatinate. Three other commercially available adsorbents were tested in the same manner and the results are reported in the table below.

Claims (1)

[Claims] 1. Melamine and formaldehyde in a ratio of 1:2 to 1:
reacting in the presence of an acidic catalyst and at least one miscible organic internal diluent in a molar ratio of 7 to 7, heating until gelation occurs and then curing the resulting resin,
It has a repeating unit of the following formula, a porosity of 0.2 ml/g or more as measured by heptane fraction, and a B. E. T. A method for producing a highly adsorptive, macroporous resin having a surface area of 10 m^2/g or more as measured by nitrogen multipoint analysis. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ 2. The proportion of miscible organic internal diluent is 5 to 5 of the total reaction mixture.
30% by volume. 3. A method according to claim 1, wherein the reaction mixture is heated to a temperature in the range of 65-95°C before gelling. 4. The method of claim 1, wherein the reaction mixture is heated before gelling at an average rate of temperature increase of 0.5°C to 5°C/min. 5. The method of claim 1, wherein the reaction is carried out at a temperature of 70-85°C and the resulting resin is cured at ambient temperature to 100°C. 6. The method of claim 5, wherein the reaction is maintained for 10 to 100 minutes before gelling and the resulting resin is cured for 2 to 20 hours. 7. A process according to claim 1, wherein the solids content of the reaction mixture is between 30 and 55% by weight of the total mixture. 8. The method of claim 1, wherein the internal diluent is n-propanol. 9. The method of claim 1, wherein the internal diluent is ethoxyethanol. 10. The method of claim 1, wherein the internal diluent is dimethylformamide. 11. The method of claim 1, wherein the catalyst is formic acid. 12 Melamine and formaldehyde in a ratio of 1:3 to 1:5
in the presence of a formic acid catalyst and an n-propanol internal diluent in an aqueous solution in a molar ratio of A method according to claim 1, characterized in that it is cured to produce a resin having a porosity of greater than 0.2 ml/g and a surface area greater than 1.00 m^2/g.