WO1990007541A1 - Thermosettable resin intermediate - Google Patents

Abstract

An intermediate compound thermosettable to an insoluble resin, useful for binding agglomerated particulate matter such as pelletized coal fines, is prepared by ammoniating an aqueous dispersion of a glucose-containing reducing sugar and a denaturable lysine-containing protein to a pH above 7. Agglomerates incorporating the intermediate resin are rendered durable and insoluble by heating to temperatures above 180°C. Preferred dispersions are comprised of dairy wastes such as the whey, whey permeate and delactosed whey permeate that are residues of the cheese making process.

Description

THERMOSETTABLE RESIN INTERMEDIATE

Field of the Invention

This invention relates to a thermosetting resin and a method of utilizing such resin to bind particulate matter into strong and water resistant agglomerates or shapes.

Background of the Invention

The damage resulting from acid deposition on the land, vegetation and surface waters downwind from coal-burning facilities is a matter of increasing international concern. Although flue-gas clean-up technology and limits on the sulfur content of coal have, to some extent, ameliorated the rate of deterioration there is still a priority need to further reduce acid-precursor emissions, particularly the oxides of sulfur.

The most prevalent form of sulfur existing in coal formations, iron pyrite, can be substantially reduced by grinding the coal to liberate the- mechanically-bound pyritic and mineral-ash inclusions, and then separating the heavier particles of pyrite and ash. This procedure permits the utilization of less expensive grades of coal with initially-higher levels of sulfur and is, therefore, gaining wider industry recognition. To maximize the removal of impurities, grinding often proceeds until the particle size has been reduced to where 100 percent will pass through a No. 20 (850 micron) mesh screen and at least 50 percent will pass a No. 200 (75 micron) screen. Particulate in this general size range is designated as ultrafine and, although much cleaner burning, its utilization presents many new problems, not the least of which are transport, handling and increased water retention. Formerly, a large portion of fine coal— material inadvertently pulverized to a size small enough to pass a No. 14 (1400 micron) screen— as largely discarded as unmarketable.

Newer facilities can be designed around or modified to accept this form of fuel, but many older and less sophisticated types of installations inherently cannot accommodate ultrafine, or even fine, coal; stoker-fired industrial boilers are one such class. The obvious remedy is the reconstitution or agglomeration of fines into pellets or compacts of a size and shape compatible with existing handling and combustion equipment. An efficient means of reconstitution would also provide the economic incentive needed for the reclamation of the substantial quantities of fine coal previously abandoned. The reconstituted product must be very durable and resist disintegration during handling, particularly after prolonged weathering, and it must yield a minimum amount of ash and no noxious substances as a result of combustion. Industrial agglomeration methodology is a well defined art that abounds with examples of technically efficacious systems for binding a variety of fines into discrete shapes. The economic realities of the current coal and energy markets, however, have effectively precluded the adoption of these techniques on a commercial scale by the coal industry. Even those binder formulations expressly developed for coal agglomeration are too costly tiy industry standards of profitability. The manufacturing methodology and equipment exist and are employed in other mineral processing industries; conspicuously absent is a binding agent that is at once functionally effective, simply prepared and processed, and yet. composed of virtually valueless ingredients.

Carbohydrate-rich dairy waste such as cheese whey would be among the most promising raw materials, were it not for their presumed solubility when employed in an orthodox binder formulation. Only a small fraction of the 40 million liquid tons of whey produced annually in' North America is marketed as dried whole whey; the remainder does not have a sizeable commercial use. Lack of an efficient and acceptable means for disposing of this vast amount of material, coupled with increasingly stringent environmental regulations, has caused serious economic dislocations within the U.S. dairy industry. The burden of compliance with environmental standards has been alleviated, to a modest extent, by the sequential derivation of new food ingredients from whey. The ultrafiltration of whole whey yields a retentate product, whey protein concentrate ( PC) , and a liquid, whey permeate. The subsequent fractionation of whey permeate yields crystalline lactose as a product and another liquid, deproteinized lactose permeate (DLP) . A residual liquid permeate remains, therefore, whether only one or both saleable products are withdrawn from whole whey. The permeate from either process is not only as difficult to dispose of as the original whey, but it is only partially reduced in volume; derivative products are primarily a means for mitigation of disposal costs. The invention disclosed herein describes the methodology developed to transform not only whey and its permeates, but other milk products as well, into a resin intermediate that is convertible directly, or by design at some later time, into a thermoset and insoluble particulate binder. The class of lactose and protein containing milk derivatives employable as raw materials in this invention includes not only the dairy wastes, whey, permeate and DLP, but milk byproducts with established market values, e.g., skim milk and WPC.

The physicochemical properties of milk byproducts, and derivatives such as whey, have been intensively studied, primarily with a view toward either preventing product deterioration or developing new food uses. As a consequence of this focus on food uses the reactive nature of these materials under extreme treatment conditions, as well as the properties of the resulting reaction products, has largely been overlooked and their full potential as chemical feedstocks neglected.

The solids content of whey is in the range of 6- 7%, with lactose and protein comprising approximately

70% and 13%, respectively. Lactose is a disaccharide reducing sugar consisting of one moiety each of D- glucose and D-galactose, occurring predominately in the pyranose ring form and joined by a glycosidic linkage. Chemical reactions of lactose involve the glycosidic linkage between rings, the hydroxyl groups, the -C-C bonds within the rings and, of special importance to this invention, the hemiacetal linkage between carbons 1 and 5 of the glucose moiety. This hemiacetal structure gives rise to an equilibrium between the two anomers, alpha and beta, which differ in steric configuration of the -OH and -H at glucose

C-l.

The anomers are distinguished by their melting- decomposition points; alpha at 202°C and beta at 252°C. The two anomers also differ in specific optical rotation and solubility, with the ratio of alpha to beta, as well as the rate of mutarotation between the anomers, affected significantly by changes in temperature or pH. Lactose is known to be particularly sensitive to ammonia; an entire solution will mutarotate to equilibrium spontaneously upon addition of a trace amount of ammonia. The dynamic equilibrium between the anomers in solution involves opening and closing of the hemiacetal ring of glucose, and at any time a small amount of the free aldehyde is present. This small amount can undergo the reactions typical of glucose aldehyde and, the entire amount of lactose in a system can enter a reaction by being channeled through the aldehyde in this manner.

That portion of the original protein that remains in whey, after the casein proteins of milk are coagulated to form cheese, is fundamentally different from casein protein and is separately classified as whey or serum protein. It is comprised mainly of globular proteins that, unlike casein proteins, can be unraveled or denatured by heat, or by pH adjustment to a level below 4 or above about 8. Denaturation exposes numerous reactive amino acid residues, including the €-amino group of lysine. A small, but significant, fraction of this whey protein survives in each permeate after the removal of whey protein concentrate or a portion of the lactose. Commercially available dry forms of whey, whey permeate and delactosed whey permeate contain whey serum protein on a specified minimum weight percent basis of 12%, 2% and 5%, respectively, in combination with at least 50% by weight lactose.

Although glucose-containing reducing sugars and lysine-containing denaturable proteins are found in numerous substances, the physical state and condition in which they coincidentally occur as dairy wastes in such abundance makes them singularly advantageous raw materials for this resin. Specifically, the minimum necessary concentration of solid reactants are each present, to the virtual exclusion of extraneous organics, in the requisite aqueous dispersion.

Characteristically, aqueous solutions of reducing sugars in the presence of amino compounds undergo the early or colorless stage of the Maillard reaction, which requires a low order of energy for initiation and exhibits autocatalytic qualities once it has started. In the text. Dairy Chemistry and Physics, published by John Wiley & Sons, N.Y., 1984, the authors, Walstra and Jenness, state in item 12. , page 165, "Maillard reactions occur at any temperature but proceed much more rapidly at higher ones", and on page 177, section 10.4.1., Chemistry of Maillard Reactions, they further comment that "The primary reaction in Maillard browning is condensation of an amino compound with the carbonyl group of a sugar in the open chain form, presumably to form a Schiff base although such a compound is not isolatable." This initial condensation is accompanied by the formation of water. The initial reaction product undergoes an Amadori rearrangement with the formation of a N-substituted 1- amino-l-deoxy-2-ketose; these are colorless compounds, which when heated, proceed in a series of reactions that lead eventually to the formation of polymers called melanoidins. Typically brown compounds of variable structure and solubility, melanoidins have unsaturated heterocyclic rings which account for their fluorescence. From studies of simplified aqueous sugar-protein systems, melanoidins have been shown to contain significant amounts of a glucose-ammonia component and are strongly bound to protein.

The decomposition of lactose in the earliest stage of the Maillard reaction is base-catalyzed by amino compounds, with the permanent loss of lysine from these compounds a measurable index of lactose reactivity. As the Maillard reaction proceeds galactose has been shown to accumulate while glucose does not, indicating that glucose is the moiety of lactose that reacts predominantly with lysine. The extent of decomposition is governed by the buffer capacity of the medium and the pH, with strong buffering slowing the shift to acid conditions. The basicity decreases dramatically if the dispersion is heated as the reaction progresses. The production of organic acids, mainly formic, increases rapidly during the reaction (in the presence of oxygen at temperatures above 100°C) and the resultant drop in pH from above 6 to 5 or below arrests the reaction. The routine Maillard reaction in milk products is, therefore, self-inhibiting and ceases after a light to moderate browning of the product.

It is known from nutritional studies that many chemical reactions that occur in sugars only at high temperatures take place at much lower temperatures once they have reacted with amino acids. This characteristic, however, has not been heretofore exploited under conditions of an ammonia-induced alkaline pH to produce industrially useful materials from sugar-protein containing dispersions.

In accordance with the practice of this invention, ammonia added to such a system at the outset is believed to behave initially as a basic catalyst, promoting protein denaturation and increasing the reactivity of the amino acid residues and the rearrangement and fragmentation of lactose. Later, at elevated temperatures, the ammoniated system is believed to counteract acid formation and promote the formation of melanoidins. Many aspects of the Maillard reaction sequence in milk derived products are incompletely defined, including the possible catalytic role of the numerous salts that become increasingly concentrated as derivative products are sequentially withdrawn.

The complexity of Maillard reactions and the multitude of products yielded is illustrated in the work reported by Aldo Ferretti et al in the Journal of Agricultural Chemistry, Vol. 18, 1970 and Vol. 19, 1971, wherein the 80 volatile compounds that were isolated and identified from model lactose-casein browning systems that had been conditioned for eight days at 80°C are enumerated.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a method of preparing a thermosettable resin intermediate for binding agglomerated particulate matter into useful products which comprises adjusting the pH of an aqueous dispersion of a glucose-containing reducing sugar and a denaturable lysine-containing protein to a pH level between 7 and 14 by adding an ammoniating agent to the dispersion to obtain a resin intermediate prior to admixing with the particulate matter. According to another aspect of the invention, there is provided a method of preparing agglomerated products from particulate matter and a thermosettable resin comprising the steps of: a) admixing to the particulate matter an aqueous dispersion of a thermosettable resin intermediate prepared as set forth above to form a thick and viscid admixture, b) shaping the admixture into formed green agglomerates by employing a suitable means for agglomerate forming, and c) drying the formed green agglomerates to fix the particulate matter in coherent and strong shaped products.

According to yet another aspect of the invention, there is provided a thermosetting resin composition prepared by adjusting the pH of a dispersion of a glucose-containing reducing sugar and a denaturable lysine-containing protein with a amount of ammonia sufficient to raise the pH level to between 7 and 14 to obtain a resin intermediate and then heating the intermediate to a temperature in the range of 190°C to 260°C until the resin intermediate polymerizes into a thermoset resin.

The invention may provide a method for combining two classes of marginal value materials, dairy processing wastes and discarded coal fines, into commercially useful fuel agglomerates that are durable and weather resistant. The invention may also provide a novel and inexpensive thermosetting resin which can be readily utilized as a particulate binder in conventional industrial agglomeration processes and equipment. Preferably, the invention provides a stable thermosettable resin intermediate that is composed essentially of dairy wastes such as whey and its lactose-protein containing derivatives.

Then invention may be accomplished by transforming the normally water soluble and dispersible constituents of dairy wastes into a liquid substance that will, once dried and set, form a strong, insoluble polymeric resin.

The elaborate physical changes and chemical reactions that accompany the ammoniation of a lactose- protein dispersion, i.e., the predisposition of lactose to spontaneous mutarotation, the denaturation of the whey proteins, and the resulting condensation of the newly accessible amino acid compounds with a constantly replenishable supply of glucose aldehydes, produce a stable resin intermediate. The intermediate thus prepared shows evidence of having undergone the early stages(s) of the Maillard reaction and is in a condition to proceed, when sufficiently heated, along an optimized advanced stage Maillard reaction pathway to a terminal polymeric compound that is infusible, insoluble and black. 10

An insoluble polymer is not produced from a dispersion that has been alkalized with a base material other than ammonia, or if either the lactose or the protein is not present in the dispersion. The specificity of ammonia in combination with lactose and the protein compounds, togetherwith its ability to participate in the formation of the melanoidins, is apparently fundamental to this high temperature, resin forming, Maillard reaction. The term ammonia as used herein is intended to include not only ammonium hydroxide as cited in the examples below, but the other common forms of the compound: anhydrous ammonia and ammonia gas.

When used as an ingredient in a resin intermediate dispersion no distinction as to origin is necessary between sweet and acid whey, or as to the physical form of the derivative raw materials; liquids, concentrates and dry powders that are the standard product forms in the milk processing industry all perform equally well and, when adjusted for water and whe protein content, are considered interchangeable. The shelf life of the liquid forms of the resin intermediate is extende indefinitely if the dairy raw material is pastuerized prior t ammoniation, ,όr the liquid intermediate is stored at temperature of 5°C or below. A dry reconstitutable powder for of the intermediate can be obtained from the aqueous dispersio by conventional water removal means such as spray-drying o evaporation.

The fully polymerized intermediate has been found to b useful as a durable and insoluble binder for sand, mineral ores metal powders and other finely divided materials, in addition t coal fines. Prior Art

The effectiveness of the disclosed thermosetting resi as a binder of agglomerated particulate matter is an intrinsi property of the combination of lactose and whey protein i aqueous dispersion when it is ammoniated to an alkaline pH an then heated to an elevated temperature; it does not requir special crosslinking additives or a cooperative chemica reaction with the material being bonded. Indeed, the resi intermediate disclosed will completely polymerize in th absence of any additional material to a black and insoluble soli under the application of sufficient heat. It is, therefore readily distinguished from compositions that utiliz carbohydrates in combination with such special additives, o wherein the material to be bound participates in a reaction wit the carbohydrates.

in the Gibbons U.S. Patents Nos. 4,085,075 & 4,085,07 and Viswanathan et al U.S. Patent No.4,524,164 the resin binde formulations, in addition to a sugar or starch ingredient incorporate a urea, phenol, formaldehde or like polyfunctiona crosslinking additive to contribute to the desired properties o strength and water resistance in a bonded or molde lignocellulose product. The above Viswanathan proces additionally specifies a preferred acidic pH level of from 3 u to 7.

Those carbohydrate containing resin binders prepared i accordance with Stofko U.S. Patent Nos. 4,107,379 & 4,183,99 and Viswanathan et al U.S. Patent No. 4,692,478, rather tha including a crosslinking additive, are all in acidic aqueou solution (pH 2 to 5) when they are combined at high temperatur (140° - 225°C) and pressure with the lignocellulosics. Thes are the classic conditions required for initiating the mil acid-catalyzed hydrolysis of cellulosics which is known t yield, among other reaction products, pentose and hexose sugars furfural and hydro y-methy1-furfural, together with organic acids such as formic and acetic. These latter acid products augment the cellulose hydrolysis and degradation reactions, thereby producing additional furan compounds that bond with the ligneous structure at newly exposed sites. This type of auto- catalyzed hydrolysis of lignocellulosics is also the underlying reaction evident in the Stofko U.S.Patent No. 4,357,194 wherein pressurized live steam is utilized to induce organic acid production and carbohydrate degradation leading to pressurized sugar-furan-lignin bonding.

Resins that rely for their effectiveness, even in part, on hydrolysis or other conjunctive reactions with the material to be bonded are inherently inferior as binders of non-reactant substances, e.g. coal fines, sand or mineral ores.

Each of the above cited patents includes, as a necessary ingredient, a sugar, a starch or a mixture thereof; none require that for functionality the carbohydrate be present specifically in combination with a protein. This combination of constituents is indispensable to the instant invention and is one of its most conclusively distinguishing features.

In the article Utilization of Whey/Lactose as an Industrial Binder, published in the Journal of Food Chemistry, Vol.27, No.4, 1979, Arthur Ferretti and James V. Chambers presented the results of binder development work demonstrating the suitablilityof whey and lactose as alternative and economic substitutes for molasses, the preferred carbohydrate in C.W. Humphrey's U.S. Patents Nos.3,567,811, 3,765,920 & 3,857,715. These patents, as well as the work reported in the referenced article, do not have as an objective a finished product wherein weather resistance and durability are properties specifically imparted by the carbohydrate binder. The function of the binder in each instance is to impart green or temporary strength during an interim period of handling, drying or, as in the case of Portland cement products, natural hydration. Products prepared by the methods of the first two patents in the series, iron ore pellets and bloated fly ash aggregate, require post- drying induration at drastically high temperatures (1000°+C) before they acquire a permanent ceramic or oxide type interparticle bond. , Until this bonding is effected, the particulate matter is merely held together¹by the carmelized carbohydrate and is immediately soluble in water. Substitution of whey in these processes does not utilize to advantage the potential contribution of the protein constituent and, therefore, provides no additional benefit, other than economic.

Representative of recent innovations in the art of coal fines reconstitution is W.W. Wen's U.S.Patent No. 4,615,712 which utilizes a humic acid based binder in an agglomeration process that is functionally analogous to the technique disclosed herein. Because of this similarity in the mechanics of agglomerate formation and treatment, the binder preparation and curing procedure of Wen is an appropriate example with which to compare the merits of the resin binder that is the subject of this invention.

To prepare the Wen binder, which is characterized as an aqueous solution of the humates extracted from oxidized carbonaceous material, very low rank coal is pulverized and oxidized by chemical or heat means (unless it occurs in a naturally oxidized state), extracted by alkaline solution at an elevated temperature and then separated from the undissolved residue. Subsequent to agglomeration by conventional means, the product must be cured for about 2 hours at 160°C before the humate binder provides the minimum necessary impact strength and water resistance.

By contrast, preparation of the intermediate form of the composition of the present invention requires only the adjustment of the water content of the dispersion of dairy waste solids and then ammoniation of that dispersion to the appropriate level of pH prior to agglomeration. Polymerization of the resin intermediate is effected by drying the agglomerate to remove virtually all free moisture and then heating it to about 190°C for the short interval needed to obtain a durable and water resistant product. There are no protracted high temperature chemical reactions involved in preparation of the resin intermediate or undesireable residual materials, and process time is minimized by a short and straightforward drying and curing procedure.

The Preferred Embodiment

Powdered whey permeate is utilized in this description as representative of that class of milk-based derivatives that all contain lactose and whey serum protein. Permeate is a nominal representative of the materials in the class as it contains, on average, the smallest weight percentage of whey protein solids and is, therefore the least effective. To realize a given concentration of protein (as in a binder formulation) permeate solids are required in a commensurately larger quantity than any other material of the class.

A widely employed agglomeration technique that is especially well suited to exhibiting the advantages of this resin involves balling dispersion-wetted coal fines on a rotating inclined disc. Experimental pelletizing trials on a laboratory scale rotating disc are particularly useful in defining the binder and process parameters as results are directly translateable to large capacity industrial equipment. The disc pelletizing procedure that yields superior quality spherical balls agglomerated from an admixture of ultrafine coal and a dispersion of the resin intermediate can be divided, for illustration, into three distinct operations:

1. preparation of the ammoniated aqueous binder dispersion; 2. admixing, the dispersion with coal fines and forming green balls on a laboratory disc pelletizer; and

3. drying and induration of the balls.

1. BINDER PREPARATION Dry permeate powder typically contains between two and ten percent whey protein solids, and it is the quantity of this reactant that governs the eventual strength of the interparticle bonds, and ultimately the physical properties of the pellet.

Lactose, in excess of the stoichemetric quantity needed to combine with the whey protein in the Maillard reaction, progressively decomposes to ash during curing. In terms of this reaction, lactose is always present in permeate (and all the materials of the class) in superabundance (typically 50 - 95% of the solids) and, therefore no special precautions are necessary regarding its quantification.

Close control over moisture content is critical to effective disc pelletizing. When the moisture content is insufficient all the coal surfaces are not wetted, capillarity is not created and air inclusions result. Excessive moisture will coat the external ball surface and neutralize the capillary forces, thereby reducing pellet green strength by more than fifty .percent. Engineering reference data indicates an appropriate moisture range of 20.8 - 22.1% for disc balling of coal fines that all pass a No. 48 (300 microns x 0) mesh sieve.

Subsequent to curing residual polymerized resin, in the form of interparticle bridges, provides pellet hardness and compressive strength. The magnitude of these features and, to some extent, pellet integrity after water immersion is a direct function of the quantity of whey protein in the resin dispersion.

For dry permeate containing about four percent whey protein solids by weight, an appropriate proportion of water to permeate is centered around a ratio of 5:1, or about seventeen percent by weight permeate solids.

in accordance with the method of the invention, such a dispersion (for example 20 grams of dry permeate mixed with 100 grams of water) must be conditioned to a state of readiness as a partially polymerized resin intermediate, before it is useful as a thermosetting binder. This is readily accomplished by ammoniation of the dispersion to a pH level of at least 8.0. In the example cited immediately above, very little buffering was noted near neutrality and only about 4 grams of twenty-six percent ammonium hydroxide were required. If the particulate ^"material to be agglomerated is highly acidic/ as may be the case with coals that still contain considerable pyrite, it may be necessary to raise the pH of the dispersion considerably above 8.0 to 11.0 or even higher to counteract this acidity.

Numerous fundamental changes occur in the character of the dispersion as a result of this single step of ammoniation: a. lactose mutarotation is accelerated and the resulting dynamic equilibrium provides the replenishable supply of glucose aldehydes needed for sustaining the Maillard reaction with the £-amino of lysine; b. the globular proteins and peptides undergo pH denaturation - the tertiary and secondary structures are unfolded and uncoiled and the reactive side chains, particularly the <?-amino groups of lysine, are exposed and become available for reaction with the aldehyde of lactose; c. the alkaline pH provides an environment conducive to initiating the base-catalyzedMaillard reaction (and subsequent production of formic acid is inhibited); d. supplemental nitrogen is available for the melanoidin formation reaction that is characteristic of advanced stage Maillard reactions; and e. dispersity (solubility) increases and the mixture appears less opaque and viscous as the pH is increased above the isoelectric point of the whey serum proteins (4-5.5).

2. COAL ADMIXING AND PELLET FORMATION

Mixtures composed of the subject binder dispersion and Coal Fines II (Table 2) that had been screened todiscrete ranges of particle sizes were run on a laboratory-scale (18 inch diameter) disc pelletizer. These preliminary trials established parameters of equipment operation and a relationship between moisture, binder solids content, viscosity and particle size. Predictably, the moisture content required to achieve the capillary state of mobile liquid force binding increased as the average particle size decreased.

Successful agglomeration of ultrafine coal, recovered, desulfurized and deslimed after years in a slurry pond, was considered a worst-case test and its accomplishment the realization of one of the invention's principal objectives. The laboratory procedure for agglomerating this type of recovered ultrafine coal was comprised of: a. admixing to one kilogram of oven dried ultrafine coal an amount of binder dispersion estimated to be slightly below the optimum needed for balling - in this instance 300 grams of binder dispersion provides a very viscous consistancy. This 1.3 kg admixture contained

19.4% (254 gms) water and 3.5% (46 gms) permeate solids; b. readjusting the pH with ammonium hydroxide, if necessary, to a range of at least 8.0 - 9.0; and c. introducing this admixture to the disc pelletizer, along with an intermittant spray of binder dispersion, until nucleation and particulate coalescence proceeds to where spherical balls of about 1.5cm predominate on the disc.

An overall material balance of several batches made in this manner provided approximate green pellet compositional data: moisture content = 20.2%; permeate solids = 3.4%. Green strength was more than adequate in this example, with green balls averaging more than 10 drops of 30 cm before any breakage.

3. DRYING AND CURING

The physical properties of dried agglomerates, especially weather resistance and strength, are in large measure dependent upon the extent of the heat treatment applied to the green balls. As the final temperature to which the agglomerates are subjected is increased ball strength and solubility in water changes over three distinct ranges:

a. the initial stage extends up to a temperature of about 170°C; products cured below this temperature rapidly disintegrate upon immersion in water; b. products dried and cured in the transition stage, fromabout 170°C to about 185°C, will slowly leach a dark brown substance when immersed and thereafter exhibit a loss in strength; and c. the final temperature stage begins at about 190°C, with products heated to, or above, this point assuming an increasingly coral-hard, abrasive and totally insoluble character.

Agglomerated balls may be dried by any convenient means thatdoes not remove moisture at a rate so rapid as to cause heat- checking or cracks in the agglomerate structure. Heating in the range of 120°-170°C, after ball drying is complete, drives the reaction to near completion. After cooling, the balls will be strong and hard but will readily and completelydissolve in water and color it a dark brown.

When the temperature range- is increased to 170°C

180°C, the pellets will not subsequently dissolve when immerse in water, but will color the water to a lesser degree and take o an eroded surface texture. Hardness and strength are degrade by prolonged immersion.

Balls heated directly, or even reheated, to temperature in the range of 190° - 250°C become extremely hard irridescent, resistant to abrasion and completely insoluble exhibiting no leaching or loss of strength after extende periods of water immersion. The gradual improvement in strength and weathe resistance of the fully dried balls during heating in th transition and final temperature ranges is accompanied by weight loss that is equivalent to approximately 1/3 to 1/2 of th original binder dispersion solids weight. This weight loss b gaseous emission indicates extensive chemical activity durin the terminal, thermosetting phase, of the Maillard reaction

Both the thermal decomposition of unreacted or surplus organi constituents of the binder solids and the crosslinking an condensation reactions that are believed to produc insolubility are likely contributors to these emissions.

EXAMPLES

The order of presentation of the Examples depicts th sequence in which particularly significant experiments wer performed. Progressively, the results and observation revealed the novel properties of this specific combination o materials and treatments; first as an insoluble particulat binder, then as a strong and black thermoset resin, and finall as a stable thermosettable resin intermediate. The descriptio of the materials utilized are listed in Table 2 at the conclusio of the Examples.

EXAMPLE 1 Unsatisfactory Comparative Results

The methods of C.W. Humphrey disclosed in U.S. Patent No 3,567,811 were utilized as general procedures in furthe investigation of the use of whey and its derivatives a replacements for molasses in the preparation of binders for th agglomeration of coal fines. A standardized dispersion of whe permeate was employed as a basic starting binder formulation i trials of variations of the Humphrey technique, as well as fo the preparation of binder formulations used in ensuing examples This standard dispersion was prepared by mixing ten parts o water by weight with two parts of dry permeate. Agglomerates of ironore and othermaterials prepared b the Humphrey method, regardless of the carbohydrate employed i the formulation, require a specific secondary treatment t obtain the desired durability and water resistance, e.g. extreme high temperature or hydration.. When subjected t temperatures in excess of 200°C, the carbohydrate in the binde of coal agglomerates carmelizes and then decomposes, leavin dissociated particles. Agglomerates dried or cured at lowe temperatures readily dissolve in water. As the ability t endure all weather storage and handling .is a requisite of commercially acceptable artificial fuel, coal agglomerate prepared by this method were examples of unacceptable results

During one such unsuccessful trial the pH of a admixture of the standard whey permeate dispersion with pyrite containing coal fines (Coal I), was observed to fall steadil over 2 hours from an initial level of 6+ to below 4 Disintegration failure of extrudates earlier prepared from thi admixture was attributed to degradation of the carbohydrate i the binder caused by sulfuric acid leached by the coal's pyriti inclusions.

EXAMPLE 2 Pyrite Neutralization

To counteract the drop in pH level previously observe thepHof damp Coal-I fines was adjusted to about 11with ammoni hydroxide prior to drying the fines and then admixing with t binder dispersion. A sufficient amount of the standard bind dispersion was added to the ammoniated and dried fines to obta a final total solids to water ratio of approximately 5:1.

A firm and void-free 20 mm diameter column of th admixture was extruded on a laboratory extruder, cut to 3 lengths, and then slowly dried and heated over a period of abo 40 minutes to a temperature of about 175°C. After cooling, the samples were found to be hard an strong and, following a 24-hour immersion, somewhat water resistant. Although the soak-water in the immediate vicinit of individual specimens was distinctly discolored dark brown the samples did not readily disintegrate and retained considerable degree of integrity.

The pH of the unused coal admixture was measured severa hours after mixing and, as in the previous example, the pH ha dropped several units, from about 11 to well below 8, indicatin a continued leaching of acid.

EXAMPLE 3 Adjustment of Binder Dispersion pH

The sample preparation procedure of Example 2 wa repeated, except that for this trial the pH of the standar binder dispersion was adjusted with ammonium hydroxide to level of about 10 prior to admixing with dried, but untreated Coal-II fines, and the heating cycle was extended to one hour b adding a twenty minute interval at 190°C.

The cooled specimens displayed further improvement i physical properties; they were stronger, extremely hard, showe no signs of deterioration after a 24-hour water immersion and significantly, the soak-water showed very little discoloration The pH of the unused admixture appeared stable over time at abou 7.0.

EXAMPLE 4

Reactive Properties of Coal

Example 3 was repeated except that dried, very-fine white silica-sand was substituted for coal fines. As th extruded samples were heated they rapidly changed color f om a off-white to brown as the temperature reached 100-120°C, an then to a very dark brown at about 160°C. At this temperatur several specimens were removed from the batch being heated an examined separately, with the remainder allowed to complete th heat cycle.

The key observations from this example were: the colo of the binder filling the intersticies of the white sand change from an off-white to almost-black well below the decompositio temperature of alpha lactose (202°C); although they were a strong and hard as fully-cured coal agglomerate (Example 3), th samples removed at 160° were soluble, unless reheated to abov 190°; and, coal appeared to playno identifiable chemical role i the binder polymerization reaction.

In all other respects there appeared to be n appreciable difference between the specimens formed of coal i Example 3 and the specimens made from sand. The much desire property of. insolubility appeared to be not only pH, bu temperature dependent and the reaction imparting it wa identified as a variation of the Maillard browning effect.

EXAMPLE 5 Comparitive Reactions of Alkaline Reagents

Separate portions of the standard dispersion wer treated with aqueous solutions of potassium hydroxide, sodiu hydroxide and ammonium hydroxide to raise the pH of each to a least 8.0. A small quantity of each treated dispersion (barel sufficient to coat the bottom) was placed in separate foil l dishes. As a comparative specimen a fourth dish contained unammoniated sample of the standard dispersion.

The four samples were simultaneously oven-dried a then observed as they were slowly heated to 200°C. Except f the sample treated with ammonium hydroxide, all mixtures behav in a somewhat similarmanner, slowly coloring to tan and then to dark-brown bubbling mass, before finally decomposing to a sof gray-black, water-soluble char.

The ammoniated specimen darkened earlier and mo rapidly, produced gases from small bubbling pores and the became a jet-black, shiny and opaque material that evenly coate the dish bottom. Upon cooling the wafer-like material release easily from the dish and, after a 24 hour immersion, retained it stiff, so e-what brittle character, and left no color or residu in soak-water.

These three alkaline reagents were subsequentl incorporated in analogous dispersions of skim milk, whey an lactose and observed while undergoing similar . hea conditioning. Except for pure lactose, the results obtaine closely paralled those observed with permeate; the ammoniate sample survived in each instance as a black, insoluble polymeri material and the other materials decomposed.

All samples composed of pure lactose remained clea solutions until they simply crystallized, carmelized, outgasse and finally began to decompose.

EXAMPLE 6 Temperature Parameters Of Milk & Byproduct Reactivity

Six liquid dispersions were prepared bymixing ten part of water with two parts of the dry solids of each of th following: skim milk, whey, WPC, permeate, lactose and DLP. small quantity of each dispersion was placed in a separat aluminum dish as a reference standard. The remainder of eac dispersion was adjusted with ammonium hydroxide to a pH level o at least 8.0.

Three aluminum dish samples of each ammoniate dispersion, together with samples of the reference dispersion o each material, were dried and slowly heated to 160°C. After te minutes at this temperature, one of each ammoniated sample wa removed for inspection. The same procedure (removing one o each type of ammoniated sample) was followed after 10 minutes a 185°C, and then 10 minutes at 250°C. (The behavior of all lactos samples was similar to that noted in Example 5: no reaction unti melting-decomposition. Its further evaluation was, therefore, discontinued.) The 160°C samples all readily dissolved in and discolored water, and all were black, with the exception of the standard samples, which were dark-brown.

At 185°C the reference samples had all decomposed to ash, but the five ammoniated materials remaining under evaluation were hard and black, and substantially insoluble in water, although they softened somewhat and slightly discolored the water over time. The specimens conditioned to 250°C were all hard, jet-black, insoluble and unchanged after water immersion, although the WPC had expanded to a rigid, but crushable, foam. The remaining four materials (skim milk, whey, permeate and DLP) exhibited a wide variety of surface characteristics ranging from a shiny and iridescent gloss (skim milk) to a flat black (DLP).

These results demonstrate that aqueous dispersions of milk solids that contain both lactose and protein, and have been ammoniated to a pH of about 8, will form apartially polymerized, but soluble, intermediate compound when dried and heated at temperatures below 185°C. This intermediate polymerizes to a substantially insoluble material at temperatures above 190°C, and becomes totally insoluble, hard and infusible at temperatures in the region of 200-250°C.

EXAMPLE 7.

Agglomerate Strength vs Binder Solids Content

Spherical agglomerates properly prepared from particulate-liquid mixtures by rotating disc pelletizing inherently contain a nearly optimum amount of moisture. In this condition balls or pellets naturally develop stron interparticle forces, or green strength, through interna liquid capillary suction. Within limits, a thermosettin bindingagent added to the mixture enhances notonlycohesion an weather resistance but several other important physica properties of the cured agglomerate. Information indicative of the extent of physical stengt enhancement attainable by increasing the solids concentratio of the binder dispersion was obtained by the destuctive testin of individual groups of disc pelletized balls agglomerated wit binders containing graduated solids-to-water ratios. The tes results in Table 1 are for groups of ten, 1.5 cm balls, prepare from recovered ultrafine Coal III that all initally containe about 20.8 percent moisture and were dried and then heated t about 250°c.

TABLE 1 Agglomerate Physical Properties

Dry Permeate to Water Ratio

Property

Green Strength (Ave. 30cm Drops)

Impact Resistance

(Ave. 45cm Drops) Abrasion Resistance 82.9 96.1 98.0 99.1 (100%, minus the weight loss)

Compressive Strength 0.7 2.9 3.7 3.1 (Kilograms) Test Conditions Summary:

Green Strength Drop Test - Uncured balls were dropped repeatedly from a height of 30 cm onto a steel plate to determine the average number of drops the balls of each admixture withstand before breaking.

Impact Resistance Drop Test,- The same procedure as in the above testexcept that cured balls were dropped from a height of 45 cm.

Abrasion Resistance Test - Approximately 100 grams of cured balls of each group were rotated in a 6 inch diameter, 10 mesh, screen cylinder at one revolution per minute for three minutes and the weight percentage of the dislodged particulate deducted from 100% (the original weight).

Compre.ssive Strength Test - The average value at which failure occurs when individual balls of each group were subjected to a slowly increasing compressive load.

27

TABLE 2 Materials Utilized in Examples

Dairy Products & Waste Byproducts Typical Dry Solids Content:

Coal I Carbondaledll.) -No. 35 x 0 High sufur & ash (Raw Slurry) Group recovered fines

Coal II Pittsburgh -No. 50 x 0 Newly mined, (Fines) No. 8 Seam cleaned __ reground

Coal III Pittsburgh -No. 100 (100%) Recovered & deslimsd; (Ultrafines) No. 8 Seam -No. 325 (50%) slurry pond

Silica Sand California -No. 60 x 0 Finest washed (Sand) Quarry crystal grade SUMMARY Disclosed herein is a method that was specifically developed to convert aqueous dispersions of lactose and whey serum protein into a thermosettable resin intermediate that can subsequently be transformed by the application of heat into an infusible and insoluble resin. A principal objective of the invention is the beneficial utilization of waste dairy products such as whey and its derivative products.

This new composition is apparently the product of an extended or terminal form of the Maillard reaction induced by the intense heating of a dispersion of a glucose-containing reducing sugar and a denaturable lysine containing protein after alkalization with ammonia. It is well known that numerous reducing sugars and other forms of protein combine when heated to exhibit the browning manifestations of the Maillard reaction. It is within the intent of the disclosure, therefore, to point out that other sources of glucose sugars, e.g., cellulose and starch, in combination with other proteinaceous materials, such as soy flour, are expected (or potential) substitute ingredients in the preparation of this or analogous intermediates and resins.

While certain preferred embodiments and examples of the invention have been specifically disclosed, it should be understood that the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

Claims

I CLAIM :

1. A method of preparing a thermosettable resin intermediat for binding agglomerated particulate matter into usefu products which comprises adjusting the pH of an aqueou dispersion of a glucose-containing reducing sugar and denaturable lysine-containing protein to a pH level between and 14 by adding an ammoniating agent to said dispersion t obtain a resin intermediate prior to admixing with th particulate matter.

2. The method of claim 1 wherein said pH adjusting ammoniatin agent is a material selected from the group consisting o ammonium hydroxide, anhydrous ammonia and ammonia gas.

3. The method of claim 1 wherein the aqueous dispersion i selected from the group consisting of skim milk, whey, whe protein concentrate, whey permeate, and delactosed whe permeate, or mixtures thereof.

4. The method of claim 1 wherein said aqueous dispersion i selected from the group of dairy waste products consisting o whey, whey permeate and delactosed whey permeate or mixture thereof.

5. As a composition of matter an aqueous dispersion of thermosettable resin intermediate prepared in accordance wit the method of claim 1.

6. The method of claim 1 which includes the additional step o preparing a powder form of said thermosettable resi intermediate by evaporating essentially all free moisture fro said ammoniated aqueous intermediate dispersion to obtain sai thermosettable resin intermediate powder.

7. A powder form of said thermosettable resin intermediate o claim 1 prepared by the method of claim 6.

8. A method of preparing agglomerated products fro particulate matter and a thermosettable resin comprising the steps of: a) admixing to said particulate matter an aqueous dispersion of a thermosettable resin intermediate prepared in accordance with claim 1 to form a thick and viscid admixture, b) shaping said admixture into formed green agglomerates by employing a suitable means for agglomerate forming, and c) drying said formed green agglomerates to fix said particulate matter in coherent and strong shaped products.

9. A product, made by the method of claim 8.

10. The method of claim 8 which includes the additional step of thermosetting said formed green agglomerates by heating said agglomerates to a temperature in the range of about 190°C to 260°C for an interval of time sufficient topolymerize said resin intermediate and produce thereby an insoluble, strong and weather resistant product.

11. A product made by the method of claim 10.

12. Ah artificial fuel product made by the method of claim 10 wherein said particulate material is coal fines.

13. An artificial fuel product made by the method of claim 10 wherein said particulate materials is waste coal fines and said aqueous dispersion is a dairy waste product.

14. A product made by the method of claim 10 wherein said aqueous dispersion is a dairy waste product.

15. A thermosetting resin composition prepared by adjusting the pHof a dispersion of a glucose-containing reducing sugarand a denaturable lysine-containing protein with an amount of ammonia sufficient to raise the pH level to between 7 and 14 to - obtain a resin intermediate and then heating said intermediate to a temperature in the range of 190°C to 260°C until said resin intermediate polymerizes into a thermoset resin.

16; A product made from the composition of claim 15.