CA1069500A - Method of catalytic crosslinking of a polyol with a polyaldehyde - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An inorganic alkali halide is employed in a binder system to catal-yze the reaction between glyoxal and polyhydroxyl compounds while permitting a controlled reaction rate and control of properties. The binder system has shown good utility as a foundry core binder.

Description

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Background of the Invention This invention relates to a method of modifying a polyol with a polyaldehyde. A more specific aspect of this invention relates to a binder system employing polyhydroxyl compounds, glyoxal and catalyst in aqueous medium. More particularly, this invention relates to use of a catalyst which controls the reaction between polyhydroxyl compounds and glyoxal allowing new uses with heretofore unattainable versatility. Particularly the invention relates to the use of polyhydroxyl compounds comprising the saccharides and polymers made up essentially of repeating saccharide units, the amylaceous materials and hydrolysis products thereof exemplifying this latter group.
This binder system has shown good utility as a foundry core binder.
The crosslinking of polyhydroxyl compounds, particularly polysac-charides like starch, with multifunctional reagents reactive with hydroxyl groups is well known and widely used. Common reagents used to crosslink starch (amylaceous materials) are formaldehyde, glyoxal, polyisocyanates, polyaldehyde resins, phenolic resins, urea formaldehyde resins ,~,,C ~

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and inorganic reagents including borates, phosphates, stan-nates and antimonates. All of these reagents have been used to crosslink cereal derived products for specific uses. When using glyoxal, the reaction proceeds so rapidly that utility of the binder system is greatly reduced. Some applications, such as foundry sand core manufacture, are difficult since the reaction takes place before the sand-binder mix can be formed into cores. This rapid reaction means that very short mixing and forming times must be employed. For making cores using the more conventional equipment such as hot box or baking type cores, a longer working life of the sand mix is required but yet the mixture must set and react rapidly with the application of heat.
; Applicants are aware of no prior art pertaining to the control of the reaction rate of polyols and polyaldehydes in an aqueous medium using alkali halides. Reference has been found to the use of base acids and organic acids.
Patents 2,867,615 to Lehmann and Gandon and 2,999,032 to Dekker show reactions between glyoxal and starch in water in the presence of acids. Rumberger Patent 3,293,057 discloses the reaction of starch, urea and a polyfunctional aldehyde.
In order to maintain acid conditions, acids or acid salts are utilized. Nickerson and Weymouth Patent 3,700,611 discloses the use of glyoxal, polyvinyl alcohol and cis 1,2 polyols or 1,3 polyols. No catalyst is used or mentioned. Williams 3~Cla) and Cosica Patent 3,597,313 relates to cyanamide modification of polyvinyl alcohol and subsequent crosslinking with glyoxal.
These products are cationic. Other patents disclosing aldehydes or other crosslinking materials used with specific starch derivatives, mainly cationic starches, include:
3,051,691 3,238,193 3,127,393 3,275,576 3,135,738 3,277,025 None of these relate to catalysis.
No prior art for a foundry binder has been located which is based on starch and polyaldehyde or on polyol and polyaldehyde. Patents disclosing starch products, some for use as foundry binders, include patents 2,894,859 to Wimmer and Meindl; 2,159 505 to Brugess and Johnson; 3,251,702 to Stickley et al; and 3,565,651 to Waggle. None of these patents are pertinent to the novel features of the present invention.
Foundry binders currently used in hot box and baked core making operations are thermosetting resins like pheno-lics, furans, urea formaldehyde and mixtures of these and oxidizable oils commonly called core oils in the industry.
These binders have the disadvantage of emitting odorous fumes during the application of heat, and if the cores are to be baked, green strength additives must be used so that the cores have sufficient strength to be put into and through an oven.
The use of the catalyzed glyoxal saccharide system ., . " . ~ ... . . .
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5~7 is applicable to foundry sand cores, cellulose press formed products, ad-hesives, coating binders and in many other areas. This wide utility is pos-sible~ in part to the great variation in wording and final properties avail-able by controlling the amounts of reactants and catalyst and by selecting the saccharide from the wide range of materials available. A particular group of materials derived from cereal grains has been found to be uniquely beneficial in the foundry core making operation. This group is characterized by being gelatinized and of low molecular weight in comparison to native cereal or heretofore available cereal foundry binder products. An unexpect-edly beneficial process to make these products is described, said processconsisting of the key steps of depolymerization followed by gèlatinization.
Summary of_the Invention In accordance with this invention there is provided in a method for modifying a polyol with a polyaldehyde, the improvement comprising the step of controlling, by accelerating or reta~ding the rate of the cross-linking reaction in a liquid solvent by the use of an inorganic alkali halide as a catalyst at such a temperature and pressure relationship as to maintain said liquid condition during the reaction, the polyol and polyaldehyde being of a type which would react in the absence of an alkali halide catalyst and being of a type which are mutually solvated in a solvent for the alkali halide.
` In a more specific aspect, this invention relates to a general binder system employing glyoxal, a polyhydroxyl compound and a unique cata-lyst comprised of inorganic alkali halides. ~ore particularly, the polyols are those which react rapidly with the glyoxal and are exemplified by sac-charides including sugars, starch, starch hydrolysates, gums, dextrins, so long as these are water hydratable or soluble and have available reactive groups, polyvinyl alcohol and proteins, again uith the restriction that these are reactive with dialdehydes and are water hydratable or soluble, such as a collagen protein and the like.

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It is a general object of this invention to make it possible for glyoxal to be used to give a low-cost, resin-forming binder system with control over the rate of setting.
A further object of the invention is to provide a method of manufacturing a formed article such as a foundry core which is non-polluting; which emits no objectionable fumes; which is capable of being mixed with sand in a muller or other mixer which is common in the foundry industry;
which has a bench life of at least between one and two hours; -~
which has a heat-activated hardening property such that it can be removed from the hot box mold, when this method is being used, in less than one minute using temperatures of between 350 - 500 F., in which the cores reach an ultimate tensile strength of at least 200 psi and have a satisfactory surface hardness to permit a good casting to be made; and in which the sand mix is blowable.
Description of the Drawings In the accompanying drawings:
Figure 1 shows the hemi-acetal formation in the first step of the reaction between the glyoxal and the poly-hydroxyl compound;
Figure 2 shows viscosity curves which demonstrate that the rate of the glyoxal-cereal reaction is accelerated by increasing temperature;
Figure 3 illustrates ehe family of viscosity curves :, .

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showing that the rate of viscosity increase is dependent upon glyoxal concentration;
Figure 4 shows a series of viscosity curves to demonstrate the effect of p~l on the rate of reaction between glyoxal and cereal flour;
Figure 5 illustrates viscosity curves which give a comparison of the reactivity of a solid glyoxal and a solu-tion glyoxal;
Figure 6 illustrates curves which demonstrate that the rate-retarding effect upon the glyoxal crosslinking reaction is dependent upon sodium chloride concentration;
and Figure 7 shows viscosity curves from the glyoxal-flour reactions in the presence of a number of different salts.
General Description We have discovered that the use of alkali halides in conjunction with aqueous dispersions of the above polyols : and glyoxal gives a degree of control over the reaction which has heretofore been unattainable. This allows an entirely new spectrum of binder applications for these polyols with : large variations in the properties of the binder system.
By changing the molecular size of the polyol, adjusting the glyoxal concentration and selecting an alkali halide and its , i. :~, . ;. :. . .
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;~ This variation of binder properties is possible for both the cured and uncured states. The alkaline halides show a definite orde~ of retardation of the reaction both regarding cation and anion. For the catio~s, this order is potassium ~ sodium> lithium, and for the anions I> Br~ Cl> F
in order of decreasiDg retardation. Thus, KCl retards the reactio~ to a greater extent than NaCl at equal molar con-centrations.
The reaction between glyoxal and polyo~s has been described variously. The general accepted precepts are that the reaction may result in hemi-acetal or acetal structures~
At pH above 7 hemi-acetal formation has been reported, while below 7 the acetal may be formed. When USiDg the salt cata-lysts, the pH effects are also operative. Evidence suggests : that the reactioo also proceeds in two distinct steps. The first step is thought to be a hemi-acetal formation, as showD
in Fig. l, and the second step acetal ~ormation. It is understood that this invention is not dependPnt OD the accuracy of ~he above postulated compound formations.
The visible effects of a reaction, in an a~ueous dispersion of wa~er hydratable polyol containing salt and glyoxal, are an initial thickening which appears to follow a -- 7 ~

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first order reaction rate and a final product which is an almost dry non-fluid mass. This latter reaction is difficult to monitor with simple techniques such as viscosity measure-ments since an apparent multi-phase system which at high solids resembles damp wood flour and at low solids a slurry is formed. Without salt, this reaction proceeds veTy rapidly, causing a fast viscosity rise and quickly resulting in a hard-to-handle multi-phasic looking system. By the use of salts, these changes can be dramatically slowed or accelerated, depending on the choice of salt.
Thus, NaI, NaBr, KBr, KCl, NaCl slow the reaction while NaF and LiCl accelerate the reaction. Increased con-centrations of the salts increase the effects.
The importance of the present invention should be apparent. It is now possible for glyoxal and polyols to be used as low cost resin forming binder systems with control over the rate of thermosetting. Practical examples of this are the formation of foundry cores and the formation of molded wood fiber asticles. In both of these examples the binder system is mixed with filler which comprises the major portion of the article. The mixture is then formed and cured to harden the resinous binder, giving the shaped article in-tegrity and durability. The most common method of cure is the application of heat, which means that the binder system must be heat activated to cure rapidly prior to solvent loss.

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If the binder system did not heat cure, dehydration would occur upon the appllcation o heat, and the resulting mass would be non-bonded or bound only by a hardening associ ated with solvent loss. This type of binding is shown by the more familiar plain amylaceous binders (no crosslinking).
The system of this invention exhibits a defi~ite wor~ing time span after which time a compaction of the binder con~aining filler mass would not give integrally bonded composite struetures, even though the initial amount of solvent (water~
is still present in the mix. Further, the strength and in-tegrity of the formed article is substantially greater when the binder system of this invention is used and cured during the working time span than is the strength and integrity of similar articles fonmed with amylaceous binders alone or with the binders o this iDvention where the working time span has elapsed prior to ar~icle formation.
In the production of foundry cores, there are a number of different methods for applyig heat to the formed cores to bring about a cure of the binder. These include cold iorming followed by baking of the cores, forming the cores in heated patterns, sometimes called a hot box, and forming the cores in a pattern or box followed by forcing heated air through the core.
The system of this invention can be used in any of the above methods. The advantages of this system are the . . - -~ 0~ ~ 5~0 use of a~ueous solvents which emit no odors or noxious fum~s and that the binder system presen-ts no air or water pollukîon hazards.
~e have further found that a particular group of cereal derived polysaccharides are uDiquely useful as binders in the a~ove-mentioned systems. These cereal based products are characterized by being hydratable in cold water and being reduced in molecular weight. We have also discovered a unique process to manufacture these cereal binders comprised of the two separate and distinct steps of chemical hydrolysis fol-lowed by a heat treatment.
Descr~ption of the Pre~erred EmbodimPnts The crosslinking of a polyol by glyoxal while con-trolling the rate by means of alkali halides can be demon-strated in a binder system alone, in the production of a formed article from a particulate material s~ch as the manufacture of ( foundry cores or in the molding of ~ood fiber articles. As previously stated, the reaction between glyoxal and polyols such as amylaceous materials apparently proceeds in ,wo steps.
~0 The first step is postulated as the formation of a hemi-ace~al and the later step as the formation of acetal linkages.
In an a~ueous dispersion of glyoxal and hydrolyzed pregelatinized amylaceous material, a rapid thickening occurs, resulting in a gel-like structure and finally proceeding to a damp paste which may actually precipitate if the solids are -~()69~Q~

at a low level. The inclusion of alkali halide alters the rate of these visible changes in the system. The easiest change to follow is the initial thickening. This can be accomplished by mixing all materials and recording the changes in viscosity with time. By using a controlled rate of heat-iDg, the initial reaction can be shown to be heat aetivated.
By varying pH, the initial reaction can be sho~n to b~ ac-celerated by rising pH.
The second step iD the reaction is more difficult to characterize, but clear evidence can be obtained by using sand mixes and forming foundry cores. In this case, the initial reaction step gives an iDcrease ln green strength of the sand mix, and the se~ond step gives a non-cohesive mix with no green strength and no thermosetting propPrties.
Prior to ~he discovery of the rate influence exerted - by alkali halides, the use of glyoxal and amylaceous binders ( was limited to those areas where a fast reaction was desired aDd/or the glyoxal and amylaceous material could be mixed with no shaping or for~ation after mixing. Thus a starch bonded clay coating could be applied to paper stock and then crosslinked by applying glyoxal. However, for the use of glyoxal and amylaceous material in a foundry core sand, the mix had a reaction so rapid that very short working times were available~ If core making and mixing were a continuous inte-grated process of a short duration such as three minutes or , : . ............... .

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less from start to finish, the production of useful cores might be possible. However, most present core making operations utilize batch processes for mixing thé sand and binders. After mixing, the batch is transferred to a core making area and used to make cores. This operation may re-quire sixty minutes for one batch of sand to be mixed and formed into cores. -Thus, without some means for controlling the reaction between glyoxal and the amylaceous material, the manufacture of foundry cores is not feasible using an amylaceous-glyoxal binder. The same limitations apply to other binder uses such as for molded articles employing cellulose fillers or for laminated articles.
Example 1 which follows demonstrates the dif-ference between foundry test cores with and without cross-linking agent and catalyst. The binder used in this example was an acid modified corn flour which was then extruded.
This binder was produced from acid modified corn flour with cold water solubles (CWS) of 12.8% and an alkaline viscosity of 20.3 seconds (1.3 g sample~. After extrusion the binder had CWS of 84.3% and an alkaline viscosity of 13.6 seconds (1.3 g sample).
The sand mixes were made in a laboratory Hobart mixer using one minute at low speed to dry blend the sand and the cereal binder and four minutes at high speed to blend the liquid ingredients which were salt dissolved in water and 40%
glyoxal solution. In the table the binder amounts are given ~069S(~Q

;3S percent o~ sand, which is co~mon practice in the foundry industry.
Example 1 Tensile % % Glyoxal % % Strength Mix Cereal 40/O Solution NaCl H20 psi 254 2.0 0.0 0.0 3.0 55.6 255 2.0 0.6 0.0 3.0 138.1 253 2.0 0.6 0.5 2.8 239.2 276 2.0 0.0 0.5 2.8 105.0 -( 10 The test cores were blown into a hot box at 400 F
and held in the box for 45 seconds. This box produced one dog bone specimen 1~' thick such as commonly used for teDsile testing by foundries. Tensile strengths represeDt the average of three specim~ns tested 4-1/2 hours after blowing.
An attempt to make a larger test batch of the ~ix No. 255 formulation in a Simpson mix muller gave specimens ( which fell apart upon removal from the hot box. Nor could çores be made from the mix No. 255 formulation after holding for a period of time after mixing.
Example 2 demonstrates the use of a Simpson mi~ muller employ-ing a 2 min. dry and 4 min. wet mixing period.

% % Glyoxal ~/~ % Tensile Cereal 40% Solution ~aCl H20 Stren~th psi

2.0 0.6 0 3.0 2,0 0.6 0.5 ~.8 273.6 , . , The above test cores were blown in a single cavity dog bone hot box at 400 F with 45 seconds retention time in the box.
Example 3 shows the performance of the salt cataly~ed binder system with time for sand mixes on the ~;
laboratory-Hobart mixer employing 1 minute low speed dry and 4 minutes high speed wet mixing. Without saltJ cores could not be made after holding the san'd mix l/2 hour.
Example 3 Hours % % % % Holding 10 Binder Glyoxal Salt WaterTime Tensile psi 2 0.6 0.5 2.8 0.5 243.1 2 0.6 0.5 2.8 1.0 214.2 2 0.6 0.5 2.8 1.5 184.4 In the first three examples American Foundry Society Testing Sand was used for all mixes. This is a grain controlled silica sand used only for test purposes. Example 4 shows the shows the favorable results of using a common foundry core sand, Portage 520, from Martin Marietta Aggregates.
Example 4 % % % %
20BinderGlyoxal Salt Water Sand Tensile psi 2 0.60.52.8 AFS 215.0 2 0.60.52.8 Portage 265.8 Cores were blown in a single cavity dog bone hot box at 400 F with a 45 second residence ti=e.

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In foundries it is often useful to know the effects o~ shorter or longer dwell times in the hot box on the strength of the cores. Example 5 illustrates the difference obtained by differeDt dwell times. All mixes were prepared in a Hobart and blown in the single cavity hot box at 400 F.
~xample 5 % % % L
Binder Glyoxal Salt Water D~ell Tensile Psi 2 0.4 0.5 2.8 30 sec. 147.5 ! lo 2 0.4 0.5 2.8 45 sec. 245.6 2 0.4 0.5 2.~ 60 sec. 243.3 This example clearly demonstrates the heat activated cure and t~e binder system tolerance ~or curing that extends through a workable range.
Example 6 demonstrates that variations in the amount of binder, glyoxal, water and salt can be tolerated and used to control the finished product properties with the same binder and sand. For this example, ~FS sand and the binder from Example 1 were used.

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xample 6 % % % %
BinderGlyoxal NaCl H20Tensile psi 2 o.b, 0.3 3,0203.1 2 0.6 0.5 2.8226.2 2 0.0 0.0 3.055.6 2 0.6 0.0 3.0138.1 1.5 0.6 0.5 2.8223.8 1.5 0.4 0.5 2.8216.9 ~10 2 0.4 0.5 2.8245.6 2 0.0 0.5 2.8106.8

3 0.4 0.3 3.0259.3 3 0.8 0.3 3.0252.5 2 0.6 0.7 3.0237.8 ~ 0.6 0.7 2.5243.1 A regression analysis on the above data resulted in the-form Tensile ~ A % Binder ~ B- % Glyoxal t C % ~aCl t D % H20 ~ E gave A ~ 38.8, B ~ 146.3, C
157.3, D = 23 and ~ - -75.2.
This gives a crud2 expression for approximating the final strength o:E a test specimen with AFS sand and a 45 second cure at 400 F. The importance of glyoxal, salt, binder and water concentrations are also shown. Because of the for~n of the regression analysis~ the lirnited data base ... : ,.

~069S(~0 and the great number of va~iables not considered,this re-:Lationship of binder system components to tensile s~rength should not be considered definitive. It does emphasize that each of the variables studied is necessary for adequate function of the binder system.
Example 7 shows the effect of di~ferent salts at equimolar concentration. In each case 12.75 gms H20 were -used per 500 gms of sand. All mixes were made in a labora-tory Hobart~ l min.low speed dry blend and 4 min. 2nd speed ( lO wet mix. Cores were blown into a single cavity dog bone core box at 425 P and cu~ed for 45 seconds in the box. All mixes had 2% binder by weight of sand and 0.4% glyoxal 40~/O
solution.
E~ample 7 Salt Gms Tensile psi NaCl 2.25 gms 215.0 ( LiCl 1.60 gms 48.8 KCl 2.88 gms 258.1 - KI 6.44 gms 175.0 NaBr 3.97 gms 85.6 KF 2H203.68 gms 31.3 Example 8 In this example salts other than alkali halides are compared to alkali halides all at equal % by weight based on sand. 2% ~inder and 0.6% glyoxal were used.

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NaBr 0.3 182.5 NaOH 0.3 57-5 Na2S04 0 3 150.0 ~a2S~3 0.3 82.5 NH4C1 0.3Too low to measure Na3P4 122 H3P~4 adjusted pH

The foregoing exa~ples hav~ demonstrated the ( lO catalytic effect of the salts on the reaction between glyoxal and a hydrolyzed gelatinized cereal product. However, this effect can be demonstrated ln another manner that more clearly shows the catalytic action by studying the postulated ~irst step in the reaction sequence. The following discussion and examples will show the effects o temp~rature, molar ratios of reagents, pH7 physical form of the glyoxal and salt types and ~ concentrations.
; We have found that aqueous dispersions of cereal flours, starches, proteins and the like increase in viscosity upon reaction with glyoxal and that this viscosity increase is a direct indication o the extent o-khe crosslinking reaction. A recording Brabender Visco/amylo/Graph (C~ W.
Brabender Instruments, Inc., South Hac~ensack, N. J.) was ound to be ideally suited for ~easuring these ~iscosity increases under controlled temperature conditions.

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The effect of temperat~re on the rate of reaction between glyoxal and an acid modîfied cereal 10ur is demon-strated by the following example.
~xample 9 One hundred fifty parts by weight of acid modified cereal flour was dispersed in 333 parts by volume of wat~r in a Waring blendor for 2 minutes. With continued mixing for 1 minute, 16,8 parts by volume o aqueous 40~/0 glyoxal was added. The pH of this slurry was adjusted to 5.8 with a few ( 10 drops o 20% sodiu~ hydroxide solution. The dispersion was transerred to the Brabender apparatus, and the reaction was allowed to proceed at 30 C. This procedure was exactly repeated except the reaction was conducted at 50 C. Figure 2 shows the viscosity curves for these two reactions.
lS The viscosity curves shown in Fig. 2 demonstrate that the rate of the glyoxal-cereal reaction is significantly accelerated by increasing temperature. Further, the viscosity c~rve at 30 C shows that the rate o reaction at near ambient temperatures is of such a magnitude that the useul life of a glyoxal-cereal binder system is quite limited in the absence of other controlling factors.
The following example will demonstrate the effect of varying the concentration of glyoxal available for reaction with a constant amount o an acid modified 10ur at constant conditions of pH and temperature.

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Exa,nple 10 Samples of 150 parts by weight of acid modified p,regelled cereal flour were dispersed in the appropriate volumes of water based upon the levels of aqueous 40% glyoxal to be added to yield constant concentrations of 30% flour solids. These dispersions were mixed for 2 minutes in a ~ariog blendDr. With continued mixing for l minute, the varying levels of 0, 8.4, ~.3, 10.5, 12.0~ 14.1, 16.8 and 21.0 parts by volume of a4ueous 40% glyoxal were add~d. The pH of each 0 mix~ure was adjusted to 5.8 with 20~ sodium hydroxide solu-tion. The dispersions were allowed to react at 30 C in the Brabender apparatus. Figure 3 shows the family of viscosity curves whic~ resulted from th~se reaction dispersions.
These curves show that the rate o viscosi~y in-crease is dependent upoo glyoxal concentration which affords one meaDs for control of this reaction. However, in many ~; end-use applications of the glyoxal-binder system, this m2thod of control is not practical.
; The viscosity curves of the following example will demonstrate the effect of pH on the rate of reaction between glyoxal and a cereal flour.
Example 11 Fifty grams of a pregelled corn flour was dispersed in 440 ml of water in a Waring blendor for 2 minutes. With continued n~i~ing for 1 minute, 5.6 ml of aclueous 40~/~ glyo~al :

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was added to the dispersion. The p~ oE this final mixture was 5.7. The mixture was transferred to the Brabender apparatus, and the reaction was allowed to proceed at 40 C.
The procedure was repeated adjusting the pH with either 10%
acetic acid or 5% sodium hydroxide solutions to give a series o~ reaction mixtures at varying pH levels. Figure 4 shows the series of viscosity curves obtained by this example.
The pH sensitivity of the glyoxal binder reaction is clearly demonstrated by these results. This method of ( 10 reaction control may also be impractical, especially in glyoxal-binder applications to high solids content systems.
Glyoxal is known to exist in vario~s monomeric, dimeric, trimeric and polymeric forms depending upon the physical state of the sample. T~e commercially available lS aqueous solutions are believed to contain pri~arily hydrated monomers and dimers of glyoxal. A so~id, trimerlc hydrated (~ form can also be obtaine~ as an item of commerce.
The following example will dernonstrate that both forms of glyoxal can be employed within the scope of this invention but that the solid form exhibits a lower reactivity toward the hydroxyl binder components, Example 12 One hundred fifty parts by wei~,ht of an acid modi-fied cereal flour was dispersed in 339 parts by volume of water as in Example 10. I~ith continued mixinO, 11.4 parts ~' .

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lby weight of 76% pure solid glyoxal trimer was added. The lP~ was adjusted to 5.8, and the reaction was carried out in the Brabender unit at 3no C. This procedure was repeated using 16.8 parts by volume of 40% ~lyoxal solution. This S volume of solution gave an equivalent molar glyoxal concen-tration on a monomeric molecular weight basis. The viscosity curves of Figure 5 give a comparison of the reactivity-of these two glyoxal forms.
This means of reaction control by selection of the physical form o~ glyoxal has a serious disadvantage in that solid glyoxal trimer is many times more costly than the aqueous solution for~.
According to the preferred embodiment of this inven-tion, the use of inorganic salts for controlling the reac~ion between hydroxyl containing polymeric materials and glyoxal affords a most practical and economic advantage over the other ` previously cited means o~ reactlon control.
The following example will illustrate th2 use of sodium chloride for retarding the ra~e of a reaction betw2en aqueous glyoxal and an acid modified pregelled flour.
Example 13 One hundred fifty parts by weight samples were dis-persed in 333 parts by volume of water containing 0, 1 and 2 moles oE dissolved sodium chloride in a Waring blendor. With continued mixing for 1 minute, 16~8 parts by volum2 o~ aqueous ..
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~o~69 5Q 0 4n% glyoxal was added to each dispersion. The~e ~ixtures were adjusted to pH 5.8. The mixtures were transferred to the Brabender apparatus, and the reactions were allowed to proceed at 30 C. The resulting viscosity curves are ex-hibited in Figure 6.
These viscosity curves demonstrate that the ra~e retarding effect upon the glyoxal crosslinkin~ reaction is sodium chloride concentration dependent. This rate retarda~
tion emp~oying salt can conveniently be overcome by rapidly ( 10 elevating the temperature of the reaction system. This important ~eature was evident in earlier exa~ples of the practical applications of glyoxal-binder-salt systems to oundry sand core moldings.
Salts other than sodium chloride were also found to significantly af~ect the rate of reaction between glyoxal and hydroxyl containing polymeric binders. Certain salts ( were actually discovered to accelerate the reaction whereas otbers almost entirely halted the reaction. These novel ; discoveries will be demonstrated by the following e~ample.
Exa~ple 14 For each reaction, 0.5 mole of the desired salt was dissolved in 443 ml o~ water in a Waring blendor. With ~` continuous blending for 2 minutes, 50.0 g of a pregelatinized corn flour was added. The resulting slurry was blended for o~e additional minute while 7.0 ml of aqueous 40% glyoxal was ~069 ~C~

added. After measuring the slurry pH, the mixtures were allowed to react in the Brabender apparatus at 30 C. The resulting viscosity curves from the glyoxal-flour reactions in the presence of several salts are given by Figure 7.
With the exceptions of sodium fluoride (NaF) and ammonium chloride (NH4Cl), the differences in reaction rates of glyoxal-flour in the presence of salts cannot be accounted for in terms of pH. For the series of reactions in the presence of the common ion as sodium, the glyoxal cross-linking reaction rates are observed to decrease with increas-; ing anion size (Rate F > Rate Cl > Rate Br ). Further, in the presence of chloride as the common ion, the reaction rates also follow the ionic size relationship (Rate Li+>
Rate Na~> Rate K~). This discovery of selective control by varying ionic size of the salt component allows for adjust-ment of the glyoxal-binder reaction rate to suit the require-ments of the end-use application. .-In the next example we demonstrate that the ini-tial reaction or thickening of the cereal and glyoxal does not preclude making sand cores from the thickened mass.
Sand cores were made in three different ways. First cores were made by dry mixing sand and cereal and adding the salt :~ .
and glyoxal dissolved in water and throughly mixing. Second-ly, the cereal was admixed with water containing the dissolved salt and the glyoxal was added and thoroughlymixed, This ':' ~:~
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~o~t3s~0 was done in a Waring b]endor. The resultant formulation was added to sand and mixed. Thirdly, the cereal, water, salt an~ glyoxal were mixed in a ~l~ring blendor~ and the mixture heated in the Brabender/visco/Amylograph. This cooked mix-ture was then added to the sand and mixed thoroughly. In all three examples the same sand, cereal and m;xer were used~
Each exampLe reduced to a formulation Oc 3120 gms sand~
62.5 gms cereal, 12.5 gms 40% glyoxal solution, 24.6 gms NaCl and 135 gms water. Cores were blown at 425 F for 45 seconds.
( 10 Core and green sand properties were measured after mixing and 1!2 hour after mixing.
Example 15 (inches) (psi) % 50 Jolt Green Core ; Binder Compact- Deform- Compression Tensile~
~ Added abilit~ ation 0 1/2 ~ 1]2 - . ~ ., _, . . .
Dry 53 0.211 0.65 1.02 306 2~1 Premixed 52 0.193 0.61 1.13 300 288 ~( Cooked 56 0.053 0.~6 0.96 309 303 It can be seen that pre-reacting the b;nder components through thefirst reaction step does not affect the cores if made from sand mixes soon after the first reaction step is carried out. It can also be seen that the first step in the reaction apparently controls the green strength of the sand mix.
This is shown by the increas~ in green strength with time for the first two mixes and the stable green strength of ~he third ~5 mix which was reacted through the irst reaction step.
.

~ 0~3 S 0 Example 16 To further demonstrate the two step nature, a binder mix similar to the second one in the preceding example was dried iD an oven at 70 C. This dried product was then ground on a laboratory hammermill and a sand mix made in the Hob~rt mixer using 10 &m~ of this produc~, 15 gm9 of water and 500 gms of A.F.S. sand. Cores were blown at 425 F, cured 45 sec-onds. These cores were too weak for tensile test measurements.
Example 17 An example of a non-cereal water dispersible poly-hydroxyl compound that reacts readily with glyoxal used alone or in combination with a cereal based product is demonstrated in the following example. Technical grade collagen proteiD
and acid modi~ied extruded corn flour were employed in the ;~ 15 following fonmulation:
A.F.S. foundry sand 500 parts by wt.
Binder (flour-protein~ 10 parts by wt.
Aqueous 40~ glyoxal 2 parts by wt.
Water12.75 parts by wt.

Sodium chloride2.25 parts by wt.
The binder portion and the sand were dry blended 1 minute at low speed in a laboratory Hobart mixer~ Salt dissolved in the water and the glyoxal were added and mixing continued 4 minutes at middle speed. This sad mix was then used to blow cores, dog bone tensile specimens at 425 F, ~B~ 26 -.

~ ~9 SO ~

45 seconds. The cores were cooled for 4 hours and the tensile s~rength wa~ measured.

% of Binder (Acid Modified- % of Binder Avg.
Extruded Flour) (Çolla~en Protein2 ~24 These results show that collagen protein functions efficiently as a sand core binder when used with the glyoxal, salt and water.
Since not all foundry cores or other products ~ 15 consi~ting of aggregate or particulate filler and a heat setting binder are formed in hot boxes or heated presses, thi~ binder system was checked for suitability to wet shaping and subsequent baking of the wet shaped piece. It was found that the surface had a tendency to dry out prior to the set or reaction, which resulted in a "loosely bonded" surface.
We found that this surface defect could be alleviated by '~ coating of the shaped article with water prior to placement iD the oven. This coating was most conveniently accomplished by spraying the su~face with water using a pressure or atomizing sp~ayer. Thi~ type of curlng requires green strength.

.... .

~o~o~

Example 18 shows a series o sand mixes made in a Simpson muller. Table ~ lists the mixes with amounts shown as % weight o~ sand. Mixing times are also sho~n.
Table B lists the green properties measured immediately after mixing a~d after 1 hour of standing. Table C lists the cured properties at different times and USiDg different oveDs for cores shaped immediately after mixing and after 1 hour. ..

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These data show the utility of the binder system for a mix, shape and bake type o~ manufacturing process.
The development of gxeen strength coincides with the earlier proposed theory of being a function of the first step in the overall reaction. The data also shows that the curing rate of this system is much faster than for more conventional dry oil or resin binders in the oven process, The following example lS presented to show the advanta~e of this binder system iD loweriDg heat and time requirements for curing. These core samples were made from a sand mix containing 2% extruded acid modified corn flour, 0.5% NaCl, 0.4% glyoxal and 3.0% H20 based on the weight of sand. This mix was made on a Simpson muller ~sing 1 minute dry blend and 10 minutes wet mixing. These cores were not sprayed with water.
Exsmple 19 Tensile_Stren~th at Cure Temperature Time 25~ F 300 F 350 F
( (Min.) This data shows the rapid curing possible with the binder system. In the previous example the conventional oil and resin binders required 60 min. in a 350 F circu-lating oven to ~ttain strengths app~oaching ma~imum. The ~ 35 -biLnder of the present invention requires less than 15 minutes at 350 F and approxima~ely 30 minu-Les at 250 F.
Thus the foundry industry could save fuel costs and/or accelexate production.
In many of the foregoing examples gelatinized acid modified corn flour was used. The use of glyoxal and alkali halide with cereal products is not limited to this general type flour. Any water dispersed or dis-persible hydroxyl containing material which reacts with ( O glyoxal has application to the use of salt to control the reaction. One example of a non-cereal product, collagen protein, has already been shown. Sugars, includ-ing those which are cereal derived such as liquid brewers adjunct which is an enzyme hydrolyzed product from corn starch, are other potentially useful products. In order to employ a different hydroxyl source, the amount of glyoxal needed to obtain a fairly continuous bondlng net~
work to provide the desired cured properties may have to be adjusted. Thus, starting with a low molecular weight saccharide like sucrose, a greater weight of glyoxal may be necessary to achieve crosslinking so that properties of - the finished article will resemble those attainable with more conventional crosslinking resin systems.
The following examples are presented to demon-strate that the low molecular weight sugars may be used to make foundry cores.

l~xample 20 lO gms of sucrose, a disaccharide, were mixed with 500 gms of silica sand for 1 minute at low speed in a Hobart mixer. 2 gms water, lO gms of glyoxal 40%
solution and 2.5 gms of KCl were mixed in a small beaker util the KCl was dissolved. This solution was added to the sand-sugar admixture and mixed 2.5 minutes at the second speed of the Hobart mixer. A core dog bone speci-men was rammed and dried in a circulating oven at 250 F
( lO for 15 minutes. This specimen had a tensile strength of 347.5 pounds per sq. inch.
Example 21 The same formulation as in Example 20 was mixed 4 minutes and the pH adjusted to 6.85 by adding 3 drops of 5% NaOH. The NaOH was added to accelerate stiffening of the sand mix. Cores were blown into a single cavity dog boDe hot box at 425 F with 45 seconds cure time followed by 4 hours of cooling. These cores gave tensile strengths of 270 psi.
2~ Example 22 The procedure of Example 20 was repeated usi~g the disaccharide maltose as a substitute for sucrose~ This formulation was mixed 4 minutes at the second speed in a Hobart mixer. Dog bone cores were blown at 425 F curing for 30 and 45 seconds.

~ . . ..

30 seconds - avg. 212 psi tensile ~5 seconds - avg. 241.3 psi tensile Example 23 A sample of co~mercial corn syrup with 82%
solids, 63-65% dextrose equivalent, was used as above, but 12~5 gm of syrup replaced the sugar and water. Cores were blown into a 425 F hot box and cured for 45 seconds.
~dditional cores were rammed and baked for 5 min. in a 350 circulating oven.
( 10 Hot DOX - 290 psi tensile Baked - 302.5 psi tensile These examples clearly sho~ the ability of the ..
crosslinking system to function with sugars.
In regard to the use of a cereal based hydroxyl source, particularly for bonding particulate masses into composite articles like foundry cores, we have found that a reduced molecular ~eight cereal grain sLarch material is particularly advantageous. We have found that such a material must be both well gelatinized and reduced in molecular weight. One means of determining approximate molecular ~eights is to measure the alkaline viscosity oi the material. This can be accomplished by dispersing the sample, 1.3 or 5.2 gms, in 50 ml of lN KOH. A micro bo~l Waring Blendor is suitable for preparing these dispersons.
The di5persion is allowed to stand 1 minute ior de-airation ~ - 38 -~06~0 and a 10 cc aliquot is pipet~ed into a #200 Cannon ~enske viscometer immersed in a 40 C water bath, The sample is moved into the ready position in the visco~eter and held there for a time sufficient to assure temperature equilibrium of the sample and bath. h total,,'~elapsed time of 12 miDutes is used, including the 1 minute of mixing and the 1 minute of de-airation. The time for the sample to flow between the measured marks on the viscometer is read and recorded as the Alkali~e ~iscosity at 1.3 or ( io 5.2 gms.
We have found that these A.V. values have double utility. First, if the par~icular sample of gelatinized amylaceous material has an A.V. greater than about 20 seconds at 1,3 ~m/50 cc 1~ KOH, there is a tendeDcy for difficult sand mix formation. Secondly, low levels of glyoxal are needed, which do not establish complete three ', ( dimensio~al crosslinked networks. We have found that the amount of glyoxal can be estimated for saccharide molecules by comparing A.V. data of the un~nown with that of sucrose.
This is done by measuring the A.V. of both sucrose and the unknown at a minimum of 2 concentrations and determin-in~ the A,V. of the lN KOH. Then using the following re-lationships:

- 3g -10~

N = measured h.V. in seconds No = lN ICOH in seconds Nr = N/No Nsp ~ Nx-l expressing the concentrations in gm/cc, plotting Nsp vs.
gm/cc and extrapolating to a lN~ value at gm/cc _ O; the approximate amount of glyoxal is shown by the amout needed for sucrose times the ratios of [N~ fox the sample and . sucrose in the form [N] sucrose . [N] sample. If a 2:1 `
( lO mole ratio of glyoxal to sucrose is need~d, this calculation will allow approximating the same mole ratio for the material o~ unknown molecular weight.
We have found that for making foundry cores the particular cereals which show unexpected benefits are the gelatinized products with an ~.V. of less than about 20 seconds at 1.3 gm/50 cc lN~KOH and of less than 100 sec.
( at 5.2 gm.
The following examples ~ill demonstrate the de-sired range of cereal pxoperties using starting materials other than corn flours which have be~n shown previously.
Example 24 shows the use of sorghum flours.

., .

~5 ~O~SOLS

Product A was made by treating 500 grns of red sorghum flour with 0.3% concentrated sulfuric acid and sufficient water to bring the acidi~ied flour to 28%
moisture. This was accomplished by mixing 20 minutes in a laboratory ~obart mixer at low speed. This flour was reacted with the acid and gelati~ized in a Wayne laboratory extruder with a 3/4" diameter barrel and a 20~ L:~ ratio, with a 2:1 compression screw, with the feed end 2/3 of the length at 220 F and the discharge end 1/3 at 320 F
( 10 using a 52 rpm sc~ew speed. After cooling the extrudate to room temperature, it was crushed and ground through a hammermill. The ground product was neutralized with gaseous a~monia until a 10% flour in water slurry gave a pH o~ 3.7-3.8.
Product B was identical except white sorghu~
flour a~d 0.2~ sulfuric acid were used as starting materials.
Cores were m~de iD a single cavity dog bone hot ~ box USiDg a sand mix with 2% cereal, 0.4% glyoxal 40% aqueous ; solution, 0.5% NaCl and 2.5% water, amounts based on the weight o~ sand.
Example 24 Z Cold Water 1.3 gm Core Product Solubles Alk Vis. Tensile psi A 73.2 11.8 230.0 B 80.0 12.6 211.3 ..
,. - .. .
. . .

~0~ 0 Exa~ple 25 Eight 500 gm samples of yellow corn flour w2re blended with 0.2 to 0.4% H2S~ and tempered to 18-24~/o moisture. The specific addition levels for each sample are shown in Table D. After addition of acid aDd water, the samples were blended for 20 minutes in a Hobart mixer at low speed. The samples were then processed in a laboratory ex~ruder employing a 220 F rear barrel tempera-` ture and 280 F for the discharge end 1/3 length. The ( 10 extruder was run at 50 rpm with a 2:1 compression screw.
The extruded samples were cooled to room temperature and ground on a hammermill. The samples were neutralized with gaseous ammonia until a 10% slurry of the sample gave a pH of 3.5 - 4.1. The products were then tested for cold water solubles, reducing sugars, alkaline viscosities, and ability to be used as hot box binders ~ith glyoxal and salt.
~( The results are shown in Table D. These results clearly show that the alkaline viscosity mus-t be kept below 20 seconds using our test method and a 1.3 g sa~ple i~ the product is to be preferred for making foundry sand cores by the hot box method. The data also shows that cold water solubles and reducing sugars are not as good a cri-teria fox judging acceptability of a product to be us~d as a foundry core binder.

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~069~n~1 The next example shows the use of corn starch.
xample 26 In this exa~ple a series of acid modified-e~truded starches was produced in which the initial acid level was varied in oxder to determine the reaction con-ditions and physical properties required to obtain optimu~
tensile streng~h in hot box cores.
Five hundred gram samples of pearl corn starch were ble~ded with 0.10% to 0.30% sulfuric acid and tempered ' (` 10 to 26% moisture as summarized by the data in Table E.
After the addition of acid and water, the starch mixtures were blended for 20 minutes in a Hobart mixer and processed, in the Wayne laboratory extruder (P~.T. 220 F; F.T. 270 F;
~peed 52 rpm). The extrudates were cooled to room tempera--15 ture and ground to pass through a herringbone screen on a Mikro Sampl Mill. The products wexe neutralized with ( gaseous ammonia aDd tested for cold i"a~er solubles, reduc-ing sugars, alkaline viscosities and tensile strengths in ~" hot box sand cores (in combination with glyoxal and salt).

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The results sho~n in Table ~ indicate that the blest product was produced with 0.133V/o acid for t~e cross-linking ratio chosen and that tensile strengths fairly co~parable to those of corn flour-based products could be S obtained.
Example 27 In this example, typical products were made from yellow corn grits.
A. A 500 g sample of yellow corn grits, generally refer-( 10 red to in the trade as cones or Kix cones, was blended with 0.3% sulfuric acid and tempered to 28% moisture.
~f~er blending in a Hobart mixer for 20 miDutes to insure uniform distribution of reagents, the material was processed OD the Wayne laboratory extruder (R.T., 220 F; F.T., 300 ~; speed, 52 rpm). The product was ground to pass through a fine herringbone screen, neutralized with gaseous ammonia and tested for solubles, reducing sugars, alkaline viscosity, p~ and tensile strength in sand cores.
B. Part A was repeated with 500 g of yellow corn grits tempered to 22% moisture and containing 0,4% sulfuric acid.

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106~500 E mple 28 In this example the importance of particle siæe on tensile strength will be demonstrated.
Five of the products described in Example 1 were reground on the Mikro Sampl Mill to pass through an extra fine herringbone screen. The materials were retested in sand cores for tensile strength and the results com~ared with the original values. As apparent from the data in Table F, all of the values obtained after regrinding were ( 10 higher than before. The greater the particle size decrease, the greater was the increase in tensile strength.

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Example 29 The next example demonstra~es the use of a com-merc:ial acid modified corn s~ar~h of 80 :~luidity which was ex~ruded af~er tempering to 28o/o mois~ur-P. Af~er cool-ing and grinding, cores were made aDd tested for tensile as in the preceding example.

Alkaline Startin~ ViscositY
Material CWS 1.3 ~m 5.2 ~m Tensile 80 fluidity 78.9%
( 10 corn starch 59% 17 83 of control The control was corn 10ur of Example 1.
Example 30 . In this example corn dry mill flour was extrusion : cooked as is customary to ~a~a a green sand cereal core . 15 binder having about 45-50~/~ CWS and a 1.3 g alkaline viscosity: between 75 aDd 90 seconds. This product was acid modiied ~( to give different alkaline viscosities-by changi~g the tim~
` of acid modification. 300 gms o~ e~truded flour was acidi-fied ~ith HCl gas to giv~ a p~ of 2.07-2.08 in a 10% aqueous slurry. These flour samples t~ere placed in covered glass : jars and heated in an oven for different lengths of time.
: After heating, samples were neutrali~ed with N~3 gas to pH
bet~eeD 3.7 and 5.1. Cores were made using a dog bone singl~
cavity hot box, 2~/o o these binders, 0.4% glyoxal 40~/~
2S solution and 2.5% water, amounts based on the weight of sand.

, .,' -' '~', '.'' ' .

Time Alkaline a~ Viscosity Core Product 70 C 1.3 g 5.2 g Tensile psi A 3 hours 16.7 99.0 177.5 B 2 hours 21.5 183.0 150.0 Mix B was more dificult to handle as the sand mix tended to be stiff. This demonstrates the preferred ùpper limit of A.V. for the cereal binder used to make sand cores.
Higher alkaline viscosity products can be used but in most cases would not be preferred.
Example 31 The products D and E from Example 26 showed rather poor tensile strengths when used with 0.4% B.O.S. glyoxal 40% aqueous solution as in that example. These products had low alkaline viscosities in the range of those preferred.
By using the alXaline viscosity data to calculate / N_~ as described earlier, values for _ N ~ of 3.1 and 2.4 were ob- ;;
tained. This indicates that substantially more glyoxal would be required, such as about 2.2% and 2.8%. Taking this into account, cores were made in the hot box using the same procedure and amounts as in Example 26 with 1.6% glyoxal 40% solution in place of 0.4% B.O.S.
Binder from Example 26Avg. Tensile psi / N_/
.
`~ 26D 232 3.1 26E 242 2.4 ...
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Compared to tensile strengths of 163 and 123, this is a dramatic increase This demonstrates the use of low range alkaline viscosity materials.
The preceding examples have shown the use of amy-laceous materials as the hydroxyl source with three different general process routes to arrive at a gelatinized hydrolyzed product. Normally one would not expect to find a marked superiority for a process route, but we unexpectedly dis-covered that acid modification followed by extrusion gela-tinization was superior to acid modification of an already extruded product or concurrent gelatinization and acid modification.
We have established that for foundry core use a cereal product which is gelatinized and has alkaline vis-cosities with the general upper limit of 20 seconds for a 1.3 gm sample and lOO seconds for a 5.2 gm sample tested in 50 ml of lN KOH is desired. These limits are preferred for baked or hot box foundry core applications, but should not be construed as limiting the scope of this invention.
The concurren* process of acid modifying and gelatinizing demands such rigorous control over conditions that it appears unfeasible in commercial practice. The ;. :
choice between acid modifying or gelatinizing as the first step would appear to be a matter of preference. When corn ~, , ' flour is gelatinized in an extruder-expander, the alkaline :i :

. , . . , . - , , .

3~

viscosity of the flGur is reduced. It would thus appear that this would provide a start toward the attainment of the desired acid modified alkaline viscosities. In prac-tice, the inverse occurs.
The following example illustrates this. 300 gm samples of an extruded-expanded corn flour with an alkaline viscosity of about 80 seconds tl.3 gm sample) and a raw corn flour of alkaline viscosity about 150 seconds were treated with dry HCl gas to reduce the pH to about 2.1 when tested in a 10% aqueous slurry. The flour samples were heated in an oven in glass jars at 70 C for the specified time.
After removal from the oven, the samples were neutralized ;.-.
with NH3 gas.
Example 32 .
Alkaline Time ViscositY (sec.) Starting Material (hrs.) 1.3 gm 5.2 gm i Pregelled flour 3 13.0 51.0 Pregelled flour 4 11.8 36.5 Raw flour 4 10.9 28.9 . .
This was repeated using a raw corn flour and three - different extruded-expanded corn flours with 1.3 g alkaline -~ viscosities between 75 and 90 seconds and CWS between 45 and 50%. All samples were kept in the same oven for three hours . ., .. o at 70 C.

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~c~;9s~v Example 33 Commercial acid modified corn flour which was processed at 168 F for 10 minutes with dry HCl at pH
2.3 and subsequently neutralized ~o about pH 4.0 with ammonia was used to prepare a binder. This starting material had a 1.3 g alkaline of about 17.8 seconds and CWS of about 13%. After extrusion through a Wayne laboratory extruder with a discharge set at 340 F and the feed set at 200 F, the hammermilled product had a ^
1.3 g alkaline viscosity of 12.5 seconds and a 5.2 gm viscosity of 42.0 seconds. This will be called Product 3.
This product and products which are duplicates of Nos. 3 and 4 from the preceding example (called 1 and 2 in this example) were screened to give 4 samples of each product with a narrow particle size range. These - samples were analyzed for 1.3 gm alkaline viscosities and pH's.

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~o~gsoo From thes data it is o~vious that the extrusion o~E a previously modifiecl product results in a more uniform blnder. This uniformity, coupled with a more rapid process, results in an unexpected and more desirable method for the production of acid modified binders within the scope of this invention.
Example 34 This example will demonstrate the use of the heat accelerated curable binder system of the present invention for the production of fiberboard. A slurry of 20 g of acid modified corn flour in 100 g of water containing 4.8 g of sodium chloride was intimately mixed with 200 g of wood ibers. The mixture was dried at 50 C for about 15 hours and then thoroughly blended with 10 ml of a solution contain-ing 1.6 g of glyoxal. The mixture was placed in a circular mold under about 1000 psi and cured for 10 minutes at about 300 F. The resulting fiberboard disk had properties com-parable to simila~ fiberboard disks employing a synthe~ic phenoi-formaldehyde resin as the binder system. The wood fibers may be sawdust, wood chips or wood particles.
Examp le_35 This example will illustrate the use of the binder system of the present invention for the production o~ a wet formed, pressed fiberboard. A solution of 40.0 g of 40~/O glyoxal and 4.5 g of sodium chloride in 600 ~1 of warm .' , , .~

water was used to prepare a slurry with 80 g of wood fibers.
Twenty g of acid modified corn flour was intimately blended into the fiber slurry for 10 minutes to insolubilize the glyoxal via hemiacetal formation with the corn flour. This mixture was de-watered on a vacuum filter to give a preform which was pressed and cured at about 230 F for 20 minutes.
The finished board had an approximate density of 0.7 g/cm and a hard, glossy surface.
Example 36 ,, - 10 This example will demonstrate the use of glutaric dialdehyde in place of glyoxal in a heat accelerated curable binder system of the present invention. A solution of 40 ml of aqueous 25% glutaric dialdehyde and 5 g of sodium chloride in 560 ml of warm water was used to prepare a slurry with 80 g of wood shavings and 20 g of acid modified corn flour.
After thoTough blending for 20 minutes, the slurry was filtered through a cloth and further de-wateTed while being formed into a mat under pressure. The resulting mat was cured in a press under 300 psi at about 200 F for 30 minutes.
The finished board had an approximate density of 0.6 g/cm3 and a haTd, glossy surface.
Example 37 This example will demonstrate the use of the heat accelerated curable system of the present inventicn as an ~: !

106~5(~

unfilled thermosetting resin. A slurry of 200 g of an acid modified corn flour in 390 g of a solution consisting of 4.1% glyoxal, 11.6% sodium chloride and 84.3% water was prepared in a high speed blendor. The resulting slurry was cast into several disk shaped pans. Several castings were cured into hard plastic-like disks by heating in an oven at 70 C for about 4 hours. Other castings set into disks upon standing at room conditions for about one week A third group of castings was cured rapidly at about 170 C for 10 minutes during which time the rapid evapora-tion of water caused the formation of foamed thermoset articles.
The polyaldehyde used in the present invention ; has the following general formula: OHC - (CH2)n - CHO, and where n is a whole number integer from O to 12.
A bonded particulate article manufactured by the method of the present invention may comprise 80% -90% particulate matter, 1% - 20% binder system, with the latter being comprised of 60% - 84% saccharide material, 3% - 27% glyoxal and 8% - 32% alkali halide.
A preferred method of manufacturing a foundry core under the present invention comprises the steps of mixing sand and a heat-accelerated curable binder system wherein the binder system is produced by the following ~069Sl)C~

steps: crosslinking 1% - 3% of saccharide-containing matter with 0.15% - 3% of 40% glyoxal aqueous solution; controlling the reaction by the use of 0.3% - 1.0% alkali halide as a catalyst using 0% - 4% water, 0% - 10% bentonite, 0% - 10 wood flour, 0% - 10% Silica flour, 0% - 10% iron oxide, and 0~ - 1% of a material selected fro~ the group comprising wax and asphalt emulsion; and forming the mixture to desired - shape and causing it to cure to a hardened state.
~ood results may be obtained by selecting the -saccharide-containing material from the group comprising sucrose, maltose, corn syrup, corn syrup solids, hydrolyzed /:
pregelled starches, hydrolyzed pregelled flours, and glyco protems.
The amylaceous material manufactured by the present invention has alkaline viscosities which are in the range of 10 to 20 seconds using a 1.3 g sample and 15 to 100 seconds using a 5.2 g sample and having cold water solubles of between 50% and 98%.
With the present invention the method of manufacturing the improved amylaceous material includes the following steps: acid hydrolysis at moistures between 5% and 12%, as is basis, using between 0.1% and 2% acid anhydrous basis; neutralization of the acid hydrolyzed amylaceous material to between pH 3 and 6 obtained on a 10% solids water slurry; gelatinization of the neutralized ~`

106~5~

acid hydrolyzed amylaceous material at moisture levels between 15% and 40% and at temperatures of between 212 and 400 F; removal of water from the gelat;nized product by allowing residual heat to flash off water and by sub-jecting it to the action of a drying medium such as air or heat; and/or commuting the amylaceous mass to pellets or flakes; and comminuting the dried amylaceous mass to a flour.
In manufacturing a resinlike mateTial, with the present invention the method may include mixing a filler material and a heat-accelerated curable binder system, wherein the binder system is produced by cross-linking a saccharide-containing substance with glyoxal in water; and controlling the reaction rate by the use of an alkali halide selected from the group comprising KCl, KBr, NaCl, and NaBr; the method also including the following steps: dissolving or dispersing the salt, saccharide-containing substance and glyoxal in water;
dispersing from 0% - 80% of fillers, extenders and/or pigments in the above mixture; shaping, forming or .
using the mixture as a coating; causing the mixture to react by the application of heat; and removing moisture from the reacted mixture.
In the preceding examples, the analytical values for alkaline viscosity were determined by the method .
.

~C~j9 S(~D

a:Lready described. The procedure for the cold water solubles (C~S) was:
A 20 gm sample was weighed aDd added to 480 g distilled water in a 600 ml beaker. A magnetic stirrer was usPd to disperse the material with s~irringcarried out for 5 minutes. (If the sample tended to lump wh~n added to the water, additivn was made by sifting the sample into the water with stirrer running using a tea strainer.) The slurry was allowed to stand one hour and O then mixed again for 2 minutes. The slurry was filtered using 18.5 cm fluted paper (Reeve Angel #80~ or equivalent?.
The flrst few cc's of filtrate were discarded. 10 ~l of the filtrate were placed in a weighed aluminum wei~hing dish and the dish and aliquot ~eighed. The aliquot was dried at 70 C in a circulatiog air oven-for 24 ~ 2 hours.
The dried residue was weighed aDd % solubles calculated.
( The preferred curable system of the present in-ventioD may further be defined in terms of molecular weight or mole ratios ~7herein the saccharide material may be con-sidered as monomeric anhydro~lucose of molecular weight 162.1, the polyaldehyde as glyoxal monomer of molecular wei~ht 58 and the alkali halide as sodium chloride of molecular weight 58.4. In these terms, the curable system may be described as containing a mole ratio of polyol to polyaldehyde of 1:1 to 10:1 and a mole ratio of polyol to "-, , ~

S~

alkali halide of 2:1 to 1:10. An alternate method of determining mole ratios is to use the actual polyol polymer molecul~r weight. In this case the mole ratio of polyol to polyaldehyde is from l:l to 1:3 and the mole ratio of polyol to alkali halide is from l:Q.~ to 1:10. These mola~ ratios are the preferred ranges of the curable system but should not be construed as limit-ing the scope of the present i~vention.

"' 10 -.

~3 -

Claims (57)

The embodiments of the invention in which an exclusive property or privilege is claimed as defined as follows:

1. In a method for modifying a polyol with a polyaldehyde, the improvement comprising the step of con-trolling, by accelerating or retarding the rate of the cross-linking reaction in a liquid solvent by the use of an inorganic alkali halide as a catalyst at such a temper-ature and pressure relationship as to maintain said liquid condition during the reaction, the polyol and polyaldehyde being of a type which would react in the absence of an alkali halide catalyst and being of a type which are mutually solvated in a solvent for the alkali halide.

2. The method of claim 1 wherein the alkali halide is selected from the group comprising KC1, KBr, KI, NaC1, NaBr, NaI, NaF, LiC1.

3. The method of claim 1 wherein the alkali ha-lide is an NH4 halide.

4. The method of claim 3 wherein the NH4 halide is NH4C1.

5. The method of claim 1 wherein the polyol is a saccharide or saccharide-containing substance.

6. The method of claim 5 wherein the poly-aldehyde is glyoxal or a polymer thereof.

7. The method of claim 5 wherein water is used as a solvent.

8. The method of claim 5 wherein the polyalde-hyde has the following general formula OHC - (CH2)n - CHO

and wherein n is a whole number integer from 0 to 12.

9. The method of claim 6 wherein water is used as the solvent.

10. The method of claim 9 wherein the alkali halide is selected from the group comprising KC1, KBr, KI, NaF, NaC1, NaBr NaI and LiC1.

11. The method of claim 7 wherein the halide is ammonium halide.

12. The method of claim 8 wherein the polyol saccharide is an amylaceous material or hydrolysate thereof.

13. The method of claim 7 wherein the polyol is selected from the group comprising hydrolyzed gelatinized corn starch, corn flour and sorghum flour.

14. The method of claim 13 wherein the polyol has an alkaline viscosity of less than 20 sec., when using a 1.3 g sample and less than 100 sec. when using a 5.2 g sample.

15. The method claimed in claim 1 wherein the mole ratio of polyol to polyaldehyde is from 1:1 to 1:3 and the mole ratio of polyol to alkali halide is from 1:0.3 to 1:10.

16. The method claimed in claim 1 wherein the mole ratio of polyol to polyaldehyde is from 1:1 to 1:3 and the alkali halide which is present in the solvent phase is from 1.0 to 5.0 molal.

17. The method claimed in claim 9 wherein the ratio of the amount of saccharide as saccharide units to glyoxal as monomer is from 1:1 to 10:1.

18. The method claimed in claim 17 wherein the alkali halide is present in ratio with the saccharide units on a mole basis of from 2:1 to 1:10.

19. The method claimed in claim 18 wherein the amount of alkali halide present in the solvent is from 1.0 to 5.0 molal.

20. The method claimed in claim 9 wherein the amount of polyol to polyaldehyde is in the ratios of equivalent weights from 1:0.25 to 1:1.

21. The method claimed in claim 20 wherein water is used as a solvent.

22. The method claimed in claim 20 wherein the alkali halide is present in an amount of at least 1 mole alkali halide per equivalent weight of polyol.

23. The method claimed in claim 21 wherein the alkali halide is present in at least 1 mole per equivalent weight of polyol.

24. The method claimed in claim 7 which includes the step of using one of the group comprising KC1 or NaC1 and mixtures thereof to control the rate of reaction be-tween glyoxal and saccharide.

25. The method claimed in claim 24 wherein the saccharide is selected from the group comprising maltose, sucrose, dextrose and glyco protein.

26. The method claimed in claim 24 wherein the saccharide is a hydrolyzed gelatinized amylaceous material having a 1.3 gm sample alkaline viscosity of not more than 20 sec. and a 5.2 gm sample alkaline viscosity of not more than 100 seconds.

27. The method claimed in claim 24 wherein the saccharide-containing material is collagen.

28. The method of claim 1 wherein the polyol is a saccharide or sac-charide-containing substance, the solvent is water, the catalyst is selected from the group consisting of KC1, KBr and NaC1, the mixture is heated to assist the reaction and moisture is removed from the reacted mixture.

29. The method of claim 28 which includes the step of dispersing fillers, extenders or pigments in an amount up to 80% by weight, based on the weight of saccharide containing substance, glyoxal and water, prior to the applica-tion of heat.

30. The method of claim 28 wherein the mole ratio of saccharide molecules to glyoxal is in the range 1:1 to 1:3 and the mole ratio of KC1, Br or NaC1 to saccharide is in the range 1:0.3 to 1:10.

31. The method of claim 28 wherein the KC1, Br or NaC1 concentration is between 1 and 5 molal.

32. The method of claim 28 wherein from 15 to 95% water, 5 to 50%
saccharide substance, 1 to 25% glyoxal and 1 to 25% KC1, KBr or NaC1 are used.

33. A method of manufacturing a bonded particulate article comprising the steps of admixing 80 to 99% of particulate material with 1 to 20% of a binder system, forming the admixture in a heated mold, removing the bonded article and allowing it to cool, wherein the binder system is a polyol modi-fied by a method according to claim 1 by admixing 60 to 84% of a polyol se-lected from the group consisting of a saccharide a saccharide polymer and a glyco protein with 3 to 27% of glyoxal and 8 to 32% of alkali halide.

34. A bonded particulate article manufactured by the steps of admixing 80 to 99% of particulate material with 1 to 20% of a binder system, forming the admixture in a heated mold, removing the bonded article and allowing it to cool, wherein the binder system is a polyol modified by a method according to claim 1 by admixing 60 to 84% of a polyol selected from the group consist-ing of a saccharide, a saccharide polymer and a glyco protein with 3 to 27%
of glyoxal and 8 to 32% of alkali halide.

35. A bonded particulate article as claimed in claim 33 wherein the par-ticulate material is sand and the bonded article is a foundry core.

36. A bonded particulate article as claimed in claim 34 wherein the particulate material is cellulosic.

37. A bonded particulate article as claimed in claim 36 wherein the cellulosic particulate material is a refined wood from the group consisting of sawdust, wood chips, wood particles and wood fiber.

38. A method of forming a bonded particulate article according to claim 35 in the form of a foundry core wherein 1 to 3% of saccharide containing matter is reacted with 0.15 to 3% of 40% glyoxal aqueous solution and the rate of reaction is controlled by the use of 0.3 to 1.0% alkali halide as catalyst using 0.4% water, 0 to 10% bentonite, 0 to 10% silica flour, 0 to 10% iron oxide, and 0 to 1% of a material selected from the group consisting of wax, wax emulsion, asphalt emulsion and wax-asphalt emulsion.

39. A method as claimed in claim 38 which includes the step of curing the core for 5 to 120 seconds in a hot box.

40. A method as claimed in claim 39 wherein the hot box is at a temper-ature between 250° and 550°F.

41. A method as claimed in claim 38 wherein the saccharide-containing matter is selected from the group comprising sucrose, maltose, corn syrup, corn syrup solids, glyco proteins, hydrolyzed pregelled starches, and hydro-lyzed pregelled flours.

42. A method as claimed in claim 38 wherein the saccharide-containing material is a hydrolyzed-gelatinized amylaceous material having alkaline vis-cosities of less than 20 seconds using a 1.3 g sample and less than 100 seconds using a 5.2 g sample.

43. A method as claimed in claim 38 where the alkali halide is selected from the group comprising KC1, KBr, KI, NaC1, NaBr, NaI or NaF.

44. A method as claimed in claim 38 where the glyoxal solution and alka-li halide are admixed with water sufficient to dissolve the alkali halide prior to admixture with the rest of the ingredients.

45. A method as claimed in claim 44 wherein the alkali halide is select-ed from the group comprising KC1, NaC1, KBr or NaBr.

46. A method as claimed in claim 45 wherein the solution of glyoxal and alkali halide with water is in the following range of composition: glyoxal 2 to 35%, alkali halide 6 to 25%, and water 45 to 92%.

47. A method as claimed in claim 38 which includes the step of removing the core from the form and drying the core.

48. A method as claimed in claim 38 which includes the step of surface coating the core with a material selected from the group comprising water and water-containing core wash prior to drying.

49. A method as claimed in claim 48 wherein the drying is performed in an oven.

50. A method as claimed in claim 47 wherein the alkali halide is KC1, KBr, NaC1 or NaBr.

51. A method as claimed in claim 50 wherein the saccharide-containing material is selected from the group comprising sucrose, maltose, corn syrup and corn syrup solids.

52. A method as claimed in claim 50 wherein the saccharide material is a hydrolyzed gelatinized amylaceous material having alkaline viscosities of less than 20 seconds for a 1.3 g sample and less than 100 seconds for a 5.2 g sample.

53. A method as claimed in claim 50 wherein the saccharide material is a glyco protein.

54. A method as claimed in claim 38 wherein the saccharide is water soluble amylaceous hydrolysate.

55. A method as claimed in claim 50 wherein the glyoxal and alkali halide are mixed prior to admixture with the rest of the ingredients.

56. A method as claimed in claim 55 wherein the glyoxal and alkali halide are mixed with water in the following range: glyoxal 2 to 35%, salt 6 to 25%, water 45 to 92% prior to adding the rest of the ingredients.

57. A method as claimed in claim 56 wherein additional water is added at the time of mixing the glyoxal and alkali halide mixture with the rest of the ingredients.