as stated above , the desired characteristics of the replacement for amylopectin starch are : ( 1 ) stable dispersions exhibiting no “ retrogradation ”; and , ( 2 ) cold water dispersability , thereby avoiding the need for hot water . the starch industry produces starches which satisfy the stability requirement , and also produces starches which satisfy the dispersability issue , but the selection of starches satisfying both requirements is limited . an array of possible starch candidates was obtained from cargill , national starch , penford products , and grain processing corporation . only one material exhibited both of the two desired characteristics , as most of the samples were not cold water dispersible . the material that exhibited both desired characteristics was a cold water - dispersible , cationic modified starch , available from grain processing corporation as an experimental product , under product number gpc x201 . this material advanced to commercial status under product number gpc g400 . cationic modified starches have been known for many years , and many examples are cited in hofreiter , b . t ., “ natural products for wet - end addition ,” in “ pulp and paper chemistry and chemical technology ,” casey , j . r ., editor , wiley , new york , n . y ., 3rd edition , 1981 , pages 1475 - 1514 ; paschall , e . f ., “ production and uses of cationic starches ,” in “ starch chemistry and technology ,” r . l . and paschall , e . f ., editors , academic press , new york , n . y ., volume ii , pages 403 - 422 ; smith , r . j ., “ characterization and analysis of starches ,” also in “ starch chemistry and technology ,” whistler , r . l . and paschall , e . f ., editors , academic press , new york , n . y ., volume ii , pages 569 - 655 ; and whistler , r . l ., bemiller , j . n ., and paschall , e . f ., “ starch : chemistry and technology ,” second edition , academic press , new york , n . y ., 1984 . cationic modified starches are generally categorized by the weight percent nitrogen incorporated into the starch and the degree of substitution . the degree of substitution ( ds ) is a measure of the average number of hydroxyl groups on each d - glucopyranosyl unit which are derivatized by substituent groups . the ds value is expressed as moles of substituent per d - glucopyranosyl group . the relationship between the added nitrogen content , the degree of substitution , and the molecular weight of the substituent is described by the following equation which is discussed in whistler , r . l ., bemiller , j . n ., and paschall , e . f ., “ starch : chemistry and technology ,” second edition , academic press , new york , n . y ., 1984 : the maximum value of the degree of substitution is 3 . the weight percent nitrogen is generally determined by the dumas method , which can be executed using a leco analyzer as described in “ nitrogen in starch , starch slurry , and glucose ,” organic application note , leco corporation , 3000 lakeview avenue , st . joseph , mich . 49085 . the cationic modified starch used in the foamable concentrate according to the invention should have a degree of substitution of at least approximately 0 . 02 , and in the range from approximately 0 . 02 to 0 . 2 . a preferred starch for use in the invention has a degree of substitution of 0 . 04 . the nitrogen content of the cationic modified starch should be at least approximately 0 . 15 %, and preferably in the range from approximately 0 . 15 % to approximately 2 . 0 %. a preferred starch for use in the invention has a nitrogen content of 0 . 35 %. the grain processing corporation ( gpc ) starch used in this development contained 0 . 35 weight % nitrogen , over and above the nitrogen background amount exhibited by most starches , which , as explained in smith , r . j ., “ characterization and analysis of starches , in “ starch chemistry and technology ,” whistler , r . l . and paschall , e . f ., editors , academic press , new york , n . y ., volume ii , pages 569 - 655 , is usually under 0 . 1 weight %. the corresponding degree of substitution was 0 . 04 moles of substituent per d - glucopyranosyl group . hofreiter , b . t ., “ natural products for wet - end addition ,” in “ pulp and paper chemistry and chemical technology ,” casey , j . r ., editor , wiley , new york , n . y ., 3 rd edition , 1981 , pages 1475 - 1514 suggests that commercial cationic starches contain between 0 . 18 and 0 . 37 weight % nitrogen . according to whistler , r . l ., bemiller , j . n ., and paschall , e . f ., “ starch : chemistry and technology ,” second edition , academic press , new york , n . y ., 1984 , common commercial ds values are below 0 . 2 . cold water dispersability is not necessarily related to the ds value , as starch is generally a water - soluble material after the granular structure has been disrupted . this means a high ds value is not required for easy dispersion . in many instances , with industrial starch , the gelatinizing process is performed at the user &# 39 ; s facility , meaning that the starch producer is selling a non - gelatinized product . granular structure disruption can be affected by pregelatinizing a starch material , and the cationic modified starch for use in the foamable concentrate of the invention is preferably pre - gelatinized , so that it can be readily combined with water . the gpc material described herein is pregelatinized , and disperses readily in cold water . in accordance with the invention , in forming the foamable concentrate , the cationic modified starch should be added to water at a temperature in the range from approximately 10 ° c . to 60 ° c . preferably , however , the water temperature is in the range from 15 ° c . to 30 ° c . at the time the starch is added , and ambient temperature , i . e ., approximately 20 ° c . to 25 ° c ., is entirely suitable . it is important to note that the foam technology benefits achieved by this development are related to the starch stability provided by the cationic substituents , while the process benefits are related to the pregelatinizing of the starch raw material . as mentioned above , the starch industry does offer an array of cationic starches . thus foam technology benefits could be obtained by cooking these non - dispersible cationic starches , thereby gelatinizing them on - site . another alternative is to purchase from the starch supplier a predispersed cationic starch , which , by definition , would have been gelatinized . these are all process alternatives and each leads to essentially the same foam technology benefits . in the following examples , the hydrolyzed keratin protein was produced by industria suma ltda in brazil , and can be obtained from martin baer & amp ; co . p . o . box 11 , essex , conn . 06426 , u . s . a . the amylopectin starch can be obtained from cargill , inc ., p . o . box 9300 , minneapolis , minn ., 55440 , u . s . a ., or national starch and chemical company , 10 finderne avenue , bridgewater , n . j . 08807 , u . s . a . the ferrous sulfate is commonly available and is preferred as the heptahydrate , feso 4 . 7h 2 o . the tsfl dispersant , a combination of ammonium and sodium lignosulfonate , is available from lignotech usa inc ., 100 grand avenue , rothchild , wis . 54474 , u . s . a . the biocide can be stepan onyxide , from stepan company , 22 w . frontage road , northfield , ill ., 60093 , u . s . a ., or nipacide bk , from nipa hardwicke , inc ., 3411 silverside road , 103 hagley building , wilmington , del . 19810 , u . s . a ., or an equivalent biocide . ammonium hydroxide is used to adjust the ph to about 6 . 5 . the cationic starch is commercially available from grain processing corporation , 1600 oregon street , muscatine , iowa 52761 . in making a foamable concentrate using the gpc starch compositions , the required amount of ambient temperature water was placed in a reactor vessel equipped with a stirrer suitable for the batch size . the dry and liquid ingredients were added while stirring was maintained . no heat was added . modest viscosity was exhibited , but only at the higher solids levels . the components were added in the following order : gpc g400 cationic modified starch , ferrous sulfate heptahydrate , hydrolyzed protein , tsfl dispersant , ammonium hydroxide , and finally the biocide . stirring was continued for a time interval sufficient to achieve a homogeneous final mixture , generally between three and ten hours , depending on batch size . in addition , the particle size of the cationic modified starch is important from a process viewpoint , but that variable does not affect the foam properties of importance , namely stiffness and drain time . in some of the development work described herein , gpc x201 , a developmental cationic modified starch having a larger particle size , was used . only about 25 % of the material , by weight , would pass through a 200 mesh screen . gpc g400 , a commercial cationic modified starch , having a smaller particle size , was also used in the development work . in the case of gpc g400 , more than 60 % of the material would pass through a 200 mesh screen . the commercial material having a smaller particle size was more difficult to disperse in that , like many wettable powders , the material formed small globules of dry material which required extra stirring time in the reactor before complete dispersion was achieved . the larger particle size material is preferred not only because it dispersed much more easily , but also because it resulted in less dust and was therefore more comfortable to use . the process schemes provided an opportunity to introduce many variables in the hope that the formulation produced would be better , or that the process itself would be faster or more efficient . a common first choice is to alter the temperature of the formulation process , anticipating that the dispersion sequence will accelerate . in fact , no significant dispersion speed advantage was realized . however , at a higher temperature , the viscosity of the final formulation is very much higher . the same result occurs if a formulation produced at room temperature is subjected to heating after the normal room temperature process is completed . in all cases , heating generates a more viscous concentrate . after a particular composition was prepared and its physical properties defined , the only other laboratory evaluation available was performed . this evaluation involved foaming the diluted material , judging the physical characteristics of the foam produced , and measuring the drain time . since the compositions are essentially all the same , and vary only with respect to concentration , the diluted , “ to - be - foamed ” liquid of a specific composition can be obtained from any of the compositions . common practice involves diluting according to the “ dilution ratio ,” which is defined as the volume of the diluted material divided by the volume of the concentrate . as an example , when one volume of concentrate is added to six volumes of water , the total volume is seven units , and the dilution ratio is seven . in the following examples , the dilution was adjusted to prepare “ to - be - foamed ” liquids with specific levels of gpc g400 starch , since that ingredient is directly related to the drain time performance . the foaming procedure is described in kittle u . s . pat . nos . 4 , 874 , 641 , 5 , 215 , 786 , 5 , 853 , 050 , 6 , 929 , 423 , and 6 , 994 , 491 , and is based on technology originally described in kroll u . s . pat . no . 4 , 474 , 680 . the disclosures of all of these patents are here incorporated by reference . the “ to - be - foamed ” liquid is pumped through a flow control orifice into a mixing block , where it is added to an expansion gas , usually compressed air , similarly controlled by a flow control orifice . the combination is discharged through a mixing zone , which can be constituted by a hose of appropriate length or by a packed bed , so that a foam is discharged onto a target substrate . the technology is fully scalable , with commercial devices having a discharge rate ranging from less than one gallon per minute liquid flow to 60 gallons per minute liquid flow . measuring the drain time for these compositions entails measurement of the “ relative ” drain time rather than attempting to define and measure absolute drain time , which is much more complex . in these cases , all that is required is a standard procedure which is : ( a ) reproducible ; ( b ) easy to carry out ; and ( c ) related to common field experience . a drain time procedure satisfying these requirements has been developed and calibrated . the procedure involves the use of a foaming system , as described above , operating at one gallon per minute liquid flow , which becomes the definition of how much liquid is collected as foam . this discharge is collected for one minute in a fifteen gallon plastic tank having a conical bottom and fitted with a gravity discharge opening at the bottom of the cone . after the calibrated foaming system has stabilized , the foam is discharged into the plastic tank for one minute . the beginning of the time interval ( t = 0 ) used as the measure of drain time is determined to be the time of completion of the discharge of foam into the tank . a collection beaker is set below the bottom of the tank . as the foam drains , liquid is collected , and the weight is incrementally defined as a function of time . since the input volume was one gallon , that is , 3785 cubic centimeters , the grams collected in each time interval can be converted to weight percent drained by dividing by 37 . 85 . the final result can be plotted as weight percent drained as a function of time . the procedure is reliable , and works best for foams having slower drain times . in the following examples , viscosity was measured after the material was allowed to rest overnight . the viscosity measurements were made using a brookfield viscometer , at spindle # 4 speeds of 6 , 12 , 30 and 60 rpm . for reference , a typical commercial batch of product , in accordance with kittle u . s . pat . no . 5 , 853 , 050 , prepared by the procedure previously outlined had the following composition : keratin protein 4 . 00 weight percent amylopectin starch 4 . 00 ferrous sulfate 8 . 00 tsfl 4 . 00 biocide 0 . 50 ammonium hydroxide 0 . 40 water 79 . 10 total 100 . 00 the physical characteristics of this composition are : ( a ) ph at room temperature , 6 . 2 - 6 . 4 ; ( b ) weight percent solids , 15 . 50 ; ( c ) viscosity after the material was allowed to rest overnight , measured using a brookfield viscometer , at room temperature , at spindle # 4 speeds of 6 , 12 , 30 , 60 , was 19000 , 10000 , 4800 , 3000 cps , respectively . by contrast when the same composition is prepared using the same ingredients , but omitting the amylopectin and substituting grain processing corporation &# 39 ; s x201 cationic modified starch , the composition was as follows : keratin protein 4 . 00 weight percent gpc x201 starch 4 . 00 ferrous sulfate 8 . 00 tsfl 4 . 00 biocide 0 . 50 ammonium hydroxide 0 . 40 water 79 . 10 total 100 . 00 , the physical characteristics were identical to those of example one , except that the viscosity was less than 100 cps . in this example , the composition of example two was extended to a higher starch level , and was as follows : keratin protein 4 . 00 weight percent gpc x201 starch 6 . 00 ferrous sulfate 8 . 00 tsfl 4 . 00 biocide 1 . 00 ammonium hydroxide 0 . 50 water 76 . 50 total 100 . 00 , the increased starch content did not significantly increase the viscosity . the ph remained in the same range , and the solids increased to 17 . 49 . repetition of the same composition demonstrated the expected reproducibility . in order to evaluate how far the concentration level could be extended , the components of the formulation ( other than the biocide ) were proportionately increased , by 25 %, while the amount of water was correspondingly decreased , so that the formulation was as follows : keratin protein 5 . 00 weight percent gpc x201 starch 7 . 50 ferrous sulfate 10 . 00 tsfl 5 . 00 biocide 1 . 00 ammonium hydroxide 0 . 60 water 70 . 90 total 100 . 00 the solids increased to 21 . 12 %, the ph remained at 6 . 3 , and the viscosity showed some increase . the viscosity at room temperature , measured using a brookfield viscometer , with spindle # 4 speeds of 6 , 12 , 30 , 60 , resulted in measured viscosities of 2000 , 1500 , 1200 , and 1100 cps , respectively , all of which are well within a usable viscosity range . in this example , the composition was again proportionately increased by about 25 % to arrive at the following composition : keratin protein 6 . 00 weight percent gpc x201 starch 9 . 00 ferrous sulfate 12 . 00 tsfl 6 . 00 biocide 1 . 00 ammonium hydroxide 0 . 70 water 65 . 30 total 100 . 00 the solids increased to 25 . 31 %, the ph stayed the same at 6 . 3 , while the viscosity increased . the viscosity at room temperature , measured using a brookfield viscometer , with spindle # 4 speeds of 6 , 12 , 30 , 60 , resulted in measured viscosities of 9000 , 6000 , 3800 , and 2700 cps , respectively , all of which are still within a usable viscosity range , even though some gel formation was observed . the following formulation was prepared at room temperature , yielding a concentrate having a ph of 6 . 5 , and spindle # 4 viscosities of 2180 , 1470 , 945 , and 510 cps , with spindle speeds of 6 , 12 , 30 , and 60 , respectively . the measurements were taken at 25 ° c . this composition used gpc g400 cationic modified starch , the commercial version of the gpc x201 starch described previously . a formulation corresponding to that of example six was prepared , but at a temperature of 50 - 55 ° c . the corresponding viscosities were 6300 , 4200 , 2820 , 2020 cps , also at 25 ° c . a sample of a scaled - up batch of the example six composition was reheated to 60 - 65 ° c . for three hours while being stirred modestly . after cooling and sitting at rest overnight , the same procedures as used for all the samples , the viscosities were measured at 25 ° c ., with spindle # 4 and the same rotational speeds , yielding viscosity values of 40000 , 25900 , 15200 , and 9900 cps . the foaming performance and drain time results for samples according to examples six , seven and eight , all evaluated under the same conditions , were essentially identical . an explanation for this behavior is that the fluid characteristics of the various concentrates are a function of the processing history , but , when each concentrate is diluted to the same “ to - be - foamed ” composition , the fluid characteristics become identical . the following composition , which is identical to the composition of example three , was prepared at room temperature , yielding expected physical properties : keratin protein 4 . 00 weight percent gpc x201 starch 6 . 00 ferrous sulfate 8 . 00 tsfl 4 . 00 biocide 1 . 00 ammonium hydroxide 0 . 50 water 76 . 50 total 100 . 00 the composition was diluted at a dilution ratio of 6 , by adding 7 . 5 pounds of the composition to 37 . 5 pounds of cold water . the mixture was stirred for a few minutes and foamed directly , as described above . the gpc x201 composition in the diluted “ to - be - foamed ” liquid was 10000 ppm , which was the original composition , 60000 ppm , divided by the dilution ratio . the foam produced was stiff by any common standard and the drain time was measured as described . the drain time results are shown in fig1 . when the same composition was diluted at a dilution ratio of 4 , by adding 10 . 0 pounds of the composition to 30 pounds of cold water , the resulting foam was stiffer . the amount of gpc x201 starch in the diluted , “ to - be - foamed ,” liquid was 15000 ppm , which was the original composition , 60000 ppm , divided by the dilution ratio . the drain time results are also shown in fig1 . when the same composition was diluted at a dilution ratio of 2 , by adding 8000 grams of the composition to 8000 grams of cold water , the resulting foam was extremely stiff . the gpc x201 composition in the diluted , “ to - be - foamed ,” liquid was 30000 ppm , which was the original composition , 60000 ppm , divided by the dilution ratio . the drain time results are shown in fig1 . evaluation of the effect of the starch concentration on the drain time results shows a generally proportional relationship between starch content and drainage . as an example , at 20 hours , the 10000 ppm composition drained about 22 % while the 30000 ppm composition drained about 2 %. when making the same comparison at 40 hours , the values are 38 % and 3 %, respectively . within this range of concentrations , tripling the starch level , 10000 ppm to 30000 ppm , produced a ten fold decrease in the percentage of the foam , which is exactly the effect being sought . a generally acceptable formulation can be prepared using the following composition , which is the same as the composition of example six , but made in a larger batch size . keratin protein 4 . 00 weight percent gpc g400 starch 9 . 00 ferrous sulfate 8 . 00 tsfl 4 . 00 biocide 1 . 00 ammonium hydroxide 0 . 60 cinnamon scent 0 . 10 water 73 . 30 total 100 . 00 the cinnamon is added to mask the hydrolyzed protein odor some find objectionable . the solids for this composition are 20 . 16 % and the ph at 20 ° c . is 6 . 4 . the viscosity profile , after overnight at rest , also at 20 ° c ., was 4100 , 2800 , 1960 , and 1420 cps at spindle # 4 speeds of 6 , 12 , 30 , 60 rpm , respectively . the development work demonstrated that this formulation achieved a suitable balance between the physical properties of the concentrate and foam performance at various dilution ratios , while various application issues were being considered . the drain time measurements were made at dilution ratios of 8 . 0 ( g400 at 11250 ppm ) and 3 . 2 ( g400 at 28125 ppm ). the drain time results are shown in fig2 . alternatively , a generally acceptable formulation can be prepared using the following composition , which is the same as the composition of example ten , but made using the cationic starch in slurry form . keratin protein 4 . 00 weight percent gpc l435 starch ( 30 %) slurry 30 . 00 ferrous sulfate heptahydrate 8 . 00 tsfl 4 . 00 biocide 1 . 00 ammonium hydroxide 0 . 60 cinnamon scent 0 . 10 water 52 . 30 the cinnamon is added to mask the hydrolyzed protein odor . the solids for this composition are 20 . 1 % and the ph at 26 ° c . is 6 . 4 . the viscosity profile , after overnight at rest , at 25 ° c ., was 360 , 200 , 190 , 175 cps at spindle # 2 speeds of 6 , 12 , 30 and 60 rpm , respectively . subsequent development work demonstrated that this formulation achieved a suitable balance between the physical properties of the concentrate and foam performance at various dilution ratios , while various application issues were being considered . the drain time measurements were made at a dilution ratio of 8 . 0 ( l435 at 11250 ppm ). the drain time results are essentially the same as those depicted in fig2 for g400 at 11250 ppm . the formulations as herein described offer a broad array of foam product performance factors unavailable from any other compositions . the basic components in a concentrate formulation can allow foaming with both stiffness and drain time control initially defined by the weight percent levels of the ingredients . since the compositions can be prepared at relatively high weight percent levels , the dilution ratio used in the field now can offer an increased range of performance . there are many applications for the invention . in landfill and hazardous waste applications , discussed by many of the patent references , stiffness and persistence are key performance factors . some mining applications utilize very stiff foams for controlling low pressure differential air flows . in these cases , extreme stiffness may be needed to avoid cold flow or self - leveling . forced recovery of landfill gas ( methane ) as described by kittle in u . s . pat . no . 6 , 929 , 423 , requires good drain time control , but not necessarily excessive stiffness , since the foam is injected into a horizontal distribution pattern , and the foam should not drain significantly until such time as the application is completed . on the other side of the spectrum , the iron component of the protein complex can be useful for controlling hydrogen sulfide as described by kittle in u . s . pat . no . 6 , 994 , 491 , where the foam also needs to be injected into reasonably compacted material . this attribute can also be extended to the control of hydrogen sulfide during mining operations , provided that the contact between the foam phase and the escaping gas is efficient . in coal mining operations , this requires foam application at the cutting interface , thereby minimizing the time between contact and control , compared to the time required for the gas to escape into the environment . in mining , the same technology can also control dust generated by the cutting operation .
foams suitable for such uses as landfill coverage , frost protection , volatile emission control , gas control in mining , are composed of a hydrolyzable protein and a pre - gelatinized cationic modified starch along with other ingredients . the foam concentrate can be made at ambient temperature , is stable over time , can be easily tailored to achieve a desired foam stiffness and drain time characteristic over wide ranges , and can be easily diluted at ambient temperature to produce a foamable composition .