MXPA98009244A - Composition of fine cells foam and method for your producc - Google Patents

Abstract

A rigid foam composition of thin cells and a method for the production of the same is described. The foam composition is non-toxic, environmentally friendly, has absorption / adsorption and improved fluid retention, is not as hard as the foam of the prior art, does not include polymerization by-products that damage the flower and plant life, and it is a foam mixture of a caustic silicate solution derived from the caustic digestion of rice husk ash that has diffuse activated carbon particles from the thermal pyrolysis of rice husks, instead of commercial solutions of sodium silicate. Valuable commercial grade byproducts including activated carbon and sodium fluoride are obtained

Description

COMPOSITION OF FOAM CELLS AND METHOD FOR PRODUCTION FIELD OF THE INVENTION The present invention relates to rigid foams, of thin cells, for the retention of liquids for floral, agricultural, nursery and horticultural uses, such as for cut flowers, plant propagation media and growth containers, soil conditioners, organic mattresses or mattresses, and the like.

BACKGROUND OF THE INVENTION Current commercial foams for flower growing and horticulture are phenol / formaldehyde foams which are potentially hazardous to health and have environmental problems because phenol and formaldehyde are toxic chemical byproducts subject to Section 313 of Title III of Super Reserve Amendments and the Reauthorization Act (SARA) of 1986 and 40 CFR Part 372 that report the requirements. Also, formaldehyde is listed as a carcinogen by the National Toxicology Program (NTP), the International Agency REF: 28703 for Cancer Research (IARC), and the North American Conference of Industrial Hygienists of the Government (ACGIH). Smithers-Oasis, USA, and other companies currently market a phenol / formaldehyde foam ("PF foams"), and California currently requires the following label on PF foams: "Warning! This product contains a chemical known in the State of California always causes cancer. " Attempts have been made to provide non-toxic, environmentally friendly foams for floral, agricultural and horticultural purposes, but to the knowledge of the applicant, none of these foams have been acceptable to the industry. One unsuccessful attempt of this type has been to develop silica foams using industrial standard sodium silicate, consisting of an aqueous solution of sodium oxide (Na20) and silicon dioxide (Si02) with the proportion of SiO2 to Na20 to 3.22, and soluble solids to 39.3 percent. This silica foam was produced in a continuous high-speed mixer by injecting a surface tension depressant (bait oil mixture) and polymer forming agent (sodium fluorosilicate) into the sodium silicate. Also, cotton reinforcement fibers, such as cotton flakes (260 microns), were mixed with sodium silicate to provide cohesive strength in the resulting foam, and coloring agents were added to provide the desired color. The final dry density of the foam was controlled by injection of compressed air or nitrogen into the mixer. While this process and these raw materials produced a silica foam product with fine cells in the 40 to 60 micron diameter range, the best achievable liquid retention was at a level of 39 volume percent, due to the repulsion by capillarity in the cellular structure. Another undesirable property of this foam was its hardness at the lowest practical density of about 64.1 kg / m3 (4 pounds per cubic foot). When used as a floral foam for the insertion of cut flowers, the hardness limits its use to large-stemmed flowers, and even then there is potential damage to the stems while the flowers are inserted. U.S. Patent Nos. 3,741,898 and 3,856,539 produced silica foam products without the inclusion of any substantial amount of fillers or reinforcers. By "substantial amounts" of fillers or reinforcers it was established that it was an amount greater than about 10 percent on a dry basis or about 3 weight percent of the alkali metal silicate (commercial sodium silicate) as a raw material, on a basis wet. These foam products were produced for use as structural and insulating materials, but were never acceptable by the floral, agricultural, nursery and horticultural industries. The terms "silica" and "silicate" have been used interchangeably in commerce. In the previous 0 speakers, it is defined that a product of silica foam from sodium silicate solution does not have above a substantial amount of filler (10 percent) of filler or reinforcement materials. In the present invention, the "filler" and reinforcement material are present in substantially more than 10 percent, such as activated carbon and cellulose fibers.; and the caustic silicate solution derived from the caustic digestion of rice husk ash has about 0.5 (1/2) weight percent of metals. It could be highly desirable to provide. • • a rigid, thin-cell foam composition that has improved absorption / adsorption and fluid retention, which is not as hard as 5-layered foams. prior art so that, when used as a floral foam for the insertion of cut flowers, the hardness does not limit its use to long-stemmed flowers and does not damage the stems of the flowers while they are inserted into the foam, which does not contain dangerous concentrations of polymerization byproducts, such as sodium fluoride which is harmful to cut flowers, which does not require the addition of expensive coloring agents, and consequently that is desirable and suitable for floral uses. It is also highly desirable to provide a suitable and useful foam composition as a propagating medium or blocks for plants and other agricultural cuts, seeds, seedlings, nursery stock, trees, as soil conditioners, mulches or organic mattresses, and the like. It is also highly desirable to provide such a foam composition which is cheap, use waste products, rice husk ash having activated charcoal diffused throughout, and has valuable by-products acceptable for various industries to which they belong.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to a rigid foam composition and to its production method which produces a rigid foam of thin cells, having a hardness so that cut flowers and vegetable cuttings can be easily and quickly inserted into the foam without damaging it. to the stems or cuttings while they are inserted, which use a caustic solution of - carbon containing amorphous silica derived from the thermal pyrolysis of rice husk ash containing diffused charcoal which has been activated with it, whose charcoal activated passes through as an inert material during caustic digestion and acts synergistically with the amorphous silica cell structure to absorb / adsorb and retain more liquid than the foams of the prior art, and which is free of sodium fluoride soluble in water and other byproducts and reagents of the foaming process. Unexpectedly, thermal pyrolysis and caustic digestion reduce the size of the activated carbon particles to where they do not deteriorate the cell-like structure of the foam, thereby improving the absorption / adsorption of liquids.

The process of the invention is the production of rigid foam composition by foaming a mixture of a caustic silicate solution comprised of amorphous silica derived from the caustic digestion of rice husk ash, which contains activated carbon formed during thermal pyrolysis and is an inert material during caustic digestion, a surface tension depressant, a polymer forming agent, and fibrous reinforcing material of the cellulose family, such as cotton flakes. The activated carbon acts synergistically with and does not interfere with the structure in the form of thin cells of the composition in the form of foam, resulting to absorb / adsorb and retain liquid and has its particle size reduced by thermal pyrolysis and caustic digestion, so that it does not deteriorate the cell-like structure of the foam composition. Any and all byproducts of foaming are eliminated, including sodium fluoride, excess reagents, and surface tension depressors. Currently commercially available rice husk ash is produced by gasification or by burning or burning rice husks in an oven. Thermal pyrolysis is a chemical change that occurs in a substance through the application of heat. The combustion is the act or process of burning or is a chemical change, especially oxidation, accompanied by the production of cilor and light. In both, mainly amorphous rice husk ash, which has activated charcoal diffused throughout, is produced. Advantageously, during the thermal pyrolysis of the rice husks and the caustic digestion of the resulting rice husk ash, the activated carbon particles are reduced to sizes that are consistently smaller than commercially available granular activated carbon (GAC) and powdered activated carbon (PAC) and which do not deteriorate the structure in the form of normal cells of the product in the form of foam. For convenience, the term "thermal pyrolysis" includes combustion, gasification and any and all forms of heat produced by rice husk ash and activated charcoal from rice husks. Any process in which thermal pyrolysis is used to produce rice husk ash and activated charcoal from rice husks can be used in the present invention.

In the current burning or burning process, the raw rice husks are continuously added to the top of the furnace, and the ash is continuously removed from the bottom. The temperatures in the furnace in general are in the range of 427 ° C (800 ° F) to about 760 ° C (1400 ° F), and the residence time for the ash in the furnace is about three minutes. After leaving the furnace, the ash is quickly cooled to provide ease of handling. When treated by this method, silica remains in a relatively pure amorphous state rather than in the crystalline forms known as quartz, tridymite, or cristobalite. The transition from the amorphous to Ci-istalino state generally occurs when the silica is maintained at very high temperatures, for example 1093 ° C (2000 ° F) for longer periods of time. The meaning of having the silica in an amorphous state is that the silica maintains a porous skeletal structure instead of migrating to form crystals, and the amorphous form of the silica does not cause silicosis, thus reducing precautionary management procedures. The burning or combustion of rice husks is related to the time-temperature and the ignition or burning of these husks under these conditions produces rice husk ash that has coal particles coming from the ignition of the husks, which activates the coal . Conventional combustion of rice husks produces from about 3 percent to about 13 percent by weight of activated carbon. The amount of activated carbon present in rice husk ash is dependent on the amount of combustion. If the amount of activated charcoal in the rice husk ash used in the foaming process and in the foamed composition can not be advantageously used in the preparation of floral, agricultural, nursery or horticultural foams, such Excess activated carbon can be separated from the solution of silicate rice husk ash, digested, caustic, and is a product of activated carbon very valuable and excessively pure. While amorphous rice husk ash is preferred, some crystalline rice husk ash may be present. In the current gasification of rice husk ash, gasification equipment is used; mineral coal, conventional. The rice husks are heated in an oven at temperatures of about 427 ° C (800 ° F), the gas is collected and then burned for energy, and the rice husk ash including the activated charcoal is recovered. The amount of activated carbon is in the range of up to 40 weight percent or more. A part or all of the excess activated carbon can be removed by conventional filtration processes and conventional equipment, and it is a valuable input. In general, in the commercial burning of rice husks as a source of energy, the resulting ash includes approximately 0.5 (1/2) percent of trace metals, such as magnesium, potassium, iron, aluminum, calcium, titanium and manganese. . The production of a caustic silicate solution from amorphous rice husk ash is a caustic digestion process. The rice husk ash is heated with a caustic digestion, such as sodium hydroxide (NaOH), which reacts with the solid silica (Si02) to create the sodium silicate solution. The main chemical reaction is characterized as follows: 2NaOH + nSi02 + H20? Na20: n (Si02) + H20 where "n" represents the weight ratio of silica / alkali.

For a current industrial standard solution, the chemical equation becomes: 2NaOH + 3.22 Si02 + H20-Na20: 3.22 (Si02) + H20. In addition to sodium hydroxide, the reaction products of carbonate / calcium oxide can be used in the caustic digestion process, the liquors of the sodium hydroxide by-product, and sources of limestone / low-grade soda ash, as well as others. The current commercial grades of the liquid sodium silicates not derived from rice husk ash are in the silica / alkali weight ratio range of about 1.6 to about 3.8. Such proportions are satisfactory for the liquid sodium silicate derived from rice husk ash, in the present invention. As previously mentioned, during the thermal pyrolysis of rice husks and the caustic digestion of amorphous rice husk ash, to produce a sodium silicate solution, the activated carbon particles are reduced to sizes that are consistently smaller than commercially available granular activated carbon (GAC) and powdered activated carbon (PAC). The sizes of granular, crushed, common activated carbon are 12 x 43 and 8 x 30 of the standard North American sieve, whose diameter range is 1,680 to 425 microns and 2,380 to 590 microns, respectively. Commercially available PACs typically have particle sizes of 65 to 90 percent by passing a standard 325 mesh American sieve (45 microns). Activated carbon in the unrefined sodium silicate solution, derived from the caustic digestion of rice husk ash, has 100 percent particle sizes that pass a standard North American 500 sieve (25 microns) with size average of approximately 12 microns in diameter. The particle sizes of the suspended solids, such as activated carbon, in the caustic silicate solution raw material are critical because the larger particles deteriorate the normal structure in the form of cells in the polymerized silicon dioxide foam product. . This rupture or deterioration results in decreased absorption / adsorption and decreased fluid retention. Also, the larger carbon particles tend to increase the hardness, which can cause damage to the stems of the flowers while they are inserted into the foam. The particle size distribution is also important because the smaller carbon particles adsorb more quickly than the larger particles. The composition of the invention comprises a product of rigid foam, of thin cells or a composition comprised of amorphous silica precipitated from the thermal pyrolysis of rice husks, activated carbon from the thermal pyrolysis of rice husks, and which it passes as an inert material through the caustic digestion process, has a non-destructive particle size of the fine cell structure of the foam composition, cellulose fibers and water of hydration. Preferably, the foam comprises by weight about 50 to 63 percent precipitated substantially amorphous silica, about 4 to 6 percent fiber, about 13 to 27 percent activated carbon, about 16 to 19 percent hydrated water, Major cell size of approximately 40 to 60 microns in diameter, has a dry density of approximately 80.1 to 96.2 kg / m3 (5.0 pounds to 6.0 pounds per cubic foot) t metals in traces of 0.5 to 1.0 percent. Accordingly, an object of the present invention is to provide a foam composition and its production method, which foam composition has reduced hardness from the prior art foams, which has improved absorption / adsorption and liquid retention, which is full of contaminants such as fluorides or excess reagents, does not need added coloring agents, and in which the stems of the cut flowers, the cuttings of plants, and the like can be easily and quickly inserted into the foam with approximately 48 at 56 percent less pressure than the foams of the prior art, and is suitable for floricultural and horticultural uses, such as propagation media or blocks for plants and other agricultural cuts, seeds, seedlings, soil conditioners, organic mattresses, has valuable by-products, and the like. A further objective of the present invention is to provide a foam composition that is inexpensive, that has larger components made from a waste product and which has valuable by-products acceptable to the industry. Other objects, features and additional advantages of the invention are described throughout the specification and the claims, and are inherent in the invention.

DESCRIPTION OF CURRENTLY PREFERRED MODALITY The present invention is directed to a process and to a foam product using a caustic silicate solution produced by the caustic digestion of rice husk ash obtained by thermal pyrolysis of the rice husks. The activated carbon is generated during this process, which passes through the caustic digestion as an inert material and which is of a particle size that does not deteriorate the cell-like structure of the foam product. The activated carbon in the foam product acts synergistically with the cell-shaped structure to absorb / adsorb and retain substantially more liquid than the foams of the prior art. The method of the invention comprises the foaming of a mixture of a caustic silicate solution which has been derived by caustic digestion of rice husk ash containing diffused activated charcoal throughout, formed from thermal pyrolysis of the rice husks, whose activated carbon passes as an inert material during the caustic digestion process and which is of reduced particle size which does not interrupt the cell-like structure of the resulting foam product, a depressant of the surface tension, a polymer forming agent, and inert reinforcing fibers, removing by-products, excess reactants and surface tension depressant, and forming the resulting foam composition into desired structural shapes, such as three-dimensional solid forms suitable for and floral, agricultural, nursery and horticultural media. Preferably for floral forms, the resulting solid forms are sprayed with a polymer solution that minimizes dust and a conservator to prolong the life of the cut flowers having their stems inserted into the solid forms. The resulting foam is a product or composition of thin cell foam, rigid comprised of amorphous precipitated silica from the thermal pyrolysis of rice husks, activated carbon from the thermal pyrolysis of rice husks and which passes as a material inert through the process of caustic digestion, has a particle size that does not deteriorate the fine cell structure of the composition of foams, cellulose fibers, and water of hydration. Preferably, the foam comprises by weight about 50 to 63 percent precipitated substantially amorphous silica, about 4 to 6 percent fiber, about 13 to 27 percent activated carbon, about 16 to 19 percent hydrated water, a majority cell size of approximately 40 to 60 microns in diameter, has a dry density of approximately 80.1 to 96.2 kg / m3 (5.0 pounds to 6.0 pounds per cubic foot) and trace metals from 0.5 to 1.0 percent. The following Example 1 is a currently preferred method for making the foam composition of the invention.

Example 1 A solution of amorphous sodium silicate from rice husk ash (RHA) is analyzed to determine the Si02 / Na20 ratio, the soluble solids (signa solids), the suspended solids (unreacted carbon + RHA), the total solids , and the weight percent of the water in the RHA sodium silicate not refined. These properties are critical for the balance of the complete chemical reaction considering the amount of polymer forming agent to be used.

The amorphous sodium silicate from RHA is premixed with 2.6 weight percent cotton flake reinforcement fibers (260 microns in length) using a mechanical stirrer. Sodium fluorosilicate (SFS, preferred polymer-forming agent) is analyzed to determine the percentage of solids in the aqueous solution. The preferred solids range of SFS is 50 percent to 60 percent by weight of the aqueous solution. A depressor of the surface tension, preferably a mixture of bait oil, is prepared by mixing 80 percent bait oil distilled with 20 percent oleic acid. The three feed streams of raw material are placed in tanks or containers of appropriate size which are connected via pipe systems to positive displacement pumps. The preferred pumps are Robbins Myers Moyno® pumps capable of pumping viscous suspensions with abrasive solids. The pumps are adjusted to feed the three streams to the following ratio in an anhydrous base (reactive solids base): Na20: Si02 - 100 parts by weight / Na2SiF6 - 36.83 parts by weight / bait oil mixture - 2 parts by weight (liquid) This is the exact theoretical stoichiometric ratio for the reaction to achieve 100 percent completion. In actual practice, the feed ratios have been varied from a low of 100 parts of Na20: Si02 to 41.7 parts of SFS; to a high of 100 parts of Na20: Si02 to 33.8 parts of SFS. The preferred ratio is as close to the stoichiometric as practical, in order to reduce unreacted components that have to be removed from the foam product by further processing. The reagents are pumped at a high continuous speed (500-600 RPM), with high cut mixer, which produces the wet foam supplied to molds. There are several commercial mixers available, including those manufactured by: E.T. Oakes Corporation (preferred), Perpetual Machine Company, Charles Ross & They are Company, and others. Consequently, a detailed description is not considered necessary. Air or compressed nitrogen is injected into the mixer at a rate to produce the desired wet foam density in the range of 192.3 to 240.4 kg / m3 (12 to 15 pounds per cubic foot). Lower densities reduce water retention because water makes the pores of cells larger. The higher densities make the foam too hard for floricultural and horticultural use. The wet foam is supplied through a hose attached to the outlet of the mixer to the molds, which are filled to capacity and then covered with a wet barrier cover. The wet foam in the molds is allowed to harden in place for a period of 24 to 48 hours to allow draining of excess liquid and the curing reaction. The wet foam is then removed from the molds and placed in a leaching facility for the removal of unwanted by-product, sodium fluoride (NaF), any excess reagents, and any residue from the bait oil mixture. The leaching process is carried out by letting hot water flow (93 to 99 ° C (200 to 210 ° F)) through the foam product for a period of two to three hours. This removes the soluble NaF in water and flushes other contaminants out of the cell structure. This leaching process is dependent on time and temperature and can be carried out with cold water for a longer period of time. The leaching with hot water is followed by a leaching with cold water for approximately the same time to cool and open the cells in the foam. Advantageously, the NaF can be precipitated or distilled from the leachate and recovered by conventional methods. The recovered NaF is 97 percent pure and hence of a degree of convenience that can be marketed. The progress in the leaching process is checked periodically by frequent measurements of leachate water for pH, total dissolved solids (TDS), and fluoride ions. This process is complete when the leachate coming from the foam product reaches the same pH, TDS, and ionic fluoride concentration as the raw initial "tap" water. The foam product is then dried by forced convection and infrared heaters. After drying, the foam product is cut into the desired three dimensional shapes and sizes, such as partitions or can be ground or converted into lumps for the organic mattress, soil remedies and the like. For the floral foam product it is approximately 22.86 cm by 10.16 by 7.62 cm (9 inches by 4 inches by 3 inches) for rectangular teibiques.

A polymeric solution is then sprayed onto the outer surfaces of the partitions to minimize the release of dust and particles during shipping. The floral foam has a commercial preservative spray applied together with the polymeric solution. A floral, horticultural, nursery and agricultural foam composition with acceptable properties with respect to absorption, adsorption, and water retention and "softness" was produced using the sodium silicate compositions of rice husk ash, as described above . The properties and composition of the foam produced by the process in Example 1 are within the ranges described in the following Table 1.

Table 1 Dry Density 80.1 to 96.2 kg / m3 (5.0 to 6.0 pounds per cubic foot) Silicon dioxide 52.34 to 62.83 percent by weight (Si02) Activated Carbon 13.10 to 26.81 percent by weight Table 1 (continued) Cotton 4.70 to 5.49 percent by weight Hydration water 15.74 to 18.93 percent by weight Sodium fluoride < 3 ppm (NaF) Metal traces 0.5 to 1.0 percent by weight It is well known that any amount of water-soluble polymer added to floral foam products can have a damaging effect on the flowers that are inserted into the foam. Therefore, the preferred compound for use in minimizing "dustiness" is polyvinylpyrrolidone, PVP K-15 or PVP K-30, which are low molecular weight polymers. Other polymers that could be used include: polyethylene glycol (PEG), acrylic or acrylate polymers, starch based acrylates with grafted side chain, certain vinyl acetate polymers and others. These are all commercially available, and no detailed description of them is given or considered necessary. The PVP polymer is manufactured by ISP Technologies Inc. and is one of the active ingredients in hair spray.

Preferably, the weight percent in the feedstocks of the rice husk ash caustic silicate solution comprises 78 percent to 81 percent, the activated carbon in the rice husk ash silicate solution comprises percent to 15 percent, and has a particle size of up to 25 microns, and preferably about 12 microns in diameter, the surface tension depressant comprises 1.00 percent to 2.00 percent, the solution of the film forming agent comprises from 17.00 percent to 22.00 percent, and reinforcement fibers 2.00 percent to 3.00 percent. While the cotton flake is the preferred reinforcing fiber, other reinforcing fibers, such as cellulose fibers, can be used. The reinforcing fibers should not be too hard to increase the hardness of the foam. The length of the reinforcement fibers should not be so long as to damage the cell structure of the foam and decrease water retention, and not so short as to reduce the cohesive strength properties of the foam. A satisfactory range of fiber length is 250 to 300 microns, and 260 microns is currently preferred, and is a standard length available in the market. Any depressant of the desired surface tension can be used, preferably from the chemical family of fatty acids, turpentine resin acid, coconut fatty acid, bait oil fatty acid (FA-3), and the like. The preferred preservative is commercially available from Floralife, Inc. Other preservatives include: sorbic acid, potassium sorbate, benzoic acid, and others. These are all commercially available, and no detailed description of them is given or considered necessary. In case the activated carbon in the caustic silicate solution is above the preferred upper limits set forth herein, it must be removed by conventional filtration methods and readily available devices on the market such as EIMCO Process Equipment, Kason Corporation, Frontier Technology, Inc., and others. If desired, all the activated carbon in the caustic silicate solution can be removed and marketed separately as a commodity.

Example 2 The following is an example of a prior art process for producing a floral foam product. The process used was to 'inject three streams of feed raw material into a high-cut, high-speed mixer, Oakes by means of positive displacement pumps. A stream of commercial sodium silicate, (not rice husk ash) had been premixed with the cotton flakes (260 microns in length) at a concentration of 2.6 weight percent. Thus, the total solids (soluble + suspended) were in the range of 41 to 42 percent in a 58-59 percent aqueous solution. The stream of the polymer forming agent was 53 percent sodium fluorosilicate powder (particle size 5 microns) plus 1.5 percent pigment solids in a 45.5 percent aqueous solution. The surface tension depressant stream was comprised of 80 percent distilled bait oil and 20 percent oleic acid. The sodium silicate / cotton flake suspension was heated to 40.5 ° C to 43.3 ° C (05 ° F to 110 ° F) prior to injection into the mixer. This reduced the viscosity and increased the reaction rate with sodium fluorosilicate. The feeding ratios were: Wet Base-300 parts of sodium silicate suspension to 77 parts of sodium fluorosilicate suspension to 6 parts of the liquid mixture of bait oil, or Dry Base of Solids: 100 parts of Na20: 3.22 Solid parts of Si02 to 36.4 parts of Na2SiF6 solids to 2 parts of the mixed liquid of bait oil. Air or nitrogen was injected at a pressure of 5.62 to 7.03 kg / cm2 (80 to 100 psig) into the sodium silicate stream just before entering the mixer. The mixer was operated at 500-600 RPM with a back pressure on the mixing head from 2.81 to 5.62 kg / cm2 (40 to 80 psig). The foam product was supplied through a hose from the outlet of the mixer to the molds. After the molds were filled to capacity, a moisture barrier covering was placed on the tops to maintain close to 100 percent moisture. The foam product was allowed to stand in the molds for a period exceeding 24 hours to allow the polymerization to proceed and to provide excess water drainage. The foam product in the molds had a wet density of 160.28 to 176.31 kg / m3 (10 to 11 pounds per cubic foot). The polymerization reaction of the prior art floral foam produced the unwanted byproduct sodium fluoride (NaF) at approximately a 25 percent concentration in weighed dry foam. After the floral foam was removed from the molds, it required further processing to remove the NaF, any excess reagents, and the residual bait oil liquid. This elimination was carried out through repeated leaching treatments with hot water solutions (higher than 93.3 ° C (> 200 ° F)) and cold (21 to 24 ° C) (70 to 75 ° F)) of soda ash (Na2C03) and potassium chloride (KCl). These repetitive treatments took from 7 to 8 hours with the temperatures of the aqueous solution in the range of 21 to 96 ° C (70 to 205 ° F). These treatments also completed the healing process for the foam product. After the leaching treatments, the floral foam was dried by a combination of convection and infrared heaters for a period of 48 to 72 hours. The prior art floral foam product had a dry density of 64.1 to 72.1 kg / m3 (4.0 to 4.5 pounds per cubic foot) with the following composition by weight: SiO2 = 71 percent, color pigment = 2 percent, cotton = 5-6 percent and water of hydration = 21 to 22 percent, and required approximately 50 percent more force to insert the stems of the cut flowers than in the foam composition of Example 1.

Example 3 This is an example of an attempt to produce an acceptable floral foam product using a commercial solution of sodium silicate with the Si02 / Na20 ratio of 3.22 to 1 and 39.2 weight percent of soluble Si: Na solids in an aqueous solution. at 60.8 percent by weight; to which 8.03 weight percent commercial granular active carbon (GAC) was added with standard North American mesh particle sizes 20 x 50 (diameter of 850 to 300 microns). The cotton flake (260 micron size) was mixed at 3.0 weight percent and additional water was added to reduce the soluble solids of Si: Na to about 34.0 weight percent. This final composition is very close to that of the sodium silicate solution from the rice husk ash used in Example 1.

The commercial solution of sodium silicate, the • stream of the polymer forming agent (60 percent sodium fluorosilicate in a 40 percent aqueous solution), the surface tension depressant current (bait oil mixture) and the compressed nitrogen were fed to the mixer high cut, high speed (500-600 RPM), to the same proportions as in Example 1. The foam product • resulting was also processed in the same way as in Example 1. The composition of the foam product using the commercial sodium silicate was within the ranges described in Table 1. However, the physical properties deteriorated with the absorption / adsorption of liquid and reduced liquid retention by 29 volume percent, compared to the acceptable foam pyroduct of Example 1. Also, the force required to insert the stems of the flowers into the foam was increased by 121 percent a a level that can cause damage to the stems while being inserted into the foam of the prior art. The additional cost of the commercial sodium silicate and the granular activated carbon (GAC) used in this example resulted in approximately increase of 115% in the cost of the raw material, compared to the use of the sodium silicate solution from RHA of Example 1.

Example 4 This example is the same as in Example 3, except that powdered activated carbon (PAC) with a particle size of about 72 percent passing a standard 325 mesh American sieve (45 microns) was used in the solution , sodium silicate commercial instead of granular activated carbon (GAC) .The processing conditions and composition of the foam product were essentially the same as in Examples 1 and 3. The absorption / adsorption and the liquid retention was 17 percent by volume less than the acceptable foam product of Example 1. The hardness as determined by the insertion force of the flower stems was approximately 32 percent greater than Example 1. Since the activated carbon in powder is more expensive, the cost of raw materials, was increased by 143 percent compared to Example 1. For agriculture and horticulture, the foam composition or the product of the present invention, it is used as a means of propagation, for example, for seeds, seedlings, plant cuttings, such as nursery material, red shepherdess or fire flower, orchids, rose cuttings, tree cuttings, and the like, or when planting as a soil conditioner, or organic mattress to control water retention levels, and cause plant cuttings to react more quickly. Additional components may be added to the foam composition or to the product of the present invention, such as nutrients and the like, which are commercially available in the market, and no description of them is given or considered necessary. Other additional uses of the foam of the present invention can be realized, such as for the attenuation of microwaves and sound, for the filtration and purification of liquid, for containment and absorption of industrial waste water, means for bioremediation, as a stop for fire in hollow-walled containers and the like. Accordingly, the present invention has the advantages and features and meets the previously described objectives. While currently preferred examples of the embodiments of the invention have been given for purposes of description, changes can be made therein, which are within the spirit of the invention. as defined by the scope of the appended claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (12)

1. A method for the manufacture of a rigid cell foam composition having a greater part of its cells of a size of about 40 to about 60 microns, characterized in the method because it comprises: the foaming of a mixture of components comprising ( a) a caustic silicate solution derived from the caustic digestion of rice husk ash from the thermal pyrolysis of rice husks, and containing diffused activated carbon formed during thermal pyrolysis, (b) a stress depressor surface, (c) a polymer forming agent, and (d) inert reinforcing fibers, and the removal of by-products including sodium fluoride and unreacted components from the rigid foam composition.

2. The method according to claim 1, characterized in that it includes: the formation of the foam composition of rigid cells in three-dimensional shapes.

3. The method according to claim 2, further characterized by comprising: spraying the three-dimensional shapes with a polymer solution in an amount effective to minimize dust.

4. The method according to claim 2, further characterized by comprising: spraying the three-dimensional shapes with a preservative in an effective amount to preserve the life of the cut flowers when their stems are inserted into the shapes.

5. The method according to claim 1, characterized in that: the caustic silicate solution of rice husk ash comprises from 78 percent to 81 percent of the mixture, the activated carbon in the caustic ash solution of caustic ash rice comprises from 6.00 percent to 15.00 percent by weight, and has a particle diameter not exceeding 25 microns, the surface tension depressant comprises 1.00 percent to 2.00 percent by weight of the mixture, the solution of the polymer forming agent comprises from 17.00 percent to 22.00 percent by weight of the mixture, and the inert reinforcing fibers in the rice husk ash caustic silicate solution comprise from 2.00 percent to 3.00 percent by weight of mix.

6. The method according to claim 5, characterized in that: the surface tension depressant comprises 80 percent distilled bait oil mixed with 20 percent oleic acid, the polymer forming agent comprises sodium fluorosilicate, and the fibers of Inert reinforcement comprises cotton flake.

7. The method according to claim 1, characterized in that the caustic silicate solution is a sodium silicate solution.

8. The method according to claim 1, further characterized in that it comprises: recovering the sodium fluoride from the resulting foam composition.

9. A method for obtaining activated carbon, characterized in that it comprises: the separation by filtration of the activated carbon from a solution of caustic silicate derived from the caustic digestion and the thermal pyrolysis of the rice husk ash containing activated carbon.

10. A rigid foam composition having a cell structure, wherein a majority of cells in the cell structure have a size of 40 to 60 microns, characterized in that it comprises: (a) silicon dioxide derived from husk ash of rice, and containing diffuse activated carbon particles from the thermal pyrolysis of the rice husk, the particles of activated carbon are of a size that does not deteriorate the cells of the rigid foam composition, (b) cellulose fibers of reinforcement, (c) hydrate and (d) less than 3.00 ppm byproduct sodium fluoride, and wherein the foam composition has a dry density of 80.1 to 96.2 kg / m2 (5.0 pounds to 6.0 pounds by weight per cubic foot) , and a sufficient hardness so that the cut flowers can be inserted into the foam composition without damaging their stems.

11. The rigid foam composition according to claim 10, characterized in that the silicon dioxide comprises about 50 percent to 63 percent by weight of the composition, the hydrate comprises about 15 percent to about 19 percent by weight of the composition , the cellulose reinforcing fibers comprise about 4.50 percent to 5.50 percent by weight of the composition, the activated carbon particles comprise about 13 percent to about 27 percent by weight of the composition, and have a diameter no greater than 25 microns, and include 0.500 to 1.00 weight percent trace metal impurities.

12. The rigid foam composition according to claim 10, characterized in that the reinforcing cellulose fibers comprise cotton flake.