Patent Application
20050103459
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The applicant has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
This invention relates to novel paper products, paper coatings, and pigment products, made using calcium silicate hydrate (“CSH”) crystalline structures.
The paper industry currently utilizes many different types of fillers as a substitute for pulp fiber, as well as to provide desired functional and end-use properties to various paper and paper products. For example, clay has long been used as a filler or fiber substitute. Importantly, the use of clay also provides an improvement in print quality. However, one disadvantage of clay is that it is relatively low in brightness. And, the use of clay in papermaking leads to a decrease in tensile strength of the paper sheet, and to reductions in paper sheet caliper and stiffness.
Calcined clay was introduced to the paper industry in an effort to improve brightness and opacity in paper. However, one significant economic limitation of calcined clay is that it is relatively expensive. Also, physically, calcined claim is highly abrasive.
Titanium dioxide, TiO2, is another example of a filler commonly used in papermaking. Most commonly, titanium dioxide is used to improve opacity of the paper sheet, and, in some cases, it is used to improve sheet brightness as well. Use of titanium dioxide is limited, though, because it is extremely expensive. Unfortunately, it is also the most abrasive pigment on the market today. This is important because highly abrasive pigments are detrimental in the paper industry since they wear down critical paper machine components, such as forming wires, printing press plates, and the like, ultimately leading to high life cycle costs due to the constant repair and maintenance costs.
When calcined clay was first introduced, it was touted as a titanium dioxide extender. Although it did succeed in extending TiO2, it is nonetheless abrasive, and it is more expensive than either standard clay or market pulp fiber.
More recently, and particularly since the mid 1980's, ground calcium carbonate (GCC) has been used as a low cost alkaline filler. Although GCC improved sheet brightness, one downside to GCC was that it too is abrasive. Moreover, use of GCC reduces tensile strength, caliper and stiffness of paper sheets. Consequently, a paper sheet containing GCC tends to be rather limp.
Finally, one of the most commonly used alkaline paper fillers is precipitated calcium carbonate(PCC). PCC is presently one of the best compromise solutions for providing a high brightness filler at an economically feasible price. However, a significant downside to the use of PCC in paper sheets is that PCC provides a lower light scattering power than either TiO2 or calcined clay. Also, it often reduces sheet strength and stiffness.
Thus, the paper industry still has an unmet need, and continues to look for, a multi-functional pigment that can simultaneously provide two or more of the following attributes:
In addition to the just stated criteria, if a paper filler could also simultaneously improve sheet porosity (i.e., provide a more closed sheet) yet provide higher sheet caliper, it would be a very highly desired filler material. To date, no single paper filler with such attributes has been brought to the market. Consequently, the development and commercial availability of such a filler would be extremely desirable.
Finally, the current industry demand for printing papers, especially the rapidly increasing demand for ink jet paper, requires a high performance paper. The performance of such paper would be enhanced by the availability of a pigment that would provide excellent water and oil absorption capacities, so that the paper could quickly capture and prevent ink from spreading or bleeding, as well as aid in surface drying of the ink.
Some of the key requirements for an ideal papermaking pigment can be summarized as set forth in Tables 1, 2 and 3 below:
Currently, the papermaking industry uses various combinations of available fillers in order to optimize the properties as may be desired in a particular papermaking application. However, because currently available fillers reduce sheet strength to at least some extent, the industry relies on strength additives, such as starch and/or polymers, to maintain the desired paper strength properties when fillers are utilized. Unfortunately, because different pigments have different particle charge characteristics, additions of multiple pigments and additives in the paper making system often create an extremely complicated chemical system which may be somewhat sensitive and difficult to control.
In summary, there remains a significant and as yet unmet need for a high quality, cost effective filler which can be used to simultaneously achieve desired optical properties and sheet strength in paper products. Further, there remains a continuing, unmet need for a method to reliably produce such a pigment which has desirable optical properties and which provides significant cost benefits when compared to the use of titanium dioxide or other pigments currently utilized in the production of paper.
Accordingly, an important objective of my invention is to provide a process for the manufacture of unique calcium silicate hydrate (“CSH”) products, which provide crystalline structures with desired brightness, opacity, and other optical properties.
Another important and related objective is to provide an economical substitute for current paper fillers such as titanium dioxide.
A related and important objective is to provide a method for the production of novel paper products using my unique calcium silicate hydrate product.
An important objective is to provide a new calcium silicate hydrate product with low bulk density, good chemical stability (particularly in aqueous solutions), and a high adsorptive capability, among other properties.
These and other advantages, and novel features of my multi-phase calcium silicate hydrates, the method for their preparation, and the improved pigments and paper products produced therewith will become evident and more fully appreciated from full evaluation and consideration of the following detailed description, as well as the accompanying tables and drawing figures.
I have now discovered the process conditions required to reliably produce unique calcium silicate hydrate products with particularly advantageous properties for use as a filler in papermaking. The products are produced by reacting, under hydrothermal conditions, a slurry of burned lime (quick lime) and a slurry of fluxed calcined diatomaceous earth (or other appropriate starting siliceous material). Preferably, a fine slurry of each of the lime and the fluxed silica are utilized.
For one of my CSH products, the lime slurry is prepared by providing about 1.54 pounds of suspended solids per gallon of lime slurry. The silica slurry is prepared by providing about 1.55 pounds of suspended solids per gallon of water. The slaking of the lime slurry raises the temperature of the slurry to near the boiling point; this is accomplished before adding the same to the fluxed silica. The slurry of fluxed calcined diatomaceous earth is heated to near the boiling point, also, before it is mixed with the lime slurry. When both slurries are near atmospheric boiling point conditions, then they are mixed together and stirred, while being retained under pressure in an autoclave or similar reactor. Temperature of the reaction slurry is raised to between about 245° C. and 260° C., and the reaction is continued for about two hours, more or less. The CaO/SiO2 ratio is maintained, in the feed materials, of about 1.35 (± about 0.10) moles CaO to 1 mole of SiO2. After the reaction is completed, the product is cooled before the pressure is released and the product crystals are harvested.
Generally, the product of the above described reaction is a multi-phase mixture (i.e., two different forms or phases are present in the product), predominantly of foshagite, with some xonotlite. Importantly, small, haystack like particles containing complex multi-phase crystalline optical fibers are produced that can be advantageously employed in papermaking for coating and for wet end fillers. However, the hydrothermally produced multi-phase crystalline optical fibers are vastly improved over previously produced hydrothermal calcium silicate hydrates of which I am aware, at least with respect to their physical properties, their optical properties, and their utility as a filler in papermaking. Moreover, my unique CSH products are suitable for multiple end uses, such as filler for value added papers, for commodity papers, for newsprint, paper coating applications, as well as for paints, rubber compositions, and other structural materials.
It is important to appreciate that my hydrothermal process for the manufacture of my unique multiple phase calcium silicate hydrates (“CSH's”), including my novel multi-phase mixture of foshagite and xonotlite, (CaO4(SiO3) (OH)2 and C6Si6O17(OH)2, respectively) results in a unique mixture of calcium silicate hydrates which have a unique and distinct X-ray diffraction pattern.
Further, the variables that affect the chemical composition of my CSH products, and the primary and secondary structure of the CSH particles and their characteristic properties, can be affected, among other things, by (a) the CaO/SiO2 mole ratio, by (b) concentration of the CaO and of the SiO2 in the reaction slurry, (c) the reaction temperature, and (d) the reaction time. By manipulating the just mentioned variables, I have been able to develop two novel pigment products. Those two products can be generally described as follows:
The first product is formed with a high CaO to SiO2 mole ratio (about a 1 to 1, to about a 1.7 to 1 ratio of CaO to SiO2), at a high temperature (˜200° C.-300° C.), with a low final slurry concentration (˜0.4-0.6 lb of solids per gallon of slurry), and with a reaction time of approximately 2 hours. It has a characteristic X-ray diffraction pattern as shown in
The second product is formed by reacting lime and silica with a low mole-ratio (about a 0.85 to 1 ratio of CaO to SiO2), a low reaction temperature (˜180° C. to 190° C.), at a high final slurry concentration (˜0.7-1.0 pounds of solids per gallon of slurry), and with a reaction time of approximately 2 hours. This calcium silicate is quite different from the first product just mentioned above and its unique X-ray diffraction pattern is given in
In summary, the unique features of these hydrothermally produced calcium silicate hydrate products include:
The result of the unique properties and physical structure enable these unique CSH products to provide a combination of beneficial properties to paper products in a manner heretofore unknown by paper fillers. For example, the use of these products in paper can increase sheet bulk and Gurley porosity, simultaneously. In addition, these products are made up of large particles, but the products can still scatter light better than PCC, GCC, clay, or even calcined clay.
The patent or application file contains at least one black and white photograph as a drawing. Copies of this patent or patent application publication with black and white drawing(s) will be provided by the U.S. Patent and Trademark Office upon request and payment of the necessary fee.
In order to enable the reader to attain a more complete appreciation of the invention, and of the novel features and the advantages thereof, attention is directed to the following detailed description when considered in connection with the accompanying drawing, wherein:
The foregoing figures, being merely exemplary, contain various aspects, properties, and elements that may be present or omitted from actual product implementations depending upon the circumstances. An attempt has been made to provide the figures in a way that illustrates at least those aspects and properties that are significant for an understanding of the various embodiments and aspects of the invention. However, variations in the illustrated aspects, elements, and properties, especially as applied for maximizing different variations of the functional properties illustrated, may be utilized in various embodiments in order to provide an advantageous calcium silicate hydrate filler for various uses in the manufacture of paper.
In order to prepare my unique calcium silicate hydrates (“CSH”) products, it is first necessary to prepare a source of calcium. This is normally accomplished by the formation of a slurry of calcious material, most commonly lime. However, there are several different sources of calcium, which may be used. Some examples are CaCO3, CaCl2, and hydrated lime. I have found it advantageous to employ pebble lime, if less than ½ inch dimension. First, the CaO was slaked in water. The amount and the rate of addition of lime were set and maintained in order to obtain a desired concentration of lime slurry. Because the slaking of lime is an exothermic process, it was necessary to control both the rate of addition of lime and the quantity of water used. When slaking, the best temperature was determined to be near boiling, i.e., close to 100° C. (212° F.) in order to form lime particles as fine as possible. Once the slaking was complete, the lime slurry was then screened through a 200 mesh screen to remove any grit and oversized particles. The screened and slaked lime slurry was tested for available lime (as CaO) and then transferred to an autoclave.
The chemistry of the slaking process can be given as follows:
CaO+H2O→Ca(OH)2 (1)
(solid) (aqueous)
Ca(OH)→Ca+++2OH− (2)
(aqueous)
The solubility of calcium hydroxide slurry is inversely proportional to the temperature, as indicated in
Next, it is necessary to prepare a slurry of siliceous material (i.e., a SiO2 slurry). Various siliceous materials such as quartz, water glass, clay, pure silica, natural silica (sand), diatomaceous earth, fluxed calcined diatomaceous earth, or any combination thereof may be utilized as a source of siliceous material. I prefer to utilize an ultra fine grade of fluxed, calcined diatomaceous earth. This raw material was prepared into a slurry of ˜1.55 lbs of solids per gallon water. The slurry was then preheated to near boiling, i.e., near 100° C.
Importantly, the solubility of silica (unlike that of Ca(OH)2), is directly proportional to temperature, as seen in
The dissolution of silica can be represented as follows:
(SiO2)n+2n(H2O)→nSi(OH)4 (3)
The solubility of silica can be increased by raising the pH, and/or by using various additives (i.e. sodium hydroxide). In addition the rate of silica solubility is also a function of particle size, thus to enhance solubilization of the silica, I prefer to utilize ultra fine fluxed calcined diatomaceous earth.
Next, the siliceous slurry was mixed with the lime slurry in an autoclave, to achieve a hydrothermal reaction of the two slurries. Important, the amount of CaO in the lime slurry and the amount of SiO2 in the fluxed calcined diatomaceous earth slurry were pre-selected to provide a predetermined CaO/SiO2 mole ratio. Also, the concentration of the two slurries (CaO and SiO2) was selected so that the final concentration of the reaction mixture in the autoclave falls between about 0.2 pounds of solid per gallon of slurry to about 1.0 pounds of solid per gallon of slurry.
The hydrothermal reaction itself was carried out in a pressurized vessel, with three major steps:
In my laboratory, the reaction autoclave was cooled by passing quenching water through an internal cooling coil, or by utilizing an external jacketed cooling system. I prefer to utilize a cool down process of from approximately 25 to 30 minutes to drop the temperature from about 230° C. to about 80° C., as indicated in
The process steps just mentioned are very important. This is because I have utilized the inverse solubilities of lime and silica with respect to temperature and time in an effort to produce the desired reaction composition, to arrive at the desired multi-phase calcium silicate hydrate product.
Without limiting my invention to any particular theory, I can postulate the following reaction during the hydro-thermal reaction between calcious material and siliceous material. First, during the heating process, very few free Ca++ ions are available. After 100° C., the silica starts going into a gel stage. Beyond 130° C., the silica ions become available for reacting. As the temperature nears 180° C., the calcium ion Ca++ reacts with the Si+ ion to form a metal silicate. The reaction can be written as follows:
x[Ca+++2OH−]+y[Si(OH)4]→CaOx(SiO2)y+(x+y)H2O (4)
Where:
The solid Ca(OH)2 particles react with SiO2 in the gel phase to give a calcium silicate hydroxide whose crystallo-chemical structure can be written as Ca6Si6O17(OH)2 (Xonotlite). As the temperature is further raised from 180° C. to 250° C., calcium silicate hydride condenses with the remaining Ca(OH)2 particles to give yet another calcium silicate hydroxide, this time with a distinct X-ray diffraction pattern and a crystallo-chemical formula of CaO4(SiO3)3(OH)2 (Foshagite)
Further, I have developed my hydrothermal reaction process so that more than one unique calcium silicate hydrate can be produced. In this respect, it is important to note that the following variables are critical in producing a desired end product:
By changing these variables, a product having several different phases of calcium silicate hydroxide can be produced. Some of these phases may include:
Although not normally important, one should note that my final product CSH composition may also contain minor amounts of calcite-aragonite, produced as a result of side reactions.
The first and most important product of my process is a multi-phase CSH composition having various amounts of phases of matter represented by CaO4 (SiO3)3 (OH)2 (Foshagite) and Ca6Si6O17(OH)2 (Xonotlite). A unique X-ray diffraction pattern for this product is provided in
Foshagite, CaO4 (SiO3)3 (OH)2 d=2.97 Å, d=2.31 Å, d=5.05 Å (Phase I)
Xonotlite, Ca6Si6O17(OH)2 d=3.107 Å, d=1.75 Å, d=3.66 Å (Phase II)
The Scanning Electron Micrographs (“SEMs”) representing this first product are provided in
The SEM of
The calcium silicate hydroxide mixture of my invention also has very high brightness characteristics. A comparison with other pigments is given below:
Various pigments and their typical published brightness values are as follows:
One of the most significant characteristics of the composition of matter produced by my process is the ability of these multiple phase calcium silicates to absorb large amounts of water. These calcium silicates can adsorb anywhere from 350% to 1000% of their weight. This high water absorption capacity makes my pigment extremely well suited for preventing ink strike through in writing and printing papers, newsprint and more.
Initially, 135.09 grams of ½″ rotary pebble lime (Mississippi Lime Co.) was accurately weighed and slaked in 410 milliliters of de-ionized water. The slaking reaction is exothermic and caused the slurry temperature to rise to near boiling. When the slurry temperature was very near boiling and before much of the water had evaporated, an additional 1190 milliliters of water was added to both dilute and cool the slurry. The slurry was then agitated for 30 minutes to insure slaking completion before being screened through a 140 mesh screen. The slurry was then transferred to 5 liter autoclave and tested for lime availability in accordance with ASTM method C25. The autoclave is fitted with an outside heating element contained in an insulated jacket housing. The autoclave is also fitted with a variable speed magnetic drive for stirring the slurry during reaction. Approximately 109.6 grams of ultra fine fluxed calcined diatomaceous earth was weighed and added to 750 ml of hot water (concentration of ˜1.22 lb/gallon). The silica slurry was heated for approximately 10 minutes, to near boiling, then added to the screened and tested lime slurry. The exact amount of silica slurry added to lime slurry was determined by the lime availability such that a mol ratio of 1.35 mol CaO/SiO2 would be maintained. The total slurry volume was also adjusted to a final concentration of 0.425 lb/gallon. The high pressure vessel was then closed, sealed, and connected to an automated heating/cooling control system (RX 330). The contents of the autoclave were under constant agitation via the magnetic drive motor mentioned above.
The high pressure reactor was heated by an externally jacketed heating element. The autoclave was continuously agitated at a constant speed of 338 rpm. The reactor was heated for approximately 100 minutes in order to reach the target temperature of 245° C. (473° F.). The temperature was maintained at 245° C. for 2 hours, after heating to the target temperature was accomplished, with the use of the heating/cooling controller. At the end of the reaction, the “quenching” water was flushed through the cooling coil built inside the autoclave. This cooling process was maintained until the inside vessel temperature reached approximately 80° C. (approximately 30 minutes). At which point, the vessel was opened and the reaction products were transferred to a holding vessel for storage. A portion of the resultant slurry was dried in a 105° C. oven for 12 hours. During the drying process, the slurry formed hard lumps, which had to be broken up through the use of a mortar and pestle. The now powdered, dry product was brushed through a 140 mesh screen to insure product uniformity when testing. The pigment in this example was designated 5XPC 12. The test carried out on the dry powder were as follows:
For the air permeability test, two numbers are reported. The first is the weight in grams of powder required to fill the capsule and is an indication of the “bulk density” of the powder. The second is the time in seconds for a controlled volume of air to pass through the compressed powder inside the capsule and is an approximate measure of the “structure” of the particle.
The process conditions are given in Table 1a and the pigment properties are given in Table 1b.
The x-ray diffraction pattern of this novel, multiphase calcium silicate hydrate is given in
The major peaks for phase I were found to indicate the presence of calcium silicate hydroxide—Foshagite—(Ca4(SiO3)3(OH)2) with major peaks at d(Å)=2.97, d(Å)=2.31 and a minor peak at d(Å)=5.05. For phase II, the x-ray diffraction pattern indicated the presence of calcium silicate hydrate—Xonotlite—(Ca6Si6O17(OH)2) with major peaks at d(Å)=3.107, d(Å)=1.75 and a minor peak at d(Å)=3.66. Thus I obtained a novel combination of Foshagite and Xonotlite from a single reaction.
The S.E.M. pictures at 10,000 times and 2000 times magnification are given in
The low magnification S.E.M. depicts the three dimensional structure of the secondary particles of calcium silicate hydrates. The structure appears to have been formed by an interlocking of the primary “fibrous” crystals and some inter-fiber bonding due to hydrogel of silica formed during the initial stages of hydro-thermal reaction. Because of these two main reasons, the secondary particles are fairly stable and do not significantly lose their 3-d structure when subjected to process shear. In addition, these particles also seem to withstand the pressure encountered during the calendering or finishing operations integral to papermaking. The median size of the secondary particles as seen, ranges from 10 to about 40 microns.
In order to evaluate this pigment in paper, handsheets were prepared for evaluation. Handsheets were prepared using the 5XPC 12 product sample in order to evaluate the papermaking characteristics of the pigment. The procedure included preparation of a standard pulp slurry made up of 75% hardwood and 25% softwood. Both pulp sources were beaten separately, in a Valley Beater, to a specific Canadian Standard Freeness of 450±10 in accordance with TAPPI test methods T-200 and T-227. Handsheets were formed from the prepared stock, on a 6″ British handsheet mold, in accordance with TAPPI test method T-205. The exceptions to the standard method were as follows. Since the goal of producing these handsheets was to test filler performance, some filler was incorporated into the handsheets at various replacement levels (usually 15%, 20%, and 25%). In order to achieve comparability between different levels, a constant basis weight was achieved via a reduction in fiber content. Thus, a 25% filled sheet would contain only 75% of the fiber that the unfilled sheet had. The next variation on the standard test method was the addition of retention aid. A retention aid (Percol 175) was added to hold the filler in the sheet until the sheet had dried completely. All other handsheet formation components were kept consistent with TAPPI test method T-205.
The handsheets were tested in accordance with TAPPI test method T-220, with one exception. Instead of using a 15 mm sample for testing tensile, a 25.4 mm sample was used and the tensile index calculations were altered accordingly. The handsheets were ashed in accordance with TAPPI test method T-211.
Paper handsheets were tested for the following properties:
A standard alkaline filler, precipitated calcium carbonate (SMI Albacar HO), was used as a reference material to gauge product performance. The results of the handsheet evaluation are given in Tables 1d and 1e.
This novel, multiphase calcium silicate hydrate was formed by hydro-thermal reaction of lime and silica. The CaO/SiO2 mol ratio used for this new product was 0.85, the final slurry concentration was ˜0.8 lb/gallon, the reaction temperature was 190° C., and the reaction time was 2.5 hours. A summary of these conditions is given in Table 2a.
A totally new product was formed using a new set of reaction conditions. First, the CaO/SiO2 mol ratio was adjusted to 0.85, the reaction temperature was set to 190° C., the slurry concentration was increased to 0.75 lbs/gallon, and the reaction time was increased to 2.5 hours. The product of this example was designated 5XPC 27.
A summary of the reaction conditions is given in Table 2a:
The resulting calcium silicate hydrate was tested for pigment brightness, water absorption, Blaine air permeability and density, and pH. Both X-ray diffraction and Scanning Electron Micrograph analyses were also performed on this product. The pigment properties are given in Table 2b. The pigment was evaluated for its performance in paper by incorporating it into handsheets as in example 1. The results of the handsheet work are given in Tables 2d and 2e. The X-ray diffraction pattern is given in
The calcium silicate hydride formed under these conditions had substantially lower brightness and water absorption characteristics than TiSil Brand CSH set forth in Example 1. However, it gave much higher sheet bulk and sheet permeability characteristics. The pigment properties of my novel 5XPC 27 pigment are given in Table 2b. It appears that this product provided a much higher sheet bulk. Also, the sheet permeability of this new product was higher than the Foshagite-Xonotlite complex as described in Example 1.
As the mole ratio of CaO/SiO2 was reduced to ˜0.85 and the reaction temperature was lowered to 190° C., I discovered another unique and useful multiple phase calcium silicate hydrate material with a distinct and unique X-ray diffraction pattern. The X-ray diffraction analysis revealed this product to be a mixture of Riversideite [Ca5Si6O16(OH)2] and Xonotlite [Ca6Si6O17(OH)2]. The X-ray diffraction pattern is given in
The major peaks for phase I were found to indicate the presence of calcium silicate hydrate—Riversideite—(Ca5Si6O16(OH)2) with major peaks at d(Å)=3.055, d(Å)=3.58 and a minor peak at d(Å)=2.80. For phase II, the pattern indicated the presence of calcium silicate hydroxide—Xonotlite—(Ca6Si6O17(OH)2) with major peaks at d(Å)=3.056, d(Å)=4.09 and a minor peak at d(Å)=2.50. The pigment also contained trace amounts of calcite (CaCO3). The other portion of the slurry was tested for the pigment performance as a filler in paper. The paper was formed into handsheets and tested using the procedures described in example 1.
The S.E.M. pictures at 10,000 times and 2000 times are given in
The 2000×magnification indicates the formation of an irregular globular particle formed by the fibrous inter-growth of a series of primary fibrous crystals. The particle size is in the range of 10-30 microns and the crystals seem to have grown randomly.
This multi-phase (primarily Riversideite and Xonotlite) calcium silicate hydrate gave lower brightness value than that of Example 1. More significantly, this material gave a much lower water absorption (around 360% -400%) as well.
To evaluate performance in paper, handsheets were formed using this pigment and then tested as in Example 1. The paper performance results are shown in Tables 2d-g.
This product, compared to pulp only, gave substantially higher stiffness and sheet bulk. Unlike the pigment provided in Example 1, (where Foshagite was the primary component), this second pigment (where Riversideite and Xonotlite are present) combination produced a much more open sheet, as shown by the low Gurley porosity numbers. The optical properties, like brightness, opacity and scattering coefficient of the sheet decreased.
Comparing the performance of this second pigment (with predominantly Riversideite and Xonotlite present) with an alkaline filler, such as precipitated calcium carbonate, the sheet stiffness and bulk improved dramatically. The optical properties (sheet opacity, sheet brightness, etc.) of the handsheets decreased, however. The decreased optical properties of this new multiphase product were clearly due to the large particle size and irregular globular structure as seen in the S.E.M. pictures.
Thus, this multiphase combination of calcium silicate hydrate was most useful in improving sheet stiffness and sheet bulk. It was also excellent for “opening up” the sheet (lowering the Gurley porosity) for more “breathing.” Due to its excellent stiffness, I refer to this product as “StiSil Brand CSH.”
Initially, 39.9 grams of pebble lime was weighed accurately and added slowly to 1.2 L of water in a beaker with constant agitation. The amount of lime, water, and the rate of lime addition were controlled in an effort to keep the slurry from boiling due to the exothermic nature of the lime slaking reaction. The slaked lime of Ca(OH)2 was screened in a 200 mesh screen. The residual material was then discarded. The filtered Ca(OH)2 slurry was tested by acidic titration to calculate the exact amount of available lime. The slaked lime was then transferred into a 2 liter autoclave. Then, 31.06 grams of ultrafine, calcined diatomaceous earth was added to 200 ml of water in order to produce a slurry of 0.1553 g/L concentration. This slurry was also preheated with constant stirring and brought to near boiling (near 100° C.). Next, the silica was added to the autoclave containing the hot slaked lime slurry. The total solids concentration of the CaO+SiO2 slurry inside the autoclave, at this point was ˜0.5 lbs/gallon. The mol ratio of lime to silica was 1.67 CaO/SiO2. The high-pressure reactor was sealed and then heated by an externally, jacketed, electrical heating element.
The autoclave was simultaneously agitated at a constant speed magnetic drive motor at 600 RPM. The autoclave was heated until a preset temperature of 220° C. was reached. At that point the reaction conditions were held constant by a system controller, RX-32. The CaO+SiO2 slurry was reacted at a temperature of 220° C. for 120 minutes. At the end of this time, the “quenching” water was passed through a cooling system built into the inside of the autoclave. Inside the pressure vessel, steam condensed and the temperature fell rapidly. The cooling water continued until the vessel reached approximately 80° C.
The silicate slurry was transferred into a holding beaker. The following describes the overall heating/cooling cycle (see
A portion of the slurry was tested for the following properties:
The reaction conditions and pigment properties are given in Tables 3a and 3b respectively.
In this example, all the reaction conditions and parameters were identical to example 3 above, except for the reaction temperature was raised from 220° C. to 233° C. The resultant calcium silicate hydrate complex was then tested as per the above-described test program and the resultant reaction conditions and pigment properties are given in Tables 3a and 3b respectively.
In this example, all of the reaction conditions and parameters were kept constant, as in example 3, except for reaction temperature. The reaction temperature was raised from 233° C. to 243° C. The calcium silicate hydrate complex formed was tested as in the above examples. The reaction conditions and pigment properties are given in Tables 3a and 3b respectively.
Note that the mid range reaction temperature of 233° C. produced the highest brightness material.
In this example, all the reaction parameters were kept constant, as in example 4, except for the CaO/SiO2 mol ratio. The CaO/SiO2 mol ratio was changed to 1.4.
Then, 69.0 g of SiO2 and 78.0 g of CaO were mixed to give a CaO/SiO2 mol ratio of 1.4. The two slurries, CaO and SiO2 were mixed in the autoclave. The concentration in the autoclave was adjusted by adding water to 0.7 lb/gal. The reaction was carried out for two hours and the autoclave was cooled and the product was handled as in example 1. The reaction temperature was kept constant at 233° C. The reaction mixture was agitated at a constant speed via a magnetic drive motor attached to the autoclave. The motor was rotated at 600 RPM. The final product was tested for key parameters and the reaction conditions and key pigment properties are shown in Tables 4a and 4b respectively.
In this example, all the reaction parameters were kept constant as in example 4, except the CaO/SiO2 mol ratio was raised to 1.6. The hydrothermal reaction was carried out using the same cycle of heating and cooling as in the previous examples and the final product was again tested for key pigment properties. The reaction conditions and key pigment properties are shown in Tables 4a and 4b respectively.
Here again, the reaction parameters were all held constant, as in example 4, except for the CaO/SiO2 mol ratio, which was raised to 1.8. The hydrothermal reaction was carried out using the same cycle of heating and cooling as in the previous examples and the final product was again tested for key pigment properties. The reaction conditions and key pigment properties are shown in Tables 4a and 4b respectively.
Note that a CaO/SiO2 mole ratio of 1.6 produced a calcium silicate hydrate with the highest water absorption capability.
In this example, all the process conditions were kept constant, as in example 7, except for the reaction time, which was lowered to 1 hour. The calcium silicate hydrate complex was tested as in the previous examples and the reaction conditions and key pigment properties are shown in Tables 5a and 5b respectively.
In this example, all the process conditions were kept constant, as in example 9, except for the reaction time, which was raised to 2 hours. The calcium silicate hydrate complex was tested as in the previous examples and the reaction conditions and key pigment properties are shown in Tables 5a and 5b respectively.
In this example, all the process conditions were kept constant, as in example 9, except for the reaction time, which was raised to 3 hours. The calcium silicate hydrate complex was tested as in the previous examples and the reaction conditions and key pigment properties are shown in Tables 5a and 5b respectively.
Note that a reaction time of 2 hours produced the highest brightness product. The longer reaction time of 3 hours produced the greatest water absorption values, but at a lower brightness.
In this example, all the reaction conditions were kept constant, as in Example 7, except for the CaO/SiO2 slurry concentration, which was lowered to 0.4 lb/gallon. To start, 49.6 g of lime was slaked, screened, and titrated for available CaO. Then, 34.2 g of ultra-fine fluxed calcined diatomaceous earth was slurried. The fluxed calcined diatomaceous earth slurry was added to the lime slurry to give the mixture an initial CaO/SiO2 mol ratio of 1.6. The reactants were then placed in a 2.0 liter autoclave and water was added to bring the final concentration of CaO+SiO2 slurry up to 0.4 lb/gallon. The reaction temperature was set at 233° C. The autoclave was set and controlled using a temperature controller for both heating and cooling cycles as shown in
EXAMPLE 13
In this reaction, all the reaction parameters were kept constant, as in example 12, except for the CaO+SiO2 slurry concentration, which was raised to 0.6 lb/gallon. The product was tested as in Example 3 and the reaction conditions and key pigment properties are shown in Tables 6a and 6b, respectively.
In this reaction, all the reaction parameters were kept constant, as in example 12, except for the CaO+SiO2 slurry concentration, which was raised to 0.8 lb/gallon. The product was tested as in example 3 and the reaction conditions and key pigment properties are shown in Tables 6a and 6b, respectively.
In this reaction, all the reaction parameters were kept constant, as in example 12, except for the CaO/SiO2 slurry concentration, which was raised to 0.9 lb/gallon. The product was tested as in example 3 and the reaction conditions and key pigment properties are shown in Tables 6a and 6b, respectively.
Note that the slurry concentration of 0.8 lb/gallon produced the highest brightness and the lowest bulk density.
In this example, the same procedures described in example 1 were used, except that the siliceous raw material was changed. Instead of using diatomaceous earth, a source of 100% pure silica was used (trade name: Min-U-Sil). The reaction was carried out at a very low CaO—SiO2 slurry concentration of 0.2 lb/gallon. The resultant calcium silicate hydrate complex was tested for the same key pigment properties as in example 1 above. The reaction conditions and key pigment properties are given in Tables 7a and 7b, respectively.
In this example, the same procedures described in example 16 were used (including using the pure silica for a siliceous source). The only difference here was that the CaO—SiO2 slurry concentration was raised to 0.4 lb/gallon, and the temperature was kept at 232° C. The calcium silicate hydrate complex formed from this reaction was tested as in example 16 above. The reaction conditions and key pigment properties are given in Tables 7a and 7b.
In this example, all the reaction procedures were kept constant as in example 1. The only difference was the addition of a different siliceous raw material source. Here, 20 parts of the fluxed calcined diatomaceous earth were replaced by liquid sodium silica Na2O—SiO2 ratio of 1:3 (P.Q. “N” product). The overall CaO/SiO2 mol ratio was kept at 1.31, the concentration of the CaO—SiO2 slurry was kept at 0.5 lb/gallon, and all the other reaction conditions were kept the same as well. This product was also tested according to the procedures in example 1. The reaction conditions and key pigment properties are given in Tables 8a and 8b, respectively.
Note that the most significant difference between this product and the previous example is the high brightness values produced.
Application of multi phase calcium silicate hydrate complex comprising predominantly Foshagite, Ca4 (SiO3)3 (OH)2 and some Xonotlite, Ca6Si6O17(OH)2 in paper according to the following process conditions. My novel calcium silicate hydrate complex, referred to as TiSil Brand CSH, was applied in paper handsheets. It was compared to commercial PCC (SMI's Albacar(HO)) and a mixture of PCC and approximately 60 lbs. per ton TiO2. The results of the testing are given in Table 9a and 9b. The graphs showing the performance of TiSil compared to PCC are given in
The TiSil brand CSH pigment seemed to improve a combination of properties, which were heretofore unattainable. For example, if sheet bulk was improved, sheet porosity would usually drop. In addition, if sheet bulk was obtained by having a larger particle size, optical properties would be significantly reduced. With my novel pigment, it is the unique composition and structure of the pigment that allows improvement in key paper properties like higher bulk and lower porosity.
In this example, the calcium silicate hydrate from example 1 (5XPC12) was compared with a mixture of SMI's Albacar(HO) containing 60 lb/ton TiO2. The results of the paper testing are placed in Tables 10a and 10b. The graphical representations of the data are given in
Here, TiSil Brand CSH has demonstrated exceptional scattering power for light, an unusual ability to close up the sheet (higher Gurley porosity) and a significant improvement in sheet bulk, stiffness, and tensile index.
In this example, the pigment of my invention, namely a calcium silicate hydrate complex (Foshagite-Xonotlite complex) was manufactured under the conditions given in Table 11a. The pigment was tested for brightness, water absorption, Blaine, and pH. The results are given in Table 11b. This product was compared as a paper-making pigment with commercially available calcium silicate, (Trade name Bulkite). The graphical representation of the results are given in
Once again, this product shows substantially significant improvement over industry standard pigments.
In this example, the multi-phase CSH Foshagite—Xonotlite was made by the same procedure as in Example 1, using the process conditions in Table 12a below.
The product was tested for brightness, water absorption, Blaine and pH. The results are given in Table 12b.
The calcium silicate hydrate complex of this invention was added to newsprint furnish (20% kraft, 80% TMP). To compare the performance of the product of my invention, handsheets were made using commercially available calcium silicate (Hubersil, JM Huber Co.) and a precipitated calcium carbonate (also by JM Huber Co). The newsprint sheets containing these pigments were tested for the following:
The actual values, interpolated to 6% ash, are given in Tables 12c and 12d. A comparison of the product of my invention and Huber's PCC and HuberSil gave the differences shown in Tables 12e and 12f. The corresponding bar graphs at 6.0% interpolated ash are given in
A comparison of my new multi-phase CSH products with Huber's calcium silicate gave the following:
Once again, my multi-phase CSH product gives better paper and printing properties than currently available commercial calcium carbonate and commercial calcium silicate fillers.
During testing of my novel multi-phase calcium silicate hydrate products, conventional industry quality control standards were observed. Brightness was tested by using a GE/TAPPI Brightness Meter, Model S-4. Where applicable, the pH was tested with a pH meter utilizing TAPPI method T-667. Pulp beating was performed using a Valley Beater according to TAPPI Method T-200. Handsheets were produced using a British Handsheet Mold according to TAPPI Method T-205. Handsheet testing was for tensile strength used a one inch strip and otherwise was conducted according to TAPPI method T-220. Where applicable, freeness was tested utilizing a Canadian Standard Freeness tester according to TAPPI standard T-227. Ashing tests were conducted at 500° C. according to TAPPI Method T-211. Air permeability testing was conducted by Blaine, ASTM Method C204. Available lime was measured according to ASTM Method C25. For fine paper testing, a standard pulp slurry was made up of 75% hardwood and 25% softwood. Both pulp sources were beaten separately, in a Valley Beater, to a specific Canadian Standard Freeness of 450±10 in accordance with TAPPI test methods T-200 and T-227. For newsprint testing, a standard newsprint pulp slurry was made up of 20% softwood kraft fibers, and 80% thermo-mechanical pulp. Both pulp sources were received with Canadian Standard Freeness values of 180 csf ±25. This freeness value was deemed sufficient and no further beating was performed on the pulp. For the disintegration of the was performed on the pulp. For the disintegration of the stock pulp solutions, hot water was added to help relax the pulp fibers and prevent fiber clumps in the final sheet. Handsheets were formed from the above prepared stock, on a 6″ British handsheet mold, in accordance with TAPPI test method T-205. However, since the goal of producing these handsheets was to test filler performance, some filler was incorporated into the handsheets at various replacement levels (usually 15%, 20%, and 25%). In order to achieve comparability between different replacement levels, a constant basis weight was achieved via a reduction in fiber content. Thus, a 25% filled sheet contained only 75% of the fiber that the unfilled sheet has. Also, a retention aid was utilized to hold the filler in the sheet until the sheet had dried completely. All other handsheet formation components were kept consistent with TAPPI test method T-205. Handsheets utilizing titanium dioxide in fine paper were similarly formed, except that they required double the amount of retention aid as required by the other fillers. In addition, when TiO2 was added in conjunction with another filler, it was necessary to first add TiO2, then add one dose of retention aid, and then add the filler and a second dose of retention aid. Handsheets formed for newsprint testing were prepared in a similar method to the fine paper handsheets. However, different filler loading levels were utilized, and the newsprint sheets were usually loaded at 3%, 6%, and 9% filler. The handsheets were tested in accordance with TAPPI test method T-220, except that a 25.4 mm sample was used and the tensile index calculations were recalculated accordingly. Handsheets were ashed in accordance with TAPPI test method T-211.
In summary, the unique crystalline microfibres produced as a product of the reactions described herein exist, in one unique product, as bundles sized from about 10 to about 40 microns, typically occurring as haystacks or balls. Preferably, individual fibers are about 0.2 microns in the largest cross-sectional dimension, with lengths of up to 4 or 5 microns, so as to have a relatively large L/D ratio.
Importantly, the crystalline microfibers as just described have advantageous properties when utilized as a paper filler, particularly in uncoated groundwood, and in coated groundwood, in uncoated fine paper, and in coated fine paper. The aforementioned adsorptive properties help to adsorb printing ink in the papers. Also, it helps the paper sheet itself to absorb fines, so that it improves overall sheet retention during the papermaking process. Overall, final paper products exhibit improved porosity, improved smoothness, improved bulk, and improved stiffness. Also, brightness and opacity are maintained or improved. Moreover, the printability of the final product is significantly improved, due to the improved ink adsorption.
It is to be appreciated that my unique, light, fluffy adsorptive calcium silicate hydrate products, and the method of producing the same, and the paper products produced using such products, each represent an appreciable improvement in the paper production arts. Although only a few exemplary embodiments of this invention have been described in detail, those skilled in the art may find that the processes described herein, and the products produced thereby, may be modified from those embodiments provided herein, without materially departing from the novel teachings and advantages provided.
It will thus bee seen that the objects set forth above, including those made apparent from the preceding description, are efficiently attained. Since certain changes may be made in carrying out production of the CSH products, and the unique paper products produce therewith, it is to be understood that my invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Many other embodiments are also feasible to attain advantageous results utilizing the principles disclosed herein. Therefor, it will be understood that the foregoing description of representative embodiments of the invention have been presented only for purposes of illustration and for providing an understanding of the invention, and are not intended to be exhaustive or restrictive, or to limit the invention to the precise embodiments disclosed. The intention is to cover all modifications, equivalents, and alternatives falling with the scope and spirit of the invention, as expressed herein above and in the appended claims. As such, the claims are intended to cover the products, processes, methods, and equivalent processes and methods. The scope of the invention, as described herein, is thus intended to included variations from the embodiments provided which are nevertheless described by the broad meaning and range properly afforded to the language herein, and as explained by and in light of the terms included herein, or by the legal equivalents thereof.
This application is a Divisional of co-pending allowed U.S. application Ser. No. 09/649,413 filed Aug. 26, 2000, assigned U.S. Pat. No. 6,726,807,to be issued on Apr. 27, 2004, which claimed priority under 35 USC § 119 (e) from U.S. Provisional Application Ser. No. 60/150,862 filed on Aug. 26, 1999, the disclosures of each of which are incorporated herein by their entirety by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 60150862 | Aug 1999 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09649413 | Aug 2000 | US |
| Child | 10831526 | Apr 2004 | US |
