Patent Application
20210148051
This Invention Patent application refers to the field of paper and cellulose manufacturing. More specifically, this application relates to a system for continuous treatment of cellulose pulps through a method and process capable of reducing, or even eliminating, the use of talc in manufacturing paper and cellulose. This system involves a mix of clays in special conditions capable of enhancing its adsorbent properties, associated or not to other chemical strategies, in order to remove dissolved contaminants and colloids and, in addition, improve retention and drainage properties with expected gains in sheet formation and drying phases.
This Invention Patent application more specifically describes an application system for mixing natural and synthetic clays in a thermodynamic equipment comprised of a continuous flow shearing chamber, under temperature and pressure, which provides the mixing of bentonite and hydrotalcite slurries, among other clays, in different ratios, with a subsequent increase in surface area and adsorbent capacity of clays, in addition to the optional addition of fixing polymers or biopolymers in different application points in order to retain fines, fibers and loads, either associated or not to a surfactant-based chemical dispersing agent and supplementary enzymatic action (lipase or esterase).
The clay mix so obtained may be applied along with talc, for partial or full replacement, depending on the desired removal level of contaminants and improvement goals for retention and drainage for subsequent phases of mass preparation, more specifically sheet formation and drying phases.
The control of deposits is invaluable for the efficiency of the paper and cellulose manufacturing process(Rojas, O. J. et al., 2006), preventing carriage with the pitch and sticky materials, as they are called in the paper manufacturing industry, which may gather inside the suction boxes, formation screens, felt and pressing rolls, even reaching up to the drying section. In addition to losses related to runnability (higher machine speed and stability), there are extreme cases of production losses caused by stoppages for cleaning felts or due to sheet breaking, in addition to inherent quality-related problems, such as stains and small holes on the paper sheet.
The pitch basically comprises natural contaminants from the wood (e.g.: resinous acids, steroids, waxes, etc.) while stickies come from recycled fibers and, therefore, are synthetic substances such as glues, adhesives, latex, among others. The challenge arises when said clusters of contaminants appear at the micrometric range, more specifically below 5 μm, which is the limit for conventional physical purification methods such as filters, sieves, washers, and flotation systems. In such cases, in which the species are dissolved or in colloidal state, more specific chemical control methods must be applied, such as use of adsorbents, fixatives, dispersing agents, surface passivation agents and hydrolytic enzymes.
Among available methodologies, the use of adsorbents such as talc is particularly interesting, since it acts both as an adhesion inhibitor for contaminants (detackifier), thus preventing agglomeration and formation of deposits, and as a fixative specially when associated to polymers, comprising an effective retention and drainage system that allows removal from the system along with the fibers, at no effect to the end quality of the paper.
More recently, concerns emerged regarding the presence of talc on paper products, particularly adsorbent papers with a higher degree of contact with the final customer. In this sense, it is known that company Johnson & Johnson submitted technical inquiries regarding the safety to human health due to the presence of asbestos (carcinogenic material) in its composition, which led to a motion from some manufacturers in order to gradually replace the use of talc in the paper manufacturing process.
This Invention Patent application entails knowledge acquired in the field contextualized above, evidencing technological advancements with special mentions to the most relevant aspects of the aforementioned talc replacement process, both in controlling pitch and stickies, and acting in retention and draining of the damp ends of paper and cellulose machines.
An interesting parallel in the pitch control area is found at the beginning of the 1990 decade, in which the challenge was overcome with the technology provided on document U.S. Pat. No. 5,292,404, when an important change in process pH took place, enforcing the need for replacing aluminum sulfate as a coagulant for “anion garbage” with cationic polymers for flocculation of said deposits, such as quaternized acrylamides.
Advances in amplifying the range of polymers as pitch control agents were observed in the following years, although a few specific deposits, such as “white pitch” that contains latex, are not prevented solely by using polymers and/or talc, thus requiring more complex chemical systems. Precisely at this point, technologies comprising microparticle systems with bentonite are applied in combination with polymers and polysilicates (WO 03/085199), in addition to the use of biopolymers such as xanthan gum (WO 01/71092) and whey protein (U.S. Pat. No. 7,052,579).
In fact, the use of microparticles containing bentonite and polymers goes beyond pitch control and has been used as a retention and drainage agent for some time. In this sense, attention in particular is drawn to advancements proposed in a Chilean patent (CL 2002002155) extended to the United States (US 20040250971), Europe (EP 1475476) and some other strategic countries in the paper industry, such as Brazil (PI 0401695). The difference is due to the possibility of applying a bentonite dispersion at concentrations higher than 5% (never went higher than 5% previously), in low dosages (lower than 1,000 g/t of dry pulp), with no need for complex application systems and in different points of the process, featuring effective results even in the absence of polymers.
Intrigued by this brutal difference in performance among bentonites, it was found that its flocculation and adsorbent properties are extremely variable, thus affecting its role in pitch control, load and fiber retention and improving the drainage behavior during the sheet forming process. Patent WO 2008/077877 was decisive in unveiling the most recent evolution in processing raw bentonite, in order to attain the best performance in these applications. In summary, it was found that the best bentonites are the calcitic ones, with a high concentration of montmorillonite, in stable slurry (around 10% suspension) through a wet milling process with temperatures around 50 to 80° C. The activation of this bentonite was provided with calcium and magnesium salts, in addition to a combined talc application, improving its properties.
Patent WO 2009/117073 considers a mix of clays in the form of slurries, including talc itself in order to tackle the problem with organic deposits in paper and cellulose, but limited to compound silicate clays (e.g.: Kaolin, bentonite, etc.), always associated to a hydrophobic ether-type modified cellulose polymer and, alternatively, a surfactant.
Also regarding application of talc in combination with other additives for pitch and stickies control, it was found in WO 2014/195478 that the use of a mix of oxides and hydroxides of alkali earth metals to improve bleaching efficiency. In addition to talc, other additives such as bentonite, diatomite, zeolite, among other adsorbents, may be applied to different points of the process, either mixed or individually, in the form of slurries, spray-dryer or pelletized.
In the search for new alternatives of adsorbent materials for replacement of talc in pitch control, in addition to other previously mentioned conventional choices, a Chinese patent was found (CN 101333787) that employs materials of the hydrotalcite type (natural or synthetic clay) as an adsorption and fixation strategy when associated to a cationic polyacrylamide, in order to gain sheet retention in addition to removal of resinous contaminants. [016] Upon deeper research in the preparation processes for hydrotalcite with other adsorbent materials, a recent Chinese patent was identified (CN 109331774) which attains a modified bentonite, reacting it with hydrotalcite under pressure and temperature in order to increase its surface area and adsorption points focused on removal of heavy metals and dyes.
It was previously stated, regarding the State of the art of this Invention Patent application, that most current technical solutions for partial or full talc replacement involve microparticle systems with adsorbent action similar to talc, employing different natural clays such as powdered bentonite (an example is seen in patent WO 03/085199), although the vast majority is within the same chemical class of silicates.
It should be highlighted, however, that every clay features inherent structural characteristics of the application, so that bentonite specifically has a hydrophilic characteristic and an exfoliation capacity that is significantly higher than talc, featuring an even higher susceptibility to the ionic character of the medium. Therefore, in addition to good affinity with colloidal contaminants (pitch and stickies), it also features a higher affinity than talc with cationic polymers that form crossed bonds with fibers and fines, more significantly affecting retention and drainage properties, which, in turn, may potentially harm the paper's damp chemistry balance. Therefore, the use of associated polymers or biopolymers (seem in patents WO 01/71092 and U.S. Pat. No. 7,052,579) is basically a premise of this type of application. For this reason, it is understood that a full talc replacement, in such cases, is unfavorable, as may be seen in practice in many applications that maintain their combined application or in various points of the paper and cellulose manufacturing process.
In addition to differences in chemical nature of the various types of bentonite which are directly related to efficiency in removal of contaminants (WO 2008/077877 shows primary differences), another aspect of bentonite that deserves mention refers to the powder application form, which is much more operationally complicated, in addition to increased exposure to human health risks due to the likelihood of inhaling suspended particles. This type of limitation was approached on patent CL 2002002155 with the application of stabilized bentonite in slurry form, although it is restricted to the application of a single bentonite-based clay type.
Such limitation in the chemical action of adsorbents was approached in patent WO 2009/117073, which provides a clay mix, in addition to the application in slurry form. However, the patent falls short when it only covers clay mixes of the same chemical class as talc (all silicates, such as bentonite and kaolin) and refrains from exploring possible synergies with other clay types, maintaining the limitation of combined application with a polymer or biopolymer (in this case, a modified cellulose ether) in order to preserve the balance of the retention and drainage system, presenting difficulties in full talc replacement. [021] In general, very few works have submitted alternatives to silicate-type clays, with a special mention to Chinese patent CN 101333787, which approaches new hydrotalcite-type clays in pitch control due to their marked lipophilic (compared to silicate-based clays) and adsorption properties. However, this work is focused on retention, particularly when hydrotalcite is associated with polyacrylamides and features no synergy action when mixed with other clays.
Based on the aforementioned problems, upon a detailed analysis carried out in order to propose the subject herein, none of the pitch and stickies control applications, retention and drainage or preparation methods of materials provided in the state of the art are in conflict with the implementations described in this Invention Patent application, which is primarily based in a mix of clay slurries, particularly natural bentonite and synthetic hydrotalcite, with significantly improved adsorption properties of dissolved and colloidal contaminants due to the combined application and synergy action through a continuous flow shearing chamber, or with no talc addition, as well as other applied chemical methodology and process methods.
Lastly, considering the scope of the patent survey featured herein, no other processes related directly to the aforementioned subjects in the INPI [Brazilian Patent and Trademark Office] archive and main worldwide patent offices were found.
As per the following detailed description, this Invention Patent application provides a system for continuous treatment of cellulose pulps, for control of pitch and stickies dissolved and colloidal contaminants, in addition to gains in sheet retention and drainage.
The method and process that substantiate this Invention Patent application, when compared to those reported in the state of the art, provide extensive benefits in paper and cellulose manufacturing, as per the principles listed below:
Full or partial talc replacement in paper and cellulose manufacturing processes. Depending on the amount of hydrotalcite used in the clay mix, due to its synergy action with silicates and adsorption properties increased in the system application, a 50%, 90% or even 100% talc reduction may be provided, which would be unlikely to be reached by using only silicate-type clays, such as bentonite. The “unique” property of talc within the silicate class should also be highlighted, an “organophilic surface” with a high affinity towards organic contaminants, while its “hydrophilic corners”, at the same time, enable good dispersion in water, thus explaining the great difficulty in finding a straightforward replacement;
New clay composition (natural and synthetic) with complementary and synergic adsorbent properties. It was seen that hydrotalcite is a peculiar clay type, as well as talc, since it also features an organophilic property with high adsorption capacity, in addition to supplementary action on bentonite due to its “positive lamellar structure, stabilized by negative counter-ions (e.g. Carbonate or sulfate), while bentonite features a “negatively charged crystalline structure”, maintaining balance of unit cells and cations (e.g. Sodium and calcium bentonite);
Use of stabilized slurries, for easier transport and handling on the field. Formulations capable of maintaining solid and concentrated slurries (mass relation between 10% and 50%) in order to avoid the logistic cost of water transportation. In addition, slurry may be pumped, which facilitates the pressurized intake to the application system and avoids applying powder which is harmful to human health;
New thermodynamic equipment for slurry mixing through a continuous flow shearing chamber which provides flexibility in varied clay and bentonite applications in different ratios (varied hydrotalcite and bentonite mass ratios, ranging from 1:1000 to 1000:1), under adjustable pressure and temperature according to flow rate and concentration of equipment inlet slurries;
In addition to the flexibility in application, the continuous flow shearing chamber is also responsible for increasing “clay delamination”, and subsequent increase in surface area and adsorption sites, also enabling the combination of adsorbents with other chemical methods that involve combined addition of in different application points of polymers/biopolymers, dispersing agents and hydrolytic enzymes.
This Invention Patent application will be described in detail with reference to the drawings listed below, in which:
Considering that the core of this Invention Patent application is a continuous treatment system for cellulose pulp based on a chemical method and processes for clay mixing in special conditions, in order to remove dissolved and colloidal contaminants, in addition to improvements in retention and drainage, the main technological advancements are described below, which also characterizes this patent application.
Initially, through the schematic representation shown in
The basis of the proposed strategy is the chemical adsorption method 102 which features the most significant results when applied individually (talc is classified as an adsorbent). In general, adsorbents in
Still regarding the diagram in
It should be understood that dispersing agents, polymers and biopolymers mentioned are the standard substances used in the State of the Art, considering the optimal dosages of applications easily recognized by area experts, but always associated to the mix of adsorbent clays proposed herein, in slurry form and applied via the system for continuous treatment of the cellulose pulp, which will be described in more detail below.
Another previously mentioned aspect which requires emphasis, considering the main focus of this invention as the full or partial talc replacement, refers to the challenge in obtaining an “alternative adsorbent system” with properties as unique as those of talc, whose layers feature an “organophilic” surface and the corners are “hydrophilic”, granting dispersibility in water medium associated to a dual action, both as a fixing agent and as a detackifier.
The fact is that direct replacement by other silicate-type adsorbent agents such as bentonite cannot fulfill the expected overall performance, thus preventing full process removal. In such cases, the use of associated methods (dispersing agents and polymers) is vital for mitigating the effects of its absence. The only way to attain this, as proposed in this invention Patent application, is through the use of a new clay mix, with a synergic and supplementary action, such as the adsorption system that involves the combined application of hydrotalcite and bentonite in an ideal ratio, in which the organophilic and hydrophilic properties are better balanced and closer to the action of talc alone, not to mention the adsorption capacity highlighted by the increase in surface areas due to forced delamination within a continuous treatment system that provides high shearing rates.
In a complementary approach to the methods above, a pre-enzymatic treatment 101A may also be deployed, capable of facilitating the release of synthetic fiber contaminants (e.g. esterase), associated or not to a post-enzymatic treatment 101B which provides the use of lipases for degrading glycerides commonly found in pitch. It should be noted that the application of associated dispersion methods through dispersing agents 103 (surfactants) and fixing polymers or biopolymers 104 may be alternated, before or after the main adsorbents 102. Another point of emphasis is that contaminants 105 are ultimately eliminated from the manufacturing process via the Effluent Treatment Station (ETE 1 Estacao de Tratamento de Efluentes) or carried along in the fiber with the product, are retained or, more specifically, “concealed” in the paper products 106.
In fact, it should be understood that pitch and stickies-type contaminants are retained (or concealed) on the surface of adsorbents which also end up acting as “inert charge”, granting a monetary advantage which is the “aggregate weight” to the sheet, neither affecting its physical or chemical properties, nor represent any type of risk to human health, except for recent problems likewise related to talc composition including asbestos, which is acknowledged as a carcinogenic material, thus reinforcing the current movement towards replacement. Alternatively, for fixation mechanisms, said contaminants may also bond in the cellulose fiber through cross bonds with polymers or biopolymers.
The chemical action of different methodological approaches may be observed in examples 1 and 2 detailed below, which measure the removal efficiency of dissolved and colloidal contaminants by adsorbents through reduction of turbidity in a simulated sticky sample (
EXAMPLE 1. For simulating stickies, a standard label (PIMACO brand) was cut in 0.5×0.5 cm pieces, up to 30 g of weight, and 970 g of tap water was added, letting it soak for 4 hours. Afterwards, the pieces were initially shredded in a blender for 90 seconds, and transferred to the fiber pulper at 10,000 RPM. The sample was filtered in a black band filter paper (7.5 μm pore) to remove the fibers. 50 g of the filtered solution was collected, adding 4 Kg/t of adsorbent products (e.g. Talc, bentonite and hydrotalcite), initially at a 1% solution. It was then stirred for 15 minutes, transferred to a tube, and centrifuged at 500 G for 5 minutes. Afterwards, the supernatant was transferred carefully to a beaker and turbidity readings were carried out. Lastly, the sample was acidified to a pH near 4.00 using a 0.5% H2SO4 solution, and a final turbidity reading was carried out.
EXAMPLE 2. A 50 g mass of the pitch-rich cellulose pulp sample was collected, adding 4 Kg/T of products to be tested (e.g. Polymers, biopolymers, and dispersing agents), from a 1% solution. The sample was stirred for 15 minutes and filtered in a 32 MESH sieve for retention of the “coarse” of the cellulose mass, subsequently filtered in black band filter paper for retention of fines. The sample was mechanically stirred (240-280 RPM) for 15 minutes. Afterwards, the sample was filtered with a black band filter, and the filtered product was diluted at a proportion of 100 μL of sample to 900 μL of distilled water. For contaminant counting, a maximum of 100 μL was deposited in the interstices formed between the slide and the Neubauer chamber as to avoid overflowing. The counting was carried out in an optical microscope with 1000× final amplification lenses, focusing the 0.050 mm long grades placed at the center of the mirrored part and counting the characteristic pitch points, scanning the entire height between the bottom of the Neubauer chamber (focused grade) and the glass slide, for a total of 2.5×10−7 cm3 in volume.
After the best chemical methodology is determined, alternatively comprising one or more associated methods, and supplementary to the adsorption, dosage points must be chosen while considering talc replacement. As for the typical case of the cellulose manufacturing process 300 (diagram shown in
At first, this invention, which provides a mix of clays from the hydrotalcite and bentonite types, applied in slurry form through a continuous treatment system of the cellulose pulp with high shearing rates, should be enough to address the problem of dissolved and colloidal contaminants in the fiber line in talc replacement; however, depending on the level of contaminants and specific retention and drainage goals, associated and complementary methods involving surfactant dispersing agents, polymers, biopolymers and enzymes may be used in combination, and are familiar to those skilled in the art.
Specifically as show in
As for the paper manufacturing process 400, in reference to
Specifically as shown in
It is therefore evident that, in a first aspect of the Invention Patent application, in addition to the special clay mix to be detailed afterwards, that the methodological strategy 100 presented herein is multifaceted and synergic in terms of chemical action, covering the peculiarities of the cellulose 300 and paper 400 manufacturing processes, although it should be noted that variations in the order of application methods and points are possible.
The embodiments provided in this invention Patent application are only possible if, by the main adsorption method 102, a mix of special clays is provided through an application system 500 (flowchart in
Therefore, the mix of talc and substitute clays in the continuous flow shearing chamber 502 may be observed in 3 dimensions on
Regarding the continuous flow shearing chamber 502, this is essentially a homogenizing device formed by two pipe sections, a lower section 502A and an upper section 502B, the first comprising a top peripheral assembly flange 502A′, whereas the second comprises a corresponding bottom peripheral assembly flange 502B′, as both flanges may be joined by screws 502C.
The lower pipe section 502A features an outlet pipeline 502D, axial to the geometric axis of said pipe section, which includes a connecting flange 502D′, in addition to a radially positioned side inlet pipeline 502E including a corresponding connecting flange 502E′.
Whereas the upper pipe section 502B comprises a first radially placed side inlet pipeline 502F including a corresponding connecting flange 502F″ and a second radially placed side inlet pipeline 502G including a connecting flange 502G″, in which the first side inlet pipeline 502F is diametrically opposed to the second side inlet pipeline 502G.
The upper pipe section 502B also comprises a third side inlet pipeline 502H, placed on the same level regarding the first and second side inlet pipelines 502F and 502G, in which said third side inlet pipeline 502H includes a respective connecting flange 502H′.
The upper pipe section 502B features a top peripheral assembly flange 502B″ against which a closure disc 502J is assembled through screws 5021.
An electric drive motor 502K is assembled at the center of the closure disc 502J, which drives a vertical shaft 502L which internally traverses both the lower pipe section 502A and the upper pipe section 502B.
Internally, the lower and upper pipe sections 502A and 502B respectively comprise internal chambers, respectively indicated as 502M and 502N.
The internal chamber 502N of the upper pipe section 502B comprises a pipe screen 5020 which hangs from the lower face of the closure disc 502J.
The vertical axis 502L comprises three pairs of homogenizing blades 502P along its full length, while the first of three sets of blades 502P is provided inside the tubular screen 5020, and the second set of blades 502N is positioned in the lower section of the chamber 502N of the upper pipe section 502B and, lastly, the third set of blades 502P is placed at the very bottom 502L′ of the vertical axis 502L, while said third set of blades 502P is placed in the middle of the internal chamber 502M of the lower pipe section 502A.
Regarding the upper pipe section 502B, the first side inlet pipeline 502F serves as an inlet for “clay 1” (bentonite), while the second side inlet pipeline 502G serves as an inlet for “clay 2” (hydrotalcite), while the third side inlet pipeline 502H serves as an alternate inlet for “clay 3” or other chemicals.
Regarding the lower pipe section 502, its side inlet pipeline 502E aims at allowing the intake of talc.
The material flows entering the continuous flow shearing chamber 502 through its upper pipe section 502B through its first, second and third side inlet pipelines 502F, 502G and 502H, are homogenized by the rotation of the vertical axis 502L and, more specifically, by the rotation of the sets of homogenizing blades 502P, which similarly occurs with the talc flow entering the lower tubular chamber 502A through its side pipe section 502E.
The homogenized flow entering the continuous flow shearing chamber 502 follows thereof through the outlet pipeline 502D towards the processes 300/400, as schematically shown in Figure
It should be noted, as previously stated in the technical background, that the clays must be in stabilized slurry form that facilitate pumping for application. Patent PI 0401695 (deriving from Chilean patent CL 2002002155) applies bentonite slurries focused on retention and drainage, but does not explore its mixing with other clays such as hydrotalcite. Similarly, the Chinese patent (CN 101333787) provides the isolated action of hydrotalcite over pitch (no mixing with other clays), as well as any gains in retention and drainage.
It is also known that raw bentonite is often not the most efficient, due to, among other reasons, composition variations inherent to the region from where they are extracted (e.g.: Brazil, Mexico, Greece, Germany, and Morocco). In this sense, this Invention Patent application prioritizes calcitics ones above 60% montmorillonite concentration, ideally between 85 and 95%, as well as those that have undergone a milling process to reach an average particle size lower than 100 μm. This does not mean that sodium bentonites, in natura, or even activated bentonites (e.g. Organophilized) and/or stabilized with various dispersing agents cannot be employed with satisfactory results.
On the other hand, a recent Chinese patent (CN 109331774) has shown that a modified bentonite may be produced by reacting with hydrotalcite in certain temperature and pressure conditions, however, the application of the material obtained herein is limited to removal of heavy materials and dyes, leaving the way open for other applications such as paper machines proposed herein for controlling pitch and stickies, as well as retention and drainage.
In addition to hydrotalcite, which are dual lamellar hydroxides belonging to the anionic clay family, featuring a structural formula comprised of bivalent and trivalent metallic cations, as well as an interleaved anion, other clays may also be used in the continuous flow shearing chamber (clay 3), such as quartz, diatomite, pyrite, mica, sepiolite, cristobalite, pyrophyllite, gypsum, limonite, perlite, vermiculite, dolomite, agalmatolite, among others.
Hydrotalcite employed in the mixes of this invention Patent application may be natural or synthesized through conventional means, such as the co-precipitation method, salt oxide, induced hydrolysis, hydrothermal, among others. The hydrotalcite may feature variations in interlamellar metals and anions, preferably comprising magnesium and aluminum such as cations, and the most common anions are chloride, nitrate, carbonate, and sulfate.
According to what proposed in this Invention Patent application, the mix of clay slurries, more specifically bentonite and hydrotalcite, may fall into proportions that ideally vary between 1:9 and 9:1, considering that the mix of clay slurries takes place preferably under pressure and temperature obtained through pumping conditions.
Lastly, in face of the foregoing advancements, in addition to the particular embodiments described and detailed herein, this Invention Patent application should not be considered limited to such descriptions. Moreover, it should be clear to those skilled in the several arts involved herein that any modifications, whether apparent or not, may be incorporated as an integral part of this invention and yet remain in agreement with the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 024382 1 | Nov 2019 | BR | national |
