BR112019021940A2 - method for stabilizing process ph in liquid or industrial aqueous suspension containing starch - Google Patents

Abstract

the present invention relates to a method for stabilizing ph in aqueous fluid or suspension, using an amylase inhibiting composition for stabilizing ph and a process for making paper or cardboard.

Description

METHOD FOR STABILIZING PH OF THE PROCESS IN LIQUID OR WATERPROOUS INDUSTRIAL SUSPENSION CONTAINING STARCH

Field of Development [0001] This development refers to a method for stabilizing the pH in an industrial fluid or aqueous suspension containing starch, using an amylase inhibiting composition to stabilize the pH and a process for making paper or cardboard.

Background [0002] Starch is an additive widely used in industry, as well as in papermaking. In fact, papermaking is the largest non-food use of starch. For example, on the wet end of a paper machine, starch is used to improve the strength of the paper. At the dry end of a paper machine, starch is used to coat paper in a process called surface bonding. This provides additional resistance to the paper and better printing properties.

We processes that use fibers recycled, the amount in starch typically varies in between 10 to 50 kg / ton in mass of dry fiber, this and the amount of starch at the process is considerable. [0003] Amylase is enzyme that catalyzes The

starch degradation. It is produced by many microorganisms, such as fungi and bacteria. Microorganisms are not able to use starch as such, but they excrete amylase enzymes outside the cells, expecting them to break down starch into glucose monomers and dimers suitable for cellular intake and carbon metabolism. Amylase enzymes are divided into three groups: α-, β- and γ-amylases.

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All of them hydrolyze α-1,4-glycosidic bonds that link glucose units of the starch molecule, β-amylase can break down only the second a-1,4-glycosidic bond, producing two glucose units (maltose), α- amylase can attack any bonds in the starch molecule and is therefore often faster than β-amylase. Γ-amylase cleaves one unit of glucose at a time and is most efficient in acidic environments.

[0004] Waste water containing starch usually contains microorganisms that can produce amylase enzymes. In the paper industry, starch degradation causes loss of starch additive functionality, leading to paper quality problems or, alternatively, forcing paper manufacturers to increase starch dosages, thereby creating unwanted additional costs. It is well known in the cellulose, paper or cardboard industry to apply biocides to control microbial growth and a specific application of biocides is to control starch degradation, both in suspensions containing starch before dosing into the paper machine and in water residues containing starch inhibiting microbial growth.

[0005] WO 2012/025228 describes a method for the manufacture of paper, in which a cellulosic material containing starch is treated with biocides, followed by the addition of an ionic polymer and an auxiliary ionic polymer, both polymers with average molecular weight different and different ionicity.

[0006] WO 2013/045638 teaches the synergistic effect of Zn ions with one or more biocides in prevention

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3/23 or reduction of starch degradation, while simultaneously inhibiting existing amylase enzymes and preventing the production of new amylase enzymes by microorganisms.

[0007] Microbial activity can lower the pH of the aqueous growth environment. This is due to the organic acids produced in the fermentation metabolism. Reducing the pH of wastewater can lead to process and quality problems related to calcium carbonate or other calcium components. The decrease in pH dissolves the calcium carbonate used as an additive in the manufacture of paper and / or cardboard. Dissolution increases the need to add calcium carbonate and causes problems such as calcium precipitates in water circulation and wastewater treatment.

[0008] The circular economy requires the effective use of raw materials, such as starch in recycled fibers. There is a need for improved methods to prevent starch degradation, stabilize the pH and prevent the dissolution of calcium components, especially calcium carbonates in the pulp, paper and cardboard manufacturing processes. This invention meets or at least alleviates those needs.

Summary [0009] The present disclosure generally relates to pH stabilization in industrial aqueous fluids and suspensions containing starch. The inventors were surprisingly able to demonstrate that the introduction of the amylase inhibitor compound (s) comprising zinc (Zn) ions to that industrial aqueous fluid or suspension effectively stabilized the system's pH and,

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4/23 thus, provided numerous advantages to the process.

[0010] The first objective of the invention is a method to stabilize the pH in the aqueous industrial fluid or suspension containing starch. According to the invention, said method comprises adding an effective amount of an amylase inhibiting composition comprising zinc (Zn) ions as an active ingredient in said fluid or suspension.

[0011] The second objective of the invention is the use of an amylase inhibiting composition to stabilize the pH in industrial wastewater containing starch.

[0012] The third objective of the invention is a process for making paper or cardboard. According to the invention, said method comprises adding an amylase inhibiting composition to the process fluid (s) and / or suspension (suspensions) in an effective amount.

Brief Description of the Figures [0013] Figure 1. Shows the pH values in RCF 20 h after additions of the amylase inhibiting composition comprising zinc ions as an active ingredient (0, 6, 12 and 24 mg / L).

[0014] Figure 2. Shows Redox values (ORP, oxidation reduction potential) in RCF, 20 h after additions of the amylase inhibitory composition comprising zinc ions as an active ingredient (0, 6, 12 and 24 mg / L).

[0015] Figure 3. Shows the concentration of starch in RCF 20 h after additions of the amylase inhibiting composition comprising zinc ions as an active ingredient, measured by the iodine staining method.

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5/23 [0016] Figure 4. Shows the pH values after the RCF tower before, during and after the addition of the amylase inhibiting composition comprising zinc ions as an active ingredient in the aqueous suspension.

Detailed Description [0017] Microorganisms can cause several problems in the pulp, paper and cardboard manufacturing processes. Without proper control, the microorganism can grow on the machine's surfaces as viscous deposits (biofilms) that cause paper defects (dirt stains, holes) or break the paper web, forcing the machine to stop for cleaning. Defects can cause high quality complaints from the end users of the article. Extra stops for cleaning cause production losses and reduce the cost-benefit of papermaking. The microbial fermentative activity can result in the formation of volatile fatty acids (VFA), which can cause damage to the final paper or cardboard or even impair air quality throughout the factory and in the neighboring city. VFAs are reducing the pH of aqueous fluids and suspensions (wastewater) and this can lead to calcium and carbonate-related process and paper quality problems. Machines for the production of paper and cardboard use biocides to control microbial growth and the formation of AGV (volatile fatty acids) and / or to dose sodium hydroxide for pH control.

[0018] These chemicals are not satisfactory due to the high cost related to the efficient control of microbes or the high doses of sodium hydroxide required. Surprisingly, it was found that,

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6/23 when adding an amylase-inhibiting composition, the pH of starch-containing aqueous fluids and suspensions (wastewater) from cellulose, paper or cardboard production remains at a higher level and is more stable, although the addition of hydroxide sodium is reduced. The decrease in the pH of waste water containing starch from the production of cellulose, paper or cardboard can be effectively controlled by adding an amylase inhibiting composition. Respectively, it is also necessary to regulate the pH in other aqueous process fluids and suspensions containing starch.

[0019] It has been surprisingly found that the use of amylase inhibitor compounds comprising zinc (Zn) ions is a more effective method than the addition of high doses of bases, such as NaOH, or dosages of toxic biocides normally used in paper mills , therefore being a safer method to stabilize the pH of aqueous fluids and suspensions.

[0020] The present invention relates to a method for stabilizing the pH in the industrial aqueous fluid or suspension containing starch. The method comprises adding an effective amount of an amylase inhibiting composition to said fluid or suspension.

[0021] As used herein, the term industrial aqueous fluid or suspension includes all fluids containing water used in industry. A term suspension refers especially to fluids containing solids (for example, 1-10% fibers). In the pulp and paper industry, these fluids and suspensions are often referred to as wastewater.

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7/23 [0022] The term pH stabilization, as

employed in this document means that pH of aqueous fluid or the suspension is maintained approximately at the same level, per example, an step of process or Department in processing (as system in storage for discards) or during a given

period of time. Preferably the delta pH is less than 0.6, preferably less than 0.5; even more preferably less than 0.4 and more preferably less than 0.3.

[0023] In this context, an amylase inhibiting composition means a composition that decreases the activity of the amylase enzyme under the same conditions in aqueous fluids and suspensions (waste water). The activity of the amylase enzyme is preferably measured as the rate of starch degradation using any method known within the field. When used in an effective amount, the decrease is at least 30%, 40%, 50%, 60%, 70%, 80%, 90% or even 95% compared to amylase activity without said inhibitor composition. The composition can comprise one or more active ingredients. The activity of the amylase enzyme can be measured using methods known within the field and, for example, by setting the rate of starch degradation. In this context, the term amylase activity refers to amylase-degrading activities of starch, such as, without reference to a specific type of amylase.

[0024] The numerical values of the effective amount to be used for the active ingredients of amylase inhibitors depend, for example, on the aqueous fluids and suspensions containing starch to be treated, type of

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8/23 inhibitory active ingredient and amount of starch, amount of starch degradation activities and process temperature. It is known that Zn ions can inhibit the amylase enzyme (Irshad et al., 1981: Effect of Zn on plant α-amylases in vitro. Phytochemistry. 20: 21232126).

[0025] In one embodiment, the active ingredient of the amylase inhibiting composition comprises the zinc ion (Zn). In one embodiment, the zinc ions are derived from an inorganic zinc salt. In another embodiment, zinc ions are derived from the organic zinc salt. Preferably, an inorganic zinc salt is used, since they do not introduce carbon usable by microbes in the process. In addition, as such, they are not strongly acid or alkaline and therefore do not directly affect pH. It was found that zinc is compatible with paper and cardboard manufacturing processes. It has been shown to be effective in concentrations that are not harmful to the environment. In addition, the use of zinc ions is improving the safety of the industrial process. Zinc ions are generally considered safe (GRAS), even in applications for human consumption (US: Food & Drug Administration; GRAS Substances Database (SCOGS)).

Beyond addition, the [002 zinc 6] In it is a cheap raw material. A way of realization, the source From ions Zn can to be a compound inorganic zinc or organic, in particular a salt zinc organic or

inorganic. Preferably, the source of zinc ions is selected from ZnBr ₂ , ZnCl ₂ , ZnF ₂ , Znl ₂ , ZnO, Zn (OH) ₂ , ZnS, ZnSe, ZnTe, Zn ₃ N ₂ , Zn ₃ P ₂ , Zn ₃ As ₂ , Zn ₃ Sb ₂ , ZnO ₂ , ZnH ₂ ,

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ZnC ₂ , ZnCO ₃ , Zn (NO ₃ ) ₂ , Zn (C10 ₃ ) ₂ , ZnSO ₄ , Zn ₃ (PO ₄ ) ₂ , ZnMo0 ₄ , ZnCrO ₄ , Zn (AsO ₂ ) ₂ , Zn (AsO ₄ ) ₂ , Zn (O ₂ CCH ₃ ) ₂ or zinc metal or a combination thereof. Preferred are ZnCl ₂ , ZnBr ₂ , ZnSO ₄ and Zn (O ₂ CCH ₃ ) ₂ . These salts are suitable, for example, as having high solubility in aqueous solution, as aqueous fluids and suspensions (process water). More preferred are ZnCl ₂ , ZnBr ₂ , ZnSO ₄ . More preferably, ZnSO ₄ or ZnCl ₂ or a combination thereof is used.

[0027] In one embodiment, an effective amount of zinc ions is at least 1 mg / L, preferably at least 2 mg / L, more preferably at least 3 mg / L, even more preferably at least 4 mg / L L, even more preferably at least 5 mg / L and most preferably at least 6 mg / L (mg of Zn ions in L of the fluid or suspension). In one embodiment, an effective amount of zinc ions is less than 40 mg / L, preferably less than 30 mg / L, more preferably less than 25 mg / L or 24 mg / ml, even more preferably less than 20 mg / L and more preferably less than 12 mg / L or even less than 6 mg / L (mg of Zn ions in I process water). In one embodiment, an effective amount of zinc ions is 1 to 40 mg / L; preferably 4 to 30 mg / L; more preferably 6 to 20 mg / L, even more preferably 6 to 15 mg / L (mg of Zn ions in 1 process water). In one embodiment, an effective amount of zinc ions is 1 to 12 mg / L (mg of Zn ions in I of process water). In one embodiment, an effective amount of zinc ions is about 6 mg / L (mg of Zn ions in 1 process water). The need for zinc ions depends on wastewater conditions, such as

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10/23 amount of starch and, mainly, amount of starch degradation activities. Based on various pH stabilization experiments in aqueous fluids or suspensions in the manufacture of paper and cardboard (initial starch content from 200 to 1,000 mg / L and uninhibited degradation rates from 2% by weight per hour to up to 21% in weight per hour, data not shown) it appears that 6 to 15 mg / L of zinc ions or 6 to 12 mg / L of zinc ions in the residual water and even less zinc ions are sufficient to prevent the pH from decreasing in each condition, however depending on the conditions also much lower doses provided satisfactory pH stabilization.

[0028] In one embodiment, the pH delta after the addition of a compound or composition that inhibits amylase, especially a compound comprising zinc ions, is less than 0.6, more preferably less than 0.5; even more preferably less than 0.4 and more preferably less than 0.3.

[0029] An embodiment of the invention, where the content of zinc ions is at least 2 mg / L, is discussed shortly below (data not shown). An amylase inhibiting composition comprising zinc ions as an active ingredient was used at 2 mg / L (calculated as total zinc in a fiber containing residual water from the storage tower). After 12 hours, it was surprisingly found that the pH delta in the storage towers was less than 0.4 units, the Redox delta (ORP, oxidation reduction potential) in the storage towers was less than 50 mV and the pH remained above of 6.7 without addition of NaOH. In these conditions, the concentration

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11/23 of soluble calcium was below 1,500 mg / L. The pH of the waste storage tower and / or cellulose storage tower was at least 0.1 units higher and the concentration of soluble calcium was at least 5% lower than before treatment. This experiment clearly demonstrates the effect of zinc ions in small quantities.

[0030] The quantities are defined in this document in ppm or mg / L, where ppm (parts per million) means the same unit as mg / L, so that these units are used interchangeably. In the present disclosure, ppm means weight of the active ingredient per volume of waste water. Process water includes solid matter, such as fibers; loads; starch; additives for papermaking, such as retention aids, chemicals for bonding, biocides, fixatives, dyes, defoamers; possible coating components, such as latex, pigments, optical brighteners, etc .; wood resin and other wood extracts; microorganisms and other process impurities. Due to the retentive properties of the fibers, the content of Zn ions in the fibrous fraction in wastewater is generally higher than in filtration water. As used in this document, the term residual water (s) refers to waste water that also contains the fiber fraction and can be used interchangeably with aqueous fluids or suspensions in the process.

[0031] The amylases in the wastewater disclosed in this document degrade starch continuously, unless amylase activity is inhibited. A time of

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12/23 longer storage or process without inhibiting the composition results in greater degradation in saccharides, serving as a carbon source for microbial growth. In the continuous process, the amylase inhibiting composition can be added continuously or at desired intervals, in order to maintain an effective inhibitory concentration.

[0032] Amylase inhibiting compositions, such as a composition comprising zinc ions, can be added continuously or sequentially to the starch-containing waters to be treated.

[0033] In one embodiment, the aqueous fluid or suspension containing starch comprises fluid or aqueous suspension from the production of cellulose, paper or cardboard; or water-based drilling fluid in the oil industry. Both processes involve pH stabilization.

[0034] Reduced starch degradation guarantees paper manufacturers significant savings in starch consumption, as less starch is required, reducing performance problems and increasing paper quality. In addition, starch is not easily degraded into smaller sugars that microbes could use for growth. Under anaerobic conditions, bacterial fermentation of these sugars can produce acids that lower the pH of the system. Reduced amount of such saccharides and reduced fermentation rate have a positive effect on pH. In paper and cardboard processes, pH below 7.0 can result in the dissolution of calcium carbonate used as a filler or as a coating component, leading to difficulties in water circulation

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13/23 and in downstream processing (for example, precipitates in wastewater treatment) and possibly also in the need to introduce new calcium carbonate for the process. All of this reflects in the process economy.

[0035] In one embodiment, the aqueous fluid or suspension containing starch is the fluid or aqueous suspension of the production of cellulose, paper or cardboard, commonly called waste water. In general, the amylase inhibiting composition can be added to a position containing starch and including components that can degrade starch. The amylase inhibiting composition can be added to the waste system, waste storage tanks, pulping system, pulping storage tanks, water entering the pulper, pulper or pulp right after the pulper, the storage tanks water or piping before cellulose storage or disposal tanks. Especially beneficial is the addition of the amylase inhibiting composition to the pulper or to the water that enters the pulper. In one embodiment, the amylase inhibiting composition is added to the water entering the pulper, for example, 5 to 30 minutes before the water enters the pulper. In particular, the amylase inhibiting composition can be used in pulping recycled fibers containing starch and / or in disposal systems. Without attaching to the theory, the addition of the amylase inhibiting composition to the composition to the water that enters the pulper and especially to the water before entering the pulper allows the inhibition of amylase in the water before contact with the material containing the fiber. Inhibitory compositions

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14/23 amylase can, to some extent, be adhered to the fibers, thus reducing the contact between the amylase and the amylase inhibiting composition.

[0036] In a specific embodiment, the amylase inhibiting composition is mixed with dry starch before introducing it into the paper or cardboard manufacturing process. In another embodiment, the amylase inhibiting composition is added to the paper or cardboard manufacturing process simultaneously with starch. The amylase inhibiting compound can be mixed with dry starch or starch suspension or applied in the paper or cardboard manufacturing process at the same time as the starch. This ensures that inhibitory activity is present from the start, increasing pH stabilization. It is clear to a person skilled in the art that zinc ions can be added in connection with other process chemicals, for example, together with polymeric fixers or PAC,

mixed already anointed or separately in the same point in dosage of system. [0037] From according to a form of achievement , O compound inhibitor gives amylase is added to waters or suspensions of production cellulose, paper or cardboard in an

enough to maintain the residual water pH at least 6.8, preferably at least 7.0. The pH above about 6, 8 keeps the calcium carbonate used as an additive in the manufacture of paper and / or cardboard in solid form and, thus, reduces the need to add calcium carbonate and problems related to calcium precipitates. In a delta pH embodiment within a process step or, for example, tank / container is

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15/23 less than 0.6, more preferably less than 0.5; even more preferably less than 0.4 and more preferably less than 0.3. Suitable process steps or tanks / containers are for example, disposal system, disposal storage tanks, pulping system, pulping storage tanks, the pulper, water storage tanks, pulping storage tanks. In another embodiment, the delta pH is less than 0.6, more preferably less than 0.5; even more preferably less than 0.4 and more preferably less than 0.3 during the desired time.

[0038] The disclosure also relates to a method of inhibiting the existing amylase activity and / or preventing or reducing the production of new amylase by microorganisms in fluid containing starch, wherein the method comprises the addition of an amylase inhibiting composition, preferably containing zinc ions to process the water. The zinc ions can be the same as those defined above. The fluid containing starch can be the same as the waste water defined above, from the production of cellulose, paper or cardboard.

[0039] The present disclosure also relates to a use of an amylase inhibiting composition, especially a composition comprising zinc ions as an active ingredient, to stabilize the pH in aqueous starch-containing fluids or suspensions. Suitable aqueous fluids or suspensions are cellulose, paper or cardboard production fluids or suspensions or water-based drilling fluids. Said use comprises adding an amylase-inhibiting composition to said fluid or

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16/23 suspension. The zinc ions can be the same as those defined above. The fluid or suspension containing starch may be the same as defined above, as a fluid or suspension from the production of cellulose, paper or cardboard. The advantages of an amylase inhibiting composition have been discussed above.

[0040] The present disclosure also relates to a process for the manufacture of paper or cardboard which comprises the addition of an amylase inhibiting composition in the fluid (s) and / or suspension (suspensions). In one embodiment, in such a process, an amylase inhibiting composition is introduced into the process simultaneously with dry starch or material containing starch. In one embodiment, the amylase inhibiting composition is added to the paper or cardboard manufacturing process simultaneously with starch. The amylase inhibiting compound can be mixed with dry starch or starch suspension or applied in the paper or

same time as the starch. That ensures that the activity inhibitory is present since the beginning, increasing the pH stabilization. [0041] The invention is illustrated down by

following non-limiting examples. It should be understood that the embodiment given in the description above and in the examples is for illustrative purposes only, and that various changes and modifications are possible within the scope of the invention.

EXAMPLES

Example 1.

[0042] Pulping sample RCF (Recycled Cellulose Fiber) from Factory 1 was collected on December 2,

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2015 and delivered to the Kemira R&D Center in Espoo, Finland. The test was started the next day. The RCF was kept in a cool place during transport. It was verified by measurement that the RCF contained about 80 mg / L of soluble starch. As the starch content was low, 500 mg / L of surface sizing starch (corn starch, Merizet 170) was added to the pulp. The RCF was divided into eight 50 ml portions and a 0, 6, 12 or 24 ppm amylase inhibitor compound (zinc ions from zinc sulfate, product pH 4-5) was added. Two replicates were made of each concentration. The samples were placed at + 45 ° C with agitation. The concentration of residual starch, pH and Redox were measured the next day, after approximately 20 hours of incubation. Starch was measured using the conventional iodine staining method at 590 nm.

[0043] The results in Figure 1 and Table 1 show that the pH in the reference samples without amylase inhibitor was 7.16 - 7.36. The samples treated with an amylase inhibitor showed a significantly higher pH, between 7.7 and 8.1. Dosing of 12 mg / L of zinc was sufficient in this experiment and higher doses gave no additional benefit.

[0044] The results in Figure 2 and Table 1 show that the Redox values in reference samples without amylase inhibitor were clearly negative, about -140 mV. The samples treated with an amylase inhibitor showed positive redox values. With 6 ppm, the redox was +95 - 100 mV, with 12 ppm of 120 - 130 mV and with 24 ppm of 140 mV.

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18/23 [0045] The results in Figure 3 and Table 1 show that there was more starch in the samples treated with the enzyme amylase inhibitor than in the samples without treatment. In the reference samples, the absorbance was 0.34 - 0.37. In five of the six samples treated, the absorbance was above 0.5, but the lowest concentration tested, 6 mg / L, provided this benefit and no improvement was seen with higher concentrations.

[0046] Table 1. pH, amounts of Redox and starch in the RCF pulp samples, 20 hours after the addition of the amylase enzyme inhibitor

Concentration of amylase inhibitor mg / L Values measured 20 hours after addition of amylase enzyme inhibitor pH Redox, mV Starch, A5 90 0 7.161 -147.1 0.337 0 7.362 -137.9 0.367 6 7,712 99, 9 0.519 6 7.899 95 0.572 12 8.106 129.6 0.573 12 7, 998 121, 9 0.554 24 7, 985 141.5 0.554 24 7.859 141, 9 0.464

Example 2.

[0047] The enzyme amylase inhibitor was tested in a cardboard factory using recycled fiber raw material (Factory 2). Zinc sulfate as an amylase inhibitor compound was administered for about 24 hours in the RCF tank, located before the RCF storage tower. The final amount was about 10 to 12 ppm of zinc. No other changes were made to the process chemicals during the experiment. Surprisingly, we found that the pH of the RCF tower was

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19/23 higher for the duration of the study with amylase inhibitor. Before the experiment, the pH of the RCF was

just above 5.9 and during and after the treatment with enzyme inhibitor amylase if showed greater than 6.0. The results are shown in Figure 4. Example 3 [0048] 0 sulfate in zinc as a compound enzyme inhibitor amylase was tested in a factory in cardboard using raw material in fiber re cycled (Figure 3).

amylase inhibitor compound was administered for one week. Two dosing points were used: pulp flow after the RCF pulper and another immediately before the RCF storage tower. The factory used 50% sodium hydroxide solution (NaOH) to adjust the pH. The data from the test period (1 week) were compared to the data from the reference period (before and after the test, 3 months). Table 2 shows that, during the test of the amylase enzyme inhibitor, the pH in the process was higher, the concentration of calcium in the effluent tower was lower and the plant still managed to reduce the consumption of sodium hydroxide. Table 3 shows the measured zinc concentrations. Before starting treatment, the zinc concentration was 0.56 mg / L. During the experiment, the concentration was 2.96 - 3.76 mg / L, except for one measurement with a lower result.

[0049] Table 2. Concentration of pH, Ca ²⁺ and consumption of NaOH during the reference period and experiment with an enzyme amylase inhibitor.

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Reference period, average Amylase enzyme inhibitor experiment period, mean pH, Disposal 6, 9 7.0 pH, Disposal sieve 6, 9 7.0 pH, Short fiber dosing tank 6, 7 7.1 Effluent tower Ca ²⁺ , mg / L 820 670 Addition of NaOH, L / ton of cardboard 6, 6 4.3

[0050] Table 3. Zinc concentrations during the experiment

RCF, pulper outlet RCF tower, exit 7/4/2016, before the experiment 0.56 5/5/2016 2.96 3.04 6/7/2016 3.76 1.0

Example 4.

[0051] The effect of the amylase inhibitor compound was tested on the pH of the RCF pulp. Table 4 shows that, without treatment, the pH decreased by 0.55 units during 24 hours of storage. With NaOH, the initial pH can be increased, but it had no effect after the storage time, and the pH change was even greater than without NaOH. Zinc sulfate as an amylase inhibitor compound reduced the pH drop, with 6 to 24 mg / L the pH drop was 0.29 to 0.39 units. The amount of soluble calcium was 187 mg / L at the beginning of the test. In the untreated sample and in the NaOH sample, the calcium concentration increased to 244 or 245 mg / L, that is, 30%. With zinc, the increase in calcium concentration was smaller and, in one sample, the measured soluble calcium even decreased.

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21/23 [0052] Table 4. pH in the recycled fiber pulp after 24 hours with and without treatment. The pH of the pulp was 7.2 at the start of the test. In the NaOH sample, the pH was adjusted to 7.5 with sodium hydroxide. After that, and the Zn additions, the samples were incubated 24 hours at + 45 ° C and the pH values were measured again.

pH Ca, mg / L, 0 h 24 h Δ pH 0 h 24 h Δ Ca No additions 7.20 6, 65 0.55 187 244 57 NaOH 7.50 6, 66 0.85 187 245 58 Zinc 6 mg / L 7.20 6.81 0.39 187 197 10 Zinc 12 mg / L 7.20 6, 82 0.38 187 229 42 Zinc 24 mg / L 7.20 6, 91 0.29 187 154 -33

Example 5 [0053] The effect of the amylase inhibiting compound was tested on the pH of the RCF pulp. Table 5 shows that, without treatment, the pH decreased by 0.55 units during 48 hours of storage. In this experiment, 6 mg / L of zinc was not enough and, in this sample, the pH drop was similar to the untreated reference. At 12 mg / L, the pH drop was significantly less, just 0.22 pH units.

[0054] Table 5. pH in recycled fiber pulp after 48 hours with and without treatment. The pH of the pulp was 7.15 at the start of the test. After adding Zn (zinc sulfate), the samples were incubated for 24 hours at + 45 ° C and the pH values were measured again.

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pH 0 h 48 h Δ pH No additions 7.15 6.60 0.55 Zinc mg / L 7.15 6, 56 0.59 Zinc mg / L 7.15 6, 93 0.22

Example 6 [0055] White water from a machine that produced fluted and recycled fiber lining was collected and tested on site at the factory. First, 7 mg / L of zinc was measured in white water and the amount of soluble zinc was measured after 15 minutes. Then 40 g / L of OCC (old corrugated cardboard, recycled fiber type) was sprayed into the water. The amount of soluble zinc was measured again after 5 minutes and 25 minutes.

[0056] In the second part of the test, 40 g of OCC were first sprayed in 1.0 L of white water. Then, 7 mg / L of zinc was added to the pulp and the amount of soluble zinc was measured 5 minutes and after 25 minutes after spraying.

[0057] Zinc was measured using the Hach ZincoVer kit according to the manufacturer's instructions and the Hach DR-900 spectrophotometer.

[0058] Table 6. Quantities of soluble zinc in the tests.

test Soluble Zn, mg / L From water, 15 minutes after addition From the pulp, 5 minutes after pulping From the pulp, 25 minutes after pulping Test 1: Zinc in water 1.65 1.27 0.73 Test 2: Zinc in the pulp 0.61 0.60

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23/23 [0059] The results in Table 6 show that when zinc was added to the water before the fibers, 1.27 mg / soluble zinc was available 5 minutes after adding the fibers. After 25 minutes, the amount was 0.73 mg / L. In the second test, zinc was added to the pulp only after the fibers were pulped. In this case, the amounts of soluble zinc were lower, after 5 minutes 0.61 mg / L and after 25 minutes 0.60 mg / L. As the soluble zinc ions react with the enzyme amylase, this experiment shows that it is beneficial to add zinc in the water before the OCC cellulose fibers, that is, in the dilution water of the recycled fiber remover.

Claims (12)

1. A method for stabilizing the pH in an industrial aqueous fluid or suspension containing starch comprising adding an effective amount of an amylase inhibiting composition comprising zinc (Zn) ions [as an active ingredient] in said fluid or suspension. A method according to claim 1, wherein the zinc ions are derived from an organic or inorganic zinc salt. 3. Method according to claim 2, wherein the organic or inorganic zinc salt is selected from: ZnBr2, ZnCÍ2, ZnF2, ZnÍ2, ZnO, Zn (0H) 2, ZnS, ZnSe, ZnTe, ZnsN2, Ζη3? 2 , ZnsAs2, ZnsSb2, Zn02, ZnH2, ZnC2, Zn (NO3) 2, Zn (0103) 2, ZnSOo Zn3 (PO4) 2, ZnMoOo ZnCrOo Zn (AsO2) 2, Zn (AsO4) 2, Zn (O2CCH3) 2, zinc metal and any combination thereof. Method according to any one of the preceding claims, wherein zinc ions are added to obtain an amount of at least 1 mg / L, preferably at least 2 mg / L, more preferably at least 3 mg / L, even more preferably at least 4 mg / L, even more preferably at least 5 mg / L and preferably at least 6 mg / L (mg of Zn ions in L of the fluid or suspension). Method according to any one of the preceding claims, wherein zinc ions are added to obtain an amount less than 40 mg / L, preferably less than 24 mg / mL and more preferably less than 12 mg / L (mg of ions Zn in L of process water Method according to any of the Petition 870190105541, of 10/18/2019, p. 32/41 2/3 preceding claims, wherein the aqueous fluid or suspension containing starch comprises: The. aqueous fluids or suspensions from the production of cellulose, paper or cardboard; or B. water-based drilling fluid. A method according to claim 5, wherein said aqueous fluid or suspension is fluid or aqueous suspension from the production of cellulose, paper or cardboard. A method according to claim 6, wherein the amylase inhibiting compound is added in an amount sufficient to maintain the residual water pH at least 6.8, preferably at least 7.0. Method according to any one of the preceding claims, wherein the pH delta after the addition of the amylase inhibitor compound in a process step or tank or container is less than 0.6, more preferably less than 0.5, still more preferably less than 0.4 and more preferably less than 0.3 A method according to claims 7 or 8, wherein the amylase inhibiting composition is added to the water located in the disposal system, disposal storage tanks, pulping system, pulp storage tanks, to water entering the pulper or, inside the pulper, in water or tubing storage tanks before cellulose or disposal storage tanks, preferably in water before entering the pulper. A method according to any one of claims 7 to 9, wherein the inhibitory composition of the Petition 870190105541, of 10/18/2019, p. 33/41 3/3 amylase is mixed with dry starch prior to introduction into the paper or cardboard manufacturing process or where the amylase inhibiting composition is added to the process simultaneously with starch. 11. Use of an amylase inhibiting composition comprising zinc (Zn) ions to stabilize the pH in industrial wastewater containing starch, such as water residuals gives production in cellulose, paper or cardboard or fluid from perforation base of water. 12. Process for paper making or cardboard which comprises the addition of an amylase inhibiting composition consisting of zinc (Zn) ions in the process fluid (s) and / or suspension (suspension) in an effective amount. Process according to claim 12, wherein said amylase inhibiting composition is introduced into the process simultaneously with dry starch or material containing starch.