Paper product, chemical mechanical paper pulp and tannin content detection method of paper product and chemical mechanical paper pulp

Abstract

The invention provides a paper product, chemical mechanical paper pulp and a tannin content detection method of the paper product and the chemical mechanical paper pulp. The detection method comprises the following steps: drying and crushing to-be-detected paper pulp to form to-be-detected powder; extracting tannin in the powder to be detected by using the solution; adding a ferric chloride solution, a phenanthroline solution and a sodium acetate solution into the extracted tannin solution, and reacting for preset time; and detecting the reacted solution at ultraviolet visible light by using a cuvette so as to determine the content of tannin. The detection method is suitable for detecting all tannin in the chemithermomechanical pulp by utilizing the reducibility of the tannin, and has the advantages of simplicity in operation, low cost and high sensitivity and accuracy; according to the method, the content of tannin in a sample can be rapidly and accurately measured through chromogenic reaction and spectrophotometer measurement, the method is suitable for quality control in the chemimechanical pulp production process, uncertain factors in the production process can be eliminated, unqualified products are effectively reduced, the production efficiency and the product quality are improved, and high practicability is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of detecting the content of substances in pulp, and in particular to a method for detecting the content of paper products, chemical-mechanical pulp and tannins therein. Background Art

[0002] Tannins precipitate when they come into contact with alkaloids and metal salts. They can then combine with other wood components to form relatively stable, non-degradable compounds, thereby increasing the wood's hardness and durability. Chemical-mechanical pulps with different raw material ratios have varying tannin contents, requiring varying amounts of fresh water washing, refining energy consumption, power, and chemical additions. Failure to effectively control tannin content during the pulping process can significantly impact pulp brightness, freeness, dust content, and water system cleanliness, increasing the risk of holes and dust on paper machines. Therefore, accurate and rapid testing of tannin content in chemical-mechanical pulp is crucial for production adjustments.

[0003] Currently, there are several methods for detecting tannin content:

[0004] The Folin-Dennis reagent method is based on the reaction of polyphenols with the Folin-Dennis reagent (a mixture of phosphotungstic and phosphomolybdic acids) to produce a blue substance whose color is proportional to the polyphenol content. The absorbance is measured colorimetrically, and the tannin content in the sample can be calculated.

[0005] Protein precipitation method: Tannins bind to proteins to form insoluble complexes. This method indirectly reflects the tannin content by measuring the amount of protein precipitation.

[0006] High Performance Liquid Chromatography (HPLC): HPLC is a highly precise analytical technique that can be used to analyze the specific components of tannins. Using a specific chromatographic column and detector, it can separate and quantitatively determine the tannin content in a sample.

[0007] Conventional methods for measuring tannin content cannot be directly applied to chemical-mechanical pulp. Controlling tannin content is crucial in the production of chemical-mechanical pulp. However, there is currently a lack of effective methods for measuring tannin content in chemical-mechanical pulp. This creates an uncontrolled factor in the production process, which can hinder long-term production control. To eliminate uncertainties in the production process and reduce the occurrence of substandard products, a simple and reliable method for measuring tannin content in chemical-mechanical pulp is urgently needed. Summary of the Invention

[0008] A first aspect of the embodiments of the present application provides a method for detecting tannin content in pulp, the method comprising:

[0009] Drying and crushing the paper pulp to be tested to form a powder to be tested;

[0010] extracting tannins from the powder to be tested using a solution;

[0011] Add ferric chloride solution, o-phenanthroline solution and sodium acetate solution to the extracted tannin solution and react for a preset time:

[0012] The solution after the reaction was detected by a cuvette under ultraviolet-visible light to determine the tannin content.

[0013] In some optional embodiments, the detection method further includes drawing a standard curve for tannin content; comprising: adding ferric chloride solution, o-phenanthroline solution and sodium acetate solution to multiple quantitative solution samples respectively for reaction, and detecting the reacted solution with a cuvette under ultraviolet-visible light to draw a standard curve; the step of detecting the reacted solution with a cuvette under ultraviolet-visible light to determine the tannin content includes: comparing with the standard curve and calculating the tannin content.

[0014] In some optional embodiments, in the step of comparing with the standard curve and calculating the tannin content, the tannin content calculation satisfies the following formula:

[0015]

[0016] Where:

[0017] X-tannin content, in %;

[0018] n-the tannin content in the volumetric flask obtained from the standard curve, in mg / L;

[0019] v-The volume of the pretreated sample added during the determination, in units of mL ;

[0020] m-extraction sample weight, in g;

[0021] f- dryness of the sample after crushing.

[0022] In some optional embodiments, in the step of extracting the tannins from the powder to be detected using a solution, multiple extractions are performed to obtain a solution containing the total amount of tannins.

[0023] In some optional embodiments, the step of drying and crushing the pulp to be tested to form a powder to be tested includes: squeezing the moisture of the pulp to be tested with a filter, spreading it flat on a tray, drying it in an oven at 50-70°C for 5-7 hours, and crushing it with a crusher to obtain the powder to be tested.

[0024] In some optional embodiments, in the step of extracting tannins from the powder to be detected using a solution, the solution is an ethanol-water solution.

[0025] In some optional embodiments, the step of extracting tannins from the powder to be tested using a solution includes: weighing a certain amount of powder to be tested and placing it in a container, adding ethanol and aqueous solution to extract for a preset time; spreading quantitative filter paper in a Büchner funnel, pouring the extracted sample into the Büchner funnel, filtering under reduced pressure with a vacuum pump, and transferring the filtrate to a quantitative volumetric flask.

[0026] In some optional embodiments, in the step of detecting the post-reaction solution with a cuvette at ultraviolet-visible light to determine the tannin content, a 2 cm cuvette is used and placed at a wavelength of 510 nm.

[0027] In a second aspect, an embodiment of the present application provides a chemical mechanical pulp, wherein the tannin content of the chemical mechanical pulp is detected using the detection method described in the above embodiment.

[0028] In a third aspect, an embodiment of the present application provides a paper product, which includes the chemical mechanical pulp described in the above embodiment.

[0029] The method for detecting the tannin content in pulp provided in the embodiments of the present application utilizes the reducing property of tannins and is applicable to the detection of all tannins in chemical-mechanical pulp. It has the advantages of simple operation, low cost, high sensitivity and accuracy, requires only conventional experimental drugs, and has strong operability and practicality. Through a simple color development reaction and spectrophotometric determination, the tannin content in the sample can be quickly and accurately determined, and is suitable for quality control in the production process of chemical-mechanical pulp. This not only helps to eliminate uncertainties in the production process, but also effectively reduces the production of unqualified products, improves production efficiency and product quality, and has high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 This is a flow chart of an embodiment of a method for detecting tannin content in pulp of the present application;

[0032] Figure 2 This is a flow chart of another embodiment of the method for detecting tannin content in pulp of the present application;

[0033] Figure 3 This is a schematic diagram of a process for drawing a tannin content standard curve according to an embodiment of the present invention;

[0034] Figure 4 It is a graph showing the total content and trend of the first extraction and the third extraction in the examples of this application. DETAILED DESCRIPTION

[0035] The present application will be further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only intended to illustrate the present application and are not intended to limit the scope of the present application. Similarly, the following examples are only some examples of the present application and not all examples. All other examples obtained by those of ordinary skill in the art without creative work are intended to fall within the scope of protection of this application.

[0036] The terms "first", "second" and "third" in the embodiments of the present application are used only for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second" and "third" may explicitly or implicitly include at least one of such features. In the description of the present application, "multiple" means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined. All directional indications in the embodiments of the present application (such as up, down, left, right, front, back...) are only used to explain the relative positional relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. The terms "including" and "having" in the embodiments of the present application and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or components inherent to these processes, methods, products or devices.

[0037] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] The present invention relates to a detection method for determining the tannin content of chemical-mechanical pulp by ultraviolet-visible spectrophotometry. Tannin is one of the main chemical components in wood. Some hardwood species with a strong structure are rich in tannin, such as eucalyptus, birch and persimmon trees. In contrast, softwood species such as pine contain less tannin. Tannins are composed of hydrolyzable tannins and condensed tannins. Hydrolyzable tannins are usually ester compounds formed by gallic acid and its dimer (digallic acid or succinic acid) and monosaccharides. This type of tannin can be hydrolyzed by acid and enzymes. Condensed tannins are condensates of catechin (flavan-3-ol) derivatives. This type of tannin is not easily hydrolyzed by acid and enzymes, and produces a high-molecular-weight amorphous red powder when heated in dilute acid. In addition, tannins are very easy to react with iron ions to develop a color. When the iron ion concentration is greater than 5ppm, tannins form a metal complex with iron to show color.

[0039] See also Figure 1 , Figure 1 1 is a flow chart of an embodiment of a method for detecting tannin content in pulp of the present application, and the detection method includes but is not limited to the following steps.

[0040] Step S100: drying and crushing the pulp to be tested to form powder to be tested.

[0041] In this step, the sample to be tested may be squeezed dry with a filter, spread on a tray, dried in an oven at 50-70° C. for 5-7 hours, and crushed with a high-speed grinder for 10 seconds to obtain a powder to be tested.

[0042] Step S200: extracting tannin from the powder to be tested using a solution.

[0043] In this step, multiple extractions may be performed to obtain a solution containing the total amount of tannin. The solution used in the extraction process may be an ethanol-water solution.

[0044] The extraction process may include: weighing 3 g of the crushed sample (powder to be tested) into a 250 mL conical flask, recording the sample weight m, adding 100 mL of a 30% ethanol aqueous solution, and extracting at 60° C. for 15 minutes; laying a quantitative filter paper flat on a Buchner funnel, pouring the extracted sample into the Buchner funnel, filtering under reduced pressure with a vacuum pump, transferring the filtrate to a 250 mL volumetric flask, placing the filter residue in the conical flask, adding 100 mL of a 30% ethanol aqueous solution, ultrasonically extracting at 60° C. for 15 minutes, and then filtering, combining the two filtrates, diluting to the mark with pure water, and shaking well to obtain the first extracted sample solution. The multiple extraction steps may include repeating the above steps with the filter residue to obtain the second extracted sample, the third extracted sample, and so on.

[0045] Step S300: adding ferric chloride solution, o-phenanthroline solution and sodium acetate solution to the tannin solution obtained by extraction and reacting for a preset time.

[0046] In step S300, the tannin solution sample obtained by extraction can be specifically tested by pipetting 3 mL of the pretreated sample (the sample amount can be increased or decreased according to the tannin content concentration of the sample) into a 50 mL volumetric flask (while making a blank), adding 0.5 mL of ferric chloride solution, 2 mL of sodium acetate, and 10 mL of 1,4-phenanthroline, adding pure water to the scale, shaking well, and letting the reaction stand for about 15 minutes. Wherein, the concentration of the ferric chloride solution can be 0.1 mol / L, the concentration of the sodium acetate solution is 0.1 mol / L, and the concentration of the 1,4-phenanthroline is 0.015 mol / L.

[0047] In step S400 , the reacted solution is detected by using a cuvette under ultraviolet-visible light to determine the tannin content.

[0048] In this step, the wavelength may be 510 nm and a 2 cm cuvette may be used.

[0049] Tannin has strong reducing properties and can reduce Fe 3+ Reduction to Fe 2+ , using o-phenanthroline and Fe 2+ The reaction generates an orange-red complex, and its absorbance is measured at 510 nm using an ultraviolet spectrophotometer and compared with the standard to determine its content.

[0050] See also Figure 2 , Figure 2 1 is a flow chart of another embodiment of the method for detecting tannin content in pulp of the present application, which includes but is not limited to the following steps.

[0051] Step S500: draw a tannin content standard curve.

[0052] See also Figure 3 , Figure 3 1 is a flow chart of an embodiment of drawing a tannin content standard curve in the present application, wherein the flow chart includes the following steps.

[0053] In step S510 , ferric chloride solution, o-phenanthroline solution and sodium acetate solution are respectively added to a plurality of quantitative solution samples to react.

[0054] For example, you can take 7 50mL volumetric flasks, add 0mL, 0.20mL, 0.40mL, 0.60mL, 0.80mL, 1.00mL, 2.00mL of tannin standard solution, 0.5mL of ferric chloride solution, 2mL of sodium acetate, and 10mL of o-phenanthroline respectively, dilute with pure water to the scale, shake well, and let it stand for 15 minutes.

[0055] In step S520 , the reacted solution is detected by using a cuvette under ultraviolet-visible light to draw a standard curve.

[0056] In this step, specifically, the absorbance is measured at a wavelength of 510 nm using a 2 cm cuvette, with 0 mL of the standard solution added as a blank, and a standard curve is drawn.

[0057] Please continue reading Figure 2 The detection method in this embodiment further includes step S100 of drying and crushing the pulp to be tested to form a powder to be tested.

[0058] In this step, the sample to be tested may be squeezed dry with a filter, spread on a tray, dried in an oven at 50-70° C. for 5-7 hours, and crushed with a high-speed grinder for 10 seconds to obtain a powder to be tested.

[0059] This step may also include experimental preparation, reagent preparation, and sample pretreatment processes.

[0060] Experimental preparation: Before the experiment, rinse the glassware once with anhydrous ethanol, and then rinse it with distilled water for more than three times.

[0061] Reagent preparation: Ethanol-water solution (30%): Weigh 150 mL of anhydrous ethanol and 350 mL of distilled water, mix well. Ferric chloride solution (0.1 mol / L): Weigh 27.02 g of FeCl₃·6H₂O and dissolve it in 500 mL of distilled water, mix well. 1,1-Phenanthroline solution (0.015 mol / L): Weigh 1.485 g of 1,1-Phenanthroline and dissolve it in 500 mL of distilled water, mix well. Sodium acetate solution (0.1 mol / L): Weigh 13.608 g of CH₃COONa·3H₂O and dissolve it in 1000 mL of distilled water, mix well. Tannin standard solution 10 μg / mL.

[0062] Sample pretreatment: Blank: Add 100 mL of 30% ethanol aqueous solution to a 250 mL conical flask, ultrasonicate at 60 ° C for 15 min, filter with quantitative filter paper, transfer the filtrate to a 250 mL volumetric flask, then add 100 mL of 30% ethanol aqueous solution to the conical flask, ultrasonicate at 60 ° C for 15 min, filter with quantitative filter paper, transfer the filtrate to the same 250 mL volumetric flask, dilute to the mark with distilled water, shake well, and set aside.

[0063] Please continue reading Figure 2 The detection method in this embodiment further includes step S200, using a solution to extract tannins from the powder to be detected.

[0064] In this step, multiple extractions can also be used to obtain a solution containing the total amount of tannin. The solution used in the extraction process can be an ethanol-water solution.

[0065] The extraction process may include: weighing 3 g of the crushed sample (powder to be tested) into a 250 mL conical flask, recording the sample weight m, adding 100 mL of a 30% ethanol aqueous solution, and extracting at 60° C. for 15 minutes; laying a quantitative filter paper flat on a Buchner funnel, pouring the extracted sample into the Buchner funnel, filtering under reduced pressure with a vacuum pump, transferring the filtrate to a 250 mL volumetric flask, placing the filter residue in the conical flask, adding 100 mL of a 30% ethanol aqueous solution, ultrasonically extracting at 60° C. for 15 minutes, and then filtering, combining the two filtrates, diluting to the mark with pure water, and shaking well to obtain the first extracted sample solution. The multiple extraction steps may include repeating the above steps with the filter residue to obtain the second extracted sample, the third extracted sample, and so on.

[0066] Step S300: adding ferric chloride solution, o-phenanthroline solution and sodium acetate solution to the tannin solution obtained by extraction and reacting for a preset time.

[0067] In step S300, the tannin solution sample obtained by extraction can be specifically tested by pipetting 3 mL of the pretreated sample (the sample amount can be increased or decreased according to the tannin content concentration of the sample) into a 50 mL volumetric flask (while making a blank), adding 0.5 mL of ferric chloride solution, 2 mL of sodium acetate, and 10 mL of 1,4-phenanthroline, adding pure water to the scale, shaking well, and letting the reaction stand for about 15 minutes. Wherein, the concentration of the ferric chloride solution can be 0.1 mol / L, the concentration of the sodium acetate solution is 0.1 mol / L, and the concentration of the 1,4-phenanthroline is 0.015 mol / L.

[0068] In step S400 , the reacted solution is detected by using a cuvette under ultraviolet-visible light to determine the tannin content.

[0069] In this step, the wavelength may be 510 nm and a 2 cm cuvette may be used.

[0070] Tannin has strong reducing properties and can reduce Fe 3+ Reduction to Fe 2+ , using o-phenanthroline and Fe 2+ The reaction generates an orange-red complex, and its absorbance is measured at 510 nm using an ultraviolet spectrophotometer and compared with the standard to determine its content.

[0071] In step S400, the tannin content can be calculated by comparing with the standard curve drawn in step S500. The tannin content calculation satisfies the following formula:

[0072]

[0073] Where:

[0074] X-tannin content, in %;

[0075] n-the tannin content in the volumetric flask obtained from the standard curve, in mg / L;

[0076] v-The volume of the pretreated sample added during the determination, in units of mL ;

[0077] m-extraction sample weight, in g;

[0078] f- dryness of the sample after crushing.

[0079] The experimental results of multiple groups of samples are shown in the following table.

[0080]

[0081] This method can extract more than 97% of tannins after one extraction. Considering the testing time and actual use, one extraction is enough to meet the adjustment requirements of the chemical-mechanical pulp production process. Figure 4 , Figure 4 This is a graph showing the total content and trend of the first extraction and the third extraction in the examples of the present application. As can be seen from the graph, there is little difference in the test results between performing one extraction and three extractions to completely extract the tannins.

[0082] Existing detection methods cannot be directly used for chemical-mechanical pulp detection. This method covers the extraction and detection process of chemical-mechanical pulp tannins. Compared with the Folin-Dennis reagent method, protein precipitation method and high-performance liquid chromatography, this method has the advantages of simple operation, low cost, high sensitivity and accuracy.

[0083] The method for detecting the tannin content in pulp provided in the embodiments of the present application utilizes the reducing property of tannins and is applicable to the detection of all tannins in chemical-mechanical pulp. It has the advantages of simple operation, low cost, high sensitivity and accuracy, requires only conventional experimental drugs, and has strong operability and practicality. Through a simple color development reaction and spectrophotometric determination, the tannin content in the sample can be quickly and accurately determined, and is suitable for quality control in the production process of chemical-mechanical pulp. This not only helps to eliminate uncertainties in the production process, but also effectively reduces the production of unqualified products, improves production efficiency and product quality, and has high practicality.

[0084] In addition, an embodiment of the present application further provides a paper product, which includes chemical mechanical pulp whose tannin content is detected using the detection method in the aforementioned embodiment. Other technical features of the paper product are within the scope of understanding of those skilled in the art and will not be described in detail here.

[0085] The above descriptions are only some embodiments of the present application and do not limit the scope of protection of the present application. Any equivalent device or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of this application.

Claims

1. A method for detecting tannin content in pulp, characterized in that: The detection method comprises: Drying and crushing the paper pulp to be tested to form a powder to be tested; extracting tannins from the powder to be tested using a solution; Adding ferric chloride solution, o-phenanthroline solution and sodium acetate solution to the tannin solution obtained by extraction and reacting for a preset time; The solution after the reaction was detected by a cuvette under ultraviolet-visible light to determine the tannin content.

2. The detection method according to claim 1, wherein The detection method further includes drawing a standard curve for tannin content, which includes: adding ferric chloride solution, o-phenanthroline solution and sodium acetate solution to multiple quantitative solution samples respectively for reaction, and detecting the reacted solution with a cuvette at ultraviolet-visible light to draw a standard curve; the step of detecting the reacted solution with a cuvette at ultraviolet-visible light to determine the tannin content includes: comparing with the standard curve and calculating the tannin content.

3. The detection method according to claim 2, characterized in that In the step of comparing with the standard curve and calculating the tannin content, the tannin content calculation satisfies the following formula: Where: X-tannin content, in %; n-the tannin content in the volumetric flask obtained from the standard curve, in mg / L; v-The volume of the pretreated sample added during the determination, in units of mL ; m-extraction sample weight, in g; f- dryness of the sample after crushing.

4. The detection method according to claim 1, wherein In the step of extracting the tannins from the powder to be detected using a solution, multiple extractions are performed to obtain a solution containing the total amount of tannins.

5. The detection method according to claim 1, wherein The step of drying and crushing the pulp to be tested to form the powder to be tested includes: squeezing the water out of the pulp to be tested with a filter, spreading it on a tray, drying it in an oven at 50-70° C. for 5-7 hours, and crushing it with a crusher to obtain the powder to be tested.

6. The detection method according to claim 1, characterized in that In the step of extracting the tannins from the powder to be detected by using a solution, the solution is an ethanol aqueous solution.

7. The detection method according to claim 6, characterized in that The step of extracting tannins from the powder to be tested using a solution includes: weighing a certain amount of the powder to be tested and placing it in a container, adding an ethanol aqueous solution and extracting for a preset time; spreading quantitative filter paper in a Buchner funnel, pouring the extracted sample into the Buchner funnel, filtering under reduced pressure with a vacuum pump, and transferring the filtrate to a quantitative volumetric flask.

8. The detection method according to claim 1, wherein In the step of detecting the reaction solution with a cuvette at ultraviolet-visible light to determine the tannin content, a 2 cm cuvette is used and placed at a wavelength of 510 nm.

9. A chemical mechanical pulp, characterized in that The tannin content of the chemical mechanical pulp is detected by the detection method according to any one of claims 1 to 8.

10. A paper product, characterized in that: The paper product comprises the chemical mechanical pulp according to claim 9.

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