JP2006299460A - Method for producing paper and additive for producing the paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing paper, capable of preventing troubles caused by anionic trash accumulated in a system of processes for producing the paper and caused by scale of calcium sulfate formed by reaction of sulfate ions with calcium ions. <P>SOLUTION: This method for producing the paper includes a paper-making process comprising using aluminum nitrate as an aluminum compound which is added to pulp slurry, further adding, if necessary, a yield improving agent, a water-filterability improving agent, etc., thereto, and conducting papermaking and dehydration. The aluminum nitrate is, concretely, supplied from a first addition apparatus 60 to a sheet machine 21 for composing the paper-making process 20 in which the pulp slurry prepared in a raw material preparation process 10 is subjected to the papermaking, so that the aluminum nitrate is added to the pulp slurry. A dehydrated and filtered liquid obtained from the paper-making process 20 is sent to a white water pit 11 through a return pipe 33, so that the liquid is cyclically utilized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a papermaking method for making paper by adding an aluminum compound to a pulp slurry, and a papermaking additive containing the aluminum compound.

  Conventionally, in a papermaking process for producing paper, various papermaking additives such as a paper strength enhancer, a sizing agent, a yield, and a drainage improver are used. Particularly in recent years, additives that improve yield and drainage (hereinafter referred to as “yield / drainage improver”) are often used in order to save papermaking materials and improve papermaking efficiency.

  On the other hand, anionic impurities (so-called “anion trash”) in the system are increasing due to an improvement in the utilization rate of waste paper as a papermaking raw material, an improvement in the blending ratio of broke pulp, and the progress of papermaking systems. An increase in anion trash not only causes pitch and defects to cause a decrease in quality of paper products, but also causes a decrease in productivity due to paper cutting and production speed reduction. In addition, the amount of mechanical pulp containing lignin as a raw material for papermaking and used paper containing fillers such as calcium carbonate is increasing year by year, so that the papermaking process contains not only anionic trash but also a lot of calcium carbonate. ing.

  Here, since the anion trash consumes a yield / drainage improver, in the paper making process for making a pulp slurry, the anion trash is usually fixed to the pulp fiber or the like by adjusting pH or charging. Conventionally, aluminum compounds such as polyaluminum chloride such as aluminum sulfate, aluminum chloride, and polyaluminum chloride have been used for this pH adjustment and charge adjustment.

  Among such aluminum compounds, aluminum chloride is rarely used, particularly when white water is circulated and used, because chloride ions are concentrated and corrode papermaking machines. In addition, polyaluminum chloride has a problem that the storage stability of the product is poor, and when the storage time is long, it becomes cloudy and the effect is lowered, and it is hardly used like aluminum chloride.

  On the other hand, aluminum sulfate is easy to handle and widely used. However, when aluminum sulfate is used in a situation where anion trash and calcium carbonate are increasing, the amount of aluminum sulfate added increases, so that sulfate ions accumulate in the system. When sulfate ions are accumulated in the system, they react with calcium ions to produce calcium sulfate scales, which are attached to the apparatus constituting the papermaking process and are a major obstacle in production.

As a method for solving such a problem of scale adhesion, various proposals such as a method of adding a scale inhibitor have been made. For example, Patent Document 1 discloses a method of adding crystals of a substance that is the same as or similar to a scale substance to a raw material adjusting process or a papermaking process for preparing a pulp slurry. According to the method described in Patent Document 1, since the scale material is precipitated using crystals of the same or similar material as the scale material added to the pulp slurry as a nucleus, the scale adheres to the members constituting the papermaking process. Can be suppressed.
JP 2000-234295 A

  As described above, in recent years, the amount of aluminum sulfate used in the papermaking process has increased, and the concentration of sulfate ions in the system has increased. Moreover, the circulation recovery rate of white water is also increasing, and the sulfate ion concentration increases as the circulation recovery rate of white water increases. For this reason, in order to reduce the sulfate ion concentration in the system, it was also necessary to dilute the sulfate ion concentration by discharging a part of white water which can be circulated and adding fresh water.

  The present invention has been made in view of the problems as described above, and eliminates manufacturing obstacles due to the calcium sulfate scale produced by the reaction of sulfate ions and calcium ions accumulated in the papermaking process system. The purpose is to do.

  As a result of intensive studies to overcome the above problems, the present inventors have found that various aluminum compounds such as aluminum sulfate, aluminum ammonium sulfate (ammonium alum), sodium aluminate, aluminum chlorate, aluminum chloride, polyaluminum chloride, etc. In particular, the present inventors have found that aluminum nitrate has an excellent effect and completed the present invention. That is, the present inventor not only does the nitrate ion in aluminum nitrate not cause scale failure when circulating white water, but also has a charge neutralizing effect, fixing of rosin sizing agent, yield and drainage improver. It has been found that it also has an auxiliary action.

  Specifically, the present invention includes a papermaking process comprising adding a nitrate / drainage improver, etc., if necessary after adding aluminum nitrate to a pulp slurry, and papermaking and dewatering. I will provide a. More specifically, the present invention provides the following.

  (1) A papermaking method including a papermaking process in which an aluminum compound is added to a pulp slurry containing pulp, followed by papermaking and dewatering, wherein the aluminum compound is aluminum nitrate.

  The amount of aluminum nitrate added is 0.01 to 1% by mass, particularly 0.02 to 0.8% by mass in terms of metallic aluminum, with respect to the insoluble suspension (SS) contained in the pulp slurry. More preferably, it is good to set it as 0.04-0.4 mass%. Solid aluminum nitrate may be added to the pulp slurry, but it is preferable to add a liquid one by dissolving it in water or the like.

  The aluminum nitrate contained in the pulp slurry neutralizes the anion trash contained in the liquid present in the papermaking process and fixes it to the pulp fiber, etc., and the cation requirement (PCD value) of the pulp slurry is within the optimum range ( In other words, it plays various roles such as adjusting to 10 to 180 μeq / L) and promoting the fixing of additives such as dyes and sizing agents, particularly anionic additives to pulp fibers. Aluminum nitrate also plays the role of adjusting the pH of the pulp slurry. Therefore, by adjusting the amount of aluminum nitrate added, the pH of the pulp slurry can be adjusted to an optimum range for stable paper production (that is, acidic papermaking). Can be adjusted to pH 3-7, and in the case of neutral papermaking, it can be adjusted to pH 7-8.5). However, in the present invention, adjusting the pH of the pulp slurry using an acid such as hydrochloric acid or sulfuric acid, or a pH adjusting agent such as an alkali such as sodium hydroxide, potassium hydroxide, or calcium hydroxide is not excluded.

  Moreover, you may add 1 type (s) or 2 or more types of a paper strength enhancer, a yield / drainage improver, and a sizing agent to the pulp slurry which added aluminum nitrate. Examples of the paper strength enhancer and the yield / drainage improver include cationic, anionic and amphoteric acrylamide copolymers, polyethyleneimine, polyvinylamine, Hoffman-modified polymers, and the like. Further, a paper strength enhancer having an effect of improving yield and drainage, such as cationized starch, may be used. In particular, a cationic or anionic polymer can be preferably used alone or in combination. Examples of the sizing agent include synthetic sizing agents such as rosin, alkenyl succinic anhydride (ASA), and alkyl ketene dimer (AKD). In particular, rosin, ASA, and the like can be preferably used. When a paper strength enhancer and a yield / drainage improver are added, the addition amount is preferably 0.002 to 0.2% by mass with respect to the dry pulp mass, and is particularly preferably 0.000 to the dry pulp mass. It is preferable to set it as 006-0.03 mass%. The addition amount of the sizing agent is preferably 0.01 to 0.5 mass% with respect to the dry pulp mass, and particularly preferably 0.1 to 0.4 mass% with respect to the dry pulp mass.

  (2) The method according to (1), further comprising a raw material adjusting step of suspending a papermaking raw material in water to obtain the pulp slurry, wherein the dehydrated filtrate discharged from the paper making step is refluxed to the raw material adjusting step. Paper making method.

  In the paper making process, the pulp slurry to which aluminum nitrate has been added is made into a sheet by a paper machine and dehydrated. Dehydrated filtrate (hereinafter simply referred to as “filtrate”) produced by dewatering pulp (hereinafter referred to as “paper sheet”) made into a sheet in the papermaking process contains aluminum nitrate. In the present invention, the filtrate is refluxed to the raw material adjusting step, whereby the papermaking raw material is suspended and reused as water for preparing a pulp slurry. In this specification, of the water in which the papermaking raw material is suspended, the water that is circulated and recycled is referred to as “white water”, and the water that is newly introduced into the papermaking process, such as city water, is referred to as “fresh water”. .

  In this invention, aluminum nitrate should just be contained in the pulp slurry before papermaking, and the addition place is not specifically limited. Specifically, aluminum nitrate can be added to a paper machine constituting the paper making process, a chest provided between the raw material adjusting process and the paper making process, and storing a pulp slurry. Further, in the invention described in (2) in which the filtrate produced in the paper making process is returned to the raw material adjusting process, aluminum nitrate may be added to the white water return pipe, the white water storage tank, or the like.

  (3) The papermaking method according to (1) or (2), wherein the pulp slurry further includes at least one selected from the group consisting of calcium carbonate, broke pulp, and recycled used paper.

  “Pulp slurry” is a liquid obtained by suspending a papermaking raw material in water. In this specification, the “pulp slurry” is referred to as a concentrated pulp slurry having an SS concentration of about 2 to 20% by mass obtained in the raw material adjusting step, and the concentrated pulp slurry has an SS concentration of about 0.1 to 2% by mass. Diluted pulp slurry for papermaking shall be included.

  Here, “papermaking raw material” is a raw material for producing paper (including paperboard), and is roughly divided into so-called virgin pulp such as chemical pulp (also referred to as “kraft pulp”) and mechanical pulp, and recycled pulp. The Examples of the recycled pulp include a manufacturing residue (waste paper) in a papermaking process called “broken pulp” and recycled waste paper. “Broken pulp” includes both wet broke pulp and drive-rooke pulp.

  (3) The invention described in (3) uses a recycled paper or broke pulp that is recycled pulp as a papermaking raw material, or a pulp slurry that contains one or more kinds of calcium carbonate derived from white water that is circulated and that is particularly susceptible to calcium scale. This is a papermaking method. According to the present invention, recycled pulp such as recycled paper and broke pulp can be included in an arbitrary amount with respect to virgin pulp, and the entire amount of the papermaking raw material can be made into recycled pulp. Recycled recycled paper may be preprocessed, such as cutting and deinking the recovered recovered paper, and supplied to the quality adjustment process as deinked wastepaper pulp, or the quality adjustment process without pretreatment May be supplied.

  In the present invention, by adding aluminum nitrate to the pulp slurry, even when using a pulp slurry that easily generates scale material, the generation of calcium scale can be prevented and paper can be produced.

  (4) The papermaking method according to any one of (1) to (3), wherein nitric acid is further added to the pulp slurry in the papermaking step.

  Nitric acid may be added either before or after the addition of aluminum nitrate. In addition, in the case of further adding a yield / drainage improver and a sizing agent, the order of addition of nitric acid, aluminum nitrate, and the yield / drainage improver is not particularly limited, but nitric acid and aluminum nitrate are added. After the addition, it is preferable to add a yield / drainage improver.

  (5) The papermaking method according to (4), wherein the nitric acid is added at 0.1 to 20% by mass with respect to the aluminum nitrate.

  As addition amount of nitric acid, it is 0.1-20 mass% with respect to aluminum nitrate, and it is preferable to set it as 1-10 mass% especially. In the present invention, by further adding nitric acid to the pulp slurry, it is possible to enhance the effect of the sizing agent, particularly the fixing of the rosin sizing agent and the yield / drainage improver. That is, by using nitric acid together, the anion charge (carboxyl group) of the anion trash is neutralized to a certain extent, and the negative charge of the anion trash is appropriately neutralized. It is presumed that the yield effect and the sizing agent fixing effect are improved in combination with the fixing action of aluminum.

  (6) A papermaking additive added to a pulp slurry containing pulp, the papermaking additive containing aluminum nitrate and nitric acid.

  (7) The additive for paper manufacture as described in (6) which contains the said nitric acid at 0.1-20 mass% with respect to the said aluminum nitrate.

  The paper additive containing aluminum nitrate and nitric acid may be a preparation in which aluminum nitrate and nitric acid are mixed, or aluminum nitrate and nitric acid may be separately formulated.

  According to the present invention, it is possible to prevent deterioration of paper product quality and production efficiency due to anion trash. Moreover, generation | occurrence | production of the calcium scale in a paper manufacturing process can be suppressed. Furthermore, the effects of the sizing agent and the yield / drainage improver can be enhanced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view schematically illustrating a papermaking process. The papermaking process 1 includes a quality adjusting process 10 and a papermaking process 20. The raw material adjustment step 10 includes a pulper 14 in which a papermaking raw material and water are introduced to prepare a pulp slurry, and a conveyor 12 that supplies the pulper 14 with a papermaking raw material such as recycled used paper. On the other hand, the paper making process 20 includes a paper machine 40, and the paper machine 40 includes a sheet machine 21 that makes a pulp slurry into a sheet, a wire part 22, a press part 23, and a dryer part 24. Further, the papermaking process 1 is provided with a white water pit 11 for storing a filtrate to be described later.

  The wire part 22 includes a wire mesh-like wire conveyor that dehydrates the paper sheet 30 made by the sheet machine 21 and sends the paper sheet 30 to the press part 23. The paper sheet is gravity or vacuum dewatered on the wire conveyor to generate a filtrate. The press part 23 is composed of a felt conveyor, and presses and dehydrates the paper sheet with the paper sheet sent from the wire part 22 sandwiched between rolls facing each other. The filtrate obtained by dehydrating the paper sheet is collected and sent to the white water pit 11 through the reflux pipe 33.

  A chest 15 for storing the prepared pulp slurry is provided between the raw material adjusting step 10 and the paper making step 20. The pulper 14 and the chest 15 are connected by a first flow path pipe 31, and the chest 15 and the sheet machine 21 are connected by a second flow path pipe 32. The reflux pipe 33 connects the paper machine 40 and the white water pit 11, and the white water pit 11 is connected to the pulper 14 and the chest 15. Thus, the filtrate (white water) discharged from the paper machine 40 is refluxed and recycled as a pulp slurry preparation liquid.

  In the present invention, in the papermaking process 1, a first addition device 60 provided with a first chemical injection pipe 61 for adding aluminum nitrate into the system, and a second addition device 70 provided with a second chemical injection pipe 71 for adding nitric acid. Is provided. In the present embodiment, the first medicine injection pipe 61 and the second medicine injection pipe 71 are connected so as to supply medicine to the sheet machine 21.

  In addition, what is necessary is just to add aluminum nitrate so that it may be contained in the pulp slurry made by the sheet machine 21, and an addition position is not limited above. Similarly, the addition position of nitric acid is not particularly limited, and in the present invention, white water circulates in the papermaking process 1, so that aluminum nitrate and nitric acid are the pulper 14, the first flow path pipe 31, and the second flow path pipe 32. , And may be added to the chest 15, the reflux pipe 33, the white water pit 11, and the like.

  Also, in the papermaking process 1, a chemical injection device (not shown) for adding additives such as a yield / drainage improver and a sizing agent as necessary is provided, and these additives are added to the pulp slurry. Then, it may be supplied to the paper machine 40.

  Next, the paper making method according to the present invention will be described. First, a papermaking raw material such as recycled used paper is supplied from the conveyor 12 to the pulper 14 in the raw material adjusting step 10, and white water and fresh water such as tap water are supplied from the white water pit 11 to prepare pulp slurry. In the present embodiment, aluminum nitrate and preferably nitric acid are added to the pulp slurry in the sheet machine 21, and a yield / drainage improver and the like are added as appropriate and sent to the papermaking step 20. In the paper making process 20, the paper sheet made by the sheet machine 21 is dehydrated and sent to the press part 23.

  In the press part 23, the paper sheet is press dehydrated and sent to a dryer part 24 equipped with a drying device. In the dryer part 24, the dehydrated paper sheet is dried to obtain a dried paper. The dried paper is appropriately sent to a coating process or the like as needed, and a coating solution or the like is applied to obtain a final product (paper product).

  In the present invention, the filtrate (white water) discharged from the paper machine 40 in the paper making process 20 is collected through the reflux pipe 33 and returned to the white water pit 11 to be fed to the pulper 14 and / or the chest 15 in the raw material adjusting process 10. It is recycled as water to be supplied. Since this white water contains aluminum nitrate, in the system constituting the papermaking process 1, the production of calcium scale is prevented while the yield / drainage improvement effect and the size fixing improvement effect are exhibited, Moreover, obstacles such as a decrease in quality of paper products and a decrease in production efficiency due to anion trash contained in the pulp slurry are reduced.

Next, examples and comparative examples will be described. The equipment, chemicals and test methods used in the examples and comparative examples are as follows.
[Used equipment]
Yield testing machine: Dynamic filtration system (Mutek)
Cation requirement meter: PCD03 (Mutech)
Sheet machine: Round sheet machine (made by Kumagai Riki Kogyo Co., Ltd.)
[Chemicals used]
Aluminum sulfate: Taki Chemical Co., Ltd. Aluminum nitrate: Wako Pure Chemical Industries, Ltd., Wako first grade (aluminum nitrate nonahydrate, purity 99.9%)
Nitric acid: Kanto Chemical Co., Ltd., deer first grade (nitric acid 1.38, purity 60-61%)
Cationized starch: Nippon NSC Co., Ltd., CATO-3212
Size agent: Arakawa Chemical Industries, Ltd. Size Pine NT-87 (rosin size agent)
Paper strength enhancer: DS429 made by Seiko PMC
Calcium carbonate: TP-121 manufactured by Okutama Kogyo Co., Ltd.
Cationic Yield / Drainage Improving Agent: Kurita Kogyo Co., Ltd., High Holder 222 (acrylamide copolymer type cationic polymer)
Anionic yield and drainage improver: Kurita Kogyo Co., Ltd., High Holder 256 (acrylamide copolymer type anionic polymer)

[Example 1]
70% by mass of bleached kraft pulp (LBKP), which is virgin pulp made from hardwood collected from a paper mill, and 30% by mass of deinked waste paper pulp (DIP), which is recycled paper Ratio), tap water was added to prepare a pulp slurry having an SS concentration of 0.8% by mass. This pulp slurry was put into a dynamic filtration system (hereinafter “DFS”), and aluminum nitrate was added. The addition rate of aluminum nitrate is an addition ratio (hereinafter referred to as “raw material”) to the papermaking raw material expressed as an insoluble suspended solid (SS), and is 0.04% by mass in terms of metallic aluminum (Al). Furthermore, the above sizing agent is 0.3% by mass with respect to the dry pulp mass (hereinafter referred to as “to pulp”), the above calcium carbonate is 10% by mass with respect to the pulp, and the above-mentioned cationic yield / drainage improver is added. A pulp slurry for papermaking (hereinafter referred to as “pulp slurry for papermaking”) was obtained at an addition rate of 0.02 mass% with respect to pulp.

  The filtrate obtained by dehydrating the papermaking pulp slurry obtained by the above-described operation with DFS was collected from DFS, and the yield rate was determined by measuring the SS concentration of the papermaking pulp slurry and the SS concentration of the filtrate. . Moreover, from the pulp slurry for papermaking and the ash content in SS contained in the filtrate, the yield rate of the ash content was determined. Further, 10 ml of the filtrate collected from DFS was placed in PCD03, 0.001N cationic polyacrylamide polymer flocculant (polyDADMAC) was added, and the required amount of cation was measured from the consumption of polyDADMAC.

  Also, the pulp slurry for papermaking is put into a round sheet machine, made into a sheet, and dried to produce a neutral medium paper. ) Was measured.

[Examples 2 to 8]
As Examples 2 to 4, papermaking pulp slurries were prepared by the same operation as in Example 1 except that the addition rate of aluminum nitrate was changed, and the same test as in Example 1 was performed. Moreover, as Example 5-8, the pulp slurry for papermaking was prepared by the same operation as Example 1 except having further added nitric acid to the pulp slurry which added aluminum nitrate, and the same test as Example 1 was done.

[Comparative Examples 1-5]
As Comparative Example 1, a papermaking pulp slurry was prepared without adding aluminum nitrate. In Comparative Example 1, the test conditions were the same as Example 1 except that aluminum nitrate was not added. About Comparative Examples 2-5, the pulp slurry for papermaking was prepared and tested by the same operation as Example 1 except having replaced with aluminum nitrate and using aluminum sulfate.

  In Table 1 in Examples 1-8 and Comparative Examples 1-5, the type and addition rate of the aluminum compound added to the pulp slurry, the addition rate of nitric acid, the pH of the resulting papermaking pulp slurry, the cation requirement (PCD), Shows the yield and size. In addition, the addition rate of aluminum sulfate is a ratio with respect to the raw material, and is expressed in terms of Al as with the addition rate of aluminum nitrate. In addition, as for the yield rate, the yield rate for all SSs is displayed as “overall”, and the yield rate for ash is displayed as “ash”.

  As shown in Table 1, in Examples 1 to 8 using aluminum nitrate as the aluminum compound, good results were obtained in both sizing and yield compared to Comparative Examples 2 to 5 using aluminum sulfate. In particular, in Examples 5 to 8 in which aluminum nitrate and nitric acid were added, high sizing and yield improvement effects were obtained.

[Examples 9 to 11]
In Example 9, 100% recycled paper that was not deinked was used as a papermaking raw material, and tap water was added to prepare a pulp slurry with an SS concentration of 1.0 mass%. This pulp slurry was put into DFS and aluminum nitrate was added. The addition rate of aluminum nitrate was 0.04% by mass in terms of Al in terms of raw material ratio. Further, after adding the above paper strength enhancer at 0.1% by mass with respect to pulp, the above-mentioned anionic retention and drainage improver is added at 0.01% by mass with respect to pulp to make paper for producing a core paperboard. A pulp slurry was obtained. Using the obtained pulp slurry for papermaking, PCD and yield were measured in the same manner as in Example 1. The yield was determined for all SSs and for ash. In Examples 9 and 10, a papermaking pulp slurry was prepared by the same operation as in Example 9 except that the addition rate of aluminum nitrate was changed, and the same test as in Example 9 was performed.

[Comparative Examples 6-9]
As Comparative Example 6, a papermaking pulp slurry was prepared without adding aluminum nitrate. In Comparative Example 6, the test conditions were the same as in Example 9 except that aluminum nitrate was not added. For Comparative Examples 7 to 9, a papermaking pulp slurry was prepared and tested in the same manner as in Example 9 except that aluminum sulfate was used instead of aluminum nitrate.

Table 2 shows the types and addition rates of the aluminum compounds added to the pulp slurry in Examples 9 to 11 and Comparative Examples 6 to 9, the addition rate of nitric acid, the pH of the resulting papermaking pulp slurry, the cation requirement (PCD), Indicates the yield rate. In addition, the addition rate of aluminum sulfate is a ratio with respect to the raw material, and is expressed in terms of Al similarly to the addition rate of aluminum nitrate.

  As shown in Table 2, in Examples 9 to 11 using aluminum nitrate as the aluminum compound, the PCD value was lower and the sizing degree and the yield ratio were improved as compared with Comparative Examples 7 to 9 using aluminum sulfate. .

[Examples 12 to 17]
In Example 12, Thermo Mechanical Pulp (TMP) 20%, which is a mechanical pulp collected from a paper mill as a papermaking raw material, and DIP at a ratio of 80% (dry mass ratio), and then an SS concentration of 0.8 mass% A pulp slurry was prepared. This pulp slurry was put into DFS and aluminum nitrate was added. The addition rate of aluminum nitrate was 0.04% by mass in terms of Al in terms of raw material ratio. Furthermore, after adding said cationized starch by 0.2 mass% with respect to pulp, said sizing agent is 0.25 mass% with respect to pulp, said calcium carbonate is 10 mass% with respect to pulp, and said cationic yield / filter. A pulp slurry for papermaking was obtained by adding 0.01% by mass of an aqueous improver to the pulp. Using the resulting pulp slurry for papermaking, PCD and yield were measured in the same manner as in Example 1. The yield was determined for all SSs and for ash.

  Further, the papermaking pulp slurry was put into a round sheet machine, made into a sheet, and dried to prepare neutral newsprint, and the size (drop size) of this neutral newsprint was measured. In Examples 13 and 14, a papermaking pulp slurry was prepared by the same operation as in Example 12 except that the addition rate of aluminum nitrate was changed, and the same test as in Example 12 was performed. Further, in Examples 15 to 17, a papermaking pulp slurry was prepared in the same manner as in Example 12 except that nitric acid was further added to the pulp slurry to which aluminum nitrate was added, and the same test as in Example 12 was performed.

[Comparative Examples 10 to 13]
As Comparative Example 10, a papermaking pulp slurry was prepared without adding aluminum nitrate. In Comparative Example 10, the test conditions were the same as in Example 12 except that aluminum nitrate was not added. About Comparative Examples 11-13, the pulp slurry for papermaking was prepared and tested by the same operation as Example 12 except having replaced with aluminum nitrate and using aluminum sulfate.

  Table 3 shows the types and addition rates of the aluminum compounds added to the pulp slurry in Examples 12 to 17 and Comparative Examples 10 to 13, the addition rate of nitric acid, the pH of the resulting papermaking pulp slurry, PCD, yield, and Indicates the size of neutral newsprint. In addition, the addition rate of aluminum sulfate is a ratio with respect to the raw material, and is expressed in terms of Al similarly to the addition rate of aluminum nitrate.

  As shown in Table 3, in Examples 12 to 17 using aluminum nitrate as an aluminum compound, the PCD value was lower than those in Comparative Examples 10 to 13 using aluminum sulfate, and the values of sizing degree and yield rate were It became bigger. In particular, in Examples 15 to 17 in which aluminum nitrate and nitric acid were added, high sizing and yield improvement effects were obtained.

[Comparative Example 14]
As Comparative Example 14, aluminum sulfate used in Comparative Example 2 is 0.32 in terms of Al as the SS (dry mass) ratio of the papermaking raw material in the sheet machine 21 of the papermaking process 1 shown in FIG. It added with the addition rate of the mass%. The pulp slurry supplied to the sheet machine 21 contains 30% by mass of TMP and 70% by mass of DIP as papermaking raw materials, has an SS concentration of 0.85% by mass, and after addition of aluminum sulfate, as a yield / drainage improver 0.015% by mass of the cationic yield / drainage improver used in Example 1 and 0.18 of rosin sizing agent (trade name “Size Pine N-780”, manufactured by Arakawa Chemical Industries, Ltd.) as a sizing agent. 2% by mass of white carbon (made by Tokuyama Co., Ltd., trade name “Tocsea GU-N”) as a filler, and epoxy modified polyamide (PY- by Harima Kasei Co., Ltd.) as a wet paper strength enhancer. 430) was added at 0.05% by mass to make a papermaking pulp slurry (pH 5). The filtrate obtained by papermaking and dewatering the papermaking pulp slurry was sent to the white water pit 11 via the liquid collection section of the papermaking machine 40 and the circulation pipe 33, and was recycled.

  By this operation, calcium sulfate crystals were generated on the draft surface of the white water pit 11, and calcium sulfate scale was also generated in the dryer part 24. Furthermore, the manufactured newsprint also suffered from a defect that was presumed to be derived from the calcium sulfate scale.

[Example 18]
In Comparative Example 14, the test was conducted using aluminum nitrate instead of aluminum sulfate. The papermaking conditions were the same as in Comparative Example 14 except that aluminum sulfate was replaced with aluminum nitrate in Example 18. Two days after the start of the operation, the calcium sulfate scale on the draft surface of the white water pit 11 was not generated, and no scale adherence was observed on the dryer part 24. In addition, the faults of the newsprint produced were suppressed.

  About the comparative example 14 and Example 18, the filtrate (white water) obtained from the liquid collection part of the paper machine 40 was extract | collected, it filtered with the filter paper of 0.5 micrometer, and the water quality was measured. The filtrate of Comparative Example 14 has a temperature of 25 ° C., a pH of 5.0, a calcium ion concentration of 700 mg / L, and a sulfate ion concentration of 2,000 mg / L. The saturation index of calcium sulfate at 25 ° C. obtained from the following formula is It was 0.2, and it was shown that it was the conditions which generate | occur | produce a scale.

In the following calculation formula, the activity coefficient γCa of calcium ions and the activity coefficient γSO ₄ of sulfate ions were determined by the Davis formula. The ionic strength was determined on the assumption that the supersaturated solution was adjusted with CaCl ₂ and Na ₂ SO ₄ . In the formula, [Ca ²⁺ ] means the molar concentration of calcium ions, [SO ₄ ²⁻ ] means the molar concentration of sulfate ions, and Ksp means the solubility product.

  On the other hand, the filtrate of Example 18 had a temperature of 25 ° C., a pH of 5.0, a calcium ion concentration of 700 mg / L, and a sulfate ion concentration of 300 mg / L, and the saturation index of calcium sulfate at 25 ° C. determined from the above formula was It was −0.4, indicating that the condition was not saturated and no scale was generated.

  In the present invention, aluminum nitrate is considered to have an effect by the following mechanism of action. That is, after the aluminum compound is added to the liquid in the papermaking process, the aluminum ions react with water to generate various cationic hydrated ion species, while neutralizing and fixing anionic trash in water, sizing agents, etc. Is fixed to the fiber. The aluminum present in the papermaking process will eventually become aluminum hydroxide, but the type and ratio of the cationic hydrated ions generated in the process and the change over time are determined by the pH of the aluminum compound when the aluminum compound is added. It is presumed that there was a difference in the fixing power of the anionic substance because it differs depending on the value of the aluminum compound and the type of counter ion of the aluminum compound (ie, sulfate ion when adding aluminum sulfate, nitrate ion when adding aluminum nitrate) Is done.

  Here, when aluminum nitrate is used, since the pH value of the liquid immediately after the addition is lower than when equimolar aluminum sulfate is used, the reaction rate to aluminum hydroxide is also slow. Therefore, when aluminum nitrate is used, the time during which cationic hydrated ions are present is longer than when aluminum sulfate is used, and as a result, it is possible to react more with anionic substances. Presumed.

  The present invention can be used for the manufacture of paper including paperboard.

It is a schematic diagram which shows a paper manufacturing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper manufacturing process 10 Raw material adjustment process 20 Paper making process 11 White water pit 14 Pulpa 22 Wire part 23 Press part 24 Dryer part

Claims (7)

A papermaking method including a papermaking step of adding paper and dewatering after adding an aluminum compound to a pulp slurry containing pulp,
The papermaking method, wherein the aluminum compound is aluminum nitrate. Further comprising a raw material adjusting step of suspending the papermaking raw material in water to obtain the pulp slurry,
The papermaking method according to claim 1, wherein the dehydrated filtrate discharged from the papermaking step is refluxed to the raw material adjusting step.   The papermaking method according to claim 1 or 2, wherein the pulp slurry further includes one or more selected from the group consisting of calcium carbonate, broke pulp, and recycled used paper.   The papermaking method according to any one of claims 1 to 3, wherein nitric acid is further added to the pulp slurry in the papermaking step.   The papermaking method according to claim 4, wherein the nitric acid is added in an amount of 0.1 to 20 mass% with respect to the aluminum nitrate.   A papermaking additive added to a pulp slurry containing pulp, the papermaking additive comprising aluminum nitrate and nitric acid.   The additive for paper manufacture of Claim 6 which contains the said nitric acid at 0.1-20 mass% with respect to the said aluminum nitrate.

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