JPH1072793A - Papermaking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the papermaking of paper or paperboard improved in yield and/or freeness by adding and mixing a specific water-soluble polymeric flocculant to a stock before a centriscreen and then adding and mixing active silicic acid with the resultant stock after the centriscreen. SOLUTION: A cationic (or amphoteric) and water-soluble polymeric flocculant, represented by the formula R<1> is H or methyl; R<2> is ethylene or propylene; R<3> and R<4> are each methyl or ethyl; R<5> is H, methyl, ethyl or benzyl; A is O or NH; X-is a counterion; [(a)+(b)+(c)] is 100mol%; (a) is 10-90mol%; (b) is 10-90mol% and (c) is 10-30mol%} and having >=3000,000 molecular weight is added and mixed with a stock in a papermaking step and the resultant stock is then passed through a centriscreen. An active silicic acid prepared by regulating the pH of a dilute aqueous solution of sodium orthosilicate at <=5wt.% concentration expressed in terms of SiO2 , within the range of 8.5-10.0 without passing thereof through an acidic state is added to the stock after the treatment with the centriscreen. The papermaking of the resultant stock is then carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a papermaking method in a papermaking process, and more particularly, to a method of adding a cationic or amphoteric acrylamide-based water-soluble polymer flocculant to a paper stock in a papermaking process in a papermaking process, and then mixing the mixture with an active material. The present invention relates to a papermaking method for paper or paperboard in which silicic acid is added and mixed for papermaking to improve the yield and / or drainage.

[0002]

2. Description of the Related Art In the papermaking process, a papermaking method for improving the yield and / or drainage by adding and mixing a cationic or amphoteric water-soluble polymer to a paper stock and then adding and mixing colloidal silica to the paper stock is known. is there. The colloidal silica mentioned here is manufactured by removing sodium ions in sodium orthosilicate (water glass) by mixing into an acid or passing through an ion exchange resin, and maintaining the acid state (PH1 to 4). (JP-A-57-51900 and JP-T-8-502016).

The specific surface area of colloidal silica is measured by the method disclosed in Sears (Analytical Chemistry), Vol. 28 (1956), pp. 1983-1. In this method, the specific surface area is determined from the titer of NaOH required to adjust the pH to 4.0 to 9.0. In view of the fact that there are many cases where the specific surface area is described in the characteristic display of the colloidal silica, the colloidal silica is in an acidic state (PH1 to PH1).
This can be an example of being manufactured while being held in 4).

On the other hand, active silicic acid is a polysilicate obtained by condensing silicate while keeping an alkaline state at all times and holding a part of sodium counterions. As a substance that partially neutralizes sodium orthosilicate (water glass), sulfuric acid, chlorine, carbon dioxide gas, ammonium sulfate, etc. Aluminum sulfate and sodium bicarbonate are mentioned.

As described in the table, active silicic acid has an unstable gelation time of less than 24 hours, and has been produced in-house in the past as an agglomeration aid for aluminum sulfate in water purification plants. But it is no longer used. Activated silicic acid has never been used in the papermaking process of the paper industry.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to improve a papermaking method in a papermaking process. In the conventional papermaking process, a water-soluble polymer flocculant is added to a stock and then mixed with colloidal silica. The method is to improve the cost of colloidal silica due to its high price, and to provide a method for making paper or paperboard which can improve the yield and / or drainage at low cost.

One of the objects of the present invention is to produce a high-quality paper by averaging the composition distribution in the thickness direction of the paper layer by using a method for improving the yield of fillers, etc. Has the advantage that it is easy to control the variation of the formed paper by making it possible to reduce the cost and to reduce the stock density, and to easily mass-produce paper of a certain quality. It is an object of the present invention to provide an inexpensive papermaking method capable of extending the life of a plastic wire.

Another object of the present invention is to improve drainage. The purpose of drainage improvement is generally to increase papermaking speed, but it is often used for the purpose of enhancing paper strength. That is, when the degree of beating of the pulp is improved, it is possible to increase the paper strength, but there is a disadvantage that the paper making speed is reduced. By using the method for improving drainage, it becomes possible to maintain the filtration speed and the drying speed of the wet paper web at the same level as the pulp having a normal beating degree even for a pulp having a high beating degree. It has been regarded as important as a papermaking method that enables the production of high-performance paper by making a stock using pulp having a high degree of beating without lowering the production speed. It is an object of the present invention to provide an inexpensive papermaking method that achieves the above object.

[0009]

SUMMARY OF THE INVENTION The present inventor has found that activated silicic acid, which has been used as a coagulant in water purification plants in the past, can be easily produced in a paper mill, and as a material for improving the yield and / or drainage. The present invention has been found to be effective. By the way, while commercial colloidal silica has a unit price of 1,000 / hundreds of yen / Kg, self-made active silicic acid can be manufactured at no more than one hundred yen / Kg, and its economic effect is great.

The invention of claim 1 of the present invention is a papermaking method characterized by adding and mixing a water-soluble polymer coagulant to a stock in a papermaking process of papermaking, and then adding and mixing active silicic acid. The difference between active silicic acid and colloidal silica is as described above, including the unit price.

According to a second aspect of the present invention, in the papermaking method according to the first aspect, the pH of a dilute aqueous solution of sodium orthosilicate is adjusted to 8.5 to 1 without passing through an acidic state.
It is characterized by adding and mixing the activated silicic acid manufactured to be adjusted to 0.0. If the pH is less than 8.5, the gel is rapidly formed, and if the pH exceeds 10.0, the effect is drastically reduced.

According to a third aspect of the present invention, in the papermaking method according to the first or second aspect, the active silicic acid is produced using an aqueous solution of sodium orthosilicate having a concentration of 5% by weight or less in terms of SiO _2. It is characterized by being added to the process. The concentration in terms of SiO ₂ is preferably 4% by weight or less, particularly preferably 1.5% by weight or less.

According to a fourth aspect of the present invention, in the papermaking method according to the first to third aspects, a pH adjuster for adjusting the pH of a dilute aqueous solution of sodium orthosilicate to 8.5 to 10.0. Is characterized in that an aqueous solution of sulfuric acid and / or aluminum sulfate is used. The PH
As a regulator, an aqueous solution of aluminum sulfate is particularly preferred from the viewpoint of safety. When an aqueous solution of aluminum sulfate is mixed with a dilute aqueous solution of sodium orthosilicate, active silicic acid and aluminum hydroxide are formed. However, aluminum hydroxide has no effect on the effect. Sulfuric acid neutralization exhibits the same effect as aluminum sulfate, but aluminum sulfate is more readily available in paper mills.

According to a fifth aspect of the present invention, in the papermaking method according to the first to fourth aspects, the water-soluble polymer coagulant is a cationic or amphoteric polymer coagulant. Anionic or nonionic polymeric flocculants have no effect.

According to a sixth aspect of the present invention, in the papermaking method according to the first to fifth aspects, the molecular weight of the water-soluble polymer coagulant is 3,000,000 or more. The higher the molecular weight of the water-soluble polymer coagulant, the more effective.

According to a seventh aspect of the present invention, in the papermaking method according to the first to sixth aspects, the structure of the water-soluble polymer coagulant is represented by the following formula (1).

[0017]

Embedded image (Wherein R ¹ is a hydrogen atom or a methyl group, R ² is an ethylene or propylene group, R ³ and R ⁴ are a methyl or ethyl group, R ⁵ is a hydrogen atom, a methyl group, an ethyl group or a benzyl group, and A is O or NH, X ⁻ represents a counter anion, and has a relationship of a + b + c = 100 mol%, a = 10 to 90 mol%, b = 10 to 90 mol%, and c = 0 to 30 mol%.

The structure of the water-soluble polymer flocculant used in the present invention is a cationic or amphoteric polymer flocculant containing a cationic vinyl monomer unit, and the cationic vinyl monomer unit is dialkylaminoalkyl ( It is selected from meth) acrylate salts or quaternaries, dialkylaminoalkyl (meth) acrylamide salts or quaternaries, and mixtures thereof. The acrylamide monomer unit is essential in the structure of the water-soluble polymer flocculant used in the present invention, and the acrylic acid monomer unit is introduced as necessary.

According to the invention of claim 8 of the present invention, in the papermaking method according to any one of claims 1 to 7, a water-soluble polymer flocculant is added before the centriscreen, and the active silicic acid is added after the centriscreen. It is characterized by. It is effective to add and mix the active silicic acid after applying the shearing force after the addition of the polymer flocculant.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION When producing the active silicic acid used in the present invention, in principle, the pH of an aqueous sodium orthosilicate solution is adjusted.
Sulfuric acid, chlorine, carbon dioxide, ammonium sulfate, aluminum sulfate, sodium bicarbonate can be used as a regulator, but in a paper mill, sulfuric acid or aluminum sulfate is easily available, and aluminum sulfate is particularly excellent in handling safety. Preferably, aluminum sulfate is used. And to produce activated silicic acid,
A method of adding and mixing an aqueous solution of aluminum sulfate or the like into an aqueous solution of sodium silicate and adjusting the pH is easy to perform, but a method of adjusting the pH by mixing an aqueous solution of sodium silicate and an aqueous solution of aluminum sulfate in a line is also large-scale. The device can be implemented economically. PH is adjusted in the range of 8.5 to 10.0 as described above. Since activated silicic acid lacks long-term storage properties, it is based on self-production and self-consumption in paper mills.

The cationic or amphoteric polymer flocculant used in the present invention is a dialkylaminoalkyl (meth) acrylate salt or quaternary compound or a dialkylaminoalkyl (meth) acrylamide salt or quaternary copolymer. is there. Examples of the salt or quaternary compound of dialkylaminoalkyl (meth) acrylate mentioned here include dimethylaminoethyl methacrylate hydrochloride, acryloyloxyethyltrimethylammonium chloride and the like.

Examples of the salt or quaternary compound of dialkylaminoalkyl (meth) acrylamide include dimethylaminopropylacrylamide hydrochloride, methylated product, benzylated product and the like. Not only one cationic monomer but also a mixture of two or more cationic monomers can be used. The molecular weight of the copolymer is desirably 3,000,000 or more, and a low molecular weight product has low cohesive strength.

As the order of chemical injection, a method is preferred in which a water-soluble polymer flocculant is added before centriscreen and active silicic acid is added after centriscreen. A method of adding and mixing active silica after applying a shearing force after adding the polymer flocculant is effective.

[0024]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

(Synthesis Example 1 of Active Silicic Acid) A sodium orthosilicate aqueous solution having a concentration of 3.8% in terms of SiO ₂ was adjusted to pH 9.2 with 5% sulfuric acid while stirring and aged for 1 hour. used. (Synthesis Example 2 of Active Silicic Acid) Aqueous sodium silicate solution having a concentration of 3.8% in terms of SiO ₂ was adjusted to pH 9.2 with an aqueous solution of aluminum sulfate in a concentration of 0.8% in terms of alumina while stirring, and aged for 1 hour. Used as activated silicic acid.

(Synthesis example of water-soluble polymer flocculant) A monomer having the composition shown in Table 1 was dissolved in deionized water to a monomer concentration of 15% by weight, and after substitution with nitrogen, sodium bisulfite and 2,2'-azobis (2-Amidinopropane) hydrochloride was added as a polymerization initiator, and samples (sample-1 to sample-6) to be subjected to an effect test described later were prepared by aqueous solution polymerization. Table 1 shows the monomer composition ratio (mol%) and molecular weight of each sample.

[0027]

[Table 1]

Example 1 Table 2 shows the results obtained by measuring the filler yield and the total yield using a brit type dynamic jar tester. The stock used for the test was talc 900
ppm, kaolin 500ppm, pulp 4000pp
m, PH 6.0, CSF 300ml. The procedure was as follows. 500 ml of the stock was charged into a brit type dynamic jar tester, stirring was started at 1500 rpm, and a 0.1% by weight aqueous solution of a water-soluble polymer coagulant (sample-1) was added 30 seconds after the addition of the aqueous solution. The active silicic acid adjusted in the above is added. After another 30 seconds, the cock for collecting white water is opened, and the white water that has passed through the 150 mesh wire is allowed to flow out. The white water for the first 10 seconds was discarded, and then the white water for 30 seconds was collected and used for measurement, and the total yield and the incineration at 600 ° C. were determined for the filler yield. The chemical addition amount is the addition amount per solid content of the stock, and the addition amount of the active silicic acid is SiO 2
Displayed in ₂ conversion. In addition, P of sodium orthosilicate aqueous solution
When H was adjusted to 8.0, all gelled within 60 minutes and were not usable. On the other hand, when an aqueous sodium orthosilicate solution whose pH was adjusted to 11.0 was added, the effect of adding the active silicic acid was not recognized.

(Examples 2 to 5) Example 1 except that water-soluble polymer flocculants (Samples 2 to 5) were used, respectively.
Table 2 shows the results obtained by measuring the filler yield and the total yield using a brit type dynamic jar tester in the same manner as in the above.

Comparative Example 1 Water-soluble polymer flocculant (sample
Table 2 shows the results obtained by measuring the filler yield and the total yield using a brit type dynamic jar tester in the same manner as in Example 1 except that 6) was used.

(Comparative Examples 2 to 6) A brit type dynamic jar was prepared in the same manner as in Example 1 except that water-soluble polymer flocculants (Samples 1 to 5) were used and no active silicic acid was used. Table 2 shows the results obtained by measuring the filler yield and the total yield with a tester.

[0032]

[Table 2]

(Example 6) An ash content of paper of 20% was obtained by a fourdrinier on-top type paper machine under the conditions of a stock PH of 8.1 to 8.3.
A high quality paper having a basis weight of 84.0 g / m ² was made. The filler composition is 80% light calcium carbonate and 20% talc. To the seed box was added cationic starch (corn starch raw material cationization rate: 3 mol%) to pulp at 5000 ppm, and a water-soluble polymer flocculant (Sample-1) was added as a 0.15% polymer aqueous solution immediately before the entrance of Centri Screen, Immediately after the outlet of the centrifugal screen, the aqueous solution of active silicic acid prepared in Synthesis Example 2 was added to make paper, and the total yield and the filler yield were determined from the SS and ash of the flow box and the white water pit. Table 3 shows the results. The chemical addition amount is the addition amount per solid content of the stock, and the addition amount of the active silicic acid is expressed in terms of SiO ₂ .

(Examples 7 to 10) Papermaking was carried out in the same manner as in Example 6 except that water-soluble polymer flocculants (Samples 2 to 5) were used, respectively. The total yield and filler yield were determined from the ash content.
Table 3 shows the results.

(Comparative Example 7) Water-soluble polymer flocculant (sample
Papermaking was carried out in the same manner as in Example 6 except that 6) was used, and the total yield and filler yield were determined from the SS and ash content of the flow box and the white water pit. Table 3 shows the results.

(Comparative Examples 8 to 12) Papermaking was carried out in the same manner as in Example 6 except that water-soluble polymer flocculants (Samples 1 to 5) were used and no active silicic acid was used. The total yield and filler yield were determined from the SS and ash content of the flow box and white water pit. Table 3 shows the results.

[0037]

[Table 3]

(Example 11) In performing a paper making test of a jute liner, productivity when a stock material having a pH of 5.8 to 6.0 was used in a fourdrinier on-top former with a non-drug injection time of 100%. Table 4 shows the papermaking speed (productivity%) under the conditions of the addition of the water-soluble polymer flocculant (sample-1) as a comparative index. A water-soluble polymer flocculant (sample-1) was added immediately before centriscreening with a 0.15% aqueous polymer solution, and the activated silicic acid aqueous solution prepared in Synthesis Example 2 was added immediately after centriscreening outlet. The chemical addition amount is the addition amount per solid content of the stock, and the addition amount of the active silicic acid is Si
It was expressed in terms of O ₂ .

(Examples 11 to 15) The papermaking speed (productivity%) was determined in the same manner as in Example 11 except that the water-soluble polymer flocculants (Sample-2 to Sample-5) were used, respectively. It is shown in Table 4.

Comparative Example 13 The papermaking speed (productivity%) was determined in the same manner as in Example 11 except that the water-soluble polymer flocculant (sample-6) was used. The results are shown in Table 4.

(Comparative Examples 14 to 18) The paper making speed (production) was the same as in Example 11 except that the water-soluble polymer flocculants (Samples 1 to 5) were used and no active silicic acid was used. %) And the results are shown in Table 4.

(Comparative Example 19) The papermaking speed (productivity%) was determined in the same manner as in Example 11 except that the water-soluble polymer flocculant and active silicic acid were not used.
Shown in

[0043]

[Table 4]

[0044]

According to the papermaking method of the present invention, the yield of cellulose fiber and filler can be improved in the papermaking process, and the effect of increasing the papermaking speed is also recognized. The achievement of the above object by using inexpensive chemicals has great economic value. Colloidal silica is expensive because it needs to have long-term storage stability to be distributed as a commercial product, whereas active silicic acid can be manufactured and supplied at low cost by ignoring long-term storage stability on the premise of self-consumption, The above economic advantages are provided.

Claims (8)

[Claims] 1. A papermaking method comprising adding and mixing a water-soluble polymer coagulant to a stock in a papermaking step of papermaking, and then adding and mixing active silicic acid. 2. The method according to claim 1, wherein the pH of the dilute aqueous solution of sodium orthosilicate is adjusted to 8.5 to 10.0 without passing through an acidic state, and the active silicic acid is added and mixed. The papermaking method described in the above. 3. An active silicic acid is produced using an aqueous solution of sodium orthosilicate having a concentration of not more than 5% by weight in terms of SiO ₂ ,
The papermaking method according to claim 1 or 2, wherein the method is added to a papermaking process. 4. The method according to claim 1, wherein an aqueous solution of sulfuric acid and / or aluminum sulfate is used as a pH adjuster for adjusting the pH of the dilute aqueous solution of sodium orthosilicate to 8.5 to 10.0. The papermaking method according to claim 3. 5. The papermaking method according to claim 1, wherein the water-soluble polymer flocculant is a cationic or amphoteric polymer flocculant. 6. The papermaking method according to claim 1, wherein the water-soluble polymer coagulant has a molecular weight of 3,000,000 or more. 7. The papermaking method according to claim 1, wherein the structure of the water-soluble polymer coagulant is represented by the following formula (1). Embedded image (Wherein R ¹ is a hydrogen atom or a methyl group, R ² is an ethylene or propylene group, R ³ and R ⁴ are a methyl or ethyl group, R ⁵ is a hydrogen atom, a methyl group, an ethyl group or a benzyl group, and A is O or NH, X ⁻ represents a counter anion, and has a relationship of a + b + c = 100 mol%, a = 10 to 90 mol%, b = 10 to 90 mol%, and c = 0 to 30 mol%. 8. The papermaking method according to claim 1, wherein the water-soluble polymer flocculant is added before the centriscreen, and the activated silicic acid is added after the centriscreen.