JP3494421B2 - How to make neutral paper - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel filler retention aid composed of a cationic polymer. The filler retention aid of the present invention improves the quality of paper and prevents the loss of raw materials, The purpose is to extend the service life.

[0002]

2. Description of the Related Art Various filler retention improvers have been proposed so far. For example, as a Hoffmann degradation product of polyacrylamide, a Mannich modified product of polyacrylamide, and an acrylic filler yield improver, JP-A-61-639.
It is known that acrylate cations such as JP-A No. 7 and JP-A No. 61-6398 are effective. Further, various amphoteric methacrylates are known as many papermaking agents.
Further, as a sludge dehydrating agent, a cationic copolymer comprising an acryloyloxyethyldimethylbenzylammonium salt structural unit, an acryloyloxyethyltrimethylammonium salt structural unit and an acrylamide structural unit (Japanese Patent Laid-Open No. 62-262799) is known. or,
Japanese Patent Application Laid-Open No. 62-110998 discloses a papermaking method in which a cellulose pulp and a filler are dispersed in water, a sheet is formed from a pulp slurry whose pH is maintained in a range of 6.5 to 10, and the sheet is dried. Describes a papermaking method for neutral paper, which comprises adding colloidal silicic acid and a cationic or amphoteric polyacrylic amide derivative together with cationic starch to make paper. The polyacrylic amide derivative referred to here is a copolymer of acrylamide with a cationic monomer having a secondary, tertiary, or quaternary amino group such as dimethylaminoethyl methacrylate, and the degree of substitution of the cationic group is 0.01 to A polymer having a molecular weight of 0.5 (that is, 1 to 50 mol%) and a molecular weight of 2,000,000 or less, and more preferably 100,000 or more and 1.3 million or less. Further, Japanese Patent Application Laid-Open No. 57-51900 discloses a technique of introducing a binder composed of colloidal silicic acid and cationic starch into a raw material before forming a sheet.

As described above, the effect of the filler retention improver is to produce high quality paper by reducing the difference between the front and back sides of the paper or to average the composition distribution in the thickness direction of the paper layer, and the loss of raw materials. It is possible to reduce the cost by preventing the above, and it is also possible to reduce the density of the stock material. Therefore, there is an advantage that it is easy to mass-produce a certain quality of paper by controlling the variation of the paper. In addition, it is general to use a plastic wire instead of bronze for the recent machine wire, and there is a drawback that the abrasion due to the wire passing filler is remarkable as a characteristic of the plastic wire. It is obvious that the filler retention improver can reduce the filler passing through the wire, and naturally has the effect of extending the life of the wire. Although such an effect was recognized even in the conventional prescription, the conventional prescription was insufficient for the above purpose and a new prescription was required.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems and to produce a high quality paper by averaging the composition distribution in the thickness direction of the paper layer by using a filler retention improver. In addition, it is possible to prevent the loss of raw materials to reduce the cost, and to reduce the density of the stock material, so that it is possible to mass-produce paper of a certain quality by controlling the variation of the papermaking. An advantage is to provide a papermaking chemical that can extend the life of a plastic wire.

[0005]

According to a first aspect of the present invention, a cellulose pulp and a filler are dispersed in water to have a PH of 6.5 to 10.
Forming a sheet from pulp slurry maintained in the range of
In the papermaking method of drying, in the pulp slurry, cationic starch and (a) acryloyloxyethyl dimethylbenzylammonium salt structural unit of 5 to 45 mol%
(B) Acryloyloxyethyltrimethylammonium salt structural unit 5 to 45 mol% (c) Acrylamide structural unit 5 to 45 mol% (d) Acrylic acid structural unit 0 to 20
It has a mole% state, and are cationic ratio 55 mol% or more, minutes
A papermaking method for neutral paper, characterized in that after adding an acrylic water-soluble polymer having a molecular weight of 3,000,000 or more and 6,000,000 or less , shearing is performed, and then colloidal silica is added, and papermaking is performed. . The acrylic water-soluble polymer used in the present invention has never been used as a paper-making agent, and has a strong cohesive force because the cationic group has a different sequence from the cationic cationic polymer. The effect as a filler retention improver is also superior to that of the methacrylate-based cationic polymer, and the addition amount is small, which is economically advantageous. The higher the cationization rate, the more effective the final agglomeration by colloidal silica, the less the formation of rough texture, and the better the water squeezing property even though the fine components are efficiently retained in the paper, and the better the wet paper drying property. , Has the effect of improving productivity while improving the quality of paper. The order of addition of the acrylic water-soluble polymer and colloidal silica cannot be changed.First, the acrylic water-soluble polymer is added, then sheared and uniformly dispersed in the paper stock, and then colloidal silica is added and mixed. The desired result can be obtained. In order to keep the pH within the above range, calcium carbonate must be blended in the filler, and P depends on the amount of calcium carbonate and sulfuric acid band added.
H varies. Further, the water-soluble acrylic polymer has a molecular weight of 3,000,000 or more and 6,000,000 or less .
The higher the molecular weight, the higher the cohesive force and the smaller the amount added, which is economically advantageous. It is possible to prevent the formation of flocs by adding shear after adding the acrylic water-soluble polymer, and the increase in the molecular weight brings only the advantage of the above economic advantage. In the invention of claim 2, the amount of the acrylic water-soluble polymer added is 30 to 300 with respect to the weight of the pulp.
ppm, and the addition amount of colloidal silica is 50 to 500 ppm with respect to the weight of pulp.
If it is less than this lower limit, the yield effect is not recognized, and if it is more than the upper limit, not only is it uneconomical, but flock formation occurs, and the quality of the paper may be impaired. Claim
In the invention No. 3, the place of addition of the cationic starch is the pre-process of the fan pump, the place of addition of the acrylic water-soluble polymer is near the inlet of the sentry screen, and the place of addition of the colloidal silica is near the outlet of the sentry screen. Is characterized by. Cationic starch, water-soluble acrylic polymer and colloidal silica become gel when mixed in advance and it is difficult to disperse them uniformly in the paper stock. In order to keep various substances in the paper, it is essential to add them individually, and the method of adding them at the above-mentioned place of addition can most effectively improve the productivity and the quality of the paper. . The invention of claim 4 is characterized in that the cationization rate of the cationic starch is 1 mol% to 7 mol%. The cationization rate is sometimes referred to as the degree of substitution, but is the ratio of cationic groups per glucose structural unit in starch. Cationic starch used for papermaking is generally within the above range, and it is not necessary to arrange a special cationic starch for the present invention. The amount of cationic starch added is 1000 to 20000 p per pulp.
pm, preferably 3000-10000 ppm
(All are weight ratio per dry weight of pulp).

Examples of the filler which can be used in the present invention include organic pigments such as heavy calcium carbonate, light calcium carbonate, talc, kaolin, titanium dioxide and plastic pigments.

As the polymerization initiator used for the synthesis of the acrylic water-soluble polymer, a known radical generator is used, and a redox type or azo type radical generator is used. PH during these synthesis, that is, at the time of polymerization is acidic so as not to cause deterioration of the cationic polymer, and the initiation temperature is selected at an appropriate temperature at which the initiator functions. The polymer of the acrylic water-soluble polymer can be obtained in any form such as aqueous solution polymerization, dispersion polymerization in salt aqueous solution, reverse phase emulsion polymerization, and reverse phase suspension polymerization.

[0008]

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) 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 were added. Was added as a polymerization initiator, and a solution sample was prepared by aqueous solution polymerization. Table 1 shows the monomer composition and molecular weight of each sample.

[0010]

[Table-1]

(Example 1) An ash content of 20 in a paper was adjusted by a fourdrinier on-top paper machine under the conditions of a paper stock PH of 8.1 to 8.3.
%, Basis weight 84.0 g / m ² of high-quality paper. The filler composition is 80% light calcium carbonate and 20% talc. Cationic starch (corn starch raw material cationization rate of 3 mol%) was added to the seed box at 7000 ppm with respect to pulp, and the water-soluble polymer shown in Table 1 was added as a 0.15% aqueous solution immediately before the entrance of the Centriscreen, and immediately after the exit of the Centriscreen. Colloidal silica (BM manufactured by Nissan Eka Nobel)
A780) was added while diluting with water to perform papermaking, and the total yield and the filler yield were determined from the SS and ash content of the flow box and white water pit. The results are shown in Table-2. In the table, BMA780 is abbreviated as silica, and the addition amount is shown as SiO ₂ .

[0012]

[Table-2]

[0013]

The sample used in the present invention is compared with the comparative sample.
It has a clear advantage in the effect of improving the filler yield and the total yield. It can be said that the existence of such a performance difference in the paper manufacturing industry is a technology that could not have been predicted in the experience so far.

Claims (4)

(57) [Claims] 1. A papermaking method in which a cellulose pulp and a filler are dispersed in water, a sheet is formed from a pulp slurry in which a pH is maintained in a range of 6.5 to 10, and the sheet is dried, in which the cationic starch, and (A) Acryloyloxyethyldimethylbenzylammonium salt structural unit 5 to 45 mol% (b) Acryloyloxyethyl trimethylammonium salt structural unit 5 to 45 mol%
(C) Acrylamide structural unit 5 to 45 mol% (d) Acrylic acid structural unit 0 to 20 mol%, cationization rate 55 mol% or more , molecular weight 3,000,000 or more, 600
A method for making a neutral paper, which comprises adding an acrylic water-soluble polymer of not more than 10,000 , shearing, and then adding colloidal silica, and then making a paper. 2. The amount of acrylic water-soluble polymer added is 30 to 300 ppm with respect to the weight of pulp, and the amount of colloidal silica added is 50 to 500 p with respect to the weight of pulp.
The neutral paper making method according to any one of claims 1 to 1 , which is pm. 3. The cationic starch is added in the pre-process of the fan pump, the acrylic water-soluble polymer is added in the vicinity of the Centriscreen inlet, and the colloidal silica is added in the vicinity of the Centriscreen outlet. The method for producing neutral paper according to claim 1 or 2 , characterized in that. 4. The method for producing neutral paper according to claim 3 , wherein the cationization rate of the cationic starch is 1 mol% to 7 mol%.