JP2960185B2 - Paper manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing paper by making a pulp slurry in a nearly neutral region, instead of acidic paper making which is currently widely industrially used. The pulp slurry contains 5% or more of cationized calcium carbonate and has a papermaking pH adjusted to 6.5 to 8.5, and has an advantage in improving opacity and paper strength. Is the method of producing the resulting paper.

[0002]

2. Description of the Related Art Conventionally, the papermaking method most commonly performed on an industrial scale in the papermaking industry is to use an aqueous slurry of fibrous pulp with additives such as a sizing agent, a filler, a dye, and a paper strength agent. In addition, so-called acidic papermaking, in which aluminum sulfate (band) is further added as a fixing agent to adjust the pH of the slurry to be acidic, has been performed. In this method, the use of aluminum sulfate is indispensable, and the strength of the paper formed during the long-term storage of the paper is reduced, discolored,
There were difficulties such as lowering printability.

[0003] Further, acidic papermaking has a drawback that calcium carbonate cannot be used as a filler. Therefore, recently, a neutral papermaking method in which aluminum sulfate is not added or a very small amount is added has attracted attention and has entered a practical use stage. In this method, since the papermaking pH is 6.5 to 8.5,
Alkaline fillers can be used.

[0004] Representative examples of the alkaline filler include heavy calcium carbonate, light calcium carbonate, aluminum hydroxide, alumina, zinc oxide, calcium hydroxide, zinc hydroxide, magnesium hydroxide and the like. In particular, calcium carbonate represented by heavy calcium carbonate and light calcium carbonate is also the only abundant resource in Japan, and is widely used as a filler for neutral papermaking.

[0005] Heavy calcium carbonate is obtained by pulverizing naturally produced limestone by mechanical force, so that its particle size is relatively large, its cost is low, the level of ash in paper is increased, and paper There are advantages such as strong paper strength and easy sizing for the middle ash level. However, light calcium carbonate is inferior to light calcium carbonate in terms of the high opacity characteristics required for fillers due to recent reduction in basis weight. In terms of operability, heavy calcium carbonate is inferior to light calcium carbonate in terms of wire abrasion of a paper machine.

[0006] On the other hand, light calcium carbonate is obtained by burning naturally produced limestone into quicklime and then synthesizing it by blowing carbon dioxide again into milk of calcium oxide dispersed in water. A relatively uniform and uniform particle size can be obtained. For this reason, as a filler, there is an advantage that the opacity characteristic is high and the wire abrasion of the paper machine is low as described above, but the specific surface area is large due to the small particle size, and the yield on the pulp fiber is poor. As a result, there are disadvantages such as difficulty in sizing and weakness in paper strength in terms of the ash content in the paper, because the bonding between fibers is easily inhibited.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the yield on pulp fiber which has been regarded as a drawback while maintaining the high opacity characteristics of light calcium carbonate, and calcium carbonate which does not reduce paper strength. An object of the present invention is to provide a method for producing a blended paper .

[0008]

It is well known that the opacity of paper is determined by the specific scattering coefficient. Factors that affect the specific scattering coefficient include the refractive index of a substance, the form of particles, and the like. The dispersion state of the particles in the paper and the arrangement of the particles can be considered. In the present invention, the above object is achieved by blending a filler containing 5% or more by weight of cationized calcium carbonate by weight and making a pulp slurry with a pulp slurry adjusted to a papermaking pH of 6.5 to 8.5. It has been found that the dispersion state of the calcium carbonate particles can be improved and the maximum specific scattering coefficient can be achieved with the minimum amount of filler.

The calcium carbonate used in the present invention may be heavy calcium carbonate or light calcium carbonate, and is not limited to a wet or dry process, but light calcium carbonate may be used in consideration of desired opacity. Is preferred.

The cationizing agent for producing the cationized calcium carbonate includes a water-soluble tertiary amine-based cationic polymer, a quaternary amine-based cationic polymer, and a total charge by combining these cationic polymers and anionic polymers. An amphoteric polymer in which is cationic is generally used. For example, a water-soluble copolymer of a copolymer of acrylamide and methacrylamide with dialkylaminoalkyl (meth) acrylate, vinylpyridine and the like, and a copolymerizable vinyl monomer, and a homopolymer of acrylamide and methacrylamide, and A typical example of a cationic polymer is a Mannich compound of a water-soluble copolymer with a copolymerizable vinyl monomer.

As typical examples of the amphoteric polymer, a Mannich compound of a water-soluble copolymer mainly composed of acrylamide is known, and a copolymer of acrylamide and unsaturated monocarboxylic acid and a copolymer of acrylamide and acrylic acid are known. There are polymers and the like. Copolymers obtained by copolymerizing acrylamide with acrylic acid and dialkylaminoethyl ethyl methacrylate or a salt thereof, and amphoteric polymers obtained by reacting polyacrylamide with sodium hypochlorite in an alkaline region are also known. Have been.

These cationic and amphoteric polymers have been conventionally used as a paper strength enhancer in the papermaking industry. However, there is no example in which they are used before being coated on the surface of calcium carbonate particles. The effect of the present invention cannot be obtained by simply using these cationic and amphoteric polymers together with calcium carbonate without performing a coating treatment in advance. The molecular weight of these cationic and amphoteric polymers is usually about 100,000 to 1,200,000. If the molecular weight is less than 100,000, the effect of improving the yield of calcium carbonate on the pulp is poor. The expected effect cannot be obtained. For this reason, those having a molecular weight of about 600,000 to 1,000,000 exhibit particularly excellent effects.

The amount of the cationic or amphoteric polymer coated or adsorbed on calcium carbonate varies depending on the particle size of the calcium carbonate, the cationicity and the type of the amphoteric polymer. The cationic and amphoteric polymer is about 0.1 to 10 parts, more preferably about 0.5 to 5 parts. If the amount of the cationic or amphoteric polymer is less than 0.1 part, the effect of improving the yield is not so much improved, while if it exceeds 10 parts, the viscosity of the pigment slurry becomes high.

The cationized calcium carbonate of the present invention is usually produced as follows. First, an aqueous solution containing at least one of the cationic and amphoteric polymers is added to an aqueous suspension having a calcium carbonate concentration of 40% by weight or less, preferably about 5 to 30% by weight, and wet pulverization and mixing are performed. Cationized calcium carbonate having a particle size distribution of 2 μm or less in a proportion of 50% by weight or more, preferably 70% by weight or more.
Get free.

As the pulverizer, various types such as a sand grinder, a ball mill, an attritor, and a Keddy mill can be used, but the sand grinder treatment is most effective. When light calcium carbonate is produced on-site by itself, a concentrator (decanter) can be used instead of the sand grinder treatment.

[0016]

The cationized carbonic acid coated according to the present invention is treated.
Calcium is in a state where its surface is uniformly adsorbed and coated with a cationic and amphoteric polymer. For this reason papermaking p
By adding H to the pulp slurry adjusted to 6.5 to 8.5, the cationized calcium carbonate is uniformly and firmly fixed on the anionic pulp surface.
High yield and high opacity can be obtained with a small amount of addition. As a result, the inhibition of the inter-fiber bonding by the filler is reduced, and the reduction in paper strength can be minimized.

[0017]

The present invention will be described below in more detail with reference to specific examples. In the following Examples and Comparative Examples, the added amount of each compound shows parts by weight on a solid basis.

Examples 1 to 6 90 parts of LBKP (CSF 450 cc), 10 parts of NBKP (CSF 500 cc)
To a pulp slurry in which 100 parts of pulp consisting of 100 parts by weight is dispersed, 25 parts of cationized calcium carbonate coated and adsorbed with a copolymer of dimethylaminoethyl acrylate and acrylamide (cationic polymer) is added, and the mixture is stirred well. 0.4 parts of a sulfuric acid band and 1.2 parts of a cationic starch (Cato3210 manufactured by Oji National) were added and stirred for 5 minutes to prepare a pulp slurry before papermaking.

Cationized light calcium carbonate is placed in a pot of a tabletop sand grinder (Igarashi Kikai) with a diameter of 1
400 g of glass beads of 400 mm in diameter, 400 g of 30% light calcium carbonate slurry, and a cationic polymer of 2% with respect to light calcium carbonate were added and stirred for 20 minutes. The calcium carbonate after completion of the stirring was filtered through 150 mesh to obtain a cationized calcium carbonate sample for papermaking. Moreover, the molecular weight of the cationic polymer is 80,000-
1,400,000 items were used.

For one-pass retention (hereinafter abbreviated as OPR), the pulp slurry prepared above was added to DDJ, and 0.025 parts of a retention aid (Percoll 57 made of Allied Colloid) was added while stirring at 800 rpm. . After 30 seconds from the addition of the retention aid, drainage was performed for 5 seconds, and then white water was sampled for 30 seconds.

The total one-pass retention (hereinafter, T)
OPR) is the pulp slurry prepared above,
It was calculated from the concentration of the sampled white water. In addition, one-pass retention of ash (hereinafter abbreviated as AOPR) is performed by incineration of the TOPR measurement sample in an electric furnace (500
° C, 4 hours) and was calculated from this weight. The opacity was determined by using a pulp slurry prepared as described above and making a 60 g / m ² basis weight paper with a TAPPI standard hand-making machine. Table 1 shows the results.

[0022]

[Table 1]

Comparative Examples 1 to 4 In Comparative Example 1, a pulp slurry was prepared in the same manner as in Example 1 except that the filler was light calcium carbonate without cationization. In Comparative Example 2, a pulp slurry was prepared in the same manner as in Example 1 except that the filler was heavy calcium carbonate without cationization. Comparative Examples 3 and 4 are cations
The molecular weight of the cationic polymer (copolymer of dimethylaminoethyl acrylate and acrylamide) used for preparing calcium carbonate is 80,000, 1,400,
A pulp slurry was prepared in the same manner as in Example 1 except that the pulp slurry was changed to 000. Table 2 shows the results.

[0024]

[Table 2]

* 1) Addition amount of cationic polymer (copolymer of dimethylaminoethyl acrylate and acrylamide) to light calcium carbonate (%) * 2) Total yield measured by DDJ (%) * 3) Measured by DDJ Ash yield (%)

Examples 7 to 11 In the preparation of Example 4, the addition amount of the cationic polymer (copolymer of dimethylaminoethyl acrylate and acrylamide) to 2% of light calcium carbonate and 0.5 to
A pulp slurry was prepared in the same manner except that the pulp slurry was changed to 10.0%. Table 3 shows the results.

[0027]

[Table 3]

Examples 12 to 14 A pulp slurry in which 100 parts of pulp made of LBKP (CSF 450 cc) was dispersed and coated with a copolymer of dimethylaminoethyl acrylate and acrylamide was adsorbed and clicked.
Add 10 to 30 parts of calcium carbonate, stir well, add 0.8 part of sulfuric acid band, 1.0 part of cationic starch (ONL-400, manufactured by Oji National) and stir for 5 minutes. Add a size additive (SPK-903, Arakawa Chemical).
One part was added and stirred to prepare a pulp slurry before papermaking.

Cationized calcium carbonate was placed in a pot of a desktop sand grinder (made by Igarashi Kikai), 400 g of glass beads having a diameter of 1 mm, 400 g of a 30% light calcium carbonate slurry, and a cationic polymer (dimethylaminoethyl acrylate) of 2% light calcium carbonate. And a copolymer of acrylamide) and stirred for 20 minutes. The calcium carbonate after completion of the stirring was filtered through 150 mesh to obtain a cationized light calcium carbonate sample for papermaking. The molecular weight of the cationic polymer is 80,
000 items were used.

While stirring using the pulp slurry prepared above, 0.020 parts of a retention aid (Percoll 57 made by Allied Colloid) was added, and a basis weight of 60 g / m ² paper was obtained using a TAPPI standard hand-making machine. Paper was made. The paper quality of these handmade papers was measured, and the ash content in the paper was measured. The ash content in the paper was calculated from this weight by incineration of the sample in an electric furnace (500 ° C., 4 hours). Table 4 shows the results.

[0031]

[Table 4]

Comparative Examples 5 to 10 In Comparative Examples 5 to 7 , pulp slurries were prepared in the same manner as in Examples 12 to 14 except that the filler was light calcium carbonate without cationization. Comparative Examples 8 to 10 were the same as in Example 1 except that the filler was heavy calcium carbonate without cationization.
A pulp slurry was prepared in the same manner as in Nos. 2 to 14. Table 5 shows the results.

[0033]

[Table 5]

[0034]

According to the present invention, the use of the cationized calcium carbonate as a filler for the production of neutral paper makes it possible to improve the yield of the filler and to obtain a highly opaque paper with a lower blending amount than before. Further, since the amount of the filler is small, it is possible to produce a paper having a minimum reduction in paper strength despite high opacity paper.

Claims (3)

(57) [Claims] (1) Light calcium carbonate (or precipitated calcium carbonate )
From cationized calcium carbonate mainly composed of
And a filler containing at least 5% by weight or more of the cationized calcium carbonate to adjust the papermaking pH to 6.5 to 6.5%.
A paper manufacturing method, comprising making a paper using the pulp slurry adjusted to 8.5. 2. The cationic and amphoteric polymer used for the cationization of the cationized calcium carbonate has a molecular weight of 100,
The method for producing paper according to claim 1 , wherein the paper weight is in the range of 000 to 1,200,000. 3. The ratio of 2 μm or less in the particle size distribution is 50% by weight.
2. The method according to claim 1 , wherein the cationized calcium carbonate is used.
Or the method for producing paper according to 2 .