JPH0610298A - Filler for paper and filled paper - Google Patents

Abstract

PURPOSE:To provide a paper filler composed of a uniformly dispersed carbonic acid salt having a prescribed specific surface area, capable of improving optical properties and physical properties of paper and useful for coating base paper, PPC paper, information business paper, etc. CONSTITUTION:The objective paper filler is produced by compounding (A) uniformly dispersed carbonic acid salts having a specific surface area of 15-30m<2>/g and obtained by compounding (i) columnar aragonite calcium carbonate crystals of 0.5-3mum long and 0.1-0.3mum diameter with (ii) plate basic magnesium carbonate crystals of 2-7mum diameter preferably at a weight ratio (i):(ii) of 95:5 to 50:50 with (B) <=90wt.% of other fillers such as talc, calcium carbonate and kaolin clay.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention improves the optical properties such as opacity and whiteness and the physical properties such as stiffness of the paper when it is embedded in paper. Information paper such as PPC paper, thermal paper, pressure-sensitive paper, thermal transfer paper, inkjet paper, electrostatic recording paper, magnetic recording paper, uncoated paper such as high-grade and intermediate-grade printing paper, and rice paper industry. The present invention relates to a paper filler which is suitably used for hybrid papers and the like and can be used in a wide range, and a paper filler containing the same.

[0002]

2. Description of the Related Art In recent years, the number of cases in which an inner filler paper is used is more than that of a non-inner filler paper mainly for improving optical characteristics. As the filler for the inner filler, talc is mainly used, and other light calcium carbonate, heavy calcium carbonate, kaolin clay, calcined clay, hydrous calcium silicate, titanium dioxide and the like are used.

Further, the neutralization of paper has been promoted from the viewpoint of long-term storage of paper, but with this, the filler has been replaced by talc from clay and calcium carbonate. Light calcium carbonate is a filler excellent in optical properties such as whiteness and opacity as compared with talc, clay, and heavy calcium carbonate, but still higher whiteness and opacity are required. In the field of paper as well, there is an increasing tendency toward weight reduction, but if the filler ratio is lowered to reduce the weight, the whiteness and opacity, which are the characteristics of the filler, decrease. In addition, the recording paper and the thin paper are required to have a high level of elasticity as a paper that does not bend or fold too much.

[0004]

Under the above circumstances, the present invention improves whiteness and opacity when filled in paper, and maintains a certain degree of whiteness and opacity even on thin paper. The purpose of the present invention is to provide a paper filler and a paper filler containing the same, which can increase the stiffness of the paper.

[0005]

Means for Solving the Problems As a result of intensive studies to develop a paper filler having the above-mentioned preferable characteristics, the present inventors have found that aragonite type columnar calcium carbonate having a specific length and diameter. It was found that homogeneously dispersed carbonates having a specific surface area and having a specific specific surface area, or a mixture of the same and other internal fillers, are suitable for the purpose. Based on this, the present invention has been completed.

That is, the present invention has a length of 0.5 to 3 μm.
m, a uniform dispersed carbonate consisting of aragonite-based columnar calcium carbonate having a diameter of 0.1 to 0.3 μm and plate-like basic magnesium carbonate having a particle diameter of 2 to 7 μm and having a specific surface area of 15 to 30 m ² / g Alternatively, the present invention provides a paper filler which is a mixture of the filler and other fillers.

The uniformly dispersed carbonates used in the paper filler of the present invention consist of aragonite type columnar calcium carbonate and plate-like basic magnesium carbonate, and the calcium carbonate has a length of 0.5 to 3 μm and 0. 1 to 0.3 μm, the magnesium carbonate has a particle size of ² to 7 μm, and has a specific surface area of 15 to 30 m ² / g, and the calcium carbonate and the basic magnesium carbonate are It must be evenly distributed with respect to each other. Further, the calcium carbonate preferably has an aspect ratio in the range of 5 to 15.

If the particle size is too small, the particles are strongly aggregated and the dispersibility decreases, and when it is used for papermaking, the whiteness and opacity decrease, and if the particle size is too large, the dispersibility increases. However, the whiteness is lowered, which is not preferable.

Further, if the specific surface area is too small, the crystallinity is lowered and the whiteness and opacity cannot be improved, and if it is too large, the physical properties are not further improved, and the bulkiness is further increased. Therefore, the viscosity of the slurry is high, the solid content concentration does not increase, and the drying requires a long time and a large amount of heat, which makes handling complicated and is industrially disadvantageous, which is not preferable.

Further, in the above carbonates, the ratio of calcium carbonate to basic magnesium carbonate is converted into the weight ratio of calcium hydroxide to magnesium hydroxide of 95:
It is preferably in the range of 5 to 50:50. If this ratio is too small, the effect of the present invention will not be sufficiently exhibited, and if it is too large, the effect commensurate with it will not be obtained, which is rather economically disadvantageous.

In the paper filler of the present invention, the above-mentioned carbonates may be used alone, or may be combined with other fillers such as talc and clay. The mixing ratio of the other internal fillers is preferably at most 90% by weight based on the total amount of the other internal fillers, and more preferably, the weight ratio of the carbonates to the other internal fillers is 90/10 to 30 /. A value of 70 is recommended. Other internal fillers include talc, kaolin clay,
Calcined clay, heavy calcium carbonate, light calcium carbonate, hydrous calcium silicate, titanium dioxide and the like are used. These internal fillers may be used alone or in combination of two or more.

If the blending ratio of the other internal filler is too large, the blending effect of the above-mentioned carbonates will not be sufficiently exhibited, and the whiteness, opacity, and firmness of the waist will be deteriorated, which is not preferable.

The above carbonates are produced by various methods.
One of the methods is to add calcium hydroxide aqueous suspension having a viscosity of 1500 cp or more at 25 ° C. and a concentration of 400 g / l and magnesium hydroxide and water or magnesium hydroxide aqueous suspension to calcium hydroxide and magnesium hydroxide. Mix in a weight ratio of 95: 5 to 50:50, the concentration is 100 to 250 g / l in terms of calcium hydroxide, and the temperature is 30 ° C.
The carbon dioxide-containing gas having a carbon dioxide concentration of 15 to 100% by volume was adjusted as described above, and the pH was 1 to 3 l / min in terms of 100% carbon dioxide per 1 kg of calcium hydroxide.
It is supplied until it becomes 1 or less, and then the gas supply amount is 5 liters based on 100% carbon dioxide conversion per 1 kg of magnesium hydroxide.
/ Min or more, the gas is supplied until the pH is 8 or less and the conductivity is constant.

This calcium hydroxide aqueous suspension is prepared by sufficiently stirring and dispersing the suspension adjusted to a predetermined concentration with a stirrer such as a high speed impeller disperser such as a Choles mixer. The viscosity of this aqueous suspension is measured using a Brooksfield viscometer (B-type viscometer) under the condition of a rotor rotation speed of 60 rpm, and is 1500 cp or more, preferably 2000 cp or more.

In another method, an aqueous suspension of calcium hydroxide and magnesium hydroxide in which the weight ratio of calcium hydroxide and magnesium hydroxide is 95: 5 to 50:50 is 100 to 250 g / l in terms of calcium hydroxide. Concentration of 5-30
Adjust to a temperature in the range of ℃
Gas containing 100% by volume of carbon dioxide is 7 to 15 l / mi in terms of 100% carbon dioxide per 1 kg of calcium hydroxide.
It is supplied until the carbonation rate of calcium hydroxide reaches about 10% with n, and then the gas supply amount is adjusted to 1
0.5 to 2 l / mi in terms of 100% carbon dioxide conversion per kg
n is supplied until the carbonation rate of calcium hydroxide reaches 40 to 60%, and the gas supply amount is more than 2 l / min in terms of 100% carbon dioxide per 1 kg of calcium hydroxide, and the pH becomes 11 or less. Then, the gas supply amount is 5 l / min or more in terms of 100% carbon dioxide per 1 kg of magnesium hydroxide, and the gas is supplied until the pH is 8 or less and the conductivity becomes constant. The starting materials used to prepare the aqueous suspension of this method may be separate magnesium hydroxide and calcium hydroxide, respectively, or calcined dolomite hydrate.

Yet another method is 25 ° C., concentration 400 g
An aqueous suspension of calcined dolomite hydrate having a viscosity of 1500 cp or more per 1 / l is 100 in terms of calcium hydroxide.
The concentration is adjusted to 250 g / l and the temperature is adjusted to 30 ° C. or higher, and a carbon dioxide-containing gas having a carbon dioxide concentration of 15 to 100% by volume is added at a pH of 1 to 3 l / min in terms of 100% carbon dioxide per 1 kg of calcium hydroxide. To 11 or less, and then supply the gas at a rate of 1k of magnesium hydroxide.
It is 5 l / min or more in terms of 100% carbon dioxide per g, and the gas is supplied until the pH is 8 or less and the conductivity becomes constant.

This aqueous suspension is prepared by thoroughly stirring and dispersing the aqueous suspension adjusted to a predetermined concentration with a stirrer such as a high speed impeller disperser such as a Choles mixer. The viscosity of this aqueous suspension was measured using a Brooksfield viscometer (B-type viscometer) with a rotor rotation speed of 60.
Measured under the condition of rpm, 1500 cp
Or more, preferably 2000 cp or more.

The carbon dioxide-containing gas used in these methods has a carbon dioxide concentration of 15 to 100% by volume, preferably 30 to 100% by volume, and it is not always necessary to use pure carbon dioxide. It may be one obtained by diluting carbon with nitrogen or the like.

The carbon dioxide supplied by blowing, dispersing, etc. first reacts with calcium hydroxide, and after the calcium hydroxide has almost completely reacted, it reacts with magnesium hydroxide.

The end point of this reaction with calcium hydroxide is p
Appearing as a decrease in H value, it is practical to catch it when the pH value becomes 11 or less.

Further, the end point of the reaction with magnesium hydroxide is further considered to be a point where the pH value further decreases to 8 or less, and the conductivity becomes constant without showing any change.

In the paper filler of the present invention, in addition to the above-mentioned essential components, various additive components usually used in conventional paper fillers are blended within a range not impairing the object of the present invention. You can As the additive component, for example, a sizing agent, a yield improving agent, a paper strengthening agent, etc. are used.

Examples of the sizing agent include neutral sizing agents such as AKD (alkyl ketene dimer) and ASA (alkenyl succinic anhydride), acidic sizing agents such as rosin and petroleum, and examples of the retention improving agent include polyacrylamide. As the paper-strengthening agent, for example, corn starch or the like is used.

Next, the present invention also includes an inner paper filler containing the paper inner filler. The inner paper filler of the present invention is usually produced by making paper by adding various kinds of pulp, in addition to the paper inner filler, to the above-mentioned sizing agent, yield improver, paper strength enhancer and the like.

The addition amount of the filler in the paper is usually expressed on the basis of ash. The ash content represents the weight ratio of the residue when the inner paper is incinerated in an electric furnace. This amount varies depending on various types of paper, about 5% for newsprint, about 10% for medium-quality paper, coated base paper, offset paper, 10-20% for high-quality paper, envelope paper, book paper, dictionary paper, and Indian paper. , Rice paper is 30-40%.

[0026]

The paper filling agent of the present invention, when filled in paper,
In order to improve optical properties such as opacity and whiteness and physical properties such as stiffness of paper, coated base paper such as art paper and coated paper, PPC paper, thermal paper, pressure sensitive paper, thermal transfer paper, inkjet It can be used in a wide range such as information paper such as paper, electrostatic recording paper, magnetic recording paper, uncoated paper such as high-grade and intermediate-grade printing paper, and industrial hybrid paper such as rice paper.

Further, since the inner paper of the present invention is excellent in the above-mentioned optical characteristics and physical characteristics, it is useful as the above-mentioned coated base paper, information paper, non-coated paper or industrial hybrid paper.

[0028]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Production Example 1 Calcium hydroxide was suspended in water, adjusted to a concentration of 400 g / l, treated with a Choles mixer and measured for viscosity at 25 ° C. (B-type viscometer 60 rpm) 2200
It was cp.

600 g of magnesium hydroxide and water were added to 6.0 l of the obtained lime milk to obtain a mixed suspension of 15 l. This mixed solution was adjusted to 40 ° C and the carbon dioxide concentration was 30% by volume.
Carbon dioxide-containing gas of 0.96 Nm ³ / hr (2 l / min per 1 kg of calcium hydroxide) was blown in until the pH reached 11, and then the amount of the gas blown was 1.2 Nm.
³ / hr (10 l / mi / kg magnesium hydroxide)
The gas was blown into n) and the reaction was stopped when the pH was 7.2 and the conductivity became constant.

The product thus obtained is SEM
And XRD have an average length of 2.3 μm and an average diameter of 0.2.
It was found to be a uniformly dispersed carbonate having a specific surface area of 17.5 m ² / g, which is composed of aragonite type columnar calcium carbonate of μm and plate-like basic magnesium carbonate having an average particle size of 5.3 μm.

Production Example 2 900 g of magnesium hydroxide and water were added to 5.3 l of the same lime milk as in Production Example 1 to obtain a mixed suspension of 15 l. This mixed solution was adjusted to 40 ° C., and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was blown thereinto at a pH of 11 at 0.85 Nm ³ / hr (2 l / min per 1 kg of calcium hydroxide), and then the gas was discharged. The blowing amount is 1.8 Nm ³ /
hr (10 l / min per 1 kg of magnesium hydroxide)
Then, the reaction was stopped when the pH became 7.2 and the conductivity became constant.

The product thus obtained has an average length of 2.1 μm and an average diameter of 0.2 μm by SEM and XRD.
It was found that the carbonate is a uniformly dispersed carbonate having a specific surface area of 21.2 m ² / g and composed of m-aragonite type columnar calcium carbonate and plate-like basic magnesium carbonate having an average particle size of 6.3 μm.

Production Example 3 1500 g of magnesium hydroxide and water were added to 3.8 liters of the same lime milk as in Production Example 1 to obtain a mixed suspension of 15 liters. This mixed solution was adjusted to 40 ° C., and a carbon dioxide-containing gas having a carbon dioxide concentration of 30% by volume was blown thereinto at a pH of 11 at 0.61 Nm ³ / hr (2 l / min per 1 kg of calcium hydroxide), and then the gas was discharged. Blowing amount of 3.0 Nm ³
/ Hr (10 l / mi per 1 kg of magnesium hydroxide)
Then, the reaction was stopped when the pH became 7.3 and the conductivity became constant.

The product thus obtained had an average length of 2.2 μm and an average diameter of 0.2 μm by SEM and XRD.
It was found that the carbonates were composed of m-aragonite type columnar calcium carbonate and plate-like basic magnesium carbonate having an average particle diameter of 6.7 μm and had a specific surface area of 27.2 m ² / g.

Examples 1 to 3 To a pulp prepared by mixing 350 csf of LBKP and 450 csf of NBKP at 7: 3, the carbonates obtained in Production Examples 1 to 3 were mixed so that the ratio of the ash content to the pulp weight was 15%. An internal filler was obtained by adding as an internal filler, a sizing agent, a yield improver and the like, and making a paper by hand.

Comparative Example 1 Instead of the carbonates of Example 1, commercially available needle-like aragonite calcium carbonate (TP having a length of 2.2 μm and a diameter of 0.2 μm) (TP) was used.
Example 1 except that -123CS) was used as the filler.
An inner paper was obtained in the same manner as.

Comparative Example 2 An inner filler paper was obtained in the same manner as in Example 1 except that a commercially available talc (ND: manufactured by Nippon Talc Co., Ltd.) was used as a filler instead of the carbonate of Example 1.

Comparative Example 3 An inner filler paper was prepared in the same manner as in Example 1 except that a commercially available heavy calcium carbonate (GL # 100: manufactured by Sankyo Flour Milling Co., Ltd.) was used as the filler instead of the carbonate of Example 1. Obtained.

Example 4 An inner filler paper was obtained in the same manner as in Example 3 except that the carbonates of Example 3 were mixed with the talc of Comparative Example 2 in a ratio of 3: 7 as a filler. .

Example 5 An inner filler paper was obtained in the same manner as in Example 4, except that the compounding ratio of the carbonate and talc in Example 4 was changed to 5: 5.

Example 6 An inner filler paper was obtained in the same manner as in Example 4 except that the compounding ratio of the carbonate and talc in Example 4 was changed to 7: 3.

Various physical properties of the inner filler papers obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were determined. The results are shown in Table 1.
Shown in.

[0044]

[Table 1]

Example 7 An inner filler paper was prepared in the same manner as in Example 3 except that the amount of ash added was 5% in Example 3 using the carbonate of Production Example 3 as the filler. Obtained.

Example 8 An inner filler paper was obtained in the same manner as in Example 7, except that the addition ratio of the filler in Example 7 was 10% in terms of ash content.

Example 9 An inner filler paper was obtained in the same manner as in Example 7, except that the addition ratio of the filler in Example 7 was changed to 20% in terms of ash content.

Example 10 An inner filler paper was obtained in the same manner as in Example 7, except that the amount of ash added in Example 7 was 30%.

Various physical properties of the inner filler papers obtained in Examples 7 to 10 were determined. The results are shown in Table 2.

[0050]

[Table 2]

The physical properties shown in Tables 1 and 2 were measured as follows. The Clark stiffness was used as an index showing the stiffness of the paper. (1) Whiteness: Measured according to JIS P8123. (2) Opacity: Measured according to JIS P8138. (3) Clark stiffness: measured by TAPPI standard method T451.

Claims (5)

[Claims] 1. A length of 0.5 to 3 μm and a diameter of 0.1 to 0.3.
μm aragonite-based columnar calcium carbonate and particle size 2
A paper filler made of a plate-like basic magnesium carbonate having a particle size of ˜7 μm and a uniformly dispersed carbonate having a specific surface area of 15 to 30 m ² / g. 2. A paper filler comprising a mixture of the uniformly dispersed carbonates according to claim 1 and other fillers. 3. The paper filler according to claim 2, wherein the proportion of the other filler is 90% by weight at most with respect to the total amount of the other filler and the uniformly dispersed carbonates. 4. The other internal filler is talc, calcium carbonate,
The paper filler according to claim 2 or 3, which is at least one selected from kaolin clay, calcined clay, hydrous calcium silicate, and titanium dioxide. 5. An inner paper filler containing the paper inner filler according to any one of claims 1 to 4.