JPH0226995A - Additive for paper-making - Google Patents

Abstract

PURPOSE:To provide a paper-making additive containing montmorillonite as a main component and cristobalite as a minor component, having specific mineral composition, cation requirement, brightness by Hunter and average particle diameter and effective in opacifying the paper, preventing the strike-through of ink, etc. CONSTITUTION:The objective paper-making additive is composed of active bentonite containing montmorillonite having lamellar crystal structure by X-ray diffraction analysis as a main component and cristobalite as a minor component and has a mineral composition of formula I-III (M is alkaline-earth metal), a cation requirement of 3-13.5meq/100g, an average particle diameter of <=10mum and a brightness by Hunter of >=70%. The additive is produced preferably by adding 1.5-3.5wt.% (in terms of anhydride) of solid sodium carbonate to a hydrous acid clay containing cristobalite, kneading the mixture at 60-100 deg.C while keeping the moisture, drying to a water-content of 1-6wt.% and crushing the dried product.

Description

Detailed Description of the Invention (Field of Application in Industry A) The present invention relates to an additive for paper manufacturing, and more specifically, it is used to be incorporated into pulp during paper manufacturing, and is used to improve the opacity of paper. The present invention also relates to papermaking additives used for the purpose of preventing cross-cutting during printing and improving the yield of pulp fillers.

(Prior Art) Conventionally, during paper manufacturing, the aim of improving the whiteness, opacity, smoothness, and printability of paper and making it cheaper is to
Various fillers are mixed into pulp, and known examples of such fillers include clay, talc, magnesium carbonate, barium sulfate, and titanium oxide. White clay for papermaking includes kaolinite, attapal guide,
Bentonite etc. are known.

Bentonite is an alkaline clay whose main component is montmorillonite, and it is produced all over the world.

Among these, clay produced in Wyoming in the United States has excellent physical properties suitable for use in muddy water, but clay produced in Japan is of relatively poor quality. For this reason, so-called activated bentonite, which is obtained by treating naturally produced bentonite with an alkali such as sodium carbonate to improve swelling properties, viscosity, etc., has come to be widely used.

Conventionally, it has already been known to produce Na-substituted montmorillonite, that is, activated bentonite, using acid clay as a raw material. For example, in Clay Science Vol. It is described that Na1i-converted montmorillonite is produced by adding and hydrothermally treating this in an autoclave.

It has been known for a long time that bentonite is used to improve paper quality and filler yield during papermaking. For example, Japanese Patent Application Laid-Open No. 152899/1989 describes the use of a combination of bentonite clay and a nonionic polymer. and JP-A-62-191598 describes the use of a combination of bentonite clay and a synthetic cationic polymer having a molecular weight of 500,000 or more.

(Problem to be solved by the invention) However, among the papermaking clays mentioned above, kaolinite and attapal guide have excellent opacity, but their oil absorption is extremely small, and they are not very effective in preventing ink bleed-through. There is no.

On the other hand, bentonite has a relatively large oil absorption capacity, but
Even naturally produced bentonite or activated bentonite contains impurities such as iron and organic substances, and the whiteness is still not satisfactory. Furthermore, when conventional bentonite is used as a filler or a paper quality and filler retention improver, the yield in paper and the opacity of the resulting paper white body or printed matter are still not fully satisfactory. .

Therefore, the object of the present invention is to provide a material that can be used for blending into pulp during papermaking, has excellent retention in its own paper, paper quality and other fillers in paper, and has low opacity in paper. The object of the present invention is to provide an activated bentonite-based papermaking additive that is excellent in improving and preventing strike-through during printing.

Another object of the present invention is to provide an activated bentonite-based papermaking filler useful for increasing paper weight, making it opaque, and preventing ink bleed-through.

Still another object of the present invention is to provide a retention improver for paper manufacturing, which can be used in combination with an organic cationic polymer if desired, and is useful for improving the retention of paper quality and other fillers.

(Means for Solving the Problems) According to the present invention, AI! contains montmorillonite as a main component and cristobalite as a minor component, which has a layered crystal structure as determined by X-ray diffraction method, and is expressed in molar ratio. , zos/5i02=0.095 to 0.16
Na, O/SiO, = 0.8 x 10-' to 4.
5 Xl0-2M0 /5iOi = 4.5 X 1
It has a chemical composition of 0-” to 9.5 xlO-2 (where M is an alkaline earth metal) and a cation requirement of 3 to 13.5 m
eq/100g, especially 4 to 13 meq/100g, with an average particle size of 10 μm or less and a Hunter whiteness of 70
% or more of activated bentonite is provided.

(Function) In the present invention, acid clay containing cristobalite as an unavoidable component is used which is converted into bentonite by alkali treatment. During the bentonite formation, the required amount of cations is within a certain range and the cristobalite substantially remains. This is based on the finding that alkaline treatment under conditions where cristobalite is not converted into sodium silicate has an unexpected effect on the performance of activated bentonite as a papermaking additive.

Acid clay belongs to the montmorillonite group of clay minerals in mineralogy, and has a three-layer structure in which two 5lo4 tetrahedral layers are sandwiched with an AgO6 octahedra layer in between. Furthermore, it is common to other montmorillonite group clay minerals in that it has a multilayer crystal structure in which many layers are stacked in the C-axis direction. However, in acid clay,
The chemical structure shows that some of the Ag atoms in the Ape6 octahedral layer in the basic three-layer structure are replaced with alkaline earth metals such as magnesium and calcium, and hydrogen ions are bonded to compensate for the valence. Due to this chemical structural feature, which is the above feature, when acid clay is suspended in saline water and its pH is measured, it shows acidity because the hydrogen ions are replaced with Na ions.

Due to its nature, acid clay inevitably contains silica compounds such as quartz and cristobalite. Quartz, which is a silica impurity, is separated using wooden tablets, elutriation, or other classification methods, but cristobalite is separated by its specific gravity and Since its particle size characteristics are similar to those of montmorillonite, it cannot be separated by normal means and is inevitably contained.

This cristobalite is crystalline silica, but it is easily reactive with alkali, and is easily converted into sodium silicate by hydrothermal treatment with alkali added.

Table 1 below shows the raw acid clay (8) used in the present invention,
The compositions of (B) and natural bentonite are shown below.

In the present invention, acid clay is used as a bentonite raw material, and this is converted into activated bentonite (Na-type bentonite).
The first characteristic is that it transforms into That is, due to its origin, acid clay has a characteristic that it contains considerably less coloring components such as iron than naturally produced bentonite. Due to this feature, a papermaking additive with a Hunter whiteness of 70% or more can be obtained by converting acid clay into activated bentonite.

Next, the second feature is that acid clay is treated with alkali so that the cristobalite therein is not converted to alkali silicate and the amount of cations required is within a certain range to produce activated bentonite. That is, in the case of a product in which cristobalite does not substantially remain in the activated bentonite and is converted into an alkali silicate, the oil absorption of the activated bentonite becomes small and the opacity also decreases. The reason for this is thought to be that when alkali silicate is generated, it destroys the surface activity of bentonite.

The present invention is also based on the knowledge that when the cation requirement of activated bentonite is selected within the above-mentioned certain range, the yield during papermaking is significantly improved. Conventional natural bentonite or activated bentonite is generally 14 meq 7
It has a large cation requirement of more than 100g. However, the problem with bentonite having such a large cation requirement is that the yield in paper is still quite low. In contrast, according to the present invention, the amount of cations required for activated bentonite largely depends on the manufacturing conditions of activated bentonite, and by setting these manufacturing conditions within a certain range, the amount of cations required for activated bentonite is reduced compared to conventional bentonite. As a result, an active bentonite-based papermaking additive with a significantly excellent yield improvement effect was obtained.

In this specification, the cation requirement is the cation neutralization capacity of the particle surface, and the fact that this is a characteristic that depends on the water content during production of activated bentonite can be seen in Table 3 of Examples described below. This becomes clearer. Note that the water content here refers to the amount of water during the activation reaction,
It should be understood that it is not affected by subsequent moisture absorption or water absorption.

The activated bentonite used in the present invention has a basic three-layer structure unique to acid clay as a skeleton, and the acid sites of acid clay are neutralized and alkali enters between the eyebrows, suppressing negative charges on the particle surface. It is estimated to be.

In relation to the basic three-layered structure characteristic of acid clay mentioned above, when M is an alkaline earth metal,
The molar ratio of MO/5102 is 4.5 Xl0-2 to 9.
5 X10-2, especially 5.0 X10-'' to 8.
One of the characteristics of the chemical composition is that it is in the range of OX10-'.

Table 2 shows the composition and properties of typical ones.

Table 2 (Description of preferred embodiments of the invention) In the present invention, acid clay is used as a raw material, but any acid clay produced in Japan may be used as the raw acid clay. Table A below shows an example of the chemical composition of acid clay.

A table 5i02 B1.0-74.0 Weight% A11
as 12. Q~23.0 Weight%Fe2e32
．． 0-3.5 wt% MgO3,0-7.0
Weight% CaO 1.0-4.0 11% by weight 20 0.3-2.0% by weight NazOO,
3-2.0% by weight Loss on ignition 5.0-10.0% by weight This acid clay contains impurities such as quartz, feldspar, and α-cristobalite in addition to montmorillonite, but the content of α-cristobalite in particular varies depending on the production area. Although it varies considerably depending on the type of mineral deposit, mining location, etc., it is generally within the range of 20 to 35% by weight, particularly 25 to 30% by weight, based on the anhydrous content of clay. According to the present invention, the cristobalite is subjected to alkali treatment without converting it into an alkali silicate. Also,
Acid clay contains water when it is produced. This water content becomes the aqueous medium necessary for the reaction of sodium carbonate. Generally, the water content in raw clay is 10 to 30% by weight.
In particular, the content should be within the range of 15 to 25% by weight.Of course, if the moisture content in the raw clay is higher than the above range, it should be dried, and if it is lower than the above range, it may be necessary to replenish the moisture content. .

It is also important that the raw clay used be uniformly mixed with the sodium carbonate, which is added in a solid state. For this purpose, it is advantageous to keep the raw clay as fine as possible before mixing.

Generally, raw clay has a particle size of 3000 μm or more.
0! It is preferable to grind the powder to an amount of i% or less, particularly 20% by weight or less.

The amount of sodium carbonate used is 1 per clay on an anhydrous basis.
It is preferable to select from the range of 5% to 5% by weight, particularly 1.5 to 3.5% by weight. Although the optimum amount of sodium carbonate varies depending on the production area of the acid clay, it is sufficient to determine the relationship between the amount added and the required amount of cations for a certain raw material clay, and determine the optimum amount added based on this.

Raw clay and solid sodium carbonate are mixed, and this mixture is kneaded at a temperature of 50° C. or higher and under water retention conditions. For kneading, a -shaft or twin-screw extrusion type kneading device, a roll type kneading device, a Banbury mixer, etc. can be used, and the inside of the device can be maintained at reduced pressure if necessary. To maintain the kneaded composition at the above temperature, frictional heat within the kneading device can be used, or external heating may be used.The temperature during the kneading reaction is 50 to 100 ° C. Especially 60
The appropriate temperature range is from 100°C to 100°C, and the reaction time is 1.
A range of 0 to 100 hours, especially 1.0 to 20 hours is suitable.

The reaction can be carried out in one stage or in multiple stages. For example, the reaction may be carried out while kneading in the -th stage, and the kneaded product may be aged at the above-mentioned temperature in a closed container, in a mulch, or in a dryer.

Next, when drying the reactant to complete the reaction, drying conditions such as drying temperature, drying time, etc., such as ensuring that the moisture content of the activated bentonite at the time of completion is 8% by weight or less, preferably 6% by weight or less, are selected. You can choose.

This dry reactant is then subjected to mild grinding and classification as described above. As already disclosed in Japanese Unexamined Patent Publication No. 61-70097, this pulverization and classification operation is carried out by components such as feldspar and quartz remaining in the active bentonite reaction product that rub against paper-making screens. At the same time, it becomes possible to remove components with relatively low oil absorption even in acid clay, and active bentonite with large oil absorption, fine particle size, and excellent Hunter whiteness is isolated.

The pulverization process is performed using a roller mill, an atomizer, a vertical grind mill, etc. so that the average particle size becomes 10 μm or less. In addition, during this crushing, quartz,
It is presumed that feldspar, acid clay components with relatively small oil absorption, or components rich in these components remain in the pulverization system without being subjected to pulverization, and are removed in the subsequent classification operation.

In the present invention, the above-mentioned pulverization and classification operations may be performed before the bentonite reaction.

The filler used in the present invention, for example as a filler for newspaper, has an oil absorption of 451/! /100g or more, especially 50 to 85
It is preferably in the range mf/100g. The strike-through prevention effect of printing ink is closely related to the oil absorption amount of the filler used, and the larger the oil absorption amount, the greater the effect. The activated bentonite according to the present invention exhibits a relatively large oil absorption amount and is excellent in this effect compared to conventional bentonite.

In addition, the Hunter whiteness of this activated bentonite is 70% or more, which is an excellent whiteness that cannot be found in conventional natural bentonite or activated bentonite.Furthermore, since it has a layered crystal structure, it is amorphous. It has the advantage of superior opacity compared to silica and the like.

The activated bentonite of the present invention has an excellent retention in paper by itself, and when combined with a known cationic polymer, it has an advantageous effect on improving the retention of paper quality and other fillers.

(Effects of the Invention) According to the present invention, acid clay is used as a starting material, has a specific cation requirement, and leaves an appropriate amount of cristobalite, and is made of activated bentonite with particularly excellent whiteness, and has excellent retention performance and opacity. We were able to provide a papermaking additive that has excellent properties such as imparting properties and preventing ink strike-through.

(Example) Example 1 120 g of raw acid clay A listed in Table 1 was taken and weighed, powdered soda carbonate was added in the range of 0.84 to 4.2 kg, and mixed using a mixer. Further, the mixture was kneaded and granulated using a shaft-type extrusion kneader.

The temperature during kneading and granulation was 52°C, and the moisture content was 30%.

Next, the reaction was continued while drying each product using a rotary dryer so that the moisture content became the value shown in Table 3, and then pulverized using an atomizer-pulverizer.

Next, each of the pulverized products was classified using a force centrifuge according to Example 1 described in JP-A-61-70097 to obtain samples according to the present invention.

The properties of this sample, the required amount of cations, the papermaking yield, etc. were determined by the following test methods, and the results are shown in Table 3.

■ Moisture It was measured according to JIS K-5101.

■ Hunter whiteness Measured according to JIS-8123.

■ Oil absorption amount Measured according to JIS K-5101.

■ pi (Measured according to JIS K-5101.

■ Particle size After processing the sample for 30 seconds in a household mixer using ion-exchanged water,
Coulter counter Model T manufactured by oronic
Measurements were made at A u using a tube with an aperture diameter of 1100 u.

■ Swelling degree Japan Bentonite Industry Association Standard Test Method J
Measured according to BAS-104-77.

■ Cation requirement: Treat 200 mg of sample with ion-exchanged water using a household mixer or ultrasonic disperser,
After moistening and swelling for more than an hour, ion-exchanged water was further added to dilute the sample to 350 ml, which was titrated using the colloid titration method using toluidine blue solution as an indicator and titration with N/200 methyl glycol chitosan solution using the following formula. The amount of cations required was determined.

CD=2.5 xf x t where, CD: cation requirement [milliequivalent 7100g
) ■ Papermaking yield Raw material pulp 1 consisting of 80 parts of LBKP and 20 parts of NBKP
After mixing 0.1 part of polyacrylamide and 10 parts of a sample (filler) previously dispersed in water with 0.00 parts by weight, the paper was made with a basis weight of 42 g/n+2 according to JIS P-8209 using Toyo Seiki Seisakusho sheet machine paper machine. Create paper and JIS P-
The yield of the sample was measured according to 8128.

(2) Whiteness of paper The paper prepared in (2) was measured in accordance with JIS P-8123.

[Phase] Paper opacity was measured in accordance with JIS P-8138 on paper prepared with ■.

■Print opacity■The wire side of the paper created with RI (Rotary I
nk) Print solidly using a testing machine, JIS I'-Bill
The paper was dried for 24 hours under the following conditions, and the whiteness of the unprinted side of the paper (the opposite side to the wire side) was measured. The ratio of the opposite whiteness of the wire surface before printing to this whiteness, i.e. (whiteness after printing/whiteness before printing) x 100 (%)
was taken as the print opacity. The printing conditions are that the ink used is W.
With eb-Kinga (manufactured by Toyo Ink), the ink supply amount is 0.
3 ml, printing speed 30 rpm.

Comparative Example 1 In the sample preparation method according to the example, the moisture content due to drying was reduced to 10.5% (Experiment NoH-1) and 13.0% (Experiment H-1).
-2) A sample was obtained in the same manner as in Example 1 except that the sample was changed to -2).

The test results for this sample are shown in the table.

Comparative Example 2 The test results of commercially available bentonite Experiment NoH-3 (manufactured by Company A) and Experiment NoH-4 (manufactured by Company B) are shown in Table 3.

Example 2 Using the samples obtained in Examples 1-3, a retention improver for neutral paper making was investigated.

Raw material valve (LBKP 80 parts, NBKP 20 parts) 100
Part, Charcoal (made by Bihoku Funka Co., Ltd., Softon 1200) is used as a filler.
), 0.5 part of the sample powder of the present invention, and 1 part of cationodebun (Matsutani Chemical Industries, Neoposibalin #35) were mixed, and paper was made in the same manner using Toyo Seiki Seisakusho sheet machine paper making equipment, and the filler yield was measured. .

As a result, the filler retention was 40% in the blank without the retention aid, but 70% in the present invention.
Met.

[Brief explanation of the drawing]

FIGS. 1 and 2 are X-ray diffraction diagrams of acid clay A, the raw material used in the present invention, and the papermaking filler obtained in Example 1 of the present invention, respectively, and M in the figures. C and F indicate diffraction line peaks of montmorillonite, cristobalite, and feldspar, respectively. FIG. 3 is a plot of the relationship between the swelling degree and the cation requirement with respect to the water content of the papermaking additive according to the present invention, and curves A and B in the figure show the swelling degree and the cation requirement, respectively. FIG. 4 shows the relationship between the cation requirement of the papermaking additive according to the present invention and the papermaking yield. Patent applicant: Mizusawa Chemical Industry Co., Ltd.

Claims (7)

[Claims] (1) Contains montmorillonite with a layered crystal structure as a main component and cristobalite as a minor component and expressed in molar ratio as Al_2O_3/Si
O_2=0.095 to 0.16Na_2O/SiO_
2 = 0.8 x 10^-^2 to 4.5 x 10^-^2M
O/SiO_2=4.5×10^-^2 to 9.5×1
It has a chemical composition of 0^-^2 (in the formula, M is an alkaline earth metal) and a cation requirement of 3 to 13.5m.
A papermaking additive comprising activated bentonite having an average particle size of 10 μm or less and a Hunter whiteness of 70% or more at eq/100g. (2) The papermaking additive according to claim 1, wherein the activated bentonite is obtained by alkaline activation treatment of cristobalite-containing acid clay and has an oil absorption of 45 to 85 ml/100 g. (3) Activated bentonite is obtained by adding 1 to 5% by weight of solid sodium carbonate (calculated as anhydride) to hydrous acid clay containing cristobalite, and adding the solid addition mixture at a temperature of 40°C or higher under moisture retention conditions. 3. The papermaking additive according to claim 1, wherein the papermaking additive is obtained by kneading the mixture with a water content of 1 to 10% by weight and under conditions where cristobalite remains. (4) The papermaking additive according to claim 1, wherein the activated bentonite has a degree of swelling of 40 ml/2 g or less. (5) The papermaking additive according to claim 1, wherein the activated bentonite has a cation requirement of 15 milliequivalents/100 g or less as measured by colloid titration. (6) A papermaking retention improver composition comprising the activated bentonite according to claim 1 and a cationic polymer. (7) A papermaking filler comprising the activated bentonite according to claim 1.