JP2958838B2 - Method for producing light calcium carbonate for internal use in papermaking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of producing a precipitated calcium carbonate for paper internally added.

[0002]

2. Description of the Related Art Calcium carbonate has been widely used as a filler in rubbers, plastics, paints, papermaking, inks and the like. Such calcium carbonate is roughly divided into heavy calcium carbonate produced by mechanically grinding natural white limestone, and light carbonate produced by chemically reacting calcium hydroxide (milk of lime) with carbon dioxide gas. Classified as calcium. Since heavy calcium carbonate is produced by mechanical pulverization and classification, the average particle diameter is generally large, specifically, 1.0 μm or more, and the particle size distribution is very wide. For this reason, it is insufficient to satisfy strictly desired physical properties in various fields, and is often mainly used as a bulking agent.

[0003] In the papermaking industry, when used as a filler for papermaking, the wire used in the dewatering part of the papermaking machine has high abrasion, and there are problems such as operability and economics (reduction of wire life), but light carbonic acid. Since calcium is synthesized by a chemical reaction, the particle size and shape can be adjusted to some extent, and the particle size distribution falls within a very narrow range. In addition, the above-mentioned problem as a filler for papermaking is almost eliminated by removing impurities and lowering hardness. In addition, in the paper
Precipitated calcium carbonate for hydrogenation is usually the BET specific surface area in terms of paper, paperboard quality (especially opacity) using the same 6
Physical properties of m ² / g or more are required.

In order to satisfy the physical properties, it is a common practice to control the temperature during carbonation after slaking and to adjust the amount of gas blown. However, when the temperature is controlled by the temperature at the time of carbonation, the reaction temperature must be lowered (25 ° C. or less) in order to increase the specific surface area. For this reason, when producing light calcium carbonate for internal use in papermaking, it is customary to limit the place where limestone as a raw material of quicklime is collected and use it. However, it is unclear about the relationship between quality and raw limestone or burnt lime quality paper internally added for precipitated calcium carbonate, without obtaining actually forced to take a method that judges try to manufacture, therefore light papermaking internally added The reality is that resources that could potentially be used as a raw material for calcium carbonate have not always been used effectively.

[0005]

The purpose of the 0008] The present invention can effectively utilize abundant limestone present as a resource, produced inexpensively with stable quality suitable precipitated calcium carbonate for the paper internally added to Japan It is in. More specifically, the paper inside without changing the light calcium carbonate production process in the conventional
Necessary characteristics of specific surface area 6 m 2 ^{/ g} or more light calcium carbonate as a additive to is to stably manufacture.

[0006]

In view of such circumstances, the present inventors have determined that a BET specific surface area of 6 m ² / g suitable for use as an internal additive for papermaking by a conventional method for synthesizing light calcium carbonate.
As a result of earnest research on obtaining the above light calcium carbonate, it has been found that there is a very close relationship between the specific component in the quicklime used as a raw material and the quality of the light calcium carbonate produced, and a BET specific surface area of 6 m ^2. / g or more manufacturing of
It succeeded in stably producing light calcium carbonate for use in paper .

That is, when various quicklimes were obtained and light calcium carbonate was synthesized by an ordinary method, the cause was investigated based on the fact that the specific surface area of the light calcium carbonate produced varied greatly depending on the type of raw quicklime. It is based on the finding that there is an extremely high correlation between the trivalent metal oxide content (hereinafter referred to as R ₂ O ₃ content) in the raw quicklime and the specific surface area of the light calcium carbonate produced.

[0008] manufacturing method of papermaking in添用precipitated calcium carbonate of the present invention, a trivalent metal oxide content as a raw material quicklime using only the following ingredients quicklime 0.4 wt% BET
It is characterized by producing light calcium carbonate having a specific surface area of 6 m ² / g or more. If the R ₂ O ₃ content exceeds 0.4% by weight, light calcium carbonate having a BET specific surface area of 6 m ² / g or more cannot be obtained. If also R ₂ O ₃ content of 0.4 wt% or less, there is no problem even if quicklime impurities other than to have or R ₂ O ₃ coloring is contained in the lime. Here, the R ₂ O ₃ content means the Al ₂ O ₃ content and the Fe ₂ O ₃ content.
₃ is the sum of the _three contents, and the Al ₂ O ₃ content and the Fe ₂ O ₃ content are values measured by the method specified in JISR9011. The present invention is characterized by producing light calcium carbonate for internal use in papermaking using quicklime having an R ₂ O ₃ content of 0.4% by weight or less as a raw material. If the R ₂ O ₃ content exceeds 0.4% by weight, BE
Light calcium carbonate having a T specific surface area of 6 m ² / g or more cannot be obtained. If also R ₂ O ₃ content of 0.4 wt% or less, there is no problem even if quicklime impurities other than to have or R ₂ O ₃ coloring is contained in the lime. Where R ₂ O
₃ The content is a value obtained by adding the content of _Al 2 _{O 3} and _Fe 2 _{O 3} content, content of _Al 2 _{O 3} and _Fe 2 _{O 3} content is measured by the method prescribed in JISR9011 Value.

There are no particular restrictions on the conditions for slaking,
CaO concentration of 10 to 35% by weight, reaction start temperature of 30 to 60
It is preferable to carry out at a temperature of ° C. Carbonation is performed by adding carbon dioxide to slaked lime milk. There are no particular restrictions on the conditions for carbonation,
Lime milk concentration 3 to 20% by weight, reaction temperature 30 to 60 ° C, introduced carbon dioxide is 0.1 to ₂ per 100 g of Ca (OH) _2.
It is preferably performed at liter / min.

The gas used here does not necessarily have to be 100% carbon dioxide gas, and nitrogen, an inert gas, and other mixed gases may be used as long as they contain carbon dioxide gas. A dispersant, a pH adjuster, and other additives may be added as long as the object of the present invention is achieved. The light calcium carbonate thus obtained has a BET specific surface area of 6 m ² /
g can be used as an internal filler for papermaking.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention, in the production of paper internally added for precipitated calcium carbonate, R ₂ O ₃ content is intended to be used exclusively with the following quicklime 0.4 wt%. Although the details are unknown, the following can be considered. Although calcined lime is obtained by calcining limestone at 900 ° C. or higher, it has been confirmed that this transition point (generally also referred to as a melting point) decreases as the R ₂ O ₃ content in limestone increases.

When firing at a constant temperature of 900 ° C. or more,
Limestone having a high R ₂ O ₃ content is adding more thermal energy in spite of becoming lime at a low temperature. As a result, the surface of quicklime is sintered firmly, the reactivity during slaking becomes poor, and good quality lime milk cannot be obtained. Generally, limestone firing furnaces are operated at a constant temperature and
Changing the temperature of the furnace according to the level of the ₂ O ₃ content is not usually performed because of problems such as complicated operation. For the above reasons, quicklime having an R ₂ O ₃ content of 0.4% by weight or less has good reactivity during slaking, and can provide high-quality lime milk having a small particle size and a light surface having a specific surface area of 6 m ² / g or more. The present inventors speculate that calcium carbonate can be obtained.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but it is needless to say that the present invention is not limited thereto. Unless otherwise specified, parts and% in the examples indicate parts by weight and% by weight, respectively. Example 1 One part of quick lime having a particle size of 5 to 25 mm and an R ₂ O ₃ content of 0.12% was slaked with 5 parts of 50 ° C. tap water for 1 hour, and this was applied to a 150-mesh screen. The residue was removed to obtain 22% milk of lime. After the lime milk was diluted and adjusted to a concentration of 8% and a temperature of 50 ° C., carbonation was carried out in a slender 6 liter reaction vessel. After the reaction,
The resultant was passed through a 150-mesh screen to obtain light calcium carbonate for internal use in papermaking .

Example 2 In the same manner as in Example 1 except that quicklime having a particle size of 5 to 25 mm and an R ₂ O ₃ content of 0.27% was used as a raw material.
Light calcium carbonate for internal addition to papermaking was obtained. Example 3 particle size 5 to 25 _mm, except that R 2 _{O 3} content using 0.35% of quicklime as a raw material, the same procedure as in Example 1
Light calcium carbonate for internal addition to papermaking was obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that calcined lime having a particle size of 5 to 25 mm and an R ₂ O ₃ content of 0.48% was used as a raw material.
Light calcium carbonate for internal addition to papermaking was obtained. Comparative Example 2 the particle diameter 5 to 25 _mm, except that R 2 _{O 3} content was used 0.53 percent of quicklime as content, in the same manner as in Example 1
Light calcium carbonate for internal addition to papermaking was obtained.

The papermaking internal additives obtained in the above Examples and Comparative Examples
Table 1 shows the values of the BET specific surface area of the light calcium carbonate for papermaking, and the light calcium carbonate for papermaking internal addition obtained in Examples and Comparative Examples by using a sheet machine, and physical properties of handmade paper are shown in Table 1 as usage examples. .

[0017]

[Table 1]

Evaluation Method BET Specific Surface Area BET specific surface area was measured by a BET one-point method using Flowsorb II2300 (manufactured by Shimadzu Corporation). Handmade paper making method Handmade paper was made using a TTS type standard square sheet machine (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance with JIS P8209 and TAPPI T205. Whiteness A digital hunter reflectometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used to comply with JIS P8123. Opacity It was based on JIS P8138 using a digital hunter reflectometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.). Actual Filling Rate According to JIS P8128 except that the ignition temperature was 450 ° C.

[0019]

Method for producing paper internally added for precipitated calcium carbonate of the present invention exhibits, trivalent metal oxide content as a raw material quicklime using only the following ingredients quicklime 0.4 wt% BE
By manufacturing the T specific surface area 6 m 2 ^{/ g} or more precipitated calcium carbonate, the required BET specific surface area 6 m 2 / ^g or more paper in添用 light <br/> as papermaking without changing the conventional manufacturing process Thus, calcium carbonate can be produced stably. In addition, limestone raw materials that have not been conventionally used for papermaking can be used if the R ₂ O ₃ content is 0.4% by weight or less, which leads to effective use of unused resources and uses inexpensive limestone. An excellent effect is brought about because it is possible to reduce the manufacturing cost.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Satoshi Araki 7-24-14 Shitake, Niigata City, Niigata Prefecture Seiryo Ryo (56) References JP-A-62-250299 (JP, A)

Claims (1)

(57) [Claims] 1. A milk of lime in the method of manufacturing the paper internally added for precipitated calcium carbonate to synthesize precipitated calcium carbonate with carbon dioxide gas, a trivalent metal oxide content as a raw material quicklime following 0.4 wt% BE using only raw lime
Method for producing paper internally added for precipitated calcium carbonate, characterized in that the production of T specific surface area 6 m 2 ^{/ g} or more precipitated calcium carbonate.