JPH0611958B2 - Non-flammable or flame-retardant paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-combustible or flame-retardant paper and a method for producing the same.

Paper is currently used in a wide range of fields, but its disadvantage is that it is easily burned. If non-combustible or flame-retardant properties can be imparted to paper, not only will it open up new fields, but it will also be extremely advantageous in the fields of current use. Therefore, it is strongly demanded to impart nonflammability or flame retardancy while maintaining various elements required for paper.

The object of the present invention is to meet the above-mentioned demand, and the object of the present invention is (a) a large number of composite secondary particles formed by entanglement of a large number of composite primary particles composed of calcium carbonate and siri. A paper sheet formed by connecting in a compressed and deformed state while being entangled with a fibrous substance, and having a fibrous substance content of 50% by weight or less of solid content, (b)
The connected state does not cause cracks on the surface when the paper is wound with a curvature of 10 mmR, and (c) the composite secondary particles are wollastonite group, tobermorite group, tricalcium silicate hydrate. And secondary particles of calcium silicate formed by entanglement of a large number of calcium silicate primary particles selected from the group of α-dicalcium silicate hydrate and contacting with carbon dioxide gas in the presence of water. It is achieved by providing a non-combustible or flame-retardant paper characterized in that secondary particles are converted into composite secondary particles of calcium carbonate and silica.

The paper of the present invention is characterized by the following points.

First, a plurality of composite secondary particles formed by entanglement of a plurality of composite primary particles composed of calcium carbonate and sili are formed by connecting a large number of fibrous substances while being compressed and deformed to form a paper sheet. That is the point. In this compressed and deformed state, since the morphology of the composite secondary particles remains fairly clearly, the composite secondary particles are significantly compressed and deformed to be almost flattened, and the shape of the original composite secondary particles is It is included up to the state of being deformed to the extent that almost nothing is left. Thus, in the paper of the present invention, the deformation state in a wide range from deformation to the extent that the shape of the composite secondary particles still remains to significantly compressed deformation to the extent that the shape of the composite secondary particles hardly remains. included.

The second feature of the paper of the present invention is that the content of the fibrous substance is 50% by weight or less.
In the paper of the present invention, the composite secondary particles composed of calcium carbonate and silica are the main raw materials, and are not used as a filler for paper, and the fibrous substance is just an auxiliary raw material.

According to the research conducted by the present inventor, when the content of the fibrous material is 40% by weight or less, particularly 30% by weight or less, calcium silicate used as a raw material for producing composite secondary particles composed of calcium carbonate and silica. It has been found that the strength of the obtained paper varies depending on the type. In particular, when calcium silicate is gyrolite, the strength of the obtained paper is greatly reduced, so that the composite secondary particles obtained from gyrolite are not used in the present invention. Also.
It was also found at the same time that when the calcium silicate as the above raw material is of the wollastonite group, paper having excellent strength can be obtained regardless of the content of the fibrous substance.

A feature of the third paper of the present invention is that the connection state between the composite secondary particles and the fibrous substance is defined by the following points. That is, when the paper of the present invention is wound with a curvature of 10 mmR, no crack occurs on the surface. The crack at this time means a state in which the connected state due to the entanglement of the composite secondary particles is substantially broken. This represents the flexibility or pliability of the paper of the present invention.

It is preferable that the paper of the present invention further has the following features.

That is, the breaking length in the papermaking direction is 0.1 km or more. The breaking length is expressed by the following equation.

This indicates that the paper of the present invention has considerable flexibility or pliability, but on the other hand, it has a considerable resistance against a certain amount of tension and cannot be broken by a little tension.

Further, the paper of the present invention has the following properties.

That is, its thickness is usually less than 1 mm and its basis weight is 4
It is not more than 00 g / m ² .

When preparing the paper of the present invention, 50% by weight or less based on the weight of solid content is added to an aqueous slurry in which composite secondary particles formed by entangling a plurality of composite primary particles composed of calcium carbonate and silica are dispersed in water. The fibrous substance of 1 is added and mixed, and then paper is made.

The slurry itself in which the composite secondary particles of the present invention are dispersed in water,
It is well known before the application of the present application, and is disclosed in, for example, Japanese Patent Publication No. 55-23790 and Japanese Patent Laid-Open No. 52-135.
No. 899 can be exemplified. In the slurry of the composite secondary particles, primary particles of calcium carbonate may be present together with the composite secondary particles composed of calcium carbonate and silica. Further, the method of producing the slurry itself is not particularly important, but rather the type of calcium silicate used when producing the slurry of the composite secondary particles is important.

According to the research conducted by the present inventor, the following facts have been clarified.
That is, (a) the tensile strength among the strengths of the obtained papers differs depending on the type of calcium silicate used when preparing the slurry of the composite secondary particles. In particular, when paper is prepared from a slurry of composite secondary particles prepared from gyrolite, the tensile strength thereof is considerably low, so gyrolite is not used in the present invention.

(B) Regarding the variation in mechanical strength of the obtained paper, that is, even a single sheet of paper has a significant difference in strength depending on the location, it depends on the type of calcium silicate used as a raw material when obtaining the composite secondary particles. It is said that the above variations are remarkable when gyrolite is used.

(C) The yield in the production of paper differs depending on the type of calcium silicate used as a raw material when obtaining the composite secondary particles, and particularly the yield decreases when gyrolite is used.

A typical method for producing a slurry composed of composite secondary particles is as follows.

It is a method of preparing a slurry of calcium carbonate-silica composite secondary particles by contacting calcium silicate secondary particles formed by entanglement of a large number of calcium silicate primary particles with carbon dioxide gas in the presence of water. .

When carbon dioxide gas is allowed to act on the calcium silicate secondary particles in the presence of water, the calcium silicate primary particles forming the secondary particles change to silica gel and calcium carbonate while maintaining their shapes, and thus calcium silicate The secondary particles do not disintegrate or disperse and leave their morphology to become composite secondary particles of silica and calcium carbonate. The solid content weight ratio of water and calcium silicate slurry is preferably 0.1 to 50: 1. Further, the carbon dioxide gas may be contacted under any conditions of normal pressure and pressure, but when contacting under pressure, the treatment time can be remarkably shortened. A known slurry itself can be used as the slurry composed of secondary particles of calcium silicate at this time. For example, JP-B-52-43494 and JP-B-53-12526.
No. 53, Japanese Patent Publication No. 53-18533, Japanese Patent Publication No. 54-4968
And those disclosed in JP-B-55-29952. Further, it is also possible to use a slurry composed of secondary particles prepared by a method other than the stirring method.For example, the raw material slurry is hydrothermally reacted without stirring in an autoclave, and if necessary, a little pulverized. You can These calcium silicate secondary particles are formed by three-dimensionally intertwining a large number of calcium silicate primary particles.

The calcium silicate secondary particles may contain the calcium silicate primary particles together with the secondary particles.
As the calcium silicate used in this case, at least one selected from the group of wollastonite group, tobermorite group, tricalcium silicate hydrate and α-dicalcium silicate hydrate can be used.

Examples of the wollastonite group include zonotolite, fossiajite and β-wollastonite, and examples of the tobermorite group include tobermorite and CSH (I). Tobermorite gel is not used.

As the fibrous substance used by mixing with the composite secondary particles of silica and calcium carbonate, one or more kinds of organic fibers and inorganic fibers can be used, and as the organic fibers, in addition to cellulose fibers, polyamide, Various synthetic fibers such as polyester and polyolefin can be exemplified, and examples of the inorganic fiber include glass fiber, rock wool, asbestos, silica fiber, ceramics fiber, carbon fiber and inorganic whiskers.

The content of the fibrous material is 50 with respect to the weight of the solid content.
It is preferably not more than 40% by weight, more preferably not more than 40% by weight. When the fibrous substance content exceeds 50% by weight, flame retardancy is substantially not exhibited. On the other hand, if the content is too small, the paper tends to crack when wound at 10 mmR. The lower limit is determined by the type of fiber, the type of composite secondary particles, the manufacturing conditions of the paper, etc., and cannot be specified, but it should be in the range that does not cause cracks when the obtained paper is wound at 10 mmR, and is generally Is 5% by weight
The above is preferable.

When the fibrous substance is added to the composite secondary particle slurry, the fibrous substance is suspended in water, and in the case of an organic fiber, it is preferably beaten to be fibrillated, and then the content is less than that of the composite secondary particle. To be added. The papermaking operation method and operation conditions may be those conventionally used, and additives such as a sizing agent are appropriately added as necessary. Examples of the additives include known agents such as paper strengthening agents, water repellents, moisture resistant resins, synthetic rubber latex, and flame retardants.
These can be added by mixing, impregnating or coating depending on the intended use of the paper.

The paper of the present invention can also be manufactured by the following method.

That is, the above-mentioned fibrous substance is mixed with the slurry of the above-mentioned calcium silicate secondary particles, and paper is made according to a conventional method to obtain calcium silicate paper, which is contacted with carbon dioxide gas in the presence of water to form paper. In this method, the secondary particles of calcium silicate are contacted with the composite secondary particles of silica and calcium carbonate. The individual secondary particles of calcium silicate that compose the calcium silicate paper must remain in their morphology and undergo a substantial change in the mutual binding state without being disintegrated or dispersed by the above reaction. Instead, it changes to composite secondary particles of silica and calcium carbonate. Therefore, the calcium silicate paper is a paper that retains the shape of the paper as it is and uses composite secondary particles of silica and calcium carbonate as a constituent material.

The fibrous substance is blended so that the content of the fibrous substance in the obtained calcium silicate paper will be 50% by weight or less. Since the weight of calcium silicate is usually increased by being converted into composite secondary particles of silica and calcium carbonate, the amount of the fibrous substance may be more than 50% by weight with respect to the fixed weight. . The conditions for converting the secondary particles of calcium silicate to the composite secondary particles of calcium carbonate and silicy are that the weight ratio of water to calcium silicate paper is 0.1 to 50: 1, preferably 1 to 3: 1. Can be contacted either under normal pressure or under pressure, but under pressure, the processing time can be shortened. The paper produced from the calcium silicate paper by the above method is superior in mechanical strength to the paper prepared from the composite secondary particle slurry.

Further, the non-combustible or flame-retardant paper of the present invention is characterized by being superior in acid resistance and moisture absorption as compared with calcium silicate paper.

In the production method of the present invention, since the composite secondary particles are used as a raw material in any method, a large contact area due to a large surface area of the particles makes it extremely easy to mix and mix fibrous substances, and the particles are fibers. There is an advantage that the formation of the paper obtained as a result is uniform without separating from the particulate matter and precipitating. Further, in the method of the present invention, a calender treatment is performed after paper making to obtain a smooth and dense paper,
Furthermore, by applying a super calendar, gloss can be imparted to the surface and beautiful paper can be obtained.

The paper of the present invention is not only excellent in nonflammability to flame retardancy and flameproofness, but also adsorbability, moisture absorption / dehumidification property, heat insulation property,
It has excellent electrical insulation and workability, so it has been used conventionally for flame-retardant and flame-proof wall materials, ceiling materials, honeycomb core materials, cushion floor materials, industrial heat insulation materials, packing materials, electrical insulation materials, air conditioning. It can also be effectively used for applications such as heat exchanger elements and gas adsorption sheets.

Further, in the paper of the present invention, when an organic fiber, a binder, a flame retardant or the like is added to the paper, even if a toxic gas or the like is generated during combustion, these gases are adsorbed by the paper itself. That is, the paper of the present invention has an adsorbing ability for these gases, and in the case of polyvinyl chloride, for example, HCl generated during combustion is adsorbed, so that only or a significantly reduced gas is generated.

Example 1 47.4 parts by weight of quicklime and 52.6 parts by weight of silica flour were mixed with 2400 parts by weight of water, then charged into an autoclave and stirred at a temperature of 200 ° C. under a saturated steam pressure of 15 kg / cm 2 while stirring. Hydrothermal reaction was carried out for 5 hours to obtain a slurry of calcium silicate crystals. The purified calcium silicate crystals were confirmed to be zonotorite crystals from the X-ray diffraction analysis results shown in FIG. The slurry obtained above was observed under an optical microscope. FIG. 2 is an optical micrograph (200 times) showing the result. As is clear from FIG. 2, the diameter of the xonotorite crystal is about 10 to 60 μm.
It was confirmed that the secondary particles in the shape of a marine algae were formed. The secondary particles of the xonotorite crystals were ultrasonically dispersed and observed under an electron microscope. FIG. 3 is an electron micrograph (10,000 times) showing the result. As is apparent from FIG. 3, the secondary particles have a width of about 0.03 to 0.3.
It was confirmed that the crystal was composed of a large number of xonotlite crystals having a length of 1 μm and a length of about 1 to 20 μm.

The slurry is then added to a water to slurry solids weight ratio of 5
It was prepared so as to have a ratio of 1/1, put into a container, and carbon dioxide gas was introduced at a ratio of 1 / min for 4 hours at 20 ° C. under normal pressure to be carbonated to obtain a slurry. The X-ray diffraction analysis result of the product is as shown in FIG. 4, and the peak based on the zonotolite crystal before carbonation disappeared and the peak of calcium carbonate was recognized.

The result of observing the above slurry under an optical microscope is as shown in FIG. 5, and the secondary particles of the zonotolite crystal are about 10 to 60 μm in diameter with their shape remaining, and are composed of substantially spherical algal-shaped silica and calcium carbonate. It was confirmed that the composite secondary particles were converted into In FIG. 5, it is the primary particles of calcium carbonate crystals that appear dark on the spherical composite secondary particles, and the primary particles of calcium carbonate crystals are finely scattered outside the spherical composite secondary particles. From this, it can be seen that the shape of the zonotolite secondary particles used as the starting material is maintained as it is even by carbonation. As shown in FIG. 6 in which the composite secondary particles were ultrasonically dispersed and observed under an electron microscope, the width was about 0.03 to 0.
It was found that it consisted of a complex of silica gel and plate-like calcium carbonate with the crystal habit of the xonotorite crystal having a length of 3 μm and a length of about 1 to 20 μm left.

Next, the slurry obtained above and the cellulose fiber (pulp) having a beating degree of SR26 ° were adjusted to a solid content weight ratio of 4/1 (No1) and the same adjusted to 3/2 (No2). Is uniformly dispersed in water, and this is paper-made with a tappy standard machine (mesh size 100 mesh), and this is pressed and dried to a thickness of 0.35 mm (N
o. 1 and No. The papers of 2) were obtained respectively. The yields at this time were 93% for No1 and 96% for No2.

The obtained paper properties are as shown in Table 1.

Incidentally, the method for measuring the content of the fibrous substance of the obtained paper is, after acid treatment of the paper, washed with water to remove the calcium content, and further to dissolve and remove the silicic acid content with sodium hydroxide,
This was done by measuring the weight (%) of the remaining fibrous material. Further, the flame retardance test method was based on the Meckel burner method of JISA1322, and the carbonization length, afterflame, and dust were measured with the heating time of 3 minutes, and the pass / fail was measured. The pH was measured according to the pH test method for paper and paperboard of JIS P8133.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

The winding test method in the present invention was carried out by winding the obtained paper once around a cylindrical rod having a curvature of 10 mmR and checking for cracks on the surface of the paper at that time.

Example 2 47 parts by weight of quick lime and 53 parts by weight of silica stone powder were mixed with 2400 parts by weight of water and then charged into an autoclave at a temperature of 200.
Hydrothermal reaction was carried out for 5 hours while stirring under saturated water pressure at 15 ° C. and a pressure of 15 kg / cm ² to obtain a slurry composed of xonotorite crystals.

When observing the slurry obtained above under an optical microscope,
The algal-like secondary particles having a diameter of about 10 to 60 μm were observed, and the slurry was ultrasonically dispersed and observed under an electron microscope to find a width of about 0.03 to 0.3 μm and a length of about 1
A large number of zonotolite needle-shaped crystals of -20 μm were observed.

Then, a slurry containing the zonotorite secondary particles obtained above and a cellulose fiber (pulp) having a beating degree of SR26 ° adjusted to a solid content weight ratio of 4/1 was uniformly dispersed in water. Was made with a tappy standard machine (mesh size 100 mesh), and this was pressed and dried. The characteristics of the calcium silicate paper thus obtained are as follows, and even when wound with a curvature of 10 mmR, no cracks were formed on the surface.

・ Fibrous substance content 20% ・ Basis weight 195 g / m ²・ Density 0.50 g / cm ³ Then, the calcium silicate paper obtained above has a water / paper solid content weight ratio of 0.3 / 1. After adjusting so that it is put in a container, carbon dioxide gas is added at a rate of 1 / min at 20 ° C. under normal pressure.
Flow for hours, carbonate, then dry to a thickness of 0.
39 mm paper was obtained.

When this was subjected to X-ray diffraction analysis, the peak based on the zonotolite crystal before carbonation disappeared, and the peak of calcium carbonate crystal and the peak of pulp were recognized.

The properties of the obtained paper are shown in Table 2.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

Example 3 A calcium silicate paper was obtained in the same manner as in Example 2. The characteristics of this calcium silicate paper are as follows, and the curvature is 1
Even when wound at 0 mmR, no crack was generated on the surface.

Fibrous substance content 20% Basis weight 187 g / m ² Density 0.53 g / cm ³ Then, the calcium silicate paper was prepared so that the water-to-paper solid content weight ratio was 2/1. Put in a container, 20 ℃,
Carbon dioxide gas was introduced at a rate of 1 / min for 5 hours under normal pressure to be carbonated and then dried to obtain a paper having a thickness of 0.35 mm.

When this was subjected to X-ray diffraction analysis, the peak based on the zonotolite crystal before carbonation disappeared, and the peak of calcium carbonate crystal and the peak of pulp were recognized.

The properties of the obtained paper are shown in Table 3.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

Example 4 A calcium silicate paper was obtained in the same manner as in Example 2. The characteristics of this calcium silicate paper are as follows, and the curvature is 1
Even when wound at 0 mmR, no crack was generated on the surface.

・ Fibrous substance content 20% ・ Basis weight 202g / m ²・ Density 0.48g / cm ³ Then, the above calcium silicate paper was prepared so that the weight ratio of water to paper solid content was 0.3 / 1. Then, put it in a pressure vessel and inject carbon dioxide gas at 20 ° C., 3 pressure and Kg / cm ² for 1.5 hours to carbonate it and then dry it to a thickness of 0.42 mm.
Got the paper.

When this was subjected to X-ray diffraction analysis, the peak based on the zonotolite crystal before carbonation disappeared, and the peak of calcium carbonate crystal and the peak of pulp were recognized.

The properties of the obtained paper are shown in Table 4.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

Example 5 Lime milk (47 parts by weight as quick lime) prepared in a sedimentation volume of 48 ml, 53 parts by weight of silica stone and water were mixed to prepare a water to solid content weight ratio of 24: 1, and then charged into an autoclave. Then, hydrothermal reaction was carried out for 4 hours while stirring under a saturated steam pressure of 200 ° C. and a pressure of 15 kg / cm ² to obtain a slurry of xonotorite crystals.

Then, the slurry obtained by carbonating the above-mentioned slurry in the same manner as in Example 1 and cellulose fibers (pulp) having a beating degree of SR26 ° adjusted to a solid content weight ratio of 3/2 were uniformly added to water. It was dispersed, papermaking was carried out by a tappy standard machine, and this was pressed and dried to obtain a paper having a thickness of 0.38 mm.

The yield at this time was 93%.

The sedimentation volume was measured according to the method described in U.S. Pat. No. 4,162,924, and the solid content weight ratio of water to lime was 2
It was carried out by allowing 50 ml of 4 times the amount of lime milk to stand in a cylindrical container having a diameter of 1.3 cm and a volume of 50 ml or more for 20 minutes, and then measuring the volume (ml) of lime particles settling.

The characteristics of the obtained paper are shown in Table 5.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

Example 6 74.4 parts by weight of quick lime and 100.6 parts by weight of silica stone powder were added to water 2
After mixing with 100 parts by weight, this was placed in an autoclave with an agitator having an internal volume of 3, sealed and heated to a temperature of 191.
A hydrothermal reaction was carried out for 5 hours while stirring under saturated air pressure at 12 ° C. and a pressure of 12 kg / cm ² .

After completion of the reaction, the reaction product was slowly cooled to normal pressure, and a slurry reaction product was taken out from the autoclave.

As a result of X-ray diffraction analysis, it was found that this reaction product was a slurry mainly containing tobermorite.

When observing the slurry obtained above under an optical microscope,
Secondary particles having a diameter of about 10 to 100 μm and a substantially spherical shape were observed.

Then, the slurry obtained by carbonizing the above slurry in the same manner as in Example 1 and pulp having a beating degree of SR30 ° of 4/1 in terms of solid content weight ratio were uniformly dispersed in water. This was paper-made by a tappy standard machine (mesh number 100 mesh), and this was pressed and dried to obtain a paper having a thickness of 0.32 mm.

The yield at this time was 93%.

The properties of the obtained paper are shown in Table 6.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

Example 7 81.2 parts by weight of quicklime and 68.8 parts by weight of silica flour were mixed with 2100 parts by weight of water, which was then placed in an autoclave with a stirrer in the contents seat 3, heated after sealing, and heated at a temperature of 200 ° C. and pressure. A hydrothermal reaction was carried out for 25 hours with stirring under a saturated water pressure of 15 kg / cm ² of water.

After completion of the reaction, the reaction product was slowly cooled to normal pressure, and a slurry reaction product was taken out from the autoclave.

As a result of X-ray diffraction analysis, it was found that this reaction product was a slurry mainly containing phosphidiaite.

When observing the slurry obtained above under an optical microscope,
Secondary particles having a diameter of about 10 to 50 μm and a substantially spherical shape were observed.

Then, the slurry obtained by carbonating the slurry obtained above in the same manner as in Example 1 and the pulp having a beating degree of SR of 30 ° were adjusted to a solid content weight ratio of 4/1, and uniformly mixed with water. After being dispersed and paper-making with a tappy standard machine (mesh number 100 mesh), this was pressed and dried to obtain a paper having a thickness of 0.34 mm.

The characteristics of the obtained paper are shown in Table 7.

Further, when the paper obtained above was wound with a curvature of 10 mmR, no crack was generated on the surface.

Comparative Example 1 5% white carbon slurry (7 as SiO ₂
1.60 g) and calcium hydroxide slurry (33.40 g as CaO) were mixed under atmospheric pressure at 25 ° C. for 1 hour, then placed in an autoclave, temperature 200 ° C., pressure 15 Kg.
Hydrothermal reaction was carried out for 15 hours while stirring under a saturated steam pressure of / cm ² .

After completion of the reaction, an X-ray diffraction analysis was carried out, and as a result, it was found that this reaction product was gyrolite-type calcium silicate.

Then, the slurry obtained by carbonizing the slurry obtained above and pulp having a beating degree of SR30 ° in the same manner as in Example 1 were adjusted so as to have a solid content weight ratio of 4/1 and uniformly dispersed in water. This was paper-made by a tappy standard machine (mesh size 100 mesh), then pressed and dried to obtain a paper having a thickness of 0.31 mm.

The yield at this time was 60%.

The properties of the obtained paper are shown in Table 8.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the result of X-ray diffraction analysis of the calcium silicate crystal obtained in Example 1. FIG. 2 is an optical micrograph (200 times) of the zonotorite secondary particles obtained in Example 1. FIG. 3 is an electron micrograph (10,000 times) of the zonotolite primary particles constituting the zonotolite secondary particles shown in FIG. FIG. 4 is the result of X-ray diffraction analysis of the product obtained by carbonating the slurry of xonolite crystals in Example 1. FIG. 5 is an optical micrograph (× 200) of composite secondary particles of calcium carbonate and silica gel obtained by carbonating the zonotorite secondary particles shown in FIG. FIG. 6 is an electron micrograph (10,000 times) of a composite primary particle composed of calcium carbonate and silica that constitutes the composite secondary particle shown in FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01B 3/52 9059-5G

Claims (5)

[Claims] 1. (a) A plurality of composite secondary particles formed by entanglement of a plurality of composite primary particles composed of calcium carbonate and silica, which are linked together in a compressed and deformed state while being entangled with a large number of fibrous substances. It is a formed paper sheet, and the content of the fibrous substance is 50% by weight or less. (B) In the connected state, when the paper is wound with a curvature of 10 mmR, the surface of the paper sheet does not crack. And (c) The composite secondary particles are made of wollastonite group, tobermorite group, tricalcium silicate hydrate and α
-Calcium silicate secondary particles formed by entanglement of a large number of calcium silicate primary particles selected from the group of dicalcium silicate hydrates are contacted with carbon dioxide gas in the presence of water to give calcium silicate secondary particles. A non-combustible or flame-retardant paper characterized by being converted into composite secondary particles of calcium carbonate and silica. 2. An aqueous slurry of a mixture of a composite secondary particle formed by entanglement of a large number of composite primary particles composed of calcium carbonate and silica and a fibrous substance in an amount of 50% by weight or less based on the weight of solid content. A method for producing a non-combustible or flame-retardant paper, which comprises: 3. (a) A large number of secondary particles of calcium silicate selected from the group of wollastonites, tobermorites, tricalcium silicate hydrates, and α-dicalcium silicate hydrates. A paper sheet formed by connecting in a compressed and deformed state while being entangled with each other, and having a fibrous substance content of 50% by weight or less, (b) the connected state is paper with a curvature of 10 mmR. Calcium silicate paper that does not crack on the surface when it is wound is brought into contact with carbon dioxide gas in the presence of water to convert the calcium silicate secondary particles into composite secondary particles of calcium carbonate and silica. A method for producing a non-combustible or flame-retardant paper, which comprises: 4. The non-combustible or flame-retardant paper according to claim 1, wherein the content of the fibrous substance is 40% by weight or less. 5. The non-combustible or flame-retardant paper according to claim 1, wherein the calcium silicate is a wollastonite group calcium silicate.