JP7065563B2 - Flame-retardant material - Google Patents

Description

The present invention relates to a flame-retardant material using a composite of flame-retardant inorganic particles and fibers.

Fibers exhibit various properties based on the functional groups on the surface, but depending on the application, it may be necessary to modify the surface, and techniques for surface modification of fibers have been developed so far. There is.

For example, regarding a technique for precipitating inorganic particles on a fiber such as a cellulose fiber, Patent Document 1 describes a complex in which crystalline calcium carbonate is mechanically bonded to the fiber. Further, Patent Document 2 describes a technique for producing a composite of pulp and calcium carbonate by precipitating calcium carbonate in a pulp suspension by a carbon dioxide gas method. Patent Document 3 is a method for improving the whiteness and cleanliness of used paper fibers by adding a large amount of filler to the fibers for paper and paperboard, in which a slurry of used paper pulp is sent to a gas-liquid contact device to flow. A technique for adhering the filler to the fiber surface by contacting the pulp with an alkali salt slurry in the direction of flow in the hydrolyzed region and sending an appropriate reactive gas to mix with the sedimenting filler has been described.

Further, Patent Documents 4 and 5 disclose a technique for producing a fiber web in which calcium carbonate is efficiently incorporated by precipitating calcium carbonate in a step of forming a fiber web (wet paper).

Japanese Unexamined Patent Publication No. 06-158585 US Pat. No. 5,679,220 US Pat. No. 5,665,205 Japanese Patent Publication No. 2013-521417 U.S. Patent Publication No. 2011/0000633

An object of the present invention is to provide a flame-retardant material using a composite of inorganic particles and fibers.

The inventors of the present invention have succeeded in developing an excellent flame-retardant material by using a composite of flame-retardant inorganic particles and fibers, and have completed the present invention.
The present invention is not limited to this, but includes the following inventions.
(1) A flame-retardant material containing a composite of flame-retardant inorganic particles and fibers.
(2) The flame-retardant material according to (1), wherein the fiber is a cellulose fiber.
(3) The flame-retardant material according to (1) or (2), wherein the flame-retardant inorganic particles are selected from the group consisting of magnesium carbonate, barium sulfate, aluminum hydroxide, and hydrotalcite.
(4) The flame-retardant material according to any one of (1) to (3), which is in the form of a sheet.
(5) The flame-retardant material according to any one of (1) to (4), wherein a composite sheet of flame-retardant inorganic particles and fibers is laminated.
(6) The flame-retardant material according to any one of (1) to (5), wherein a composite sheet of flame-retardant inorganic particles and fibers is bonded to a base material.
(7) The flame-retardant material according to any one of (1) to (6), wherein the average primary particle diameter of the flame-retardant inorganic particles is 1.5 μm or less.
(8) The flame-retardant material according to any one of (1) to (7), wherein the weight ratio of the flame-retardant inorganic particles to the fiber is 5/95 to 95/5.

According to the present invention, it is possible to provide a flame-retardant material using a fiber whose surface is covered with flame-retardant inorganic particles.
When a composite of inorganic particles and fibers is used in the present invention, such a composite has the characteristics of both fibers and inorganic particles, and according to the present invention, it has excellent flame retardancy. It becomes possible to obtain flame-retardant materials. Further, since the composite in which the inorganic particles are attached to the fibers is used, the flame-retardant material can be easily produced, and the yield of the inorganic particles (ash content yield) is also good.

FIG. 1 is a schematic diagram of a reactor used for synthesizing sample 1 (P: pump). FIG. 2 is a schematic diagram of the reactor used for the synthesis of sample 2 (P: pump). FIG. 3 is a schematic diagram of the test device. FIG. 4 is an external photograph of the sample after the combustion test (from the upper left, the pulp sheet, the sheet 1, the sheet 2, and from the lower left, the sheet 3, the sheet 4). FIG. 5 is a schematic diagram of the reactor used for the synthesis of sample 3-3 (left figure, P: pump). The right side of FIG. 5 is an enlarged schematic view of an ultrafine bubble generating portion. FIG. 6A is an external photograph of the sample A after the combustion test (left: combustion surface, right: back surface). FIG. 6B is an external photograph of sample B after the combustion test (left: combustion surface, right: back surface). FIG. 6C is an external photograph of the sample C after the combustion test (left: enlarged combustion surface, right: combustion surface). FIG. 6D is an external photograph of the sample D after the combustion test (left: combustion surface, right: back surface). FIG. 6E is an external photograph of the sample E after the combustion test (left: combustion surface, right: back surface). FIG. 6F is an external photograph of the sample F after the combustion test (left: combustion surface, right: back surface). FIG. 6G is an external photograph of the sample G after the combustion test (left: combustion surface, right: back surface). FIG. 6H is an external photograph of the sample H after the combustion test. FIG. 6I is an external photograph of the sample I after the combustion test (left: combustion surface, right: back surface). FIG. 6J is an external photograph of the sample J after the combustion test (left: combustion surface, right: back surface).

The present invention relates to a flame-retardant material using a composite of inorganic particles and fibers.
fiber
In the present invention, fibers such as cellulose fibers and aramid fibers are complexed with inorganic particles. The fibers constituting the composite are preferably cellulose fibers, but for example, not only natural cellulose fibers but also regenerated fibers (semi-synthetic fibers) such as rayon and lyocell and synthetic fibers can be used without limitation. .. Examples of raw materials for cellulose fibers include pulp fibers (wood pulp and non-wood pulp), cellulose nanofibers, bacterial cellulose, animal-derived cellulose such as squirrel, and algae. Wood pulp is produced by pulping wood raw materials. Just do it. Wood raw materials include red pine, black pine, todo pine, ezo pine, beni pine, larch, fir, tsuga, sugi, hinoki, larch, shirabe, spruce, hiba, douglas fir, hemlock, white fur, spruce, balsam fur, cedar, pine, Conifers such as Merck pine and radiata pine, and their mixed lumbers such as beech, hippo, hannoki, nara, tab, shii, white hippo, larch, poplar, tamo, douglas fir, eucalyptus, mangrove, lauan, acacia and their mixture. The material is exemplified.

The method for pulping a natural material such as a wood raw material (wood raw material) is not particularly limited, and an example is a pulping method generally used in the paper industry. Wood pulp can be classified by the pulping method, for example, chemical pulp distilled by a method such as craft method, sulfite method, soda method, polysulfide method; mechanical pulp obtained by pulping by mechanical force such as refiner, grinder, etc .; chemicals. Examples thereof include semi-chemical pulp; used paper pulp; and deinked pulp obtained by pulping by mechanical force after pretreatment with. The wood pulp may be in an unbleached state (before bleaching) or in a bleached state (after bleaching).

Examples of non-wood-derived pulp include cotton, hemp, sisal hemp, Manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, kozo, and honey.

The pulp fiber may be unbeaten or beaten, and may be selected according to the physical characteristics of the complex sheet, but it is preferable to beat the pulp fiber. This can be expected to improve the sheet strength and promote the fixing of inorganic particles.

Composite fibers of synthetic fibers and cellulose fibers can also be used in the present invention, and for example, composite fibers of polyester fibers, polyamide fibers, polyolefins, acrylic fibers, glass fibers, carbon fibers, various metal fibers and the like and cellulose fibers are also used. be able to.

Further, these cellulose raw materials are further treated to carry out powdered cellulose, chemically modified cellulose such as oxidized cellulose, and cellulose nanofibers: CNF (microfibrillated cellulose: MFC, TEMPO oxidized CNF, phosphoric acid esterified CNF, carboxymethylation). It can also be used as CNF, mechanically crushed CNF, etc.). The powdered cellulose used in the present invention has a constant particle size in the shape of a rod shaft, which is produced by, for example, a method of purifying and drying an undecomposed residue obtained after acid hydrolysis of selected pulp, pulverizing and sieving. A crystalline cellulose powder having a distribution may be used, or commercially available products such as KC Flock (manufactured by Nippon Paper Co., Ltd.), Theoras (manufactured by Asahi Kasei Chemicals), and Abyssel (manufactured by FMC) may be used. The degree of polymerization of cellulose in powdered cellulose is preferably about 100 to 1500, the degree of crystallinity of powdered cellulose by X-ray diffraction is preferably 70 to 90%, and the volume average particle diameter by a laser diffraction type particle size distribution measuring device. Is preferably 1 μm or more and 100 μm or less. The cellulose oxide used in the present invention can be obtained by oxidizing in water with an oxidizing agent in the presence of, for example, an N-oxyl compound and a compound selected from the group consisting of bromide, iodide or a mixture thereof. can. As the cellulose nanofiber, the method of defibrating the cellulose raw material is used. As a defibration method, for example, an aqueous suspension of chemically modified cellulose such as cellulose or oxidized cellulose is mechanically ground or beaten with a refiner, a high-pressure homogenizer, a grinder, a uniaxial or multiaxial kneader, a bead mill or the like. Thereby, a method of defibrating can be used. Cellulose nanofibers may be produced by combining one or more of the above methods. The fiber diameter of the produced cellulose nanofibers can be confirmed by observation with an electron microscope or the like, and is, for example, in the range of 5 nm to 1000 nm, preferably 5 nm to 500 nm, and more preferably 5 nm to 300 nm. When producing this cellulose nanofiber, an arbitrary compound may be further added before and / or after the cellulose is defibrated and / or finely divided to react with the cellulose nanofiber to obtain a modified hydroxyl group. can. Functional groups to be modified include acetyl group, ester group, ether group, ketone group, formyl group, benzoyl group, acetal, hemiacetal, oxime, isonitrile, allen, thiol group, urea group, cyano group, nitro group and azo group. , Aryl group, aralkyl group, amino group, amide group, imide group, acryloyl group, methacryloyl group, propionyl group, propioloyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyle group, octanoyl group, nonanoyl group. , Decanoyl group, undecanoyl group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyyl group, isonicotinoyl group, floyl group, cinnamoyl group and other acyl groups, 2-methacryloyloxyethyl isothia Isocyanate group such as noyl group, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl. Examples thereof include an alkyl group such as a group, an undecyl group, a dodecyl group, a myristyl group, a palmityl group and a stearyl group, an oxylan group, an oxetane group, an oxyl group, a thiilan group and a thietan group. Hydrogen in these substituents may be substituted with a functional group such as a hydroxyl group or a carboxy group. Further, a part of the alkyl group may have an unsaturated bond. The compound used for introducing these functional groups is not particularly limited, and is, for example, a compound having a phosphoric acid-derived group, a compound having a carboxylic acid-derived group, a compound having a sulfuric acid-derived group, or a sulfonic acid-derived compound. Examples thereof include a compound having a group of, a compound having an alkyl group, a compound having a group derived from an amine, and the like. The compound having a phosphoric acid group is not particularly limited, and examples thereof include phosphoric acid, lithium dihydrogen phosphate which is a lithium salt of phosphoric acid, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate. .. Further, examples thereof include sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and sodium polyphosphate, which are sodium salts of phosphoric acid. Further, potassium dihydrogen phosphate, which is a potassium salt of phosphoric acid, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate can be mentioned. Further, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium polyphosphate and the like, which are ammonium salts of phosphoric acid, can be mentioned. Of these, phosphoric acid, a sodium salt of phosphoric acid, a potassium salt of phosphoric acid, and an ammonium salt of phosphoric acid are preferable, and sodium dihydrogen phosphate is preferable from the viewpoint of high efficiency of introducing a phosphoric acid group and easy industrial application. , Disodium hydrogen phosphate is more preferred, but is not particularly limited. The compound having a carboxyl group is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. .. The acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Be done. The derivative of the compound having a carboxyl group is not particularly limited, and examples thereof include an acid anhydride derivative of the compound having a carboxyl group and an acid anhydride derivative of the compound having a carboxyl group. The imide of the acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include an imide of a dicarboxylic acid compound such as maleimide, succinateimide, and phthalateimide. The derivative of the acid anhydride of the compound having a carboxyl group is not particularly limited. For example, at least a part of the hydrogen atom of the acid anhydride of a compound having a carboxyl group, such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, diphenylmaleic acid anhydride, etc., is a substituent (for example, an alkyl group, a phenyl group, etc.). ) Is substituted. Among the compounds having a group derived from the carboxylic acid, maleic anhydride, succinic anhydride, and phthalic anhydride are preferable because they are easily applied industrially and easily gasified, but are not particularly limited. Further, the cellulose nanofibers may be modified in such a manner that the modifying compound physically adsorbs to the cellulose nanofibers without chemically binding. Examples of the compound that is physically adsorbed include a surfactant and the like, and any of anionic, cationic and nonionic compounds may be used. If the above modification is performed before the cellulose is defibrated and / or pulverized, these functional groups can be desorbed and returned to the original hydroxyl group after the defibration and / or pulverization. By applying the above modifications, it is possible to promote the defibration of the cellulose nanofibers and facilitate the mixing with various substances when the cellulose nanofibers are used.

The fibers shown above may be used alone or in combination of two or more. Among them, it is preferable to contain wood pulp or a combination of wood pulp and non-wood pulp and / or synthetic fiber, and more preferably only wood pulp.

In a preferred embodiment, the fibers constituting the complex of the present invention are pulp fibers. Further, for example, the fibrous substance recovered from the wastewater of the paper mill may be supplied to the carbonation reaction of the present invention. By supplying such a substance to the reaction vessel, various composite particles can be synthesized, and fibrous particles and the like can be synthesized in terms of shape.

In the present invention, in addition to the fiber, a substance that is incorporated into the inorganic particles as a product to form composite particles can be used. In the present invention, fibers such as pulp fibers are used, but in addition to these, these substances are further incorporated by synthesizing inorganic particles in a solution containing inorganic particles, organic particles, polymers and the like. It is possible to produce composite particles.

The fiber length of the composited fiber is not particularly limited, but for example, the average fiber length can be about 0.1 μm to 15 mm, and may be 1 μm to 12 mm, 100 μm to 10 mm, 500 μm to 8 mm, or the like.

It is preferable to use the composite fiber in an amount such that 15% or more of the fiber surface is covered with the inorganic particles. For example, the weight ratio of the fiber to the inorganic particles is 5/95 to 95/5. It can be 10/90 to 90/10, 20/80 to 80/20, 30/70 to 70/30, 40/60 to 60/40.

In the composite according to the present invention, 15% or more of the fiber surface is coated with flame-retardant inorganic particles, and if the cellulose fiber surface is coated with such an area ratio, the flame retardancy increases, while the fiber Surface-induced features are reduced.

Flame- retardant inorganic particles In the present invention, a composite composite of flame-retardant inorganic particles and fibers is used as a flame-retardant material. Examples of the flame-retardant inorganic particles include magnesium carbonate, aluminum hydroxide, barium sulfate, hydrotalcite, magnesium hydroxide, calcium carbonate, calcium phosphate and silica, but magnesium carbonate, aluminum hydroxide and barium sulfate are particularly preferable. , Hydrotal site, etc.

(Magnesium carbonate)
In a preferred embodiment, the present invention uses a composite of magnesium carbonate and fibers as a flame retardant material. The average particle size of the magnesium carbonate fine particles constituting the composite according to the present invention is preferably less than 50 μm, but magnesium carbonate having an average particle size of 30 μm or less can also be used. Further, in a preferred embodiment, the average primary particle size of the magnesium carbonate fine particles can be about 10 nm to 3 μm.

Further, the magnesium carbonate obtained in the present invention may take the form of secondary particles in which fine primary particles are aggregated, so that secondary particles can be generated according to the intended use, and the aggregates can be finely divided by pulverization. You can also do it. As crushing methods, ball mills, sand grinder mills, impact mills, high-pressure homogenizers, low-pressure homogenizers, dyno mills, ultrasonic mills, kanda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, breakers, and beaters. , Short-screw extruder, twin-screw extruder, ultrasonic stirrer, household juicer mixer and the like.

In the present invention, magnesium carbonate can be synthesized from a raw material selected from the group consisting of, for example, magnesium oxide, magnesite, dolomite, huntite, magnesium carbonate, magnesium hydroxide, brucite and mixtures thereof. In a preferred embodiment, the magnesium carbonate of the present invention is synthesized from magnesium hydroxide.

The complex according to the present invention may, for example, synthesize magnesium carbonate in a solution containing fibers. Fibers can be dispersed in the reaction solution at the time of obtaining magnesium hydroxide from a magnesium hydroxide precursor typified by magnesium oxide or the like. Further, the fibers can be dispersed in the step of obtaining magnesium carbonate from magnesium hydroxide. In either case, since the reaction solution is alkaline, the fibers can be swelled by immersing the reaction solution in the reaction solution, and a composite of magnesium carbonate and the fibers can be efficiently obtained. The carbonation reaction can be started immediately after the fibers are dispersed, or the carbonation reaction can be started after further promoting the swelling of the fibers by stirring for 15 minutes or more. For example, magnesium carbonate may be synthesized by injecting an aqueous suspension containing magnesium hydroxide into the reaction vessel. As will be described later, it is a preferred embodiment to generate cavitation bubbles when injecting an aqueous suspension of magnesium hydroxide into the reaction vessel, and to synthesize magnesium carbonate in the presence of the cavitation bubbles.

In the present invention, magnesium carbonate fine particles are synthesized in a solution containing fibers, but the method for synthesizing magnesium carbonate can be a known method. For example, magnesium hydroxide can be synthesized from magnesium hydroxide and carbon dioxide gas, and basic magnesium carbonate can be synthesized from magnesium bicarbonate via normal magnesium carbonate. Magnesium carbonate can be obtained from magnesium bicarbonate, normal magnesium carbonate, basic magnesium carbonate and the like by a synthetic method, but it is particularly preferable that the magnesium carbonate according to the complex of the present invention is a basic magnesium carbonate. This is because magnesium bicarbonate has relatively low stability, and normal magnesium carbonate, which is a columnar (needle-shaped) crystal, may be difficult to fix to the fiber. On the other hand, by chemically reacting with basic magnesium carbonate in the presence of fibers, a composite of magnesium carbonate and fibers having the fiber surface coated in a scaly shape can be obtained.

In a preferred embodiment of the present invention, 15% or more of the fiber surface is coated with magnesium carbonate. In a preferred embodiment, the composite of the present invention has a fiber coverage (area ratio) of 25% or more, more preferably 40% or more, but according to the present invention, the coverage is 60% or more. It is also possible to produce 80% or more of the complex.

When magnesium carbonate and fibers are complexed according to the present invention, not only is magnesium carbonate easier to yield to the product, but also a product in which magnesium carbonate is uniformly dispersed without agglomeration, as compared with the case where magnesium carbonate is simply mixed with the fibers. Obtainable. That is, according to the present invention, the yield of the composite of magnesium carbonate and fiber to the product (the weight ratio of the added magnesium carbonate remaining in the product) can be 60% or more, and 70% or more or 90. It can be% or more.

In the present invention, it is preferable that cavitation bubbles are present when synthesizing magnesium carbonate. In this case, it is not necessary to have cavitation bubbles in all of the magnesium carbonate synthetic routes, but cavitation bubbles may be present in at least one step.

For example, in the case of producing basic magnesium carbonate, magnesium oxide MgO is used as a magnesium source, and magnesium carbonate Mg (HCO ₃ ) obtained by blowing carbon dioxide gas CO ₂ into magnesium hydroxide Mg (OH) ₂ obtained from magnesium oxide. ) ₂ is obtained, and basic magnesium carbonate is obtained from magnesium bicarbonate via normal magnesium carbonate MgCO _{3.3H 2O} . By allowing the fiber to be present when synthesizing magnesium carbonate, basic magnesium carbonate can be synthesized on the fiber. In a preferred embodiment, cavitation bubbles may be present when synthesizing magnesium carbonate, but in the present invention, cavitation bubbles may be present at any one of the synthesis steps of magnesium carbonate. In a preferred embodiment, cavitation bubbles can be present at the stage of synthesizing magnesium hydroxide from magnesium hydroxide. In yet another embodiment, cavitation bubbles can be present at the stage of synthesizing basic magnesium carbonate from magnesium bicarbonate or normal magnesium carbonate. In yet another embodiment, the basic magnesium carbonate can be present at the time of aging after synthesis.

Generally, a gas blowing type device and a mechanical stirring type device are known as reaction vessels for producing magnesium carbonate. In the gas blowing type, carbon dioxide gas is blown into a reaction tank containing magnesium hydroxide for reaction, but it is difficult to control the size of bubbles uniformly and finely by simply blowing carbon dioxide gas, and from the viewpoint of reaction efficiency. Has restrictions. On the other hand, in the mechanical stirring type device, a stirrer is provided inside the device, and carbon dioxide gas is introduced near the stirrer to make the carbon dioxide gas into fine bubbles and improve the reaction efficiency with the carbon dioxide gas.

However, when stirring is performed with a stirrer provided inside the reaction tank as in the mechanical stirring type, if the concentration of the reaction solution is high or the carbonization reaction proceeds, the resistance of the reaction solution becomes large and sufficient stirring becomes difficult. It may be difficult to accurately control the chemical reaction, or a considerable load may be applied to the stirrer to perform sufficient stirring, which may be disadvantageous in terms of energy. In addition, if the gas inlet is located at the bottom of the reaction tank and the blades of the stirrer are installed near the bottom of the reaction tank to improve stirring, the components with low solubility stay at the bottom and the gas inlet Or upset the balance of the stirrer. Further, in the conventional method, in addition to the reaction tank, a stirrer and equipment for introducing carbon dioxide gas into the reaction tank are required, which is costly in terms of equipment. In the mechanical stirring type device, the reaction efficiency is improved by finely dividing the carbon dioxide gas supplied near the stirrer by the stirrer, but the carbon dioxide gas cannot be sufficiently refined when the concentration of the reaction solution is high. In terms of carbon dioxide reaction, it was sometimes difficult to accurately control the morphology of the generated inorganic particles. In the present invention, by synthesizing magnesium carbonate in the presence of cavitation bubbles, it becomes possible to efficiently proceed the carbonation reaction and produce uniform magnesium carbonate fine particles on the fiber. In particular, by using jet cavitation, sufficient stirring can be performed without a mechanical stirrer such as a blade. In the present invention, a conventionally known reaction vessel can be used, and of course, a gas blowing type or mechanical stirring type apparatus as described above can be used without any problem, and a nozzle or the like is used for these vessels. It may be combined with the jet cavitation.

When synthesizing magnesium carbonate according to the present invention, the solid content concentration of the aqueous suspension of magnesium hydroxide is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, still more preferably 1 to 1 to 40% by weight. It is about 20% by weight. If the solid content concentration is low, the reaction efficiency is low and the production cost is high, and if the solid content concentration is too high, the fluidity is poor and the reaction efficiency is low. In the present invention, since magnesium carbonate is synthesized in the presence of cavitation bubbles, the reaction solution and the carbon dioxide gas can be suitably mixed even if a suspension (slurry) having a high solid content concentration is used.

As the aqueous suspension containing magnesium hydroxide, a commonly used suspension can be used, and for example, magnesium hydroxide can be mixed with water to prepare the suspension, or magnesium oxide can be added to the water to prepare the suspension. The conditions for preparing a magnesium hydroxide slurry from magnesium oxide are not particularly limited. For example, the concentration of MgO is 0.1% by weight or more, preferably 1% by weight or more, and the temperature is 20 to 100 ° C., preferably 30. It is preferable to treat at ~ 100 ° C. for, for example, 5 minutes to 5 hours (preferably within 2 hours). The device may be a batch type or a continuous type. In the present invention, the preparation of the magnesium hydroxide slurry and the carbonation reaction may be carried out using separate devices or may be carried out in one reaction tank.

(Barium sulfate)
In the present invention, when a complex of a fiber such as a cellulose fiber and barium sulfate is used, it can be synthesized by a known method. Barium sulfate is an ionic crystalline compound composed of barium ions and sulfate ions represented by BaSO ₄ , and is often in the form of a plate or a column, and is sparingly soluble in water. Pure barium sulfate is a colorless crystal, but when it contains impurities such as iron, manganese, strontium, and calcium, it becomes yellowish brown or blackish gray and becomes translucent. It can be obtained as a natural mineral, but it can also be synthesized by a chemical reaction. In particular, synthetic products produced by chemical reactions are used for medical purposes (X-ray contrast agents), and are also widely used in paints, plastics, storage batteries, etc. by applying their chemically stable properties.

In the present invention, a complex of barium sulfate and fiber can be produced by synthesizing barium sulfate in a solution in the presence of fiber. For example, a method of reacting an acid (sulfuric acid or the like) with a base by neutralization, a method of reacting an inorganic salt with an acid or a base, or a method of reacting inorganic salts with each other can be mentioned. For example, barium sulfate can be obtained by reacting barium hydroxide with sulfuric acid or aluminum sulfate, or barium chloride can be added to an aqueous solution containing a sulfate to precipitate barium sulfate.

(Aluminum hydroxide)
In a preferred embodiment, the present invention can use a composite of aluminum hydroxide and fibers as a flame-retardant material. There are various methods for synthesizing aluminum hydroxide, which can be synthesized by adding an alkaline solution to a substance containing an aluminum salt. For example, it can be obtained by adding sodium hydroxide to aluminum sulfate. Further, when aluminum sulfate is used as a raw material for synthesizing the above-mentioned barium sulfate, it is possible to synthesize not only barium sulfate but also aluminum hydroxide at the same time.

(Hydrotalcite)
In general, hydrotalcite is [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] [Ann- _{x / n} ^· mH2O] (in the formula, M ²⁺ is a divalent metal ion and M ³⁺ is a trivalent metal ion. Represents a metal ion of, Ann− _{x / n} ^represents an interlayer anion, and is represented by the general formula of 0 <x <1, where n is the valence of A, 0 ≦ m <1). Here, M ²⁺ , which is a divalent metal ion, is a trivalent metal ion such as Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Ca ²⁺ , Ba ²⁺ , Cu ²⁺ , Mn ²⁺ , etc. An M ³⁺ is, for example, Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Ga ³⁺ , etc., and An-, which is an interlayer anion, has an ^n- value such as OH-, ^{Cl- ,} CO _3- ^, SO _4- ^, etc. Anions can be mentioned, where x is generally in the range 0.2-0.33. The crystal structure has a laminated structure consisting of a two-dimensional basic layer in which the brucite units of a regular octahedron having a positive charge are lined up and an intermediate layer having a negative charge.

Hydrotalcite has been used for various applications utilizing its anion exchange function, for example, for ion exchange materials, adsorbents, deodorants and the like. In addition, by utilizing the combination of constituent metal ions and heating and dehydrating hydrotalcite in which each constituent metal ion is in a good mixed state, or by further heating and calcining, a composite oxide having a uniform composition can be easily obtained. There are also examples of its use in catalyst applications.

The ratio of hydrotalcite in the complex of the present invention can be 10% or more, 20% or more, and preferably 40% or more. The ash content of the complex of hydrotalcite and fiber can be measured according to JIS P 8251: 2003. In the present invention, the ash content of the complex of hydrotalcite and the fiber can be 10% or more, 20% or more, and preferably 40% or more. Further, the complex of the hydrotalcite and the fiber of the present invention preferably contains magnesium or zinc in an ash content of 10% or more, and more preferably 40% or more. The content of magnesium or zinc in the ash can be quantified by X-ray fluorescence analysis.

In the present invention, in a preferred embodiment, 15% or more of the fiber surface is covered with hydrotalcite. In a preferred embodiment, the composite of the present invention has a fiber coverage (area ratio) of 25% or more, more preferably 40% or more, but a coverage of 60% or more according to the present invention. It is also possible to produce a complex of 80% or more. Further, in the composite of hydrotalcite and fiber according to the present invention, in a preferred embodiment, it is possible that hydrotalcite is not only fixed on the outer surface of the fiber or inside the lumen, but also generated on the inside of the microfibril. It is clear from the results of microscopic observation.

When hydrotalcite and fibers are complexed according to the present invention, not only is hydrotalcite easier to yield to the product, but also hydrotalcite is uniformly dispersed without agglomeration, as compared with the case where hydrotalcite is simply mixed with fibers. You can get the product. That is, according to the present invention, the yield of the composite of hydrotalcite and fiber (the weight ratio of the charged hydrotalcite remaining in the product) can be 65% or more, and 70% or more. It can also be 85% or more.

In the present invention, a complex of hydrotalcite and fiber can be produced by synthesizing hydrotalcite in a solution in the presence of fiber.
The method for synthesizing hydrotalcite can be a known method. For example, a fiber is immersed in a carbonate aqueous solution containing carbonate ions constituting an intermediate layer and an alkaline solution (sodium hydroxide, etc.) in a reaction vessel, and then an acid solution (divalent metal ions and trivalents constituting the basic layer) is immersed. A metal salt solution containing metal ions) is added, and hydrotalcite is synthesized by a co-precipitation reaction by controlling the temperature, pH, and the like. Further, in the reaction vessel, the fiber is immersed in an acid solution (a metal salt aqueous solution containing divalent metal ions and trivalent metal ions constituting the basic layer), and then a carbonate aqueous solution containing carbonate ions constituting the intermediate layer. It is also possible to synthesize hydrotalcite by a co-precipitation reaction by dropping an alkaline solution (sodium hydroxide or the like) and controlling the temperature, pH, etc. Although the reaction under normal pressure is common, there is also a method of obtaining it by a hydrothermal reaction using an autoclave or the like (Japanese Patent Laid-Open No. 60-6619).

In the present invention, various chlorides, sulfides, glass oxides, and sulfates of magnesium, zinc, barium, calcium, iron, copper, cobalt, nickel, and manganese are used as sources of divalent metal ions constituting the basic layer. Can be used. Further, as a source of trivalent metal ions constituting the basic layer, various chlorides, sulfides, glass oxides and sulfates of aluminum, iron, chromium and gallium can be used.

In the present invention, water is used for preparing a suspension, and as this water, ordinary tap water, industrial water, groundwater, well water, etc. can be used, as well as ion-exchanged water, distilled water, and ultrapure water. Pure water, industrial wastewater, and water obtained during the manufacturing process can be preferably used.

In the present invention, carbonate ion, nitrate ion, chloride ion, sulfate ion, phosphate ion and the like can be used as the interlayer anion. When carbonate ions are used as interlayer anions, sodium carbonate is used as a source. However, sodium carbonate can be replaced with a gas containing carbon dioxide (carbon dioxide gas), and may be a substantially pure carbon dioxide gas or a mixture with other gases. For example, exhaust gas discharged from an incinerator of a paper mill, a coal boiler, a heavy oil boiler, or the like can be suitably used as a carbon dioxide-containing gas. In addition, a carbonation reaction can be carried out using carbon dioxide generated from the lime firing step.

(Synthesis of complex)
The complex of the present invention can be obtained in one preferred embodiment by synthesizing inorganic particles in the presence of fibers such as cellulose fibers. This is because the fiber surface provides a suitable field for the precipitation of inorganic particles, so that a complex of fibers and inorganic particles can be easily synthesized.

As one preferred embodiment, the average primary particle diameter of the inorganic particles in the composite of the present invention can be, for example, 1.5 μm or less, but the average primary particle diameter can also be 1200 nm or less or 900 nm or less. Further, the average primary particle diameter can be 200 nm or less or 150 nm or less. Further, the average primary particle diameter of the inorganic particles can be 10 nm or more. The average primary particle size can be measured by electron micrograph.

Further, the inorganic particles in the composite of the present invention may take the form of secondary particles in which fine primary particles are aggregated, and secondary particles suitable for the intended use can be generated by the aging step, and by pulverization. It is also possible to make the agglomerates finer. As crushing methods, ball mills, sand grinder mills, impact mills, high-pressure homogenizers, low-pressure homogenizers, dyno mills, ultrasonic mills, kanda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, breakers, and beaters. , Short-screw extruder, twin-screw extruder, ultrasonic stirrer, household juicer mixer and the like.

The complex obtained by the present invention can be used in various shapes, for example, powders, pellets, molds, aqueous suspensions, pastes, sheets, and other shapes. Further, it is also possible to form a molded product such as a mold or particles / pellets by using the composite as a main component together with other materials. The dryer for drying into powder is not particularly limited, but for example, an air flow dryer, a band dryer, a spray dryer and the like can be preferably used.

The composite obtained by the present invention can be used for various purposes by taking advantage of its flame retardant property, for example, paper, fiber, cellulosic composite material, filter material, paint, plastic or other resin, rubber, etc. Elastomers, ceramics, glass, tires, building materials (asphalt, asbestos, cement, boards, concrete, bricks, tiles, plywood, fiberboards, wall materials, ceiling materials, partition boards, wallpaper, etc.), various carriers (catalyst carriers, pharmaceuticals, etc.) Carriers, pesticide carriers, microbial carriers, etc.), excipients (impurity removal, deodorization, dehumidification, etc.), anti-wrinkle agents, clay, abrasives, modifiers, repair materials, heat insulating materials, heat-resistant materials, heat-dissipating materials, moisture-proof materials , Water repellent material, water resistant material, light shielding material, sealant, shield material, insect repellent, adhesive, ink, cosmetics, medical material, paste material, discoloration inhibitor, food additive, tablet excipient, dispersant, retention Shapers, water retention agents, filter aids, essential oil materials, oil treatment agents, oil modifiers, radio wave absorbers, insulating materials, sound insulation materials, vibration isolation materials, semiconductor encapsulants, radiation blocking materials, cosmetics, fertilizers, feeds. , Fragrances, additives for paints and adhesives, sanitary products (disposable diapers, sanitary napkins, incontinence pads, breast milk pads, etc.). Further, it can be used as various fillers, coating agents and the like in the above-mentioned applications. Among these, it can be particularly preferably used for building materials (wall materials, ceiling materials, partition boards, wallpaper, etc.) because of its excellent flame retardancy performance and substance absorption / desorption performance.

Further, when the complex obtained by the present invention is used, particles generally called inorganic fillers and organic fillers and various fibers can be used in combination. For example, as an inorganic filler, calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin, deramikaolin). ), Tarku, zinc oxide, zinc stearate, titanium dioxide, silica made from sodium silicate and mineral acid (white carbon, silica / calcium carbonate complex, silica / titanium dioxide complex), white clay, bentonite, diatomaceous clay, Examples thereof include calcium sulfate, zeolite, an inorganic filler that regenerates and utilizes ash obtained from the deinking process, and an inorganic filler that forms a complex with silica or calcium carbonate in the process of regeneration. As the calcium carbonate-silica composite, in addition to calcium carbonate and / or a light calcium carbonate-silica composite, amorphous silica such as white carbon may be used in combination. Organic fillers include urea-formalin resin, polystyrene resin, phenolic resin, microhollow particles, acrylamide composites, wood-derived substances (fine fibers, microfibril fibers, powdered kenaf), modified insolubilized starch, ungelatinized starch, etc. Can be mentioned. The fibers include not only natural fibers such as cellulose, but also synthetic fibers artificially synthesized from raw materials such as petroleum, recycled fibers (semi-synthetic fibers) such as rayon and lyocell, and inorganic fibers without limitation. Can be used.

The average particle diameter, shape, and the like of the inorganic particles constituting the composite of the present invention can be confirmed by observation with an electron microscope. Further, by adjusting the synthetic conditions of the inorganic particles, the inorganic particles having various sizes and shapes can be composited with the fiber.

The method for producing a complex according to the present invention requires the synthesis of inorganic particles in a solution containing fibers. The synthesis of a complex of barium sulfate and fiber will be described below as an example, but barium sulfate may be another inorganic particle. When using a composite of barium sulfate and fiber, for example, when using an alkaline barium sulfate precursor typified by barium hydroxide as a raw material, the fiber is dispersed in a solution of barium sulfate precursor in advance. Can be swelled, so that a composite of inorganic particles and fibers can be efficiently obtained. The reaction can be started after promoting the swelling of the fibers by stirring these for 15 minutes or more after mixing, but the reaction may be started immediately after mixing. The form of the reaction vessel and the stirring conditions for obtaining the present complex are not particularly limited. For example, a solution containing a precursor of fiber and barium sulfate is stirred and mixed in an open type reaction vessel to synthesize a complex. Alternatively, it may be synthesized by injecting an aqueous suspension containing a precursor of fiber and barium sulfate into a reaction vessel. As will be described later, when an aqueous suspension of a precursor of barium sulfate is injected into a reaction vessel, cavitation bubbles may be generated and barium sulfate may be synthesized in the presence thereof.

In the present invention, the liquid may be sprayed under conditions that generate cavitation bubbles in the reaction vessel, or may be sprayed under conditions that do not generate cavitation bubbles. Further, the reaction vessel is preferably a pressure vessel in any case. The pressure vessel in the present invention is a vessel capable of applying a pressure of 0.005 MPa or more. Under conditions that do not generate cavitation bubbles, the pressure in the pressure vessel is preferably 0.005 MPa or more and 0.9 MPa or less in static pressure.

(Cavitation bubbles)
When synthesizing the complex according to the present invention, barium sulfate can be precipitated in the presence of cavitation bubbles. In the present invention, cavitation is a physical phenomenon in which bubbles are generated and disappear in a short time due to a pressure difference in a fluid flow, and is also called a cavity phenomenon. Bubbles generated by cavitation (cavitation bubbles) are generated as nuclei of very small "bubble nuclei" of 100 microns or less existing in a liquid when the pressure in the fluid becomes lower than the saturated vapor pressure for a very short time.

In the present invention, cavitation bubbles can be generated in the reaction vessel by a known method. For example, cavitation bubbles are generated by injecting a fluid at high pressure, cavitation is generated by stirring at high speed in the fluid, cavitation is generated by causing an explosion in the fluid, and ultrasonic vibration. It is conceivable that cavitation is generated by the child (vibration fluid cavitation).

In particular, in the present invention, since it is easy to generate and control cavitation bubbles, it is preferable to generate cavitation bubbles by injecting a fluid at a high pressure. In this embodiment, by compressing the injected liquid using a pump or the like and injecting it through a nozzle or the like at high speed, cavitation bubbles are generated at the same time as the liquid itself expands due to an extremely high shear force in the vicinity of the nozzle and a rapid depressurization. .. The method using a fluid jet has a high efficiency of generating cavitation bubbles and can generate cavitation bubbles having a stronger decay impact force. In the present invention, controlled cavitation bubbles are present when synthesizing barium sulfate, which is clearly different from cavitation bubbles that cause uncontrollable harm spontaneously occurring in fluid machines.

In the present invention, a reaction solution such as a raw material can be used as it is as an injection liquid to generate cavitation, or some fluid can be injected into the reaction vessel to generate cavitation bubbles. The fluid formed by the liquid jet may be any solid such as liquid, gas, powder or pulp as long as it is in a fluid state, or may be a mixture thereof. Further, if necessary, another fluid such as carbon dioxide gas can be added to the above fluid as a new fluid. The above fluid and the new fluid may be uniformly mixed and jetted, or may be jetted separately.

A liquid jet is a jet of a liquid or a fluid in which solid particles or gas are dispersed or mixed in the liquid, and is a liquid jet containing raw material slurry or bubbles of pulp or inorganic particles. The gas referred to here may contain bubbles due to cavitation.

Further, when injecting the injection liquid through a nozzle or an orifice pipe to generate cavitation, the pressure of the injection liquid (upstream pressure) is preferably 0.01 MPa or more and 30 MPa or less, and 0.7 MPa or more and 20 MPa or less. It is preferably 2 MPa or more and 15 MPa or less, more preferably. If the upstream pressure is less than 0.01 MPa, a pressure difference is unlikely to occur between the upstream pressure and the downstream pressure, and the effect is small. Further, if it is higher than 30 MPa, a special pump and a pressure vessel are required, and energy consumption becomes large, which is disadvantageous in terms of cost. On the other hand, the pressure inside the container (downstream pressure) is preferably 0.005 MPa or more and 0.9 MPa or less as a static pressure.
The ratio of the pressure in the container to the pressure of the jet liquid is preferably in the range of 0.001 to 0.5.

In the present invention, it is also possible to synthesize inorganic particles by injecting an injection liquid under conditions that do not generate cavitation bubbles. Specifically, it is more preferable that the pressure of the injection liquid (upstream side pressure) is 2 MPa or less, preferably 1 MPa or less, and the pressure of the injection liquid (downstream side pressure) is released to 0.05 MPa or less.

The jet velocity of the jet liquid is preferably in the range of 1 m / sec or more and 200 m / sec or less, and preferably in the range of 20 m / sec or more and 100 m / sec or less. When the jet velocity is less than 1 m / sec, the pressure drop is low and cavitation is unlikely to occur, so that the effect is weak. On the other hand, if it is larger than 200 m / sec, high pressure is required and a special device is required, which is disadvantageous in terms of cost.

The place where cavitation is generated in the present invention may be generated in a reaction vessel for precipitating inorganic particles. It is also possible to process with one pass, but it is also possible to circulate as many times as necessary. Further, it can be processed in parallel or in order by using a plurality of generation means.

The injection of the liquid to generate cavitation may be done in a container open to the atmosphere, but preferably in a pressure vessel to control cavitation.

When cavitation is generated by liquid injection, the solid content concentration of the reaction solution is preferably 30% by weight or less, more preferably 20% by weight or less. This is because such a concentration makes it easy for the cavitation bubbles to act uniformly on the reaction system. Further, the aqueous suspension of slaked lime as a reaction solution preferably has a solid content concentration of 0.1% by weight or more from the viewpoint of reaction efficiency.

When synthesizing a complex in the present invention, if the pH of the reaction solution changes as the reaction progresses, the reaction can be controlled by monitoring the pH of the reaction solution.

In the present invention, by increasing the injection pressure of the liquid, the flow velocity of the injection liquid increases, and the pressure decreases accordingly, so that stronger cavitation can be generated. Further, by pressurizing the pressure in the reaction vessel, the pressure in the region where the cavitation bubbles collapse increases, and the pressure difference between the bubbles and the surroundings increases, so that the bubbles collapse violently and the impact force can be increased. The reaction temperature is preferably 0 ° C. or higher and 90 ° C. or lower, and particularly preferably 10 ° C. or higher and 60 ° C. or lower. Generally, it is considered that the impact force is maximized at the midpoint between the melting point and the boiling point. Therefore, in the case of an aqueous solution, about 50 ° C. is preferable, but even if the temperature is lower than that, it is affected by the vapor pressure. Therefore, a high effect can be obtained within the above range.

In the present invention, the energy required to generate cavitation can be reduced by adding a surfactant. The surfactants used include known or novel surfactants, such as nonionic surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, alkylene oxide adducts such as fatty acids. , Anionic surfactants, cationic surfactants, amphoteric surfactants and the like. It may be composed of these single components or a mixture of two or more kinds of components. The amount to be added may be any amount necessary to reduce the surface tension of the sprayed liquid and / or the sprayed liquid.

In one embodiment of the present invention, the complex can be synthesized by synthesizing the inorganic particles in a solution containing fibers, but the method for synthesizing the inorganic particles can be a known method.

In the present invention, water is used for preparing a suspension, and as this water, ordinary tap water, industrial water, groundwater, well water, etc. can be used, as well as ion-exchanged water, distilled water, and super water. Pure water, industrial wastewater, and water obtained when separating and dehydrating the reaction solution can be preferably used.

Further, in the present invention, the reaction solution in the reaction vessel can be circulated and used. By circulating the reaction solution in this way to promote stirring of the solution, the reaction efficiency is increased and it becomes easy to obtain a desired complex.

When producing the complex of the present invention, various known auxiliaries can be further added. For example, a chelating agent can be added, specifically, polyhydroxycarboxylic acids such as citric acid, malic acid and tartaric acid, dicarboxylic acids such as oxalic acid, sugar acids such as gluconic acid, iminodiacetic acid and ethylenediamine tetra. Aminopolycarboxylic acids such as acetic acid and alkali metal salts thereof, alkali metal salts of polyphosphates such as hexamethaphosphate and tripolyphosphate, amino acids such as glutamic acid and aspartic acid and their alkali metal salts, acetylacetone, methyl acetate acetate, acetacetic acid. Examples thereof include ketones such as allyl, saccharides such as sucrose, and polyols such as sorbitol. In addition, as a surface treatment agent, saturated fatty acids such as palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid and linoleic acid, resinous acids such as alicyclic carboxylic acid and avietic acid, their salts, esters and ethers, and alcohol-based materials. Activators, sorbitan fatty acid esters, amide-based and amine-based surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ethers, sodium alphaolefin sulfonate, long-chain alkyl amino acids, amine oxides, alkylamines, fourth A tertiary ammonium salt, an aminocarboxylic acid, a phosphonic acid, a polyvalent carboxylic acid, a condensed phosphoric acid and the like can be added. Further, a dispersant can also be used if necessary. Examples of the dispersant include sodium polyacrylic acid, sucrose fatty acid ester, glycerin fatty acid ester, acrylic acid-maleic acid copolymer ammonium salt, methacrylic acid-naphthoxypolyethylene glycol acrylate copolymer, and methacrylic acid-polyethylene glycol. There are monomethacrylate copolymer ammonium salt, polyethylene glycol monoacrylate and the like. These can be used alone or in combination of two or more. Further, the timing of addition may be before or after the synthetic reaction. Such additives can be added in an amount of preferably 0.001 to 20%, more preferably 0.1 to 10%, based on the inorganic particles.

When synthesizing a complex in the present invention, the reaction conditions are not particularly limited and can be appropriately set according to the intended use. For example, the temperature of the synthesis reaction can be 0 to 90 ° C, preferably 10 to 70 ° C. The reaction temperature can be controlled by a temperature control device, and when the temperature is low, the reaction efficiency is lowered and the cost is high, while when the temperature exceeds 90 ° C., coarse inorganic particles tend to increase.

Further, in the present invention, the reaction can be a batch reaction or a continuous reaction. In general, it is preferable to carry out a batch reaction step because of the convenience of discharging the residue after the reaction. The scale of the reaction is not particularly limited, but the reaction may be carried out on a scale of 100 L or less, or may be reacted on a scale of more than 100 L. The size of the reaction vessel may be, for example, about 10 L to 100 L, or may be about 100 L to 1000 L.

Further, the reaction can be controlled by the conductivity and the reaction time of the reaction solution, and specifically, the time during which the reaction product stays in the reaction vessel can be adjusted and controlled. In addition, in the present invention, the reaction can be controlled by stirring the reaction solution in the reaction vessel or by making the reaction a multi-step reaction.

In the present invention, since the complex as a reaction product is obtained as a suspension, it may be stored in a storage tank or subjected to treatments such as concentration, dehydration, pulverization, classification, aging and dispersion as necessary. Can be done. These can be performed by a known process, and may be appropriately determined in consideration of the application, energy efficiency, and the like. For example, the concentration / dehydration treatment is performed using a centrifugal dehydrator, a sedimentation concentrator, or the like. Examples of this centrifugal dehydrator include a decanter, a screw decanter, and the like. There is no particular limitation on the type of filter or dehydrator, and general ones can be used. For example, a pressurized dehydrator such as a filter press, a drum filter, a belt press, or a tube press can be used. A vacuum drum dehydrator such as an Oliver filter can be preferably used to prepare a calcium carbonate cake. As crushing methods, ball mills, sand grinder mills, impact mills, high-pressure homogenizers, low-pressure homogenizers, dyno mills, ultrasonic mills, kanda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, breakers, and beaters. , Short-screw extruder, twin-screw extruder, ultrasonic stirrer, household juicer mixer and the like. Examples of the classification method include a sieve such as a mesh, an outward type or inward type slit or round hole screen, a vibration screen, a heavy foreign matter cleaner, a lightweight foreign matter cleaner, a reverse cleaner, and a sieving tester. Examples of the dispersion method include a high-speed disperser and a low-speed kneader.

The complex obtained by the present invention can be blended in a filler or a pigment in a suspension state without being completely dehydrated, or can be dried into a powder. The dryer in this case is also not particularly limited, but for example, an air flow dryer, a band dryer, a spray dryer, or the like can be preferably used.

The complex obtained by the present invention can be modified by a known method. For example, in some embodiments, the surface can be made hydrophobic to improve miscibility with a resin or the like.

Flame- retardant material using a composite In the present invention, the above-mentioned composite is used to form a flame-retardant material. For example, when the complex obtained by the present invention is made into a sheet, a sheet having a high ash content can be easily produced, and this can be used as a flame-retardant material. Further, the obtained sheets can be bonded together to make a laminated body (multilayer sheet or multi-layer board) as a flame-retardant material. Examples of the paper machine (paper machine) used for sheet production include a long net paper machine, a round net paper machine, a gap former, a hybrid former, a multi-layer paper machine, and a known paper machine that combines the paper making methods of these devices. Be done. The press line pressure in the paper machine and the calendar line pressure in the case of performing the calendar processing in the subsequent stage can be set within a range that does not affect the operability and the performance of the complex sheet. Further, starch, various polymers, pigments and mixtures thereof may be applied to the formed sheet by impregnation or coating.

At the time of sheeting, a wet and / or dry paper strength agent (paper strength enhancer) can be added. Thereby, the strength of the complex sheet can be improved. Examples of paper strength agents include urea formaldehyde resin, melamine formaldehyde resin, polyamide, polyamine, epichlorohydrin resin, vegetable gum, latex, polyethyleneimine, glyoxal, gum, mannogalactan polyethyleneimine, polyacrylamide resin, and polyvinylamine. , Polyvinyl alcohol and the like; composite polymer or copolymer polymer composed of two or more kinds selected from the above resins; starch and processed starch; carboxymethyl cellulose, guar gum, urea resin and the like. The amount of the paper strength agent added is not particularly limited.

Further, a high molecular polymer or an inorganic substance can be added in order to promote the fixing of the filler to the fiber or to improve the yield of the filler or the fiber. For example, as the coagulant, polyethyleneimine and modified polyethyleneimine containing a tertiary and / or quaternary ammonium group, polyalkyleneimine, dicyandiamide polymer, polyamine, polyamine / epiclohydrin polymer, and dialkyldiallyl quaternary ammonium monomer, dialkyl. Aminoalkyl acrylates, dialkylaminoalkylmethacrylates, dialkylaminoalkylacrylamides, dialkylaminoalkylmethacrylate and acrylamide polymers, polymers consisting of monoamines and epihalohydrin, polymers with polyvinylamine and vinylamine moieties, and cations such as mixtures thereof. In addition to the sex polymer, a cation-rich amphoteric polymer in which an anionic group such as a carboxyl group or a sulfone group is copolymerized in the molecule of the polymer, or a mixture of a cationic polymer and an anionic or amphoteric polymer is used. be able to. Further, as the retention agent, a cationic or anionic or amphoteric polyacrylamide-based substance can be used. In addition to these, a yield system called a so-called dual polymer, in which at least one kind of cationic or anionic polymer is used in combination, can be applied, and at least one kind of anionic bentonite, colloidal silica, polysilicic acid, etc. can be applied. It is a multi-component yield system that uses one or more of inorganic fine particles such as polysilicic acid or polysilicate microgels and their aluminum modifiers, and organic fine particles with a particle size of 100 μm or less, which are so-called micropolymers cross-linked and polymerized with acrylamide. May be good. In particular, when the polyacrylamide-based substance used alone or in combination has a weight average molecular weight of 2 million daltons or more by the ultimate viscosity method, a good yield can be obtained, preferably 5 million daltons or more, more preferably. Can obtain a very high yield when it is the above-mentioned acrylamide-based substance of 10 million daltons or more and less than 30 million daltons. The form of this polyacrylamide-based substance may be an emulsion type or a solution type. The specific composition is not particularly limited as long as the substance contains an acrylamide monomer unit as a structural unit, but for example, a copolymer of a quaternary ammonium salt of an acrylic acid ester and acrylamide, or acrylamide. An ammonium salt quaternized after copolymerizing with and an acrylate ester can be mentioned. The cationic charge density of the cationic polyacrylamide-based substance is not particularly limited.

In addition, depending on the purpose, inorganic particles such as drainage improver, internal sizing agent, pH adjuster, defoaming agent, pitch control agent, slime control agent, bulking agent, calcium carbonate, kaolin, talc, silica, etc. (so-called) Filling fee) and the like. The amount of each additive used is not particularly limited.

The basis weight of the sheet can be appropriately adjusted according to the purpose, but when it is 40 to 1200 g / m ² , the flame retardant effect is high and the drying load at the time of manufacturing is low, which is good. Further, the basis weight of the sheet can be 60 to 1000 g / m ² or 100 to 600 g / m ² .

It is also possible to use a molding method other than sheeting. For example, a method called pulp molding in which a raw material is poured into a mold for suction dehydration and drying, or a method of spreading and drying on the surface of a molded product such as resin or metal is used. After that, molded products having various shapes can be obtained by a method of peeling from the base material or the like. Further, it can be molded into a plastic by mixing a resin, or it can be molded into a ceramic by adding a mineral such as silica or alumina and firing it. In the compounding / drying / molding shown above, only one type of complex may be used, or two or more types of complexes may be mixed and used. When two or more types of complexes are used, a mixture thereof may be used in advance, or a compound, dried, and molded product of each may be mixed later. Further, when the composite sheets are laminated and used, for example, 2 to 20 sheets can be used, preferably 3 to 15 sheets are used, and 4 to 10 sheets are further used. preferable. By forming a laminated body (multilayer sheet or multi-layer board) in which composite sheets are stacked in this way, flame retardancy is greatly improved. When laminating the sheets, a binder or the like may be used as appropriate.

Further, the composite sheet can be bonded to one side or both sides of the base material to obtain a flame-retardant composite board. The number of complex sheets to be bonded may be one or a plurality, but when a plurality of complex sheets are bonded, for example, 2 to 20 sheets can be used, and 3 to 15 sheets can be used. It is preferable to use a sheet, and it is more preferable to use 4 to 10 sheets. The base material is not particularly limited, but various plate materials such as wood, paper, and non-woven fabric can be preferably used.

Further, various organic substances such as polymers and various inorganic substances such as pigments may be added to the molded product of the complex later. For example, a desired substance can be laminated on the surface by applying (coating) to a sheet (including a laminated one or a board-shaped one). For example, a binder such as starch or PVA, a hydrophobic agent such as a sizing agent, an organic or inorganic flame retardant, or the like can be applied. Further, it is possible to further enhance the function by impregnating the sheet (including the laminated one and the board-shaped one) with various substances.

These sheets, laminates and boards can be further processed into a three-dimensional structure such as a honeycomb structure.

The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to such specific examples. Further, unless otherwise specified in the present specification, the concentration, parts and the like are based on weight, and the numerical range is described as including the end points thereof.

Experiment 1: Production of composite sheet and evaluation of flame retardancy (1) Synthesis of composite With the composite of magnesium carbonate and pulp fiber (samples 1-1 to 1-3) and hydrotalcite by the procedure shown below. A pulp fiber composite (Sample 2) was synthesized.

(Sample 1-1: Complex of magnesium carbonate and pulp fiber)
An aqueous suspension was prepared by adding 350 g of magnesium hydroxide (Ube Material Industries, Ltd., UD653) and 350 g of kraft pulp (LBKP / NBKP = 1/1, CSF: 370 ml, average fiber length: 0.9 mm) into water.

As shown in FIG. 1, 35 L of this aqueous suspension is placed in a cavitation device (45 L volume), and while circulating the reaction solution, carbon dioxide gas is blown into the reaction vessel to form magnesium carbonate fine particles and fibers by the carbon dioxide gas method. The complex was synthesized. The reaction start temperature was about 40 ° C., the carbon dioxide gas was a commercially available liquefied gas as a supply source, and the amount of carbon dioxide gas blown was 20 L / min. When the pH of the reaction solution reached about 7.8, the introduction of CO ₂ was stopped (pH before the reaction was 10.3), and then cavitation was generated and the slurry was circulated in the apparatus for 30 minutes. A composite of magnesium carbonate fine particles and pulp fibers was obtained (Sample 1-1, average primary particle size of inorganic particles: 0.8 μm).

In the synthesis of the complex, cavitation bubbles were generated in the reaction vessel by circulating the reaction solution and injecting it into the reaction vessel. Specifically, the reaction solution was sprayed at high pressure through a nozzle (nozzle diameter: 1.5 mm) to generate cavitation bubbles, but the jet speed was about 70 m / s and the inlet pressure (upstream pressure) was high. It was 7 MPa and the outlet pressure (downstream pressure) was 0.3 MPa.

When the weight ratio of fiber: inorganic particles was measured for the obtained complex, it was 50:50 (ash content: 50%). For the weight ratio (ash content), after suction filtration of the complex slurry (3 g in terms of solid content) using filter paper, the residue is dried in an oven (105 ° C., 2 hours), and the organic content is further burned at 525 ° C. , Calculated from the weight before and after combustion.

(Sample 1-2: Composite of magnesium carbonate and pulp fiber)
Except that the amount of magnesium hydroxide charged was 1200 g, the type of kraft pulp used was LBKP (CSF = 490 mL, average fiber length = 0.75 mm), the amount of pulp charged was 300 g, and the total amount of aqueous suspension was 30 L. The composite was synthesized in the same manner as in Sample 1-1 (average primary particle size of inorganic particles: 0.8 μm). The ash content of the obtained complex was 70%.

(Sample 1-3: Composite of magnesium carbonate and pulp fiber)
A complex was synthesized in the same manner as in Sample 1-1 except that the inlet pressure of the apparatus during the reaction was 2 MPa and the outlet pressure was 0.2 MPa (average primary particle size of inorganic particles: 1 μm). The ash content of the obtained complex was 49%.

(Sample 2: Hydrotalcite and pulp fiber complex)
To synthesize Mg ₆ Al ₂ (OH) ₁₆ CO _{3.4H 2} O as hydrotalcite (HT), Na ₂ CO ₃ (Wako Pure Chemicals) and NaOH (Wako Pure Chemicals) as alkaline solutions (A solution). As a mixed aqueous solution and an acid solution (B solution), a mixed aqueous solution of MgCl ₂ (Wako Pure Medicine) and AlCl ₃ (Wako Pure Medicine) was prepared.
-Alkaline solution (A solution, Na ₂ CO ₃ concentration: 0.05 M, NaOH concentration: 0.8 M)
-Acid solution (B solution, Mg-based, MgCl ₂ concentration: 0.3M, AlCl ₃ concentration: 0.1M)
Cellulose fiber was used as the fiber to be composited. Specifically, it contains broad-leaved bleached kraft pulp (LBKP, manufactured by Nippon Paper) and softwood bleached kraft pulp (NBKP, manufactured by Nippon Paper) in a weight ratio of 8: 2, and is a Canadian standard drainage using a single disc refiner (SDR). Pulp fibers adjusted to 390 ml were used (average fiber length 0.8 mm).

Pulp fibers were added to the alkaline solution to prepare an aqueous suspension containing the pulp fibers (pulp fiber concentration: 1.56%, pH: about 12.4). This aqueous suspension (pulp solid content 30 g) is placed in a 10 L reaction vessel, and an acid solution (Mg-based) is dropped while stirring the aqueous suspension to form a complex of hydrotalcite fine particles and fibers. Synthesized. Using an apparatus as shown in FIG. 2, the reaction temperature was 60 ° C., the dropping rate was 15 ml / min, and dropping was stopped when the pH of the reaction solution reached about 7. After the completion of the dropping, the reaction solution was stirred for 30 minutes and washed with 10 times the amount of water to remove the salt to obtain Sample 2 (average primary particle size of inorganic particles: 20 nm). The ash content of sample 2 was 47%.

(2) Manufacture of hand-made sheet The manufactured complex was made into a sheet by the following procedure. For reference, a hand-made sheet was manufactured using LBKP (CSF: 370 ml). The basis weight of each sheet was measured based on JIS P 8124: 1998, and the ash content was measured based on JIS P 8251: 2003.

(Sheet 1 to Sheet 3)
100 ppm of cationic retentant (ND300, manufactured by Hymo) and anionic retentant (FA230, manufactured by Hymo) are added to the aqueous slurry (about 0.5%) of the complex (samples 1-1 to 1-3). ) Was added, and the mixture was stirred at 500 rpm to prepare a suspension. From the obtained suspension, a complex sheet having a basis weight of 90 to 200 g / m ² was produced by a square hand-making machine based on JIS P 8222.

(Sheet 4)
The aqueous slurry of the composite (Sample 2) was prepared to 0.5%, and a composite with a basis weight of 450 g / m ² was prepared by a square hand-scraper based on JIS P 8222 without adding a retention agent. Manuscript body sheet was manufactured.

(Pulp sheet: comparative example)
Using LBKP (CSF: 370 ml), a sheet having a basis weight of about 130 g / m ² was produced.

(3) Evaluation of flame retardancy of the sheet The flammability of the sheet was evaluated by the following procedure based on JIS A 1322 (JIS Z 2150).

A sheet cut to a certain size (sheets 1 to 3: 25 cm x 25 cm, sheet 4: 20 cm x 30 cm) is dried at 50 ° C. for 48 hours, and then left in a desiccator containing silica gel for drying for 24 hours for combustion. It was used as a sample for the test (heating test).

After attaching the sample to the support frame (25 cm x 16 cm) and attaching it to the heating test device without slack, and igniting the gas burner, the sheet 4 is heated for 30 seconds, and the others are heated for 10 seconds. The residual flame time and residual dust time were measured (Fig. 3).

A 45 ° combustibility tester (FL-45M manufactured by Suga Test Instruments Co., Ltd.) was used for the combustion test. A Meckel burner (height 160 mm, inner diameter 20 mm) was used for heating, and only gas was sent in and burned without mixing primary air. The fuel used was liquefied petroleum gas No. 5 (mainly butane and butylene, JIS K 2240), and the flame length was adjusted to 65 mm without a sample attached.
-Carbonization length: The maximum length in the longitudinal direction of the support frame is measured for the carbonized part (carbonized and the strength obviously changes) of the heated surface of the test piece.
・ Residual flame time: Measure the time that the test piece raises the flame and continues to burn from the end of heating.
・ Residual dust: A state in which flameless combustion has occurred since the end of heating.

In JIS A 1322 (JIS Z 2150), the fire protection grade for flame retardancy is defined as follows.
・ Fire protection class 1: carbonization length 5 cm or less, no residual flame, no residual dust after 1 minute ・ Fire protection class 2: carbonization length 10 cm or less, no residual flame, residual dust does not exist after 1 minute ・ Fire protection class 3: carbonization Length 15 cm or less, no residual flame, no residual dust after 1 minute

Tables 1 and 4 show the results of heating with a gas burner for a certain period of time. As is clear from the results, Sheets 1 to 3 (sheets made of a composite of magnesium carbonate and fibers) have a higher flame spread after ignition than pulp sheets (sheets made of LBKP, upper left in FIG. 4). It was confirmed that there were few. In particular, for Sheet 2 (Sheet of Sample 1-2, upper right of FIG. 4) and Sheet 3 (Sheet of Sample 1-3, lower left of FIG. 4), the flame hardly spreads and is equivalent to flameproof first grade. It was confirmed that it has flame retardancy. Further, it was clarified that the sheet 4 (sheet of sample 2, lower right of FIG. 4) has flame retardancy equivalent to flameproof class 2 with a combustion time of 30 seconds.

Experiment 2: Manufacture of complex board and evaluation of flame retardancy (1) Synthesis of complex (Sample 3-1: Composite of magnesium carbonate and fiber)
A composite of magnesium carbonate and fiber was synthesized in the same manner as in Sample 1-3 (ash content: 49%, average primary particle size of inorganic particles: 1 μm).

(Sample 3-2: Composite of magnesium carbonate and fiber)
The amount of magnesium hydroxide charged was 5250 g, the type of kraft pulp used was LBKP (CSF = 500 mL, average fiber length = 0.76 mm), the amount of pulp charged was 3500 g, and the total amount of the aqueous suspension was 170 L. Other than that, it was synthesized in the same manner as in Sample 1-1. The ash content of the obtained complex was 55%, and the average primary particle size of the inorganic particles was 0.8 μm.

(Sample 3-3: Calcium carbonate and fiber complex)
A complex of calcium carbonate and fiber was synthesized by a carbon dioxide gas method using a reaction device as shown on the left of FIG. Ultra fine bubble generator (UFB generator, YJ-9,) for 1500 L of aqueous suspension of calcium hydroxide (Okutama Kogyo, Tama Ace U) 15 kg and LBKP (CSF = 500 mL, average fiber length = 0.76 mm) 15 kg. The reaction solution was circulated at a pump flow rate of 80 L / min using Envirovision Co., Ltd. (Fig. 5, right) (injection speed from the nozzle: 125 L / min · cm ² ). By blowing carbon dioxide gas from the air supply port of the ultrafine bubble generator, a large amount of fine bubbles (diameter 1 μm or less, average particle diameter: 137 nm) containing carbon dioxide gas are generated in the reaction solution, and calcium carbonate is generated on the pulp fiber. Particles were synthesized. The reaction was carried out at a reaction temperature of 20 ° C. and a carbon dioxide gas blowing amount of 20 L / min, and the reaction was stopped when the pH of the reaction solution reached about 7, to obtain Sample 3-3 (pH before the reaction was). About 13). The ash content of the obtained composite of calcium carbonate and pulp fiber was 57%, and the average primary particle size of the inorganic particles was 50 nm.

(Sample 3-4: Barium Sulfate and Aluminum Hydroxide and Fiber Complex)
2% pulp slurry (LBKP / NBKP = 8/2, CSF = 390 mL, average fiber length: about 1.3 mm, solid content 25 kg) and barium hydroxide octahydrate in a container (machine chest, volume: 4 m ³ ) (Nippon Chemical Industrial Co., Ltd., 75 kg) was added and mixed, and then aluminum sulfate (aluminum sulfate band, 98 kg) was added dropwise at about 500 g / min using a perister pump. After completion of the dropping, stirring was continued for 30 minutes as it was to obtain a complex. The ash content of the obtained complex was 75%, and the average temporary particle size of the inorganic particles was about 100 nm.

(2) Manufacture of complex sheet (Sheet 3-1)
In the same manner as in Experiment 1, a sheet was produced by hand from the composite (Sample 3-1) (Sheet 3-1A: Basis weight 600 g / m ² , Sheet 3-1B: 750 g / m ² ).

(Sheet 3-2)
After adjusting the slurry of sample 3-2 to a concentration of about 1%, a cationic retention agent (ND300, Hymo) and an anionic retention agent (FA230, Hymo) are added at 100 ppm each with respect to the solid content to prepare a paper material. A slurry was prepared. Next, a sheet was produced from this paper slurry at a papermaking speed of 10 m / min using a long net paper machine (basis weight: about 150 g / m ² , ash content: about 46%).

(Sheet 3-3: Calcium carbonate complex)
Sample 3-3 was made into a sheet using a Nagami paper machine in the same manner as in Sheet 3-2 (basis weight: about 150 g / m ² , ash content: about 45%).

(Sheet 3-4: LBKP only)
In the same manner as in Sheet 3-2, LBKP (CSF = 500 mL, average fiber length = 0.76 mm) was made into a sheet using a long net paper machine to obtain a sheet consisting only of LBKP (basis weight: about 150 g / m). ^2. Ash content: 0%).

(Sheet 3-5)
To sample 3-4 (concentration: 1%), a cationic retentant (ND300, Hymo) and an anionic retentant (FA230, Hymo) are added at 100 ppm each with respect to solid content to prepare a paper slurry. bottom. Next, a sheet was produced from this paper slurry at a papermaking speed of 10 m / min using a long net paper machine. The basis weight of the obtained sheet was 180 g / m ² , and the ash content was about 67%.

(Sheet 3-6)
A sheet was produced from sample 3-2 in the same manner as in sheet 3-2 except that the basis weight was about 190 g / m ² (basis weight: about 190 g / m ² , ash content: about 46%).

(3) Fabrication of composite board (composite board A, basis weight: approx. 1700 g / m ² , FIG. 6A)
After attaching sheets 3-1A one by one using a vinyl acetate binder to the front and back of a water resistant base paper (manufactured by Nippon Paper Industries, basis weight 500 g / m ² , thickness 0.76 mm, ash content 11%). A composite board was produced by pressing once (4.8 MPa) with a press machine.

(Composite board B, basis weight: approx. 2000 g / m ² , Fig. 6B)
A composite board was produced in the same manner as the composite board A except that the sheet 3-1B was used instead of the sheet 3-1A.

(Composite board C, basis weight: approx. 1250 g / m ² , Fig. 6C)
A composite board was produced in the same manner as the composite board B except that the sheet 3-1B was bonded to only one side of the water resistant base paper.

(Composite board D, basis weight: approx. 2000 g / m ² , Fig. 6D)
A composite board was produced in the same manner as the composite board A except that 5 sheets 3-2 were used on each side.

(Composite board E, basis weight: approx. 2180 g / m ² , Fig. 6E)
Two sheets 3-2 are bonded between two water-resistant base papers (Nippon Paper Industries, basis weight 190 g / m ² , thickness 0.28 mm, ash content 11%), and the outside of the water-resistant base paper. A composite board was prepared by laminating 5 sheets 3-2 on the sheet.

(Composite board F, basis weight: approx. 2000 g / m ² , Fig. 6F)
A composite board was produced in the same manner as the composite board D except that the sheet 3-3 was used instead of the sheet 3-2.

(Composite board G, basis weight: approx. 2000 g / m ² , Fig. 6 G)
A composite board was produced in the same manner as the composite board D except that the sheet 3-4 was used instead of the sheet 3-2.

(Composite board H, basis weight: approx. 2250 g / m ² , Fig. 6H)
Three water-resistant base papers (manufactured by Nippon Paper Industries, basis weight 750 g / m ² , thickness 1 mm, ash content 11%) were laminated to prepare a bonded board.

(Composite board I, basis weight: approx. 1800 g / m ² , Fig. 6I)
Ten sheets 3-5 were bonded together with a vinyl acetate-based binder to prepare a composite board.

(Composite board J, basis weight: approx. 2560 g / m ² , Fig. 6J)
Two sheets 3-6 were bonded to the front and back of the composite board I to prepare a composite board.

After preparing the composite board, it was dried in an oven at 105 ° C. for one night or more, and then a heating experiment was conducted under the same conditions as in Experiment 1. However, in this experiment, the carbonized area was measured instead of the carbonized length, and the heating time was set to 2 minutes. The carbonized area was calculated by measuring the maximum length and the maximum width of the carbonized portion (carbonized and the strength clearly changed) of the heated surface of the test piece, and multiplying them.

The results of the heating test are shown in the table. Further, FIG. 6 shows a photograph of the appearance of the sample after the heating test. As is clear from the experimental results, the composite board (A, B, D, E) in which the magnesium carbonate composite sheet is bonded to the front and back of the water-resistant base paper has a small carbonization area, residual flame time, and residual dust time. It had excellent flame retardancy. Comparing composite boards B and C using the same magnesium carbonate composite sheet, the carbonized area and residual flame time were the same, but the composite board C with the magnesium carbonate sheet bonded to only one side had the remaining dust time. It's been long.

On the other hand, the composite board F (calcium carbonate) and the composite board G (LBKP) both have a long residual flame time of 5 minutes or more, and the composite board H made only of the water-resistant base paper has residual flame and residual dust. The time was as long as 20 minutes or more, and the flame retardancy was low.

Further, although the composite board I had a residual flame time of 20 seconds, there was no residual flame and the carbonized area was relatively small. The composite board J with magnesium carbonate sheets bonded on the front and back has a residual flame time of 10 seconds or less, a residual dust time of 30 seconds or less, and a carbonized area of 50 cm ² or less. Meet (Fire and Disaster Management Agency "Flameproof Knowledge and Practice").

Claims (5)

A flame-retardant material containing a complex in which flame-retardant inorganic particles are fixed on the surface of cellulose fibers.
In the composite, 80 % or more of the surface of the cellulose fiber is coated with flame-retardant inorganic particles, the average primary particle diameter of the flame-retardant inorganic particles is 900 nm or less, and the flame-retardant inorganic particles are carbonic acid. The flame retardant material selected from the group consisting of magnesium and hydrotalcite. The flame-retardant material according to claim 1 , which is in the form of a sheet. The flame-retardant material according to claim 1 or 2 , wherein a composite sheet of flame-retardant inorganic particles and fibers is laminated. The flame-retardant material according to any one of claims 1 to 3 , wherein a composite sheet of flame-retardant inorganic particles and fibers is bonded to a base material. The flame-retardant material according to any one of claims 1 to 4 , wherein the weight ratio of the flame-retardant inorganic particles to the fiber is 5/95 to 95/5.

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