JP2021075599A - Flame-retardant material containing composite fiber and method for producing the same - Google Patents

Abstract

To provide a flame-retardant material containing a composite fiber of an inorganic particle and a fiber.SOLUTION: The present disclosure provides a flame-retardant material containing (a) a composite fiber of a flame-retardant inorganic particle and a fiber and (b) aluminum hydroxide.SELECTED DRAWING: Figure 5

Description

The present invention relates to a flame-retardant material and a method for producing the same. In particular, the present invention relates to flame-retardant materials containing composite fibers of inorganic particles and fibers.

Technologies for improving the incombustibility of materials are being studied in various fields. For example, since wood-based materials such as wood and natural fibers are relatively flammable, they are treated with a chemical such as a flame retardant to make them hard to burn (Patent Documents 1 and 2).

On the other hand, fibers such as wood fibers exhibit various properties based on the functional groups on the surface thereof, but depending on the application, it may be necessary to modify the surface, and so far, the fibers have been surface-modified. Quality technology has been developed. For example, regarding a technique for precipitating inorganic particles on a fiber such as a cellulose fiber, Patent Document 3 describes a composite in which crystalline calcium carbonate is mechanically bonded onto the fiber. Further, Patent Document 4 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.

Japanese Unexamined Patent Publication No. 8-73212 Japanese Unexamined Patent Publication No. 2003-291110 Japanese Unexamined Patent Publication No. 06-158585 U.S. Pat. No. 5,679,220

An object of the present invention is to provide an excellent flame-retardant material.

As a result of diligent research on the above-mentioned problems, it was found that the above-mentioned problems can be solved by using a composite fiber of flame-retardant inorganic particles and fibers in combination with aluminum hydroxide, and the present invention has been completed.

The present invention is not limited to this, but includes the following inventions.
[1] A flame-retardant material containing (a) a composite fiber of flame-retardant inorganic particles and fibers, and (b) aluminum hydroxide.
[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, hydrotalcite, aluminum hydroxide, and silica / alumina.
[4] The flame-retardant material according to [3], wherein the divalent metal ion of the hydrotalcite is magnesium or zinc.
[5] The flame-retardant material according to [3] or [4], wherein the trivalent metal ion of the hydrotalcite is aluminum.
[6] The flame-retardant material according to any one of [1] to [5], wherein 60% or more of the surface of the composite fiber is coated with hydrotalcite fine particles.
[7] The flame-retardant material according to any one of [1] to [6], wherein the ash content of the composite fiber is 10% or more.
[8] The flame-retardant material according to any one of [1] to [7], which is in the form of a sheet.
[9] The flame-retardant material according to any one of [1] to [8], wherein the weight ratio of the composite fiber to aluminum hydroxide is 10/90 to 95/5.
[10] The method for producing a flame-retardant material according to any one of [1] to [9], which comprises forming a flame-retardant material from an aqueous suspension containing the composite fiber and aluminum hydroxide. , The above method.

In the present invention, by further adding aluminum hydroxide to the composite fiber of the flame-retardant inorganic particles and the fiber, an excellent flame-retardant material can be obtained. Further, since the fiber in which the inorganic particles are attached to the fiber is used, the flame-retardant material can be easily produced and the drainage is also good.

FIG. 1 is a schematic view of the synthesizer used in the experiment. FIG. 2 is an electron micrograph of the composite fiber (Sample 1, left: 3000 times, right: 50,000 times). FIG. 3 is an electron micrograph of the composite fiber (Sample 2, left: 3000 times, right: 50,000 times). FIG. 4 is a photograph showing the state of the flammability test (Experiment 2). FIG. 5 is a photograph showing the results of the flammability test (Experiment 2). FIG. 6 is a photograph showing the state of the flammability test (Experiment 3). FIG. 7 is a photograph showing the results of the flammability test (Experiment 3).

The present invention relates to flame-retardant materials containing composite fibers (composites). In the present invention, an excellent flame-retardant material can be obtained by adding aluminum hydroxide after using a composite fiber in which inorganic particles are fixed to the fiber as a base material.

Flame-retardant material (flame-retardant material)
In the present invention, "flame retardant" means hard to burn, "flame retardant" means hard to burn, and "flame retardant material" (flame retardant material) means hard to burn, "flame retardant" (flame retardant). Flame retardant) means an additive that makes the material incombustible. Laws and regulations have been established depending on the material and its use, and detailed standards and evaluation methods for "flame retardant" have been standardized. Among them, terms such as "non-combustible" which means that combustion with flame cannot be performed, "flameproof" which means that the fire does not spread, and other terms such as "fireproof" and "fireproof" are used. However, in the present invention, all of these terms are included in the definition of "flame retardant".

The flame retardant is sometimes called a non-combustible (chemical) agent, and is an agent that improves the incombustibility of the processed product. In the flame-retardant material according to the present invention, the composite fiber is used in combination with aluminum hydroxide. According to the present invention, the drainage of water when forming a sheet or the like from an aqueous suspension is improved. It is presumed that the reason is that since the composite fibers are coated with inorganic particles, the voids of the mat formed during drainage are not filled with aluminum hydroxide, and dehydration is less likely to be inhibited.

In the present invention, the weight ratio of the composite fiber to aluminum hydroxide is preferably 10/90 to 95/5, such as 15/85 to 90/10, 20/80 to 80/20, and 30/70 to 70/30. You can also do it. If the weight ratio of aluminum hydroxide exceeds 90%, the amount of aluminum hydroxide that comes out of the wire during molding increases, so the yield decreases, and if it falls below 5%, it may become non-uniform and a certain flame retardant performance cannot be imparted.

The particle size of aluminum hydroxide used in the present invention is not particularly limited, but for example, one having an average particle size of about 1 nm to 200 μm can be used, and 100 nm to 100 μm, 200 nm to 80 μm, etc. may be used, but preferably 500 nm. It is preferably about 70 μm, more preferably about 1 μm to 60 μm. When the average particle size is 1 μm or less, aluminum hydroxide is filled in the voids of the mat during the production of the molded product, and the production efficiency is lowered due to the deterioration of drainage. When the average particle size is 60 μm or more, the powder is powdered from the dried molded product. It drops and the quality is significantly reduced.

In the present invention, a flame retardant different from aluminum hydroxide may be used in combination, a flame retardant aid or the like may be used in combination, and the amount used may be adjusted according to the desired performance. The flame retardant used together with aluminum hydroxide is not particularly limited, and examples thereof include a boron-based flame retardant containing a boron atom such as boric acid or a salt thereof, polyborate, and zinc borate. Further, a silicon-based flame retardant containing a silicon atom such as silicate or silicone can also be preferably used. In addition, a nitrogen-based flame retardant containing a nitrogen atom such as guanidine or a salt thereof, ammonium sulfate, melamine sulfate, phosphoric acid or a salt thereof, polyphosphate, diethylethylphosphonate, dimethyl (methacryloyloxyethyl phosphate), Phosphate-based difficulties containing phosphorus atoms such as diethyl-2- (acryloyloxy) ethyl phosphate, triethyl phosphate, diethyl-2- (methacryloyl ethyl) phosphate, triphenyl phosphate, tricresyl phosphate, phosphate ester, red phosphorus Flame retardants, compounds containing phosphorus and nitrogen elements (melamine phosphate, guanidine phosphate, guanyl urea phosphate, melamine metaphosphate, melamine polyphosphate, melamine-coated ammonium polyphosphate), guanidine hydrochloride, guanidine hydrobromide, etc. Bromine-based flame retardants such as halogen-containing amino acid salt, decabromodiphenyl ether, tetrabromobisphenol A, hexabromocyclododecane, ethylenebis (tetrabromophthalimide), bis (pentabromophenyl) ethane, and hexabromobenzene, phosphorus. Flame retardant, hydrated aluminum hydroxide, hydrated, consisting of a compound containing two or more of the above elements, such as ammonium salts such as ammonium acid, ammonium sulfate, ammonium borate, ammonium sulfamate, ammonium chloride, ammonium polyphosphate, etc. Hydrometal compounds such as magnesium hydroxide and hydrotalcite, compounds containing antimon such as antimon trioxide, antimon tetraoxide, and antimon pentoxide, tin compounds such as zinc hydroxide and zinc trioxide, and titanium oxide. Examples thereof include inorganic flame retardants such as metal compounds used for general pigments such as.

In the case of a liquid, for example, these flame retardants can be treated by impregnation, coating, or spraying, and as the method, a general impregnation or coating (coating) method can be used. For example, forward rotation roll coater, air knife coater, blade coater, bill blade coater, two-stream coater, twin blade coater, rod coater (bar coater), gate roll coater, reverse roll coater, gravure roll coater, notch bar coater, die coater. , A bead coater, a curtain coater, an impregnation coater, a Seiden coater, a spray coater, or the like can be used to apply the flame retardant.

The timing of the flame retardant treatment may be any of before, during, and after molding into a sheet, mold, board, block, or the like. The process can be shortened if the treatment is performed before or during the molding, and the content of the flame retardant can be easily adjusted if the treatment is performed after the molding.

(Composite fiber of flame-retardant inorganic particles and fiber)
The present invention uses fibers whose surfaces are coated with inorganic particles, and in a preferred embodiment, composite fibers (fiber-inorganic composites) in which 15% or more of the fiber surface is coated with inorganic particles.

In the composite fiber according to the present invention, the fiber and the inorganic particle are not simply mixed, but the fiber and the inorganic particle are bound by a hydrogen bond or the like, so that the inorganic particle is removed from the fiber even by a disintegration treatment or the like. There are few things. The strength of binding of fibers and inorganic particles in the complex can be evaluated, for example, by a numerical value such as ash yield (%, that is, ash content of the sheet ÷ ash content of the complex before dissociation × 100). Specifically, the complex is dispersed in water, adjusted to a solid content concentration of 0.2%, dissociated with a standard disintegrator specified in JIS P 820-1: 2012 for 5 minutes, and then according to JIS P 8222: 2015. The ash yield when sheeted using a 150 mesh wire can be used for evaluation, and the ash yield is 20% by mass or more in a preferable embodiment, and the ash yield is 50% by mass or more in a more preferable embodiment. is there.

(Inorganic particles)
In the present invention, the flame-retardant inorganic particles to be composited with the fiber are not particularly limited, but are preferably water-insoluble or sparingly soluble inorganic particles. Since the synthesis of inorganic particles may be carried out in an aqueous system and the fiber composite may be used in an aqueous system, it is preferable that the inorganic particles are insoluble or sparingly soluble in water.

The inorganic particles referred to here refer to metals or metal compounds. Also the metal compound, a metal cation ^{(e.g., Na +, Ca 2+, Mg} 2+, Al 3+, Ba 2+ , etc.) and anions _{^{(e.g., O 2-, OH -, CO}} 3 2-, PO 4 3 ⁻ , SO ₄ ^2- , NO ₃ −, Si ₂ O ₃ ^2- , SiO ₃ ^2- , Cl ⁻ , F ⁻ , S ^2-, etc.) are bonded by ionic bonding, and are generally called inorganic salts. Say. In the present invention, it is preferable that at least a part of the inorganic particles is a metal salt of calcium, silicic acid, magnesium, barium, aluminum, or a metal particle containing titanium, copper, silver, iron, manganese or zinc.

The method for synthesizing these inorganic particles can be a known method, and either a gas-liquid method or a liquid-liquid method may be used. As an example of the gas-liquid method, there is a carbon dioxide gas method. For example, magnesium carbonate can be synthesized by reacting magnesium hydroxide with carbon dioxide gas. Examples of the liquid-liquid method include reacting an acid (hydrochloric acid, sulfuric acid, etc.) with a base (sodium hydroxide, potassium hydroxide, etc.) by neutralization, reacting an inorganic salt with an acid or base, or using inorganic salts with each other. There is a method of reacting. For example, barium sulfate is obtained by reacting barium hydroxide with sulfuric acid, aluminum hydroxide is obtained by reacting aluminum sulfate with sodium hydroxide, and calcium and aluminum are obtained by reacting calcium carbonate with aluminum sulfate. Complex inorganic particles can be obtained. Further, when synthesizing the inorganic particles in this way, any metal or metal compound can coexist in the reaction solution. In this case, the metal or the metal compound is efficiently incorporated into the inorganic particles and is composited. Can be converted. For example, when phosphoric acid is added to calcium carbonate to synthesize calcium phosphate, titanium dioxide is allowed to coexist in the reaction solution to obtain composite particles of calcium phosphate and titanium.

In the case of synthesizing calcium carbonate, for example, calcium carbonate can be synthesized by a carbon dioxide gas method, a soluble salt reaction method, a lime / soda method, a soda method, or the like, and in a preferred embodiment, calcium carbonate is produced by the carbon dioxide gas method. Synthesize.

Generally, when calcium carbonate is produced by the carbon dioxide gas method, lime (lime) is used as a calcium source, _{and a reconciliation step of adding water to quicklime CaO to obtain slaked lime Ca (OH) 2} and blowing carbon dioxide gas into the slaked lime. Calcium carbonate is synthesized by a _{carbonization step of obtaining CaCO 3 of calcium carbonate.} At this time, a suspension of slaked lime prepared by adding water to quicklime may be passed through a screen to remove low-solubility lime grains contained in the suspension. Further, slaked lime may be directly used as a calcium source. When calcium carbonate is synthesized by the carbon dioxide gas method in the present invention, the carbonation reaction can also be carried out in the presence of cavitation bubbles.

Generally, as a reaction vessel (carbonation reactor: carbonator) for producing calcium carbonate by the carbon dioxide gas method, a gas blowing type carbonator and a mechanical stirring type carbonator are known. In the gas blowing type carbonator, carbon dioxide gas is blown into a carbonation reaction tank containing a slaked lime suspension (lime milk) to react the slaked lime with carbon dioxide gas, but simply blowing carbon dioxide gas is the size of bubbles. Is difficult to control uniformly and finely, and there is a limit in terms of reaction efficiency. On the other hand, in the mechanical stirring type carbonator, a stirrer is provided inside the carbonator, and carbon dioxide gas is introduced near the stirrer to make carbon dioxide gas into fine bubbles and improve the reaction efficiency between slaked lime and carbon dioxide gas. ("Cement, Carbon Dioxide, Lime Handbook", Gihodo Publishing Co., Ltd., 1995, p. 495).

However, when stirring is performed with a stirrer provided inside the carbonation reaction tank like a mechanical stirring type carbonator, 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 is difficult. Therefore, it may be difficult to accurately control the carbonation 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, the gas inlet is located at the bottom of the carbonator, and the blades of the stirrer are installed near the bottom of the carbonator for better stirring. The low-solubility lime screen residue always stays at the bottom due to its rapid settling, blocking the gas outlet and causing the stirrer to become unbalanced. Further, in the conventional method, in addition to the carbonator, a stirrer and equipment for introducing carbon dioxide gas into the carbonator are required, which is costly in terms of equipment. In the mechanical stirring type carbonator, the carbon dioxide gas supplied near the stirrer is finely divided by the stirrer to improve the reaction efficiency between slaked lime and carbon dioxide gas, but the carbon dioxide gas is sufficiently high when the concentration of the reaction solution is high. In terms of carbonation reaction, it was sometimes difficult to accurately control the morphology of the calcium carbonate produced. By synthesizing calcium carbonate in the presence of cavitation bubbles, the carbonation reaction can be efficiently promoted, and uniform calcium carbonate fine particles can be produced. 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 carbonator or a mechanical stirring type carbonator as described above can be used without any problem, and a nozzle or the like can be used in these containers. May be combined with jet cavitation using.

When calcium carbonate is synthesized by the carbon dioxide method, the solid content concentration of the aqueous suspension of slaked lime is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, still more preferably 1 to 20%. It is about% 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. When calcium carbonate is synthesized in the presence of cavitation bubbles, the reaction solution and 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 slaked lime, those generally used for calcium carbonate synthesis can be used. For example, slaked lime is mixed with water to prepare, or quicklime (calcium oxide) is dissolved (digested) with water. Can be prepared. The conditions for reconciliation are not particularly limited, but for example, the concentration of CaO can be 0.1% by weight or more, preferably 1% by weight or more, and the temperature can be 20 to 100 ° C., preferably 30 to 100 ° C. .. The average residence time in the scavenging reaction tank (slaker) is also not particularly limited, but can be, for example, 5 minutes to 5 hours, preferably 2 hours or less. As a matter of course, the slaker may be a batch type or a continuous type. In the present invention, the carbonation reaction tank (carbonator) and the scavenging reaction tank (slaker) may be separated, or one reaction tank may be used as the carbonation reaction tank and the scavenging reaction tank. Good.

When synthesizing magnesium carbonate, 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 hydroxide via normal magnesium carbonate. Magnesium carbonate can be obtained from magnesium bicarbonate, normal magnesium carbonate, basic magnesium carbonate, etc. by a synthetic method, but it is particularly preferable that the magnesium carbonate according to the composite fiber of the present invention is a basic magnesium carbonate. This is because magnesium carbonate 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, it is possible to obtain a composite fiber of magnesium carbonate and fibers in which the fiber surface is coated in a scaly shape or the like.

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 and increasing the contact between the reaction solution and the carbon dioxide gas, the reaction efficiency is increased and it becomes easy to obtain desired inorganic particles.

In the present invention, a gas such as carbon dioxide (carbon dioxide) can be blown into the reaction vessel and mixed with the reaction solution. According to the present invention, carbon dioxide gas can be supplied to the reaction solution without a gas supply device such as a fan or a blower, and the carbon dioxide gas is refined by cavitation bubbles or ultrafine bubbles, so that the reaction is efficient. It can be carried out.

In the present invention, the carbon dioxide concentration of the gas containing carbon dioxide is not particularly limited, but a higher carbon dioxide concentration is preferable. The amount of carbon dioxide gas introduced into the injector is not limited and can be appropriately selected. For example, it is preferable to use carbon dioxide gas having a flow rate of 100 to 10,000 L / hour per 1 kg of slaked lime.

The carbon dioxide-containing gas of the present invention may be a substantially pure carbon dioxide gas or a mixture with other gases. For example, in addition to carbon dioxide gas, a gas containing an inert gas such as air or nitrogen can be used as the gas containing carbon dioxide. As the gas containing carbon dioxide, in addition to carbon dioxide gas (carbon dioxide gas), exhaust gas discharged from an incinerator of a papermaking factory, a coal boiler, a heavy oil boiler, or the like can be suitably used as the carbon dioxide-containing gas. In addition, a carbonation reaction can be carried out using carbon dioxide generated from the lime firing step.

When synthesizing hydrotalcite, a known method can be used for synthesizing hydrotalcite. For example, the fibers are 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 trivalent metal ions constituting the basic layer) is immersed. (Aqueous metal salt solution containing metal ions) is added, and the temperature, pH, etc. are controlled to synthesize hydrotalcite by a co-precipitation reaction. Further, in the reaction vessel, the fibers are 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. Hydrotalcite can also be synthesized by dropping an alkaline solution (sodium hydroxide or the like) and controlling the temperature, pH, etc. by a co-precipitation reaction. Although the reaction at normal pressure is common, there is also a method of obtaining the reaction 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, 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 substantially pure carbon dioxide gas or a mixture with other gases. For example, exhaust gas emitted from an incinerator, a coal boiler, a heavy oil boiler, or the like in a paper mill 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.

When synthesizing alumina and / or silica, one or more of an inorganic acid or an aluminum salt is used as a starting material for the reaction, and an alkali silicate is added to the synthesis. Alkaline silicate is used as the starting material, and one or more of the inorganic acid and the aluminum salt can be added for synthesis, but it is more produced when the inorganic acid and / or the aluminum salt is used as the starting material. Good fixation of substances to fibers. The silica and / or alumina composite fiber obtained in the present invention has a Si / Al of 4 or more as a result of measuring ash baked at 525 ° C. for 2 hours in an electric furnace by fluorescent X-ray diffraction. It is preferably 4 to 30, more preferably 4 to 20, and even more preferably 4 to 10. Further, since the silica and / or alumina obtained in the present invention is an amorphous substance, a clear peak derived from the crystalline substance is not detected when the ash is measured by X-ray diffraction. The inorganic acid is not particularly limited, and for example, sulfuric acid, hydrochloric acid, nitric acid and the like can be used. Of these, sulfuric acid is particularly preferable from the viewpoint of cost and handling. Examples of the aluminum salt include aluminum sulfate band, aluminum chloride, polyaluminum chloride, alum, potassium alum and the like, and among them, the aluminum sulfate band can be preferably used. Examples of the alkali silicate include sodium silicate and potassium silicate, but sodium silicate is preferable because it is easily available. The molar ratio of silicic acid to alkali may be any, but generally, the one distributed as No. 3 silicic acid has _{a molar ratio of about SiO 2} : Na ₂ O = 3 to 3.4: 1, and this is preferably used. Can be used. In the present invention, water is used for the preparation of suspensions and the like, and as the water, ordinary tap water, industrial water, groundwater, well water and the like can be used, as well as ion-exchanged water and distilled water. Ultra-pure water, industrial waste water, and water obtained in the carbonization step can be preferably used.

When synthesizing calcium sulfate, a known method can be used for synthesizing calcium sulfate. For example, calcium sulfate can be synthesized as a salt obtained by a neutralization reaction of sulfuric acid and calcium hydroxide in a system by immersing fibers in a reaction vessel.

When synthesizing calcium silicate, a known method can be used for synthesizing calcium silicate. For example, it can be obtained by hydrothermal synthesis by adding a calcium source such as calcium oxide or calcium hydroxide and a silica source such as α-quartz to an autoclave.

The composite fiber of the present invention can be obtained by synthesizing inorganic particles in the presence of fibers such as cellulose fibers. This is because the fiber surface serves as a suitable field for the precipitation of inorganic particles, so that composite fibers can be easily synthesized. As a method for synthesizing the composite fiber, for example, a solution containing a precursor of the fiber and the inorganic particle may be stirred and mixed in an open reaction tank to synthesize the composite, or a precursor of the fiber and the inorganic particle may be synthesized. It may be synthesized by injecting an aqueous suspension containing the above into a reaction vessel. As will be described later, when an aqueous suspension of an inorganic precursor is injected into the reaction vessel, cavitation bubbles or ultrafine bubbles may be generated, and the inorganic particles may be synthesized in the presence of the cavitation bubbles.

In the present invention, the liquid may be injected under conditions that cause cavitation bubbles or ultrafine bubbles in the reaction vessel, or may be injected under conditions that do not generate cavitation bubbles or ultrafine 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 composite fiber according to the present invention, inorganic particles 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 aspect, 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 shearing force near 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 inorganic particles, which is clearly different from cavitation bubbles that cause uncontrollable harm spontaneously occurring in a fluid machine.

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 a liquid, a gas, a solid such as powder or pulp, or a mixture thereof as long as it is in a fluid state. 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 injected, or may be injected 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 refers to 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.

Flow velocity and pressure are of particular importance because cavitation occurs when the liquid is accelerated and the local pressure drops below the vapor pressure of the liquid. The cavitation state is represented by the cavitation number σ, which is a dimensionless number, and a large cavitation number indicates that the flow field is in a state in which cavitation is unlikely to occur.

As for the cavitation conditions in the present invention, the above-mentioned cavitation number σ is preferably 0.001 or more and 0.5 or less, preferably 0.003 or more and 0.2 or less, and 0.01 or more and 0.1 or less. Is particularly preferable. When the cavitation number σ is less than 0.001, the effect is small because the pressure difference with the surroundings when the cavitation bubbles collapse is small, and when it is larger than 0.5, the pressure difference of the flow is low and the cavitation is It becomes difficult to occur.

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 with the downstream pressure is unlikely to occur 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 in static pressure. The ratio of the pressure in the container to the pressure of the injection 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 a jet solution 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 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 synthesizing inorganic particles. It is also possible to process with one pass, but it is also possible to circulate as many times as necessary. Furthermore, it can be processed in parallel or in a permutation using a plurality of generating means.

The injection of the liquid to generate cavitation may be done in a container open to the atmosphere, but is preferably done 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, which is a reaction solution, preferably has a solid content concentration of 0.1% by weight or more from the viewpoint of reaction efficiency.

In the present invention, for example, when synthesizing a complex of calcium carbonate and cellulose fibers, the pH of the reaction solution is on the basic side at the start of the reaction, but changes to neutral as the carbonation reaction proceeds. Therefore, 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. Furthermore, it is possible to promote the dissolution and dispersion of the carbon dioxide gas to be introduced. 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 consist of these single components or a mixture of two or more components. The amount added may be any amount necessary to reduce the surface tension of the injection liquid and / or the injection liquid.

(Ultra fine bubble)
In the present invention, an ultrafine bubble containing carbon dioxide can be generated by injecting a gas and a liquid containing carbon dioxide into the reaction vessel. The average particle size of the ultrafine bubbles is not particularly limited as long as it is 1000 nm or less, preferably 1 to 800 nm, more preferably 10 to 500 nm, and may be 50 to 300 nm. In the present invention, since it is not necessary to generate cavitation bubbles by injecting a liquid at a high pressure, it becomes possible to synthesize inorganic particles such as calcium carbonate without consuming a large amount of energy.

Further, the ultrafine bubble containing carbon dioxide gas preferably exists in the system for 10 seconds or more, and can exist for 60 seconds or more from the generation of the ultrafine bubble to the disappearance of the ultrafine bubble. Is more preferable. Among them, the ultrafine bubble according to the present invention is more preferably those that can be present in the system for 5 minutes or more, particularly preferably those that can be present for 15 minutes or more, and may be those that can be present for 60 minutes or more. If it is an ultrafine bubble that can exist in the system for a long time, bubbles containing carbon dioxide gas can stay in the reaction solution for a long time, so that fine inorganic carbonate particles can be efficiently produced. ..

Ultrafine bubbles can be generated according to a known production method. For example, it can be manufactured by a gas-liquid mixing shear type, a static mixer type, a Venturi type, a cavitation type, a steam condensing type, an ultrasonic type, a swirling jet type, a pressure melting type, a micropore type, or the like. Among these, the gas-liquid mixed shear type and the swirling jet type are preferable because ultrafine bubbles can be easily generated by using a pump or the like. In a preferred embodiment, carbon dioxide can be taken in by naturally aspirated from the intake section (self-priming type).

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. Although cavitation bubbles can be generated in the reaction vessel by a known method, the conventional method requires a large amount of energy and cannot be said to be efficient. 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 the present invention, a reaction solution such as a raw material can be used as it is as an injection liquid to generate ultrafine bubbles, or some fluid can be injected into the reaction vessel to generate ultrafine bubbles. The fluid formed by the liquid jet may be a liquid, a gas, a solid such as powder or pulp, or a mixture thereof as long as it is in a fluid state. 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 injected, or may be injected 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 refers to a liquid jet containing a slurry or bubbles of pulp or inorganic particles. In the present invention, bubbles containing carbon dioxide gas may be contained.

Ultrafine bubbles can be generated using a known device. For example, when the injection liquid is injected through a nozzle or an orifice tube to generate bubbles, the pressure at the place where the injection liquid is injected from the nozzle into the reaction vessel ( P1 (also referred to as upstream pressure in the present specification) is not particularly limited, but is preferably 0.05 to 4.5 MPa, for example. In another embodiment, the pressure P1 can be 5 MPa or more and 10 MPa or less. If the upstream pressure is less than 0.01 MPa, a pressure difference between the reaction vessel outlet pressure (P2, also referred to as the downstream pressure in the present specification) is unlikely to occur, 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 static pressure (P2) at the outlet of the reaction vessel is preferably 0.005 MPa or more and 0.9 MPa or less. The ratio (P2 / P1) of the pressure in the container to the pressure of the injection liquid is preferably in the range of 0.001 to 0.5. The pressure (dynamic pressure) can be measured using a pressure gauge.

The flow velocity when the gas containing carbon dioxide gas and the liquid are injected from the nozzle is preferably 100 to 640 L / min · cm2, and may be 100 to 300 L / min · cm2. 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 ultrafine bubbles are unlikely to occur, so 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 the bubbles are generated in the present invention may be generated in the reaction vessel where the reaction by the carbon dioxide gas method occurs. It is also possible to process with one pass, but it is also possible to circulate as many times as necessary. Furthermore, it can be processed in parallel or in a permutation using a plurality of generating means.

The injection of the liquid may be carried out in a container open to the atmosphere, but is preferably carried out in a closed pressure vessel.
When ultrafine bubbles are generated by liquid injection, the solid content concentration of the aqueous suspension of slaked lime as a 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 bubbles to act uniformly on the reaction system. Further, the aqueous suspension of slaked lime, which is a reaction solution, preferably has a solid content concentration of 0.1% by weight or more from the viewpoint of reaction efficiency.

In the present invention, the pH of the reaction solution is on the basic side at the start of the reaction, but changes to neutral as the carbonation reaction proceeds. Therefore, the reaction can be controlled by monitoring the pH of the reaction solution.

In the present invention, 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 ultrafine bubbles 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 consist of these single components or a mixture of two or more components. The amount added may be any amount necessary to reduce the surface tension of the injection liquid and / or the injection liquid.

As one preferred embodiment, the average primary particle size of the inorganic particles in the composite fiber of the present invention can be, for example, 1.5 μm or less, but the average primary particle size is 1200 nm or less, 900 nm or less, 700 nm or less, 500 nm or less. , 300 nm or less, and further, the average primary particle size can be 200 nm or less, 150 nm or less, or 100 nm. Further, the average primary particle diameter of the inorganic particles can be 10 nm or more, 30 nm or more, and 50 nm or more. The average primary particle size can be measured by electron micrograph.

Further, the inorganic particles in the composite fiber 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 an aging step, or by pulverization. The agglomerates can also be made finer. As a crushing method, a ball mill, a sand grinder mill, an impact mill, a high pressure homogenizer, a low pressure homogenizer, a dyno mill, an ultrasonic mill, a kanda grinder, an attritor, a stone mill, a vibration mill, a cutter mill, a jet mill, an extruder, and a beating machine. , Short-screw extruder, twin-screw extruder, ultrasonic stirrer, household juicer mixer and the like.

(Synthesis of composite fibers)
In one embodiment of the present invention, the composite can be synthesized by synthesizing the inorganic particles in a solution containing fibers, and the method for synthesizing the inorganic particles can be a known method.

When barium sulfate is used as the inorganic particles, barium sulfate may be synthesized in a solution containing fibers. For example, when an alkaline barium sulfate precursor typified by barium hydroxide is used as a raw material, the fibers can be swelled by dispersing the fibers in a solution of the barium sulfate precursor in advance, so that the fibers can be swelled efficiently. And a composite of fibers can be 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 composite fiber are not particularly limited. For example, a solution containing a precursor of fiber and barium sulfate is stirred and mixed in an open reaction tank to synthesize a composite. Alternatively, it may be synthesized by injecting an aqueous suspension containing a precursor of fiber and barium sulfate into a reaction vessel. In this step, an aging time may be provided during or after the reaction for the purpose of controlling the particle size of the inorganic substance and optimizing the reaction conditions (nucleation reaction and growth reaction). For example, if the inorganic substance can be easily synthesized in the low pH band, the state may be maintained, or if the growth reaction of the inorganic particles takes a long time, the solution may be continuously stirred. Further, in this case, the aging time and the pH are not particularly limited, and any of a neutral range of pH 6 to 8, an acidic range of pH 6 or less, and an alkaline range of pH 8 or higher can be applied.

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 and promoting the stirring of the solution, the reaction efficiency is increased and it becomes easy to obtain a desired complex of inorganic particles and fibers.

When producing the composite fiber 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. Amino polycarboxylic acids such as acetic acid and alkali metal salts thereof, alkali metal salts of polyphosphates such as hexametaphosphate and tripolyphosphate, amino acids such as glutamic acid and aspartic acid and alkali metal salts thereof, acetylacetone, methyl acetoacetate, acetoacetic acid. Examples thereof include ketones such as allyl, sugars 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, resin acids such as alicyclic carboxylic acid and avietic acid, their salts, esters and ethers, and alcohols. Activators, sorbitan fatty acid esters, amide and amine surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ether, 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 polyacrylate, 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 composite fiber 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 controller, 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 the 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, for example, may be about ^{10L~100L, 100L~1000L,} may be 1m 3 (1000L) ~100m about ^3.

Further, the reaction can be controlled by the conductivity of the reaction solution and the reaction time, 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 making the reaction a multi-step reaction.

In the present invention, since the composite fiber which is 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 do. 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 make a cake. As a crushing method, a ball mill, a sand grinder mill, an impact mill, a high pressure homogenizer, a low pressure homogenizer, a dyno mill, an ultrasonic mill, a kanda grinder, an attritor, a stone mill, a vibration mill, a cutter mill, a jet mill, an extruder, and a beating machine. , 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 composite fiber in the present invention can be blended with 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 composite fiber of 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.

(fiber)
The composite fiber used in the present invention is a composite of cellulose fiber and inorganic particles. As the cellulose fibers constituting the composite fiber, 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 the raw material of the cellulose fiber include plant-derived pulp fiber, cellulose nanofiber, bacterial cellulose, animal-derived cellulose such as squirrel, and algae. Wood pulp may be produced by pulping the wood raw material. Wood raw materials include red pine, black pine, todo pine, spruce, beni pine, larch, fir, tsuga, sugi, hinoki, larch, shirabe, spruce, hiba, douglas fur, hemlock, white fur, spruce, balsam fur, cedar, pine, Coniferous trees such as Merck pine and Radiata pine, and their mixed materials, beech, hippopotamus, hannoki, nara, tab, shii, white hippopotamus, larch, poplar, tamo, doroyanagi, eucalyptus, mangrove, lauan, acacia and other broad-leaved trees 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 a pulping method generally used in the paper industry is exemplified. Wood pulp can be classified by the pulping method, for example, chemical pulp that has been vaporized by methods such as the craft method, sulfite method, soda method, and polysulfide method; mechanical pulp obtained by pulping with mechanical force such as a refiner and grinder; 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 (before bleaching) state or in a bleached (after bleaching) state.

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 mitsumata.

The pulp fiber may be unbeaten or beaten, and may be selected depending on the use of the composite fiber. By beating, it is possible to improve the strength of the sheet, improve the BET specific surface area, and promote the fixation of the inorganic particles. On the other hand, by using the composite fiber without beating, it is possible to suppress the risk that the inorganic substance is detached together with the fibrils when the composite fiber is stirred and / or kneaded in the matrix, and it is also used as a reinforcing material for cement and the like. In some cases, the effect of improving the strength is enhanced because the fiber length can be maintained for a long time. The degree of beating of fibers can be expressed by the Canadian Standard freeness (CSF) specified in JIS P 811-2: 2012. As the beating progresses, the drainage state of the fiber decreases, and the degree of drainage decreases. The fiber used for synthesizing the composite fiber can be of any degree of drainage, but a fiber of 600 mL or less can be preferably used. For example, in the case of producing a sheet using the composite fiber of the present invention, it is possible to suppress paper breakage during continuous papermaking of cellulose fibers having a drainage degree of 600 mL or less. That is, if a treatment for increasing the fiber surface area such as beating is performed in order to improve the strength and the specific surface area of the composite fiber sheet, the degree of drainage decreases, but the cellulose fiber subjected to such treatment can also be preferably used. The lower limit of the drainage degree of the cellulose fiber is more preferably 50 mL or more, and further preferably 100 mL or more. When the degree of drainage of the cellulose fibers is 200 mL or more, the operability of continuous papermaking is good.

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 oxide CNF, phosphoric acid esterified CNF, carboxymethylation). It can also be used as CNF, machine crushed CNF, etc.). The powdered cellulose used in the present invention has a constant particle size in the shape of a rod, 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. Crystalline cellulose powder having a distribution may be used, or commercially available products such as KC Flock (manufactured by Nippon Paper Industries), 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. it can. As the cellulose nanofiber, the method of defibrating the above-mentioned 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 the cellulose nanofibers, before and / or after the cellulose is defibrated and / or finely divided, an arbitrary compound may be further added and reacted with the cellulose nanofibers to modify the hydroxyl groups. it can. Functional groups to be modified include acetyl group, ester group, ether group, ketone group, formyl group, benzoyl group, acetal, hemiacetal, oxime, isonitrile, allene, 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, heptanoil group, octanoyl group, nonanoyl group. , Decanoyl group, undecanoyl group, dodecanoyl group, myritoyl 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 thiirane 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 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, and 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 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, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium polyphosphate, which are sodium salts of phosphoric acid, can be mentioned. Further, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium polyphosphate, which are potassium salts of phosphoric acid, 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 from the viewpoint of high efficiency of introducing a phosphoric acid group and easy industrial application, and sodium dihydrogen phosphate. , Disodium hydrogen phosphate is more preferable, but it 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 imide of an acid anhydride of a compound having a carboxyl group and a derivative of an acid anhydride of a 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 hydrogen atoms of the acid anhydride of a compound having a carboxyl group such as dimethylmaleic anhydride, diethylmalic anhydride, diphenylmaleic anhydride and the like are substituents (for example, alkyl group, phenyl group and the like). ) Replaced by). 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 way that the compound to be modified physically adsorbs to the cellulose nanofibers without being chemically bonded. 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 defibration and / or pulverization of cellulose, these functional groups can be eliminated after defibration and / or pulverization to return to the original hydroxyl group. By applying the above modifications, it is possible to promote the defibration of the cellulose nanofibers and to facilitate mixing with various substances when the cellulose nanofibers are used.

Synthetic fibers include polypropylene, polyester, polyamide, polyolefin, acrylic fibers, nylon, polyurethane, aramid, semi-synthetic fibers include acetate, triacetate, promix, and recycled fibers include rayon, polynosic, lyocell, cupra, and bemberg. Examples of the inorganic fiber include glass fiber, ceramic fiber, eco-soluble inorganic fiber, carbon fiber, and various metal fibers.

The fibers shown above may be used alone or in combination of two or more. For example, the fibrous material recovered from the wastewater of a 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 fibers, a substance that is incorporated into 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.

The fiber diameter of the fiber to be composited is not particularly limited, but for example, the average fiber diameter can be about 1 nm to 100 μm, 10 nm to 100 μm, 0.15 μm to 100 μm, 1 μm to 90 μm, 3 to 50 μm, 5 to 30 μm. And so on.

The composite fiber is preferably used in an amount such that 15% or more of the fiber surface is covered with 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 a preferred embodiment, the composite fiber according to the present invention has 15% or more of the fiber surface coated with inorganic particles, and if the surface of the cellulose fiber is coated with such an area ratio, the characteristics caused by the inorganic particles are largely generated. On the other hand, the features caused by the fiber surface become smaller. In a preferred embodiment of the present invention, 30% or more of the fiber surface is coated with inorganic particles, more preferably 50% or more of the fiber surface, and further preferably 60% or more of the fiber surface is coated with inorganic particles. More than 80% of the fiber surface may be coated with inorganic particles.

Forms of Flame Retardant Materials The flame retardant materials according to the present invention can be used in various shapes, for example, powders, pellets, molds, aqueous suspensions, pastes, sheets, boards, blocks, threads. , Other shapes can be used. Further, it is also possible to form a molded product such as a mold or particles / pellets by using a composite fiber 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 flame-retardant material according to the present invention can be used for various purposes, for example, paper, fiber, cellulose-based composite material, filter material, paint, plastic or other resin, rubber, elastomer, ceramic, glass, tire, and the like. Building materials (asphalt, asbestos, cement, boards, concrete, bricks, tiles, plywood, fiberboards, decorative boards, ceiling materials, wall materials, flooring materials, roofing materials, etc.), furniture, various carriers (catalyst carriers, pharmaceutical carriers, etc.) Agricultural chemical carriers, microbial carriers, etc.), adsorbents (impurity removal, deodorization, dehumidification, etc.), anti-wrinkle agents, clay, abrasives, modifiers, repair materials, heat insulating materials, heat resistant materials, heat radiating materials, moisture proofing materials, repellent Water material, water resistant material, light-shielding material, sealant, shield material, insect repellent, adhesive, medical material, paste material, discoloration inhibitor, radio wave absorber, insulating material, sound insulation material, interior material, anti-vibration material, semiconductor encapsulation It can be widely used in all applications such as materials, radiation blocking materials, and flame-retardant materials. Further, it can be used as various fillers, coating agents and the like in the above-mentioned applications. Of these, radiation shielding materials, flame-retardant materials, building materials, furniture, interior materials, and heat insulating materials are preferable.

The flame-retardant material of the present invention may be applied to papermaking applications, for example, printing paper, newspaper, inkjet paper, PPC paper, kraft paper, high-quality paper, coated paper, finely coated paper, wrapping paper, thin leaf paper, color. High-quality paper, cast-coated paper, non-carbon paper, label paper, heat-sensitive paper, various fancy papers, water-soluble paper, release paper, process paper, wallpaper base paper, flame-retardant paper (non-combustible paper), laminated board base paper, printed electronics paper , Battery separator, cushion paper, tracing paper, impregnated paper, ODP paper, building material paper (wallpaper, etc.), decorative paper, envelope paper, tape paper, heat exchange paper, synthetic fiber paper, sterilized paper, water resistant paper, oil resistant Paper, heat-resistant paper, photocatalyst paper, decorative paper (greasy paper, etc.), various sanitary papers (toilet paper, tissue paper, wipers, diapers, sanitary goods, etc.), tobacco paper, paperboard (liner, core base paper, white paperboard, etc.) , Paper plate base paper, cup base paper, baking paper, abrasive paper, synthetic paper and the like. That is, according to the present invention, it is possible to obtain a composite of inorganic particles having a small primary particle size and a narrow particle size distribution and fibers, which is different from the conventional inorganic filler having a particle size of more than 2 μm. It is possible to exert the characteristics. Furthermore, unlike the case where the inorganic particles are simply blended with the fiber, if the inorganic particles are complexed with the fiber, not only the inorganic particles can be easily retained on the sheet, but also the sheet is uniformly dispersed without agglomeration. Obtainable. It has been clarified from the results of electron microscopic observation that the inorganic particles in the present invention are formed not only on the outer surface of the fiber and inside the lumen but also on the inside of the microfibril in a preferable embodiment.

Further, when the flame-retardant material according to 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, fire-resistant clay, 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. In addition to the above, natural fibers include protein-based fibers such as wool, silk thread and collagen fiber, and composite sugar chain-based fibers such as chitin / chitosan fiber and alginic acid fiber. Examples of the cellulosic raw material include plant-derived pulp fibers, bacterial cellulose, animal-derived cellulose such as squirrel, and algae. Wood pulp may be produced by pulping the wood raw material. Wood raw materials include red pine, black pine, todo pine, spruce, beni pine, larch, fir, tsuga, sugi, hinoki, larch, shirabe, spruce, hiba, douglas fur, hemlock, white fur, spruce, balsam fur, cedar, pine, Coniferous trees such as Merck pine and Radiata pine, and their mixed materials, beech, hippopotamus, hannoki, nara, tab, shii, white hippopotamus, larch, poplar, tamo, doroyanagi, eucalyptus, mangrove, lauan, acacia and other broad-leaved trees and their mixture. The material is exemplified. The method for pulping a wood raw material is not particularly limited, and a pulping method generally used in the paper industry is exemplified. Wood pulp can be classified by the pulping method, for example, chemical pulp that has been vaporized by methods such as the craft method, sulfite method, soda method, and polysulfide method; mechanical pulp obtained by pulping with mechanical force such as a refiner and grinder; 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 (before bleaching) state or in a bleached (after bleaching) state. 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 mitsumata. The wood pulp and non-wood pulp may be either unbeaten or beaten. 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 oxide CNF, phosphoric acid esterified CNF, carboxymethylation). It can also be used as CNF, machine crushed CNF). Examples of synthetic fibers include polyester, polyamide, polyolefin, acrylic fiber, and semi-synthetic fibers include rayon and acetate. Examples of inorganic fibers include glass fiber, ceramic fiber, biosoluble ceramic fiber, carbon fiber, and various metal fibers. Can be mentioned. Regarding the above, these may be used alone or in combination of two or more types.

The average particle size, shape, and the like of the inorganic particles constituting the composite fiber of the present invention can be confirmed by observation with an electron microscope. Furthermore, by adjusting the conditions for synthesizing the inorganic particles, the inorganic particles having various sizes and shapes can be complexed with the fibers.
In the present invention, by treating the above-mentioned composite fiber with a flame retardant, it is possible to obtain a flame-retardant composite fiber having greatly improved incombustibility. The form of the obtained composite fiber is not particularly limited, and various molded products (body) can be produced. For example, when the composite fiber of the present invention is made into a sheet, a sheet having a high ash content can be easily obtained. Further, the obtained sheets can be pasted together to form a multi-layer sheet. Examples of the paper machine (paper machine) used for sheet production include a long net paper machine, a circular 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 when the calendar processing is performed in the subsequent stage can be set within a range that does not affect the operability and the performance of the composite fiber sheet. Further, starch, various polymers, pigments and mixtures thereof may be applied to the formed sheet by impregnation or coating.

Wet and / or dry paper strength agents (paper strength enhancers) can be added during sheeting. Thereby, the strength of the composite fiber 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, mannogalactanpolyethyleneimine, polyacrylamide resin, and polyvinylamine. , Polyvinyl alcohol and the like; composite polymers or copolymer polymers 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.

In addition, a high molecular polymer or an inorganic substance can be added in order to promote the fixation of the filler to the fiber and to improve the yield of the filler and the fiber. For example, as a coagulant, polyethyleneimine and modified polyethyleneimine containing a tertiary and / or quaternary ammonium group, polyalkyleneimine, dicyandiamide polymer, polyamine, polyamine / epiclohydrin polymer, and dialkyldialyl quaternary ammonium monomer, dialkyl. Aminoalkyl acrylates, dialkylaminoalkylmethacrylates, dialkylaminoalkylacrylamides, dialkylaminoalkylmethacrylate and acrylamide polymers, polymers consisting of monoamines and epihalohydrins, 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 or more cation or anionic polymers are used in combination, can be applied, and at least one or more 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 modified products, 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, and is, for example, a copolymer of a quaternary ammonium salt of an acrylic acid ester and acrylamide, or acrylamide. And an acrylate ester are copolymerized with each other, and then a quaternary ammonium salt is 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, defoamer, 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 used as a building material, for example, 60 to 1200 g / m ² is good because it has high strength and a low drying load during manufacturing. Further, in order to improve flame retardancy, the higher the basic weight of the sheet (weight per square meter) is, the more advantageous it is. Therefore, the basis weight can be set to 1200 g / m ² or more, for example. It can also be 2000 to 110000 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. It can also be mixed with resin and molded into a plastic shape. It can also be formed into a board shape or a block shape by pressure / heat press molding, which is generally used for making an inorganic board such as cement or gypsum. Generally, the sheet can be bent or rolled up, but can be made into a board if more strength is required. It can also be molded into a block shape, which is a thick mass, and can be molded into, for example, a rectangular parallelepiped or a cube. All of the above pulp molds, boards, and blocks can express an uneven pattern by adding a pattern to the mold at the time of molding, and can also be deformed by bending after molding.

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, those that are mixed in advance can be used, or those that are mixed, dried, and molded can be mixed later.

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.
Printing can be applied to the molded product produced by the product of the present invention. This printing method is not particularly limited, but for example, offset printing, silk screen printing, screen printing, gravure printing, micro gravure printing, flexo printing, typographic printing, sticker printing, form printing, on-demand printing, fanniquet. It can be performed by a known method such as shear roll printing or inkjet printing. Among these, ink jet printing is preferable because it is not necessary to prepare a block copy unlike offset printing, and it is relatively easy to increase the size of an inkjet printer, so that printing on a large sheet is also possible. Further, since flexographic printing can be suitably used for molded products having relatively large surface irregularities, it can also be suitably used when molded into a shape such as a board, a mold, or a block.

Further, the type of the pattern of the printed image formed by printing is not particularly limited, and for example, a wood grain pattern, a stone grain pattern, a cloth grain pattern, an abstract pattern, a geometric pattern, characters, symbols, or a combination thereof, etc. It is optional, and may be a solid color.

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

In this specification, "broad-leaved bleached kraft pulp" may be abbreviated as "LBKP" and "coniferous bleached kraft pulp" may be abbreviated as "NBKP". In addition, the Canadian standard drainage (CSF) of pulp was adjusted using a single disc refiner (SDR), a double disc refiner (DDR) or a Niagara beater. Furthermore, the average fiber length of the pulp in the pulp slurry was measured with a fiber tester (Lorentzen & Wettre).

In the following experiments, both LBKP and NBKP used were made by Nippon Paper Industries.
Experiment 1. Synthesis of composite fibers of inorganic particles and fibers (Sample 1) Composite fibers of hydrotalcite particles and cellulose fibers First, a solution for synthesizing hydrotalcite (HT) was prepared. As an alkaline solution (Solution A _{), a mixed aqueous solution of Na 2} CO ₃ (Wako Pure Drug) and NaOH (Wako Pure Drug) was prepared. Further, as an acid solution (B solution), _{a mixed aqueous solution of sulfonyl 4} (Wako pure drug) and Al ₂ (SO ₄ ) ₃ (Wako pure drug) was prepared.
-Alkaline solution (A solution): Na ₂ CO ₃ concentration: 0.1M, NaOH concentration: 1.6M
-Acid solution (B solution): sulfonyl ₄ concentration: 0.6M, Al ₂ (SO ₄ ) ₃ concentration: 0.1M
Next, pulp fibers (LBKP / NBKP = 8/2, CSF: 392 mL) were added to the alkaline solution (A solution) to prepare an aqueous suspension containing pulp fibers (pulp solid content 30 g, pulp fiber concentration: 1). .56%, pH: about 12.4). This aqueous suspension was placed in a 10 L reaction vessel, and while stirring the aqueous suspension, an acid solution (solution B) was added dropwise to synthesize a composite fiber of hydrotalcite particles and fibers (of solution A). Amount: 1.1 L, Amount of B solution: 1.1 L). Using an apparatus as shown in FIG. 1, the reaction temperature was 60 ° C., the dropping rate was 5 ml / min, and dropping was stopped when the pH of the reaction solution reached about 7. After 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.

(Sample 2) Composite fiber of hydrotalcite particles and cellulose fiber A alkaline solution (solution A) and an acid solution (solution B) were prepared in the same manner as in the case of synthesizing sample 1. Next, pulp fibers (NBKP, CSF: 687 mL) were added to an alkaline solution (solution A) to prepare an aqueous suspension containing pulp fibers (pulp solid content 30 g, pulp fiber concentration: 2.5%, pH: About 12.8). This aqueous suspension was placed in a 2 L reaction vessel, and while stirring the aqueous suspension, an acid solution (solution B) was added dropwise to synthesize a composite fiber of hydrotalcite particles and fibers (of solution A). Amount: about 230 g, amount of liquid B: about 230 g). Using an apparatus as shown in FIG. 1, the reaction temperature was 60 ° C., the dropping rate was 5 ml / min, and dropping was stopped when the pH of the reaction solution reached about 7. After 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.

<Evaluation of composite fiber sample>
The composite fiber slurry (3 g in terms of solid content) was suction-filtered using a filter paper, and then the residue was dried in an oven (105 ° C., 2 hours), and the weight ratio of the composite fiber fiber: inorganic particles was measured.

In addition, each composite fiber sample was washed with ethanol and then observed with an electron microscope (FIGS. 2 and 3). As a result, it was observed that the fiber surface was covered with an inorganic substance and self-fixed in all the samples. From the results of electron microscope observation, the primary particle diameters of the inorganic particles are as shown in Table 1 below.

Experiment 2. Manufacture and evaluation of composite fiber sheets 2-1. Production of Composite Fiber Sheet The composite fiber sample synthesized in Experiment 1 was made into a sheet by the following procedure (sheet basis weight: 500 g / m ² , sheet diameter: about 95 mm). 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) Sheet containing sample 1 and aluminum hydroxide An aqueous suspension (about 1.8) containing sample 1 and aluminum hydroxide (manufactured by Showa Denko, brand: H-32, average particle size: 8 μm). %, Sample 1: Aluminum hydroxide = 76: 24) was poured into a Buchner funnel in which filter paper (manufactured by ADVANTEC, standard filter paper No. 5B, diameter 90 mm) was set. After allowing to stand for 10 seconds, the wet paper obtained by suction filtration was dried to produce Sheet 1.

(Sheet 2) Sheet containing sample 1 and aluminum hydroxide An aqueous suspension (about 1.8%, sample 1: water) containing sample 1 and aluminum hydroxide (manufactured by Showa Denko, brand: H-32). Aluminum oxide = 58:42) was poured into a Buchner funnel in which filter paper (manufactured by ADVANTEC, standard filter paper No. 5B, diameter 90 mm) was set. After allowing to stand for 10 seconds, the wet paper obtained by suction filtration was dried to produce a sheet.

(Sheet 3) Sheet containing sample 2 and aluminum hydroxide An aqueous suspension (about 1.8%, sample 1: water) containing sample 2 and aluminum hydroxide (manufactured by Showa Denko, brand: H-32). Aluminum oxide = 46: 54) was poured into a Buchner funnel in which filter paper (manufactured by ADVANTEC, standard filter paper No. 5B, diameter 90 mm) was set. After allowing to stand for 10 seconds, the wet paper obtained by suction filtration was dried to produce a sheet.

(Sheet 4: Comparative Example) Sheet 4 in the same manner as the above sheet 1 except that the sheet sample 1 containing pulp fiber and aluminum hydroxide was made of pulp fiber (LBKP / NBKP = 8/2, CSF: 392 mL). Manufactured.

(Sheet 5: Comparative Example) A Buchner funnel in which an aqueous suspension (about 1.8%) of a sheet sample 1 containing sample 1 is set with a filter paper (manufactured by ADVANTEC, standard filter paper No. 5B, diameter 90 mm). Pour into. After allowing to stand for 10 seconds, the wet paper obtained by suction filtration was dried to produce a sheet.

2-2. Evaluation of drainage water drainage was evaluated by defining the time from the start to the end of suction filtration as the "water drainage time" (seconds) when forming a sheet.

The results are shown in the table below. The average drainage time of Sheet 1 was 104 ± 4.0 seconds, whereas that of Sheet 4 was 119 ± 4.2 seconds. The formulation of Sheet 1 has been shown to improve drainage during production.

2-3. Evaluation of flammability The flammability of the obtained sheet was evaluated. First, each sample was dried at 105 ° C. for 3 hours and then left in a desiccator containing silica gel for drying for 2 hours to be subjected to the following flammability test.

The upper part of the sample was attached to a clip and allowed to stand in the air. A lighter ignited at the bottom of the sample (flame length 30 mm without contact with the sample) was quickly brought close to it, fixed with the flame in contact with the sample by 10 mm, and continued to heat for 10 seconds. (Fig. 4). Observe how the fire spreads at that time, and for the test piece after heating, the presence or absence of flame (flame on the sample during and after heating) and the remaining dust time (flameless combustion from the end of heating) The time that the state of being in the state lasts) was evaluated.

The evaluation results are shown in the table below and FIG. 5. In the sheet 5 using pulp fibers, the sheet 5 burned to the upper end of the sample with a flame, and the remaining dust time continued for 13 seconds even after the flame was extinguished. On the other hand, in the sheet 1 using the composite fiber, although the sheet had the same inorganic content, no flame ignition or flameless combustion was observed on the sample, only the heated portion was carbonized, and the carbonized portion was also small. From this, it was suggested that high flame resistance can be imparted by using the composite fiber and aluminum hydroxide in combination.

Experiment 3. Manufacture and evaluation of composite fiber sheets 3-1. Production of composite fiber sheet A cation was added to an aqueous suspension (about 0.5%, sample 1: aluminum hydroxide = 76: 24) containing sample 1 and aluminum hydroxide (Showa Denko, brand: H-32). 200 ppm of a sex retention agent (ND300, manufactured by Hymo) and 200 ppm of an anionic retention agent (FA230, manufactured by Hymo) were added, and the suspension was prepared by stirring at 500 rpm. A handmade sheet was produced from the obtained suspension with a square hand-scraper based on JIS P 8222 (basis weight: 668 g / m ² , cellulose fiber: 40%, hydrotalcite: 40%, aluminum hydroxide). : 20%).

3-2. Evaluation of flammability The sample was dried at 50 ° C. for 48 hours and then left in a desiccator containing silica gel for drying for 24 hours to be subjected to a flammability test.

The sample was attached to a support frame (25 cm × 16 cm) and attached to a flammability test device so as not to sag. After igniting the gas burner, the sample was heated for 1 minute, and the carbonization length, residual flame time, and residual dust time were measured. For this combustion test, a 45 ° flammability tester (manufactured by Suga Testing Machine, FL-45M) was used. (Fig. 6). For heating, a Meckel burner (height 160 mm, inner diameter 20 mm) was used, 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.

Then, the test piece after heating was evaluated according to the regulation by JIS A 1322 (JIS Z 2150).
(Carbonization length) The maximum length of the support frame in the longitudinal direction is measured for the carbonized part (carbonized and the strength changes obviously) on 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) Measure the time of flameless combustion from the end of heating.
(Flameproof grade for flame retardancy)
・ Flameproof 1st grade: Carbonization length 5 cm or less, no residual flame, no residual dust after 1 minute ・ Flameproof 2nd grade: Carbonization length 10 cm or less, no residual flame, no residual dust after 1 minute ・ Flameproof 3 Class: Carbonization length 15 cm or less, no residual flame, no residual dust after 1 minute The evaluation results are shown in Fig. 7. No residual flame or residual dust was observed, and the carbonization length was 5.0 cm or less. The performance was equivalent to JIS flameproof class 1.

Experiment 4. An aqueous suspension (about 2) containing a production sample 1 of a composite fiber molded body, aluminum hydroxide (manufactured by Showa Denko, brand: H-32), and a cationic retention agent (ND-300, manufactured by Hymo) at 200 ppm). A molded product was produced from 0.0%, sample 1: aluminum hydroxide = 76: 24).

A square pillar mold (350 mm × 350 mm × 50 mm) having a metal mesh (40 mesh) at the bottom was attached to the tip of the water absorption vacuum cleaner, and suction of the aqueous suspension was started using the mold. After sucking for about 6 seconds, the mold was pulled up and suction was continued for 30 seconds. After the suction was completed, the contents were removed from the mold and dried for 20 minutes using a dryer at 100 to 190 ° C. to prepare a molded product (thickness: about 1.3 mm, cellulose fiber: 50%, hydro). Hydrotalcite: 35%, aluminum hydroxide: 15%).

Claims (10)

A flame-retardant material containing (a) a composite fiber of flame-retardant inorganic particles and fibers, and (b) aluminum hydroxide. The flame-retardant material according to claim 1, wherein the fiber is a cellulose fiber. The flame-retardant material according to claim 1 or 2, wherein the flame-retardant inorganic particles are selected from the group consisting of magnesium carbonate, calcium carbonate, hydrotalcite, aluminum hydroxide, and silica / alumina. The flame-retardant material according to claim 3, wherein the divalent metal ion of the hydrotalcite is magnesium or zinc. The flame-retardant material according to claim 3 or 4, wherein the trivalent metal ion of the hydrotalcite is aluminum. The flame-retardant material according to any one of claims 1 to 5, wherein 60% or more of the surface of the composite fiber is coated with hydrotalcite fine particles. The flame-retardant material according to any one of claims 1 to 6, wherein the composite fiber has an ash content of 10% or more. The flame-retardant material according to any one of claims 1 to 7, which is in the form of a sheet. The flame-retardant material according to any one of claims 1 to 8, wherein the weight ratio of the composite fiber to aluminum hydroxide is 10/90 to 95/5. A method for producing a flame-retardant material according to any one of claims 1 to 9.
The above method comprising forming a flame retardant material from an aqueous suspension containing the composite fibers and aluminum hydroxide.

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