Laminate

Abstract

To develop a technology that imparts excellent flame retardancy and water resistance to a sheet containing composite fibers with inorganic particles fixed on the fibers.SOLUTION: There is provided a technology that imparts excellent flame retardancy and water resistance to a sheet containing composite fibers with inorganic particles fixed on the fibers. The technology is obtained by laminating a resin containing one or more of polypropylene, polyethylene terephthalate, and polyphenylene sulfide onto the sheet.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate obtained by laminating a sheet containing composite fibers of fibers and inorganic particles with a resin. [Background technology]

[0002] By combining fibers and inorganic particles, a unique composite can be obtained that has the characteristics of both fibers and inorganic particles. For example, Patent Document 1 describes the production of a laminate from a sheet containing a composite of fibers and inorganic particles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication WO2018 / 097324 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes forming a sheet from composite fibers with magnesium carbonate fixed on the fibers and laminating the sheet with low-density polyethylene. However, although the laminate described in Patent Document 1 is imparted with water resistance by the laminated low-density polyethylene, it has the problem of low flame retardancy.

[0005] In view of the above circumstances, an object of the present invention is to develop a technology for imparting excellent flame retardancy and water resistance to a sheet comprising composite fibers having inorganic particles fixed onto the fibers. [Means for solving the problem]

[0006] As a result of intensive research into the above-mentioned problems, the inventors discovered that by laminating a specific resin to a sheet containing composite fibers having inorganic particles fixed to the fibers, it is possible to achieve both excellent flame retardancy and water resistance, and thus completed the present invention.

[0007] That is, the present invention includes the following inventions, but is not limited thereto. [1] A laminate comprising a layer containing a composite fiber of inorganic particles and fibers and a laminate layer, wherein the laminate layer contains one or more of polypropylene, polyethylene terephthalate, or polyphenylene sulfide. [2] The laminate according to [1], wherein the fibers are cellulose fibers. [3] The laminate according to [1] or [2], wherein the inorganic particles include at least one selected from the group consisting of metal salts of calcium, magnesium, barium, and aluminum, metal particles containing titanium, copper, and zinc, and silicates. [4] The laminate according to any one of [1] to [3], wherein the inorganic particles are one or more selected from the group consisting of magnesium carbonate, aluminum hydroxide, barium sulfate, and hydrotalcite. [5] The laminate according to any one of [1] to [4], wherein the composite fiber of inorganic particles and fibers is a composite fiber in which 15% or more of the fiber surface is covered with inorganic particles. [6] A method for producing the laminate according to any one of [1] to [5], synthesizing inorganic particles in a solution containing fibers to obtain composite fibers; forming the aqueous slurry containing the composite fibers into a sheet; and providing a laminate layer on the composite fiber-containing sheet; The above method, comprising: [7] The method according to [6], wherein the laminate layer is formed by a dry lamination method. [Effects of the Invention]

[0008] According to the present invention, excellent flame retardancy and water resistance can be imparted to a sheet containing composite fibers having inorganic particles fixed onto the fibers. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of the reaction apparatus used in Production Example 2 (P: pump). [Figure 2] FIG. 2 is a schematic diagram of the reaction apparatus used in Production Example 3 (P: pump). DETAILED DESCRIPTION OF THE INVENTION

[0010] In the present invention, a laminate having excellent flame retardancy and water resistance is produced by providing a laminate layer containing a specific resin on a sheet containing composite fibers having inorganic particles fixed to the fibers.

[0011] Laminate layer In the present invention, a laminate layer containing a specific resin is provided on a sheet containing composite fibers of inorganic particles and fibers, and therefore the laminate according to the present invention includes a layer containing composite fibers of inorganic particles and fibers and a laminate layer containing a thermoplastic resin.

[0012] In the present invention, the thermoplastic resin may be one or more of polypropylene, polyethylene terephthalate, or polyphenylene sulfide resin. Other examples include polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, ABS resin, polyamide, polyacetal, polycarbonate, polybutylene terephthalate, Teflon (registered trademark), polyether ether ketone, polyamide-imide, polyvinylidene fluoride, polysulfone, polyether sulfone, polyarylate, polyimide, and copolymers of ethylene and acrylic acid or acrylic acid ester. A filler such as an inorganic pigment may also be added to the thermoplastic resin. Examples of such fillers include titanium oxide, calcium carbonate, silica, talc, kaolin, carbon black, and metal powder.

[0013] In one embodiment of the present invention, the laminate sheet is manufactured by dry lamination or extrusion lamination. In the dry lamination method, film sheets are bonded together with a two-component adhesive, for example, a urethane resin base with an isocyanate curing agent, to obtain a laminate sheet. In the extrusion lamination method, a sheet layer is formed by extruding a thermoplastic resin, and before the extruded thermoplastic resin solidifies, this sheet layer is bonded to a gel precursor layer to obtain a laminate sheet.

[0014] The operating conditions in the dry lamination method, such as the lamination temperature and lamination speed, can be appropriately set depending on the type of film and the equipment used, and are not particularly limited. Generally, the lamination temperature is about 60 to 150°C, and the lamination speed is about 0.5 to 250 m / min.

[0015] In the extrusion lamination method, the operating conditions such as the melting temperature of the resin and the lamination speed can be appropriately set depending on the type of resin and the equipment used, but are not particularly limited, and generally, for example, the melting temperature is about 200 to 350°C, and the lamination speed is about 10 to 200 m / min. Furthermore, it is preferable to use nip rolls with a hardness of 70 degrees or more (JIS K-6253), and to perform pressing and bonding at a linear pressure of 15 kgf / cm or more.

[0016] Furthermore, when laminating two or more thermoplastic resin layers, such as when forming a sheet layer from multiple thermoplastic resin layers, a suitable method is to use multiple extruders to introduce each thermoplastic resin in a molten state into a separate T-die and simultaneously extrude them from the T-die to laminate and bond them together, in terms of adhesion between the thermoplastic resin layers and production efficiency. This method, which can simultaneously form multiple thermoplastic resin layers, is called a co-extrusion lamination method, among other extrusion lamination methods. Furthermore, an adhesive resin layer may be sandwiched between the thermoplastic resin layers to enhance adhesion between the resin layers. In either case, corona treatment, ozone treatment, or the like may be performed as needed to improve the adhesion between the gel precursor layer and the thermoplastic resin.

[0017] Layer containing composite fibers of inorganic particles and fibers The laminate according to the present invention has a layer containing composite fibers having inorganic particles fixed thereon. The layer containing composite fibers can be obtained by forming composite fibers into a sheet by a known method.

[0018] Examples of sheet-forming methods include feeding the composite fiber slurry to a continuous papermaking machine and continuously producing sheets derived from the slurry. Alternatively, a laminated sheet may be produced by feeding multiple types of composite fiber-containing slurries to a continuous papermaking machine and continuously producing sheets derived from each slurry in a laminated state.

[0019] (fiber) The fibers constituting the composite are not particularly limited as long as they are fibers, and for example, not only natural fibers but also regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, synthetic fibers, etc. can be used without limitation. Examples of raw materials for the fibers include pulp fibers (wood pulp and non-wood pulp), cellulose nanofiber, bacterial cellulose, animal-derived cellulose such as sea squirts, and algae, and wood pulp can be produced by pulping wood raw materials. Examples of wood raw materials include conifers such as red pine, black pine, Abies sachalinensis, Siberian spruce, red pine, larch, fir, hemlock, cedar, cypress, larch, Shirabe, spruce, hiba, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, Merkusima pine, and radiata pine, as well as mixtures thereof; and hardwoods such as beech, birch, alder, oak, tabu, chinquapin, white birch, cottonwood, poplar, ash, mud willow, eucalyptus, mangrove, lauan, and acacia, as well as mixtures thereof.

[0020] The method for pulping natural materials such as wood raw materials (woody raw materials) is not particularly limited, and examples include pulping methods commonly used in the papermaking industry. Wood pulp can be classified by pulping method, and examples include chemical pulp obtained by cooking using methods such as the Kraft method, sulfite method, soda method, and polysulfide method; mechanical pulp obtained by pulping using mechanical forces such as a refiner or grinder; semi-chemical pulp obtained by pretreatment with chemicals followed by mechanical pulping; recycled paper pulp; and deinked pulp. Wood pulp may be in an unbleached state (before bleaching) or in a bleached state (after bleaching).

[0021] Examples of non-wood pulp include cotton, hemp, sisal, Manila hemp, flax, straw, bamboo, bagasse, kenaf, sugarcane, corn, rice straw, paper mulberry, and mitsumata.

[0022] The pulp fibers may be either unbeaten or beaten, and the choice may be made depending on the physical properties of the composite sheet, but beating is preferred, as this is expected to improve the sheet strength and promote the fixation of inorganic particles.

[0023] These cellulose raw materials can also be further processed to produce finely pulverized cellulose, chemically modified cellulose such as oxidized cellulose, and cellulose nanofibers (CNF) (microfibrillated cellulose (MFC), TEMPO-oxidized CNF, phosphate-esterified CNF, carboxymethylated CNF, mechanically pulverized CNF, etc.). The finely pulverized cellulose used in the present invention includes both what is generally called powdered cellulose and the mechanically pulverized CNF described above. Powdered cellulose may be, for example, mechanically pulverized untreated selected pulp, or a cylindrical crystalline cellulose powder with a specific particle size distribution produced by purifying, drying, pulverizing, and sieving the undecomposed residue obtained after acid hydrolysis. Alternatively, commercially available products such as KC Floc (Nippon Paper Industries Co., Ltd.), Ceolus (Asahi Kasei Chemicals Corporation), and Avicel (FMC Corporation) may also be used. The degree of polymerization of the cellulose in the powdered cellulose is preferably approximately 100 to 1500, the degree of crystallinity of the powdered cellulose as measured by X-ray diffraction is preferably 70 to 90%, and the volume average particle size as measured by a laser diffraction particle size analyzer is preferably 1 μm or less but 100 μm or less. The oxidized cellulose used in the present invention can be obtained, for example, by oxidation in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds, bromides, iodides, or mixtures thereof. Cellulose nanofibers can be produced by defibrating the above-mentioned cellulose raw material. For example, an aqueous suspension of cellulose or chemically modified cellulose such as oxidized cellulose can be defibrated by mechanically grinding or beating it using a refiner, high-pressure homogenizer, grinder, single- or multi-screw kneader, bead mill, or the like. Cellulose nanofibers can also be produced by using one or a combination of the above methods. The fiber diameter of the produced cellulose nanofibers can be confirmed by observation under 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 these cellulose nanofibers, any compound can be further added to react with the cellulose nanofibers before and / or after defibrating and / or pulverizing the cellulose to modify the hydroxyl groups. Examples of functional groups to modify include acetyl groups, ester groups, ether groups, ketone groups, formyl groups, benzoyl groups, acetal, hemiacetal, oxime, isonitrile, allene, thiol groups, urea groups, cyano groups, nitro groups, azo groups, aryl groups, aralkyl groups, amino groups, amide groups, imide groups, acryloyl groups, methacryloyl groups, propionyl groups, propioloyl groups, butyryl groups, 2-butyryl groups, pentanoyl groups, hexanoyl groups, heptanoyl groups, octanoyl groups, nonanoyl groups, decanoyl groups, undecanoyl groups, dodecanoyl groups, myristoyl groups, palmitoyl groups, and sucralose groups. Examples of suitable alkyl groups include acyl groups such as tearoyl, pivaloyl, benzoyl, naphthoyl, nicotinoyl, isonicotinoyl, furoyl, and cinnamoyl; isocyanate groups such as 2-methacryloyloxyethylisocyanoyl; alkyl groups such as methyl, ethyl, propyl, 2-propyl, butyl, 2-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, myristyl, palmityl, and stearyl; and oxirane, oxetane, oxyl, thiirane, and thietane groups. Hydrogen in these substituents may be substituted with functional groups such as hydroxyl and carboxyl groups. Furthermore, some of the alkyl groups may be unsaturated. The compounds used to introduce these functional groups are not particularly limited, and examples thereof include compounds having a group derived from phosphoric acid, compounds having a group derived from carboxylic acid, compounds having a group derived from sulfuric acid, compounds having a group derived from sulfonic acid, compounds having an alkyl group, and compounds having a group derived from amine. The compounds having a phosphate group are not particularly limited, and examples thereof include phosphoric acid, and lithium salts of phosphoric acid such as lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate. Further examples thereof include sodium salts of phosphoric acid such as sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and sodium polyphosphate.Further examples include potassium salts of phosphoric acid, such as potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate. Further examples include ammonium salts of phosphoric acid, such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate. Among these, from the viewpoint of high efficiency of phosphate group introduction and ease of industrial application, phosphoric acid, sodium salts of phosphoric acid, potassium salts of phosphoric acid, and ammonium salts of phosphoric acid are preferred, with sodium dihydrogen phosphate and disodium hydrogen phosphate being more preferred, but are not particularly limited thereto. Compounds having a carboxyl group are not particularly limited, but 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. Acid anhydrides of compounds having a carboxyl group are not particularly limited, but include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Derivatives of compounds having a carboxyl group include, but are not limited to, imidized products of acid anhydrides of compounds having a carboxyl group and derivatives of acid anhydrides of compounds having a carboxyl group. Imidized products of acid anhydrides of compounds having a carboxyl group include, but are not limited to, imidized products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide. Derivatives of acid anhydrides of compounds having a carboxyl group are also not limited to. Examples include acid anhydrides of compounds having a carboxyl group, such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride, in which at least some of the hydrogen atoms are substituted with a substituent (e.g., an alkyl group, a phenyl group, etc.). Among the compounds having a carboxylic acid-derived group, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred due to their ease of industrial application and gasification, but are not particularly limited thereto. Furthermore, cellulose nanofibers may be modified by physically adsorbing the modifying compound to the cellulose nanofibers, without chemical bonding.Examples of physically adsorbing compounds include surfactants, and any of anionic, cationic, and nonionic surfactants may be used. If the above-mentioned modifications are carried out before defibrating and / or pulverizing the cellulose, these functional groups can be eliminated after defibrating and / or pulverizing, returning the cellulose to its original hydroxyl groups. Such modifications can promote defibration of cellulose nanofibers and make them easier to mix with various substances when used.

[0024] A composite fiber of a synthetic fiber and a fiber can also be used in one embodiment of the present invention. For example, a composite fiber of a fiber and a polyester, polyamide, polyolefin, acrylic fiber, glass fiber, carbon fiber, various metal fibers, etc. can also be used.

[0025] The fibers listed above may be used alone or in combination. Among them, it is preferable to use wood pulp or a combination of wood pulp and non-wood pulp and / or synthetic fibers, and it is more preferable to use wood pulp alone.

[0026] In a preferred embodiment, the fibers constituting the composite of the present invention are cellulose fibers or pulp fibers. Alternatively, for example, fibrous materials recovered from wastewater from a paper mill may be supplied to the carbonation reaction of the present invention. By supplying such materials to the reaction vessel, various composite particles can be synthesized, and fibrous particles can also be synthesized.

[0027] In one embodiment of the present invention, in addition to fibers, substances that are not directly involved in the carbonation reaction but that are incorporated into the inorganic particles that are the product to form composite particles can be used. In one embodiment of the present invention, fibers such as pulp fibers are used, but it is also possible to produce composite particles that further incorporate these substances by synthesizing inorganic particles in a solution containing inorganic particles, organic particles, polymers, etc.

[0028] The fiber length of the composite fibers 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, or 500 μm to 8 mm.

[0029] (Inorganic particles) In one embodiment of the present invention, the inorganic particles to be composited with the fibers are not particularly limited, but are preferably inorganic particles that are insoluble or poorly soluble in water. Since the inorganic particles may be synthesized in an aqueous system and the composite may be used in an aqueous system, it is preferable that the inorganic particles be insoluble or poorly soluble in water.

[0030] The inorganic particles referred to here are metals or metal compounds. Metal compounds are metal cations (e.g., Na 2+ , Ca 2+ , Mg 2+ , Al 3+ , Ba 2+ ) and anions (e.g., O 2- , O.H. - , CO3 2- , PO4 3- , SO4 2- , NO3 - , Si2O3 2- , SiO3 2- , Cl - , F - , S 2-The term "inorganic particles" refers to particles generally referred to as inorganic salts, which are formed by ionic bonding of metals such as calcium, magnesium, barium, and aluminum, metal particles containing titanium, copper, and zinc, and silicates. Specific examples of inorganic particles include compounds containing at least one metal selected from the group consisting of calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, barium sulfate, magnesium hydroxide, zinc hydroxide, calcium phosphate, zinc oxide, zinc stearate, titanium dioxide, silica produced from sodium silicate and mineral acid (white carbon, silica / calcium carbonate composite fiber, silica / titanium dioxide composite fiber, aluminum silicate, aluminosilicate), calcium sulfate, zeolite, and hydrotalcite. The calcium carbonate-silica composite may contain amorphous silica such as white carbon in addition to calcium carbonate and / or light calcium carbonate-silica composite. The inorganic particles listed above may be used alone or in combinations of two or more types, as long as they do not inhibit the reactions that synthesize each other in the solution containing the fibers. When the composite fiber is to have flame retardant properties, calcium carbonate, magnesium carbonate, aluminum hydroxide, barium sulfate, hydrotalcite, magnesium hydroxide, calcium carbonate, calcium phosphate, silica, and aluminum silicate are preferred, and magnesium carbonate, aluminum hydroxide, barium sulfate, and hydrotalcite are particularly preferred.

[0031] These inorganic particles can be synthesized by known methods, including either a gas-liquid method or a liquid-liquid method. One example of a gas-liquid method is the carbon dioxide method, which can synthesize magnesium carbonate by reacting magnesium hydroxide with carbon dioxide. Liquid-liquid methods include neutralizing an acid (e.g., hydrochloric acid, sulfuric acid, etc.) with a base (e.g., sodium hydroxide, potassium hydroxide, etc.), reacting an inorganic salt with an acid or base, or reacting inorganic salts with each other. For example, barium sulfate can be obtained by reacting barium hydroxide with sulfuric acid, aluminum hydroxide can be obtained by reacting aluminum sulfate with sodium hydroxide, or calcium carbonate with aluminum sulfate can be used to obtain composite inorganic particles of calcium and aluminum. Furthermore, when synthesizing inorganic particles in this manner, any metal or metal compound can be present in the reaction solution. In this case, the metal or metal compound can be efficiently incorporated into the inorganic particles and composited. For example, when synthesizing calcium phosphate by adding phosphoric acid to calcium carbonate, adding titanium dioxide to the reaction solution can produce composite particles of calcium phosphate and titanium.

[0032] (composite fiber synthesis) In one embodiment of the present invention, the composite can be obtained by synthesizing inorganic particles in the presence of fibers. This is because the fiber surface is a suitable site for the deposition of inorganic particles, making it easy to synthesize a composite of inorganic particles and fibers.

[0033] The method for synthesizing a composite according to the present invention essentially involves synthesizing inorganic particles in a solution containing fibers. For example, the composite may be synthesized by stirring and mixing a solution containing fibers and inorganic particle precursors in an open reaction vessel, or by injecting an aqueous suspension containing fibers and inorganic particle precursors into a reaction vessel. When injecting the aqueous suspension of inorganic precursors into the reaction vessel, cavitation bubbles may be generated, and inorganic particles may be synthesized in the presence of these bubbles.

[0034] When one of the inorganic particle precursors is alkaline, dispersing the fibers in the alkaline precursor solution beforehand allows the fibers to swell, resulting in an efficient inorganic particle-fiber composite. The reaction can be initiated by stirring for 15 minutes or more after mixing to promote fiber swelling, but it can also be initiated immediately after mixing. Furthermore, when using a substance that easily interacts with cellulose, such as aluminum sulfate (aluminum sulfate, polyaluminum chloride, etc.), as part of the inorganic particle precursor, mixing the aluminum sulfate with the fibers beforehand can sometimes improve the rate at which the inorganic particles adhere to the fibers.

[0035] In one embodiment of the present invention, the liquid may be injected into the reaction vessel under conditions that generate cavitation bubbles, or under conditions that do not generate cavitation bubbles. In either case, the reaction vessel is preferably a pressure vessel. In the present invention, a pressure vessel refers to a vessel to which a pressure of 0.005 MPa or more can be applied. When the conditions do not generate cavitation bubbles, the pressure inside the pressure vessel is preferably 0.005 MPa or more and 0.9 MPa or less in static pressure.

[0036] In one preferred embodiment, the average primary particle size of the inorganic particles in the composite of the present invention can be, for example, 1 μm or less. However, inorganic particles having an average primary particle size of 500 nm or less, inorganic particles having an average primary particle size of 200 nm or less, or even inorganic particles having an average primary particle size of 100 nm or less, or inorganic particles having an average primary particle size of 50 nm or less can also be used. The average primary particle size of the inorganic particles can also be 10 nm or more. The average primary particle size can be measured using a laser diffraction particle size distribution analyzer or electron microscope photography.

[0037] In one embodiment of the present invention, various known auxiliary agents can be further added when producing a complex. For example, a chelating agent can be added, and specific examples include polyhydroxycarboxylic acids such as citric acid, malic acid, and tartaric acid, dicarboxylic acids such as oxalic acid, sugar acids such as gluconic acid, aminopolycarboxylic acids such as iminodiacetic acid and ethylenediaminetetraacetic acid and alkali metal salts thereof, alkali metal salts of polyphosphoric acids such as hexametaphosphoric acid and tripolyphosphoric acid, amino acids such as glutamic acid and aspartic acid and alkali metal salts thereof, ketones such as acetylacetone, methyl acetoacetate, and allyl acetoacetate, sugars such as sucrose, and polyols such as sorbitol. Surface treatment agents that can be added include saturated fatty acids such as palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid and linoleic acid, alicyclic carboxylic acids, resin acids such as abietic acid, their salts, esters, and ethers, alcohol-based surfactants, sorbitan fatty acid esters, amide-based and amine-based surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ether, sodium alpha-olefin sulfonate, long-chain alkyl amino acids, amine oxides, alkylamines, quaternary ammonium salts, aminocarboxylic acids, phosphonic acids, polycarboxylic acids, and condensed phosphoric acids. Dispersants can also be used if necessary. Examples of dispersants include sodium polyacrylate, sucrose fatty acid esters, glycerin fatty acid esters, acrylic acid-maleic acid copolymer ammonium salts, methacrylic acid-naphthoxy polyethylene glycol acrylate copolymers, methacrylic acid-polyethylene glycol monomethacrylate copolymer ammonium salts, and polyethylene glycol monoacrylate. These can be used alone or in combination. They can be added either before or after the synthesis reaction. Such additives can be added in an amount of preferably 0.001 to 20% by weight, more preferably 0.1 to 10% by weight, based on the inorganic particles.

[0038] In one embodiment of the present invention, when synthesizing a composite, the reaction conditions are not particularly limited and can be set appropriately depending on the application. For example, the temperature of the synthesis reaction can be set to 0 to 90°C, preferably 10 to 80°C, more preferably 50 to 70°C, and particularly preferably about 60°C. The reaction temperature can be controlled by a temperature regulator, and a low temperature reduces the reaction efficiency and increases costs, while a temperature above 90°C tends to increase the amount of coarse inorganic particles.

[0039] In one embodiment of the present invention, the reaction can be a batch reaction or a continuous reaction. Generally, a batch reaction is preferred for the convenience of discharging the residue after the reaction. The scale of the reaction is not particularly limited, but the reaction can be carried out on a scale of 100 L or less, or on a scale of more than 100 L. The size of the reaction vessel can be, for example, about 10 L to 100 L, or about 100 L to 1000 L.

[0040] Furthermore, the reaction can be controlled, for example, by monitoring the pH of the reaction solution. Depending on the pH profile of the reaction solution, in the case of a carbonation reaction of calcium carbonate, the reaction can be carried out until the pH reaches, for example, less than pH 9, preferably less than pH 8, more preferably around pH 7.

[0041] On the other hand, the reaction can also be controlled by monitoring the conductivity of the reaction solution. In the case of the carbonation reaction of calcium carbonate, for example, it is preferable to carry out the carbonation reaction until the conductivity drops to 1 mS / cm or less.

[0042] Furthermore, the reaction can be controlled simply by adjusting the reaction time, specifically, by adjusting the residence time of the reactants in the reaction vessel. In addition, in one embodiment of the present invention, the reaction can also be controlled by stirring the reaction solution in the reaction vessel or by carrying out the reaction as a multi-stage reaction.

[0043] The weight ratio of the fibers to the inorganic particles can be 5 / 95 to 95 / 5, and may also be 10 / 90 to 90 / 10, 20 / 80 to 80 / 20, 30 / 70 to 70 / 30, or 40 / 60 to 60 / 40.

[0044] In one embodiment of the present invention, the reaction product, that is, the composite, is obtained as a suspension. If necessary, the suspension can be stored in a storage tank or subjected to other processes, such as concentration, dehydration, pulverization, classification, aging, and dispersion. These processes can be performed by known processes, and can be appropriately determined taking into account the intended use, energy efficiency, and the like. For example, concentration and dehydration processes can be performed using a centrifugal dehydrator, a sedimentation concentrator, or the like. Examples of centrifugal dehydrators include a decanter and a screw decanter. When using a filter or dehydrator, there are no particular limitations on the type, and common types can be used. However, calcium carbonate cake can be obtained by suitably using, for example, a pressure dehydrator such as a filter press, a drum filter, a belt press, or a tube press, or a vacuum drum dehydrator such as an Oliver filter. Grinding methods include ball mills, sand grinder mills, impact mills, high-pressure homogenizers, low-pressure homogenizers, Dyno-mills, ultrasonic mills, Kanda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, disintegrators, beaters, single-screw extruders, twin-screw extruders, ultrasonic agitators, and household juicer mixers. Classification methods include mesh sieves, outward or inward slit or round-hole screens, vibrating screens, heavy foreign matter cleaners, light foreign matter cleaners, reverse cleaners, and sieving testers. Dispersion methods include high-speed dispersers and low-speed kneaders.

[0045] The composite obtained according to one embodiment of the present invention can be used in the form of a suspension without being completely dehydrated, or can be dried to form a powder. In this case, there are no particular limitations on the dryer used, and suitable dryers include, for example, a flash dryer, a band dryer, and a spray dryer.

[0046] In one embodiment of the present invention, water is used for preparing the suspension, etc., and as this water, ordinary tap water, industrial water, groundwater, well water, etc. can be used. In addition, ion-exchanged water, distilled water, ultrapure water, industrial wastewater, and water obtained during the production process can also be suitably used.

[0047] The composite obtained according to one embodiment of the present invention can be modified by known methods. For example, in one embodiment, the surface can be made hydrophobic to enhance miscibility with resins, etc.

[0048] In one embodiment, the fiber composite of the present invention has 15% or more of the fiber surface covered with inorganic particles. When the fiber surface is covered at this area ratio, the characteristics attributable to the inorganic particles are enhanced, while the characteristics attributable to the fiber surface are diminished. The coverage may be 30% or more, 50% or more, 60% or more, or even 80% or more. The coverage can be roughly estimated visually from an image taken with an electron microscope. Alternatively, the electron microscope image can be binarized so that areas where inorganic matter is present are white and areas where fibers are present are black, and the proportion of white areas, i.e., areas where inorganic matter is present, relative to the entire image (area ratio) can be calculated. The coverage can be calculated using, for example, image processing software (Image J, National Institutes of Health, USA).

[0049] In one embodiment of the present invention, a composite of fibers and inorganic particles is not simply a mixture of fibers and inorganic particles, but rather the fibers and inorganic particles are bound to each other by hydrogen bonds or the like without the intervention of a binder or the like, so that the inorganic particles are less likely to fall off even after disintegration. The strength of the bond between the fibers and inorganic particles in the composite can be evaluated, for example, by the ash retention (%), i.e., a numerical value such as (ash content of the sheet ÷ ash content of the composite before disintegration) × 100. Specifically, the composite is dispersed in water to a solids concentration of 0.2%, disintegrated for 5 minutes using a standard disintegrator specified in JIS P 8220-1:2012, and then sheeted using a 150-mesh wire according to JIS P 8222:1998. The ash retention can be used for evaluation. In a preferred embodiment, the ash retention is 20% by mass or more, and in a more preferred embodiment, the ash retention is 50% by mass or more. [Example]

[0050] The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to the following specific examples. In this specification, unless otherwise specified, all "%" means "% by weight" and numerical ranges include their endpoints.

[0051] Experiment 1: Composite fiber production 1-1. Manufacturing Example 1: Composite fiber of aluminum hydroxide and cellulose fiber A 2% pulp slurry (100% NBKP, CSF = 400 mL, average fiber length: approximately 1.3 mm, solids content: 188 kg) and sodium hydroxide (Nippon Light Metals, concentration: 48%, 972 kg) were added to a container (machine chest, volume: 4 m) and mixed. Afterwards, aluminum sulfate (aluminum sulfate, concentration: 27%, 1117 kg) was added dropwise at approximately 32 kg / min using a peristaltic pump. After the addition was completed, stirring was continued for 30 minutes to obtain composite fibers. Analysis of the resulting composite fibers revealed that the weight fraction (ash content) of inorganic particles was approximately 70%, and the average primary particle size of the inorganic particles was approximately 100 nm. Furthermore, visual inspection of the area ratio of the fiber surface covered by inorganic particles revealed a coverage rate of approximately 90%.

[0052] 1-2. Manufacturing Example 2: Composite fiber of hydrotalcite and cellulose fiber Mg6Al2(OH) as hydrotalcite (HT) 16 To synthesize CO3·4H2O, a mixed aqueous solution of Na2CO3 and NaOH was prepared as the alkaline solution (solution A), and a mixed aqueous solution of MgCl2 and AlCl3 was prepared as the acid solution (solution B). Note that Na2CO3, NaOH, MgCl2, and AlCl3 were all reagents manufactured by Fujifilm Wako Pure Chemical Industries. Alkaline solution (solution A, Na2CO3 concentration: 0.05M, NaOH concentration: 0.8M) ·Acid solution (B solution, Mg type, MgCl2 concentration: 0.3M, AlCl3 concentration: 0.1M) Cellulose fibers were used as the composite fiber. Specifically, the pulp fibers were made from bleached hardwood kraft pulp (LBKP, Nippon Paper Industries Co., Ltd.) and bleached softwood kraft pulp (NBKP, Nippon Paper Industries Co., Ltd.) in a weight ratio of 8:2, and were refined to a Canadian standard freeness of 390 ml using a single disc refiner (SDR) (average fiber length 0.8 mm).

[0053] Pulp fiber was added to an alkaline solution to prepare an aqueous suspension containing pulp fiber (pulp fiber concentration: 1.56%, pH: approximately 12.4). This aqueous suspension (30 g of pulp solids) was placed in a 10 L reaction vessel, and while stirring the aqueous suspension, an acid solution (Mg-based) was added dropwise to synthesize a composite of hydrotalcite microparticles and fiber. Using the apparatus shown in Figure 1, the reaction temperature was 60 °C, the dropping rate was 22 ml / min, and the dropping was stopped when the pH of the reaction solution reached approximately 7. After the dropping was completed, the reaction solution was stirred for 30 minutes and then washed with 10 times the amount of water to remove salt, yielding a composite fiber (average primary particle size of inorganic particles: 20 nm, inorganic particle weight ratio: approximately 70%, fiber surface coverage: approximately 80%).

[0054] 1-3. Manufacturing Example 3: Magnesium carbonate and cellulose fiber composite fiber An aqueous suspension was prepared by adding 490 g of magnesium hydroxide (Ube Materials, UD653) and 350 g of kraft pulp (LBKP / NBKP = 1 / 1, CSF: 370 ml, average fiber length: 0.9 mm) to water.

[0055] As shown in Figure 2, 35 L of this aqueous suspension was placed in a cavitation apparatus (45 L capacity). Carbon dioxide gas was blown into the reaction vessel while circulating the reaction solution, synthesizing a composite of magnesium carbonate microparticles and fibers by the carbon dioxide gas method. The reaction started at approximately 40°C, and the carbon dioxide gas was supplied from a commercially available liquefied gas at a rate of 20 L / min. The introduction of carbon dioxide gas was stopped when the pH of the reaction solution reached approximately 7.8 (pH before the reaction was 10.3). Cavitation and circulation of the slurry within the apparatus were continued for the next 30 minutes, yielding composite fibers of magnesium carbonate microparticles and pulp fibers (average primary particle size of inorganic particles: 0.8 μm, inorganic particle weight ratio: approximately 70%, fiber surface coverage: approximately 80%).

[0056] In the synthesis of composite fibers, cavitation bubbles were generated in the reaction vessel by circulating the reaction solution and injecting it into the reaction vessel. Specifically, the reaction solution was injected at high pressure through a nozzle (nozzle diameter: 1.5 mm) to generate cavitation bubbles. The jet velocity was approximately 70 m / s, the inlet pressure (upstream pressure) was 7 MPa, and the outlet pressure (downstream pressure) was 0.3 MPa.

[0057] The weight proportion of inorganic particles contained in the composite fiber was calculated by suction filtering the composite slurry (3 g in terms of solid content) using filter paper, drying the residue in an oven (105°C, 2 hours), and then burning the organic content at 525°C, and then calculating the weight before and after burning.

[0058] Experiment 2: Fabrication and evaluation of composite fiber sheets 2-1. Sample 1 A cationic retention aid (ND300, Heimo) and an anionic retention aid (FA230, Heimo) were added to the aqueous slurry of composite fiber obtained in Production Example 1 (composite fiber concentration: 1 wt%) in an amount of 100 ppm based on solids to prepare a stock slurry. Sheets were then produced from this stock slurry using a Fourdrinier paper machine at a papermaking speed of 5 m / min (basis weight: 300 g / m). 2 , thickness: 416μm).

[0059] Next, a laminate layer was formed on the obtained sheet by dry lamination. Specifically, a polyethylene terephthalate (manufactured by Futamura Chemical, density: 1.38 g / cm) was laminated on the sheet using a roller laminator (manufactured by Asuka Corporation, L405A3). 3 The laminated layer was laminated on both sides of the sheet (lamination temperature: about 140°C, lamination speed: about 1.0 m / min). The total weight of the laminated layer on both sides was about 32 g / m 2 It was.

[0060] 2-2. Sample 2 Instead of polyethylene terephthalate, polypropylene (Futamura Chemical, density: 0.91 g / cm 3 A sheet having laminate layers on both sides was prepared in the same manner as in Sample 1, except that a polyester resin (polymerizable copolymer, melting point: 160°C) was used.

[0061] 2-3. Sample 3 Instead of polyethylene terephthalate, polyphenylene sulfide (manufactured by Toray, density: 1.35 g / cm 3 A sheet having laminate layers on both sides was prepared in the same manner as in Sample 1, except that a polyester resin (polymerizable copolymer, melting point: 275°C) was used.

[0062] 2-4. Sample 4 A sheet having laminate layers on both sides was produced in the same manner as Sample 1, except that the composite fiber obtained in Production Example 2 was used instead of the composite fiber obtained in Production Example 1.

[0063] 2-5. Sample 5 A sheet having laminate layers on both sides was produced in the same manner as Sample 1, except that the composite fiber obtained in Production Example 2 was used instead of the composite fiber obtained in Production Example 1.

[0064] 2-6. Sample 6 A sheet was produced from the stock slurry in the same manner as in Sample 1, and then a laminate layer of polyethylene terephthalate was formed on both sides of the sheet by extrusion lamination. Specifically, polyethylene terephthalate (Unitika, density 1.38 g / cm) was laminated on both sides of the sheet using an extrusion molding machine (Musashino Kikai, tandem extrusion laminator) equipped with a T-die. 3 The two sheets were laminated by extrusion lamination at a melting temperature of 300°C to a thickness of 30 μm on each side, and immediately pressed and pressed together with a cooling roll and a nip roll (hardness 70 degrees) at a linear pressure of 15 kgf / cm.

[0065] 2-7. Sample 7 (Comparative Example) A cationic retention aid (ND300, Hymo) and an anionic retention aid (FA230, Hymo) were added to the pulp slurry (LBKP / NBKP = 8 / 2, CSF = 380 mL, average fiber length: 1.5 mm) at 100 ppm based on solids, and paper was produced using a Fourdrinier paper machine (basis weight: 300 g / m 2 , thickness: 350 μm, moisture content: 8.0% by mass. Then, in the same manner as in Sample 1, laminate layers were provided on both sides of the obtained paper.

[0066] 2-8. Sample 8 (Comparative Example) Instead of polyethylene terephthalate, polypropylene (Futamura Chemical, density 0.91 g / cm 3 A sheet having a laminate layer was prepared in the same manner as in Sample 7, except that a cellulose ester resin (having a melting point of 160° C.) was used.

[0067] 2-9. Sample 9 (Comparative Example) A sheet was prepared in the same manner as Sample 1, except that no laminate layer was provided. 2-10. Sample 10 (Comparative Example) Instead of polyethylene terephthalate, polyethylene (Japan Polyethylene, LC602A, density: 0.92 g / cm 3 A sheet having laminate layers on both sides was prepared in the same manner as in Sample 1, except that a polyester resin (polymerizable copolymer, melting point: 107°C) was used.

[0068] Experiment 3: Evaluation of composite fiber sheets The samples obtained in Experiment 2 were evaluated based on the following procedures. 3-1. Strength (ISO bending resistance) The bending resistance of the obtained sheet was measured using an L&W BENDING TESTER in accordance with ISO 2493-1. Specifically, the resistance value (load) when the sample was bent 15° was measured, and the ISO bending resistance was calculated using the following formula. ISO bending resistance (mN / m) = bending load (mN) x 0.003352 The evaluation criteria for strength are as follows: Good: ISO bending resistance of 2.5 mN / m or more △ (normal): ISO bending resistance is 1.5 mN / m or more and less than 2.5 mN / m × (bad): ISO bending resistance less than 1.5 mN / m 3-2.Flame retardancy (fireproof grade) The sample was attached to a support frame (25 cm x 16 cm) and placed in the flammability test device without any slack. After igniting the gas burner, the sample was heated for 1 minute and the flame retardancy of the sample was evaluated. A 45° flammability tester (FL-45M, manufactured by Suga Test Instruments) was used for this combustion test. A Meckel burner (height 160 mm, inner diameter 20 mm) was used for heating, and combustion was carried out by feeding in only the gas without mixing in primary air. Liquefied petroleum gas No. 5 (mainly butane and butylene, JIS K 2240) was used as fuel, and the flame length was adjusted to 65 mm without the sample attached.

[0069] Based on JIS A 1322 (JIS Z 2150), the char length, after-flame time, and after-flame time were measured, and the flame retardancy grade of the sample was determined. (Char length) The maximum length in the longitudinal direction of the support frame is measured for the charred portion (where the strength has clearly changed due to charring) on ​​the heated surface of the test specimen. (Afterflame time) Measure the time that the test specimen continues to burn after heating is completed. (Afterglow) Measure the time of flameless combustion from the end of heating. Flame retardant grade 1: Char length 5cm or less, no residual flame, no residual dust after 1 minute Flame retardant grade 2: Char length 10cm or less, no residual flame, no residual dust after 1 minute Flame retardant level 3: Char length 15cm or less, no residual flame, no residual dust after 1 minute 3-3.Water resistance A drop of water (0.05 ml) was dropped onto the sheet, and the time it took for the entire sheet to soak in was measured. The evaluation criteria for water resistance are as follows: 〇 (Good): Time to soak into the sheet is longer than 30 seconds △ (Normal): Soaks into the sheet in 5 to 30 seconds × (bad): Time taken for the liquid to penetrate the sheet is less than 5 seconds

[0070] [Table 1]

[0071] The laminate of the present invention was superior in water resistance while maintaining strength and flame retardancy compared to the laminates shown in the comparative examples. In particular, Sample 10 (laminating material: polyethylene) had poor flame retardancy, whereas the sheet laminated with the specific resin of the present invention had excellent water resistance while maintaining strength and flame retardancy.

Claims

1. A laminated sheet including a layer containing composite fibers of inorganic particles and cellulose fibers, and a laminate layer, The above laminated sheet, wherein the laminate layer contains one or more of polypropylene, polyethylene terephthalate, or polyphenylene sulfide, and the inorganic particles are one or more selected from the group consisting of magnesium carbonate, aluminum hydroxide, barium sulfate, and hydrotalcite.

2. A laminated sheet as described in claim 1, wherein in the composite fiber, 15% or more of the cellulose fiber surface is covered with inorganic particles.

3. A method for producing the laminated sheet according to claim 1 or 2, comprising: A step of synthesizing inorganic particles in a solution containing cellulose fibers to obtain composite fibers; forming the aqueous slurry containing the composite fibers into a sheet; and providing a laminate layer on the composite fiber-containing sheet; The above method, comprising:

4. The method of claim 3, wherein the laminate layer is applied by a dry lamination method.

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