Binder and method for producing molded body

Abstract

To provide a binding material preferably applicable to manufacturing of a molded body having a high whiteness degree by a dry method, and a method for manufacturing a molded body capable of preferably manufacturing a molded body having a high whiteness degree by a dry method.SOLUTION: The binding material of the present invention is used for obtaining a molded body by mutually binding fibers, and includes: a thermoplastic resin; and a fluorescent whitener. The melting point of the fluorescent whitener is higher than a melting point of the thermoplastic resin. The melting point of the fluorescent whitener is preferably 200°C or higher. A content of the fluorescent whiter in the binding material is preferably 1.0 mass% or less. The binding material preferably further contains a white pigment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a binder and a method for producing a molded body. [Background technology]

[0002] Obtaining a sheet-like molded product by exerting bonding forces between deposited fibers has been practiced for a long time. A typical example is the production of paper by papermaking using water. The equipment used for papermaking often requires large utilities such as water, electricity, and drainage facilities, making it difficult to miniaturize. For these reasons, a method called the dry method, which uses little or no water at all, is expected to replace the papermaking method for producing sheets.

[0003] Patent Document 1 discloses the use of a composite containing a resin and a coloring agent for binding fibers, which are constituent components of the sheet, when forming the sheet by a dry method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2015-092032 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when producing a sheet using a dry method, it is necessary to heat the sheet at a high temperature to melt the resin, and this heating may result in a sheet not having the intended color. [Means for solving the problem]

[0006] The present invention has been made to solve the above-mentioned problems, and can be realized as the following application examples.

[0007] The binder according to the application example of the present invention is a binder used to obtain a molded body by binding fibers together, the binder includes a thermoplastic resin and a fluorescent whitening agent; The melting point of the fluorescent whitening agent is higher than the melting point of the thermoplastic resin.

[0008] A method for producing a molded article according to an application example of the present invention includes a mixing step of mixing the binder according to an application example of the present invention and fibers in a gas phase to obtain a mixture; and a molding step of pressurizing and heating the mixture to obtain a molded body. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a manufacturing apparatus capable of manufacturing a sheet-shaped molded body. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will now be described in detail. [1] Binding material First, the binder of the present invention will be described.

[0011] The binder of the present invention is used to obtain a molded article by binding fibers together. The binder of the present invention contains a thermoplastic resin and a fluorescent whitening agent, and the melting point of the fluorescent whitening agent is higher than the melting point of the thermoplastic resin.

[0012] This configuration provides a binder that can be suitably applied to the production of molded articles with high whiteness by a dry process. Even when the heating temperature during molding is relatively high, the whiteness of the resulting molded article can be effectively prevented from decreasing, allowing the resin to be sufficiently melted and softened, resulting in a molded article with sufficiently high strength and allowing the shape and surface condition of the molded article to be suitably controlled.

[0013] In the present invention, the melting point refers to the T1 / 2 temperature measured by a flow tester. The melting point is measured, for example, under a load of 20 kg / cm 2 The melting point can be determined by measurement under the following conditions: temperature rise rate: 5.0°C / min, die diameter: 1.0 mm, die length: 1.0 mm. An elevated flow tester can be used to measure the melting point. An example of an elevated flow tester is the CFT500 model manufactured by Shimadzu Corporation.

[0014] In the present invention, the term "dry method" refers to a method that uses almost no water or no water at all, and more specifically, refers to a method in which the binder and fibers are mixed in a gas phase rather than in water.

[0015] [1-1]Thermoplastic resin The binder of the present invention contains a thermoplastic resin, which mainly functions to increase the bonding strength between fibers in a molded article produced using the binder of the present invention.

[0016] Examples of thermoplastic resins include AS resin, ABS resin, polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylic resin, polyester resin, polyethylene terephthalate, polyphenylene ether, polybutylene terephthalate, nylon, polyamide, polycarbonate, polyacetal, polyphenylene sulfide, polyether ether ketone, biodegradable resins such as polylactic acid, polybutylene succinate, and polyhydroxybutanoic acid, as well as copolymers and modified products thereof. One or a combination of two or more selected from these may be used, but polyester resin is preferred.

[0017] This makes it possible to improve the strength of the molded article produced using the binder of the present invention.

[0018] When the binder of the present invention contains multiple components as a thermoplastic resin, the proportion of polyester resin in the total thermoplastic resin is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. This makes the above-mentioned effects more pronounced.

[0019] The melting point of the thermoplastic resin is preferably 70°C or higher and 150°C or lower, more preferably 80°C or higher and 140°C or lower, and even more preferably 85°C or higher and 130°C or lower.

[0020] This allows the binder of the present invention to be more suitably melted and softened while preventing the high-melting-point fluorescent brightening agent from melting during the production of the molded body, thereby improving the moldability, productivity, strength, etc. of the molded body.

[0021] The content of the thermoplastic resin in the binder of the present invention is preferably 75.0 mass% or more and 98.0 mass% or less, more preferably 80.0 mass% or more and 95.0 mass% or less, and even more preferably 85.0 mass% or more and 92.0 mass% or less.

[0022] This makes it possible to make the molded article produced using the binder of the present invention have sufficiently excellent whiteness and also have excellent strength.

[0023] [1-2] High-melting fluorescent whitening agent The binder of the present invention contains an optical brightener having a melting point higher than that of the thermoplastic resin. In the following description, such an optical brightener is also referred to as a "high melting point optical brightener."

[0024] The high-melting-point fluorescent brightening agent mainly functions to enhance the whiteness of molded articles produced using the binder of the present invention. In particular, by using a high-melting-point fluorescent brightening agent having a melting point higher than that of the thermoplastic resin, melting of the fluorescent brightening agent due to heating during the production of the molded article can be more effectively prevented. As a result, the fluorescent brightening agent can be maintained in a well-dispersed state in the molded article, and the molded article can have excellent whiteness.

[0025] The melting point of the high-melting fluorescent whitening agent may be any value higher than the melting point of the thermoplastic resin, but is preferably 200°C or higher, more preferably 250°C or higher and 450°C or lower, and even more preferably 280°C or higher and 400°C or lower.

[0026] This makes it possible to improve the dispersion state of the fluorescent brightening agent in the molded article produced using the binder of the present invention, and the effects of the present invention as described above are more significantly exhibited.

[0027] When the melting point of the thermoplastic resin is T1 [°C] and the melting point of the high-melting-point fluorescent brightener is T2 [°C], it is preferable to satisfy the condition 70≦T2−T1≦350, more preferably 110≦T2−T1≦330, and even more preferably 150≦T2−T1≦300.

[0028] This allows the above-mentioned effects to be more pronounced, and also makes it easier to control the temperature during the production of the molded article.

[0029] Examples of high-melting fluorescent whitening agents include 1,4-bis(2-benzoxazolyl)naphthalene (melting point: 212°C), 4,4'-bis(2-benzoxazolyl)stilbene (melting point: 355°C), 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene (melting point: 201°C), 4-(2-benzoxazolyl)-4'-(5-methyl-2-benzoxazolyl)stilbene (melting point: 292°C), ), 7-(2H-naphthalene[1,2-D]triazol-2-yl)-3-phenyl-2H-1-benzopyran-2-one (melting point: 250°C), 1,1'-biphenyl-4,4'-bis-benzoxazole (melting point: 220°C), etc., and one or more selected from these can be used in combination, but among them, 4,4'-bis(2-benzoxazolyl)stilbene is preferred. This makes the above-mentioned effects more pronounced.

[0030] When the binder of the present invention contains multiple components as a high-melting fluorescent brightener, the proportion of 4,4'-bis(2-benzoxazolyl)stilbene in the entire high-melting fluorescent brightener is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. This makes the above-mentioned effects more pronounced.

[0031] The content of the high melting point fluorescent brightener in the binder of the present invention is preferably 1.0 mass % or less, more preferably 0.01 mass % to 0.8 mass % or less, and even more preferably 0.03 mass % to 0.5 mass % or less.

[0032] This more effectively prevents concentration quenching and the color of the high-melting-point fluorescent brightening agent itself from adversely affecting the whiteness of the molded article, thereby improving the whiteness of molded articles produced using the binder of the present invention.

[0033] When the content of the thermoplastic resin in the binder of the present invention is X1 [mass%] and the content of the high-melting point fluorescent brightener in the binder of the present invention is X2 [mass%], it is preferable to satisfy the relationship of 0.00010≦X2 / X1≦0.013, it is more preferable to satisfy the relationship of 0.00011≦X2 / X1≦0.010, and it is even more preferable to satisfy the relationship of 0.00030≦X2 / X1≦0.0060.

[0034] This allows the molded article produced using the binder of the present invention to have both high levels of whiteness and strength.

[0035] In the binder of the present invention, the high-melting-point fluorescent brightening agent may be contained in a form separate from the thermoplastic resin, but it is preferably contained in a dispersed state in particles containing the thermoplastic resin.

[0036] This makes it possible to improve the whiteness of the molded article produced using the binder of the present invention.

[0037] [1-3] White pigment The binder of the present invention may further contain a white pigment in addition to the above-mentioned thermoplastic resin and high-melting-point fluorescent whitening agent.

[0038] This makes it possible to improve the whiteness of the molded article produced using the binder of the present invention.

[0039] Examples of white pigments include titanium oxide, calcium carbonate, aluminum oxide, zinc oxide, cerium oxide, magnesium oxide, zirconium oxide, strontium titanate, and barium titanate, and one or more selected from these can be used in combination.

[0040] Among these, calcium carbonate is preferably contained as the white pigment. This allows the whiteness of the molded body produced using the binder of the present invention to be improved. Furthermore, for example, the kneadability with the thermoplastic resin during the production of the binder can be improved, resulting in a binder with the white pigment more suitably dispersed in the thermoplastic resin. Furthermore, since the specific gravity of the binder can be made relatively small, the binder can be more suitably supplied to a manufacturing apparatus such as that described below. Furthermore, calcium carbonate decomposes when heated at high temperatures and releases carbon dioxide, which is also preferable for improving the flame retardancy of the molded body. Furthermore, it can more effectively prevent the specific gravity of the molded body from becoming unnecessarily high. Furthermore, calcium carbonate is inexpensive and stably available among various white pigments, making it preferable from the perspectives of reducing the production costs of binders and molded bodies, ensuring a stable supply of binders and molded bodies, and so on.

[0041] The average particle size of the white pigment is preferably from 0.01 μm to 10 μm, more preferably from 0.02 μm to 1 μm, and even more preferably from 0.03 μm to 0.5 μm, which allows the molded article produced using the binder of the present invention to have better whiteness.

[0042] When the binder of the present invention contains multiple components as a white pigment, the proportion of calcium carbonate in the entire white pigment is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. This makes the above-mentioned effects more pronounced.

[0043] The content of the white pigment in the binder of the present invention is preferably less than 20.0% by mass, more preferably 3.0% to 18.0% by mass, and even more preferably 5.0% to 15.0% by mass.

[0044] This makes it possible to improve the whiteness of a molded article produced using the binder of the present invention and also improve the strength of the molded article.

[0045] When the content of the high-melting point fluorescent brightening agent in the binder of the present invention is X2 [mass%] and the content of the white pigment is X3 [mass%], it is preferable to satisfy the relationship 0.00050≦X2 / X3≦1.0, more preferably the relationship 0.00060≦X2 / X3≦0.026, and even more preferably the relationship 0.0020≦X2 / X3≦0.10.

[0046] This makes it possible to improve the whiteness of the molded article produced using the binder of the present invention.

[0047] In the binder of the present invention, the white pigment may be contained in a form separate from the thermoplastic resin, but it is preferably contained in a dispersed state in particles containing the thermoplastic resin.

[0048] This makes it possible to improve the whiteness of the molded article produced using the binder of the present invention.

[0049] [1-4] Aggregation inhibitors The binder of the present invention may contain, for example, an aggregation inhibitor as a component other than those described above.

[0050] This effectively prevents, for example, aggregation of particles containing a thermoplastic resin in the binder of the present invention, and favorably prevents undesired uneven distribution of the thermoplastic resin in a molded article produced using the binder of the present invention. As a result, the strength of the molded article can be improved. Furthermore, undesired aggregation of high-melting-point fluorescent whitening agents, white pigments, etc. can be prevented in a molded article produced using the binder of the present invention. As a result, undesired color unevenness in the molded article can be more favorably prevented.

[0051] Examples of the aggregation inhibitor include fumed silica and so-called nanoparticles, which are materials used as the white pigments described above and have an average particle size smaller than that of the white pigments, with an average particle size of 0.001 μm or more and 0.5 μm or less, preferably 0.005 μm or more and 0.05 μm or less. By using an aggregation inhibitor with an average particle size smaller than that of the white pigment, aggregation of particles containing a thermoplastic resin can be effectively prevented.

[0052] The content of the aggregation inhibitor in the binder of the present invention is preferably 0.10% by mass or more and 3.0% by mass or less, more preferably 0.20% by mass or more and 2.0% by mass or less, and even more preferably 0.30% by mass or more and 1.5% by mass or less.

[0053] [1-5] Other ingredients The binder of the present invention may further contain components other than those described above. Hereinafter, in this section, such components will also be referred to as "other components."

[0054] Examples of other components include flame retardants, colorants, surfactants, antifungal agents, preservatives, antioxidants, ultraviolet absorbers, oxygen absorbers, resins other than the thermoplastic resins described above, fluorescent brighteners other than high-melting-point fluorescent brighteners, fibers, release agents, resin modifiers, and pigment dispersants.

[0055] However, the content of other components in the binder of the present invention is preferably 7.0% by mass or less, more preferably 5.0% by mass or less, and even more preferably 3.0% by mass or less.

[0056] In particular, when the binder of the present invention contains a fluorescent brightening agent other than a high-melting-point fluorescent brightening agent, the content of the fluorescent brightening agent other than a high-melting-point fluorescent brightening agent in the binder of the present invention is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less.

[0057] [1-6] Other conditions The form of the binder of the present invention is not particularly limited, but it is preferably in powder form.

[0058] This makes it easier to handle the binder, and allows the binder and fibers to be mixed more uniformly when producing the molded body, thereby improving the reliability of the molded body produced.

[0059] When the binder of the present invention is in powder form, the average particle size of the particles constituting the binder of the present invention is preferably 0.5 μm or more and 100.0 μm or less, more preferably 1.0 μm or more and 50.0 μm or less, and even more preferably 2.0 μm or more and 30.0 μm or less. This makes the above-mentioned effects more pronounced.

[0060] In this specification, the average particle size refers to the average particle size on a volume basis. The average particle size can be determined by measurement using a particle size distribution analyzer that uses a laser diffraction / scattering method as its measurement principle, i.e., a laser diffraction particle size distribution analyzer, such as the LA910 manufactured by Horiba, Ltd.

[0061] [2] Manufacturing method of binder The binder of the present invention can be suitably produced, for example, by a method including a kneading step of kneading materials containing a thermoplastic resin and a high-melting-point fluorescent whitening agent to obtain a kneaded mixture, and a crushing step of crushing the kneaded mixture.

[0062] The material to be subjected to the kneading step may contain, for example, a white pigment in addition to the thermoplastic resin and the high-melting-point fluorescent whitening agent.

[0063] The heating temperature in the kneading step is preferably a temperature below the melting point of the high-melting-point fluorescent brightener. In particular, where T1 [°C] is the melting point of the thermoplastic resin and T2 [°C] is the melting point of the high-melting-point fluorescent brightener, the heating temperature is preferably (T1 + 10)°C or higher and (T2 - 10)°C or lower, more preferably (T1 + 20)°C or higher and (T2 - 20)°C or lower, and even more preferably (T1 + 30)°C or higher and (T2 - 30)°C or lower.

[0064] The kneaded product obtained in the kneading step may be pelletized to obtain pellets having a size within a predetermined range.

[0065] The pulverization step can be carried out using, for example, a hammer mill, a jet mill, etc. The pulverization step may be carried out in two or more stages.

[0066] The pulverized product obtained in the pulverization step may be subjected to, for example, classification treatment, that is, the classification step may be carried out after the pulverization step.

[0067] Furthermore, when the binder of the present invention contains an agglomeration inhibitor, an agglomeration inhibitor mixing step is carried out in which the pulverized material obtained through the pulverization step is mixed with the agglomeration inhibitor, thereby making it possible to suitably adhere the agglomeration inhibitor to the surfaces of the particles constituting the pulverized material.

[0068] [3] Manufacturing method for molded body Next, a method for producing the molded article of the present invention will be described.

[0069] The method for producing a molded body of the present invention includes a mixing step of mixing the binder of the present invention and fibers in a gas phase to obtain a mixture, and a molding step of pressurizing and heating the mixture to obtain a molded body.

[0070] This provides a method for producing a molded article by a dry process that can suitably produce a molded article with high whiteness. Furthermore, even if the heating temperature during molding of the molded article is relatively high, the whiteness of the resulting molded article can be effectively prevented from decreasing, allowing the resin to be sufficiently melted and softened, making it possible to ensure that the strength of the resulting molded article is sufficiently excellent, and also allowing the shape, surface condition, etc. of the molded article to be suitably controlled.

[0071] [3-1]Mixing process In the mixing step, the binder of the present invention and fibers are mixed in a gas phase to obtain a mixture.

[0072] [3-1-1] Fiber Examples of fibers include polyolefin fibers such as polyethylene and polypropylene, synthetic resin fibers such as polyester fibers and polyamide fibers, and natural resin fibers such as cellulose fibers, keratin fibers and fibroin fibers. One or a combination of two or more types selected from these may be used, with cellulose fibers being preferred.

[0073] Cellulose fibers are renewable natural materials and are inexpensive and easily available among various fibers, which makes them advantageous from the viewpoints of reducing the production costs of molded articles, ensuring stable production, reducing environmental impact, etc. Furthermore, cellulose fibers have particularly high theoretical strength among various fibers, which makes them advantageous from the viewpoint of improving the strength of molded articles.

[0074] In this specification, the cellulose fiber may be any fiber containing cellulose as a compound as the main component, and may contain, in addition to cellulose, for example, hemicellulose or lignin.

[0075] However, the lignin content in the cellulose fibers is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less.

[0076] The cellulose content in the cellulose fibers is preferably 50.0% by mass or more, more preferably 60.0% by mass or more, and even more preferably 80.0% by mass or more.

[0077] The cellulose fibers may be those that have been subjected to a treatment such as bleaching, etc. The cellulose fibers may also be those that have been subjected to a treatment such as ultraviolet irradiation treatment, ozone treatment, or plasma treatment.

[0078] Examples of cellulose fibers that can be used include wood pulp for papermaking, such as chemical pulp or mechanical pulp prepared from softwood and / or hardwood trees, recycled paper pulp, linters, and other non-wood plant fibers prepared from hemp, cotton, kenaf, etc.

[0079] The average length of the fibers is not particularly limited, but is preferably 10 μm or more and 50 mm or less, more preferably 20 μm or more and 5.0 mm or less, and even more preferably 30 μm or more and 3.0 mm or less, in terms of length-length weighted average fiber length. This allows the strength and other properties of the produced molded article to be improved.

[0080] The average thickness of each fiber is preferably 1.0 μm or more and 1000 μm or less, and more preferably 2.0 μm or more and 100.0 μm or less.

[0081] This makes it possible to improve the strength of the molded article to be produced, and also to more effectively prevent the occurrence of undesired irregularities on the surface of the molded article to be produced.

[0082] In addition, when the cross section of the fiber is not circular, the diameter of a circle having an area equal to the area of ​​the cross section is assumed to be the thickness of the fiber.

[0083] The average aspect ratio of the fibers, that is, the average length to the average thickness, is not particularly limited, but is preferably 10 or more and 1,000 or less, and more preferably 15 or more and 500 or less.

[0084] This makes it possible to improve the strength of the molded article to be produced, and also to more effectively prevent the occurrence of undesired irregularities on the surface of the molded article to be produced.

[0085] In this specification, the term "fiber" can refer to a single fiber or to an aggregate of multiple fibers. The fiber can also be fibers that have been untangled into fibers by subjecting a material to defibration treatment, i.e., a defibrated material. Examples of materials to be defibrated include pulp sheets, paper, waste paper, tissue paper, kitchen paper, cleaners, filters, liquid absorbents, sound absorbers, cushioning materials, mats, cardboard, and other materials in which fibers are entangled or bound together.

[0086] In this step, multiple types of fibers may be used. For example, fibers with different properties may be used for different parts of the molded article to be produced.

[0087] [3-1-2] Binding material In this step, the binder of the present invention described above is mixed with fibers.

[0088] In this step, the binder of the present invention to be mixed with the fibers preferably satisfies the above-mentioned conditions.

[0089] In this step, multiple types of binders of the present invention may be used. For example, binders of the present invention with different conditions may be used depending on the parts of the molded body to be produced.

[0090] The binder of the present invention used in this step is preferably 0.1 parts by mass or more and 40.0 parts by mass or less, more preferably 1.0 parts by mass or more and 35.0 parts by mass or less, and even more preferably 2.0 parts by mass or more and 30.0 parts by mass or less, per 100 parts by mass of fiber.

[0091] This allows the produced molded article to have both high levels of whiteness and strength.

[0092] [3-1-3] Other compositions In this step, the binder of the present invention and fibers are mixed together, but other compositions may also be mixed in. Hereinafter, such components will also be referred to as "other compositions" in this section.

[0093] However, the amount of other compositions used is preferably 10.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.0 part by mass or less, per 100 parts by mass of fibers.

[0094] [3-1-4] Mixing conditions In this step, at least the binder of the present invention and fibers are mixed in a gas phase to obtain a mixture, but it is preferable to carry out the step so as to satisfy the following conditions. That is, it is preferable to mix the binder of the present invention with defibrated fibers.

[0095] This allows the binder and fibers to be mixed more uniformly, and undesired compositional variations in the molded article to be more effectively suppressed, resulting in improved strength, reliability, etc. of the molded article.

[0096] The mixing of the binder of the present invention with the fibers in this step may be carried out in a gas phase, but is preferably carried out in air.

[0097] This step may be carried out under a reduced pressure atmosphere, or in an atmosphere in which at least a part of the air has been replaced with a gas such as nitrogen.

[0098] In this step, it is preferable to mix the binder of the present invention with the fibers in an air current generated by a blower or the like.

[0099] This allows the binder and fibers to be mixed more uniformly, and undesired compositional variations in the molded article to be more effectively suppressed, resulting in improved strength, reliability, etc. of the molded article.

[0100] In this step, a predetermined amount of the binder of the present invention and a predetermined amount of fibers may be supplied and then mixed, or at least one of them may be supplied at multiple times.

[0101] Furthermore, when other compositions are used in this step, a predetermined amount of the other compositions may be supplied together with a predetermined amount of the binder of the present invention and a predetermined amount of fibers, and then these may be mixed, or the other compositions may be supplied at multiple times. This step is preferably carried out at a relatively low temperature.

[0102] More specifically, the maximum temperature of the gas phase in this step is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 50°C or lower.

[0103] This makes it possible to more effectively prevent, for example, the thermoplastic resin constituting the binder from being unintentionally unevenly distributed in the resulting mixture, thereby improving the strength, reliability, etc. of the molded body produced.

[0104] Furthermore, when the melting point of the thermoplastic resin is T1 [°C], the maximum temperature of the gas phase in this step is preferably (T1-20)°C or less, more preferably (T1-30)°C or less, and even more preferably (T1-50)°C or less.

[0105] This makes it possible to more effectively prevent, for example, the thermoplastic resin constituting the binder from being unintentionally unevenly distributed in the resulting mixture, thereby improving the strength, reliability, etc. of the molded body produced.

[0106] [3-2] Molding process In the molding step, the mixture obtained in the mixing step is pressurized and heated to obtain a molded body.

[0107] This step can be carried out using, for example, a heat press, a heat roller, a three-dimensional molding machine, or the like.

[0108] The heating temperature in this step is preferably a temperature equal to or higher than the melting point of the thermoplastic resin and equal to or lower than the melting point of the high-melting fluorescent whitening agent.

[0109] This allows the produced molded article to have better whiteness, strength, reliability, etc. Furthermore, the time required for the molding step can be shortened, and the productivity of the molded article can be improved.

[0110] In particular, when the melting point of the thermoplastic resin is T1 [°C] and the melting point of the high-melting-point fluorescent brightener is T2 [°C], the heating temperature in this step preferably satisfies the condition of (T1 + 10)°C or higher and (T2 - 10)°C or lower, more preferably (T1 + 20)°C or higher and (T2 - 20)°C or lower, and even more preferably (T1 + 30)°C or higher and (T2 - 30)°C or lower.

[0111] This allows the aforementioned effects to be more pronounced. Furthermore, even if the processing time in the molding step is relatively short, the strength, reliability, etc. of the obtained molded body can be sufficiently excellent, and the productivity of the molded body can be further improved.

[0112] The specific heating temperature in this step is preferably 170°C or higher, more preferably 175°C or higher and 220°C or lower, and even more preferably 180°C or higher and 200°C or lower.

[0113] This allows the produced molded article to have better whiteness, strength, reliability, etc. Furthermore, the time required for the molding step can be shortened, and the productivity of the molded article can be improved.

[0114] The pressure when molding the mixture in this step is not particularly limited, but is preferably 0.5 MPa or more and 8.0 MPa or less, more preferably 0.8 MPa or more and 6.0 MPa or less, and even more preferably 1.0 MPa or more and 5.0 MPa or less.

[0115] This makes it possible to improve the productivity of the molded article while ensuring that the strength, reliability, etc. of the obtained molded article are sufficiently excellent.

[0116] The heating and pressurizing time in this step is preferably 0.5 seconds or more and 300.0 seconds or less, more preferably 1.0 seconds or more and 60.0 seconds or less, and even more preferably 1.5 seconds or more and 45.0 seconds or less.

[0117] This makes it possible to improve the productivity of the molded article while ensuring that the strength, reliability, etc. of the obtained molded article are sufficiently excellent, and is also preferable from the viewpoint of energy saving.

[0118] [3-3] Other processes The method for producing a molded body may further include other steps in addition to the steps described above, such as a cutting step of cutting the produced molded body into an appropriate size and shape.

[0119] [4] Molded body Next, the molded article according to the present invention will be described. The molded article according to the present invention is produced using the binder of the present invention described above.

[0120] The molded article according to the present invention contains at least fibers, a thermoplastic resin, and a high-melting-point fluorescent whitening agent.

[0121] The fiber content in the molded body is preferably 70.0% by mass or more and 99.9% by mass or less, more preferably 74.0% by mass or more and 99.0% by mass or less, and even more preferably 76.0% by mass or more and 98.0% by mass or less. This allows the molded article to have both high levels of whiteness and strength.

[0122] The content of the thermoplastic resin in the molded body is preferably 0.08% by mass or more and 29.4% by mass or less, more preferably 0.8% by mass or more and 24.5% by mass or less, and even more preferably 1.7% by mass or more and 22.0% by mass or less.

[0123] This allows the molded body to have sufficiently excellent whiteness and also to have excellent strength.

[0124] The content of the high melting point fluorescent brightener in the molded product is preferably 0.00001 to 0.3% by mass, more preferably 0.0001 to 0.2% by mass, and even more preferably 0.006 to 0.12% by mass.

[0125] This more effectively prevents concentration quenching and the color of the high-melting-point fluorescent brightening agent itself from adversely affecting the whiteness of the molded article, thereby improving the whiteness of the molded article.

[0126] Furthermore, when the molded body contains a white pigment, the content of the white pigment in the molded body is preferably 0.001% by mass or more and 6.0% by mass or less, more preferably 0.03% by mass or more and 4.5% by mass or less, and even more preferably 0.1% by mass or more and 3.5% by mass or less.

[0127] This allows the molded body to have better whiteness and strength.

[0128] The shape and size of the molded body according to the present invention are not particularly limited, but when the molded body is in the form of a sheet, its thickness is preferably 0.01 mm or more and 3 mm or less, and more preferably 0.05 mm or more and 1 mm or less.

[0129] [5] Molded body manufacturing equipment Next, a manufacturing apparatus that can be used to manufacture the molded article of the present invention will be described.

[0130] FIG. 1 is a diagram schematically illustrating an example of a manufacturing apparatus capable of manufacturing a sheet-shaped molded body.

[0131] As shown in FIG. 1, the manufacturing apparatus 100 has a supply section 10, a crushing section 12, a defibrating section 20, a sorting section 40, a first web forming section 45, a rotating body 49, a mixing section 50, a deposition section 60, a second web forming section 70, a formed body forming section 80, a cutting section 90, and a humidifying section 78.

[0132] The supply unit 10 supplies raw material to the crushing unit 12. The supply unit 10 is, for example, an automatic feed unit for continuously feeding raw material into the crushing unit 12. The raw material supplied to the crushing unit 12 may be any material containing fiber, but materials containing cellulose fiber, such as waste paper, are preferably used. The following mainly describes the case where the raw material supplied to the crushing unit 12 contains cellulose fiber.

[0133] The crushing unit 12 cuts the raw material supplied by the supply unit 10 into small pieces in air, such as in the atmosphere. The small pieces have a shape and size of, for example, several centimeters square. In the example shown in the figure, the crushing unit 12 has crushing blades 14, which can cut the input raw material. A shredder, for example, is used as the crushing unit 12. The raw material cut by the crushing unit 12 is received in a hopper 1 and then transported to the defibrating unit 20 via a pipe 2.

[0134] The defibrating unit 20 defibrates the raw material cut by the crushing unit 12. Here, "defibrating" refers to unraveling the raw material, which is made up of multiple fibers bound together, i.e., the material to be defibrated, into individual fibers. The defibrating unit 20 also has the function of separating substances such as resin particles, ink, toner, fillers, and anti-bleed agents adhering to the raw material from the fibers.

[0135] The material that has passed through the defibrating unit 20 is called the "defibrated material." In addition to the defibrated fibers, the "defibrated material" may also contain resin particles that have separated from the fibers when the fibers are defibrated, colorants such as ink, toner, and fillers, and additives such as anti-bleeding agents and paper strength agents. Examples of resin particles that have separated from the fibers include particles containing resin that binds multiple fibers together.

[0136] The defibrator unit 20 performs defibration using a dry method. A dry method is one in which defibration and other processes are performed in air such as the atmosphere, rather than a wet method in which the material is dissolved into a slurry in a liquid such as water. In this embodiment, an impeller mill is used as the defibrator unit 20. The defibrator unit 20 has the function of generating an airflow that sucks in the raw material and discharges the defibrated material. This allows the defibrator unit 20 to suck in the raw material together with the airflow from the inlet 22 using the airflow it generates, defibrate the material, and transport the defibrated material to the outlet 24. The defibrated material that has passed through the defibrator unit 20 is transferred to the sorting unit 40 via pipe 3. The airflow used to transport the defibrated material from the defibrator unit 20 to the sorting unit 40 may be the airflow generated by the defibrator unit 20, or an airflow generated by an airflow generating device such as a blower may be provided and used.

[0137] The sorting unit 40 introduces the defibrated material defibrated by the defibrator unit 20 through an inlet 42 and sorts it by fiber length. The sorting unit 40 has a drum unit 41 and a housing unit 43 that houses the drum unit 41. The drum unit 41 can be, for example, a sieve. The drum unit 41 has a mesh and can separate a first sorted material, which is fibers or particles that are smaller than the mesh opening size and pass through the mesh, from a second sorted material, which is fibers, undefibrated pieces, or lumps that are larger than the mesh opening size and do not pass through the mesh. For example, the first sorted material is transferred to the mixing unit 50 via pipe 7. The second sorted material is returned to the defibrator unit 20 from a discharge port 44 via pipe 8. Specifically, the drum unit 41 is a cylindrical sieve that is rotated by a motor. The mesh of the drum portion 41 may be, for example, a wire mesh, an expanded metal made by stretching a metal plate with slits, or a punched metal made by forming holes in a metal plate with a press or the like.

[0138] The first web forming section 45 conveys the first sorted material that has passed through the sorting section 40 to the mixing section 50. The first web forming section 45 includes a mesh belt 46, a tension roller 47, and a suction section .

[0139] The suction unit 48 can suck the first sorted material that has passed through the openings of the sorting unit 40, i.e., the openings in the mesh, and dispersed into the air, onto the mesh belt 46. The first sorted material is deposited on the moving mesh belt 46, forming a web V. The basic configuration of the mesh belt 46, tension roller 47, and suction unit 48 is the same as that of the mesh belt 72, tension roller 74, and suction mechanism 76 of the second web forming unit 70, which will be described later.

[0140] The web V is formed into a soft, puffy state containing a lot of air by passing through the sorting section 40 and the first web forming section 45. The web V deposited on the mesh belt 46 is fed into the pipe 7 and transported to the mixing section 50.

[0141] The rotating body 49 can cut the web V before the web V is transported to the mixing section 50. In the example shown, the rotating body 49 has a base 49a and protrusions 49b protruding from the base 49a. The protrusions 49b have, for example, a plate-like shape. In the example shown, four protrusions 49b are provided, and the four protrusions 49b are provided at equal intervals. By rotating the base 49a in the direction R, the protrusions 49b can rotate around the base 49a as an axis. By cutting the web V with the rotating body 49, it is possible to reduce fluctuations in the amount of defibrated material supplied to the deposition section 60 per unit time, for example.

[0142] The rotating body 49 is provided near the first web forming unit 45. In the illustrated example, the rotating body 49 is provided near the tension roller 47a located downstream in the path of the web V, i.e., next to the tension roller 47a. The rotating body 49 is provided at a position where the protrusions 49b can come into contact with the web V but do not come into contact with the mesh belt 46 on which the web V is deposited. The shortest distance between the protrusions 49b and the mesh belt 46 is, for example, not less than 0.05 mm and not more than 0.5 mm.

[0143] The mixing section 50 mixes the first sorted material that has passed through the screening section 40, in other words, the first sorted material containing fibers transported by the first web forming section 45, with the binder of the present invention. The mixing section 50 has a binder supply section 52 that supplies the binder of the present invention, a pipe 54 that transports the first sorted material and the binder of the present invention, and a blower 56. In the example shown in the figure, the binder of the present invention is supplied from the binder supply section 52 to the pipe 54 via a hopper 9. The pipe 54 is continuous with the pipe 7.

[0144] In the mixing section 50, an airflow is generated by a blower 56, and the first sorted material and the binder of the present invention can be mixed and transported in the pipe 54. The mechanism for mixing the first sorted material and the binder of the present invention is not particularly limited, and may be one that uses a blade that rotates at high speed to mix, or one that uses the rotation of a container, such as a V-type mixer.

[0145] The binder supply unit 52 may be a screw feeder as shown in Fig. 1 or a disk feeder (not shown). The fibers are not bonded together when the binder of the present invention is supplied from the binder supply unit 52. The thermoplastic resin contained in the binder of the present invention is partially melted as it passes through the molded body forming unit 80, bonding together the fibers in the surface region of the molded body WS.

[0146] The mixture that has passed through the mixing section 50 , that is, the composition for manufacturing a compact, which is a mixture of the first sorted material and the binder of the present invention, is transferred to the deposition section 60 via a pipe 54 .

[0147] The depositing unit 60 introduces the mixture that has passed through the mixing unit 50 from an inlet 62, loosens the defibrated material of tangled fibers, and drops it down while dispersing it in the air. This allows the depositing unit 60 to deposit the mixture uniformly onto the second web forming unit 70.

[0148] The deposition unit 60 has a drum unit 61 and a housing unit 63 that houses the drum unit 61. A rotating cylindrical sieve is used as the drum unit 61. The drum unit 61 has a mesh and causes fibers or particles that are smaller than the mesh size and are contained in the mixture that has passed through the mixing unit 50 to fall. The configuration of the drum unit 61 is the same as that of the drum unit 41, for example.

[0149] The "sieve" of the drum unit 61 does not have to have the function of separating out a specific object. In other words, the "sieve" used as the drum unit 61 means one equipped with a mesh, and the drum unit 61 may allow all of the mixture introduced into the drum unit 61 to fall.

[0150] The second web forming unit 70 deposits the material that has passed through the depositing unit 60 to form a web W, which is a deposit that will become the formed body WS. The second web forming unit 70 has, for example, a mesh belt 72, a tension roller 74, and a suction mechanism 76.

[0151] As the mesh belt 72 moves, it deposits materials that have passed through the openings of the deposition section 60, i.e., the openings of the net. The mesh belt 72 is stretched by tension rollers 74, and is configured to be impervious to materials that have passed through it but allow air to pass through. The mesh belt 72 moves as the tension rollers 74 rotate. As the mesh belt 72 moves continuously, materials that have passed through the deposition section 60 continuously fall and accumulate, forming a web W on the mesh belt 72. The mesh belt 72 is made of, for example, metal, resin, cloth, nonwoven fabric, etc.

[0152] The suction mechanism 76 is provided below the mesh belt 72, i.e., on the opposite side from the deposition unit 60. The suction mechanism 76 can generate a downward airflow, i.e., an airflow directed from the deposition unit 60 toward the mesh belt 72. This suction mechanism 76 can suck the mixture dispersed in the air by the deposition unit 60 onto the mesh belt 72. This can increase the discharge speed from the deposition unit 60. Furthermore, the suction mechanism 76 can form a downflow in the falling path of the mixture, which can prevent the defibrated material and the binder of the present invention from becoming entangled while falling.

[0153] As described above, the web W is formed in a soft, puffy state containing a lot of air through the web forming process performed in the deposition unit 60 and the second web forming unit 70. The web W deposited on the mesh belt 72 is transported to the formed body forming unit 80.

[0154] The formed body forming section 80 heats the web W deposited on the mesh belt 72 to form a formed body WS. In the formed body forming section 80, the web W, which is a deposit of the mixture of defibrated material and the binder of the present invention mixed in the second web forming section 70, is heated to soften and melt the thermoplastic resin, thereby bonding the multiple fibers.

[0155] The molded body forming section 80 includes a heating section 84 that heats the web W. The heating section 84 may be, for example, a heat press or a heating roller, but the following description will be given using an example in which a heating roller is used. The number of heating rollers in the heating section 84 is not particularly limited. In the illustrated example, the heating section 84 includes a pair of heating rollers 86. By configuring the heating section 84 as heating rollers 86, the molded body WS can be molded while continuously transporting the web W.

[0156] The heating rollers 86 are arranged, for example, so that their rotation axes are parallel to one another. The roller radius of the heating rollers 86 is preferably 2.0 cm or more and 5.0 cm or less, more preferably 2.5 cm or more and 4.0 cm or less, and even more preferably 2.5 cm or more and 3.5 cm or less.

[0157] The heating roller 86 comes into contact with the web W and heats the web W while sandwiching and transporting the web W.

[0158] The rotation speed of the heating roller 86 is, for example, preferably 20 rpm or more and 500 rpm or less, more preferably 30 rpm or more and 350 rpm or less, and even more preferably 50 rpm or more and 300 rpm or less. This allows the surface area of ​​the web W to be heated sufficiently and more accurately.

[0159] The heating rollers 86 sandwich and transport the web W, forming a formed body WS of a predetermined thickness. Here, the pressure applied to the web W by the heating roller 86 is preferably 0.5 MPa or more and 8.0 MPa or less, more preferably 0.8 MPa or more and 6.0 MPa or less, and even more preferably 1.0 MPa or more and 5.0 MPa or less.

[0160] The surface temperature of the heating roller 86 when heating the web W is preferably 170°C or higher, more preferably 175°C or higher and 220°C or lower, and even more preferably 180°C or higher and 200°C or lower.

[0161] The manufacturing apparatus 100 of this embodiment may include a cutting section 90, if necessary. In the illustrated example, the cutting section 90 is provided downstream of the heating section 84. The cutting section 90 cuts the molded body WS molded by the molded body forming section 80. In the illustrated example, the cutting section 90 includes a first cutting section 92 that cuts the molded body WS in a direction intersecting the conveying direction of the molded body WS, and a second cutting section 94 that cuts the molded body WS in a direction parallel to the conveying direction. The second cutting section 94 cuts the molded body WS that has passed through the first cutting section 92, for example.

[0162] The manufacturing apparatus 100 of this embodiment may also include a humidifying unit 78. In the illustrated example, the humidifying unit 78 is provided downstream of the cutting unit 90 and upstream of the discharge unit 96. The humidifying unit 78 can apply water or water vapor to the formed body WS. Specific embodiments of the humidifying unit 78 include, for example, spraying a mist of water or an aqueous solution, spraying water or an aqueous solution, and ejecting water or an aqueous solution from an inkjet head to deposit the water or aqueous solution.

[0163] The manufacturing apparatus 100 includes a humidifying unit 78, which allows the formed molded body WS to be moistened. This allows the fibers to absorb moisture and become soft. Therefore, when the molded body WS is used to form a three-dimensional container or the like, wrinkles and tears are less likely to occur. Furthermore, by moistening the molded body WS, if the fibers are cellulose, hydrogen bonds are more likely to form between the cellulose fibers, thereby increasing the density of the molded body WS and improving, for example, its strength.

[0164] 1, the humidifying unit 78 is provided downstream of the cutting unit 90, but the same effect as above can be obtained if the humidifying unit 78 is provided downstream of the heating unit 84. That is, the humidifying unit 78 may be provided downstream of the heating unit 84 and upstream of the cutting unit 90.

[0165] According to the manufacturing apparatus as described above, the method for manufacturing a molded article of the present invention can be suitably carried out.

[0166] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0167] For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0168] Furthermore, the method for producing a molded article of the present invention is not limited to being carried out using the above-mentioned apparatus, and may be carried out using any apparatus. [Example]

[0169] Next, specific examples of the present invention will be described. [6] Manufacturing of binders The binder was prepared as follows.

[0170] Example 1 First, 89.9 parts by mass of polyester resin (Vylon 220, manufactured by Toyobo Co., Ltd., melting point: 101°C) as a thermoplastic resin, 10.0 parts by mass of calcium carbonate (Hakuenka CC, manufactured by Shiraishi Kogyo Co., Ltd.) as a white pigment, and 0.1 parts by mass of 1,4-bis(2-benzoxazolyl)naphthalene (melting point: 212°C, manufactured by Tokyo Chemical Industry Co., Ltd.) as a fluorescent whitening agent were mixed in a high-speed mixer (FM-type mixer FM-10C, manufactured by Nippon Coke Co., Ltd.) to obtain a resin-pigment mixture. The T1 / 2 temperature, which is the melting point of the thermoplastic resin, was measured using an elevated flow tester (CFT500, manufactured by Shimadzu Corporation) under a load of 20 kg / cm. 2 The temperature was measured under the following conditions: temperature rise rate: 5.0°C / min, die diameter: 1.0 mm, die length: 1.0 mm.

[0171] This resin-pigment mixture was fed from the hopper of a twin-screw kneading extruder (Toshiba Machine Co., Ltd., TEM-26SS), melt-kneaded, and pelletized to obtain pellets of approximately 3 mm.

[0172] The pellets were pulverized in a hammer mill (Dalton, Lab Mill LM-5) to particles with a diameter of 1 mm or less, and the pulverized particles were further pulverized in a jet mill (Nippon Pneumatic, PJM-80SP) to obtain particles with a maximum particle size of 40 μm or less. These particles were classified in an air classifier (Nippon Pneumatic, MDS-3) to obtain an aggregate of colored resin particles with a volume average particle size of 10.0 μm.

[0173] 100.0 parts by mass of the above colored resin particles and 1.0 part by mass of fumed silica (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) as an aggregation inhibitor were added to a blender (Waring Blender 7012, manufactured by Waring Co., Ltd.) and mixed at a rotation speed of 15,600 rpm for 60 seconds to obtain the binder of Example 1.

[0174] A portion of the binder obtained as described above was placed in a glass container and left at room temperature for 24 hours. The colored resin particles did not aggregate and form clumps, and remained in a fluid powder state. This confirmed that the aggregation inhibitor coated the surface of the colored resin particles, maintaining a non-aggregating state.

[0175] Example 2 A binder was produced in the same manner as in Example 1, except that a styrene-acrylic resin (FSR-068 (melting point: 130° C.) manufactured by Fujikura Chemical Industries, Ltd.) was used as the thermoplastic resin.

[0176] Example 3 A binder was produced in the same manner as in Example 1, except that 4,4'-bis(2-benzoxazolyl)stilbene (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: 355°C) was used as the fluorescent whitening agent.

[0177] Example 4 A binder was produced in the same manner as in Example 3, except that titanium oxide was used as the white pigment.

[0178] Example 5 The binder was produced in the same manner as in Example 3, except that the amount of thermoplastic resin used in preparing the resin pigment mixture was 89.0 parts by mass, the amount of white pigment used was 10.0 parts by mass, and the amount of fluorescent whitening agent used was 1.0 part by mass.

[0179] Example 6 The binder was produced in the same manner as in Example 3, except that the amount of thermoplastic resin used in preparing the resin pigment mixture was 88.0 parts by mass, the amount of white pigment used was 10.0 parts by mass, and the amount of fluorescent whitening agent used was 2.0 parts by mass.

[0180] Example 7 The binder was produced in the same manner as in Example 3, except that the amount of thermoplastic resin used in preparing the resin pigment mixture was 79.9 parts by mass, the amount of white pigment used was 20.0 parts by mass, and the amount of fluorescent whitening agent used was 0.1 parts by mass.

[0181] Example 8 The binder was produced in the same manner as in Example 3, except that the amount of thermoplastic resin used in preparing the resin pigment mixture was 69.9 parts by mass, the amount of white pigment used was 30.0 parts by mass, and the amount of fluorescent whitening agent used was 0.1 parts by mass.

[0182] (Comparative Example 1) A binder was produced in the same manner as in Example 1, except that a thermoplastic resin was used alone instead of a resin pigment mixture which was a mixture of a thermoplastic resin, a white pigment, and a fluorescent whitening agent.

[0183] (Comparative Example 2) A binder was produced in the same manner as in Example 1, except that a mixture of 90.0 parts by mass of thermoplastic resin and 10.0 parts by mass of white pigment was used instead of a resin-pigment mixture that was a mixture of thermoplastic resin, white pigment, and fluorescent brightener. In other words, the binder of this comparative example does not contain a fluorescent brightener.

[0184] (Comparative Example 3) A binder was produced in the same manner as in Example 3, except that 7-diethylamino-4-methylcoumarin (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: 74° C.) was used as the fluorescent whitening agent.

[0185] [7] Manufacturing of molded bodies Using the binder of Example 1, a sheet-shaped molded body was produced as follows.

[0186] First, as the fiber source for the molded product, commercially available copy paper was printed with a monochrome pattern at a coverage rate of 10% using an inkjet printer (Seiko Epson, PX-M7050) and the resulting paper was defibrated using a high-speed mill to prepare defibrated fibers. The average diameter of these defibrated fibers was measured using a fiber tester (Lorenzen & Wettre, Fiber Tester) and found to be 20.0 μm.

[0187] 80.0 parts by mass of this defibrated fiber and 20.0 parts by mass of the binder from Example 1 were added to a blender (Waring Blender Model 7012, manufactured by Waring Co.) and mixed at a rotation speed of 3100 rpm for 7 seconds to obtain a mixture of fiber and binder.

[0188] The resulting mixture was placed on a 200 mm diameter sieve with 0.6 mm mesh and then piled onto a 250 mm diameter (1 mm thick) fluororesin-coated aluminum disc (Sumitomo Electric Fine Polymers, Inc., Sumiflon Coated Aluminum) using an electric sieve shaker (Retsch, AS-200). Another fluororesin-coated aluminum disc of the same diameter was placed on top of the piled mixture, and the sheet was pressed with a press to a pressure of 1.0 MPa.

[0189] The pressurized mixture was sandwiched between aluminum plates and placed in a heating press, where it was heated at 180°C for 2.0 seconds. The pressure was released, and the mixture was left to cool to room temperature. The mixture was peeled off from the aluminum plates to obtain a sheet-like compact. The sheet had a thickness of 130 μm.

[0190] Sheet-like molded bodies were produced in the same manner as above, except that the binder of Example 1 was replaced by the binders of Examples 2 to 8 and Comparative Examples 1 to 3.

[0191] [8] Evaluation The sheet-like molded articles of each of the Examples and Comparative Examples obtained as described above were evaluated as follows.

[0192] [8-1] Whiteness The ISO whiteness of the sheet-like molded products of each of the Examples and Comparative Examples was measured using a PF7000 manufactured by Nippon Denshoku Industries Co., Ltd. Based on the measurement results, the relative value of the whiteness of each molded product was calculated, assuming that the whiteness of the molded product of Comparative Example 1 was 1, and the molded products were evaluated according to the following criteria. The larger this relative value, the higher the whiteness, and the more preferable it is.

[0193] A: The relative value to the whiteness of Comparative Example 1 is more than 1.10. B: The relative value to the whiteness of Comparative Example 1 is more than 1.05 and 1.10 or less. C: The relative value to the whiteness of Comparative Example 1 is more than 1.00 and 1.05 or less. D: The relative value to the whiteness of Comparative Example 1 is 1.00 or less.

[0194] [8-2] Tensile strength Tensile tests were conducted on the sheet-like molded articles of each of the Examples and Comparative Examples in accordance with JIS P 8113. More specifically, test pieces with a total length of 180 mm were cut out from each molded article, and then set in a tensile testing machine (Shimadzu Corporation, AGS-X) and subjected to tensile tests at an elongation rate of 20 mm / min. The breaking stress of the test piece was calculated from the maximum load until the test piece broke, and this was taken as the tensile strength. The tensile tests were conducted in accordance with JIS P 8111 at room temperature of 23°C and humidity of 50%.

[0195] Based on the measurement results, the relative value of the tensile strength of each molded body was calculated, assuming that the tensile strength of the molded body of Comparative Example 1 was 1, and evaluated according to the following criteria. The larger this relative value, the stronger the tensile strength, which is preferable.

[0196] A: The relative value to the tensile strength of Comparative Example 1 is more than 0.9. B: The relative value to the tensile strength of Comparative Example 1 is more than 0.8 and 0.9 or less. C: The relative value to the tensile strength of Comparative Example 1 is 0.8 or less.

[0197] These results are summarized in Table 1, along with the binder compositions of the examples and comparative examples.

[0198] [Table 1]

[0199] As is clear from Table 1, excellent results were obtained in the present invention, whereas satisfactory results were not obtained in the comparative examples.

[0200] Furthermore, for the binders of each of the examples and comparative examples, sheet-shaped molded bodies were produced using the manufacturing apparatus shown in FIG. 1, and the same evaluations as above were carried out on these molded bodies, and the same results as above were obtained. [Explanation of symbols]

[0201] 1...hopper, 2,3,7,8...pipe, 9...hopper, 10...supply section, 12...crushing section, 14...crushing blade, 20...defibration section, 22...inlet, 24...discharge outlet, 40...sorting section, 41...drum section, 42...inlet, 43...housing section, 44...discharge outlet, 45...first web forming section, 46...mesh belt, 47, 47a...tension roller, 48...suction section, 49...rotating body, 49a...base, 49b...projection, 50...mixing section, 52...binder supply section, 54...pipe, 56...blower, 60...accumulation section, 61...drum section, 62...inlet, 63...housing section, 70...second web forming section, 72...mesh belt, 74...tension roller, 76...suction mechanism, 78...humidifying section, 80...molded body forming section, 84...heating section, 86...heating roller, 90...cutting section, 92...first cutting section, 94...second cutting section, 96...discharge section, 100...manufacturing apparatus, R...direction, V...web, W...web, WS...molded body

Claims

1. A thermoplastic resin and an optical brightener having a melting point higher than that of the thermoplastic resin are included. a mixing step of mixing the binder and the fibers in a gas phase to obtain a mixture; and a molding step of pressurizing and heating the mixture to obtain a molded body. 。

2. The heating temperature in the molding step is a temperature equal to or higher than the melting point of the thermoplastic resin, and The method for producing a molded article according to claim 1, wherein the temperature is equal to or lower than the melting point of the fluorescent whitening agent.

3. 3. The composition according to claim 1 or 2, wherein the heating temperature in the molding step is 170°C or higher. Method of manufacturing the shape.

4. The method for producing a molded body according to any one of claims 1 to 3, wherein the binder contains an aggregation inhibitor. Law.

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