Composition for wood fiber board, wood fiber board, resin molded article, method for producing pellet, and method for producing resin molded article

Abstract

Provided is a composition for a woody fiber plate, including lignocellulose fiber and an isocyanate compound, the content of the isocyanate compound being 0.5-6 mass% with respect to the total mass of the lignocellulose fiber and the isocyanate compound. Provided is a wood fiber board including lignocellulose fiber and a reaction product of an isocyanate compound and water, the content of the reaction product in terms of the isocyanate compound being is 0.5-6 mass% with respect to the total mass of the lignocellulose fiber and the reaction product.

Description

Composition for wood fiber board, wood fiber board, resin molded product, pellet manufacturing method, and resin molded product manufacturing method

[0001] The present invention relates to a composition for wood fiber boards, a wood fiber board, a resin molded product, a method for producing pellets, and a method for producing a resin molded product. This application claims priority based on Japanese Patent Application No. 2024-062004, filed on April 8, 2024, the contents of which are incorporated herein by reference.

[0002] As a board-shaped material to replace wood, wood fiberboards have been developed which are made from wood fibers obtained by steaming and defibrating wood chips and synthetic resins as adhesives.

[0003] Patent Literature 1 describes a method for producing pellets or granules using wood fibers, which are used as raw materials for wood fiberboards. Examples of the method for producing pellets or granules include a method for producing wood pellets (comminuted material) or granules containing fibers of lignocellulosic materials or natural fibers, which are used as a feedstock in plastics production, by transporting loose fibers or separated fibers or fiber bundles produced by mechanically, thermomechanically, chemothermomechanically, or chemomechanically comminuting the lignocellulosic materials or natural fibers in a dry or wet air stream, applying a liquid formulation containing one or more polymers, monomers, or oligomers to the fibers while transporting the fibers, forming the fibers into a solid product, and comminuting the solid product to produce the wood pellets or granules. The wood pellets or granules contain 0.3 to 25 parts of one or more polymers, monomers, or oligomers per 100 parts of fiber, by dry weight.

[0004] Patent Document 2 describes a method in which a liquid thermoplastic resin is added to lignocellulose fibers, and a lignocellulose fiberboard is formed using a heat press method, and then the lignocellulose fiberboard is fragmented.

[0005] Patent Document 3 describes a method for producing a fiber-plastic composite product, in which a thermoplastic binder is added to natural fibers, the lignocellulosic fibers are thermoformed using a heat press to produce a molded plate, the molded plate is subdivided, and the resulting plate is kneaded with a thermoplastic resin.

[0006] Patent Document 4 describes a method for producing a fiber-plastic composite product, in which both a thermosetting resin and a thermoplastic resin binder are applied to natural fibers, a solid product is formed, the solid product is subdivided, and then the resulting product is kneaded with a thermoplastic resin.

[0007] Patent Document 5 describes a technique in which cotton or hemp fibers and thermoplastic synthetic resin fibers are mixed together, melted in a heat press to form a molded sheet, and then cut into pellets.

[0008] Non-Patent Document 1 describes a method in which the hydroxyl groups of lignocellulose materials are esterified using an isocyanate compound to reduce the polarity of celluloses and improve their affinity with low-polarity resins such as polyolefins.

[0009] Non-Patent Documents 2 to 4 describe a method in which a blocked isocyanate resin is used, and the blocking group is dissociated during melt-kneading with a thermoplastic resin, allowing the resin to function as a reactive compatibilizer.

[0010] Non-Patent Document 5 describes a technology in which an emulsion-type isocyanate compound is diluted with water, and the compound is impregnated into pulp and cured, thereby kneading unconstrained (free) fibers with increased water resistance with a resin.

[0011] Japanese Patent No. 5481066 International Publication No. 2006 / 001717 International Publication No. 2007 / 073218 International Publication No. 2011 / 002314 Japanese Patent No. 5911755

[0012] Cellulose Chem. Technol., 46(5-6), 381-387 (2012). Journal of Plastics and Composites, 27(16-17), 1679-1687 (2008). Carbon Hydrate Polymers, 68, 537-543 (2007). Carbon Hydrate Polymers, 74, 106-113 (2008). Composites: Part A, 61, 245-257 (2014).

[0013] However, the method described in Patent Document 1 has the problem of being expensive and difficult to obtain because it uses a thermoplastic resin adhesive, which is expensive and difficult to obtain, making it costly, and also of generating a high rate of dust when the solid product is broken down into wood pellets or granules, resulting in a low yield of wood pellets.

[0014] The method described in Patent Document 2 has the following problems: (1) it is expensive because it uses a liquid thermoplastic resin, particularly a resin emulsion or dispersion; (2) liquid thermoplastic resin is different from the binder used to produce ordinary fiberboard, so using a liquid thermoplastic resin in a fiberboard manufacturing device can cause contamination between products; (3) dust is easily generated when the fiberboard is broken down, which can worsen the working environment and reduce yields; (4) when mixed with the resin, the formaldehyde resin thermally decomposes and generates gas, which reduces the quality of the compound; (5) components contained in the gas cause the wood fibers to darken; and (6) the amount of aldehydes emitted from the compound and molded products increases.

[0015] The method described in Patent Document 3 has the same problems as those described in Patent Document 2, namely, (1) to (5) above.

[0016] The method described in Patent Document 4 has the same problems as those described in Patent Document 2, namely, (1) to (5) above.

[0017] The present invention has been made in consideration of the above circumstances, and aims to provide a composition for wood fiber boards, a method for producing wood fiber boards, resin molded products, and pellets, and a method for producing resin molded products, which have a low rate of dust generation when producing fragmented products and a high yield when producing fragmented products.

[0018] The present invention has the following aspects. [1] A composition for wood fiberboards, comprising lignocellulose fibers and an isocyanate compound, wherein the content of the isocyanate compound relative to the total mass of the lignocellulose fibers and the isocyanate compound is 0.5% by mass or more and 6% by mass or less. [2] The composition for wood fiberboards according to [1], wherein the isocyanate compound is an aromatic isocyanate compound. [3] A wood fiberboard, comprising lignocellulose fibers and a reaction product of an isocyanate compound and water, wherein the content of the reaction product, calculated as an isocyanate compound, relative to the total mass of the lignocellulose fibers and the reaction product is 0.5% by mass or more and 6% by mass or less. [4] The wood fiberboard according to [3], wherein the isocyanate compound is an aromatic isocyanate compound. [5] An overall density of 500 kg / m ３ or more, maximum density is 800 kg / m ３ [6] The wood fiber board according to any one of [3] to [5], having a thickness of 6 mm or less. [7] The wood fiber board according to [3], comprising a mixture of the fragmented wood fiber board according to [3] and a thermoplastic resin, and having a formaldehyde emission rate of 100 μg / m3 or less when collected at 65°C in accordance with JASO M902 Automotive Parts - Interior Materials - Volatile Organic Compound (VOC) Emission Measurement Method (Sampling Bag Method). ３ [8] A resin molded product comprising a mixture of the fragmented wood fiberboard according to [3] and a thermoplastic resin, wherein the amount of acetaldehyde emitted at 65°C is 48 μg / m according to JASO M902 Automotive Parts - Interior Materials - Volatile Organic Compound (VOC) Emission Measurement Method (Sampling Bag Method). ３[9] A method for producing pellets, comprising the steps of: processing the wood fiber board according to any one of [3] to [6] to obtain fragments having a length of 1 mm to 6 mm; drying the fragments so that the moisture content is 5% by mass or less; kneading the dried fragments with a thermoplastic resin to obtain a kneaded mixture; and fragmenting the kneaded mixture into pellets of any size.

[10] A method for producing a resin molded product, comprising the steps of obtaining pellets by the pellet manufacturing method according to [9]; and thermoforming the pellets to obtain a resin molded product.

[0019] According to the present invention, it is possible to provide a composition for wood fiberboards, a method for producing wood fiberboards, resin molded products, and pellets, and a method for producing resin molded products, which have a low rate of dust generation when producing fragmented products and a high yield when producing fragmented products.

[0020] 1 is a photograph showing the appearance of the strand-shaped kneaded products obtained in Example 8 and Comparative Example 7.

[0021] The present invention relates to a composition for wood fiberboards, a wood fiberboard, a resin molded product, a method for producing pellets, and a method for producing a resin molded product. The present invention is specifically described below to provide a better understanding of the gist of the invention, and does not limit the scope of the invention unless otherwise specified.

[0022] [Wood Fiber Board Composition] A wood fiber board composition according to one embodiment of the present invention contains lignocellulose fibers and an isocyanate compound.

[0023] <Lignocellulose Fibers> Lignocellulose is a component of plant cell walls and morphologically has a three-dimensional network hierarchical structure in which cellulose is firmly bound to lignin and hemicellulose. Lignocellulose refers to cellulose formed by regular aggregation of monomolecules to form crystalline microfibrils (cellulose nanofibers) of several dozens. Here, however, the term "lignocellulose" refers to a general term for cellulosic fibers primarily derived from plants, including lignin and hemicellulose. The lignocellulose fibers used in the present invention preferably have a cellulose content of 10 to 90% by mass, more preferably 20 to 80% by mass, a hemicellulose content of 1 to 30% by mass, more preferably 2 to 20% by mass, and a lignin content of 1 to 60% by mass, more preferably 5 to 50% by mass. The lignocellulosic fibers used in the present invention are obtained by mechanically, thermomechanically, chemically, chemomechanically, or chemothermo-mechanically treating wood or non-wood plant-derived lignocellulosic materials to soften, destroy, disentangle, or refine the middle layer that adhesively binds the fibers. Such materials can be used as lignocellulosic fibers without any particular restrictions. Wood may be either softwood or hardwood. Examples of non-wood plant-derived lignocellulosic fibers include straw pulp, bagasse pulp, reed pulp, kenaf pulp, linen pulp, ramie pulp, hemp pulp, sisal pulp, flax pulp, and bamboo pulp. Furthermore, the terms "fiber" and "pulp" also include powders such as wood flour, finely ground materials, and sawdust.

[0024] As the lignocellulose fiber used in the present invention, for example, lignocellulose powder, semi-chemical pulp, chemi-ground pulp, refiner ground pulp, thermomechanical pulp, and groundwood pulp can be preferably used, but from a cost perspective, it is preferable to use a fiber containing 5% by mass or more of lignin. Among them, the use of mechanical pulp or fiberboard fiber is preferred from the viewpoints of production efficiency, physical properties, and cost. Examples of mechanical pulp include refiner ground pulp, thermomechanical pulp, and groundwood pulp. From the same perspective, thermomechanical pulp is more preferable. Thermomechanical pulp also includes fiberboard fiber. In a broad sense, fiberboard fiber refers to thermomechanical pulp, and in a narrow sense, it refers to relatively coarse fibers within thermomechanical pulp.

[0025] Lignocellulose fibers contain lignin and / or hemicellulose, unlike pulp that has been bleached (delignified) to a certain extent. Lignocellulose fibers may be used singly or in combination of two or more types.

[0026] As a method for converting lignocellulose material into lignocellulose fibers, any known method can be used without particular limitation, and for example, a conventional method for producing pulp, a conventional method for producing fibers for fiberboard, a mill for powdering chips, etc. can be appropriately used. One example of a method for converting lignocellulose material into lignocellulose fibers is a method in which the lignocellulose material is crushed into chips, then steamed under a pressure of about 1 to 10 bar using a preheater or a press steamer to soften the lignin and hemicellulose that are components of the lignocellulose material, and then defibrated into fibers or fiber bundles using a disc-type blade under pressure in a pressure refiner to produce the desired fibers.

[0027] Furthermore, in many cases, lignocellulose fibers are dried for the purposes of transportation, preservation, storage, and improved handling. Known methods can be used to dry lignocellulose fibers without particular limitations. Examples include a method used in the paper and pulp industries in which wet lignocellulose fibers are discharged onto a roller or wire, dehydrated by suction or pressure, and then thermally dried. Other examples include a method used in the production of fibers for fiberboards in which wet lignocellulose fibers are thermally dried under an airflow through a pipe through which hot air flows. Drying of lignocellulose fibers is preferably carried out at a temperature of, for example, 60°C or higher and 200°C or lower, more preferably 80°C or higher and 160°C or lower, and even more preferably 100°C or higher and 140°C or lower. In recent years, methods for producing defibrated fibers under dry conditions without using hydrothermal conditions have also become widespread. In some cases, fibers other than those produced under hydrothermal conditions are acceptable due to cost and quality considerations. In such cases, dry-produced fibers are also acceptable.

[0028] Lignocellulose fibers are typically long fibers. The average length of the lignocellulose fibers is preferably 0.1 mm or more and 10 mm or less, more preferably 0.5 mm or more and 9 mm or less, and even more preferably 1 mm or more and 8 mm or less. When the average length of the lignocellulose fibers is equal to or greater than the lower limit, they are easily formed into fiberboards and are easily reinforcing when kneaded with resin. If the average length of the lignocellulose fibers is less than the lower limit, they are difficult to form into fiberboards or are difficult to reinforcing when kneaded with resin. If the average length of the lignocellulose fibers is equal to or less than the upper limit, a kneaded product of the fibers and resin is easily obtained and the appearance is less likely to deteriorate. If the average length of the lignocellulose fibers exceeds the upper limit, the fibers become coarse, making kneading with resin difficult and the appearance of the kneaded product is likely to deteriorate.

[0029] The average length of lignocellulose fibers can be measured using, for example, a commercially available device for measuring the length and shape of various pulp and other fibers, or by physically measuring the length of a microscopically enlarged fiber image.

[0030] The average aspect ratio of the lignocellulose fibers is preferably 10 or more and 1000 or less, more preferably 20 or more and 750 or less, and even more preferably 30 or more and 500 or less. When the average aspect ratio of the lignocellulose fibers is equal to or greater than the lower limit, a reinforcing effect is easily obtained when kneaded with a resin. If the average aspect ratio of the lignocellulose fibers is less than the lower limit, a reinforcing effect is difficult to obtain when kneaded with a resin. If the average aspect ratio of the lignocellulose fibers is equal to or less than the upper limit, dispersibility is easily obtained when kneaded with a resin. If the average aspect ratio of the lignocellulose fibers exceeds the upper limit, dispersibility is likely to decrease when kneaded with a resin.

[0031] An example of a specific method for measuring the average length and average aspect ratio of lignocellulose fibers is described below. The average length of lignocellulose fibers is determined by taking electron microscope images of a sufficient number of lignocellulose fibers (e.g., 100 or more) using an electron microscope (e.g., SEM or TEM), measuring the lengths of these lignocellulose fibers, and calculating the arithmetic average. The length of lignocellulose fibers should be measured in a straight, stretched state; however, in reality, many lignocellulose fibers are bent. Therefore, the projected diameter and projected area of ​​microfibers are calculated from the electron microscope image using an image analyzer, and then calculated from the following formula, assuming a cylindrical shape: Length = Projected Area / Projected Diameter Similarly, the diameters of lignocellulose fibers are measured from the electron microscope image, and the average diameter is determined by arithmetic averaging, and the average aspect ratio (average length / average diameter) of the lignocellulose fibers is calculated.

[0032] <Isocyanate Compound> As the isocyanate compound, aromatic isocyanate compounds, aliphatic isocyanate compounds, etc. can be used as desired. Examples of aliphatic isocyanate compounds include hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Examples of aromatic isocyanate compounds include diphenylmethane diisocyanate (MDI) and toliylene diisocyanate (TDI). Of these, from the viewpoint of ease of availability, etc., MDI is preferred as the isocyanate compound. Examples of MDI include 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI, monomeric MDI), and polymeric MDI (polymethylene polyphenyl polyisocyanate). These may be used alone or in combination of two or more. As is well known, polymeric MDI is a mixture of monomeric MDI and its polynuclear form, and is included in diphenylmethane diisocyanate (MDI).

[0033] Furthermore, MDI may be a modified product. Examples of the modified product include a diphenylmethane skeleton (Ph-CH ２ -Ph), and examples thereof include a dimer of MDI, carbodiimide-modified MDI, uretonimine-modified MDI, (trimer) isocyanurate-modified MDI, etc. Any one of these may be used alone, or two or more may be used in combination.

[0034] The content of the isocyanate compound relative to the total mass of the lignocellulose fibers and the isocyanate compound is 0.5% by mass or more and 6% by mass or less, preferably 0.5% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 4% by mass or less. In one aspect of the present invention, the content of the isocyanate compound relative to the total mass of the lignocellulose fibers and the isocyanate compound is preferably more than 2% by mass or less and 6% by mass or less, and more preferably 2.5% by mass or more and 5% by mass or less. When the content of the isocyanate compound is equal to or greater than the lower limit, handling problems are unlikely to occur in the wood fiberboard, and the dust generation rate during fragmentation can be kept low. When the content of the isocyanate compound is equal to or less than the upper limit, the dispersibility of the fibers is unlikely to be impaired when kneaded with resin.

[0035] <Other Components> In addition to the lignocellulose fibers and the isocyanate compound, the wood fiberboard composition according to this embodiment may contain a water repellent (wax), a curing accelerator, a crosslinking agent, a mildew inhibitor, a preservative, an insect repellent, a release agent, a VOC catcher, water, etc.

[0036] <Composition Ratio> In the wood fiberboard composition according to this embodiment, the ratio of the total mass of the lignocellulose fibers and the isocyanate compounds to the total mass of the wood fiberboard composition ((total mass of the lignocellulose fibers and the isocyanate compounds) / total mass of the wood fiberboard composition × 100) is preferably 80% or more and 99.5% or less, more preferably 85% or more and 99.5% or less, and even more preferably 90% or more and 99.5% or less. When this ratio is equal to or greater than the lower limit, an excessive amount is not required when kneading and blending with the resin. When this ratio is less than the lower limit, an excessive amount is required when kneading and blending with the resin. When this ratio is equal to or less than the upper limit, problems with handling of the wood fiberboard are unlikely to occur. When this ratio exceeds the upper limit, molding of the wood fiberboard becomes difficult.

[0037] [Method for Producing a Composition for Wood Fiberboard] The composition for wood fiberboard of this embodiment can be obtained by mixing lignocellulose fibers with an isocyanate compound, or by spraying an isocyanate compound onto lignocellulose fibers.

[0038] According to the composition for wood fiberboards of this embodiment, the composition contains lignocellulose fibers and an isocyanate compound, and the content of the isocyanate compound relative to the total mass of the lignocellulose fibers and the isocyanate compound is 0.5 mass% or more and 10 mass% or less, so the rate of dust generation when producing the fragmented material is low and the yield when producing the fragmented material is high.

[0039] [Wood Fiber Board] A wood fiber board according to one embodiment of the present invention contains lignocellulose fibers and a reaction product of an isocyanate compound and water.

[0040] Examples of the lignocellulose fibers include the same lignocellulose fibers as those in the composition for wood fiberboard of the above-described embodiment.

[0041] The isocyanate compound may be the same as the isocyanate compound in the composition for wood fiberboards of the above-described embodiment. The reaction product of the isocyanate compound and water is a compound such as an amine, polyamine, or urea compound produced by the reaction of the isocyanate group (-NCO) of the isocyanate compound with the hydroxyl group (-OH) of water.

[0042] The content of the reaction product, calculated as an isocyanate compound, relative to the total mass of the lignocellulose fibers and the reaction product is 0.5% by mass or more and 6% by mass or less, preferably 0.5% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 4% by mass or less. When the content of the reaction product, calculated as an isocyanate compound, is equal to or greater than the lower limit, problems are less likely to occur during molding of the wood fiberboard, and the dust generation rate during fragmentation can be kept low. If the content of the reaction product, calculated as an isocyanate compound, is less likely to occur during molding of the wood fiberboard, and the dust generation rate during fragmentation increases. If the content of the reaction product, calculated as an isocyanate compound, is equal to or less than the upper limit, fiber dispersibility is less likely to be impaired during kneading with resin. If the content of the reaction product, calculated as an isocyanate compound, exceeds the upper limit, fiber dispersibility is more likely to be impaired during kneading with resin.

[0043] In addition to the lignocellulose fibers and isocyanate compounds, the wood fiberboard of this embodiment may also contain water repellents (wax), curing accelerators, crosslinking agents, mildew inhibitors, preservatives, insect repellents, release agents, VOC catchers, water, etc.

[0044] In the wood fiberboard of this embodiment, the ratio of the total mass of lignocellulose fibers and isocyanate compounds to the total mass of the wood fiberboard ((total mass of lignocellulose fibers and isocyanate compounds) / total mass of wood fiberboard × 100) is preferably 80% or more and 100% or less, more preferably 85% or more and 100% or less, and even more preferably 90% or more and 100% or less. If this ratio is equal to or greater than the lower limit, no excessive amount is required when kneading and blending with the resin. However, if this ratio is less than the lower limit, an excessive amount is required when kneading and blending with the resin.

[0045] The wood fiberboard of this embodiment has an overall density of 500 kg / m ３ More than 800kg / m ３ Preferably, it is 525 kg / m or less. ３ More than 750kg / m ３ More preferably, it is 550 kg / m or less. ３ More than 700kg / m ３ It is more preferable that the density is equal to or less than the lower limit. When the overall density is equal to or greater than the lower limit, an excessive amount is not required when kneading and blending with the resin. If the overall density is less than the lower limit, the volume (bulk density) of the fragmented product increases. If the overall density is equal to or less than the upper limit, the dispersibility of the fibers is less likely to be hindered when kneading with the resin. If the overall density exceeds the upper limit, the dispersibility of the fibers is more likely to be hindered when kneading with the resin. Furthermore, the bulk density of the fibers does not become excessive when kneading with the resin, making it less likely that a volume imbalance (segregation) will occur with the resin. Furthermore, the production weight per hour increases. Furthermore, the efficiency of transportation, etc. is improved.

[0046] The density of the wood fiber board of this embodiment can be measured, for example, by dividing the dry weight of the wood fiber board by its volume.

[0047] The wood fiberboard of this embodiment has a maximum density of 500 kg / m ３ Super 850kg / m３ Preferably, it is 500 kg / m or less. ３ Super 800kg / m ３ More preferably, it is 550 kg / m or less. ３ Super 750kg / m ３ More preferably, it is 600 kg / m or less. ３ Super 700kg / m ３ It is more preferable that the maximum density is not more than the lower limit. When the maximum density is above the lower limit, an excessive amount of the fiber does not need to be added when kneading with the resin. When the maximum density is not more than the upper limit, the dispersibility of the fiber is less likely to be impaired when kneading with the resin.

[0048] The maximum density of a wood fiber board refers to the maximum density in the density distribution in the thickness direction of a given location on the wood fiber board. To measure the maximum density of the wood fiber board of this embodiment, for example, a commercially available density profiler can be used. An example of a commercially available density profiler is the "DAX6000" manufactured by GreCon. There are no particular restrictions on the measurement position of the maximum density; however, it can be measured by cutting out a given location on the wood fiber board and measuring it with the device. The density measurement for obtaining the density distribution is performed in the thickness direction of the wood fiber board, for example, at intervals of 20 μm.

[0049] The wood fiber board of this embodiment preferably has a thickness of 6 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less. If the thickness of the wood fiber board is equal to or less than the upper limit, it is easy to fragment the wood fiber board using a fragmentation device. The lower limit of the thickness of the wood fiber board may be 1 mm or more, 2 mm or more, or 2.5 mm or more.

[0050] The thickness of the wood fiberboard of this embodiment is measured, for example, by using a vernier caliper.

[0051] [Method for manufacturing wood fiber board] The method for manufacturing a wood fiber board of this embodiment includes a step of mixing lignocellulose fiber and an isocyanate compound to obtain the composition for wood fiber board of the above-mentioned embodiment (hereinafter referred to as "step A1"), and a step of hot-press molding the composition for wood fiber board (hereinafter referred to as "step B1").

[0052] Step A1 is the same as the above-mentioned method for producing a composition for a wood fiberboard.

[0053] Step B1 is a step of hot-press molding the composition for a wood fiberboard using a hot-press molding machine to obtain a wood fiberboard of a predetermined thickness.

[0054] In step B1, the temperature at which the wood fiberboard composition is hot-press molded is not particularly limited, but is preferably 140°C or higher and 240°C or lower, more preferably 160°C or higher and 230°C or lower, and even more preferably 180°C or higher and 220°C or lower. When the temperature is higher than the lower limit, the isocyanate compound is well cured. When the temperature is lower than the upper limit, the wood fiberboard can be easily molded.

[0055] In step B1, the time for hot press molding the wood fiberboard composition is not particularly limited, but is preferably 1 second or more and 30 seconds or less per 1 mm of thickness, more preferably 2 seconds or more and 25 seconds or less, and even more preferably 3 seconds or more and 20 seconds or less. If the time is equal to or greater than the lower limit, heat is easily transmitted to the interior of the wood fiberboard. If the time is less than the lower limit, heat is not easily transmitted to the interior of the wood fiberboard, and moldability is likely to decrease. If the time is equal to or less than the upper limit, productivity is ensured. If the time exceeds the upper limit, productivity decreases.

[0056] In step B1, the pressure for hot-press molding the wood fiberboard composition is not particularly limited, but is preferably 0.1 MPa to 5 MPa, more preferably 0.2 MPa to 4 MPa, and even more preferably 0.3 MPa to 3 MPa. A pressure equal to or greater than the lower limit is preferable for ensuring binding strength. A pressure equal to or less than the upper limit is preferable for adjusting thickness and density.

[0057] The wood fiberboard of this embodiment contains lignocellulose fibers and a reaction product of an isocyanate compound and water, and the content of the reaction product, converted into an isocyanate compound, relative to the total mass of the lignocellulose fibers and the reaction product is 0.5 mass% or more and 10 mass% or less. Therefore, when the wood fiberboard is pelletized, it can be kneaded with a thermoplastic resin without forming lumps.

[0058] [Method for manufacturing pellets] A method for manufacturing pellets according to one embodiment of the present invention includes the steps of processing the wood fiber board according to the above embodiment to obtain fragments having a length of 1 mm or more and 6 mm or less (hereinafter referred to as "step A2"), drying the fragments so that the moisture content is 5 mass% or less (hereinafter referred to as "step B2"), kneading the dried fragments with a thermoplastic resin to obtain a kneaded product (hereinafter referred to as "step C2"), and breaking down the kneaded product into pellets of any size (hereinafter referred to as "step D2").

[0059] Step A2 is a step of processing the wood fiber board using, for example, a grinder or a sheet pelletizer (square pelletizer) to obtain fragments having a length of 1 mm to 6 mm. The length of the fragments is preferably 1 mm to 6 mm, more preferably 2 mm to 5 mm. The method of processing the wood fiber board to obtain fragments can be appropriately selected, for example, a method of processing into dice-shaped cubes using a sheet pelletizer, a method of crushing using a cutter mill, or a combination of these methods. The shape of the fragments is not particularly limited, and can be appropriately selected from approximately cubes, approximately rectangular parallelepipeds, cylindrical, irregular shapes, and combinations thereof. The length of the fragments mentioned above is the length of one side if the fragments are approximately cubes, the length of the longest side if they are approximately rectangular parallelepipeds, and the major axis (long axis diameter) if they are cylindrical or irregular. Furthermore, if the average volume of the fragments is 1 mm ３ 216mm or more ３ Preferably, it is 5 mm ３ More than 200 mm ３ More preferably, it is 10 mm ３ More than 100 mm ３ It is more preferable that:

[0060] In the pellet manufacturing method according to this embodiment, the amount of dust generated when obtaining the fragmented material in step A2 is small.

[0061] Step B2 is a step of drying the comminuted material using a dryer so that the moisture content is 5% by mass or less, preferably 4% by mass or less, and more preferably 3% by mass or less. As a method for drying the comminuted material, for example, a blower drying hopper, a box-type hot air dryer, a conveyor-type dryer, or the like can be suitably used.

[0062] Any known method can be suitably used to measure the moisture content. Examples include a method using a Karl Fischer moisture meter and a method using a dryer to calculate the weight loss rate before and after drying as the moisture content.

[0063] Step C2 is a step of kneading the dried comminuted material and the thermoplastic resin by twin-screw extrusion kneading using a twin-screw extrusion kneader to obtain a kneaded material.

[0064] The thermoplastic resin is not particularly limited, but examples thereof include polyolefin resins such as polyethylene resin and polypropylene resin, polyamide resin, polyacetal resin, ABS resin, and vinyl chloride resin.

[0065] The content of the fragmented material relative to the total mass of the dried fragmented material and the thermoplastic resin is preferably 1% by mass or more and 80% by mass or less, more preferably 5% by mass or more and 70% by mass or less, and even more preferably 10% by mass or more and 60% by mass or less. When the content of the fragmented material is equal to or greater than the lower limit, a reinforcing effect is obtained. Note that, when the content of the fragmented material is less than the lower limit, it is difficult to obtain a reinforcing effect. When the content of the fragmented material is equal to or less than the upper limit, kneading is easy. Note that, when the content of the fragmented material exceeds the upper limit, kneading is difficult.

[0066] The kneaded product may contain additives other than the fragmented product and the thermoplastic resin, such as a compatibilizer such as maleic anhydride-modified polypropylene resin, an elastomer, an antioxidant, a lubricant, a stabilizer, a pigment, a wax, a preservative, an insect repellent, an antifungal agent, a VOC catcher, and water.

[0067] Step D2 is a step in which, for example, the kneaded material is extruded into a rod shape (strand shape) and the extrudate is cut to a desired length or crushed to obtain pellets or fragments (hereinafter referred to as "pellets"). The length (longitudinal length) of the pellets is preferably, for example, 1 mm or more and 10 mm or less. The length (diameter) of the pellets in the lateral direction is preferably, for example, 1 mm or more and 8 mm or less.

[0068] The pellets thus obtained are subjected to the method for producing a resin molded product described below.

[0069] The wood fiberboard used in the pellet manufacturing method of this embodiment contains a reaction product of an isocyanate compound and water. The isocyanate compound generates less volatile organic compounds (VOCs) (formaldehyde, acetaldehyde) than formaldehyde-based resins. Therefore, according to the pellet manufacturing method of this embodiment, the wood fiberboard of the above embodiment is used as the fragmented material, and therefore, the generation of gases (VOCs) derived from the binder can be suppressed when the fragmented material and thermoplastic resin are kneaded.

[0070] Furthermore, according to the pellet manufacturing method of this embodiment, a wood fiberboard containing a reaction product of an isocyanate compound and water is used, thereby reducing the dust generation rate during the process of breaking down the kneaded material. The reason why the use of an isocyanate compound can reduce the dust generation rate during breakup of the kneaded material will be explained below. Conventionally, polyolefin resin emulsions used as binders for wood fiberboards, as disclosed in Patent Document 1 and elsewhere, are non-polar resins, and therefore have low affinity with highly polar wood fibers and poor ability to bind and hold the wood fibers. Therefore, dust is likely to be generated during breakup of the kneaded material. Isocyanate compounds are particularly polar and have a high affinity with wood containing many hydroxyl groups, resulting in a high ability to bind and hold the wood fibers. Furthermore, upon reaction with the surface of the wood fibers or moisture in the air, the isocyanate compound foams while generating carbon dioxide gas. The resulting cured product increases in volume, effectively filling the gaps between the fibers and is therefore likely to bind and hold the wood fibers together at multiple points. Furthermore, while an isocyanate compound itself fulfills the binding function as a 100% component, for example, a urea-formaldehyde resin, even at the same solid content, does not actually have 100% of the component that exhibits the binding effect. For these reasons, the urea-formaldehyde resin is inferior to an isocyanate compound in its ability to maintain the binding effect on wood fibers, and it is expected that this will affect the rate of dust generation when the kneaded material is comminuted.

[0071] [Method for manufacturing a resin molded product] A method for manufacturing a resin molded product according to one embodiment of the present invention includes a step of obtaining pellets by the pellet manufacturing method of the above-described embodiment (hereinafter referred to as "step A3"), and a step of thermoforming the pellets to obtain a resin molded product (hereinafter referred to as "step B3").

[0072] Step A3 is a step of obtaining pellets by the pellet manufacturing method of the above embodiment.

[0073] Step B3 is a step of thermoforming the pellets to obtain a resin molded product.

[0074] The thermoforming method is not particularly limited, but examples thereof include injection molding, extrusion molding, and blow molding.

[0075] The resin molded articles thus obtained are used in the transportation industry such as automobiles, electrical appliances, daily necessities, packaging materials, building materials, and the like.

[0076] The resin molded product obtained in this manner emits less volatile organic compounds (VOCs). Specifically, the amount of VOCs emitted, measured at 65°C in accordance with JASO M902 Automotive Parts - Interior Materials - Volatile Organic Compound (VOC) Emission Measurement Method (Sampling Bag Method), can be reduced by approximately 70% to 90% compared to a molded product using a conventional urea-formaldehyde resin as a binder. Specifically, the resin molded product emits 100 μg / m of formaldehyde collected at 65°C in accordance with JASO M902 Automotive Parts - Interior Materials - Volatile Organic Compound (VOC) Emission Measurement Method (Sampling Bag Method). ３ Furthermore, the resin molded article preferably has an acetaldehyde emission rate of 100 μg / m or less when collected at 65° C. in accordance with JASO M902 Automotive Parts - Interior Materials - Volatile Organic Compound (VOC) Emission Measurement Method (Sampling Bag Method). ３ It is preferable that:

[0077] According to the method for producing a resin molded product of the present embodiment, the pellets obtained by the method for producing pellets of the above-described embodiment are thermoformed to obtain a resin molded product, so that generation of volatile organic compounds (VOCs) such as formaldehyde and acetaldehyde derived from the binder in the resin molded product can be suppressed.

[0078] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0079] Example 1: A wood fiberboard composition was obtained by spraying MDI onto softwood fibers (also known as thermomechanical pulp or MDF fibers) and commercially available diphenylmethane diisocyanate (MDI, manufactured by Tosoh Corporation) as a binder, so that the amount (content) of MDI added was 4% by mass relative to the total mass. Next, using a hot press, the resulting wood fiberboard composition was hot-press molded under the following conditions: press temperature: 190°C, press time: 60 seconds, press pressure: 3 MPa (maximum) to produce a wood fiberboard with a thickness of 4 mm and a size of 300 mm x 300 mm. Next, using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.), the resulting wood fiberboard was fragmented into pieces measuring 4 mm x 4 mm to obtain fragmented pieces. Next, the fragmented material was sieved through a #2 mm metal mesh sieve for 60 seconds, and the fraction that passed through the #2 mm metal mesh sieve was calculated as dust. The dust rate was calculated according to the following formula (1). The results are shown in Table 1. Dust rate (mass%) = {(mass of fragmented material that passed through the #2 mm metal mesh sieve) / (mass of wood fiberboard before fragmentation)} x 100 (1)

[0080] [Example 2] A pulverized product was obtained in the same manner as in Example 1, except that the amount of MDI added was 2 mass% relative to the total mass of wood fiber and MDI. The dust rate of the obtained pulverized product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0081] Comparative Example 1 A pulverized product was obtained in the same manner as in Example 1, except that urea-formaldehyde resin (manufactured by Oshika Co., Ltd.) was used instead of MDI and the amount of urea-formaldehyde resin added was 4 mass% relative to the total mass of the wood fiber and urea-formaldehyde resin. The dust rate of the obtained pulverized product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0082] Comparative Example 2 A pulverized product was obtained in the same manner as in Example 1, except that a polypropylene resin dispersion (manufactured by Michelman) was used instead of MDI and the amount of polypropylene resin dispersion added was 4 mass% relative to the total mass of the wood fiber and polypropylene resin dispersion. The dust rate of the obtained pulverized product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0083] [Comparative Example 3] A fragmented product was obtained in the same manner as in Example 1, except that only wood fibers were used without using a binder. The dust rate of the obtained fragmented product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0084]

[0085] From the results shown in Table 1, Examples 1 and 2 have a low amount of dust (dust rate) generated during fragmentation, making it possible to provide a high yield and a good working environment with less dust. On the other hand, Comparative Examples 1-3 have a high dust rate.

[0086] [Experimental Example] A wood fiberboard composition was obtained by spraying urea-formaldehyde resin onto softwood fibers (also known as thermomechanical pulp or MDF fibers) and a binder (manufactured by Oshika Co., Ltd.) so that the amount of urea-formaldehyde resin added (content) was 4% by mass relative to the total mass of the wood fibers. The resulting wood fiberboard composition was then hot-pressed using a hot press under conditions of a press temperature of 170°C, a press time of 60 seconds, and a press pressure of 3 MPa (maximum) to produce a wood fiberboard with a thickness of 4 mm and a size of 300 mm x 300 mm. The cross-sectional density distribution of the resulting wood fiberboard was measured using a density distribution meter (trade name: DAX6000, manufactured by GreCon Co., Ltd.). The cross-sectional density of the wood fiberboard was adjusted by varying the moisture content of the fibers before heat pressing and the speed at which the press closed (the pressing speed of the press plate) during heat pressing. The overall density was adjusted by varying the amount of wood fiber charged into a 300 x 300 mm molding frame installed in the press. Next, using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.), the obtained wood fiberboard was fragmented into pieces measuring 4 mm x 4 mm and dried in an oven at 105 °C for 2 hours to obtain fragmented wood fiberboard with a moisture content of approximately 1%. Next, 69% by mass of polypropylene resin, 30% by mass of the fragmented material, and 1% by mass of maleic anhydride-modified polypropylene resin as a compatibilizer were blended and kneaded in a twin-screw extrusion kneader (Labo Plastomill, Toyo Seiki Seisakusho Co., Ltd.) to obtain a kneaded mixture. The kneading temperature was 180 °C, the rotation speed was 100 RPM, and the kneading time was 5 minutes. Next, the kneaded material was collected and molded into a film with a thickness of approximately 0.1 mm to 0.5 mm using a heat press, and the fiber dispersibility of the resulting film was evaluated using transmitted light. A film with no agglomerates or a lump of less than 2 mm in size that was acceptable was rated "good," a film with one agglomerate of 2 mm to 5 mm in size that was acceptable was rated "moderate agglomerate," and a film with multiple agglomerates of 2 mm to 5 mm in size or agglomerates exceeding 5 mm in size was rated "coarse agglomerate." The results are shown in Table 2.

[0087] [Example 3] Wood fiberboards were produced in the same manner as in the Experimental Example, except that MDI (manufactured by Tosoh Corporation) was used instead of urea-formaldehyde resin. The cross-sectional density distribution of the obtained wood fiberboards was measured in the same manner as in the Experimental Example. Films were formed using the obtained wood fiberboards in the same manner as in the Experimental Example. The dispersion of fibers in the obtained films was evaluated in the same manner as in the Experimental Example. The results are shown in Table 2.

[0088] [Example 4] Wood fiberboards were produced in the same manner as in the experimental example, except that MDI (manufactured by Tosoh Corporation) was used instead of urea-formaldehyde resin and the amount of wood fiber charged into the molding frame was increased to increase the overall density. The cross-sectional density distribution of the obtained wood fiberboards was measured in the same manner as in the experimental example. Films were formed using the obtained wood fiberboards in the same manner as in the experimental example. The dispersion of fibers in the obtained films was evaluated in the same manner as in the experimental example. The results are shown in Table 2.

[0089] [Comparative Example 4] Wood fiberboards were produced in the same manner as in the Experimental Example, except that the maximum density was changed. The cross-sectional density distribution of the obtained wood fiberboards was measured in the same manner as in the Experimental Example. Films were formed using the obtained wood fiberboards in the same manner as in the Experimental Example. The dispersion of fibers in the obtained films was evaluated in the same manner as in the Experimental Example. The results are shown in Table 2.

[0090] Comparative Example 5: A wood fiberboard was produced in the same manner as in the Experimental Example, except that MDI (manufactured by Tosoh Corporation) was used instead of urea-formaldehyde resin. The cross-sectional density distribution of the obtained wood fiberboard was measured in the same manner as in the Experimental Example. A film was formed using the obtained wood fiberboard in the same manner as in the Experimental Example. The dispersion of fibers in the obtained film was evaluated in the same manner as in the Experimental Example. The results are shown in Table 2.

[0091] Comparative Example 6 A wood fiberboard was produced in the same manner as in Example 3, except that a polypropylene resin dispersion (manufactured by Michelman) was used instead of the urea-formaldehyde resin. The cross-sectional density distribution of the obtained wood fiberboard was measured in the same manner as in Example 3. A film was formed using the obtained wood fiberboard in the same manner as in Example 3. The dispersion of fibers in the obtained film was evaluated in the same manner as in Example 3. The results are shown in Table 2.

[0092]

[0093] From the results shown in Table 2, as shown in Examples 3 and 5, the density of the densest part of the wood fiberboard (maximum density) was 805 kg / m ３ It was found that even wood fiberboards made with a thermosetting MDI binder can be dispersed in resin by setting the density of the densest part of the wood fiberboard (maximum density) to 920 kg / m ３ As a result of the above, it was found that it was not possible to disperse wood fiberboard in resin.

[0094] Example 5 The wood fiberboard obtained in Example 1 was fragmented into 4 mm x 4 mm pieces using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) and dried in the same manner as in the experimental example to obtain fragmented material with a moisture content of approximately 1%. Next, 69% by mass of polypropylene resin, 30% by mass of the fragmented material, and 1% by mass of maleic anhydride-modified polypropylene resin as a compatibilizer were blended and kneaded in a twin-screw extrusion kneader (Labo Plastomill, manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain pellets. The kneading temperature was set to the temperature shown in Table 3, the rotation speed was set to 250 RPM, and the output rate was set to 10 kg / hr. The cylinder of the twin-screw extrusion kneader was divided into 10 compartments along the axial direction, and the numbers 1 to 10 in Table 3 represent the compartment numbers in order from upstream to downstream. The temperature of each compartment could be set independently, and the temperatures shown in Table 3 represent the temperatures of each compartment or nozzle.

[0095]

[0096] Here, the appearance of the kneaded product was evaluated because the state of gas generation from the kneaded product can be judged from the appearance of the kneaded product. The results are shown in Figure 1.

[0097] [Comparative Example 7] A strand-shaped kneaded product was obtained in the same manner as in Example 5, except that the wood fiberboard obtained in Comparative Example 1 was used. The appearance of the kneaded product was evaluated in the same manner as in Example 5. The results are shown in Figure 1.

[0098] From the results shown in FIG. 1, the kneaded product of Comparative Example 7 (bottom of the photograph in FIG. 1) had a fuzzy surface compared to the kneaded product of Example 5 (top of the photograph in FIG. 1). This indicates that excessive gas was generated from the kneaded product of Comparative Example 7. Fluffing of the kneaded product is undesirable because it not only leads to poor appearance but also to problems such as clogging of the strand cutting device, excessive generation of dust, excessive introduction of strand cooling water, and reduced fluidity of the pellets obtained by cutting the strands. Furthermore, when the resin temperature was measured in the next step, the resin temperatures were also found to be almost the same, so it is thought that the amount of gas generated was not due to differences in the temperature of the kneaded product but was generated by thermal decomposition of the urea-formaldehyde resin used as the binder in Comparative Example 1.

[0099] Example 6 The wood fiberboard obtained in Example 1 was fragmented into 4 mm x 4 mm pieces using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.). The fragmented material was dried in the same manner as in the experimental example to obtain fragmented material with a moisture content of approximately 1%. Next, 68.5% by mass of polypropylene resin, 30% by mass of the fragmented material, 0.5% by mass of adipic acid dihydrazide as an aldehyde catcher, and 1% by mass of maleic acid-modified polypropylene as a compatibilizer were blended and kneaded in a twin-screw extrusion kneader (Labo Plastomill, manufactured by Toyo Seiki Seisakusho, Ltd.) to obtain pellets. The kneading temperature was 180°C, the rotation speed was 250 RPM, and the output rate was 10 kg / hr. The resulting pellets were molded into flat plates measuring 2 mm thick x 80 mm long x 80 mm wide using an injection molding machine, and formaldehyde and acetaldehyde were collected at 65°C and the amount of emission was measured in accordance with "JASO M902 Automotive parts - Interior materials - Volatile organic compound (VOC) emission measurement method (sampling bag method)." The results are shown in Table 4.

[0100] [Comparative Example 8] Using the wood fiberboard obtained in Comparative Example 1, 68.0% by mass of polypropylene resin, 30% by mass of the fragmented product, 0.5% by mass of adipic acid dihydrazide as an aldehyde catcher, and 1% by mass of maleic acid-modified polypropylene as a compatibilizer were blended, and pellets were obtained in the same manner as in Example 6. Formaldehyde and acetaldehyde were collected from the obtained pellets at 65°C in the same manner as in Example 6, and the amounts of emission were measured. The results are shown in Table 4.

[0101]

[0102] From the results shown in Table 4, Example 6 and Comparative Example 8 show that when MDI was used as the binder, the formaldehyde and acetaldehyde emissions were lower than when urea-formaldehyde resin was used as the binder, and Example 6 was also below the indoor VOC guideline values ​​set forth by the Ministry of Health, Labor and Welfare (regarding indoor concentration guideline values ​​for chemicals in indoor air: https: / / www.mhlw.go.jp / web / t_doc?dataId=00tc3866&dataType=1&pageNo=1, confirmed February 27, 2024). Furthermore, Example 6 and Comparative Example 8 suggest that the increase in the amount of aldehydes emitted in Comparative Example 8 is due to the urea-formaldehyde resin used as the binder.

[0103] Example 7 The wood fiberboard obtained in Example 1 was fragmented into pieces measuring 4 mm x 4 mm using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) to obtain fragmented material. The fragmented material was then processed for 60 seconds using a #2 mm metal mesh sieve. An appropriate amount of the fragmented material was then placed in a stainless steel tray and allowed to stand in a hot air dryer at 150°C for 30 minutes. The tray was then removed from the hot air dryer, and the fragmented material on the tray was gently kneaded by hand to loosen it, and the state of crumbling of the fragmented material was observed. The results are shown in Table 5.

[0104] Comparative Example 9 The state of crumbling of the fragmented material was observed in the same manner as in Example 7, except that the wood fiberboard obtained in Comparative Example 1 was used. The results are shown in Table 5.

[0105]

[0106] From Example 7 and Comparative Example 9, it was confirmed that when MDI was used as the binder, the shape of the fragmented material was less likely to collapse when handled after drying in a dryer before being kneaded with the binder, compared to when urea-formaldehyde resin was used as the binder. Because plant fibers absorb moisture from the air, they are usually dried before being kneaded with the binder. Since the dried plant fibers undergo processes in which physical external forces are applied, such as transportation and loading into a hopper, shape retention after heating is an important factor.

Claims

1. A composition for wood fiberboards comprising lignocellulose fibers and an isocyanate compound, wherein the content of the isocyanate compound relative to the total mass of the lignocellulose fibers and the isocyanate compound is 0.5 mass% or more and 6 mass% or less.

2. The wood fiberboard composition according to claim 1, wherein the isocyanate compound is an aromatic isocyanate compound.

3. A wood fiberboard comprising a reaction product of lignocellulose fibers and an isocyanate compound and water, wherein the content of the reaction product, calculated as an isocyanate compound, relative to the total mass of the lignocellulose fibers and the reaction product is 0.5% by mass or more and 6% by mass or less.

4. The wood fiberboard according to claim 3, wherein the isocyanate compound is an aromatic isocyanate compound.

5. Overall density is 500 kg / m ３ or more, maximum density is 800 kg / m ３ 4. The wood fiber board according to claim 3, wherein:

6. The wood fiber board according to claim 3, having a thickness of 6 mm or less.

7. A product containing a mixture of the fragmented wood fiberboard of claim 3 and a thermoplastic resin, and having a formaldehyde emission rate of 100 μg / m3 when collected at 65°C in accordance with JASO M902 Automotive Parts - Interior Materials - Volatile Organic Compound (VOC) Emission Measurement Method (Sampling Bag Method). ３ The following is a resin molded product.

8. A mixture of the fragmented wood fiberboard of claim 3 and a thermoplastic resin, in which the amount of acetaldehyde emitted at 65°C is 48 μg / m according to JASO M902 Automotive parts - Interior materials - Volatile organic compound (VOC) emission measurement method (sampling bag method). ３ The following is a resin molded product.

9. A method for producing pellets, comprising the steps of: processing the wood fiberboard according to any one of claims 3 to 6 to obtain fragments having a length of 1 mm to 6 mm; drying the fragments so that the moisture content is 5 mass % or less; kneading the dried fragments with a thermoplastic resin to obtain a kneaded mixture; and cutting the kneaded mixture into pellets of any size.

10. A method for producing a resin molded product, comprising the steps of: obtaining pellets by the pellet producing method according to claim 9; and thermoforming the pellets to obtain a resin molded product.

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