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

Abstract

Provided are a composition for wood fiberboards that generates a low rate of dust when producing fragmented products and has a high yield when producing fragmented products, a method for producing wood fiberboards, resin molded products, and pellets, and a method for producing resin molded products. [Solution] 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.

Description

[Technical Field]

[0001] 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. [Background technology]

[0002] As a substitute for 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 Document 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 products) or granules containing fibers of lignocellulosic materials or natural fibers, which are used as 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, and applying a liquid formulation containing one or more polymers, monomers, or oligomers to the fibers while transporting the fibers; molding 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 lignocellulose fibers are thermally molded using a heat press to produce a molded board, the molded board is then subdivided, and the resulting board 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 broken down into small pieces, and then the pieces are 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 lignocellulosic 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, impregnated into pulp, and cured to form unconstrained (free) fibers with increased water resistance, which are then kneaded with resin. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 5481066 [Patent Document 2] International Publication No. 2006 / 001717 [Patent Document 3] International Publication No. 2007 / 073218 [Patent Document 4] International Publication No. 2011 / 002314 [Patent Document 5] Patent No. 5911755 [Non-patent literature]

[0012] [Non-Patent Document 1] Cellulose Chem. Technol., 46(5-6), 381-387(2012). [Non-patent document 2] Journal of Reinforced Plastics and Composites,Vol.27,No.16-17,1679-1687(2008). [Non-patent document 3] Carbon Hydrate Polymers,68,537-543(2007). [Non-patent document 4] Carbon Hydrate Polymers,74,106-113(2008). [Non-patent document 5] Composites:Part A,61,245-257(2014). Summary of the Invention [Problem to be solved by the invention]

[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, which reduces the yield of wood pellets produced.

[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 liquid thermoplastic resin in fiberboard manufacturing equipment can lead to contamination between products; (3) dust is easily generated when fiberboard is broken down, which can worsen the working environment and reduce yields; (4) formaldehyde resin thermally decomposes when mixed with resin, generating 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 Patent Document 2, namely, the problems (1) to (5) above.

[0016] The method described in Patent Document 4 has the same problems as Patent Document 2, namely, the problems (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. [Means for solving the problem]

[0018] The present invention has the following aspects. [1] A method for producing a lignocellulose fiber, comprising: A composition for wood fiberboards, wherein the content of the isocyanate compound is 0.5% by mass or more and 6% by mass or less relative to the total mass of the lignocellulose fibers and the isocyanate compound. [2] The composition for wood fiberboards according to [1], wherein the isocyanate compound is an aromatic isocyanate compound. [3] A method for producing a lignocellulosic fiber, a reaction product of an isocyanate compound, and water, A wood fiberboard, 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] Overall density is 500 kg / m 3 or more, maximum density 800 kg / m 3 The wood fiberboard according to [3] or [4] below. [6] The wood fiberboard according to any one of [3] to [5], which has a thickness of 6 mm or less. [7] [3] A mixture of fragmented wood fiberboard and thermoplastic resin, In accordance with JASO M902 Automotive parts - Interior materials - Volatile organic compounds (VOC) emission measurement method (sampling bag method), formaldehyde emission collected at 65°C is 100 μg / m 3 The following is a resin molded product. [8] [3] A mixture of fragmented wood fiberboard and thermoplastic resin, In accordance with JASO M902 Automotive parts - Interior materials - Volatile organic compounds (VOC) emission measurement method (sampling bag method), the amount of acetaldehyde emitted at 65°C was 48 μg / m 3 The following is a resin molded product. [9] A step of processing the wood fiber board according to any one of [3] to [6] to obtain fragments having a side length of 1 mm to 6 mm; a step of drying the comminuted material so that the moisture content is 5% by mass or less; a step of kneading the dried pulverized material with a thermoplastic resin to obtain a kneaded material; and a step of dividing the kneaded mixture into pellets of any size.

[10] A step of obtaining pellets by the pellet manufacturing method described in [9]; and thermoforming the pellets to obtain a resin molded product. [Effects of the Invention]

[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. [Brief explanation of the drawings]

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

[0021] Embodiments of the composition for wood fiberboard, wood fiberboard, resin molded product, method for producing pellets, and method for producing resin molded product of the present invention will be described below. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0022] [Wood fiberboard composition] A composition for a wood fiberboard according to one embodiment of the present invention contains lignocellulose fibers and an isocyanate compound.

[0023] As lignocellulosic fibers, woody fibers (all types) or herbaceous fibers (hemp, flax, kenaf jute, sisal, bamboo, other agricultural residues, etc.) are particularly preferred.

[0024] Lignocellulose fibers are typically long fibers. The 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 length of the lignocellulose fibers is equal to or greater than the lower limit, they are easily formed into fiberboards and easily provide a reinforcing effect when kneaded with resin. When the length of the lignocellulose fibers is less than the lower limit, they are difficult to form into fiberboards or to provide a reinforcing effect when kneaded with resin. When the length of the lignocellulose fibers is equal to or less than the upper limit, a blend of the fibers and resin is easily obtained and the appearance is less likely to deteriorate. When the length of the lignocellulose fibers exceeds the upper limit, the fibers become coarse, making it difficult to knead them with resin and also reducing the appearance of the blend.

[0025] The 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.

[0026] The aspect ratio of the lignocellulose fibers (length / maximum diameter in the short direction) 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 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 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 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 aspect ratio of the lignocellulose fibers exceeds the upper limit, dispersibility is likely to decrease when kneaded with a resin.

[0027] The isocyanate compound may be any of aromatic isocyanate compounds, aliphatic isocyanate compounds, etc. 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).

[0028] The content of the isocyanate compound relative to the total mass of the lignocellulose fiber 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. When the content of the isocyanate compound is above the lower limit, problems with handling of the wood fiberboard are unlikely to occur, and the dust generation rate during fragmentation can be kept low. When the content of the isocyanate compound is below the upper limit, the dispersibility of the fiber is unlikely to be impaired when kneaded with resin.

[0029] In addition to the lignocellulose fibers and the isocyanate compound, the composition for wood fiberboard 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.

[0030] 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. Meanwhile, 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. Meanwhile, when this ratio exceeds the upper limit, molding of the wood fiberboard becomes difficult.

[0031] [Method for producing a composition for wood fiberboard] The composition for wood fiberboard of this embodiment can be obtained by a method of mixing lignocellulose fibers with an isocyanate compound, or a method of spraying an isocyanate compound onto lignocellulose fibers.

[0032] The composition for wood fiberboards of this embodiment 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 that the rate of dust generation when producing the fragmented material is low and the yield when producing the fragmented material is high.

[0033] [Wood fiberboard] A wood fiberboard according to one embodiment of the present invention comprises lignocellulosic fibers and a reaction product of an isocyanate compound and water.

[0034] Examples of the lignocellulose fibers include the same lignocellulose fibers as those in the composition for wood fiberboard of the above-described embodiment.

[0035] Examples of the isocyanate compound include the same isocyanate compounds as those in the composition for wood fiberboards of the above-described embodiment. The reaction product of an isocyanate compound and water is a compound such as an amine or polyamine produced by the reaction of the isocyanate group (-NCO) of the isocyanate compound with the hydroxyl group (-OH) of water.

[0036] The content of the reaction product, calculated as an isocyanate compound, relative to the total mass of the lignocellulose fiber 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, the dispersibility of the fiber 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, the dispersibility of the fiber is more likely to be impaired during kneading with resin.

[0037] In addition to the lignocellulose fibers and isocyanate compounds, the wood fiberboard of this embodiment may contain water repellents (wax), curing accelerators, crosslinking agents, mildew inhibitors, preservatives, insect repellents, release agents, VOC catchers, water, etc.

[0038] 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.

[0039] 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 3More 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 of additive is not required when kneading and blending with 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 resin. If the overall density exceeds the upper limit, the dispersibility of the fibers is more likely to be hindered when kneading with resin. Furthermore, the bulk density of the fibers does not become excessive when kneading with 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.

[0040] 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.

[0041] The wood fiberboard of this embodiment has a maximum density of 500 kg / m 3 Super 800kg / m 3 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.

[0042] The maximum density of the wood fiber board refers to the maximum density at any point in the thickness direction of the wood fiber board. The maximum density of the wood fiberboard of this embodiment can be measured using, for example, a commercially available density profiler. There are no particular restrictions on the measurement position of the maximum density, but it can be measured by cutting out any part of the wood fiberboard and measuring it with the device.

[0043] The thickness of the wood fiber board of this embodiment is preferably 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 less than the above upper limit, it becomes easy to fragment 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.

[0044] The thickness of the wood fiberboard of this embodiment is measured, for example, by using a vernier caliper.

[0045] [Wood fiberboard manufacturing method] The method for producing a wood fiberboard of this embodiment includes a step of mixing lignocellulose fibers and an isocyanate compound to obtain the wood fiberboard composition of the above-mentioned embodiment (hereinafter referred to as "step A1"), and a step of hot-press molding the wood fiberboard composition (hereinafter referred to as "step B1").

[0046] Step A1 is the same as the above-mentioned method for producing a composition for a wood fiberboard.

[0047] 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.

[0048] In step B1, the temperature at which the composition for wood fiberboard 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 cured well. When the temperature is lower than the upper limit, the wood fiberboard can be easily molded.

[0049] 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 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 transferred to the interior of the wood fiberboard. If the time is less than the lower limit, heat is not easily transferred 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.

[0050] 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.

[0051] 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.

[0052] [Pellet manufacturing method] A method for producing pellets according to one embodiment of the present invention includes the steps of processing the wood fiber board of the above-described embodiment to obtain fragments with a side 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 mixture (hereinafter referred to as "step C2"), and fragmenting the mixture to any size (hereinafter referred to as "step D2").

[0053] Step A2 is a step in which the wood fiber board is processed using, for example, a grinder or a sheet pelletizer (square pelletizer) to obtain fragments with a side length of 1 mm to 6 mm. The method of processing the wood fiber board to obtain fragments can be appropriately selected, for example, a method of processing the board into dice-shaped cubes using a sheet pelletizer, a method of crushing the board using a cutter mill, or a combination of these methods.

[0054] In the pellet manufacturing method according to this embodiment, the amount of dust generated when obtaining the pulverized material in step A2 is small.

[0055] Step B2 is a step of drying the comminuted material using a dryer so that the moisture content is 5% 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, etc. can be suitably used.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The kneaded material may contain additives in addition to the comminuted material and the thermoplastic resin. Examples of additives include compatibilizers such as maleic anhydride modified polypropylene resin, elastomers, antioxidants, lubricants, stabilizers, pigments, waxes, preservatives, insect repellents, mildew inhibitors, VOC catchers, and water.

[0060] Step D2 is a step in which, for example, the kneaded material is extruded into a rod shape (strand shape) and the extrusion molded product is cut to a desired length or crushed to obtain pellets or fragmented products (hereinafter referred to as "pellets"). The length (length in the longitudinal direction) of the pellet is preferably, for example, 1 mm or more and 10 mm or less, and the length (diameter) in the lateral direction of the pellet is preferably, for example, 1 mm or more and 8 mm or less.

[0061] The pellets thus obtained are subjected to the method for producing a resin molded product described below.

[0062] 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, since the wood fiberboard of the above embodiment is used as the fragmented material, the generation of gases (VOCs) derived from the binder can be suppressed when the fragmented material and thermoplastic resin are mixed.

[0063] Furthermore, according to the pellet manufacturing method of this embodiment, since a wood fiberboard containing a reaction product of an isocyanate compound and water is used, the rate of dust generation can be reduced in the step of breaking down the kneaded material. The reason why the use of an isocyanate compound can reduce the rate of dust generation when the kneaded material is broken down will be explained below. Conventionally, polyolefin resin emulsions used as binders for wood fiberboards, such as those disclosed in Patent Document 1, are non-polar resins, and therefore have low affinity with highly polar wood fibers and are poor at binding and holding the wood fibers together. As a result, it is expected that dust will be generated when the kneaded material is broken down. Isocyanate compounds are particularly polar and have a high affinity for wood, which has many hydroxyl groups, and are therefore highly capable of binding and holding wood fibers together. Furthermore, upon reacting with the surface of wood fibers or with moisture in the air, the isocyanate compounds foam while generating carbon dioxide. The resulting cured product expands in volume, effectively filling the gaps between fibers and holding the wood fibers together at multiple points. Furthermore, while isocyanate compounds themselves function as a 100% component, urea-formaldehyde resins, for example, do not actually contain 100% of the components that exhibit binding effects, even at the same solid content. For these reasons, urea-formaldehyde resins are less effective at binding and holding wood fibers together than isocyanate compounds, which is expected to affect the rate of dust generation when the kneaded material is comminuted.

[0064] [Method of manufacturing resin molded products] A method for producing a resin molded product according to one embodiment of the present invention includes a step of obtaining pellets by the pellet producing method according to 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").

[0065] Step A3 is a step of obtaining pellets by the pellet manufacturing method of the above embodiment.

[0066] Step B3 is a step of thermoforming the pellets to obtain a resin molded product.

[0067] The thermoforming method is not particularly limited, but examples thereof include injection molding, extrusion molding, and blow molding.

[0068] 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.

[0069] 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 molded products using a conventional urea-formaldehyde resin as a binder. Specifically, the resin molded product emits less than 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 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:

[0070] According to the method for producing a resin molded product of the present embodiment, the pellets obtained by the pellet producing method 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 from the resin molded product can be suppressed. [Example]

[0071] 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.

[0072] [Example 1] A composition for wood fiberboards was obtained by spraying commercially available diphenylmethane diisocyanate (MDI, manufactured by Tosoh Corporation) onto coniferous wood fibers (also called thermomechanical pulp or MDF fibers) and MDI as a binder so that the amount (content) of MDI added was 4 mass% relative to the total mass of the wood fibers. Next, the obtained composition for wood fiberboard was hot-press molded using a hot press machine under the conditions of press temperature: 190°C, press time: 60 seconds, and press pressure: 3 MPa (maximum) to produce a wood fiberboard having a thickness of 4 mm and a size of 300 mm x 300 mm. Next, the obtained wood fiberboard was fragmented into pieces of 4 mm x 4 mm using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) to obtain fragmented pieces. Next, the pulverized material was processed 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 (1) below, and the results are shown in Table 1. Dust rate (mass%) = {(mass of fragmented products passing through a 2 mm metal mesh sieve) / (mass of wood fiberboard before fragmentation)} × 100 (1)

[0073] [Example 2] A fragmented 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 the wood fiber and MDI. The dust ratio of the resulting fragmented product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0074] [Comparative Example 1] The fragmented material 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 ratio of the resulting fragmented product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0075] Comparative Example 2 The fragmented material was obtained in the same manner as in Example 1, except that 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 ratio of the resulting fragmented product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0076] Comparative Example 3 A fragmented product was obtained in the same manner as in Example 1, except that no binder was used and only wood fibers were used. The dust ratio of the resulting fragmented product was calculated in the same manner as in Example 1. The results are shown in Table 1.

[0077] [Table 1]

[0078] 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 little dust. On the other hand, in Comparative Example 1-3, the dust rate was high.

[0079] [Experimental Example] A composition for wood fiberboard was obtained by spraying urea-formaldehyde resin onto the wood fibers (also called thermomechanical pulp or MDF fibers) so that the amount (content) of urea-formaldehyde resin added was 4 mass% relative to the total mass of coniferous wood fibers (also called thermomechanical pulp or MDF fibers) and urea-formaldehyde resin (manufactured by Oshika Co., Ltd.) used as a binder. The resulting wood fiberboard composition was then hot-pressed to produce a 4 mm thick, 300 mm x 300 mm wood fiberboard using a hot press under the following conditions: temperature: 170°C, time: 60 seconds, and pressure: 3 MPa (maximum). The cross-sectional density distribution of the resulting wood fiberboard was measured using a density distribution meter (product name: DAX6000, manufactured by GreCon). The cross-sectional density of the wood fiberboard was adjusted by adjusting the moisture content of the fibers before hot pressing and the speed at which the press was closed (the speed at which the press plate was pressed down) during hot pressing. Next, the obtained wood fiberboard was fragmented into pieces of 4 mm x 4 mm using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) to obtain fragmented pieces. Next, 69% by mass of polypropylene resin, 30% by mass of the pulverized 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, 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 approximately 0.1 mm to 0.5 mm thick using a heat press. The resulting film was evaluated for fiber dispersion using transmitted light. A sample was rated "good" if there were no lumps or if the lumps were less than 2 mm and acceptable; "medium lumps" if one lumpy lump between 2 mm and 5 mm was acceptable; and "coarse lumps" if multiple lumps between 2 mm and 5 mm were observed, or if one lumpy lump was greater than 5 mm. The results are shown in Table 2.

[0080] [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. The obtained wood fiberboard was used to form a film 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, and the results are shown in Table 2.

[0081] [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. The cross-sectional density distribution of the obtained wood fiberboards was measured in the same manner as in the experimental example. The obtained wood fiberboard was used to form a film 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, and the results are shown in Table 2.

[0082] 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. The obtained wood fiberboard was used to form a film 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, and the results are shown in Table 2.

[0083] Comparative Example 5 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. The obtained wood fiberboard was used to form a film 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, and the results are shown in Table 2.

[0084] 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. Using the obtained wood fiber board, a film was formed in the same manner as in Example 3. The dispersibility of fibers in the obtained film was evaluated in the same manner as in Example 3. The results are shown in Table 2.

[0085] [Table 2]

[0086] 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 by doing the following, even wood fiberboard made with a thermosetting MDI binder can be dispersed in resin. On the other hand, as shown in Comparative Examples 4 to 6, the density of the densest part of the wood fiberboard (maximum density) is 920 kg / m 3 As a result of the above, it was found that it was not possible to disperse wood fiberboard in resin.

[0087] [Example 5] The wood fiberboard obtained in Example 1 was fragmented into pieces of 4 mm x 4 mm using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) to obtain fragmented materials. Next, 69% by mass of polypropylene resin, 30% by mass of the pulverized product, 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, 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.

[0088] [Table 3]

[0089] 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.

[0090] 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 FIG.

[0091] 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 found to be almost the same. Therefore, it is believed 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.

[0092] [Example 6] The wood fiber board obtained in Example 1 was fragmented into pieces of 4 mm x 4 mm using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) to obtain fragmented pieces. Next, 68.5% by mass of polypropylene resin, 30% by mass of the fragments, 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 extruder kneader (Labo Plastomill, 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 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.

[0093] [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 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 pellets were obtained in the same manner as in Example 6. Formaldehyde and acetaldehyde were collected from the obtained pellets at 65° C. and the amounts emitted were measured in the same manner as in Example 6. The results are shown in Table 4.

[0094] [Table 4]

[0095] From the results shown in Table 4, it was found that in Example 6 and Comparative Example 8, when MDI was used as the binder, the amount of formaldehyde and acetaldehyde emitted was lower than when urea-formaldehyde resin was used as the binder, and that Example 6 also fell below the guideline values ​​for indoor VOCs set forth by the Ministry of Health, Labor and Welfare (regarding indoor concentration guideline values ​​for chemical substances in indoor air: https: / / www.mhlw.go.jp / web / t_doc?dataId=00tc3866&dataType=1&pageNo=1, confirmed on February 27, 2024). Furthermore, it is suggested from Example 6 and Comparative Example 8 that the increase in the amount of aldehydes emitted in Comparative Example 8 is due to the urea-formaldehyde resin used as the binder.

[0096] [Example 7] The wood fiberboard obtained in Example 1 was fragmented into pieces of 4 mm x 4 mm using a sheet pelletizer (product name: SCG-220, manufactured by HORAI Co., Ltd.) to obtain fragmented materials. The comminuted material was then passed through a #2 mm metal mesh sieve for 60 seconds. Next, an appropriate amount of the comminuted material was 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 comminuted material on the tray was gently kneaded by hand to observe how it crumbled. The results are shown in Table 5.

[0097] 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.

[0098] [Table 5]

[0099] 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 mixed with a binder. Since the dried plant fibers undergo processes in which they are subjected to physical external forces, such as transportation and being placed in a hopper, shape retention after heating is an important factor.

Claims

1. Contains lignocellulose fibers and an isocyanate compound, 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, Overall density is 550 kg / m ３ More than 700kg / m ３ Below, the maximum density is 550 kg / m ３ Super 750kg / m ３ Below is a wood fiberboard.

2. 2. The wood fiber board according to claim 1, having a thickness of 6 mm or less.

3. A mixture of the fragmented wood fiber board of claim 1 and a thermoplastic resin, According to JASO M902 Automotive parts - Interior materials - Volatile organic compounds (VOC) emission measurement method (sampling bag method), the formaldehyde emission amount collected at 65°C is 100 μg / m ３ The following is a resin molded product.

4. A mixture of the fragmented wood fiber board of claim 1 and a thermoplastic resin, A resin molded product whose acetaldehyde emission amount collected at 65°C is 48 μg / m3 or less in accordance with JASO M902 Automotive parts - Interior materials - Volatile organic compound (VOC) emission measurement method (sampling bag method).

5. A step of processing the wood fiber board according to claim 1 or 2 to obtain fragments each having a side length of 1 mm to 6 mm; a step of drying the comminuted material so that the moisture content is 5% by mass or less; a step of kneading the dried pulverized material with a thermoplastic resin to obtain a kneaded material; and a step of dividing the kneaded mixture into pellets of any size.

6. obtaining pellets by the pellet manufacturing method according to claim 5; and thermoforming the pellets to obtain a resin molded product.

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