Wood-grain sheets and composite materials

Abstract

We provide wood-grain sheets with excellent flame retardancy. [Solution] The wood-grain sheet according to this disclosure contains polyolefin resin and wood powder and is a single layer.

Description

Technical Field

[0001] The present invention relates to a woody sheet and a composite material.

Background Art

[0002] An integrally extruded body including a core material and a coating layer containing wood powder is known as a conventional technique (for example, Patent Documents 1 and 2). Such an integrally extruded body has a woody texture and is used for building members, decorative members, and the like.

[0003] In addition, Patent Document 3 discloses a decorative sheet having polishing marks by sanding on the surface in order to create a woody texture.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional techniques as described above had room for further improvement from the viewpoint of flame retardancy. One aspect of the present invention aims to realize a woody sheet having excellent flame retardancy.

Means for Solving the Problems

[0006] In order to solve the above problems, a woody sheet according to one aspect of the present invention includes a polyolefin resin and wood powder and is a single layer.

Effects of the Invention

[0007] According to one aspect of the present invention, a wood-grain sheet with excellent flame retardancy can be provided. [Modes for carrying out the invention]

[0008] One embodiment of the present invention will be described below, but the present invention is not limited thereto. Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B".

[0009] [1. Wood-grain sheet] A wood-grain sheet according to one embodiment of the present invention comprises a polyolefin resin and wood powder, and is a single layer. In this specification, "wood-grain sheet" means a sheet having a wood-like texture on its surface, for example, having a wood-grain pattern on its surface. "Single layer" means that it exists as an independent single layer sheet. For example, "single layer" in this specification means that the wood-grain sheet is not a coating layer molded integrally and inseparably with the substrate by integral extrusion molding. Note that "single layer" does not mean anything other than using the wood-grain sheet laminated on a substrate. As described later, the wood-grain sheet can also be used laminated on a substrate.

[0010] Since the wood-grain sheet is formed as a single layer sheet that is not integrated with the base material, its thickness can be reduced compared to when it is integrally extruded with the base material. A thinner wood-grain sheet reduces the amount of heat generated during combustion. Furthermore, by including wood powder, the wood-grain sheet can reduce the amount of heat generated compared to when it is made only of resin. Due to the synergistic effect of reducing the thickness and including wood powder, the wood-grain sheet exhibits excellent flame retardancy.

[0011] The flame retardancy can be evaluated, for example, by a cone calorimeter test in accordance with ISO 5660-1, and specifically by the method described in the examples. The wood-grain sheet preferably meets the standards for flame-retardant materials stipulated in the Building Standards Act, more preferably meets the standards for semi-noncombustible materials, and even more preferably meets the standards for noncombustible materials.

[0012] Examples of the polyolefin resin include polypropylene and polyethylene (e.g., high-density polyethylene, medium-density polyethylene, low-density polyethylene), with polypropylene being preferred from the viewpoint of chemical resistance, abrasion resistance, and impact resistance. The wood-grain sheet may contain only polyolefin resin as the resin, or it may contain a resin other than polyolefin resin in addition to the polyolefin resin. Examples of resins other than polyolefin resin include polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid, polyacrylate, polyacrylic acid ester, polybutadiene, polyisoprene, polychloroprene, ethylene propylene rubber, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-ethylene propylene rubber-styrene copolymer, ethylene vinyl acetate copolymer, etc. These may be used individually or in combination of two or more.

[0013] The content of polyolefin resin per 100% by weight of the wood-grain sheet is preferably 10% by weight or more and 90% by weight or less, and more preferably 50% by weight or more and 75% by weight or less. The content of resins other than polyolefin resin per 100% by weight of the wood-grain sheet may be 0% by weight or more and 70% by weight or less, or 0% by weight or more and 95% by weight or less.

[0014] From the viewpoint of environmental compatibility, it is preferable that the polyolefin resin and resins other than polyolefin resins are resins made from waste plastic materials.

[0015] Examples of the wood powder include wood powder obtained by crushing waste wood or unused wood. The smaller the particle size of the wood powder, the more uniformly it mixes during kneading in the manufacturing process, which is preferable as it improves the appearance of the wood-grain sheet. For example, the wood powder is preferably of a particle size that can pass through a sieve with a mesh count of 40, but it is not limited to this, and powders with larger particle sizes can also be used. The above mesh count is specified in JIS standards (JIS G 3556, JIS G 4309).

[0016] The wood powder is preferably present in an amount of more than 0% and 15% or less by weight relative to 100% by weight of the wood-grain sheet, more preferably 1% or more and 10% or less by weight, and even more preferably 5% or more and 10% or less by weight. Including more than 0% by weight of wood powder further improves the flame retardancy and matte finish. By setting the wood powder content to 15% by weight or less, sufficient strength can be achieved.

[0017] The wood-like sheet may or may not contain cellulosic components other than wood flour. Examples of cellulosic components other than wood flour include bamboo flour, pulp, bagasse, kenaf, sawdust, wood fibers, rice husks, crushed chips, fruit husk powder, and recycled paper. The content of cellulosic components other than wood flour relative to 100% by weight of the wood-like sheet may be 0% to 5% by weight, 0% to 3% by weight, or 0% to 1% by weight.

[0018] The wood powder and cellulose-based components other than the wood powder preferably have a moisture content of 5% or less. Further, it is preferable that the wood powder and cellulose-based components other than the wood powder have the content of extraction components such as terpenes, wood vinegar, and rosin volatilized in advance and reduced as much as possible. Thereby, the formability and appearance of the woody sheet can be made more excellent. From this viewpoint, specifically, by performing heat treatment or vacuum degassing treatment, etc. on the woody material serving as the raw material in advance, the content of the volatile components including moisture and the above extraction components in the woody material serving as the raw material is preferably 0.5% by weight or less.

[0019] The woody sheet may contain calcium carbonate. Thereby, the water absorption expansion of the woody sheet can be effectively suppressed. With respect to 100% by weight of the woody sheet, it is preferable that calcium carbonate is contained at 10% by weight or more and 80% by weight or less. Calcium carbonate may be derived from, for example, eggshells discarded in a food manufacturing factory or the like.

[0020] In addition to the components described above, the woody sheet may also contain a compatibilizer, a lubricant, a pigment, a weathering agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a flame retardant, a conductive agent, etc.

[0021] The compatibilizer is an additive for making the lipophilic polyolefin resin and the hydrophilic wood powder compatible and mixing them well. As the compatibilizer, a heat - plastic resin modified with an acid can be preferably used. Specifically, a resin in which the molecular side chain or the terminal of the heat - plastic resin is substituted with an unsaturated acid such as maleic acid can be used. In particular, in order to improve the affinity with the polyolefin resin, it is advisable to add a polyolefin resin modified with an unsaturated carboxylic acid or its derivative. Examples of the unsaturated carboxylic acid include maleic anhydride, itaconic anhydride, citraconic anhydride, maleic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, mesaconic acid, angelic acid, sorbic acid, acrylic acid, methacrylic acid, etc. Examples of the derivative of the unsaturated carboxylic acid include metal salts, amides, imides, esters, etc. of the unsaturated carboxylic acid. These may be used alone or in combination of two or more kinds.

[0022] As the lubricant, for example, calcium stearate and zinc stearate can be used. The lubricant is an additive for improving the slipperiness between the mold and the material. Therefore, by adding the lubricant, the moldability and appearance of the wood - like sheet can be improved.

[0023] As the pigment, various colorants can be used. For example, titanium dioxide, cobalt oxide, ultramarine blue, indigo blue, safflower, vermilion, lead white, red lead, lead yellow, strontium chromate, titanium yellow, titanium black, zinc chromate, iron black, molybdenum red, molybdenum white, litharge, lithopone, emerald green, guinea green, cadmium yellow, cadmium red, cobalt blue, azo pigment, phthalocyanine blue, isoindolinone, quinacridone, dioxazine violet, perinone perylene, etc. can be utilized. These may be used alone or in combination of two or more kinds.

[0024] Examples of flame retardants include magnesium hydroxide-based flame retardants and phosphorus-based flame retardants. However, since the wood-grain sheet has improved flame retardancy, it does not need to contain a flame retardant. In this specification, "flame retardant-free" means that the amount of flame retardant is below the detection limit when measured by methods such as hot water extraction, resin composition analysis, and elemental analysis.

[0025] The wood-grain sheet is preferably 0.1 mm or more and 1.0 mm or less in thickness, more preferably 0.11 mm or more and 0.5 mm or less, even more preferably 0.12 mm or more and 0.3 mm or less, and particularly preferably 0.13 mm or more and 0.2 mm or less. A thickness of 0.1 mm or more can provide more sufficient strength. A thickness of 1.0 mm or less further improves the flame retardant effect.

[0026] The wood-grain sheet may have an embossed or sanded surface to represent the texture of wood. Preferably, the wood-grain sheet has an embossed surface. Embossing, which is also applicable when the sheet is thin, can represent the texture of wood.

[0027] As described above, the wood-grain sheet can utilize waste plastic as a raw material for the polyolefin resin, waste wood or unused wood as a raw material for the wood powder, and discarded eggshells as a raw material for the calcium carbonate. Therefore, the wood-grain sheet can contribute to achieving, for example, Goal 12 of the United Nations' Sustainable Development Goals (SDGs), "Ensure sustainable consumption and production patterns."

[0028] The aforementioned wood-grain sheet can be manufactured by kneading polyolefin resin, wood powder, and other components as needed, and then molding the mixture. Molding methods include extrusion molding, calendering, and press molding.

[0029] [2. Composite materials] A composite material according to one embodiment of the present invention comprises a base material and the wood-grain sheet described above laminated on the base material. This composite material has improved flame retardancy compared to conventional composite materials formed by integral extrusion molding.

[0030] The material and shape of the base material are not particularly limited. Examples of base material materials include metals, resins, and other materials. Examples of metals include iron, aluminum, plated steel sheets, etc.

[0031] The composite material may have an adhesive layer between the base material and the wood-grain sheet. The adhesive layer may contain, for example, a urethane resin, a polyester resin, an epoxy resin, or the like.

[0032] One method for manufacturing the composite material is to include a step of laminating the wood-grain sheet described above onto a substrate. For example, an adhesive layer may be laminated onto the substrate, and then the wood-grain sheet may be laminated on top of that.

[0033] The applications of composite materials are not particularly limited, but examples include building materials (decorative materials, decking materials, louvering materials, etc.), furniture, fixtures, interiors, automotive parts, ornaments, and objects.

[0034] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0035] One embodiment of the present invention may include the following configuration: <1> A wood-grain sheet containing polyolefin resin and wood powder, consisting of a single layer. <2> The wood powder is contained in an amount greater than 0% and less than or equal to 15% by weight of the wood-grain sheet (100% by weight). <1> The wood-grain sheet described above. <3> The thickness is 0.1 mm or more and 1.0 mm or less. <1> or <2> The wood-grain sheet described above. <4> A base material and laminated on the base material <1> ~ <3> A composite material comprising a wood-grain sheet as described in any one of the following. [Examples]

[0036] One embodiment of the present invention is described below.

[0037] [Evaluation Method] The flame retardancy of the composite material obtained in Example 1 below was evaluated by a cone calorimeter test in accordance with ISO 5660-1. A cone calorimeter III manufactured by Toyo Seiki Seisakusho Co., Ltd. was used as the apparatus. Specifically, the composite material was subjected to a maximum heat generation rate of 200 kW / m². 2 The device was heated for 20 minutes. The total heat output and maximum heat output rate were measured, as well as the time (seconds) until the total heat output reached 8 MJ. The results were evaluated as follows in accordance with the Building Standards Act. 300 seconds: Flame-retardant material. 600 seconds: Semi-non-combustible material. 1200 seconds: Non-combustible material.

[0038] Furthermore, as a requirement for non-combustible materials, the heat generation rate must be 200 kW / m². 2 This also confirmed that combustion does not continue for more than 10 seconds.

[0039] [Reference example 1] Polypropylene and calcium carbonate were kneaded together. The resulting mixture was pressed to obtain a resin sheet with a thickness of 0.16 mm. The calcium carbonate content was approximately 60% by weight of 100% by weight of the obtained resin sheet. The resin sheet was bonded to an aluminum plate via an adhesive layer to obtain a composite material.

[0040] [Example 1] A wood-grain sheet with a thickness of 0.14 to 0.16 mm was obtained in the same manner as in Reference Example 1, except that wood powder was added and kneaded to polypropylene and calcium carbonate. The wood powder content in the obtained wood-grain sheet was approximately 7 to 9% by weight per 100% by weight. A composite material was also obtained in the same manner as in Reference Example 1.

[0041] [Evaluation Results] The evaluation results are shown in Table 1.

[0042] [Table 1]

[0043] The resin sheet in Reference Example 1 reached a total heat output of 8 MJ in 1200 seconds or more, thus meeting the standards for non-combustible materials. Furthermore, the resin sheet in Reference Example 1 had a heat output rate of 200 kW / m². 2 The burning time in the above case was 9 seconds. From this perspective, the resin sheet in Reference Example 1 also met the standards for non-combustible materials.

[0044] The wood-grain sheet in Example 1 reached a total heat output of 8 MJ in 1200 seconds or more, meeting the standards for non-combustible materials. Furthermore, the wood-grain sheet in Example 1 had a lower total heat output than Reference Example 1, and a heat output rate of 200 kW / m². 2 The burning time was 0 seconds. From this perspective, it was found that the wood-grain sheet of Example 1 meets the standards for non-combustible materials and is more flame-retardant than the resin sheet of Reference Example 1. [Industrial applicability]

[0045] One aspect of the present invention can be used, for example, in the manufacture of composite materials.

Claims

1. A wood-grain sheet containing polyolefin resin and wood powder, consisting of a single layer.

2. The wood-grain sheet according to claim 1, wherein the wood powder is contained in an amount of more than 0% and 15% or less by weight relative to 100% by weight of the wood-grain sheet.

3. The wood-grain sheet according to claim 1, wherein the thickness is 0.1 mm or more and 1.0 mm or less.

4. A composite material comprising a base material and a wood-grain sheet according to any one of claims 1 to 3 laminated on the base material.

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