Resin molded product and method for manufacturing the same

Abstract

To provide a resin molding and a production method thereof not only allowing visual and tactile wood texture to be acquired but also enabling a natural impression to be exhibited even when a plurality thereof are continuously arranged.SOLUTION: A resin molding 100 having a longitudinal direction and a transverse direction is configured to have a wood grain pattern 3 formed on its surface, the wood grain pattern 3 including a plurality of patterns among a cross grain pattern 33, a regular grain pattern 34, and a figured grain pattern 35, and being arranged in a width direction so that different patterns appear. This allows, when a plurality of the resin moldings are continuously arranged in the longitudinal and lateral directions, not only visual and tactile wood texture to be exhibited, but also enables an impressive pattern to be moderately softened by relatively milder patterns, thereby providing a moderate wood texture and a natural impression, and enabling a natural impression to be maintained even when a plurality of the resin moldings are continuously arranged.SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] The present invention relates to a resin molded product having a wood-grain surface used for outdoor decks, interior materials of buildings, etc., and a method for producing the same. [[Background Art]]

[0002] Wood as a building material has been used since ancient times in various countries around the world because it is lightweight yet strong, has good texture, and is readily available. However, due to problems such as expanded deforestation, corrosion, and insect damage, the use of alternative materials has been on an increasing trend. Among these, building materials using resin molded products with high production efficiency, light weight and high strength are also increasing in usage.

[0003] However, the surface and texture of resins differ greatly from those of wood, and they lack the aesthetic appeal required for buildings and structures, so resin molded products with wood-toned designs on their surfaces have been developed. For example, there are methods of printing wood-grain patterns, and methods of forming wood-grain patterns by press molding with a mold.

[0004] Conventionally, techniques for expressing unevenness using printing inks have been developed. For example, in the technique disclosed in Patent Document 1, after printing a wood-grain pattern on a base material, build-up printing is performed in predetermined areas by gravure printing to form portions with surface gloss, and printing with matte ink is performed on other areas, which is described as enabling acquisition of a wood texture rich in three-dimensional effect both visually and tactilely.

[0005] In addition to printing, techniques for forming wood-grain patterns on the surface of resin molded products by pressing with an embossing roll have also been developed. For example, in the technique of Patent Document 2, a wood-grain pattern with a predetermined depth is formed by an embossing roll. In this technique, in addition to embossing with the embossing roll, roughening processing is also performed on non-embossed portions, thereby adding streak patterns with a predetermined surface roughness to further improve wood texture.

[0006] In the technology described in Patent Document 1, as shown in Figure 7, a wood grain pattern such as a mountain shape, wave, or spiral is arranged on the surface. This wood grain pattern is configured so that one large pattern is arranged over a predetermined width. The same applies to Patent Document 2, where, as shown in Figure 8, a single large wood grain pattern is arranged on the surface. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 56-5788 [Patent Document 2] Japanese Patent Publication No. 2018-8512 [Overview of the project] [Problems that the invention aims to solve]

[0008] Wood has different grain patterns depending on the direction of processing during sawing, such as flat grain, quarter grain, and figured grain. However, quarter grain has a pattern of roughly parallel lines, and even if this is reproduced on the surface of a resin molded product, it will appear as a monotonous pattern and will be inferior to the texture of wood. Therefore, it is common to reproduce flat grain or figured grain, which are more characteristic patterns of wood, on the surface. On the other hand, in the case of decking materials and interior / exterior building materials, plate-shaped members of a predetermined size are used by arranging them continuously in both the longitudinal and transverse directions.

[0009] In natural wood, even within flat-sawn or figured-grain wood, boards with varying grain sizes and knot patterns will be mixed together. Furthermore, decks and interior / exterior finishes are sometimes constructed by mixing straight-sawn boards with flat-sawn or figured-grain boards.

[0010] However, for resin molded products with wood grain patterns, it is not economical to prepare a lineup of various grain patterns such as flat grain and straight grain, as is done with natural wood. Therefore, resin molded products with a wood grain pattern formed using a single press die are used by arranging them continuously in the longitudinal and transverse directions. As mentioned earlier, conventional resin molded products create a large single grain pattern to mimic the look of wood. However, when resin molded products with only one grain pattern are arranged in a continuous pattern, the large grain patterns are arranged in a continuous, flat surface, resulting in an extremely unnatural appearance.

[0011] This invention has been made in view of the above-mentioned problems, and its objective is to provide a resin molded product and a method for manufacturing the same that not only provides a visual and tactile wood-like texture, but also gives a natural impression even when multiple units are arranged in a row. [Means for solving the problem]

[0012] The means employed by the inventors to solve the above problems are described below. The resin molded product of the present invention is a resin molded product having a longitudinal direction and a transverse direction, and has a wood grain pattern formed on its surface. The wood grain pattern may include straight grain patterns, flat grain patterns, figured grain patterns, etc., and may include some or all of these. Furthermore, the wood grain pattern includes multiple of these patterns: flat grain, straight grain, and figured grain, and the wood grain pattern has different patterns in the width direction. Each with 3 or more columns They are arranged in multiple configurations so that they appear as a whole.

[0013] In this invention, a single resin molded body contains multiple patterns in the width direction, including straight grain, flat grain, and figured grain, and these patterns are arranged in such a way that different patterns appear sequentially. As a result, even when multiple resin molded products are arranged side by side, the more subtle patterns moderately soften the more striking patterns, giving a pleasant wood-like texture and a natural impression.

[0014] In order to solve the aforementioned problems, the present invention employs, in addition to the above-mentioned means, the shorter dimension is set to 100 mm or more and 300 mm or less, and the structure is configured such that three or more rows of either a flat grain pattern or a straight grain pattern are arranged.

[0015] Among wood grain patterns, flat grain patterns are striking in their appearance, while straight grain patterns have a softer impression. On the other hand, decking materials and interior / exterior boards are generally made up of materials with a width of 300 mm or less. For widths of 300mm or less, arranging the straight grain pattern and the flat grain pattern in three or more rows results in a natural appearance when multiple resin molded products are arranged consecutively vertically and horizontally, as the striking flat grain pattern and the softer straight grain pattern are arranged alternately.

[0016] Another means employed by the present invention to solve the aforementioned problems is to set the dimension in the shorter direction to 100 mm or more and 300 mm or less, and to configure the pitch between flat grain patterns or between straight grain patterns to be 20 mm or more and 100 mm or less. In the dimensions commonly used for decking and interior / exterior lumber, arranging the planks so that the pitch of the flat grain or quarter-sawn pattern is between 20mm and 100mm results in an appropriate spacing between the striking flat grain pattern and the softer quarter-sawn pattern, creating a natural appearance.

[0017] Incidentally, in the straight grain pattern, the embossed recesses are formed in a continuous line without being interrupted in the longitudinal direction. Therefore, in any of the above configurations, by using a wood grain pattern that includes a straight grain pattern, even if water accumulates in the resin molded product, it can be easily drained through the continuous embossed lines, resulting in good drainage.

[0018] Another means of the present invention is to form the wood grain pattern by creating indentations and recesses through press processing, and to configure the wood grain pattern so that the difference in the ratio of the area of ​​the embossed portion within each range when the short side is divided into strips of 10 mm intervals is within 50%. When a wood grain pattern is formed by creating indentations and protrusions through press processing, the embossed areas are those formed by the mold pressing down, while the non-embossed areas are those not pressed down by the mold. In the areas pressed down by the mold, a force acts that causes the resin molded body itself to bend and deform. However, depending on the structure of the resin molded body, there may be parts that are easily deformed and parts that are not.

[0019] For example, when a resin molded article is not simply a plate but has a hollow shape with a predetermined internal space, a rib may be formed in the hollow portion. In this case, since the rib acts as a support at a position directly above the rib, bending caused by pressing of the mold is unlikely to occur, but bending easily occurs at a position between the ribs when the mold is pressed.

[0020] In such a case, if only a predetermined position in the width direction is pressed intensively, the resin molded article bends at the pressed position, making it difficult to form a wood grain pattern with sufficient depth on the surface. On the other hand, at the position directly above the rib, the resin molded article is less likely to bend due to pressing of the mold, and the wood grain pattern can be reliably transferred.

[0021] In the present invention, the transverse direction is divided into 10 mm-wide strips, and the wood grain pattern is configured such that the difference in the area ratio of the embossed portions in each divided range is 50% or less, whereby the pressure distribution in the width direction of the molded article can be made uniform. Thereby, in press working of a molded article, the difference in pressure distribution across the width direction of the press die is reduced, and a wood grain pattern with a uniform depth as a whole can be formed.

[0022] In addition, when pressing force is locally concentrated during press working, the mold at that portion is prone to wear. In the present invention, with the area ratio of the embossed portions as described above, the pressure distribution in the width direction of the molded article can be made uniform, and wear resistance is also improved.

[0023] In the present invention, a resin molded article having a wood grain pattern with a longitudinal direction and a transverse direction, where different patterns are present in the width direction, Each with 3 or more columns can also be manufactured by a method of forming a wood grain pattern on the surface by roll pressing. Here, the wood grain pattern includes a plurality of patterns selected from the group consisting of plain grain patterns, straight grain patterns, and figured grain patterns.

[0024] In the above manufacturing method, the dimensions in the shorter direction can be set to 100 mm or more and 300 mm or less, and a wood grain pattern can be formed on the surface with three or more rows of either a flat grain pattern or a straight grain pattern. Furthermore, within the dimensions mentioned above, it is also possible to arrange the plank grain patterns or quarter-sawn patterns so that the pitch between them is between 20 mm and 100 mm.

[0025] Furthermore, it is possible to form a wood grain pattern on the surface such that the difference in the ratio of the embossed area within each range when the shorter side is divided into strips of 10 mm intervals is within 50%. [Effects of the Invention]

[0026] As described above, the resin molded product of the present invention is a resin molded product having a longitudinal direction and a transverse direction, and multiple wood grain patterns formed on the surface are arranged alternately in the width direction. As a result, when the resin molded product is arranged continuously in the longitudinal and transverse directions, not only is a visual and tactile wood texture obtained, but the relatively softer pattern moderately softens the impressive pattern, giving a moderate wood texture and a natural impression, and it also has the effect of giving a natural impression even when multiple pieces are arranged continuously. [Brief explanation of the drawing]

[0027] [Figure 1] These are a plan view and an enlarged cross-sectional view showing the surface of the resin molded product of the present invention. [Figure 2] This is an explanatory diagram showing the different ranges of the wood grain pattern of the resin molded product of the present invention. [Figure 3] This graph shows the proportion of recesses in each segment of the resin molded product of the present invention. [Figure 4] This is an explanatory diagram illustrating the method for manufacturing a resin molded product according to the present invention. [Figure 5] This is an explanatory diagram of an embossing roll used in the manufacturing method of resin molded articles of the present invention. [Figure 6] This is a plan view illustrating a modified example of the present invention. [Figure 7] This is a plan view representing a conventional example described in Patent Document 1. [Figure 8] This is a perspective view showing a conventional example described in Patent Document 2. [Modes for carrying out the invention]

[0028] Embodiments for carrying out the present invention will be described below with reference to Figures 1 to 4. Please note that each diagram is a schematic representation for explanatory purposes, and dimensions and shapes may be exaggerated or simplified in some cases.

[0029] The resin molded product 100 of the present invention is used for decking materials for terraces and promenades, benches, wall materials, flooring materials, furniture, louver materials for windows, etc., and as shown in Figure 1, it is a plate-shaped extruded product having a predetermined cross-sectional shape. The resin molded product 100 has a two-layer structure in which a base member 1 that forms the structure and a surface layer 2 that covers the outer circumference of the base member 1, excluding both end faces, are integrated.

[0030] Both the base member 1 and the surface layer 2 are made of synthetic resin. For example, the base member 1 can be made of polyvinyl chloride (PVC) resin or acrylonitrile-butadiene-styrene (ABS) resin. The surface layer 2 can be made of acrylonitrile-styrene-acrylic acid ester (ASA) resin. Other resins that can be used include, for example, polyethylene (PE) resin, polypropylene (PP) resin, ethylene vinyl acetate (EVA) resin, and polystyrene (PS) resin. These resins may also be supplemented with additives such as pigments, foaming agents, UV absorbers, and flame retardants as needed.

[0031] Furthermore, to enhance the woody texture, it is preferable to include wood powder in all of them. The higher the wood powder content in the synthetic resin, the greater the rigidity. On the other hand, molding defects such as deterioration of appearance are more likely to occur during molding. Therefore, it is preferable to include a larger amount of wood powder in the base member 1, which is a non-exterior part, in order to achieve rigidity that can withstand the loads during embossing and use, and to include less wood powder in the surface layer 2 than in the base member 1, prioritizing appearance. Specifically, it is preferable that the wood powder content of the base member 1 be 10% or more higher than that of the surface layer 2, and more preferably 15% or more higher.

[0032] The surface 21 and back surface 22 of the surface layer 2 have a wood grain pattern 3 formed by embossing using a roll press, as described later, but the right side surface 23 and left side surface 24 do not have a wood grain pattern 3. In addition, both the front and rear end surfaces are cut surfaces that have been cut to a predetermined length, and the base member 1 is exposed. The cross-sectional shape is a horizontally elongated rectangle, and ribs 11·11… are formed in the longitudinal direction at predetermined intervals in the hollow section to prevent deflection.

[0033] The wood grain pattern 3 formed on the surface 21 and back surface 22 has an embossed portion 31 that is recessed relative to the surface and an unembossed portion 32. A streaky pattern may be formed on the unembossed portion 32 by roughening, and the wood texture can be improved by setting the arithmetic mean roughness of the unembossed portion 32 to 2 μm or more and 30 μm or less.

[0034] The thickness of the base member 1 and the ribs 11 is designed appropriately according to the required strength. For strength, the spacing between the ribs 11 is preferably 10 mm to 30 mm, and in the configuration shown in Figure 1, nine ribs are arranged at 16 mm intervals. The surface layer 2 has a substantially uniform thickness throughout, and its thickness is preferably set to 0.5 mm to 5 mm depending on the depth of the embossing. Furthermore, the width of the resin molded product 100 is preferably, for example, 100 mm to 300 mm, and may be set to approximately 160 mm for decking material and approximately 100 mm for louver material. The length in the longitudinal direction can be cut to any dimension depending on the application.

[0035] In the configuration shown in Figure 1, the wood grain pattern 3 formed on the surface 21 consists of multiple alternating flat grain patterns 33 and straight grain patterns 34 arranged in the width direction. It is preferable that the flat grain pattern 33 and the straight grain pattern 34 are arranged in three or more rows. In the embodiment shown in Figure 1, on the surface 21 of the resin molded product 2, which is 160 mm wide, the flat grain pattern 33 and the straight grain pattern 34 are arranged alternately in four rows each in the width direction. The same applies to the back surface 22, but the surface surface 21 will be described as a representative example from here on.

[0036] The resin molded product 100 is rarely used individually; multiple products are arranged continuously in the width and length directions depending on the application. Therefore, if the resin molded product 100 has a prominent wood grain pattern 33, when arranged continuously, the wood grain pattern 33 will be visible everywhere, causing an unnatural appearance. Therefore, by arranging the flat grain pattern 33 and the straight grain pattern 34 alternately in at least three rows each, the flat grain pattern 33 provides a woody texture, while the straight grain pattern 34 moderately softens the impression of the flat grain pattern 34, reducing the sense of incongruity when they are arranged continuously and resulting in a more natural appearance.

[0037] Furthermore, in the configuration shown in Figure 1, the pitch between the flat grain patterns 33-33 and the quarter-sawn patterns 34-34 is set to be between 20 mm and 40 mm. The pitch between each pattern, including the flat grain patterns 33-33, quarter-sawn patterns 34-34, and other wood grain patterns not shown, is between 20 mm and 100 mm, depending on the width of the resin molded product 100, to provide a good balance between the wood texture and a natural impression. More preferably, the pitch is between 20 mm and 80 mm, and even more preferably between 20 mm and 65 mm.

[0038] The depth of the embossed portion 31 constituting the wood grain pattern 3 is preferably 100 μm or more and 2 mm or less, more preferably 150 μm or more and 1.5 mm or less, and even more preferably 200 μm or more and 1 mm or less. By setting the depth to this extent, the wood texture can be improved, and in the case of the straight grain pattern 34, even if water accumulates on the surface 21, the water can be absorbed into the embossed portion 31 and easily drained in the longitudinal direction.

[0039] Embossing is formed by the convex portion of the embossing roll, described later, pressing against the surface 21 and causing plastic deformation. Therefore, a load acting in a direction that causes the surface 21 of the resin molded product 100 to bend is applied to the pressing portion that forms the embossed portion 31. In this case, if the embossed portion 31 is directly above the rib 11 in the cross-sectional shape, the load from the convex portion of the embossing roll can be supported by the rib 11. As a result, the surface 21 does not bend and escape under the load, and an emboss can be firmly formed on the surface 21 for the height of the convex portion of the embossing roll.

[0040] However, if the intermediate portion of the ribs 11, 11 is the embossed portion 31, then the rib 11 is not directly below the load-bearing portion, causing the surface 21 to flex and escape due to the load from the convex portion of the embossing roll. In this case, not only will the embossed portion 31 be shallower than the height of the embossing roll's protrusions, but the ridge line that forms the boundary between the embossed portion 31 and the non-embossed portion 32 will also become unclear, resulting in a loss of the wood-like texture.

[0041] Therefore, in the present invention, as shown in Figure 2, a wood grain pattern 3 is formed on the surface 21 of the resin molded product 100 such that the difference in the ratio of the area of ​​the embossed portion within each range when the short side is divided into strips of 10 mm each is within 50%.

[0042] The larger the proportion of the embossed area within each range, the greater the load applied by the embossing roll in that range. In this invention, the proportion of the embossed area is determined for each narrow 10 mm range, and the wood grain pattern 3 is constructed such that the difference between the range with the largest proportion and the range with the smallest proportion in the width direction is within 50%.

[0043] Figure 2 shows a binarized image of the wood grain pattern 3 divided into 10mm wide sections. The 160mm width is divided into 16 sections. Black pixels correspond to the embossed areas 31, and white pixels correspond to the non-embossed areas 32. Using this image, count the number of black pixels relative to the total number of pixels in each range and calculate the ratio. If fractional values ​​occur, allocate them to both ends and exclude those ranges from evaluation. Furthermore, if the range at both ends is 10 mm or less, it may be excluded from evaluation because these ends are less prone to bending due to the right side 23 and left side 24.

[0044] Figure 3 is a graph that normalizes the area ratio of the embossed parts (black pixels) in each range. Section 14, which had the largest proportion of black, is set to 100%, and the graph shows how much smaller the proportion in each section is compared to section 14. In other words, it shows the difference in proportion in each range relative to section 14, which had the largest proportion in the width direction. Thus, it can be seen that the wood grain pattern 3 is such that when the difference between the range with the smallest proportion and the range with the largest proportion of the embossed area in the entire range is calculated, the difference is within 50%.

[0045] By creating this wood grain pattern 3, the difference in pressing force by the embossing roll is reduced, whether directly above the ribs 11 or between the ribs 11, allowing for uniform embossing across the entire width of the surface 21. Consequently, variations in the depth and clarity of the embossed areas 31 are eliminated across the entire surface 21, resulting in a natural wood texture. Furthermore, by applying a uniform pressing force in the width direction of the embossing roll, wear of the embossing roll, which is a press die, can be suppressed.

[0046] Such a resin molded product 100 can be manufactured by a co-extrusion molding method as shown in Figure 4. Specifically, the material of the base member 1 and the material of the surface layer 2 are melted separately and extruded into a single mold M from separate extrusion heads to obtain a primary molded product P with a two-layer structure in which the base member 1 and the surface layer 2 are integrated.

[0047] In the configuration shown in Figure 4, the surface 21 and back surface 22 of the surface layer 2 of the primary molded product P obtained by extrusion molding are roughened. The roughening is performed by creating a groove pattern using a belt sander B or the like. The wood-like texture is improved by adjusting the processing conditions so that the arithmetic mean roughness of this groove pattern is between 2 μm and 30 μm.

[0048] Then, after roughening, embossing is performed using the embossing roll R shown in Figure 5. The embossing roll R is, for example, a roll with a width of 180 mm, and the resin molded product is held between two rolls, one above the other, spaced apart according to the thickness of the primary molded product P, and a predetermined pressing force is applied. Each embossing roll R·R is heated above the thermal distortion temperature of the resin, and the temperature is appropriately selected depending on the resin, but is generally around 90°C to 200°C.

[0049] This embossed roll R·R has a wood grain pattern 3 formed in a reversed state of relief and relief, such that the difference in the ratio of the area of ​​the embossed portion within each range when the roll is divided into strips of 10 mm each in the width direction is within 50%. In this case, if the embossing roll R on the surface 21 side and the embossing roll R on the back side 22 side are formed so that the bumps and depressions of the wood grain pattern 3 correspond to each other, the balance of the upper and lower loads during embossing will be improved. However, the upper and lower embossed parts 31 may have different patterns.

[0050] Although the width of the embossing roll R is greater than the width of the primary molded product P, by using an embossing roll R with the above proportion of wood grain pattern 3 formed on it, it is possible to process the resin molded product 100 with uniform pressing force regardless of the position in the width direction of the embossing roll R as it passes through, and a wood grain pattern 3 of uniform depth can be obtained over the entire width direction of the resin molded product 100.

[0051] As described above, with the resin molded article 100 and its manufacturing method of the present invention, when multiple resin molded articles 100 are arranged side by side, not only is a visual and tactile wood-like texture obtained, but the relatively soft impression of the straight-grain pattern 32 moderately softens the impressive flat-grain pattern 31, giving a moderate wood-like texture and a natural impression, and a natural impression can be given even when they are arranged continuously in the long and short directions.

[0052] "Differentiation Example 1" The present invention is not limited to the above-described form, and other forms can also be adopted. For example, as shown in Figure 6, the resin molded product 101 can be configured such that the wood grain pattern 3 is arranged between the flat grain pattern 33 and the straight grain pattern 34, with the figured grain pattern 35 included. Wood grain refers to the complex patterns that appear when wood is cut from areas with localized twists, curves, or burls, and it is a distinctive pattern that gives the impression of natural wood.

[0053] Even in this modified form, the flat grain pattern 33 and figured grain pattern 35 provide a woody texture, while the straight grain pattern 34 moderately softens the impression of the flat grain pattern 33 and figured grain pattern 35, reducing the sense of incongruity when they are arranged in a continuous pattern and resulting in a more natural appearance. [Explanation of symbols]

[0054] 100,101 Resin molded products 1 Base member 11 Ribs 2 Surface layer 21 Surface 22 Back 23 Right side 24 Left side 3 Wood grain pattern 31 Embossed part 32 Non-embossed area 33. Wood grain pattern 34 Straight grain pattern 35 Wood grain pattern M mold B Belt Sander R Embossing Roll P Primary molded product

Claims

1. A resin molded product having a longitudinal direction and a transverse direction, The dimension in the shorter direction is between 100mm and 300mm. A wood grain pattern is formed on the surface. The aforementioned wood grain pattern includes multiple patterns from among flat grain, straight grain, and figured grain. A resin molded product characterized by having multiple pieces arranged such that three or more rows of different patterns appear in the width direction.

2. The resin molded product according to Claim 1, characterized in that the pitch between flat grain patterns or between straight grain patterns is 20 mm or more and 100 mm or less.

3. A resin molded product having a longitudinal direction and a transverse direction, A wood grain pattern is formed on the surface. The aforementioned wood grain pattern includes multiple patterns from among flat grain, straight grain, and figured grain. Multiple arrangements are made so that different patterns appear in the width direction. The pitch between flat grain patterns or between straight grain patterns is 20 mm or more and 100 mm or less. The aforementioned wood grain pattern is formed by the unevenness created by pressing, A resin molded product characterized in that the difference in the ratio of the area of ​​the embossed portion within each range when the shorter direction is divided into strips of 10 mm intervals is within 50%.

4. A method for manufacturing a resin molded product having a wood grain pattern with longitudinal and transverse directions, The dimension in the shorter direction is between 100mm and 300mm. The aforementioned wood grain pattern includes multiple patterns from among flat grain, straight grain, and figured grain. A method for manufacturing a resin molded product, characterized by forming a wood grain pattern on the surface by roll pressing such that three or more rows of different patterns appear in the width direction.

5. The method for manufacturing a resin molded product according to Claim 4, characterized in that a wood grain pattern is formed on the surface such that the pitch between flat grain patterns or straight grain patterns is 20 mm or more and 100 mm or less.

6. A method for manufacturing a resin molded product having a wood grain pattern having longitudinal and transverse directions, wherein the wood grain pattern includes a plurality of flat grain patterns, straight grain patterns, and figured grain patterns. A wood grain pattern is formed on the surface by a roll press so that different patterns appear in the width direction. A wood grain pattern is formed on the surface, with the spacing between flat grain patterns or straight grain patterns being between 20 mm and 100 mm. A method for manufacturing a resin molded product, characterized by forming a wood grain pattern on the surface such that the difference in the ratio of the area of ​​the embossed portion within each range when the shorter direction is divided into strips of 10 mm intervals is within 50%.

Images