Construction sheet

Abstract

To provide a sheet for construction work which has practical strength as construction work and looks beautiful.SOLUTION: A sheet for construction work is made of fabrics composed of two types of multifilament yarns that are aligned or plied, one is a non-thermally fused multifilament yarn composed of single-phase polyester fiber containing pigment, and the other is a heat-sealable multifilament yarn composed of a core-sheath type composite polyester fiber having a core made of high-melting point polyester, a sheath made of low-melting point polyester, and containing pigment, by melting and solidifying the sheath that constitutes the heat-sealable multifilament yarn, the core-sheath type composite polyester fibers are integrated, a heat-fusible multifilament yarn and a non-heat-fusible multifilament yarn are integrated by melting and solidifying low-melting polyester, the amount of pigment contained in the single phase type polyester fiber is larger than the amount of pigment contained in the core-sheath type composite polyester fiber.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sheet for construction work.

Background Art

[0002] A sheet for construction work is a sheet used for preventing scattering at a construction site, and a mesh-shaped sheet having good air permeability and being lightweight for preventing wind pressure accidents is used. In addition, since a sheet for construction work is also required to have a function of giving aesthetic appearance by covering the construction site, usually, many sheets are colored.

[0003] Patent Document 1 discloses a mesh sheet using a multifilament yarn made of core-sheath type composite polyester fiber containing a coloring agent. According to this mesh sheet, since intersections which are the mesh of the mesh sheet are melt-bonded by the sheath part, a process of joining intersections by resin processing or the like can be omitted, and it is lightweight and has good handleability. However, since the sheath part of the core-sheath type composite polyester fiber functions as a thermal adhesive, there is a concern that the whole sheet becomes hard.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors of this invention sought to obtain a lightweight, breathable sheet for construction work that does not undergo resin processing or other treatments. They considered using a core-sheath composite polyester fiber with heat-sealing properties and a high-melting-point polyester fiber that does not fuse, thereby preventing the entire sheet from becoming rigid and allowing the high-melting-point polyester fiber to provide strength. In the process of this investigation, they also considered the aesthetic aspect required for construction work sheets and found that by using two specific types of fibers and setting the pigment content in these fibers in a specific relationship, a sheet with good pigment color development could be obtained. The object of this invention is to provide a lightweight, breathable, and aesthetically pleasing construction work sheet that does not undergo resin processing. [Means for solving the problem]

[0006] The present invention relates to a fabric composed of yarn made by combining or twisting together two types of multifilament yarns. Two types of multifilament to Of the yarns, one multifilament yarn is a non-heat-fusible multifilament yarn composed of single-phase polyester fibers containing pigment. The other multifilament yarn is a heat-sealable multifilament yarn composed of core-sheath type composite polyester fibers containing pigment, with a core made of high-melting-point polyester and a sheath made of low-melting-point polyester. The heat-fusible multifilament yarn is formed by the melting and solidification of the low-melting-point polyester in the sheath portion, thereby integrating the core-sheath type composite polyester fibers with each other, and also by the melting and solidification of the low-melting-point polyester in a non-heat-fusible multifilament yarn that is formed by aligning or twisting the heat-fusible multifilament yarn with the low-melting-point polyester. The pigment contained in single-phase polyester fibers and the pigment contained in core-sheath composite polyester fibers are the same type of coloring pigment. The gist of this invention is a construction sheet characterized by the fact that the amount of pigment contained in single-phase polyester fibers is greater than the amount of pigment contained in core-sheath type composite polyester fibers. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a lightweight, easy-to-handle, and aesthetically pleasing sheet for construction work. [Modes for carrying out the invention]

[0008] The present invention will be described in detail below. The present invention relates to a sheet for construction work, and the sheet is made of a woven fabric composed of yarn made by combining or twisting together two types of multifilament yarns.

[0009] Of the two types of multifilament yarns, one is a non-heat-fusible multifilament yarn formed by bundling multiple single-phase polyester fibers containing pigment. Since the multifilament yarn made of single-phase polyester fibers is not affected by heat at the melting temperature of the sheath portion of the core-sheath composite polyester fiber described later, it is a non-heat-fusible multifilament yarn. Furthermore, because it is not affected by heat, it maintains its mechanical strength as a fiber, contributing to improved sheet strength. The polymer constituting the single-phase polyester fiber is preferably polyethylene terephthalate due to its excellent mechanical strength, weather resistance, and versatility. Alternatively, it may be a mixture of polyethylene terephthalate and a small amount of polybutylene terephthalate.

[0010] The fineness of the single-phase polyester fibers is typically around 5 to 15 decitex. Approximately 30 to 200 of these single-phase polyester fibers are bundled together to form a non-heat-fusible multifilament yarn.

[0011] The other type of multifilament yarn is a heat-sealable multifilament yarn formed by bundling together multiple core-sheath type composite polyester fibers, each consisting of a high-melting-point polyester core and a low-melting-point polyester sheath. Preferably, the difference in melting points between the high-melting-point polyester core and the low-melting-point polyester sheath is 30°C or more. This is because, at the temperature at which the low-melting-point polyester melts, the high-melting-point polyester is unaffected by heat, maintaining its fiber form and contributing to its strength. More specifically, a preferred example is one in which the core is made of polyethylene terephthalate (melting point approximately 255°C) and the sheath is made of copolymerized polyester with a melting point of 120-190°C. The polyethylene terephthalate core may also contain a small amount of polybutylene terephthalate (melting point approximately 225°C).

[0012] The core-sheath type composite polyester fiber typically has a fineness of around 5 to 15 decitex. Approximately 30 to 200 of these core-sheath type composite polyester fibers are bundled together to form a heat-fusible multifilament yarn.

[0013] In this invention, the above-mentioned heat-fusible multifilament yarn and non-heat-fusible multifilament yarn are used in the form of a twisted yarn or a drawn yarn. The fabric in this invention is woven using a yarn made by twisting or drawing together two types of multifilament yarns, and because the sheath portion of the core-sheath type composite polyester fiber constituting the heat-fusible multifilament yarn is melted and solidified, the two types of multifilament yarns are more strongly integrated. When using a twisted yarn, the number of twists is arbitrary, but approximately 50 to 200 twists / meter is preferable.

[0014] Furthermore, when twisting or aligning heat-fusible multifilament yarn and non-heat-fusible multifilament yarn, the composite ratio (fineness ratio) is preferably equal or the ratio of non-heat-fusible multifilament yarn is increased, taking into consideration the effects of the present invention and sheet strength, and a range of heat-fusible multifilament yarn:non-heat-fusible multifilament yarn = 1:1 to 3 (fineness ratio) is preferred.

[0015] In this invention, both the single-phase polyester fibers constituting the non-heat-fusible multifilament yarn and the core-sheath composite polyester fibers constituting the heat-fusible multifilament yarn contain a coloring pigment. By including a coloring pigment in the fibers constituting either multifilament yarn, an aesthetically pleasing building sheet can be obtained. The color of the pigment can be selected as appropriate, and examples include blue, black, green, and brown. Furthermore, in order to obtain the desired color for the building sheet, it is preferable to use a mixture of two or more pigments as appropriate. The coloring pigments contained in the single-phase polyester fibers and the core-sheath composite polyester fibers should be of the same type.

[0016] Regarding the amount of pigment in the fibers constituting each multifilament yarn, the amount of pigment contained in the single-phase polyester fiber is greater than the amount of pigment contained in the core-sheath type composite polyester fiber. When the pigment content in the fibers is not the same in the single-phase polyester fiber and the core-sheath type composite polyester fiber, a difference in color intensity naturally occurs, and a twisted yarn or drawn yarn made from two types of multifilament yarns with different intensity levels will produce a heathered color due to the difference in intensity. However, in this invention, after weaving using this twisted yarn or drawn yarn that produces a heathered color with different intensity levels, the sheath portion of the core-sheath type composite polyester fiber is melted and solidified by heat treatment. As a result, the fibers fuse together due to the melting and solidification of the sheath portion, the surface of the heat-fused multifilament yarn becomes smooth due to the melting and solidification, and the two multifilaments fuse together and become tightly attached, the difference in color intensity is softened and the heathered effect is eliminated, resulting in a glossy and aesthetically pleasing product. The amount of pigment in the fibers constituting each multifilament yarn is such that the amount of pigment contained in the single-phase polyester fibers is greater than the amount of pigment contained in the core-sheath type composite polyester fibers, that is, the amount of pigment in the core-sheath type composite polyester fibers that melts and softens is reduced to achieve the above effect. Conversely, if the amount of pigment contained in the single-phase polyester fibers is the same as or less than the amount of pigment contained in the core-sheath type composite polyester fibers, the above effect will not be achieved, and the aesthetically pleasing construction sheet that is the aim of this invention cannot be obtained.

[0017] Furthermore, in the case of single-phase polyester fibers and core-sheath composite polyester fibers, single-phase polyester fibers have higher strength due to their fiber structure. However, by reducing the pigment content in core-sheath composite polyester fibers, a decrease in fiber strength in the core-sheath composite fibers can be prevented, resulting in good handling without the difference in fiber strength between the two becoming too large. In addition, when twisting or aligning the two types of multifilament yarns, creating a difference in shade between the two types of multifilament yarns provides visual identification, preventing mishandling and improving work efficiency.

[0018] The pigment content of single-phase polyester fibers and core-sheath composite polyester fibers can be selected according to the type and color of the pigment. However, the pigment content in single-phase polyester fibers is preferably 0.01 to 1% by mass, taking into consideration fiber strength and color development. The ratio of the pigment content in single-phase polyester fibers to the pigment content in core-sheath composite polyester fibers is preferably 1.5 to 3 / 1. Furthermore, the pigment content in core-sheath composite polyester fibers is preferably 0.0003 to 0.7% by mass.

[0019] In the case of core-sheath type composite polyester fibers, pigment may be contained in both the core and the sheath. However, in order to achieve the glossy appearance after melting and solidifying as described above, and to develop good color, it is preferable to contain the pigment only in the core rather than in the sheath that melts and solidifies. Furthermore, when the pigment is contained only in the core, the pigment content in the core of the core-sheath type composite polyester fiber should be equal to or less than the pigment content in the fibers of single-phase type polyester fiber, and it is even more preferable that the pigment content in the core is low.

[0020] The polyester constituting the single-phase polyester fiber and the high-melting-point polyester and low-melting-point polyester constituting the core-sheath type composite polyester are each preferably flame-retardant. In particular, in order to prevent the risk of fire at a construction site, it is preferable to use a flame-retardant polymer. To impart flame retardancy, a flame retardant may be mixed in the polyester constituting the fiber, or it is also preferable to use a copolymer obtained by copolymerizing a flame retardant compound such as a phosphorus compound in the polyester molecule.

[0021] The construction sheet of the present invention is a woven fabric made of the above two types of multifilament yarns. As the weave structure, a plain weave structure is preferable because it is excellent in abrasion resistance and durability. After weaving, by heat treatment, the shape as the weave structure is fixed by the melting and solidification of the sheath portion of the core-sheath type composite polyester fiber, and no eyelet or warp occurs.

[0022] The construction sheet of the present invention is provided with eyelets or the like at the edge of the sheet and is attached to a temporary structure at a construction site and is used for preventing the fall of materials, preventing the scattering of dust, or preventing wind. In particular, as a sheet defined in Class 2 of JIS A 8952 Construction Sheet, it can be suitably used to exhibit good appearance and aesthetic properties.

[0023] In the present invention, a sheet for construction work can be manufactured by the following method. First, a non-heat-fusible multifilament yarn composed of single-phase polyester fibers containing the above-mentioned pigment and a heat-fusible multifilament yarn composed of core-sheath type composite polyester fibers in which the core is made of high-melting-point polyester and the sheath is made of low-melting-point polyester, and which contains less pigment than the amount of pigment contained in the single-phase polyester fibers are prepared. These two types of multifilament yarns are then joined together or twisted together to obtain joined yarn or twisted yarn made of the two types of multifilament yarns. At this time, because there is a difference in the content of coloring pigment in the fibers that make up each multifilament yarn, the non-heat-fusible multifilament yarn is darker in color, and the heat-fusible multifilament yarn is lighter in color than the non-heat-fusible multifilament yarn, so the joined yarn or twisted yarn is a yarn with varying shades. A fabric is obtained by weaving using the obtained joined yarn or twisted yarn. At this time as well, since the joined yarn or twisted yarn is a yarn with varying shades, the obtained fabric (raw fabric) exhibits a heathered color. Next, the obtained fabric (raw material) is heat-treated at a temperature at which the low-melting-point polyester, which is the sheath portion of the core-sheath composite polyester fibers constituting the heat-fusible multifilament yarn, melts, while the high-melting-point polyester core and the constituent fibers of the non-heat-fusible multifilament yarn are not affected by the heat, thereby solidifying the low-melting-point polyester and obtaining a sheet for construction work. The heat treatment temperature at this time should be 10 to 20°C higher than the melting point of the low-melting-point polyester. The heat treatment time can be appropriately selected according to the heat treatment setting temperature, etc., but should be about 30 seconds to a few minutes. There are no particular limitations on the method of solidifying the low-melting-point polyester melted by heat treatment, and it is acceptable to cool it using methods such as air cooling, air cooling, wind cooling, furnace cooling, or water cooling. [Examples]

[0024] Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0025] Example 1 [Preparation of non-heat-sealable multifilament yarn] As a base chip, a polyethylene terephthalate resin with a relative viscosity of 1.42 was prepared by copolymerizing an ethylene oxide adduct of (2,5-dihydroxyphenyl)diphenylphosphine oxide as a flame retardant at a phosphorus concentration of 4200 ppm. In addition, a master chip was prepared by kneading 65% by mass of polyethylene terephthalate, 12% by mass of polybutylene terephthalate, 20% by mass of copper phthalocyanine as a pigment, and 3% by weight of a perinone-based organic pigment. The base chip and master chip were drive-blended in a mass ratio of base chip:master chip = 32:1 (the pigment concentration in the fiber is 0.70% by mass). Dry-blended chips were spun using a standard melt spinning apparatus, fitted with a spinneret with a pore size of 0.55 mm and 48 holes, at a spinneret temperature of 280°C. After passing through a 20 cm long heating cylinder at 200°C located directly below the spinneret, the spun material was cooled in a 150 cm long horizontal spraying device at a cooling temperature of 15°C and a speed of 0.7 m / sec. Next, the yarn was coated with an oil agent and taken onto a non-heated single roller, then continuously stretched to 1.01 times its original length on two rollers at a temperature of 75°C. It was then passed through a steam treatment machine that emitted steam at a temperature of 500°C and a pressure of 0.4 MPa at a 45-degree angle toward the direction of fiber progression from two orifices with a diameter of 2.2 mm positioned symmetrically in the yarn path. The yarn was stretched to 5.2 times its original length on three rollers at a temperature of 140°C, then relaxed by 2.5% on four rollers at a temperature of 140°C and by 1% on five rollers at a temperature of 130°C, and after applying a 0.2% relaxation, it was wound onto a winder at a speed of 3000 m / min to obtain a non-heat-fusible multifilament yarn made of dark blue flame-retardant, single-phase polyester fiber with a density of 470 dtex / 48 filaments.

[0026] [Preparation of heat-sealable multifilament yarn] A polyethylene terephthalate resin with a relative viscosity of 1.42 was prepared as the base tip for the polyester core. A master tip containing the pigment used in the preparation of the non-heat-sealable multifilament yarn was also prepared. The base tip and master tip were drive-blended in a mass ratio of base tip:master tip = 64:1. (The pigment concentration in the core is 0.35% by mass.) Furthermore, as the polyester to be placed in the sheath portion, a copolymerized polyester with a melting point of 160°C was prepared by copolymerizing an oligomer obtained by the esterification reaction of terephthalic acid component and ethylene glycol component, in which the molar ratio of terephthalic acid component to ethylene glycol component was 1:1.13, with ε-caprolactone at a ratio of 15 mol% relative to the acid component and 1,4-butanediol at a ratio of 50 mol% relative to the diol component.

[0027] Using a standard composite melt spinning apparatus, a core-sheath type composite spinning die with a pore diameter of 0.8 mm and 48 holes was attached, and the spinning was performed at a die temperature of 280°C and a core-sheath mass ratio of 2.7 / 1 (the pigment concentration in the fiber was 0.26 mass%). After passing through a 20 cm long heating cylinder at a temperature of 200°C located directly below the spinning die, the fiber was cooled in a 150 cm long horizontal spraying device at a cooling temperature of 15°C and a speed of 0.7 m / sec. Next, the yarn was coated with an oil agent and taken onto a non-heated single roller. It was then continuously stretched to 1.01 times its original length on two rollers at a temperature of 70°C. The yarn was then passed through a steam treatment machine that emitted steam at 500°C and 0.2 MPa at a 45-degree angle toward the direction of fiber travel from two orifices with a diameter of 1.8 mm positioned symmetrically in the yarn path. The yarn was then stretched to 4.8 times its original length on three rollers at a temperature of 135°C, relaxed by 1.5% on four rollers at a temperature of 130°C, and relaxed by 0.5% on five rollers at a temperature of 115°C. After applying a 0.2% relaxation, the yarn was wound onto a winder at a speed of 3000 m / min to obtain a heat-fusible multifilament yarn of 280 dtex / 48 filaments made of core-sheath type composite polyester fibers with a circular cross-sectional shape (core and sheath arranged approximately concentrically). The obtained heat-fusible multifilament yarn was a light blue color compared to the non-heat-fusible multifilament yarn.

[0028] [Twisted yarn - for making construction sheets] One strand each of the non-heat-fusible multifilament yarn and the heat-fusible multifilament yarn obtained above were twisted together under the condition of S-120T / m to obtain a plied yarn. Using the obtained plied yarn, a mesh-like plain weave structure with a warp density of 17.8 threads / inch and a weft density of 17.7 threads / inch was woven on a standard rapier loom to obtain a raw fabric. The obtained raw fabric was heat-treated using a standard pintenter-type heat treatment device at a temperature of 170°C for a treatment time of 1 minute to melt and solidify the sheath portion of the core-sheath type composite polyester fiber, thereby obtaining the construction sheet of the present invention. The raw fabric had a blue heathered appearance, but the construction sheet obtained by heat treatment had a glossy finish and exhibited a vivid blue color throughout, resulting in excellent aesthetic appeal. Furthermore, the resulting construction sheet had a tensile strength of 603N in the warp direction and 594N in the weft direction, and a tear strength of 292N in the warp and 329N in the weft. It was also lightweight, easy to fold and roll, and had good handling characteristics.

[0029] In the examples, tensile strength and tear strength were measured in accordance with the method described in JIS A 8952.

[0030] Example 2 [Preparation of non-heat-sealable multifilament yarn] As the base tip, the same non-heat-sealable multifilament yarn as in Example 1 was prepared. In addition, a master tip was prepared by kneading 99% by mass of polyethylene terephthalate, 0.5% by mass of carbon black, and 0.5% by mass of cyanine blue. The base chip and master chip were drive-blended in a mass ratio of base chip:master chip = 80:1 (the pigment concentration in the fiber is 0.012% by mass). Except as described above, a dark gray non-heat-sealable multifilament yarn was obtained in the same manner as in Example 1.

[0031] [Preparation of heat-sealable multifilament yarn] As the polyester for the core, we prepared the base chip used in the core of the heat-fusible multifilament yarn in Example 1 and the master chip used in the non-heat-fusible multifilament yarn in Example 2. The base chip and master chip were drive-blended in a mass ratio of base chip:master chip = 100:1. (The pigment concentration in the core was 0.010% by mass.) Except as described above, a heat-fusible multifilament yarn was obtained in the same manner as in Example 1. The obtained heat-fusible multifilament yarn (with a pigment concentration of 0.007% by mass in the fiber) was a lighter gray color compared to the dark gray non-heat-fusible multifilament yarn described above.

[0032] Using the obtained non-heat-fusible multifilament yarn and heat-fusible multifilament yarn, a construction sheet was obtained in the same manner as in Example 1. The raw fabric had a gray, mottled appearance, but the construction sheet obtained by heat treatment had a glossy finish and exhibited a vivid gray color throughout, resulting in excellent aesthetics. Furthermore, the obtained construction sheet had a tensile strength of 628N in the warp direction and 608N in the weft direction, and a tear strength of 285N in the warp and 306N in the weft. It was lightweight, easy to fold and roll, and had good handling properties.

[0033] Example 3 [Preparation of non-heat-sealable multifilament yarn] As the base tip, the same non-heat-sealable multifilament yarn as in Example 1 was prepared. In addition, a master tip was prepared by kneading 95% by mass of polyethylene terephthalate and 5% by mass of cyanine green.

[0034] The base chip and master chip were drive-blended in a mass ratio of base chip:master chip = 50:1 (the pigment concentration in the fiber is 0.098% by mass). Except as described above, a dark green non-heat-sealable multifilament yarn was obtained in the same manner as in Example 1.

[0035] [Preparation of heat-sealable multifilament yarn] As the polyester for the core, we prepared the base chip used in the core of the heat-fusible multifilament yarn in Example 1 and the master chip used in the non-heat-fusible multifilament yarn in Example 3. The base chip and master chip were drive-blended in a mass ratio of base chip:master chip = 100:1. (The pigment concentration in the core is 0.050% by mass.) Except as described above, a heat-fusible multifilament yarn was obtained in the same manner as in Example 1. The obtained heat-fusible multifilament yarn (with a pigment concentration of 0.036% by mass in the fiber) was a lighter green color compared to the dark green non-heat-fusible multifilament yarn described above.

[0036] Using the obtained non-heat-fusible multifilament yarn and heat-fusible multifilament yarn, a construction sheet was obtained in the same manner as in Example 1. The raw fabric had a green heathered appearance, but the construction sheet obtained by heat treatment had a glossy finish and exhibited a vivid green color throughout, resulting in excellent aesthetics. Furthermore, it had a tensile strength of 611N in the warp direction and 608N in the weft direction, and a tear strength of 279N in the warp and 328N in the weft. It was lightweight, easy to fold and roll, and had good handling properties.

[0037] Comparative Example As a non-thermally fused multifilament yarn, the non-thermally fused multifilament yarn used in Example 1 was prepared.

[0038] [Preparation of heat-sealable multifilament yarn] In Example 1, the polyester used in the core was a drive blend of base chip and master chip in a mass ratio of base chip:master chip = 20:1 (the pigment concentration in the core was 1.10% by mass).

[0039] Except as described above, a heat-fusible multifilament yarn was obtained in the same manner as in Example 1. The obtained heat-fusible multifilament yarn (with a pigment concentration of 0.80% by mass in the fibers) was a dark blue color, comparable to that of the dark blue non-heat-fusible multifilament yarn described above.

[0040] Using the obtained non-heat-fusible multifilament yarn and heat-fusible multifilament yarn, a construction sheet was obtained in the same manner as in Example 1. The raw material exhibited a nearly uniform dark blue color, but the construction sheet obtained by heat treatment had areas of dark blue and areas of even darker blue, and did not possess the aesthetic qualities intended by the present invention.

Claims

1. A fabric composed of yarn made by combining or twisting together two types of multifilament yarns. Of the two types of multifilament yarns, one is a non-heat-fusible multifilament yarn composed of single-phase polyester fibers containing pigment. The other multifilament yarn is a heat-sealable multifilament yarn composed of core-sheath type composite polyester fibers containing pigment, with a core made of high-melting-point polyester and a sheath made of low-melting-point polyester. The heat-fusible multifilament yarn is formed by the melting and solidification of the low-melting-point polyester in the sheath portion, thereby integrating the core-sheath type composite polyester fibers with each other, and also by the melting and solidification of the low-melting-point polyester in a non-heat-fusible multifilament yarn that is formed by aligning or twisting the heat-fusible multifilament yarn with the low-melting-point polyester. The pigment contained in single-phase polyester fibers and the pigment contained in core-sheath composite polyester fibers are the same type of coloring pigment. A construction sheet characterized by having a greater amount of pigment in single-phase polyester fibers than in core-sheath composite polyester fibers.

2. Single-phase polyester fibers are composed of polyethylene terephthalate polymers. The core-sheath type composite polyester fiber is characterized in that the core portion is composed of a polyethylene terephthalate polymer and the sheath portion is composed of copolymerized polyester, as described in claim 1 for construction work.

3. A construction sheet according to claim 1 or 2, characterized in that the core of the core-sheath type composite polyester fiber contains a pigment.

4. A construction sheet according to any one of claims 1 to 3, characterized in that the fabric has a plain weave structure.

5. Non-heat-fusible multifilament yarn composed of single-phase polyester fibers containing pigment, Prepare a heat-fusible multifilament yarn composed of a core-sheath type composite polyester fiber in which the core is made of high-melting-point polyester and the sheath is made of low-melting-point polyester, and which contains the same type of coloring pigment as the pigment contained in the single-phase polyester fiber, but in a smaller amount than the amount of pigment contained in the single-phase polyester fiber. Then, align or twist these two types of multifilament yarns together. After weaving using the obtained plied yarn or twisted yarn, A method for manufacturing construction sheets, characterized by applying heat treatment at a temperature at which low-melting-point polyester melts, thereby melting and solidifying the low-melting-point polyester.