Flame-retardant resin sheet and method for manufacturing the same

Abstract

To provide a flame-retardant resin sheet that has both excellent smoke generation amount inhibitory effect and high tensile strength which satisfy the acceptance standard of 8 ft. (2.4 m) Parallel Panel Test regulated in Class Number 4910, June 2009, and a method for manufacturing the resin sheet.SOLUTION: A flame-retardant resin sheet includes a vinyl chloride-based resin, contains 3 pts.mass or more of chlorinated polyethylene per 100 pts.mass of the vinyl chloride-based resin, has a ratio (MD / TD ratio) of strain at break in an MD direction to strain at break in a TD direction, measured in accordance with JIS K7161, of 0.5 or more and 2.0 or less, and in the Cleanroom Materials Flammability Test Protocol (FMRC) cited as Class Number 4910, June 2009, a smoke generation rate specified in "Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI" is 0.23 g / sec or less, and total smoke is 60 g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a flame-retardant resin sheet and a method for producing the same. [Background technology]

[0002] Generally, vinyl chloride resins have good moldability, are inexpensive, and have good chemical resistance, and are therefore widely used in a variety of fields, including industrial materials.

[0003] Although molded products of vinyl chloride resins have good flame retardancy due to their large chlorine content, when exposed to high temperatures of 200°C or higher due to a fire or other cause, they undergo thermal decomposition, producing a large amount of smoke and corrosive gases such as chlorine gas and hydrogen chloride gas. To reduce this risk of fire, there are known techniques for improving the flame retardancy of vinyl chloride resins by adding phosphorus-based flame retardants, halogen-based flame retardants, magnesium hydroxide, titanium oxide, or the like (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2008 / 018521 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-208250 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the vinyl chloride resin compositions and molded articles thereof described in Patent Documents 1 and 2 do not sufficiently suppress smoke generation, leaving room for improvement. Specifically, conventional products have difficulty meeting the pass criteria for Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI (hereinafter referred to as the "8 ft. (2.4 m) Parallel Panel Test" or simply "Parallel Panel Test"), newly specified in Column 4.4 of the Cleanroom Materials Flammability Test Protocol (FMRC) listed as Class Number 4910, June 2009, established by Factory Mutual Global, a North American-based industrial insurance organization. The 8 ft. (2.4 m) Parallel Panel Test is also referred to as the "Large-scale test."

[0006] The present disclosure has been made in view of the above points, and an object of the present disclosure is to provide a flame-retardant resin sheet that has both excellent smoke generation suppression effect and high tensile strength and meets the passing criteria of Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI [8 ft. (2.4 m) Parallel Panel Test] specified in Class Number 4910, June 2009, and a method for producing the same. [Means for solving the problem]

[0007] The present inventors have found that by specifying the content of chlorinated polyethylene contained in a resin composition (raw material) containing a vinyl chloride resin and the length / width ratio of the breaking strain (MD / TD ratio described below) of a molded product (resin sheet) of the resin composition within predetermined ranges, it is possible to obtain a flame-retardant resin sheet that has an excellent smoke generation suppression effect that meets the pass criteria of an 8 ft. (2.4 m) Parallel Panel Test, and that maintains high tensile strength equivalent to that of conventional products.

[0008] In order to achieve the above object, the flame-retardant resin sheet of the present disclosure is a flame-retardant resin sheet containing a vinyl chloride resin, The composition contains 3 parts by mass or more of chlorinated polyethylene per 100 parts by mass of the vinyl chloride resin, The ratio of the strain at break in the MD direction to the strain at break in the TD direction (MD / TD ratio), measured in accordance with JIS K7161, is 0.5 or more and 2.0 or less, In the Cleanroom Materials Flammability Test Protocol (FMRC) listed as Class Number 4910, June 2009, the smoke generation rate (maximum smoke generation amount) specified in Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI is 0.23 g / sec or less, and the total smoke (total smoke generation amount) is 60 g or less.

[0009] A method for producing a flame-retardant resin sheet according to the present disclosure is a method for producing the flame-retardant resin sheet, comprising: preparing a flame-retardant resin composition containing a vinyl chloride resin and 3 parts by mass or more of chlorinated polyethylene per 100 parts by mass of the vinyl chloride resin; a step of calendering the flame-retardant resin composition to obtain a calendered sheet having a thickness of 1 mm or less; and a step of laminating a plurality of the calendered sheets and pressing them at a temperature of 190°C or less to obtain a flame-retardant resin sheet having a thickness of less than 6 mm. [Effects of the Invention]

[0010] The present disclosure provides a flame-retardant resin sheet that has both excellent smoke suppression effect and high tensile strength and meets the passing criteria of Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI [8 ft. (2.4 m) Parallel Panel Test] specified in Class Number 4910, June 2009, and a method for manufacturing the same. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present embodiment will be described in detail below. The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the present invention, its applications, or its uses.

[0012] <Flame-retardant resin sheet> The flame-retardant resin sheet according to this embodiment is a molded article of a flame-retardant resin composition, which is used as a raw material for the resin sheet. The resin sheet is not particularly limited as long as it is a plate-shaped plastic, and is synonymous with, for example, a resin plate.

[0013] The flame-retardant resin sheet satisfies the following physical properties, and therefore has both an excellent effect of suppressing the amount of smoke generated and high tensile strength.

[0014] [Ratio of strain at break (MD / TD ratio)] The flame-retardant resin sheet has a ratio of the strain at break in the MD direction to the strain at break in the TD direction (hereinafter also referred to as the "MD / TD ratio") of 0.5 or more and 2.0 or less, measured in accordance with JIS K7161 (JIS K 7161-1, 7161-2:2014).

[0015] The MD (Machine Direction) direction is the direction of resin flow, and refers to the molding direction of the sheet along the length (vertical) direction of the flame-retardant resin sheet. The TD (Transverse Direction) direction is the direction perpendicular to the MD direction, and refers to the width (horizontal) direction of the flame-retardant resin sheet. Therefore, the MD / TD ratio means the longitudinal / lateral ratio of the breaking strain of the flame-retardant resin sheet.

[0016] The MD / TD ratio of the flame-retardant resin sheet is 0.5 or more and 2.0 or less, preferably 0.8 or more and 2.0 or less, and more preferably 1.0 or more and 1.8 or less, from the viewpoint of improving the smoke generation suppression effect.

[0017] The reason why the MD / TD ratio of a flame-retardant resin sheet is related to flame retardancy (particularly its smoke suppression effect) is predicted as follows. When the MD / TD ratio of a flame-retardant resin sheet is far from 1.0 (e.g., less than 0.5 or more than 2.0), heat (fire) carbonizes the surface of the sheet, followed by melting and significant deformation of the middle portion of the sheet in the thickness direction, which in turn deforms the charred layer on the surface of the sheet. As a result, cracks form in the charred layer, and new burning surfaces appear in the cracked areas, which is thought to increase the amount of smoke generated. On the other hand, when the MD / TD ratio of a flame-retardant resin sheet is close to 1.0 (e.g., between 0.5 and 2.0), the amount of deformation due to melting of the middle portion is small, which reduces the impact on the charred layer on the surface of the sheet. As a result, a strong charred layer is formed on the surface of the sheet, making it less likely to crack, which is thought to lead to suppression of smoke generation.

[0018] The strain at break in the MD and TD directions of the flame-retardant resin sheet is, for example, 15% or more, from the viewpoint of ensuring high tensile strength similar to that of conventional flame-retardant resin sheets.

[0019] [Smoke generation rate (maximum smoke generation rate), total smoke (total smoke generation rate)] One of the indicators of flame resistance is the FM (Factory Mutual) standard, established by Factory Mutual Global, a North American-based industrial mutual insurance organization. The FM standard is measured based on the Cleanroom Materials Flammability Test Protocol (FMRC), and specifies the Fire Propagation Index (FPI), which indicates flame resistance, the Smoke Damage Index (SDI), which indicates smoke generation, and the Corrosion Index (CDI), which indicates corrosive gas generation.

[0020] Class Number 4910, June 2009, newly specifies in section 4.4 that Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI (8 ft. (2.4 m) Parallel Panel Test).

[0021] The flame-retardant resin sheet has a smoke generation rate (maximum smoke generation amount) of 0.23 g / sec or less and a total smoke amount of 60 g or less as specified in the Parallel Panel Test. In other words, the flame-retardant resin sheet meets the pass criteria for the smoke generation rate and total smoke measured based on the Parallel Panel Test, and therefore has an excellent smoke suppression effect. Therefore, the flame-retardant resin sheet can be said to be a highly fire-safe material (molded product) that not only limits the spread of fire in a clean room, but also significantly reduces the risk of contamination of the clean room environment due to smoke generation.

[0022] [Thickness] The thickness of the flame-retardant resin sheet is preferably less than 6 mm, more preferably 2 mm or more and less than 6 mm, in accordance with the Parallel Panel Test rule that "Testing Samples are less than 6 mm (0.25 inches) thick."

[0023] [Flame-retardant resin composition] The flame-retardant resin composition used as a raw material for the flame-retardant resin sheet contains a vinyl chloride resin. In other words, the flame-retardant resin sheet contains a vinyl chloride resin and, as necessary, the components described below. Each of the following components may be used alone or in combination of two or more. Each component may be a commercially available product or a synthetic product.

[0024] (Vinyl chloride resin) Vinyl chloride resin is the main component of the flame-retardant resin sheet (flame-retardant resin composition). The main component refers to a component that accounts for more than 50% by mass relative to 100% by mass of the total amount of components contained in the flame-retardant resin sheet (flame-retardant resin composition).

[0025] The vinyl chloride resin preferably contains a post-chlorinated vinyl chloride resin (C-PVC) having a chlorination degree of 60% by mass to 69% by mass and a number-average degree of polymerization of 400 to 1200. The vinyl chloride resin may be composed solely of post-chlorinated vinyl chloride resin (100% by mass), or may be a resin mixture of post-chlorinated vinyl chloride resin and other resins. Examples of resin mixtures include resins obtained by mixing post-chlorinated vinyl chloride resin with vinyl chloride resins other than post-chlorinated vinyl chloride resin (PVC, chlorination degree of about 56% by mass, number-average degree of polymerization of about 500 to 1400), vinyl acetate resin, acrylic resin, etc. The chlorination degree refers to the ratio of chlorine contained in the resin alone.

[0026] When the vinyl chloride resin contains a resin mixture, the content of the post-chlorinated vinyl chloride resin may be appropriately adjusted so that the ratio of chlorine content (chlorine content in the organic components) to the total amount (100 mass%) of organic components (resin components) contained in the flame-retardant resin sheet (flame-retardant resin composition) is approximately 50 mass% or more and 64 mass% or less.

[0027] (chlorinated polyethylene) The flame-retardant resin composition contains chlorinated polyethylene (chlorinated PE). The chlorinated polyethylene is contained in an amount of 3 parts by mass or more per 100 parts by mass of vinyl chloride resin (when two or more types are contained, the total content of each type; the same applies below). This improves impact resistance and provides an excellent smoke suppression effect that satisfies the pass criteria of the Parallel Panel Test. The content of chlorinated polyethylene (when two or more types are contained, the total content of each type) per 100 parts by mass of vinyl chloride resin is 3 parts by mass or more, preferably 5 parts by mass or more, from the viewpoint of improving the smoke suppression effect. The upper limit is not particularly limited, but is, for example, 10 parts by mass or less.

[0028] The chlorinated polyethylene preferably has a chlorine content of 30% by mass or more, and more preferably has a chlorine content of 30% by mass or more and 40% by mass or less.

[0029] (additives) The flame-retardant resin composition may contain, as components (additives) other than the vinyl chloride resin and chlorinated polyethylene, for example, flame retardants, lubricants, impact modifiers, fillers, stabilizers, processing aids, weather resistance improvers, etc., within the scope of not impairing the object of the present invention. As the other components, those generally known in the technical field can be used.

[0030] Examples of flame retardants include metal hydroxides (metal hydrates such as aluminum hydroxide and magnesium hydroxide), antimony-based flame retardants (antimony trioxide, etc.), phosphorus-based flame retardants, melamine-based flame retardants, halogen-based flame retardants, and molybdic acid-based flame retardants.

[0031] Examples of the lubricant include polyethylene-based lubricants, acrylic-based lubricants, and ester-based lubricants (such as polyhydric alcohol esters).

[0032] Examples of impact modifiers include MBS-based impact modifiers (a copolymer of styrene butadiene rubber (SBR) and polymethyl methacrylate, number average particle size: approximately 0.19 μm, rubber component ratio: approximately 70% by mass, glass transition point of the rubber component: approximately −58°C), and silicone-based impact modifiers (a copolymer of silicone rubber and polymethyl methacrylate, number average particle size: approximately 0.30 μm, rubber component ratio: approximately 90% by mass, glass transition point of the rubber component: approximately −125°C).

[0033] Examples of fillers include titanium oxide and calcium carbonate.

[0034] Examples of the stabilizer include organic tin stabilizers such as butyltin maleate stabilizers (such as dibutyltin maleate) and butyltin stabilizers; organic lead stabilizers; and calcium zinc stabilizers.

[0035] Examples of the processing aid include acrylic processing aids.

[0036] Examples of weather resistance improvers include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-hydroxy-4-methoxybenzophenone, and 2-ethylhexyl salicylate.

[0037] The content of each additive (the total content of each additive when two or more types are included) can be adjusted appropriately depending on the required physical properties of the flame-retardant resin sheet, and is, for example, 0 to 20 parts by mass of flame retardant, 0 to 5 parts by mass (preferably 1 to 3 parts by mass) of lubricant, 0 to 10 parts by mass (preferably 1 to 8 parts by mass) of impact resistance modifier, 0 to 10 parts by mass (preferably 1 to 5 parts by mass) of filler, 0 to 5 parts by mass of stabilizer, 0 to 5 parts by mass (preferably 1 to 3 parts by mass) of processing aid, and 0 to 1 part by mass (preferably 0.01 to 0.5 parts by mass) of weather resistance improver, relative to 100 parts by mass of vinyl chloride resin.

[0038] <Method for manufacturing flame-retardant resin sheet> The flame-retardant resin sheet according to this embodiment can be produced by, for example, a calendar press molding method. The method for producing the flame-retardant resin sheet according to this embodiment includes at least a preparation step, a calendar sheet step, and a pressing step.

[0039] (Preparation process) In the preparation step, a flame-retardant resin composition is prepared that contains a vinyl chloride resin (preferably a post-chlorinated vinyl chloride resin (C-PVC)) and 3 or more parts by mass of chlorinated polyethylene (chlorinated PE) per 100 parts by mass of the vinyl chloride resin. The flame-retardant resin composition can be produced by blending the above components in predetermined amounts and mixing them using a known method. As a result, the flame-retardant resin sheet, which is a molded product of the flame-retardant resin composition, contains a vinyl chloride resin and 3 or more parts by mass of chlorinated polyethylene per 100 parts by mass of the vinyl chloride resin.

[0040] (calendar sheet process) In the calendering process, the prepared flame-retardant resin composition is calendered to produce a calendered sheet having a thickness of 1 mm or less. A commonly known calender roll (CR) can be used for calendering. In this process, the following conditions may be appropriately adjusted so that the calendered sheet obtained after the process has a thickness of 1 mm or less. From the viewpoint of maintaining the MD / TD ratio within a predetermined range, the CR temperature is preferably 150°C or higher and 180°C or lower, more preferably 155°C or higher and lower than 170°C, and even more preferably 160°C or higher and 165°C or lower. In the calendering process, the draw ratio between the take-up roll and the calender roll (CR) (hereinafter also referred to as "take-up / CR (draw ratio)") is preferably 95 to 105, more preferably 98 to 103. The rolling time is approximately 1 to 5 minutes. The thickness of the calendered sheet obtained by this process is preferably 0.3 mm or higher and 1 mm or lower.

[0041] (pressing process) In the pressing step, a plurality of the obtained calendar sheets are stacked and pressed (thermocompression bonded) at a temperature of 190°C or less. A generally known press can be used. The number of calendar sheets to be stacked can be appropriately determined depending on the thickness of the calendar sheets, the desired thickness of the flame-retardant resin sheet, etc., and is, for example, about 3 to 10 sheets. In this step, the following conditions can be appropriately adjusted so that the thickness of the flame-retardant resin sheet obtained after the step is less than 6 mm (preferably 2 mm or more and less than 6 mm). The pressing temperature is preferably 150°C or more and 190°C or less, more preferably 160°C or more and 180°C or less, and even more preferably 160°C or more and 170°C or less, from the viewpoint of keeping the MD / TD ratio within a predetermined range. The pressing time is about 10 minutes to 2 hours.

[0042] (Other processes) The method for producing a flame-retardant resin sheet according to this embodiment may include, as a step other than the preparation step, the calendering step, and the pressing step, an annealing step or the like, as long as the object of the present invention is not impaired.

[0043] (Annealing process) The obtained pressed plate (flame-retardant resin sheet) may be subjected to an annealing treatment, if necessary. A generally known incubator can be used for the annealing treatment. The annealing treatment time is, for example, about 5 hours to 3 days. The annealing temperature is, for example, about 60 to 90°C.

[0044] Through the above steps, a single-layer pressed plate (flame-retardant resin sheet) is obtained, in which multiple laminated calender sheets made from the flame-retardant resin composition are thermocompression-bonded together. By appropriately adjusting the conditions in the calender sheet process and the pressing process, a flame-retardant resin sheet having a thickness of less than 6 mm (preferably 2 mm or more and less than 6 mm) and an MD / TD ratio of 0.5 or more and 2.0 or less can be obtained. Furthermore, a flame-retardant resin sheet having a thickness and an MD / TD ratio within the specified range satisfies the pass criteria of the Parallel Panel Test. In other words, the flame-retardant resin sheet can be said to have both excellent smoke suppression effect and high tensile strength.

[0045] <Other embodiments> The flame-retardant resin sheet may be molded by a known continuous press method. Alternatively, the flame-retardant resin sheet may be molded into a plate shape by a known extrusion molding method or injection molding method after uniformly kneading the flame-retardant resin composition. In the known extrusion molding method or injection molding method, instead of a plate-shaped flame-retardant resin sheet, a molded article may be molded into a desired shape such as a rod shape, a tube shape, or an irregular shape. [Example]

[0046] The present disclosure will be described below based on examples. Note that the present disclosure is not limited to the following examples, and the following examples can be modified or changed based on the spirit of the present disclosure, and such modifications are not excluded from the scope of the present disclosure.

[0047] <Preparation of flame-retardant resin composition (preparation step)> The components shown in Table 1 were blended and mixed in the amounts (parts by mass) shown in Table 1 to prepare flame-retardant resin compositions of the examples and comparative examples.

[0048] <Flame-retardant resin sheet> Using the obtained flame-retardant resin composition, a pressed plate (a flame-retardant resin sheet containing a vinyl chloride resin, a PVC resin plate) having the thickness shown in Table 1 was produced by calendar press molding including the following steps. (calendar sheet process) A calendered sheet having a thickness shown in Table 1 was produced under the conditions of the calender roll (CR) temperature shown in Table 1, the take-up / CR (draw ratio) shown in Table 1, and a roll time of 3 minutes. (pressing process) Six of the obtained calendar sheets were stacked together and thermocompressed together using a heat press under the conditions shown in Table 1 for a pressing temperature and a pressing time of 20 minutes.

[0049] <Evaluation of physical properties of flame-retardant resin sheets> (Tensile test) The resulting flame-retardant resin sheet was subjected to a tensile test in accordance with JIS K 7161-1 (and 7161-2):2014. Specifically, a Type 1B test piece was prepared and subjected to a tensile test using a tensile tester (Shimadzu Corporation, product name: Autograph AG-5000A) at a temperature of 25°C and a tensile speed of 100 mm / min. The MD and TD strains at break were measured as the tensile properties of the flame-retardant resin sheet. From the obtained measured values, the ratio of the MD strain at break to the TD strain at break (MD / TD ratio) was calculated. The results are shown in Table 1.

[0050] (FM certification test, flame retardant test) The resulting flame-retardant resin sheet was subjected to a flame-retardant test in accordance with Section 4.4 of Class Number 4910 (June 2009), which requires testing samples less than 6 mm (0.25 inches) thick and resolution of uncertain ranges of FPI (8 ft. (2.4 m) Parallel Panel Test). Specifically, as described in Figure 5 (Parallel Panel under the 5 MW Fire Products Collector) in Section 4.4, two test panels made of flame-retardant resin sheet with a length (height, MD) of 8.0 ft (2.4 m), a width (width, TD) of 2.0 ft (0.6 m), and the thicknesses shown in Table 1 were fixed parallel and perpendicular to each other across a gas burner. The distance between the opposing test panels was 1.0 ft (0.3 m). A parallel panel test was performed with the test panels set up as described above, and the smoke generation rate (maximum smoke generation rate) and total smoke generation rate were measured. The results are shown in Table 1.

[0051] [Table 1]

[0052] Details of each component contained in the flame-retardant resin composition shown in Table 1 are shown below. [C-PVC (post-chlorinated polyvinyl chloride resin)] HA-27H: Sekisui HA-27H, degree of polymerization 700, chlorine concentration 65.5%, manufactured by Tokuyama Sekisui Kogyo Co., Ltd. HA-27F: Sekisui HA-27F, degree of polymerization 700, chlorine concentration 64.5%, manufactured by Tokuyama Sekisui Kogyo Co., Ltd. [Chlorinated PE (chlorinated polyethylene)] 351A: Elaslen 351A, chlorine content 34-37%, Resonac Co., Ltd. (formerly Showa Denko). [Additives] L-1000: Metablen (registered trademark) L-1000, acrylic lubricant, manufactured by Mitsubishi Chemical Corporation. P-551A: Metablen (registered trademark) P-551A, acrylic processing aid, manufactured by Mitsubishi Chemical Corporation. B-564: Kane Ace (registered trademark) B-564, MBS (methyl methacrylate-butadiene-styrene copolymer) impact modifier, manufactured by Kaneka Corporation. · JF-77: Weather resistance improver (UVA), 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, manufactured by Johoku Chemical Industry Co., Ltd. JR-701: Titanium oxide, filler, manufactured by Teika Co., Ltd.

[0053] <Discussion of Table 1> Comparing Example 1 with Comparative Example 1, the resin sheet of Example 1, which is a molded article of a flame-retardant resin composition containing 3 parts by mass or more of chlorinated polyethylene (chlorinated PE) per 100 parts by mass of polyvinyl chloride resin (C-PVC) and has an MD / TD ratio of 0.5 to 2.0, was confirmed to satisfy the pass criteria of the Parallel Panel Test, as its smoke generation rate (maximum amount of smoke generated) was 0.23 g / sec or less and its total smoke was 60 g or less, as measured based on the Parallel Panel Test. On the other hand, a comparison between Example 1 and Comparative Example 2 confirmed that the resin sheet of Comparative Example 2, which was a molded article of the above-mentioned flame-retardant resin composition but had an MD / TD ratio outside the above-mentioned range (2.2), emitted more than 60 g of total smoke and did not meet the pass criteria of the Parallel Panel Test. It was confirmed that Example 1 and Comparative Examples 1 and 2 had the same breaking strain in the MD and TD directions. From the above, it was found that the resin sheet of Example 1 is a flame-retardant resin sheet that has both an excellent smoke generation suppression effect that meets the pass criteria of the Parallel Panel Test and high tensile strength. [Industrial Applicability]

[0054] As described above, the present disclosure is suitable for a flame-retardant resin sheet containing a vinyl chloride resin.

Claims

1. A flame-retardant resin sheet containing a vinyl chloride resin, The composition contains 3 parts by mass or more of chlorinated polyethylene per 100 parts by mass of the vinyl chloride resin, The ratio of the strain at break in the MD direction to the strain at break in the TD direction (MD / TD ratio), measured in accordance with JIS K7161, is 0.5 or more and 2.0 or less; A flame-retardant resin sheet characterized in that, in the Cleanroom Materials Flammability Test Protocol (FMRC) listed as Class Number 4910, June 2009, the smoke generation rate (maximum smoke generation amount) specified in Testing Samples Less than 6 mm (0.25 inches) thick and Resolution of Uncertain Ranges of FPI is 0.23 g / sec or less and the total smoke (total smoke generation amount) is 60 g or less.

2. 2. The flame-retardant resin sheet according to claim 1, wherein the vinyl chloride resin contains a post-chlorinated vinyl chloride resin having a chlorination degree of 60% by mass or more and 69% by mass or less and a number-average polymerization degree of 400 or more and 1,200 or less.

3. 2. The flame-retardant resin sheet according to claim 1, wherein the chlorinated polyethylene has a chlorine content of 30% by mass or more.

4. 2. The flame-retardant resin sheet according to claim 1, which has a thickness of less than 6 mm.

5. A method for producing the flame-retardant resin sheet according to any one of claims 1 to 4, preparing a flame-retardant resin composition containing a vinyl chloride resin and 3 parts by mass or more of chlorinated polyethylene per 100 parts by mass of the vinyl chloride resin; a step of calendering the flame-retardant resin composition to obtain a calendered sheet having a thickness of 1 mm or less; and a step of stacking a plurality of the calendered sheets and pressing them at a temperature of 190°C or less to obtain a flame-retardant resin sheet having a thickness of less than 6 mm.

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