JP6276549B2 - Low fuming PVC sheet - Google Patents

Description

  The present invention relates to a low fuming polyvinyl chloride sheet having high design properties.

  A flexible polyvinyl chloride sheet obtained by adding a plasticizer such as phthalate to a polyvinyl chloride resin is used as a building material, an industrial film, or the like. In addition, this flexible polyvinyl chloride sheet is widely used as an interior material for buildings, railway vehicles, aircrafts and the like because it has flexibility and is excellent in workability and adhesiveness.

  Polyvinyl chloride resin is highly transparent, so a highly transparent layer is set on the surface to be observed as the appearance, and a design layer with a printed pattern is set underneath it. Sex interior materials can be provided.

  Polyvinyl chloride resin, on the other hand, has a drawback in that it interferes with evacuation and fire fighting activities because a large amount of smoke is generated during combustion. For this reason, studies on the reduction of smoke emission of polyvinyl chloride have been conducted, and methods using various additives have been proposed.

For example, polyvinyl chloride resin compositions containing inorganic flame retardants such as magnesium hydroxide, antimony oxide compounds, and zinc compounds are used (Patent Documents 1 and 2).

JP-A-5-51504 JP-A-8-208925

When the inorganic flame retardant is added to the polyvinyl chloride resin composition, there is a problem that the transparency of the transparent layer is lowered and the design properties are impaired. That is, the layer made of the polyvinyl chloride resin composition to which an amount of an inorganic flame retardant necessary for exhibiting a low smoke generation effect was not satisfied with transparency. As described above, it has been difficult to achieve both transparency and low smoke generation by the conventional technique in which an inorganic flame retardant is added to a polyvinyl chloride resin.
If the required transparency is maintained, not only the inorganic flame retardant necessary for low smoke generation cannot be added, but also the addition of other fillers is limited. Therefore, the compounding quantity of the polyvinyl chloride resin and the plasticizer with respect to a polyvinyl chloride resin composition increases, and the amount of smoke generation increases.
Thus, if transparency is satisfied, the addition of fillers containing inorganic flame retardants is restricted, and as a result, the amount of smoke generated tends to increase due to the increased amount of polyvinyl chloride resin and plasticizer. Therefore, it has been difficult to obtain a polyvinyl chloride sheet having a transparent layer and low smoke generation.

Therefore, in view of the above situation, an object of the present invention is to provide a low-smoky polyvinyl chloride sheet having a transparent resin layer and reducing the amount of smoke generated during combustion.

The gist of the means used by the present invention to solve the above-mentioned problems is to laminate a transparent layer and a layer containing a filler, and use a polyester plasticizer or a sulfonate ester plasticizer as a plasticizer. .
More specifically, it contains 100 parts by weight of a vinyl chloride resin and 5 to 50 parts of a plasticizer that is at least one selected from polyester-based plasticizers or sulfonate-based plasticizers, and contains an inorganic filler substantially. A transparent layer (A) comprising a polyvinyl chloride resin composition (a) not contained in the composition, laminated on the transparent layer (A), 100 parts by weight of a vinyl chloride resin, and a polyester plasticizer or a sulfonate ester plasticizer 5 to 100 parts of a plasticizer selected from the group consisting of calcium carbonate, silica, clay, inorganic layered compound, and 100 to 300 parts of an inorganic filler selected from hollow balloons. It is to make it a low smoke emitting polyvinyl chloride sheet having a base material layer (B) made of a vinyl resin composition (b).

  The low fuming polyvinyl chloride sheet of the present invention has a transparent layer and a high design, and the effect of reducing the amount of fuming during combustion is obtained.

It is sectional drawing of a low smoke generating polyvinyl chloride sheet | seat provided with the transparent layer and base material layer which concern on embodiment of this invention. It is sectional drawing of the low smoke generation polyvinyl chloride sheet | seat which concerns on other embodiment of this invention provided with a transparent layer, an intermediate | middle layer, and a base material layer.

Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 shows a cross-sectional view of an embodiment according to the low smoke emitting polyvinyl chloride sheet of the present invention having a transparent layer 1 and a base material layer 2.

The transparent layer of this embodiment consists of a resin composition containing 5 to 50 parts of a plasticizer that is at least one selected from a polyester plasticizer or a sulfonate plasticizer. Thereby, transparency is high and wear resistance and contamination resistance are obtained.
Moreover, the base material layer of this embodiment is a plasticizer 5-100 parts filler 50- which is at least 1 sort (s) chosen from a polyester plasticizer or a sulfonate plasticizer with respect to 100 weight part of polyvinyl chloride resin. It consists of a resin composition containing 300 parts. Thereby, the base material layer excellent in moderate softness | flexibility, adhesiveness with a foundation | substrate, and workability is obtained.

Thus, the amount of smoke generation can be reduced by laminating the base layer containing the transparent layer and the filler. Here, in order to reduce the amount of smoke, there are methods such as complete combustion, reduction of decomposition products, and no release of carbide into the gas phase. Further, since smoke generation occurs with combustion, it is considered that the amount of smoke increases as the combustion temperature rises and decreases as the temperature of complete combustion is reached. The transparent layer is more organic than the base material layer and has a structure in which the decomposition products during combustion increase. In consideration of the fact that there are many cases where complete combustion is not achieved in the smoke generation test, it is considered that the amount of smoke generation can be reduced by lowering the temperature of the transparent layer during combustion.
Therefore, the amount of smoke generation was reduced by laminating heat of the transparent layer by laminating a layer having a higher thermal conductivity on the transparent layer and making the temperature rise of the transparent layer more gradual. Since the base material layer containing the filler has a higher thermal conductivity than the transparent layer, it is assumed that the amount of smoke generation can be reduced by laminating the transparent layer and the base material layer.
Furthermore, from the viewpoint of reducing decomposition products, polyester plasticizers and sulfonate ester plasticizers that reduce the amount of fuming are used.

<Plasticizer>
As the plasticizer used for the transparent layer and the base material layer, it is preferable to use a plasticizer that generates a small amount of smoke during combustion.

  Examples of plasticizers having low fuming properties include sulfonate ester plasticizers, polyester plasticizers, aliphatic dibasic ester plasticizers, epoxy plasticizers, aliphatic ester plasticizers, and chlorine-containing plasticizers. It is done. These plasticizers may be used alone or in combination.

Among them, it is more preferable to use a sulfonate ester plasticizer or a polyester plasticizer because it is excellent in terms of contributing to low smoke generation and effectively imparting flexibility.
The reason why smoke generation is reduced by adding sulfonate plasticizers and polyester plasticizers has not been fully studied, but for sulfonate ester plasticizers, the sulfonic acid groups crosslink with vinyl chloride resin. It is assumed that the carbonized layer increases by doing. In addition, it is assumed that the polyester plasticizer has little fuming property derived from the polyester plasticizer.

  Plasticizers other than those described above may be added, but it is not preferable to add a large amount because the amount of smoke generated increases.

  The addition amount of these sulfonate ester plasticizers and polyester plasticizers is 5 to 50 parts by weight, preferably 15 to 45 parts by weight, and more preferably 20 to 40 parts by weight in the transparent layer with respect to 100 parts by weight of the vinyl chloride resin. Part. Moreover, in a base material layer, it is 5-100 weight part, Preferably it is 40-80 weight part, More preferably, it is 50-75 weight part.

  As the sulfonate ester plasticizer, an alkylphenyl ester represented by the following general formula (Formula 1) can be used.

（式中、Ｒ１は炭素数が１０〜２１のアルキル基）

(Wherein R1 is an alkyl group having 10 to 21 carbon atoms)

The polyester plasticizer is preferably a polycondensate of an aliphatic dibasic acid and a diol. Examples of the aliphatic dibasic acid include succinic acid, maleic acid, fumaric acid, glutamic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. Examples of the diol include 1,2-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5- Pentanediol, 2,2-diethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl- 1,3-propanediol, 2-methyl-1,8-octanediol, 1,12-octadecanediol, and the like.
Of these, an adipic acid-based polyester plasticizer is preferably used. This is because the plasticizing efficiency is excellent and the amount of smoke generation is small.

<Filler>
The filler is not particularly limited, but inorganic fillers such as calcium carbonate, silica, clay, inorganic layered compounds such as talc and mica, and hollow balloons such as fly ash can be used.

  Here, in the case of using a sheet attached to a base or the like like an interior material, the amount of smoke generated per surface area of the sheet becomes a problem. Therefore, when the low smoke emitting polyvinyl chloride sheet is used as an interior sheet for buildings, railway vehicles, ships, aircrafts, etc., it is important to reduce the amount of smoke emitted per unit area.

Further, it is considered that the amount of smoke generated decreases as the amount of non-combustible material such as an inorganic filler contained in a sample of a certain area increases, and the amount of smoke generated tends to increase as the amount of inorganic filler decreases.
Therefore, by adding the inorganic filler, the addition ratio of the combustible material in the polyvinyl chloride sheet is reduced, and the amount of smoke generation can be suppressed.

Therefore, the low smoke emitting polyvinyl chloride sheet is composed of at least a transparent layer and a base material layer, relatively reduces the amount of inorganic filler added to the transparent layer, and reduces the amount of inorganic filler added to the base material layer. By increasing the amount, it is possible to obtain a low fuming polyvinyl chloride sheet which is excellent in design by the transparent layer while adding a large amount of an inorganic filler to suppress the fuming amount.
Specifically, the blending amount of the inorganic filler is preferably 50 to 300 parts by weight, more preferably 100 to 300 parts by weight, and still more preferably 150 to 250 parts by weight in the base material layer.

<Polyvinyl chloride resin>
Examples of the polyvinyl chloride resin include polyvinyl chloride homopolymer resin, polychlorinated vinyl chloride resin, polyvinyl chloride copolymer resin (for example, vinyl acetate-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, etc. ), Vinyl chloride graft copolymers (for example, ethylene-vinyl acetate-vinyl chloride graft copolymers, polyurethane-vinyl chloride graft copolymers, etc.), etc., and these may be used alone or in combination of two or more. be able to.

<Zinc stannate compound>
Examples of the zinc stannate compound include zinc stannate and zinc hydroxystannate.

<Molybdate compound>
As the molybdate compound, molybdenum oxide, molybdenum trioxide, molybdate, potassium molybdate, sodium molybdate, calcium molybdate, zinc molybdate, calcium calcium molybdate, ammonium molybdate, ammonium dimolybdate, ammonium heptamolybdate, Ammonium octamolybdate, ammonium decamolybdate, molybdenum disulfide, phosphomolybdic acid, potassium phosphomolybdate, calcium phosphomolybdate, zinc phosphomolybdate, melamine β-molybdate, etc. Alternatively, two or more kinds in an appropriate combination can be mixed and used.

<Other additives>
A flame retardant may be added to the low smoke emitting polyvinyl chloride sheet as necessary. Examples of the flame retardant include a metal hydroxide flame retardant, a nitrogen-containing compound flame retardant, and an inorganic flame retardant. Examples of the metal hydroxide flame retardant include magnesium hydroxide and aluminum hydroxide, and examples of the nitrogen-containing compound flame retardant include ammonium phosphate, ammonium carbonate and boron nitride. Examples of the boric acid compound include zinc borate.

  If necessary, a stabilizer, a lubricant, an ultraviolet absorber, a pigment, a light stabilizer, an antioxidant, an antibacterial agent, and a foaming agent may be added to the low smoke emitting polyvinyl chloride sheet.

  Furthermore, an inorganic material such as an oligomer lubricant or silica can be added to the low smoke emitting polyvinyl chloride sheet for the purpose of reducing the plate-out of the plasticizer. The addition amount of the oligomeric lubricant is preferably 0.5 to 5 parts by weight, more preferably 0.7 to 3 parts by weight with respect to 100 parts by weight of the vinyl chloride resin.

<Thermal conductivity>
When the vinyl chloride resin composition burns at a certain temperature or higher due to heat energy generated in a fire, the vinyl chloride resin composition is thermally decomposed, and a combustible substance and a carbonized layer are generated. The generated combustible substance becomes smoke and heat energy by the combustion energy of the fire. That is, as the combustion progresses, the amount of smoke increases as the thermal energy increases.

It is conceivable to disperse the generated energy as a method of reducing the amount of smoke generated.
When the interior material burns due to a fire or the like, combustion starts from the surface observed as the appearance.
Therefore, it is desirable to dissipate the thermal energy of the surface observed as an appearance in order to reduce smoke generation, particularly early smoke generation.
Since combustion burns on the surface observed as the appearance, the heat energy can be dispersed in the lower direction of the surface observed as the appearance as a dissipating place of the heat energy.

For the transfer of thermal energy, the thermal conductivity λ is expressed as a scale. The thermal conductivity λ represents the speed of heat flowing between surfaces with a certain temperature difference, and is defined as the amount of heat flowing through a material with a temperature difference of 1 K, a cross-sectional area of 1 square meter, and a thickness of 1 mm. The unit is W / m · K. expressed.

  Therefore, in order to disperse the thermal energy in the back direction of the surface observed as the appearance, the thermal conductivity λ (A) of the transparent layer (A) and the thermal conductivity λ (B) of the base material layer (B) The thermal conductivity ratio λ (B) / λ (A) is preferably larger than 1.

  A filler is added to the base material layer, and the thermal conductivity is higher than that of the transparent layer. For this reason, thermal energy is easily diffused into the base material layer having a higher thermal conductivity than the transparent layer, and the entire sheet is reduced in smoke generation.

<Layer structure of low fuming polyvinyl chloride sheet>
The thickness of the transparent layer (A) is preferably 2/5 or less of the thickness of the base material layer (B). When it becomes 2/5 or more, since the heat energy at the time of combustion increases because the combustibles in the transparent layer increase, the heat dissipation effect to the base material layer may be reduced.

  Here, the thickness of the transparent layer (A) is preferably 0.1 mm to 1.2 mm. When used as an interior sheet, the thickness can be set according to the surface wear characteristics and the like. In addition, it is transparent in flooring materials for heavy walk applications such as public facilities, commercial facilities, trains, buses, airplanes, ships, etc. that are required to have higher wear resistance, and walking on so-called slabs or where trolleys and stretchers pass. The layer is preferably thicker.

  Moreover, the thickness of the base material layer is preferably 0.5 mm to 2.9 mm. When used as an interior sheet, 0.5 mm to 2.0 mm is preferable in consideration of durability and workability.

  Further, as shown in FIG. 2, an intermediate layer 3 can be further provided under the transparent layer 1. The intermediate layer 3 is provided between the transparent layer 1 and the base material layer 2. That is, the transparent layer 1, the intermediate layer 3, and the base material layer 2 are laminated in this order from the side observed as a normal appearance. Furthermore, layers other than the transparent layer 1, the base material layer 2, and the intermediate layer 3 may be laminated between the transparent layer 1 and the intermediate layer 3 or between the intermediate layer 3 and the base material layer 2.

  The intermediate layer is preferably a layer made of a polyvinyl chloride resin from the viewpoint of at least a thermoplastic resin and excellent adhesion to the surface layer and the base material layer.

  Here, the thickness of the intermediate layer is preferably 0.1 mm to 0.5 mm. The intermediate layer is preferably a design layer that can be visually recognized from above the transparent layer as a colored layer or a printed layer.

  The thickness of the low smoke emitting polyvinyl chloride sheet is preferably 0.1 mm to 5.0 mm, more preferably 0.8 mm to 4.0 mm, and more preferably 1.0 mm to 3.0 mm when used as an interior material, particularly a flooring material. More preferably, 1.2 mm-2.5 mm are still more preferable.

  A reinforcing layer may be provided on the low smoke emitting polyvinyl chloride sheet. A woven fabric, a nonwoven fabric, etc. are used for a reinforcement layer. As the fibers constituting the woven fabric and the nonwoven fabric, natural fibers, chemical fibers, synthetic fibers, inorganic fibers such as glass, and the like can be used. The reinforcing layer may be provided below the base material layer, or may be provided between the base material layer and a surface layer or an intermediate layer. Further, a reinforcing layer may be provided in the middle of the base material layer, and for example, a structure such as a surface layer, a base material layer, a reinforcing layer, or a base material layer may be formed.

<Measurement of smoke generation>
The amount of smoke in this specification can be measured according to standards such as ASTM E662. In these measurement methods, the sample is placed vertically in a closed smoke box, and in the flameless combustion test, radiant heat is applied by an electric heater to generate smoke, and in the flammable combustion test, combustion is performed with an electric heater and a gas burner. It is something that smokes. The smoke generated is obtained by obtaining a light extinction coefficient from the intensity of light transmitted through the phototube and obtaining a specific optical density (amount of smoke emitted per unit area).
Usually, the smoke generation amount is evaluated by Ds (4.0) indicating the smoke generation amount after 4 minutes and Ds (max) indicating the maximum value. Here, Ds (max) is the maximum amount of smoke within the test time.
The test time is 20 minutes at the maximum, but if the maximum amount of smoke is continued for 3 minutes, the test ends at that point.

  Here, how much smoke is allowed depends on the application, but Ds (max) may be required to be 450 or less in the interior material of a building. Of course, it is more preferable that the amount of smoke generated is small, so it is more preferable to set Ds (max) to 300 or less in these applications. In some cases, Ds (max) is required to be 200 or less in a railway vehicle or an aircraft.

<Manufacturing method>
Each layer such as a surface layer, a base material layer, and an intermediate layer constituting the low smoke emitting polyvinyl chloride sheet can be obtained by mixing predetermined materials and molding them with a molding machine such as an extruder or a calendar. And a low smoke generating polyvinyl chloride sheet can be obtained by laminating these layers with heat or an adhesive. It can also be obtained by forming each layer at once using a multilayer extruder and laminating. Furthermore, when laminating a reinforcing layer, it is possible to use a production method such as laminating a reinforcing layer when molding each layer with an extruder or a calendar, or laminating a reinforcing layer when laminating each layer. .

Next, the present invention will be described more specifically with reference to examples and comparative examples.
Reference examples and examples are shown in Tables 2 and 3 below. Each layer of the reference example and the example kneaded the composition of each layer described in Table 2 and Table 3, and the obtained compound was formed into a sheet by a roll at 175 ° C. And the sheet | seat of each obtained layer was press-processed (180 degreeC), and the low smoke generation polyvinyl chloride sheet | seat which has a surface layer and a base material layer as shown in FIG. 1 was obtained. Further, these low-smokeness polyvinyl chloride sheets were evaluated according to the evaluation methods shown below, and the results are shown in Tables 2 and 3.
Moreover, about the comparative example, it manufactured by the method similar to an Example by the mixing | blending and structure shown in Table 4, and also shown in Table 4 about the evaluation result.
Specimens 1 and 2 are sheets obtained by forming a compound obtained by kneading the compounding composition shown in Table 1 with a roll at 175 ° C., and the thermal conductivity of each of the specimens is shown below. Table 1 shows the results measured by the above.
(Materials used)
Vinyl chloride resin: degree of polymerization 1000
Phthalate ester: DOP
Sulfonate ester plasticizer: alkylphenyl ester represented by the general formula (Chemical Formula 1) (a mixture of alkyl group (R1) having 10 to 21 carbon atoms)
Polyester plasticizer 1: Adipic acid polyester plasticizer Viscosity: 150 mPa · s / 25 ° C. Molecular weight: 750
Polyester plasticizer 2: Adipic acid polyester plasticizer Viscosity: 200 mPa · s / 25 ° C. Molecular weight: 800
Stabilizer: Barium zinc stabilizer Filler: Calcium carbonate Zinc stannate compound: Zinc hydroxystannate Molybdate compound: Mixture of calcium molybdate and zinc molybdate (test method)
<Thermal conductivity> Probe method Kyoto Electronics Industry Co., Ltd. Measured by Chemtherm QTM-D3.
<Smokeability> ASTM E662 (flaming test method)
A test piece of 76mm square was heated by the provision of chamber with electric heater (heat 25KW / ^{m 2)} and the pilot burner (propane gas flow rate 50 cm ³ / min and a mixed gas of air 500cm ³ / min), light from the generated smoke The maximum smoke concentration (Ds (max)) was evaluated by measuring the attenuation of transmittance.
(Evaluation criteria)
Ds (max)
◎: 200 or less ○: More than 200 and 450 or less ×: More than 450 <Contamination resistance>
In accordance with JIS A1454, 2 mL of contaminants are dropped on the test specimen at a temperature of 23 ± 2 ° C. and a humidity of 50 ± 10%, washed with household detergent after 24 hours, and wiped with industrial alcohol after 1 hour. The surface condition was evaluated.
(Pollutant)
2% sodium hydroxide 5% hydrochloric acid cement paste 5% acetic acid (evaluation criteria)
○: No influence of discoloration etc. on all pollutants ×: Influence of discoloration etc. on any of the pollutants <Abrasion resistance>
Based on JIS A 1454, the abrasion property in 1000 rotations was evaluated using the Taber type abrasion tester.
(Evaluation criteria)
○: Hard to wear (wear thickness is less than 0.1 mm)
×: Easily worn (wear thickness reduction 0.1 mm or more)

  Examples 1 to 5 were not only excellent in smoke generation but also good results in the stain resistance test and the abrasion resistance test. On the other hand, Comparative Example 1 is composed of only a transparent layer, so the amount of smoke generation is large, and Comparative Example 2 has a surface layer plasticizer of 60 parts by weight, and the thickness ratio of the transparent layer to the back layer is 1: 1. The amount of smoke is increasing. Further, Comparative Example 3 contains 60 parts by weight of the polyester plasticizer in the surface layer, so that the amount of smoke generation is increased compared to the Examples, and Comparative Example 4 is an opaque layer containing 30 parts by weight of filler in the surface layer. Poor contamination resistance. Comparative Example 5 contains 40 parts by weight of calcium carbonate as a filler in the base material layer, and the amount of smoke generation is increased as compared with the Examples.

  On the other hand, the test bodies 1 and 2 in Table 1 show the thermal conductivity of the transparent layer (A) and the base material layer (B) in Examples 2 and 4, and the base material layer has a higher thermal conductivity. It was. The thermal conductivity ratios λ (B) / λ (A) of Examples 2 and 4 are 1.57. Since Comparative Example 1 is composed of only the transparent layer (A), the thermal conductivity ratio is 1. Conceivable. Therefore, in Examples 2 and 4 in which the thermal conductivity ratio λ (B) / λ (A) is larger than 1, the amount of smoke generation is reduced by setting the thermal conductivity ratio to be larger than 1.

Here, reference example 1 and examples 2 and 4 have different plasticizers, but reference examples 1, 2, and 3 have the same blending structure and the same plasticizer, and an aluminum plate having a high thermal conductivity is bonded to the sheet. It is pasted with. Comparing Reference Examples 1 to 3, the smoke generation was reduced as the thickness of the aluminum plate increased. Therefore, it is suggested that the smoke generation property is reduced by stacking a layer having a high thermal conductivity on the sheet and increasing the volume of the layer having a high thermal conductivity so that the heat capacity is increased.
Therefore, in Examples 2 and 4, the base material layer (B) having a higher thermal conductivity than the transparent layer (A) is laminated, and the base material layer (B) is made thicker than the transparent layer (A) so as to emit smoke. Is considered to be a factor that reduces
Further, when Example 2 and Comparative Example 2 are compared, there is an influence of the amount of the plasticizer, but since the thickness ratio of the transparent layer and the base material layer is 1: 1, the volume (base) of the layer having high thermal conductivity is high. Since the volume of the material layer is relatively low, the amount of smoke generation is considered to have increased as a whole.

  Moreover, in Example 4, smoke generation is further reduced by adding a molybdate compound to the back layer.

1 Transparent layer 2 Base material layer 3 Intermediate layer

Claims (5)

Polyvinyl chloride containing 100 parts by weight of a vinyl chloride resin and 5 to 50 parts of a plasticizer that is at least one selected from a polyester plasticizer or a sulfonate plasticizer , and substantially free of an inorganic filler A transparent layer (A) composed of a resin-based resin composition (a);
Laminated on the transparent layer (A), 100 parts by weight of a vinyl chloride resin, 5 to 100 parts of a plasticizer that is at least one selected from a polyester plasticizer or a sulfonate plasticizer, calcium carbonate, silica, Low smoke generation comprising a base material layer (B) comprising a polyvinyl chloride resin composition (b) containing at least one inorganic filler 100 to 300 parts selected from clay, an inorganic layered compound, and a hollow balloon Conductive polyvinyl chloride sheet.   The thermal conductivity ratio λ (B) / λ (A) between the thermal conductivity λ (A) of the transparent layer (A) and the thermal conductivity λ (B) of the base material layer (B) is greater than 1. Item 2. The low fuming polyvinyl chloride sheet according to Item 1.   The low fuming property polychlorination according to claim 1 or 2 whose thickness of said transparent layer (A) is 2/5 or less of the thickness of said base material layer (B), and the sum total of thickness is 1 mm-3 mm. Vinyl-based sheet.   The low smoke generating polyvinyl chloride sheet according to any one of claims 1 to 3, wherein a maximum smoke concentration (Ds (max)) measured in accordance with ASTM E662 is 450 or less.   The polyvinyl chloride resin composition (b) contains 1 to 20 parts of an additive which is at least one selected from a zinc stannate compound and a molybdate compound. The low smoke emitting polyvinyl chloride sheet according to the item.

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