JP5759240B2 - Flame retardant styrene resin composition and liquid crystal TV back cover using the same - Google Patents

Description

  The present invention relates to a flame retardant styrenic resin composition and a molded body comprising the same. Specifically, it is a flame retardant styrene-based resin composition excellent in the balance characteristics of moldability, impact strength, heat resistance, and flame retardancy required for large molded articles. The present invention also relates to a molded body obtained by injection molding of the flame retardant styrene resin composition, particularly a liquid crystal TV back cover.

  Styrenic resins are used in a wide range of applications by taking advantage of their properties. Above all, flame retardant styrene resin compositions with advanced flame retardancy are used in a wide variety of fields, including office automation equipment such as word processors, personal computers, printers and copiers, and home appliances such as TVs, VTRs and audios. Used in. In these fields such as OA equipment and home appliances, cost reduction is required, and thinning of plastic parts is required. In addition, the liquid crystal TV is increased in size, and the resin composition used to cope with these needs to have strength, heat resistance, and moldability in addition to flame retardancy. Usually, a lubricant is added to improve the moldability, but the heat resistance is lowered depending on the amount of lubricant added (see Patent Document 1 (paragraph number 31, Examples, etc.)). Further, to improve the moldability, it can be dealt with by lowering the molecular weight of the resin as the main component of the resin composition and increasing the fluidity, but the heat resistance and impact strength are reduced (Patent Document 2 (paragraph 0007, See Table 2). Further, when the injection pressure is increased by changing the injection molding conditions, molding defects such as warping and burrs are generated. On the other hand, when the molding temperature is increased, mold contamination is unfavorable. In order to solve these problems, a thin molded part can be obtained at a molding temperature or injection pressure at which a molded product using a general flame retardant styrene resin composition can be obtained without impairing necessary characteristics of the liquid crystal TV back cover. There is a need for an improved flame retardant resin composition with good moldability that can be filled without increasing the molding temperature and injection pressure.

JP 2001-151974 A JP 10-36603 A

  The subject of the present invention is the UL combustion test V-0, which can fill the end of a thin molded part of a large molded product without particularly increasing the molding temperature and injection pressure and has an excellent balance of heat resistance and impact strength. And a liquid crystal TV back cover obtained by injection molding the flame retardant resin composition.

  As a result of intensive studies on the above problems, the present inventor has selected a specific rubber-modified styrene-based resin and added a specific flame retardant, a flame retardant aid, and an inorganic filler in a specific amount of composition ratio, thereby Completed the invention.

That is, the present invention is as follows.
1. (A) With respect to 100 parts by mass of the rubber-modified styrenic resin having a reduced viscosity of the matrix part of 0.65 dl / g or more and a gel content of the rubber-like polymer of 19.0% by mass or more, 15.0-23.0 parts by mass of brominated flame retardant of 4,6-tris (2,4,6-tribromophenoxy) -1,3,5-triazine, (C) antimony oxide 2 as flame retardant auxiliary A flame-retardant styrene-based resin composition containing 0.0 to 5.0 parts by mass and (D) 2.5 to 9.0 parts by mass of talc, and further has a shear rate of 610 sec-1 at a melting temperature of 240 ° C. A flame-retardant styrene-based resin composition that sometimes has a melt viscosity of 100 Pa · s or more and a melt speed of 1000 Pa · s or less at a shear rate of 6.1 sec-1.
2. 2. The melting temperature of 240 ° C., wherein the melt viscosity is 100 to 150 Pa · s when the shear rate is 610 sec−1, and the melt viscosity is 650 to 1000 Pa · s when the shear rate is 6.1 sec−1. Flame retardant styrene resin composition.
3. The flame-retardant styrene resin composition according to any one of 1 to 2 above, which has V-0 in a UL94 combustion test.
4). 4. A liquid crystal TV back cover obtained from the flame retardant styrene resin composition according to any one of 1 to 3 above.

  The flame-retardant styrene-based resin composition according to the present invention is a flame-retardant styrene-based resin having a UL flame test V-0 that has improved moldability for large molded products and has an excellent balance between heat resistance and impact strength. It is a composition. Taking advantage of this advantage, the liquid crystal TV back cover contributes to the progress of thinning and enlargement, and its industrial utility value is extremely large.

Examples 2 and 6 and Comparative Examples 7 and 8 are graphs showing the relationship between shear rate and melt viscosity at a melt temperature of 240 ° C.

  The (A) rubber-modified styrenic resin of the present invention refers to a polymer in which a rubber-like polymer is dispersed in the form of particles in an aromatic vinyl polymer matrix. For example, a polymer obtained by dissolving a rubber-like polymer in a mixture of an aromatic vinyl monomer and an inert solvent and stirring to perform bulk polymerization, suspension polymerization, solution polymerization, etc. It is not limited to legality. Further, a mixture obtained by dissolving a rubbery polymer in a mixed liquid of an aromatic vinyl monomer and an inert solvent and a separately obtained aromatic vinyl polymer may be mixed. .

  The aromatic vinyl monomer is mainly styrene. Although o-methyl styrene, m-methyl styrene, p-methyl styrene, 2,4-dimethyl styrene and the like can be mentioned, styrene is most preferable. Two or more of these monomers can be used in combination.

  Examples of the rubbery polymer include polybutadiene, polyisoprene, and styrene-butadiene copolymer, and polybutadiene is preferable. Examples of the polybutadiene include high cis polybutadiene having a high cis bond content and low cis polybutadiene having a low cis bond content. They can be used alone or in combination.

The molecular weight of the matrix portion is 0.65 dl / g or more, preferably 0.67 dl / g or more in terms of reduced viscosity (ηsp / C). If it is less than 0.65 dl / g, there is a problem that practically sufficient strength cannot be exhibited. Further, the upper limit of the reduced viscosity is limited to a range satisfying the regulation of the melt viscosity. In general, when the reduced viscosity is increased, the fluidity is deteriorated, and unless the molding temperature is raised, the molding of the thin portion is hindered. Therefore, it is preferable not to exceed 0.75 dl / g.
The reduced viscosity (ηsp / C) was determined by adding a mixed solvent of 15 ml of methyl ethyl ketone and 15 ml of acetone to 1 g of (A) rubber-modified styrenic resin, shaking and dissolving at a temperature of 25 ° C. for 2 hours, and then precipitating the insoluble matter by centrifugation. The supernatant is taken out by decantation, 500 ml of methanol is added to precipitate the resin, and this is dried. The resin component obtained by the same operation was dissolved in toluene to prepare a sample solution having a polymer concentration of 0.4% (mass / volume). The sample solution and pure toluene are brought to a constant temperature of 30 ° C., the solution flowing seconds are measured with an Ubbelohde viscometer, and the following formula is calculated.
ηsp / C = (t1 / t0-1) / C
t0: Pure toluene flow down seconds t1: Sample solution flow down seconds C: Polymer concentration

Further, the gel content of the rubbery polymer is 19.0% by mass or more, preferably 20.0% by mass or more. When the gel content of the rubber-like polymer is less than 19.0% by mass, there is a problem that practically sufficient strength cannot be exhibited. Moreover, the upper limit of gel content is restrict | limited to the range which satisfy | fills prescription | regulation of melt viscosity. In general, when the gel content is increased, the fluidity is deteriorated, and unless the molding temperature is raised, the molding of the thin portion is hindered. It is preferable not to exceed 23.0% by mass.
The gel content of the rubber-like polymer is the ratio of rubber-like dispersed particles in the rubber-modified styrene resin, and 1 g of the rubber-modified styrene resin composition is added to a mixed solvent of 15 ml of methyl ethyl ketone and 15 ml of acetone, After shaking and dissolving at 25 ° C. for 2 hours, the insoluble matter is settled by centrifugation, and the supernatant is removed by decantation to obtain an insoluble matter, which is vacuum-dried at 70 ° C. for about 15 hours, and in a desiccator for 20 minutes. After cooling, the mass G (g) of the dried insoluble matter can be measured and obtained by the following formula.
Gel content (% by mass) = (G / 1) × 100

  Although there is no restriction | limiting in particular about rubber-like polymer content, 5-15 mass% generally used for rubber-modified styrene resin is suitable. The rubbery polymer content is desirably determined in consideration of the balance between impact strength and rigidity necessary for the molded product. The average particle size of the rubber-like polymer is not particularly limited, but is generally 0.4 to 6.0 μm, preferably 0.5 to 3.0 μm. When the particle size of the rubbery polymer is too small, the impact strength is drastically lowered, and when the particle size is increased, the appearance such as surface gloss of the molded product tends to be deteriorated.

  (B) As the flame retardant, 2,4,6-tris (2,4,6-tribromophenoxy) -1,3,5-triazine is used. The amount of the flame retardant added is 15.0 to 23.0 parts by mass with respect to 100 parts by mass of (A) the rubber-modified styrene resin. Preferably it is 16.0-21.0 mass parts. When the addition amount of the flame retardant is less than 15.0 parts by mass relative to the (A) rubber-modified styrene resin, the flame retardancy is inferior, and the V-0 level in the UL94 combustion test cannot be ensured with a test piece thickness of 1.5 mm. . Exceeding 23.0 parts by mass is not preferable because practically sufficient heat resistance cannot be obtained.

(C) a flame retardant aid, antimony trioxide, antimony tetroxide, antimony pentoxide, sodium antimonate and the like can be mentioned (B) is intended to further improve working the flame retardant effect of flame retardants, as the acid antimony It is done. Among them, it is particularly preferable to use antimony trioxide.

  (C) The addition amount of a flame retardant adjuvant is 2.0-5.0 mass parts with respect to 100 mass parts of (A) rubber-modified styrene resin. When the amount of (C) flame retardant auxiliary added is less than 2.0 parts by mass relative to (A) rubber-modified styrene resin, the flame retardancy is inferior and the V-0 level in the UL94 combustion test cannot be secured. Exceeding 5.0 parts by mass is not preferable because it increases the glowing behavior during combustion.

  (D) Talc is used as an inorganic filler. The amount of talc added is 2.5 to 9.0 parts by mass with respect to (A) 100 parts by mass of the rubber-modified styrene resin. Preferably it is 3.0-6.5 mass parts. If the talc is less than 2.5 parts by mass relative to the rubber-modified styrene resin (A), the heat resistance is inferior, and if it exceeds 9.0 parts by mass, a practically sufficient strength cannot be exhibited.

  In the present invention, (A) the reduced viscosity of the matrix is 0.65 dl / g or more and the gel content of the rubbery polymer is 19 parts by mass or more with respect to 100 parts by mass of the rubber-modified styrenic resin, 4,6-tris (2,4,6-tribromophenoxy) -1,3,5-triazine brominated flame retardant 15.0-23.0 parts by mass, (C) flame retardant auxiliary 2.0- A flame-retardant styrene-based resin composition containing 5.0 parts by mass and (D) 2.5 to 9.0 parts by mass of talc, and melts when the shear rate at a melting temperature of 240 ° C. is 610 sec-1. It is essential that the viscosity is 100 Pa · s or higher and the melt viscosity is 1000 Pa · s or lower when the shear rate is 6.1 sec-1.

When the shear rate is 610 sec-1, the melt viscosity is less than 100 Pa · s, and when the shear rate is 6.1 sec-1, the melt viscosity is 1000 Pa · s or less, the fluidity is good but the heat resistance is low. .
On the other hand, if the melt viscosity is 100 Pa · s or more when the shear rate is 610 sec −1 and the melt viscosity exceeds 1000 Pa · s when the shear rate is 6.1 sec −1, the fluidity is deteriorated.
Furthermore, at a melting temperature of 240 ° C., the melt viscosity is preferably in the range of 100 to 150 Pa · s when the shear rate is 610 sec−1. Further, at a melting temperature of 240 ° C., the melt viscosity is preferably 650 to 1000 Pa · s when the shear rate is 6.1 sec−1.

In addition, the melt viscosity of this invention says the value measured on condition of the following based on JISK7199 at the temperature of 240 degreeC.
Measuring device: Capillograph 1D (manufactured by Toyo Seiki Co., Ltd.)
Melting temperature: 240 ° C
Cylinder inner diameter: 9.55mm
Die length: 40mm
Die diameter: 1mm
Residual heat time: 6 minutes Standby time during measurement: Shear rate: 6.1 sec-1 to 6100 sec-1 until test pressure stabilizes within ± 3%

  The flame retardant styrene-based resin composition of the present invention may contain other additives such as plasticizers, lubricants, stabilizers, ultraviolet absorbers, fillers, reinforcing agents and the like as long as the purpose is not impaired.

  A known mixing technique can be applied to the method for mixing the flame-retardant styrene resin composition of the present invention. For example, a uniform flame-retardant resin composition can be obtained by further melt-kneading a mixture previously mixed with a mixing apparatus such as a mixer-type mixer, a V-type blender, and a tumbler-type mixer. There is no particular limitation on melt kneading, and a known melting technique can be applied. Suitable melt kneaders include Banbury mixers, kneaders, rolls, single screw extruders, special single screw extruders, and twin screw extruders. Furthermore, there is a method of separately adding an additive such as a flame retardant from the middle of a melt-kneading apparatus such as an extruder.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples.

(A-1) to (A-9) rubber-modified styrenic resins used in Examples and Comparative Examples have the following compositions, respectively.
(A-1) The composition of the rubber-modified styrene resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.68 dl / g, the rubbery polymer content is 7.1% by mass, and the gel content of the rubbery polymer is 21.9. The rubbery polymer used was a high-cis polybutadiene rubber and a low-cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 50/50.
(A-2) The composition of the rubber-modified styrene resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.73 dl / g, the rubbery polymer content is 6.8% by mass, and the rubbery polymer gel content is 20.6. A high-cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more was used as the rubber-like polymer in mass%.
(A-3) The composition of the rubber-modified styrenic resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.70 dl / g, the rubbery polymer content is 7.5% by mass, and the rubbery polymer gel content is 22.6. The rubbery polymer used was a high cis polybutadiene rubber and a low cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 56/44.
(A-4) The composition of the rubber-modified styrenic resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.73 dl / g, the rubbery polymer content is 7.1% by mass, and the gel content of the rubbery polymer is 21.9. The rubbery polymer used was a high cis polybutadiene rubber and a low cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 50/50.
(A-5) The composition of the rubber-modified styrene resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.70 dl / g, the content of rubbery polymer is 7.6% by mass, and the gel content of rubbery polymer is 23.3. The rubbery polymer used was a high cis polybutadiene rubber and a low cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 50/50.
(A-6) The composition of the rubber-modified styrenic resin is a ratio of 50/50 high-cis polybutadiene rubber and low-cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more as the rubber-like polymer. 1% by mass of styrene-butadiene-styrene copolymer tufprene 315P (manufactured by Asahi Kasei Chemicals Co., Ltd.) is added to the rubber-modified styrene resin used in the above. The reduced viscosity of polystyrene in the matrix portion after addition is 0.69 dl / g, the rubbery polymer content is 9.3% by mass, and the gel content of the rubbery polymer is 26.5%.
(A-7) The composition of the rubber-modified styrene resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.63 dl / g, the rubbery polymer content is 7.1% by mass, and the gel content of the rubbery polymer is 21.9. The rubbery polymer used was a high cis polybutadiene rubber and a low cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 50/50.
(A-8) The composition of the rubber-modified styrene resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.76 dl / g, the rubbery polymer content is 7.1% by mass, and the gel content of the rubbery polymer is 21.9. The rubbery polymer used was a high cis polybutadiene rubber and a low cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 50/50.
(A-9) The composition of the rubber-modified styrene resin is such that the reduced viscosity of polystyrene in the matrix portion is 0.68 dl / g, the content of rubbery polymer is 6.2% by mass, and the gel content of rubbery polymer is 17.8. The rubbery polymer used was a high cis polybutadiene rubber and a low cis polybutadiene rubber containing cis 1,4 bonds in a ratio of 90 mol% or more in a ratio of 50/50.

The reduced viscosity (ηsp / C) was measured by adding a mixed solvent of 15 ml of methyl ethyl ketone and 15 ml of acetone to 1 g of a rubber-modified styrenic resin, dissolving by shaking at a temperature of 25 ° C. for 2 hours, and then precipitating insoluble matter by centrifugation. The supernatant was taken out by decantation, 500 ml of methanol was added to precipitate the resin component, and the insoluble component was filtered and dried. The resin component obtained by the same operation was dissolved in toluene to prepare a sample solution having a polymer concentration of 0.4% (mass / volume). This sample solution and pure toluene were measured at a constant temperature of 30 ° C. using a Ubbelohde viscometer, and the number of seconds during which the solution flowed was measured.
ηsp / C = (t1 / t0-1) / C
t0: Pure toluene flow down seconds
t1: Sample solution flow down seconds
C: Polymer concentration

The gel content of the rubber-like polymer was determined by adding 1 g of a rubber-modified styrene resin composition to a mixed solvent of 15 ml of methyl ethyl ketone and 15 ml of acetone, shaking and dissolving at a temperature of 25 ° C. for 2 hours, and then centrifuging to remove insoluble matter. Settling and removing the supernatant by decantation to obtain an insoluble matter, followed by vacuum drying at a temperature of 70 ° C. for about 15 hours, cooling in a desiccator for 20 minutes, and then measuring the mass G (g) of the dried insoluble matter. The following formula was used.
Gel content (mass%) of rubber-like polymer = (G / 1) × 100

  The rubber-like polymer content was measured by dissolving a rubber-modified styrene resin in chloroform, adding a certain amount of iodine monochloride / carbon tetrachloride solution and leaving it in the dark for about 1 hour, and then adding 15 mass / volume iodinated. Potassium solution and 50 ml of pure water were added, excess iodine monochloride was titrated with 0.1N sodium thiosulfate / ethanol aqueous solution, and the amount of iodine monochloride added was calculated.

  (B) For the flame retardant, (B-1) 2,4,6-tris (2,4,6-tribromophenoxy) -1,3,5-triazine, trade name of Daiichi Kogyo Seiyaku Co., Ltd. Pyroguard SR245 was used. Moreover, the brand name SAYTEX-8010 (henceforth S8010 abbreviation) by the Albemarle company which is (B-2) ethylenebispentabromobenzene was used as a flame retardant for comparison.

  (C) Suzuhiro Chemical Co., Ltd. product name AT-3CN (antimony trioxide) was used for the flame retardant aid.

  (D) The product name KP talc manufactured by Fuji Talc was used as the talc.

  Next, a method for mixing the flame-retardant styrene resin composition of the present invention will be described. (A) Rubber-modified styrenic resin, (B) flame retardant, (C) flame retardant aid, and (D) talc in the blending amounts shown in Tables 1 to 3, all of these components were added to a Henschel mixer (Mitsui Mitsui) The mixture was premixed with Kako Kogyo Co., Ltd. (FM20B), supplied to a twin screw extruder (Toshiki Machine Co., Ltd., TEM26SS) to form a strand, cooled with water, then led to a pelletizer and pelletized. At this time, the cylinder temperature was 230 ° C. and the supply amount was 30 kg / hour.

  During the premixing, a mixture of sodium aluminosilicate and A-type zeolite, calcium stearate, mineral oil, and inorganic colorant were also added at the same time.

  Various measurements shown in Examples and Comparative Examples were performed by the following methods.

(1) Measurement of melt viscosity The melt viscosity was measured based on JIS K 7199.
Measuring device: Capillograph 1D (manufactured by Toyo Seiki Co., Ltd.)
Melting temperature: 240 ° C
Cylinder inner diameter: 9.55mm
Shear rate: 6.1 sec-1 to 6100 sec-1 Die length: 40 mm
Die diameter: 1mm
Residual heat time: 6 minutes Standby time during measurement: Until test pressure stabilizes within ± 3%

(2) Measurement of flame retardancy The flame retardancy was measured according to the vertical combustion test method of Subject No. 94 of US Underwriters Laboratories, Inc., and the combustibility with a specimen thickness of 1.5 mm was evaluated. The evaluation results are shown as follows.
94V-0 was accepted.

(3) Measurement of Charpy impact strength Charpy impact strength was measured based on JIS K7111-1.
Measuring device: Charpy testing machine (manufactured by Toyo Seiki)
Notch type: Type A
Stroke direction: Edgewise Measurement environment: 23 ° C
If the Charpy impact strength is less than 7 KJ / m 2, the strength of the molded product of the liquid crystal TV back cover is insufficient. Therefore, a composition satisfying 7 KJ / m 2 or more was regarded as acceptable.

(4) Deflection temperature under load (HDT)
The deflection temperature under load was measured based on JIS K 7191.
Measuring device: No. 148-HD-PC-3 (manufactured by Yasuda Seiki)
Stress: 1.80 MPa
Distance between fulcrums: 64mm
Specimen size: Length 80mm Width 10mm Height 4mm Flatwise If the deflection temperature under load is less than 70 ° C, the molded product of the LCD TV back cover is insufficient in heat resistance. did.

(5) Large-size molding: 42-inch LCD TV back cover molding Average wall thickness of 2.0 mm
Molding model: Mitsubishi MMV clamping force 2000t
Cylinder temperature: 235 ° C
If conditions were found that would not increase the molding cycle even if the injection pressure, injection speed, mold temperature, etc. were changed, and that molding defects (such as warping, burrs, and shorts) did not occur, the test was accepted.

Preparation conditions of test pieces for various tests A Charpy impact strength test piece and a deflection temperature test piece under load were measured by an injection molding machine (manufactured by Nippon Steel Works Co., Ltd., J100E-P) as A type described in JIS K 7139. A test piece (dumbbell) was molded. The molding conditions at this time were performed according to JIS K 6926-2. The Charpy impact strength test piece was cut out from the center of the dumbbell piece, cut into a notch (type A, r = 0.25 mm), and used for the test. Moreover, the load deflection temperature test piece was cut out from the center part of the dumbbell piece and used for the test.

  The test piece for evaluation of combustibility was formed as a 127 × 12.7 × 1.5 mm combustion test piece with an injection molding machine (manufactured by Nippon Steel Works, J100E-P). At this time, the cylinder temperature was 190 ° C. and the mold temperature was 30 ° C.

  The respective formulations and results of Examples 1 to 6 and Comparative Examples 1 to 12 are shown in Tables 1 to 3.

  From the examples, it can be seen that the flame-retardant styrene-based resin composition of the present invention has improved moldability, impact resistance, heat resistance, and flame retardancy in a well-balanced manner.

  However, in the flame-retardant styrene resin composition obtained in the comparative example that does not satisfy the provisions of the present invention, all of the moldability, impact resistance, heat resistance, and flame retardancy may be excellent. It is clear that there is nothing better than

  For example, if the amount of (D) talc is less than the specified amount, the heat resistance decreases (Comparative Example 1), and if it is large, the Charpy impact strength decreases (Comparative Example 2). (B) If the amount of the flame retardant is less than the specified amount, the flame retardancy is inferior and the V-0 level in the UL94 combustion test cannot be ensured (Comparative Example 3), and if it is large, the heat resistance decreases (Comparative Example 4). Further, when the melt viscosity at a melting temperature of 240 ° C. and a shear rate of 6.1 sec-1 is 1000 Pa · s or more, large-scale molding is inferior (Comparative Examples 5 to 8, 10, and 12). Further, when the reduced viscosity or gel content of (A) the rubber-modified styrene resin is smaller than the specified value, the Charpy impact strength is lowered (Comparative Examples 9 and 11). Moreover, when other brominated flame retardant S8010 is used, Charpy impact strength and large formability are inferior (Comparative Example 12).

Claims (4)

(A) With respect to 100 parts by mass of the rubber-modified styrenic resin having a reduced viscosity of the matrix part of 0.65 dl / g or more and a gel content of the rubber-like polymer of 19.0% by mass or more, 1,6-tris (2,4,6-tribromophenoxy) -1,3,5-triazine brominated flame retardant 15.0 to 23.0 parts by mass, (C) antimony oxide as a flame retardant auxiliary; A flame-retardant styrene-based resin composition comprising 0 to 5.0 parts by mass and (D) 2.5 to 9.0 parts by mass of talc, and further having a shear rate of 610 sec-1 at a melting temperature of 240 ° C. A flame-retardant styrene-based resin composition having a melt viscosity of 100 Pa · s or more and a melt viscosity of 1000 Pa · s or less at a shear rate of 6.1 sec−1.   The melt viscosity is 100 to 150 Pa · s when the shear rate is 610 sec-1 at a melting temperature of 240 ° C, and the melt viscosity is 650 to 1000 Pa · s when the shear rate is 6.1 sec-1. The flame-retardant styrene-based resin composition described.   The flame-retardant styrene resin composition according to any one of claims 1 to 2, which has V-0 in a UL94 combustion test.   A liquid crystal TV back cover obtained from the flame retardant styrene resin composition according to any one of claims 1 to 3.

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