JP2016216659A - Flame-retardant polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film having high flame retardancy imparted thereto while maintaining an intrinsic property of a polyester resin.SOLUTION: The flame-retardant polyester film is provided that contains an organic phosphorous-based flame-retardant compound and satisfies the following formula (1). 27.25/T+0.26≤P≤34.06/T+1.02≤2.00...(1), where T means thickness of the polyester film (μm) and P means phosphorus element content percentage (wt.%) in the polyester film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polyester film that has excellent flame resistance and can be stably produced while maintaining high heat resistance, electrical insulation, chemical resistance, mechanical properties, etc. inherent to the polyester film. .

  Polyester resin products can be manufactured at a low cost, and are excellent in heat resistance, electrical insulation, chemical resistance, mechanical strength, and the like, and thus are widely used in all fields regardless of industrial use for general households.

  The polyester resin is preferably flame retardant for use in such a wide range of applications. Particularly in the field of electrical and electronic products, due to the recent demand for smaller size and lighter weight, there is a problem of densification of the product and the accompanying increase in heat generation.

  Typical flame retardant compounds that can impart flame retardancy to polyester resins include organic halogen compounds, halogen-containing organic phosphorus compounds, metal hydroxides typified by magnesium hydroxide, and inorganic phosphorus compounds typified by red phosphorus. And organic phosphorus compounds such as phosphoric acid ester compounds, phosphonic acid compounds and phosphinic acid compounds. Among them, organic phosphorus-based flame retardant compounds are preferable from the viewpoint of environmental compatibility and compatibility with resins.

  As one method for flame retarding a polyester resin using an organic phosphorus flame retardant compound, Patent Document 1 discloses a method of copolymerizing the compound with polyester.

  However, the copolymer type flame retardant polyester resin has a low melting point and has a drawback that the heat resistance is worse than that of the non-flame retardant polyester resin. This is presumably because the phosphorus compound incorporated in the molecular chain of the polyester inhibits the crystallization of the resin, and the softening point or melting point of the phosphorus compound itself is low.

  In view of this problem, Patent Document 2 discloses a method in which an organic phosphorus oligomer having an average molecular weight of a certain level or more is added as a flame retardant compound without copolymerizing the flame retardant compound. Since foreign matters do not intervene in the polyester molecular chain, a decrease in heat resistance is suppressed, and by having a certain molecular weight, bleed-out which becomes a problem when a low molecular compound is added is also suppressed.

  However, the flame retardant compound used in the above-mentioned Patent Document 2 has a low IV (Intrinsic Viscosity = intrinsic viscosity) because the compound structural unit is an oligomer. The IV of the polyester resin is also lowered. Since IV has a positive correlation with molecular weight, products using low-IV polyester resins do not have excellent durability and tensile properties. Especially when used in films, the film frequently breaks during production due to insufficient strength. However, there is a concern that production efficiency will deteriorate. Although film tearing can be reduced by lowering production speed, production efficiency is still lowered. Since the presence of a large amount of other additives also becomes a problem during recycling, the amount of the flame retardant compound should be kept as low as possible as long as the required flame retardant level can be achieved.

Japanese Patent No. 3575605 JP 2012-184399 A Japanese Patent Publication No.59-5216

  This invention is made | formed in view of the said situation, The solution subject is to provide the polyester film to which the high flame retardance was provided, maintaining the original characteristic of a polyester resin.

  As a result of intensive studies in view of the above problems, the present inventor has found that it is possible to provide a polyester film that achieves both high flame retardancy and the inherent heat resistance and mechanical properties of the polyester resin, thereby completing the present invention. I came to let you.

That is, the gist of the present invention resides in a polyester film containing an organophosphorus flame retardant compound and satisfies the following formula (1).
27.25 / T + 0.26 ≦ P ≦ 34.06 / T + 1.02 ≦ 2.00 (1)
(In the above formula, T is the thickness (μm) of the polyester film, and P means the phosphorus element content (% by weight) in the polyester film)

  ADVANTAGE OF THE INVENTION According to this invention, the flame-retardant polyester film which has the outstanding flame retardance, heat resistance, and a mechanical characteristic can be provided. The industrial value of the present invention is very high.

Combustion test equipment

  The polyester film referred to in the present invention is a polyester resin itself, or one obtained by adding one or more optional components to a polyester resin and heating and mixing it into a thin and flat shape. Although there is no clear definition of the upper limit of the thickness, it is general to call a sheet more than 250 to 300 μm and a film less than that to a film. The layer structure of the film cross section is not limited, and may be a single layer structure or a structure in which two or more layers having different compositions are laminated in the thickness direction.

  The kind of the above-mentioned “optional component” is not limited at all, and any additive can be selected as necessary. For example, the base polyester is all polymer materials including polyesters (compatible or incompatible), pigments, organic particles, inorganic particles, UV absorbers, infrared absorbers, heat stabilizers, antioxidants. Agents, antistatic agents, lubricants, plasticizers, nucleating agents, molecular chain extenders, crosslinking agents, fillers for resin reinforcement, and the like. The addition amount of these additives is not limited, and may be more than the compounding amount of the base polyester resin as long as it can be formed as a film.

  In the present invention, the method for heating and mixing the polyester resin and other components is not particularly limited. For example, the polyester resin and other components can be continuously produced by introducing them into various extruders, or in a container. A method of mixing by heating and stirring in bulk can be mentioned. In film production, a method of continuous production using an extruder is preferred, and from the viewpoint of handling, it is more preferred that these components are preliminarily formed into a high-concentration masterbatch. There is another method of adding at the polymerization stage of the polyester, but based on the gist of the present invention that maintains the inherent heat resistance of the polyester resin, the copolymerization that causes the low melting point should be avoided. The component added in the polyester polymerization stage is preferably a substance that does not react with the polyester molecule.

  In the present invention, the method for forming the polyester resin into a film is not particularly limited, and various generally well-known methods such as an inflation method, a T-die method, and a calendar method can be used. The method of laminating each layer when producing a multilayer film of two or more layers is also not particularly limited, and various generally well-known methods such as a coextrusion method, a laminating method, and a heat sealing method can be used. From the viewpoint of production efficiency, the coextrusion method is preferable.

  The polyester film of the present invention is preferably stretched and heat-fixed in the biaxial direction. Either the sequential biaxial stretching method or the simultaneous biaxial stretching method may be used. For example, when the sequential biaxial stretching method is used, the unstretched polyester sheet is stretched 2 to 6 times in the longitudinal direction at 70 to 145 ° C. Then, after forming into a longitudinally uniaxially stretched film, it is preferable to stretch 2 to 6 times at 90 to 160 ° C in the transverse direction, and then heat treatment at 150 to 250 ° C for 1 to 600 seconds. At this time, it is preferable to add a 0.1 to 20% relaxation step in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the exit of the heat treatment. Moreover, after forming into a biaxially stretched film, a longitudinal stretch and / or a lateral stretch process can also be added as needed.

  The film IV of the present invention is usually 0.50 dl / g or more, preferably 0.53 dl / g or more, more preferably 0.56 dl / g or more. When the IV is less than 0.50 dl / g, the film strength is insufficient, so that the film frequently breaks during production and the production efficiency may be deteriorated. Furthermore, when IV is less than 0.43 dl / g, it may be difficult to form the film itself. The upper limit of the film IV is not particularly limited, but considering the load on the extruder, the limit is about 0.90 dl / g.

  The polyester resin used in the present invention is not particularly limited, and is mainly a polyester obtained using aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 60% or more of the repeating structural units are present. Polyester having ethylene terephthalate units or ethylene-2,6-naphthalate units. And if it is the conditions which do not deviate from said range, the other 3rd component may be contained. For example, mixing with polyester-type resin, such as a polycarbonate, compatible with resin is mentioned.

  Examples of the aromatic dicarboxylic acid component include, in addition to terephthalic acid and dimethyl terephthalate and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid) Acid, etc.) can be used. In particular, terephthalic acid or dimethyl terephthalate is preferably used.

  As an example of the glycol component, in addition to ethylene glycol, for example, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like can be used. In particular, it is preferable to use ethylene glycol.

  Although the kind of flame retardant compound used in the present invention is not particularly limited, it is preferable to use an organic phosphorus flame retardant compound, for example, carboxymethylphenyl phosphate, (2-carboxyethyl) phenyl phosphate, (2-carboxyethyl) ) Toluyl phosphate, (2-carboxyethyl) 2,5-dimethylphenyl phosphate, (2-carboxyethyl) cyclohexyl phosphate, (carboxypropyl) phenyl phosphate, (4-carboxyphenyl) phenyl phosphate, (3-carboxyphenyl) phenyl Phosphate, (2-carboxyethyl) methyl phosphate, (2-carboxyethyl) ethyl phosphate, triphenyl phosphate, tributyl phosphate, t-butyl diphenyl phosphate, tri (2-ethylhexyl) phosphate, bisphenol A bis (diphenyl phosphate)-1,3-phenyl-bis (diphenyl phosphate), include the compounds described in phosphonitrilic acid diphenyl ester or the following chemical formula (1). These compounds can be used alone or in combination of two or more as required.

  In the above chemical formula (1), A is a divalent or trivalent organic residue, preferably a methylene group, a lower alkylene group such as ethylene, 1,2-propylene or 1,3-propylene, 1,3 And divalent groups such as arylene group, 1,3-xylylene, 1,4-xylylene, and the like such as -phenylene and 1,4-phenylene.

  In the chemical formula (1), Q is a hydrocarbon group having 1 to 18 carbon atoms, and examples thereof include an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, and an allyloxy group. In the chemical formula (1), Z is an ester-forming functional group, and specifically, an alkyl ester, cycloalkyl ester, aryl ester, hydroxy group, carbon having 1 to 6 carbon atoms in a carboxy group or a carboxyl group. Examples thereof include a hydroxyl alkoxycarbonyl group having 2 to 7 atoms.

  As described above, the structure of the flame retardant compound used in the present invention is not limited, but it is particularly preferable to use the oligomer described in the following chemical formula (2). This compound contains a phosphorus atom in the molecule, and the lower limit of the average molecular weight by GPC measurement is usually 1170, preferably 2290 or more, more preferably 3410 or more. That is, the lower limit value of n in the chemical formula (2) is usually 3, preferably 6 or more, more preferably 9 or more. When the average molecular weight is less than 1170, for example, when the polyester film of the present invention is produced, volatilization of the organophosphorus compound, inhibition of crystallization of the polyester film, and further bleeding of the flame retardant compound cause film machinery. May lead to a decrease in the strength of the target. The upper limit of the average molecular weight of the flame retardant compound is not particularly defined, but if the molecular weight is excessively increased, the dispersibility in the polyester resin may deteriorate.

  The preferable phosphorus element content in the polyester film of the present invention varies depending on the thickness of the film, and the thinner the content, the higher the content tends to be required. This is presumably because the thinner the film, the greater the specific surface area and the easier the combustion proceeds. Specifically, it is necessary to satisfy 27.25 / T + 0.26 ≦ P ≦ 34.06 / T + 1.02 ≦ 2.00 when the phosphorus element content is P wt% and the film thickness is T μm. .52 / T + 0.34 ≦ P ≦ 34.06 / T + 0.85 ≦ 2.00, preferably 31.79 / T + 0.43 ≦ P ≦ 34.06 / T + 0.69 ≦ 2.00 Is more preferable. Further, it is more preferable that P ≦ 1.50 while satisfying the above conditions. When P <27.25 / T + 0.26, sufficient flame retardancy cannot be obtained. When P> 2.00, the film strength and productivity decrease due to the presence of an excessive flame retardant compound. When 34.06 / T + 1.02 <P <2.00, further improvement in flame retardancy is not expected even if a flame retardant compound is added. Rather, demerits such as reduced film strength and increased production costs are conspicuous. become. The addition amount of the flame retardant compound should be as small as possible within a range in which the required flame retardant class can be realized.

  In the present invention, the method for adding a flame retardant compound to a polyester film production system when producing a polyester film is not particularly limited, but a method for directly adding a flame retardant compound during polyester film production or a high concentration in advance. The method of preparing a flame retardant masterbatch is preferred. In addition, there is a method of adding at the time of polyester polymerization. In this case, the polyester and the flame retardant compound are copolymerized, and the melting point of the polyester is lowered. As a result, there is a concern that mechanical properties and heat resistance deteriorate. The

  The polyester film of the present invention may contain various inactive fine particles as necessary. The average particle diameter is preferably 0.5 μm or more and 3.0 μm or less, and more preferably 0.8 μm or more and 2.0 μm. Further, the addition amount of the fine particles is preferably 0.005 wt% or more and 0.5 wt% or less, and more preferably 0.01 wt% or more and 0.1 wt% or less. If the average particle size of the fine particles exceeds 3.0 μm or the addition amount exceeds 0.5% by weight, the flatness and / or transparency of the film may be impaired.

  Examples of the aforementioned inert fine particles include aluminum oxide, silicon oxide, titanium oxide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, calcium phosphate, lithium phosphate, magnesium phosphate, Examples thereof include lithium fluoride, zeolite, celite, kaolin, talc, carbon black, and crosslinked polymer fine particles as described in Patent Document 3. These fine particles can be used alone or in combination of two or more as required.

  The polyester film obtained in the present invention may be provided with a coating layer. As for the coating layer, it may be provided by in-line coating, which treats the film surface during the stretching process of the polyester film, or may be applied off-system on the film once manufactured, and may employ both offline coating. You may use together. In-line coating is preferably used in that it can be applied at the same time as film formation, and thus can be manufactured at low cost, and the thickness of the coating layer can be changed by the draw ratio.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

  Examples of the aqueous polymer that is dissolved, emulsified or suspended in water as the binder in the coating liquid composition include, for example, polyurethane resins, polyacrylic resins, polyester resins, epoxy resins, polyvinyl alcohol resins, and polyvinylidene chloride. Resin, polystyrene resin, polyvinyl pyrrolidone and copolymers thereof, but are not limited thereto. These compounds can be used alone or in combination of two or more.

  It is preferable that a crosslinking agent is also contained as a component in the coating liquid composition. Cross-linking agents include methylolated or alkylolized urea-based, melamine-based, guanamine-based, acrylamide-based, amide-based compounds, epoxy compounds, aziridine compounds, polyisocyanurates, block polyisocyanates, water-soluble polymers containing oxazoline groups , Silane coupling agents, titanium coupling agents, and zirco-aluminate coupling agents. In the coating solution, in order to improve applicability, inorganic and organic particles, lubricants, antistatic agents, antifoaming agents, applicability improvers, thickeners, as long as the effects of the present invention are not impaired. You may contain an antistatic agent, UV absorber, antioxidant, a foaming agent, dye, etc.

The coating layer of the present invention may be a coating layer containing an organosilane compound. Examples of the organosilane compound include monoalkoxysilane, dialkoxysilane, trialkoxysilane, tetraalkoxysilane, and the like, and a mixture or condensation reaction product thereof may be used. In particular, alkoxysilane having an organic functional machine in the molecule is preferable. A typical example thereof is an organic silane compound represented by the following general formula, and these are known as silane coupling agents.
XR ² Si (OR ¹ ) ₃ and (XR ² ) (YR ³ ) Si (OR ¹ ) ₂
(Here, R ¹ is a substituted alkyl group such as an alkyl group represented by a methyl group or an ethyl group or a methoxyalkyl group, and R ² and R ³ are each independently an alkylene group such as a propylene group, X, Y Are each independently an organic functional group).

  In the above general formula, the organic functional group of X or Y is preferably an amino group, an epoxy group, a vinyl group, a hydroxyl group, a carboxyl group, an epoxycyclohexyl group, a mercapto group, or a glycidyl group. The organic functional group may be a substituted amino group such as an N-β (aminoethyl) amino group or a substituted group such as polyethyleneimine. Specific examples of the silane coupling agent having an organic functional group include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-mercaptopropyltrimethoxysilane and the like are preferably exemplified. These may be used alone or in combination of two or more and, if necessary, a mixture or condensate containing an alkoxysilane having no functional group.

  The organosilane compound can be used after diluted with an alcohol solvent, but is preferably an aqueous system, and in this case, various surfactants can be blended for the purpose of improving coating properties. Further, if necessary, one or more of the above-mentioned aqueous polymers may be used in combination to improve the coating property. In addition, inorganic particles or organic particles may be added to the coating agent of the present invention for the purpose of ensuring the slipperiness of the coated surface.

  It is also possible to contain particles in the coating layer in order to improve the slipperiness and blocking of the coating layer. Examples of the particles used include inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

(1) Phosphorus element content measurement The phosphorus element content in a sample was measured using the ICP emission spectrometer (730-ES made from Varian). In the measurement, SPST XSTC-22 (phosphorus content: 100 ppm) was used as a standard solution, and calibration curves were prepared from three types of solutions: stock solution, 10-fold dilution (10 ppm) and 100-fold dilution (1 ppm). .

(2) IV measurement A sample was added to a 1: 1 phenol / 1,1,2,2-tetrachloroethane weight ratio solution to a concentration of 1.0 g · dl ⁻¹ . This solution was heated at 110 ° C. for 20 minutes to dissolve the polyester resin composition, and then the container was immersed in tap water for 30 minutes and allowed to cool to room temperature. Using a capillary viscometer “VMS-022UPC • F10” (manufactured by Hosei Co., Ltd.), the flow time of this solution and the flow time of only the phenol / 1,1,2,2-tetrachloroethane solution (reference solution) were measured. From these time ratios, the intrinsic viscosity was calculated using the Huggins equation. At that time, the Huggins constant was assumed to be 0.33. The unit of IV is “dl · g ⁻¹ ”.

(3) Flame retardance A flame test of a polyester film was conducted with reference to a VTM test of UL94, a flammability test standard for plastic materials issued by Underwriters Laboratories (UL). Since the VTM test often varies in result, for the purpose of further improving the reliability of the evaluation, a test was normally performed 10 times for each type of polyester film sample 10 times. Below, a flame-retardant evaluation procedure is demonstrated.

(I) Sample preparation The film was cut into 200 mm x 50 mm, and a marked line was put in the width direction of the sample at 125 mm from the lower end of the sample. The vertical axis of the sample was tightly wound around the vertical axis of a rod having a diameter of 12.7 mm to form a cylindrical shape with a length of 200 mm in which a 125 mm line was exposed to the outside. Cellotape (registered trademark) was wound around and fixed at a position 5 mm above the marked line (75 mm side) and 5 mm below the upper end of the sample. Finally, the rod was pulled out to obtain a test piece.

(Ii) Conditioning The test piece obtained in (i) above was treated for 48 hours or more in an environment of (a) temperature 23 ± 2 ° C. and relative humidity 50 ± 5%. (B) 168 ± at temperature 70 ° C. ± 2 ° C. After the treatment for 2 hours, prepare 10 pieces each cooled for 4 hours or more at an air temperature of 23 ± 2 ° C. and a relative humidity of 20% or less. (A) is called an acceptance state, and (b) is called an aging state.

(Iii) Fixing the test piece The vertical axis of the test piece of (ii) is fixed with a clamp with a spring at a position of 6 mm in the length of the upper end, and the upper end of the cylinder is closed to provide a chimney effect during the test. Prevent it from occurring. Immediately under the test piece, a piece of 0.05 g absorbent cotton (50 mm × 50 mm) having a maximum thickness of 6 mm is placed horizontally, and the lower end of the test piece is 300 mm above the absorbent cotton (FIG. 1). reference).

(Iv) Burner adjustment Adjust so that a blue flame with a height of 20 mm comes out from the burner. In order to put out the flame, the supply amount of the combustible gas is adjusted so that a blue flame having a yellow tip and a height of 20 mm comes out. Then increase the air supply until the yellow tip disappears. Then measure the flame height again and readjust as necessary. Methane is used as the combustible gas, and the flow rate of the methane gas supply to the burner is adjusted by a method according to “ASTM D 5207”.

(V) First flame contact The flame is applied to the center point of the lower end of the test piece that is not wound, and the tip of the burner is 10 ± 1 mm below the center point. Continue flame contact for 3 seconds. However, since the length and center position of the test piece change due to combustion, the position of the burner is moved according to the change. If melt or fumes are dripping during flame contact, tilt the burner angle up to 45 degrees and just enough of the specimen to prevent them from falling into the burner tube. Move from below. Meanwhile, a distance of 10 ± 1 mm must be maintained between the center of the tip of the burner and the remaining portion of the test piece. Immediately after 3 seconds of indirect flame, the burner is moved away from the test piece at a rate of about 300 mm per second by at least 150 mm, and at the same time, the afterflame time t ₁ is started to be measured in seconds by the aging device.

(Vi) Second flame contact When the after flame of the test piece resulting from the first flame contact disappears (even if the burner is not further away from the test piece to more than 150 mm), immediately remove the burner to the test piece. The burner is held at a location 10 mm ± 1 mm away from the lower end of the remaining part of the test piece. However, if necessary, the burner is moved so that the behavior of falling objects due to combustion can be confirmed without any obstructions. Immediately after the 3 second indirect flame, the burner is moved away from the test piece at a rate of about 300 mm per second by at least 150 mm, and at the same time, the afterflame time t ₂ is started to be measured in seconds by the aging device.

(Vii) Flame Retardancy Evaluation Criteria UL94 VTM tests are performed on 10 samples each in the accepting state and the aging state, and all samples are evaluated by whether or not the conditions in Table 1 below are satisfied. However, if only one sample out of 10 is rejected, the sample is accepted. This reflects the fact that the actual VTM test is performed with 5 samples as a set, and if only one failure is received, retesting is allowed only once.

  The manufacturing method of the raw material used in the Example and the comparative example is as follows. However, these are merely examples for explaining the present invention, and do not limit the raw materials that can be used in the present invention.

≪Production of flame retardant compounds≫
9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (the following chemical formula (3)) was added to a 3 L glass flask equipped with a stirrer, thermometer, gas inlet and distillation port. ) 7.8 mol and 25.97 mol of ethylene glycol were added and the flask was heated until the temperature of the contents reached 100 ° C. to dissolve the components. Next, 7.96 mol of itaconic acid was added with stirring, and the flask was heated from the distillation port through a vacuum device in a vacuum state of 30 Torr to bring the contents to a boil. At this point, the produced water was removed by adjusting the distillation rate of the distillation port. Furthermore, while maintaining the boiling state of the contents, the temperature in the flask was raised, and the degree of vacuum was also lowered accordingly. As a breakdown, it took 4 hours for the temperature of the contents to reach 185 ° C., and the degree of vacuum at this point was 430 Torr. Further, the heating was continued, and finally the contents were heated until the temperature reached 200 ° C. After confirming this point, nitrogen gas was blown into the reactor to return the flask to normal pressure. The reaction mixture is an ethylene glycol solution of the following chemical formula (4). Moreover, a solid compound of the following chemical formula (4) can be purified by removing ethylene glycol under reduced pressure.

Subsequently, 130 g of ethylene glycol containing 0.33 g of antimony trioxide (Sb ₂ O ₃ ) and zinc acetate dihydrate [(AcO) ₂ Zn · 2H ₂ O] was added into the flask. The inside of the flask was maintained at 200 ° C., and the degree of vacuum was gradually increased to obtain a vacuum state of 1 Torr or less. Furthermore, the temperature of the content was raised to 220 ° C., and the point at which the distillation of ethylene glycol was extremely reduced was determined as the reaction end point. After confirming this point, the content is solidified in a SUS container while pressurizing with nitrogen gas, so that it is a yellowish transparent glassy solid, a flame-retardant organic phosphorus compound, that is, the following chemical formula (5) 2- (9,10-dihydro-9-oxa-10-oxide-10-phosphaphenanthrene-10-yl) methylsuccinic acid bis- (2-hydroxyethyl) represented by the formula: It was.

  By repeating the above operation, 2- (9,10-dihydro-9-oxa-10-oxide-10-phosphaphenanthrene-10-yl) methyl succinic acid bis- (2) added in Examples and Comparative Examples described later is used. The required amount of deethylene glycol polycondensate of (hydroxyethyl) was ensured.

  Regarding this flame-retardant organophosphorus compound, the weight average molecular weight (Mw) was 6,800 from GPC analysis of the product. In this analysis, a peak in the low molecular weight region, which is estimated to be an acid anhydride of a compound represented by the following chemical formula (6) or a cyclic ester of a compound represented by the chemical formula (6) and ethylene glycol, was also observed. It was. Further, XRF measurement showed that the phosphorus content was 8.31 wt%. Therefore, the average value of n of the flame retardant organophosphorus compound was equivalent to 18.1. The flame retardant organophosphorus compound is hereinafter referred to as FR1.

≪Manufacture of polyester A≫
100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol are used as starting materials, 0.02 part by weight of magnesium acetate tetrahydrate as a catalyst is taken in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was terminated. After adding 0.03 part by weight of ethyl acid phosphate to this reaction mixture, it was transferred to a polycondensation tank, 0.04 part by weight of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to IV = 0.64 due to a change in stirring power of the reaction vessel, and polyester A was obtained.

≪Manufacture of polyester B≫
Polyester B was obtained by using polyester A as a starting material and increasing the molecular weight by solid phase polymerization at 220 ° C. under vacuum. The obtained polyester B had an IV of 0.85.

≪Manufacture of polyester C≫
The recyclable PET bottle was washed, dried, crushed, re-pelleted and then re-pelletized polyester, and then subjected to high-molecular weight polymerization at 220 ° C. under vacuum to obtain pellet-like polyester C. The obtained polyester C had an IV of 1.10.

≪Production of polyester D≫
Polyester A and FR1 were compounded in a twin screw extruder with a vent at a ratio of 65:35 to obtain polyester D which is a flame retardant compound MB. The obtained polyester D had an IV of 0.43.

≪Manufacture of polyester E≫
In the production of polyester A, polyester E was obtained in the same manner as the polyester A prepolymer except that 0.1 part by weight of silica particles having an average particle size of 2.30 μm was blended at the end of the transesterification reaction. The obtained polyester E had an IV of 0.62.

Examples 1-15:
The polyester resin mixed at the ratio shown in Table 2 was fed into the same direction twin screw extruder set at 270 ° C. This polyester resin is extruded through a gear pump and a filter from a base into a sheet shape, rapidly cooled and solidified using an electrostatic cooling method with a rotary cooling drum whose surface temperature is set to 30 ° C., and is substantially amorphous. A sheet was obtained. The obtained amorphous sheet was stretched 3.0 times at 85 ° C. in the longitudinal direction, then stretched 3.0 times at 125 ° C. in the transverse direction, heat treated at 215 ° C., and biaxially stretched with a thickness of 50 to 250 μm. A polyester film was obtained. The film obtained in any of the examples exhibited excellent flame retardancy and production was stable.

Comparative Example 1:
By processing the polyester resin mixed at the ratio shown in Table 2 in the same manner as in the example, a biaxially stretched polyester film having a thickness of 50 μm was obtained. Although this film could be produced very stably, it was inferior in flame retardancy.

Comparative Example 2:
An attempt was made to process the polyester resin mixed at the ratio shown in Table 2 in the same manner as in the Examples. However, the IV resin was extremely low and could not be formed into a film.

Comparative Example 3:
By processing the polyester resin mixed at the ratio shown in Table 2 in the same manner as in the example, a biaxially stretched polyester film having a thickness of 100 μm was obtained. This film was inferior in flame retardancy as in Comparative Example 1.

Comparative Example 4:
By processing the polyester resin mixed at the ratio shown in Table 2 in the same manner as in the example, a biaxially stretched polyester film having a thickness of 100 μm was obtained. Although this film was excellent in flame retardancy, the film frequently broke during production, and stable production was difficult.

Comparative Example 5:
By processing the polyester resin mixed at the ratio shown in Table 2 in the same manner as in the example, a biaxially stretched polyester film having a thickness of 188 μm was obtained. This film was inferior in flame retardancy as in Comparative Example 1.

According to the present invention, it is possible to provide a polyester film that achieves both high flame retardancy and inherent heat resistance and mechanical properties of a polyester resin in a specific thickness range. The industrial value of the present invention is high.

1 Clamp 2 Tape 3 125mm Mark 4 Burner 5 Cotton

Claims (6)

A flame retardant polyester film which is a polyester film containing an organic phosphorus flame retardant compound and satisfies the following formula (1).
27.25 / T + 0.26 ≦ P ≦ 34.06 / T + 1.02 ≦ 2.00 (1)
(In the above formula, T is the thickness (μm) of the polyester film, and P means the phosphorus element content (% by weight) in the polyester film) The flame-retardant polyester film according to claim 1, which satisfies the following formula (2).
29.52 / T + 0.34 ≦ P ≦ 34.06 / T + 0.85 (2) The flame-retardant polyester film according to claim 1, which satisfies the following formula (3).
1.79 / T + 0.43 ≦ P ≦ 34.06 / T + 0.69 (3) The flame-retardant polyester film according to claim 1, wherein the polyester film has a thickness T of 100 μm or more. Intrinsic viscosity is 0.50 or more, The flame-retardant polyester film in any one of Claims 1-4. The flame retardant polyester film according to claim 1, wherein the flame retardant compound is a compound represented by the following chemical formula.