JP3397022B2 - Polyester film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester film. More specifically, it relates to a polyester film having excellent flame retardancy, heat resistance, and hydrolysis resistance.

[0002]

2. Description of the Related Art Polyester represented by polyethylene terephthalate has excellent physical and chemical properties and is widely used as fibers, films and molded articles. Especially for textiles, clothes, bedding, curtains, carpets, etc.
In addition to magnetic tapes, capacitors, and photographs, films are also used in a wide range of applications such as home appliances, electronic machines, etc.

On the other hand, polyester is generally flammable, and it is desired to impart flame retardancy to various processed polyester products from the viewpoint of fire prevention.

[0004] Halogen compounds and phosphorus compounds are known as flame retardants capable of imparting flame retardancy to polyester, but in recent years there has been a move toward non-halogenation, which corresponds to the danger of ozone layer destruction, and weather resistance. Phosphorus compounds are excellent in terms of properties and coloring.

Conventionally, as a method of imparting flame retardancy to polyester, a method of copolymerizing a flame retardant during production of polyester (copolymerization method) is known as a method having high industrial value.

Therefore, many methods of copolymerizing a phosphorus compound with polyester for the purpose of imparting flame retardancy have been proposed. For example, JP-B-49-22958 discloses a method of copolymerizing a phosphoric ester with polyester as a phosphorus compound, and JP-A-59-91122 discloses a method of copolymerizing phosphonic acid as a phosphorus compound. 20
771 and JP-A-52-142796, a method of incorporating a phosphorus compound having a special ester-forming functional group, and JP-B-53-13479 disclose a method of copolymerizing carboxyphosphinic acid. 1-4052
JP-A-1 discloses a method of copolymerizing a phosphine oxide derivative.

However, in the case where a polyester is copolymerized with a phosphoric acid ester, the melting point (Tm) is lowered by copolymerizing the phosphoric acid ester until the polyester is rendered flame-retardant, so that the heat resistance is deteriorated. There are drawbacks such as. In addition, it is thought that this is mainly due to the weakness of the PO bond in the phosphate ester compound, but the hydrolysis resistance of the polyester is reduced, and the main chain is cleaved during molding, resulting in a decrease in molecular weight. There are drawbacks. That is, if the amount of copolymerization is increased to obtain higher flame retardancy, heat resistance and hydrolysis resistance will be worse, and heat resistance, hydrolysis resistance and flame retardance cannot be achieved at the same time. It was the current situation that the range was limited.

On the other hand, many techniques related to so-called blending, in which a flame retardant is added to a polyester after polymerization and kneaded, are well known. For example, JP-A-48-559
Japanese Patent Publication No. 50 discloses a flame-retardant polyester composition containing a compound containing halogen and phosphorus in the molecule. Further, JP-A-48-91318, JP-A-49-10242, and JP-A-59-59916 also disclose a method of kneading and blending a phosphorus compound. However, these known methods are not ones in which halogen is contained in the flame retardant, flame retardancy, heat resistance, hydrolysis resistance, and bleedout resistance are all sufficiently satisfied, and the method used as a film It did not disclose any specific thought, let alone the particular effect in that case.
Further, JP-A-63-227623 discloses a method of using a composition blended with a phosphorus compound as a film, but it has sufficient heat resistance and hydrolysis resistance.
The mechanical properties, flame retardancy, and bleedout resistance were not all satisfied.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a laminated polyester film excellent in flame retardancy, heat resistance and hydrolysis resistance.

[0010]

The above object is to add an organic phosphorus compound to a polyester in an amount of 0.0
Containing 5～3Wt%, crystal fusion endothermic peak temperature Tm measured by a differential scanning calorimeter (℃) is not less 240 ° C. or higher, and the following relationship between the total amount of phosphorus contained a Tm (a ) Is established, at least one film layer (A layer) made of a polyester composition is provided.
Laminated polyester film consisting of at least two layers
Achieved by Rum .

Tm ≧ Tmb-6P (a) (where Tm (° C.) is the crystal melting endothermic peak temperature, Tmb
(° C) is the crystal melting endothermic peak temperature when the organophosphorus compound is not contained (base polymer), P (wt%) is the total amount of phosphorus contained)

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention is mainly composed of a dicarboxylic acid residue and a glycol residue.

In the present invention, the dicarboxylic acid residue can be formed from dicarboxylic acid or its ester-forming derivative. Specifically, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4 ' Examples thereof include diphenyl ether dicarboxylic acid, 4,4′-diphenyl sulfone dicarboxylic acid and their ester-forming derivatives.

As the glycol component, ethylene glycol, 1,2-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,
5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2- Examples thereof include aliphatic, alicyclic and aromatic diols such as bis (4'-β-hydroxyethoxyphenyl) propane.

Further, phosphorus-containing dicarboxylic acid, diol, or oxycarboxylic acid can also be used as a copolymerization component. Examples of such compounds include bis (2-carboxyethyl) -1,1,3,3-tetramethylbutylphosphine oxide, bis (2-carboxyethyl)
-1,1,3,3-Tetraethylbutylphosphine oxide, bis (2-carboxymethyl) -1,1,3,3-tetramethylbutylphosphine oxide, bis (2-carboxyethyl)-
tert-butylphosphine oxide, bis (2-carboxymethyl) -tert-butylphosphine oxide, bis (2-
Examples thereof include carboxyethyl) -methylphosphine oxide and bis (2-carboxymethyl) -methylphosphine oxide.

Only one copolymerization component such as dicarboxylic acid, diol, or oxycarboxylic acid may be used,
Further, two or more kinds may be used in combination, but if the amount of the copolymerization component is too much with respect to the main constituent unit component, heat resistance is deteriorated, which is not preferable. Therefore, in the case of copolymerization, the total amount is preferably 5 mol% or less with respect to the main constituent unit component.

The method for producing a polyester in the present invention is a method for producing a low polymer by subjecting an aromatic dicarboxylic acid or its ester-forming derivative and a glycol, and further the above-mentioned copolymerization component to an esterification reaction or a transesterification reaction. It can be produced by a one-step reaction, a second-step reaction of polycondensing this low polymer, and further adding and kneading a flame-retardant compound to the polyester thus obtained.

The polyester of the present invention is obtained by adding and blending an organic phosphorus compound to the polyester as a base. The method of adding these organophosphorus compounds to the polyester is not particularly limited, but a method of adding just before the completion of the above polyester polymerization or a method of kneading the above polyester chips with a biaxial kneading extruder is simple and preferable.

The addition amount of the organic phosphorus compound is 0.05 to 3 wt% as the phosphorus amount based on the polyester in order to have high flame retardancy and not to impair the heat resistance, and it is preferable.
It is 0.1 to 2.5 wt%.

Further, nitrogen-based and other flame-retardant aids such as melamine and particles of titanium oxide, calcium carbonate, silica, alumina and the like may be added to such an extent that the physical properties of the film are not deteriorated.

The polyester composition and film of the present invention have a crystal melting endothermic peak temperature Tm of 240 ° C. or more measured by a differential scanning calorimeter, and the following relationship between Tm and the total amount of phosphorus contained. The formula (a) is established. Further, it is preferable that Tm is 245 ° C. or higher and the following relational expression (b) is established.

Tm ≧ Tmb -6P (a) Tm ≧ Tmb -5P (b) (where Tm (° C) is the crystal melting endothermic peak, Tmb (° C)
Is the crystal melting endothermic peak when no organic phosphorus compound is contained (base polymer), P (wt%) is the total amount of phosphorus contained)

The crystal melting endothermic peak is one index showing the heat resistance of the polymer, and the higher it is, the higher the heat resistance is. Therefore, in order to obtain sufficient heat resistance as the target flame-retardant insulating film, at least Tm needs to be 240 ° C. or higher. On the other hand, the larger the amount of phosphorus, the more the flame retardancy improves.Therefore, the degree of decrease in Tm with the increase in the amount of phosphorus means that the higher the flame retardancy, the more the heat resistance decreases. It is preferable that the degree of decrease in Tm with an increase in the amount of phosphorus is small. From this point of view, the crystal melting endothermic peak Tm of the polyester composition and film of the present invention preferably satisfies the relational expression (a) and the relational expression (b).

As the above-mentioned organic phosphorus compound, it is excellent in terms of heat resistance and hydrolysis resistance to use a compound having a structure represented by the following chemical formula (1).

[0025]

[Chemical 2] (Wherein, X is a phenylene group, a naphthalene group, a biphenyl group or the aromatic group selected from alkylene substituents of 0-5 carbon atoms, Ar ₁ to Ar ₄ is an alkylene substituted phenylene group having a carbon number of 1 to 5)

The aromatic group of X is a phenylene group, a naphthalene group, a biphenyl group, or a carbon number of 0 to 5 thereof.
Selected from the alkylene-substituted compounds, and preferably a phenylene group or a biphenyl group.

The use of a flame retardant having such a structure is also disclosed in JP-A-48-91318, in which a phenylene group was selected as Ar1 to Ar4. The important difference is in the choice of Ar1 to Ar4. That is, the blend type flame retardant is not preferable when the molecular weight is too large as compared with the amount of phosphorus contained, since the amount of addition necessary for producing the target flame retardancy increases accordingly, while the molecular weight is If it is too low, the volatility will increase,
Not only is it easy to scatter out of the system during the reaction, but bleed-out is also likely to occur, which is not preferable. Therefore, the flame retardant in the present invention has 1 to 1 carbon atoms as Ar1 to Ar4.
A phenylene group in which one or more hydrogen atoms are substituted with an alkyl group of 5 is preferred, and a xylene group is preferred.

Therefore, the compound represented by the chemical formula (1) is, for example, 1,3-bis (di-2,6-xylenoxy).
Phosphoryloxy) benzene, 1,4-bis- (di-2,6-xylenoxyphosphoryloxy) benzene, 4,4'-bis-
(Di-2,6-xylenoxyphosphoryloxy) biphenyl, 3,5-bis- (di-2,6-xylenoxyphosphoryloxy) biphenyl, 3,3'-bis- (di-2,6-xylenoxyphosphoryloxy) Biphenyl etc. can be given.

The method for producing the base polymer will be specifically described. For example, when polyethylene terephthalate is used as the base polymer, dimethyl terephthalate and ethylene glycol are subjected to transesterification reaction according to a conventional method. Then, the pressure is gradually reduced, and a polycondensation reaction is performed at a temperature of 200 to 300 ° C. under a reduced pressure of 0.001 to 3 torr to obtain a polyester. It can also be produced by a conventionally known direct polymerization method using dicarboxylic acid as the acid component. As the reaction catalyst, conventionally known titanium compounds, lithium compounds, calcium compounds, magnesium compounds, antimony compounds, germanium compounds and the like can be used. Further, it is also possible to increase the molecular weight by solid phase polymerization.

The polyester thus obtained is
According to a conventional method, a biaxially stretched film can be completed by drying, then melt-extruding to obtain an unstretched sheet, followed by biaxially stretching and heat treatment. Biaxial stretching may be either longitudinal or transverse sequential stretching or biaxial simultaneous stretching, and the stretching ratio is not particularly limited, but usually 2.0 to 5.0 times both longitudinal and transverse are suitable. Alternatively, after longitudinal or transverse stretching, it may be re-stretched in either the longitudinal or transverse direction.

Further, a polyester having a composition different in the amount of phosphorus and the like may be further used to form a film having a laminated structure of two or more layers. When using a laminated film,
In a confluent block of two or more layers having a rectangular laminated portion, after extruding in a sheet form from a T-shaped die so that each layer is laminated with a target thickness ratio and composition, and an unstretched sheet is obtained. Similarly to the case of the above-mentioned single layer, it can be obtained by forming a biaxially stretched film according to a conventional method.

When such a film having a laminated structure of two or more layers is used, it is possible to meet various required characteristics and uses by changing the structure. Therefore, in the case of a laminated film, it is preferable to change the phosphorus concentration of each layer to give each layer different characteristics.
To do so, the amount of phosphorus contained in layer A should be 0.05 to 3 wt.
%, The amount of phosphorus contained in the other layer is preferably 0 to 2 wt%, and the amount of phosphorus contained in the layer A is preferably larger than the amount of phosphorus contained in the other layer.

Here, the role given to the A layer is to give the laminated film high flame retardancy. Therefore, the amount of phosphorus contained in the A layer is 0.05 to 3 wt%, preferably
It is 0.1 to 2.5 wt%. If the phosphorus content is 0.05 wt% or less, sufficient flame retardancy cannot be obtained. Further, if it is 3 wt% or more, sufficient heat resistance cannot be obtained.

On the other hand, the role given to the other layers is to impart bleed-out resistance, heat resistance and hydrolysis resistance to the laminated film. For this purpose, the amount of phosphorus contained in the other layers is preferably 0 to 2 wt%, more preferably 0.01 to 1.5 wt%.
% Is preferred. When the phosphorus content is 2 wt% or more, sufficient heat resistance cannot be obtained, and the other layers themselves are likely to absorb water, so that hydrolysis easily occurs, and bleeding out may occur, which is not preferable.

By forming a laminated film from these two or more kinds of films with various arrangements and thickness ratios, it is possible to meet various required characteristics and uses.

For example, when bleed-out is a problem, another layer having a low phosphorus compound concentration protects the A layer having a high phosphorus compound concentration, thereby suppressing the bleed-out of the phosphorus compound from the A layer. can do. Further, when the phosphorus compound is contained in a high concentration, it becomes easy to absorb water, so that the layer A, which easily absorbs water, is also protected from moisture in the outside air, and hydrolysis resistance and mechanical properties are improved. In this case, since the layer having a low phosphorus concentration is on the outside (the layer in contact with oxygen), the A layer having a high phosphorus concentration needs to be sufficiently thick in order to maintain high flame retardancy. For this purpose, the thickness ratio of the layer A to the total thickness of the film may be 50% or more, and preferably 60% or more. If it is less than 50%, sufficient flame retardancy may not be obtained. On the other hand, it is preferable that the thickness ratio of the A layer is as high as possible, because higher flame retardancy can be realized.

For example, when a film having a two-layer structure is prepared as an insulating protective film for a printed circuit board, an A layer having a high phosphorus concentration is contained on the side to be attached to the printed circuit board and a blend compound is contained in the other B layer. When the film is formed so as to be a PET single layer that does not exist, the B layer can suppress the bleeding out from the A layer and can protect the A layer from the moisture of the outside air.

On the other hand, when flame retardancy, heat resistance and mechanical properties are required to be higher than bleed-out resistance and hydrolysis resistance, the thickness ratio of the layer A to the total thickness of the film is 5
It may be configured to be less than 0%, more preferably less than 45%. If the thickness ratio of the A layer is 50% or more, the required high heat resistance and mechanical properties cannot be obtained. In this case, the higher the phosphorus concentration of the film surface layer that is in contact with oxygen in the outside air, the higher the flame retardancy can be obtained. Is preferred.

Further, by forming the laminated structure to have three or more layers and covering both sides of the A layer with another layer having a low phosphorus concentration, the bleed-out resistance can be obtained even when both sides of the film are exposed to the outside air. A film having high properties can be obtained. On the contrary, by making both layers of the other layer having a low phosphorus concentration covered with the A layer, higher flame retardancy and heat resistance,
It is possible to obtain a film having both mechanical properties.
In this way, the use range can be further widened by adopting a structure having three or more layers.

Further, in the case where these laminated structures are used, by forming one of the layers using polyester copolymerized with a phosphorus compound, flame retardancy, heat resistance, mechanical properties, bleed-out resistance, It is also possible to provide a film that is well balanced in hydrolysis resistance.

The polyester film of the present invention thus obtained is very useful, for example, as an insulating film for a print substrate or an insulating tape wound around a shield wire.

[0042]

EXAMPLES The present invention will now be described in more detail by way of examples. The properties in the examples were measured as follows.

A. Crystal melting endothermic peak Tm (° C.) measured by a differential scanning calorimeter (hereinafter referred to as DSC) at 16 ° C.
The measurement was performed under a temperature rising / falling condition of 1 / min. The polyester used as the kneading base polymer in this example had Tmb = 253 ° C.

B. Intrinsic viscosity of polymer ([η]) This is a value measured at 25 ° C. using o-chlorophenol as a solvent.

C. The total phosphorus atom content of polyester and film was measured by a fluorescent X-ray method [TFK3064 type (manufactured by Geiger Flex Co.)].

D. Flame resistance of polyester film A 10 cm x 5 mm strip type test piece is made from the obtained polyester film, and a flameproof test device manufactured by Daiei Kagaku Seiki Seisakusho
With the SFT-30, the 45 ° Meckel microburner method was used, and the test piece burning distance after one-time flame contact for 15 seconds was evaluated as follows.

[0047] ◎: Burning length 0 to 4 cm ○: Burning length 4 to 7 cm ×: Burning length 7 to 10 cm (burnt down)

E. A heat-resistant film sample of a polyester film is heat-treated in a hot air oven at a temperature of 160 ° C., the breaking elongation is measured by sampling, and the breaking elongation is measured at a ratio of 50% to the breaking elongation of an untreated film. The retention half-life was used as an index of heat resistance. The evaluation results are shown below.

[0049] ⊚: Break elongation retention half-life of 200 hours or more ◯: Breaking elongation retention rate half-life is 100 to 200 hours X: Breaking elongation retention half-life is 100 hours or less

F. 5 g of polyester chips together with 3 g of water were placed in a hydrolysis resistance test tube, which was placed in a pressure resistant pot containing 50 g of water and sealed, and heated in a polyethylene glycol bath at 150 ° C. for 1 hour. In this case, the amount of increase in the carboxyl terminal group was quantified and used as an index of hydrolysis resistance. The evaluation results are shown below.

[0051] A: Increase amount is 0 to 50 equivalents / t ◯: Increase amount is 50 to 100 equivalents / t X: Increase amount is 100 equivalents / t or more

G. The bleed-out resistant film was heated in a hot air oven at 150 ° C. for 1 hour, and the surface was visually compared and judged. ⊚: No bleed-out substances are observed on the surface. ◯: Some bleed-out substances are observed on the surface. X: A large amount of bleed-out substances are observed on the surface. The abbreviations in the table indicate the following compounds. M: 1,3-bis- (di-2,6-xylenoxyphosphoryloxy) benzene P: 1,4-bis- (di-2,6-xylenoxyphosphoryloxy) benzene B: 4,4'-bis (di -2,6-xylenoxy phosphoryloxy) biphenyl CMP: carboxymethyl-ethylphosphinic acid

Reference Example 1 The polyester as the base polymer used in each of the examples was manufactured as follows.

In a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 wt of magnesium acetate based on the amount of dimethyl terephthalate.
%, And diantimony trioxide (0.04 wt%) were added, and a transesterification reaction was carried out by heating with a conventional method and heating.

Next, 0.026 wt% of trimethyl phosphate is added to the transesterification reaction product with respect to the amount of dimethyl terephthalate, and then the product is transferred to the polycondensation reaction layer.

Then, the reaction system was gradually decompressed while heating and raising the temperature, and polymerization was carried out by a conventional method at 290 ° C. under a reduced pressure of 1 mmHg to obtain a polyester chip having an intrinsic viscosity [η] of 0.65 dl / g.

[0057] and polyester chips 100 parts by weight produced in Experiment Example 1 Reference Example 1, 1,3-bis were mixed (di-2,6-xylenoxy phosphoryloxy) benzene 25 parts by weight, vented using a feeder The mixture was supplied to a twin-screw extruder, the vent port was maintained at a vacuum degree of 10 torr, and the mixture was kneaded at a temperature of 290 ° C. for a residence time of 5 minutes to obtain the target polyester. The Tm of this polyester was 246 ° C., and the phosphorus content in the polyester was 1.7 wt%.

The polyester chips were sufficiently dried, supplied to an extruder, melted at 290 ° C., extruded in a sheet form from a T-shaped die, and cooled and solidified by a cooling drum at 30 ° C. to obtain an unstretched film. Then unstretched film 9
It is heated to 5 ℃ and stretched 3.3 times in the machine direction.
The film was heated to 0 ° C., stretched 3.3 times in the transverse direction, and heat treated at 200 ° C. to obtain a film having a thickness of 100 μm. This film had good flame retardancy and hydrolysis resistance, and had a half-life of retention of elongation at break of 300 hours, which was excellent in heat resistance. The results are shown in Table 1.

[0059]

[Table 1] Experimental Examples 2 and 3 1,3-bis - (di-2,6-xylenoxy phosphoryloxy)
1,4-bis- (di-2,6-xylenoxy) instead of benzene
Phosphoryloxy) benzene, or 4,4'-bis (di-
Except for using 2,6-xylenoxy phosphoryloxy) biphenyl were obtained experiment the same manner as in Example 1, a polyester, a film. As shown in the table, a film having good flame retardancy, heat resistance and hydrolysis resistance was obtained.

[0060] In addition to the amount of experimental example 4-9 organophosphorus compound to be added was changed as shown in the table, to obtain a polyester and film in the same manner as Experiment Example 1. The results are shown in Table 1.

[0061] Using the polyester polymerized in Comparative Example 1 Reference Example 1, it was subjected to film formation in Experiment Example 1 and the same method. Although the film was excellent in heat resistance, it was obviously inferior in flame retardancy.

Comparative Example 2 To a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 wt% of magnesium acetate and 0.04 wt% of diantimony trioxide were added with respect to the amount of dimethyl terephthalate. The temperature was raised by the method to carry out the transesterification reaction. Next, 0.026 wt% of trimethyl phosphate is added to the transesterification reaction product with respect to the amount of dimethyl terephthalate, and then the product is transferred to the polycondensation reaction layer. Next, 8.5 parts by weight of carboxymethyl-ethylphosphinic acid was added, and the reaction system was gradually depressurized while heating and heating to a pressure of 1 mmHg, and
Polymerized by a conventional method at 90 ℃, intrinsic viscosity [η] 0.73dl
A polyester chip of / g was obtained. Using this polyester, to obtain a film having a thickness of 100μm in the same manner as Experiment Example 1.

Although this film exhibits sufficient flame retardancy, it has a low Tm of 228 ° C. and a half-life of retention of elongation at break of 3%.
The film was inferior in heat resistance to 0 hours, and was also poor in hydrolysis resistance.

[0064] The mixing amount of Comparative Example 3-8 organophosphorus compounds, except for changing the amounts shown in Table was obtained experiment the same manner as in Example 1, a polyester, a film. Comparative Examples 4, 6 and 8 with a large phosphorus content were inferior in heat resistance and hydrolysis resistance, and Comparative Examples 3, 5 and 7 with a small phosphorus content were inferior in flame retardancy.

[0065] The three-layer junction block having a rectangular lamination portion which is adjusted to Example 1 290 ° C., the same polyester as that used in Experiment Example 4 in the main layer, was used in Reference Example 1 on both sides sublayer laminated portion The polyester is supplied and the thickness ratio of outer layer / inner layer / outer layer is 1 from the T-type die.
/ 8/1 was extruded into a sheet and cooled and solidified in a cooling drum at 30 ° C. to obtain an unstretched laminated film. Then, the unstretched film is heated to 95 ° C. to 3.3 in the longitudinal direction.
The film was double-stretched, further heated to 100 ° C., laterally stretched 3.3 times, and heat-treated at 200 ° C. to obtain a film having a thickness of 100 μm.

It showed sufficient flame retardancy, heat resistance and hydrolysis resistance, and no bleed-out product was observed in the bleed-out test.

[0067] The same polyester as that used in Experiment Example 4 Example 2 main layer, except for supplying a polyester used in Experiment Example 7 on both sides sublayer laminated part, the film in the same manner as in Example 1 Obtained. Example
Similar to No. 1 , sufficient flame resistance, heat resistance, hydrolysis resistance, and bleed-out resistance were obtained.

[0068] The same polyester as that used in Example 3 main layer in Reference Example 1, except that supplying polyester used in Experiment Example 4 on both sides sublayer laminated unit, to obtain a film in the same manner as in Example 1 It was Although it is slightly inferior in heat resistance and hydrolysis resistance as compared with Examples 1 and 2 ,
A film having excellent flame retardancy was obtained .

Comparative Example 9 A film was obtained in the same manner as in Example 1 except that the thickness ratio of outer layer / inner layer / outer layer was 3/4/3. Sufficient flame retardancy could not be obtained because the phosphorus content in the entire film was low and a thick layer of low phosphorus concentration, which was easy to burn, was laminated.

Comparative Example 10 A film was obtained in the same manner as in Example 3 except that the thickness ratio of outer layer / inner layer / outer layer was 3/4/3. It shows high flame retardancy, and has reached a certain level of heat resistance and hydrolysis resistance, but it was insufficient for applications requiring high heat resistance.

[0071]

EFFECT OF THE INVENTION The polyester film obtained by the present invention is excellent in flame retardancy, and also has high heat resistance and hydrolysis resistance, and is particularly useful for insulating home electric appliances and electronic appliances. .

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 5/18 C08L 67/00-67/02

Claims (8)

(57) [Claims] 1. A crystalline melting endothermic peak temperature Tm measured by a differential scanning calorimeter , which contains an organic phosphorus compound in an amount of 0.05 to 3 wt% as a total amount of phosphorus based on polyester.
(C) is 240 ° C. or higher, and the following relational expression (a) is satisfied between Tm and the total amount of phosphorus contained in the film layer (A).
At least two layers with at least one layer)
A laminated polyester film consisting of . Tm ≥ Tmb-6P (a) (where Tm (° C) is the crystal melting endothermic peak temperature, Tm
b (° C.) is the peak temperature of heat of crystal fusion when no organic phosphorus compound is contained (base polymer), P (wt%) is the total amount of phosphorus contained) 2. The laminated polyester according to claim 1, wherein the organic phosphorus compound is represented by the following chemical formula (1).
Steal film. [Chemical 1] (Wherein, X is a phenylene group, a naphthalene group, a biphenyl group or the aromatic group selected from alkylene substituents of 0-5 carbon atoms, Ar ₁ to Ar ₄ is an alkylene substituted phenylene group having a carbon number of 1 to 5) 3. The amount of phosphorus contained in the A layer is 0.05.
~ 3 wt%, the amount of phosphorus contained in other layers is 0-2 wt%
, And the and also claim 1 the amount of phosphorus contained in the A layer is equal to or greater than the amount of phosphorus contained in the other layers
Is the laminated polyester film described in 2 . Claim thickness ratio of said A layer to 4. The total thickness of the film is characterized in that 50% or more 1-3
The laminated polyester film according to any one of 1 . Claim thickness ratio of said A layer to 5. The total thickness of the film is equal to or less than 50% 1-3
The laminated polyester film according to any one of 1 . 6. A laminated polyester film of three or more layers, according to claim 1, other layers on both sides of the A layer is disposed
The laminated polyester film according to any one of items 1 to 5. 7. A laminated polyester film of three or more layers, laminated polyester film according to claim 1 or 5 wherein A layer on both the outer layer is arranged. 8. The polyester film for electrical insulation according to any one of claims 1-7.