JPH06128369A - Modified polyester and film - Google Patents

Abstract

PURPOSE:To obtain the title polyester excellent in adhesion, transparency and recovery from curling by incorporating a specified ether-bond-containing dicarboxylic acid, an esterifiable alkali metal sulfonate compound, and an at least trifunctional esterifiable compound in the polyester. CONSTITUTION:The polyester is obtained by incorporating 1-20wt.%, based on the polyester, ether-bond-containing dicarboxylic acid or its esterifiable derivative, 1-15mol%, based on the dicarboxylic acid component of the polyester, esterifiable alkali metal sulfonate compound and 0.1-2mol%, based on the dicarboxylic acid component, at least trifunctional esterifiable compound in the polyester. In the formula, R<1> is a 4C or higher bivalent hydrocarbon group; R<2> and R<3> which may be the same or different from each other are each hydrogen or alkyl; k and j are each an integer of 2-4; g is 0 or 1; p is an integer of 1-3; and m and n are each an integer of 0 or greater and m+n>=4).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to modified polyesters and films, and more particularly to excellent adhesiveness,
The present invention relates to a modified polyester and a film having transparency, curl curl recovery property, and rigidity retention ability when immersed in water. More specifically, modified polyesters and films having excellent adhesiveness, transparency, curl curl recovery, and rigidity retention when immersed in water, suitable for photographic supports, packaging, general industry, magnetic tapes, etc. It is about.

[0002]

Polyester, especially polyethylene terephthalate, polybutylene terephthalate or poly-
1,4-Cyclohexanedimethylene terephthalate and polyesters containing these as a main component have excellent physical and chemical properties, and are widely used as fibers, films or sheets, and molded articles thereof.

In particular, since polyester film has excellent properties in heat resistance, chemical resistance and mechanical properties, it is used in many applications such as magnetic tape, electricity, photography, packaging and drawing. There is. However, since polyester itself is generally inactive, there is a problem in that the adhesiveness to a vapor deposition layer and the like and the printability with a hydrophilic ink are poor.
Conventionally, a method of subjecting the film surface to corona discharge treatment or coating with an adhesive substance to improve the adhesiveness of the polyester film is known. However, these methods have drawbacks that not only the process is complicated and the cost is increased, but also the transparency of the film is lowered.

Therefore, it has been attempted to improve the adhesiveness from the base film itself without requiring these steps. For example, in JP-A-52-151365, polyalkylene glycol is used to copolymerize a polyether segment to improve the adhesiveness and printability of the film, but its adhesive property is not sufficient.

On the other hand, as the photographic support, a plastic film made of triacetyl cellulose and polyester typified by polyethylene terephthalate is generally used. However, although the polyester film has excellent mechanical properties, transparency, and dimensional stability, it has a strong curl curl in the roll form, and thus has poor handleability after development processing, and is not suitable for X-ray film and plate-making film. Its scope has been limited to use in sheet form.

As a method of improving such a defect, the present applicant has previously proposed that an ester-forming alkali metal sulfonate compound is contained in an amount of 1 to 30% by weight based on polyester and an ether bond-containing dicarboxylic acid represented by the following formula (I). A modified polyester characterized in that it contains 1 to 20% by weight of an acid or its ester-forming derivative has been proposed (Japanese Patent Application Laid-Open No. Hei 4-
No. 224822). ^{_{R 2 OOC (CH 2) p}} O (C k H 2k O) m (R 1 O) q (C j H 2j O) n (CH 2) p COO R 3 (I) ( where in the formula, ^{R 1} Is a divalent hydrocarbon group having 4 or more carbon atoms, R ² and R ³ are the same or different groups and represent hydrogen or an alkyl group, and k and j are each independently 2
To an integer of 4, q is 0 or 1, p is an integer of 1 to 3, m and n are each independently an integer of 0 or more (provided that m + n.
≧ 4))). By this method, it becomes possible to provide a modified polyester and a film which have excellent adhesiveness without requiring extra high-order processing, and which also satisfy the transparency and the curl curl recovery property. .

However, it is preferable that the photographic support used in the roll form has a small decrease in rigidity which occurs when it is immersed in a developing solution from the viewpoint of transportability at the time of development in an automatic developing machine. The film obtained according to the invention of 1) is not sufficient in terms of the rigidity retaining ability when soaked in water, and there has been a demand for further improvement.

[0008]

The object of the present invention is to prevent deterioration of rigidity during the above-mentioned water immersion, thereby maintaining excellent adhesiveness, transparency and curl curl recovery, and further during water immersion. Another object of the present invention is to provide a modified polyester and a film that also have the ability to retain the rigidity.

[0009]

The above-mentioned object of the present invention is to have 1 to 20% by weight of an ether bond-containing dicarboxylic acid represented by the following formula (I) or an ester-forming derivative thereof, based on polyester. Further, the modification is characterized by having 1 to 15 mol% of an ester-forming alkali metal salt compound and 0.1 to 2 mol% of a trifunctional or more functional ester-forming compound with respect to the dicarboxylic acid component of the polyester. Can be achieved with polyester. ^{_{R 2 OOC (CH 2) p}} O (C k H 2k O) m (R 1 O) q (C j H 2j O) n (CH 2) p COO R 3 (I) ( where in the formula, ^{R 1} Is a divalent hydrocarbon group having 4 or more carbon atoms, R ² and R ³ are the same or different groups and represent hydrogen or an alkyl group, and k and j are each independently 2
To an integer of 4, q is 0 or 1, p is an integer of 1 to 3, m and n are each independently an integer of 0 or more (provided that m + n.
Satisfying ≧ 4))

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid or an alicyclic dicarboxylic acid and a diol as main constituent components. Examples of the aromatic dicarboxylic acid component include 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 aromatic dicarboxylic acids such as ′ -diphenyl ether dicarboxylic acid and 4,4′-diphenyl sulfone dicarboxylic acid. Examples of the alicyclic dicarboxylic acid component include 1,4-cyclohexanedicarboxylic acid. Two or more kinds of these acid components may be used in combination, and further, an aliphatic dicarboxylic acid such as adipic acid, suberic acid, sebacic acid and dodecanedioic acid, and an oxy acid such as hydroxyethoxybenzoic acid are partially copolymerized. May be. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol and 1,5-pentanediol. , 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2'-bis (4 Examples thereof include aliphatic, alicyclic and aromatic diols such as ′ -β-hydroxyethoxyphenyl) propane. These diol components may be used alone or in combination of two or more. Representative examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-1,4-cyclohexane dimethylene terephthalate, and the like.

The ether bond-containing dicarboxylic acid or its ester-forming derivative in the present invention is represented by the following formula (I). ^{_{R 2 OOC (CH 2) p}} O (C k H 2k O) m (R 1 O) q (C j H 2j O) n (CH 2) p COO R 3 (I) In the above formula, ^{R 1} Is a divalent hydrocarbon group having 4 or more carbon atoms, preferably a divalent hydrocarbon group having an integer of 4 to 8 carbon atoms. Further, R ¹ may contain halogen, oxygen, or sulfur. For example, straight chain or side chain aliphatic hydrocarbon groups such as tetramethylene, hexylene, and 2,2-dimethylpropylene, aliphatic hydrocarbon groups having aliphatic rings such as cyclohexylene, and aromatic hydrocarbons such as phenylene. Groups and the like.

In the above formula, k and j are each independently an integer of 2 to 4, q is 0 or 1, and p is 1 to 1.
The integer of 3, m and n are each independently an integer of 0 or more (provided that m + n ≧ 4 is satisfied). When m + n is less than 4, heat resistance and mechanical properties are deteriorated, and curling curl recovery is insufficient. The preferred value of m + n is 30 to
It is 500, and when m + n exceeds 500, there may be a problem that transparency is deteriorated. Further, m + n is particularly preferably 60 to 300. The preferred value of n is 30 to
500. In the formula, R ² and R ³ are the same or different groups and represent hydrogen or an alkyl group, preferably hydrogen or a lower alkyl group having 1 to 4 carbon atoms.
The molecular weight of the ether bond-containing dicarboxylic acid or its ester-forming derivative is preferably in the range of 500 to 25,000 in terms of number average molecular weight from the viewpoint of mechanical properties and transparency, and more preferably 1000 to 20000, especially 2
Those in the range of 000 to 10,000 are preferable.

A particularly preferred ether bond-containing dicarboxylic acid or its ester-forming derivative is represented by the following formula (II). R ² OOCCH ₂ O (C ₂ H ₄ O) _n CH ₂ COOR ³ (II) (R ² and R ³ are the same as defined above, and n is an integer of 4 or more.)

The amount of the ether bond-containing dicarboxylic acid or its ester-forming derivative in the present invention must be 1 to 20% by weight, preferably 3 to 10% by weight, based on the polyester used in the present invention (that is, the base polyester).
It is 17% by weight, more preferably 5 to 15% by weight.
If it is less than 1% by weight, the adhesive performance and curl curl recovery are not sufficient, while if it exceeds 20% by weight, the mechanical properties and heat resistance deteriorate.

In the present invention, the ether bond-containing dicarboxylic acid or its ester-forming derivative, the ester-forming sulfonic acid alkali metal salt compound and the tri- or more functional ester-forming compound have their ester-forming functional groups reacted with the diol component. It may be either copolymerized in the modified polyester or simply unblended and blended.

As the ester-forming sulfonic acid alkali metal salt compound in the present invention, sulfoterephthalic acid,
5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4
-Sulfoisophthalic acid, 4-sulfonaphthalene-2,6
-Alkali metal salts such as dicarboxylic acids and their ester-forming derivatives can be mentioned. Among them 5-
The sodium and potassium salts of sulfoisophthalic acid and sulfoterephthalic acid are more preferably used. The amount of the ester-forming sulfonic acid alkali metal salt compound needs to be 1 to 15 mol%, preferably 3 to 10 mol%, and more preferably 3 to 10 mol%, based on the dicarboxylic acid component of the polyester (that is, the base polyester) used in the present invention. Preferably 5
~ 8 mol%.

The amount of the ester-forming sulfonic acid alkali metal salt compound is 1 with respect to the dicarboxylic acid component of the polyester.
If it is less than mol%, sufficient rigidity cannot be obtained before and during the immersion. On the other hand, when it exceeds 15 mol%, the adhesiveness reaches saturation and, on the contrary, a high molecular weight polyester cannot be obtained, making it difficult to form a film or lowering the mechanical strength of the obtained film.

The trifunctional or higher functional ester-forming compound in the present invention may be aliphatic, alicyclic or aromatic as long as it has a trivalent or higher functional ester-forming group. Examples of the ester-forming functional group include, for example,
A carboxyl group, a -COOR group (R is a monovalent organic group),
-COX group (X is a halogen atom), hydroxyl group, -OCOR
'Group (R' is a monovalent organic group) etc. can be mentioned.
Here, R and R ′ are not particularly limited as long as they are monovalent organic groups, but are preferably lower aliphatic hydrocarbon groups such as methyl group and ethyl group. These ester-forming functional groups may be the same or different in the molecule. Such compounds include trimellitic acid, hemimellitic acid, trimesic acid,
Tricarboxylic or higher polycarboxylic acids such as prenitic acid, melophanoic acid and pyromellitic acid, and their esters, ester-forming derivatives such as acid anhydrides and acid halides, glycerol, sorbitol, trimethylolpropane, pentaerythritol, 2, Trivalent or higher valent polyols such as 2,6,6-tetramethylolcyclohexanol, 1,3,5-trimethylolbenzene and their ester-forming derivatives, 2,4-dioxybenzoic acid, 4-oxyisophthalic acid, 2 5,5-dioxyterephthalic acid, glyceric acid and their esters, acid anhydrides, ester-forming derivatives such as acid halides, and the like. Among the above compounds, a trifunctional compound is particularly preferable, and a carboxyl group is preferable as the functional group. Among them, trimellitic acid and trimethyl trimellitate are more preferably used.

The amount of the trifunctional or higher functional ester-forming compound must be 0.1 to 2 mol%, and preferably 0.5 to 2 mol% with respect to the dicarboxylic acid component of the polyester (that is, the base polyester) used in the present invention. It is 1.5 mol%. When the amount of the trifunctional or higher functional ester-forming compound is less than 0.1 mol%, sufficient rigidity retention ability during water immersion cannot be obtained. On the other hand, if it exceeds 2 mol%, gelation occurs,
It is difficult to form the film, or the mechanical strength of the obtained film decreases. The method for copolymerizing or blending the ester-forming alkali metal sulfonate compound of the present invention, the ether bond-containing dicarboxylic acid or its ester-forming derivative and the trifunctional or more functional ester-forming compound with the base polyester is not particularly limited. Absent. The method and timing of blending or addition to the base polyester are arbitrary and are not particularly limited. It may be added to the base polyester in the form of powder or melt. As for the timing of blending and addition, they may be blended and added during the base polyester synthesis reaction, in the molten state after the reaction, in the pellet state, or before the molding.
In particular, it is preferable that the base polyester is compounded and added during the reaction for synthesizing the base polyester between before the reaction and after the reaction until the molten state.

As a specific method for producing the modified polyester of the present invention, for example, a polyethylene terephthalate-based modified polyester comprising a terephthalic acid component and an ethylene glycol component will be described. Direct esterification of terephthalic acid, ester-forming sulfonic acid alkali metal salt compound (for example, 5-sodium sulfoisophthalic acid), ether bond-containing dicarboxylic acid, ethylene glycol and trifunctional or higher functional ester-forming compound (for example, trimellitic acid) Or dimethyl terephthalate, ester-forming alkali metal sulfonate compound (eg, dimethyl 5-sodium sulfoisophthalate), ester-forming derivative of dicarboxylic acid containing ether bond and ethylene glycol and 3
A method of producing by a first step reaction of transesterification with a functional or higher ester-forming compound (for example, trimethyl trimellitate) and a second step of polycondensation reaction product of the first step, B. Terephthalic acid or its ester-forming derivative,
This reaction product is subjected to a polycondensation reaction after the completion of the first step of a direct esterification reaction or a transesterification reaction between an ester-forming alkali metal sulfonate compound and a tri- or more-functional ester-forming compound and ethylene glycol. In the second step, the ether bond-containing dicarboxylic acid or its ester-forming derivative may be added during any time until the polyester is produced, and the like. At this time, as a reaction catalyst, conventionally known alkali metals, alkaline earth metals, manganese,
Cobalt, zinc, antimony, germanium, titanium compounds and the like are used, and phosphorus compounds and the like may be used as a coloring preventing agent.

The glass transition temperature of the modified polyester of the present invention is preferably 35 ° C. or higher, more preferably 45 ° C. or higher, and particularly preferably 50 ° C. or higher in that the molded film has good heat resistance and is less likely to undergo thermal deformation. Is preferred. The intrinsic viscosity of the modified polyester of the present invention is preferably 0.3 or more, more preferably 0.4 or more, and particularly preferably 0.5 or more in order to enhance the strength of the formed film.

The modified polyester and film of the present invention may optionally contain a flame retardant, a heat stabilizer, an ultraviolet absorber,
Organic lubricants such as pigments, dyes, fatty acid esters and waxes, or defoaming agents such as polysiloxanes may be added, and clay, mica, titanium oxide, calcium carbonate, kaolin, wet type may be added for the purpose of imparting lubricity. In addition, dry process silica, inorganic particles such as colloidal silica, calcium phosphate, barium sulfate, and alumina, and organic particles including acrylic acid, styrene, and the like as constituent components may be blended.

After the modified polyester obtained above is dried, it is supplied to a known melt extrusion unit, extruded into a sheet form from a slit die, and cooled and solidified to give an unstretched sheet. The target film can be obtained by biaxially stretching the sheet. As a stretching method, a sequential stretching method or a simultaneous biaxial stretching method can be used. In the case of the sequential biaxial stretching method, it is general to stretch in the longitudinal direction and then in the width direction, but the stretching may be performed in the reverse order. The stretching ratio is not particularly limited, but normally 2.0 to 5.0 times in each of the length and width is suitable. After biaxial stretching, it may be re-stretched either longitudinally or laterally. Further, the film of the present invention may be heat-treated thereafter. The heat treatment condition is not particularly limited, but usually 150 to 225 ° C., and the time is suitably 0.5 to 60 seconds.

Further, in the melt extrusion, a film having a multilayer structure composed of the modified polyester of the present invention and another polymer can be used. The number of layers of the multilayer film is not particularly limited, but preferably 2 or 3 layers. The thickness ratio of the film layer of the modified polyester of the present invention and the other polymer is not particularly limited, but in the case of a two-layer film, one layer consisting of the modified polyester of the present invention is preferably the multilayer film. The total thickness is 10% or more, and particularly preferably 20% or more. In the case of a film having three or more layers, the total thickness of the layers made of the modified polyester of the present invention is preferably 10% or more, and particularly preferably 20% or more of the total thickness of the multilayer film. The layer composed of the modified polyester of the present invention may be the outermost layer or the inner layer of the multilayer film, but from the viewpoint of adhesiveness, at least one outermost layer of the multilayer film is the modified layer of the present invention. It is preferably polyester. Other polymers used for the laminated film are not particularly limited, and typical examples thereof include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-1,
Examples thereof include polyesters such as 4-cyclohexanedimethylene terephthalate, and these may be partially copolymerized with other known components.

Further, the film of the present invention is provided with an undercoat layer on at least one surface thereof, and a surface layer agent such as a halogenated emulsifying agent is further coated on the undercoat layer to provide a photographic film having the film of the present invention as a support. It can also be a photosensitive material. In addition to the above-mentioned film, fibers and other molded products can be produced from the modified polyester of the present invention by a conventional method.

[0026]

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. Intrinsic viscosity; [η] was measured at 25 ° C using o-chlorophenol solvent.

B. Glass transition temperature (Tg) Measured with a differential scanning calorimeter.

C. Transparency The film haze was measured according to ASTM-D1003-59. When used as a photographic support, if the film haze is 3.0 or less, there is no problem in practical use and it is judged that the transparency is good.

D. Adhesiveness Aluminum was vapor-deposited on the surface of the film, cellophane tape was pressure-bonded to the vapor-deposited surface, and the state (area of the peeled portion) when peeled off was evaluated. ⊚: The cellophane tape is not peeled off. ◯: 20% or less of the portion peeled off to the side of the cellophane tape. Δ: 20% to 70% of the portion is peeled off to the side of the cellophane tape. X: A portion of 70% or more is peeled off to the side of the cellophane tape.

E. Rigidity before and after soaking (Young's modulus) A sample with a length of 10 mm width x 50 mm was made from the film, and the pulling speed was 300 mm for each sample before soaking and after soaking in water at 24 ° C for 2 hours. It was measured in minutes.

F. Curling curl recovery A sample of 35mm width x 133mm length is made from the film,
Wrap around a core with a diameter of 10 mm, 70 ° C x 30% RH x 72h
The process of r was performed. Then, after releasing from the core and soaking in distilled water at 40 ° C for 30 minutes, the sample was hung vertically and
Was applied for 5 minutes and dried in an air thermostat at 50 ° C. for 5 minutes. The treated film sample was placed on a flat surface, the sample length was measured, and the curl curl recovery was evaluated by the ratio (%) to the original sample length of 133 mm.

Example 1 100 parts by weight of dimethyl terephthalate, 6.5 mol% of dimethyl 5-sodium sulfoisophthalate with respect to dimethyl terephthalate, 1 mol% of trimethyl trimellitate with respect to dimethyl terephthalate, and 70 parts by weight of ethylene glycol. , 0.06 parts by weight of magnesium acetate as a transesterification catalyst and 0.00 of lithium acetate
2 parts by weight of antimony trioxide as a polycondensation reaction catalyst.
After adding 03 parts by weight and carrying out a transesterification reaction according to a conventional method, 0.023 parts by weight of trimethyl phosphate was added. Followed by the addition of several polyethyleneoxy diglycolic acid having an average molecular weight _{4000 (PEOG) HOOCCH 2 O (} C 2 H 4 O) n CH 2 COOH 11 parts by weight ether bond-containing dicarboxylic acid. Then gradually raise the temperature and reduce the pressure,
Finally, a polycondensation reaction was performed at 280 ° C. and 1 mmHg or less to obtain a polyester. The contents of polyethyleneoxydiglycolic acid, dimethyl 5-sodium sulfoisophthalate and trimellitic acid in the obtained modified polyester were determined from the results of analysis such as NMR. The intrinsic viscosity was 0.58 and Tg was 68 ° C.

The modified polyester thus obtained was formed into a film by a film forming machine at 275 ° C., and then drawn by a biaxial drawing machine at a longitudinal draw ratio of 3.3 times and a transverse draw ratio of 3.5 times, and then 200
The film was heat-treated at 0 ° C. for 5 seconds to obtain a film having a thickness of 90 μm. The characteristics of the obtained film are shown in Table 2. The haze of the film was 1.1%, the adhesiveness was good, and the curl curl recovery was evaluated. Young's modulus before and after soaking is 410 kg / mm ² and 3 respectively.
It was 60 kg / mm ² , and the rate of decrease was 12.2%.

Comparative Example 1 Example 1 except that trimethyl trimellitate was not added.
A polyester and a film were obtained in the same manner as in. The intrinsic viscosity of polyester was 0.60, and the adhesiveness, transparency, and curl recovery were all good, but the Young's modulus before and after soaking was 400 kg / mm ² and 260 kg / mm, respectively.
^{It was 2} , and the rate of decrease was 35.0%, which was poor. The results are shown in Table 2.

Examples 2 to 9 and Comparative Examples 2 to 6 As shown in Table 1, various 3 types were prepared in the same manner as in Example 1.
Polyesters and films were obtained in which the types and contents of the functional or higher ester-forming compound, the ester-forming sulfonic acid alkali metal salt compound and the ether bond-containing dicarboxylic acid were changed.

[Table 1] The abbreviations in the table indicate the following compounds. TMTM: trimellitic acid SSIA: 5-sodium sulfoisophthalic acid PEOG: polyethyleneoxy diglycolic acid _{HOOCCH 2 O (C 2 H 4} O) n CH 2 COOH TMP: Table 2 Characteristics of polyester and film obtained trimethylolpropane It was shown to.

[Table 2] Examples 2 to 9 were within the scope of the present invention, and the film haze, adhesiveness, curl curl recovery, and Young's modulus decrease rate during water immersion were good. On the other hand, in Comparative Example 2, the ester-forming alkali metal sulfonate compound was not added, and although the film had good haze, adhesiveness, and curl curl recovery, the Young's modulus before soaking was 2
The result was 90 kg / mm ² , which was poor. Comparative Example 3 was one in which the ether bond-containing dicarboxylic acid was not added, and although the haze of the film was good, both the adhesiveness and the curl curl recovery were poor. In Comparative Example 4, the content of the trifunctional or higher functional ester-forming compound is outside the range of the present invention,
A polymer could not be stably obtained because gelation occurred during the polymerization. In Comparative Example 5, the content of the ester-forming alkali metal sulfonate compound was outside the range of the present invention, and although the haze of the film was good, the adhesiveness,
Both Young's modulus before pickling and curl curl recovery were poor. Comparative Example 6 has an ether bond-containing dicarboxylic acid content outside the scope of the present invention, is flexible and has no self-supporting property,
Film formation was difficult.

[0037]

EFFECT OF THE INVENTION The modified polyether and film of the present invention have excellent adhesiveness, transparency, curl curl recovery, and rigidity retention when immersed in water, and are used for photographic supports, packaging, and general industry. It is preferably used for a magnetic tape, a magnetic tape, and the like.

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Claims (3)

[Claims] 1. A polyester having 1 to 20% by weight of an ether bond-containing dicarboxylic acid represented by the following formula (I) or an ester-forming derivative thereof, and further forming an ester with respect to the dicarboxylic acid component of the polyester. 1 to 15 mol% of a sulfonic acid alkali metal salt compound and 0.1 to 2 mol% of a trifunctional or higher functional ester-forming compound
A modified polyester having. ^{_{R 2 OOC (CH 2) p}} O (C k H 2k O) m (R 1 O) q (C j H 2j O) n (CH 2) p COO R 3 (I) ( where in the formula, ^{R 1} Is a divalent hydrocarbon group having 4 or more carbon atoms, R ² and R ³ are the same or different groups and represent hydrogen or an alkyl group, k and j are each independently an integer of 2 to 4, and q is 0 or 1. , P is an integer from 1 to 3, m and n
Are each independently an integer of 0 or more (provided that m + n ≧ 4 is satisfied). 2. A film comprising the modified polyester according to claim 1. 3. A laminated film, which is a film having a multi-layer structure, at least one layer of which is the modified polyester according to claim 1.