JPH10168141A - Antimicrobial material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antimicrobial material that mainly comprises a specific graft polymer bearing phosphonium base and can retain a suitable amount of the phosphonium base to manifest excellent antimicrobial properties without discoloration and deterioration in physical properties and is useful as a packaging film, a magnetic tape and the like. SOLUTION: This antimicrobial material mainly comprises a polymer substance (Z) bearing phosphonium base (Y<1> ), As a Z, a macromolecular substance grafted with a hydrophilic group-bearing vinyl polymer on its side-chains is used, where, for example, Z is a polymer bearing acidic groups (Y<2> ) and Y<1> bonding to the Y<2> (for the safety on use), actually a polyester copolymer mainly containing a dicarboxylic acid component (Z<1> ) and a glycol component (Z<2> ) and 1-50mol% of dicarboxylic acid of the formula (A is an aromatic group; X1 and X2 are eater-forming functional group; R1 -R4 are each an alkyl where at least one of them is a 10-20C alkyl).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antibacterial material comprising a polymer substance having a phosphonium base, and more particularly to an antibacterial film, an antibacterial sheet, an antibacterial fiber, an antibacterial plastic molded product, and the like. Antibacterial material.

[0002]

2. Description of the Related Art Conventionally, various antibacterial materials have been used in many fields such as industrial use, agricultural use, and food use.

Most of the antibacterial materials currently used are occupied by natural products such as chitin and chitosan, ultrafine particles of zinc oxide, inorganic products such as silver-containing zeolite, and various synthetic products. Among them, natural products and inorganic products are safe in terms of toxicity, and have recently attracted attention. On the other hand, synthetic products generally have better antibacterial activity than natural products and inorganic products.However, because a surface treatment method is used as a method for imparting antibacterial properties, antibacterial materials are easily volatilized and separated, and They are often avoided because of toxicity. This is because the antibacterial material is easily dissolved in water, an organic solvent, or the like, and recently, an insoluble, nontoxic, immobilized antibacterial material has been developed. There are the following disclosure examples as such improvement methods.

For example, Japanese Patent Application Laid-Open No. 54-86584 discloses a polymer substance containing an antibacterial material component having a quaternary ammonium base ionically bonded to an acidic group such as a carboxyl group or a sulfonic acid group. The antimicrobial material described above is described.

[0005] JP-A-61-245378 describes a fiber comprising a polyester copolymer containing an antibacterial material component having a basic group such as an amidine group or a quaternary ammonium group.

JP-A-57-204286, 63-609
030, 62-114903, JP-A-1-93596,
According to JP-A-2-240090, phosphonium salt compounds, as well as various nitrogen-containing compounds, are known as biologically active chemicals having a broad spectrum of activity against bacteria. These publications disclose inventions in which the above phosphonium salt is immobilized on a polymer substance to try to expand applications.

JP-A-4-266912 discloses an antibacterial material of a phosphonium salt-based vinyl polymer, and JP-A-4-814365 discloses an antibacterial material of a vinylbenzylphosphonium-based vinyl polymer. .

Further, JP-A-5-310820 discloses an antibacterial material mainly composed of a polymer substance containing an antibacterial component having an acidic group and a phosphonium base ionically bonded to the acidic group. . In that example, a polyester using a phosphonium salt of sulfoisophthalic acid is disclosed.

Further, the present inventors have disclosed the technique disclosed in Japanese Patent Laid-Open No. 4-266.
No. 912, 4-814365, 5-310820, and a phosphonium base-containing vinyl polymer and a copolymerized polyester are synthesized in accordance with the examples to form a structure such as a fiber or a film. The antibacterial activity was not always sufficient, although they were applied on the formed body and examined for their antibacterial activity.

Further, even if an attempt is made to bond trinormal butyl dodecylphosphonium base to the polyester in an amount of 50 mol% or more in order to improve the antibacterial properties, the coloring of the polymer and the decrease in the mechanical properties due to the decrease in the glass transition point become remarkable. In addition, there has been a problem that sufficient antibacterial properties cannot be obtained.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned problems and provided an antibacterial material which improves antibacterial properties while maintaining an appropriate amount of phosphonium base which is an antibacterial component in a polymer substance. The purpose is to:

[0012]

In order to achieve the above object, an antibacterial material according to the present invention is an antibacterial material mainly composed of a polymer substance having a phosphonium base, wherein the polymer substance is a polymer. It is characterized by being a polymer substance in which a vinyl polymer having a hydrophilic group bonded to a side chain is grafted.

The antibacterial material of the present invention having the above constitution is characterized in that its antibacterial activity is significantly enhanced.

In this case, the high-molecular polymer may contain an acidic group and a phosphonium base ionically bonded to the acidic group.

The antibacterial material having the above structure is stable when used.

In this case, the high molecular polymer contains a dicarboxylic acid component and a glycol component as main components, and a phosphonium salt of a sulfonic acid group-containing aromatic dicarboxylic acid represented by the following formula (1): ~ 50 mol%
It can be a copolymerized polyester. (Where A is an aromatic group, X ₁ and X ₂ are ester-forming functional groups, R _1, R _2, R _{3 and} R ₄ are the same or different alkyl groups, at least one of which is a carbon atom) An alkyl group of several 10 to 20)

The antibacterial material having the above constitution can be easily formed into a fiber, a film, or the like by a melt extrusion method or a solution extrusion method, or can be coated to maintain the antibacterial property.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the antibacterial material of the present invention will be described in detail.

The antibacterial material of the present invention is an antibacterial material mainly composed of a polymer substance having a phosphonium base,
The polymer is a polymer obtained by grafting a vinyl polymer having a hydrophilic group bonded to a side chain of the polymer,
Preferred examples of the high molecular polymer include a phosphonium salt of a sulfonic acid group-containing aromatic dicarboxylic acid represented by the above-mentioned formula (1), which contains a dicarboxylic acid component and a glycol component as main components, and contains 1 to 50 of all dicarboxylic acids. Mol%
And copolymerized polyesters. Such a copolyester has a remarkable effect of improving antibacterial properties by grafting a vinyl polymer having a hydrophilic group bonded thereto.

Examples of R ₁ , R ₂ , R ₃ and R ₄ of the dicarboxylic acid (formula 1) constituting the copolymerized polyester are as follows:
Alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, dodecyl, pentadecyl, hexadecyl, oftadecyl are typical, and examples of X include fluorine, chlorine, bromine or iodine. Halogen ion and the like.

Specific examples of the dicarboxylic acid component constituting the copolymerized polyester include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and heterocyclic dicarboxylic acids. As aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, phthalic acid, 2,6-
There are naphthalenedicarboxylic acid, 4,4-dicarboxylbenzophenone, bis (4-carboxylphenyl) ethane and derivatives thereof, and the alicyclic dicarboxylic acid includes cyclohexane-1,4-dicarboxylic acid and derivatives thereof. Aliphatic dicarboxylic acids include adipic acid, sebacic acid, dodecanedioic acid, eicosandioic acid, dimer acid and derivatives thereof, and heterocyclic dicarboxylic acids include pyridine carboxylic acid and derivatives thereof. In addition to such a dicarboxylic acid component, p
It is also possible to include polyfunctional groups such as oxycarboxylic acids such as oxybenzoic acid, trimellitic acid, pyromellitic acid and derivatives thereof. As the glycol component, ethylene glycol, 1,2-propylene glycol, 1,
3-propylene glycol, 1,4-butanediol,
1,6-hexanediol, neopentyl glycol,
Examples thereof include diethylene glycol, 1,4-cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. In addition, a compound containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be contained.

Examples of the phosphonium salt of a sulfonic acid group-containing aromatic dicarboxylic acid include tri-n-sulfoisophthalic acid.
Butyldecylphosphonium salt, tri-n-butyloctadecylphosphonium sulfoisophthalate, tri-n-butylhexadecylphosphonium sulfoisophthalate, tri-n-butyltetradecylphosphonium sulfoisophthalate, tri-n-sulfoisophthalate Butyl dodecyl phosphonium salt, tri-n-sulfoterephthalate
-Butyldecylphosphonium salt, tri-n-butyloctadecylphosphonium sulfoterephthalate, tri-n-butylhexadecylphosphonium sulfoterephthalate, tri-n-butyltetradecylphosphonium sulfoterephthalate, tri-n sulfoterephthalate -Butyldodecylphosphonium salt, 4-sulfonaphthalene-2,
Tri-n-butyldecylphosphonium 7-dicarboxylate, tri-n-butyloctadecylphosphonium 4-sulfonaphthalene-2,7-dicarboxylate, tri-n-butylhexa-4-sulfonaphthalene-2,7-dicarboxylate Decylphosphonium salt, 4-sulfonaphthalene-
2,7-dicarboxylic acid tri-n-butyltetradecylphosphonium salt, 4-sulfonaphthalene-2,7-dicarboxylic acid tri-n-butyldodecylphosphonium salt and the like. n
-Butylhexadecylphosphonium salt, tri-n-butyltetradecylphosphonium sulfoisophthalate, and tri-n-butyldodecylphosphonium sulfoisophthalate are particularly preferred.

The above-mentioned phosphonium salts of aromatic dicarboxylic acids include aromatic dicarboxylic acids or their sodium, potassium, ammonium salts and the like, as well as tri-n-butylhexadecylphosphonium bromide, tri-n-butyltetradecylphosphonium bromide, tri-n -Butyl dodecylphosphonium bromide or the like, and is obtained by reacting the same. The reaction solvent is not particularly limited,
Water is most preferred.

For the purpose of improving the heat resistance so that the copolymerized polyester is free from coloring, gelation, etc., magnesium salts such as magnesium acetate and magnesium chloride, calcium salts such as calcium acetate and calcium chloride, manganese acetate, chloride and the like. It is also possible to add 20 to 300 ppm of a manganese salt such as manganese as a metal ion and 20 to 200 ppm of a phosphoric acid or a phosphoric acid ester derivative such as trimethyl phosphate or triethyl phosphate as a P atom. If the metal ion exceeds 300 ppm, the coloring of the polymer becomes remarkable. If the metal ion content is less than 20 ppm, no improvement in the heat resistance of the polymer is observed.

From the viewpoint of heat resistance of the antibacterial material, the molar ratio of P to the metal ion (formula 2) is preferably 0.4 to 1.0.

The molar ratio of the additive = (total number of moles of phosphoric acid, alkyl phosphate, or derivative thereof) / (total number of moles of Mg ion, Ca ion, and Mn ion) (formula 2)

When the molar ratio of the P to the metal ion is less than 0.4 or more than 1.0, the coloring of the polymer and the generation of coarse particles become remarkable, and the molding of fibers, films, plastics, etc. It becomes difficult to apply.

The method for producing the copolymerized polyester which is the main component of the present invention in the above-mentioned typical example is a direct polymerization method in which an aromatic dicarboxylic acid and a glycol are directly reacted, a so-called direct polymerization method, and a method in which a dimethyl ester of an aromatic dicarboxylic acid is used. Any known production method such as a so-called transesterification method in which a glycol and a transesterification reaction are performed can be applied.

The timing of adding the metal ions, phosphoric acid and derivatives thereof is not particularly limited, but it is preferable that the metal ions be added during the preparation of the raw materials and that the phosphoric acids be added before the polymerization reaction.

Another specific preferred polymer as the high molecular polymer used in the antibacterial material of the present invention is the following (formula 3)
And a phosphonium salt-based vinyl polymer represented by the following formula:

[0031] (R ₅ , R ₆ , and R ₇ are a hydrogen atom, a linear or branched alkyl group having 1 to 18 carbon atoms, an aryl group, an alkyl group substituted with a hydroxyl group or an alkoxy group, an aryl group, or an aralkyl group; , Ph represents a phenylene group, X ⁻ represents an anion, and n is an integer of 2 or more.)

Examples of the above R ₅ , R ₆ and R ₇ include methyl,
Alkyl groups such as ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, dodecyl, phenyl,
Examples include an aryl group such as tolyl and xylyl, an aralkyl group such as benzyl and phenyl, a hydroxyl group and an alkoxyl group, and an alkyl group and an aryl group are preferred. R ₅ , R ₆ and R ₇ may be the same group or different groups. X ^- is an anion, for example, a halogen ion such as fluorine, chlorine, bromine or iodine, a sulfate ion, a phosphate ion, a perchlorate ion and the like, with a halogen ion being preferred. n is not particularly limited, but is 2 to 500,
Preferably, it is 10-300.

Examples of the vinyl monomer having a hydrophilic group which can be grafted onto the polymer in the present invention include those containing a carboxyl group, a hydroxyl group, a sulfonic acid group, an amide group and the like. Groups that can be changed to include acid anhydride groups, glycidyl groups,
And those containing a chloro group. Among them, a vinyl monomer having a carboxyl group is most preferable. For example, monomers containing a carboxyl group or a salt thereof such as acrylic acid, methacrylic acid and salts thereof, and alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate and t-butyl acrylate , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate and other alkyl methacrylates, 2-hydroxyethyl acrylate, hydroxy-containing monomers such as 2-hydroxyethyl methacrylate, acrylamide, methacrylamide , N-methylacrylamide, N
Amide group-containing monomers such as -methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N, N-dimethylolacrylamide, N-phenylacrylamide, and glycidyl acrylate And epoxy group-containing monomers such as glycidyl methacrylate. Other vinyl monomers having a hydrophilic group include, for example, monomers containing an epoxy group such as allyl glycidyl ether, monomers containing a sulfonic acid group or a salt thereof such as styrene sulfonic acid, vinyl sulfonic acid and salts thereof, crotone Examples include monomers containing a carboxyl group or a salt thereof, such as acids, itaconic acid, maleic acid, fumaric acid, and salts thereof, and monomers containing acid anhydrides, such as maleic anhydride and itaconic anhydride. These can be used in combination with other monomers. Examples of other monomers include, for example, vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, acrylonitrile, methacrylonitrile, vinylidene chloride, vinyl acetate, vinyl chloride, and the like. Copolymerization can be carried out using two or more kinds. The ratio of the vinyl monomer having a hydrophilic group to the other vinyl monomer is 30/70 in molar ratio.
The range of 範 囲 100/0 is preferred. If the ratio of the vinyl monomer having a hydrophilic group is less than 30 mol%, the effect of enhancing the antibacterial property is not sufficiently exhibited.

A known graft polymerization method can be used as a method for grafting a vinyl-based monomer having a hydrophilic group to a polymer. The following method is mentioned as a typical example.

For example, a radical polymerization method in which radicals are generated in a high-molecular polymer of the main chain by light, heat, radiation, or the like, and then the monomers are graft-polymerized, or AlCl _3,
There are a cation polymerization method in which cations are generated using a catalyst such as TiCl ₄ and an anion polymerization method in which anions are generated using metal Na and metal Li.

Further, there is a method in which a polymerizable unsaturated double bond is previously introduced into a high-molecular polymer having a main chain, and a vinyl monomer is reacted with the polymerizable unsaturated double bond. Examples of the monomer having a polymerizable unsaturated double bond used therein include fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, 2,5-norbornene dicarboxylic anhydride, tetrahydrophthalic anhydride and the like. be able to. The most preferred of these are fumaric acid, maleic acid and 2,5-norbornene dicarboxylic acid.

The average particle size varies depending on the purpose, and is not particularly limited. Generally, the average particle size is 0.0
The thickness is preferably 1 to 5 μm, and the amount of addition is preferably 5% by weight or less. When the addition amount of the particles exceeds 5% by weight, coarse particles in the polymer substance become remarkable, and coarse protrusions are conspicuous on the surface of a molded product such as a film or a fiber obtained from an antibacterial material using the same. The quality and friction resistance of the molded body are reduced.

The resin composition containing the antibacterial material of the present invention as a main component can be formed into fibers, films, sheets, plastics, etc. by melt extrusion, solution extrusion, or the like. It is also possible to laminate on an inorganic substrate such as glass or an organic substrate such as fiber, film, sheet or plastic by a coating method or the like.

The molded product thus obtained is used, for example, as a packaging film, a magnetic tape film, an industrial film, a plastic, a fiber, a binder and the like.

When the film is used, any of an unstretched film, a uniaxially oriented film and a biaxially oriented film may be used, but a biaxially oriented film is particularly preferred.

Since the antimicrobial material of the present invention contains a hydrophilic group in the side chain of the phosphonium base-containing polymer substance, the antibacterial property of the phosphonium base-containing polymer substance significantly exceeds the intrinsic antibacterial property. I have.

[0042]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Next, methods for measuring the physical properties of the antibacterial materials obtained in Examples and Comparative Examples will be described.

(Antibacterial test) S. cerevisiae diluted with 1/50 broth aureus (Staphylococcus aureus) 0.1cc of a bacterial solution (concentration 10 ⁷ cells / cc) was sterilized with high pressure steam in advance by 5 cm ×
A vinylidene chloride film sterilized by high-pressure steam was adhered to the film dropped on a film having a size of 6 cm. The test piece was transferred to a sterile petri dish and cultured at 37 ° C. for 24 hours. Then, the bacteria on the film were washed out with 10 cc of SCDLP medium, diluted 10-fold, and spread on an ordinary agar plate. After 24 hours, the number of colonies formed on the ordinary agar plate was counted.

(Production Example of Polymer) In a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 436.5 parts of dimethyl terephthalate, 436.5 parts of dimethyl isophthalate, 5-sulfo 161 parts of dimethylisophthalate tri-n-butyldodecylphosphonium salt, 511.5 parts of ethylene glycol, 236.6 parts of neopentyl glycol and 0.52 part of tetra-n-butyl titanate were charged, and the mixture was heated at 160 to 220 ° C. The transesterification was performed over time. Then, 29 parts of fumaric acid was added, the temperature was raised from 200 ° C to 220 ° C over 1 hour, and the pressure of the reaction system was gradually reduced.
The reaction was carried out under a reduced pressure of mHg for 1 hour and 30 minutes to obtain a polyester (A-1). The composition of the polyester (A-1) is as shown below.

Dicarboxylic acid component Terephthalic acid 45 mol% Isophthalic acid 45 mol% C12 phosphonium salt 5 mol% Fumaric acid 5 mol% Diol component Ethylene glycol 65 mol% Neopentyl glycol 35 mol%

In the same manner, various polyesters (A-2, A-3) shown in Table 1 were produced. Table 1 shows the results of the composition analysis of each polyester.

[0048]

[Table 1]

(Production Example 1 of Graft Polymer) 300 parts of polyester (A-1) and 360 parts of methyl ethyl ketone were placed in a reactor equipped with a stirrer, a thermometer, a reflux device and a fixed-rate dropping device.
And 120 parts of isopropyl alcohol, and heated and stirred to dissolve the resin under reflux. After the resin is completely dissolved, a mixture of 35 parts of acrylic acid, 65 parts of ethyl acrylate, 1.5 parts of octyl mercaptan, and 6 parts of azobisisobutyronitrile are dissolved in a mixture of 90 parts of methyl ethyl ketone and 30 parts of isopropyl alcohol. And 1.
The solution was dropped into the polyester solution over 5 hours, and reacted for 3 hours to obtain a graft polymer solution. After the graft polymer solution was cooled to room temperature, 59 parts of triethylamine was added to neutralize it, and then ion-exchanged water 800
And stirred for 30 minutes. Thereafter, the solvent remaining in the solvent was distilled off by heating to obtain an aqueous dispersion (B-1).

The polyester (A-
2) and (A-3) were graft-polymerized to obtain graft polymers (B-2) and (B-3).

(Production Example 2 of Graft Polymer) In Production Example 1 of the graft polymer, the amount of acrylic acid was changed to 4.2 parts,
A graft polymer aqueous dispersion (B-4) was obtained in the same manner as in Production Example 1, except that the amount of ethyl acrylate was changed to 7.8 parts.

(Production Example 3 of Graft Polymer) A method similar to that of Production Example 1 except that ethyl acrylate and 85 parts of vinyl acetate were used as the grafting monomer in Production Example 1 of the graft polymer. Thus, a graft polymer aqueous dispersion (B-5) was obtained.

(Example 1) Polyester having an intrinsic viscosity of 0.62 was melt-extruded onto a rotary cooling drum and had a thickness of 6
After stretching the 50 μm unstretched film 3.5 times in the machine direction, the aqueous graft polymer dispersion (B-1) was applied on the uniaxially stretched film, and then stretched 3.7 times in the transverse direction at 120 ° C. And heat-setting at 220 ° C. to obtain a 50 μm biaxially stretched polyester film. The average thickness of the coating layer on this film was 0.2 μm.

Table 2 shows the results of the antibacterial test of the obtained film.

[0055]

[Table 2]

Comparative Example 1 For comparison, an antibacterial test was performed on a biaxially stretched polyester film having a thickness of 50 μm to which no aqueous dispersion of a graft polymer was applied. Table 2 shows the results of the antibacterial test.

Comparative Example 2 The procedure of Example 1 was repeated except that a polyester resin solution in which the polyester (A-1) was dissolved in a mixed solvent of methyl ethyl ketone and isopropyl alcohol was applied instead of the aqueous dispersion of the graft polymer. A biaxially stretched polyester film was obtained in the same manner as in Example 1. Table 2 shows the results of the antibacterial test of the obtained film.

Comparative Example 3 A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the aqueous graft polymer dispersion (B-4) was applied. Table 2 shows the results of the antibacterial test of the obtained film.

(Example 2) A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the aqueous graft polymer dispersion (B-2) was applied. Table 2 shows the results of the antibacterial test of the obtained film.

Comparative Example 4 A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the aqueous graft polymer dispersion (B-3) was applied. Table 2 shows the results of the antibacterial test of the obtained film.

Comparative Example 5 A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the aqueous graft polymer dispersion (B-5) was applied. Table 2 shows the results of the antibacterial test of the obtained film.

[0062]

The antibacterial material according to the first aspect of the present invention has a high antibacterial activity and is excellent.

The antibacterial material according to claim 2 is stable when used.

The antibacterial material according to the third aspect can be easily formed into a fiber, a film or the like by a melt extrusion method or a solution extrusion method, and can be coated to keep the antibacterial property.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiro Seko 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (3)

[Claims] An antibacterial material mainly comprising a polymer substance having a phosphonium base, wherein the polymer substance is obtained by grafting a vinyl polymer having a hydrophilic group bonded to a side chain of the polymer. An antibacterial material, characterized in that: 2. The antibacterial material according to claim 1, wherein the high molecular polymer contains an acidic group and a phosphonium base ionically bonded to the acidic group. 3. A polymer comprising a dicarboxylic acid component and a glycol component as main components, and a phosphonium salt of a sulfonic acid group-containing aromatic dicarboxylic acid represented by the following formula (1): The antibacterial material according to claim 1 or 2, wherein the antibacterial material is a copolymerized polyester obtained by copolymerizing mol%. (Wherein A is an aromatic group, X ₁ and X ₂ are ester-forming functional groups, R _1, R _2, R _{3 and} R ₄ are the same or different alkyl groups, at least one of which is a carbon atom) An alkyl group of several 10 to 20)