JPH06145313A - Aliphatic polyester and its production - Google Patents

Abstract

PURPOSE:To provide an aliphatic polyester which is biodegradable and usable in the form of a molding and to provide a process for its production. CONSTITUTION:An aliphatic polyester comprising repeating units of the formula wherein x is an integer of 2-20, y is an integer of 0-16, and n is an integer of 5-500 and having a number-average molecular weight of 5000-100000 (in terms of polystyrene) as determined by gel permeation chromatography(GPC).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high molecular weight aliphatic polyester having biodegradability which is easily decomposed by microorganisms in soil and can be used as a molded article, and a method for producing the same.

[0002]

2. Description of the Related Art Plastics, which are used as synthetic fibers, films, and other molded products, have the advantages of being light and durable, and can be supplied inexpensively and in large quantities in a stable manner. It has brought convenience and built a modern society that can be called a plastic civilization. However, in recent years, in response to environmental problems on a global scale, there has been a demand for the development of polymer materials that decompose in the natural environment. Among them, plastics that are decomposed by microorganisms are especially environmentally friendly. There are great expectations in the industry as materials and new types of functional materials.

It has been well known that aliphatic polyesters are biodegradable, and among them, poly-3-hydroxybutyric acid ester (PHB) produced by microorganisms and poly-polymer which is a synthetic polymer are known. ε-caprolactone (PCL) and polyglycolic acid (PGA) are typical ones.

The biopolyester mainly composed of PHB is industrially produced because it has excellent environmental compatibility and physical properties, but it is poor in productivity and is typified by polyethylene from the viewpoint of cost. There are limits to what can be substituted as general-purpose plastics (Fiber and Industry, 47, 53
See page 2 (1991)). Regarding PCL, although a high degree of polymerization that can be formed into fibers and films has been obtained, it has a melting point of 65 ° C or less and poor heat resistance and cannot be used for a wide range of applications [Polymer Science Technology (Polym. .Technol.), 3
Vol. 61 (1973)]. Furthermore, PGA and glycolide-lactide (9: 1) copolymers, which have been put into practical use as bioabsorbable sutures, are metabolized and absorbed in vivo after undergoing abiotic hydrolysis, but are expensive. In addition to that, it has poor water resistance and is not suitable for use as general-purpose plastics.

On the other hand, α, ω-aliphatic diols and α, ω
An aliphatic polyester produced by melt polycondensation with an aliphatic dicarboxylic acid, such as polyethylene succinate (PES) or polyethylene adipate (PEA)
It has been confirmed that it is a polymer that has been known for a long time, can be manufactured at low cost, and that it is biodegraded by microorganisms even when it is buried in the soil [Int. Biodetetlet].
n. Bull. ), Vol. 11, p. 127 (1975), and Polymer Science Technology (Polym.
Sci. Technol. ), Vol. 3, p. 61 (197)
3)], but these polymers have poor thermal stability and undergo a decomposition reaction at the time of polycondensation.
Only those having a molecular weight of about 2,000 to 6,000 were obtained, which was not sufficient for processing into fibers or films.

In order to increase the molecular weight of these aliphatic polyesters, it has been reported that the aliphatic polyesters are treated with diisocyanates such as hexamethylene diisocyanate and toluene diisocyanate [Polymer Journal (Po
Lymer J. ), Vol. 2, p. 387 (1971), and Japanese Patent Application Laid-Open No. 4-189822], there is a disclosure that these methods have an effect of increasing the molecular weight, but no disclosure about biodegradability. It has not been.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a high molecular weight aliphatic polyester which is biodegradable and can be used as a molded article, and to easily provide the high molecular weight aliphatic polyester. The present invention provides a method for producing a high molecular weight aliphatic polyester that can be obtained.

[0008]

As a result of various studies to solve the above-mentioned problems, the present inventors have found that a specific aliphatic polyester obtained by chain-extending an aliphatic polyester with tetracarboxylic dianhydride has the above-mentioned problems. Based on this finding, the inventors arrived at the present invention.
That is, firstly, the gist of the present invention is an aliphatic polyester comprising a repeating unit represented by the general formula (1) and having a polystyrene reduced number average molecular weight of 5,000 to 100,000 as determined by GPC. To do.

[0009]

[Chemical 2]

(In the formula, x is 2 to 20, y is 0 to 16, n
Represents an integer of 5 to 500. )

Secondly, it has hydroxyl groups at both ends and has a number average molecular weight (value determined by end group titration) of 1,
The gist of the present invention is to provide a method for producing a high molecular weight aliphatic polyester, which comprises reacting an aliphatic polyester having a molecular weight of 000 or more with a tetracarboxylic acid dianhydride.

The present invention will be described in detail below. The aliphatic polyester of the present invention has a number average molecular weight in terms of polystyrene of 5,000 to 100, which is determined by GPC.
000, and all are represented by the above general formula (1) in which all are connected by an ester bond and a carboxyl group is introduced into the side chain. Further, the introduced carboxyl group can be identified by a terminal group measuring method. The introduced carboxyl group is a hydrophilic group and has a function of favorably affecting biodegradability.

As described above, the polyester of the present invention is biodegradable because it is linked by an ester bond, and has a high number average molecular weight, so that it has good moldability. When the number average molecular weight of this aliphatic polyester is less than 5,000, the moldability is poor, and when the number average molecular weight exceeds 100.000, it has no biodegradability.

In such a polyester, an aliphatic polyester having hydroxyl groups at both ends and having a number average molecular weight of 1,000 or more determined by an end group measurement method is reacted with tetracarboxylic dianhydride. Can be obtained by The aliphatic polyester used in the present invention having hydroxyl groups at both ends and having a number average molecular weight of 1,000 or more as determined by the terminal group measurement method includes:
For example, α, ω-aliphatic diol (hereinafter referred to as glycol) and α, ω-aliphatic dicarboxylic acid (hereinafter referred to as dicarboxylic acid) or α, ω-dicarboxylic acid diester (hereinafter referred to as dicarboxylic acid diester) Can be obtained by esterification or transesterification in the molten state in the presence of excess glycol to form an oligomer, and then dehydration and deglycolization in the presence of a catalyst for polymerization.

Examples of the glycol used here include compounds represented by the general formula (2). _{HO- (CH 2) x -OH (} 2) ( wherein, x is an integer of 2 to 20 carbon atoms.)

Specific examples thereof include ethylene glycol, propylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, Examples thereof include dodecamethylene glycol, tridecamethylene glycol, eicosane methylene glycol and the like, among which ethylene glycol and tetramethylene glycol are preferable.

The dicarboxylic acid used here is
Examples thereof include compounds represented by the general formula (3). _{HOOC- (CH 2) y -COOH (} 3) ( wherein, y is to an integer of 0 to 16.)

Specific examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid,
Examples thereof include decanedicarboxylic acid and hexadecanedicarboxylic acid, with oxalic acid and succinic acid being preferred.

Further, the dicarboxylic acid diester used here includes compounds represented by the general formula (4). _{ROOC- (CH 2) y -COOR (} 4) ( wherein, y represents an integer of 0 to 16, R is C1-8
Represents an aliphatic saturated hydrocarbon. )

Specific examples thereof include dimethyl oxalate, diethyl oxalate, dibutyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, diethyl succinate, dibutyl succinate, dimethyl glutarate, diethyl glutarate. , Dimethyl adipate, diethyl adipate, dioctyl adipate, dimethyl pimelate, dimethyl azelate, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, dioctyl sebacate, dityl nonanedicarboxylate, dimethyl decanedicarboxylate, hexadecanedicarboxylic acid Examples thereof include dimethyl, and among them, dimethyl oxalate, diethyl oxalate, dimethyl succinate, and diethyl succinate are preferable.

In the present invention, when an aliphatic polyester having hydroxyl groups at both ends is produced, the charging ratio of dicarboxylic acid or dicarboxylic acid diester and glycol is usually 1: 1 to 1: 2.2 in terms of molar ratio. The ratio is preferably 1: 1.05 to 1: 1.6, more preferably 1: 1.1 to 1: 1.5. Regarding the reaction conditions, when an oligomer is produced by esterification (including transesterification reaction), the range of 100 to 190 ° C. for 1 to 10 hours is preferable,
The range of 150 to 190 ° C. and 2 to 5 hours is more preferable.
In addition, the polymerization reaction by dehydration and deglycolization is less than 0.
1 ~ 5mmHg under reduced pressure, 190 ~ 260 ℃ 1 ~
It is preferably carried out for 10 hours, more preferably at 200-250 ° C. for 2-5 hours under a reduced pressure of 0.1-1 mmHg.

As the polymerization catalyst, a catalyst generally used in producing polyethylene terephthalate can be applied, and examples thereof include lithium, sodium, potassium, cesium, magnesium, calcium, barium, strontium, zinc, aluminum, Examples include metals such as titanium, cobalt, germanium, tin, lead, antimony, bismuth, boron, iron, manganese, nickel, organometallic compounds thereof, organic acid salts, metal alkoxides, metal oxides and the like. Particularly preferred compounds are calcium acetate, zinc acetate, manganese acetate, antimony trioxide, germanium dioxide, tetra n-butyl titanate, stannous chloride and the like, and two or more kinds of these catalysts may be used. At that time, the amount of catalyst used is 1 × with respect to 1 mol of dicarboxylic acid or dicarboxylic acid diester.
10 ^{−4 to} 5 × 10 ⁻³ mol is preferable, and 2 × 10 ⁻⁴ to 1 ×
It is more preferable to use it in the range of 10 ⁻³ mol.

The aliphatic polyester thus obtained has hydroxyl groups at both ends, and has a number average molecular weight of 1,000 to 10 as determined by the OH end group titration method.
000, usually about 2,000 to 6,000, and with such a number average molecular weight, only brittle ones can be obtained even when formed into films, fibers, sheets and the like. However, when this aliphatic polyester is treated with the tetracarboxylic dianhydride described below, the polyester and the tetracarboxylic dianhydride are linked by an ester bond, and a high molecular weight polyester having a number average molecular weight of 5,000 or more is obtained. The obtained product has moldability without impairing the original property of biodegradability.

Examples of the tetracarboxylic acid dianhydride used in the present invention include 1,2-, 3,4-butanetetracarboxylic acid dianhydride and 1,3-, 2,4-butanetetracarboxylic acid dianhydride. Anhydride, 1,4-, 2,3-tetracarboxylic dianhydride, pyromellitic dianhydride, 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3'4,4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic dianhydride , 3,3 ', 4,4'-diphenyl ether tetracarboxylic acid dianhydride, ethylene glycol bis (anhydrotrimellitate), and also those which become tetracarboxylic acid dianhydride by heating. , Such concrete examples are 1, 2,
3,4-butanetetracarboxylic acid can be mentioned. Among them, 1,2-, 3,4-butanetetracarboxylic dianhydride, 1,3-, 2,4-butanetetracarboxylic dianhydride, ethylene glycol bis (anhydrotrimellitate), 1, 2,3,4-butanetetracarboxylic acid is preferable, and these can be used as a mixture.

In the present invention, the amount of the tetracarboxylic dianhydride to be reacted with the aliphatic polyester having hydroxyl groups at both ends is such that the carboxylic anhydride is 0 relative to 1 equivalent of the hydroxyl group of the aliphatic polyester. ．
It may be 3 to 2 equivalents (0.15 to 1 mol of tetracarboxylic dianhydride), preferably 0.5 to 1.1 equivalents. If the equivalent of the carboxylic acid anhydride of the tetracarboxylic dianhydride is smaller than 0.3 or larger than 2, it is difficult to obtain the target high molecular weight aliphatic polyester. Also, if the number average molecular weight of the aliphatic polyester used in the reaction is less than 1,000, not only a high molecular weight aliphatic polyester cannot be obtained, but also acid anhydride units increase in the polymer, resulting in low biodegradability. Become.

The reaction conditions for the aliphatic polyester having hydroxyl groups at both ends and the tetracarboxylic dianhydride are selected depending on the aliphatic polyester and tetracarboxylic dianhydride used, but usually 100 to 20.
At 0 ℃, under normal pressure nitrogen for 0.5-5 hours, or 0.1
It is preferably carried out under reduced pressure of 10 mmHg.

Since the aliphatic polyester of the present invention is thermoplastic and has moldability, it can be applied to various uses. For example, as a biodegradable polymer, it can be processed into a film, a fiber or a sheet, and used as various bottles, shopping bags, packaging materials, synthetic threads, fishing lines, fishing nets, non-woven fabrics, agricultural multi-films and the like. Besides the above, the aliphatic polyester of the present invention can be used as a base resin for hot melt adhesives, paints, and urethane elastomers.

When the aliphatic polyester of the present invention is used as a biodegradable polymer, the microbial selectivity is not particularly clear, but it is a burial test in ordinary soil and activated sludge explosion used in sewage treatment plants. The biodegradability can be easily confirmed by the method of dipping in the tank. That is, it can be confirmed by immersing the molded product in soil for a predetermined period of time and then measuring the molecular weight of this molded product or comparing its surface morphology with that before burial.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples. Each value was obtained as follows. (1) OH number The polymer (aliphatic polyester) is reacted with excess succinic anhydride in the molten state to convert the terminal into a COOH group, and then the polymer is dissolved in chloroform or dimethylsulfoxide, and then with acetone. It was purified by repeating reprecipitation, and determined by non-aqueous titration with N / 50 sodium hydroxide ethanol solution using phenolphthalein as an indicator.

(2) COOH value The polymer is dissolved in chloroform or dimethylsulfoxide, and phenolphthalein is used as an indicator.
It was determined by non-water titration with a N / 50 sodium hydroxide ethanol solution.

(3) Number average molecular weight (Mn) by end group measurement method: It was determined by the following formula.

[0032]

[Equation 1]

(4) Number-average molecular weight in terms of polystyrene determined from GPC A polystyrene-converted value was determined using a GPC measuring device manufactured by Waters (Waters). Measurement conditions Examples 1 to 5: Chloroform was used as an eluent, and 35
It was measured at ° C. Example 6: Using dimethyl sulfoxide as eluent,
It was measured at 60 ° C.

(5) Reduced Specific Viscosity (ηsp / c) The viscosity was determined by measuring the viscosity of the polymer solution at a concentration of 0.5 g / deciliter using an Ubbelohde viscometer, and used as a standard for the molecular weight. Measurement conditions Examples 1 to 5: Chloroform was used as a solvent at 35 ° C.
It was measured at. Example 6: Using dimethyl sulfoxide as a solvent, 6
It was measured at 0 ° C.

(6) Melting point Using a trace melting point measuring device MP-S3 manufactured by Yanaco Co., Ltd., the melting point was measured at a temperature rising rate of 1 to 2 ° C./min.

(7) Appearance It was judged by visual observation or optical microscope observation. A: Severe damage B: Significant damage C: Some damage
D: unchanged

(8) Film Strength In accordance with JIS K-7327, a sample of a predetermined size was prepared and measured using a precision universal tester 2020 manufactured by Intesco.

Example 1 118 g (1.00 mol) of succinic acid and 8 parts of ethylene glycol were placed in a three-necked flask equipped with a stirrer and a gas introduction tube.
Add 0.7 g (1.30 mol) and 0.053 g (3.0 × 10 ⁻⁴ mol) of calcium acetate monohydrate, and add 180
The mixture was melted by immersion in a 0 ° C. oil bath. Nitrogen was slowly flowed into the melt, the esterification reaction was carried out at a temperature of 180 ° C. for 2 hours, and the produced water and excess ethylene glycol were distilled off. Then, antimony trioxide 0.087g
(3.0 × 10 ^-4 mol) was added, the temperature was raised to 240 ° C., and nitrogen was flowed under a reduced pressure of 20 mmHg for 1 hour, 5
1 hour under reduced pressure of mmHg, and 3 under reduced pressure of 1 mmHg or less.
By heating for a period of time, 144 g of a viscous polymer liquid was obtained. The OH number of this polymer is 0.36 meq / g, C
The OOH value was 0.012 meq / g, the polymer was substantially a hydroxyl group at both ends, and the Mn was 5,400. Further, ηsp / c was 0.19 (concentration: 0.5 g / dl, 30 ° C, in chloroform), and the melting point was 103 ° C.

Next, the temperature of the polymer viscous liquid is set to 180.
℃, ethylene glycol bis [(anhydrotrimeritate), Shin Nippon Rika Co., Ltd., Rikashido TMEG-
200] 10.6 g [0.026 mol, carboxylic acid anhydride / OH = 1.0 (equivalent ratio)] was added and reacted at 180 ° C. for 1 hour under a nitrogen stream to obtain a target polymer. . The ηsp / c of this polymer was 0.43 (concentration: 0.5 g / dl, 30 ° C., in chloroform), the melting point was 101 ° C., and the polystyrene reduced number average molecular weight determined by GPC was 1.2 × 10. ^{Was 4} .

Example 2 Ethylene glycol bis (anhydrotrimellitate)
Instead of 10.6 g, 1,2-, 3,4-butanetetracarboxylic dianhydride 3.60 g (0.018 mol) and 1,3-, 2,4-butanetetracarboxylic dianhydride 1 A target polymer was obtained in exactly the same manner as in Example 1 except that a mixture with 0.54 g (0.008 mol) was used. Ηsp / c of this polymer was 0.67 (concentration: 0.
5 g / dl, 30 ° C. in chloroform), melting point is 1
The temperature was 01 ° C., and the polystyrene reduced number average molecular weight determined by GPC was 2.2 × 10 ⁴ .

Example 3 118 g (1.00 mol) of succinic acid and 108 g (1.20 mol) of tetramethylene glycol were placed in a three-necked flask equipped with a stirrer and a gas introduction tube, and placed in an oil bath at 180 ° C. The pot mixture was melted. Nitrogen was slowly flowed into the melt, the esterification reaction was carried out at a temperature of 180 ° C. for 3 hours, and the produced water and excess tetramethylene glycol were distilled off. Then tetra-n-butyl titanate 0.
10 g (3.0 x 10 ^-4 mol) were added, then the temperature was raised to 2
Raise the temperature to 40 ° C, and under a reduced pressure of 20 mmHg while flowing nitrogen, 1
By heating for 1 hour under reduced pressure of 5 mmHg, and further for 2 hours under reduced pressure of 1 mmHg or less, a viscous polymer liquid 1
72 g were obtained. The OH value of this polymer is 0.35 meq / g, COOH value is 0.010 meq / g,
It was a polymer substantially having hydroxyl groups at both ends, and Mn was 5,500. Also, ηsp / c is 0.25
(Concentration 0.5 g / dl, 30 ° C., in chloroform), and melting point was 111 ° C.

Next, the temperature of the polymer viscous liquid is set to 180.
C., ethylene glycol bis (anhydrotrimellitate) 11.1 g (0.027 mol, acid anhydride / O
H = 0.9 (equivalent ratio)) was added, the mixture was reacted at 180 ° C for 0.5 hour under a nitrogen stream, and then reacted at 180 ° C under a reduced pressure of 1 mmHg for 1 hour to obtain the target polymer. . Ηsp / c of this polymer is 0.50 (concentration 0.5
g / dl, 30 ° C., in chloroform), melting point 10
The temperature was 8 ° C., and the polystyrene reduced number average molecular weight determined by GPC was 2.2 × 10 ⁴ .

Example 4 Ethylene glycol bis (anhydrotrimellitate)
Instead of 11.1 g, 1,2-, 3,4-butanetetracarboxylic dianhydride 3.76 g (0.019 mol) and 1,3-, 2,4-butanetetracarboxylic dianhydride 1 A target polymer was obtained in exactly the same manner as in Example 3 except that a mixture with 0.61 g (0.0081 mol) was used. This polymer had an ηsp / c of 0.62 (concentration: 0.5 g / dl, 30 ° C., in chloroform), a melting point of 111 ° C., and a polystyrene-equivalent number average molecular weight of 1.5 × 10 ^{4 as} determined by GPC. Met.

Example 5 Instead of 10.6 g of ethylene glycol bis (anhydrotrimellitate) in Example 1, 1,2,
3,4-butanetetracarboxylic acid 6.08 g (0.02
A desired polymer was obtained in exactly the same manner as in Example 1 except that 6 mol) was used. Ηsp / c of this polymer was 0.38 (concentration: 0.5 g / dl, 30 ° C., in chloroform), melting point was 100 ° C., and polystyrene conversion number average molecular weight determined by GPC was 9.2 × 10. ^{Was 3} .

Example 6 In a polymerization reaction tube equipped with a side tube, dimethyl oxalate 59.
0 g (0.50 mol), ethylene glycol 62.1 g
(1.0 mol), and tetra n-butyl titanate 0.
Add 10 g (2.9 × 10 ^-4 mol) and put 120 in a reaction tube.
The mixture was melted by immersing it in an oil bath at 0 ° C., and the capillary was put so that it reached the bottom of the reaction tube. Pour nitrogen slowly into the melt,
It took 2 hours at a temperature of 180 ° C. to distill off the produced methanol and excess ethylene glycol. Then set the temperature to 1
Keep the temperature at 80 ° C, and under a reduced pressure of 20 mmHg with flowing nitrogen, 1
By heating for 5 hours under a reduced pressure of 5 mmHg and further for 3 hours under a reduced pressure of 1 mmHg or less, a viscous polymer liquid 5
8.0 g was obtained. This polymer had an OH value of 1.6 meq / g, a COOH value of 0, was a polymer having hydroxyl groups at both ends, and had an Mn of 1050. Further, ηsp / c was 0.13 (concentration: 0.5 g / dl, 60 ° C, in dimethylsulfoxide), and the melting point was 178 ° C.

Next, the temperature of the polymer solution was kept at 180 ° C., and 6.43 g (0.032 mol) of 1,2-, 3,4-butanetetracarboxylic dianhydride and 1,3-, 2. Four
-Butanetetracarboxylic dianhydride 2.76 g (0.0
14 mol) with carboxylic acid anhydride / OH =
Insert so that it becomes 1.0 (equivalent ratio), 180 ℃, 1mmHg
The desired polymer was obtained by reacting under the following reduced pressure for 1 hour. Ηsp / c of this polymer is 0.32
(Concentration: 0.5 g / dl, 60 ° C., in dimethylsulfoxide), the melting point was 175 ° C., and the polystyrene reduced number average molecular weight determined by GPC was 8000.

Reference Examples 1 to 6 The polymers obtained in Examples 1 to 6 were melt-pressed at a temperature 10 to 20 ° C. higher than their melting points using a hot press machine to easily prepare a film having a thickness of 100 μm. I was able to. This film is cut into 5 cm x 5 cm, embedded in the soil (in the yard of a private house, at a surface layer of 5 to 10 cm), and the condition of the film after the initial, 3 months, and 6 months is examined,
The biodegradability was evaluated. The results are shown in Table 1. As a comparative example, a commercially available polyethylene film and polyester film (both having a thickness of 100 μm) were used in the same manner, but neither the appearance nor the film strength was changed. From Table 1, it is clear that the aliphatic polyester of the present invention has biodegradability.

[0048]

[Table 1]

[0049]

INDUSTRIAL APPLICABILITY As described above, the aliphatic polyester of the present invention is biodegradable because it is linked by an ester bond, and is excellent in moldability because it has a high number average molecular weight. Therefore, the aliphatic polyester of the present invention can be used as a biodegradable film, fiber, sheet, or processed into various shapes for use. Further, according to the production method of the present invention, the high molecular weight aliphatic polyester can be produced easily and at low cost.

Claims (2)

[Claims] 1. A polystyrene-equivalent number-average molecular weight of 5,000 as determined by gel filtration chromatography (GPC), which comprises repeating units represented by the following general formula (1).
Aliphatic polyester which is 0-100,000. [Chemical 1] (In the formula, x is 2 to 20, y is 0 to 16, and n is 5 to 500.
Represents the integer. ) 2. An aliphatic polyester having hydroxyl groups at both ends and having a number average molecular weight (value determined by end group titration) of 1,000 or more is reacted with tetracarboxylic dianhydride. The method for producing an aliphatic polyester according to claim 1, which is characterized in that.