JP2556907B2 - Aliphatic polyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has properties as a thermoplastic elastomer,
The present invention relates to an aliphatic polyester having excellent heat resistance, mechanical strength and moldability.

(Prior Art) Generally, in order for a material to exhibit rubber elasticity, it is necessary that an amorphous polymer whose molecular chain can easily rotate is partially crosslinked. For example, in elastic rubber, sulfur molecules form a network structure by bridging the molecular chains by chemical bonds. In addition to rubber, materials combining various polymer compounds and crosslinking agents have been proposed. A cross-linking process is required to mold these materials, and since they do not exhibit thermoplasticity after being chemically cross-linked, cross-linked materials cannot be molded by injection molding or extrusion.

In recent years, a thermoplastic elastomer that exhibits rubber elasticity at room temperature and is plasticized at high temperature has been developed, and various types of thermoplastic elastomers are manufactured and marketed. This thermoplastic elastomer does not require a long-time cross-linking step unlike the conventional rubber, and can be molded by injection molding or extrusion molding. A characteristic of the molecular structure of thermoplastic elastomers is a cross-link that does not rely on a strong chemical bond, that is, a system that applies some kind of inter-polymer constraint that is effective only at around room temperature, and is a polymer assembly consisting of soft and hard segments. The body is the typical structure of thermoplastic elastomers. The soft segment and the hard segment have different chemical structures from each other. In the hybrid composition of the two, the homogenous parts agglomerate, and the heterogeneous parts form a micro-unbalanced structure in which the phases are separated from each other. The agglutinated portion shows a binding effect between the molecules.

Examples of the thermoplastic elastomer include styrene type, olefin type, urethane type, ester type and amide type. In the styrene series, polystyrene forms a frozen phase as a hard segment and binds between molecular chains, resulting in rubber elasticity. In the olefin system, the polypropylene crystal phase acts as a hard segment. In the urethane type, the polyurethane segment causes physical crosslinks between molecular chains by hydrogen bonds. Further, the ester-based polybutylene terephthalate chain acts as a hard segment, and the amide-based nylon chain such as 6-nylon or 6,6-nylon acts as a hard segment.

(Problems to be Solved by the Invention) As described above, since the thermoplastic elastomer exhibits rubber elasticity at room temperature and can be molded, it is widely used for automobile parts and various industrial products. However, conventional thermoplastic elastomers have lower heat resistance due to the restriction of the softening melting point of the part because cross-linking is performed by physical restraint as compared with cross-linking type rubber, and the elastic modulus and breaking strength at high temperature are low. ，
The physical properties such as elongation at break were inferior.

In aliphatic polyesters containing a dihydroxy or monohydroxy compound having a p-terphenyl or p-quaterphenyl skeleton as a constituent component, the transition point (melting point) of the hydroxy compound from the crystalline state to the liquid crystal state reflects its characteristic molecular structure. Since it is extremely high, it is a thermoplastic elastomer that brings about very strong physical crosslinks with high heat resistance, is excellent in heat resistance and mechanical properties, and is also excellent in moldability. By the way, in producing such an aliphatic polyester, it is necessary to lengthen the reaction time to polymerize the polymer in order to obtain a thermoplastic elastomer with particularly high physical properties. In order to increase the production efficiency, that is, to improve the productivity, it is desired to shorten the reaction time.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fat that has properties as a thermoplastic elastomer, is excellent in heat resistance and mechanical properties, and is also excellent in molding processability. An object of the present invention is to provide an aliphatic polyester capable of producing a group polyester in a shorter time than ever before.

(Means for Solving the Problems) The inventors of the present invention substantially shorten the reaction time required for producing a polyester having a predetermined molecular weight by adding a branching agent during the production of the above aliphatic polyester. The present invention has been completed, and it was found that the obtained aliphatic polyester does not impair the properties as an elastomer and, in addition, it has a strong mechanical property by forming a network structure.

The aliphatic polyester of the present invention has the following general formula [I]
An aliphatic dicarboxylic acid represented by formula (1), an aliphatic diol, at least one of a dihydroxy compound represented by the following formula [II] and a monohydroxy compound represented by the following formula [III], and 3 to 6 At least one branching agent selected from the group consisting of a hydroxyl group-containing polyol, 3-4 carboxyl group-containing polycarboxylic acid, and a hydroxyl group- and carboxyl group-containing oxy acid group having 3-6 groups. As a constituent component, the content ratio of the dihydroxy compound is 0.1 to 30 mol% in all monomers constituting the aliphatic polyester, and the content ratio of the monohydroxy compound is all monomers constituting the aliphatic polyester. 0.1 to 20 mol% of the total amount, the branching agent is contained in 0.25 to 2.5 equivalents per 100 mol of the aliphatic dicarboxylic acid, and dilute orthochlorophenol. Use the liquid 30 ℃
Intrinsic viscosity of 0.4 or more measured by Ubbelohde viscometer
It is 2.0 or less, thereby achieving the above-mentioned object.

HOOC- (CH ₂₎ n-COOH (I) (wherein, n represents an integer of 0.) (In the formula, R ¹ and R ² independently represent an alkylene group, p is 3 or 4, and q and r are independently 0 or 1.) (In the formula, R ³ represents an alkylene group, l is 2 or 3, and
m is 0 or 1. In the above aliphatic dicarboxylic acid, if a dicarboxylic acid having more than 10 carbon atoms is used, the physical properties of the molded product obtained from the aliphatic polyester are deteriorated. As the dicarboxylic acid, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid are preferably used.

Examples of the aliphatic diol include glycol and polyalkylene oxide. Examples of the glycol include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3
-Butanediol, 1-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, cyclopentane-1,2 -Diol, cyclohexane-1,2-diol, cyclohexane-1,3-diol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, and the like, which may be used alone,
Two or more kinds may be used in combination.

Examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyhexamethylene oxide and the like, and these may be used alone or in combination of two or more kinds. When the number average molecular weight of polyalkylene oxide is small, the ability to impart flexibility to the resulting aliphatic polyester is reduced, and when it is too large, physical properties such as thermal stability of the obtained aliphatic polyester are reduced. ~ 20,000, more preferably 500 ~
It is 5,000.

The dihydroxy compound represented by the above formula [II] is a low molecular weight compound exhibiting liquid crystallinity, the alkylene groups R ¹ and R ² are preferably ethylene groups or propylene groups, and q and r are 0 or 1
And 4,4 ″ -dihydroxy- represented by the following formula [A]:
p-terphenyl, 4,4-dihydroxy-p-quaterphenyl represented by the following formula [B] and 4,4-di (2-hydroxyethoxy) -p-quaterphenyl represented by the following formula [C] Etc. are preferably used.

The transition temperature of 4,4 ″ -dihydroxy-p-terphenyl [A] from the crystalline state to the liquid crystal state is 260 ° C., and that of 4,4-dihydroxy-p-quarterphenyl [B] is 33 ° C.
6 ° C, that of 4,4-di (2-hydroxyethoxy) -p-quaterphenyl [C] is 403 ° C. The liquid crystal state means a state in which the compound is in a molten state and the molecules maintain the alignment state. The above dihydroxy compounds [II] may be used alone or in combination.

Liquid crystal molecules generally have high crystallinity, and as described above,
4,4 "-dihydroxy-p-terphenyl [A], 4,4
-Dihydroxy-p-quaterphenyl [B] and 4,
Since 4-di (2-hydroxyethoxy) -p-quaterphenyl [C] has a high transition point from its crystal to the liquid crystal state, when these dihydroxy compounds [II] are incorporated in the polymer chain, Polymers show unique properties.

That is, the dihydroxy compound [II] exhibits crystallinity,
Moreover, because of its high transition point, dihydroxy compounds [I
Even when the compounding amount of I] is small, a strong and heat-resistant physical crosslink is formed. As a result, it is presumed that a thermoplastic elastomer having high heat resistance can be obtained without impairing the flexibility derived from the soft segment.

The monohydroxy compound represented by the above formula [III] is a rigid low molecular weight compound having a paraphenylene skeleton, and the melting point of these compounds is extremely high, reflecting the characteristic molecular structure. Furthermore, the paraphenylene skeleton is known to be effective as a mesogen for low-molecular liquid crystal compounds, which means that the skeleton has a strong cohesive force not only in a solid state but also in a high temperature state (molten state). It shows. Therefore, when the above-mentioned monohydroxy compound [III] is incorporated into the polymer terminal, it results in very strong physical crosslinks with high heat resistance, and a thermoplastic elastomer excellent in heat resistance is produced.

In the monohydroxy compound represented by the above formula (III), R ³ is preferably an ethylene group or a propylene group, and n
Is 0 or 1 and l is 2 or 3. Examples of the monohydroxy compound include 4-hydroxy-p-
Examples thereof include terphenyl, 4-hydroxy-p-quaterphenyl, 4- (2-hydroxyethoxy) -p-terphenyl, 4- (2-hydroxyethoxy) -p-quaterphenyl and the like. Monohydroxy compound [III]
May be used alone or in combination.

The composition of the aliphatic polyester of the present invention is as described above, and further, a poly-silicone having two hydroxyl groups,
Lactone or aromatic hydroxycarboxylic acid may be contained as a constituent component.

The above-mentioned poly-silicone has two hydroxyl groups, and a poly-silicone having two hydroxyl groups at the molecular ends is preferable. For example, dimethyl polysiloxane, diethyl polysiloxane having two hydroxyl groups at both ends of the molecule, Examples thereof include diphenylpolysiloxane. The lower the number average molecular weight of the polysilicone, the lower the ability to impart flexibility to the resulting polyester, and the higher it becomes.
Since it becomes difficult to form polyester, 100 to 20,000 is preferable, and 500 to 5,000 is more preferable.

The above-mentioned lactone is one that opens a ring and reacts with an acid and a hydroxyl group to add an aliphatic chain, imparts flexibility to a polyester, and has one having 4 or more carbon atoms in the ring. It is preferably a 5-membered to 8-membered ring, and examples thereof include ε-caprolactone, δ-valerolactone, γ-butyrolactone and the like.

The aromatic hydroxycarboxylic acid imparts rigidity and liquid crystallinity to the polyester, and includes salicylic acid, metahydroxybenzoic acid, parahydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 3-bromo-4-hydroxyl. Benzoic acid, 3-methoxy-4-hydroxybenzoic acid, 3-
Methyl-4-hydroxybenzoic acid, 3-phenyl-4-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 4-
Examples thereof include hydroxy-4′-carboxybiphenyl, and preferred are parahydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, and 4-hydroxy-4′-carboxybiphenyl.

Further, the above aliphatic polyester may contain an aromatic diol other than the dihydroxy compound [II] or an aromatic dicarboxylic acid as a constituent component in order to improve the mechanical properties of the polyester.

Aromatic diols include hydroquinone, resorcin, chlorohydroquinone, bromohydroquinone, methylhydroquinone, phenylhydroquinone, methoxyhydroquinone, phenoxyhydroquinone, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether,
4,4'-dihydroxydiphenyl sulfide, 4,4'-
Dihydroxydiphenyl sulfone, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, bisphenol A, 1,1-di (4-hydroxyphenyl) cyclohexane, 1,2-bis (4-hydroxyphenoxy) ethane, 1 Examples thereof include 4,4-dihydroxynaphthalene and 2,6-dihydroxynaphthalene.

Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, metal salts of 5-sulfoisophthalic acid, 4,4′-dicarboxybiphenyl, 4,4′-dicarboxydiphenyl ether, 4,4′-dicarboxydiphenyl sulfide, Four,
4'-dicarboxydiphenyl sulfone, 3,3'-dicarboxybenzophenone, 4,4'-dicarboxybenzophenone, 1,2-bis (4-carboxyphenoxy) ethane,
Examples include 1,4-dicarboxynaphthalene, 2,3-dicarboxynaphthalene and the like.

In the aliphatic polyester composed of dihydroxy compound [II], aliphatic diol and aliphatic dicarboxylic acid, heat resistance decreases as the content of dihydroxy compound [II] decreases, and elastic modulus increases and flexibility decreases as the content of dihydroxy compound [II] decreases. However, since it becomes unsuitable as a thermoplastic elastomer, the content of the dihydroxy compound [II] is preferably 0.1 to 30 mol% in all monomers constituting the polyester, and more preferably 0.5 to 20 mol%. More preferably 1.0 to 10
Mol%. When polyalkylene oxide or polysilicone is used as the diol other than the aromatic, its structural unit is counted as one monomer. That is, the degree of polymerization is 10
Polyethylene oxide is counted as 10 monomers.

Further, in the aliphatic polyester composed of the monohydroxy compound [III], the aliphatic diol and the aliphatic dicarboxylic acid, the heat resistance is lowered when the content of the monohydroxy compound [III] is decreased, and the molecular weight of the aliphatic polyester is increased when the content of the monohydroxy compound [III] is increased. Since it does not rise sufficiently and becomes inferior in physical properties, it is 0.1 to 2 in all monomers constituting the aliphatic polyester.
It is preferably 0 mol%. An aliphatic polyester composed of a dihydroxy compound [II], a monohydroxy compound [III], an aliphatic diol and an aliphatic dicarboxylic acid contains a hydroxy compound obtained by combining the dihydroxy compound [II] and the monohydroxy compound [III]. When the amount is too small, the heat resistance is lowered, and when it is too large, the flexibility is not lowered and a sufficient increase in the molecular weight cannot be obtained. Therefore, it is preferably 0.1 to 30 mol% in all the monomers constituting the aliphatic polyester. In this case, the ratio of the dihydroxy compound [II] and the monohydroxy compound [III] is preferably in the range satisfying 0 <[III] / [II] + [III] <2/3.

The branching agent includes a polyol having 3 to 6 hydroxyl groups, 3
A polycarboxylic acid having 4 to 4 carboxyl groups, and 3
Has ~ 6 hydroxyl groups and carboxyl groups, and the number of groups is 3
There are oxyacids that are ~ 6.

Examples of the above-mentioned polyols include glycerin, trimethylolpropane, pentaerythritol, 1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakishydroxymethylcyclohexane, tris (2-hydroxyethyl) isocyanurate, diether. Pentaerythritol and the like can be mentioned.

Examples of the polycarboxylic acid include hemimellitic acid, trimellitic acid, trimesic acid, pyromellitic acid,
1,1,2,2-ethanetetracarboxylic acid, 1,1,2-ethanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 1,2,3,4-
Cyclopentane tetracarboxylic acid etc. are mentioned. These polycarboxylic acids may be used as they are, but it is preferable to use them in the form of lower alkyl ester.

Examples of the oxy acid include citric acid, tartaric acid, 3
-Hydroxyglutaric acid, mucus acid, trihydroxyglutaric acid, 4-β-hydroxyethylphthalic acid and the like can be mentioned.

These branching agents are not limited to one kind, and a plurality of kinds may be used, and 0.25 to 2.5 equivalents are used per 100 mol of the aliphatic dicarboxylic acid. If the amount of the branching agent used is less than 0.25 equivalent, the resulting polyester will not be sufficiently branched, so that an aliphatic polyester having the desired physical properties cannot be obtained. The amount of branching agent used
If it exceeds 2.5 equivalents, gelation occurs during production, and the limited physical properties of the aliphatic polyester are degraded.

The aliphatic polyester composed of the above constituents can be produced by any of the following generally known polycondensation methods.

A method in which a dicarboxylic acid and a diol component (including an aliphatic diol, a dihydroxy compound, a monohydroxy compound, etc.) are directly reacted.

A method of reacting a lower ester of dicarboxylic acid and a diol component by transesterification.

A method of reacting a dicarboxylic acid halide and a diol component in a suitable solvent such as pyridine.

A method of reacting a metal alcoholate of a diol component with a dicarboxylic acid halide.

A method of reacting an acetylated diol component and a dicarboxylic acid by transesterification.

The type of branching agent and the method of addition are usually different depending on the polycondensation method used. When the method (1) is used, it is preferable to add the polyol, polycarboxylic acid or oxyacid to the reaction medium before the reaction is completed. When the method (1) is used, it is preferable to add the lower ester of polycarboxylic acid or polyol before the completion of the transesterification reaction. When the method (1) is used, it is preferable to add a polycarboxylic acid halide or polyol to the solvent. When the above method is used, it is preferable to react the polyol with a metal alcoholate and to react it with a polycarboxylic acid as a halide. When the method (1) is used, it is preferable to add the acetylated product of the polyol or the polycarboxylic acid by the end of the transesterification reaction.

In the polycondensation, a catalyst generally used in producing polyester may be used. As this catalyst, lithium, sodium, potassium, cesium, magnesium, calcium, barium, strontium,
Metals such as zinc, aluminum, titanium, cobalt, germanium, tin, lead, antimony, arsenic, cerium, boron, cadmium and manganese, their organometallic compounds,
Examples thereof include organic acid salts, metal alkoxides, metal oxides and the like.

Particularly preferred catalysts are calcium acetate, diacyl stannous tin, tetraacyl stannic tin, dibutyltin oxide, dibutyltin dilaurate, dimethyltin malate, tin dioctanoate, tin tetraacetate, triisobutylaluminum, tetrabutyltitanate, germanium dioxide, and trisodium. It is antimony oxide. Two or more of these catalysts may be used in combination. In addition, water, alcohol, glycol, etc., which are by-products of polymerization, are efficiently distilled off,
In order to obtain a high molecular weight polymer, the reaction system is
It is preferable to reduce the pressure to 1 mmHg or less. The reaction temperature is generally between 150 and 350 ° C.

The following additives may be added during or after the production of the polyester of the present invention as long as the practicality is not impaired. That is, glass fiber, carbon fiber, boron fiber, silicon carbide fiber, alumina fiber, amorphous fiber, silicon
Inorganic fiber such as titanium / carbon fiber, organic fiber such as aramid fiber, inorganic filler such as calcium carbonate, titanium oxide, mica, talc, triphenyl phosphite, trilauryl phosphite, trisnonyl phenyl phosphite, 2- Thermal stabilizers such as tert-butyl-α- (3-tert-butyl-4-hydroxyphenyl) -p-cumenylbis (p-nonylphenyl) phosphite, hexabromocyclododecane, tris- (2,3-dichloropropyl) ) Phosphates, flame retardants such as pentabromophenylallyl ether, p-tert-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4
-Methoxy-2'-carboxybenzophenone, 2,4,5-
UV absorbers such as trihydroxybutyrophenone, butylhydroxyanisole, butylhydroxytoluene,
Antioxidants such as distearyl thiodipropionate, dilauryl thiodipropionate, hindered phenolic antioxidants, N, N-bis (hydroxyethyl) alkylamines, alkylallyl sulfonates, alkyl sulfanates, etc. Antistatic agent, barium sulfate, alumina,
Inorganic substances such as silicon oxide; higher fatty acid salts such as sodium stearate, barium stearate, sodium palmitate; organic compounds such as benzyl alcohol and benzophenone; crystallization of highly crystallized polyethylene terephthalate, polytrans-cyclohexanedimethanol terephthalate, etc. Examples include accelerators and the like.

Furthermore, the aliphatic polyesters of the present invention can be used for other thermoplastic resins such as polyolefins, modified polyolefins,
It may be used by mixing it with polystyrene, polyamide, polycarbonate, polysulfone, polyester or the like, or by mixing it with a rubber component to improve its properties.

The aliphatic polyester of the present invention is formed into a molded product by press molding, extrusion molding, injection molding, blow molding or the like. The physical properties of the molded article can be arbitrarily changed depending on its constituent components, its compounding ratio and the like. When polyester is prepared as a thermoplastic elastomer, the molded article is preferably used for flexible molded articles such as automobile parts, hoses, belts and packings, paints, adhesives and the like.

(Example) Below, this invention is demonstrated based on an Example.

Example 1 A glass flask having an inner volume of 1 equipped with a stirrer, a thermometer, a gas blowing port and a distillation port was charged with dimethyl adipate 8
7.1g (0.5mol), ethylene glycol 74.4g (1.2mol)
And 4,4-dihydroxy-p-quaterphenyl (hereinafter referred to as DHQ) 17.8 g, methyl trimellitate as a branching agent (hereinafter referred to as TMT) 441 mg (dicarboxylic acid 100 mol
0.75 equivalents), and 172 mmg of calcium acetate and 36 mmg of germanium oxide were added as catalysts. After replacing the flask with nitrogen, the temperature of the flask was raised to 180 ° C. 2 at this temperature
While maintaining the time, the ester conversion reaction was performed. During this reaction,
Methanol was distilled from the reaction mixture. Next, the flask was heated to 300 ° C., stirred for 30 minutes, depressurized to 1 mmgHg or less, and the polycondensation reaction was performed for 15 minutes in this state. With the reaction, ethylene glycol was distilled out, and an extremely viscous liquid was produced in the flask.

Next, the intrinsic viscosity of the obtained polymer was measured. The intrinsic viscosity [η] was measured in orthochlorophenol at 30 ℃. Table 1 shows the results.

The obtained polymer was injection molded at an injection pressure of 1500 kgf / cm ² , a mold temperature of 70 ° C and a cylinder temperature of 190 ° C.
No. 3 dumbbell was created. Using this Shimadzu Autograph AG-5000B in accordance with JIS K6301, the elastic modulus,
The breaking strength and the breaking strain were measured. Each physical property is room temperature, 50 ℃,
The measurement was performed under the temperature conditions of 80 ° C and 100 ° C, respectively. The results are shown in Table 2.

Comparative Examples 1 to 3 Polymers were obtained in the same manner as in Example 1 except that the amount of the branching agent TMT used and the polycondensation time were changed. The physical properties were measured.
The results are shown in Tables 1 and 2.

The following can be seen from the results of Table 1 and Table 2.

When TMT is not added (Comparative Example 1) and when the amount of TMT added is small (Comparative Example 2), the polymerization time becomes long. When an appropriate amount of TMT is added (Example 1), the polymerization time is shortened,
Furthermore, the elastic modulus, breaking strength and breaking strain of the molded product are 50 ° C.
It is larger than the molded product made from the one without TMT or the small addition amount at the above high temperature. Also, T
When the amount of MT added is too large (Comparative Example 3), the polymerization time is shortened, but gelation occurs and desired physical properties cannot be obtained.

(Effects of the Invention) The aliphatic polyester of the present invention can be easily produced by using an appropriate amount of a branching agent, has a network structure in its performance, is excellent in heat resistance and mechanical properties, and is a thermoplastic elastomer. Can be suitably used as.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Niki 2-2 Hyakusan, Shimamoto-cho, Mishima-gun, Osaka (72) Inventor Torasuke Saito 5-17-21 Yamatedai, Ibaraki-shi, Osaka (72) Inventor Hiroki Kadomachi 7-20 Otemachi, Ibaraki-shi, Osaka (72) Inventor Daishiro Kishimoto 2-11-20 Mishimaoka, Ibaraki-shi, Osaka Umeyama Mansion 102 (56) Reference Soviet Union Patent 186124 (SU, A)

Claims (1)

(57) [Claims] 1. An aliphatic dicarboxylic acid represented by the general formula [I] below, an aliphatic diol, a dihydroxy compound represented by the general formula [II] below, and a monohydric compound represented by the following formula [III]: At least one of the hydroxy compounds, a polyol having 3 to 6 hydroxyl groups, a polycarboxylic acid having 3 to 4 carboxyl groups, and an oxy acid having a hydroxyl group and a carboxyl group, the number of which is 3 to 6 At least one branching agent selected from the group consisting of as a constituent component, the content ratio of the dihydroxy compound is 0.1 to 30 mol% in all monomers constituting the aliphatic polyester,
The content ratio of the monohydroxy compound is 0.1 to 20 mol% in all monomers constituting the aliphatic polyester, and the branching agent is contained in an amount of 0.25 to 2.5 equivalents per 100 mol of the aliphatic dicarboxylic acid. An aliphatic polyester having an intrinsic viscosity of 0.4 or more and 2.0 or less as measured by an Ubbelohde viscometer using a dilute solution of the above. HOOC- (CH ₂₎ n-COOH (I) (wherein, n represents an integer of 0.) (In the formula, R ¹ and R ² independently represent an alkylene group, and p is 3
Or 4, and q and r are independently 0 or 1. ) (In the formula, R ³ represents an alkylene group, l is 2 or 3, and m is 0 or 1.)