JPH10265555A - Production of lactic acid-based polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly obtain the subject polymer having a high molecular weight and excellent biodegradability, mechanical properties and storage stability by reacting a polyester compound partially having carboxyl groups at the chain end with epoxides and thereafter reacting with a lactide. SOLUTION: (A) A polyester partially having carboxyl groups at the chain end is reacted with (B) epoxides to obtain a polyester compound having a low acid value and the resultant compound is reacted with (C) a lactide. Preferably, the component A has >=4×10<4> number-average molecular weight and 8×10<4> -30×10<4> weight-average molecular weight. Preferably, the component B is a monofunctional epoxide induced by diol, concretely ethylene oxide, propylene oxide, etc., as a raw material of the component A by hydrolysis. Preferably, the component A having 5-100 milliequivalent/kg acid value is reacted with the component B to obtain a polyester compound having 0.5-20 milliequivalent/kg acid value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyester compound (A ') having a low acid value, which is obtained by reacting a polyester compound (A) having a partial carboxyl group at a terminal with an epoxide (C). A lactic acid-based polyester (E) characterized by reacting a polyester compound (A ′) having a low acid value with a lactide (B), and having a high molecular weight having excellent physical properties such as heat resistance. The present invention relates to a method for producing a lactic acid-based polyester, which can rapidly produce a lactic acid-based polyester, and in which the obtained lactic acid-based polyester has excellent storage stability.

[0002]

2. Description of the Related Art The development of biodegradable plastics is regarded as a promising answer to the problem of garbage. In particular, polylactic acid-aliphatic polyester block copolymers are relatively inexpensive because they can be chemically synthesized. Moreover, there is a characteristic that the physical properties can be adjusted by changing the amount and type of the aliphatic polyester. Among these lactic acid-based polyesters, a lactic acid-based polyester having a high molecular weight is preferable from the viewpoint of heat resistance and physical properties, and therefore various methods for efficiently producing a high-molecular-weight-containing lactic acid-based polyester have been studied.

However, in a conventional method of obtaining a lactic acid-based polyester by copolymerizing an aliphatic polyester and lactide in the presence of a carboxylic anhydride, first, a carboxylic anhydride used for increasing the molecular weight of the aliphatic polyester is used. There have been problems such as that the carboxyl group derived from the polymerization slows down the rate of polymerization with lactide and accelerates the hydrolysis of the obtained polymer itself.

[0004]

The problem to be solved by the present invention is to rapidly produce a high molecular weight lactic acid-based polyester having excellent mechanical properties such as biodegradability and heat resistance, and to obtain the obtained lactic acid-based polyester. It is an object of the present invention to provide a method for producing a lactic acid-based polyester having excellent storage stability.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above problems, and as a result, reacted a polyester compound (A) having a partial carboxyl group at the terminal with an epoxide (C). After the lactide (B)
It was found that the reaction with lactide accelerates the ring-opening polymerization of lactide (B) and suppresses the hydrolysis of the produced lactic acid-based polyester, thereby completing the present invention.

That is, the present invention provides: (1) a polyester compound (A ') having a low acid value by reacting a polyester compound (A) partially having a carboxyl group at a terminal with an epoxide (C). And then reacting the polyester compound (A ′) having a low acid value with the lactide (B) to produce a lactic acid-based polyester (E),

(2) The polyester compound (A) having a partial carboxyl group at the terminal has an acid value of 5 to 100.
And the acid value of the “polyester compound having a low acid value” (A ′) is 0.5 to 20 meq / k.
g, the method for producing a lactic acid-based polyester (E) according to (1),

(3) The polyester compound (A) having a partial carboxyl group at the terminal is a polyester compound whose molecular weight is increased by an acid anhydride (D) (1) or (2). A method for producing a lactic acid-based polyester according to

(4) The weight average molecular weight (M) of the polyester compound (A) having a partial carboxyl group at the terminal
w) is 10,000 to 300,000, the method for producing a lactic acid-based polyester (E) according to any one of (1) to (3), and

(5) The method for producing a lactic acid-based polyester (E) according to (4), wherein the weight-average molecular weight of the lactic acid-based polyester (E) is 50,000 to 700,000.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyester compound (A) having a carboxyl group partially at the terminal, even a polyester compound consisting of a diol and a dicarboxylic acid alone, a diol and a dicarboxylic acid and a part thereof are 2 mol%.
Polyester compounds substituted with a certain degree of polyhydric alcohol and / or polycarboxylic acid derivative or those having a hydroxycarboxylic acid unit can be used in the present invention.

The diol and dicarboxylic acid used in the production of the polyester compound (A) partially having a carboxyl group at the terminal have a bond other than a carbon-carbon bond at a portion other than the carboxyl group or hydroxyl group. Can also be used, including an ether bond, an ester bond, a thioether bond, an amide bond, a urethane bond, a urea bond, and a carbonate bond. In particular, an ether bond is preferable in terms of improving the heat resistance and mechanical strength of the obtained lactic acid-based polyester, though it depends on the content.

The presence of a hydrogen bond-forming bond such as an amide bond, a urethane bond or a urea bond is preferable because it improves the mechanical strength of the molded product at high temperatures and the moldability of films and sheets. Degradability tends to be inferior to ester bonds, and these should be selected according to the intended use of the lactic acid-based polyester.

The diol used in the production of the "polyester compound partially having a carboxyl group at the terminal" (A) may be an aromatic diol or an aliphatic diol, and known diols may be used. . Specific examples include, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, and heptanediol. , Octanediol, nonanediol, decanediol, undecanediol, dodecanediol,

Tridecanediol, tetradecanediol, pentadecanediol, hexadecanediol, heptadecanediol, octadecanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 2,2-dimethyl-1,3-propanediol, , 2-bis (4-
Hydroxyphenyl) propane, bis (4-hydroxyphenyl) ether,

Bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) thioether, bis (4-hydroxyphenyl) sulfone, hydroquinone, 2,6-naphthalene diol, 2,7-naphthalene diol, polyethylene glycol, polypropylene Glycol, polytetramethylene glycol, poly (1,
2-butylene glycol), polyethylene glycol-polypropylene glycol copolymer, cyclohexane dimethanol, etc., and aliphatic diols having 1 to 8 carbon atoms, which are particularly inexpensive and are expected to have good biodegradability. Or mixtures thereof.

The polyol used for producing the polyester compound (A) having a carboxyl group partially at the terminal includes glycerin, trimethylolmethane,
Examples include trimethylolethane, trimethylolpropane, pentaerythritol and the like.

The dicarboxylic acid used for the production of the polyester compound (A) having a carboxyl group at a terminal partially includes known and commonly used carbonic acid, oxalic acid, malonic acid, and the like.
Succinic acid, methylsuccinic acid, glutaric acid, adipic acid,
1,5-dicarboxypentane, 1,6-dicarboxyhexane, 1,7-dicarboxyheptane, 1,8-dicarboxyoctane, 1,9-dicarboxynonane,

1,10-dicarboxydecane, 1,11
-Dicarboxyundecane, 1,12-dicarboxydodecane, 1,13-dicarboxytridecane, 1,14
-Dicarboxytetradecane, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like. However, it is desirable to use an aliphatic dicarboxylic acid having 4 to 12 carbon atoms or a mixture thereof from the viewpoints of biodegradability and the price of the polymer, which are the original purposes.

Examples of the polyvalent carboxylic acid used for producing the polyester compound (A) having a terminal carboxyl group include pyromellitic acid, trimellitic acid, butanetetracarboxylic acid and the like.

The hydroxycarboxylic acid unit contained in the polyester compound (A) partially having a carboxyl group at the terminal includes mandelic acid, hydroxyacetic acid, 3-hydroxypropionic acid, 2-hydroxybutyric acid, and 3-hydroxybutyric acid. 4-hydroxybutyric acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxycaproic acid, 3-hydroxycaproic acid, 4-hydroxycaproic acid, 5-hydroxy Caproic acid,

Examples thereof include 6-hydroxycaproic acid, 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, and 2-hydroxybenzoic acid. Partially, for example, about 2% by weight of a polyfunctional apple It may be replaced by an acid, dimethylolpropionic acid, dimethylolbutanoic acid, or the like.

Examples of the acid anhydride (D) include dibasic acid anhydrides such as succinic anhydride, glutaric anhydride and phthalic anhydride, trimellitic anhydride and pyromellitic anhydride. Such acid anhydrides of polybasic acids, carboxylic acid anhydrides having unsaturated bonds such as maleic anhydride can be used, and particularly preferred are pyromellitic anhydrides which are anhydrides of polybasic acids. It is an anhydride of polybasic acid.

The polyester compound (A) having a carboxyl group partially at the terminal using the components exemplified above has a number average molecular weight (Mn) of 500.
0 or more, weight average molecular weight (Mw, hereinafter abbreviated) 100
00 or more, more preferably Mn
Is 40000 or more and Mw is 80000 or more. By using such a polyester, a lactic acid-based polymer having excellent mechanical strength can be produced.

On the other hand, the epoxides (C) to be reacted with the polyester compound (A) partially having a carboxyl group at the terminal include monofunctional epoxide compounds,
Although an epoxide compound having two or more functionalities may be used, it is preferably a monofunctional epoxide, and
It is desirable to use an epoxide derived from a diol used in the polyester compound (A) having a partial carboxyl group at the terminal, such as ethylene oxide, propylene oxide, phenyl glycidyl ether, butyl glycidyl ether, and hexene oxide. I can do it.

It is preferable to use an epoxide compound having 6 or less carbon atoms, since the excess epoxide compound (C) can be easily removed and no odor remains. Further, the addition amount is preferably about 0.5 to 1.5 times the acid value,
If it is larger than that, the epoxide compound is wasted, and if it is smaller, the effectiveness is reduced.

The method for adding the epoxides (C) is as follows.
The polyester compound (A) having a partial carboxyl group at the terminal may be added dropwise or added all at once. On the other hand, the reaction temperature and reaction time are from room temperature to about 100 ° C., and a reaction time of 3 hours or less is sufficient.

If the polyester compound (A) having a partial carboxyl group at the end is a solid and it is expected that it is difficult to mix the epoxide compound (C) uniformly, a solvent is used. It is also preferred. It is particularly preferable that the solvent has a boiling point of about 140 ° C. or lower and has no active hydrogen. Examples thereof include benzene, toluene, xylene, ethylbenzene, THF, dioxane, chloroform, methylene chloride, and tetrachloride. Examples thereof include carbon, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.

After removing the solvent, lactide (B)
May be reacted with lactide (B) without removal. When reacting the epoxide (C), it is also preferable to use a catalyst that improves the reaction rate of the epoxide, and various commonly known quaternary phosphonium salts and quaternary ammonium salts can also be used.

Further, the conditions for reacting the polyester compound (A ') having a low acid value with the lactide (B) are ordinary reaction conditions, preferably from 80 ° C. to 200 ° C.
The reaction is preferably carried out for 7 hours, more preferably 13 hours
It is desirable to react at 0 ° C. to 180 ° C. for about 2 to 5 hours.

For the reaction between the polyester compound (A ') having a low acid value and the lactide (B), ordinary ring-opening polymerization catalysts can be suitably used. Examples thereof include tin octoate, Tin catalysts such as stannous chloride, tin acetate, stannous oxide, etc., germanium catalysts such as acid value germanium and tetrabutoxygermanium, titanium catalysts such as titanium tetrabutoxide and titanium tetraisopropoxide, tetraphenylporphyrinato Examples of the catalyst include aluminum and aluminum catalysts such as aluminum isopropoxide, and lanthanoid catalysts such as yttrium trichloride and lanthanum triisopropoxide.

The reactor used for these reactions is suitable for industrial production in consideration of the conditions such as the viscosity of the reaction system, such as a reactor equipped with a usual stirring blade, a static mixer, an extruder type reactor and the like. It can be manufactured using an object.

[0033]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In these examples, Mn indicates a number average molecular weight and Mw indicates a weight average molecular weight, and was measured by GPC using monodisperse polystyrene as a reference substance and THF as a solvent. The acid value was determined by titration with a KOH / methanol solution using THF as a solvent with an automatic potentiometer AT-310J manufactured by Kyoto Electronics. Also, in the following, it is easy to use
Was expressed as meq / kg.

Example 1 Polyethylene Sebacate 1
To 5.0 kg (Mn = 15200, Mw = 22000), 45.02 g of pyromellitic dianhydride was added, and 2
The pressure was reduced at 0.2 kPa at 40 ° C. for 3 hours. The acid value of the produced polyester compound (A1) partially having a carboxyl group at the end was 80 meq / kg. After pelletizing the produced polymer, 1 kg was subdivided, and 1.5 kg of toluene was added and dissolved. Then, 5.8 g of propylene oxide was added, and the mixture was stirred at room temperature for 3 hours in a flask while stirring with stirring blades. Reacted.

The resulting polyester compound (A′1) having a low acid value has an acid value of 10.1 meq / kg and Mn of 17
300 and Mw were 65,000. Generated (A '
1) was subdivided into 15.0 g, and 34.3 g of L-lactide and 0.7 g of D-lactide were added to 15 ml of toluene.
And 50 mg of tin octoate at 170 ° C. for 7 hours. The obtained lactic acid-based polyester was transparent and elastic, and had Mn = 27500 and Mw = 78000.

Example 2 Polypropylene Sebacate 1
60.1 g of pyromellitic dianhydride was added to 5.3 kg (Mn = 25300, Mw = 46000), and 24
Vacuum was applied at 0.2 kPa for 3 hours at 0 ° C. The acid value of the “polyester compound partially having a carboxyl group at the terminal” (A2) was 92 meq / kg.
After subdividing 1 kg of this, 5.8 g of propylene oxide was added.
g, and the mixture was reacted at room temperature for 4 hours while stirring with a stirring blade.

The obtained polyester compound having a low acid value "
(A'2) has an acid value of 6.4 meq / kg and Mn of 300.
00, Mw was 72,000. Generated (A'2)
Was divided into 15.0 g portions, and 34.3 g of L-lactide,
0.7 g of D-lactide was copolymerized at 170 ° C. for 7 hours in the presence of 15 ml of toluene and 50 mg of tin octoate. The obtained lactic acid-based polyester was transparent and elastic, and had Mn = 45000 and Mw = 102000.

Example 3 15.0 kg of polyethylene sebacate polyhexamethylene sebacate random copolymer (1 mol: 1 mol) (Mn = 22300, Mw =
41000) and pyromellitic dianhydride 45.0.
g was added and the pressure was reduced at 0.2 kPa for 3 hours at 240 ° C. The acid value of the resulting polyester compound (A3) having a partial carboxyl group at the terminal is 53 meq / k.
g. After subdividing 1 kg of this, 5.8 g of propylene oxide was added, and the mixture was reacted in a flask at room temperature for 4 hours while stirring with a stirring blade.

The resulting polyester compound (A'3) having a low acid value has an acid value of 6.0 meq / kg and Mn of 280.
00, Mw was 71,000. Generated (A'3)
Was divided into 15.0 g portions, and 34.3 g of L-lactide,
0.7 g of D-lactide was copolymerized at 170 ° C. for 7 hours in the presence of 15 ml of toluene and 50 mg of tin octoate. The resulting lactic acid-based polyester was transparent and elastic, with Mn = 41,000 and Mw = 98,000.

Example 4 Polypropylene Sebacate 1
25.0 g of pyromellitic dianhydride was added to 5.3 kg (Mn = 25300, Mw = 46000), and 24
Vacuum was applied at 0.2 kPa for 3 hours at 0 ° C. The resulting polyester (A4) having a partial carboxyl group at the terminal had an acid value of 47 meq / kg. This one
After subdividing kg, 5.8 g of 1-hexene oxide was added, and the mixture was reacted at room temperature for 4 hours in a flask while stirring with a stirring blade.

The resulting polyester compound (A'4) having a low acid value has an acid value of 6.4 meq / kg and Mn of 260
00, Mw was 57000. Generated (A'4)
Was divided into 15.0 g portions, and 34.3 g of L-lactide,
0.7 g of D-lactide was copolymerized at 170 ° C. for 7 hours in the presence of 15 ml of toluene and 50 mg of tin octoate. The obtained lactic acid-based polyester was transparent and elastic, and had Mn = 27500 and Mw = 70000.

Comparative Example 1 To 15 g of the compound (A1) produced in the course of Example 1, 0.7 g of D-lactide was added in the presence of 15 ml of toluene and 50 mg of tin octoate.
g and 34.3 g of L-lactide were copolymerized. The resulting polymer is transparent and elastic, Mn = 27000,
Mw = 78500.

Comparative Example 2 To 15 g of the compound (A2) produced in the course of Example 2, 0.7 g of D-lactide was added in the presence of 15 ml of toluene and 50 mg of tin octoate.
g and 34.3 g of L-lactide were copolymerized. The resulting polymer is transparent and elastic, Mn = 44000,
Mw = 102000.

Comparative Example 3 D-lactide 0.7 in the presence of 15 ml of toluene and 50 mg of tin octoate was added to 15 g of the compound (A2) produced in the course of Example 3.
g and 34.3 g of L-lactide were copolymerized. The resulting polymer is transparent and elastic, Mn = 42000,
Mw = 98,000.

Comparative Example 4 D-lactide 0.7 in the presence of 15 ml of toluene and 50 mg of tin octoate was added to 15 g of the compound (A2) produced in the course of Example 4.
g and 34.3 g of L-lactide were copolymerized. The resulting polymer is transparent and elastic, Mn = 42000,
Mw = 98,000.

Example 5 The lactic acid-based polyester obtained in Examples 1 to 4 was vacuum-dried in a drier at 90 ° C. for 2 hours to remove lactide, and dried at 170 ° C. for 2 minutes at 200 kg / c.
The sheet was formed into a sheet having a thickness of 200 μm under the condition of m ² and kept in a thermo-hygrostat at a temperature of 35 ° C. and a humidity of 80% for 4 weeks, and the molecular weight was measured. Table 1 shows the retention ratio of the Mw of the lactic acid-based polyester to the original Mw after 4 weeks.

[0047]

[Table 1]

Comparative Example 5 The lactic acid-based polyester obtained in Comparative Examples 1 to 4 was vacuum-dried at 90 ° C. for 2 hours to remove lactide, and was dried at 170 ° C. for 2 minutes at 200 kg / cm ² at a thickness of 200 μm. It is formed into a sheet and heated at a temperature of 35
The molecular weight was measured after being kept for 4 weeks in a thermo-hygrostat at 80 ° C. and 80%. Table 2 shows the retention ratio of Mw of the lactic acid-based polyester to the original Mw after 4 weeks.

[0049]

[Table 2] [Example 6] Table 3 shows the lactide residual ratio in samples collected every hour in the reaction for obtaining the lactic acid-based polyesters of Examples 1-4. From the GPC chart area of the lactide, the time required for the residual lactide, which can be considered to be almost the end of the reaction, to be 3% or less was about 2-3 hours.

[0050]

[Table 3]

[Comparative Example 7] Table 4 shows the residual ratio of lactide in samples collected every hour in the reaction for obtaining the lactic acid-based polyesters of Comparative Examples 1 to 4. The time required until the remaining lactide, which can be regarded as almost the end of the reaction, became 3% or less was about 5 to 6 hours.

[0052]

[Table 4]

[0053]

Industrial Applicability According to the present invention, a lactic acid-based polyester having high mechanical properties such as biodegradability and heat resistance can be rapidly produced, and the obtained lactic acid-based polyester has excellent storage stability. A method for producing a polyester can be provided.

Claims (5)

[Claims] 1. A polyester compound (A) having a partial carboxyl group at a terminal and an epoxide (C) are reacted to give a polyester compound (A ′) having a low acid value, and then a low acid value. A method for producing a lactic acid-based polyester (E), which comprises reacting a polyester compound (A ') with a lactide (B). 2. The polyester compound (A) having a partial carboxyl group at its terminal has an acid value of 5 to 100 meq / kg and a low acid value of the polyester compound “(A ′)”. Is 0.5 to 20 meq / kg, the method for producing a lactic acid-based polyester (E) according to claim 1, wherein 3. The polyester compound according to claim 1, wherein the polyester compound (A) having a partial carboxyl group at the terminal is a polyester compound whose molecular weight has been increased by an acid anhydride (D). A method for producing a lactic acid-based polyester. 4. A weight average molecular weight (Mw) of a polyester compound (A) having a carboxyl group partially at a terminal.
Is from 10,000 to 300,000, the method for producing a lactic acid-based polyester (E) according to any one of claims 1 to 3. 5. The method for producing a lactic acid-based polyester (E) according to claim 4, wherein the weight-average molecular weight of the lactic acid-based polyester (E) is 50,000 to 700,000.