JP3396296B2 - Method for producing biodegradable aliphatic polyester - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a biodegradable aliphatic polyester which has excellent affinity for hydrophilic organic polymers such as cellulose and starch and is easily biodegradable under specific conditions while maintaining practically sufficient physical properties. The present invention relates to a manufacturing method of.

[0002]

2. Description of the Related Art It is well known that an aliphatic polyester exhibits biodegradability, and the present inventors have made some proposals. For example, JP-A-5-70579 discloses a polyester synthesized from ethylene glycol and succinic acid (or its anhydride). That is, this polyester is obtained by polycondensing ethylene glycol and succinic acid to synthesize a polyester having a number average molecular weight of 10,000 or more, and reacting with 0.1 to 5 parts by weight of polyvalent isocyanate per 100 parts by weight of this polyester. The number average molecular weight obtained by the above process contains a small amount of urethane bonds of 30,000 or more.

It has been confirmed that when this polyester is buried in the soil, it will start to disintegrate in about 6 months to 1 year, depending on the conditions, and eventually lose its original shape. It is also known that this phenomenon occurs in activated sludge.

[0004]

However, although the above-mentioned polyester shows biodegradability, its rate is not always high. Also, the affinity for hydrophilic organic polymers such as cellulose and starch was not sufficient. Depending on the intended use of polyester, while sufficient physical properties and retention thereof are maintained in the air for a long period of time, it may be desirable that the polyester decomposes and disappears as quickly as possible after a certain period of time when immersed in water. However, it must not be water-soluble or water-swellable. The present invention solves the conventional problems as described above, has excellent affinity for hydrophilic organic polymers such as cellulose and starch, and is easily biodegradable under specific conditions while maintaining practically sufficient physical properties. An object of the present invention is to provide a method for producing a polyaliphatic polyester.

[0005]

[Means for Solving the Problems] The inventors of the present invention have a good affinity for hydrophilic organic polymers such as cellulose and starch, and decompose under specific conditions, for example, in water, while maintaining practically sufficient physical properties. As a result of various studies in order to obtain a biodegradable aliphatic polyester that is easy to do, it is possible to achieve the object by imparting hydrophilicity to a part of the polyester. More specifically, polyethylene glycol is suitable as the hydrophilic part. It was possible to complete the present invention by finding

That is, the present invention provides [A] (1) a glycol component containing 80 mol% or more of ethylene glycol (excluding polyethylene glycol described below) and (2) a dicarboxylic acid containing 80 mol% or more of succinic acid (or its anhydride). (3) 1 to 30 parts by weight of polyethylene glycol having a number average molecular weight of 200 or more is added to 100 parts by weight of the total amount of the components), and then the components (1), (2) and (3) are polycondensed. 0.1 to 10 parts by weight of [B] polyvalent isocyanate is added to 100 parts by weight of the aliphatic polyester (a) having a number average molecular weight of 10,000 or more and a melting point of 70 ° C. or more, which is obtained in the molten state. Added to the group polyester (a) and reacted,
The present invention provides a method for producing a biodegradable aliphatic polyester, which has a number average molecular weight of 30,000 or more.

The present invention also provides the above method, wherein the polyethylene glycol has a number average molecular weight of 600 to 3,000.

The present invention will be described in more detail below. The terminal group of the aliphatic polyester synthesized in the step [A] of the present invention is substantially a hydroxyl group. The aliphatic polyester is used as a raw material together with the glycol component and the dicarboxylic acid (or its anhydride) component.

The glycol component used in the present invention is 80 mol% or more of ethylene glycol. Examples of the glycol component that can be used in combination include 1,4-butanediol, 1,6-hexanediol, 1,8-octylene glycol, 1,10-decamethylene glycol, and 1,
4-cyclohexane dimethanol etc. are mentioned. The glycol component may be all ethylene glycol. It should be noted that the glycol component as used herein means one excluding polyethylene glycol. When the proportion of ethylene glycol in the glycol component is less than 80 mol%, a polyester having a desired melting point cannot be obtained.

The dicarboxylic acid (or its anhydride) component used in the present invention is 80 mol% or more of succinic acid (or its anhydride). Other dicarboxylic acid components that can be used in combination include, for example, adipic acid, suberic acid,
Sebacic acid, dodecanedioic acid, 1,4-cyclohexanedicarboxylic acid and the like can be mentioned. The dicarboxylic acid (or its anhydride) component may be all succinic acid (or its anhydride). When the proportion of succinic acid (or its anhydride) in the dicarboxylic acid (or its anhydride) component is less than 80 mol%, a polyester having a desired melting point cannot be obtained.

The glycol component and the dicarboxylic acid (or its anhydride) component are preferably used in a proportion of about 1.05 to 1.2 mol of the glycol component with respect to 1 mol of the dicarboxylic acid (or its anhydride) component. .

In the present invention, the total amount of the glycol component and the dicarboxylic acid (or its anhydride) component is 1
1 to 30 parts by weight of polyethylene glycol having a number average molecular weight (hereinafter, simply referred to as molecular weight) of 200 or more with respect to 00 parts by weight.
One feature is that, in addition to parts by weight, these components are polycondensed to introduce the polyethylene glycol component into the polyester structure.

If the polyethylene glycol used in the present invention has a molecular weight of 200 or more, one of the purposes of the present invention, that is, the rate of biodegradability in water can be increased. However, with regard to the molecular weight of polyethylene glycol, when a certain amount is used, the higher the molecular weight is, the lower the melting point of the polyester produced is less, but from the viewpoint of biodegradability, it is desirable to use a type with a low molecular weight as much as possible. From the molecular weight of polyethylene glycol is 600 ~
An appropriate range is 3,000.

As described above, the amount of polyethylene glycol used is 1 to 3 parts by weight per 100 parts by weight of the total amount of the glycol component and the dicarboxylic acid (or its anhydride) component.
0 parts by weight. Depending on the selected molecular weight of polyethylene glycol, if it exceeds 30 parts by weight, the melting point of the resulting biodegradable aliphatic polyester is greatly lowered, and its water resistance is also reduced, which is not practical. On the other hand, if it is less than 1 part by weight, the meaning of modification is poor and the effect is not exhibited.

In the present invention, a polyfunctional alcohol having a functionality of 3 or more is used within a range that does not impair the purpose in the polycondensation reaction.
When at least one polyfunctional compound selected from the group consisting of polyfunctional carboxylic acids (or their anhydrides) having functionality or higher and oxycarboxylic acids having functionality of 3 or higher is used in combination, for example, branching is introduced and the molecular weight distribution thereof is increased. Is preferred, and as a result, diversification of properties is achieved, which is preferable.

Examples of trifunctional or higher polyhydric alcohols include glycerin, trimethylolpropane, pentaerythritol, triallyl isocyanurate ethylene oxide adduct and the like. It is also possible to use the dehydrated form of the monoepoxy compound glycidol.

As the trifunctional or higher functional oxycarboxylic acid,
Although all commercially available products can be used, malic acid, tartaric acid and citric acid are preferable from the viewpoint of being available at low cost.

Examples of trifunctional or higher polycarboxylic acids (or their anhydrides) include trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic anhydride,
Examples thereof include benzophenone tetracarboxylic acid anhydride and cyclopentatetracarboxylic acid anhydride. Particularly, trimellitic anhydride and pyromellitic anhydride are preferable.

The respective components of the above polyfunctional compounds can be mixed and used as needed. The amount of the polyfunctional compound used is 10 parts of the total amount of the dicarboxylic acid (or its anhydride) component.
It is 0.1 to 5 mol% in total with respect to 0 mol%, and can be added from the beginning of the polycondensation reaction. If the amount of the polyfunctional compound used is less than 0.1 mol%, the meaning of addition is poor, and if it is more than 5 mol%, the risk of gelation during the reaction increases.

In the present invention, the number average molecular weight of the aliphatic polyester obtained in the step [A] is 10,000.
It is necessary to set the melting point to 70 ° C. or higher.
This can be achieved by polycondensing each of the above-mentioned raw materials and then performing a deglycol reaction. In addition, when the number average molecular weight of the aliphatic polyester obtained in this [A] stage is less than 10,000 and the melting point is less than 70 ° C., even if the molecular weight is increased in the subsequent [B] stage, the required physical properties are required. Can't get

The polycondensation reaction is carried out at 160 to 230 ° C. for 5 to 1
It can be carried out for 6 hours, preferably under an inert gas atmosphere. When the temperature is lower than this temperature, the reaction rate is slow and the practicality is poor. If the temperature is higher than this temperature, the risk of decomposition becomes high and it is better to avoid it. Therefore, it is preferable to carry out the [A] stage polycondensation reaction at a temperature between 180 and 220 ° C. In the polycondensation reaction, the acid value of the aliphatic polyester is 30.
The following is carried out until it reaches 15 or less, preferably 10 or less. In this case, the larger the molecular weight, the smoother the increase in the molecular weight due to the deglycolization reaction.
High molecular weight is desirable.

The deglycol reaction is carried out at 170 to 230 ° C. for 2 to 16 hours under a reduced pressure of 5 Torr or less. More preferably, it is carried out at 180 to 210 ° C. under a high vacuum of 1 Torr or less from the viewpoint of reaction rate and prevention of decomposition. The resulting aliphatic polyester has a hydroxyl group as a terminal group and has an acid value of zero. In the deglycolization reaction, it is necessary to use a catalyst together. Examples of these are titanium, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum,
An organic or inorganic metal compound of at least one metal selected from the group consisting of magnesium, calcium and strontium can be used, and the amount used is 0.001 per 100 parts by weight of the aliphatic polyester produced.
~ 0.5 parts by weight. The amount of metal compound catalyst used is 0.0
If the amount is less than 01 parts by weight, the deglycolization reaction will be delayed and not practical, and if the amount is more than 0.5 parts by weight, the decomposition reaction will be intensified, which is not preferable. The preferred amount of use varies depending on the type of metal, but 0.005-
It is 0.2 parts by weight. As the metal compound catalyst, for example, metal alkoxides, organic acid salts, chelates, oxides and the like are used, and in particular, organic compounds of titanium such as alkyl titanate esters, titanium oxyacetylacetonate and titanium oxalate are useful. is there. So-called biodegradable polyesters are subject to microbial degradation in soil or water, but metal catalysts or metals are expected to remain in the soil and must therefore be a safe type. From such a point of view, the preferable metal is titanium,
Examples include germanium, zinc, magnesium and calcium.

The present invention further comprises 100 parts by weight of a melted aliphatic polyester (a) having a number average molecular weight of 10,000 or more and a melting point of 70 ° C. or more obtained in the step [A],
The step [B] includes reacting 0.1 to 10 parts by weight of a polyvalent isocyanate to a molecular weight of 30,000 or more. The biodegradable aliphatic polyester containing a small amount of urethane bond produced by this shows practically sufficient physical properties and desired biodegradability, and can be molded into a desired molded product by a conventional molding method such as inflation, blow molding or injection molding. You can get the goods.

The polyvalent isocyanate used is, for example, a type having two or more isocyanate groups in one molecule, and an aliphatic or cycloaliphatic type is preferable from the viewpoint of avoiding coloring of the molded product. Examples thereof include hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and an adduct of a polyvalent isocyanate with a polyhydric alcohol, which has an isocyanate group. Examples thereof include compounds having two or more molecules in one molecule, and trimers of these.

The amount of the polyvalent isocyanate added is, as described above, the aliphatic polyester (a) obtained in the step [A].
100 parts by weight is 0.1 to 10 parts by weight of polyisocyanate. If it is less than 0.1 part by weight, the effect of utilizing the polyvalent isocyanate is poor, and if it is used in excess of 10 parts by weight, the risk of gelation increases only and there is no point in increasing the amount. More preferably, it is 0.3 to 1 part by weight.

The biodegradable aliphatic polyester obtained according to the present invention, when put to practical use, may contain desired additives such as an inorganic or organic filler, a reinforcing material, a coloring agent, a lubricant, and a stabilizer, if necessary. Of course, they can be used together.

[0027]

EXAMPLES The present invention will be described below with reference to examples. Example 1 In a 1-liter separable flask equipped with a stirrer, a fractionating condenser, a thermometer, and a gas introduction tube, 195 g of ethylene glycol, 354 g of succinic acid, 1.5 g of glycerin,
After 28 g of polyethylene glycol having a molecular weight of 1,000 was charged and polycondensed at 195 to 200 ° C. under a nitrogen stream to an acid value of 9.2, tetraisopropoxy titanium was 0.07 g.
Was added, and a deglycolization reaction was further performed under a reduced pressure of 0.6 Torr for 3 hours at 215 to 220 ° C., and the number average molecular weight was 27,400, the weight average molecular weight was 87,000, and the melting point was 103 ° C. in a pale yellow color. A waxy aliphatic polyester (a) was obtained. 300 g of aliphatic polyester (a)
Was weighed into another separable flask of 1 liter, melted at 190 ° C. under a nitrogen stream, and 0.1 g of phosphorous acid was added.
The color became almost colorless. Next, 4 g of 1,6-hexamethylene diisocyanate was added. The viscosity increased rapidly but did not gel. 3 at the same temperature (190 ° C)
The reaction was continued for 0 minutes with slow stirring. The obtained biodegradable aliphatic polyester (A) was a pale ivory white crystalline substance, had a number average molecular weight of 42,000, a weight average molecular weight of 169,600 and a melt flow value (2.
16kgf / 190 ℃, the number of grams when kept for 10 minutes, JI
SK7210) was 42.0 g / 10 min. Also,
The melting point measured by DSC was 103 ° C. For reference, the DSC curve of the biodegradable aliphatic polyester (A) obtained in Example 1 is shown in FIG. The biodegradable aliphatic polyester (A) thus obtained showed good film-forming property. Biodegradable aliphatic polyester (A) at 150 ° C, 1
00kg / cm after ^two press molding, the tensile strength of the film having a thickness of about 40μ obtained was stretched 3 times at 60 ° C. (JIS
(Measured by K6760) was 13.4 kg / mm ² and was tough.

In the present specification, the number average and weight average molecular weights are values measured by GPC under the following conditions. GPC measurement conditions Shodex GPC SYSTEM-11 (manufactured by Showa Denko KK) Eluent CF ₃ COONa 5 mmol / hexafluoroisopropyl alcohol (HFIP) (1 liter) Column sample column HFIP-800P HFIP-80M × 2 reference columns HFIP- 800R x 2 columns Column temperature 40 ° C Flow rate 1.0 ml / min Detector Shodex RI STD: PMMA (Shodex STANDARD M-75)

Comparative Example 1 Example 1 was repeated except that polyethylene glycol was not used to obtain a biodegradable aliphatic polyester (B) having a number average molecular weight of 40,900 and a weight average molecular weight of 167,000. The biodegradable aliphatic polyester (B) has a melting point of 104 ° C and a melt flow value of 39.1 g / 10.
The film had a tensile strength of 15.1 kg / mm ² and was a light yellowish-brown crystal.

The films made of the biodegradable aliphatic polyesters (A) and (B) obtained in the above Example 1 and Comparative Example 1 were cut into a rectangle of 10 cm × 5 cm and buried 20 cm below the sand dunes on the coast. When a biodegradation test was carried out with the aid of polyethylene glycol, the film of the biodegradable aliphatic polyester (A) to which polyethylene glycol was added disappeared completely after 12 weeks, but the film of the polyester (B) completely decomposed. Needed 20 weeks.

Example 2 A 1-liter separable flask equipped with a stirrer, a fractionating condenser, a thermometer, and a gas inlet tube was charged with 205 g of ethylene glycol, 270 g of succinic anhydride, and 69 of dodecanedioic acid.
g, tetraisopropyl titanate 0.06 g, molecular weight 3,
5,000 polyethylene glycol (55 g) was charged and polycondensed at 195 to 200 ° C under a nitrogen stream to give an acid value of 10.9, then at 215 to 220 ° C for 5 hours, and finally 0.6T.
Deglycolization reaction under reduced pressure of orr, number average molecular weight 21,400, weight average molecular weight 54,000, melting point about 98
A pale ivory waxy aliphatic polyester (d) at 0 ° C. was obtained. Aliphatic polyester (d) 300
After weighing g, melting at 190 ° C., adding 0.05 g of phosphorous acid, and then adding 4.5 g of isophorone diisocyanate. The viscosity increased rapidly but did not gel. The biodegradable aliphatic polyester (D) obtained by stirring for 30 minutes is white crystals having a pale ivory color and has a number average molecular weight of 39,
100, weight average molecular weight 104,000, melting point about 100
It was ℃.

Comparative Example 2 Example 2 was repeated except that polyethylene glycol was not used. The aliphatic polyester (e) thus obtained was a light ivory wax in the form of a number average molecular weight of 20,700, a weight average molecular weight of 52,100, a melting point of about 100 ° C. The biodegradable aliphatic polyester (E) obtained after the addition of isophorone diisocyanate had a number average molecular weight of 38,900, a weight average molecular weight of 109,000, a melting point of about 100 ° C., and an ivory wax form.

100 parts by weight of the biodegradable aliphatic polyester (D) obtained in Example 2 and the biodegradable aliphatic polyester (E) obtained in Comparative Example 2 were mixed with corn starch at 120 ° C. Roll kneading was performed. The above polyester (D) having a polyethylene glycol structure
Was able to mix 100 parts by weight of corn starch, but the polyester (E) had a limit of 30 parts by weight, and a marked difference in miscibility between the two was observed.
About 100 parts by weight of the polyester (D) was mixed with 70 parts by weight of corn starch and press-molded at 100 kg / cm ² and 150 ° C. The film having a thickness of about 100 μm completely disappeared in an aeration tank in 5 weeks. Was confirmed.

[0034]

INDUSTRIAL APPLICABILITY According to the present invention, a biodegradable aliphatic polyester having excellent affinity for hydrophilic organic polymers such as cellulose and starch and being easily biodegradable under specific conditions while maintaining practically sufficient physical properties is produced. A method is provided.

[Brief description of drawings]

FIG. 1 is a view showing a DSC curve of a biodegradable aliphatic polyester (A) obtained in Example 1.

Claims (2)

(57) [Claims] 1. [A] (1) 80 parts ethylene glycol
Glycol component containing more than mol% (excluding polyethylene glycol below) and (2) 80 mol% succinic acid
(3) 1 to 30 parts by weight of polyethylene glycol having a number average molecular weight of 200 or more is added to 100 parts by weight of the total amount of the dicarboxylic acid (or its anhydride) component contained above, and then (1), (2) and (3) Number average molecular weight of 10,000 or more and melting point of 70 obtained by polycondensing the components
0.1 to 10 parts by weight of [B] polyvalent isocyanate is added to 100 parts by weight of the aliphatic polyester (a) at a temperature of not less than 0 ° C., and the mixture is reacted with the aliphatic polyester (a) in a molten state,
A method for producing a biodegradable aliphatic polyester, which has a number average molecular weight of 30,000 or more. 2. The method according to claim 1, wherein the number average molecular weight of polyethylene glycol is 600 to 3,000.