KR19980028015A - Method for preparing biodegradable aliphatic polyester - Google Patents

Abstract

The present invention relates to a method for producing biodegradable aliphatic polyester for blown-film having practical biodegradability, high molecular weight, and excellent tensile strength and formability.

In the present invention, in preparing an aliphatic polyester through polymerization of an aliphatic glycol and dicarboxylic acid, a titanium compound is preferably used as a coupling agent to the aliphatic glycol and the dicarboxylic acid component as a magnesium oxide or zinc oxide and as a reaction accelerator. To prepare a polyester prepolymer having a high molecular weight band, which is then prepared by adding an isocyanate compound as a binder in the extruder as a secondary reaction.

The aliphatic polyester produced in the present invention can replace some special uses of the generally used polyethylene terephthalate resin, and furthermore, a great effect in terms of environmental pollution prevention can be expected.

Description

Method for preparing biodegradable aliphatic polyester

The present invention relates to a method for producing a biodegradable aliphatic polyester for blown-film having practically biodegradability and having a sufficiently high molecular weight and excellent tensile strength and formability through a secondary reaction by addition of a binder during the extrusion process. will be.

In general, polyester used as a material for medical, packaging, agriculture, etc. has already been widely used in a variety of products because of excellent physical and chemical properties such as corrosion resistance, high strength and the like. As such polyester, polyethylene terephthalate (abbreviated PET) which is a condensate of terephthalic acid and ethylene glycol having a number average molecular weight of about 20,000 is used.

However, the above components may cause stabilization of landfill due to poor decomposability during disposal, excessive landfill capacity, delayed decomposition of internally decomposable substances, soil degradation and soil pollution. Moreover, in view of the domestic situation in which the plastic content of the trash is high in the waste discharge, development of degradable polymers is required.

Recently, the production of high molecular weight polymers by ring-opening polymerization of caprolactone has been known, and the production of petrochemical products, films, and molded products using aliphatic polyesters capable of biodegradation is steadily increasing. However, in this case, due to the disadvantage that the final polymer has a low melting point of about 62 ° C. and high cost is required for production, it is only used for a limited use such as some medical fibers. It is not widely used in household products, etc. This is due to the disadvantage that the decomposition temperature of these polymers is similar to the melting point, thereby resulting in inadequate molding tendency and low mechanical strength such as tensile / tension strength.

Such conventional biodegradable resins include degradable resins copolymerized with aliphatic polyesters to natural polymers (Korean Patent No. 95-18124), degradable resins containing inorganic fillers (Republic of Korea Patent No. 96-22744), biodegradable Polyester containing a ketone group to impart photodegradability to an aliphatic polyester having a compound (Korean Patent No. 95-18116), a biodegradable resin containing starch in ethylene and an aliphatic polyester (Korean Patent No. 95-18214), Biodegradable resin (Republic of Korea Patent No. 95-10984) added with natural polymer, automatic oxidizer, photosensitizer, plasticizer, colorant, etc., based on thermoplastic resin, heterocylic to low molecular weight polyester with lactic acid as the main repeating unit Biodegradable polyester (Korean Patent No. 95-23663) which added chain extenders, such as a click compound, microbial synthetic aliphatic polyester And it may be a chemical synthetic co-polymer (Republic of Korea Patent Publication No. 96-22669), of an aliphatic polyester.

In addition, the ring-opening polymerization has been attempted to glycolic acid, lactic acid, etc., but is also limited to a few medical applications, and is not applied to various fields.

Of course, biodegradable polymers through microbial fermentation rather than artificial synthesis, such as polyhydroxy butylate (abbreviated PHB) or biodegradable polymers incorporating starch into general synthetic polymers, have been introduced. It is uneconomical due to low production yield, and moreover, melting point and decomposition temperature are similar, which causes difficulty in molding. In the latter case, it is a biodegradable polymer rather than a strictly biodegradable polymer in terms of being split into pieces according to the decomposition of starch.

Therefore, in order to prevent environmental pollution and practicality, development of aliphatic polyester having excellent thermal stability and mechanical strength while being easily decomposed by microorganisms is required.

The present invention is to solve the above problems, to provide a method for producing a polymeric aliphatic polyester which is practical, excellent in biodegradability, and has excellent thermal stability and mechanical strength.

In the present invention, a polymer having a moderate level of thermal stability is first synthesized through polymerization of an aliphatic diol compound and a dicarboxylic acid, and then sufficiently high through a secondary reaction of adding an isocyanate compound as a chain extender in an extruder as a binder. It is characterized by producing a biodegradable aliphatic polyester of molecular weight band.

Hereinafter, the present invention will be described in detail.

In the present invention, in order to impart sufficient mechanical strength, that is, tensile strength or nodule strength, a polyester prepolymer having a molecular weight of a high molecular weight having a hydroxyl group at the end is formed first, and then the polyester prepolymer and a coupling agent are mentioned. Reaction to make a uniform high molecular weight polymer.

In the production of rubbers, foams, coating materials and adhesives, polyurethanes are reacted by reacting a low molecular weight polyester prepolymer having a hydroxyl group at the terminal group with a molecular weight of 2,000 to 2,500 and a diisocyanate as a binder. What can be obtained is known art. However, in order to prepare a practical polyurethane, diisocyanate should be added in an amount corresponding to 20 to 30% by weight of a low molecular weight prepolymer, but gelatin may occur if a large amount of binder is added at 150 ° C or higher. . Therefore, the method of adding a large amount of binder to the low molecular weight polyester prepolymer is not suitable for the production for the blown film in the present invention, and therefore, an appropriate amount of binder is required.

In the present invention, it is intended to produce aliphatic polyester of high molecular weight having high thermal stability and mechanical strength by polymerizing aliphatic components of glycol and dicarboxylic acid.

Synthesis of high molecular weight polymer having the above physical properties can be obtained by adding ① deglycol reaction catalyst, ② adding coupling agent, ③ adding thermal stabilizer.

That is, in the present invention, a magnesium compound or zinc oxide as a coupling agent and a titanium compound as a reaction promoter are added to the glycol and dicarboxylic acid components to synthesize a polyester prepolymer having a high molecular weight band, and then an isocyanate compound in an extruder. Induction of the binding of the end group by the addition of a binder gives an increase in the molecular weight and imparts appropriate mechanical strength.

The aliphatic polyester in the present invention is obtained by the reaction of glycol and dicarboxylic acid two components, if necessary, as a third component, a polyol, oxycarboxylic acid, and polybasic carboxyl of a trifunctional or tetrafunctional group. A component with at least one polyfunctional group selected from the group consisting of acids can be added. Such a third component can lead to branching of the long chain, thereby increasing molecular weight, and consequently imparting desirable properties to the polyester prepolymer in the molten state.

As the dicarboxylic acid, one selected from succinic acid, adipic acid, decanoic acid and dodecanoic acid is used, and glycols include ethylene glycol, 1,4-butanediol, 1,3-butanediol, 1,6-butanediol, One selected from 1,6-hexanediol is used.

In the present invention, a relatively high molecular weight polyester prepolymer having a hydroxyl group at the end group and an isocyanate which is a chain extender for increasing molecular weight as a binder are reacted in a twin screw extruder to make a uniform high molecular weight polymer. The component with the multifunctional group added without gelation induction, i.e., the binder, is added in an amount of 1.8 to 2.4% by weight based on the total aliphatic dicarboxylic acid component and the glycol component. Hexamethylene diisocyanate etc. can be used as an isocyanate compound used as a binder in this invention.

In preparing a polyester prepolymer having a relatively high molecular weight, it is accompanied by esterification and deglycol reaction, and at this time, a catalyst for promoting the deglycol reaction is required. In the present invention, a titanium compound is aliphatic as the catalyst. It is added in the amount of 0.1-1 weight% with respect to the total usage amount of a dicarboxylic acid component and a glycol component.

In the present invention, the aliphatic polyester has a hydroxyl group at the terminal group and has a melting point of 60 ° C. or higher so as to have a relatively high molecular weight band of at least 5,000, preferably 10,000 or more, and more preferably about 20,000 to 50,000. As mentioned above, aliphatic polyester is manufactured by making glycol and dibasic carboxylic acid react in presence of a catalyst.

Coupling agents used when using prepolymers having a number average molecular weight of 5,000 or more may be used in a small amount, such as 0.01 to 0.1% by weight, to provide sufficient physical properties to the polyester for film forming. When the polyester prepolymer has a molecular weight of 5,000 or more, and the hydroxyl group is 30 or less, even a small amount of coupling agent can be used to produce a high molecular weight polyester under stringent conditions, and no gelation by the remaining catalyst occurs.

Tetrabutyl titanate may be used as a titanium compound which is a reaction accelerator added to promote the deglycolization reaction during the esterification reaction of the present invention, and the amount of use is based on the total amount of aliphatic dicarboxylic acid component and glycol component. 0.1 to 1% by weight, preferably 0.25 to 0.75% by weight, is suitable. As the coupling agent, it is appropriate to add magnesium oxide or zinc oxide in an amount of 0.01 to 0.1% by weight, preferably 0.02 to 0.06% by weight, based on the total amount of the aliphatic dicarboxylic acid component and the glycol component. If the amount of the coupling agent is less than 0.01% by weight, the coupling reaction is likely to be insufficient, and when it exceeds 0.1% by weight, gelation is likely to occur.

The aliphatic polyester synthesized through the above method is produced by adding an isocyanate compound as a binder to melt in a general melt extruder with a nozzle, and then extruding it. At this time, the extrusion temperature is suitable for 160-240 ℃ and if it exceeds 240 ℃ gelation and rapid thermal decomposition of the polymer may occur. In addition, an appropriate amount of antioxidant and heat stabilizer may be added to increase the stability of the molecule as needed during extrusion, and the antioxidant may be added in an amount of 0.01 to 0.25 wt% based on the aliphatic polyester. As the heat stabilizer, trimethyl phosphate, a phosphate-based heat stabilizer, is added in an amount of 0.01 to 0.1 wt% based on the aliphatic polyester.

The final biodegradable polymer produced through the extrusion reaction has a melt viscosity of 190 ° C, 2.16Kgf, 1.0-10g / 10min melt temperature and 70-150 ° C melt temperature, and tensile strength of 2.5-3.0kgf, elongation. 20-130%. The polymer for blown-film of the present invention has a number average molecular weight of at least 5,000 or more, preferably 10,000 or more, more preferably about 20,000 to 50,000, and a repetitive chain of polyester prepolymer composed of aliphatic glycol and aliphatic dicarboxylic acid. It has a structure and has a urethane bond derived from diisocyanate.

In addition, the polyester of the present invention is biodegradable when buried in the ground, and has a lower heat of combustion than polyethylene and polypropylene.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the following Examples do not limit the scope of the present invention.

Example 1

9,538 g of 1,4-butanediol and 8,928 g of succinic acid are mixed with a stirring tank, a distillation capacitor, a thermometer, and a gas inlet tube in a state where nitrogen gas flows to the G value (the ratio of 1,4-butanediol to succinic acid ) Was added to 1.3-1.4 to directly esterify at a temperature of 210 ℃. The esterification reaction time is determined by the conversion rate, the pure water by measuring the refractive index of the mixture of water and 1,4-butanediol as the reaction proceeds After evaluating the amount of water generated from the reaction, the esterification reaction was terminated. At this time, the reaction rate in the D.E reaction (esterification reaction) was maintained at 98 ± 2%. After raising the esterified product at a temperature of 250 ° C., 6.5 g of magnesium oxide and 65 g of tetrabutyl titanate were added thereto, and reacted under low vacuum of 0.5 torr or less for 3 hours to prepare an aliphatic polyester in a chip state. The resin thus obtained was vacuum dried at 100 ° C. for 24 hr and then 2.4% by weight of hexamethylene diisocyanate at an extrusion temperature of 230 ° C. using a 30Ф twin screw extruder, and 0.25 mg of Iganox 1010 was used to prevent oxidation by external oxygen inflow during extrusion. 0.01% by weight of trimethylphosphate, a phosphate-based thermal stabilizer, was added to prepare a polymer having a melt flow viscosity of 8.0 g / 10 min at a melting temperature of 190 ° C. and 2.16 Kgf. The results of the measurement of the physical properties are shown in Table 1 below.

Example 2

An aliphatic polyester was prepared under the same conditions as in Example 1 except that the content of Tetrabutyl titanate was changed to 52 g in Example 1, and the results are shown in Table 1 below.

Example 3

An aliphatic polyester was prepared under the same conditions as in Example 1 except that the content of Tetrabutyl titanate was changed to 58.5 g in Example 1, and the results are shown in Table 1 below.

Comparative Example 1

An aliphatic polyester was prepared under the same conditions as in Example 1 except that trimethylol propane was used in an amount of 6.5 g instead of magnesium oxide as a coupling agent in Example 1, and the results are shown in Table 1 below.

Comparative Example 2

In Example 1, an aliphatic polyester was prepared under the same conditions as in Example 1, except that 7.8 g of magnesium oxide was added and 0.25 wt% of Iganox B1171 instead of Iganox 1010 as an antioxidant. Shown in

Number average molecular weight MFR (g / 10 min) Melt viscosity Example 1 40,000 8 3.0 × 10 ₃ Example 2 30,000 10 1.5 × 10 ³ Example 3 45,000 4 2.0 × 10 ³ Comparative Example 1 25,000 40 1.5 × 10 ³ Comparative Example 2 16,000 30 0.8 × 10 ³

※ Number average molecular weight is evaluated by GPC

MFR (Melt Flow Rate): 190 ℃, 2.16Kgf

Melt viscosity: Shear rate 1,000sec ^-1 , 190 ℃

The aliphatic polyester produced in the present invention can replace some special uses of the generally used polyethylene terephthalate resin, and furthermore, a great effect in terms of environmental pollution prevention can be expected. The conventionally used polyethylene terephthalate resin is not completely decomposed in soil or sewage, and even if it is decomposed, it takes a long time of about 50 years or more, so there are many factors causing serious environmental pollution. The replacement of the resulting biodegradable aliphatic polyesters can minimize such factors. In addition to the above-mentioned applications, a wide range of applications are possible, such as industrial articles such as fishing lines, fishing nets and nonwoven fabrics, laminate films, and disposable molded articles.

Claims (5)

In preparing aliphatic polyester through the polymerization of aliphatic glycol and dicarboxylic acid, the titanium compound is first added by adding magnesium oxide or zinc oxide as a coupling agent to the aliphatic glycol and dicarboxylic acid, and a reaction accelerator. A method for producing a biodegradable aliphatic polyester, characterized in that it is prepared by synthesizing a polyester prepolymer having a molecular weight band and then adding an isocyanate compound as a binder in an extruder as a secondary reaction. The method of claim 1, wherein the produced aliphatic polyester has a high molecular weight band of tensile strength of 2.5 ~ 3.0kgf, elongation 20 ~ 130%, number average molecular weight 20,000 ~ 50,000. According to claim 1, dicarboxylic acid is selected from succinic acid, adipic acid, decanoic acid, dodecanoic acid, and the like selected as glycol, ethylene glycol, 1,4-butanediol, 1,3-butanediol, 1, Method for producing a biodegradable aliphatic polyester, characterized in that one selected from 6-butanediol, 1,6-hexanediol. The method of claim 1, wherein the titanium compound as a reaction accelerator is used in an amount of 0.1 to 1% by weight based on the total amount of dicarboxylic acid and glycol components, the coupling agent is used in an amount of 0.01 to 0.1% by weight Method for producing biodegradable aliphatic polyester. The method of claim 1, wherein the isocyanate compound used in the secondary reaction is used in an amount of 1.8 to 2.4% by weight based on the total amount of dicarboxylic acid and glycol component.