JP2001031853A - Polylactic acid-based polymer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable polylactic acid-based polymer composition completely degradable in a natural environment, having excellent moldability, making the best use of rigidity being a characteristic of polylactic acid, having a balance excellent in impact resistance. SOLUTION: This composition is obtained by compounding 70-95 wt.% of a polylactic acid (A) with 4-29 wt.% of an aliphatic polyester (B) and 1-9 wt.% of a polycaprolactone (C). In the operation, preferably the aliphatic polyester (B) is a polyester polymer consisting essentially of succinic acid and/or adipic acid, ethylene glycol and/or butanediol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biodegradable polylactic acid-based polymer composition having excellent impact resistance.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protection of the natural environment, biodegradable polymers that can be decomposed in the natural environment and molded products thereof have been demanded. . In particular, polylactic acid is most promising in terms of cost and physical properties, and is greatly expected as a transparent thermoplastic resin. On the other hand, due to its rigid molecular structure, it has drawbacks of poor elongation and flexibility and low impact resistance.

[0003] By blending or copolymerizing polylactic acid with an aliphatic polyester other than polylactic acid for the purpose of improving the drawbacks of polylactic acid, a material having excellent flexibility and excellent impact resistance can be obtained. In this case, although excellent in flexibility in this case, there is no material that reduces the rigidity of polylactic acid, makes use of the rigidity characteristic of polylactic acid, and has a balance with excellent impact resistance. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a balance that is completely decomposable in a natural environment, has excellent moldability, makes use of the rigidity characteristic of polylactic acid, and has excellent impact resistance. An object of the present invention is to provide a biodegradable polylactic acid-based polymer composition.

[0005]

Means for Solving the Problems In order to solve such problems, the present inventors have made intensive studies and as a result, by mixing polylactic acid, aliphatic polyester and polycaprolactone at a specific weight ratio, the above-mentioned method has been proposed. I found that my goal was achieved.

That is, the biodegradable polylactic acid-based polymer composition of the present invention comprises 70 to 95% by weight of polylactic acid (A), 4 to 29% by weight of aliphatic polyester (B), and 1 to 4% of polycaprolactone (C). It is a polymer composition mixed at a ratio of 9% by weight.

The present invention also relates to an aliphatic polyester (B)
Contains a polymer composition which is mainly a polyester polymer of succinic acid and / or adipic acid and ethylene glycol and / or butanediol, and at least two or more aliphatic polyesters (B). It is a united composition.

Hereinafter, polylactic acid, aliphatic polyester and the like used in the present invention will be described step by step.

[0009] In the present invention, polylactic acid is a polymer consisting essentially of monomer units derived from L-lactic acid and / or D-lactic acid. Here, “substantially” means
This means that other monomer units not derived from L-lactic acid or D-lactic acid may be contained as long as the effects of the present invention are not impaired.

As a method for producing polylactic acid, any known polymerization method can be employed. The most commonly known method is a method in which lactide which is an anhydrous cyclic dimer of lactic acid is subjected to ring-opening polymerization (lactide method). However, lactic acid may be directly subjected to condensation polymerization.

When the polylactic acid consists solely of monomer units derived from L-lactic acid and / or D-lactic acid, the polymer is crystalline and has a high melting point. In addition, by changing the ratio of monomer units derived from L-lactic acid and D-lactic acid (abbreviated as L / D ratio), the crystallinity and melting point can be freely adjusted. Can be controlled.

Further, another hydroxycarboxylic acid or the like may be copolymerized to the extent that the properties of polylactic acid are not impaired. In order to further increase the molecular weight, a small amount of a chain extender,
For example, a diisocyanate compound, an epoxy compound, an acid anhydride and the like can be used. The weight average molecular weight of the polymer is preferably in the range of 50,000 to 1,000,000. If the ratio is less than the above range, mechanical properties and the like are not sufficiently exhibited.

In the present invention, the aliphatic polyester is, for example, a polymer composed of an aliphatic carboxylic acid component and an aliphatic alcohol component and a polymer composed of an aliphatic hydroxycarboxylic acid component. In the present invention, polylactic acid and polycaprolactone are used. The homopolymer and its copolymer are essential components and are not included in the aliphatic polyester (B).

As a method for producing an aliphatic polyester,
There are a method of directly polymerizing these to obtain a high molecular weight substance, and an indirect method of polymerizing to about an oligomer and then obtaining a high molecular weight substance with a chain extender or the like.

The aliphatic polyester used in the present invention is, for example, an aliphatic polyester comprising a dicarboxylic acid and a diol. Examples of the aliphatic dicarboxylic acid include compounds such as succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanoic acid, and anhydrides and derivatives thereof.

On the other hand, as the aliphatic diol, glycol compounds such as ethylene glycol, butanediol, hexanediol, octanediol and cyclohexanedimethanol, and derivatives thereof are generally used.
Each is a compound having an alkylene group, a cyclocyclic group or a cycloalkylene group having 2 to 10 carbon atoms, and is produced by condensation polymerization. In any of the carboxylic acid component and the alcohol component, two or more kinds may be used.

In order to improve the melt viscosity, a carboxylic acid, alcohol or hydroxycarboxylic acid having three or more functional groups may be used for the purpose of providing a branch in the polymer. When these components are used in a large amount, the resulting polymer may have a crosslinked structure and become non-thermoplastic, or even if it is thermoplastic, a microgel having a partially highly crosslinked structure may be produced. Therefore, the proportion of these trifunctional or higher functional components in the polymer is very small, and is contained to such an extent that the chemical and physical properties of the polymer are not largely affected.

As the polyfunctional component, malic acid, tartaric acid,
For example, citric acid, trimellitic acid, pyromellitic acid, pentaerythritol, trimethylolpropane, or the like can be used.

Among the production methods, the direct polymerization method is a method in which the above compounds are selected to obtain a high molecular weight product while removing water contained in the compounds or generated during the polymerization.

In the indirect polymerization method, after the above compound is selected and polymerized to an oligomer, a small amount of a chain extender such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, etc. is used for the purpose of increasing the molecular weight. And a method of obtaining an aliphatic polyester carbonate by using a carbonate compound.

The other aliphatic polyester (B) used in the present invention is, for example, an aliphatic polyester comprising a polycondensate of an aliphatic hydroxycarboxylic acid. Examples of the aliphatic hydroxycarboxylic acid include glycolic acid, β-hydroxybutyric acid, hydroxypivalic acid, hydroxyvaleric acid and the like, and a high molecular weight product can be obtained by polycondensing these. These can also be used as derivatives such as esters and cyclic esters, and high molecular weight compounds can be obtained by ring-opening polymerization of cyclic esters.

Among these aliphatic polyesters (B), in the present invention, particularly, succinic acid and / or adipic acid,
A polymer composition which is a polyester polymer with ethylene glycol and / or butanediol is preferred from the viewpoint of physical properties and availability. In addition, a chain extender or the like may be used in these aliphatic polyesters for increasing the molecular weight. By including two or more of these aliphatic polyesters, superior impact resistance can be obtained as compared with a single mixture.

The polycaprolactone (C) used in the present invention is a homopolymer of polycaprolactone or a copolymer of caprolactone and another aliphatic polyester. The homopolymer of polycaprolactone is obtained by ring-opening polymerization of ε-caprolactone,
It may be one obtained by dehydration polycondensation of hydroxycaproic acid or one obtained by polymerizing / mixing both.

Further, another hydroxycarboxylic acid or the like may be copolymerized to the extent that the properties of polycaprolactone are not impaired. Further, for the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an ethoxy compound and an acid anhydride can be used. The weight average molecular weight of the polymer is preferably in the range of 50,000 to 1,000,000. If the ratio is less than the above range, mechanical properties and the like are not sufficiently exhibited.

The composition ratio of the polylactic acid-based polymer composition of the present invention is as follows: 70-95% by weight of polylactic acid (A), 4-29% by weight of aliphatic polyester (B) and polycaprolactone (C).
It is a ratio of 1 to 9% by weight.

If the content of polylactic acid (A) is more than 95% by weight, it is difficult to improve the impact resistance. If the content is less than 70% by weight, the high rigidity characteristic of polylactic acid is impaired. On the other hand, if the amount of the aliphatic polyester (B) is more than 29% by weight, not only the high rigidity of polylactic acid cannot be utilized, but also the high transparency is impaired, and if it is less than 4% by weight, toughness cannot be obtained. Further, if the polycaprolactone (C) is more than 9% by weight, the heat resistance is inferior due to the influence of its melting point (about 60 ° C.), and if it is less than 1% by weight, the effect of its addition is low, and the balance between toughness and transparency is poor. .

The composition of the present invention is easily produced by mixing polylactic acid (A), aliphatic polyester (B) and polycaprolactone (C). The mixing method and the mixing apparatus are not particularly limited, but those capable of continuous processing are industrially advantageous and preferred. For example, these pellets may be mixed at a predetermined ratio, melted by a single-screw extruder or a twin-screw kneading extruder, and immediately formed. Alternatively, both components may be melt-mixed, then pelletized once, and then melt-molded as needed. Similarly, the polymers may be melted in different extruders or the like, mixed at a predetermined ratio by a static mixer and / or a mechanical stirrer, and then immediately molded or pelletized. Mixing by mechanical stirring such as an extruder and a static mixer may be combined. A solvent may be used and mixed in a solution state.

In the melt mixing method, deterioration, alteration,
It is necessary to substantially prevent the formation of a copolymer by transesterification, and it is preferable to mix at a temperature as low as possible and within a short time. For example, the temperature is below 210 ° C., preferably 1
It is preferable that the mixing is performed at 90 ° C. or less and the time is within 20 minutes, preferably within 10 minutes. In order to prevent denaturation and transesterification due to melting, it is preferable to remove or reduce hydroxyl groups and carboxyl groups at the molecular terminals, residual monomers and polymerization catalyst. When the transesterification reaction substantially occurs to the extent that it cannot be ignored, the crystallinity and heat resistance of the composition decrease.

Further, the polylactic acid-based polymer composition of the present invention can be variously modified by adding a secondary additive. Examples of secondary additives include stabilizers, antioxidants,
UV absorbers, pigments, colorants, various fillers, electrostatic agents,
Release agents, plasticizers, fragrances, antibacterial agents, nucleating agents, and other similar substances are included.

In the present invention and the following examples, the weight average molecular weight (Mw) of the polymer is a value measured by GPC analysis in terms of polystyrene, and the melting point is a value measured by a scanning differential calorimeter (DSC). The tensile test was performed according to JIS-K7113, and the Izod impact test was measured according to JIS-K7110. Further, the transparency was measured by measuring the transmittance at a light wavelength of 700 nm and used as an index.

[0031]

The present invention will be described more specifically with reference to examples and comparative examples. In this example, experiments were performed using the following four types of aliphatic polyesters. <Polylactic acid (A)> Poly L-lactic acid Lacty # 5000 manufactured by Shimadzu Corporation, melting point 175 ° C <Aliphatic polyester (B1)> Polybutylene succinate Showa Polymer Bionole # 1001, melting point 115 ° C <Aliphatic polyester (B2) )> Polybutylene succinate adipate Bionore # 3001, manufactured by Showa Polymer, melting point 90 ° C. <Polycaprolactone (C)> Cell Green PH7, manufactured by Daicel Chemical, melting point 60 ° C.

(Example 1) Polylactic acid (A), (B1) as an aliphatic polyester, and polycaprolactone (C) were each vacuum-dried to sufficiently reduce the water content, and then the mixing ratio (A) / ( B1) / (C) = 85/10/5, mixed in a V-type blender, continuously supplied to a 30 mm co-axial twin-screw extruder, melt-extruded, and formed into strands and pelletized to prepare main raw materials. did. After the obtained pellets are dried to a completely dry state by vacuum drying, a business card large plate (1 mmt), a tensile test piece (JIS-2 test piece), and an Izod impact test piece (JIS-2A test piece) are formed by injection molding. Was prepared, and a transmittance measurement, a tensile test, and an Izod impact test were performed.

(Examples 2 to 5) The mixing ratio of each polymer is set in the same manner as in Example 1 as shown in Table 1 below.

(Comparative Example 1) Polylactic acid (A) and polycaprolactone (C) were each dried sufficiently in vacuum to reduce the water content, and then mixed at a mixing ratio (A1) / (C) = 80/20. The mixture was mixed in a mold blender, continuously supplied to a 30 mm co-axial twin-screw extruder, melt-extruded, and formed into strands and pelletized to prepare main raw materials. After the obtained pellets are made absolutely dry by vacuum drying, a business card size plate (1 mmt) and a tensile test piece (JIS) are formed by injection molding.
No.-2 test piece) and an Izod impact test piece (JIS-2A test piece), and a transmittance measurement, a tensile test and an Izod impact test were performed.

(Comparative Examples 2 to 4) The mixing ratio of each polymer is set in the same manner as in Comparative Example 1 as shown in Table 1 below.

[0036]

[Table 1]

[0037]

According to the present invention, polylactic acid, aliphatic polyester and polycaprolactone can be completely decomposed in a natural environment by mixing polylactic acid, aliphatic polyester and polycaprolactone in a specific ratio as described above. It is possible to provide a biodegradable polylactic acid-based polymer composition that makes use of the rigidity characteristic of polylactic acid and has a good balance of impact resistance. This biodegradable polylactic acid-based polymer can be used for various applications such as packaging materials, medical materials, industrial materials, industrial supplies, containers and the like. Furthermore, since it has biodegradability, the problem of waste disposal like conventional plastics is reduced.

Continued on the front page F term (reference) 4J002 CF032 CF181 CF193 FD010 FD020 FD030 FD050 FD070 FD090 FD160 FD180 FD200 GB01 GG01 GG02 GT00

Claims (3)

[Claims] 1. A polymer composition comprising 70 to 95% by weight of polylactic acid (A), 4 to 29% by weight of aliphatic polyester (B) and 1 to 9% by weight of polycaprolactone (C). 2. The polymer composition according to claim 1, wherein the aliphatic polyester (B) is a polyester polymer of succinic acid and / or adipic acid and ethylene glycol and / or butanediol. 3. The polymer composition according to claim 1, comprising at least two kinds of aliphatic polyesters (B).