JP3419575B2 - Polylactic acid composition and molded product thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to improved polylactic acid compositions.

[0002]

BACKGROUND OF THE INVENTION Polymers that are biodegradable or that decompose in the natural environment have attracted attention from the standpoint of environmental protection. A polymer containing lactic acid as a main component is excellent in decomposability, heat resistance, melt moldability, strength, and the like, and lactic acid, which is a main raw material, is also obtained from agricultural products. Expected to be one.

In general, degradable polymers are required to have different decomposition rates and lifespans depending on the purpose and application. Therefore, a degradable polymer that can change the decomposition rate in a wide range is preferable. However, the degradability of conventional degradable polymers is limited, and it is desired that the degradability can be changed over a wider range and freely.

[0004]

A polymer containing lactic acid as a main component generally has a degradability due to a decrease in crystallinity due to the mixing or copolymerization of the third component and a hydrophilization due to the copolymerization or mixing of the hydrophilic component. You can improve. On the other hand, improvement of polymer purity and crystallinity is effective for reducing degradability.

However, for example, by copolymerizing the second component,
Molded products with improved impact strength and toughness may have a problem that only degradable (short-lived) products can be obtained because the crystallinity decreases, and it is necessary to suppress degradability. is there. Further, even unmodified (high-purity) polylactic acid may be required to have lower degradability depending on the application.

An object of the present invention is to provide a novel polymer composition containing lactic acid as a main component and having suppressed degradability.

[0007]

Means for Solving the Problems As a result of diligent studies, the present inventor has found that a polymer containing lactic acid as a main component contains paraffin,
It has been found that mixing a small amount of a hydrophobic substance such as amide suppresses the decomposition rate of the composition and its molded product, and has completed the present invention.

That is, the present invention provides a polymer containing lactic acid as a main component and at least one selected from the following groups (a) and (b):
It is a polylactic acid composition with suppressed degradability, characterized in that various compounds are mixed at a predetermined mixing ratio. (a) Paraffin with a molecular weight of 150 or more, mixing ratio 0.1 to 4% by weight
(Excluding 0.3% by weight or less) (b) Amide of aliphatic carboxylic acid having 10 or more carbon atoms, mixing ratio
0.1 to 4% by weight (excluding 1.0% by weight or less)

In the present invention, the polymer containing lactic acid as a main component means that the component derived from lactic acid in the polymer is 50% by weight or more,
In particular, the amount is 70% by weight or more, for example, poly L-lactic acid homopolymer, poly D-lactic acid homopolymer, poly L / D-lactic acid copolymer and the polylactic acid containing the third component in an amount of 50% by weight or less, particularly 30%. % Or less copolymerized. When the third component is copolymerized with polylactic acid, the crystallinity of the polymer is lowered and the melting point and heat resistance are lowered, but impact strength, toughness,
The dyeability and degradability tend to increase, and the copolymerization component and the copolymerization ratio are selected according to the purpose and application. Generally, the copolymerization ratio is 0.1 to 50% by polymerization, particularly 0.3 to 30%, and most preferably 1 to 20%. Examples of the third component to be copolymerized include polyethers such as polyethylene glycol, aliphatic polyesters such as polyhexane adipate and polyglycolic acid, aromatic polyesters such as polyethylene isophthalate, and vidroxycarboxylic acid, lactone, dicarboxylic acid, Examples thereof include ester bond-forming monomers such as diols.

The paraffin used in the present invention has a molecular weight of 150 or more, preferably 200 to less than 1,000.

The higher aliphatic carboxylic acid used in the present invention is
Preferred are those having 10 or more carbon atoms, such as lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, sebacic acid, and decanedicarboxylic acid. Similarly, their esters and ammonia with, for example, methanol, ethanol, propanol, butanol, glycerin, hexanol, etc., methylamine, ethylamine, butylamine, hexamethylenediamine,
Also suitable are amides with phenylerediamine and the like. The polyamide produced by the reaction of dicarboxylic acid and diamine also preferably has a molecular weight of 20,000 or less, and particularly preferably 10,000 or less.

As the metal salt of higher aliphatic carboxylic acid used in the present invention, salts such as sodium, potassium, lithium, calcium, magnesium and zinc are preferable, and salts of calcium, magnesium and zinc are particularly preferable.

The mixing ratio of the above-mentioned hydrophobic substance to the polymer containing lactic acid as a main component is 0.1 to 4% by weight, preferably 0.3 to 3% by weight, and most preferably 0.6 to 2% by weight. This is because if the mixing ratio is too large, the physical properties of the polymer are significantly deteriorated, and if it is too small, the decomposition rate suppressing effect is insufficient.

In order to mix (add) the above-mentioned hydrophobic substance to the polymer containing lactic acid as a main component, paraffin having a low reactivity can be mixed and stirred in the polymerization raw material or the reaction system during polymerization. I can. On the other hand, for example, the method of melt mixing after polymerization, spinning, film formation, or molding can be applied to all the above hydrophobic substances. As a mixing device, in addition to an ordinary agitator, a screw extruder, a twin-screw kneading extruder, a static mixer,
A gear pump or the like can be applied.

In the case of melt mixing, the water accompanying the hydrophobic substance tends to hydrolyze the polymer containing lactic acid as a main component, so the hydrophobic substance should be sufficiently dried and dehydrated before addition and mixing. Is desirable. The water content in the additive is preferably 100 ppm or less, more preferably 50 ppm or less, most preferably 10 ppm or less.

The polymer having lactic acid as a main component has a molecular weight of 5
˜500,000, especially 80,000 to 300,000 is preferable. In addition to the above hydrophobic substances, antioxidants, stabilizers, ultraviolet absorbers,
Pigments, colorants, inorganic particles, and other additives can be included.

In the molded article of the composition of the present invention mixed with the above-mentioned hydrophobic compound, the hydrophobic compound diffuses in the polymer, and 1 part leaches on the surface to impart water repellency to the molded article, resulting in decomposition of polylactic acid. Sex is suppressed. Generally, those having a small molecular weight tend to have a high diffusion rate. In order to enhance the endurance of the effect of suppressing decomposition, it is preferable to use two or more kinds having different diffusion rates together. For example, a combination of paraffin and polyethylene, paraffin and modified polyethylene, aliphatic alcohol or its derivative with polyethylene or modified polyethylene, aliphatic carboxylic acid or its derivative with polyethylene or modified polyethylene, and the like are preferable. Similarly,
A combination of those having different molecular weights of 300 or more, preferably 500 or more is preferable.

The present invention provides a polymer containing lactic acid as a main component,
A small amount of a hydrophobic substance such as paraffin or a amide of a higher aliphatic carboxylic acid is mixed to suppress the decomposition rate without impairing the physical properties such as crystallinity of the composition and its molded product.

[0019]

EXAMPLES In the present invention, parts and% are parts by weight and% by weight unless otherwise specified. In the following examples, the molecular weight of the polymer containing lactic acid as a main component is the chloroform of the sample.
It is the weight average value of the dispersion of GPC (calibrated by polystyrene standard sample) polymer (excluding molecular weight of 500 or less) in 0.1% solution.

With respect to L-lactide having an optical purity of 99.9% or more, 2.5% of polyethylene glycol having a molecular weight of 8,600, polymerization catalyst tin octylate 0.2%, antioxidant Irganox
0.2% of 1010, 0.5% of paraffin having a molecular weight of 380 as a decomposition inhibitor, 5% of vinyl alcohol copolymerized with a molecular weight of 6,
000 modified polyethylene 0.5% was mixed and fed to a twin-screw kneader, polymerized at 190 ° C. for 15 minutes, extruded from a nozzle having a hole diameter of 2 mm, cooled and cut to obtain chips. The chips were placed in a metal tank, heated in nitrogen at 2 atm at 140 ° C for 10 hours, and then gradually depressurized and heated at 1 Torr for 48 hours. It is melted in a machine, spun out from an orifice with a hole diameter of 0.2 mm and a temperature of 195 ° C, cooled in air, oiled and wound at a speed of 800 m / min, then stretched 4.0 times at a stretching temperature of 70 ° C and tensioned at 120 ° C.
Heat treatment was carried out at 0 ° C. to obtain a drawn yarn Y5 having a fineness of 150 denier / 48 filaments.

In a similar manner, except as a decomposition inhibitor,
Stearamide 1.0%, paraffin with a molecular weight of 380 1.0
% Were added and mixed at the end of the polymerization step, and drawn yarns Y6 and Y8 were obtained in the same manner as drawn yarn Y5. Similarly, the drawn yarn obtained without using the decomposition inhibitor is designated as Y9. Table 1 shows the half-life of the strength of the drawn yarn when it is buried in the soil. As seen in Table 1, the mixture with the decomposition inhibitor has a longer half-life than the comparative example (Y9), and the decomposition rate is suppressed.

[0022]

[Table 1]

[0023]

EFFECTS OF THE INVENTION The composition of the present invention and various products obtained therefrom have suppressed degradability and are suitably used for applications requiring longer life. For example, films, fibers, and various molded products produced from the composition of the present invention have a longer life, and include clothing, non-clothing, packaging materials, containers, machine parts, furniture parts, building materials, industrial product members, and agricultural products. ,
It is preferably used for forestry supplies, gardening supplies, medical supplies, hygiene products and the like. Further, the product according to the present invention is excellent in moldability, fluidity at the time of molding, mold releasability at the time of molding, has a low surface friction coefficient, and can obtain a more flexible product.

The above effects generally become more remarkable as the addition rate of the hydrophobic compound increases, but if the addition rate is too high, the crystallinity, heat resistance, durability, stability, etc. of the polymer deteriorate. It is preferable to use it in an appropriate range.

[0025]

[0026]

[0027]

[0028]

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Ozeki 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto City Shimadzu Corporation Sanjo Factory (72) Inventor Yoshikazu Kondo 2-3-531, Hokoku, Hofu-shi, Yamaguchi (72) ) Inventor Yoshiaki Hirai 1-16-1, Tomobuchi-cho, Miyakojima-ku, Osaka-shi, Osaka (56) Reference JP-A-6-287338 (JP, A) JP-A-6-65484 (JP, A) JP JP 5-179110 (JP, A) JP 4-136066 (JP, A) JP 8-151439 (JP, A) JP 8-27363 (JP, A) International publication 94/028061 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 67/04

Claims (2)

(57) [Claims] 1. A polymer containing lactic acid as a main component, which comprises the following (a)
A polylactic acid composition with suppressed degradability, which comprises mixing at least one compound selected from the group (b) at a predetermined mixing ratio. (a) Paraffin with a molecular weight of 150 or more, mixing ratio 0.1 to 4% by weight
(Excluding 0.3% by weight or less) (b) Amide of aliphatic carboxylic acid having 10 or more carbon atoms, mixing ratio
0.1 to 4% by weight (excluding 1.0% by weight or less) 2. A molded article comprising the composition according to claim 1.