JPH08183898A - Polylactic acid composition and its molded product - Google Patents

Abstract

PURPOSE: To obtain a new polymer composition based on lactic acid and having controlled degradability. CONSTITUTION: This composition is prepared by mixing a polylatic acid based on lactic acid with 0.1-4wt.% at least one compound selected from the group consisting of a paraffin of a molecular weight of 150 or above, a polyethylene of a moleular weight of 50000 or below, a modified polyethylene of a molecular weight of 50000 or below, a 10 C or higher aliphatic alcohol, a 10 C or higher aliphatic carboxylic acid or its metal salt, a 10 C or higher aliphatic carboyxlic acid amide, a 10 C or higher aliphatic carboxylic acid ester, and a 10 C or higher aliphatic alcohol ester.

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 and copolymerization of the third component and a hydrophilization due to the copolymerization and 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 high degradability (short life) 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 the composition and its molded product are suppressed in the decomposition rate by mixing a small amount of a hydrophobic substance such as polyethylene, higher aliphatic alcohol, higher aliphatic carboxylic acid, their metal salts, esters and amides, The present invention has been completed.

That is, the present invention provides a polylactic acid composition prepared by mixing 0.1 to 4% by weight of at least one compound selected from the following groups (1) to a polylactic acid polymer containing lactic acid as a main component. It is a thing. Paraffin with a molecular weight of 150 or more, polyethylene with a molecular weight of 50,000 or less, modified polyethylene with a molecular weight of 50,000 or less, and the number of carbon atoms in one molecule (hereinafter abbreviated as carbon number) is 1
0 or more aliphatic alcohol, C 10 or more aliphatic carboxylic acid and its metal salt, C 10 or more aliphatic carboxylic acid amide, C 10 or more aliphatic carboxylic acid ester, and C 10 or more Esters of fatty alcohols.

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.
The above is preferably 200 to less than 1,000. Similarly, polyethylene and modified polyethylene used in the present invention have a molecular weight of 50,000 or less, preferably 1,000 to 30,000. The modified polyethylene is a copolymer of ethylene with another vinyl monomer, and as the copolymerizable monomer, for example, maleic acid, fumaric acid, acrylic acid and its metal salt, acrylic acid ester, vinyl acetate, vinyl alcohol and the like are preferable. Used. The copolymerization ratio of those copolymerized monomers is 1 to 25% by weight, particularly 2 to 20% by weight.
Is preferred. This is because if the degree of modification is too large, the stability is poor, and if the degree of modification is small, the miscibility with polylactic acid is poor. Similarly, if the molecular weights of polyethylene and modified polyethylene are too large, the miscibility with polylactic acid is poor, so the molecular weight is
Most preferred is 30,000 or less, especially 2,000 to 20,000.

The higher aliphatic alcohol used in the present invention is
Preferred are those having 10 or more carbon atoms, such as decyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, and oleyl alcohol. Their organic acid esters are similarly useful. Examples of the organic acid that constitutes the ester include acetic acid, adipic acid, sepatic acid, benzoic acid, phthalic acid, isophthalic acid, and terephthalic acid. The higher aliphatic carboxylic acid used in the present invention has 10 or more carbon atoms, such as lauric acid,
Palmitic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, sebacic acid, decanedicarboxylic acid and the like are preferable. Similarly, those such as methanol,
Ethanol, propanol, butanol, glycerin,
Also suitable are esters with hexanol and the like, and amides with ammonia, methylamine, ethylamine, butylamine, hexamethylenediamine, phenylelediamine and the like. In the esterification reaction of dicarboxylic acid and diol,
Although polyester may be produced, the molecular weight is preferably 20,000 or less, particularly preferably 10,000 or less for the purpose of the present invention. Similarly, the polyamide produced by the reaction of a dicarboxylic acid and a diamine preferably has a molecular weight of 20,000 or less, particularly 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, polyethylene, or modified polyethylene having a low reactivity is mixed with the polymerization raw material or the reaction system during the polymerization. , Can be stirred.
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 the mixing device, a screw extruder, a twin-screw kneading extruder, a static mixer, a gear pump, or the like can be applied in addition to a normal stirrer.

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.

[0018]

In the present invention, a polymer containing lactic acid as a main component is mixed with a small amount of a hydrophobic substance such as paraffin, polyethylene, higher aliphatic alcohol, higher aliphatic carboxylic acid, their metal salts, esters and amides. , To suppress the decomposition rate 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.

Example 1 0.2% tin octylate as a polymerization catalyst for L-lactide having an optical purity of 99.9% or more,
Ciba Geigy Irganox 1010 as an antioxidant
0.1%, magnesium stearate as a decomposition inhibitor 0.
4%, 4% fumaric acid 6% copolymerized 0.4% powdered modified polyethylene with a molecular weight of 4,000 was mixed and fed to a twin-screw kneader, polymerized at 190 ° C. for 15 minutes, and extruded from a nozzle having a hole diameter of 2 mm and cooled, It was cut to obtain chips. Place the chips in a metal tank at 10 ° C in nitrogen at 2 atm.
After heating for an hour, gradually reduce the pressure and heat at 1 Torr for 48 hours.
Solid-state polymerization was performed to obtain a polymer P1.

A polymer P2 was obtained in substantially the same manner as the polymer P1 except that 0.8% of magnesium stearate was used as a decomposition inhibitor. Similarly, polymer P1
In the same manner as described above, but using 0.8% of the modified polyethylene as the decomposition inhibitor, the polymer P3 is obtained. In addition, as a comparative example, a polymer P1 was prepared in the same manner as the polymer P1 except that the decomposition inhibitor was not used.
Set to 4.

Polymer P1 was melted by a screw extruder at 200 ° C., spun out from an orifice having a hole diameter of 0.2 mm and a temperature of 195 ° C., cooled in air and oiled to 800 m / mi.
It was wound at a speed of n, then drawn 4.0 times at a drawing temperature of 70 ° C., and heat-treated at 120 ° C. under tension to obtain a drawn yarn Y1 having a fineness of 150 denier / 48 filaments. Strength of yarn Y1
It was 4.4 g / d, the elongation was 33.1%, and the molecular weight was 122,000.

Similarly, the drawn yarns obtained from the polymers P2 to P4 are designated as Y2 to Y4, respectively. The strengths of the yarns Y2 to Y4 are 4.3 g / d, 4.4 g / d, 4.6 g / d, and the elongations are 33.0% and 34.1, respectively.
% And 33.6%, and the molecular weights are 135,000 and 121, respectively.
It was 1,000, 134,000.

The yarns Y1 to Y4 were buried in the soil, and a deterioration test for one year was performed to determine the time at which the strength became 1/2 of the initial strength. The results are shown in Table 1. As shown in Table 1, the half-life of the fiber according to the present invention is longer than that of the comparative example, and the decomposition rate is suppressed.

[Table 1] Example 2 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 with a molecular weight of 380 as a decomposition inhibitor, 5% of vinyl alcohol with 5% of molecular weight 6,
000 modified polyethylene 0.5% was mixed and the following Example 1
Polymerization was carried out in the same manner as in P1 and spinning and drawing were carried out in the same manner as in Y1 to obtain a yarn Y5.

In a similar manner, except as a decomposition inhibitor,
Stearamide 1.0%, cetyl alcohol diester of adipic acid 1.0%, paraffin of molecular weight 380 1.0
% Were added and mixed at the end of the polymerization step, and drawn yarns Y6 to Y8 were obtained in the same manner as in Example 1 below. Similarly, the drawn yarn obtained without using the decomposition inhibitor is designated as Y9. Threads Y6 to Y9
Table 2 shows the half-life of strength of the soil when it was buried in the soil. As shown in Table 2, the mixture of the decomposition inhibitor has a longer half-life than the comparative example (Y9) in this example in which polyethylene glycol is copolymerized.

[0026]

[Table 2]

[0027]

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-mentioned effects generally become more remarkable as the addition rate of the above-mentioned hydrophobic compound becomes higher. However, if the addition rate is too high, the crystallinity, heat resistance, durability, stability, etc. of the polymer deteriorate. It is preferable to use in an appropriate range of

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08K 5/10 KJV 5/20 KJY // (C08L 67/04 23:04) (72) Inventor Eiichi Koseki 1 Nishinokyo Kuwahara-cho, Nakagyo-ku, Kyoto City Stock company Shimadzu Sanjo Factory (72) Inventor Yoshikazu Kondo 2-3-5-31 Kokubei, Hofu City, Yamaguchi Prefecture (72) Yoshiaki Hirai Miyajima, Osaka City, Osaka Prefecture 1-6-1, Tobuchicho 1-306

Claims (4)

[Claims] 1. A polymer containing lactic acid as a main component and 0.1 to 0.1% of at least one compound selected from the following groups
A polylactic acid composition with suppressed degradability, characterized by being mixed in an amount of 4% by weight. Paraffin with a molecular weight of 150 or more, polyethylene with a molecular weight of 50,000 or less, modified polyethylene with a molecular weight of 50,000 or less, and the number of carbon atoms in one molecule (hereinafter abbreviated as carbon number) is 1
0 or more aliphatic alcohol, C 10 or more aliphatic carboxylic acid and its metal salt, C 10 or more aliphatic carboxylic acid amide, C 10 or more aliphatic carboxylic acid ester, and C 10 or more Esters of fatty alcohols 2. A polymer containing lactic acid as a main component and having a molecular weight of 2
Paraffin of 00 or more and less than 1,000, molecular weight of 1,000 or more
A polylactic acid composition comprising 0.3 to 3% by weight of at least one compound selected from the group consisting of polyethylene of 30,000 or less and modified polyethylene having a molecular weight of 1,000 or more and 30,000 or less. 3. A polymer containing lactic acid as a main component and having 1 carbon atom
0-20 aliphatic alcohols, C12-20 aliphatic carboxylic acids and metal salts thereof, amides of C10-20 aliphatic carboxylic acids, esters of C12-20 aliphatic carboxylic acids, and A polylactic acid composition containing 0.3 to 3% by weight of at least one compound selected from the group of aliphatic alcohol esters having 12 to 20 carbon atoms. 4. A film, a sheet, a fiber, a knitted fabric, a woven fabric, a non-woven fabric, a paper, a rope, which comprises the composition according to claim 1.
Nets, containers, machine parts, furniture and various equipment parts, and various molded products.