JPH1036652A - Polylactic acid composition - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a novel polylactic acid-based composition which can have various decomposition rates depending on the intended use under a natural environment. [Constitution] Aliphatic polyester containing lactic acid as a main component (A)
99 to 60%, at least one polyether selected from the group of "polyethers having an alkyl group having 2 to 4 carbon atoms and surfactants having the polyether segment and an alkyl group having 6 or more carbon atoms" Compound (B) 0.5 to 35
% And a metal salt of a fatty acid having a saturated or unsaturated alkyl group having 2 or more carbon atoms and a carboxyl group (C) 0.5 to 2
A polylactic acid composition containing 5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to novel polylactic acid-based compositions having various decomposition rates.

[0002]

2. Description of the Related Art At present, synthetic resins, which are consumed in large quantities as fibers, films and various molded products, have a very low decomposition rate under a natural environment, generate a large amount of heat when incinerated, and damage the furnace and cause carbon dioxide in the atmosphere. There are problems such as increasing gas, and it is necessary to review it from the viewpoint of protecting the natural environment.
Aliphatic polyesters are generally spontaneously degradable, but low-melting aliphatic polyesters having a melting point of 150 ° C. or less have a problem in practicality in terms of heat resistance. On the other hand, high-melting aliphatic polyesters having a melting point of 150 ° C. or higher include polyglycolic acid (melting point of about 230 ° C.), polylactic acid (melting point of about 175 ° C.), polyhydroxybutyrate (melting point of about 180 ° C.), and those containing these as main components. Copolymers and the like are known, and among them, polylactic acid is a raw material of agricultural products, so it has little adverse effect on the environment and has many excellent physical properties. However, polylactic acid, particularly a homopolymer, has a problem that the decomposition rate in a natural environment is low because of high crystallinity and glass transition point and low decomposability by enzymes.
A low decomposition rate is suitable for applications requiring a long life, but depending on the application, it is necessary to decompose quickly. That is, polymers that can have various decomposition rates are desired depending on the application. However, at present, technology for controlling the decomposition rate of polylactic acid has not been developed.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved novel polylactic acid composition capable of widely changing the decomposition rate in a natural environment.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aliphatic polyester (A) containing lactic acid as a main component, a polyether having an alkyl group having 2 to 4 carbon atoms, A nonionic surfactant having an alkyl group of at least 6
A polyether compound (B) and a metal salt (C) of a fatty acid having a saturated or / and unsaturated alkyl group and a carboxyl group having 1 or more carbon atoms, wherein Polyester (A) ratio of 9
Polylactic acid, wherein the proportion of the polyether compound (B) is 0.5 to 35% and the proportion of the fatty acid metal salt (C) is 0.5 to 25%. Achieved by the composition.

[0005] Here, the aliphatic polyester (A) containing lactic acid as a main component is one in which the component derived from lactic acid occupies 50% by weight or more in the polymer. For example, (1) polylactic acid homopolymer, (2) ) Polylactic acid obtained by copolymerizing other polyester-forming raw materials in a small amount (50% or less) (block or random copolymerization), and (3) those obtained by mixing small amounts (50% or less) of other components with them .

Examples of aliphatic polyester-forming raw materials that can be copolymerized with polylactic acid include (a) aliphatic hydroxycarboxylic acids such as glycolic acid and hydroxybutyl carboxylic acid, and (b) glycolide, butyrolactone, and caprolactone. Aliphatic lactones, (c) aliphatic diols such as ethylene glycol, propylene glycol, butanediol, hexanediol, etc., (d) diethylene glycol, triethylene glycol, ethylpropyl ether glycol, bishydroxyethylpropane, bishydroxypropylbutane, Aliphatic polyether glycols such as polyethylene glycol, polypropylene glycol, polybutylene ether, copolymers and oligomers thereof, (e) dihydroxybutyl Sulfonates, dihydroxy hexyl carbonate, polybutylene carbonate (glycol)
Examples thereof include aliphatic polycarbonate glycols such as polyhexane carbonate (same as above) and polyoctane carbonate (same as above), copolymers and oligomers thereof, and (f) aliphatic dicarboxylic acids such as succinic acid, adipic acid and sebacic acid.

Polymers obtained from the above polyester raw materials, for example, polycaprolactone, polyglycolic acid, polyethylene adipate, polyethylene sebacate, polybutylene succinate, polybutylene adipate, polybutylene sebacate, polyhexane adipate, polyhexane sebacate, etc. Block copolymerization with polylactic acid is easy. In addition, for example, phthalic acid, terephthalic acid, isophthalic acid, and other aromatic polyester raw materials other than the aliphatic raw materials can be copolymerized in a small amount (for example, 20% or less). Similarly, a small amount (50% or less) of the aliphatic polyester obtained from the above raw materials can be mixed with polylactic acid.

The purpose of modifying polylactic acid by copolymerization or mixing is to lower the crystallinity, lower the melting point (lower the polymerization temperature, molding temperature, and processing temperature), melt fluidity, toughness, flexibility and elastic recovery. Improvement or reduction of friction coefficient, surface roughness, adhesion, mixing, heat resistance and glass transition temperature, improvement of gas barrier properties, moisture permeability, improvement of hydrophilicity and water repellency, improvement of dyeability, improvement of decomposability In addition, modified polylactic acid can be applied to the present invention according to the purpose. For example, polylactic acid obtained by block copolymerizing a small amount (about 1 to 10%) of polyether is excellent in miscibility (miscibility) with polyether and is particularly suitable for the purpose of the present invention.

The polyether having an alkyl group having 2 to 4 carbon atoms used in the polyether compound (B) of the present invention includes polyethylene glycol, polypropylene glycol, polybutylene ether, copolymers thereof, and fatty acids at their molecular terminals. Derivatives in which a group component or the like is bound or blocked are included. A surfactant having a polyether segment and an alkyl group having 6 or more carbon atoms (saturated or unsaturated) is
For example, it can be obtained by addition polymerization of a saturated or unsaturated aliphatic alcohol, an aliphatic carboxylic acid, an aliphatic amine, etc. with ethylene oxide and / or propylene oxide. The segment means a part of the polymer molecular chain, and is also called a block.

In the present invention, a compound having a saturated carbon number of 1 or more and / or
Examples of the fatty acid having an unsaturated alkyl group and a carboxyl group include (a) acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, and lauric acid. Acids, tridecylic acid, myristic acid, pentadecylic acid, stearic acid, nonadecanoic acid, arachinic acid, behenic acid and other saturated fatty acids and hydroxycarboxylic acids, (b) undecylenic acid, oleic acid, setreic acid, sorbic acid, linoleic acid, linolenic Unsaturated fatty acids such as acids, (c) aliphatic polycarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid and decansicarboxylic acid, and (d) unsaturated compounds such as unsaturated alcohols and unsaturated fatty acids. Is reacted with unsaturated fatty acids such as acrylic acid, crotonic acid and oleic acid. And the like. The metal salts of these fatty acids are miscible with the polyether. Among them, those having an alkyl group having about 2 to 50 carbon atoms, particularly about 4 to 30 carbon atoms, are preferably excellent in miscibility with the polyether. Those having an alkyl group having 6 to 20 carbon atoms are most excellent in miscibility and stability and are preferred.

In the present invention, the fatty acids are Na, K,
Alkali metal salts such as Li, Mg, Ca, Ba and the like are preferably used.
Salts such as a, K, and Li are preferred because of their high hydrophilicity. Also, salts of silver, copper, zinc and the like can be used. For the purpose of the present invention, fatty acids having an alkyl group having high biodegradability, for example, those having an alkyl group contained in natural fatty acids and fats and oils are particularly preferred.

In the present invention, the polyether compound (B) and the fatty acid metal salt (C) act as a polylactic acid decomposition accelerator. Although the mechanism of action is not necessarily clear, it is presumed that water is adsorbed or absorbed on the surface or inside of the polylactic acid by the hydrophilic component or polar group, thereby promoting hydrolysis. In addition, the decrease in the crystallinity of polylactic acid due to the mixing of these components may be one of the reasons for accelerating the decomposability. In general, the degradation of polylactic acid in a natural environment is presumed to be caused by a chemical hydrolysis that causes a reduction in molecular weight or a monomer, followed by a degradation process by a monomer or an organism. It appears that the rate of both initial hydrolysis and subsequent biodegradation is often enhanced.

In the present invention, when the polyether and the fatty acid metal salt coexist, the effect of promoting decomposition is remarkable. In general,
Fatty acid metal salts have a high water absorption and a low melt fluidity, so that it is quite difficult to directly melt-mix them with polylactic acid. However, it is relatively easy to melt-mix a fatty acid metal salt with a polyether or a surfactant having a polyether segment, and it is also easy to dehydrate the molten mixture under reduced pressure, for example. /
It is easy to mix the fatty acid metal salt mixture with the molten polylactic acid-based polymer. That is, the polyether and the polyether-based surfactant not only act as a decomposition accelerator but also have an important function as an admixture for mixing a fatty acid metal salt with polylactic acid. It is presumed that by mixing both, the mixing stability of the polymer is increased, and the water absorption and the decomposing action of polylactic acid are further enhanced.

The higher the mixing ratio of the polyether compound (B) and the fatty acid metal salt (C), the higher the decomposition rate of the resulting composition. That is, by adjusting the mixing ratio according to the purpose and application, a composition having a wide range of decomposition rates can be obtained. However, if the mixing ratio is too high, the physical properties of the composition are significantly deteriorated.
It needs to be in the range of 5 to 35%, preferably 2 to 20%, and the range of 3 to 15% is most widely used. Similarly,
The mixing ratio of the fatty acid metal salt needs to be in the range of 0.5 to 25%, preferably 2 to 20%, and the range of 3 to 15% is most widely used. Polyethylene glycol has the strongest effect of promoting decomposition of polyether, followed by polypropylene glycol, and polybutylene ether has the lowest effect. However, all are effective as admixtures. on the other hand,
Since the effect of the fatty acid metal salt depends on the alkali metal salt, the weight ratio of the alkali metal, especially Na, K, Li, etc. in the whole composition is important, and the content of the metal in the composition is 0.01%. As described above, the range of 0.05 to 5% is particularly preferable, and the range of 0.1 to 5% is most widely used.

The molecular weight of the aliphatic polyester (A) containing lactic acid as a main component is not particularly limited, but is preferably 50,000 or more, more preferably 70,000 to 300,000, and particularly preferably 80,000 to 200,000 in view of the strength of a molded product. The range is most widely used. Similarly, the molecular weight of the polyether is not particularly limited.
00 or more, preferably about 5000 to 500,000, most preferably 6,000 to 300,000, and
The range of 0,000 is most widely used. Although the molecular weight of the surfactant having a polyether segment is not particularly limited, it is often in the range of about 200 to 3000, particularly 3
The range of 00 to 2000 is widely used.

The method of mixing the components (A), (B) and (C) is not particularly limited, but first, as described above, the polyether compound (B) and the fatty acid metal salt (C) are melted and mixed.
The mixture and the polyester (A) may be mixed by mechanical stirring such as a screw extruder, a twin-screw kneading extruder, a kneader, a gear pump, a kneading roll, a tank having a stirrer, and the like. And a static mixer that repeats merging may be applied, or they may be used in combination. The mixing may be performed by a batch method or a continuous method. Of course, a continuous method, for example, a screw extruder, a twin-screw kneading extruder, a static mixer, or the like is preferable because of high efficiency. further,
The mixing may be carried out, for example (when the mutual reactivity is negligible), in the raw materials before the polymerization step, or in the polymerization step (particularly in the latter half, etc.). Of course, after the polymerization step, it may be mixed before the molding step or during the molding step.

The composition of the present invention may contain, if necessary, a coloring agent such as a pigment or a dye, a filler such as an inorganic or organic particle, glass fiber, whisker or mica, a nucleating agent, an antioxidant, Stabilizers such as UV absorbers, lubricants, release agents,
Water repellents, plasticizers, antibacterial agents and other secondary additives can be incorporated. In particular, polyethers have poor stability. Therefore, hindered phenols, hindered amines and other antioxidants are used, for example, in an amount of 0.01% or more, particularly 0.05 to 0.05%.
It is desirable to mix about 5%.

The composition of the present invention can be used as various molded products such as fibers, yarns, ropes, knits, woven fabrics, nonwoven fabrics, papers, films, sheets, tubes, plates, bars, containers, bags, parts and the like.
It can be suitably used in agriculture, fishing, forestry, horticulture, medicine, sanitary goods, clothing, non-clothing, packaging, and other fields.

[0019]

EXAMPLES In the following examples,% and parts are by weight unless otherwise specified. The molecular weight of the aliphatic polyester is
In GPC analysis of a 0.1% chloroform solution of a sample, it is a weight average value of dispersion of a high molecular component excluding components having a molecular weight of 500 or less. In the decomposition test in soil, the sample fiber is buried in ordinary field soil at a depth of 10 cm, taken out every month for one year and every three months after one year, and the strength is measured. Was estimated by the interpolation method or the extrapolation method, and it was defined as the (practical) life.

Example 1 100 parts of L-lactide having an optical purity of 99.5% or more and 100 ppm of a tin octylate polymerization catalyst were continuously fed to a twin-screw kneading extruder and reacted at 188 ° C. for an average of 8 minutes. After extruding, cooling in water, cutting and drying, chip C1
I got Further, the chip C1 was placed in a nitrogen stream at 140 ° C. for 4 hours.
After heating (solid-state polymerization) for a time, polymer P1 was obtained. The polymer P1 is poly L-lactic acid having a molecular weight of 193,000 and a melting point of 1
At 76 ° C., the residual monomer amount was 0.1%.

Approximately as for polymer P1, except that L
-A mixture of lactide with a molecular weight of 12000, 3% of polyethylene glycol having a hydroxyl group at both ends (hereinafter referred to as PEG), and 0.1% of an antioxidant Irganox 1010 manufactured by Ciba-Geigy Co., Ltd. Obtained. The polymer P2 was obtained by block copolymerization of poly L-lactic acid with about 3% of polyethylene glycol, and had a molecular weight of 178,000, a melting point of 175 ° C., and a residual monomer amount of 0.1%.

100 parts of PEG having a molecular weight of 20,000 and high purity sodium stearate (hereinafter referred to as STA-Na) powder 3
0 parts and 0.5 parts of the above Irganox were melt-mixed at 200 ° C. using a tank equipped with a stirrer, depressurized gradually for 30 minutes, and kept at 1 Torr for 30 minutes to dehydrate. The above polymer P1 is melted at 220 ° C. with a screw extruder while dewatered P
The EG / STA-Na mixture was continuously mixed by 7%, passed through a Kenix-type static mixer having 30 elements, then spun from an orifice having a diameter of 0.2 mm and 226 ° C, and cooled and oiled in air. The film was wound at a speed of 1500 m / min and further stretched 4.5 times at 80 ° C. to obtain a yarn F1 of 75 denier / 24 filament. The strength of the yarn F1 was 4.7 g / d (gram / denier), and the elongation was 28%.

In the same manner as for the yarn F1, except that the polymer P1
Is used in place of the polymer P2, and a yarn obtained in the same manner is hereinafter referred to as F2. The yarn F2 has a strength of 4.5 g / d and an elongation of 2
8%.

For comparison, only the polymer P2 was used (P
Hereinafter, a yarn having a strength of 4.8 g / d and an elongation of 29% obtained in the same manner as the yarn F1 will be referred to as F3. Similarly, for comparison, only PEG was 5.4% in the polymer P1.
After mixing, a strength of 4.5 g /
d, A yarn having an elongation of 28% is defined as F4. The polymer P1
When only using it, the sample was not collected because the yarn was easily cut in the stretching step.

Each yarn is buried in the soil and subjected to a decomposition test.
Table 1 shows the results obtained for the life. The PEG mixing ratio in the table indicates the mixed PEG, and does not include the copolymerized PEG. As shown in Table 1, the yarn F using the composition of the present invention
1 and F2 have a considerably shorter life than the yarns F3 and F4 of Comparative Example, and the effect of the combined use of fatty acid metal salts is apparent. Table 1 Sample PEG mixing ratio Na content Lifetime Remark F1 5.4% 0.1% 10.2 months Present invention F2 5.4 0.1 8.8 Present invention F30027 Comparative example F4 5.4020 Comparative Example In this example, an example of a fiber having a large surface area was shown, but a thick molded product such as a film, a sheet, and a bottle was used.
In general, they have a much longer lifetime than this example. However, the effect of accelerating the decomposition of the present invention in these molded articles is almost the same as that of the present embodiment. Example 2 A block copolymer P5 was obtained in the same manner as in the polymer P2 of Example 1, except that polybutylene succinate having a molecular weight of 125,000 and having a hydroxyl group at a terminal was used instead of PEG. P5 had a molecular weight of 1490,000 and a melting point of 174 ° C. To the polymer P5, a 7% mixture of a nonionic surfactant obtained by addition polymerization of 30 mol of ethylene oxide with stearyl alcohol and 3/1 of sodium stearate was mixed, and the yarn F5 was prepared in the same manner as the yarn F1 of Example 1. Obtained. Yarn F5 had a strength of 4.5 g / d and an elongation of 27%. The life span of the thread F5 in the soil was 6.6 months.

[0026]

According to the present invention, the problem of polylactic acid having a low decomposition rate in a natural environment is improved, and various decomposition rates can be obtained according to the purpose of use. By changing the mixing ratio of polyether and fatty acid metal salt as active ingredients,
The decomposition rate can be freely changed over a wide range, and the use of polylactic acid is expected to expand and contribute to the protection of the natural environment. The present invention has a feature that it can be easily carried out at a relatively low cost, and further, the mixing ratio of the active ingredient is, for example, 3%.
As described above, particularly at 5% or more, a secondary effect that the flexibility and antistatic property of the obtained product are improved is also recognized. The composition of the present invention includes fibers, films, sheets, containers, tableware,
As a bottle, packaging material, and various other general-purpose molded products, it is highly practical in fields such as agriculture, forestry, horticulture, civil engineering, industry, packaging, and household goods, and is also useful in special fields such as medical and hygiene products. Is high.

Claims (2)

[Claims] 1. An aliphatic polyester containing lactic acid as a main component (A), "a polyether having an alkyl group having 2 to 4 carbon atoms, and a surface activity having a segment of the polyether and an alkyl group having 6 or more carbon atoms. At least one polyether compound (B) selected from the group of "agents" and a metal salt of a fatty acid having a saturated or / and unsaturated alkyl group having 1 or more carbon atoms and a carboxyl group (C). A composition, wherein the ratio of the polyester (A) to the total weight is 99 to 60%, the ratio of the polyether compound (B) is 0.5 to 35%, and the ratio of the fatty acid metal salt (C) is also the same. Is 0.5 to 25%. 2. A polyether compound (B) based on the total weight.
The polylactic acid composition according to claim 1, wherein the weight ratio of the fatty acid metal salt is 2 to 20%.