JP2000191895A - Polylactic acid composition and its molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition which gives a molding excellent in softness, flexibility, transparency and gloss and scarcely suffering surface contamination due to bleeding of a plasticizer by blending a polymer comprising mainly lactic acid with an aliphatic polyester comprising mainly an aliphatic dicarboxylic acid and a chain diol. SOLUTION: Examples of the polymer comprising mainly lactic acid include polylactic acid homopolymers comprising, e.g. poly(L-lactic acid) and a poly(D- lactic acid), poly(L- and D-lactic acid) copolymers, and polylactic acid copolymers obtained by copolymerizing these polymerizable materials capable of forming an ester linkage, wherein the component derived from lactic acid accounts for at least 50 wt.% of the copolymer. A 4-50C linear dicarboxylic acid is suitably used as the aliphatic dicarboxylic acid, an constituent of the aliphatic polyester. Examples of the chain diol used include 2-20C chain diols, polyalkylene ethers and copolymers and oligomers thereof, and polyalkylene carbonates and oligomers thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasticized biodegradable polylactic acid composition and a molded product thereof.

[0002]

2. Description of the Related Art Polymers that are biodegradable or decompose in the natural environment are attracting attention from the viewpoint of environmental protection. In particular, polylactic acid is advantageous in resources because it uses agricultural products as raw materials,
Further, they are most expected because of their excellent melt moldability and heat resistance. However, an unmodified polylactic acid homopolymer has high crystallinity and a rigid molecular structure, so that it is hard and brittle, and a molded product is easily damaged. In addition, depending on the application, for example, a part for a film or a molded product requires high flexibility.

For this reason, conventionally, the third component has been copolymerized or mixed to enhance flexibility and improve brittleness.

[0004]

However, according to the copolymerization method, there arises a problem that the melting point and the heat resistance decrease with the decrease in crystallinity. According to the method of mixing the plasticizer,
Since the affinity between the plasticizer and the parent polylactic acid is low, there arises a problem that the plasticizer oozes out and stains the surface of the composition, and the transparency and gloss of the molded product are impaired.

The present invention has improved flexibility, flexibility, transparency, and gloss without excessively impairing the crystallinity and heat resistance, and has reduced surface contamination due to leaching of a plasticizer. It is intended to provide a polylactic acid composition and an applied product thereof.

[0006]

In order to achieve the object of the present invention, the polylactic acid composition of the present invention comprises a polymer (A) containing lactic acid as a main component, an aliphatic dicarboxylic acid and a chain. And an aliphatic polyester (B) containing a diol as a main component.

[0007] The polymer (A) containing lactic acid as a main component here means a polylactic acid homopolymer such as poly-L-lactic acid or poly-D-lactic acid, a poly-L / D-lactic acid copolymer, and an ester thereof. A polylactic acid copolymer obtained by copolymerizing a bond-forming polymer material, wherein the weight ratio of lactic acid-derived components in the copolymer is
50% or more.

Examples of the polymer material capable of forming an ester bond copolymerizable with polylactic acid include hydroxyalkyl carboxylic acids such as glycolic acid and hydroxybutyl carboxylic acid, lactones such as glycolide, butyrolactone and ε-caprolactone, aliphatic and lactone. Examples thereof include aromatic dicarboxylic acids, aliphatic diols, polyalkylene ethers having hydroxyl group terminals and oligomers thereof, and polyalkylene carbonates and oligomers (diols) thereof.

As the aliphatic dicarboxylic acid, for example, dicarboxylic acids having 4 to 20 carbon atoms such as succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid and dodecanedicarboxylic acid are preferable. As the aromatic dicarboxylic acid, phthalic acid, isophthalic acid, 5-sulfoisophthalic acid and metal (Na, K, etc.) salts thereof, terephthalic acid, naphthalenedicarboxylic acid and the like are preferable.

As the aliphatic diol, ethylene glycol, propylene glycol, butanediol,
Those having 2 to 20 carbon atoms, such as hexanediol, octanediol, decanediol and dodecanediol, are preferred.

Examples of the polyalkylene ether (glycol) include polyethylene glycol, polypropylene glycol, polybutylene ether, and copolymers thereof, such as polyethylene / propylene glycol and polyethylene / butylene ether.
These oligomers, particularly those having a molecular weight of less than 2,000, preferably 1,000 or less, for example, diethylene glycol, triethylene glycol, etc. are most preferred.
As the copolymerized alkylene ether, for example, 2 mol of ethylene oxide can be added to 1 mol of polypropylene glycol to obtain ethylene / propylene ether glycol having an average degree of polymerization of 3, and 3 mol of ethylene oxide can be added to 1 mol of butanediol. By reacting, ethylene / butylene ether glycol having an average degree of polymerization of 4 can be obtained. Similarly, a propylene oxide can be obtained by addition reaction of diols with propylene oxide.

The diol and the dicarboxylic acid are combined so as to be substantially equimolar to form a copolymer component. For example, if equimolar ethylene glycol and adipic acid react, one end is a hydroxyl group and the other is a carboxyl group of polyethylene adipate, and the molar ratio is 101/100.
To give a polyethylene adipate having a degree of polymerization of 101 and hydroxyl groups at both ends and copolymerizing with both lactide to obtain a good polylactic acid / polyethylene adipate block copolymer.

Such a copolymer component accounts for less than 50% by weight of the copolymer (A) containing lactic acid as a main component. As the amount of the copolymer component increases, the copolymer (A) is modified, crystallinity and heat resistance are reduced, and decomposability is increased. The copolymerization ratio can be arbitrarily selected depending on the purpose and application, but in most cases, it is 1
~ 40%, especially 3 ~ 30% is often used, 2 ~ 20% is the most widely used.

In general, copolymerization of an aliphatic component has the effect of improving flexibility and impact resistance, but tends to lower the glass transition point and heat resistance. Further, the copolymerization of the aromatic component tends to improve the glass transition point and the heat resistance. However, copolymer components having a very high melting point (for example, a polyester composed of an aromatic dicarboxylic acid and a diol) have problems from the viewpoint of copolymerization operation and melt moldability. 200
It is desirable to select ones that are not more than 180 ° C, especially not more than 180 ° C.

For the copolymerization of such a copolymer component with lactic acid or polylactic acid, both random copolymerization and block copolymerization can be used. However, in order to minimize the crystallinity, melting point, heat resistance and the like due to copolymerization, block copolymerization is particularly preferred. In the block copolymerization, for example, a polymer or oligomer having a hydroxyl group at a molecular terminal is preliminarily polymerized to form a polymer or an oligomer, and then lactide is polymerized using the terminal hydroxyl group as a polymerization starting point. Polymer (polyester)
It is possible to obtain a block copolymer in which segments are bonded. In addition, polylactic acid having a hydroxyl group or a carboxyl group at the molecular terminal and a polyester which is a copolymer component having a functional group at the terminal, and dicarboxylic acid, dicarboxylic anhydride, dicarboxylic acid halide, diisocyanate, diamine and the like The block copolymer can be obtained by reacting and linking with a bifunctional compound.

The base (matrix) polymer of the composition of the present invention is a polymer (A) containing lactic acid as a main component and an aliphatic polyester (B) containing aliphatic dicarboxylic acid and a chain diol as main components. It is characterized by doing.

Examples of the aliphatic dicarboxylic acid which is one of the constituent components of the aliphatic polyester (B) include succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid and the like, particularly those having 4 to 50 carbon atoms. A linear dicarboxylic acid having 4 to 20 carbon atoms is preferred, but those having a side chain or a double bond can also be used.

Examples of the chain diol which is another main component of the aliphatic polyester (B) include those having 2 to 20 carbon atoms such as ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, decanediol and dodecanediol. And polyalkylene ethers such as polyethylene glycol, polypropylene glycol and polybutylene ether, and copolymers and oligomers thereof, and polyalkylene carbonates and oligomers thereof. The oligomer of the polyalkylene ether and the polyalkylene carbonate preferably has a molecular weight of less than 2,000, particularly preferably 1,000 or less.

The main components of the aliphatic polyester (B) are the above-mentioned aliphatic dicarboxylic acids and chain diols.
Components other than these may be included as a secondary component. As the secondary components, for example, lactic acid, glycols, hydroxyalkyl carboxylic acids such as hydroxybutyl carboxylic acid, butyrolactone, lactones such as ε-caprolactone, diamines, diisocyanates and the like can be applied.

Although the degree of polymerization and the molecular weight of the aliphatic polyester (B) are not particularly limited, generally, the smaller the molecular weight, the greater the plasticizing effect, but the lower the stability, and the more the leaching to the surface of the molded product causes stains. It will be easier. In many cases, the molecular weight of the aliphatic polyester (B) is preferably 500 or more, particularly preferably 1000 or more, more preferably 3000 or more, and
~ 200,000 is most widely used.

One of the features of the present invention is that it has a low glass transition point and a large plasticizing effect because it contains an aliphatic polyester as a main component, and gives a molded product high flexibility and impact resistance. . In addition, if necessary, a high-molecular weight plasticizer can be used, so that there is little leaching to the surface of the molded product, a stable effect is continuously exhibited, and a decrease in strength due to plasticization is minimized. be able to. Such an effect as a polymer plasticizer is clearly exhibited at a molecular weight of 3,000 or more, and is particularly remarkable at a molecular weight of 10,000 or more.

The terminal of the aliphatic polyester (B) may be a carboxyl group, a hydroxyl group, or the like, or may be blocked with a compound having an alkyl group, an allyl group, an alkylallyl group, or another functional group. When the terminal has a carboxyl group or a hydroxyl group, it has a high affinity for the base polymer (A), but is unstable from the viewpoint of stability, and conversely reacts with the base polymer (A) or reacts with air in the air. It tends to absorb moisture and promote the decomposition of the base polymer (A). The terminal functional group of the aliphatic polyester may be arbitrarily selected depending on the purpose of use of the composition, but is preferably a blocked one from the viewpoint of the stability of the composition described above. For example, if both ends are blocked with a higher alkyl group such as a stearyl group, the plasticizing effect of the higher alkyl group itself is added, and a composition excellent in both stability and plasticizing effect can be obtained.

Further, in the present invention, a component which is the same as or similar to the aliphatic dicarboxylic acid and the chain diol which are the constituent components of the aliphatic polyester (B) is added to the base polymer (A).
By using the copolymer as a copolymer component, the closeness of the molecular structure between the base polymer (A) and the aliphatic polyester (B) can be improved.

The similarity of the molecular structure of the polymers can be represented by the similarity of the number of carbon atoms and the number of oxygen atoms of the structural units (dicarboxylic acid, diol, hydroxycarboxylic acid, etc.) constituting the main chain. For example, if the difference between the number of carbon atoms and the number of oxygen atoms of the two types of constituent units is 4 or less, similarity is recognized. If the difference is 2 or less, the similarity is fairly high. For example, ethylene adipate, ethylene sebacate, butylene adipate, butylene sebacate, and the like have high mutual approximation. Similarly, a polyester ether of diethylene glycol and adipic acid has high similarity to polybutylene adipate. The number of atoms in the repeating unit of the main chain of polylactic acid is 2 carbons and 1 oxygen. The number of atoms in the repeating unit of polyglycolic acid is exactly the same as that of polylactic acid, and both have the highest similarity. Similarly, that of hydroxybutyl carboxylic acid also closely resembles lactic acid. Polyester composed of a dicarboxylic acid and a diol, ethylene succinate having a small number of atoms in the repeating unit is carbon 6 and oxygen 2, but contains two ester bonds in it, In terms of the average number of atoms between ester bonds, it can be said that carbon 3 and oxygen 1 are quite close to polylactic acid. That is, a polyester comprising a dicarboxylic acid or diol having 6 or less carbon atoms, particularly 4 or less, shows high similarity to polylactic acid.

As described above, those having high molecular structure similarity can be obtained by combining the base polymer (A) and the aliphatic polyester (B)
, Excellent miscibility, plasticity, transparency and the like can be realized. In addition, the higher the similarity of the molecular structures of the base polymer (A) and the aliphatic polyester (B), the better the action and effect, and the effect is most remarkable when both have the same constituent components. For example, if at least one of the copolymer components in the base polymer (A) is the same as an aliphatic dicarboxylic acid or a chain diol which is a constituent component of the aliphatic polyester (B), the affinity between the two is extremely high, The highest affinity is achieved if both the dicarboxylic acid component and the diol component are the same. That is, by using the same kind of polyester composed of the same aliphatic dicarboxylic acid / chain diol as the copolymer component in the base polymer (A) and also as the main component of the aliphatic polyester (B), the highest affinity is obtained. And the one most suitable for the purpose of the present invention is obtained. Of course, the aliphatic polyester (segment) which is shared by the base polymer (A) and the aliphatic polyester (B) is sufficient if the constituent diol and dicarboxylic acid are the same, and the degree of polymerization is different. You may.

The mixing ratio of the aliphatic polyester (B) to the base polymer (A) varies depending on the purpose.
The greater the mixing ratio, the more remarkable the plasticization. In order to impart impact resistance without significantly impairing the heat resistance of the molded product, the mixing ratio of the aliphatic polyester (B) is about 1 to 15%, particularly 3 to 15%.
About 10% is often used. Conversely, when high flexibility is required, the mixing ratio of the aliphatic polyester (B) is 10%.
About 50%, especially about 15 to 40% is often used. Since the copolymer component in the base polymer (A) also acts as a plasticizer, the mixing ratio of the aliphatic polyester (B) may be relatively small when the copolymer component is large. The total weight fraction of the copolymer component and the aliphatic polyester (B) from the viewpoint of the whole composition is 2 to 70% in many cases, particularly preferably 5 to 50%, and most preferably 8 to 40%.

The aliphatic polyester (B) is often mixed after the polymerization of the base polymer (A). It is not impossible to mix the raw materials for the base polymer (A) and the polymerization step, but it is not possible to copolymerize with the base polymer by a transesterification reaction or to decompose the plasticizer, and to obtain a desired mixing ratio and plastic effect. In order to effectively realize the above, it is preferable to mix them after the polymerization of the base polymer and before or during the molding step.

The mixing method is optional, but it may be mixed in a molten state or a solution by mechanical stirring or by a static mixer, or may be mixed in a powder or particle form and melted or dissolved. The composition of the present invention has high affinity between the base polymer (A) and the aliphatic polyester (B), and can be easily and uniformly mixed.

In the composition of the present invention, in addition to the base polymer (A) and the aliphatic polyester (B), which are the main components, other components may be added as a secondary component. Examples of secondary additives include stabilizers, antioxidants, ultraviolet absorbers, pigments, colorants, various inorganic particles, various fillers, water repellents, hydrophilic agents, antistatic agents, release agents, plasticizers , Bioactive substances, preservatives, fragrances,
Antimicrobial agents, foaming agents, and the like are included.

In the following examples, parts and percentages are indicated by weight unless otherwise specified. The molecular weight of the polylactic acid and the polylactic acid copolymer is a weight average value of the dispersion of the high molecular substances excluding those having a molecular weight of 500 or less in terms of polystyrene by GPC analysis of a chloroform 0.1% solution of the sample.

[0031]

<Example 1> 95 parts of L-lactide having an optical purity of 99% or more, 5 parts of polyethylene adipate having a hydroxyl group at both ends and a molecular weight of 9000 and titanium oxide particles having a diameter of 0.05 µm (crystal nucleus) were used as copolymerization components. Agent) 0.5%, tin octylate 0.05
%, Ciba-Geigy Corporation Irganox 1010 (Antioxidant)
0.2% was mixed and reacted (preliminarily) polymerized continuously at 180 ° C. in a nitrogen atmosphere at 180 ° C. for an average of 30 minutes in a twin-screw mixing liquid feeder in which two screws mesh with each other, and then 0.1% of tin octylate was added. Using a twin-screw kneader consisting of a group of screws that mesh with each other and a group of oval (two-flight) stirring elements that mesh with each other, polymerize at 190 ° C for an average of 15 minutes, and then melt from the final vent hole to reduce the water content to 10 ppm or less. After supplying and mixing 5% of the plasticizer P1, the mixture was further passed through a cylinder containing 60 Kenics static mixing elements, extruded from a die, cooled and solidified with water, and cut to obtain a chip C1. Was.

The plasticizer P1 has a molecular weight of about 4500 in which the hydroxyl groups at both ends of polyethylene adipate having a molecular weight of about 4000 are esterified with stearic acid and blocked, and 0.3% of triethylene glycol is further mixed as a solid phase polymerization initiator. Things.

The chip C1 was heat-treated in nitrogen at 120 ° C. and 1.5 kg / cm 2 for 12 hours, and further heat-treated (solid state polymerization) at 160 ° C. and normal pressure for 48 hours to obtain a chip C2. Chip C2
Has an average molecular weight of 162,000 and a residual monomer (lactide) of
0.2%. Using chip C2, it was injection molded to prepare an impact test piece with a V-shaped notch. Similarly, the chip C2 was melted at 210 ° C. with a screw extruder, extruded through a slit of a T-shaped die, cooled, and then stretched 3.1 times in the vertical direction and 2.9 times in the horizontal direction at 90 ° C. to form a 50 μm thick film. Created.

A chip C3 is obtained in substantially the same manner as the chip C2 except that 5% of a plasticizer P1 is added to and mixed with a polylactic acid homopolymer obtained without adding a copolymerization component during lactide polymerization. Chip C3 had a molecular weight of 163,000 and a residual monomer content of 0.2%. From chip C3 to chip C
In the same manner as in Example 2, an impact test piece and a stretched film were prepared.

A chip C4 was obtained in substantially the same manner as the chip C2 except that no plasticizer was added to the polylactic acid homopolymer obtained without adding a copolymerization component during lactide polymerization. Chip C4 had a molecular weight of 169,000 and a residual monomer content of 0.2%. From the chip C4, an impact test piece and a stretched film were prepared in the same manner as the chip C2.

The chip C5 is obtained in substantially the same manner as the chip C2 except that a polyε-caprolactone having a molecular weight of about 4500 is added and mixed in place of the plasticizer P1, and the solid phase polymerization is carried out in the same manner. Chip C5 had a molecular weight of 153,000 and a residual monomer content of 0.3%. From chip C5, an impact test piece and a stretched film were prepared in the same manner as chip C2.

In the same manner as in chip C2, except that no copolymerization component is added during the polymerization of lactide, poly-ε-caprolactone having a molecular weight of about 4500 is added and mixed in place of the plasticizer P1, and the solid phase polymerization is performed in the same manner. Got what you get, chip C6
And Chip C6 had a molecular weight of 154,000 and a residual monomer content of 0.3%. From the chip C6, an impact test piece and a stretched film were prepared in the same manner as the chip C2.

The impact strength was measured using each of the test pieces obtained from the chips C2 to C6. The transparency of each stretched film was visually determined. Table 1 shows the results. As shown in Table 1, the impact strength and the transparency of the composition of the present invention are superior to those of the comparative examples, and particularly, those obtained from the chip C2 having the same copolymer component as the base polymer and the plasticizer have the best performance. Is shown.

[0039]

[Table 1]

<Example 2> In the same manner as in chip C2 of Example 1, except that polyester ether obtained by polymerizing diethylene glycol and adipic acid during lactide polymerization was used.
5% of molecular weight of about 9000, both ends hydroxyl group copolymerized,
Then, instead of the plasticizer P1, it is a polyester ether obtained by polymerizing diethylene glycol and adipic acid, and both ends are esterified with lauric acid and the molecular weight is about 60.
A sample obtained by adding 5% of the sample No. 00 and performing chip formation and solid-phase polymerization in the same manner is hereinafter referred to as chip C7. Chip C7 had a molecular weight of 171,000 and a residual monomer content of 0.1%. The impact strength of the test piece obtained from chip C7 was 6.3 kg · cm / cm,
The transparency of the stretched film was equivalent to the film obtained from the chip C2, and was extremely excellent.

[0041]

According to the present invention, a wide range of combinations of the compositions of the base polymer (A) and the aliphatic polyester (B) can be obtained, and various plasticized polylactic acid compositions can be obtained according to the purpose and application. Can be In particular, by combining a base polymer and a plasticizer having high affinity, a molded product having excellent flexibility, impact resistance, and transparency can be obtained, and contamination due to surface leaching of the plasticizer can be suppressed. Similarly, by using a plasticizer having a high molecular weight, it is possible to obtain a molded product excellent in the persistence and stability of the plasticizing effect and with less surface contamination. These excellent effects become more remarkable by introducing a component having a high similarity to the polymer (A) containing lactic acid as a main component as a base polymer and the aliphatic polyester (B). The most significant effect can be obtained by introducing the components.

In addition, aliphatic dicarboxylic acids and aliphatic diols are excellent in decomposability, and aliphatic polyesters obtained therefrom are also excellent in decomposability, and the base polymer (A) and aliphatic polyester (B) into which these are introduced are also decomposable. Excellent in nature. In general, when the number of carbon atoms in the alkyl group of the aliphatic dicarboxylic acid or aliphatic diol increases, the water repellency increases, and the decomposability of the base polymer (A) or the aliphatic polyester (B) containing them as a constituent is suppressed. However, these compositions have a long life and are suitable for applications requiring low degradation.

When a polyalkylene ether, particularly an oligomer thereof, for example, diethylene glycol or triethylene glycol, a low molecular weight polyethylene glycol, a polypropylene glycol, or the like is applied, a molded article excellent in a plastic effect, particularly excellent in flexibility can be obtained. In addition, biodegradability is sufficiently recognized, and it is effective for environmental protection and the like. Further, by adjusting the amount of the plasticizer added, the decomposability and physical properties of the molded product can be significantly changed, and the molded product can be suitably used for a wide range of applications. In particular, when a high molecular weight plasticizer is used, even if a large amount of the plasticizer is mixed, deterioration of characteristics (such as strength) is less than that of a low molecular weight plasticizer, and an excellent flexible product can be obtained.

The composition of the present invention can be used for fibers, knits, wovens, non-wovens, papers, felts, nets, ropes, films, sheets,
Depending on the use of plates, rods, tubes, porous molded products, various containers, various parts, various composite materials, various other molded products, etc., it can be improved to optimal characteristics and used suitably. it can.

Claims (7)

[Claims] 1. A polylactic acid composition comprising a mixed composition of a polymer (A) containing lactic acid as a main component and an aliphatic polyester (B) containing aliphatic dicarboxylic acid and a chain diol as main components. 2. The polymer (A) containing lactic acid as a main component is a polylactic acid homopolymer, a poly L / D-lactic acid copolymer, or a polylactic acid obtained by copolymerizing these with a polymer material capable of forming an ester bond. The polylactic acid composition according to claim 1, which is a copolymer. 3. The aliphatic dicarboxylic acid of the aliphatic polyester (B) containing an aliphatic dicarboxylic acid and a chain molecular diol as main components is succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, and dodecanedicarboxylic acid. The polylactic acid composition according to claim 1 or 2. 4. A chain diol of an aliphatic polyester (B) containing an aliphatic dicarboxylic acid and a chain molecular diol as main components is ethylene glycol, propylene glycol,
2 to 2 carbon atoms such as butanediol, hexanediol, octanediol, decanediol, dodecanediol
20, and polyethylene glycol, polypropylene glycol, polyalkylene ethers such as polybutylene ether and copolymers and oligomers thereof,
The polylactic acid composition according to any one of claims 1 to 3, wherein the composition is a polyalkylene carbonate or an oligomer thereof. 5. The polylactic acid composition according to claim 1, wherein the weight ratio of the aliphatic polyester (B) is less than 50%. 6. The aliphatic polyester (B) having a molecular weight of 5
The polylactic acid composition according to any one of claims 1 to 5, which has a molecular weight of 000 to 200,000. 7. A fiber, a knit, a woven fabric, a nonwoven fabric, a paper, a felt, a net, a rope, a film, a sheet, a plate, a rod, a tube, and a porous molded product comprising the polylactic acid composition according to claim 1. , Various containers, various parts, and other molded products.