JP3406692B2 - Aliphatic poly (β-hydroxycarboxylic acid) composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an aliphatic poly (β) which is a plastic material which is decomposed by the action of microorganisms in the environment.
-Hydroxycarboxylic acid) to a stable composition that suppresses spontaneous decomposition such as thermal decomposition during melt molding and hydrolysis during storage.

[0002]

2. Description of the Related Art Aliphatic poly (β having a hydrogen atom at the α-position
-Hydroxycarboxylic acid) is an aliphatic polyester having an ester structure of β-hydroxycarboxylic acid having a hydrogen atom at the α-position as a basic repeating unit of the main chain, some of which are environmentally affected by the action of microorganisms. It is known to decompose inside. In particular, poly (2-oxetanone) and poly (β-hydroxybutyric acid) are decomposed by many kinds of enzymes (Mukai, Doi, Sema, Tomita, Polymer Collection,
Vol.50, No.10, 715-722 (1993)) and that many degrading microorganisms are present in the degrading environment (H. Nishida and
Y. Tokiwa, Journal of Environmental Polymer Degrad
ation, Vol.1, No.3, 227-233 (1993)), etc. have been found. In addition, it has become clear that many bacteria in the environment biosynthesize various kinds of aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position in cells as an energy storage substance (H. Brandl. , RA Gross, R.
W. Lenz, and RC Fuller, Advances in Biochemical
Engineering / Biotechnology, Vol.41, 77-93 (199
0)). These results suggest that most of poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position may be a polymer that is decomposed by microorganisms.
As one of the measures against the serious waste problem in recent years, plastics that decompose in the environment are desired, and aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position is
It is exactly the plastic material that has been demanded.

Aliphatic poly (β- having a hydrogen atom in the α-position
Among (hydroxycarboxylic acid), poly (2-oxetanone) is a polyester synthesized by a chemical reaction from 2-oxetanone. 2-Oxetanone to poly (2
-Oxetanone) has the following reaction formula.

[0004]

[Chemical 1]

Poly (β that is biosynthesized by bacteria
-Hydroxybutyric acid) is a perfect D-form, and such an optically active polymer has also been obtained by chemical synthesis (Y. Hori, M. Suzuki, A. Yamaguchi, and T. Nishish.
ita, Macromolecules, Vol.26,5533-5534 (1993)).

Aliphatic poly (β- having a hydrogen atom in the α-position
(Hydroxycarboxylic acid) is a material having good biodegradability, but it is also a material that easily decomposes by heating. For example, for poly (2-oxetanone), Gresham et al.
Thermal decomposition at ℃ / 80mmHg yields 275g of crude acrylic acid (TLGresham, JE Jansen, and FWShave
r, Journal of American Chemical Society, 70 , 998 (194
8)). Jax et al. Investigated thermal decomposition of poly (2-oxetanone) in the range of 180 to 220 ° C. and reported that thermal decomposition occurs randomly in the molecular chain and proceeds from the end ( V.Jaacks, S.Iwabuti, and F.
Galil, Kinetics and Mechanism of Polyreactions, In
t. Symp. Macromol. Chem. Prepr., 5 , 375 (1969)). Regarding poly (β-hydroxycarboxylic acid) biosynthesized by bacteria, Kunioka et al. Reported that at a temperature of 170 ° C. or higher, random cleavage of the main chain ester group occurs (M. Kunioka and Y. .Doi, Macromolecules,
Vol.23, 1933-1936 (1990)). All of these thermal decomposition reactions are due to the presence of active hydrogen at the α-position of the carbonyl group and the bond of ester oxygen at the β-position. It is reported to proceed. Such a thermal decomposition reaction is performed by poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position.
The thermal decomposition of poly (γ-hydroxycarboxylic acid) proceeds by intramolecular transesterification (R. A.
bate, A. Ballistreri, G. Montaudo, and G. Impallom
eni, Macromolecules, Vol.27, 332-336 (1993)), poly (α-hydroxycarboxylic acid) also undergoes thermal decomposition by an intramolecular transesterification reaction to form cyclic compounds such as glycolide and lactide. Therefore, in general, an aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom in the α-position is
Its thermal decomposition temperature is lower than that of other similar aliphatic polyesters (D. Garozzo, M. Giuffrida, and G. Monta
udo, Macromolecules, Vol. 19, 1643-1649 (1986)).

Further, the aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position is a material which is also susceptible to hydrolysis. Matisson studied the hydrolyzability of poly (2-oxetanone) fibers and films,
It was reported that poly (2-oxetanone) was gradually decomposed in a buffer solution at 37 ° C, and molecular weight reduction and physical property reduction progressed (Torbjorn Mathisen, Monica Lewis, and Ann-Chr.
istine Albertsson, Jounal of Applied Polymer Scien
ce, 39 , 591-601 (1990), 42 , 2365-2370 (1991)).

In general, most plastic materials are
Although there is a difference in degree, thermal decomposition proceeds. Due to the thermal decomposition, the molecular weight of the plastic is lowered, and accordingly, the physical properties of the molded article are also lowered. In particular, since thermoplastic plastic materials are manufactured into products by melt-molding, the property of easily thermally decomposing is a big problem. Further, a plastic material having a structural unit such as an ester bond and an amide bond which is easily hydrolyzed in the main chain causes a decrease in the molecular weight, albeit little by little, due to the action of water, and the plastic material or product is stored for a long time or is used. During that time, the physical properties deteriorate.

For such a chain of decomposition → reduction of molecular weight → reduction of physical properties, a unique stabilization method corresponding to the cause of the decomposition has been studied and developed for each plastic material. However, aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position such as poly (2-oxetanone) and poly (β-hydroxybutyric acid) suppresses spontaneous decomposition such as thermal decomposition and hydrolysis. No effective stabilization method has been found yet.

[0010]

Pyrolysis during the melt molding of aliphatic poly (β-hydroxycarboxylic acid) s having a hydrogen atom at the α-position such as poly (2-oxetanone) and poly (β-hydroxybutyric acid). Another object was to develop an aliphatic poly (β-hydroxycarboxylic acid) composition that suppresses spontaneous decomposition during storage and use, facilitates melt molding into a film, and imparts long-term stability.

[0011]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that aliphatic poly (2-oxetanone) and other aliphatic poly () having a hydrogen atom at the α-position. It was found that the thermal decomposition and spontaneous decomposition of the polymer can be suppressed by adding a specific inorganic compound to (β-hydroxycarboxylic acid), and the present invention has been completed.

That is, the present invention relates to 100 parts by weight of poly (2-oxetanone), and an alkaline earth metal hydrochloride,
A poly (2-oxetanone) composition comprising 0.1 to 70 parts by weight of at least one alkaline earth metal salt selected from the group consisting of sulfates, carbonates and silicates.

Another invention is a fat containing 100 parts by weight of an aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom in the α-position, and 0.1 to 2 parts by weight of an alkaline earth metal hydrochloride. It is a group poly (β-hydroxycarboxylic acid) composition.

In the present invention, poly (2-oxetanone) is basically a polymer having a structure obtained by ring-opening polymerization of 2-oxetanone, but a cyclic ester other than 2-oxetanone as a monomer unit. Compound 0.1
Also included are polymers copolymerized in an amount of up to 20% by weight. Examples of the cyclic ester compound include β-butyrolactone,
Examples include pivalolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone. Hereinafter, the above-mentioned copolymer will be simply referred to as poly (2-oxetanone). The poly (2-oxetanone) is a polymer having a number average molecular weight and a weight average molecular weight of usually 10,000 or more.

In the present invention, the aliphatic poly (β-hydroxycarboxylic acid) having a hydrogen atom at the α-position [hereinafter referred to as β-polyester] means that at least one of the two hydrogen atoms at the α-position is substituted with an alkyl group. Not β-
It is an aliphatic polyester having a repeating unit of an ester structure of hydroxycarboxylic acid.

Illustratively, α- and β-positions such as poly (2-oxetanone) -unsubstituted; poly (β-hydroxybutyric acid), poly (β-hydroxyvaleric acid), poly (β-hydroxy) Hexanoate), β-position-1 substitution product such as (β-hydroxybutyric acid / β-hydroxyvaleric acid) copolymer; β-position-2 substitution product such as poly (β-hydroxyisovaleric acid); poly (α -Methyl-β-propiolactone) and α-position-1 substitution products such as poly (α-propyl-β-propiolactone). Of these, α- and β-position-unsubstituted products and β-position-1 substituted products are preferably selected from the viewpoint of excellent biodegradability.

The alkaline earth metal in the present invention includes calcium, magnesium, barium and the like, but calcium and magnesium are particularly publicly preferable from the viewpoint of the influence on the environment.

The alkaline earth metal hydrochlorides, sulfates, carbonates and silicates (hereinafter collectively referred to as alkaline earth metal salts) in the present invention specifically include
Hydrochlorides such as calcium chloride and magnesium chloride; Sulfates such as magnesium sulfate and barium sulfate; Carbonates such as magnesium carbonate and calcium carbonate; Calcium orthosilicate, calcium metasilicate, dicalcium silicate, tricalcium silicate, silicic acid Silicates such as calcium sodium, aluminum calcium silicate, magnesium orthosilicate, magnesium metasilicate, talc and other hydrous magnesium silicate, magnesium calcium silicate and the like. Among these alkaline earth metal salts, the hydrochloride is most preferably used in terms of its stabilizing effect, and the silicate is most preferably used in terms of its low hygroscopicity and easy handling. Each of these alkaline earth metal salts may be used alone or in combination.

The above-mentioned alkaline earth metal salt poly (2-
The amount added to oxetanone) should be selected according to the application, taking into consideration the processability of poly (2-oxetanone) after addition and changes in the mechanical properties of the molded product after addition / processing. Poly (2-oxetanone) 10
0.1 to 70 parts by weight with respect to 0 parts by weight is a range that can be preferably carried out. If the amount added is less than 0.1 part by weight, the effect of stabilizing the poly (2-oxetanone) by the additive is very small. On the other hand, if the addition amount exceeds 70 parts by weight, problems such as deterioration of processability of the poly (2-oxetanone) composition and deterioration of mechanical properties occur rather than the stabilizing effect. However,
With respect to the alkaline earth metal hydrochloride, since it has a relatively high hygroscopicity, a more limited range, specifically 0.1 to
It is more preferable to add 2 parts by weight.

The alkaline earth metal hydrochloride is not limited to poly (2-oxetanone), but also exhibits a stabilizing effect on the aforementioned β-polyester. The addition amount is 0.1 to 100 parts by weight of β-polyester.
2 parts by weight is the range in which it can be preferably carried out. When a molded product is obtained by one-time melt processing after producing β-polyester,
Even if more than 2 parts by weight and up to 70 parts by weight are contained as described above, its thermal stabilizing effect is sufficiently exerted, but when a molded product is obtained through a plurality of melt processing steps of two or more times, It is particularly preferable that the content is less than or equal to parts by weight. If the content exceeds 2 parts by weight, the processed body absorbs moisture relatively quickly after processing, and the heat stabilizing effect at the time of the second and subsequent melt processing is reduced due to the absorbed moisture. That is, when the alkaline earth metal hydrochloride is contained in an amount of 0.1 to 2 parts by weight, the large thermal stabilization effect is maintained even after a plurality of melt processing steps, and the effect of preventing the decrease of the molecular weight is remarkable.

Regarding the method of adding and blending the above-mentioned alkaline earth metal salt to β-polyester such as poly (2-oxetanone), ordinary blending techniques and mixing techniques are used. As the alkaline earth metal salt, it is desirable to use an anhydride in order to avoid hydrolysis of the β-polyester as much as possible, or to add and mix it to the β-polyester after drying treatment by a generally known means. As the addition and mixing means,
For example, additive mixing using a device such as a super mixer, ribbon blender, Banbury mixer, or extruder is possible.

As one of the methods for adding and blending the alkaline earth metal salt to poly (2-oxetanone), a polymerization initiator of 2-oxetanone, for example, quaternary ammonium carboxylates, is added onto the alkaline earth metal salt. Alkaline earth metal salt-containing poly (2-) obtained by carrying out seed polymerization of 2-oxetanone using these carrying initiators and carrying crown ether complexes of alkali metal carboxylate and the like.
Oxetanone) can be used as the composition of the present invention.

The seed polymerization of 2-oxetanone is, for example, a method of producing poly (2-oxetanone) by the following method. A poly (2-oxetanone) is deposited on the surface of the alkaline earth metal salt by contacting the above-mentioned alkaline earth metal salt-supporting initiator with 2-oxetanone in the form of gas, liquid or solution to produce a seed for polymerization. This is a method for producing a particulate poly (2-oxetanone) by performing precipitation polymerization of 2-oxetanone with the seed for polymerization as it is or by further supporting an initiator.

The composition of the present invention may be an auxiliary agent such as an antioxidant, a release agent, a weathering agent, an antistatic agent, a coloring agent, a reinforcing material, a surfactant, an inorganic filler, etc., depending on its purpose and application. Target components can also be added.

As a method for producing a molded article such as a film by melt-molding the composition of the present invention, a usual molding method is used. For example, extrusion molding method, injection molding method, blow molding method, calender molding method, etc. can be adopted,
Further, for film formation, a uniaxial or biaxial stretching method such as a roll stretching method, a tenter method, or an inflation method can be used.

For molding the composition of the present invention, appropriate molding conditions are selected depending on the type of β-polyester, the molding method, and the type of molded article, but usually 80 ° C to 250 ° C.
It is carried out in the temperature range of ° C.

The composition in the present invention is a concept that includes not only a mixture of the above essential components and optional components, but also pellets and a melt-processed molded product.

[0028]

The alkaline earth metal salt in the composition of the present invention suppresses a decrease in the molecular weight of poly (2-oxetanone) during melt molding, storage of molded articles, and use. Further, the alkaline earth metal hydrochloride is a β-containing poly (2-oxetanone).
It exerts a remarkable effect on the suppression of the decrease in the molecular weight of polyester. The reason for expressing such properties is not yet clear, but as shown in the following formula, the alkaline earth metal mainly reacts with the carboxylic acid group at the β-polyester terminal to form an ionic bond. it is conceivable that.

[0029]

[Chemical 2]

It is speculated that such an ionic bond reaction suppresses thermal decomposition and hydrolysis proceeding from the molecular end of the β-polyester. Further, since the alkaline earth metal is divalent, it can react with two β-polyester ends, and as a result, it is considered that it also has a function of increasing the molecular weight of β-polyester.

It is presumed that the anion component of the salt suppresses the alkaline earth metal from directly acting on the main chain portion of the β-polyester to cause an alkaline hydrolysis reaction.

[0032]

By using the composition of the present invention, it is possible to suppress the decrease in the molecular weight of β-polyester such as poly (2-oxetanone) during melt molding, storage and use, and the physical properties A better β-polyester molded article is obtained, which is stable for a longer period of time.

Using the composition of the present invention, various products, for example, films such as garbage bags and shopping bags, paper diapers, sanitary products such as sanitary products, mulch film, binding tape,
It is possible to melt-mold seedling pots, fishing nets, materials for agriculture and forestry such as laver nets, food trays, food related products such as egg packs. A product molded from the composition of the present invention is decomposed by microorganisms even when left in a natural environment, and converted into compost by a compost plant.

[0034]

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 6 and Comparative Examples 1 to 3 Alkaline earth metal salts shown in Table 1 in 100 parts by weight of poly (2-oxetanone) having a weight average molecular weight of 453 and 400,
And as a comparative example, an alkaline earth metal hydroxide and 5 parts by weight of a typical vinyl chloride resin heat stabilizer are added,
A CSI MAX mixing extruder (manufactured by Custom Scientific Instruments) was used to melt mix at 130 ° C. and extrude from a die to form a strand. However, only in Comparative Example 1, the alkaline earth metal salt and other additives used in the present invention were not added at all. The obtained strand was measured for molecular weight using size exclusion chromatography. The weight average molecular weight of each composition obtained is also shown in Table 1. From the results in Table 1, it is clear that the molecular weights of the compositions of the Examples were higher than those of the Comparative Examples, and that the compound added suppressed the decrease in the molecular weight of the poly (2-oxetanone) during the melt molding. .

[0036]

[Table 1]

Examples 7 to 11 and Comparative Examples 4 and 5 Talc was added as an additive to 100 parts by weight of poly (2-oxetanone) having a weight average molecular weight of 453 and 400, and Examples 1 to 6 were added. In the same manner as CSIMAX
Using a mixing extruder, a strand was formed while melt mixing at 130 ° C. The obtained strand was measured for molecular weight using size exclusion chromatography. The weight average molecular weight of each composition obtained is also shown in Table 2.

[0038]

[Table 2]

Examples 12 to 17, Comparative Example 6 Pellets of samples were prepared by cutting the strands molded in Examples 1 to 6 and Comparative Example 1, and a hydrolysis acceleration test of these samples under heating was conducted. went. That is, 50
The sample was placed in an oven in an atmosphere of ° C / 100% humidity and kept for a predetermined time, then the pellet sample was taken out, dissolved in chloroform, and the molecular weight was measured using size exclusion chromatography. The obtained weight average molecular weight is shown in Table 3. From the results in Table 3, compared with the additive-free poly (2-oxetanone) of Comparative Example 6, Examples 12 to 17 were obtained.
It is clear that the decrease in the molecular weight of the is slow and the hydrolysis under heating and humidification is suppressed.

[0040]

[Table 3]

Examples 18 to 23, Comparative Example 7 To 100 parts by weight of poly (2-oxetanone) having a weight average molecular weight of 334,000, anhydrous calcium chloride in an amount shown in Table 4 was added, and a CSI MAX mixing extruder was used. (Custom Scientific Instruments) was used to melt-mix at 130 ° C. and extruded from a die to form a strand. The extruded strand was cut with a chopper to form pellets. Melt extrusion->strand-> pelletization was repeated twice more. However, in Comparative Example 7 only, no calcium chloride was added. The resulting pellets were molecular weight measured using size exclusion chromatography.
The weight average molecular weight of each composition obtained is also shown in Table 4.
From the results in Table 4, it is clear that the molecular weights of the compositions of the Examples were higher than those of the Comparative Examples, and the compound added suppressed the decrease in the molecular weight of the poly (2-oxetanone) during melt molding. .

[0042]

[Table 4]

Example 24, Comparative Example 8 To 100 parts by weight of poly (β-hydroxybutyric acid) having a weight average molecular weight of 314,000, 1 part by weight of anhydrous calcium chloride was added, and a CSI MAX mixing extruder (custom scientific) was added. (Manufactured by Instruments) was melt-mixed at 175 ° C. and extruded from a die to form a strand. The obtained strand was measured for molecular weight using size exclusion chromatography. As a result, the weight average molecular weight was 283,00.
It was 0. On the other hand, in Comparative Example 8, it was carried out without adding calcium chloride. The weight average molecular weight of the obtained strand was similarly analyzed by size exclusion chromatography, and it was 234,000. From these results, it is clear that the added calcium chloride suppressed the decrease in the molecular weight of poly (β-hydroxybutyric acid) during melt molding.

Example 25, Comparative Example 9 β-hydroxybutyric acid having a weight average molecular weight of 381,000 /
To 100 parts by weight of β-hydroxyvaleric acid copolymer (β-hydroxyvaleric acid content 8%), 1 part by weight of anhydrous calcium chloride was added, and a CSI MAX mixing extruder (manufactured by Custom Scientific Instruments) was added. The strands were formed by melt mixing at 170 ° C. and extruding from a die. The obtained strand was measured for molecular weight using size exclusion chromatography. As a result, the weight average molecular weight was 33.
It was 5,000. On the other hand, in Comparative Example 9, it was carried out without adding calcium chloride. The weight average molecular weight of the obtained strand was analyzed by size exclusion chromatography in the same manner and found to be 297,000. From these results, it is clear that the added calcium chloride suppressed the decrease in the molecular weight of the (β-hydroxybutyric acid / β-hydroxyvaleric acid) copolymer during melt molding.

Examples 26 and 27 To 100 parts by weight of poly (2-oxetanone) having a weight average molecular weight of 334,000, the amount of alkaline earth metal hydrochloride shown in Table 5 was added, and a CSI MAX mixing extruder (custom Strands were formed by melt-mixing at 130 ° C. and extruding from a die using Scientific Instruments. The obtained strand was measured for molecular weight using size exclusion chromatography. The weight average molecular weights obtained are shown in Table 5.
It was shown to. Compared with the results of Comparative Examples 10 and 11, it is clear that the decrease in the molecular weight of poly (2-oxetanone) during melt molding was suppressed.

Comparative Examples 10 and 11 Example 2 except that potassium chloride was added in the amount shown in Table 5 in place of the alkaline earth metal hydrochloride of Examples 26 and 27.
Strand molding and molecular weight measurement were performed in the same manner as in Nos. 5 and 26. The obtained weight average molecular weight is also shown in Table 5.

[0047]

[Table 5]

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Claims (2)

(57) [Claims] 1. 100 parts by weight of poly (2-oxetanone) and at least one alkaline earth metal salt selected from the group consisting of alkaline earth metal hydrochlorides, sulfates, carbonates and silicates. A poly (2-oxetanone) composition comprising 1 to 70 parts by weight. 2. An aliphatic poly (β having a hydrogen atom at the α-position
-Hydroxycarboxylic acid) 100 parts by weight, and 0.1 to 2 parts by weight of an alkaline earth metal hydrochloride, an aliphatic poly (β-hydroxycarboxylic acid) composition.