JPH06345956A - Microbially biodegradable polyethylene carbonate resin composition - Google Patents

Abstract

PURPOSE:To obtain a new plastic material being nondeleterious to the environment and having excellent microbial biodegradability, incinerability and processability by mixing a polyethylene carbonate resin with a microbially biodegradable synthetic polymer and/or a natural polymer in a specified mixing ratio. CONSTITUTION:This resin composition is prepared by mixing 5-99wt.% polyethylene carbonate resin with 95-1wt.% microbially biodegradable polymer and/or natural polymer. Examples of the microbially biodegradable synthetic polymers which can be desirably used include aliphatic polyester resins such as poly(3- hydroxybutyrate), polycaprolactone and poly(3-hydroxy-valeric acid). Examples of the natural polymers used include starch, cellulose, pulp, pullulan, chitin, chitosan, gluten and keratin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyethylene carbonate resin composition which is decomposed by the action of microorganisms in the environment. More specifically, it has excellent processability and moldability as a plastic material, and is used for molded articles such as garbage bags for garbage, shopping bags, agricultural films, disposable diapers, hygiene products, etc. Relates to a polyethylene carbonate resin composition that can be subjected to a microbial decomposition treatment.

[0002]

2. Description of the Related Art As one of the solutions to the problem of plastic waste, which is one of the environmental problems, the demand for plastic materials that naturally decompose in the environment is increasing. As a method of imparting degradability in the environment to plastics, many products formed by mixing degradable materials such as natural polymers have been developed. However, nowadays, in order to avoid the risk of secondary pollution, a plastic material which is completely hydrolyzed, photodegradable or disintegratable, and which is completely decomposed by microorganisms has been required.

The number of biodegradable plastic materials is limited. Currently known synthetic biodegradable polymers are poly (3-hydroxybutyric acid), polycaprolactone, polypropiolactone, polyethylene adipate, polyethylene oxide, polyvinyl alcohol, polyisoprene and the like. It is not possible to adapt these polymers alone to many plastic applications. In particular, a problem common to many of the above microbial-degradable synthetic polymers is the lack of processability.

Therefore, in order to solve these problems, methods of polymer alloying such as polymer blending, grafting and blocking have been proposed. For example, Japanese Patent Laid-Open No. 3-1
57450 proposes a molded article composed of polycaprolactone and poly (3-hydroxybutyric acid). In addition, JP-A-4-114044 and JP-A-4-2688
51, a composition of a microbial degradable synthetic polymer and a natural polymer material is proposed. Furthermore, Polymer Preprints, Japan, Vol.41, No.6, 2204-22
06 (1992)) for several combinations of blends.

As described above, the types of currently known biodegradable synthetic polymers are limited to aliphatic polyesters, aliphatic polyethers, polyvinyl alcohols and polyisoprenes, and combinations of these or New plastic materials achieved in combination with natural polymeric materials are also limited. Therefore, a new type of microbial degradable polymer is desired in order to obtain a wider variety of microbially degradable plastic materials, particularly excellent in processability.

Since aliphatic polycarbonate resins such as polyethylene carbonate contain many oxygen atoms in their molecules, they have been used as binders for ceramics, etc. as a resin that completely burns when burned. In connection with the problem, the complete flammability of this polycarbonate resin has received much attention.

On the other hand, polyethylene carbonate and polypropylene carbonate can be decomposed in vivo (Yoji Imai, Koichi Kojima, Eiichi Masuhara, Artificial Organs, 8
Vol. 246 (1979) and Yoji Imai, Koichi Kojima, Akihiko Watanabe, Eiichi Masuhara, Artificial Organs, Vol. 4, 344 (1975)) and Nakano (Masahiro Nakano, Synthetic Organic Chemistry, Vol. 42, No. 7, 665). (198
4)). That is, it is known as a bioabsorbable material. However, nothing is known about the microbial degradability that decomposes by the action of microorganisms in the environment.

The bioabsorbability and the microbial degradability do not necessarily correlate with each other. For example, it is known that the biodegradability of polylactic acid and polyglycolic acid, which are already known as bioabsorbable materials, has been obtained. Absent. Further, as described later, the biodegradability of the polypropylene carbonate has not been confirmed.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made with the object of providing a new environmentally friendly plastic material having excellent microbial decomposability and excellent combustibility and processability. It is a thing.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that among polycarbonate resins, polyethylene carbonate resin is
I found that it was decomposed by microorganisms. further,
By blending this polyethylene carbonate resin with a conventionally known biodegradable synthetic polymer and a natural polymer material, it has been found that a new biodegradable plastic material having more excellent processability can be obtained.
The present invention has been completed.

That is, the present invention comprises (A) a polyethylene carbonate resin of 5 to 99% by weight, and (B) a microbial degradable synthetic polymer and / or a natural polymer of 95 to 1% by weight.
The present invention relates to a microbial degradable polyethylene carbonate resin composition, characterized by comprising:

The polyethylene carbonate resin in the present invention includes not only polyethylene carbonate which is a homopolymer but also other alkylene carbonate units such as propylene carbonate and butylene carbonate within 20 monomer unit% and preferably within 10 monomer unit%. It also includes an embodiment in which it is randomly present in polyethylene carbonate. A homopolymer is most preferable from the viewpoint of microbial degradability, but the degradability is not particularly hindered as long as it is a random copolymer within the above range.

The microbial-degradable synthetic polymer in the present invention is specifically poly (3-hydroxybutyric acid), poly (3-hydroxyvaleric acid), (3-hydroxybutyric acid / 3
-Hydroxyvaleric acid) copolymer, (3-hydroxybutyric acid / 4-hydroxybutyric acid) copolymer, polycaprolactone, polypropiolactone, polyethylene adipate,
Aliphatic polyesters such as polyethylene succinate and polybutylene succinate, and random of these,
Aliphatic polyester resins composed of block and graft copolymers; polyethylene oxide, polyvinyl alcohol, polyisoprene and the like.

Among these microbial degradable synthetic polymers, the aliphatic polyester resin is most preferably used in terms of easiness of microbial degradability, blendability, and physical properties of the finally obtained polyethylene carbonate resin composition. To be

Among the above-mentioned microbial-degradable synthetic polymers, poly (3-hydroxybutyric acid), poly (3-hydroxyvaleric acid), (3-hydroxybutyric acid / 3-hydroxyvaleric acid) copolymer, Regarding the (3-hydroxybutyric acid / 4-hydroxybutyric acid) copolymer, not only the chemical compound,
It also includes those synthesized by fermentation synthesis using microorganisms in a bioreactor.

The natural polymer in the present invention is specifically starch, cellulose, pulp, paper, pullulan, chitin, chitosan, silk, and various proteins such as gluten and keratin.

The composition ratio of each resin component of the polyethylene carbonate resin composition of the present invention is such that (A) the polyethylene carbonate resin is 5 to 99% by weight, and (B) the microbial degradable synthetic polymer and / or the natural polymer. 95 to 1% by weight. When the polyethylene carbonate resin component is less than the total amount of other components, the polyethylene carbonate resin acts as a processability improver. However, if the polyethylene carbonate resin is 5% by weight or less, the effect is small. When the polyethylene carbonate resin component is large relative to the total of other components, the polyethylene carbonate resin is
Acts as a flammability improver. However, for example, since the glass transition temperature of polyethylene carbonate is as low as 10 ° C., it is preferable that the composition ratio of the polyethylene carbonate resin is 5 to 50% by weight in applications where strength and heat resistance are required.

The total amount of the biodegradable synthetic polymer and / or natural polymer is 95 to 1% by weight, but 1 to 60% by weight in the case of a natural polymer having no thermoplasticity and poor processability, It is more preferably 1 to 50% by weight from the viewpoint of moldability. However, in general, biodegradability is as follows: natural polymer> microbial-degradable synthetic polymer>
Since it tends to be a polyethylene carbonate resin, the composition ratio may be appropriately determined depending on the use and purpose of the molded product.

In the resin composition of the present invention, in addition to the above essential resin components, a compatibilizer, a heat stabilizer, a lubricant, an antioxidant,
Antistatic agents, flame retardants, inorganic fillers, surfactants, release agents, UV inhibitors, pigments, and yeast extracts, vitamins, glucose, phosphates to promote microbial degradation,
You may add a nitrogen compound etc. as needed.

There is no particular limitation on the production of the resin composition of the present invention, and a conventionally known method can be used. For example, the (A) resin component, the (B) resin component, and various additive components used as desired may be homogeneously mixed using a tumbler mixer, a high-speed rotary mixer, a V blender, a ribbon blender, or the like. , A single-screw or twin-screw extruder, a Banbury mixer, a high-speed rotating mixer and the like may be kneaded into pellets after kneading the above components,
Alternatively, the mixing and kneading treatments may be combined. Further, a molded article can be produced by using the above-mentioned mixing and kneading composition, by adopting conventional molding means such as ordinary injection molding, extrusion molding, blow molding, press molding, sheet molding and various foam moldings. . In addition, there is also a method in which all resin components are dissolved using an appropriate solvent, solution blending is performed, and then casting molding is performed.

Therefore, in the present invention, the polyethylene carbonate resin composition means both components such as a mere mixture of the above-mentioned essential (A) and (B) resin components, a kneaded product such as pellets and a molded product thereof, or a casting product. It means a composition in all states including.

[0022]

The microbial degradability of the polyethylene carbonate resin found in the present invention is a new fact that has never been reported before. Although various methods have been used to confirm microbial degradability, the confirmation method used in the present invention is a method called a clear zone method. There have been many reports on this method. For example, Chu Fury (AAChowdhury, Archiv fur Mikrobiologie, Vo
l.47, 167-200 (1963)), and Delafield et al. (F.
P.Delafield, M.Doudoroff, NJPalleroni, CJLust
y, and R. Contopoulos, J. Bacteriol., Vol.90, No.5,
1455-1466 (1965)), Gilmore et al. (DFGilmore, RCF
uller, and R. Lenz, Degradable Materials, CRC Pres
s, pp.481-514 (1990)), and Nishida et al. (H. Nishida and
Y. Tokiwa, Proceedings of the American Chemical Soc
iety, Division of Polymeric Materials: Science and
Engineering, Fall Meeting, Washington, DC, Vol.6
7, 137-138 (1992)) has confirmed the biodegradability of poly (3-hydroxybutyric acid) using the clear zone method.

The microbial degradability of the polyethylene carbonate resin, which was first discovered in the present invention, was specifically confirmed by the following method, for example.

That is, on the medium in which polyethylene carbonate was emulsified and finely dispersed, there were 8 microorganism sources, namely, Tokyo Bay landfill leachate, Tokorozawa sewage sludge compost, surplus sludge supernatant,
Dilute and inoculate pine cedar forest soil, upland soil, paddy soil, sand dust on paved roads, and pond mud, resulting in the degradation of polyethylene carbonate around some of the colonies formed by microbial growth. I confirmed that a transparent area (this is called a clear zone) that appeared due to the appearance was appeared. On the other hand, regarding polypropylene carbonate, the formation of colonies was sufficiently observed, but the appearance of clear zones was not observed.

Therefore, although there are microorganisms which decompose polyethylene carbonate resin in the above-mentioned microorganism sources,
It is concluded that there may be no microorganisms that degrade the polypropylene carbonate resin.

Since the polyethylene carbonate resin composition of the present invention containing the above-mentioned polyethylene carbonate resin is a blend with a microbial degradable polymer and / or a natural polymer, it is disintegrated by a degrading microorganism peculiar to each. For example, polyethylene carbonate /
A resin composition composed of poly (3-hydroxybutyric acid) / starch is a polyethylene carbonate-degrading microorganism, poly (3-
It is disintegrated by both (hydroxybutyric acid) degrading microorganisms and starch degrading microorganisms, and the increase in surface area caused by the disintegration further promotes microbial degradation. That is, the introduction of a new type of microbial degradable polymer, a polyethylene carbonate resin, increases the types of microorganisms that lead the resin composition to disintegrate and diversifies the chance of disintegration. Furthermore, as a result of the disintegration, the surface area was increased and the complete decomposition was promoted.

As described above, the polyethylene carbonate resin composition of the present invention is a resin composition obtained by combining polymers having biodegradability with each other, and is a plastic material having further improved biodegradability.

The action of the polyethylene carbonate resin on the workability is manifested as the effect of imparting the workability and the effect of reducing the softening point. In general, natural polymers cannot be processed and molded because they are not thermoplastic and are thermally decomposable. Further, poly (3-hydroxybutyric acid) has a melting point and a thermal decomposition temperature close to each other, and it is desired to reduce the melting point. Since the polyethylene carbonate resin is thermoplastic, it functions as a processability-imparting agent when blended with a natural polymer material. Further, since polyethylene carbonate has a low glass transition temperature of 10 ° C., it functions as a softening point reducing agent by blending with poly (3-hydroxybutyric acid) or the like.

[0029]

EFFECTS OF THE INVENTION The polyethylene carbonate resin composition of the present invention has excellent processability and moldability as a plastic and various microbial degradability, and further has excellent flammability when burned as waste. Show. Therefore, the polyethylene carbonate resin composition of the present invention is preferably used for plastic films, sheets, foams, fibers, etc., which are required to have microbial degradability, and the wastes of the molded products are subjected to microbial degradation treatment such as compost. It is an environmentally friendly plastic material that can be reused as compost by.

[0030]

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

Reference Example 1 (1) Polyethylene carbonate resin finely dispersed inorganic salts /
Preparation of yeast extract plate medium Yeast extract 0.25g per 1L of inorganic salt medium consisting of Table 1
(250 ppm) and phosphate ester type surfactant 1
The pH was adjusted to 7.1 by adding 00 ppm.

[0032]

[Table 1]

1.00 g of polyethylene carbonate having a number average molecular weight of 50,000 was dissolved in 40 ml of methylene chloride.

The above medium and a methylene chloride solution of polyethylene carbonate were mixed and emulsified using a homogenizer. Agar (15 g) was added to the emulsion, and the mixture was heated and stirred on a boiling water bath to vaporize and remove methylene chloride and dissolve the agar. With heating, methylene chloride was first vaporized and then agar was dissolved. After the dissolution of agar was completed, the medium in which polyethylene carbonate was finely dispersed was placed in an autoclave for 120
Sterilization was performed at 20 ° C. for 20 minutes. After sterilization, about 20 ml each was distributed and spread in a petri dish. Agar solidified with cooling, and polyethylene carbonate fine particles were uniformly dispersed over the whole plate to obtain a polyethylene carbonate resin finely dispersed inorganic salts / yeast extract plate medium (PEC-BM plate).

(2) Preparation of polypropylene carbonate resin finely dispersed inorganic salts / yeast extract plate medium Polypropylene carbonate having a number average molecular weight of 50,000 1.0
A polypropylene carbonate resin finely dispersed inorganic salts / yeast extract plate medium (PPC-BM plate) was prepared in exactly the same manner as (1) except that 0 g was used.

(3) Colony formation of microorganisms on PEC and PPC-BM plates and evaluation of microbial degradability by the clear zone method In order to evaluate microbial degradability of polyethylene carbonate and polypropylene carbonate in each environment,
Microbial source samples such as soil shown in Table 2 were collected.

[0037]

[Table 2]

The inorganic salt medium shown in Table 1 was adjusted to pH 7.0 to prepare a diluting solution. An appropriate amount of the sample such as soil collected was added to the dilution liquid that had been sterilized by an autoclave to give a diluted stock solution (also shown in Table 2). Diluted stock solution is 10 times more, 1
00 times, 1,000 times, 10,000 times, and 10 times
It was diluted 10,000 times to obtain a diluted solution.

0.1 ml was taken from the diluted stock solution and the diluted solution, and this was used with a cone large rod (1) and (2).
It was spread and spread on the PEC-BM plate and PPC-BM plate prepared in. Then each plate is 30
Static culture was performed in an incubator at ℃.

Colonies formed on each plate with the culture time. After 15 days of culturing, the appearance of colonies and clear zones around some colonies was confirmed on the PEC-BM plate. On the other hand, on the PPC-BM plate, the appearance of a clear zone was not recognized although colonies were formed.

In FIG. 1, 15 on the PEC-BM plate.
The results of counting the number of colonies formed and the number of appearance of clear zones after culturing for one day are shown. The numerical line represented by percentage in the figure is a line showing the percentage of the number of appearance of the clear zone with respect to the total number of colonies formed. Further, FIG. 2 shows the same result after culturing on the PPC-BM plate for 10 days. As a result, polyethylene carbonate-degrading microorganisms were present in the collected samples from the three environments, and clear zones were formed around those colonies. However, in the case of polypropylene carbonate, the clear zone was not recognized.

Examples 1 to 5 Polyethylene carbonate, poly (3-hydroxybutyric acid), and / or polycaprolactone were weighed out in the amounts shown in Table 3 and dissolved in 100 ml of chloroform. This chloroform solution was transferred into a petri dish, and chloroform was spontaneously vaporized to prepare a cast film. The biodegradability of the cast film was measured by the following method.

[Microbial Degradability] Yeast extract was added to the inorganic salt medium shown in Table 1 to a concentration of 250 ppm, and the pH was adjusted to 7.1. 100 ml of the liquid medium thus prepared was placed in a Sakaguchi flask having a volume of 500 ml. The Sakaguchi flask was stoppered with a silicon stopper and then sterilized in an autoclave at 120 ° C. for 20 minutes. After sterilization, cast film (20 mm x 20 mm, approx.
0 mg) was added. Furthermore, after adding 100 mg of field soil in Tsukuba city in which the presence of polyethylene carbonate-degrading microorganisms was confirmed in Reference Example 1 and plugging again with a silico stopper,
Shaking culture was performed at 30 degrees and 130 strokes / min. 6
After culturing for 0 days, the culture solution was added with TOYO No. 2 It filtered using the qualitative filter paper and the remaining film was collect | recovered. The recovered residual film was vacuum dried and then weighed to determine the decomposition rate.
The results of the decomposition rate are also shown in Table 3. From the result of the decomposition rate, it can be seen that the resin composition of the present invention decomposes almost completely.

[0044]

[Table 3]

Example 6 30 g of polyethylene carbonate having an average molecular weight of 50,000,
20 g of starch and 50 g of polyhydroxybutyric acid with a molecular weight of 220,000 were homogenized in an internal mixer operating at 180 ° C. This mixed resin composition was formed into a sheet having a thickness of 100 μ by hot pressing at 180 ° C. A sheet having a smooth surface was obtained. When this sheet was put into a garbage composting device and subjected to a microbial decomposition test, the shape of the sheet disappeared in one week.

Comparative Example 1 Starch 20 g and polyhydroxybutyric acid 50 having a molecular weight of 220,000
From g, a sheet was formed in the same manner as in Example 6, but only a brittle flaky product was obtained, and no sheet was formed. Examples 7 to 11 Polyethylene carbonate (number average molecular weight 50,000) and polypropiolactone (number average molecular weight 106,020) are shown in Table 4.
It was weighed in the amount shown in, and dissolved in 20 ml of chloroform. This chloroform solution was transferred into a petri dish, and chloroform was spontaneously vaporized to prepare a cast film.

[0047]

[Table 4]

[Microbial Degradability] The biodegradability of the cast film was examined by introducing it into a garbage composting apparatus and conducting a microbial decomposition test. The debris after disassembly became unrecoverable.

[Measurement of Physical Properties] The cast film was melted at 130 ° C. for 30 minutes under reduced pressure with a vacuum pump. afterwards,
It was left to cool to obtain a molten film. Width of molten film is about 1 cm
Cut into strips at 23 ℃, pulling speed 10mm /
A tensile test was performed at min. The results of breaking strength and breaking elongation are shown in Table 5.

[0050]

[Table 5]

[Brief description of drawings]

FIG. 1 shows the number of microorganisms degrading polyethylene carbonate formed on the PEC-BM plate obtained in Reference Example 1 (that is, the number of clear zones) and the number of all microorganisms (that is, the number of all colonies). Show.

FIG. 2 shows the number of microorganisms that decompose polypropylene carbonate formed on the PPC-BM plate obtained in Reference Example 1 (that is, the number of clear zones) and the number of all microorganisms (that is, the number of all colonies). Show.

Claims (2)

[Claims] 1. A microbial decomposition comprising (A) a polyethylene carbonate resin of 5 to 99% by weight and (B) a microbial degradable synthetic polymer and / or a natural polymer of 95 to 1% by weight. -Resistant polyethylene carbonate resin composition. 2. The microbial degradable polyethylene carbonate resin composition according to claim 1, wherein the microbial degradable synthetic polymer is a microbial degradable aliphatic polyester resin.