JPH07100739B2 - Biodegradable resin molded article and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to poly-3-hydroxybutyra (Poly (3-hydroxybutyra), which has an excellent biodegradation function.
te): hereinafter also referred to as PHB), which has the property of being easily disintegrated or decomposed by organisms such as microorganisms, insects and plants, enzymes secreted by these organisms, etc. (Referred to as degradability) and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a processed molded article that disintegrates due to the action of microorganisms, for example, a film sheet in which a polymer such as cornstarch is blended in a resin to promote the disintegration of the molded article by microorganisms, etc. However, there is a concern about environmental pollution in these molded products because the parts that are not decomposed in the ecosystem remain.

On the other hand, PHB is known as a polymer material having a biodegradable function that is decomposed at the molecular level by an ecosystem, and Journal of the Japanese Society of Agricultural Chemistry, 50.
Vol. 9, No. 431-436 (1976).

[0004]

However, at present, a PHB that fully utilizes the biodegradation function of PHB or a molded article containing this as a main component and having excellent biodegradability has been proposed. Absent. That is, as to a method for molding a molded article of a copolymer having a hydroxybutyric acid unit as a main component, JP-A-57-150393 discloses that after melt extrusion,
A melt-molding method is shown in which the polymer is cooled above its glass transition temperature. However, the biodegradability of the PHB molded product molded by such a molding method is still low, and there is room for improvement.

[0005] As described above, PHB, which essentially has an excellent biodegradability, has not sufficiently exhibited its properties, and it is desired to develop a molded article and a molding method having excellent biodegradability. ing.

[0006]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, the crystallinity of PHB in PHB resin molded products is greatly related to its biodegradability. It was found that the biodegradability was remarkably improved by lowering the crystallinity of the PHB below a certain crystallinity, and completed the present invention. That is, the present invention provides a biodegradable resin molded article made of poly-3-hydroxybutyric acid (PHB) having a crystallinity of less than 50%.

In the present invention, PHB manufactured by a known method is used without particular limitation. In general, PHB produced by the PHB-producing bacteria
Is separated by a known method such as extraction with chloroform, and has an average molecular weight of 10,000 or more, preferably 50,000 or more.

The resin molded product of the present invention may contain other resin to the extent that it does not adversely affect the biodegradability by PHB. As the resin, any known polymer can be generally used as long as it is a polymer that can be melt-molded with PHB. Among them, a polymer that does not mix with PHB at the molecular level is preferable. That is, such a polymer does not affect the biodegradation function of PHB, and easily exhibits an auxiliary effect on the biodegradation function in the sense of increasing the surface area. Specific examples of polymers suitably used with PHB include thermoplastic resins such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polycaprolactone. Further, the blending ratio of the resin is preferably 50% by weight or less, and more preferably 20% by weight or less, based on PHB.

The most characteristic feature of the resin molded product of the present invention is that the crystallinity is less than 50%, preferably 49.8% or less.
It consists of B. That is, by configuring the resin molded product with PHB having such crystallinity, the biodegradation function of the PHB can be dramatically improved, and the collapse or decomposition of the resin molded product in the ecosystem can be achieved in a short period of time. can do.

Heretofore, no resin molded article made of PHB having a PHB crystallinity of less than 50% has been reported at all. For example, Macromolecules (Macr
omolecules), Vol. 22, 694-697 (1989), PHB having a crystallinity of about 55% obtained by the casting method is shown. However, the above document does not disclose PHB having a crystallinity of less than 50% at all, and the biodegradation function of PHB is remarkably improved by making the crystallinity of less than 50%. There is no description of the technical idea of.

In the present invention, the crystallinity of PHB is X.
It is the value measured by the line diffraction method. That is, CuKα rays are used as X-rays and 2θ is 6 by the reflection concentration method.
The diffraction intensity from ° to 40 ° is measured. From this diffraction intensity curve, the crystallinity can be obtained by the following calculation.

Crystallinity (%) = P × 100 / (Q−R) (where P is the area of the peak portion based on the crystal, Q is the total area under the curve, and R is the area of the diffuse scattering portion). ) The area of the diffuse scattering part mentioned above is 2 where 6 is 40 from 2 °.
It represents the area under the straight line connecting the points. In the crystallinity measurement by this X-ray diffraction method, the orientation of crystals has a great influence on the crystallinity, and therefore the molded product used as the measurement sample is
Non-oriented or finely ground powder is generally used.

For a resin composition obtained by blending PHB with another polymer, an analysis pattern of the resin composition is measured in advance, and then an analytical strength curve of the entire resin composition is obtained with an analytical strength corresponding to the blending ratio. By subtracting more, PHB
Based on the analysis curve, the crystallinity of PHB may be obtained from the analysis curve using the above calculation formula.

In the present invention, the biodegradation function means a function of being decomposed at the molecular level by an ecosystem, and specifically, biodegradation function depolymerase and other degrading enzymes, depolymerase-producing bacteria, specifically, Means that it is degraded by PHB-degrading bacteria, depolymerase-containing substances, and the like. Also,
The biodegradability of a resin molded article refers to the property of being easily disintegrated or decomposed by organisms such as microorganisms, insects and plants, and enzymes secreted by these organisms due to the biodegradation function. Generally, in an environment in which such an enzyme and / or bacterium exists, for example, in a natural environment such as soil, a partial natural environment such as a landfill, municipal waste, surplus sludge from a sewage treatment plant, pig excrement, etc. The resin molding may be disintegrated or further decomposed under a rapid composting treatment environment under aerobic conditions known as a treatment method.

The method for producing the molded article of the present invention is not particularly limited. A typical example of the production method is as follows. After melting poly-3-hydroxybutyric acid, it is rapidly cooled and solidified to obtain a molded product having a PHB crystallinity of less than 50%, which is a biodegradable resin molded product. The manufacturing method of is mentioned. That is, the present inventors have found that PHB or PH containing the thermoplastic resin is used.
It was found that a resin molded article having excellent biodegradability can be easily and reproducibly obtained by rapidly cooling and solidifying B after melting and molding. The quenching temperature is
The lower the temperature, the better, but generally, the molten resin may be cooled to a temperature not higher than the glass transition temperature of PHB, specifically not higher than 15 ° C, preferably not higher than 5 ° C, more preferably not higher than 0 ° C.

The molding method after the melting is not particularly limited. For example, various molding methods such as extrusion molding, injection molding, blow molding, casting, vacuum molding, melt spinning, calender molding, and foam molding are used.

In the above-mentioned molding method, for the rapid cooling, an appropriate cooling means is appropriately adopted in each molding method. For example, in the case of forming a film or sheet in extrusion molding, a pair of chilled rolls in which a cooling medium is flowed to cool the roll surface to the cooling temperature is attached near the outlet of the T die of the extrusion molding machine. , T
A method such as rapid cooling of the melt extruded from the die can be adopted. Further, in injection molding, quenching can be performed by flowing a coolant into the mold and setting the mold temperature to the cooling temperature.

Further, in the above-mentioned rapid cooling, the rapid cooling time may be appropriately determined within a range in which the crystallinity of PHB is less than 50% with respect to the set cooling temperature in consideration of the thickness of the resin molded product. Good, but it is desirable to be as short as possible. Generally, 30 seconds or less, preferably 10 seconds or less is suitable.

The resin molded product of the present invention can have any shape such as a film, a sheet, a thread, a tape, a plate and a structure, but the biodegradability of the resin molded product is most exerted. Is a thin molded product having a wall thickness of 2 mm or less, such as a film, a sheet, a thread, or a tape, whose crystallinity can be easily controlled by the manufacturing method described later. Specific embodiments of the resin molded body, fibers, films, packing, cases, bottles, paper diapers, daily necessities such as disposable packaging materials such as various foam containers, greenhouse film, film for surface coating, seedling pot, Agricultural and forestry materials such as strings, fertilizer bags, sustained-release pesticide materials, fishing nets and fishing line materials, leisure bags, fishing gear packaging materials and other leisure products and drug delivery system materials,
Examples include sutures, bone-bonding materials, and medical materials such as hygiene products.

[0020]

[Effect] The biodegradable resin molded product of the present invention is a resin molded product having a high crystallinity produced by ordinary melt molding or a resin obtained by casting, as shown in Examples and Comparative Examples described later. The biodegradation function of PHB is higher than that of the molded product, and thus excellent biodegradability can be exhibited.

Therefore, when the resin molded product of the present invention is buried in soil and subjected to decomposition treatment by microorganisms, the resin molded product can be efficiently detoxified in a shorter period of time.

Further, according to the method for producing a biodegradable resin molded product of the present invention, the resin molded product having good biodegradability can be easily obtained with good reproducibility, and the quenching condition is appropriately changed. Therefore, it is also useful as a means for controlling the biodegradability of the obtained resin molding within a certain range.

[0023]

EXAMPLES Examples will be given below to more specifically describe the present invention, but the present invention is not limited to these examples.

Examples 1 and 2 and Comparative Examples 1 and 2 (1) Preparation of Resin Sheets Having Different Crystallinity A cotton-like resin (microorganism: Alcaligenes eutrophus was fermented and synthesized and dissolved in a chloroform / hexane system). The product purified by the reprecipitation treatment and having a molecular weight of about 200,000) was dissolved in chloroform at a concentration of about 4% by weight / volume. This was transferred to a petri dish and allowed to stand at room temperature to produce a cast film (thickness: about 0.4 to 0.5 mm). Next, four test pieces of 16 × 12 mm were cut out from this sheet. Each of the cut-out test pieces was held in a template in an oven at 190 ° C for about 1 minute.
Hold for 3 minutes to melt. The molten resin was rapidly cooled within 10 seconds by the cooling method shown in Table 1, and A to
A molded product of D was obtained.

(2) Measurement of Crystallinity The crystallinity of each sample obtained in (1) above was measured under the following measurement conditions.

Measurement method: Reflection focusing method X-ray: CuKα (wavelength 1.54056 angstrom) Tube voltage: 50 KV Conducting current: 32 mA Goniometer: Wide-angle goniometer 2θ: 6 ° -40 ° Scanning speed: 2.000 ° / min Divergence slit 1 ° Scattering slit: 1 ° Measurement temperature: room temperature The crystallinity of each sample was calculated from the obtained diffraction curve intensity from the above-mentioned calculation formula. The results are shown in Table 1. The diffraction curves of Sample A and Sample C are shown in FIGS. 1 and 2, respectively.

(3) Measurement of biodegradability Using PHB-degrading bacterium SC-17 strain isolated from soil, degradation was carried out in a medium having the following composition.

Degradability evaluation medium (medium I) Inorganic salt solution 100 ml Yeast Extract 100 ppm pH 7.1 500 ml of the above medium I in a 500 cc Erlenmeyer flask
Was put in, and a cotton plug was applied, followed by sterilization by autoclave at 121 ° C. for 20 minutes. Next, the sample sheet prepared in (1) was sterilized with ethanol, weighed, and then put.
Subsequently, 1 ml of a culture solution of PH-17-degrading strain SC-17 strain, which had been cultured in advance, was inoculated. After inoculation, microbial decomposition was carried out by stirring culture at 30 ° C. and 180 rpm for 72 hours using a rotary shaker. Then, the remaining sample sheet was taken out from the culture solution, washed with pure water, and vacuum dried overnight at room temperature. The sample weight before decomposition (Xg) and the sample weight dried after decomposition (Yg) were weighed, and the rate of decrease in weight calculated by the following formula was defined as the biodegradation rate.

Biodegradation rate (%) = (X−Y) × 100 / X The results of the biodegradation rate are also shown in Table 1.

[0030]

[Table 1]

Example 3 and Comparative Example 3 (1) Preparation of resin sheets having different crystallinity PHB in pellet form (manufactured by Imperial Chemical Industries PLC of England, trade name: BX
Extrusion molding was performed using GV9 (EE) as a raw material. The cylinder temperature was set to 185 ° C, and the sheet extruded from the T-die was rapidly cooled by passing it through a pair of chilled rolls mounted near the exit of the T-die and cooled to a surface temperature of -10 ° C. Immediately after the chilled roll, about 0.
A 5 mm thick sheet was introduced to obtain a resin molded product (Sample E) made of a PHB sheet.

On the other hand, for comparison, a resin molded product (Sample F) was obtained by the same operation except that the temperature of the chilled roll was set to 60 ° C. and the temperature of the water tank was set to about 30 ° C.

(2) Measurement of Crystallinity After cooling a part of each molded product obtained in (1) above with liquid nitrogen, it was made into a fine powder using a pulverizer to obtain a crystallinity measurement sample. . The crystallinity was measured and calculated under the same measurement conditions as in Example 1 to determine the crystallinity. The results are shown in Table 2.

(3) Measurement of biodegradability A 16 × 12 mm sample for biodegradability evaluation was cut out from the sheet prepared in (1) above, and the biodegradability was measured in the same manner as in Example 1. The results are also shown in Table 2.

[0035]

[Table 2]

Example 4 and Comparative Example 4 (1) Preparation of resin molded products having different crystallinity PHB pellets (manufactured by Imperial Chemical Industries PLC, England, trade name: BX
Injection molding was performed using GV9 (EE)) as a raw material to mold a pot-shaped container (thickness: about 0.5 mm). Cylinder temperature 1
90 ℃, mold temperature is -5 ℃ (Sample G) and 35 ℃
Molding was performed by setting two cooling temperatures of (Sample H). The holding time was 90 seconds.

(2) Measurement of Crystallinity A portion of each molded product obtained in (1) above was cooled with liquid nitrogen, and then finely powdered using a pulverizer to obtain a crystallinity measurement sample. . The crystallinity was measured and calculated under the same measurement conditions as in Example 1, and the crystallinity was calculated. The results are shown in Table 3.

(3) Measurement of biodegradability Further, from the molded product obtained in (1) above, 16 × 12 mm
The sample for biodegradability evaluation was cut out, and microbial degradation was performed in the same manner as in Example 1 to calculate the degradation rate. The results are also shown in Table 3.

[0039]

[Table 3]

Example 5 (1) Preparation of resin sheet having different crystallinity PHB in pellet form (manufactured by Imperial Chemical Industries PLC, England, trade name: BX
GV9 (EE) 90% by weight and polystyrene 10% by weight as a raw material, extrusion molding was carried out in the same manner as in Example 3 by using a resin as a raw material, and a resin molded product made of a PHB sheet having a thickness of about 0.5 mm. (Sample I) was obtained.

On the other hand, for comparison, a resin molded product (Sample J) was obtained by the same operation except that the temperature of the chilled roll was set to 60 ° C. and the temperature of the water tank was set to about 30 ° C.

(2) Measurement of Crystallinity A part of the molded product obtained in (1) above was cooled with liquid nitrogen and then made into fine powder using a pulverizer to obtain a crystallinity measurement sample. The crystallinity was measured in the same manner as in Example 1. The crystallinity was calculated by reducing the X-ray analysis pattern of the polystyrene-only sheet obtained by the same method as the above-mentioned sheet, according to the compounding ratio.

(3) Measurement of biodegradability Further, from the molded product obtained in (1) above, 16 × 12 mm
The sample for biodegradability evaluation was cut out, and microbial degradation was performed in the same manner as in Example 1 to calculate the degradation rate. The results are shown in Table 4.

[0044]

[Table 4]

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction curve of Sample A obtained in Example 1.

FIG. 2 shows an X-ray diffraction curve of Sample C obtained in Comparative Example 1.

Claims (2)

[Claims] 1. A biodegradable resin molded article comprising poly-3-hydroxybutyric acid having a crystallinity of less than 50%. 2. A method for producing a biodegradable resin molded article, which comprises melting poly-3-hydroxybutyric acid, followed by rapid solidification to obtain a molded product having a crystallinity of the polyhydroxybutyric acid of less than 50%. .