JP2530557B2 - Biodegradable resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has excellent moldability and mechanical performance, and is used as a packaging member for chemicals, cosmetics, foods and industrial materials / equipment, machine parts, fibers, monofilaments, clothing and the like. The present invention relates to a resin composition having excellent biodegradability.

[0002]

2. Description of the Related Art Conventionally, many plastics have been used in various industrial fields as molding materials for packaging materials, clothing, fibers / monofilaments and industrial machine parts. At the same time, from the standpoint of environmental protection, the reuse of plastics is being called for, and there is a strong social demand for the development of biodegradable polymer materials that are completely decomposed by the action of microorganisms under natural environmental conditions. Among the biodegradable polymer materials known so far, poly β-hydroxybutyric acid (hereinafter abbreviated as PHB) and polycaprolactone (hereinafter P
CL (abbreviated as CL) has excellent biodegradability that completely decomposes under natural environmental conditions and is thermoplastic, and therefore its use for various applications by the existing molding method is being actively investigated.
However, PHB has a melting point (170 to 180 ° C)
Molding is difficult because it easily decomposes in the vicinity, and it has high tensile and bending strengths, but has the drawback of low elongation and low impact resistance. On the other hand, PCL has the drawbacks of high elongation and impact strength, but low shape retention due to low elastic modulus, and poor heat resistance due to low melting point of 60 ° C. For these reasons, PHB and PCL are
Despite having excellent biodegradability to meet social demands for environmental protection, it has not yet been fully utilized in various industrial fields.

Some of the inventors of the present invention have completely decomposed microorganisms by first mixing PCL and PHB,
Moreover, it was found that a plastic applicable as a plastic molding material was obtained, and a patent application (Japanese Patent Laid-Open No. 3-1574)
50). Although this plastic is excellent in biodegradability, it is still insufficient in practicality as a molding material. That is, in the case of this conventional technique, as is clear from the description of the embodiment, PHB and P
CL is mixed with equal weight, and PH is mixed in the mixture.
By allowing the copolymer of B and PCL to be present, a film having a good elongation rate is obtained. However, this film, on the contrary, presents various new problems due to the presence of its copolymer. For example, the presence of the copolymer is
Since the crystallization speed of the molten mixture of B and PCL is slowed down, there is a problem that the cooling time becomes long in order to obtain a completely crystallized molded product during its molding.
In addition, the presence of the copolymer of PHB and PCL lowers the crystallinity of the molded product and deteriorates the gas barrier property of the molded product.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above problems found in the prior art, has excellent moldability, and gives a molded article having excellent physical properties, which is a highly practical biodegradable resin composition. The task is to provide things.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, poly (β-hydroxybutyric acid) having a viscosity of n (A) at 185 ° C. and 185
A polycaprolactone having a viscosity of n (B) at 0 ° C., a mixing ratio c (A) of the poly β-hydroxybutyric acid in the range of 55 to 85% by weight, and n (A),
There is provided a biodegradable resin composition having excellent moldability and mechanical performance, characterized in that n (B) and c (A) satisfy the following formula. 4 × 10 ⁻³ × c (A) -1.7 ≦ log (n (A) / n (B)) ≦ 4 × 10 ⁻³ × c (A) -1.3

The PHB used in the present invention is a polymer having a melt viscosity of 500 Poise or more, and may be produced by any of the microbial method and the chemical synthesis method. However, at present, the chemical synthesis method is very difficult industrially and can be easily produced by the microbial method. It has been clarified that this PHB is completely decomposed by a microorganism or an enzyme (PHB depolymerase). The PHB used in the present invention may contain a plasticizer for improving moldability and a nucleating agent / crystallization accelerator for increasing the crystallization rate.

The PCL used in the present invention is a polyester synthesized by a chemical reaction, for example, it is produced by a ring-opening polyaddition reaction of caprolactone, and also by hydrolysis of caprolactone or another chemical method. It can be synthesized by a polycondensation reaction of the synthesized hydroxycarboxylic acid or hydroxycarboxylic acid ester. It has been clarified that this PCL is also completely decomposed by microorganisms or enzymes (lipase or esterase).

In the present invention, the mixing ratio of PHB in the composition is 55 to 85% by weight, preferably 55 to 75% by weight, based on the total amount of PHB and PCL, and the mixing ratio of PCL is
It is necessary that the total amount of PHB and PCL be 45 to 15% by weight, preferably 45 to 25% by weight. P
A composition having an HB ratio of less than 55% by weight and having a proportion of around 50% by weight does not give a uniform melt mixture, and causes uneven discharge during molding, unevenness of the surface of the molded product, and poor appearance of the molded product. However, it causes inconvenience that the mechanical performances of products after molding differ greatly among products. It is considered that the non-uniformity of the molten mixture is caused by the fact that the mixing ratios of both materials are close to each other, and therefore both materials tend to become a continuous phase or a dispersed phase in the mixed material, so that the mixed state is not stable. To be If the mixing ratio of PHB exceeds 85% by weight, the effect of modifying the elongation and impact resistance of the molded product will be insufficient.

Further, the composition of the present invention is required to satisfy the following formula. 4 × 10 ⁻³ × c (A) -1.7 ≦ log (n (A) / n (B)) ≦ 4 × 10 ⁻³ × c (A) -1.3 In the above formula, c (A) Indicates the mixing ratio of PHB (% by weight), n (A) indicates the melt viscosity (poise) of PHB at 185 ° C., and n (B) indicates the melt viscosity (poise) of PCL at 185 ° C. The range of compositions satisfying the above formula is shown in FIG. In FIG. 1, a straight line 1 and a straight line 2 are represented by the following equations (1) and (2), respectively. log (n (A) / n (B)) = 4 × 10 ⁻³ × c (A) -1.3 (1) log (n (A) / n (B)) = 4 × 10 ⁻³ × c (A) -1.7 (2) Further, in FIG. 1, straight lines 3 and 4 are c
(A) shows 55% and 85%.

The composition of the present invention has a straight line 1 in FIG.
It is necessary to be within the range surrounded by 2, 3 and 4. Melt viscosity ratio of HLB and PCL (n (A) / n
The composition in which the mixing ratio c (A) of (B)) and HLB is out of the above range deteriorates the homogeneity of the molten mixture of HLB and PCL, and the molded product is inferior in appearance and mechanical properties. Becomes

The composition of the present invention may contain conventional additives such as colorants, plasticizers, fillers, crystal nucleating agents and antioxidants.

The compositions of the present invention do not require the addition of compatibilizers such as PHB and PCL copolymers as used in the prior art. In the case of the composition of the present invention, it is possible to obtain a uniform melt mixture having excellent moldability without using such a compatibilizer, and it is excellent in mechanical strength, heat resistance and gas barrier properties. Moreover, a molded product having excellent biodegradability can be obtained.

The composition of the present invention comprises injection molding, injection blow molding, injection stretch blow molding, extrusion, extrusion blow molding, extrusion stretch blow molding, stretching, rolling, thermoforming, spinning, spinning with stretching, spinning and spinning. Converted to products such as sheets, films, soft and hard containers / bottles, tubes, monofilaments, fibers, non-woven fabrics, woven fabrics, machine parts, sports equipment parts, etc. by a molding processing method that is generally applicable to thermoplastic resins such as be able to. As a particularly specific use of these molded products, materials that are impossible or difficult to collect or reuse after use, such as medical instruments and equipment,
It may include containers for foods, drugs, perfumes, bags for garbage, fishing lines, threads such as fishing nets, nets, clothes, industrial cloths, and other industrial and agricultural materials.

[0014]

EXAMPLES The present invention will be described below in greater detail by giving Examples, but the present invention is not limited thereto. The melt viscosity, tensile properties, impact properties and melting points shown below were measured as follows. Also, PHB
Is produced by a method using a microorganism described in JP-A-62-055094, and PCL is referred to as Union Carbide Corporation (hereinafter abbreviated as UCC) and Daicel Chemical Industries Ltd. (hereinafter abbreviated as Daicel). ) Products were used.

(1) Melt viscosity It was measured using a capillary rheometer (Shimadzu Corporation, trade name: Flow Tester CFT-500). Capillary dimensions: Diameter 1mm φ Length 10mm Measurement temperature: 185 ℃ Pressure: 10kg / cm ²

(2) Tensile test [Tensile test using injection-molded dumbbell-shaped test piece] Apparatus: Tensile tester (Custom Scientific Instruments Co., Ltd. (hereinafter abbreviated as CSI), manufactured by CSI (USA),
Product name: MINI MAX TENSILETESTER, CS-183TI) Specimen shape: Round bar dumbbell type Specimen size: Round bar diameter 1.6mm, Same length 8.0mm, Chuck fixing part diameter 4.5mm Chuck fixing part length 4.5mm Tension speed : 0.233 inch / min [Tensile test using sheet strip type tester] Equipment: Tensile tester (Tensilon manufactured by Orientec Co., Ltd.)
UHM III) Test piece shape: strip type length 100 mm, width 10 mm, chuck space 5
0mm Peeling speed: 50mm / min Measuring condition: Temperature 23 ℃, Relative humidity 50%

(3) Impact test device: Izod impact tester (CSI (USA), trade name: MINI MAX IMPACTTESTER CS-183TI) Test piece shape: square bar Test piece size: 6.22 mm width, 3.2 mm thickness , Length 3.2mm, notch depth 0.142mm Measurement conditions: notch, temperature 23 ℃, relative humidity 50%

(4) Melting point The endothermic peak from the DSC analysis corresponding to the melting of the crystal part was adopted as the melting point. DSC analysis conditions Equipment: Seiko Electronics Co., Ltd., SSC / 560 Temperature rising rate: 10 ° C / min

Examples 1-2 PHB (melting point: 171 ° C., melt viscosity at 185 ° C. 1100 Pois
e) and PCL (manufactured by UCC, USA, PCL-P787, melting point: 61)
℃, melt viscosity at 185 ℃ 24000 Poise) (PHB
The melt viscosity ratio of PCL and PCL is 1100/24000 ≒ 1/22), and both polymers are mixed at a weight ratio of 80/20 or 60/40, and the mixture is taken out in a strand state by air cooling and pelletized by a rotary cutter. Disconnected. The obtained mixed polymer pellets were molded with an injection molding machine (manufactured by CSI, trade name: MINIMAX MOLDER, CS-183MMX) at a cylinder temperature of 185 ° C and a gold foil temperature of 50 to 55 ° C. Tensile and impact tests were performed on the rod dumbbell-shaped molded pieces to evaluate the mechanical performance. Table 1 shows the results.

Comparative Example 1 PCL (PCL-P767, manufactured by UCC, USA, melting point: 6)
Same as Example 1 except that the melt viscosity at 1 ° C and 185 ° C is 2800 Poise) (PHB and PCL melt viscosity ratio is 1100/2800 ≈ 1 / 2.5), and PHB and PCL are 60/40 in weight ratio. Then, a molded piece was prepared. The resulting molded piece was subjected to tensile and impact tests to evaluate the mechanical performance. Table 1 shows the results.

COMPARATIVE EXAMPLE 2 Example 2 was repeated except that the same PHB and PCL (melt viscosity ratio of PHB and PCL was about 1/22) as in Example 1 were used and both polymers were mixed at a weight ratio of 50/50. Pellets and molded pieces were prepared in the same manner as in 1. Tensile and impact tests were performed on the obtained molded pieces to evaluate the mechanical performance. Table 1 shows the results. When a molded piece was obtained in this experiment, the discharge state during extrusion with an extruder was unstable, and the obtained strand had a non-uniform thickness. Further, the tensile strength and the tensile elongation of the obtained molded piece have a very large difference between the molded pieces,
It is considered that the mixed state of both polymers is not stable.

Comparative Examples 3 to 5 Only PHB used in Example 1 (Comparative Example 3), only PCL used in Example 1 (Comparative Example 4) and P used in Comparative Example 1
A molded piece was produced in the same manner as in Example 1 except that only CL (Comparative Example 5) was used. The resulting molded piece was subjected to tensile and impact tests to evaluate its mechanical performance. Table 1 shows the results.

Incidentally, c (A) and c (B) shown in Table 1
Indicates the mixing ratio (% by weight) of PHB and PCL in the composition, respectively. n (A) and n (B) show melt viscosity at 185 ° C. of PHB and PCL to be blended, respectively. The numerical value in parentheses after the value of tensile elongation indicates the coefficient of variation (V) of tensile strength calculated by the following formula. V = (standard deviation / average value) × 100%

[0024]

[Table 1]

Example 3 80 parts by weight of PHB (melting point: 171 ° C., melt viscosity at 185 ° C. 1
100 Poise) and 20 parts by weight of PCL (manufactured by Daicel, Plaxel-H7, melting point: 61 ° C, melt viscosity at 185 ° C 26000)
Poise) pellets (PHB and PCL melt viscosity ratio: 110
(0/26000 ≒ 1/24) is mixed, and the cylinder temperature is 170-185 ° C and the die temperature is 185 ° C using an extruder [Toyo Seiki Co., Ltd., Labo Plastomill, screw diameter: 20mm].
As a sheet, a sheet having a thickness of about 250 μm was produced by the T-die / cooling roll method (cooling roll temperature: 20 to 55 ° C.). A strip-shaped test piece having a length of 100 mm and a width of 10 mm was cut out from the obtained sheet and subjected to a tensile test. The results are shown in Table 2.

Comparative Example 6 As PCL, PCL (manufactured by Daicel) Plaxel-H4,
A sheet having a thickness of about 250 μm was prepared in the same manner as in Example 3 except that a melting viscosity of 640 Poise at a melting point of 61 ° C. and 185 ° C. was used. (The melt viscosity ratio of PHB and PCL in this case is
1100/640 ≒ 1 / 0.6). 100 mm length from the obtained sheet,
A strip type test piece having a width of 10 mm was cut out and subjected to a tensile test.
The results are shown in Table 2.

Comparative Example 7 A sheet having a thickness of about 250 μm was prepared in the same manner as in Example 3 except that only PHB used in Example 3 was used and PCL was not mixed. Length 100 mm, width 1 from the obtained sheet
A 0 mm strip-shaped test piece was cut out and subjected to a tensile test. The results are shown in Table 2.

[0028]

[Table 2]

As can be seen from the results shown in Tables 1 and 2, the melt viscosity ratio of PHB and PCL (n (A) / n
The mixing ratio (n (A)) of (B)) and PHB is shown in FIG.
By holding within the specific range shown in,
A molded product having excellent tensile properties and impact strength can be obtained. Further, the mixing ratio of PHB (c (A)) is 50% by weight.
, The melt viscosity ratio of PHB and PCL (n
Even if (A) / n (B)) is within the range of the present invention, good results are not obtained.

Example 4 PHB (melting point: 171 ° C., melt viscosity at 185 ° C. 1100 Pois
e) and pellets of PCL (manufactured by Daicel, Plaxel-H7, melting point: 61 ° C, melt viscosity 26000 Poise at 185 ° C) (melt viscosity ratio of PHB and PCL: 1100/26000 ≈ 1/2)
4) Mix both polymers at a weight ratio of 60/40, and mix this mixture with an extruder [screw diameter: 40 mm], a cylindrical die and a mold (50
Blow molding machine consisting of (for 0 ml bottle), blow molding under conditions of extrusion temperature: 170-180 ℃, die temperature: 25 ℃, mold temperature: 25 ℃, internal volume: 500 ml, surface area: 0.042 m ²
I made a bottle of. The moldability, shape retention and biodegradability of this bottle were evaluated as follows.
Table 3 shows the results. Further, the average thickness (mm) of the container wall of the obtained bottle and the oxygen permeability (cc / bottle · day · atm) of the bottle were measured by a conventional method. Table 3 shows the results.

(Moldability) It was examined whether or not the molding compound could be molded into a practical bottle and whether or not the pinch-off portion at the bottom of the bottle had good adhesiveness. The moldability evaluation criteria are as follows. Good: Molding into a bottle is possible and the pinch-off portion at the bottom of the bottle has good adhesiveness. Poor: Molding into a bottle is impossible, or the pinch-off portion at the bottom of the bottle has poor adhesion. (Shape Retention) When the bottle was left standing in an air circulation constant temperature bath for 30 minutes, it was evaluated at the maximum temperature at which no deformation of the bottle was visually confirmed. (Biodegradability) The weight loss rate (%) after keeping in soil for 12 months was evaluated.

Comparative Example 8 Only PHB shown in Example 4 was used as a molding material,
An attempt was made to obtain a blow molded product in the same manner as in Example 4,
In this case, the pinch-off part under the parison was not sufficiently adhered, and the blown air leaked and a bottle could not be obtained.

Comparative Example 9 A bottle was prepared in the same manner as in Example 4, except that only PCL shown in Example 4 was used as the molding material.

Comparative Example 10 In Example 4, the weight ratio of PHB to PCL was 50:
The experiment was conducted in the same manner except that the value was changed to 50. Table 3 shows the results.

[0035]

[Table 3]

[0036]

INDUSTRIAL APPLICABILITY The composition of the present invention has excellent moldability as well as excellent mechanical strength such as tensile strength and impact resistance, and further has excellent heat resistance, gas barrier property and biodegradability. give.

[Brief description of drawings]

FIG. 1 is a graph showing the composition range of the present invention.

Front page continued (72) Inventor Akira Iwamoto 2-16 Higashi 2-chome, Tsukuba, Ibaraki Prefecture No. 101 Ohno Heights 101 (72) Inventor Masahiro Harada 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Mitsubishi Gas Chemical Co., Ltd. Plastics Inside the center (72) Inventor Shigeki Imagawa Niigata City, Niigata Prefecture, Niigata City, Niigata 182, Shinryo Institute of Chemicals Niigata Research Institute (72) Inventor Sadaharu Urakami 2-5-2, Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Gas Chemical In-house Examiner Yoshihiro Fuji (56) References JP-A-3-157450 (JP, A) JP-A-5-245996 (JP, A) JP-A-3-505541 (JP, A)

Claims (1)

(57) [Claims] 1. Poly (β-hydroxybutyric acid) having a viscosity of n (A) at 185 ° C. and n at 185 ° C.
(B) consisting of polycaprolactone,
The mixing ratio c (A) of hydroxybutyric acid is in the range of 55 to 85% by weight, and n (A), n (B) and c
A biodegradable resin composition having excellent moldability and mechanical performance, characterized in that (A) satisfies the following formula. 4 × 10 ⁻³ × c (A) -1.7 ≦ log (n (A) / n (B)) ≦ 4 × 10 ⁻³ × c (A) -1.3