POLY(3-HYDROXYBUTYRATE) RESIN TUBE AND METHOD FOR PRODUCING SAME

Abstract

Provided is a poly(3-hydroxybutyrate) resin tube including a poly(3-hydroxybutyrate) resin, the tube having a wall thickness of 0.1 to 0.6 mm. The difference between the melting point peak temperature and the melting point peak end temperature in differential scanning calorimetry analysis of the poly(3-hydroxybutyrate) resin is preferably 10° C. or higher. Preferably, production of the tube includes the step of melting a poly(3-hydroxybutyrate) resin in an extruder, then extruding the resin from an annular die, and introducing the resin into water, the annular die temperature being set to a temperature between the melting point peak temperature and the melting point peak end temperature in differential scanning calorimetry analysis of the poly(3-hydroxybutyrate) resin.

Claims

1. A poly(3-hydroxybutyrate) resin tube, comprising; a poly(3-hydroxybutyrate) resin, wherein the tube has a wall thickness of 0.1 to 0.6 mm.

2. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein a difference between a melting point peak temperature and a melting point peak end temperature in differential scanning calorimetry analysis of the poly(3-hydroxybutyrate) resin is 10° C. or higher.

3. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the poly(3-hydroxybutyrate) resin is poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).

4. A method for producing the poly(3-hydroxybutyrate) resin tube of claim 1, the method comprising: melting a poly(3-hydroxybutyrate) resin in an extruder; extruding the melted poly(3-hydroxybutyrate) resin from an annular die; and introducing the extruded poly(3-hydroxybutyrate) resin into water, wherein a temperature of the annular die is set to be between a melting point peak temperature and a melting point peak end temperature in differential scanning calorimetry analysis of the poly(3-hydroxybutyrate) resin.

5. The method according to claim 4, wherein the poly(3-hydroxybutyrate) resin has a melt viscosity at 160° C. of 10,000 poise or more.

6. The method according to claim 4, further comprising: mixing at least two types of poly(3-hydroxybutyrate) resins.

7. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the poly(3-hydroxybutyrate) resin has a melt viscosity at 160° C. of 10,000 poise or more.

8. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein a difference between a melting point peak temperature and a melting point peak end temperature in differential scanning calorimetry analysis of the poly(3-hydroxybutyrate) resin is 12° C. or higher and 50° C. or lower.

9. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the tube comprises a plurality of tubes having different diameters connectable with a stopper portion such that the tube is extensible.

10. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the tube has a bellows portion such that the tube is bendable at the bellows portion.

11. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the poly(3-hydroxybutyrate) resin comprises at least two types of poly(3-hydroxybutyrate) resins.

12. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the tube has an outer diameter of from 2 to 10 mm and a length of from 50 to 350 mm.

13. The poly(3-hydroxybutyrate) resin tube according to claim 1, wherein the poly(3-hydroxybutyrate) resin has a melt viscosity at 160° C. of 13,000 poise or more and 30,000 poise or less.

Description

EXAMPLES

[0051] Hereinafter, the present invention will be described in more detail by way of examples and comparative examples, which do not limit the present invention.

[0052] (Resin Raw Material Used)

[0053] Resin raw material 1: Kaneka Biodegradable Polymer PHBH (trademark) 151C manufactured by Kaneka Corporation [pol y(3-hydroxybutyrate-co-3-hydroxyhexan oate)] (melting point peak temperature: 125° C., melting point peak end temperature: 167° C.)

[0054] Resin raw material 2: Kaneka biodegradable polymer PHBH (trademark) X13 lA manufactured by Kaneka Corporation [poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)]

[0055] (Differential Scanning Calorimetry Analysis Evaluation)

[0056] In an endothermic curve obtained when an aluminum pan was filled with 4 to 10 mg of a resin sample, and using a differential scanning calorimeter, the resin sample was melted by elevating the temperature at a speed of 10° C./min from 30° C. to 180° C. under nitrogen flow, the temperature at which the amount of absorption of heat was maximum was defined as a melting point peak temperature, and the temperature at which the melting point ended and absorption of heat did not occur was defined as a melting point peak end temperature.

[0057] (Method for Measuring Melt Viscosity) A capillograph (cylinder diameter: 10 mm) heated to 160° C. and provided with an orifice having a diameter of 1 mm, a length of 10 mm and an inlet angle of 45° was filled with 15 g of a resin sample, and preheated for 5 minutes, and a piston was then moved down at a speed of 10 mm/min to extrude the molten resin through the orifice. From the stress applied to the piston at this time, a melt viscosity at a shear rate of 122/s was calculated.

[0058] (Evaluation of Shape of Tube)

[0059] The maximum and minimum values of the outer diameter at a certain position in the tube were measured with a caliper. A flatness was calculated by dividing a difference between the maximum value and the minimum value by the maximum value.

[0060] A wall thickness of the tube was measured at each of arbitrary three points on a cross-section of the tube with a caliper, and an arithmetic mean thickness thereof was calculated.

[0061] (Evaluation of Flexibility of Tube)

[0062] A 50 mm end part of the tube cut to a length of 250 mm was held, the opposite end part was pressed with a force of IN using a push gauge, and evaluation was performed on the basis of the following criteria.

[0063] Good: the amount of displacement of the end part by flex of the tube is 30 mm or more.

[0064] Poor: the amount of displacement of the end part by flex of the tube is less than 30 mm.

[0065] (Evaluation of Biodegradability of Tube in Seawater)

[0066] 6 L of seawater (collected from the port in Takasago City, Hyogo Prefecture) freed of foreign substances using a mesh with an aperture of 80 μ, 3 g of ammonium chloride, and 0.6 g of dipotassium phosphate were put into a plastic container in accordance with ASTM D-7081, the tube cut to a length of 2 cm was introduced into the container, and a weight retention ratio after 3 months was calculated. The temperature of seawater was maintained at 23° C.

[0067] (Evaluation of Secondary-Processability of Tube)

[0068] The tube cut to a length of 30 mm was introduced in a hot air oven set to a predetermined temperature (130° C. or 140° C.) shown in Table 3, and was preheated for 5 minutes. The tube was then taken out from the oven, the tube shape was visually examined, the tube end part was quickly sandwiched with a clip (Binder Clip No. 107 manufactured by LION OFFICE PRODUCTS CORP.) to form a narrow portion, and held for 1 minute without change. Then, the clip was removed, and whether the narrow portion was welded or not was visually examined. Shape retainability and moldability were evaluated on the basis of the following criteria.

[0069] (Shape Retainability)

[0070] Good: the initial tube shape is maintained even after preheating.

[0071] Poor: the tube shape is deformed by preheating.

[0072] (Moldability)

[0073] Good: the narrow portion is welded 1 minute after the tube is sandwiched with a clip.

[0074] Poor: the narrow portion is not welded 1 minute after the tube is sandwiched with a clip.

[0075] [Production of poly(3-hydroxybutyrate) Resin Pellet]

[0076] The resin raw material 1 and the resin raw material 2 were mixed at a combination ratio as shown in Table 1, 1 part by weight of pentaerythritol was combined with a total of 100 parts by weight of both the resin raw materials in total and the mixture was dry-blended. The obtained resin material was introduced into a φ26 mm unidirectional twin-screw extruder with a cylinder temperature set to 190° C. and a die temperature set to 150° C., extruded, and caused to pass through a water tank filled with hot water at 45° C., thereby solidifying the resin material into a strand. The strand was cut with a pelletizer to obtain resin pellets 1 to 3.

[0077] In addition, similarly to above, the obtained resin material was introduced into the twin-screw extruder with a cylinder temperature and a die temperature each set to 150° C., extruded, and caused to pass through a water tank filled with hot water at 45° C., thereby solidifying the resin material into a strand. The strand was cut with a pelletizer to obtain a resin pellet 4.

[0078] Table 1 shows the production conditions and the melting point properties of the resin pellets.

TABLE-US-00001 TABLE 1 Combination Melting point property Resin raw Resin raw Cylinder Peak End Difference between peak Melt material 1 material 2 temperature temperature temperature temperature and end viscosity (parts by weight) (parts by weight) (° C.) (° C.) (° C.) temperature (° C.) (poise) Resin pellet 1 0 100 190 142 150 8 8.100 Resin pellet 2 25 75 190 141 161 20 8.700 Resin pellet 3 50 50 190 139 165 26 8.800 Resin pellet 4 50 50 150 137 165 28 13.900

Example 1

[0079] The cylinder temperature and the die temperature of a φ12 mm single-screw extruder to which an annular die (outer diameter: 3 mm) is connected were each set to 145° C., the resin pellet 1 was introduced into the extruder, extruded in a tubular form, and caused to pass through a water bath at 30° C. which was located 30 mm away from the annular die, thereby obtaining a tube having an outer diameter of 3 mm and a wall thickness of 0.2 mm. The obtained tube had a perfect-circle cross-section with substantially no difference between the maximum outer diameter value and the minimum outer diameter value. Table 2 shows evaluation results.

Example 2

[0080] Except that the resin pellet used for processing was changed to the resin pellet 2, the same procedure as in Example 1 was carried out to obtain a tube. Table 2 shows evaluation results for the obtained tubes.

Example 3

[0081] Except that the resin pellet used for processing was changed to the resin pellet 3, and the cylinder temperature and the die temperature were each set to 140° C., the same procedure as in Example 1 was carried out to obtain a tube. Table 2 shows evaluation results for the obtained tubes.

Comparative Example 1

[0082] Except that the resin raw material used for processing was changed to polylactic acid (Ingeo 10361D manufactured by NatureWorks LLC), and the cylinder temperature and the die temperature were each set to 160° C., the same procedure as in Example 1 was carried out to obtain a tube. Table 2 shows evaluation results for the obtained tubes.

TABLE-US-00002 TABLE 2 Tube shape Degradability Maximum outer Minimum outer Wall in seawater Resin diameter value diameter value Flatness thickness Weight retainability pellet (mm) (mm) (%) (mm) Flexibility (%) Example 1 Resin pellet 1 3.0 2.9 3 0.2 Good 0 Example 2 Resin pellet 2 3.0 2.9 3 0.2 Good 0 Example 3 Resin pellet 3 3.0 3.0 0 0.2 Good 0 Example 4 Resin pellet 3 6.5 6.0 8 0.5 Good 27 Example 5 Resin pellet 4 6.3 6.1 3 0.3 Good 0 Comparative PLA 3.0 3.0 0 0.2 Poor 100 Example 1 Comparative Resin pellet 3 6.3 6.2 2 0.7 Poor 65 Example 2

[0083] Since the tubes of Examples 1 to 3 are not flattened, have a perfect-circular cross section, and are rated good for flexibility evaluation, the tubes are hardly broken, and can be safely used as straws. On the other hand, the tube of Comparative Example 1, which is formed from polylactic acid, is rated poor for flexibility evaluation, and is easily broken. The tubes of Examples 1 to 3 are biodegraded in seawater, whereas the tube of Comparative Example 1 is not biodegraded at all in seawater.

Example 4

[0084] The cylinder temperature and the die temperature of a φ40 mm single-screw extruder to which an annular die (outer diameter: 11 mm) is connected were each set to 160° C., the resin pellet 3 was introduced into the extruder, extruded in a tubular form, and caused to pass through a water bath located 50 mm away from the annular die, thereby obtaining a tube having an outer diameter of 6 mm and a wall thickness of 0.5 mm. The obtained tube had slight flatness under the effect of hydraulic pressure in the water bath, and it was difficult to further thin the tube with this outer diameter. Table 2 shows evaluation results.

Comparative Example 2

[0085] Except that the screw rotation speed of the single-screw extruder was adjusted to set the wall thickness of the tube to 0.7 mm, the same procedure as in Example 4 was carried out to obtain a tube having an outer diameter of 6.3 mm. Table 2 shows evaluation results for the obtained tubes.

Example 5

[0086] Except that the resin pellet used for processing was changed to the resin pellet 4, the same procedure as in Example 4 was carried out to obtain a tube having an outer diameter of 6 mm and a wall thickness of 0.3 mm. Table 2 shows evaluation results.

[0087] The tube of Example 4 had a slightly larger flatness because its outer diameter was increased, but the tube was determined to be usable as a straw. The tube has a relatively large wall thickness of 0.5 mm, but is biodegradable in seawater. The tube is rated good for flexibility evaluation, and is hardly broken when used as a straw. On the other hand, the tube of Comparative Example 2 has a low flatness and a good shape, but has a large wall thickness of 0.7 mm, and therefore is not sufficiently biodegradable in seawater. In addition, the tube is rated poor for flexibility evaluation, and is easily broken.

[0088] The tube of Example 5 included a resin having a high melt viscosity, and therefore it was possible to reduce the flatness even when the tube was thinned with a large outer diameter.

[0089] Comparison of Examples 1 to 5 with Comparative Example 2 shows that a poly(3-hydroxybutyrate) resin tube having a larger wall thickness is biodegraded at a lower rate in seawater.

[0090] For the tubes of Examples 1 to 3, further the secondary-processability was evaluated. Table 3 shows evaluation results thereof.

TABLE-US-00003 TABLE 3 Tube material Secondary-processability Peak End Difference between peak 130° C. 140° C. Resin temperature temperature temperature and end Shape Shape pellet (° C.) (° C.) temperature (° C.) retainability Moldability retainability Moldability Example 1 Resin pellet 1 142 150 8 Good Poor Poor Good Example 2 Resin pellet 2 141 161 20 Good Good Good Good Example 3 Resin pellet 3 139 165 26 Good Good Good Good

[0091] The tube of Example 1 in which the difference between the melting point peak temperature and the melting point peak end temperature of the resin raw material used was lower than 10° C. had had poor moldability after preheating while having good shape retainability during preheating at a preheating temperature of 130° C., and had poor shape retainability during preheating while having good moldability after preheating at a preheating temperature of 140° C.

[0092] This shows that the tube of Example 1 did not have both good shape retainability during preheating and good moldability after preheating at any of preheating temperatures of 130° C. and 140° C. On the other hand, the tubes of Examples 2 and 3 in which the temperature difference is 10° C. or higher each have both good shape retainability during preheating and good moldability after preheating at any of preheating temperatures of 130° C. and 140° C., and are excellent in secondary-processability.