JP7151139B2 - Polylactic acid container and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polylactic acid container manufactured by biaxial stretch blow molding and heat setting, and a method for manufacturing the same. It relates to a manufacturing method that enables manufacturing with high productivity.

In order to prevent various environmental problems caused by global warming, the use of bioplastics, which are plant-produced resins, is expected as a measure to reduce the concentration of greenhouse gases in the atmosphere. Consideration is being given to recycling technology aimed at converting conventional petroleum-based plastics to plant-derived plastics (bioplastics) and reusing the resin. Among them, polylactic acid (PLLA), which is an aliphatic polyester, has attracted attention as a bioplastic that is industrially mass-produced and easily available.

Polylactic acid is a polyester obtained by polymerizing L-lactic acid as a monomer, lactic acid fermented starch of cereal starch such as corn, tuberous roots such as cassava, tubers such as potato, or corms such as taro. . Generally, it is produced by a direct polycondensation method of L-lactic acid or a ring-opening polymerization method of lactide, which is a dimer of L-lactic acid. Unlike conventional petroleum-based plastics, there is no concern about depletion of resources, and even if discarded in the natural world, it can be composted by microbial decomposition, and is finally decomposed into water and carbon dioxide. However, since the generated carbon dioxide is re-incorporated into the plants on the ground, it does not accumulate in the atmosphere. Therefore, polylactic acid is expected to be put into practical use as a completely recyclable plastic material that is born from plants and returns to plants.

Various containers made of polylactic acid have also been proposed. For example, in Patent Document 1 below, polylactic acid having an optically active isomer (d) content of 4.0% or less is subjected to biaxial stretch blow molding and heat setting. In the formed container, the half-value width (X) of the diffraction peak at 2θ = 10 to 25° determined by wide-angle X-ray measurement on the side wall is in the range of 0.624° to 1.220°. A biaxially stretch blow heat set molded container is proposed, and the biaxial stretch blow molding is described as a one-mold method and a two-mold method.

Japanese Patent No. 4294475

As described in Patent Document 1 above, in the case of the two-molding method, once a preform with a bottom is expanded and stretched into a predetermined shape, the whole is once thermally shrunk by heating, and then a desired bottle-shaped mold is used. A method of re-stretch blow molding is employed. Therefore, a two-stage stretch blow molding is required, which increases the size of the equipment and the investment in the corresponding equipment, resulting in an increase in the unit price of the bottle. In particular, in the case of products with a small production lot (number), it has been pointed out that the one-mold molding method, which has a low production cost, is preferable.

On the other hand, in the one-mold method, it is possible to effectively form oriented crystals in areas such as the side wall (body) where the stretch ratio can be secured, and the stretch blow molding and heat setting of the mold can achieve excellent heat resistance and mechanical strength. However, for the lower shoulder and bottom of the nozzle where stretching molding is difficult, satisfactory stretching cannot be performed and the formation of oriented crystals becomes insufficient. , forming spherulites, becoming hard and brittle, and reducing mechanical strength.

For the lower shoulder of the nozzle, the lower part of the preform nozzle, which corresponds to the shoulder, is narrowed in the radial direction. After injection molding, the diameter of the preform is expanded and stretched to a predetermined shoulder shape to ensure the draw ratio. However, since the bottom of the bottle is in contact with the mold at a low draw ratio, it was difficult to draw. Such a bottom part is heat sterilized or sterilized with hot water at around 60 ° C. Depending on the conditions, the bottom part may be thermally shrunk, the bottom height may decrease, or the bottom may crack when the bottle is dropped, resulting in container deformation or mechanical damage. In terms of strength, there were still problems to be solved.

Therefore, the object of the present invention is to improve the heat resistance of the bottom of a container, which is difficult to stretch and mold, so that sufficient heat resistance can be secured even under the thermal history conditions of heat sterilization and sterilization, and mechanical strength that can withstand impacts such as dropping is provided. The object of the present invention is to provide a polylactic acid container having a

According to the present invention, there is provided a polylactic acid container obtained by biaxially stretching and blow-molding a polylactic acid preform having an optically active isomer (d) content of 2.5 % or less and heat-setting the container. has a central flat portion, an annular ground portion, an inner raised portion rising from the annular ground portion to the inner side of the container, and an inclined portion connecting the inner raised portion to the central flat portion, and the side wall portion of the container includes: The half width (X) of the diffraction peak at 2θ = 10 to 25 ° determined by wide-angle X-ray measurement is in the range of 0.624 ° to 0.970 °, and the inner rising portion is determined by wide-angle X-ray measurement. A polylactic acid container characterized by having a diffraction peak at 2θ=10 to 25° is provided .

According to the present invention, a polylactic acid container is produced by biaxial stretch blow molding and heat setting a preform made of polylactic acid having an optically active isomer (d) content of 2.5 % or less. The method, wherein the bottom of the container comprises a central flat portion, an annular ground portion, an inner raised portion rising from the annular ground portion to the inside of the container , and an inclined portion leading from the inner raised portion to the central flat portion, wherein the blow molding is performed. The mold has a cavity mold and a bottom mold movable in the axial direction of the container , and at the initial stage of blowing the blow air, the bottom mold is arranged at a position lower than a predetermined position with the blow mold closed, and the inside rises. After expanding and extending the part to be the inclined part below the lower end of the cavity mold, the bottom mold is moved to a predetermined position where the blow mold is closed while applying a pressurized fluid. , the bottom of the container is the product of the lateral draw ratio (DH) calculated from the outer diameter ratio of the preform and the container and the longitudinal draw ratio (DL') calculated based on the movement distance (DL) of the bottom mold ( DH×DL') is in the range of 4.0 to 10.0, and the ratio (DH/DL') of the transverse draw ratio (DH) to the longitudinal draw ratio (DL') is 0.5 to 2.0. 0 and heat-setting the blow mold at a temperature of 70 to 150° C., the diffraction peak at 2θ=10 to 25° obtained by wide-angle X-ray measurement at the side wall portion. The half width (X) is in the range of 0.624° to 0.970°, and the inner rising portion has a diffraction peak at 2θ = 10 to 25° obtained by wide-angle X-ray measurement. A method for manufacturing a polylactic acid container is provided.

In the polylactic acid container of the present invention, the half width (X) of the diffraction peak at 2θ = 10 to 25° determined by wide-angle X-ray measurement is in the range of 0.624° to 1.220° in the side wall portion. In addition, the bottom also has a diffraction peak at 2θ = 10 to 25° by wide-angle X-ray measurement, and the bottom is clearly stretched sufficiently and has excellent heat resistance and mechanical strength. This is clear from the results of the examples described later, and the axial shrinkage rate at a temperature of 55 ° C. is 4% or less, which is excellent in dimensional stability, and the shape stability of the bottom part and mechanical strength at the bottom part. Excellent stability.
In addition, there is no whitening due to overstretching or thermal crystallization (lamellarization), and the haze at the sidewall portion is 10% or less, which is excellent in transparency.
Furthermore, in the method for producing a polylactic acid container of the present invention, the above-described polylactic acid container can be molded by a one-mold method, and is excellent in moldability and productivity.

FIG. 2 is a diagram showing the relationship between the thermal shrinkage initiation temperature (Y,° C.) and the half width (X) obtained by thermomechanical analysis (TMA) of the side walls of polylactic acid containers obtained in Examples and Comparative Examples. 1 is a side view showing an example of a polylactic acid container of the present invention; FIG. 1 is a side sectional view showing an example of a polylactic acid preform used in the present invention; FIG. FIG. 4 is a diagram for explaining the state of a blow mold at the initial stage of blowing air in biaxial stretch blow molding. FIG. 4 is a diagram for explaining a state in which a bottom mold starts to rise in biaxial stretch blow molding. It is a figure for demonstrating the state which the bottom type|mold raised in biaxial stretch blow molding.

(Polylactic acid container)
The first feature of the polylactic acid container of the present invention is that it is made of polylactic acid (PLLA) having an optically active isomer (d) content of 4.0% or less.
Commercially available polylactic acid is a polymer based primarily on L-lactic acid, but contains D-lactic acid units to varying degrees. The content of this optically active isomer (d) has a great influence on the heat setting effect of the stretched molded product, that is, on the formation of oriented crystals.
In the present invention, the content of the optically active isomer (d) in the polylactic acid resin is 4.0% or less, preferably 3% or less, so that the degree of oriented crystallization by heat setting can be enhanced. can.

When a preform made of polylactic acid is stretched at a temperature above the glass transition temperature, it exhibits a stretching stress pattern similar to that of polyethylene terephthalate (PET), and the mechanical strength of stretched polylactic acid becomes equivalent to that of stretched PET (not shown). However, the oriented crystal structure formed by stretching is different from aromatic polyesters such as PET. PET forms a plane-oriented (β-sheet) structure of benzene rings, whereas polylactic acid has a 3 ₁ helix structure. It forms two types of rod-like helix structures (oriented crystal structures) of 10 ₃ helices. In addition, since this helix structure has weak intermolecular (helix-helix) interaction, the more the rod-like helix structure is aligned in the same direction (the more aligned), the easier it is to split in the alignment direction of the oriented crystal. or break easily.
In other words, in the case where the oriented crystals formed by stretch molding, such as polylactic acid (PLLA), have a rod-like helix structure, stable mechanical strength can be expressed as long as they are stretched at the same magnification both lengthwise and widthwise. However, when it is preferentially aligned on either the vertical axis or the horizontal axis (when it is stretched at different magnifications), anisotropy in mechanical strength derived from the anisotropy of the stretching ratio occurs, and it breaks when dropped. (decrease in impact resistance strength), etc., the performance of the container deteriorates in terms of mechanical strength.

In the polylactic acid container of the present invention, the side wall portion is isotropically stretched in the longitudinal direction and the lateral direction, and the oriented crystals formed are uniformly distributed on the surface in the direction of the stretching axis. The half width (X) of the diffraction peak at 2θ = 10 to 25° determined by measurement is in the range of 0.624° to 1.220°, especially 1.100° or less, and has excellent heat resistance and mechanical properties. strength. The above diffraction peak is based on the oriented crystal structure of polylactic acid, and the fact that the half width (X) of this diffraction peak is within the above range means that the arrangement of the oriented crystals of the polylactic acid container of the present invention is stable. It means that

In the present invention, the thermal shrinkage start temperature (Y, ° C.) obtained by thermomechanical analysis (TMA) of the container side wall and the half width (X) of the container side wall are expressed by the following formula (1)
Y≧4000exp(−10X)+54 (1)
It is also preferable with respect to the heat resistance of the container that the relationship is satisfied.
The thermal shrinkage initiation temperature (Y, °C) in thermomechanical analysis (TMA) is obtained as the temperature corresponding to the inflection point from the differential value of the temperature-strain curve, as will be detailed later.
FIG. 1 shows the results of plotting the side wall portions of polylactic acid containers obtained in Examples and Comparative Examples, which will be described later, with the heat shrinkage initiation temperature (Y) as the vertical axis and the half width (X) as the horizontal axis. ing.
Y=4000exp(-10X)+54 (1a)
is equivalent to
According to this result, in the region below the curve (1a), the heat resistance of the container is unsatisfactory, while in the region above the curve (1a), after storage at 55 ° C. for 18 days can be suppressed to less than 4%, and satisfactory heat resistance can be obtained.

Furthermore, since the crystals of the side wall formed by such stretch molding are suppressed in spherulization, the haze of the side wall of the container is 10% or less, particularly 4% or less. It also has the advantage of excellent appearance properties.

In the bottom part of the container, as will be described later, a bottom mold that can move in the bottle axial direction (vertical direction) is used, and during the stretch blow molding process, the bottom mold is moved while molding, so that the bottom part of the container is moved in the vertical direction.・The film can be stretch-molded within a range in which the anisotropy of the mechanical strength in the horizontal direction does not occur, and the formation of oriented crystals and their balance can be controlled, ensuring sufficient heat resistance and mechanical strength. Moreover, oriented crystals are formed even in the bottom portion, and excellent transparency is obtained because the formation of spherulites is suppressed.
FIG. 2 is a side view showing one example of the polylactic acid container of the present invention. As is clear from FIG. 2, the bottom portion 5 includes a central flat portion 6, an annular ground portion 7, an inner raised portion 8 rising from the annular ground portion 7 toward the inside of the container, and an inclined portion connecting the inner raised portion 8 to the central flat portion. 9.
As will be described later, in the polylactic acid container of the present invention, the inner raised portion 8, the inclined portion 9, and the central flat portion of the bottom are stretched to form oriented crystals. As a result, diffraction peaks derived from the oriented crystals are measured as in the side wall of the body.

[Polylactic acid]
The polylactic acid used in the present invention has the following formula (I)
-[-OC(CH ₃ )H-CO-] (I)
wherein the constituent unit is substantially L-lactic acid, and the content of optical isomer D-lactic acid is 4.0% or less, preferably 3% or less.

The polylactic acid used in the present invention is, of course, not limited to this, but preferably has a weight average molecular weight (Mw) in the range of 10,000 to 300,000, particularly 20,000 to 250,000. Further, it preferably has a density of 1.26 to 1.20 g/cm ³ , a melting point of 160 to 200° C., and a melt flow rate (ASTM D1238, 190° C.) of 2 to 20 g/10 minutes.

Various coloring agents, fillers, inorganic or organic reinforcing agents, lubricants, anti-blocking agents, plasticizers, leveling agents, surfactants and thickeners may be added to the polylactic acid container of the present invention depending on the application. , a viscosity reducer, a stabilizer, an antioxidant, an ultraviolet absorber, etc., can be blended according to known formulations.

In addition, the polylactic acid container of the present invention may be a single layer container of the polylactic acid, or may have a laminated structure with other resins depending on the properties of the content. For example, for applications that require barrier properties against oxygen, it is used in the form of a laminate with a gas barrier resin such as ethylene-vinyl alcohol copolymer or metaxylylene adipamide (MXD6). For applications requiring gas barrier properties against water, a laminate with a water vapor barrier resin such as a cyclic olefin copolymer can be used. Furthermore, the polylactic acid container of the present invention may be provided with a coating layer of metal oxide or the like in order to improve gas barrier properties.

(Production method)
As described above, the polylactic acid container of the present invention is produced by biaxially stretching and blow-molding a bottomed preform made of polylactic acid (PLLA) having an optical isomer (D) content of 4% or less, followed by heat setting. Manufactured by
Such a bottomed preform is manufactured by a method known per se such as injection molding, compression molding, extrusion molding, etc. For example, in the case of injection molding, molten polylactic acid is injected to form a final container. A bottomed preform having a mouth-and-neck portion is manufactured in an amorphous state.
FIG. 3 is a side sectional view of a bottomed preform that can be suitably used for the biaxial stretch blow molding of the present invention. The preform, whose entirety is denoted by 10, has a mouth and neck portion 11, and a reduced diameter portion 12 narrowed in the inner diameter direction below the mouth and neck portion 11 is formed. ing. As a result, in the biaxial stretching blowing, the shoulder portion of the container is stretched to expand its diameter, thereby securing a stretch ratio and forming oriented crystals.

Preforms can be supplied to the biaxial stretch blow molding process by heating the preform in a supercooled state to the stretching temperature (cold parison method), or by using residual heat of the preform to be molded. A method (hot parison method) or the like in which stretching is performed by stretching is adopted.
The preform heating temperature (stretching temperature) for stretching is generally 70 to 150°C, preferably 80 to 120°C.

4 to 6 are diagrams for explaining the method of manufacturing the polylactic acid container of the present invention, and FIG. 4 is a diagram showing the state at the start of blowing air. FIG. 5 shows a state in which the blow mold is closed with the bottom mold placed at a lower position, and the preform bottom bulges into the space formed by the lower placement of the bottom mold. FIG. 6 shows a state in which the bottom mold is moved upward while blowing air, and the bottle is being blown into a predetermined bottle shape.
The blow mold 20 used in the present invention comprises a cavity mold 21 consisting of two left and right split molds 21a and 21b (for forming the side walls of the body), a bottom mold 22 movable between upper and lower positions in the axial direction of the bottle, And, although not shown, a clamp die for clamping the mouth and neck of the preform is provided. The state in which the blow mold 20 is closed is a state in which the desired container shape is formed by the cavity mold 21 and the bottom mold 22, specifically the state shown in FIG.

The preform 10 set in the blow molding die 20 and at the stretching temperature is longitudinally stretched by stretching rods 23 in the blow molding die, and at the same time, is laterally stretched in the circumferential direction by blowing blow air (pressurized fluid). be done.
In the present invention, as shown in FIG. 4, the bottom mold 22 is positioned below the predetermined position of the closed blow mold at the initial stage of blowing air.
At the time of biaxial stretch blow molding, the longitudinal draw ratio is 1.5 to 5.0 times, especially 2 to 3 times, the circumferential transverse stretch ratio is 1.5 to 5.0 times, especially 2 to 3 times, and the areal draw ratio. is 2.25 to 9.0 times, particularly 4 to 7 times, and the biaxial stretch blow molding is preferably carried out.

The pressure of the pressurized fluid used is preferably as high as possible, and although it varies depending on the capacity of the final container and the thickness of the preform, generally the initial pressure of the fluid used is 20 kg/ ^cm2 or more, and 30 to 40 kg/cm2. It is preferably in the range of ² . The pressure applied inside the preform may be uniform during molding, or a high pressure may be applied at the beginning. Unheated air or inert gas or heated air or inert gas can be used as the pressurizing fluid.

As shown in FIG. 5, the preform 10 is stretched so as to protrude downward into the vicinity of the upper end of the bottom mold 22 arranged below. As a result, the inner rising portion 8 of the container bottom and the portion to be the inclined portion 9 and the central flat portion 6 of the bottom portion are sufficiently stretched.
In the present invention, in the stretching of the bottom portion of the preform, the lateral stretching ratio (DH) calculated from the ratio of the outer diameter of the preform to the outer diameter of the bottle and the lateral stretching ratio calculated based on the moving distance (DL) of the bottom die. (DL′) and the product of the longitudinal draw ratio (DH×DL′) is in the range of 4.0 to 10.0, and the ratio of the transverse draw ratio to the longitudinal draw ratio (DH/DL′) is It is desirable to be stretched within the range of 0.5 to 2.0. As a result, stretch molding can be performed at a predetermined draw ratio within a range in which the anisotropy of mechanical strength is not expressed in the transverse direction and the longitudinal direction. and mechanical strength can be ensured.
The transverse draw ratio (DH) at the bottom is the ratio of the outer diameter (H ₀ ) of the bottom of the preform shown in FIG. 3 to the outer diameter (H ₁ ) of the bottom of the bottle shown in FIG. (DL) from which is shown in FIG.

Next, in a state in which the downwardly protruding hemispherical bottom of the preform is in contact with the upper end of the bottom mold 22, the bottom mold 22 is moved upward while applying a pressurized fluid to the inner rising portion 8 and the inclined portion. 9, and the part to be the central flat part 6 is pushed up from the annular grounding part 7 to the inside of the container to form the final container 30 shape. In this case, the longitudinal draw ratio (DL') calculated based on the movement distance (DL) between the lower position (Fig. 4) and the upper position (Fig. 6) of the bottom mold 22 and the transverse draw ratio (DH ).

In the present invention, it is important to heat set the container having the shape of the final molded product formed by biaxial stretch blow molding. can improve the physical strength. The heat setting temperature is preferably in the range of 70-150°C, particularly 90-120°C. Although the degree of oriented crystallinity increases as the heat setting temperature increases, it is preferable that the temperature is within the above range from the viewpoint of ease of removal from the mold (prevention of deformation during removal).
After heat setting, the temperature of the blow mold may be maintained at the above heat setting temperature so that the final molded product (container) is not rapidly cooled, or the final molded product may be immediately cooled by blowing cold air or the like. may be performed.

The invention is illustrated by the following examples. In addition, the present invention is not limited to the following examples.

(Molding of preform)
Polylactic acid having a weight-average molecular weight and an optically active isomer (d%) composition shown in Table 1 was used and compressed inward under the nozzle neck ring shown in FIG. A diameter-shaped preform was injection molded.
The dimensions of the preform are: nozzle outer diameter 31.8mmφ, straight shape with reduced diameter below the nozzle, barrel outer diameter (DH: 23.0mmφ: wall thickness 2.0mm), neck ring The length from the bottom to the bottom gate center position is 61.0 mm, and the preform height (length) corresponding to the bottom here is 10 mm from the preform bottom (described later), so the bottle bottom is formed. A portion equivalent to 50 mm, excluding the area (height from the bottom of 10 mm), was stretch-molded on the side wall of the bottle (body + shoulder).

evaluation:
(blow moldability)
In the process of stretch blow molding the bottle, if the bottle burst (broken body/bottom) or if the molded bottle became too thin to stand on its own due to the thin wall of the annular contact portion, the blow moldability was evaluated as poor. The other bottles were evaluated for moldability as ◯.

(heat shrinkable)
The bottles were stored in a 55°C constant temperature bath for 18 days. The bottle full content before and after storage for 18 days in a 55°C constant temperature bath is obtained from the filling amount of 20°C tap water, and from the full content W1 after storage time and the initial full content W0, the following formula (2)
Thermal shrinkage rate (%) = (W0-W1)/W0 x 100 (2)
The thermal shrinkage rate was calculated with. A bottle with a heat shrinkage rate of less than 4% was rated as ◯, and a bottle with a heat shrinkage rate of 4% or more was rated as x.

(Thermo-mechanical analysis)
A 15 mm x 5 mm square was cut from the flat portion of the bottle side wall, and TMA measurement was performed under a constant load condition (10 gf), an initial temperature of 30°C, a measurement end temperature of 90°C, and a heating rate of 5°C/min at a distance between chucks of 10 mm. The resulting temperature-strain curve was differentiated to obtain the inflection point, which was taken as the heat shrinkage start temperature (° C.).

(Wide-angle X-ray analysis measurement)
A 25 mm×25 mm square flat portion of the bottle side wall was cut out and fixed to a 20 mm×15 mm square aperture, and then wide-angle X-ray measurement was performed using an X-ray diffractometer. Next, the peak half width was obtained from the obtained peak.
Also, an 8 mm×8 mm square (maximum) was cut out from the flat portion of the inner raised portion of the bottom of the bottle, fixed to a 20 mm×15 mm square aperture, and then subjected to wide-angle X-ray measurement using an X-ray diffractometer. The presence or absence of diffraction peaks was confirmed.

(Drop strength)
After the bottle was filled with 400 ml of 20° C. water, it was sealed with a cap, left in a constant temperature room of 38° C. for 24 hours, and dropped from a height of 1.5 m in an upright state. Of the 10 dropped tubes, the case where no damage occurred was evaluated as ◯, and the case where one or more cables were damaged was evaluated as x.

[Example 1]
A preform was molded using polylactic acid having an optically active isomer (d%) of d%=1.4% and an average weight molecular weight of 200,000, and this preform was molded using a one-mold stretch blow molding machine. , cavity mold, and bottom mold Using a movable bottom mold, biaxial stretch blow molding and heat setting were performed at a mold temperature of 70°C.
The shape of the bottle was 52.0 mmφ in diameter, and the vertical distance from the bottom of the neck ring to the bottom ring-shaped contact portion was 122 mm in height. In this case, the height direction of the preform is marked in increments of 5 mm, and the preform portion corresponding to the side wall (body) is actually measured from the relationship between the preform marking position and the bottle marking position after blow molding. A value of 50.0 mm was obtained. It was equivalent to 85% of the vertical distance from the bottom of the neck ring to the bottom annular contact area. Therefore, the length of the side wall portion of the bottle (region of the body portion) after subtracting the portion corresponding to 18 mm of the bottom portion of the bottle is drawn by the preform length (50 mm) described above, and the longitudinal draw ratio is 2.0 mm. 1 times was found. The horizontal (circumferential) draw ratio was 2.3 times the outer diameter of the preform and the molded bottle outer diameter, and the area draw ratio of the side wall portion (body portion) was approximately 4.8 times.

As for the bottom part, the preform part corresponding to the bottom part (Fig. 2) is equivalent to 10 mm from the bottom part of the preform toward the nozzle part (equivalent to 15% of the perpendicular distance from the bottom contact part to the bottom of the neck ring), Since the original height (length) of the bottom portion was 18 mm, the original longitudinal draw ratio was 1.8 times. Here, when the bottom mold is moved downward by 20.0 mm to expand and stretch the preform bottom, the bottom mold is moved upward to a predetermined position to form the final bottle shape. ) is (20 mm + 18 mm) / 10 mm, which is 3.8 times, and the lateral draw ratio of the bottle bottom is 2.3 times from the ratio of the outer diameter of the preform to the outer diameter of the bottle bottom, so the bottom area draw ratio is 8.74 times. became.

The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the side wall was 0.964°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 57.4°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottles.

[Example 2]
The procedure of Example 1 was repeated except that the temperature of both the cavity mold and the bottom mold was set to 100°C.
The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the sidewall portion was 0.629°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 73.2°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottles.

[Example 3]
In the same manner as in Example 1, except that polylactic acid having an optically active isomer (d%) of d%=1.9% and an average weight molecular weight of 200,000 was used, and the temperature was set to 100° C. for both the cavity mold and the bottom mold. gone.
The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the side wall was 0.652°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 67.5°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottles.

[Example 4]
In the same manner as in Example 1, except that polylactic acid having an optically active isomer (d%) of d%=2.5% and an average weight molecular weight of 200,000 was used, and the temperature was set to 80° C. for both the cavity mold and the bottom mold. gone.
The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the sidewall portion was 0.767°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 57.3°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottles.

[Example 5]
The same procedure as in Example 1 was carried out, except that the moving distance of the bottom mold was set to 5 mm. The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the sidewall portion was 0.968°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 57.4°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottle.

[Example 6]
The same procedure as in Example 1 was carried out, except that the moving distance of the bottom mold was set to 10 mm. The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the side wall portion was 0.969°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 57.2°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottle.

[Example 7]
The same procedure as in Example 1 was carried out, except that the moving distance of the bottom mold was set to 22 mm. The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the side wall portion was 0.962°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 57.5°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships show that the half width (X) is 1.220° or less and satisfies the above formula (1). Table 1 shows the blow moldability, 1.5 m drop test results, and heat shrinkability results of the obtained bottles.

[Comparative Example 1]
The procedure of Example 1 was repeated except that the stretch blow molding was carried out without moving the bottom mold. The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the sidewall portion was 0.963°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 57.5°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). These relationships were such that the half width (X) was 1.220° or less and satisfied the above formula (1). As for the contractility, the deformation of the bottom contact part and the bottom buckling increased the satisfactory content. Although not described in the evaluation method, deformation of the bottom shape due to bottom buckling was evaluated as x because container performance was not ensured.

[Comparative Example 2]
The procedure of Example 1 was repeated except that polylactic acid having an optically active isomer (d%) of d%=4.2% and an average weight molecular weight of 200,000 was used. The half width (X) of the diffraction peak obtained from wide-angle X-ray measurement of the side wall portion was 1.271°, and the thermal shrinkage starting point temperature (Y) obtained from thermomechanical analysis was 51.5°C. FIG. 1 shows the relationship between the half width (X) and the temperature at which thermal shrinkage starts (Y). In these relationships, the half width (X) was 1.220° or less and satisfied the above formula (1), but the thermal shrinkage of the body was large and the thermal shrinkage rate was x. .

[Comparative Example 3]
The same procedure as in Example 1 was carried out, except that the moving distance of the bottom mold was set to 34 mm. As the moving distance of the bottom die increased, the bottom part burst and the bottle shape could not be formed. It was speculated that this was because the appropriate draw ratio for polylactic acid was exceeded as the movement of the bottom mold increased. The results obtained are summarized in Table 1.

The polylactic acid container of the present invention has excellent heat resistance and mechanical strength as well as excellent transparency, and can be suitably used as a container for beverages.

1 polylactic acid container, 2 neck, 3 shoulder, 4 side wall, 5 bottom, 10 preform, 11 neck, 12 diameter reduction, 13 body, 14 bottom, 20 blow mold, 21 cavity mold, 22 bottom mold, 23 extension rod.

Claims (2)

A polylactic acid container obtained by biaxially stretching blow molding and heat setting a polylactic acid preform having an optically active isomer (d) content of 2.5 % or less,
The bottom portion of the container includes a central flat portion, an annular ground portion, an inner raised portion rising from the annular ground portion to the inner side of the container, and an inclined portion connecting the inner raised portion to the central flat portion,
The side wall of the container has a half width (X) of a diffraction peak at 2θ = 10 to 25° determined by wide-angle X-ray measurement in the range of 0.624° to 0.970 °,
A container made of polylactic acid, wherein the inner rising portion has a diffraction peak at 2θ=10 to 25° determined by wide-angle X-ray measurement. In a method for producing a polylactic acid container comprising biaxial stretch blow molding and heat setting a preform made of polylactic acid having an optically active isomer (d) content of 2.5 % or less,
The bottom portion of the container includes a central flat portion, an annular ground portion, an inner raised portion rising from the annular ground portion to the inner side of the container, and an inclined portion connecting the inner raised portion to the central flat portion,
The blow mold has a cavity mold and a bottom mold movable in the axial direction of the container ,
At the initial stage of blowing the blow air, the bottom mold is placed at a position lower than the predetermined position in which the blow mold is closed, and the inner rising portion and the inclined portion are expanded below the lower end of the cavity mold. After stretching, the bottom mold is moved to a predetermined position where the blow mold is closed while applying a pressurized fluid, and the bottom of the container is calculated from the outer diameter ratio of the preform and the container. The product (DH × DL') of the longitudinal draw ratio (DL') calculated based on the transverse draw ratio (DH) and the moving distance (DL) of the bottom die is in the range of 4.0 to 10.0 and the above Stretching is performed so that the ratio (DH/DL') of the transverse draw ratio (DH) and the longitudinal draw ratio (DL') is within the range of 0.5 to 2.0, and the blow mold is set to 70 to By heat setting at a temperature of 150 ° C., the half width (X) of the diffraction peak at 2θ = 10 to 25 ° obtained by wide-angle X-ray measurement at the side wall is in the range of 0.624 ° to 0.970 °. A method for producing a polylactic acid container , wherein the inner rising portion has a diffraction peak at 2θ=10 to 25° determined by wide-angle X-ray measurement .

Images