JPH07308961A - Thermally molded processed product of polylactic acid polymer - Google Patents

Abstract

PURPOSE:To provide a thermally molded and processed product improved in fragility and good in transparency composed of a polylactic acid polymer being a degradable polymer. CONSTITUTION:A thermally molded and processed product of a polylactic acid polymer is obtained by molding a sheet with glass transition temp. of 35 deg. or higher composed of a polylactic acid polymer with a wt. average mol. wt. of 60,000 or more under such a condition that molding temp. is 50-90 deg.C and stretching area magnification is 2-20 times and characterized by that the average of the in-plane orientation degree AP of the molded and processed part of the molded product is 2X10<-3>-30X10<-3>.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to poly-L-lactic acid and poly-D.
-A thermoformed product such as a degradable blister container or a PTP container made of polylactic acid-based polymer such as lactic acid or a copolymer thereof.

[0002]

2. Description of the Related Art Blister processed products, which are widely used for display and packaging of various products, are made by forming a resin sheet and then forming the sheet by a thermoforming method such as vacuum forming or pressure forming. It is generally made by. The blister processed product is preferably transparent so that the product inside can be seen through the package. From this point of view, sheets of polyvinyl chloride, polyethylene terephthalate, polystyrene and the like are often used as the material sheets for the blister processed products that are actually used.

Further, a container for PTP (press through pack) packaging used for packaging tablets, capsules and the like of pharmaceuticals is also formed by the same thermoforming method, and as a material sheet, transparency, formability and steam are used. From the viewpoint of barrier properties, sheets of polyvinyl chloride, polyethylene terephthalate, polypropylene, etc. are often used.

However, since these materials are chemically and biologically stable, they remain and accumulate with almost no decomposition even when left in a natural environment. These not only scatter in the natural environment and pollute the living environment of plants and animals,
Even if it is landfilled, it remains without being decomposed and shortens the life of the landfill.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a thermoformed product which has no problems of disposal and environmental pollution, is tough and has good transparency, and is excellent in shape stability over time. However, the gist is that the weight average molecular weight is 60,0.
A sheet made of a polylactic acid-based polymer having a temperature of 00 or higher and having a glass transition temperature of 35 ° C. or higher is molded at a molding temperature of 50 to 90
Molded in the range of 2 ° C. and a draw area ratio of 2 to 20, and the average in-plane orientation degree ΔP of the molded portion of the molded product is 2 × 1.
It is a thermoformed product of a polylactic acid polymer characterized by being in the range of 0 ⁻³ to 30 × 10 ⁻³ .

[0006] It is known that polylactic acid has a so-called biodegradability in which hydrolysis is naturally carried out in the soil, the original form is not left in the soil, and then the product is harmlessly decomposed by microorganisms. However, the polylactic acid-based polymer has brittleness, and it is difficult to use it as it is in the form of a sheet, but in the present invention, the molecular orientation is imparted to the molding processed portion by thermoforming, and the unmolded portion is formed. Since a support such as paper comes into contact with the product, a tough thermoformed product that can withstand distribution and storage as a whole can be obtained.

The present invention will be described in detail below. The polylactic acid-based polymer used in the present invention is polylactic acid or a copolymer of lactic acid and another hydroxycarboxylic acid, or a mixture thereof, and other polymer materials within a range that does not impair the effects of the present invention. May be mixed. In addition, additives such as plasticizers, lubricants, inorganic fillers, and ultraviolet absorbers for the purpose of adjusting molding processability and physical properties of sheets and processed products,
It is also possible to add modifiers.

Lactic acid includes L-lactic acid and D-lactic acid, and other hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid and 4-hydroxyvaleric acid. Typical examples include 6-hydroxycaproic acid and the like.

As these polymerization methods, any known method such as condensation polymerization method and ring-opening polymerization method can be adopted. Furthermore, a small amount of a chain extender for the purpose of increasing the molecular weight, for example, You may use a diisocyanate compound, a diepoxy compound, an acid anhydride. The weight average molecular weight of the polymer is 60,000 to 1,000,
The range of 000 is preferable, and if it is less than the range, practical physical properties are hardly expressed, and the sheet cannot retain strength during thermoforming. On the other hand, if it exceeds, the melt viscosity becomes too high and the moldability becomes poor.

The raw material sheet of the thermoformed product of the present invention is formed into a sheet by a general melt-forming method such as an extrusion method, a calendering method and a pressing method after sufficiently drying these polymers to remove water. It is obtained by molding and then quenching. Practically, it is preferable to bring the polymer melt-extruded into a sheet into contact with a rotating casting drum (cooling drum) to quench it. It is suitable that the temperature of the casting drum is 50 ° C. or lower. If the temperature is higher than 50 ° C., the polymer adheres to the casting drum and it becomes difficult to take it off. Further, crystallization is promoted and spherulites develop to make transparency. As the temperature decreases, thermoforming becomes difficult. Therefore, it is preferable to rapidly cool the sheet within the above temperature range to obtain a substantially amorphous sheet.

The glass transition temperature of the obtained sheet is 3
It is important in the present invention that the temperature is 5 ° C or higher, particularly preferably 40 ° C or higher. When the glass transition temperature is lower than 35 ° C., it is not preferable because the dimension tends to change with time at room temperature after molding into a thermoformed product. Further, spherulites grow on the sheet or the processed product while it is left at room temperature, which makes it difficult to form the sheet, and the processed product causes problems such as brittleness and reduced transparency. The glass transition temperature mainly depends on the composition of the polylactic acid-based polymer, the molecular weight, the content of oligomers, and the kind and amount of additives such as a plasticizer.

Next, thermoforming will be described. The sheet obtained as described above, infrared heater, hot plate heater,
It is preheated to the molding temperature with hot air and then thermoformed. As the thermoforming method, there are a vacuum forming method, a plug assist forming method, a pressure forming method, a male / female forming method, a method of deforming a sheet along the forming male die, and then expanding the forming male die. The thickness of the sheet is not particularly limited as long as it can be used in a usual thermoforming technique. Specifically, about 30 to 10
The range of 00 μm is included.

The thermoformed product comprises a thermoformed convex portion and a flat portion on which the sheet remains. Since the flat portion is not stretched during thermoforming, physical properties are not improved and the strength is poor, but it is usually supported by pasting paper or the like. On the other hand, the convex portion is required to have high strength because of its morphology, and it is necessary to improve brittleness. In the present invention, the strength and the brittleness can be improved by increasing the molecular orientation of the protrusions. The degree of in-plane orientation ΔP is a measure of the degree of molecular orientation.

The in-plane orientation degree ΔP represents the orientation degree in the surface direction with respect to the thickness direction of the wall of the molded part, and is usually calculated by the following formula by measuring the refractive index in the directions of three orthogonal axes. ΔP = {(γ + β) / 2} −α (α <β <γ) where γ and β are biaxial refractive indices orthogonal to the sheet surface (wall surface), and α is a refractive index in the sheet thickness direction. is there.

ΔP depends on the crystallinity and the crystal orientation, but largely depends on the in-plane molecular orientation. That is, by increasing the molecular orientation with respect to the in-plane, ΔP which is less than 1.0 × 10 ⁻³ in the non-oriented sheet is defined in the present invention. 2
It can be increased to × 10 ^-3 or more, preferably 3 × 10 ^-3 or more. However, if ΔP exceeding 30 × 10 ⁻³ is attempted, stable molding cannot be performed and the sheet frequently breaks.

Further, it is important that the thermoformed products such as the blister processed products are transparent for their use, and it is necessary to avoid whitening during the thermoforming. The transparency can be represented by haze, and in the present invention, a thermoformed product having a haze of 20% or less, preferably 10% or less can be obtained.

Thermoforming to obtain a processed product having a ΔP and haze in the above range is within a molding temperature range of 50 to 90 ° C., and a stretched area ratio of the molded part is 2 to 20 times, preferably 4 to 15 times. Do so that the range is doubled. If the molding temperature (that is, the stretching temperature) is less than 50 ° C., the softening of the sheet is insufficient, the sheet cannot be thermoformed, and the sheet is broken, or the adhesion to the mold is insufficient. On the other hand, when the temperature is higher than 90 ° C., ΔP is small and the strength is not improved, and the sheet may draw down due to heating to make molding difficult, or crystallization may be whitened to lose transparency.

If the stretched area ratio of the molded portion is less than 2 times, ΔP does not reach 2 × 10 ^-3 and no improvement in physical properties is observed. On the other hand, if the stretched area ratio exceeds 20 times, the molded product is broken, and a molded product cannot be stably obtained.

The thermoformed product of the present invention requires the transparency of contents such as blister packaging and PTP containers by utilizing the strength / transparency of the processed part, the water vapor barrier property, etc. It is suitable for being used in contact with a support. For example, in the case of a blister package used for product packaging and display, it is customary to store the product in a convex shaped processed portion and attach a mount to the opening from the molded processed portion to the surrounding unprocessed portion. As the mount, in addition to cardboard, metal foil, various plastic sheets, etc. can be applied, but assuming that the blister processed product is discarded together with the mount, a biodegradable paper is suitable as the mount. Is. The mount is heat-sealed with a blister processed product, or an adhesive, preferably unvulcanized natural rubber,
It is closely joined by a protein system such as casein and a biodegradable adhesive such as starch and glue. Also,
1 on both sides of the unformed part (so-called flange) on the back side
It may be bent at 80 ° and another mount may be slidably mounted in the groove.

The PTP container is usually sealed with an aluminum foil lid member. Since aluminum does not pollute the environment and is naturally reducible, it can be discarded even when it is bonded to the polylactic acid-based polymer sheet. Examples will be shown below, but the present invention is not limited thereto. The measured values shown in the examples were measured and calculated under the following conditions.

(1) Average value of ΔP Sheet-shaped from a portion corresponding to the stretched area ratio of the molded portion, that is, a portion having a thickness corresponding to a value obtained by dividing the thickness of the original sheet by the stretched area ratio. The sample of is cut out and the refractive index (α, β,
γ) was measured and calculated by the following formula.

ΔP = {(γ + β) / 2} −α (α <β <γ) γ: Maximum refractive index in the sample surface β: Refractive index in the sample in-plane direction orthogonal thereto α: Refraction in the sample thickness direction rate

(2) Stretching Area Magnification The surface area of the molded portion after molding was divided by the area of the stretched original sheet to obtain the stretching area ratio. (3) Haze It was measured based on JIS-K7105. (4) Moldability Good stretchability during thermoforming is indicated by ◯, stretchable but uneven stretching is indicated by Δ, and breakage during stretching is indicated by x.

(5) Appearance After molding, a product having a good appearance is represented by ◯, a product having a slight amount of granular whitening parts is represented by Δ, and a product having flow-like unevenness or streak-like whitening parts is represented by x. (6) Brittleness Judgment by touch is indicated by ○ when brittleness is not felt, Δ when slightly brittle, and X when brittle. (7) Comprehensive evaluation Comprehensively judging the above-mentioned evaluation items (4), (5), and (6), good ones are ○, slightly inferior ones, and inferior ones ×.
And (8) Glass transition temperature Using DSC-7 manufactured by Perkin Elmer, JIS-K71
21 was measured.

[0025]

【Example】

(Example 1) Poly L having a weight average molecular weight of about 200,000
-Lactic acid is melt extruded from a T-die at 180 ° C and rapidly cooled on a casting drum kept at 35 ° C to give a thickness of 500μ.
An unstretched sheet of m was obtained. The glass transition temperature is 50 ° C.

The obtained sheet was clamped in a thermoforming machine (PLAVAC-FE36PH type manufactured by Sanwa Kogyo Co., Ltd.), preheated to the forming temperature by an infrared heater, and then pushed into the mold by a plug to carry out preforming, and then. The inside of the mold was evacuated to form a cup. The samples shown in Table 1 were obtained by changing the molding temperature and the stretching area ratio. The stretched area ratio was changed by changing various plugs and molds.

[0027]

[Table 1]

From the results in Table 1, No. Nos. 3 and 6 were within the range of the molding conditions of the present invention, brittleness was improved, and molded articles having excellent transparency were obtained. No. 5 is slightly brittle, N
o. No. 8 has a low transparency and some defects, but is excellent in moldability and judged to be in a practical range. On the other hand, No. No. 2 had a low molding temperature and could not be molded satisfactorily. In No. 4, the draw ratio was low and ΔP did not increase, and the brittleness was not improved. No. No. 7 has a too high draw ratio and cannot be stably molded. No. 9
In Nos. 10 to 10, the molding temperature was too high, the moldability was poor, and there were problems in brittleness and transparency.

(Embodiment 2) Embodiment 1, No. 1 From the side surface of the cup-shaped molded product of No. 5, a 30 mm x 30 mm sheet-shaped sample is cut out from the side and from the bottom side, a 30 mm x 30 mm sheet-shaped sample is cut out and placed in a constant temperature bath at 30 ° C for 1 month to measure its dimensions. When measured and calculated the shrinkage ratio with respect to the original dimension, it was 2.5% in the longitudinal direction on the side surface of the molded part, 2.0% in the lateral direction, and 1.6% x 1.8% on the bottom surface, which was It was confirmed that the dimensional change was small and the original size was maintained.

COMPARATIVE EXAMPLE 1 L-lactic acid (85% by weight) and caprolactone (15% by weight) were used, and the average molecular weight was about 200.
000 polylactic acid copolymer was melt extruded from a T-die at 170 ° C. and rapidly cooled on a casting drum kept at 25 ° C. to obtain an unstretched sheet. Glass transition temperature is 33 ° C
Met.

The obtained sheet was No. 1 in Example 1. When heat-molded into a cup shape under the same conditions as in Example 5, and the shrinkage ratio was measured in the same manner as in Example 2, the side surface of the molded portion was 26% in the vertical direction, 22% in the horizontal direction, and 19% in the bottom surface.
It was 1%, and the dimensional change with time was large, and the molding portion was greatly shrunk.

(Comparative Example 2) Weight average molecular weight of about 50,000
0 poly L-lactic acid was melt extruded from a T die at 180 ° C.,
It was rapidly cooled on a casting drum kept at 35 ° C. to obtain an unstretched sheet having a thickness of 500 μm. The glass transition temperature is 50 ° C.

The obtained sheet was processed in the same manner as in Example 1,
When an attempt was made to perform thermoforming at a forming temperature of 65 ° C., the tension in the softened state was low, the sheet was drawn down, making it difficult to form, and uneven thickness and breakage occurred.

[0034]

According to the present invention, by molding a thermoformed article having specific characteristics from a polylactic acid polymer which is a degradable polymer, brittleness is improved and strength is improved in the molded portion. It is possible to obtain a transparent thermoformed product which is excellent and shows the same practical strength as the unformed part comes into contact with the support and has a small dimensional change with time.

Claims (1)

[Claims] 1. A sheet made of a polylactic acid-based polymer having a weight average molecular weight of 60,000 or more and having a glass transition temperature of 35 ° C. or more is molded at a molding temperature of 50 to 90 ° C. and a stretching area ratio of 2 to 20 times. The average in-plane orientation degree ΔP of the molded portion of the molded product is 2 × 10 ⁻³ to 30 × 1.
A thermoformed product of a polylactic acid-based polymer characterized by being in the range of 0 ^-3 .