JPH0858796A - Biodegradable composite container and manufacture thereof - Google Patents

Abstract

PURPOSE: To save a resin to be used without losing its strength and physical properties of a container by combining a draw-blown container made of biodegradable plastic and paper. CONSTITUTION: Polylactic acid and fatty acid ester which are highly suitable for draw-blow molding is preferably used as biodegradable plastic and molded by draw-blowing. At this time, paper is preferably inserted into a metallic mold in advance and draw-blow molded. Paper 6 to be combined with a draw- blow molded container 5 is a precursor of a container which has been shaped in advance, while a pattern or characters may be printed on a surface and used as a label. Thus an amount of the biodegradable plastic to be used can be reduced as well as no problem occurs in strength, whereby an entire container which is made unnecessary can be biodegraded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable plastic container which can be decomposed by burying it in soil, immersing it in sewage, etc., and a method for producing the same.

[0002]

Biodegradable plastics such as polylactic acid, aliphatic polyesters, hydroxypolyesters, and polycaptolactones are known as resins that are hydrolyzed and biodegraded by microorganisms when they are buried in soil or immersed in sewage. ing.

However, the resin has a problem in economic efficiency because the polymerization method has not been clarified, the polymerization is carried out by a microorganism, and the catalyst is expensive.

For these reasons, measures have been taken to reduce the amount of resin used when molding by using the resin. However, there is a limit to the molding of the container in terms of strength and physical properties of the molded product. For example, when the contents are filled, the container swells and the buckling strength becomes weak.

On the other hand, as a conventional method for reducing the amount of plastic, there is known a method in which a plastic container, which is reduced in weight and thinned in thickness and has a problem in strength, is covered with paper or the like to maintain the strength. However, when the container of the method is no longer needed, the plastic does not decompose even if it is buried in the soil, etc., and the volume does not decrease, which is often a problem in the processing method.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems. The problem is that the amount of biodegradable plastic used is small.
Moreover, it is an object of the present invention to provide a biodegradable composite container and a method for producing the same, which has no problem in strength (particularly, swelling of the barrel when filled with contents) and can biodegrade the entire container that is no longer needed.

[0007]

In order to solve this problem, the present invention is characterized in that a stretch blow container made of biodegradable plastic is covered with paper at least partially or entirely. A degradable composite container is provided. Also provided is a biodegradable composite container in which the paper is a label, a preformed container precursor, and the biodegradable plastic is polylactic acid or an aliphatic polyester. Further, the present invention provides a method for producing a biodegradable composite container, which comprises inserting the paper in advance into a mold for stretch-blowing a biodegradable plastic and performing stretch-blow molding.

The details of the present invention will be described below. The biodegradable plastic used in the present invention may be any thermoplastic biodegradable plastic such as polylactic acid, aliphatic polyester, hydroxypolyester, polycaptolactone, etc., preferably polylactic acid having high stretch blow molding suitability,
Aliphatic polyester is used.

As polylactic acid, even a single polylactic acid,
Polylactic acid, which is a copolymer with tartaric acid, glycolic acid, α-malic acid, polyethylene glycol, lactone or the like, may be used.

The aliphatic polyester may be an aliphatic polyester obtained by polycondensation of a dicarboxylic acid such as adipic acid, succinic acid or oxalic acid and a glycol such as ethylene glycol, propylene glycol or butanediol.

As a method of molding these biodegradable resins,
Stretch blow molding is used. Stretch blow molding is the main feature of the present invention. By stretching the biodegradable plastic, the strength of the container can be increased and the wall thickness can be reduced, so the amount of resin used in the biodegradable plastic can be reduced. Can be reduced.

FIG. 1 shows a conceptual diagram of stretch blow molding of biodegradable plastic. The preform comprises a screw part (1), a flange part (2) which plays a role of supporting the preform at the time of stretch molding, and a bottomed cylindrical part (3) of the preform body.

As a stretch blow molding method, a cold parison method in which a preform molding step and a stretch blow molding step are divided into two steps is also used. In the hot blow method, the preform molding step and the stretch blow molding step are performed in a series of steps. The parison method can also be used to mold biodegradable plastics.

The paper to be combined may be used as a label by printing a picture or letters on the surface. Even if the whole container is not covered, as shown in FIG. 3, the strength can be improved by covering only the weak portion of the biodegradable plastic container. As a method of combining with a paper, two methods are conceivable: a method of covering a stretch blow container with paper after molding and a method of inserting paper at the time of molding the stretch blow container.

[0015]

The thickness of the stretch-blow molded container of biodegradable plastic is preferably low in the amount of resin used and thin in terms of the decomposability when it is no longer needed and the economical efficiency, but the container strength is weak. Become. In the present invention, in order to maintain the strength of the container, correction is performed using paper. FIG. 2 shows a conceptual diagram of a composite container of a stretch blow container and paper, but the composite container of the present invention is not limited to these and various forms are possible.

[0016]

【Example】

Example 1 As a biodegradable resinous plastic, glass transition temperature = 56.8 ° C., crystallization temperature = 107.8 ° C., melting point = 160.3 ° C., weight average molecular weight / number average molecular weight (Mw).
/Mn)=2.4 15 g of polylactic acid was injection molded at a cylinder temperature of 200 ° C. and a mold temperature of 15 ° C., and the diameter was 30 m.
m flange, 27.4 mm diameter body, length 120
A preform (bottom parison) having a thickness of 2.2 mm and a thickness of 2.2 mm was obtained.

The preform is reheated to 94 ° C. (reheating temperature) and gradually cooled to a uniform preform temperature of 75 ° C.
(Stretching temperature), stretching rod pressure; 7 kgf / c
m ^2, the primary blow; 3.3 kgf / cm ^2, 1s, secondary blow; and stretch blow molded at 15 kgf / cm ^2, 3s, longitudinal stretching ratio 2.1 times, transverse stretching ratio 2.6 times, bottles A 1000 ml stretch blow container made of polylactic acid having a height of 250 mm and a diameter of 78 mm was obtained. The container thus obtained had a transparent appearance and a wall thickness of 0.2 mm. The preform was also transparent.

The resulting stretch blow container made of polylactic acid was put in a paper box as shown in FIG. 2 (1) to make a composite container.
The results of measuring the buckling strength and the drop strength of the container are shown in Table 1. When the container was buried in soil for 6 months, the strength of the container was severely reduced and the shape-retaining ability was lost. However, the appearance of the container left in the air for 6 months did not change.

<Example 2> When the stretch blow container made of polylactic acid of Example 1 is molded, a paper box is previously inserted into the mold in the stretch blow molding step, and stretch blow molding is performed. A composite container having a bottle height of 250 mm, a diameter of 78 mm, and a capacity of 900 ml as shown in 2 (2) was obtained. The stretched blow bottle made of polylactic acid in the composite container had a wall thickness of 0.2 mm. The results of measuring the buckling strength and the drop strength of the container are shown in Table 1. When the container was buried in soil for 6 months, the strength of the container was severely reduced and the shape-retaining ability was lost. However, the appearance of the container left in the air for 6 months did not change.

Example 3 As a biodegradable plastic, weight average molecular weight / number average molecular weight = 3, difference between melting temperature and recrystallization temperature = 30.4 ° C. (melting temperature = 93.8 ° C., recrystallization temperature) = 63.4 ° C.), heat of fusion = 35.9 J / g aliphatic polyester 1 composed of dicarboxylic acid and glycol
0g injection molded, 30mm diameter flange, diameter 2
A preform (bottom parison) having a body portion of 8 mm, a length of 100 mm, a thickness of 2.0 mm and a weight of 10 g was obtained.

The preform is reheated to 94 ° C. (reheating temperature) and gradually cooled to a uniform preform temperature of 70 ° C.
(Stretching temperature), stretching rod pressure; 7 kgf / c
m ^2, the primary blow; 3.3 kgf / cm ^2, 2s, secondary blow; and stretch blow molded at 30 kgf / cm ^2, 5s, longitudinal stretching ratio 1.4 times, transverse stretching ratio 2.2 times, bottles A 350 ml stretch blow container made of an aliphatic polyester having a height of 140 mm and a diameter of 62 mm was obtained. The obtained stretch blow container made of aliphatic polyester had a wall thickness of 0.3 mm.

The stretch blow container made of the aliphatic polyester was put in a carton to obtain a composite container shown in FIG. 2 (3). The results of measuring the buckling strength and the drop strength of the container are shown in Table 1.
Shown in When the container was buried in soil for 6 months, the strength of the container was severely reduced and the shape-retaining ability was lost. However, the appearance of the container left in the air for 6 months did not change.

<Comparative Example 1> The stretch blow container made of polylactic acid molded in Example 1 was placed in a paper box without buckling strength.
The results of measuring the drop strength are shown in Table 1. Compared with the composite container of Example 1, both buckling strength and drop strength were weak containers.

Comparative Example 2 A container having the same shape as the stretch blow container made of polylactic acid molded in Example 1 and having the same buckling strength and drop strength was obtained by direct blow molding.
The container was placed in a paper box in the same manner as in Example 1,
A composite container having the same shape as was obtained. Compared to the composite container of Example 1, the amount of biodegradable plastic used was 20 g, which was 5 g more than in Example 1.

<Comparative Example 3> 16 g of polyethylene terephthalate was used in place of the polylactic acid of Example 1 to obtain a composite container similar to that of Example 1. When the container was buried in the soil, the surrounding paper was broken for 6 months, but the strength of the stretch-blown container made of polyethylene terephthalate was not decreased even after 1 year. The above results are summarized in Table 1.

[0026]

[Table 1]

[0027]

As described above in detail, the biodegradable composite container in which the stretch blow container using the biodegradable plastic and the paper are combined and the method for producing the composite container, the container strength and the physical properties are not impaired and the biodegradability is improved. The amount of plastic resin used can be reduced, and it has become possible to solve economic problems and strength problems.

[0028]

[Brief description of drawings]

FIG. 1 is a conceptual diagram of stretch blow molding.

FIG. 2 is an explanatory view showing the shape of an embodiment of a biodegradable composite container.

FIG. 3 is an explanatory view showing the shape of an embodiment of a biodegradable composite container.

FIG. 4 is an explanatory view showing a cross-sectional shape of an example of the biodegradable composite container.

[Explanation of symbols]

1 ... screw part 2 ... flange part 3 ... body part bottomed cylindrical part 4
... Stretching rod 5 ... Biodegradable stretch blow container 6 ... Paper 7 ... Biodegradable composite container

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29B 17/00 9350-4F B29L 22:00

Claims (5)

[Claims] 1. A biodegradable composite container, characterized in that a stretch blow container made of biodegradable plastic is at least partially or entirely covered with paper. 2. The biodegradable composite container according to claim 1, wherein the paper is a label. 3. The biodegradable composite container according to claim 1, wherein the paper is a preformed container precursor. 4. The biodegradable composite container according to claim 1, wherein the biodegradable plastic is polylactic acid or an aliphatic polyester. 5. A method for producing a biodegradable composite container, characterized in that a stretch blow container made of biodegradable plastic is at least partially or entirely covered with paper. A method for producing a biodegradable composite container, which comprises inserting the biodegradable plastic into a mold in advance for stretch blow molding and performing stretch blow molding.