JP2001088261A - Biodegradable heat-shrinkable multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable heat-shrinkable multilayer film which has superior transparency, gloss and slip performance and can be thermally sealed. SOLUTION: The film having a specific shrinkage factor is obtained by stretching a multilayer film at least in one direction. The multilayer film has outer layers of a mixture C consisting of a polylactic acid polymer A containing an L-lactic acid and a D-lactic acid by a composition ratio of 94:6-79:21, and an aliphatic polyhydric alcohol/aliphatic dicarboxylic acid copolymer B synthesized essentially from an aliphatic polyhydric alcohol and an aliphatic dicarboxylic acid or its derivative. A ratio of the B exceeds 0 wt.% and is not larger than 30 wt.%. Moreover, at least one layer is provided between the outer layers, which consists of the A and/or B. A ratio of the A and B in all layers of the multilayer film holds A:B=30:70-75:25 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat-shrinkable multilayer film having biodegradability.

[0002]

2. Description of the Related Art Conventionally, a large amount of heat shrinkable film has been used in the field of packaging. Examples of the synthetic resin used for the heat shrinkable film include a polypropylene resin, a polyethylene resin, a vinyl chloride resin, and a polystyrene resin. However, when heat-shrinkable films made of these synthetic resins are discarded into the natural environment after use, they do not decompose due to their chemical stability, remain in the natural environment for a long time, and cause pollution of the natural environment. It has contributed. Recently, composting of garbage has been promoted from the viewpoint of garbage reduction. However, the film used in the heat shrink wrapping field has a very small thickness. Yes, hindering composting.

Under these circumstances, Japanese Patent Application Laid-Open No. 5-221790 discloses a heat-shrinkable film for labels as a biodegradable heat-shrinkable film. However, the film proposed by the publication is a high-temperature shrinkable film having a high shrinkage temperature, and is required to prevent deterioration of contents caused by heat when shrinking the film, such as shrinkable packaging of general goods and foods. It is difficult to use for applications and can only be used for specific applications. In addition, improvement of the operation speed in the automatic packaging process using the heat shrink film,
Alternatively, from the viewpoint of preventing fusion between products after heat shrink wrapping, slipperiness is mentioned as a performance required for this type of film. However, the glass transition temperature of the ordinary polylactic acid-based polymer is approximately 50 to 60 ° C., which is close to the environmental temperature in the automatic packaging process, and the temperature of the heat shrinking process (temperature of the heat shrinking tunnel). There were problems of workability and heat fusion between packaged products.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a biodegradable heat-shrinkable multilayer film which is excellent in transparency, gloss, sliding performance and heat seal. That is the task.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that a specific polylactic acid-based polymer and a specific aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer have been obtained. By using a multilayer film having a resin layer as a constituent layer as a base layer, the film can be stretched, and as a result, the heat shrinkage required for the shrink wrapping material, the sliding performance, and the transparency are excellent. It was found that a heat-shrinkable film capable of heat sealing was obtained,
The present invention has been reached. That is, the present invention relates to L-
A polylactic acid-based polymer (A) having a composition ratio of lactic acid to D-lactic acid of 94: 6 to 79:21, and an aliphatic polyhydric alcohol mainly synthesized from an aliphatic polyhydric alcohol and an aliphatic dicarboxylic acid or a derivative thereof Alcohol / aliphatic dicarboxylic acid copolymer (B), wherein the ratio of aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) exceeds 0% by weight,
Weight% or less of both outer layers comprising the mixture (C), and a polylactic acid-based polymer (A) between the outer layers, and / or
It has at least one layer composed of an aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B), and comprises a polylactic acid-based polymer (A) and an aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer in all layers. The ratio of the combined (B) is (A):
(B) = a film obtained by stretching a multilayer film having a ratio of 30: 70% by weight to 75: 25% by weight in at least one direction, wherein the shrinkage after immersion in glycerin at 90 ° C. for 30 seconds. Is the MD and TD of the film
An object of the present invention is to provide a biodegradable heat-shrinkable multilayer film characterized by being at least 20% in at least one of the directions.

In a more preferred embodiment, the resin composition ratio of both outer layers is (A) :( B) = 99: 1% by weight to 7%.
The biodegradable heat-shrinkable multilayer film described above is characterized in that it is 0: 30% by weight.

Further, as an even more preferred form, an aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B)
Is a polybutylene succinate-adipate copolymer, wherein the biodegradable heat-shrinkable multilayer film is provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in detail. The polylactic acid-based polymer (A) used in the present invention comprises:
The polylactic acid-based polymer has a composition ratio of L-lactic acid and D-lactic acid of 94: 6 to 79:21. In addition, as such a polylactic acid-based polymer, "EcoPLA6310D" (trade name) commercially available from Cargill can be exemplified.

When the composition ratio of L-lactic acid exceeds 94, the difference in melting point between the aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) becomes large and the polylactic acid-based polymer (A) and the aliphatic When a multilayer unstretched raw material of the polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) is formed, thermal deterioration of the aliphatic polyester (B) is caused, and physical properties of the obtained heat shrinkable film are reduced, which is preferable. Absent. Further, in a layer using a mixture of the aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) and the polylactic acid-based polymer (A), the compatibility of both resins is deteriorated and the transparency of the entire film is reduced. It is not preferable because it causes a decrease. Conversely, if the composition ratio of L-lactic acid is less than 79, heat resistance is lowered, and a film having heat shrink properties suitable for the packaging field cannot be obtained, which is not preferable.

The aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) used in the present invention is an aliphatic polyester mainly synthesized from an aliphatic polyhydric alcohol and an aliphatic dicarboxylic acid or a derivative thereof. More specifically, polybutylene succinate obtained by increasing the molecular weight of a polyester resin obtained using 1,4-butanediol as an aliphatic polyhydric alcohol component and succinic acid as an aliphatic dicarboxylic acid component using polyisocyanate, 1,4-butanediol as a dihydric alcohol component,
It is a polybutylene succinate-adipate copolymer obtained by increasing the molecular weight of a polyester resin obtained from succinic acid and adipic acid as an aliphatic dicarboxylic acid component using a polyisocyanate. In addition, among polybutylene succinate and polybutylene succinate-adipate copolymer, if a polybutylene succinate-adipate copolymer is used, it is possible to set the stretching temperature to be low, and thus better low-temperature shrinkage can be obtained. It is preferably used because it is obtained. Incidentally, such aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymers are commercially available from Showa Polymer Co., Ltd. under the trade names “Bionore # 1001”,
Bionole # 3001 ″, etc. Hereinafter, this type of aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer is simply referred to as aliphatic polyester.

In the present invention, the resin constituting both outer layers is a mixture (C) of a polylactic acid-based polymer (A) and an aliphatic polyester (B), and the aliphatic polyester occupied in the mixture (C). The proportion of (B) is 0% by weight.
And less than 30% by weight.

The resin constituting both outer layers is (A):
(B) = 99: 1 to 70: 30% by weight is preferred. Further, (A) :( B) = 99: 1% by weight to 8
0: 20% by weight is more preferred.

By using a mixture (C) of a polylactic acid-based polymer (A) and an aliphatic polyester (B) as the resin for both outer layers, the stretching behavior of both resins differs during stretching. The surface of the obtained film is appropriately roughened, the coefficient of friction is reduced, and the sliding property is improved. However, when the proportion of the aliphatic polyester (B) exceeds 30% by weight, the transparency and gloss of the stretched film tend to deteriorate. When the ratio of the polylactic acid-based polymer (A) and the aliphatic polyester (B) is within the above range, the mixture (C) of the polylactic acid-based polymer (A) and the aliphatic polyester (B) in both outer layers is used. The composition of ()) may not be the same.

When the aliphatic polyester (B) is used alone as the resin for both outer layers, the transparency and gloss of the stretched film are undesirably deteriorated.

The weight ratio of the polylactic acid-based polymer (A) and the aliphatic polyester (B) in the whole film is (A) :( B) = 30: 70% by weight to 75: 25% by weight. is there. If the proportion of the polylactic acid-based polymer (A) is less than this range, the stretch processability is lowered and the low-temperature shrinkage is not developed, which is not preferable. On the other hand, when the proportion of the polylactic acid-based polymer (A) exceeds this range, the flexibility of the obtained film is undesirably reduced.

Incidentally, by adding a lubricant to the resin of both outer layers, it is possible to improve the slipperiness of the film. However, when an aliphatic amide-based or metal soap is used as a lubricant, the biodegradability of the obtained heat-shrinkable film may be significantly impaired depending on the kind or the amount of addition. Therefore, it is preferable not to add a lubricant or to keep the addition amount to the minimum necessary. That is, as shown in the present invention, a mixture (C) of a polylactic acid-based resin (A) and an aliphatic polyester (B) is formed on both outer layers.
The use of retains practically no problem sliding performance,
This is important in obtaining a heat-shrinkable film having good biodegradability.

On the other hand, as the resin used in the layers other than the outer layers of the present invention, the weight ratio of the polylactic acid-based polymer (A) and the aliphatic polyester (B) in the whole film is as follows.
(A): (B) = 30: 70% by weight to 75: 25% by weight
Can be selected freely within the range When the mixture of the polylactic acid-based polymer (A) and the aliphatic polyester (B) used for the layers other than both outer layers is (D), the configuration of the multilayer film of the present invention is (C) / (B) / ( C), (C) / (D)
/ (C), (C) / (D) / (B) / (D) / (C),
(C) / (B) / (D) / (B) / (C), (C) /
(D) / (A) / (D) / (C), (C) / (B) /
(D) / (C), etc., but if it is essential that (C) be located in both outer layers, it can be arbitrarily set according to the purpose.

The mixture (D) of the polylactic acid-based polymer (A) and the aliphatic polyester (B) used in the layers other than the outer layers is
Virgin materials of polylactic acid-based polymer (A) and aliphatic polyester (B) can be blended and used,
It is also possible to regenerate and reduce slitter loss and the like generated during film production.

Polylactic acid type polymer (A) used for both outer layers
The mixture (C) of the polyester and the aliphatic polyester (B) can be used by blending the virgin raw materials of the polylactic acid-based polymer (A) and the aliphatic polyester (B), as well as the slitter loss generated during film production. And the like can be regenerated and reduced. However, considering the deterioration of the resin due to heat history, the virgin raw materials of the polylactic acid-based polymer (A) and the aliphatic polyester (B) are blended in both outer layers, which affect the transparency, gloss, and slipperiness. It is more preferable to use.

It should be noted that, within a range not to impair the object of the present invention,
In addition to the above-mentioned polylactic acid-based polymer (A) and aliphatic polyester (B), other kinds of biodegradable resins such as polycaprolactone-based resin, starch-based resin, polyhydroxybutyrate, lubricant, plasticizer, and anti-blocking Agent, anti-fog agent,
Additives such as antioxidants, fillers and colorants can be used in combination.

The method for producing the biodegradable heat-shrinkable multilayer film of the present invention by using the above-mentioned composition is as follows.
After forming the composition into a film by a known method such as an inflation method or a T-die method, a method of performing uniaxial stretching, simultaneous biaxial stretching, or sequential biaxial stretching by a tenter method may be used. Further, there is a method in which tubular biaxial stretching is performed subsequent to film formation by an inflation method.

The film obtained by stretching according to the above method is used for packaging a heat-shrinkable film made of a conventional polypropylene resin, polyethylene resin, vinyl chloride resin, polystyrene resin, or the like. Heat-sealing with a machine and a sealing machine is possible.

On the other hand, the biodegradable heat-shrinkable multilayer film of the present invention has a shrinkage ratio after immersion in glycerin at 90 ° C. for 30 seconds of at least MD (vertical direction of film) and TD (horizontal direction of film) of the film. More than 20% in one direction. If the shrinkage is less than 20% in at least one of the MD and TD directions of the film, it cannot be applied to shrink wrapping applications. Accordingly, the stretching ratio at the time of the above stretching process is such that the shrinkage in at least one direction of MD and TD of the obtained film is 20 in accordance with the resin composition constituting the film and the heat shrinkage property of the target heat shrinkable film.
% Is appropriately selected so as to be not less than%.

The thickness of the biodegradable heat-shrinkable multilayer film of the present invention varies depending on the use, but is preferably about 5 to 300 μm.

[0025]

The present invention will be described more specifically with reference to the following examples. Note that the present invention is not limited by the matters described below.

The polylactic acid-based polymer (A) and aliphatic polyester (B) used are as follows. -Polylactic acid 1: L-lactic acid / D-lactic acid = 89.5 / 10.
Polylactic acid-based polymer consisting of 5 (manufactured by Cargill, trade name:
EcoPLA6310D)..., Hereinafter abbreviated as PLA1.・ Polylactic acid 2: L-lactic acid / D-lactic acid = 98.6 / 1.4
Polylactic acid polymer (Cargill, trade name: E
coPLA4030D)... hereinafter abbreviated as PLA2. -Aliphatic polyester: polybutylene succinate-adipate copolymer (manufactured by Showa Polymer Co., Ltd., trade name: Bionole # 3001) ... hereinafter abbreviated as PBSA.

The following procedures were used to evaluate the transparency (haze), gloss (gloss), heat shrinkage, slipperiness, and heat sealability of the film. Transparency (haze): Measured with a haze meter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd. Gloss (gloss): Measured with a digital variable-angle gloss meter VG-1D manufactured by Nippon Denshoku Industries Co., Ltd. -Heat shrinkage: MD (vertical direction) by cutting the stretched film,
A test piece having a TD (lateral direction) of 100 mm is prepared.
After immersing this test piece in a glycerin constant temperature bath at 90 ° C. for 30 seconds, the dimensions of MD and TD of the test piece are measured, and the shrinkage is calculated using the following equation. Shrinkage (%) = 100 × (100−L) / 100 [L: length (mm) of test piece after immersion in glycerin at 90 ° C. for 30 seconds] Static coefficient of friction: slip manufactured by Tester Sangyo Co., Ltd. Measure with a tester.・ Heat sealing: Impulse sealing machine (fused type)
Is evaluated to determine whether sealing is possible. If sealing is possible, a seal portion is sampled with a width of 15 mm, and the breaking strength is measured at a tensile speed of 300 mm / min to measure the sealing strength.

[Examples 1 to 4] Using a co-extruder equipped with three single-screw extruders and a three-layer die, the structure of each layer and the structure of the whole film were as shown in Table 1. ,
PLA1 and PBSA were extruded and quenched with a casting roll to obtain an unstretched film having a thickness of about 300 μm. Next, using a biaxial stretching apparatus (Iwamoto Seisakusho Co., Ltd.), simultaneous biaxial stretching was performed at a stretching ratio of 4 times in both the longitudinal and transverse directions to obtain a heat-shrinkable multilayer film having a film thickness of 18 μm. The transparency (haze), gloss (gloss), heat shrinkage, slipperiness and heat sealability of the obtained film were evaluated. Table 1 shows the results.

[0029]

[Table 1]

From Table 1, it can be seen that the biodegradable heat-shrinkable multilayer films of the present invention shown in Examples 1 to 4 have good heat shrinkability, and also have good transparency, gloss, slipperiness and heat sealability. You can see that there is.

[Comparative Examples 1 to 5] Using a co-extruder equipped with three single-screw extruders and a three-layer die, the structure of each layer and the structure of the whole film were as shown in Table 2. ,
PLA1 and PBSA were extruded and quenched with a casting roll to obtain an unstretched film having a thickness of about 300 μm. Next, using a biaxial stretching apparatus (Iwamoto Seisakusho Co., Ltd.), simultaneous biaxial stretching was performed at a stretching ratio of 4 times in both the longitudinal and transverse directions to obtain a heat-shrinkable multilayer film having a film thickness of 18 μm. The transparency (haze), gloss (gloss), heat shrinkage, and slipperiness of the obtained film were evaluated. Table 2 shows the results.

[0032]

[Table 2]

As shown in Comparative Example 1 in Table 2, when PLA1 was used for both outer layers, heat shrinkage, transparency (haze), and gloss (gloss) were very excellent.
As a result, a film comparable to that obtained was obtained. However, the coefficient of static friction is 1.25, which is inferior in terms of sliding performance.

As shown in Comparative Example 2, P
The weight ratio of LA1 and PBSA is the same as in Examples 1 to 5
0: 50% by weight, and at the same time, the P of both outer layers
A film (substantially a single-layer film) using the mixture (C) in which the ratio of LA1 to PBSA was also set to 50: 50% by weight was a result that the stretchability was not inferior to that of the example. It can be seen that transparency (haze) and gloss (gloss) are inferior to those of the examples.

As shown in Comparative Examples 3 to 5, the weight ratio of PLA1 and PBSA in all layers was set to be equal to those in Examples 1 to 3, and PLA1: PBSA = 6 in both outer layers.
In the film using the mixture of 0: 40% by weight to 0: 100% by weight, the stretchability was as good as that of the example, but the transparency (haze) and gloss (gloss) were the same as those of the example. It turns out that it is inferior.

From the above results, in order to obtain a heat-shrinkable film having transparency (haze), gloss (gloss) and sliding performance, the resin constituting both outer layers is composed of a polylactic acid-based polymer (A) and a fat. Is a mixture (C) of the aliphatic polyester (B), and the proportion of the aliphatic polyester (B) in the mixture (C) is more than 0% by weight and not more than 30% by weight. is there.

[Comparative Examples 6 and 7] Using three coaxial extruders having three single-screw extruders and three-layer dies, the structure of each layer and the structure of the entire film were as shown in Table 3. ,
PLA2 and PBSA were extruded and quenched with a casting roll to obtain an unstretched film having a thickness of about 300 μm. Next, using a biaxial stretching apparatus (Iwamoto Seisakusho Co., Ltd.), simultaneous biaxial stretching was performed at a stretching ratio of 4 times in both the vertical and horizontal directions. However, although the stretching temperature was changed to 80 to 120 ° C. and an appropriate stretching temperature was searched, stretching could not be performed.

[0038]

[Table 3]

From the results of Comparative Examples 6 and 7, L-lactic acid and D-lactic acid
It is apparent that a biodegradable heat-shrinkable multilayer film suitable for the shrink wrapping field cannot be obtained unless polylactic acid containing lactic acid in the ratio as shown in the present invention is used.

In the above Examples and Comparative Examples, attention was paid to the transparency, gloss, heat shrinkage, stretching properties, slipperiness and heat sealability of the obtained samples, and the biodegradability was daringly mentioned. However, it is obvious that the biodegradable heat-shrinkable multilayer film of the present invention has complete biodegradability due to the characteristics of the two synthetic resins used in the present invention.

[0041]

The biodegradable heat-shrinkable multilayer film of the present invention has excellent heat-shrinkability, especially heat-shrinkability at low temperatures, and also has excellent transparency, gloss and sliding performance, and can be used for sheet sealing. There is a feature that there is. In addition, since it is mainly composed of a polylactic acid-based polymer and an aliphatic polyester, it is biodegraded in the natural environment when discarded, and does not adversely affect the natural environment. Furthermore, even if incinerated, there is no risk of generating toxic gas during incineration because chlorine is not present in the molecule of both the polylactic acid-based polymer and the aliphatic polyester. As described above, the biodegradable heat-shrinkable multilayer film provided by the present invention is a packaging material that does not impose a load on the natural environment, and is usefully used in the art.

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Claims (3)

[Claims] 1. The composition ratio of L-lactic acid to D-lactic acid is 94: 6.
To 79:21, and an aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) mainly synthesized from an aliphatic polyhydric alcohol and an aliphatic dicarboxylic acid or a derivative thereof. Wherein the proportion of the aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) is more than 0% by weight and not more than 30% by weight. A lactic acid-based polymer (A) and / or at least one layer composed of an aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B), and a polylactic acid-based polymer (A) in all layers; The ratio of the aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) is (A) :( B) = 30: 70% by weight to 75: 2.
A film obtained by stretching a multilayer film, which is 5% by weight, in at least one direction,
Shrinkage after immersion in glycerin for 30 seconds is 20 in at least one of the MD and TD directions of the film.
% Of the biodegradable heat-shrinkable multilayer film. 2. The resin composition ratio of both outer layers is (A) :( B)
The biodegradable heat-shrinkable multilayer film according to claim 1, wherein the content is from 99: 1 wt% to 70:30 wt%. 3. The biodegradable composition according to claim 1, wherein the aliphatic polyhydric alcohol / aliphatic dicarboxylic acid copolymer (B) is a polybutylene succinate / adipate copolymer. Heat shrink multilayer film.