JP2002193343A - Vegetable and fruit packaging bag made of lactic acid based copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vegetable and fruit packaging bag made of a lactic acid based copolymer, which has appropriate moisture permeability and biodegradability, is flexible and excellent in machinability in bag-making and also has an excellent fog resistance. SOLUTION: The vegetable and fruit packaging bag made of the lactic acid based copolymer which contains 2 to 50 wt.% of a polyester structural unit comprising a dicarboxylic acid and a diol which are dehydrated and condensed and/or a polyether structural unit comprising a dicarboxylic acid and a polyether polyol which are dehydrated and condensed has appropriate moisture permeability to food, vegetable and fruit in particular and excellent fog resistance and is excellent in machinability in bag-making. Finding this fact has led to completion of the invention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a food packaging bag made of a biodegradable lactic acid copolymer which is excellent in keeping freshness and antifogging property and is used as a packaging bag for food. More specifically, the present invention relates to a packaging bag for fruits and vegetables made of a biodegradable lactic acid-based copolymer which is particularly excellent in keeping freshness of fruits and vegetables.

[0002]

2. Description of the Related Art In recent years, as bags for packaging food, for example, polyethylene (PE), polypropylene (PP), and expanded polystyrene (OP), all of which are petroleum products, have been used.
A packaging bag made of S) is used.

[0003] However, PE and PP have low moisture permeability,
Vegetables are damaged by the moisture of fruits and vegetables that condenses and accumulates inside the bag,
It was difficult to maintain the freshness for a long time. In addition, processing such as application of an antifogging material was required to suppress internal fogging due to condensation.

[0004] OPS which has improved moisture permeability by stretching for keeping freshness of fruits and vegetables is excellent in keeping freshness, but suffers from environmental load such as high heat during incineration and generation of harmful substances.

Very little of these PE, PP and OPS food packaging bags are reused, and most of them are incinerated after one-way use. The generation of toxic substances by incineration of such petroleum products and the depletion of resources due to large-scale use have become a major social problem at present.

In order to solve these problems, research and development for using biodegradable polymers as various packaging materials have been actively conducted. Among them, lactic acid polymers are PE, P
It has the same high transparency as P and OPS, low heat generated by incineration, and eventually biodegrades, so PE, PP, OPS
It is expected as a substitute for main food packaging materials.

However, since neat polylactic acid has too high rigidity and lacks flexibility, problems such as poor workability and difficulty in bag making arise.

[0008] In addition, since polylactic acid has too high a water vapor transmission rate, there is a problem that the moisture of fruits and vegetables which should be maintained at an appropriate level is lowered and freshness cannot be maintained for a long time.

Therefore, for fruits and vegetables comprising a lactic acid-based copolymer which is transparent, flexible, has good processability, has good moisture permeability suitable for preserving fruits and vegetables, maintains freshness of fruits and vegetables, is excellent in antifogging properties, and is excellent in biodegradability. The development of packaging bags was expected.

[0010]

The problems to be solved by the present invention are transparent, flexible, have good bag-making processability, have good moisture permeability suitable for preserving fruits and vegetables, and have excellent freshness retention and antifogging properties of the fruits and vegetables. Another object of the present invention is to provide a packaging bag for fruits and vegetables comprising a lactic acid-based copolymer excellent in biodegradability.

[0011]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a packaging bag made of a specific lactic acid-based copolymer has an appropriate moisture permeability and an excellent antifogging property for foods, especially fruits and vegetables. The inventors have found that the present invention has excellent bag-making processability and have completed the present invention.

That is, according to the present invention, the lactic acid-based copolymer comprises 2 to 50% by weight of a polyester structural unit obtained by dehydration-condensation of a dicarboxylic acid and a diol and / or a polyether structural unit obtained by dehydration-condensation of a dicarboxylic acid and a polyether polyol. It is an object of the present invention to provide a packaging bag for fruits and vegetables comprising a lactic acid-based copolymer, which is preferably a lactic acid-based polymer containing 3 to 40% by weight.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The lactic acid-based copolymer used in the present invention means a copolymer containing a lactic acid unit (residue), and specifically, a lactic acid-based copolymer composed of a lactic acid unit and a glycolic acid unit, or a lactic acid unit and a polyester unit And a lactic acid-based polyester copolymer consisting of

[0014] These lactic acid-based copolymers have a suitable moisture permeability for preserving food, and are therefore preferred as food packaging bags. In addition, a lactic acid-based copolymer composed of a lactic acid unit and a glycolic acid unit is particularly preferable from the viewpoint of flexibility characteristics essential for processability.

The lactic acid unit is a block unit having a block chain length of 1 to 3000 lactic acid units, more preferably a block unit of 100 to 3000 lactic acid units.

In the case where lactic acid is used as a raw material to polymerize a polylactic acid or a copolymer having a lactic acid unit, the lactic acid-based copolymer can be produced by a commonly known polycondensation reaction. That is, in the presence or absence of a solvent,
Further, it is produced by performing dehydration polycondensation in the presence or absence of a catalyst. Of course, it may be performed under reduced pressure.

When lactic acid and glycolide, which is a cyclic dimer of glycolic acid, are used as raw materials to polymerize polylactic acid or a copolymer comprising glycolic acid units and lactic acid units, the polymerization is carried out in the presence of a ring-opening polymerization catalyst. It can be produced by ring polymerization. As the catalyst used here, any catalyst generally known as an esterification catalyst or a ring-opening polymerization catalyst can be used. For example, Sn, Ti, Zr, Zn, Ge, C
Alkoxides such as o, Fe, Al and Mn, acetates, oxides, chlorides and the like are used.

Among them, tin octylate, dibutyltin dilaurate, tetraisopropyl titanate, tetrabutoxytitanium, titanium oxyacetylacetonate, iron (III) acetylacetonate, iron (III) ethoxide, aluminum isopropoxide, and aluminum acetylacetonate The reaction is fast and preferred. The amount of the catalyst to be used is generally 10 to 1000 ppm, preferably 50 to 500 ppm, relative to the reactants.

Lactide as a raw material includes L-lactide composed of two molecules of L-lactic acid and D-lactide composed of two molecules of D-lactic acid.
Mes comprising lactide, L-lactic acid and D-lactic acid
o-Lactide is present. L-lactide or D-
A copolymer containing only lactide is easily crystallized, and a high melting point is obtained.

In the lactic acid-based polymer of the present invention, by combining these three lactides, preferable resin characteristics according to the intended use can be realized. In particular, in the present invention, L-lactide is preferably contained in 75% or more of the total lactide in order to express high thermophysical properties, and in order to express higher thermophysical properties, L-lactide is preferably contained in 8% of total lactide.
Those containing 0% or more are preferred.

The lactic acid-based polyester can be obtained by polycondensation of lactic acid with a polyhydric carboxylic acid or a polyhydric alcohol, polycondensation of lactic acid with a polyester, or copolymerization of lactide with a polyester. In particular, lactide and polyester are preferably copolymerized with a ring-opening polymerization catalyst because the reaction is quick, the molecular weight can be easily controlled, and the physical properties are excellent. It is preferable to use a catalyst for these polymerizations, and the same catalyst as described above can be used.

Next, the polyhydric carboxylic acid and polyhydric alcohol which are the raw materials of the polyester component will be described. The polyvalent carboxylic acid is not particularly limited, but terephthalic acid,
Aromatic carboxylic acids such as isophthalic acid, succinic acid having 4 to 14 carbon atoms, adipic acid, azelaic acid, sebacic acid, brassic acid, aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, and other dimer acids. 2
More than one kind may be used.

The polyhydric alcohol is not particularly limited, but is preferably a diol having 2 to 10 carbon atoms or a polyether polyol. Specifically, ethylene glycol,
1,3-propanediol, propylene glycol,
1,4-butylene glycol, 1,3-butylene glycol, pentanediol, hexamethylene glycol,
Octanediol, neopentyl glycol, cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, copolymers of polyethylene glycol and polypropylene glycol,
Polytetramethylene glycol may be used, and two or more of these may be used.

The polyester polymerized from the above-mentioned polycarboxylic acids and polyhydric alcohols is not particularly limited. Examples thereof include aromatic polyesters, aromatic / aliphatic polyesters, aliphatic polyesters, and polyε-caprolactone. Such a lactone-based polyester can be used. However, in consideration of biodegradability, it is preferable to use an aliphatic polyester.

Next, a specific method for producing a lactic acid-based copolymer using lactide will be described. The reaction of a lactic acid-based copolymer obtained by ring-opening copolymerization of lactide and polyester is as follows:
After heating and melting the mixture or diluting and mixing the reaction product with a solvent, a polymerization catalyst is added. The polymerization temperature is preferably 100 ° C. or higher and 240 ° C. or lower, which is higher than the melting point of lactide, in view of the equilibrium of polymerization, and can prevent coloring of the lactic acid-based polymer due to the decomposition reaction.
0-220 ° C.

In order to prevent the decomposition and coloring of lactide,
It is preferable that all reactions are performed under a dry inert gas atmosphere. In particular, the etching is performed in a nitrogen or argon gas atmosphere or in a state in which an inert gas is bubbled. At the same time, it is preferable to remove moisture from the polyester as a raw material by drying under reduced pressure or the like. Further, an antioxidant such as a phosphite compound or a phenol compound may be used.

Since lactide can be dissolved in a solvent,
Polymerization can be performed using a solvent. Specific examples of the solvent include, for example, benzene, toluene, ethylbenzene, xylene,
Examples include cyclohexanone, methyl ethyl ketone, and isopropyl ether. These solvents are also dried,
It is preferable to remove the water because variation in the molecular weight of the obtained lactic acid-based polymer can be suppressed. As the catalyst used in this polymerization reaction, the same catalyst as described above can be used.

The lactic acid copolymer used in the present invention is preferably devolatilized under a reduced pressure or washed and removed with a solvent in order to maintain the storage stability after the production, and to remove residual monomers such as glycolide and lactide. The residual monomer content is 0.5% by weight or less, more preferably 0.2% by weight or less. A quenching agent having the ability to deactivate the polymerization catalyst may be contained in order to suppress back-bitting of the lactic acid-based copolymer due to heat history and re-generation of monomers such as glycolide and lactide.

The weight-average molecular weight of the lactic acid-based copolymer used in the present invention is suitably from 20,000 to 600,000, and preferably from 50,000 to 600,000, in order to sufficiently exhibit resin strength and the like when formed into a film. 000 to 400,000. If the weight average molecular weight is less than 20,000, the strength after film processing cannot be maintained. Conversely, if the weight average molecular weight exceeds 600,000, film processing becomes difficult.

The thickness of the film of the packaging bag for fruits and vegetables comprising the lactic acid-based copolymer in the present invention is preferably 10 μm to 100 μm, as in the conventional packaging bag, and more preferably,
It is 35 μm to 50 μm.

The lactic acid-based copolymer used herein is not particularly limited as long as it has a lactic acid unit as described above. For example, a polyester structure obtained by dehydrating and condensing a lactic acid unit, a dicarboxylic acid and a diol is used. The ratio of units and / or polyetherester structural units obtained by dehydrating and condensing dicarboxylic acid and polyether polyol is such that the lactic acid unit is 50 to 98% by weight, preferably 60 to 9% by weight.
0% by weight, more preferably 60 to 85% by weight, the polyester unit and / or the polyether polyester unit is 2 to 50% by weight, preferably 10 to 40% by weight, more preferably 15 to 40% by weight. .

In the packaging bag for fruits and vegetables made of the lactic acid copolymer of the present invention, an inorganic filler, an antiblocking agent, an antistatic agent, a plasticizer,
Other additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, a heat stabilizer, a coloring inhibitor, and a pigment may be added.

These inorganic fillers have an average particle diameter in the range of 0.01 to 10 μm, especially 0.1 to 5 μm.
Those having a range of μm are preferred. These inorganic fillers may be used alone or in combination of two or more. The compounding amount of the inorganic filler is 0.5 to 20% by weight, preferably 1 to 15% by weight, based on 100% by weight of the lactic acid-based polymer. If the amount is less than 0.5% by weight, the heat-retaining effect is not sufficiently exhibited, and if it exceeds 20% by weight, when formed into a film, the tensile strength and the tear strength are reduced.

Specific examples of the anti-blocking agent include:
Silica calcium carbonate, titania, mica, talc and the like can be mentioned. Among them, silica having an average particle diameter of 7 to 50 nm is preferable from the viewpoint of transparency of the obtained film. If the average particle size is less than 7 nm, the particles are likely to aggregate,
If it exceeds 50 nm, fine irregularities are formed on the film surface, and the appearance becomes opaque.

Preferably, the silica contains 95% or more of SiO _2, and more preferably, SiO ₂ is anhydrous silica. The amount used is 0.1 to 5% by weight, preferably 0.1 to 2% by weight, based on 100% by weight of the lactic acid polymer.
% By weight. When the amount is less than 0.1% by weight, the effect of addition to the obtained film is not exhibited, and when it exceeds 2% by weight, the moldability of the film is reduced, and the flatness, transparency and the like of the obtained film are further reduced.

As a method for producing a film, melt extrusion molding can be mentioned. Extrusion temperatures range from 130 to 280C, preferably from 150 to 250C. If the molding temperature is low, the molding stability deteriorates. On the other hand, if the molding temperature is high, the lactic acid-based polymer is decomposed, and the molecular weight is reduced, the strength is reduced, and coloring is not preferable.

The packaging bag for fruits and vegetables comprising the lactic acid-based copolymer of the present invention may be unstretched or stretched. However, in terms of moisture permeability and strength, the obtained film is stretched uniaxially or biaxially. Is preferred. In the case of uniaxial stretching, it is preferable to stretch 1.3 to 10 times in the machine direction or the transverse direction by longitudinal stretching by a roll method or transverse stretching by a tenter.

In the case of biaxial stretching, longitudinal stretching by a roll method and transverse stretching by a tenter can be mentioned. As the method, even if the uniaxial stretching and the biaxial stretching are sequentially performed,
You may go at the same time. The stretching ratio is preferably 1.3 to 5 times in the longitudinal and transverse directions, respectively. If the stretching ratio is lower than this, it is difficult to obtain a film having sufficiently satisfactory strength, and if it is high, the film is broken at the time of stretching, which is not good.

The stretching temperature is preferably in the range of glass transition point (hereinafter referred to as Tg) Tg to (Tg + 50) ° C. of the lactic acid copolymer, and more preferably Tg to (Tg + 30).
It is in the range of ° C. If the stretching temperature is lower than Tg, stretching is difficult, and if it exceeds (Tg + 50) ° C., the strength may not be improved by stretching.

Further, in order to improve the heat resistance, it is preferable to perform a heat setting treatment under tension after stretching. The heat setting temperature can be performed at a temperature of 70 ° C. or higher and lower than the melting point of the lactic acid polymer, and is preferably 70 to 150 ° C., more preferably 90 to 140 ° C., not only for heat resistance but also for tensile elongation and the like. Is also desirable because it also improves the film physical properties. The heat setting processing time is usually 1 second to 30 minutes, but considering practicality such as productivity, the shorter the time, the better,
Preferably it is 1 second to 3 minutes, more preferably 1 second to 1 minute.

The packaging bag for fruits and vegetables comprising the lactic acid-based copolymer of the present invention is made by a fusing-sealing method when stretched or heat set after stretching. If it is not stretched, it is made by heat sealing.

The packaging bag for fruits and vegetables made of the lactic acid-based copolymer of the present invention can have fine holes formed by a special processing at the time of stretching. Specifically, use a roll with needle-like projections when stretching a sheet or film, and take up the winding speed,
By adjusting the stretching ratio, a hole can be formed in the sheet or film. The open area ratio of the holes is preferably about 2 × 10 ⁻⁶ to 3 × 10 ⁻⁶ % based on the area of the entire bag.

In the present invention, the term "vegetables" in the packaging bag for fruits and vegetables means all kinds of vegetables including fruits and vegetables such as leafy vegetables, root vegetables, mushrooms or cut vegetables, fruits and fresh flowers. In order to keep these fruits and vegetables fresh longer, a packaging bag having a suitable moisture permeability is required.

As described above, the packaging bag for fruits and vegetables of the present invention can maintain an appropriate moisture permeability with respect to the fruits and vegetables and has a film thickness of 35 to 50%.
Moisture permeability at 50 μm is 120 to 250 g / m ² · 24
h, preferably ○ to ○ g / m ² · 24h.

Since the packaging bag for fruits and vegetables of the present invention has the above moisture permeability, the fruits and vegetables can be kept longer and fresher. Further, the packaging bag for fruits and vegetables of the present invention has antifogging property, rigidity,
It has excellent impact resistance, and has excellent thermal processability and flexibility, and is excellent in bag making processability.

[0046]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The test method used in this example is as follows.

(1) Molecular Weight The molecular weight of the polyether polyol is measured by a terminal group quantification method, and the other molecular weights are measured by a GPC measuring device (hereinafter, referred to as “GPC”).
Abbreviated as GPC. HLC-85020 manufactured by Tosoh Corporation
(Column temperature: 40 ° C., tetrahydrofuran solvent).

(2) Moisture Permeability The moisture permeability was measured according to JISZ0208. Each film placed in a moisture-permeable cup specified by JIS is left in a thermo-hygrostat at a temperature of 40 ± 0.5 ° C. and a relative humidity of 90 ± 2%, and the weight of the moisture-permeable cup after a predetermined time is measured. Then, the moisture permeability of each sheet was evaluated.

(3) Dew-Condensation Each sheet is folded in two, two opposing sides are made by heat sealing or fusing seal, respectively, and 50 g of lettuce is put into the prepared bag, and the mouth of the bag is heat sealed or fusing sealed. And seal. Each bag was left in a refrigerator maintained at a temperature of 8 ° C., and after a lapse of a predetermined time, the total weight, the weight of water accumulated inside the bag, and the weight of vegetables were weighed, and dew condensation inside the bag was confirmed. The evaluation criteria are as follows. 4: No dew condensation was observed. 3: The occurrence of dew condensation is recognized very slightly. 2: Dew condensation was observed, and moisture was accumulated inside the bag. 1: An extremely large amount of dew was observed, and a large amount of water had accumulated inside the bag.

(4) Antifogging property In the test of (3), the antifogging property inside the packaging bag together with the dew was evaluated according to the following criteria. 4: Fogging inside the bag occurred in a range of less than 10% of the whole. 3: Fogging inside the bag occurred in a range of less than 20% of the whole. 2: Fogging inside the bag occurs in a range of 20% or more and less than 50% of the whole. 1: Fogging inside the bag occurred in a range of 50% or more of the whole.

(5) Retention of Vegetable Freshness Each sample bag prepared in the manner of the above (3) was taken out at predetermined time intervals, and the retention of freshness of the vegetables was evaluated based on changes in appearance, touch, and the like. The evaluation criteria are as follows.

4: No decrease in freshness of vegetables is observed. 3: A slight decrease in freshness of vegetables is observed. 2: A decrease in freshness of vegetables is observed. 1: Significant decrease in freshness of vegetables is observed.

[Production Example 1] Polycondensation of raw material 1 (aliphatic polyester) 15.4 kg of dimer acid and 8.0 kg of adipic acid were placed in a 50 L pressure vessel (SUS316L) equipped with a stirrer, rectification tower and nitrogen gas inlet tube. And 8.4 kg of propylene glycol, and melt-mixed at 160 ° C. for 0.5 hour in a nitrogen atmosphere.
The mixture was stirred while the temperature was raised to ° C.

After 8 hours, 1.7 g of titanium tetrabutoxide was added, and the pressure was reduced. 2 hours later, 0.1P
The pressure was reduced to a, and the glycol removal reaction was performed at 220 ° C. for another 5 hours. The resulting aliphatic polyester had a number average molecular weight of 34,000 and a weight average molecular weight of 67,000 (hereinafter abbreviated as A1).

[Production Example 2] Polycondensation of raw material 2 (aliphatic polyester) 7.7 kg of dimer acid and 3. adipic acid were placed in a 50 L pressure vessel (SUS316L) equipped with a stirrer, rectification tower and nitrogen gas inlet tube. 9 kg and 4.2 kg of propylene glycol were charged and melt-mixed at 160 ° C. for 0.5 hour under a nitrogen atmosphere.
The mixture was stirred while the temperature was raised to ° C.

After 7 hours, 17.5 kg of polypropylene glycol having a Mn of 3,000 (manufactured by Sanyo Chemical) was added to the kettle, 1.7 g of titanium tetrabutoxide was added, and the pressure was reduced. After 2 hours, the pressure was reduced to 0.1 Pa,
The glycol removal reaction was performed at 0 ° C. for another 5 hours. The resulting aliphatic polyester had a number average molecular weight of 31,000 and a weight average molecular weight of 62,000 (hereinafter abbreviated as A2).

[Production Example 3] Polymerization of lactic acid-based polymer 1 (polylactic acid) In a 100 L pressure vessel (SUS316L) equipped with a stirrer, a rectification tower and a nitrogen gas inlet tube, 48 kg of L-lactide was added.
-2.0 kg of lactide, 25 g of Irganox 1012 (manufactured by Ciba-Geigy Corporation) and 10 kg of toluene were charged,
After melt-mixing at 190 ° C. for 0.5 hour in a nitrogen atmosphere, 15 g of tin octoate was added.

After 4 hours, the obtained polylactic acid was taken out from the bottom of the kettle with a gear pump and kept in a molten state.
It was conveyed to a screw extruder. While adding AP-8 (manufactured by Daihachi Chemical Industry Co., Ltd.) to the polylactic acid at 500 ppm from the vent port closest to the extruder inlet, 0.1 Pa, 2 Pa
The residual lactide was devolatilized with a twin-screw extruder under conditions of 10 ° C. and 130 rpm, and then pelletized. The molecular weight of the obtained polylactic acid (hereinafter abbreviated as P1) is Mn = 150,000, M
w = 290,000, no residual lactide was detected by GPC (residual lactide is 0.01% or less from the detection limit of GPC).

[Production Example 4] Polymerization of lactic acid-based polymer 2 (lactic acid-based polyester) 46.6k of L-lactide was placed in a 100L pressure vessel (SUS316L) equipped with a stirrer, rectification tower, and nitrogen gas inlet tube.
g, 1.9 kg of D-lactide, 1.5 kg of A2,
25 g of Irganox 1010 (manufactured by Ciba Geigy),
10 kg of toluene was charged, and the temperature was 190 ° C. under a nitrogen atmosphere.
After melt mixing for 0.5 hour, 15 g of tin octoate was added.

After 4 hours, the obtained lactic acid-based polyester was taken out from the bottom of the kettle by a gear pump, and transported in a molten state to a twin-screw extruder equipped with a three-pressure vent. From the vent port closest to the extruder inlet, while adding AP-8 (manufactured by Daihachi Chemical Industry Co., Ltd.) to the lactic acid-based polyester so as to be 500 ppm, under conditions of 0.1 Pa, 210 ° C. and 130 rpm.
The residual lactide was devolatilized by a twin-screw extruder and then pelletized. The molecular weight of the obtained lactic acid-based polyester (hereinafter abbreviated as P2) is Mn = 130,000, Mw = 260,000,
No residual lactide was detected by GPC.

[Production Example 5] Polymerization of lactic acid-based polymer 3 (lactic acid-based polyester) 43.6 kL-lactide was placed in a 100 L pressure vessel (SUS316L) equipped with a stirrer, rectification tower, and nitrogen gas inlet tube.
g, D-lactide 4.9 kg, A2 7.5 kg,
25 g of Irganox 1010 (manufactured by Ciba Geigy),
10 kg of toluene was charged, and the temperature was 190 ° C. under a nitrogen atmosphere.
After melt mixing for 0.5 hour, 15 g of tin octoate was added.

After 4 hours, the obtained lactic acid-based polyester was taken out from the bottom of the kettle by a gear pump, and transported in a molten state to a twin-screw extruder equipped with a three-pressure vent. From the vent port closest to the extruder inlet, while adding AP-8 (manufactured by Daihachi Chemical Industry Co., Ltd.) to the lactic acid-based polyester so as to be 500 ppm, under conditions of 0.1 Pa, 210 ° C. and 130 rpm.
The residual lactide was devolatilized by a twin-screw extruder and then pelletized. The molecular weight of the obtained lactic acid-based polyester (hereinafter abbreviated as P3) is Mn = 124,000, Mw = 249,000,
No residual lactide was detected by GPC.

[Production Example 6] Polymerization of lactic acid-based polymer 4 (lactic acid-based polyester) 34.0k of L-lactide was placed in a 100L pressure vessel (SUS316L) equipped with a stirrer, a rectification tower, and a nitrogen gas inlet tube.
g, 8.5 kg of D-lactide, 7.5 kg of A1,
25. Irganox 1076 (manufactured by Ciba Geigy)
After charging 0 g and melting and mixing at 190 ° C. for 0.5 hour under a nitrogen atmosphere, 15 g of tin octoate was added.

After 4 hours, the obtained lactic acid-based polyester was taken out from the bottom of the kettle with a gear pump, and conveyed in a molten state to a twin-screw extruder equipped with a three-vacuum vent. While adding AP-8 (manufactured by Daihachi Chemical Industry Co., Ltd.) to the lactic acid-based polyester at a concentration of 500 ppm from the vent port closest to the extruder inlet, under conditions of 0.1 Pa, 195 ° C., and 130 rpm.
The residual lactide was devolatilized by a twin-screw extruder and then pelletized. The molecular weight of the obtained lactic acid-based polyester (hereinafter abbreviated as P4) is Mn = 130,000, Mw = 260,000,
No residual lactide was detected by GPC.

[Production Example 7] Polymerization of lactic acid-based polymer 5 (lactic acid-based polyester) L-lactide was charged at 35.0 k in a 100-L pressure vessel (SUS316L) equipped with a stirrer, a rectification tower, and a nitrogen gas inlet tube.
g, 15.0 kg of A1, 30 g of Greg P626 (manufactured by Dainippon Ink and Chemicals), and 10 kg of toluene,
After melt-mixing at 190 ° C. for 0.5 hour in a nitrogen atmosphere, 15 g of tin octoate was added.

After 4 hours, the obtained lactic acid-based polyester was taken out from the bottom of the kettle with a gear pump, and conveyed in a molten state to a twin-screw extruder equipped with a three-vacuum vent. While adding AP-8 (manufactured by Daihachi Chemical Industry Co., Ltd.) to the lactic acid-based polyester at a concentration of 500 ppm from the vent port closest to the extruder inlet, under conditions of 0.1 Pa, 210 ° C., and 130 rpm.
The residual lactide was devolatilized by a twin-screw extruder and then pelletized. The molecular weight of the obtained lactic acid-based polyester (hereinafter abbreviated as P5) was Mn = 82,000, Mw = 159,000, and residual lactide was not detected by GPC. Table 1 shows the composition and properties of the lactic acid-based polymer produced.

[0067]

[Table 1]

Examples 1 to 5 [Examples 1 to 3] P as a film for packaging bags for fruits and vegetables
1, Extrusion molding using P2, P3 pellets, 50μ
m was obtained. Each of the obtained films was cut into a rectangle of an arbitrary size, and the folded fold was set at the bottom, and two sides in the vertical direction were heat-sealed to obtain a packaging bag for fruits and vegetables.

[Examples 4 and 5] As a film for a packaging bag for fruits and vegetables, 100 μm films obtained by extrusion molding using P1, P2 and P3 pellets were heated to 60 ° C., and then lengthwise. The film is stretched 2.5 times by the roll method, and further stretched 2.5 times using a tenter in the lateral direction, and then is stretched at 140 ° C. for 2 minutes under tension to stretch and heat set to a thickness of about 50 μm. A film was obtained. Each of the obtained films was cut into a rectangle of an arbitrary size, and the folded fold was set at the bottom, and two sides in the vertical direction were sealed by fusing to obtain a packaging bag for fruits and vegetables.

[Examples 6 and 7] P4 and P5 pellets were extruded as films for packaging bags for fruits and vegetables,
A 0 μm film was obtained. Each of the obtained films was cut into a rectangle of an arbitrary size, and the folded fold was used as a bottom, and two sides in the vertical direction were heat-sealed to obtain a packaging bag for fruits and vegetables.

Examples 8 to 9 100 μm films extruded using P4 and P5 pellets as films for packaging bags for fruits and vegetables were each heated to 60 ° C. and then rolled in the length direction. The film is stretched 2.5 times with a tenter in the transverse direction, and then stretched at a temperature of 140 ° C. for 2 minutes under tension.
A heat-set film was obtained. Each of the obtained films was cut into a rectangle of an arbitrary size, and the folded fold was set at the bottom, and two sides in the vertical direction were sealed by fusing to obtain a packaging bag for fruits and vegetables.

Comparative Example 1 A 50 μm film was obtained by extrusion molding using LDPE pellets manufactured by Mitsubishi Chemical Corporation. Each of the obtained films was cut into a rectangle of an arbitrary size, and the folded fold was made the bottom, and two sides in the vertical direction were heat-sealed to obtain a packaging bag for fruits and vegetables.

Comparative Example 2 A 50 μm film was obtained by extrusion molding using HOPP pellets manufactured by Idemitsu Kagaku. Each of the obtained films was cut into a rectangle of an arbitrary size, and the folded fold was made the bottom, and two sides in the vertical direction were heat-sealed to obtain a packaging bag for fruits and vegetables.

Comparative Example 3 Commercially available OPS having a thickness of 50 μm
The film was cut into a rectangle of an arbitrary size, the folded fold was made the bottom, and two sides in the vertical direction were sealed by fusing to obtain a packaging bag for fruits and vegetables. Tables 2 to 4 show the properties of the obtained packaging bag for fruits and vegetables.

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

[Table 4]

When the packaging materials of Examples 1 to 9 were treated with an automatic composting machine heated to 58 ° C. for 2 weeks, they were decomposed so that the original shape could not be maintained.

[0079]

Industrial Applicability According to the present invention, lactic acid which is transparent, flexible, has good bag-making processability, has good moisture permeability suitable for preserving fruits and vegetables, has excellent freshness retention and antifogging properties of fruits and vegetables, and has excellent biodegradability It is possible to provide a packaging bag for fruits and vegetables made of the copolymer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 C08L 67:04 C08L 67:04 F Term (Reference) 3E064 AA03 BA60 BC18 BC20 EA18 EA30 FA01 HD02 HE01 3E067 AA11 AB08 AB09 BA12A BB14A BB18A CA10 CA23 CA24 CA30 GD01 3E086 AD01 BA15 BA33 BB01 BB51 BB72 CA17 CA18 DA03 4F071 AA08 A44A01A44A01A44A01AA08 QC01 QC05 QC06 QG01 QG18 QW21

Claims (5)

[Claims] 1. Vegetables and fruits comprising a lactic acid-based copolymer containing 2 to 50% by weight of a polyester structural unit obtained by dehydration-condensation of a dicarboxylic acid and a diol and / or a polyether ester structural unit obtained by dehydration-condensation of a dicarboxylic acid and a polyether polyol. Packaging bag. 2. A film having a moisture permeability of 120 at a film thickness of 35 to 50 μm.
Seika packaging bag according to claim 1 which is ~250g / m ² · 24h. 3. The method according to claim 1, wherein the lactic acid-based copolymer is a polycarboxylic acid,
The packaging bag for fruits and vegetables according to claim 1 or 2, which is a lactic acid-based copolymer whose molecular weight has been increased by adding a polymeric agent such as an acid anhydride or a polyvalent isocyanate. 4. The open area ratio of holes on one side or both sides of the bag is 2 × 10 ^{-6 to} 3 × 10
^The packaging bag for fruits and vegetables according to any one of claims 1 to 3, characterized in that it is ^-6 %. 5. The method according to claim 1, wherein the uniaxial direction or the biaxial direction is 1.3 to 1
The packaging bag for fruits and vegetables according to any one of claims 1 to 4, which is heat-set after being stretched 0 times.