JP3130731B2 - Heat-shrinkable aliphatic polyester film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION
The present invention relates to a heat-shrinkable aliphatic polyester film having excellent thermal stability and mechanical strength formed from an aliphatic polyester having a practically sufficient high molecular weight having a number average molecular weight of 20,000 or more.

[0002]

2. Description of the Related Art High-molecular-weight polyesters (hereinafter, referred to as "polyesters") conventionally used for molding films, fibers, and other molded articles.
The term "high molecular weight polyester" as used herein means a number average molecular weight of 20,000 or more. ) Was limited to polyethylene terephthalate, which is a condensate of terephthalic acid (including dimethyl terephthalate) and ethylene glycol, or butylene terephthalate from terephthalic acid and butylene glycol.

[0003] However, these films have high rigidity and high strength as ordinary blown film or cast film due to the molecular structural factor of terephthalic acid, but remain unstretched. Then, it was brittle and had no value as a film, and was widely used as a stretched film. Although stretched polyester film is extremely excellent in transparency, strength, etc., it has a disadvantage in heat sealing property due to its high melting point, and as a film for heat seal packaging, a polyolefin resin or film having excellent heat sealability is used. It could only be used as a laminated laminate. Further, the heat-shrinkable film was inferior in shrinkage due to its high melting point and was hardly used.

For this improvement, instead of terephthalic acid,
Although there is an example using 2,6-naphthalenedicarboxylic acid,
There have been almost no examples in which a polyester using an aliphatic dicarboxylic acid as the dicarboxylic acid is formed into a sheet, film, fiber, or the like.

[0005] One of the reasons for not being put to practical use is that even if it is crystalline, the melting point of aliphatic polyester is almost 100 ° C or less, and furthermore, it has poor thermal stability upon melting. More importantly, the properties of the aliphatic polyester, particularly the mechanical properties represented by tensile strength, are extremely low, and even at the same level of the number average molecular weight as polyethylene terephthalate, it shows only a remarkably inferior value. There is no other way than it was.

Further, since aromatic polyesters such as polyethylene terephthalate do not have microbial decomposability, there is a problem that simply discarding them after use makes them remain indefinitely, and requires incineration for complete treatment. Had.

Particularly, in the field of packaging, a heat-shrinkable film which has not only requirements such as strength but also has high transparency, can be heat-sealed, is easy to dispose of, and has microbial decomposability and low combustion heat generation. Development was strongly desired.

[0008]

DISCLOSURE OF THE INVENTION The present invention has very excellent transparency, has a practically sufficient high molecular weight, is excellent in mechanical properties represented by thermal stability and tensile strength, and Even if discarded after use, the calorific value of combustion is small, it can be further decomposed by microorganisms, etc., and it is easy to discard, and furthermore, it has heat sealability as it is, showing large heat shrinkage at a temperature of 150 ° C or less, It is another object of the present invention to provide a heat-shrinkable aliphatic polyester film having excellent moisture-proof properties.

[0009]

Means for Solving the Problems The object of the present invention is to provide: [1] a temperature of 190 ° C. and a shear rate of 1 synthesized mainly from glycol and an aliphatic dibasic acid or a derivative thereof.
The melt viscosity at 00 (sec ⁻¹ ) is 2,000 to 1
It has a melting point of 70 to 200 ° C., a number average molecular weight of 20,000 or more, and an MFR (190
C) is not more than 200 μm and the haze is not more than 10%.
Under heat-shrinkable aliphatic polyester stretched film moisture permeability has the following moisture resistance ^{100g / m 2 · 24hr, [} 2] the thermal shrinkage at 90 ° C. of the film (MD) is 30
% Or more, a heat-shrinkable heat-shrinkable aliphatic polyester stretched film having heat-sealing properties and microbial degradability according to the above [1] , and [3] mainly a glycol and an aliphatic dibasic acid or the same.
190 ° C., shear rate 1
The melt viscosity at 00 (sec ⁻¹ ) is 2,000 to 1
It has a melting point of 70-200 ° C.
Has a number average molecular weight of 20,000 or more and an MFR (190
C) is 20 g / 10 minutes or less.
Unstretched film molded at a molding temperature of 120 to 240 ° C
With an air gap of 10 mm or less and a stretching temperature of 70 to 15
Stretching in a uniaxial manner at 0 ° C. and a stretching ratio of 2 to 10 times
The heat shrinkability as described in [1] or [2] above,
Manufactures a method for manufacturing a stretched aliphatic polyester film
It can be solved by a method of.

The aliphatic polyester referred to in the present invention is mainly composed of a polyester synthesized mainly from glycols and an aliphatic dibasic acid or an acid anhydride thereof. In order to sufficiently increase the molecular weight, This is obtained by synthesizing a relatively high molecular weight polyester prepolymer having a hydroxyl group at a terminal, and then coupling these prepolymers with a coupling agent.

Conventionally, a low molecular weight polyester prepolymer having a hydroxyl group at the terminal group and having a number average molecular weight of 2,000 to 2,500 is reacted with diisocyanate to form a polyurethane, rubber, foam, paint, and adhesive. It is widely used as an agent.

However, the polyester prepolymers used for these polyurethane foams, paints and adhesives are low molecular weight prepolymers having a number average molecular weight of 2,000 to 2,500.
In order to obtain practical physical properties as a polyurethane with respect to 00 parts by weight, the amount of diisocyanate used should be 10 to
It must be 20 parts by weight. However, if such a large amount of diisocyanate is added to a low-molecular-weight polyester melted at 150 ° C. or higher, gelation occurs, and a melt-moldable resin cannot be obtained.

Further, as in the case of polyurethane rubber,
A method of converting a hydroxyl group into an isocyanate group by adding a diisocyanate and further increasing the number average molecular weight with a glycol may be considered, but the amount of the diisocyanate used may be reduced as described above. 10 parts by weight or more is required per part by weight. At this time, if a heavy metal-based catalyst is used for the synthesis of the polyester, the reactivity of the isocyanate group is remarkably promoted, resulting in poor storage stability, crosslinking reaction, and branch formation, so that the polyester prepolymer is synthesized without a catalyst. As a result, the number average molecular weight is limited to about 2,500 at the highest.

The polyester prepolymer for obtaining the aliphatic polyester used in the present invention has a terminal group obtained mainly by reacting a glycol with an aliphatic dibasic acid or an anhydride thereof, substantially having a hydroxyl group. The number average molecular weight is 5,000 or more, preferably 10,
It is a saturated aliphatic polyester having a relatively high molecular weight of 000 or more and a melting point of 60 ° C. or more.

When the number average molecular weight is less than 5,000,
Even with a small amount of the coupling agent of 0.1 to 5 parts by weight, a polyester having good physical properties cannot be obtained. Polyester prepolymers having a number average molecular weight of 5,000 or more have a hydroxyl value of 30 or less, and use of a small amount of a coupling agent does not cause gelation during the reaction even under severe conditions such as a molten state. Polyester can be synthesized.

The glycols used include, for example, ethylene glycol, 1,4-butanediol, 1,6
-Hexanediol, decamethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol and the like. Ethylene oxide can also be used. These glycols may be used in combination.

The aliphatic dibasic acids or derivatives thereof which form aliphatic polyesters by reacting with glycols include succinic acid, adipic acid, suberic acid, sebacic acid, and the like.
There are lower alcohol esters such as dodecane diacid, succinic anhydride, adipic anhydride and dimethyl ester thereof, and these are commercially available and can be used in the present invention. A dibasic acid or an acid anhydride thereof may be used in combination.

These glycols and dibasic acids are mainly composed of aliphatic compounds, but may be used in combination with small amounts of other components, for example, trifunctional or tetrafunctional polyhydric alcohols, oxycarboxylic acids or polycarboxylic acids. preferable.

The trifunctional polyhydric alcohol component is typically trimethylolpropane, glycerin or an anhydride thereof, and the tetrafunctional polyhydric alcohol component is pentaerythritol.

As the trifunctional oxycarboxylic acid, malic acid is practically advantageous, and citric acid is practical because the commercially available tetrafunctional oxycarboxylic acid component can be easily obtained at low cost.

As the trifunctional polycarboxylic acid (or its acid anhydride) component, for example, trimesic acid, propanetricarboxylic acid and the like can be used, but trimellitic anhydride is advantageous in practical use.

Examples of the tetrafunctional polycarboxylic acid (or acid anhydride thereof) include pyromellitic anhydride, benzophenonetetracarboxylic anhydride, cyclopentanetetracarboxylic anhydride and the like.

The proportion of the polyfunctional component used is such that the mole number of either the glycol component or the aliphatic (including cycloaliphatic) dicarboxylic acid (or acid anhydride) component is 100.
In the case of a trifunctional component, it is 5 mol% or less, preferably 0.5 mol% or more and 3 mol% or less, and in the case of a tetrafunctional component, it is 3 mol% or less, preferably 0.2 mol%. Not less than 2 mol%.

If the proportion of the trifunctional component is more than 5 mol%, or if the proportion of the tetrafunctional component is more than 3 mol%, the risk of gelling during the esterification reaction is significantly increased.

The polyester prepolymer for aliphatic polyester used in the present invention has a hydroxyl group at the terminal group substantially. For this purpose, glycols and dibasic acids (or acid anhydrides thereof) used in the synthesis reaction are used. The proportion used requires the use of some excess of glycols.

In order to synthesize a polyester prepolymer having a relatively high molecular weight, it is necessary to use a deglycol-reaction catalyst during the deglycolization reaction following the esterification.

Examples of the deglycol-reaction catalyst include titanium compounds such as acetoacetoyl-type titanium chelate compounds and organic alkoxytitanium compounds.
These titanium compounds can be used in combination. Examples of these include diacetacetoxyoxytitanium (“Nasem Titanium” manufactured by Nippon Chemical Industry Co., Ltd.), tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium and the like. The use ratio of the titanium compound is 0.001 to 100 parts by weight of the polyester prepolymer.
To 1 part by weight, preferably 0.01 to 0.1 part by weight. The titanium compound may be added from the beginning of the esterification, or may be added immediately before the deglycolization reaction.

As a result, the polyester prepolymer usually has a number average molecular weight of 5,000 or more, preferably 20,000 or more.
Those having a melting point of not less than 00 and a melting point of not less than 60 ° C. are easily obtained, and it is more preferable that they have crystallinity.

In order to obtain the aliphatic polyester of the present invention, the number average molecular weight is more than 5,000, preferably 1
Coupling agents are used to increase the number average molecular weight of polyester prepolymers having at least 000 terminal hydroxyl groups.

Examples of the coupling agent include diisocyanates, oxazolines, diepoxy compounds, acid anhydrides, etc., with diisocyanates being particularly preferred.

In the case of an oxazoline or diepoxy compound, it is necessary to react a hydroxyl group with an acid anhydride or the like, convert the terminal to a carboxyl group, and then use a coupling agent.

The diisocyanate is not particularly limited,
For example, 2,4-tolylene diisocyanate, 2,4-
A mixture of tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, Isophorone diisocyanate is preferred, and hexamethylene diisocyanate is particularly preferred from the viewpoints of the hue of the formed resin, reactivity when adding polyester, and the like.

The addition amount of these coupling agents is 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight based on 100 parts by weight of the polyester prepolymer.

If the amount is less than 0.1 part by weight, the coupling reaction is insufficient, and if it exceeds 5 parts by weight, gelation occurs.

The addition is desirably carried out under conditions in which the polyester prepolymer is in a uniform molten state and can be easily stirred. It can be added to a solid polyester prepolymer and melted and mixed through an extruder, but it is added to an aliphatic polyester production apparatus or to a molten polyester prepolymer (for example, in a kneader). It is practical.

The aliphatic polyester resin has a temperature of 190.
The melt viscosity at 100 ° C. and a shear rate of 100 (sec ⁻¹ ) is 2,000-100,000 poise, and the MFR (19
0 ° C.) is 20 g / 10 min or less. Particularly preferred is 5,000 to 50,000 poise, and if it is less than 2,000 poise, it becomes difficult to form a stable and uniform unstretched film in extrusion molding. The flow was extremely poor, and heat generation and flow unevenness occurred from the die outlet, so that a high-quality unstretched film could not be obtained. MFR (190 ° C)
Is required to be 20 g / 10 min or less, and MFR
Is more than 20 g / 10 min.

The film has an aliphatic polyester having a number average molecular weight of 20,000 or more and a melting point of 70 to 200 ° C.
Wherein the urethane bond is particularly 0.03-3.
It is desirably 0% by weight. Number average molecular weight is 20,
For the first time, a stretched film having a strength of at least 000 or more as described above can be obtained, and can be used in various applications. 2
If it is less than 000, it becomes brittle in terms of strength, which is not preferable as a stretched film having practical strength.

In order to produce a uniaxially stretched heat-shrinkable aliphatic polyester film, it is necessary to first produce an unstretched film (raw fabric). The unstretched film is formed by an air-cooled inflation method, Any of a water-cooled inflation method and a T-die molding method may be used.

The air-cooled inflation method is an example of an unstretched film. The resin is sufficiently melted and mixed in an extruder, and then uniformly extruded from a circular die in a state where the resin temperature is made uniform. By expanding the blow ratio to about 0.5 to 4.0 by a system, a tubular film having a film thickness of about 40 μm to 400 μm can be obtained. In particular, setting of the molding temperature is important, and the temperature of the cylinder and the die of the extruder is 120 to 240 ° C, preferably 160 to 190 ° C.
If the temperature is lower than 120 ° C., the viscosity is too high to form a stable film. On the other hand, when the temperature exceeds 240 ° C., the resin is deteriorated, gels and foreign substances are frequently generated, and it becomes difficult to form a high-quality film.

The unstretched film (raw material) thus obtained generally has insufficient transparency (haze) (10% or more). However, by stretching this film uniaxially between two sets of rolls, the film becomes transparent. Heat-shrinkable polyester film having remarkably excellent properties (10% or less, preferably 5% or less), uniform film thickness without stretching unevenness, excellent film strength, and low moisture permeability and excellent moisture-proof properties I found that

Here, the diameter of the roll is 200 mmφ or less,
Roll temperature is 70 to 150 ° C, preferably 80 to 130
C. and the draw ratio is generally 2.0 to 10.0, preferably 3.0 to 8.0. The air gap is generally 10 mm or less.

The physical properties of the heat-shrinkable aliphatic polyester film thus obtained are such that it has a high transparency of not more than 10% and a tensile strength at break (MD) of 800 kg / cm.
² or more, the elongation at break is 100% or less, and the Young's modulus of the film is 10,000 kg / cm ² or more. Having a breaking strength of at least 800 kg / cm ² is generally excellent in strength as a packaging film, can be used for packaging heavy objects, and exhibits a heat shrinkage of at least 30% at 90 ° C. As a great feature. In addition, an unstretched film of an aliphatic polyester tends to have a high moisture permeability (having a moisture permeability of more than 100 g / m ² · 24 hr),
Although there was a problem in the moisture proof property, the film obtained by this method also had low moisture permeability (100 g / m ² · 24 hr or less)
It was found to be excellent in moisture resistance.

When using the polyester of the present invention, it is needless to say that a lubricant, a wax, a coloring agent, a filler, and the like can be used in combination, if necessary. In particular, when forming a film of this resin, besides the conventional lubricant, it is especially VITO
A lubricant such as N was very effective in obtaining a film of good quality, particularly a film having good surface smoothness.

[0044]

The present invention has been developed for the purpose of providing a film having high transparency, microbial decomposability, heat sealability, large heat shrinkage, moisture proofing, and low combustion heat generation.

First, an aliphatic polyester is selected from resins satisfying the requirements of biodegradability and low combustion heat generation,
Using a small amount of a coupling agent, a melting point of 70 to 200 ° C, a temperature of 190 ° C, and a shear rate of 100 seconds
a melt viscosity at c ^-1 of 2,000 to 100,000;
The problem was overcome by using an aliphatic polyester resin having a number average molecular weight of 20,000 or more.

[0046]

【Example】

(Example 1) After replacing a 700 L reactor with nitrogen,
183 kg of 1,4-butanediol, 224 k of succinic acid
g. The temperature was increased in a nitrogen stream, and 192
At 220 ° C. for 3.5 hours, further stopping nitrogen and
The esterification reaction by dehydration condensation was performed for 3.5 hours under a reduced pressure of 2 mmHg. The collected sample had an acid value of 9.2 mg / g, a number average molecular weight (Mn) of 5,160,
The weight average molecular weight (Mw) was 10,670.
Subsequently, 34 g of tetraisopropoxytitanium as a catalyst was added under a nitrogen stream at normal pressure. The temperature was raised, and a deglycol-reaction was performed at a temperature of 215 to 220 ° C under a reduced pressure of 15 to 0.2 mmHg for 5.5 hours. The collected sample had a number average molecular weight (Mn) of 16,800 and a weight average molecular weight (Mw) of 43,600. The yield of this polyester (A1) was 339 kg excluding condensed water.

To a reactor containing 339 kg of polyester (A1), 5420 g of hexamethylene diisocyanate was added, and a coupling reaction was carried out at 180 to 200 ° C. for 1 hour. The viscosity increased rapidly but no gelling occurred. Next, 1700 g of Irganox 1010 (manufactured by Ciba Geigy) as an antioxidant and 1700 g of calcium stearate as a lubricant were added, and stirring was further continued for 30 minutes. This reaction product was extruded into water with an extruder and cut into a pellet by a cutter. 90 ° C
The yield of the polyester (B1) after vacuum-drying for 6 hours was 300 kg.

The obtained polyester (B1) is a slightly ivory white wax-like crystal having a melting point of 110.
° C, the number average molecular weight (Mn) is 35,500, the weight average molecular weight (Mw) is 170,000, the MFR (190 ° C) is 1.0 g / 10 min, the viscosity of a 10% solution of orthochlorophenol is 230 poise, Temperature 190 ° C, shear rate 10
The melt viscosity at ⁰ sec ^-1 was 1.5 × 10 ⁴ poise. The average molecular weight is measured by Shodex GPC
System-11 (gel chromatography manufactured by Showa Denko KK), solvent: CF ₃ COONa 5 mmol solution of hexafluoroisopropyl alcohol, concentration 0.1% by weight, calibration curve: PMMA standard sample manufactured by Showa Denko KK
Performed on a Shodex Standard M-75.

Next, the polyester resin (B1) was extruded using an extruder having a screw diameter of 65 mmφ and L / D = 28.
At a resin temperature of 170 ° C (cylinder and die), 100
mmφ spiral die (lip gap 1.2m
m) and extruded, cooled with air from an air ring by the usual air-cooled inflation method, and withdrawal speed of 10 m
/ Min, folded diameter 300mm (blow ratio 1.9), thickness 1
A 10 μm tubular unstretched film was formed. Stable film formation was achieved by adjusting the air volume of the blower and the air ring to control the cooling conditions.

This unstretched film is stretched to a stretching roll diameter of 80.
The film was stretched at a roll temperature (stretching temperature) of 80 ° C. to a stretch ratio of 3.5 with an air gap of 3 mm between two sets of rolls having a diameter of mm to obtain a stretched film having a thickness of 30 μm.

The obtained stretched film was formed by a haze (ASTM).
D 523, hereinafter the same) is 3.2%, and the tensile strength at break (JIS Z 1702, hereinafter the same) is 1800 kg /
cm ^{2, which} is very strong and has a tensile elongation at break (JIS Z 17
02, the same applies hereinafter) is 50% and the Young's modulus (ASTM D
822, the same applies hereinafter) at 16000 kg / cm ² , sufficient physical properties as a packaging film were obtained. The film can be heat-sealed with a heat sealer on a hot plate.
800 g at 20 ° C., time 1 sec, pressure 1 kg / cm ²
/ 15mm width seal strength and heat shrinkage (JIS
Z 1709, same hereafter) is also 33% in MD (90 ° C)
And a large shrinkage ratio, and an excellent heat-shrinkable film was obtained. Further, the moisture permeability of the film (JIS Z 020)
8, hereinafter the same) is as small as 38 g / m ² · 24 hr, and the moisture permeability of an unstretched film (30 μm) of the same thickness is 120 g / m ^2.
It is remarkably smaller than m ² · 24 hr and has excellent moisture-proof properties.

When this film was buried in the soil for 2 months and the strength was measured, the breaking strength and elongation were significantly reduced to 300 kg / cm ² and 3%, respectively. It became clear that there was.

Example 2 The polyester resin (B1) used in Example 1 was screwed with a screw diameter of 65 mmφ and L / D = 2.
Extruder is extruded from a 100 mmφ spiral die (lip gap 1.2 mm) at a resin temperature of 200 ° C. (cylinder and die) using an extruder of No. 8, cooled by air from an air ring by a usual air-cooled inflation method, and a take-up speed of 7 m / min, a tube-shaped unstretched film having a folding diameter of 300 mm (blow ratio 1.9) and a thickness of 150 μm was formed. Stable film formation was achieved by adjusting the air volume of the blower and the air ring to control the cooling conditions.

This unstretched film is stretched at a roll temperature of 90 ° C., at an air gap of 3 mm, at a stretch ratio of 7.0 times between two sets of stretch rolls having a diameter of 80 mmφ, and has a thickness of 20 μm.
m of the stretched film was obtained.

[0055] The resulting film haze of 2%, tensile strength at break is very strong and 2100kg / cm ^2, tensile elongation of 20%, a Young's modulus of sufficient physical properties are obtained as a packaging film in 19000kg / cm ² Was done. The film can be heat-sealed with a heat sealer on a hot plate.
800 g at 20 ° C., time 1 sec, pressure 1 kg / cm ²
A seal strength of / 15 mm width was obtained, and the heat shrinkage (MD) at 90 ° C. showed a large heat shrinkability of 54%. Also,
The moisture permeability of this film is 62 g / m ² · 24 hr, and the unstretched film (20 μm) of the same thickness is 170 g / m ² · 2
It turns out that it is remarkably smaller than 4 hours and excellent in moistureproofness.

Example 3 A 700 L reactor was purged with nitrogen, and 177 kg of 1,4-butanediol, 198 kg of succinic acid and 25 kg of adipic acid were charged. The temperature is increased under a nitrogen stream, and the temperature is increased to 190 to 210 ° C. for 3.5 hours.
2. Further stop nitrogen, and under a reduced pressure of 20 to 2 mmHg.
The esterification reaction by dehydration condensation was performed for 5 hours. The collected sample had an acid value of 9.6 mg / g, a number average molecular weight (Mn) of 6,100, and a weight average molecular weight (M
w) was 12,200. Subsequently, 20 g of tetraisopropoxy titanium as a catalyst was added under a nitrogen stream at normal pressure. Raise the temperature to 15 at a temperature of 210-220 ° C.
The deglycol-reaction was performed under a reduced pressure of 0.2 mmHg for 6.5 hours. The collected sample has a number average molecular weight (M
n) is 17,300 and the weight average molecular weight (Mw) is 4
6,400. The yield of this polyester (A2) was 337 kg excluding condensed water.

4.66 kg of hexamethylene diisocyanate was placed in a reactor containing 333 kg of polyester (A2).
Was added and a coupling reaction was performed at 180 to 200 ° C. for 1 hour. The viscosity increased rapidly but no gelling occurred. Then Irganox 1010 was used as an antioxidant.
1.70 kg (manufactured by Ciba-Geigy) and 1.70 kg of calcium stearate as a lubricant were added, and an additional 30
Stirring was continued for minutes. This reaction product was extruded into water with an extruder and cut into a pellet by a cutter. The yield of the polyester (B2) after vacuum drying at 90 ° C. for 6 hours was 300 kg.

The obtained polyester (B2) is a slightly ivory white wax-like crystal having a melting point of 103.
° C, number average molecular weight (Mn) is 36,000, weight average molecular weight (Mw) is 200,900, MFR (190 ° C) is 0.52 g / 10 min, and 10% of orthochlorophenol.
The solution has a viscosity of 680 poise, a temperature of 190 ° C. and a shear rate of 1.
The melt viscosity at 00 sec ^-1 was 2.2 × 10 ⁴ poise.

This polyester resin (B2) was extruded at a resin temperature of 170 ° C. (cylinder and die) using an extruder having a screw diameter of 65 mmφ and L / D = 100 mm.
Extruded from a spiral die (lip gap 1.2 mm), cooled with air from an air ring by a normal air-cooled inflation method, and the take-up speed was 20 m / mi.
n, folded diameter 160mm (blow ratio 1.0), thickness 110μ
m of a tubular unstretched film. Stable film formation was achieved by adjusting the air volume of the blower and the air ring to control the cooling conditions.

The unstretched film is stretched at a roll temperature of 70 ° C., at a stretch ratio of 3.0 times with an air gap of 3 mm between two pairs of stretch rolls having a diameter of 80 mmφ and a thickness of 35 μm.
m of the stretched film was obtained.

[0061] The resulting film haze of 2.8%, tensile strength at break is very strong and 1400 kg / cm ^2, tensile elongation of 40%, physical properties enough as a packaging film Young's modulus in 12000kg / cm ² was gotten. The film can be heat-sealed with a heat sealer of a hot plate, and heated at a temperature of 115 ° C. for 1 ^second at a pressure of 1 kg / cm ² .
A seal strength of 00 g / 15 mm width was obtained, and the heat shrinkage (MD) at 90 ° C. was as large as 40%, showing excellent heat shrinkability. Furthermore, moisture permeability of the film is 48g / m ² · ²
In 4 hours, 14 unstretched films (35 μm) of the same thickness
It is smaller than 3 g / m ² · 24 hr, and is excellent in moisture resistance.

When this film was buried in soil for 3 months and the strength was measured, the breaking strength and elongation were significantly reduced to 180 kg / cm ² and 3%, respectively, and decomposition occurred in the soil. It became clear that.

Example 4 The polyester resin (B2) used in Example 3 was screwed with a screw diameter of 55 mmφ and L / D = 2.
Using an extruder of No. 8, extrude from a 50 mmφ spiral die (lip gap 1.2 mm) at a resin temperature of 150 ° C. (cylinder and die), and cool with water from a water cooling ring (water temperature of 10 ° C.) by a normal water cooling inflation method. And take-off speed 10m / min, folding diameter 200mm
(Blow ratio: 2.55), a tubular unstretched film having a thickness of 100 μm was formed. Stable film formation was achieved by adjusting the amount of water in the water-cooled ring and the distance between the dice and the water-cooled ring to control the cooling conditions.

The unstretched film was stretched at a roll temperature of 80 ° C. and stretched at a stretch ratio of 4 × with an air gap of 3 mm between two sets of rolls having a stretch roll diameter of 80 mmφ and a thickness of 25 mm.
A μm stretched film was obtained.

[0065] The resulting film haze of 1.2%, tensile strength at break is very strong and 1500 kg / cm ^2, tensile elongation of 60%, a Young's modulus sufficient properties as a packaging film 12000kg / cm ² was gotten. This film can be heat-sealed with a heat sealer of a hot plate, and heated at a temperature of 115 ° C. for 1 ^second at a pressure of 1 kg / cm ² .
A seal strength of 00 g / 15 mm width was obtained, and the heat shrinkage (MD) at 90 ° C. was as large as 62%. Further, the moisture permeability of this film was ^{68g / m 2 · 24hr, 157g} / m 2 of the unstretched film of the same thickness (25 [mu] m)
・ Smaller than 24 hours and excellent in moisture resistance.

When this film was buried in soil for 3 months and the strength was measured, the breaking strength and elongation were greatly reduced to 320 kg / cm ² and 3.10 %, respectively. It has become clear that this has occurred.

(Comparative Example 1) Thickness 15 obtained in Example 2
Using an unstretched film of 0 μm, stretching is performed at a stretching temperature of 7.0 times with an air gap of 50 mm between two stretching rolls having a diameter of 80 mm at a roll temperature of 90 ° C. and a thickness of about 20 μm.
Was obtained. The haze of the obtained film is 1
Transparency was as large as 8%. Further, the thickness unevenness of the film was large, and a good quality packaging film could not be obtained.

(Comparative Example 2) Thickness 10 obtained in Example 4
Using an unstretched film having a thickness of 0 μm, the film was stretched at a roll temperature of 60 ° C. between two stretching rolls having a diameter of 80 mmφ with an air gap of 3 mm and a stretching magnification of 4.0 times to obtain a stretched film having a thickness of 25 μm. The haze of the obtained film is 12%
And the moisture permeability of this film is 240 g / m ²
It was remarkably large at 24 hours, and high transparency and excellent moisture-proof properties as in the present invention could not be obtained.

[0069]

According to the present invention, an aliphatic prepolymer having a terminal hydroxyl group having a relatively high molecular weight is prepared, and this is converted into a high molecular weight aliphatic polyester resin without gelation using a small amount of a coupling agent, and this is molded. The present invention relates to a heat-shrinkable polyester film exhibiting a large heat shrinkage at a low temperature by stretching and having moisture proof properties.

Although the film of the present invention is a polyester film, it is a film having biodegradability and heat-sealing property unlike a conventional polyester film (polyethylene terephthalate resin film). This is a heat-shrinkable aliphatic polyester film which has a lower heat generation value for combustion than polyolefin resins such as polyethylene and polypropylene and has a moisture-proof property with little problem of disposal.

Further, since the film is subjected to the coupling treatment while being an aliphatic polyester resin, the film is excellent in heat stability and mechanical strength, has moisture-proof properties, and is used as a heat-shrinkable packaging material having heat sealability as it is. Can be used.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B29K 105: 02 105: 32 C08L 67:00 (72) Inventor Takashi Fujimaki 634-4-442 Nobamachi, Konan-ku, Yokohama-shi, Kanagawa 56) References JP-A-7-47598 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 B29C 55/04 B29C 61/06 C08G 63/16

Claims (3)

(57) [Claims] ^1. A melt viscosity of 2,000 at a temperature of 190 ° C. and a shear rate of 100 (sec ⁻¹ ) mainly synthesized from glycol and an aliphatic dibasic acid or a derivative thereof.
0-100,000 poise, melting point 70-200
° C, number average molecular weight is 20,000 or more, MFR
(190 ° C.) 20 g / 10 min or less, formed from an aliphatic polyester having a thickness of 200 μm or less, and a haze of
10% or less, heat-shrinkable aliphatic polyester stretched fill <br/> arm moisture permeability has the following <br/> moistureproof 100g ^/ m 2 · 24hr. 2. Heat shrinkage (MD) at 90 ° C. of a film
The heat-shrinkable heat-shrinkable aliphatic polyester stretched film having moisture resistance according to claim 1 , which has a heat sealing property of 30% or more and has a biodegradability . 3. A melt viscosity of 2,000 at a temperature of 190 ° C. and a shear rate of 100 (sec ⁻¹ ) mainly synthesized from glycol and an aliphatic dibasic acid or a derivative thereof.
0-100,000 poise, melting point 70-200
° C, number average molecular weight is 20,000 or more, MFR
An unstretched film obtained by molding an aliphatic polyester having a temperature (190 ° C.) of 20 g / 10 min or less at a molding temperature of 120 to 240 ° C. has an air gap of 10 mm or less and a stretching temperature of 7
The method for producing a heat-shrinkable aliphatic polyester stretched film according to claim 1, wherein the stretched film is stretched in a uniaxial manner at 0 to 150 ° C. and a stretch ratio of 2 to 10 times .