JPH0885144A - Method for producing biodegradable aliphatic polyester film - Google Patents

Abstract

(57) [Summary] [Structure] After melt-extruding a biodegradable polyester having a ring-opening structure of poly (2-oxetanone) as a main repeating unit and a molecular weight in the range of 20,000 to 2,000,000 from a T-die extruder. A method for producing a T-die melt-extruded film of biodegradable polyester, which comprises cooling and solidifying with a cooling roll having a roll surface temperature controlled to 10 to 40 ° C. [Effect] The production method of the present invention enables production of a melt-extruded film from a biodegradable polyester containing poly (2-oxetanone), which has not been produced conventionally, as a main structural component. That is, the manufacturing method of the present invention is
The crystallization speed is slower than that of polyolefin, and the polarity is high, so that it is easily attached to a metal surface, and further, the biodegradable polyester film whose molding conditions are extremely difficult because it easily decomposes due to water, By controlling the surface in a specific temperature range, it accelerates the crystallization speed and improves the peelability from the surface of the chill roll, and stabilizes the shape of the film after winding, resulting in practical productivity. Enables the production of the polyester film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a melt-extruded film of biodegradable aliphatic polyester which is decomposed by the action of microorganisms in the environment.

[0002]

2. Description of the Related Art As the problem of waste treatment becomes a social problem, the study of recycling garbage is being considered in various fields. For example, composting of raw garbage discharged from homes is being considered as one means of recycling this garbage resource. Actually, raw garbage is separated and collected in various places and processed at composting plants.

Paper bags are currently used for the separate collection of raw garbage for composting. Since paper is a natural material, it can be composted. But it also has many problems. For example, it is easy to be broken by water in raw garbage, its contents are not identifiable because it is opaque and it cannot prevent the mixture of composting incompatible substances, it requires a string of natural material to close its mouth, it needs a place to store because it is bulky. In addition, there are problems in use such as slow biodegradation of paper and global environmental problems such as consumption of wood resources. Such problems are also a factor to suppress the recycling of garbage.

[0004] It is plastic waste that causes the greatest problems in the separate collection. In particular, plastic films are easy to scatter in the environment, do not rot and disappear, the incinerator is easily damaged due to the large amount of combustion heat, and the appearance is large, which shortens the life of landfill sites. Is causing serious problems. Biodegradable plastic materials are attracting attention as one of the solutions to these plastic waste problems.

[0005] For example, it is desired to use the garbage bag for garbage which is more suitable for composting. Specifically, it is water resistant and does not break due to water in garbage, it is transparent or translucent and its contents can be confirmed, it is thin and not bulky, and it can tie the bag entrance, especially a string etc. There is an urgent need to develop a material that does not require heat treatment and that has the strength to withstand the weight of the contents.

[0006] In addition to garbage bags for garbage, fertilizer bags, bags for agricultural and horticultural wastes, etc. are bags that can be used or recycled as they are without processing the bags after removing the contents. Development is desired.

In recent years, various biodegradable plastic materials have been developed. However, a material satisfying biodegradability, film moldability, processed physical properties, etc. and being used to such an extent as to actually reduce the waste problem has not yet been developed.

For example, since poly (3-hydroxybutyric acid) biosynthesized by microorganisms has a melting point and a decomposition temperature close to each other,
There is a problem with moldability. In addition, the compound with starch has a problem of water resistance, and the chemical compound is concerned about biodegradability.

Poly (2-oxetanone), which is a polyester synthesized from 2-oxetanone, is known to be well decomposed by the action of enzymes secreted by microorganisms, and is a material that can cope with the problem of plastic waste. Is expected to be developed (Mukai et al., Polymers, 50
Volume 10, 715-722 (1993)).

The polymerization reaction formula from 2-oxetanone to poly (2-oxetanone) is as follows.

[0011]

Embedded image

The fact that poly (2-oxetanone) is a material having good biodegradability is reported by Fields et al. In 1975 (RD Fields and F. Rodriguez, Proc. Int. Biodeg.
radation Symp. 3rd, 775 (1975)), it is well known, but physical properties other than biodegradability have not been reported in detail. Kagaya et al. Have a film-forming ability when the absolute viscosity [η] of the solution is 0.5 or more.
The above-mentioned materials are reported to be capable of fiber-forming ability and cold stretching of the film (Taku Kaguya, Musashi Saina, Kenichi Fukui, Journal of Industrial Chemistry, Vol. 67, No. 6, 951 (1964)). Kazuo et al. Made a film made from chloroform by solvent casting method at room temperature and hot water at 65 ° C at 500-700%.
Stretching and conducting spectroscopic research on film structure (Takeshi Wazai, Takeo Saegusa, Junji Furukawa, Journal of Industrial Chemistry,
67, No. 4, 601 (1964)). Matissen et al. Reported a good value of 103 MPa, in which poly (2-oxetanone) was sandwiched between mylar films, which was heated and compressed to form a 0.5 mm-thick sheet, which was stretched. (T. Mathisen, M. Monica, and A.-C. Albe
rtsson, Journal of Applied Polymer Science, Vol.4
2, 2365 (1991)).

As described above, poly (2-oxetanone)
The development of is limited to the experimental scale stage, and there is no clear report that a film satisfying the various physical properties to be industrially practically used has been formed. Regarding the physical properties of the film, only the tensile strength and melting point have been reported. The reason is that it is not easy to synthesize high molecular weight poly (2-oxetanone) that can be formed into a film, and even if relatively high molecular weight poly (2-oxetanone) can be synthesized, the film forming process is difficult. This seems to have been due to the fact that it is difficult to synthesize as much as possible, and that the conditions for forming and processing the film have yet to be developed.

However, since the results suggesting good biodegradability and tensile strength were obtained, poly (2
-Oxetanone) is expected to grow, and urgent development of practical films such as garbage bags is desired.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is to
Biodegradability of oxetanone as the main structural component of the ring-opening structure,
It is intended to provide a method for producing a practical film having excellent mechanical properties and molding processability.

[0016]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have manufactured a polyester having a specific molecular weight with a ring-opened structure of 2-oxetanone as a main structural component in a specific production process. It was found that a film of biodegradable aliphatic polyester having good physical properties that can be put to practical use can be obtained by melt extrusion molding under the conditions, and the present invention has been completed.

That is, the present invention provides the following formula (1):

[0018]

[Chemical 3]

A biodegradable aliphatic polyester having a repeating unit represented by the formula (1) as a main repeating unit and having a weight average molecular weight in the range of 2 to 2,000,000 is added to T of a T-die extruder.
After melt extrusion from the die, the roll surface temperature is 10-40
A method for producing a biodegradable aliphatic polyester film, which comprises cooling with a cooling roll at a temperature of ℃.

The aliphatic polyester film in the present invention basically comprises a biodegradable polyester having a repeating unit represented by the above formula (1) as a main repeating unit.

The polyester composed of only the main repeating unit is poly (2-oxetanone),
By ring-opening polymerization of oxetanone, or
It can also be obtained by dehydration polycondensation of hydroxypropionic acid.

In the biodegradable polyester of the present invention, in addition to the repeating unit represented by the formula (1), a ring-opening structural unit of a cyclic ester compound other than 2-oxetanone and a cyclic ether compound is used as a monomer unit. 20% by weight
Copolymers copolymerized below are also included. Examples of the cyclic ester include β-butyrolactone, pivalolactone, δ-valerolactone and ε-caprolactone. Examples of the cyclic ether compound other than 2-oxetanone include ethylene oxide,
Propylene oxide etc. can be mentioned.

The biodegradable polyester in the present invention is
It is necessary that the polymer has a weight average molecular weight of 20,000 or more. If the weight average molecular weight is less than 20,000, mechanical properties such as strength and elongation may be insufficient depending on the purpose of use and method of the film, and it is difficult to put it into practical use. On the other hand, when the weight average molecular weight is extremely high, processing may be difficult due to high viscosity during melting. Therefore, it is suitable that the molecular weight is preferably 2,000,000 or less.

The melt extruded film can be obtained by a generally known melt extrusion molding method, and one of the processing methods particularly preferably used is the T-die extrusion molding of the present invention. The T-die extrusion molding is a flat film die (also called a T-die, a T-die or a T-die) for extruding a polymer in a fluid state by being melted at a screw portion at the tip of an extruder into a film or a sheet.
Is a molding method in which a die or film is attached and the film or sheet is molded.

The T-die in the present invention is a general term for the entire flat film die including a straight manifold type having a zero manifold angle, a coat hanger die having an angle, and a combination thereof.

The T-die extruder used in the present invention is as follows:
Various T-die extruders equipped with the above-mentioned T-dies used for forming a film of a thermoplastic resin such as polyethylene can be used. A single-screw or twin-screw extruder is preferably used, and the temperature of the barrel or T-die, the screw shape, the number of rotations, depending on the molecular weight of the biodegradable polyester of the present invention, the shape of the molded film, the application, and the like. Melting conditions such as, are appropriately selected.

When carrying out T-die extrusion molding, the biodegradable polyester is usually supplied to the T-die extruder in the form of powder and particles after polymerization and film-formed. Prior to film formation, the biodegradable polyester is used. Pelletization of can also be suitably carried out.

In the method for producing a melt-extruded film of the present invention, the melting and processing conditions preferably carried out are barrel and die temperatures of 80 to 180 ° C., more preferably,
100-150 degreeC is preferable. If the temperature is lower than 80 ° C., the biodegradable polyester of the present invention is insufficiently melted, and if the temperature is higher than 180 ° C., the thermal decomposition of the biodegradable polyester of the present invention becomes remarkable, which is not preferable. However, the barrel temperature just below the hopper can be carried out even at a temperature lower than 80 ° C.

The poly (2-oxetanone) melt melt-extruded from the T-die is cooled by a cooling roll to be solidified, and then peeled off from the cooling roll and wound into a film. In order to cool and solidify and wind the film with good productivity, the melted and unstable state must be changed to a stable state on the cooling roll.
The stable state of the film means that in the case of a crystalline polymer, crystallization proceeds sufficiently. By sufficiently advancing crystallization, the size of the film becomes stable, peeling from the chill roll becomes easy, and the film after winding does not change.

In the present invention, it is important to control the surface temperature of the cooling roll in order to promote the crystallization of the film and to produce the film more efficiently. The surface temperature slightly differs depending on the thickness of the melt-extruded poly (2-oxetanone), the additive, the filler, the extrusion amount, and the like, but the surface temperature of the cooling roll is commonly 10 to 40. It is essential to be in the range of ° C. More preferably, it is in the range of 15 to 35 ° C. When the temperature of the chill roll surface is less than 10 ° C,
The crystallization speed becomes slow, and the film size changes during winding and the film deforms after winding as described above. There is also a problem of roll touch. The roll touch property is a phenomenon in which the surface smoothness is lost when a molten polymer comes into contact with an excessively cooled roll surface. Further, condensation of water on the cooled roll surface is also a problem. For example, when the water condensed on the roll surface adheres to the film surface and is heated while containing the water, the hydrolysis of the biodegradable polyester may be promoted. Therefore, the process becomes complicated, for example, a drying process is required when the formed film is further processed. On the contrary, when the chill roll surface temperature exceeds 40 ° C,
Similarly, the solidification of the crystal is delayed and the above problems occur. In this case, a notable problem is adhesion to the surface of the chill roll. The biodegradable polyester of the present invention has a high polarity because it has an ester structure in its main chain, and therefore is extremely easily attached to the metal surface as compared with polyolefin. This adhesion makes it difficult to peel the film from the roll surface, and as a result, the productivity of the film is significantly reduced. In the present invention, the cooling roll means a cooling roll which the film extruded from the T-die first contacts for the purpose of cooling. Therefore, when using a plurality of cooling rolls, it means the first cooling roll.

The melt-extruded film formed by the production method of the present invention can be further improved in its mechanical properties by forming a stretched film. As a stretching method, a generally known stretching method such as roll stretching or stretching by a tenter method can be used without any limitation. The stretching conditions may be a temperature range of room temperature to 80 ° C. and a stretching ratio of 2 to 15 times. In order to increase the processing speed and improve the efficiency, it is more preferably carried out in the temperature range of 70 to 80 ° C. Stretching can be carried out in any manner such as uniaxial stretching for forming a uniaxially oriented film, sequential biaxial stretching for biaxial orientation, and simultaneous biaxial stretching for plane orientation. When stretched, the tensile breaking strength in the stretching direction is usually 500 to 5000 kgf / cm ² .

In the present invention, the film preferably has a thickness in the range of 1 to 300 μm. The melt extruded film formed by the production method of the present invention is formed from the biodegradable polyester of the present invention. Since the biodegradable polyester usually has crystallinity, the crystal phase formed in the film becomes transparent. Affect. The transparency of a film changes depending on the thickness of the film, and the transparency decreases as the thickness of the film increases. For example, in order to develop a translucent to transparent mode in which the contents of a bag-shaped product formed from the film can be identified, the film thickness is 300.
It is preferably not more than μm, and in order to maintain flexibility as a film and sufficient mechanical strength, it is 1 to 10
The range of 0 μm is more preferable.

A filler can be added to the melt-extruded film formed by the production method of the present invention within a range in which physical properties are not particularly deteriorated. As the filler that can be added, generally known fillers can be used without any limitation, but in particular, talc in terms of accelerating the solidification rate and facilitating peeling from the chill roll, and also of the biodegradable polyester of the present invention. An alkaline earth metal salt is more preferably used because it contributes to stabilization.

Here, the alkaline earth metal is calcium, magnesium, barium, etc., but calcium and magnesium are particularly preferable in view of the influence on the environment. Further, the alkaline earth metal salts are hydrochlorides, sulfates, carbonates and silicates of alkaline earth metals,
Specifically, hydrochlorides such as calcium chloride and magnesium chloride; sulfates such as magnesium sulfate and barium sulfate; carbonates such as magnesium carbonate and calcium carbonate; calcium orthosilicate, calcium metasilicate,
It is a hydrated magnesium silicate such as dicalcium silicate, tricalcium silicate, sodium calcium silicate, calcium aluminum silicate, magnesium orthosilicate, magnesium metasilicate, talc, and magnesium silicate. Among these alkaline earth metal salts, silicates having low hygroscopicity and easy to handle are most preferably used. Each of the above alkaline earth metal salts may be used alone or in combination.

The above-mentioned alkaline earth metal salt is preferably used in the film in an amount of 20% by weight or less based on the biodegradable polyester of the present invention.

The melt-extruded film formed by the production method of the present invention has an antioxidant, a release agent, a weathering agent, an antistatic agent, a coloring agent, a reinforcing material, a surfactant, and Supplementary ingredients such as inorganic fillers can also be added.

[0037]

The essential point of the production method of the present invention is to provide a method for efficiently cooling and solidifying a melt of the polyester extruded from a T-die on the surface of a chill roll and then peeling the melt from the surface of the chill roll. .

In the case of a crystalline polymer such as poly (2-oxetanone), the essence of cooling and solidifying on the surface of the chill roll lies in the progress of crystallization. Crystallization of a crystalline polymer generally proceeds in the temperature range between its glass transition temperature and its melting point. The glass transition temperature of poly (2-oxetanone) has been reported by Matisson to be -4 ° C (T. Mathisen, M. Lewis, and A.-C. Alber.
tsson, Journal of Applied Polymer Science, Vol.42,
2365 (1991)). On the other hand, the melting point of poly (2-oxetanone) is generally 70 to 80 ° C. in the unoriented state. The range between the glass transition temperature and the melting point is the range in which crystallization can theoretically occur. But,
The closer to the glass transition temperature or melting point, the slower the crystallization rate, and the actually effective crystallization rate is limited to a narrower range.

The range of the cooling roll surface temperature of 10 to 40 ° C. presented in the present invention causes a sufficient cooling and solidifying rate in the T-die melt extrusion molding of an actual poly (2-oxetanone) film to reach the cooling roll surface. And the mutual adhesion of the wound film rolls, thus,
It was found that the temperature range was such that sufficient productivity of the film could be maintained.

The remarkable adhesion to the surface of the chill roll at 40 ° C. or higher is considered to be because poly (2-oxetanone) has an ester structure with high polarity in its main chain. Further, since poly (2-oxetanone) is a resin having a high hygroscopic property and a hydrolyzability, the temperature range where the surface temperature of the cooling roll is low and water is condensed on the surface is not limited to productivity. , Impair the storage stability of the film. That is, the adhesion of water to the surface of the film causes the decomposition of the film to be easily promoted during subsequent secondary processing and storage.

[0041]

The production method of the present invention enables the production of a melt-extruded film from a biodegradable polyester containing poly (2-oxetanone), which has not been produced so far, as a main structural component. . That is, in the production method of the present invention, the crystallization rate is slower than that of polyolefin, the polarity is high, the metal surface is likely to be attached, and the decomposability due to water is likely to occur. Degradable polyester film, by controlling the surface of the cooling roll in a specific temperature range, accelerate the crystallization rate, improve the peelability from the surface of the cooling roll, and stabilize the shape of the film after winding. ,
As a result, it is possible to manufacture the polyester film with practical productivity.

Using the biodegradable polyester film produced by the production method of the present invention, various products, for example, bags such as garbage bags and shopping bags, paper diapers, sanitary products such as sanitary products, mulch films, and bindings. It can be put to practical use in agricultural and forestry and fishery materials such as tapes and pots for seedlings, food packaging materials, and food-related products such as egg packs. The biodegradable film produced by the production method of the present invention is decomposed by microorganisms even when left in a natural environment,
It is also converted into compost by a compost plant.

[0043]

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Polymerization Example 1 Poly (2-oxetanone) used in Example 1 of the present invention
Was produced by the following polymerization method. Example 2 The following poly (2-oxetanone) was prepared according to the polymerization example.

3 equipped with stirrer and condenser
The inner surface of a 5 L capacity stainless steel polymerization container and the blue margin / propeller type stirring blade were spray-coated with an aerosol containing fine particles of tetrafluoroethylene resin to make it non-polar.

Poly (2-oxetanone) having a particle size of 150 to 350 μm (weight average molecular weight 455,000) 100
g, tetramethyl ammonium acetate 1.03 g
A supported polymerization initiator carrying (7.73 mmol) and 10 L of isopropyl chloride were added to a polymerization vessel whose inner surface was depolarized. Next, 5 kg of 2-oxetanone
A (69.39 mol) / isopropyl chloride (15 L) solution was added. Then, stirring was started at a stirring speed of 150 rpm, and the polymerization container was externally heated to 35 ° C. to start the polymerization. The polymerization was performed for 20 hours, and then the reaction liquid was filtered to separate the particulate poly (2-oxetanone), the solvent and the unreacted monomer. The poly (2-oxetanone) was weighed after completely removing the solvent and the unreacted monomer under reduced pressure, and as a result, the polymerization rate was 99.2%. As a result of measuring the molecular weight using size exclusion chromatography, the weight average molecular weight was 412,000 and the number average molecular weight was 183,000. Bulk specific gravity is 0.37
It was 88 g / ml.

Example 1 Preparation of a T-die extruded film: Poly (2-oxetanone) particles (weight average molecular weight 412000, number average molecular weight 183000) having a diameter of 4 attached to a T-die.
Extruder with a barrel of 0 mmφ (V-S40 gruel extruder VFC40-2 manufactured by Tanabe Plastics Co., Ltd.
49) and fed into the extruder barrel having a barrel set temperature of 90 to 110 ° C. and a T die set temperature of 106 to 110 ° C. by a screw, and the molten film was extruded from the T die slit. Extruded molten poly (2
-Oxetanone) was cooled and solidified with a cooling roll in which water having a water temperature of about 23 to 26 ° C circulates, and wound on a winder to prepare an unstretched film roll having a thickness of about 250 to 280 µm.

There was almost no adhesion of the film to the cooling roll, and good peelability was recognized. The surface of the film was also smooth and uniform, there was no deformation of the film after winding, and the width of the wound film was constant. Furthermore, no adhesion between the wound films was observed.

Example 2 Preparation of T-Die Extruded Film: Poly (2-oxetanone) particles (weight average molecular weight 407,000, number average molecular weight 158000) were mixed with 5% by weight of talc, and this mixture was attached to a diameter of T-die. It is supplied to an extruder having a 40 mmφ barrel (the same as in Example 1), and the barrel set temperature is 90 to 110 ° C. and the T die set temperature is 106 to 1.
The molten film was extruded through a T-die slit into the extruder barrel at 10 ° C by a screw. Extruded molten poly (2-oxetanone) /
The talc mixture is cooled and solidified by a cooling roll in which water having a water temperature of about 23 to 26 ° C. circulates, and wound on a winder to have a thickness of about 25.
An unstretched film roll of 0 to 280 μm was prepared.
There was almost no adhesion of the film to the cooling roll, and good peelability was observed. The surface of the film was also smooth and uniform, there was no deformation of the film after winding, and the width of the wound film was constant. Furthermore, no adhesion between the wound films was observed.

Examples 3 to 7 and Comparative Examples 1 and 2 Poly (2-oxetanone) particles (weight average molecular weight 412
000, number average molecular weight 183000) and an extruder having a barrel with a diameter of 30 mm and equipped with a T-die (S30 粍 extruder VD3 manufactured by Tanabe Plastics Co., Ltd.)
0-10), barrel setting temperature 90 ~ 105 ℃,
The molten film was extruded from the T-die slit through a screw into the extruder barrel having a T-die set temperature of 105 ° C. Extruded molten poly (2-
The oxetanone) was cooled and solidified on a cooling roll adjusted to the temperature shown in Table 1, and then wound on a winder. The roll touch property was evaluated from the peelability from the roll surface after cooling on the cooling roll and the surface condition of the film wound on the winder. The evaluation was judged visually, and the evaluation criteria were as follows.

[Film peeling property] Adhesion on roll surface: Adhering to cooling roll, continuous production is not possible. A: Continuous production is possible although there is a slight adhering tendency. Good: No adhering tendency, continuous production [Roll touch property] Not possible : Surface is roughened and / or deformed Good: Surface is smooth and not deformed Evaluation results are also shown in Table 1. As a result, 10 ℃ ~ 40 ℃
It is clear that in the above range, good peeling property and roll touch property are exhibited.

In order to evaluate the storage stability of the films produced in Example 5 and Comparative Example 2, 1
It was cut into 0 cm square, kept as it was in an oven at 50 ° C. for 1 week, and its change in weight molecular weight was measured using size exclusion chromatography. The measurement results are shown in Table 2. The larger decrease in the molecular weight of Comparative Example 2 as compared with Example 5 is due to the fact that the condensed water adheres to the film on the surface of the chill roll that is excessively cooled during the film production, and this water content causes the molecular weight of the film when heated in an oven. It is thought that it caused the decline.

[0053]

[Table 1]

[0054]

[Table 2]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29L 7:00

Claims (1)

[Claims] 1. The following formula (1): The repeating unit represented by is the main repeating unit,
A biodegradable aliphatic polyester having a weight average molecular weight in the range of 2 to 2,000,000 is melt-extruded into a film form from a T-die of a T-die extruder, and a roll surface temperature is 10 to 40.
A method for producing a biodegradable aliphatic polyester film, which comprises cooling with a cooling roll at 0 ° C.