JPH10147653A - Biodegradable oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film having excellent tensile strength, tensile modulus, and haze value, by at least unidirectionally orienting a composition in which a hydroxybutyrate/hydroxyvalerate copolymer and a polylactic acid- based polymer are the essential components. SOLUTION: This film is obtained by melting/blending a composition in which (A) a 3-hydroxybutyrate/3-hydroxyvalerate copolymer and (B) a polylactic acid-based polymer are the essential components, followed by extrusion, cooling, and then orientation at least unidirectionally. The component A includes an aliphatic polyester-based biodegradable polymer having a melting point of 140-180 deg.C and a number average molecular weight (Mn ) of 10<4> -10<6> , which is produced by a microorganism such as Alkaligenes eutrophus. The weight ratio of the component A vs. the component B is (80:20)-(20:80), preferably (70:30)-(30:70). This method allows to produce the objective film that is finally biologically degraded in nature into harmless water and carbon dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate,
The composition comprising a polylactic acid-based polymer as an essential component,
The present invention relates to providing a microbial degradable stretched film having excellent tensile strength, tensile modulus and haze value by stretching in at least one direction.

[0002]

2. Description of the Related Art Conventionally, films made of thermoplastics such as polyvinyl chloride and polyolefin have been used as films for packaging, agriculture, fishing, civil engineering, garbage packaging, and the like. When the intended use is completed, the waste is incinerated and landfilled. However, such thermoplastics have a high burning calorie and tend to damage incinerators and the like in incineration treatment, and do not decompose when buried in soil or the like, so they remain in the natural world forever, and the landfill site is insufficient. It tends to be a problem.

In recent years, as a solution to this problem, there has been proposed a biodegradable polyester polymer such as poly (3-hydroxybutyrate) and poly (3-hydroxyvalylate) which is completely decomposed by microorganisms in soil or water. −g), 3
It has been proposed to use a copolymer of -hydroxybutyrate and 3-hydroxyvalerate, poly (ε-caprolactone), polybutylene succinate, polyethylene succinate and a combination thereof.

[0004]

The biodegradable polyester polymers such as poly (3-hydroxybutyrate) and poly (3-hydroxyvalerate) described above have high crystallinity, are hard and brittle. For this reason, films made of such a biodegradable polyester-based polymer have particularly high tensile modulus and poor flexibility, and have a practical problem. In addition, 3-hydroxybutyrate and 3-hydroxybutyrate having improved the above-mentioned disadvantages of the biodegradable polyester-based polymer can be used.
-A copolymer with hydroxyvalerate is a crystalline, low melting point, soft copolymer.However, a biodegradable film made of this copolymer has practically sufficient performance, such as a tensile modulus. However, its use tended to be limited. A stretched poly (ε-caprolactone) -based film has high strength and elongation and is excellent in transparency, but has a relatively low melting point of poly (ε-caprolactone), and thus has poor heat resistance. When used as such, there has been a tendency that the suitability for packaging machines is inferior and the practicality is limited.

On the other hand, as a method for improving the strength and tensile modulus of a film or the like, stretching the film or the like in at least one direction is generally adopted. However, films made of poly (3-hydroxybutyrate), poly (3-hydroxyvalerate), and a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate have relatively high crystallinity, Since it is brittle, it tends to be difficult to stretch. Further, a film made of poly (ε-caprolactone) tends to have poor heat resistance and film formation stability. As a method for improving these drawbacks, a film comprising a composition obtained by mixing the above-mentioned copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and poly (ε-caprolactone) in a specific ratio is used. By using
A method for producing a biodegradable stretched film having improved high crystallinity, hardness and brittleness, having stable stretchability, stretched in at least one direction, and having excellent strength and flexibility for practical use has also been proposed. However, the film also tends to have insufficient heat resistance and transparency. Stretched films made of polylactic acid-based polymers have excellent heat resistance, transparency, and strength (tensile strength and tensile modulus), but have a higher degradation rate in natural environments than other biodegradable polymers. Is very slow, and furthermore, the film is hard, so that the flexibility is poor and the use tends to be limited.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation. An object of the present invention is to
A composition comprising a copolymer of hydroxybutyrate and 3-hydroxyvalerate, and a polylactic acid-based polymer as essential components is melt-kneaded, extruded, cooled, and then stretched in at least one direction to obtain a longitudinal and transverse tensile elasticity. The average of the rate (Young's modulus)
10,000 kg / cm2 or more, 40,000 kg / c
m2 or less and a haze value of 20% or less.

The microbial degradable stretched film according to the present invention comprises only a copolymer comprising 3-hydroxybutyrate and 3-hydroxyvalerate and a polylactic acid-based polymer as essential components. Other components may be blended as long as the properties of the stretched microbial degradable film are not impaired. At this time, the proportion of the composition constituting the stretched microbial degradable film is usually 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate used in the microbial degradable stretched film of the present invention, a microorganism such as a hydrogen bacterium, Alkarigenes eurotroph
For example, aliphatic polyester-based biodegradable resins having a melting point of 140 to 180 ° C. and a number average molecular weight (Mn) of 10,000 to 1,000,000, preferably 400,000 to 750,000 produced by s or the like can be exemplified. Furthermore, considering workability, the content of 3-hydroxyvalerate is preferably 1 to 20 mol%. 3
When the content of -hydroxyvalerate is less than 1 mol%, the crystallinity is high, so that it tends to be hard and brittle, and when it exceeds 20 mol%, the crystallinity and melting point tend to decrease, and it tends to be too soft. These numerical values are not particularly limited.

The polylactic acid-based polymer used for the microbial degradable stretched film according to the present invention includes, for example, L
-Lactic acid, D-lactic acid and a polymer obtained by directly dehydrating polycondensation of D, L-lactic acid, or any of these lactic acids and another hydroxycarboxylic acid (for example, glycolic acid, 3-hydroxybutyrate) And 4-hydroxybutyrate, 3-hydroxyvalerate, 4-hydroxyvalerate, 6-hydroxycaproic acid, etc.) and lactide which is a cyclic dimer of lactic acid Or a cyclic ester intermediate of the above lactide and hydroxycarboxylic acid [eg, dimer of glycolic acid (glycolide), caprolactone which is a cyclic ester of 6-hydroxycaproic acid, etc.] Copolymers obtained by ring-opening polycondensation by appropriately using a copolymerizable monomer can be exemplified. As understood from this, polylactic acid includes all lactic acid-based polymers, and of course includes copolymers. One or more of these polylactic acids can be used as appropriate.

In the case of direct dehydration polycondensation, the above lactic acid or lactic acid and another hydroxycaproic acid are azeotropically dehydrated and condensed in the presence of, for example, an organic solvent, particularly a phenyl ether-based solvent, and a solvent distilled off by azeotropic distillation is obtained. A method of returning a substantially anhydrous solvent to a reaction system by removing water can obtain a high-molecular-weight polylactic acid having excellent strength for polymerization, but is not particularly limited to the above method. At this time, the number average molecular weight (Mn) of the polylactic acid according to the present invention is not particularly limited,
The number average molecular weight (Mn) is preferably about 50,000 to 1,000,000. If the number average molecular weight (Mn) is less than 50,000, the strength tends to be weak, and if it exceeds 1,000,000, the moldability tends to be poor.

The stretched microbial degradable film according to the present invention is formed from a composition comprising a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and a polylactic acid-based polymer as essential components. The mixing ratio of such a composition is
The copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and the polylactic acid-based polymer are in a weight ratio of 80:
20 to 20:80, preferably 70:30 to
The ratio is 30:70, more preferably 60:40 to 40:60. If the content of the polylactic acid-based polymer is less than 20% by weight (the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate exceeds 80% by weight), the stretchability tends to be extremely poor. If the amount exceeds 30% by weight (the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate is less than 20% by weight), the film tends to be hard and the biodegradability tends to decrease.

Further, in the present invention, a composition comprising a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and a polylactic acid-based polymer is provided with a composition comprising 3-hydroxybutyrate and 3-hydroxyvalerate. And a polymer having microbial degradability other than a polylactic acid-based polymer. Examples of the biodegradable polymer other than the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and the polylactic acid-based polymer include polybutylene succinate, polyethylene succinate, polybutylene succinate adipate, and the like. It can be exemplified, and the compounding amount may be appropriately selected, and it does not matter if there is no particular limitation.

The stretched microbial degradable film according to the present invention needs to be stretched in at least one direction in order to improve the strength (tensile strength, tensile modulus). At this time, the stretching ratio is preferably at least 1.5 times or more in one direction. If the stretching ratio is less than 1.5 times, improvement in tensile strength and tensile modulus tends not to be expected, which is not preferable. At this time, the average value of the tensile elastic modulus (Young's modulus) in the longitudinal direction and the transverse direction is 10,000 kg / cm.
It is preferably 2 or more and 40,000 kg / cm2 or less. If the ratio is out of the above range, improvement in strength or imparting of flexibility cannot be expected, which is not preferable in practical use and the application is limited. However, it can be used depending on the application.

The method for preparing a composition comprising a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and a polylactic acid-based polymer constituting the microbial degradable stretched film according to the present invention as essential components is as follows. There is no particular limitation, and a method commonly used in a conventional method for producing a composition of a thermoplastic resin such as a polyolefin-based polymer, for example, a method using a kneader such as a kneader, a Banbury mixer, or a roll, single-screw or twin-screw extrusion The method can be carried out by a method of heating and melt-kneading using a mixer to granulate pellets, a method of blending with a ribbon blender, a Hensel mixer, a tumbler or the like, and is not particularly limited.

[0015] Further, a composition comprising a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and a polylactic acid-based polymer constituting the microbial-degradable stretched film according to the present invention as essential components: If desired, other synthetic resins, various additives and fillers such as heat stabilizers, antioxidants, antistatics, lubricants, antibacterials, pigments or dyes, titanium oxide, calcium carbonate, calcium sulfate, sulfuric acid Barium, magnesium hydroxide, silica, talc and the like may be added. The other synthetic resin is not particularly limited, but includes, for example, other biodegradable resins. For example, poly (3-hydroxybutyrate), poly (3-hydroxyvalerate), a copolymer of 3-hydroxybutyrate and 3-hydroxypropionate,
A polyhydroxyalkanoate such as a copolymer of 3-hydroxybutyrate and 4-hydroxybutyrate can be blended as required.

As a method for producing a microbial degradable stretched film according to the present invention, for example, a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, a polylactic acid A composition comprising a base polymer and, if necessary, other biodegradable resins, additives, fillers, etc. is supplied, and then the extruder is set to a cylinder temperature of 170 to 190 ° C. and a T-die temperature. 180
Heating to ~ 190 ° C, melt-kneading, extruding, cooling rolls with a surface temperature of about 20 to 40 ° C or cooling and solidifying with water cooling, air cooling, etc., and film forming by the T-die method of winding up can be exemplified. It is not limited to. As a method other than the T-die method, for example, an inflation method, a calender method, a rolling method, and the like in which a film is formed using an annular die can be exemplified. Among these, the T-die method is preferred in which the mixture is melt-kneaded using a T-die and extruded.

Further, the microbial degradable stretched film according to the present invention needs to be stretched at least 1.5 times or more in at least one direction in order to improve tensile strength, tensile elasticity, transparency and the like. The stretching method is not particularly limited, but the film formed above is, for example, a flat film, a uniaxial stretching method, a sequential biaxial stretching method, a simultaneous biaxial stretching method, or the like. What is necessary is just to stretch by an appropriate method, such as a tube stretching method. In particular, in the uniaxial stretching, continuous with the film formation of the above film, for example, a heating roll stretching method capable of stretching in the longitudinal direction, and in biaxial stretching,
Continuing with the above film formation, longitudinal stretching (or horizontal stretching)
Subsequently, a sequential biaxial stretching method in which transverse stretching (or longitudinal stretching) is performed is preferable, but there is no particular limitation, and film formation and stretching may be performed in separate steps.

Specifically, in the case of uniaxial stretching, the roll surface temperature is 50 to 90 ° C., more preferably 60 ° C., depending on the rotation speed ratio between the slow drive roll (front) and the fast drive roll (rear). In the case of biaxial stretching, a method of stretching at a stretching ratio of 1.5 times or more at a temperature of up to 80 ° C. is performed in a transverse direction using a tenter, continuously with the above-described longitudinal stretching, and an atmosphere temperature in the tenter of 50 to 90 ° C. And more preferably a method of successively biaxially stretching at 60 to 70 ° C. at a stretching ratio of 1.5 times or more. At this time, if the stretching temperature is less than 50 ° C., the load on the stretching machine is large, and the stretching tends to be difficult.
If the temperature exceeds 0 ° C., crystallization of the polylactic acid-based polymer proceeds, and the film tends to be easily broken during stretching.

The stretched microbial degradable film according to the present invention may be heat-set after stretching, if necessary.
The method of heat setting is not particularly limited, and in the case of uniaxial stretching, a method of contacting a roll having a surface temperature higher than the stretching temperature after stretching, or a method of immersing in hot water higher than the stretching temperature and performing heat fixing. Etc. can be exemplified. In the case of sequential biaxial stretching, generally, in the rear chamber of the tenter, following the transverse stretching, at a temperature higher than the stretching temperature, relax in the width direction by several% (for example, 0.5 to 2.0%). While a method of heat setting for 1.0 to 20 seconds can be exemplified, there is no particular limitation. At this time, it is not necessary to heat-fix. When not heat-fixed, it can be used as a heat-shrinkable film.

The thickness of the microbial degradable stretched film according to the present invention is not particularly limited, and the performance required according to the application,
For example, an appropriate thickness may be set according to the mechanical strength (tensile strength, tensile modulus), biodegradation rate, price, and the like of the microbial degradable stretched film. Generally, a thickness of about 10 to 200 μm can be exemplified, but there is no particular limitation.

Further, the microbial degradable stretched film according to the present invention may be subjected to a surface treatment for the purpose of improving printability, suitability for lamination, suitability for coating and the like. Examples of the surface treatment method include a corona discharge treatment, a plasma treatment, a flame treatment, and an acid treatment. In the present invention, any of the methods can be used. Corona discharge treatment, plasma treatment, flame treatment, etc. are preferable because they can be continuously processed and can be easily installed before the winding step in the film formation process, and among these, corona is preferred from the viewpoint of simplicity. Discharge treatment can be exemplified as the most preferable one.

The microbial degradable stretched film according to the present invention can be used for various applications without any particular limitation. For example, packaging films, garbage packaging bags, shopping bags, hygiene products, laminating films, food trays, gardening (eg,
Sheets for pots), films for root winding of plants and plants, films for agricultural use, sheets, sheets for cards, etc.
There is no particular limitation, and other uses can be expected.

[0023]

EXAMPLES The present invention will be described below with reference to examples, but it is needless to say that the present invention is not limited to the following examples. In the following examples of the present invention, the measurement method and evaluation of each inspection item were performed by the following methods.

[Thickness]: Measured and evaluated with a Digic Nestester manufactured by Toyo Seiki Co., Ltd.

[Haze]: Measured and evaluated according to JIS K-6782.

[Tensile strength]: Measured and evaluated according to JIS K-6732.

[Tensile modulus (Young's modulus)]: ASTM
The measurement was evaluated according to D882.

[Heat resistance]: Two 10 × 10 cm films were stacked, left under a load of 50 g / cm 2 at 80 ° C. for 24 hours, and the presence or absence of blocking (fusion) between the films was visually evaluated. [A --- No fusion. X --- fused. ]

[Microbial degradability]: Weight of a 10 × 10 cm film immersed at 25 ° C. for 28 days and 56 days in returned sludge collected and treated at the Purification Center (Shuna Prefectural Sewerage Corporation, Konan Central Office). Evaluation was made based on the reduction rate.

Examples 1-2 A ring-opening polymerization of a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (3-hydroxyvalerate content 8 mol%) and lactide of L-lactic acid Polylactic acid and the composition shown in Table 1 were supplied to an extruder having a cylinder diameter of 40 mm set at a cylinder temperature of 190 ° C. and a T-die temperature of 180 ° C., melt-kneaded, extruded, and cooled. An unstretched film having a thickness of 200 μm was formed. Subsequently, the unstretched film was stretched longitudinally at a magnification shown in Table 1 with a heating roll having a surface temperature of 60 ° C. using a biaxial stretching machine, and then shown in Table 1 horizontally with a tenter at an ambient temperature of 70 ° C. The film was stretched at a magnification to obtain a biodegradable stretched film. Thickness of the microbial degradable stretched film, haze,
Table 1 shows the tensile strength, tensile modulus, heat resistance and microbial degradability.
It was shown to.

Comparative Example 1 The copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (content of 3-hydroxyvalerate 8 mol%) used in Example 1 and lactide of L-lactic acid were opened. Polylactic acid 1 obtained by ring-opening polymerization of lactide of L-lactic acid instead of a composition obtained by blending with polylactic acid obtained by ring polymerization.
A microbial degradable stretched film was obtained in the same manner as in Example 1 except that 00% by weight was used. Table 1 shows the thickness, haze, tensile strength, tensile modulus, heat resistance and microbial degradability of the microbial degradable stretched film.

Comparative Example 2 The copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (content of 3-hydroxyvalerate 8 mol%) used in Example 1 and lactide of L-lactic acid were opened. Instead of the composition obtained by blending polylactic acid obtained by ring polymerization, 3-hydroxybutyrate and 3-hydroxybutyrate used in Example 1 were used.
An attempt was made to form a microbial degradable stretched film in the same manner as in Example 1 except that 100% by weight of a copolymer with hydroxyvalerate (content of 3-hydroxyvalerate 8 mol%) was used. When the film was axially stretched, the film was frequently torn and could not be stretched.

Comparative Example 3 The copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (content of 3-hydroxyvalerate 8 mol%) used in Example 1 and lactide of L-lactic acid were opened. In the same manner as in Example 1 except that poly (ε-caprolactone) was used instead of the composition obtained by mixing the polylactic acid obtained by ring polymerization, and the extrusion temperature was set to 150 ° C. and the stretching temperature was set to 50 ° C. Thus, a biodegradable stretched film was obtained. The thickness of the biodegradable stretched film, haze, tensile strength,
Table 1 shows the tensile modulus, heat resistance and microbial degradability.

As is clear from Table 1, Examples 1 and 2 according to the present invention have excellent mechanical strength (tensile strength and tensile modulus), transparency, and heat resistance, and have appropriate flexibility. Biodegraded in the natural environment. On the other hand, the stretched microbial biodegradable film of Comparative Example 1 has poor flexibility and its use tends to be limited, has a very low biodegradation rate, and is not sufficiently practical as a biodegradable raw film. The film of Comparative Example 2 is easily broken by longitudinal stretching, and in the case of transverse stretching, the film frequently breaks and has extremely poor stretchability, which is not suitable for a biodegradable film. In addition, mechanical strength (particularly, tensile modulus) and heat resistance are inferior, and its use as a microbial degradable film is greatly restricted, making it less practical.

[0035]

The microbial degradable stretched film according to the present invention is excellent in mechanical strength (tensile strength, tensile elasticity), transparency and heat resistance, has appropriate flexibility, and is biodegradable in a natural environment. It is eventually broken down into harmless water and carbon dioxide.
Moreover, the biodegradable stretched film of the present invention can appropriately adjust the biodegradability rate by adjusting the mixing ratio of the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and the polylactic acid-based polymer. You can choose.

[Table 1]

Claims (5)

[Claims] 1. A composition comprising a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate and a polylactic acid-based polymer as essential components is melt-kneaded, extruded, cooled, and then stretched in at least one direction. Microbial degradable stretched film. 2. The mixing ratio of a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate to a composition containing a polylactic acid-based polymer as an essential component is 80:20 by weight.
The stretched microbial degradable film according to claim 1, wherein the ratio is up to 20:80. 3. The stretch ratio in at least one direction is 1.5.
The stretched microbial degradable film according to any one of claims 1 and 2, which is at least twice as large. 4. A composition comprising a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, a polylactic acid-based polymer and a biodegradable polymer or copolymer other than those described above, are melt-kneaded. The stretched microbial degradable film according to any one of claims 1 to 3, wherein the stretched film is extruded and cooled and then stretched in at least one direction. 5. An average tensile elastic modulus (Young's modulus) in the machine direction and the transverse direction is 10,000 kg / cm 2 or more.
000 kg / cm 2 or less and a haze value of 20
% Or less of the biodegradable stretched film according to claim 1.