JPH1180524A - Biodegradable mulching film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film biodegradable with a microorganism, etc., even in allowing the film to stand in the natural world as it is, finally to be eliminated, useful in the field of agriculture, etc., by forming a film of a composition containing an aliphatic polyester-based polymer and a copolymer of a hydroxybutyrate, etc., in a specific ratio. SOLUTION: This film is obtianed by forming a composition comprising (A) 50-97 wt.% of an aliphatic polyester-based polymer (e.g. a polybutylene/ adipate copolymer, etc.), preferably having 1-40 g/10 minutes melt flow rate and about 50,000-300,000 number-average molecular weight and (B) 50-3 wt.% of a copolymer of (i) 3hydroxybutyrate and (ii) 3-hydroxyvalerate as essential components into a film by a T-die method. The component A is obtained, for example, by subjecting a glycol such as 1,4-butanediol and an aliphatic dicarboxylic acid such as succinic acid to polycondensation through dehydration. Preferably, the component B contains 1-20 mol.% of the component (ii).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mulching film widely used in the fields of agriculture and horticulture. More specifically, the present invention relates to a biodegradable mulching film comprising a composition comprising an aliphatic polyester-based polymer and a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate as essential components.

[0002]

2. Description of the Related Art Conventionally, in the fields of agriculture and horticulture, mulching materials and the like have been used around trunks and roots of trees and crops, and in flowerpots such as houseplants for the purpose of, for example, weeding, heat and moisture retention, and air permeability. Is laid. As such a mulching material,
Films made of general-purpose plastics such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyacetal, and nylon are generally widely used.

[0003]

However, since the mulching film made of such a plastic does not have biodegradability, it does not decompose even after its purpose is completed, and it has a problem that debris and other debris that has collapsed during use. Those buried in the ground are left in the natural world, and problems such as environmental pollution in the natural world and poor landscape have been pointed out. Therefore, it is necessary to collect a mulching film that has completed its purpose, a fragment that has collapsed and scattered during use, a mulching film buried in the ground, and the like.

[0004] However, it is physically impossible to recover the incinerator, and when the recovered material is incinerated, there is a problem that the incinerator is damaged due to high combustion calories.
An object of the present invention is to provide a biodegradable mulching film which completes its purpose of use and is biodegraded by natural microorganisms and eventually disappears even when left in the natural world.

[0005]

Means for Solving the Problems In view of the above-mentioned situation, the present inventors have made intensive studies and arrived at the present invention. The characteristic feature of the present invention is that the aliphatic polyester polymer is 50 to 97% by weight and the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate is 50 to 3% by weight.
The present invention is directed to providing a single-layer or multilayer biodegradable mulching film composed of a composition containing, as an essential component.

The biodegradable mulching film comprises only a composition comprising 50 to 97% by weight of an aliphatic polyester polymer and 50 to 3% by weight of a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate. It may be constituted, and other components may be further blended as long as the biodegradability is not impaired. The composition ratio of the composition and other components in the biodegradable mulching film is such that the composition constituting the mulching film is usually at least 10% by weight, preferably at least 50% by weight, more preferably at least 70% by weight. And particularly preferably 90% by weight or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the aliphatic polyester polymer used in the present invention, two components of a glycol and a dicarboxylic acid (or an acid anhydride thereof) or, if necessary, a third component is used. At least one polyfunctional component selected from the group consisting of trifunctional or tetrafunctional polyhydric alcohols, oxycarboxylic acids and polycarboxylic acids (or acid anhydrides) is added as a component, and the molecules are subjected to a dehydration polycondensation reaction to produce molecules. For example, a polyester prepolymer having a hydroxy group at a terminal is prepared, and a high molecular weight is prepared by using a coupling agent (for example, diisocyanate).

The aliphatic polyester polymer has a number average molecular weight (Mn) of 10,000 or more, preferably 40,000 or more.
000 or more, more preferably 50,000 to 300,0.
About 00 can be exemplified. Number average molecular weight (Mn) is 10,
If it is less than 000, there is a tendency that a biodegradable mulching film having excellent toughness and strength (tensile elongation, impact resistance, tear strength, etc.) cannot be formed.

As the aliphatic polyester polymer, those represented by the following general formula can be exemplified.

[0010]

Embedded image (Wherein, m is an integer of 2 to 6, preferably 2 to 4, and n is 2
To 6, preferably 2 to 4, and N represents a number at which the molecular weight of the polymer becomes 10,000 or more, preferably 40,000 or more, more preferably about 50,000 to 300,000. )

Specific examples of the aliphatic polyester polymer include polyethylene succinate (m = 2, n = 2), polybutylene succinate (m = 4, n = 2), and polybutylene succinate adipate (m = 2). 4, n = 2, 4)
Can be exemplified as preferable ones.

The glycols constituting the aliphatic polyester polymer according to the present invention include ethylene glycol, 1,4-butanediol, 1,6-hexanedi-
, Decamethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc.
And aliphatic or alicyclic glycols having 10 to 10 linear or branched chains. Further, these glycols may be used in combination. Among them, 1,4-butanediol can be mentioned as a preferable one.

The dicarboxylic acids (including acid anhydrides) that constitute the aliphatic polyester polymer by reacting with the above-mentioned glycols include succinic acid, adipic acid, speric acid,
Sebacic acid, dodecanoic acid, succinic anhydride, adipic anhydride and the like can be mentioned, and these dicarboxylic acids may be used alone or in combination of two or more. Particularly preferred dicarboxylic acids include succinic acid and adipic acid.

In addition to the above dicarboxylic acids (eg, succinic acid and adipic acid), if necessary, as a third component, 3
Or a tetrafunctional polyhydric alcohol component (eg, trimethylolpropane, glycerin, pentaerythrate, etc.), or a trifunctional or tetrafunctional polyhydric oxycarboxylic acid (eg, malic acid,
Citric acid, tartaric acid, etc., tri- or tetrafunctional polycarboxylic acids and anhydrides thereof (for example, trimesic acid, propanetricarboxylic acid, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, cyclopentanetetracarboxylic anhydride) And the like, may be added to synthesize an aliphatic polyester-based polymer.

The addition of the above third component tends to cause long-chain branching in the branch, which tends to increase the molecular weight and broaden the molecular weight distribution. Thus, favorable properties as a biodegradable multi-ing film (eg, tensile strength) (E.g., high elongation, impact strength, and tear strength) can be expected. At this time, the addition amount of the third component is about 0.1 to 5 mol% with respect to the entire aliphatic dicarboxylic acid (including acid anhydride) so as not to form a gel, and 0.1 to 5 mol% with respect to the entirety of the tetrafunctional component. 1 to
About 3 mol% can be exemplified.

The aliphatic polyester polymer according to the present invention has a melt flow rate (MFR; 190 ° C., 2.16 k
g) is 1 to 40 g / 10 min, preferably 5 to 30 g /
It is 10 minutes, and particularly preferably 8 to 20 g / 10 minutes. If the melt flow rate is less than 1 g / 10 minutes, for example, in the case of a biodegradable mulching film used by making holes, it tends to tear when making holes, and if it exceeds 40 g / 10 minutes, film formation tends to be difficult. is there.

The copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate used in the present invention includes:
Microorganisms such as hydrogen bacteria (Alcaligenes e)
biosynthesis, melting point 1
An aliphatic polyester resin having a biodegradability of 00 to 180 ° C can be exemplified. As such a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, a copolymer having a content of 3-hydroxyvalerate of 1 to 20 mol% is preferable in consideration of processability. At this time, if the amount of 3-hydroxyvalerate is less than 1 mol%, the crystallinity is high, so that it becomes hard and brittle, and since the melting point is high, it tends to be thermally degraded at the time of film forming, and exceeds 20 mol%. However, the crystallinity and the melting point of the film tend to be unfavorably low as a mulching film due to a decrease in melting point and excessive softening, but the above range is not particularly limited.

The biodegradable mulching film according to the present invention comprises the aliphatic polyester-based polymer 50 to 50 described above.
The film is formed from a composition containing 97% by weight and 50 to 3% by weight of a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate as essential components. When the composition ratio of such a composition is less than 50% by weight of the aliphatic polyester polymer (50% by weight or more of the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate), the biodegradable mulching film Has a too high biodegradation rate and tends to be biodegraded before the intended use is completed, and is not practically preferable as a mulching film, and its use is restricted. When the amount of the aliphatic polyester polymer exceeds 97% by weight (the amount of the copolymer of 3-hydroxybutyrate and 3hydroxyvalerate is 3% by weight or less), the adhesiveness becomes strong, the roll separation during molding becomes poor, and the molding speed is increased. Tends to decrease. Further, there is a problem that the biodegradation rate is slowed down, and the mulching film remains without being biodegraded at the next cropping and must be removed.

The method for preparing the composition constituting the biodegradable mulching film of the present invention is not particularly limited, and may be any of the methods commonly used in the production of conventional compositions such as polyolefin resins, for example, ribbon blenders, Hensel A method of blending with a mixer or the like, a method of using a kneader such as a kneader, a Banbury mixer, a roll, or the like, a method of heat-melting and kneading using a single-screw or twin-screw extruder or the like, and granulating into pellets and the like are exemplified.

The composition according to the present invention may contain, if necessary, other synthetic resins and various additives within a range that does not impair the properties of the biodegradable mulching film according to the present invention, for example, strength and biodegradability. Agents, fillers such as heat stabilizers, antioxidants, antistatic agents, lubricants, antibacterial agents, pigments or dyes, titanium oxide, calcium carbonate, calcium sulfate, barium sulfate, magnesium hydroxide, silica, talc, etc. No problem.

The other synthetic resin is not particularly limited, and examples thereof include other biodegradable resins.
For example, poly-3-hydroxybutyrate, poly-3-hydroxyvalerate, 3-hydroxybutyrate and 3-
A copolymer of hydroxypropionate, a copolymer of 3-hydroxybutyrate and 4-hydroxybutyrate, a poly-3-hydroxyalkanoate, a polycaprolactone, a lactic acid-containing polymer, and the like can be blended as necessary. .

The method for producing the biodegradable mulching film is not particularly limited as long as it is a conventionally known method. For example, T to melt and extrude from a T die to form a flat film
The film may be formed by a die method or an inflation method or the like in which a gas such as compressed air is blown at the same time as melt extrusion from a circular die to form a tubular film.
If necessary, it may be stretched uniaxially or biaxially,
Thereafter, heat fixing may be performed, and there is no particular limitation.

Specifically, for example, a composition (preferably in the form of pellets) containing an aliphatic polyester-based polymer and a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate as essential components is charged at a cylinder temperature of 150 ° C. ~ 200
C., T-die Temperature is set in an extruder equipped with a T-die set at 160 to 200 ° C., melted, kneaded and extruded, and cooled with a cooling roll or water or air to form a flat film. . Further, if necessary, following film formation, for example, a roll having a stretching temperature of 35 to 100 ° C. in a longitudinal direction is 3 to 1 roll.
After stretching 5 times, the stretching temperature is set to 60 in the transverse direction using a tenter.
Stretching can be performed by a sequential biaxial stretching method in which the film is stretched 3 to 15 times at １００100 ° C. If necessary, after stretching, for example, 70 to 1
A method of heat-setting at 00 ° C. to form a biodegradable mulching film having improved toughness, strength and the like can be exemplified,
There is no particular limitation.

Further, the biodegradable mulching film according to the present invention comprises a layer comprising a composition comprising an aliphatic polyester-based polymer and a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate as essential components ( It may have a multilayer structure in which at least two layers of A) and a layer (B) of the same and / or different from the above composition and composed of the other biodegradable resin described above. The method for producing a multi-layered biodegradable mulching film is not particularly limited as long as it is a conventionally known method. For example, lamination is performed by a coextrusion method, a melt extrusion lamination method, a dry lamination method, a thermocompression bonding method, a hot melt lamination method, or the like. Then, a method of forming a multilayer structure can be given.

Specifically, for example, one of at least two extruders connected to a co-extrusion T-die is provided with a biodegradable high molecular weight aliphatic polyester polymer and 3-hydroxybutyrate. (A) consisting of a composition comprising a copolymer of and 3-hydroxyvalerate as an essential component
Is supplied to another extruder with another biodegradable resin described above, for example, a lactic acid-containing polymer (B). Then, the mixture is melted and kneaded at, for example, a cylinder temperature of 180 ° C. and a die temperature of 170 ° C., and is cooled and solidified by an extruded cooling roll or water-cooling, and is then cooled by (A) / (B) or (A) / (B) /
The method of forming a multi-layered biodegradable mulching film (A) can be exemplified. If necessary, the film may be successively biaxially stretched and heat-set in the same manner as in the case of the single-layer film, and there is no particular limitation.

The thickness of the above-mentioned biodegradable mulching film may be appropriately set according to the purpose, purpose, period until harvesting, period after plowing and until the next cropping. For example, 10 to 100 μm for applications, 10 to 100 μm for heat retention and moisture retention, and 10 to 30 μm for air permeability (including a perforated film), and there is no particular limitation.

[0027]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples and Comparative Examples.

Each evaluation in the following Examples and Comparative Examples was measured by the following methods.

[Biodegradability test]: thickness 20 μm × length 1
A test piece of 0 cm × 10 cm width is immersed in returned sludge to be collected and treated at the Purification Center (in Shiga Prefectural Sewerage Corporation, Konan Central Office) under the condition of 25 ° C. The biodegradation state was visually evaluated.

[Tensile strength]: Measured according to JIS K-6782.

[Tensile elongation]: Measured according to JIS K-6782.

[Impact resistance]: Measured according to JIS P-8134.

[Right angle tear strength]: JIS K-6732
It measured according to.

Example 1 Succinic acid and adipic acid were dehydrated and polycondensed with 1,4-butanediol, and the number average molecular weight (Mn) obtained by increasing the molecular weight with a coupling agent was 92,000. (MFR) 10 g / 10 min (190 ° C., load 2.16 kg) 95% by weight of polybutylene succinate adipate copolymer (PBSA) and 3-hydroxybutyrate having a content of 3-hydroxyvalerate of 8 mol% Melt blended using a T-die extruder set at a cylinder temperature of 180 ° C. and a die temperature of 170 ° C., and then a surface temperature of about 20 ° C. Was extruded on a cooling roll and cooled and solidified to obtain a biodegradable mulching film having a thickness of 20 μm. Table 1 shows the tensile strength, tensile elongation, impact strength and perpendicular tear strength of the biodegradable mulching film. Further, as a measure of biodegradability, a weight loss rate after immersing a film having a predetermined area composed of the biodegradable mulching film in activated sludge at 25 ° C. for 30 days was measured, and the biodegradation state was visually evaluated. . As a result, the weight loss rate is about 80%
As described above, the mulching film is decomposed to such an extent that the shape of the mulching film is not recognized, and can be used as a biodegradable mulching film.

Example 2 In place of polybutylene succinate adipate (PBSA), a number average molecular weight (Mn) obtained by dehydration polycondensation of succinic acid and 1,4-butanediol and increasing the molecular weight with a coupling agent = 85,000, melt flow rate (MFR) 10 g / 10 min (190 ° C., load 2.16
kg) of polybutylene succinate (PBS) and 50% by weight of succinic acid, adipic acid and 1,4-butanediol by dehydration polycondensation, and the number average molecular weight (Mn) obtained by increasing the molecular weight with a coupling agent = 92,000, melt flow rate (MFR) 10 g / 10 min (190 ° C.,
A biodegradable mulching film was obtained in the same manner as in Example 1 except that 45% by weight of polybutylene succinate adipate (PBSA) with a load of 2.16 kg) was used. Table 1 shows the tensile strength, tensile elongation, impact resistance and perpendicular tear strength of the biodegradable mulching film. Also,
Regarding biodegradability, the measurement of the weight loss rate and the biodegradation state were visually evaluated in the same manner as in Example 1. As a result, the weight reduction rate was about 40% or more, and biodegradation was observed to the extent that the shape of the mulching film was not recognized. It can be suitably used as a biodegradable mulching film.

Example 3 Succinic acid and adipic acid were dehydrated and polycondensed with 1,4-butanediol, and the number average molecular weight (Mn) obtained by increasing the molecular weight with a coupling agent was 92,000. MFR) 90% by weight of polybutylene succinate adipate (PBSA) of 10 g / 10 minutes (190 ° C., load: 2.16 kg), 3-hydroxybutyrate and 3-hydroxy with a 3-hydroxyvalerate content of 8 mol% A composition prepared by blending 10% by weight of a valerate copolymer was subjected to a cylinder temperature of 180 ° C. and a die temperature of 17 ° C.
After melt-kneading using a T-die extruder set at 0 ° C., the mixture was extruded onto a cooling roll having a surface temperature of about 20 ° C., and was 240 μm thick.
Sheet was obtained. Subsequently, the sheet was stretched three times in the machine direction (extrusion direction) using a roll heated to 45 ° C., and then, in a transverse direction (perpendicular to the extrusion direction) under the condition of an ambient temperature of 50 ° C. using a tenter. Direction). Thereafter, the film was further heat-set in a post-tenter room at a temperature of 80 ° C. to obtain a biodegradable mulching film having a thickness of 20 μm. Table 1 shows the tensile strength, tensile elongation, impact resistance and perpendicular tear strength of the biodegradable mulching film. Also,
Regarding biodegradability, the weight loss rate was measured and the biodegradation state was visually evaluated in the same manner as in Example 1. As a result, the weight loss rate was about 60% or more, and the shape of the mulching film was decomposed to the extent that it was not recognized. It can be suitably used as a biodegradable mulching film.

Example 4 A biodegradable sheet having a thickness of 240 μm was obtained in the same manner as in Example 1 except that the composition used in Example 2 was used. This sheet is stretched three times in the machine direction (extrusion direction) by a roll heated to 45 ° C., and then transversely (at right angles to the extrusion direction) under the condition of an ambient temperature of 50 ° C. using a tenter. The film was heat-set at 80 ° C. in the rear chamber of the tenter to obtain a biodegradable mulching film having a thickness of 20 μm. Table 1 shows the tensile strength, tensile elongation, impact resistance and perpendicular tear strength of the biodegradable mulching film. Regarding the biodegradability, the measurement of the weight loss rate and the biodegradation state were visually evaluated in the same manner as in Example 1. As a result, the weight loss rate was about 40% or more, and the mulching film was biodegraded to such an extent that the shape was not recognized. It can be suitably used as a biodegradable mulching film.

Example 5 Succinic acid, adipic acid and 1,4-butanediol were dehydrated and polycondensed in two of three extruders connected to a co-extrusion T-die, and the molecular weight was increased by a coupling agent. Average molecular weight (Mn) 85,000, melt flow rate (MFR) 10 g / 10 min (190 ° C., load 2.1
6 kg) of polybutylene succinate adipate (P
BSA) 95% by weight and 3-hydroxybutyrate having a content of 8 mol% of 3-hydroxybutyrate and 5% by weight of a copolymer of 3-hydroxyvalerate were used as a composition (A). Average molecular weight (Mn) which is a polymer obtained by ring-opening polymerization of lactide of L-lactic acid in an extruder
80,000 polylactic acid (B) was supplied. Next, the extruder is heated to a cylinder temperature of 180 ° C. and a die temperature of 180 ° C., and the composition is made of the above polybutylene succinate adipate (PBSA) and a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate. (A) and polylactic acid (B) are melted and kneaded, and extruded on a cooling roll having a surface temperature of about 20 ° C. Thickness (A) / (B) / (A) = 20
A biodegradable mulching film having a composition of two / three layers with a thickness of 10/10/20 = 50 μm was obtained. Table 1 shows the tensile strength, tensile elongation, impact strength, and perpendicular tear strength of the biodegradable mulching film having the three-layer structure. Regarding the biodegradability, the measurement of the weight loss rate and the biodegradation state were visually evaluated in the same manner as in Example 1. As a result, the weight loss rate was about 70% or more, and the biodegradable mulching film was biodegraded to a perforated shape. It can be suitably used as a biodegradable mulching film.

Comparative Example 1 Polyethylene was charged into a T-die extruder set at a cylinder temperature of 180 ° C. and a die temperature of 170 ° C., melt-kneaded, extruded onto a roll having a surface temperature of 20 ° C., cooled and solidified to form a 20 μm thick film. A film was formed. Table 1 shows the tensile strength, tensile elongation, impact resistance, and perpendicular tear strength of the film. A biodegradation test was performed on the film in the same manner as in Example 1. However, the film did not decompose at all, and was not suitable as a biodegradable mulching film.

[0040]

As described above, the biodegradable mulching film according to the present invention is decomposed by natural microorganisms and finally almost disappears even when left in the natural world, so that no environmental pollution or the like occurs.

[Table 1]

Claims (4)

[Claims] 1. An aliphatic polyester polymer 50 to 97
A biodegradable mulching film comprising a composition comprising, as essential components, 3% by weight and 50 to 3% by weight of a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate. 2. The biodegradable mulching film according to claim 1, wherein the aliphatic polyester polymer is a high molecular weight polyester polymer obtained by dehydration polycondensation of a glycol and an aliphatic dicarboxylic acid. 3. The biodegradable mulching film according to claim 1, wherein the aliphatic polyester polymer has a melt flow rate (MFR) of 1 to 40 g / 10 minutes. 4. A layer (A) comprising a composition comprising an aliphatic polyester-based polymer and a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate as essential components; The biodegradable mulching film according to any one of claims 1 to 3, wherein the film has a multilayer structure with a layer (B) made of a different biodegradable polymer from the above composition.