JP5350910B2 - Biodegradable agricultural coating materials - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable agricultural covering material having an initial strength and elongation high enough to be endurable for practical use, excellent in light transmission properties and resistance to weather, and almost completely dissolvable by the action of microorganisms after used so as to be easy to dispose of. <P>SOLUTION: The agricultural covering material includes a spunbonded nonwoven fabric having conjugated fiber as a constituent fiber. The biodegradable agricultural covering material is such that the conjugated fiber contains a polylactic acid-based polymer with a melting point of not less than 160&deg;C, and an aliphatic polyester polymer with a melting point being 50&deg;C or more lower than that of the polylactic acid-based polymer, the aliphatic polyester polymer forms at least part of a fiber surface, and the aliphatic polyester polymer has 1,4-butanediol and succinic acid as constituent components, and contains 0.1-1 mass% of at least one selected from higher fatty acids, its metal salts, and phenylphosphonic acid metal salts. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention is a covering material used in outdoor cultivation, tunnel cultivation, house cultivation, etc., and after use, it is almost completely decomposed by the action of microorganisms and can be easily disposed of. The present invention relates to a covering material for agriculture that is preferably used as a so-called sticky sheet.

  Conventionally, various non-woven fabrics have been widely used as agricultural materials such as a herbicidal sheet, a lining curtain in a house, and a paddy rice seedling required sheet. One application is a solid sheet. Solid betting sheets are made by taking advantage of the breathability, water permeability, and lightness of nonwoven fabrics. By directly covering the sheets with crops, various types of heat retention, water retention, frost prevention, insect protection, bird protection, wind protection, etc. It is possible to achieve effects such as promoting the growth of crops, improving quality, and increasing yield.

  In recent years, in the agricultural field, how to treat various used materials without polluting the natural environment has become a major issue. In order to cope with this problem, fibers made of aliphatic polyester that biodegrades in nature have been developed and are expected to contribute to environmental protection. Among aliphatic polyesters, polylactic acid polymers have a relatively high melting point, and are therefore expected to be applied to a wide range of fields. The present applicant also specifically proposes application to agricultural materials. (Patent Document 1).

  Patent Document 1 relates to a solid sheet made of a long-fiber nonwoven fabric composed only of a polylactic acid-based polymer, and this sheet is excellent in translucency and weather resistance. However, a solid sheet made of a long-fiber non-woven fabric composed only of a polylactic acid-based polymer can be used satisfactorily when the area of use is small, such as in a home garden, but it can be used on a farm with a large area of use. In use, the load on the sheet becomes very large when spreading over a large area, and there is a risk of tearing without being able to withstand the tension during the stretching. In addition, since the load due to external environmental factors such as wind and rain is large even after the stretching, if the initial strength of the sheet is small, it cannot withstand these and cause tearing.

Japanese Patent No. 3494404

  The present invention solves the above problems, the initial high elongation is high enough to withstand practical use, has good translucency and weather resistance, and is decomposed almost completely by the action of microorganisms after use and is disposed of by disposal. It is an object to provide an easy biodegradable agricultural covering material.

  As a result of studies to achieve the above problems, the present inventors have selected a specific polymer as an aliphatic polyester polymer that forms at least a part of the fiber surface, and further added an organic additive to the polymer. By adding and applying the spunbond method, it was found that a non-woven fabric having biodegradability with improved initial strength was obtained, and the present invention was achieved.

That is, the present invention is an agricultural covering material composed of a spunbonded nonwoven fabric having a composite fiber as a constituent fiber. The composite fiber comprises a polylactic acid polymer having a melting point of 160 ° C. or higher and a polylactic acid polymer. And an aliphatic polyester polymer having a melting point of 50 ° C. or lower, and the aliphatic polyester polymer forms at least a part of the fiber surface, and the aliphatic polyester polymer is 1,4-butanediol. And succinic acid as constituents (excluding aliphatic polyester copolymers that contain aliphatic diol, aliphatic dicarboxylic acid and aliphatic hydroxycarboxylic acid as constituents) .) with a calcium montanate salt, and at least one selected from a phenylphosphonic acid zinc salt containing 0.1 to 1 wt% Biodegradable agricultural covering materials, characterized the door is to the subject matter.

  Hereinafter, the present invention will be described in detail.

  The biodegradable agricultural covering material of the present invention comprises a spunbonded nonwoven fabric having composite fibers as constituent fibers, and the composite fibers include a polylactic acid polymer and a specific aliphatic polyester polymer.

  As the polylactic acid polymer used in the present invention, a polymer having a melting point of 160 ° C. or higher or a blend of polymers having a melting point of 160 ° C. or higher is used. When the melting point of the polylactic acid polymer is 160 ° C. or higher, the polylactic acid polymer has high crystallinity and thus has a function of improving the mechanical strength of the composite fiber, thereby improving the initial strength of the spunbonded nonwoven fabric. In addition, since the melting point difference from the aliphatic polyester to be compounded can be sufficiently provided, the polylactic acid polymer is not easily affected by heat in the melt spinning process during the production of the nonwoven fabric, and the compound can sufficiently maintain the strength. Fiber can be obtained.

  The melting point of poly-L-lactic acid and poly-D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C. When a copolymer of L-lactic acid and D-lactic acid is used as the polylactic acid polymer, the copolymerization ratio of the monomer components is determined so that the melting point of the copolymer is 160 ° C. or higher. That is, the copolymerization ratio of L-lactic acid and D-lactic acid is (L-lactic acid) / (D-lactic acid) = 2/98 to 0/100 or (L-lactic acid) / (D- Lactic acid) = 98/2 to 100/0 is used. If the copolymerization ratio is out of the above range, the melting point of the copolymer becomes less than 160 ° C., and the object of the present invention cannot be achieved. More preferably, the melting point is 165 ° C. or higher.

Aliphatic polyester polymer used in the present invention, 1,4-butanediol and succinic acid is a polymer of a configuration component, having a low melting point 50 ° C. or higher than polylactic acid polymer. The reason why the melting point difference with the polylactic acid polymer is 50 ° C. or more is that, as described above, the polylactic acid polymer is not easily affected by heat in the melt spinning process during the production of the nonwoven fabric, and has sufficient strength. It is that the composite fiber which can be obtained can be obtained. The lower limit of the melting point of the aliphatic polyester polymer is about 90 ° C. in consideration of practicality. As the aliphatic polyester polymer used in the present invention, specifically, trade name GSPla (crystal melting point 110 ° C.) manufactured by Mitsubishi Chemical Corporation can be preferably used. Further, as the aliphatic Poriesueru polymer as a constituent component and 1,4-butanediol and succinic acid, when a polymer isocyanate is not added, it is possible to use in the present invention. When an isocyanate is added, an aliphatic polyester containing a urethane bond is not preferable because when it is made into a non-woven fabric, there is a possibility that problems such as coloring or generation of microgel may occur depending on conditions. In addition, since the composite fiber in the present invention has a sufficient melting point difference between the polylactic acid polymer and the aliphatic polyester polymer, the composite fiber has heat sealing properties using the aliphatic polyester polymer as a heat bonding component. Thus, the obtained agricultural covering material can be heat sealed.

As will be described later, the aliphatic polyester used in the present invention contains at least one selected from calcium montanate and zinc phenylphosphonate, but in its raw material stage (calcium montanate and phenylphosphonate) (In the case of an aliphatic polyester polymer in which no zinc additive is contained), the temperature is increased to 200 ° C. at a temperature increase rate of 500 ° C./min using a DSC apparatus, and held in that state for 5 minutes, and then the temperature decrease rate is 500 The crystallization rate index (hereinafter sometimes abbreviated as “tmax”) when the temperature is lowered to 90 ° C. and held at 90 ° C./min, and is then isothermally crystallized and subjected to differential thermal analysis is 3 to 10 minutes. Choose one. This crystallization rate index tmax is the time (minutes) required to reach half the crystallinity finally reached when the polymer is cooled from the molten state at 200 ° C. and crystallized at 90 ° C. The smaller the index, the faster the crystallization rate. Therefore, as the aliphatic polyester polymer used as the raw material of the composite fiber, the one having a high crystallization rate such that the crystallization rate index tmax is 3 to 10 minutes as described above can be used for cooling when melt spinning. Therefore, it is possible to prevent blocking during the fiber opening. Furthermore, the crystallization rate can be further increased by adding the montanic acid calcium salt and phenylphosphonic acid zinc salt described later to the aliphatic polyester polymer.

  The aliphatic polyester polymer has a melt viscosity gradient of 10 g / g, which is the difference between the melt flow rate at 230 ° C. and the melt flow rate at 210 ° C. measured according to the method described in ASTM-D-1238 (E). The range is preferably 10 minutes or less. A polymer having such characteristics has a small change in fluidity of the polymer in response to a change in temperature and can be said to be a higher order structure close to a crosslinked structure. For this reason, the crystallization rate index tmax is 3 to 10 as described above. The cooling property when melt spinning is improved, and blocking can be made difficult to occur during fiber opening.

The aliphatic polyester polymer contains a predetermined amount by melting and mixing at least one selected from calcium montanate and zinc phenylphosphonate. By adding this to the aliphatic polyester, the crystallization speed of the aliphatic polyester polymer is increased, and the friction resistance between the fibers in the fiber opening process is reduced, and blocking occurs in the fiber opening process. Can be effectively prevented. As a result, it is possible to obtain a non-woven fabric having a good texture without being uneven in the presence of fibers while having a low basis weight, and an agricultural covering material having no translucency or strength unevenness can be obtained. The aliphatic polyester copolymer obtained by melt-mixing at least one selected from calcium montanate and zinc phenylphosphonate can have a crystallization rate index (tmax) of 2 minutes or less.

The purpose of the present invention of increasing the crystallization rate of the fat-aliphatic polyester polymer, Ca salt of montanic acid can be suitably used.

When using a Ca salt of montanic acid, openability is further improved. The reason is assumed to be due to the form of the composite fiber. That is, by adding montanic acid Ca salt to an aliphatic polyester polymer having the above characteristics and melt spinning, the reason is not well understood,
(A) A fine concave part is formed on the fiber surface (b) A fine convex part is formed on the fiber surface (c) A concave part is formed in the fiber axis direction on the fiber surface in a line shape. It is possible to exhibit at least one kind of shape. And when these recessed parts and convex parts are formed on the fiber surface, it is presumed that the surface friction between the fibers and the fibers constituting the non-woven fabric becomes small, and a good fiber opening state is obtained at the time of fiber opening.

  FIG. 1 shows the appearance of the surface of a composite fiber obtained when a Ca salt of montanic acid is used. As shown in the figure, fine irregularities are formed on the fiber surface.

Further, from the object of the present invention of increasing the crystallization rate of the aliphatic polyester polymer, phenylphosphonic acid zinc salt are particularly preferably used.

When using phenylphosphonic acid zinc salt, the fiber opening property is also good. The reason why it is better than other additives is presumed to be the same reason because the surface form of the fibers constituting the nonwoven fabric is the same as that of Ca montanate.

FIG. 2 shows the appearance of the surface of the composite fiber obtained when zinc phenylphosphonic acid salt is used. As shown, fine irregularities are formed on the fiber surface. The uneven portions in this case are finer uneven portions than the uneven portions on the surface of the long fiber obtained when the Ca salt of montanic acid is used.

  In the present invention, as described above, by adding a specific additive, the crystallization rate of the aliphatic polyester polymer is further increased, and fine irregularities are formed on the fiber surface. The fiber-to-fiber friction resistance in the fiber process can be reduced to effectively prevent the occurrence of blocking in the fiber opening process. It is possible to obtain an agricultural covering material free from translucency and strength spots.

The amount of the montanic acid calcium salt and phenylphosphonic acid zinc salt contained in the aliphatic polyester polymer is 0.1 to 1% by mass, preferably 0.1 to 0.7% by mass, More preferably, it is 0.5 mass%. If the blending amount is less than 0.1% by mass, the frictional resistance between the fibers cannot be reduced, which is insufficient for suppressing the occurrence of blocking in the fiber opening process. By setting the upper limit to 1% by mass or less, it is possible to more effectively achieve the effect of including the additive in consideration of the balance with the cost.

  In the present invention, the polylactic acid-based polymer and the aliphatic polyester polymer each include various additives such as a matting agent, a pigment, and a crystal nucleating agent, as necessary, within a range that does not impair the effects of the present invention. May be added. In particular, the addition of a crystal nucleating agent such as talc, titanium oxide, calcium carbonate, and magnesium carbonate is effective in preventing fusion (blocking) between yarns in the spinning cooling step. The crystal nucleating agent is useful when used in the range of 0.1 to 3% by mass.

  In the conjugate fiber in the present invention, the aliphatic polyester polymer forms at least a part of the surface of the fiber. As the fiber cut shape for constituting such a form, for example, a side-by-side composite cross section in which a polylactic acid polymer and an aliphatic polyester polymer are bonded together, the polylactic acid polymer forms a core and is aliphatic. Examples include a core-sheath composite cross section in which a polyester polymer forms a sheath, a split composite cross section in which a polylactic acid polymer and an aliphatic polyester polymer are alternately present on the fiber surface, and a multileaf composite cross section. It is done. In consideration of improving the initial strength of the nonwoven fabric, the core-sheath composite cross section is preferred in which the polylactic acid polymer forms the core and the aliphatic polyester polymer forms the sheath. The composite ratio (mass ratio) of the polylactic acid polymer and the aliphatic polyester polymer constituting the composite fiber is preferably polylactic acid polymer / aliphatic polyester polymer = 3/1 to 1/3. .

  The single yarn fineness of the composite fiber in the present invention is preferably 3 to 10 dtex. When the single yarn fineness is less than 3 dtex, depending on the basis weight, the number of constituent fibers occupying the unit area is relatively increased, so that the gap between the fibers tends to be small, and the translucency and air permeability are reduced. Tend to. On the other hand, when the single yarn fineness exceeds 10 dtex, the number of constituent fibers occupying the unit area is relatively decreased, so that the gap between the fibers is increased and the functions such as heat retention and frost resistance can be sufficiently performed. It is easy to disappear. For these reasons, the single yarn fineness is more preferably 5 to 8 dtex.

  The agricultural covering material of the present invention is a spunbonded nonwoven fabric on which the above-described composite fibers are deposited. As a form of a nonwoven fabric, the thing which heat-bonds fibers and is maintaining the shape by melting or softening an aliphatic polyester polymer component is good. As a form of heat bonding, it may be one that is heat-bonded via a molten or softened aliphatic polyester polymer at a contact point between fibers, or partially formed by passing through a heat embossing device. The heat-bonding part and the other non-heat-bonding part may be included, and the aliphatic polyester polymer component may be melted or softened and held in the form of a nonwoven fabric in the heat-bonding part. What is heat-bonded by passing through a heat embossing device has good dimensional stability because the fibers maintain their shape at the heat-bonded part, and the non-heat-bonded part is not affected by heat. Since the mechanical strength is maintained and flexibility is high, it is a preferable form as a covering material for agriculture.

The basis weight of the agricultural covering material of the present invention may be appropriately selected according to the place of use. For example, when used as a solid sheet, a range of 10 to 30 g / m ² is preferable.

In the case where the agricultural covering material of the present invention is used as a solid sheet, the transmissivity is preferably 70% or more when it is composed of a nonwoven fabric having a basis weight in the range of 10 to 30 g / m ² . By setting the light transmittance to 70% or more, it is possible to sufficiently transmit sunlight and give sufficient light to the growth of crops.

Since the agricultural covering material of the present invention has the above-described configuration, it is excellent in initial tensile strength and elongation. That is, the agricultural covering material composed of the spunbonded nonwoven fabric of the present invention has an initial tensile strength of 20 N or more in the CD direction (direction perpendicular to the machine direction (MD direction)), for example, in a nonwoven fabric having a basis weight of 20 g / m ^2. The elongation can be 20% or more and 60% or less, and the initial tensile strength and the initial elongation are set to the above values, so that even when laid in a large area, it can withstand the tension at the time of stretching. It can be obtained, and it is difficult for tearing to occur even after stretching. Note that the lower limit value in the CD direction is specified in spunbonded nonwoven fabrics because of the characteristics of the manufacturing method. Usually, continuous fibers are easily arranged in the machine direction and the strength in the MD direction is higher. This is because the strength in the CD direction, which is difficult to arrange, is inferior to the machine direction.

  The agricultural covering material of the present invention preferably has an initial tear strength in the MD direction of 1 N or more. By setting the covering material to 1N or more, it is difficult to cause the material to be torn from the portion of the pile used at the time of expansion after the covering material is expanded, or to be unusable due to being torn at a windy time. Further, the stronger the initial tear strength, the better. However, the upper limit is practically about 5N, so that it can be used.

In the weathering test conducted according to JIS B 7753, the coating material of the present invention preferably has a tensile strength retention rate, elongation retention rate, and tear strength retention rate of 80% or more after irradiation for 300 hours. . Each retention rate is expressed by the following formula.
Tensile strength retention ratio (%) = (S ₃₀₀ / S ₀ ) × 100 ≧ 80
Elongation retention (%) = (E ₃₀₀ / E ₀ ) × 100 ≧ 80
Tearing strength retention rate (%) = (TS ₃₀₀ / TS ₀ ) × 100 ≧ 80
S ₃₀₀ : Tensile strength of sample after 300 hours irradiation (N)
S ₀ : Tensile strength of sample before irradiation (N)
E ₃₀₀ : elongation (%) of the sample after 300 hours of irradiation
E ₀ : Elongation (%) of sample before irradiation
TS ₃₀₀ : Tear strength of sample after irradiation for 300 hours (N)
TS ₀ : Tear strength of sample before irradiation (N)

  The above-mentioned various retention rates indicating the weather resistance of the covering material are indicators that indicate whether the strength and elongation are not reduced by changes in the climate before the covering material is broken down by biodegradation. If the tensile strength, elongation, and tear strength of the coating material are reduced before it is used, the material will be easily damaged, and the original translucency and heat retention will not be demonstrated during use, which is good for crop growth. Can no longer contribute. In the present invention, the tensile strength retention rate, the elongation retention rate, and the tear strength retention rate are each 80% or more, so that it is possible to contribute to the growth of crops well in continuous use.

  The agricultural covering material of the present invention also has flexibility. The flexibility required for the covering material for agriculture means the flexibility to follow to some extent the shape of the ridge to plant the crop in alley cultivation, tunnel cultivation or house cultivation. In addition, it means that it can cope with external environmental factors such as wind when it is extended and used. In particular, since the spread covering material is fluttered by the wind, the quality of the crop can be maintained without damaging the crop if it is a flexible material. The agricultural covering material of the present invention is composed of a nonwoven fabric composed of a composite fiber composed of a polylactic acid polymer and a specific aliphatic polyester polymer having a melting point lower than that of the polylactic acid polymer. Since the flexible aliphatic polyester polymer occupies at least a part, it is excellent in flexibility. In addition, the specific aliphatic polyester polymer has a strong elastic property although the reason is not clear. Therefore, the property is reflected in the nonwoven fabric, and it is flexible but has an elastic property. Even if it is exposed to external environmental factors (wind, etc.) when used as a covering material, it will not break or damage the crop, and it will be a period required as a covering material. Can be used over a wide range.

The biodegradable agricultural coating material of the present invention comprises a nonwoven fabric formed by a spunbond method using composite fibers as constituent fibers, and the composite fibers comprise a polylactic acid polymer having a melting point of 160 ° C. or higher, and the polylactic acid. And an aliphatic polyester copolymer having a melting point lower by 50 ° C. or more than the base polymer, and the aliphatic polyester copolymer forms at least part of the fiber surface, the aliphatic polyester copolymer is , 1,4-butanediol and succinic acid with a configuration component, calcium montanate, since at least one selected from a phenylphosphonic acid zinc salt and 0.1 to 1.0 wt% The initial strength and elongation are high enough to withstand practical use, and have good translucency and weather resistance. After use, they are almost completely decomposed by the action of microorganisms and are easy to dispose of. In addition, a biodegradable agricultural coating material can be provided.

It is a figure which shows the mode of the surface of the composite fiber obtained when the Ca salt of montanic acid is used. It is a figure which shows the mode of the surface of the composite fiber obtained when a phenylphosphonic acid metal salt is used.

  Next, based on an Example, this invention is demonstrated concretely. However, the present invention is not limited only to these examples.

Various physical property values in the following examples and comparative examples were measured by the following methods.
(1) Melting point (° C.): Using a differential scanning calorimeter (manufactured by Perkin Elma, DSC-2 type), the sample mass was measured at 5 mg and the heating rate was 10 ° C./min. The temperature giving the maximum value of was the melting point (° C.).

(2) Melt flow rate (g / 10 min): Melt flow rate “MFR1” measured under conditions of a temperature of 210 ° C. and a load of 20.2 N (2160 gf) according to the method described in ASTM-D-1238 (E). And a melt flow rate “MFR2” measured at 230 ° C. and a load of 20.2 N (2160 gf).

(3) Crystallization rate index (min): Using a differential scanning calorimeter (Perkin Elma, DSC-2 type), 5 mg of the sample was heated to 200 ° C. at a heating rate of 500 ° C./min. After being held for 5 minutes in the state, the temperature was lowered to 90 ° C. at a temperature lowering rate of 500 ° C./min, held at 90 ° C. to cause isothermal crystallization, and differential thermal analysis was performed to measure the crystallization rate index (tmax). In the measurement, the crystallization rate index (tmax) of the aliphatic polyester polymer itself and at least one selected from a higher fatty acid, a metal salt thereof, and a metal salt of phenylphosphonic acid are melt mixed with the aliphatic polyester polymer. The crystallization rate index (tmax) of the molten mixture extruded at a melting temperature of 200 ° C. was determined.

(4) Single yarn fineness (decitex): The diameter of 50 fibers in the web state was measured with an optical microscope, and the average value obtained by density correction was taken as the fineness.

(5) Weight per unit area (g / m ² ): Ten sample pieces having a length of 10 cm and a width of 5 cm were prepared from a sample in a standard state, the mass (g) of each sample piece was weighed, and the average value of the obtained values Was converted to a unit area (g / m ² ).

(6) Tensile strength (N / 5 cm width) and elongation (%) in the CD direction: JIS-L-1096 Tensile strength and elongation were measured according to the B method (grab method). Ten sample pieces of 15 cm length x 10 cm width were prepared so that the length direction would be the CD direction, and using a constant speed extension type tensile tester (Tensilon UTM-4-1-100 manufactured by Orientec Corp.) Gripping distance is 7.6 cm, the size of the grip is 2.54 cm x 2.54 cm on the front side and 5.1 cm x 2.54 cm on the back side, and stretched at a pulling speed of 30 cm / min. The average value of load (N) was defined as tensile strength (N / 5 cm width), and the average value of breaking elongation at the time of cutting was defined as elongation (%).

(7) Tear strength in the MD direction (N): Measured according to the pendulum method described in JIS-L-1906. That is, five sample pieces of length 6.5 cm × width 10 cm were prepared so that the length direction was the CD direction, the tear strength was obtained for each sample piece, and the average value of the obtained values was determined as the sample value. The tear strength (N) in the CD direction was determined.

(8) Transmissivity (%): The illuminance of the light source was measured as 2000 lux according to the translucency described in JIS-L-1906.

(9) Tensile strength retention rate (%), elongation retention rate (%), tear strength retention rate (%): The strength retention rate, which is an indicator of weather resistance, was determined as follows. That is, according to JIS-B-7753, a weather resistance test was performed using a model S80DHB sunshine weather meter manufactured by Suga Test Instruments Co., Ltd., and the sample after the weather resistance test was subjected to the above (6) tensile strength in the CD direction (N / 5 cm width) and elongation (%) described above, and (7) the CD direction tear strength (N) described above, the respective values are obtained, and the retention rate after irradiation for 300 hours from the following formula ( %).
Tensile strength retention ratio (%) = (S ₃₀₀ / S ₀ ) × 100 ≧ 80
Elongation retention (%) = (E ₃₀₀ / E ₀ ) × 100 ≧ 80
Tearing strength retention rate (%) = (TS ₃₀₀ / TS ₀ ) × 100 ≧ 80
S ₃₀₀ : Tensile strength of sample after 300 hours irradiation (N)
S ₀ : Tensile strength of sample before irradiation (N)
E ₃₀₀ : elongation (%) of the sample after 300 hours of irradiation
E ₀ : Elongation (%) of sample before irradiation
TS ₃₀₀ : Tear strength of sample after irradiation for 300 hours (N)
TS ₀ : Tear strength of sample before irradiation (N)

(10) Biodegradability: A sample is embedded in an aged compost maintained at about 58 ° C., taken out after 3 months, or the non-woven fabric as the sample does not retain its form, or retains its form Also, when the tensile strength was reduced to 50% or less with respect to the initial strength value before embedding, the biodegradability was evaluated as good and indicated by ○. On the other hand, when the strength exceeded 50% of the initial strength value before embedding, the biodegradation performance was evaluated as poor and indicated by x.

Example 1
A polylactic acid polymer (trade name U6201D manufactured by NatureWorks, hereinafter abbreviated as “P1”) having a melting point of 168 ° C., MFR1 of 23 g / 10 min, and MFR2 of 52 g / min was prepared as a core component.

  In addition, an aliphatic polyester polymer having a melting point of 110 ° C., an MFR1 of 22 g / 10 min, and an MFR2 of 25 g / min and having an aliphatic diol and an aliphatic dicarboxylic acid as constituents (trade names GSPla, FZ71PD manufactured by Mitsubishi Chemical Corporation; (Hereinafter abbreviated as “P2”). The crystallization rate index of this aliphatic polyester polymer was 7.4 minutes.

  Further, a master batch containing 20% by mass of talc (TA) as a crystal nucleating agent based on P1 was prepared.

  Then, the composite ratio of P1 and P2 is P1: P2 = 1: 1 in terms of mass ratio, and the mass of P2 is such that 0.5% by mass of talc is contained in the molten polymer of P1. After individually weighing so that the molten polymer may contain 0.5% by mass of montanic acid Ca salt (trade name: “Recommon CaV101” manufactured by Clariand Co., Ltd.), which is a metal salt of higher fatty acid, Is melted at a temperature of 200 ° C. using a separate extruder-type melt extruder, and using a spinneret having a cross section of a core-sheath type composite fiber, a polylactic acid-based polymer constitutes the core, and an aliphatic polyester polymer. Was melt-spun under the condition of a single-hole discharge rate of 1.56 g / min.

  After cooling the spun yarn with a known cooling device, it is subsequently pulverized at a traction speed of 2000 m / min with an air soccer provided below the spinneret, and opened using a known fiber opening device, It was collected and deposited as a web on a moving screen conveyor. At the time of opening, most of the constituent fibers were separated, and no contact yarn and convergent yarn were observed, and the opening property was good. The single yarn fineness of the deposited composite fiber was 7.7 dtex.

Next, the web was passed through a hot embossing device composed of an embossing roll and a smooth metal roll, and heat treated to obtain an agricultural covering material composed of a spunbonded nonwoven fabric having a basis weight of 20 g / m ² . As heat embossing conditions, the surface temperature of both rolls is 90 ° C., and the embossing roll is a circular sculpture pattern with an individual area of 0.6 mm ² , the pressure contact density is 20 / cm ² , and the pressure contact area ratio is 15 % Was used.

Example 2
In Example 1, a polylactic acid polymer having a melting point of 176 ° C., an MFR1 of 22 g / 10 min, and an MFR2 of 45 g / min (trade name “U'zS-17” manufactured by Toyota); And abbreviated as “P3”), the single hole discharge rate during melt spinning was set to 0.70 g / min, and the traction speed was set to 1990 m / min by air soccer. In the same manner as in No. 1, an agricultural covering material having a basis weight of 20 g / m ² constituted by a spunbonded nonwoven fabric composed of a composite fiber having a single yarn fineness of 3.5 dtex was obtained.

Example 3
In Example 1, the amount of the montanic acid Ca salt added to the aliphatic polyester polymer was 0.3% by mass, the single hole discharge amount was changed, and the single fiber fineness was 3.5 decitex composite fiber and Except having done, it carried out similarly to Example 1, and obtained the agricultural coating | coated material of 20 g / m < ² > of fabric weights comprised with the spun bond nonwoven fabric.

Example 4
In Example 1, 1 mass% of phenylphosphonic acid zinc salt (trade name: PPA-Zn, manufactured by Nissan Chemical Co., Ltd.) was added to the melt polymer instead of talc as a crystal nucleating agent to be added to the polylactic acid polymer. In addition, as an additive to be added to the aliphatic polyester polymer, 0.5 mass of phenylphosphonic acid zinc salt (manufactured by Nissan Chemical Co., Ltd., trade name “PPA-Zn”) instead of montanic acid Ca salt in the molten polymer. % In the same manner as in Example 1 except that it was added so that it was contained and melted at a temperature of 210 ° C. using an extruder type melt extruder to a single hole discharge rate of 0.70 g / min. An agricultural covering material having a basis weight of 20 g / m ² constituted by a spunbonded nonwoven fabric composed of a composite fiber having a fineness of 3.5 dtex was obtained.

Example 5
In Example 2, except that the basis weight of the spunbond nonwoven fabric was 15 g / m ² , a basis weight of 15 g constituted by a spunbond nonwoven fabric composed of a composite fiber having a single yarn fineness of 3.5 dtex was performed in the same manner as in Example 2. An agricultural covering material of / m ² was obtained.

Comparative Example 1
L-lactic acid / D-lactic acid = 98.4 / 1.6 mol% L-lactic acid / D-lactic acid copolymer only with melting point of 168 ° C., MFR1 of 65 g / 10 min, MFR2 of 100 g or more / 10 min The melt polymer was melted at a temperature of 210 ° C. so as to contain 0.5% by mass of talc, and a single-phase yarn was melt-spun under the condition of a single-hole discharge rate of 1.70 g / min. And the pulling speed was 5000 m / min, and the heat embossing conditions were the same as in Example 1 except that the surface temperature of both rolls was 130 ° C., and the single yarn fineness was 3.3 dtex and the basis weight was 20 g / m ² . A spunbond nonwoven fabric was obtained.

  The performances of the obtained Examples 1 to 5 and Comparative Example 1 are shown in Table 1.

As is apparent from Table 1, the agricultural coating materials of Examples 1 to 5 of the present invention have an initial strength that is twice or more that of Comparative Example 1 consisting only of a polylactic acid polymer. Yes. Moreover, the result in a weather resistance test is also favorable and it turns out that the initial strength can be maintained over a long period of time.

Claims (5)

A covering material for agriculture comprising a spunbonded nonwoven fabric comprising a composite fiber, the composite fiber having a polylactic acid polymer having a melting point of 160 ° C. or higher, and a melting point of 50 ° C. or higher than the polylactic acid polymer. A low aliphatic polyester polymer, and the aliphatic polyester polymer forms at least part of the fiber surface, and the aliphatic polyester polymer comprises 1,4-butanediol and succinic acid. A component polymer (however, an aliphatic diol, an aliphatic dicarboxylic acid, and an aliphatic hydroxycarboxylic acid are used as constituent components, and a crosslinked aliphatic polyester copolymer is excluded) , and montanic acid raw component, wherein the calcium salt, that contains at least one 0.1-1 wt% selected from the phenylphosphonic acid zinc salt Sex agricultural covering materials. Composite fibers, polylactic acid polymer to form a core, an aliphatic polyester polymer coating biodegradable agricultural claim 1 Symbol mounting characterized in that it is a core-sheath type composite fiber to form a sheath Materials. The biodegradable covering material for agriculture according to claim 1 or 2 , wherein fine concave portions and / or convex portions are formed on the surface of the composite long fiber. Single filament fineness of 3 to 10 dtex composite fibers, biodegradable agricultural covering material according to any one of claims 1-3, wherein the basis weight of the nonwoven fabric is 10 to 30 g / m ^2. A solid sheet comprising the biodegradable agricultural covering material according to claim 4 .