JPH11117164A - Biodegradable laminated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable laminated sheet capable of being readily degraded by microorganisms, having an arbitrary controllable degrading rate thereof, and excellent in texture, strength and flexibility. SOLUTION: This biodegradable laminated sheet consists of a meltblown nonwoven fabric and spunbonded nonwoven fabrics, and has a three layer structure having the spunbonded nonwoven fabrics laminated on both sides of the meltblown nonwoven fabric and thermally fused to adhere to each other. The meltblown nonwoven fabric is composed of an aliphatic polyester resin having biodegradability, and has a fiber diameter within the range of 0.5-2.0 μm. The proportion of the weight of the meltblown nonwoven fabric based on the laminated sheet is within the range of 10-30 wt.%, and the spunbonded nonwoven fabric consists of continuous filaments composed of a polybutylene succinate synthesized from 1,4-buthane diol and succinic acid, and formed into the high molecular one by an urethane bond. The density of the spunbonded nonwoven fabric measured based on JIS L 1906 (calculated from the thickness under 2 kPa load) is within the range of 0.15-0.25 g/cc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biodegradable composition,
In addition, the present invention relates to a laminate sheet whose biodegradation rate can be arbitrarily controlled and is excellent in strength, flexibility and formation, and can be used in a wide range of fields such as medical and sanitary materials and general industrial materials.

[0002]

2. Description of the Related Art In recent years, spunbonded nonwoven fabrics using long fibers as constituent fibers have been used for various purposes because they are higher in strength and relatively inexpensive than short fiber nonwoven fabrics containing short fibers as constituent fibers. I have. In particular, in disposable applications, the demand for use is rapidly increasing due to the low labor and hygiene of use,
Spread-bonded nonwoven fabrics that can be manufactured at low cost are increasingly used in disposable applications, and the demand for them is also increasing rapidly.

As a fiber material constituting the spunbonded nonwoven fabric, polymers such as polyethylene, polypropylene, polyester, and polyamide are generally used. However, spunbonded nonwoven fabrics made of these materials have no self-decomposability and are chemically very stable under ordinary natural environments. Therefore, spunbonded nonwoven fabrics used for disposable purposes are currently treated by incineration or landfill after use. In the case of incineration, not only is a large cost required for incineration, but in the case of nylon-based non-woven fabrics made of polyamide, for example, toxic gas such as cyan gas may be generated. Pollution caused by plastic is also becoming a problem, and how to solve this problem of disposal of waste plastic is a major social problem in terms of protection of the natural environment and living environment.

On the other hand, landfills have a problem that they remain in their original state for a long time in soil because the materials are chemically stable. As a method for solving such a problem, a new nonwoven fabric that can be decomposed in a short period of time by using a material having natural degradability has been demanded. Examples of biodegradable polymers include polysaccharides such as chitin, proteins and polypeptides (polyamino acids) such as cut gut (intestinal tract) and regenerated collagen, and poly-3-hydroxybutyrate and polysaccharides produced by microorganisms in nature. -3-
Synthetic aliphatic polyesters such as hydroxyvalerate and polylactide are known.

However, when producing fibers from these polymers, especially when producing spunbonded nonwoven fabrics, there is a problem that the melt spinnability is extremely poor and processing cannot be carried out using a commonly used apparatus for producing spunbonded nonwoven fabrics. is there. In addition, since the cost of the material is extremely high, it is not suitable for general disposable living materials such as disposable diapers, sanitary materials such as cover stock for sanitary products, wipes, and packaging materials.

In order to solve the above problems, Japanese Patent Laid-Open No.
Japanese Patent No. 57953 discloses a spunbonded nonwoven fabric made of polyethylene containing 3 to 30% by weight of polycaprolactone as a biodegradable polymer. However, in this case, since polyethylene does not decompose semipermanently, it cannot be said that polyethylene is a biodegradable nonwoven fabric in its original meaning.

[0007] Japanese Patent Application Laid-Open No. Hei 5-214648 discloses a spunbond nonwoven fabric comprising poly-ε-caprolactone and / or poly-β-propiolactone. In this case, the material can be completely biodegradable, but the melting point of poly-ε-caprolactone is 60%.
℃, the melting point of poly-β-propiolactone is 100
° C and poor thermal stability, which is not suitable for practical materials.

Further, JP-A-7-34369, JP-A-7-48768 and JP-A-8-60513 are characterized in that glycols and aliphatic dicarboxylic acids or derivatives thereof are contained as constituent units. A spunbonded nonwoven fabric made of an aliphatic polyester resin is disclosed. Although this nonwoven fabric substantially solves the above-mentioned problems, it is at present the case that it is not a practical material satisfying both spinnability and biodegradability. That is, as the aliphatic polyester resin which is suitable for melt spinning and can be used for a spunbond nonwoven fabric which can be produced at a low cost, a polybutylene succinate polymer synthesized from 1,4-butanediol and succinic acid has a high molecular weight by a urethane bond. In this case, it is possible to produce a spunbonded nonwoven fabric having good melt spinnability and excellent strength and texture and having biodegradability, but there is a problem that biodegradability is slow.

A polybutylene succinate-adipate copolymer, which is an aliphatic polyester synthesized from 1,4-butanediol and succinic acid and adipic acid,
On the other hand, the biodegradation rate is fast, but the crystallization rate is slow and the solidification of the filament on the melt spinning line is slow. Therefore, unless the spinning length (the distance from the exit of the die to the entrance of the ejector) is extremely long, ordinary spunbond nonwoven fabric In a manufacturing apparatus, fusion between yarns is liable to occur, and the texture of the resulting spunbonded nonwoven fabric is inferior, and the flexibility is reduced. Therefore, it is not suitable as a resin used for the spunbonded nonwoven fabric.

On the other hand, the manufacturing process of the melt blown nonwoven fabric is as follows.
At the same time as melting the thermoplastic resin and extruding it from the nozzle,
Since this is a spinning process in which the molten resin obtained by high-temperature, high-speed air in the vicinity of the nozzle is thinned to form ultra-fine fibers, spunbonded nonwoven fabrics do not require the necessary melt-spinning properties, making it possible to produce nonwoven fabrics It is.

Further, since the fibers constituting the melt-blown nonwoven fabric are ultrafine fibers, the fiber surface area of the obtained nonwoven fabric is larger than that of the spunbonded nonwoven fabric. As a result, the contact area with microorganisms is increased. Therefore, if the melt-blown nonwoven fabric and the spun-bonded nonwoven fabric are made of the same resin, the biodegradation rate of the melt-blown nonwoven fabric is higher.

However, the fibers constituting the melt-blown non-woven fabric are ultrafine fibers, and the short fibers are not drawn and the polymer chains are not oriented, so that the strength of the non-woven fabric is low and the productivity is low. Is expensive compared to spunbonded nonwoven fabrics. Furthermore, when it is necessary to control the biodegradation rate according to the application, the current situation is that the current biodegradable spunbonded nonwoven fabric and meltblown nonwoven fabric are still not at a satisfactory level.

[0013]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a biodegradable laminate sheet which can be easily decomposed by microorganisms, its decomposition rate can be arbitrarily controlled, and it is excellent in formation, strength and flexibility. Is to provide.

[0014]

In view of the above situation, the present inventors have conducted intensive studies and have found that the excellent biodegradability of the melt-blown nonwoven fabric and the excellent melt spinnability and span properties of the polybutylene succinate polymer. Focusing on the strength when processed into a bonded nonwoven fabric, a spunbonded nonwoven fabric made of a polybutylene succinate polymer with a high molecular weight by urethane bonding is laminated on both sides of a melt blown nonwoven fabric made of aliphatic polyester resin having biodegradability By doing so, it has been found that a biodegradable laminate sheet that can be produced relatively inexpensively, can control the biodegradation rate arbitrarily, and is excellent in flexibility, formation, and strength can be obtained. Reached.

The present invention provides a laminated sheet having a three-layer structure comprising a biodegradable melt-blown nonwoven fabric and a spunbonded nonwoven fabric, wherein a spunbonded nonwoven fabric is laminated on both sides of the meltblown nonwoven fabric and heat-sealed. The fiber diameter of the short fibers constituting the melt-blown nonwoven fabric made of an aliphatic polyester resin having degradability is 0.5 to 2.0 μm
m, and the ratio of the basis weight of the melt blown nonwoven fabric to the laminate sheet is in the range of 10 to 30% by weight, and the spunbonded nonwoven fabric is made of poly synthesized from 1,4-butanediol and succinic acid. The butylene succinate polymer obtained by increasing the molecular weight by urethane bonds is composed of continuous long fibers, and the spunbond nonwoven fabric has a density of 0.15 to 0.25 g / JIS L 1906 (calculated from a thickness of 2 kPa under load). It is a biodegradable laminated sheet characterized by being in the range of cc.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a method for producing a laminated sheet having a three-layer structure comprising a melt-blown non-woven fabric and a spun-bonded non-woven fabric, a melt-blown non-woven fabric using an aliphatic polyester resin having thermoplasticity and biodegradability, -Each of spunbonded nonwoven fabrics using a polybutylene succinate polymer synthesized from butanediol and succinic acid and having a high molecular weight by urethane bond is prepared in advance, and may be laminated and bonded. Polyester resin having thermoplasticity and biodegradability by melt blow method on a spunbonded nonwoven fabric made of polybutylene succinate polymer synthesized from 1,4-butanediol and succinic acid and having a high molecular weight by urethane bond Is melt-spun from a known melt extrusion spinning machine, collected and deposited to form a web, Thereafter, any method of laminating a spunbonded nonwoven fabric made of a polybutylene succinate polymer synthesized from 1,4-butanediol and succinic acid and having a high molecular weight by urethane bond is adopted. good.

In the present invention, a method of directly forming a nonwoven fabric on a spunbonded nonwoven fabric by a known melt blowing method will be described. Examples of the aliphatic polyester resin used in the spunbonded nonwoven fabric of the present invention include 1,4
-A polybutylene succinate polymer synthesized from butanediol and succinic acid, isocyanate is further added, and a urethane polymerization is performed between the polybutylene succinate polymers, and the number average molecular weight is 10,000 or more,
The melting point is in the range of 110 to 120 ° C and JIS K
Temperature 190 as measured by the method described in 7210.
The melt flow rate under the conditions of a temperature of 2.degree. C. and a load of 2.16 kg is in a range of 15 to 70 g / 10 minutes, and a product commercially available under the trade name of Bionole (manufactured by Showa Kogaku KK) is used.

If the melt flow rate is less than 15 g / 10 minutes, the melt viscosity is too high and the texture of the resulting nonwoven fabric becomes hard, which is not suitable. Conversely, if the melt flow rate exceeds 70 g / 10 minutes, thread breakage is likely to occur in the spinning step, and not only the texture of the obtained long-fiber nonwoven fabric will decrease, but also the strength will decrease, which is not suitable.

When the spunbonded nonwoven fabric is manufactured, the aliphatic polyester resin is heated and melted in an extrusion spinning machine, and the melting temperature when spinning is 50 degrees below the melting point of the resin.
Increase by ~ 135 ° C. When the melting temperature is higher than the melting point of the polymer by less than 50 ° C., the viscosity of the molten resin is high,
Not suitable for spinning. Conversely, the melting temperature is 13
If the temperature is higher than 5 ° C., the temperature difference from the melting point of the resin is too large, so that it is difficult to cool the resin when spinning the resin from a large number of spinnerets of an extrusion spinning machine, and the fusion of the fibers and the breakage of the yarn may occur. Not only is it easier, but also the stability of the resin is reduced, and decomposition may occur. Furthermore, the aliphatic polyester resin is hydrophilic, and contains water in the resin. However, if spinning is performed in a state containing water, the resin is decomposed, so that a drying treatment is performed prior to spinning. There is a need. The water content of the resin is 0.2% by weight or less,
Preferably it is 0.05% by weight or less.

A large number of long fiber filaments extruded from a spinneret of an extruder and drawn by high-pressure air from an ejector are triboelectrically charged by hitting a collision plate, and each of the long fibers is repelled by an electric charge. Let open. in this case,
As a charging method, a corona discharge treatment may be performed on the long fibers to charge the long fibers. A large number of uniformly opened filaments are collected and deposited on a support such as a moving wire mesh belt to form a web. The fineness of this long fiber is 1 to
It is in the range of 10 denier. If the fineness of the long fiber is less than 1 denier, it is difficult to spin the long fiber stably. Conversely, if the fineness of the long fiber exceeds 10 denier, the fiber diameter becomes too large and the texture of the spunbonded nonwoven fabric becomes poor. Not suitable as it will decrease.

In the present invention, self-fused areas of fibers are provided at regular intervals for the purpose of imparting sheet-like shape retention and strength to the web. The self-fusing area is formed by introducing the web between the heated uneven roll and the smooth roll, applying heat and pressure treatment, and fusing the portion corresponding to the convex portion of the uneven roll. . In this case, the temperature of the roll is a temperature lower by 5 to 50 ° C. than the melting point of the resin constituting the long fiber used. If the difference between the roll temperature and the melting point of the resin is less than 5 ° C., the fibers will adhere to the roll during thermocompression treatment by the roll, causing a manufacturing trouble. Conversely, if the difference between the roll temperature and the melting point of the resin exceeds 50 ° C., the formation of the self-fused portion becomes insufficient, and the strength of the spunbonded nonwoven fabric is remarkably reduced.

The linear pressure when the thermocompression bonding is performed with the uneven roll and the smooth roll is 10 to 80 kg / cm. If the linear pressure is less than 10 kg / cm, the self-bonding area by the thermocompression bonding process is insufficiently formed, and if it exceeds 80 kg / cm, the long fiber is cut by the convex portion of the uneven roll during the thermocompression bonding process. In any case, the strength of the spunbonded nonwoven fabric is reduced, so that it is not suitable.

JIS of the obtained spun bond nonwoven fabric
The density calculated from the thickness of L 1906 measured under a load of 2 kPa is in the range of 0.15 to 0.25 g / cc.
When the density of the spunbonded nonwoven fabric is less than 0.15 g / cc, the gap between long fibers constituting the spunbonded nonwoven fabric becomes too coarse, and the formation of the spunbonded nonwoven fabric is reduced. Is not suitable because it decreases. Conversely, the density of the spunbond nonwoven fabric is 0.25 g /
If it exceeds cc, the interstices between the long fibers constituting the spunbonded nonwoven fabric become too dense, and the surface area of the long fibers constituting the spunbonded nonwoven fabric becomes too small, so that the decomposition rate becomes slow, and as a result, the biodegradation rate It is not suitable because it becomes difficult to control

Next, a melt blown nonwoven fabric is spun on the surface of the produced spunbonded nonwoven fabric as follows. The resin used for the melt blown nonwoven fabric is not particularly limited as long as it is an aliphatic polyester resin having thermoplasticity and biodegradability. For example, polybutylene synthesized from 1,4-butanediol and succinic acid and adipic acid Succinate adipate copolymer (trade name: Bionole 3000, manufactured by Showa Polymer Co., Ltd.) or 1,4
-A polybutylene succinate polymer synthesized from butanediol and succinic acid, which has a high molecular weight by urethane bond (trade name: Bionole 1000, manufactured by Showa Polymer Co., Ltd.);

As described above for the spunbonded nonwoven fabric, the aliphatic polyester resin contains water in the polymer because the polymer itself is hydrophilic. Since decomposition occurs, it is necessary to perform a drying treatment prior to spinning. The water content is 0.2% by weight or less, preferably 0.05% by weight or less.

The melting temperature of the resin during melt blow spinning is as follows:
Considering the melting point, melt flow rate and the like of the resin to be used, the temperature may be at least the melting point of the resin. The resin melted in the extruder is extruded from the nozzle, and at the same time, is drawn by a high-temperature high-speed air flow near the nozzle to form ultrafine fibers having a fiber diameter of 0.5 to 2.0 μm. The web is formed by collecting and accumulating a large number of ultrafine fibers transported by the above method into a spunbonded nonwoven fabric placed on a support made of a wire mesh belt. If the fiber diameter of this ultrafine fiber is less than 0.5 μm,
The production conditions became severe, and it became difficult to produce ultrafine fibers stably. On the contrary, the fiber diameter of the ultrafine fibers was 2.0 μm.
When it exceeds, not only the fiber surface area becomes small and the biodegradation rate cannot be increased, but also the melt-blown nonwoven fabric becomes hard, and as a result, the laminate sheet with the spunbonded nonwoven fabric also has a poor texture. Not suitable. The fiber diameter of the ultrafine fibers is also affected by the conditions of the high-temperature high-speed air flow.

Furthermore, the distance from the nozzle to the support (hereinafter referred to as the collecting distance) can be selected as appropriate. However, when the collecting distance is small, the obtained melt-blown nonwoven fabric is dense and has high density, and the strength is large. On the other hand, when the collecting distance is long, the sheet becomes bulky and low in density, and the sheet becomes small in strength but flexible. Subsequently, on the melt-blown non-woven fabric surface of the laminate of the spun-bonded non-woven fabric and the melt-blown non-woven fabric manufactured as described above, the laminated sheet having a three-layer structure in which another spun-bonded non-woven fabric prepared in advance is arranged. I do.

For the purpose of imparting shape retention and strength to the laminate as a sheet, self-bonding areas are provided at regular intervals in the same manner as in the case of the spunbonded nonwoven fabric, and each fiber is interposed between the spunbonded nonwoven fabric and the meltblown nonwoven fabric. This causes a fused portion between the portions. The fused area is formed by introducing a three-layered laminate composed of a spunbonded nonwoven fabric, a meltblown nonwoven fabric, and a spunbonded nonwoven fabric between a heated uneven roll and a smooth roll, and applying heat and pressure to the uneven surface. The fibers are formed by fusing each fiber of the sheet portion corresponding to the convex portion of the roll.

In this case, the temperature of the roll is a temperature lower by 5 to 50 ° C. than the melting point of the resin constituting the long fiber of the spunbonded nonwoven fabric. If the difference between the roll temperature and the melting point of the polymer is less than 5 ° C., the fibers will adhere to the roll during thermocompression treatment with the roll, causing a production trouble. Conversely, if the difference between the roll temperature and the melting point of the polymer exceeds 50 ° C., the formation of the fused portion becomes insufficient and the strength of the laminate sheet is significantly reduced, which is not suitable. The linear pressure when the thermocompression treatment is performed with the uneven roll and the smooth roll is 10 to 80 kg / cm. If the linear pressure is less than 10 kg / cm, the formation of the fused area by the thermocompression bonding process becomes insufficient, and if it exceeds 80 kg / cm, the long fiber is cut by the projections of the uneven roll during the thermocompression bonding process. However, these are not suitable because the strength of the laminate sheet is reduced.

The basis weight of the obtained laminate sheet having a three-layer structure is in the range of 10 to 150 g / m ² . The basis weight is 10 g / m ²
If it is less than 1, the proportion of the melt-blown nonwoven fabric in the laminate sheet is too small, and it is not only difficult to increase the biodegradation rate, but also it is not possible to impart good texture and texture to the laminate sheet. Conversely, the basis weight is 150 g
If it exceeds / m ² , the laminate sheet will be hard and the texture will be reduced, which is not suitable.

The proportion of the melt blown nonwoven fabric in the laminate sheet is in the range of 10 to 30% by weight. If the proportion of the melt-blown non-woven fabric is less than 10% by weight, the melt-blown non-woven fabric is too small, so that not only is it difficult to accelerate the biodegradability, but also the melt-blown non-woven fabric has a too small basis weight and the ultrafine fibers become non-uniform, resulting in a laminate. It is not suitable because the texture, texture and flexibility of the body sheet decrease. Conversely, if the proportion of the meltblown nonwoven fabric exceeds 30% by weight, the effect of the meltblown nonwoven fabric as a biodegradation promoter in the laminate sheet will level off and the cost of the laminate sheet will increase, which is not suitable.

As described above, a polybutylene succinate polymer synthesized from 1,4-butanediol and succinic acid is bonded to both sides of a melt-blown nonwoven fabric made of an aliphatic polyester resin having biodegradability by urethane bonding. A spunbonded nonwoven fabric having a molecular weight is arranged, the fiber diameter of the short fibers constituting the meltblown nonwoven fabric is in the range of 0.5 to 2.0 μm, and the weight ratio of the meltblown nonwoven fabric to the laminate sheet is 10%.
JIS L 1906 of the spunbonded nonwoven fabric (calculated from the thickness under a load of 2 kPa).
The laminate sheet having a three-layer structure having a density of 0.15 to 0.25 g / cc in the range has biodegradability and can control the speed, and is excellent in strength, flexibility and formation. It can be used in a wide range of fields such as medical and sanitary materials and general industrial materials.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. In Examples and Comparative Examples,% is% by weight unless otherwise specified.

Example 1 The aliphatic polyester resin has a melt flow rate of 3
Polybutylene succinate polymer synthesized from 1,4-butanediol and succinic acid at 2 g / 10 min and further added with isocyanate to form a urethane bond between the polybutylene succinate polymers (trade name: Bionole) 1
030, manufactured by Showa Polymer Co., Ltd., melting point 115 ° C.), heated and melted at 190 ° C. in a melt spinning machine, extruded and spun through fine holes of a spinneret, and spun continuous filament filaments at high speed by an ejector. After drawing and drawing while stretching with high-pressure air, the fiber is collected and deposited on a running support made of stainless steel mesh, and has a basis weight of 25 g / m2.
^Two webs were formed. The fineness of this long fiber is 2.1 denier, and the density of the spunbonded nonwoven fabric is 0.17 g /
cc.

Next, the obtained web is introduced between the uneven roll and the smooth roll heated to a temperature of 105 ° C., and a portion corresponding to the convex portion of the uneven roll is fused to form a spunbond nonwoven fabric. And wound up in a roll.

Next, the melt flow rate was 310 g /
Isocyanate is further added to the polybutylene succinate polymer synthesized from 1 / 10th of 1,4-butanediol and succinic acid, and 20 mol% of adipic acid is added to the urethane-bonded polybutylene succinate polymer. Using a polybutylene succinate-adipate copolymer (trade name: Bionole 3300, manufactured by Showa Polymer Co., Ltd., melting point: 96 ° C.), the resin was heated and melted at 190 ° C. using a known melt blow nozzle. Then, a melt-blown nonwoven fabric was produced on the spunbonded nonwoven fabric placed on a moving wire mesh support.

The melt blow nozzle used at this time has fine holes having a diameter of 0.4 mm arranged at intervals of 1 mm in the width direction. The discharge amount of the molten resin is 1.0 g / min per nozzle hole. The spun-bonded nonwoven fabric is placed on a support, and the melt-blown fibers reduced by spraying heated and pressurized air are collected and deposited on the surface of the spun-bonded nonwoven fabric while moving, and the web having a basis weight of 20 g / m ² is obtained. Was formed. The collection distance was 350 mm, and the fiber diameter of the melt blown fibers was 1.8 μm.

[0038] On the melt-blown non-woven fabric of the laminate obtained by laminating the spun-bonded non-woven fabric and the melt-blown non-woven fabric as described above, it is prepared in advance as described above,
The same spunbonded nonwoven fabric that had been wound was laminated, and thus a three-layer laminated sheet having the spunbonded nonwoven fabric disposed on both sides of the meltblown nonwoven fabric was obtained.

Further, in order to impart morphological stability to the laminated sheet, the laminated sheet is introduced into an uneven roll and a smooth roll heated to a temperature of 105 ° C., and a portion corresponding to the convex portion of the irregular roll is fused. The laminated sheet thus obtained was obtained. The weight of the obtained laminate sheet was 70 g / m ² .

The obtained laminate sheet having a three-layer structure was tested by the following test method, and its quality was evaluated. Test method (1) Tensile strength of laminated sheet Measured according to JIS L 1906, and performed in the longitudinal direction at a width of 50 mm of the laminated sheet.

(2) Flexibility of Laminated Sheet The evaluation was performed by sensory evaluation by 20 monitors. The monitor rubbed the non-woven fabric by hand, showed the flexibility by 1 to 5 points, represented the total score (out of 100 points) as flexibility, and scored 90 points or more as acceptable. 5 points: extremely flexible. 4 points: Flexible. 3 points: flexibility is normal. 2 points: Slightly inferior in flexibility. 1 point: Poor flexibility.

(3) Biodegradation rate Five laminated sheets each having a size of 10 cm × 25 cm and whose weight was measured in advance, 5 sheets each, 1-10 Shinonome, Shinonome, Koto-ku, Tokyo.
No. 6, Oji Paper Co., Ltd., buried at 25cm depth in the ground in Shinonome Research Center, excavated after 6 months, measured the weight, calculated the average value of the weight reduction rate, the following three steps Was evaluated. ：: Weight loss rate is 50% or more Δ: Weight loss rate is 30% or more and less than 50% X: Weight loss rate is less than 30%

Example 2 The same aliphatic polyester resin as used in Example 1 was melt-spun under the same conditions except that a spunbond nonwoven fabric having a basis weight of 10 g / m ² was prepared. A bonded nonwoven fabric was produced. The fineness of this long fiber is 2.2
Denier, density of spunbond nonwoven fabric is 0.23
g / cc. Next, the same as in Example 1, the basis weight 3
A melt-blown nonwoven fabric of g / m ² was formed to produce a laminate. The fiber diameter of this melt blown nonwoven fabric is 0.7 μm
Met. Further, a previously prepared spunbonded nonwoven fabric having a basis weight of 10 g / m ² was laminated on the laminate side of the spunbonded nonwoven fabric and the meltblown nonwoven fabric, and the same operation as in Example 1 was repeated to obtain a laminate having a three-layer structure. I got a sheet. The basis weight of the obtained laminate sheet was 23 g / m ² . The obtained laminate sheet was tested by the test method described above, and its quality was evaluated.

Example 3 The same aliphatic polyester resin as used in Example 1 was melt-spun under the same conditions, except that a spunbond nonwoven fabric having a basis weight of 55 g / m ² was prepared. A bonded nonwoven fabric was produced. The fineness of this long fiber is 2.1
Denier, density of spunbond nonwoven fabric is 0.20
g / cc. Next, the same as in Example 1, the basis weight 3
A melt-blown nonwoven fabric of 3 g / m ² was formed to produce a laminate. The fiber diameter of this melt blown nonwoven fabric is 1.1 μm.
m. Further, a previously prepared spunbonded nonwoven fabric having a basis weight of 55 g / m ² was laminated on the laminate side of the spunbonded nonwoven fabric and the meltblown nonwoven fabric, and the same operation as in Example 1 was repeated to obtain a laminate having a three-layer structure. I got a sheet. The weight of the obtained laminate sheet is 143 g / m.
^{Was 2} . The obtained laminate sheet was tested by the test method described above, and its quality was evaluated.

Comparative Example 1 The same aliphatic polyester resin as used in Example 1 was melt-spun under the same conditions, except that a spunbond nonwoven fabric having a basis weight of 25 g / m ² was prepared. A bonded nonwoven fabric was produced. The fineness of this long fiber is 2.0
Denier, density of spunbond nonwoven fabric is 0.23
g / cc. Next, in the same manner as in Example 1, the basis weight 4
A melt-blown nonwoven fabric of g / m ² was formed to produce a laminate. The fiber diameter of this melt blown nonwoven fabric is 1.8 μm
Met. Furthermore, a spunbonded nonwoven fabric having a basis weight of 25 g / m ² was laminated on the laminate side of the spunbonded nonwoven fabric and the melt-blown nonwoven fabric, and the same operation as in Example 1 was repeated to obtain a laminate having a three-layer structure. I got a sheet. The weight of the obtained laminate sheet was 54 g / m ² . The obtained laminate sheet was tested by the test method described above, and its quality was evaluated.

Comparative Example 2 The same aliphatic polyester resin as used in Example 1 was melt-spun under the same conditions, except that a spunbond nonwoven fabric having a basis weight of 25 g / m ² was prepared. A bonded nonwoven fabric was produced. The fineness of this long fiber is 2.2
Denier, density of spunbond nonwoven fabric is 0.20
g / cc. Next, in the same manner as in Example 1, the basis weight 2
A melt-blown nonwoven fabric of 0 g / m ² was formed to produce a laminate. The fiber diameter of this melt blown nonwoven fabric is 2.2μ.
m. Furthermore, a spunbonded nonwoven fabric having a basis weight of 25 g / m ² was laminated on the laminate side of the spunbonded nonwoven fabric and the melt-blown nonwoven fabric, and the same operation as in Example 1 was repeated to obtain a laminate having a three-layer structure. I got a sheet. The weight of the obtained laminate sheet is 70 g / m ^2.
Met. The obtained laminate sheet was tested by the test method described above, and its quality was evaluated.

Comparative Example 3 The same aliphatic polyester resin as that used in Example 1 was melt-spun under the same conditions except that a spunbond nonwoven fabric having a basis weight of 23 g / m ² was prepared. A bonded nonwoven fabric was produced. The fineness of this long fiber is 1.8
Denier, density of spunbond nonwoven fabric is 0.27
g / cc. Next, in the same manner as in Example 1,
A melt-blown nonwoven fabric of 5 g / m ² was formed to produce a laminate. The fiber diameter of this melt blown nonwoven fabric is 1.9μ.
m. Further, a previously prepared spunbonded nonwoven fabric having a basis weight of 23 g / m ² was laminated on the laminate side of the spunbonded nonwoven fabric and the melt-blown nonwoven fabric, and the same operation as in Example 1 was repeated. I got a sheet. The weight of the obtained laminate sheet is 61 g / m ^2.
Met. The obtained laminate sheet was tested by the test method described above, and its quality was evaluated.

Comparative Example 4 The same aliphatic polyester resin as used in Example 1 was melt-spun under the same conditions, except that a spunbond nonwoven fabric having a basis weight of 20 g / m ² was prepared. A bonded nonwoven fabric was produced. The fineness of this long fiber is 2.7
Denier, density of spunbond nonwoven fabric is 0.13
g / cc. Next, in the same manner as in Example 1,
A melt-blown nonwoven fabric of 0 g / m ² was formed to produce a laminate. The fiber diameter of this melt blown nonwoven fabric is 1.6μ.
m. Further, a previously prepared spunbonded nonwoven fabric having a basis weight of 20 g / m ² was laminated on the laminate side of the spunbonded nonwoven fabric and the meltblown nonwoven fabric, and the same operation as in Example 1 was repeated to obtain a laminate having a three-layer structure. I got a sheet. The basis weight of the obtained laminate sheet is 50 g / m ^2.
Met. The obtained laminate sheet was tested by the test method described above, and its quality was evaluated. Table 1 shows the results obtained in the examples and comparative examples.

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[Table 1]

As is clear from Table 1, the laminate sheet having a three-layer structure obtained according to the present invention has excellent flexibility, high strength and quick biodegradability (Examples 1 to 3). In contrast, when the proportion of the melt-blown nonwoven fabric in the laminate sheet is smaller than the specified range, the effect of increasing the biodegradation rate is not sufficient, and good texture and flexibility cannot be provided ( Comparative example 1). Also,
When the fiber diameter of the ultrafine fibers constituting the meltblown nonwoven fabric is larger than the specified range or when the density of the spunbonded nonwoven fabric is larger than the specified range, the effect of increasing the biodegradation rate is not sufficient (Comparative Example 2, 3). When the density of the spunbonded nonwoven fabric is smaller than the specified range, the formation and flexibility of the obtained laminate sheet deteriorate (Comparative Example 4).

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Industrial Applicability The present invention has biodegradability, is capable of arbitrarily controlling the biodegradation rate, is excellent in strength, formation and flexibility, is a medical / sanitary material, general industrial material. This provides an effect of providing a biodegradable laminate sheet suitable for a wide range of fields such as.

Claims (1)

[Claims] 1. A laminated sheet having a three-layer structure comprising a melt-blown nonwoven fabric and a spunbonded nonwoven fabric, wherein a spunbonded nonwoven fabric is laminated on both sides of the meltblown nonwoven fabric, and wherein the meltblown nonwoven fabric has biodegradability. When the fiber diameter of the short fibers is in the range of 0.5 to 2.0 μm, and the weight ratio of the melt-blown nonwoven fabric to the laminate sheet is in the range of 10 to 30% by weight. Furthermore, the spunbonded nonwoven fabric is made of continuous long fibers obtained by increasing the molecular weight of a polybutylene succinate polymer synthesized from 1,4-butanediol and succinic acid by urethane bonds, and the JIS of the spunbonded nonwoven fabric L 1
906 (calculated from the thickness of the load of 2 kPa) is 0.
A biodegradable laminate sheet having a mass in the range of 15 to 0.25 g / cc.