JPH09142485A - Biodegradable bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bag which can be quickly decomposed by microbe while keeping a practical waterproofness, and is equipped with a practical strength and a processability even when being thin by a method wherein one part or the whole part of a contact part between a cellulose based fiber and a biodegradable aliphatic polyester fiber, is made of a non-woven fabric which is heat- bonded. SOLUTION: A biodegradable bag consists of a mixed fiber of a cellulose based fiber and a biodegradable aliphatic polyester fiber, and one part or the whole part of a contact part between the cellulose based fiber and the biodegradable aliphatic polyester fiber is made of a non-woven fabric which is heat- bonded. The cellulose based fiber is a short fiber of which the fiber length is 5-120mm, or a filament. Also, for the biodegradable aliphatic polyester, making the melt spinning temperature at a melting point or higher and 230 deg.C or lower to perform the melt spinning, is preferable, in addition, the mixing ratio of the cellulose based fiber and the biodegradable aliphatic polyester fiber of the non-woven fabric to form the biodegradable bag, is 90/10-10/90 (weight ratio).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable bag, and more particularly to a biodegradable bag using a non-woven fabric which is biodegradable in nature and has excellent water resistance and adhesive workability.

[0002]

2. Description of the Related Art Conventionally, woven and knitted fabrics, non-woven fabrics and films made of thermoplastic polymers such as polyester, polyolefin and polyamide are widely used as materials for bags which are conventionally used for daily life materials, sanitary materials, medical materials and the like. ing. However, these woven and knitted fabrics, nonwoven fabrics, films and the like have various problems because they are difficult to decompose when left in the natural environment after use. For example, when these bags are filled with garbage, dead leaves, etc. in the soil, they have low biodegradability and remain in the soil for a long period of time, so there is a limit to how to use the land thereafter. It was

In order to solve such a problem, it is considered to use a material made of a polymer which is easily decomposed in soil.

That is, as the biodegradable polymer for the above purpose, cellulosic cotton, regenerated cellulose fiber, poly-3-hydroxybutyrate or 3 produced by microorganisms.
A copolymer of -hydroxybutyrate and 3-hydroxyvalerate, polycaprolactone and the like are known.

Of these, cellulosic cotton,
Although regenerated cellulose fibers are easily available, they require a binder because they are not thermoplastic, and when polyolefin fibers, polyester fibers, or the like are used as the binder fibers, there is a problem that these fibers remain because they are difficult to decompose in the natural world.

Further, poly-3-hydroxybutyrate, a copolymer of 3-hydroxybutyrate and hydroxyvalerate, etc. produced by microorganisms are not easy to obtain because they have only low strength fibers and are not suitable for use. Is limited.

Polycaprolactone is a biodegradable polymer that is relatively easily available, but its melting point is as low as about 60 ° C., so that it is at a temperature at which the fibers can melt during the distribution stage in the natural world in summer. There was a problem in terms of heat resistance.

[0008] On the other hand, fibers obtained by mixing polyethylene with starch have been studied as an easily available material, but polyethylene is not biodegradable and fibers with uniform mechanical properties have not been obtained.

In recent years, however, household composters have come to be used for garbage processing, and there is an increasing demand for processing garbage bags (drainage bags) together with garbage in the poster.

[0010]

The bag made of the conventional biodegradable material is relatively easy to obtain, has a practical water resistance, is rapidly decomposed by microorganisms, and is practical even if it is thin. It was not possible to obtain a bag having sufficient strength and workability.

An object of the present invention is to provide a biodegradable bag that achieves the above object.

[0012]

In order to achieve the above object, the biodegradable bag of the present invention comprises a mixed fiber of a cellulosic fiber and a biodegradable aliphatic polyester fiber, and comprises the above cellulose fiber and biodegradability. It is characterized in that a part or the whole of the contact portion with the aliphatic polyester fiber is made of a non-woven fabric which is heat-bonded.

Cellulosic fibers used in the biodegradable bag of the present invention having the above-mentioned constitution are cotton, hemp, rayon,
Polynosic etc. can be used alone or in combination of two or more kinds. Cellulosic fibers have a fiber length of 5 to 12
0 mm, preferably 10-80 mm, more preferably 10-30 mm short fibers or filaments,
The single fiber diameter is 1 to 10 denier, preferably 1.5 to 6 denier. The number of crimps of cellulosic fibers is 5 to 40/2
It is preferably 5 mm. 5 crimps / 25mm
If the size is smaller, defibration is likely to occur when the card is passed, and if it is larger than 40 pieces / 25 mm, defibration is likely to occur, which is not preferable.

The biodegradable aliphatic polyester used in the present invention includes polylactic acid and its copolymers, poly-ω-hydroxyalkanoate polyesters such as poly-ε-caprolactone, poly-β-propiolactone and their copolymers. Can be shown.

The biodegradable aliphatic polyester may be an anionic surfactant such as potassium lauryl phosphate in consideration of antistatic property and sizing property, if necessary.
Cationic surfactants such as quaternary ammonium salts, nonionic surfactants such as aliphatic higher alcohols and ethylene oxide adducts of higher fatty acids, polyalkylene glycols such as polyethylene glycol, polyethylene glycol / polypropylene glycol block copolymers, etc. ,
One or more kinds of silicone oils such as dimethylpolysiloxane, polyether modified silicone oil and higher alkoxy modified silicone oil may be contained or attached to the surface.

Further, the biodegradable aliphatic polyester used in the present invention includes polymers such as polyalkylene glycol and polyamino acid, inorganic substances such as talc, calcium carbonate, calcium sulfate and calcium chloride, starch, protein, food additives and the like. One kind or two or more kinds can be mixed in an appropriate amount, and various mechanical properties, biodegradability, etc. can be changed.

The biodegradable aliphatic polyester used in the present invention is preferably melt-spun at a melt spinning temperature of from the melting point to 230 ° C. When it exceeds 230 ° C, the thermal stability of the biodegradable aliphatic polyester may be affected.

The melt-spun undrawn yarn is air-cooled or 2
After cooling in a water bath or oil bath at 0 ° C to 60 ° C, it is usually wound once and then stretched in a stretching step of one step or two steps or more. The total draw ratio depends on the purpose of use and the required performance, but it is necessary to draw the film at a draw ratio of 2 to 8 times. Also,
As the melt spinning method, a spin draw method or a high speed spinning method can also be used.

The biodegradable aliphatic polyester fiber used in the present invention has a strength of 2 g / d or more, preferably 3 g / d or more. If the strength is less than 2 g / d, the processability is not good when a nonwoven fabric is produced, and the strength of the nonwoven fabric cannot be obtained, which is not preferable. The single fiber diameter is preferably 1 to 20 denier.

The non-woven fabric for obtaining the biodegradable bag of the present invention is made from a cellulosic fiber and a biodegradable aliphatic polyester fiber into a web with a parallel webber, a random webber or the like, and if necessary, needle punching or hydroentanglement. Treated, then the resulting web is partially applied by a heated embossing roller or calender roller,
Or heat-bond it as a whole. The heat-bonding area by the embossing roller is usually 5 to 50%, preferably 10 to 3
0%.

The heat-bonding temperature is usually 30 ° C. below the melting point of the biodegradable aliphatic polyester to 30 ° C. above the melting point. If the heat-bonding temperature exceeds the melting point, the strength of the non-woven fabric tends to decrease, and if the temperature exceeds 30 ° C. higher than the melting point, it is unfavorable because it may wind around the embossing roller or calender roller or stain the surface. To increase the bonding temperature, it is better to increase the mixing ratio of cellulosic fibers.

A part or all of the contact portion between the cellulosic fiber and the biodegradable aliphatic polyester fiber is heat-bonded, which is composed of a mixed fiber of the obtained cellulosic fiber and biodegradable aliphatic polyester fiber. The present non-woven fabric can be made into a bag by using a known bag making method.

For example, by utilizing the thermal adhesiveness of the above-mentioned non-woven fabric, two superposed non-woven fabrics are heat-bonded by a three-side sealing bag making machine. Further, it is also possible to fit the nonwoven fabric into a tubular shape and perform palm-sealing with a center seal machine. Alternatively, the bag may be formed by using a biodegradable polymer as an adhesive.

In the biodegradable bag of the present invention, the mixing ratio of the cellulosic fibers and the biodegradable aliphatic polyester fibers constituting the non-woven fabric, the respective fiber diameters or fiber lengths, or the degree of thermal adhesion thereof is changed. By doing so, the biodegradability, strength, water resistance, etc. of the bag can be controlled, and it is not necessary to have a complicated structure.

When the biodegradable bag of the present invention is used as a garbage bag used for treating household garbage such as a composter for household use, the garbage bag (drainage bag) is treated together with the garbage in the poster. However, not only is it biodegradable, but it can also be disassembled and disassembled without the dust bag getting entangled in the stirrer or the like.

The biodegradable bag of the present invention is characterized in that both the cellulosic fiber and the biodegradable aliphatic polyester fiber are short fibers.

The biodegradable bag of the present invention having the above structure does not easily retain its original shape when used as a composter for treating garbage, and is easily biodegraded together with garbage. In this case, the fiber length of the cellulosic fiber and the biodegradable aliphatic polyester fiber is preferably 80 mm or less. If it exceeds 80 mm, there is a strong tendency to get entangled with the stirring rod in the composter.

Short fibers of biodegradable aliphatic polyester are
It can be obtained by melt spinning and stretching, or by high speed spinning and then cutting. The biodegradable aliphatic polyester fiber can be mechanically crimped before being cut. As the mechanical crimping process, a pushing gear method, a stuffing box method or the like can be used. The number of crimps is 5 to 50/25 mm, preferably 10
-30 pieces / 25 mm is given, and the cut length is 10-80 mm,
Preferably 15 to 60 mm, more preferably 15 to 3
Cut to 0 mm. Number of crimps is 5/25 when manufacturing non-woven fabric
If it is less than mm, the unopened portion is likely to occur when opening, and 50
If the number exceeds 25 / mm, uniform opening cannot be obtained.

The crimping rate is 5% or more, preferably 8% or more. If the crimp ratio is less than 5%, a uniform wave cannot be obtained when applied to a card, and a sparse / dense portion is generated, which is not good.

In the biodegradable bag of the present invention, the mixing ratio of the cellulosic fibers of the nonwoven fabric forming the bag and the biodegradable aliphatic polyester fiber is 90/10 to 10/90 (weight ratio). It is characterized by

In the biodegradable bag having the above structure, the strength and the ease of biodegradability can be adjusted by the mixing ratio of the cellulosic fiber and the biodegradable aliphatic polyester fiber. It is preferably 30/70 to 80/20, more preferably 40/60 to 70/30. 10/90
If it is smaller, the workability is not good during adhesion processing. Again 90
If it is larger than / 10, the strength cannot be obtained even if the adhesive is processed, which is not preferable.

The biodegradable bag of the present invention is characterized in that the nonwoven fabric forming the bag has a biodegradable aliphatic polyester fiber having a melting point of 120 ° C to 200 ° C.

The biodegradable bag of the present invention having the above structure does not cause heat fusion even when the product is stored at a temperature of about 80 ° C. in summer. It is practical that the melting point of the biodegradable aliphatic polyester fiber is 120 ° C. or higher, preferably 130 ° C. or higher.

In the biodegradable bag of the present invention, the polymer of the biodegradable aliphatic polyester of the non-woven fabric forming the bag is polylactic acid and / or a thermoplastic polymer mainly composed of polylactic acid. Characterize.

The biodegradable bag of the present invention having the above structure,
It is easy to obtain and has excellent workability. The viscosity average molecular weight of the polylactic acid and / or the thermoplastic polymer mainly composed of polylactic acid is 5,000 or more, preferably 10 4 to 10 6. If it is 5000 or less, sufficient strength as a fiber cannot be obtained. On the other hand, if the viscosity average molecular weight is 10 6 or more, the melt viscosity becomes high during spinning, and the spinnability is poor, which is not preferable.

Thermoplastic fibers mainly composed of polylactic acid include lactic acid, cyclic lactones such as ε-caprolactone, and α
-One or two kinds of α-oxy acids such as hydroxybutyric acid, α-hydroxyisobutyric acid and α-hydroxyvaleric acid, glycols such as ethylene glycol and 1,4-butanediol, dicarboxylic acids such as succinic acid and sebacic acid The thing copolymerized above can be used. A random copolymer and / or a block copolymer can be used for the copolymer.

The hydroxyl group at the polymer terminal is preferably esterified at the polymer molecular terminal with a compound having a carboxyl group at the molecular terminal represented by aliphatic carboxylic acids such as lauric acid and stearic acid. The thermal decomposition stability during melt spinning can be improved.

The carbonyl group at the terminal of the polymer is a compound having a hydroxyl group at the molecular end, which is represented by higher alcohols such as octyl alcohol, lauryl alcohol, stearyl alcohol and the like, and it is preferable to subject the end of the polymer molecule to esterification. It is possible to improve the thermal stability during melt spinning and the temporal stability of fibers during melt spinning.

Polylactic acid and / or used in the present invention
Alternatively, the acid value of the thermoplastic polymer mainly composed of polylactic acid is preferably within the range of Formula 1. Acid value ≦ 60 / (ηsp / C) (Formula 1) Acid value ≦ 40 / (ηsp / C) More preferably, acid value ≦ 30 / (ηsp / C). When the acid value is out of the range of Formula 1, the thermal stability during melt spinning and the room temperature storage stability are not good.

When the biodegradable bag of the present invention is used as a garbage bag for treating garbage (drainage bag), holes or cuts may be provided to increase the draining speed. In the case of holes, make holes with a diameter of 1 to 5 mm and open area ratio 0.5 to 20%.
It is good to set it to about 3 to 1 in the case of notch
It is advisable to make a cut of 0 mm at a cut rate of about 0.2 to 1 line / cm 2.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the biodegradable bag of the present invention will be described below based on Examples.

[0042]

EXAMPLES The method of measuring the characteristic values in the examples is as follows. (1) Reduced specific viscosity: Chloroform was used as a solvent, 0.5 g / d1 of a sample polymer was precisely weighed, and the dissolved sample solution was measured using an Ubbelohde viscometer.

(2) Acid value: A sample polymer was precisely weighed and dissolved in a mixed solvent of chloroform / methanol (volume ratio 1: 1), and the solution was titrated with a sodium methoxide / methanol solution.

(3) Tensile strength: Measured according to JIS L1906.

(4) Elongation at break: Measured according to JIS L1906.

(5) Melting point: The temperature was measured at a rate of 10 ° C./min using DSC-50 manufactured by Shimadzu Corporation.

(6) Strength retention rate: 2 in water at room temperature of 25 ° C.
It was obtained from Formula 2 from the strength after being left for 4 hours and the strength after drying and the strength before treatment. Strength retention rate (%) = T / T0 × 100 (Formula 2) T: Tensile strength (g) after standing in water at room temperature of 25 ° C. for 2 hours
/ 5 cm) T0: Initial tensile strength (g / 5 cm)

(7) Biodegradability: A trash bag was buried in the soil, and the state of degradation after 6 months was observed by a scanning electron microscope (SEM) and evaluated. A: Fiber shape is lost (good biodegradability) B: Fiber shape is partially retained C: Fiber shape remains the same (no biodegradability)

(8) Adhesive workability for bag-making: The processability when adhered with a heat sealer was evaluated in three stages from the adhesiveness of the sealing surface and the operability. A: Good bag-making adhesive workability B: Good bag-making adhesive workability C: No bag-making adhesive workability

(9) Degradability of composter: about 20 garbage
0 g was put in a garbage bag and put into a household garbage disposer (BGD-10 type) manufactured by Hitachi Ltd., and the state of decomposition after 24 hours was evaluated. A: It is decomposed without being entangled with the stirring bar B: It is slightly entangled with the stirring bar C: It is slightly entangled with the stirring bar D: It is entangled with the original shape of the nonwoven fabric kept: Not measurable ( Bag making is not done)

Fiber Example 1 Polylactic acid having a reduced specific viscosity of 1.52 and a terminal carboxyl group of a molecule esterified with lauryl alcohol was spun at a spinning temperature of 190 ° C. from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm. Melt spinning was performed at a speed of 500 m / min. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., and the single yarn fineness was 2.0 d, the reduced specific viscosity was 1.46, and the acid value =
Fibers having a melting point of 170 ° C. and 20 (eq / 10 3 kg) were obtained. (Fiber 1) Fiber Example 2 From a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at a spinning temperature of 200 ° C., polylactic acid having a reduced specific viscosity of 1.93 and esterified with lauryl alcohol at the terminal carboxyl group of the molecule. High-speed melt spinning was performed at a spinning speed of 3500 m / min. Single yarn fineness 2.2d, reduced specific viscosity 1.86, acid value =
Fibers having a melting point of 172 ° C. and 16 (eq / 10 3 kg) were obtained. (Fiber 2) -Fiber Example 3 A polylactic acid / polycaprolactone block copolymer having a reduced specific viscosity of 1.52 (polymerization molar ratio lactic acid / caprolactone = 90: 10) is used and the diameter is 0.3 mm at a spinning temperature of 190 ° C.
Spinning speed of 500m / from a spinning nozzle with 20 spinning holes
Melt spinning was performed at min. After winding the undrawn yarn once,
Stretched 4.5 times at 130 ° C., single yarn fineness 2.0d, reduced specific viscosity 1.47, acid value = 30 (eq / 10 3 kg),
Short fibers having a melting point of 168 ° C. were obtained. (Fiber 3) Fiber Example 4 A commercially available rayon staple yarn having a single yarn fineness of 2 denier was used. (Fiber 4) -Manufacture of non-woven fabric and bag and test The biodegradable fibers obtained in Fibers 1 to 3 were crimped by a stuffing box method and then cut to obtain short fibers for cards. The short fibers and the fibers of the fibers 4 were webbed by a random webber, and then embossed or calendered to obtain a nonwoven fabric. The heat-bonded area by embossing was 25%, and the number of bonding points was 10 pieces / cm 2.
The number of adhesion points by calendering was 10 pieces / cm 2. The obtained non-woven fabric was cut, and two sheets were stacked to produce a bag with a three-side seal bag making machine. Bag size is vertical 25c
m, 25 cm wide. Table 1 shows those characteristic values.

[0052]

[Table 1]

From Table 1, the biodegradable bag of the present invention is water resistant,
It can be seen that it has excellent biodegradability and has practical strength even if it is thin.

[0054]

The biodegradable bag of the invention according to claim 1 is relatively easy to obtain, has a practical water resistance, and is rapidly decomposed by microorganisms, and has a practical strength and processing even if it is thin. Have sex. The biodegradable bag of the invention according to claim 2 is
When used as a composter for treating food waste, it does not easily retain its original shape and is easily biodegraded together with food waste. According to the biodegradable bag of the invention of claim 3, the bag strength and biodegradability are well balanced. The biodegradable bag of the invention according to claim 4 does not cause heat fusion between the bags even during storage in summer. The biodegradable bag according to the invention of claim 5 is easy to obtain and excellent in workability.

Claims (5)

[Claims] 1. A mixed fiber of a cellulosic fiber and a biodegradable aliphatic polyester fiber, and a part or all of the contact portion between the cellulose fiber and the biodegradable aliphatic polyester fiber is heat-bonded. A biodegradable bag made of a non-woven fabric. 2. The biodegradable bag according to claim 1, wherein both the cellulosic fiber and the biodegradable aliphatic polyester fiber are short fibers. 3. The mixing ratio of the cellulosic fiber and the biodegradable aliphatic polyester fiber is 90/10 to 10/90.
(Weight ratio), The biodegradable bag according to claim 1 or 2, wherein. 4. The melting point of the biodegradable aliphatic polyester is 1.
20-200 degreeC, Claim 1, 2 characterized by the above-mentioned.
Or the biodegradable bag described in 3. 5. The biodegradable bag according to claim 1, 2, 3 or 4, wherein the biodegradable aliphatic polyester is polylactic acid and / or a thermoplastic polymer mainly containing polylactic acid.